Science.gov

Sample records for linear parallel-plate active

  1. Nondimensional analysis of semi-active electrorheological and magnetorheological dampers using approximate parallel plate models

    NASA Astrophysics Data System (ADS)

    Wereley, Norman M.; Pang, Li

    1998-10-01

    We develop nonlinear quasi-steady electrorheological (ER) and magnetorheological (MR) damper models using an idealized Bingham plastic shear flow mechanism. Dampers with cylindrical geometry are investigated, where damping forces are developed in an annular bypass via Couette (shear mode), Poiseuille (flow mode) flow, or combined Couette and Poiseiulle flow (mixed mode). Models are based on parallel plate or rectangular duct geometry, and are compared to our prior 1D axisymmetric models. Three nondimensional groups are introduced for damper analysis, namely, the Bingham number, 0964-1726/7/5/015/img1, the nondimensional plug thickness, 0964-1726/7/5/015/img2, and the area coefficient defined as the ratio of the piston head area, 0964-1726/7/5/015/img3, to the cross-sectional area of the annular bypass, 0964-1726/7/5/015/img4. The approximate parallel plate analysis compares well with the 1D axisymmetric analysis when the Bingham number is small, or 0964-1726/7/5/015/img5, or the nondimensional plug thickness is small, 0964-1726/7/5/015/img6. Damper performance is characterized in terms of the damping coefficient, which is the ratio of the equivalent viscous damping constant, 0964-1726/7/5/015/img7, to the Newtonian viscous damping constant, C. In shear mode, the damping coefficient is a linear function of the Bingham number. In flow mode, the damping coefficient is a function of the nondimensional plug thickness only. For the mixed mode damper, the damping coefficient reduces to that for the flow mode case when the area coefficient is large. The quasi-steady damping coefficient versus nondimensional plug thickness diagram is experimentally validated using measured 10 Hz hysteresis cycles for a electrorheological mixed mode damper.

  2. Identification of wheat varieties with a parallel-plate capacitance sensor using fisher linear discriminant analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fisher’s linear discriminant (FLD) models for wheat variety classification were developed and validated. The inputs to the FLD models were the capacitance (C), impedance (Z), and phase angle ('), measured at two frequencies. Classification of wheat varieties was obtained as output of the FLD mod...

  3. ASSEMBLY OF PARALLEL PLATES

    DOEpatents

    Groh, E.F.; Lennox, D.H.

    1963-04-23

    This invention is concerned with a rigid assembly of parallel plates in which keyways are stamped out along the edges of the plates and a self-retaining key is inserted into aligned keyways. Spacers having similar keyways are included between adjacent plates. The entire assembly is locked into a rigid structure by fastening only the outermost plates to the ends of the keys. (AEC)

  4. True Shear Parallel Plate Viscometer

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin; Kaukler, William

    2010-01-01

    This viscometer (which can also be used as a rheometer) is designed for use with liquids over a large temperature range. The device consists of horizontally disposed, similarly sized, parallel plates with a precisely known gap. The lower plate is driven laterally with a motor to apply shear to the liquid in the gap. The upper plate is freely suspended from a double-arm pendulum with a sufficiently long radius to reduce height variations during the swing to negligible levels. A sensitive load cell measures the shear force applied by the liquid to the upper plate. Viscosity is measured by taking the ratio of shear stress to shear rate.

  5. Fringe Capacitance of a Parallel-Plate Capacitor.

    ERIC Educational Resources Information Center

    Hale, D. P.

    1978-01-01

    Describes an experiment designed to measure the forces between charged parallel plates, and determines the relationship among the effective electrode area, the measured capacitance values, and the electrode spacing of a parallel plate capacitor. (GA)

  6. Multipactor saturation in parallel-plate waveguides

    SciTech Connect

    Sorolla, E.; Mattes, M.

    2012-07-15

    The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. The impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high.

  7. Parallel-Plate Electrostatic Dual Mass Oscillator

    SciTech Connect

    Allen, James J.; Dyck, Christopher W.; Huber, Robert J.

    1999-07-22

    A surface-micromachined two-degree-of-freedom system that was driven by parallel-plate actuation at antiresonance was demonstrated. The system consisted of an absorbing mass connected by folded springs to a drive mass. The system demonstrated substantial motion amplification at antiresonance. The absorber mass amplitudes were 0.8-0.85 pm at atmospheric pressure while the drive mass amplitudes were below 0.1 pm. Larger absorber mass amplitudes were not possible because of spring softening in the drive mass springs. Simple theory of the dual-mass oscillator has indicated that the absorber mass may be insensitive to limited variations in strain and damping. This needs experimental verification. Resonant and antiresonant frequencies were measured and compared to the designed values. Resonant frequency measurements were difficult to compare to the design calculations because of time-varying spring softening terms that were caused by the drive configuration. Antiresonant frequency measurements were close to the design value of 5.1 kHz. The antiresonant frequency was not dependent on spring softening. The measured absorber mass displacement at antiresonance was compared to computer simulated results. The measured value was significantly greater, possibly due to neglecting fringe fields in the force expression used in the simulation.

  8. Particle Transport in Parallel-Plate Reactors

    SciTech Connect

    Rader, D.J.; Geller, A.S.

    1999-08-01

    A major cause of semiconductor yield degradation is contaminant particles that deposit on wafers while they reside in processing tools during integrated circuit manufacturing. This report presents numerical models for assessing particle transport and deposition in a parallel-plate geometry characteristic of a wide range of single-wafer processing tools: uniform downward flow exiting a perforated-plate showerhead separated by a gap from a circular wafer resting on a parallel susceptor. Particles are assumed to originate either upstream of the showerhead or from a specified position between the plates. The physical mechanisms controlling particle deposition and transport (inertia, diffusion, fluid drag, and external forces) are reviewed, with an emphasis on conditions encountered in semiconductor process tools (i.e., sub-atmospheric pressures and submicron particles). Isothermal flow is assumed, although small temperature differences are allowed to drive particle thermophoresis. Numerical solutions of the flow field are presented which agree with an analytic, creeping-flow expression for Re < 4. Deposition is quantified by use of a particle collection efficiency, which is defined as the fraction of particles in the reactor that deposit on the wafer. Analytic expressions for collection efficiency are presented for the limiting case where external forces control deposition (i.e., neglecting particle diffusion and inertia). Deposition from simultaneous particle diffusion and external forces is analyzed by an Eulerian formulation; for creeping flow and particles released from a planar trap, the analysis yields an analytic, integral expression for particle deposition based on process and particle properties. Deposition from simultaneous particle inertia and external forces is analyzed by a Lagrangian formulation, which can describe inertia-enhanced deposition resulting from particle acceleration in the showerhead. An approximate analytic expression is derived for particle

  9. The temperature and pressure in the plasma parallel plate accelerator

    NASA Astrophysics Data System (ADS)

    Koníček, P.; Maloch, J.

    1993-06-01

    This paper presents the results of plasma temperature and pressure calculations in the parallel plate accelerator during the accelerating process. The plasma pressure is calculated by means in Dalton's law.

  10. Parallel plate ionization chamber in low pressure helium gas

    NASA Astrophysics Data System (ADS)

    Frank, D.; Heinz, A.; Winkler, R.; Qian, J.; Casperson, R. J.; Terry, J. R.

    2007-10-01

    A parallel plate ionization chamber was constructed for beam intensity monitoring. The chamber is placed in a gas-filled volume 1.5m upstream from the gas-filled separator SASSYER. Its output current will be used to determine absolute reaction cross sections. In a dedicated test experiment with a 100 MeV ^32S beam and an applied potential of 300V, the signal current had an average standard deviation of 0.4%, and demonstrated a linear relationship (R^2 = 0.9894) with the beam intensity. Also, at an intensity of 6 particle nanoamperes, the current exhibited a linear dependence (R^2 = 0.9813) on voltage, indicating that the chamber was operating in the proportional counter region. Our results agreed well with predictions made using extrapolated Townsend coefficients, though we observed a constant systematic and constant deviation between these estimates and our output current. This work was supported under US DOE grant number DE-FG0291ER-40609 and the Yale College Dean's Fellowship for Research in the Sciences.

  11. Do transform faults parallel plate motion?

    NASA Astrophysics Data System (ADS)

    Mishra, J. K.; Gordon, R. G.; Demets, C.; Argus, D.

    2009-12-01

    A central principle of plate tectonics is that relative plate motion is parallel to transform faults. Several workers have convincingly argued, however, that transform fault valleys widen with age due to horizontal thermal contraction of the lithosphere [Collette 1974; Roest et al 1986 ; Sandwell 1986]. If so, then the transform fault zone, which is the locus of active strike-slip faulting in a transform fault, may not be parallel to the direction of relative plate motion, but parallel to the relative velocity of the walls of the transform valley. Here we apply a recent model for horizontal contraction of oceanic lithosphere as a function of age [Kumar & Gordon 2009] to calculate this bias in transform azimuth as a function of offset, spreading rate, and ridge length, with slightly different formulations for crenelate and stepping mid-ocean ridge segments. The calculated bias increases with increasing length of ridge segments between transform faults and decreases with increasing offset of ridge segments along transform faults. We used the calculated bias to estimate corrections of azimuths of transform faults on eight plate boundaries from the MORVEL data set [DeMets, Argus, & Gordon, 2009]. The largest correction is 2.3 degrees, but the median correction is merely 0.2 degrees. We express the null hypothesis (no thermal contraction) and our hypothesis (thermal contraction as predicted by Kumar and Gordon [2009]), in terms of a parameter α, which is zero for no thermal contraction and 1 for predicted thermal contraction. When the results for the 8 plate pairs are combined, we find that α = 1.1 ± 0.7 (95% confidence limits), thus excluding the null hypothesis (no thermal contraction), but consistent with the hypothesis of horizontal thermal contraction.

  12. Do transform faults parallel plate motion?

    NASA Astrophysics Data System (ADS)

    Mishra, J. K.; Gordon, R. G.

    2008-12-01

    A central principle of plate tectonics is that relative plate motion is parallel to transform faults. Several workers have convincingly argued, however, that transform fault valleys widen with age due to horizontal thermal contraction of the lithosphere (Collette 1974; Roest et al 1986 ; Sandwell 1986). If so, then the transform fault zone, which is the locus of active strike-slip faulting in a transform fault, is not parallel to the direction of plate motion. It is also affected by the ridge-parallel contraction of the lithosphere and is biased by a predictable amount. Here we apply a recent model for horizontal contraction of oceanic lithosphere as a function of age (Kumar & Gordon 2008) to calculate this bias as a function of offset, spreading rate, and ridge length, with slightly different formulations for crenelate and stepping mid-ocean ridge segments. The bias causes right-slipping transform faults to be counter-clockwise of the true plate motion direction while left-slipping transform faults are clockwise of the true plate motion direction. The bias is larger for longer ridge segments, smaller offsets, and slower spreading. The bias ranges in magnitude from about 0.1 degree to 1.5 degrees for stepping boundaries and 0.2 degree to 3 degrees for crenelate boundaries. Application of the bias correction to NUVEL-1 transform fault azimuths about the Rodrigues, Juan Fernandez, Galapagos, and Bouvet triple junctions improves the closure of the triple junction in the first three cases but makes it slightly worse in the fourth case. Additional applications will be presented.

  13. Parallel Plate System for Collecting Data Used to Determine Viscosity

    NASA Technical Reports Server (NTRS)

    Kaukler, William (Inventor); Ethridge, Edwin C. (Inventor)

    2013-01-01

    A parallel-plate system collects data used to determine viscosity. A first plate is coupled to a translator so that the first plate can be moved along a first direction. A second plate has a pendulum device coupled thereto such that the second plate is suspended above and parallel to the first plate. The pendulum device constrains movement of the second plate to a second direction that is aligned with the first direction and is substantially parallel thereto. A force measuring device is coupled to the second plate for measuring force along the second direction caused by movement of the second plate.

  14. Parallel-Plate Acoustic Absorbers For Hot Environments

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph; Parrot, Tony L.

    1995-01-01

    Stacking patterns and materials chosen to suppress noise. Acoustic liners incorporating parallel-plate absorbing elements proposed for use in suppressing broadband aerodynamic noise originating in flows of hot gases in ducts. One potential application lies in suppressing noise generated in exhaust-jet mixer/ejectors in propulsion system of proposed High-Speed Civil Transport. In addition, such absorbers useful in any situation in which high temperature limits use of such conventional resonant acoustic-liner materials as perforated face sheets bonded to honey-comb-core panels.

  15. Excitation of a Parallel Plate Waveguide by an Array of Rectangular Waveguides

    NASA Technical Reports Server (NTRS)

    Rengarajan, Sembiam

    2011-01-01

    This work addresses the problem of excitation of a parallel plate waveguide by an array of rectangular waveguides that arises in applications such as the continuous transverse stub (CTS) antenna and dual-polarized parabolic cylindrical reflector antennas excited by a scanning line source. In order to design the junction region between the parallel plate waveguide and the linear array of rectangular waveguides, waveguide sizes have to be chosen so that the input match is adequate for the range of scan angles for both polarizations. Electromagnetic wave scattered by the junction of a parallel plate waveguide by an array of rectangular waveguides is analyzed by formulating coupled integral equations for the aperture electric field at the junction. The integral equations are solved by the method of moments. In order to make the computational process efficient and accurate, the method of weighted averaging was used to evaluate rapidly oscillating integrals encountered in the moment matrix. In addition, the real axis spectral integral is evaluated in a deformed contour for speed and accuracy. The MoM results for a large finite array have been validated by comparing its reflection coefficients with corresponding results for an infinite array generated by the commercial finite element code, HFSS. Once the aperture electric field is determined by MoM, the input reflection coefficients at each waveguide port, and coupling for each polarization over the range of useful scan angles, are easily obtained. Results for the input impedance and coupling characteristics for both the vertical and horizontal polarizations are presented over a range of scan angles. It is shown that the scan range is limited to about 35 for both polarizations and therefore the optimum waveguide is a square of size equal to about 0.62 free space wavelength.

  16. Numerical Simulation of Flow Field Within Parallel Plate Plastometer

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    2002-01-01

    Parallel Plate Plastometer (PPP) is a device commonly used for measuring the viscosity of high polymers at low rates of shear in the range 10(exp 4) to 10(exp 9) poises. This device is being validated for use in measuring the viscosity of liquid glasses at high temperatures having similar ranges for the viscosity values. PPP instrument consists of two similar parallel plates, both in the range of 1 inch in diameter with the upper plate being movable while the lower one is kept stationary. Load is applied to the upper plate by means of a beam connected to shaft attached to the upper plate. The viscosity of the fluid is deduced from measuring the variation of the plate separation, h, as a function of time when a specified fixed load is applied on the beam. Operating plate speeds measured with the PPP is usually in the range of 10.3 cm/s or lower. The flow field within the PPP can be simulated using the equations of motion of fluid flow for this configuration. With flow speeds in the range quoted above the flow field between the two plates is certainly incompressible and laminar. Such flows can be easily simulated using numerical modeling with computational fluid dynamics (CFD) codes. We present below the mathematical model used to simulate this flow field and also the solutions obtained for the flow using a commercially available finite element CFD code.

  17. Characterization tests of a new parallel plate ionization chamber for use in electron beams

    NASA Astrophysics Data System (ADS)

    Nonato, Fernanda B. C.; Sakuraba, Roberto K.; da Cruz, José Carlos; Caldas, Linda V. E.

    2014-11-01

    Linear accelerators with electron beams are used in several Brazilian hospitals. Consequently, there is an increasing demand for parallel-plate ionization chambers, to be utilized for dosimetry of electron beams. In Brazil, the commercial ionization chambers utilized are imported. The ionization chambers have usually a simple construction, using different materials and geometries. A homemade ionization chamber was developed to be used in electron beams of linear accelerator. The ionization chamber body is made of acrylic and the collecting electrode is painted with graphite powder mixed with nail polish. Several tests were applied, and the results showed values better than the limits established by the international recommendations, except for the polarity effect test, but the response of the developed ionization chamber, for this test, is similar in relation to the response of other commercial ionization chambers from the literature.

  18. A proposed experimental search for chameleons using asymmetric parallel plates

    NASA Astrophysics Data System (ADS)

    Burrage, Clare; Copeland, Edmund J.; Stevenson, James A.

    2016-08-01

    Light scalar fields coupled to matter are a common consequence of theories of dark energy and attempts to solve the cosmological constant problem. The chameleon screening mechanism is commonly invoked in order to suppress the fifth forces mediated by these scalars, sufficiently to avoid current experimental constraints, without fine tuning. The force is suppressed dynamically by allowing the mass of the scalar to vary with the local density. Recently it has been shown that near future cold atoms experiments using atom-interferometry have the ability to access a large proportion of the chameleon parameter space. In this work we demonstrate how experiments utilising asymmetric parallel plates can push deeper into the remaining parameter space available to the chameleon.

  19. Pre-distorted sinewave-driven parallel-plate electrostatic actuator for harmonic displacement

    NASA Astrophysics Data System (ADS)

    de Graaf, G.; Mol, L.; Rocha, L. A.; Cretu, E.; Wolffenbuttel, R. F.

    2005-07-01

    Harmonic displacement of a parallel-plate electrostatic actuator up to 50% of the static pull-in displacement has been achieved despite the non-linear voltage-to-displacement function using a driving voltage with a pre-distorted waveform. The microstructure is fabricated in an epi-poly process and the circuit is implemented in a CMOS process and designed for operation of the MEMS in a frequency range up to 1 kHz. The pre-distorted waveform is synthesized using 16 samples per period with 16 non-uniformly spaced quantization levels, using a ladder with accurately scaled resistors. Harmonic actuation has been demonstrated with 34 dB reduction of second-order distortion compared to systems with sinusoidal actuation. The residual second harmonic content in the harmonic displacement is typically -42 dB.

  20. Terahertz microfluidic sensing using a parallel-plate waveguide sensor.

    PubMed

    Astley, Victoria; Reichel, Kimberly; Mendis, Rajind; Mittleman, Daniel M

    2012-01-01

    Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials. Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides, asymmetric split-ring resonators, and photonic band gap structures integrated into parallel-plate waveguides. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc. The sensor design we use here is based on a simple parallel-plate waveguide. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE1) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index. Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can

  1. Aperture-based antihydrogen gravity experiment: Parallel plate geometry

    SciTech Connect

    Rocha, J. R.; Hedlof, R. M.; Ordonez, C. A.

    2013-10-15

    An analytical model and a Monte Carlo simulation are presented of an experiment that could be used to determine the direction of the acceleration of antihydrogen due to gravity. The experiment would rely on methods developed by existing antihydrogen research collaborations. The configuration consists of two circular, parallel plates that have an axis of symmetry directed away from the center of the earth. The plates are separated by a small vertical distance, and include one or more pairs of circular barriers that protrude from the upper and lower plates, thereby forming an aperture between the plates. Antihydrogen annihilations that occur just beyond each barrier, within a “shadow” region, are asymmetric on the upper plate relative to the lower plate. The probability for such annihilations is determined for a point, line and spheroidal source of antihydrogen. The production of 100,000 antiatoms is predicted to be necessary for the aperture-based experiment to indicate the direction of free fall acceleration of antimatter, provided that antihydrogen is produced within a sufficiently small antiproton plasma at a temperature of 4 K.

  2. Parallel-plate fluid flow systems for bone cell stimulation.

    PubMed

    Huesa, Carmen; Helfrich, Miep H; Aspden, Richard M

    2010-04-19

    Bone responds to changes in its mechanical environment, but the mechanisms by which it does so are poorly understood. One hypothesis of mechanosensing in bone states that osteocytes can sense the flow of fluid through the canalicular system. To study this in vitro a number of fluid flow devices have been designed in which cells are placed between parallel plates in sealed chambers. Fluid flows through the chambers at controlled rates, most commonly driven by a peristaltic pump. In addition to fluid flow, high pressures have been observed in these chambers, but the effect of this on the cellular responses has generally been ignored or considered irrelevant, something challenged by recent cellular experiments using pressure only. We have, therefore, devised a system in which we can considerably reduce the pressure while maintaining the flow rate to enable study of their effects individually and in combination. As reducing pressure also reduces the risk of leaks in flow chambers, our system is suitable for real-time microscopical experiments. We present details of the new systems and of experiments with osteoblasts to illustrate the effects of fluid flow with and without additional pressure on the translocation of beta-catenin to the nucleus.

  3. Wave propagation in parallel-plate waveguides filled with nonlinear left-handed material

    NASA Astrophysics Data System (ADS)

    Burhan, Zamir; Rashid, Ali

    2011-01-01

    A theoretical investigation of field components for transverse electric mode in the parallel-plate waveguides has been studied. In this analysis two different types of waveguide structures have been discussed, i.e., (a) normal good/perfect conducting parallel-plate waveguide filled with nonlinear left-handed material and (b) high-temperature-superconducting parallel-plate waveguide filled with nonlinear left-handed material. The dispersion relations of transverse electric mode have also been discussed for these two types of waveguide structures.

  4. Mesoscale MEMS motion transformer and amplifier electrostatically actuated by parallel plate electrodes

    NASA Astrophysics Data System (ADS)

    Gerson, Y.; Nachmias, T.; Maimon, R.; Krylov, S.

    2015-05-01

    We report on the design, fabrication and characterization of a mesoscale microelectromechanical motion transformer and amplifier with integrated actuation. The device incorporates an electrostatic transducer with multiple parallel plate electrodes and an elastic suspension realized as a compliant mechanism, which converts small linear motion of the transducer into mechanically amplified angular motion of a rotating lever. By combining highly efficient small-gap actuation with the motion amplification the device is designed to provide a large, more than 60 µm, lever tip displacement along with a calculated blocking force increasing from the initial value of 0.8 mN up to 26 mN in the maximal stroke configuration when actuated at 150 V. The devices were fabricated from a silicon on insulator (SOI) wafer with (1 1 1) front surface orientation and a 150 µm thick device layer using deep reactive ion etching (DRIE) and their functionality was demonstrated experimentally. Good agreement between the results provided by finite elements analysis and the experimental data was observed. Our results demonstrate an ability to achieve both large displacements and high blocking forces in an electrostatically actuated mesoscale compliant mechanisms.

  5. Development of Parallel Plate Avalanche Counter (PPAC) for BigRIPS fragment separator

    NASA Astrophysics Data System (ADS)

    Kumagai, H.; Ohnishi, T.; Fukuda, N.; Takeda, H.; Kameda, D.; Inabe, N.; Yoshida, K.; Kubo, T.

    2013-12-01

    We have developed a position-sensitive Parallel Plate Avalanche Counter (PPAC), which has been used as a focal plane detector in the BigRIPS fragment separator and the subsequent RI-beam delivery lines at the RIKEN Nishina Center RI Beam Factory. The PPAC detector plays an important role not only in the tuning of the separator and delivery lines but also in the particle identification of rare isotope (RI) beams. The PPAC detector has a sensitive area of 240 mm × 150 mm, and the position information is obtained by a delay-line readout method. Being called double PPAC, it is composed of two full PPACs, each measuring the particle locus in two dimensions. High detection efficiency has been made possible by the twofold measurement using the double PPAC detector. The sensitivity uniformity is also found to be excellent. The root-mean-square position resolution is measured to be 0.25 mm using an α source, while the position linearity is as good as ±0.1 mm for the detector size of 240 mm. Characteristics, operating principles, specifications, performance and issues of the PPAC detector are presented, including its signal transmission system using optical fiber cables.

  6. Use of Adomian decomposition method in the study of parallel plate flow of a third grade fluid

    NASA Astrophysics Data System (ADS)

    Siddiqui, A. M.; Hameed, M.; Siddiqui, B. M.; Ghori, Q. K.

    2010-09-01

    In this paper, Adomian's decomposition method is used to solve non-linear differential equations which arise in fluid dynamics. We study basic flow problems of a third grade non-Newtonian fluid between two parallel plates separated by a finite distance. The technique of Adomian decomposition is successfully applied to study the problem of a non-Newtonian plane Couette flow, fully developed plane Poiseuille flow and plane Couette-Poiseuille flow. The results obtained show the reliability and efficiency of this analytical method. Numerical solutions are also obtained by solving non-linear ordinary differential equations using Chebyshev spectral method. We present a comparative study between the analytical solutions and numerical solutions. The analytical results are found to be in good agreement with numerical solutions which reveals the effectiveness and convenience of the Adomian decomposition method.

  7. Parallel-Plate Waveguide for Volume Radio Frequency Transmission in MRI

    PubMed Central

    Lu, Hai; Shang, Shuo; Wang, Shumin

    2015-01-01

    Purpose Radiofrequency coils in MRI are narrowband resonant structures. The high-quality factor makes their performance sensitive to loading and other operating conditions. We developed a new coil to provide volume transmit in a broad frequency band. Methods The proposed coil is a parallel-plate waveguide. When operating in the transverse electromagnetic mode, a uniform magnetic field is generated between the plates for imaging. The impedance of the transverse electromagnetic mode is matched by a broadband matching circuit. The two plates are actively driven with broadband Wilkinson power dividers and combiners. Re-entrant design is further applied to improve the overall efficiency. Results We developed a prototype of a coil to image the human forearm with a bandwidth of more than one octave. Its feasibility was demonstrated by proton imaging and phosphorous spectroscopy at 7T. Conclusions The proposed coil structure is compact and relatively easier to construct. It can be applied for volume radiofrequency transmit in MRI in a broad frequency band. PMID:25394268

  8. A comparison between orthogonal and parallel plating methods for distal humerus fractures: a prospective randomized trial.

    PubMed

    Lee, Sang Ki; Kim, Kap Jung; Park, Kyung Hoon; Choy, Won Sik

    2014-10-01

    With the continuing improvements in implants for distal humerus fractures, it is expected that newer types of plates, which are anatomically precontoured, thinner and less irritating to soft tissue, would have comparable outcomes when used in a clinical study. The purpose of this study was to compare the clinical and radiographic outcomes in patients with distal humerus fractures who were treated with orthogonal and parallel plating methods using precontoured distal humerus plates. Sixty-seven patients with a mean age of 55.4 years (range 22-90 years) were included in this prospective study. The subjects were randomly assigned to receive 1 of 2 treatments: orthogonal or parallel plating. The following results were assessed: operating time, time to fracture union, presence of a step or gap at the articular margin, varus-valgus angulation, functional recovery, and complications. No intergroup differences were observed based on radiological and clinical results between the groups. In our practice, no significant differences were found between the orthogonal and parallel plating methods in terms of clinical outcomes, mean operation time, union time, or complication rates. There were no cases of fracture nonunion in either group; heterotrophic ossification was found 3 patients in orthogonal plating group and 2 patients in parallel plating group. In our practice, no significant differences were found between the orthogonal and parallel plating methods in terms of clinical outcomes or complication rates. However, orthogonal plating method may be preferred in cases of coronal shear fractures, where posterior to anterior fixation may provide additional stability to the intraarticular fractures. Additionally, parallel plating method may be the preferred technique used for fractures that occur at the most distal end of the humerus.

  9. Broadband terahertz transmission within the symmetrical plastic film coated parallel-plate waveguide.

    PubMed

    Liu, Jiamin; Liang, Huawei; Zhang, Min; Su, Hong

    2014-09-10

    We report on the broadband terahertz (THz) transmission within a symmetrical plastic film coated parallel-plate waveguide. We theoretically study the antiresonant reflecting mechanism of the waveguide, and we find that the broadband THz wave can transmit in this waveguide with ultralow loss. The loss of the TM mode in this waveguide can be 4 orders of magnitude lower than the uncoated parallel-plate waveguide. The transmission bandwidth of this waveguide is up to 5.12 THz. We further show the mode field distributions which explain the loss mechanism.

  10. Parallel-plate heat pipe apparatus having a shaped wick structure

    DOEpatents

    Rightley, Michael J.; Adkins, Douglas R.; Mulhall, James J.; Robino, Charles V.; Reece, Mark; Smith, Paul M.; Tigges, Chris P.

    2004-12-07

    A parallel-plate heat pipe is disclosed that utilizes a plurality of evaporator regions at locations where heat sources (e.g. semiconductor chips) are to be provided. A plurality of curvilinear capillary grooves are formed on one or both major inner surfaces of the heat pipe to provide an independent flow of a liquid working fluid to the evaporator regions to optimize heat removal from different-size heat sources and to mitigate the possibility of heat-source shadowing. The parallel-plate heat pipe has applications for heat removal from high-density microelectronics and laptop computers.

  11. The polarizability and the capacitance change of a bounded object in a parallel plate capacitor

    NASA Astrophysics Data System (ADS)

    Kristensson, Gerhard

    2012-09-01

    A method for solving the change in capacitance (or charge) if an object is introduced in a parallel plate capacitor is developed. The integral representation of the potential is exploited in a systematic way to solve the potential everywhere inside the capacitor. In particular, the change in capacitance is extracted. The method shows similarities with the null field approach for solving dynamic problems.

  12. An adjustable parallel-plate capacitor instrument—Test of the theoretical capacitance formula

    NASA Astrophysics Data System (ADS)

    Wells, Beau; Baker, Emily; Farwell, Austin; Foster, Harrison; Gao, Xiaohan; Gruber, Benjamin; Jones, Erica; Vu, Dennis; Xu, Sonya; Ye, Jingbo

    2016-09-01

    We describe an adjustable parallel-plate capacitor apparatus designed for use in an undergraduate laboratory that permits precise variation of plate separation distances and overlap area. Two experiments are performed with the device to test the ideal capacitor formula derived from Gauss's Law. After correcting for edge effects and minor plate tilt, the device yields capacitance values within 3% of theoretical values.

  13. The restoring force on a dielectric in a parallel plate capacitor

    NASA Astrophysics Data System (ADS)

    Staunton, L. P.

    2014-09-01

    We investigate the restoring force on a dielectric slab being pulled from within the volume of a parallel plate capacitor connected to a battery. Using a conformal mapping to treat the fringing electric field exactly, we numerically obtain an expected Hooke's Law restoring force for small displacements, and a diminishing force for a displacement up to half the length of the dielectric.

  14. Theoretical and Experimental Study of the Primary Current Distribution in Parallel-Plate Electrochemical Reactors

    ERIC Educational Resources Information Center

    Vazquez Aranda, Armando I.; Henquin, Eduardo R.; Torres, Israel Rodriguez; Bisang, Jose M.

    2012-01-01

    A laboratory experiment is described to determine the primary current distribution in parallel-plate electrochemical reactors. The electrolyte is simulated by conductive paper and the electrodes are segmented to measure the current distribution. Experiments are reported with the electrolyte confined to the interelectrode gap, where the current…

  15. Electron beam guiding by grooved SiO{sub 2} parallel plates without energy loss

    SciTech Connect

    Xue, Yingli; Yu, Deyang Liu, Junliang; Zhang, Mingwu; Yang, Bian; Zhang, Yuezhao; Cai, Xiaohong

    2015-12-21

    Using a pair of grooved SiO{sub 2} parallel plates, stably guided electron beams were obtained without energy loss at 800–2000 eV. This shows that the transmitted electrons are guided by a self-organized repulsive electric field, paving the way for a self-adaptive manipulation of electron beams.

  16. Simulating Capacitances to Silicon Quantum Dots: Breakdown of the Parallel Plate Capacitor Model

    NASA Astrophysics Data System (ADS)

    Thorbeck, Ted; Fujiwara, Akira; Zimmerman, Neil M.

    2012-09-01

    Many electrical applications of quantum dots rely on capacitively coupled gates; therefore, to make reliable devices we need those gate capacitances to be predictable and reproducible. We demonstrate in silicon nanowire quantum dots that gate capacitances are reproducible to within 10% for nominally identical devices. We demonstrate the experimentally that gate capacitances scale with device dimensions. We also demonstrate that a capacitance simulator can be used to predict measured gate capacitances to within 20%. A simple parallel plate capacitor model can be used to predict how the capacitances change with device dimensions; however, the parallel plate capacitor model fails for the smallest devices because the capacitances are dominated by fringing fields. We show how the capacitances due to fringing fields can be quickly estimated.

  17. Cerenkov and cyclotron Cerenkov instabilities in a dielectric loaded parallel plate waveguide sheet electron beam system

    SciTech Connect

    Zhao Ding; Ding Yaogen

    2011-09-15

    A dielectric loaded parallel plate waveguide sheet electron beam system can be taken as a reliable model for the practical dielectric loaded rectangular waveguide sheet beam system that has a transverse cross section with a large width to height ratio. By using kinetic theory, the dispersion equations for Cerenkov and cyclotron Cerenkov instabilities in the parallel plate waveguide sheet beam system have been obtained rigorously. The dependences of the growth rate of both instabilities on the electric and structural parameters have also been investigated in detail through numerical calculations. It is worthwhile to point out that adopting an electron beam with transverse velocity can evidently improve the growth rate of Cerenkov instability, which seems like the case of cyclotron Cerenkov instability.

  18. Neutron In-beam Moessbauer Spectroscopy with a Parallel Plate Avalanche Counter

    SciTech Connect

    Kubo, M.K.; Kobayashi, Y.; Yamada, Y.; Nemoto, Y.; Saito, T.; Sakai, Y.; Shoji, H.; Yonezawa, C.; Matsue, H.; Nakada, M.

    2005-04-26

    An in-beam 57Fe Moessbauer spectroscopy system using a parallel plate avalanche counter has been developed for characterizing chemical species produced after neutron capture reactions. The high signal-to-background ratio of the detector enabled us to obtain the first spectrum of semiconductor iron disulfide. A new chemical species of iron, different from the parent compound, arising from the nuclear reaction was clearly observed.

  19. Study of the onset of the acoustic streaming in parallel plate resonators with pulse ultrasound.

    PubMed

    Castro, Angelica; Hoyos, Mauricio

    2016-03-01

    In a previous study, we introduced pulse mode ultrasound as a new method for reducing and controlling the acoustic streaming in parallel plate resonators (Hoyos and Castro, 2013). Here, by modifying other parameters such as the resonator geometry and the particle size, we have found a threshold for particle manipulation with ultrasonic standing waves in confined resonators without the influence of the acoustic streaming. We demonstrate that pulse mode ultrasound open the possibility of manipulating particles smaller than 1 μm size.

  20. Parallel-plate transmission line type of EMP simulators: Systematic review and recommendations

    NASA Astrophysics Data System (ADS)

    Giri, D. V.; Liu, T. K.; Tesche, F. M.; King, R. W. P.

    1980-05-01

    This report presents various aspects of the two-parallel-plate transmission line type of EMP simulator. Much of the work is the result of research efforts conducted during the last two decades at the Air Force Weapons Laboratory, and in industries/universities as well. The principal features of individual simulator components are discussed. The report also emphasizes that it is imperative to hybridize our understanding of individual components so that we can draw meaningful conclusions of simulator performance as a whole.

  1. Electromagnetic pulse coupling through an aperture into a two-parallel-plate region

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Y.

    1978-01-01

    Analysis of electromagnetic-pulse (EMP) penetration via apertures into cavities is an important study in designing hardened systems. In this paper, an integral equation procedure is developed for determining the frequency and consequently the time behavior of the field inside a two-parallel-plate region excited through an aperture by an EMP. Some discussion of the numerical results is also included in the paper for completeness.

  2. Investigation of the charging characteristics of micrometer sized droplets based on parallel plate capacitor model.

    PubMed

    Zhang, Yanzhen; Liu, Yonghong; Wang, Xiaolong; Shen, Yang; Ji, Renjie; Cai, Baoping

    2013-02-01

    The charging characteristics of micrometer sized aqueous droplets have attracted more and more attentions due to the development of the microfluidics technology since the electrophoretic motion of a charged droplet can be used as the droplet actuation method. This work proposed a novel method of investigating the charging characteristics of micrometer sized aqueous droplets based on parallel plate capacitor model. With this method, the effects of the electric field strength, electrolyte concentration, and ion species on the charging characteristics of the aqueous droplets was investigated. Experimental results showed that the charging characteristics of micrometer sized droplets can be investigated by this method.

  3. A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers.

    PubMed

    de Jong, J A; Wijnant, Y H; de Boer, A

    2014-03-01

    A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic systems. The model is implementable in existing (quasi-)1D thermoacoustic codes, such as DeltaEC. Examples of generated results show good agreement with literature results. The model allows for arbitrary wave phasing; however, it is shown that the wave phasing does not significantly influence the heat transfer.

  4. Squeezed film damping measurements on a parallel-plate MEMS in the free molecule regime

    NASA Astrophysics Data System (ADS)

    Mol, L.; Rocha, L. A.; Cretu, E.; Wolffenbuttel, R. F.

    2009-07-01

    This paper provides experimental validation of the predictions by two recent models for squeezed film damping in the free molecule regime. Measurements were carried out using a parallel-plate microstructure with a 2.29 µm gap operated at pressures from 105 to 101 Pa (corresponding to Knudsen numbers from 0.03 to 300). Experiments are in good agreement with the modelling based on molecular dynamics at Knudsen numbers over 10. The result also indicates that modelling based on the modified Reynolds equation including inertia effects underestimates the damping due to end effects; however, it correctly predicts the trend for lower Knudsen numbers.

  5. A parallel plate chamber with pixel read-out for very high data rate

    SciTech Connect

    Angelini, F.; Bellazzini, R.; Brez, A.; Massai, M.; Torquati, M.R.

    1989-02-01

    The authors report the preliminary test results on the performance of a device specially designed for the imaging of X rays at a very high data rate. A prototype having 256 read-out channels has been built and tested in our lab. The detector is a two step parallel plate chamber. The anode is made up of a chess-board of pads, onto which a thin germanium layer is evaporated to restore the electrical continuity. Each individual pad can be read out independently on the back of the board.

  6. Energy deposition in parallel-plate plasma accelerators. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Dicapua, M. S.

    1971-01-01

    To appraise the ratio of energy deposition into kinetic and thermal modes in plasma accelerators, a parallel-plate plasma accelerator has been operated in the quasi-steady mode with current pulses in the range of 10 to 100 kilo-amperes (kA), durations of the order of one millisecond, and argon mass flows up to 100 grams/sec. From photographic observations, spectroscopic measurements of velocity and electron density, and pressure measurements with a fast-rise piezoelectric transducer it is found that, for currents between 50 and 90 kA, the accelerated argon plasma is supersonic with ion velocities of 5 to 6 kilometers/sec.

  7. A multiple parallel-plate avalanche counter for fission-fragment detection

    NASA Astrophysics Data System (ADS)

    Wu, C. Y.; Henderson, R. A.; Haight, R. C.; Lee, H. Y.; Taddeucci, T. N.; Bucher, B.; Chyzh, A.; Devlin, M.; Fotiades, N.; Kwan, E.; O'Donnell, J. M.; Perdue, B. A.; Ullmann, J. L.

    2015-09-01

    A new low-mass multiple gas-filled parallel-plate avalanche counter for the fission-fragment detection has been developed to mark the fission occurrence in measurements of the prompt fission neutron energy spectrum as a function of incident neutron energy. It was used successfully for the neutron-induced fission of 235U and 239Pu with a total mass near 100 mg each and the spontaneous fission of 252Cf. Both the incident neutron energy and the prompt fission neutron energy are measured by using the time-of-flight method. The design and performance of this avalanche counter are described.

  8. A tunable universal terahertz filter using artificial dielectrics based on parallel-plate waveguides

    NASA Astrophysics Data System (ADS)

    Mendis, Rajind; Nag, Abhishek; Chen, Frank; Mittleman, Daniel M.

    2010-09-01

    Using parallel-plate waveguides (PPWGs) that mimic artificial dielectrics, we demonstrate a universal filter that provides low-pass, high-pass, band-pass, and band-stop (or notch) filtering functionalities in the terahertz (THz) frequency regime. The device essentially consists of two PPWGs in a complementary geometry. The filtering functionality is achieved by positioning an appropriate amplitude mask in the path of the spatially chirped THz beam between the two waveguides. By varying the position of the mask, we experimentally and theoretically demonstrate continuous tunability of the respective 3 dB cutoff frequencies within the frequency range from about 0.3 to 0.7 THz.

  9. Super-resolution non-parametric deconvolution in modelling the radial response function of a parallel plate ionization chamber.

    PubMed

    Kulmala, A; Tenhunen, M

    2012-11-01

    The signal of the dosimetric detector is generally dependent on the shape and size of the sensitive volume of the detector. In order to optimize the performance of the detector and reliability of the output signal the effect of the detector size should be corrected or, at least, taken into account. The response of the detector can be modelled using the convolution theorem that connects the system input (actual dose), output (measured result) and the effect of the detector (response function) by a linear convolution operator. We have developed the super-resolution and non-parametric deconvolution method for determination of the cylinder symmetric ionization chamber radial response function. We have demonstrated that the presented deconvolution method is able to determine the radial response for the Roos parallel plate ionization chamber with a better than 0.5 mm correspondence with the physical measures of the chamber. In addition, the performance of the method was proved by the excellent agreement between the output factors of the stereotactic conical collimators (4-20 mm diameter) measured by the Roos chamber, where the detector size is larger than the measured field, and the reference detector (diode). The presented deconvolution method has a potential in providing reference data for more accurate physical models of the ionization chamber as well as for improving and enhancing the performance of the detectors in specific dosimetric problems.

  10. A new parallel plate shear cell for in situ real-space measurements of complex fluids under shear flow.

    PubMed

    Wu, Yu Ling; Brand, Joost H J; van Gemert, Josephus L A; Verkerk, Jaap; Wisman, Hans; van Blaaderen, Alfons; Imhof, Arnout

    2007-10-01

    We developed and tested a parallel plate shear cell that can be mounted on top of an inverted microscope to perform confocal real-space measurements on complex fluids under shear. To follow structural changes in time, a plane of zero velocity is created by letting the plates move in opposite directions. The location of this plane is varied by changing the relative velocities of the plates. The gap width is variable between 20 and 200 microm with parallelism better than 1 microm. Such a small gap width enables us to examine the total sample thickness using high numerical aperture objective lenses. The achieved shear rates cover the range of 0.02-10(3) s(-1). This shear cell can apply an oscillatory shear with adjustable amplitude and frequency. The maximum travel of each plate equals 1 cm, so that strains up to 500 can be applied. For most complex fluids, an oscillatory shear with such a large amplitude can be regarded as a continuous shear. We measured the flow profile of a suspension of silica colloids in this shear cell. It was linear except for a small deviation caused by sedimentation. To demonstrate the excellent performance and capabilities of this new setup we examined shear induced crystallization and melting of concentrated suspensions of 1 microm diameter silica colloids.

  11. Dynamic pull-in of parallel plate and torsional electrostatic MEMS actuators.

    SciTech Connect

    Nielson, Gregory N.; Barbastathis, George

    2005-02-01

    An analysis of the dynamic characteristics of pull-in for parallel-plate and torsional electrostatic actuators is presented. Traditionally, the analysis for pull-in has been done using quasi-static assumptions. However, it was recently shown experimentally that a step input can cause a decrease in the voltage required for pull-in to occur. We propose an energy-based solution for the step voltage required for pull-in that predicts the experimentally observed decrease in the pull-in voltage. We then use similar energy techniques to explore pull-in due to an actuation signal that is modulated depending on the sign of the velocity of the plate (i.e., modulated at the instantaneous mechanical resonant frequency). For this type of actuation signal, significant reductions in the pull-in voltage can theoretically be achieved without changing the stiffness of the structure. This analysis is significant to both parallel-plate and torsional electrostatic microelectromechanical systems (MEMS) switching structures where a reduced operating voltage without sacrificing stiffness is desired, as well as electrostatic MEMS oscillators where pull-in due to dynamic effects needs to be avoided.

  12. Preliminary Diffusive Clearance of Silicon Nanopore Membranes in a Parallel Plate Configuration for Renal Replacement Therapy.

    PubMed

    Kim, Steven; Heller, James; Iqbal, Zohora; Kant, Rishi; Kim, Eun Jung; Durack, Jeremy; Saeed, Maythem; Do, Loi; Hetts, Steven; Wilson, Mark; Brakeman, Paul; Fissell, William H; Roy, Shuvo

    2016-01-01

    Silicon nanopore membranes (SNMs) with compact geometry and uniform pore size distribution have demonstrated a remarkable capacity for hemofiltration. These advantages could potentially be used for hemodialysis. Here, we present an initial evaluation of the SNM's mechanical robustness, diffusive clearance, and hemocompatibility in a parallel plate configuration. Mechanical robustness of the SNM was demonstrated by exposing membranes to high flows (200 ml/min) and pressures (1,448 mm Hg). Diffusive clearance was performed in an albumin solution and whole blood with blood and dialysate flow rates of 25 ml/min. Hemocompatibility was evaluated using scanning electron microscopy and immunohistochemistry after 4 hours in an extracorporeal porcine model. The pressure drop across the flow cell was 4.6 mm Hg at 200 ml/min. Mechanical testing showed that SNM could withstand up to 775.7 mm Hg without fracture. Urea clearance did not show an appreciable decline in blood versus albumin solution. Extracorporeal studies showed blood was successfully driven via the arterial-venous pressure differential without thrombus formation. Bare silicon showed increased cell adhesion with a 4.1-fold increase and 1.8-fold increase over polyethylene glycol (PEG)-coated surfaces for tissue plasminogen factor (t-PA) and platelet adhesion (CD41), respectively. These initial results warrant further design and development of a fully scaled SNM-based parallel plate dialyzer for renal replacement therapy.

  13. ER Effect of Liquid Crystal Flowing Between Two Parallel-Plate Electrodes

    NASA Astrophysics Data System (ADS)

    Tsukiji, Tetsuhiro; Tanabe, Shinsuke

    Liquid crystal is one of homogeneous ER(Electro-rheological) fluids in some range of temperature. Transient responses of pressure drop are examined when liquid crystal flows between two parallel-plate electrodes for constant flow rates. When voltages are applied on the liquid crystal and removed, the pressure responses of the inlet of electrodes are measured with the pressure transducer. At the same time, liquid crystal between the transparent electrodes made of glass is visualized with the high-speed video camera to investigate the time history of the director of the liquid crystal. Outlet of the flow channel with two parallel-plate electrodes is atmosphere. Relation between the flow visualization results and the changes of pressure drop is investigated especially for transient period. In the present experiment the flow rates change from 0.001 cc/sec(velocity is 1 mm/sec) to 0.003 cc/sec and the electric field intensity is from 0.2 kV/mm to 1 kV/mm. The gap of the electrodes is 0.2 mm. The isotropic-nematic transition is 35.5°C and smectic-nematic transition is 23.1°C. The open-loop test facility with the liquid crystal is set in a pyrostat to keep the temperature constant.

  14. Parametric electroconvection in a weakly conducting fluid in a horizontal parallel-plate capacitor

    NASA Astrophysics Data System (ADS)

    Kartavykh, N. N.; Smorodin, B. L.; Il'in, V. A.

    2015-07-01

    We study the flows of a nonuniformly heated weakly conducting fluid in an ac electric field of a horizontal parallel-plate capacitor. Analysis is carried out for fluids in which the charge formation is governed by electroconductive mechanism associated with the temperature dependence of the electrical conductivity of the medium. Periodic and chaotic regimes of fluid flow are investigated in the limiting case of instantaneous charge relaxation and for a finite relaxation time. Bifurcation diagrams and electroconvective regimes charts are constructed. The regions where fluid oscillations synchronize with the frequency of the external field are determined. Hysteretic transitions between electroconvection regimes are studied. The scenarios of transition to chaotic oscillations are analyzed. Depending on the natural frequency of electroconvective system and the external field frequency, the transition from periodic to chaotic oscillations can occur via quasiperiodicity, a subharmonic cascade, or intermittence.

  15. Rolling and slipping motion of a water droplet sandwiched between two parallel plates coated with fluoroalkylsilanes

    NASA Astrophysics Data System (ADS)

    Suzuki, Shunsuke; Nakajima, Akira; Sakai, Munetoshi; Hashimoto, Ayako; Yoshida, Naoya; Kameshima, Yoshikazu; Okada, Kiyoshi

    2008-12-01

    Si plates were treated using two fluoroalkylsilanes (FAS17 and FAS3), and the internal fluidity of a water droplet sliding between two parallel plates on a slope was observed directly using particle image velocimetry (PIV) method with a high-speed camera system. The interfacial caterpillar-like rotation flows with slip motion at the solid-liquid interface were related to the combination of top and bottom wettabilities. The water droplets accelerated by a rolling and slipping motion on FAS17 coatings; the acceleration was dominated by a rolling motion on FAS3 coatings. A droplet's shape, solid-liquid molecular interaction, and the gravitic force will be important factors determining the sliding mode on a solid surface.

  16. Microwave response of octagon-shaped parallel plates: Low-loss metamaterial

    NASA Astrophysics Data System (ADS)

    Sabah, C.

    2012-10-01

    A very low-loss metamaterial formed by a pair of homogeneous octagon-shaped parallel plates separated by a dielectric substrate is presented to achieve simultaneous negative permittivity and permeability in the microwave region. The double-negative behavior with a high figure of merit (FOM=|Re(n)/Im(n)|=80 at 24.7 GHz) leads to reduced losses in this proposed metamaterial. The high quality feature of the structure can make the applications of the negative refractive index metamaterial more efficient and applicable, such as perfect- or super-lenses at microwave frequencies since FOM≈64.5, where the real part of the refractive index ≈-1 at 25.3 GHz.

  17. A study of turbulent flow between parallel plates by a statistical method

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Giddens, D. P.; Bangert, L. H.; Wu, J. C.

    1976-01-01

    Turbulent Couette flow between parallel plates was studied from a statistical mechanics approach utilizing a model equation, similar to the Boltzmann equation of kinetic theory, which was proposed by Lundgren from the velocity distribution of fluid elements. Solutions to this equation are obtained numerically, employing the discrete ordinate method and finite differences. Two types of boundary conditions on the distribution function are considered, and the results of the calculations are compared to available experimental data. The research establishes that Lundgren's equation provides a very good description of turbulence for the flow situation considered and that it offers an analytical tool for further study of more complex turbulent flows. The present work also indicates that modelling of the boundary conditions is an area where further study is required.

  18. Wall Slip during the Flow of Carbopol Solutions through a Parallel Plate Channel

    NASA Astrophysics Data System (ADS)

    de Souza Mendes, Paulo R.; Pédron, Jonathan; Pereira, Renata A. B.

    2008-07-01

    Experiments were performed to investigate the phenomenon of wall slip during the flow of aqueous solutions of carbopol through a parallel plate channel. The Reynolds number is low for all cases investigated, to ensure negligible development length. In the experiments, the pressure drop is measured for different flow rate values, and the results are presented in the form of curves of dimensionless average velocity versus dimensionless wall shear stress. We also performed experiments with glycerol, and the results agreed with the analytical solution available in the literature. Moreover, this agreement ensures the absence of wall slip for this Newtonian case. Comparisons between the experimental and numerical results show that (apparent) wall slip occurs when the wall shear stress is below a threshold stress of a few times the yield stress. Above this threshold, the numerical and experimental curves tend to merge.

  19. Pressure Response of ER Fluids between Two Parallel-Plate Electrodes

    NASA Astrophysics Data System (ADS)

    Tsukiji, Tetsuhiro; Hori, Ken-Ichi

    The frequency response of the pressure drop of the ER fluids between two parallel-plate electrodes to sine-wave changes in the applied electric field is investigated for constant flow rates. The electrodes gap is set at 2mm. The ER fluids used in the present study consist of cellulose suspended in silicone oil. Unipolar and bipolar sinusoidal electric fields, and constant ones are used. The frequency of the electric fields is changed from 0.1 to 1000Hz. The averages and the amplitudes of the pressure drop are measured. Dependence of the pressure drop on electrical excitation frequency is investigated. Furthermore the microscopic behavior of ER suspension structure between two fixed electrodes is visualized for the flowing ER fluids with high speed video camera under application of the electric fields. The effect of electrical change on the pressure drop is discussed from the results of the flow visualization.

  20. Electrothermal MEMS parallel plate rotation for single-imager stereoscopic endoscopes.

    PubMed

    Jang, Kyung-Won; Yang, Sung-Pyo; Baek, Seung-Hwan; Lee, Min-Suk; Park, Hyeon-Cheol; Seo, Yeong-Hyeon; Kim, Min H; Jeong, Ki-Hun

    2016-05-01

    This work reports electrothermal MEMS parallel plate-rotation (PPR) for a single-imager based stereoscopic endoscope. A thin optical plate was directly connected to an electrothermal MEMS microactuator with bimorph structures of thin silicon and aluminum layers. The fabricated MEMS PPR device precisely rotates an transparent optical plate up to 37° prior to an endoscopic camera and creates the binocular disparities, comparable to those from binocular cameras with a baseline distance over 100 μm. The anaglyph 3D images and disparity maps were successfully achieved by extracting the local binocular disparities from two optical images captured at the relative positions. The physical volume of MEMS PPR is well fit in 3.4 mm x 3.3 mm x 1 mm. This method provides a new direction for compact stereoscopic 3D endoscopic imaging systems.

  1. Electrothermal MEMS parallel plate rotation for single-imager stereoscopic endoscopes.

    PubMed

    Jang, Kyung-Won; Yang, Sung-Pyo; Baek, Seung-Hwan; Lee, Min-Suk; Park, Hyeon-Cheol; Seo, Yeong-Hyeon; Kim, Min H; Jeong, Ki-Hun

    2016-05-01

    This work reports electrothermal MEMS parallel plate-rotation (PPR) for a single-imager based stereoscopic endoscope. A thin optical plate was directly connected to an electrothermal MEMS microactuator with bimorph structures of thin silicon and aluminum layers. The fabricated MEMS PPR device precisely rotates an transparent optical plate up to 37° prior to an endoscopic camera and creates the binocular disparities, comparable to those from binocular cameras with a baseline distance over 100 μm. The anaglyph 3D images and disparity maps were successfully achieved by extracting the local binocular disparities from two optical images captured at the relative positions. The physical volume of MEMS PPR is well fit in 3.4 mm x 3.3 mm x 1 mm. This method provides a new direction for compact stereoscopic 3D endoscopic imaging systems. PMID:27137580

  2. Guided modes in chiroplasma-filled perfect electromagnetic conductor parallel-plate waveguides

    NASA Astrophysics Data System (ADS)

    Ghaffar, A.; Alkanhal, Majeed A. S.

    2015-10-01

    Theoretical analysis of electromagnetic wave propagation in a perfect electromagnetic conductor (PEMC) parallel-plate waveguide filled with a chiroplasma material is presented in this article. The derived formulations are general and can analyze perfect electric, perfect magnetic, or PEMC waveguides filled with any general isotropic/anisotropic material including plasma and metamaterials. The characteristic equation for the modes in this waveguide is obtained, and the behavior of the dispersion curves and the energy flux are examined and evaluated numerically. The results demonstrate that the chirality parameter, the plasma frequency, and the cyclotron frequency influence the behavior of the energy flux transported in the guide, in magnitude and orientation. The bifurcated mode cutoff frequencies are sensitive to the variations in the filling material parameters and likewise effected by the variations in the PEMC walls admittance parameter.

  3. Effects of transverse magnetic field on a rotating micropolar fluid between parallel plates with heat transfer

    NASA Astrophysics Data System (ADS)

    Mehmood, Rashid; Nadeem, S.; Masood, S.

    2016-03-01

    Hydromagnetic flow of a micropolar fluid between two horizontal parallel plates in a rotating system has been investigated. The governing partial differential equations for momentum, energy and micro-rotation are presented and transformed into ordinary differential equations by means of similarity transformations. The solutions for velocity, temperature and micro-rotation profiles are expressed through graphs against various emerging physical parameters such as coupling parameter, viscosity parameter, Hartman number, Reynold number, rotation parameter, porosity parameter and peclet number using optimal homotopy analysis method (OHAM). Local skin friction co-efficient and local heat fluxes are computed analytically using OHAM as well as numerically through mid-point integration scheme and they are found to be in excellent agreement. It has been observed that local skin friction is higher for the case of strong concentration compare to the case of weak concentration. Moreover, influence of strong and weak concentration on Nusselt number is also examined.

  4. Parametric electroconvection in a weakly conducting fluid in a horizontal parallel-plate capacitor

    SciTech Connect

    Kartavykh, N. N.; Smorodin, B. L. Il’in, V. A.

    2015-07-15

    We study the flows of a nonuniformly heated weakly conducting fluid in an ac electric field of a horizontal parallel-plate capacitor. Analysis is carried out for fluids in which the charge formation is governed by electroconductive mechanism associated with the temperature dependence of the electrical conductivity of the medium. Periodic and chaotic regimes of fluid flow are investigated in the limiting case of instantaneous charge relaxation and for a finite relaxation time. Bifurcation diagrams and electroconvective regimes charts are constructed. The regions where fluid oscillations synchronize with the frequency of the external field are determined. Hysteretic transitions between electroconvection regimes are studied. The scenarios of transition to chaotic oscillations are analyzed. Depending on the natural frequency of electroconvective system and the external field frequency, the transition from periodic to chaotic oscillations can occur via quasiperiodicity, a subharmonic cascade, or intermittence.

  5. Parallel Plate Flow of a Third-Grade Fluid and a Newtonian Fluid With Variable Viscosity

    NASA Astrophysics Data System (ADS)

    Yıldız, Volkan; Pakdemirli, Mehmet; Aksoy, Yiğit

    2016-07-01

    Steady-state parallel plate flow of a third-grade fluid and a Newtonian fluid with temperature-dependent viscosity is considered. Approximate analytical solutions are constructed using the newly developed perturbation-iteration algorithms. Two different perturbation-iteration algorithms are used. The velocity and temperature profiles obtained by the iteration algorithms are contrasted with the numerical solutions as well as with the regular perturbation solutions. It is found that the perturbation-iteration solutions converge better to the numerical solutions than the regular perturbation solutions, in particular when the validity criteria of the regular perturbation solution are not satisfied. The new analytical approach produces promising results in solving complex fluid problems.

  6. A method to increase the nominal range resolution of a stack of parallel-plate ionization chambers

    NASA Astrophysics Data System (ADS)

    Rinaldi, I.; Brons, S.; Jäkel, O.; Voss, B.; Parodi, K.

    2014-09-01

    A detector prototype based on a stack of 61 parallel-plate ionisation chambers (PPIC) interleaved with absorber plates of polymethyl methacrylate (PMMA) was assembled for transmission imaging purposes in ion beam therapy. The thickness of the absorber sheets in the PPIC stack determines the nominal range resolution of the detector. In the current set-up, 3 mm PMMA slabs are used. The signal of the 61 active channels of the stack thereby provides a discrete approximation of the Bragg curve in the detector. In this work, a data processing method to increase the range resolution (MIRR) in a stack of ionization chambers is presented. In the MIRR the position of the maximum of the Bragg curve is deduced from the ratio of measured signals in adjacent PPIC channels. The method is developed based on Bragg curves obtained from Monte Carlo simulations and validated with experimental data of a wedge-shaped PMMA phantom acquired with the PPIC stack using carbon ion beams. The influence of the initial beam energy and of phantom inhomogeneities on the MIRR is quantitatively evaluated. Systematic errors as well as inaccuracies related to signal noise are discussed and quantified. It is shown that with the MIRR an increased range resolution of 0.7 mm PMMA equivalent or 0.8 mm water equivalent thickness is achieved for the considered experimental data.

  7. Parallel plate capacitor analogy of equatorial plasma bubble and associated fringe fields with implications to equatorial valley region irregularities

    NASA Astrophysics Data System (ADS)

    Mukherjee, S.; Patra, A. K.

    2014-08-01

    VHF radar echoes from the valley region plasma irregularities, displaying ascending pattern, are often observed during the active phase of equatorial plasma bubble in the close vicinity of the geomagnetic equator and have been attributed to bubble-related fringe field effect. These irregularities however are not observed at a few degrees away from the equator. In this paper, we attempt to understand this contrasting observational result by comparing fringe field at the geomagnetic equator and low latitudes. We use parallel plate capacitor analogy of equatorial plasma bubble and choose a few capacitor configurations, consistent with commonly observed dimension and magnetic field-aligned property of plasma bubble, for computing fringe field. Results show that fringe field decreases significantly with decreasing altitude as expected. Further, fringe field decreases remarkably with latitude, which clearly indicates the role of magnetic field-aligned property of plasma bubble in reducing the magnitude of fringe field at low latitudes compared to that at the geomagnetic equator. The results are presented and discussed in the light of current understanding of plasma bubble-associated fringe field-induced plasma irregularities in the valley region.

  8. Parallel-plate lab-on-a-chip based on digital microfluidics for on-chip electrochemical analysis

    NASA Astrophysics Data System (ADS)

    Yu, Yuhua; Chen, Jianfeng; Zhou, Jia

    2014-01-01

    This paper describes an electrowetting on dielectric (EWOD) digital microfluidic-based lab-on-a-chip (LOC) integrated with on-chip electrochemical microsensor by IC compatible fabrication process, and its application for the entire online biosensing process capable of fully automatic analysis for ferrocenemethanol (FcM) and dopamine (DA). In this work, we made full use of the parallel-plate structure of the EWOD digital microfluidic device to fabricate the microfluidic module on the bottom plate and the three-microelectrode-system-integrated electrochemical cell together with patterned ground electrode on the top plate. The proposed LOC possesses the multifunction of: (1) creating, merging and transporting of microliter-level sample droplets, (2) online biosensing, and (3) droplets recycling. The three-electrode-integrated microsensor not only reveals a sensitive electrochemical detection for FcM in a wide concentration range (10 µM-1.0 mM), but also shows good stability, selectivity and reproducibility for surface-controlled detection of DA. The calibration of DA was linear for concentration from 1.0 to 50.0 µM with a high sensitivity of 2145 nA µM-1 cm-2 (R2 = 0.9933) and estimated detection limit of 0.42 µM (signal/noise ratio of 3). This work shows the promise of state-of-the-art digital microfluidic biosensors for fully automatic online bioanalysis in a future LOC to perform on-chip biomedical protocols in vitro diagnostic assays.

  9. Monte Carlo Simulation of an Ar RF Parallel Plate Discharge Plasma Employing LPWS

    NASA Astrophysics Data System (ADS)

    Horie, Ikuya; Suzuki, Takuma; Ohmori, Yoshiyuki; Kitamori, Kazutaka; Maruyama, Koichi

    The geometry, pressure and power coupling conditions of most plasma sources for semiconductor manufacturing lend themselves to particle simulations such as Monte Carlo simulations(here after MCS). Usually the kinetics solvers are coupled to solvers for Poisson’s Equation. MCS usually employ averaging over discrete regions of parameter space. When the number of discrete regions is increased, two problems result: one is the instability of the solution because of a statistical change and the other is the increase of the calculation time. Ventzek and Kitamori (J. Appl. Phys., vol. 75, pp. 3785-3788, 1994) proposed Legendre Polynomial Weighted Sampling (here after LPWS) which aimed to optimize sampling statistics with an economy of particles. In this paper, we characterize an Ar RF parallel plate discharge using a MCS employing LPWS based on the Date’s model (T. IEE Japan, 111-A, 11, pp. 962-972, 1991). The method is shown to replicate the behavior of RF discharges with high fidelity.

