WorldWideScience

Sample records for langmuir probe system

  1. RF-Compensated Langmuir Probe Measurements in an IPVD System

    Science.gov (United States)

    Juliano, Daniel R.; Ruzic, David N.

    1998-10-01

    The experimental apparatus consists of a commercial-scale magnetron with an RF coil between the target and substrate holder. This coil creates a secondary inductive plasma that ionizes a significant portion of the sputter flux en route from target to substrate. In order to understand and predict the ionization of the sputter flux arriving at the substrate, Langmuir probe measurements of this secondary inductive plasma were made under various combinations of powers (magnetron and RF), pressures, and working gas mixtures. The probe apparatus is RF-compensated in order to keep the voltage difference between the probe tip and plasma constant throughout the RF cycle. In order to yield accurate measurements in the dirty depositing environment of the IPVD system, the back of probe tip is recessed in a small ceramic tube, preventing shorting. Further, the potential on the probe tip is kept low except during the data-collecting voltage sweeps in order to continuously clean it and maintain stable electrical characterisitics.

  2. Advanced Langmuir Probe (LP)

    Science.gov (United States)

    Voronka, N. R.; Block, B. P.; Carignan, G. R.

    1991-01-01

    The dynamic response of the MK-2 version of the Langmuir probe amplifier was studied. The settling time of the step response is increased by: (1) stray node-to-ground capacitance at series connections between high value feedback resistors; and (2) input capacitance due to the input cable, FET switches, and input source follower. The stray node-to-ground capacitances can be reduced to tolerable levels by elevating the string of feedback resistors above the printing board. A new feedback network was considered, with promising results. The design uses resistances having much lower nominal values, thereby minimizing the effect of stray capacitances. Faster settling times can be achieved by using an operational amplifier having a higher gain-bandwidth product.

  3. Time-Resolved Langmuir Probe Measurements in an Ionized PVD System

    Science.gov (United States)

    Juliano, D. R.; Hayden, D. B.; Ruzic, D. N.

    1997-10-01

    The experimental apparatus consists of a commercial-scale magnetron (Donated by Materials Research Corporation) with an RF coil between the target and substrate holder. This coil creates a secondary inductive plasma that ionizes a significant portion of the sputter flux en route from target to substrate. Ionization of the metal atoms that make up the sputter flux is highly sensitive to the high energy tail of the electron energy distribution, which in turn is highly dependent on the background gas mixture. Since there is some capacitive coupling from the coil this high energy population could change through the RF cycle. Time-averaged Langmuir probe measurements would not reveal either the extent of this high energy population or its time dependence. Further, if the probe voltage were held constant for such time-resolved measurements, they would yield incorrect results. At probe voltages above the plasma potential minimum the sheath is disrupted so that at points in the phase for which the probe voltage is below plasma potential the data is invalid. Therefore in order to take valid measurements at all phase points, it is necessary for the probe voltage to follow the RF variation in plasma potential. Using such a system, we have made time-resolved Langmuir probe measurements. Current-voltage traces as a function of phase then reveal plasma parameters as a function of time over the RF cycle for various background gases and operating parameters.

  4. The fixed-bias Langmuir probe on the Communication/Navigation Outage Forecast System satellite: calibration and validation.

    Science.gov (United States)

    Klenzing, J; Rowland, D

    2012-11-01

    A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication/Navigation Outage Forecast System (C/NOFS) satellite. C/NOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H(+) and O(+). The ion current collected by the probe surface per unit plasma density is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the C/NOFS satellite. The application of the calibration is discussed with respect to future fixed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on C/NOFS.

  5. The Fixed-Bias Langmuir Probe on the Communication-Navigation Outage Forecast System Satellite: Calibration and Validation

    Science.gov (United States)

    Klenzing, J.; Rowland, D.

    2012-01-01

    A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication Navigation Outage Forecast System (CNOFS) satellite.CNOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H+ and O+. The ion current collected by the probe surface per unit plasma density is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the CNOFS satellite. The application of the calibration is discussed with respect to future fixed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on CNOFS.

  6. A new compact and low cost Langmuir Probe and associated onboard data handling system for CubeSat

    Science.gov (United States)

    Muralikrishna, Polinaya; Domingos, Sinval; Paredes, Andres; Abrahão Dos Santos, Walter

    2016-07-01

    A new compact and low cost Langmuir Probe and associated onboard data handling system are being developed at Instituto Nacional de Pesquisas Espaciais for launching on board one of the future 2U CubeSat missions. The system is a simplified and compacted version of the Langmuir Probe payloads launched on board several Brazilian SONDA III rockets and also developed for the Brazilian scientific satellites SACI-1 and SACI-2. The onboard data handling system will have the dual functions of preprocessing the data collected by the Langmuir Probe and acting as the interface between the experiment and the on board computer. The Langmuir Probe sensor in the form of two rectangular stainless steel strips of total surface area of approximately 80cm2 will be deployed soon after the injection of the CubeSat into orbit. A sweep voltage varying linearly from 0V to 3.0V in about 1.5 seconds and then remaining fixed at 3.0V for 1 second will be applied to the LP sensor to obtain both the electron density and electron temperature. A high sensitivity preamplifier will be used to convert the sensor current expected to be in the range of a few nano amperes to a few micro amperes into a varying potential. In order to cover the large dynamic range of the expected sensor current the preamplifier output will be further amplified by a logarithmic amplifier before being sampled and sent to the data handling system. The data handling system is projected to handle 8 analog channels and 4 digital words of 8 bits each. The incoming data will be stored in a RAM and later sent to the on board computer using a serial RS422 communication protocol. The interface unit will process the telecommands received from the on board computer. The interface is also projected to do FFT analysis of the LP sensor data and send the averaged FFT spectral amplitudes in place of the original unprocessed data. The system details are presented here.

  7. Langmuir probe in collisionless and collisional plasma including dusty plasma

    Science.gov (United States)

    Bose, Sayak; Kaur, Manjit; Chattopadhyay, P. K.; Ghosh, J.; Saxena, Y. C.; Pal, R.

    2017-04-01

    Measurements of local plasma parameters in dusty plasma are crucial for understanding the physics issues related to such systems. The Langmuir probe, a small electrode immersed in the plasma, provides such measurements. However, designing of a Langmuir probe system in a dusty plasma environment demands special consideration. First, the probe has to be miniaturized enough so that its perturbation on the ambient dust structure is minimal. At the same time, the probe dimensions must be such that a well-defined theory exists for interpretation of its characteristics. The associated instrumentation must also support the measurement of current collected by the probe with high signal to noise ratio. The most important consideration, of course, comes from the fact that the probes are prone to dust contamination, as the dust particles tend to stick to the probe surface and alter the current collecting area in unpredictable ways. This article describes the design and operation of a Langmuir probe system that resolves these challenging issues in dusty plasma. In doing so, first, different theories that are used to interpret the probe characteristics in collisionless as well as in collisional regimes are discussed, with special emphasis on application. The critical issues associated with the current-voltage characteristics of Langmuir probe obtained in different operating regimes are discussed. Then, an algorithm for processing these characteristics efficiently in presence of ion-neutral collisions in the probe sheath is presented.

  8. Fast Diagnosis of Transient Plasma by Langmuir Probe

    Institute of Scientific and Technical Information of China (English)

    TANG En-ling; ZHANG Qing-ming; OUYANG Ji-ting

    2007-01-01

    A method for the fast measurement of electron temperature and density with temporal resolution in transient plasma has been implemented by Langmuir probe. The diagnostic system consists of a single Langmuir probe driven by a high frequency sinusoidal voltage. The current and voltage spectrum on the probe were detected synchronously by an oscilloscope with sampling rate being at least 5 times higher than the frequency of sweep voltage. The system has been used to diagnose the transient plasma generated by hypervelocity-impact of LY12 aluminum projectile into LY12 aluminum target.

  9. Langmuir probe analysis in electronegative plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bredin, Jerome, E-mail: jerome.bredin@lpp.polytechnique.fr; Chabert, Pascal; Aanesland, Ane [Laboratoire de Physique des Plasmas, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ Paris-Sud, Ecole Polytechnique, 91128 Palaiseau (France)

    2014-12-15

    This paper compares two methods to analyze Langmuir probe data obtained in electronegative plasmas. The techniques are developed to allow investigations in plasmas, where the electronegativity α{sub 0} = n{sub –}/n{sub e} (the ratio between the negative ion and electron densities) varies strongly. The first technique uses an analytical model to express the Langmuir probe current-voltage (I-V) characteristic and its second derivative as a function of the electron and ion densities (n{sub e}, n{sub +}, n{sub –}), temperatures (T{sub e}, T{sub +}, T{sub –}), and masses (m{sub e}, m{sub +}, m{sub –}). The analytical curves are fitted to the experimental data by adjusting these variables and parameters. To reduce the number of fitted parameters, the ion masses are assumed constant within the source volume, and quasi-neutrality is assumed everywhere. In this theory, Maxwellian distributions are assumed for all charged species. We show that this data analysis can predict the various plasma parameters within 5–10%, including the ion temperatures when α{sub 0} > 100. However, the method is tedious, time consuming, and requires a precise measurement of the energy distribution function. A second technique is therefore developed for easier access to the electron and ion densities, but does not give access to the ion temperatures. Here, only the measured I-V characteristic is needed. The electron density, temperature, and ion saturation current for positive ions are determined by classical probe techniques. The electronegativity α{sub 0} and the ion densities are deduced via an iterative method since these variables are coupled via the modified Bohm velocity. For both techniques, a Child-Law sheath model for cylindrical probes has been developed and is presented to emphasize the importance of this model for small cylindrical Langmuir probes.

  10. The theory of Langmuir probes in strong electrostatic potential structures

    Science.gov (United States)

    Borovsky, J. E.

    1986-01-01

    The operation of collecting and emitting Langmuir probes and double probes within time-stationary strong electrostatic potential structures is analyzed. The cross sections of spherical and cylindrical probes to charged particles within the structures are presented and used to obtain the current-voltage characteristics of idealized probes. The acquisition of plasma parameters from these characteristics is outlined, and the operation of idealized floating double-probe systems is analyzed. Probe surface effects are added to the idealized theory, and some surface effects pertinent to spacecraft probes are quantified. Magnetic field effects on idealized probes are examined, and the time required for floating probes to change their potentials by collecting charge and by emitting photoelectrons is discussed. Calculations on the space-charge effects of probe-perturbed beams and on the space-charge limiting of electron emission are given in an appendix.

  11. Test of a new tip material for Langmuir probe diagnostic

    Science.gov (United States)

    Naz, M. Y.; Shukrullah, S.; Ghaffar, A.; Rehman, N. U.; Khan, Y.

    2016-03-01

    The objective of the work is to test a nickel-chrome alloy as a probe tip material for characterization of discharge plasmas. In order to meet the objective, a symmetric triple Langmuir probe diagnostic system and an associated driving circuit are designed and tested in an inductively coupled plasma generated by a 13.56-MHz radio frequency source coupled with an automated impedance match network. This probe is used to measure the electron temperature, electron number density, and ion saturation current as functions of the input power of the radio frequency source and the filling gas pressure. An increasing trend is noticed in the electron temperature and electron number density with an increase in the input power, whilst a decreasing trend is evident in these parameters with an increase in the nitrogen gas pressure. The overall inaccuracies in electron temperature and electron number density measurements are 5-12% and 3-13%, respectively.

  12. Study of a Laser-Produced Plasma by Langmuir Probes

    DEFF Research Database (Denmark)

    Chang, C. T.; Hasimi, M.; Pant, H. C.

    1977-01-01

    The structure, the parameters and the expansion of the plasma produced by focusing a 7 J, 20 ns Nd-glass laser on stainless-steel and glass targets suspended in a high-vacuum chamber were investigated by Langmuir probes. It was observed that the probe signals consisted of a photoelectric...

  13. Revisiting plasma hysteresis with an electronically compensated Langmuir probe

    Science.gov (United States)

    Srivastava, P. K.; Singh, S. K.; Awasthi, L. M.; Mattoo, S. K.

    2012-09-01

    The measurement of electron temperature in plasma by Langmuir probes, using ramped bias voltage, is seriously affected by the capacitive current of capacitance of the cable between the probe tip and data acquisition system. In earlier works a dummy cable was used to balance the capacitive currents. Under these conditions, the measured capacitive current was kept less than a few mA. Such probes are suitable for measurements in plasma where measured ion saturation current is of the order of hundreds of mA. This paper reports that controlled balancing of capacitive current can be minimized to less than 20 μA, allowing plasma measurements to be done with ion saturation current of the order of hundreds of μA. The electron temperature measurement made by using probe compensation technique becomes independent of sweep frequency. A correction of ≤45% is observed in measured electron temperature values when compared with uncompensated probe. This also enhances accuracy in the measurement of fluctuation in electron temperature as δTpk-pk changes by ˜30%. The developed technique with swept rate ≤100 kHz is found accurate enough to measure both the electron temperature and its fluctuating counterpart. This shows its usefulness in measuring accurately the temperature fluctuations because of electron temperature gradient in large volume plasma device plasma with frequency ordering ≤50 kHz.

  14. Measurement of electron temperatures of Argon Plasmas in a High-Density Inductively-Coupled Remote Plasma System by Langmuir Probe and Optical-Emission Spectroscopy

    NARCIS (Netherlands)

    Boogaard, A.; Kovalgin, Alexeij Y.; Aarnink, Antonius A.I.; Wolters, Robertus A.M.; Holleman, J.; Brunets, I.; Schmitz, Jurriaan

    2006-01-01

    We measured electron density and electron energy distribution function (EEDF) in our reactor by a Langmuir probe. The EEDF of Ar plasma in the reactor could largely be described by the Maxwell-Boltzmann distribution function, but it also contained a fraction (~10-3) of electrons which were much

  15. An investigation of dust particles orbiting a Langmuir probe

    Energy Technology Data Exchange (ETDEWEB)

    Ramazanov, T S; Kodanova, S K; Dzhumagulova, K N; Dosbolayev, M K; Jumabekov, A N [IETP, Al Farabi Kazakh National University, Tole Bi 96a, 050012 Almaty (Kazakhstan); Petrov, O F; Antipov, S N [Joint Institute for High Temperatures of RAS, 13-2, Izhorskaya St, Moscow 125412 (Russian Federation)

    2009-05-29

    In the present work, the behavior of dust particles near an attracting Langmuir cylindrical probe in glow discharge plasma was investigated experimentally. Trajectories of dust particles for different initial kinetic energies and impact parameters were analyzed numerically. The comparision between experimental and simulation results are made. The results obtained can be used for the development of new dusty plasma diagnostic techniques.

  16. Langmuir-Probe Measurements in Flowing-Afterglow Plasmas

    Science.gov (United States)

    Johnsen, R.; Shunko, E. V.; Gougousi, T.; Golde, M. F.

    1994-01-01

    The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing- afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the electron densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.

  17. Designs of Langmuir probes for W7-X

    Energy Technology Data Exchange (ETDEWEB)

    Laube, Ralph, E-mail: ralph.laube@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstr. 1, D-17491 Greifswald (Germany); Laux, Michael; Ye, Min You [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstr. 1, D-17491 Greifswald (Germany); Greuner, Henri; Lindig, Stefan [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstr. 2, D-85748 Garching (Germany)

    2011-10-15

    Several designs of Langmuir probes for the stellarator Wendelstein 7-X (W7-X) are described. Different types of probes are proposed for the different divertors to be used during different operational phases of W7-X. Comb-like arrays of stiff probes, arrays of flexible probes, and fixed inlay probes are reviewed. For the initial phase of W7-X it was decided to install arrays of fixed inlay probes. Two mockups were manufactured and one of them was tested with success in the high heat flux test facility GLADIS. For long-pulse operation of W7-X different conceptual designs are proposed and are still developed further. This paper summarizes the different design constrains for the Langmuir probes in the different divertor surroundings, describes the design of the array of inlay probes for the initial phase and the result of the GLADIS test, and gives a preview of the conceptual designs of probes for the long-pulse operational phase of W7-X.

  18. Langmuir Probe Spacecraft Potential End Item Specification Document

    Science.gov (United States)

    Gilchrist, Brian; Curtis, Leslie (Technical Monitor)

    2001-01-01

    This document describes the Langmuir Probe Spacecraft Potential (LPSP) investigation of the plasma environment in the vicinity of the ProSEDS Delta II spacecraft. This investigation will employ a group of three (3) Langmuir Probe Assemblies, LPAs, mounted on the Delta II second stage to measure the electron density and temperature (n(sub e) and T(sub e)), the ion density (n(sub i)), and the spacecraft potential (V(sub s)) relative to the surrounding ionospheric plasma. This document is also intended to define the technical requirements and flight-vehicle installation interfaces for the design, development, assembly, testing, qualification, and operation of the LPSP subsystem for the Propulsive Small Expendable Deployer System (ProSEDS) and its associated Ground Support Equipment (GSE). This document also defines the interfaces between the LPSP instrument and the ProSEDS Delta II spacecraft, as well as the design, fabrication, operation, and other requirements established to meet the mission objectives. The LPSP is the primary measurement instrument designed to characterize the background plasma environment and is a supporting instrument for measuring spacecraft potential of the Delta II vehicle used for the ProSEDS mission. Specifically, the LPSP will use the three LPAs equally spaced around the Delta II body to make measurements of the ambient ionospheric plasma during passive operations to aid in validating existing models of electrodynamic-tether propulsion. These same probes will also be used to measure Delta II spacecraft potential when active operations occur. When the electron emitting plasma contractor is on, dense neutral plasma is emitted. Effective operation of the plasma contactor (PC) will mean a low potential difference between the Delta II second stage and the surrounding plasma and represents one of the voltage parameters needed to fully characterize the electrodynamic-tether closed circuit. Given that the LP already needs to be well away from any

  19. Solar extreme ultraviolet sensor and advanced langmuir probe

    Science.gov (United States)

    Voronka, N. R.; Block, B. P.; Carignan, G. R.

    1992-01-01

    For more than two decades, the staff of the Space Physics Research Laboratory (SPRL) has collaborated with the Goddard Space Flight Center (GSFC) in the design and implementation of Langmuir probes (LP). This program of probe development under the direction of Larry Brace of GSFC has evolved methodically with innovations to: improve measurement precision, increase the speed of measurement, and reduce the weight, size, power consumption and data rate of the instrument. Under contract NAG5-419 these improvements were implemented and are what characterize the Advanced Langmuir Probe (ALP). Using data from the Langmuir Probe on the Pioneer Venus Orbiter, Brace and Walter Hoegy of GSFC demonstrated a novel method of monitoring the solar extreme ultraviolet (EUV) flux. This led to the idea of developing a sensor similar to a Langmuir probe specifically designed to measure solar EUV (SEUV) that uses a similar electronics package. Under this contract, a combined instrument package of the ALP and SEUV sensor was to be designed, constructed, and laboratory tested. Finally the instrument was to be flight tested as part of sounding rocket experiment to acquire the necessary data to validate this method for possible use in future earth and planetary aeronomy missions. The primary purpose of this contract was to develop the electronics hardware and software for this instrument, since the actual sensors were suppied by GSFC. Due to budget constraints, only a flight model was constructed. These electronics were tested and calibrated in the laboratory, and then the instrument was integrated into the rocket payload at Wallops Flight Facility where it underwent environmental testing. After instrument recalibration at SPRL, the payload was reintegrated and launched from the Poker Flat Research Range near Fairbanks Alaska. The payload was successfully recovered and after refurbishment underwent further testing and developing to improve its performance for future use.

  20. Langmuir probe study of plasma expansion in pulsed laser ablation

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1999-01-01

    Langmuir probes were used to monitor the asymptotic expansion of the plasma produced by the laser ablation of a silver target in a vacuum. The measured angular and temporal distributions of the ion flux and electron temperature were found to be in good agreement with the self-similar isentropic...... and adiabatic solution of the gas dynamics equations describing the expansion. The value of the adiabatic index gamma was about 1.25, consistent with the ablation plume being a low temperature plasma....

  1. A dual-cable noise reduction method for Langmuir probes

    Science.gov (United States)

    Yang, T. F.; Zu, Q. X.; Liu, Ping

    1995-07-01

    To obtain fast time response plasma properties, electron density and electron temperature, with a Langmuir probe, the applied probe voltage has to be swept at high frequency. Due to the RC characteristics of coaxial cables, an induced noise of a square-wave form will appear when a sawtooth voltage is applied to the probe. Such a noise is very annoying and difficult to remove, particularly when the probe signal is weak. This paper discusses a noise reduction method using a dual-cable circuit. One of the cables is active and the other is a dummy. Both of them are of equal length and are laid parallel to each other. The active cable carries the applied probe voltage and the probe current signal. The dummy one is not connected to the probe. After being carefully tuned, the induced noises from both cables are nearly identical and therefore can be effectively eliminated with the use of a differential amplifier. A clean I-V characteristic curve can thus be obtained. This greatly improves the accuracy and the time resolution of the values of ne and Te.

  2. Utilization of Double Langmuir Probes on Proto-MPEX

    Science.gov (United States)

    Kafle, Nischal; Caughman, John B.; Caneses, Juan F. M.; Goulding, Richard H.; Martin, Elijah. H.; Donovan, David. C.

    2016-10-01

    Langmuir probes (LP) are a robust, simply constructed, and inexpensive diagnostic tool. They are routinely used to measure the electron temperature and density in plasmas. However, the uncompensated single-tip LP has demonstrated limitations in time fluctuating plasma potential. The measurement quality can be improved by implementing compensation or by using a double-tipped probe. Double Langmuir probes (DLPs) are referenced against each other instead of the device vessel and therefore are less susceptible to fluctuations in RF plasmas. DLPs are being used to measure plasma parameters at multiple locations in the Proto-MPEX experiment at Oak Ridge National Laboratory. Proto-MPEX is a linear plasma device that combines a helicon plasma source with additional microwave and radio frequency heating to deliver a high plasma heat flux at a target. An electron temperature of 3-6 eV and density of 3e19 - >5e19 m-3 has been measured near the target in Proto-MPEX for different magnetic field configurations, with peak magnetic fields >1 T. Plasma density and temperature tend to be higher closer to the plasma source and are strongly dependent on operating pressure. This presentation will give an overview of DLP and will provide results from multiple locations and for different operating conditions. This work was supported by the U.S. D.O.E. contract DE-AC05-00OR22725.

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

    Science.gov (United States)

    Roche, T.; Sun, X.; Armstrong, S.; Knapp, K.; Slepchenkov, M.

    2014-11-01

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

  4. The accuracy of determining ion parameters by means of a cylindrical Langmuir probe

    Science.gov (United States)

    Georgieva, K. Ia.; Kirov, B. B.; Kraleva, L. Kh.

    A method is presented whereby a cylindrical Langmuir probe can be used to obtain an estimate of the concentration distribution of two prevalent kinds of ions in space plasmas when their masses are known. In many cases, the use of a Langmuir probe can thus compensate for the absence of a mass spectrometer. The probe can also be used as a backup if the data obtained by other instruments are not dependable.

  5. Langmuir Probe Distortions and Probe Compensation in an Inductively Coupled Plasma

    Science.gov (United States)

    Ji, J. S.; Cappelli, M. A.; Kim, J. S.; Rao, M. V. V. S.; Sharma, S. P.

    1999-01-01

    In many RF discharges, Langmuir probe measurements are usually made against a background of sinusoidal (and not so sinusoidal) fluctuations in the plasma parameters such as the plasma potential (Vp), the electron number density (ne), and the electron temperature (Te). The compensation of sinusoidal fluctuations in Vp has been extensively studied and is relatively well understood. Less attention has been paid to the possible distortions introduced by small fluctuations in plasma density and/or plasma temperature, which may arise in the sheath and pre-sheath regions of RF discharges. Here, we present the results of a model simulation of probe characteristics subject to fluctuations in both Vp and ne. The modeling of probe distortion due to possible fluctuations in Te is less straightforward. A comparison is presented of calculations with experimental measurements using a compensated and uncompensated Langmuir probe in an inductively coupled GEC reference cell plasma, operating on Ar and Ar/CF4 mixtures. The plasma parameters determined from the compensated probe characteristics are compared to previous measurements of others made in similar discharges, and to our own measurements of the average electron density derived from electrical impedance measurements.

  6. Means to remove electrode contamination effect of Langmuir probe measurement in space

    Energy Technology Data Exchange (ETDEWEB)

    Oyama, K.-I.; Lee, C. H.; Fang, H. K.; Cheng, C. Z. [Plasma and Space Science Center, National Cheng Kung University, No.1 Ta-Hsueh Rd., Tainan 70101, Taiwan (China)

    2012-05-15

    Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

  7. Langmuir probe studies on a RF ion source for NBI

    Energy Technology Data Exchange (ETDEWEB)

    McNeely, P. E-mail: p.mcneely@ipp.mpg.de; Heineman, B.; Kraus, W.; Riedl, R.; Speth, E.; Vollmer, O

    2001-10-01

    IPP Garching has been developing a RF ion source for H{sup -} production. In order to improve the data quality a new scanning probe system with passive RF compensation has been installed on the Type VI ion source on the BATMAN test stand. Using this probe, measurements have been carried out to study changes to the plasma parameters (electron density, electron temperature, and plasma potential) due to variation in the source operating conditions. The data were collected at a source pressure of 0.5 Pa and with 60{+-}5 kW applied RF power. Presented are some of the results of these measurements, focusing on the effect of: argon seeding, addition of Cs to the source, and the newly added Faraday screen. The electron density behaves in a fashion that agrees with the theory of ambipolar diffusion. Typically there is little change to the average electron energy observed regardless of which effect is considered. The plasma potential shows the most significant changes with external source conditions, both in value for all cases and shape when the Faraday screen was added.

  8. Langmuir probe Diagnostic for local parameter measurement in Magnetized Plasma using LabVIEW

    Directory of Open Access Journals (Sweden)

    Bijal Vara

    2014-03-01

    Full Text Available In recent years, plasma technology is used by Semiconductor, thin film industries for deposit layers, etching process and surface modification. So it is necessary to understanding internal plasma parameter. Langmuir probe is one of the simplest techniques which is used to measure wide range of plasma parameter like plasma potential, floating potential, electron temperature, electron energy distribution function (EEDF etc. Langmuir current voltage characteristic is obtained by varying bias voltage of the probe. LabVIEW is most powerful Microsoft window compatible software which is used to immediate data acquisition and analysis. In this paper describes analysis of Langmuir data using LabVIEW software which automatically measure I-V Plasma probe Characteristics and obtain EEDF of plasma.

  9. Combined Impedance Probe and Langmuir Probe Studies of the Low-Latitude E Region

    Science.gov (United States)

    Rowland, D. E.; Pfaff, R. F.; Steigies, C. T.

    2008-01-01

    The EQUIS-2 sounding rocket and radar campaign, launched from Kwajalein Atoll in 2004, included a mission to study low-latitude irregularities and electrodynamics, led by NASA GSFC. This mission included two instrumented rockets launched into the nighttime E region (apogee near 120 km), which included comprehensive electrodynamics and neutral density instrumentation. These rockets carried the first of a new generation of impedance probes, that utilize a wide-band drive signal to simultaneously measure the impedance of an antenna in a plasma as a function of frequency from 7 kEIz to 4 MHz. at a rapid cadence. This technique promises to permit true plasma spectroscopy, and resulted in the identification of multiple plasma resonances and accurate measurements of the plasma density, even in the low density nighttime E region. We present analyses of the technique and resulting spectra, and show how these data may be combined with fixed-bias Langmuir Probe data to infer the temperature structure of the E region as well as providing accurate absolute calibrations for the very high time resolution fixed-bias probe data. The data is shown to agree well with data from ionosonde, the ALTAIR radar, and the Peruvian beacon experiment.

  10. Magnetic and Langmuir Probe Measurements on the Plasmoid Thruster Experiment (PTX)

    Science.gov (United States)

    Koelfgen, Syri J.; Eskridge, Richard; Lee, Michael H.; Martin, Adam; Hawk, Clark W.; Fimognan, Peter

    2004-01-01

    The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and ejecting them at high velocity. A plasmoid is a plasma with an imbedded closed magnetic field structure. The shape and magnetic field structure of the translating plasmoids have been measured with of an array of magnetic field probes. Six sets of two B-dot probes were constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes are wound on a square G10 form, and have an average (calibrated) NA of 9.37 x l0(exp -5) square meters, where N is the number of turns and A is the cross-sectional area. The probes were calibrated with a Helmholtz coil, driven by a high-voltage pulser to measure NA, and by a signal generator to determine the probe's frequency response. The plasmoid electron number density n(sub e) electron temperature T(sub e), and velocity ratio v/c(sub m), (where v is the bulk plasma flow velocity and c(sub m), is the ion thermal speed) have also been measured with a quadruple Langmuir probe. The Langmuir probe tips are 10 mm long, 20-mil diameter stainless steel wire, housed in a 6-inch long 4-bore aluminum rod. Measurements on PTX with argon and hydrogen from the magnetic field probes and quadruple Langmuir probe will be presented in this paper.

  11. Langmuir Probe Measurements in an Inductively Coupled GEC Reference Cell Plasma

    Science.gov (United States)

    Ji, J. S.; Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

    1998-01-01

    Measurements of electron number density, electron temperature, and electron energy distribution function (EEDF) using a compensated Langmuir probe have been performed on an inductively (transformer ) coupled Gaseous Electronics Conference (GEC) reference cell plasma. The plasma source is operated with CH4, CF4, or their mixtures with argon. The effect of independently driving the electrode supporting the wafer on the probe data is studied. In particular, we find that the plasma structure depends on the phase in addition to the magnitude of the power coupled to the electrode relative to that of the transformer coil. The Langmuir probe is translated in a plane parallel to the electrode to investigate the spatial structure of the plasma. The probe data is also compared with fluid model predictions.

  12. LabVIEW software for analyzing Langmuir probe characteristics in magnetized plasma

    Science.gov (United States)

    Gandhi, S.; Binwal, S.; Kabariya, H.; Karkari, S. K.

    2016-03-01

    This paper describes the methodology for processing Ampere-Volts (I-V) characteristics of the Langmuir probe in magnetized plasma using graphical programming language based on LabVIEW. Computing the plasma parameters from I-V characteristic involves several steps that include signal processing, interpolation, linear and non-linear curve fitting based on physical models, finding the derivatives of the experimental curve and determining the zero-crossing of the probe current as a function of the applied voltage. These operations are practically tedious to perform manually causing systematic errors in output parameters. To overcome this challenge, software is developed to analyze the planar Langmuir probe characteristics in magnetized plasma. The software allows simultaneous display of different plasma parameters that helps to verify the consistency of the analyzed plasma parameters with the standard probe theory. Using this software, plasma parameters are obtained in a linear plasma device and its characteristics are discussed.

  13. Radicals as EPR probes of magnetization of gadolinium stearate Langmuir-Blodgett film

    DEFF Research Database (Denmark)

    Koksharov, Y.A.; Bykov, I.V.; Malakho, A.P.;

    2002-01-01

    In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...

  14. Radial Density Profile in the SSX Plasma Wind Tunnel using a Double Langmuir Probe

    Science.gov (United States)

    Weinhold, D. L.; Flanagan, K.; Gray, T.; Brown, M. R.

    2011-10-01

    We present preliminary results from a moveable double Langmuir probe in the present plasma wind tunnel configuration of SSX. The probe is designed to measure radial profiles of electron density (ne) and electron temperature (Te) across the midplane with a 1 cm resolution. Line-averaged densities from He-Ne interferometry show densities of 1 - 5 ×1015 cm-3 . In addition to mean values, we will also present electrostatic fluctuations and correlations with magnetic field measurements. The double Langmuir probe also measures local Te. Line-averaged measurements from VUV spectroscopy indicate Te ~ 10 eV . The Langmuir probe stalk diameter measures 6 . 5 mm and tip spacing is 1 . 1 mm . The SSX plasma wind tunnel has dimensions L ≅ 1 m and R = 0 . 08 m . Plasma flow speeds are v >= 50 km / s . The cylindrical copper boundary and probe surfaces are baked and cleaned in a He glow discharge to maintain excellent vacuum and surface conditions. Electrostatic measurements during merging will be presented if available. Work supported by US DOE and CMSO.

  15. On the issue of the surface contamination of a Langmuir Probe sensor: Demeter ISL results

    Science.gov (United States)

    Lebreton, J. P.

    2011-10-01

    The Demeter Instrument Sonde de Langmuir (ISL) comprises two Langmuir Probe sensors. It includes a classical cylindrical sensor and a 6-sector spherical Segmented Langmuir Probe (SLP) sensor. The CNES Demeter satellite was launched in June 2004 on a 700-km altitude high-inclination orbit. ISL worked flawlessly till the satellite was decommissioned in March 2011. It provided more than 6 years of data. For operational reasons, the science payload was only operated below magnetic latitude 65°. It was switched off twice per orbit when above 65°. A transient behavior of the ISL sensors was systematically observed each time it was turned on at the beginning of each half-orbit segment. This transient behavior is attributed to surface contamination of the sensors. Some surface contamination of the sensor is indeed inferred from the recording of a series of I-V curves at different sweep rates using a special mode designed to monitor the evolution of the surface state of the sensor during the mission. As independently observed from the comparison between Demeter ISL measurements and Ground-based radar ionospheric sounding measurements, (J.-L. Berthelier, private communication, 2011) it is shown that the electron temperature measurements performed by a contaminated Langmuir Probe are significantly higher than the true physical value. Based on the work of Piel at al., a method was developed to determine the electrical characteristics of the surface contamination layer, and to remove the effect of the contamination layer on the determination of the main plasma parameters from the analysis of the I-V curve (the plasma electron density Ne and the Electron temperature Ne). Potential contamination issues for Langmuir Probes on future planetary mission orbiters will be addressed and ways to avoid or at least mitigate the effects of will be discussed.

  16. Plasma monitoring of the RLVIP-process with a Langmuir probe

    Science.gov (United States)

    Huber, D.; Hallbauer, A.; Pulker, H. K.

    2005-09-01

    The aim of this investigation was to study the characteristics of a reactive-low-voltage-high-current-ion-plating plasma and to correlate the observed plasma data with the properties of films deposited under such conditions. A Langmuir probe system (Smart Probe - Scientific Systems) was inserted into a Balzers BAP 800 ion plating plant above the e-gun evaporation source close to the insulated substrate holder. In this position during RLVIP deposition, plasma potential, floating potential, self-bias voltage, electron temperature, ion current density, and particle number density were measured and calculated, respectively. All measurements were performed in dependence of arc current (20-80A) and oxygen partial pressure (1 - 36 x 10-4mbar). With rising arc current the number of charged particles, the self-bias voltage between plasma and substrates as well as the energy of the condensing and bombarding species were increased. These data explain the increase of density, refractive index and mechanical stress of RLVIP-metal-oxide-layers, like Ta2O5 and Nb2O5, deposited with higher arc currents. An increase of gas pressure decreased the energy of the particles and therefore reduced slightly film density and refractive index. However, it improved chemistry and eliminated unwanted residual optical absorption and also decreased compressive mechanical film stress.

  17. Ion collection by planar Langmuir probes: Sheridan's model and its verification

    Science.gov (United States)

    Lee, Dongsoo; Hershkowitz, Noah

    2007-03-01

    Data analysis from planar Langmuir probes normally assumes that the sheath effects are not significant in determining electron density and temperature when the Debye length is small compared to the probe radius. However, analysis of ion saturation current requires careful attention due to sheath expansion near the probe electrode. It is experimentally verified for the first time that Sheridan's numerical model [T. E. Sheridan, Phys. Plasmas 7, 3084 (2000)] provides a correct method to measure the ion saturation current for which the ion density agrees with the electron density in argon plasmas.

  18. On the interpretation of Langmuir probe data inside a spacecraft sheath

    Energy Technology Data Exchange (ETDEWEB)

    Olson, J.; Brenning, N. [Space and Plasma Physics, Royal Institute of Technology (KTH), Teknikringen 31, SE-10044 Stockholm (Sweden); Wahlund, J.-E. [Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala (Sweden); Gunell, H. [Belgian Institute for Space Aeronomy, Avenue Circulaire 3, B-1180 Brussels (Belgium)

    2010-10-15

    If a Langmuir probe is located inside the sheath of a negatively charged spacecraft, there is a risk that the probe characteristic is modified compared to that of a free probe in the ambient plasma. We have studied this probe-in-spacecraft-sheath problem in the parameter range of a small Langmuir probe (with radius r{sub LP}<<{lambda}{sub D}) using a modified version of the orbit motion limited (OML) probe theory. We find that the ambient electron contribution I{sub e}(U{sub LP}) to the probe characteristic is suitably analyzed in terms of three regions of applied probe potential U{sub LP}. In region I, where the probe is negatively charged (i.e., U{sub LP}probe position), the probe characteristic I{sub e}(U{sub LP}) is close to that of OML theory for a free probe in the ambient plasma. In the probe potential range U{sub LP}>U{sub 1}, there is first a transition region II in applied potential, U{sub 1}probe and the ambient plasma. This minimum gives the depth U{sub pl}-U{sub M} of a potential barrier that prevents the lowest energy ambient electrons from reaching the probe. For a high enough positive probe potential, in region III, the barrier becomes small. Here, I{sub e}(U{sub LP}) again approaches OML theory for a free probe. The boundary U{sub 2} between regions II and III is somewhat arbitrary; we propose a condition on the barrier, U{sub pl}-U{sub M}<probe characteristic is likely to depart from usual OML in crucial respects: (1) the ambient plasma potential U{sub pl} falls into the transition

  19. Langmuir Probe Measurements of Capacitive Radio Frequency Discharge for Mixture Gases

    Science.gov (United States)

    Tanisli, Murat; Sahin, Neslihan; Demir, Suleyman

    2016-10-01

    Radio frequency discharges at low pressure have been used for very much applications, but their properties have not well-known for plasma diagnostics. In this study, mixture discharges are obtained at the quartz glass reactor for different powers and flow rates under the laboratory conditions, and then the optical properties of gas discharges are examined by means of Langmuir probe. When the flow rates of gases and power values are changed, it can be investigated that how the plasma parameters change. Debye length is one of the important plasma parameters. Thus, the relationship between the mixture amount of two different gases and Debye length is determined from Langmuir probe data. The graphs obtained by using these data will give information about generating the discharge of mixture gases, in detail. Therefore, the results may be the useful reference for future works of industrial applications.

  20. Experimental Studies of Low-Pressure Plasma Jet by Means of Langmuir Probes and Emission Spectra

    Institute of Scientific and Technical Information of China (English)

    LIU Lei; CAO Jinxiang; NIU Tianye; WANG Liang; MENG Gang; LIU Xin; YUAN Lei; WU Runhui; ZHANG Shengjun; REN Aimin

    2009-01-01

    An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.

  1. Interfacial Water Structure in Langmuir Monolayer and Gibbs Layer Probed by Sum Frequency Generation Vibrational Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    张贞; 郭源

    2012-01-01

    Langmuir monolayer and Gibbs layer exhibit surface-active properties and it can be used as simple model systems to investigate the physicochemical properties of biological membranes. In this report, we presented the OH stretching vibration of H2O in the 4"-n-pentyl-4-cyano-p-terphenyl (5CT), nonadecanenitrile (C18CN) Langmuir monolayer and compared them with CH3CN Gibbs layer at the air/water interface with polarization SFG-VS. This study demonstrated that the hydrogen bond network is different in the Langmuir monolayer of 5CT, C18CN from CH3CN Gibbs layer at the air/water interface which showed two different water structures on the different surface layer. The results provided a deeper insight into understanding the hydrogen bond on the interfaces.

  2. High heat flux Langmuir probe array for the DIII-D divertor platesa)

    Science.gov (United States)

    Watkins, J. G.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.; Nygren, R. E.

    2008-10-01

    Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m2 for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5° surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of Jsat, Te, and Vf with 4 mm spatial resolution are shown.

  3. The Use of Langmuir Probes in Non-Maxwellian Space Plasmas

    Science.gov (United States)

    Hoegy, Walter R.; Brace, Larry H.

    1998-01-01

    Disturbance of the Maxwellian plasma may occur in the vicinity of a spacecraft due to photoemission, interactions between the spacecraft and thermospheric gases, or electron emissions from other devices on the spacecraft. Significant non-maxwellian plasma distributions may also occur in nature as a mixture of ionospheric and magnetospheric plasmas or secondaries produced by photoionization in the thermosphere or auroral precipitation. The general formulas for current collection (volt-ampere curves) by planar, cylindrical, and spherical Langmuir probes in isotropic and anisotropic non-maxwellian plasmas are examined. Examples are given of how one may identify and remove the non-maxwellian components in the Langmuir probe current to permit the ionospheric parameters to be determined. Theoretical volt-ampere curves presented for typical examples of non-maxwellian distributions include: two-temperature plasmas and a thermal plasma with an energetic electron beam. If the non-ionospheric electrons are Maxwellian at a temperature distinct from that of the ionosphere electrons, the volt-ampere curves can be fitted directly to obtain the temperatures and densities of both electron components without resorting to differenting the current. For an arbitrary isotropic distribution, the current for retarded particles is shown to be identical for the three geometries. For anisotropic distributions, the three probe geometries are not equally suited for measuring the ionospheric electron temperature and density or for determining the distribution function in the presence of non-maxwellian back-round electrons.

  4. Thermal ion imagers and Langmuir probes in the Swarm electric field instruments

    Science.gov (United States)

    Knudsen, D. J.; Burchill, J. K.; Buchert, S. C.; Eriksson, A. I.; Gill, R.; Wahlund, J.-E.; Åhlen, L.; Smith, M.; Moffat, B.

    2017-02-01

    The European Space Agency's three Swarm satellites were launched on 22 November 2013 into nearly polar, circular orbits, eventually reaching altitudes of 460 km (Swarm A and C) and 510 km (Swarm B). Swarm's multiyear mission is to make precision, multipoint measurements of low-frequency magnetic and electric fields in Earth's ionosphere for the purpose of characterizing magnetic fields generated both inside and external to the Earth, along with the electric fields and other plasma parameters associated with electric current systems in the ionosphere and magnetosphere. Electric fields perpendicular to the magnetic field B→ are determined through ion drift velocity v→i and magnetic field measurements via the relation E→⊥=-v→i×B→. Ion drift is derived from two-dimensional images of low-energy ion distribution functions provided by two Thermal Ion Imager (TII) sensors viewing in the horizontal and vertical planes; v→i is corrected for spacecraft potential as determined by two Langmuir probes (LPs) which also measure plasma density ne and electron temperature Te. The TII sensors use a microchannel-plate-intensified phosphor screen imaged by a charge-coupled device to generate high-resolution distribution images (66 × 40 pixels) at a rate of 16 s-1. Images are partially processed on board and further on the ground to generate calibrated data products at a rate of 2 s-1; these include v→i, E→⊥, and ion temperature Ti in addition to electron temperature Te and plasma density ne from the LPs.

  5. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak

    Science.gov (United States)

    Xu, J. C.; Wang, L.; Xu, G. S.; Luo, G. N.; Yao, D. M.; Li, Q.; Cao, L.; Chen, L.; Zhang, W.; Liu, S. C.; Wang, H. Q.; Jia, M. N.; Feng, W.; Deng, G. Z.; Hu, L. Q.; Wan, B. N.; Li, J.; Sun, Y. W.; Guo, H. Y.

    2016-08-01

    In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.

  6. Influence of temperature fluctuations on plasma turbulence investigations with Langmuir probes

    CERN Document Server

    Nold, B; Ramisch, M; Huang, Z; Müller, H W; Scott, B D; Stroth, U

    2011-01-01

    The reliability of Langmuir probe measurements for plasma-turbulence investigations is studied on GEMR gyro-fluid simulations and compared with results from conditionally sampled I-V characteristics as well as self-emitting probe measurements in the near scrape-off layer of the tokamak ASDEX Upgrade. In this region, simulation and experiment consistently show coherent in-phase fluctuations in density, plasma potential and also in electron temperature. Ion-saturation current measurements turn out to reproduce density fluctuations quite well. Fluctuations in the floating potential, however, are strongly influenced by temperature fluctuations and, hence, are strongly distorted compared to the actual plasma potential. These results suggest that interpreting floating as plasma-potential fluctuations while disregarding temperature effects is not justified near the separatrix of hot fusion plasmas. Here, floating potential measurements lead to corrupted results on the ExB dynamics of turbulent structures in the cont...

  7. Dual Langmuir-probe array for 3D plasma studies in TORPEX

    Science.gov (United States)

    Baquero-Ruiz, M.; Avino, F.; Chellai, O.; Fasoli, A.; Furno, I.; Jacquier, R.; Manke, F.; Patrick, S.

    2016-11-01

    We have designed and installed a new Langmuir-probe (LP) array diagnostic to determine basic three-dimensional (3D) features of plasmas in TORPEX. The diagnostic consists of two identical LP arrays, placed on opposite sides of the apparatus, which provide comprehensive coverage of the poloidal cross section at the two different toroidal locations. Cross correlation studies of signals from the arrays provide a basic way to extract 3D information from the plasmas, as experiments show. Moreover, the remarkable signal-to-noise performance of the front-end electronics allows us to follow a different approach in which we combine information from all probes in both arrays to reconstruct elementary 3D plasma structures at each acquisition time step. Then, through data analysis, we track the structures as they evolve in time. The LP arrays include a linear-motion mechanism that can displace radially the probes located on the low field side for experiments that require fine-tuning of the probe locations, and for operational compatibility with the recently installed in-vessel toroidal conductor.

  8. Ion temperature measurements by means of a combined force - Mach - Langmuir probe

    Energy Technology Data Exchange (ETDEWEB)

    Lunt, T.; Hidalgo, C.; Calderon, E.

    2005-07-01

    With respect to plasma-wall interactions, particle and energy fluxes are commonly of particular interest. Although typical pressures in plasma experiments are four (edge layer of fusion devices) to six (cold discharges) orders of magnitude smaller than atmospheric pressure, a force sensor such as that developed by Chavers [1] shown in Fig.1, immersed in a streaming plasma is sensitive enough to measure momentum fluxes on its target surface. In the edge layer of fusion plasmas, the measurement of ion temperature constitutes a particular problem. Although ion sensitive electrical probes, developed by Katsumata [2] and Ratynskaia et al.[3] and tested by Ezumi [4] offer advantages like a high spatial and temporal resolution, considerable theoretical efforts [5] have to be made to interpret the measured data. The probes, due to their working principle based on the difference in Lamor radii, are sensitive to strength and orientation of the magnetic field. Charge exchange measurements, on the other hand, become ineffective for ion temperatures lower than ?100 eV and are thus unsuitable for the edge layer. As electron temperature and density can be determined by Langmuir probes, the missing parameter can also be obtained from the force sensor, which is sensitive to the total pressure p = n(Ti+Te). Although this type of diagnostic will have a limited time resolution due to mechanical inertia as compared to electrical probes, the interpretation of data will be less questionable. Furthermore the sensor will also be applicable to fully ionized plasmas, where optical methods fail. (Author)

  9. Plasma gas identification using the single Langmuir probe at the PUPR mirror-cusp

    Energy Technology Data Exchange (ETDEWEB)

    Gaudier, Jorge R; Rivera, Ramon; Colmenares, Franklin; Lleonart, Giovanni; Carrera, Miguel A; Mollina, Omar; Gonzalez, Angel; Leal-Quiros, Edbertho; Prelas, Mark A [University of Missouri-Columbia, Columbia, MO (United States); Plasma Physics Laboratory, Polytechnic University of Puerto Rico, San Juan (Puerto Rico)

    2008-10-15

    Plasma can be produced by ionizing gas particles. Different gases will produce different plasma parameters. Using the single Langmuir probe, the characteristics of argon, nitrogen, hydrogen and residual gas (no gas injected) can be compared. Using a mass spectrometer, we can identify the elements present in the chamber and relate the probe characteristic curve with its respective elements. Each gas has its own characteristic appearance; by looking at the form of the curve it is possible to identify the gas producing the plasma. Plasma parameters may vary due to a number of factors; probe position, microwave power, magnetic confinement, gas and pressure are the factors that we can control. In order to compare gases, operation parameters must remain the same for all tests. Plasma tests were administered on different gases using a microwave power of 198 W to heat the gas and initiate ionization and a coil current of 390 A, while running in mirror mode; that is, the current flowing through two parallel solenoid magnets (coils) used to confine plasma runs in the same direction, making the magnetic field complementary in the direction of the probe. The coils, distance from center to center was fixed at 60 cm. In mirror mode, plasma is confined in a hot electron ring produced between the coils. The ring contains the highest plasma density in the chamber, but the center remains at lower density. The probe was submerged into the plasma 110 cm from the flange, the collector (disc) was 14 cm from the center of the chamber and 18.12 cm from the electron ring. Low power (4% of a 5 kW microwave generator) was used to protect the probes from burning at that close range. The pressure at the chamber was 2.9E-4 Torr. Good readings were taken and analyzed. Measurements with variable microwave power and variable magnetic field strength were also studied to determine whether there is a linear relationship between the machine setup and plasma conditions.

  10. Langmuir probe study of an inductively coupled magnetic-pole-enhanced helium plasma

    Science.gov (United States)

    Younus, Maria; Rehman, N. U.; Shafiq, M.; Naeem, M.; Zaka-ul-Islam, M.; Zakaullah, M.

    2017-03-01

    This study reports the effects of RF power and filling gas pressure variation on the plasma parameters, including the electron number density n e , electron temperature T e , plasma potential V p , skin depth δ, and electron energy probability functions (EEPFs) in a low-pressure inductively coupled helium plasma source with magnetic pole enhancement. An RF compensated Langmuir probe is used to measure these plasma parameters. It is observed that the electron number density increases with both the RF power and the filling gas pressure. Conversely, the electron temperature decreases with increasing RF power and gas pressure. It is also noted that, at low RF powers and gas pressures, the EEPFs are non-Maxwellian, while at RF powers of ≥50 W, they evolve into a Maxwellian distribution. The dependences of the skin depth and plasma potential on the RF power are also studied and show a decreasing trend.

  11. Understanding narrow SOL power flux component in COMPASS limiter plasmas by use of Langmuir probes

    Energy Technology Data Exchange (ETDEWEB)

    Dejarnac, R., E-mail: dejarnac@ipp.cas.cz [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic); Stangeby, P.C. [University of Toronto, Institute for Aerospace Studies, 4925 Dufferin St., Toronto M3H 5T6 (Canada); Goldston, R.J. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States); Gauthier, E. [CEA, IRFM, F-13108 St Paul-lez-Durance (France); Horacek, J.; Hron, M. [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic); Kocan, M. [ITER Organisation, Route de Vinon-sur-Verdon, CS 90 046, F-13067 St Paul-lez-Durance cedex (France); Komm, M.; Panek, R. [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic); Pitts, R.A. [ITER Organisation, Route de Vinon-sur-Verdon, CS 90 046, F-13067 St Paul-lez-Durance cedex (France); Vondracek, P. [Institute of Plasma Physics, ASCR, Za Slovankou 3, 182 00 Prague (Czech Republic)

    2015-08-15

    The narrow scrape-off layer power component observed in COMPASS inner wall limiter circular discharges by means of IR thermography is investigated by Langmuir probes embedded in the limiter. The power flux profiles are in good agreement with IR observations and can be described by a double-exponential decay with a short decay length (<5 mm) just outside the separatrix and a longer one (∼50 mm) for the rest of the profile in the main scrape-off layer. Non-ambipolar currents measured at the limiter apex play a relatively modest role in the formation of the narrow component. The fraction of the deposited power due to non-ambipolarity varies between 2% and 45%. On the other hand, the measured power widths are roughly consistent in magnitude with a model that takes into account drift effects, suggesting these effects may be dominant.

  12. Microwave power coupling with electron cyclotron resonance plasma using Langmuir probe

    Indian Academy of Sciences (India)

    S K Jain; V K Senecha; P A Naik; P R Hannurkar; S C Joshi

    2013-07-01

    Electron cyclotron resonance (ECR) plasma was produced at 2.45 GHz using 200 – 750 W microwave power. The plasma was produced from argon gas at a pressure of 2 × 10−4 mbar. Three water-cooled solenoid coils were used to satisfy the ECR resonant conditions inside the plasma chamber. The basic parameters of plasma, such as electron density, electron temperature, floating potential, and plasma potential, were evaluated using the current–voltage curve using a Langmuir probe. The effect of microwave power coupling to the plasma was studied by varying the microwave power. It was observed that the optimum coupling to the plasma was obtained for ∼ 600 W microwave power with an average electron density of ∼ 6 × 1011 cm−3 and average electron temperature of ∼ 9 eV.

  13. Soft Particle Spectrometer, Langmuir Probe, and Data Analysis for Aerospace Magnetospheric/Thermospheric Coupling Rocket Program

    Science.gov (United States)

    Sharber, J. R.; Frahm, R. A.; Scherrer, J. R.

    1997-01-01

    Under this grant two instruments, a soft particle spectrometer and a Langmuir probe, were refurbished and calibrated, and flown on three instrumented rocket payloads as part of the Magnetosphere/Thermosphere Coupling program. The flights took place at the Poker Flat Research Range on February 12, 1994 (T(sub o) = 1316:00 UT), February 2, 1995 (T(sub o) = 1527:20 UT), and November 27, 1995 (T(sub o) = 0807:24 UT). In this report the observations of the particle instrumentation flown on all three of the flights are described, and brief descriptions of relevant geophysical activity for each flight are provided. Calibrations of the particle instrumentation for all ARIA flights are also provided.

  14. Langmuir probe study in the nonresonant current drive regime of helicon discharge

    Indian Academy of Sciences (India)

    Manash Kumar Paul; Dhiraj Bora

    2008-07-01

    Characterization of the current drive regime is done for helicon wave-generated plasma in a torus, at a very high operating frequency. A radiofrequency-compensated Langmuir probe is designed and used for the measurement of plasma parameters along with the electron energy distributions in radial scans of the plasma. The electron energy distribution patterns obtained in the operational regime suggest that Landau damping cannot be responsible for the efficient helicon discharge in the present study. A typical peaked radial density profile, high plasma temperature and absence of an appreciable amount of energetic electrons for resonant wave–particle interactions, suggest that the chosen operational regime is suitable for the study of nonresonant current drive by helicon wave. Successful and significant current drive achieved in our device clearly demonstrates the capability of nonresonant current drive by helicon waves in the present operational regime.

  15. Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from Radio Frequency plasma) experiment: tests in BATMAN (BAvarian Test Machine for Negative ions).

    Science.gov (United States)

    Brombin, M; Spolaore, M; Serianni, G; Pomaro, N; Taliercio, C; Dalla Palma, M; Pasqualotto, R; Schiesko, L

    2014-11-01

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  16. Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

    Energy Technology Data Exchange (ETDEWEB)

    Brombin, M., E-mail: matteo.brombin@igi.cnr.it; Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R. [Consorzio RFX, Corso Stati Uniti 4, I-35127 Padova (Italy); Schiesko, L. [Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching (Germany)

    2014-11-15

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors’ holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  17. Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

    Science.gov (United States)

    Brombin, M.; Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R.; Schiesko, L.

    2014-11-01

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  18. Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

    Energy Technology Data Exchange (ETDEWEB)

    Prevosto, L.; Mancinelli, B. R. [Grupo de Descargas Electricas, Departamento Ingenieria Electromecanica, Facultad Regional Venado Tuerto (UTN), Laprida 651, (2600) Venado Tuerto, Santa Fe (Argentina); Kelly, H. [Grupo de Descargas Electricas, Departamento Ingenieria Electromecanica, Facultad Regional Venado Tuerto (UTN), Laprida 651, (2600) Venado Tuerto, Santa Fe (Argentina) and Instituto de Fisica del Plasma (CONICET), Departamento de Fisica, Facultad de Ciencias Exactas y Naturales UBA Ciudad Universitaria Pab. I, (1428) Buenos Aires (Argentina)

    2012-09-15

    Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processes inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.

  19. Magnetic field and quadruple Langmuir probe measurements in the plume of the plasmoid thruster experiment

    Science.gov (United States)

    Koelfgen, Syri Jo

    The development of high specific impulse rocket engines is essential for fast and efficient space travel. The plasmoid thruster, a novel propulsion concept with the potential for producing a high specific impulse, was investigated in light of this need. This pulsed inductive rocket utilizes the Lorentz force to accelerate plasmoids and produce thrust. The Plasmoid Thruster Experiment (PTX) was designed to experimentally evaluate the thruster concept. PTX operates by producing plasmoids in a conical theta-pinch coil and ejecting them at high velocity. Measurements of the plasmoid magnetic fields, electron temperature (Te), electron number density (n e) and Mach number (M) were taken in the PTX plume with a B˙ probe array and a quadruple Langmuir probe. The measurements were used for calculating exit velocity and Isp. High-speed photographs were also obtained for capturing images of the plasmoids and estimating their velocity. The magnetic field data showed behavior characteristic of plasmoids, such as the occurrence of the maximum axial magnetic field on axis and magnetic field reversal. The quadruple Langmuir probe data revealed several factors that influence thruster operation, including propellant choice, supply pressure and propellant injection timing (tpuff). For Ar propellant at supply pressures of 14--34 psig and tpuff = 2200 mus, Te ranged from 2--7 eV, ne ranged from 1.5 x 1020 m-3 to 3.5 x 1020 m-3, and M ranged from 3.3--3.8 in PTX. For H2 propellant, T e ranged from 15--27 eV, ne ranged from 0.8 x 1020 m-3 to 1.5 x 1020 m-3, and M ranged from 1.4--2.6, for supply pressures of 9--38 psig and tpuff = 1200--2400 mus. Analysis of the plume measurements yielded high thruster exit velocities, indicating that the plasmoid thruster can produce a high Isp. Velocities of 24 km/s, 35 km/s and 46 km/s were calculated for supply pressures of 38 psig, 24 psig and 9 psig of H2 propellant, respectively. These exit velocities deliver Isp values of 2,400 s, 3,500 s and 4

  20. Langmuir Probe Measurements in an Inductively Coupled Ar/CF4 Plasmas

    Science.gov (United States)

    Rao, M. V. V. S.; Meyyappan, M.; Sharma, S. P.; Arnold, James O. (Technical Monitor)

    2000-01-01

    Technological advancement in the microelectronics industry requires an understanding of the physical and chemical processes occurring in plasmas of fluorocarbon gases, such as carbon tetrafluoride (CF4) which is commonly used as an etchant, and their mixtures to optimize various operating parameters. In this paper we report data on electron number density (ne), electron temperature'(Te), electron energy distribution function (EEDF), mean electron energy, ion number density (ni), and plasma potential (Vp) measured by using Langmuir probe in an inductively coupled 13.56 MHz radio frequency plasmas generated in 50%Ar:50%CF4 mixture in the GEC cell. The probe data were recorded at various radial positions providing radial profiles of these plasma parameters at 10-50 mTorr pressures and 200 W and 300 W of RF power. Present measurements indicate that the electron and ion number densities increase with increase in pressure and power. Whereas the plasma potential and electron temperature decrease with increase in pressure, and they weakly depend on RF power. The radial profiles exhibit that the electron and ion number densities and the plasma potential peak at the center of the plasma with an exponential fall away from it, while the electron temperature has a minimum at the center and it increases steadily towards the electrode edge. The EEDFs have a characteristic drop near the low energy end at all pressures and pressures and their shapes represent non-Maxwellian plasma and exhibit more like Druyvesteyn energy distribution.v

  1. Langmuir probe study of a titanium pulsed filtered cathodic arc discharge

    Energy Technology Data Exchange (ETDEWEB)

    Andruczyk, D [School of Physics, University of Sydney, NSW 2006 (Australia); Tarrant, R N [School of Physics, University of Sydney, NSW 2006 (Australia); James, B W [School of Physics, University of Sydney, NSW 2006 (Australia); Bilek, M M M [School of Physics, University of Sydney, NSW 2006 (Australia); Warr, G B [School of Physics, University of Sydney, NSW 2006 (Australia)

    2006-08-01

    A Langmuir probe has been used to make measurements of plasma parameters as a function of time at the substrate position in a magnetically-filtered pulsed cathodic arc discharge. Electron density, n{sub e}, and effective electron temperature, T{sub eff}, were calculated as a function of time from the I-V curves. The Druyvesteyn method was used to determine the electron energy distribution. Ion density was calculated using the assumption of plasma quasi-neutrality and an average ion charge state. Results show that over the plateau region (350-600 {mu}s) of the pulse, the electron energy distribution is Maxwellian with T{sub eff} = T{sub e} = (10 {+-} 1) eV. During the rise and fall times of the pulse, the electron energy distribution is non-Maxwellian with an effective temperature of up to 15 to 20 eV during the rise time and {approx}7 eV during the fall time. The electron density during the plateau is n{sub e} = (3.0-6.0 {+-} 0.5) x 10{sup 17} m{sup -3}.

  2. Characterization of RF He-N2/Ar mixture plasma via Langmuir probe and optical emission spectroscopy techniques

    Science.gov (United States)

    Younus, Maria; Rehman, N. U.; Shafiq, M.; Hussain, S. S.; Zakaullah, M.; Zaka-ul-Islam, M.

    2016-08-01

    A Magnetic Pole Enhanced inductively coupled RF H e - N 2 / A r plasma is characterized using a Langmuir probe and optical emission spectroscopy (OES) techniques. The effect of helium mixing on electron density ( n e ) and temperature ( T e ) , electron energy probability functions (EEPFs), [ N ] atomic density, and N 2 dissociation is investigated. A Langmuir probe and a zero slope method based on trace rare gas-optical emission spectroscopy (TRG-OES) are employed to measure the electron temperature. It is noted that the electron temperature shows an increasing trend for both methods. However, the temperature measured by a zero slope method T e ( Z . S ) approaches the temperature measured by a Langmuir probe; T e ( L . P ) at 56% and above helium concentration in the discharge. "Advance actinometry" is employed to monitor the variation in [ N ] atomic density with helium concentration and gas pressure. It is noted that [ N ] atomic density increases at 56% and above helium in the discharge, which is consistent with the trend of electron temperature and EEPFs. A drastic enhancement in N 2 dissociation fraction D 1 determined by "advance actinometry" is noted at 56% and above helium concentration in the mixture due to modifications in different population and depopulation mechanisms. However, it is also noted that the dissociation fraction D 2 determined by intensity ratio method increases linearly with helium addition.

  3. Langmuir Probe and Mass Spectroscopic Measurements in Inductively Coupled CF4 Plasmas

    Science.gov (United States)

    Rao, M. V. V. S.; Sharma, Surendra; Cruden, B. A.; Meyyappan, M.

    2001-01-01

    Abstract Electron and ion energy distribution functions and other plasma parameters such as plasma potential (V(sub p)) , electron temperature (T(sub e)), and electron and ion number densities (n (sub e) and n(sub i)) in low pressure CF4 plasmas have been measured. The experiments were conducted in a GEC cell using an inductively coupled plasma (ICP) device powered by a 13.56 MHz radio-frequency (rf) power source. The measurements were made at 300 W of input rf power at 10, 30 and 50 mTorr gas pressures. Langmuir probe measurements suggest that n(sub e), n(sub i) and V(sub p) remain constant over 60% of the central electrode area, beyond which they decrease. Within the limits of experimental error (+/- 0.25 eV), T(sub e) remains nearly constant over the electrode area. T(sub e) and V(sub p) increase with a decrease in pressure. n(sub e) and n(sub i) are not affected as significantly as T(sub e) or V(sub p) by variation in the gas pressure. The electron energy distribution function (EEDF) measurements indicate a highly non-Maxwellian plasma. CF3+ is the most dominant ion product of the plasma, followed by CF2+ and CF+. The concentrations of CF2+ and CF+ are much larger than that is possible from direct electron impact ionization of the parent gas. The cross-section data suggest that the direct electron impact ionization of fragment neutrals and negative ion production by electron attachment may be responsible for increase of the minor ions.

