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Sample records for subluminal pulse reflection

  1. Subluminal and superluminal pulse propagation influenced by strong nonlinear effects

    Science.gov (United States)

    Chang, Zengguang; Qi, Yihong; Niu, Yueping; Zhang, Jingtao; Gong, Shangqing

    2012-12-01

    A scheme is proposed for control of pulse propagation from subluminal to superluminal in a four-level Λ-type atomic system. With the relatively intense probe laser and the appropriate detuning of control field, the medium exhibits much lower absorption in the spectral ranges where the dispersion changes from normal to abnormal in the double electromagnetically induced transparency system than in the single electromagnetically induced transparency system. The transmission intensity can be enhanced by several times for the subluminal pulse propagation and by several orders of magnitude for the superluminal pulse propagation without the large distortion in the former compared with those in the latter. We attribute the dramatic absorption reduction to the enhanced nonlinear effects.

  2. Time-frequency dynamics of superluminal pulse transition to the subluminal regime

    Science.gov (United States)

    Dorrah, Ahmed H.; Ramakrishnan, Abhinav; Mojahedi, Mo

    2015-03-01

    Spectral reshaping and nonuniform phase delay associated with an electromagnetic pulse propagating in a temporally dispersive medium may lead to interesting observations in which the group velocity becomes superluminal or even negative. In such cases, the finite bandwidth of the superluminal region implies the inevitable existence of a cutoff distance beyond which a superluminal pulse becomes subluminal. In this paper, we derive a closed-form analytic expression to estimate this cutoff distance in abnormal dispersive media with gain. Moreover, the method of steepest descent is used to track the time-frequency dynamics associated with the evolution of the center of mass of a superluminal pulse to the subluminal regime. This evolution takes place at longer propagation depths as a result of the subluminal components affecting the behavior of the pulse. Finally, the analysis presents the fundamental limitations of superluminal propagation in light of factors such as the medium depth, pulse width, and the medium dispersion strength.

  3. Subluminal and superluminal pulse propagation in inhomogeneous media of nonspherical particles

    Energy Technology Data Exchange (ETDEWEB)

    Ma Yu [Department of Physics, Suzhou University, Suzhou 215006 (China); Gao Lei [CCAST (World Laboratory), P.O. Box 8730, Beijing 100080 (China) and Department of Physics, Suzhou University, Suzhou 215006 (China)]. E-mail: lgaophys@pub.sz.jsinfo.net

    2006-07-10

    We study the pulse propagation through a metal/dielectric composites of nonspherical particles enclosed by two gold mirrors. To account for the shape effect, we first adopt Maxwell-Garnett type approximation to obtain the effective dielectric function of composites. Based on the group index, phase time and pulse shape calculations, we find that the particles' shape (characterized by the depolarization factor) plays an important role in determining the subluminal and superluminal pulse propagations through the system. When the inclusions' shape is not spherical, it is possible to observe significant superluminal behavior of the pulse propagation, although the volume fraction is the same. The shape-dependent critical volume fraction is predicted, above which superluminal propagation appears. Furthermore, the Hartman effect in such a system is also investigated.

  4. Subluminal and superluminal parametric doppler effects in the case of light reflection from a moving smooth medium inhomogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Rozanov, N. N., E-mail: nrosanov@yahoo.com [Vavilov State Optical Institute (Russian Federation)

    2012-12-15

    The reflection of test radiation from a smooth inhomogeneity of medium characteristics propagating with a subluminal or superluminal velocity is analyzed. The equations describing the propagation of the forward- and counter-propagating waves in such an inhomogeneous medium are derived. Quasi-phase conjugation is demonstrated in the case of superluminal inhomogeneities. The Bragg resonance conditions are formulated and the conditions for increasing the reflection coefficient of radiation from an inhomogeneity are discussed.

  5. Subluminal to superluminal propagation of an optical pulse in an f-deformed Bose-Einstein condensate

    Energy Technology Data Exchange (ETDEWEB)

    Haghshenasfard, Z; Naderi, M H; Soltanolkotabi, M [Quantum Optics Group, Department of Physics, University of Isfahan, Hezar Jerib, 81746-73441 Isfahan (Iran, Islamic Republic of)], E-mail: zhaghshenas@hotmail.com, E-mail: mhnaderi2001@yahoo.com, E-mail: soltan@sci.ui.ac.ir

    2008-08-28

    In this paper, we investigate the propagation of a weak optical probe pulse in an f-deformed Bose-Einstein condensate of a gas with the {lambda}-type three-level atoms in the electromagnetically induced transparency regime. We use an f-deformed generalization of an effective two-level quantum model of the three-level {lambda} configuration in which Gardiner's phonon operators for Bose-Einstein condensates are deformed by an operator-valued function, f(n-circumflex), of the particle-number operator n-circumflex. By making use of the quantum approach of the angular momentum theory, we obtain the eigenvalues and eigenfunctions of the system up to a first-order approximation. We consider the collisions between the atoms as a special kind of f-deformation. The collision rate {kappa} is regarded as the deformation parameter and light propagation in the deformed Bose-Einstein condensate is analysed. In particular, we show that the absorptive and dispersive properties of the deformed condensate can be controlled effectively by changing the deformation parameter {kappa} and the total number of atoms. We find that by increasing the value of {kappa} the group velocity of the probe pulse changes, through deformed condensate, from subluminal to superluminal.

  6. Enhanced effects of subluminal and superluminal propagation

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Feng; Guo Hong; Li Luming; Liu Cheng; Chen Xuzong

    2004-06-21

    We have experimentally investigated the enhanced effects of subluminal and superluminal propagation, based on electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA), respectively. By adding only an incoherently pumping laser to each case, the slower subluminal group velocity, and the faster superluminal pulse propagation are, respectively, observed. By only changing the intensity of the incoherent pumping beam, we are able to control, respectively, the subluminal group velocity continuously from v{sub g}=c/20000 to v{sub g}=c/8300, and superluminal group velocity from v{sub g}=-c/1667 to v{sub g}=-c/3030. Qualitative explanations for the two cases are given.

  7. Superluminal pulse reflection and transmission in a slab system doped with dispersive materials.

    Science.gov (United States)

    Wang, Li-Gang; Chen, Hong; Zhu, Shi-Yao

    2004-12-01

    The reflection and transmission of a pulse through a slab which is doped with two-level or three-level atoms are investigated theoretically. The doped atoms can be passive (absorptive) or active (gain). We find that both the reflected and transmitted pulses can be superluminal simultaneously for the slab doped with absorptive two-level atoms at the slab thickness equal to (2m+1) lambda(0) /4 sqrt[epsilon(b)] (where lambda(0) is the center wavelength of the incident pulse, and epsilon(b) is the background dielectric constant of the slab) or with active three-level atoms at any thickness. By adjusting the thickness or background dielectric constant of the slab, the reflected pulse can be controlled from superluminal to subluminal or vice versa for the slab doped with absorptive two-level or absorptive three-level atoms. The energy percentage in the reflected pulse can also be controlled by changing the thickness of the slab, and the doped atoms.

  8. Superluminal pulse reflection from a weakly absorbing dielectric slab.

    Science.gov (United States)

    Wang, Li-Gang; Zhu, Shi-Yao

    2006-07-15

    Group delay for a reflected light pulse from a weakly absorbing dielectric slab is theoretically investigated, and large negative group delay is found for weak absorption near a resonance of the slab [Re(kd)=mpi]. The group delay for both the reflected and transmitted pulses will be saturated with an increase of the absorption.

  9. Efficient reflection grisms for pulse compression and dispersion compensation of femtosecond pulses.

    Science.gov (United States)

    Gibson, Emily A; Gaudiosi, David M; Kapteyn, Henry C; Jimenez, Ralph; Kane, Steve; Huff, Rachel; Durfee, Charles; Squier, Jeff

    2006-11-15

    Efficient reflection grisms for pulse-compression and material-dispersion compensation have been designed and demonstrated in a 40 fs, 300 microJ, 5 kHz downchirped pulse amplification system for the first time to our knowledge. A grism design for 800 nm femtosecond laser pulse dispersion compensation applications is realized by using standard, commercial diffraction gratings.

  10. Long wavelength superluminal pulse propagation in a defect slab doped with GaAs/AlGaAs multiple quantum well nanostructure

    Science.gov (United States)

    Panahi, M.; Solookinejad, G.; Sangachin, E. Ahmadi; Asadpour, S. H.

    2015-12-01

    In this paper, long wavelength superluminal and subluminal properties of pulse propagation in a defect slab medium doped with four-level GaAs/AlGaAs multiple quantum wells (MQWs) with 15 periods of 17.5 nm GaAs wells and 15 nm Al0.3Ga0.7As barriers is theoretically discussed. It is shown that exciton spin relaxation (ESR) between excitonic states in MQWs can be used for controlling the superluminal and subluminal light transmissions and reflections at different wavelengths. We also show that reflection and transmission coefficients depend on the thickness of the slab for the resonance and nonresonance conditions. Moreover, we found that the ESR for nonresonance condition lead to superluminal light transmission and subluminal light reflection.

  11. Particle reflection along the magnetic field in nonlinear magnetosonic pulses

    Science.gov (United States)

    Ohsawa, Yukiharu

    2017-11-01

    Reflection of electrons and positrons in oblique, nonlinear magnetosonic pulses is theoretically analyzed. With the use of the parallel pseudo potential F, which is the integral of the parallel electric field along the magnetic field, a simple equation for reflection conditions is derived, which shows that reflection along the magnetic field is caused by two forces: one arising from the parallel pseudo potential multiplied by the particle charge and the other from the magnetic mirror effect. The two forces push electrons in the opposite directions. In compressive solitons, in which the magnetic field is intensified, electrons with large magnetic moments can be reflected by the magnetic mirror effect, whereas in rarefactive solitons, in which the magnetic field is weaker than outside, electrons with small magnetic moments can be reflected by the parallel pseudo potential. Although F is basically positive and large in shock waves, it occasionally becomes negative in some regions behind the shock front in nonstationary wave evolution. These negative spikes of F can reflect electrons. In contrast to the case of electrons, the two forces push positrons in the same direction. For this reason, compressive solitons in an electron-positron-ion plasma reflect a large fraction of positrons compared with electrons, whereas rarefactive solitons will reflect no positrons. A shock wave can reflect a majority of positrons with its large F. However, in a pure electron-positron plasma, in which F becomes zero, positron reflection will rarely occur.

  12. Switching from subluminal to superluminal light propagation via a coherent pump field in a four-level atomic system

    Energy Technology Data Exchange (ETDEWEB)

    Kuang Shangqi [College of Physics, Jilin University, Changchun 130023 (China); Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Educational Ministry of China, Changchun 130021 (China); Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Wan Rengang; Kou Jun; Jiang Yun; Gao Jinyue [College of Physics, Jilin University, Changchun 130023 (China); Key Lab of Coherent Light, Atomic and Molecular Spectroscopy, Educational Ministry of China, Changchun 130021 (China)

    2009-12-15

    We theoretically investigate the influence of a coherent pump field on the propagation of a weak light pulse of a probe field in a four-level atomic system. Due to the modulation of the pump field, the light pulse can be manipulated from subluminal to superluminal with negligible distortion. This scheme can be realized in both the ultracold and Doppler-broadened atomic systems. We also demonstrate that the spectral linewidth with an anomalous dispersion is reduced by thermal averaging; therefore, one can obtain a larger negative group refractive index in room-temperature vapor than the largest value achieved in ultracold atomic gas.

  13. An Electronic Patch for Wearable Health Monitoring by Reflectance Pulse Oximetry

    DEFF Research Database (Denmark)

    Haahr, Rasmus Grønbek; Duun, Sune Bro; Toft, Mette H.

    2012-01-01

    . In this paper the Electronic Patch is demonstrated with a new optical biomedical sensor for reflectance pulse oximetry so that the Electronic Patch in this case can measure the pulse and the oxygen saturation. The reflectance pulse oximetry solution is based on a recently developed annular backside silicon...

  14. Superluminal pulse propagation through one-dimensional photonic crystals with a dispersive defect.

    Science.gov (United States)

    Liu, Nian-Hua; Zhu, Shi-Yao; Chen, Hong; Wu, Xiang

    2002-04-01

    The propagation of a pulse through one-dimensional photonic crystals that contain a dispersive and absorptive defect layer doped with two-level atoms is discussed. The dynamical evolution of the pulse inside the photonic crystal is presented. Superluminal negative group velocity (the peak appears at the exit end before it reaches the input end) is discovered. Although the group velocity is larger than c and even negative, the velocity of energy propagation never exceeds the vacuum light speed. The appearance of the superluminal advance or subluminal delay of the pulse peak inside the photonic crystal or at the exit end is due to the wave interference from Bragg reflections.

  15. Light propagation from subluminal to superluminal in a three-level {lambda}-type system

    Energy Technology Data Exchange (ETDEWEB)

    Sun Hui [CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China); Guo Hong [CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China) and CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China)]. E-mail: hongguo@pku.edu.cn; Bai, Yanfeng [CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); Han Dingan [CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China); Fan Shuangli [CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China); Chen Xuzong [CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

    2005-01-31

    We show that the group velocity of a weak electromagnetic pulse can be manipulated by adjusting the relative phase of the probing and the pumping fields applied to a {lambda}-type three-level system, whose two lower states are coupled by an external control magnetic field. Such control field can, in principle, cause the light propagation to be changed from subluminal to superluminal by modulating the relative phase. The same effect can be obtained by varying the intensities of the pumping and the control magnetic fields, but it is different with Agarwal's [Phys. Rev. A 64 (2001) 053809]. The effect of Doppler broadening on the dispersion is also investigated.

  16. A Novel Photodiode for Reflectance Pulse Oximetry in low-power applications

    DEFF Research Database (Denmark)

    Haahr, Rasmus Grønbek; Duun, Sune; Birkelund, Karen

    2007-01-01

    The amount of light collected is crucial for low-power applications of pulse oximetry. In this work a novel ring-shaped backside photodiode has been developed for a wearable reflectance pulse oximeter. The photodiode is proven to work with a dual LED with wavelengths of 660 nm and 940 nm. For the...

  17. Internal reflection as a cause of the correlation of counterpropagating pulses in superradiance

    Energy Technology Data Exchange (ETDEWEB)

    Trifonov, E.D. [Herzen Russian State Pedagogical Univ., St. Petersburg (Russian Federation)

    1994-07-01

    Resonant reflection from boundaries as an excitation region is considered as a cause of a correlation of counterpropagating pulses in superradiance. Criteria for the pulse synchronization are obtained, both for pure superradiance and for the case when phase relaxation is present. 11 refs.

  18. Stretching of picosecond laser pulses with uniform reflecting volume Bragg gratings

    Science.gov (United States)

    Mokhov, Sergiy; Spiro, Alexander; Smirnov, Vadim; Kaim, Sergiy; Zeldovich, Boris; Glebov, Leonid

    2017-08-01

    This study shows that a uniform reflecting volume Bragg grating (VBG) can be used as a compact monolithic stretcher of high-power picosecond laser pulses, which is important for cases in which chirped Bragg gratings with the required chirp rate are difficult to fabricate. When an incident short pulse propagates along a grating and experiences local Bragg diffraction, a chirp-free reflected stretched pulse with an almost rectangular shape is generated. The increase in the duration of the reflected pulse is approximately equal to twice the propagation time along the grating. We derive an analytic expression for the diffraction efficiency, which incorporates the incident pulse duration, grating thickness, and amplitude of the refractive index modulation, enabling selection of the optimum grating for pulse stretching. Theoretical models of the extended pulse profiles are found to be in good agreement with experimental autocorrelation measurements. We also propose a simple and reliable method to control the temporal parameters of high-power picosecond pulses using the same laser source and a VBG of variable thickness, which can simplify experiments requiring different pulse durations significantly.

  19. Net electron energy gain induced by superluminal phase velocity and subluminal group velocity of a laser in a plasma channel

    Science.gov (United States)

    Cheng, Li-Hong; Yao, Zheng-Wei; Zhang, Xiao-Bo; Xue, Ju-Kui

    2017-08-01

    We examine electron dynamics induced by laser-plasma interaction in a two-dimensional plasma channel, taking into action the laser phase velocity as well as the group velocity. The coupled effects of phase velocity, group velocity, and plasma channel on electron dynamics are discussed in detail. The superluminal phase velocity and the corresponding subluminal group velocity of the laser result in rich and complex electron dynamics, which are depicted in the plane of the phase velocity and plasma charge density. For weak superluminosity of the phase velocity, the effects of the phase velocity and the group velocity can be neglected. For moderate superluminosity of the phase velocity, a cross-over region can exist, where the highly energetic electron could be found and the net energy gain is several times greater than the energy gain in vacuum. For strong superluminosity of the phase velocity, the dephasing rate increases and thus limits the electron energy gain from the laser. However, the asymmetric laser pulse, attributed by the superluminal phase velocity and the subluminal group velocity, results in the electron getting adjustable net energy gain from the laser. The electron oscillations are no longer limited by the charge density threshold and the electron can always get net energy from the laser. These electron dynamics can also be modified by adjusting the polarization of the laser.

  20. Experimental observation of superluminal pulse reflection in a double-Lorentzian photonic band gap.

    Science.gov (United States)

    Longhi, S; Marano, M; Laporta, P; Belmonte, M; Crespi, P

    2002-04-01

    We report on the experimental observation of superluminal reflection of picosecond optical pulses at 1.5 microm using a specially designed 30-cm-long fiber Bragg grating (FBG) that realizes a spectral reflectivity profile given by the superposition of two closely spaced Lorentzian lines. Probing pulses of 380 ps duration tuned midway between the two Lorentzian lines are reflected without appreciable distortion with a measured peak pulse advancement of approximately 60 ps. The achievement of the negative group delay is due to the interference of the two resonance modes of the FBG structure and has a close connection to the phenomenon of negative group velocity for pulse propagation in an inverted medium possessing a doublet line.

  1. Glycemic index, glycemic load, and pulse wave reflection in adults.

    Science.gov (United States)

    Recio-Rodriguez, J I; Gomez-Marcos, M A; Patino-Alonso, M-C; Rodrigo-De Pablo, E; Cabrejas-Sánchez, A; Arietaleanizbeaskoa, M S; Repiso-Gento, I; Gonzalez-Viejo, N; Maderuelo-Fernandez, J A; Agudo-Conde, C; Garcia-Ortiz, L

    2015-01-01

    Diets with a high glycemic index (GI), high glycemic load (GL), or both, increase the risk of cardiovascular disease. This study examined the association of GI and GL in a regular diet with the peripheral augmentation index (i.e., a marker of vascular aging) in a sample of adults. Cross-sectional study. The findings presented in this manuscript are a subanalysis of the EVIDENT study whose purpose was to analyze the relationship between lifestyle and arterial aging. For the sample population, 1553 individuals aged 20-80 years were selected through random sampling from the patients of general practitioners at six health centers in Spain. GI and GL for each patient's diet were calculated from a previously validated, semi-quantitative, 137-item food frequency questionnaire. The peripheral augmentation index corrected for a heart rate of 75 bpm (PAIx75) was measured with pulse-wave application software (A-Pulse CASP). Based on a risk factor adjusted regression model, for every 5 unit increase in GI, the PAIx75 increased by 0.11 units (95% CI: 0.04-0.19). Similarly, for every increase in 10 units in GL, the PAIx75 increased by 1.13 (95% CI: 0.21-2.05). High PAIx75 values were observed in individuals with diets in the third GI tertile (i.e., the highest), and lower PAIx75 values in those with diets in the first tertile (i.e., the lowest), (93.1 vs. 87.5, respectively, p = 0.001). GI and GL were directly associated with PAIx75 values in adults without cardiovascular diseases regardless of age, gender, physical activity, and other confounders. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Development of a luminous textile for reflective pulse oximetry measurements

    Science.gov (United States)

    Krehel, Marek; Wolf, Martin; Boesel, Luciano F.; Rossi, René M.; Bona, Gian-Luca; Scherer, Lukas J.

    2014-01-01

    In this paper, a textile-based sensing principle for long term photopletysmography (PPG) monitoring is presented. Optical fibers were embroidered into textiles such that out-coupling and in-coupling of light was possible. The “light-in light-out” properties of the textile enabled the spectroscopic characterization of human tissue. For the optimization of the textile sensor, three different carrier fabrics and different fiber modifications were compared. The sample with best light coupling efficiency was successfully used to measure heart rate and SpO2 values of a subject. The latter was determined by using a modified Beer-Lambert law and measuring the light attenuation at two different wavelengths (632 nm and 894 nm). Moreover, the system was adapted to work in reflection mode which makes the sensor more versatile. The measurements were additionally compared with commercially available system and showed good correlation. PMID:25136484

  3. Effects of isosorbide mononitrate and AII inhibition on pulse wave reflection in hypertension.

    Science.gov (United States)

    Stokes, Gordon S; Barin, Edward S; Gilfillan, Kerry L

    2003-02-01

    The aortic pulse wave contour in isolated systolic hypertension often shows a prominent reflection peak, which combines with the incident wave arising from cardiac ejection so as to widen pulse pressure. We investigated the effects of an extended-release nitrate preparation and of 2 angiotensin II (AII) inhibitors (an AII receptor antagonist and an ACE inhibitor) on the aortic pulse wave contour and systemic blood pressure in hypertensive subjects with high augmentation index caused by exaggerated pulse wave reflection. Two double-blind, randomized, placebo-controlled crossover studies were carried out in a total of 16 elderly patients with systolic hypertension resistant to conventional antihypertensive therapy. In 1 study, pharmacodynamic responses to single doses of placebo, isosorbide mononitrate, eprosartan, and captopril were determined; in the other, single-dose isosorbide mononitrate and placebo were compared in subjects treated with AII inhibitors at baseline. Blood pressure was measured by sphygmomanometry and pulse wave components by applanation tonometry at the radial artery. All 3 agents were shown to decrease brachial systolic blood pressure, aortic systolic blood pressure, and aortic pulse pressure. Qualitative effects on the aortic pulse wave contour differed: augmentation index was not significantly altered by either captopril or eprosartan but was decreased (PAII inhibition.

  4. Superluminal pulse reflection in asymmetric one-dimensional photonic band gaps.

    Science.gov (United States)

    Longhi, S

    2001-09-01

    Superluminal pulse reflection is shown to occur in a class of one-dimensional asymmetric photonic band gaps in which a spectral window inside the gap is opened. By means of a coupled-mode equation analysis, we describe in detail two possible realizations of superluminal pulse reflection that can be achieved using fiber Bragg gratings. The former method is based on the introduction of a defect into the otherwise periodic dielectric structure, whereas the latter one exploits the interference of two closely-spaced resonance modes and simulates the dispersion properties of an inverted medium possessing a doublet line.

  5. Non-invasive detection of murals with pulsed terahertz reflected imaging system

    Science.gov (United States)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Ye, Jiasheng; Wang, Sen; Zhang, Qunxi; Zhang, Yan

    2015-11-01

    Pulsed terahertz reflected imaging technology has been expected to have great potential for the non-invasive analysis of artworks. In this paper, three types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by a pulsed terahertz reflected imaging system. These preset defects include a circular groove, a cross-shaped slit and a piece of "Y-type" metal plate built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. Additionally, three-dimensional analyses have been performed in order to reveal the internal structure of defects. Terahertz reflective imaging can be applied to the defect investigation of the murals.

  6. Measurements of plasma mirror reflectivity and focal spot quality for tens of picosecond laser pulses

    Science.gov (United States)

    Forestier-Colleoni, Pierre; Williams, Jackson; Scott, Graeme; Mariscal, Dereck. A.; McGuffey, Christopher; Beg, Farhat N.; Chen, Hui; Neely, David; Ma, Tammy

    2017-10-01

    The Advanced Radiographic Capability (ARC) laser at the NIF (LLNL) is high-energy ( 4 kJ) with a pulse length of 30ps, and is capable of focusing to an intensity of 1018W/cm2 with a 100 μm focal spot. The ARC laser is at an intensity which can be used to produce proton beams. However, for applications such as radiography and warm dense matter creation, a higher laser intensity may be desired to generate more energetic proton beams. One possibility to increase the intensity is to decrease the focused spot size by employing a smaller f-number optic. But it is difficult to implement such an optic or to bring the final focusing parabola closer to the target within the complicated NIF chamber geometry. A proposal is to use ellipsoidal plasma mirrors (PM) for fast focusing of the ARC laser light, thereby increasing the peak intensity. There is uncertainty, however, in the survivability and reflectivity of PM at such long pulse durations. Here, we show experimental results from the Titan laser to study the reflectivity of flat PM as a function of laser pulse length. A calorimeter was used to measure the PM reflectivity. We also observed degradation of the far and near field energy distribution of the laser after the reflection by the PM for pulse-lengths beyond 10ps. Contract DE-AC52-07NA27344. Funded by the LLNL LDRD program: tracking code 17-ERD-039.

  7. Reflectivity of plasmas created by high-intensity, ultra-short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Gold, David Michael [Univ. of California, Davis, CA (United States)

    1994-06-01

    Experiments were performed to characterize the creation and evolution of high-temperature (T e~100eV), high-density (ne>1022cm-3) plasmas created with intense (~1012-1016W/cm2), ultra-short (130fs) laser pulses. The principle diagnostic was plasma reflectivity at optical wavelengths (614nm). An array of target materials (Al, Au, Si, SiO2) with widely differing electronic properties tested plasma behavior over a large set of initial states. Time-integrated plasma reflectivity was measured as a function of laser intensity. Space- and time-resolved reflectivity, transmission and scatter were measured with a spatial resolution of ~3μm and a temporal resolution of 130fs. An amplified, mode-locked dye laser system was designed to produce ~3.5mJ, ~130fs laser pulses to create and nonintrusively probe the plasmas. Laser prepulse was carefully controlled to suppress preionization and give unambiguous, high-density plasma results. In metals (Al and Au), it is shown analytically that linear and nonlinear inverse Bremsstrahlung absorption, resonance absorption, and vacuum heating explain time-integrated reflectivity at intensities near 1016W/cm2. In the insulator, SiO2, a non-equilibrium plasma reflectivity model using tunneling ionization, Helmholtz equations, and Drude conductivity agrees with time-integrated reflectivity measurements. Moreover, a comparison of ionization and Saha equilibration rates shows that plasma formed by intense, ultra-short pulses can exist with a transient, non-equilibrium distribution of ionization states. All targets are shown to approach a common reflectivity at intensities ~1016W/cm2, indicating a material-independent state insensitive to atomic or solid-state details.

  8. Terahertz pulse imaging in reflection geometry of human skin cancer and skin tissue

    Energy Technology Data Exchange (ETDEWEB)

    Woodward, Ruth M [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge (United Kingdom); Cole, Bryan E [TeraView Limited, 302/304 Cambridge Science Park, Milton Road, Cambridge (United Kingdom); Wallace, Vincent P [TeraView Limited, 302/304 Cambridge Science Park, Milton Road, Cambridge (United Kingdom); Pye, Richard J [Department of Dermatology, Addenbrooke' s Hospital, Cambridge (United Kingdom); Arnone, Donald D [TeraView Limited, 302/304 Cambridge Science Park, Milton Road, Cambridge (United Kingdom); Linfield, Edmund H [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge (United Kingdom); Pepper, Michael [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge (United Kingdom)

    2002-11-07

    We demonstrate the application of terahertz pulse imaging (TPI) in reflection geometry for the study of skin tissue and related cancers both in vitro and in vivo. The sensitivity of terahertz radiation to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the skin and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Basal cell carcinoma has shown a positive terahertz contrast, and inflammation and scar tissue a negative terahertz contrast compared to normal tissue. In vivo measurements on the stratum corneum have enabled visualization of the stratum corneum-epidermis interface and the study of skin hydration levels. These results demonstrate the potential of terahertz pulse imaging for the study of skin tissue and its related disorders, both in vitro and in vivo.

  9. Understanding subluminal and superluminal propagation through superposition of frequency components.

    Science.gov (United States)

    Guo, Wei

    2006-01-01

    Propagation of a light pulse through a dielectric slab is discussed theoretically in this paper. It is exhibited via a multiple-scattering approach that the slab can modify the phase of the pulse's frequency components, so that, when the frequency components are superposed, they cause the peak in the output pulse to appear to travel either faster or slower than in vacuum, depending on whether the slab is absorbing or amplifying. The expressions of the corresponding advancement and delay of the peak are derived and argued to be limited in magnitude by the pulse's duration.

  10. Reflectance of thin silver film on the glass substrate at the interaction with femtosecond laser pulses

    Science.gov (United States)

    Petrov, Yu V.; Khokhlov, V. A.; Inogamov, N. A.; Khishchenko, K. V.; Anisimov, S. I.

    2016-11-01

    The optical response of thin silver film (of 60 nm thickness) coated on a glass prism (Kretschmann configuration) and heated by the femtosecond laser pulse of small intensity is investigated by the computational modeling. We have calculated the reflectance of p-polarized probe laser beam when it is incident onto the metal film from the glass side. Reflectance is calculated at incidence angles close to the surface plasmon resonance angle. We have considered first 100 ps after the action of femtosecond laser pulse onto the film surface. Changes in thermodynamic state and hydrodynamic motion of film material are described by the system of hydrodynamic equations taking into account different temperatures of electrons and ions (two- temperature state) and consequently two-temperature thermodynamics and kinetics at such early times. These changes define the changes in electron-ion and electron-electron collision frequencies. The collision frequencies of conduction electrons, being calculated in dependence on the density and electron and ion temperatures, allow us to find the Drude part of dielectric permittivity. Together with the interband contribution it gives possibility to calculate reflectance depending on the state of metal surface. It is shown a great importance of electron-electron interactions in the temporal behavior of reflectance at early times of laser-film interaction.

  11. Full-wave reflection of lightning long-wave radio pulses from the ionospheric D- region

    Science.gov (United States)

    Jacobson, A. R.; Shao, X.; Holzworth, R.

    2008-12-01

    A model is developed for calculating ionospheric reflection of electromagnetic pulses emitted by lightning, with most energy in the long-wave spectral region (f = 3 - 100 kHz). The building-block of the calculation is a differential-equation full-wave solution of Maxwell's Equations for the complex reflection of individual plane waves incident from below, by the anisotropic, dissipative, diffuse dielectric profile of the lower ionosphere. This full-wave solution is then put into a summation over plane waves in an angular Direct Fourier Transform to obtain the reflection properties of curved wavefronts. This step models also the diffraction effects of long- wave ionospheric reflections observed at short or medium range (200 - 500 km). The calculation can be done with any arbitrary but smooth dielectric profile versus altitude. For an initial test, we use the classic D- region exponential profiles of electron density and collision rate given by Wait. With even these simple profiles, our model of full-wave reflection of curved wavefronts captures some of the basic attributes of observed reflected waveforms recorded with the Los Alamos Sferic Array.

  12. High quantum efficiency annular backside silicon photodiodes for reflectance pulse oximetry in wearable wireless body sensors

    DEFF Research Database (Denmark)

    Duun, Sune Bro; Haahr, Rasmus Grønbek; Hansen, Ole

    2010-01-01

    The development of annular photodiodes for use in a reflectance pulse oximetry sensor is presented. Wearable and wireless body sensor systems for long-term monitoring require sensors that minimize power consumption. We have fabricated large area 2D ring-shaped silicon photodiodes optimized....../2) cm(-1) are achieved. The photodiodes are incorporated into a wireless pulse oximetry sensor system embedded in an adhesive patch presented elsewhere as 'The Electronic Patch'. The annular photodiodes are fabricated using two masked diffusions of first boron and subsequently phosphor. The surface...... is passivated with a layer of silicon nitride also serving as an optical filter. As the final process, after metallization, a hole in the center of the photodiode is etched using deep reactive ion etch....

  13. Reflection of femtosecond pulses from soft X-ray free-electron laser by periodical multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Ksenzov, D.; Grigorian, S.; Pietsch, U. [Faculty of Physics, University of Siegen (Germany); Hendel, S.; Bienert, F.; Sacher, M.D.; Heinzmann, U. [Faculty of Physics, University of Bielefeld (Germany)

    2009-08-15

    Recent experiments on a soft X-ray free-electron laser (FEL) source (FLASH in Hamburg) have shown that multilayers (MLs) can be used as optical elements for highly intense X-ray irradiation. An effort to find most appropriate MLs has to consider the femtosecond time structure and the particular photon energy of the FEL. In this paper we have analysed the time response of 'low absorbing' MLs (e.g. such as La/B{sub 4}C) as a function of the number of periods. Interaction of a pulse train of Gaussian shaped sub-pulses using a realistic ML grown by electron-beam evaporation technique has been analysed in the soft-X-ray range. The structural parameters of the MLs were obtained by reflectivity measurements at BESSY II and subsequent profile fittings. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  14. Simultaneous time-space resolved reflectivity and interferometric measurements of dielectrics excited with femtosecond laser pulses

    Science.gov (United States)

    Garcia-Lechuga, M.; Haahr-Lillevang, L.; Siegel, J.; Balling, P.; Guizard, S.; Solis, J.

    2017-06-01

    Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results have been simulated in the frame of a multiple-rate equation model including light propagation. The comparison of the temporal evolution of the reflectivity and the interferometric measurements at 400 nm clearly shows that the two techniques interrogate different material volumes during the course of the process. While the former is sensitive to the evolution of the plasma density in a very thin ablating layer at the surface, the second yields an averaged plasma density over a larger volume. It is shown that self-trapped excitons do not appreciably contribute to carrier relaxation in fused silica at fluences above the ablation threshold, most likely due to Coulomb screening effects at large excited carrier densities. For both materials, at fluences well above the ablation threshold, the maximum measured plasma reflectivity shows a saturation behavior consistent with a scattering rate proportional to the plasma density in this fluence regime. Moreover, for both materials and for pulse energies above the ablation threshold and delays in the few tens of picoseconds range, a simultaneous "low reflectivity" and "low transmission" behavior is observed. Although this behavior has been identified in the past as a signature of femtosecond laser-induced ablation, its origin is alternatively discussed in terms of the optical properties of a material undergoing strong isochoric heating, before having time to substantially expand or exchange energy with the surrounding media.

  15. Use of reflectance spectrophotometry to predict the response of port wine stains to pulsed dye laser.

    Science.gov (United States)

    Halachmi, Shlomit; Azaria, Ron; Inbar, Roy; Ad-El, Dean; Lapidoth, Moshe

    2014-01-01

    Reflectance spectroscopy can be used to quantitate subtle differences in color. We applied a portable reflectance spectrometer to determine its utility in the evaluation of pulsed dye laser treatment of port wine stains (PWS) and in prediction of clinical outcome, in a prospective study. Forty-eight patients with PWS underwent one to nine pulsed dye laser treatments. Patient age and skin color as well as PWS surface area, anatomic location, and color were recorded. Pretreatment spectrophotometric measurements were performed. The subjective clinical results of treatment and the quantitative spectrophotometry results were evaluated by two independent teams, and the findings were correlated. The impact of the clinical characteristics on the response to treatment was assessed as well. Patients with excellent to good clinical results of laser treatments had pretreatment spectrophotometric measurements which differed by more than 10%, whereas patients with fair to poor results had spectrophotometric measurements with a difference of of less than 10%. The correlation between the spectrophotometric results and the clinical outcome was 73% (p Spectrophotometry has a higher correlation with clinical outcome and a better predictive value than other nonmeasurable, nonquantitative, dependent variables.

  16. An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova

    Science.gov (United States)

    Vennes, S.; Nemeth, P.; Kawka, A.; Thorstensen, J. R.; Khalack, V.; Ferrario, L.; Alper, E. H.

    2017-08-01

    Subluminous Type Ia supernovae, such as the Type Iax-class prototype SN 2002cx, are described by a variety of models such as the failed detonation and partial deflagration of an accreting carbon-oxygen white dwarf star or the explosion of an accreting, hybrid carbon-oxygen-neon core. These models predict that bound remnants survive such events with, according to some simulations, a high kick velocity. We report the discovery of a high proper motion, low-mass white dwarf (LP 40-365) that travels at a velocity greater than the Galactic escape velocity and whose peculiar atmosphere is dominated by intermediate-mass elements. Strong evidence indicates that this partially burnt remnant was ejected following a subluminous Type Ia supernova event. This supports the viability of single-degenerate supernova progenitors.

  17. Subluminal and superluminal propagation of light in an N-type medium

    Energy Technology Data Exchange (ETDEWEB)

    Han Dingan [CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China) and CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)]. E-mail: handingan@163.com; Guo Hong [CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China) and CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)]. E-mail: hongguo@pku.edu.cn; Bai Yanfeng [CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China); CREAM Group, Key Laboratory for Quantum Information and Measurements of Ministry of Education, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); Sun Hui [CREAM Group, Laboratory of Light Transmission Optics, South China Normal University, Guangzhou 510631 (China)

    2005-01-10

    For a three-level electromagnetically induced transparency (EIT) atomic system, we show that, adding a third driving field coupled to a fourth state, the properties of the weak probe light propagation are greatly changed. Due to the increase of the driving field, when the driving and the coupling detunings are zero, the light propagation can be changed from subluminal to superluminal. Also, the analytical solution exhibiting superluminal group velocity is given at the zero probe detuning.

  18. Experimental and clinical evaluation of a noninvasive reflectance pulse oximeter sensor.

    Science.gov (United States)

    Takatani, S; Davies, C; Sakakibara, N; Zurick, A; Kraenzler, E; Golding, L R; Noon, G P; Nose, Y; DeBakey, M E

    1992-10-01

    The objective of this study was to evaluate a new reflectance pulse oximeter sensor. The prototype sensor consists of 8 light-emitting diode (LED) chips (4 at 665 nm and 4 at 820 nm) and a photodiode chip mounted on a single substrate. The 4 LED chips for each wavelength are spaced at 90-degree intervals around the substrate and at an equal radial distance from the photodiode chip. An optical barrier between the photodiode and LED chips prevents a direct coupling effect between them. Near-infrared LEDs (940 nm) in the sensor warm the tissue. The microthermocouple mounted on the sensor surface measures the temperature of the skin-sensor interface and maintains it at a present level by servoregulating the current in the 940-nm LEDs. An animal study and a clinical study were performed. In the animal study, 5 mongrel dogs (weight, 10-20 kg) were anesthetized, mechanically ventilated, and cannulated. In each animal, arterial oxygen saturation (SaO2) was measured continuously by a standard transmission oximeter probe placed on the dog's earlobe and a reflectance oximeter sensor placed on the dog's tongue. In the first phase of the experiment, signals from the reflectance sensor were recorded while the dog was immersed in ice water until its body temperature decreased to 30 degrees C. In the second phase, the animal's body temperature was normal, and the oxygen content of the ventilator was varied to alter the SaO2. In the clinical study, 18 critically ill patients were monitored perioperatively with the prototype reflectance sensor. The first phase of the study investigated the relationship between local skin temperature and the accuracy of oximeter readings with the reflectance sensor. Each measurement was taken at a high saturation level as a function of local skin temperature. The second phase of the study compared measurements of oxygen saturation by a reflectance oximeter (SpO2[r]) with those made by a co-oximeter (SaO2[IL]) and a standard transmission oximeter (Sp

  19. Reconfigurable optofluidic switch for generation of optical pulse width modulation based on tunable reflective interface.

    Science.gov (United States)

    Mansuori, M; Zareei, G H; Hashemi, H

    2015-10-01

    We present a numerical method for generation of optical pulse width modulation (PWM) based on tunable reflective interface by using a microfluidic droplet. We demonstrate a single layer, planar, optofluidic PWM switch that is driven by excited alternating microbubbles. The main parameters of generation of this PWM such as frequency and speed of switching can be controlled by the mass flow rates of input fluids, and the shape of plug or droplet. Advantages of this design are the reconfigurability in design and the easy control of the switching parameters. The validation of the proposed design is carried out by employing the finite element method (FEM) for the mechanical simulation and the finite-difference time-domain (FDTD) for the optical simulation.