  10. Preventing Electrical Shorts in Parallel-Plate Capacitors with Single-Printed Dielectric Layer

    NASA Astrophysics Data System (ADS)

    Horvat, Maša; Vidmar, Tjaša; Maček, Marijan; Klanjšek Gunde, Marta

    2015-07-01

    Double-printing of dielectric layers is commonly used to prevent electrical shorts in parallel-plate capacitors, but this increases the thickness of the dielectric layer and diminishes the corresponding capacitance. Double-printing also complicates the production process and increases production costs. In this paper, it is demonstrated that capacitors with single-printed dielectric layers are without shorts if the layer is completely polymerized. Therefore, electrical shorts could also be related to the state of polymerization in a defect-free dielectric layer. To demonstrate this, the electrical functionality of capacitors with single-printed dielectric layers was studied in terms of intrinsic properties of the ultraviolet (UV) curable dielectric layer, which were varied according to the curing energy. The chemical structure of the cured layer was analyzed with infrared spectroscopy to obtain the appearance of polymerizable groups and crosslinks within the polymer structure. Differential scanning calorimetry was used to measure the glass transition temperature of the dielectric material. It increases rapidly with UV curing until the polymerization is completed, whereas a small increase with further curing confirms crosslinking of the polymer. The influence of structuring effects within a dielectric layer in the presence of electrical shorts between electrodes is discussed. This research confirms that a completely polymerized layer forms a barrier to leakage and helps to prevent the formation of conductive paths between electrodes. Therefore, a connection between the structure of polymerized layer and its electrical properties is highly reasonable.

  11. A study of Gd-based parallel plate avalanche counter for thermal neutrons by MC simulation

    NASA Astrophysics Data System (ADS)

    Rhee, J. T.; Kim, H. G.; Ahmad, Farzana; Jeon, Y. J.; Jamil, M.

    2013-12-01

    In this work, we demonstrate the feasibility and characteristics of a single-gap parallel plate avalanche counter (PPAC) as a low energy neutron detector, based on Gd-converter coating. Upon falling on the Gd-converter surface, the incident low energy neutrons produce internal conversion electrons which are evaluated and detected. For estimating the performance of the Gd-based PPAC, a simulation study has been performed using GEANT4 Monte Carlo (MC) code. The detector response as a function of incident neutron energies in the range of 25-100 meV has been evaluated with two different physics lists. Using the QGSP_BIC_HP physics list and assuming 5 μm converter thickness, 11.8%, 18.48%, and 30.28% detection efficiencies have been achieved for the forward-, the backward-, and the total response of the converter-based PPAC. On the other hand, considering the same converter thickness and detector configuration, with the QGSP_BERT_HP physics list efficiencies of 12.19%, 18.62%, and 30.81%, respectively, were obtained. These simulation results are briefly discussed.

  12. Parallel-plate and spherical capacitors in Born-Infeld electrostatics: An analytical study

    NASA Astrophysics Data System (ADS)

    Moayedi, S. K.; Shafabakhsh, M.

    2016-03-01

    In 1934, Max Born and Leopold Infeld suggested and developed a nonlinear modification of Maxwell electrodynamics, in which the electrostatic self-energy of an electron was a finite value. In this paper, after a brief introduction to Lagrangian formulation of Born-Infeld electrodynamics with an external source, the explicit forms of Gauss's law and the electrostatic energy density in Born-Infeld theory are obtained. The capacitance and the stored electrostatic energy for a parallel-plate and spherical capacitors are computed in the framework of Born-Infeld electrostatics. We show that the usual relations U=1/2C_{Maxwell}(triangle φ)2 and U=q2/2C_{Maxwell} are not valid for a capacitor in Born-Infeld electrostatics. Numerical estimations in this research show that the nonlinear corrections to the capacitance and the stored electrostatic energy for a capacitor in Born-Infeld electrostatics are considerable when the potential difference between the plates of a capacitor is very large.

  13. Oscillatory flow at the end of parallel-plate stacks: phenomenological and similarity analysis

    NASA Astrophysics Data System (ADS)

    Mao, Xiaoan; Jaworski, Artur J.

    2010-10-01

    This paper addresses the physics of the oscillatory flow in the vicinity of a series of parallel plates forming geometrically identical channels. This type of flow is particularly relevant to thermoacoustic engines and refrigerators, where a reciprocating flow is responsible for the desirable energy transfer, but it is also of interest to general fluid mechanics of oscillatory flows past bluff bodies. In this paper, the physics of an acoustically induced flow past a series of plates in an isothermal condition is studied in detail using the data provided by PIV imaging. Particular attention is given to the analysis of the wake flow during the ejection part of the flow cycle, where either closed recirculating vortices or alternating vortex shedding can be observed. This is followed by a similarity analysis of the governing Navier-Stokes equations in order to derive the similarity criteria governing the wake flow behaviour. To this end, similarity numbers including two types of Reynolds number, the Keulegan-Carpenter number and a non-dimensional stack configuration parameter, d/h, are considered and their influence on the phenomena are discussed.

  14. Parallel plate waveguide with anisotropic graphene plates: Effect of electric and magnetic biases

    NASA Astrophysics Data System (ADS)

    Malekabadi, Ali; Charlebois, Serge A.; Deslandes, Dominic

    2013-03-01

    The performances of a parallel plate waveguide (PPWG) supported by perfect electric conductor (PEC)-graphene and graphene-graphene plates are evaluated. The graphene plate behavior is modeled as an anisotropic medium with both diagonal and Hall conductivities derived from Kubo formula. The PPWG modes supported by PEC-graphene and graphene-graphene plates are studied. Maxwell's equations are solved for these two waveguides, while the graphene layers are biased with an electric field only and with both electric and magnetic fields. It is shown that when both electric and magnetic biases are applied to the graphene, a hybrid mode (simultaneous transverse electric (TE) and transverse magnetic (TM) modes) will propagate inside the waveguide. The intensity of each TE and TM modes can be adjusted with the applied external bias fields. Study of different waveguides demonstrates that by decreasing the plate separation (d), the wave confinement improves. However, it increases the waveguide attenuation. A dielectric layer inserted between the plates can also be used to improve the wave confinement. The presented analytical procedure is applicable to other guiding structures having walls with isotropic or anisotropic conductivities.

  15. Measurement and Characterization of Terahertz Radiation Propagating Through a Parallel Plate Waveguide

    NASA Astrophysics Data System (ADS)

    Wachsmuth, Matthew George

    As the amount of study into the terahertz (THz) region of the electromagnetic spectrum steadily increases, the parallel plate waveguide has emerged as a simple and effective fixture to perform many experiments. The ability to concentrate THz radiation into a small area or volume enables us to analyze smaller samples and perform more repeatable measurements, which is essential for future research. While the fundamental physics of PPW transmission are understood mathematically, the practical knowledge of building such a fixture for the THz domain and taking measurements on it with a real system needs to be built up through experience. In this thesis, multiple PPW configurations are built and tested. These include waveguides of different lengths and opening heights, using lenses and antennas to focus and collect radiation from the input and output, and different amounts of polish on the waveguide surface. A basic resonator structure is also built and measured as a proof of concept for future research. The two most useful propagation modes through the waveguide, the lowest order transverse magnetic (TEM) and transverse electric (TE) modes, were characterized on all of the setups. Additionally, a flexible fixture was designed and measured which will allow future work in the THz field to be much more reliable and repeatable.

  16. Velocity profiles of electric-field-induced backflows in liquid crystals confined between parallel plates

    NASA Astrophysics Data System (ADS)

    Tsuji, Tomohiro; Chono, Shigeomi; Matsumi, Takanori

    2015-02-01

    For the purpose of developing liquid crystalline microactuators, we visualize backflows induced between two parallel plates for various parameters such as the twist angle, cell gap, applied voltage, and molecular configuration mode. We use 4-cyano-4'-pentyl biphenyl, a typical low-molar-mass nematic liquid crystal. By increasing the twist angle from 0° to 180°, the velocity component parallel to the anchoring direction of the lower plate changes from an S-shaped profile to a distorted S-shaped profile before finally becoming unidirectional. In contrast, the velocity component perpendicular to the anchoring direction evolves from a flat profile at 0° into an S-shaped profile at 180°. Because both an increase in the applied voltage and a decrease in the cell gap increase the electric field intensity, the backflow becomes large. The hybrid molecular configuration mode induces a larger backflow than that for the planar aligned mode. The backflow develops in two stages: an early stage with a microsecond time scale and a later stage with a millisecond time scale. The numerical predictions are in qualitative agreement with the measurements, but not quantitative agreement because our computation ignores the plate edge effect of surface tension.

  17. Spin wave and vortex excitations of superfluid 3He-A in parallel-plate geometry.

    PubMed

    Yamashita, Minoru; Izumina, Ken; Matsubara, Akira; Sasaki, Yutaka; Ishikawa, Osamu; Takagi, Takeo; Kubota, Minoru; Mizusaki, Takao

    2008-07-11

    Quantized vortices with half-integer circulation, which are forbidden from existing in a conventional superfluid because of the single valueness of the wave function, are theoretically predicted to exist in superfluid 3He-A if the order parameters l over and d over form l over perpendicular d over texture. To form the l over perpendicular d over texture, we confined the superfluid between parallel plates with a 12.5 microm gap and applied a magnetic field of H=26.7 mT perpendicular to the plates to take NMR and orient d over perpendicular to l over. NMR spectra exhibit a negative-shift peak which probes that the uniform l over perpendicular d over texture is realized in our cell and show a new satellite signal under rotation. The rotation dependence of the satellite signal is interpreted that a Fréedericksz transition of l over texture is induced by rotation above 1.0 rad/s and vortices start to appear above 1.8 rad/s.

  18. Preparation of magnetized nanodusty plasmas in a radio frequency-driven parallel-plate reactor

    SciTech Connect

    Tadsen, Benjamin Greiner, Franko; Piel, Alexander

    2014-10-15

    Nanodust is produced in an rf-driven push-pull parallel-plate reactor using argon with an acetylene admixture at 5–30 Pa. A scheme for the preparation of nanodust clouds with particle radii up to 400 nm for investigations in magnetized plasmas is proposed. The confinement that keeps the nanodust of different radii inside a moderately magnetized discharge (B ≤ 500 mT) is investigated by a comparison of 2d-Langmuir probe measurements in the dust-free plasma without and with a magnetic field and by the analysis of scattered light of nanodust clouds. It is shown that the dust cloud changes its shape when the dust density changes. This results in a reversed α-γ{sup ′} transition from a dense dust cloud with a central disk-like void to a dilute dust cloud with a toroidal void. When the dust density is further reduced, filaments are observed in the central part of the cloud, which were absent in the high-density phase. It is concluded that the dense nanodust cloud is able to suppress plasma filamentation in magnetized plasmas.

  19. Mathematical model of a parallel plate ammonia electrolyzer for combined wastewater remediation and hydrogen production.

    PubMed

    Estejab, Ali; Daramola, Damilola A; Botte, Gerardine G

    2015-06-15

    A mathematical model was developed for the simulation of a parallel plate ammonia electrolyzer to convert ammonia in wastewater to nitrogen and hydrogen under basic conditions. The model consists of fundamental transport equations, the ammonia oxidation kinetics at the anode, and the hydrogen evolution kinetics at the cathode of the electrochemical reactor. The model shows both qualitative and quantitative agreement with experimental measurements at ammonia concentrations found within wastewater (200-1200 mg L(-1)). The optimum electrolyzer performance is dependent on both the applied voltage and the inlet concentrations. Maximum conversion of ammonia to nitrogen at the rates of 0.569 and 0.766 mg L(-1) min(-1) are achieved at low (0.01 M NH4Cl and 0.1 M KOH) and high (0.07 M NH4Cl and 0.15 M KOH) inlet concentrations, respectively. At high and low concentrations, an initial increase in the cell voltage will cause an increase in the system response - current density generated and ammonia converted. These system responses will approach a peak value before they start to decrease due to surface blockage and/or depletion of solvated species at the electrode surface. Furthermore, the model predicts that by increasing the reactant and electrolyte concentrations at a certain voltage, the peak current density will plateau, showing an asymptotic response.

  20. Optimal and Numerical Solutions for an MHD Micropolar Nanofluid between Rotating Horizontal Parallel Plates

    PubMed Central

    Nadeem, Sohail; Masood, Sadaf; Mehmood, Rashid; Sadiq, Muhammad Adil

    2015-01-01

    The present analysis deals with flow and heat transfer aspects of a micropolar nanofluid between two horizontal parallel plates in a rotating system. The governing partial differential equations for momentum, energy, micro rotation and nano-particles concentration are presented. Similarity transformations are utilized to convert the system of partial differential equations into system of ordinary differential equations. The reduced equations are solved analytically with the help of optimal homotopy analysis method (OHAM). Analytical solutions for velocity, temperature, micro-rotation and concentration profiles are expressed graphically against various emerging physical parameters. Physical quantities of interest such as skin friction co-efficient, local heat and local mass fluxes are also computed both analytically and numerically through mid-point integration scheme. It is found that both the solutions are in excellent agreement. Local skin friction coefficient is found to be higher for the case of strong concentration i.e. n=0, as compared to the case of weak concentration n=0.50. Influence of strong and weak concentration on Nusselt and Sherwood number appear to be similar in a quantitative sense. PMID:26046637

  1. Steady-state parallel plate apparatus for measurement of diffusion coefficient in supercritical carbon dioxide

    SciTech Connect

    Tuan, D.Q.; Zollweg, J.A.; Rizvi, S.S.H.; Yener, M.E. |

    1999-02-01

    A new, steady-state experimental system for measurement of the Fickian diffusion coefficients for solutes in supercritical carbon dioxide (SC-CO{sub 2}) was designed and evaluated. Mass transfer between a liquid solute and SC-CO{sub 2} was carried out in a parallel plate geometry where a porous metal sheet, immersed in the liquid phase, stabilized the interface. The SC-CO{sub 2} flowed over the porous metal sheet containing the liquid phase which was presaturated with CO{sub 2}. The use of the porous metal sheet and a thin mobile layer allowed flow rates high enough to achieve the necessary pressure drop to eliminate the commonly encountered, density-induced stagnation of SC-CO{sub 2} at the interface while avoiding surface-tension-related problems. The binary diffusion coefficients of methyl oleate in SC-CO{sub 2} at finite concentrations were measured at 40, 50, and 60 C and at pressures ranging from 10.6 to 14.0 MPa. The experimentally measured values were 1.5--4.6 times lower than those predicted for infinite dilution and were found to decrease with solute concentration at constant pressure and temperature. This technique offers advantages over other commonly used methods in that the concentration dependence of diffusion coefficients in multicomponent systems can be studied.

  2. Optimal and Numerical Solutions for an MHD Micropolar Nanofluid between Rotating Horizontal Parallel Plates.

    PubMed

    Nadeem, Sohail; Masood, Sadaf; Mehmood, Rashid; Sadiq, Muhammad Adil

    2015-01-01

    The present analysis deals with flow and heat transfer aspects of a micropolar nanofluid between two horizontal parallel plates in a rotating system. The governing partial differential equations for momentum, energy, micro rotation and nano-particles concentration are presented. Similarity transformations are utilized to convert the system of partial differential equations into system of ordinary differential equations. The reduced equations are solved analytically with the help of optimal homotopy analysis method (OHAM). Analytical solutions for velocity, temperature, micro-rotation and concentration profiles are expressed graphically against various emerging physical parameters. Physical quantities of interest such as skin friction co-efficient, local heat and local mass fluxes are also computed both analytically and numerically through mid-point integration scheme. It is found that both the solutions are in excellent agreement. Local skin friction coefficient is found to be higher for the case of strong concentration i.e. n=0, as compared to the case of weak concentration n=0.50. Influence of strong and weak concentration on Nusselt and Sherwood number appear to be similar in a quantitative sense. PMID:26046637

  3. A transient analysis of frost formation on a parallel plate evaporator

    SciTech Connect

    Martinez-Frias, J.; Aceves, S.M.; Hernandez-Guerrero, A.

    1996-12-31

    This paper presents the development of a transient model for evaluating frost formation on a parallel plate evaporator for heat pump applications. The model treats the frost layer as a porous substance, and applies the equations of conservation of mass, momentum and energy to calculate the growth and densification of the frost layer. Empirical correlations for thermal conductivity and tortuosity as a function of density are incorporated from previous studies. Frost growth is calculated as a function of time, Reynolds number, longitudinal location, plate temperature, and ambient air temperature and humidity. The main assumptions are: ideal gas behavior for air and water vapor, uniform frost density and thermal conductivity across the thickness of the frost layer; and quasi-steady conditions during the whole process. The mathematical model is validated by comparing the predicted values of frost thickness and frost density with results obtained in recent experimental studies. A good agreement was obtained in the comparison. The frost formation model calculates pressure drop and heat transfer resistance that result from the existence of the frost layer, and it can therefore be incorporated into a heat pump model to evaluate performance losses due to frosting as a function of weather conditions and time of operation since the last evaporator defrost.

  4. Parallel plate waveguide time domain spectroscopy to study terahertz conductivity of utltrathin materials

    NASA Astrophysics Data System (ADS)

    Razanoelina, Manjakavahoaka; Bagsican, Filchito R.; Kawayama, Iwao; Zhang, Xiang; Ma, Lulu; Murakami, Hironaru; Vajtai, Robert; Ajayan, Pulickel M.; Kono, Junichiro; Mittleman, Daniel M.; Tonouchi, Masayoshi

    2016-04-01

    The newly discovered atomically thin and layered materials which host electronic system that respond to longwavelength light in extraordinary manner can lead to a major breakthrough in the field of terahertz (THz) optics and photonics. However, their low conductivities due to either low densities or low mobility make it challenging to characterize their basic THz properties with the standard spectroscopic method. Here, we develop a THz spectroscopic technique based on parallel plate waveguide (PPWG) to overcome the limitations of the conventional THz time domain spectroscopy (TDS) technique. The present method is particularly suitable to ultrathin conductive materials with low carrier density. We report in details the derivation of the dispersion equations of the terahertz wave propagation in a PPWG loaded by a thin conductive materials with zero-thickness. These dispersion equations for transverse magnetic (TM) and transverse electric (TE) waveguide modes are the core of the optical parameters extraction algorithm in the THz-PPWG-TDS analysis. We demonstrate the effectiveness of the waveguide approach by characterizing low conductive CVD graphene. The high sensitivity of THz-PPWG-TDS technique enables us to study the carrier dynamics in graphene with Drude and Drude-Smith model.

  5. Deposition and disinfection of Escherichia coli O157:H7 on naturally occurring photoactive materials in a parallel plate chamber.

    PubMed

    Taylor, Alicia A; Chowdhury, Indranil; Gong, Amy S; Cwiertny, David M; Walker, Sharon L

    2014-02-01

    Dissolved organic matter in combination with iron oxides has been shown to facilitate photochemical disinfection through the production of reactive oxygen species (ROS) under UV and visible light. However, due to the extremely short lifetime of these radicals, the disinfection efficiency is limited by the successful transport of ROS to bacterial surfaces. This study was designed to quantitatively investigate three collector surfaces with various potentials to produce ROS [bare quartz, hematite (α-Fe2O3) coated quartz, and Suwannee River humic acid (SRHA)] and the effects of extracellular polymeric substance (EPS) (full or partial coating) and solution chemistry (ionic strength, IS) on the interactions between bacteria and the ROS-producing substrates. With few exceptions, bacterial deposition studies in a parallel plate (PP) flow chamber have revealed increasing cell adhesion with IS. Furthermore, interactions between collector surfaces and cells can be explained by electrostatic forces, with negatively charged SRHA reducing and positively charged α-Fe2O3 enhancing bacterial deposition significantly. Increased deposition was also observed with full EPS content, indicating the ability of EPS to facilitate interaction between cells and surfaces in the aquatic environment. In complementary disinfection studies conducted with simulated light, viability loss was observed for cells fully coated with EPS when attached to α-Fe2O3 under all IS conditions. Based upon our prior study in which EPS was found to not inhibit hydroxyl radical activity toward bacteria, we proposed that EPS might therefore promote disinfection by facilitating cell attachment to ROS-producing surfaces where higher concentrations of ROS are expected at closer proximities to reactive substrates (e.g., SRHA and α-Fe2O3). Our findings on the mechanism and controlling factors of cell interactions with photoactive substrates provide insight as to the role of ionic strength in photochemical disinfection

  6. Deposition and disinfection of Escherichia coli O157:H7 on naturally occurring photoactive materials in a parallel plate chamber†

    PubMed Central

    Taylor, Alicia A.; Chowdhury, Indranil; Gong, Amy S.; Cwiertny, David M.; Walker, Sharon L.

    2014-01-01

    Dissolved organic matter in combination with iron oxides has been shown to facilitate photochemical disinfection through the production of reactive oxygen species (ROS) under UV and visible light. However, due to the extremely short lifetime of these radicals, the disinfection effciency is limited by the successful transport of ROS to bacterial surfaces. This study was designed to quantitatively investigate three collector surfaces with various potentials to produce ROS [bare quartz, hematite (α-Fe2O3) coated quartz, and Suwannee River humic acid (SRHA)] and the effects of extracellular polymeric substance (EPS) (full or partial coating) and solution chemistry (ionic strength, IS) on the interactions between bacteria and the ROS-producing substrates. With few exceptions, bacterial deposition studies in a parallel plate (PP) flow chamber have revealed increasing cell adhesion with IS. Furthermore, interactions between collector surfaces and cells can be explained by electrostatic forces, with negatively charged SRHA reducing and positively charged α-Fe2O3 enhancing bacterial deposition significantly. Increased deposition was also observed with full EPS content, indicating the ability of EPS to facilitate interaction between cells and surfaces in the aquatic environment. In complementary disinfection studies conducted with simulated light, viability loss was observed for cells fully coated with EPS when attached to α-Fe2O3 under all IS conditions. Based upon our prior study in which EPS was found to not inhibit hydroxyl radical activity toward bacteria, we proposed that EPS might therefore promote disinfection by facilitating cell attachment to ROS-producing surfaces where higher concentrations of ROS are expected at closer proximities to reactive substrates (e.g., SRHA and α-Fe2O3). Our findings on the mechanism and controlling factors of cell interactions with photoactive substrates provide insight as to the role of ionic strength in photochemical disinfection

  7. Determination of thermal accommodation coefficients from heat transfer measurements between parallel plates.

    SciTech Connect

    Gallis, Michail A.; Castaneda, Jaime N.; Rader, Daniel John; Torczynski, John Robert; Trott, Wayne Merle

    2010-10-01

    Thermal accommodation coefficients have been derived for a variety of gas-surface combinations using an experimental apparatus developed to measure the pressure dependence of the conductive heat flux between parallel plates at unequal temperature separated by a gas-filled gap. The heat flux is inferred from temperature-difference measurements across the plates in a configuration where the plate temperatures are set with two carefully controlled thermal baths. Temperature-controlled shrouds provide for environmental isolation of the opposing test plates. Since the measured temperature differences in these experiments are very small (typically 0.3 C or less over the entire pressure range), high-precision thermistors are used to acquire the requisite temperature data. High-precision components have also been utilized on the other control and measurement subsystems in this apparatus, including system pressure, gas flow rate, plate alignment, and plate positions. The apparatus also includes the capability for in situ plasma cleaning of the installed test plates. Measured heat-flux results are used in a formula based on Direct Simulation Monte Carlo (DSMC) code calculations to determine the thermal accommodation coefficients. Thermal accommodation coefficients have been determined for three different gases (argon, nitrogen, helium) in contact with various surfaces. Materials include metals and alloys such as aluminum, gold, platinum, and 304 stainless steel. A number of materials important to fabrication of Micro Electro Mechanical Systems (MEMS) devices have also been examined. For most surfaces, coefficient values are near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Only slight differences in accommodation as a function of surface roughness have been seen. Surface contamination appears to have a more significant effect: argon plasma treatment has been observed to reduce thermal accommodation by as much as 0.10 for helium. Mixtures of argon and

  8. Exact analytical solutions for the Poiseuille and Couette-Poiseuille flow of third grade fluid between parallel plates

    NASA Astrophysics Data System (ADS)

    Danish, Mohammad; Kumar, Shashi; Kumar, Surendra

    2012-03-01

    Exact analytical solutions for the velocity profiles and flow rates have been obtained in explicit forms for the Poiseuille and Couette-Poiseuille flow of a third grade fluid between two parallel plates. These exact solutions match well with their numerical counter parts and are better than the recently developed approximate analytical solutions. Besides, effects of various parameters on the velocity profile and flow rate have been studied.

  9. Explorations of Space-Charge Limits in Parallel-Plate Diodes and Associated Techniques for Automation

    NASA Astrophysics Data System (ADS)

    Ragan-Kelley, Benjamin

    Space-charge limited flow is a topic of much interest and varied application. We extend existing understanding of space-charge limits by simulations, and develop new tools and techniques for doing these simulations along the way. The Child-Langmuir limit is a simple analytic solution for space-charge limited current density in a one-dimensional diode. It has been previously extended to two dimensions by numerical calculation in planar geometries. By considering an axisymmetric cylindrical system with axial emission from a circular cathode of finite radius r and outer drift tube R > r and gap length L, we further examine the space charge limit in two dimensions. We simulate a two-dimensional axisymmetric parallel plate diode of various aspect ratios (r/L), and develop a scaling law for the measured two-dimensional space-charge limit (2DSCL) relative to the Child-Langmuir limit as a function of the aspect ratio of the diode. These simulations are done with a large (100T) longitudinal magnetic field to restrict electron motion to 1D, with the two-dimensional particle-in-cell simulation code OOPIC. We find a scaling law that is a monotonically decreasing function of this aspect ratio, and the one-dimensional result is recovered in the limit as r >> L. The result is in good agreement with prior results in planar geometry, where the emission area is proportional to the cathode width. We find a weak contribution from the effects of the drift tube for current at the beam edge, and a strong contribution of high current-density "wings" at the outer-edge of the beam, with a very large relative contribution when the beam is narrow. Mechanisms for enhancing current beyond the Child-Langmuir limit remain a matter of great importance. We analyze the enhancement effects of upstream ion injection on the transmitted current in a one-dimensional parallel plate diode. Electrons are field-emitted at the cathode, and ions are injected at a controlled current from the anode. An analytic

  10. Characteristics of a miniature parallel-plate free-air ionization chamber for measuring the intensity of synchrotron radiation from an undulator

    NASA Astrophysics Data System (ADS)

    Nariyama, Nobuteru

    2004-09-01

    In order to develop an absolute intensity monitor for synchrotron radiation from an undulator, the characteristics of a parallel-plate free-air ionization chamber with a plate separation of 4.2 mm, which was considered to be as narrow as possible, were investigated using 8-30 keV monoenergetic photons at SPring-8. Using a Si-PIN photodiode as the reference monitor, saturation was confirmed at 8-30 keV at a photon intensity of an order of 1013 photons/s. The collection efficiency became almost unity at 8 and 10 keV within 3.8% and 1.1%, respectively, which gradually decreased with increasing energy and attained 0.52 at 30 keV because some of the high-energy electrons escaped from the sensitive volume. When the pair of electrodes was transferred from the upper and lower sides to the left and right sides of the beam axis in order to investigate the influence of linear polarization of synchrotron radiation, a decrease in the collection efficiency was observed. Monte Carlo simulations considering linear polarization showed that the plate separation required for no electron loss was 26, 14, and 8 mm for 30, 20, and 15 keV photons, respectively. For 20 keV photons, saturation characteristics were investigated using an ionization chamber with 14 mm plate separation.

  11. Approximate longitudinal space charge impedances of a round beam between parallel plates and inside a rectangular chamber

    NASA Astrophysics Data System (ADS)

    Li, Yingjie; Wang, Lanfa

    2015-01-01

    This paper presents the approximate analytical solutions to the longitudinal space charge (LSC) impedances of a round beam with uniform transverse distribution and sinusoidal line density modulations under two boundary conditions: (a) between parallel plates (b) inside a rectangular chamber, respectively. When the ratio of beam diameter to chamber height is small, the image charge fields of the round beam can be approximated by those of a line charge, the approximate analytical LSC impedances can be obtained by image method. The derived theoretical LSC impedances are valid at any perturbation wavelength and are consistent well with the numerical simulation results in a large range of ratios of beam diameters to chamber heights.

  12. Extraction of depth-dependent perturbation factors for parallel-plate chambers in electron beams using a plastic scintillation detector

    SciTech Connect

    Lacroix, Frederic; Guillot, Mathieu; McEwen, Malcolm; Cojocaru, Claudiu; Gingras, Luc; Beddar, A. Sam; Beaulieu, Luc

    2010-08-15

    Purpose: This work presents the experimental extraction of the overall perturbation factor P{sub Q} in megavoltage electron beams for NACP-02 and Roos parallel-plate ionization chambers using a plastic scintillation detector (PSD). Methods: The authors used a single scanning PSD mounted on a high-precision scanning tank to measure depth-dose curves in 6, 12, and 18 MeV clinical electron beams. The authors also measured depth-dose curves using the NACP-02 and PTW Roos chambers. Results: The authors found that the perturbation factors for the NACP-02 and Roos chambers increased substantially with depth, especially for low-energy electron beams. The experimental results were in good agreement with the results of Monte Carlo simulations reported by other investigators. The authors also found that using an effective point of measurement (EPOM) placed inside the air cavity reduced the variation of perturbation factors with depth and that the optimal EPOM appears to be energy dependent. Conclusions: A PSD can be used to experimentally extract perturbation factors for ionization chambers. The dosimetry protocol recommendations indicating that the point of measurement be placed on the inside face of the front window appear to be incorrect for parallel-plate chambers and result in errors in the R{sub 50} of approximately 0.4 mm at 6 MeV, 1.0 mm at 12 MeV, and 1.2 mm at 18 MeV.

  13. A negative-capacitance equivalent circuit model for parallel-plate capacitive-gap-transduced micromechanical resonators.

    PubMed

    Akgul, Mehmet; Wu, Lingqi; Ren, Zeying; Nguyen, Clark T-C

    2014-05-01

    A small-signal equivalent circuit for parallel-plate capacitive-gap-transduced micromechanical resonators is introduced that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates circuit analysis, that better elucidates the mechanisms behind certain potentially puzzling measured phenomena, and that inspires circuit topologies that maximize performance in specific applications. For this work, a micromechanical disk resonator serves as the vehicle with which to derive the equivalent circuits for both radial-contour and wine-glass modes, which are then used in circuit simulations (via simulation) to match measurements on actual fabricated devices. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive- gap-transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for applications that must be stable against environmental perturbations, such as acceleration or power supply variations. Measurements on fabricated devices confirm predictions by the new model of up to 4× improvement in frequency stability against dc-bias voltage variations for contour- mode disk resonators as the resistance loading their ports increases. By enhancing circuit visualization, this circuit model makes more obvious the circuit design procedures and topologies most beneficial for certain mechanical circuits, e.g., filters and oscillators.

  14. Linear and non-linear fluorescence imaging of neuronal activity

    NASA Astrophysics Data System (ADS)

    Fisher, Jonathan A. N.

    Optical imaging of neuronal activity offers new possibilities for understanding brain physiology. The predominant methods in neuroscience for measuring electrical activity require electrodes inserted into the tissue. Such methods, however, provide limited spatial information and are invasive. Optical methods are less physically invasive and offer the possibility for simultaneously imaging the activity of many neurons. In this thesis one- and two-photon fluorescence microscopy techniques were applied to several in vivo and in vitro mammalian preparations. Using one-photon absorption fluorescence microscopy and gradient index (GRIN) lens optics, cortical electrical activity in response to electric stimulation was resolved in three-dimensions at high-speed in the primary somatosensory cortex of the mouse in vivo using voltage-sensitive dyes. Imaging at depths up to 150 mum below the cortex surface, it was possible to resolve depth-dependent patterns of neuronal activity in response to cortical and thalamic electric stimulation. The patterns of activity were consistent with known cortical cellular architecture. In a qualitatively different set of experiments, one-photon fluorescence microscopy via voltage-sensitive dyes was successfully employed to image an in vitro preparation of the perfused rat brainstem during the process of respiratory rhythmogenesis. Imaging results yielded insights into the spatial organization of the central respiratory rhythm generation region in the ventrolateral medulla. A multifocal two-photon scanning microscope was constructed, and design and operation principles are described. Utilizing the novel device, anatomical and functional two-photon imaging via potentiometric dyes and calcium dyes is described, and the results of in vivo versus in vitro imaging are compared. Anatomical imaging results used either functional probe background fluorescence or green fluorescent protein (GFP) expression. Spectroscopic experiments measuring the two

  15. A parallel-plate electrochemical reactor model for the destruction of nitrate and nitrite in alkaline waste solutions

    SciTech Connect

    Coleman, D.H.; White, R.E.; Hobbs, D.T.

    1995-04-01

    The electrochemical treatment of nuclear waste is the subject of much current interest. After radioactive decontamination, the liquid waste from nuclear fuel processing still contains many hazardous substances, among them nitrate and nitrite. A parallel-plate electrochemical reactor model with multiple reactions at both electrodes and anolyte and catholyte recirculation tanks was modeled for the electrochemical destruction of nitrate and nitrite species in an alkaline solution. The model can be used to predict electrochemical reaction current efficiencies and outlet concentrations of species from the reactor, given inlet feed conditions and cell operating conditions. Also, predictions are made for off-gas composition and liquid-phase composition in the recirculation tanks. The results of case studies at different applied potentials are shown here. At lower applied potentials, the model predictions show that the destruction process is more energy efficient, but the time required to destroy a given amount of waste is increased.

  16. Comprehensive Analysis of Convective Heat Transfer in Parallel Plate Microchannel with Viscous Dissipation and Constant Heat Flux Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Kushwaha, Hari Mohan; Sahu, Santosh Kumar

    2016-06-01

    This paper reports the hydrodynamically and thermally fully developed, laminar, incompressible, forced convective heat transfer characteristics of gaseous flows through a parallel plate microchannel with different constant heat flux boundary conditions. The first order velocity slip and viscous dissipation effects are considered in the analysis. Here, three different thermal boundary conditions such as: both plates kept at different constant heat fluxes, both plates kept at equal constant heat fluxes and one plate kept at constant heat flux and other one insulated are considered for the analysis. The deviation in Nusselt number between the model that considers both first order velocity slip and temperature jump and the one that considers only velocity slip is reported. Also, the effect of various heat flux ratios on the Nusselt number is reported in this analysis. In addition, the deviation in Nusselt number between first and second order slip model is discussed in this study.

  17. Experimental study on the influence of the porosity of parallel plate stack on the temperature decrease of a thermoacoustic refrigerator

    NASA Astrophysics Data System (ADS)

    Setiawan, Ikhsan; Bambang Setio Utomo, Agung; Mitrayana; Katsuta, Masafumi; Nohtomi, Makoto

    2013-04-01

    Thermoacoustic refrigerators are cooling devices which are environmentally friendly because they don't use hazardous gases like chlorofuorocarbons (CFCs) or hydrofuorocarbons (HFCs) but rather air or inert gases as working medium. They apply sound wave with high intensity to pump heat from the cold to hot the regions through a stack in a resonator tube. One of the important parameters of thermoacoustic refrigerators is the porosity (blockage ratio) of stack which is a fraction of cross sectional area of the resonator unblocked for the gas movement by the stack. This paper describes an experimental study on how the porosity of parallel plate stack affects the temperature decrease of a thermoacoustic refrigerator. The porosity of parallel plate stack is specified by the thickness of plates and the spacing between plates. We measured the maximum temperature decreases of thermacoustic refrigerator using stacks with various porosities in the range of 0.5 - 0.85, with plate spacing from 0.5 mm to 1.5 mm and plate thicknesses 0.3 mm, 0.4 mm, and 0.5 mm. The measurements were done with two resonators with length of 0.8 m and 1.0 m, with air at atmospheric pressure and room temperature, correspond to thermal penetration depths (δκ) of 0.26 mm and 0.29 mm, respectively. It was found that there is an optimum porosity which gives the largest temperature decreases, and there is a tendency that the optimum porosity shifts to a larger value and the temperature decrease become larger when we used a stack with thinner plates. On the other hand, the study on the dependence of the temperature decrease on the plate thickness and the plate spacing reveals more useful information than that on the stack porosity itself. We found that stack with thinner plates tends to give larger temperature decrease, and the plate spacing of around 4δκ leads to the largest temperature decrease.

  18. Study of the parallel-plate EMP simulator and the simulator-obstacle interaction. Final technical report

    SciTech Connect

    Gedney, S.D.

    1990-12-01

    The Parallel-Plate Bounded-Wave EMP Simulator is typically used to test the vulnerability of electronic systems to the electromagnetic pulse (EMP) produced by a high altitude nuclear burst by subjecting the systems to a simulated EMP environment. However, when large test objects are placed within the simulator for investigation, the desired EMP environment may be affected by the interaction between the simulator and the test object. This simulator/obstacle interaction can be attributed to the following phenomena: (1) mutual coupling between the test object and the simulator, (2) fringing effects due to the finite width of the conducting plates of the simulator, and (3) multiple reflections between the object and the simulator's tapered end-sections. When the interaction is significant, the measurement of currents coupled into the system may not accurately represent those induced by an actual EMP. To better understand the problem of simulator/obstacle interaction, a dynamic analysis of the fields within the parallel-plate simulator is presented. The fields are computed using a moment method solution based on a wire mesh approximation of the conducting surfaces of the simulator. The fields within an empty simulator are found to be predominately transversse electromagnetic (TEM) for frequencies within the simulator's bandwidth, properly simulating the properties of the EMP propagating in free space. However, when a large test object is placed within the simulator, it is found that the currents induced on the object can be quite different from those on an object situated in free space. A comprehensive study of the mechanisms contributing to this deviation is presented.

  19. Turbulent forced convection with sinusoidal variation of inlet temperature between two parallel-plates

    SciTech Connect

    Arik, M.; Kakac, S.; Santos, C.A.C.

    1996-12-01

    The thermal entry region heat transfer due to turbulent forced convection, subjected to a sinusoidally varying inlet temperature is solved by employing a hybrid numerical-analytical solution technique under linear variation of wall temperature and constant wall temperature as boundary condition and is verified with the experimental results. The analytical solution of the problem is obtained through extending the generalized integral transform technique. An experimental set-up was built and used in order to validate the employed mathematical modeling. Analytical solutions are compared with the experimental findings. Satisfactory agreement is obtained between theoretically and experimentally determined heat transfer characteristics for different axial positions along the channel. Heat transfer characteristics of flow have been determined for linear wall temperature and constant wall temperature boundary conditions. Results obtained from the analytical-numerical solution technique and experimental studies have been presented in graphical and tabular forms.

  20. Dynamic analysis of the parallel-plate EMP (Electromagnetic Pulse) simulator using a wire-mesh approximation and the numerical electromagnetics code. Final report

    SciTech Connect

    Gedney, S.D.

    1987-09-01

    The electromagnetic pulse (EMP) produced by a high-altitude nuclear blast presents a severe threat to electronic systems due to its extreme characteristics. To test the vulnerability of large systems, such as airplanes, missiles, or satellites, they must be subjected to a simulated EMP environment. One type of simulator that has been used to approximate the EMP environment is the Large Parallel-Plate Bounded-Wave Simulator. It is a guided-wave simulator which has properties of a transmission line and supports a single TEM model at sufficiently low frequencies. This type of simulator consists of finite-width parallel-plate waveguides, which are excited by a wave launcher and terminated by a wave receptor. This study addresses the field distribution within a finite-width parallel-plate waveguide that is matched to a conical tapered waveguide at either end. Characteristics of a parallel-plate bounded-wave EMP simulator were developed using scattering theory, thin-wire mesh approximation of the conducting surfaces, and the Numerical Electronics Code (NEC). Background is provided for readers to use the NEC as a tool in solving thin-wire scattering problems.

  1. Nondestructive measurement of moisture content of different types of wheat using a single calibration with a parallel-plate capacitance sensor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A simple, low cost instrument that measures impedance and phase angle was used along with a parallel-plate capacitance system to estimate the moisture content (MC) of six types of wheat. Moisture content of grain is important and is measured at various stages of their processing and storage. A sampl...

  2. Expansion of a shock plasma in the accelerating field of a parallel-plate capacitor in a time-of-flight mass spectrometer

    NASA Astrophysics Data System (ADS)

    Semkin, N. D.; Pomel'nikov, R. A.; Telegin, A. M.

    2014-05-01

    We have solved the problem of expansion of a multicomponent shock plasma (initiated by an impact of a fast microprojectile against a solid target) to vacuum in the electric field of a parallel-plate capacitor. The results of calculations can be used in the development of a dust impact mass spectrometer for studying the elemental composition of micrometeorites.

  3. Characteristics and generation of elastic turbulence in a three-dimensional parallel plate channel using direct numerical simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Na; Li, Feng-Chen; Li, Xiao-Bin; Li, Dong-Yang; Cai, Wei-Hua; Yu, Bo

    2016-09-01

    Direct numerical simulations (DNSs) of purely elastic turbulence in rectilinear shear flows in a three-dimensional (3D) parallel plate channel were carried out, by which numerical databases were established. Based on the numerical databases, the present paper analyzed the structural and statistical characteristics of the elastic turbulence including flow patterns, the wall effect on the turbulent kinetic energy spectrum, and the local relationship between the flow motion and the microstructures’ behavior. Moreover, to address the underlying physical mechanism of elastic turbulence, its generation was presented in terms of the global energy budget. The results showed that the flow structures in elastic turbulence were 3D with spatial scales on the order of the geometrical characteristic length, and vortex tubes were more likely to be embedded in the regions where the polymers were strongly stretched. In addition, the patterns of microstructures’ elongation behave like a filament. From the results of the turbulent kinetic energy budget, it was found that the continuous energy releasing from the polymers into the main flow was the main source of the generation and maintenance of the elastic turbulent status. Project supported by the National Natural Science Foundation of China (Grant Nos. 51276046 and 51506037), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (Grant No. 51421063), the China Postdoctoral Science Foundation (Grant No. 2016M591526), the Heilongjiang Postdoctoral Fund, China (Grant No. LBH-Z15063), and the China Postdoctoral International Exchange Program.

  4. A boundary-integral model for drop deformation between two parallel plates with non-unit viscosity ratio drops

    NASA Astrophysics Data System (ADS)

    Janssen, P. J. A.; Anderson, P. D.

    2008-10-01

    A boundary-integral method is presented for drop deformation between two parallel walls for non-unit viscosity ratio systems. To account for the effect of the walls the Green's functions are modified and all terms for the double-layer potential are derived. The full three-dimensional implementation is validated, and the model is shown to be accurate and consistent. The method is applied to study drop deformation in shear flow. An excellent match with small-deformation theory is found at low capillary numbers, and our results match with other BIM simulations for pressure-driven flows. For shear flow with moderate capillary numbers, we see that the behavior of a low-viscosity drop is similar to that of drop with a viscosity ratio of unity. High-viscosity drops, on the other hand, are prevented from rotating in shear flow, which results in a larger deformation, but less overshoot in the drop axes is observed. In contrast with unconfined flow, high-viscosity drops can be broken in shear flow between parallel plates; for low-viscosity drops the critical capillary number is higher in confined situations.

  5. Heat/Fluid Flow Performance of Binary Gas Mixtures Formed with Helium Across Parallel-Plate Channels

    NASA Astrophysics Data System (ADS)

    Campo, Antonio; Manchu, Sreedhar

    2006-11-01

    The present study examines the trade-off between heat transfer enhancement and pressure drop increments caused by the flow of laminar binary gases in parallel-plate channels. Helium is the primary gas and carbon dioxide, methane, nitrogen, oxygen and xenon are the secondary gases. From fluid physics, two thermophysical properties: viscosity and density affect the gas flow, whereas four thermophysical properties: viscosity, density, thermal conductivity, and heat capacity at constant pressure influence the forced convection. From physical-chemistry, the collection of four thermophysical properties depends on temperature, pressure and molar gas composition. The simultaneous development of laminar velocity and temperature of each binary gas mixture is predicted using the finite volume method for two Reynolds numbers based on hydraulic diameter, i.e., 1000 and 2000. The two target parameters are the total heat transfer or mean convection coefficient and the pressure drop. The beneficial connectedness of the two target parameters changing with the molar gas composition is reported in terms of a proper figure-of-merit, the heat/fluid flow performance parameter for the two Reynolds numbers.

  6. MHD Two-Fluid Flow and Heat Transfer between Two Inclined Parallel Plates in a Rotating System

    PubMed Central

    Sri Ramachandra Murty, P.; Balaji Prakash, G.

    2014-01-01

    Two-phase magnetohydrodynamic convective flow of electrically conducting fluid through an inclined channel is studied under the action of a constant transverse magnetic field in a rotating system. The fluids in the two phases are steady, incompressible, laminar, immiscible, and electrically conducting, having different densities, viscosities, and thermal and electrical conductivities. The transport properties of both the fluids are assumed constant. The bounding infinite inclined parallel plates are maintained at different constant temperatures, making an angle ϕ with the horizontal. Approximate solutions for velocity and temperature distributions are obtained by using a straightforward regular perturbation technique. An in-depth study has been done on the effects of rotation parameter, Hartmann number, inclination angle, the ratio of electrical conductivities, and viscosities of two fluids on the flow. It is observed that the effect of increasing rotation is to decrease the primary velocity. Further it is noticed that as the rotation increases, the secondary velocity increases for smaller rotation, while for larger rotation it decreases. It is also found that the temperature distribution decreases as the rotation increases. PMID:27351017

  7. Characteristics and generation of elastic turbulence in a three-dimensional parallel plate channel using direct numerical simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Na; Li, Feng-Chen; Li, Xiao-Bin; Li, Dong-Yang; Cai, Wei-Hua; Yu, Bo

    2016-09-01

    Direct numerical simulations (DNSs) of purely elastic turbulence in rectilinear shear flows in a three-dimensional (3D) parallel plate channel were carried out, by which numerical databases were established. Based on the numerical databases, the present paper analyzed the structural and statistical characteristics of the elastic turbulence including flow patterns, the wall effect on the turbulent kinetic energy spectrum, and the local relationship between the flow motion and the microstructures’ behavior. Moreover, to address the underlying physical mechanism of elastic turbulence, its generation was presented in terms of the global energy budget. The results showed that the flow structures in elastic turbulence were 3D with spatial scales on the order of the geometrical characteristic length, and vortex tubes were more likely to be embedded in the regions where the polymers were strongly stretched. In addition, the patterns of microstructures’ elongation behave like a filament. From the results of the turbulent kinetic energy budget, it was found that the continuous energy releasing from the polymers into the main flow was the main source of the generation and maintenance of the elastic turbulent status. Project supported by the National Natural Science Foundation of China (Grant Nos. 51276046 and 51506037), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (Grant No. 51421063), the China Postdoctoral Science Foundation (Grant No. 2016M591526), the Heilongjiang Postdoctoral Fund, China (Grant No. LBH-Z15063), and the China Postdoctoral International Exchange Program.

  8. Comparison of lead zirconate titanate thin films for microelectromechanical energy harvester with interdigitated and parallel plate electrodes.

    PubMed

    Chidambaram, Nachiappan; Mazzalai, Andrea; Balma, Davide; Muralt, Paul

    2013-08-01

    Lead zirconate titanate (PZT) thin films on insulator- buffered silicon substrates with interdigitated electrodes (IDEs) have the potential to harvest more energy than parallel plate electrode (PPE) structures because the former exploit the longitudinal piezoelectric effect, which is about twice as high as the transverse piezoelectric effect used by PPE structures. In this work, both options are compared with respect to dielectric, ferroelectric, and piezoelectric properties, leakage currents, and figure of merit (FOM) for energy harvesting. The test samples were silicon beams with {100} PZT thin films in the case of the PPE geometry, and random PZT thin films for the IDE geometry. Both films were obtained by an identical sol-gel route. Almost the same dielectric constants were derived when the conformal mapping method was applied for the IDE capacitor to correct for the IDE geometry. The dielectric loss was smaller in the IDE case. The ferroelectric loops showed a higher saturation polarization, a higher coercive field, and less back-switching for the IDE case. The leakage current density of the IDE structure was measured to be about 4 orders of magnitude lower than that of the PPE structure. The best FOM of the IDE structures was 20% superior to that of the PPE structures while also having a voltage response that was ten times higher (12.9 mV/μ strain). PMID:25004526

  9. Predicted Sensitivity for Tests of Short-range Gravity with a Novel Parallel-plate Torsion Pendulum

    NASA Astrophysics Data System (ADS)

    Richards, Matthew; Baxley, Brandon; Hoyle, C. D.; Leopardi, Holly; Shook, David

    2011-11-01

    The parallel-plate torsion pendulum apparatus at Humboldt State University is designed to test the Weak Equivalence Principle (WEP) and the gravitational inverse-square law (ISL) of General Relativity at unprecedented levels in the sub-millimeter regime. Some versions of String Theory predict additional dimensions that might affect the gravitational inverse-square law (ISL) at sub-millimeter levels. Some models also predict the existence of unobserved subatomic particles, which if exist, could cause a violation in the WEP at short distances. Short-range tests of gravity and the WEP are also instrumental in investigating possible proposed mechanisms that attempt to explain the accelerated expansion of the universe, generally attributed to Dark Energy. The weakness of the gravitational force makes measurement very difficult at small scales. Testing such a minimal force requires highly isolated experimental systems and precise measurement and control instrumentation. Moreover, a dedicated test of the WEP has not been performed below the millimeter scale. This talk will discuss the improved sensitivity that we expect to achieve in short-range gravity tests with respect to previous efforts that employ different experimental configurations.

  10. On the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams

    SciTech Connect

    Zink, K.; Wulff, J.

    2011-02-15

    Purpose: In recent years, several Monte Carlo studies have been published concerning the perturbation corrections of a parallel-plate chamber in clinical electron beams. In these studies, a strong depth dependence of the relevant correction factors (p{sub wall} and p{sub cav}) for depth beyond the reference depth is recognized and it has been shown that the variation with depth is sensitive to the choice of the chamber's effective point of measurement. Recommendations concerning the positioning of parallel-plate ionization chambers in clinical electron beams are not the same for all current dosimetry protocols. The IAEA TRS-398 as well as the IPEM protocol and the German protocol DIN 6800-2 interpret the depth of measurement within the phantom as the water equivalent depth, i.e., the nonwater equivalence of the entrance window has to be accounted for by shifting the chamber by an amount {Delta}z. This positioning should ensure that the primary electrons traveling from the surface of the water phantom through the entrance window to the chamber's reference point sustain the same energy loss as the primary electrons in the undisturbed phantom. The objective of the present study is the determination of the shift {Delta}z for a NACP-02 chamber and the calculation of the resulting wall perturbation correction as a function of depth. Moreover, the contributions of the different chamber walls to the wall perturbation correction are identified. Methods: The dose and fluence within the NACP-02 chamber and a wall-less air cavity is calculated using the Monte Carlo code EGSnrc in a water phantom at different depths for different clinical electron beams. In order to determine the necessary shift to account for the nonwater equivalence of the entrance window, the chamber is shifted in steps {Delta}z around the depth of measurement. The optimal shift {Delta}z is determined from a comparison of the spectral fluence within the chamber and the bare cavity. The wall perturbation

  11. Monte Carlo study of the depth-dependent fluence perturbation in parallel-plate ionization chambers in electron beams

    SciTech Connect

    Zink, K.; Czarnecki, D.; Voigts-Rhetz, P. von; Looe, H. K.; Harder, D.

    2014-11-01

    Purpose: The electron fluence inside a parallel-plate ionization chamber positioned in a water phantom and exposed to a clinical electron beam deviates from the unperturbed fluence in water in absence of the chamber. One reason for the fluence perturbation is the well-known “inscattering effect,” whose physical cause is the lack of electron scattering in the gas-filled cavity. Correction factors determined to correct for this effect have long been recommended. However, more recent Monte Carlo calculations have led to some doubt about the range of validity of these corrections. Therefore, the aim of the present study is to reanalyze the development of the fluence perturbation with depth and to review the function of the guard rings. Methods: Spatially resolved Monte Carlo simulations of the dose profiles within gas-filled cavities with various radii in clinical electron beams have been performed in order to determine the radial variation of the fluence perturbation in a coin-shaped cavity, to study the influences of the radius of the collecting electrode and of the width of the guard ring upon the indicated value of the ionization chamber formed by the cavity, and to investigate the development of the perturbation as a function of the depth in an electron-irradiated phantom. The simulations were performed for a primary electron energy of 6 MeV. Results: The Monte Carlo simulations clearly demonstrated a surprisingly large in- and outward electron transport across the lateral cavity boundary. This results in a strong influence of the depth-dependent development of the electron field in the surrounding medium upon the chamber reading. In the buildup region of the depth-dose curve, the in–out balance of the electron fluence is positive and shows the well-known dose oscillation near the cavity/water boundary. At the depth of the dose maximum the in–out balance is equilibrated, and in the falling part of the depth-dose curve it is negative, as shown here the

  12. Deposition and survival of Escherichia coli O157:H7 on clay minerals in a parallel plate flow system.

    PubMed

    Cai, Peng; Huang, Qiaoyun; Walker, Sharon L

    2013-02-19

    Understanding bacterial pathogens deposition and survival processes in the soil-groundwater system is crucial to protect public health from soilborne and waterborne diseases. However, mechanisms of bacterial pathogen-clay interactions are not well studied, particularly in dynamic systems. Also, little is known about the viability of bacterial pathogens when attached to clays. In this study, a parallel plate flow system was used to determine the deposition kinetics and survival of Escherichia coli O157:H7 on montmorillonite, kaolinite, and goethite over a wide range of ionic strengths (IS) (0.1-100 mM KCl). E. coli O157:H7 deposition on the positively charged goethite is greater than that on the negatively charged kaolinite and montmorillonite. Although the zeta potential of kaolinite was more negative than that of montmorillonite, kaolinite showed a greater deposition for E. coli O157:H7 than montmorillonite, which is attributed to the chemical heterogeneity of clay minerals. Overall, increasing IS resulted in an increase of E. coli O157:H7 deposition on montmorillonite and kaolinite, and a decrease on goethite. Interaction energy calculations suggest that E. coli O157:H7 deposition on clays was largely governed by DLVO (Derjaguin-Landau-Verwey-Overbeek) forces. The loss of bacterial membrane integrity was investigated as a function of time using the Live/Dead BacLight viability assay. During the examined period of 6 h, E. coli O157:H7 retained its viability in suspension and when attached to montmorillonite and kaolinite; however, interaction with the goethite was detrimental. The information obtained in this study is of fundamental significance for the understanding of the fate of bacterial pathogens in soil environments.

  13. Optimizing terahertz surface plasmons of a monolayer graphene and a graphene parallel plate waveguide using one-dimensional photonic crystal

    NASA Astrophysics Data System (ADS)

    Hajian, H.; Soltani-Vala, A.; Kalafi, M.

    2013-07-01

    Through analytical calculations, the transverse magnetic surface plasmon (SP) dispersion relations for a monolayer graphene and a graphene parallel-plate waveguide (PPWG) in the presence of a one-dimensional photonic crystal (1D PC) as a substrate and a symmetric/asymmetric cladding medium are obtained. For the monolayer graphene case, we show that the presence of the 1D PC leads to significant modification in propagation length (PL) and localization length (LL) of THz SPs, as compared with the SPs of monolayer graphene on SiO2 substrate. And the SPs with largest PL and small LL, named as optimized SPs, could be supported when the 1D PC is used only as a substrate. For the graphene PPWG case with the plate separation "D" (here, 10 nm≤D≤1 μm), in addition to support of typical upper and lower branches of coupled THz SPs, presence of the 1D PC leads to support of an extra branch when 10 nm≪D≤1 μm. Moreover, as far as supporting optimized 0-2 THz SPs are concerned, the case in which the graphene PPWG with D = 1 μm is sandwiched between two symmetric 1D PC could be the best candidate. Whereas the graphene PPWG on the 1D PC, with D = 10 nm, supports optimized SPs in a frequency range from 2 to 4.5 THz. Therefore, using 1D PC improves the capability of monolayer graphene and also graphene PPWG for sensing and waveguide applications in THz frequencies.

  14. A fluid–structure interaction model to characterize bone cell stimulation in parallel-plate flow chamber systems

    PubMed Central

    Vaughan, T. J.; Haugh, M. G.; McNamara, L. M.

    2013-01-01

    Bone continuously adapts its internal structure to accommodate the functional demands of its mechanical environment and strain-induced flow of interstitial fluid is believed to be the primary mediator of mechanical stimuli to bone cells in vivo. In vitro investigations have shown that bone cells produce important biochemical signals in response to fluid flow applied using parallel-plate flow chamber (PPFC) systems. However, the exact mechanical stimulus experienced by the cells within these systems remains unclear. To fully understand this behaviour represents a most challenging multi-physics problem involving the interaction between deformable cellular structures and adjacent fluid flows. In this study, we use a fluid–structure interaction computational approach to investigate the nature of the mechanical stimulus being applied to a single osteoblast cell under fluid flow within a PPFC system. The analysis decouples the contribution of pressure and shear stress on cellular deformation and for the first time highlights that cell strain under flow is dominated by the pressure in the PPFC system rather than the applied shear stress. Furthermore, it was found that strains imparted on the cell membrane were relatively low whereas significant strain amplification occurred at the cell–substrate interface. These results suggest that strain transfer through focal attachments at the base of the cell are the primary mediators of mechanical signals to the cell under flow in a PPFC system. Such information is vital in order to correctly interpret biological responses of bone cells under in vitro stimulation and elucidate the mechanisms associated with mechanotransduction in vivo. PMID:23365189

  15. A fluid-structure interaction model to characterize bone cell stimulation in parallel-plate flow chamber systems.

    PubMed

    Vaughan, T J; Haugh, M G; McNamara, L M

    2013-04-01

    Bone continuously adapts its internal structure to accommodate the functional demands of its mechanical environment and strain-induced flow of interstitial fluid is believed to be the primary mediator of mechanical stimuli to bone cells in vivo. In vitro investigations have shown that bone cells produce important biochemical signals in response to fluid flow applied using parallel-plate flow chamber (PPFC) systems. However, the exact mechanical stimulus experienced by the cells within these systems remains unclear. To fully understand this behaviour represents a most challenging multi-physics problem involving the interaction between deformable cellular structures and adjacent fluid flows. In this study, we use a fluid-structure interaction computational approach to investigate the nature of the mechanical stimulus being applied to a single osteoblast cell under fluid flow within a PPFC system. The analysis decouples the contribution of pressure and shear stress on cellular deformation and for the first time highlights that cell strain under flow is dominated by the pressure in the PPFC system rather than the applied shear stress. Furthermore, it was found that strains imparted on the cell membrane were relatively low whereas significant strain amplification occurred at the cell-substrate interface. These results suggest that strain transfer through focal attachments at the base of the cell are the primary mediators of mechanical signals to the cell under flow in a PPFC system. Such information is vital in order to correctly interpret biological responses of bone cells under in vitro stimulation and elucidate the mechanisms associated with mechanotransduction in vivo.

  16. Theoretical study of the effect of liquid desiccant mass flow rate on the performance of a cross flow parallel-plate liquid desiccant-air dehumidifier

    NASA Astrophysics Data System (ADS)

    Mohammad, Abdulrahman Th.; Mat, Sohif Bin; Sulaiman, M. Y.; Sopian, K.; Al-abidi, Abduljalil A.

    2013-11-01

    A computer simulation using MATLAB is investigated to predict the distribution of air stream parameters (humidity ratio and temperature) as well as desiccant parameters (temperature and concentration) inside the parallel plate absorber. The present absorber consists of fourteen parallel plates with a surface area per unit volume ratio of 80 m2/m3. Calcium chloride as a liquid desiccant flows through the top of the plates to the bottom while the air flows through the gap between the plates making it a cross flow configuration. The model results show the effect of desiccant mass flow rate on the performance of the dehumidifier (moisture removal and dehumidifier effectiveness). Performance comparisons between present cross-flow dehumidifier and another experimental cross-flow dehumidifier in the literature are carried out. The simulation is expected to help in optimizing of a cross flow dehumidifier.

  17. Use of a new type of radiochromic film, a new parallel-plate micro-chamber, MOSFETs, and TLD 800 microcubes in the dosimetry of small beams.

    PubMed

    Francescon, P; Cora, S; Cavedon, C; Scalchi, P; Reccanello, S; Colombo, F

    1998-04-01

    The dosimetry of the fields usually employed in radiosurgery requires the use of small detectors to measure Total Scatter Factor (Sc,p), Tissue Maximum Ratio (TMR), Percentage Depth Dose (PDD), and Off Axis Ratio (OAR). In this paper new dosimeters are investigated: a new type of radiochromic film, a micro parallel-plate chamber (filled with both air and tetramethylsilane, TMS), MOSFETs, and TLD-800 microcubes. Their behavior has been compared with the response of radiographic film and with the values obtained with BEAM Monte Carlo simulation. The experimental data confirm that dosimetry with radiochromic films and TLDs gives consistent results for all beam diameters. The parallel-plate micro chamber underestimates the Sc,p for the smallest field diameters (4.4 mm and 6.7 mm); MOSFETs show an over-estimation for the Sc,p of the 4.4 mm, 6.7 mm, and 10.5 mm field diameters. BEAM Monte Carlo simulation employing a parallel beam and a standard 6 MV x-ray spectrum has been used to obtain a correction factor as a function of the field size for both the parallel-plate micro chamber and MOSFETs. High accuracy measurements of PDD and TMR have been made in a water phantom both with radiochromic film and with the micro parallel-plate chamber and have been compared with the data computed by BEAM Monte Carlo simulation. The latter dosimeter is preferred because of the quicker and simpler use and because it gives immediate readout. Measurements of OAR made with radiochromic films and with radiographic films give differences in the 80%-20% penumbra width within 0.6 mm for field diameters ranging from 4.4 mm to 19 mm.

  18. Treatment of industrial effluents by electrochemical generation of H2O2 using an RVC cathode in a parallel plate reactor.