  4. Progress on Langmuir Probe, Data Analysis, Acquisition and Optimization Innovations at the Coast Guard Academy Plasma Lab (CGAPL)

    Science.gov (United States)

    Wright, Erin; Frank, John; Azzari, Phil; James, Royce; Hopson, Jordan; Duke-Tinson, Omar; Paolino, Richard; Sandi, Eva; Sherman, Justin; Turk, Jeremy

    2016-10-01

    CGAPL houses four major plasma experiments that span large temperature, density, energy and functionality regimes. Often automation and remote operation of intelligent devices are required in adverse operating environments for digital and analogue systems. Plasma data collected by a multitude of diagnostics and sensors (to include Langmuir probes) over long timescales mandates CGAPL's 40-channel Data Acquisition (DAQ) system that collects and stores data plus controls CGAPL. The ability to remotely control and operate lab diagnostics then collect and store data through a LabView collective Graphic User Interface (GUI) currently under construction, enable users to remotely control, collect, and store CGAPL experimental data. Innovative solutions to optimize data collection and apparatus command and control, will enhance the ability to run experiments remotely, improve the validity of results, and advance participation in fusion grade diagnostic development. Instrument automation, optimization, and data collection obstacles, solutions, and procedures will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15-16.

  5. Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-457Mv2 Hall Thruster

    Science.gov (United States)

    Shastry, Rohit; Huang, Wensheng; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

    2012-01-01

    In order to further the design of future high-power Hall thrusters and provide experimental validation for ongoing modeling efforts, plasma potential and Langmuir probe measurements were performed on the 50-kW NASA-457Mv2. An electrostatic probe array comprised of a near-field Faraday probe, single Langmuir probe, and emissive probe was used to interrogate the near-field plume from approximately 0.1 - 2.0 mean thruster diameters downstream of the thruster exit plane at the following operating conditions: 300 V, 400 V and 500 V at 30 kW and 500 V at 50 kW. Results have shown that the acceleration zone is limited to within 0.4 mean thruster diameters of the exit plane while the high-temperature region is limited to 0.25 mean thruster diameters from the exit plane at all four operating conditions. Maximum plasma potentials in the near-field at 300 and 400 V were approximately 50 V with respect to cathode potential, while maximum electron temperatures varied from 24 - 32 eV, depending on operating condition. Isothermal lines at all operating conditions were found to strongly resemble the magnetic field topology in the high-temperature regions. This distribution was found to create regions of high temperature and low density near the magnetic poles, indicating strong, thick sheath formation along these surfaces. The data taken from this study are considered valuable for future design as well as modeling validation.

  6. Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA 300M Hall Thruster

    Science.gov (United States)

    Herman, Daniel A; Shastry, Rohit; Huang, Wensheng; Soulas, George C.; KamHawi, Hani

    2012-01-01

    In order to aid in the design of high-power Hall thrusters and provide experimental validation for existing modeling efforts, plasma potential and Langmuir probe measurements were performed in the near-field plume of the NASA 300M Hall thruster. A probe array consisting of a Faraday probe, Langmuir probe, and emissive probe was used to interrogate the plume from approximately 0.1 - 2.0 DT,m downstream of the thruster exit plane at four operating conditions: 300 V, 400 V, and 500 V at 20 kW as well as 300 V at 10 kW. Results show that the acceleration zone and high-temperature region were contained within 0.3 DT,m from the exit plane at all operating conditions. Isothermal lines were shown to strongly follow magnetic field lines in the nearfield, with maximum temperatures ranging from 19 - 27 eV. The electron temperature spatial distribution created large drops in measured floating potentials in front of the magnetic pole surfaces where the plasma density was small, which suggests strong sheaths at these surfaces. The data taken have provided valuable information for future design and modeling validation, and complements ongoing internal measurement efforts on the NASA 300 M.

  7. Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-300M Hall Thruster

    Science.gov (United States)

    Herman, Daniel A.; Shastry, Rohit; Huang, Wensheng; Soulas, George C.; Kamhawi, Hani

    2012-01-01

    In order to aid in the design of high-power Hall thrusters and provide experimental validation for existing modeling efforts, plasma potential and Langmuir probe measurements were performed in the near-field plume of the NASA-300M Hall thruster. A probe array consisting of a Faraday probe, Langmuir probe, and emissive probe was used to interrogate the plume from approximately 0.1 - 2.0 mean thruster diameters downstream of the thruster exit plane at four operating conditions: 300 V, 400 V, and 500 V at 20 kW as well as 300 V at 10 kW. Results show that the acceleration zone and high-temperature region were contained within 0.3 mean thruster diameters from the exit plane at all operating conditions. Isothermal lines were shown to strongly follow magnetic field lines in the near-field, with maximum temperatures ranging from 19 - 27 eV. The electron temperature spatial distribution created large drops in measured floating potentials in front of the magnetic pole surfaces where the plasma density was low, which suggests strong sheaths at these surfaces. The data taken have provided valuable information for future design and modeling validation, and complements ongoing internal measurement efforts on the NASA-300M.

  8. Development of a novel sweeping Langmuir probe instrument for monitoring the upper ionosphere on board a pico-satellite

    Science.gov (United States)

    Ranvier, Sylvain; De Keyser, Johan; Cardoen, Pepijn; Pieroux, Didier

    2014-05-01

    A novel Langmuir probe instrument, which will fly on board the Pico-Satellite for Atmospheric and Space Science Observations (PICASSO), is under development at the Belgian Institute for Space Aeronomy. PICASSO was initiated to join the QB50 project as scientific in-orbit demonstrator. The sweeping Langmuir probe (SLP) instrument is designed to measure both plasma density and electron temperature at an altitude varying from about 400 km up to 700 km from a high inclination orbit. Therefore, the plasma density is expected to fluctuate over a wide range, from about 1e6/m³ at high latitude and high altitude up to 1e12/m³ at low/mid latitude and low altitude. The electron temperature is expected to lie between approximately 1000 K and 3000 K. Given the high inclination of the orbit, the SLP instrument will allow a global monitoring of the ionosphere with a maximum spatial resolution of the order of 150 m. The main goals are to study 1) the ionosphere-plasmasphere coupling, 2) the subauroral ionosphere and corresponding magnetospheric features, 3) auroral structures, 4) polar caps, and 5) ionospheric dynamics via coordinated observations with EISCAT's heating radar. To achieve the scientific objectives described above, the instrument includes four thin cylindrical probes whose electrical potential is swept in such a way that both plasma density and electron temperature can be derived. In addition, since at least two probes will be out of the spacecraft's wake at any given time, differential measurements can be performed to increase the accuracy. Along the orbit, the Debye length is expected to vary from a few millimetres up to a few meters. Due to the tight constraints in terms of mass and volume inherent to pico-satellites, the use of long booms, which would guarantee that the probes are outside the sheath of the spacecraft (several Debye lengths away), is not possible. Consequently, the probes might be in the sheath of the spacecraft in polar regions. Extensive

  9. An improved model to analyze Langmuir probe assisted photo-detachment signal for measuring electronegative plasma parameters

    Science.gov (United States)

    Sirse, Nishant; Oudini, Noureddine; Bendib, Abderrezeg; Ellingboe, Albert R.

    2016-09-01

    A diagnostic technique for measuring negative ion parameters based on Langmuir probe assisted laser photo-detachment relies on a theoretical model which relates the rise in the electron saturation current to electronegativity in the plasma. The existing model depend on various assumptions and neglect electrostatic potential barrier formed between the laser column (electropositive column) and the surrounding electronegative plasma in order to prevent the outward flow of electrons from the electropositive plasma column. These assumptions leads to erroneous estimation of the plasma electronegativity. In the present work, we present an analytical model to analyze Langmuir probe assisted photo-detachment signal in order to improve the accuracy of measured electronegativity and extended this technique for measuring electron temperature and charged species density. The analytical model is validated using both experiments and particle-in-cell simulation. The results shows improved accuracy in the measured parameters when compared to existing model. This work was supported by the Korea Institute for the Advancement of Technology and Ministry of Knowledge Economy (L-2010-1438-000), Republic of Korea, Enterprise Ireland and the European Regional Development Fund (ERDF) under NSRF 2007-2013.

  10. Langmuir-magnetic probe measurements of ELMs and dithering cycles in the EAST tokamak

    DEFF Research Database (Denmark)

    Yan, Ning; Naulin, Volker; Xu, G. S.

    2014-01-01

    Measurements of the dynamical behavior associated with edge localized modes (ELMs) have been carried out in the Experimental Advanced Superconducting Tokamak (EAST) by direct probing near the separatrix and far scrape-off layer (SOL) using electrostatic as well as magnetic probes. Type-III ELMs...

  11. Indium-chlorine and gallium-chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir-Blodgett nanolayers--spectroscopic investigations.

    Science.gov (United States)

    Bursa, B; Wróbel, D; Biadasz, A; Kędzierski, K; Lewandowska, K; Graja, A; Szybowicz, M; Durmuş, M

    2014-07-15

    The paper deals with spectroscopic characterization of metallic phthalocyanines (Pc's) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate.

  12. PICASSO-SLP: a Langmuir probe instrument for monitoring the upper ionosphere on board a pico-satellite

    Science.gov (United States)

    Ranvier, Sylvain; Anciaux, Michel; Cardoen, Pepijn; Gamby, Emmanuel; Bonnewijn, Sabrina; De Keyser, Johan; Echim, Marius; Pieroux, Didier

    2016-04-01

    A novel Langmuir probe instrument, which will fly on board the Pico-Satellite for Atmospheric and Space Science Observations (PICASSO), is under development at the Royal Belgian Institute for Space Aeronomy. PICASSO, an ESA in-orbit demonstrator, is a triple unit CubeSat of dimensions 340.5x100x100 mm. The sweeping Langmuir probe (SLP) instrument, which includes four thin cylindrical probes whose electrical potential is swept, is designed to measure both plasma density and electron temperature at an altitude varying from about 400 km up to 700 km from a high inclination orbit. Therefore, the plasma density is expected to fluctuate over a wide range, from about 1e8/m³ at high latitude and high altitude up to several times 1e12/m³ at low/mid latitude and low altitude. The electron temperature is expected to lie between approximately 1.000 K and 10.000 K. Given the high inclination of the orbit, the SLP instrument will allow a global monitoring of the ionosphere with a maximum spatial resolution of the order of 150 m for the electron density and temperature, and up to a few meters for electron density only. The main goals are to study 1) the ionosphere-plasmasphere coupling, 2) the subauroral ionosphere and corresponding magnetospheric features, 3) auroral structures, 4) polar caps, 5) for the density, the multi-scale behaviour, spectral properties and turbulence of processes typical for the auroral regions, and 6) ionospheric dynamics via coordinated observations with EISCAT's heating radar. Along the orbit, the Debye length is expected to vary from a few millimetres up to a few meters. Due to the tight constraints in terms of mass and volume inherent to pico-satellites, the use of long booms, which would guarantee that the probes are outside the sheath of the spacecraft (several Debye lengths away), is not possible. Consequently, the probes might be in the sheath of the spacecraft in polar regions. Extensive modelling and simulations of the sheath effects on the

  13. Multi-pin Langmuir probe measurement for identification of blob propagation characteristics in the Large Helical Device

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, H., E-mail: tanaka.hirohiko@lhd.nifs.ac.jp [National Institute for Fusion Science, Toki 509-5292 (Japan); Masuzaki, S. [National Institute for Fusion Science, Toki 509-5292 (Japan); Ohno, N. [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan); Morisaki, T. [National Institute for Fusion Science, Toki 509-5292 (Japan); Tsuji, Y. [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan)

    2015-08-15

    In order to investigate the blobby plasma transport in the Large Helical Device, we have measured electrostatic fluctuations around the divertor leg by using a newly-designed multi-pin reciprocating Langmuir probe. Near the low-field side edge of the divertor leg, positive spikes of ion saturation current fluctuation were observed. In addition, the electric field which correlates with the ion saturation current fluctuation was firstly evaluated with the neighboring floating potential measurement. Considering the positional relationship with the magnetic geometry, the identified direction of the electric field inside the blobs is consistent with the theoretically predicted E × B motion. By applying the conditional averaging method, a quantitative speed of the blobs was preliminary estimated.

  14. Measurement of Electron Density Using the Multipole Resonance Probe, Langmuir Probe and Optical Emission Spectroscopy in Low Pressure Plasmas with Different Electron Energy Distribution Functions

    Science.gov (United States)

    Oberberg, Moritz; Bibinov, Nikita; Ries, Stefan; Awakowicz, Peter; Institute of Electrical Engineering; Plasma Technology Team

    2016-09-01

    In recently publication, the young diagnostic tool Multipole Resonance Probe (MRP) for electron density measurements was introduced. It is based on active plasma resonance spectroscopy (APRS). The probe was simulated und evaluated for different devices. The geometrical and electrical symmetry simplifies the APRS model, so that the electron density can be easily calculated from the measured resonance. In this work, low pressure nitrogen mixture plasmas with different electron energy distribution functions (EEDF) are investigated. The results of the MRP measurement are compared with measurements of a Langmuir Probe (LP) and Optical Emission Spectroscopy (OES). Probes and OES measure in different regimes of kinetic electron energy. Both probes measure electrons with low kinetic energy (<10 eV), whereas the OES is influenced by electrons with high kinetic energy which are needed for transitions of molecule bands. By the determination of the absolute intensity of N2(C-B) and N2+(B-X)electron temperature and density can be calculated. In a non-maxwellian plasma, all plasma diagnostics need to be combined.

  15. Predictions of VRF on a Langmuir Probe under the RF Heating Spiral on the Divertor Floor on NSTX-U

    Energy Technology Data Exchange (ETDEWEB)

    Hosea, J C [PPPL; Perkins, R J [PPPL; Jaworski, M A [PPPL; Kramer, G J [PPPL; Ahn, J-W [ORNL

    2014-07-01

    RF heating deposition spirals are observed on the divertor plates on NSTX as shown in for a NB plus RF heating case. It has been shown that the RF spiral is tracked quite well by the spiral mapping of the strike points on the divertor plate of magnetic field lines passing in front of the high harmonic fast wave (HHFW) antenna on NSTX. Indeed, both current instrumented tiles and Langmuir probes respond to the spiral when it is positioned over them. In particular, a positive increment in tile current (collection of electrons) is obtained when the spiral is over the tile. This current can be due to RF rectification and/or RF heating of the scrape off layer (SOL) plasma along the magnetic field lines passing in front of the the HHFW antenna. It is important to determine quantitatively the relative contributions of these processes. Here we explore the properties of the characteristics of probes on the lower divertor plate to determine the likelyhood that the primary cause of the RF heat deposition is RF rectification.

  16. Application of an RF Biased Langmuir Probe to Etch Reactor Chamber Matching, Fault Detection and Process Control

    Science.gov (United States)

    Keil, Douglas; Booth, Jean-Paul; Benjamin, Neil; Thorgrimsson, Chris; Brooks, Mitchell; Nagai, Mikio; Albarede, Luc; Kim, Jung

    2008-10-01

    Semiconductor device manufacturing typically occurs in an environment of both increasing equipment costs and per unit sale price shrinkage. Profitability in such a conflicted economic environment depends critically on yield, throughput and cost-of-ownership. This has resulted in increasing interest in improved fault detection, process diagnosis, and advanced process control. Achieving advances in these areas requires an integrated understanding of the basic physical principles driving the processes of interest and the realities of commercial manufacturing. Following this trend, this work examines the usefulness of an RF-biased planar Langmuir probe^1. This method delivers precise real-time (10 Hz) measurements of ion flux and tail weighted electron temperature. However, it is also mechanically non-intrusive, reliable and insensitive to contamination and deposition on the probe. Since the measured parameters are closely related to physical processes occurring at the wafer-plasma interface, significant improvements in process control, chamber matching and fault detection are achieved. Examples illustrating the improvements possible will be given. ^1J.P. Booth, N. St. J. Braithwaite, A. Goodyear and P. Barroy, Rev.Sci.Inst., Vol.71, No.7, July 2000, pgs. 2722-2727.

  17. Real-time control of divertor detachment in H-mode with impurity seeding using Langmuir probe feedback in JET-ITER-like wall

    Science.gov (United States)

    Guillemaut, C.; Lennholm, M.; Harrison, J.; Carvalho, I.; Valcarcel, D.; Felton, R.; Griph, S.; Hogben, C.; Lucock, R.; Matthews, G. F.; Perez Von Thun, C.; Pitts, R. A.; Wiesen, S.; contributors, JET

    2017-04-01

    Burning plasmas with 500 MW of fusion power on ITER will rely on partially detached divertor operation to keep target heat loads at manageable levels. Such divertor regimes will be maintained by a real-time control system using the seeding of radiative impurities like nitrogen (N), neon or argon as actuator and one or more diagnostic signals as sensors. Recently, real-time control of divertor detachment has been successfully achieved in Type I ELMy H-mode JET-ITER-like wall discharges by using saturation current (I sat) measurements from divertor Langmuir probes as feedback signals to control the level of N seeding. The degree of divertor detachment is calculated in real-time by comparing the outer target peak I sat measurements to the peak I sat value at the roll-over in order to control the opening of the N injection valve. Real-time control of detachment has been achieved in both fixed and swept strike point experiments. The system has been progressively improved and can now automatically drive the divertor conditions from attached through high recycling and roll-over down to a user-defined level of detachment. Such a demonstration is a successful proof of principle in the context of future operation on ITER which will be extensively equipped with divertor target probes.

  18. Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probe.

    Science.gov (United States)

    Schmitzer, C; Kronberger, M; Lettry, J; Sanchez-Arias, J; Störi, H

    2012-02-01

    The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H(-) volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e(-) and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H(-) ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H(-) ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

  19. A measurement of the TPMU - PROBA II Microsatellite Instrument and its comparison with the SWARM Langmuir Probes results

    Science.gov (United States)

    Podolska, Katerina; Hruska, Frantisek; Truhlik, Vladimir

    2016-04-01

    This contribution deals with the long-term measurement of the floating potential (FP) and the electron temperature (Te) provided by the Thermal Plasma Measurement Unit (TPMU) scientific instrument on-board the PROBA II microsatellite. The device is working with limitations of scientific measurements caused very probably by installed on-board software. This brings lower data volume as it was planned. Affected are the ion measurement and partially the electron temperature measurement. We present comparisons of the TPMU long-term measurement of the FP and the Te with the Te and the FP SWARM Langmuir Probes measured data. We implement the method of stochastic comparison of the probability distribution between measurements of FP and Te of both instruments to recognize seasonal and solar activity similarities. The analysis is performed for all seasons of the period from the years 2013 - 2015 for the Equatorial region, North and South hemisphere. The data are divided into the three groups by the geographical latitude to the Nothern hemisphere (lat>15'), the Southern hemisphere (latreflect also changes of the Kp index. Changes over the solar cycle are also visible. The main TPMU goal is the validation and testing of new design of the instrument which is necessary for possible applications of TPMU design for future scientific missions.

  20. Langmuir Probe Measurements of Inductively Coupled CHF3/Ar and Ar/CHF3/O2 Plasmas

    Science.gov (United States)

    Sharma, S. P.; Rao, M. V. V. S.; Meyyappan, M.

    2000-01-01

    Plasma parameters, such as, electron number density (ne), electron temperature (Te), y electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp), have been measured by using Langmuir probe in low-pressure (10-50 mTorr) inductively coupled CHF3/Ar and CHF3/Ar/O2 plasmas generated in the GEC cell. The measurements were made at the center of the plasma, keeping the lower electrode grounded, for various CHF3/Ar and Ar/CHF3/O2 mixtures operating at 10-50 mTorr pressures and two input RF power levels, 200 and 300 W. EEDF data show a strong Druyvesteyn distribution with relatively lower number of low energy electrons as compared to a Maxwell distribution and a large electron population with energies higher than the plasma potential. The results further show that at low CHF3 concentrations (less than 50%) the electron number density remains nearly constant with increase in pressure. At higher CHF3 concentrations, however, it decreases with increase in pressure. Plasma potential and electron temperature increase with decrease in pressure and with increase in CHF3 concentration. An analysis of the above observations and mechanisms will be presented.

  1. Estimation of Al2O3 critical temperature using a Langmuir probe in laser ablation

    Science.gov (United States)

    Yahiaoui, K.; Abdelli-Messaci, S.; Messaoud Aberkane, S.; Kellou, A.

    2016-11-01

    Pulsed laser deposition (PLD) has demonstrated its capacity in thin films growing under the moderate laser intensity. But when the laser intensity increases, the presence of droplets on the thin film limits the PLD efficiency such that the process needs an optimization study. In this way, an experimental study has been conducted in order to correlate between the appearance of those droplets and the laser fluence. The comprehension of the physical mechanism during ablation and the control of the deposition parameters allowed to get a safe process. Our experiment consists in measuring the amount of ejected matter from polycrystalline alumina target as a function of the laser fluence when irradiated by a KrF laser. According to laser fluence, several kinds of ablation regimes have been identified. Below a threshold value found as 12 J/cm2, the mechanism of ablation was assigned to normal evaporation, desorption and nonthermal processes. While above this threshold value, the mechanism of ablation was assigned to phase explosion phenomenon which is responsible of droplets formation when the surface temperature approaches the critical temperature T tc. A negative charge collector was used to collect the positive ions in the plume. Their times of flight (TOF) signal were used to estimate the appropriate T tc for alumina target. Ions yield, current as well as kinetic energy were deduced from the TOF signal. Their evolutions show the occurrence of an optical breakdown in the vapor plume which is well correlated with the onset of the phase explosion phenomenon. At 10 J/cm2, the ions velocities collected by the probe have been compared to those obtained from optical emission spectroscopy diagnostic and were discussed. To prove the occurrence of phase explosion by the appearance of droplets, several thin films were elaborated on Si (100) substrate at different laser fluence into vacuum. They have been characterized by scanning electron microscope. The results were well

  2. Probing the Solar System

    Science.gov (United States)

    Wilkinson, John

    2013-01-01

    Humans have always had the vision to one day live on other planets. This vision existed even before the first person was put into orbit. Since the early space missions of putting humans into orbit around Earth, many advances have been made in space technology. We have now sent many space probes deep into the Solar system to explore the planets and…

  3. Probing the Solar System

    Science.gov (United States)

    Wilkinson, John

    2013-01-01

    Humans have always had the vision to one day live on other planets. This vision existed even before the first person was put into orbit. Since the early space missions of putting humans into orbit around Earth, many advances have been made in space technology. We have now sent many space probes deep into the Solar system to explore the planets and…

  4. Langmuir Probes for Obstanovka Experiment Aboard the Russian Segment of the International Space Station

    Science.gov (United States)

    2010-08-04

    PWC - Data processing and interpretation 15. SUBJECT TERMS EOARD, Electrostatics, Spacecraft Charging 16. SECURITY ...modified ZigBee protocol) is used realized on JN 5138 modules of the firm Jennic  Elaboration of Control Test System for the flight instruments...Power 3.3 V EEPROM 2x64 K ZigBee : N51xx Wireless communication UART1 I2C UART2 5 ZigBee is the newest wireless technology with the best

  5. Observed Coupling Between the International Space Station PCU Plasma and a FPMU Langmuir Probe Facilitated by the Geomagnetic Field

    Science.gov (United States)

    Hartman, William; Koontz, Steven L.

    2010-01-01

    Electrical charging of the International Space Station (ISS) is a matter of serious concern resulting from the possibility of vehicle arcing and electrical shock hazard to crew during extravehicular activity (EVA). A Plasma Contactor Unit (PCU) was developed and integrated into ISS in order to control the ISS floating potential, thereby, minimize vehicle charging and associated hazards. One of the principle factors affecting ISS electrical charging is the ionosphere plasma state (i.e., electron temperature and density). To support ISS electrical charging studies a Floating Potential Monitoring Unit (FPMU) is also integrated into ISS in order to measure the ionosphere properties using Langmuir probes (LP). The FPMU was located on the Starboard side of ISS. The PCU is located near the center of ISS with its plasma exhaust pointed to port. From its integration on ISS in 2006 through November of 2009, the FPMU data exhibited nominal characteristics during PCU operation. On November 21, 2009 the FPMU was relocated from the Starboard location to a new Port location. After relocation significant enhanced noise was observed in both the LP current-voltage sweeps and the derived electron temperature data. The enhanced noise only occurred when the PCU was in discharge and at unique and repeatable locations of the ISS orbit. The cause of this enhanced noise was investigated. It was found that there is coupling occurring between the PCU plasma and the FPMU LP. In this paper we shall 1) present the on-orbit data and the presence of enhanced noise, 2) demonstrate that the coupling of the PCU plasma and the FPMU measurements is geomagnetically organized, 3) show that coupling of the PCU plasma and the FPMU is primarily due to and driven by particle-wave interaction and 4) show that the ionosphere conditions are adequate for Alfven waves to be generated by the PCU plasma.

  6. Comparative analysis and approximations of space-charge formation in Langmuir probes with plane, cylindrical and spherical electrodes including temperature effects

    Energy Technology Data Exchange (ETDEWEB)

    Valdeblanquez, Eder [Departamento de Fisica, Facultad de IngenierIa, Universidad del Zulia, Apartado 4011- A 526, Maracaibo, Venezuela and Centro de Investigacion de Matematicas Aplicadas Facultad de IngenierIa, Universidad del Zulia, Apartado 10486, Maracaibo (Venezuela, Bolivarian Republic of)], E-mail: eder@luz.edu.ve

    2008-10-15

    In this paper the space-charge effects in Langmuir probes are compared for different kinds of symmetries: plane, cylindrical and spherical. A detailed analysis is performed here including temperature effects, and therefore kinetic theory is used instead of fluid equations as used by other authors. The nonlinear equations obtained here have been solved first by numerical computation and later by approximations using Bessel functions. The accuracy of each approximation is also discussed. Space-charge effects are more important in plane geometries than in the case of cylindrical or spherical symmetries.

  7. Laser-produced Sm{sub 1-x}Nd{sub x}NiO{sub 3} plasma dynamic through Langmuir probe and ICCD imaging combined analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ngom, B.D. [Universite Cheikh Anta Diop de Dakar (UCAD), Laboratoire de Photonique et Nano-Fabrication, Groupe de Physique du Solide et Sciences des Materiaux (GPSSM), Faculte des Sciences et Techniques, Dakar-Fann Dakar (Senegal); University of South Africa, UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology, College of Graduate Studies, Pretoria (South Africa); National Research Foundation, Nanosciences African Network (NANOAFNET), iThemba LABS, Somerset West, Western Cape (South Africa); Lafane, S.; Abdelli-Messaci, S.; Kerdja, T. [Centre de Developpement des Technologies Avancees, Division des Milieux Ionises et Laser, Baba Hassen (Algeria); Maaza, M. [University of South Africa, UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology, College of Graduate Studies, Pretoria (South Africa); National Research Foundation, Nanosciences African Network (NANOAFNET), iThemba LABS, Somerset West, Western Cape (South Africa)

    2016-01-15

    The dynamics of laser-produced plasma of Sm{sub 1-x}Nd{sub x}NiO{sub 3} is studied over oxygen pressure ranging from vacuum up to 2 mbar via Langmuir probe, and intensified charge-coupled device-imaging techniques. The analysis of the oxygen pressure dependence of the ion yield points out to four different regimes. More accurately, the specific ionic current shows a first drop at about 2 x 10{sup -2} mbar corresponding to the appearance of two peaks in the profile of the ionic signal. Likewise, this pressure marks the early stage of the plume splitting into two prominent components as observed by the ICCD imaging. Below 2 x 10{sup -2} mbar, the dynamic of the plume is directive (1D), while a quasi-stable behavior on the ionic current signal is observed. In the 0.2- to 0.5-mbar region, a quasi-stationary regime is obtained. More accurately, both the ionic yield and the plume stopping distance vary very slowly in such pressures range. Above 0.5 mbar, the ionic yield is altered again corresponding to the appearance of the diffusion regime. At a pressure of 1.5 mbar we observe a second appearance of an ionic signal peak. A correlation between the results obtained by Langmuir probe and ICCD imaging is made, presented, and discussed within this contribution. (orig.)

  8. The influence of an antitumor lipid - erucylphosphocholine - on artificial lipid raft system modeled as Langmuir monolayer.

    Science.gov (United States)

    Wnętrzak, Anita; Łątka, Kazimierz; Makyła-Juzak, Katarzyna; Zemla, Joanna; Dynarowicz-Łątka, Patrycja

    2015-01-01

    Outer layer of cellular membrane contains ordered domains enriched in cholesterol and sphingolipids, called 'lipid rafts', which play various biological roles, i.e., are involved in the induction of cell death by apoptosis. Recent studies have shown that these domains may constitute binding sites for selected drugs. For example alkylphosphocholines (APCs), which are new-generation antitumor agents characterized by high selectivity and broad spectrum of activity, are known to have their molecular targets located at cellular membrane and their selective accumulation in tumor cells has been hypothesized to be linked with the alternation of biophysical properties of lipid rafts. To get a deeper insight into this issue, interactions between representative APC: erucylphosphocholine, and artificial lipid raft system, modeled as Langmuir monolayer (composed of cholesterol and sphingomyelin mixed in 1:2 proportion) were investigated. The Langmuir monolayer experiments, based on recording surface pressure-area isotherms, were complemented with Brewster angle microscopy results, which enabled direct visualization of the monolayers structure. In addition, the investigated monolayers were transferred onto solid supports and studied with AFM. The interactions between model raft system and erucylphosphocholine were analyzed qualitatively (with mean molecular area values) as well as quantitatively (with ΔG(exc) function). The obtained results indicate that erucylphosphocholine introduced to raft-mimicking model membrane causes fluidizing effect and weakens the interactions between cholesterol and sphingomyelin, which results in phase separation at high surface pressures. This leads to the redistribution of cholesterol molecules in model raft, which confirms the results observed in biological studies.

  9. Small Probe Reentry System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Global Aerospace Corporation (GAC), and its research partner, Cal Poly San Luis Obispo (CPSLO), will develop an integrated Small Probe Reentry System (SPRS) for low...

  10. An indigenously developed electronic control system for Langmuir-Blodgett film deposition set-up

    Indian Academy of Sciences (India)

    C P Navathe; B L Dashora; Archana Jaiswal; D S Thakur; U N Roy; L M Kukreja

    2001-06-01

    An indigenous and simple electronic control system for Langmuir-Blodgett (LB) film deposition set-up has been developed. This set-up consists of a microstepping circuit to drive the stepper motors with precision and smooth motion, essential for controlled movement of the barriers and substrate in the LB set-up. Linear variable differential transformer (LVDT)-based displacement measuring device has been developed and used to measure the surface pressure of the monolayer material spread on the water surface. A control program is written which incorporates all operational modes required to drive the set-up and to acquire the data in situ using a set of user-friendly commands. This control set-up has been successfully used to plot the pressure-area isotherm of various amphiphilic compounds such as ferric stearate, zinc arachidate etc. and for deposition of ordered LB films of ferric stearate.

  11. Long-range excitation energy transfer in Langmuir-Blodgett multilayer systems

    Science.gov (United States)

    Draxler, Sonja; Lippitsch, Max E.; Aussenegg, Franz R.

    1989-07-01

    In Langmuir-Blodgett films containing organic dyes, efficient energy transfer over distances exceeding 100 nm is observed. This exceptionally long-range transfer is interpreted as due to special mutual orientation of the dye molecules.

  12. Langmuir Probe Measurements Within the Discharge Channel of the 20-kW NASA-300M and NASA-300MS Hall Thrusters

    Science.gov (United States)

    Shastry, Rohit; Huang, Wensheng; Haag, Thomas W.; Kamhawi, Hani

    2013-01-01

    NASA is presently developing a high-power, high-efficiency, long-lifetime Hall thruster for the Solar Electric Propulsion Technology Demonstration Mission. In support of this task, studies have been performed on the 20-kW NASA-300M Hall thruster to aid in the overall design process. The ability to incorporate magnetic shielding into a high-power Hall thruster was also investigated with the NASA- 300MS, a modified version of the NASA-300M. The inclusion of magnetic shielding would allow the thruster to push existing state-of-the-art technology in regards to service lifetime, one of the goals of the Technology Demonstration Mission. Langmuir probe measurements were taken within the discharge channels of both thrusters in order to characterize differences at higher power levels, as well as validate ongoing modeling efforts using the axisymmetric code Hall2De. Flush-mounted Langmuir probes were also used within the channel of the NASA-300MS to verify that magnetic shielding was successfully applied. Measurements taken from 300 V, 10 kW to 600 V, 20 kW have shown plasma potentials near anode potential and electron temperatures of 4 to 12 eV at the walls near the thruster exit plane of the NASA-300MS, verifying magnetic shielding and validating the design process at this power level. Channel centerline measurements on the NASA-300M from 300 V, 10 kW to 500 V, 20 kW show the electron temperature peak at approximately 0.1 to 0.2 channel lengths upstream of the exit plane, with magnitudes increasing with discharge voltage. The acceleration profiles appear to be centered about the exit plane with a width of approximately 0.3 to 0.4 channel lengths. Channel centerline measurements on the NASA-300MS were found to be more challenging due to additional probe heating. Ionization and acceleration zones appeared to move downstream on the NASA-300MS compared to the NASA-300M, as expected based on the shift in peak radial magnetic field. Additional measurements or alternative

  13. Deriving the characteristics of warm electrons (100-500 eV) in the magnetosphere of Saturn with the Cassini Langmuir probe

    Science.gov (United States)

    Garnier, P.; Holmberg, M. K. G.; Wahlund, J.-E.; Lewis, G. R.; Schippers, P.; Coates, A.; Gurnett, D. A.; Waite, J. H.; Dandouras, I.

    2014-12-01

    Though Langmuir probes (LP) are designed to investigate cold plasma regions (e.g. ionospheres), a recent analysis revealed a strong sensitivity of the Cassini LP measurements to hundreds of eV electrons. These warm electrons impact the surface of the probe and generate a significant current of secondary electrons, that impacts both the DC level and the slope of the current-voltage curve of the LP (for negative potentials) through energetic contributions that may be modeled with a reasonable precision. We show here how to derive information about the incident warm electrons from the analysis of these energetic contributions, in the regions where the cold plasma component is small with an average temperature in the range ~ [ 100 - 500 ] eV. First, modeling the energetic contributions (based on the incident electron flux given by a single anode of the CAPS spectrometer) allows us to provide information about the pitch angle anisotropies of the incident hundreds of eV electrons. The modeling reveals indeed sometimes a large variability of the estimated maximum secondary electron yield (which is a constant for a surface material) needed to reproduce the observations. Such dispersions give evidence for strong pitch angle anisotropies of the incident electrons, and using a functional form of the pitch angle distribution even allows us to derive the real peak angle of the distribution. Second, rough estimates of the total electron temperature may be derived in the regions where the warm electrons are dominant and thus strongly influence the LP observations, i.e. when the average electron temperature is in the range ~ [ 100 - 500 ] eV. These regions may be identified from the LP observations through large positive values of the current-voltage slope at negative potentials. The estimated temperature may then be used to derive the electron density in the same region, with estimated densities between ~ 0.1 and a few particles /cm3 (cc). The derived densities are in better

  14. Polythiophene-gold nanoparticle hybrid systems: Langmuir-Blodgett assembly of nanostructured films

    Science.gov (United States)

    Jayaraman, Sundaramurthy; Yu, Liew Ting; Srinivasan, M. P.

    2013-03-01

    In this work, we demonstrate a simple method of synthesizing nanoscale polythiophene-gold nanoparticle (AuNP) hybrid systems assembled by the Langmuir-Blodgett (LB) method. Regio-regular poly(3-(2-methoxyethoxy)ethoxymethyl)thiophene-2,5-diyl (PMEEMT) and poly(3-dodecylthiophene) (PDDT) were employed as the polymeric constituents. The presence of PDDT improved the amphiphilicity of PMEEMT by addressing the phase separation that occurred due to convective hydrodynamic instability on the substrate. 4 layer stacks of 90% and 99% PMEEMT films exhibited uniform film structure with a significant reduction in phase separation. A detailed mechanism for minimization of the surface effect has been proposed based on the interaction of polythiophenes with the substrate. For the first time, an ex situ approach has been adopted to incorporate AuNPs into LB films without affecting the film morphology and uniformity. The incorporation of AuNPs into the polythiophene matrix, aided by the affinity of sulphur for gold, was strongly dependent on the molecular arrangement of the matrix, which in turn depended on the composition of the matrix. The hybrid polythiophene films exhibited enhanced conductivity and can be applied in sensors, photovoltaics and memory devices.In this work, we demonstrate a simple method of synthesizing nanoscale polythiophene-gold nanoparticle (AuNP) hybrid systems assembled by the Langmuir-Blodgett (LB) method. Regio-regular poly(3-(2-methoxyethoxy)ethoxymethyl)thiophene-2,5-diyl (PMEEMT) and poly(3-dodecylthiophene) (PDDT) were employed as the polymeric constituents. The presence of PDDT improved the amphiphilicity of PMEEMT by addressing the phase separation that occurred due to convective hydrodynamic instability on the substrate. 4 layer stacks of 90% and 99% PMEEMT films exhibited uniform film structure with a significant reduction in phase separation. A detailed mechanism for minimization of the surface effect has been proposed based on the interaction

  15. Numerical experiment to estimate the validity of negative ion diagnostic using photo-detachment combined with Langmuir probing

    Energy Technology Data Exchange (ETDEWEB)

    Oudini, N. [Laboratoire des plasmas de décharges, Centre de Développement des Technologies Avancées, Cité du 20 Aout BP 17 Baba Hassen, 16081 Algiers (Algeria); Sirse, N.; Ellingboe, A. R. [Plasma Research Laboratory, School of Physical Sciences and NCPST, Dublin City University, Dublin 9 (Ireland); Benallal, R. [Unité de Recherche Matériaux et Energies Renouvelables, BP 119, Université Abou Bekr Belkaïd, Tlemcen 13000 (Algeria); Taccogna, F. [Istituto di Metodologie Inorganiche e di Plasmi, CNR, via Amendola 122/D, 70126 Bari (Italy); Aanesland, A. [Laboratoire de Physique des Plasmas, (CNRS, Ecole Polytechnique, Sorbonne Universités, UPMC Univ Paris 06, Univ Paris-Sud), École Polytechnique, 91128 Palaiseau Cedex (France); Bendib, A. [Laboratoire d' Electronique Quantique, Faculté de Physique, USTHB, El Alia BP 32, Bab Ezzouar, 16111 Algiers (Algeria)

    2015-07-15

    This paper presents a critical assessment of the theory of photo-detachment diagnostic method used to probe the negative ion density and electronegativity α = n{sub -}/n{sub e}. In this method, a laser pulse is used to photo-detach all negative ions located within the electropositive channel (laser spot region). The negative ion density is estimated based on the assumption that the increase of the current collected by an electrostatic probe biased positively to the plasma is a result of only the creation of photo-detached electrons. In parallel, the background electron density and temperature are considered as constants during this diagnostics. While the numerical experiments performed here show that the background electron density and temperature increase due to the formation of an electrostatic potential barrier around the electropositive channel. The time scale of potential barrier rise is about 2 ns, which is comparable to the time required to completely photo-detach the negative ions in the electropositive channel (∼3 ns). We find that neglecting the effect of the potential barrier on the background plasma leads to an erroneous determination of the negative ion density. Moreover, the background electron velocity distribution function within the electropositive channel is not Maxwellian. This is due to the acceleration of these electrons through the electrostatic potential barrier. In this work, the validity of the photo-detachment diagnostic assumptions is questioned and our results illustrate the weakness of these assumptions.

  16. Polythiophene-gold nanoparticle hybrid systems: Langmuir-Blodgett assembly of nanostructured films.

    Science.gov (United States)

    Jayaraman, Sundaramurthy; Yu, Liew Ting; Srinivasan, M P

    2013-04-01

    In this work, we demonstrate a simple method of synthesizing nanoscale polythiophene-gold nanoparticle (AuNP) hybrid systems assembled by the Langmuir-Blodgett (LB) method. Regio-regular poly(3-(2-methoxyethoxy)ethoxymethyl)thiophene-2,5-diyl (PMEEMT) and poly(3-dodecylthiophene) (PDDT) were employed as the polymeric constituents. The presence of PDDT improved the amphiphilicity of PMEEMT by addressing the phase separation that occurred due to convective hydrodynamic instability on the substrate. 4 layer stacks of 90% and 99% PMEEMT films exhibited uniform film structure with a significant reduction in phase separation. A detailed mechanism for minimization of the surface effect has been proposed based on the interaction of polythiophenes with the substrate. For the first time, an ex situ approach has been adopted to incorporate AuNPs into LB films without affecting the film morphology and uniformity. The incorporation of AuNPs into the polythiophene matrix, aided by the affinity of sulphur for gold, was strongly dependent on the molecular arrangement of the matrix, which in turn depended on the composition of the matrix. The hybrid polythiophene films exhibited enhanced conductivity and can be applied in sensors, photovoltaics and memory devices.

  17. Mass Spectrometric and Langmuir Probe Measurements in Inductively Coupled Plasmas in Ar, CHF3/Ar and CHF3/Ar/O2 Mixtures

    Science.gov (United States)

    Kim, J. S.; Rao, M. V. V. S.; Cappelli, M. A.; Sharma, S. P.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2000-01-01

    Absolute fluxes and energy distributions of ions in inductively coupled plasmas of Ar, CHF3/Ar, and CHF3/Ar/O2 have been measured. These plasmas were generated in a Gaseous Electronics Conference (GEC) cell modified for inductive coupling at pressures 10-50 mTorr and 100-300 W of 13.56 MHz radio frequency (RF) power in various feedgas mixtures. In pure Ar plasmas, the Ar(+) flux increases linearly with pressure as well as RF-power. Total ion flux in CHF3 mixtures decreases with increase in pressure and also CHF3 concentration. Relative ion fluxes observed in the present studies are analyzed with the help of available cross sections for electron impact ionization and charge-exchange ion-molecule reactions. Measurements of plasma potential, electron and ion number densities, electron energy distribution function, and mean electron energy have also been made in the center of the plasma with a RF compensated Langmuir probe. Plasma potential values are compared with the mean ion energies determined from the measured ion energy distributions and are consistent. Electron temperature, plasma potential, and mean ion energy vary inversely with pressure, but increase with CHF3 content in the mixture.

  18. DESIGN NOTE: A control system for Langmuir-Blodgett film deposition set-up based on microstepping

    Science.gov (United States)

    Navathe, C. P.; Dashora, B. L.; Roy, U. N.; Singh, R.; Maheswari, S.; Kukreja, L. M.

    1998-03-01

    A control system for Langmuir-Blodgett (LB) film set-up has been developed based on the principle of microstepping of the stepper motors to drive the barriers and the substrate with precision and smooth motion. The stepper motors and the Wilhelmy plate used to measure the monolayer surface pressure are interfaced to a microcomputer for automatic operation. This home-made LB film set-up has been successfully used to fabricate LB films of cadmium arachidate of high crystalline quality.

  19. Langmuir and Langmuir-Blodgett films revisited

    OpenAIRE

    2016-01-01

    A review on Langmuir and Langmuir-Blodgett films The Langmuir and Langmuir-Blodgett (LB) technique has been applied for a long time. It exist several books and reviews on the subject. Also, a big number of works and papers have been made. This work only intends to afford a revision of the subject under the point of view of the author, and centered mostly in new references.

  20. Edge turbulence measurement in Heliotron J using a combination of hybrid probe system and fast cameras

    Energy Technology Data Exchange (ETDEWEB)

    Nishino, N., E-mail: nishino@hiroshima-u.ac.jp [Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima (Japan); Zang, L. [Kyoto University, Gokasho, Uji, Kyoto (Japan); Takeuchi, M. [JAEA, Naka, Ibaraki (Japan); Mizuuchi, T.; Ohshima, S. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kasajima, K.; Sha, M. [Kyoto University, Gokasho, Uji, Kyoto (Japan); Mukai, K. [NIFS, Toki, Gifu (Japan); Lee, H.Y. [Kyoto University, Gokasho, Uji, Kyoto (Japan); Nagasaki, K.; Okada, H.; Minami, T.; Kobayashi, S.; Yamamoto, S.; Konoshima, S.; Nakamura, Y.; Sano, F. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2013-07-15

    The hybrid probe system (a combination of Langmuir probes and magnetic probes), fast camera and gas puffing system were installed at the same toroidal section to study edge plasma turbulence/fluctuation in Heliotron J, especially blob (intermittent filament). Fast camera views the location of the probe head, so that the probe system yields the time evolution of the turbulence/fluctuation while the camera images the spatial profile. Gas puff at the same toroidal section was used to control the plasma density and simultaneous gas puff imaging technique. Using this combined system the filamentary structure associated with magnetic fluctuation was found in Heliotron J at the first time. The other kind of fluctuation was also observed at another experiment. This combination measurement enables us to distinguish MHD activity and electro-static activity.

  1. Heavy-ion-induced desorption of organic molecules studied with Langmuir-Blodgett multilayer systems (DE)

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, R.; Schoppmann, C.; Brandl, D.; Ostrowski, A.; Voit, H. (Physikalisches Institut der Universitaet Erlangen-Nuernberg D-8520 Erlangen, (Germany)); Johannsmann, D.; Knoll, W. (Max-Planck-Institut fuer Polymerforschung Mainz D-6500 Mainz, (Germany))

    1991-07-01

    Heavy-ion-induced desorption has been studied with samples consisting of Langmuir-Blodgett films made from Cd salts of fatty acids. The experiments confirm the result of previous works that heavy ions drill a crater into the sample surface. The explicit dependence of the crater depth on the electronic energy loss could be determined from the experiments. The craters exhibit the shape of a symmetric cone as obtained from a desorption model applied to the experimental data.

  2. Zero voltage mass spectrometry probes and systems

    Energy Technology Data Exchange (ETDEWEB)

    Cooks, Robert Graham; Wleklinski, Michael Stanley; Bag, Soumabha; Li, Yafeng

    2017-10-10

    The invention generally relates to zero volt mass spectrometry probes and systems. In certain embodiments, the invention provides a system including a mass spectrometry probe including a porous material, and a mass spectrometer (bench-top or miniature mass spectrometer). The system operates without an application of voltage to the probe. In certain embodiments, the probe is oriented such that a distal end faces an inlet of the mass spectrometer. In other embodiments, the distal end of the probe is 5 mm or less from an inlet of the mass spectrometer.

  3. Probing Signal Design for Power System Identification

    Energy Technology Data Exchange (ETDEWEB)

    Pierre, John W.; Zhou, Ning; Tuffner, Francis K.; Hauer, John F.; Trudnowski, Daniel J.; Mittelstadt, William

    2010-05-31

    This paper investigates the design of effective input signals for low-level probing of power systems. In 2005, 2006, and 2008 the Western Electricity Coordinating Council (WECC) conducted four large-scale system wide tests of the western interconnected power system where probing signals were injected by modulating the control signal at the Celilo end of the Pacific DC intertie. A major objective of these tests is the accurate estimation of the inter-area electromechanical modes. A key aspect of any such test is the design of an effective probing signal that leads to measured outputs rich in information about the modes. This paper specifically studies low-level probing signal design for power-system identification. The paper describes the design methodology and the advantages of this new probing signal which was successfully applied during these tests. This probing input is a multi-sine signal with its frequency content focused in the range of the inter-area modes. The period of the signal is over two minutes providing high-frequency resolution. Up to 15 cycles of the signal are injected resulting in a processing gain of 15. The resulting system response is studied in the time and frequency domains. Because of the new probing signal characteristics, these results show significant improvement in the output SNR compared to previous tests.

  4. Controlled fabrication of hexagonally close-packed Langmuir-Blodgett silica particulate monolayers from binary surfactant and solvent systems.

    Science.gov (United States)

    Guo, Yudi; Tang, Dongyan; Du, Yunchen; Liu, Binbin

    2013-03-05

    We describe a controllable method to fabricate hexagonally close-packed Langmuir-Blodgett (LB) monolayers with stearic acid (SA) as co-surfactant and methanol as co-solvent. The optimal SA concentrations and volume ratios of chloroform to methanol are 0.8 mg/mL and 3:1 for particles of 140 nm, 0.50 mg/mL and 4:1 for particles of 300 nm, and 0.05 mg/mL and 5:1 for particles of 550 nm, respectively. Additionally, SEM detections of the monolayers transferred at different surface pressures indicate that the monolayers deposited from the binary systems are more compressible. The experimental results indicate that the interparticle repulsions and particle-water interactions can be enhanced without decreasing the particle hydrophobicity by adding SA and methanol; thus, particulate monolayers with large hexagonally close-packed domains composed of small silica particles can be successfully fabricated using LB technique. We propose that the enhanced interparticle repulsion is attributed to the Columbic repulsion resulting from the attachment of SA molecules to the CTAB modified particles around the three phase contact line.

  5. Langmuir monolayers of cerebroside originated from Linckia laevigata: binary systems of cerebrosides and phospholipid.

    Science.gov (United States)

    Maruta, Tomoki; Hoda, Kazuki; Inagaki, Masanori; Higuchi, Ryuichi; Shibata, Osamu

    2005-08-01

    The surface pressure (pi)-area (A), the surface potential (DeltaV)-A and the dipole moment (mu( perpendicular))-A isotherms were obtained for six cerebrosides of LLC-2, LLC-2-1, LLC-2-8, LLC-2-10, LLC-2-12, and LLC-2-15, which were isolated from Linckia laevigata, and two-component monolayers of two different cerebrosides (LLC-2 and LLC-2-8) with phospholipid of dipalmitoylphosphatidylcholine (DPPC) on a subphase of 0.15 M sodium chloride solution as a function of cerebroside compositions in the two-component systems by employing the Wilhelmy method, the ionizing electrode method, and the fluorescence microscopy. The new finding was that LLC-2 showed a stable and liquid expanded type film. Four of them (LLC-2-8, -10, -12, and -15) had the phase transition from the liquid-expanded (LE) to the liquid-condensed (LC) states at 298.2 K. The apparent molar quantity changes (Deltas(gamma), Deltah(gamma), and Deltau(gamma)) on their phase transition on 0.15M at 298.2 K were calculated. The miscibility of cerebroside and phospholipid in the two-component monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the cerebroside molar fraction (X(cerebroside)), using the additivity rule. From the A-X(cerebroside) and DeltaV(m)-X(phospholipid) plots, a partial molecular surface area (PMA) and an apparent partial molecular surface potential (APSP) were determined at the discrete surface pressure. The PMA and APSP with the mole fraction were extensively discussed for the miscible systems. Judging from the two-dimensional phase diagrams, these were found to be one type, a positive azeotropic type; all the cerebrosides were miscible with DPPC. Furthermore, assuming a regular surface mixture, the Joos equation for the analysis of the collapse pressure of two-component monolayers allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltavarepsilon) between the cerebrosides and DPPC. The

  6. Raman spectroscopy system with hollow fiber probes

    Science.gov (United States)

    Liu, Bing-hong; Shi, Yi-Wei

    2012-11-01

    A Raman remote spectroscopy system was realized using flexible hollow optical fiber as laser emittion and signal collection probes. A silver-coated hollow fiber has low-loss property and flat transmission characteristics in the visible wavelength regions. Compared with conventional silica optical fiber, little background fluorescence noise was observed with optical fiber as the probe, which would be of great advantages to the detection in low frequency Raman shift region. The complex filtering and focusing system was thus unnecessary. The Raman spectra of CaCO3 and PE were obtained by using the system and a reasonable signal to noise ratio was attained without any lens. Experiments with probes made of conventional silica optical fibers were also conducted for comparisons. Furthermore, a silver-coated hollow glass waveguide was used as sample cell to detect liquid phase sample. We used a 6 cm-long hollow fiber as the liquid cell and Butt-couplings with emitting and collecting fibers. Experiment results show that the system obtained high signal to noise ratio because of the longer optical length between sample and laser light. We also give the elementary theoretical analysis for the hollow fiber sample cell. The parameters of the fiber which would affect the system were discussed. Hollow fiber has shown to be a potential fiber probe or sample cell for Raman spectroscopy.

  7. Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak

    Science.gov (United States)

    Brunner, D.; Kuang, A. Q.; LaBombard, B.; Burke, W.

    2017-07-01

    A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density—through use of a mirror Langmuir probe bias system—combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. In addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.

  8. Modelling and simulation of photocatalytic oxidation mechanism of chlorohalogenated substituted phenols in batch systems: Langmuir-Hinshelwood approach.

    Science.gov (United States)

    Khuzwayo, Z; Chirwa, E M N

    2015-12-30

    This study investigated, modelled and simulated the influence of multi-chlorohalogenation in heterogeneous photocatalytic degradation of substituted phenols (pentachlorophenol (PCP), trichlorophenol (TCP), dichlorophenol (DCP), and monochlorophenol (CP)). The Langmuir-Hinshelwood approach was applied to determine oxidation kinetics. Aquasim 2.0 computational software was used to model, simulate and estimate model parameters of the different chlorophenols. Chemical adsorption equilibrium isotherms for the four chlorophenols and phenol were studied and modelled for adsorption onto titanium dioxide (TiO2) semiconductor catalyst. Langmuir adsorption parameters were determined and used to calculate adsorption constant and maximum adsorption capacity. The adsorption of chloride phenolics onto titanium dioxide catalyst increased in the order of 4 - CP Photocatalytic studies analysed the efficiency of oxidation and found improved degradation with higher chloride substituted phenolics in the order of PCP > TCP > DCP ≥ 4 - CP. Photocatalytic parameters were calculated and estimated along with sensitivity and uncertainty analyses.

  9. A Langmuir film approach to elucidating interactions in lipid membranes: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine/cholesterol/metal cation systems.

    Science.gov (United States)

    Korchowiec, Beata; Paluch, Maria; Corvis, Yohann; Rogalska, Ewa

    2006-01-01

    The interactions between two membrane lipids, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and cholesterol (CHOL), were studied in Langmuir films using surface pressure isotherms and Brewster angle microscopy. The DPPE/CHOL interactions were probed for chosen monolayer and subphase (Na(+), Ca(2+)) composition at 20, 25, and 30 degrees C. The results obtained show that DPPE and CHOL are miscible for the cholesterol mol fractions x(CHOL)=0.3-0.5. Cholesterol induces condensation of the DPPE monolayers. The most significant condensation of the DPPE/CHOL monolayers was observed in the presence of Ca(2+) ions in the subphase at x(CHOL)=0.4. The negative deviation of the molecular surface area (MMA) additivity from the ideal behavior together with negative values of excess free enthalpy of mixing in the monolayers were interpreted in terms of attractive interactions between lipid molecules.

  10. Properties of the Langmuir films made by petroleum asphaltenes. Model systems of crude oil-water emulsions; Proprietes des films de Langmuir formes par des asphaltenes du petrole. Systemes modeles des emulsions eau - petrole brut

    Energy Technology Data Exchange (ETDEWEB)

    Deghais, S.; Solimando, R. [Institut National Polytechnique de Lorraine, Ecole Nationale Superieure des Industries Chimiques, Lab. de Thermodynamique des Separations, 54 - Nancy (France); Zywocinski, A.; Rogalska, E. [Universite Henri Poincare, Lab. de Physco-Chimie des Colloides, UMR CNRS 7565, 54 - Vandoeuvre les Nancy (France); Rogalski, M.; Rogalska, E. [Metz Univ., Lab. de Thermodynamique et d' Analyse Chimique, 57 (France)

    2001-07-01

    This work deals with the analysis of the properties of the water-petroleum fluid interfaces using the Langmuir films technique. The stability of the water-petroleum emulsions is ensured by complex interactions which exist at the interface between paraffins and heavy petroleum compounds like asphaltenes and resins. The experiments performed have shown that the stabilizing properties of the asphaltene films depend on the dielectric constant of the fluid, on the presence or not of resins, and on the presence of possible paraffinic depositions. (J.S.)

  11. Evidence for Langmuir Oscillations and a Low Density Cavity in the Venus Magnetotail

    Science.gov (United States)

    Ho, C. M.; Strangeway, R. J.; Russell, C. T.

    1993-01-01

    We report the discovery of Langmuir oscillations in a very low plasma density region in the Venus magnetotail. These waves are observed more often at 30 kHz, but also at 5.4 kHz indicating densities as low as 0.3/cu cm in the central tail lobe. The Langmuir probe on board the Pioneer Venus Orbiter cannot resolve such a low plasma density. We use the magnetic field strength and the assumption of total pressure balance to infer the electron temperature as a test of the Langmuir wave interpretation. By investigating the spatial distribution of this wave activity we find that the plasma cavity is ordered in a coordinate system defined by the interplanetary magnetic field and is found at either side of the central tail current sheet.

  12. Gravity Probe B data system description

    Science.gov (United States)

    Bennett, Norman R.

    2015-11-01

    The Gravity Probe B data system, developed, integrated, and tested by Lockheed Missiles & Space Company, and later Lockheed Martin Corporation, included flight and ground command, control, and communications software. The development was greatly facilitated, conceptually and by the transfer of key personnel, through Lockheed’s earlier flight and ground test software development for the Hubble Space Telescope (HST). Key design challenges included the tight mission timeline (17 months, 9 days of on-orbit operation), the need to tune the system once on-orbit, and limited 2 Kbps real-time data rates and ground asset availability. The result was a completely integrated space vehicle and Stanford mission operations center, which successfully collected and archived 97% of the ‘guide star valid’ data to support the science analysis. Lessons learned and incorporated from the HST flight software development and on-orbit support experience, and Lockheed’s independent research and development effort, will be discussed.

  13. Domain Relaxation in Langmuir Films

    Science.gov (United States)

    Bernoff, Andrew J.; Alexander, James C.; Mann, Elizabeth K.; Mann, J. Adin; Zou, Lu; Wintersmith, Jacob R.

    2007-11-01

    We report on an experimental, theoretical and computational study of a molecularly thin polymer Langmuir layer domain on the surface of a subfluid. When stretched (by a transient stagnation flow), the Langmuir layer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the circular minimum energy configuration. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments as a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. We process the digital images of the experiment to extract the domain shape, use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics, and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%.

  14. Langmuir and Langmuir-Blodgett films of bidisperse silica nanoparticles.

    Science.gov (United States)

    Detrich, Adám; Deák, András; Hild, Erzsébet; Kovács, Attila L; Hórvölgyi, Zoltán

    2010-02-16

    We present the studies on the structure and optical properties of bidisperse Stöber silica nanoparticulate Langmuir films prepared at the air/water interface in a Wilhelmy film balance and transferred onto glass slides using the Langmuir-Blodgett technique. Three different compositions (covered area ratios: 4:1; 1:1, and 1:4) of two bidisperse systems were used in the experiments. Bidisperse samples (B1 and B2) were prepared by mixing the appropriate amount of monodisperse sols of particles with 61 and 100 nm diameters (B1) and those with 37 and 100 nm diameters (B2). By surface pressure-area isotherms and (transmission and scanning) electron microscopy images we provide information about the structure of the films. Optical properties of the supported films were measured with UV-vis spectroscopy and the transmittance spectra were evaluated in terms of an optical model which allows monotonous in-depth variation of the refractive index across the film. (1) We have found that the refractive index decreased from the substrate-layer interface toward the air-layer interface when the smaller particles were in majority, and increased otherwise. That would suggest that the smaller particles of each bidisperse system can be positioned at the air side of the film if they are in minority in the sample and they can be situated on the substrate if they are in majority. The scanning electron microscope images of bidisperse films supported the in-depth film structure suggested by optical studies.

  15. Structure of binary mixed polymer Langmuir layers

    NARCIS (Netherlands)

    Bernardini, C.

    2012-01-01

    The possibility of preparing 2D stable emulsions through mixing of homopolymers in a Langmuir monolayer is the core topic of this thesis. While colloid science has achieved well established results in the study of bulk dispersed systems, accounts on properties of mixed monomolecular films are fewer,

  16. Structure of binary mixed polymer Langmuir layers

    NARCIS (Netherlands)

    Bernardini, C.

    2012-01-01

    The possibility of preparing 2D stable emulsions through mixing of homopolymers in a Langmuir monolayer is the core topic of this thesis. While colloid science has achieved well established results in the study of bulk dispersed systems, accounts on properties of mixed monomolecular films are fewer,

  17. A brightness exceeding simulated Langmuir limit

    Energy Technology Data Exchange (ETDEWEB)

    Nakasuji, Mamoru [2-15-11, Serigaya-chou, Kounan-ku, Yokohama-shi, Kanagawa-ken (Japan)

    2013-08-15

    When an excitation of the first lens determines a beam is parallel beam, a brightness that is 100 times higher than Langmuir limit is measured experimentally, where Langmuir limits are estimated using a simulated axial cathode current density which is simulated based on a measured emission current. The measured brightness is comparable to Langmuir limit, when the lens excitation is such that an image position is slightly shorter than a lens position. Previously measured values of brightness for cathode apical radii of curvature 20, 60, 120, 240, and 480 μm were 8.7, 5.3, 3.3, 2.4, and 3.9 times higher than their corresponding Langmuir limits, respectively, in this experiment, the lens excitation was such that the lens and the image positions were 180 mm and 400 mm, respectively. From these measured brightness for three different lens excitation conditions, it is concluded that the brightness depends on the first lens excitation. For the electron gun operated in a space charge limited condition, some of the electrons emitted from the cathode are returned to the cathode without having crossed a virtual cathode. Therefore, method that assumes a Langmuir limit defining method using a Maxwellian distribution of electron velocities may need to be revised. For the condition in which the values of the exceeding the Langmuir limit are measured, the simulated trajectories of electrons that are emitted from the cathode do not cross the optical axis at the crossover, thus the law of sines may not be valid for high brightness electron beam systems.

  18. Langmuir Solitons in Magnetized Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Mjølhus, E.; Pécseli, Hans;

    1978-01-01

    The authors have considered the nonlinear interaction between a high frequency (Langmuir) wave, which propagates at an arbitrary angle to a weak, constant magnetic field, and low frequency (ion-cyclotron or ion-sound) perturbations. In studying Langmuir envelope solitons they have unified...

  19. Development of a reciprocating probe servomotor control system with real-time feedback on plasma position for the Alcator C-Mod tokamak

    Science.gov (United States)

    Brunner, D.; Kuang, A. Q.; Labombard, B.; Burke, W.

    2015-11-01

    Reciprocating probe drives are one of the diagnostic workhorses in the boundary of magnetic confinement fusion experiments. The probe is scanned into an exponentially increasing heat flux, which demands a prompt and precise turn around to maintain probe integrity. A new linear servomotor controlled reciprocating drive utilizing a commercial linear servomotor and drive controller has been developed for the Alcator C-Mod tokamak. The quick response of the controller (able to apply an impulse of 50A in about 1ms) along with real-time plasma measurements from a Mirror Langmuir Probe (MLP) allows for real-time control of the probe trajectory based on plasma conditions at the probe tip. Since the primary concern for probe operation is overheating, an analog circuit has been created that computes the surface temperature of the probe from the MLP measurements. The probe can be programmed to scan into the plasma at various times and then turns around when the computed surface temperature reaches a set threshold, maximizing the scan depth into the plasma while avoiding excessive heating. Design, integration, and first measurements with this new system will be presented. This work was supported by U.S. Department of Energy award DE-FC02-99ER54512, using Alcator C-Mod, A DOE SC User Facility.

  20. Tamm-Langmuir surface waves

    Science.gov (United States)

    Golenitskii, K. Â. Yu.; Koshelev, K. Â. L.; Bogdanov, A. Â. A.

    2016-10-01

    In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states—we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

  1. Tamm-Langmuir surface waves

    CERN Document Server

    Golenitskii, K U; Bogdanov, A A

    2016-01-01

    In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states - we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

  2. Phenomenological Modeling for Langmuir Monolayers

    Science.gov (United States)

    Baptiste, Dimitri; Kelly, David; Safford, Twymun; Prayaga, Chandra; Varney, Christopher N.; Wade, Aaron

    Experimentally, Langmuir monolayers have applications in molecular optical, electronic, and sensor devices. Traditionally, Langmuir monolayers are described by a rigid rod model where the rods interact via a Leonard-Jones potential. Here, we propose effective phenomenological models and utilize Monte Carlo simulations to analyze the phase behavior and compare with experimental isotherms. Research reported in this abstract was supported by UWF NIH MARC U-STAR 1T34GM110517-01.