  20. Arterial Stiffness and Pulse Wave Reflection in Young Adult Heterozygous Sickle Cell Carriers

    Directory of Open Access Journals (Sweden)

    Tünzale Bayramoğlu

    2013-12-01

    Full Text Available OBJECTIVE: Pulse wave velocity (PWV and aortic augmentation index (AI are indicators of arterial stiffness. Pulse wave reflection and arterial stiffness are related to cardiovascular events and sickle cell disease. However, the effect of these parameters on the heterozygous sickle cell trait (HbAS is unknown. The aim of this study is to evaluate the arterial stiffness and wave reflection in young adult heterozygous sickle cell carriers. METHODS: We enrolled 40 volunteers (20 HbAS cases, 20 hemoglobin AA [HbAA] cases aged between 18 and 40 years. AI and PWV values were measured by arteriography. RESULTS: Aortic blood pressure, aortic AI, and brachial AI values were significantly higher in HbAS cases compared to the control group (HbAA (p=0.033, 0.011, and 0.011, respectively. A statistically significant positive correlation was found between aortic pulse wave velocity and mean arterial pressure, age, aortic AI, brachial AI, weight, and low-density lipoprotein levels (p=0.000, 0.017, 0.000, 0.000, 0.034, and 0.05, respectively in the whole study population. Aortic AI and age were also significantly correlated (p=0.026. In addition, a positive correlation between aortic PWV and systolic blood pressure and a positive correlation between aortic AI and mean arterial pressure (p=0.027 and 0.009, respectively were found in HbAS individuals. Our study reveals that mean arterial pressure and heart rate are independent determinants for the aortic AI. Mean arterial pressure and age are independent determinants for aortic PWV. CONCLUSION: Arterial stiffness measurement is an easy, cheap, and reliable method in the early diagnosis of cardiovascular disease in heterozygous sickle cell carriers. These results may depend on the amount of hemoglobin S in red blood cells. Further studies are required to investigate the blood pressure changes and its effects on arterial stiffness in order to explain the vascular aging mechanism in the HbAS trait population.

  1. Determination of thermal wave reflection coefficient to better estimate defect depth using pulsed thermography

    Science.gov (United States)

    Sirikham, Adisorn; Zhao, Yifan; Mehnen, Jörn

    2017-11-01

    Thermography is a promising method for detecting subsurface defects, but accurate measurement of defect depth is still a big challenge because thermographic signals are typically corrupted by imaging noise and affected by 3D heat conduction. Existing methods based on numerical models are susceptible to signal noise and methods based on analytical models require rigorous assumptions that usually cannot be satisfied in practical applications. This paper presents a new method to improve the measurement accuracy of subsurface defect depth through determining the thermal wave reflection coefficient directly from observed data that is usually assumed to be pre-known. This target is achieved through introducing a new heat transfer model that includes multiple physical parameters to better describe the observed thermal behaviour in pulsed thermographic inspection. Numerical simulations are used to evaluate the performance of the proposed method against four selected state-of-the-art methods. Results show that the accuracy of depth measurement has been improved up to 10% when noise level is high and thermal wave reflection coefficients is low. The feasibility of the proposed method in real data is also validated through a case study on characterising flat-bottom holes in carbon fibre reinforced polymer (CFRP) laminates which has a wide application in various sectors of industry.

  2. Noninvasive measurement of arterial oxyhemoglobin saturation with a heated and a non-heated skin reflectance pulse oximeter sensor.

    Science.gov (United States)

    Mendelson, Y; Yocum, B L

    1991-01-01

    The feasibility of measuring arterial oxyhemoglobin saturation (SaO2) noninvasively using a skin reflectance pulse oximeter sensor attached to the scalp, neck, and thigh regions of anesthetized swine was investigated. The optical reflectance sensor used consisted of a pair of red and infrared light-emitting diodes and a concentric array of six identical photodiodes. Two prototype sensor assemblies were evaluated: one assembly housed only the optical sensor, whereas the other also included a miniature heater. Measurements made from the scalp and neck regions were obtained with the non-heated skin reflectance sensor, and measurements from the thigh were made with the heated prototype. Each sensor was interfaced to a commercial transmittance pulse oximeter adapted to perform as a reflectance pulse oximeter. SaO2 values obtained by the reflectance pulse oximeters (SpO2(r) were compared simultaneously with SaO2 values obtained from arterial blood samples and analyzed in vitro with a CO-oximeter. The equations for the best-fitted linear regression lines describing the relationships between SpO2(r) and SaO2 values in the range between 30 and 100% were: SpO2(r) = 10.7 + 0.90 (SaO2), n = 321, r = 0.97; SpO2(r) = 16.72 + 0.82 (SaO2), n = 217, r = 0.95; and SpO2(r) = 20.21 + 0.77 (SaO2), n = 37, r = 0.97 for the neck, thigh, and scalp measurements, respectively. The regression analysis revealed significant correlation and a relatively small standard error of estimate (SEE = 4.05% for the neck, 4.79% for the thigh, and 3.50% for the scalp measurements). This study demonstrated the feasibility of measuring SaO2 noninvasively over a wide range of values utilizing the principle of reflectance pulse oximetry.

  3. A total internal reflection-fluorescence correlation spectroscopy setup with pulsed diode laser excitation

    Science.gov (United States)

    Weger, Lukas; Hoffmann-Jacobsen, Kerstin

    2017-09-01

    Fluorescence correlation spectroscopy (FCS) measures fluctuations in a (sub-)femtoliter volume to analyze the diffusive behavior of fluorescent particles. This highly sensitive method has proven to be useful for the analysis of dynamic biological systems as well as in chemistry, physics, and material sciences. It is routinely performed with commercial fluorescence microscopes, which provide a confined observation volume by the confocal technique. The evanescent wave of total internal reflectance (TIR) is used in home-built systems to permit a surface sensitive FCS analysis. We present a combined confocal and TIR-FCS setup which uses economic low-power pulsed diode lasers for excitation. Excitation and detection are coupled to time-correlated photon counting hardware. This allows simultaneous fluorescence lifetime and FCS measurements in a surface-sensitive mode. Moreover, the setup supports fluorescence lifetime correlation spectroscopy at surfaces. The excitation can be easily switched between TIR and epi-illumination to compare the surface properties with those in liquid bulk. The capabilities of the presented setup are demonstrated by measuring the diffusion coefficients of a free dye molecule, a labeled polyethylene glycol, and a fluorescent nanoparticle in confocal as well as in TIR-FCS.

  4. Implantable reflectance pulse transit time blood pressure sensor with oximetry capability

    Science.gov (United States)

    Fiala, J.; Gehrke, R.; Theodor, M.; Bingger, P.; Förster, K.; Heilmann, C.; Beyersdorf, F.; Zappe, H.; Seifert, A.

    2010-04-01

    We present a novel implantable multi-wavelength reflectance sensor for the measurement of blood pressure with pulse transit time (PTT). Continuous long-term monitoring of blood pressure and arterial oxygen saturation is vital for medical diagnostics and the ensuing therapy of cardiovascular diseases. Conventional cuff-based blood pressure monitors do not provide continuous data and put severe constraints on the patients' daily lives. An implantable sensor would eliminate such problems. The new biocompatible sensor is placed subcutaneously on blood perfused tissue. The PTT is calculated by photoplethysmograms and the ECG-signal, that is recorded with intracorporal electrodes. In addition, the sensor detects the arterial oxygen saturation. An ensuing spectralphotometric analysis of the light intensity changes delivers data on the concentration of dysfunctional hemoglobin derivatives. Experimental measurements showed a clear correlation between the estimated PTT and the systolic blood pressure reference. These initial results demonstrate the potential of the sensor as part of an fully implantable sensor system for the longterm-monitoring of cardiovascular parameters.

  5. Does the estimation of light attenuation in tissue increase the accuracy of reflectance pulse oximetry at low oxygen saturations in vivo?

    Science.gov (United States)

    Kisch-Wedel, H; Bernreuter, P; Kemming, G; Albert, M; Zwissler, B

    2009-09-01

    A new technique was validated in vivo in reflectance pulse oximetry for measuring low oxygen saturations. Two pairs of light emitter/detector diodes allow for estimation of light attenuation (LA) in tissue, which is assumed to be responsible for the inaccuracy of pulse oximetry at less than 70 % arterial oxygen saturation. For validation, 17 newborn piglets were desaturated stepwise from 21 % to 1.25 % inspiratory oxygen concentration during general anesthesia, and arterial oxygen saturation was measured with the reflectance pulse oximeter adjusted for LA in tissue, with a standard transmission pulse oximeter and a hemoximeter. LA in tissue could be quantified and was different between snout and foreleg (probability level (p) arterial oxygen saturations above 70 %, the bias between the methods was at 0 %-1 % and the variability 4 %-5 %. From 2 % to 100 % arterial oxygen saturation, the reflectance pulse oximeter estimated oxyhemoglobin saturation more accurately than a conventional transmission pulse oximeter (p < 0.05). At low oxygen saturations below 70 %, the bias and variability of the reflectance pulse oximeter calibration were closer to the hemoximeter measurements than the transmission pulse oximeter (p < 0.05). The variability of the reflectance pulse oximeter was slightly lower than the traditional oximeter by taking into account the LA in tissue (9 % versus 11 % -15 %, ns), and thus, the quality of the individual calibration lines improved (correlation coefficient, p < 0.05).

  6. Ultrashort pulse fiber delivery with optimized dispersion control by reflection grisms at 800 nm.

    Science.gov (United States)

    Kalashyan, Meri; Lefort, Claire; Martínez-León, Lluís; Mansuryan, Tigran; Mouradian, Levon; Louradour, Frederic

    2012-11-05

    We experimentally demonstrate a compact and efficient arrangement for fiber delivery of sub-30 fs energetic light pulses at 800 nm. Pulses coming from a broadband Ti:Sapphire oscillator are negatively pre-chirped by a grism-pair stretcher that allows for the control of second and third orders of dispersion. At the direct exit of a 2.7-m long large mode area (LMA) photonic crystal fiber 1-nJ pulses are temporally compressed to 29 fs producing close to 30 kW of peak power. The tunability of the device is studied. Comparison between LMA fibers and standard SMF fibers is also discussed.

  7. Transition between superluminal and subluminal light propagation in photorefractive Bi12SiO20 crystals.

    Science.gov (United States)

    Bo, Fang; Zhang, Guoquan; Xu, Jingjun

    2005-10-03

    We demonstrated superluminal light propagation with a negative group velocity of -5.7 m/s in a photorefractive Bi 12SiO20 crystal by using the dispersive phase coupling effect in a nondegenerate two-wave mixing process. To the best of our knowledge, this is the first experimental demonstration of superluminal light propagation at room temperature in solids by using a classical wave mixing technique. In addition, we showed the tunability of the group velocity of light between the negative (superluminal light) and the positive (subluminal light) by simply tuning the experimental conditions such as the frequency of the coupling beam, the incident intensity, and the externally applied electric fields.

  8. Subluminal and superluminal terahertz radiation in metamaterials with electromagnetically induced transparency.

    Science.gov (United States)

    Bai, Zhengyang; Hang, Chao; Huang, Guoxiang

    2013-07-29

    We propose a scheme to design a new type of optical metamaterial that can mimic the functionality of four-state atomic systems of N-type energy-level configuration with electromagnetically induced transparency (EIT). We show that in such metamaterial a transition from a single EIT to a double EIT of terahertz radiation may be easily achieved by actively tuning the intensity of the infrared pump field or passively tuning the geometrical parameters of resonator structures. In addition, the group velocity of the terahertz radiation can be varied from subluminal to superluminal by changing the pump field intensity. The scheme suggested here may be used to construct chip-scale slow and fast light devices and to realize rapidly responded switching of terahertz radiation at room temperature.

  9. Switching freely between superluminal and subluminal light propagation in a monolayer MoS2 nanoresonator.

    Science.gov (United States)

    Li, Jian-Bo; Xiao, Si; Liang, Shan; He, Meng-Dong; Kim, Nam-Chol; Luo, Yongfeng; Luo, Jian-Hua; Chen, Li-Qun

    2017-06-12

    We theoretically propose a feasible scheme to advance or slow the propagation of light in a monolayer MoS2 nanoresonator (NR). The scheme allows one to easily turn on or off the fast (superluminal) and slow (subluminal) light effects and switch freely between fast and slow light propagation by only adjusting the frequency or intensity of the pump field. As the exciton interacts strongly with the phonons in MoS2, the slow light effect will appear along with a large dispersion with a very steep negative slope and a sharp absorption peak. Especially, the maximal group velocity index of the slow light in the monolayer MoS2 NR can reach two orders of magnitude larger than that in a carbon nanotube resonator. These results provide a new way to measure the exciton-phonon coupling strength and may prove useful in device applications such as optical switching and optical signal processing.

  10. Subluminal and superluminal light propagation in a superconducting quantum circuit via Josephson coupling energy

    Energy Technology Data Exchange (ETDEWEB)

    Hamedi, H.R., E-mail: hamid.r.hamedi@gmail.com

    2015-05-15

    We investigate the dispersion-group index, as well as the transmission coefficient properties of a weak probe field in a superconducting quantum circuit with a tunable V-type artificial molecule constructed by two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. It is realized that the slope of dispersion can be changed from negative to positive or vice versa through the ratio of the Josephson coupling energy to the capacitive coupling strength which provides an extra controlling parameter for controlling the slope of dispersion. The temporal behavior of the probe dispersion and the required switching time for switching the superluminal light propagation to the subluminal light propagation are also discussed. The results may be useful for understanding the switching feature of slow light-based systems and have potential application in optical information processing.

  11. Subluminal and superluminal light propagation in a superconducting quantum circuit via Josephson coupling energy

    Science.gov (United States)

    Hamedi, H. R.

    2015-05-01

    We investigate the dispersion-group index, as well as the transmission coefficient properties of a weak probe field in a superconducting quantum circuit with a tunable V-type artificial molecule constructed by two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. It is realized that the slope of dispersion can be changed from negative to positive or vice versa through the ratio of the Josephson coupling energy to the capacitive coupling strength which provides an extra controlling parameter for controlling the slope of dispersion. The temporal behavior of the probe dispersion and the required switching time for switching the superluminal light propagation to the subluminal light propagation are also discussed. The results may be useful for understanding the switching feature of slow light-based systems and have potential application in optical information processing.

  12. Full-wave reflection of lightning long-wave radio pulses from the ionospheric D region: Numerical model

    Science.gov (United States)

    Jacobson, Abram R.; Shao, Xuan-Min; Holzworth, Robert

    2009-03-01

    A model is developed for calculating ionospheric reflection of electromagnetic pulses emitted by lightning, with most energy in the long-wave spectral region (f ~ 3-100 kHz). The building block of the calculation is a differential equation full-wave solution of Maxwell's equations for the complex reflection of individual plane waves incident from below, by the anisotropic, dissipative, diffuse dielectric profile of the lower ionosphere. This full-wave solution is then put into a summation over plane waves in an angular direct Fourier transform to obtain the reflection properties of curved wavefronts. This step models also the diffraction effects of long-wave ionospheric reflections observed at short or medium range (~200-500 km). The calculation can be done with any arbitrary but smooth dielectric profile versus altitude. For an initial test, this article uses the classic D region exponential profiles of electron density and collision rate given by Volland. With even these simple profiles, our model of full-wave reflection of curved wavefronts captures some of the basic attributes of observed reflected waveforms recorded with the Los Alamos Sferic Array. A follow-on article will present a detailed comparison with data in order to retrieve ionospheric parameters.

  13. Using a Force Probe to Study Transverse Pulses and Reflections on a Plucked Elastic Cord

    Science.gov (United States)

    Hamalainen, Ari; Abbott, David

    2010-01-01

    Before the advent of microcomputer-based labware (MBL), "time-of-flight" measurements for the speed of a transverse pulse on a string required elegant apparatus. This paper describes how to use an off-the-shelf MBL force sensor and a computer to perform the measurement. The data shown in this paper were collected using Vernier Software's wireless…

  14. Passive system with tunable group velocity for propagating electrical pulses from sub- to superluminal velocities.

    Science.gov (United States)

    Haché, Alain; Essiambre, Sophie

    2004-05-01

    We report an observation of tunable group velocity from sub-luminal to superluminal in a completely passive system. Electric pulses are sent along a spatially periodic conducting medium containing a punctual nonlinearity, and the resulting amplitude-dependent phase shift allows us to control dispersion and the propagation velocity at the stop band frequency.

  15. Arterial stiffness and pulse wave reflection are increased in patients suffering from severe periodontitis.

    Directory of Open Access Journals (Sweden)

    Yvonne Jockel-Schneider

    Full Text Available AIM: This single blind cross-sectional study compared the vascular health of subjects suffering from severe chronic periodontitis, severe aggressive periodontitis and periodontal healthy controls by evaluating pulse wave velocity (PWV, augmentation index (AIx and pulse pressure amplification (PPA. MATERIAL AND METHODS: In a total of 158 subjects, 92 suffering from severe periodontitis and 66 matched periodontal healthy controls, PWV, AIx, central and peripheral blood pressure were recorded using an oscillometric device (Arteriograph. RESULTS: Subjects suffering from severe chronic or aggressive periodontitis exhibited significantly higher PWV (p = 0.00004, higher AIx (p = 0.0049 and lower PPA (p = 0.028 than matched periodontal healthy controls. CONCLUSIONS: The results of this study confirm the association between periodontal inflammation and increased cardiovascular risk shown by impaired vascular health in case of severe periodontitis. As impaired vascular health is a common finding in patients suffering from severe periodontal disease a concomitant routine cardiovascular evaluation may be advised.

  16. A wireless reflectance pulse oximeter with digital baseline control for unfiltered photoplethysmograms.

    Science.gov (United States)

    Li, Kejia; Warren, Steve

    2012-06-01

    Pulse oximeters are central to the move toward wearable health monitoring devices and medical electronics either hosted by, e.g., smart phones or physically embedded in their design. This paper presents a small, low-cost pulse oximeter design appropriate for wearable and surface-based applications that also produces quality, unfiltered photo-plethysmograms (PPGs) ideal for emerging diagnostic algorithms. The design's "filter-free" embodiment, which employs only digital baseline subtraction as a signal compensation mechanism, distinguishes it from conventional pulse oximeters that incorporate filters for signal extraction and noise reduction. This results in high-fidelity PPGs with thousands of peak-to-peak digitization levels that are sampled at 240 Hz to avoid noise aliasing. Electronic feedback controls make these PPGs more resilient in the face of environmental changes (e.g., the device can operate in full room light), and data stream in real time across either a ZigBee wireless link or a wired USB connection to a host. On-board flash memory is available for store-and-forward applications. This sensor has demonstrated an ability to gather high-integrity data at fingertip, wrist, earlobe, palm, and temple locations from a group of 48 subjects (20 to 64 years old).

  17. [O I] λλ6300, 6364 IN THE NEBULAR SPECTRUM OF A SUBLUMINOUS TYPE Ia SUPERNOVA

    Energy Technology Data Exchange (ETDEWEB)

    Taubenberger, S.; Kromer, M.; Hillebrandt, W. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); Pakmor, R. [Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Pignata, G. [Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago (Chile); Maeda, K. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Hachinger, S. [Julius-Maximilians-Universität Würzburg, Emil-Fischer-Str. 31, D-97074 Würzburg (Germany); Leibundgut, B. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany)

    2013-10-01

    In this Letter, a late-phase spectrum of SN 2010lp, a subluminous Type Ia supernova (SN Ia), is presented and analyzed. As in 1991bg-like SNe Ia at comparable epochs, the spectrum is characterized by relatively broad [Fe II] and [Ca II] emission lines. However, instead of narrow [Fe III] and [Co III] lines that dominate the emission from the innermost regions of 1991bg-like supernovae (SNe), SN 2010lp shows [O I] λλ6300, 6364 emission, usually associated with core-collapse SNe and never previously observed in a subluminous thermonuclear explosion. The [O I] feature has a complex profile with two strong, narrow emission peaks. This suggests that oxygen is distributed in a non-spherical region close to the center of the ejecta, severely challenging most thermonuclear explosion models discussed in the literature. We conclude that, given these constraints, violent mergers are presently the most promising scenario to explain SN 2010lp.

  18. A Novel Ring Shaped Photodiode for Reflectance Pulse Oximetry in Wireless Applications

    DEFF Research Database (Denmark)

    Duun, Sune; Haahr, Rasmus Grønbek; Birkelund, Karen

    2007-01-01

    gives optimal gathering of light and thereby enabling lower LED drive currents and lower power consumption. To further optimize the photodiode a two layer SiO2/SiN interference filter is employed yielding 98% transmission at the wavelengths of the LED and damping of other wavelengths. The presented...... photodiode has an inner-outer radius of 3.29 -4.07 mm and an area of 18 mm2 , however, photodiodes with ring center radii ranging from 2.8 -4.9 mm have been fabricated. Using the pulse oxymetry sensor photoplethysmograms clearly showing the cardiovascular cycle are recorded. An on-chip integrated Au...

  19. ENERGY-EFFICIENT PASSIVE ANTENNA CODE PULSE MODULATION DUE TO THE REFLECTION OF MICROWAVE SIGNAL

    Directory of Open Access Journals (Sweden)

    T. A. Ismailov

    2015-01-01

    Full Text Available The article describes an antenna in a corner reflector with a p-i-n-diodes, integrated with the housing transceiver, which allows not only to provide bidirectional communication with the base station as a result of multipath radio three times, but with minimal energy consumption to provide digitally transmit information on the reflected wave flow of any complexity, which allow to eliminate energy in the transmit path and extend the life of the device. 

  20. RESEARCH OF THE ENTRANCE ANGLE EFFECT ON THE REFLECTANCE SPECTRA OF THE STAINLESS STEEL SURFACE OXIDIZED BY PULSED LASER RADIATION

    Directory of Open Access Journals (Sweden)

    V. P. Veiko

    2016-05-01

    Full Text Available Subject of Research.Oxide films on the metal surfaces can be obtained both by surface-uniform infrared heating and local laser treatment e.g. by sequence of nanosecond laser pulses. Due to interference in created films the coloration of treated area is observed. The present work shows the results of spectrophotometric measurements for various light entrance angles in the range of 10-60°. Method. AISI 304 stainless steel plates were oxidized by two methods: in muffle furnace FM - 10 (Т= 500-600° С, t = 5-7 min. and at line-by-line scanning by sequence of nanosecond laser pulses (λ = 1.06 μm, τ =100 ns, r = 25 μm,q=2.91∙107 W/cm2, Nx = 30, Ny = 1. Surface research in optical resolution was realized by Carl Zeiss Axio Imager A1M. Reflectance spectra were obtained with spectrophotometer Lambda Perkin 1050 with integrating sphere at different fixed light incidence angles. Topographic features were detected by scanning probe microscopy investigation with NanoEducator equipment. Main Results. The quantitative surface geometry characteristics of AISI 304 stainless steel patterns treated by different methods are obtained. It was found that the increase of light entrance angle has no influence on the form of reflection coefficient dependence from a wavelength, but a blue-shift occurs especially for the case of laser treatment. This difference can be caused by surface topology formed by laser heating and variety of oxide film thickness. This effect results in more significant change in observed sample color for laser treatment then for infrared heating. Practical Relevance. The results obtained in the present work can be used to implement a new element of product protection against forgery with the product marking.

  1. Temporal cross-correlation of x-ray free electron and optical lasers using soft x-ray pulse induced transient reflectivity.

    Science.gov (United States)

    Krupin, O; Trigo, M; Schlotter, W F; Beye, M; Sorgenfrei, F; Turner, J J; Reis, D A; Gerken, N; Lee, S; Lee, W S; Hays, G; Acremann, Y; Abbey, B; Coffee, R; Messerschmidt, M; Hau-Riege, S P; Lapertot, G; Lüning, J; Heimann, P; Soufli, R; Fernández-Perea, M; Rowen, M; Holmes, M; Molodtsov, S L; Föhlisch, A; Wurth, W

    2012-05-07

    The recent development of x-ray free electron lasers providing coherent, femtosecond-long pulses of high brilliance and variable energy opens new areas of scientific research in a variety of disciplines such as physics, chemistry, and biology. Pump-probe experimental techniques which observe the temporal evolution of systems after optical or x-ray pulse excitation are one of the main experimental schemes currently in use for ultrafast studies. The key challenge in these experiments is to reliably achieve temporal and spatial overlap of the x-ray and optical pulses. Here we present measurements of the x-ray pulse induced transient change of optical reflectivity from a variety of materials covering the soft x-ray photon energy range from 500eV to 2000eV and outline the use of this technique to establish and characterize temporal synchronization of the optical-laser and FEL x-ray pulses.

  2. Reflections

    Indian Academy of Sciences (India)

    REFLECTIONS. A freer life and independent work made of the quiet, dreamy boy a happy, outgoing, universally liked young man. He also began to familiarize himself with classical German literature. Though at first he was acquainted only with Milan and Pavia, Italy made a great impression on him even with this limitation.

  3. Enhanced Group Delay of the Pulse Reflection with Graphene Surface Plasmon via Modified Otto Configuration

    Directory of Open Access Journals (Sweden)

    Guimei Li

    2017-01-01

    Full Text Available In this paper, the group delay of the transverse magnetic (TM polarized wave reflected from a modified Otto configuration with graphene surface plasmon is investigated theoretically. The findings show that the optical group delay in this structure can be enhanced negatively and can be switched from negative to positive due to the excitation of surface plasmon by graphene. It is clear that the negative group delay can be actively tuned through the Fermi energy of the graphene. Furthermore, the delay properties can also be manipulated by changing either the relaxation time of graphene or the distance between the coupling prism and the graphene. These tunable delay characteristics are promising for fabricating grapheme-based optical delay devices and other applications in the terahertz regime.

  4. SN 2009js AT THE CROSSROADS BETWEEN NORMAL AND SUBLUMINOUS TYPE IIP SUPERNOVAE: OPTICAL AND MID-INFRARED EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Gandhi, P. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Yamanaka, M.; Itoh, R. [Department of Physical Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan); Tanaka, M. [National Astronomical Observatory, Mitaka, Tokyo (Japan); Nozawa, T.; Maeda, K.; Moriya, T. J. [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa (Japan); Kawabata, K. S. [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Saviane, I. [European Southern Observatory, Alonso de Cordova 3107, Santiago 19 (Chile); Hattori, T. [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Sasada, M. [Department of Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2013-04-20

    We present a study of SN 2009js in NGC 918. Multi-band Kanata optical photometry covering the first {approx}120 days shows the source to be a Type IIP SN. Reddening is dominated by that due to our Galaxy. One-year-post-explosion photometry with the New Technology Telescope and a Subaru optical spectrum 16 days post-discovery both imply a good match with the well-studied subluminous SN 2005cs. The plateau-phase luminosity of SN 2009js and its plateau duration are more similar to the intermediate luminosity IIP SN 2008in. Thus, SN 2009js shares characteristics with both subluminous and intermediate luminosity supernovae (SNe). Its radioactive tail luminosity lies between SN 2005cs and SN 2008in, whereas its quasi-bolometric luminosity decline from peak to plateau (quantified by a newly defined parameter {Delta}logL, which measures adiabatic cooling following shock breakout) is much smaller than both the others'. We estimate the ejected mass of {sup 56}Ni to be low ({approx}0.007 M{sub Sun }). The SN explosion energy appears to have been small, similar to that of SN 2005cs. SN 2009js is the first subluminous SN IIP to be studied in the mid-infrared. It was serendipitously caught by Spitzer at very early times. In addition, it was detected by WISE 105 days later with a significant 4.6 {mu}m flux excess above the photosphere. The infrared excess luminosity relative to the photosphere is clearly smaller than that of SN 2004dj, which has been extensively studied in the mid-infrared. The excess may be tentatively assigned to heated dust with mass {approx}3 Multiplication-Sign 10{sup -5} M{sub Sun }, or to CO fundamental emission as a precursor to dust formation.

  5. Subluminal and superluminal propagation in a three-level atom in the radiative limit based on coherent population oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalo, Isabel [Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid (Spain)], E-mail: igonzalo@fis.ucm.es; Anton, M.A.; Carreno, F.; Calderon, Oscar G. [Escuela Universitaria de Optica, Universidad Complutense de Madrid, Arcos de Jalon, 28037 Madrid (Spain)

    2008-10-13

    We investigate a three-level atomic system in the radiative limit to control the light propagation from the subluminal regime to the superluminal one. Here the three levels are connected between them by radiative transitions. We show that depending on the decay rates, this scheme, which is based on coherent population oscillations, allows to switch from one regime to the other by changing the Rabi frequencies of the driving fields. We also show that this scheme is also capable of producing absorptionless self-phase modulation.

  6. Wind turbines and bat mortality: Doppler shift profiles and ultrasonic bat-like pulse reflection from moving turbine blades.

    Science.gov (United States)

    Long, Chloe V; Flint, James A; Lepper, Paul A

    2010-10-01

    Bat mortality resulting from actual or near-collision with operational wind turbine rotors is a phenomenon that is widespread but not well understood. Because bats rely on information contained in high-frequency echoes to determine the nature and movement of a target, it is important to consider how ultrasonic pulses similar to those used by bats for echolocation may be interacting with operational turbine rotor blades. By assessing the characteristics of reflected ultrasonic echoes, moving turbine blades operating under low wind speed conditions (<6 m s(-1)) were found to produce distinct Doppler shift profiles at different angles to the rotor. Frequency shifts of up to ±700-800 Hz were produced, which may not be perceptible by some bat species. Monte Carlo simulation of bat-like sampling by echolocation revealed that over 50 rotor echoes could be required by species such as Pipistrellus pipistrellus for accurate interpretation of blade movement, which may not be achieved in the bat's approach time-window. In summary, it was found that echoes returned from moving blades had features which could render them attractive to bats or which might make it difficult for the bat to accurately detect and locate blades in sufficient time to avoid a collision.

  7. Eplerenone attenuates pulse wave reflection in chronic kidney disease stage 3-4--a randomized controlled study.

    Directory of Open Access Journals (Sweden)

    Lene Boesby

    Full Text Available Patients with chronic kidney disease (CKD have high cardiovascular mortality and morbidity associated with increased arterial stiffness. Plasma aldosterone levels are increased in CKD, and aldosterone has been found to increase vascular inflammation and fibrosis. It was hypothesized that aldosterone receptor inhibition with eplerenone could reduce arterial stiffness in CKD stage 3-4.The design was randomized, open, parallel group. Measurements of arterial stiffness markers were undertaken at weeks 1 and 24.24 weeks of add-on treatment with 25-50 mg eplerenone or standard medication.Primary outcome parameter was carotid-femoral pulse wave velocity (cfPWV. Secondary outcomes were augmentation index (AIx, ambulatory arterial stiffness index (AASI and urinary albumin excretion.Fifty-four CKD patients (mean eGFR 36 mL/min/1.73 m(2, SD 11 were randomized. Forty-six patients completed the trial. The mean difference in cfPWV changes between groups was 0.1 m/s (95%CI: -1.0, 1.3, P = 0.8. The mean difference in AIx changes between groups was 4.4% (0.1, 8.6, P = 0.04. AASI was unchanged in both groups. The ratio of change in urinary albumin excretion in the eplerenone group compared to the control was 0.61 (0.37, 1.01, P = 0.05. Four patients were withdrawn from the eplerenone group including three because of possible side effects; one was withdrawn from the control group. Mild hyperkalemia was seen on three occasions and was easily managed.The full planned number of patients was not attained. The duration of the trial may have been too short to obtain full effect of eplerenone on the arteries.Add-on treatment with eplerenone in CKD stage 3-4 did not significantly reduce cfPWV. There may be beneficial vascular effects leading to attenuated pulse wave reflection. Treatment was well-tolerated.ClinicalTrials.govNCT01100203.

  8. Design and implementation of an optimal laser pulse front tilting scheme for ultrafast electron diffraction in reflection geometry with high temporal resolution

    Directory of Open Access Journals (Sweden)

    Francesco Pennacchio

    2017-07-01

    Full Text Available Ultrafast electron diffraction is a powerful technique to investigate out-of-equilibrium atomic dynamics in solids with high temporal resolution. When diffraction is performed in reflection geometry, the main limitation is the mismatch in group velocity between the overlapping pump light and the electron probe pulses, which affects the overall temporal resolution of the experiment. A solution already available in the literature involved pulse front tilt of the pump beam at the sample, providing a sub-picosecond time resolution. However, in the reported optical scheme, the tilted pulse is characterized by a temporal chirp of about 1 ps at 1 mm away from the centre of the beam, which limits the investigation of surface dynamics in large crystals. In this paper, we propose an optimal tilting scheme designed for a radio-frequency-compressed ultrafast electron diffraction setup working in reflection geometry with 30 keV electron pulses containing up to 105 electrons/pulse. To characterize our scheme, we performed optical cross-correlation measurements, obtaining an average temporal width of the tilted pulse lower than 250 fs. The calibration of the electron-laser temporal overlap was obtained by monitoring the spatial profile of the electron beam when interacting with the plasma optically induced at the apex of a copper needle (plasma lensing effect. Finally, we report the first time-resolved results obtained on graphite, where the electron-phonon coupling dynamics is observed, showing an overall temporal resolution in the sub-500 fs regime. The successful implementation of this configuration opens the way to directly probe structural dynamics of low-dimensional systems in the sub-picosecond regime, with pulsed electrons.

  9. Coherent control of light-pulse propagation in a Raman induced grating

    Science.gov (United States)

    Arkhipkin, V. G.; Myslivets, S. A.

    2017-05-01

    We study light-pulse propagation in a dynamically controllable periodic structure (grating) resulting from Raman interaction of a weak probe pulse with a standing-wave pump and a second control laser field in N-type four-level atomic media. The grating is induced due to periodic spatial modulation of the Raman gain in a standing pump field (Raman gain grating). We show that it is possible to control both the probe pulse amplitude and the group velocity of the pulse from subluminal to superluminal by varying the pump or control field. Such a grating is of interest for all-optical switches and transistors.

  10. Giant Kerr nonlinearity and superluminal and subluminal polaritonic solitons in a Bose-Einstein condensate via superradiant scattering

    Science.gov (United States)

    Hang, Chao; Gabadadze, Gregory; Huang, Guoxiang

    2015-09-01

    We propose a setup to generate giant Kerr nonlinearity and polaritonic solitons via matter-wave superradiant scattering. The system we consider is a long cigar-shaped Bose-Einstein condensate (BEC), pumped by a red-detuned laser field with a space-dependent intensity distribution in transverse directions. The pump and the scattered fields propagate along the longitudinal direction. We show that by means of the atom-photon and atom-atom interactions in the system it is possible to produce a giant nonlinear optical effect. We further show that a backward scattering of the laser field from the BEC is favorable for the formation and stable propagation of polaritonic solitons, which are collective nonlinear excitations of the BEC coupled with the scattered laser field. In the case of backward Stokes (anti-Stokes) scattering the system may support robust bright (dark) polaritonic solitons propagating with superluminal (subluminal) velocity.

  11. Sub- and superluminal propagation of intense pulses in media with saturated and reverse absorption.

    Science.gov (United States)

    Agarwal, G S; Dey, Tarak Nath

    2004-05-21

    We develop models for the propagation of intense pulses in solid state media which can have either saturated absorption or reverse absorption. We model subluminal propagation in ruby and superluminal propagation in alexandrite as three and four level systems, respectively, coupled to Maxwell's equations. We present results well beyond the traditional pump-probe approach and explain the experiments of Bigelow et al. [Phys. Rev. Lett. 90, 113903 (2003)]Science 301, 200 (2003)

  12. Subluminal and superluminal light propagation via interference of incoherent pump fields

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoudi, M. [Department of Physics, Zanjan University, P.O. Box 45195-313, Zanjan (Iran, Islamic Republic of) and Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-159, Zanjan (Iran, Islamic Republic of)]. E-mail: mahmoudi@iasbs.ac.ir; Sahrai, M. [Department of Physics, Zanjan University, P.O. Box 45195-313, Zanjan (Iran, Islamic Republic of); Research Institute for Applied Physics and Astronomy, Tabriz University, Tabriz (Iran, Islamic Republic of); Tajalli, H. [Research Institute for Applied Physics and Astronomy, Tabriz University, Tabriz (Iran, Islamic Republic of)

    2006-08-28

    We investigate the dispersion and the absorption properties of a weak probe field in a four-level atomic system by using the incoherent pumping fields. It is shown that the slope of the dispersion changes from positive to negative with the interference of incoherent pumping process. It is also demonstrated that the group velocity of the light pulse can be controlled with the rates of incoherent pumping fields.

  13. Nonlinear reflection of a nanosecond laser pulse from thin aluminum film in the temperature range 2-14 kK

    Science.gov (United States)

    Karabutov, A. A.; Kaptilniy, A. G.; Ksenofontov, D. M.; Makarov, V. A.; Cherepetskaya, E. B.; Podymova, N. B.

    2015-11-01

    This letter aims to experimentally demonstrate the possibility of measuring the temporal dependencies of the surface temperature of an aluminum film confined by a transparent dielectric in the range below and above the critical temperature of aluminum (from 2 kK to 14 kK). Such temperatures are achieved under the action of a powerful linearly-polarized laser pulse of one nanosecond in duration onto the film’s surface. To find the temporal dependencies of the temperature of the aluminum film the nonlinear reflection coefficient of its irradiated surface is measured to determine the radiation of a Q-switched Nd:YAG laser at the fundamental wavelength.

  14. Beneficial effects on arterial stiffness and pulse-wave reflection of combined enalapril and candesartan in chronic kidney disease--a randomized trial.

    Directory of Open Access Journals (Sweden)

    Marie Frimodt-Møller

    Full Text Available Cardiovascular disease (CVD is highly prevalent in patients with chronic kidney disease (CKD. Inhibition of the renin-angiotensinsystem (RAS in hypertension causes differential effects on central and brachial blood pressure (BP, which has been translated into improved outcome. The objective was to examine if a more complete inhibition of RAS by combining an angiotensin converting enzyme inhibitor (ACEI and an angiotensin receptor antagonist (ARB compared to monotherapy has an additive effect on central BP and pulse-wave velocity (PWV, which are known markers of CVD.Sixty-seven CKD patients (mean GFR 30, range 13-59 ml/min/1.73 m(2 participated in an open randomized study of 16 weeks of monotherapy with either enalapril or candesartan followed by 8 weeks of dual blockade aiming at a total dose of 16 mg candesartan and 20 mg enalapril o.d. Pulse-wave measurements were performed at week 0, 8, 16 and 24 by the SphygmoCor device.Significant additive BP independent reductions were found after dual blockade in aortic PWV (-0.3 m/s, P<0.05 and in augmentation index (-2%, P<0.01 compared to monotherapy. Furthermore pulse pressure amplification was improved (P<0.05 and central systolic BP reduced (-6 mmHg, P<0.01.Dual blockade of the RAS resulted in an additive BP independent reduction in pulse-wave reflection and arterial stiffness compared to monotherapy in CKD patients.Clinical trial.gov NCT00235287.

  15. Pulse pressure variation does not reflect stroke volume variation in mechanically ventilated rats with lipopolysaccharide-induced pneumonia.

    Science.gov (United States)

    Cherpanath, Thomas G V; Smeding, Lonneke; Lagrand, Wim K; Hirsch, Alexander; Schultz, Marcus J; Groeneveld, Johan A B

    2014-01-01

    1. The present study examined the relationship between centrally measured stroke volume variation (SVV) and peripherally derived pulse pressure variation (PPV) in the setting of increased total arterial compliance (CA rt ). 2. Ten male Wistar rats were anaesthetized, paralysed and mechanically ventilated before being randomized to receive intrapulmonary lipopolysaccharide (LPS) or no LPS. Pulse pressure (PP) was derived from the left carotid artery, whereas stroke volume (SV) was measured directly in the left ventricle. Values of SVV and PPV were calculated over three breaths. Balloon inflation of a catheter positioned in the inferior vena cava was used, for a maximum of 30 s, to decrease preload while the SVV and PPV measurements were repeated. Values of CA rt were calculated as SV/PP. 3. Intrapulmonary LPS increased CA rt and SV. Values of SVV and PPV increased in both LPS-treated and untreated rats during balloon inflation. There was a correlation between SVV and PPV in untreated rats before (r = 0.55; P = 0.005) and during (r = 0.69; P mechanically ventilated rats. Our data caution against their interchangeability in human sepsis. © 2013 Wiley Publishing Asia Pty Ltd.

  16. A Ring-shaped photodiode designed for use in a reflectance pulse oximetry sensor in wireless health monitoring applications

    DEFF Research Database (Denmark)

    Duun, Sune; Haahr, Rasmus Grønbek; Birkelund, Karen

    2010-01-01

    enable very low light-emitting diode (LED) driving currents for the pulse oximeter. The photodiode also have a two layer SiO2/SiN interference filter yielding 98% transmission at the measuring wavelengths, 660 nm and 940 nm, and suppressing other wavelengths down to 50% transmission. The photodiode has...... an on-chip integrated Au thermistor for measuring the skin temperature of the body. The thermistor has a Temperature Coefficient of Resistance of 2.7·10-3 K-1 and a repeatability on temperature measurements of ±0.26°C. The photodiode is fabricated in a clean room environment by two diffusion...