    PubMed

    Bustos, Yaneth A; Rangel-Peraza, Jesús Gabriel; Rojas-Valencia, Ma Neftalí; Bandala, Erick R; Álvarez-Gallegos, Alberto; Vargas-Estrada, Laura

    2016-01-01

    Electrochemical techniques have been used for the discolouration of synthetic textile industrial wastewater by Fenton's process using a parallel plate reactor with a reticulated vitreous carbon (RVC) cathode. It has been shown that RVC is capable of electro-generating and activating H2O2 in the presence of Fe(2+) added as catalyst and using a stainless steel mesh as anode material. A catholyte comprising 0.05 M Na2SO4, 0.001 M FeSO4.7H2O, 0.01 M H2SO4 and fed with oxygen was used to activate H2O2.The anolyte contained only 0.8 M H2SO4. The operating experimental conditions were 170 mA (2.0 V < ΔECell < 3.0 V) to generate 5.3 mM H2O2. Synthetic effluents containing various concentrations (millimolar - mM) of three different dyes, Blue Basic 9 (BB9), Reactive Black 5 (RB5) and Acid Orange 7 (AO7), were evaluated for discolouration using the electro-assisted Fenton reaction. Water discolouration was measured by UV-VIS absorbance reduction. Dye removal by electrolysis was a function of time: 90% discolouration of 0.08, 0.04 and 0.02 mM BB9 was obtained at 14, 10 and 6 min, respectively. In the same way, 90% discolouration of 0.063, 0.031 and 0.016 mM RB5 was achieved at 90, 60 and 30 min, respectively. Finally, 90% discolouration of 0.14, 0.07 and 0.035 mM AO7 was achieved at 70, 40 and 20 min, respectively. The experimental results confirmed the effectiveness of electro-assisted Fenton reaction as a strong oxidizing process in water discolouration and the ability of RVC cathode to electro-generate and activate H2O2 in situ.

  19. Treatment of industrial effluents by electrochemical generation of H2O2 using an RVC cathode in a parallel plate reactor.

    PubMed

    Bustos, Yaneth A; Rangel-Peraza, Jesús Gabriel; Rojas-Valencia, Ma Neftalí; Bandala, Erick R; Álvarez-Gallegos, Alberto; Vargas-Estrada, Laura

    2016-01-01

    Electrochemical techniques have been used for the discolouration of synthetic textile industrial wastewater by Fenton's process using a parallel plate reactor with a reticulated vitreous carbon (RVC) cathode. It has been shown that RVC is capable of electro-generating and activating H2O2 in the presence of Fe(2+) added as catalyst and using a stainless steel mesh as anode material. A catholyte comprising 0.05 M Na2SO4, 0.001 M FeSO4.7H2O, 0.01 M H2SO4 and fed with oxygen was used to activate H2O2.The anolyte contained only 0.8 M H2SO4. The operating experimental conditions were 170 mA (2.0 V < ΔECell < 3.0 V) to generate 5.3 mM H2O2. Synthetic effluents containing various concentrations (millimolar - mM) of three different dyes, Blue Basic 9 (BB9), Reactive Black 5 (RB5) and Acid Orange 7 (AO7), were evaluated for discolouration using the electro-assisted Fenton reaction. Water discolouration was measured by UV-VIS absorbance reduction. Dye removal by electrolysis was a function of time: 90% discolouration of 0.08, 0.04 and 0.02 mM BB9 was obtained at 14, 10 and 6 min, respectively. In the same way, 90% discolouration of 0.063, 0.031 and 0.016 mM RB5 was achieved at 90, 60 and 30 min, respectively. Finally, 90% discolouration of 0.14, 0.07 and 0.035 mM AO7 was achieved at 70, 40 and 20 min, respectively. The experimental results confirmed the effectiveness of electro-assisted Fenton reaction as a strong oxidizing process in water discolouration and the ability of RVC cathode to electro-generate and activate H2O2 in situ. PMID:26419746

  20. An analytical and numerical study on the start-up flow of slightly rarefied gases in a parallel-plate channel and a pipe

    NASA Astrophysics Data System (ADS)

    Avramenko, A. A.; Tyrinov, A. I.; Shevchuk, I. V.

    2015-04-01

    The paper presents results of an investigation of the response of an incompressible fluid in a circular micropipe and a parallel-plate microchannel to a sudden time-independent pressure drop. Solutions of the problem were obtained analytically using the Laplace transform technique and numerically using the lattice Boltzmann method. The unsteady velocity profiles in the pipe and in the channel were obtained with the help of the infinite series solutions validated against numerical simulations. In line with the expectations, the flow asymptotically tends to the fully developed pattern, which is attained quicker for smaller Knudsen numbers. The solution enabled also obtaining relations to estimate the hydraulic resistance coefficient.

  1. Linear and non-linear control techniques applied to actively lubricated journal bearings

    NASA Astrophysics Data System (ADS)

    Nicoletti, R.; Santos, I. F.

    2003-03-01

    The main objectives of actively lubricated bearings are the simultaneous reduction of wear and vibration between rotating and stationary machinery parts. For reducing wear and dissipating vibration energy until certain limits, one can use the conventional hydrodynamic lubrication. For further reduction of shaft vibrations one can use the active lubrication action, which is based on injecting pressurized oil into the bearing gap through orifices machined in the bearing sliding surface. The design and efficiency of some linear (PD, PI and PID) and a non-linear controller, applied to a tilting-pad journal bearing, are analysed and discussed. Important conclusions about the application of integral controllers, responsible for changing the rotor-bearing equilibrium position and consequently the "passive" oil film damping coefficients, are achieved. Numerical results show an effective vibration reduction of unbalance response of a rigid rotor, where the PD and the non-linear P controllers show better performance for the frequency range of study (0-80 Hz). The feasibility of eliminating rotor-bearing instabilities (phenomena of whirl) by using active lubrication is also investigated, illustrating clearly one of its most promising applications.

  2. Investigation and performance tests of a new parallel plate ionization chamber with double sensitive volume for measuring diagnostic X-rays

    NASA Astrophysics Data System (ADS)

    Sharifi, B.; Zamani Zeinali, H.; Soltani, J.; Negarestani, A.; Shahvar, A.

    2015-01-01

    Medical diagnostic equipment, like diagnostic radiology and mammography require a dosimeter with high accuracy for dosimetry of the diagnostic X-ray beam. Ionization chambers are suitable instruments for dosimetry of diagnostic-range X-ray beams because of their appropriate response and high reliability. This work introduces the design and fabrication of a new parallel plate ionization chamber with a PMMA body, graphite-coated PMMA windows (0.5 mm thick) and a graphite-foil central electrode (0.1 mm thick, 0.7 g/cm3 dense). This design improves upon the response characteristics of existing designs through the specific choice of materials as well as the appropriate size and arrangement of the ionization chamber components. The results of performance tests conducted at the Secondary Standard Dosimetry laboratory in Karaj-Iran demonstrated the short and long-term stability, the low leakage current, the low directional dependence, and the high ion collection efficiency of the design. Furthermore, the FLUKA Monte Carlo simulations confirmed the low effect of central electrode on this new ionization chamber response. The response characteristics of the parallel plate ionization chamber presented in this work makes the instrument suitable for use as a standard dosimeter in laboratories.

  3. SU-E-T-448: On the Perturbation Factor P-cav of the Markus Parallel Plate Ion Chambers in Clinical Electron Beams, Monte Carlo Based Reintegration of An Historical Experiment

    SciTech Connect

    Voigts-Rhetz, P von; Zink, K

    2014-06-01

    Purpose: All present dosimetry protocols recommend well-guarded parallel-plate ion chambers for electron dosimetry. For the guard-less Markus chamber an energy dependent fluence perturbation correction pcav is given. This perturbation correction was experimentally determined by van der Plaetsen by comparison of the read-out of a Markus and a NACP chamber, which was assumed to be “perturbation-free”. Aim of the present study is a Monte Carlo based reiteration of this experiment. Methods: Detailed models of four parallel-plate chambers (Roos, Markus, NACP and Advanced Markus) were designed using the Monte Carlo code EGSnrc and placed in a water phantom. For all chambers the dose to the active volume filled with low density water was calculated for 13 clinical electron spectra (E{sub 0}=6-21 MeV) at the depth of maximum and at the reference depth under reference conditions. In all cases the chamber's reference point was positioned at the depth of measurement. Moreover, the dose to water DW was calculated in a small water voxel positioned at the same depth. Results: The calculated dose ratio D{sub NACP}/D{sub Markus}, which according to van der Plaetsen reflects the fluence perturbation correction of the Markus chamber, deviates less from unity than the values given by van der Plaetsen's but exhibits a similar energy dependence. The same holds for the dose ratios of the other well guarded chambers. But, in comparison to water, the Markus chamber reveals the smallest overall perturbation correction which is nearly energy independent at both investigated depths. Conclusion: The simulations principally confirm the energy dependence of the dose ratio D{sub NACP}/D{sub Markus} as published by van der Plaetsen. But, as shown by our simulations of the ratio D{sub W}/D{sub Markus}, the conclusion drawn in all dosimetry protocols is questionable: in contrast to all well-guarded chambers the guard-less Markus chamber reveals the smallest overall perturbation correction and

  4. Recognizing Human Activities Using Non-linear SVM Decision Tree

    NASA Astrophysics Data System (ADS)

    Zhao, Haiyong; Liu, Zhijing; Zhang, Hao

    This paper presents a new method of human activity recognition, which is based on R transform and non-linear SVM Decision Tree (NSVMDT). For a key binary human silhouette, R transform is employed to represent low-level features. The advantage of the R transform lies in its low computational complexity and geometric invariance. We utilize NSVMDT to train and classify video sequences, and demonstrate the usability with many sequences. Compared with other methods, ours is superior because the descriptor is robust to frame loss in superior because the descriptor is robust to frame loss in activities recognition, simple representation, computational complexity and template generalization. Sufficient experiments have proved the efficiency.

  5. Theory, simulation, and experiment of a single module coax-to-parallel-plate transition for the transformer section of PBFA II

    SciTech Connect

    Johnson, W.A.; Schneider, L.X.; Neau, E.L.

    1989-01-01

    Techniques are being developed to gain understanding of energy transport efficiencies through changes in pulsed power transmission line geometries. These techniques are being applied to design study of the PBFA-II accelerator which has the goal of increasing the energy available for ICF experiments. Transverse electromagnetic (TEM) wave analysis yields a simple circuit model of the new coax-to- parallel-plate transition. This simple model gives insight into the dominant physics of the device and suggests design improvements that will lead to the desired energy efficiencies. Insights gained by this simple model are confirmed and refined by 3-dimensional, time dependent computer simulations with the SOS code and scale model experiments. Simulations have predicted experimental results to high degree of accuracy which adds confidence in both the simulations and the scale model experiments. 1 ref., 11 figs., 1 tab.

  6. Dielectric dispersion of BaxSr1-xTiO3 thin film with parallel-plate and coplanar interdigital electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Yu; Song, Qing; Xu, Feng; Sheng, Su; Wang, Peng; Ong, C. K.

    2009-03-01

    Ferroelectric BaxSr1-xTiO3 (BST) thin films with x = 0.25 and 0.5 were grown by pulsed laser deposition on single crystal LaAlO3 and Pt/Ti/SiO2/Si substrates, respectively. Capacitors were then fabricated from the BST thin films based on coplanar interdigital electrodes (CIEs) and parallel-plate electrodes (PPEs). The dielectric properties of the BST film with CIE and PPE were investigated and compared over a wide frequency range from 100 Hz to 10 GHz. The dielectric dispersion in PPE configuration, caused by the interfacial polarization in film/electrode interfaces, exhibited a strong dependence on frequency. However, the permittivity ɛCIE in CIE configuration shows a gentle variation with the frequency indicating interfacial polarization substantially suppressed. The influence upon the dielectric properties of the columnar BST grains due to the use of different forms of electrodes was discussed.

  7. Spatial frequency multiplier with active linearly tapered slot antenna array

    NASA Astrophysics Data System (ADS)

    Simons, Rainee N.; Lee, Richard Q.

    1994-02-01

    A frequency multiplier with active linearly tapered slot antennas (LTSA's) has been demonstrated at the second harmonic frequency. In each antenna element, a GaAs monolithic microwave integrated circuit (MMIC) distributed amplifier is integrated with two LTSA's. The multiplier has a very wide bandwidth and large dynamic range. The fundamental-to-second harmonic conversion efficiency is 8.1 percent. The spatially combined second harmonic signal is 50 dB above the noise level. The design is suitable for constructing a large array using monolithic integration techniques.

  8. Space Power Amplification with Active Linearly Tapered Slot Antenna Array

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1993-01-01

    A space power amplifier composed of active linearly tapered slot antennas (LTSA's) has been demonstrated and shown to have a gain of 30 dB at 20 GHz. In each of the antenna elements, a GaAs monolithic microwave integrated circuit (MMIC) three-stage power amplifier is integrated with two LTSA's. The LTSA and the MMIC power amplifier has a gain of 11 dB and power added efficiency of 14 percent respectively. The design is suitable for constructing a large array using monolithic integration techniques.

  9. Spatial frequency multiplier with active linearly tapered slot antenna array

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1994-01-01

    A frequency multiplier with active linearly tapered slot antennas (LTSA's) has been demonstrated at the second harmonic frequency. In each antenna element, a GaAs monolithic microwave integrated circuit (MMIC) distributed amplifier is integrated with two LTSA's. The multiplier has a very wide bandwidth and large dynamic range. The fundamental-to-second harmonic conversion efficiency is 8.1 percent. The spatially combined second harmonic signal is 50 dB above the noise level. The design is suitable for constructing a large array using monolithic integration techniques.

  10. Linearity and efficiency improvement by active compensation in IMPATT amplifiers

    NASA Astrophysics Data System (ADS)

    Riris, A.; Aitchison, C. S.

    1985-02-01

    The application of active compensation to IMPATT amplifiers operating under large-signal conditions, including the effects of diode reactance, in order to enhance the linearity and improve the efficiency is discussed. Theoretical predictions using a large-signal equivalent circuit of an IMPATT diode show an improvement in the 1-dB compression point of up to 18 dB. It is shown that the output power of the actively compensated amplifier is double that of two uncompensated amplifiers connected in parallel using hybrid couplers, for the same input power, thus indicating an efficiency improvement of 100 percent. The technique is of value for both terrestrial and satellite communication-system microwave power sources.

  11. Linear analysis of active-medium two-beam accelerator

    NASA Astrophysics Data System (ADS)

    Voin, Miron; Schächter, Levi

    2015-07-01

    We present detailed development of the linear theory of wakefield amplification by active medium and its possible application to a two-beam accelerator (TBA) is discussed. A relativistic train of triggering microbunches traveling along a vacuum channel in an active medium confined by a cylindrical waveguide excites Cherenkov wake in the medium. The wake is a superposition of azimuthally symmetric transverse magnetic modes propagating along a confining waveguide, with a phase velocity equal to the velocity of the triggering bunches. The structure may be designed in such a way that the frequency of one of the modes is close to active-medium resonant frequency, resulting in amplification of the former and domination of a single mode far behind the trigger bunches. Another electron bunch placed in proper phase with the amplified wakefield may be accelerated by the latter. Importantly, the energy for acceleration is provided by the active medium and not the drive bunch as in a traditional TBA. Based on a simplified model, we analyze extensively the impact of various parameters on the wakefield amplification process.

  12. A linearly and circularly polarized active integrated antenna

    NASA Astrophysics Data System (ADS)

    Khoshniat, Ali

    This thesis work presents a new harmonic suppression technique for microstrip patch antennas. Harmonic suppression in active integrated antennas is known as an effective method to improve the efficiency of amplifiers in transmitter side. In the proposed design, the antenna works as the radiating element and, at the same time, as the tuning load for the amplifier circuit that is directly matched to the antenna. The proposed active antenna architecture is easy to fabricate and is symmetric, so it can be conveniently mass-produced and designed to have circular polarization, which is preferred in many applications such as satellite communications. The antenna simulations were performed using Ansoft High Frequency System Simulator (HFSS) and all amplifier design steps were simulated by Advanced Design System (ADS). The final prototypes of the linearly polarized active integrated antenna and the circularly polarized active integrated antenna were fabricated using a circuit board milling machine. The antenna radiation pattern was measured inside Utah State University's anechoic chamber and the results were satisfactory. Power measurements for the amplifiers' performance were carried out inside the chamber and calculated by using the Friis transmission equation. It is seen that a significant improvement in the efficiency is achieved compared to the reference antenna without harmonic suppression. Based on the success in the single element active antenna design, the thesis also presents a feasibility of applying the active integrated antenna in array configuration, in particular, in scanning array design to yield a low-profile, low-cost alternative to the parabolic antenna transmitter of satellite communication systems.

  13. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam.

    PubMed

    Groetz, J-E; Ounoughi, N; Mavon, C; Belafrites, A; Fromm, M

    2014-08-01

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™ and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  14. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

    NASA Astrophysics Data System (ADS)

    Groetz, J.-E.; Ounoughi, N.; Mavon, C.; Belafrites, A.; Fromm, M.

    2014-08-01

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  15. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

    SciTech Connect

    Groetz, J.-E. Mavon, C.; Fromm, M.; Ounoughi, N.; Belafrites, A.

    2014-08-15

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  16. Decentralized two-stage sewage treatment by chemical-biological flocculation combined with microalgae biofilm for nutrient immobilization in a roof installed parallel plate reactor.

    PubMed

    Zamalloa, Carlos; Boon, Nico; Verstraete, Willy

    2013-02-01

    In this lab-scale study, domestic wastewater is subjected to a chemical biological adsorption (A-stage), followed by treatment in an innovative roof installed parallel plate microalgae biofilm reactor for nutrient immobilization (I-stage). The A-stage process was operated at a hydraulic retention time (HRT) of 1h and a solid retention time of 1day (FeSO(4) as flocculant). The I-stage, which consequently received the effluent of the A-stage process, was operated at an HRT of 1day and exposed to natural light. The overall system removed on average 74% of the total chemical oxygen demand, 82% of the total suspended solids, 67% of the total nitrogen and 96% of the total phosphorous in the wastewater. The design involves a relatively low capital and operating cost which is in the order of 0.5€/m(3) wastewater treated. These aspects suggest that the A/I process can be used as a decentralized domestic wastewater treatment system.

  17. Measurement of the absolute penetration depth and surface resistance of superconductors and normal metals with the variable spacing parallel plate resonator

    NASA Astrophysics Data System (ADS)

    Talanov, Vladimir V.; Mercaldo, Lucia V.; Anlage, Steven M.; Claassen, John H.

    2000-05-01

    The variable spacing parallel plate resonator (VSPPR) is a microwave transmission line resonator with a continuously variable thickness of the dielectric spacer between the superconducting or metallic plates, filled by cryogenic liquid or vacuum. We measure the dielectric spacer thickness dependencies of the resonator frequency and quality factor, and fit them to theoretical forms, in order to extract the absolute values of penetration depth, λ, and surface resistance, Rs. A cryogenic micropositioning setup is developed to vary the spacer thickness from 0 to 100 μm with a resolution of 8.5 nm, and to maintain parallelism of the resonator plates. Measurement of ac capacitance between the plates is utilized to directly determine the separation between the resonator plates and to reduce the effect of their tilt and nonflatness on the accuracy of the measured Rs and λ. Because the operating temperature is fixed (77 K), the result for a superconductor is independent of an a priori model for the penetration depth versus temperature. This technique can also be employed as a surface impedance standard for characterization of high temperature superconducting films for microwave applications.

  18. Exact solution for chameleon field, self-coupled through the Ratra-Peebles potential with n =1 and confined between two parallel plates

    NASA Astrophysics Data System (ADS)

    Ivanov, A. N.; Cronenberg, G.; Höllwieser, R.; Jenke, T.; Pitschmann, M.; Wellenzohn, M.; Abele, H.

    2016-10-01

    We calculate the chameleon field profile, confined between two parallel plates, filled with air at pressure P =10-4 mbar and room temperature and separated by the distance L , in the chameleon field theory with Ratra-Peebles self-interaction potential with index n =1 . We give the exact analytical solution in terms of Jacobian elliptic functions, depending on the mass density of the ambient matter. The obtained analytical solution can be used in qBounce experiments, measuring transition frequencies between quantum gravitational states of ultracold neutrons and also for the calculation of the chameleon field induced Casimir force for the CANNEX experiment. We show that the chameleon-matter interactions with coupling constants β ≤1 04 can be probed by qBounce experiments with sensitivities Δ E ≤10-18 eV . At L =30.1 μ m we reproduce the result β <5.8 ×1 08 , obtained by Jenke et al. [Phys. Rev. Lett. 112, 151105 (2014)] at sensitivity Δ E ˜10-14 eV . In the vicinity of one of the plates our solution coincides with the solution, obtained by Brax and Pignol [Phys. Rev. Lett. 107, 111301 (2011)] [see also Ivanov et al. Phys. Rev. D 87, 105013 (2013)] above a plate at zero density of the ambient matter.

  19. Unsteady MHD convective flow of Second grade fluid through a porous medium in a Rotating parallel plate channel with temperature dependent source

    NASA Astrophysics Data System (ADS)

    VeeraKrishna, M.; Subba Reddy, G.

    2016-09-01

    In this paper, we make an initial vale investigation of hydromagnetic convective flow of a viscous electrically conducting second grade fluid through a porous medium in a rotating parallel plate channel in the presence of a temperature dependent heat source. The perturbations in the flow are created by a constant pressure gradient along the plates in addition to non-torsional oscillations of the lower plate. The exact solutions of the velocity and the temperature fields consist of the steady state and the transient components using Laplace transform technique. The time required for the transient effects to decay is discussed in detail and the ultimate steady state consists of boundary layers on the plates and an interior. Attention is focused on the physical nature of the solutions, and the structure of the various kinds of boundary layers formed on the plates. The final steady state velocity and temperature fields are numerically discussed for different values of the governing parameters. The shear stresses and the Nusselt number are tabulated. Particular case when both the plates are at rest has also been computed and analyzed.

  20. Fate of linear alkylbenzene sulfonate (LAS) in activated sludge plants.

    PubMed

    Temmink, H; Klapwijk, Bram

    2004-02-01

    Monitoring data were collected in a pilot-scale municipal activated sludge plant to assess the fate of the C12-homologue of linear alkyl benzene sulfonate (LAS-C12). The pilot-plant was operated at influent LAS-C12 concentrations between 2 and 12 mg l(-1) and at sludge retention times of 10 and 27 days. Effluent and waste sludge concentrations varied between 5 and 10 microg l(-1) and between 37 and 69 microg g(-1) VSS, respectively. In the sludge samples only 2-8% was present as dissolved LAS-C12, whereas the remaining 92-98% was found to be adsorbed to the sludge. In spite of this high degree of sorption, more than 99% of the LAS-C12 load was removed by biodegradation, showing that not only the soluble fraction but also the adsorbed fraction of LAS-C12 is readily available for biodegradation. Sorption and biodegradation of LAS-C12 were also investigated separately. Sorption was an extremely fast and reversible process and could be described by a linear isotherm with a partition coefficient of 3.2 l g(-1) volatile suspended solids. From the results of biodegradation kinetic tests it was concluded that primary biodegradation of LAS-C12 cannot be described by a (growth) Monod model, but a secondary utilisation model should be used instead. The apparent affinity of the sludge to biodegrade LAS-C12 increased when the sludge was loaded with higher influent concentrations of LAS-C12.

  1. Nanocapillary Adhesion between Parallel Plates.

    PubMed

    Cheng, Shengfeng; Robbins, Mark O

    2016-08-01

    Molecular dynamics simulations are used to study capillary adhesion from a nanometer scale liquid bridge between two parallel flat solid surfaces. The capillary force, Fcap, and the meniscus shape of the bridge are computed as the separation between the solid surfaces, h, is varied. Macroscopic theory predicts the meniscus shape and the contribution of liquid/vapor interfacial tension to Fcap quite accurately for separations as small as two or three molecular diameters (1-2 nm). However, the total capillary force differs in sign and magnitude from macroscopic theory for h ≲ 5 nm (8-10 diameters) because of molecular layering that is not included in macroscopic theory. For these small separations, the pressure tensor in the fluid becomes anisotropic. The components in the plane of the surface vary smoothly and are consistent with theory based on the macroscopic surface tension. Capillary adhesion is affected by only the perpendicular component, which has strong oscillations as the molecular layering changes.

  2. Nanocapillary Adhesion between Parallel Plates.

    PubMed

    Cheng, Shengfeng; Robbins, Mark O

    2016-08-01

    Molecular dynamics simulations are used to study capillary adhesion from a nanometer scale liquid bridge between two parallel flat solid surfaces. The capillary force, Fcap, and the meniscus shape of the bridge are computed as the separation between the solid surfaces, h, is varied. Macroscopic theory predicts the meniscus shape and the contribution of liquid/vapor interfacial tension to Fcap quite accurately for separations as small as two or three molecular diameters (1-2 nm). However, the total capillary force differs in sign and magnitude from macroscopic theory for h ≲ 5 nm (8-10 diameters) because of molecular layering that is not included in macroscopic theory. For these small separations, the pressure tensor in the fluid becomes anisotropic. The components in the plane of the surface vary smoothly and are consistent with theory based on the macroscopic surface tension. Capillary adhesion is affected by only the perpendicular component, which has strong oscillations as the molecular layering changes. PMID:27413872

  3. Nonlinear Learning of Linear Algebra: Active Learning through Journal Writing

    ERIC Educational Resources Information Center

    Hamdan, May

    2005-01-01

    Students find difficulty in learning linear algebra because of the abstraction and formalism associated with concepts such as vector space, linear independence, rank and invertible matrices. Learning the necessary procedures becomes insufficient, and imitating worked examples does not guarantee the maturity level necessary for understanding these…

  4. A high frequency analysis of electromagnetic plane wave scattering by perfectly-conducting semi-infinite parallel plate and rectangular waveguides with absorber coated inner walls

    NASA Technical Reports Server (NTRS)

    Noh, H. M.; Pathak, P. H.

    1986-01-01

    An approximate but sufficiently accurate high frequency solution which combines the uniform geometrical theory of diffraction (UTD) and the aperture integration (AI) method is developed for analyzing the problem of electromagnetic (EM) plane wave scattering by an open-ended, perfectly-conducting, semi-infinite hollow rectangular waveguide (or duct) with a thin, uniform layer of lossy or absorbing material on its inner wall, and with a planar termination inside. In addition, a high frequency solution for the EM scattering by a two dimensional (2-D), semi-infinite parallel plate waveguide with a absorber coating on the inner walls is also developed as a first step before analyzing the open-ended semi-infinite three dimensional (3-D) rectangular waveguide geometry. The total field scattered by the semi-infinite waveguide consists firstly of the fields scattered from the edges of the aperture at the open-end, and secondly of the fields which are coupled into the waveguide from the open-end and then reflected back from the interior termination to radiate out of the open-end. The first contribution to the scattered field can be found directly via the UTD ray method. The second contribution is found via the AI method which employs rays to describe the fields in the aperture that arrive there after reflecting from the interior termination. It is assumed that the direction of the incident plane wave and the direction of observation lie well inside the forward half space tht exists outside the half space containing the semi-infinite waveguide geometry. Also, the medium exterior to the waveguide is assumed to be free space.

  5. Linearization of the full activated sludge model No 1 for interaction analysis.

    PubMed

    Benhalla, Abdelhay; Houssou, Mohamed; Charif, Moussa

    2010-08-01

    This paper deals with the linearization of the full activated sludge model No 1 (ASM1) in the scope of interaction analysis. For consistency, the linearization procedure is developed and validated within the BSM1 simulation benchmark framework. It is based on reaction rate approximation by linear combinations of states. The linear rate models are identified and incorporated in the mass balance equations, yielding a linear locally equivalent to the ASM1 model. Linear models for anoxic and aerated compartments are proposed. It is observed that the presented models track very closely the nonlinear ASM1 responses to various influent data. The key feature of this linearization strategy is that the gotten linear version of the ASM1 model is linear time invariant (LTI) and that it conserves the states biological interpretation and the original ASM1 dimension. It allows, therefore, application of interaction analysis methods and makes it possible to determine motivated control configurations for the ASM1 model. PMID:20131068

  6. Measurement of activity distribution using photostimulable phosphor imaging plates in decommissioned 10 MV medical linear accelerator.

    PubMed

    Fujibuchi, Toshioh; Yonai, Shunsuke; Yoshida, Masahiro; Sakae, Takeji; Watanabe, Hiroshi; Abe, Yoshihisa; Itami, Jun

    2014-08-01

    Photonuclear reactions generate neutrons in the head of the linear accelerator. Therefore, some parts of the linear accelerator can become activated. Such activated materials must be handled as radioactive waste. The authors attempted to investigate the distribution of induced radioactivity using photostimulable phosphor imaging plates. Autoradiographs were produced from some parts of the linear accelerator (the target, upper jaw, multileaf collimator and shielding). The levels of induced radioactivity were confirmed to be non-uniform within each part from the autoradiographs. The method was a simple and highly sensitive approach to evaluating the relative degree of activation of the linear accelerators, so that appropriate materials management procedures can be carried out.

  7. Antimicrobial activity of human α-defensin 5 and its linear analogs: N-terminal fatty acylation results in enhanced antimicrobial activity of the linear analogs.

    PubMed

    Mathew, Basil; Nagaraj, Ramakrishnan

    2015-09-01

    Human α-defensin 5 (HD5) exhibits broad spectrum antimicrobial activity and plays an important role in mucosal immunity of the small intestine. Although there have been several studies, the structural requirements for activity and mechanism of bacterial killing is yet to be established unequivocally. In this study, we have investigated the antimicrobial activity of HD5 and linear analogs. Cysteine deletions attenuated the antibacterial activity considerably. Candidacidal activity was affected to a lesser extent. Fatty acid conjugated linear analogs showed antimicrobial activity comparable activity to HD5. Effective surface charge neutralization of bacteria was observed for HD5 as compared to the non-fatty acylated linear analogs. Our results show that HD5 and non-fatty acylated linear analogs enter the bacterial cytoplasm without causing damage to the bacterial inner membrane. Although fatty acylated peptides exhibited antimicrobial activity comparable to HD5, their mechanism of action involved permeabilization of the Escherichia coli inner membrane. HD5 and analogs had the ability to bind plasmid DNA. HD5 had greater binding affinity to plasmid DNA as compared to the analogs. The three dimensional structure of HD5 favors greater interaction with the bacterial cell surface and also with DNA. Antibacterial activity of HD5 involves entry into bacterial cytoplasm and binding to DNA which would result in shut down of the bacterial metabolism leading to cell death. We show how a moderately active linear peptide derived from the α-defensin HD5 can be engineered to enhance antimicrobial activity almost comparable to the native peptide. PMID:26206286

  8. Search for the return of activity in active asteroid 176P/LINEAR

    SciTech Connect

    Hsieh, Henry H.; Denneau, Larry; Jedicke, Robert; Kaluna, Heather M.; Keane, Jacqueline V.; Kleyna, Jan; MacLennan, Eric M.; Meech, Karen J.; Riesen, Timm; Schunova, Eva; Urban, Laurie; Vereš, Peter; Wainscoat, Richard J.; Fitzsimmons, Alan; Lacerda, Pedro; Hainaut, Olivier R.; Ishiguro, Masateru; Moskovitz, Nick A.; Snodgrass, Colin; Trujillo, Chadwick A.; and others

    2014-04-01

    We present the results of a search for the reactivation of active asteroid 176P/LINEAR during its 2011 perihelion passage using deep optical observations obtained before, during, and after that perihelion passage. Deep composite images of 176P constructed from data obtained between 2011 June and 2011 December show no visible signs of activity, while photometric measurements of the object during this period also show no significant brightness enhancements similar to that observed for 176P between 2005 November and 2005 December when it was previously observed to be active. An azimuthal search for dust emission likewise reveals no evidence for directed emission (i.e., a tail, as was previously observed for 176P), while a one-dimensional surface brightness profile analysis shows no indication of a spherically symmetric coma at any time in 2011. We conclude that 176P did not in fact exhibit activity in 2011, at least not on the level on which it exhibited activity in 2005, and suggest that this could be due to the devolatization or mantling of the active site responsible for its activity in 2005.

  9. Non-linear dynamics of the complement system activation.

    PubMed

    Korotaevskiy, Andrey A; Hanin, Leonid G; Khanin, Mikhail A

    2009-12-01

    The complement system (CS) plays a prominent role in the immune defense. The goal of this work is to study the dynamics of activation of the classic and alternative CS pathways based on the method of mathematical modeling. The principal difficulty that hinders modeling effort is the absence of the measured values of kinetic constants of many biochemical reactions forming the CS. To surmount this difficulty, an optimization procedure consisting of constrained minimization of the total protein consumption by the CS was designed. The constraints made use of published data on the in vitro kinetics of elimination of the Borrelia burgdorferi bacteria by the CS. Special features of the problem at hand called for a significant modification of the general constrained optimization procedure to include a mathematical model of the bactericidal effect of the CS in the iterative setting. Determination of the unknown kinetic constants of biochemical reactions forming the CS led to a fully specified mathematical model of the dynamics of cell killing induced by the CS. On the basis of the model, effects of the initial concentrations of complements and their inhibitors on the bactericidal action of the CS were studied. Proteins playing a critical role in the regulation of the bactericidal action of the CS were identified. Results obtained in this work serve as an important stepping stone for the study of functioning of the CS as a whole as well as for developing methods for control of pathogenic processes. PMID:19854207

  10. The use of non-linear analysis for differentiating the biomagnetic activity in ovarian lesions.

    PubMed

    Anninos, P A; Anastasiadis, P; Kotini, A

    1999-05-01

    In this study we investigated the biomagnetic activity measured with the superconducting quantum interference device (SQUID) in benign and malignant ovarian lesions using non-linear analysis. We used a single channel biomagnetometer SQUID in order to measure the magnetic field emitted from benign and malignant ovarian lesions. We can differentiate such biomagnetic activities using non-linear analysis. Using the application of non-linear analysis in the ovarian lesions together with the use of dimensional calculations we have observed a clear saturation value for the dimension of malignant ovarian lesions and non-saturation for benign ovarian lesions. The biomagnetic measurements with the SQUID and the application of non-linear analysis in benign and malignant ovarian lesions, is a promising procedure in assessing and differentiating ovarian tumours. PMID:15512296

  11. Effect of light intensity on linear shrinkage of photo-activated composite resins during setting.

    PubMed

    Inoue, K; Howashi, G; Kanetou, T; Masumi, S; Ueno, O; Fujii, K

    2005-01-01

    The purpose of this investigation was to examine the effects of light intensity on linear shrinkage of photo-activated composite resins during setting. The materials used were four commercially available photo-activated composite resins. Three light-irradiation instruments were selected and prepared so as to obtain four light intensities (200, 480, 800 and 1600 mW cm(-2)). The linear shrinkage during setting was examined 10 min after light irradiation using a trial balance plastometer, and the specimen thickness was 2.0 mm for all materials. The depth of cure was examined according to the test method described in the International Organization for Standardization (ISO/FDIS 4049: 2000(E)). In measuring the linear shrinkage 60 s from the start of light irradiation for 10 s, there was a significant correlation (r = 0.89-0.94) between the amount of linear shrinkage and the light intensity: an increase in light intensity produced a greater linear shrinkage. Furthermore, there was a significant correlation (r = 0.92-1.0) between the linear shrinkage and the irradiation time: an increase in irradiation time resulted in a greater linear shrinkage. Values of the depth of cure ranged from 1.69 to 3.75 mm. PMID:15634297

  12. Linear active disturbance rejection control of underactuated systems: the case of the Furuta pendulum.

    PubMed

    Ramírez-Neria, M; Sira-Ramírez, H; Garrido-Moctezuma, R; Luviano-Juárez, A

    2014-07-01

    An Active Disturbance Rejection Control (ADRC) scheme is proposed for a trajectory tracking problem defined on a nonfeedback linearizable Furuta Pendulum example. A desired rest to rest angular position reference trajectory is to be tracked by the horizontal arm while the unactuated vertical pendulum arm stays around its unstable vertical position without falling down during the entire maneuver and long after it concludes. A linear observer-based linear controller of the ADRC type is designed on the basis of the flat tangent linearization of the system around an arbitrary equilibrium. The advantageous combination of flatness and the ADRC method makes it possible to on-line estimate and cancels the undesirable effects of the higher order nonlinearities disregarded by the linearization. These effects are triggered by fast horizontal arm tracking maneuvers driving the pendulum substantially away from the initial equilibrium point. Convincing experimental results, including a comparative test with a sliding mode controller, are presented.

  13. Non-linear dynamic modeling of an automobile hydraulic active suspension system

    NASA Astrophysics Data System (ADS)

    Mrad, R. Ben; Levitt, J. A.; Fassois, S. D.

    1994-09-01

    Motived by the strong need for realistically describing the dynamical behaviour of automotive systems through adequate mathematical models, a computer-stimulation-suitable non-linear quarter-car model of a hydraulic active suspension system is developed. Unlike previously available linear models characterised by idealised actuator and component behaviour, the developed model accounts for the dynamics of the main system components, including the suspension bushing, pump, accumulator, power and bypass valves, and hydraulic actuator, while also incorporating preliminary versions of the system controllers. Significant system characteristics, such as non-linear pressure-flow relationships, fluid compressibility, pump and valve non-linearities, leakages, as well as Coulomb friction, are also explicitly accounted for, and the underpinning assumptions are discussed. Simulation results obtained by exercising the model provide insight into the system behavior, illustrate the importance of the actuator/component dynamics and their associated non-linearities and reveal the inadequacy of the idealised linear models in capturing the system behaviour, demonstrate specific effects of valve leakage and fluid bulk modulus, are in qualitative agreement with experimental measurements, and stress the need for proper control law design and tuning. The developed model is particularly suitable for analysis, design, control law optimisation, and diagnostic strategies development.

  14. Re-Mediating Classroom Activity with a Non-Linear, Multi-Display Presentation Tool

    ERIC Educational Resources Information Center

    Bligh, Brett; Coyle, Do

    2013-01-01

    This paper uses an Activity Theory framework to evaluate the use of a novel, multi-screen, non-linear presentation tool. The Thunder tool allows presenters to manipulate and annotate multiple digital slides and to concurrently display a selection of juxtaposed resources across a wall-sized projection area. Conventional, single screen presentation…

  15. Linear/Nonlinear Relations of Activity and Fitness with Children’s Academic Achievement

    PubMed Central

    Hansen, David M.; Herrmann, Stephen D.; Lambourne, Kate; Lee, Jaehoon; Donnelly, Joseph E.

    2014-01-01

    A growing research base suggests the benefits of physical activity (PA) and aerobic fitness for children extend beyond overall health/well-being to include academic achievement (AA). The majority of research studies on relations of PA and fitness with AA have utilized linear-only analytic approaches, thereby precluding the possibility that PA and fitness could have a differing impact on AA for those more/less active or fit. Objective Evaluate both linear and non-linear associations of PA and aerobic fitness with children’s AA among a sample of 687 2nd and 3rd grade students from 17 Midwest schools. Study Design Using baseline data (fall 2011) from a larger 3-year intervention trial, multi-level regression analyses examined the linear and non-linear associations of AA with PA and with PACER laps (i.e., aerobic fitness), controlling for relevant covariates. Results Fitness, but not PA, had a significant quadratic association with both spelling and math achievement. Results indicate that 22–28 laps on the PACER was the point at which the associated increase in achievement per lap plateaued for spelling and math. Conclusions Increasing fitness could potentially have the greatest impact on children’s AA for those below the 50th fitness percentile on the PACER. PMID:24781896

  16. Strong variable linear polarization in the cool active star II Peg

    NASA Astrophysics Data System (ADS)

    Rosén, Lisa; Kochukhov, Oleg; Wade, Gregg A.

    2014-08-01

    Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular polarization is used. On the other hand, linear polarization is sensitive to the transverse component of the magnetic field. By including linear polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was linear polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong linear polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.

  17. Activated-sludge nitrification in the presence of linear and branched-chain alkyl benzene sulfonates.

    PubMed

    Baillod, C R; Boyle, W C

    1968-01-01

    The effects of biodegradable linear alkyl benzene sulfonate and branched-chain alkyl benzene sulfonate detergents on activated-sludge nitrification were investigated by administering a synthetic waste containing up to 23 mg of each detergent per liter to eight bench-scale, batch, activated-sludge units. It was found that both detergents tended to promote complete oxidation of ammonia to nitrate, whereas control units produced approximately equal amounts of nitrite and nitrate. Various hypotheses are offered to explain the phenomenon.

  18. Two New FRET Imaging Measures: Linearly Proportional to and Highly Contrasting the Fraction of Active Molecules

    PubMed Central

    Yamao, Masataka; Aoki, Kazuhiro; Yukinawa, Naoto; Ishii, Shin; Matsuda, Michiyuki; Naoki, Honda

    2016-01-01

    We developed two new FRET imaging measures for intramolecular FRET biosensors, called linearly proportional (LP) and highly contrasting (HC) measures, which can be easily calculated by the fluorescence intensities of donor and acceptor as a ratio between their weighted sums. As an alternative to the conventional ratiometric measure, which non-linearly depends on the fraction of active molecule, we first developed the LP measure, which is linearly proportional to the fraction of active molecules. The LP measure inherently unmixes bleed-through signals and is robust against fluorescence noise. By extending the LP measure, we furthermore designed the HC measure, which provides highly contrasting images of the molecular activity, more than the ratiometric measure. In addition to their advantages, these measures are insensitive to the biosensor expression level, which is a fundamental property of the ratiometric measure. Using artificial data and FRET imaging data, we showed that the LP measure effectively represents the fraction of active molecules and that the HC measure improves visual interpretability by providing high contrast images of molecular activity. Therefore, the LP and HC measures allow us to gain more quantitative and qualitative insights from FRET imaging than the ratiometric measure. PMID:27780260

  19. Induced Voltage Linear Extraction Method Using an Active Kelvin Bridge for Disturbing Force Self-Sensing

    PubMed Central

    Yang, Yuanyuan; Wang, Lei; Tan, Jiubin; Zhao, Bo

    2016-01-01

    This paper presents an induced voltage linear extraction method for disturbing force self-sensing in the application of giant magnetostrictive actuators (GMAs). In this method, a Kelvin bridge combined with an active device is constructed instead of a conventional Wheatstone bridge for extraction of the induced voltage, and an additional GMA is adopted as a reference actuator in the self-sensing circuit in order to balance the circuit bridge. The linear fitting of the measurement data is done according to the linear relationship between the disturbing forces and the integral of the induced voltage. The experimental results confirm the good performance of the proposed method, and the self-sensitivity of the disturbing forces is better than 2.0 (mV·s)/N. PMID:27213399

  20. Skin Sympathetic Nerve Activity is Modulated during Slow Sinusoidal Linear Displacements in Supine Humans

    PubMed Central

    Bolton, Philip S.; Hammam, Elie; Kwok, Kenny; Macefield, Vaughan G.

    2016-01-01

    Low-frequency sinusoidal linear acceleration (0.08 Hz, ±4 mG) modulates skin sympathetic nerve activity (SSNA) in seated subjects (head vertical), suggesting that activation of the utricle in the peripheral vestibular labyrinth modulates SSNA. The aim of the current study was to determine whether SSNA is also modulated by input from the saccule. Tungsten microelectrodes were inserted into the common peroneal nerve to record oligounitary SSNA in 8 subjects laying supine on a motorized platform with the head aligned with the longitudinal axis of the body. Slow sinusoidal (0.08 Hz, 100 cycles) linear acceleration-decelerations (peak ±4 mG) were applied rostrocaudally to predominately activate the saccules, or mediolaterally to predominately activate the utricles. Cross-correlation histograms were constructed between the negative-going sympathetic spikes and the positive peaks of the sinusoidal stimuli. Sinusoidal linear acceleration along the rostrocaudal axis or mediolateral axis both resulted in sinusoidal modulation of SSNA (Median, IQR 27.0, 22–33% and 24.8, 17–39%, respectively). This suggests that both otolith organs act on sympathetic outflow to skin and muscle in a similar manner during supine displacements. PMID:26909019

  1. Starspots and active regions on IN Com: UBVRI photometry and linear polarization

    NASA Astrophysics Data System (ADS)

    Alekseev, I. Yu.; Kozlova, O. V.

    2014-06-01

    The activity of the variable star IN Com is considered using the latest multicolor UBVRI photometry and linear polarimetric observations carried out during a decade. The photometric variability of the star is fully described using the zonal spottedness model developed at the Crimean Astrophysical Observatory (CrAO). Spotted regions cover up to 22% of the total stellar surface, with the difference in temperatures between the quiet photosphere and the spot umbra being 600 K. The spots are located at middle and low latitudes (40°-55°). The intrinsic broad-band linear polarization of IN Com and its rotational modulation in the U band due to local magnetic fields at the most spotted (active) stellar longitudes were detected for the first time.

  2. k-Nearest neighbour local linear prediction of scalp EEG activity during intermittent photic stimulation.

    PubMed

    Erla, Silvia; Faes, Luca; Tranquillini, Enzo; Orrico, Daniele; Nollo, Giandomenico

    2011-05-01

    The characterization of the EEG response to photic stimulation (PS) is an important issue with significant clinical relevance. This study aims to quantify and map the complexity of the EEG during PS, where complexity is measured as the degree of unpredictability resulting from local linear prediction. EEG activity was recorded with eyes closed (EC) and eyes open (EO) during resting and PS at 5, 10, and 15 Hz in a group of 30 healthy subjects and in a case-report of a patient suffering from cerebral ischemia. The mean squared prediction error (MSPE) resulting from k-nearest neighbour local linear prediction was calculated in each condition as an index of EEG unpredictability. The linear or nonlinear nature of the system underlying EEG activity was evaluated quantifying MSPE as a function of the neighbourhood size during local linear prediction, and by surrogate data analysis as well. Unpredictability maps were obtained for each subject interpolating MSPE values over a schematic head representation. Results on healthy subjects evidenced: (i) the prevalence of linear mechanisms in the generation of EEG dynamics, (ii) the lower predictability of EO EEG, (iii) the desynchronization of oscillatory mechanisms during PS leading to increased EEG complexity, (iv) the entrainment of alpha rhythm during EC obtained by 10 Hz PS, and (v) differences of EEG predictability among different scalp regions. Ischemic patient showed different MSPE values in healthy and damaged regions. The EEG predictability decreased moving from the early acute stage to a stage of partial recovery. These results suggest that nonlinear prediction can be a useful tool to characterize EEG dynamics during PS protocols, and may consequently constitute a complement of quantitative EEG analysis in clinical applications. PMID:21216649

  3. Shigella flexneri suppresses NF-κB activation by inhibiting linear ubiquitin chain ligation.

    PubMed

    de Jong, Maarten F; Liu, Zixu; Chen, Didi; Alto, Neal M

    2016-01-01

    The linear ubiquitin chain assembly complex (LUBAC) is a multimeric E3 ligase that catalyses M1 or linear ubiquitination of activated immune receptor signalling complexes (RSCs). Mutations that disrupt linear ubiquitin assembly lead to complex disease pathologies including immunodeficiency and autoinflammation in both humans and mice, but microbial toxins that target LUBAC function have not yet been discovered. Here, we report the identification of two homologous Shigella flexneri type III secretion system effector E3 ligases IpaH1.4 and IpaH2.5, which directly interact with LUBAC subunit Heme-oxidized IRP2 ubiquitin ligase-1 (HOIL-1L) and conjugate K48-linked ubiquitin chains to the catalytic RING-between-RING domain of HOIL-1-interacting protein (HOIP). Proteasomal degradation of HOIP leads to irreversible inactivation of linear ubiquitination and blunting of NF-κB nuclear translocation in response to tumour-necrosis factor (TNF), IL-1β and pathogen-associated molecular patterns. Loss of function studies in mammallian cells in combination with bacterial genetics explains how Shigella evades a broad spectrum of immune surveillance systems by cooperative inhibition of receptor ubiquitination and reveals the critical importance of LUBAC in host defence against pathogens. PMID:27572974

  4. Treatment of pretreated coking wastewater by flocculation, alkali out, air stripping, and three-dimensional electrocatalytic oxidation with parallel plate electrodes.

    PubMed

    Wen-wu, Liu; Xiu-ping, Wang; Xue-yan, Tu; Chang-yong, Wang

    2014-10-01

    The coking wastewater generally comprises highly concentrated, recalcitrant, and toxic organic pollutants, so its treatment has been of great importance to prevent living beings and their environment from these hazardous contaminations. The treatment of pretreated coking wastewater by flocculation-coagulation, alkali out, air stripping, and three-dimensional (3-D) electrocatalytic oxidation was performed (gap between the used β-PbO2/Ti anode and titanium cathode, 12 mm; mass ratio of Cu-Mn/granular activated carbon (GAC) to effluent, 1:4; cell voltage, 7 V). The results showed that the pH adjusting from 3.7 to 6.1 was necessary for coagulants; alkali out played an important role because it brought up precipitation containing higher fatty acids as well as other contaminants to decrease the chemical oxygen demand (COD) in the effluent, and it had also forced the reduction of ammonia nitrogen (NH3-N) by incorporating with air stripping; for 3-D electrocatalytic oxidation with a bleaching liquid assisting, the initial pH 8.5 of effluent was suitable for Cu-Mn/GAC; moreover, it was considered that its Cu component was dedicated to the decrease of COD and NH3-N, while the Mn component specialized in the decay of NH3-N. The residual COD and NH3-N values in the final effluent with pH 6.5 were 95.8 and 8.8 mg/L, respectively, demonstrating that the whole processes applied were feasible and low in cost.

  5. Active linear head motion improves dynamic visual acuity in pursuing a high-speed moving object.

    PubMed

    Hasegawa, Tatsuhisa; Yamashita, Masayuki; Suzuki, Toshihiro; Hisa, Yasuo; Wada, Yoshiro

    2009-04-01

    We usually move both our eyes and our head when pursuing a high-speed moving object. However, the vestibulo-ocular reflex (VOR), evoked by head motion, seems to disturb smooth pursuit eye movement because the VOR stabilizes the gaze against head motion. To determine whether head motion is advantageous for pursuing a high-speed moving object, we examined dynamic visual acuity (DVA) for a high-speed (80 degrees /s) rightward moving object with and without active linear rightward head motion (HM) at a maximum of 50 cm/s in nine healthy subjects. Furthermore, we analyzed eye and head movements to investigate the contribution of linear VOR (LVOR) and smooth eye movement under these conditions. In most subjects, active linear head motion improved DVA for a high-speed moving object. Subjects with higher DVA scores under HM had robust rightward gaze (eye + head) velocities (>60 cm/s), i.e., rightward smooth eye movements (>10 degrees /s). With the head stationary (HS), faster smooth eye movements (>40 degrees /s) were generated when the subjects pursued a high-speed moving object. They also showed anticipatory smooth eye movements under conditions HM and HS. However, the level of suppression of their LVOR abilities was equal to that of the others. These results suggest that the ability to generate anticipatory smooth pursuit eye movements for following a high-speed moving object against the LVOR is a determining factor for improvement of DVA under HM.

  6. Preparation of linear maltodextrins using a hyperthermophilic amylopullulanase with cyclodextrin- and starch-hydrolysing activities.

    PubMed

    Li, Xiaolei; Li, Dan

    2015-03-30

    A novel method for the preparation of linear maltodextrins from cyclodextrins and starch was proposed. To accomplish this process, an amylopullulanase from hyperthermophilic archaeon Caldivirga maquilingensis (CMApu) was characterized and used. CMApu with an estimated molecular mass of 62.7 kDa by SDS-PAGE had a maximal pullulan-hydrolysing activity at 100°C and pH 5.0. It could also hydrolyse amylopectin (AP), starch, β-CD and amylose (AM), in a decreasing order of relative activities from 88.96% to 57.17%. TLC and HPAEC analysis revealed that CMApu catalyzed the debranching and degrading reactions to produce linear malto-oligosaccharides (≤ G8-G1) from G8-β-CD and/or normal CDs, amylodextrins (DP6-96) from AM, and amylodextrins (DP1-76) from AP and potato starch. Our results showed that CMApu had a great potential for the industrial preparation of linear maltodextrins from normal starch instead of waxy starch, malto-oligosaccharides or sucrose. And the high optimal temperature of CMApu facilitated the simultaneous gelatinization and hydrolysis of cereal starch.

  7. Multistability and Instability of Neural Networks With Discontinuous Nonmonotonic Piecewise Linear Activation Functions.

    PubMed

    Nie, Xiaobing; Zheng, Wei Xing

    2015-11-01

    In this paper, we discuss the coexistence and dynamical behaviors of multiple equilibrium points for recurrent neural networks with a class of discontinuous nonmonotonic piecewise linear activation functions. It is proved that under some conditions, such n -neuron neural networks can have at least 5(n) equilibrium points, 3(n) of which are locally stable and the others are unstable, based on the contraction mapping theorem and the theory of strict diagonal dominance matrix. The investigation shows that the neural networks with the discontinuous activation functions introduced in this paper can have both more total equilibrium points and more locally stable equilibrium points than the ones with continuous Mexican-hat-type activation function or discontinuous two-level activation functions. An illustrative example with computer simulations is presented to verify the theoretical analysis.

  8. Mechanochemical activation of vincamine mediated by linear polymers: assessment of some "critical" steps.

    PubMed

    Hasa, Dritan; Perissutti, Beatrice; Grassi, Mario; Chierotti, Michele R; Gobetto, Roberto; Ferrario, Valerio; Lenaz, Davide; Voinovich, Dario

    2013-09-27

    The aim of the research was to investigate three "critical steps" that deserve particular attention during the mechanochemical activation of vincamine. The first step consisted in the selection of the best polymeric carrier/most affine stabiliser between linear PVP and NaCMC by using the GRID and the GRID based AutoDock software packages which permit to calculate their surface features and interactions. Moreover, the calculation of the partial and total solubility parameters supported the results obtained by GRID and AutoDock software. Then, after the selection of linear PVP-K30 as the suitable carrier, the influence of process and formulation variables on the amorphisation degree and solubility enhancement was studied, to select the most suitable process conditions and formulation parameters. Subsequently, the best performing samples were widely characterised using XRPD, TEM and SSNMR (including the proton relaxation ((1)H T1 NMR) time) techniques. These studies highlighted that all the coground samples were nanocrystalline solid dispersions indicating a dramatic difference between the amorphisation capacities of linear PVP-K30 and cross-linked PVP, used in previous analogous experiences. In particular, (13)C, (15)N and (1)H T1 NMR data point to a description of the system as a dispersion of nanocrystals in the polymer. In these dispersions vincamine is in a disordered crystalline state due to extensive interactions and contacts with PVP-K30 but the main hydrogen bonding motif characterising its packing remains. Again, differently from cross-linked PVP, dissolution studies revealed that linear PVP-K30 was able to promote a complete in vitro solubilisation of vincamine in some coground samples. What is more important, by using a linear polymer, drug-to-polymer and milling time variables appeared less influent on the solid state and in vitro properties of the composites. Finally, stability studies conducted for a period of 1year highlighted the high physical

  9. Nanosilver based anionic linear globular dendrimer with a special significant antiretroviral activity.

    PubMed

    Ardestani, Mehdi Shafiee; Fordoei, Alireza Salehi; Abdoli, Asghar; Ahangari Cohan, Reza; Bahramali, Golnaz; Sadat, Seyed Mehdi; Siadat, Seyed Davar; Moloudian, Hamid; Nassiri Koopaei, Nasser; Bolhasani, Azam; Rahimi, Pooneh; Hekmat, Soheila; Davari, Mehdi; Aghasadeghi, Mohammad Reza

    2015-05-01

    HIV is commonly caused to a very complicated disease which has not any recognized vaccine, so designing and development of novel antiretroviral agents with specific application of nanomedicine is a globally interested research subject worldwide. In the current study, a novel structure of silver complexes with anionic linear globular dendrimer was synthesized, characterized and then assessed against HIV replication pathway in vitro as well. The results showed a very good yield of synthesis (up to 70%) for the nano-complex as well as a very potent significant (P < 0.05) antiretroviral activity with non-severe toxic effects in comparison with the Nevirapine as standard drug in positive control group. According to the present data, silver anionic linear globular dendrimers complex may have a promising future to inhibit replication of HIV viruse in clinical practice.

  10. Nanosilver based anionic linear globular dendrimer with a special significant antiretroviral activity.

    PubMed

    Ardestani, Mehdi Shafiee; Fordoei, Alireza Salehi; Abdoli, Asghar; Ahangari Cohan, Reza; Bahramali, Golnaz; Sadat, Seyed Mehdi; Siadat, Seyed Davar; Moloudian, Hamid; Nassiri Koopaei, Nasser; Bolhasani, Azam; Rahimi, Pooneh; Hekmat, Soheila; Davari, Mehdi; Aghasadeghi, Mohammad Reza

    2015-05-01

    HIV is commonly caused to a very complicated disease which has not any recognized vaccine, so designing and development of novel antiretroviral agents with specific application of nanomedicine is a globally interested research subject worldwide. In the current study, a novel structure of silver complexes with anionic linear globular dendrimer was synthesized, characterized and then assessed against HIV replication pathway in vitro as well. The results showed a very good yield of synthesis (up to 70%) for the nano-complex as well as a very potent significant (P < 0.05) antiretroviral activity with non-severe toxic effects in comparison with the Nevirapine as standard drug in positive control group. According to the present data, silver anionic linear globular dendrimers complex may have a promising future to inhibit replication of HIV viruse in clinical practice. PMID:25893388

  11. Active vibration control for nonlinear vehicle suspension with actuator delay via I/O feedback linearization

    NASA Astrophysics Data System (ADS)

    Lei, Jing; Jiang, Zuo; Li, Ya-Li; Li, Wu-Xin

    2014-10-01

    The problem of nonlinear vibration control for active vehicle suspension systems with actuator delay is considered. Through feedback linearization, the open-loop nonlinearity is eliminated by the feedback nonlinear term. Based on the finite spectrum assignment, the quarter-car suspension system with actuator delay is converted into an equivalent delay-free one. The nonlinear control includes a linear feedback term, a feedforward compensator, and a control memory term, which can be derived from a Riccati equation and a Sylvester equation, so that the effects produced by the road disturbances and the actuator delay are compensated, respectively. A predictor is designed to implement the predictive state in the designed control. Moreover, a reduced-order observer is constructed to solve its physical unrealisability problem. The stability proofs for the zero dynamics and the closed-loop system are provided. Numerical simulations illustrate the effectiveness and the simplicity of the designed control.

  12. Consequences of Laughter Upon Trunk Compression and Cortical Activation: Linear and Polynomial Relations.

    PubMed

    Svebak, Sven

    2016-08-01

    Results from two studies of biological consequences of laughter are reported. A proposed inhibitory brain mechanism was tested in Study 1. It aims to protect against trunk compression that can cause health hazards during vigorous laughter. Compression may be maximal during moderate durations and, for protective reasons, moderate in enduring vigorous laughs. Twenty-five university students volunteered to see a candid camera film. Laughter responses (LR) and the superimposed ha-responses were operationally assessed by mercury-filled strain gauges strapped around the trunk. On average, the thorax compression amplitudes exceeded those of the abdomen, and greater amplitudes were seen in the males than in the females after correction for resting trunk circumference. Regression analyses supported polynomial relations because medium LR durations were associated with particularly high thorax amplitudes. In Study 2, power changes were computed in the beta and alpha EEG frequency bands of the parietal cortex from before to after exposure to the comedy "Dinner for one" in 56 university students. Highly significant linear relations were calculated between the number of laughs and post-exposure cortical activation (increase of beta, decrease of alpha) due to high activation after frequent laughter. The results from Study 1 supported the hypothesis of a protective brain mechanism that is activated during long LRs to reduce the risk of harm to vital organs in the trunk cavity. The results in Study 2 supported a linear cortical activation and, thus, provided evidence for a biological correlate to the subjective experience of mental refreshment after laughter.

  13. Consequences of Laughter Upon Trunk Compression and Cortical Activation: Linear and Polynomial Relations.

    PubMed

    Svebak, Sven

    2016-08-01

    Results from two studies of biological consequences of laughter are reported. A proposed inhibitory brain mechanism was tested in Study 1. It aims to protect against trunk compression that can cause health hazards during vigorous laughter. Compression may be maximal during moderate durations and, for protective reasons, moderate in enduring vigorous laughs. Twenty-five university students volunteered to see a candid camera film. Laughter responses (LR) and the superimposed ha-responses were operationally assessed by mercury-filled strain gauges strapped around the trunk. On average, the thorax compression amplitudes exceeded those of the abdomen, and greater amplitudes were seen in the males than in the females after correction for resting trunk circumference. Regression analyses supported polynomial relations because medium LR durations were associated with particularly high thorax amplitudes. In Study 2, power changes were computed in the beta and alpha EEG frequency bands of the parietal cortex from before to after exposure to the comedy "Dinner for one" in 56 university students. Highly significant linear relations were calculated between the number of laughs and post-exposure cortical activation (increase of beta, decrease of alpha) due to high activation after frequent laughter. The results from Study 1 supported the hypothesis of a protective brain mechanism that is activated during long LRs to reduce the risk of harm to vital organs in the trunk cavity. The results in Study 2 supported a linear cortical activation and, thus, provided evidence for a biological correlate to the subjective experience of mental refreshment after laughter. PMID:27547260

  14. SU-E-T-543: Measurement of Neutron Activation From Different High Energy Varian Linear Accelerators

    SciTech Connect

    Thatcher, T; Madsen, S; Sudowe, R; Meigooni, A Soleimani

    2015-06-15

    Purpose: Linear accelerators producing photons above 10 MeV may induce photonuclear reactions in high Z components of the accelerator. These liberated neutrons can then activate the structural components of the accelerator and other materials in the beam path through neutron capture reactions. The induced activity within the accelerator may contribute to additional dose to both patients and personnel. This project seeks to determine the total activity and activity per activated isotope following irradiation in different Varian accelerators at energies above 10 MeV. Methods: A Varian 21IX accelerator was used to irradiate a 30 cm × 30 cm × 20 cm solid water phantom with 15 MV x-rays. The phantom was placed at an SSD of 100 cm and at the center of a 20 cm × 20 cm field. Activation induced gamma spectra were acquired over a 5 minute interval after 1 and 15 minutes from completion of the irradiation. All measurements were made using a CANBERRA Falcon 5000 Portable HPGe detector. The majority of measurements were made in scattering geometry with the detector situated at 90° to the incident beam, 30 cm from the side of the phantom and approximately 10 cm from the top. A 5 minute background count was acquired and automatically subtracted from all subsequent measurements. Photon spectra were acquired for both open and MLC fields. Results: Based on spectral signatures, nuclides have been identified and their activities calculated for both open and MLC fields. Preliminary analyses suggest that activities from the activation products in the microcurie range. Conclusion: Activation isotopes have been identified and their relative activities determined. These activities are only gross estimates since efficiencies have not been determined for this source-detector geometry. Current efforts are focused on accurate determination of detector efficiencies using Monte Carlo calculations.