  3. Compact and high-particle-flux thermal-lithium-beam probe system for measurement of two-dimensional electron density profile.

    Science.gov (United States)

    Shibata, Y; Manabe, T; Kajita, S; Ohno, N; Takagi, M; Tsuchiya, H; Morisaki, T

    2014-09-01

    A compact and high-particle-flux thermal-lithium-beam source for two-dimensional measurement of electron density profiles has been developed. The thermal-lithium-beam oven is heated by a carbon heater. In this system, the maximum particle flux of the thermal lithium beam was ~4 × 10(19) m(-2) s(-1) when the temperature of the thermal-lithium-beam oven was 900 K. The electron density profile was evaluated in the small tokamak device HYBTOK-II. The electron density profile was reconstructed using the thermal-lithium-beam probe data and this profile was consistent with the electron density profile measured with a Langmuir electrostatic probe. We confirm that the developed thermal-lithium-beam probe can be used to measure the two-dimensional electron density profile with high time and spatial resolutions.

  4. Positional order in Langmuir monolayers

    DEFF Research Database (Denmark)

    Kaganer, V.M.; Brezesinski, G.; Möhwald, H.;

    1998-01-01

    We find that a structural solid-solid phase transition in a two-dimensional Langmuir film is accompanied by strong positional disorder. Specifically, we find by a grazing-incidence x-ray diffraction experiment that in monolayers of octadecanol both the hexagonal phase LS and the centered rectangu......We find that a structural solid-solid phase transition in a two-dimensional Langmuir film is accompanied by strong positional disorder. Specifically, we find by a grazing-incidence x-ray diffraction experiment that in monolayers of octadecanol both the hexagonal phase LS and the centered...

  5. About supramolecular systems for dynamically probing cells

    NARCIS (Netherlands)

    Brinkmann, J.; Cavatorta, E.; Sankaran, S.; Schmidt, B.; van Weerd, Jasper; Jonkheijm, Pascal

    2014-01-01

    This article reviews the state of the art in the development of strategies for generating supramolecular systems for dynamic cell studies. Dynamic systems are crucial to further our understanding of cell biology and are consequently at the heart of many medical applications. Increasing interest has

  6. Probing water motion in heterogeneous systems.

    NARCIS (Netherlands)

    Dusschoten, van D.

    1996-01-01

    In this Thesis a practical approach is presented to study water mobility in heterogeneous systems by a number of novel NMR sequences. The major part of this Thesis describes how the reliability of diffusion measurements can be improved using some of the novel NMR sequences. The reliability of the da

  7. Design study for electronic system for Jupiter Orbit Probe (JOP)

    Science.gov (United States)

    Elero, B. P., Jr.; Carignan, G. R.

    1978-01-01

    The conceptual design of the Jupiter probe spectrometer is presented. Block and circuit diagrams are presented along with tabulated parts lists. Problem areas are considered to be (1) the schedule, (2) weight limitations for the electronic systems, and (3) radiation hardness of the electronic devices.

  8. Dichromatic Langmuir waves in degenerate quantum plasma

    Science.gov (United States)

    Dubinov, A. E.; Kitayev, I. N.

    2015-06-01

    Langmuir waves in fully degenerate quantum plasma are considered. It is shown that, in the linear approximation, Langmuir waves are always dichromatic. The low-frequency component of the waves corresponds to classical Langmuir waves, while the high-frequency component, to free-electron quantum oscillations. The nonlinear problem on the profile of dichromatic Langmuir waves is solved. Solutions in the form of a superposition of waves and in the form of beatings of its components are obtained.

  9. Probing TRAPPIST-1-like Systems with K2

    OpenAIRE

    Demory, Brice-Olivier; Queloz, Didier; Alibert, Yann; Gillen, Ed; Gillon, Michaël

    2016-01-01

    The search for small planets orbiting late M dwarfs holds the promise of detecting Earth-size planets for which their atmospheres could be characterized within the next decade. The recent discovery of TRAPPIST-1 entertains hope that these systems are common around hosts located at the bottom of the main sequence. In this Letter, we investigate the ability of the repurposed Kepler mission (K2) to probe planetary systems similar to TRAPPIST-1. We perform a consistent data analysis of 189 spectr...

  10. Analysis of kinetic Langmuir model. Part I: Integrated kinetic Langmuir equation (IKL): a new complete analytical solution of the Langmuir rate equation.

    Science.gov (United States)

    Marczewski, Adam W

    2010-10-05

    In the article, a new integrated kinetic Langmuir equation (IKL) is derived. The IKL equation is a simple and easy to analyze but complete analytical solution of the kinetic Langmuir model. The IKL is compared with the nth-order, mixed 1,2-order, and multiexponential kinetic equations. The impact of both equilibrium coverage θ(eq) and relative equilibrium uptake u(eq) on kinetics is explained. A newly introduced Langmuir batch equilibrium factor f(eq) that is the product of both parameters θ(eq)u(eq) is used to determine the general kinetic behavior. The analysis of the IKL equation allows us to understand fully the Langmuir kinetics and explains its relation with respect to the empirical pseudo-first-order (PFO, i.e., Lagergren), pseudo-second-order (PSO), and mixed 1,2-order kinetic equations, and it shows the conditions of their possible application based on the Langmuir model. The dependence of the initial adsorption rate on the system properties is analyzed and compared to the earlier published approximate equations.

  11. Langmuir and langmuir-blodgett films of metallosupramolecular polyelectrolyte-amphiphile complexes.

    Science.gov (United States)

    Lehmann, Pit; Symietz, Christian; Brezesinski, Gerald; Krass, Henning; Kurth, Dirk G

    2005-06-21

    A detailed analysis of a metallosupramolecular polyelectrolyte-amphiphile complex (PAC) at the air-water interface is presented. Langmuir isotherms, Brewster angle microscopy, and X-ray reflectance and diffraction methods are employed to investigate the structure of the Langmuir monolayers. The PAC is self-assembled from 1,3-bis[4'-oxa-(2,2':6',2' '-terpyridinyl)]propane, iron acetate, and dihexadecyl phosphate (DHP). Spreading the PAC at the air-water interface results in a monolayer that consists of two strata. DHP forms a monolayer at the top of the interface, while the metallosupramolecular polyelectrolyte is immersed in the aqueous subphase. Both strata are coupled to each other through electrostatic interactions. The monolayers can be transferred onto solid substrates, resulting in well-ordered multilayers. Such multilayers are model systems for well-ordered metal ions in two dimensions.

  12. Probing multipartite entanglement in a coupled Jaynes-Cummings system

    CERN Document Server

    Xue, Peng; Sanders, Barry C

    2012-01-01

    We show how to probe multipartite entanglement in $N$ coupled Jaynes-Cummings cells where the degrees of freedom are the electronic energies of each of the $N$ atoms in separate single-mode cavities plus the $N$ single-mode fields themselves. Specifically we propose probing the combined system as though it is a dielectric medium. The spectral properties and transition rates directly reveal multipartite entanglement signatures. It is found that the Hilbert space of the $N$ cell system can be confined to the totally symmetric subspace of two states only that are maximally-entangled W states with 2N degrees of freedom. The subspace of the remaining $2N-2$ states is comprises optically inactive quadripartite states.

  13. Development of Touch Probing System Using a Fiber Stylus

    Directory of Open Access Journals (Sweden)

    Hiroshi Murakami

    2016-08-01

    Full Text Available This paper presents a system that can be used for micro-hole measurement; the system comprises an optical fiber stylus that is 5 µm in diameter. The stylus deflects when it comes into contact with the measured surface; this deflection is measured optically. In this study, the design parameters of the optical system are determined using a ray-tracing method, and a prototype of the probing system is fabricated to verify ray-tracing simulation results; furthermore, the performance of the system is evaluated experimentally. The results show that the design parameters of this system can be determined using ray-tracing; the resolution of the measurement system using this shaft was approximately 3 nm, and the practicality of this system was confirmed by measuring the shape of a micro-hole 100 µm in diameter and 475 µm in depth.

  14. Evaluation of the NDP (neutron diagnostic probe) system

    Energy Technology Data Exchange (ETDEWEB)

    Pentaleri, E.A.; Eisen, Y.Y.

    1990-12-01

    The neutron diagnostic probe (NDP), an explosive detection system developed by Consolidated Controls Corporation and based on the associated-alpha-particle technique, was evaluated. Although many problems were found with the prototype system that make it useless for most practical applications, the NDP system may be considered a successful proof-of-principle for the basic explosive detection system design. In addition to evaluating the design and performance of the present system, models were developed to estimate the performance that might reasonably be expected from full scale systems of different conceptual design. Specific examples involved various types of bulk and sheet explosives contained in a suitcase and a large crate. Also considered were the effects of innocuous materials surrounding explosives in different scenarios, including the deliberate use of shielding materials as a countermeasure to detection. 11 refs., 46 figs., 24 tabs.

  15. Lipid reassembly in asymmetric Langmuir-Blodgett/Langmuir-Schaeffer bilayers.

    Science.gov (United States)

    Yuan, Jie; Hao, Changchun; Chen, Maohui; Berini, Pierre; Zou, Shan

    2013-01-08

    Molecular-reorganization-induced morphology alteration in asymmetric substrate-supported lipid bilayers (SLBs) was directly visualized by means of atomic force microscopy (AFM) and total internal reflection fluorescence (TIRF) microscopy. SLB samples were fabricated on mica-on-glass and glass substrates by Langmuir-Blodgett (LB)/Langmuir-Schaeffer (LS) using binary lipid mixtures, namely, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and ternary mixtures DOPC/DPPC/1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS), labeled with 0.2 mol % Texas Red 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (TR-DHPE) dye. Phase segregations were characterized by TIRF imaging, and DPPC-enriched domain structures were also observed. Interestingly for ∼40% (n = 6) of the samples with binary mixtures in the LB leaflet and a single component in the LS leaflet, that is, (DOPC/DPPC)(LB)+DOPC(LS), the contrast of the DPPC domains changed from the original dark (without dye) to bright (more TR dye partitioning) on TIRF images, returning to dark again. This contrast reverse was also correlated to AFM height images, where a DPPC-DPPC gel phase was spotted after the TIRF image contrast returned to dark. The rupture force mapping results measured on these binary mixture samples also confirmed unambiguously the formation of DPPC-DPPC gel domain components during the contrast change. The samples were tracked over 48 h to investigate the lipid molecule movements in both the DPPC domains and the DOPC fluid phase. The fluorescence contrast changes from bright to dark in SLBs indicate that the movement of dye molecules was independent of the movement of lipid molecules. In addition, correlated multimodal imaging using AFM, force mapping, and fluorescence provides a novel route to uncover the reorganization of lipid molecules at the solid-liquid interface, suggesting that the dynamics of dye molecules is highly

  16. Strong Langmuir turbulence at Jupiter?

    Science.gov (United States)

    Cairns, Iver H.; Robinson, P. A.

    1992-01-01

    Langmuir wave packets with short scale lengths less than an approximately equal to 100 lambda e have been observed in Jupiter's foreshock. Theoretical constraints on the electric fields and scale sizes of collapsing wave packets are summarized, extended and placed in a form suitable for easy comparison with Voyager and Ulysses data. The published data are reviewed and possible instrumental underestimation of fields discussed. New upper limits for the fields of the published wave packets are estimated. Wave packets formed at the nucleation scale from the observed large-scale fields cannot collapse because they are disrupted before collapse occurs. The published wave packets are quantitatively inconsistent with strong turbulence collapse. Strict constraints exist for more intense wave packets to be able to collapse: E greater than or approximately equals to 1-8 mV/m for scales less than or approximately equal to 100 lambda e. Means for testing these conclusions using Voyager and Ulysses data are suggested.

  17. Probing TRAPPIST-1-like Systems with K2

    Science.gov (United States)

    Demory, Brice-Olivier; Queloz, Didier; Alibert, Yann; Gillen, Ed; Gillon, Michael

    2016-07-01

    The search for small planets orbiting late M dwarfs holds the promise of detecting Earth-size planets for which their atmospheres could be characterized within the next decade. The recent discovery of TRAPPIST-1 entertains hope that these systems are common around hosts located at the bottom of the main sequence. In this Letter, we investigate the ability of the repurposed Kepler mission (K2) to probe planetary systems similar to TRAPPIST-1. We perform a consistent data analysis of 189 spectroscopically confirmed M5.5 to M9 late M dwarfs from Campaigns 1-6 to search for planet candidates and inject transit signals with properties matching TRAPPIST-1b and c. We find no transiting planet candidates across our K2 sample. Our injection tests show that K2 is able to recover both TRAPPIST-1 planets for 10% of the sample only, mainly because of the inefficient throughput at red wavelengths resulting in Poisson-limited performance for these targets. Increasing injected planetary radii to match GJ 1214b’s size yields a recovery rate of 70%. The strength of K2 is its ability to probe a large number of cool hosts across the different campaigns, out of which the recovery rate of 10% may turn into bona fide detections of TRAPPIST-1-like systems within the next two years.

  18. Nanoscale Probing of Electrical Signals in Biological Systems

    Science.gov (United States)

    2012-03-18

    has been studied and utilized for a wide range of applications including electrochromic devices , pH sensing, and neural stimulation. IrOx is...Variations in Bulk Heterojunction Organic Photovoltaic Devices , The Journal of Physical Chemistry C, (11 2011): 0. doi: 10.1021/jp209570h 2012/03...Photovoltaic Devices , Langmuir, (03 2010): . doi: 2010/09/02 16:22:46 9 A. L. Lipson, D. J. Comstock, M. C. Hersam. Nanoporous templates and membranes formed

  19. Limitations to Using Linearized Langmuir Equations

    Science.gov (United States)

    One of the most commonly used models for describing solute sorption to soils is the Langmuir model. Because the Langmuir model is nonlinear, fitting the model to sorption data requires that the model be solved iteratively using an optimization program. To avoid the use of optimization programs, a li...

  20. Optically nonlinear Langmuir Blodgett films

    CERN Document Server

    Amiri, M A

    2003-01-01

    A series of novel amphiphilic molecules plus a new class of chevron-shaped materials, without aliphatic tails, were designed, synthesised and non-centrosymmetrically aligned by the Langmuir-Blodgett technique. Their LB films exhibited optical second-harmonic generation (SHG). The chevron-shaped molecules have a central cationic acceptor and two pi-bridged donor groups with an angle of ca. 120 deg between the charge-transfer axes of the D-pi-(A sup +)-pi-D unit. A monolayer LB film of a representative example, 1-butyl-2,6-bis[2- (4-dibutylaminophenyl)vinyl]pyridinium iodide, has an effective susceptibility, chi sup ( sup 2 sup ) sub e sub f sub f , of 120 pm V sup - sup 1 at 1064 nm, a thickness of 1.16 nm and an area in contact with the substrate of 0.91 nm sup 2 molecule sup - sup 1. The second-harmonic intensity (1.6 x 10 sup - sup 4 versus quartz) is similar to those of the extensively studied conventional amphiphilic hemicyanines but as a result of non-centrosymmetric alignment, without the need for long ...

  1. Gravity Probe B Gyroscope Electrostatic Suspension System (GSS)

    Science.gov (United States)

    Bencze, William; Hipkins, David; Holmes, Tom; Buchman, Saps; Brumley, Robert

    2007-04-01

    Presented here is a hybrid digital/analog electrostatic suspension control system for the Gravity Probe B Relativity Mission's science gyroscopes. The chief challenge for this system is to operate over 8 orders of force magnitude while minimizing classical torques on the gyroscope. A novel, adaptive LQE digital control algorithm was developed to meet the high dynamic range requirements for rotor suspension, while minimizing suspension-induced torques. A set of three backup, all-analog proportional-derivative (PD) controllers were provided to maintain rotor centering in the event of computer faults during all phases of the mission. The capacitive position sensing system measured rotor position to a noise floor of 0.15 nm/Hz in the science band (5 - 30 mHz). In addition, this system also applied controlled torques to perform a post spin-up alignment of the gyroscope spin axes to within 10 arc-sec of a desired orientation, and measured the rotor charge to the 2 pC (2 mV) level. The GSS contributed to drag-free operation of the space vehicle by using one of the gyroscopes as an isolated, inertial proof mass and was able to resolve accelerations to the 10-12 g level. On-orbit performance of this system will be discussed in detail.

  2. Generalized Langmuir Waves in Magnetized Kinetic Plasmas

    Science.gov (United States)

    Willes, A. J.; Cairns, Iver H.

    2000-01-01

    The properties of unmagnetized Langmuir waves and cold plasma magnetoionic waves (x, o, z and whistler) are well known. However, the connections between these modes in a magnetized kinetic plasma have not been explored in detail. Here, wave properties are investigated by numerically solving the dispersion equation derived from the Vlasov equations both with and without a beam instability present. For omega(sub p)>Omega(sub e), it is shown that the generalized Langmuir mode at oblique propagation angles has magnetic z-mode characteristics at low wave numbers and thermal Langmuir mode characteristics at high wave numbers. For omega(sub p)Langmuir mode instead connects to the whistler mode at low wave numbers. The transition from the Langmuir/z mode to the Langmuir/whistler mode near omega(sub p) = Omega(sub e) is rapid. In addition, the effects on wave dispersion and polarization after adding a beam are investigated. Applications of this theory to magnetized Langmuir waves in Earth's foreshock and the solar wind, to waves observed near the plasma frequency in the auroral regions, and to solar type III bursts are discussed.

  3. Optical sensors and their applications for probing biological systems

    DEFF Research Database (Denmark)

    Palanco, Marta Espina

    and mammalian cells. First, we performed Surface Enhanced Raman Spectroscopy (SERS) studies on intact plant materials via using silver plasmonic nanostructures. Our studies showed strong Raman signals which resemble to the presence of typical constituents such as carbohydrates, proteins and lipids of different......There is a great interest in exploring and developing new optical sensitive methodologies for probing complex biological systems. In this project we developed non-invasive and sensitive biosensor strategies for studying physiologically relevant chemical and physical properties of plant...... biological sample to provide a SERS-template where silver nanoparticles can grow, thus providing a new insight into SERS-based sensors for chemically sensing in-situ plant constituents. Optical manipulation techniques have been used to investigate mechanical properties of soft membrane cells, i.e. mammalian...

  4. The Gravity Probe B electrostatic gyroscope suspension system (GSS)

    Science.gov (United States)

    Bencze, W. J.; Brumley, R. W.; Eglington, M. L.; Hipkins, D. N.; Holmes, T. J.; Parkinson, B. W.; Ohshima, Y.; Everitt, C. W. F.

    2015-11-01

    A spaceflight electrostatic suspension system was developed for the Gravity Probe B (GP-B) Relativity Mission’s cryogenic electrostatic vacuum gyroscopes which serve as an indicator of the local inertial frame about Earth. The Gyroscope Suspension System (GSS) regulates the translational position of the gyroscope rotors within their housings, while (1) minimizing classical electrostatic torques on the gyroscope to preserve the instrument’s sensitivity to effects of General Relativity, (2) handling the effects of external forces on the space vehicle, (3) providing a means of precisely aligning the spin axis of the gyroscopes after spin-up, and (4) acting as an accelerometer as part of the spacecraft’s drag-free control system. The flight design was tested using an innovative, precision gyroscope simulator Testbed that could faithfully mimic the behavior of a physical gyroscope under all operational conditions, from ground test to science data collection. Four GSS systems were built, tested, and operated successfully aboard the GP-B spacecraft from launch in 2004 to the end of the mission in 2008.

  5. Langmuir-Blodgett Films of Graphene Derivatives

    DEFF Research Database (Denmark)

    Petersen, Søren Vermehren

    The work presented in this PhD thesis can be divided into two main categories: 1) Syn-thesis and Langmuir-Blodgett assembly of graphene derivatives and 2) Application and characterization of graphene derivatives as an interface material in molecular electron-ics. While the first category could...... be divided further, the synthesis and Langmuir-Blodgett results are intertwined in such a way that it would be more confusing to pre-sent them separately. The Langmuir-Blodgett deposition also played a crucial, but more isolated, part in the investigation of graphene derivatives as interface material...... were investigated using the Langmuir-Blodgett technique. It was found that reduction of graphene oxide back into graphene did not seem possible in solution, while still maintaining its monolayer character. Instead, an alternative route for graphene synthesis was then designed. This involved...

  6. Abegg, Lewis, Langmuir, and the Octet Rule.

    Science.gov (United States)

    Jensen, William B.

    1984-01-01

    Discusses major events leading to the development of the octet rule. Three conclusions based on the work of Mendeleev, Abegg, Thompson, Kossel, Lewis, and Langmuir are considered as is the debate over the rule's validity. (JN)

  7. Quenchant Characterization System Based on Application of Thermal Probes of Typical Steels

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-ting; ZHANG Li-wen; PEI Ji-bin; WANG Fu-gang; YU Cheng-xin

    2004-01-01

    A system was developed to identify characteristics of quenchants. It consists of computerized hardware,temperature acquisition software as well as changeable probes of steels. The feature of the ability to use probes made of any metallic material enables evaluation of hardening power of quenchants. Three thermal couples located on the same cross-section plane in the middle of probe's length give cooling curves that present cooling behavior at different depths from the surface of probe. Microstructure and hardness of the quenched probes on the same plane in the middle of probe's length from surface to center was investigated to estimate hardening effect. A number of quenchants were tested by this characterization system with several thermal probes of typical steels. Experimental data were stored in QuenDB quenchant database, which was designed for quenchants identification and hardness distribution storage.

  8. All-optical photoacoustic imaging system using fiber ultrasound probe and hollow optical fiber bundle.

    Science.gov (United States)

    Miida, Yusuke; Matsuura, Yuji

    2013-09-23

    An all-optical 3D photoacoustic imaging probe that consists of an optical fiber probe for ultrasound detection and a bundle of hollow optical fibers for excitation of photoacoustic waves was developed. The fiber probe for ultrasound is based on a single-mode optical fiber with a thin polymer film attached to the output end surface that works as a Fabry Perot etalon. The input end of the hollow fiber bundle is aligned so that each fiber in the bundle is sequentially excited. A thin and flexible probe can be obtained because the probe system does not have a scanning mechanism at the distal end.

  9. Probing TRAPPIST-1-like systems with K2

    CERN Document Server

    Demory, Brice-Olivier; Alibert, Yann; Gillen, Ed; Gillon, Michael

    2016-01-01

    The search for small planets orbiting late M dwarfs holds the promise of detecting Earth-size planets for which their atmospheres could be characterised within the next decade. The recent discovery of TRAPPIST-1 entertains hope that these systems are common around hosts located at the bottom of the main sequence. In this Letter, we investigate the ability of the repurposed Kepler mission (K2) to probe planetary systems similar to TRAPPIST-1. We perform a consistent data analysis of 189 spectroscopically confirmed M5.5 to M9 late M dwarfs from campaigns 1-6 to search for planet candidates and inject transit signals with properties matching TRAPPIST-1b and c. We find no transiting planet candidates across our K2 sample. Our injection tests show that K2 is able to recover both TRAPPIST-1 planets for 10% of the sample only, mainly because of the inefficient throughput at red wavelengths resulting in Poisson-limited performance for these targets. Increasing injected planetary radii to match GJ1214b's size yields a...

  10. Performance Assessment of a New Variable Stiffness Probing System for Micro-CMMs

    Directory of Open Access Journals (Sweden)

    Khalid Alblalaihid

    2016-04-01

    Full Text Available When designing micro-scale tactile probes, a design trade-off must be made between the stiffness and flexibility of the probing element. The probe must be flexible enough to ensure sensitive parts are not damaged during contact, but it must be stiff enough to overcome attractive surface forces, ensure it is not excessively fragile, easily damaged or sensitive to inertial loads. To address the need for a probing element that is both flexible and stiff, a novel micro-scale tactile probe has been designed and tested that makes use of an active suspension structure. The suspension structure is used to modulate the probe stiffness as required to ensure optimal stiffness conditions for each phase of the measurement process. In this paper, a novel control system is presented that monitors and controls stiffness, allowing two probe stiffness values (“stiff” and “flexible” to be defined and switched between. During switching, the stylus tip undergoes a displacement of approximately 18 µm, however, the control system is able ensure a consistent flexible mode tip deflection to within 12 nm in the vertical axis. The overall uncertainty for three-dimensional displacement measurements using the probing system is estimated to be 58 nm, which demonstrates the potential of this innovative variable stiffness micro-scale probe system.

  11. Development of a novel nanoindentation technique by utilizing a dual-probe AFM system.

    Science.gov (United States)

    Cinar, Eyup; Sahin, Ferat; Yablon, Dalia

    2015-01-01

    A novel instrumentation approach to nanoindentation is described that exhibits improved resolution and depth sensing. The approach is based on a multi-probe scanning probe microscopy (SPM) tool that utilizes tuning-fork based probes for both indentation and depth sensing. Unlike nanoindentation experiments performed with conventional AFM systems using beam-bounce technology, this technique incorporates a second probe system with an ultra-high resolution for depth sensing. The additional second probe measures only the vertical movement of the straight indenter attached to a tuning-fork probe with a high spring constant and it can also be used for AFM scanning to obtain an accurate profiling. Nanoindentation results are demonstrated on silicon, fused silica, and Corning Eagle Glass. The results show that this new approach is viable in terms of accurately characterizing mechanical properties of materials through nanoindentation with high accuracy, and it opens doors to many other exciting applications in the field of nanomechanical characterization.

  12. Development of a novel nanoindentation technique by utilizing a dual-probe AFM system

    Directory of Open Access Journals (Sweden)

    Eyup Cinar

    2015-10-01

    Full Text Available A novel instrumentation approach to nanoindentation is described that exhibits improved resolution and depth sensing. The approach is based on a multi-probe scanning probe microscopy (SPM tool that utilizes tuning-fork based probes for both indentation and depth sensing. Unlike nanoindentation experiments performed with conventional AFM systems using beam-bounce technology, this technique incorporates a second probe system with an ultra-high resolution for depth sensing. The additional second probe measures only the vertical movement of the straight indenter attached to a tuning-fork probe with a high spring constant and it can also be used for AFM scanning to obtain an accurate profiling. Nanoindentation results are demonstrated on silicon, fused silica, and Corning Eagle Glass. The results show that this new approach is viable in terms of accurately characterizing mechanical properties of materials through nanoindentation with high accuracy, and it opens doors to many other exciting applications in the field of nanomechanical characterization.

  13. Development of radially movable multichannel Reynolds stress probe system for a cylindrical laboratory plasma

    Energy Technology Data Exchange (ETDEWEB)

    Nagashima, Yoshihiko; Yamada, Takuma; Takase, Yuichi [GSFS, University of Tokyo, Kashiwa, Chiba 816-8561 (Japan); Inagaki, Shigeru; Kamakaki, Kunihiro; Yagi, Masatoshi; Fujisawa, Akihide; Itoh, Sanae-I. [RIAM, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Arakawa, Hiroyuki; Kawai, Yoshinobu [IGSES, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan); Shinohara, Shunjiro [IE, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Itoh, Kimitaka [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

    2011-03-15

    A new radially movable multichannel azimuthal probe system has been developed for measuring azimuthal and radial profiles of electrostatic Reynolds stress (RS) per mass density of microscale fluctuations for a cylindrical laboratory plasma. The system is composed of 16 probe units arranged azimuthally. Each probe unit has six electrodes to simultaneously measure azimuthal and radial electric fields for obtaining RS. The advantage of the system is that each probe unit is radially movable to measure azimuthal RS profiles at arbitrary radial locations as well as two-dimensional structures of fluctuations. The first result from temporal observation of fluctuation azimuthal profile presents that a low-frequency fluctuation (1-2 kHz) synchronizes oscillating Reynolds stress. In addition, radial scanning of the probe system simultaneously demonstrates two-dimensional patterns of mode structure and nonlinear forces with frequency f= 1.5 kHz and azimuthal mode number m= 1.

  14. Suprathermal Solar Wind Electrons and Langmuir Turbulence

    Science.gov (United States)

    Kim, Sunjung; Yoon, Peter H.; Choe, G. S.; moon, Y.-J.

    2016-09-01

    The steady-state model recently put forth for the solar wind electron velocity distribution function during quiet time conditions, was originally composed of three population electrons (core, halo, and superhalo) with the core remaining nonresonant with any plasma waves while the halo and superhalo separately maintained steady-state resonance with whistler- and Langmuir-frequency range fluctuations, respectively. However, a recent paper demonstrates that whistler-range fluctuations in fact have no significant contribution. The present paper represents a consummation of the model in that a self-consistent model of the suprathermal electron population, which encompasses both the halo and the superhalo, is constructed solely on the basis of the Langmuir fluctuation spectrum. Numerical solutions to steady-state particle and wave kinetic equations are obtained on the basis of an initial trial electron distribution and Langmuir wave spectrum. Such a finding offers a self-consistent explanation for the observed steady-state electron distribution in the solar wind.

  15. Extended oil spill spreading with Langmuir circulation.

    Science.gov (United States)

    Simecek-Beatty, Debra; Lehr, William J

    2017-09-15

    When spilled in the ocean, most crude oils quickly spread into a thin film that ruptures into smaller slicks distributed over a larger area. Observers have also reported the film tearing apart into streaks that eventually merge forming fewer but longer bands of floating oil. Understanding this process is important to model oil spill transport. First, slick area is calculated using a spreading model. Next, Langmuir circulation models are used to approximate the merging of oiled bands. Calculations are performed on Troll blended and Alaska North Slope crude oils and results compared with measurements from the 1990s North Sea field experiments. Langmuir circulation increases the oil area but decreases the surface coverage of oil. This work modifies existing oil spreading formulas by providing a surface area correction due to the effects of Langmuir circulation. The model's simplicity is advantageous in situations with limited data, such as emergency oil spill response. Published by Elsevier Ltd.

  16. Epidemic Intelligence. Langmuir and the Birth of Disease Surveillance

    Directory of Open Access Journals (Sweden)

    Lyle Fearnley

    2010-12-01

    Full Text Available In the wake of the SARS and influenza epidemics of the past decade, one public health solution has become a refrain: surveillance systems for detection of disease outbreaks. This paper is an effort to understand how disease surveillance for outbreak detection gained such paramount rationality in contemporary public health. The epidemiologist Alexander Langmuir is well known as the creator of modern disease surveillance. But less well known is how he imagined disease surveillance as one part of what he called “epidemic intelligence.” Langmuir developed the practice of disease surveillance during an unprecedented moment in which the threat of biological warfare brought civil defense experts and epidemiologists together around a common problem. In this paper, I describe how Langmuir navigated this world, experimenting with new techniques and rationales of epidemic control. Ultimately, I argue, Langmuir′s experiments resulted in a set of techniques and infrastructures – a system of epidemic intelligence – that transformed the epidemic as an object of human art.

  17. Development of ion diagnostic system based on electrostatic probe in the boundary plasma of the JFT-2M tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Uehara, Kazuya; Kawakami, Tomohide [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Amemiya, Hiroshi; Hoethker, K.; Cosler, A.; Bieger, W.

    1995-06-01

    An ion diagnostic system using electrostatic probes for measurements in the JFT-2M tokamak boundary plasma has been developed under the collaboration program between KFA and JAERI. The rotating double probe system, on which the Hoethker double probe and Amemiya asymmetric probe can mounted, are manufactured at KFA workshop while the linear driver to support the rotating double probe, the ion toothbrush probe, the Katsumata probe and the cubic Mach probe are developed at JAERI. This report describes the hardware of this probe system for ion diagnostics in the boundary plasma and preliminary data obtained by means of this system. Furthermore, results on the transport are estimated on the basis of these probe data. (author).

  18. Langmuir and Langmuir-Blodgett films of multifunctional, amphiphilic polyethers with cholesterol moieties.

    Science.gov (United States)

    Reuter, Sascha; Hofmann, Anna M; Busse, Karsten; Frey, Holger; Kressler, Jörg

    2011-03-01

    Langmuir films of multifunctional, hydrophilic polyethers containing a hydrophobic cholesterol group (Ch) were studied by surface pressure-mean molecular area (π-mmA) measurements and Brewster angle microscopy (BAM). The polyethers were either homopolymers or diblock copolymers of linear poly(glycerol) (lPG), linear poly(glyceryl glycidyl ether) (lPGG), linear poly(ethylene glycol) (lPEG), or hyperbranched poly(glycerol) (hbPG). Surface pressure measurements revealed that the homopolymers lPG and hbPG did not stay at the water surface after spreading and solvent evaporation, in contrast to lPEG. Because of the incorporation of the Ch group in the polymer structure, stable Langmuir films were formed by Ch-lPG(n), Ch-lPGG(n), and Ch-hbPG(n). The Ch-hbPG(n), Ch-lPEG(n), Ch-lPEG(n)-b-lPG(m), Ch-lPEG(n)-b-lPGG(m), and Ch-lPEG(n)-b-hbPG(m) systems showed an extended plateau region assigned to a phase transition involving the Ch groups. Typical hierarchically ordered morphologies of the LB films on hydrophilic substrates were observed for all Ch-initiated polymers. All LB films showed that Ch of the Ch-initiated homopolymers is able to crystallize. This strong tendency of self-aggregation then triggers further dewetting effects of the respective polyether entities. Fingerlike morphologies are observed for Ch-lPEG(69), since the lPEG(69) entity is able to undergo crystallization after transfer onto the silicon substrate.

  19. Acceleration of Flare Protons by Langmuir Plasmons

    Institute of Scientific and Technical Information of China (English)

    李晓卿; 张航

    2002-01-01

    We analytically study the turbulent acceleration of solar protons by strong Langmuir plasmons in Cerenkov processes. It is shown that among the wave spectra with self-retained source only the Pelletier spectrum (Wk ∝ k-7/2) can result in the energy spectrum of non-relativistic protons, which gives a good fit to that observed from solarflare events. It is quite possible that strong Langmuir turbulence presents in coronal active region, with three-dimensional, isotropic and stationary spectrum proportional to k-7/2, and is responsible for the acceleration offlare protons.

  20. Langmuir wave filamentation in the kinetic regime

    CERN Document Server

    Silantyev, Denis A; Rose, Harvey A

    2016-01-01

    Nonlinear Langmuir wave in the kinetic regime $k\\lambda_D\\gtrsim0.2$ has a transverse instability, where $k$ is the wavenumber and $\\lambda_D$ is the Debye length. The nonlinear stage of that instability development leads to the filamentation of Langmuir waves. Here we study the linear stage of transverse instability of both Bernstein-Greene-Kruskal (BGK) modes and dynamically prepared BGK-like initial conditions to find the same instability growth rate suggesting the universal mechanism for the kinetic saturation of stimulated Raman scatter in laser-plasma interaction experiments. Multidimensional Vlasov simulations results are compared to the theoretical predictions.

  1. Langmuir films of petroleum at the air-water interface.

    Science.gov (United States)

    Vieira, Vinícius C C; Severino, Divinomar; Oliveira, Osvaldo N; Pavinatto, Felippe J; Zaniquelli, Maria E D; Ramos, Ana Paula; Baptista, Maurício S

    2009-11-03

    Understanding the behavior of petroleum films at the air/water interface is crucial for dealing with oil slicks and reducing the damages to the environment, which has normally been attempted with studies of Langmuir films made of fractions of petroleum. However, the properties of films from whole petroleum samples may differ considerably from those of individual fractions. Using surface pressure and surface potential measurements and Brewster angle and fluorescence microscopy, we show that petroleum forms a nonhomogeneous Langmuir film at the air-water interface. The surface pressure isotherms for petroleum Langmuir films exhibit gas (G), liquid-expanded (LE), and liquid-condensed phases, with almost no hysteresis in the compression-decompression cycles. Domains formed upon compression from the G to the LE phase were accompanied by an increase in fluorescence intensity with excitation at 400-440 nm owing to an increase in the surface density of the chromophores in the petroleum film. The surface pressure and the fluorescence microscopy data pointed to self-assembling domains into a pseudophase in thermodynamic equilibrium with other less emitting petroleum components. This hypothesis was supported by Brewster angle microscopy images, whereby the appearance of water domains even at high surface pressures confirms the tendency of petroleum to stabilize emulsion systems. The results presented here suggest that, for understanding the interaction with water, it may be more appropriate to use the whole petroleum samples rather than its fractions.

  2. Langmuir mixing effects on global climate: WAVEWATCH III in CESM

    Science.gov (United States)

    Li, Qing; Webb, Adrean; Fox-Kemper, Baylor; Craig, Anthony; Danabasoglu, Gokhan; Large, William G.; Vertenstein, Mariana

    2016-07-01

    Large-Eddy Simulations (LES) have shown the effects of ocean surface gravity waves in enhancing the ocean boundary layer mixing through Langmuir turbulence. Neglecting this Langmuir mixing process may contribute to the common shallow bias in mixed layer depth in regions of the Southern Ocean and the Northern Atlantic in most state-of-the-art climate models. In this study, a third generation wave model, WAVEWATCH III, has been incorporated as a component of the Community Earth System Model, version 1.2 (CESM1.2). In particular, the wave model is now coupled with the ocean model through a modified version of the K-Profile Parameterization (KPP) to approximate the influence of Langmuir mixing. Unlike past studies, the wind-wave misalignment and the effects of Stokes drift penetration depth are considered through empirical scalings based on the rate of mixing in LES. Wave-Ocean only experiments show substantial improvements in the shallow biases of mixed layer depth in the Southern Ocean. Ventilation is enhanced and low concentration biases of pCFC-11 are reduced in the Southern Hemisphere. A majority of the improvements persist in the presence of other climate feedbacks in the fully coupled experiments. In addition, warming of the subsurface water over the majority of global ocean is observed in the fully coupled experiments with waves, and the cold subsurface ocean temperature biases are reduced.

  3. Thermal behavior of H-aggregate in a mixed Langmuir-Blodgett film of merocyanine dye, arachidic acid, and n-octadecane ternary system investigated by UV-visible and IR absorption spectroscopy.

    Science.gov (United States)

    Hirano, Yoshiaki; Tateno, Shinsuke; Yamashita, Yoshihide; Ozaki, Yukihiro

    2008-11-13

    We have investigated the thermal behavior of H-aggregate in a mixed Langmuir-Blodgett (LB) film of the merocyanine dye (MS18)-arachidic acid (C20)- n-octadecane (AL18) ternary system by means of UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR spectra indicate that the temperature-dependent variation in MS 18 aggregation state is linked not only with the degree of intramolecular charge transfer and the behavior of packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain but also with the presence and absence of AL18. The H-aggregate dissociates from 25 up to 50 degrees C, which is caused by the AL18 evaporation from the mixed LB film and the increment of thermal mobility of the MS18 hydrocarbon chain. From 110 to 160 degrees C, blue-shifted bands, attributed to the oligomeric MS18 aggregation, appear near 515 nm in the MS18-C 20-AL18 ternary system as well. The temperature at which the 515 nm band occurs is identical for both present ternary system and previously investigated MS18-deuterated arachidic acid (C20- d) binary system, and it is in good agreement with the melting point (110 degrees C) of cadmium arachidate (CdC20). Therefore, it is indicated that the driving force which induces the 515 nm band comes from the melting phenomenon of CdC20 molecules which are phase-separated from MS 18 molecules in as-deposited LB films.

  4. Langmuir and Langmuir-Blodgett films of a maleic anhydride derivative: effect of subphase divalent cations.

    Science.gov (United States)

    Martín-García, B; Velázquez, M Mercedes; Pérez-Hernández, J A; Hernández-Toro, J

    2010-09-21

    We report the study of the equilibrium and dynamic properties of Langmuir monolayers of poly(styrene-co-maleic anhydride) partial 2-buthoxyethyl ester cumene terminated polymer and the effect of the Mg(NO(3))(2) addition in the water subphase on the film properties. Results show that the polymer monolayer becomes more expanded when the electrolyte concentration in the subphase increases. Dense polymer films aggregate at the interface. The aggregates are transferred onto silicon wafers using the Langmuir-Blodgett methodology and the morphology is observed by AFM. The structure of aggregates depends on the subphase composition of the Langmuir film transferred onto the silicon wafer.

  5. Single Camera 3-D Coordinate Measuring System Based on Optical Probe Imaging

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new vision coordinate measuring system——single camera 3-D coordinate measuring system based on optical probe imaging is presented. A new idea in vision coordinate measurement is proposed. A linear model is deduced which can distinguish six freedom degrees of optical probe to realize coordinate measurement of the object surface. The effects of some factors on the resolution of the system are analyzed. The simulating experiments have shown that the system model is available.

  6. Surgical guidance system using hand-held probe with accompanying positron coincidence detector

    Energy Technology Data Exchange (ETDEWEB)

    Majewski, Stanislaw; Weisenberger, Andrew G.

    2017-10-10

    A surgical guidance system offering different levels of imaging capability while maintaining the same hand-held convenient small size of light-weight intra-operative probes. The surgical guidance system includes a second detector, typically an imager, located behind the area of surgical interest to form a coincidence guidance system with the hand-held probe. This approach is focused on the detection of positron emitting biomarkers with gamma rays accompanying positron emissions from the radiolabeled nuclei.

  7. THz radiation by beating Langmuir waves

    CERN Document Server

    Son, S; Park, J Y

    2013-01-01

    An intense terahertz (THz) radiation generated by the beating of two Langmuir waves, which are excited by the forward Raman scattering, is analyzed theoretically. The radiation energy per shot can be as high as 0.1 J, with the duration of 10 pico-second. Appropriate plasma density and the laser characteristics are examined.

  8. Observations of Langmuir Circulation From FLIP

    Science.gov (United States)

    Smith, J. A.

    2002-12-01

    Langmuir circulation has significance across the marine disciplines. Enhanced deepening and inhibited re-stratification can alter the surface temperature and hence net air-sea exchanges. Organization of bubbles into windrows introduces dramatic sound speed variability and also affects air/sea gas fluxes. Organization of seaweed and plankton affects marine life, including pelagic fisheries. Finally, dispersal by Langmuir circulation is a major component in models for oil-spill tracking and for search-and-rescue operations. To get an adequate picture of the forcing and response of Langmuir circulation (and the wind-mixed layer in general), the observations needed include windstress, directional waves, wave breaking, heat and moisture fluxes, stratification (temperature and salinity profiles), velocity profiles across the mixed layer and thermocline, spacing and orientation of windrows, and a measure of the strength of the circulation (e.g., surface rms velocities). These measurements span both the air/sea interface and the thermocline, and must be maintained continuously for many days to span storms and daily, tidal, and inertial cycles. In addition, the total power requirements exceed that comfortably supplied by batteries or local generation by wind or solar energy. It appears that FLIP is uniquely qualified as a platform from which the required range of measurements may all be made. Findings concerning the evolution and dynamics of Langmuir circulation that were facilitated by FLIP are reviewed and summarized, with emphasis on observations from 1990, 1995, and 2002.

  9. Langmuir Turbulence: Proposal for a Closure

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Espedal, M. S.; Pécseli, Hans

    1986-01-01

    The Wigner formalism is applied to the standard equations for weakly nonlinear Langmuire waves. On the basis of this formulation, a closed set of equations is obtained to describe the statistical evolution of the average field intensity and the intensity correlation function. The analysis allows...

  10. Mode of interaction of ganglioside Langmuir monolayer originated from echinoderms: three binary systems of ganglioside/DPPC, ganglioside/DMPE, and ganglioside/cholesterol.

    Science.gov (United States)

    Hoda, Kazuki; Ikeda, Yuriko; Kawasaki, Hideya; Yamada, Koji; Higuchi, Ryuichi; Shibata, Osamu

    2006-09-01

    The surface pressure (pi)-area (A), the surface potential (DeltaV)-A, and the dipole moment (mu( perpendicular))-A isotherms were obtained for monolayers made from a ganglioside originated from echinoderms [Diadema setosum ganglioside (DSG-1)], dipalmitoylphosphatidylcholine (DPPC), dimyristoylphosphatidylethanolamine (DMPE), cholesterol (Ch), and their combinations. Monolayers spread on several different substrates were investigated at the air/water interface by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM) and atomic force microscopy (AFM). Surface potentials (DeltaV) of pure components were analyzed using the three-layer model proposed by Demchak and Fort [R.J. Demchak, T. Fort, J. Colloid Interface Sci. 46 (1974) 191-202]. The new finding was that DSG-1 was stable and showed a liquid-expanded film and that its monolayer behavior of DeltaV was sensitive for the change of the NaCl concentration in the subphase. Moreover, the miscibility of DSG-1 and three major lipids in the two-component monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the DSG-1 molar fraction (X(DSG-1)), using the additivity rule. From the A-X(DSG-1) and DeltaV(m)-X(DSG-1) plots, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined at the discrete surface pressure. The PMA and APSP with the mole fraction were extensively discussed for the miscible system. The miscibility was also investigated from the two-dimensional phase diagrams. Furthermore, a regular surface mixture, for which the Joos equation was used for the analysis of the collapse pressure of two-component monolayers, allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltavarepsilon) between them. The observations using fluorescence microscopy and AFM image also provide us the miscibility in the monolayer state.

  11. Miniaturized In Situ Atmospheric Probe Sampling Inlet System for Uranus or Saturn Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thorleaf Research, Inc. proposes to develop a miniaturized in situ atmospheric probe sampling inlet system for measuring chemical and isotopic composition of the...

  12. Miniaturized, Low Power Cryogenic Inlet System with Sampling Probes for Titan Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thorleaf Research, Inc. proposes to develop a miniature, low power cryogenic inlet system with sampling probes for Titan. This addresses a key technology gap for...

  13. The fast reciprocating magnetic probe system on the J-TEXT tokamak

    Science.gov (United States)

    Li, Fuming; Chen, Zhipeng; Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-01

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  14. Development of simple designs of multitip probe diagnostic systems for RF plasma characterization.

    Science.gov (United States)

    Naz, M Y; Shukrullah, S; Ghaffar, A; Rehman, N U

    2014-01-01

    Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures.

  15. Development of Simple Designs of Multitip Probe Diagnostic Systems for RF Plasma Characterization

    Directory of Open Access Journals (Sweden)

    M. Y. Naz

    2014-01-01

    Full Text Available Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP generated by a 13.56 MHz radio frequency (RF source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures.

  16. Sounding-Rocket Studies of Langmuir-Wave Microphysics in the Auroral Ionosphere

    Science.gov (United States)

    Dombrowski, Micah P.

    agreement with expected signatures of beating between pure, field-aligned, linearly polarized Langmuir waves and obliquely propagating, elliptically polarized, hybrid whistler-Langmuir waves. Finally, an autonomous digital signal processor/receiver has been refined and augmented to achieve high time- and frequency-resolution radio observations, synchronized sampling between multiple receivers, and on-board processing of data. This system was deployed on the CHARM-II rocket, resulting in measurements of the polarization of fine structures in auroral roar emissions.

  17. Langmuir-Blodgett Films of Graphene Derivatives

    DEFF Research Database (Denmark)

    Petersen, Søren Vermehren

    . Solution processable graphene in the form of chemically derived graphene has been synthesized through the modified Hummers method with subsequent reduction into reduced graphene oxide with hydrazine. The completeness of oxidation, the effect of the refinement steps and the reduction of the graphene oxide...... were investigated using the Langmuir-Blodgett technique. It was found that reduction of graphene oxide back into graphene did not seem possible in solution, while still maintaining its monolayer character. Instead, an alternative route for graphene synthesis was then designed. This involved...... immobilization of the monolayered graphene oxide via the Langmuir-Blodgett deposition technique prior to a three step reduction scheme involving hydrazine reduc-tion, sulfuric acid de-oxygenation, and thermal annealing. This method resulted in wrin-kle-free reduced graphene oxide with a negligible oxygen content...

  18. Collapse of Langmuir solitons in inhomogeneous plasmas

    CERN Document Server

    Chen, Y A; Nishida, Y; Cheng, C Z

    2016-01-01

    Propagation of Langmuir solitons in inhomogeneous plasmas is investigated numerically. Through numerical simulation solving Zakharov equations, the solitons are accelerated toward the low density side. As a consequence, isolated cavities moving at ion sound velocities are emitted. When the acceleration is further increased, solitons collapse and the cavities separate into two lumps released at ion sound velocities. The threshold is estimated by an analogy between the soliton and a particle overcoming the self-generated potential well.

  19. Langmuir-Blodgett films - From micron to angstrom

    Science.gov (United States)

    Bourdieu, L.; Silberzan, P.; Chatenay, D.

    1991-10-01

    Combining optical microscopy and atomic force microscopy, a complete characterization of Langmuir-Blodgett bilayers made of arachidic acid has been performed. At macroscopic scales, both techniques can be used to control the homogeneity of the transferred films. By atomic force microscopy, roughness and thickness of the bilayers could be determined. These are compatible with a normal orientation of the fully extended aliphatic chains with respect to the substrate. Molecular-resolution images give the first direct experimental evidence for the presence of pairs of dislocations in those systems.

  20. Compact probing system using remote imaging for industrial plant maintenance

    Science.gov (United States)

    Ito, F.; Nishimura, A.

    2014-03-01

    Laser induced breakdown spectroscopy (LIBS) and endoscope observation were combined to design a remote probing device. We use this probing device to inspect a crack of the inner wall of the heat exchanger. Crack inspection requires speed at first, and then it requires accuracy. Once Eddy Current Testing (ECT) finds a crack with a certain signal level, another method should confirm it visually. We are proposing Magnetic particle Testing (MT) using specially fabricated the Magnetic Particle Micro Capsule (MPMC). For LIBS, a multichannel spectrometer and a Q-switch YAG laser were used. Irradiation area is 270 μm, and the pulse energy was 2 mJ. This pulse energy corresponds to 5-2.2 MW/cm2. A composite-type optical fiber was used to deliver both laser energy and optical image. Samples were prepared to heat a zirconium alloy plate by underwater arc welding in order to demonstrate severe accidents of nuclear power plants. A black oxide layer covered the weld surface and white particles floated on water surface. Laser induced breakdown plasma emission was taken into the spectroscope using this optical fiber combined with telescopic optics. As a result, we were able to simultaneously perform spectroscopic measurement and observation. For MT, the MPMC which gathered in the defective area is observed with this fiber. The MPMC emits light by the illumination of UV light from this optical fiber. The size of a defect is estimated with this amount of emission. Such technology will be useful for inspection repair of reactor pipe.

  1. Bulk organisation and alignment in Langmuir and Langmuir-Blodgett films of tetrachloroperylene tetracarboxylic acid esters

    Science.gov (United States)

    Modlińska, Anna; Filipowicz, Marek; Martyński, Tomasz

    2016-12-01

    Perylene derivatives with chlorine atoms attached at the bay position to the dye core are expected to affect organisation and tendency to aggregation in Langmuir and Langmuir-Blodgett (LB) films. Therefore, newly synthesized core-twisted homologous series of tetrachloroperylene tetracarboxylic acid esters with n = 1,4,5,6,9 carbon atoms in terminal alkyl chains were studied. Phase transitions and crystalline structures were specified by differential scanning calorimetry (DSC) and single crystal X-ray diffraction (XRD), respectively. Intermolecular interactions and organisation of the dyes in monomolecular films were investigated by means of Brewster angle microscope (BAM), UV-Vis absorption and emission spectroscopy, fluorescence microscopy and atomic force microscopy (AFM). The dyes investigated do not form thermotropic mesogenic phases in bulk. The crystalline triclinic elementary cell with P-1 symmetry is revealed from X-ray experiments. In Langmuir and Langmuir-Blodgett films molecular tilted head-on alignment is postulated. Spectroscopic research confirmed by AFM texture images of the LB films show that in the Langmuir and LB films the dyes, depending on length of terminal chains, have a tendency to create H or I molecular aggregates. The impact of the twisted core on the molecular behavior in a bulk and thin films is discussed.

  2. Langmuir wave electric fields induced by electron beams in the heliosphere

    Science.gov (United States)

    Reid, Hamish A. S.; Kontar, Eduard P.

    2017-01-01

    Solar electron beams responsible for type III radio emission generate Langmuir waves as they propagate out from the Sun. The Langmuir waves are observed via in situ electric field measurements. These Langmuir waves are not smoothly distributed but occur in discrete clumps, commonly attributed to the turbulent nature of the solar wind electron density. Exactly how the density turbulence modulates the Langmuir wave electric fields is understood only qualitatively. Using weak turbulence simulations, we investigate how solar wind density turbulence changes the probability distribution functions, mean value and variance of the beam-driven electric field distributions. Simulations show rather complicated forms of the distribution that are dependent upon how the electric fields are sampled. Generally the higher magnitude of density fluctuations reduce the mean and increase the variance of the distribution in a consistent manor to the predictions from resonance broadening by density fluctuations. We also demonstrate how the properties of the electric field distribution should vary radially from the Sun to the Earth and provide a numerical prediction for the in situ measurements of the upcoming Solar Orbiter and Solar Probe Plus spacecraft.

  3. Resolution enhancement of scanning four-point-probe measurements on two-dimensional systems

    DEFF Research Database (Denmark)

    Hansen, Torben Mikael; Stokbro, Kurt; Hansen, Ole;

    2003-01-01

    A method to improve the resolution of four-point-probe measurements of two-dimensional (2D) and quasi-2D systems is presented. By mapping the conductance on a dense grid around a target area and postprocessing the data, the resolution can be improved by a factor of approximately 50 to better than 1....../15 of the four-point-probe electrode spacing. The real conductance sheet is simulated by a grid of discrete resistances, which is optimized by means of a standard optimization algorithm, until the simulated voltage-to-current ratios converges with the measurement. The method has been tested against simulated...... data as well as real measurements and is found to successfully deconvolute the four-point-probe measurements. In conjunction with a newly developed scanning four-point probe with electrode spacing of 1.1 µm, the method can resolve the conductivity with submicron resolution. ©2003 American Institute...

  4. Monte Carlo studies of model Langmuir monolayers.

    Science.gov (United States)

    Opps, S B; Yang, B; Gray, C G; Sullivan, D E

    2001-04-01

    This paper examines some of the basic properties of a model Langmuir monolayer, consisting of surfactant molecules deposited onto a water subphase. The surfactants are modeled as rigid rods composed of a head and tail segment of diameters sigma(hh) and sigma(tt), respectively. The tails consist of n(t) approximately 4-7 effective monomers representing methylene groups. These rigid rods interact via site-site Lennard-Jones potentials with different interaction parameters for the tail-tail, head-tail, and head-head interactions. In a previous paper, we studied the ground-state properties of this system using a Landau approach. In the present paper, Monte Carlo simulations were performed in the canonical ensemble to elucidate the finite-temperature behavior of this system. Simulation techniques, incorporating a system of dynamic filters, allow us to decrease CPU time with negligible statistical error. This paper focuses on several of the key parameters, such as density, head-tail diameter mismatch, and chain length, responsible for driving transitions from uniformly tilted to untilted phases and between different tilt-ordered phases. Upon varying the density of the system, with sigma(hh)=sigma(tt), we observe a transition from a tilted (NNN)-condensed phase to an untilted-liquid phase and, upon comparison with recent experiments with fatty acid-alcohol and fatty acid-ester mixtures [M. C. Shih, M. K. Durbin, A. Malik, P. Zschack, and P. Dutta, J. Chem. Phys. 101, 9132 (1994); E. Teer, C. M. Knobler, C. Lautz, S. Wurlitzer, J. Kildae, and T. M. Fischer, J. Chem. Phys. 106, 1913 (1997)], we identify this as the L'(2)/Ov-L1 phase boundary. By varying the head-tail diameter ratio, we observe a decrease in T(c) with increasing mismatch. However, as the chain length was increased we observed that the transition temperatures increased and differences in T(c) due to head-tail diameter mismatch were diminished. In most of the present research, the water was treated as a hard

  5. A Probe into Reform of Rural Homestead Acquisition System

    Institute of Scientific and Technical Information of China (English)

    Jun; TAN

    2013-01-01

    Using the methods of literature research,normative analysis,and empirical analysis,this study is intended to analyze the acquisition system of homestead in rural area of China.By adopting questionnaire survey and face-to-face interview,this study explores the problems of current homestead acquisition system and the dilemma of homestead management.The results indicate that homestead acquisition reform is the key aspect to the homestead management system reform.A new homestead acquisition system,which includes primitive acquisition,inheritance acquisition,and supporting system,is suggested in this study.The findings of this study will provide important policy implications for rural homestead system reform.The new homestead acquisition system could guarantee the farmers’property right and help improve social justice and rational utilization of nature resources.

  6. Probe Storage

    NARCIS (Netherlands)

    Gemelli, Marcellino; Abelmann, Leon; Engelen, Johan B.C.; Khatib, Mohammed G.; Koelmans, Wabe W.; Zaboronski, Olog; Campardo, Giovanni; Tiziani, Federico; Laculo, Massimo

    2011-01-01

    This chapter gives an overview of probe-based data storage research over the last three decades, encompassing all aspects of a probe recording system. Following the division found in all mechanically addressed storage systems, the different subsystems (media, read/write heads, positioning, data chan

  7. Effects of Buoyancy on Langmuir Circulation

    Institute of Scientific and Technical Information of China (English)

    SONG Jun; SONG Jin-Bao

    2008-01-01

    Based on the Navier-Stokes equation,an equation describing the Langmuir circulation is derived by a perturbation method when the influences of Coriolis force and buoyancy force are both considered.The approach used in the analysis is similar to the works carried out by Craik and Leibovich[J.Fluid Mech.73 (1976)401],Leibovich [J.Fluid Mech.79 (1977) 715]and Huang[J.Fluid Mech.91 (1979) 191].Potential applications of the equation proposed are discussed in the area of Antarctic circumpolar current.

  8. Strong Langmuir turbulence in Kappa distributed plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Liu Sanqiu [Department of Physics and School of Materials Science and Engineering, Nanchang University, Nanchang, 330047 (China); Chen Hui [School of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China)

    2012-01-15

    Superthermal electrons are often observed in space and astrophysics and can be appropriate modeled by the family of Kappa distribution functions. Taking the nonlinear wave-wave, wave-particle interactions and the effect of superthermal electrons into account, the strong Langmuir turbulence is investigated in kinetic regime. The modified Zakharov equations are obtained for the case of no damping or driving terms. On the basis of these equations, dynamics of collapse have been studied by the means of the general virial theorem, and the collapse thresholds which are strong modified by superthermal index {kappa}{sub e} are given.

  9. Polarization of Hemicyanine Langmuir-Blodgett Films

    Institute of Scientific and Technical Information of China (English)

    LI Shu-Hong; MU Jian; WANG Wen-Jun; MA Shi-Hong; SUN Jing-Lan; CHU Jun-Hao; WANG Wen-Cheng

    2004-01-01

    @@ The polarization dependence of electric field for hemicyanine layers deposited by the Langmuir-Blodgett (LB)technique has been measured. The experimental results show that ferroelectricity exists not only in thick films(200nm) but also in thinner films (30nm), and the remnant polarization is related to film thickness. In order to interpret the measured results, a planar rotor model was introduced, and a relation between polarization and film thickness was obtained by perturbation theory. The theory fitting agrees with experimental results well. It is confirmed that ferroelectricity in organic molecular LB films mainly arose from altering of molecular orientation.

  10. Automated measurement system employing eddy currents to adjust probe position and determine metal hardness

    Science.gov (United States)

    Prince, James M.; Dodson, Michael G.; Lechelt, Wayne M.

    1989-01-01

    A system for measuring the hardness of cartridge cases employs an eddy current probe for inducing and sensing eddy currents in each cartridge case. A first component of the sensed signal is utilized in a closed loop system for accurately positioning the probe relative to the cartridge case both in the lift off direction and in the tangential direction, and a second component of the sensed signal is employed as a measure of the hardness. The positioning and measurement are carried out under closed loop microprocessor control facilitating hardness testing on a production line basis.

  11. Automatically Tuned Probe Head System for Pulsed NQR Spectroscopy in Extreme Thermodynamic Conditions

    Science.gov (United States)

    Ostafin, Michał; Maćkowiak, Mariusz; Bojarski, Marek

    1994-02-01

    A complete N Q R probe-head system operating in the frequency ranges 0.5 -150 and 150- 300 MHz is described. The head is particularly suited for NQR experiments carried out at a remote location, for example in a low-temperature cryostat or high-pressure chamber. Moreover, the head system includes a microprocessor-controller for automated tuning of the probe to the operating frequency of the associated NQR spectrometer. The controller can be easily interfaced to a PC via standard serial port.

  12. Probing other solar systems with current and future adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Macintosh, B; Marois, C; Phillion, D; Poyneer, L; Graham, J; Zuckerman, B; Gavel, D; Veran, J; Wilhelmsen-Evans, J; Mellis, C

    2008-09-08

    Over the past decade, the study of extrasolar planets through indirect techniques--primarily Doppler measurements--has revolutionized our understanding of other solar systems. The next major step in this field will be the direct detection and characterization, via imaging and spectroscopy, of the planets themselves. To achieve this, we must separate the light from the faint planet from the extensive glare of its parent star. We pursued this goal using the current generation of adaptive optics (AO) systems on large ground-based telescopes, using infrared imaging to search for the thermal emission from young planets and developing image processing techniques to distinguish planets from telescope-induced artifacts. Our new Angular Differential Imaging (ADI) technique, which uses the sidereal rotation of the Earth and telescope, is now standard for ground-based high-contrast imaging. Although no young planets were found in our surveys, we placed the strongest limits yet on giant planets in wide orbits (>30 AU) around young stars and characterized planetary companion candidates. The imaging of planetary companions on solar-system-like scales (5-30 AU) will require a new generation of advanced AO systems that are an order of magnitude more powerful than the LLNL-built Keck AO system. We worked to develop and test the key technologies needed for these systems, including a spatially-filtered wavefront sensor, efficient and accurate wavefront reconstruction algorithms, and precision AO wavefront control at the sub-nm level. LLNL has now been selected by the Gemini Observatory to lead the construction of the Gemini Planet Imager, a $24M instrument that will be the most advanced AO system in the world.

  13. Probing other solar systems with current and future adaptive optics

    Energy Technology Data Exchange (ETDEWEB)

    Macintosh, B; Marois, C; Phillion, D; Poyneer, L; Graham, J; Zuckerman, B; Gavel, D; Veran, J; Wilhelmsen-Evans, J; Mellis, C

    2008-09-08

    Over the past decade, the study of extrasolar planets through indirect techniques--primarily Doppler measurements--has revolutionized our understanding of other solar systems. The next major step in this field will be the direct detection and characterization, via imaging and spectroscopy, of the planets themselves. To achieve this, we must separate the light from the faint planet from the extensive glare of its parent star. We pursued this goal using the current generation of adaptive optics (AO) systems on large ground-based telescopes, using infrared imaging to search for the thermal emission from young planets and developing image processing techniques to distinguish planets from telescope-induced artifacts. Our new Angular Differential Imaging (ADI) technique, which uses the sidereal rotation of the Earth and telescope, is now standard for ground-based high-contrast imaging. Although no young planets were found in our surveys, we placed the strongest limits yet on giant planets in wide orbits (>30 AU) around young stars and characterized planetary companion candidates. The imaging of planetary companions on solar-system-like scales (5-30 AU) will require a new generation of advanced AO systems that are an order of magnitude more powerful than the LLNL-built Keck AO system. We worked to develop and test the key technologies needed for these systems, including a spatially-filtered wavefront sensor, efficient and accurate wavefront reconstruction algorithms, and precision AO wavefront control at the sub-nm level. LLNL has now been selected by the Gemini Observatory to lead the construction of the Gemini Planet Imager, a $24M instrument that will be the most advanced AO system in the world.