  17. A PROPELLER MODEL FOR THE SUB-LUMINOUS STATE OF THE TRANSITIONAL MILLISECOND PULSAR PSR J1023+0038

    Energy Technology Data Exchange (ETDEWEB)

    Papitto, A.; Torres, D. F. [Institute of Space Sciences (CSIC-IEEC), Campus UAB, Carrer de Can Magrans, S/N, E-08193, Cerdanyola del Vallés, Barcelona (Spain)

    2015-07-01

    The discovery of millisecond pulsars switching between states powered either by the rotation of their magnetic field or by the accretion of matter has recently proved the tight link shared by millisecond radio pulsars and neutron stars in low-mass X-ray binaries. Transitional millisecond pulsars also show an enigmatic intermediate state in which the neutron star is surrounded by an accretion disk and emits coherent X-ray pulsations, but is sub-luminous in X-rays with respect to accreting neutron stars, and is brighter in gamma-rays than millisecond pulsars in the rotation-powered state. Here, we model the X-ray and gamma-ray emission observed from PSR J1023+0038 in such a state based on the assumptions that most of the disk in-flow is propelled away by the rapidly rotating neutron star magnetosphere, and that electrons can be accelerated to energies of a few GeV at the turbulent disk–magnetosphere boundary. We show that the synchrotron and self-synchrotron Compton emission coming from such a region, together with the hard disk emission typical of low states of accreting compact objects, is able to explain the radiation observed in the X-ray and gamma-ray bands. The average emission observed from PSR J1023+0038 is modeled by a disk in-flow with a rate of 1–3 × 10{sup −11} M{sub ⊙} yr{sup −1}, truncated at a radius ranging between 30 and 45 km, compatible with the hypothesis of a propelling magnetosphere. We compare the results we obtained with models that assume that a rotation-powered pulsar is turned on, showing how the spin-down power released in similar scenarios is hardly able to account for the magnitude of the observed emission.

  18. Pulse shaping with transmission lines

    Science.gov (United States)

    Wilcox, Russell B.

    1987-01-01

    A method and apparatus for forming shaped voltage pulses uses passive reflection from a transmission line with nonuniform impedance. The impedance of the reflecting line varies with length in accordance with the desired pulse shape. A high voltage input pulse is transmitted to the reflecting line. A reflected pulse is produced having the desired shape and is transmitted by pulse removal means to a load. Light activated photoconductive switches made of silicon can be utilized. The pulse shaper can be used to drive a Pockels cell to produce shaped optical pulses.

  19. Superluminal propagation of light pulses: A result of interference.

    Science.gov (United States)

    Wang, Li-Gang; Liu, Nian-Hua; Lin, Qiang; Zhu, Shi-Yao

    2003-12-01

    The propagation of pulses through dispersive media was investigated by solving Maxwell's equations without any approximation. We show that the superluminal propagation of pulses through anomalous dispersive media is a result of the interference of different frequency components composed of the pulse. The coherence of the pulse plays an important role for the superluminal propagation. With the decrease of the coherence of the pulse, the propagation changes from superluminal to subluminal. We have shown that the anomalous dispersion (the real part of the susceptibility) not the amplification (the imaginary part of the susceptibility) plays the essential role in the superluminal propagation. Although the superluminality always exists as long as the spectrum of the coherent pulse is within the anomalously dispersive region, both the energy propagation velocity and the frontal velocity never exceed the light speed in the vacuum. The output pulse through the medium is not the original pulse; instead it carries the information of the original pulse and the information of the prepared medium.

  20. Artificial construction of the layered Ruddlesden-Popper manganite La2Sr2Mn3O10 by reflection high energy electron diffraction monitored pulsed laser deposition.

    Science.gov (United States)

    Palgrave, Robert G; Borisov, Pavel; Dyer, Matthew S; McMitchell, Sean R C; Darling, George R; Claridge, John B; Batuk, Maria; Tan, Haiyan; Tian, He; Verbeeck, Jo; Hadermann, Joke; Rosseinsky, Matthew J

    2012-05-09

    Pulsed laser deposition has been used to artificially construct the n = 3 Ruddlesden-Popper structure La(2)Sr(2)Mn(3)O(10) in epitaxial thin film form by sequentially layering La(1-x)Sr(x)MnO(3) and SrO unit cells aided by in situ reflection high energy electron diffraction monitoring. The interval deposition technique was used to promote two-dimensional SrO growth. X-ray diffraction and cross-sectional transmission electron microscopy indicated that the trilayer structure had been formed. A site ordering was found to differ from that expected thermodynamically, with the smaller Sr(2+) predominantly on the R site due to kinetic trapping of the deposited cation sequence. A dependence of the out-of-plane lattice parameter on growth pressure was interpreted as changing the oxygen content of the films. Magnetic and transport measurements on fully oxygenated films indicated a frustrated magnetic ground state characterized as a spin glass-like magnetic phase with the glass temperature T(g) ≈ 34 K. The magnetic frustration has a clear in-plane (ab) magnetic anisotropy, which is maintained up to temperatures of 150 K. Density functional theory calculations suggest competing antiferromagnetic and ferromagnetic long-range orders, which are proposed as the origin of the low-temperature glassy state.

  1. Superluminal propagation of pulsed pseudo-thermal light in atomic vapor.

    Science.gov (United States)

    Bae, In-Ho; Cho, Young-Wook; Lee, Hee Jung; Kim, Yoon-Ho; Moon, Han Seb

    2010-09-13

    We report an experimental demonstration of slow and superluminal propagation of pseudo-thermal (chaotic) light in the Λ-type system of the 5S(1/2)-5P(1/2) transition of (87)Rb atom. The slowed propagation of pulsed pseudo-thermal light was demonstrated in an electromagnetically-induced transparency medium while the superluminal propagation was demonstrated with the enhanced absorption scheme where the coupling field takes the form of a standing wave.We have also demonstrated that the photon number statistics of the pseudo-thermal light is preserved for both the subluminal and superluminal cases.

  2. Thermally-fluctuated single-flux-quantum pulse intervals reflected in input-output characteristics of a double-flux-quantum amplifier

    Science.gov (United States)

    Mizugaki, Yoshinao; Urai, Yoshiaki; Shimada, Hiroshi

    2017-07-01

    A double-flux-quantum amplifier (DFQA) is a voltage multiplier of quantum accuracy, which we have employed at the final stage of a single-flux-quantum (SFQ) digital-to-analog converter (DAC). We recently found that experimental input-output (IO) characteristics of DFQAs were always slightly different from numerical results assuming ideally-periodic SFQ pulse trains. That is, experimental IO characteristics obtained using an over-biasing method were gradually deteriorated near their maximum operation voltages. Numerical simulation including the over-biasing method at a finite temperature suggested that the difference was likely to be attributed to thermally-fluctuated intervals of input SFQ pulses.

  3. Production and characterisation of periodic and chirped La/B{sub 4}C-multilayer-mirrors for the reflection of ultra short XUV-pulses

    Energy Technology Data Exchange (ETDEWEB)

    Lass, Maike; Hendel, Stefan; Bienert, Florian; Sacher, Marc D.; Hachmann, Wiebke; Heinzmann, Ulrich [Molecular and Surface Physics, Bielefeld University (Germany); Schaefers, Franz [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Elektronenspeicherring BESSY II (Germany)

    2009-07-01

    The applicability of reflective optical components for the soft X-ray region depends upon the existence of multilayer-optics. For the photon energy range of 100-190eV Lanthanum (La) is favoured as the absorber material and boroncarbide (B{sub 4}C) as the spacer material. Thin periodic and aperiodic (chirped) layer systems of those materials with double layer periods of 3.5 nm have been produced by UHV electron beam evaporation combined with ion polishing to decrease the interface roughness and thus to increase the reflectivity. In-situ layer thickness control is done by X-ray reflectometry and single-wavelength ellipsometry. The characterisation of the layer purity is done by ex-situ sputter Auger spectroscopy, whilst structural analysis is performed by X-ray diffraction, transmission electron microscopy and at-wavelength reflectivity measurements with synchrotron radiation at the BESSY II facility. We report on reflectivities of periodic and aperiodic multilayer-mirrors.

  4. Pulse on Pulse

    DEFF Research Database (Denmark)

    Schmidt, Ulrik; Carlson, Merete

    2012-01-01

    of the visitor’s beating heart to the blink of a fragile light bulb, thereby transforming each light bulb into a register of individual life. But at the same time the blinking light bulbs together produce a chaotically flickering light environment composed by various layers of repetitive rhythms, a vibrant...... and pulsating ‘room’. Hence, the visitors in Pulse Room are invited into a complex scenario that continuously oscillates between various aspects of signification (the light bulbs representing individual lives; the pulse itself as the symbolic ‘rhythm of life’) and instants of pure material processuality...... (flickering light bulbs; polyrhythmic layers). Taking our point of departure in a discussion of Gilles Deleuze’s concepts of modulation and signaletic material in relation to electronic media, we examine how the complex orchestration of pulsation between signification and material modulation produces...

  5. Reflecting reflection in supervision

    DEFF Research Database (Denmark)

    Lystbæk, Christian Tang

    Reflection has moved from the margins to the mainstream in supervision. Notions of reflection have become well established since the late 1980s. These notions have provided useful framing devices to help conceptualize some important processes in guidance and counseling. However, some applications...... of reflection, rehabilitate them in order to capture broader connotations or move to new ways of regarding reflection that are more in keeping with not only reflective but also emotive, normative and formative views on supervision. The paper presents a critical perspective on supervision that challenge...

  6. Subluminous X-ray binaries

    NARCIS (Netherlands)

    Armas Padilla, M.

    2013-01-01

    The discovery of the first X-ray binary, Scorpius X-1, by Giacconi et al. (1962), marked the birth of X-ray astronomy. Following that discovery, many additional X-ray sources where found with the first generation of X-ray rockets and observatories (e.g., UHURU and Einstein). The short-timescale

  7. Producing High Intense Attosecond Pulse Train by Interaction of Three-Color Pulse and Overdense Plasma

    Science.gov (United States)

    Salehi, M.; Mirzanejad, S.

    2017-05-01

    Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of {{ω }}1, {{ω }}2 and {{ω }}3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.

  8. RF Pulsed Heating

    Energy Technology Data Exchange (ETDEWEB)

    Pritzkau, David P.

    2002-01-03

    RF pulsed heating is a process by which a metal is heated from magnetic fields on its surface due to high-power pulsed RF. When the thermal stresses induced are larger than the elastic limit, microcracks and surface roughening will occur due to cyclic fatigue. Pulsed heating limits the maximum magnetic field on the surface and through it the maximum achievable accelerating gradient in a normal conducting accelerator structure. An experiment using circularly cylindrical cavities operating in the TE{sub 011} mode at a resonant frequency of 11.424 GHz is designed to study pulsed heating on OFE copper, a material commonly used in normal conducting accelerator structures. The high-power pulsed RF is supplied by an X-band klystron capable of outputting 50 MW, 1.5 {micro}s pulses. The test pieces of the cavity are designed to be removable to allow testing of different materials with different surface preparations. A diagnostic tool is developed to measure the temperature rise in the cavity utilizing the dynamic Q change of the resonant mode due to heating. The diagnostic consists of simultaneously exciting a TE{sub 012} mode to steady-state in the cavity at 18 GHz and measuring the change in reflected power as the cavity is heated from high-power pulsed RF. Two experimental runs were completed. One run was executed at a calculated temperature rise of 120 K for 56 x 10{sup 6} pulses. The second run was executed at a calculated temperature rise of 82 K for 86 x 10{sup 6} pulses. Scanning electron microscope pictures show extensive damage occurring in the region of maximum temperature rise on the surface of the test pieces.

  9. The reflective learning continuum: reflecting on reflection

    OpenAIRE

    Peltier, J; Hay, A.; Drago, W

    2005-01-01

    The importance of reflection to marketing educators is increasingly recognized. However, there is a lack of empirical research which considers reflection within the context of both the marketing and general business education literature. This paper describes the use of an instrument which can be used to measure four identified levels of a reflection hierarchy: habitual action, understanding, reflection and intensive reflection and two conditions for reflection: instructor to student interacti...

  10. Pulse Oximetry

    Science.gov (United States)

    ... people need more oxygen when asleep than when awake. Some need more oxygen with activity than when ... oxygen saturation levels (below 80%) or with very dark skin. When should I use a pulse oximeter? ...

  11. Reflective Writing

    DEFF Research Database (Denmark)

    Ahrenkiel Jørgensen, Andriette

    2016-01-01

    a contribution to the discussions about the role of reflection in design work and in learning situations at large. By engaging with the dialogic reflection, which is one of the four essential types of reflection, (the three others being descriptive writing, descriptive reflection and critical reflection...

  12. Tunable pulse-shaping with gated graphene nanoribbons

    DEFF Research Database (Denmark)

    Prokopeva, Ludmila; Emani, Naresh K.; Boltasseva, Alexandra

    2014-01-01

    We propose a pulse-shaper made of gated graphene nanoribbons. Simulations demonstrate tunable control over the shapes of transmitted and reflected pulses using the gating bias. Initial fabrication and characterization of graphene elements is also discussed.......We propose a pulse-shaper made of gated graphene nanoribbons. Simulations demonstrate tunable control over the shapes of transmitted and reflected pulses using the gating bias. Initial fabrication and characterization of graphene elements is also discussed....

  13. Pulse plating

    CERN Document Server

    Hansal, Wolfgang E G; Green, Todd; Leisner, Peter; Reichenbach, Andreas

    2012-01-01

    The electrodeposition of metals using pulsed current has achieved practical importance in recent years. Although it has long been known that changes in potential, with or without polarity reversal, can significantly affect the deposition process, the practical application of this has been slow to be adopted. This can largely be explained in terms of the complex relationship between the current regime and its effect on the electrodeposition process. In order to harness these effects, an understanding of the anodic and cathodic electrochemical processes is necessary, together with the effects of polarity reversal and the rate of such reversals. In this new monograph, the basics of metal electrodeposition from solution are laid out in great detail in seven distinct chapters. With this knowledge, the reader is able to predict how a given pulse train profile can be adopted to achieve a desired outcome. Equally important is the choice of a suitable rectifier and the ancillary control circuits to enable pulse platin...

  14. Development of a Cardiovascular Simulator for Studying Pulse Diagnosis Mechanisms

    Directory of Open Access Journals (Sweden)

    Min Jang

    2017-01-01

    Full Text Available This research was undertaken to develop a cardiovascular simulator for use in the study of pulse diagnosis. The physical (i.e., pulse wave transmission and reflection and physiological (i.e., systolic and diastolic pressure, pulse pressure, and mean pressure characteristics of the radial pulse wave were reproduced by our simulator. The simulator consisted of an arterial component and a pulse-generating component. Computer simulation was used to simplify the arterial component while maintaining the elastic modulus and artery size. To improve the reflected wave characteristics, a palmar arch was incorporated within the simulator. The simulated radial pulse showed good agreement with clinical data.

  15. Quantifying Reflection

    DEFF Research Database (Denmark)

    Alcock, Gordon Lindsay

    2013-01-01

    This paper documents 1st semester student reflections on “learning to learn” in a team-based PBL environment with quantitative and qualitative student reflective feedback on the learning gains of 60 Architectural Technology and Construction Management students at VIA University College, Denmark....... It contrasts the students’ self-assessment in a range of ‘product’ skills such as Revit, Structural Design, Mathematics of construction, Technical Installations; as well as ‘process’ competencies such as ‘Working in a team’, Sharing knowledge, Maintaining a portfolio and Reflecting ON learning and FOR learning......´ These are all based on Blooms taxonomy and levels of competence and form a major part of individual student and group learning portfolios. Key Words :Project-Based learning, Reflective Portfolios, Self assessment, Defining learning gains, Developing learning strategies , Reflections on and for learning...

  16. Pulse front adaptive optics: a new method for control of ultrashort laser pulses.

    Science.gov (United States)

    Sun, Bangshan; Salter, Patrick S; Booth, Martin J

    2015-07-27

    Ultrafast lasers enable a wide range of physics research and the manipulation of short pulses is a critical part of the ultrafast tool kit. Current methods of laser pulse shaping are usually considered separately in either the spatial or the temporal domain, but laser pulses are complex entities existing in four dimensions, so full freedom of manipulation requires advanced forms of spatiotemporal control. We demonstrate through a combination of adaptable diffractive and reflective optical elements - a liquid crystal spatial light modulator (SLM) and a deformable mirror (DM) - decoupled spatial control over the pulse front (temporal group delay) and phase front of an ultra-short pulse was enabled. Pulse front modulation was confirmed through autocorrelation measurements. This new adaptive optics technique, for the first time enabling in principle arbitrary shaping of the pulse front, promises to offer a further level of control for ultrafast lasers.

  17. Analysis of folded pulse forming line operation

    Science.gov (United States)

    Domonkos, M. T.; Watrous, J.; Parker, J. V.; Cavazos, T.; Slenes, K.; Heidger, S.; Brown, D.; Wilson, D.

    2014-09-01

    A compact pulse forming line (CPFL) concept based on a folded transmission line and high-breakdown strength dielectric was explored through an effort combining proof-of-principle experiments with electromagnetic modeling. A small-scale folded CPFL was fabricated using surface-mount ceramic multilayer capacitors. The line consisted of 150 capacitors close-packed in parallel and delivered a 300 ns flat-top pulse. The concept was carried to a 10 kV class device using a polymer-ceramic nanocomposite dielectric with a permittivity of 37.6. The line was designed for a 161 ns FWHM length pulse into a matched load. The line delivered a 110 ns FWHM pulse, and the pulse peak amplitude exceeded the matched load ideal. Transient electromagnetic analysis using the particle-in-cell code ICEPIC was conducted to examine the nature of the unexpected pulse shortening and distortion. Two-dimensional analysis failed to capture the anomalous behavior. Three-dimensional analysis replicated the pulse shape and revealed that the bends were largely responsible for the pulse shortening. The bends not only create the expected reflection of the incident TEM wave but also produce a non-zero component of the Poynting vector perpendicular to the propagation direction of the dominant electromagnetic wave, resulting in power flow largely external to the PFL. This analysis explains both the pulse shortening and the amplitude of the pulse.

  18. Reflection ciphers

    DEFF Research Database (Denmark)

    Boura, Christina; Canteaut, Anne; Knudsen, Lars Ramkilde

    2017-01-01

    study the necessary properties for this coupling permutation. Special care has to be taken of some related-key distinguishers since, in the context of reflection ciphers, they may provide attacks in the single-key setting.We then derive some criteria for constructing secure reflection ciphers...... and analyze the security properties of different families of coupling permutations. Finally, we concentrate on the case of reflection block ciphers and, as an illustration, we provide concrete examples of key schedules corresponding to several coupling permutations, which lead to new variants of the block...

  19. X-ray induced optical reflectivity

    Directory of Open Access Journals (Sweden)

    Stephen M. Durbin

    2012-12-01

    Full Text Available The change in optical reflectivity induced by intense x-ray pulses can now be used to study ultrafast many body responses in solids in the femtosecond time domain. X-ray absorption creates photoelectrons and core level holes subsequently filled by Auger or fluorescence processes, and these excitations ultimately add conduction and valence band carriers that perturb optical reflectivity. Optical absorption associated with band filling and band gap narrowing is shown to explain the basic features found in recent measurements on an insulator (silicon nitride, Si3N4, a semiconductor (gallium arsenide, GaAs, and a metal (gold, Au, obtained with ∼100 fs x-ray pulses at 500-2000 eV and probed with 800 nm laser pulses. In particular GaAs exhibits an abrupt drop in reflectivity, persisting only for a time comparable to the x-ray excitation pulse duration, consistent with prompt band gap narrowing.

  20. Ablation of steel by microsecond pulse trains

    Science.gov (United States)

    Windeler, Matthew Karl Ross

    Laser micromachining is an important material processing technique used in industry and medicine to produce parts with high precision. Control of the material removal process is imperative to obtain the desired part with minimal thermal damage to the surrounding material. Longer pulsed lasers, with pulse durations of milli- and microseconds, are used primarily for laser through-cutting and welding. In this work, a two-pulse sequence using microsecond pulse durations is demonstrated to achieve consistent material removal during percussion drilling when the delay between the pulses is properly defined. The light-matter interaction moves from a regime of surface morphology changes to melt and vapour ejection. Inline coherent imaging (ICI), a broadband, spatially-coherent imaging technique, is used to monitor the ablation process. The pulse parameter space is explored and the key regimes are determined. Material removal is observed when the pulse delay is on the order of the pulse duration. ICI is also used to directly observe the ablation process. Melt dynamics are characterized by monitoring surface changes during and after laser processing at several positions in and around the interaction region. Ablation is enhanced when the melt has time to flow back into the hole before the interaction with the second pulse begins. A phenomenological model is developed to understand the relationship between material removal and pulse delay. Based on melt refilling the interaction region, described by logistic growth, and heat loss, described by exponential decay, the model is fit to several datasets. The fit parameters reflect the pulse energies and durations used in the ablation experiments. For pulse durations of 50 us with pulse energies of 7.32 mJ +/- 0.09 mJ, the logisitic growth component of the model reaches half maximum after 8.3 mus +/- 1.1 us and the exponential decays with a rate of 64 mus +/- 15 us. The phenomenological model offers an interpretation of the material

  1. Reflective Learning

    African Journals Online (AJOL)

    dell

    students who used learning log and those who did not especially for the course Pschopharmacology, but the mean scores did not show a significant difference for the course Psychology of Gender. The reflective reports of the students also roughly indicated that the students developed positive attitudes towards using ...

  2. PERSONAL REFLECTIONS

    Indian Academy of Sciences (India)

    IAS Admin

    Resonance journal of science education. April 2015 Volume 20 Number 4. GENERALARTICLES ... Development of. Probability Theory. K B Athreya. Classroom. Tutorial on Phyloge- netic Inference –1. Felix Bast. 360. 346. 286. PERSONAL REFLECTIONS. 368 The Road to IISc. M L Munjal (Transcribed by Maneesh Kunte).

  3. Theory of reflection reflection and transmission of electromagnetic, particle and acoustic waves

    CERN Document Server

    Lekner, John

    2016-01-01

    This book deals with the reflection of electromagnetic and particle waves by interfaces. The interfaces can be sharp or diffuse. The topics of the book contain absorption, inverse problems, anisotropy, pulses and finite beams, rough surfaces, matrix methods, numerical methods,  reflection of particle waves and neutron reflection. Exact general results are presented, followed by long wave reflection, variational theory, reflection amplitude equations of the Riccati type, and reflection of short waves. The Second Edition of the Theory of Reflection is an updated and much enlarged revision of the 1987 monograph. There are new chapters on periodically stratified media, ellipsometry, chiral media, neutron reflection and reflection of acoustic waves. The chapter on anisotropy is much extended, with a complete treatment of the reflection and transmission properties of arbitrarily oriented uniaxial crystals. The book gives a systematic and unified treatment reflection and transmission of electromagnetic and particle...

  4. Exploring subluminous X-ray binaries

    NARCIS (Netherlands)

    Degenaar, N.D.

    2010-01-01

    Halfway the twentieth century, technological developments made it possible to carry detection instruments outside the absorbing layers of the Earth’s atmosphere onboard rockets and satellites. This opened up the opportunity to detect the emission from celestial objects at X-ray wavelengths, thereby

  5. Inductive Pulse Generation

    OpenAIRE

    Lindblom, Adam

    2006-01-01

    Pulsed power generators are a key component in compact systems for generation of high-power microwaves (HPM). HPM generation by virtual cathode devices such as Vircators put high demands on the source. The rise time and the pulse length of the source voltage are two key issues in the generation of HPM radiation. This thesis describes the construction and tests of several inductive high power pulse generators. The pulse generators were designed with the intent to deliver a pulse with fast rise...

  6. Influence of a pulsed CO2 laser operating at 9.4  μm on the surface morphology, reflectivity, and acid resistance of dental enamel below the threshold for melting.

    Science.gov (United States)

    Kim, Jin Wan; Lee, Raymond; Chan, Kenneth H; Jew, Jamison M; Fried, Daniel

    2017-02-01

    Below the threshold for laser ablation, the mineral phase of enamel is converted into a purer phase hydroxyapatite with increased acid resistance. Studies suggest the possibility of achieving the conversion without visible surface alteration. In this study, changes in the surface morphology, reflectivity, and acid resistance were monitored with varying irradiation intensity. Bovine enamel specimens were irradiated using a CO 2 laser operating at 9.4 ?? ? m with a Gaussian spatial beam profile—1.6 to 3.1 mm in diameter. After laser treatment, samples were subjected to demineralization to simulate the acidic intraoral conditions of dental decay. The resulting demineralization and erosion were assessed using polarization-sensitive optical coherence tomography, three-dimensional digital microscopy, and polarized light microscopy. Distinct changes in the surface morphology and the degree of inhibition were found within the laser-treated area in accordance with the laser intensity profile. Subtle visual changes were noted below the melting point for enamel that appear to correspond to thresholds for denaturation of the organic phase and thermal decomposition of the mineral phase. There was significant protection from laser irradiation in areas in which the reflectivity was not increased significantly, suggesting that aesthetically sensitive areas of the tooth can be treated for caries prevention.

  7. Influence of a pulsed CO2 laser operating at 9.4 μm on the surface morphology, reflectivity, and acid resistance of dental enamel below the threshold for melting

    Science.gov (United States)

    Kim, Jin Wan; Lee, Raymond; Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2017-02-01

    Below the threshold for laser ablation, the mineral phase of enamel is converted into a purer phase hydroxyapatite with increased acid resistance. Studies suggest the possibility of achieving the conversion without visible surface alteration. In this study, changes in the surface morphology, reflectivity, and acid resistance were monitored with varying irradiation intensity. Bovine enamel specimens were irradiated using a CO2 laser operating at 9.4 μm with a Gaussian spatial beam profile-1.6 to 3.1 mm in diameter. After laser treatment, samples were subjected to demineralization to simulate the acidic intraoral conditions of dental decay. The resulting demineralization and erosion were assessed using polarization-sensitive optical coherence tomography, three-dimensional digital microscopy, and polarized light microscopy. Distinct changes in the surface morphology and the degree of inhibition were found within the laser-treated area in accordance with the laser intensity profile. Subtle visual changes were noted below the melting point for enamel that appear to correspond to thresholds for denaturation of the organic phase and thermal decomposition of the mineral phase. There was significant protection from laser irradiation in areas in which the reflectivity was not increased significantly, suggesting that aesthetically sensitive areas of the tooth can be treated for caries prevention.

  8. Pulsed water jet generated by pulse multiplication

    Czech Academy of Sciences Publication Activity Database

    Dvorský, R.; Sitek, Libor; Sochor, T.

    2016-01-01

    Roč. 23, č. 4 (2016), s. 959-967 ISSN 1330-3651 R&D Projects: GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : high-pressure pulses * pulse intensifier * pulsed water jet * water hammer effect Subject RIV: JQ - Machines ; Tools Impact factor: 0.723, year: 2016 http://hrcak.srce.hr/163752?lang=en

  9. Pulse Propagation on close conductors

    CERN Document Server

    Dieckmann, A

    2001-01-01

    The propagation and reflection of arbitrarily shaped pulses on non-dispersive parallel conductors of finite length with user defined cross section is simulated employing the discretized telegraph equation. The geometry of the system of conductors and the presence of dielectric material determine the capacities and inductances that enter the calculation. The values of these parameters are found using an iterative Laplace equation solving procedure and confirmed for certain calculable geometries including the line charge inside a box. The evolving pulses and the resulting crosstalk can be plotted at any instant and - in the Mathematica notebook version of this report - be looked at in an animation. As an example a differential pair of microstrips as used in the ATLAS vertex detector is analysed.

  10. Enhancement of photon number reflected by the relativistic flying mirror.

    Science.gov (United States)

    Kando, M; Pirozhkov, A S; Kawase, K; Esirkepov, T Zh; Fukuda, Y; Kiriyama, H; Okada, H; Daito, I; Kameshima, T; Hayashi, Y; Kotaki, H; Mori, M; Koga, J K; Daido, H; Faenov, A Ya; Pikuz, T; Ma, J; Chen, L-M; Ragozin, E N; Kawachi, T; Kato, Y; Tajima, T; Bulanov, S V

    2009-12-04

    Laser light reflection by a relativistically moving electron density modulation (flying mirror) in a wake wave generated in a plasma by a high intensity laser pulse is investigated experimentally. A counterpropagating laser pulse is reflected and upshifted in frequency with a multiplication factor of 37-66, corresponding to the extreme ultraviolet wavelength. The demonstrated flying mirror reflectivity (from 3 x 10(-6) to 2 x 10(-5), and from 1.3 x 10(-4) to 0.6 x 10(-3), for the photon number and pulse energy, respectively) is close to the theoretical estimate for the parameters of the experiment.

  11. Anomalous photo-induced response by double-pulse excitation in the organic conductor (EDO-TTF)2PF6

    Science.gov (United States)

    Onda, Ken; Ogihara, Sho; Ishikawa, Tadahiko; Okimoto, Yoichi; Shao, Xiangfeng; Nakano, Yoshiaki; Yamochi, Hideki; Saito, Gunzi; Koshihara, Shin-ya

    2009-02-01

    We measured ultrafast reflectivity changes induced by double-pulse excitation in the organic conductor (EDO-TTF)2PF6. Using double-pulse excitation with a relatively high intensity, the sign of reflectivity change became reversed at around 0.8 ps and subsequently the reflectivity change reverted to that of the normal photo-induced state after about 1 ps. Using a optically phase-locked double-pulse with low intensity, we found that the temporal profile excited by an in-phase double-pulse differs from that by an out-of-phase double-pulse despite the time difference between the double-pulses being only 1.31 fs. This was true even when there is almost no overlap between each pulse in the double-pulse. These results indicate that the photo-response in this material to double-pulse excitation differs greatly from the linear sum of the responses to single pulses.

  12. TDR Using Autocorrelation and Varying-Duration Pulses

    Science.gov (United States)

    Lucena, Angel; Mullinex, Pam; Huang, PoTien; Santiago, Josephine; Mata, Carlos; Zavala, Carlos; Lane, John

    2008-01-01

    In an alternative to a prior technique of time-domain-reflectometry (TDR) in which very short excitation pulses are used, the pulses have very short rise and fall times and the pulse duration is varied continuously between a minimum and a maximum value. In both the present and prior techniques, the basic idea is to (1) measure the times between the generation of excitation pulses and the reception of reflections of the pulses as indications of the locations of one or more defects along a cable and (2) measure the amplitudes of the reflections as indication of the magnitudes of the defects. In general, an excitation pulse has a duration T. Each leading and trailing edge of an excitation pulse generates a reflection from a defect, so that a unique pair of reflections is associated with each defect. In the present alternative technique, the processing of the measured reflection signal includes computation of the autocorrelation function R(tau) identical with fx(t)x(t-tau)dt where t is time, x(t) is the measured reflection signal at time t, and taus is the correlation interval. The integration is performed over a measurement time interval short enough to enable identification and location of a defect within the corresponding spatial interval along the cable. Typically, where there is a defect, R(tau) exhibits a negative peak having maximum magnitude for tau in the vicinity of T. This peak can be used as a means of identifying a leading-edge/trailing-edge reflection pair. For a given spatial interval, measurements are made and R(tau) computed, as described above, for pulse durations T ranging from the minimum to the maximum value. The advantage of doing this is that the effective signal-to-noise ratio may be significantly increased over that attainable by use of a fixed pulse duration T.

  13. On Reflection

    DEFF Research Database (Denmark)

    Blasco, Maribel

    2012-01-01

    This article explores how the concept of reflexivity is used in intercultural education. Reflexivity is often presented as a key learning goal in acquiring intercultural competence (ICC). Yet, reflexivity can be defined in different ways, and take different forms across time and space, depending...... on the concepts of selfhood that prevail and how notions of difference are constructed. First, I discuss how the dominant usages of reflexivity in intercultural education reflect and reproduce a Cartesian view of the self that shapes how ICC is conceptualized and taught. I discuss three assumptions that this view...... in designing learning objectives in intercultural education and in devising ways to attain them. Greater attention is also needed in intercultural education to the ways in which selfhood, and hence also reflexivity and constructions of difference, differ across space and time....

  14. Pulse-to-pulse variations in accreting X-ray pulsars

    Directory of Open Access Journals (Sweden)

    Kretschmar Peter

    2014-01-01

    Full Text Available In most accreting X-ray pulsars, the periodic signal is very clear and easily shows up as soon as data covering sufficient pulse periods (a few ten are available. The mean pulse profile is often quite typical for a given source and with minor variations repeated and recognisable across observations done years or even decades apart. At the time scale of individual pulses, significant pulse-to-pulse variations are commonly observed. While at low energies some of these variations might be explained by absorption, in the hard X-rays they will reflect changes in the accretion and subsequent emission. The amount of these variations appears to be quite different between sources and contains information about the surrounding material as well ass possibly interactions at the magnetosphere. We investigate such variations for a sample of well-known sources.

  15. Nonadiabatic interaction between a charged particle and an MHD pulse

    Directory of Open Access Journals (Sweden)

    Y. Kuramitsu

    2008-03-01

    Full Text Available Interaction between a magnetohydrodynamic~(MHD pulse and a charged particle is discussed both numerically and theoretically. Charged particles can be accelerated efficiently in the presence of spatially correlated MHD waves, such as short large amplitude magnetic structures, by successive mirror reflection (Fermi process. In order to understand this process, we study the reflection probability of particles by the MHD pulses, focusing on the adiabaticity on the particle motion. When the particle velocity is small (adiabatic regime, the probability that the particle is reflected by the MHD pulse is essentially determined only by the pitch angle, independent from the velocity. On the other hand, in the non-adiabatic regime, the reflection probability is inversely proportional to the square root of the normalized velocity. We discuss our numerical as well as analytical results of the interaction process with various pulse amplitude, pulse shape, and the pulse winding number. The reflection probability is universally represented as a power law function independent from above pulse properties.

  16. Demonstration of light reflection from the relativistic mirror

    Energy Technology Data Exchange (ETDEWEB)

    Pirozhkov, A S; Esirkepov, T Z; Kando, M; Fukuda, Y; Ma, J; Chen, L-M; Daito, I; Ogura, K; Homma, T; Hayashi, Y; Kotaki, H; Sagisaka, A; Mori, M; Koga, J K; Kawachi, T; Daido, H; Bulanov, S V; Kimura, T; Kato, Y; Tajima, T [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai, Kizugawa, Kyoto 619-0215 (Japan)], E-mail: pirozhkov.alexander@jaea.go.jp

    2008-05-01

    Electromagnetic wave frequency upshifting upon reflection from a relativistic mirror (the double Doppler effect) can be used for the generation of coherent high-frequency radiation. The reflected high-frequency pulse inherits the coherence, polarization, and temporal shape from the original laser pulse. A partly reflecting relativistic mirror (flying mirror) can be formed by a breaking wake wave created by a strong laser pulse propagating in underdense plasma [Bulanov S V et al. 2003 Phys. Rev. Lett. 91, 085001]. We present the results of the proof-of-principle experiment for frequency upshifting of the laser pulse reflected from the flying mirror. In the experiment, the breaking wake wave is created by a Ti:S laser pulse (2 TW, 76 fs) in helium plasma with the electron density of {approx}5x10{sup 19} cm{sup -3}. The incidence angle of the second laser pulse on the flying mirror is 45 deg. The reflected signal is observed in 24 shots, with the wavelength from 7 to 14 nm, which corresponds to the frequency upshifting factors from 55 to 114 and the relativistic gamma-factors from 4 to 6. The reflected signal contains at least 3x10{sup 7} photons/sr. The new source promises the generation of coherent ultrashort XUV and x-ray pulses with tunable wavelength and duration, with the possibility of focusing to record intensities.

  17. Zeptosecond precision pulse shaping.

    Science.gov (United States)

    Köhler, Jens; Wollenhaupt, Matthias; Bayer, Tim; Sarpe, Cristian; Baumert, Thomas

    2011-06-06

    We investigate the temporal precision in the generation of ultrashort laser pulse pairs by pulse shaping techniques. To this end, we combine a femtosecond polarization pulse shaper with a polarizer and employ two linear spectral phase masks to mimic an ultrastable common-path interferometer. In an all-optical experiment we study the interference signal resulting from two temporally delayed pulses. Our results show a 2σ-precision of 300 zs = 300 × 10(-21) s in pulse-to-pulse delay. The standard deviation of the mean is 11 zs. The obtained precision corresponds to a variation of the arm's length in conventional delay stage based interferometers of 0.45 Å. We apply these precisely generated pulse pairs to a strong-field quantum control experiment. Coherent control of ultrafast electron dynamics via photon locking by temporal phase discontinuities on a few attosecond timescale is demonstrated.

  18. Pulse-train control of photofragmentation at constant field energy

    DEFF Research Database (Denmark)

    Tiwari, Ashwani Kumar; Henriksen, Niels Engholm

    2014-01-01

    We consider a phaselocked two-pulse sequence applied to photofragmentation in the weak-field limit. The two pulses are not overlapping in time, i.e., the energy of the pulse-train is constant for all time delays. It is shown that the relative yield of excited Br* in the nonadiabatic process: I + Br......*←IBr → I + Br, changes as a function of time delay when the two excited wave packets interfere. The underlying mechanisms are analyzed and the change in the branching ratio as a function of time delay is only a reflection of a changing frequency distribution of the pulse train; the branching ratio does...

  19. Room acoustic transition time based on reflection overlap

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho; Brunskog, Jonas; Jacobsen, Finn

    2013-01-01

    at time t, which is mainly controlled by the absorption characteristics of the boundary surfaces of the room. Scattering, diffuse reflections, and diffraction, which facilitate the overlapping process, have not been taken into account. Measured impulse responses show that the transition occurs earlier......A transition time is defined based on the temporal overlap of reflected pulses in room impulse responses. Assuming specular reflections only, the temporal distance between adjacent reflections, which is proportional to the volume of a room, is compared with the characteristic width of a pulse...... in a room with nonuniform absorption and furniture than in a room that satisfies the underlying assumptions....

  20. Room acoustic transition time based on reflection overlap

    DEFF Research Database (Denmark)

    Jeong, Cheol-Ho; Brunskog, Jonas; Jacobsen, Finn

    2010-01-01

    at time t, which is mainly controlled by the absorption characteristics of the boundary surfaces of the room. Scattering, diffuse reflections, and diffraction, which facilitate the overlapping process, have not been taken into account. Measured impulse responses show that the transition occurs earlier......A transition time is defined based on the temporal overlap of reflected pulses in room impulse responses. Assuming specular reflections only, the temporal distance between adjacent reflections, which is proportional to the volume of a room, is compared with the characteristic width of a pulse...... in a room with nonuniform absorption and furniture than in a room that satisfies the underlying assumptions....

  1. A numerical study of ultra-short-pulse reflectometry

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, B.I.; Afeyan, B.B. [Lawrence Livermore National Lab., CA (United States); Chou, A.E. [Univ. of California, Los Angeles, CA (United States). Dept. of Electrical Engineering]|[California Univ., Davis, CA (United States). Dept. of Applied Science; Luhmann, N.C. Jr. [California Univ., Davis, CA (United States). Dept. of Applied Science

    1994-05-01

    Ultra-short-pulse reflectometry is studied by means of the numerical integration of a one-dimensional full-wave equation for ordinary modes propagating in a plasma. The numerical calculations illustrate the potential of using the reflection of ultra-short-pulse, microwaves as an effective probe of the density profile even in the presence of significant density fluctuations. The difference in time delays of differing frequency components of the microwaves can be used to deduce the density profile. The modification of the reflected pulses in the presence of density fluctuations is examined and can be understood based on considerations of Bragg resonance. A simple and effective profile-reconstruction algorithm using the zero-crossings of the reflected pulse and subsequent Abel inversion is demonstrated. The robustness of the profile reconstruction algorithm in the presence of a sufficiently small amplitude density perturbation is assessed.

  2. Pulse Tube Refrigerator

    Science.gov (United States)

    Matsubara, Yoichi

    The pulse tube refrigerator is one of the regenerative cycle refrigerators such as Stirling cycle or Gifford-McMahon cycle which gives the cooling temperature below 150 K down to liquid helium temperature. In 1963, W. E. Gifford invented a simple refrigeration cycle which is composed of compressor, regenerator and simple tube named as pulse tube which gives a similar function of the expander in Stirling or Gifford-McMahon cycle. The thermodynamically performance of this pulse tube refrigerator is inferior to that of other regenerative cycles. In 1984, however, Mikulin and coworkers made a significant advance in pulse tube configuration called as orifice pulse tube. After this, several modifications of the pulse tube hot end configuration have been developed. With those modifications, the thermodynamic performance of the pulse tube refrigerator became the same order to that of Stirling and Gifford-McMahon refrigerator. This article reviews the brief history of the pulse tube refrigerator development in the view point of its thermodynamically efficiency. Simplified theories of the energy flow in the pulse tube have also been described.