  15. Linear Superposition and Prediction of Bacterial Promoter Activity Dynamics in Complex Conditions

    PubMed Central

    Rothschild, Daphna; Dekel, Erez; Hausser, Jean; Bren, Anat; Aidelberg, Guy; Szekely, Pablo; Alon, Uri

    2014-01-01

    Bacteria often face complex environments. We asked how gene expression in complex conditions relates to expression in simpler conditions. To address this, we obtained accurate promoter activity dynamical measurements on 94 genes in E. coli in environments made up of all possible combinations of four nutrients and stresses. We find that the dynamics across conditions is well described by two principal component curves specific to each promoter. As a result, the promoter activity dynamics in a combination of conditions is a weighted average of the dynamics in each condition alone. The weights tend to sum up to approximately one. This weighted-average property, called linear superposition, allows predicting the promoter activity dynamics in a combination of conditions based on measurements of pairs of conditions. If these findings apply more generally, they can vastly reduce the number of experiments needed to understand how E. coli responds to the combinatorially huge space of possible environments. PMID:24809350

  16. Multiphysics modeling of non-linear laser-matter interactions for optically active semiconductors

    NASA Astrophysics Data System (ADS)

    Kraczek, Brent; Kanp, Jaroslaw

    Development of photonic devices for sensors and communications devices has been significantly enhanced by computational modeling. We present a new computational method for modelling laser propagation in optically-active semiconductors within the paraxial wave approximation (PWA). Light propagation is modeled using the Streamline-upwind/Petrov-Galerkin finite element method (FEM). Material response enters through the non-linear polarization, which serves as the right-hand side of the FEM calculation. Maxwell's equations for classical light propagation within the PWA can be written solely in terms of the electric field, producing a wave equation that is a form of the advection-diffusion-reaction equations (ADREs). This allows adaptation of the computational machinery developed for solving ADREs in fluid dynamics to light-propagation modeling. The non-linear polarization is incorporated using a flexible framework to enable the use of multiple methods for carrier-carrier interactions (e.g. relaxation-time-based or Monte Carlo) to enter through the non-linear polarization, as appropriate to the material type. We demonstrate using a simple carrier-carrier model approximating the response of GaN. Supported by ARL Materials Enterprise.

  17. Non-linear modelling and control of semi-active suspensions with variable damping

    NASA Astrophysics Data System (ADS)

    Chen, Huang; Long, Chen; Yuan, Chao-Chun; Jiang, Hao-Bin

    2013-10-01

    Electro-hydraulic dampers can provide variable damping force that is modulated by varying the command current; furthermore, they offer advantages such as lower power, rapid response, lower cost, and simple hardware. However, accurate characterisation of non-linear f-v properties in pre-yield and force saturation in post-yield is still required. Meanwhile, traditional linear or quarter vehicle models contain various non-linearities. The development of a multi-body dynamics model is very complex, and therefore, SIMPACK was used with suitable improvements for model development and numerical simulations. A semi-active suspension was built based on a belief-desire-intention (BDI)-agent model framework. Vehicle handling dynamics were analysed, and a co-simulation analysis was conducted in SIMPACK and MATLAB to evaluate the BDI-agent controller. The design effectively improved ride comfort, handling stability, and driving safety. A rapid control prototype was built based on dSPACE to conduct a real vehicle test. The test and simulation results were consistent, which verified the simulation.

  18. Active disturbance rejection based trajectory linearization control for hypersonic reentry vehicle with bounded uncertainties.

    PubMed

    Shao, Xingling; Wang, Honglun

    2015-01-01

    This paper investigates a novel compound control scheme combined with the advantages of trajectory linearization control (TLC) and alternative active disturbance rejection control (ADRC) for hypersonic reentry vehicle (HRV) attitude tracking system with bounded uncertainties. Firstly, in order to overcome actuator saturation problem, nonlinear tracking differentiator (TD) is applied in the attitude loop to achieve fewer control consumption. Then, linear extended state observers (LESO) are constructed to estimate the uncertainties acting on the LTV system in the attitude and angular rate loop. In addition, feedback linearization (FL) based controllers are designed using estimates of uncertainties generated by LESO in each loop, which enable the tracking error for closed-loop system in the presence of large uncertainties to converge to the residual set of the origin asymptotically. Finally, the compound controllers are derived by integrating with the nominal controller for open-loop nonlinear system and FL based controller. Also, comparisons and simulation results are presented to illustrate the effectiveness of the control strategy.

  19. Vestibular modulation of muscle sympathetic nerve activity during sinusoidal linear acceleration in supine humans

    PubMed Central

    Hammam, Elie; Bolton, Philip S.; Kwok, Kenny; Macefield, Vaughan G.

    2014-01-01

    The utricle and saccular components of the vestibular apparatus preferentially detect linear displacements of the head in the horizontal and vertical planes, respectively. We previously showed that sinusoidal linear acceleration in the horizontal plane of seated humans causes a pronounced modulation of muscle sympathetic nerve activity (MSNA), supporting a significant role for the utricular component of the otolithic organs in the control of blood pressure. Here we tested the hypothesis that the saccule can also play a role in blood pressure regulation by modulating lower limb MSNA. Oligounitary MSNA was recorded via tungsten microelectrodes inserted into the common peroneal nerve in 12 subjects, laying supine on a motorized platform with the head aligned with the longitudinal axis of the body. Slow sinusoidal linear accelerations-decelerations (peak acceleration ±4 mG) were applied in the rostrocaudal axis (which predominantly stimulates the saccule) and in the mediolateral axis (which also engages the utricle) at 0.08 Hz. The modulation of MSNA in the rostrocaudal axis (29.4 ± 3.4%) was similar to that in the mediolateral axis (32.0 ± 3.9%), and comparable to that obtained by stimulation of the utricle alone in seated subjects with the head vertical. We conclude that both the saccular and utricular components of the otolithic organs play a role in the control of arterial pressure during postural challenges. PMID:25346657

  20. Direct air activation measurements at a 15-MV medical linear accelerator.

    PubMed

    Saeed, M K; Poppe, B; Fischer, H W

    2015-02-01

    Direct radiometric determination of (14)N (γ, n) (13)N air activation was achieved at a 15-MV medical linear accelerator operating in a high-energy photon mode. (13)N was identified by irradiating a gas-tight Marinelli beaker filled with nitrogen gas and later observing the 10-min half-life of the 511-keV positron-electron annihilation line using high-resolution gamma spectroscopy. Quantitative evaluation of the spectral signal yielded a (13)N production rate of 836.8 ± 32 Bq Gy(-1) in air per 40 × 40 cm(2) field cross section at 100 cm source-surface distance.

  1. Active transport improves the precision of linear long distance molecular signalling

    NASA Astrophysics Data System (ADS)

    Godec, Aljaž; Metzler, Ralf

    2016-09-01

    Molecular signalling in living cells occurs at low copy numbers and is thereby inherently limited by the noise imposed by thermal diffusion. The precision at which biochemical receptors can count signalling molecules is intimately related to the noise correlation time. In addition to passive thermal diffusion, messenger RNA and vesicle-engulfed signalling molecules can transiently bind to molecular motors and are actively transported across biological cells. Active transport is most beneficial when trafficking occurs over large distances, for instance up to the order of 1 metre in neurons. Here we explain how intermittent active transport allows for faster equilibration upon a change in concentration triggered by biochemical stimuli. Moreover, we show how intermittent active excursions induce qualitative changes in the noise in effectively one-dimensional systems such as dendrites. Thereby they allow for significantly improved signalling precision in the sense of a smaller relative deviation in the concentration read-out by the receptor. On the basis of linear response theory we derive the exact mean field precision limit for counting actively transported molecules. We explain how intermittent active excursions disrupt the recurrence in the molecular motion, thereby facilitating improved signalling accuracy. Our results provide a deeper understanding of how recurrence affects molecular signalling precision in biological cells and novel medical-diagnostic devices.

  2. Dynamical Behaviors of Multiple Equilibria in Competitive Neural Networks With Discontinuous Nonmonotonic Piecewise Linear Activation Functions.

    PubMed

    Nie, Xiaobing; Zheng, Wei Xing

    2016-03-01

    This paper addresses the problem of coexistence and dynamical behaviors of multiple equilibria for competitive neural networks. First, a general class of discontinuous nonmonotonic piecewise linear activation functions is introduced for competitive neural networks. Then based on the fixed point theorem and theory of strict diagonal dominance matrix, it is shown that under some conditions, such n -neuron competitive neural networks can have 5(n) equilibria, among which 3(n) equilibria are locally stable and the others are unstable. More importantly, it is revealed that the neural networks with the discontinuous activation functions introduced in this paper can have both more total equilibria and locally stable equilibria than the ones with other activation functions, such as the continuous Mexican-hat-type activation function and discontinuous two-level activation function. Furthermore, the 3(n) locally stable equilibria given in this paper are located in not only saturated regions, but also unsaturated regions, which is different from the existing results on multistability of neural networks with multiple level activation functions. A simulation example is provided to illustrate and validate the theoretical findings.

  3. The Extremely Low Activity Comet 209P/LINEAR During Its Extraordinary Close Approach in 2014

    NASA Astrophysics Data System (ADS)

    Schleicher, David G.; knight, Matthew m.

    2016-10-01

    We present results from our observing campaign of Comet 209P/LINEAR during its exceptionally close approach to Earth during 2014 May, the third smallest perigee of any comet in two centuries. These circumstances permitted us to pursue several studies of this intrinsically faint object, including measurements of gas and dust production rates, searching for coma morphology, and direct detection of the nucleus to measure its properties. Indeed, we successfully measured the lowest water production rates of an intact comet in over 35 years and a corresponding smallest active area, ∼0.007 km2. When combined with the nucleus size found from radar, this also yields the smallest active fraction for any comet, ∼0.024%. In all, this strongly suggests that 209P/LINEAR is on its way to becoming an inert object. The nucleus was detected but could not easily be disentangled from the inner coma due to seeing variations and changing spatial scales. Even so, we were able to measure a double-peaked lightcurve consistent with the shorter of two viable rotational periods found by Hergenrother. Radial profiles of the dust coma are quite steep, similar to that observed for some other very anemic comets, and suggest that vaporizing icy grains are present.

  4. Insights into antioxidant activity of 1-adamantylthiopyridine analogs using multiple linear regression.

    PubMed

    Worachartcheewan, Apilak; Nantasenamat, Chanin; Owasirikul, Wiwat; Monnor, Teerawat; Naruepantawart, Orapan; Janyapaisarn, Sayamon; Prachayasittikul, Supaluk; Prachayasittikul, Virapong

    2014-02-12

    A data set of 1-adamantylthiopyridine analogs (1-19) with antioxidant activity, comprising of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide dismutase (SOD) activities, was used for constructing quantitative structure-activity relationship (QSAR) models. Molecular structures were geometrically optimized at B3LYP/6-31g(d) level and subjected for further molecular descriptor calculation using Dragon software. Multiple linear regression (MLR) was employed for the development of QSAR models using 3 significant descriptors (i.e. Mor29e, F04[N-N] and GATS5v) for predicting the DPPH activity and 2 essential descriptors (i.e. EEig06r and Mor06v) for predicting the SOD activity. Such molecular descriptors accounted for the effects and positions of substituent groups (R) on the 1-adamantylthiopyridine ring. The results showed that high atomic electronegativity of polar substituent group (R = CO2H) afforded high DPPH activity, while substituent with high atomic van der Waals volumes such as R = Br gave high SOD activity. Leave-one-out cross-validation (LOO-CV) and external test set were used for model validation. Correlation coefficient (QCV) and root mean squared error (RMSECV) of the LOO-CV set for predicting DPPH activity were 0.5784 and 8.3440, respectively, while QExt and RMSEExt of external test set corresponded to 0.7353 and 4.2721, respectively. Furthermore, QCV and RMSECV values of the LOO-CV set for predicting SOD activity were 0.7549 and 5.6380, respectively. The QSAR model's equation was then used in predicting the SOD activity of tested compounds and these were subsequently verified experimentally. It was observed that the experimental activity was more potent than the predicted activity. Structure-activity relationships of significant descriptors governing antioxidant activity are also discussed. The QSAR models investigated herein are anticipated to be useful in the rational design and development of novel compounds with antioxidant activity. PMID

  5. Space shuttle active-pogo-suppressor control design using linear quadratic regulator techniques

    NASA Technical Reports Server (NTRS)

    Lehtinen, B.; Lorenz, C. F.

    1979-01-01

    Two methods of active pogo suppression (stabilization) for the space shuttle vehicle were studied analytically. The basis for both approaches was the linear quadratic regulator, state space technique. The first approach minimized root-mean-square pump inlet pressure by using either fullstate feedback, partial-state feedback, or output feedback with a Kalman filter. The second approach increased the modal damping associated with the critical structural modes by using either full-state feedback or reconstructed state feedback. A number of implementable controls were found by both approaches. The designs were analyzed with respect to sensitivity, complexity, and controller energy requirements, as well as controller performance. Practical controllers resulting from the two design approaches tended to use pressure and flow as feedback variables for the minimum-rms method and structural accelerations or velocities for the modal control method. Both approaches are suitable for the design of active pogo-suppression controllers.

  6. Consequences of Laughter Upon Trunk Compression and Cortical Activation: Linear and Polynomial Relations

    PubMed Central

    Svebak, Sven

    2016-01-01

    Results from two studies of biological consequences of laughter are reported. A proposed inhibitory brain mechanism was tested in Study 1. It aims to protect against trunk compression that can cause health hazards during vigorous laughter. Compression may be maximal during moderate durations and, for protective reasons, moderate in enduring vigorous laughs. Twenty-five university students volunteered to see a candid camera film. Laughter responses (LR) and the superimposed ha-responses were operationally assessed by mercury-filled strain gauges strapped around the trunk. On average, the thorax compression amplitudes exceeded those of the abdomen, and greater amplitudes were seen in the males than in the females after correction for resting trunk circumference. Regression analyses supported polynomial relations because medium LR durations were associated with particularly high thorax amplitudes. In Study 2, power changes were computed in the beta and alpha EEG frequency bands of the parietal cortex from before to after exposure to the comedy “Dinner for one” in 56 university students. Highly significant linear relations were calculated between the number of laughs and post-exposure cortical activation (increase of beta, decrease of alpha) due to high activation after frequent laughter. The results from Study 1 supported the hypothesis of a protective brain mechanism that is activated during long LRs to reduce the risk of harm to vital organs in the trunk cavity. The results in Study 2 supported a linear cortical activation and, thus, provided evidence for a biological correlate to the subjective experience of mental refreshment after laughter. PMID:27547260

  7. Antiproliferative effect and apoptotic activity of linear geranylphenol derivatives from phloroglucinol and orcinol.

    PubMed

    Taborga, Lautaro; Espinoza, Luis; Moller, Alejandra; Carrasco, Héctor; Cuellar, Mauricio; Villena, Joan

    2016-03-01

    Sixteen synthetic linear derivatives geranylphenols, were obtained from phloroglucinol and orcinol, and cytotoxic activity was evaluated in vitro against cancer cell lines (HT-29, PC-3, MDA-MB231, DU-145) and one non-tumor cell line, human dermal fibroblast (HDF). IC50 values were determined at concentrations of 0-100 μM of each compound for 72 h. Compounds 12, 13, 17, 21, 22 and 25, showed cytotoxic activity. To elucidate whether these compounds reduce cell viability by inducing apoptosis, cell lines MCF-7, PC-3 and DHF were treated with each active compound 12, 13, 17, 21, 22 and 25 and were examined after Hoechst 33342 staining. The compounds 12, 13 and 17 induced apoptosis in various cancer cell lines, as shown by nuclear condensation and/or fragmentation. In addition, it was found that compounds 12 and 13, induced changes in mitochondrial membrane permeability in those cancer cell lines. Such induction was associated with the depletion of mitochondrial membrane potential. These activities led to the cleavage of caspases inducing the cell death process. PMID:26826267

  8. Transonic-Small-Disturbance and Linear Analyses for the Active Aeroelastic Wing Program

    NASA Technical Reports Server (NTRS)

    Wiesman, Carol D.; Silva, Walter A.; Spain, Charles V.; Heeg, Jennifer

    2005-01-01

    Analysis serves many roles in the Active Aeroelastic Wing (AAW) program. It has been employed to ensure safe testing of both a flight vehicle and wind tunnel model, has formulated models for control law design, has provided comparison data for validation of experimental methods and has addressed several analytical research topics. Aeroelastic analyses using mathematical models of both the flight vehicle and the wind tunnel model configurations have been conducted. Static aeroelastic characterizations of the flight vehicle and wind tunnel model have been produced in the transonic regime and at low supersonic Mach numbers. The flight vehicle has been analyzed using linear aerodynamic theory and transonic small disturbance theory. Analyses of the wind-tunnel model were performed using only linear methods. Research efforts conducted through these analyses include defining regions of the test space where transonic effects play an important role and investigating transonic similarity. A comparison of these aeroelastic analyses for the AAW flight vehicle is presented in this paper. Results from a study of transonic similarity are also presented. Data sets from these analyses include pressure distributions, stability and control derivatives, control surface effectiveness, and vehicle deflections.

  9. Active learning for semi-supervised clustering based on locally linear propagation reconstruction.

    PubMed

    Chang, Chin-Chun; Lin, Po-Yi

    2015-03-01

    The success of semi-supervised clustering relies on the effectiveness of side information. To get effective side information, a new active learner learning pairwise constraints known as must-link and cannot-link constraints is proposed in this paper. Three novel techniques are developed for learning effective pairwise constraints. The first technique is used to identify samples less important to cluster structures. This technique makes use of a kernel version of locally linear embedding for manifold learning. Samples neither important to locally linear propagation reconstructions of other samples nor on flat patches in the learned manifold are regarded as unimportant samples. The second is a novel criterion for query selection. This criterion considers not only the importance of a sample to expanding the space coverage of the learned samples but also the expected number of queries needed to learn the sample. To facilitate semi-supervised clustering, the third technique yields inferred must-links for passing information about flat patches in the learned manifold to semi-supervised clustering algorithms. Experimental results have shown that the learned pairwise constraints can capture the underlying cluster structures and proven the feasibility of the proposed approach.

  10. Linear glandular trichomes of Helianthus (Asteraceae): morphology, localization, metabolite activity and occurrence

    PubMed Central

    Aschenbrenner, Anna-Katharina; Horakh, Silke; Spring, Otmar

    2013-01-01

    Capitate glandular trichomes of sunflower are well investigated, but detailed studies are lacking for the linear glandular trichomes (LGT), a second type of physiologically active plant hair present on the surface of sunflowers. Light, fluorescence and scanning electron microscopy as well as histochemical staining were used to investigate the structure and metabolite deposition of LGT. Consisting of 6–11 linearly arranged cells, LGT were found on the surface of most plant organs of Helianthus annuus. They were associated with the leaf vascular system, and also occurred along petioles, stems and the abaxial surface of chaffy bracts, ray and disc florets. The highest density was found on the abaxial surface of phyllaries. Phenotypically similar LGT were common in all species of the genus, but also occurred in most other genera of the Helianthinae so far screened. Brownish and fluorescent metabolites of an as yet unknown chemical structure, together with terpenoids, were produced and stored in apical cells of LGT. The deposition of compounds gradually progressed from the tip cell to the basal cells of older trichomes. This process was accompanied by nucleus degradation in metabolite-accumulating cells. The localization of these trichomes on prominent plant parts of the apical bud and the capitulum combined with the accumulation of terpenoids and other as yet unknown compounds suggests a chemo-ecological function of the LGT in plant–insect or plant–herbivore interaction.

  11. Origin of the effective mobility in non-linear active micro-rheology

    NASA Astrophysics Data System (ADS)

    Santamaría-Holek, I.; Pérez-Madrid, A.

    2016-10-01

    The distinction between the damping coefficient and the effective non-linear mobility of driven particles in active micro-rheology of supercooled liquids is explained in terms of individual and collective dynamics. The effective mobility arises as a collective effect which gives insight into the energy landscape of the system. On the other hand, the damping coefficient is a constant that modulates the effect of external forces over the thermal energy which particles have at their disposition to perform Brownian motion. For long times, these thermal fluctuations become characterized in terms of an effective temperature that is a consequence of the dynamic coupling between kinetic and configurational degrees of freedom induced by the presence of the strong external force. The interplay between collective mobility and effective temperature allows to formulate a generalized Stokes-Einstein relation that may be used to determine the collective diffusion coefficient. The explicit relations we deduce reproduce simulation data remarkably well.

  12. WATER-ICE-DRIVEN ACTIVITY ON MAIN-BELT COMET P/2010 A2 (LINEAR)?

    SciTech Connect

    Moreno, F.; Ortiz, J. L.; Cabrera-Lavers, A.; Augusteijn, T.; Liimets, T.; Lindberg, J. E.; Pursimo, T.; RodrIguez-Gil, P.; Vaduvescu, O.

    2010-08-01

    The dust ejecta of Main-Belt Comet P/2010 A2 (LINEAR) have been observed with several telescopes at the Observatorio del Roque de los Muchachos on La Palma, Spain. Application of an inverse dust tail Monte Carlo method to the images of the dust ejecta from the object indicates that a sustained, likely water-ice-driven, activity over some eight months is the mechanism responsible for the formation of the observed tail. The total amount of the dust released is estimated to be 5 x 10{sup 7} kg, which represents about 0.3% of the nucleus mass. While the event could have been triggered by a collision, this cannot be determined from the currently available data.

  13. Linear Closed-form Solution and Finite-element Analysis of an Active Tensegrity Unit

    NASA Astrophysics Data System (ADS)

    Kmeť, Stanislav; Platko, Peter

    2012-11-01

    Results of the linear closed form solution of an active or adaptive tensegrity unit, as well as its numerical analysis using finite element method are presented in the paper. The shape of the unit is an octahedral cell with a square base and it is formed by thirteen members (four bottom and four top cables, four edge struts and one central strut). The central strut is designed as an actuator that allows for an adjustment of the shape of the unit which leads to changes of tensile forces in the cables. Due to the diagonal symmetry of the 3D tensegrity unit the closed-form analysis is based on the 2D solution of the equivalent planar biconvex cable system with one central strut under a vertical point load.

  14. A theoretical model of linearly filtered reverberation for pulsed active sonar in shallow water.

    PubMed

    Murray, John J

    2014-11-01

    This paper presents a statistical model useful for characterizing pulsed active sonar reverberation in shallow water. The model is based on the fundamental assumption that reverberation consists of echoes from point scatterers having random positions, strengths, and Doppler dilations. Receive array beam patterns, simple propagation losses, and planar bistatic geometry are included. The probability distribution of uniformly dense scatterers as a function of echo delay and bearing is explicitly related to the change in the area from which scatterer echoes contribute to the reverberation, and is presented in closed form. The cross Q-function of the transmitted waveform and the linear filter applied to the received signal arises naturally from the development. This function, along with environmental spreading, determines the shape of the reverberation along the Doppler axis. The assumptions and simplifications under which the reverberation decouples into independent spatial (delay and bearing) and Doppler terms are presented.

  15. Biodegradation of various molecular weights of linear polyethylene glycol (PEG) in activated sludge

    SciTech Connect

    Hansmann, M.A.; Bookland, E.A.; Keough, T.W.; Larson, R.J.

    1995-12-31

    Linear polyethylene glycols (PEG) of various average molecular weights (PEG 1000, PEG 3400, PEG 8000, PEG 20000) were tested in a semi-continuous activated sludge test (SCAS), followed by a CO{sub 2} production test to determine which MWs are inherently biodegradable. Complete biodegradation was confirmed analytically using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI TOF MS). The SCAS test estimates the removal of the test substance during wastewater treatment in activated sludge. SCAS removal, as measured by soluble organic carbon (SOC) was > 90% for the PEG 1000, PEG 3400, and PEG 8000, while PEG 20000 showed a SCAS removal of 28%. These results indicate that SCAS removal was largely due to degradation. The CO{sub 2} production test measures the mineralization of the test substance using activated sludge from the SCAS units as the inoculum. The CO{sub 2} test results show that PEG 1000, PEG 3400, and PEG 8000 are inherently biodegradable, with an average %TC02 > 80% by day 50 and remaining SOC < 10% as measured at day 50. Complete loss of material was confirmed by MALDI TOF MS. The PEG 20000 showed 40% TCO2 by day 50, with 50% SOC remaining. MALDI TOF MS confirmed the presence of parent material. Based on these results, PEGs of MW 8000 and less appear to be biodegradable.

  16. Inhibitory activities of short linear motifs underlie Hox interactome specificity in vivo

    PubMed Central

    Baëza, Manon; Viala, Séverine; Heim, Marjorie; Dard, Amélie; Hudry, Bruno; Duffraisse, Marilyne; Rogulja-Ortmann, Ana; Brun, Christine; Merabet, Samir

    2015-01-01

    Hox proteins are well-established developmental regulators that coordinate cell fate and morphogenesis throughout embryogenesis. In contrast, our knowledge of their specific molecular modes of action is limited to the interaction with few cofactors. Here, we show that Hox proteins are able to interact with a wide range of transcription factors in the live Drosophila embryo. In this context, specificity relies on a versatile usage of conserved short linear motifs (SLiMs), which, surprisingly, often restrains the interaction potential of Hox proteins. This novel buffering activity of SLiMs was observed in different tissues and found in Hox proteins from cnidarian to mouse species. Although these interactions remain to be analysed in the context of endogenous Hox regulatory activities, our observations challenge the traditional role assigned to SLiMs and provide an alternative concept to explain how Hox interactome specificity could be achieved during the embryonic development. DOI: http://dx.doi.org/10.7554/eLife.06034.001 PMID:25869471

  17. Fate of free and linear alcohol-ethoxylate-derived fatty alcohols in activated sludge.

    PubMed

    Federle, Thomas W; Itrich, Nina R

    2006-05-01

    Pure homologues of [1-14C] C12, C14, and C16 alcohols and the linear alcohol ethoxylates, AE [1-14C alkyl] C13E9 and C16E9 were tested in a batch-activated sludge die-away system to assess their biodegradation kinetics and to predict levels of free alcohol derived from AE biodegradation in treated effluent. First-order rates for primary biodegradation were similar for all alcohols (86-113 h(-1)) and were used to predict removal under typical treatment conditions. Predicted removals of fatty alcohols ranged from 99.76% to 99.85%, consistent with published field data. During the biodegradation of the AE homologues, lower than expected levels of fatty alcohol based upon the assumption that biodegradation occurs through central fission were observed. Rather than fatty alcohols, the major metabolites were polar materials resulting from omega oxidation of the alkyl chain prior to or concurrent with central cleavage. The amounts of free fatty alcohols that were formed from AEs in influent and escape into effluent were negligible due both to their rapid degradation and to the finding that formation of free alcohol through central cleavage is only a minor degradation pathway in activated sludge. PMID:16026837

  18. A new iterative linear integral isoconversional method for the determination of the activation energy varying with the conversion degree.

    PubMed

    Cai, Junmeng; Chen, Siyu

    2009-10-01

    The conventional linear integral isoconversional methods may lead to important errors in the determination of the activation energy when the significant variation of the activation energy with the conversion degree occurs. Vyazovkin proposed an advanced nonlinear isoconversional method, which allows the activation energy to be accurately determined [Vyazovkin, J Comput Chem 2001, 22, 178]. However, the use of the Vyazovkin method raises the problem of the time-consuming minimization without derivatives. A new iterative linear integral isoconversional method for the determination of the activation energy as a function of the conversion degree has been proposed, which is capable of providing valid values of the activation energy even if the latter strongly varies with the conversion degree. Also, the new method leads to the correct values of the activation energy in much less time than the Vyazovkin method. The application of the new method is illustrated by processing of theoretically simulated data of a strongly varying activation energy process.

  19. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains.

    PubMed

    Jeong, Cheol; Douglas, Jack F

    2015-10-14

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ∼ M(β), is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from -1.8 to -2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature Tg where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔHa and entropy ΔSa of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a "critical" chain length, n ≈ 17. A close examination of this phenomenon indicates that a "buckling transition" from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔSa ∝ ΔHa, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔHa and ΔSa with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  20. Mass dependence of the activation enthalpy and entropy of unentangled linear alkane chains

    SciTech Connect

    Jeong, Cheol; Douglas, Jack F.

    2015-10-14

    The mass scaling of the self-diffusion coefficient D of polymers in the liquid state, D ∼ M{sup β}, is one of the most basic characteristics of these complex fluids. Although traditional theories such as the Rouse and reptation models of unentangled and entangled polymer melts, respectively, predict that β is constant, this exponent for alkanes has been estimated experimentally to vary from −1.8 to −2.7 upon cooling. Significantly, β changes with temperature T under conditions where the chains are not entangled and at temperatures far above the glass transition temperature T{sub g} where dynamic heterogeneity does not complicate the description of the liquid dynamics. Based on atomistic molecular dynamics simulations on unentangled linear alkanes in the melt, we find that the variation of β with T can be directly attributed to the dependence of the enthalpy ΔH{sub a} and entropy ΔS{sub a} of activation on the number of alkane backbone carbon atoms, n. In addition, we find a sharp change in the melt dynamics near a “critical” chain length, n ≈ 17. A close examination of this phenomenon indicates that a “buckling transition” from rod-like to coiled chain configurations occurs at this characteristic chain length and distinct entropy-enthalpy compensation relations, ΔS{sub a} ∝ ΔH{sub a}, hold on either side of this polymer conformational transition. We conclude that the activation free energy parameters exert a significant influence on the dynamics of polymer melts that is not anticipated by either the Rouse and reptation models. In addition to changes of ΔH{sub a} and ΔS{sub a} with M, we expect changes in these free energy parameters to be crucial for understanding the dynamics of polymer blends, nanocomposites, and confined polymers because of changes of the fluid free energy by interfacial interactions and geometrical confinement.

  1. On the uniqueness of linear moving-average filters for the solar wind-auroral geomagnetic activity coupling

    NASA Technical Reports Server (NTRS)

    Vassiliadis, D.; Klimas, A. J.

    1995-01-01

    The relation between the solar wind input to the magetosphere, VB(sub South), and the auroral geomagnetic index AL is modeled with two linear moving-average filtering methods: linear prediction filters and a driven harmonic oscillator in the form of an electric circuit. Although the response of the three-parameter oscillator is simpler than the filter's, the methods yield similar linear timescales and values of the prediction-observation correlation and the prediction Chi(exp 2). Further the filter responses obtained by the two methods are similar in their long-term features. In these aspects the circuit model is equivalent to linear prediction filtering. This poses the question of uniqueness and proper interpretation of detailed features of the filters such as response peaks. Finally, the variation of timescales and filter responses with the AL activity level is discussed.

  2. Linear quadratic tracking problems in Hilbert space - Application to optimal active noise suppression

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Silcox, R. J.; Keeling, S. L.; Wang, C.

    1989-01-01

    A unified treatment of the linear quadratic tracking (LQT) problem, in which a control system's dynamics are modeled by a linear evolution equation with a nonhomogeneous component that is linearly dependent on the control function u, is presented; the treatment proceeds from the theoretical formulation to a numerical approximation framework. Attention is given to two categories of LQT problems in an infinite time interval: the finite energy and the finite average energy. The behavior of the optimal solution for finite time-interval problems as the length of the interval tends to infinity is discussed. Also presented are the formulations and properties of LQT problems in a finite time interval.

  3. Methanogenic activity inhibition by increasing the linear alkylbenzene sulfonate (LAS) concentration.

    PubMed

    Souza, Luiza F C; Florencio, Lourdinha; Gavazza, Savia; Kato, Mario T

    2016-07-01

    The effect of the initial concentration of linear alkylbenzene sulfonate (LAS) on specific methanogenic activity (SMA) was investigated in this work. Six anaerobic flasks reactors with 1 L of total volume were inoculated with anaerobic sludge (2 g VSS L(-1)). The reactors were assayed for 42 days, and fed with volatile fatty acids, nutrients, and LAS. The initial LAS concentrations were 0, 10, 30, 50, 75, and 100 mg L(-1) for the treatment flasks T1 (control), T2, T3, T4, T5, and T6, respectively. When compared with T1, T2 exhibited a 30% reduction in maximum SMA and total methane production (TMP). In treatment T3 through T6, the reductions were 44-97% (T3-T6) for SMA, and 30-90% (T3-T6) for TMP. Total LAS removal increased following the increase in the initial LAS concentration (from 36% at T1 to 76% at T6), primarily due to the high degree of sludge adsorption. LAS biodegradation also occurred (32% in all treatments), although this was most likely associated with the formation of non-methane intermediates. Greater removal by adsorption was observed in long-chain homologues, when compared to short-chain homologues (C13 > C10), whereas the opposite occurred for biodegradation (C10 > C13). The C13 homologue was adsorbed to a great extent (in mass) in T4, T5 and T6, and may also have inhibited methane formation in these treatments. PMID:27088975

  4. Dielectric loss analysis using linear resonators with different impedances

    NASA Astrophysics Data System (ADS)

    Sarabi, Bahman; Khalil, M. S.; Khasawneh, M. A.; Stoutimore, M. J. A.; Gladchenko, Sergiy; Wellstood, F. C.; Lobb, C. J.; Osborn, K. D.

    2012-02-01

    It is known that amorphous dielectrics are a major source of decoherence in superconducting qubits due to energy absorption by two-level systems coupled to the electric fields. Linear resonators have been applied extensively to study loss in different dielectrics used in qubit circuits due to their versatility and relative simplicity in design, fabrication and measurement. We have designed linear resonators with multi-turn inductors and parallel-plate capacitors with resonance frequencies of 4.8-6.4 GHz. We achieve substantially different L/C values and capacitor volumes by varying the number of inductance turns and the area of the capacitors. We will present results of continuous wave measurements with SiNx capacitors and show how loss tangent and phase noise are related to impedance and capacitor volume.

  5. [Application of linear and nonlinear characteristics of heart rate variability in assessment of autonomic nervous system activity].

    PubMed

    Shi, Ping; Yu, Hongliu

    2014-04-01

    Calculation of linear parameters, such as time-domain and frequency-domain analysis of heart rate variability (HRV), is a conventional method for assessment of autonomic nervous system activity. Nonlinear phenomena are certainly involved in the genesis of HRV. In a seemingly random signal the Poincaré plot can easily demonstrate whether there is an underlying determinism in the signal. Linear and nonlinear analysis methods were applied in the computer words inputting experiments in this study for physiological measurement. This study therefore demonstrated that Poincaré plot was a simple but powerful graphical tool to describe the dynamics of a system.

  6. Beyond endoscopic assessment in inflammatory bowel disease: real-time histology of disease activity by non-linear multimodal imaging

    PubMed Central

    Chernavskaia, Olga; Heuke, Sandro; Vieth, Michael; Friedrich, Oliver; Schürmann, Sebastian; Atreya, Raja; Stallmach, Andreas; Neurath, Markus F.; Waldner, Maximilian; Petersen, Iver; Schmitt, Michael; Bocklitz, Thomas; Popp, Jürgen

    2016-01-01

    Assessing disease activity is a prerequisite for an adequate treatment of inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis. In addition to endoscopic mucosal healing, histologic remission poses a promising end-point of IBD therapy. However, evaluating histological remission harbors the risk for complications due to the acquisition of biopsies and results in a delay of diagnosis because of tissue processing procedures. In this regard, non-linear multimodal imaging techniques might serve as an unparalleled technique that allows the real-time evaluation of microscopic IBD activity in the endoscopy unit. In this study, tissue sections were investigated using the non-linear multimodal microscopy combination of coherent anti-Stokes Raman scattering (CARS), two-photon excited auto fluorescence (TPEF) and second-harmonic generation (SHG). After the measurement a gold-standard assessment of histological indexes was carried out based on a conventional H&E stain. Subsequently, various geometry and intensity related features were extracted from the multimodal images. An optimized feature set was utilized to predict histological index levels based on a linear classifier. Based on the automated prediction, the diagnosis time interval is decreased. Therefore, non-linear multimodal imaging may provide a real-time diagnosis of IBD activity suited to assist clinical decision making within the endoscopy unit. PMID:27406831

  7. Beyond endoscopic assessment in inflammatory bowel disease: real-time histology of disease activity by non-linear multimodal imaging

    NASA Astrophysics Data System (ADS)

    Chernavskaia, Olga; Heuke, Sandro; Vieth, Michael; Friedrich, Oliver; Schürmann, Sebastian; Atreya, Raja; Stallmach, Andreas; Neurath, Markus F.; Waldner, Maximilian; Petersen, Iver; Schmitt, Michael; Bocklitz, Thomas; Popp, Jürgen

    2016-07-01

    Assessing disease activity is a prerequisite for an adequate treatment of inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis. In addition to endoscopic mucosal healing, histologic remission poses a promising end-point of IBD therapy. However, evaluating histological remission harbors the risk for complications due to the acquisition of biopsies and results in a delay of diagnosis because of tissue processing procedures. In this regard, non-linear multimodal imaging techniques might serve as an unparalleled technique that allows the real-time evaluation of microscopic IBD activity in the endoscopy unit. In this study, tissue sections were investigated using the non-linear multimodal microscopy combination of coherent anti-Stokes Raman scattering (CARS), two-photon excited auto fluorescence (TPEF) and second-harmonic generation (SHG). After the measurement a gold-standard assessment of histological indexes was carried out based on a conventional H&E stain. Subsequently, various geometry and intensity related features were extracted from the multimodal images. An optimized feature set was utilized to predict histological index levels based on a linear classifier. Based on the automated prediction, the diagnosis time interval is decreased. Therefore, non-linear multimodal imaging may provide a real-time diagnosis of IBD activity suited to assist clinical decision making within the endoscopy unit.

  8. Beyond endoscopic assessment in inflammatory bowel disease: real-time histology of disease activity by non-linear multimodal imaging.

    PubMed

    Chernavskaia, Olga; Heuke, Sandro; Vieth, Michael; Friedrich, Oliver; Schürmann, Sebastian; Atreya, Raja; Stallmach, Andreas; Neurath, Markus F; Waldner, Maximilian; Petersen, Iver; Schmitt, Michael; Bocklitz, Thomas; Popp, Jürgen

    2016-01-01

    Assessing disease activity is a prerequisite for an adequate treatment of inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis. In addition to endoscopic mucosal healing, histologic remission poses a promising end-point of IBD therapy. However, evaluating histological remission harbors the risk for complications due to the acquisition of biopsies and results in a delay of diagnosis because of tissue processing procedures. In this regard, non-linear multimodal imaging techniques might serve as an unparalleled technique that allows the real-time evaluation of microscopic IBD activity in the endoscopy unit. In this study, tissue sections were investigated using the non-linear multimodal microscopy combination of coherent anti-Stokes Raman scattering (CARS), two-photon excited auto fluorescence (TPEF) and second-harmonic generation (SHG). After the measurement a gold-standard assessment of histological indexes was carried out based on a conventional H&E stain. Subsequently, various geometry and intensity related features were extracted from the multimodal images. An optimized feature set was utilized to predict histological index levels based on a linear classifier. Based on the automated prediction, the diagnosis time interval is decreased. Therefore, non-linear multimodal imaging may provide a real-time diagnosis of IBD activity suited to assist clinical decision making within the endoscopy unit. PMID:27406831

  9. Non-linear quantitative structure-activity relationship for adenine derivatives as competitive inhibitors of adenosine deaminase

    SciTech Connect

    Sadat Hayatshahi, Sayyed Hamed; Khajeh, Khosro

    2005-12-16

    Logistic regression and artificial neural networks have been developed as two non-linear models to establish quantitative structure-activity relationships between structural descriptors and biochemical activity of adenosine based competitive inhibitors, toward adenosine deaminase. The training set included 24 compounds with known k {sub i} values. The models were trained to solve two-class problems. Unlike the previous work in which multiple linear regression was used, the highest of positive charge on the molecules was recognized to be in close relation with their inhibition activity, while the electric charge on atom N1 of adenosine was found to be a poor descriptor. Consequently, the previously developed equation was improved and the newly formed one could predict the class of 91.66% of compounds correctly. Also optimized 2-3-1 and 3-4-1 neural networks could increase this rate to 95.83%.

  10. Single-layer-coated surfaces with linearized reflectance versus angle of incidence: application to passive and active silicon rotation sensors

    NASA Astrophysics Data System (ADS)

    Azzam, R. M. A.; Howlader, M. M. K.; Georgiou, T. Y.

    1995-08-01

    A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectance-versus-angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p -polarized, s -polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO2 film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis of this rotation sensor are presented.

  11. The Use of Linear Models for Determining School Workload and Activity Level.

    ERIC Educational Resources Information Center

    Vicino, Frank L.

    This paper outlines the design and use of two linear models as decision-making tools in a school district. The problem to be solved was the allocation of resources for both clerical and custodial personnel. A solution was desired that could be quantified and documented and objectively serve the needs of the district. A clerical support model was…

  12. Evaluation of topical Matricaria chamomilla extract activity on linear incisional wound healing in albino rats.

    PubMed

    Jarrahi, Morteza; Vafaei, Abbas Ali; Taherian, Abbas Ali; Miladi, Hossein; Rashidi Pour, Ali

    2010-05-01

    In this investigation, the effect of Matricaria chamomilla extract on linear incisional wound healing was studied. Thirty male Wistar rats were subjected to a linear 3 cm incision made over the skin of the back. The animals were randomly divided into three experimental groups, as control, olive oil, and treatment. Control group did not receive any drug or cold cream. Olive oil group received topical olive oil once a day from beginning of experiments to complete wound closure. Treatment group were treated topically by M. chamomilla extract dissolved in olive oil at the same time. For computing the percentage of wound healing, the area of the wound measured at the beginning of experiments and the next 2, 5, 8, 11, 14, 17, and 20 days. The percentage of wound healing was calculated by Walker formula after measurement of the wound area. Results showed that there were statistically significant differences between treatment and olive oil animals (p < 0.05) in most of the days. We conclude that the extract of M. chamomilla administered topically has wound healing potential in linear incisional wound model in rats.

  13. Development of magnetically preloaded air bearings for a linear slide: active compensation of three degrees of freedom motion errors.

    PubMed

    Ro, Seung-Kook; Kim, Soohyun; Kwak, Yoonkeun; Park, Chun-Hong

    2008-03-01

    This article describes a linear air-bearing stage that uses active control to compensate for its motion errors. The active control is based on preloads generated by magnetic actuators, which were designed to generate nominal preloads for the air bearings using permanent magnets to maintain the desired stiffness while changing the air-bearing clearance by varying the magnetic flux generated by the current in electromagnetic coils. A single-axis linear stage with a linear motor and 240 mm of travel range was built to verify this design concept and used to test its performance. The motion of the table in three directions was controlled with four magnetic actuators driven by current amplifiers and a DSP (Digital Signal Processor)-based digital controller. The motion errors were measured using a laser interferometer combined with a two-probe method, and had 0.085 microm of repeatability for the straightness error. As a result of feed-forward active compensation, the errors were reduced from 1.09 to 0.11 microm for the vertical motion, from 9.42 to 0.18 arcsec for the pitch motion, and from 2.42 to 0.18 arcsec for the roll motion. PMID:18377049

  14. Linearized Model of an Actively Controlled Cable for a Carlina Diluted Telescope

    NASA Astrophysics Data System (ADS)

    Andersen, T.; Le Coroller, H.; Owner-Petersen, M.; Dejonghe, J.

    2014-04-01

    The Carlina thinned pupil telescope has a focal unit (``gondola'') suspended by cables over the primary mirror. To predict the structural behavior of the gondola system, a simulation building block of a single cable is needed. A preloaded cable is a strongly non-linear system and can be modeled either with partial differential equations or non-linear finite elements. Using the latter, we set up an iteration procedure for determination of the static cable form and we formulate the necessary second-order differential equations for such a model. We convert them to a set of first-order differential equations (an ``ABCD''-model). Symmetrical in-plane eigenmodes and ``axial'' eigenmodes are the only eigenmodes that play a role in practice for a taut cable. Using the model and a generic suspension, a parameter study is made to find the influence of various design parameters. We conclude that the cable should be as stiff and thick as practically possible with a fairly high preload. Steel or Aramid are suitable materials. Further, placing the cable winches on the gondola and not on the ground does not provide significant advantages. Finally, it seems that use of reaction-wheels and/or reaction-masses will make the way for more accurate control of the gondola position under wind load. An adaptive stage with tip/tilt/piston correction for subapertures together with a focus and guiding system for freezing the fringes must also be studied.

  15. Active vibration suppression of lightweight railway vehicle body by combined use of piezoelectric actuators and linear actuators

    NASA Astrophysics Data System (ADS)

    Kamada, Takayoshi; Hiraizumi, Kazuyuki; Nagai, Masao

    2010-12-01

    In recent years, railway vehicle are becoming lighter because this corresponds not only to the improvement of the running speed but also to the reduction of running cost and environmental noise, especially for ultra-high-speed vehicle such as new Shinkansen and MAGLEV vehicle. However, this causes the deterioration of riding comfort. Bending vibration control method using piezoelectric actuators were proposed and good control performances were obtained through simulations and experiments. In this paper, active vibration control by combined use of piezoelectric actuators and linear actuators is investigated. Elastic vibrations are suppressed by piezoelectric actuators and rigid-body vibrations are reduced by linear actuators. Simulation studies and experiments using scale model were conducted and the effectiveness of the proposed control was confirmed.

  16. Early Parallel Activation of Semantics and Phonology in Picture Naming: Evidence from a Multiple Linear Regression MEG Study.

    PubMed

    Miozzo, Michele; Pulvermüller, Friedemann; Hauk, Olaf

    2015-10-01

    The time course of brain activation during word production has become an area of increasingly intense investigation in cognitive neuroscience. The predominant view has been that semantic and phonological processes are activated sequentially, at about 150 and 200-400 ms after picture onset. Although evidence from prior studies has been interpreted as supporting this view, these studies were arguably not ideally suited to detect early brain activation of semantic and phonological processes. We here used a multiple linear regression approach to magnetoencephalography (MEG) analysis of picture naming in order to investigate early effects of variables specifically related to visual, semantic, and phonological processing. This was combined with distributed minimum-norm source estimation and region-of-interest analysis. Brain activation associated with visual image complexity appeared in occipital cortex at about 100 ms after picture presentation onset. At about 150 ms, semantic variables became physiologically manifest in left frontotemporal regions. In the same latency range, we found an effect of phonological variables in the left middle temporal gyrus. Our results demonstrate that multiple linear regression analysis is sensitive to early effects of multiple psycholinguistic variables in picture naming. Crucially, our results suggest that access to phonological information might begin in parallel with semantic processing around 150 ms after picture onset.

  17. Early Parallel Activation of Semantics and Phonology in Picture Naming: Evidence from a Multiple Linear Regression MEG Study

    PubMed Central

    Miozzo, Michele; Pulvermüller, Friedemann; Hauk, Olaf

    2015-01-01

    The time course of brain activation during word production has become an area of increasingly intense investigation in cognitive neuroscience. The predominant view has been that semantic and phonological processes are activated sequentially, at about 150 and 200–400 ms after picture onset. Although evidence from prior studies has been interpreted as supporting this view, these studies were arguably not ideally suited to detect early brain activation of semantic and phonological processes. We here used a multiple linear regression approach to magnetoencephalography (MEG) analysis of picture naming in order to investigate early effects of variables specifically related to visual, semantic, and phonological processing. This was combined with distributed minimum-norm source estimation and region-of-interest analysis. Brain activation associated with visual image complexity appeared in occipital cortex at about 100 ms after picture presentation onset. At about 150 ms, semantic variables became physiologically manifest in left frontotemporal regions. In the same latency range, we found an effect of phonological variables in the left middle temporal gyrus. Our results demonstrate that multiple linear regression analysis is sensitive to early effects of multiple psycholinguistic variables in picture naming. Crucially, our results suggest that access to phonological information might begin in parallel with semantic processing around 150 ms after picture onset. PMID:25005037

  18. Preliminary In Vitro and In Vivo Evaluation of Antidiabetic Activity of Ducrosia anethifolia Boiss. and Its Linear Furanocoumarins

    PubMed Central

    Shalaby, Nagwa M. M.; Abd-Alla, Howaida I.; Aly, Hanan F.; Albalawy, Marzougah A.; Shaker, Kamel H.; Bouajila, Jalloul

    2014-01-01

    Aim. Ducrosia anethifolia is used as flavoring additive. There have been little detailed phytochemical reports on this genus and the antidiabetic activity of this plant is not yet evaluated. Method. Structure of compounds was deduced by spectroscopic analyses. Preliminary in vitro evaluation of the antidiabetic activity of crude extract and its furanocoumarins was carried out (α-amylase, α-glucosidase, and β-galactosidase). The in vivo activity was investigated by measuring some oxidative stress markers. Biomarkers of liver injury and kidney were also determined. Results. Eight linear furanocoumarins, psoralen, 5-methoxypsoralen, 8-methoxypsoralen, imperatorin, isooxypeucedanin, pabulenol, oxypeucedanin methanolate, oxypeucedanin hydrate, and 3-O-glucopyranosyl-β-sitosterol, were isolated. All compounds were reported for the first time from the genus Ducrosia except pabulenol. The blood glucose level, liver function enzymes, total protein, lipid, and cholesterol levels were significantly normalized by extract treatment. The antioxidant markers, glucolytic, and gluconeogenic enzymes were significantly ameliorated and the elevated level of kidney biomarkers in the diabetic groups was restored. The compounds showed inhibitory activity in a concentration dependant manner. Imperatorin and 5-methoxypsoralen showed the most potent inhibiting power. Conclusion. D. anethifolia extract showed hypoglycemic, hypolipidemic, and antioxidant effect as well as ameliorating kidney function. This extract and some linear furanocoumarins exhibited carbohydrate metabolizing enzymes inhibitory effect. PMID:24800231

  19. Vestibular modulation of muscle sympathetic nerve activity by the utricle during sub-perceptual sinusoidal linear acceleration in humans.

    PubMed

    Hammam, Elie; Hau, Chui Luen Vera; Wong, Kwok-Shing; Kwok, Kenny; Macefield, Vaughan G

    2014-04-01

    We assessed the capacity for the vestibular utricle to modulate muscle sympathetic nerve activity (MSNA) during sinusoidal linear acceleration at amplitudes extending from imperceptible to clearly perceptible. Subjects (n = 16) were seated in a sealed room, eliminating visual cues, mounted on a linear motor that could deliver peak sinusoidal accelerations of 30 mG in the antero-posterior direction. Subjects sat on a padded chair with their neck and head supported vertically, thereby minimizing somatosensory cues, facing the direction of motion in the anterior direction. Each block of sinusoidal motion was applied at a time unknown to subjects and in a random order of amplitudes (1.25, 2.5, 5, 10, 20 and 30 mG), at a constant frequency of 0.2 Hz. MSNA was recorded via tungsten microelectrodes inserted into muscle fascicles of the common peroneal nerve. Subjects used a linear potentiometer aligned to the axis of motion to indicate any perceived movement, which was compared with the accelerometer signal of actual room movement. On average, 67% correct detection of movement did not occur until 6.5 mG, with correct knowledge of the direction of movement at ~10 mG. Cross-correlation analysis revealed potent sinusoidal modulation of MSNA even at accelerations subjects could not perceive (1.25-5 mG). The modulation index showed a positive linear increase with acceleration amplitude, such that the modulation was significantly higher (25.3 ± 3.7%) at 30 mG than at 1.25 mG (15.5 ± 1.2%). We conclude that selective activation of the vestibular utricle causes a pronounced modulation of MSNA, even at levels well below perceptual threshold, and provides further evidence in support of the importance of vestibulosympathetic reflexes in human cardiovascular control. PMID:24504198

  20. Neutron activation processes simulation in an Elekta medical linear accelerator head.

    PubMed

    Juste, B; Miró, R; Verdú, G; Díez, S; Campayo, J M

    2014-01-01

    Monte Carlo estimation of the giant-dipole-resonance (GRN) photoneutrons inside the Elekta Precise LINAC head (emitting a 15 MV photon beam) were performed using the MCNP6 (general-purpose Monte Carlo N-Particle code, version 6). Each component of LINAC head geometry and materials were modelled in detail using the given manufacturer information. Primary photons generate photoneutrons and its transport across the treatment head was simulated, including the (n, γ) reactions which undergo activation products. The MCNP6 was used to develop a method for quantifying the activation of accelerator components. The approach described in this paper is useful in quantifying the origin and the amount of nuclear activation.

  1. Linear Resonance Compressor for Stirling-Type Cryocoolers Activated by Piezoelectric Stack-Type Elements

    NASA Astrophysics Data System (ADS)

    Sobol, S.; Grossman, G.

    2015-12-01

    A novel type of a PZT- based compressor operating at mechanical resonance, suitable for pneumatically-driven Stirling-type cryocoolers was developed theoretically and built practically during this research. A resonance operation at relatively low frequency was achieved by incorporating the piezo ceramics into the moving part, and by reducing the effective piezo stiffness using hydraulic amplification. The detailed concept, analytical model and the test results of the preliminary prototype were reported earlier and presented at ICC17 [2]. A fine agreement between the simulations and experiments spurred development of the current actual compressor designed to drive a miniature Pulse Tube cryocooler, particularly our MTSa model, which operates at 103 Hz and requires an average PV power of 11 W, filling pressure of 40 Bar and a pressure ratio of 1.3. The paper concentrates on design aspects and optimization of the governing parameters. The small stroke to diameter ratio (about 1:10) allows for the use of a composite diaphragm instead of a clearance-seal piston. The motivation is to create an adequate separation between the working fluid and the buffer gas of the compressor, thus preventing possible contamination in the cryocooler. Providing efficiency and power density similar to those of conventional linear compressors, the piezo compressor may serve as a good alternative for cryogenic applications requiring extreme reliability and absence of magnetic field interference.

  2. An efficient feedback active noise control algorithm based on reduced-order linear predictive modeling of FMRI acoustic noise.

    PubMed

    Kannan, Govind; Milani, Ali A; Panahi, Issa M S; Briggs, Richard W

    2011-12-01

    Functional magnetic resonance imaging (fMRI) acoustic noise exhibits an almost periodic nature (quasi-periodicity) due to the repetitive nature of currents in the gradient coils. Small changes occur in the waveform in consecutive periods due to the background noise and slow drifts in the electroacoustic transfer functions that map the gradient coil waveforms to the measured acoustic waveforms. The period depends on the number of slices per second, when echo planar imaging (EPI) sequencing is used. Linear predictability of fMRI acoustic noise has a direct effect on the performance of active noise control (ANC) systems targeted to cancel the acoustic noise. It is shown that by incorporating some samples from the previous period, very high linear prediction accuracy can be reached with a very low order predictor. This has direct implications on feedback ANC systems since their performance is governed by the predictability of the acoustic noise to be cancelled. The low complexity linear prediction of fMRI acoustic noise developed in this paper is used to derive an effective and low-cost feedback ANC system.

  3. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

    SciTech Connect

    Premkumar, S.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin; Jawahar, A.

    2015-06-24

    The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material.

  4. Polarimeter with linear response for measuring optical activity in organic compounds

    NASA Astrophysics Data System (ADS)

    Flores, Jorge L.; Montoya, Marcial; Garcia-Torales, G.; Gonzalez Alvarez, Alejandro

    2005-08-01

    A polarimeter designed for measuring small rotation angles on the polarization plane of light is described. The experimental device employs one fixed polarizer and a rotating analyzer. The system generates a periodical intensity signal, which is then Fourier analyzed. The coefficients of Fourier Transform contain information about rotation angles produced by organic compounds that exhibited optical activity. The experimental device can be used to determine the sugar concentration in agave juice.

  5. Linear models of activation cascades: analytical solutions and coarse-graining of delayed signal transduction.

    PubMed

    Beguerisse-Díaz, Mariano; Desikan, Radhika; Barahona, Mauricio

    2016-08-01

    Cellular signal transduction usually involves activation cascades, the sequential activation of a series of proteins following the reception of an input signal. Here, we study the classic model of weakly activated cascades and obtain analytical solutions for a variety of inputs. We show that in the special but important case of optimal gain cascades (i.e. when the deactivation rates are identical) the downstream output of the cascade can be represented exactly as a lumped nonlinear module containing an incomplete gamma function with real parameters that depend on the rates and length of the cascade, as well as parameters of the input signal. The expressions obtained can be applied to the non-identical case when the deactivation rates are random to capture the variability in the cascade outputs. We also show that cascades can be rearranged so that blocks with similar rates can be lumped and represented through our nonlinear modules. Our results can be used both to represent cascades in computational models of differential equations and to fit data efficiently, by reducing the number of equations and parameters involved. In particular, the length of the cascade appears as a real-valued parameter and can thus be fitted in the same manner as Hill coefficients. Finally, we show how the obtained nonlinear modules can be used instead of delay differential equations to model delays in signal transduction.

  6. Linear models of activation cascades: analytical solutions and coarse-graining of delayed signal transduction.

    PubMed

    Beguerisse-Díaz, Mariano; Desikan, Radhika; Barahona, Mauricio

    2016-08-01

    Cellular signal transduction usually involves activation cascades, the sequential activation of a series of proteins following the reception of an input signal. Here, we study the classic model of weakly activated cascades and obtain analytical solutions for a variety of inputs. We show that in the special but important case of optimal gain cascades (i.e. when the deactivation rates are identical) the downstream output of the cascade can be represented exactly as a lumped nonlinear module containing an incomplete gamma function with real parameters that depend on the rates and length of the cascade, as well as parameters of the input signal. The expressions obtained can be applied to the non-identical case when the deactivation rates are random to capture the variability in the cascade outputs. We also show that cascades can be rearranged so that blocks with similar rates can be lumped and represented through our nonlinear modules. Our results can be used both to represent cascades in computational models of differential equations and to fit data efficiently, by reducing the number of equations and parameters involved. In particular, the length of the cascade appears as a real-valued parameter and can thus be fitted in the same manner as Hill coefficients. Finally, we show how the obtained nonlinear modules can be used instead of delay differential equations to model delays in signal transduction. PMID:27581482

  7. Linear models of activation cascades: analytical solutions and coarse-graining of delayed signal transduction

    PubMed Central

    Desikan, Radhika

    2016-01-01

    Cellular signal transduction usually involves activation cascades, the sequential activation of a series of proteins following the reception of an input signal. Here, we study the classic model of weakly activated cascades and obtain analytical solutions for a variety of inputs. We show that in the special but important case of optimal gain cascades (i.e. when the deactivation rates are identical) the downstream output of the cascade can be represented exactly as a lumped nonlinear module containing an incomplete gamma function with real parameters that depend on the rates and length of the cascade, as well as parameters of the input signal. The expressions obtained can be applied to the non-identical case when the deactivation rates are random to capture the variability in the cascade outputs. We also show that cascades can be rearranged so that blocks with similar rates can be lumped and represented through our nonlinear modules. Our results can be used both to represent cascades in computational models of differential equations and to fit data efficiently, by reducing the number of equations and parameters involved. In particular, the length of the cascade appears as a real-valued parameter and can thus be fitted in the same manner as Hill coefficients. Finally, we show how the obtained nonlinear modules can be used instead of delay differential equations to model delays in signal transduction. PMID:27581482

  8. Dynamical mean-field theory and weakly non-linear analysis for the phase separation of active Brownian particles.

    PubMed

    Speck, Thomas; Menzel, Andreas M; Bialké, Julian; Löwen, Hartmut

    2015-06-14

    Recently, we have derived an effective Cahn-Hilliard equation for the phase separation dynamics of active Brownian particles by performing a weakly non-linear analysis of the effective hydrodynamic equations for density and polarization [Speck et al., Phys. Rev. Lett. 112, 218304 (2014)]. Here, we develop and explore this strategy in more detail and show explicitly how to get to such a large-scale, mean-field description starting from the microscopic dynamics. The effective free energy emerging from this approach has the form of a conventional Ginzburg-Landau function. On the coarsest scale, our results thus agree with the mapping of active phase separation onto that of passive fluids with attractive interactions through a global effective free energy (motility-induced phase transition). Particular attention is paid to the square-gradient term necessary for the phase separation kinetics. We finally discuss results from numerical simulations corroborating the analytical results.

  9. Dynamical mean-field theory and weakly non-linear analysis for the phase separation of active Brownian particles

    SciTech Connect

    Speck, Thomas; Menzel, Andreas M.; Bialké, Julian; Löwen, Hartmut

    2015-06-14

    Recently, we have derived an effective Cahn-Hilliard equation for the phase separation dynamics of active Brownian particles by performing a weakly non-linear analysis of the effective hydrodynamic equations for density and polarization [Speck et al., Phys. Rev. Lett. 112, 218304 (2014)]. Here, we develop and explore this strategy in more detail and show explicitly how to get to such a large-scale, mean-field description starting from the microscopic dynamics. The effective free energy emerging from this approach has the form of a conventional Ginzburg-Landau function. On the coarsest scale, our results thus agree with the mapping of active phase separation onto that of passive fluids with attractive interactions through a global effective free energy (motility-induced phase transition). Particular attention is paid to the square-gradient term necessary for the phase separation kinetics. We finally discuss results from numerical simulations corroborating the analytical results.

  10. Dynamical mean-field theory and weakly non-linear analysis for the phase separation of active Brownian particles.

    PubMed

    Speck, Thomas; Menzel, Andreas M; Bialké, Julian; Löwen, Hartmut

    2015-06-14

    Recently, we have derived an effective Cahn-Hilliard equation for the phase separation dynamics of active Brownian particles by performing a weakly non-linear analysis of the effective hydrodynamic equations for density and polarization [Speck et al., Phys. Rev. Lett. 112, 218304 (2014)]. Here, we develop and explore this strategy in more detail and show explicitly how to get to such a large-scale, mean-field description starting from the microscopic dynamics. The effective free energy emerging from this approach has the form of a conventional Ginzburg-Landau function. On the coarsest scale, our results thus agree with the mapping of active phase separation onto that of passive fluids with attractive interactions through a global effective free energy (motility-induced phase transition). Particular attention is paid to the square-gradient term necessary for the phase separation kinetics. We finally discuss results from numerical simulations corroborating the analytical results. PMID:26071703

  11. Dynamical mean-field theory and weakly non-linear analysis for the phase separation of active Brownian particles

    NASA Astrophysics Data System (ADS)

    Speck, Thomas; Menzel, Andreas M.; Bialké, Julian; Löwen, Hartmut

    2015-06-01

    Recently, we have derived an effective Cahn-Hilliard equation for the phase separation dynamics of active Brownian particles by performing a weakly non-linear analysis of the effective hydrodynamic equations for density and polarization [Speck et al., Phys. Rev. Lett. 112, 218304 (2014)]. Here, we develop and explore this strategy in more detail and show explicitly how to get to such a large-scale, mean-field description starting from the microscopic dynamics. The effective free energy emerging from this approach has the form of a conventional Ginzburg-Landau function. On the coarsest scale, our results thus agree with the mapping of active phase separation onto that of passive fluids with attractive interactions through a global effective free energy (motility-induced phase transition). Particular attention is paid to the square-gradient term necessary for the phase separation kinetics. We finally discuss results from numerical simulations corroborating the analytical results.