  14. Langmuir and Langmuir-Blodgett films of hybrid amphiphiles with a polyoxometalate headgroup.

    Science.gov (United States)

    Wang, Xiao-Le; Wang, Yong-Liang; Miao, Wen-Ke; Hu, Min-Biao; Tang, Jing; Yu, Wei; Hou, Zhan-Yao; Zheng, Ping; Wang, Wei

    2013-06-04

    A hybrid was at first synthesized by a postfunctionalization of an aminomethane trisalkoxo-functionalized Anderson-type polyoxometalate (POM) encapsulated by three tetrabutylammonium ions using a 3,5-bis(tetradecyloxy)benzoic acid by amidation. Then the three TBA(+) counter cations were programmatically replaced by protons (H(+)) following a molecule-to-amphiphile conversion. In this way one hybrid and three POM-containing hybrid amphiphiles (PCHAs) were acquired by adjusting the number (n) of TBA(+) ions and number (3 - n) of H(+) ions (n = 3, 2, 1, and 0). These compounds can be spread onto a water surface to form a Langmuir monolayer film at the air-water interface. Surface pressure-molecular area measurements exhibit the TBA(+) (H(+)) number playing an important role in the forming ability and stability of Langmuir monolayer films. Also, the Langmuir-Blodgett (LB) technique has been used to transfer the monolayer film onto solid supports to fabricate solid multilayer films. It was found that the PCHA with three H(+) ions had the best Langmuir film-forming ability and thus formed stable LB films with a two-dimensional ordered structure. Our findings are instructive in fabricating and using solid films of the amphiphiles with POM headgroups.

  15. PERFORMACE OF MULTI-PROBE CORROSION MONITORING SYSTEMS AT THE HANFORD SITE

    Energy Technology Data Exchange (ETDEWEB)

    CAROTHERS KD; BOOMER KD; ANDA VS; DAHL MM; EDGEMON GL

    2010-01-14

    Between 2007 and 2009, several different multi-probe corrosion monitoring systems were designed and installed in high-level nuclear waste tanks at the U.S. Department of Energy's Hanford Site in WaShington State. The probe systems are being monitored to ensure waste tanks operate in regions that minimize localized corrosion (i.e., pitting) and stress corrosion cracking. The corrosion monitoring systems have been installed in wastes with different chemistry types. An ongoing effort during the same time period has generated non-radioactive simulants that are tested in the laboratory to establish baseline corrosion monitoring system performance and characterize data to allow interpretation of readings from the multiple corrosion monitoring systems. Data collection from these monitoring systems has reached the point where the results allow comparison with the laboratory testing. This paper presents analytical results from the corrosion monitoring system development program.

  16. Probing Interactions in Complex Molecular Systems through Ordered Assembly

    Energy Technology Data Exchange (ETDEWEB)

    De Yoreo, J J; Bartelt, M C; Orme, C A; Villacampa, A; Weeks, B L; Miller, A E

    2002-01-31

    Emerging from the machinery of epitaxial science and chemical synthesis, is a growing emphasis on development of self-organized systems of complex molecular species. The nature of self-organization in these systems spans the continuum from simple crystallization of large molecules such as dendrimers and proteins, to assembly into large organized networks of nanometer-scale structures such as quantum dots or nanoparticles. In truth, self-organization in complex molecular systems has always been a central feature of many scientific disciplines including fields as diverse as structural biology, polymer science and geochemistry. But over the past decade, changes in those fields have often been marked by the degree to which researchers are using molecular-scale approaches to understand the hierarchy of structures and processes driven by this ordered assembly. At the same time, physical scientists have begun to use their knowledge of simple atomic and molecular systems to fabricate synthetic self-organized systems. This increasing activity in the field of self-organization is testament to the success of the physical and chemical sciences in building a detailed understanding of crystallization and epitaxy in simple atomic and molecular systems, one that is soundly rooted in thermodynamics and chemical kinetics. One of the fundamental challenges of chemistry and materials science in the coming decades is to develop a similarly well-founded physical understanding of assembly processes in complex molecular systems. Over the past five years, we have successfully used in situ atomic force microscopy (AFM) to investigate the physical controls on single crystal epitaxy from solutions for a wide range of molecular species. More recently, we have combined this method with grazing incidence X-ray diffraction and kinetic Monte Carlo modeling in order to relate morphology to surface atomic structure and processes. The purpose of this proposal was to extend this approach to assemblies

  17. Characterizing Electron Trapping Nonlinearity in Langmuir Waves

    CERN Document Server

    Strozzi, D J; Rose, H A; Hinkel, D E; Langdon, A B; Banks, J W

    2012-01-01

    We assess when electron trapping nonlinearities are expected to be important in Langmuir waves. The basic criterion is that the effective lifetime, t_d, of resonant electrons in the trapping region of velocity space must exceed the period of trapped motion for deeply-trapped electrons, tau_B = (n_e/delta n)^{1/2} 2pi/omega_pe. A unitless figure of merit, the "bounce number" N_B = t_d/tau_B, encapsulates this condition and allows an effective threshold amplitude for which N_B=1 to be defined. The lifetime is found for convective loss (transverse and longitudinal) out of a spatially finite Langmuir wave. Simulations of driven waves with a finite transverse profile, using the 2D-2V Vlasov code Loki, show trapping nonlinearity increases continuously with N_B for side loss, and is significant for N_B ~ 1. The lifetime due to Coulomb collisions (both electron-electron and electron-ion) is also found, with pitch-angle scattering and parallel drag and diffusion treated in a unified way. A simple way to combine convec...

  18. Langmuir Blodgett films of porphyrins and phthalocyanines

    CERN Document Server

    Portus, D

    2002-01-01

    Phthalocyanines and porphyrins have been studied for many years as bulk, thick and thin films. Their use in Langmuir and Langmuir-Blodgett films is governed by their peripheral substituents. These can enhance or reduce their ability to form 'quality' ultra-thin films. There are a number of potential and current applications for thin films of porphyrins and phthalocyanines, which include CD-R discs and gas-sensors. It is the latter that this PhD has focussed on. Ultra-thin films of phthalocyanines, porphyrins and a porphyrin/phthalocyanine hybrid dye were deposited onto glass microscope slides, gold-coated glass microscope slides and quartz crystals. These assemblies were then characterised using Ultraviolet-Visible spectroscopy, pressure-area isotherms, surface plasmon resonance and a quartz crystal microbalance to try and determine the nature of the molecules on the surface of the substrate. The thin films were exposed to chlorine gas and the change in their absorption spectrum and (in some cases) their surf...

  19. Active Probing Feedback based Self Configurable Intelligent Distributed Antenna System

    DEFF Research Database (Denmark)

    Kumar, Ambuj

    challenge through a viable solution that is based on injecting intelligence and services in parallel layers through a Distributed Antenna Systems (DAS) network. This approach would enable the remote sites to acquire intelligence and a resource pool at the same time, thereby managing the network dynamics...... as Self Configurable Distributed Antenna System (SCIDAS)....... collectively as Place Time Coverage & Capacity (PTC2). The dissertation proves through the concept of the PTC2 that the network performance can severely be degraded by the excessive and unrealistic site demands, the network management inefficiency, and the consequence of the accumulation of subscribers...

  20. Quasiperiodic behavior in beam-driven strong Langmuir turbulence

    Science.gov (United States)

    Robinson, P. A.; Newman, D. L.

    1989-01-01

    The evolution of unmagnetized beam-driven strong Langmuir turbulence is studied in two dimensions by numerically integrating the Zakharov equations for systems pumped by monochromatic and broadband negative-damping drivers with nonzero central wavenumber. Long-time statistically steady states are reached for which the dependence of the evolution on the driver wavenumber, growth rate, and bandwidth is examined in detail. For monochromatic drivers, a quasiperiodic cycle is found to develop if the driver wavenumber is sufficiently large. The characteristic frequency of the quasiperiodic cycle and the average system energy are both approximately proportional to the growth rate. Broadening of the driver in wavenumber tends to degrade the system-wide coherence of the cycle, but its main features appear to survive on the scale of the coherence length of the driver.

  1. Probing quantum frustrated systems via factorization of the ground state.

    Science.gov (United States)

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2010-05-21

    The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures.

  2. Simulation of weak and strong Langmuir collapse regimes

    Energy Technology Data Exchange (ETDEWEB)

    Hadzievski, L.R.; Skoric, M.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); Kono, M.; Sato, T.

    1998-01-01

    In order to check the validity of the self-similar solutions and the existence of weak and strong collapse regimes, direct two dimensional simulation of the time evolution of a Langmuir soliton instability is performed. Simulation is based on the Zakharov model of strong Langmuir turbulence in a weakly magnetized plasma accounting for the full ion dynamics. For parameters considered, agreement with self-similar dynamics of the weak collapse type is found with no evidence of the strong Langmuir collapse. (author)

  3. Low frequency magnetic signals associated with Langmuir waves

    Science.gov (United States)

    Kellogg, Paul J.; Goetz, K.; Lin, N.; Monson, S. J.; Balogh, A.; Forsyth, R. J.; Stone, R. G.

    1992-01-01

    With the URAP experiment on Ulysses, low frequency signals with a magnetic component in close time correlation with electrostatic Langmuir waves at the plasma frequency are observed. In most, if not all, of these cases, the Langmuir waves are part of a Type III solar burst. This effect is investigated and it is shown that the low frequency waves are in the whistler mode and are most likely due to nonlinear effects involving Langmuir waves.

  4. Development of the STPX Spheromak System

    Science.gov (United States)

    Williams, R. L.; Clark, J.; Weatherford, C. A.

    2015-11-01

    The progress made in starting up the STPX Spheromak system, which is now installed at the Florida A&M University, is reviewed. Experimental, computational and theoretical activities are underway. The control system for firing the magnetized coaxial plasma gun and for collecting data from the diagnostic probes, based on LabView, is being tested and adapted. Preliminary results of testing the installed magnetic field probes, Langmuir triple probes, cylindrical ion probes, and optical diagnostics will be discussed. Progress in modeling this spheromak using simulation codes, such as NIMROD, will be discussed. Progress in investigating the use of algebraic topology to describe this spheromak will be reported.

  5. Probing LINEAR Collider Final Focus Systems in SuperKEKB

    CERN Document Server

    Thrane, Paul Conrad Vaagen

    2017-01-01

    A challenge for future linear collider final focus systems is the large chromaticity produced by the final quadrupoles. SuperKEKB will be correcting high levels of chromaticity using the traditional scheme which has been also proposed for the CLIC FFS. We present early simulation results indicating that lowering β*у in the SuperKEKB Low Energy Ring might be possible given on-axis injection and low bunch current, opening the possibility of testing chromaticity correction beyond FFTB level, similar to ILC and approaching that of CLIC. CLIC – Note – 1077

  6. Chemical probes for the study of the endogenous cannabinoid system

    OpenAIRE

    Rueda Zubiaurre, Ainoa

    2016-01-01

    La química biológica nació hace dos décadas con objeto de estudiar la interfase entre la química y la biología, utilizando para ello herramientas capaces de interrogar los distintos sistemas biológicos, facilitando así la comprensión de los mismos.1-3 Sin embargo, existen sistemas biológicos de gran relevancia cuyo estudio no ha sido abordado hasta ahora. Uno de ellos es el sistema cannabinoide endógeno (endogenous cannabinoid system, ECS), que durante los últimos años ha sido relacionado con...

  7. Complications with flush-mounted probe analysis beyond sheath-expansion

    Science.gov (United States)

    Kuang, A. Q.; Labombard, B.; Brunner, D.

    2016-10-01

    In a reactor relevant divertor, the heat-flux onto the target plate would be too large and traditional proud Langmuir probes will melt. By making the probes flush with the surface of the target plate they become nearly as robust as the divertor plates themselves. However, without a theoretically rigorous derivation of the sheath thickness, sheath expansion has been a primary concern for the interpretation of flush mounted probe data. Following the installation of a flush-mounted Langmuir probe system at Alcator C-Mod (toroidally-elongated and field-aligned to give it a `rail' geometry) that effectively mitigates the effects of sheath expansion down to incident field line angles of 0.5 degree, further complications have arisen that cannot be explained by sheath-expansion. The `rail' probes systematically measure lower densities and higher temperatures but have the same pressure. The evolution of the scrape-off layer profiles measured on the divertor target plate from sheath-limited to detached regimes is also different. These are indicative of important physics, perhaps unique to conditions in a vertical-target plate divertor with small field-line attack angles, that affects the I-V characteristics and is not currently included in probe data analyses. Controlled experiments performed at Alcator C-Mod mapped out this discrepancy and the results will be presented. Supported by USDoE Awards DE-FC02-99ER54512.

  8. TANK 241-AN-102 MULTI-PROBE CORROSION MONITORING SYSTEM PROJECT LESSONS LEARNED

    Energy Technology Data Exchange (ETDEWEB)

    TAYLOR T; HAGENSEN A; KIRCH NW

    2008-07-07

    During 2007 and 2008, a new Multi-Probe Corrosion Monitoring System (MPCMS) was designed and fabricated for use in double-shell tank 241-AN-102. The system was successfully installed in the tank on May 1, 2008. The 241-AN-102 MPCMS consists of one 'fixed' in-tank probe containing primary and secondary reference electrodes, tank material electrodes, Electrical Resistance (ER) sensors, and stressed and unstressed corrosion coupons. In addition to the fixed probe, the 241-AN-102 MPCMS also contains four standalone coupon racks, or 'removable' probes. Each rack contains stressed and unstressed coupons made of American Society of Testing and Materials A537 CL1 steel, heat-treated to closely match the chemical and mechanical characteristics of the 241-AN-102 tank wall. These coupon racks can be removed periodically to facilitate examination of the attached coupons for corrosion damage. Along the way to successful system deployment and operation, the system design, fabrication, and testing activities presented a number of challenges. This document discusses these challenges and lessons learned, which when applied to future efforts, should improve overall project efficiency.

  9. Probing the geometric nature of particles mass in graphene systems

    CERN Document Server

    Dolce, Donatello

    2014-01-01

    According to undulatory mechanics, the Compton periodicity, which is the intrinsic proper-time recurrence of a wave function, determines the mass of the corresponding elementary particles. This provides a geometric description of the rest mass which can be consistently applied to derive the effective mass spectrum and electronic properties of the elementary charge carriers in carbon nanotubes and other condensed matter systems. The Compton periodicity is determined by the boundary conditions associated to the curled-up dimension of carbon nanotubes or analogous constraints of the charge carrier wave function. This approach shows an interesting interplay between particle physics and relativistic space-time, as well as analogies with the Kaluza-Klein theory and Holography.

  10. Experimental probes of emergent symmetries in the quantum Hall system

    CERN Document Server

    Lutken, C A

    2011-01-01

    Experiments studying renormalization group flows in the quantum Hall system provide significant evidence for the existence of an emergent holomorphic modular symmetry Gamma(0)(2). We briefly review this evidence and show that, for the lowest temperatures, the experimental determination of the position of the quantum critical points agrees to the parts per mille level with the prediction from Gamma(0)(2). We present evidence that experiments giving results that deviate substantially from the symmetry predictions are not cold enough to be in the quantum critical domain. We show how the modular symmetry extended by a non-holomorphic particle hole duality leads to an extensive web of dualities related to those in plateau insulator transitions, and we derive a formula relating dual pairs (B, B(d)) of magnetic field strengths across any transition. The experimental data obtained for the transition studied so far is in excellent agreement with the duality relations following from this emergent symmetry, and rule out...

  11. SPIN POLARIZED PHOTOELECTRON SPECTROSCOPY AS A PROBE OF MAGNETIC SYSTEMS.

    Energy Technology Data Exchange (ETDEWEB)

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01

    Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

  12. The Use of Coumarins as Environmentally-Sensitive Fluorescent Probes of Heterogeneous Inclusion Systems

    Directory of Open Access Journals (Sweden)

    Brian D. Wagner

    2009-01-01

    Full Text Available Coumarins, as a family of molecules, exhibit a wide range of fluorescence emission properties. In many cases, this fluorescence is extremely sensitive to the local environment of the molecule, especially the local polarity and microviscosity. In addition, coumarins show a wide range of size, shape, and hydrophobicity. These properties make them especially useful as fluorescent probes of heterogeneous environments, such as supramolecular host cavities, micelles, polymers and solids. This article will review the use of coumarins to probe such heterogeneous systems using fluorescence spectroscopy.

  13. Resolution enhancement of scanning four-point-probe measurements on two-dimensional systems.

    OpenAIRE

    Hansen, Torben Mikael; Stokbro, Kurt; Hansen, Ole; Hassenkam, T.; Shiraki, I.; Hasegawa, S.; Bøggild, Peter

    2003-01-01

    A method to improve the resolution of four-point-probe measurements of two-dimensional (2D) and quasi-2D systems is presented. By mapping the conductance on a dense grid around a target area and postprocessing the data, the resolution can be improved by a factor of approximately 50 to better than 1/15 of the four-point-probe electrode spacing. The real conductance sheet is simulated by a grid of discrete resistances, which is optimized by means of a standard optimization algorithm, until the ...

  14. Spatial Four Wave Mixing, Probe Images, and Fluorescence Signals in Dressed Three-Level System

    Science.gov (United States)

    Lan, Huayan; Sun, Jia; Wu, Zhenkun; Zhang, Dan; Zhang, Yiqi; Zheng, Huaibin; Zhang, Yanpeng

    2013-10-01

    We investigate the spatial images of the probe, generated four wave mixing (FWM) signal and the accompanying fluorescence spectrum signal simultaneously in FWM process in a cascade three-level atomic system for the first time. We experimentally observe and theoretically investigate the three spectrum signals versus the probe field as well as the dressing field frequency detunings. Utilizing the experimental results of spectrum signals, the cross phase modulation and the relative position between the weak and strong beams, we analyze the characteristics indicated in the spatial images of probe transmission and FWM, such as focusing or defocusing, shift and splitting in detail. Such studies can be used in all-optical controlled spatial signal transmission.

  15. Nanoelectrical probing with multiprobe SPM Systems compatible with scanning electron microscopes

    Science.gov (United States)

    Lewis, Aaron; Ignatov, Andrey; Taha, Hesham; Zhinoviev, Oleg; Komissar, Anatoly; Krol, Alexander; Lewis, David

    2011-03-01

    A scanning electron microscope compatible platform that permits multiprobe atomic force microscopy based nanoelectrical characterization will be described. To achieve such multiple parameter nanocharacterization with scanning electron microscope compatibility involves a number of innovations both in instrument and probe design. This presentation will focus on how these advances were achieved and the results obtained with such instrumentation on electrical nano-characterization and electrical nano-manipulation. The advances include: 1. Specialized scanners; 2. An ultrasensitive feedback mechanism based on tuning forks with no optical feedback interference that can induce carriers in semiconductor devices; and 3. Unique probes compatible with multiprobe geometries in which the probe tips can be brought into physical contact with one another. Experiments will be described with such systems that will include multiprobe electrical measurements with metal and glass coated coaxial nanowires of platinum. This combination of scanning electron microscopes integrated with multiprobe instrumentation allows for important applications not available today in the field of semiconductor processing technology.

  16. Langmuir Blodgett multilayers and related nanostructures

    Indian Academy of Sciences (India)

    S S Major; S S Talwar; R S Srinivasa

    2006-07-01

    Langmuir Blodgett (LB) process is an important route to the development of organized molecular layered structures of a variety of organic molecules with suitably designed architecture and functionality. LB multilayers have also been used as templates and precursors to develop nano-structured thin films. In this article, studies on the molecular packing and three-dimensional structure of prototypic cadmium arachidate (CdA), zinc arachidate (ZnA) and mixed CdA–ZnA LB multilayers are presented. The formation of semiconducting nano-clusters of CdS, ZnS and CdZn1−S alloys within the organic multilayer matrix, using arachidate LB multilayers as precursors is also discussed.

  17. Physical properties of a wound-probe-system; Physikalische Parameter einer Gamma-Wundsonde

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, F.; Ogris, E.; Weidlich, G. [Donauspital Wien (Austria). Abt. fuer Nuklearmedizinische Diagnostik und Therapie; Lauer, D.; Aiginger, H. [Atominstitut der Oesterreichischen Universitaeten, Vienna (Austria)

    1998-12-31

    In our department a probe-system was purchased, for the detection of wound contamination. The probe utilizes a CdTe-detector with a diameter of 8 mm. Countrate is displayed by a ratemeter. This paper describes the efficiency of the probe from 30 to 400 keV. Spatial resolution is represented in terms of full width at half maximum: 2.3 cm for a distance of 2 cm. The dependence of geometrical efficiency was measured with Tc-99m and I-131 point sources. Although not equipped with a special collimator, the probe provides good spatial resolution. The overall quality of the system is in the range of a probe designed specially for usage during intraoperative nuclide search. It could be demonstrated during surgery, that the wound-probe fits the need for Lymphoscintigraphy. (orig.) [Deutsch] Am Donauspital wurde fuer die Feststellung von Kontaminationen im Wundbereich eine Gamma-Wundsonde beschafft. Die Sonde verwendet einen CdTe-Detektor mit einem Durchmesser von 8 mm, als Anzeigeinstrument fungiert ein Ratemeter. Neben der Empfindlichkeit im Energiebereich von 30 bis 400 keV wurde das raeumliche Aufloesungsvermoegen (FWHM in 2 cm Abstand: 2,3 cm) und die Abhaengigkeit der Sondenempfindlichkeit von den geometrischen Rahmenbedingungen fuer die Nuklide Tc-99m und I-131 ermittelt. Sowohl in der Ebene parallel zur Koerperoberflaeche als auch in der Ebene senkrecht dazu konnte auch ohne Kollimator eine ausgepraegte Winkelempfindlichkeit bei geringen Distanzen festgestellt werden. Die physikalischen Parameter (Efficiency, Ortsaufloesung und Richtungsempfindlichkeit) des Sondensystems sind nur geringfuegig schlechter, als jene einer speziell fuer den intraoperativen Einsatz konstruierten Sonde. Dies konnte auch bei einem versuchsweisen Einsatz an einem Patienten bestaetigt werden. (orig.)

  18. Diacetylene mixed Langmuir monolayers for interfacial polymerization.

    Science.gov (United States)

    Ariza-Carmona, Luisa; Rubia-Payá, Carlos; García-Espejo, G; Martín-Romero, María T; Giner-Casares, Juan J; Camacho, Luis

    2015-05-19

    Polydiacetylene (PDA) and its derivatives are promising materials for applications in a vast number of fields, from organic electronics to biosensing. PDA is obtained through polymerization of diacetylene (DA) monomers, typically using UV irradiation. DA polymerization is a 1-4 addition reaction with both initiation and growth steps with topochemical control, leading to the "blue" polymer form as primary reaction product in bulk and at interfaces. Herein, the diacetylene monomer 10,12-pentacosadiynoic acid (DA) and the amphiphilic cationic N,N'-dioctadecylthiapentacarbocyanine (OTCC) have been used to build a mixed Langmuir monolayer. The presence of OTCC imposes a monolayer supramolecular structure instead of the typical trilayer of pure DA. Surface pressure, Brewster angle microscopy, and UV-vis reflection spectroscopy measurements, as well as computer simulations, have been used to assess in detail the supramolecular structure of the DA:OTCC Langmuir monolayer. Our experimental results indicate that the DA and OTCC molecules are sequentially arranged, with the two OTCC alkyl chains acting as spacing diacetylene units. Despite this configuration is expected to prevent photopolymerization of DA, the polymerization takes place without phase segregation, thus exclusively leading to the red polydiacetylene form. We propose a simple model for the initial formation of the "blue" or "red" PDA forms as a function of the relative orientation of the DA units. The structural insights and the proposed model concerning the supramolecular structure of the "blue" and "red" forms of the PDA are aimed at the understanding of the relation between the molecular and macroscopical features of PDAs.

  19. Photosystem I in Langmuir-Blodgett and Langmuir-Schaefer monolayers.

    Science.gov (United States)

    Yan, Xun; Faulkner, Christopher J; Jennings, G Kane; Cliffel, David E

    2012-10-23

    Photosystem I (PSI) is a membrane protein complex that generates photoinduced electrons and transfers them across the thylakoid membrane during photosynthesis. The PSI complex, separated from spinach leaves, was spread onto the air-water interface as a monolayer and transferred onto a gold electrode surface that was precoated with a self-assembled monolayer (SAM). The electrochemical properties of the transferred PSI monolayer, including cyclic voltammetry and photoinduced chronoamperometry, were measured. The results showed that PSI retained its bioactivity after the manipulation. Its capability of converting photoenergy into electrical potential was demonstrated by its reducing an electron acceptor, dichloroindophenol (DCIP), and by oxidizing an electron donor, sodium ascorbate (ASC). We have shown that the protein has two possible orientations at the water interface. The orientation distribution was determined by comparing the controlled reductive and oxidative photocurrents generated from Langmuir-Blodgett and Langmuir-Schaefer monolayers.

  20. Microsecond resolved electron density measurements with a hairpin resonator probe in a pulsed ICP discharge

    CERN Document Server

    Peterson, David; Larson, Lynda; Shannon, Steven

    2016-01-01

    Time resolved electron density measurements in pulsed RF discharges are shown using a hairpin resonance probe using low cost electronics, on par with normal Langmuir probe boxcar mode operation. Time resolution of less than one microsecond has been demonstrated. A signal generator produces the applied microwave frequency; the reflected waveform is passed through a directional coupler and filtered to remove the RF component. The signal is heterodyned with a frequency mixer and read by an oscilloscope. At certain points during the pulse, the plasma density is such that the applied frequency is the same as the resonance frequency of the probe/plasma system, creating a dip in the reflected signal. The applied microwave frequency is shifted in small increments in a frequency boxcar routine to determine the density as a function of time. The system uses a grounded probe to produce low cost, high fidelity, and highly reproducible electron density measurements that can work in harsh chemical environments. Measurement...

  1. Two-dimensional atom localization via probe absorption in a four-level atomic system

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Ping; Ge Qiang; Ruan Yu-Hua; Yu Ben-Li

    2013-01-01

    We have investigated the two-dimensional (2D) atom localization via probe absorption in a coherently driven fourlevel atomic system by means of a radio-frequency field driving a hyperfine transition.It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters.As a result,our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.

  2. Investigating the momentum balance of a plasma pinch: An air-side stereoscopic imaging system for locating probes

    Energy Technology Data Exchange (ETDEWEB)

    Sears, Jason, E-mail: jason.sears@alum.mit.edu; Intrator, T. P.; Feng, Y.; Swan, H. O.; Klarenbeek, J.; Gao, K. [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

    2014-10-01

    The momentum balance of a plasma pinch in the Reconnection Scaling Experiment (RSX) is examined in three dimensions using several repositionable, insertable probes. A new camera-based system described here triangulates the locations of the probe tips so that their measurements are spatially registered. The optical system locates probes to within ±1.5 mm of their absolute 3D position in the vessel and to within ±0.7 mm relative to other probes, on the order of the electron inertial length (1–2 mm)

  3. Mixing alternating copolymers containing fluorenyl groups with phospholipids to obtain Langmuir and Langmuir-Blodgett films.

    Science.gov (United States)

    Santos, Thays C F; Péres, Laura O; Wang, Shu H; Oliveira, Osvaldo N; Caseli, Luciano

    2010-04-20

    The control of molecular architectures may be essential to optimize materials properties for producing luminescent devices from polymers, especially in the blue region of the spectrum. In this Article, we report on the fabrication of Langmuir-Blodgett (LB) films of polyfluorene copolymers mixed with the phospholipid dimyristoyl phosphatidic acid (DMPA). The copolymers poly(9,9-dioctylfluorene)-co-phenylene (copolymer 1) and poly(9,9-dioctylfluorene)-co-quaterphenylene) (copolymer 2) were synthesized via Suzuki reaction. Copolymer 1 could not form a monolayer on its own, but it yielded stable films when mixed with DMPA. In contrast, Langmuir monolayers could be formed from either the neat copolymer 2 or when mixed with DMPA. The surface pressure and surface potential measurements, in addition to Brewster angle microscopy, indicated that DMPA provided a suitable matrix for copolymer 1 to form a stable Langmuir film, amenable to transfer as LB films, while enhancing the ability of copolymer 2 to form LB films with enhanced emission, as indicated by fluorescence spectroscopy. Because a high emission was obtained with the mixed LB films and since the molecular-level interactions between the film components can be tuned by changing the experimental conditions to allow for further optimization, one may envisage applications of these films in optical devices such as organic light-emitting diodes (OLEDs).

  4. Using Weighted Least Squares Regression for Obtaining Langmuir Sorption Constants

    Science.gov (United States)

    One of the most commonly used models for describing phosphorus (P) sorption to soils is the Langmuir model. To obtain model parameters, the Langmuir model is fit to measured sorption data using least squares regression. Least squares regression is based on several assumptions including normally dist...

  5. Evidence for Langmuir wave collapse in the interplanetary plasma

    Science.gov (United States)

    Kellogg, Paul J.; Goetz, K.; Howard, R. L.; Monson, S. J.

    1992-01-01

    With the Fast Envelope Sampler part of the URAP experiment on Ulysses, there is observed much rapidly varying structure in plasma waves in the solar wind. Extremely narrow (1 ms) structures observed together with electrostatic Langmuir waves, as well as some broader Langmuir wave packets are discussed.

  6. Electrochemical studies of redox probes in self-organized lyotropic liquid crystalline systems

    Indian Academy of Sciences (India)

    P Suresh Kumar; V Lakshminarayanan

    2009-09-01

    Lyotropic liquid crystalline phases formed by surfactants are of special importance due to their close resemblance to biological systems. The redox reactions in such ordered media are of fundamental interest in understanding several complex processes occurring in the biological media, where the former can act as model systems. In this work, we have carried out the redox reactions of benzoquinone| hydroquinone, methyl viologen and ferrocenemethanol probes in a lyotropic hexagonal columnar phase (H1 phase) using cyclic voltammetry and electrochemical impedance spectroscopic studies. The liquid crystalline phase we have studied is made up of the non-ionic surfactant, Triton X-100 and water. Polarizing optical microscopic examination confirmed that the columnar hexagonal phase is retained even after the addition of redox probe as well as the supporting electrolyte. Our studies show a significant shift in the half-peak potentials of the redox probes in the H1 phase as compared to the solvent phase. The diffusion coefficient values for different redox probes in the H1 phase were also found to be significantly reduced when compared to the corresponding solvent media.

  7. Landau damping of Langmuir twisted waves with kappa distributed electrons

    Energy Technology Data Exchange (ETDEWEB)

    Arshad, Kashif, E-mail: kashif.arshad.butt@gmail.com; Aman-ur-Rehman [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Mahmood, Shahzad [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)

    2015-11-15

    The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].

  8. Micromachined Silicon Stimulating Probes with CMOS Circuitry for Use in the Central Nervous System

    Science.gov (United States)

    Tanghe, Steven John

    1992-01-01

    Electrical stimulation in the central nervous system is a valuable technique for studying neural systems and is a key element in the development of prostheses for deafness and other disorders. This thesis presents a family of multielectrode probe structures, fulfilling the need for chronic multipoint stimulation tools essential for interfacing to the highly complex neural networks in the brain. These probes are batch-fabricated on silicon wafers, employing photoengraving techniques to precisely control the electrode site and array geometries and to allow the integration of on-chip CMOS circuitry for signal multiplexing and stimulus current generation. Silicon micromachining is used to define the probe shapes, which have typical shank dimensions of 3 mm in length by 100 mu m in width by 15 μm in thickness. Each shank supports up to eight planar iridium oxide electrode sites capable of delivering charge densities in excess of 3 mC/cm^2 during current pulse stimulation. Three active probe circuits have been designed with varied complexity and capability. All three can deliver biphasic stimulus currents through 16 sites using only 5 external leads, and they are all compatible with the same external control system. The most complex design interprets site addresses and stimulus current amplitudes from 16-bit words shifted into the probe at 4 MHz. Sixteen on-chip, biphasic, 8-bit digital-to-analog converters deliver analog stimulus currents in the range of +/- 254 muA to any combination of electrode sites. These DACs exhibit full-scale internal linearity to better than +/-1/2 LSB and can be calibrated by varying the positive power supply voltage. The entire probe circuit dissipates only 80 muW from +/-5 V supplies when not delivering stimulus currents, it includes several safety features, and is testable from the input pads. Test results from the fabricated circuits indicate that they all function properly at clocking frequencies as high as 10 MHz, meeting or exceeding

  9. Recognition- and reactivity-based fluorescent probes for studying transition metal signaling in living systems.

    Science.gov (United States)

    Aron, Allegra T; Ramos-Torres, Karla M; Cotruvo, Joseph A; Chang, Christopher J

    2015-08-18

    Metals are essential for life, playing critical roles in all aspects of the central dogma of biology (e.g., the transcription and translation of nucleic acids and synthesis of proteins). Redox-inactive alkali, alkaline earth, and transition metals such as sodium, potassium, calcium, and zinc are widely recognized as dynamic signals, whereas redox-active transition metals such as copper and iron are traditionally thought of as sequestered by protein ligands, including as static enzyme cofactors, in part because of their potential to trigger oxidative stress and damage via Fenton chemistry. Metals in biology can be broadly categorized into two pools: static and labile. In the former, proteins and other macromolecules tightly bind metals; in the latter, metals are bound relatively weakly to cellular ligands, including proteins and low molecular weight ligands. Fluorescent probes can be useful tools for studying the roles of transition metals in their labile forms. Probes for imaging transition metal dynamics in living systems must meet several stringent criteria. In addition to exhibiting desirable photophysical properties and biocompatibility, they must be selective and show a fluorescence turn-on response to the metal of interest. To meet this challenge, we have pursued two general strategies for metal detection, termed "recognition" and "reactivity". Our design of transition metal probes makes use of a recognition-based approach for copper and nickel and a reactivity-based approach for cobalt and iron. This Account summarizes progress in our laboratory on both the development and application of fluorescent probes to identify and study the signaling roles of transition metals in biology. In conjunction with complementary methods for direct metal detection and genetic and/or pharmacological manipulations, fluorescent probes for transition metals have helped reveal a number of principles underlying transition metal dynamics. In this Account, we give three recent

  10. Comparative Analysis and Approximations of Space -Charge Formation in Langmuir Electrodes Including Temperature Effects.

    Science.gov (United States)

    Valdeblànquez, Eder

    2001-10-01

    Eder Valdeblànquez,Universidad del Zulia,Apartado 4011-A 526,Maracaibo,Venezuela. ABSTRACT: In this paper by space charge effect in Langmuir probes are compared for different kind of symmetries; plane, cylindrical and spherical. A detailed analysis is performed here including temperature effects, and therefore kinetic theory is used instead of fluid equations as other authors. The strongly non-linear equations obtained here have been solved first by numerical analysis and later by approximations using Bessel functions. The accuracy of each approximaton is also discussed. Space Charge effects are important in plane geometries than in the case of cylindrical or spherical symmetries.

  11. A multi-probe thermophoretic soot sampling system for high-pressure diffusion flames

    Science.gov (United States)

    Vargas, Alex M.; Gülder, Ömer L.

    2016-05-01

    Optical diagnostics and physical probing of the soot processes in high pressure combustion pose challenges that are not faced in atmospheric flames. One of the preferred methods of studying soot in atmospheric flames is in situ thermophoretic sampling followed by transmission electron microscopy imaging and analysis for soot sizing and morphology. The application of this method of sampling to high pressures has been held back by various operational and mechanical problems. In this work, we describe a rotating disk multi-probe thermophoretic soot sampling system, driven by a microstepping stepper motor, fitted into a high-pressure chamber capable of producing sooting laminar diffusion flames up to 100 atm. Innovative aspects of the sampling system design include an easy and precise control of the sampling time down to 2.6 ms, avoidance of the drawbacks of the pneumatic drivers used in conventional thermophoretic sampling systems, and the capability to collect ten consecutive samples in a single experimental run. Proof of principle experiments were performed using this system in a laminar diffusion flame of methane, and primary soot diameter distributions at various pressures up to 10 atm were determined. High-speed images of the flame during thermophoretic sampling were recorded to assess the influence of probe intrusion on the flow field of the flame.

  12. On-line Scanned Probe Microscopy Transparently Integrated with DualBeam SEM/FIB Systems

    Science.gov (United States)

    Ignatov, Andrey; Komissar, Anatoly; Lewis, Aaron

    2013-03-01

    A multifunctional scanning probe microscope (SPM) will be described that transparently integrates with a DualBeam SEM/FIB System. This is done without perturbing any of the capabilities of the Dual Beam in terms of detectors, gas injectors, analyzers etc while allowing for a completely exposed probe tip to be imaged online even with immersion objectives at working distances as short as 4 mm. In addition, the completely free motion of the rotation axis of the stage is maintained with the probe tip at the eucentric point, this makes it possible to orient the sample in any direction on any structure The X and Y scan range of the atomic force microscopic (AFM) imaging achieves 35 microns with rough motion over 10 millimeters. This permits the SPM to tilt into position perpendicular to the SEM or FIB or under an angle for rapid and accurate placement of the probe tip at or on structures such as biopolymeric materials that are nanometric in X, Y and Z extent. Thus, not only can a structure's nanometric height be accurately profiled but this can be accomplished with the on-line excellence of SEM for X, Y metrology. Furthermore, electron and ion beam sensitive samples can be imaged and characterized by AFM at high resolution.

  13. How to get spatial resolution inside probe volumes of commercial 3D LDA systems

    Energy Technology Data Exchange (ETDEWEB)

    Strunck, V.; Sodomann, T.; Mueller, H.; Dopheide, D. [Section of Fluid Flow Measuring Techniques, Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116, Braunschweig (Germany)

    2004-01-01

    In laser Doppler anemometry (LDA) it is often the aim to determine the velocity profile for a given fluid flow. The spatial resolution of such velocity profiles is limited in principal by the size of the probe volume. The method of using time of flight data from two probe volumes allows improvements of the spatial resolution by at least one order of magnitude and measurements of small-scale velocity profiles inside the measuring volume along the optical axis of commercial available 3D anemometers without moving the probe. No change of the optical set-up is necessary. An increased spatial resolution helps to acquire more precise data in areas where the flow velocity changes rapidly as shown in the vicinity of the stagnation point of a cuboid. In the overlapping region of three measuring volumes a spatially resolved 3D velocity vector profile is obtained in the direction of the optical axis in near plane flow conditions. In plane laminar flows the probe volume is extended by a few millimetres. The limitation of the method to a plane flow is that it would require a two-component LDA in a very special off-axis arrangement, but this arrangement is available in most commercial 3D systems. (orig.)

  14. Electronic nose system combined with membrane interface probe for detection of VOCs in water

    Science.gov (United States)

    Cho, Junghwan; Howard, Zachary; Kurup, Pradeep

    2011-09-01

    This paper describes a novel electronic nose system combined with a membrane interface probe (MIP) for detecting volatile organic compounds (VOCs) in water. The MIP is an in situ tool that allows the detection of certain VOCs in the soil via a pushed or driven probe. The MIP was combined with a sensor array consisting of four different tin-oxide gas sensors known as an electronic nose (e-nose). The designed e-nose system was calibrated in aqueous media spiked with benzene, toluene, ethylbenzene, and p-xylene (BTEX) at concentrations of 100, 250, and 500 ppm. Since the experiment was conducted utilizing five repetitions for each analyte, a data set of 60 measurements was prepared for principal components analysis (PCA). The results of the PCA showed that two principal components contain more than 99% variance information and each VOC is separable and detectable by the e-nose.

  15. Hand-held probe based optical imaging system towards breast cancer diagnosis

    Science.gov (United States)

    Ge, Jiajia; Jayachandran, Bhavani; Regalado, Steven; Zhu, Banghe; Godavarty, Anuradha

    2007-02-01

    Near-infrared (NIR) optical imaging is an emerging noninvasive modality for breast cancer diagnosis. However, the currently available optical imaging systems towards tomography studies are limited either by instrument portability, patient comfort, or flexibility to image any given tissue volume. Herein, a hand-held based optical imaging system is developed such that it can possibly overcome some of the above limitations. The unique features of the hand-held optical probe are: (i) to perform simultaneous multiple point illumination and detection, thus decreasing the total imaging time and improving the overall signal strength; (ii) to adapt to the contour of tissue surface, thus decreasing the leakage of excitation and emission signal at contact surface; and (iii) to obtain trans-illumination measurements apart from reflectance measurements, thus improving the depth information. The increased detected signal strength as well as total interrogated tissue volume is demonstrated by simulation studies (i.e. forward model) over a 5×10×10 cc slab phantom. The appropriate number and layout of the source and detection points on the probe head is determined and the hand-held optical probe is developed. A frequency-domain ICCD (intensified charge coupled device) detection system, which allows simultaneous multiple points detection, is developed and coupled to the hand-held probe in order to perform fluorescence-enhanced optical imaging of tissue phantoms. In the future, imaging of homogenous liquid phantoms will be used for the assessment of this hand-held system, followed by extensive imaging studies on different phantoms types under various experimental conditions.

  16. The cervical cancer detection system based on an endoscopic rotary probe

    Science.gov (United States)

    Yang, Yanshuang; Hou, Qiang; Zhao, Huijuan; Qin, Zhuanping; Gao, Feng

    2012-03-01

    To acquire the optical diffuse tomographic image of the cervix, a novel endoscopic rotary probe is designed and the frequency domain measurement system is developed. The finite element method and Gauss-Newton method are proposed to reconstruct the image of the phantom. In the optical diffuse tomographic imaging of the cervix, an endoscopic probe is needed and the detection of light at different separation to the irradiation spot is necessary. To simplify the system, only two optical fibers are adopted for light irradiation and collection, respectively. Two small stepper motors are employed to control the rotation of the incident fiber and the detection fiber, respectively. For one position of source fiber, the position of the detection fiber is changed from -61.875° to -50.625° and 50.625° to 61.875° to the source fiber, respectively. Then, the position of the source fiber is changed to another preconcerted position, which deviates the precious source position in an angle of 11.25°, and the detection fiber rotates within the above angles. To acquire the efficient irradiation and collection of the light, a gradient-index (GRIN) lens is connected at the head of the optical fiber. The other end of the GRIN lens is cut to 45°. With this design, light from optical fiber is reflected to the cervix wall, which is perpendicular to the optical fiber or vice versa. Considering the cervical size, the external diameter of the endoscopic probe is made to 20mm. A frequency domain (FD) near-infrared diffuse system is developed aiming at the detection of early cervical cancer, which modulates the light intensity in radio frequency and measures the amplitude attenuation and the phase delay of the diffused light using heterodyne detection. Phantom experiment results demonstrate that the endoscopic rotary scan probe and the system perform well in the endoscopic measurement.

  17. Competition between Buneman and Langmuir Instabilities

    Institute of Scientific and Technical Information of China (English)

    GUO Jun; YU Bin

    2012-01-01

    The electron-ion beam instabilities are studied by one-dimensional electrostatic particle-in-cell simulation.The simulation results show that both the low-frequency Buneman mode and high-frequency Langmuir wave (LW) are excited in the nonlinear phase. The power of Buneman instability is stronger than that of the LW.The Buneman instability is firstly excited.Then the backward LW appears,which is probably excited by the particles trapped in the wave potential and moving opposite to the original beam direction.After some time,the forward LW can be found,which has a larger maximum frequency than that of the backward LW.With the decrease of the electron drift velocity,the instabilities become weaker; the LW appears to have almost equal intensities and becomes symmetric for forward and backward propagation directions. The LW can also heat the electron,so the relative drift speed cannot far exceed the electron thermal speed,which is not helpful to the development of Buneman instability.

  18. Probe tip heating assembly

    Science.gov (United States)

    Schmitz, Roger William; Oh, Yunje

    2016-10-25

    A heating assembly configured for use in mechanical testing at a scale of microns or less. The heating assembly includes a probe tip assembly configured for coupling with a transducer of the mechanical testing system. The probe tip assembly includes a probe tip heater system having a heating element, a probe tip coupled with the probe tip heater system, and a heater socket assembly. The heater socket assembly, in one example, includes a yoke and a heater interface that form a socket within the heater socket assembly. The probe tip heater system, coupled with the probe tip, is slidably received and clamped within the socket.

  19. Sensor probes and phantoms for advanced transcranial magnetic stimulation system developments

    Science.gov (United States)

    Meng, Qinglei; Patel, Prashil; Trivedi, Sudhir; Du, Xiaoming; Hong, Elliot; Choa, Fow-Sen

    2015-05-01

    Transcranial magnetic stimulation (TMS) has become one of the most widely used noninvasive method for brain tissue stimulation and has been used as a treatment tool for various neurological and psychiatric disorders including migraine, stroke, Parkinson's disease, dystonia, tinnitus and depression. In the process of developing advanced TMS deep brain stimulation tools, we need first to develop field measurement devices like sensory probes and brain phantoms, which can be used to calibrate the TMS systems. Currently there are commercially available DC magnetic or electric filed measurement sensors, but there is no instrument to measure transient fields. In our study, we used a commercial figure-8 shaped TMS coil to generate transient magnetic field and followed induced field and current. The coil was driven by power amplified signal from a pulse generator with tunable pulse rate, amplitude, and duration. In order to obtain a 3D plot of induced vector electric field, many types of probes were designed to detect single component of electric-field vectors along x, y and z axis in the space around TMS coil. We found that resistor probes has an optimized signal-to-noise ratio (SNR) near 3k ohm but it signal output is too weak compared with other techniques. We also found that inductor probes can have very high output for Curl E measurement, but it is not the E-field distribution we are interested in. Probes with electrical wire wrapped around iron coil can directly measure induced E-field with high sensitivity, which matched computer simulation results.

  20. Measuring the inboard side scrape-off layer of DIII-D plasmas using Swing-Probes

    Science.gov (United States)

    Tsui, Cedric

    The scrape-off layer (SOL) plasma of a tokamak often has a complicated spatial dependence. The temperatures, densities and flow speeds can vary significantly on the same magnetic flux tube at different poloidal locations. To fully understand the plasma variation, we must make active measurements along the full length of the flux tubes by expanding our diagnostic capability to include the critically under-diagnosed inboard side. To accomplish this, a new pair of in-situ reciprocating Mach probes called Swing-Probes have been developed and deployed on the DIII D centerpost. This design is unique in that the probe swings vertically through the SOL plasma, taking measurements along a 180° arc with a 20 cm radius. Two electrodes maintain a Mach-pair orientation throughout the swing and provide measurements of saturation current, electron temperature, and parallel flow speeds. The probes can handle very high heat fluxes and have taken measurements up to the Last Closed Flux Surface (LCFS) in high-powered H-Mode at 10 MW. The Swing-Probe temperature and density measurements have been verified against the floor Langmuir probes, the core Thomson scattering and the divertor Thomson scattering systems in DIII-D for conditions where poloidal variation are expected to be small. Measurements have been taken across a wide range of plasma conditions and provide informative relationships between the plasma parameters at the entrance of the inner divertor and the crown of the plasma. The low-turbulence plasmas on the inboard scrape-off layer make it possible to clearly quantify the sheath-expansion around Langmuir probes. An I-V fitter has been developed which can account for sheath-expansion in a theoretically consistent way, improving the reliability of Langmuir probe data analysis. In an inner-wall limited experiment in DIII-D requested by ITER, the Swing-Probes made the first Langmuir probe measurements of an enhanced heat flux feature just outside the LCFS. These measurements

  1. Low cost FPGA based data acquisition system for a gamma imaging probe

    Science.gov (United States)

    Fysikopoulos, E.; Georgiou, M.; Loudos, G.; Matsopoulos, G.

    2013-11-01

    We present the development of a low cost field programmable gate arrays (FPGA) based data acquisition system for a gamma imaging probe proposed for sentinel lymph node (SLN) mapping. Radioguided surgery using a gamma probe is an established practice and has been widely introduced in SLN biopsies. For such applications, imaging systems require compact readout electronics and flexibility. Embedded systems implemented in the FPGA technology offer new possibilities in data acquisition for nuclear medicine imagers. FPGAs are inexpensive compared to application specific integrated circuits (ASICs), usually used for the readout electronics of dedicated gamma cameras and their size is rather small. In this study, cost effective analog to digital converters (ADCs) were used and signal processing algorithms were implemented in the FPGA to extract the energy and position information. The analog front-end electronics were carefully designed taking into account the low sampling rate of the ADCs. The reference gamma probe has a small field of view (2.5 cm × 2.5 cm) and is based on the R8900U-00-C12 position sensitive photomultiplier tube (PSPMT) coupled to a pixellated CsI(Na) scintillator with 1 mm × 1 mm × 5 mm crystal element size. Measurements were carried out using a general purpose collimator and 99mTc sources emitted at 140 keV. Performance parameters for the imaging gamma probe were compared with those obtained when data were acquired using the standard NIM (Nuclear Instrumentation Modules) electronics and found to be in very good agreement, which demonstrates the efficiency of the proposed implementation.

  2. Two-component model of strong Langmuir turbulence - Scalings, spectra, and statistics of Langmuir waves

    Science.gov (United States)

    Robinson, P. A.; Newman, D. L.

    1990-01-01

    A simple two-component model of strong turbulence that makes clear predictions for the scalings, spectra, and statistics of Langmuir waves is developed. Scalings of quantities such as energy density, power input, dissipation power wave collapse, and number density of collapsing objects are investigated in detail and found to agree well with model predictions. The nucleation model of wave-packet formation is strongly supported by the results. Nucleation proceeds with energy flowing from background to localized states even in the absence of a driver. Modulational instabilities play little or no role in maintaining the turbulent state when significant density nonuniformities are present.

  3. Initial Results in Power System Identification from Injected Probing Signals Using a Subspace Method

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ning; Pierre, John W.; Hauer, John F.

    2006-08-01

    In this paper, the authors use the Numerical algorithm for Subspace State Space System IDentification (N4SID) to extract dynamic parameters from phasor measurements collected on the western North American Power Grid. The data were obtained during tests on June 7, 2000, and they represent wide area response to several kinds of probing signals including Low-Level Pseudo-Random Noise (LLPRN) and Single-Mode Square Wave (SMSW) injected at the Celilo terminal of the Pacific HVDC In-tertie (PDCI). An identified model is validated using a cross vali-dation method. Also, the obtained electromechanical modes are compared with the results from Prony analysis of a ringdown and with signal analysis of ambient data measured under similar op-erating conditions. The consistent results show that methods in this class can be highly effective even when the probing signal is small.

  4. Auto-tuning system for NMR probe with LabView

    Science.gov (United States)

    Quen, Carmen; Mateo, Olivia; Bernal, Oscar

    2013-03-01

    Typical manual NMR-tuning method is not suitable for broadband spectra spanning several megahertz linewidths. Among the main problems encountered during manual tuning are pulse-power reproducibility, baselines, and transmission line reflections, to name a few. We present a design of an auto-tuning system using graphic programming language, LabVIEW, to minimize these problems. The program is designed to analyze the detected power signal of an antenna near the NMR probe and use this analysis to automatically tune the sample coil to match the impedance of the spectrometer (50 Ω). The tuning capacitors of the probe are controlled by a stepper motor through a LabVIEW/computer interface. Our program calculates the area of the power signal as an indicator to control the motor so disconnecting the coil to tune it through a network analyzer is unnecessary. Work supported by NSF-DMR 1105380

  5. Propulsion System and Mission Design of AMSAT P5-A Mars Probe

    Science.gov (United States)

    Peukert, M.; Riehle, M.

    2002-01-01

    The ham radio operators group AMSAT is currently preparing studies about the feasibility of developing a low cost mission to mars. The probe, called P5-A shall be mainly based on the design of the amateur radio satellite P3-D, launched in November 2000 atop Ariane 507. The satellite design team of AMSAT is lead by the German subsidiary of this international organisation and is supported by ASTRIUM in Lampolshausen, Germany. The support of ASTRIUM may encompass the delivery of major propulsion system components like the bi-propellant Apogee Engine, as already done for former AMSAT projects. Further on propulsion system experts from ASTRIUM have offered support to AMSAT during the design process and during critical satellite operations (e.g. fuelling on launch site). The present paper describes the mission design and the general layout of the P5-A mars probe with strong emphasise on the propulsion system. Probe Design Communication and development of the corresponding techniques is the main field of activities of the amateur radio operators. Thus the main payload of the probe will be an extensive and sophisticated communication equipment. Other organisations even have shown interest to use this mars probe as data relay for their own missions. To save costs, the design of the recently developed satellite P3-D shall be used as far as possible. One side of the hexagonal shaped structure of the satellite will be occupied by a dish antenna to establish from mars orbit a high data download rate of 50,000 bits/sec at the frequency of 10.5 GHz. As counterpart on ground the 20 m Cassegrain-reflector of Bochum University will be used. Due to the fixed antenna the probe has to be 3- axis stabilised. Therefore the use of magnetic wheels in conjunction with thrusters is foreseen. The paper will describe the propulsion system layout and design. For impulsive manoeuvres the ASTRIUM built 400N Apogee Engine is foreseen. For interplanetary corrections or thrust phases the use of an

  6. The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems.

    Science.gov (United States)

    Miccoli, I; Edler, F; Pfnür, H; Tegenkamp, C

    2015-06-10

    The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

  7. The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems

    Science.gov (United States)

    Miccoli, I.; Edler, F.; Pfnür, H.; Tegenkamp, C.

    2015-06-01

    The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

  8. Experimental signatures of localization in Langmuir wave turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Rose, H.A.; DuBois, D.F.; Russell, D.; Bezzerides, B.

    1988-01-01

    Features in certain laser-plasma and ionospheric experiments are identified with the basic properties of Langmuir wave turbulence. Also, a model of caviton nucleation is presented which leads to certain novel scaling predictions. 12 refs., 19 figs.

  9. Inhibition of oil plume dilution in Langmuir ocean circulation

    National Research Council Canada - National Science Library

    Yang, Di; Chamecki, Marcelo; Meneveau, Charles

    2014-01-01

    Oil spills from deep‐water blowouts rise through and interact with the ocean mixed layer and Langmuir turbulence, leading to considerable diversity of oil slick dilution patterns observed on the ocean surface...

  10. Parametric decay of wide band Langmuir wave spectra

    Science.gov (United States)

    Kono, Mitsuo; Pécseli, Hans L.

    2016-12-01

    Previous results obtained for modulational instability of a Langmuir wave spectrum are extended to account also for the Langmuir wave decay. The general model is tested by considering first the parametric decay of single-mode Langmuir waves, and also two-wave models, where several combinations are considered: one wave is modulationally unstable, another decay unstable and one where both waves are unstable with respect to decay. For the general case with continuous wave spectra it is found that distribution of the Langmuir wave energy over a wide wavenumber band reduces the decay rate when the correlation length for the spectrum becomes comparable to the wavelength of the most unstable sound wave among the possible decay products.

  11. Comparative analyses of plasma probe diagnostics techniques

    Energy Technology Data Exchange (ETDEWEB)

    Godyak, V. A. [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts 02446 (United States); Alexandrovich, B. M. [Plasma Sensors, Brookline, Massachusetts 02446 (United States)

    2015-12-21

    The subject of this paper is a comparative analysis of the plasma parameters inferred from the classical Langmuir probe procedure, from different theories of the ion current to the probe, and from measured electron energy distribution function (EEDF) obtained by double differentiation of the probe characteristic. We concluded that the plasma parameters inferred from the classical Langmuir procedure can be subjected to significant inaccuracy due to the non-Maxwellian EEDF, uncertainty of locating the plasma potential, and the arbitrariness of the ion current approximation. The plasma densities derived from the ion part of the probe characteristics diverge by as much as an order of magnitude from the density calculated according to Langmuir procedure or calculated as corresponding integral of the measured EEDF. The electron temperature extracted from the ion part is always subjected to uncertainty. Such inaccuracy is attributed to modification of the EEDF for fast electrons due to inelastic electron collisions, and to deficiencies in the existing ion current theories; i.e., unrealistic assumptions about Maxwellian EEDFs, underestimation of the ion collisions and the ion ambipolar drift, and discounting deformation of the one-dimensional structure of the region perturbed by the probe. We concluded that EEDF measurement is the single reliable probe diagnostics for the basic research and industrial applications of highly non-equilibrium gas discharge plasmas. Examples of EEDF measurements point up importance of examining the probe current derivatives in real time and reiterate significance of the equipment technical characteristics, such as high energy resolution and wide dynamic range.

  12. Nonlinear Langmuir Wave Modulation in Weakly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Pécseli, Hans

    1978-01-01

    influence on the modulation stability of plane Langmuir waves. As in the unmagnetized case, kinetic results were found to deviate considerably from those obtained by using a fluid description for the ion dynamics. With particular attention to ionospheric phenomena, the effect is included of the spatially...... varying electron heating in the amplitude modulated Langmuir wave. For modulations travelling almost perpendicular to the magnetic field, this effect has a profound influence on a modulational instability...

  13. Intelligent MTconnect. Eddy-Current Valve Probe Pilot Project within the High Pressure Gas Facility (HPGF) Liquid Nitrogen Evaporator Systems

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will perform real-time collection of prognostic valve operational data by deploying smart eddy-current probes with the use of the MTconnect® system,...

  14. Hard real-time beam scheduler enables adaptive images in multi-probe systems

    Science.gov (United States)

    Tobias, Richard J.

    2014-03-01

    Real-time embedded-system concepts were adapted to allow an imaging system to responsively control the firing of multiple probes. Large-volume, operator-independent (LVOI) imaging would increase the diagnostic utility of ultrasound. An obstacle to this innovation is the inability of current systems to drive multiple transducers dynamically. Commercial systems schedule scanning with static lists of beams to be fired and processed; here we allow an imager to adapt to changing beam schedule demands, as an intelligent response to incoming image data. An example of scheduling changes is demonstrated with a flexible duplex mode two-transducer application mimicking LVOI imaging. Embedded-system concepts allow an imager to responsively control the firing of multiple probes. Operating systems use powerful dynamic scheduling algorithms, such as fixed priority preemptive scheduling. Even real-time operating systems lack the timing constraints required for ultrasound. Particularly for Doppler modes, events must be scheduled with sub-nanosecond precision, and acquired data is useless without this requirement. A successful scheduler needs unique characteristics. To get close to what would be needed in LVOI imaging, we show two transducers scanning different parts of a subjects leg. When one transducer notices flow in a region where their scans overlap, the system reschedules the other transducer to start flow mode and alter its beams to get a view of the observed vessel and produce a flow measurement. The second transducer does this in a focused region only. This demonstrates key attributes of a successful LVOI system, such as robustness against obstructions and adaptive self-correction.

  15. Towards local electromechanical probing of cellular and biomolecular systems in a liquid environment

    Energy Technology Data Exchange (ETDEWEB)

    Kalinin, Sergei V [Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37931 (United States); Rodriguez, Brian J [Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37931 (United States); Jesse, Stephen [Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37931 (United States); Seal, Katyayani [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37931 (United States); Proksch, Roger [Asylum Research, Santa Barbara, CA 93117 (United States); Hohlbauch, Sophia [Asylum Research, Santa Barbara, CA 93117 (United States); Revenko, Irene [Asylum Research, Santa Barbara, CA 93117 (United States); Thompson, Gary Lee [Department of Bioengineering, Clemson University, Clemson, SC 29634 (United States); Vertegel, Alexey A [Department of Bioengineering, Clemson University, Clemson, SC 29634 (United States)

    2007-10-24

    Electromechanical coupling is ubiquitous in biological systems, with examples ranging from simple piezoelectricity in calcified and connective tissues to voltage-gated ion channels, energy storage in mitochondria, and electromechanical activity in cardiac myocytes and outer hair cell stereocilia. Piezoresponse force microscopy (PFM) originally emerged as a technique to study electromechanical phenomena in ferroelectric materials, and in recent years has been employed to study a broad range of non-ferroelectric polar materials, including piezoelectric biomaterials. At the same time, the technique has been extended from ambient to liquid imaging on model ferroelectric systems. Here, we present results on local electromechanical probing of several model cellular and biomolecular systems, including insulin and lysozyme amyloid fibrils, breast adenocarcinoma cells, and bacteriorhodopsin in a liquid environment. The specific features of PFM operation in liquid are delineated and bottlenecks on the route towards nanometre-resolution electromechanical imaging of biological systems are identified.

  16. A Thermal Melt Probe System for Extensive, Low-Cost Instrument Deployment Within and Beneath Ice Sheets

    Science.gov (United States)

    Winebrenner, D. P.; Elam, W. T.; Carpenter, M.; Kintner, P., III

    2014-12-01

    component and system testing. We are therefore revising the probe heaters using a newer but more development-intensive technology. With probe systems now validated in our tests, this will result in a reliable means to emplace instruments for studies of subglacial hydrology, ice dynamics, and possible subglacial ecologies.

  17. Super-ASTROD: Probing primordial gravitational waves and mapping the outer solar system

    CERN Document Server

    Ni, Wei-Tou

    2008-01-01

    Super-ASTROD (Super Astrodynamical Space Test of Relativity using Optical Devices or ASTROD III) is a mission concept with 3-5 spacecraft in 5 AU orbits together with an Earth-Sun L1/L2 spacecraft ranging optically with one another to probe primordial gravitational-waves with frequencies 0.1 microHz - 1 mHz, to test fundamental laws of spacetime and to map the outer solar system. In this paper we address to its scientific goals, orbit and payload selection, and sensitivity to gravitational waves.

  18. System-Level Design of an Integrated Receiver Front End for a Wireless Ultrasound Probe

    DEFF Research Database (Denmark)

    di Ianni, Tommaso; Hemmsen, Martin Christian; Llimos Muntal, Pere;

    2016-01-01

    In this paper, a system-level design is presented for an integrated receive circuit for a wireless ultrasound probe, which includes analog front ends and beamformation modules. This paper focuses on the investigation of the effects of architectural design choices on the image quality. The point......). The designs that minimally satisfy the specifications are based on an 8-b 30-MSPS Nyquist converter and a single-bit third-order 240-MSPS modulator, with an SNR for the LNA in both cases equal to 64 dB. The mean lateral FWHM and CR are 2.4% and 7.1% lower for the architecture compared with the Nyquistrate one...

  19. The Modeling of Pulmonary Particulate Matter Transport Using Langmuir Monolayers

    Science.gov (United States)

    Eaton, Jeremy M.

    The effects of a barrier in proximity to the air-water interface on the dynamics of a Langmuir monolayer system are observed. A monolayer of Survanta, bovine lung surfactant, is deposited onto the interface of an aqueous buffer solution. Polystyrene particles one micron in diameter and tagged with fluorescent carboxylate groups are distributed evenly throughout the monolayer surface. The bead-monolayer system is compressed and expanded to induce folding. A polydimethylsiloxane (PDMS) substrate is placed below the monolayer in the buffer solution to study interactions between the folding monolayer and a barrier. The presence of the substrate is shown to shift surface pressure-area isotherms toward regions of lower area by an average of 8.9 mN/m. The surface of the PDMS substrate can be imaged using fluorescence microscopy to detect the presence of particles or surfactant that may have been transported there from the air-water interface during folding. Images show the transferral of particles and monolayer together suggesting the pinch-off of a fold or the direct interaction of a fold with the barrier.

  20. Science Instrument Support Electronics Systems for the Relativity Mission Satellite, Gravity Probe B

    Science.gov (United States)

    Bencze, W. J.; Brumley, R. W.; Buchman, S.; Clarke, B.; Hipkins, D. N.; Farley, R.; Shestople, P.; Meriwether, D.; Gray, C.

    The Relativity Mission, Gravity Probe B (GP-B), uses four redundant high precision electrostatically suspended mechanical gyroscopes for measuring the relativistic precessions of the frame of reference in a 640 km polar orbit. The two precessions to be measured are predicted in General Relativity are the geodetic effect, 6.6 arcsec/year, and the frame dragging effect, 0.042 arcsec/year. The Science Instrument Support Electronics or Payload Electronics Package enables this measurement to be performed by providing the necessary control and monitoring functions for the Science Instrument Assembly that contains the four gyroscopes and reference star tracking telescope. This paper describes the overall architecture of the Payload Electronics system and the design and operation of its component parts: 1) the SQUID Readout electronics (SRE) for gyroscope orientation measurement, 2) The Gyroscope Suspension System (GSS) for gyroscope electrostatic suspension and spin axis alignment, 3) the Telescope Readout Electronics (TRE) for measurement of the reference star location, 4) the Experiment Control Unit (ECU) for heater, valve, and rotor electrostatic charge control and thermometry, 5) the custom GPS receiver for orbital position determination and time reference generation, and 6) the Gas Management Assembly (GMA) that controls and routes the gaseous helium used for initial gyroscope spin-up. Contingent upon a successful launch of Gravity Probe on April 17 2004, preliminary performance results will be presented along side the predicated performance estimates derived from system analysis and test on the ground prior to launch.