  3. Ultrashort Laser Pulse Phenomena

    CERN Document Server

    Diels, Jean-Claude

    2006-01-01

    Ultrashort Laser Pulse Phenomena, 2e serves as an introduction to the phenomena of ultra short laser pulses and describes how this technology can be used to examine problems in areas such as electromagnetism, optics, and quantum mechanics. Ultrashort Laser Pulse Phenomena combines theoretical backgrounds and experimental techniques and will serve as a manual on designing and constructing femtosecond (""faster than electronics"") systems or experiments from scratch. Beyond the simple optical system, the various sources of ultrashort pulses are presented, again with emphasis on the basic

  4. A Reflective Look at Reflecting Teams

    Science.gov (United States)

    Pender, Rebecca L.; Stinchfield, Tracy

    2012-01-01

    This article reviewed existing literature and research on the reflecting team process. There is a dearth of empirical research that explores the reflecting team process and the outcome of counseling that uses reflecting teams. Implications of using reflecting teams for counselors, counselor educators, and clients will be discussed. A call for…

  5. The reflection of airborne UV laser pulses from the ocean

    Science.gov (United States)

    Hoge, F. E.; Krabill, W. B.; Swift, R. N.

    1984-01-01

    It is experimentally shown here for the first time that the normalized laser backscatter cross-section of the sea surface is a function of elevation or height position on teh ocean wave. All data were taken off-nadir, resulting in incidence angles of about 6.5 deg measured relative to the normal to mean sea level (MSL). In the limited data sets analyzed to date, the normalized backscatter cross-section was found to be higher in wave crest regions and lower in wave troughs for a swell-dominated sea over which the wind speed was 5 m/s. The reverse was found to be the case for a sea that was driven by a 14 m/s wind. These isolated results show that the MSL, as measured by an off-nadir and/or multibeam type satellite laser altimeter, will be found above, at, or below the true MSL, depending on the local sea conditions existing in the footprint of the altimeter. Airborne nadir-pointed laser altimeter data for a wide variety of sea conditions are needed before a final determination can be made of the effect of sea state on the backscatter cross-section as measured by a down-looking satellite laser system.

  6. Pulse oximetry: fundamentals and technology update

    Directory of Open Access Journals (Sweden)

    Nitzan M

    2014-07-01

    Full Text Available Meir Nitzan,1 Ayal Romem,2 Robert Koppel31Department of Physics/Electro-Optics, Jerusalem College of Technology, Jerusalem, Israel; 2Pulmonary Institute, Shaare Zedek Medical Center, Jerusalem, Israel; 3Neonatal/Perinatal Medicine, Cohen Children's Medical Center of New York/North Shore-LIJ Health System, New Hyde Park, NY, United StatesAbstract: Oxygen saturation in the arterial blood (SaO2 provides information on the adequacy of respiratory function. SaO2 can be assessed noninvasively by pulse oximetry, which is based on photoplethysmographic pulses in two wavelengths, generally in the red and infrared regions. The calibration of the measured photoplethysmographic signals is performed empirically for each type of commercial pulse-oximeter sensor, utilizing in vitro measurement of SaO2 in extracted arterial blood by means of co-oximetry. Due to the discrepancy between the measurement of SaO2 by pulse oximetry and the invasive technique, the former is denoted as SpO2. Manufacturers of pulse oximeters generally claim an accuracy of 2%, evaluated by the standard deviation (SD of the differences between SpO2 and SaO2, measured simultaneously in healthy subjects. However, an SD of 2% reflects an expected error of 4% (two SDs or more in 5% of the examinations, which is in accordance with an error of 3%–4%, reported in clinical studies. This level of accuracy is sufficient for the detection of a significant decline in respiratory function in patients, and pulse oximetry has been accepted as a reliable technique for that purpose. The accuracy of SpO2 measurement is insufficient in several situations, such as critically ill patients receiving supplemental oxygen, and can be hazardous if it leads to elevated values of oxygen partial pressure in blood. In particular, preterm newborns are vulnerable to retinopathy of prematurity induced by high oxygen concentration in the blood. The low accuracy of SpO2 measurement in critically ill patients and newborns

  7. Pulse Distortion in Saturated Fiber Optical Parametric Chirped Pulse Amplification

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Da Ros, Francesco; Rottwitt, Karsten

    2012-01-01

    Fiber optical parametric chirped pulse amplification is experimentally compared for different chirped pulses in the picosecond regime. The amplified chirped pulses show distortion appearing as pedestals after recompression when the amplifier is operated in saturation....

  8. Chaotic Pulse Trains

    CERN Document Server

    Balmforth, N J; Spiegel, E A

    1993-01-01

    Abstract: We study a third-order nonlinear ordinary differential equation whose solutions, under certain specific conditions, are individual pulses. These correspond to homoclinic orbits in the phase space of the equation and we study the possible pulse types in some detail. Sufficiently close to the conditions under which a homoclinic orbit exists, the solutions take the form of trains of well-separated pulses. A measure of closeness to homoclinic conditions provides a small parameter for the development of an asymptotic solution consisting of superposed, isolated pulses. The solvability condition in the resulting singular perturbation theory is a {\\its timing map} relating successive pulse spacings. This map of the real line onto itself, together with the known form of the homoclinic orbit, provides a concise and accurate solution of the equation.

  9. Ultrashort-pulse wave-front autocorrelation.

    Science.gov (United States)

    Grunwald, R; Neumann, U; Griebner, U; Reimann, K; Steinmeyer, G; Kebbel, V

    2003-12-01

    Combined spatially resolved collinear autocorrelation and Shack-Hartmann wave-front sensing of femtosecond laser pulses is demonstrated for the first time to our knowledge. The beam is divided into multiple nondiffracting subbeams by thin-film micro-optical arrays. With hybrid refractive-reflective silica/silver microaxicons, wave-front autocorrelation is performed in oblique-angle reflection. Simultaneous two-dimensional detection of local temporal structure and wave-front tilt of propagating few-cycle wave packets is demonstrated.

  10. THz generation using a reflective stair-step echelon

    CERN Document Server

    Ofori-Okai, Benjamin K; Huang, W Ronny; Nelson, Keith A

    2015-01-01

    We present a novel method for THz generation in lithium niobate using a reflective stair-step echelon structure. The echelon produces a discretely tilted pulse front with less angular dispersion compared to a high groove-density grating. The THz output was characterized using both a 1-lens and 3-lens imaging system to set the tilt angle at room and cryogenic temperatures. Using broadband 800 nm pulses with a pulse energy of 0.95 mJ and a pulse duration of 70 fs (24 nm FWHM bandwidth, 39 fs transform limited width), we produced THz pulses with field strengths as high as 500 kV/cm and pulse energies as high as 3.1 $\\mu$J. The highest conversion efficiency we obtained was 0.33%. In addition, we find that the echelon is easily implemented into an experimental setup for quick alignment and optimization.

  11. Challenging Narcissus, or Reflecting on Reflecting.

    Science.gov (United States)

    Achilles, C. M.

    The concept of reflective practice and teaching people to be reflective practitioners is examined. The document begins with a look at professional knowledge according to three prominent professionals in the educational administration field: Schon, Schein, and Achilles. "Reflective" strategies that could be incorporated into courses and…

  12. High performance pulse generator

    Science.gov (United States)

    Grothaus, Michael G.; Moran, Stuart L.; Hardesty, Leonard W.

    1992-06-01

    The device is a compact Marx-type generator capable of producing a high-voltage burst of pulses having risetimes less than 10 nanoseconds at repetition rates up to 10 kHz. High-pressure hydrogen switches are used as the switching elements to achieve high rep-rate. A small coaxial design provides low inductance and a fast risetime. The device may be used as a high-rep-rate high-voltage trigger generator, or as a high-voltage pulse source capable of producing up to 1 MV pulses at high repetition rates.

  13. Pulse joining cartridges

    Energy Technology Data Exchange (ETDEWEB)

    Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

    2017-09-26

    A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

  14. SHORT PULSE STRETCHER

    Science.gov (United States)

    Branum, D.R.; Cummins, W.F.

    1962-12-01

    >A short pulse stretching circuit capable of stretching a short puise to enable it to be displayed on a relatively slow sweeping oscilloscope is described. Moreover, the duration of the pulse is increased by charging a capacitor through a diode and thereafter discharging the capacitor at such time as is desired. In the circuit the trigger pulse alone passes through a delay line, whereas the main signal passes through the diode only, and results in over-all circuit losses which are proportional to the low losses of the diode only. (AEC)

  15. DogPulse

    DEFF Research Database (Denmark)

    Skovgaard, Christoffer; Thomsen, Josephine Raun; Verdezoto, Nervo

    2015-01-01

    This paper presents DogPulse, an ambient awareness system to support the coordination of dog walking among family members at home. DogPulse augments a dog collar and leash set to activate an ambient shape-changing lamp and visualize the last time the dog was taken for a walk. The lamp gradually...... changes its form and pulsates its lights in order to keep the family members aware of the dog walking activity. We report the iterative prototyping of DogPulse, its implementation and its preliminary evaluation. Based on our initial findings, we present the limitations and lessons learned as well...

  16. Time-Domain UWB RFID Tag Based on Reflection Amplifier

    OpenAIRE

    Girbau, D.; Villarino, R.; Ramos, A.; Lazaro, A.

    2013-01-01

    10.1109/LAWP.2013.2257653 This letter describes an active ultrawideband (UWB) tag for radio frequency identification (RFID) and wireless sensor applications. The tag is composed by a UWB antenna connected to a one-port reflection amplifier. A UWB impulse radar is used as the reader. The reader sends a short pulse, and its echo is amplified and reflected back due to the return gain of the tag amplifier. The amplitude of the reflected pulse is modulated by controlling the amplifier bias. Th...

  17. Pulsed spallation Neutron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, J.M. [Argonne National Lab., IL (United States)

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  18. Generation of frequency-chirped optical pulses with felix

    Energy Technology Data Exchange (ETDEWEB)

    Knippels, G.M.H.; Meer, A.F.G. van der; Mols, R.F.X.A.M. [FOM-Institute for Plasma Physics, Nieuwegein (Netherlands)] [and others

    1995-12-31

    Frequency-chirped optical pulses have been produced in the picosecond regime by varying the energy of the electron beam on a microsecond time scale. These pulses were then compressed close to their bandwidth limit by an external pulse compressor. The amount of chirp can be controlled by varying the sweep rate on the electron beam energy and by cavity desynchronisation. To examine the generated chirp we used the following diagnostics: a pulse compressor, a crossed beam autocorrelator, a multichannel electron spectrometer and multichannel optical spectrometer. The compressor is build entirely using reflective optics to permit broad band operation. The autocorrelator is currently operating from 6 {mu}m to 30 {mu}m with one single crystal. It has been used to measure pulses as short as 500 fs. All diagnostics are evacuated to prevent pulse shape distortion or pulse lengthening caused by absorption in ambient water vapour. Pulse length measurements and optical spectra will be presented for different electron beam sweep rates, showing the presence of a frequency chirp. Results on the compression of the optical pulses to their bandwidth limit are given for different electron sweep rates. More experimental results showing the dependence of the amount of chirp on cavity desynchronisation will be presented.

  19. CO{sub 2} laser pulse shortening by laser ablation of a metal target

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, T.; Mazoyer, M.; Lynch, A.; O' Sullivan, G.; O' Reilly, F.; Dunne, P.; Cummins, T. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)

    2012-03-15

    A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO{sub 2} laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to {approx}2 ns and to remove the low power, long duration tails that are present in TEA CO{sub 2} pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is {approx}10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.

  20. A Computer Controlled Pulse Programmer for Pulsed NQR Experiments

    OpenAIRE

    Horiuchi, Keizo; 堀内, 敬三

    1987-01-01

    We constructed a computer controlled pulse programmer for the measurement of nuclear quadrupole resonance relaxation times. Programmable interval timer 8253 was used as device for pulse programming. The circuit is very simple and construction is also easy in comparison with the usual pulse programmer. This programmer is sufficiently useful concerning the pulse programming of slimple pulse sequences such as π-τ-π/2 and π/2-τ-π, which are usually used in the measurement of relaxation times. We ...

  1. SUBSTATIONS OF DISTRICT HEATING SYSTEMS WITH PULSE COOLANT CIRCULATION

    Directory of Open Access Journals (Sweden)

    Andrey N. Makeev

    2017-01-01

    Full Text Available Abstract. Objectives The aim of the study is to generalise the results of the application of technologies and means for organising pulse coolant flow within a district heating system in order to increase its energy efficiency based on the organisation of local hydraulic shocks and the subsequent use of their energy to ensure the purification of heat energy equipment, intensify the heat transfer process and realise the possibility of transforming the available head from one hydraulic circuit to another. Methods Substations connecting the thermal power installations of consumers with heat networks via dependent and independent schemes are analytically generalised. The use of pulse coolant circulation is proposed as a means of overcoming identified shortcomings. Results Principal schemes of substations with pulse coolant circulation for dependent and independent connection of thermal power installations are detailed. A detailed description of their operation is given. The advantages of using pulse coolant circulation in substations are shown. The materials reflecting the results of the technical implementation and practical introduction of this technology are presented. Conclusion Theoretical analysis of the operation of the basic schemes of substations with pulse coolant circulation and the results of their practical application, as well as the materials of scientific works devoted to the use of the energy of a hydraulic impact and the study of the effect of pulse coolant flow on thermal and hydrodynamic processes, have yielded a combination of factors reflecting technical and economic rationality of application of pulse coolant circulation. 

  2. [Pulse oximetry in pediatric practice].

    Science.gov (United States)

    Brackel, H J; van Essen-Zandvliet, E E; de Jongste, J C; Kerrebijn, K F

    1990-02-01

    Pulse oximetry is a reliable technique for continuous, transcutaneous measurement of oxygen saturation and pulse frequency. Common indications for pulse oximetry in general pediatrics include: monitoring of oxygenation during an asthma attack, detection of apnea or hypoventilation, diagnosis of hypoxemia in patients with chronic respiratory insufficiency and monitoring of oxygen suppletion. In this article we discuss the various applications and limitations of pulse oximetry in clinical practice and describe a method to store, analyse and present pulse oximeter-results.

  3. Lunar surface reflectance by LALT aboard KAGUYA

    Science.gov (United States)

    Noda, H.; Araki, H.; Ishihara, Y.; Tazawa, S.; Sasaki, S.; Kawano, N.

    2009-12-01

    The Laser Altimeter (LALT) aboard Japanese lunar explorer KAGUYA (SELENE) is a ranging instrument which measures the distance between the satellite and the lunar surface with accuracy of 1 m by detecting the timing delay of the reflected laser light. The main science goal of the LALT is to obtain the lunar global topographic data including polar regions for the study of the origin and the evolution of the Moon [1]. Besides, the LALT is equipped with an intensity monitor of the returned pulses. The intensity of the returned pulses contains information concerning surface roughness and reflectance of the footprints, which will contribute to the study of the lunar surface maturity and age. The reflectance at LALT wavelength (1064nm) is sensitive to the surface maturity and composition. The data should be particularly important at lunar polar regions where camera instruments should suffer from phase angle effects in the surface reflectance and moreover cannot obtain reflectance data at the permanently shadowed area. The normal operation of the LALT began on 30th, December 2007 after two months’ commissioning phase. Before the end of the normal operation phase in October 2008, the LALT measured more than 10 million range data. Unfortunately, due to the laser power decrease and also possible smaller surface reflectance than the expected value before launch (15 % at 1 micro meter), the return pulse intensity during the nominal mission phase is so small that they are not reliable enough to discuss the surface property. During the extended mission phase, which started November 2008, the satellite altitude decreased to 50 km. Due to the malfunction of the reaction wheel and high-voltage instruments were shutdown, the observation was suspended until 11th of February, 2009. LALT successfully resumed observation on 12th February and continued observation until the controlled crash of KAGUYA onto the Moon on 10th of June, 2009. Thanks to the lower orbit during this phase, the

  4. Internal strain measurement using pulsed neutron diffraction at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Goldstone, J.A.; Bourke, M.A.M.; Shi, N. [Los Alamos National Lab., NM (United States). Manuel Lujan Jr. Neutron Scattering Center

    1994-12-01

    The presence of residual stress in engineering components can effect their mechanical properties and structural integrity. Neutron diffraction in the only technique that can make nondestructive measurements in the interior of components. By recording the change in crystalline lattice spacings, elastic strains can be measured for individual lattice reflections. Using a pulsed neutron source, all lattice reflections are recorded in each measurement, which allows for easy examination of heterogeneous materials such as metal matrix composites. Measurements made at the Manuel Lujan Jr. Neutron Scattering Center (LANSCE) demonstrate the potential at pulsed sources for in-situ stress measurements at ambient and elevated temperatures.

  5. Pulsed welding plasma source

    Science.gov (United States)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Tyasto, A.

    2016-04-01

    It is shown that in order to form the current pulse of a near rectangular shape, which provides conversion of the welding arc into a dynamic mode, it is rational to connect a forming element made on the basis of an artificial forming line in series to the welding DC circuit. The paper presents a diagram of a pulsed device for welding with a non-consumable electrode in argon which was developed using the forming element. The conversion of the arc into the dynamic mode is illustrated by the current and voltage oscillograms of the arc gap and the dynamic characteristic of the arc within the interval of one pulse generation time in the arc gap. The background current travels in the interpulse interval.

  6. Discharge pulse phenomenology

    Science.gov (United States)

    Frederickson, A. R.

    1985-01-01

    A model was developed which places radiation induced discharge pulse results into a unified conceptual framework. Only two phenomena are required to interpret all space and laboratory results: (1) radiation produces large electrostatic fields inside insulators via the trapping of a net space charge density; and (2) the electrostatic fields initiate discharge streamer plasmas similar to those investigated in high voltage electrical insulation materials; these streamer plasmas generate the pulsing phenomena. The apparent variability and diversity of results seen is an inherent feature of the plasma streamer mechanism acting in the electric fields which is created by irradiation of the dielectrics. The implications of the model are extensive and lead to constraints over what can be done about spacecraft pulsing.

  7. Two pulse recoupling

    Science.gov (United States)

    Khaneja, Navin; Kumar, Ashutosh

    2017-08-01

    The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called two pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π)ϕ(π) - ϕ where ϕ =π/4n, and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ(π) - ϕ(π) π + ϕ(π) π - ϕ . The heteronuclear recoupling pulse sequence consists of a building block (π)ϕ1(π)-ϕ1 and (π)ϕ2(π)-ϕ2 on channel I and S, where ϕ1 = 3π/8n, ϕ2 = π/8n and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ1(π)-ϕ1(π) π +ϕ1(π) π -ϕ1 and (π)ϕ2(π)-ϕ2(π) π +ϕ2(π) π -ϕ2 on two channels respectively. The recoupling pulse sequences mix the z magnetization. Experimental quantification of this method is shown for 13Cα-13CO homonuclear recoupling in a sample of Glycine and 15N-13Cα heteronuclear recoupling in Alanine. Application of this method is demonstrated on a sample of tripeptide N-formyl-[U-13C,15N]-Met-Leu-Phe-OH (MLF). Compared to R-sequences (Levitt, 2002), these sequences are more robust to rf-inhomogeneity and give better sensitivity, as shown in Fig. 3.

  8. Millimicrosecond pulse techniques

    CERN Document Server

    Lewis, Ian A D

    1959-01-01

    Millimicrosecond Pulse Techniques, Second Edition focuses on millimicrosecond pulse techniques and the development of devices of large bandwidth, extending down to comparatively low frequencies (1 Mc/s). Emphasis is on basic circuit elements and pieces of equipment of universal application. Specific applications, mostly in the field of nuclear physics instrumentation, are considered. This book consists of eight chapters and opens with an introduction to some of the terminology employed by circuit engineers as well as theoretical concepts, including the laws of circuit analysis, Fourier analysi

  9. Pulsed ESP handles AFBC

    Energy Technology Data Exchange (ETDEWEB)

    Larva, J.; Wilkomm, T.; Lugar, T.; Follett, R.E.

    1988-08-01

    The Black Dog 2 retrofit AFBC at Burnsville, Minnesota started coal firing in June 1986 using the units' existing precipitators for particulate control. The effects of various fuel blends, bed material, pulse power supplies and air atomized water injection flue gas conditioning were studied. The plant has been used for tests in the following areas: fired clay bed material, higher sulfur coal blends, ash recycle optimization, improved boiler operation, improved air heater thermal performance, improved rapper effectiveness, barbed wire electrodes, intermittent energization controls, pulse energization, and water injection. 4 refs., 4 figs., 1 tab.

  10. Pulse Doppler radar

    CERN Document Server

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  11. Diffraction of X-ray free-electron laser femtosecond pulses on single crystals in the Bragg and Laue geometry.

    Science.gov (United States)

    Bushuev, V A

    2008-09-01

    A solution of the problem of dynamical diffraction for X-ray pulses with arbitrary dimensions in the Bragg and Laue cases in a crystal of any thickness and asymmetry coefficient of reflection is presented. Analysis of pulse form and duration transformation in the process of diffraction and propagation in a vacuum is conducted. It is shown that only the symmetrical Bragg case can be used to avoid smearing of reflected pulses.

  12. SNMR pulse sequence phase cycling

    Science.gov (United States)

    Walsh, David O; Grunewald, Elliot D

    2013-11-12

    Technologies applicable to SNMR pulse sequence phase cycling are disclosed, including SNMR acquisition apparatus and methods, SNMR processing apparatus and methods, and combinations thereof. SNMR acquisition may include transmitting two or more SNMR pulse sequences and applying a phase shift to a pulse in at least one of the pulse sequences, according to any of a variety cycling techniques. SNMR processing may include combining SNMR from a plurality of pulse sequences comprising pulses of different phases, so that desired signals are preserved and indesired signals are canceled.

  13. Optogenetic light pulses generator

    Science.gov (United States)

    Erofeev, A. I.; Matveev, M. V.; Zakharova, O. A.; Terekhin, S. G.; Kilimnik, V. A.; Bezprozvanny, I. B.; Vlasova, O. L.

    2017-11-01

    To date, optogenetics is one of the most popular methods in the world in neuroscience. There are new equipment and devices created to keep the progress of this method. This article describes a light pulse generator developed at the Laboratory of Molecular Neurodegeneration, designed for optogenetic experiments.

  14. Pulsed electric fields

    Science.gov (United States)

    The concept of pulsed electric fields (PEF) was first proposed in 1967 to change the behavior or microorganisms. The electric field phenomenon was identified as membrane rupture theory in the 1980s. Increasing the membrane permeability led to the application of PEF assisted extraction of cellular co...

  15. Pulse Wave Propagation in the Arterial Tree

    Science.gov (United States)

    van de Vosse, Frans N.; Stergiopulos, Nikos

    2011-01-01

    The beating heart creates blood pressure and flow pulsations that propagate as waves through the arterial tree that are reflected at transitions in arterial geometry and elasticity. Waves carry information about the matter in which they propagate. Therefore, modeling of arterial wave propagation extends our knowledge about the functioning of the cardiovascular system and provides a means to diagnose disorders and predict the outcome of medical interventions. In this review we focus on the physical and mathematical modeling of pulse wave propagation, based on general fluid dynamical principles. In addition we present potential applications in cardiovascular research and clinical practice. Models of short- and long-term adaptation of the arterial system and methods that deal with uncertainties in personalized model parameters and boundary conditions are briefly discussed, as they are believed to be major topics for further study and will boost the significance of arterial pulse wave modeling even more.

  16. Pulsed electromagnetic field radiation from a narrow slot antenna with a dielectric layer

    OpenAIRE

    Stumpf, M.; de Hoop, A. T.; Lager, I. E.

    2010-01-01

    Analytic time domain expressions are derived for the pulsed electromagnetic field radiated by a narrow slot antenna with a dielectric layer in a two?dimensional model configuration. In any finite time window of observation, exact pulse shapes for the propagated, reflected, and refracted wave constituents are constructed with the aid of the modified Cagniard method (Cagniard?DeHoop method). Numerical results are presented for vanishing slot width and field pulse shapes at the dielectric/free s...

  17. A compact nanosecond pulse modulator

    Science.gov (United States)

    Sha, Jizhang; Xue, Jianchao; Qiang, Bohan

    Two circuits of nanosecond pulse modulator which generate two different width rectangular pulses respectively are described. The basic configuration of the modulator is the Marx circuit, in which avalanche transistors are used as switching devices. In order to obtain the rectangular pulses a pulse-forming network (PFN) is introduced and fitted into the Marx. A multi-parallel arrangement of the Marx is used to satisfy the broad pulse requirement. Experiments have shown that the two different width rectangular pulses which have 130 V amplitudes and 30 and 200 ns widths respectively can be obtained at a 50 ohms load. The two pulses have steep front edges (3.6 ns and 10 ns respectively) and flat tops with less than + or - 5 percent ripples. Therefore, the modulator can meet the requirements of the nanosecond pulse radar.

  18. Wide spectrum microwave pulse measurement

    Energy Technology Data Exchange (ETDEWEB)

    King, R.J.

    1986-01-01

    Various techniques are postulated as diagnostics for wide band microwave pulses. The diagnostics include determinations of both the instantaneous amplitude and the frequency content of one-shot pulses. 6 refs., 11 figs. (WRF)

  19. Temperature-reflection I

    DEFF Research Database (Denmark)

    McGady, David A.

    2017-01-01

    -temperature path integrals for quantum field theories (QFTs) should be T-reflection invariant. Because multi-particle partition functions are equal to Euclidean path integrals for QFTs, we expect them to be T-reflection invariant. Single-particle partition functions though are often not invariant under T......In this paper, we revisit the claim that many partition functions are invariant under reflecting temperatures to negative values (T-reflection). The goal of this paper is to demarcate which partition functions should be invariant under T-reflection, and why. Our main claim is that finite...... that T-reflection is unrelated to time-reversal. Finally, we study the interplay between T-reflection and perturbation theory in the anharmonic harmonic oscillator in quantum mechanics and in Yang-Mills in four-dimensions. This is the first in a series of papers on temperature-reflections....

  20. Sequentially pulsed traveling wave accelerator

    Science.gov (United States)

    Caporaso, George J [Livermore, CA; Nelson, Scott D [Patterson, CA; Poole, Brian R [Tracy, CA

    2009-08-18

    A sequentially pulsed traveling wave compact accelerator having two or more pulse forming lines each with a switch for producing a short acceleration pulse along a short length of a beam tube, and a trigger mechanism for sequentially triggering the switches so that a traveling axial electric field is produced along the beam tube in synchronism with an axially traversing pulsed beam of charged particles to serially impart energy to the particle beam.

  1. Bacterial inactivation using pulsed light

    OpenAIRE

    Elmnasser, Noura; Ritz, Magali; Leroi, Francoise; Orange, Nicole; Bakhrouf, Amina; Federighi, Michel

    2007-01-01

    Pulsed light is a new method intended for the decontamination of food surfaces using short, high frequency pulses of an intense broad spectrum. The effects of broad spectrum pulsed light on the survival of Listeria monocytogenes Scott A, Listeria monocytogenes CNL, Pseudomonas fluorescens MF37 and Photobacterium phosphoreum SF680 populations on agar and in a liquid medium were investigated during this study. The sterilisation system generated 1.5 J cm(-2) per pulse with eight lamps for 300 mu...

  2. Liberating Moral Reflection

    Science.gov (United States)

    Horell, Harold D.

    2013-01-01

    The author argues that if we are to foster life-giving and liberating moral reflection, we must first liberate moral reflection from distortions; specifically, from the distorting effects of moral insensitivity, destructive moral relativism, and confusions resulting from a failure to understand the dynamics of moral reflection. The author proposes…

  3. Imaging Seismic Reflections

    NARCIS (Netherlands)

    op 't Root, T.J.P.M.; Op 't Root, Timotheus Johannes Petrus Maria

    2011-01-01

    The goal of reflection seismic imaging is making images of the Earth subsurface using surface measurements of reflected seismic waves. Besides the position and orientation of subsurface reflecting interfaces it is a challenge to recover the size or amplitude of the discontinuities. We investigate

  4. Method for spatially modulating X-ray pulses using MEMS-based X-ray optics

    Science.gov (United States)

    Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

    2015-03-10

    A method and apparatus are provided for spatially modulating X-rays or X-ray pulses using microelectromechanical systems (MEMS) based X-ray optics. A torsionally-oscillating MEMS micromirror and a method of leveraging the grazing-angle reflection property are provided to modulate X-ray pulses with a high-degree of controllability.

  5. Influence of laser pulse frequency on the microstructure of aluminum nitride thin films synthesized by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Antonova, K., E-mail: krasa@issp.bas.bg [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Duta, L. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania); Szekeres, A. [Institute of Solid State Physics, Bulgarian Academy of Sciences, Tzarigradsko Chaussee 72, Sofia 1784 (Bulgaria); Stan, G.E. [National Institute of Materials Physics, 105 bis Atomistilor Street, 077125 Magurele (Romania); Mihailescu, I.N. [National Institute for Lasers, Plasma, and Radiation Physics, 409 Atomistilor Street, 077125 Magurele (Romania); Anastasescu, M.; Stroescu, H.; Gartner, M. [Institute of Physical Chemistry, “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania)

    2017-02-01

    Highlights: • Study of pulsed laser deposited AlN films at different laser pulse frequencies. • Higher laser pulse frequency promotes nanocrystallites formation at temperature 450 °C. • AFM and GIXRD detect randomly oriented wurtzite AlN structures. • Characterization of the nanocrystallites’ orientation by FTIR reflectance spectra. • Berreman effect is registered in p-polarised radiation at large incidence angles. - Abstract: Aluminum Nitride (AlN) thin films were synthesized on Si (100) wafers at 450 °C by pulsed laser deposition. A polycrystalline AlN target was multipulsed irradiated in a nitrogen ambient, at different laser pulse repetition rate. Grazing Incidence X-Ray Diffraction and Atomic Force Microscopy analyses evidenced nanocrystallites with a hexagonal lattice in the amorphous AlN matrix. The thickness and optical constants of the layers were determined by infrared spectroscopic ellipsometry. The optical properties were studied by Fourier Transform Infrared reflectance spectroscopy in polarised oblique incidence radiation. Berreman effect was observed around the longitudinal phonon modes of the crystalline AlN component. Angular dependence of the A{sub 1}LO mode frequency was analysed and connected to the orientation of the particles’ optical axis to the substrate surface normal. The role of the laser pulse frequency on the layers’ properties is discussed on this basis.

  6. Response of variable impedance stripline to pulse excitation

    Energy Technology Data Exchange (ETDEWEB)

    McWright, G.

    1984-12-15

    We describe a simple method to predict the transient response of variable impedance stripline to pulse excitation. The method uses a finite difference based, quasi-static impedance formulation to calculate the reflection coefficient at each point along the direction of pulse propagation and the subsequent short pulse behavior of a variable impedance structure. A Fortran computer program is written to determine the quasi-static impedance. Excellent agreement of better than 1% between the finite difference impedance predictions and experimental results is noted. A second computer program is written utilizing previous results but essentially incorporating reflection and transmission from several discontinuities to analyze the transient response of the structure. This transient analysis yields good agreement between predictions and results obtained by means of time domain reflectometry.

  7. RHEED study of titanium dioxide with pulsed laser deposition

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Pryds, Nini; Schou, Jørgen

    2009-01-01

    Reflection high-energy electron diffraction (RHEED) operated at high pressure has been used to monitor the growth of thin films of titanium dioxide (TiO2) on (1 0 0) magnesium oxide (MgO) substrates by pulsed laser deposition (PLD). The deposition is performed with a synthetic rutile TiO2 target...

  8. Pulse wave analysis with diffusing-wave spectroscopy.

    Science.gov (United States)

    Belau, Markus; Scheffer, Wolfgang; Maret, Georg

    2017-07-01

    Hypertension is a major risk factor for cardiovascular disease and thus at the origin of many deaths by e.g. heart attack or stroke. Hypertension is caused by many factors including an increase in arterial stiffness which leads to changes in pulse wave velocity and wave reflections. Those often result in an increased left ventricular load which may result in heart failure as well as an increased pulsatile pressure in the microcirculation l to damage to blood vessels. In order to specifically treat the different causes of hypertension it is desirable to perform a pulse wave analysis as a complement to measurements of systolic and diastolic pressure by brachial cuff sphygmomanometry. Here we show that Diffusing Wave Spectroscopy, a novel non-invasive portable tool, is able to monitor blood flow changes with a high temporal resolution. The measured pulse travel times give detailed information of the pulse wave blood flow profile.

  9. Investigating murals with terahertz reflective tomography

    Science.gov (United States)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Wang, Sen; Zhang, Qunxi; Ye, Jiasheng; Zhang, Yan

    2015-08-01

    Terahertz time-domain spectroscopy (THz-TDS) imaging technology has been proposed to be used in the non-invasive detection of murals. THz-TDS images provide structural data of the sample that cannot be obtained with other complementary techniques. In this paper, two types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by the terahertz reflected time domain spectroscopy imaging system. These preset defects include a leaf slice and a slit built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. With this THz tomography, different defects with the changes of optical thickness and their relative refractive index have been identified. The application of reflective pulsed terahertz imaging has been extended to the defect detection of the murals.

  10. International magnetic pulse compression

    Science.gov (United States)

    Kirbie, H. C.; Newton, M. A.; Siemens, P. D.

    1991-04-01

    Although pulsed-power engineering traditionally has been practiced by a fairly small, close community in the areas of defense and energy research, it is becoming more common in high-power, high-energy commercial pursuits such as material processing and lasers. This paper is a synopsis of the Feb. 12-14, 1990 workshop on magnetic switching as it applies primarily to pulse compression (power transformation). During the course of the Workshop at Granlibakken, a great deal of information was amassed and a keen insight into both the problems and opportunities as to the use of this switching approach was developed. The segmented workshop format proved ideal for identifying key aspects affecting optimum performance in a variety of applications. Individual groups of experts addressed network and system modeling, magnetic materials, power conditioning, core cooling and dielectrics, and finally circuits and application. At the end, they came together to consolidate their input and formulate the workshop's conclusions, identifying roadblocks or suggesting research projects, particularly as they apply to magnetic switching's trump card - its high-average-power-handling capability (at least on a burst-mode basis). The workshop was especially productive both in the quality and quantity of information transfer in an environment conducive to a free and open exchange of ideas. We will not delve into the organization proper of this meeting, rather we wish to commend to the interested reader this volume, which provides the definitive and most up-to-date compilation on the subject of magnetic pulse compression from underlying principles to current state of the art as well as the prognosis for the future of magnetic pulse compression as a consensus of the workshop's organizers and participants.

  11. PULSE Pilot Certification Results

    Directory of Open Access Journals (Sweden)

    Pamela Pape-Lindstrom

    2015-08-01

    Full Text Available The pilot certification process is an ambitious, nationwide endeavor designed to motivate important changes in life sciences education that are in line with the recommendations of the 2011 Vision and Change Report: A Call to Action (American Association for the Advancement of Science [AAAS], 2011.  It is the goal of the certification process to acknowledge departments that have progressed towards full implementation of the tenets of Vision and Change and to motivate departments that have not begun to adopt the recommendations to consider doing so.  More than 70 life science departments applied to be part of the pilot certification process, funded by a National Science Foundation grant, and eight were selected based on initial evidence of transformed and innovative educational practices.  The programs chosen represent a wide variety of schools, including two-year colleges, liberal-arts institutions, regional comprehensive colleges, research universities and minority serving institutions.  Outcomes from this pilot were released June 1, 2015 (www.pulsecommunity.org, with all eight programs being recognized as having progressed along a continuum of change.  Five levels of achievement were defined as PULSE Pilot Progression Levels.  Of the eight departments in the pilot, one achieved “PULSE Progression Level III: Accomplished”.  Six departments achieved “PULSE Progression Level II: Developing” and one pilot department achieved “PULSE Progression Level I: Beginning”.  All of the schools have made significant movement towards the recommendations of Vision and Change relative to a traditional life sciences curriculum.  Overall, the response from the eight pilot schools has been positive. 

  12. STUCTURE OF PULSED BED

    Directory of Open Access Journals (Sweden)

    I. A. Bokun

    2014-01-01

    Full Text Available The structure of pulsed layer is proposed which can be suggested as a state of particulates that is blown by intermittent gas flow with speed which has the force to start material moving. Layer during one cycle is in a suspension, falling down and immobile state resulting in changes of particles arrangement as well as ways of gas flowing through layer. Moreover, it allows carrying out effective interphase heat exchange even adamant real granulation.The process of formation of impact flows is considered aw well as their influence on formation of air bubbles in pulsed layer. At startup of air blast the balance between the force of hydro-dynamic resistance is broken, on one side, and forces of gravity, particles inertia and their links with walls on the other side. The layer is transferred in the state of pulsed pseudo-fluidization, and presents gas-disperse mixture, inside of which impulse of pressure increasing is spreading to all sides as pressure waves (compression. These waves are the sources of impact flows’ formation, the force of which is two times more than during the stationary flow.The waves of pressure are divided into weak and strong ones depending on movement velocity within gas-disperse system. Weak waves are moving with a sound speed and strong ones in active phase of pulsed layer are moving over the speed of sound limit within gas-disperse system. The peculiarity of strong wave is that parameters of system (pressure, density and others are changing in discrete steps.The article describes the regime of layer’s falling down in the passive stage of cycle, which begins after finishing of gas impulse action. And suspension layer of moving up granular material is transferred in the state of falling resulting in change of the layer structure.

  13. Modeling Pilot Pulse Control

    Science.gov (United States)

    Bachelder, Edward; Hess, Ronald; Godfroy-Cooper, Martine; Aponso, Bimal

    2017-01-01

    In this study, behavioral models are developed that closely reproduced pulsive control response of two pilots from the experimental pool using markedly different control techniques (styles) while conducting a tracking task. An intriguing find was that the pilots appeared to: 1) produce a continuous, internally-generated stick signal that they integrated in time; 2) integrate the actual stick position; and 3) compare the two integrations to issue and cease pulse commands. This suggests that the pilots utilized kinesthetic feedback in order to perceive and integrate stick position, supporting the hypothesis that pilots can access and employ the proprioceptive inner feedback loop proposed by Hess' pilot Structural Model. The Pulse Models used in conjunction with the pilot Structural Model closely recreated the pilot data both in the frequency and time domains during closed-loop simulation. This indicates that for the range of tasks and control styles encountered, the models captured the fundamental mechanisms governing pulsive and control processes. The pilot Pulse Models give important insight for the amount of remnant (stick output uncorrelated with the forcing function) that arises from nonlinear pilot technique, and for the remaining remnant arising from different sources unrelated to tracking control (i.e. neuromuscular tremor, reallocation of cognitive resources, etc.).

  14. Petawatt pulsed-power accelerator

    Science.gov (United States)

    Stygar, William A.; Cuneo, Michael E.; Headley, Daniel I.; Ives, Harry C.; Ives, legal representative; Berry Cottrell; Leeper, Ramon J.; Mazarakis, Michael G.; Olson, Craig L.; Porter, John L.; Wagoner; Tim C.

    2010-03-16

    A petawatt pulsed-power accelerator can be driven by various types of electrical-pulse generators, including conventional Marx generators and linear-transformer drivers. The pulsed-power accelerator can be configured to drive an electrical load from one- or two-sides. Various types of loads can be driven; for example, the accelerator can be used to drive a high-current z-pinch load. When driven by slow-pulse generators (e.g., conventional Marx generators), the accelerator comprises an oil section comprising at least one pulse-generator level having a plurality of pulse generators; a water section comprising a pulse-forming circuit for each pulse generator and a level of monolithic triplate radial-transmission-line impedance transformers, that have variable impedance profiles, for each pulse-generator level; and a vacuum section comprising triplate magnetically insulated transmission lines that feed an electrical load. When driven by LTD generators or other fast-pulse generators, the need for the pulse-forming circuits in the water section can be eliminated.

  15. Foundations of pulsed power technology

    CERN Document Server

    Lehr, Janet

    2018-01-01

    Pulsed power technologies could be an answer to many cutting-edge applications. The challenge is in how to develop this high-power/high-energy technology to fit current market demands of low-energy consuming applications. This book provides a comprehensive look at pulsed power technology and shows how it can be improved upon for the world of today and tomorrow. Foundations of Pulsed Power Technology focuses on the design and construction of the building blocks as well as their optimum assembly for synergetic high performance of the overall pulsed power system. Filled with numerous design examples throughout, the book offers chapter coverage on various subjects such as: Marx generators and Marx-like circuits; pulse transformers; pulse-forming lines; closing switches; opening switches; multi-gigawatt to multi-terawatt systems; energy storage in capacitor banks; electrical breakdown in gases; electrical breakdown in solids, liquids and vacuum; pulsed voltage and current measurements; electromagnetic interferen...

  16. Noninvasive continuous monitoring of digital pulse waves during hemodialysis

    DEFF Research Database (Denmark)

    Burkert, Antje; Scholze, Alexandra; Tepel, Martin

    2009-01-01

    Intermittent hemodynamic instability during hemodialysis treatment is a frequent complication in patients with end-stage renal failure. A noninvasive method for continuous hemodynamic monitoring is needed. We used noninvasive digital photoplethysmography and an algorithm for continuous, investiga......Intermittent hemodynamic instability during hemodialysis treatment is a frequent complication in patients with end-stage renal failure. A noninvasive method for continuous hemodynamic monitoring is needed. We used noninvasive digital photoplethysmography and an algorithm for continuous......, investigator-independent, automatic analysis of digital volume pulse in 10 healthy subjects and in 20 patients with end-stage renal failure during the hemodialysis session. The reflective index was defined representing the diastolic component of the digital pulse wave. The properties of the reflective index...... were studied in healthy control subjects (n=10). An increased reflective index was due to increased peripheral pulse wave reflection (e.g., vasoconstriction). During a hemodialysis session, the reflective index increased significantly from 36+/-3 arbitrary units to 41+/-3 arbitrary units (n=20; p...