  12. Combining support vector machines with linear quadratic regulator adaptation for the online design of an automotive active suspension system

    NASA Astrophysics Data System (ADS)

    Chiou, J.-S.; Liu, M.-T.

    2008-02-01

    As a powerful machine-learning approach to pattern recognition problems, the support vector machine (SVM) is known to easily allow generalization. More importantly, it works very well in a high-dimensional feature space. This paper presents a nonlinear active suspension controller which achieves a high level performance by compensating for actuator dynamics. We use a linear quadratic regulator (LQR) to ensure optimal control of nonlinear systems. An LQR is used to solve the problem of state feedback and an SVM is used to address the question of the estimation and examination of the state. These two are then combined and designed in a way that outputs feedback control. The real-time simulation demonstrates that an active suspension using the combined SVM-LQR controller provides passengers with a much more comfortable ride and better road handling.

  13. Instrumental photon activation analysis using the linear accelerator at the Naval Postgraduate School. Master's thesis

    SciTech Connect

    Fisher, W.A.

    1982-10-01

    Charcoal, charcoal residue, potting soil, aluminum foil, bismuth germanate, and petroleum samples have been investigated using instrumental photon activation analysis (i.e., no radiochemistry). The major and minor elements routinely observed by this nondestructive method were: C, C1, Ca, Fe, Mg, Si, and K. A compreshensive review of the principles of IPAA was also included in the study. The principles were applied to a theroetical analysis of an oil sample in which the trace element concentrations were known. It was concluded that IPAA is a highly sensitive technique which could be used to fingerprint oils.

  14. Instrumental photon activation analysis using the linear accelerator at the Naval Postgraduate School

    NASA Astrophysics Data System (ADS)

    Fisher, W. A.

    1982-10-01

    Charcoal, charcoal residue, potting soil, aluminum foil, bismuth germanate, and petroleum samples have been investigated using instrumental photon activation analysis (i.e., no radiochemistry). The major and minor elements routinely observed by this nondestructive method were: C, C1, Ca, Fe, Mg, Si, and K. A comprehensive review of the principles of IPAA was also included in the study. The principles were applied to a theoretical analysis of an oil sample in which the trace element concentrations were known. It was concluded that IPAA is a highly sensitive technique which could be used to fingerprint oils.

  15. Activity Descriptor Identification for Oxygen Reduction on Platinum-Based Bimetallic Nanoparticles: In Situ Observation of the Linear Composition–Strain–Activity Relationship

    PubMed Central

    2016-01-01

    Despite recent progress in developing active and durable oxygen reduction catalysts with reduced Pt content, lack of elegant bottom-up synthesis procedures with knowledge over the control of atomic arrangement and morphology of the Pt–alloy catalysts still hinders fuel cell commercialization. To follow a less empirical synthesis path for improved Pt-based catalysts, it is essential to correlate catalytic performance to properties that can be easily controlled and measured experimentally. Herein, using Pt–Co alloy nanoparticles (NPs) with varying atomic composition as an example, we show that the atomic distribution of Pt-based bimetallic NPs under operating conditions is strongly dependent on the initial atomic ratio by employing microscopic and in situ spectroscopic techniques. The PtxCo/C NPs with high Co content possess a Co concentration gradient such that Co is concentrated in the core and gradually depletes in the near-surface region, whereas the PtxCo/C NPs with low Co content possess a relatively uniform distribution of Co with low Co population in the near-surface region. Despite their different atomic structure, the oxygen reduction reaction (ORR) activity of PtxCo/C and Pt/C NPs is linearly related to the bulk average Pt–Pt bond length (RPt–Pt). The RPt–Pt is further shown to contract linearly with the increase in Co/Pt composition. These linear correlations together demonstrate that (i) the improved ORR activity of PtxCo/C NPs over pure Pt NPs originates predominantly from the compressive strain and (ii) the RPt–Pt is a valid strain descriptor that bridges the activity and atomic composition of Pt-based bimetallic NPs. PMID:25559440

  16. Activity descriptor identification for oxygen reduction on platinum-based bimetallic nanoparticles: in situ observation of the linear composition-strain-activity relationship.

    PubMed

    Jia, Qingying; Liang, Wentao; Bates, Michael K; Mani, Prasanna; Lee, Wendy; Mukerjee, Sanjeev

    2015-01-27

    Despite recent progress in developing active and durable oxygen reduction catalysts with reduced Pt content, lack of elegant bottom-up synthesis procedures with knowledge over the control of atomic arrangement and morphology of the Pt-alloy catalysts still hinders fuel cell commercialization. To follow a less empirical synthesis path for improved Pt-based catalysts, it is essential to correlate catalytic performance to properties that can be easily controlled and measured experimentally. Herein, using Pt-Co alloy nanoparticles (NPs) with varying atomic composition as an example, we show that the atomic distribution of Pt-based bimetallic NPs under operating conditions is strongly dependent on the initial atomic ratio by employing microscopic and in situ spectroscopic techniques. The PtxCo/C NPs with high Co content possess a Co concentration gradient such that Co is concentrated in the core and gradually depletes in the near-surface region, whereas the PtxCo/C NPs with low Co content possess a relatively uniform distribution of Co with low Co population in the near-surface region. Despite their different atomic structure, the oxygen reduction reaction (ORR) activity of PtxCo/C and Pt/C NPs is linearly related to the bulk average Pt-Pt bond length (RPt-Pt). The RPt-Pt is further shown to contract linearly with the increase in Co/Pt composition. These linear correlations together demonstrate that (i) the improved ORR activity of PtxCo/C NPs over pure Pt NPs originates predominantly from the compressive strain and (ii) the RPt-Pt is a valid strain descriptor that bridges the activity and atomic composition of Pt-based bimetallic NPs.

  17. High-speed linear optics quantum computing using active feed-forward.

    PubMed

    Prevedel, Robert; Walther, Philip; Tiefenbacher, Felix; Böhi, Pascal; Kaltenbaek, Rainer; Jennewein, Thomas; Zeilinger, Anton

    2007-01-01

    As information carriers in quantum computing, photonic qubits have the advantage of undergoing negligible decoherence. However, the absence of any significant photon-photon interaction is problematic for the realization of non-trivial two-qubit gates. One solution is to introduce an effective nonlinearity by measurements resulting in probabilistic gate operations. In one-way quantum computation, the random quantum measurement error can be overcome by applying a feed-forward technique, such that the future measurement basis depends on earlier measurement results. This technique is crucial for achieving deterministic quantum computation once a cluster state (the highly entangled multiparticle state on which one-way quantum computation is based) is prepared. Here we realize a concatenated scheme of measurement and active feed-forward in a one-way quantum computing experiment. We demonstrate that, for a perfect cluster state and no photon loss, our quantum computation scheme would operate with good fidelity and that our feed-forward components function with very high speed and low error for detected photons. With present technology, the individual computational step (in our case the individual feed-forward cycle) can be operated in less than 150 ns using electro-optical modulators. This is an important result for the future development of one-way quantum computers, whose large-scale implementation will depend on advances in the production and detection of the required highly entangled cluster states.

  18. Linear parameter-varying model and adaptive filtering technique for detecting neuronal activities: an fNIRS study

    NASA Astrophysics Data System (ADS)

    Kamran, M. Ahmad; Hong, Keum-Shik

    2013-10-01

    Objective. Functional near-infrared spectroscopy (fNIRS) is an emerging non-invasive brain imaging technique that measures brain activities by using near-infrared light of 650-950 nm wavelength. The major advantages of fNIRS are its low cost, portability, and good temporal resolution as a plausible solution to real-time imaging. Recent research has shown the great potential of fNIRS as a tool for brain-computer interfaces. Approach. This paper presents the first novel technique for fNIRS-based modelling of brain activities using the linear parameter-varying (LPV) method and adaptive signal processing. The output signal of each channel is assumed to be an output of an LPV system with unknown coefficients that are optimally estimated by the affine projection algorithm. The parameter vector is assumed to be Gaussian. Main results. The general linear model (GLM) is very popular and is a commonly used method for the analysis of functional MRI data, but it has certain limitations in the case of optical signals. The proposed model is more efficient in the sense that it allows the user to define more states. Moreover, unlike most previous models, it is online. The present results, showing improvement, were verified by random finger-tapping tasks in extensive experiments. We used 24 states, which can be reduced or increased depending on the cost of computation and requirements. Significance. The t-statistics were employed to determine the activation maps and to verify the significance of the results. Comparison of the proposed technique and two existing GLM-based algorithms shows an improvement in the estimation of haemodynamic response. Additionally, the convergence of the proposed algorithm is shown by error reduction in consecutive iterations.

  19. Polarized light propagation in multiply scattering media exhibiting both linear birefringence and optical activity: Monte Carlo model and experimental methodology.

    PubMed

    Wood, Michael F G; Guo, Xinxin; Vitkin, I Alex

    2007-01-01

    A Monte Carlo model for polarized light propagation in birefringent, optically active, multiply scattering media is developed in an effort to accurately represent the propagation of polarized light in biological tissue. The model employs the Jones N-matrix formalism to combine both linear birefringence and optical activity into a single effect that can be applied to photons as they propagate between scattering events. Polyacrylamide phantoms with strain-induced birefringence, sucrose-induced optical activity, and polystyrene microspheres as scattering particles are used for experimental validation. Measurements are made using a Stokes polarimeter that detects scattered light in different geometries, and compared to the results of Monte Carlo simulations run with similar parameters. The results show close agreement between the experimental measurements and Monte Carlo calculations for phantoms exhibiting turbidity and birefringence, as well as for phantoms exhibiting turbidity, birefringence, and optical activity. Other scattering-independent polarization properties can be incorporated into the developed Jones N-matrix formalism, enabling quantification of the polarization effects via an accurate polarization-sensitive Monte Carlo model. PMID:17343504

  20. Pt/ZnO nanoarray nanogenerator as self-powered active gas sensor with linear ethanol sensing at room temperature

    NASA Astrophysics Data System (ADS)

    Zhao, Yayu; Lai, Xuan; Deng, Ping; Nie, Yuxin; Zhang, Yan; Xing, Lili; Xue, Xinyu

    2014-03-01

    A self-powered gas sensor that can actively detect ethanol at room temperature has been realized from a Pt/ZnO nanoarray nanogenerator. Pt nanoparticles are uniformly distributed on the whole surface of ZnO nanowires. The piezoelectric output of Pt/ZnO nanoarrays can act not only as a power source, but also as a response signal to ethanol at room temperature. Upon exposure to dry air and 1500 ppm ethanol at room temperature, the piezoelectric output of the device under the same compressive strain is 0.672 and 0.419 V, respectively. Moreover, a linear dependence of the sensitivity on the ethanol concentration is observed. Such a linear ethanol sensing at room temperature can be attributed to the atmosphere-dependent variety of the screen effect on the piezoelectric output of ZnO nanowires, the catalytic properties of Pt nanoparticles, and the Schottky barriers at Pt/ZnO interfaces. The present results can stimulate research in the direction of designing new material systems for self-powered room-temperature gas sensing.

  1. Situational Awareness of Influenza Activity Based on Multiple Streams of Surveillance Data Using Multivariate Dynamic Linear Model

    PubMed Central

    Lau, Eric H. Y.; Cheng, Calvin K. Y.; Ip, Dennis K. M.; Cowling, Benjamin J.

    2012-01-01

    Background Multiple sources of influenza surveillance data are becoming more available; however integration of these data streams for situational awareness of influenza activity is less explored. Methods and Results We applied multivariate time-series methods to sentinel outpatient and school absenteeism surveillance data in Hong Kong during 2004–2009. School absenteeism data and outpatient surveillance data experienced interruptions due to school holidays and changes in public health guidelines during the pandemic, including school closures and the establishment of special designated flu clinics, which in turn provided ‘drop-in’ fever counts surveillance data. A multivariate dynamic linear model was used to monitor influenza activity throughout epidemics based on all available data. The inferred level followed influenza activity closely at different times, while the inferred trend was less competent with low influenza activity. Correlations between inferred level and trend from the multivariate model and reference influenza activity, measured by the product of weekly laboratory influenza detection rates and weekly general practitioner influenza-like illness consultation rates, were calculated and compared with those from univariate models. Over the whole study period, there was a significantly higher correlation (ρ = 0.82, p≤0.02) for the inferred trend based on the multivariate model compared to other univariate models, while the inferred trend from the multivariate model performed as well as the best univariate model in the pre-pandemic and the pandemic period. The inferred trend and level from the multivariate model was able to match, if not outperform, the best univariate model albeit with missing data plus drop-in and drop-out of different surveillance data streams. An overall influenza index combining level and trend was constructed to demonstrate another potential use of the method. Conclusions Our results demonstrate the potential use of

  2. Effect of torsional twist on 2nd order non-linear optical activity of anthracene and pyrene tricyanofuran derivatives.

    PubMed

    Planells, Miquel; Pizzotti, Maddalena; Nichol, Gary S; Tessore, Francesca; Robertson, Neil

    2014-11-14

    Tricyanofuran (TCF) derivatives attached to both anthracene and pyrene moieties were synthesised and characterised by optical, electrochemical and computational techniques. Both compounds exhibited similar absorption profile as well as electrochemical behaviour, however the pyrene derivative showed 20-fold higher non-linear optical activity measured by the EFISH technique. This huge difference has been assigned to (i) a lower molar absorption and (ii) a higher torsion angle for the anthracene derivative, confirmed by both experimental X-ray diffraction and DFT calculations. Furthermore, we note that the μβ1.907 value of -1700 × 10(-48) esu recorded for the pyrene derivative in CHCl3/pyridine is remarkable for a NLO chromophore lacking a classical push-pull structure. PMID:25264846

  3. Multistability of neural networks with discontinuous non-monotonic piecewise linear activation functions and time-varying delays.

    PubMed

    Nie, Xiaobing; Zheng, Wei Xing

    2015-05-01

    This paper is concerned with the problem of coexistence and dynamical behaviors of multiple equilibrium points for neural networks with discontinuous non-monotonic piecewise linear activation functions and time-varying delays. The fixed point theorem and other analytical tools are used to develop certain sufficient conditions that ensure that the n-dimensional discontinuous neural networks with time-varying delays can have at least 5(n) equilibrium points, 3(n) of which are locally stable and the others are unstable. The importance of the derived results is that it reveals that the discontinuous neural networks can have greater storage capacity than the continuous ones. Moreover, different from the existing results on multistability of neural networks with discontinuous activation functions, the 3(n) locally stable equilibrium points obtained in this paper are located in not only saturated regions, but also unsaturated regions, due to the non-monotonic structure of discontinuous activation functions. A numerical simulation study is conducted to illustrate and support the derived theoretical results.

  4. Kalman estimator- and general linear model-based on-line brain activation mapping by near-infrared spectroscopy

    PubMed Central

    2010-01-01

    Background Near-infrared spectroscopy (NIRS) is a non-invasive neuroimaging technique that recently has been developed to measure the changes of cerebral blood oxygenation associated with brain activities. To date, for functional brain mapping applications, there is no standard on-line method for analysing NIRS data. Methods In this paper, a novel on-line NIRS data analysis framework taking advantages of both the general linear model (GLM) and the Kalman estimator is devised. The Kalman estimator is used to update the GLM coefficients recursively, and one critical coefficient regarding brain activities is then passed to a t-statistical test. The t-statistical test result is used to update a topographic brain activation map. Meanwhile, a set of high-pass filters is plugged into the GLM to prevent very low-frequency noises, and an autoregressive (AR) model is used to prevent the temporal correlation caused by physiological noises in NIRS time series. A set of data recorded in finger tapping experiments is studied using the proposed framework. Results The obtained results suggest that the method can effectively track the task related brain activation areas, and prevent the noise distortion in the estimation while the experiment is running. Thereby, the potential of the proposed method for real-time NIRS-based brain imaging was demonstrated. Conclusions This paper presents a novel on-line approach for analysing NIRS data for functional brain mapping applications. This approach demonstrates the potential of a real-time-updating topographic brain activation map. PMID:21138595

  5. Linear free energy relationships between aqueous phase hydroxyl radical reaction rate constants and free energy of activation.

    PubMed

    Minakata, Daisuke; Crittenden, John

    2011-04-15

    The hydroxyl radical (HO(•)) is a strong oxidant that reacts with electron-rich sites on organic compounds and initiates complex radical chain reactions in aqueous phase advanced oxidation processes (AOPs). Computer based kinetic modeling requires a reaction pathway generator and predictions of associated reaction rate constants. Previously, we reported a reaction pathway generator that can enumerate the most important elementary reactions for aliphatic compounds. For the reaction rate constant predictor, we develop linear free energy relationships (LFERs) between aqueous phase literature-reported HO(•) reaction rate constants and theoretically calculated free energies of activation for H-atom abstraction from a C-H bond and HO(•) addition to alkenes. The theoretical method uses ab initio quantum mechanical calculations, Gaussian 1-3, for gas phase reactions and a solvation method, COSMO-RS theory, to estimate the impact of water. Theoretically calculated free energies of activation are found to be within approximately ±3 kcal/mol of experimental values. Considering errors that arise from quantum mechanical calculations and experiments, this should be within the acceptable errors. The established LFERs are used to predict the HO(•) reaction rate constants within a factor of 5 from the experimental values. This approach may be applied to other reaction mechanisms to establish a library of rate constant predictions for kinetic modeling of AOPs. PMID:21410278

  6. Detection of epileptiform activity in EEG signals based on time-frequency and non-linear analysis.

    PubMed

    Gajic, Dragoljub; Djurovic, Zeljko; Gligorijevic, Jovan; Di Gennaro, Stefano; Savic-Gajic, Ivana

    2015-01-01

    We present a new technique for detection of epileptiform activity in EEG signals. After preprocessing of EEG signals we extract representative features in time, frequency and time-frequency domain as well as using non-linear analysis. The features are extracted in a few frequency sub-bands of clinical interest since these sub-bands showed much better discriminatory characteristics compared with the whole frequency band. Then we optimally reduce the dimension of feature space to two using scatter matrices. A decision about the presence of epileptiform activity in EEG signals is made by quadratic classifiers designed in the reduced two-dimensional feature space. The accuracy of the technique was tested on three sets of electroencephalographic (EEG) signals recorded at the University Hospital Bonn: surface EEG signals from healthy volunteers, intracranial EEG signals from the epilepsy patients during the seizure free interval from within the seizure focus and intracranial EEG signals of epileptic seizures also from within the seizure focus. An overall detection accuracy of 98.7% was achieved.

  7. Detection of epileptiform activity in EEG signals based on time-frequency and non-linear analysis

    PubMed Central

    Gajic, Dragoljub; Djurovic, Zeljko; Gligorijevic, Jovan; Di Gennaro, Stefano; Savic-Gajic, Ivana

    2015-01-01

    We present a new technique for detection of epileptiform activity in EEG signals. After preprocessing of EEG signals we extract representative features in time, frequency and time-frequency domain as well as using non-linear analysis. The features are extracted in a few frequency sub-bands of clinical interest since these sub-bands showed much better discriminatory characteristics compared with the whole frequency band. Then we optimally reduce the dimension of feature space to two using scatter matrices. A decision about the presence of epileptiform activity in EEG signals is made by quadratic classifiers designed in the reduced two-dimensional feature space. The accuracy of the technique was tested on three sets of electroencephalographic (EEG) signals recorded at the University Hospital Bonn: surface EEG signals from healthy volunteers, intracranial EEG signals from the epilepsy patients during the seizure free interval from within the seizure focus and intracranial EEG signals of epileptic seizures also from within the seizure focus. An overall detection accuracy of 98.7% was achieved. PMID:25852534

  8. Non-linear responsivity characterisation of a CMOS Active Pixel Sensor for high resolution imaging of the Jovian system

    NASA Astrophysics Data System (ADS)

    Soman, M.; Stefanov, K.; Weatherill, D.; Holland, A.; Gow, J.; Leese, M.

    2015-02-01

    The Jovian system is the subject of study for the Jupiter Icy Moon Explorer (JUICE), an ESA mission which is planned to launch in 2022. The scientific payload is designed for both characterisation of the magnetosphere and radiation environment local to the spacecraft, as well as remote characterisation of Jupiter and its satellites. A key instrument on JUICE is the high resolution and wide angle camera, JANUS, whose main science goals include detailed characterisation and study phases of three of the Galilean satellites, Ganymede, Callisto and Europa, as well as studies of other moons, the ring system, and irregular satellites. The CIS115 is a CMOS Active Pixel Sensor from e2v technologies selected for the JANUS camera. It is fabricated using 0.18 μ m CMOS imaging sensor process, with an imaging area of 2000 × 1504 pixels, each 7 μ m square. A 4T pixel architecture allows for efficient correlated double sampling, improving the readout noise to better than 8 electrons rms, whilst the sensor is operated in a rolling shutter mode, sampling at up to 10 Mpixel/s at each of the four parallel outputs.A primary parameter to characterise for an imaging device is the relationship that converts the sensor's voltage output back to the corresponding number of electrons that were detected in a pixel, known as the Charge to Voltage Factor (CVF). In modern CMOS sensors with small feature sizes, the CVF is known to be non-linear with signal level, therefore a signal-dependent measurement of the CIS115's CVF has been undertaken and is presented here. The CVF is well modelled as a quadratic function leading to a measurement of the maximum charge handling capacity of the CIS115 to be 3.4 × 104 electrons. If the CIS115's response is assumed linear, its CVF is 21.1 electrons per mV (1/47.5 μ V per electron).

  9. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  10. Rheology of the Active Cell Cortex in Mitosis.

    PubMed

    Fischer-Friedrich, Elisabeth; Toyoda, Yusuke; Cattin, Cedric J; Müller, Daniel J; Hyman, Anthony A; Jülicher, Frank

    2016-08-01

    The cell cortex is a key structure for the regulation of cell shape and tissue organization. To reach a better understanding of the mechanics and dynamics of the cortex, we study here HeLa cells in mitosis as a simple model system. In our assay, single rounded cells are dynamically compressed between two parallel plates. Our measurements indicate that the cortical layer is the dominant mechanical element in mitosis as opposed to the cytoplasmic interior. To characterize the time-dependent rheological response, we extract a complex elastic modulus that characterizes the resistance of the cortex against area dilation. In this way, we present a rheological characterization of the cortical actomyosin network in the linear regime. Furthermore, we investigate the influence of actin cross linkers and the impact of active prestress on rheological behavior. Notably, we find that cell mechanics values in mitosis are captured by a simple rheological model characterized by a single timescale on the order of 10 s, which marks the onset of fluidity in the system. PMID:27508442

  11. A comparative examination of the adsorption mechanism of an anionic textile dye (RBY 3GL) onto the powdered activated carbon (PAC) using various the isotherm models and kinetics equations with linear and non-linear methods

    NASA Astrophysics Data System (ADS)

    Açıkyıldız, Metin; Gürses, Ahmet; Güneş, Kübra; Yalvaç, Duygu

    2015-11-01

    The present study was designed to compare the linear and non-linear methods used to check the compliance of the experimental data corresponding to the isotherm models (Langmuir, Freundlich, and Redlich-Peterson) and kinetics equations (pseudo-first order and pseudo-second order). In this context, adsorption experiments were carried out to remove an anionic dye, Remazol Brillant Yellow 3GL (RBY), from its aqueous solutions using a commercial activated carbon as a sorbent. The effects of contact time, initial RBY concentration, and temperature onto adsorbed amount were investigated. The amount of dye adsorbed increased with increased adsorption time and the adsorption equilibrium was attained after 240 min. The amount of dye adsorbed enhanced with increased temperature, suggesting that the adsorption process is endothermic. The experimental data was analyzed using the Langmuir, Freundlich, and Redlich-Peterson isotherm equations in order to predict adsorption isotherm. It was determined that the isotherm data were fitted to the Langmuir and Redlich-Peterson isotherms. The adsorption process was also found to follow a pseudo second-order kinetic model. According to the kinetic and isotherm data, it was found that the determination coefficients obtained from linear method were higher than those obtained from non-linear method.

  12. Linear, Mannitol-Based Poly(anhydride-esters) with High Ibuprofen Loading and Anti-Inflammatory Activity.

    PubMed

    Stebbins, Nicholas D; Yu, Weiling; Uhrich, Kathryn E

    2015-11-01

    Sugar alcohols, such as mannitol and xylitol, are biocompatible polyols that have been used to make highly cross-linked polyester elastomers and dendrimers for tissue engineering and drug delivery. However, research that utilizes the secondary hydroxyl groups as sites for pendant bioactive attachment and subsequent polymerization is limited. This work is the first report of a linear, completely biodegradable polymer with a sugar alcohol backbone and chemically incorporated pendant bioactives that exhibits sustained bioactive release and high bioactive loading (∼70%). With four pendant esters per repeat unit, this poly(anhydride-ester) has high loading and biodegrades into three biocompatible products: bioactive, sugar alcohol, and alkyl-based diacid. Ibuprofen serves as a representative bioactive, whereas mannitol is a representative polyol. Polymerization was achieved through reaction with (trimethylsilyl)ethoxyacetylene. Drug release via polymer degradation was quantified by high performance liquid chromatography. Additionally, a cytocompatibility study with fibroblast cells was performed to elucidate the polymer's suitability for in vivo use and a cyclooxygenase-2 (COX-2) assay was performed on the degradation media to ensure that released ibuprofen retained its anti-inflammatory activity. This work enables the future development of novel, biodegradable polymers exhibiting two key features: (i) polymer backbones with easily modified pendant groups, such as targeting moieties, and (ii) high drug loading using a multitude of bioactive classes.

  13. Active fault detection and isolation of discrete-time linear time-varying systems: a set-membership approach

    NASA Astrophysics Data System (ADS)

    Mojtaba Tabatabaeipour, Seyed

    2015-08-01

    Active fault detection and isolation (AFDI) is used for detection and isolation of faults that are hidden in the normal operation because of a low excitation signal or due to the regulatory actions of the controller. In this paper, a new AFDI method based on set-membership approaches is proposed. In set-membership approaches, instead of a point-wise estimation of the states, a set-valued estimation of them is computed. If this set becomes empty the given model of the system is not consistent with the measurements. Therefore, the model is falsified. When more than one model of the system remains un-falsified, the AFDI method is used to generate an auxiliary signal that is injected into the system for detection and isolation of faults that remain otherwise hidden or non-isolated using passive FDI (PFDI) methods. Having the set-valued estimation of the states for each model, the proposed AFDI method finds an optimal input signal that guarantees FDI in a finite time horizon. The input signal is updated at each iteration in a decreasing receding horizon manner based on the set-valued estimation of the current states and un-falsified models at the current sample time. The problem is solved by a number of linear and quadratic programming problems, which result in a computationally efficient algorithm. The method is tested on a numerical example as well as on the pitch actuator of a benchmark wind turbine.

  14. Recent seismic activity at Cephalonia (Greece): a study through candidate electromagnetic precursors in terms of non-linear dynamics

    NASA Astrophysics Data System (ADS)

    Potirakis, Stelios M.; Contoyiannis, Yiannis; Melis, Nikolaos S.; Kopanas, John; Antonopoulos, George; Balasis, Georgios; Kontoes, Charalampos; Nomicos, Constantinos; Eftaxias, Konstantinos

    2016-08-01

    The preparation process of two recent earthquakes (EQs) that occurred in Cephalonia (Kefalonia), Greece, ((38.22° N, 20.53° E), 26 January 2014, Mw = 6.0, depth ˜ 20 km) and ((38.25° N, 20.39° E), 3 February 2014, Mw = 5.9, depth ˜ 10 km), respectively, is studied in terms of the critical dynamics revealed in observables of the involved non-linear processes. Specifically, we show, by means of the method of critical fluctuations (MCF), that signatures of critical, as well as tricritical, dynamics were embedded in the fracture-induced electromagnetic emissions (EMEs) recorded by two stations in locations near the epicentres of these two EQs. It is worth noting that both the MHz EMEs recorded by the telemetric stations on the island of Cephalonia and the neighbouring island of Zante (Zakynthos) reached a simultaneously critical condition a few days before the occurrence of each earthquake. The critical characteristics embedded in the EME signals were further verified using the natural time (NT) method. Moreover, we show, in terms of the NT method, that the foreshock seismic activity also presented critical characteristics before each event. Importantly, the revealed critical process seems to be focused on the area corresponding to the western Cephalonia zone, following the seismotectonic and hazard zoning of the Ionian Islands area near Cephalonia.

  15. Effect of laundry activities on in-stream concentrations of linear alkylbenzene sulfonate in a small rural South African river.

    PubMed

    Gordon, A K; Muller, W J; Gysman, N; Marshall, S J; Sparham, C J; O'Connor, S M; Whelan, M J

    2009-07-15

    In many parts of the world clothes are washed near to or in rivers and streams. Little information is available on resulting concentrations of detergent ingredients or on any potential effects caused. In this study, the fate of a commonly used anionic surfactant, linear alkylbenzene sulphonate (LAS) was investigated in a reach of the Balfour River (Eastern Cape Province, South Africa) which was regularly used as a site for laundry activity. Samples of river water were collected upstream of the main washing site and at a number of locations downstream on several occasions in winter and summer. Sediment samples were also collected and analysed. In addition, a household survey was conducted to ascertain the amount of detergent used and the distribution of washing practices. The results of the survey suggested that the use of riverside locations for laundry activities was seasonal. Most washing tended to be done at home during the winter with riverside sites used more frequently during the summer months. The monitoring data showed that LAS concentrations in water were very variable. They were occasionally high in the immediate vicinity of the laundry site (up to 342 microg L(-1)) but were generally very low (<11 microg L(-1)) at downstream monitoring stations, suggesting that LAS was rapidly dissipated by a combination of degradation, hydrodynamic dispersion and dilution. Concentrations in the immediate vicinity of the washing site were lower than expected on the basis of the household survey because most waste water was disposed of on the river bank rather than directly in the river. No ecological effects are expected from LAS emissions at this site.

  16. A20 inhibits LUBAC-mediated NF-κB activation by binding linear polyubiquitin chains via its zinc finger 7

    PubMed Central

    Verhelst, Kelly; Carpentier, Isabelle; Kreike, Marja; Meloni, Laura; Verstrepen, Lynn; Kensche, Tobias; Dikic, Ivan; Beyaert, Rudi

    2012-01-01

    Linear polyubiquitination of proteins has recently been implicated in NF-κB signalling and is mediated by the linear ubiquitin chain assembly complex (LUBAC), consisting of HOIL-1, HOIP and Sharpin. However, the mechanisms that regulate linear ubiquitination are still unknown. Here, we show that A20 is rapidly recruited to NEMO and LUBAC upon TNF stimulation and that A20 inhibits LUBAC-induced NF-κB activation via its C-terminal zinc-finger 7 (ZF7) domain. Expression of a polypeptide corresponding to only ZF7 was sufficient to inhibit TNF-induced NF-κB activation. Both A20 and ZF7 can form a complex with NEMO and LUBAC, and are able to prevent the TNF-induced binding of NEMO to LUBAC. Finally, we show that ZF7 preferentially binds linear polyubiquitin chains in vitro, indicating A20–ZF7 as a novel linear ubiquitin-binding domain (LUBID). We thus propose a model in which A20 inhibits TNF- and LUBAC-induced NF-κB signalling by binding to linear polyubiquitin chains via its seventh zinc finger, which prevents the TNF-induced interaction between LUBAC and NEMO. PMID:23032186

  17. Linear Colliders

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Yokoya, Kaoru

    2015-02-01

    An overview of linear collider programs is given. The history and technical challenges are described and the pioneering electron-positron linear collider, the SLC, is first introduced. For future energy frontier linear collider projects, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are introduced and their technical features are discussed. The ILC is based on superconducting RF technology and the CLIC is based on two-beam acceleration technology. The ILC collaboration completed the Technical Design Report in 2013, and has come to the stage of "Design to Reality." The CLIC collaboration published the Conceptual Design Report in 2012, and the key technology demonstration is in progress. The prospects for further advanced acceleration technology are briefly discussed for possible long-term future linear colliders.

  18. Linear Colliders

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Yokoya, Kaoru

    An overview of linear collider programs is given. The history and technical challenges are described and the pioneering electron-positron linear collider, the SLC, is first introduced. For future energy frontier linear collider projects, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) are introduced and their technical features are discussed. The ILC is based on superconducting RF technology and the CLIC is based on two-beam acceleration technology. The ILC collaboration completed the Technical Design Report in 2013, and has come to the stage of "Design to Reality." The CLIC collaboration published the Conceptual Design Report in 2012, and the key technology demonstration is in progress. The prospects for further advanced acceleration technology are briefly discussed for possible long-term future linear colliders.

  19. The Force Singularity for Partially Immersed Parallel Plates

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Rajat; Finn, Robert

    2016-05-01

    In earlier work, we provided a general description of the forces of attraction and repulsion, encountered by two parallel vertical plates of infinite extent and of possibly differing materials, when partially immersed in an infinite liquid bath and subject to surface tension forces. In the present study, we examine some unusual details of the exotic behavior that can occur at the singular configuration separating infinite rise from infinite descent of the fluid between the plates, as the plates approach each other. In connection with this singular behavior, we present also some new estimates on meniscus height details.

  20. Reactive Ion Etching in a VHF Parallel Plate Reactor

    NASA Technical Reports Server (NTRS)

    Dahi, H.; Murnick, D. E.; Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

    1997-01-01

    VHF (very high frequency) capacitive plasma reactors may allow development of new RIE (reactive ion etching) systems with high etch rates, excellent uniformity and anisotropy and low damage. High ion and radical fluxes can be obtained by raising the RF (radio frequency) frequency which increases plasma density dramatically at a fixed voltage. The effects of variation in frequency (25-120 MHz), pressure (10-250 mTorr), and flow rate (1-100 sccm) in a CF4 discharge have been investigated. The RF current versus voltage characteristics and spatially resolved optical emission are used as diagnostics. Experiments on etch rates, etch uniformity and anisotropy in silicon, silicon dioxide and silicon nitride will be discussed. Results of fluid model simulations are used to interpret the experimental data.

  1. Radiant Heat Transfer Between Nongray Parallel Plates of Tungsten

    NASA Technical Reports Server (NTRS)

    Branstetter, J. Robert

    1961-01-01

    Net radiant heat flow between two infinite, parallel, tungsten plates was computed by summing the monochromatic energy exchange; the results are graphically presented as a function of the temperatures of the two surfaces. In general these fluxes range from approximately a to 25 percent greater than the results of gray-body computations based on the same emissivity data. The selection of spectral emissivity data and the computational procedure are discussed. The present analytical procedure is so arranged that, as spectral emissivity data for a material become available, these data can be readily introduced into the NASA data-reduction equipment, which has been programmed to compute the net heat flux for the particular geometry and basic assumptions cited in the text. Nongray-body computational techniques for determining radiant heat flux appear practical provided the combination of select spectral emissivity data and the proper mechanized data-reduction equipment are brought to bear on the problem.

  2. Hydrodynamics of Gas-Liquid Counterflow Through Corrugated Parallel Plates

    SciTech Connect

    de Almeida, V.F.

    1999-11-05

    Structured packings utilized in today's distillation packed towers consist of stacked units of many vertically oriented parallel corrugated plates. The V-shaped corrugations are oriented at a fixed angle with respect to the vertical direction, and the corrugation angle in adjacent plates are oriented in reverse direction. Points of contact, at the crests of the corrugations, between adjacent plates, form an unconsolidated porous medium with known topology. Modern structured packings have been gaining acceptance in several separation processes, particularly distillation where gas/vapor and liquid flow countercurrently through the packing. In addition, structured packings have been credited with relatively low pressure drop, high efficiency, low holdup, and higher capacity; the packing also can be made corrosion resistive.

  3. Development of acute toxicity quantitative structure activity relationships (QSAR) and their use in linear alkylbenzene sulfonate species sensitivity distributions.

    PubMed

    Belanger, Scott E; Brill, Jessica L; Rawlings, Jane M; Price, Brad B

    2016-07-01

    Linear Alkylbenzene Sulfonate (LAS) is high tonnage and widely dispersed anionic surfactant used by the consumer products sector. A range of homologous structures are used in laundry applications that differ primarily on the length of the hydrophobic alkyl chain. This research summarizes the development of a set of acute toxicity QSARs (Quantitative Structure Activity Relationships) for fathead minnows (Pimephales promelas) and daphnids (Daphnia magna, Ceriodaphnia dubia) using accepted test guideline approaches. A series of studies on pure chain length LAS from C10 to C14 were used to develop the QSARs and the robustness of the QSARs was tested by evaluation of two technical mixtures of differing compositions. All QSARs were high quality (R(2) were 0.965-0.997, p < 0.0001). Toxicity normalization employing QSARs is used to interpret a broader array of tests on LAS chain length materials to a diverse group of test organisms with the objective of developing Species Sensitivity Distributions (SSDs) for various chain lengths of interest. Mixtures include environmental distributions measured from exposure monitoring surveys of wastewater effluents, various commercial mixtures, or specific chain lengths. SSD 5th percentile hazardous concentrations (HC5s) ranged from 0.129 to 0.254 mg/L for wastewater effluents containing an average of 11.26-12 alkyl carbons. The SSDs are considered highly robust given the breadth of species (n = 19), use of most sensitive endpoints from true chronic studies and the quality of the underlying statistical properties of the SSD itself. The data continue to indicate a low hazard to the environment relative to expected environmental concentrations.

  4. Linear solvation energy relationship of the limiting partition coefficient of organic solutes between water and activated carbon

    USGS Publications Warehouse

    Luehrs, Dean C.; Hickey, James P.; Nilsen, Peter E.; Godbole, K.A.; Rogers, Tony N.

    1995-01-01

    A linear solvation energy relationship has been found for 353 values of the limiting adsorption coefficients of diverse chemicals:  log K = −0.37 + 0.0341Vi − 1.07β + D + 0.65P with R = 0.951, s = 0.51, n = 353, and F = 818.0, where Vi is the intrinsic molar volume; β is a measure of the hydrogen bond acceptor strength of the solute; D is an index parameter for the research group which includes the effects of the different types of carbon used, the temperature, and the length of time allowed for the adsorption equilibrium to be established; and P is an index parameter for the flatness of the molecule. P is defined to be unity if there is an aromatic system in the molecule or if there is a double bond or series of conjugated double bonds with no more that one non-hydrogen atom beyond the double bond and zero otherwise. A slightly better fit is obtained if the two-thirds power of Vi is used as a measure of the surface area in place of the volume term:  log K = −1.75 + 0.227V2/3 − 1.10β + D + 0.60P with R = 0.954, s = 0.49, n = 353, and F = 895.39. This is the first quantitative measure of the effect of the shape of the molecule on its tendency to be adsorbed on activated carbon.

  5. Development of acute toxicity quantitative structure activity relationships (QSAR) and their use in linear alkylbenzene sulfonate species sensitivity distributions.

    PubMed

    Belanger, Scott E; Brill, Jessica L; Rawlings, Jane M; Price, Brad B

    2016-07-01

    Linear Alkylbenzene Sulfonate (LAS) is high tonnage and widely dispersed anionic surfactant used by the consumer products sector. A range of homologous structures are used in laundry applications that differ primarily on the length of the hydrophobic alkyl chain. This research summarizes the development of a set of acute toxicity QSARs (Quantitative Structure Activity Relationships) for fathead minnows (Pimephales promelas) and daphnids (Daphnia magna, Ceriodaphnia dubia) using accepted test guideline approaches. A series of studies on pure chain length LAS from C10 to C14 were used to develop the QSARs and the robustness of the QSARs was tested by evaluation of two technical mixtures of differing compositions. All QSARs were high quality (R(2) were 0.965-0.997, p < 0.0001). Toxicity normalization employing QSARs is used to interpret a broader array of tests on LAS chain length materials to a diverse group of test organisms with the objective of developing Species Sensitivity Distributions (SSDs) for various chain lengths of interest. Mixtures include environmental distributions measured from exposure monitoring surveys of wastewater effluents, various commercial mixtures, or specific chain lengths. SSD 5th percentile hazardous concentrations (HC5s) ranged from 0.129 to 0.254 mg/L for wastewater effluents containing an average of 11.26-12 alkyl carbons. The SSDs are considered highly robust given the breadth of species (n = 19), use of most sensitive endpoints from true chronic studies and the quality of the underlying statistical properties of the SSD itself. The data continue to indicate a low hazard to the environment relative to expected environmental concentrations. PMID:27105149

  6. Discovery of an ultra-short linear antibacterial tetrapeptide with anti-MRSA activity from a structure-activity relationship study.

    PubMed

    Lau, Qiu Ying; Ng, Fui Mee; Cheong, Jin Wei Darryl; Yap, Yi Yong Alvin; Tan, Yoke Yan Fion; Jureen, Roland; Hill, Jeffrey; Chia, Cheng San Brian

    2015-11-13

    The overuse and misuse of antibiotics has resulted in the emergence of drug-resistant pathogenic bacteria, including meticillin-resistant Staphylococcus aureus (MRSA), the primary pathogen responsible for human skin and soft-tissue infections. Antibacterial peptides are known to kill bacteria by rapidly disrupting their membranes and are deemed plausible alternatives to conventional antibiotics. One advantage of their membrane-targeting mode of action is that bacteria are unlikely to develop resistance as changing their cell membrane structure and morphology would likely involve extensive genetic mutations. However, major concerns in using peptides as antibacterial drugs include their instability towards plasma proteases, toxicity towards human cells due to their membrane-targeting mode of action and high manufacturing cost. These concerns can be mitigated by developing peptides as topical agents, by the judicial selection of amino acids and developing very short peptides respectively. In this preliminary report, we reveal a linear, non-hemolytic tetrapeptide with rapid bactericidal activity against MRSA developed from a structure-activity relationship study based on the antimicrobial hexapeptide WRWRWR-NH2. Our finding opens promising avenues for the development of ultra-short antibacterials to treat multidrug-resistant MRSA skin and soft tissue infections. PMID:26489599

  7. Linear Collisions

    ERIC Educational Resources Information Center

    Walkiewicz, T. A.; Newby, N. D., Jr.

    1972-01-01

    A discussion of linear collisions between two or three objects is related to a junior-level course in analytical mechanics. The theoretical discussion uses a geometrical approach that treats elastic and inelastic collisions from a unified point of view. Experiments with a linear air track are described. (Author/TS)

  8. MBAS (Methylene Blue Active Substances) and LAS (Linear Alkylbenzene Sulphonates) in Mediterranean coastal aerosols: Sources and transport processes

    NASA Astrophysics Data System (ADS)

    Becagli, S.; Ghedini, C.; Peeters, S.; Rottiers, A.; Traversi, R.; Udisti, R.; Chiari, M.; Jalba, A.; Despiau, S.; Dayan, U.; Temara, A.

    2011-12-01

    Methylene Blue Active Substances (MBAS) and Linear Alkylbenzene Sulphonates (LAS) concentrations, together with organic carbon and ions were measured in atmospheric coastal aerosols in the NW Mediterranean Basin. Previous studies have suggested that the presence of surfactants in coastal aerosols may result in vegetation damage without specifically detecting or quantifying these surfactants. Coastal aerosols were collected at a remote site (Porquerolles Island-Var, France) and at a more anthropised site (San Rossore National Park-Tuscany, Italy). The chemical data were interpreted according to a comprehensive local meteorological analysis aiming to decipher the airborne source and transport processes of these classes of compounds. The LAS concentration (anthropogenic surfactants) was measured in the samples using LC-MS/MS, a specific analytical method. The values were compared with the MBAS concentration, determined by a non-specific analytical method. At Porquerolles, the MBAS concentration (103 ± 93 ng m -3) in the summer samples was significantly higher than in the winter samples. In contrast, LAS concentrations were rarely greater than in the blank filters. At San Rossore, the mean annual MBAS concentration (887 ± 473 ng m -3 in PM10) contributed about 10% to the total atmospheric particulate organic matter. LAS mean concentration in these same aerosol samples was 11.5 ± 10.5 ng m -3. A similar MBAS (529 ± 454 ng m -3) - LAS (7.1 ± 4.1 ng m -3 LAS) ratio of ˜75 was measured in the fine (PM2.5) aerosol fraction. No linear correlation was found between MBAS and LAS concentrations. At San Rossore site the variation of LAS concentrations was studied on a daily basis over a year. The LAS concentrations in the coarse fraction (PM10-2.5) were higher during strong sea storm conditions, characterized by strong air flow coming from the sea sector. These events, occurring with more intensity in winter, promoted the formation of primary marine aerosols containing LAS

  9. Linear Stability Analysis of a Channel Flow with Porous Walls

    NASA Astrophysics Data System (ADS)

    Tilton, Nils

    2005-11-01

    This study is motivated by the extensive use of wall-transpiration in numerical studies related to inhibition and control of wall-turbulence. In general, wall-transpiration has been implemented by providing the wall-normal velocity and imposing a no-slip condition on the wall-tangential velocity. Physically, however, the pores cannot be infinitesimally small and, consequently, it is important to address how the presence of the pores affects the slip velocity at the wall and the stability of the boundary layer. Moreover, our work is motivated by the existence of only few studies on the linear stability of channels with porous walls. Our study considers a parallel-plate channel with porous walls such that a longitudinal pressure gradient induces a laminar flow in both the open channel region and the porous walls. Simplified counterparts to the Orr-Sommerfeld and Squire equations are derived for the porous regions that are valid for small permeablities. The linear stability analysis takes account of the coupling between the three disturbance fields through boundary conditions recently derived by Ochoa-Tapia and Whitaker (Int. J. Heat Mass Transfer, Vol. 38, 1995, pp 2635-2646). The resulting Orr-Sommerfeld spectrum and eigenfunctions reduce to those for Poiseuille flow as the permeability of the walls tends to zero, but are altered for greater values. We discuss symmetrical flows where parameters at both porous walls are identical as well as skewed flows where parameters at the two walls differ.

  10. LINEAR ACCELERATOR

    DOEpatents

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  11. Positional isomers of linear sodium dodecyl benzene sulfonate: solubility, self-assembly, and air/water interfacial activity.

    PubMed

    Ma, Jian-Guo; Boyd, Ben J; Drummond, Calum J

    2006-10-10

    Commercial linear alkyl benzene sulfonates (ABS) are a very important class of anionic surfactants that are employed in a wide variety of applications, especially those involving wetting and detergency. Linear ABS surfactants generally consist of a complex mixture of different chain lengths and positional isomers. This diversity and level of complexity makes it difficult to develop fundamental structure-property correlations for the commercial surfactants. In this work, six monodisperse headgroup positional isomers of sodium para-dodecyl benzene sulfonate (Na-x-DBS, x = 1-6) have been studied. The influence of headgroup position and added electrolyte (NaCl) on the solubility and self-assembly (micellar and vesicular aggregation and lyotropic liquid crystalline phase behavior) in the temperature range from 10 to 90 degrees C have been investigated. Additionally, the air-aqueous solution interfacial adsorption at 25 (no added NaCl) and 50 degrees C (from 0 to 1.0 M added NaCl) has been examined. The observed physicochemical behavior is interpreted in terms of local molecular packing constraints, and in the case of the lyotropic liquid crystalline behavior global aggregate packing constraints as well.

  12. Linear and nonlinear analyses of multi-channel mechanomyographic recordings reveal heterogeneous activation of wrist extensors in presence of delayed onset muscle soreness.

    PubMed

    Madeleine, Pascal; Hansen, Ernst A; Samani, Afshin

    2014-12-01

    In this study, we applied multi-channel mechanomyographic (MMG) recordings in combination with linear and nonlinear analyses to investigate muscular and musculotendinous effects of high intensity eccentric exercise. Twelve accelerometers arranged in a 3 × 4 matrix over the dominant elbow muscles were used to detect MMG activity in 12 healthy participants. Delayed onset muscle soreness was induced by repetitive high intensity eccentric contractions of the wrist extensor muscles. Average rectified values (ARV) as well as percentage of recurrence (%REC) and percentage of determinism (%DET) extracted from recurrence quantification analysis were computed from data obtained during static-dynamic contractions performed before exercise, immediately after exercise, and in presence of muscle soreness. A linear mixed model was used for the statistical analysis. The ARV, %REC, and %DET maps revealed heterogeneous MMG activity over the wrist extensor muscles before, immediately after, and in presence of muscle soreness (P<0.01). The ARVs were higher while the %REC and %DET were lower in presence of muscle soreness compared with before exercise (P<0.05). The study provides new key information on linear and nonlinear analyses of multi-channel MMG recordings of the wrist extensor muscles following eccentric exercise that results in muscle soreness. Recurrence quantification analysis can be suggested as a tool for detection of MMG changes in presence of muscle soreness.

  13. Multistability of memristive Cohen-Grossberg neural networks with non-monotonic piecewise linear activation functions and time-varying delays.

    PubMed

    Nie, Xiaobing; Zheng, Wei Xing; Cao, Jinde

    2015-11-01

    The problem of coexistence and dynamical behaviors of multiple equilibrium points is addressed for a class of memristive Cohen-Grossberg neural networks with non-monotonic piecewise linear activation functions and time-varying delays. By virtue of the fixed point theorem, nonsmooth analysis theory and other analytical tools, some sufficient conditions are established to guarantee that such n-dimensional memristive Cohen-Grossberg neural networks can have 5(n) equilibrium points, among which 3(n) equilibrium points are locally exponentially stable. It is shown that greater storage capacity can be achieved by neural networks with the non-monotonic activation functions introduced herein than the ones with Mexican-hat-type activation function. In addition, unlike most existing multistability results of neural networks with monotonic activation functions, those obtained 3(n) locally stable equilibrium points are located both in saturated regions and unsaturated regions. The theoretical findings are verified by an illustrative example with computer simulations.

  14. Active resonator reset in the non-linear regime of circuit QED to improve multi-round quantum parity checks

    NASA Astrophysics Data System (ADS)

    Bultink, Cornelis Christiaan; Rol, M. A.; Fu, X.; Dikken, B. C. S.; de Sterke, J. C.; Vermeulen, R. F. L.; Schouten, R. N.; Bruno, A.; Bertels, K. L. M.; Dicarlo, L.

    Reliable quantum parity measurements are essential for fault-tolerant quantum computing. In quantum processors based on circuit QED, the fidelity and speed of multi-round quantum parity checks using an ancillary qubit can be compromised by photons remaining in the readout resonator post measurement, leading to ancilla dephasing and gate errors. The challenge of quickly depleting photons is biggest when maximizing the single-shot readout fidelity involves strong pulses turning the resonators non-linear. We experimentally demonstrate the numerical optimization of counter pulses for fast photon depletion in this non-analytic regime. We compare two methods, one using digital feedback and another running open loop. We assess both methods by minimizing the average number of rounds to ancilla measurement error. We acknowledge funding from the EU FP7 project SCALEQIT, FOM, and an ERC Synergy Grant.

  15. LINEAR ACCELERATOR

    DOEpatents

    Colgate, S.A.

    1958-05-27

    An improvement is presented in linear accelerators for charged particles with respect to the stable focusing of the particle beam. The improvement consists of providing a radial electric field transverse to the accelerating electric fields and angularly introducing the beam of particles in the field. The results of the foregoing is to achieve a beam which spirals about the axis of the acceleration path. The combination of the electric fields and angular motion of the particles cooperate to provide a stable and focused particle beam.

  16. Formation of linear aldehydes during surface water preozonization and their removal in water treatment in relation to mutagenic activity and sum parameters.

    PubMed

    Van Hoof, F; Janssens, J; Van Dijck, H

    1985-12-01

    Low molecular weight aldehydes were formed during surface water preozonization, their levels showing a positive correlation with increasing ozone dose applied and with increasing water temperature. A strong negative correlation was observed between aldehyde levels and U.V. absorbance at 254 nm. Coagulation had no influence on the aldehydes present and the influence of rapid double layer filtration varied strongly with temperature: significant removals were only observed above 10 degrees C. Mutagenic activity generated by preozonization in Salmonella typhimurium TA98 shows an ozone dose depending relationship different from the formation of linear aldehydes. Its removal by coagulation is not effective but rapid double layer filtration reduces mutagenic activity to marginal levels. In this respect too no clear parallel can be drawn between the presence of low molecular weight aldehydes and mutagenic activity.

  17. Population pharmacokinetic modelling of non-linear brain distribution of morphine: influence of active saturable influx and P-glycoprotein mediated efflux

    PubMed Central

    Groenendaal, D; Freijer, J; de Mik, D; Bouw, M R; Danhof, M; de Lange, E C M

    2007-01-01

    Background and purpose: Biophase equilibration must be considered to gain insight into the mechanisms underlying the pharmacokinetic-pharmacodynamic (PK-PD) correlations of opioids. The objective was to characterise in a quantitative manner the non-linear distribution kinetics of morphine in brain. Experimental approach: Male rats received a 10-min infusion of 4 mg kg−1 of morphine, combined with a continuous infusion of the P-glycoprotein (Pgp) inhibitor GF120918 or vehicle, or 40 mg kg−1 morphine alone. Unbound extracellular fluid (ECF) concentrations obtained by intracerebral microdialysis and total blood concentrations were analysed using a population modelling approach. Key results: Blood pharmacokinetics of morphine was best described with a three-compartment model and was not influenced by GF120918. Non-linear distribution kinetics in brain ECF was observed with increasing dose. A one compartment distribution model was developed, with separate expressions for passive diffusion, active saturable influx and active efflux by Pgp. The passive diffusion rate constant was 0.0014 min−1. The active efflux rate constant decreased from 0.0195 min−1 to 0.0113 min−1 in the presence of GF120918. The active influx was insensitive to GF120918 and had a maximum transport (Nmax/Vecf) of 0.66 ng min−1 ml−1 and was saturated at low concentrations of morphine (C50=9.9 ng ml−1). Conclusions and implications: Brain distribution of morphine is determined by three factors: limited passive diffusion; active efflux, reduced by 42% by Pgp inhibition; low capacity active uptake. This implies blood concentration-dependency and sensitivity to drug-drug interactions. These factors should be taken into account in further investigations on PK-PD correlations of morphine. PMID:17471182

  18. The linear structure of β-glucan from baker's yeast and its activation of macrophage-like RAW264.7 cells.

    PubMed

    Zheng, Xing; Zou, Siwei; Xu, Hui; Liu, Qingye; Song, Jianhui; Xu, Min; Xu, Xiaojuan; Zhang, Lina

    2016-09-01

    Yeast β-glucan has many formulations with different chemical structures, water solubility and purity. In particular, the purity of β-glucan in these formulations is variable and relatively low, contributing to different data on its biological activity. In this study, the major polysaccharide component in the crude Baker's yeast polysaccharides coded as BBG with high purity of 99% was obtained, and its chemical structure was determined to be a linear β-(1,3)-glucan. It was found that BBG interacted with complement receptor 3 (CR3) and toll-like receptor 2 (TLR2) on the surface of macrophage-like RAW264.7 cells, and initiated activation of RAW264.7 cells characterized by significant production of tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP-1). Additionally, activation of the nuclear factor kappaB p65 (NF-κB p65), c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) induced by BBG, were also observed, further confirming the stimulation of RAW264.7 cells by BBG. All these findings provided important scientific evidences for better understanding the molecular mechanism of action for the linear β-(1,3)-glucan in cells. PMID:27185116

  19. Linear Clouds

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03667 Linear Clouds

    These clouds are located near the edge of the south polar region. The cloud tops are the puffy white features in the bottom half of the image.

    Image information: VIS instrument. Latitude -80.1N, Longitude 52.1E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. Extension of the stability of motions in a combustion chamber by non- linear active control based on hysteresis

    SciTech Connect

    Knoop, P.; Culick, F.E.C.; Zukoski, E.E.

    1996-07-01

    This report presents the first quantitative data establishing the details of hysteresis whose existence in dynamical behavior was reported by Sterling and Zukoski. The new idea was demonstrated that the presence of dynamical hysteresis provides opportunity for a novel strategy of active nonlinear control of unsteady motions in combustors. A figure shows the hysteresis exhibited for the amplitude of pressure oscillations as a function of equivalence ratio in a combustor having a recirculation zone, in this case a dump combustor.

  1. Synchronization, non-linear dynamics and low-frequency fluctuations: Analogy between spontaneous brain activity and networked single-transistor chaotic oscillators

    SciTech Connect

    Minati, Ludovico E-mail: ludovico.minati@unitn.it

    2015-03-15

    In this paper, the topographical relationship between functional connectivity (intended as inter-regional synchronization), spectral and non-linear dynamical properties across cortical areas of the healthy human brain is considered. Based upon functional MRI acquisitions of spontaneous activity during wakeful idleness, node degree maps are determined by thresholding the temporal correlation coefficient among all voxel pairs. In addition, for individual voxel time-series, the relative amplitude of low-frequency fluctuations and the correlation dimension (D{sub 2}), determined with respect to Fourier amplitude and value distribution matched surrogate data, are measured. Across cortical areas, high node degree is associated with a shift towards lower frequency activity and, compared to surrogate data, clearer saturation to a lower correlation dimension, suggesting presence of non-linear structure. An attempt to recapitulate this relationship in a network of single-transistor oscillators is made, based on a diffusive ring (n = 90) with added long-distance links defining four extended hub regions. Similarly to the brain data, it is found that oscillators in the hub regions generate signals with larger low-frequency cycle amplitude fluctuations and clearer saturation to a lower correlation dimension compared to surrogates. The effect emerges more markedly close to criticality. The homology observed between the two systems despite profound differences in scale, coupling mechanism and dynamics appears noteworthy. These experimental results motivate further investigation into the heterogeneity of cortical non-linear dynamics in relation to connectivity and underline the ability for small networks of single-transistor oscillators to recreate collective phenomena arising in much more complex biological systems, potentially representing a future platform for modelling disease-related changes.

  2. Synchronization, non-linear dynamics and low-frequency fluctuations: analogy between spontaneous brain activity and networked single-transistor chaotic oscillators.

    PubMed

    Minati, Ludovico; Chiesa, Pietro; Tabarelli, Davide; D'Incerti, Ludovico; Jovicich, Jorge

    2015-03-01

    In this paper, the topographical relationship between functional connectivity (intended as inter-regional synchronization), spectral and non-linear dynamical properties across cortical areas of the healthy human brain is considered. Based upon functional MRI acquisitions of spontaneous activity during wakeful idleness, node degree maps are determined by thresholding the temporal correlation coefficient among all voxel pairs. In addition, for individual voxel time-series, the relative amplitude of low-frequency fluctuations and the correlation dimension (D2), determined with respect to Fourier amplitude and value distribution matched surrogate data, are measured. Across cortical areas, high node degree is associated with a shift towards lower frequency activity and, compared to surrogate data, clearer saturation to a lower correlation dimension, suggesting presence of non-linear structure. An attempt to recapitulate this relationship in a network of single-transistor oscillators is made, based on a diffusive ring (n = 90) with added long-distance links defining four extended hub regions. Similarly to the brain data, it is found that oscillators in the hub regions generate signals with larger low-frequency cycle amplitude fluctuations and clearer saturation to a lower correlation dimension compared to surrogates. The effect emerges more markedly close to criticality. The homology observed between the two systems despite profound differences in scale, coupling mechanism and dynamics appears noteworthy. These experimental results motivate further investigation into the heterogeneity of cortical non-linear dynamics in relation to connectivity and underline the ability for small networks of single-transistor oscillators to recreate collective phenomena arising in much more complex biological systems, potentially representing a future platform for modelling disease-related changes.

  3. Reasoning with Linear Orders: Differential Parietal Cortex Activation in Sub-Clinical Depression. An fMRI Investigation in Sub-Clinical Depression and Controls

    PubMed Central

    Hinton, Elanor C.; Wise, Richard G.; Singh, Krish D.; von Hecker, Ulrich

    2015-01-01

    The capacity to learn new information and manipulate it for efficient retrieval has long been studied through reasoning paradigms, which also has applicability to the study of social behavior. Humans can learn about the linear order within groups using reasoning, and the success of such reasoning may vary according to affective state, such as depression. We investigated the neural basis of these latter findings using functional neuroimaging. Using BDI-II criteria, 14 non-depressed (ND) and 12 mildly depressed volunteers took part in a linear-order reasoning task during functional magnetic resonance imaging. The hippocampus, parietal, and prefrontal cortices were activated during the task, in accordance with previous studies. In the learning phase and in the test phase, greater activation of the parietal cortex was found in the depressed group, which may be a compensatory mechanism in order to reach the same behavioral performance as the ND group, or evidence for a different reasoning strategy in the depressed group. PMID:25646078

  4. Perisomatic voltage-gated sodium channels actively maintain linear synaptic integration in principal neurons of the medial superior olive

    PubMed Central

    Scott, Luisa L.; Mathews, Paul J.; Golding, Nace L.

    2010-01-01

    Principal neurons of the medial superior olive (MSO) compute azimuthal sound location by integrating phase-locked inputs from each ear. While previous experimental and modeling studies have proposed that voltage-gated sodium channels (VGSCs) play an important role in synaptic integration in the MSO, these studies appear at odds with the unusually weak active backpropagation of action potentials into the soma and dendrites. To understand the spatial localization and biophysical properties of VGSCs, we isolated sodium currents in MSO principal neurons in gerbil brainstem slices. Nucleated and cell-attached patches revealed that VGSC density at the soma is comparable to that of many other neuron types, but channel expression is largely absent from the dendrites. Further, while somatic VGSCs activated with conventional voltage dependence (V1/2 = −30 mV), they exhibited an unusually negative range of steady-state inactivation (V1/2 = − 77 mV), leaving ~92% of VGSCs inactivated at the resting potential (~ −58 mV). In current-clamp experiments, non-inactivated VGSCs were sufficient to amplify subthreshold EPSPs near action potential threshold, counterbalancing the suppression of EPSP peaks by low voltage-activated potassium channels. EPSP amplification was restricted to the perisomatic region of the neuron, and relatively insensitive to preceding inhibition. Finally, computational modeling showed that the exclusion of VGSCs from the dendrites equalizes somatic EPSP amplification across synaptic locations and lowered the threshold for bilateral vs. unilateral excitatory synaptic inputs. Taken together, these findings suggest that the pattern of sodium channel expression in MSO neurons contributes to these neurons’ selectivity for coincident binaural inputs. PMID:20147532

  5. Linear association between social anxiety symptoms and neural activations to angry faces: from subclinical to clinical levels.