  1. Fluorescent iron lines as a probe of astrophysical black hole systems

    CERN Document Server

    Reynolds, C S; Reynolds, Christopher S.; Nowak, Michael A.

    2003-01-01

    (abridged) With most physicists and astrophysicists in agreement that black holes do indeed exist, the focus of astrophysical black hole research has shifted to the detailed properties of these systems. Nature has provided us with an extremely useful probe of the region very close to an accreting black hole - X-ray irradiation of relatively cold material in the vicinity of the black hole can imprint characteristic features into the X-ray spectra of black hole systems, most notably the Kalpha fluorescent line of iron. Detailed X-ray spectroscopy of these features can be used to study Doppler and gravitational redshifts, thereby providing key information on the location and kinematics of the cold material. This is a powerful tool that allows us to probe within a few gravitational radii, or less, of the event horizon. Here, we present a comprehensive review of relativistic iron line studies for both accreting stellar mass black holes (i.e., Galactic Black Hole Candidate systems; GBHCs), and accreting supermassiv...

  2. Precision electrostatic suspension system for the Gravity Probe B relativity mission’s science gyroscopes

    Science.gov (United States)

    Bencze, W. J.; Eglington, M. E.; Brumley, R. W.; Buchman, S.

    Presented here is a hybrid digital/analog electrostatic suspension control system for the NASA/Stanford University Gravity Probe B Relativity Mission’s science gyroscopes. An adaptive LQE algorithm, called Authority-on-Demand (AOD), has been developed to meet the high dynamic range requirements for mission’s electrostatic suspension, while minimizing suspension induced torques on the rotor. AOD is novel because it uses plant state estimates, rather than plant parameter estimates, as inputs for adaptation. In addition minimizing disturbance torques on the gyroscope, this suspension system can also maximize and control disturbances torques to perform a post spin-up alignment of the gyroscope spin axes. A backup all-analog proportional-derivative (PD) controller subsystem is provided to maintain control of the rotor in the event of computer faults/radiation induced upsets. A precision mechanical simulation of the gyroscope’s capacitive interface and dynamic response is used to verify performance of the overall system.

  3. Inverting pump-probe spectroscopy for state tomography of excitonic systems.

    Science.gov (United States)

    Hoyer, Stephan; Whaley, K Birgitta

    2013-04-28

    We propose a two-step protocol for inverting ultrafast spectroscopy experiments on a molecular aggregate to extract the time-evolution of the excited state density matrix. The first step is a deconvolution of the experimental signal to determine a pump-dependent response function. The second step inverts this response function to obtain the quantum state of the system, given a model for how the system evolves following the probe interaction. We demonstrate this inversion analytically and numerically for a dimer model system, and evaluate the feasibility of scaling it to larger molecular aggregates such as photosynthetic protein-pigment complexes. Our scheme provides a direct alternative to the approach of determining all Hamiltonian parameters and then simulating excited state dynamics.

  4. Measurement of rare probes with the silicon tracking system of the CBM experiment at FAIR

    Science.gov (United States)

    Heuser, Johann; Friese, Volker

    2014-11-01

    The Compressed Baryonic Matter (CBM) experiment at FAIR will explore the phase diagram of strongly interacting matter at highest net baryon densities and moderate temperatures. The CBM physics program will be started with beams delivered by the SIS 100 synchrotron, providing energies from 2 to 14 GeV/nucleon for heavy nuclei, up to 14 GeV/nucleon for light nuclei, and 29 GeV for protons. The highest net baryon densities will be explored with ion beams up to 45 GeV/nucleon energy delivered by SIS 300 in the next stage of FAIR. Collision rates up to 107 per second are required to produce very rare probes with unprecedented statistics in this energy range. Their signatures are complex. These conditions call for detector systems designed to meet the extreme requirements in terms of rate capability, momentum and spatial resolution, and a novel DAQ and trigger concept which is not limited by latency but by throughput. In this paper we outline the concepts of CBM's central detector, the Silicon Tracking System, and of the First-Level Event Selector, a dedicated computing farm to reduce on-line the raw data volume by up to three orders of magnitude to a recordable rate. Progress with the development of detector and software algorithms are discussed and examples of performance studies on the reconstruction of rare probes at SIS 100 and SIS 300 energies given.

  5. Resolution limit of probe-forming systems with magnetic quadrupole lens triplets and quadruplets

    CERN Document Server

    Ponomarev, A G; Miroshnichenko, V I; Storizhko, V E; Sulkio-Cleff, B

    2003-01-01

    Over the past decade, in MeV ion beam microanalysis efforts to achieve a spatial resolution better than 0.1 mu m with a beam current of approx 100 pA have been connected with microprobes of new generation where the probe is formed by means of separated magnetic quadrupole lens structures . However, as was pointed out in , no dramatic improvements in spatial resolution have been produced so far. For better understanding of the situation the authors carried out theoretical studies of multiparameter sets of probe-forming systems based on separated triplets and quadruplets of magnetic quadrupole lenses. Comparisons were made between the highest current values attained at different systems for a given beam spot size. The maximum parasitic sextupole and octupole field components were found whose contributions to spot broadening are tolerable. It is shown that the use of modern electrostatic accelerators and precision magnetic quadrupole lenses makes it possible to eliminate the effect of chromatic aberrations and s...

  6. Measurement of rare probes with the silicon tracking system of the CBM experiment at FAIR

    Energy Technology Data Exchange (ETDEWEB)

    Heuser, Johann; Friese, Volker

    2014-11-15

    The Compressed Baryonic Matter (CBM) experiment at FAIR will explore the phase diagram of strongly interacting matter at highest net baryon densities and moderate temperatures. The CBM physics program will be started with beams delivered by the SIS 100 synchrotron, providing energies from 2 to 14 GeV/nucleon for heavy nuclei, up to 14 GeV/nucleon for light nuclei, and 29 GeV for protons. The highest net baryon densities will be explored with ion beams up to 45 GeV/nucleon energy delivered by SIS 300 in the next stage of FAIR. Collision rates up to 10{sup 7} per second are required to produce very rare probes with unprecedented statistics in this energy range. Their signatures are complex. These conditions call for detector systems designed to meet the extreme requirements in terms of rate capability, momentum and spatial resolution, and a novel DAQ and trigger concept which is not limited by latency but by throughput. In this paper we outline the concepts of CBM's central detector, the Silicon Tracking System, and of the First-Level Event Selector, a dedicated computing farm to reduce on-line the raw data volume by up to three orders of magnitude to a recordable rate. Progress with the development of detector and software algorithms are discussed and examples of performance studies on the reconstruction of rare probes at SIS 100 and SIS 300 energies given.

  7. Role of strongly modulated coherence in transient evolution dynamics of probe absorption in a three-level atomic system

    Science.gov (United States)

    Panchadhyayee, Pradipta

    2013-11-01

    We investigate the dynamical behaviour of atomic response in a closed three-level V-type atomic system with the variation of different relevant parameters to exhibit transient evolution of absorption, gain and transparency in the probe response. The oscillations in probe absorption and gain can be efficiently modulated by changing the values of the Rabi frequency, detuning and the collective phase involved in the system. The interesting outcome of the work is the generation of coherence controlled loop-structure with varying amplitudes in the oscillatory probe response of the probe field at various parameter conditions. The prominence of these structures is observed when the coherence induced in a one-photon excitation path is strongly modified by two-step excitations driven by the coherent fields operating in closed interaction contour. In contrast to purely resonant case, the time interval between two successive loops gets significantly reduced with the application of non-zero detuning in the coherent fields.

  8. Development of a coumarin-furan conjugate as Zn2 + ratiometric fluorescent probe in ethanol-water system

    Science.gov (United States)

    Li, Chao-rui; Li, Si-liang; Yang, Zheng-yin

    2017-03-01

    In this study, a novel coumarin-derived compound bearing the furan moiety called 7-diethylamino-3-formylcoumarin (2‧-furan formyl) hydrazone (1) has been designed, synthesized and evaluated as a Zn2 + ratiometric fluorescent probe in ethanol-water system. This probe 1 showed good selectivity and high sensitivity towards Zn2 + over other metal ions investigated, and a decrease in fluorescence emission intensity at 511 nm accompanied by an enhancement in fluorescence emission intensity at 520 nm of this probe 1 was observed in the presence of Zn2 + in ethanol-water (V : V = 9 : 1) solution, which provided ratiometric fluorescence detection of Zn2 +. Additionally, the ratiometric fluorescence response of 1 to Zn2 + was nearly completed within 0.5 min, which suggested that this probe 1 could be utilized for sensing and monitoring Zn2 + in environmental and biological systems for real-time detection.

  9. Molecular Dynamic Studies on Langmuir Monolayers of Stearic Acid

    Institute of Scientific and Technical Information of China (English)

    KONG Chui-peng; ZHANG Hong-xing; ZHAO Zeng-xia; ZHENG Qing-chuan

    2013-01-01

    Compression isotherm for stearic acid was obtained by means of molecular dynamic simulation and compared to experimentally measured values for the Langmuir monolayers.Compared to the previous simulation,the present simulation has provided a method to reproduce the compression of the monolayer.The result is consistent with other experimental results.By analyzing the alkyl tails,the configuration of stearic acid molecules during the compression process was studied and a uniform monolayer was obtained after compression.Stearic acid molecules were observed to form fine organized monolayer from completely random structure.Hexatic order of the arrangement has been identified for the distribution of stearic acid molecules in the monolayer.At the end of the compression,the stearic acid molecules were tightly packed in the gap of two other molecules.At last,the hydrogen bonds in the system were analyzed.The main hydrogen bonds were from stearic acid-water interaction and their intensities constantly decreased with the decreased of surface area per molecule.The weak hydrogen bond interaction between stearic acid molecules may be the reason of easy collapse.

  10. Study of a vibrating fiber probing system for 3-D micro-structures: performance improvement

    Science.gov (United States)

    Murakami, H.; Katsuki, A.; Sajima, T.; Suematsu, T.

    2014-09-01

    This paper presents a system for measuring 3D micro-structures that uses an optical fiber probe equipped with a piezo element that causes the probe to vibrate. The optical fiber probe consists of a stylus shaft with a diameter of 3 µm and a glass ball with a diameter of 5 µm attached to the tip. The stylus is vibrated in a circular motion in a single plane. The vibrator mechanism is introduced to prevent adhesion of the stylus tip to the surface being measured. This adhesion, which adversely affects the accuracy and time of the measurement, is caused by intermolecular, electrostatic, and liquid bridge forces. The measuring principle involves monitoring the vibrational amplitude of the stylus shaft that is required to prevent the adhesion of the stylus tip to the surface being measured, this amplitude being measured optically. In our previous report (Murakami et al 2012 Key Eng. Mater. 523-524 907-12), we found that the stylus shaft actually moves in an elliptical motion when it is set to describe a circular motion in the X-Y plane. Therefore, when a measurement is taken, it is necessary to adjust the motion of the piezoelectric tube to compensate for the difference between the diameter of the perfect circle and the actual elliptical motion of the stylus shaft displacement. In this study, the stylus characteristics were examined and the motion of the stylus shaft was then corrected to attain the desired circular motion. Next, the expansion of the measuring area by using a line laser was investigated. Finally, an experiment involving the measurement of a micro-hole was performed to demonstrate the practicality of the vibrating fiber probe. As a result, it was shown that the displacement between the diameter of the perfect circle and the actual elliptical motion of the stylus tip was about 0.034 µm after compensation. In addition, it was confirmed that the measurement area can be expanded by using an optical slit, but the standard deviation of the

  11. Probe Amplification with or without Population Inversion in a Five-Level Atomic System with Double-Dark Resonances

    Institute of Scientific and Technical Information of China (English)

    LI Jia-Hua; XIE Xiao-Tao; LUO Jin-Ming; LIU Ji-Bing

    2006-01-01

    @@ We theoretically investigate the response of the probe amplification in a five-level atomic system in the presence of interacting double-dark resonances disturbed by introducing an additional signal field. It is found that a large enhancement of the probe amplification with or without population inversion can be achieved by properly adjusting the strengths of the microwave driving field and the signal laser field. From viewpoint of physics, we qualitatively explain these results in terms of quantum interference and dressed states.

  12. All-optical optoacoustic microscopy system based on probe beam deflection technique

    Science.gov (United States)

    Maswadi, Saher M.; Tsyboulskic, Dmitri; Roth, Caleb C.; Glickman, Randolph D.; Beier, Hope T.; Oraevsky, Alexander A.; Ibey, Bennett L.

    2016-03-01

    It is difficult to achieve sub-micron resolution in backward mode OA microscopy using conventional piezoelectric detectors, because of wavefront distortions caused by components placed in the optical path, between the sample and the objective lens, that are required to separate the acoustic wave from the optical beam. As an alternate approach, an optoacoustic microscope (OAM) was constructed using the probe beam deflection technique (PBDT) to detect laserinduced acoustic signals. The all-optical OAM detects laser-generated pressure waves using a probe beam passing through a coupling medium, such as water, filling the space between the microscope objective lens and sample. The acoustic waves generated in the sample propagate through the coupling medium, causing transient changes in the refractive index that deflect the probe beam. These deflections are measured with a high-speed, balanced photodiode position detector. The deflection amplitude is directly proportional to the magnitude of the acoustic pressure wave, and provides the data required for image reconstruction. The sensitivity of the PBDT detector expressed as noise equivalent pressure was 12 Pa, comparable to that of existing high-performance ultrasound detectors. Because of the unimpeded working distance, a high numerical aperture objective lens, i.e. NA = 1, was employed in the OAM to achieve near diffraction-limited lateral resolution of 0.5 μm at 532nm. The all-optical OAM provides several benefits over current piezoelectric detector-based systems, such as increased lateral and axial resolution, higher sensitivity, robustness, and potentially more compatibility with multimodal instruments.

  13. Probing the Catalytic Charge-Relay System in Alanine Racemase with Genetically Encoded Histidine Mimetics.

    Science.gov (United States)

    Sharma, Vangmayee; Wang, Yane-Shih; Liu, Wenshe R

    2016-12-16

    Histidine is a unique amino acid with an imidazole side chain in which both of the nitrogen atoms are capable of serving as a proton donor and proton acceptor in hydrogen bonding interactions. In order to probe the functional role of histidine involved in hydrogen bonding networks, fine-tuning the hydrogen bonding potential of the imidazole side chain is required but not feasible through traditional mutagenesis methods. Here, we show that two close mimetics of histidine, 3-methyl-histidine and thiazole alanine, can be genetically encoded using engineered pyrrolysine incorporation machinery. Replacement of the three histidine residues predicted to be involved in an extended charge-relay system in alanine racemase with 3-methyl-histidine or thiazole alanine shows a dramatic loss in the enzyme's catalytic efficiency, implying the role of this extended charge-relay system in activating the active site residue Y265, a general acid/base catalyst in the enzyme.

  14. Commercial-Off-The-Shelf Microelectromechanical Systems (MEMS) Flow-Measurement Probes Fabricated And Assembled

    Science.gov (United States)

    Redding, Chip

    2002-01-01

    As an alternative to conventional tubing instrumentation for measuring airflow, designers and technicians at the NASA Glenn Research Center have been fabricating packaging components and assembling a set of unique probes using commercial-off-the-shelf microelectromechanical systems (MEMS) integrated circuits (computer chips). Using MEMS as an alternative has some compelling advantages over standard measurement devices. Sensor technologies have matured through high-production usage in industries such as automotive and aircraft manufacturers. Currently, MEMS are the choice in applications such as tire pressure monitors, altimeters, pneumatic controls, cable leak detectors, and consumer appliances. Conventional instrumentation uses tubing buried in the model aerodynamic surfaces or wind tunnel walls. The measurements are made when pressure is introduced at the tube opening. The pressure then must travel the tubing for lengths ranging from 20 to hundreds of feet before reaching an electronic signal conditioner. This condition causes a considerable amount of damping and requires measurements to be made only after the test rig has reached steady-state operation. The electronic MEMS pressure sensor is able to take readings continuously under dynamic states in nearly real time. The use of stainless steel tubing for pressure measurements requires many tubes to be cleaned, cut to length, carefully installed, and delicately deburred and spliced for use. A cluster of a few hundred 1/16-in.- (0.0625-in.-) diameter tubes (not uncommon in research testing facilities) can be several inches in diameter and may weigh enough to require two men to handle. Replacing hard tubing with electronic chips can eliminate much of the bulk. Each sensor would fit on the tip of the 1/16-in. tubing with room to spare. The P592 piezoresistive silicon pressure sensor (Lucas NovaSensor, Fremont, CA) was chosen for this project because of its cost, availability, and tolerance to extreme ambient

  15. Conductivity Probe

    Science.gov (United States)

    2008-01-01

    The Thermal and Electrical Conductivity Probe (TECP) for NASA's Phoenix Mars Lander took measurements in Martian soil and in the air. The needles on the end of the instrument were inserted into the Martian soil, allowing TECP to measure the propagation of both thermal and electrical energy. TECP also measured the humidity in the surrounding air. The needles on the probe are 15 millimeters (0.6 inch) long. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  16. Probing into the local structure of quadrupolar spin systems with MRFM

    Science.gov (United States)

    Verhagen, Rieko; Hilbers, Cees; Kentgens, Arno; van Kempen, Herman

    2001-03-01

    Magnetic Resonance Force Microscopy is a method to enhance the sensitivity of conventional inductive Nuclear Magnetic Resonance. It combines the advantages of Atomic Force Microscopy with those of NMR, resulting in a method that has both high spatial resolution and sub-surface sensitivity. This gives the capability of 3D imaging and/or spectral characterization of nanoscale structures. We have adapted a conventional MRFM probe to observe nuclei other than protons. The objective of this modification lays in the possibility to observe nuclear spins with spin quantum numbers other than 1/2. In an external magnetic field (Zeeman interaction), these nuclei have multiple spin-transitions with equal energy differences, causing a single spectral line. However, the nuclei have a quadrupole moment and therefore interact with the electrical field gradient caused by charge distributions in the local environment. This shifts the spin energy levels differently so that several transitions occur at different NMR frequencies. The quadrupolar interaction can be used as a probe for obtaining information on the local structure. Since the quadrupolar splitting can be large compared to the spectral resolution of the MRFM detection method it may be imaged using MRFM. We present some methods and first results of MRFM on quadrupolar spin systems, specifically ^23Na (S=3/2) at 4.2T. It is shown that the method is capable of observing the splitting and may obtain local disorders in the lattice structure by scanning the sample.

  17. Systems-based approaches to probing metabolic variation within the Mycobacterium tuberculosis complex.

    Directory of Open Access Journals (Sweden)

    Emma K Lofthouse

    Full Text Available The Mycobacterium tuberculosis complex includes bovine and human strains of the tuberculosis bacillus, including Mycobacterium tuberculosis, Mycobacterium bovis and the Mycobacterium bovis BCG vaccine strain. M. bovis has evolved from a M. tuberculosis-like ancestor and is the ancestor of the BCG vaccine. The pathogens demonstrate distinct differences in virulence, host range and metabolism, but the role of metabolic differences in pathogenicity is poorly understood. Systems biology approaches have been used to investigate the metabolism of M. tuberculosis, but not to probe differences between tuberculosis strains. In this study genome scale metabolic networks of M. bovis and M. bovis BCG were constructed and interrogated, along with a M. tuberculosis network, to predict substrate utilisation, gene essentiality and growth rates. The models correctly predicted 87-88% of high-throughput phenotype data, 75-76% of gene essentiality data and in silico-predicted growth rates matched measured rates. However, analysis of the metabolic networks identified discrepancies between in silico predictions and in vitro data, highlighting areas of incomplete metabolic knowledge. Additional experimental studies carried out to probe these inconsistencies revealed novel insights into the metabolism of these strains. For instance, that the reduction in metabolic capability observed in bovine tuberculosis strains, as compared to M. tuberculosis, is not reflected by current genetic or enzymatic knowledge. Hence, the in silico networks not only successfully simulate many aspects of the growth and physiology of these mycobacteria, but also provide an invaluable tool for future metabolic studies.

  18. Test evaluation of potential heat shield contamination of an Outer Planet Probe's atmospheric sampling system

    Science.gov (United States)

    Kessler, W. C.; Woeller, F. H.; Wilkins, M. E.

    1975-01-01

    An Outer Planets Probe which retains the charred heatshield during atmospheric descent must deploy a sampling tube through the heatshield to extract atmospheric samples for analysis. Once the sampling tube is deployed, the atmospheric samples ingested must be free of contaminant gases generated by the heatshield. Outgassing products such as methane and water vapor are present in planetary atmospheres and hence, ingestion of such species would result in gas analyzer measurement uncertainties. This paper evaluates the potential for, and design impact of, the extracted atmospheric samples being contaminated by heatshield outgassing products. Flight trajectory data for Jupiter, Saturn and Uranus entries are analyzed to define the conditions resulting in the greatest potential for outgassing products being ingested into the probe's sampling system. An experimental program is defined and described which simulates the key flow field features for a planetary flight in a ground-based test facility. The primary parameters varied in the test include: sampling tube length, injectant mass flow rate and angle of attack. Measured contaminant levels predict the critical sampling tube length for contamination avoidance. Thus, the study demonstrates the compatibility of a retained heatshield concept and high quality atmospheric trace species measurements.

  19. Hard scattering of partons as a probe of collisions at RHIC using the STAR detector system

    Energy Technology Data Exchange (ETDEWEB)

    Christie, W.B. [Brookhaven National Lab., Upton, NY (United States)

    1995-07-15

    Presented here is the current state of the author`s investigations into the use of hard probes to study pp, pA, and AA collisions at the Relativistic Heavy Ion Collider (RHIC) being built at Brookhaven National Laboratory. The overall goal of the RHIC program is the discovery and study of the Quark-Gluon Plasma (QGP), which is predicted to be formed at the high energy densities reached at RHIC in high energy AA collisions. The term {open_quotes}Hard probes{close_quotes} as used in this document includes those particles whose origin is the result of a direct hard parton scatter (i.e qq, qg, or gg). The final states of these hard parton scatters which the author proposes to study include dijets, gamma-jet coincidences, and inclusive high P{sub t} particle spectra. A brief discussion of the physics objectives is given in section 1. This is followed by an introduction to the STAR detector system in section 2, with particular details given for the proposed STAR Electromagnetic Calorimeter (EMC). The present simulation studies and results are given in section 3. The author concludes with a summary and a discussion of future plans in section 4.

  20. The response of the Ocean Surface Boundary Layer and Langmuir turbulence to tropical cyclones

    Science.gov (United States)

    Wang, Dong; Kukulka, Tobias; Reichl, Brandon; Hara, Tetsu; Ginis, Isaac

    2016-11-01

    The interaction of turbulent ocean surface boundary layer (OSBL) currents and the surface waves' Stokes drift generates Langmuir turbulence (LT), which enhances OSBL mixing. This study investigates the response of LT to extreme wind and complex wave forcing under tropical cyclones (TCs), using a large eddy simulation (LES) approach based on the wave-averaged Navier-Stokes equations. We simulate the OSBL response to TC systems by imposing the wind forcing of an idealized TC storm model, covering the entire horizontal extent of the storm systems. The Stokes drift vector that drives the wave forcing in the LES is determined from realistic spectral wave simulations forced by the same wind fields. We find that the orientations of Langmuir cells are vertically uniform and aligned with the wind in most regions despite substantial wind-wave misalignment in TC conditions. LT's penetration depth is related to Stokes drift depth and limited by OSBL depth. A wind-projected surface layer Langmuir number is proposed and successfully applied to scale turbulent vertical velocity variance in extreme TC conditions. Current affiliation: Princeton University/NOAA GFDL.

  1. On the Transfer and Control of Space Probes Around the L1 Point of the Sun-Earth+Moon System

    Science.gov (United States)

    Hou, Xi-Yun; Liu, Lin

    2008-01-01

    The motion around the collinear libration points in the restricted three body problem is unstable. But there exist conditionally stable periodic orbits around these points. Special-purpose space probes located in the vicinity of these points (e.g., ISEE-3, SOHO) can benefit from this dynamical property, in regard to maintaining the orbit in position and the energy required of placing the probe in position. As an example, we study in this paper the launch and orbital control of a space probe around the L1 libration point in the system consisting of the Sun and the Earth-Moon. We present some theoretical and numerical simulations' results, which may serve as a basis for the realization of such a space probe in future.

  2. Irving langmuir: o milagre da ciência

    Directory of Open Access Journals (Sweden)

    Gugliotti Marcos

    2001-01-01

    Full Text Available Irving Langmuir received the Nobel Prize in Chemistry in 1932 "...for his outstanding discoveries and investigations within the field of surface chemistry", according to the Swedish Academy. However, few people know that his work comprises other very important contributions, and not only for chemistry, such as the discovery of plasma, the atomic hydrogen, the pure thermoionic phenomenon, the development of the cloud seeding technique for weather modification, among many others. This paper summarizes Langmuir's most important discoveries and theories, with an especial mention for his practical inventions and his work on the atomic theory.

  3. Group-specific small-subunit rRNA hybridization probes to characterize filamentous foaming in activated sludge systems.

    Science.gov (United States)

    de los Reyes, F L; Ritter, W; Raskin, L

    1997-03-01

    Foaming in activated sludge systems is characterized by the formation of a thick, chocolate brown-colored scum that floats on the surface of aeration basins and secondary clarifiers. These viscous foams have been associated with the presence of filamentous mycolic acid-containing actinomycetes. To aid in evaluating the microbial representation in foam, we developed and characterized group-, genus-, and species-specific oligonucleotide probes targeting the small subunit rRNA of the Mycobacterium complex, Gordona spp., and Gordona (Nocardia) amarae, respectively. The use of a universal base analog, 5-nitroindole, in oligonucleotide probe design was evaluated by comparing the characteristics of two different versions of the Mycobacterium complex probe. The temperature of dissociation of each probe was determined. Probe specificity studies with a diverse collection of 67 target and nontarget rRNAs demonstrated the specificity of the probes to the target groups. Whole-cell hybridizations with fluorescein- and rhodamine-labeled probes were performed with pure cultures of various members of the Mycobacterium complex as well as with environmental samples from a full-scale activated sludge plant which experienced foaming. Quantitative membrane hybridizations with activated sludge and anaerobic digester foam showed that 15.0 to 18.3% of the total small-subunit rRNAs could be attributed to members of the Mycobacterium complex, of which a vast majority consisted of Gordona rRNA. Several G. amarae strains made up only a very small percentage of the Gordona strains present. We demonstrated that group-specific rRNA probes are useful tools for the in situ monitoring and identification of filamentous bacteria in activated sludge systems.

  4. The design and testing of the Gravity Probe B suspension and charge control systems

    Science.gov (United States)

    Buchman, Saps; Bencze, William; Brumley, Robert; Clarke, Bruce; Keiser, G. M.

    1998-12-01

    The Relativity Mission Gravity Probe B (GP-B), is designed to verify two rotational effects predicted by gravitational theory. The GP-B gyroscopes (which also double as drag free sensors) are suspended electrostatically, their position is determined by capacitative sensing, and their charge is controlled using electrons generated by ultraviolet photoemission. The main suspension system is digitally controlled, with an analog backup system. Its functional range is 10 m/s2 to 10-7 m/s2. The suspension system design is optimized to be compatible with gyroscope Newtonian drift rates of less than 0.1 marcsec/year (3×10-12 deg/hr), as well as being compatible with the functioning of an ultra low noise dc SQUID magnetometer. Testing of the suspension and charge management systems is performed on the ground using flight gyroscopes, as well as a gyroscope simulator designed to verify performance over the entire functional range. We describe the design and performance of the suspension, charge management, and gyroscope simulator systems.

  5. System identification: a multi-signal approach for probing neural cardiovascular regulation.

    Science.gov (United States)

    Xiao, Xinshu; Mullen, Thomas J; Mukkamala, Ramakrishna

    2005-06-01

    Short-term, beat-to-beat cardiovascular variability reflects the dynamic interplay between ongoing perturbations to the circulation and the compensatory response of neurally mediated regulatory mechanisms. This physiologic information may be deciphered from the subtle, beat-to-beat variations by using digital signal processing techniques. While single signal analysis techniques (e.g., power spectral analysis) may be employed to quantify the variability itself, the multi-signal approach of system identification permits the dynamic characterization of the neural regulatory mechanisms responsible for coupling the variability between signals. In this review, we provide an overview of applications of system identification to beat-to-beat variability for the quantitative characterization of cardiovascular regulatory mechanisms. After briefly summarizing the history of the field and basic principles, we take a didactic approach to describe the practice of system identification in the context of probing neural cardiovascular regulation. We then review studies in the literature over the past two decades that have applied system identification for characterizing the dynamical properties of the sinoatrial node, respiratory sinus arrhythmia, and the baroreflex control of sympathetic nerve activity, heart rate and total peripheral resistance. Based on this literature review, we conclude by advocating specific methods of practice and that future research should focus on nonlinear and time-varying behaviors, validation of identification methods, and less understood neural regulatory mechanisms. Ultimately, we hope that this review stimulates such future investigations by both new and experienced system identification researchers.

  6. Interstellar Silicate Dust Grain Properties in Distant Galaxies Probed by Quasar Absorption Systems

    Science.gov (United States)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam

    2015-01-01

    Dust grains are a fundamental component of the interstellar medium, and significantly impact many of the physical processes driving galaxy evolution, including star formation, and the heating, cooling and ionization of interstellar material. Using the absorption features produced by dust in the spectra of luminous background quasars, it is possible to study the properties of extragalactic interstellar dust grains. We will present results from an ongoing program utilizing existing Spitzer Space Telescope infrared quasar spectra to probe silicate dust grain properties in z<1.4 quasar absorption systems. In combination with complementary ground-based data on associated gas-phase metal absorption lines, we explore connections between the interstellar dust and gas in the quasar absorption systems. Our project yields clear detections of the 10 micron silicate dust absorption feature in the studied systems, as well as detections of the 18 micron silicate dust absorption feature in sources with adequate spectral coverage. Based on measured variations in the breath, peak wavelength, and substructure of the 10 micron absorption features, there appear to be differences in the silicate dust grain properties from system-to-system. We also show indications of trends between the gas-phase metal properties, such as metallicity and gas velocity spread, with the silicate dust grain absorption properties. Support for this work is provided by NASA through an award issued by JPL/Caltech and through NASA grant NNX14AG74G, and from National Science Foundation grants AST-0908890 and AST-1108830 to the University of South Carolina.

  7. Some studies on a solid state sulfur probe for coal gasification systems

    Science.gov (United States)

    Jacob, K. T.; Rao, D. B.; Nelson, H. G.

    1977-01-01

    Measurements on the solid electrolyte cell (Ar + H(2) + H(2)S/CaS + CaF(2) + (Pt)//CaF(2)//(Pt) + CaF(2) + CaS/H(2) + H(2)+Ar) show that the emf of the cell is directly related to the difference in sulfur potentials established at the Ar + H(2) + H(2)S/electrode interfaces. The electrodes convert the sulfur potential gradient across the calcium fluoride electrolyte into an equivalent fluorine potential gradient. Response time of the probe varies from approximately 9 hr at 990 K to 2.5 hr at 1225 K. The conversion of calcium sulfide and/or calcium fluoride into calcium oxide is not a problem anticipated in commercial coal gasification systems. Suggestions are presented for improving the cell for such commercial applications.

  8. Friedel oscillations in graphene-based systems probed by Scanning Tunneling Microscopy

    Science.gov (United States)

    Mallet, Pierre; Brihuega, Iván; Cherkez, Vladimir; Gómez-Rodríguez, Jose Marìa; Veuillen, Jean-Yves

    2016-03-01

    For the last 25 years, scientists have demonstrated the capabilities of Scanning Tunneling Microscopy (STM) to visualize in real space the response of a two-dimensional electron gas to atomic-scale impurities. The analysis of the Friedel oscillations surrounding the impurities yields valuable information regarding the elastic scattering properties, the band structure, the doping level and the symmetry of the electronic states in the two-dimensional host system. We will address in this article the use of this technique for probing the electronic properties of graphene, the star two-dimensional compound of the last decade. In particular, we will emphasize how this technique can be pushed up to unravel the electronic pseudospin, a distinctive degree of freedom of graphene's Dirac fermions.

  9. A broadband proton backlighting platform to probe shock propagation in low-density systems

    Science.gov (United States)

    Sio, H.; Hua, R.; Ping, Y.; McGuffey, C.; Beg, F.; Heeter, R.; Li, C. K.; Petrasso, R. D.; Collins, G. W.

    2017-01-01

    A proton backlighting platform has been developed for the study of strong shock propagation in low-density systems in planar geometry. Electric fields at the converging shock front in inertial confinement fusion implosions have been previously observed, demonstrating the presence of—and the need to understand—strong electric fields not modeled in standard radiation-hydrodynamic simulations. In this planar configuration, long-pulse ultraviolet lasers are used to drive a strong shock into a gas-cell target, while a short-pulse proton backlighter side-on radiographs the shock propagation. The capabilities of the platform are presented here. Future experiments will vary shock strength and gas fill, to probe shock conditions at different Z and Te.

  10. A Rational Method for Probing Macromolecules Dissociation: The Antibody-Hapten System

    CERN Document Server

    Henriques, Elsa S

    2007-01-01

    The unbinding process of a protein-ligand complex of major biological interest was investigated by means of a computational approach at atomistic classical mechanical level. An energy minimisation-based technique was used to determine the dissociation paths of the system by probing only a relevant set of generalized coordinates. The complex problem was reduced to a low-dimensional scanning along a selected distance between the protein and the ligand. Orientational coordinates of the escaping fragment (the ligand) were also assessed in order to further characterise the unbinding. Solvent effects were accounted for by means of the Poisson--Boltzmann continuum model. The corresponding dissociation time was derived from the calculated barrier height, in compliance with the experimentally reported Arrhenius-like behaviour. The computed results are in good agreement with the available experimental data.

  11. Fine structure of Langmuir waves observed upstream of the bow shock at Venus

    Science.gov (United States)

    Hospodarsky, G. B.; Gurnett, D. A.; Kurth, W. S.; Kivelson, M. G.; Strangeway, R. J.; Bolton, S. J.

    1994-01-01

    Highly structured Langmuir waves, also known as electron plasma oscillations, have been observed in the foreshock of Venus using the plasma wave experiment on the Galileo spacecraft during the gravity assist flyby on February 10, 1990. The Galileo wideband sampling system provides digital electric field waveform measurements at sampling rates up to 201,600 samples per second, much higher than any previous instrument of this type. The main Langmuir wave emission band occurs near the local electron plasma frequency, which was approximately 43 kHz. The Langmuir waves are observed to shift above and below the plasma frequency, sometimes by as much as 20 kHz. The shifts in frequency are closely correlated with the downstream distance from the tangent field line, implying that the shifts are controlled by the electron beam velocity. Considerable fine structure is also evident, with timescales as short as 0.15 ms, corresponding to spatial scales of a few tens of Debye lengths. The frequency spectrum often consists of beat-type waveforms, with beat frequencies ranging from 0.2 to 7 kHz, and in a few cases, isolated wave packets. The peak electric field strengths are approximately 1 mV/m. These field strengths are too small for strongly nonlinear processes to be important. The beat-type waveforms are suggestive of a parametric decay process.

  12. The Gravity Probe B Drag-free and Attitude Control System

    Science.gov (United States)

    Adams, Michael; Debra, Daniel

    2007-04-01

    The Gravity Probe B is first space vehicle provide active control of the vehicle's six degrees of freedom (DOF), three in translation and three in attitude. The Attitude and Translation Control (ATC) uses helium boil-off gas from the cryogenic system as a propellant for 16 proportional cold gas thrusters. Differential thruster operation provides forces and torques on the vehicle, common mode operation controls the net flow rate from the dewar that is used in turn to control the liquid helium bath temperature. The pointing system controls the pointing of the guide star tracking telescope to 30 marc-sec at the space vehicle roll period (77.5) and maintained roll phase to 40 arc-sec. The translation control system used acceleration measurements from one science gyroscope's suspension system to null out the effects of external forces from the on-orbit environment (solar wind, radiation pressure, etc). In this way, the vehicle was controlled to fly in a near-perfect gravitational orbit; transverse accelerations on the science gyroscopes were reduced to the 5x10-12 g level. The precise pointing and orbital geometry are essential for minimizing disturbances to the science gyroscopes, and the dewar control is important in maximizing the length of the data collection period..

  13. Spoofing cyber attack detection in probe-based traffic monitoring systems using mixed integer linear programming

    KAUST Repository

    Canepa, Edward S.

    2013-09-01

    Traffic sensing systems rely more and more on user generated (insecure) data, which can pose a security risk whenever the data is used for traffic flow control. In this article, we propose a new formulation for detecting malicious data injection in traffic flow monitoring systems by using the underlying traffic flow model. The state of traffic is modeled by the Lighthill- Whitham-Richards traffic flow model, which is a first order scalar conservation law with concave flux function. Given a set of traffic flow data generated by multiple sensors of different types, we show that the constraints resulting from this partial differential equation are mixed integer linear inequalities for a specific decision variable. We use this fact to pose the problem of detecting spoofing cyber attacks in probe-based traffic flow information systems as mixed integer linear feasibility problem. The resulting framework can be used to detect spoofing attacks in real time, or to evaluate the worst-case effects of an attack offliine. A numerical implementation is performed on a cyber attack scenario involving experimental data from the Mobile Century experiment and the Mobile Millennium system currently operational in Northern California. © American Institute of Mathematical Sciences.

  14. Spoofing cyber attack detection in probe-based traffic monitoring systems using mixed integer linear programming

    KAUST Repository

    Canepa, Edward S.

    2013-01-01

    Traffic sensing systems rely more and more on user generated (insecure) data, which can pose a security risk whenever the data is used for traffic flow control. In this article, we propose a new formulation for detecting malicious data injection in traffic flow monitoring systems by using the underlying traffic flow model. The state of traffic is modeled by the Lighthill-Whitham- Richards traffic flow model, which is a first order scalar conservation law with concave flux function. Given a set of traffic flow data, we show that the constraints resulting from this partial differential equation are mixed integer linear inequalities for some decision variable. We use this fact to pose the problem of detecting spoofing cyber-attacks in probe-based traffic flow information systems as mixed integer linear feasibility problem. The resulting framework can be used to detect spoofing attacks in real time, or to evaluate the worst-case effects of an attack offline. A numerical implementation is performed on a cyber-attack scenario involving experimental data from the Mobile Century experiment and the Mobile Millennium system currently operational in Northern California. © 2013 IEEE.

  15. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    2013-01-01

    Mobile probing is a method, developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time and space......). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings point...... to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  16. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    2012-01-01

    Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  17. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    2012-01-01

    Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  18. Terahertz generation by beating two Langmuir waves in a warm and collisional plasma

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiao-Bo; Qiao, Xin; Cheng, Li-Hong; Tang, Rong-An; Zhang, Ai-Xia; Xue, Ju-Kui, E-mail: xuejk@nwnu.edu.cn [Key Laboratory of Atomic & Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronics Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2015-09-15

    Terahertz (THz) radiation generated by beating of two Langmuir waves in a warm and collisional plasma is discussed theoretically. The critical angle between the two Langmuir waves and the critical wave-length (wave vector) of Langmuir waves for generating THz radiation are obtained analytically. Furthermore, the maximum radiation energy is obtained. We find that the critical angle, the critical wave-length, and the generated radiation energy strongly depend on plasma temperature and wave-length of the Langmuir waves. That is, the THz radiation generated by beating of two Langmuir waves in a warm and collisional plasma can be controlled by adjusting the plasma temperature and the Langmuir wave-length.

  19. SYNTHESIS, PHYSICAL CHARACTERIZATIONS, AND LANGMUIR FILMS OF NEW METHANOFULLERENES

    NARCIS (Netherlands)

    RAVAINE, S; LEPECQ, F; MINGOTAUD, C; DELHAES, P; HUMMELEN, JC; WUDL, F; PATTERSON, LK

    1995-01-01

    Various methanofullerenes functionalized with either hydrophobic or polar groups have been synthesized. Studies of such compounds by surface pressure measurements and in situ UV-visible spectroscopy in Langmuir films show that these two types of functionalizations do not prevent the formation of

  20. Non-Linear Langmuir Wave Modulation in Collisionless Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Pécseli, Hans

    1977-01-01

    A non-linear Schrodinger equation for Langmuir waves is presented. The equation is derived by using a fluid model for the electrons, while both a fluid and a Vlasov formulation are considered for the ion dynamics. The two formulations lead to significant differences in the final results, especially...

  1. Langmuir adsorption isotherm for sulfolobus acidocaldarius on coal particles

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.Y.; Skidmore, D.R.

    1987-03-01

    Sulfolobus acidocaldarius attachment to coal particles was observed in 20% coal slurry at 72 C and pH 2.0. The rate and extent of attachment were determined and the data fit the Langmuir adsorption model. The results compared qualitatively with selected adsorption data from other investigators for Thiobacillus ferrooxidans. 11 refs.

  2. Features in Formation and Properties of Langmuir-Blodgett Monolayers

    Directory of Open Access Journals (Sweden)

    A.P. Kuzmenko

    2013-12-01

    Full Text Available Features in formation of Langmuir-Blodgett films and possible control and study of their properties directly in deposing them onto sub-strates are studied. Linearity of the dependence of polarization on the slope angle of the static dipole moment for C18H36O2 and C18H34O2 has been checked.

  3. Langmuir turbulence in the auroral ionosphere 1: Linear theory

    Science.gov (United States)

    Newman, D. L.; Goldman, M. V.; Ergun, R. E.; Boehm, M. H.

    1994-01-01

    Intense bursts of Langmuir waves with electric fields of 50 to 500 mV / m have been frequently observed at altitudes greater than 500 km in the auroral ionosphere. These bursts are driven by 20 eV to 4 keV field-aligned electrons, which are embedded in an approximately isotropic nonthermal tail of scattered electrons. The Langmuir bursts are often observed at altitudes where the ionosphere is moderately magnetized (OMEGA (sub e) approximately equals omega (sub pe)). Both the moderate magnetization and the scattered electrons have a major influence on the linear dispersion and damping of Langmuir waves. In particular, the linear dispersion is topologically different depending on whether the magnetic field is subcritical (OMEGA (sub e) less than omega (sub pe)) or supercritical (OMEGA (sub e) greater than omega (sub pe)). The correct dispersion and damping can account for the observed polarization of the Langmuir waves, which is very nearly parallel to the geomagnetic field. Inferred properties of the linear instability driven by the field-aligned electrons are discussed. The linear dispersion and damping derived here provide the basis for a nonlinear turbulence study described in a companion paper (Newman et al., this issue).

  4. Architecture, modeling, and analysis of a plasma impedance probe

    Science.gov (United States)

    Jayaram, Magathi

    Variations in ionospheric plasma density can cause large amplitude and phase changes in the radio waves passing through this region. Ionospheric weather can have detrimental effects on several communication systems, including radars, navigation systems such as the Global Positioning Sytem (GPS), and high-frequency communications. As a result, creating models of the ionospheric density is of paramount interest to scientists working in the field of satellite communication. Numerous empirical and theoretical models have been developed to study the upper atmosphere climatology and weather. Multiple measurements of plasma density over a region are of marked importance while creating these models. The lack of spatially distributed observations in the upper atmosphere is currently a major limitation in space weather research. A constellation of CubeSat platforms would be ideal to take such distributed measurements. The use of miniaturized instruments that can be accommodated on small satellites, such as CubeSats, would be key to achieving these science goals for space weather. The accepted instrumentation techniques for measuring the electron density are the Langmuir probes and the Plasma Impedance Probe (PIP). While Langmuir probes are able to provide higher resolution measurements of relative electron density, the Plasma Impedance Probes provide absolute electron density measurements irrespective of spacecraft charging. The central goal of this dissertation is to develop an integrated architecture for the PIP that will enable space weather research from CubeSat platforms. The proposed PIP chip integrates all of the major analog and mixed-signal components needed to perform swept-frequency impedance measurements. The design's primary innovation is the integration of matched Analog-to-Digital Converters (ADC) on a single chip for sampling the probes current and voltage signals. A Fast Fourier Transform (FFT) is performed by an off-chip Field-Programmable Gate Array (FPGA

  5. New effects in Langmuir and Langmuir-Blodgett monolayers from fluorescently labelled phospholipids and their possible use for water quality control

    Science.gov (United States)

    Ivanov, G. R.; Geshev, N. I.

    2016-02-01

    Secondary water contamination poses significant challenges to the sensitivity and selectivity of sensors used for its detection and monitoring. Currently only lab tests can detect these contaminants and by the time this happens the contaminated water has entered the city water supply system. Fluorescent chromophore NitroBenzoxaDiazole (NBD) is very suitable and had been successfully used in biosensor applications due to its high sensitivity to close proximity polarity of the medium. Over the years we have discovered 3 new effects in NBD- labelled phospholipids which can significantly improve the performance of biosensors. The phospholipid matrix provides flexible biocompatible environment for immobilization of selectively reacting enzymes, microorganisms, DNA, immunoagents, whole cells. Use of single layer (3.1 nm thickness) films at the air-water interface (Langmuir films) or deposited on solid support as Langmuir-Blodgett (LB) film gives fast response times for real time monitoring (no slow diffusion processes) and precise molecule ordering and orientation. The first new effect was fluorescence self-quenching in Langmuir and LB films. In the liquid phase films exhibit normal fluorescence. Upon transition to solid phase fluorescence intensity is almost completely self-quenched and fluorescence lifetimes in the nanosecond region decrease 2 times. This is easily measured. Usually large heavy metal atoms quench fluorescence. We observed the opposite new effect when LB film is deposited in the solid phase from a subphase containing heavy metals. The third new effect is the obtaining of nanosized cylinders with bilayer thickness, which remain stable at least for months, when LB monolayer is deposited in the phase coexistence region at thermodynamic equilibrium. This greatly increases reacting surface and sensitivity of possible sensors. Almost all possible optical experimental methods were used for this research. This includes polarized ATR FTIR and polarized UV

  6. Collective transport of weakly interacting molecular motors with Langmuir kinetics

    Science.gov (United States)

    Chandel, Sameep; Chaudhuri, Abhishek; Muhuri, Sudipto

    2015-04-01

    Filament-based intracellular transport involves the collective action of molecular motor proteins. Experimental evidences suggest that microtubule (MT) filament bound motor proteins such as kinesins weakly interact among themselves during transport and with the surrounding cellular environment. Motivated by these observations we study a driven lattice gas model for collective unidirectional transport of molecular motors on open filament. This model incorporates short-range next-nearest-neighbour (NNN) interactions between the motors and couples the transport process on filament with surrounding cellular environment through adsorption-desorption Langmuir kinetics (LK) of the motors. We analyse this model within the framework of a mean-field (MF) theory in the limit of weak interactions between the motors. We point to the mapping of this model with the non-conserved version of the Katz-Lebowitz-Spohn (KLS) model. The system exhibits rich phase behavior with a variety of inhomogeneous phases including localized shocks in the bulk of the filament. We obtain the steady-state density and current profiles, analyse their variation as a function of the strength of interaction and construct the non-equilibrium MF phase diagram. We compare these MF results with Monte Carlo simulations and find that the MF analysis shows reasonably good agreement with simulation results as long as the motors are weakly interacting. For sufficently strong NNN interaction between the motors, the mean-field results deviate significantly, and for very strong NNN interaction in the absence of LK, the current in the lattice is determined solely by the NNN interaction parameter and it becomes independent of entry and exit rates of motors at the filament boundaries.

  7. Genetically-encoded tools for cAMP probing and modulation in living systems.

    Directory of Open Access Journals (Sweden)

    Valeriy M Paramonov

    2015-09-01

    Full Text Available Intracellular 3'-5'-cyclic adenosine monophosphate (cAMP is one of the principal second messengers downstream of a manifold of signal transduction pathways, including the ones triggered by G protein-coupled receptors. Not surprisingly, biochemical assays for cAMP have been instrumental for basic research and drug discovery for decades, providing insights into cellular physiology and guiding pharmaceutical industry. However, despite impressive track record, the majority of conventional biochemical tools for cAMP probing share the same fundamental shortcoming - all the measurements require sample disruption for cAMP liberation. This common bottleneck, together with inherently low spatial resolution of measurements (as cAMP is typically analyzed in lysates of thousands of cells, underpin the ensuing limitations of the conventional cAMP assays: 1 genuine kinetic measurements of cAMP levels over time in a single given sample are unfeasible; 2 inability to obtain precise information on cAMP spatial distribution and transfer at subcellular levels, let alone the attempts to pinpoint dynamic interactions of cAMP and its effectors. At the same time, tremendous progress in synthetic biology over the recent years culminated in drastic refinement of our toolbox, allowing us not only to bypass the limitations of conventional assays, but to put intracellular cAMP life-span under tight control – something, that seemed scarcely attainable before. In this review article we discuss the main classes of modern genetically-encoded tools tailored for cAMP probing and modulation in living systems. We examine the capabilities and weaknesses of these different tools in the context of their operational characteristics and applicability to various experimental set-ups involving living cells, providing the guidance for rational selection of the best tools for particular needs.

  8. Prospects for Probing Strong Gravity with a Pulsar-Black Hole System

    Science.gov (United States)

    Wex, N.; Liu, K.; Eatough, R. P.; Kramer, M.; Cordes, J. M.; Lazio, T. J. W.

    2012-01-01

    The discovery of a pulsar (PSR) in orbit around a black hole (BH) is expected to provide a superb new probe of relativistic gravity and BH properties. Apart from a precise mass measurement for the BH, one could expect a clean verification of the dragging of space-time caused by the BH spin. In order to measure the quadrupole moment of the BH for testing the no-hair theorem of general relativity (GR), one has to hope for a sufficiently massive BH. In this respect, a PSR orbiting the super-massive BH in the center of our Galaxy would be the ultimate laboratory for gravity tests with PSRs. But even for gravity theories that predict the same properties for BHs as GR, a PSR-BH system would constitute an excellent test system, due to the high grade of asymmetry in the strong field properties of these two components. Here we highlight some of the potential gravity tests that one could expect from different PSR-BH systems.

  9. Adaptive filter based two-probe noise suppression system for transient evoked otoacoustic emission detection.

    Science.gov (United States)

    Subotić, Miško; Šarić, Zoran; Jovičić, Slobodan T

    2012-03-01

    Transient otoacoustic emission (TEOAE) is a method widely used in clinical practice for assessment of hearing quality. The main problem in TEOAE detection is its much lower level than the level of environmental and biological noise. While the environmental noise level can be controlled, the biological noise can be only reduced by appropriate signal processing. This paper presents a new two-probe preprocessing TEOAE system for suppression of the biological noise by adaptive filtering. The system records biological noises in both ears and applies a specific adaptive filtering approach for suppression of biological noise in the ear canal with TEOAE. The adaptive filtering approach includes robust sign error LMS algorithm, stimuli response summation according to the derived non-linear response (DNLR) technique, subtraction of the estimated TEOAE signal and residual noise suppression. The proposed TEOAE detection system is tested by three quality measures: signal-to-noise ratio (S/N), reproducibility of TEOAE, and measurement time. The maximal TEOAE detection improvement is dependent on the coherence function between biological noise in left and right ears. The experimental results show maximal improvement of 7 dB in S/N, improvement in reproducibility near 40% and reduction in duration of TEOAE measurement of over 30%.

  10. Prospects for Probing Strong Gravity with a Pulsar-Black Hole System

    Science.gov (United States)

    Wex, N.; Liu, K.; Eatough, R. P.; Kramer, M.; Cordes, J. M.; Lazio, T. J. W.

    2012-01-01

    The discovery of a pulsar (PSR) in orbit around a black hole (BH) is expected to provide a superb new probe of relativistic gravity and BH properties. Apart from a precise mass measurement for the BH, one could expect a clean verification of the dragging of space-time caused by the BH spin. In order to measure the quadrupole moment of the BH for testing the no-hair theorem of general relativity (GR), one has to hope for a sufficiently massive BH. In this respect, a PSR orbiting the super-massive BH in the center of our Galaxy would be the ultimate laboratory for gravity tests with PSRs. But even for gravity theories that predict the same properties for BHs as GR, a PSR-BH system would constitute an excellent test system, due to the high grade of asymmetry in the strong field properties of these two components. Here we highlight some of the potential gravity tests that one could expect from different PSR-BH systems.

  11. Phylogeny and FISH probe analysis of the “Candidatus Competibacter”-lineage in wastewater treatment systems

    DEFF Research Database (Denmark)

    Nittami, Tadashi; McIlroy, Simon Jon; Kanai, Eri

    . This study aimed at resolving the phylogeny and reassessing FISH probes for coverage of the diversity of the lineage in EBPR systems. Analysis of the level of 16S rRNA gene sequence diversity of lineage members (> 89%) suggests that it is more appropriately viewed as a family rather than a single genus......Our understanding of the microbial ecology of enhanced biological phosphorus removal (EBPR) wastewater treatment systems has been greatly advanced through the application of molecular methods such as fluorescence in situ hybridization (FISH). Considerable attention has been directed...... the gammaproteobacterial “Candidatus Competibacter”-lineage. The group is currently delineated by 8 FISH probe defined phylotypes, although further undescribed phylogenetic diversity beyond what is covered by these probes is evident. Where studied, marked differences in physiology between members are observed, including...

  12. Unidirectional Photo-induced Charge Separation and Thermal Charge Recombination of Cofacially Aligned Donor-Acceptor System Probed by Ultrafast Visible-Pump/Mid-IR-Probe Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyeongmook; Lim, Manho; Chung, Young Keun; Kang, Youn K. [Seoul National Univ., Seoul (Korea, Republic of); Park, Jaeheung [Pusan National Univ., Busan (Korea, Republic of); Noh, Hee Chang [Sangmyung Univ., Seoul (Korea, Republic of)

    2014-02-15

    Similar to its precedent, [Ru(6-(2-cyclohexa-2',5'-diene-1,4-dione)-2,2':6',2''-terpyridine) (2,2':6',2-terpyridine)][PF6]2 (TQ{sub T}), this system has a cofacial alignment of terpyridine (tpy) ligand and quinonyl (Q) group, which facilitates an electron transfer through π-stacked manifold. Despite the presence of lowest-energy charge transfer transition from the Ru-based-HOMO-to-Q-based-LUMO (MQCT) predicted by theoretical calculations by using time-dependent density functional theory (TD-DFT), the experimental steady-state absorption spectrum does not exhibit such a band. The selective excitation to the Ru-based occupied orbitalsto-tpy-based virtual orbital MLCT state was thus possible, from which charge separation (CS) reaction occurred. The photo-induced CS and thermal charge recombination (CR) reactions were probed by using ultrafast visible-pump/mid-IR-probe (TrIR) spectroscopic method. Analysis of decay kinetics of Q and Q{sup -} state CO stretching modes as well as aromatic C=C stretching mode of tpy ligand gave time constants of <1 ps for CS, 1-3 ps for CR, and 10-20 ps for vibrational cooling processes. The electron transfer pathway was revealed to be Ru-tpy-Q rather than Ru-bpy-imidazol-Q.

  13. Molecular arrangement in Langmuir and Langmuir-Blodgett films of a mesogenic bent-core carboxylic acid.

    Science.gov (United States)

    Giner, Ignacio; Gascón, Ignacio; Vergara, Jorge; López, M Carmen; Ros, M Blanca; Royo, Félix M

    2009-10-20

    A different alternative to previous research on Langmuir and Langmuir-Blodgett (LB) films of bent-core liquid crystals is reported in this work. A bent-shaped molecule wearing a terminal carboxylic group has been used to obtain monomolecular films with their long molecular axis almost perpendicular to the aqueous surface. Langmuir films at the air-liquid interface (pH=9) have been characterized by a combination of surface pressure and surface potential versus area per molecule isotherms, Brewster angle microscopy, and ultraviolet reflection spectroscopy. A condensed phase is reached at surface pressures up to 20 mN x m-1. In this condensed phase, molecules are packed forming H-aggregates with a well-defined molecular orientation. Langmuir films have been transferred onto quartz and silicon substrates and characterized by means of UV-vis spectroscopy and XRR. The transference is Z-type, with a constant deposition of the monolayers. The total LB monolayer film thickness is evaluated to be about 5.8 nm, which is in good agreement with the deduced orientation at the air-liquid interface as well as with the lamellar order observed within the solid obtained by cooling the sample from the mesophase.

  14. The Production of PEO Polymer Brushes via Langmuir-Blodgett and Langmuir-Schaeffer Methods: Incomplete Transfer and Its Consequences

    NARCIS (Netherlands)

    Vos, de W.M.; Keizer, de A.; Kleijn, J.M.; Cohen Stuart, M.A.

    2009-01-01

    Using fixed-angle ellipsometry, we investigate the degree of mass transfer upon vertically dipping a polystyrene surface through a layer of a polystyrene-poly(ethylene oxide) (PS-PEO) block copolymer at the air water interface (Langmuir-Blodgett or LB transfer). The transferred mass is proportional

  15. A novel electro-optical pump-probe system for bioelectromagnetic investigations

    Science.gov (United States)

    De Angelis, Annalisa; Couderc, Vincent; Leproux, Philippe; Labruyère, Alexis; Tonello, Alessandro; El Amari, Saad; Arnaud-Cormos, Delia; Leveque, Philippe

    2012-10-01

    In the area of bioelectromagnetic studies there is a growing interest to understand the mechanisms leading to nanosecond electric fields induced electroporation. Real-time imaging techniques at molecular level could probably bring further advances on how electric fields interact with living cells. However the investigations are limited by the present-day lack of these kinds of advanced instrumentations. In this context, we present an innovative electro-optical pump-probe system. The aim of our project is to provide a performing and compact device for electrical stimulation and multiplex Coherent anti-Stokes Raman Scattering (M-CARS) imaging of biological cells at once. The system consists of a 1064 nm sub-nanosecond laser source providing both a monochromatic pump and a polychromatic Stokes optical beam used in a CARS process, as well as the trigger beam for the optoelectronic switching-based electrical pulse generator. The polychromatic Stokes beam (from 600 to 1700 nm) results from a supercontinuum generation in a photonic crystal fiber (PCF). A detailed spectro-temporal characterization of such a broadband spectrum shows the impact of the nonlinear propagation in the fiber on the Stokes wave. Despite the temporal distortions observable on Stokes pulse profiles, their spectral synchronization with the pump pulse remains possible and efficient in the interesting region between 1100 nm and 1700 nm. The electrical stimulation device consists of a customized generator combining microstrip-line technology and laser-triggered photoconductive semiconductor switches. Our experimental characterization highlights the capability for such a generator to control the main pulse parameters (profile, amplitude and duration) and to be easily synchronized with the imaging system. We finally test and calibrate the system by means of a KDP crystal. The preliminary results suggest that this electro-optical system provides a suitable tool for real-time investigation of

  16. Laser-produced plasma sensor-probe system for in situ molten metal analysis. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Y.W.

    1997-01-28

    The radically new methodology of in-situ laser-produced plasma (LPP) analysis of molten metals, as developed at Lehigh University, has been implemented into an LPP sensor-probe system, ready for deployment at steelmaking facilities. The system consists of an LPP sensor-probe head, which is immersed into the molten metal bath for the short duration of measurement, a control console, an umbilical cord connecting the above two units, and a support console providing coolants and pneumatic supports to the control console. The Department of Energy funding has supported Phase III-A and -B of the project in a joint sponsorship with AISI, CTU 5-2 Consortium, and Lehigh University. The objectives have been to: (1) implement the molten metal calibration protocol for the LPP analysis methodology; (2) implement the methodology in the form of a second-generation LPP sensor-probe system, which facilitates real-time process control by in-situ determination of elemental composition of molten steel alloys; (3) deploy such developmental systems in steelmaking facilities; (4) upgrade the systems to a third-generation design; and (5) effect technology transfer by selecting a manufacturer of commercial LPP sensor-probe systems. Four of the five objectives have been fully met. The deployment objective has been partially realized at present. The full LPP sensor-probe system has been put through trial immersion runs at a foundry, but its deployment at steelmaking facilities has progressed to a stage where various issues of financial and legal nature are being codified into a formal agreement between a host site and Lehigh University.

  17. The gyroscope testbed: A verification of the gravity probe B suspension system

    Science.gov (United States)

    Brumley, Robert Willard

    The verification of precision control systems for use in space-based applications can be extremely challenging. Often, the presence of the 1-g field substantively changes the control problem, making it impossible to test directly on the Earth. This talk discusses a new approach to testing and verification of the gyroscope suspension system for the Gravity Probe B (GP-B) experimental test of General Relativity. The verification approach involves the creation of a new testbed that has the same input-output characteristics and dynamics as a GP-B gyroscope. This involves real physical hardware that moves like a real gyroscope, allowing the suspension system's performance to be measured directly without the need to break any internal connections or bypass internal subsystems. The user free to define any set of disturbances from a 1-g ground levitation to a 10-8 g science mission. The testbed has two main subsystems. The mechanical subsystem is comprised of six parallel plate capacitors whose spacing is controlled by precision actuators. These actuators are the physical interface to the suspension system and create the electrode-rotor capacitances present in a real gyroscope. The closed-loop positioning noise of the system is approximately 10 pm/√Hz, enabling the commanding of position variations a fraction the size of a single atom of Silicon. The control subsystem has a DSP-based high-speed nonlinear controller that forces the actuators to follow the dynamics of a gyroscope. The device has been shown to faithfully represent a gyroscope in 1-g levitation, and a robustness analysis has been performed to prove that it correctly tests the stability of the on-orbit system. The testbed is then used to measure directly suspension system performance in a variety of on-orbit scenarios. Gyroscope levitation in 10-8 g conditions is demonstrated. The robustness of gyroscope levitation to transient disturbances such as micrometeorite impacts on the space vehicle and transitions

  18. THE ROTATION BARRIER OF ELECTRON SPIN PROBE IN THE STUDY OF POLYMER SYSTEM

    Institute of Scientific and Technical Information of China (English)

    YU Tongyin; GUO Shiqing; GE Mingtao

    1984-01-01

    In the study of molecular motion of polymer by means of ESR in combination with spin probe,owing to that the ESR spectrum depicts only the behavior of spin probe, the information obtained is of indirect nature. Hence the relationship between them must first be investigated before any conclusion could be drawn. In this paper, two parameters TR and CR are introduced to characterize the changing of tumbling rate of spin probe, and the concept of rotation barrier of spin probe is proposed. It is considered that the magnitude of the rotation barrier is determined by the internal cavity size and distribution in polymer. When the temperature is raised, the size and distribution of the cavities change accordingly, thus the tumbling of spin probe changes gradually from a slower to a higher rate.

  19. A versatile variable field module for Asylum Cypher scanning probe system

    Science.gov (United States)

    Liu, Hongxue; Comes, Ryan; Lu, Jiwei; Wolf, Stuart; Hodgson, Jim; Rutgers, Maarten

    2013-03-01

    Atomic force microscopy (AFM) has become one of the most widely used techniques for measuring and manipulating various characteristics of materials at the nanoscale. However, there are very limited option for the characterization of field dependence properties. In this work, we demonstrate a versatile variable field module (VFM) with magnetic field up to 1800 Oe for the Asylum Research Cypher system. The magnetic field is changed by adjusting the distance between a rare earth magnet and the AFM probe. A built-in Hall sensor makes it possible to perform in-situ measurements of the field. Rotating the magnet makes it possible to do angular field dependent measurements. The capability of the VFM system is demonstrated by degaussing a floppy disk media with increasing magnetic field. The written bits are erased at about 800 Oe. Angular dependence measurements clearly show the evolution of magnetic domain structures. A completely reversible magnetic force microscopy (MFM) phase contrast is observed when the magnetic field is rotated by 180°. Further demonstration of successful magnetic switching of CoFe2O4 pillars in CoFe2O4-BiFeO3 nanocomposites will be presented and field dependent MFM and piezoresponse force microscopy (PFM) will be discussed. The work at University of Virginia was supported by DARPA under contract no. HR-0011-10-1-0072.