  17. Dissenting in Reflective Conversations

    DEFF Research Database (Denmark)

    Bjørn, Pernille; Boulus, Nina

    2011-01-01

    Reflective monitoring of research practices is essential. However, we often lack formal training in the practices of doing action research, and descriptions of actual inquiry practice are seldom included in publications. Our aim is to provide a glimpse of self-reflective practices based on our...... gradually evolved into second-person inquiry. We argue that enacting second-person reflective conversations renders alternative strategies for handling uncertainties through articulation of the tacit assumptions within particular empirical situations. Finally, we argue that reflective conversations should...... a methodological reflective approach that provides space for taking seriously uncertainties experienced in the field as these can be a catalyst for learning and sharpening our theoretical and empirical skills as action researchers. Through first-person inquiry, we investigate how our reflective conversations...

  18. Laser pulse detection method and apparatus

    Science.gov (United States)

    Goss, W.; Janesick, J. R.

    1984-02-01

    A sensor is described for detecting the difference in phase of a pair of returned light pulse components, such as two components of a light pulse of an optical gyro. In an optic gyro, the two light components have passed in opposite directions through a coil of optical fiber, with the difference in phase of the returned light components determining the intensity of light shining on the sensor. The sensor includes a CCD (charge coupled device) that receives the pair of returned light components to generate a charge proportional to the number of photons in the received light. The amount of the charge represents the phase difference between the two light components. At a time after the transmission of the light pulse and before the expected time of arrival of the interfering light components, charge accumulating in the CCD as a result of reflections from components in the system, are repeatedly removed from the CCD, by transferring out charges in the CCD and dumping these charges.

  19. Tandem resonator reflectance modulator

    Science.gov (United States)

    Fritz, I.J.; Wendt, J.R.

    1994-09-06

    A wide band optical modulator is grown on a substrate as tandem Fabry-Perot resonators including three mirrors spaced by two cavities. The absorption of one cavity is changed relative to the absorption of the other cavity by an applied electric field, to cause a change in total reflected light, as light reflecting from the outer mirrors is in phase and light reflecting from the inner mirror is out of phase with light from the outer mirrors. 8 figs.

  20. Media for Reflection

    DEFF Research Database (Denmark)

    Knudsen, Morten

    2016-01-01

    This article develops the concept media for reflection in the interest of conceptualizing the interpretative frames that enable and limit reflection in management and leadership education. The concept ‘media for reflection’ allows us to conceptualize the social and cultural mediation of reflection...... of the mediations is analysed as well as the societal and organizational background. Furthermore, the means by which the two media enable and limit reflection in different ways is compared. Finally, the article discusses possible implications of the analysis in terms of management and leadership education....

  1. Coiled transmission line pulse generators

    Science.gov (United States)

    McDonald, Kenneth Fox

    2010-11-09

    Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.

  2. Measurement of particle speed through optical reflective sensing

    Energy Technology Data Exchange (ETDEWEB)

    McCardle, John [Univ. of Florida, Gainesville, FL (United States)

    1993-01-01

    Two methods determine the speed of 3 m glass spheres using optical reflective sensors embedded in a micro-processor system. The first method, which will be referred to as the one pulse method, is sensitive to particle size and shape. The pulse width of a detected particle is measured and normalized by a shape correction factor resulting in a speed estimate. Three models are developed to correct for effects due to particle shape and light scattering inhomogeneities. The second method, which will be referred to as the two pulse method, measures individual particle velocity components independent of size and shape with two detectors spaced a known distance apart. This distance is divided by the delay between the two detector output pulses to determine speed. A by-product of both methods is a localized particle flux. The microprocessor subsystem automates the pulse detection, timing, velocity calculation and display which are accomplished by the micro-processor subsystem. In the laboratory, a chute is used to generate particle flows with different characteristics. The detection system is tested in the chute for two different flows. A mechanical speed measurement is used for comparison to the one pulse method. The one pulse method is used for comparison to the two pulse method. A mechanical average mass flow rate is used for comparison to the flow rate measurements. Results obtained indicate that the one pulse method estimate is within 4% of the mechanically measured speed. The two pulse method gives erroneous results, in this application, due to detector separation distance greater than 3 particle diameters. The mass flow rate measurement gives erroneous results due to detector head placement. Solutions are proposed to correct discrepancies.

  3. Microwave and Pulsed Power

    Energy Technology Data Exchange (ETDEWEB)

    Freytag, E.K.

    1993-03-01

    The goals of the Microwave and Pulsed Power thrust area are to identify realizable research and development efforts and to conduct high-quality research in those pulse power and microwave technologies that support existing and emerging programmatic requirements at Lawrence Livermore National Laboratory (LLNL). Our main objective is to work on nationally important problems while enhancing our basic understanding of enabling technologies such as component design and testing, compact systems packaging, exploratory physics experiments, and advanced systems integration and performance. During FY-92, we concentrated our research efforts on the six project areas described in this report. (1) We are investigating the superior electronic and thermal properties of diamond that may make it an ideal material for a high-power, solid-state switch. (2) We are studying the feasibility of using advanced Ground Penetrating Imaging Radar technology for reliable non-destructive evaluation of bridges and other high-value concrete structures. These studies include conceptual designs, modeling, experimental verifications, and image reconstruction of simulated radar data. (3) We are exploring the efficiency of pulsed plasma processing techniques used for the removal of NO{sub x} from various effluent sources. (4) We have finished the investigation of the properties of a magnetically delayed low-pressure gas switch, which was designed here at LLNL. (5) We are applying statistical electromagnetic theory techniques to help assess microwave effects on electronic subsystems, by using a mode stirred chamber as our measurement tool. (6) We are investigating the generation of perfluoroisobutylene (PFIB) in proposed CFC replacement fluids when they are subjected to high electrical stresses and breakdown environments.

  4. Dispersion management for a sub-10-fs, 10 TW optical parametric chirped-pulse amplifier.

    Science.gov (United States)

    Tavella, Franz; Nomura, Yutaka; Veisz, Laszlo; Pervak, Vladimir; Marcinkevicius, Andrius; Krausz, Ferenc

    2007-08-01

    We report the amplification of three-cycle, 8.5 fs optical pulses in a near-infrared noncollinear optical parametric chirped-pulse amplifier (OPCPA) up to energies of 80 mJ. Improved dispersion management in the amplifier by means of a combination of reflection grisms and a chirped-mirror stretcher allowed us to recompress the amplified pulses to within 6% of their Fourier limit. The novel ultrabroad, ultraprecise dispersion control technology presented in this work opens the way to scaling multiterawatt technology to even shorter pulses by optimizing the OPCPA bandwidth.

  5. Intense pulsed light therapy.

    Science.gov (United States)

    Soltes, Barbara

    2010-12-01

    Intense Pulsed Light (IPL) is an FDA-approved photo therapy for the treatment of a variety of conditions such as acne and hirsutism. It utilizes the principle of selective photothermolysis. Photothermolysis allows a specific wavelength to be delivered to a chromophore of a designated tissue while leaving the surrounding tissue unaffected. The results of IPL are similar to that of laser treatments but it offers the advantage of a relative low cost. It is a safe and rapid treatment with minimal discomfort to the patient. Copyright © 2010 Elsevier Inc. All rights reserved.

  6. A Pulsed Sphere Tutorial

    Energy Technology Data Exchange (ETDEWEB)

    Cullen, Dermott E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-01-30

    Here I attempt to explain what physically happens when we pulse an object with neutrons, specifically what we expect the time dependent behavior of the neutron population to look like. Emphasis is on the time dependent emission of both prompt and delayed neutrons. I also describe how the TART Monte Carlo transport code models this situation; see the appendix for a complete description of the model used by TART. I will also show that, as we expect, MCNP and MERCURY, produce similar results using the same delayed neutron model (again, see the appendix).

  7. Africa's Pulse, October 2014

    OpenAIRE

    Punam, Chuhan-Pole; Ferreira, Francisco H. G.

    2014-01-01

    Africa’s Pulse is a biannual publication containing an analysis of the near-term macro-economic outlook for the region. It also includes a section focusing on a topic that represents a particular development challenges for the continent. It is produced by the Office of the Chief Economist for the Africa Region.This issue is an analysis of issues shaping Africa's economic future. Growth remains stable in Sub-Saharan Africa. Some countries are seeing a slowdown, but the region's economic pros...

  8. Terahertz pulsed imaging study of dental caries

    Science.gov (United States)

    Karagoz, Burcu; Altan, Hakan; Kamburoglu, Kıvanç

    2015-07-01

    Current diagnostic techniques in dentistry rely predominantly on X-rays to monitor dental caries. Terahertz Pulsed Imaging (TPI) has great potential for medical applications since it is a nondestructive imaging method. It does not cause any ionization hazard on biological samples due to low energy of THz radiation. Even though it is strongly absorbed by water which exhibits very unique chemical and physical properties that contribute to strong interaction with THz radiation, teeth can still be investigated in three dimensions. Recent investigations suggest that this method can be used in the early identification of dental diseases and imperfections in the tooth structure without the hazards of using techniques which rely on x-rays. We constructed a continuous wave (CW) and time-domain reflection mode raster scan THz imaging system that enables us to investigate various teeth samples in two or three dimensions. The samples comprised of either slices of individual tooth samples or rows of teeth embedded in wax, and the imaging was done by scanning the sample across the focus of the THz beam. 2D images were generated by acquiring the intensity of the THz radiation at each pixel, while 3D images were generated by collecting the amplitude of the reflected signal at each pixel. After analyzing the measurements in both the spatial and frequency domains, the results suggest that the THz pulse is sensitive to variations in the structure of the samples that suggest that this method can be useful in detecting the presence of caries.

  9. Dual-pulse frequency compounded superharmonic imaging.

    Science.gov (United States)

    van Neer, Paul L M J; Danilouchkine, Mikhail G; Matte, Guillaume M; van der Steen, Anton F W; de Jong, Nico

    2011-11-01

    Tissue second-harmonic imaging is currently the default mode in commercial diagnostic ultrasound systems. A new modality, superharmonic imaging (SHI), combines the third through fifth harmonics originating from nonlinear wave propagation through tissue. SHI could further improve the resolution and quality of echographic images. The superharmonics have gaps between the harmonics because the transducer has a limited bandwidth of about 70% to 80%. This causes ghost reflection artifacts in the superharmonic echo image. In this work, a new dual-pulse frequency compounding (DPFC) method to eliminate these artifacts is introduced. In the DPFC SHI method, each trace is constructed by summing two firings with slightly different center frequencies. The feasibility of the method was established using a single-element transducer. Its acoustic field was modeled in KZK simulations and compared with the corresponding measurements obtained with a hydrophone apparatus. Subsequently, the method was implemented on and optimized for a setup consisting of an interleaved phased-array transducer (44 elements at 1 MHz and 44 elements at 3.7 MHz, optimized for echocardiography) and a programmable ultrasound system. DPFC SHI effectively suppresses the ghost reflection artifacts associated with imaging using multiple harmonics. Moreover, compared with the single-pulse third harmonic, DPFC SHI improved the axial resolution by 3.1 and 1.6 times at the -6-dB and -20-dB levels, respectively. Hence, DPFC offers the possibility of generating harmonic images of a higher quality at a cost of a moderate frame rate reduction.

  10. Experimental set-up for a pulsed CO2 laser rangefinder with heterodyne detection

    Science.gov (United States)

    Bloem, J.

    1990-08-01

    The creation of a pulsed CO2 laser range finder with heterodyne detection is described. The range finder uses a hybrid CW-TEA (Continuous Wave-Transversely Excited Atmospheric pressure) laser as emitter and an RF laser as local oscillator. The laser stabilization is described. The frequency offset between the transmitted laser pulse and the local oscillator laser is locked at 20 MHz. The long term (20 to 30 min) variation of this offset frequency is limited to 50 kHz. The effects of pulsing on this stabilization were eliminated. The signal processing was started. A rough model of the laser pulse and its frequency characteristics was developed. An AM demodulator was developed to determine the envelope of the reflected pulses. The system created can be used to measure the range to (and in the future also the speed of) diffuse reflecting targets.

  11. Nonlinear spatial focusing in random layered media by spectral pulse shaping

    Science.gov (United States)

    Han, Alex C.; Milner, Valery

    2016-02-01

    We demonstrate numerically a method of focusing two-photon fields inside one-dimensional random media. The approach is based on coherent control of backscattering achieved by adaptive spectral pulse shaping. The spectral phases of a femtosecond laser pulse are adjusted for the constructive interference of its backward-traveling components, resulting in an enhanced reflection from within the random system. A delayed forward-propagating second pulse overlaps with the controlled reflection, increasing the interpulse multiphoton field at a location determined by the delay between the two pulses. The technique is shown to be robust against the variations of the disorder and to work with realistic pulse-shaping parameters, hence enabling applications in controlling random lasing and multiphoton imaging in scattering materials.

  12. Nonlinear interaction of charged particles with strong laser pulses in a gaseous media

    Directory of Open Access Journals (Sweden)

    H. K. Avetissian

    2007-07-01

    Full Text Available The charged particles nonlinear dynamics in the field of a strong electromagnetic wave pulse of finite duration and certain form of the envelope, in the refractive medium with a constant and variable refraction indexes, is investigated by means of numerical integration of the classical relativistic equations of motion. The particle energy dependence on the pulse intensity manifests the nonlinear threshold phenomenon of a particle reflection and capture by actual laser pulses in dielectric-gaseous media that takes place for a plane electromagnetic wave in the induced Cherenkov process. Laser acceleration of the particles in the result of the reflection from the pulse envelope and in the capture regime with the variable refraction index along the pulse propagation direction is investigated.

  13. Anomalous reflection of water surface during laser ablation

    Science.gov (United States)

    Nikiforov, S. M.; Alimpiev, S. S.; George, M. W.; Sartakov, B. G.; Simanovsky, Y. O.

    2000-08-01

    The temporal behaviour of KrF laser pulses reflected from a water surface was analysed over a broad range of laser fluences and absorption coefficients. We observed that the surface reflectivity strongly changes when the volume energy density exceeds a value of 1000 J/cm 3. The change in surface reflectivity, with increasing volume energy, depends on whether we have an air/water interface, where the reflectivity is increased, or a glass/water interface, where the reflectivity is decreased. We estimate the refraction index of water, which decreases from n=1.38 to ca. 1.1 for open water surface with the increase in volume energy. The mechanism of anomalous reflectivity is discussed and we suggest that this is due to heating of the absorbing solution above the water critical point, which is followed by a process of thermal expansion of the superheated layer.

  14. Reflective Lifeworld Research

    African Journals Online (AJOL)

    2009-05-01

    May 1, 2009 ... Reflective Lifeworld Research is a suitable title for a text that argues for, and gives convincing philosophical credence to, a qualitative sensibility in the human sciences. The key concept is 'reflective'. This is a rightful scientific attitude, the implications of which become the main theme of an academic.

  15. Earth's Reflection: Albedo

    Science.gov (United States)

    Gillette, Brandon; Hamilton, Cheri

    2011-01-01

    When viewing objects of different colors, you might notice that some appear brighter than others. This is because light is reflected differently from various surfaces, depending on their physical properties. The word "albedo" is used to describe how reflective a surface is. The Earth-atmosphere has a combined albedo of about 30%, a number that is…

  16. Reflective Learning in Practice.

    Science.gov (United States)

    Brockbank, Anne, Ed.; McGill, Ian, Ed.; Beech, Nic, Ed.

    This book contains 22 papers on reflective learning in practice. The following papers are included: "Our Purpose" (Ann Brockbank, Ian McGill, Nic Beech); "The Nature and Context of Learning" (Ann Brockbank, Ian McGill, Nic Beech); "Reflective Learning and Organizations" (Ann Brockbank, Ian McGill, Nic Beech);…

  17. Bipolar pulse forming line

    Science.gov (United States)

    Rhodes, Mark A.

    2008-10-21

    A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  18. Heat driven pulse pump

    Science.gov (United States)

    Benner, Steve M (Inventor); Martins, Mario S. (Inventor)

    2000-01-01

    A heat driven pulse pump includes a chamber having an inlet port, an outlet port, two check valves, a wick, and a heater. The chamber may include a plurality of grooves inside wall of the chamber. When heated within the chamber, a liquid to be pumped vaporizes and creates pressure head that expels the liquid through the outlet port. As liquid separating means, the wick, disposed within the chamber, is to allow, when saturated with the liquid, the passage of only liquid being forced by the pressure head in the chamber, preventing the vapor from exiting from the chamber through the outlet port. A plurality of grooves along the inside surface wall of the chamber can sustain the liquid, which is amount enough to produce vapor for the pressure head in the chamber. With only two simple moving parts, two check valves, the heat driven pulse pump can effectively function over the long lifetimes without maintenance or replacement. For continuous flow of the liquid to be pumped a plurality of pumps may be connected in parallel.

  19. Assembly delay line pulse generators

    CERN Multimedia

    CERN PhotoLab

    1971-01-01

    Assembly of six of the ten delay line pulse generators that will power the ten kicker magnet modules. One modulator part contains two pulse generators. Capacitors, inductances, and voltage dividers are in the oil tank on the left. Triggered high-pressure spark gap switches are on the platforms on the right. High voltage pulse cables to the kicker magnet emerge under the spark gaps. In the centre background are the assembled master gaps.

  20. Reflection: A Socratic approach

    Science.gov (United States)

    Van Seggelen – Damen, Inge C. M.; Van Hezewijk, René; Helsdingen, Anne S.; Wopereis, Iwan G. J. H.

    2017-01-01

    Reflection is a fuzzy concept. In this article we reveal the paradoxes involved in studying the nature of reflection. Whereas some scholars emphasize its discursive nature, we go further and underline its resemblance to the self-biased dialogue Socrates had with the slave in Plato’s Meno. The individual and internal nature of the reflection process creates difficulty for studying it validly and reliably. We focus on methodological issues and use Hans Linschoten’s view of coupled systems to identify, analyze, and interpret empirical research on reflection. We argue that researchers and research participants can take on roles in several possible system couplings. Depending on who controls the manipulation of the stimulus, who controls the measuring instrument, who interprets the measurement and the response, different types of research questions can be answered. We conclude that reflection may be validly studied by combining different couplings of experimenter, manipulation, stimulus, participant, measurement, and response. PMID:29249867

  1. Self-Reflection

    DEFF Research Database (Denmark)

    Fausing, Bent

    2016-01-01

    and physical bodies are constantly broken with technology. Perception and reflection are in synergy. Reflection means etymologically to bend back, to mirror, and to think. My presentation will take its point of departure in this etymology and make perspectives to modern use of refection in digital media. I...... will take a look at the establishing of the modern self and possibilities of self-reflection, too. My examples will be from the so-called dark-selfies and from a new selfie form, which merge the present with the previous progressing into the future. I will discuss the media reflections as loos and/or gain....... As another but short viewpoint telepresence, Skype, will be discussed, where new screen types, presence and reflections are established. In a perspective, I debate my term sore-society in relation to my topic and especially the dark selfies....

  2. Lead paint removal with high-intensity light pulses.

    Science.gov (United States)

    Grapperhaus, Michael J; Schaefer, Raymond B

    2006-12-15

    This paper presents the results of an initial investigation into using high-intensity incoherent light pulses to strip paint. Measurements of light pulse characteristics, the reflectivity of different paints and initial experiments on the threshold for paint removal, and paint removal are presented, along with an approximate model consistent with experimental results. Paint removal tests include lead paint, the reduction of lead levels to below levels required for lead abatement, as well as air and light emissions measurements that are within regulatory guidelines.

  3. Mapping the lattice-vibration potential using terahertz pulses

    Science.gov (United States)

    Korpa, C. L.; Tóth, Gy; Hebling, J.

    2018-02-01

    We develop a method for mapping the anharmonic lattice potential using the time-dependent electric field of the transmitted pulse through thin sample supported by a substrate of non-negligible thickness. Assuming linear propagation in the substrate we fully take into account internal reflection in it while the sample can show arbitrary nonlinear response. We examine the effect of frequency averaging appropriate for broad-band pulse and compare the results taking into account the full frequency dependence. We illustrate the procedure applying it to a model based on recently observed ferroelectric soft mode nonlinearity in SrTiO3.

  4. A finger-free wrist-worn pulse oximeter for the monitoring of chronic obstructive pulmonary disease

    Science.gov (United States)

    Chu, Chang-Sheng; Chuang, Shuang-Chao; Lee, Yeh Wen; Fan, Chih-Hsun; Chung, Lung Pin; Li, Yu-Tang; Chen, Jyh-Chern

    2016-03-01

    Herein, a finger-free wrist-worn pulse oximeter is presented. This device allows patients to measure blood oxygen level and pulse rate without hindering their normal finger movement. This wrist-worn pulse oximeter is built with a reflectance oximetry sensor, which consists of light emitting diodes and photodiode light detectors located side by side. This reflectance oximetry sensor is covered with an optical element with micro structured surface. This micro structured optical element is designed to modulate photon propagation beneath the skin tissue so that the photoplethysmogram signals of reflected lights or backscattered lights detected by the photodetector are therefore enhanced.

  5. Pulse Dispersion in Phased Arrays

    Directory of Open Access Journals (Sweden)

    Randy L. Haupt

    2017-01-01

    Full Text Available Phased array antennas cause pulse dispersion when receiving or transmitting wideband signals, because phase shifting the signals does not align the pulse envelopes from the elements. This paper presents two forms of pulse dispersion that occur in a phased array antenna. The first results from the separation distance between the transmit and receive antennas and impacts the definition of far field in the time domain. The second is a function of beam scanning and array size. Time delay units placed at the element and/or subarrays limit the pulse dispersion.

  6. Analysis of Pulse Modulated Control Systems (Ⅲ) Stability of Systems with Pulse Frequency Modulation and Systems with Combined Pulse Frequency and Pulse Width Modulation

    OpenAIRE

    OI,Shigemitsu

    1993-01-01

    Sufficient conditions for finite pulse stability of interconnected systems with combined pulse frequency and pulse width modulation are developed in this paper using a direct method. The stability criteria established provide upper bounds on the number of pulses emitted by each modulator. The results are also applicable to those systems which contain a finite number of pulse frequency modulators and a finite number of combined pulse frequency and pulse width modulators

  7. Modeling of ultrashort pulse generation in mode-locked VECSELs

    Science.gov (United States)

    Kilen, I.; Koch, S. W.; Hader, J.; Moloney, J. V.

    2016-03-01

    We present a study of various models for the mode-locked pulse dynamics in a vertical external-cavity surface emitting laser with a saturable absorber. The semiconductor Bloch equations are used to model microscopically the light-matter interaction and the carrier dynamics. Maxwell's equations describe the pulse propagation. Scattering contributions due to higher order correlation effects are approximated using effective rates that are found from a comparison to solving the microscopic scattering equations on the second Born-Markov level. It is shown that the simulations result in the same mode-locked final state whether the system is initialized with a test pulse close to the final mode-locked pulse or the full field build-up from statistical noise is considered. The influence of the cavity design is studied. The longest pulses are found for a standard V-cavity while a linear cavity and a V-cavity with an high reflectivity mirror in the middle are shown to produce similar, much shorter pulses.

  8. Reflectivity in Research Practice

    Directory of Open Access Journals (Sweden)

    Luigina Mortari

    2015-11-01

    Full Text Available The article grounds on the assumption that researchers, in order to be not mere technicians but competent practitioners of research, should be able to reflect in a deep way. That means they should reflect not only on the practical acts of research but also on the mental experience which constructs the meaning about practice. Reflection is a very important mental activity, both in private and professional life. Learning the practice of reflection is fundamental because it allows people to engage into a thoughtful relationship with the world-life and thus gain an awake stance about one’s lived experience. Reflection is a crucial cognitive practice in the research field. Reflexivity is largely practiced in qualitative research, where it is used to legitimate and validate research procedures. This study introduces different perspectives of analysis by focusing the discourse on the main philosophical approaches to reflection: pragmatistic, critical, hermeneutic, and finally phenomenological. The thesis of this study is that the phenomenological theory makes possible to analyze in depth the reflective activity and just by that to support an adequate process of training of the researcher.

  9. Pulse-shaping strategies in short-pulse fiber amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Schimpf, Damian Nikolaus

    2010-02-09

    Ultrashort pulse lasers are an important tool in scientific and industrial applications. However, many applications are demanding higher average powers from these ultrashort pulse sources. This can be achieved by combining direct diode pumping with novel gain media designs. In particular, ultrashort pulse fiber lasers are now delivering average powers in the kW range. However, the design of fiber lasers, producing pulses with high peak-powers, is challenging due to the impact of nonlinear effects. To significantly reduce these detrimental effects in ultrashort pulse fiber amplifers, the combination of chirped pulse amplification (CPA) and large mode area fibers is employed. Using these methods, the pulse energy of fiber lasers has been steadily increasing for the past few years. Recently, a fiber-based CPA-system has been demonstrated which produces pulse energies of around 1 mJ. However, both the stretching and the enlargement of the mode area are limited, and therefore, the impact of nonlinearity is still noticed in systems employing such devices. The aim of this thesis is the analysis of CPA-systems operated beyond the conventional nonlinear limit, which corresponds to accumulated nonlinear phase-shifts around 1 rad. This includes a detailed discussion of the influence of the nonlinear effect self-phase modulation on the output pulse of CPA-systems. An analytical model is presented. Emphasis is placed on the design of novel concepts to control the impact of self-phase modulation. Pulse-shaping is regarded as a powerful tool to accomplish this goal. Novel methods to control the impact of SPM are experimentally demonstrated. The design of these concepts is based on the theoretical findings. Both amplitude- and phase-shaping are studied. Model-based phase-shaping is implemented in a state-of-the-art fiber CPA-system. The influence of the polarization state is also highlighted. Additionally, existing techniques and recent advances are put into context. (orig.)

  10. Pulsed depressed collector

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Mark A

    2015-11-03

    A high power RF device has an electron beam cavity, a modulator, and a circuit for feed-forward energy recovery from a multi-stage depressed collector to the modulator. The electron beam cavity include a cathode, an anode, and the multi-stage depressed collector, and the modulator is configured to provide pulses to the cathode. Voltages of the electrode stages of the multi-stage depressed collector are allowed to float as determined by fixed impedances seen by the electrode stages. The energy recovery circuit includes a storage capacitor that dynamically biases potentials of the electrode stages of the multi-stage depressed collector and provides recovered energy from the electrode stages of the multi-stage depressed collector to the modulator. The circuit may also include a step-down transformer, where the electrode stages of the multi-stage depressed collector are electrically connected to separate taps on the step-down transformer.

  11. Nanofabrication with Pulsed Lasers

    Directory of Open Access Journals (Sweden)

    Kabashin AV

    2010-01-01

    Full Text Available Abstract An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3, is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.

  12. Capacitor discharge pulse analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Baker, Michael Sean; Griffiths, Stewart K.; Tanner, Danelle Mary

    2013-08-01

    Capacitors used in firing sets and other high discharge current applications are discharge tested to verify performance of the capacitor against the application requirements. Parameters such as capacitance, inductance, rise time, pulse width, peak current and current reversal must be verified to ensure that the capacitor will meet the application needs. This report summarizes an analysis performed on the discharge current data to extract these parameters by fitting a second-order system model to the discharge data and using this fit to determine the resulting performance metrics. Details of the theory and implementation are presented. Using the best-fit second-order system model to extract these metrics results in less sensitivity to noise in the measured data and allows for direct extraction of the total series resistance, inductance, and capacitance.

  13. Reflectance Reference Targets (OTTER)

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: Spectral reflectance measurements of flat field targets as reference points representative of pseudo-invariant targets as measured by Spectron SE590...

  14. Reflectance Reference Targets (OTTER)

    Data.gov (United States)

    National Aeronautics and Space Administration — Spectral reflectance measurements of flat field targets as reference points representative of pseudo-invariant targets as measured by Spectron SE590 spectrophotometer

  15. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  16. Electrode cartridge for pulse welding

    Energy Technology Data Exchange (ETDEWEB)

    Bonnen, John Joseph Francis; Golovashchenko, Sergey Fedorovich; Mamutov, Alexander; Maison, Lloyd Douglas

    2017-06-14

    A cartridge assembly for a tool includes a cartridge body or casing that contains a conductor. A conductor is connected to a pulse generator or source of stored charge that is discharged to vaporize the conductor and create an electro-hydraulic or electro-magnetic shockwave that is used to impact or pulse weld two parts together.

  17. Pulse Characteristic Curves of Vidicons,

    Science.gov (United States)

    microamps, and in vidicons with heterotransition screens, up to 10 microamps. The use of static modulation characteristic curves of vidicons for the...determination of the pulse beam current can lead to an error > 100%. With the help of pulse-modulation characteristic curves, it is possible to obtain the

  18. Thoughts on Reflection (Editorial

    Directory of Open Access Journals (Sweden)

    Denise Koufogiannakis

    2010-06-01

    Full Text Available There has been some acknowledgement in the published literature that reflection is a crucial element of the evidence based library and information practice (EBLIP model we have adopted (Booth 2004, 2006; Grant 2007; Helliwell 2007. As we work through a problem and try to incorporate the best available evidence into our decision making, reflection is required at several stages, including the very identification of the problem through to our assessment of the process itself and what we have learned in order to inform future practice. However, reflection and reflective writing have not fully been integrated into the process we espouse, and very little has been done to look more closely at this element of the model and how it can be integrated into professional learning.In a recently published research article, Sen (2010 confirms the relationship between reflection and several aspects of professional practice. These include critical review and decision making, two aspects that are tied closely to the evidence based process. Sen notes: Students were more likely to show evidence of learning, self‐development, the ability to review issues crucially, awareness of their own mental functions, ability to make decision [sic] and being empowered when they had mastered the art of reflective practice and the more deeply analytical reflective writing. (p.84 EBLIP (the journal tries to incorporate elements of reflection within the articles we publish. While we clearly believe in the need for our profession to do quality research and publish that research so that it can be accessible to practitioners, we also know that research cannot be looked at in isolation. Our evidence summaries are one way of reflecting critically on previously published research, and in the same vein, our classics bring older research studies back to the foreground. This work needs to continue to be discussed and looked at for its impact on our profession.More directly, the Using

  19. Hot subluminous stars: Highlights from the MUCHFUSS and Kepler missions

    Directory of Open Access Journals (Sweden)

    Geier S.

    2013-03-01

    Full Text Available Research into hot subdwarf stars is progressing rapidly. We present recent important discoveries. First we review the knowledge about magnetic fields in hot subdwarfs and highlight the first detection of a highly-magnetic, helium-rich sdO star. We briefly summarize recent discoveries based on Kepler light curves and finally introduce the closest known sdB+WD binary discovered by the MUCHFUSS project and discuss its relevance as a progenitor of a double-detonation type Ia supernova.

  20. Pulsed Ejector Wave Propogation Test Program

    Science.gov (United States)

    Fernandez, Rene; Slater, John W.; Paxson, Daniel E.

    2003-01-01

    The development of, and initial test data from, a nondetonating Pulse Detonation Engine (PDE) simulator tested in the NASA Glenn 1 x 1 foot Supersonic Wind Tunnel (SWT) is presented in this paper. The concept is a pulsed ejector driven by the simulated exhaust of a PDE. This pro- gram is applicable to a PDE entombed in a ramjet flowpath, i.e., a PDE combined-cycle propulsion system. The ejector primary flow is a pulsed, uiiderexpanded, supersonic nozzle simulating the supersonic waves ema- nating from a PDE, while the ejector secondary flow is the 1 x 1 foot SWT test section operated at subsonic Mach numbers. The objective is not to study the detonation details, but the wave physics including t,he start- ing vortices, the extent of propagation of the wave front, the reflection of the wave from the secondary flowpath walls, and the timing of these events of a pulsed ejector, and correlate these with Computational Fluid Dynamics (CFD) code predictions. Pulsed ejectors have been shown to result in a 3 to 1 improvement in LID (length-to-diameter) and a near 2 to 1 improvement in thrust augmentation over a steady ejector. This program will also explore the extent of upstream interactions between an inlet and large, periodically applied, backpressures to the inlet as would be present due to combustion tube detonations in a PDE. These interactions could result in inlet unstart or buzz for a supersonic mixed compression inlet. The design of the present experiment entailed the use of an 2-t diagram characteristics code to study the nozzle filling and purging timescales as well as a series of CFD analyses conducted using the WIND code. The WIND code is a general purpose CFD code for solution of the Reynolds averaged Navier-Stokes equations and can be applied to both steady state and time-accurate calculations. The first, proof-of-concept, test entry (spring 2001) pressure distributions shown here indicate the simulation concept was successful and therefore the experimental

  1. Reliability of conventional and new pulse oximetry in neonatal patients.

    Science.gov (United States)

    Hay, William W; Rodden, Donna J; Collins, Shannon M; Melara, Diane L; Hale, Kathy A; Fashaw, Lucy M

    2002-01-01

    Pulse oximetry is widely used in the NICU, but clinicians often distrust the displayed values during patient motion, i.e., questionable oxygen saturation (SpO(2)) and pulse rate (PR) values. Masimo Corporation (Irvine, CA) has developed pulse oximetry with claims of resistance to sources of interference. To test this premise, we compared the performance of the Masimo SET pulse oximeter to a conventional device, Nellcor N-200, and then with three other new-generation pulse oximeters, Nellcor N-395, Novametrix MARS, and Philips Viridia 24C. We studied 26 nonsedated NICU infants who were on supplemental oxygen and/or mechanical ventilation. ECG heart rate (HR) from a bedside monitor and SpO(2) and PR from the two pulse oximeters were captured by a PC for a total of 156 hours. The ECG HR and pulse oximeter spectral waveform were analyzed at alarms for hypoxemia (SpO(2)changes in HR. Compared with Nellcor, Masimo SET had 86% fewer false alarms, which also were shorter in duration, resulting in 92% less total alarm time. Masimo SET also identified nearly all bradycardias versus 14% for the Nellcor. Compared with the new-generation pulse oximeters, false desaturations, data drop-outs, and false bradycardias were lowest for Masimo SET, as was the capture of true desaturations and bradycardias. Notably, the new-generation devices differed greatly in their ability to detect changes in HR (i.e., the frequency of frozen PR during times of ECG HR change was 0, 6, 11, and 46 for Masimo, Nellcor, Philips, and Novametrix, respectively). Masimo SET pulse oximetry recorded markedly fewer false SpO(2) and PR alarms and identified more true hypoxic and bradycardic events than either conventional or other new-generation pulse oximeters. Masimo SET also most closely reflected the ECG rate irrespective of accelerations or decelerations in HR. Routine use of Masimo SET pulse oximetry in the NICU could improve clinician confidence in the parameter leading to more judicious titration of

  2. Creation, Identity and Reflection

    Directory of Open Access Journals (Sweden)

    Alina Beatrice Cheşcă

    2015-05-01

    Full Text Available The paper “Creation, Identity and Reflection” approaches the identification in the “mirror” of reality with creation, in other words seeking the authors’ identity in the reflected images. Reflection means attempting to find oneself, the mirror being the main principle of creation. Many characters become interesting only when they step into the world beyond the mirror, when their faces are doubled by the other self or when their selves are returned by other characters. The narcissistic concept of the mirror, i.e. the reflection in the mirror and the representation of the mirror itself, is a recurrent one in literature, but the reflection of the self which is not the self (as it is a reflection does not necessarily appear in a mirror or in a photograph or portrait. Sometimes, the not-self is returned to the self by another person or character. As far as Oscar Wilde’s theories are concerned, the main idea is that people are interesting for their masks, not for their inner nature. What Wilde calls “inner nature” is the characters’ un-reflected self and the mask is the reflection, the self in the mirror. Some characters’ relationships develop within a fiction that they dramatically try to preserve and protect with the risk of suffering. They refuse to take off the masks which define them in the others’ minds and hearts; the narcissistic individuals (both artists and characters seek and love their own image which they project upon facts, thus creating a fictive realm.

  3. Quantification of wave reflection in the human aorta from pressure alone: a proof of principle

    NARCIS (Netherlands)

    Westerhof, Berend E.; Guelen, Ilja; Westerhof, Nico; Karemaker, John M.; Avolio, Alberto

    2006-01-01

    Wave reflections affect the proximal aortic pressure and flow waves and play a role in systolic hypertension. A measure of wave reflection, receiving much attention, is the augmentation index (AI), the ratio of the secondary rise in pressure and pulse pressure. AI can be limiting, because it depends

  4. Pulse shaping using a spatial light modulator

    CSIR Research Space (South Africa)

    Botha, N

    2009-07-01

    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  5. Influence of laser pulse frequency on the microstructure of aluminum nitride thin films synthesized by pulsed laser deposition

    Science.gov (United States)

    Antonova, K.; Duta, L.; Szekeres, A.; Stan, G. E.; Mihailescu, I. N.; Anastasescu, M.; Stroescu, H.; Gartner, M.

    2017-02-01

    Aluminum Nitride (AlN) thin films were synthesized on Si (100) wafers at 450 °C by pulsed laser deposition. A polycrystalline AlN target was multipulsed irradiated in a nitrogen ambient, at different laser pulse repetition rate. Grazing Incidence X-Ray Diffraction and Atomic Force Microscopy analyses evidenced nanocrystallites with a hexagonal lattice in the amorphous AlN matrix. The thickness and optical constants of the layers were determined by infrared spectroscopic ellipsometry. The optical properties were studied by Fourier Transform Infrared reflectance spectroscopy in polarised oblique incidence radiation. Berreman effect was observed around the longitudinal phonon modes of the crystalline AlN component. Angular dependence of the A1LO mode frequency was analysed and connected to the orientation of the particles' optical axis to the substrate surface normal. The role of the laser pulse frequency on the layers' properties is discussed on this basis.

  6. Pulse source requirements for OTDM systems

    DEFF Research Database (Denmark)

    Clausen, Anders; Poulsen, Henrik Nørskov; Oxenløwe, Leif Katsuo

    2003-01-01

    A simulation model for investigating the impact of incoherent crosstalk due to pulse tail overlapping is proposed. Requirements to pulse width and pulse tail extinction ratio introducing a maximum of 1 dB penalty is extracted.......A simulation model for investigating the impact of incoherent crosstalk due to pulse tail overlapping is proposed. Requirements to pulse width and pulse tail extinction ratio introducing a maximum of 1 dB penalty is extracted....

  7. Bomb pulse biology

    Energy Technology Data Exchange (ETDEWEB)

    Falso, Miranda J. Sarachine [Center for Accelerator Mass Spectrometry, Mail Stop L-397, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States); Buchholz, Bruce A., E-mail: buchholz2@llnl.gov [Center for Accelerator Mass Spectrometry, Mail Stop L-397, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States)

    2013-01-15

    The past decade has seen an explosion in use of the {sup 14}C bomb pulse to do fundamental cell biology. Studies in the 1960s used decay counting to measure tissue turnover when the atmospheric {sup 14}C/C concentration was changing rapidly. Today bulk tissue measurements are of marginal interest since most of the carbon in the tissue resides in proteins, lipids and carbohydrates that turn over rapidly. Specific cell types with specialized functions are the focus of cell turnover investigations. Tissue samples need to be fresh or frozen. Fixed or preserved samples contain petroleum-derived carbon that has not been successfully removed. Cell or nuclear surface markers are used to sort specific cell types, typically by fluorescence-activated cell sorting (FACS). Specific biomolecules need to be isolated with high purity and accelerator mass spectrometry (AMS) measurements must accommodate samples that generally contain less than 40 {mu}g of carbon. Furthermore, all separations must not add carbon to the sample. Independent means such as UV absorbance must be used to confirm molecule purity. Approaches for separating specific proteins and DNA and combating contamination of undesired molecules are described.

  8. Extending ultra-short pulse laser texturing over large area

    Energy Technology Data Exchange (ETDEWEB)

    Mincuzzi, G., E-mail: girolamo.mincuzzi@alphanov.com; Gemini, L.; Faucon, M.; Kling, R.