    PubMed

    Carré, Arnaud; Gierski, Fabien; Lemogne, Cédric; Tran, Eric; Raucher-Chéné, Delphine; Béra-Potelle, Céline; Portefaix, Christophe; Kaladjian, Arthur; Pierot, Laurent; Besche-Richard, Chrystel; Limosin, Frédéric

    2014-06-01

    Social anxiety disorder (SAD), which is characterized by the fear of being rejected and negatively evaluated, involves altered brain activation during the processing of negative emotions in a social context. Although associated temperament traits, such as shyness or behavioral inhibition, have been studied, there is still insufficient knowledge to support the dimensional approach, which assumes a continuum from subclinical to clinical levels of social anxiety symptoms. This study used functional magnetic resonance imaging (fMRI) to examine the neural bases of individual differences in social anxiety. Our sample included participants with both healthy/subclinical as well as clinical levels of social anxiety. Forty-six participants with a wide range of social anxiety levels performed a gender decision task with emotional facial expressions during fMRI scanning. Activation in the left anterior insula and right lateral prefrontal cortex in response to angry faces was positively correlated with the level of social anxiety in a regression analysis. The results substantiate, with a dimensional approach, those obtained in previous studies that involved SAD patients or healthy and subclinical participants. It may help to refine further therapeutic strategies based on markers of social anxiety.

  6. Removal of toxic zinc from water/wastewater using eucalyptus seeds activated carbon: non-linear regression analysis.

    PubMed

    Senthil Kumar, Ponnusamy; Saravanan, Anbalagan; Anish Kumar, Kodyingil; Yashwanth, Ramesh; Visvesh, Sridharan

    2016-08-01

    In the present study, a novel activated carbon was prepared from low-cost eucalyptus seeds, which was utilised for the effectively removal of toxic zinc from the water/wastewater. The prepared adsorbent was studied by Fourier transform infrared spectroscopy and scanning electron microscopic characterisation studies. Adsorption process was experimentally performed for optimising the influencing factors such as adsorbent dosage, solution pH, contact time, initial zinc concentration, and temperature for the maximum removal of zinc from aqueous solution. Adsorption isotherm of zinc removal was ensued Freundlich model, and the kinetic model ensued pseudo-second order model. Langmuir monolayer adsorption capacity of the adsorbent for zinc removal was evaluated as 80.37 mg/g. The results of the thermodynamic studies suggested that the adsorption process was exothermic, thermodynamically feasible and impulsive process. Finally, a batch adsorber was planned to remove zinc from known volume and known concentration of wastewater using best obeyed model such as Freundlich. The experimental details showed the newly prepared material can be effectively utilised as a cheap material for the adsorption of toxic metal ions from the contaminated water. PMID:27463796

  7. Approximation of the first passage time density of a Wiener process to an exponentially decaying boundary by two-piecewise linear threshold. Application to neuronal spiking activity.

    PubMed

    Tamborrino, Massimiliano

    2016-06-01

    The first passage time density of a diffusion process to a time varying threshold is of primary interest in different fields. Here, we consider a Brownian motion in presence of an exponentially decaying threshold to model the neuronal spiking activity. Since analytical expressions of the first passage time density are not available, we propose to approximate the curved boundary by means of a continuous two-piecewise linear threshold. Explicit expressions for the first passage time density towards the new boundary are provided. First, we introduce different approximating linear thresholds. Then, we describe how to choose the optimal one minimizing the distance to the curved boundary, and hence the error in the corresponding passage time density. Theoretical means, variances and coefficients of variation given by our method are compared with empirical quantities from simulated data. Moreover, a further comparison with firing statistics derived under the assumption of a small amplitude of the time-dependent change in the threshold, is also carried out. Finally, maximum likelihood and moment estimators of the parameters of the model are derived and applied on simulated data. PMID:27106189

  8. Approximation of the first passage time density of a Wiener process to an exponentially decaying boundary by two-piecewise linear threshold. Application to neuronal spiking activity.

    PubMed

    Tamborrino, Massimiliano

    2016-06-01

    The first passage time density of a diffusion process to a time varying threshold is of primary interest in different fields. Here, we consider a Brownian motion in presence of an exponentially decaying threshold to model the neuronal spiking activity. Since analytical expressions of the first passage time density are not available, we propose to approximate the curved boundary by means of a continuous two-piecewise linear threshold. Explicit expressions for the first passage time density towards the new boundary are provided. First, we introduce different approximating linear thresholds. Then, we describe how to choose the optimal one minimizing the distance to the curved boundary, and hence the error in the corresponding passage time density. Theoretical means, variances and coefficients of variation given by our method are compared with empirical quantities from simulated data. Moreover, a further comparison with firing statistics derived under the assumption of a small amplitude of the time-dependent change in the threshold, is also carried out. Finally, maximum likelihood and moment estimators of the parameters of the model are derived and applied on simulated data.

  9. [The Analysis for Probable Reasons of Cd4+ T-Cell Activation Non-Linear Dependence on Extra Cellular Calcium Ion Concentration in Human Peripheral Blood in vitro].

    PubMed

    Litvinov, I S

    2015-01-01

    The analysis for probable reasons of CD4+ T-cell activation non-linear dependence on [Ca2+]o in HPB in vitro is the general aim of current work. At the beginning we pursued the analysis of receptor-dependent (the mixture of monoclonal antibodies (mAbs) to CD3 and CD28 molecules) and receptor-independent (phorbol-myristate-acetate and ionomycin mixture) means to activate T cells in vitro with different [Ca2+]o in HPB. The key role of intracellular T-cell signaling systems in activated T cells in their non-similar sensitivity to calcium ions in the blood was shown. The analysis of differentiation next stages of CD4+ T-cell activation in vitro relatively [Ca2+]o in PHB demonstrates the key role of the earliest induction stages in non-similar sensitivity to calcium ions in CD4+ T-cell activation in vitro. According to the pursued analysis; the non-similar sensitivity of CD4+ T-cell in vitro to activation is in no-way connected with pace differences on the primary stages of activation process. The comparison of CD4+ memory T cells with their naive T-cell precursors in the cell activation process in hypocalcemia conditions was made in the separate experimental series. The 1st maximum consists in average of 85% CD4+CD45R0high CD69+ memory T cells. Naive CD4+CD45RAlowCD69+ T cells constitute the remainder 15%. The 2nd maximum almost completely consists of CD4+CD45R0+CD69+ memory T cells. The ratio between CD4+CD69+ T cell maximums depends on donor ages and represents linear dependence with R = -0.981. The most probable candidate on the role of CD4+ T cell, being capable of activation in hypocalcemia conditions, are memory T lymphocytes, being resistant to ionomycin action (I R) subset. To check this assumption the mononuclear cells and their IR-fraction were prepared from donor PB. Then the mononuclear cells and their IR-fraction were activated by mAbs mixture at different [EGTA] values. For IR-fraction, enriched with CD4+CD45RA-CD45R0+ memory T cells, slightly seen 1st

  10. Differentiation of regioisomeric aromatic ketocarboxylic acids by positive mode atmospheric pressure chemical ionization collision-activated dissociation tandem mass spectrometry in a linear quadrupole ion trap mass spectrometer.

    PubMed

    Amundson, Lucas M; Owen, Benjamin C; Gallardo, Vanessa A; Habicht, Steven C; Fu, Mingkun; Shea, Ryan C; Mossman, Allen B; Kenttämaa, Hilkka I

    2011-04-01

    Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS(n)) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer. Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some of the reactions were examined by H/D exchange reactions and molecular orbital calculations.

  11. Distant activity of Comet C/2002 VQ94 (LINEAR): Optical spectrophotometric monitoring between 8.4 and 16.8 au from the Sun

    NASA Astrophysics Data System (ADS)

    Korsun, Pavlo P.; Rousselot, Philippe; Kulyk, Irina V.; Afanasiev, Viktor L.; Ivanova, Oleksandra V.

    2014-04-01

    Spectrophotometric monitoring of distant Comet C/2002 VQ94 (LINEAR) was performed with the 6-m telescope of SAO RAS (Special Astrophysical Observatory of Russian Academy of Sciences) and with the 2.5-m Nordic Optical Telescope (Observatory del Roque de los Muchachos, Canarias, Spain) between 2008 and 2013. During this period the comet was on the outbound segment of its orbit, between heliocentric distances of 8.36 au and 16.84 au. Analysis of the spectra revealed the presence of the CO+ and N2+ emissions in the cometary coma at a distance of 8.36 au from the Sun. This distance is larger than ionic emissions have been detected in any previous objects. Only continuum, with no traces of emissions, was detected in the spectrum obtained in 2009 when the comet was at a distance of 9.86 au. From the spectra obtained in 2008, average column densities of 2.04 × 109 mol cm-2 for N2+ and 3.26 × 1010 mol cm-2 for CO+ were measured in the cometary coma. The derived values correspond to N2+/CO=0.06 within the projected slit. Images obtained through a red continuum filter in 2008 showed a bright, dust coma, indicating a high level of physical activity. A considerably lower level of activity was observed in 2009 and 2011 at distances of 9.86 au and 13.40 au respectively. No noticeable activity was detected in 2013 at a heliocentric distance of 16.84 au. The Afρ parameter, which is used as an indicator of cometary activity, was measured as 2000 cm in 2008, and 800 cm in 2009 and 2011. The Afρ values correspond to dust production rates between 10-20 kg s-1, 4-6 kg s-1 and 3-5 kg s-1 at 8.36, 9.86, and 13.40 au respectively. There is an obvious correlation between the decrease of the dust production rate of the nucleus and the disappearance of the emissions in the spectrum of C/2002 VQ94 (LINEAR) at heliocentric distances greater than 9 au. The colors and size of the nucleus of C/2002 VQ94 (LINEAR) were estimated from the images obtained during the late stage at a heliocentric

  12. Conjugation of 10 kDa Linear PEG onto Trastuzumab Fab' Is Sufficient to Significantly Enhance Lymphatic Exposure while Preserving in Vitro Biological Activity.

    PubMed

    Chan, Linda J; Ascher, David B; Yadav, Rajbharan; Bulitta, Jürgen B; Williams, Charlotte C; Porter, Christopher J H; Landersdorfer, Cornelia B; Kaminskas, Lisa M

    2016-04-01

    The lymphatic system is a major conduit by which many diseases spread and proliferate. There is therefore increasing interest in promoting better lymphatic drug targeting. Further, antibody fragments such as Fabs have several advantages over full length monoclonal antibodies but are subject to rapid plasma clearance, which can limit the lymphatic exposure and activity of Fabs against lymph-resident diseases. This study therefore explored ideal PEGylation strategies to maximize biological activity and lymphatic exposure using trastuzumab Fab' as a model. Specifically, the Fab' was conjugated with single linear 10 or 40 kDa PEG chains at the hinge region. PEGylation led to a 3-4-fold reduction in binding affinity to HER2, but antiproliferative activity against HER2-expressing BT474 cells was preserved. Lymphatic pharmacokinetics were then examined in thoracic lymph duct cannulated rats after intravenous and subcutaneous dosing at 2 mg/kg, and the data were evaluated via population pharmacokinetic modeling. The Fab' displayed limited lymphatic exposure, but conjugation of 10 kDa PEG improved exposure by approximately 11- and 5-fold after intravenous (15% dose collected in thoracic lymph over 30 h) and subcutaneous (9%) administration, respectively. Increasing the molecular weight of the PEG to 40 kDa, however, had no significant impact on lymphatic exposure after intravenous (14%) administration and only doubled lymphatic exposure after subcutaneous administration (18%) when compared to 10 kDa PEG-Fab'. The data therefore suggests that minimal PEGylation has the potential to enhance the exposure and activity of Fab's against lymph-resident diseases, while no significant benefit is achieved with very large PEGs.

  13. Novel chlorambucil-conjugated anionic linear-globular PEG-based second-generation dendrimer: in vitro/in vivo improved anticancer activity

    PubMed Central

    Assadi, Artin; Najafabadi, Vahideh Sharifi; Shandiz, Seyed Ataollah Sadat; Boroujeni, Azadah Shayeq; Ashrafi, Sepehr; Vaziri, Ali Zaman; Ghoreishi, Seyedeh Masoumeh; Aghasadeghi, Mohammad Reza; Ebrahimi, Seyed Esmaeil Sadat; Pirali-Hamedani, Morteza; Ardestani, Mehdi Shafiee

    2016-01-01

    Evaluating the efficacy of anticancer drugs is an evolving and research-oriented issue. The objective of this study was to reduce the insolubility of chlorambucil (CBL) in water and improve the anticancer activity of CBL in vitro and in vivo through the conjugation of CBL with anionic linear-globular dendrimer (second generation, G2). In the current study, the anticancer activity among three groups that include CBL, CBL–G2 dendrimer, and control was measured in vitro and in vivo. In vitro studies showed that G2 anionic linear-globular polyethylene-glycol-based dendrimer, which conjugated to the CBL exterior through an ester linkage, was able to significantly improve the treatment efficacy over clinical CBL alone with respect to proliferation assay, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide; half maximal inhibitory concentration (IC50) was calculated to be 141 µg/mL for CBL alone and 27.7 µg/mL for CBL–G2 dendrimer; P<0.05. In addition, CBL–G2 dendrimer conjugate forestalled the growth of MCF-7 cancerous cells in addition to enhancing the number of apoptotic and necrotic cells as demonstrated by an annexin V-fluorescein isothiocyanate assay. CBL–G2 dendrimer conjugate was able to checkmate antiapoptotic Bcl-2 expression and Bcl-2/Bax ratio in a large scale compared with the control group and CBL alone (P<0.005). In vivo studies showed that tumor treatment by CBL–G2 dendrimer conjugate outstrips the efficacy of treatment compared with CBL alone. The evaluation was based on reduction in tumor volume and tumor growth inhibition of murine 4T1 mammary tumor cells. Tumor volume of 140%±8% was measured in the treatment with CBL–G2 dendrimer, whereas 152%±13.5% was calculated in the treatment with free CBL (P<0.05). However, there were no significant differences in histological assay among the three groups. In conclusion, tumor growth suppression potential of CBL–G2 dendrimer, which was assessed in both in vitro and in vivo

  14. Novel chlorambucil-conjugated anionic linear-globular PEG-based second-generation dendrimer: in vitro/in vivo improved anticancer activity

    PubMed Central

    Assadi, Artin; Najafabadi, Vahideh Sharifi; Shandiz, Seyed Ataollah Sadat; Boroujeni, Azadah Shayeq; Ashrafi, Sepehr; Vaziri, Ali Zaman; Ghoreishi, Seyedeh Masoumeh; Aghasadeghi, Mohammad Reza; Ebrahimi, Seyed Esmaeil Sadat; Pirali-Hamedani, Morteza; Ardestani, Mehdi Shafiee

    2016-01-01

    Evaluating the efficacy of anticancer drugs is an evolving and research-oriented issue. The objective of this study was to reduce the insolubility of chlorambucil (CBL) in water and improve the anticancer activity of CBL in vitro and in vivo through the conjugation of CBL with anionic linear-globular dendrimer (second generation, G2). In the current study, the anticancer activity among three groups that include CBL, CBL–G2 dendrimer, and control was measured in vitro and in vivo. In vitro studies showed that G2 anionic linear-globular polyethylene-glycol-based dendrimer, which conjugated to the CBL exterior through an ester linkage, was able to significantly improve the treatment efficacy over clinical CBL alone with respect to proliferation assay, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide; half maximal inhibitory concentration (IC50) was calculated to be 141 µg/mL for CBL alone and 27.7 µg/mL for CBL–G2 dendrimer; P<0.05. In addition, CBL–G2 dendrimer conjugate forestalled the growth of MCF-7 cancerous cells in addition to enhancing the number of apoptotic and necrotic cells as demonstrated by an annexin V-fluorescein isothiocyanate assay. CBL–G2 dendrimer conjugate was able to checkmate antiapoptotic Bcl-2 expression and Bcl-2/Bax ratio in a large scale compared with the control group and CBL alone (P<0.005). In vivo studies showed that tumor treatment by CBL–G2 dendrimer conjugate outstrips the efficacy of treatment compared with CBL alone. The evaluation was based on reduction in tumor volume and tumor growth inhibition of murine 4T1 mammary tumor cells. Tumor volume of 140%±8% was measured in the treatment with CBL–G2 dendrimer, whereas 152%±13.5% was calculated in the treatment with free CBL (P<0.05). However, there were no significant differences in histological assay among the three groups. In conclusion, tumor growth suppression potential of CBL–G2 dendrimer, which was assessed in both in vitro and in vivo

  15. Novel chlorambucil-conjugated anionic linear-globular PEG-based second-generation dendrimer: in vitro/in vivo improved anticancer activity.

    PubMed

    Assadi, Artin; Najafabadi, Vahideh Sharifi; Shandiz, Seyed Ataollah Sadat; Boroujeni, Azadah Shayeq; Ashrafi, Sepehr; Vaziri, Ali Zaman; Ghoreishi, Seyedeh Masoumeh; Aghasadeghi, Mohammad Reza; Ebrahimi, Seyed Esmaeil Sadat; Pirali-Hamedani, Morteza; Ardestani, Mehdi Shafiee

    2016-01-01

    Evaluating the efficacy of anticancer drugs is an evolving and research-oriented issue. The objective of this study was to reduce the insolubility of chlorambucil (CBL) in water and improve the anticancer activity of CBL in vitro and in vivo through the conjugation of CBL with anionic linear-globular dendrimer (second generation, G2). In the current study, the anticancer activity among three groups that include CBL, CBL-G2 dendrimer, and control was measured in vitro and in vivo. In vitro studies showed that G2 anionic linear-globular polyethylene-glycol-based dendrimer, which conjugated to the CBL exterior through an ester linkage, was able to significantly improve the treatment efficacy over clinical CBL alone with respect to proliferation assay, 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide; half maximal inhibitory concentration (IC50) was calculated to be 141 µg/mL for CBL alone and 27.7 µg/mL for CBL-G2 dendrimer; P<0.05. In addition, CBL-G2 dendrimer conjugate forestalled the growth of MCF-7 cancerous cells in addition to enhancing the number of apoptotic and necrotic cells as demonstrated by an annexin V-fluorescein isothiocyanate assay. CBL-G2 dendrimer conjugate was able to checkmate antiapoptotic Bcl-2 expression and Bcl-2/Bax ratio in a large scale compared with the control group and CBL alone (P<0.005). In vivo studies showed that tumor treatment by CBL-G2 dendrimer conjugate outstrips the efficacy of treatment compared with CBL alone. The evaluation was based on reduction in tumor volume and tumor growth inhibition of murine 4T1 mammary tumor cells. Tumor volume of 140%±8% was measured in the treatment with CBL-G2 dendrimer, whereas 152%±13.5% was calculated in the treatment with free CBL (P<0.05). However, there were no significant differences in histological assay among the three groups. In conclusion, tumor growth suppression potential of CBL-G2 dendrimer, which was assessed in both in vitro and in vivo experiments

  16. Impact of UV radiation on activity of linear furanocoumarins and Bacillus thuringiensis var. kurstaki against Spodoptera exigua: Implications for tritrophic interactions

    SciTech Connect

    Trumble, J.T.; Moar, W.J.; Brewer, M.J.; Carson, W.G. )

    1991-05-01

    Acidic fogs with a pH of 2.0 and duration of 2 hr did not reduce the efficacy of Bacillus thuringiensis var. kurstaki. Therefore, the impact of UV radiation was investigated on the interactions between (1) levels of the antibacterial linear furanocoumarins psoralen, bergapten, and xanthotoxin in Apium graveolens (L.) occurring following a 2.0 pH acidic fog episode, (2) the noctuid Spodoptera exigua, and (3) a sublethal dosage of the microbial pathogen B. thuringiensis var. kurstaki. Mean time to pupation in the absence of UV radiation was significantly extended by the addition of either psoralens or B. thuringiensis. Larvae developing on diets containing B. thuringiensis plus psoralens required nearly 40% longer to pupate than controls, but their effects were additive as the interaction was not significant. Mean time to mortality, a weighted average time of death, was not significantly affected by any of the treatments. In a 2 {times} 2 {times} 2 factorial analysis, all main effects reduced survival significantly, as did the three-way interaction. Thus, antagonistic interactions with psoralens that would reduce the effectiveness of B. thuringiensis in the field were not observed. When pairs of main effects were nested within the two levels of the third factor, several two-way interactions were found. Interestingly, the activity of B. thuringiensis and the psoralens, individually or in combination, was enhanced by exposure to UV radiation. Implications of this research are discussed for both natural and agricultural ecosystems.

  17. Enhancement of Ion Activation and Collision-Induced Dissociation by Simultaneous Dipolar Excitation of Ions in x- and y-Directions in a Linear Ion Trap.

    PubMed

    Dang, Qiankun; Xu, Fuxing; Xie, Xiaodong; Xu, Chongsheng; Dai, Xinhua; Fang, Xiang; Ding, Li; Ding, Chuan-Fan

    2015-06-01

    Collision-induced dissociation (CID) in linear ion traps is usually performed by applying a dipolar alternating current (AC) signal to one pair of electrodes, which results in ion excitation mainly in one direction. In this paper, we report simulation and experimental studies of the ion excitation in two coordinate directions by applying identical dipolar AC signals to two pairs of electrodes simultaneously. Theoretical analysis and simulation results demonstrate that the ion kinetic energy is higher than that using the conventional CID method. Experimental results show that more activation energy (as determined by the intensity ratio of the a4/b4 fragments from the CID of protonated leucine enkephalin) can be deposited into parent ions in this method. The dissociation rate constant in this method was about 3.8 times higher than that in the conventional method under the same experimental condition, at the Mathieu parameter qu (where u = x, y) value of 0.25. The ion fragmentation efficiency is also significantly improved. Compared with the conventional method, the smaller qu value can be used in this method to obtain the same internal energy deposited into ions. Consequently, the "low mass cut-off" is redeemed and more fragment ions can be detected. This excitation method can be implemented easily without changing any experimental parameters.

  18. Compressible or incompressible blend of interacting monodisperse linear polymers near a surface.

    PubMed

    Batman, Richard; Gujrati, P D

    2007-08-28

    We consider a lattice model of a mixture of repulsive, attractive, or neutral monodisperse linear polymers of two species, A and B, with a third monomeric species C, which may be taken to represent free volume. The mixture is confined between two hard, parallel plates of variable separation whose interactions with A and C may be attractive, repulsive, or neutral, and may be different from each other. The interactions with A and C are all that are required to completely specify the effect of each surface on all three components. We numerically study various density profiles as we move away from the surface, by using the recursive method of Gujrati and Chhajer [J. Chem. Phys. 106, 5599 (1997)] that has already been previously applied to study polydisperse solutions and blends next to surfaces. The resulting density profiles show the oscillations that are seen in Monte Carlo simulations and the enrichment of the smaller species at a neutral surface. The method is computationally ultrafast and can be carried out on a personal computer (PC), even in the incompressible case, when Monte Carlo simulations are not feasible. The calculations of density profiles usually take less than 20 min on a PC.

  19. Application of least squares support vector regression and linear multiple regression for modeling removal of methyl orange onto tin oxide nanoparticles loaded on activated carbon and activated carbon prepared from Pistacia atlantica wood.

    PubMed

    Ghaedi, M; Rahimi, Mahmoud Reza; Ghaedi, A M; Tyagi, Inderjeet; Agarwal, Shilpi; Gupta, Vinod Kumar

    2016-01-01

    Two novel and eco friendly adsorbents namely tin oxide nanoparticles loaded on activated carbon (SnO2-NP-AC) and activated carbon prepared from wood tree Pistacia atlantica (AC-PAW) were used for the rapid removal and fast adsorption of methyl orange (MO) from the aqueous phase. The dependency of MO removal with various adsorption influential parameters was well modeled and optimized using multiple linear regressions (MLR) and least squares support vector regression (LSSVR). The optimal parameters for the LSSVR model were found based on γ value of 0.76 and σ(2) of 0.15. For testing the data set, the mean square error (MSE) values of 0.0010 and the coefficient of determination (R(2)) values of 0.976 were obtained for LSSVR model, and the MSE value of 0.0037 and the R(2) value of 0.897 were obtained for the MLR model. The adsorption equilibrium and kinetic data was found to be well fitted and in good agreement with Langmuir isotherm model and second-order equation and intra-particle diffusion models respectively. The small amount of the proposed SnO2-NP-AC and AC-PAW (0.015 g and 0.08 g) is applicable for successful rapid removal of methyl orange (>95%). The maximum adsorption capacity for SnO2-NP-AC and AC-PAW was 250 mg g(-1) and 125 mg g(-1) respectively. PMID:26414425

  20. Electrothermal linear actuator

    NASA Technical Reports Server (NTRS)

    Derr, L. J.; Tobias, R. A.

    1969-01-01

    Converting electric power into powerful linear thrust without generation of magnetic fields is accomplished with an electrothermal linear actuator. When treated by an energized filament, a stack of bimetallic washers expands and drives the end of the shaft upward.

  1. A linear programming manual

    NASA Technical Reports Server (NTRS)

    Tuey, R. C.

    1972-01-01

    Computer solutions of linear programming problems are outlined. Information covers vector spaces, convex sets, and matrix algebra elements for solving simultaneous linear equations. Dual problems, reduced cost analysis, ranges, and error analysis are illustrated.

  2. Understanding Linear Functions and Their Representations

    ERIC Educational Resources Information Center

    Wells, Pamela J.

    2015-01-01

    Linear functions are an important part of the middle school mathematics curriculum. Students in the middle grades gain fluency by working with linear functions in a variety of representations (NCTM 2001). Presented in this article is an activity that was used with five eighth-grade classes at three different schools. The activity contains 15 cards…

  3. Linear-Algebra Programs

    NASA Technical Reports Server (NTRS)

    Lawson, C. L.; Krogh, F. T.; Gold, S. S.; Kincaid, D. R.; Sullivan, J.; Williams, E.; Hanson, R. J.; Haskell, K.; Dongarra, J.; Moler, C. B.

    1982-01-01

    The Basic Linear Algebra Subprograms (BLAS) library is a collection of 38 FORTRAN-callable routines for performing basic operations of numerical linear algebra. BLAS library is portable and efficient source of basic operations for designers of programs involving linear algebriac computations. BLAS library is supplied in portable FORTRAN and Assembler code versions for IBM 370, UNIVAC 1100 and CDC 6000 series computers.

  4. Azide addition to Sc2@C66: favorable activity on unsaturated linear triquinanes and dramatic reactivity difference compared with the free C66 cage.

    PubMed

    Li, Qiao-Zhi; Zheng, Jia-Jia; Zhao, Xiang

    2015-08-28

    Density functional theory calculations on methyl azide additions to C66 and Sc2@C2v(4059)-C66 suggest that the best addition sites type E[5,6]-56 bond e2 and the new type D[5,6]-55 bond d for C66 and type G[5,5]-66 bond g for Sc2@C66 are located on the unsaturated linear triquinane moieties. PMID:26198755

  5. Linear collider: a preview

    SciTech Connect

    Wiedemann, H.

    1981-11-01

    Since no linear colliders have been built yet it is difficult to know at what energy the linear cost scaling of linear colliders drops below the quadratic scaling of storage rings. There is, however, no doubt that a linear collider facility for a center of mass energy above say 500 GeV is significantly cheaper than an equivalent storage ring. In order to make the linear collider principle feasible at very high energies a number of problems have to be solved. There are two kinds of problems: one which is related to the feasibility of the principle and the other kind of problems is associated with minimizing the cost of constructing and operating such a facility. This lecture series describes the problems and possible solutions. Since the real test of a principle requires the construction of a prototype I will in the last chapter describe the SLC project at the Stanford Linear Accelerator Center.

  6. Linear mass actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III (Inventor); Crossley, Edward A., Jr. (Inventor); Jones, Irby W. (Inventor); Miller, James B. (Inventor); Davis, C. Calvin (Inventor); Behun, Vaughn D. (Inventor); Goodrich, Lewis R., Sr. (Inventor)

    1992-01-01

    A linear mass actuator includes an upper housing and a lower housing connectable to each other and having a central passageway passing axially through a mass that is linearly movable in the central passageway. Rollers mounted in the upper and lower housings in frictional engagement with the mass translate the mass linearly in the central passageway and drive motors operatively coupled to the roller means, for rotating the rollers and driving the mass axially in the central passageway.

  7. Linear phase compressive filter

    DOEpatents

    McEwan, Thomas E.

    1995-01-01

    A phase linear filter for soliton suppression is in the form of a laddered series of stages of non-commensurate low pass filters with each low pass filter having a series coupled inductance (L) and a reverse biased, voltage dependent varactor diode, to ground which acts as a variable capacitance (C). L and C values are set to levels which correspond to a linear or conventional phase linear filter. Inductance is mapped directly from that of an equivalent nonlinear transmission line and capacitance is mapped from the linear case using a large signal equivalent of a nonlinear transmission line.

  8. Linear phase compressive filter

    DOEpatents

    McEwan, T.E.

    1995-06-06

    A phase linear filter for soliton suppression is in the form of a laddered series of stages of non-commensurate low pass filters with each low pass filter having a series coupled inductance (L) and a reverse biased, voltage dependent varactor diode, to ground which acts as a variable capacitance (C). L and C values are set to levels which correspond to a linear or conventional phase linear filter. Inductance is mapped directly from that of an equivalent nonlinear transmission line and capacitance is mapped from the linear case using a large signal equivalent of a nonlinear transmission line. 2 figs.

  9. Fault tolerant linear actuator

    DOEpatents

    Tesar, Delbert

    2004-09-14

    In varying embodiments, the fault tolerant linear actuator of the present invention is a new and improved linear actuator with fault tolerance and positional control that may incorporate velocity summing, force summing, or a combination of the two. In one embodiment, the invention offers a velocity summing arrangement with a differential gear between two prime movers driving a cage, which then drives a linear spindle screw transmission. Other embodiments feature two prime movers driving separate linear spindle screw transmissions, one internal and one external, in a totally concentric and compact integrated module.

  10. Linearly polarized fiber amplifier

    SciTech Connect

    Kliner, Dahv A.; Koplow, Jeffery P.

    2004-11-30

    Optically pumped rare-earth-doped polarizing fibers exhibit significantly higher gain for one linear polarization state than for the orthogonal state. Such a fiber can be used to construct a single-polarization fiber laser, amplifier, or amplified-spontaneous-emission (ASE) source without the need for additional optical components to obtain stable, linearly polarized operation.

  11. SLAC Linear Collider

    SciTech Connect

    Richter, B.

    1985-12-01

    A report is given on the goals and progress of the SLAC Linear Collider. The status of the machine and the detectors are discussed and an overview is given of the physics which can be done at this new facility. Some ideas on how (and why) large linear colliders of the future should be built are given.

  12. Examining Non-Linear Associations between Accelerometer-Measured Physical Activity, Sedentary Behavior, and All-Cause Mortality Using Segmented Cox Regression.

    PubMed

    Lee, Paul H

    2016-01-01

    Healthy adults are advised to perform at least 150 min of moderate-intensity physical activity weekly, but this advice is based on studies using self-reports of questionable validity. This study examined the dose-response relationship of accelerometer-measured physical activity and sedentary behaviors on all-cause mortality using segmented Cox regression to empirically determine the break-points of the dose-response relationship. Data from 7006 adult participants aged 18 or above in the National Health and Nutrition Examination Survey waves 2003-2004 and 2005-2006 were included in the analysis and linked with death certificate data using a probabilistic matching approach in the National Death Index through December 31, 2011. Physical activity and sedentary behavior were measured using ActiGraph model 7164 accelerometer over the right hip for 7 consecutive days. Each minute with accelerometer count <100; 1952-5724; and ≥5725 were classified as sedentary, moderate-intensity physical activity, and vigorous-intensity physical activity, respectively. Segmented Cox regression was used to estimate the hazard ratio (HR) of time spent in sedentary behaviors, moderate-intensity physical activity, and vigorous-intensity physical activity and all-cause mortality, adjusted for demographic characteristics, health behaviors, and health conditions. Data were analyzed in 2016. During 47,119 person-year of follow-up, 608 deaths occurred. Each additional hour per day of sedentary behaviors was associated with a HR of 1.15 (95% CI 1.01, 1.31) among participants who spend at least 10.9 h per day on sedentary behaviors, and each additional minute per day spent on moderate-intensity physical activity was associated with a HR of 0.94 (95% CI 0.91, 0.96) among participants with daily moderate-intensity physical activity ≤14.1 min. Associations of moderate physical activity and sedentary behaviors on all-cause mortality were independent of each other. To conclude, evidence from this

  13. Linear force device

    NASA Technical Reports Server (NTRS)

    Clancy, John P.

    1988-01-01

    The object of the invention is to provide a mechanical force actuator which is lightweight and manipulatable and utilizes linear motion for push or pull forces while maintaining a constant overall length. The mechanical force producing mechanism comprises a linear actuator mechanism and a linear motion shaft mounted parallel to one another. The linear motion shaft is connected to a stationary or fixed housing and to a movable housing where the movable housing is mechanically actuated through actuator mechanism by either manual means or motor means. The housings are adapted to releasably receive a variety of jaw or pulling elements adapted for clamping or prying action. The stationary housing is adapted to be pivotally mounted to permit an angular position of the housing to allow the tool to adapt to skewed interfaces. The actuator mechanisms is operated by a gear train to obtain linear motion of the actuator mechanism.

  14. Linear models: permutation methods

    USGS Publications Warehouse

    Cade, B.S.; Everitt, B.S.; Howell, D.C.

    2005-01-01

    Permutation tests (see Permutation Based Inference) for the linear model have applications in behavioral studies when traditional parametric assumptions about the error term in a linear model are not tenable. Improved validity of Type I error rates can be achieved with properly constructed permutation tests. Perhaps more importantly, increased statistical power, improved robustness to effects of outliers, and detection of alternative distributional differences can be achieved by coupling permutation inference with alternative linear model estimators. For example, it is well-known that estimates of the mean in linear model are extremely sensitive to even a single outlying value of the dependent variable compared to estimates of the median [7, 19]. Traditionally, linear modeling focused on estimating changes in the center of distributions (means or medians). However, quantile regression allows distributional changes to be estimated in all or any selected part of a distribution or responses, providing a more complete statistical picture that has relevance to many biological questions [6]...

  15. Permafrost Hazards and Linear Infrastructure

    NASA Astrophysics Data System (ADS)

    Stanilovskaya, Julia; Sergeev, Dmitry

    2014-05-01

    The international experience of linear infrastructure planning, construction and exploitation in permafrost zone is being directly tied to the permafrost hazard assessment. That procedure should also consider the factors of climate impact and infrastructure protection. The current global climate change hotspots are currently polar and mountain areas. Temperature rise, precipitation and land ice conditions change, early springs occur more often. The big linear infrastructure objects cross the territories with different permafrost conditions which are sensitive to the changes in air temperature, hydrology, and snow accumulation which are connected to climatic dynamics. One of the most extensive linear structures built on permafrost worldwide are Trans Alaskan Pipeline (USA), Alaska Highway (Canada), Qinghai-Xizang Railway (China) and Eastern Siberia - Pacific Ocean Oil Pipeline (Russia). Those are currently being influenced by the regional climate change and permafrost impact which may act differently from place to place. Thermokarst is deemed to be the most dangerous process for linear engineering structures. Its formation and development depend on the linear structure type: road or pipeline, elevated or buried one. Zonal climate and geocryological conditions are also of the determining importance here. All the projects are of the different age and some of them were implemented under different climatic conditions. The effects of permafrost thawing have been recorded every year since then. The exploration and transportation companies from different countries maintain the linear infrastructure from permafrost degradation in different ways. The highways in Alaska are in a good condition due to governmental expenses on annual reconstructions. The Chara-China Railroad in Russia is under non-standard condition due to intensive permafrost response. Standards for engineering and construction should be reviewed and updated to account for permafrost hazards caused by the

  16. The glycosylphosphatidylinositol-PLC in Trypanosoma brucei forms a linear array on the exterior of the flagellar membrane before and after activation.

    PubMed

    Hanrahan, Orla; Webb, Helena; O'Byrne, Robert; Brabazon, Elaine; Treumann, Achim; Sunter, Jack D; Carrington, Mark; Voorheis, H Paul

    2009-06-01

    Bloodstream forms of Trypanosoma brucei contain a glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) that cleaves the GPI-anchor of the variable surface glycoprotein (VSG). Its location in trypanosomes has been controversial. Here, using confocal microscopy and surface labelling techniques, we show that the GPI-PLC is located exclusively in a linear array on the outside of the flagellar membrane, close to the flagellar attachment zone, but does not co-localize with the flagellar attachment zone protein, FAZ1. Consequently, the GPI-PLC and the VSG occupy the same plasma membrane leaflet, which resolves the topological problem associated with the cleavage reaction if the VSG and the GPI-PLC were on opposite sides of the membrane. The exterior location requires the enzyme to be tightly regulated to prevent VSG release under basal conditions. During stimulated VSG release in intact cells, the GPI-PLC did not change location, suggesting that the release mechanism involves lateral diffusion of the VSG in the plane of the membrane to the fixed position of the GPI-PLC.

  17. The Glycosylphosphatidylinositol-PLC in Trypanosoma brucei Forms a Linear Array on the Exterior of the Flagellar Membrane Before and After Activation

    PubMed Central

    Hanrahan, Orla; Webb, Helena; O'Byrne, Robert; Brabazon, Elaine; Treumann, Achim; Sunter, Jack D.; Carrington, Mark; Voorheis, H. Paul

    2009-01-01

    Bloodstream forms of Trypanosoma brucei contain a glycosylphosphatidylinositol-specific phospholipase C (GPI-PLC) that cleaves the GPI-anchor of the variable surface glycoprotein (VSG). Its location in trypanosomes has been controversial. Here, using confocal microscopy and surface labelling techniques, we show that the GPI-PLC is located exclusively in a linear array on the outside of the flagellar membrane, close to the flagellar attachment zone, but does not co-localize with the flagellar attachment zone protein, FAZ1. Consequently, the GPI-PLC and the VSG occupy the same plasma membrane leaflet, which resolves the topological problem associated with the cleavage reaction if the VSG and the GPI-PLC were on opposite sides of the membrane. The exterior location requires the enzyme to be tightly regulated to prevent VSG release under basal conditions. During stimulated VSG release in intact cells, the GPI-PLC did not change location, suggesting that the release mechanism involves lateral diffusion of the VSG in the plane of the membrane to the fixed position of the GPI-PLC. PMID:19503825

  18. Linear magnetic bearing

    NASA Technical Reports Server (NTRS)

    Studer, P. A. (Inventor)

    1983-01-01

    A linear magnetic bearing system having electromagnetic vernier flux paths in shunt relation with permanent magnets, so that the vernier flux does not traverse the permanent magnet, is described. Novelty is believed to reside in providing a linear magnetic bearing having electromagnetic flux paths that bypass high reluctance permanent magnets. Particular novelty is believed to reside in providing a linear magnetic bearing with a pair of axially spaced elements having electromagnets for establishing vernier x and y axis control. The magnetic bearing system has possible use in connection with a long life reciprocating cryogenic refrigerator that may be used on the space shuttle.

  19. Enhanced Polysaccharide Binding and Activity on Linear β-Glucans through Addition of Carbohydrate-Binding Modules to Either Terminus of a Glucooligosaccharide Oxidase

    PubMed Central

    Foumani, Maryam; Vuong, Thu V.; MacCormick, Benjamin; Master, Emma R.

    2015-01-01

    The gluco-oligosaccharide oxidase from Sarocladium strictum CBS 346.70 (GOOX) is a single domain flavoenzyme that favourably oxidizes gluco- and xylo- oligosaccharides. In the present study, GOOX was shown to also oxidize plant polysaccharides, including cellulose, glucomannan, β-(1→3,1→4)-glucan, and xyloglucan, albeit to a lesser extent than oligomeric substrates. To improve GOOX activity on polymeric substrates, three carbohydrate binding modules (CBMs) from Clostridium thermocellum, namely CtCBM3 (type A), CtCBM11 (type B), and CtCBM44 (type B), were separately appended to the amino and carboxy termini of the enzyme, generating six fusion proteins. With the exception of GOOX-CtCBM3 and GOOX-CtCBM44, fusion of the selected CBMs increased the catalytic activity of the enzyme (kcat) on cellotetraose by up to 50%. All CBM fusions selectively enhanced GOOX binding to soluble and insoluble polysaccharides, and the immobilized enzyme on a solid cellulose surface remained stable and active. In addition, the CBM fusions increased the activity of GOOX on soluble glucomannan by up to 30 % and on insoluble crystalline as well as amorphous cellulose by over 50 %. PMID:25932926

  20. A small linear peptide encompassing the NGF N-terminus partly mimics the biological activities of the entire neurotrophin in PC12 cells.

    PubMed

    Travaglia, Alessio; Pietropaolo, Adriana; Di Martino, Rossana; Nicoletti, Vincenzo G; La Mendola, Diego; Calissano, Pietro; Rizzarelli, Enrico

    2015-08-19

    Ever since the discovery of its neurite growth promoting activity in sympathetic and sensory ganglia, nerve growth factor (NGF) became the prototype of the large family of neurotrophins. The use of primary cultures and clonal cell lines has revealed several distinct actions of NGF and other neurotrophins. Among several models of NGF activity, the clonal cell line PC12 is the most widely employed. Thus, in the presence of NGF, through the activation of the transmembrane protein TrkA, these cells undergo a progressive mitotic arrest and start to grow electrically excitable neuritis. A vast number of studies opened intriguing aspects of NGF mechanisms of action, its biological properties, and potential use as therapeutic agents. In this context, identifying and utilizing small portions of NGF is of great interest and involves several human diseases including Alzheimer's disease. Here we report the specific action of the peptide encompassing the 1-14 sequence of the human NGF (NGF(1-14)), identified on the basis of scattered indications present in literature. The biological activity of NGF(1-14) was tested on PC12 cells, and its binding with TrkA was predicted by means of a computational approach. NGF(1-14) does not elicit the neurite outgrowth promoting activity, typical of the whole protein, and it only has a moderate action on PC12 proliferation. However, this peptide exerts, in a dose and time dependent fashion, an effective and specific NGF-like action on some highly conserved and biologically crucial intermediates of its intracellular targets such as Akt and CREB. These findings indicate that not all TrkA pathways must be at all times operative, and open the possibility of testing each of them in relation with specific NGF needs, biological actions, and potential therapeutic use.

  1. Linear Accelerator (LINAC)

    MedlinePlus

    ... is the device most commonly used for external beam radiation treatments for patients with cancer. The linear ... shape of the patient's tumor and the customized beam is directed to the patient's tumor. The beam ...

  2. Isolated linear blaschkoid psoriasis.

    PubMed

    Nasimi, M; Abedini, R; Azizpour, A; Nikoo, A

    2016-10-01

    Linear psoriasis (LPs) is considered a rare clinical presentation of psoriasis, which is characterized by linear erythematous and scaly lesions along the lines of Blaschko. We report the case of a 20-year-old man who presented with asymptomatic linear and S-shaped erythematous, scaly plaques on right side of his trunk. The plaques were arranged along the lines of Blaschko with a sharp demarcation at the midline. Histological examination of a skin biopsy confirmed the diagnosis of psoriasis. Topical calcipotriol and betamethasone dipropionate ointments were prescribed for 2 months. A good clinical improvement was achieved, with reduction in lesion thickness and scaling. In patients with linear erythematous and scaly plaques along the lines of Blaschko, the diagnosis of LPs should be kept in mind, especially in patients with asymptomatic lesions of late onset. PMID:27663156

  3. Inertial Linear Actuators

    NASA Technical Reports Server (NTRS)

    Laughlin, Darren

    1995-01-01

    Inertial linear actuators developed to suppress residual accelerations of nominally stationary or steadily moving platforms. Function like long-stroke version of voice coil in conventional loudspeaker, with superimposed linear variable-differential transformer. Basic concept also applicable to suppression of vibrations of terrestrial platforms. For example, laboratory table equipped with such actuators plus suitable vibration sensors and control circuits made to vibrate much less in presence of seismic, vehicular, and other environmental vibrational disturbances.

  4. Linear Alopecia Areata.

    PubMed

    Shetty, Shricharith; Rao, Raghavendra; Kudva, R Ranjini; Subramanian, Kumudhini

    2016-01-01

    Alopecia areata (AA) over scalp is known to present in various shapes and extents of hair loss. Typically it presents as circumscribed patches of alopecia with underlying skin remaining normal. We describe a rare variant of AA presenting in linear band-like form. Only four cases of linear alopecia have been reported in medical literature till today, all four being diagnosed as lupus erythematosus profundus. PMID:27625568

  5. Linear Alopecia Areata

    PubMed Central

    Shetty, Shricharith; Rao, Raghavendra; Kudva, R Ranjini; Subramanian, Kumudhini

    2016-01-01

    Alopecia areata (AA) over scalp is known to present in various shapes and extents of hair loss. Typically it presents as circumscribed patches of alopecia with underlying skin remaining normal. We describe a rare variant of AA presenting in linear band-like form. Only four cases of linear alopecia have been reported in medical literature till today, all four being diagnosed as lupus erythematosus profundus.

  6. Linear Alopecia Areata

    PubMed Central

    Shetty, Shricharith; Rao, Raghavendra; Kudva, R Ranjini; Subramanian, Kumudhini

    2016-01-01

    Alopecia areata (AA) over scalp is known to present in various shapes and extents of hair loss. Typically it presents as circumscribed patches of alopecia with underlying skin remaining normal. We describe a rare variant of AA presenting in linear band-like form. Only four cases of linear alopecia have been reported in medical literature till today, all four being diagnosed as lupus erythematosus profundus. PMID:27625568

  7. Curcumin Regulates Low-Linear Energy Transfer {gamma}-Radiation-Induced NF{kappa}B-Dependent Telomerase Activity in Human Neuroblastoma Cells

    SciTech Connect

    Aravindan, Natarajan; Veeraraghavan, Jamunarani; Madhusoodhanan, Rakhesh; Herman, Terence S.; Natarajan, Mohan

    2011-03-15

    Purpose: We recently reported that curcumin attenuates ionizing radiation (IR)-induced survival signaling and proliferation in human neuroblastoma cells. Also, in the endothelial system, we have demonstrated that NF{kappa}B regulates IR-induced telomerase activity (TA). Accordingly, we investigated the effect of curcumin in inhibiting IR-induced NF{kappa}B-dependent hTERT transcription, TA, and cell survival in neuroblastoma cells. Methods and Materials: SK-N-MC or SH-SY5Y cells exposed to IR and treated with curcumin (10-100 nM) with or without IR were harvested after 1 h through 24 h. NF{kappa}B-dependent regulation was investigated either by luciferase reporter assays using pNF{kappa}B-, pGL3-354-, pGL3-347-, or pUSE-I{kappa}B{alpha}-Luc, p50/p65, or RelA siRNA-transfected cells. NF{kappa}B activity was analyzed using an electrophoretic mobility shift assay and hTERT expression using the quantitative polymerase chain reaction. TA was determined using the telomerase repeat amplification protocol assay and cell survival using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium bromide and clonogenic assay. Results: Curcumin profoundly inhibited IR-induced NF{kappa}B. Consequently, curcumin significantly inhibited IR-induced TA and hTERT mRNA at all points investigated. Furthermore, IR-induced TA is regulated at the transcriptional level by triggering telomerase reverse transcriptase (TERT) promoter activation. Moreover, NF{kappa}B becomes functionally activated after IR and mediates TA upregulation by binding to the {kappa}B-binding region in the promoter region of the TERT gene. Consistently, elimination of the NF{kappa}B-recognition site on the telomerase promoter or inhibition of NF{kappa}B by the I{kappa}B{alpha} mutant compromises IR-induced telomerase promoter activation. Significantly, curcumin inhibited IR-induced TERT transcription. Consequently, curcumin inhibited hTERT mRNA and TA in NF{kappa}B overexpressed cells. Furthermore, curcumin enhanced

  8. Hydromagnetic natural convection flow between vertical parallel plates with time-periodic boundary conditions

    NASA Astrophysics Data System (ADS)

    Adesanya, S. O.; Oluwadare, E. O.; Falade, J. A.; Makinde, O. D.

    2015-12-01

    In this paper, the free convective flow of magnetohydrodynamic fluid through a channel with time periodic boundary condition is investigated by taking the effects of Joule dissipation into consideration. Based on simplifying assumptions, the coupled governing equations are reduced to a set of nonlinear boundary valued problem. Approximate solutions are obtained by using semi-analytical Adomian decomposition method. The effect of pertinent parameters on the fluid velocity, temperature distribution, Nusselt number and skin friction are presented graphically and discussed. The result of the computation shows that an increase in the magnetic field intensity has significant influence on the fluid flow.

  9. A new look at natural convection from isothermal vertical parallel plates

    SciTech Connect

    Li, H.H.; Chung, B.T.F.

    1996-12-31

    Natural convection between isothermal plates is solved numerically by applying the full Navier-Stokes equations. The elliptic formulation allows separating the effect of the Rayleigh number, Ra, and the aspect ratio, L/B. Calculations are made on a wide range of the Rayleigh number and the aspect ratio, and the Nusselt number is provided as a function of both Ra and B/L. The conventional correlations in the literature presenting the Nusselt number in terms of a single parameter, RaB/L, have been found inaccurate. At a small value of RaB/L, multiple values of Nusselt number are obtained for different combinations of Ra and B/L. Previous results are found to be the special cases of the present study. A minimum Rayleigh number is also obtained above which a fully-developed flow is possible. To simulate the natural convective flow, the ambient pressure is given at the exit while the pressure at the entrance is related to the ambient pressure by the Bernoulli equation. Velocities at the entrance and exit are also solved from the Navier-Stokes equations.

  10. Analysis of the Mutual Inductance between Two Parallel Plates for the Detection of Surface Flaws

    NASA Technical Reports Server (NTRS)

    Namking, M.; Clendenin, C. G.; Fulton, J. P.; Wincheski, B.

    1992-01-01

    There has recently been much effort behind the development of NDE methods applicable to the detection of surface/subsurface flaws in thin metallic structures with a rapid scan capability. One such method, an electromagnetic technique using a current-sheet parallel to the surface of a specimen in order to induce eddy current flow shows a high potential for satisfying the rapid scan requirement stated above. The technique is based on the detection of flaw-induced magnetic field components normal to the specimen surface by an appropriate detection mechanism positioned above the current-sheet as shown schematically in Fig. 1. As indicated in this figure, the current-sheet separates the source of the normal magnetic field components from the detector in such a way that the electric and magnetic properties of the current-sheet can be a major factor affecting the strength of the detected signals. The purpose of the present study is, therefore, to perform a detailed investigation on the effect of the material properties of the current-sheet on the detected signal strength and to establish a simple theoretical model for the detection mechanism.

  11. CHICO2, a two-dimensional pixelated parallel-plate avalanche counter

    DOE PAGESBeta

    Wu, C. Y.; Cline, D.; Hayes, A.; Flight, R. S.; Melchionna, A. M.; Zhou, C.; Lee, I. Y.; Swan, D.; Fox, R.; Anderson, J. T.

    2016-01-27

    CHICO2 (Compact Heavy Ion COunter), is a large solid-angle, charged-particle detector array developed to provide both θ and Φ angle resolutions matching those of GRETINA (Gamma-Ray Energy Tracking In-beam Nuclear Array). CHICO2 was successfully tested at the Argonne National Laboratory where it was fielded as an auxiliary detector with GRETINA for γ-ray spectroscopic studies of nuclei using a 252Cf spontaneous fission source, stable beams, and radioactive beams from CARIBU. In field tests of the 72,76Ge beams on a 0.5 mg/cm2208Pb target at the sub-barrier energy, CHICO2 provided charged-particle angle resolutions (FWHM) of 1.55° in θ and 2.47° in Φ. Thismore » achieves the design goal for both coordinates assuming a beam-spot size (>3 mm) and the target thickness (>0.5 mg/cm 2). The combined angular resolution of GRETINA/CHICO2 resulted in a Doppler-shift corrected energy resolution of 0.60% for 1 MeV coincident de-excitation γ-rays. This is nearly a factor of two improvements in resolution and sensitivity compared to Gammasphere/CHICO. Kinematically-coincident detection of scattered ions by CHICO2 still maintains the mass resolution (ΔM/M) of ~5% that enhanced isolation of scattered weak beams of interest from scattered contaminant beams.« less

  12. Discharge and photo-luminance properties of a parallel plates electron emission lighting device.

    PubMed

    Li, Chia-Hung; Liu, Ming-Chung; Chiang, Chang-Lin; Li, Jung-Yu; Chen, Shih-Pu; Hsieh, Tai-Chiung; Chou, Yen-I; Lin, Yi-Ping; Wang, Po-Hung; Chun, Ming-Shin; Zeng, Hui-Kai; Juang, Jenh-Yih

    2011-01-01

    The gas discharge and photo-luminance properties of a planar lighting source featuring highly uniform light emission and mercury-free design were studied. The current density-voltage characteristics and the associated gas discharge of the devices operating with the values of the ratio of electric field to gas pressure (E/p) between 4.3 kV/Torr-cm and 35.7 kV/Torr-cm indicate that the width of the cathode fall extends over the entire gap between the two electrodes and the device is mostly in the obstructed discharge regime. The optical emission analysis confirmed the electron collision-induced gas emissions and strong effect of gas pressure on the phosphor emission when operated at constant current density, both are indicative of the primary roles played by the electron energy. PMID:21263712

  13. Analytical theory of coherent synchrotron radiation wakefield of short bunches shielded by conducting parallel plates

    NASA Astrophysics Data System (ADS)

    Stupakov, Gennady; Zhou, Demin

    2016-04-01

    We develop a general model of coherent synchrotron radiation (CSR) impedance with shielding provided by two parallel conducting plates. This model allows us to easily reproduce all previously known analytical CSR wakes and to expand the analysis to situations not explored before. It reduces calculations of the impedance to taking integrals along the trajectory of the beam. New analytical results are derived for the radiation impedance with shielding for the following orbits: a kink, a bending magnet, a wiggler of finite length, and an infinitely long wiggler. All our formulas are benchmarked against numerical simulations with the CSRZ computer code.

  14. Radiative heat conductances between dielectric and metallic parallel plates with nanoscale gaps

    NASA Astrophysics Data System (ADS)

    Song, Bai; Thompson, Dakotah; Fiorino, Anthony; Ganjeh, Yashar; Reddy, Pramod; Meyhofer, Edgar

    2016-06-01

    Recent experiments have demonstrated that radiative heat transfer between objects separated by nanometre-scale gaps considerably exceeds the predictions of far-field radiation theories. Exploiting this near-field enhancement is of great interest for emerging technologies such as near-field thermophotovoltaics and nano-lithography because of the expected increases in efficiency, power conversion or resolution in these applications. Past measurements, however, were performed using tip-plate or sphere-plate configurations and failed to realize the orders of magnitude increases in radiative heat currents predicted from near-field radiative heat transfer theory. Here, we report 100- to 1,000-fold enhancements (at room temperature) in the radiative conductance between parallel-planar surfaces at gap sizes below 100 nm, in agreement with the predictions of near-field theories. Our measurements were performed in vacuum gaps between prototypical materials (SiO2–SiO2, Au–Au, SiO2–Au and Au–Si) using two microdevices and a custom-built nanopositioning platform, which allows precise control over a broad range of gap sizes (from <100 nm to 10 μm). Our experimental set-up will enable systematic studies of a variety of near-field-based thermal phenomena, with important implications for thermophotovoltaic applications, that have been predicted but have defied experimental verification.

  15. Radiative heat conductances between dielectric and metallic parallel plates with nanoscale gaps

    NASA Astrophysics Data System (ADS)

    Song, Bai; Thompson, Dakotah; Fiorino, Anthony; Ganjeh, Yashar; Reddy, Pramod; Meyhofer, Edgar

    2016-06-01

    Recent experiments have demonstrated that radiative heat transfer between objects separated by nanometre-scale gaps considerably exceeds the predictions of far-field radiation theories. Exploiting this near-field enhancement is of great interest for emerging technologies such as near-field thermophotovoltaics and nano-lithography because of the expected increases in efficiency, power conversion or resolution in these applications. Past measurements, however, were performed using tip-plate or sphere-plate configurations and failed to realize the orders of magnitude increases in radiative heat currents predicted from near-field radiative heat transfer theory. Here, we report 100- to 1,000-fold enhancements (at room temperature) in the radiative conductance between parallel-planar surfaces at gap sizes below 100 nm, in agreement with the predictions of near-field theories. Our measurements were performed in vacuum gaps between prototypical materials (SiO2-SiO2, Au-Au, SiO2-Au and Au-Si) using two microdevices and a custom-built nanopositioning platform, which allows precise control over a broad range of gap sizes (from <100 nm to 10 μm). Our experimental set-up will enable systematic studies of a variety of near-field-based thermal phenomena, with important implications for thermophotovoltaic applications, that have been predicted but have defied experimental verification.

  16. CHICO2, a two-dimensional pixelated parallel-plate avalanche counter

    NASA Astrophysics Data System (ADS)

    Wu, C. Y.; Cline, D.; Hayes, A.; Flight, R. S.; Melchionna, A. M.; Zhou, C.; Lee, I. Y.; Swan, D.; Fox, R.; Anderson, J. T.

    2016-04-01

    CHICO2 (Compact Heavy Ion COunter), is a large solid-angle, charged-particle detector array developed to provide both θ and ϕ angle resolutions matching those of GRETINA (Gamma-Ray Energy Tracking In-beam Nuclear Array). CHICO2 was successfully tested at the Argonne National Laboratory where it was fielded as an auxiliary detector with GRETINA for γ-ray spectroscopic studies of nuclei using a 252Cf spontaneous fission source, stable beams, and radioactive beams from CARIBU. In field tests of the 72,76Ge beams on a 0.5 mg/cm2208Pb target at the sub-barrier energy, CHICO2 provided charged-particle angle resolutions (FWHM) of 1.55° in θ and 2.47° in ϕ. This achieves the design goal for both coordinates assuming a beam-spot size (>3 mm) and the target thickness (>0.5 mg/cm2). The combined angular resolution of GRETINA/CHICO2 resulted in a Doppler-shift corrected energy resolution of 0.60% for 1 MeV coincident de-excitation γ-rays. This is nearly a factor of two improvements in resolution and sensitivity compared to Gammasphere/CHICO. Kinematically-coincident detection of scattered ions by CHICO2 still maintains the mass resolution (ΔM/M) of ~5% that enhanced isolation of scattered weak beams of interest from scattered contaminant beams.

  17. Temperature-stable parallel-plate dielectric cell for broadband liquid impedance measurements

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Chandra, Satyan; Mellor, Brett L.; Arellano, Jesus

    2010-12-01

    A liquid impedance cell for broadband impedance measurements up to 110 MHz is presented. The design incorporates temperature control and minimizes parasitic capacitance and inductance. The cell is simple to fabricate and uses chemically resistant materials, stainless steel, and Teflon. This dielectric cell can be used in a variety of liquid measurements, particularly those related to impedance measurements of biological objects in solution. Temperature control is illustrated in measurements of the permittivity of deionized water from 5 to 55 °C. Numerical fitting procedures employed on the relaxation curves indicate good agreement with previous studies on beta-lactoglobulin and hen lysozyme. Titration capability is demonstrated through dielectric titration of hen lysozyme and beta-lactoglobulin.

  18. An instrument to control parallel plate separation for nanoscale flow control

    NASA Astrophysics Data System (ADS)

    White, J.; Ma, H.; Lang, J.; Slocum, A.

    2003-11-01

    The handling of extremely small samples of gases and liquids has long been a subject of research among biologists, chemists, and engineers. A few scientific instruments, notably the surface force apparatus, have been used extensively to investigate very short-range molecular phenomena. This article describes the design, fabrication, and characterization of an easily manufactured, gas and liquid flow control device called the Nanogate. The Nanogate controls liquid flows under very high planar confinement, wherein the liquid film is, in one dimension, on the scale of nanometers, but is on the scale of hundreds of microns in its other dimensions. The liquid film is confined between a silica (Pyrex) surface with a typical roughness of Ra≈6 nm and a gold-covered silicon surface with a typical roughness of Ra≈2 nm. During the manufacturing process, the Pyrex flows and conforms to the gold-covered silicon surface, improving the mating properties of the two surfaces. The fluid film thickness can be controlled within 2 Å, from sub-10 nm up to 1 μm. Control of helium gas flow rates in the 10-9 atm cm3/s range, and sub-nl/s flow rates of water and methanol have been predicted and experimentally verified.

  19. Differential adhesion, activity, and carbohydrate: Protein ratios ofPseudomonas atlantica monocultures attaching to stainless steel in a linear shear gradient.