  20. Supramolecular architectures of iron phthalocyanine Langmuir-Blodgett films: The role played by the solution solvents

    Science.gov (United States)

    Rubira, Rafael Jesus Gonçalves; Aoki, Pedro Henrique Benites; Constantino, Carlos José Leopoldo; Alessio, Priscila

    2017-09-01

    The developing of organic-based devices has been widely explored using ultrathin films as the transducer element, whose supramolecular architecture plays a central role in the device performance. Here, Langmuir and Langmuir-Blodgett (LB) ultrathin films were fabricated from iron phthalocyanine (FePc) solutions in chloroform (CHCl3), dichloromethane (CH2Cl2), dimethylformamide (DMF), and tetrahydrofuran (THF) to determine the influence of different solvents on the supramolecular architecture of the ultrathin films. The UV-vis absorption spectroscopy shows a strong dependence of the FePc aggregation on these solvents. As a consequence, the surface pressure vs. mean molecular area (π-A) isotherms and Brewster angle microscopy (BAM) reveal a more homogeneous (surface morphology) Langmuir film at the air/water interface for FePc in DMF. The same morphological pattern observed for the Langmuir films is preserved upon LB deposition onto solid substrates. The Raman and FTIR analyses indicate the DMF-FePc interaction relies on coordination bonds between N atom (from DMF) and Fe atom (from FePc). Besides, the FePc molecular organization was also found to be affected by the DMF-FePc chemical interaction. It is interesting to note that, if the DMF-FePc leads to less aggregated FePc either in solution or ultrathin films (Langmuir and LB), with time (one week) the opposite trend is found. Taking into account the N-Fe interaction, the performance of the FePc ultrathin films with distinct supramolecular architectures composing sensing units was explored as proof-of-principle in the detection of trace amounts of atrazine herbicide in water using impedance spectroscopy. Further statistical and computational analysis reveal not only the role played by FePc supramolecular architecture but also the sensitivity of the system to detect atrazine solutions down to 10-10 mol/L, which is sufficient to monitor the quality of drinking water even according to the most stringent international

  1. MODEL ADSORPSI LANGMUIR GAS DINITROGEN MONOKSIDA DALAM SISTEM BIOFILTER DENGAN MEDIUM PUPUK KOMPOS

    Directory of Open Access Journals (Sweden)

    Tania Surya Utami

    2012-04-01

    Full Text Available  LANGMUIR ADSORPTION MODEL FOR DINITROGEN MONOXIDE IN BIOFILTER SYSTEM USING COMPOST FERTILIZER MEDIUM. Nitrous oxide (N2O is mostly emitted from various industrial processes and agricultural activities. This gas causes serious environmental problems and is considered as a dangerous pollutant. In the past, traditional control technologies, such as Selective Catalytic Reduction (SCR and Selective Non-Catalytic Reduction (SNCR, were applied to control N2O emissions in some industries. However, these two processes required high temperatures and the use of catalysts. Economic and technical constraints in SCR and SNCR methods motivated researchers to develop new, cost-effective processes to remove N2O. Biofiltration is an emerging technology that offers a number of advantages over traditional methods of air pollution control. The purpose of this research is to modelise the biofiltration experimental results into the Langmuir adsorption model. This research is conducted in laboratory scale biofilter column, with parameters studied are effect of biofilter length and N2O gas flowrate. The result of the model is simulated into sensitivity analysis. The average Langmuir constant obtained in the model of the research is 16.006 liter/mol. Dinitrogen Monoksida (N2O merupakan emisi dari proses industri dan kegiatan pertanian. Gas tersebut merupakan gas polutan berbahaya dan menyebabkan masalah lingkungan yang serius. Sebelumnya, teknologi kontrol tradisional seperti Selective Catalytic Reduction (SCR dan Selective Non-Catalytic Reduction (SNCR digunakan untuk mengontrol emisi N2O pada kegiatan-kegiatan industri. Akan tetapi, kedua proses ini membutuhkan suhu yang tinggi dan penggunaan katalis. Adanya masalah dari segi ekonomi dan teknis memotivasi peneliti untuk mengembangkan teknologi baru yang lebih murah dan efisien untuk menghilangkan N2O dari gas buangan. Pengolahan N2O secara biologis dalam proses biofiltrasi adalah salah satu alternatif ramah

  2. Functional network macroscopes for probing past and present Earth system dynamics (Invited)

    Science.gov (United States)

    Donges, J. F.

    2013-12-01

    probing past and present Earth system dynamics: Complex hierarchical interactions, tipping points, and beyond" by J.F. Donges, Humboldt University, Berlin, Germany, 2012. URL: http://nbn-resolving.de/urn:nbn:de:kobv:11-100207126.

  3. Immobilization of ɛ-polylysine onto the probe surface for molecular adsorption type endotoxin detection system

    Science.gov (United States)

    Ooe, Katsutoshi; Tsuji, Akihito; Nishishita, Naoki; Hirano, Yoshiaki

    2007-04-01

    adsorption reaction between ɛ-polylysine and endotoxin. ɛ-polylysine has the structure of straight chain molecule composed by 25-30 residues made by lysine, and it is used as an antimicrobial agent, moreover, cellulose beads with immobilized ɛ-polylysine is used as the barrier filter for endotoxin removal. Therefore, it is expected that the endotoxin be adsorbed to the immobilized ɛ-polylysine onto the probe. As the result of this reaction, the mass of the probe is increased, and endotoxin can be detected by using of Quartz Crystal Microbalance (QCM). In our previous research, we have already acquired the proteins immobilization technique onto Au and Si surface. In this report, the proposal of molecular adsorption type endotoxin detection system, and the immobilization of ɛ-polylysine onto the probe are described. We use X-ray Photoelectron Spectroscopy (XPS) to confirm the ɛ-polylysine immobilization, and the adsorptive activity of immobilized ɛ-polylysine is measured by XPS and AFM. The purpose of this study is to bring about the realization of "Real-time endotoxin detection system".

  4. Optical properties of an inhomogeneously broadened multilevel V-system in the weak and strong probe regimes

    CERN Document Server

    Kaur, Paramjit; Wasan, Ajay

    2015-01-01

    We present a theoretical model, using density matrix approach, to study the effect of weak as well as strong probe field on the optical properties of an inhomogeneously broadened multilevel V-system of the $^{87}$Rb D2 line. We consider the case of stationary as well as moving atoms and perform thermal averaging at room temperature. The presence of multiple excited states results in asymmetric absorption and dispersion profiles. In the weak probe regime, we observe the partial transparency window due to the constructive interference occurs between transition pathways at the line center. In a room temperature vapour, we obtain an increased linewidth of the transparency window and steep positive dispersion. For a strong probe regime, the transparency window with normal dispersion switches to enhanced absorption with anomalous dispersion at the line center. Here, we show how the electromagnetically induced transparency (EIT) depends on the polarizations of the applied fields. We also discuss the transient behavi...

  5. Cross-section analysis of the Magnum-PSI plasma beam using a 2D multi-probe system

    Science.gov (United States)

    Costin, C.; Anita, V.; Ghiorghiu, F.; Popa, G.; De Temmerman, G.; van den Berg, M. A.; Scholten, J.; Brons, S.

    2015-02-01

    The linear plasma generator Magnum-PSI was designed for the study of plasma-surface interactions under relevant conditions of fusion devices. A key factor for such studies is the knowledge of a set of parameters that characterize the plasma interacting with the solid surface. This paper reports on the electrical diagnosis of the plasma beam in Magnum-PSI using a multi-probe system consisting of 64 probes arranged in a 2D square matrix. Cross-section distributions of floating potential and ion current intensity were registered for a hydrogen plasma beam under various discharge currents (80-175 A) and magnetic field strengths (0.47-1.41 T in the middle of the coils). Probe measurements revealed a high level of flexibility of plasma beam parameters with respect to the operating conditions.

  6. Surface dilatational viscosity of Langmuir monolayers

    Science.gov (United States)

    Lopez, Juan; Vogel, Michael; Hirsa, Amir

    2003-11-01

    With increased interest in microfluidic systems, interfacial phenomena is receiving more attention. As the length scales of fluid problems decrease, the surface to volume ratio increases and the coupling between interfacial flow and bulk flow becomes increasingly dominated by effects due to intrinsic surface viscosities (shear and dilatational), in comparison to elastic effects (due to surface tension gradients). The surface shear viscosity is well-characterized, as cm-scale laboratory experiments are able to isolate its effects from other interfacial processes (e.g., in the deep-channel viscometer). The same is not true for the dilatational viscosity, because it acts in the direction of surface tension gradients. Their relative strength scale with the capillary number, and for cm-scale laboratory flows, surface tension effects tend to dominate. In microfluidic scale flows, the scaling favors viscosity. We have devised an experimental apparatus which is capable of isolating and enhancing the effects of dilatational viscosity at the cm scales by driving the interface harmonically in time, while keeping the interface flat. In this talk, we shall present both the theory for how this works as well as experimental measurements of surface velocity from which we deduce the dilatational viscosity of several monolayers on the air-water interface over a substantial range of surface concentrations. Anomalous behavior over some range of concentration, which superficially indicates negative viscosity, maybe explained in terms of compositional effects due to large spatial and temporal variations in concentration and corresponding viscosity.

  7. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    2013-01-01

    to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  8. A novel approach to study the structure-property relationships and applications in living systems of modular Cu2+ fluorescent probes

    Science.gov (United States)

    She, Mengyao; Yang, Zheng; Hao, Likai; Wang, Zhaohui; Luo, Tianyou; Obst, Martin; Liu, Ping; Shen, Yehua; Zhang, Shengyong; Li, Jianli

    2016-08-01

    A series of Cu2+ probe which contains 9 probes have been synthesized and established. All the probes were synthesized using Rhodamine B as the fluorophore, conjugated to various differently substituted cinnamyl aldehyde with C=N Schiff base structural motif as their core moiety. The structure-property relationships of these probes have been investigated. The change of optical properties, caused by different electronic effect and steric effect of the recognition group, has been analyzed systematically. DFT calculation simulation of the Ring-Close and Ring-Open form of all the probes have been employed to illuminate, summarize and confirm these correlations between optical properties and molecular structures. In addition, biological experiment demonstrated that all the probes have a high potential for both sensitive and selective detection, mapping of adsorbed Cu2+ both in vivo and environmental microbial systems. This approach provides a significant strategy for studying structure-property relationships and guiding the synthesis of probes with various optical properties.

  9. Reacting to nuclear power systems in space: American public protests over outer planetary probes since the 1980s

    Science.gov (United States)

    Launius, Roger D.

    2014-03-01

    The United States has pioneered the use of nuclear power systems for outer planetary space probes since the 1970s. These systems have enabled the Viking landings to reach the surface of Mars and both Pioneers 10 and 11 and Voyagers 1 and 2 to travel to the limits of the solar system. Although the American public has long been concerned about safety of these systems, in the 1980s a reaction to nuclear accidents - especially the Soviet Cosmos 954 spacecraft destruction and the Three Mile Island nuclear power plant accidents - heightened awareness about the hazards of nuclear power and every spacecraft launch since that time has been contested by opponents of nuclear energy. This has led to a debate over the appropriateness of the use of nuclear power systems for spacecraft. It has also refocused attention on the need for strict systems of control and rigorous checks and balances to assure safety. This essay describes the history of space radioisotope power systems, the struggles to ensure safe operations, and the political confrontation over whether or not to allow the launch the Galileo and Cassini space probes to the outer planets. Effectively, these efforts have led to the successful flights of 12 deep space planetary probes, two-thirds of them operated since the accidents of Cosmos 954, Three Mile Island, and Chernobyl.

  10. Impact of the probe solutes set on orthogonality evaluation in reverse phase chromatographic systems.

    Science.gov (United States)

    Al Bakain, Ramia; Rivals, Isabelle; Sassiat, Patrick; Thiébaut, Didier; Hennion, Marie-Claire; Euvrard, Guillaume; Vial, Jérôme

    2012-04-06

    Two-dimensional liquid chromatography (2DLC) is a very attractive technique for the characterization of complex samples due to its separation power obtained via the coupling of two separation modes exhibiting different mechanisms, i.e. orthogonality. In reverse phase, orthogonality is mainly governed by three factors: the pH of the mobile phase, the structure of the stationary phase and the nature of the organic modifier. In the present paper, we studied the impact of the nature of the probe solutes on orthogonality evaluation. A set of 63 compounds with various physicochemical properties was used to evaluate 32 reverse phase chromatographic systems (2 pH × 8 stationary phases × 2 organic modifiers). Principle component analysis revealed that the solutes could be split into three subsets according to their charge in the experimental conditions. The factors affecting orthogonality and the magnitude of their effect were shown to depend on the charge of the compounds. For positively charged (basic) compounds, the pH was the most important factor, followed by the nature of the stationary phase. For negatively charged (acidic) compounds, the nature of the stationary phase had the highest impact. For neutral compounds, only the nature of the stationary phase and, to a smaller extent, the organic modifier had an influence. The present study also showed that a reduced set of only 9 test compounds instead of whole set of the 63 could enable an appropriate orthogonality evaluation.

  11. Space Systems Failures Disasters and Rescues of Satellites, Rockets and Space Probes

    CERN Document Server

    Harland, David M

    2005-01-01

    In the 1960s and 1970s deep space missions were dispatched in pairs in case one was lost in launch or failed during its journey. Following the triumphs of the Viking landings on Mars in 1976 and both Voyagers spacecraft successfully surveying the outer giant planets of the Solar System, it was decided by NASA to cut costs and send out just a single probe. Although Magellan successfully mapped Venus by radar, it suffered from problems during the flight. Then came the loss of Mars Observer, whose engine exploded as it was preparing to enter Mars’ orbit because it was using technology designed for Earth’s satellites and the engine was not suited to spending several months in space. Later came the high-profile losses of Mars Climate Observer and Mars Polar Lander - a consequence of the faster, better, cheaper philosophy introduced by Dan Goldin in 1993. Even the highly successful Galileo mission suffered a major setback when its high-gain antenna (also based on satellite mission suffered a major setback when ...

  12. Natural flavonoids interact with dinitrobenzene system in aprotic media: an electrochemical probing.

    Science.gov (United States)

    Arshad, Nasima; Janjua, Naveed K; Khan, Athar Y; Yaqub, Azra; Burkholz, Torsten; Jacob, Claus

    2012-03-01

    Three structurally related natural flavonoids (FlOH), quercetin (Q), rutin (R) and morin (M), were investigated by cyclic voltammetry to probe their interactions with hazardous 1,4-dinitrobenzene (1,4-DNB) using a glassy carbon electrode. Scavenging of 1,4-DNB by FlOH was inferred from a positive shift in reduction potential, decrease in anodic peak current, and irreversible electrochemical behavior of 1,4-DNB on increasing the flavonoid concentration. The homogeneous bi-molecular rate constant (k2) was determined using the Nicholson-Shain equation and found to be higher for the dianion. Morin posed a comparatively higher k2 value for its interaction with the 1,4-DNB electrochemical system owing to its more acidic nature and least intramolecular hydrogen bonding. The cyclic voltammetric (CV) results were further supported by HyperchemPM3 quantum mechanical semi-empirical calculations, which point towards E(r)C(i) interactions between flavonoids and 1,4-DNB. The present investigation is biologically significant in terms of natural flavonoidal scavenging activity toward toxins such as dinitroaromatics.

  13. Probing Interstellar Silicate Dust Grain Properties in Quasar Absorption Systems at Redshifts z<1.4

    CERN Document Server

    Aller, Monique C; York, Donald G; Welty, Daniel E; Vladilo, Giovanni; Som, Debopam

    2014-01-01

    Absorption lines in the spectra of distant quasars whose sightlines pass through foreground galaxies provide a valuable tool to probe the dust and gas compositions of the interstellar medium (ISM) in galaxies. The first evidence of silicate dust in a quasar absorption system (QAS) was provided through our detection of the 10 micron silicate feature in the z=0.52 absorber toward the quasar AO 0235+164. We present results from 2 follow-up programs using archival Spitzer Space Telescope infrared spectra to study the interstellar silicate dust grain properties in a total of 13 QASs at 0.1

  14. Evaluating a hybrid three-dimensional metrology system: merging data from optical and touch probe devices

    Science.gov (United States)

    Gerde, Janice R.; Christens-Barry, William A.

    2011-08-01

    In a project to meet requirements for CBP Laboratory analysis of footwear under the Harmonized Tariff Schedule of the United States (HTSUS), a hybrid metrology system comprising both optical and touch probe devices has been assembled. A unique requirement must be met: To identify the interface-typically obscured in samples of concern-of the "external surface area upper" (ESAU) and the sole without physically destroying the sample. The sample outer surface is determined by discrete point cloud coordinates obtained using laser scanner optical measurements. Measurements from the optically inaccessible insole region are obtained using a coordinate measuring machine (CMM). That surface similarly is defined by point cloud data. Mathematically, the individual CMM and scanner data sets are transformed into a single, common reference frame. Custom software then fits a polynomial surface to the insole data and extends it to intersect the mesh fitted to the outer surface point cloud. This line of intersection defines the required ESAU boundary, thus permitting further fractional area calculations to determine the percentage of materials present. With a draft method in place, and first-level method validation underway, we examine the transformation of the two dissimilar data sets into the single, common reference frame. We also will consider the six previously-identified potential error factors versus the method process. This paper reports our on-going work and discusses our findings to date.

  15. System-Level Design of an Integrated Receiver Front End for a Wireless Ultrasound Probe

    DEFF Research Database (Denmark)

    di Ianni, Tommaso; Hemmsen, Martin Christian; Llimos Muntal, Pere

    2016-01-01

    In this paper, a system-level design is presented for an integrated receive circuit for a wireless ultrasound probe, which includes analog front ends and beamformation modules. This paper focuses on the investigation of the effects of architectural design choices on the image quality. The point...... spread function is simulated in Field II from 10 to 160 mm using a convex array transducer. A noise analysis is performed, and the minimum signal-to-noise ratio (SNR) requirements are derived for the low-noise amplifiers (LNAs) and A/D converters (ADCs) to fulfill the design specifications of a dynamic......). The designs that minimally satisfy the specifications are based on an 8-b 30-MSPS Nyquist converter and a single-bit third-order 240-MSPS modulator, with an SNR for the LNA in both cases equal to 64 dB. The mean lateral FWHM and CR are 2.4% and 7.1% lower for the architecture compared with the Nyquistrate one...

  16. PHOTOEMISSION AS A PROBE OF THE COLLECTIVE EXCITATIONS IN CONDENSED MATTER SYSTEMS.

    Energy Technology Data Exchange (ETDEWEB)

    JOHNSON, P.D.; VALLA, T.

    2006-08-01

    New developments in instrumentation have recently allowed photoemission measurements to be performed with very high energy and momentum resolution.[1] This has allowed detailed studies of the self-energy corrections to the lifetime and mass renormalization of excitations in the vicinity of the Fermi level. These developments come at an opportune time. Indeed the discovery of high temperature superconductivity in the cuprates and related systems is presenting a range of challenges for condensed matter physics.[2] Does the mechanism of high T{sub c} superconductivity represent new physics? Do we need to go beyond Landau's concept of the Fermi liquid?[3] What, if any, is the evidence for the presence or absence of quasiparticles in the excitation spectra of these complex oxides? The energy resolution of the new instruments is comparable to or better than the energy or temperature scale of superconductivity and the energy of many collective excitations. As such, photoemission has again become recognized as an important probe of condensed matter. Studies of the high T{sub c} superconductors and related materials are aided by the observation that they are two dimensional. To understand this, we note that the photoemission process results in both an excited photoelectron and a photohole in the final state. Thus the experimentally measured photoemission peak is broadened to a width reflecting contributions from both the finite lifetime of the photohole and the momentum broadening of the outgoing photoelectron.

  17. Pulsed field probe of real time magnetization dynamics in magnetic nanoparticle systems

    Science.gov (United States)

    Foulkes, T.; Syed, M.; Taplin, T.

    2015-05-01

    Magnetic nanoparticles (MNPs) are extensively used in biotechnology. These applications rely on magnetic properties that are a keen function of MNP size, distribution, and shape. Various magneto-optical techniques, including Faraday Rotation (FR), Cotton-Mouton Effect, etc., have been employed to characterize magnetic properties of MNPs. Generally, these measurements employ AC or DC fields. In this work, we describe the results from a FR setup that uses pulsed magnetic fields and an analysis technique that makes use of the entire pulse shape to investigate size distribution and shape anisotropy. The setup employs a light source, polarizing components, and a detector that are used to measure the rotation of light from a sample that is subjected to a pulsed magnetic field. This magnetic field "snapshot" is recorded alongside the intensity pulse of the sample's response. This side by side comparison yields useful information about the real time magnetization dynamics of the system being probed. The setup is highly flexible with variable control of pulse length and peak magnitude. Examining the raw data for the response of bare Fe3O4 and hybrid Au and Fe3O4 nanorods reveals interesting information about Brownian relaxation and the hydrodynamic size of these nanorods. This analysis exploits the self-referencing nature of this measurement to highlight the impact of an applied field on creating a field induced transparency for a longitudinal measurement. Possible sources for this behavior include shape anisotropy and field assisted aggregate formation.

  18. Langmuir films of chiral lipid molecules and Pattern Formation .

    Science.gov (United States)

    Basnet, Prem; Mann, Elizabeth; Chaieb, Sahraoui

    2009-03-01

    Langmuir films of 1,2-bis(10,12 Tricosadiynoyl)-sn-Glycero-3-Phosphoethanolamine form spiral and target patterns when compressed between two movable barriers in a Langmuir trough above 30^0C, up to the chain-melting transition at ˜37^0C. The critical pressure, at which spirals appear, increases with temperature. The patterns themselves also depend on temperature, with single-armed spirals with many defects forming near 30^0C and defect-free target patterns at higher temperatures. The mechanism of spiral formation could be a competition among elasticity, chirality, and the boundary conditions at the core of the domains. Optical anisotropy and the growth rate of internal structures test this suggested mechanism. .

  19. Moment equations for chromatography based on Langmuir type reaction kinetics.

    Science.gov (United States)

    Miyabe, Kanji

    2014-08-22

    Moment equations were derived for chromatography, in which the reaction kinetics between solute molecules and functional ligands on the stationary phase was represented by the Langmuir type rate equation. A set of basic equations of the general rate model of chromatography representing the mass balance, mass transfer rate, and reaction kinetics in the column were analytically solved in the Laplace domain. The moment equations for the first absolute moment and the second central moment in the real time domain were derived from the analytical solution in the Laplace domain. The moment equations were used for predicting the chromatographic behavior under hypothetical HPLC conditions. The influence of the parameters relating to the adsorption equilibrium and to the reaction kinetics on the chromatographic behavior was quantitatively evaluated. It is expected that the moment equations are effective for a detailed analysis of the influence of the mass transfer rates and of the Langmuir type reaction kinetics on the column efficiency.

  20. A new approach to the Child-Langmuir law

    CERN Document Server

    Gonzalez, Gabriel

    2015-01-01

    We analyze the motion of charged particles in a vacuum tube diode using a new set of variables. We obtain the space charge limited current for a charged particle moving non-relativistically in one dimension for the case of zero and non zero initial velocity. Our approach gives a new physical insight into the Child-Langmuir law and avoids the need of solving a nonlinear differential equation.

  1. 2-D Polymerized Langmuir-Blodgett Films Studied by STM

    Science.gov (United States)

    1993-10-20

    Langmuir polymerization of 3- hexadecyl pyrrole. By spreading monomer at room temperature on an oxidizing subphase (0.03 M ammonium persulfate ) and...used to image LB films 9 ,10. In our case, the intrinsic conductivity of the polypyrrole backbone should change the contrast and allow us to image...polymerization. All monolayer samples were prepared by one upstroke of the MoS 2 substrate, placing the hydrophilic pyrrole rings or the polypyrrole

  2. Planktonic interactions and chaotic advection in Langmuir circulation

    DEFF Research Database (Denmark)

    Bees, Martin Alan; Mezic, I.; McGlade, J.

    1998-01-01

    The role of unsteady laminar flows for planktonic communities is investigated. Langmuir circulation is used, as a typical medium-scale structure, to illustrate mechanisms for the generation of plankton patches. Two behaviours are evident: chaotic regions that help to spread plankton and locally c...... coherent regions that do not mix with the chaotic regions and which persist for long periods of time. The interaction of populations of phytoplankton with zooplankton is discussed, taking into account the variations in plankton buoyancy....

  3. Optimal Requirements of a Data Acquisition System for a Quadrupolar Probe Employed in Electrical Spectroscopy

    CERN Document Server

    Settimi, A; Baskaradas, J A; Bianchi, C

    2009-01-01

    This paper discusses the development and engineering of electrical spectroscopy for simultaneous and non invasive measurement of electrical resistivity and dielectric permittivity. A quadrupolar probe is able to perform measurements on a subsurface with inaccuracies below a fixed limit in a band of low frequencies. The probe should be connected to an appropriate analogical digital converter (ADC) which samples in uniform or in phase and quadrature (IQ) mode. If the probe is characterized by a galvanic contact with the surface, the inaccuracies in the measurement of resistivity and permittivity, due to the uniform or IQ sampling ADC, are analytically expressed. A large number of numerical simulations prove that the performance of the probe depends on the selected sampler and that the IQ is better compared to the uniform mode under the same operating conditions, i.e. bit resolution and medium.

  4. Observations of a doubly driven V system probed to a fourth level in laser-cooled rubidium

    CERN Document Server

    D'Echaniz, S R; Durrant, A V; Segal, D M; Marangos, J P; Vaccaro, J A; Greentree, Andrew D.

    2001-01-01

    Observations of a doubly driven V system probed to a fourth level in an N configuration are reported. A dressed state analysis is also presented. The expected three-peak spectrum is explored in a cold rubidium sample in a magneto-optic trap. Good agreement is found between the dressed state theory and the experimental spectra once light shifts and uncoupled absorptions in the rubidium system are taken into account.

  5. Functionalization of a viscosity-sensitive fluorophore for probing of biological systems.

    Science.gov (United States)

    Petric, A; Jacobson, A F; Barrio, J R

    1998-06-16

    Functionalization of a viscosity-sensitive visible wavelength fluorophore 2-(1,1-dicyanopropenyl-2)-6-dimethylaminonaphthalene (DDNP), with the intent to incorporate its favorable optical properties into a probe for structural and functional imaging by fluorescence microscopy, is described. Spiperone, a highly potent ligand for the dopamine D2 receptors, was conjugated via an ethylpiperazine moiety to the fluorophore giving fluorescent probes that can be excited in the UV and Vis range.

  6. Accelerated electron populations formed by Langmuir wave-caviton interactions

    CERN Document Server

    Sircombe, N J; Dendy, R O

    2004-01-01

    Direct numerical simulations of electron dynamics in externally driven electrostatic waves have been carried out using a relativistic two-fluid one-dimensional Vlasov-Poisson code. When the driver wave has sufficiently large amplitude, ion density holes (cavitons) form. The interaction between these cavitons and other incoming Langmuir waves gives rise to substantial local acceleration of groups of electrons, and fine jet-like structures arise in electron phase space. We show that these jets are caused by wave-breaking when finite amplitude Langmuir waves experience the ion density gradient at the leading edge of the holes, and are not caused by caviton burn-out. An analytical two-fluid model gives the critical density gradient and caviton depth for which this process can occur. In particular, the density gradient critically affects the rate at which a Langmuir wave, moving into the caviton, undergoes Landau damping. This treatment also enables us to derive analytical estimates for the maximum energy of accel...

  7. Saturation of Langmuir waves in laser-produced plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Baker, K.L.

    1996-04-01

    This dissertation deals with the interaction of an intense laser with a plasma (a quasineutral collection of electrons and ions). During this interaction, the laser drives large-amplitude waves through a class of processes known as parametric instabilities. Several such instabilities drive one type of wave, the Langmuir wave, which involves oscillations of the electrons relative to the nearly-stationary ions. There are a number of mechanisms which limit the amplitude to which Langmuir waves grow. In this dissertation, these mechanisms are examined to identify qualitative features which might be observed in experiments and/or simulations. In addition, a number of experiments are proposed to specifically look for particular saturation mechanisms. In a plasma, a Langmuir wave can decay into an electromagnetic wave and an ion wave. This parametric instability is proposed as a source for electromagnetic emission near half of the incident laser frequency observed from laser-produced plasmas. This interpretation is shown to be consistent with existing experimental data and it is found that one of the previous mechanisms used to explain such emission is not. The scattering version of the electromagnetic decay instability is shown to provide an enhanced noise source of electromagnetic waves near the frequency of the incident laser.

  8. Unexpected bilayer formation in Langmuir films of nucleolipids.

    Science.gov (United States)

    Desbat, Bernard; Arazam, Nessim; Khiati, Salim; Tonelli, Giovanni; Neri, Wilfrid; Barthélémy, Philippe; Navailles, Laurence

    2012-05-01

    Langmuir monolayers have been extensively investigated by various experimental techniques. These studies allowed an in-depth understanding of the molecular conformation in the layer, phase transitions, and the structure of the multilayer. As the monolayer is compressed and the surface pressure is increased beyond a critical value, usually occurring in the minimal closely packed molecular area, the monolayer fractures and/or folds, forming multilayers in a process referred to as collapse. Various mechanisms for monolayer collapse and the resulting reorganization of the film have been proposed, and only a few studies have demonstrated the formation of a bilayer after collapse and with the use of a Ca(2+) solution. In this work, Langmuir isotherms coupled with imaging ellipsometry and polarization modulation infrared reflection absorption spectroscopy were recorded to investigate the air-water interface properties of Langmuir films of anionic nucleolipids. We report for these new molecules the formation of a quasi-hexagonal packing of bilayer domains at a low compression rate, a singular behavior for lipids at the air-water interface that has not yet been documented.

  9. A Study of Uranus' Bow Shock Motions Using Langmuir Waves

    Science.gov (United States)

    Xue, S.; Cairns, I. H.; Smith, C. W.; Gurnett, D. A.

    1996-01-01

    During the Voyager 2 flyby of Uranus, strong electron plasma oscillations (Langmuir waves) were detected by the plasma wave instrument in the 1.78-kHz channel on January 23-24, 1986, prior to the inbound bow shock crossing. Langmuir waves are excited by energetic electrons streaming away from the bow shock. The goal of this work is to estimate the location and motion of Uranus' bow shock using Langmuir wave data, together with the spacecraft positions and the measured interplanetary magnetic field. The following three remote sensing analyses were performed: the basic remote sensing method, the lag time method, and the trace-back method. Because the interplanetary magnetic field was highly variable, the first analysis encountered difficulties in obtaining a realistic estimation of Uranus' bow shock motion. In the lag time method developed here, time lags due to the solar wind's finite convection speed are taken into account when calculating the shock's standoff distance. In the new trace-back method, limits on the standoff distance are obtained as a function of time by reconstructing electron paths. Most of the results produced by the latter two analyses are consistent with predictions based on the standard theoretical model and the measured solar wind plasma parameters. Differences between our calculations and the theoretical model are discussed.

  10. A self-adjustable four-point probing system using polymeric three dimensional coils and non-toxic liquid metal

    Energy Technology Data Exchange (ETDEWEB)

    Oyunbaatar, Nomin-Erdene; Choi, Young Soo; Lee, Dong-Weon, E-mail: mems@jnu.ac.kr [MEMS and Nanotechnology Laboratory, School of Mechanical Engineering, Chonnam National University, Gwangju 500757 (Korea, Republic of)

    2015-12-15

    This paper describes a self-adjustable four-point probe (S4PP) system with a square configuration. The S4PP system consists of 3D polymer coil springs for the independent operation of each tungsten (W) probe, microfluidic channels filled with a nontoxic liquid metal, and a LabView-based control system. The 3D coil springs made by PMMA are fabricated with a 3D printer and are positioned in a small container filled with the non-toxic liquid metal. This unique configuration allows independent self-adjustment of the probe heights for precise measurements of the electrical properties of both flexible and large-step-height microsamples. The feasibility of the fabricated S4PP system is evaluated by measuring the specific resistance of Cr and Au thin films deposited on silicon wafers. The system is then employed to evaluate the electrical properties of a Au thin film deposited onto a flexible and easily breakable silicon diaphragm (spring constant: ∼3.6 × 10{sup −5} N/m). The resistance of the Cr thin films (thickness: 450 nm) with step heights of 60 and 90 μm is also successfully characterized. These experimental results indicate that the proposed S4PP system can be applied to common metals and semiconductors as well as flexible and large-step-height samples.

  11. A self-adjustable four-point probing system using polymeric three dimensional coils and non-toxic liquid metal.

    Science.gov (United States)

    Oyunbaatar, Nomin-Erdene; Choi, Young Soo; Choi, Yong Soo; Lee, Dong-Weon

    2015-12-01

    This paper describes a self-adjustable four-point probe (S4PP) system with a square configuration. The S4PP system consists of 3D polymer coil springs for the independent operation of each tungsten (W) probe, microfluidic channels filled with a nontoxic liquid metal, and a LabView-based control system. The 3D coil springs made by PMMA are fabricated with a 3D printer and are positioned in a small container filled with the non-toxic liquid metal. This unique configuration allows independent self-adjustment of the probe heights for precise measurements of the electrical properties of both flexible and large-step-height microsamples. The feasibility of the fabricated S4PP system is evaluated by measuring the specific resistance of Cr and Au thin films deposited on silicon wafers. The system is then employed to evaluate the electrical properties of a Au thin film deposited onto a flexible and easily breakable silicon diaphragm (spring constant: ∼3.6 × 10(-5) N/m). The resistance of the Cr thin films (thickness: 450 nm) with step heights of 60 and 90 μm is also successfully characterized. These experimental results indicate that the proposed S4PP system can be applied to common metals and semiconductors as well as flexible and large-step-height samples.

  12. An introduction to ultrathin organic films from Langmuir-Blodgett to self-assembly

    CERN Document Server

    Ulman, Abraham

    1991-01-01

    The development of oriented organic monomolecular layers by the Langmuir-Blodgett (LB) and self-assembly (SA) techniques has led researchers toward their goal of assembling individual molecules into highly ordered architectures. Thus the continually growing contribution of LB and SA systems to the chemistry and physics of thin organic films is widely recognized. Equally well-known is the difficulty in keeping up to date with the burgeoning multidisciplinary research in this area. Dr. Ulman provides a massive survey of the available literature. The book begins with a section on analytical tools

  13. Design of Portable Mass Spectrometers with Handheld Probes: Aspects of the Sampling and Miniature Pumping Systems

    Science.gov (United States)

    Chen, Chien-Hsun; Chen, Tsung-Chi; Zhou, Xiaoyu; Kline-Schoder, Robert; Sorensen, Paul; Cooks, R. Graham; Ouyang, Zheng

    2015-02-01

    Miniature mass spectrometry analytical systems of backpack configuration fitted with sampling probes could potentially be of significant interest for in-field, real-time chemical analysis. In this study, various configurations were explored in which a long narrow tube was used to connect the turbo and backing pumps used to create and maintain vacuum. Also, for the first time we introduced two new types of pumps for miniature mass spectrometers, the Creare 130 g drag pump and Creare 350 g scroll backing pump. These pumps, along with another Creare 550 turbo pump and the commercially available Pfeiffer HiPace 10 turbo and KnF diaphragm backing pumps, were tested with the backpack configurations. The system performance, especially the scan time, was characterized when used with a discontinuous atmospheric pressure interface (DAPI) for ion introduction. The pumping performance in the pressure region above 1 mtorr is critical for DAPI operation. The 550 g turbo pump was shown to have a relatively higher pumping speed above 1 mtorr and gave a scan time of 300 ms, almost half the value obtained with the larger, heavier HiPace 10 often used with miniature mass spectrometers. The 350 g scroll pump was also found to be an improvement over the diaphragm pumps generally used as backing pumps. With a coaxial low temperature plasma ion source, direct analysis of low volatility compounds glass slides was demonstrated, including 1 ng DNP (2,4-Dinitrophenol) and 10 ng TNT (2,4,6-trinitrotoluene) with Creare 550 g turbo pump as well as 10 ng cocaine and 20 ng DNP with Creare 130 g drag pump.

  14. Validation of break-apart and fusion MYC probes using a digital fluorescence in situ hybridization capture and imaging system

    Directory of Open Access Journals (Sweden)

    Michael Liew

    2016-01-01

    Full Text Available Introduction: Detection of MYC translocations using fluorescence in situ hybridization (FISH is important in the evaluation of lymphomas, in particular, Burkitt lymphoma and diffuse large B-cell lymphoma. Our aim was to validate a digital FISH capture and imaging system for the detection of MYC 8q24 translocations using LSI-MYC (a break-apart probe and MYC 8;14 translocation using IGH-MYC (a fusion probe. Materials and Methods: LSI-MYC probe was evaluated using tissue sections from 35 patients. IGH-MYC probe was evaluated using tissue sections from forty patients. Sections were processed for FISH and analyzed using traditional methods. FISH slides were then analyzed using the GenASIs capture and analysis system. Results: Results for LSI-MYC had a high degree of correlation between traditional method of FISH analysis and digital FISH analysis. Results for IGH-MYC had a 100% concordance between traditional method of FISH analysis and digital FISH analysis. Conclusion: Annotated whole slide images of H and E and FISH sections can be digitally aligned, so that areas of tumor within a section can be matched and evaluated with a greater degree of accuracy. Images can be archived permanently, providing a means for examining the results retrospectively. Digital FISH imaging of the MYC translocations provides a better diagnostic tool compared to traditional methods for evaluating lymphomas.

  15. Design and characterization of a novel multimodal fiber-optic probe and spectroscopy system for skin cancer applications

    Science.gov (United States)

    Sharma, Manu; Marple, Eric; Reichenberg, Jason; Tunnell, James W.

    2014-08-01

    The design and characterization of an instrument combining Raman, fluorescence, and reflectance spectroscopic modalities is presented. Instrument development has targeted skin cancer applications as a novel fiber-optic probe has been specially designed to interrogate cutaneous lesions. The instrument is modular and both its software and hardware components are described in depth. Characterization of the fiber-optic probe is also presented, which details the probe's ability to measure diagnostically important parameters such as intrinsic fluorescence and absorption and reduced scattering coefficients along with critical performance metrics such as high Raman signal-to-noise ratios at clinically practical exposure times. Validation results using liquid phantoms show that the probe and system can extract absorption and scattering coefficients with less than 10% error. As the goal is to use the instrument for the clinical early detection of skin cancer, preliminary clinical data are also presented, which indicates our system's ability to measure physiological quantities such as relative collagen and nicotinamide adenine dinucleotide concentration, oxygen saturation, blood volume fraction, and mean vessel diameter.

  16. Validation of break-apart and fusion MYC probes using a digital fluorescence in situ hybridization capture and imaging system

    Science.gov (United States)

    Liew, Michael; Rowe, Leslie; Clement, Parker W.; Miles, Rodney R.; Salama, Mohamed E.

    2016-01-01

    Introduction: Detection of MYC translocations using fluorescence in situ hybridization (FISH) is important in the evaluation of lymphomas, in particular, Burkitt lymphoma and diffuse large B-cell lymphoma. Our aim was to validate a digital FISH capture and imaging system for the detection of MYC 8q24 translocations using LSI-MYC (a break-apart probe) and MYC 8;14 translocation using IGH-MYC (a fusion probe). Materials and Methods: LSI-MYC probe was evaluated using tissue sections from 35 patients. IGH-MYC probe was evaluated using tissue sections from forty patients. Sections were processed for FISH and analyzed using traditional methods. FISH slides were then analyzed using the GenASIs capture and analysis system. Results: Results for LSI-MYC had a high degree of correlation between traditional method of FISH analysis and digital FISH analysis. Results for IGH-MYC had a 100% concordance between traditional method of FISH analysis and digital FISH analysis. Conclusion: Annotated whole slide images of H and E and FISH sections can be digitally aligned, so that areas of tumor within a section can be matched and evaluated with a greater degree of accuracy. Images can be archived permanently, providing a means for examining the results retrospectively. Digital FISH imaging of the MYC translocations provides a better diagnostic tool compared to traditional methods for evaluating lymphomas. PMID:27217970

  17. Adaptive Embedded Digital System for Plasma Diagnostics

    Science.gov (United States)

    González, Angel; Rodríguez, Othoniel; Mangual, Osvaldo; Ponce, Eduardo; Vélez, Xavier

    2014-05-01

    An Adaptive Embedded Digital System to perform plasma diagnostics using electrostatic probes was developed at the Plasma Engineering Laboratory at Polytechnic University of Puerto Rico. The system will replace the existing instrumentation at the Laboratory, using reconfigurable hardware to minimize the equipment and software needed to perform diagnostics. The adaptability of the design resides on the possibility of replacing the computational algorithm on the fly, allowing to use the same hardware for different probes. The system was prototyped using Very High Speed Integrated Circuits Hardware Description Language (VHDL) into an Field Programmable Gate Array (FPGA) board. The design of the Embedded Digital System includes a Zero Phase Digital Filter, a Derivative Unit, and a Computational Unit designed using the VHDL-2008 Support Library. The prototype is able to compute the Plasma Electron Temperature and Density from a Single Langmuir probe. The system was tested using real data previously acquired from a single Langmuir probe. The plasma parameters obtained from the embedded system were compared with results computed using matlab yielding excellent matching. The new embedded system operates on 4096 samples versus 500 on the previous system, and completes its computations in 26 milliseconds compared with about 15 seconds on the previous system.

  18. Force probe simulations of a reversibly rebinding system: Impact of pulling device stiffness

    Science.gov (United States)

    Jaschonek, Stefan; Diezemann, Gregor

    2017-03-01

    We present a detailed study of the parameter dependence of force probe molecular dynamics (FPMD) simulations. Using a well studied calix[4]arene catenane dimer as a model system, we systematically vary the pulling velocity and the stiffness of the applied external potential. This allows us to investigate how the results of pulling simulations operating in the constant velocity mode (force-ramp mode) depend on the details of the simulation setup. The system studied has the further advantage of showing reversible rebinding meaning that we can monitor the opening and the rebinding transition. Many models designed to extract kinetic information from rupture force distributions work in the limit of soft springs and all quantities are found to depend solely on the so-called loading rate, the product of spring stiffness and pulling velocity. This approximation is known to break down when stiff springs are used, a situation often encountered in molecular simulations. We find that while some quantities only depend on the loading rate, others show an explicit dependence on the spring constant used in the FPMD simulation. In particular, the force versus extension curves show an almost stiffness independent rupture force but the force jump after the rupture transition does depend roughly linearly on the value of the stiffness. The kinetic rates determined from the rupture force distributions show a dependence on the stiffness that can be understood in terms of the corresponding dependence of the characteristic forces alone. These dependencies can be understood qualitatively in terms of a harmonic model for the molecular free energy landscape. It appears that the pulling velocities employed are so large that the crossover from activated dynamics to diffusive dynamics takes place on the time scale of our simulations. We determine the effective distance of the free energy minima of the closed and the open configurations of the system from the barrier via an analysis of the

  19. System-Level Design of an Integrated Receiver Front End for a Wireless Ultrasound Probe.

    Science.gov (United States)

    Di Ianni, Tommaso; Hemmsen, Martin Christian; Llimos Muntal, Pere; Jorgensen, Ivan Harald Holger; Jensen, Jorgen Arendt

    2016-11-01

    In this paper, a system-level design is presented for an integrated receive circuit for a wireless ultrasound probe, which includes analog front ends and beamformation modules. This paper focuses on the investigation of the effects of architectural design choices on the image quality. The point spread function is simulated in Field II from 10 to 160 mm using a convex array transducer. A noise analysis is performed, and the minimum signal-to-noise ratio (SNR) requirements are derived for the low-noise amplifiers (LNAs) and A/D converters (ADCs) to fulfill the design specifications of a dynamic range of 60 dB and a penetration depth of 160 mm in the B-mode image. Six front-end implementations are compared using Nyquist-rate and Σ∆ modulator ADCs. The image quality is evaluated as a function of the depth in terms of lateral full-width at half-maximum (FWHM) and -12-dB cystic resolution (CR). The designs that minimally satisfy the specifications are based on an 8-b 30-MSPS Nyquist converter and a single-bit third-order 240-MSPS Σ∆ modulator, with an SNR for the LNA in both cases equal to 64 dB. The mean lateral FWHM and CR are 2.4% and 7.1% lower for the Σ∆ architecture compared with the Nyquist-rate one. However, the results generally show minimal differences between equivalent architectures. Advantages and drawbacks are finally discussed for the two families of converters.

  20. Probing Interstellar Silicate Dust Grain Properties in Quasar Absorption Systems at Redshifts z<1.4

    Science.gov (United States)

    Aller, M.; Kulkarni, V. P.; York, D. G.; Welty, D. E.; Vladilo, G.; Som, D.

    Absorption lines in the spectra of distant quasars whose sightlines serendipitously pass through foreground galaxies provide a valuable tool to simultaneously probe the dust and gas compositions of the interstellar medium (ISM) in galaxies. In particular, the damped and sub-damped Lyman- α (DLA/sub-DLA) absorbers trace gas-rich galaxies, independent of the intrinsic luminosities or star-formation rates of the associated galaxy stellar populations. The first evidence of silicate dust in a quasar absorption system was provided through our detection of the 10 µ m silicate feature in the z=0.52 DLA absorber toward the quasar AO 0235+164. We present results from 2 follow-up programs using archival Spitzer Space Telescope infrared spectra to study the interstellar silicate dust grain properties in a total of 13 quasar absorption systems at 0.1 < z < 1.4. We find clear detections of the 10 µ m silicate feature in the quasar absorption systems studied. In addition, we also detect the 18 µ m silicate feature in the sources with adequate spectral coverage. We find variations in the breadth, peak wavelength, and substructure of the 10 µ m interstellar silicate absorption features among the absorbers. This suggests that the silicate dust grain properties in these distant galaxies may differ relative to one another, and relative to those in the Milky Way. We also find suggestions in several sources, based on comparisons with laboratory-derived profiles from the literature, that the silicate dust grains may be significantly more crystalline than those in the amorphous Milky Way ISM. This is particularly evident in the z=0.89 absorber toward the quasar PKS 1830-211, where substructure near 10 µ m is consistent with a crystalline olivine composition. If confirmed, these grain property variations may have implications for both dust and galaxy evolution over the past 9 Gyrs, and for the commonly-made assumption that highredshift dust is similar to local dust. We also discuss

  1. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design

    Science.gov (United States)

    Rifai, Damhuji; Abdalla, Ahmed N.; Razali, Ramdan; Ali, Kharudin; Faraj, Moneer A.

    2017-01-01

    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient. PMID:28335399

  2. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design.

    Science.gov (United States)

    Rifai, Damhuji; Abdalla, Ahmed N; Razali, Ramdan; Ali, Kharudin; Faraj, Moneer A

    2017-03-13

    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient.

  3. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design

    Directory of Open Access Journals (Sweden)

    Damhuji Rifai

    2017-03-01

    Full Text Available The use of the eddy current technique (ECT for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM. The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient.

  4. S-(N-dansylaminoethyl)-6-mercaptoguanosine as a fluorescent probe for the uridine transport system in human erythrocytes.

    Science.gov (United States)

    Shohami, E; Koren, R

    1979-02-15

    A fluorescent derivative of 6-mercaptoguanosine, S-(N-dansylaminoethyl)-6-mercaptoguanosine, was synthesized, and found to be a strong inhibitor of the uridine transport system of erythrocyte (Ki approximately 0.3 microM). The emission spectrum of this compound has peaks at 400 and 550 nm. The emission at 550, but not that a 400 nm, in environment-sensitive. A method was devised for preparing a suspension of erythrocyte-membrane fragments with sufficiently low light scattering so that a detailed study could be made of the fluorescence of the probe when bound to membranes. Direct binding measurements showed the existence of a tight binding site, with a dissociation constant of the same order of magnitude as the inhibition constant. Binding of probe and substrate are not mutually exclusive, but the fluorescence and affinity of the bound probe are sensitive to the presence of uridine. The emission spectrum suggests that the bound probe penetrates into the bilayer region of the membrane.

  5. TEST PLAN AND PROCEDURE FOR THE EXAMINATION OF TANK 241-AY-101 MULTI-PROBE CORROSION MONITORING SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    WYRWAS RB; PAGE JS; COOKE GS

    2012-04-19

    This test plan describes the methods to be used in the forensic examination of the Multi-probe Corrosion Monitoring System (MPCMS) installed in the double-shell tank 241-AY-101 (AY-101). The probe was designed by Applied Research and Engineering Sciences (ARES) Corporation. The probe contains four sections, each of which can be removed from the tank independently (H-14-107634, AY-101 MPCMS Removable Probe Assembly) and one fixed center assembly. Each removable section contains three types of passive corrosion coupons: bar coupons, round coupons, and stressed C-rings (H-14-l07635, AY-101 MPCMS Details). Photographs and weights of each coupon were recorded and reported on drawing H-14-107634 and in RPP-RPT-40629, 241-AY-101 MPCMS C-Ring Coupon Photographs. The coupons will be the subject of the forensic analyses. The purpose of this examination will be to document the nature and extent of corrosion of the 29 coupons. This documentation will consist of photographs and photomicrographs of the C-rings and round coupons, as well as the weights of the bar and round coupons during corrosion removal. The total weight loss of the cleaned coupons will be used in conjunction with the surface area of each to calculate corrosion rates in mils per year. The bar coupons were presumably placed to investigate the liquid-air-interface. An analysis of the waste level heights in the waste tank will be investigated as part of this examination.

  6. Equatorial Scintillation Predictions from C/NOFS Planar Langmuir Probe Electron Density Fluctuation Data

    Science.gov (United States)

    2014-09-05

    Brasil Tel: 55 21 3527 1682; Fax: 55 21 3527 1154 E-mail: epoc@cetuc.puc-rio.br FINAL PERFORMANCE REPORT Equatorial scintillation...Costa Centro de Estudos em Telecomunicações/CETUC Rua Marquês de São Vicente, 225 – Gávea 22451-900 Rio de Janeiro - RJ – Brasil Tel: 55 21 3527...Emanoel Costa Centro de Estudos em Telecomunicações/CETUC Rua Marquês de São Vicente, 225 – Gávea 22451-900 Rio de Janeiro - RJ – Brasil Tel: 55

  7. Nonlinear circuit analysis of harmonic currents in a floating Langmuir probe with a capacitive load

    Science.gov (United States)

    Kim, Kyung-Hyun; Kim, Dong-Hwan; Chung, Chin-Wook

    2017-02-01

    Plasma diagnostics using the floating harmonic technique were first used to obtain the electron temperature in a tokamak plasma. In this technique, the electron temperature depends on the ratio of the harmonic currents in a resistive sheath. Because these harmonic currents are determined by a modulated sheath voltage, calculation of the exact modulated voltage across the sheath is important; in general, the voltage is calculated using a phase of the first harmonic current. However, when a series load capacitance is present, the second harmonic currents are abnormally reduced compared to those expected by the conventional floating harmonic model, resulting in an unreliable measurement of the electron temperature. To describe this phenomenon, we used a modified floating harmonic model by applying the harmonic balance technique, a method that analyzes nonlinear circuits. Theoretical prediction of the harmonic current obtained from the modified model was compared with the experimental results, and they are in good agreement. In addition, the degrees of sheath nonlinearity, defined as the ratio of the second harmonic current (or voltage) to the fundamental current (or voltage), are discussed.

  8. Langmuir Probe Measurements of Inductively Coupled Plasma in CF4/AR/O2 Mixtures

    Science.gov (United States)

    Rao, M. V. V. S.; Cruden, Brett; Sharma, Surendra; Meyyappan, Meyya

    2001-01-01

    Inductively coupled plasmas of CF4:Ar:O2, which have been of importance to material processing, were studied in the GEC cell at 80:10:10, 60:20:20, and 40:30:30 mixture ratios. Radial distributions of plasma potential (V(sub p)), electron and ion number densities (n(sub e) and n(sub i)), electron temperature (T(sub e)), and electron energy distribution functions (EEDFs) were measured in the mid-plane of plasma across the electrodes in the pressure range of 10-50 mTorr, and RF power of 200 and 300 W. V(sub p), n(sub e) and n(sub i), which peak in the center of the plasma, increase with decrease of pressure. T(sub e) also increases with pressure but peaks toward the electrode edge. Both V(sub p) and T(sub e) remain nearly independent of RF power, whereas n(sub e) and n(sub i) increase with power. In all conditions the EEDFs exhibit non-Maxwellian shape and are more like Druyvesteyn form at higher energies. They exhibit a broad lip in the energy range 0-10 eV suggesting an electron loss mechanism, which could be due to via resonance electron attachment processes producing negative ions in this rich electronegative gas mixture. This behavior is more prominent towards the electrode edge.

  9. Langmuir Probe Measurements of Inductively Coupled Plasmas in CF4/Ar/O2 Mixtures

    Science.gov (United States)

    Rao, M. V. V. S.; Cruden, Brett; Sharma, Surendra; Meyyappan, Meyya

    2001-01-01

    Inductively coupled plasmas of CF4:Ar:O2, which have been of importance to material processing, were studied in the GEC cell at 80:10:10, 60:20:20, and 40:30:30 mixture ratios. Radial distributions of plasma potential (V(sub p)), electron and ion number densities (n(sub e) and n(sub i), electron temperature (T(sub e)), and electron energy distribution functions (EEDFs) were measured in the mid-plane of plasma across the electrodes in the pressure range of 10-50 mTorr, and RF (radio frequency) power of 200 and 300 W. V(sub p), n(sub e) and n(sub i), which peak in the center of the plasma, increase with decrease of pressure. T(sub e) also increases with pressure but peaks toward the electrode edge. Both V(sub p) and T(sub e) remain nearly independent of RF power, whereas n(sub e) and n(sub i) increase with power. In all conditions the EEDFs exhibit non-Maxwellian shape and are more like Druyvesteyn form at higher energies. They exhibit a broad dip in the energy range 0-10 eV suggesting an electron loss mechanism, which could be due to via resonance electron attachment processes producing negative ions in this rich electronegative gas mixture. This behavior is more prominent towards the electrode edge.

  10. Theoretical Investigation of Dynamic Properties of Magnetic Molecule Systems as Probed by NMR and Pulsed Fields Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Rousochatzakis, Ioannis [Iowa State Univ., Ames, IA (United States)

    2005-12-17

    The field of molecular magnetism[l-6] has become a subject of intense theoretical and experimental interest and has rapidly evolved during the last years. This inter-disciplinary field concerns magnetic systems at the molecular or "nanoscopic" level, whose realization has become feasible due to recent advances in the field of chemical synthesis. The present theoretical work provides a first step towards exploiting the possibilities that are offered by probing magnetic molecules using external magnetic fields with high sweep rates. These probes, apart for providing information specific to magnetic molecules, offer the possibility of conducting a detailed study of the relaxational behavior of interacting spin systems as a result of their coupling with a "heat bath" and in particular the excitations of the host lattice. Development of a broad theoretical framework for dealing with relaxational phenomena induced by dynamical magnetic fields is indeed a worthy goal.

  11. Bare PCB inspection system with SV-GMR sensor eddy-current testing probe

    OpenAIRE

    Chomsuwan, K.; Yamada, Sotoshi; Iwahara, Masayoshi

    2007-01-01

    This paper describes bare printed circuit board (PCB) inspection based on eddy-current testing (ECT) technique with high scanning speed. A high-frequency ECT probe composed of a meander coil as an exciting coil and the spin-valve giant magnetoresistance (SV-GMR) sensor was fabricated and is proposed. The ECT probe was designed based on crack inspection over flat surface, especially suitable for microdefect detection on high-density bare PCB. The ECT signal detected by the SV-GMR sensor was ac...

  12. Group-specific small-subunit rRNA hybridization probes to characterize filamentous foaming in activated sludge systems.

    OpenAIRE

    de los Reyes, F L; Ritter, W; Raskin, L.

    1997-01-01

    Foaming in activated sludge systems is characterized by the formation of a thick, chocolate brown-colored scum that floats on the surface of aeration basins and secondary clarifiers. These viscous foams have been associated with the presence of filamentous mycolic acid-containing actinomycetes. To aid in evaluating the microbial representation in foam, we developed and characterized group-, genus-, and species-specific oligonucleotide probes targeting the small subunit rRNA of the Mycobacteri...

  13. In Situ Probing Nucleation, Growth, and Aggregation of Iron Oxides in Geochemical Aquatic Systems

    Science.gov (United States)

    Jun, Y.; Hu, Y.; Ray, J. R.

    2012-12-01

    Nucleation, growth, and aggregation of iron oxide nanoparticles can significantly alter the fate of organic and inorganic contaminants in geochemical aquatic systems. This talk will address how we can improve our understanding of nucleation, growth, and aggregation of iron oxide nanoparticles by providing more accurate quantitative and qualitative empirical information. In this study, a novel environmental setup—which allows time-resolved simultaneous measurements of small angle x-ray scattering (SAXS) and grazing incidence small-angle scattering (GISAXS) in the presence of bulk solution—was utilized for real-time monitoring of nanoparticle formation at water-mineral interfaces. This setup enabled us to probe the size, shape, and location of iron oxide nanoparticles on the substrate and in solution without dehydration of samples. Experiments were conducted with 10-4 M ferric ions in the presence of environmentally important and abundant anions (nitrate, chlorite, sulfate) and cations (aluminum) at pH = 3.7 ± 0.1. The substrates used were geologically ubiquitous media such as quartz, mica, and organic polymer-coated surfaces. Once ferric solutions were introduced, the homogeneous and heterogeneous nucleation of iron oxides occurred and the size and volume evolution of nanoparticles were monitored. To complement these observations, atomic force microscopy, high-resolution transmission electron microscopy, high-resolution x-ray diffraction, contact angle analysis, dynamic light scattering, and electrophoretic mobility analysis were utilized. Based on in situ measurements of initial nuclei evolution at aqueous interfaces, this approach provided new, important information for upscaling such as size, volume, surface area, and location (i.e., in solution vs. on mineral surfaces) of iron oxides precipitates formed in the presence of organic matter and different substrate morphological and chemical properties. Using this quantitative information, we identified the

  14. A modified Langmuir-Freundlich isotherm model for simulating pH-dependent adsorption effects

    Science.gov (United States)

    Jeppu, Gautham P.; Clement, T. Prabhakar

    2012-03-01

    Analytical isotherm equations such as Langmuir and Freundlich isotherms are widely used for modeling adsorption data. However, these isotherms are primarily useful for simulating data collected at a fixed pH value and cannot be easily adapted to simulate pH-dependent adsorption effects. Therefore, most adsorption studies currently use numerical surface-complexation models (SCMs), which are more complex and time consuming than traditional analytical isotherm models. In this work, we propose a new analytical isotherm model, identified as the modified Langmuir-Freundlich (MLF) isotherm, which can be used to simulate pH-dependent adsorption. The MLF isotherm uses a linear correlation between pH and affinity coefficient values. We validated the proposed MLF isotherm by predicting arsenic adsorption onto two different types of sorbents: pure goethite and goethite-coated sand. The MLF model gave good predictions for both experimental and surface complexation-model predicted datasets for these two sorbents. The proposed analytical isotherm framework can help reduce modeling complexity, model development time, and computational efforts. One of the limitations of the proposed method is that it is currently valid only for single-component systems. Furthermore, the model requires a system-specific pH. vs. affinity coefficient relation. Despite these limitations, the approach provides a promising analytical framework for simulating pH-dependent adsorption effects.

  15. Whistler-Langmuir oscillitons and their relation to auroral hiss

    Directory of Open Access Journals (Sweden)

    K. Sauer

    2011-10-01

    Full Text Available A new type of oscilliton (soliton with superimposed spatial oscillations is described which arises in plasmas if the electron cyclotron frequency Ωe is larger than the electron plasma frequency ωe, which is a typical situation for auroral regions in planetary magnetospheres. Both high-frequency modes of concern, the Langmuir and the whistler wave, are completely decoupled if they propagate parallel to the magnetic field. However, for oblique propagation two mixed modes are created with longitudinal and transverse electric field components. The lower mode (in the literature commonly called the whistler mode, e.g. Gurnett et al., 1983 has whistler wave characteristics at small wave numbers and asymptotically transforms into the Langmuir mode. As a consequence of the coupling between these two modes, with different phase velocity dependence, a maximum in phase velocity appears at finite wave number. The occurrence of such a particular point where phase and group velocity coincide creates the condition for the existence of a new type of oscillating nonlinear stationary structure, which we call the whistler-Langmuir (WL oscilliton. After determining, by means of stationary dispersion theory, the parameter regime in which WL oscillitons exist, their spatial profiles are calculated within the framework of cold (non-relativistic fluid theory. Particle-in-cell (PIC simulations are used to demonstrate the formation of WL oscillitons which seem to play an important role in understanding electron beam-excited plasma radiation that is observed as auroral hiss in planetary magnetospheres far away from the source region.

  16. Langmuir monolayers composed of single and double tail sulfobetaine lipids.

    Science.gov (United States)

    Hazell, Gavin; Gee, Anthony P; Arnold, Thomas; Edler, Karen J; Lewis, Simon E

    2016-07-15

    Owing to structural similarities between sulfobetaine lipids and phospholipids it should be possible to form stable Langmuir monolayers from long tail sulfobetaines. By modification of the density of lipid tail group (number of carbon chains) it should also be possible to modulate the two-dimensional phase behaviour of these lipids and thereby compare with that of equivalent phospholipids. Potentially this could enable the use of such lipids for the wide array of applications that currently use phospholipids. The benefit of using sulfobetaine lipids is that they can be synthesised by a one-step reaction from cheap and readily available starting materials and will degrade via different pathways than natural lipids. The molecular architecture of the lipid can be easily modified allowing the design of lipids for specific purposes. In addition the reversal of the charge within the sulfobetaine head group relative to the charge orientation in phospholipids may modify behaviour and thereby allow for novel uses of these surfactants. Stable Langmuir monolayers were formed composed of single and double tailed sulfobetaine lipids. Surface pressure-area isotherm, Brewster Angle Microscopy and X-ray and neutron reflectometry measurements were conducted to measure the two-dimensional phase behaviour and out-of-plane structure of the monolayers as a function of molecular area. Sulfobetaine lipids are able to form stable Langmuir monolayers with two dimensional phase behaviour analogous to that seen for the well-studied phospholipids. Changing the number of carbon tail groups on the lipid from one to two promotes the existence of a liquid condensed phase due to increased Van der Waals interactions between the tail groups. Thus the structure of the monolayers appears to be defined by the relative sizes of the head and tail groups in a predictable way. However, the presence of sub-phase ions has little effect on the monolayer structure, behaviour that is surprisingly different to

  17. Probing the electric field in organic double layer-system by optical second harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Eunju; Shibata, Yoshinori; Manaka, Takaaki [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Iwamoto, Mitsumasa, E-mail: iwamoto@ome.pe.titech.ac.j [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2009-11-30

    Optical electric field induced second harmonic generation (EFISHG) measurements were employed to probe the electric field in the active layer of organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs). The OFETs used were double-layered with an active layer of pentacene/poly (3-hexyl thiophene) P3HT on SiO{sub 2} gate insulator with Au source and drain electrodes. It was shown that SHG from the P3HT bottom layer could be selectively probed at a wavelength of 450 nm. Similarly, by using OLEDs comprised of a double layer of Tris(8-hydroxyquinolinato) aluminium (Alq{sub 3}) and N'-di(1-naphthyl)-N,N'-diphenylbenzidine ({alpha}-NPD) with a device structure of indium-zinc oxide (IZO)/{alpha}-NPD/Alq{sub 3}/Al, it was shown that EFISHG from the Alq{sub 3} layer could be selectively probed at a wavelength of 1000 nm by reflective laser beam irradiation from IZO-side. The results show that the spectroscopic nature of materials allows us to selectively probe the electric field distribution in each layer of multi-layer in organic devices.

  18. Passivated diamond film temperature sensing probe and measuring system employing same

    Science.gov (United States)

    Young, Jack P.; Mamantov, Gleb

    1998-01-01

    A high temperature sensing probe includes an optical fiber or rod having a distal end and a proximal end. The optical fiber or rod has a coating secured to the distal end thereof, wherein the coating is capable of producing a Raman spectrum when exposed to an exciting radiation source.