    2016-11-15

    Highlights: • We carried out metal surface texturing (Ripples, micro grooves, Spikes) using a high power, high repetition rate, industrial, Ultra-short pulses laser. • Extremely Fast processing is shown (Laser Scan speed as high as 90 m/s) with a polygon scanner head. • Stainless steel surface blackening with Ultra-short pulses laser has been obtained with unprecedented scanspeed. • Full SEM surface characterization was carried out for all the different structures obtained. • Reflectance measurements were carried out to characterize surface reflectance. - Abstract: Surface texturing by Ultra-Short Pulses Laser (UPL) for industrial applications passes through the use of both fast beam scanning systems and high repetition rate, high average power P, UPL. Nevertheless unwanted thermal effects are expected when P exceeds some tens of W. An interesting strategy for a reliable heat management would consists in texturing with a low fluence values (slightly higher than the ablation threshold) and utilising a Polygon Scanner Heads delivering laser pulses with unrepeated speed. Here we show for the first time that with relatively low fluence it is possible over stainless steel, to obtain surface texturing by utilising a 2 MHz femtosecond laser jointly with a polygonal scanner head in a relatively low fluence regime (0.11 J cm{sup −2}). Different surface textures (Ripples, micro grooves and spikes) can be obtained varying the scan speed from 90 m s{sup −1} to 25 m s{sup −1}. In particular, spikes formation process has been shown and optimised at 25 m s{sup −1} and a full morphology characterization by SEM has been carried out. Reflectance measurements with integrating sphere are presented to compare reference surface with high scan rate textures. In the best case we show a black surface with reflectance value < 5%.

  9. [Dynamic pulse signal acquisition and processing].

    Science.gov (United States)

    Zhang, Aihua; Chou, Yongxin

    2012-03-01

    In order to obtain and process pulse signal in real-time, the integer coefficients notch, low-pass filters and an envelope filtering method were designed in consideration of the characteristics of disturbances in pulse signal and then were verified by MATLAB. The pulse signal was processed on DSP in time domain and frequency domain after simplifying the programming. The pulse wave height and pulse rate were calculated in real-time, and the pulse signal's spectrum was illustrated by FFT. The results show that the filters can effectively suppress the interference in pulse signal, and the system can detect and analyze the dynamic pulse signal in real-time.

  10. Hohlraum glint and laser pre-pulse detector for NIF experiments using velocity interferometer system for any reflector.

    Science.gov (United States)

    Moody, J D; Clancy, T J; Frieders, G; Celliers, P M; Ralph, J; Turnbull, D P

    2014-11-01

    Laser pre-pulse and early-time laser reflection from the hohlraum wall onto the capsule (termed "glint") can cause capsule imprint and unwanted early-time shocks on indirect drive implosion experiments. In a minor modification to the existing velocity interferometer system for any reflector diagnostic on NIF a fast-response vacuum photodiode was added to detect this light. The measurements show evidence of laser pre-pulse and possible light reflection off the hohlraum wall and onto the capsule.

  11. The Reflective Foundation

    DEFF Research Database (Denmark)

    Lunde Jørgensen, Ida

    Private foundations and cultural philanthropy by élites is viewed with increasing skepticism in recent years, begging the question of the extent to which foundations reflect on their role vis a vis wider societal norms. Through the prism of the New Carlsberg Foundation, financed by the brewery...... Carlsberg A/S, the paper seeks to elucidate the way in which one culturally significant foundation from Denmark has reflected on - and legitimated - its work and investments at critical moments in the past decades. The paper indicates a foundation with a high degree of reflection on the wider societal...... pressures, and position as a mediator between culture and capital. The paper draws inspiration from the institutional logics perspective and Boltanski and Thévenot’s convention theoretical work, to analyse the legitimations pursued by the foundation....

  12. Pulsed ultrasonic stir welding method

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  13. Reflections and Interpretations

    DEFF Research Database (Denmark)

    Reflections and Interpretations is an anthology on The Freedom Writers’ methodology. It is an anthology for all those with a professional need for texts explaining, not only how The Freedom Writers’ tools are being used, but also why they work so convincingly well. It is not an anthology of guide......Reflections and Interpretations is an anthology on The Freedom Writers’ methodology. It is an anthology for all those with a professional need for texts explaining, not only how The Freedom Writers’ tools are being used, but also why they work so convincingly well. It is not an anthology...

  14. Reflections on Leadership

    Science.gov (United States)

    2008-06-01

    Reflections on Leadership ROBERT GATES Last year I read Partners in Command, a book by Mark Perry. It is an ac-count of the unique relationship...TITLE AND SUBTITLE Reflections on Leadership 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e...Long War, but the Long War is interested in us. How America’s military and civilian leadership grapples with these transcendent issues and dilemmas will

  15. Invisibility via reflecting coating

    OpenAIRE

    Burdzy, Krzysztof; Kulczycki, Tadeusz

    2012-01-01

    We construct a subset $A$ of the unit disc with the following properties. (i) The set $A$ is the finite union of disjoint line segments. (ii) The shadow of $A$ is arbitrarily close to the shadow of the unit disc in "most" directions. (iii) If the line segments are considered to be mirrors reflecting light according to the classical law of specular reflection then most light rays hitting the set emerge on the other side of the disc moving along a parallel line and shifted by an arbitrarily sma...

  16. Postscript: Delving into Reflection

    Directory of Open Access Journals (Sweden)

    Susan Noffke

    2005-09-01

    Full Text Available Although, the authors presented an earlier version of the paper, "The Dimensions of Reflection: A Conceptual and Contextual Analysis", at the Annual Meeting of the American Educational Research Association, New Orleans, April, 1988, they did not have a chance to publish the paper till today. This postscript is about why the paper stayed as an “unpublished” conference paper for so long. Editors believe that the authors’ reflection on their academic journey with the paper in the postscript could be seen as an outstanding practical exemplar, a moral-political narrative of how to shape and create well-formed academic lives and identities.

  17. Measurement and modeling of pulsed microchannel plate operation (invited).

    Science.gov (United States)

    Rochau, G A; Wu, M; Kruschwitz, C; Joseph, N; Moy, K; Bailey, J; Krane, M; Thomas, R; Nielsen, D; Tibbitts, A

    2008-10-01

    Microchannel plates (MCPs) are a standard detector for fast-framing x-ray imaging and spectroscopy of high-temperature plasmas. The MCP is coated with conductive striplines that carry short duration voltage pulses to control the timing and amplitude of the signal gain. This gain depends on the voltage to a large exponent so that small reflections or impedance losses along the striplines can have a significant impact on the position-dependent amplitude and pulse width of the gain. Understanding the pulsed gain response therefore requires careful measurements of the position- and time-dependent surface voltage coupled with detailed modeling of the resulting electron cascade. We present measurements and modeling of the time- and space-dependent gain response of MCP detectors designed for use at Sandia National Laboratories' Z facility. The pulsed gain response is understood through measurements using a high impedence probe to determine the voltage pulse propagating along the stripline surface. Coupling the surface voltage measurements with Monte Carlo calculations of the electron cascade in the MCP provides a prediction of the time- and position-dependent gain that agrees with measurements made on a subpicosecond UV laser source to within the 25% uncertainty in the simulations.

  18. Applications of tunable resistive pulse sensing.

    Science.gov (United States)

    Weatherall, Eva; Willmott, Geoff R

    2015-05-21

    Tunable resistive pulse sensing (TRPS) is an experimental technique that has been used to study and characterise colloidal particles ranging from approximately 50 nm in diameter up to the size of cells. The primary aim of this Review is to provide a guide to the characteristics and roles of TRPS in recent applied research. Relevant studies reflect both the maturation of the technique and the growing importance of submicron colloids in fields such as nanomedicine and biotechnology. TRPS analysis of extracellular vesicles is expanding particularly swiftly, while TRPS studies also extend to on-bead assays using DNA and aptamers, drug delivery particles, viruses and bacteria, food and beverages, and superparamagnetic beads. General protocols for TRPS measurement of particle size, concentration and charge have been developed, and a summary of TRPS technology and associated analysis techniques is included in this Review.

  19. Pulsed light and pulsed electric field for foods and eggs.

    Science.gov (United States)

    Dunn, J

    1996-09-01

    Two new technologies for use in the food industry are described. The first method discussed uses intense pulse of light. This pulsed light (PureBright) process uses short duration flashes of broad spectrum "white" light to kill all exposed microorganisms, including vegetative bacteria, microbial and fungal spores, viruses, and protozoan oocysts. Each pulse, or flash, of light lasts only a few hundred millionths of a second (i.e., a few hundred microseconds). The intensity of each flash of light is about 20,000 times the intensity of sunlight at the earth's surface. The flashes are typically applied at a rate of about one to tens of flashes per second. For most applications, a few flashes applied in a fraction of a second provide an effective treatment. High microbial kill can be achieved, for example, on the surfaces of packaging materials, on packaging and processing equipment, foods, and medical devices as well as on many other surfaces. In addition, some bulk materials such as water and air that allow penetration of the light can be sterilized. The results of tests to measure the effects of pulsed light on Salmonella enteritiditis on eggs are presented. The second method discussed uses multiple, short duration, high intensity electric field pulses to kill vegetative microorganisms in pumpable products. This pulsed electric field (or CoolPure) process can be applied at modest temperatures at which no appreciable thermal damage occurs and the original taste, color, texture, and functionality of products can be retained.

  20. Nature of quantum states created by one photon absorption: pulsed coherent vs pulsed incoherent light.

    Science.gov (United States)

    Han, Alex C; Shapiro, Moshe; Brumer, Paul

    2013-08-29

    We analyze electronically excited nuclear wave functions and their coherence when subjecting a molecule to the action of natural, pulsed incoherent solar-like light and to that of ultrashort coherent light assumed to have the same center frequencies and spectral bandwidths. Specifically, we compute the spatiotemporal dependence of the excited wave packets and their electronic coherence for these two types of light sources, on different electronic potential energy surfaces. The resultant excited state wave functions are shown to be dramatically different, reflecting the light source from which they originated. In addition, electronic coherence is found to decay significantly faster for incoherent light than for coherent ultrafast excitation, for both continuum and bound wave packets. These results confirm that the dynamics observed from ultrashort coherent excitation does not reflect what happens in processes induced by solar-like radiation, and conclusions drawn from one do not, in general, apply to the other. These results provide further support to the view that the dynamics observed in studies using ultrashort coherent pulses can be significantly different than those that would result from excitation with natural incoherent light.

  1. Localized wave pulses in the keyport experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D.H.; Lewis, D.K.

    1998-02-17

    Localized wave (LW) pulses were produced using a standard Navy array in the anechoic tank at Navy Underwater Weapons Center (NUWC) Keyport. The LW pulses used were the MPS pulse first derived by Ziolkowski, and a new type of pulse based on a superposition of Gaussian beam modes. This new type is motivated by a desire to make a comparison of the MPS pulse with another broad band pulse built from solutions to the wave equation. The superposed Gaussian pulse can be described by parameters which are analogous to those describing the MPS pulse. We compare the directivity patternsand the axial energy decay between the pulses. We find the behavior of the pulses to be similar so that the superposed Gaussian could be another candidate in the class of low diffractive pulses known as localized waves.

  2. Prefire identification for pulse power systems

    Energy Technology Data Exchange (ETDEWEB)

    Longmire, Jerry L. (Los Alamos, NM); Thuot, Michael E. (Espanola, NM); Warren, David S. (Los Alamos, NM)

    1985-01-01

    Prefires in a high-power, high-frequency, multi-stage pulse generator are detected by a system having an EMI shielded pulse timing transmitter associated with and tailored to each stage of the pulse generator. Each pulse timing transmitter upon detection of a pulse triggers a laser diode to send an optical signal through a high frequency fiber optic cable to a pulse timing receiver which converts the optical signal to an electrical pulse. The electrical pulses from all pulse timing receivers are fed through an OR circuit to start a time interval measuring device and each electrical pulse is used to stop an individual channel in the measuring device thereby recording the firing sequence of the multi-stage pulse generator.

  3. Prefire identification for pulse power systems

    Energy Technology Data Exchange (ETDEWEB)

    Longmire, J. L.; Thuot, M. E.; Warren, D. S.

    1985-04-09

    Prefires in a high-power, high-frequency, multi-stage pulse generator are detected by a system having an EMI shielded pulse timing transmitter associated with and tailored to each stage of the pulse generator. Each pulse timing transmitter upon detection of a pulse triggers a laser diode to send an optical signal through a high frequency fiber optic cable to a pulse timing receiver which converts the optical signal to an electrical pulse. The electrical pulses from all pulse timing receivers are fed through an OR circuit to start a time interval measuring device and each electrical pulse is used to stop an individual channel in the measuring device thereby recording the firing sequence of the multi-stage pulse generator.

  4. Prefire identification for pulse-power systems

    Energy Technology Data Exchange (ETDEWEB)

    Longmire, J.L.; Thuot, M.E.; Warren, D.S.

    1982-08-23

    Prefires in a high-power, high-frequency, multi-stage pulse generator are detected by a system having an EMI shielded pulse timing transmitter associated with and tailored to each stage of the pulse generator. Each pulse timing transmitter upon detection of a pulse triggers a laser diode to send an optical signal through a high frequency fiber optic cable to a pulse timing receiver which converts the optical signal to an electrical pulse. The electrical pulses from all pulse timing receivers are fed through an OR circuit to start a time interval measuring device and each electrical pulse is used to stop an individual channel in the measuring device thereby recording the firing sequence of the multi-stage pulse generator.

  5. Luminal pulse velocity in a superluminal medium

    Science.gov (United States)

    Amano, Heisuke; Tomita, Makoto

    2015-12-01

    To investigate the physical meaning of pulse peak in fast and slow light media, we investigated propagation of differently shaped pulses experimentally, controlling the sharpness of the pulse peak. Symmetric behavior with respect to fast and slow light was observed in traditional Gaussian pulses; that is, propagated pulses were advanced or delayed, respectively, whereas the pulse shape remained unchanged. This symmetry broke down when the pulse peak was sharpened; in the fast light medium, the sharp pulse peak propagated with luminal velocity, and the transmitted pulse deformed into a characteristic asymmetric profile. In contrast, in the slow light medium, a time-delayed smooth peak appeared with a bending point at t =0 . This symmetry breaking with respect to fast and slow light is a universal characteristic of pulse propagation in causal dispersive systems. The sharp pulse peak can be recognized as a bending nonanalytical point and may be capable of transferring information.

  6. Single laser pulse compression via strongly coupled stimulated Brillouin scattering in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Peng, H.; Wu, Z. H.; Zhang, Z. M. [Laser Fusion Research Center, China Academy of Engineering Physics, P.O. Box 919-988, Mianyang 621900 (China); Science and Technology on Plasma Physics Laboratory, P.O. Box 919-988, Mianyang 621900 (China); Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai 200240 (China); Zuo, Y. L.; Zhou, K. N.; Su, J. Q., E-mail: Sujingqin@caep.ac.cn [Laser Fusion Research Center, China Academy of Engineering Physics, P.O. Box 919-988, Mianyang 621900 (China); Science and Technology on Plasma Physics Laboratory, P.O. Box 919-988, Mianyang 621900 (China)

    2016-07-15

    Laser amplification in plasma, including stimulated Raman scattering amplification and strongly coupled stimulated Brillouin scattering (sc-SBS) amplification, is very promising to generate ultrahigh-power and ultrashort laser pulses. But both are quite complex in experiments: at least three different laser pulses must be prepared; temporal delay and spatial overlap of these three pulses are difficult. We propose a single pulse compression scheme based on sc-SBS in plasma. Only one moderately long laser is applied, the front part of which ionizes the gas to produced plasma, and gets reflected by a plasma mirror at the end of the gas channel. The reflected front quickly depletes the remaining part of the laser by sc-SBS in the self-similar regime. The output laser is much stronger and shorter. This scheme is at first considered theoretically, then validated by using 1D PIC simulations.

  7. Experimental and theoretical study of Al plasma under femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Komarov, P S; Ashitkov, S I; Ovchinnikov, A V; Sitnikov, D S; Veysman, M E; Levashov, P R; Povarnitsyn, M E; Agranat, M B; Andreev, N E; Khishchenko, K V; Fortov, V E [Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya St. 13, Bd. 2, Moscow 125412 (Russian Federation)], E-mail: bme@ihed.ras.ru

    2009-05-29

    The amplitude and phase of the complex reflection coefficient of a weak probe laser pulse from strongly coupled Al plasma created on the surface of a metallic target by pump femtosecond laser pulses with intensities I {approx}< 10{sup 15} W cm{sup -2} were measured using femtosecond interference microscopy. A theoretical model developed for the interaction of intense ultrashort laser pulses with solid targets on the basis of a two-temperature equation of state for an irradiated substance was used for numerical simulations of the dynamics of the formation and expansion of the plasma. A comparison of the experimental data with the simulated results shows that the model is suitable up to I {approx} 10{sup 14} W cm{sup -2}. At higher intensities of the heating laser pulse, lower values of the reflection coefficient amplitude of Al plasma are observed in the experiment.

  8. Pulse oximetry for perioperative monitoring

    DEFF Research Database (Denmark)

    Pedersen, Tom; Nicholson, Amanda; Hovhannisyan, Karen

    2014-01-01

    of hypoxaemia reduce morbidity and mortality in the perioperative period.3. Use of pulse oximetry per se reduces morbidity and mortality in the perioperative period.4. Use of pulse oximetry reduces unplanned respiratory admissions to the intensive care unit (ICU), decreases the length of ICU readmission or both....... SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 5), MEDLINE (1966 to June 2013), EMBASE (1980 to June 2013), CINAHL (1982 to June 2013), ISI Web of Science (1956 to June 2013), LILACS (1982 to June 2013) and databases of ongoing trials; we also....... Results indicated that hypoxaemia was reduced in the pulse oximetry group, both in the operating theatre and in the recovery room. During observation in the recovery room, the incidence of hypoxaemia in the pulse oximetry group was 1.5 to three times less. Postoperative cognitive function was independent...

  9. All about Heart Rate (Pulse)

    Science.gov (United States)

    ... result of taking a drug such as a beta blocker . A lower heart rate is also common for ... 100. Medication use: Meds that block your adrenaline (beta blockers) tend to slow your pulse, while too much ...

  10. Next generation Chirped Pulse Amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nees, J.; Biswal, S.; Mourou, G. [Univ. Michigan, Center for Ultrafast Optical Science, Ann Arbor, MI (United States); Nishimura, Akihiko; Takuma, Hiroshi

    1998-03-01

    The limiting factors of Chirped Pulse Amplification (CPA) are discussed and experimental results of CPA in Yb:glass regenerative amplifier are given. Scaling of Yb:glass to the petawatt level is briefly discussed. (author)

  11. Self-Reflection

    DEFF Research Database (Denmark)

    Fausing, Bent

    2016-01-01

    Reflecting has a double meaning, mirroring and thinking. The seminar will investigate how these two meanings intervene in each other. As we perceive we are already in pre-refectory state, and thinking involves a lot of not only thoughts, but also of senses and sensing, wherefrom our thoughts star...

  12. Value reflected health education

    DEFF Research Database (Denmark)

    Wistoft, Karen; Nordentoft, Helle Merete

    2011-01-01

    This article examines the impact of a value-reflected approach in health education by demonstrating the nature of professional competence development connected to this approach. It is based on findings from two three-year health educational development projects carried out by school health nurses...... develop pedagogical competences in health education improving school childrens’ health....

  13. Reflection on Political Representation

    DEFF Research Database (Denmark)

    Kusche, Isabel

    2017-01-01

    This article compares how Members of Parliament in the United Kingdom and Ireland reflect on constituency service as an aspect of political representation. It differs from existing research on the constituency role of MPs in two regards. First, it approaches the question from a sociological...

  14. Reflections on Software Research

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 17; Issue 8. Reflections on Software Research. Dennis M Ritchie. Classics Volume 17 Issue 8 August 2012 pp 810-816. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/017/08/0810-0816. Author Affiliations.

  15. Reflections on "La Esperanza"

    Science.gov (United States)

    Cortez, Anita

    2007-01-01

    The author was recently asked to reflect on her "educational journey." As far as she can remember she has been hungry to learn. A friend once described her as having "hambres atrasadas," which he described as a kind of "hunger nipping at her heels." It goes back, of course, to her parents: Her father's and her early…

  16. Wave Reflection Model Tests

    DEFF Research Database (Denmark)

    Burcharth, H. F.; Larsen, Brian Juul

    The investigation concerns the design of a new internal breakwater in the main port of Ibiza. The objective of the model tests was in the first hand to optimize the cross section to make the wave reflection low enough to ensure that unacceptable wave agitation will not occur in the port. Secondly...... wave overtopping was studied as well....

  17. Teaching as Reflective Practice.

    Science.gov (United States)

    Kennedy, Rosa L.; Wyrick, Amy M.

    This paper describes a method of reflective practice called "critical incident" which was used to examine teacher trainees' educational assumptions. A qualitative case study of one fifth-year teaching intern (Amy) at the University of Tennessee represents the experience of seven other master's level students already practicing within the…

  18. Reflectance Hashing for Material Recognition

    OpenAIRE

    Zhang, Hang; Dana, Kristin; Nishino, Ko

    2015-01-01

    We introduce a novel method for using reflectance to identify materials. Reflectance offers a unique signature of the material but is challenging to measure and use for recognizing materials due to its high-dimensionality. In this work, one-shot reflectance is captured using a unique optical camera measuring {\\it reflectance disks} where the pixel coordinates correspond to surface viewing angles. The reflectance has class-specific stucture and angular gradients computed in this reflectance sp...

  19. Pulsed ultrasonic stir welding system

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  20. Pulsed feedback defers cellular differentiation.

    Directory of Open Access Journals (Sweden)

    Joe H Levine

    2012-01-01

    Full Text Available Environmental signals induce diverse cellular differentiation programs. In certain systems, cells defer differentiation for extended time periods after the signal appears, proliferating through multiple rounds of cell division before committing to a new fate. How can cells set a deferral time much longer than the cell cycle? Here we study Bacillus subtilis cells that respond to sudden nutrient limitation with multiple rounds of growth and division before differentiating into spores. A well-characterized genetic circuit controls the concentration and phosphorylation of the master regulator Spo0A, which rises to a critical concentration to initiate sporulation. However, it remains unclear how this circuit enables cells to defer sporulation for multiple cell cycles. Using quantitative time-lapse fluorescence microscopy of Spo0A dynamics in individual cells, we observed pulses of Spo0A phosphorylation at a characteristic cell cycle phase. Pulse amplitudes grew systematically and cell-autonomously over multiple cell cycles leading up to sporulation. This pulse growth required a key positive feedback loop involving the sporulation kinases, without which the deferral of sporulation became ultrasensitive to kinase expression. Thus, deferral is controlled by a pulsed positive feedback loop in which kinase expression is activated by pulses of Spo0A phosphorylation. This pulsed positive feedback architecture provides a more robust mechanism for setting deferral times than constitutive kinase expression. Finally, using mathematical modeling, we show how pulsing and time delays together enable "polyphasic" positive feedback, in which different parts of a feedback loop are active at different times. Polyphasic feedback can enable more accurate tuning of long deferral times. Together, these results suggest that Bacillus subtilis uses a pulsed positive feedback loop to implement a "timer" that operates over timescales much longer than a cell cycle.

  1. Artistic Representation with Pulsed Holography

    Science.gov (United States)

    Ishii, S.

    2013-02-01

    This thesis describes artistic representation through pulsed holography. One of the prevalent practical problems in making holograms is object movement. Any movement of the object or film, including movement caused by acoustic vibration, has the same fatal results. One way of reducing the chance of movement is by ensuring that the exposure is very quick; using a pulsed laser can fulfill this objective. The attractiveness of using pulsed laser is based on the variety of materials or objects that can be recorded (e.g., liquid material or instantaneous scene of a moving object). One of the most interesting points about pulsed holograms is that some reconstructed images present us with completely different views of the real world. For example, the holographic image of liquid material does not appear fluid; it looks like a piece of hard glass that would produce a sharp sound upon tapping. In everyday life, we are unfamiliar with such an instantaneous scene. On the other hand, soft-textured materials such as a feather or wool differ from liquids when observed through holography. Using a pulsed hologram, we can sense the soft touch of the object or material with the help of realistic three-dimensional (3-D) images. The images allow us to realize the sense of touch in a way that resembles touching real objects. I had the opportunity to use a pulsed ruby laser soon after I started to work in the field of holography in 1979. Since then, I have made pulsed holograms of activities, including pouring water, breaking eggs, blowing soap bubbles, and scattering feathers and popcorn. I have also created holographic art with materials and objects, such as silk fiber, fabric, balloons, glass, flowers, and even the human body. Whenever I create art, I like to present the spectator with a new experience in perception. Therefore, I would like to introduce my experimental artwork through those pulsed holograms.

  2. Optical pulses, lasers, measuring techniques

    CERN Document Server

    Früngel, Frank B A

    1965-01-01

    High Speed Pulse Technology: Volume II: Optical Pulses - Lasers - Measuring Techniques focuses on the theoretical and engineering problems that result from the capacitor discharge technique.This book is organized into three main topics: light flash production from a capacitive energy storage; signal transmission and ranging systems by capacitor discharges and lasers; and impulse measuring technique. This text specifically discusses the air spark under atmospheric conditions, industrial equipment for laser flashing, and claims for light transmitting system. The application of light impulse sign

  3. Pulsed laser ablation of copper

    Science.gov (United States)

    Jordan, R.; Cole, D.; Lunney, J. G.; Mackay, K.; Givord, D.

    1995-02-01

    The laser ablation of copper with a 532 nm, 6 ns laser has been investigated in the regime normally used for pulsed laser deposition. The ablation depth per pulse and the flux and energy distribution of the ions in the plume were measured and compared to the deposition rate as measured by a quartz microbalance. These measurements were compared with an analytic model of ablation via a laser sustained plasma. It is shown that self-sputtering of the growing film is significant.

  4. Focused electromagnetic doughnut pulses and their interaction with interfaces and nanostructures

    Science.gov (United States)

    Raybould, Tim; Fedotov, Vassili; Papasimakis, Nikitas; Youngs, Ian; Zheludev, Nikolay

    2016-02-01

    We study the propagation properties and light-matter interactions of the focused doughnut pulses, broadband, single-cycle electromagnetic perturbations of toroidal topology first described by Hellwarth and Nouchi in 1996. We show how focused doughnuts are reflected and refracted at planar metallic and vacuum-dielectric interfaces leading to complex distortions of the field structure. We also identify the conditions under which these toroidal pulses excite dominant dynamic toroidal dipoles in spherical dielectric particles.

  5. Music decreases aortic stiffness and wave reflections.

    Science.gov (United States)

    Vlachopoulos, Charalambos; Aggelakas, Angelos; Ioakeimidis, Nikolaos; Xaplanteris, Panagiotis; Terentes-Printzios, Dimitrios; Abdelrasoul, Mahmoud; Lazaros, George; Tousoulis, Dimitris

    2015-05-01

    Music has been related to cardiovascular health and used as adjunct therapy in patients with cardiovascular disease. Aortic stiffness and wave reflections are predictors of cardiovascular risk. We investigated the short-term effect of classical and rock music on arterial stiffness and wave reflections. Twenty healthy individuals (22.5±2.5 years) were studied on three different occasions and listened to a 30-min music track compilation (classical, rock, or no music for the sham procedure). Both classical and rock music resulted in a decrease of carotid-femoral pulse wave velocity (PWV) immediately after the end of music listening (all pclassical or rock music in a more sustained way (nadir by 6.0% and 5.8%, respectively, at time zero post-music listening, all pmusic preference was taken into consideration, both classical and rock music had a more potent effect on PWV in classical aficionados (by 0.20 m/s, p=0.003 and 0.13 m/s, p=0.015, respectively), whereas there was no effect in rock aficionados (all p=NS). Regarding wave reflections, classical music led to a more potent response in classical aficionados (AIx decrease by 9.45%), whereas rock led to a more potent response to rock aficionados (by 10.7%, all pMusic, both classical and rock, decreases aortic stiffness and wave reflections. Effect on aortic stiffness lasts for as long as music is listened to, while classical music has a sustained effect on wave reflections. These findings may have important implications, extending the spectrum of lifestyle modifications that can ameliorate arterial function. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  6. Switchable UWB pulse generation using a polarization maintaining fiber Bragg grating as frequency discriminator.

    Science.gov (United States)

    Feng, Xinhuan; Li, Zhaohui; Guan, Bai-Ou; Lu, C; Tam, H Y; Wai, P K A

    2010-02-15

    We propose and successfully demonstrate a novel approach to optically generate ultrawideband (UWB) pulse with switchable shape and polarity by using a polarization-maintaining fiber Bragg grating (PM-FBG) as frequency discriminator. Depending on the shape of the reflective spectrum of the PM-FBG, the system can function as a first- or second-order differentiator for the generation of Gaussian UWB monocycle or doublet pulses. Consequently, the shape and the polarity of the generated UWB pulse can be switched by simple adjustment of a polarization controller (PC). Gaussian monocycle and doublet pulses were successfully obtained with fractional bandwidths of about 188% and 152%, respectively. Higher-order UWB pulses with spectrum covering from 2.9 GHz to 9.8 GHz have also been obtained through adjustment of the PC.

  7. Influence of consecutive picosecond pulses at 532 nm wavelength on laser ablation of human teeth

    Science.gov (United States)

    Mirdan, Balsam M.; Antonelli, Luca; Batani, Dimitri; Jafer, Rashida; Jakubowska, Katarzyna; Tarazi, Saad al; Villa, Anna Maria; Vodopivec, Bruno; Volpe, Luca

    2014-07-01

    The interaction of 40 ps pulse duration laser emitting at 532 nm wavelength with human dental tissue (enamel, dentin, and dentin-enamel junction) has been investigated. The crater profile and the surface morphology have been studied by using a confocal auto-fluorescence microscope (working in reflection mode) and a scanning electron microscope. Crater profile and crater morphology were studied after applying consecutive laser pulses and it was found that the ablation depth increases with the number of consecutive pulses, leaving the crater diameter unchanged. We found that the thermal damage is reduced by using short duration laser pulses, which implies an increased retention of restorative material. We observe carbonization of the irradiated samples, which does not imply changes in the chemical composition. Finally, the use of 40 ps pulse duration laser may become a state of art in conservative dentistry.

  8. Pulse picker for synchrotron radiation driven by a surface acoustic wave.

    Science.gov (United States)

    Vadilonga, Simone; Zizak, Ivo; Roshchupkin, Dmitry; Petsiuk, Andrei; Dolbnya, Igor; Sawhney, Kawal; Erko, Alexei

    2017-05-15

    A functional test for a pulse picker for synchrotron radiation was performed at Diamond Light Source. The purpose of a pulse picker is to select which pulse from the synchrotron hybrid-mode bunch pattern reaches the experiment. In the present work, the Bragg reflection on a Si/B4C multilayer was modified using surface acoustic wave (SAW) trains. Diffraction on the SAW alters the direction of the x rays and it can be used to modulate the intensity of the x rays that reach the experimental chamber. Using electronic modulation of the SAW amplitude, it is possible to obtain different scattering conditions for different x-ray pulses. To isolate the single bunch, the state of the SAW must be changed in the short time gap between the pulses. To achieve the necessary time resolution, the measurements have been performed in conical diffraction geometry. The achieved time resolution was 120 ns.

  9. Extracting infrared absolute reflectance from relative reflectance measurements.

    Science.gov (United States)

    Berets, Susan L; Milosevic, Milan

    2012-06-01

    Absolute reflectance measurements are valuable to the optics industry for development of new materials and optical coatings. Yet, absolute reflectance measurements are notoriously difficult to make. In this paper, we investigate the feasibility of extracting the absolute reflectance from a relative reflectance measurement using a reference material with known refractive index.

  10. Reflecting differently. New dimensions: reflection-before-action and reflection-beyond-action

    Directory of Open Access Journals (Sweden)

    Sharon Edwards

    2017-05-01

    Full Text Available Background: This article attempts to move reflection forward from a process currently identified as two-dimensional (reflection-in-action and reflection-on-action to a four-dimensional process by adding reflection-before-action and reflection-beyond-action. In nursing clinical practice reflection-in-action is the required skill, but reflection-on-action is often advocated in nurse education through the application of reflective models in assignments. Nurse education draws on practice but generally, when using reflective practice, applies some sort of method or guide to direct student learning. This approach does not fully recognise that much learning arises from individual students’ own clinical practice experiences. The notion that undertaking reflection-on-action assignments develops the reflection-in-action skills needed for clinical practice is not demonstrated in the literature. Yet it is reflection-in-action that can aid professional practice and enhance learning. This is why it is important to explore a broader approach to reflection. Aims: To show more value can be gained from engaging with two additional dimensions of reflection – those of reflection-before-action and reflection-beyond-action, and to demonstrate how these can be linked to the better known concepts reflection-in-action and reflection-on-action, and to the author’s doctoral research, practice experience and practice development activities. Findings: Nursing reflection-on-action is widely used for a range of purposes, but restricting reflection in nurse education to this neglects the full potential of a broader application of reflection. A lifelong application of reflection can demonstrate its value for a more holistic and practical development approach. Conclusions: This article expands reflection and provides two additional dimensions. Instead of identifying reflection as two-dimensional, this article proposes that reflection can better serve learning from practice

  11. Square pulse linear transformer driver

    Directory of Open Access Journals (Sweden)

    A. A. Kim

    2012-04-01

    Full Text Available The linear transformer driver (LTD technological approach can result in relatively compact devices that can deliver fast, high current, and high-voltage pulses straight out of the LTD cavity without any complicated pulse forming and pulse compression network. Through multistage inductively insulated voltage adders, the output pulse, increased in voltage amplitude, can be applied directly to the load. The usual LTD architecture [A. A. Kim, M. G. Mazarakis, V. A. Sinebryukhov, B. M. Kovalchuk, V. A. Vizir, S. N Volkov, F. Bayol, A. N. Bastrikov, V. G. Durakov, S. V. Frolov, V. M. Alexeenko, D. H. McDaniel, W. E. Fowler, K. LeCheen, C. Olson, W. A. Stygar, K. W. Struve, J. Porter, and R. M. Gilgenbach, Phys. Rev. ST Accel. Beams 12, 050402 (2009PRABFM1098-440210.1103/PhysRevSTAB.12.050402; M. G. Mazarakis, W. E. Fowler, A. A. Kim, V. A. Sinebryukhov, S. T. Rogowski, R. A. Sharpe, D. H. McDaniel, C. L. Olson, J. L. Porter, K. W. Struve, W. A. Stygar, and J. R. Woodworth, Phys. Rev. ST Accel. Beams 12, 050401 (2009PRABFM1098-440210.1103/PhysRevSTAB.12.050401] provides sine shaped output pulses that may not be well suited for some applications like z-pinch drivers, flash radiography, high power microwaves, etc. A more suitable power pulse would have a flat or trapezoidal (rising or falling top. In this paper, we present the design and first test results of an LTD cavity that generates such a type of output pulse by including within its circular array a number of third harmonic bricks in addition to the main bricks. A voltage adder made out of a square pulse cavity linear array will produce the same shape output pulses provided that the timing of each cavity is synchronized with the propagation of the electromagnetic pulse.

  12. Nonlinear response to picosecond pulse excitations in metal backed magnetic layers (abstract)

    Science.gov (United States)

    How, H.; Vittoria, C.; Trott, K.

    1993-05-01

    For years there has been great interest in the radar survivability communities concerning the response of materials to narrow picosecond pulse excitation. In this report, we have calculated the nonlinear response of magnetodielectric thin layers to picosecond excitation utilizing direct time-domain integration. This is in contrast to our previous frequency-domain calculations,1 where the nonlinear properties of the material were dealt with only in an approximate manner. Using time domain calculations, relaxations, hysteresis, and magnetization phenomena associated with the response are, therefore, investigated in depth. The purpose of this calculation was to provide an analytical method by which physical properties of materials can be identified under picosecond pulse excitation as well as to explore special cases of excitations in which picosecond pulses are efficiently absorbed. The calculations indicate that by examining the reflected wave form of the incident rectangular picosecond pulse the amount of magnetic hysteresis and saturation of the material may be estimated. It is shown that magnetic hysteresis will affect the shape of the trailing edge of the reflected signal, whereas the magnetic saturation effect can be identified from the slope of the reflected pulse step. Examples of designing effective picosecond pulse screening structures have also been illustrated. The difference in between the time domain and frequency domain calculations are, therefore, discussed and compared.

  13. River water remediation using pulsed corona, pulsed spark or ozonation

    Energy Technology Data Exchange (ETDEWEB)

    Izdebski, T.; Dors, M. [Polish Academy of Sciences, Szewalski Inst. of Fluid Flow Machiney, Fiszera (Poland). Centre for Plasma and Laser Engineering; Mizeraczyk, J. [Polish Academy of Sciences, Szewalski Inst. of Fluid Flow Machiney, Fiszera (Poland). Centre for Plasma and Laser Engineering; Gdynia Maritime Univ., Morska (Poland). Dept. of Marine Electronics

    2010-07-01

    The most common reason for epidemic formation is the pollution of surface and drinking water by wastewater bacteria. Pathogenic microorganisms that form the largest part of this are fecal bacteria, such as escherichia coli (E. coli). Wastewater treatment plants reduce the amount of the fecal bacteria by 1-3 orders of magnitude, depending on the initial number of bacteria. There is a lack of data on waste and drinking water purification by the electrohydraulic discharges method, which causes the destruction and inactivation of viruses, yeast, and bacteria. This paper investigated river water cleaning from microorganisms using pulsed corona, spark discharge and ozonization. The paper discussed the experimental setup and results. It was concluded that ozonization is the most efficient method of water disinfection as compared with pulsed spark and pulsed corona discharges. The pulsed spark discharge in water was capable of killing all microorganism similarly to ozonization, but with much lower energy efficiency. The pulsed corona discharge was found to be the less effective method of water disinfection. 21 refs., 4 figs.

  14. Determinants of radial artery pulse wave analysis in asymptomatic individuals.

    Science.gov (United States)

    Duprez, Daniel A; Kaiser, Daniel R; Whitwam, Wayne; Finkelstein, Stanley; Belalcazar, Andres; Patterson, Robert; Glasser, Stephen; Cohn, Jay N

    2004-08-01

    Noninvasive techniques to evaluate arterial stiffness include noninvasive radial artery pulse contour analysis. Diastolic pulse contour analysis provides a separate assessment of large (C1) and small artery (C2) elasticity. Analysis of the systolic pulse contour identifies two pressure peaks (P1 and P2) that relate to incident and reflected waves. This study aimed to compare indices from systolic and diastolic pulse contour analysis from the radial pressure waveform and to correlate these indices with traditional risk factors in asymptomatic individuals screened for cardiovascular disease. In 298 consecutive subjects (206 male and 92 female healthy subjects with a mean age of 50 +/- 12 years), noninvasive radial artery pressure waveforms were acquired with a piezoelectric transducer and analyzed for 1) diastolic indices of C1 and C2 from the CR-2000 CVProfiler, and 2) systolic indices of augmentation as defined by augmentation pressure (AP), augmentation index (AIx), and systolic reflective index (SRI = P2/P1). These indices were then correlated to each other as well as to individual traditional risk factors and the Framingham Risk Score. Diastolic indices were significantly and inversely correlated to systolic indices with C2 showing a stronger inverse association than C1. C2 and Alx were significantly correlated with height, weight, and body mass index in men but not in women. All indices correlated better to blood pressure in women than men. In women, only systolic indices were significantly correlated to HDL cholesterol and only diastolic indices were significantly correlated to LDL cholesterol. All indices were significantly correlated to the Framingham Risk Score, which was stronger in women then men, but when adjusted for age only diastolic indices remained significant in women. Diastolic and systolic indices of pulse contour analysis correlate differently with traditional risk factors in men and women. Copyright 2004 American Journal of Hypertension, Ltd.

  15. Clinical linguistics: conversational reflections.

    Science.gov (United States)

    Crystal, David

    2013-04-01

    This is a report of the main points I made in an informal "conversation" with Paul Fletcher and the audience at the 14th ICPLA conference in Cork. The observations arose randomly, as part of an unstructured 1-h Q&A, so they do not provide a systematic account of the subject, but simply reflect the issues which were raised by the conference participants during that time.

  16. Landsat surface reflectance data

    Science.gov (United States)

    ,

    2015-01-01

    Landsat satellite data have been produced, archived, and distributed by the U.S. Geological Survey since 1972. Users rely on these data for historical study of land surface change and require consistent radiometric data processed to the highest science standards. In support of the guidelines established through the Global Climate Observing System, the U.S. Geological Survey has embarked on production of higher-level Landsat data products to support land surface change studies. One such product is Landsat surface reflectance.

  17. Behavioral studies of the auditory discrimination of paired pulses with identical pulse spacings by a dolphin

    Science.gov (United States)

    Sukhoruchenko, M. N.

    2008-11-01

    For a bottlenose dolphin, the thresholds of discrimination of paired pulses with pulse spacings of 50 1000 μs and different peak values of the second pulse in the test pair are investigated. It is shown that the pair discrimination thresholds depend on both the absolute level of pulses and the ratio between the pulse levels in the standard pair. As the pulse delay in a pair increases, the thresholds monotonically decrease. A possibility of the paired pulse discrimination by the total energy of pulses in a pair is considered for the case of pulse delays both within the critical interval (300 μs) and beyond it.