    PubMed

    Mittelman, M W; Nivens, D E; Low, C; White, D C

    1990-05-01

    Biofilm formation on metallic surfaces in marine and freshwater environments often precedes corrosion and other biofouling conditions. Attachment is mediated by such environmental factors as the presence of surface conditioning films, fluid dynamics, bulk-phase nutrient levels, and surface chemistry. In this study, we utilized a Fowler Cell Adhesion Measurement Module to demonstrate that the changes in cellular concentration and composition of a monoculture ofPseudomonas atlantica biofilms on stainless steel were a function of the applied shear force. At shear forces in the range of 3-10 dynes cm(-2) (1.0 liter min(-1)), attachment as measured by acridine orange direct microscopic counts was greatest at the higher shear forces.(14)C-Acetate uptake activity on the stainless steel surfaces increased with shear stress. Acetate incorporation ranged from 1×10(-5) to 19×10(-5) μmol cm(-2) between 0.15 and 30 dynes cm(-2) for 30 min uptake periods. On a per cell basis, however, activity decreased with shear, indicating a shift in metabolism. Fourier transform infrared spectroscopy revealed that protein and carbohydrate concentrations also increased with the applied shear. Increased biofilm C∶N ratios and total fatty acids were associated with the higher shear stresses. Neither radius of interaction nor biofilm age appeared to significantly influence the relationship between fluid shear and attachment and cellular composition ofP. atlantica biofilms in the range of 1-10 dynes cm(-2). PMID:24196364

  20. Superconducting linear actuator

    NASA Technical Reports Server (NTRS)

    Johnson, Bruce; Hockney, Richard

    1993-01-01

    Special actuators are needed to control the orientation of large structures in space-based precision pointing systems. Electromagnetic actuators that presently exist are too large in size and their bandwidth is too low. Hydraulic fluid actuation also presents problems for many space-based applications. Hydraulic oil can escape in space and contaminate the environment around the spacecraft. A research study was performed that selected an electrically-powered linear actuator that can be used to control the orientation of a large pointed structure. This research surveyed available products, analyzed the capabilities of conventional linear actuators, and designed a first-cut candidate superconducting linear actuator. The study first examined theoretical capabilities of electrical actuators and determined their problems with respect to the application and then determined if any presently available actuators or any modifications to available actuator designs would meet the required performance. The best actuator was then selected based on available design, modified design, or new design for this application. The last task was to proceed with a conceptual design. No commercially-available linear actuator or modification capable of meeting the specifications was found. A conventional moving-coil dc linear actuator would meet the specification, but the back-iron for this actuator would weigh approximately 12,000 lbs. A superconducting field coil, however, eliminates the need for back iron, resulting in an actuator weight of approximately 1000 lbs.

  1. Designing linear systolic arrays

    SciTech Connect

    Kumar, V.K.P.; Tsai, Y.C. . Dept. of Electrical Engineering)

    1989-12-01

    The authors develop a simple mapping technique to design linear systolic arrays. The basic idea of the technique is to map the computations of a certain class of two-dimensional systolic arrays onto one-dimensional arrays. Using this technique, systolic algorithms are derived for problems such as matrix multiplication and transitive closure on linearly connected arrays of PEs with constant I/O bandwidth. Compared to known designs in the literature, the technique leads to modular systolic arrays with constant hardware in each PE, few control lines, lexicographic data input/output, and improved delay time. The unidirectional flow of control and data in this design assures implementation of the linear array in the known fault models of wafer scale integration.

  2. Linear encoding device

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    1993-01-01

    A Linear Motion Encoding device for measuring the linear motion of a moving object is disclosed in which a light source is mounted on the moving object and a position sensitive detector such as an array photodetector is mounted on a nearby stationary object. The light source emits a light beam directed towards the array photodetector such that a light spot is created on the array. An analog-to-digital converter, connected to the array photodetector is used for reading the position of the spot on the array photodetector. A microprocessor and memory is connected to the analog-to-digital converter to hold and manipulate data provided by the analog-to-digital converter on the position of the spot and to compute the linear displacement of the moving object based upon the data from the analog-to-digital converter.

  3. Immunoblot analysis of linear polyubiquitination of NEMO.

    PubMed

    Sasaki, Yoshiteru; Fujita, Hiroaki; Nakai, Misa; Iwai, Kazuhiro

    2015-01-01

    Stimulation with inflammatory cytokines such as TNF-α and IL-1 activates the canonical NF-κB pathway through the activation of the IKK complex. The mechanism underlying IKK activation has been extensively studied and the involvement of the ubiquitin system has been well documented. We have recently reported that a novel ubiquitin ligase complex, LUBAC is involved in the activation of the IKK complex. LUBAC consists of one catalytic subunit, HOIP and two accessory molecules, HOIL-1L and SHARPIN and activates the IKK complex by conjugating the linear polyubiquitin chains to NEMO (IKKγ), the regulatory subunit of IKK complex. In this chapter, we describe the protocol for the detection of the linear polyubiquitination of NEMO by the immunoblotting using anti-linear ubiquitin antibody.

  4. Linearly Adjustable International Portfolios

    NASA Astrophysics Data System (ADS)

    Fonseca, R. J.; Kuhn, D.; Rustem, B.

    2010-09-01

    We present an approach to multi-stage international portfolio optimization based on the imposition of a linear structure on the recourse decisions. Multiperiod decision problems are traditionally formulated as stochastic programs. Scenario tree based solutions however can become intractable as the number of stages increases. By restricting the space of decision policies to linear rules, we obtain a conservative tractable approximation to the original problem. Local asset prices and foreign exchange rates are modelled separately, which allows for a direct measure of their impact on the final portfolio value.

  5. Improved Electrohydraulic Linear Actuators

    NASA Technical Reports Server (NTRS)

    Hamtil, James

    2004-01-01

    A product line of improved electrohydraulic linear actuators has been developed. These actuators are designed especially for use in actuating valves in rocket-engine test facilities. They are also adaptable to many industrial uses, such as steam turbines, process control valves, dampers, motion control, etc. The advantageous features of the improved electrohydraulic linear actuators are best described with respect to shortcomings of prior electrohydraulic linear actuators that the improved ones are intended to supplant. The flow of hydraulic fluid to the two ports of the actuator cylinder is controlled by a servo valve that is controlled by a signal from a servo amplifier that, in turn, receives an analog position-command signal (a current having a value between 4 and 20 mA) from a supervisory control system of the facility. As the position command changes, the servo valve shifts, causing a greater flow of hydraulic fluid to one side of the cylinder and thereby causing the actuator piston to move to extend or retract a piston rod from the actuator body. A linear variable differential transformer (LVDT) directly linked to the piston provides a position-feedback signal, which is compared with the position-command signal in the servo amplifier. When the position-feedback and position-command signals match, the servo valve moves to its null position, in which it holds the actuator piston at a steady position.

  6. Tissue non-linearity.

    PubMed

    Duck, F

    2010-01-01

    The propagation of acoustic waves is a fundamentally non-linear process, and only waves with infinitesimally small amplitudes may be described by linear expressions. In practice, all ultrasound propagation is associated with a progressive distortion in the acoustic waveform and the generation of frequency harmonics. At the frequencies and amplitudes used for medical diagnostic scanning, the waveform distortion can result in the formation of acoustic shocks, excess deposition of energy, and acoustic saturation. These effects occur most strongly when ultrasound propagates within liquids with comparatively low acoustic attenuation, such as water, amniotic fluid, or urine. Attenuation by soft tissues limits but does not extinguish these non-linear effects. Harmonics may be used to create tissue harmonic images. These offer improvements over conventional B-mode images in spatial resolution and, more significantly, in the suppression of acoustic clutter and side-lobe artefacts. The quantity B/A has promise as a parameter for tissue characterization, but methods for imaging B/A have shown only limited success. Standard methods for the prediction of tissue in-situ exposure from acoustic measurements in water, whether for regulatory purposes, for safety assessment, or for planning therapeutic regimes, may be in error because of unaccounted non-linear losses. Biological effects mechanisms are altered by finite-amplitude effects. PMID:20349813

  7. Linear motion valve

    NASA Technical Reports Server (NTRS)

    Chandler, J. A. (Inventor)

    1985-01-01

    The linear motion valve is described. The valve spool employs magnetically permeable rings, spaced apart axially, which engage a sealing assembly having magnetically permeable pole pieces in magnetic relationship with a magnet. The gap between the ring and the pole pieces is sealed with a ferrofluid. Depletion of the ferrofluid is minimized.

  8. Resistors Improve Ramp Linearity

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L.

    1982-01-01

    Simple modification to bootstrap ramp generator gives more linear output over longer sweep times. New circuit adds just two resistors, one of which is adjustable. Modification cancels nonlinearities due to variations in load on charging capacitor and due to changes in charging current as the voltage across capacitor increases.

  9. On Solving Linear Recurrences

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2013-01-01

    A direct method is given for solving first-order linear recurrences with constant coefficients. The limiting value of that solution is studied as "n to infinity." This classroom note could serve as enrichment material for the typical introductory course on discrete mathematics that follows a calculus course.

  10. Characterising the interaction of individual-wheel drives with traction by linear parameter-varying model: a method for analysing the role of traction in torsional vibrations in wheel drives and active damping

    NASA Astrophysics Data System (ADS)

    Zhun Yeap, Khang; Müller, Steffen

    2016-02-01

    A model-based approach for characterising the interaction of individual-wheel drives with traction is contributed in this article. The primary aim is to investigate the influence of traction on torsional vibration behaviour in the drive train. The essence of this approach lies in reformulating the nonlinear traction behaviour into its differential form, which enables an analytical description of this interaction in its linear parameter-varying model equivalence. Analytical statements on the vibration behaviour for different driving scenarios are inferred from this model and validated with measurement samples from a high-performance electric road vehicle. Subsequent influences of traction on the performance of active damping of torsional vibrations are derived from this model.

  11. Application of linear multivariate calibration techniques to identify the peaks responsible for the antioxidant activity of Satureja hortensis L. and Oliveria decumbens Vent. essential oils by gas chromatography-mass spectrometry.

    PubMed

    Samadi, Naser; Masoum, Saeed; Mehrara, Bahare; Hosseini, Hossein

    2015-09-15

    Satureja hortensis L. and Oliveria decumbens Vent. are known for their diverse effects in drug therapy and traditional medicine. One of the most interesting properties of their essential oils is good antioxidant activity. In this paper, essential oils of aerial parts of S. hortensis L. and O. decumbens Vent. from different regions were obtained by hydrodistillation and were analyzed by gas chromatography-mass spectrometry (GC-MS). Essential oils were tested for their free radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay to identify the peaks potentially responsible for the antioxidant activity from chromatographic fingerprints by numerous linear multivariate calibration techniques. Because of its simplicity and high repeatability, orthogonal projection to latent structures (OPLS) model had the best performance in indicating the potential antioxidant compounds in S. hortensis L. and O. decumbens Vent. essential oils. In this study, P-cymene, carvacrol and β-bisabolene for S. hortensis L. and P-cymene, Ç-terpinen, thymol, carvacrol, and 1,3-benzodioxole, 4-methoxy-6-(2-propenyl) for O. decumbens Vent. are suggested as the potentially antioxidant compounds. PMID:26262598

  12. Application of linear multivariate calibration techniques to identify the peaks responsible for the antioxidant activity of Satureja hortensis L. and Oliveria decumbens Vent. essential oils by gas chromatography-mass spectrometry.

    PubMed

    Samadi, Naser; Masoum, Saeed; Mehrara, Bahare; Hosseini, Hossein

    2015-09-15

    Satureja hortensis L. and Oliveria decumbens Vent. are known for their diverse effects in drug therapy and traditional medicine. One of the most interesting properties of their essential oils is good antioxidant activity. In this paper, essential oils of aerial parts of S. hortensis L. and O. decumbens Vent. from different regions were obtained by hydrodistillation and were analyzed by gas chromatography-mass spectrometry (GC-MS). Essential oils were tested for their free radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay to identify the peaks potentially responsible for the antioxidant activity from chromatographic fingerprints by numerous linear multivariate calibration techniques. Because of its simplicity and high repeatability, orthogonal projection to latent structures (OPLS) model had the best performance in indicating the potential antioxidant compounds in S. hortensis L. and O. decumbens Vent. essential oils. In this study, P-cymene, carvacrol and β-bisabolene for S. hortensis L. and P-cymene, Ç-terpinen, thymol, carvacrol, and 1,3-benzodioxole, 4-methoxy-6-(2-propenyl) for O. decumbens Vent. are suggested as the potentially antioxidant compounds.

  13. Reciprocating linear motor

    NASA Technical Reports Server (NTRS)

    Goldowsky, Michael P. (Inventor)

    1987-01-01

    A reciprocating linear motor is formed with a pair of ring-shaped permanent magnets having opposite radial polarizations, held axially apart by a nonmagnetic yoke, which serves as an axially displaceable armature assembly. A pair of annularly wound coils having axial lengths which differ from the axial lengths of the permanent magnets are serially coupled together in mutual opposition and positioned with an outer cylindrical core in axial symmetry about the armature assembly. One embodiment includes a second pair of annularly wound coils serially coupled together in mutual opposition and an inner cylindrical core positioned in axial symmetry inside the armature radially opposite to the first pair of coils. Application of a potential difference across a serial connection of the two pairs of coils creates a current flow perpendicular to the magnetic field created by the armature magnets, thereby causing limited linear displacement of the magnets relative to the coils.

  14. General linear chirplet transform

    NASA Astrophysics Data System (ADS)

    Yu, Gang; Zhou, Yiqi

    2016-03-01

    Time-frequency (TF) analysis (TFA) method is an effective tool to characterize the time-varying feature of a signal, which has drawn many attentions in a fairly long period. With the development of TFA, many advanced methods are proposed, which can provide more precise TF results. However, some restrictions are introduced inevitably. In this paper, we introduce a novel TFA method, termed as general linear chirplet transform (GLCT), which can overcome some limitations existed in current TFA methods. In numerical and experimental validations, by comparing with current TFA methods, some advantages of GLCT are demonstrated, which consist of well-characterizing the signal of multi-component with distinct non-linear features, being independent to the mathematical model and initial TFA method, allowing for the reconstruction of the interested component, and being non-sensitivity to noise.

  15. Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling.

    PubMed

    Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L; Emelko, Monica B

    2015-12-11

    Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or "sag effect" was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition.

  16. Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

    PubMed Central

    Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

    2015-01-01

    Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition. PMID:26658159

  17. Non-linear, non-monotonic effect of nano-scale roughness on particle deposition in absence of an energy barrier: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Jin, Chao; Glawdel, Tomasz; Ren, Carolyn L.; Emelko, Monica B.

    2015-12-01

    Deposition of colloidal- and nano-scale particles on surfaces is critical to numerous natural and engineered environmental, health, and industrial applications ranging from drinking water treatment to semi-conductor manufacturing. Nano-scale surface roughness-induced hydrodynamic impacts on particle deposition were evaluated in the absence of an energy barrier to deposition in a parallel plate system. A non-linear, non-monotonic relationship between deposition surface roughness and particle deposition flux was observed and a critical roughness size associated with minimum deposition flux or “sag effect” was identified. This effect was more significant for nanoparticles (<1 μm) than for colloids and was numerically simulated using a Convective-Diffusion model and experimentally validated. Inclusion of flow field and hydrodynamic retardation effects explained particle deposition profiles better than when only the Derjaguin-Landau-Verwey-Overbeek (DLVO) force was considered. This work provides 1) a first comprehensive framework for describing the hydrodynamic impacts of nano-scale surface roughness on particle deposition by unifying hydrodynamic forces (using the most current approaches for describing flow field profiles and hydrodynamic retardation effects) with appropriately modified expressions for DLVO interaction energies, and gravity forces in one model and 2) a foundation for further describing the impacts of more complicated scales of deposition surface roughness on particle deposition.

  18. Electrostatic Linear Actuator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.; Curry, Kenneth C.

    1990-01-01

    Electrically charged helices attract or repel each other. Proposed electrostatic linear actuator made with intertwined dual helices, which holds charge-bearing surfaces. Dual-helix configuration provides relatively large unbroken facing charged surfaces (relatively large electrostatic force) within small volume. Inner helix slides axially in outer helix in response to voltages applied to conductors. Spiral form also makes components more rigid. Actuator conceived to have few moving parts and to be operable after long intervals of inactivity.

  19. Linear induction accelerator

    DOEpatents

    Buttram, M.T.; Ginn, J.W.

    1988-06-21

    A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities. 4 figs.

  20. Relativistic Linear Restoring Force

    ERIC Educational Resources Information Center

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  1. Combustion powered linear actuator

    DOEpatents

    Fischer, Gary J.

    2007-09-04

    The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

  2. Representation of linear orders.

    PubMed

    Taylor, D A; Kim, J O; Sudevan, P

    1984-01-01

    Two binary classification tasks were used to explore the associative structure of linear orders. In Experiment 1, college students classified English letters as targets or nontargets, the targets being consecutive letters of the alphabet. The time to reject nontargets was a decreasing function of the distance from the target set, suggesting response interference mediated by automatic associations from the target to the nontarget letters. The way in which this interference effect depended on the placement of the boundaries between the target and nontarget sets revealed the relative strengths of individual interletter associations. In Experiment 2, students were assigned novel linear orders composed of letterlike symbols and asked to classify pairs of symbols as being adjacent or nonadjacent in the assigned sequence. Reaction time was found to be a joint function of the distance between any pair of symbols and the relative positions of those symbols within the sequence. The effects of both distance and position decreased systematically over 6 days of practice with a particular order, beginning at a level typical of unfamiliar orders and converging on a level characteristic of familiar orders such as letters and digits. These results provide an empirical unification of two previously disparate sets of findings in the literature on linear orders, those concerning familiar and unfamiliar orders, and the systematic transition between the two patterns of results suggests the gradual integration of a new associative structure.

  3. Anti- (conjugate) linearity

    NASA Astrophysics Data System (ADS)

    Uhlmann, Armin

    2016-03-01

    This is an introduction to antilinear operators. In following Wigner the terminus antilinear is used as it is standard in Physics. Mathematicians prefer to say conjugate linear. By restricting to finite-dimensional complex-linear spaces, the exposition becomes elementary in the functional analytic sense. Nevertheless it shows the amazing differences to the linear case. Basics of antilinearity is explained in sects. 2, 3, 4, 7 and in sect. 1.2: Spectrum, canonical Hermitian form, antilinear rank one and two operators, the Hermitian adjoint, classification of antilinear normal operators, (skew) conjugations, involutions, and acq-lines, the antilinear counterparts of 1-parameter operator groups. Applications include the representation of the Lagrangian Grassmannian by conjugations, its covering by acq-lines. As well as results on equivalence relations. After remembering elementary Tomita-Takesaki theory, antilinear maps, associated to a vector of a two-partite quantum system, are defined. By allowing to write modular objects as twisted products of pairs of them, they open some new ways to express EPR and teleportation tasks. The appendix presents a look onto the rich structure of antilinear operator spaces.

  4. Linearized Kernel Dictionary Learning

    NASA Astrophysics Data System (ADS)

    Golts, Alona; Elad, Michael

    2016-06-01

    In this paper we present a new approach of incorporating kernels into dictionary learning. The kernel K-SVD algorithm (KKSVD), which has been introduced recently, shows an improvement in classification performance, with relation to its linear counterpart K-SVD. However, this algorithm requires the storage and handling of a very large kernel matrix, which leads to high computational cost, while also limiting its use to setups with small number of training examples. We address these problems by combining two ideas: first we approximate the kernel matrix using a cleverly sampled subset of its columns using the Nystr\\"{o}m method; secondly, as we wish to avoid using this matrix altogether, we decompose it by SVD to form new "virtual samples," on which any linear dictionary learning can be employed. Our method, termed "Linearized Kernel Dictionary Learning" (LKDL) can be seamlessly applied as a pre-processing stage on top of any efficient off-the-shelf dictionary learning scheme, effectively "kernelizing" it. We demonstrate the effectiveness of our method on several tasks of both supervised and unsupervised classification and show the efficiency of the proposed scheme, its easy integration and performance boosting properties.

  5. The Stanford Linear Collider

    SciTech Connect

    Rees, J.R.

    1989-10-01

    April, 1989, the first Z zero particle was observed at the Stanford Linear Collider (SLC). The SLC collides high-energy beams of electrons and positrons into each other. In break with tradition the SLC aims two linear beams at each other. Strong motives impelled the Stanford team to choose the route of innovation. One reason being that linear colliders promise to be less expensive to build and operate than storage ring colliders. An equally powerful motive was the desire to build an Z zero factory, a facility at which the Z zero particle can be studied in detail. More than 200 Z zero particles have been detected at the SLC and more continue to be churned out regularly. It is in measuring the properties of the Z zero that the SLC has a seminal contribution to make. One of the primary goals of the SLC experimental program is to determine the mass of the Z zero as precisely as possible.In the end, the SLC's greatest significance will be in having proved a new accelerator technology. 7 figs.

  6. The Linearity Prototype for Graphs: Cognitive and Sociocultural Perspectives

    ERIC Educational Resources Information Center

    Hadjidemetriou, Constantia; Williams, Julian

    2010-01-01

    Linear models are frequently inappropriately applied to various situations. When misapplied, linearity is traditionally referred to as a tendency, a misconception, or an error. Cognitive linguistic, situated cognition, and sociocultural or cultural-historical activity theory, on the other hand, suggest that linear models are adopted by learners…

  7. Sparse linear programming subprogram

    SciTech Connect

    Hanson, R.J.; Hiebert, K.L.

    1981-12-01

    This report describes a subprogram, SPLP(), for solving linear programming problems. The package of subprogram units comprising SPLP() is written in Fortran 77. The subprogram SPLP() is intended for problems involving at most a few thousand constraints and variables. The subprograms are written to take advantage of sparsity in the constraint matrix. A very general problem statement is accepted by SPLP(). It allows upper, lower, or no bounds on the variables. Both the primal and dual solutions are returned as output parameters. The package has many optional features. Among them is the ability to save partial results and then use them to continue the computation at a later time.

  8. Ultrasonic linear measurement system

    NASA Technical Reports Server (NTRS)

    Marshall, Scot H. (Inventor)

    1991-01-01

    An ultrasonic linear measurement system uses the travel time of surface waves along the perimeter of a three-dimensional curvilinear body to determine the perimeter of the curvilinear body. The system can also be used piece-wise to measure distances along plane surfaces. The system can be used to measure perimeters where use of laser light, optical means or steel tape would be extremely difficult, time consuming or impossible. It can also be used to determine discontinuities in surfaces of known perimeter or dimension.

  9. [Congenital linear nevus sebaceus].

    PubMed

    Linnemann, Anders; Bygum, Anette; Fenger-Grøn, Jesper

    2011-09-01

    An unusual case of nevus sebaceous is described. Nevus sebaceous is a congenital epidermal hamartoma of the skin and the predilection site is the head or neck. In this case the nevus followed the lines of Blaschko along the back of the left lower extremity. The linear lesion seemed papulovesicular which caused suspicion of incontinentia pigmenti or infection, and the boy received antimicrobial treatment until a biopsy revealed the correct diagnosis. We wish to emphasize this clinical picture to spare the patient and relatives from unnecessary tests, treatment and concern. PMID:21893006

  10. Lead screw linear actuator

    NASA Technical Reports Server (NTRS)

    Perkins, Gerald S. (Inventor)

    1980-01-01

    A linear actuator which can apply high forces is described, which includes a reciprocating rod having a threaded portion engaged by a nut that is directly coupled to the rotor of an electric motor. The nut is connected to the rotor in a manner that minimizes loading on the rotor, by the use of a coupling that transmits torque to the nut but permits it to shift axially and radially with respect to the rotor. The nut has a threaded hydrostatic bearing for engaging the threaded rod portion, with an oilcarrying groove in the nut being interrupted.

  11. Faraday-active Fabry-Perot resonator: transmission, reflection, and emissivity.

    PubMed

    Liptuga, Anatoliy; Morozhenko, Vasyl; Pipa, Viktor; Venger, Evgen; Kostiuk, Theodor

    2012-05-01

    The propagation of light within a semiconductor Faraday-active Fabry-Perot resonator is investigated theoretically and experimentally. It is shown that an external magnetic field radically changes the angular and spectral characteristics of transmission, reflection, and emissivity of the resonator not only for polarized, but also for unpolarized, light. Suppression of interference patterns and phase inversion of the interference extrema were observed in both monochromatic and polychromatic light. The investigations were carried out for the plane-parallel plates of n-InAs in the spectral range of free charge carrier absorption. The results can be used to create new controllable optical and spectroscopic devices for investigation of Faraday-active material properties and for control of parameters of plane-parallel layers and structures.

  12. Faraday-Active Fabry-Perot Resonator: Transmission, Reflection, and Emissivity

    NASA Technical Reports Server (NTRS)

    Liptuga, Anatoliy; Morozhenko, Vasyl; Pipa, Viktor; Venger, Evgen; Kostiuk, Theodor

    2011-01-01

    The propagation of light within a semiconductor Faraday-active Fabry-Perot resonator (FAFR) is investigated theoretically and experimentally. It is shown that an external magnetic field radically changes the angular and spectral characteristics of transmission, reflection and emissivity of the resonator not only for polarized, but also for unpolarized light. Suppression of interference patterns and phase inversion of the interference extrema were observed in both monochromatic and polychromatic light. The investigations were carried out for the plane-parallel plates of n-InAs in the spectral range of free charge carrier absorption. The results can be used to create new controllable optical and spectroscopic devices for investigation of Faraday-active material properties and for control of parameters of plane-parallel layers and structures.

  13. Induction linear accelerators

    NASA Astrophysics Data System (ADS)

    Birx, Daniel

    1992-03-01

    Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

  14. Pseudo Linear Gyro Calibration

    NASA Technical Reports Server (NTRS)

    Harman, Richard; Bar-Itzhack, Itzhack Y.

    2003-01-01

    Previous high fidelity onboard attitude algorithms estimated only the spacecraft attitude and gyro bias. The desire to promote spacecraft and ground autonomy and improvements in onboard computing power has spurred development of more sophisticated calibration algorithms. Namely, there is a desire to provide for sensor calibration through calibration parameter estimation onboard the spacecraft as well as autonomous estimation on the ground. Gyro calibration is a particularly challenging area of research. There are a variety of gyro devices available for any prospective mission ranging from inexpensive low fidelity gyros with potentially unstable scale factors to much more expensive extremely stable high fidelity units. Much research has been devoted to designing dedicated estimators such as particular Extended Kalman Filter (EKF) algorithms or Square Root Information Filters. This paper builds upon previous attitude, rate, and specialized gyro parameter estimation work performed with Pseudo Linear Kalman Filter (PSELIKA). The PSELIKA advantage is the use of the standard linear Kalman Filter algorithm. A PSELIKA algorithm for an orthogonal gyro set which includes estimates of attitude, rate, gyro misalignments, gyro scale factors, and gyro bias is developed and tested using simulated and flight data. The measurements PSELIKA uses include gyro and quaternion tracker data.

  15. Comet LINEAR Splits Further

    NASA Astrophysics Data System (ADS)

    2001-05-01

    Third Nucleus Observed with the VLT Summary New images from the VLT show that one of the two nuclei of Comet LINEAR (C/2001 A2), now about 100 million km from the Earth, has just split into at least two pieces . The three fragments are now moving through space in nearly parallel orbits while they slowly drift apart. This comet will pass through its perihelion (nearest point to the Sun) on May 25, 2001, at a distance of about 116 million kilometres. It has brightened considerably due to the splitting of its "dirty snowball" nucleus and can now be seen with the unaided eye by observers in the southern hemisphere as a faint object in the southern constellation of Lepus (The Hare). PR Photo 18a/01 : Three nuclei of Comet LINEAR . PR Photo 18b/01 : The break-up of Comet LINEAR (false-colour). Comet LINEAR splits and brightens ESO PR Photo 18a/01 ESO PR Photo 18a/01 [Preview - JPEG: 400 x 438 pix - 55k] [Normal - JPEG: 800 x 875 pix - 136k] ESO PR Photo 18b/01 ESO PR Photo 18b/01 [Preview - JPEG: 367 x 400 pix - 112k] [Normal - JPEG: 734 x 800 pix - 272k] Caption : ESO PR Photo 18a/01 shows the three nuclei of Comet LINEAR (C/2001 A2). It is a reproduction of a 1-min exposure in red light, obtained in the early evening of May 16, 2001, with the 8.2-m VLT YEPUN (UT4) telescope at Paranal. ESO PR Photo 18b/01 shows the same image, but in a false-colour rendering for more clarity. The cometary fragment "B" (right) has split into "B1" and "B2" (separation about 1 arcsec, or 500 km) while fragment "A" (upper left) is considerably fainter. Technical information about these photos is available below. Comet LINEAR was discovered on January 3, 2001, and designated by the International Astronomical Union (IAU) as C/2001 A2 (see IAU Circular 7564 [1]). Six weeks ago, it was suddenly observed to brighten (IAUC 7605 [1]). Amateurs all over the world saw the comparatively faint comet reaching naked-eye magnitude and soon thereafter, observations with professional telescopes indicated

  16. On the linear programming bound for linear Lee codes.

    PubMed

    Astola, Helena; Tabus, Ioan

    2016-01-01

    Based on an invariance-type property of the Lee-compositions of a linear Lee code, additional equality constraints can be introduced to the linear programming problem of linear Lee codes. In this paper, we formulate this property in terms of an action of the multiplicative group of the field [Formula: see text] on the set of Lee-compositions. We show some useful properties of certain sums of Lee-numbers, which are the eigenvalues of the Lee association scheme, appearing in the linear programming problem of linear Lee codes. Using the additional equality constraints, we formulate the linear programming problem of linear Lee codes in a very compact form, leading to a fast execution, which allows to efficiently compute the bounds for large parameter values of the linear codes.

  17. Positrons for linear colliders

    SciTech Connect

    Ecklund, S.

    1987-11-01

    The requirements of a positron source for a linear collider are briefly reviewed, followed by methods of positron production and production of photons by electromagnetic cascade showers. Cross sections for the electromagnetic cascade shower processes of positron-electron pair production and Compton scattering are compared. A program used for Monte Carlo analysis of electromagnetic cascades is briefly discussed, and positron distributions obtained from several runs of the program are discussed. Photons from synchrotron radiation and from channeling are also mentioned briefly, as well as positron collection, transverse focusing techniques, and longitudinal capture. Computer ray tracing is then briefly discussed, followed by space-charge effects and thermal heating and stress due to showers. (LEW)

  18. Non Linear Conjugate Gradient

    2006-11-17

    Software that simulates and inverts electromagnetic field data for subsurface electrical properties (electrical conductivity) of geological media. The software treats data produced by a time harmonic source field excitation arising from the following antenna geometery: loops and grounded bipoles, as well as point electric and magnetic dioples. The inversion process is carried out using a non-linear conjugate gradient optimization scheme, which minimizes the misfit between field data and model data using a least squares criteria.more » The software is an upgrade from the code NLCGCS_MP ver 1.0. The upgrade includes the following components: Incorporation of new 1 D field sourcing routines to more accurately simulate the 3D electromagnetic field for arbitrary geologic& media, treatment for generalized finite length transmitting antenna geometry (antennas with vertical and horizontal component directions). In addition, the software has been upgraded to treat transverse anisotropy in electrical conductivity.« less

  19. Linear response at criticality

    NASA Astrophysics Data System (ADS)

    Svenkeson, Adam; Bologna, Mauro; Grigolini, Paolo

    2012-10-01

    We study a set of cooperatively interacting units at criticality, and we prove with analytical and numerical arguments that they generate the same renewal non-Poisson intermittency as that produced by blinking quantum dots, thereby giving a stronger support to the results of earlier investigation. By analyzing how this out-of-equilibrium system responds to harmonic perturbations, we find that the response can be described only using a new form of linear response theory that accounts for aging and the nonergodic behavior of the underlying process. We connect the undamped response of the system at criticality to the decaying response predicted by the recently established nonergodic fluctuation-dissipation theorem for dichotomous processes using information about the second moment of the fluctuations. We demonstrate that over a wide range of perturbation frequencies the response of the cooperative system is greatest when at criticality.

  20. HEAVY ION LINEAR ACCELERATOR

    DOEpatents

    Van Atta, C.M.; Beringer, R.; Smith, L.

    1959-01-01

    A linear accelerator of heavy ions is described. The basic contributions of the invention consist of a method and apparatus for obtaining high energy particles of an element with an increased charge-to-mass ratio. The method comprises the steps of ionizing the atoms of an element, accelerating the resultant ions to an energy substantially equal to one Mev per nucleon, stripping orbital electrons from the accelerated ions by passing the ions through a curtain of elemental vapor disposed transversely of the path of the ions to provide a second charge-to-mass ratio, and finally accelerating the resultant stripped ions to a final energy of at least ten Mev per nucleon.

  1. Linear Proof Mass Actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III

    1994-01-01

    This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The linear proof mass actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (mass, upper housing, lower housing, and center support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operating testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

  2. Linear Proof Mass Actuator

    NASA Technical Reports Server (NTRS)

    Holloway, S. E., III

    1995-01-01

    This paper describes the mechanical design, analysis, fabrication, testing, and lessons learned by developing a uniquely designed spaceflight-like actuator. The Linear Proof Mass Actuator (LPMA) was designed to attach to both a large space structure and a ground test model without modification. Previous designs lacked the power to perform in a terrestrial environment while other designs failed to produce the desired accelerations or frequency range for spaceflight applications. Thus, the design for a unique actuator was conceived and developed at NASA Langley Research Center. The basic design consists of four large mechanical parts (Mass, Upper Housing, Lower Housing, and Center Support) and numerous smaller supporting components including an accelerometer, encoder, and four drive motors. Fabrication personnel were included early in the design phase of the LPMA as part of an integrated manufacturing process to alleviate potential difficulties in machining an already challenging design. Operational testing of the LPMA demonstrated that the actuator is capable of various types of load functions.

  3. Investigation of an Immunoassay with Broad Specificity to Quinolone Drugs by Genetic Algorithm with Linear Assignment of Hypermolecular Alignment of Data Sets and Advanced Quantitative Structure-Activity Relationship Analysis.

    PubMed

    Chen, Jiahong; Lu, Ning; Shen, Xing; Tang, Qiushi; Zhang, Chijian; Xu, Jun; Sun, Yuanming; Huang, Xin-An; Xu, Zhenlin; Lei, Hongtao

    2016-04-01

    A polyclonal antibody against the quinolone drug pazufloxacin (PAZ) but with surprisingly broad specificity was raised to simultaneously detect 24 quinolones (QNs). The developed competitive indirect enzyme-linked immunosorbent assay (ciELISA) exhibited limits of detection (LODs) for the 24 QNs ranging from 0.45 to 15.16 ng/mL, below the maximum residue levels (MRLs). To better understand the obtained broad specificity, a genetic algorithm with linear assignment of hypermolecular alignment of data sets (GALAHAD) was used to generate the desired pharmacophore model and superimpose the QNs, and then advanced comparative molecular field analysis (CoMFA) and advanced comparative molecular similarity indices analysis (CoMSIA) models were employed to study the three-dimensional quantitative structure-activity relationship (3D QSAR) between QNs and the antibody. It was found that the QNs could interact with the antibody with different binding poses, and cross-reactivity was mainly positively correlated with the bulky substructure containing electronegative atom at the 7-position, while it was negatively associated with the large bulky substructure at the 1-position of QNs.

  4. Computer Program For Linear Algebra

    NASA Technical Reports Server (NTRS)

    Krogh, F. T.; Hanson, R. J.

    1987-01-01

    Collection of routines provided for basic vector operations. Basic Linear Algebra Subprogram (BLAS) library is collection from FORTRAN-callable routines for employing standard techniques to perform basic operations of numerical linear algebra.

  5. Scaffolding Conceptual Understanding for Linear Measurement

    ERIC Educational Resources Information Center

    Erbilgin, Evrim

    2015-01-01

    This article describes a series of two linear measurement activities designed to integrate the related content and processes of Common Core State Standards for Mathematics (CCSSM) into classroom practice using nonstandard units. In the article, nonstandard units refer to same-size, repeatable units (e.g., paper clips, feet) for a specified…

  6. Tried and True: Springing into Linear Models

    ERIC Educational Resources Information Center

    Darling, Gerald

    2012-01-01

    In eighth grade, students usually learn about forces in science class and linear relationships in math class, crucial topics that form the foundation for further study in science and engineering. An activity that links these two fundamental concepts involves measuring the distance a spring stretches as a function of how much weight is suspended…

  7. Towards a Future Linear Collider and The Linear Collider Studies at CERN

    ScienceCinema

    None

    2016-07-12

    During the week 18-22 October, more than 400 physicists will meet at CERN and in the CICG (International Conference Centre Geneva) to review the global progress towards a future linear collider. The 2010 International Workshop on Linear Colliders will study the physics, detectors and accelerator complex of a linear collider covering both the CLIC and ILC options. Among the topics presented and discussed will be the progress towards the CLIC Conceptual Design Report in 2011, the ILC Technical Design Report in 2012, physics and detector studies linked to these reports, and an increasing numbers of common working group activities. The seminar will give an overview of these topics and also CERN’s linear collider studies, focusing on current activities and initial plans for the period 2011-16. n.b: The Council Chamber is also reserved for this colloquium with a live transmission from the Main Auditorium.

  8. LINEAR - DERIVATION AND DEFINITION OF A LINEAR AIRCRAFT MODEL

    NASA Technical Reports Server (NTRS)

    Duke, E. L.

    1994-01-01

    The Derivation and Definition of a Linear Model program, LINEAR, provides the user with a powerful and flexible tool for the linearization of aircraft aerodynamic models. LINEAR was developed to provide a standard, documented, and verified tool to derive linear models for aircraft stability analysis and control law design. Linear system models define the aircraft system in the neighborhood of an analysis point and are determined by the linearization of the nonlinear equations defining vehicle dynamics and sensors. LINEAR numerically determines a linear system model using nonlinear equations of motion and a user supplied linear or nonlinear aerodynamic model. The nonlinear equations of motion used are six-degree-of-freedom equations with stationary atmosphere and flat, nonrotating earth assumptions. LINEAR is capable of extracting both linearized engine effects, such as net thrust, torque, and gyroscopic effects and including these effects in the linear system model. The point at which this linear model is defined is determined either by completely specifying the state and control variables, or by specifying an analysis point on a trajectory and directing the program to determine the control variables and the remaining state variables. The system model determined by LINEAR consists of matrices for both the state and observation equations. The program has been designed to provide easy selection of state, control, and observation variables to be used in a particular model. Thus, the order of the system model is completely under user control. Further, the program provides the flexibility of allowing alternate formulations of both the state and observation equations. Data describing the aircraft and the test case is input to the program through a terminal or formatted data files. All data can be modified interactively from case to case. The aerodynamic model can be defined in two ways: a set of nondimensional stability and control derivatives for the flight point of

  9. Generalized Linear Covariance Analysis

    NASA Astrophysics Data System (ADS)

    Markley, F. Landis; Carpenter, J. Russell

    2009-01-01

    This paper presents a comprehensive approach to filter modeling for generalized covariance analysis of both batch least-squares and sequential estimators. We review and extend in two directions the results of prior work that allowed for partitioning of the state space into "solve-for" and "consider" parameters, accounted for differences between the formal values and the true values of the measurement noise, process noise, and a priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and a priori solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator's epoch time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the "variance sandpile" and the "sensitivity mosaic," and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.

  10. Generalized Linear Covariance Analysis

    NASA Technical Reports Server (NTRS)

    Carpenter, James R.; Markley, F. Landis

    2014-01-01

    This talk presents a comprehensive approach to filter modeling for generalized covariance analysis of both batch least-squares and sequential estimators. We review and extend in two directions the results of prior work that allowed for partitioning of the state space into solve-for'' and consider'' parameters, accounted for differences between the formal values and the true values of the measurement noise, process noise, and textita priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator's epoch time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the variance sandpile'' and the sensitivity mosaic,'' and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.

  11. Winding for linear pump

    DOEpatents

    Kliman, Gerald B.; Brynsvold, Glen V.; Jahns, Thomas M.

    1989-01-01

    A winding and method of winding for a submersible linear pump for pumping liquid sodium is disclosed. The pump includes a stator having a central cylindrical duct preferably vertically aligned. The central vertical duct is surrounded by a system of coils in slots. These slots are interleaved with magnetic flux conducting elements, these magnetic flux conducting elements forming a continuous magnetic field conduction path along the stator. The central duct has placed therein a cylindrical magnetic conducting core, this core having a cylindrical diameter less than the diameter of the cylindrical duct. The core once placed to the duct defines a cylindrical interstitial pumping volume of the pump. This cylindrical interstitial pumping volume preferably defines an inlet at the bottom of the pump, and an outlet at the top of the pump. Pump operation occurs by static windings in the outer stator sequentially conveying toroidal fields from the pump inlet at the bottom of the pump to the pump outlet at the top of the pump. The winding apparatus and method of winding disclosed uses multiple slots per pole per phase with parallel winding legs on each phase equal to or less than the number of slots per pole per phase. The slot sequence per pole per phase is chosen to equalize the variations in flux density of the pump sodium as it passes into the pump at the pump inlet with little or no flux and acquires magnetic flux in passage through the pump to the pump outlet.

  12. Winding for linear pump

    DOEpatents

    Kliman, G.B.; Brynsvold, G.V.; Jahns, T.M.

    1989-08-22

    A winding and method of winding for a submersible linear pump for pumping liquid sodium are disclosed. The pump includes a stator having a central cylindrical duct preferably vertically aligned. The central vertical duct is surrounded by a system of coils in slots. These slots are interleaved with magnetic flux conducting elements, these magnetic flux conducting elements forming a continuous magnetic field conduction path along the stator. The central duct has placed therein a cylindrical magnetic conducting core, this core having a cylindrical diameter less than the diameter of the cylindrical duct. The core once placed to the duct defines a cylindrical interstitial pumping volume of the pump. This cylindrical interstitial pumping volume preferably defines an inlet at the bottom of the pump, and an outlet at the top of the pump. Pump operation occurs by static windings in the outer stator sequentially conveying toroidal fields from the pump inlet at the bottom of the pump to the pump outlet at the top of the pump. The winding apparatus and method of winding disclosed uses multiple slots per pole per phase with parallel winding legs on each phase equal to or less than the number of slots per pole per phase. The slot sequence per pole per phase is chosen to equalize the variations in flux density of the pump sodium as it passes into the pump at the pump inlet with little or no flux and acquires magnetic flux in passage through the pump to the pump outlet. 4 figs.

  13. Linear induction pump

    DOEpatents

    Meisner, John W.; Moore, Robert M.; Bienvenue, Louis L.

    1985-03-19

    Electromagnetic linear induction pump for liquid metal which includes a unitary pump duct. The duct comprises two substantially flat parallel spaced-apart wall members, one being located above the other and two parallel opposing side members interconnecting the wall members. Located within the duct are a plurality of web members interconnecting the wall members and extending parallel to the side members whereby the wall members, side members and web members define a plurality of fluid passageways, each of the fluid passageways having substantially the same cross-sectional flow area. Attached to an outer surface of each side member is an electrically conductive end bar for the passage of an induced current therethrough. A multi-phase, electrical stator is located adjacent each of the wall members. The duct, stators, and end bars are enclosed in a housing which is provided with an inlet and outlet in fluid communication with opposite ends of the fluid passageways in the pump duct. In accordance with a preferred embodiment, the inlet and outlet includes a transition means which provides for a transition from a round cross-sectional flow path to a substantially rectangular cross-sectional flow path defined by the pump duct.

  14. Generalized Linear Covariance Analysis

    NASA Technical Reports Server (NTRS)

    Carpenter, J. Russell; Markley, F. Landis

    2008-01-01

    We review and extend in two directions the results of prior work on generalized covariance analysis methods. This prior work allowed for partitioning of the state space into "solve-for" and "consider" parameters, allowed for differences between the formal values and the true values of the measurement noise, process noise, and a priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and a priori solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator s anchor time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the "variance sandpile" and the "sensitivity mosaic," and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.

  15. Global Linear Instability

    NASA Astrophysics Data System (ADS)

    Theofilis, Vassilios

    2011-01-01

    This article reviews linear instability analysis of flows over or through complex two-dimensional (2D) and 3D geometries. In the three decades since it first appeared in the literature, global instability analysis, based on the solution of the multidimensional eigenvalue and/or initial value problem, is continuously broadening both in scope and in depth. To date it has dealt successfully with a wide range of applications arising in aerospace engineering, physiological flows, food processing, and nuclear-reactor safety. In recent years, nonmodal analysis has complemented the more traditional modal approach and increased knowledge of flow instability physics. Recent highlights delivered by the application of either modal or nonmodal global analysis are briefly discussed. A conscious effort is made to demystify both the tools currently utilized and the jargon employed to describe them, demonstrating the simplicity of the analysis. Hopefully this will provide new impulses for the creation of next-generation algorithms capable of coping with the main open research areas in which step-change progress can be expected by the application of the theory: instability analysis of fully inhomogeneous, 3D flows and control thereof.

  16. Berkeley Proton Linear Accelerator

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Bradner, H.; Franck, J.; Gordon, H.; Gow, J. D.; Marshall, L. C.; Oppenheimer, F. F.; Panofsky, W. K. H.; Richman, C.; Woodyard, J. R.

    1953-10-13

    A linear accelerator, which increases the energy of protons from a 4 Mev Van de Graaff injector, to a final energy of 31.5 Mev, has been constructed. The accelerator consists of a cavity 40 feet long and 39 inches in diameter, excited at resonance in a longitudinal electric mode with a radio-frequency power of about 2.2 x 10{sup 6} watts peak at 202.5 mc. Acceleration is made possible by the introduction of 46 axial "drift tubes" into the cavity, which is designed such that the particles traverse the distance between the centers of successive tubes in one cycle of the r.f. power. The protons are longitudinally stable as in the synchrotron, and are stabilized transversely by the action of converging fields produced by focusing grids. The electrical cavity is constructed like an inverted airplane fuselage and is supported in a vacuum tank. Power is supplied by 9 high powered oscillators fed from a pulse generator of the artificial transmission line type.

  17. Exploring Linear Measure.

    ERIC Educational Resources Information Center

    Cox, Philip L.

    This material is an instructional unit on measuring and estimating. A variety of activities are used with manipulative devices, worksheets, and discussion questions included. Major topics are estimating lengths, accuracy of measurement, metric system, scale drawings, and conversion between different units. A teacher's guide is also available.…

  18. Linear Algebraic Method for Non-Linear Map Analysis

    SciTech Connect

    Yu,L.; Nash, B.

    2009-05-04

    We present a newly developed method to analyze some non-linear dynamics problems such as the Henon map using a matrix analysis method from linear algebra. Choosing the Henon map as an example, we analyze the spectral structure, the tune-amplitude dependence, the variation of tune and amplitude during the particle motion, etc., using the method of Jordan decomposition which is widely used in conventional linear algebra.

  19. Linear Proof-Mass Actuator

    NASA Technical Reports Server (NTRS)

    Holloway, Sidney E., III; Crossley, Edward A.; Miller, James B.; Jones, Irby W.; Davis, C. Calvin; Behun, Vaughn D.; Goodrich, Lewis R., Sr.

    1995-01-01

    Linear proof-mass actuator (LPMA) is friction-driven linear mass actuator capable of applying controlled force to structure in outer space to damp out oscillations. Capable of high accelerations and provides smooth, bidirectional travel of mass. Design eliminates gears and belts. LPMA strong enough to be used terrestrially where linear actuators needed to excite or damp out oscillations. High flexibility designed into LPMA by varying size of motors, mass, and length of stroke, and by modifying control software.

  20. Linear collider development at SLAC

    SciTech Connect

    Irwin, J.

    1993-08-01

    Linear collider R&D at SLAC comprises work on the present Stanford Linear Collider (SLC) and work toward the next linear collider (NLC). Recent SLC developments are summarized. NLC studies are divided into hardware-based and theoretical. We report on the status of the NLC Test Accelerator (NLCTA) and the final focus test beam (FFTB), describe plans for ASSET, an installation to measure accelerator structure wakefields, and mention IR design developments. Finally we review recent NLC theoretical studies, ending with the author`s view of next linear collider parameter sets.

  1. Quantization of general linear electrodynamics

    SciTech Connect

    Rivera, Sergio; Schuller, Frederic P.

    2011-03-15

    General linear electrodynamics allow for an arbitrary linear constitutive relation between the field strength 2-form and induction 2-form density if crucial hyperbolicity and energy conditions are satisfied, which render the theory predictive and physically interpretable. Taking into account the higher-order polynomial dispersion relation and associated causal structure of general linear electrodynamics, we carefully develop its Hamiltonian formulation from first principles. Canonical quantization of the resulting constrained system then results in a quantum vacuum which is sensitive to the constitutive tensor of the classical theory. As an application we calculate the Casimir effect in a birefringent linear optical medium.

  2. Linear magnetic bearings

    NASA Technical Reports Server (NTRS)

    Goldowskiy, M. P.

    1984-01-01

    A self regulating, nonfrictional, active magnetic bearing is disclosed which has an elongated cylindrical housing for containing a shaft type armature with quadrature positioned shaft position sensors and equidistantly positioned electromagnets located at one end of the housing. Each set of sensors is responsive to orthogonal displacement of the armature and is used to generate control signals to energize the electromagnets to center the armature. A bumper magnet assembly is located at one end of the housing for dampening any undesired axial movement of the armature or to axially move the armature either continuously or fixedly.

  3. Linear equality constraints in the general linear mixed model.

    PubMed

    Edwards, L J; Stewart, P W; Muller, K E; Helms, R W

    2001-12-01

    Scientists may wish to analyze correlated outcome data with constraints among the responses. For example, piecewise linear regression in a longitudinal data analysis can require use of a general linear mixed model combined with linear parameter constraints. Although well developed for standard univariate models, there are no general results that allow a data analyst to specify a mixed model equation in conjunction with a set of constraints on the parameters. We resolve the difficulty by precisely describing conditions that allow specifying linear parameter constraints that insure the validity of estimates and tests in a general linear mixed model. The recommended approach requires only straightforward and noniterative calculations to implement. We illustrate the convenience and advantages of the methods with a comparison of cognitive developmental patterns in a study of individuals from infancy to early adulthood for children from low-income families.

  4. A Riccati approach for constrained linear quadratic optimal control

    NASA Astrophysics Data System (ADS)

    Sideris, Athanasios; Rodriguez, Luis A.

    2011-02-01

    An active-set method is proposed for solving linear quadratic optimal control problems subject to general linear inequality path constraints including mixed state-control and state-only constraints. A Riccati-based approach is developed for efficiently solving the equality constrained optimal control subproblems generated during the procedure. The solution of each subproblem requires computations that scale linearly with the horizon length. The algorithm is illustrated with numerical examples.

  5. Linear Algebra and Image Processing

    ERIC Educational Resources Information Center

    Allali, Mohamed

    2010-01-01

    We use the computing technology digital image processing (DIP) to enhance the teaching of linear algebra so as to make the course more visual and interesting. Certainly, this visual approach by using technology to link linear algebra to DIP is interesting and unexpected to both students as well as many faculty. (Contains 2 tables and 11 figures.)

  6. Linear algebra and image processing

    NASA Astrophysics Data System (ADS)

    Allali, Mohamed

    2010-09-01

    We use the computing technology digital image processing (DIP) to enhance the teaching of linear algebra so as to make the course more visual and interesting. Certainly, this visual approach by using technology to link linear algebra to DIP is interesting and unexpected to both students as well as many faculty.

  7. Linear Programming across the Curriculum

    ERIC Educational Resources Information Center

    Yoder, S. Elizabeth; Kurz, M. Elizabeth

    2015-01-01

    Linear programming (LP) is taught in different departments across college campuses with engineering and management curricula. Modeling an LP problem is taught in every linear programming class. As faculty teaching in Engineering and Management departments, the depth to which teachers should expect students to master this particular type of…

  8. Passive linearization of nonlinear resonances

    NASA Astrophysics Data System (ADS)

    Habib, G.; Grappasonni, C.; Kerschen, G.

    2016-07-01

    The objective of this paper is to demonstrate that the addition of properly tuned nonlinearities to a nonlinear system can increase the range over which a specific resonance responds linearly. Specifically, we seek to enforce two important properties of linear systems, namely, the force-displacement proportionality and the invariance of resonance frequencies. Numerical simulations and experiments are used to validate the theoretical findings.

  9. Spatial Processes in Linear Ordering

    ERIC Educational Resources Information Center

    von Hecker, Ulrich; Klauer, Karl Christoph; Wolf, Lukas; Fazilat-Pour, Masoud

    2016-01-01

    Memory performance in linear order reasoning tasks (A > B, B > C, C > D, etc.) shows quicker, and more accurate responses to queries on wider (AD) than narrower (AB) pairs on a hypothetical linear mental model (A -- B -- C -- D). While indicative of an analogue representation, research so far did not provide positive evidence for spatial…

  10. Who Will Win?: Predicting the Presidential Election Using Linear Regression

    ERIC Educational Resources Information Center

    Lamb, John H.

    2007-01-01

    This article outlines a linear regression activity that engages learners, uses technology, and fosters cooperation. Students generated least-squares linear regression equations using TI-83 Plus[TM] graphing calculators, Microsoft[C] Excel, and paper-and-pencil calculations using derived normal equations to predict the 2004 presidential election.…

  11. Radio frequency quadrupole resonator for linear accelerator

    DOEpatents

    Moretti, Alfred

    1985-01-01

    An RFQ resonator for a linear accelerator having a reduced level of interfering modes and producing a quadrupole mode for focusing, bunching and accelerating beams of heavy charged particles, with the construction being characterized by four elongated resonating rods within a cylinder with the rods being alternately shorted and open electrically to the shell at common ends of the rods to provide an LC parallel resonant circuit when activated by a magnetic field transverse to the longitudinal axis.

  12. ALPS: A Linear Program Solver

    NASA Technical Reports Server (NTRS)

    Ferencz, Donald C.; Viterna, Larry A.

    1991-01-01

    ALPS is a computer program which can be used to solve general linear program (optimization) problems. ALPS was designed for those who have minimal linear programming (LP) knowledge and features a menu-driven scheme to guide the user through the process of creating and solving LP formulations. Once created, the problems can be edited and stored in standard DOS ASCII files to provide portability to various word processors or even other linear programming packages. Unlike many math-oriented LP solvers, ALPS contains an LP parser that reads through the LP formulation and reports several types of errors to the user. ALPS provides a large amount of solution data which is often useful in problem solving. In addition to pure linear programs, ALPS can solve for integer, mixed integer, and binary type problems. Pure linear programs are solved with the revised simplex method. Integer or mixed integer programs are solved initially with the revised simplex, and the completed using the branch-and-bound technique. Binary programs are solved with the method of implicit enumeration. This manual describes how to use ALPS to create, edit, and solve linear programming problems. Instructions for installing ALPS on a PC compatible computer are included in the appendices along with a general introduction to linear programming. A programmers guide is also included for assistance in modifying and maintaining the program.

  13. Linearization algorithms for line transfer

    SciTech Connect

    Scott, H.A.

    1990-11-06

    Complete linearization is a very powerful technique for solving multi-line transfer problems that can be used efficiently with a variety of transfer formalisms. The linearization algorithm we describe is computationally very similar to ETLA, but allows an effective treatment of strongly-interacting lines. This algorithm has been implemented (in several codes) with two different transfer formalisms in all three one-dimensional geometries. We also describe a variation of the algorithm that handles saturable laser transport. Finally, we present a combination of linearization with a local approximate operator formalism, which has been implemented in two dimensions and is being developed in three dimensions. 11 refs.

  14. Precision magnetic suspension linear bearing

    NASA Technical Reports Server (NTRS)

    Trumper, David L.; Queen, Michael A.

    1992-01-01

    We have shown the design and analyzed the electromechanics of a linear motor suitable for independently controlling two suspension degrees of freedom. This motor, at least on paper, meets the requirements for driving an X-Y stage of 10 Kg mass with about 4 m/sq sec acceleration, with travel of several hundred millimeters in X and Y, and with reasonable power dissipation. A conceptual design for such a stage is presented. The theoretical feasibility of linear and planar bearings using single or multiple magnetic suspension linear motors is demonstrated.

  15. Characterizations of linear sufficient statistics

    NASA Technical Reports Server (NTRS)

    Peters, B. C., Jr.; Redner, R.; Decell, H. P., Jr.

    1976-01-01

    A necessary and sufficient condition is developed such that there exists a continous linear sufficient statistic T for a dominated collection of totally finite measures defined on the Borel field generated by the open sets of a Banach space X. In particular, corollary necessary and sufficient conditions are given so that there exists a rank K linear sufficient statistic T for any finite collection of probability measures having n-variate normal densities. In this case a simple calculation, involving only the population means and covariances, determines the smallest integer K for which there exists a rank K linear sufficient statistic T (as well as an associated statistic T itself).

  16. Practical Session: Simple Linear Regression

    NASA Astrophysics Data System (ADS)

    Clausel, M.; Grégoire, G.

    2014-12-01

    Two exercises are proposed to illustrate the simple linear regression. The first one is based on the famous Galton's data set on heredity. We use the lm R command and get coefficients estimates, standard error of the error, R2, residuals …In the second example, devoted to data related to the vapor tension of mercury, we fit a simple linear regression, predict values, and anticipate on multiple linear regression. This pratical session is an excerpt from practical exercises proposed by A. Dalalyan at EPNC (see Exercises 1 and 2 of http://certis.enpc.fr/~dalalyan/Download/TP_ENPC_4.pdf).

  17. Features in visual search combine linearly

    PubMed Central

    Pramod, R. T.; Arun, S. P.

    2014-01-01

    Single features such as line orientation and length are known to guide visual search, but relatively little is known about how multiple features combine in search. To address this question, we investigated how search for targets differing in multiple features (intensity, length, orientation) from the distracters is related to searches for targets differing in each of the individual features. We tested race models (based on reaction times) and co-activation models (based on reciprocal of reaction times) for their ability to predict multiple feature searches. Multiple feature searches were best accounted for by a co-activation model in which feature information combined linearly (r = 0.95). This result agrees with the classic finding that these features are separable i.e., subjective dissimilarity ratings sum linearly. We then replicated the classical finding that the length and width of a rectangle are integral features—in other words, they combine nonlinearly in visual search. However, to our surprise, upon including aspect ratio as an additional feature, length and width combined linearly and this model outperformed all other models. Thus, length and width of a rectangle became separable when considered together with aspect ratio. This finding predicts that searches involving shapes with identical aspect ratio should be more difficult than searches where shapes differ in aspect ratio. We confirmed this prediction on a variety of shapes. We conclude that features in visual search co-activate linearly and demonstrate for the first time that aspect ratio is a novel feature that guides visual search. PMID:24715328

  18. Overdetermined Systems of Linear Equations.

    ERIC Educational Resources Information Center

    Williams, Gareth

    1990-01-01

    Explored is an overdetermined system of linear equations to find an appropriate least squares solution. A geometrical interpretation of this solution is given. Included is a least squares point discussion. (KR)

  19. Acoustic emission linear pulse holography

    DOEpatents

    Collins, H.D.; Busse, L.J.; Lemon, D.K.

    1983-10-25

    This device relates to the concept of and means for performing Acoustic Emission Linear Pulse Holography, which combines the advantages of linear holographic imaging and Acoustic Emission into a single non-destructive inspection system. This unique system produces a chronological, linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. The innovation is the concept of utilizing the crack-generated acoustic emission energy to generate a chronological series of images of a growing crack by applying linear, pulse holographic processing to the acoustic emission data. The process is implemented by placing on a structure an array of piezoelectric sensors (typically 16 or 32 of them) near the defect location. A reference sensor is placed between the defect and the array.

  20. Ada Linear-Algebra Program

    NASA Technical Reports Server (NTRS)

    Klumpp, A. R.; Lawson, C. L.

    1988-01-01

    Routines provided for common scalar, vector, matrix, and quaternion operations. Computer program extends Ada programming language to include linear-algebra capabilities similar to HAS/S programming language. Designed for such avionics applications as software for Space Station.

  1. Optimal piecewise locally linear modeling

    NASA Astrophysics Data System (ADS)

    Harris, Chris J.; Hong, Xia; Feng, M.

    1999-03-01

    Associative memory networks such as Radial Basis Functions, Neurofuzzy and Fuzzy Logic used for modelling nonlinear processes suffer from the curse of dimensionality (COD), in that as the input dimension increases the parameterization, computation cost, training data requirements, etc. increase exponentially. Here a new algorithm is introduced for the construction of a Delaunay input space partitioned optimal piecewise locally linear models to overcome the COD as well as generate locally linear models directly amenable to linear control and estimation algorithms. The training of the model is configured as a new mixture of experts network with a new fast decision rule derived using convex set theory. A very fast simulated reannealing (VFSR) algorithm is utilized to search a global optimal solution of the Delaunay input space partition. A benchmark non-linear time series is used to demonstrate the new approach.

  2. SLC: The first linear collider

    NASA Astrophysics Data System (ADS)

    Phinney, Nan

    The Stanford Linear Collider (SLC) was built in the 1980s at the Stanford Linear Accelerator Center (SLAC) in California. Like LEP, it was designed to study the properties of the Z boson at a center-of-mass energy of about 91 GeV. The SLC was also a prototype for an entirely new approach to electron-positron colliders. The development of a new technology was motivated by the fact that in an electron storage ring, the electrons radiate synchrotron radiation as they are bent around the ring. To avoid excessive energy loss from this radiation, the circumference of the ring has to increase as the square of the desired energy, making very high energy rings prohibitively large and expensive. With a linear accelerator, the electrons do not need to bend and the tunnel length only grows linearly with energy...

  3. Spacetime metric from linear electrodynamics

    NASA Astrophysics Data System (ADS)

    Obukhov, Yuri N.; Hehl, Friedrich W.

    1999-07-01

    The Maxwell equations are formulated on an arbitrary (1+3)-dimensional manifold. Then, imposing a (constrained) linear constitutive relation between electromagnetic field (E,B) and excitation (D,ℌ), we derive the metric of spacetime therefrom.

  4. Linear Back-Drive Differentials

    NASA Technical Reports Server (NTRS)

    Waydo, Peter

    2003-01-01

    Linear back-drive differentials have been proposed as alternatives to conventional gear differentials for applications in which there is only limited rotational motion (e.g., oscillation). The finite nature of the rotation makes it possible to optimize a linear back-drive differential in ways that would not be possible for gear differentials or other differentials that are required to be capable of unlimited rotation. As a result, relative to gear differentials, linear back-drive differentials could be more compact and less massive, could contain fewer complex parts, and could be less sensitive to variations in the viscosities of lubricants. Linear back-drive differentials would operate according to established principles of power ball screws and linear-motion drives, but would utilize these principles in an innovative way. One major characteristic of such mechanisms that would be exploited in linear back-drive differentials is the possibility of designing them to drive or back-drive with similar efficiency and energy input: in other words, such a mechanism can be designed so that a rotating screw can drive a nut linearly or the linear motion of the nut can cause the screw to rotate. A linear back-drive differential (see figure) would include two collinear shafts connected to two parts that are intended to engage in limited opposing rotations. The linear back-drive differential would also include a nut that would be free to translate along its axis but not to rotate. The inner surface of the nut would be right-hand threaded at one end and left-hand threaded at the opposite end to engage corresponding right- and left-handed threads on the shafts. A rotation and torque introduced into the system via one shaft would drive the nut in linear motion. The nut, in turn, would back-drive the other shaft, creating a reaction torque. Balls would reduce friction, making it possible for the shaft/nut coupling on each side to operate with 90 percent efficiency.