  19. Thermionic phenomena the collected works of Irving Langmuir

    CERN Document Server

    Suits, C Guy

    1961-01-01

    Thermionic Phenomena is the third volume of the series entitled The Collected Works of Irving Langmuir. This volume compiles articles written during the 1920's and early 1930's, the period when the science of thermionics is beginning to be of importance. This text is divided into two parts. The first part discusses vacuum pumps, specifically examining the effect of space charge and residual gases on thermionic currents in high vacuum. This part also explains fundamental phenomena in electron tubes having tungsten cathodes and the use of high-power vacuum tubes. The second part of this text loo

  20. Surface acoustic wave devices including Langmuir-Blodgett films (Review)

    Science.gov (United States)

    Plesskii, V. P.

    1991-06-01

    Recent theoretical and experimental research related to the use of Langmuir-Blodgett (LB) films in surface acoustic wave (SAW) devices is reviewed. The sensitivity of the different cuts of quartz and lithium niobate to inertial loading is investigated, and it is shown that some cuts in lithium niobate are twice as sensitive to mass loading than the commonly used YZ-cut. The large variety of organic compounds suitable for the production of LB films makes it possible to create SAW sensors reacting selectively to certain substances. The existing SAW sensors based on LB films are characterized by high sensitivity and fast response.

  1. Excitation of ultrasonic Lamb waves using a phased array system with two array probes: phantom and in vitro bone studies.

    Science.gov (United States)

    Nguyen, Kim-Cuong T; Le, Lawrence H; Tran, Tho N H T; Sacchi, Mauricio D; Lou, Edmond H M

    2014-07-01

    Long bones are good waveguides to support the propagation of ultrasonic guided waves. The low-order guided waves have been consistently observed in quantitative ultrasound bone studies. Selective excitation of these low-order guided modes requires oblique incidence of the ultrasound beam using a transducer-wedge system. It is generally assumed that an angle of incidence, θi, generates a specific phase velocity of interest, co, via Snell's law, θi=sin(-1)(vw/co) where vw is the velocity of the coupling medium. In this study, we investigated the excitation of guided waves within a 6.3-mm thick brass plate and a 6.5-mm thick bovine bone plate using an ultrasound phased array system with two 0.75-mm-pitch array probes. Arranging five elements as a group, the first group of a 16-element probe was used as a transmitter and a 64-element probe was a receiver array. The beam was steered for six angles (0°, 20°, 30°, 40°, 50°, and 60°) with a 1.6-MHz source signal. An adjoint Radon transform algorithm mapped the time-offset matrix into the frequency-phase velocity dispersion panels. The imaged Lamb plate modes were identified by the theoretical dispersion curves. The results show that the 0° excitation generated many modes with no modal discrimination and the oblique beam excited a spectrum of phase velocities spread asymmetrically about co. The width of the excitation region decreased as the steering angle increased, rendering modal selectivity at large angles. The phenomena were well predicted by the excitation function of the source influence theory. The low-order modes were better imaged at steering angle ⩾30° for both plates. The study has also demonstrated the feasibility of using the two-probe phased array system for future in vivo study.

  2. Langmuir-Blodgett films of amylose-esters and chiral azo-dyes : structure and second order nonlinear optical behaviour

    NARCIS (Netherlands)

    Schoondorp, Monique Annette

    1992-01-01

    This thesis describes the structure and second order nonlinear optical behaviour of several Langmuir-Blodgett films. Langmuir-Blodgett (LB) films are ultra thin films produced by the Langmuir-Blodgett technique, named after their inventors (Irving Langmuir and Katharina Blodgett).

  3. On the use of the dual process Langmuir model for predicting unary and binary isosteric heats of adsorption.

    Science.gov (United States)

    Bhadra, Shubhra J; Ebner, Armin D; Ritter, James A

    2012-05-01

    Analytic expressions for unary and binary isosteric heats of adsorption as a function of the adsorbed phase loading were derived from the dual process Langmuir (DPL) model using the Clausius-Clapeyron equation. Unary isosteric heats of adsorption predicted from these expressions for several adsorbate-adsorbent systems were compared to values in the literature predicted from the well-accepted graphical approach using Toth and unilan models (Adsorption Equilibrium Data Handbook; Prentice Hall: NJ, 1989). Predictions from the DPL model were also compared to rare experimental unary and binary isosteric heats of adsorption in the literature for another adsorbate-adsorbent system. In all cases, very good agreement was obtained, showing that the DPL model can be used in adsorption process modeling for accurately predicting not only ideal and nonideal mixed-gas adsorption equilibria (Langmuir 2011, 27, 4700), but also unary and even binary isosteric heats of adsorption.

  4. Optomechanical oscillator pumped and probed by optically two isolated photonic crystal cavity systems.

    Science.gov (United States)

    Tian, Feng; Sumikura, Hisashi; Kuramochi, Eiichi; Taniyama, Hideaki; Takiguchi, Masato; Notomi, Masaya

    2016-11-28

    Optomechanical control of on-chip emitters is an important topic related to integrated all-optical circuits. However, there is neither a realization nor a suitable optomechanical structure for this control. The biggest obstacle is that the emission signal can hardly be distinguished from the pump light because of the several orders' power difference. In this study, we designed and experimentally verified an optomechanical oscillation system, in which a lumped mechanical oscillator connected two optically isolated pairs of coupled one-dimensional photonic crystal cavities. As a functional device, the two pairs of coupled cavities were respectively used as an optomechanical pump for the lumped oscillator (cavity pair II, wavelengths were designed to be within a 1.5 μm band) and a modulation target of the lumped oscillator (cavity pair I, wavelengths were designed to be within a 1.2 μm band). By conducting finite element method simulations, we found that the lumped-oscillator-supported configurations of both cavity pairs enhance the optomechanical interactions, especially for higher order optical modes, compared with their respective conventional side-clamped configurations. Besides the desired first-order in-plane antiphase mechanical mode, other mechanical modes of the lumped oscillator were investigated and found to possibly have optomechanical applications with a versatile degree of freedom. In experiments, the oscillator's RF spectra were probed using both cavity pairs I and II, and the results matched those of the simulations. Dynamic detuning of the optical spectrum of cavity pair I was then implemented with a pumped lumped oscillator. This was the first demonstration of an optomechanical lumped oscillator connecting two optically isolated pairs of coupled cavities, whose biggest advantage is that one cavity pair can be modulated with an lumped oscillator without interference from the pump light in the other cavity pair. Thus, the oscillator is a suitable

  5. A new centering method of the measuring probe for spiral scanning-based surface profile measurement systems

    Science.gov (United States)

    Du, Hui-Lin; Zeng, Pei-Yang; Ju, Bing-Feng; Zhou, Zhao-Zhong; Xu, Shaoning; Sun, Anyu

    2017-02-01

    Spiral scanning is a high-efficiency scanning mode for surface profile measurement systems. The most important priority to realize the spiral scanning mode is to accurately align the measuring probe with the rotational centre of the spindle. This paper proposes a novel centre alignment method of the measuring probe, which is considered to be suitable for any type of spiral scanning surface measurement systems. The proposed method, which only needs a tilted flat mirror as the artefact, makes the time-consuming centre alignment process of the measuring probe become much easier and faster. The operational steps of the proposed method are presented. Experiments have also been carried out based on a self-developed optical profiler with spiral scanning operation to verity the feasibility of the proposed method. The experimental results show that the proposed method is capable of conducting a fast alignment (only takes 3 min) while maintaining a high alignment accuracy. Evaluation of the alignment accuracy shows that the centering error is less than 10 µm on the mechanical guide rail stage and about 1.7 µm on the air-bearing stage.

  6. Quantum interference effects on the probe amplification without and with inversion in a four-level system

    Institute of Scientific and Technical Information of China (English)

    Zhang Bing; Xu Wei-Hua; Zhang Hui-Fang; Gao Jin-Yue

    2004-01-01

    A four-level system driven by two coherent fields is considered. It is shown that in the presence of an incoherent pump, the probe gain at a short wavelength can be achieved due to the quantum interference. Our density matrix calculation provides the conditions for probe amplification from different origins, including gain without population inversion on any state basis, gain with population inversion on the dressed-state basis, and gain with population inversion on the bare-state basis. Also, by controlling the Rabi frequency of the coupling field a total change from non-inversion to inversion can be achieved which does not depend on the intensity of the incoherent pump.

  7. Development of Radar Control system for Multi-mode Active Phased Array Radar for atmospheric probing

    Science.gov (United States)

    Yasodha, Polisetti; Jayaraman, Achuthan; Thriveni, A.

    2016-07-01

    Modern multi-mode active phased array radars require highly efficient radar control system for hassle free real time radar operation. The requirement comes due to the distributed architecture of the active phased array radar, where each antenna element in the array is connected to a dedicated Transmit-Receive (TR) module. Controlling the TR modules, which are generally few hundreds in number, and functioning them in synchronisation, is a huge task during real time radar operation and should be handled with utmost care. Indian MST Radar, located at NARL, Gadanki, which is established during early 90's, as an outcome of the middle atmospheric program, is a remote sensing instrument for probing the atmosphere. This radar has a semi-active array, consisting of 1024 antenna elements, with limited beam steering, possible only along the principle planes. To overcome the limitations and difficulties, the radar is being augmented into fully active phased array, to accomplish beam agility and multi-mode operations. Each antenna element is excited with a dedicated 1 kW TR module, located in the field and enables to position the radar beam within 20° conical volume. A multi-channel receiver makes the radar to operate in various modes like Doppler Beam Swinging (DBS), Spaced Antenna (SA), Frequency Domain Interferometry (FDI) etc. Present work describes the real-time radar control (RC) system for the above described active phased array radar. The radar control system consists of a Spartan 6 FPGA based Timing and Control Signal Generator (TCSG), and a computer containing the software for controlling all the subsystems of the radar during real-time radar operation and also for calibrating the radar. The main function of the TCSG is to generate the control and timing waveforms required for various subsystems of the radar. Important components of the RC system software are (i) TR module configuring software which does programming, controlling and health parameter monitoring of the

  8. A highly selective ratiometric fluorescent pH probe based on a PAMAM wavelength-shifting bichromophoric system

    Science.gov (United States)

    Alamry, Khalid A.; Georgiev, Nikolai I.; El-Daly, Samy Abdullah; Taib, Layla A.; Bojinov, Vladimir B.

    2015-01-01

    A novel PAMAM wavelength-shifting bichromophoric system has been successfully developed. Novel compound was configured as a light harvesting antenna where the system surface is labeled with yellow-green emitting 4-(N,N-dimethylamino)ethylamino-1,8-naphthalimide "donor" units capable of absorbing light and efficiently transferring the energy to a focal Rhodamine 6G "acceptor". The periphery of the system was designed on the "fluorophore-spacer-receptor" format, capable of acting as a molecular fluorescence photoinduced electron transfer based probe. Due to the both effects, photoinduced electron transfer in the periphery of the system and pH dependent rhodamine core absorption, novel antenna is able to act as a selective ratiometric pH fluorescence probe in aqueous medium. Thus, the distinguishing features of the fluorescence resonance energy transfer systems were successfully combined with the properties of classical ring-opening charge transfer systems, which may be beneficially for monitoring pH variations in complex samples.

  9. Choosing an efficient option of the combined propulsion system and flight profile of the INTERHELIO-PROBE spacecraft

    Science.gov (United States)

    Platov, I. V.; Simonov, A. V.; Konstantinov, M. S.

    2016-12-01

    The paper is devoted to the design features of the prospective Russian INTERHELIO-PROBE spacecraft using, depending on the configuration version, an electric or chemical propulsion system as a sustainer. The scientific goal of the mission is the study of near-solar space from close distances (60-70 solar radii). The paper presents the description of several versions of the spacecraft options depending on the installed propulsion system, as well as the main characteristics of the flight profile depending on the engine type.

  10. Determination of Contact Potential Difference by the Kelvin Probe (Part II) 2. Measurement System by Involving the Composite Bucking Voltage

    Science.gov (United States)

    Vilitis, O.; Rutkis, M.; Busenbergs, J.; Merkulovs, D.

    2016-12-01

    The present research is devoted to creation of a new low-cost miniaturised measurement system for determination of potential difference in real time and with high measurement resolution. Furthermore, using the electrode of the reference probe, Kelvin method leads to both an indirect measurement of electronic work function or contact potential of the sample and measurement of a surface potential for insulator type samples. The bucking voltage in this system is composite and comprises a periodically variable component. The necessary steps for development of signal processing and tracking are described in detail.

  11. Phase equilibria in model surfactants forming Langmuir monolayers.

    Science.gov (United States)

    Ramírez, E; Santana, A; Cruz, A; López, G E

    2007-12-14

    The study of Langmuir monolayers has generated the attention of researchers because of their unique properties and their not well understood phase equilibrium. These monolayers exhibit interesting phase diagrams where the unusual liquid-liquid equilibrium can be observed for a single component monolayer. Monte Carlo computer simulations in the virtual Gibbs ensemble were used to obtain the phase diagram of Langmuir monolayers. The liquid-vapor and liquid-liquid phase equilibria were considered by constructing the Cailletet-Mathias phase diagrams. By using the Ising model and the rectilinear approximations the identification of the critical properties for both equilibria was determined. These critical parameters were calculated as a function of the strength of the interaction between the surfactant molecules and the aqueous subphase. As a result, we have identified the coexistence between a liquid expanded state (LES)-vapor and the liquid condensed state-LES, in agreement with experimental and theoretical evidence in the literature. We obtained a clear separation of phases and a strong dependence on the strength of the solvent used. Namely, as the interaction between the solvent and the head of the surfactant increases, the critical properties also increase. Equilibrium states were characterized by computing thermodynamic quantities as a function of temperature and solvent strength.

  12. Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Fernández, Raquel; Mondragon, Iñaki [‘Materials - Technologies’ Group, Department of Chemical and Environmental Engineering, Polytechnic School, Universidad País Vasco/Euskal Herriko Unibertsitatea, Pza Europa 1, 20018 Donostia-San Sebastián (Spain); Sanfelice, Rafaela C.; Pavinatto, Felippe J.; Oliveira, Osvaldo N. [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Centro, CEP 13560-970, São Carlos (Brazil); Oyanguren, Patricia [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina); Galante, María J., E-mail: galant@fi.mdp.edu.ar [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina)

    2013-04-01

    In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n = 0.03) and the azochromophore Disperse Orange 3 (DO3) cured with two monoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LB method may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery. Highlights: ► Langmuir Blodgett (LB) films of epoxy-based azopolymers were obtained and analyzed. ► Optical properties of LB and spin coated (SC) films were compared. ► Azo content, structure, laser power and number of layers were main factors studied. ► LB films had larger free volume for the azobenzenes isomerization than SC. ► LB films led to higher birefringence and faster dynamics compared to SC.

  13. Slosh wave excitation in the gravity probe-B spacecraft propulsion system

    Science.gov (United States)

    Hung, R. J.; Lee, C. C.; Leslie, Fred W.

    1991-01-01

    The dynamical behavior of fluids in a Gravity Probe-B Spacecraft tank imposed by various frequencies of gravity jitters have been investigated. Fluid stress distribution also have been investigated. Results show that fluid stress distribution exerted on the outer and inner walls of rotating dewar are closely related to the characteristics of slosh waves excited on the liquid-vapor interface in the rotating dewar tank.

  14. Development of an Optically Modulated Scatterer Probe for a Near-Field Measurement System

    Science.gov (United States)

    2016-09-08

    proportional to the gain of the AUT after normalizing by the antenna pattern of the known receiver. If the scattering strength of the probe is modulated...optical power until no change was observed. The real and imaginary components of the impedance for the PDA photodiode with no light ( dark ) and at various...GHz there was a change in impedance between the dark (off) and maximum optical power (on) states of 40 Ohm in the real component and 80 Ohm in the

  15. 2D "soap"-assembly of nanoparticles via colloid-induced condensation of mixed Langmuir monolayers of fatty surfactants.

    Science.gov (United States)

    Babenko, Denis I; Ezhov, Alexander A; Turygin, Dmitry S; Ivanov, Vladimir A; Ivanov, Vladimir K; Arslanov, Vladimir V; Kalinina, Maria A

    2012-01-10

    We describe a new type of colloidal 2D gels formed in mixed Langmuir monolayers of stearic acid and octadecylamine on a surface of gold hydrosol. The adsorption of gold nanoparticles on the mixed monolayer led to an increase of interactions between oppositely charged surfactants giving a "soap" of mixed fatty salt. The observed effect is equivalent to a virtual "cooling" of floating monolayer, which undergoes rapid condensation on a surface of aqueous colloid. The consequent shrinking and rearrangement of the monolayer resulted in aggregation of nanoparticles into colloidal 2D "soap"-gels, which represented arrested colloidal phases within nonadsorbing organic medium. When sequentially deposited onto solids by Langmuir-Blodgett technique, the 2D "soap"-gels separated into organic and colloidal phases and gave dendrite-like bilateral organic crystallites coated with gold nanoparticles. The reported colloidal "soap"-assembly can offer a new opportunity to design 2D colloidal systems of widely variable chemistry and structures.

  16. Langmuir and Langmuir-Blodgett films of capsules of haemoglobin at air/water and solid/air interfaces

    Indian Academy of Sciences (India)

    J Maheshkumar; A Dhathathreyan

    2013-03-01

    Organized assemblies of capsules of haemoglobin (Hb), in the size range of 0.1 to 0.3 in Langmuir films have been studied at air/water interface below and above the isoelectric point. Spread films of these organizates suggest that there is no expulsion of individual particles or particle assemblies at the interface and the particles are stable. Dynamic surface tension and the associated dilational and shear visco-elasticity in these films suggest that the capsules are highly elastic. Multilayer films of the capsules using Langmuir-Blodgett technique have been fabricated by sequential deposition on solid surfaces. These films have been characterized by circular dichroism spectroscopy (CD), atomic force microscopy (AFM), quartz crystal microbalance (QCM) and Fourier transform infrared with reflection absorption spectroscopy (FTIR-RAS). No appreciable change in the secondary structural features of Hb is seen from CD studies indicating the stability of the protein in these organized assemblies. Sizes of these capsules change near the isoelectric point and large swollen multiwalled capsules are formed. The elastic films of capsules of Hb provide a useful post preparation approach for modification of the surface roughness, porosity, and permeability of pre-assembled polypeptide microcapsules.

  17. Interaction between Langmuir and Langmuir-Blodgett films of two calix[4]arenes with aqueous copper and lithium ions.

    Science.gov (United States)

    Supian, Faridah L; Richardson, Tim H; Deasy, Mary; Kelleher, Fintan; Ward, James P; McKee, Vickie

    2010-07-06

    The binding interactions between aqueous copper (Cu(2+)) and lithium (Li(+)) ions and Langmuir monolayers and Langmuir-Blodgett (LB) multilayers have been investigated by studying surface pressure-area (Pi-A) isotherms and surface potential-area (DeltaV-A) behavior in order to find the effective dipole moment, mu(perpendicular), of the calixarene molecules in the uncomplexed and complexed states. The orientation of both calix[4]arenes, namely, 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarbonyl methyleneoxy-26,28-dihydroxycalix[4]arene and 5,17-(9H-fluoren-2-yl)methyleneamino)-11,23-di-tert-butyl-25,27-diethoxycarbonyl methyleneoxy-26,28-dihydroxycalix[4]arene, is such that the plane of the calix ring is parallel with the plane of the water surface regardless of the ion content of the subphase. The Gibbs equation was used to interpret the adsorption of ions with both calix[4]arenes as a function of the concentration. Effective dipole moments have been calculated from surface potential values using the Helmholtz equation. In this work, new LB films have been prepared employing two novel amphiphilic calix[4]arene derivatives bearing different upper rim substituents. Thus, the effect of modifiying the upper rim has been observed. The results have shown that these calixarenes may be useful components of ion sensors.

  18. The Langmuir isotherm: a commonly applied but misleading approach for the analysis of protein adsorption behavior.

    Science.gov (United States)

    Latour, Robert A

    2015-03-01

    The Langmuir adsorption isotherm provides one of the simplest and most direct methods to quantify an adsorption process. Because isotherm data from protein adsorption studies often appear to be fit well by the Langmuir isotherm model, estimates of protein binding affinity have often been made from its use despite that fact that none of the conditions required for a Langmuir adsorption process may be satisfied for this type of application. The physical events that cause protein adsorption isotherms to often provide a Langmuir-shaped isotherm can be explained as being due to changes in adsorption-induced spreading, reorientation, clustering, and aggregation of the protein on a surface as a function of solution concentration in contrast to being due to a dynamic equilibrium adsorption process, which is required for Langmuir adsorption. Unless the requirements of the Langmuir adsorption process can be confirmed, fitting of the Langmuir model to protein adsorption isotherm data to obtain thermodynamic properties, such as the equilibrium constant for adsorption and adsorption free energy, may provide erroneous values that have little to do with the actual protein adsorption process, and should be avoided. In this article, a detailed analysis of the Langmuir isotherm model is presented along with a quantitative analysis of the level of error that can arise in derived parameters when the Langmuir isotherm is inappropriately applied to characterize a protein adsorption process.

  19. How electron two-stream instability drives cyclic Langmuir collapse and continuous coherent emission

    Science.gov (United States)

    Che, Haihong; Goldstein, Melvyn L.; Diamond, Patrick H.; Sagdeev, Roald Z.

    2017-02-01

    Continuous plasma coherent emission is maintained by repetitive Langmuir collapse driven by the nonlinear evolution of a strong electron two-stream instability. The Langmuir waves are modulated by solitary waves in the linear stage and electrostatic whistler waves in the nonlinear stage. Modulational instability leads to Langmuir collapse and electron heating that fills in cavitons. The high pressure is released via excitation of a short-wavelength ion acoustic mode that is damped by electrons and reexcites small-scale Langmuir waves; this process closes a feedback loop that maintains the continuous coherent emission.

  20. Test evaluation of potential heatshield contamination of an outer planet probe's gas sampling system

    Science.gov (United States)

    Kessler, W. C.

    1975-01-01

    The feasibility of retaining the heat shield for outer planet probes was investigated as a potential source of atmospheric sample contamination by outgassing. The onboard instruments which are affected by the concept are the pressure sensor, temperature sensor, IR detector, nephelometer, and gas sampling instruments. It was found that: (1) The retention of the charred heatshield and the baseline atmospheric sampling concepts are compatible with obtaining noncontaminated atmospheric samples. (2) Increasing the sampling tube length so that it extends beyond the viscous boundary layer eliminates contamination of the atmospheric sample. (3) The potential for contamination increases with angle of attack.

  1. Blue Straggler Stars in Globular Clusters: a powerful tool to probe the internal dynamical evolution of stellar systems

    CERN Document Server

    Ferraro, Francesco R; Dalessandro, Emanuele; Mucciarelli, Alessio; Lovisi, Loredana

    2014-01-01

    This chapter presents an overview of the main observational results obtained to date about Blue Straggler Stars (BSSs) in Galactic Globular Clusters (GCs). The BSS specific frequency, radial distribution, chemical composition and rotational properties are presented and discussed in the framework of using this stellar population as probe of GC internal dynamics. In particular, the shape of the BSS radial distribution has been found to be a powerful tracer of the dynamical age of stellar systems, thus allowing the definition of the first empirical "dynamical clock".

  2. The spacing of Langmuir circulation under modest wind

    Institute of Scientific and Technical Information of China (English)

    LI Shuang; SONG Jinbao

    2012-01-01

    Spacing characteristics of Langmuir circulation (LC) are computed by large eddy simulation (LES) model under modest wind.LC is an organized vertical motion,evidenced as buoyant materials forming lines nearly parallel to the wind direction.The horizontal distribution of velocity computed by LES shows clear lines formed by LC.These lines grow and parallel to each other for a while,which we call the stable state,before they finally form Y-junctions.We computed spacing between every two parallel lines by averaging them under the stable state.Statistically,spacing results of 154 tests (seven wind speed cases of 22 test runs each) show high correlations berween spacing and wind speed,as well as mixed layer depth.The relationship of spacing and wind is important for future LC parameterization of upper-ocean mixing.

  3. Stable Langmuir solitons in plasma with diatomic ions

    Directory of Open Access Journals (Sweden)

    M. Dvornikov

    2013-08-01

    Full Text Available We study stable axially and spherically symmetric spatial solitons in plasma with diatomic ions. The stability of a soliton against collapse is provided by the interaction of induced electric dipole moments of ions with the rapidly oscillating electric field of a plasmoid. We derive the new cubic-quintic nonlinear Schrödinger equation, which governs the soliton dynamics and numerically solve it. Then we discuss the possibility of implementation of such plasmoids in realistic atmospheric plasma. In particular, we suggest that spherically symmetric Langmuir solitons, described in the present work, can be excited at the formation stage of long-lived atmospheric plasma structures. The implication of our model for the interpretation of the results of experiments for the plasmoids generation is discussed.

  4. Properties of Langmuir wave bursts associated with magnetic holes

    Science.gov (United States)

    MacDowall, R. J.; Lin, N.; Kellogg, P. J.; Phillips, J. L.; Neugebauer, M.; Balogh, A.; Forsyth, R. J.

    1995-01-01

    The radio and plasma wave receivers on the Ulysses spacecraft have detected thousands of short-duration bursts of waves at approximately the electron plasma frequency. These wave events believed to be Langmuir waves are usually less than approximately 5 minutes in duration. They occur in or at the boundaries of depletions in the magnetic field amplitude known as magnetic holes. Using the 16 sec time resolution provided by the plasma frequency receiver, it is possible to examine the density structure inside of magnetic holes. Even higher time resolutions are sometimes available from the radio receiver data. The Ulysses observations show that these wave bursts occur more frequently at high heliographic latitudes; the occurrence rates depend on both latitude and distance from the Sun. We review the statistics for the wave events, compare them to magnetic and plasma parameters, and review the reasons for the more frequent occurrence at high heliographic latitudes.

  5. Langmuir-like waves and radiation in planetary foreshocks

    Science.gov (United States)

    Cairns, Iver H.; Robinson, P. A.; Anderson, R. R.; Gurnett, D. A.; Kurth, W. S.

    1995-01-01

    The basic objectives of this NASA Grant are to develop theoretical understandings (tested with spacecraft data) of the generation and characteristics of electron plasma waves, commonly known as Langmuir-like waves, and associated radiation near f(sub p) and 2f(sub p) in planetary foreshocks. (Here f(sub p) is plasma frequency.) Related waves and radiation in the source regions of interplanetary type III solar radio bursts provide a simpler observational and theoretical context for developing and testing such understandings. Accordingly, applications to type III bursts constitute a significant fraction of the research effort. The testing of the new Stochastic Growth Theory (SGT) for type III bursts, and its extension and testing for foreshock waves and radiation, constitutes a major longterm strategic goal of the research effort.

  6. TRANSPOSICION DIDACTICA DEL MODELO CIENTIFICO DE LEWIS-LANGMUIR

    OpenAIRE

    Janneth Isabel Herreño Chaves; Rómulo Gallego Badillo; Royman Pérez Miranda

    2010-01-01

    Este artículo presenta las conclusiones obtenidas en un proyecto de investigación, en el que se auscultó la transposición didáctica que hacen del modelo de Lewis-Langmuir, diez de los textos para la enseñanza de la química más empleados por algunos profesores universitarios y de educación secundaria. Para el análisis se tuvo en cuenta lo histórico, lo epistemológico y lo didáctico. Los resultados muestran que en estos textos no hay referencia a la historia de la construcción del modelo y solo...

  7. Sequential injection system for phospholipase A2 activity evaluation: studies on liposomes using an environment-sensitive fluorescent probe.

    Science.gov (United States)

    Araujo, André R T S; Gaspar, Diana; Lúcio, Marlene; Reis, Salette; Saraiva, M Lúcia M F S; Lima, José L F C

    2009-09-15

    This work reports the development of an automatic methodology based on the use of 1-anilinonaphthalene-8-sulfonate (ANS) as an interfacial fluorescent probe for detecting the hydrophobic environment shift around the probe, caused by the hydrolytic action of PLA(2) on the liposomes. The implementation of this reaction in a sequential injection analysis (SIA) system along with the use of the mixing chambers permitted the evaluation of PLA(2) activity and assessment of the inhibitory effect of the non-steroidal anti-inflammatory drugs (NSAIDs) on PLA(2) activity. Several studies were performed with the aim of establishing the appropriate flow system configuration: the liposome substrate; PLA(2) and ANS optimum concentrations and incubation times before and after the enzyme addition. Based on these studies, the optimum reaction conditions were selected. It was shown that PLA(2) is effectively inhibited by the NSAIDs tested (meloxicam, tolmetin and ibuprofen) and by the alpha-lipoic acid, used as a positive control. Results obtained from the flow system are in agreement with those provided by the comparison batch procedures. The proposed methodology is in fact more efficient and rapid than the comparison batch experiments, enabling the exact timing of fluidic manipulations and precise control of the reaction conditions.

  8. Rupture mechanism of aromatic systems from graphite probed with molecular dynamics simulations.

    Science.gov (United States)

    Leng, Yumin; Chen, Jian; Zhou, Beifei; Gräter, Frauke

    2010-07-01

    Intermolecular interactions involving aromatic rings are of pivotal importance in many areas of chemistry, biology and materials science. Mimicking recent atomic force microscopy (AFM) experiments that measured the adhesion forces of single pi-pi complexes, here interactions between pyrene/coronene and graphite have been probed by force-probe molecular dynamics (FPMD) simulations. The pyrene or coronene molecule was connected to a virtual spring through a flexible poly(ethylene glycol) (PEG) linker and was pulled away from graphite in water under constant velocity. Pyrene and coronene showed similar unbinding pathways featuring four states, with a transition and an intermediate state connecting the bound and unbound states in terms of distance and interplanar angles. Transient conformations with tilted orientations (approximately 40 degrees) and with one side of the aromatic structure still in contact with the graphite surface (approximately 70 degrees) were identified as the transition and intermediate states, respectively, similar to previously observed perpendicularly stacked benzene dimers. The distance to transition state x(tr) was determined to be 0.23 +/- 0.03 nm both for pyrene/graphite and coronene/graphite. The complexes share similar unbinding pathways, but coronene binds to graphite more strongly than to pyrene.

  9. Some studies on a solid-state sulfur probe for coal gasification systems

    Science.gov (United States)

    Jacob, K. T.; Rao, D. B.; Nelson, H. G.

    1978-01-01

    As a part of a program for the development of a sulfur probe for monitoring the sulfur potential in coal gasification reactors, an investigation was conducted regarding the efficiency of the solid electrolyte cell Ar+H2+H2S/CaS+CaF2+(Pt)//CaF2//Pt)+CaF2+CaS/H2S+H2+Ar. A demonstration is provided of the theory, design, and operation of a solid-state sulfur probe based on CaF2 electrolyte. It was found that the cell responds to changes in sulfur potential in a manner predicted by the Nernst equation. The response time of the cell at 1225 K, after a small change in temperature or gas composition, was 2.5 Hr, while at a lower temperature of 990 K the response time was approximately 9 hr. The cell emf was insensitive to a moderate increase in the flow rate of the test gas and/or the reference gas. The exact factors affecting the slow response time of galvanic cells based on a CaF2 electrolyte have not yet been determined. The rate-limiting steps may be either the kinetics of electrode reactions or the rate of transport through the electrolyte.

  10. Probing the Exhaust System of the Most Powerful Engines with VSOP-2

    Science.gov (United States)

    Meier, D. L.

    2009-08-01

    I review the current magneto-hydrodynamic mechanisms for the production and propagation of relativistic jets from accreting black holes. There has been quite a bit of progress recently in describing the processes that launch, collimate, and ultimately accelerate jets to their final relativistic speeds. VSOP2 should be able to probe much of this collimation and acceleration region. There also has been a lot of progress on how magnetized jets propagate through the initial few parsecs of interstellar medium in radio galaxies and quasars that can be observed directly. Finally, there has been a bit of progress in understanding how the jet engine very near the black hole ultimately relates to the accretion power plant that supplies its energy, although it is still unknown exactly how some types of black hole jets tie directly into the accretion flow. While VSOP2 will not probe this region directly, it may be able to constrain certain theoretical models of these processes. There may be some surprises in store for us, and we should be ready for them when the data begins coming in.

  11. Structural characterization of a mixed Langmuir-Blodgett film of a merocyanine dye derivative-deuterated arachidic acid binary system and the influence of successive hydrothermal treatment in the liquid phase on the film as investigated by polarized UV-visible and IR absorption spectroscopy.

    Science.gov (United States)

    Hirano, Yoshiaki; Yamazaki, Asuka; Maio, Ari; Kitahama, Yasutaka; Ozaki, Yukihiro

    2010-08-26

    We have investigated the structure of the mixed Langmuir-Blodgett (LB) film of a merocyanine dye derivative (MO(18))-deuterated arachidic acid (C(20)-d) binary system and the influence of successive hydrothermal treatment in the liquid phase (HTTL) on the mixed LB film by means of polarized UV-visible and IR absorption spectroscopy. The visible absorption band with in-plane anisotropy at 503 nm before HTTL transforms into an absorption band with in-plane isotropy at 557 nm after HTTL for 16-18 min through a peak maximum near 520 nm after HTTL for 2-12 min. The degree of total MO(18) intramolecular charge transfer for the 503 nm band is the largest among those for all of the bands. Therefore, the 503 nm band is ascribed to the MO(18) H-like aggregation, based on its shape, peak height, and in-plane anisotropy, the subsequent change to two kinds of visible peaks by successive HTTL, and the most degree of MO(18) intramolecular charge transfer among all of the aggregation states. While the MO(18) hydrocarbon chain takes the all-trans conformation before HTTL, its conformation and orientation are most disarranged after HTTL for 2 min. Subsequently, the original conformation and orientation are recovered by degrees with successive HTTL, except after final HTTL for 18 min, when the orientation is again changed. On the other hand, the C(20)-d hydrocarbon chain maintains the all-trans conformation before and after HTTL. The orientation of the C(20)-d hydrocarbon chain after HTTL for 2 min is more ordered than that before HTTL, with the nature of the C(20)-d subcell packing changing from hexagonal to orthorhombic. During successive HTTL from 2 to 18 min, the C(20)-d orientation is gradually disorganized but with the orthorhombic nature remaining constant. Thus, the variations in the conformation and orientation of the MS(18) hydrocarbon chain and in the orientation of the C(20)-d hydrocarbon chain tend to change from ordered and disordered structures and turn to more

  12. Electrochemical reverse engineering: A systems-level tool to probe the redox-based molecular communication of biology.

    Science.gov (United States)

    Li, Jinyang; Liu, Yi; Kim, Eunkyoung; March, John C; Bentley, William E; Payne, Gregory F

    2016-12-29

    The intestine is the site of digestion and forms a critical interface between the host and the outside world. This interface is composed of host epithelium and a complex microbiota which is "connected" through an extensive web of chemical and biological interactions that determine the balance between health and disease for the host. This biology and the associated chemical dialogues occur within a context of a steep oxygen gradient that provides the driving force for a variety of reduction and oxidation (redox) reactions. While some redox couples (e.g., catecholics) can spontaneously exchange electrons, many others are kinetically "insulated" (e.g., biothiols) allowing the biology to set and control their redox states far from equilibrium. It is well known that within cells, such non-equilibrated redox couples are poised to transfer electrons to perform reactions essential to immune defense (e.g., transfer from NADH to O2 for reactive oxygen species, ROS, generation) and protection from such oxidative stresses (e.g., glutathione-based reduction of ROS). More recently, it has been recognized that some of these redox-active species (e.g., H2O2) cross membranes and diffuse into the extracellular environment including lumen to transmit redox information that is received by atomically-specific receptors (e.g., cysteine-based sulfur switches) that regulate biological functions. Thus, redox has emerged as an important modality in the chemical signaling that occurs in the intestine and there have been emerging efforts to develop the experimental tools needed to probe this modality. We suggest that electrochemistry provides a unique tool to experimentally probe redox interactions at a systems level. Importantly, electrochemistry offers the potential to enlist the extensive theories established in signal processing in an effort to "reverse engineer" the molecular communication occurring in this complex biological system. Here, we review our efforts to develop this

  13. Polymer compatibility in two dimensions. Modeling of phase behavior of mixed polymethacrylate Langmuir films.

    Science.gov (United States)

    Bernardini, C; Stuart, M A Cohen; Stoyanov, S D; Arnaudov, L N; Leermakers, F A M

    2012-04-03

    We analyze the possibility of polymer blends undergoing phase separation in two dimensions. To this end, we investigate a model system consisting of water-supported Langmuir monolayers, obtained from binary polyalkyl-methacrylate mixtures (PXMA, where X stands for any of the type of ester side groups used: M, methyl-; E, ethyl-; B, butyl-; H, hexyl-; O, octyl-; L, lauryl-methacrylate), by means of self consistent field (SCF) calculations. In particular, we address the conditions which determine demixing and phase separation in the two-dimensional system, showing that a sufficient chain length mismatch in the ester side group moieties is able to drive the polymer demixing. When the difference in length of the alkyl chain of the ester moieties on the two types of polymers is progressively reduced, from 11 carbon atoms (PMMA/PLMA) to 4 carbons only (POMA/PLMA), the demixing tendency is also reduced. The polymer/subphase interactions affect more the distribution of the polymer coils in the POMA/PLMA blend monolayer. Mixing of the two polymers is observed, but also a partial layering along the vertical direction. We also add, to a PMMA/PLMA blended monolayer, a third component, namely, a symmetrical diblock copolymer of the type PLMA-b-PMMA. We observe adsorption of the diblock copolymer exclusively at the contact line between the two homopolymer domains, and a concomitant lowering of the line tension. The line tension varies with the chemical potential of the diblock copolymer according to Gibbs' law, which demonstrates that PLMA-b-PMMA can act as a "lineactant" (the equivalent of a surfactant in two-dimensional systems) in the binary demixed PMMA/PLMA Langmuir monolayer.

  14. Comparison of the FFT/matrix inversion and system matrix techniques for higher-order probe correction in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav

    2011-01-01

    Two higher-order probe-correction techniques for spherical near-field antenna measurements are compared in details for the accuracy they provide and their computational cost. The investigated techniques are the FFT/matrix inversion and the system matrix inversion. Each of these techniques allows...... and a higher-order probe....... correction of general high-order probes, including non-symmetric dual-polarized antennas with independent ports. The investigation was carried out by processing with each technique the same measurement data for a challenging case with an antenna under test significantly offset from the center of rotation...

  15. Silk coating as a novel delivery system and reversible adhesive for stiffening and shaping flexible probes

    Directory of Open Access Journals (Sweden)

    Cinzia Metallo

    2015-02-01

    Full Text Available The performance of any implantable electrode depends not only on its recording or stimulation capabilities but also on its position in relation to the target site. Electrode displacement during or after implantation represents a major issue as it might result in tissue damage or incorrect recording or stimulation location, complicating the interpretation of experimental data. Although thin-film electrode arrays have overcome some of the main limitations of more traditional, stiffer probes, their intrinsic flexibility and unilateral contacts represent a new challenge: they tend to bend during insertion and are difficult to implant simultaneously while maintaining a specific relative position. Here, we present a method that addresses all these issues using a coating of silk fibroin, a versatile protein derived from silkworm cocoons. The method is demonstrated by acquiring electromyographic (EMG recordings in Manduca sexta, a soft-bodied animal that exemplifies the issues of electrode insertion and placement in delicate and deformable tissues.

  16. Dynamic Probe Window Based Optimization for Surveillance in Home Security System

    Directory of Open Access Journals (Sweden)

    Bhaskar Kapoor

    2010-02-01

    Full Text Available Tracking of a moving object is very important for video surveillance in a real time scenario. The proposedalgorithm uses dynamic probe window based approach & combines the conventional edge based and framedifferencing approach to achieve better algorithmic time complexity as well as improved results. First itcomputes the edge map of two consecutive frames with the help of first order differential sobel operator dueto its noise resistant attributes and applies the frame differencing method between the two consecutive edgemaps. Apart from the above optimization, our method doesn’t differentiate between the scenario when motionoccurs and when it doesn’t, that is, almost same computation overhead is required even if motion is not thereso it reduces the time complexity of the algorithm when no motion is detected. The effectiveness of theproposed motion detection algorithm is demonstrated in a real time environment and the evaluation resultsare reported.

  17. Lattice Instability in High Temperature Superconducting Cuprates and FeAs Systems: Polarons Probed by EXAFS

    Directory of Open Access Journals (Sweden)

    H. Oyanagi

    2010-01-01

    Full Text Available Carrier-induced lattice distortion (signature of polaron in oxypnictide superconductors is found by an instantaneous local probe, extended X-ray absorption fine structure (EXAFS. Polaron formation is detected as two distinct nearest neighbor distances (Fe-As, implying an incoherent local mode that develops coherence at the critical temperature. Comparing the results with the unusual lattice response in cuprate superconductors, intimate correlation between evolution of local lattice mode and superconductivity is revealed. The results suggest that strong electron-lattice interaction is present as a common ingredient in the microscopic mechanism of superconducting transition. The effect of magnetic impurity atoms in cuprates further indicates that magnetic scattering becomes diluted as long as polaron formation is conserved. We argue that polaron coherence dominates electrical conduction and magnetic interaction in oxypnictide and cuprate superconductors.

  18. Size Characterisation Method and Detection Enhancement of Plasmonic Nanoparticles in a Pump–Probe System

    Directory of Open Access Journals (Sweden)

    Rafael Fuentes-Domínguez

    2017-08-01

    Full Text Available The optical resonance of metal nanoparticles can be used to enhance the generation and detection of their main vibrational mode. In this work, we show that this method allows the accurate characterisation of the particle’s size because the vibrational frequency of plasmonic nanoparticles only depends on their mechanical properties. Moreover, by a careful selection of the particle size and/or probe laser wavelength, the detected signal can be increased by a large factor (∼9 for the particles used in this work under the same illumination conditions. Finally, we show experimentally that particles of different sizes inside the point spread function can be observed due to the differences in their vibrational states, which could provide a feasible route to super-resolution.

  19. Using proper regression methods for fitting the Langmuir model to sorption data

    Science.gov (United States)

    The Langmuir model, originally developed for the study of gas sorption to surfaces, is one of the most commonly used models for fitting phosphorus sorption data. There are good theoretical reasons, however, against applying this model to describe P sorption to soils. Nevertheless, the Langmuir model...

  20. Macroscopic alignment of graphene stacks by Langmuir-Blodgett deposition of amphiphilic hexabenzocoronenes

    DEFF Research Database (Denmark)

    Laursen, B.W.; Nørgaard, K.; Reitzel, N.;

    2004-01-01

    e present structural studies of Langmuir V and Langmuir-Blodgett (LB) films of new amphiphilic hexa-peri-hexabenzocoronene (HBC) discotics, carrying five branched alkyl side chains and one polar group. The polar group is either a carboxylic acid moiety or an electron acceptor moiety (anthraquinone...

  1. Evidence for magnetic ordering in ultrathin gadolinium Langmuir-Blodgett films

    DEFF Research Database (Denmark)

    Tishin, A.M.; Koksharov, Yu.A.; Bohr, Jakob

    1997-01-01

    Magnetic ultrathin Langmuir-Blodgett films containing rare earths are investigated. Electron paramagnetic resonance measurements suggest the possible existence of a transition from a paramagnetic to a magnetically ordered state. In Langmuir-Blodgett films with one hundred layers of Gd, a transiti...

  2. Revisiting a Statistical Shortcoming When Fitting the Langmuir Model to Sorption Data

    Science.gov (United States)

    The Langmuir model is commonly used for describing sorption behavior of reactive solutes to surfaces. Fitting the Langmuir model to sorption data requires either the use of nonlinear regression or, alternatively, linear regression using one of the linearized versions of the model. Statistical limit...

  3. The production of PEO polymer brushes via Langmuir-Blodgett and Langmuir-Schaeffer methods: incomplete transfer and its consequences.

    Science.gov (United States)

    de Vos, Wiebe M; de Keizer, Arie; Kleijn, J Mieke; Cohen Stuart, Martien A

    2009-04-21

    Using fixed-angle ellipsometry, we investigate the degree of mass transfer upon vertically dipping a polystyrene surface through a layer of a polystyrene-poly(ethylene oxide) (PS-PEO) block copolymer at the air water interface (Langmuir-Blodgett or LB transfer). The transferred mass is proportional to the PS-PEO grafting density at the air-water interface, but the transferred mass is not equal to the mass at the air-water interface. We find that depending on the chain length of the PEO block only a certain fraction of the polymers at the air-water interface is transferred to the solid surface. For the shortest PEO chain length (PS36-PEO148), the mass transfer amounts to 94%, while for longer chain lengths (PS36-PEO370 and PS38-PEO770), a transfer of, respectively 57% and 19%, is obtained. We attribute this reduced mass transfer to a competition for the PS surface between the PEO block and the PS block. Atomic force microscopy shows that after transfer the material is evenly spread over the surface. However, upon a short heating of these transferred layers (95 degrees C, 5 min) a dewetting of the PS-PEO layer takes place. These results have a significant impact on the interpretation of the results in a number of papers in which the above-described transfer method was used to produce PEO polymer brushes, in a few cases in combination with heating. We briefly review these papers and discuss their main results in light of this new information. Furthermore, we show that, by using Langmuir-Schaeffer (LS, horizontal) dipping, much higher mass transfers can be reached than with the LB method. When the LB or LS methods are carefully applied, it is a very powerful technique to produce PEO brushes, as it gives full control over both the grafting density and the chain length.

  4. Improving Intrusion Detection System Based on Snort Rules for Network Probe Attacks Detection with Association Rules Technique of Data Mining

    Directory of Open Access Journals (Sweden)

    Nattawat Khamphakdee

    2015-07-01

    Full Text Available The intrusion detection system (IDS is an important network security tool for securing computer and network systems. It is able to detect and monitor network traffic data. Snort IDS is an open-source network security tool. It can search and match rules with network traffic data in order to detect attacks, and generate an alert. However, the Snort IDS  can detect only known attacks. Therefore, we have proposed a procedure for improving Snort IDS rules, based on the association rules data mining technique for detection of network probe attacks.  We employed the MIT-DARPA 1999 data set for the experimental evaluation. Since behavior pattern traffic data are both normal and abnormal, the abnormal behavior data is detected by way of the Snort IDS. The experimental results showed that the proposed Snort IDS rules, based on data mining detection of network probe attacks, proved more efficient than the original Snort IDS rules, as well as icmp.rules and icmp-info.rules of Snort IDS.  The suitable parameters for the proposed Snort IDS rules are defined as follows: Min_sup set to 10%, and Min_conf set to 100%, and through the application of eight variable attributes. As more suitable parameters are applied, higher accuracy is achieved.

  5. Stirring competes with chemical induction in chiral selection of Langmuir monolayer domains

    Directory of Open Access Journals (Sweden)

    Petit-Garrido Nuria

    2013-08-01

    Full Text Available Chirality, the absence of mirror symmetry, can be equally invoked in relation to physical forces and chemical induction processes, yet a competition between these two types of influences is rarely reported. Here, we employ Langmuir monolayers of azobenzene surfactants as a prototypical self-assembled two-dimensional system in which chiral selection is controlled by the combined independent action of a chiral dopant and vortical stirring. The two effects can be arbitrarily coupled, either constructively or destructively, leading to a situation of perfect compensation. The induced enantiomorphic excess is measured in terms of the statistical imbalance of an ensemble of sub-millimeter monolayer domains, where achiral molecules self-assemble with a well-defined orientational chirality, which is unambiguously resolved using Brewster angle microscopy.

  6. Langmuir hydrogen dissociation approach in radiolabeling carbon nanotubes and graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Badun, Gennadii A.; Chernysheva, Maria G.; Eremina, Elena A.; Egorov, Alexander V. [Lomonosov Moscow State Univ. (Russian Federation). Dept. of Chemistry; Grigorieva, Anastasia V. [Lomonosov Moscow State Univ., Moscow (Russian Federation). Dept. of Materials Science

    2016-11-01

    Carbon-based nanomaterials have piqued the interest of several researchers. At the same time, radioactive labeling is a powerful tool for studying processes in different systems, including biological and organic; however, the introduction of radioactive isotopes into carbon-based nanomaterial remains a great challenge. We have used the Langmuir hydrogen dissociation method to introduce tritium in single-walled carbon nanotubes and graphene oxide. The technique allows us to achieve a specific radioactivity of 107 and 27 Ci/g for single-layer graphene oxide and single-walled carbon nanotubes, respectively. Based on the analysis of characteristic Raman modes at 1350 and 1580 cm{sup -1}, a minimal amount of structural changes to the nanomaterials due to radiolabeling was observed. The availability of a simple, nondestructive, and economic technique for the introduction of radiolabels to single-walled carbon nanotubes and graphene oxide will ultimately expand the applicability of these materials.

  7. Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films.

    Science.gov (United States)

    Fernández, Raquel; Mondragon, Iñaki; Sanfelice, Rafaela C; Pavinatto, Felippe J; Oliveira, Osvaldo N; Oyanguren, Patricia; Galante, María J

    2013-04-01

    In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n=0.03) and the azochromophore Disperse Orange 3 (DO3) cured with two monoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LB method may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery.

  8. Nanoscale Hybrid Langmuir-Blodgett Films Based on Cerium-Substituted Heteropolymolybdate and Polyquinoline

    Institute of Scientific and Technical Information of China (English)

    王峥; 柳士忠; 杜祖亮; 胡振纲; 张洪杰

    2003-01-01

    Nanoscale hybrid organic/inorganic Langmuir-Blodgett films of cerium-substituted heteropolymolybdates(Ce-HPMo) and π-conjugated macromolecule poly(1,2-dihydro-2,2,4-trimethyl)quinoline(PQ) were obtained with auxiliary film-forming material stearic acid(SA) or octadecylamine(ODA). The surface pressure-area isotherms illuminate the formation of the hybrid LB films of PQ/ODA/Ce-HPMo and P Q/SA/Ce-HPMo. The different film-forming mechanism was discussed when the different auxiliary film-forming materials were used in the system. The absorption spectra indicate that the molecules of PQ and Ce-HPMo are incorporated into the LB films. Tapping-mode AFM image reveals a granular surface texture of nanosized Ce-substituted heteropolymolybdate. STM image shows that the conductivity is greatly improved after Ce-substituted heteropolymolybdates are incorporated in the films.

  9. Simultaneous evaluation of one-electron reducing systems and radical reactions in cells by nitroxyl biradical as probe.

    Science.gov (United States)

    Araki, Yoko; Koshiishi, Ichiro

    2016-07-01

    In the present study, a novel probe for the simultaneous evaluation of one-electron reducing systems (electron transport chain) and one-electron oxidizing systems (free radical reactions) in cells by electron chemical detection was developed. Six-membered cyclic nitroxyl radicals (2,2,6,6-tetramethylpiperidine-1-oxyl; TEMPO series) are sensitive to one-electron redox systems, generating the hydroxylamine form [TEMPO(H)] via one-electron reduction, and the secondary amine form [TEMPO(N)] via one-electron oxidation in the presence of thiols. In contrast, the sensitivities of five-membered cyclic nitroxyl radicals (2,2,5,5-tetramethylpyrrolidine-1-oxyl; PROXYL series) to the one-electron redox systems are comparatively low. The electron chemical detector can detect 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), TEMPO(H) and PROXYL but not TEMPO(N). Therefore, nitroxyl biradical, TEMPO-PROXYL, as a probe for the evaluation of one-electron redox systems was employed. TEMPO-PROXYL was synthesized by the conjunction of 4-amino-TEMPO with 3-carboxyl-PROXYL via the conventional dicyclohexyl carbodiimide reaction. TEMPO-PROXYL, TEMPO(H)-PROXYL and TEMPO(N)-PROXYL were simultaneously quantified by HPLC with Coularray detection. Calibration curves for the quantification of TEMPO-PROXYL, TEMPO(H)-PROXYL and TEMPO(N)-PROXYL were linear in the range from 80 nm to 80 μm, and the lowest quantification limit of each molecule was estimated to be <80 nm. The relative standard deviations at 0.8 and 80 μm were within 10% (n = 5). Copyright © 2015 John Wiley & Sons, Ltd.

  10. Statistical behavior of Langmuir wave packets observed inside the electron foreshock of Saturn

    Science.gov (United States)

    Pisa, David; Hospodarsky, George B.; Kurth, Willam S.; Gurnett, Donald A.; Santolik, Ondrej; Soucek, Jan

    2014-05-01

    We present a statistical study of Langmuir wave packets in the Saturnian foreshock using Cassini Wideband Receiver electric field waveforms. We analyzed all foreshock crossings from 2004 to 2012 using an automatic method for the identification of Langmuir wave signatures. Observed waveforms exhibit a shape similar to Langmuir solitons or monochromatic wave packets with a slowly varying envelope. This is in agreement with a variety of previous observations of Langmuir waves in the terrestrial foreshock and associated with Type III radio bursts. We determined the peak amplitude for all wave packets, and found the distributions of amplitude appeared to follow a power law with P(E) ≈ E-2. We confirm that the most intense electron plasma waves are observed near the foreshock boundary. We estimated the energy density ratio to be about one order below previously reported values at Saturn. Finally, we discuss the properties of the Langmuir wave packets at different locations in the foreshock.

  11. Cultural probes

    DEFF Research Database (Denmark)

    Madsen, Jacob Østergaard

    2016-01-01

    The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation.......The aim of this study was thus to explore cultural probes (Gaver, Boucher et al. 2004), as a possible methodical approach, supporting knowledge production on situated and contextual aspects of occupation....

  12. Software system for three-dimensional visualization of micro-object surfaces for scanning probe microscopy using OpenGL graphics library

    Science.gov (United States)

    Vakuliuk, Nickolay V.

    2002-07-01

    The software system for 3D visualization of micro objects surfaces for scanning probe microscopy is developed. The system is used as a software part of software/hardware complex of scanning probe microscope (SPM) and its kinds. The system represent the results of microscope work in 3D- view. System has convenient GUI and high level of functionality in modes of visualization and in saving result images. Program allows to operate with image of surface in real time by performing scaling, rotation, moving, setting of lighting and color values, setting level of detail for surface in real time by performing scaling, rotation, moving, setting of lighting and color values, setting level of detail for surface rendering. This viewer works together with another part of software system that is responsible for controlling the SPM. The program also can be used as an independent view of scanning probe microscope files.

  13. Study of the aggregation of human insulin Langmuir monolayer.

    Science.gov (United States)

    Liu, Wei; Johnson, Sheba; Micic, Miodrag; Orbulescu, Jhony; Whyte, Jeffrey; Garcia, Andrew R; Leblanc, Roger M

    2012-02-21

    The human insulin (HI) Langmuir monolayer at the air-water interface was systematically investigated in the presence and absence of Zn(II) ions in the subphase. HI samples were dissolved in acidic (pH 2) and basic (pH 9) aqueous solutions and then spread at the air-water interface. Spectroscopic data of aqueous solutions of HI show a difference in HI conformation at different pH values. Moreover, the dynamics of the insulin protein showed a dependence on the concentration of Zn(II) ions. In the absence of Zn(II) ions in the subphase, the acidic and basic solutions showed similar behavior at the air-water interface. In the presence of Zn(II) ions in the subphase, the surface pressure-area and surface potential-area isotherms suggest that HI may aggregate at the air-water interface. It was observed that increasing the concentration of Zn(II) ions in the acidic (pH 2) aqueous solution of HI led to an increase of the area at a specific surface pressure. It was also seen that the conformation of HI in the basic (pH 9) medium had a reverse effect (decrease in the surface area) with the increase of the concentration of Zn(II) ions in solution. From the compression-decompression cycles we can conclude that the aggregated HI film at air-water interface is not stable and tends to restore a monolayer of monomers. These results were confirmed from UV-vis and fluorescence spectroscopy analysis. Infrared reflection-absorption and circular dichroism spectroscopy techniques were used to determine the secondary structure and orientation changes of HI by zinc ions. Generally, the aggregation process leads to a conformation change from α-helix to β-strand and β-turn, and at the air-water interface, the aggregation process was likewise seen to induce specific orientations for HI in the acidic and basic media. A proposed surface orientation model is presented here as an explanation to the experimental data, shedding light for further research on the behavior of insulin as a Langmuir

  14. Probing Human NK Cell Biology Using Human Immune System (HIS) Mice.

    Science.gov (United States)

    Li, Yan; Di Santo, James P

    2016-01-01

    Our incomplete understanding of the mechanisms that orchestrate human lymphocyte differentiation and condition human immune responses is in part due to the limited access to normal human tissue samples that can inform on these complex processes. In addition, in vitro culture conditions fail to recapitulate the three-dimensional microenvironments that influence cell-cell interactions and impact on immune outcomes. Small animals provide a preclinical model to dissect and probe immunity and over the past decades, development of immunodeficient hosts that can be engrafted with human hematopoietic precursors and mature cells have led to the development of new in vivo models to study human lymphocyte development and function. Natural killer (NK) cells are implicated in the recognition and elimination of pathogen-infected and transformed cells and belong to a family of diverse innate lymphoid cells (ILCs) that provide early immune defense against disease. Here, we summarize the use of humanized mouse models for the study of NK cell and group 1 ILCs and their respective roles in immunity and tissue homeostasis.

  15. An Initial Probe into Indian Electoral System%印度选举制度初探

    Institute of Scientific and Technical Information of China (English)

    吴展

    2005-01-01

    India is a constitutional democracy with a parliamentary system of government, in the heart of which is an electoral system. Regular, free and fair elections of this electoral system determine the composition of the government, the membership of the two houses of parliament, the state and union territory of legislative assemblies, and the presidency and vicepresidency. Meanwhile, operation of this electoral system involves tremendous political mobilization and organizational complexity on an amazing scale. India is a country with numerous internal and external elements and that may cause upheavals. However,this electoral system plays a vital role in maintaining its stability and continuous development.

  16. Magnetic volcanos in gadolinium Langmuir-Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Tishin, A.M. E-mail: amt@mailaps.org; Snigirev, O.V.; Khomutov, G.B.; Gudoshnikov, S.A.; Bohr, J

    2001-09-01

    Magnetic, structural and electronic properties of Langmuir-Blodgett films with incorporated Gd{sup 3+} ions has been detected using a scanning DC SQUID microscope, scanning electron microscope and X-ray diffraction. The magnetic images of 28 and 50 layer thick films at 77 K have been obtained after in-plane and out-of-plane pre-magnetization in a field of 1.4 T at 300 K. Randomly placed 'magnetic volcanos' with a remanent magnetic moment of the order of 10{sup -13} A m{sup 2} was observed. A decay of the remanent magnetization with a characteristic time of about 120 h was observed. It is suggested that the magnetic order is relatively long ranged, and that topological defects (vortices) lead to the observed out-of-plane field lines, and are responsible for the magnetic volcanos. Finally, it is hypothesized that a similar topology of field lines is responsible for superconductivity as observed in ceramic high-T{sub C} superconductors.

  17. Langmuir-Blodgett films of ethylenedithiotetrathiafulvalene derivative containing hydroxyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, Shilpa N., E-mail: stawde@barc.gov.i [Chemistry Division, BARC, Trombay-400085 (India); Kulshreshtha, S.K. [Chemistry Division, BARC, Trombay-400085 (India); Yakhmi, J.V. [Technical Physics and Prototype Engineering Division, BARC, Trombay-400085 (India); Doble, Mukesh [Department of Biotechnology, IIT Madras, Chennai-600 036 (India); Miyazaki, Akira; Enoki, Toshiaki [Department of Chemistry, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, 152-8551 (Japan)

    2010-08-02

    Langmuir-Blodgett (LB) films of an ethylenedithiotetrathiafulvalene (EDT-TTF) derivative containing hydroxyl groups, 4, 5-bis(11-hydroxyundecylthio)-4', 5'-ethylenedithiotetrathiafulvalene were deposited without using stabilizer molecules. Doping of the film with iodine leads to oxidation of EDT-TTF moiety as evidenced by UV-vis and IR spectroscopy. X-ray diffraction studies reveal the presence of layered arrangement of the EDT-TTF derivative molecules in the LB film. Cyclic voltammetry studies indicate that the electrochemical oxidation of the EDT-TTF derivative in its LB film is irreversible. Due to the insulating nature of the alkyl chains, only the first layer of the LB film was found to be redox-active. The electrical conductivity of the 25 layer LB film was found to increase by two orders of magnitude on doping with iodine. On equilibrating the doped film in air, the conductivity gradually reduced with time and finally reached the conductivity of undoped film. This reversibility could be because of the steric hindrance induced by the two long alkyl groups. The alkyl chains help in rendering the EDT-TTF molecule amiable to LB film formation but are found to reduce the electrical conductivity of the films and also cause instability of the doped state. The hydroxyl groups at the end of the alky chain impart amphiphilic nature to the molecules and help in stabilizing the film at the air-water interface.

  18. LES of Langmuir supercells under constant crosswind tidal forcing

    Science.gov (United States)

    Walker, Rachel; Zhang, Jie; Juha, Mario; Gosch, Chester; Tejada-Martinez, Andres

    2015-11-01

    We report on the impact of a crosswind tidal current on Langmuir supercells (LSCs) in shallow water computed via LES. LSCs consist of parallel counter rotating vortices engulfing the water column in unstratified conditions. These cells have been observed in shallow continental shelf regions of ~15 meters depth during the passage of storms. The cells are aligned roughly in the wind direction and are generated by the interaction of the wind-driven shear current with the Stokes drift velocity induced by surface gravity waves. Without tides, LES reveals that the typical crosswind width of a LSC is ~4 times the water column depth (H). Under a relatively weak crosswind tidal current (weaker than the downwind current), the constant crosswind tidal forcing applied causes a merging of cells leading to cells of width ~8H. The opposite occurs under a crosswind tidal current stronger than the downwind current as the constant crosswind tidal force is able to break up the LSCs giving rise to smaller scale cells with different turbulent structure than that associated with LSC. Statistics of the turbulence during strong and weak crosswind tides will be contrasted and implications of an oscillating crosswind tidal force will be discussed. Support from the US National Science Foundation and the Gulf of Mexico Research Initiative is gratefully acknowledged.

  19. Photopatterning of heterostructured polymer Langmuir-Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Li Tiesheng [Department of Chemistry, Key Lab of Biological Chemistry and Organic Chemistry of Henan Province, Zhengzhou University, Daxue road 75, Zhengzhou 450052 (China); Key Lab of Advanced Information Nano-materials of Zhengzhou, Daxue road 75, Zhengzhou 450052 (China)], E-mail: lts34@zzu.edu.cn; Mitsuishi, Masaya [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Aobaku, 2-1-1, Katahira, Sendai (Japan); Miyashita, Tokuji [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Aobaku, 2-1-1, Katahira, Sendai (Japan)], E-mail: miya@tagen.tohoku.ac.jp

    2008-02-29

    Heterostructured polymer Langmuir-Blodgett (LB) film prepared by using poly(N-dodecylacrylamide-co-t-butyl 4-vinylphenyl carbonate) (p(DDA-tBVPC53)) and poly(N-neopentyl methacrylamide-co-9-anthrylmethyl methacrylate) (p(nPMA-AMMA10)) polymer LB films which can act as photogenerator layers were investigated. Patterns with a resolution of 0.75 {mu}m were obtained on heterostructured polymer LB films composed of 4 layers of p(nPMA-AMMA10) LB film (top layers) and 40 layers of p(DDA-tBVPC53) LB film (under layers) on a silicon wafer by deep UV irradiation followed by development with 1% tetramethylammonium hydroxide aqueous solution. The sensitivity of the heterostructured polymer LB films was improved without loss of the resolution compared with p(DDA-tBVPC53) LB film. The etch resistance of the heterostructured polymer LB films was sufficiently good to allow patterning of a copper film suitable for photomask fabrication.