  18. Topology optimization problems for reflection and dissipation of elastic waves

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    2007-01-01

    This paper is devoted to topology optimization problems for elastic wave propagation. The objective of the study is to maximize the reflection or the dissipation in a finite slab of material for pressure and shear waves in a range of frequencies. The optimized designs consist of two or three...... material phases: a host material and scattering and/or absorbing inclusions. The capabilities of the optimization algorithm are demonstrated with two numerical examples in which the reflection and dissipation of ground-borne wave pulses are maximized....

  19. Pulsed Corona Discharge Generated By Marx Generator

    Science.gov (United States)

    Sretenovic, G. B.; Obradovic, B. M.; Kovacevic, V. V.; Kuraica, M. M.; Puric J.

    2010-07-01

    The pulsed plasma has a significant role in new environmental protection technologies. As a part of a pulsed corona system for pollution control applications, Marx type repetitive pulse generator was constructed and tested in arrangement with wire-plate corona reactor. We performed electrical measurements, and obtained voltage and current signals, and also power and energy delivered per pulse. Ozone formation by streamer plasma in air was chosen to monitor chemical activity of the pulsed corona discharge.

  20. Root-flipped multiband refocusing pulses.

    Science.gov (United States)

    Sharma, Anuj; Lustig, Michael; Grissom, William A

    2016-01-01

    To design low peak power multiband refocusing radiofrequency pulses, with application to simultaneous multislice spin echo MRI. Multiband Shinnar-Le Roux β polynomials were designed using convex optimization. A Monte Carlo algorithm was used to determine patterns of β polynomial root flips that minimized the peak power of the resulting refocusing pulses. Phase-matched multiband excitation pulses were also designed to obtain linear-phase spin echoes. Simulations compared the performance of the root-flipped pulses with time-shifted and phase-optimized pulses. Phantom and in vivo experiments at 7T validated the function of the root-flipped pulses and compared them to time-shifted spin echo signal profiles. Averaged across number of slices, time-bandwidth product, and slice separation, the root-flipped pulses have 46% shorter durations than time-shifted pulses with the same peak radiofrequency amplitude. Unlike time-shifted and phase-optimized pulses, the root-flipped pulses' excitation errors do not increase with decreasing band separation. Experiments showed that the root-flipped pulses excited the desired slices at the target locations, and that for equivalent slice characteristics, the shorter root-flipped pulses allowed shorter echo times, resulting in higher signal than time-shifted pulses. The proposed root-flipped multiband radiofrequency pulse design method produces low peak power pulses for simultaneous multislice spin echo MRI. © 2015 Wiley Periodicals, Inc.

  1. Pulse oximetry in pediatric practice.

    Science.gov (United States)

    Fouzas, Sotirios; Priftis, Kostas N; Anthracopoulos, Michael B

    2011-10-01

    The introduction of pulse oximetry in clinical practice has allowed for simple, noninvasive, and reasonably accurate estimation of arterial oxygen saturation. Pulse oximetry is routinely used in the emergency department, the pediatric ward, and in pediatric intensive and perioperative care. However, clinically relevant principles and inherent limitations of the method are not always well understood by health care professionals caring for children. The calculation of the percentage of arterial oxyhemoglobin is based on the distinct characteristics of light absorption in the red and infrared spectra by oxygenated versus deoxygenated hemoglobin and takes advantage of the variation in light absorption caused by the pulsatility of arterial blood. Computation of oxygen saturation is achieved with the use of calibration algorithms. Safe use of pulse oximetry requires knowledge of its limitations, which include motion artifacts, poor perfusion at the site of measurement, irregular rhythms, ambient light or electromagnetic interference, skin pigmentation, nail polish, calibration assumptions, probe positioning, time lag in detecting hypoxic events, venous pulsation, intravenous dyes, and presence of abnormal hemoglobin molecules. In this review we describe the physiologic principles and limitations of pulse oximetry, discuss normal values, and highlight its importance in common pediatric diseases, in which the principle mechanism of hypoxemia is ventilation/perfusion mismatch (eg, asthma exacerbation, acute bronchiolitis, pneumonia) versus hypoventilation (eg, laryngotracheitis, vocal cord dysfunction, foreign-body aspiration in the larynx or trachea). Additional technologic advancements in pulse oximetry and its incorporation into evidence-based clinical algorithms will improve the efficiency of the method in daily pediatric practice.

  2. Radial flow pulse jet mixer

    Science.gov (United States)

    VanOsdol, John G.

    2013-06-25

    The disclosure provides a pulse jet mixing vessel for mixing a plurality of solid particles. The pulse jet mixing vessel is comprised of a sludge basin, a flow surface surrounding the sludge basin, and a downcoming flow annulus between the flow surface and an inner shroud. The pulse jet mixing vessel is additionally comprised of an upper vessel pressurization volume in fluid communication with the downcoming flow annulus, and an inner shroud surge volume separated from the downcoming flow annulus by the inner shroud. When the solid particles are resting on the sludge basin and a fluid such as water is atop the particles and extending into the downcoming flow annulus and the inner shroud surge volume, mixing occurs by pressurization of the upper vessel pressurization volume, generating an inward radial flow over the flow surface and an upwash jet at the center of the sludge basin.

  3. Global South: Anthropological Reflections

    DEFF Research Database (Denmark)

    Steur, Luisa Johanna; Kalb, Don

    2015-01-01

    The global south is a complex and dynamic concept that straddles multiple social science and humanist disciplines. Emerging around 2000, it reflects the agenda of two ascending forces in those years: the antiglobalist (alterglobalist/global justice) movement and the World Social Forum, on the one...... hand, and an alliance of Southern states within the World Trade Organization on the other. Generally seen as an inheritor of the emancipatory thought behind the notion of the ‘third world,’ in the social sciences the idea of the ‘global south’ is also entangled with more classical academic themes...

  4. High power ultrashort pulse lasers

    Energy Technology Data Exchange (ETDEWEB)

    Perry, M.D.

    1994-10-07

    Small scale terawatt and soon even petawatt (1000 terawatt) class laser systems are made possible by application of the chirped-pulse amplification technique to solid-state lasers combined with the availability of broad bandwidth materials. These lasers make possible a new class of high gradient accelerators based on the large electric fields associated with intense laser-plasma interactions or from the intense laser field directly. Here, we concentrate on the laser technology to produce these intense pulses. Application of the smallest of these systems to the production of high brightness electron sources is also introduced.

  5. Pulse compressor with aberration correction

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, Marian [Electron Optica, Inc., Palo Alto, CA (United States)

    2015-11-30

    In this SBIR project, Electron Optica, Inc. (EOI) is developing an electron mirror-based pulse compressor attachment to new and retrofitted dynamic transmission electron microscopes (DTEMs) and ultrafast electron diffraction (UED) cameras for improving the temporal resolution of these instruments from the characteristic range of a few picoseconds to a few nanoseconds and beyond, into the sub-100 femtosecond range. The improvement will enable electron microscopes and diffraction cameras to better resolve the dynamics of reactions in the areas of solid state physics, chemistry, and biology. EOI’s pulse compressor technology utilizes the combination of electron mirror optics and a magnetic beam separator to compress the electron pulse. The design exploits the symmetry inherent in reversing the electron trajectory in the mirror in order to compress the temporally broadened beam. This system also simultaneously corrects the chromatic and spherical aberration of the objective lens for improved spatial resolution. This correction will be found valuable as the source size is reduced with laser-triggered point source emitters. With such emitters, it might be possible to significantly reduce the illuminated area and carry out ultrafast diffraction experiments from small regions of the sample, e.g. from individual grains or nanoparticles. During phase I, EOI drafted a set of candidate pulse compressor architectures and evaluated the trade-offs between temporal resolution and electron bunch size to achieve the optimum design for two particular applications with market potential: increasing the temporal and spatial resolution of UEDs, and increasing the temporal and spatial resolution of DTEMs. Specialized software packages that have been developed by MEBS, Ltd. were used to calculate the electron optical properties of the key pulse compressor components: namely, the magnetic prism, the electron mirror, and the electron lenses. In the final step, these results were folded

  6. High-speed pulse techniques

    CERN Document Server

    Coekin, J A

    1975-01-01

    High-Speed Pulse Techniques covers the many aspects of technique in digital electronics and encompass some of the more fundamental factors that apply to all digital systems. The book describes the nature of pulse signals and their deliberate or inadvertent processing in networks, transmission lines and transformers, and then examines the characteristics and transient performance of semiconductor devices and integrated circuits. Some of the problems associated with the assembly of these into viable systems operating at ultra high speed are also looked at. The book examines the transients and w

  7. Athletic Differences in the Characteristics of the Photoplethysmographic Pulse Shape: Effect of Maximal Oxygen Uptake and Maximal Muscular Voluntary Contraction

    Directory of Open Access Journals (Sweden)

    Anran Wang

    2015-01-01

    Full Text Available This study aimed to investigate the athletic differences in the characteristics of the photoplethysmographic (PPG pulse shape. 304 athletes were enrolled and divided into three subgroups according to a typical sport classification in terms of the maximal oxygen uptake (MaxO2_low, MaxO2_middle and MaxO2_high groups or the maximal muscular voluntary contraction (MMVC_low, MMVC_middle, and MMVC_high groups. Finger PPG pulses were digitally recorded and then normalized to derive the pulse area, pulse peak time Tp, dicrotic notch time Tn, and pulse reflection index (RI. The four parameters were finally compared between the three subgroups categorized by MaxO2 or by MMVC. In conclusion, it has been demonstrated by quantifying the characteristics of the PPG pulses in different athletes that MaxO2, but not MMVC, had significant effect on the arterial properties.

  8. 35 Volt, 180 Ampere Pulse Generator with Droop Control for Pulsing Xenon Arcs

    DEFF Research Database (Denmark)

    Hviid, T.; Nielsen, S. O.

    1972-01-01

    The pulse generator described works as a combined switch and series current regulator and allows the shape of the current pulse to be adjusted at each optical wavelength to produce a flat pulse of monochromatic light.......The pulse generator described works as a combined switch and series current regulator and allows the shape of the current pulse to be adjusted at each optical wavelength to produce a flat pulse of monochromatic light....

  9. Dynamic Characterization of Fiber Optical Chirped Pulse Amplification for Sub-ps Pulses

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Rishøj, Lars Søgaard

    2013-01-01

    We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation.......We investigate experimentally the propagation of sub-picosecond pulses in fiber optical parametric chirped pulse amplifiers, showing a significant broadening of the pulses from 450 fs up to 720 fs due to dispersion and self-phase modulation....

  10. Modelling and experiments of self-reflectivity under femtosecond ablation conditions

    CERN Document Server

    Zhang, H; Krol, D M; Dijkhuis, J I; van Oosten, D

    2014-01-01

    We present a numerical model which describes the propagation of a single femtosecond laser pulse in a medium of which the optical properties dynamically change within the duration of the pulse. We use a Finite Difference Time Domain (FDTD) method to solve the Maxwell's equations coupled to equations describing the changes in the material properties. We use the model to simulate the self-reflectivity of strongly focused femtosecond laser pulses on silicon and gold under laser ablation condition. We compare the simulations to experimental results and find excellent agreement.

  11. Matter reflects Antimatter

    CERN Document Server

    Bianconi, A.; Cristiano, A.; Leali, M.; Lodi Rizzini, E.; Venturelli, L.; Zurlo, N.

    2008-01-01

    It is common belief that the interaction between antimatter and ordinary solid matter is dominated by annihilation. However, non-destructive processes may play a relevant role too. One century ago E. Rutherford wrote about the "diffuse reflection" of alpha and beta particles by thin layers of different metals: "The observations ... of Geiger and Marsden on the scattering of alpha rays indicate that some of the alpha particles must suffer a deflexion of more than a right angle at a single encounter.... It will be shown that the main deductions from the theory are independent of whether the central charge is supposed to be positive or negative". Although the theory of electromagnetic scattering is in first approximation independent of the relative sign of the colliding particles, in the case where projectile antiprotons are shot against a wall of solid matter the Rutherford diffuse reflection mechanism competes with the annihilation process. So it is not obvious at all that a relevant part of an antiproton beam...

  12. Reflection on photographs.

    Science.gov (United States)

    Brand, Gabrielle; McMurray, Anne

    2009-11-01

    Nursing students' exposure to clinical placements with older adults is instrumental in helping them adopt positive attitudes toward care of that population. This qualitative pilot study analyzed perceptions and expectations of a group of first-year students prior to a clinical placement with older adults. A photo-elicitation technique, involving viewing of realistic photographs of older adults being cared for, was used to help students clarify expectations. This was followed by thematic analysis of their perceptions and expectations. Analysis revealed five main themes: Dissecting What It Means to Be a Nurse, Revisioning Therapeutic Relationships in Terms of Dignity, Youthful Reflection on the Differences Between Young and Old, Feeling Challenged and Confronted, and Experiencing Sensitivity and Awkwardness Toward Older Adults' Nakedness. Engagement with images of older adults encouraged students to anticipate their clinical placement in an aged care setting in a more meaningful, reflective way than they may have done without prior exposure, suggesting a need for realistic pre-practice education. Copyright 2009, SLACK Incorporated.

  13. Fostering and evaluating reflective capacity in medical education: developing the REFLECT rubric for assessing reflective writing.

    Science.gov (United States)

    Wald, Hedy S; Borkan, Jeffrey M; Taylor, Julie Scott; Anthony, David; Reis, Shmuel P

    2012-01-01

    Reflective writing (RW) curriculum initiatives to promote reflective capacity are proliferating within medical education. The authors developed a new evaluative tool that can be effectively applied to assess students' reflective levels and assist with the process of providing individualized written feedback to guide reflective capacity promotion. Following a comprehensive search and analysis of the literature, the authors developed an analytic rubric through repeated iterative cycles of development, including empiric testing and determination of interrater reliability, reevaluation and refinement, and redesign. Rubric iterations were applied in successive development phases to Warren Alpert Medical School of Brown University students' 2009 and 2010 RW narratives with determination of intraclass correlations (ICCs). The final rubric, the Reflection Evaluation for Learners' Enhanced Competencies Tool (REFLECT), consisted of four reflective capacity levels ranging from habitual action to critical reflection, with focused criteria for each level. The rubric also evaluated RW for transformative reflection and learning and confirmatory learning. ICC ranged from 0.376 to 0.748 for datasets and rater combinations and was 0.632 for the final REFLECT iteration analysis. The REFLECT is a rigorously developed, theory-informed analytic rubric, demonstrating adequate interrater reliability, face validity, feasibility, and acceptability. The REFLECT rubric is a reflective analysis innovation supporting development of a reflective clinician via formative assessment and enhanced crafting of faculty feedback to reflective narratives.

  14. Femtosecond pulse shaping using the geometric phase.

    Science.gov (United States)

    Gökce, Bilal; Li, Yanming; Escuti, Michael J; Gundogdu, Kenan

    2014-03-15

    We demonstrate a femtosecond pulse shaper that utilizes polarization gratings to manipulate the geometric phase of an optical pulse. This unique approach enables circular polarization-dependent shaping of femtosecond pulses. As a result, it is possible to create coherent pulse pairs with orthogonal polarizations in a 4f pulse shaper setup, something until now that, to our knowledge, was only achieved via much more complex configurations. This approach could be used to greatly simplify and enhance the functionality of multidimensional spectroscopy and coherent control experiments, in which multiple coherent pulses are used to manipulate quantum states in materials of interest.

  15. Pulse image recognition using fuzzy neural network.

    Science.gov (United States)

    Xu, L S; Meng, Max Q -H; Wang, K Q

    2007-01-01

    The automatic recognition of pulse images is the key in the research of computerized pulse diagnosis. In order to automatically differentiate the pulse patterns by using small samples, a fuzzy neural network to classify pulse images based on the knowledge of experts in traditional Chinese pulse diagnosis was designed. The designed classifier can make hard decision and soft decision for identifying 18 patterns of pulse images at the accuracy of 91%, which is better than the results that achieved by back-propagation neural network.

  16. Return stroke current reflections in rocket-triggered lightning

    Science.gov (United States)

    Caicedo, J. A.; Biagi, C.; Uman, M. A.; Jordan, D. M.; Hare, B.

    2016-03-01

    Ten upward propagating return stroke currents in eight triggered lightning flashes have been observed to reflect downward from 140 to 300 m altitude by way of measurements of the channel base current, close electric field and electric field derivative, and high-speed video. The current reflections appear as dips in the measured channel base current and in the electric fields and as bipolar pulses in the electric field derivative waveforms. The current dips occur 2.7 to 13.9 μs after the initiation of the return stroke current at ground. The observed phenomenon results from a portion of the upward propagating return stroke current wave being reflected from a channel impedance discontinuity apparently associated with an isolated section of unexploded triggering wire, as inferred from high-speed video records. A transmission line model is used to model the close electric field and electric field derivative of the postulated initial and reflected current waves, starting with the measured channel base current, and the results are compared favorably with measurements made at 92 to 326 m. From the measured time between the return stroke current initiation at the ground and the time the current reflection reaches the channel base and produces the current dip, along with the reflection height inferred from the video records, we find the average of the upward and downward reflected return stroke current speed for each of the 10 strokes to be between 0.81 and 2.06 × 108 m s-1.

  17. Wave equations for pulse propagation

    Science.gov (United States)

    Shore, B. W.

    1987-06-01

    Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity.

  18. Anaesthetic Monitoring - the Pulse Oximeter

    African Journals Online (AJOL)

    the pulse oximeter: 1. It is a teaching tool showing the physiology of oxygen delivery. 2. It is especially useful to evaluate the efficacy of oxygen therapy during recovery from an- aesthesia and surgery and on the ward. 3. It shows when tracheal intubation is too slow. It shows when the tube is in the wrong place or blocked or ...

  19. Nonparametric estimation of ultrasound pulses

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Leeman, Sidney

    1994-01-01

    An algorithm for nonparametric estimation of 1D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori...

  20. Atomic collisions involving pulsed positrons

    DEFF Research Database (Denmark)

    Merrison, J. P.; Bluhme, H.; Field, D.

    2000-01-01

    instantaneous intensities be achieved with in-beam accumulation, but more importantly many orders of magnitude improvement in energy and spatial resolution can be achieved using positron cooling. Atomic collisions can be studied on a new energy scale with unprecedented precion and control. The use...... of accelerators for producing intense positron pulses will be discussed in the context of atomic physics experiments....

  1. Pulses and waves of contractility.

    Science.gov (United States)

    Wu, Min

    2017-12-04

    The nature of signal transduction networks in the regulation of cell contractility is not entirely clear. In this study, Graessl et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201706052) visualized and characterized pulses and waves of Rho activation in adherent cells and proposed excitable Rho signaling networks underlying cell contractility. © 2017 Wu.

  2. Teachers’ way of reflecting

    DEFF Research Database (Denmark)

    Lund, Lea

    2016-01-01

    of the Danish study was to investigate and understand teachers’ classroom experiences using Fenstermacher’s approach to develop a practical argument, as these classroom experiences are regarded as a potential source of learning for teachers. A three-level scale model from the study describes the teach-ers......’ reflections on practice. Based on this model, the paper provides a proposal regarding how to work with teachers’ professional development and learning processes. Educational implications and future research directions are discussed.......This paper contributes to insights on teachers’ thinking and practice by building partly on the large amount of prior research in the field of continuing professional development (in line with ISATT), and partly on examples from an empirical small-scale study executed in Denmark. The purpose...

  3. Reflections on conformal spectra

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyungrok; Kravchuk, Petr [Walter Burke Institute for Theoretical Physics, Caltech,Pasadena, California 91125 (United States); School of Natural Sciences, Institute for Advanced Study,Princeton, New Jersey 08540 (United States); Ooguri, Hirosi [Walter Burke Institute for Theoretical Physics, Caltech,Pasadena, California 91125 (United States); School of Natural Sciences, Institute for Advanced Study,Princeton, New Jersey 08540 (United States); Kavli Institute for the Physics and Mathematics of the Universe (WPI),University of Tokyo,Kashiwa 277-8583 (Japan)

    2016-04-29

    We use modular invariance and crossing symmetry of conformal field theory to reveal approximate reflection symmetries in the spectral decompositions of the partition function in two dimensions in the limit of large central charge and of the four-point function in any dimension in the limit of large scaling dimensions Δ{sub 0} of external operators. We use these symmetries to motivate universal upper bounds on the spectrum and the operator product expansion coefficients, which we then derive by independent techniques. Some of the bounds for four-point functions are valid for finite Δ{sub 0} as well as for large Δ{sub 0}. We discuss a similar symmetry in a large spacetime dimension limit. Finally, we comment on the analogue of the Cardy formula and sparse light spectrum condition for the four-point function.

  4. Reflecting Contemporary Design Research

    DEFF Research Database (Denmark)

    Engholm, Ida

    2017-01-01

    In recent years, design research has been the object of growing attention in universities and academies throughout the world. The present paper addresses the heterogeneous character of design research and the current need for reflection on the various approaches and interests. For this purpose......, the paper follows two steps. First, it proposes a categorization of the field in the form of a position model. The paper’s underlying assumption is that design research as a discipline exists in many different forms that cannot necessarily be brought together under one common academic research tradition......; instead it is necessary to attempt to define the field in order to initiate discussions about what constitutes the various research bases for design. Second, the paper discusses the implication for future design research when it is an interdisciplinary field that involves many disciplines, mindsets...

  5. Reflections on Conformal Spectra

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    We use modular invariance and crossing symmetry of conformal field theory to reveal approximate reflection symmetries in the spectral decompositions of the partition function in two dimensions in the limit of large central charge and of the four-point function in any dimension in the limit of large scaling dimensions Δ0 of external operators. We use these symmetries to motivate universal upper bounds on the spectrum and the operator product expansion coefficients, which we then derive by independent techniques. Some of the bounds for four-point functions are valid for finite Δ0 as well as for large Δ0. We discuss a similar symmetry in a large spacetime dimension limit. Finally, we comment on the analogue of the Cardy formula and sparse light spectrum condition for the four-point function. (based on 1510.08772 with Kim & Ooguri). This seminar will be given via videolink

  6. Reflections on academic video

    Directory of Open Access Journals (Sweden)

    Thommy Eriksson

    2012-11-01

    Full Text Available As academics we study, research and teach audiovisual media, yet rarely disseminate and mediate through it. Today, developments in production technologies have enabled academic researchers to create videos and mediate audiovisually. In academia it is taken for granted that everyone can write a text. Is it now time to assume that everyone can make a video essay? Using the online journal of academic videos Audiovisual Thinking and the videos published in it as a case study, this article seeks to reflect on the emergence and legacy of academic audiovisual dissemination. Anchoring academic video and audiovisual dissemination of knowledge in two critical traditions, documentary theory and semiotics, we will argue that academic video is in fact already present in a variety of academic disciplines, and that academic audiovisual essays are bringing trends and developments that have long been part of academic discourse to their logical conclusion.

  7. Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

    Science.gov (United States)

    Hugenschmidt, Manfred

    1986-10-01

    The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

  8. Arterial stiffness and wave reflections in marathon runners.

    Science.gov (United States)

    Vlachopoulos, Charalambos; Kardara, Despina; Anastasakis, Aris; Baou, Katerina; Terentes-Printzios, Dimitrios; Tousoulis, Dimitris; Stefanadis, Christodoulos

    2010-09-01

    Regular aerobic exercise has beneficial effects on the cardiovascular system. Marathon running is an aerobic and extremely vigorous exercise. Arterial stiffness and wave reflections are independent predictors of cardiovascular risk. We investigated the acute effect of marathon race on aortic stiffness and wave reflections, as well as possible chronic alterations of these indexes in marathon runners. We studied 49 marathon runners (age 38 +/- 9 years) and 46 recreationally active control subjects (age 37 +/- 5 years). To investigate the acute effect of marathon race, a subgroup of 20 runners was evaluated after the race as well. Aortic stiffness was evaluated with carotid-femoral pulse wave velocity (PWV) and wave reflections with augmentation index (AIx). Marathon runners had significantly higher systolic, diastolic, pulse (both aortic and brachial), and mean pressures compared to controls (P Marathon runners had significantly higher PWV (6.89 m/s vs. 6.33 m/s, P Marathon race caused a significant fall in both AIx (12.2% vs. -5.8%, P marathon race, whereas aortic stiffness was not altered. Moreover, marathon runners have increased aortic stiffness and pressures, whereas wave reflections indexes do not differ compared to controls.

  9. Quantitative Hyperspectral Reflectance Imaging

    Directory of Open Access Journals (Sweden)

    Ted A.G. Steemers

    2008-09-01

    Full Text Available Hyperspectral imaging is a non-destructive optical analysis technique that can for instance be used to obtain information from cultural heritage objects unavailable with conventional colour or multi-spectral photography. This technique can be used to distinguish and recognize materials, to enhance the visibility of faint or obscured features, to detect signs of degradation and study the effect of environmental conditions on the object. We describe the basic concept, working principles, construction and performance of a laboratory instrument specifically developed for the analysis of historical documents. The instrument measures calibrated spectral reflectance images at 70 wavelengths ranging from 365 to 1100 nm (near-ultraviolet, visible and near-infrared. By using a wavelength tunable narrow-bandwidth light-source, the light energy used to illuminate the measured object is minimal, so that any light-induced degradation can be excluded. Basic analysis of the hyperspectral data includes a qualitative comparison of the spectral images and the extraction of quantitative data such as mean spectral reflectance curves and statistical information from user-defined regions-of-interest. More sophisticated mathematical feature extraction and classification techniques can be used to map areas on the document, where different types of ink had been applied or where one ink shows various degrees of degradation. The developed quantitative hyperspectral imager is currently in use by the Nationaal Archief (National Archives of The Netherlands to study degradation effects of artificial samples and original documents, exposed in their permanent exhibition area or stored in their deposit rooms.

  10. Cryosurgery with Pulsed Electric Fields

    Science.gov (United States)

    Daniels, Charlotte S.; Rubinsky, Boris

    2011-01-01

    This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to

  11. Cryosurgery with pulsed electric fields.

    Directory of Open Access Journals (Sweden)

    Charlotte S Daniels

    Full Text Available This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused

  12. Wave equations for pulse propagation

    Energy Technology Data Exchange (ETDEWEB)

    Shore, B.W.

    1987-06-24

    Theoretical discussions of the propagation of pulses of laser radiation through atomic or molecular vapor rely on a number of traditional approximations for idealizing the radiation and the molecules, and for quantifying their mutual interaction by various equations of propagation (for the radiation) and excitation (for the molecules). In treating short-pulse phenomena it is essential to consider coherent excitation phenomena of the sort that is manifest in Rabi oscillations of atomic or molecular populations. Such processes are not adequately treated by rate equations for excitation nor by rate equations for radiation. As part of a more comprehensive treatment of the coupled equations that describe propagation of short pulses, this memo presents background discussion of the equations that describe the field. This memo discusses the origin, in Maxwell's equations, of the wave equation used in the description of pulse propagation. It notes the separation into lamellar and solenoidal (or longitudinal and transverse) and positive and negative frequency parts. It mentions the possibility of separating the polarization field into linear and nonlinear parts, in order to define a susceptibility or index of refraction and, from these, a phase and group velocity. The memo discusses various ways of characterizing the polarization characteristics of plane waves, that is, of parameterizing a transverse unit vector, such as the Jones vector, the Stokes vector, and the Poincare sphere. It discusses the connection between macroscopically defined quantities, such as the intensity or, more generally, the Stokes parameters, and microscopic field amplitudes. The material presented here is a portion of a more extensive treatment of propagation to be presented separately. The equations presented here have been described in various books and articles. They are collected here as a summary and review of theory needed when treating pulse propagation.

  13. PLD fabrication of a soft X-ray multilayer mirror and LPP reflectance test

    Science.gov (United States)

    Weaver, I.; Lewis, C. L. S.; MacPhee, A. G.; Warwick, P. J.; Jordan, R.; Lunney, J. G.

    1998-05-01

    A soft X-ray mirror based on a molybdenum-silicon (Mo/Si) multilayer structure has been fabricated by the pulsed laser deposition (PLD) technique. The multilayer was designed to reflect at 196 Å for normal incidence operation. An iterative graphical procedure was used to calculate the optimum periodic multilayer structure. The normal incidence reflectance of the multilayer was determined using a continuum source of soft X-rays from a laser-produced plasma (LPP). The multilayer peak reflectance was 7.3% at 190 Å, with the magnitude of reflectance consistent with an effective interfacial roughness within the structure equal to ˜15 Å.

  14. Silver-halide sensitized gelatin (SHSG) processing method for pulse holograms recorded on VRP plates

    Science.gov (United States)

    Evstigneeva, Maria K.; Drozdova, Olga V.; Mikhailov, Viktor N.

    2002-06-01

    One of the most important area of holograph applications is display holography. In case of pulse recording the requirement for vibration stability is easier than compared to CW exposure. At the same time it is widely known that the behavior of sliver-halide holographic materials strongly depends on the exposure duration. In particular the exposure sensitivity drastically decreases under nanosecond pulse duration. One of the effective ways of the diffraction efficiency improvement is SHSG processing method. This processing scheme is based on high modulation of refractive index due to microvoids appearance inside emulsion layer. It should be mentioned that the SHSG method was used earlier only in the cases when the holograms were recorded by use of CW lasers. This work is devoted to the investigation of SHSG method for pulse hologram recording on VRP plates. We used a pulsed YLF:Nd laser with pulse duration of 25 nanoseconds and wavelength of 527 nm. Both transmission and reflection holograms were recorded. The different kinds of bleaching as well as developing solutions were investigated. Our final processing scheme includes the following stages: 1) development in non-tanning solution, 2) rehalogenating bleach, 3) intermediate alcohol drying, 4) uniform second exposure, 5) second development in diluted developer, 6) reverse bleaching, 7) fixing and 8) gradient drying in isopropyl alcohol. Diffraction efficiency of transmission holograms was of about 60 percent and reflection mirror holograms was of about 45 percent. Thus we have demonstrated the SHSG processing scheme for producing effective holograms on VRP plates under pulse exposure.

  15. Multiple-pulse irradiation of dental hard tissues at CO2 laser wavelengths

    Science.gov (United States)

    Fried, Daniel; Glena, Richard E.; Featherstone, John D. B.; Seka, Wolf D.

    1995-05-01

    Surface temperatures were monitored using pulsed photothermal radiometry (PPTR) during multiple pulse carbon dioxide laser irradiation ((lambda) equals 9.3, 9.6, 10.3 and 10.6 micrometers ). Permanent changes in the optical properties (reflectance and absorption) were observed at fluences greater than 2 J/cm2 for dentin and 5 J/cm2 for enamel. The laser irradiation changes the thermal and the optical properties of these tissues, substantially changing the energy deposition for subsequent laser pulses. The temperature response of enamel and dentin and the reflectance of dentin changed considerably with successive laser pulses. After 10 to 50 pulses the surface stabilized and no further changes were noted. Scanning electron micrographs of the laser conditioned surfaces showed large crystals of modified hydroxyapatite (approximately equals 500 nm) devoid of the organic matrix. Presumably, the water and the interwoven biopolymer matrix had been carbonized nd vaporized. Caries inhibition measurements after multiple pulse irradiation of enamel indicate that the stable laser conditioned surface is more resistant to acid dissolution than untreated enamel.

  16. Characteristics of retinal reflectance changes induced by transcorneal electrical stimulation in cat eyes.

    Directory of Open Access Journals (Sweden)

    Takeshi Morimoto

    Full Text Available Transcorneal electrical stimulation (TES activates retinal neurons leading to visual sensations. How the retinal cells are activated by TES has not been definitively determined. Investigating the reflectance changes of the retina is an established technique and has been used to determine the mechanism of retinal activation. The purpose of this study was to evaluate the reflectance changes elicited by TES in cat eyes. Eight eyes of Eight cats were studied under general anesthesia. Biphasic electrical pulses were delivered transcornealy. The fundus images observed with near-infrared light (800-880 nm were recorded every 25 ms for 26 s. To improve the signal-to-noise ratio, the images of 10 consecutive recordings were averaged. Two-dimensional topographic maps of the reflective changes were constructed by subtracting images before from those after the TES. The effects of different stimulus parameters, e.g., current intensity, pulse duration, frequency, and stimulus duration, on the reflective changes were studied. Our results showed that after TES, the reflective changes appeared on the retinal vessels and optic disc. The intensity of reflectance changes increased as the current intensity, pulse duration, and stimulation duration increased (P<0.05 for all. The maximum intensity of the reflective change was obtained when the stimulus frequency was 20 Hz. The time course of the reflectance changes was also altered by the stimulation parameters. The response started earlier and returned to the baseline later with higher current intensities, longer pulse durations, but the time of the peak of the response was not changed. These results showed that the reflective changes were due to the activation of retinal neurons by TES and might involve the vascular changes induced by an activation of the retinal neurons.

  17. Linear transformer driver for pulse generation

    Science.gov (United States)

    Kim, Alexander A; Mazarakis, Michael G; Sinebryukhov, Vadim A; Volkov, Sergey N; Kondratiev, Sergey S; Alexeenko, Vitaly M; Bayol, Frederic; Demol, Gauthier; Stygar, William A

    2015-04-07

    A linear transformer driver includes at least one ferrite ring positioned to accept a load. The linear transformer driver also includes a first power delivery module that includes a first charge storage devices and a first switch. The first power delivery module sends a first energy in the form of a first pulse to the load. The linear transformer driver also includes a second power delivery module including a second charge storage device and a second switch. The second power delivery module sends a second energy in the form of a second pulse to the load. The second pulse has a frequency that is approximately three times the frequency of the first pulse. The at least one ferrite ring is positioned to force the first pulse and the second pulse to the load by temporarily isolating the first pulse and the second pulse from an electrical ground.

  18. Coherent combining pulse bursts in time domain

    Energy Technology Data Exchange (ETDEWEB)

    Galvanauskas, Almantas

    2018-01-09

    A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies using a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.

  19. Treatment Pulse Application for Magnetic Stimulation

    Directory of Open Access Journals (Sweden)

    Sun-Seob Choi

    2011-01-01

    Full Text Available Treatment and diagnosis can be made in difficult areas simply by changing the output pulse form of the magnetic stimulation device. However, there is a limitation in the range of treatments and diagnoses of a conventional sinusoidal stimulation treatment pulse because the intensity, width, and form of the pulse must be changed according to the lesion type. This paper reports a multidischarge method, where the stimulation coils were driven in sequence via multiple switching control. The limitation of the existing simple sinusoidal pulse form could be overcome by changing the intensity, width, and form of the pulse. In this study, a new sequential discharge method was proposed to freely alter the pulse width. The output characteristics of the stimulation treatment pulse were examined according to the trigger signal delay applied to the switch at each stage by applying a range of superposition pulses to the magnetic simulation device, which is widely used in industry and medicine.

  20. Peak holding circuit for extremely narrow pulses

    Science.gov (United States)

    Oneill, R. W. (Inventor)

    1975-01-01

    An improved pulse stretching circuit comprising: a high speed wide-band amplifier connected in a fast charge integrator configuration; a holding circuit including a capacitor connected in parallel with a discharging network which employs a resistor and an FET; and an output buffer amplifier. Input pulses of very short duration are applied to the integrator charging the capacitor to a value proportional to the input pulse amplitude. After a predetermined period of time, conventional circuitry generates a dump pulse which is applied to the gate of the FET making a low resistance path to ground which discharges the capacitor. When the dump pulse terminates, the circuit is ready to accept another pulse to be stretched. The very short input pulses are thus stretched in width so that they may be analyzed by conventional pulse height analyzers.

  1. Pulsed lasers in speckle photography: error owing to pulse width.

    Science.gov (United States)

    Joenathan, C; Blair, S M; Ganesan, A R

    1993-01-10

    The effect of the pulse width of a pulsed laser in the studies of speckle velocimetry and transient vibration analysis is discussed. Because of the motion of the object during an exposure, a sine function is obtained by using the pointwise filtering method. This function modulates the halo along with the Young's fringes. It is shown that for high object velocities the sinc function modifies the halo distribution; as a result, the error in calculating the fringe position increases. An aperture geometry for which the autocorrelation halo is made constant in certain regions is proposed in which the intensity variation in this region is the result of the modulating sinc function only. A closed-form solution for the shift in the position of the fringes in this region is obtained. Experimental results of the simulation are presented.

  2. Sensors and Methods for Electromagnetic Pulse Identification

    OpenAIRE

    Pavel FIALA; Drexler, Petr

    2006-01-01

    There are some suitable methods for the measurement of ultra-short solitary electromagnetic pulses that can be generated by high power pulsed generators. The measurement methods properties have to correspond to the fact whether we want to measure pulses of voltage, current or free-space electromagnetic wave. The need for specific measurement methods occurred by the development of high power microwave pulse generator. Applicable methods are presented in this paper. The method utilizing Faraday...

  3. First Optical Observations of Interhemispheric Electron Reflections Within Pulsating Aurora

    Science.gov (United States)

    Samara, M.; Michell, R. G.; Khazanov, G. V.

    2017-01-01

    A case study of a pulsating auroral event imaged optically at high time resolution presents direct observational evidence in agreement with the interhemispheric electron bouncing predicted by the Super Thermal Electron Transport model. Pulsation-on times are identified and subsequent equally spaced fainter pulsations are also noted and can be explained by a portion/percentage of the primary precipitating electrons reflecting upward from the ionosphere, traveling to the opposite hemisphere and reflecting upward again. The high time resolution of these data, combined with the short duration of the pulsation-on time (approx. 1 s) and the relatively long spacing between pulsations (approx. 6 to 9 s) made it possible to observe the faint optical pulses caused by the reflected electrons coming from the opposite hemisphere.

  4. Finite pulse effects in CPMG pulse trains on paramagnetic materials.

    Science.gov (United States)

    Leskes, Michal; Grey, Clare P

    2015-09-14

    The Carr-Purcell-Meiboom-Gill (CPMG) sequence is commonly used in high resolution NMR spectroscopy and in magnetic resonance imaging for the measurement of transverse relaxation in systems that are subject to diffusion in internal or external gradients and is superior to the Hahn echo measurement, which is more sensitive to diffusion effects. Similarly, it can potentially be used to study dynamic processes in electrode materials for lithium ion batteries. Here we compare the (7)Li signal decay curves obtained with the CPMG and Hahn echo sequences under static conditions (i.e., in the absence of magic angle spinning) in paramagnetic materials with varying transition metal ion concentrations. Our results indicate that under CPMG pulse trains the lifetime of the (7)Li signal is substantially extended and is correlated with the strength of the electron-nuclear interaction. Numerical simulations and analytical calculations using Floquet theory suggest that the combination of large interactions and a train of finite pulses, results in a spin locking effect which significantly slows the signal's decay. While these effects complicate the interpretation of CPMG-based investigations of diffusion and chemical exchange in paramagnetic materials, they may provide a useful approach to extend the signal's lifetime in these often fast relaxing systems, enabling the use of correlation experiments. Furthermore, these results highlight the importance of developing a deeper understanding of the effects of the large paramagnetic interactions during multiple pulse experiments in order to extend the experimental arsenal available for static and in situ NMR investigations of paramagnetic materials.

  5. Bidirectional reflectance of zinc oxide

    Science.gov (United States)

    Scott, R.

    1973-01-01

    This investigation was undertaken to determine original and useful information about the bidirection reflectance of zinc oxide. The bidirectional reflectance will be studied for the spectra between .25-2.5 microns and the hemisphere above the specimen. The following factors will be considered: (1) surface conditions; (2) specimen preparation; (3) specimen substrate, (4) polarization; (5) depolarization; (6) wavelength; and (7) angles of incident and reflection. The bidirectional reflectance will be checked by experimentally determined angular hemispherical measurements or hemispherical measurements will be used to obtain absolute bidirectional reflectance.

  6. Intense γ ray generated by refocusing laser pulse on wakefield accelerated electrons

    Science.gov (United States)

    Feng, Jie; Wang, Jinguang; Li, Yifei; Zhu, Changqing; Li, Minghua; He, Yuhang; Li, Dazhang; Wang, Weimin; Chen, Liming

    2017-09-01

    Ultrafast x/γ ray emission from the combination of laser wake-field acceleration and plasma mirror has been investigated as a promising Thomson scattering source. However, the photon energy and yield of radiation are limited to the intensity of reflected laser pulses. We use the 2D particle in cell simulation to demonstrate that a 75TW driven laser pulse can be refocused on the accelerated electron bunches through a hemispherical plasma mirror with a small f number of 0.25. The energetic electrons with the maximum energy about 350 MeV collide with the reflected laser pulse of a0 = 3.82 at the focal spot, producing high order multi-photon Thomson scattering, and resulting in the scattering spectrum which extends up to 21.2 MeV. Such a high energy γ ray source could be applied to photonuclear reaction and materials science.