  5. Polarized Electrons for Linear Colliders

    NASA Astrophysics Data System (ADS)

    Clendenin, J. E.; Brachmann, A.; Garwin, E. L.; Kirby, R. E.; Luh, D.-A.; Maruyama, T.; Prescott, C. Y.; Sheppard, J. C.; Turner, J.; Prepost, R.

    2005-08-01

    Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting RF structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a DC-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%.

  6. Polarized Electrons for Linear Colliders

    SciTech Connect

    Clendenin, J.

    2004-11-19

    Future electron-positron linear colliders require a highly polarized electron beam with a pulse structure that depends primarily on whether the acceleration utilizes warm or superconducting rf structures. The International Linear Collider (ILC) will use cold structures for the main linac. It is shown that a dc-biased polarized photoelectron source such as successfully used for the SLC can meet the charge requirements for the ILC micropulse with a polarization approaching 90%.

  7. Linear superposition in nonlinear equations.

    PubMed

    Khare, Avinash; Sukhatme, Uday

    2002-06-17

    Several nonlinear systems such as the Korteweg-de Vries (KdV) and modified KdV equations and lambda phi(4) theory possess periodic traveling wave solutions involving Jacobi elliptic functions. We show that suitable linear combinations of these known periodic solutions yield many additional solutions with different periods and velocities. This linear superposition procedure works by virtue of some remarkable new identities involving elliptic functions. PMID:12059300

  8. Transformation matrices between non-linear and linear differential equations

    NASA Technical Reports Server (NTRS)

    Sartain, R. L.

    1983-01-01

    In the linearization of systems of non-linear differential equations, those systems which can be exactly transformed into the second order linear differential equation Y"-AY'-BY=0 where Y, Y', and Y" are n x 1 vectors and A and B are constant n x n matrices of real numbers were considered. The 2n x 2n matrix was used to transform the above matrix equation into the first order matrix equation X' = MX. Specially the matrix M and the conditions which will diagonalize or triangularize M were studied. Transformation matrices P and P sub -1 were used to accomplish this diagonalization or triangularization to return to the solution of the second order matrix differential equation system from the first order system.

  9. A nanoscale linear-to-linear motion converter of graphene.

    PubMed

    Dai, Chunchun; Guo, Zhengrong; Zhang, Hongwei; Chang, Tienchong

    2016-08-14

    Motion conversion plays an irreplaceable role in a variety of machinery. Although many macroscopic motion converters have been widely used, it remains a challenge to convert motion at the nanoscale. Here we propose a nanoscale linear-to-linear motion converter, made of a flake-substrate system of graphene, which can convert the out-of-plane motion of the substrate into the in-plane motion of the flake. The curvature gradient induced van der Waals potential gradient between the flake and the substrate provides the driving force to achieve motion conversion. The proposed motion converter may have general implications for the design of nanomachinery and nanosensors.

  10. LINEAR COUNT-RATE METER

    DOEpatents

    Henry, J.J.

    1961-09-01

    A linear count-rate meter is designed to provide a highly linear output while receiving counting rates from one cycle per second to 100,000 cycles per second. Input pulses enter a linear discriminator and then are fed to a trigger circuit which produces positive pulses of uniform width and amplitude. The trigger circuit is connected to a one-shot multivibrator. The multivibrator output pulses have a selected width. Feedback means are provided for preventing transistor saturation in the multivibrator which improves the rise and decay times of the output pulses. The multivibrator is connected to a diode-switched, constant current metering circuit. A selected constant current is switched to an averaging circuit for each pulse received, and for a time determined by the received pulse width. The average output meter current is proportional to the product of the counting rate, the constant current, and the multivibrator output pulse width.

  11. Belos Block Linear Solvers Package

    2004-03-01

    Belos is an extensible and interoperable framework for large-scale, iterative methods for solving systems of linear equations with multiple right-hand sides. The motivation for this framework is to provide a generic interface to a collection of algorithms for solving large-scale linear systems. Belos is interoperable because both the matrix and vectors are considered to be opaque objects--only knowledge of the matrix and vectors via elementary operations is necessary. An implementation of Balos is accomplished viamore » the use of interfaces. One of the goals of Belos is to allow the user flexibility in specifying the data representation for the matrix and vectors and so leverage any existing software investment. The algorithms that will be included in package are Krylov-based linear solvers, like Block GMRES (Generalized Minimal RESidual) and Block CG (Conjugate-Gradient).« less

  12. QUANTUM OPTICS. Universal linear optics.

    PubMed

    Carolan, Jacques; Harrold, Christopher; Sparrow, Chris; Martín-López, Enrique; Russell, Nicholas J; Silverstone, Joshua W; Shadbolt, Peter J; Matsuda, Nobuyuki; Oguma, Manabu; Itoh, Mikitaka; Marshall, Graham D; Thompson, Mark G; Matthews, Jonathan C F; Hashimoto, Toshikazu; O'Brien, Jeremy L; Laing, Anthony

    2015-08-14

    Linear optics underpins fundamental tests of quantum mechanics and quantum technologies. We demonstrate a single reprogrammable optical circuit that is sufficient to implement all possible linear optical protocols up to the size of that circuit. Our six-mode universal system consists of a cascade of 15 Mach-Zehnder interferometers with 30 thermo-optic phase shifters integrated into a single photonic chip that is electrically and optically interfaced for arbitrary setting of all phase shifters, input of up to six photons, and their measurement with a 12-single-photon detector system. We programmed this system to implement heralded quantum logic and entangling gates, boson sampling with verification tests, and six-dimensional complex Hadamards. We implemented 100 Haar random unitaries with an average fidelity of 0.999 ± 0.001. Our system can be rapidly reprogrammed to implement these and any other linear optical protocol, pointing the way to applications across fundamental science and quantum technologies. PMID:26160375

  13. Design and performance of A 3He-free coincidence counter based on parallel plate boron-lined proportional technology

    DOE PAGESBeta

    Henzlova, D.; Menlove, H. O.; Marlow, J. B.

    2015-07-01

    Thermal neutron counters utilized and developed for deployment as non-destructive assay (NDA) instruments in the field of nuclear safeguards traditionally rely on 3He-based proportional counting systems. 3He-based proportional counters have provided core NDA detection capabilities for several decades and have proven to be extremely reliable with range of features highly desirable for nuclear facility deployment. Facing the current depletion of 3He gas supply and the continuing uncertainty of options for future resupply, a search for detection technologies that could provide feasible short-term alternative to 3He gas was initiated worldwide. As part of this effort, Los Alamos National Laboratory (LANL) designedmore » and built a 3He-free full scale thermal neutron coincidence counter based on boron-lined proportional technology. The boronlined technology was selected in a comprehensive inter-comparison exercise based on its favorable performance against safeguards specific parameters. This paper provides an overview of the design and initial performance evaluation of the prototype High Level Neutron counter – Boron (HLNB). The initial results suggest that current HLNB design is capable to provide ~80% performance of a selected reference 3He-based coincidence counter (High Level Neutron Coincidence Counter, HLNCC). Similar samples are expected to be measurable in both systems, however, slightly longer measurement times may be anticipated for large samples in HLNB. The initial evaluation helped to identify potential for further performance improvements via additional tailoring of boron-layer thickness.« less

  14. Terahertz mirage: Deflecting terahertz beams in an inhomogeneous artificial dielectric based on a parallel-plate waveguide

    NASA Astrophysics Data System (ADS)

    Mendis, Rajind; Liu, Jingbo; Mittleman, Daniel M.

    2012-09-01

    The field of metamaterials and the formalism of transformation optics have provided a prescription for constructing artificial dielectrics with unique properties such as light trapping and cloaking. Here, we describe a different approach to creating an inhomogeneous artificial medium, based on waveguide techniques, which does not rely on engineered subwavelength-scale components. We demonstrate a mirage effect in which an object several times larger than the selected wavelength is rendered invisible by bending a beam around it.

  15. A numerical analysis of forces exerted by laminar flow on spreading cells in a parallel plate flow chamber assay.

    PubMed

    Olivier, L A; Truskey, G A

    1993-10-01

    Exposure of spreading anchorage-dependent cells to laminar flow is a common technique to measure the strength of cell adhesion. Since cells protrude into the flow stream, the force exerted by the fluid on the cells is a function of cell shape. To assess the relationship between cell shape and the hydrodynamic force on adherent cells, we obtained numerical solutions of the velocity and stress fields around bovine aortic endothelial cells during various stages of spreading and calculated the force required to detach the cells. Morphometric parameters were obtained from light and scanning electron microscopy measurements. Cells were assumed to have a constant volume, but the surface area increased during spreading until the membrane was stretched taut. Two-dimensional models of steady flow were generated using the software packages ANSYS (mesh generation) and FIDAP (problem solution). The validity of the numerical results was tested by comparison with published results for a semicircle in contact with the surface. The drag force and torque were greatest for round cells making initial contact with the surface. During spreading, the drag force and torque declined by factors of 2 and 20, respectively. The calculated forces and moments were used in adhesion models to predict the wall shear stress at which the cells detached. Based upon published values for the bond force and receptor number, round cells should detach at shear stresses between 2.5 and 6 dyn/cm(2), whereas substantially higher stresses are needed to detach spreading and fully spread cells. Results from the simulations indicate that (1) the drag force varies little with cell shape whereas the torque is very sensitive to cell shape, and (2) the increase in the strength of adhesion during spreading is due to increased contact area and receptor densities within the contact area.

  16. Parallel-plate submicron gap formed by micromachined low-density pillars for near-field radiative heat transfer

    SciTech Connect

    Ito, Kota; Miura, Atsushi; Iizuka, Hideo; Toshiyoshi, Hiroshi

    2015-02-23

    Near-field radiative heat transfer has been a subject of great interest due to the applicability to thermal management and energy conversion. In this letter, a submicron gap between a pair of diced fused quartz substrates is formed by using micromachined low-density pillars to obtain both the parallelism and small parasitic heat conduction. The gap uniformity is validated by the optical interferometry at four corners of the substrates. The heat flux across the gap is measured in a steady-state and is no greater than twice of theoretically predicted radiative heat flux, which indicates that the parasitic heat conduction is suppressed to the level of the radiative heat transfer or less. The heat conduction through the pillars is modeled, and it is found to be limited by the thermal contact resistance between the pillar top and the opposing substrate surface. The methodology to form and evaluate the gap promotes the near-field radiative heat transfer to various applications such as thermal rectification, thermal modulation, and thermophotovoltaics.

  17. Parallel-plate flow chamber and continuous flow circuit to evaluate endothelial progenitor cells under laminar flow shear stress.

    PubMed

    Lane, Whitney O; Jantzen, Alexandra E; Carlon, Tim A; Jamiolkowski, Ryan M; Grenet, Justin E; Ley, Melissa M; Haseltine, Justin M; Galinat, Lauren J; Lin, Fu-Hsiung; Allen, Jason D; Truskey, George A; Achneck, Hardean E

    2012-01-01

    The overall goal of this method is to describe a technique to subject adherent cells to laminar flow conditions and evaluate their response to well quantifiable fluid shear stresses. Our flow chamber design and flow circuit (Fig. 1) contains a transparent viewing region that enables testing of cell adhesion and imaging of cell morphology immediately before flow (Fig. 11A, B), at various time points during flow (Fig. 11C), and after flow (Fig. 11D). These experiments are illustrated with human umbilical cord blood-derived endothelial progenitor cells (EPCs) and porcine EPCs. This method is also applicable to other adherent cell types, e.g. smooth muscle cells (SMCs) or fibroblasts. The chamber and all parts of the circuit are easily sterilized with steam autoclaving. In contrast to other chambers, e.g. microfluidic chambers, large numbers of cells (> 1 million depending on cell size) can be recovered after the flow experiment under sterile conditions for cell culture or other experiments, e.g. DNA or RNA extraction, or immunohistochemistry (Fig. 11E), or scanning electron microscopy. The shear stress can be adjusted by varying the flow rate of the perfusate, the fluid viscosity, or the channel height and width. The latter can reduce fluid volume or cell needs while ensuring that one-dimensional flow is maintained. It is not necessary to measure chamber height between experiments, since the chamber height does not depend on the use of gaskets, which greatly increases the ease of multiple experiments. Furthermore, the circuit design easily enables the collection of perfusate samples for analysis and/or quantification of metabolites secreted by cells under fluid shear stress exposure, e.g. nitric oxide (Fig. 12).

  18. Numerical analysis of natural convection for non-Newtonian fluid conveying nanoparticles between two vertical parallel plates

    NASA Astrophysics Data System (ADS)

    Sahebi, S. A. R.; Pourziaei, H.; Feizi, A. R.; Taheri, M. H.; Rostamiyan, Y.; Ganji, D. D.

    2015-12-01

    In this paper, natural convection of non-Newtonian bio-nanofluids flow between two vertical flat plates is investigated numerically. Sodium Alginate (SA) and Sodium Carboxymethyl Cellulose (SCMC) are considered as the base non-Newtonian fluid, and nanoparticles such as Titania ( TiO2 and Alumina ( Al2O3 were added to them. The effective thermal conductivity and viscosity of nanofluids are calculated through Maxwell-Garnetts (MG) and Brinkman models, respectively. A fourth-order Runge-Kutta numerical method (NUM) and three Weighted Residual Methods (WRMs), Collocation (CM), Galerkin (GM) and Least-Square Method (LSM) and Finite-Element Method (FEM), are used to solve the present problem. The influence of some physical parameters such as nanofluid volume friction on non-dimensional velocity and temperature profiles are discussed. The results show that SCMC- TiO2 has higher velocity and temperature values than other nanofluid structures.

  19. Relating the Stored Magnetic Energy of a Parallel-Plate Inductor to the Work of External Forces

    ERIC Educational Resources Information Center

    Gauthier, N.

    2007-01-01

    Idealized models are often used in introductory physics courses. For one, such models involve simple mathematics, which is a definite plus since complex mathematical manipulations quickly become an obstacle rather than a tool for a beginner. Idealized models facilitate a student's understanding and grasp of a given physical phenomenon, yet they…

  20. Numerical prediction for laminar forced convection heat transfer in parallel-plate channels with streamwise-periodic rod disturbances

    NASA Astrophysics Data System (ADS)

    Yuan, Zhong-Xian; Tao, Wen-Quan; Wang, Qiu-Wang

    1998-12-01

    A numerical study has been performed for the periodically fully-developed flow in two-dimensional channels with streamwise-periodic round disturbances on its two walls. To accurately describe the round disturbance boundary condition, a body fitted grid was used. The flow and heat transfer have been studied in the range of Reynolds number, Re=50-700, and Prandtl number Pr=0.71. The influences of disturbance parameters and Reynolds number on heat transfer and friction have been investigated in detail. Some of the solutions have been examined using both steady and unsteady finite difference schemes; and the same results have been obtained. The results show that different flow patterns can occur with different deployments of the disturbances. With appropriate configuration of the disturbances, the Nusselt number can reach a value four times greater than in a smooth channel at the same condition, with the penalty of a much greater pressure drop. On the other hand, if the disturbances are not deployed properly, augmentation of heat transfer cannot be acquired.

  1. Particle-in-cell simulation of multipactor discharge on a dielectric in a parallel-plate waveguide

    NASA Astrophysics Data System (ADS)

    Sakharov, A. S.; Ivanov, V. A.; Konyzhev, M. E.

    2016-06-01

    An original 2D3V (two-dimensional in coordinate space and three-dimensional in velocity space) particle-in-cell code has been developed for simulation of multipactor discharge on a dielectric in a parallelplate metal waveguide with allowance for secondary electron emission (SEE) from the dielectric surface and waveguide walls, finite temperature of secondary electrons, electron space charge, and elastic and inelastic scattering of electrons from the dielectric and metal surfaces. The code allows one to simulate all stages of the multipactor discharge, from the onset of the electron avalanche to saturation. It is shown that the threshold for the excitation of a single-surface multipactor on a dielectric placed in a low-profile waveguide with absorbing walls increases as compared to that in the case of an unbounded dielectric surface due to escape of electrons onto the waveguide walls. It is found that, depending on the microwave field amplitude and the SEE characteristics of the waveguide walls, the multipactor may operate in two modes. In the first mode, which takes place at relatively low microwave amplitudes, a single-surface multipactor develops only on the dielectric, the surface of which acquires a positively potential with respect to the waveguide walls. In the second mode, which occurs at sufficiently high microwave intensities, a single-surface multipactor on the dielectric and a two-surface multipactor between the waveguide walls operate simultaneously. In this case, both the dielectric surface and the interwall space acquire a negative potential. It is shown that electron scattering from the dielectric surface and waveguide walls results in the appearance of high-energy tails in the electron distribution function.

  2. Numerical modelling of the effect of dry air traces in a helium parallel plate dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Lazarou, C.; Belmonte, T.; Chiper, A. S.; Georghiou, G. E.

    2016-10-01

    A validated numerical model developed for the study of helium barrier discharges in the presence of dry air impurities is presented in this paper. The model was used to numerically investigate the influence of air traces on the evolution of the helium dielectric barrier discharge (DBD). The level of dry air used as impurity was in the range from 0 to 1500 ppm, which corresponds to the most commonly encountered range in atmospheric pressure discharge experiments. The results presented in this study clearly show that the plasma chemistry and consequently the discharge evolution is highly affected by the concentration level of impurities in the mixture. In particular, it was observed that air traces assist the discharge ignition at low concentration levels (~55 ppm), while on the other hand, they increase the burning voltage at higher concentration levels (~1000 ppm). Furthermore, it was found that the discharge symmetry during the voltage cycle highly depends on the concentration of air. For the interpretation of the results, a detailed analysis of the processes that occur in the discharge gap is performed and the main reaction pathways of ion production are described. Thanks to this approach, useful insight into the physics behind the evolution of the discharge is obtained.

  3. Temperature effects on the hydrophobic interaction of parallel plates in the framework of the probabilistic approach to hydrogen bonding.

    PubMed

    Djikaev, Y S; Ruckenstein, Eli

    2010-03-15

    Recently, we have proposed a probabilistic approach to examine the effect of water-water hydrogen bond networks around two foreign hydrophobic particles (immersed in water) on their interaction. Because of the proximity to a particle, a water molecule in the first hydration shell around it forms a smaller number of hydrogen bonds compared to a bulk molecule. The probabilistic approach allows one to analytically evaluate the former number if the latter is known (which is usually the case). On the other hand, the former bonds may be slightly (energetically) enhanced compared to the latter if at least one of the two bonded molecules lie in the first hydration shell and does not form a bond with a nearest neighbor site on the particle surface. When two hydrophobic particles are sufficiently close to each other, the overlap of boundary water-water hydrogen bond networks gives rise to an additional attractive force between them. In this paper we use the probabilistic approach to examine the effect of solvent temperature on the solvent-mediated interaction of two hydrophobic particles. Their hydrophobic attraction is affected by the solvent (water) temperature because the density of the solvent, strength of a hydrogen bonds, and number of hydrogen bonds per molecule are sensitive thereto (the pressure effects are not considered here). The probabilistic approach predicts that the solvent-mediated attraction of hydrophobic solutes is driven by the favorable entropic component ("-temperature x entropy") of the potential of mean force that dominates the unfavorable energetic component. This attraction decreases as the temperature increases.

  4. Vanilla technicolor at linear colliders

    NASA Astrophysics Data System (ADS)

    Frandsen, Mads T.; Järvinen, Matti; Sannino, Francesco

    2011-08-01

    We analyze the reach of linear colliders for models of dynamical electroweak symmetry breaking. We show that linear colliders can efficiently test the compositeness scale, identified with the mass of the new spin-one resonances, until the maximum energy in the center of mass of the colliding leptons. In particular we analyze the Drell-Yan processes involving spin-one intermediate heavy bosons decaying either leptonically or into two standard model gauge bosons. We also analyze the light Higgs production in association with a standard model gauge boson stemming also from an intermediate spin-one heavy vector.

  5. Characterizations of linear sufficient statistics

    NASA Technical Reports Server (NTRS)

    Peters, B. C., Jr.; Reoner, R.; Decell, H. P., Jr.

    1977-01-01

    A surjective bounded linear operator T from a Banach space X to a Banach space Y must be a sufficient statistic for a dominated family of probability measures defined on the Borel sets of X. These results were applied, so that they characterize linear sufficient statistics for families of the exponential type, including as special cases the Wishart and multivariate normal distributions. The latter result was used to establish precisely which procedures for sampling from a normal population had the property that the sample mean was a sufficient statistic.

  6. Linear Corrugating - Final Technical Report

    SciTech Connect

    Lloyd Chapman

    2000-05-23

    Linear Corrugating is a process for the manufacture of corrugated containers in which the flutes of the corrugated medium are oriented in the Machine Direction (MD) of the several layers of paper used. Conversely, in the conventional corrugating process the flutes are oriented at right angles to the MD in the Cross Machine Direction (CD). Paper is stronger in MD than in CD. Therefore, boxes made using the Linear Corrugating process are significantly stronger-in the prime strength criteria, Box Compression Test (BCT) than boxes made conventionally. This means that using Linear Corrugating boxes can be manufactured to BCT equaling conventional boxes but containing 30% less fiber. The corrugated container industry is a large part of the U.S. economy, producing over 40 million tons annually. For such a large industry, the potential savings of Linear Corrugating are enormous. The grant for this project covered three phases in the development of the Linear Corrugating process: (1) Production and evaluation of corrugated boxes on commercial equipment to verify that boxes so manufactured would have enhanced BCT as proposed in the application; (2) Production and evaluation of corrugated boxes made on laboratory equipment using combined board from (1) above but having dual manufactures joints (glue joints). This box manufacturing method (Dual Joint) is proposed to overcome box perimeter limitations of the Linear Corrugating process; (3) Design, Construction, Operation and Evaluation of an engineering prototype machine to form flutes in corrugating medium in the MD of the paper. This operation is the central requirement of the Linear Corrugating process. Items I and II were successfully completed, showing predicted BCT increases from the Linear Corrugated boxes and significant strength improvement in the Dual Joint boxes. The Former was constructed and operated successfully using kraft linerboard as the forming medium. It was found that tensile strength and stretch

  7. Linear summation of cat motor cortex outputs.

    PubMed

    Ethier, Christian; Brizzi, Laurent; Darling, Warren G; Capaday, Charles

    2006-05-17

    Recruitment of movement-related muscle synergies involves the functional linking of motor cortical points. We asked how the outputs of two simultaneously stimulated motor cortical points would interact. To this end, experiments were done in ketamine-anesthetized cats. When prolonged (e.g., 500 ms) trains of intracortical microstimulation were applied in the primary motor cortex, stimulus currents as low as 10-20 microA evoked coordinated movements of the contralateral forelimb. Paw kinematics in three dimensions and the electromyographic (EMG) activity of eight muscles were simultaneously recorded. We show that the EMG outputs of two cortical points simultaneously stimulated are additive. The movements were represented as displacement vectors pointing from initial to final paw position. The displacement vectors resulting from simultaneous stimulation of two cortical points pointed in nearly the same direction as the algebraic resultant vector. Linear summation of outputs was also found when inhibition at one of the cortical points was reduced by GABAA receptor antagonists. A simple principle emerges from these results. Notwithstanding the underlying complex neuronal circuitry, motor cortex outputs combine nearly linearly in terms of movement direction and muscle activation patterns. Importantly, simultaneous activation does not change the nature of the output at each point. An additional implication is that not all possible movements need be explicitly represented in the motor cortex; a large number of different movements may be synthesized from a smaller repertoire.

  8. Broader Impacts of the International Linear Collider

    SciTech Connect

    Bardeen, M.; Ruchti, R.

    2005-08-01

    Large-scale scientific endeavors such as the International Linear Collider Project can have a lasting impact on education and outreach to our society. The ILC will provide a discovery platform for frontier physical science and it will also provide a discovery platform for broader impacts and social science. The importance of Broader Impacts of Science in general and the ILC in particular are described. Additionally, a synopsis of education and outreach activities carried out as an integral part of the Snowmass ILC Workshop is provided.

  9. Rf power sources for linear colliders

    SciTech Connect

    Allen, M.A.; Callin, R.S.; Caryotakis, G.; Deruyter, H.; Eppley, K.R.; Fant, K.S.; Farkas, Z.D.; Fowkes, W.R.; Hoag, H.A.; Feinstein, J.; Ko, K.; Koontz, R.F.; Kroll, N.M.; Lavine, T.L.; Lee, T.G.; Loew, G.A.; Miller, R.H.; Nelson, E.M.; Ruth, R.D.; Vlieks, A.E.; Wang, J.W.; Wilson, P.B. ); Boyd, J.K.; Houk, T.; Ryne, R.D.; Westenskow, G.A.; Yu, S.S. (Lawrence Live

    1990-06-01

    The next generation of linear colliders requires peak power sources of over 200 MW per meter at frequencies above 10 GHz at pulse widths of less than 100 nsec. Several power sources are under active development, including a conventional klystron with rf pulse compression, a relativistic klystron (RK) and a crossed-field amplifier. Power from one of these has energized a 0.5 meter two- section High Gradient Accelerator (HGA) and accelerated a beam at over 80 MeV meter. Results of tests with these experimental devices are presented here.

  10. Linear Programming Applied to a Simple Circuit.

    ERIC Educational Resources Information Center

    Boyd, J. N.; Raychowdhury, P. N.

    1980-01-01

    Discusses what is meant by a linear program and states and illustrates two of the theorems upon which the methods of linear programing rest. This description is intended as an introduction to linear programing of physics students. (HM)

  11. New directions in linear accelerators

    SciTech Connect

    Jameson, R.A.

    1984-01-01

    Current work on linear particle accelerators is placed in historical and physics contexts, and applications driving the state of the art are discussed. Future needs and the ways they may force development are outlined in terms of exciting R and D challenges presented to today's accelerator designers. 23 references, 7 figures.

  12. Linear electric field mass spectrometry

    SciTech Connect

    McComas, D.J.; Nordholt, J.E.

    1991-03-29

    A mass spectrometer is described having a low weight and low power requirement, for use in space. It can be used to analyze the ionized particles in the region of the spacecraft on which it is mounted. High mass resolution measurements are made by timing ions moving through a gridless cylindrically sysmetric linear electric field.

  13. Linear electric field mass spectrometry

    DOEpatents

    McComas, D.J.; Nordholt, J.E.

    1992-12-01

    A mass spectrometer and methods for mass spectrometry are described. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field. 8 figs.

  14. Linear electric field mass spectrometry

    DOEpatents

    McComas, David J.; Nordholt, Jane E.

    1992-01-01

    A mass spectrometer and methods for mass spectrometry. The apparatus is compact and of low weight and has a low power requirement, making it suitable for use on a space satellite and as a portable detector for the presence of substances. High mass resolution measurements are made by timing ions moving through a gridless cylindrically symmetric linear electric field.

  15. Linearization of Conservative Nonlinear Oscillators

    ERIC Educational Resources Information Center

    Belendez, A.; Alvarez, M. L.; Fernandez, E.; Pascual, I.

    2009-01-01

    A linearization method of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force which allows us to obtain a frequency-amplitude relation which is valid not only for small but also for large amplitudes and, sometimes, for…

  16. Feedback Systems for Linear Colliders

    SciTech Connect

    1999-04-12

    Feedback systems are essential for stable operation of a linear collider, providing a cost-effective method for relaxing tight tolerances. In the Stanford Linear Collider (SLC), feedback controls beam parameters such as trajectory, energy, and intensity throughout the accelerator. A novel dithering optimization system which adjusts final focus parameters to maximize luminosity contributed to achieving record performance in the 1997-98 run. Performance limitations of the steering feedback have been investigated, and improvements have been made. For the Next Linear Collider (NLC), extensive feedback systems are planned as an integral part of the design. Feedback requirements for JLC (the Japanese Linear Collider) are essentially identical to NLC; some of the TESLA requirements are similar but there are significant differences. For NLC, algorithms which incorporate improvements upon the SLC implementation are being prototyped. Specialized systems for the damping rings, rf and interaction point will operate at high bandwidth and fast response. To correct for the motion of individual bunches within a train, both feedforward and feedback systems are planned. SLC experience has shown that feedback systems are an invaluable operational tool for decoupling systems, allowing precision tuning, and providing pulse-to-pulse diagnostics. Feedback systems for the NLC will incorporate the key SLC features and the benefits of advancing technologies.

  17. Parameterized Linear Longitudinal Airship Model

    NASA Technical Reports Server (NTRS)

    Kulczycki, Eric; Elfes, Alberto; Bayard, David; Quadrelli, Marco; Johnson, Joseph

    2010-01-01

    A parameterized linear mathematical model of the longitudinal dynamics of an airship is undergoing development. This model is intended to be used in designing control systems for future airships that would operate in the atmospheres of Earth and remote planets. Heretofore, the development of linearized models of the longitudinal dynamics of airships has been costly in that it has been necessary to perform extensive flight testing and to use system-identification techniques to construct models that fit the flight-test data. The present model is a generic one that can be relatively easily specialized to approximate the dynamics of specific airships at specific operating points, without need for further system identification, and with significantly less flight testing. The approach taken in the present development is to merge the linearized dynamical equations of an airship with techniques for estimation of aircraft stability derivatives, and to thereby make it possible to construct a linearized dynamical model of the longitudinal dynamics of a specific airship from geometric and aerodynamic data pertaining to that airship. (It is also planned to develop a model of the lateral dynamics by use of the same methods.) All of the aerodynamic data needed to construct the model of a specific airship can be obtained from wind-tunnel testing and computational fluid dynamics

  18. Linear or Exponential Number Lines

    ERIC Educational Resources Information Center

    Stafford, Pat

    2011-01-01

    Having decided to spend some time looking at one's understanding of numbers, the author was inspired by "Alex's Adventures in Numberland," by Alex Bellos to look at one's innate appreciation of number. Bellos quotes research studies suggesting that an individual's natural appreciation of numbers is more likely to be exponential rather than linear,…

  19. Non-linear mirror instability

    NASA Astrophysics Data System (ADS)

    Rincon, F.; Schekochihin, A. A.; Cowley, S. C.

    2015-02-01

    Slow dynamical changes in magnetic-field strength and invariance of the particles' magnetic moments generate ubiquitous pressure anisotropies in weakly collisional, magnetized astrophysical plasmas. This renders them unstable to fast, small-scale mirror and firehose instabilities, which are capable of exerting feedback on the macroscale dynamics of the system. By way of a new asymptotic theory of the early non-linear evolution of the mirror instability in a plasma subject to slow shearing or compression, we show that the instability does not saturate quasi-linearly at a steady, low-amplitude level. Instead, the trapping of particles in small-scale mirrors leads to non-linear secular growth of magnetic perturbations, δB/B ∝ t2/3. Our theory explains recent collisionless simulation results, provides a prediction of the mirror evolution in weakly collisional plasmas and establishes a foundation for a theory of non-linear mirror dynamics with trapping, valid up to δB/B = O(1).

  20. Phycotoxicity of linear alkylbenzene sulfonate

    SciTech Connect

    Chawla, G.; Viswanathan, P.N.; Devi, S.

    1988-04-01

    Dose- and time-dependent effects of linear alkylbenzene sulfonate, a major component of synthetic detergent, to the blue-green alga Nostoc muscorum, were studied under laboratory conditions. Toxicity was evident, at doses above 0.001%, from the decrease in biomass, heterocyst number, and protein content and pathomorphological alterations.

  1. Virtual Estimator for Piecewise Linear Systems Based on Observability Analysis

    PubMed Central

    Morales-Morales, Cornelio; Adam-Medina, Manuel; Cervantes, Ilse; Vela-Valdés and, Luis G.; García Beltrán, Carlos Daniel

    2013-01-01

    This article proposes a virtual sensor for piecewise linear systems based on observability analysis that is in function of a commutation law related with the system's outpu. This virtual sensor is also known as a state estimator. Besides, it presents a detector of active mode when the commutation sequences of each linear subsystem are arbitrary and unknown. For the previous, this article proposes a set of virtual estimators that discern the commutation paths of the system and allow estimating their output. In this work a methodology in order to test the observability for piecewise linear systems with discrete time is proposed. An academic example is presented to show the obtained results. PMID:23447007

  2. T-Slide Linear Actuators

    NASA Technical Reports Server (NTRS)

    Vranish, John

    2009-01-01

    T-slide linear actuators use gear bearing differential epicyclical transmissions (GBDETs) to directly drive a linear rack, which, in turn, performs the actuation. Conventional systems use a rotary power source in conjunction with a nut and screw to provide linear motion. Non-back-drive properties of GBDETs make the new actuator more direct and simpler. Versions of this approach will serve as a long-stroke, ultra-precision, position actuator for NASA science instruments, and as a rugged, linear actuator for NASA deployment duties. The T slide can operate effectively in the presence of side forces and torques. Versions of the actuator can perform ultra-precision positioning. A basic T-slide actuator is a long-stroke, rack-and-pinion linear actuator that, typically, consists of a T-slide, several idlers, a transmission to drive the slide (powered by an electric motor) and a housing that holds the entire assembly. The actuator is driven by gear action on its top surface, and is guided and constrained by gear-bearing idlers on its other two parallel surfaces. The geometry, implemented with gear-bearing technology, is particularly effective. An electronic motor operating through a GBDET can directly drive the T slide against large loads, as a rack and pinion linear actuator, with no break and no danger of back driving. The actuator drives the slide into position and stops. The slide holes position with power off and no brake, regardless of load. With the T slide configuration, this GBDET has an entire T-gear surface on which to operate. The GB idlers coupling the other two T slide parallel surfaces to their housing counterpart surfaces provide constraints in five degrees-of-freedom and rolling friction in the direction of actuation. Multiple GB idlers provide roller bearing strength sufficient to support efficient, rolling friction movement, even in the presence of large, resisting forces. T-slide actuators can be controlled using the combination of an off

  3. Synaptic dynamics: linear model and adaptation algorithm.

    PubMed

    Yousefi, Ali; Dibazar, Alireza A; Berger, Theodore W

    2014-08-01

    In this research, temporal processing in brain neural circuitries is addressed by a dynamic model of synaptic connections in which the synapse model accounts for both pre- and post-synaptic processes determining its temporal dynamics and strength. Neurons, which are excited by the post-synaptic potentials of hundred of the synapses, build the computational engine capable of processing dynamic neural stimuli. Temporal dynamics in neural models with dynamic synapses will be analyzed, and learning algorithms for synaptic adaptation of neural networks with hundreds of synaptic connections are proposed. The paper starts by introducing a linear approximate model for the temporal dynamics of synaptic transmission. The proposed linear model substantially simplifies the analysis and training of spiking neural networks. Furthermore, it is capable of replicating the synaptic response of the non-linear facilitation-depression model with an accuracy better than 92.5%. In the second part of the paper, a supervised spike-in-spike-out learning rule for synaptic adaptation in dynamic synapse neural networks (DSNN) is proposed. The proposed learning rule is a biologically plausible process, and it is capable of simultaneously adjusting both pre- and post-synaptic components of individual synapses. The last section of the paper starts with presenting the rigorous analysis of the learning algorithm in a system identification task with hundreds of synaptic connections which confirms the learning algorithm's accuracy, repeatability and scalability. The DSNN is utilized to predict the spiking activity of cortical neurons and pattern recognition tasks. The DSNN model is demonstrated to be a generative model capable of producing different cortical neuron spiking patterns and CA1 Pyramidal neurons recordings. A single-layer DSNN classifier on a benchmark pattern recognition task outperforms a 2-Layer Neural Network and GMM classifiers while having fewer numbers of free parameters and

  4. Muscle sympathetic outflow during horizontal linear acceleration in humans.

    PubMed

    Cui, J; Iwase, S; Mano, T; Katayama, N; Mori, S

    2001-08-01

    To elucidate the effects of linear acceleration on muscle sympathetic nerve activity (MSNA) in humans, 16 healthy men were tested in a linear accelerator. Measurements of MSNA, electrocardiogram, blood pressure, and thoracic impedance were undertaken during linear acceleration. Sinusoidal linear acceleration with peak values at +/-0.10, +/-0.15, and +/-0.20 G was applied in anteroposterior (+/-G(x), n = 10) or lateral (+/-G(y), n = 6) directions. The total activity and burst rate of MSNA decreased significantly during forward, backward, left, or right linear accelerations. The total activity of MSNA decreased to 50.5 +/- 6.9, 52.5 +/- 4.4, 71.2 +/- 9.6, and 67.6 +/- 8.2% from the baselines (100%) during linear accelerations with peak values at +/-0.20 G in the four directions, respectively. These results suggest that dynamic stimulation of otolith organs in horizontal directions in humans might inhibit MSNA directly in order to quickly redistribute blood to muscles during postural reflexes induced by passive movement, which supports the concept that the vestibular system contributes to sympathetic regulation in humans.

  5. Superstructure of linear duplex DNA.

    PubMed Central

    Vollenweider, H J; Koller, T; Parello, J; Sogo, J M

    1976-01-01

    The superstructure of a covalently closed circular DNA (of bacteriophage PM 2) was compared by electron microscopy with that of a linear duplex DNA (of bacteriophage T7) when ionic strength and benzyldimethylalkylammonium chloride concentration were varied. In parallel studies the sedimentation behavior of these DNAs was studied by analytical ultracentrifugation, but for technical reasons these had to be without benzyldimethylalkylammonium chloride. By combining the information from the two methods one has to conclude that with increasing ionic strength the linear duplex T7 DNA spontaneously forms a structure similar to that of the superhelical structure of closed circular PM 2 DNA. The superstructure is destroyed under premelting conditions and in the presence of an excess of ethidium bromide. Images PMID:1069302

  6. Linear regression in astronomy. II

    NASA Technical Reports Server (NTRS)

    Feigelson, Eric D.; Babu, Gutti J.

    1992-01-01

    A wide variety of least-squares linear regression procedures used in observational astronomy, particularly investigations of the cosmic distance scale, are presented and discussed. The classes of linear models considered are (1) unweighted regression lines, with bootstrap and jackknife resampling; (2) regression solutions when measurement error, in one or both variables, dominates the scatter; (3) methods to apply a calibration line to new data; (4) truncated regression models, which apply to flux-limited data sets; and (5) censored regression models, which apply when nondetections are present. For the calibration problem we develop two new procedures: a formula for the intercept offset between two parallel data sets, which propagates slope errors from one regression to the other; and a generalization of the Working-Hotelling confidence bands to nonstandard least-squares lines. They can provide improved error analysis for Faber-Jackson, Tully-Fisher, and similar cosmic distance scale relations.

  7. Spatial processes in linear ordering.

    PubMed

    von Hecker, Ulrich; Klauer, Karl Christoph; Wolf, Lukas; Fazilat-Pour, Masoud

    2016-07-01

    Memory performance in linear order reasoning tasks (A > B, B > C, C > D, etc.) shows quicker, and more accurate responses to queries on wider (AD) than narrower (AB) pairs on a hypothetical linear mental model (A - B - C - D). While indicative of an analogue representation, research so far did not provide positive evidence for spatial processes in the construction of such models. In a series of 7 experiments we report such evidence. Participants respond quicker when the dominant element in a pair is presented on the left (or top) rather than on the right (or bottom). The left-anchoring tendency reverses in a sample with Farsi background (reading/writing from right to left). Alternative explanations and confounds are tested. A theoretical model is proposed that integrates basic assumptions about acquired reading/writing habits as a scaffold for spatial simulation, and primacy/dominance representation within such spatial simulations. (PsycINFO Database Record PMID:26641448

  8. Linear inflation from quartic potential

    NASA Astrophysics Data System (ADS)

    Kannike, Kristjan; Racioppi, Antonio; Raidal, Martti

    2016-01-01

    We show that if the inflaton has a non-minimal coupling to gravity and the Planck scale is dynamically generated, the results of Coleman-Weinberg inflation are confined in between two attractor solutions: quadratic inflation, which is ruled out by the recent measurements, and linear inflation which, instead, is in the experimental allowed region. The minimal scenario has only one free parameter — the inflaton's non-minimal coupling to gravity — that determines all physical parameters such as the tensor-to-scalar ratio and the reheating temperature of the Universe. Should the more precise future measurements of inflationary parameters point towards linear inflation, further interest in scale-invariant scenarios would be motivated.

  9. Is a highly linear relationship between the dose of quercetin and the pharmacological effect possible? - a comment on Liu, et al. Evaluation of antioxidant and immunity activities of quercetin in isoproterenol-treated rats. Molecules 2012, 17, 4281-4291.

    PubMed

    Mladěnka, Přemysl; Hrdina, Radomír; Filipský, Tomáš; Ríha, Michal; Palicka, Vladimir

    2014-07-07

    We wish to offer some comments on the article by H. Liu et al. entitled "Evaluation of antioxidant and immunity activities of quercetin in isoproterenol-treated rats", published in Molecules in 2012 [1]. [...].

  10. Positive fractional linear electrical circuits

    NASA Astrophysics Data System (ADS)

    Kaczorek, Tadeusz

    2013-10-01

    The positive fractional linear systems and electrical circuits are addressed. New classes of fractional asymptotically stable and unstable electrical circuits are introduced. The Caputo and Riemann-Liouville definitions of fractional derivatives are used to analysis of the positive electrical circuits composed of resistors, capacitors, coils and voltage (current) sources. The positive fractional electrical and specially unstable different types electrical circuits are analyzed. Some open problems are formulated.

  11. Segmented rail linear induction motor

    DOEpatents

    Cowan, Jr., Maynard; Marder, Barry M.

    1996-01-01

    A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces.

  12. Segmented rail linear induction motor

    DOEpatents

    Cowan, M. Jr.; Marder, B.M.

    1996-09-03

    A segmented rail linear induction motor has a segmented rail consisting of a plurality of nonferrous electrically conductive segments aligned along a guideway. The motor further includes a carriage including at least one pair of opposed coils fastened to the carriage for moving the carriage. A power source applies an electric current to the coils to induce currents in the conductive surfaces to repel the coils from adjacent edges of the conductive surfaces. 6 figs.

  13. Logistic systems with linear feedback

    NASA Astrophysics Data System (ADS)

    Son, Leonid; Shulgin, Dmitry; Ogluzdina, Olga

    2016-08-01

    A wide variety of systems may be described by specific dependence, which is known as logistic curve, or S-curve, between the internal characteristic and the external parameter. Linear feedback between these two values may be suggested for a wide set of systems also. In present paper, we suggest a bifurcation behavior for systems with both features, and discuss it for two cases, which are the Ising magnet in external field, and the development of manufacturing enterprise.

  14. Precision linear ramp function generator

    DOEpatents

    Jatko, W. Bruce; McNeilly, David R.; Thacker, Louis H.

    1986-01-01

    A ramp function generator is provided which produces a precise linear ramp unction which is repeatable and highly stable. A derivative feedback loop is used to stabilize the output of an integrator in the forward loop and control the ramp rate. The ramp may be started from a selected baseline voltage level and the desired ramp rate is selected by applying an appropriate constant voltage to the input of the integrator.

  15. Precision linear ramp function generator

    DOEpatents

    Jatko, W.B.; McNeilly, D.R.; Thacker, L.H.

    1984-08-01

    A ramp function generator is provided which produces a precise linear ramp function which is repeatable and highly stable. A derivative feedback loop is used to stabilize the output of an integrator in the forward loop and control the ramp rate. The ramp may be started from a selected baseline voltage level and the desired ramp rate is selected by applying an appropriate constant voltage to the input of the integrator.

  16. Cast dielectric composite linear accelerator

    DOEpatents

    Sanders, David M.; Sampayan, Stephen; Slenes, Kirk; Stoller, H. M.

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  17. Rf-driver linear colliders

    SciTech Connect

    Wilson, P.B.

    1987-05-01

    The next generation of linear collider after the SLC (Stanford Linear Collider) will probably have an energy in the range 300 GeV-1 TeV per linac. A number of exotic accelerating schemes, such as laser and plasma acceleration, have been proposed for linear colliders of the far future. However, the technology which is most mature and which could lead to a collider in the above energy range in the relatively near future is the rf-driven linac, in which externally produced rf is fed into a more or less conventional metallic accelerating structure. Two basic technologies have been proposed for producing the required high peak rf power: discrete microwave power sources, and various two-beam acceleration schemes in which the rf is produced by a high current driving beam running parallel to the main accelerator. The current status of experimental and analytic work on both the discrete source and the two-beam methods for producing rf is discussed. The implications of beam-beam related effects (luminosity, disruption and beamstrahlung) for the design of rf-driven colliders are also considered.

  18. BLAS- BASIC LINEAR ALGEBRA SUBPROGRAMS

    NASA Technical Reports Server (NTRS)

    Krogh, F. T.

    1994-01-01

    The Basic Linear Algebra Subprogram (BLAS) library is a collection of FORTRAN callable routines for employing standard techniques in performing the basic operations of numerical linear algebra. The BLAS library was developed to provide a portable and efficient source of basic operations for designers of programs involving linear algebraic computations. The subprograms available in the library cover the operations of dot product, multiplication of a scalar and a vector, vector plus a scalar times a vector, Givens transformation, modified Givens transformation, copy, swap, Euclidean norm, sum of magnitudes, and location of the largest magnitude element. Since these subprograms are to be used in an ANSI FORTRAN context, the cases of single precision, double precision, and complex data are provided for. All of the subprograms have been thoroughly tested and produce consistent results even when transported from machine to machine. BLAS contains Assembler versions and FORTRAN test code for any of the following compilers: Lahey F77L, Microsoft FORTRAN, or IBM Professional FORTRAN. It requires the Microsoft Macro Assembler and a math co-processor. The PC implementation allows individual arrays of over 64K. The BLAS library was developed in 1979. The PC version was made available in 1986 and updated in 1988.

  19. Non-Linear Dynamics of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.

    2015-04-01

    Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average: 2-10x is possible Results of driven N-body systems by Stuart Robbins: Even unforced rings show large variations; Forcing triggers aggregation; Some limit cycles and phase lags seen, but not always as predicted by predator-prey model. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like 'straw' that can explain the halo structure and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; Surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km); We propose 'straw'. Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing. Ring dynamics and history implications: Moon

  20. Non-Linear Dynamics of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.

    2015-10-01

    Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average: 2-10x is possible. Results of driven N-body systems by Stuart Robbins: Even unforced rings show large variations; Forcing triggers aggregation; Some limit cycles and phase lags seen, but not always as predicted by predator-prey model. Summary of Halo Results: A predatorprey model for ring dynamics produces transient structures like 'straw' that can explain the halo structure and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; Surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km); We propose 'straw'. Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing. Ring dynamics and history implications: Moon

  1. Linear summation of outputs in a balanced network model of motor cortex

    PubMed Central

    Capaday, Charles; van Vreeswijk, Carl

    2015-01-01

    Given the non-linearities of the neural circuitry's elements, we would expect cortical circuits to respond non-linearly when activated. Surprisingly, when two points in the motor cortex are activated simultaneously, the EMG responses are the linear sum of the responses evoked by each of the points activated separately. Additionally, the corticospinal transfer function is close to linear, implying that the synaptic interactions in motor cortex must be effectively linear. To account for this, here we develop a model of motor cortex composed of multiple interconnected points, each comprised of reciprocally connected excitatory and inhibitory neurons. We show how non-linearities in neuronal transfer functions are eschewed by strong synaptic interactions within each point. Consequently, the simultaneous activation of multiple points results in a linear summation of their respective outputs. We also consider the effects of reduction of inhibition at a cortical point when one or more surrounding points are active. The network response in this condition is linear over an approximately two- to three-fold decrease of inhibitory feedback strength. This result supports the idea that focal disinhibition allows linear coupling of motor cortical points to generate movement related muscle activation patterns; albeit with a limitation on gain control. The model also explains why neural activity does not spread as far out as the axonal connectivity allows, whilst also explaining why distant cortical points can be, nonetheless, functionally coupled by focal disinhibition. Finally, we discuss the advantages that linear interactions at the cortical level afford to motor command synthesis. PMID:26097452

  2. Microfluidic rheology of active particle suspensions: Kinetic theory.

    PubMed

    Alonso-Matilla, Roberto; Ezhilan, Barath; Saintillan, David

    2016-07-01

    We analyze the effective rheology of a dilute suspension of self-propelled slender particles confined between two infinite parallel plates and subject to a pressure-driven flow. We use a continuum kinetic model to describe the configuration of the particles in the system, in which the disturbance flows induced by the swimmers are taken into account, and use it to calculate estimates of the suspension viscosity for a range of channel widths and flow strengths typical of microfluidic experiments. Our results are in agreement with previous bulk models, and in particular, demonstrate that the effect of activity is strongest at low flow rates, where pushers tend to decrease the suspension viscosity whereas pullers enhance it. In stronger flows, dissipative stresses overcome the effects of activity leading to increased viscosities followed by shear-thinning. The effects of confinement and number density are also analyzed, and our results confirm the apparent transition to superfluidity reported in recent experiments on pusher suspensions at intermediate densities. We also derive an approximate analytical expression for the effective viscosity in the limit of weak flows and wide channels, and demonstrate good agreement between theory and numerical calculations.

  3. Fractional non-linear modelling of ultracapacitors

    NASA Astrophysics Data System (ADS)

    Bertrand, Nicolas; Sabatier, Jocelyn; Briat, Olivier; Vinassa, Jean-Michel

    2010-05-01

    In this paper, it is demonstrated that an ultracapacitor exhibits a non-linear behaviour in relation to the operating voltage. A set of fractional order linear systems resulting from a frequency analysis of the ultracapacitor at various operating points is first obtained. Then, a non-linear model is deduced from the linear systems set, so that its Taylor linearization around the considered operating points (for the frequency analysis), produces the linear system set. The resulting non-linear model is validated on a Hybrid Electric Vehicle (HEV) application.

  4. Inside of the Linear Relation between Dependent and Independent Variables

    PubMed Central

    Jäntschi, Lorentz; Pruteanu, Lavinia L.; Cozma, Alina C.; Bolboacă, Sorana D.

    2015-01-01

    Simple and multiple linear regression analyses are statistical methods used to investigate the link between activity/property of active compounds and the structural chemical features. One assumption of the linear regression is that the errors follow a normal distribution. This paper introduced a new approach to solving the simple linear regression in which no assumptions about the distribution of the errors are made. The proposed approach maximizes the probability of observing the event according to the random error. The use of the proposed approach is illustrated in ten classes of compounds with different activities or properties. The proposed method proved reliable and was showed to fit properly the observed data compared to the convenient approach of normal distribution of the errors. PMID:26101543

  5. Inside of the Linear Relation between Dependent and Independent Variables.

    PubMed

    Jäntschi, Lorentz; Pruteanu, Lavinia L; Cozma, Alina C; Bolboacă, Sorana D

    2015-01-01

    Simple and multiple linear regression analyses are statistical methods used to investigate the link between activity/property of active compounds and the structural chemical features. One assumption of the linear regression is that the errors follow a normal distribution. This paper introduced a new approach to solving the simple linear regression in which no assumptions about the distribution of the errors are made. The proposed approach maximizes the probability of observing the event according to the random error. The use of the proposed approach is illustrated in ten classes of compounds with different activities or properties. The proposed method proved reliable and was showed to fit properly the observed data compared to the convenient approach of normal distribution of the errors.

  6. Non-linear HRV indices under autonomic nervous system blockade.

    PubMed

    Bolea, Juan; Pueyo, Esther; Laguna, Pablo; Bailón, Raquel

    2014-01-01

    Heart rate variability (HRV) has been studied as a non-invasive technique to characterize the autonomic nervous system (ANS) regulation of the heart. Non-linear methods based on chaos theory have been used during the last decades as markers for risk stratification. However, interpretation of these nonlinear methods in terms of sympathetic and parasympathetic activity is not fully established. In this work we study linear and non-linear HRV indices during ANS blockades in order to assess their relation with sympathetic and parasympathetic activities. Power spectral content in low frequency (0.04-0.15 Hz) and high frequency (0.15-0.4 Hz) bands of HRV, as well as correlation dimension, sample and approximate entropies were computed in a database of subjects during single and dual ANS blockade with atropine and/or propranolol. Parasympathetic blockade caused a significant decrease in the low and high frequency power of HRV, as well as in correlation dimension and sample and approximate entropies. Sympathetic blockade caused a significant increase in approximate entropy. Sympathetic activation due to postural change from supine to standing caused a significant decrease in all the investigated non-linear indices and a significant increase in the normalized power in the low frequency band. The other investigated linear indices did not show significant changes. Results suggest that parasympathetic activity has a direct relation with sample and approximate entropies.

  7. Activities.

    ERIC Educational Resources Information Center

    Kincaid, Charlene; And Others

    1993-01-01

    Presents an activity in which students collect and organize data from a real-world simulation of the scientific concept of half life. Students collect data using a marble sifter, analyze the data using a graphing calculator, and determine an appropriate mathematical model. Includes reproducible worksheets. (MDH)

  8. Activities.

    ERIC Educational Resources Information Center

    Mathematics Teacher, 1982

    1982-01-01

    The material presented is designed to help students explore geometric patterns involving Fibonnaci numbers and the golden ratio, and to aid in review of basic geometry skills. Worksheet masters intended for duplication are provided. Suggestions are made of possible classroom extensions to the initial activities. (MP)

  9. Nonferromagnetic linear variable differential transformer

    DOEpatents

    Ellis, James F.; Walstrom, Peter L.

    1977-06-14

    A nonferromagnetic linear variable differential transformer for accurately measuring mechanical displacements in the presence of high magnetic fields is provided. The device utilizes a movable primary coil inside a fixed secondary coil that consists of two series-opposed windings. Operation is such that the secondary output voltage is maintained in phase (depending on polarity) with the primary voltage. The transducer is well-suited to long cable runs and is useful for measuring small displacements in the presence of high or alternating magnetic fields.

  10. Linear readout of object manifolds

    NASA Astrophysics Data System (ADS)

    Chung, SueYeon; Lee, Daniel D.; Sompolinsky, Haim

    2016-06-01

    Objects are represented in sensory systems by continuous manifolds due to sensitivity of neuronal responses to changes in physical features such as location, orientation, and intensity. What makes certain sensory representations better suited for invariant decoding of objects by downstream networks? We present a theory that characterizes the ability of a linear readout network, the perceptron, to classify objects from variable neural responses. We show how the readout perceptron capacity depends on the dimensionality, size, and shape of the object manifolds in its input neural representation.

  11. A linear Fick's law calorimeter

    NASA Astrophysics Data System (ADS)

    Alpert, Seymour S.; Bryant, Pat D.; Woodside, William F.

    1982-10-01

    A small animal calorimeter is described that is based on the direct application of Fick's law. Heat flow is channeled through a circular disk of magnesium and the temperature difference between the inside and outside surface of the disk is detected by means of solid-state temperature transducers. The device is calibrated using a light-weight electrical resistive source and is shown to be linear in its response and to have an e-folding time of 4.8 min. A rat was introduced into the calorimeter and its heat energy expenditure rate was observed in both the sedated and unsedated states.

  12. A terabyte linear tape recorder

    NASA Technical Reports Server (NTRS)

    Webber, John C.

    1994-01-01

    A plan has been formulated and selected for a NASA Phase 2 SBIR award for using the VLBA tape recorder for recording general data. The VLBA tape recorder is a high-speed, high-density linear tape recorder developed for Very Long Baseline Interferometry (VLBI) which is presently capable of recording at rates up to 2 Gbit/sec and holding up to 1 Terabyte of data on one tape, using a special interface and not employing error correction. A general-purpose interface and error correction will be added so that the recorder can be used in other high-speed, high-capacity applications.

  13. ALPS - A LINEAR PROGRAM SOLVER

    NASA Technical Reports Server (NTRS)

    Viterna, L. A.

    1994-01-01

    Linear programming is a widely-used engineering and management tool. Scheduling, resource allocation, and production planning are all well-known applications of linear programs (LP's). Most LP's are too large to be solved by hand, so over the decades many computer codes for solving LP's have been developed. ALPS, A Linear Program Solver, is a full-featured LP analysis program. ALPS can solve plain linear programs as well as more complicated mixed integer and pure integer programs. ALPS also contains an efficient solution technique for pure binary (0-1 integer) programs. One of the many weaknesses of LP solvers is the lack of interaction with the user. ALPS is a menu-driven program with no special commands or keywords to learn. In addition, ALPS contains a full-screen editor to enter and maintain the LP formulation. These formulations can be written to and read from plain ASCII files for portability. For those less experienced in LP formulation, ALPS contains a problem "parser" which checks the formulation for errors. ALPS creates fully formatted, readable reports that can be sent to a printer or output file. ALPS is written entirely in IBM's APL2/PC product, Version 1.01. The APL2 workspace containing all the ALPS code can be run on any APL2/PC system (AT or 386). On a 32-bit system, this configuration can take advantage of all extended memory. The user can also examine and modify the ALPS code. The APL2 workspace has also been "packed" to be run on any DOS system (without APL2) as a stand-alone "EXE" file, but has limited memory capacity on a 640K system. A numeric coprocessor (80X87) is optional but recommended. The standard distribution medium for ALPS is a 5.25 inch 360K MS-DOS format diskette. IBM, IBM PC and IBM APL2 are registered trademarks of International Business Machines Corporation. MS-DOS is a registered trademark of Microsoft Corporation.

  14. Fast feedback for linear colliders

    SciTech Connect

    Hendrickson, L.; Adolphsen, C.; Allison, S.; Gromme, T.; Grossberg, P.; Himel, T.; Krauter, K.; MacKenzie, R.; Minty, M.; Sass, R.

    1995-05-01

    A fast feedback system provides beam stabilization for the SLC. As the SLC is in some sense a prototype for future linear colliders, this system may be a prototype for future feedbacks. The SLC provides a good base of experience for feedback requirements and capabilities as well as a testing ground for performance characteristics. The feedback system controls a wide variety of machine parameters throughout the SLC and associated experiments, including regulation of beam position, angle, energy, intensity and timing parameters. The design and applications of the system are described, in addition to results of recent performance studies.

  15. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. D.; Busse, L. J.; Lemon, D. K.

    1985-07-30

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  16. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. Dale; Busse, Lawrence J.; Lemon, Douglas K.

    1985-01-01

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  17. Linearized Bekenstein varying α models

    NASA Astrophysics Data System (ADS)

    Avelino, P. P.; Martins, C. J.; Oliveira, J. C.

    2004-10-01

    We study the simplest class of Bekenstein-type, varying α models, in which the two available free functions (potential and gauge kinetic function) are Taylor-expanded up to linear order. Any realistic model of this type reduces to a model in this class for a certain time interval around the present day. Nevertheless, we show that no such model is consistent with all existing observational results. We discuss possible implications of these findings, and, in particular, clarify the ambiguous statement (often found in the literature) that “the Webb results are inconsistent with Oklo.”

  18. Elementary principles of linear accelerators

    NASA Astrophysics Data System (ADS)

    Loew, G. A.; Talman, R.

    1983-09-01

    A short chronology of important milestones in the field of linear accelerators is presented. Proton linacs are first discussed and elementary concepts such as transit time, shunt impedance, and Q are introduced. Critical issues such as phase stability and transverse forces are addressed. An elementary discussion of waveguide acclerating structures is also provided. Finally, electron accelerators addressed. Taking SLAC as an exmple, various topics are discussed such as structure design, choice of parameters, frequency optmization, beam current, emittance, bunch length and beam loading. Recent developments and future challenges are mentioned briefly.

  19. Production of medical radioisotopes with linear accelerators.

    PubMed

    Starovoitova, Valeriia N; Tchelidze, Lali; Wells, Douglas P

    2014-02-01

    In this study, we discuss producing radioisotopes using linear electron accelerators and address production and separation issues of photoneutron (γ,n) and photoproton (γ,p) reactions. While (γ,n) reactions typically result in greater yields, separating product nuclides from the target is challenging since the chemical properties of both are the same. Yields of (γ,p) reactions are typically lower than (γ,n) ones, however they have the advantage that target and product nuclides belong to different chemical species so their separation is often not such an intricate problem. In this paper we consider two examples, (100)Mo(γ,n)(99)Mo and (68)Zn(γ,p)(67)Cu, of photonuclear reactions. Monte-Carlo simulations of the yields are benchmarked with experimental data obtained at the Idaho Accelerator Center using a 44MeV linear electron accelerator. We propose using a kinematic recoil method for photoneutron production. This technique requires (100)Mo target material to be in the form of nanoparticles coated with a catcher material. During irradiation, (99)Mo atoms recoil and get trapped in the coating layer. After irradiation, the coating is dissolved and (99)Mo is collected. At the same time, (100)Mo nanoparticles can be reused. For the photoproduction method, (67)Cu can be separated from the target nuclides, (68)Zn, using standard exchange chromatography methods. Monte-Carlo simulations were performed and the (99)Mo activity was predicted to be about 7MBq/(g(⁎)kW(⁎)h) while (67)Cu activity was predicted to be about 1MBq/(g(⁎)kW(⁎)h). Experimental data confirm the predicted activity for both cases which proves that photonuclear reactions can be used to produce radioisotopes. Lists of medical isotopes which might be obtained using photonuclear reactions have been compiled and are included as well. PMID:24374071

  20. Production of medical radioisotopes with linear accelerators.

    PubMed

    Starovoitova, Valeriia N; Tchelidze, Lali; Wells, Douglas P

    2014-02-01

    In this study, we discuss producing radioisotopes using linear electron accelerators and address production and separation issues of photoneutron (γ,n) and photoproton (γ,p) reactions. While (γ,n) reactions typically result in greater yields, separating product nuclides from the target is challenging since the chemical properties of both are the same. Yields of (γ,p) reactions are typically lower than (γ,n) ones, however they have the advantage that target and product nuclides belong to different chemical species so their separation is often not such an intricate problem. In this paper we consider two examples, (100)Mo(γ,n)(99)Mo and (68)Zn(γ,p)(67)Cu, of photonuclear reactions. Monte-Carlo simulations of the yields are benchmarked with experimental data obtained at the Idaho Accelerator Center using a 44MeV linear electron accelerator. We propose using a kinematic recoil method for photoneutron production. This technique requires (100)Mo target material to be in the form of nanoparticles coated with a catcher material. During irradiation, (99)Mo atoms recoil and get trapped in the coating layer. After irradiation, the coating is dissolved and (99)Mo is collected. At the same time, (100)Mo nanoparticles can be reused. For the photoproduction method, (67)Cu can be separated from the target nuclides, (68)Zn, using standard exchange chromatography methods. Monte-Carlo simulations were performed and the (99)Mo activity was predicted to be about 7MBq/(g(⁎)kW(⁎)h) while (67)Cu activity was predicted to be about 1MBq/(g(⁎)kW(⁎)h). Experimental data confirm the predicted activity for both cases which proves that photonuclear reactions can be used to produce radioisotopes. Lists of medical isotopes which might be obtained using photonuclear reactions have been compiled and are included as well.