  20. Oleic acid disorders stratum corneum lipids in Langmuir monolayers.

    Science.gov (United States)

    Mao, Guangru; VanWyck, Dina; Xiao, Xin; Mack Correa, M Catherine; Gunn, Euen; Flach, Carol R; Mendelsohn, Richard; Walters, Russel M

    2013-04-16

    Oleic acid (OA) is well-known to affect the function of the skin barrier. In this study, the molecular interactions between OA and model stratum corneum (SC) lipids consisting of ceramide, cholesterol, and palmitic acid (PA) were investigated with Langmuir monolayer and associated techniques. Mixtures with different OA/SC lipid compositions were spread at the air/water interface, and the phase behavior was tracked with surface pressure-molecular area (π-A) isotherms. With increasing OA levels in the monolayer, the films became more fluid and more compressible. The thermodynamic parameters derived from π-A isotherms indicated that there are preferential interactions between OA and SC lipids and that films of their mixtures were thermodynamically stable. The domain structure and lipid conformational order of the monolayers were studied through Brewster angle microscopy (BAM) and infrared reflection absorption spectroscopy (IRRAS), respectively. Results indicate that lower concentrations of OA preferentially mix with and disorder the ceramide-enriched domains, followed by perturbation of the PA-enriched domains and disruption of SC lipid domain separation at higher OA levels.

  1. High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

    Directory of Open Access Journals (Sweden)

    G. Thejappa

    2004-01-01

    Full Text Available Short wavelength ion sound waves (2-4kHz are detected in association with the Langmuir waves (~15-30kHz in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

  2. Surface chemistry of lipid raft and amyloid Aβ (1-40) Langmuir monolayer.

    Science.gov (United States)

    Thakur, Garima; Pao, Christine; Micic, Miodrag; Johnson, Sheba; Leblanc, Roger M

    2011-10-15

    Lipid rafts being rich in cholesterol and sphingolipids are considered to provide ordered lipid environment in the neuronal membranes, where it is hypothesized that the cleavage of amyloid precursor protein (APP) to Aβ (1-40) and Aβ (1-42) takes place. It is highly likely that the interaction of lipid raft components like cholesterol, sphingomylein or GM1 leads to nucleation of Aβ and results in aggregation or accumulation of amyloid plaques. One has investigated surface pressure-area isotherms of the lipid raft and Aβ (1-40) Langmuir monolayer. The compression-decompression cycles and the stability of the lipid raft Langmuir monolayer are crucial parameters for the investigation of interaction of Aβ (1-40) with the lipid raft Langmuir monolayer. It was revealed that GM1 provides instability to the lipid raft Langmuir monolayer. Adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing neutral (POPC) or negatively charged phospholipid (DPPG) was examined. The adsorption isotherms revealed that the concentration of cholesterol was important for adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing POPC whereas for the lipid raft Langmuir monolayer containing DPPG:cholesterol or GM1 did not play any role. In situ UV-vis absorption spectroscopy supported the interpretation of results for the adsorption isotherms.

  3. From Langmuir kinetics to first- and second-order rate equations for adsorption.

    Science.gov (United States)

    Liu, Yu; Shen, Liang

    2008-10-21

    So far, the first- and second-order kinetic equations have been most frequently employed to interpret adsorption data obtained under various conditions, whereas the theoretical origins of these two equations still remain unknown. Using the Langmuir kinetics as a theoretical basis, this study showed that the Langmuir kinetics can be transformed to a polynomial expression of dtheta t /d t = k 1(theta e - theta t ) + k 2(theta e - theta t ) (2), a varying-order rate equation. The sufficient and necessary conditions for simplification of the Langmuir kinetics to the first- and second-order rate equations were put forward, which suggested that the relative magnitude of theta e over k 1/ k 2 governs the simplification of the Langmuir kinetics. In cases where k 1/ k 2 is greater than theta e or k 1/ k 2 is very close to theta e, adsorption kinetics would be reasonably described by the first-order rate equation, whereas the Langmuir kinetics would be reduced to the second-order equation only at k 1/ k 2 Langmuir kinetics indeed is determined by C 0. Detailed C 0-depedent boundary conditions for simplifying the Langmuir kinetics were also established and were verified by experimental data.

  4. Probing the interplay between factors determining reaction rates on silica gel using termolecular systems.

    Science.gov (United States)

    Kirkpatrick, Iain; Worrall, David R; Williams, Siân L; Buck, Craig J T; Meseguer, Rafael G

    2012-10-01

    In this study we have compared energy and electron transfer reactions in termolecular systems using a nanosecond diffuse reflectance laser flash photolysis technique. We have previously investigated these processes on silica gel surfaces for bimolecular systems and electron transfer in termolecular systems. The latter systems involved electron transfer between three arene molecules with azulene acting as a molecular shuttle. In this study we present an alternative electron transfer system using trans β-carotene as an electron donor in order to effectively immobilise all species except the shuttle, providing the first unambiguous evidence for radical ion mobility. In the energy transfer system we use naphthalene, a structural isomer of azulene, as the shuttle, facilitating energy transfer from a selectively excited benzophenone sensitiser to 9-cyanoanthracene. Bimolecular rate constants for all of these processes have been measured and new insights into the factors determining the rates of these reactions on silica gel have been obtained.

  5. Trajectory-probed instability and statistics of desynchronization events in coupled chaotic systems

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Gilson F. de, E-mail: gilson@otica.ufpb.br; Chevrollier, Martine; Oriá, Marcos [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900 João Pessoa-PB (Brazil); Passerat de Silans, Thierry [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900 João Pessoa-PB (Brazil); UAF, Universidade Federal de Campina Grande, 58429-900 Campina Grande, PB (Brazil); Souza Cavalcante, Hugo L. D. de [Departamento de Informática, Centro de Informática, Universidade Federal da Paraíba, Av. dos Escoteiros s/n, Mangabeira VII, 58055-000 João Pessoa, PB (Brazil)

    2015-11-15

    Complex systems, such as financial markets, earthquakes, and neurological networks, exhibit extreme events whose mechanisms of formation are not still completely understood. These mechanisms may be identified and better studied in simpler systems with dynamical features similar to the ones encountered in the complex system of interest. For instance, sudden and brief departures from the synchronized state observed in coupled chaotic systems were shown to display non-normal statistical distributions similar to events observed in the complex systems cited above. The current hypothesis accepted is that these desynchronization events are influenced by the presence of unstable object(s) in the phase space of the system. Here, we present further evidence that the occurrence of large events is triggered by the visitation of the system's phase-space trajectory to the vicinity of these unstable objects. In the system studied here, this visitation is controlled by a single parameter, and we exploit this feature to observe the effect of the visitation rate in the overall instability of the synchronized state. We find that the probability of escapes from the synchronized state and the size of those desynchronization events are enhanced in attractors whose shapes permit the chaotic trajectories to approach the region of strong instability. This result shows that the occurrence of large events requires not only a large local instability to amplify noise, or to amplify the effect of parameter mismatch between the coupled subsystems, but also that the trajectories of the system wander close to this local instability.

  6. Trajectory-probed instability and statistics of desynchronization events in coupled chaotic systems

    Science.gov (United States)

    de Oliveira, Gilson F.; Chevrollier, Martine; Passerat de Silans, Thierry; Oriá, Marcos; de Souza Cavalcante, Hugo L. D.

    2015-11-01

    Complex systems, such as financial markets, earthquakes, and neurological networks, exhibit extreme events whose mechanisms of formation are not still completely understood. These mechanisms may be identified and better studied in simpler systems with dynamical features similar to the ones encountered in the complex system of interest. For instance, sudden and brief departures from the synchronized state observed in coupled chaotic systems were shown to display non-normal statistical distributions similar to events observed in the complex systems cited above. The current hypothesis accepted is that these desynchronization events are influenced by the presence of unstable object(s) in the phase space of the system. Here, we present further evidence that the occurrence of large events is triggered by the visitation of the system's phase-space trajectory to the vicinity of these unstable objects. In the system studied here, this visitation is controlled by a single parameter, and we exploit this feature to observe the effect of the visitation rate in the overall instability of the synchronized state. We find that the probability of escapes from the synchronized state and the size of those desynchronization events are enhanced in attractors whose shapes permit the chaotic trajectories to approach the region of strong instability. This result shows that the occurrence of large events requires not only a large local instability to amplify noise, or to amplify the effect of parameter mismatch between the coupled subsystems, but also that the trajectories of the system wander close to this local instability.

  7. Using NV centers to probe magnetization dynamics in normal metal/magnetic insulator hybrid system at the nanoscale

    Science.gov (United States)

    Zhang, Huiliang; Ku, Mark J. H.; Han, Minyong; Casola, Francesco; van der Sar, Toeno; Yacoby, Amir; Walsworth, Ronald L.

    2016-05-01

    Understanding magnetization dynamics induced by electric current is of great interest for both fundamental and practical reasons. Great endeavor has been dedicated to spin-orbit torques (SOT) in metallic structures, while quantitative study of analogous phenomena in magnetic insulators remains challenging where transport measurements are not feasible. Recently we have developed techniques using nitrogen vacancy (NV) centers in diamond to probe few-nanometre-scale correlated-electron magnetic excitations (i.e., spin waves). Here we demonstrate how this powerful tool can be implemented to study magnetization dynamics inside ferromagnetic insulator, Yttrium iron garnet (YIG) with spin injection from electrical current through normal metal (Platinum in our case). Particularly our work will focus on NV magnetic detection, imaging, and spectroscopy of coherent auto-oscillations in Pt/YIG microdisc. Magnetic fluctuations and local temperature measurements, both with nearby NV centers, will also be interesting topics relevant to SOT physics in Pt/YIG hybrid system.

  8. Probing the Pulsar Wind in the gamma-ray Binary System PSR B1259-63/SS 2883

    CERN Document Server

    Takata, Jumpei

    2009-01-01

    The spectral energy distribution from the X-ray to the very high energy regime ($>100$ GeV) has been investigated for the $\\gamma$-ray binary system PSR B1259-63/SS2883 as a function of orbital phase within the framework of a simple model of a pulsar wind nebula. The emission model is based on the synchrotron radiation process for the X-ray regime and the inverse Compton scattering process boosting stellar photons from the Be star companion to the very high energy (100GeV-TeV) regime. With this model, the observed temporal behavior can, in principle, be used to probe the pulsar wind properties at the shock as a function of the orbital phase. Due to theoretical uncertainties in the detailed microphysics of the acceleration process and the conversion of magnetic energy into particle kinetic energy, the observed X-ray data for the entire orbit are fit using two different methods.

  9. Probing lithium germanide phase evolution and structural change in a germanium-in-carbon nanotube energy storage system.

    Science.gov (United States)

    Tang, Wei; Liu, Yanpeng; Peng, Chengxin; Hu, Mary Y; Deng, Xuchu; Lin, Ming; Hu, Jian Zhi; Loh, Kian Ping

    2015-02-25

    Lithium alloys of group IV elements such as silicon and germanium are attractive candidates for use as anodes in high-energy-density lithium-ion batteries. However, the poor capacity retention arising from volume swing during lithium cycling restricts their widespread application. Herein, we report high reversible capacity and superior rate capability from core-shell structure consisting of germanium nanorods embedded in multiwall carbon nanotubes. To understand how the core-shell structure helps to mitigate volume swings and buffer against mechanical instability, transmission electron microscopy, X-ray diffraction, and in situ (7)Li nuclear magnetic resonance were used to probe the structural rearrangements and phase evolution of various Li-Ge alloy phases during (de)alloying reactions with lithium. The results provide insights into amorphous-to-crystalline transition and lithium germanide alloy phase transformation, which are important reactions controlling performance in this system.

  10. Probe Improvement of Inductive Sensor for Online Health Monitoring of Mechanical Transmission Systems

    DEFF Research Database (Denmark)

    Wang, Chao; Liu, Xiao; Chen, Zhe

    2015-01-01

    Metal debris in lubricating oil contains abundant information regarding the ageing and wear/damage of mechanical transmission systems. The health condition of the lubricated systems can be indicated by the concentration and size of the metal abrasive particles, which may provide very early warnin...

  11. On Acoustic Feedback Cancellation Using Probe Noise in Multiple-Microphone and Single-Loudspeaker Systems

    DEFF Research Database (Denmark)

    Guo, Meng; Elmedyb, Thomas Bo; Jensen, Søren Holdt;

    2012-01-01

    of the adaptive estimation is significantly decreased when keeping the steady-state error unchanged. The goal of this work is to derive analytic expressions for the system behavior such as convergence rate and steady-state error for a multiple-microphone and single-loudspeaker audio system, where the acoustic...

  12. Reproducibility of the cutoff probe for the measurement of electron density

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Oh, W. Y. [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); You, S. J., E-mail: sjyou@cnu.ac.kr [Department of Physics, Chungnam National University, Daejeon 305-701 (Korea, Republic of); Kwon, J. H.; You, K. H.; Seo, B. H.; Kim, J. H., E-mail: jhkim86@kriss.re.kr [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); Yoon, J.-S. [Plasma Technology Research Center, National Fusion Research Institute, Gunsan 573-540 (Korea, Republic of)

    2016-06-15

    Since a plasma processing control based on plasma diagnostics attracted considerable attention in industry, the reproducibility of the diagnostics using in this application has become a great interest. Because the cutoff probe is one of the potential candidates for this application, knowing the reproducibility of the cutoff probe measurement becomes quit important in the cutoff probe application research. To test the reproducibility of the cutoff probe measurement, in this paper, a comparative study among the different cutoff probe measurements was performed. The comparative study revealed remarkable result: the cutoff probe has a great reproducibility for the electron density measurement, i.e., there are little differences among measurements by different probes made by different experimenters. The discussion including the reason for the result was addressed via this paper by using a basic measurement principle of cutoff probe and a comparative experiment with Langmuir probe.

  13. Miscibility and Molecular Orientation of Carbazole in Mixed Langmuir and Langrnuir-Blodgett Films

    Institute of Scientific and Technical Information of China (English)

    Md. N. Islam; D. Bhattacharjee; S. A. Hussain

    2007-01-01

    We report the miscibility and molecular orientation of carbazole (CA) molecules in the mixed Langmuir and Langmuir-Blodgett (LB) films of CA in polymethyl methacrylate (PMMA) and stearic acid (SA) matrices. The r-A isotherm confirms the formation of stable Langmuir films of CA mixed with either PMMA or SA at airwater interface. Characteristics of area per molecule versus molefraction and collapse pressure versus molefraction reveal complete demixing of CA and the matrix PMMA/SA molecules in the mixed films. Absorption spectroscopy certainly confirms the fact that CA molecules have preferred orientation on the substrate of the LB films.

  14. Dust charge fluctuation effects on Langmuir waves with kappa distributed electrons

    Science.gov (United States)

    Jamshidi, M.; Rouhani, M. R.; Hakimi Pajouh, H.

    2016-03-01

    Using a kinetic description, dust charge fluctuations due to the inelastic collisions between dust particles and plasma particles are studied in unmagnetized dusty plasmas. Most astrophysical and space plasmas are observed to have non-Maxwellian high energy tail. Therefore, a kappa distribution for electrons in the equilibrium is assumed. The dispersion relation and damping rates for Langmuir waves are obtained. Considering the dust charge fluctuations increases the damping rate of Langmuir waves. It is shown that the damping rate of Langmuir waves depends on the spectral index and the dust density parameter.

  15. Fabrication and structure of Langmuir-Blodgett films of ferroelectric liquid crystal

    Institute of Scientific and Technical Information of China (English)

    WEN Zi; JIANG Qing; T.Kenji; O.Yukihiro

    2005-01-01

    The molecular aggregation, orientation, and structure in Langmuir-Blodgett films of ferroelectric liquid crystal were studied by ultraviolet and Fourier transform infrared spectra. The results show that medium strong H-aggregates in the Langmuir-Blodgett films of ferroelectric liquid crystal are formed by chromophores where the alkyl chains are nearly perpendicular to the film surface. Compared with the cast films, the CO stretching bands, due to the rotational isomerism around the O-C axis of the chiral part, can be identified clearly in Langmuir-Blodgett films.

  16. The SLUGGS survey: Probing the supermassive black hole connection with bulges and haloes using red and blue globular cluster systems

    CERN Document Server

    Pota, Vincenzo; Forbes, Duncan A; Romanowsky, Aaron J; Brodie, Jean P; Strader, Jay

    2013-01-01

    Understanding whether the bulge or the halo provides the primary link to the growth of supermassive black holes has strong implications for galaxy evolution and supermassive black hole formation itself. In this paper, we approach this issue by investigating extragalactic globular cluster (GC) systems, which can be used to probe the physics of both the bulge and the halo of the host galaxy. We study the relation between the supermassive black hole masses M_BH and the globular cluster system velocity dispersions sigma_GC using an updated and improved sample of 21 galaxies. We exploit the dichotomy of globular cluster system colours, to test if the blue and red globular clusters correlate differently with black hole mass. This may be expected if they trace the potentially different formation history of the halo and of the bulge of the host galaxy respectively. We find that M_BH correlates with the total GC system velocity dispersion, although not as strongly as claimed by recent work of Sadoun & Colin. We al...

  17. Miniaturized, Low Power Cryogenic Inlet System with Sampling Probes for Titan Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thorleaf Research, Inc. has demonstrated feasibility in Phase 1 and now proposes a Phase 2 effort to develop a miniature, low power cryogenic inlet system with...

  18. Single Molecule Photobleaching Probes the Exciton Wavefunction in a Multichromophoric System

    NARCIS (Netherlands)

    Hernando, J.; Hoogenboom, J.P.; Dijk, van E.M.H.P.; Garcia-Lopez, J.J.; Crego Calama, M.; Reinhoudt, D.N.; Hulst, van N.F.; Garcia-Parajo, M.F.

    2004-01-01

    The exciton wave function of a trichromophoric system is investigated by means of single molecule spectroscopy at room temperature. Individual trimers exhibit superradiance and loss of vibronic structure in emission spectrum, features proving exciton delocalization. We identify two distinct photodeg

  19. Photoacoustic imaging of hidden dental caries by using a fiber-based probing system

    Science.gov (United States)

    Koyama, Takuya; Kakino, Satoko; Matsuura, Yuji

    2017-04-01

    Photoacoustic method to detect hidden dental caries is proposed. It was found that high frequency ultrasonic waves are generated from hidden carious part when radiating laser light to occlusal surface of model tooth. By making a map of intensity of these high frequency components, photoacoustic images of hidden caries were successfully obtained. A photoacoustic imaging system using a bundle of hollow optical fiber was fabricated for using clinical application, and clear photoacoustic image of hidden caries was also obtained by this system.

  20. Improved Analysis Techniques for Cylindrical and Spherical Double Probes (Preprint)

    Science.gov (United States)

    2012-03-21

    accounts for the finite, but non -negligible extent of the plasma sheath. One of the most extensive assessments of ion collection by a biased cylindrical...Approved for public release; distribution unlimited. 4 regardless of rP/λD so long as the electron distribution function is Maxwellian such that...731. 3 J.G. Laframboise, Theory of Spherical and Cylindrical Langmuir Probes in a Collisionless, Maxwellian Plasma at Rest, (University of Toronto

  1. Fabricação e caracterização de filmes Langmuir e Langmuir-Blodgett de derivados do politiofeno

    OpenAIRE

    Nunes, Bruno Moser

    2012-01-01

    Os politiofenos apresentam algumas vantagens em relação aos demais polímeros conjugados como, por exemplo, a facilidade de síntese química e a relativa facilidade de funcionalização de suas cadeias laterais. A maioria dos derivados do politiofeno são insolúveis em água, o que torna possível o processamento desses na forma de filmes ultrafinos pelas técnicas de Langmuir-Blodgett (LB) ou de Langmuir-Schaefer, gerando filmes nanoestruturados e com espessura controlada. Dentro deste contexto, est...

  2. Non linear dynamic of Langmuir and electromagnetic waves in space plasmas; Dinamica nao linear de ondas de Langmuir e eletromagneticas em plasmas espaciais

    Energy Technology Data Exchange (ETDEWEB)

    Guede, Jose Ricardo Abalde

    1995-11-01

    The aim of this work is to study the nonlinear dynamics of Langmuir and electromagnetic waves in space plasmas. Firstly, the generalized Zakharov equations are derived which are used to study the hybrid parametric instability involving the generation of daughter Langmuir, electromagnetic and ion-acoustic waves induced by two counter-propagating Langmuir pump waves with different amplitudes based on a coupled dispersion relation. Secondly, starting from the generalized Zakharov equations the linear and nonlinear coupled mode theories of three-wave and four-wave parametric interactions are developed, respectively. In three-waves processes, a Langmuir wave decays into another Langmuir wave and an ion-acoustic wave (electrostatic parametric decay) or into an electromagnetic wave and an ion-acoustic wave (electromagnetic parametric decay). In four-wave (modulational) processes, the interaction involves two wave triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplets: in the decay triplet a pump wave couples with a low-frequency wave to generate a Stokes wave, and in the fusion triplet the coupling of a pump wave with a low-frequency wave generate an anti-Stokes wave. These modulational processes are convective and resonant processes wherein the low-frequency modes are Eigenmodes of plasma and are known as the stimulated modulational processes. Four such processes are investigated in this thesis: two with Langmuir pump waves (electrostatic and hybrid stimulated modulation processes) and the other two with electromagnetic pump waves (stimulated modulation Brillouin scattering and electromagnetic stimulated modulation process). Applications of the theoretical results in space plasmas are discussed. In particular, it is shown that the electrostatic and electromagnetic parametric decay processes of Langmuir waves can model the generation and modulation of radio emissions and Langmuir waves in the

  3. Laser spectroscopic probing of coexisting superfluid and insulating states of an atomic Bose-Hubbard system

    Science.gov (United States)

    Kato, Shinya; Inaba, Kensuke; Sugawa, Seiji; Shibata, Kosuke; Yamamoto, Ryuta; Yamashita, Makoto; Takahashi, Yoshiro

    2016-04-01

    A system of ultracold atoms in an optical lattice has been regarded as an ideal quantum simulator for a Hubbard model with extremely high controllability of the system parameters. While making use of the controllability, a comprehensive measurement across the weakly to strongly interacting regimes in the Hubbard model to discuss the quantum many-body state is still limited. Here we observe a great change in the excitation energy spectra across the two regimes in an atomic Bose-Hubbard system by using a spectroscopic technique, which can resolve the site occupancy in the lattice. By quantitatively comparing the observed spectra and numerical simulations based on sum rule relations and a binary fluid treatment under a finite temperature Gutzwiller approximation, we show that the spectra reflect the coexistence of a delocalized superfluid state and a localized insulating state across the two regimes.

  4. Radioactive contamination mapping of northeastern and eastern Japan by a car-borne survey system, Radi-Probe.

    Science.gov (United States)

    Kobayashi, Shingo; Shinomiya, Takayuki; Kitamura, Hisashi; Ishikawa, Takahiro; Imaseki, Hitoshi; Oikawa, Masakazu; Kodaira, Satoshi; Miyaushiro, Norihiro; Takashima, Yoshio; Uchihori, Yukio

    2015-01-01

    We constructed a new car-borne survey system called Radi-Probe with a portable germanium gamma-ray spectrometer onboard a cargo truck, to identify radionuclides and quantify surface contamination from the accident at Fukushima Dai-ichi Nuclear Power Station. The system can quickly survey a large area and obtain ambient dose equivalent rates and gamma-ray energy spectra with good energy resolution. We also developed a new calibration method for the system to deal with an actual nuclear disaster, and quantitative surface deposition densities of radionuclides, such as (134)Cs and (137)Cs, and kerma rates of each radionuclide can be calculated. We carried out car-borne survey over northeastern and eastern Japan (Tohoku and Kanto regions of Honshu) from 25 September through 7 October 2012. We discuss results of the distribution of ambient dose equivalent rate H(∗)(10), (134)Cs and (137)Cs surface deposition densities, spatial variation of (134)Cs/(137)Cs ratio, and the relationship between surface deposition densities of (134)Cs/(137)Cs and H(∗)(10). The ratio of (134)Cs/(137)Cs was nearly constant within our measurement precision, with average 1.06 ± 0.04 in northeastern and eastern Japan (decay-corrected to 11 March, 2011), although small variations from the average were observed.

  5. Probing the history of Solar System through the cratering records on Vesta and Ceres

    CERN Document Server

    Turrini, D; Coradini, A

    2009-01-01

    Dawn space mission will provide the first, detailed data of two of the major bodies in the Main Belt, Vesta and Ceres. In the framework of our studies on the origin of Solar System, we modelled the accretion of Jupiter and, through an N-Body code developed on purpose, we evaluated the flux of impactors on Vesta and Ceres keeping track of their formation zones. We also studied the effects of the possible inward migration of Jupiter on the rate and the characteristics of the impacts. We here describe the different scenarios and their implications for the evolution of Solar System.

  6. The LC resonance probe for determining local plasma density

    Energy Technology Data Exchange (ETDEWEB)

    Boris, D R; Fernsler, R F; Walton, S G, E-mail: david.boris.ctr@nrl.navy.mi [Naval Research Laboratory, Charge Particle Physics Branch-Code 6752, Plasma Physics Division, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)

    2011-04-15

    We present a novel plasma diagnostic for measuring local plasma density in reactive-gas plasmas, and depositing plasmas. The diagnostic uses a network analyzer to measure the LC resonance (LCR) frequency of a parallel plate capacitor with inductive leads. The location of the LCR ({omega}{sub R}) in frequency space is then used as a measure of the plasma dielectric constant bold varepsilon{sub p} between the plates. By properly constructing the LCR probe, {omega}{sub R} can be tuned such that {omega}{sub R} >> {omega}{sub ce}, where {omega}{sub ce} is the electron-cyclotron frequency. Thus, the probe can be used in plasmas with varying degrees of magnetization while avoiding complications introduced to bold varepsilon{sub p} when {omega} is comparable to {omega}{sub ce}. Density measurements from the LCR probe are compared with Langmuir probe measurements in an electron-beam generated plasma in which density varied from 10{sup 9} to 10{sup 11} cm{sup -3}. An axial magnetic field, typically used to confine the electron beam, was varied between 0 to 300 G. The LCR probe showed good agreement with a Langmuir probe across the entire range of magnetic fields.

  7. Mobile probes

    DEFF Research Database (Denmark)

    2016-01-01

    A project investigating the effectiveness of a collection of online resources for teachers' professional development used mobile probes as a data collection method. Teachers received questions and tasks on their mobile in a dialogic manner while in their everyday context as opposed to in an inter......A project investigating the effectiveness of a collection of online resources for teachers' professional development used mobile probes as a data collection method. Teachers received questions and tasks on their mobile in a dialogic manner while in their everyday context as opposed...... to in an interview. This method provided valuable insight into the contextual use, i.e. how did the online resource transfer to the work practice. However, the research team also found that mobile probes may provide the scaffolding necessary for individual and peer learning at a very local (intra-school) community...... level. This paper is an initial investigation of how the mobile probes process proved to engage teachers in their efforts to improve teaching. It also highlights some of the barriers emerging when applying mobile probes as a scaffold for learning....

  8. Probing the Nature of Deficits in the "Approximate Number System" in Children with Persistent Developmental Dyscalculia

    Science.gov (United States)

    Bugden, Stephanie; Ansari, Daniel

    2016-01-01

    In the present study we examined whether children with Developmental Dyscalculia (DD) exhibit a deficit in the so-called "Approximate Number System" (ANS). To do so, we examined a group of elementary school children who demonstrated persistent low math achievement over 4 years and compared them to typically developing (TD), aged-matched…

  9. A framework for privacy and security analysis of probe-based traffic information systems

    KAUST Repository

    Canepa, Edward S.

    2013-01-01

    Most large scale traffic information systems rely on fixed sensors (e.g. loop detectors, cameras) and user generated data, this latter in the form of GPS traces sent by smartphones or GPS devices onboard vehicles. While this type of data is relatively inexpensive to gather, it can pose multiple security and privacy risks, even if the location tracks are anonymous. In particular, creating bogus location tracks and sending them to the system is relatively easy. This bogus data could perturb traffic flow estimates, and disrupt the transportation system whenever these estimates are used for actuation. In this article, we propose a new framework for solving a variety of privacy and cybersecurity problems arising in transportation systems. The state of traffic is modeled by the Lighthill-Whitham-Richards traffic flow model, which is a first order scalar conservation law with concave flux function. Given a set of traffic flow data, we show that the constraints resulting from this partial differential equation are mixed integer linear inequalities for some decision variable. The resulting framework is very flexible, and can in particular be used to detect spoofing attacks in real time, or carry out attacks on location tracks. Numerical implementations are performed on experimental data from the Mobile Century experiment to validate this framework. © 2013 ACM.

  10. Four-point probe electrical resistivity scanning system for large area conductivity and activation energy mapping.

    Science.gov (United States)

    Shimanovich, Klimentiy; Bouhadana, Yaniv; Keller, David A; Rühle, Sven; Anderson, Assaf Y; Zaban, Arie

    2014-05-01

    The electrical properties of metal oxides play a crucial role in the development of new photovoltaic (PV) systems. Here we demonstrate a general approach for the determination and analysis of these properties in thin films of new metal oxide based PV materials. A high throughput electrical scanning system, which facilitates temperature dependent measurements at different atmospheres for highly resistive samples, was designed and constructed. The instrument is capable of determining conductivity and activation energy values for relatively large sample areas, of about 72 × 72 mm(2), with the implementation of geometrical correction factors. The efficiency of our scanning system was tested using two different samples of CuO and commercially available Fluorine doped tin oxide coated glass substrates. Our high throughput tool was able to identify the electrical properties of both resistive metal oxide thin film samples with high precision and accuracy. The scanning system enabled us to gain insight into transport mechanisms with novel compositions and to use those insights to make smart choices when choosing materials for our multilayer thin film all oxide photovoltaic cells.

  11. Langmuir Wave Electric Fields Induced by Electron Beams in the Heliosphere

    CERN Document Server

    Reid, Hamish A S

    2016-01-01

    Solar electron beams responsible for type III radio emission generate Langmuir waves as they propagate out from the Sun. The Langmuir waves are observed via in-situ electric field measurements. These Langmuir waves are not smoothly distributed but occur in discrete clumps, commonly attributed to the turbulent nature of the solar wind electron density. Exactly how the density turbulence modulates the Langmuir wave electric fields is understood only qualitatively. Using weak turbulence simulations, we investigate how solar wind density turbulence changes the probability distribution functions, mean value and variance of the beam-driven electric field distributions. Simulations show rather complicated forms of the distribution that are dependent upon how the electric fields are sampled. Generally the higher magnitude of density fluctuations reduce the mean and increase the variance of the distribution in a consistent manor to the predictions from resonance broadening by density fluctuations. We also demonstrate ...

  12. Excitation and diagnosis of cascading Langmuir waves in ionospheric plasmas at Gakona, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Burton, L M; Cohen, J A; Pradipta, R; Labno, A; Lee, M C; Batishchev, O; Rokusek, D L [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Kuo, S P [Polytechnic University, Brooklyn, NY 11201 (United States); Watkins, B J; Oyama, S [University of Alaska Fairbanks, Fairbanks, AK 99775 (United States)], E-mail: mclee@mit.edu

    2008-12-15

    Ionospheric plasma heating experiments were conducted at Gakona, Alaska to investigate cascading spectra of Langmuir wave turbulence, excited by parametric instabilities diagnosed by Modular UHF Ionospheric Radar (MUIR). This work is aimed at testing the recent theory of Kuo and Lee (2005 J. Geophys. Res. 110 A01309) that addresses how the cascade of Langmuir waves can distribute spatially via the resonant and non-resonant decay processes. The non-resonant cascade proceeds at the location where parametric decay instability (PDI) or oscillating two-stream instability (OTSI) is excited and severely hampered by the frequency mismatch effect. By contrast, the resonant cascade, which takes place at lower matching heights, has to overcome the propagation loss of the Langmuir pump waves in each cascade step. Our experimental results have corroborated these predictions about the generation of cascading Langmuir waves by the HAARP heater.

  13. Langmuir-Blodgett films of alkane chalcogenice (S, Se, Te) stabilized gold nanoparticles

    DEFF Research Database (Denmark)

    Brust, M.; Stuhr-Hansen, N.; Norgaard, K.

    2001-01-01

    Gold nanoparticles stabilized by alkanethiolates, alkaneselenides, and alkanetellurides have been prepared by analogous methods. Chloroform solutions of thiolate and selenide stabilized particles were spread and evaporated on the water/air interface where the particles formed well-defined Langmuir...

  14. Calibration Issues and Operating System Requirements for Electron-Probe Microanalysis

    Science.gov (United States)

    Carpenter, P.

    2006-01-01

    Instrument purchase requirements and dialogue with manufacturers have established hardware parameters for alignment, stability, and reproducibility, which have helped improve the precision and accuracy of electron microprobe analysis (EPMA). The development of correction algorithms and the accurate solution to quantitative analysis problems requires the minimization of systematic errors and relies on internally consistent data sets. Improved hardware and computer systems have resulted in better automation of vacuum systems, stage and wavelength-dispersive spectrometer (WDS) mechanisms, and x-ray detector systems which have improved instrument stability and precision. Improved software now allows extended automated runs involving diverse setups and better integrates digital imaging and quantitative analysis. However, instrumental performance is not regularly maintained, as WDS are aligned and calibrated during installation but few laboratories appear to check and maintain this calibration. In particular, detector deadtime (DT) data is typically assumed rather than measured, due primarily to the difficulty and inconvenience of the measurement process. This is a source of fundamental systematic error in many microprobe laboratories and is unknown to the analyst, as the magnitude of DT correction is not listed in output by microprobe operating systems. The analyst must remain vigilant to deviations in instrumental alignment and calibration, and microprobe system software must conveniently verify the necessary parameters. Microanalysis of mission critical materials requires an ongoing demonstration of instrumental calibration. Possible approaches to improvements in instrument calibration, quality control, and accuracy will be discussed. Development of a set of core requirements based on discussions with users, researchers, and manufacturers can yield documents that improve and unify the methods by which instruments can be calibrated. These results can be used to

  15. Probing correlated quantum many-body systems at the single-particle level

    Energy Technology Data Exchange (ETDEWEB)

    Endres, Manuel

    2013-02-27

    The detection of correlation and response functions plays a crucial role in the experimental characterization of quantum many-body systems. In this thesis, we present novel techniques for the measurement of such functions at the single-particle level. Specifically, we show the single-atom- and single-site-resolved detection of an ultracold quantum gas in an optical lattice. The quantum gas is described by the Bose-Hubbard model, which features a zero temperature phase transition from a superfluid to a Mott-insulating state, a paradigm example of a quantum phase transition. We used the aforementioned detection techniques to study correlation and response properties across the superfluid-Mott-insulator transition. The single-atom sensitivity of our method is achieved by fluorescence detection of individual atoms with a high signal-to-noise ratio. A high-resolution objective collects the fluorescence light and yields in situ 'snapshots' of the quantum gas that allow for a single-site-resolved reconstruction of the atomic distribution. This allowed us to measure two-site and non-local correlation-functions across the superfluid-Mott-insulator transition. Non-local correlation functions are based on the information of an extended region of the system and play an important role for the characterization of low-dimensional quantum phases. While non-local correlation functions were so far only theoretical tools, our results show that they are actually experimentally accessible. Furthermore, we used a new thermometry scheme, based on the counting of individual thermal excitations, to measure the response of the system to lattice modulation. Using this method, we studied the excitation spectrum of the system across the two-dimensional superfluid-Mott-insulator transition. In particular, we detected a 'Higgs' amplitude mode in the strongly-interacting superfluid close to the transition point where the system is described by an effectively Lorentz

  16. Técnicas de caracterização para investigar interações no nível molecular em filmes de Langmuir e Langmuir-Blodgett (LB) Characterization techniques to investigate molecular-level interactions in Langmuir and Langmuir-Blodgett (LB) films

    OpenAIRE

    2005-01-01

    This paper discusses fundamental concepts for the characterization of Langmuir monolayers and Langmuir-Blodgett (LB) films, with emphasis on investigations of material properties at the molecular level. By way of illustration, results for phospholipid monolayers interacting with the drug dipyridamole are highlighted. These results were obtained with several techniques, including in situ grazing incidence X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, fluorescence microscop...

  17. Laser Induced Breakdown Spectroscopy of meteorites as a probe of the early solar system

    Science.gov (United States)

    Dell'Aglio, M.; De Giacomo, A.; Gaudiuso, R.; De Pascale, O.; Longo, S.

    2014-11-01

    This paper presents an evaluation of Laser Induced Breakdown Spectroscopy (LIBS) as a technique for gathering data relevant to Solar System geophysics. Two test cases were demonstrated: elemental analysis of chondrules in a chondrite meteorite, and space- resolved analysis of the interface between kamacite and taenite crystals in an octahedrite iron meteorite. In particular most major and minor elements (Fe, Mg, Si, Ti, Al, Cr, Mn, Ca, Fe, Ni, Co) in Sahara 98222 (chondrite) and its chondrules, as well as the profile of Ni content in Toluca (iron meteorite), were determined with the Calibration Free (CF) method. A special attention was devoted to exploring the possibilities offered by variants of the basic technique, such as the use of Fe I Boltzmann distribution as an intensity calibration method of the spectroscopic system, and the use of spatially resolved analysis.

  18. Development of a microwave dielectric spectroscopy system for materials characterization using the open-ended coaxial probe technique

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Ruiz, I.; Aviles-Castro, D. [Centro Nacional de Metrologia, Queretaro (Mexico); Jardon-Aguilar, H. [Instituto Politecnico Nacional, Mexico, D. F. (Mexico)

    2001-02-01

    Dielectric spectroscopy is a measurement technique to characterize the interaction between electromagnetic energy and macroscopic samples as a function of frequency. It is based on the measurement of complex permittivity plus conductivity and it has shown to be very useful to provide information about internal structure of matter. It has some advantages over others like optical or chemical analysis: it is very fast, easy to implement, requires little or no preparation of the sample, it can be non-destructive and/or minimally intrusive. In this paper the development of a dielectric spectroscopy system for the microwave frequency range (50 MHz-20 GHz), using an open-ended coaxial probe as sensor, is described. The complete system includes a vector network analyzer, a microwave coaxial cable, the probe, a sample holder and a computer to automate measurements and further data processing. This system has been used to measure some liquid and solid materials such as alcohol, water and Teflon. The real and imaginary parts of permittivity as function of frequency, for several sugarcane alcohol and deionised water mixtures, tequilas and Teflon samples are given. Measurement repeatability and accuracy considerations were taken and it was identified that uncertainty of reference standards and system repeatability are the most important error sources. Also, it was found that open-ended coaxial probe technique is appropriate for measuring not only liquids but also solid materials. Some of the obtained results were compared to those reported in literature and good convergence was observed. [Spanish] La espectroscopia dielectrica es una tecnica moderna de medicion para caracterizar la interaccion entre la energia electromagnetica y muestras macroscopicas como funcion de la frecuencia. Esta tecnica se basa en la medicion de la permitividad compleja y conductividad de los materiales y ha mostrado ser muy util para proporcionar informacion sobre la estructura interna de estos. Tiene

  19. Laser Induced Breakdown Spectroscopy of meteorites as a probe of the early solar system

    Energy Technology Data Exchange (ETDEWEB)

    Dell' Aglio, M., E-mail: marcella.dellaglio@ba.imip.cnr.it [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); De Giacomo, A. [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Chemistry Department, University of Bari, Via Orabona 4, 70126 Bari (Italy); Gaudiuso, R.; De Pascale, O. [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Longo, S. [Chemistry Department, University of Bari, Via Orabona 4, 70126 Bari (Italy); INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, Firenze (Italy)

    2014-11-01

    This paper presents an evaluation of Laser Induced Breakdown Spectroscopy (LIBS) as a technique for gathering data relevant to Solar System geophysics. Two test cases were demonstrated: elemental analysis of chondrules in a chondrite meteorite, and space- resolved analysis of the interface between kamacite and taenite crystals in an octahedrite iron meteorite. In particular most major and minor elements (Fe, Mg, Si, Ti, Al, Cr, Mn, Ca, Fe, Ni, Co) in Sahara 98222 (chondrite) and its chondrules, as well as the profile of Ni content in Toluca (iron meteorite), were determined with the Calibration Free (CF) method. A special attention was devoted to exploring the possibilities offered by variants of the basic technique, such as the use of Fe I Boltzmann distribution as an intensity calibration method of the spectroscopic system, and the use of spatially resolved analysis. - Highlights: • LIBS of meteorites can supply data relevant to the early evolution of solar system. • CF-LIBS was applied to two different test cases. • Chemical identification of chondrules embedded in a chondrite meteorite • Experimental and theoretical profiles of Ni content in an iron meteorite.

  20. Probing the Structure and Photophysics of Porphyrinoid Systems for Functional Materials

    Science.gov (United States)

    Farley, Christopher

    Porphyrins (Pors) and their many cousins, including phthalocyanines (Pcs), corroles (Cors), subphthalocyanines (SubPcs), porphyrazines (Pzs), and naphthalocyanines (NPcs), play amazingly diverse roles in biological and non-biological systems because of their unique and tunable physical and chemical properties. These compounds, collectively known as porphyrinoids, can be employed in any number of functional devices that have the potential to address the challenges of modern society. Their incorporation into such devices, however, depends on many structural factors that must be well understood and carefully controlled in order to achieve the desired behavior. Self-assembly and self-organization are key processes for developing these new technologies, as they will allow for inexpensive, efficient, and scalable designs. The overall goal of this dissertation is to elucidate and ultimately control the interplay between the hierarchical structure and the photophysical properties of these kinds of systems. This includes several case studies concerning the design and spectroscopic analysis of supramolecular systems formed through simple, scalable synthetic methods. We also present detailed experimental and computational studies on some porphyrin and phthalocyanine compounds that provide evidence for fundamental changes in their molecular structure. In addition to their impact on the photophysics, these changes also have implications for the organization of these molecules into higher order materials and devices. It is our hope that these findings will help to drive chemists and engineers to look more closely at every level of hierarchical structure in the search for the next generation of advanced materials.

  1. Probing influence of mesophasic transformation on performance of self-emulsifying system: effect of ion.

    Science.gov (United States)

    Patil, Sharvil S; Venugopal, Edakkal; Bhat, Suresh; Mahadik, Kakasaheb R; Paradkar, Anant R

    2012-02-06

    Self-emulsifying systems are mixtures of oils and surfactants, ideally isotropic, sometimes including cosolvents, which emulsify under conditions of gentle agitation, similar to those which would be encountered in the gastrointestinal tract. The process of self-emulsification has remained the center of attraction for most researchers. Controlled hydration of self-emulsifying systems shows formation of an intermediate gel phase which upon rupture forms an emulsion. Current work was undertaken to understand and explore the microstructural properties of intermediate gel phase which are believed to influence the performance (droplet size) of the final formulation. The effect of additives on microstructural properties of intermediate gel phase has also been investigated. Microstructural elucidation of hydrated samples of intermediate regimes was done by using techniques such as small angle X-ray scattering, differential scanning calorimetry and rheology. Samples from intermediate regimes showed formation of local lamellar structure which swelled with hydration. In the present work, the effect of addition of salt form of naproxen (sodium and potassium) and naproxen (base) on microstructural properties of intermediate regimes was investigated. Systems containing naproxen salts formed larger droplets whereas naproxen base formed smaller ones. Microstructural properties of intermediate lamellar structures were well correlated with performance of the final formulation. The current studies indicate that by controlling the properties of intermediate regimes optimized formulations with desired performance can be tailor-made.

  2. Structure-rheology relationship in weakly amphiphilic block copolymer Langmuir monolayers.

    Science.gov (United States)

    Li Destri, Giovanni; Miano, Fausto; Marletta, Giovanni

    2014-04-01

    The linear viscoelastic behavior in the low-frequency regime at the water/air interface of three different polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) copolymer monolayers, with block length ratio varying from 66-33 to 50-50 and 25-75 in molecular units, was studied and related to the interfacial behavior, characterized by means of Langmuir isotherms, and their structure, characterized by means of the atomic force microscopy technique. The two monolayers with the highest PMMA amount showed a single phase transition at about 12 mN/m, the viscoelastic behavior changing from a predominantly elastic to a viscoelastic one. This change in the viscoelastic properties was ascribed to the beginning of entanglement among the PMMA coronas of the predominantly circular quasi-2D micelles formed by the two copolymer systems. Conversely, the polymer with the lowest PMMA amount, despite having the same PMMA block length of the PS-PMMA 50-50 block copolymer, was found to behave as a viscoelastic system at any surface pressure value. This characteristic behavior cannot therefore be simply related to the molecular weight difference, but it has been put in connection to the irregular micelle structure observed in this case, consisting of a mixture of spherical and wormlike micelles, and to the different conformation adopted by the PMMA block. By blending this copolymer with an immiscible elastic homopolymer, namely poly(2-vinylpyridine), it was possible to tune the micelle nanostructure, obtaining regular circular quasi-2D micelles, with viscoelastic properties as expected for the PMMA-rich copolymer monolayers. To the best of our knowledge, this study shows for the first time the explicit dependence upon the relative block length and, in turn, upon the nanostructure of the quasi-2D micelles, of the viscoelastic properties of Langmuir monolayers and suggests that molecular weight and intermolecular interactions are not the only parameters governing the polymer conformation and

  3. Reciprocating Probe Measurements of L-H Transition in LHCD H-mode on EAST

    DEFF Research Database (Denmark)

    Peng, Liu; Guosheng, Xu; Huiqian, Wang

    2013-01-01

    only. Reciprocating Langmuir probe measurements at the outer midplane showed that the electron density ne and electron temperature Te in the scrape-off layer (SOL) were significantly reduced in the ELM-free phase, resulting in the increase of lower-hybrid wave (LHW) reflection. It was found...

  4. Modeling Nonlinear Adsorption with a Single Chemical Parameter: Predicting Chemical Median Langmuir Binding Constants.

    Science.gov (United States)

    Davis, Craig Warren; Di Toro, Dominic M

    2015-07-07

    Procedures for accurately predicting linear partition coefficients onto various sorbents (e.g., organic carbon, soils, clay) are reliable and well established. However, similar procedures for the prediction of sorption parameters of nonlinear isotherm models are not. The purpose of this paper is to present a procedure for predicting nonlinear isotherm parameters, specifically the median Langmuir binding constants, K̃L, obtained utilizing the single-chemical parameter log-normal Langmuir isotherm developed in the accompanying work. A reduced poly parameter linear free energy relationship (pp-LFER) is able to predict median Langmuir binding constants for graphite, charcoal, and Darco granular activated carbon (GAC) adsorption data. For the larger F400 GAC data set, a single pp-LFER model was insufficient, as a plateau is observed for the median Langmuir binding constants of larger molecular volume sorbates. This volumetric cutoff occurs in proximity to the median pore diameter for F400 GAC. A log-linear relationship exists between the aqueous solubility of these large compounds and their median Langmuir binding constants. Using this relationship for the chemicals above the volumetric cutoff and the pp-LFER below the cutoff, the median Langmuir binding constants can be predicted with a root-mean square error for graphite (n = 13), charcoal (n = 11), Darco GAC (n = 14), and F400 GAC (n = 44) of 0.129, 0.307, 0.407, and 0.424, respectively.

  5. Vibrationally excited CS: A new probe of conditions in young protostellar systems

    Science.gov (United States)

    Walker, Christopher K.; Maloney, Philip R.; Serabyn, E.

    1994-01-01

    We present the first detection of vibrationally excited C(32)S J = 10-9 and J = 7-6 emission toward a young stellar object (YSO). Toward IRAS 16293-2422, the vibrationally excited C(32)S emission is redshifted approximately 3.9 km/s from the systemic velocity of the core. The emission must arise in warm (T greater than or approximately equal 1000 K), dense (n greater than or approximately equal to 10(exp 11)-10(exp 12) per cc) gas. The most plausible origin for the emission appears to be self-gravitating instabilities in a protostellar accretion disk, which produce waves and shocks.

  6. Probing violation of quantum mechanics in the K0-(bar K)0 system

    Science.gov (United States)

    Huet, P.

    1994-08-01

    I present a recent study made in collaboration with M.E. Peskin, on the time dependence of a kaon beam propagating according to the '(alpha)(beta)(gamma)' generalization of quantum mechanics due to Ellis, Hagelin, Nanopoulos and Srednicki, in which CP- and CPT-violating signatures arise from the evolution of pure states to mixed states. The magnitude of two of its parameters (beta) and (gamma) are constrained on the basis of existing experimental data. New facilities such as (phi)-Factories are shown to be particularly adequate to study this generalization from quantum mechanics and to disentangle its parameters from other CPT violating perturbations of the kaon system.

  7. Adsorbate-induced quantum Hall system probed by scanning tunneling spectroscopy combined with transport measurements

    Energy Technology Data Exchange (ETDEWEB)

    Masutomi, Ryuichi, E-mail: masutomi@phys.s.u-tokyo.ac.jp; Okamoto, Tohru [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-06-22

    An adsorbate-induced quantum Hall system at the cleaved InSb surfaces is investigated in magnetic fields up to 14 T using low-temperature scanning tunneling microscopy and spectroscopy combined with transport measurements. We show that an enhanced Zeeman splitting in the Shubnikov-de Haas oscillations is explained by an exchange enhancement of spin splitting and potential disorder, both of which are obtained from the spatially averaged density of states (DOS). Moreover, the Altshuler–Aronov correlation gap is observed in the spatially averaged DOS at 0 T.

  8. The Matrix: a new tool for probing the whisker-to-barrel system with natural stimuli.

    Science.gov (United States)

    Jacob, Vincent; Estebanez, Luc; Le Cam, Julie; Tiercelin, Jean-Yves; Parra, Patrick; Parésys, Gérard; Shulz, Daniel E

    2010-05-30

    The whisker to barrel system in rodents has become one of the major models for the study of sensory processing. Several tens of whiskers (or vibrissae) are distributed in a regular manner on both sides of the snout. Many tactile discrimination tasks using this system need multiple contacts with more than one whisker to be solved. With the aim of mimicking those multi-whisker stimuli during electrophysiological recordings, we developed a novel mechanical stimulator composed of 24 independent multi-directional piezoelectric benders adapted to the five rows and the five caudal arcs of the rat whisker pad. The most widely used technology for producing mechanical deflections of the whiskers is based on piezoelectric benders that display a non-linear behavior when driven with high frequency input commands and, if not compensated, show high unwanted ringing at particular resonance frequencies. If not corrected, this non-linear behavior precludes the application of high frequency deflections and the study of cortical responses to behaviorally relevant stimuli. To cope with the ringing problem, a mechanical and a software based solutions have been developed. With these corrections, the upper bound of the linear range of the bender is increased to 1 kHz. This new device allows the controlled delivery of large scale natural patterns of whisker deflections characterized by rapid high frequency vibrations of multiple whiskers. (c) 2010 Elsevier B.V. All rights reserved.

  9. A supersonic gas injection system for fuelling and probing fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Collis, Scott [Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Howard, John [Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Blackwell, Boyd [Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Carlsson, Peter [Department of Physics and Engineering Physics, Chalmers University of Technology, SE-412 96 Goeteburg (Sweden); Abelsson, Mattias [Department of Physics and Engineering Physics, Chalmers University of Technology, SE-412 96 Goeteburg (Sweden); Powell, Ben [Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200 (Australia)

    2006-11-01

    The large gas reservoir surrounding the H-1NF plasma leads to difficulties in achieving the density control required to maximize the plasma temperature. We have designed and tested an alternative fuelling system which uses a double conical nozzle to generate a directed flow of particles into the plasma without adding to the gas inventory in the rest of the vacuum vessel. By using a closed plenum at a programmable pressure and a piezo-electric valve, the particle flux can be dynamically changed in a controlled and quantitative manner. Measurements of the gas jet using constant temperature hot wire anemometry show that, for plenum pressures between 500 and 1000 Torr, the particle injection rate (helium) ranges between 2 x 10{sup 20} and 4 x 10{sup 20} s{sup -1} with half-cone angles between 5 deg. and 20 deg. The system has been installed on the H-1NF device and first plasma results indicate localized gas injection consistent with test tank anemometry measurements.

  10. Mouse hypothalamic growth hormone-releasing hormone and somatostatin responses to probes of signal transduction systems.

    Science.gov (United States)

    Sato, M; Downs, T R; Frohman, L A

    1993-01-01

    Signal transduction mechanisms involved in mouse growth hormone-releasing hormone (GRH) and somatostatin (SRIH) release were investigated using an in vitro perifusion system. Hypothalamic fragments were exposed to depolarizing agents, protein kinase A and C activators, and a calcium ionophore. The depolarizing agents, KCl (60 mM) and veratridine (50 microM), induced similar patterns of GRH and SRIH release. Somatostatin release in response to both agents was twofold greater than that of GRH. Forskolin (10 microM and 100 microM), an adenylate cyclase activator, stimulated both GRH and SRIH release, though with different secretory profiles. The SRIH response was prolonged and persisted beyond removal of the drug from the system, while the GRH response was brief, ending even prior to forskolin removal. Neither GRH nor SRIH were stimulated by 1,9-dideoxy-forskolin (100 microM), a forskolin analog with cAMP-independent actions. A23187 (5 microM), a calcium ionophore, stimulated the release of SRIH to a much greater extent than that of GRH. The GRH and SRIH secretory responses to PMA (1 microM), a protein kinase C activator, were similar, though delayed. The results suggest that 1) GRH and SRIH secretion are regulated by both protein kinase A and C pathways, and 2) depolarizing agents are important for the release of both hormones.

  11. Study of PEGylated lipid layers as a model for PEGylated liposome surfaces: molecular dynamics simulation and Langmuir monolayer studies.

    Science.gov (United States)

    Stepniewski, Michał; Pasenkiewicz-Gierula, Marta; Róg, Tomasz; Danne, Reinis; Orlowski, Adam; Karttunen, Mikko; Urtti, Arto; Yliperttula, Marjo; Vuorimaa, Elina; Bunker, Alex

    2011-06-21

    We have combined Langmuir monolayer film experiments and all-atom molecular dynamics (MD) simulation of a bilayer to study the surface structure of a PEGylated liposome and its interaction with the ionic environment present under physiological conditions. Lipids that form both gel and liquid-crystalline membranes have been used in our study. By varying the salt concentration in the Langmuir film experiment and including salt at the physiological level in the simulation, we have studied the effect of salt ions present in the blood plasma on the structure of the poly(ethylene glycol) (PEG) layer. We have also studied the interaction between the PEG layer and the lipid bilayer in both the liquid-crystalline and gel states. The MD simulation shows two clear results: (a) The Na(+) ions form close interactions with the PEG oxygens, with the PEG chains forming loops around them and (b) PEG penetrates the lipid core of the membrane for the case of a liquid-crystalline membrane but is excluded from the tighter structure of the gel membrane. The Langmuir monolayer results indicate that the salt concentration affects the PEGylated lipid system, and these results can be interpreted in a fashion that is in agreement with the results of our MD simulation. We conclude that the currently accepted picture of the PEG surface layer acting as a generic neutral hydrophilic polymer entirely outside the membrane, with its effect explained through steric interactions, is not sufficient. The phenomena we have observed may affect both the interaction between the liposome and bloodstream proteins and the liquid-crystalline-gel transition and is thus relevant to nanotechnological drug delivery device design.

  12. Improved performance of PACE 2 with modified collection system in combination with probe competition assay for detection of Chlamydia trachomatis in urethral specimens from males

    NARCIS (Netherlands)

    J.A.J.W. Kluytmans (Jan); W.H.F. Goessens (Wil); J.H. van Rijsoort-Vos; H.G.M. Niesters (Bert); E. Stolz (Ernst)

    1994-01-01

    textabstractThe Gen-Probe PACE 2 assay (GP) in combination with a modified collection system was compared with cell culture (CC) for the detection of Chlamydia trachomatis in urethral specimens from males. Analysis of discordant results was performed by PCR. The modific

  13. COMPARISON OF GEOPROBE PRT AND AMS GVP SOIL-GAS SAMPLING SYSTEMS WITH DEDICATED VAPOR PROBES IN SANDY SOILS AT THE RAYMARK SUPERFUND SITE

    Science.gov (United States)

    A study was conducted near the Raymark Superfund Site in Stratford, Connecticut to compare results of soil-gas sampling using dedicated vapor probes, a truck-mounted direct-push technique - the Geoprobe Post-Run-Tubing (PRT) system, and a hand-held rotary hammer technique - the A...

  14. Amphibole megacrysts as a probe into the deep plumbing system of Merapi volcano, Central Java, Indonesia

    Science.gov (United States)

    Peters, Stefan T. M.; Troll, Valentin R.; Weis, Franz A.; Dallai, Luigi; Chadwick, Jane P.; Schulz, Bernhard

    2017-04-01

    Amphibole has been discussed to potentially represent an important phase during early chemical evolution of arc magmas, but is not commonly observed in eruptive arc rocks. Here, we present an in-depth study of metastable calcic amphibole megacrysts in basaltic andesites of Merapi volcano, Indonesia. Radiogenic Sr and Nd isotope compositions of the amphibole megacrysts overlap with the host rock range, indicating that they represent antecrysts to the host magmas rather than xenocrysts. Amphibole-based barometry suggests that the megacrysts crystallised at pressures of >500 MPa, i.e., in the mid- to lower crust beneath Merapi. Rare-earth element concentrations, in turn, require the absence of magmatic garnet in the Merapi feeding system and, therefore, place an uppermost limit for the pressure of amphibole crystallisation at ca. 800 MPa. The host magmas of the megacrysts seem to have fractionated significant amounts of amphibole and/or clinopyroxene, because of their low Dy/Yb ratios relative to the estimated compositions of the parent magmas to the megacrysts. The megacrysts' parent magmas at depth may thus have evolved by amphibole fractionation, in line with apparently coupled variations of trace element ratios in the megacrysts, such as e.g., decreasing Zr/Hf with Dy/Yb. Moreover, the Th/U ratios of the amphibole megacrysts decrease with increasing Dy/Yb and are lower than Th/U ratios in the basaltic andesite host rocks. Uranium in the megacrysts' parent magmas, therefore, may have occurred predominantly in the tetravalent state, suggesting that magmatic fO2 in the Merapi plumbing system increased from below the FMQ buffer in the mid-to-lower crust to 0.6-2.2 log units above it in the near surface environment. In addition, some of the amphibole megacrysts experienced dehydrogenation (H2 loss) and/or dehydration (H2O loss), as recorded by their variable H2O contents and D/ H and Fe3+/Fe2+ ratios, and the release of these volatile species into the shallow plumbing

  15. Langmuir and Langmuir-Blodgett films of amphiphilic hexa-peri-hexabenzocoronene: New phase transitions and electronic properties controlled by pressure

    DEFF Research Database (Denmark)

    Reitzel, N.; Hassenkam, T.; Balashev, K.;

    2001-01-01

    We present the synthesis as well as the structural and electronic properties of an amphiphilic derivative of hexaalkylhexa-peri-hexabenzocoronene (HBC), which contains one alkyl substituent that is terminated with a carboxylic acid group. The molecules form well-defined Langmuir films when spread...

  16. Engineered red blood cells as carriers for systemic delivery of a wide array of functional probes.

    Science.gov (United States)

    Shi, Jiahai; Kundrat, Lenka; Pishesha, Novalia; Bilate, Angelina; Theile, Chris; Maruyama, Takeshi; Dougan, Stephanie K; Ploegh, Hidde L; Lodish, Harvey F

    2014-07-15

    We developed modified RBCs to serve as carriers for systemic delivery of a wide array of payloads. These RBCs contain modified proteins on their plasma membrane, which can be labeled in a sortase-catalyzed reaction under native conditions without inflicting damage to the target membrane or cell. Sortase accommodates a wide range of natural and synthetic payloads that allow modification of RBCs with substituents that cannot be encoded genetically. As proof of principle, we demonstrate site-specific conjugation of biotin to in vitro-differentiated mouse erythroblasts as well as to mature mouse RBCs. Thus modified, RBCs remain in the bloodstream for up to 28 d. A single domain antibody attached enzymatically to RBCs enables them to bind specifically to target cells that express the antibody target. We extend these experiments to human RBCs and demonstrate efficient sortase-mediated labeling of in vitro-differentiated human reticulocytes.

  17. Probing the history of Solar System through the cratering records on Vesta and Ceres

    Science.gov (United States)

    Magni, G.; Turrini, D.; Coradini, A.; Fonte, S.

    2009-04-01

    Dawn mission will provide detailed images of Vesta and Ceres surfaces and supply crucial information to constrain their mineralogical and elemental composition through VIR, its imaging spectrometer. Thanks to these data, we will be able to study in depth the crater record on the surface of both Vesta and Ceres. We discuss the cratering process of Vesta and Ceres at the time of Jupiter formation. In our model we consider Jupiter's gas accretion and displacement due to angular momentum exchange with the surrounding nebula. The gas accretion model used has been described in Coradini et al. (2004). Jupiter's migration has been included to estimate the effect of increasing displacements. To explore the early collisional history of Vesta and Ceres we simulated the dynamical evolution of a section of the young Solar System at the time of Jupiter's core formation and the subsequent accretion of the gaseous envelope. Our scheme of the forming Solar System was composed of the Sun, the accreting Jupiter and a swarm of massless particles representing the planetesimals. The massless particles were initially distributed into a limited spatial region, which has been chosen after a set of numerical experiments aiming to determine the region of Solar System influenced by the forming Jupiter on the considered timespan to optimise the computational requirements. We didn't model the giant planet formation process directly through hydrodynamical computations. In our simulations we reproduced the evolution of Jupiter through an analytical approach: the parameters on which the model was based, however, were derived from the results of hydrodynamical simulations performed with the code described in Coradini et al. (2004). During the dynamical evolution of our template of the Solar System we evaluated through a statistic approach the probability of planetesimals impacting against Vesta and Ceres. In the following subsections we will describe in detail the initial conditions and the

  18. Optical and microwave communications system conceptual design for a realistic interstellar probe

    Science.gov (United States)

    Boone, Bradley G.; Bokulic, Robert S.; Andrews, G. B.; McNutt, Ralph L., Jr.; Dagalakis, Nicholas G.

    2002-12-01

    The concept of a realistic interstellar explorer has been addressed by the Johns Hopkins University Applied Physics Laboratory with support from the NASA Institute for Advanced Concepts. This paper discusses the requirements, conceptual design and technology issues associated with the optical and RF communications systems envisioned for this mission, in which the spacecraft has a projected range of 1000 AU. Well before a range of 100 AU interactive control of the spacecraft becomes nearly impossible, necessitating a highly autonomous craft and one-way communications to Earth. An approach is taken in which the role of the optical downlink is emphasized for data transfer and that of the microwave uplink emphasized for commands. The communication system is strongly influenced by the large distances involved, the high velocities as well as the requirements for low-mass, low prime power, reliability, and spacecraft autonomy. An optical terminal concept is described that has low mass and prime power in a highly integrated and novel architecture, but new technologies are needed to meet the range, mass, and power requirements. These include high-power, 'wall-plug' efficient diode-pumped fiber lasers; compact, lightweight, and low-power micro-electromechanical (MEM) beam steering elements; and lightweight diffractive quasi-membrane optics. In addition, a very accurate star tracking mechanism must be fully integrated with the laser downlink to achieve unprecedented pointing accuracy. The essential optical, structural, mechanical, and electronic subsystems are described that meet the mission requirements, and the key features of advanced technologies that need to be developed are discussed. The conclusion from this preliminary effort is that an optical communications downlink out to 1000 astronomical units is within the realm of technical feasibility in the next 5-10 years if the identified technical risks for the new technologies can be retired.

  19. Plasma diagnostics by means of electric probes; Diagnostico del plasma por medio de sondas electricas

    Energy Technology Data Exchange (ETDEWEB)

    Colunga S, S

    1991-04-15

    In this work a summary of the classical theoretical models to interpret the characteristic curve of a Langmuir electric probe placed in a plasma without magnetic field and with the one is made. The methodology for the electron temperature calculation and the density of the plasma in both cases is given, starting from the characteristic curve of the probe, as well as the approaches for the correct application of this diagnostic method of the plasma. (Author)

  20. Pollution Probe.

    Science.gov (United States)

    Chant, Donald A.

    This book is written as a statement of concern about pollution by members of Pollution Probe, a citizens' anti-pollution group in Canada. Its purpose is to create public awareness and pressure for the eventual solution to pollution problems. The need for effective government policies to control the population explosion, conserve natural resources,…