  7. A Clinical Study of the Pulse Wave Characteristics at the Three Pulse Diagnosis Positions of Chon, Gwan and Cheok

    Directory of Open Access Journals (Sweden)

    Young J. Jeon

    2011-01-01

    Full Text Available In this work, we analyze the baseline, signal strength, aortic augmentation index (AIx, radial AIx, time to reflection and P_T2 at Chon, Gwan, and Cheok, which are the three pulse diagnosis positions in Oriental medicine. For the pulse measurement, we used the SphygmoCor apparatus, which has been widely used for the evaluation of the arterial stiffness at the aorta. By two-way repeated measures analysis of variance, we tested two independent measurements for repeatability and investigated their mean differences among Chon, Gwan and Cheok. To characterize further the parameters that were shown to be different between each palpation position, we carried out Duncan's test for the multiple comparisons. The baseline and signal strength were statistically different (<.05 among Chon, Gwan and Cheok, respectively, which supports the major hypothesis of Oriental medicine that all of the three palpation positions contain different clinical information. On the other hand, aortic AIx and time to reflection were found to be statistically different between Chon and the others, and radial AIx and P_T2 did not show any difference between pulse positions. In the clinical sense, however, the aortic AIx at each palpation position was found to fall within the 90% confidence interval of normal arterial compliance. The results of the multiple comparisons indicate that the parameters of arterial stiffness were independent of the palpation positions. This work is the first attempt to characterize quantitatively the pulse signals at Chon, Gwan and Cheok with some relevant parameters extracted from the SphygmoCor apparatus.

  8. <3> OMEGA pulse-forming network

    CERN Multimedia

    1974-01-01

    Adjustement of the 3 W pulse-forming network of the SPS beam dumping system. When charged at 60 kV, this PFN gives 10 kA, 25 ms current pulses, with oscillations, superimposed on the pulse flat top, of an amplitude of +/- 1 Ka.

  9. A Study of New Pulse Auscultation System

    Directory of Open Access Journals (Sweden)

    Ying-Yun Chen

    2015-04-01

    Full Text Available This study presents a new type of pulse auscultation system, which uses a condenser microphone to measure pulse sound waves on the wrist, captures the microphone signal for filtering, amplifies the useful signal and outputs it to an oscilloscope in analog form for waveform display and storage and delivers it to a computer to perform a Fast Fourier Transform (FFT and convert the pulse sound waveform into a heartbeat frequency. Furthermore, it also uses an audio signal amplifier to deliver the pulse sound by speaker. The study observed the principles of Traditional Chinese Medicine’s pulsing techniques, where pulse signals at places called “cun”, “guan” and “chi” of the left hand were measured during lifting (100 g, searching (125 g and pressing (150 g actions. Because the system collects the vibration sound caused by the pulse, the sensor itself is not affected by the applied pressure, unlike current pulse piezoelectric sensing instruments, therefore, under any kind of pulsing pressure, it displays pulse changes and waveforms with the same accuracy. We provide an acquired pulse and waveform signal suitable for Chinese Medicine practitioners’ objective pulse diagnosis, thus providing a scientific basis for this Traditional Chinese Medicine practice. This study also presents a novel circuit design using an active filtering method. An operational amplifier with its differential features eliminates the interference from external signals, including the instant high-frequency noise. In addition, the system has the advantages of simple circuitry, cheap cost and high precision.

  10. Experiments on sediment pulses in mountain rivers

    Science.gov (United States)

    Y. Cui; T. E. Lisle; J. E. Pizzuto; G. Parker

    1998-01-01

    Pulses of sediment can be introduced into mountain rivers from such mechanisms as debris flows, landslides and fans at tributary confluences. These processes can be natural or associated with the activities of humans, as in the case of a pulse created by sediment derived from timber harvest or the removal of a dam. How does the river digest these pulses?

  11. Third Harmonic Imaging using a Pulse Inversion

    DEFF Research Database (Denmark)

    Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt

    2011-01-01

    The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd...

  12. High speed, high current pulsed driver circuit

    Science.gov (United States)

    Carlen, Christopher R.

    2017-03-21

    Various technologies presented herein relate to driving a LED such that the LED emits short duration pulses of light. This is accomplished by driving the LED with short duration, high amplitude current pulses. When the LED is driven by short duration, high amplitude current pulses, the LED emits light at a greater amplitude compared to when the LED is driven by continuous wave current.

  13. Double pulse Thomson scattering system at RTP

    NARCIS (Netherlands)

    Beurskens, M. N. A.; Barth, C. J.; Chu, C.C.; Donne, A. J. H.; Herranz, J. A.; Cardozo, N. J. L.; van der Meiden, H. J.; Pijper, F.J.

    1997-01-01

    In this article a double pulse multiposition Thomson scattering diagnostic, under construction at RTP, is discussed. Light from a double pulsed ruby laser (pulse separation: 10-800 mu s, max. 2x12.5 J) is scattered by the free electrons of the tokamak plasma and relayed to a Littrow polychromator

  14. Holographic reflector for reflective LCDs

    Science.gov (United States)

    Sato, Atsushi; Murillo-Mora, Luis M.; Iwata, Fujio

    1997-05-01

    We describe a new holographic optical element to improve the image's quality of a reflective liquid crystal displays (LCDs). This new holographic reflector consists basically of 2 layers: a volume type transmission hologram layer and a metallic reflection layer. Compared with conventional reflectors for reflective LCDs, a high optical efficiency can be obtained because the hologram is able to concentrate the reflected light to the observer's eyes. Also, it avoids the problems of glare in the LCDs by deviating the reflected incident light (used for display) away from the direction of the direct reflection light. The transmission hologram's low wavelength selectivity permits us to obtain a near white color reflector for reflective LCDs which for multiple applications is the preferable color for the background.

  15. Numerical and experimental study of an annular pulse tube used in the pulse tube cooler

    Science.gov (United States)

    Pang, Xiaomin; Chen, Yanyan; Wang, Xiaotao; Dai, Wei; Luo, Ercang

    2017-12-01

    Multi-stage pulse tube coolers normally use a U-type configuration. For compactness, it is attractive to build a completely co-axial multi-stage pulse tube cooler. In this way, an annular shape pulse tube is inevitable. Although there are a few reports about previous annular pulse tubes, a detailed study and comparison with a circular pulse tube is lacking. In this paper, a numeric model based on CFD software is carried out to compare the annular pulse tube and circular pulse tube used in a single stage in-line type pulse tube cooler with about 10 W of cooling power at 77 K. The length and cross sectional area of the two pulse tubes are kept the same. Simulation results show that the enthalpy flow in the annular pulse tube is lower by 1.6 W (about 11% of the enthalpy flow) compared to that in circular pulse tube. Flow and temperature distribution characteristics are also analyzed in detail. Experiments are then conducted for comparison with an in-line type pulse tube cooler. With the same acoustic power input, the pulse tube cooler with a circular pulse tube obtains 7.88 W of cooling power at 77 K, while using an annular pulse tube leads to a cooling power of 7.01 W, a decrease of 0.9 W (11.4%) on the cooling performance. The study sets the basis for building a completely co-axial two-stage pulse tube cooler.

  16. Patterns of digital volume pulse waveform and pulse transit time in ...

    African Journals Online (AJOL)

    Introduction: Arterial wall changes underlie many disorders of aging and the complications of diseases like hypertension and diabetes mellitus. Analyzing the pulse wave is an easy, noninvasive method used to assess vessel wall stiffness and pulse changes. In this study the digital volume pulse wave and the pulse transit ...

  17. The Reflective Methodologists

    DEFF Research Database (Denmark)

    Kjær, Bjørg

    2013-01-01

    In recent years, a focus on inclusion and vulnerable children has reignited discussions about the quality of pedagogical work. It has also initiated processes of change that have challenged the Danish kindergarten tradition and the identity of the pedagogue in a number of different ways. In this ......In recent years, a focus on inclusion and vulnerable children has reignited discussions about the quality of pedagogical work. It has also initiated processes of change that have challenged the Danish kindergarten tradition and the identity of the pedagogue in a number of different ways...... in which the practical sense and tacit knowledge are related to questions of power and social actors’ strategies for positioning themselves within a social space. This demands a particular focus on the historical effect of the concept of ‘the reflective practitioner’ as a symbolic marker of identity...... in the cultural logic of the pedagogical field. I also address the way in which this logic considers practice to be the exponent of all that is good, meaningful and correct. My use of Schön’s concept also serves to illuminate that it has been a theoretical source of inspiration, which has undergone so many...

  18. FPGA-based design and implementation of arterial pulse wave generator using piecewise Gaussian-cosine fitting.

    Science.gov (United States)

    Wang, Lu; Xu, Lisheng; Zhao, Dazhe; Yao, Yang; Song, Dan

    2015-04-01

    Because arterial pulse waves contain vital information related to the condition of the cardiovascular system, considerable attention has been devoted to the study of pulse waves in recent years. Accurate acquisition is essential to investigate arterial pulse waves. However, at the stage of developing equipment for acquiring and analyzing arterial pulse waves, specific pulse signals may be unavailable for debugging and evaluating the system under development. To produce test signals that reflect specific physiological conditions, in this paper, an arterial pulse wave generator has been designed and implemented using a field programmable gate array (FPGA), which can produce the desired pulse waves according to the feature points set by users. To reconstruct a periodic pulse wave from the given feature points, a method known as piecewise Gaussian-cosine fitting is also proposed in this paper. Using a test database that contains four types of typical pulse waves with each type containing 25 pulse wave signals, the maximum residual error of each sampling point of the fitted pulse wave in comparison with the real pulse wave is within 8%. In addition, the function for adding baseline drift and three types of noises is integrated into the developed system because the baseline occasionally wanders, and noise needs to be added for testing the performance of the designed circuits and the analysis algorithms. The proposed arterial pulse wave generator can be considered as a special signal generator with a simple structure, low cost and compact size, which can also provide flexible solutions for many other related research purposes. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. CW seeded optical parametric amplifier providing wavelength and pulse duration tunable nearly transform limited pulses.

    Science.gov (United States)

    Hädrich, S; Gottschall, T; Rothhardt, J; Limpert, J; Tünnermann, A

    2010-02-01

    An optical parametric amplifier that delivers nearly transform limited pulses is presented. The center wavelength of these pulses can be tuned between 993 nm and 1070 nm and, at the same time, the pulse duration is varied between 206 fs and 650 fs. At the shortest pulse duration the pulse energy was increased up to 7.2 microJ at 50 kHz repetition rate. Variation of the wavelength is achieved by applying a tunable cw seed while the pulse duration can be varied via altering the pump pulse duration. This scheme offers superior flexibility and scaling possibilities.

  20. Extreme Ultraviolet Stokesmeter for Pulsed Magneto-Optics

    Directory of Open Access Journals (Sweden)

    Mabel Ruiz-Lopez

    2015-02-01

    Full Text Available Several applications in material science and magnetic holography using extreme ultraviolet (EUV radiation require the measurement of the degree and state of polarization. In this work, an instrument to measure simultaneously both parameters from EUV pulses is presented. The instrument determines the Stokes parameters after a reflection on an array of multilayer mirrors at the Brewster angle. The Stokesmeter was tested at Swiss Light Source at different EUV wavelengths. The experimental Stokes patterns of the source were compared with the simulated pattern.

  1. Unsplit bipolar pulse forming line

    Science.gov (United States)

    Rhodes, Mark A [Pleasanton, CA

    2011-05-24

    A bipolar pulse forming transmission line module and system for linear induction accelerators having first, second, third, and fourth planar conductors which form a sequentially arranged interleaved stack having opposing first and second ends, with dielectric layers between the conductors. The first and second planar conductors are connected to each other at the first end, and the first and fourth planar conductors are connected to each other at the second end via a shorting plate. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short at the first end a high voltage from the third planar conductor to the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  2. Sub-10 fs deep-ultraviolet pulses generated by chirped-pulse four-wave mixing.

    Science.gov (United States)

    Kida, Yuichiro; Liu, Jun; Teramoto, Takahiro; Kobayashi, Takayoshi

    2010-06-01

    We propose and demonstrate experimentally a novel way of generating sub-10fs deep-UV pulses. The technique is based on chirped-pulse four-wave mixing induced by a broadband near-IR (NIR) pulse and a near-UV pulse. The broadband IR pulse is prepared by preliminarily broadening the spectral width of an NIR pulse by self-phase modulation. The positively chirped broadband IR pulse is suitable for generating a negatively chirped deep-UV pulse, which can be compressed by normal group-velocity dispersion in a transparent medium. Self-compression of the generated deep-UV pulse in air has been demonstrated to produce sub-10fs deep-UV pulses with excellent temporal and spectral profiles for ultrafast spectroscopy in the deep UV.

  3. Pulsed Scophony laser projection system

    Science.gov (United States)

    Lowry, J. B.; Welford, W. T.; Humphries, M. R.

    1988-10-01

    A novel laser TV projection display has been developed by PA Technology employing the Scophony system with acousto-optic modulators and pulsed lasers. This results in a projection system with greater optical simplicity, higher reliability and reduced power and cooling requirements over similar laser projectors. The technique has been successfully implemented in British Aerospace's Microdome missile training simulator. This paper describes the underlying principles of the design, its operational features and its implementation in the Microdome.

  4. Metal silicides with energetic pulses

    Science.gov (United States)

    D'Anna, E.; Leggieri, G.; Luches, A.; Majni, G.; Nava, F.; Ottaviani, G.

    1986-07-01

    Samples formed of a thin metal film deposited on silicon single crystal were annealed with electron and laser (ruby and excimer) pulses over a wide range of fluences. From a comparison of the experimental results with the temperature profiles of the irradiated samples, it turns out that suicide formation starts when the metal/silicon interface reaches the lowest eutectic temperature of the binary metal/silicon system. The growth rate of reacted layers is of the order of 1 m/s.

  5. Pulse amplitude modulated chlorophyll fluorometer

    Energy Technology Data Exchange (ETDEWEB)

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  6. High Voltage Nanosecond Pulse Generator.

    Science.gov (United States)

    1978-11-01

    pulse to a laser load was desiqned , built , and tested . —- -~~~-~~~~----j ‘~ ~~ _)— ~ --. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CoIx ~r 1 I

  7. Generation of synchronized signal and pump pulses for an optical ...

    Indian Academy of Sciences (India)

    2015-11-27

    pass geometry in a grating pair based pulse stretcher unit. The pump pulse has been further amplified in a high gain regenerative amplifier. This amplified pulse was used as the pump in an optical parametric chirped pulse ...

  8. Electromagnetic pulses bone healing booster

    Science.gov (United States)

    Sintea, S. R.; Pomazan, V. M.; Bica, D.; Grebenisan, D.; Bordea, N.

    2015-11-01

    Posttraumatic bone restoration triggered by the need to assist and stimulate compensatory bone growth in periodontal condition. Recent studies state that specific electromagnetic stimulation can boost the bone restoration, reaching up to 30% decrease in recovery time. Based on the existing data on the electromagnetic parameters, a digital electronic device is proposed for intra oral mounting and bone restoration stimulation in periodontal condition. The electrical signal is applied to an inductive mark that will create and impregnate magnetic field in diseased tissue. The device also monitors the status of the electromagnetic field. Controlled wave forms and pulse frequency signal at programmable intervals are obtained with optimized number of components and miniaturized using surface mounting devices (SMD) circuits and surface mounting technology (SMT), with enhanced protection against abnormal current growth, given the intra-oral environment. The system is powered by an autonomous power supply (battery), to limit the problems caused by powering medical equipment from the main power supply. Currently the device is used in clinical testing, in cycles of six up to twelve months. Basic principles for the electrical scheme and algorithms for pulse generation, pulse control, electromagnetic field control and automation of current monitoring are presented, together with the friendly user interface, suitable for medical data and patient monitoring.

  9. Materials for phantoms for terahertz pulsed imaging

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Gillian C [Academic Unit of Medical Physics, University of Leeds, Wellcome Wing, Leeds General Infirmary, Great George Street, Leeds, LS1 3EX (United Kingdom); Berry, Elizabeth [Academic Unit of Medical Physics, University of Leeds, Wellcome Wing, Leeds General Infirmary, Great George Street, Leeds, LS1 3EX (United Kingdom); Smye, Stephen W [Department of Medical Physics and Engineering, Leeds Teaching Hospitals NHS Trust, St James University Hospital, Leeds, LS9 7TF (United Kingdom); Brettle, David S [Department of Medical Physics and Engineering, Leeds Teaching Hospitals NHS Trust, St James University Hospital, Leeds, LS9 7TF (United Kingdom)

    2004-11-07

    Phantoms are commonly used in medical imaging for quality assurance, calibration, research and teaching. They may include test patterns or simulations of organs, but in either case a tissue substitute medium is an important component of the phantom. The aim of this work was to identify materials suitable for use as tissue substitutes for the relatively new medical imaging modality terahertz pulsed imaging. Samples of different concentrations of the candidate materials TX151 and napthol green dye were prepared, and measurements made of the frequency-dependent absorption coefficient (0.5 to 1.5 THz) and refractive index (0.5 to 1.0 THz). These results were compared qualitatively with measurements made in a similar way on samples of excised human tissue (skin, adipose tissue and striated muscle). Both materials would be suitable for phantoms where the dominant mechanism to be simulated is absorption ({approx}100 cm{sup -1} at 1 THz) and where simulation of the strength of reflections from boundaries is not important; for example, test patterns for spatial resolution measurements. Only TX151 had a frequency-dependent refractive index close to that of tissue, and could therefore be used to simulate the layered structure of skin, the complexity of microvasculature or to investigate frequency-dependent interference effects that have been noted in terahertz images. (note)

  10. Electromagnetic pulsed thermography for natural cracks inspection

    Science.gov (United States)

    Gao, Yunlai; Tian, Gui Yun; Wang, Ping; Wang, Haitao; Gao, Bin; Woo, Wai Lok; Li, Kongjing

    2017-02-01

    Emerging integrated sensing and monitoring of material degradation and cracks are increasingly required for characterizing the structural integrity and safety of infrastructure. However, most conventional nondestructive evaluation (NDE) methods are based on single modality sensing which is not adequate to evaluate structural integrity and natural cracks. This paper proposed electromagnetic pulsed thermography for fast and comprehensive defect characterization. It hybrids multiple physical phenomena i.e. magnetic flux leakage, induced eddy current and induction heating linking to physics as well as signal processing algorithms to provide abundant information of material properties and defects. New features are proposed using 1st derivation that reflects multiphysics spatial and temporal behaviors to enhance the detection of cracks with different orientations. Promising results that robust to lift-off changes and invariant features for artificial and natural cracks detection have been demonstrated that the proposed method significantly improves defect detectability. It opens up multiphysics sensing and integrated NDE with potential impact for natural understanding and better quantitative evaluation of natural cracks including stress corrosion crack (SCC) and rolling contact fatigue (RCF).

  11. Electromagnetic pulsed thermography for natural cracks inspection

    Science.gov (United States)

    Gao, Yunlai; Tian, Gui Yun; Wang, Ping; Wang, Haitao; Gao, Bin; Woo, Wai Lok; Li, Kongjing

    2017-01-01

    Emerging integrated sensing and monitoring of material degradation and cracks are increasingly required for characterizing the structural integrity and safety of infrastructure. However, most conventional nondestructive evaluation (NDE) methods are based on single modality sensing which is not adequate to evaluate structural integrity and natural cracks. This paper proposed electromagnetic pulsed thermography for fast and comprehensive defect characterization. It hybrids multiple physical phenomena i.e. magnetic flux leakage, induced eddy current and induction heating linking to physics as well as signal processing algorithms to provide abundant information of material properties and defects. New features are proposed using 1st derivation that reflects multiphysics spatial and temporal behaviors to enhance the detection of cracks with different orientations. Promising results that robust to lift-off changes and invariant features for artificial and natural cracks detection have been demonstrated that the proposed method significantly improves defect detectability. It opens up multiphysics sensing and integrated NDE with potential impact for natural understanding and better quantitative evaluation of natural cracks including stress corrosion crack (SCC) and rolling contact fatigue (RCF). PMID:28169361

  12. Pulse growth dynamics in laser mode locking

    Science.gov (United States)

    Popov, Mark; Gat, Omri

    2018-01-01

    We analyze theoretically and numerically the nonlinear process of pulse formation in mode-locked lasers, starting from a perturbation of a continuous wave. Focusing on weak-to-moderate dispersion systems, we show that pulse growth is initially slow, dominated by a cascade of energy from low to high axial modes, followed by fast strongly nonlinear growth, and finally relaxation to the stable pulse wave form. The pulse grows initially by condensing a fixed amount of energy into a decreasing time interval, with peak power growing toward a finite-time singularity that is checked when the gain bandwidth is saturated by the pulse.

  13. Slow light pulse propagation in dispersive media

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Mørk, Jesper; Lavrinenko, Andrei

    2009-01-01

    We present a theoretical and numerical analysis of pulse propagation in a semiconductor photonic crystal waveguide with embedded quantum dots in a regime where the pulse is subjected to both waveguide and material dispersion. The group index and the transmission are investigated by finite...... broadening or break-up of the pulse may be observed. The transition from linear to nonlinear pulse propagation is quantified in terms of the spectral width of the pulse. To cite this article: T.R. Nielsen et al., C. R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All...

  14. Few-cycle pulse characterization with an acousto-optic pulse shaper.

    Science.gov (United States)

    Cousin, S L; Forget, N; Grün, A; Bates, P K; Austin, Dane R; Biegert, J

    2011-08-01

    An acousto-optic pulse shaper has been used to characterize few-cycle pulses generated in a hollow-core fiber. A grism pair precompensates for the dispersion of the acousto-optic crystal, allowing the full pulse-shaping window to be used for replica generation rather than self-compensation. A 9.4 fs pulse was measured, the shortest ever measured with an acousto-optic pulse shaper, to our knowledge. © 2011 Optical Society of America

  15. Characteristics of Retinal Reflectance Changes Induced by Transcorneal Electrical Stimulation in Cat Eyes

    Science.gov (United States)

    Morimoto, Takeshi; Kanda, Hiroyuki; Miyoshi, Tomomitsu; Hirohara, Yoko; Mihashi, Toshifumi; Kitaguchi, Yoshiyuki; Nishida, Kohji; Fujikado, Takashi

    2014-01-01

    Transcorneal electrical stimulation (TES) activates retinal neurons leading to visual sensations. How the retinal cells are activated by TES has not been definitively determined. Investigating the reflectance changes of the retina is an established technique and has been used to determine the mechanism of retinal activation. The purpose of this study was to evaluate the reflectance changes elicited by TES in cat eyes. Eight eyes of Eight cats were studied under general anesthesia. Biphasic electrical pulses were delivered transcornealy. The fundus images observed with near-infrared light (800–880 nm) were recorded every 25 ms for 26 s. To improve the signal-to-noise ratio, the images of 10 consecutive recordings were averaged. Two-dimensional topographic maps of the reflective changes were constructed by subtracting images before from those after the TES. The effects of different stimulus parameters, e.g., current intensity, pulse duration, frequency, and stimulus duration, on the reflective changes were studied. Our results showed that after TES, the reflective changes appeared on the retinal vessels and optic disc. The intensity of reflectance changes increased as the current intensity, pulse duration, and stimulation duration increased (Preflective change was obtained when the stimulus frequency was 20 Hz. The time course of the reflectance changes was also altered by the stimulation parameters. The response started earlier and returned to the baseline later with higher current intensities, longer pulse durations, but the time of the peak of the response was not changed. These results showed that the reflective changes were due to the activation of retinal neurons by TES and might involve the vascular changes induced by an activation of the retinal neurons. PMID:24651530

  16. Laser data transmission with the application of reflectance modulator

    Science.gov (United States)

    Knysak, Piotr; Mierczyk, Zygmunt; Zygmunt, Marek; Wojtanowski, Jacek; Traczyk, Maciej

    2016-12-01

    The article presents the main aspects related to the development of nonconventional asymmetric laser data transmission system. It describes the principle of data transmission in both the direction away from the laser transmitter, wherein a pulse position modulation is used, and in the opposite direction, where the modulation of the reflected radiation is performed. The results presented in the article confirm the possibility of using the described technology in the civilian area for monitoring and telemetry, where devices without radiation sources are taken into account. In military applications, the system can be used to identify own objects and forces on the battlefield by the application of pulsed laser rangefinders which are currently a standard battle equipment.

  17. Pulse compression radar reflectometry for density measurements on fusion plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Costley, A.; Prentice, R. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Laviron, C. [Compagnie Generale des Matieres Nucleaires (COGEMA), 78 - Velizy-Villacoublay (France); Prentice, R. [Toulouse-3 Univ., 31 (France). Centre d`Etude Spatiale des Rayonnements

    1994-07-01

    On tokamaks and other toroidal machines, reflectometry is a very rapidly developing technique for density profile measurements, particularly near the edge. Its principle relies on the total reflection of an electromagnetic wave at a cutoff layer, where the critical density is reached and the local refractive index goes to zero. With the new fast frequency synthesizers now available, a method based on pulse compression radar is proposed for plasma reflectometry, overcoming the limitations of the previous reflectometry methods. The measurement can be made on a time-scale which is effectively very short relatively to the plasma fluctuations, and the very high reproducibility and stability of the source allows an absolute calibration of the waveguides to be made, which corrects for the effects of the parasitic reflections. 2 refs., 5 figs.

  18. Design and application of pulse information acquisition and analysis ...

    African Journals Online (AJOL)

    Background: To design the pulse information which includes the parameter of pulse-position, pulse-number, pulse-shape and pulse-force acquisition and analysis system with function of dynamic recognition, and research the digitalization and visualization of some common cardiovascular mechanism of single pulse.

  19. Enabling honest reflection: a review.

    Science.gov (United States)

    Gostelow, Naomi; Gishen, Faye

    2017-12-01

    Reflective practice provides a backbone to professionalism, a commitment to lifelong learning and competency-based education in the form of reflective portfolios. Changes in health care culture have promoted a move towards openness and reflection on challenging clinical encounters. Engagement with reflection has historically proved challenging to clinical educators. This Faculty Development Review examines this using a case study from the UK in which a postgraduate trainee was asked to disclose their reflective portfolio by a patient's legal representation. Critics have consequently questioned whether the educational benefit of reflection warrants these potential legal implications. In the context of pressure from accrediting bodies to demonstrate evidence of reflection, how can learners face this potential conflict of professional versus legal repercussions? We combine professional guidance from the UK and educational rationale from international settings to produce a guide for good practice. We offer guidance on facilitating reflection for learners in an open and honest way without diluting educationally effective critical reflection. Themes of anonymity, taking a balanced approach, seeking senior advice, focusing on learning outcomes and role-modelling are discussed. How can learners face this potential conflict of professional versus legal repercussions? Integrating reflection within the curriculum improves engagement and is key to experiential learning. Clinical educators should be aware of legal and professional guidance applicable to their own context. Both educators and learners should be aware that written reflection is an educational not a clinical tool, and so requires little or no patient-identifiable data, thereby ensuring safer reflective practice. © 2017 John Wiley & Sons Ltd and The Association for the Study of Medical Education.

  20. A Time-Domain Reflectometry Method with Variable Needle Pulse Width for Measuring the Dielectric Properties of Materials

    OpenAIRE

    Andrzej Wilczek; Agnieszka Szypłowska; Marcin Kafarski; Wojciech Skierucha

    2016-01-01

    Time-domain reflectometry (TDR) methods used for measuring the dielectric properties of materials mostly utilize step or needle electrical pulses of constant amplitudes and shapes. Our novel approach enables determining the dielectric relaxation time of a sample using the analysis of the amplitudes of reflected pulses of two widths, in addition to bulk dielectric permittivity and electrical conductivity commonly obtained by the TDR technique. The method was developed for various values of ele...

  1. Wave reflection and transmission in multiply stented blood vessels

    Science.gov (United States)

    Papathanasiou, T. K.; Movchan, A. B.; Bigoni, D.

    2017-06-01

    Closed circulatory systems display an exquisite balance between vascular elasticity and viscous fluid effects, to induce pulse-smoothing and avoid resonance during the cardiac cycle. Stents in the arterial tree alter this balance through stiffening and because a periodic structure is introduced, capable of interacting with the fluid in a complex way. While the former feature has been investigated, the latter received no attention so far. But periodic structures are the building blocks of metamaterials, known for their `non-natural' behaviour. Thus, the investigation of a stent's periodic microstructure dynamical interactions is crucial to assess possible pathological responses. A one-dimensional fluid-structure interaction model, simple enough to allow an analytical solution for situations of interest involving one or two interacting stents, is introduced. It is determined: (i) whether or not frequency bands exist in which reflected blood pulses are highly increased and (ii) if these bands are close to the characteristic frequencies of arteries and finally, (iii) if the internal structure of the stent can sensibly affect arterial blood dynamics. It is shown that, while the periodic structure of an isolated stent can induce anomalous reflection only in pathological conditions, the presence of two interacting stents is more critical, and high reflection can occur at frequencies not far from the physiological values.

  2. Berlin Reflectance Spectral Library (BRSL)

    Science.gov (United States)

    Henckel, D.; Arnold, G.; Kappel, D.; Moroz, L. V.; Markus, K.

    2017-09-01

    The Berlin Reflectance Spectral Library (BRSL) provides a collection of reflectance spectra between 0.3 and 17 µm. It was originally dedicated to support space missions to small solar system bodies. Meanwhile the library includes selections of biconical reflectance spectra for spectral data analysis of other planetary bodies as well. The library provides reference spectra of well-characterized terrestrial analogue materials and meteorites for interpretation of remote sensing reflectance spectra of planetary surfaces. We introduce the BRSL, summarize the data available, and access to use them for further relevant applications.

  3. Cultivating Reflective Practitioners in Technology Preparation: Constructing TPACK through Reflection

    Directory of Open Access Journals (Sweden)

    Liangyue Lu

    2013-12-01

    Full Text Available Teaching is a complex profession, which is further complicated by the integration of technology into classrooms. Reflection can help teachers unpack the complexity in their practice. Reflection can be an effective instructional strategy in helping preservice teachers develop technological pedagogical content knowledge (TPACK, the complex and dynamic knowledge necessary for effective technology integration into instruction. In this study, reflective activities were integrated into a Learning By Design (LBD environment, which was created to help preservice teachers develop TPACK. This paper investigated the participants’ TPACK development and examined how reflection helped them construct TPACK. Through content analysis of the participants’ reflective journals, the researcher found that the preservice teachers developed initial TPACK awareness. However, their reflection in technology knowledge and the content aspects of TPACK were limited and superficial. Interviews with the participants showed reflection helped the preservice teachers remember what they learned by describing and elaborating on their in-class experiences, pushed them to think about how to apply what they learned in their future classrooms, and helped them become more reflective and open-minded about using technology in classrooms. Finally, the researcher discussed this study’s implications for teacher educators and researchers.

  4. Cultivating Reflective Practitioners in Technology Preparation: Constructing TPACK through Reflection

    Science.gov (United States)

    Lu, Liangyue

    2014-01-01

    Teaching is a complex profession, which is further complicated by the integration of technology into classrooms. Reflection can help teachers unpack the complexity in their practice. Reflection can be an effective instructional strategy in helping preservice teachers develop technological pedagogical content knowledge (TPACK), the complex and…

  5. Reflecting on the History, Ethics, and Application of Teacher Reflection.

    Science.gov (United States)

    Hankes, Judith Elaine

    Three social factors are related to the evolution of the discourse on teacher reflection: the role of educational researchers and teacher educators; the social and economic crisis and its impact on education; and the shift from behaviorism to cognitivism. By relating the discourse of teacher change through reflection to these social factors, it…

  6. Postgraduate Education to Support Organisation Change: A Reflection on Reflection

    Science.gov (United States)

    Stewart, Jim; Keegan, Anne; Stevens, Pam

    2008-01-01

    Purpose: This paper aims to explore how teaching and assessing reflective learning skills can support postgraduate practitioners studying organisational change and explores the challenges for tutors in assessing these journals. Design/methodology/approach: Assessment criteria were developed from the literature on reflective practice and…

  7. Studies of the Reflection, Refraction and Internal Reflection of Light

    Science.gov (United States)

    Lanchester, P. C.

    2014-01-01

    An inexpensive apparatus and associated experiments are described for studying the basic laws of reflection and refraction of light at an air-glass interface, and multiple internal reflections within a glass block. In order to motivate students and encourage their active participation, a novel technique is described for determining the refractive…

  8. A comparison of a new reflectance oximeter with the Hewlett-Packard ear oximeter.

    Science.gov (United States)

    Decker, M J; Dickensheets, D; Arnold, J L; Cheung, P W; Strohl, K P

    1990-01-01

    The purpose of this study was to characterize the accuracy and dynamic response characteristics of traditional transmittance pulse oximeters and a new reflectance pulse oximeter with regard to the current standard in oximetry, the Hewlett-Packard ear oximeter. Studies were performed with 15 healthy male and female subjects. A rebreathing technique was employed to produce a steady fall in oxygen saturation and to maintain constant, eucapnic, end-tidal CO2 levels. The oximeters' analog outputs were recorded by a Western Graphtec Linearecorder and by an IBM-PC utilizing an analog-to-digital converter for data collection at 5 Hz. The agreement between two clinical methods of measurement was used as the statistical technique of comparing new technology (pulse oximetry) with the current standard (Hewlett-Packard ear oximetry). The mean of the difference between the Hewlett-Packard and the pulse oximeter with reflectance sensor was 0.28%, with a range of difference of +/- 3.49%. This value was similar to that of the transmittance oximeters (Criticare 501+: 0.92 +/- 2.11), (Physio-Control: 3.15 +/- 2.04), (Ohmeda 3700: 2.05 +/- 2.06). There was virtually no response-time difference between the reflectance oximeter with the sensor placed on the subject's forehead and the Hewlett-Packard ear oximeter. The authors conclude that the accuracy of the reflectance oximeter is within the limits of clinical acceptance for monitoring and trending of arterial oxygen saturation in healthy subjects.

  9. Cavity ring-down technique for measurement of reflectivity of high ...

    Indian Academy of Sciences (India)

    Abstract. A simple, accurate and reliable method for measuring the reflectivity of laser- grade mirrors (R > 99.5%) based on cavity ring-down (CRD) technique has been success- fully demonstrated in our laboratory using a pulsed Nd:YAG laser. A fast photomultiplier tube with an oscilloscope was used to detect and analyse ...

  10. Audible reflection density for different late reflection criteria in rooms

    DEFF Research Database (Denmark)

    Krueger, Donata; Jeong, Cheol-Ho; Brunskog, Jonas

    2012-01-01

    For reasonably accurate but practical auralizations, some simplifications and approximations are needed. The main issue in the present investigation is that the reflection density of a room impulse response, in theory, increases so fast as a quadratic function of the elapsed time, even assuming...... only specular reflections. Therefore in this study, the upper threshold for audible reflection density is investigated for four different transition times of 25, 50, 75, and 100 ms through a headphone listening test. Binaural impulse responses and speech signals simulated in three rooms with different...... characteristics (an empty office, a lecture room, and an auditorium) are used as stimuli. Subjects are asked to increase/decrease the reflection density of a stimulus until they cannot distinguish it from the stimulus that follows the theoretical reflection density for the different transition times in the three...

  11. Pulsed strain release on the Altyn Tagh fault, northwest China

    Science.gov (United States)

    Gold, Ryan D.; Cowgill, Eric; Arrowsmith, J. Ramón; Friedrich, Anke M.

    2017-01-01

    Earthquake recurrence models assume that major surface-rupturing earthquakes are followed by periods of reduced rupture probability as stress rebuilds. Although purely periodic, time- or slip-predictable rupture models are known to be oversimplifications, a paucity of long records of fault slip clouds understanding of fault behavior and earthquake recurrence over multiple ruptures. Here, we report a 16 kyr history of fault slip—including a pulse of accelerated slip from 6.4 to 6.0 ka—determined using a Monte Carlo analysis of well-dated offset landforms along the central Altyn Tagh strike-slip fault (ATF) in northwest China. This pulse punctuates a median rate of 8.1+1.2/−0.9 mm/a and likely resulted from either a flurry of temporally clustered ∼Mw 7.5 ground-rupturing earthquakes or a single large >Mw 8.2 earthquake. The clustered earthquake scenario implies rapid re-rupture of a fault reach >195 km long and indicates decoupled rates of elastic strain energy accumulation versus dissipation, conceptualized as a crustal stress battery. If the pulse reflects a single event, slip-magnitude scaling implies that it ruptured much of the ATF with slip similar to, or exceeding, the largest documented historical ruptures. Both scenarios indicate fault rupture behavior that deviates from classic time- or slip-predictable models.

  12. Pulsed zero field NMR of solids and liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Thayer, A.M.

    1987-02-01

    This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs.

  13. Ubuntu feminism: Tentative reflections

    Directory of Open Access Journals (Sweden)

    Drucilla Cornell

    2015-06-01

    Full Text Available The starting-point for the article is to provide a brief background on the Ubuntu Project that Prof. Drucilla Cornell convened in 2003; most notably the interviews conducted in Khayamandi, the support of a sewing collective, and the continued search to launch an Ubuntu Women�s Centre. The article will reflect on some of the philosophical underpinnings of ubuntu, whereafter debates in Western feminism will be revisited. Ubuntu feminism is suggested as a possible response to these types of feminisms. The authors support an understanding of ubuntu as critique and ubuntu feminism accordingly as a critical intervention that recalls a politics of refusal. The article ends by raising the importance of thinking about spatiality through ubuntu, and vice versa. It may seem strange to title an article Ubuntu feminism when feminism itself has often been identified as a European or Western idea. But, this article will argue that ubuntu offers conceptions of transindividuality and ways of social belonging that could respond in a meaningful way to some of European feminism�s own dilemmas and contradictions. Famously, one of the most intense debates in feminism was between those who defended an ethic of care in a relational view of the self, on one side, and those feminists who held on to more traditional conceptions of justice, placing an emphasis on individuality and autonomy, on the other side. The authors will suggest that ubuntu could address this tension in feminism. Thus, in this article the focus will not simply be on ubuntu, in order to recognise that there are other intellectual heritages worthy of consideration, other than those in Europe and the United States. It will also take a next step in arguing that ubuntu may be a better standpoint entirely from which to continue thinking about what it means to be a human being, as well as how to conceive of the integral interconnection human beings all have with one another. This connection through

  14. Assessment of pulse rate variability by the method of pulse frequency demodulation

    Science.gov (United States)

    Hayano, Junichiro; Barros, Allan Kardec; Kamiya, Atsunori; Ohte, Nobuyuki; Yasuma, Fumihiko

    2005-01-01

    Background Due to its easy applicability, pulse wave has been proposed as a surrogate of electrocardiogram (ECG) for the analysis of heart rate variability (HRV). However, its smoother waveform precludes accurate measurement of pulse-to-pulse interval by fiducial-point algorithms. Here we report a pulse frequency demodulation (PFDM) technique as a method for extracting instantaneous pulse rate function directly from pulse wave signal and its usefulness for assessing pulse rate variability (PRV). Methods Simulated pulse wave signals with known pulse interval functions and actual pulse wave signals obtained from 30 subjects with a trans-dermal pulse wave device were analyzed by PFDM. The results were compared with heart rate and HRV assessed from simultaneously recorded ECG. Results Analysis of simulated data revealed that the PFDM faithfully demodulates source interval function with preserving the frequency characteristics of the function, even when the intervals fluctuate rapidly over a wide range and when the signals include fluctuations in pulse height and baseline. Analysis of actual data revealed that individual means of low and high frequency components of PRV showed good agreement with those of HRV (intraclass correlation coefficient, 0.997 and 0.981, respectively). Conclusion The PFDM of pulse wave signal provides a reliable assessment of PRV. Given the popularity of pulse wave equipments, PFDM may open new ways to the studies of long-term assessment of cardiovascular variability and dynamics. PMID:16259639

  15. Single attosecond pulse production with an ellipticity-modulated driving IR pulse

    Energy Technology Data Exchange (ETDEWEB)

    Strelkov, V [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Zair, A [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Tcherbakoff, O [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Lopez-Martens, R [Department of Physics, Lund Institute of Technology, PO Box 118, S-22100, Lund (Sweden); Cormier, E [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Mevel, E [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Constant, E [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France)

    2005-05-28

    We theoretically study attosecond pulse production via high-harmonic generation using a driving laser pulse with a time-dependent ellipticity. The theoretical approach produces results that agree with our experimental data obtained using 35 fs driving laser pulses and is further used to study the generation of single attosecond pulses with shorter laser pulses. We find an equation for the duration of the temporal window created by the time-varying driving laser polarization in which high-harmonic emission can occur. We formulate the necessary requirements concerning the driving laser field in order to confine the high-harmonic emission in the form of a single attosecond pulse. Indeed, we show that using incident 12 fs laser pulses single attosecond pulses can be produced for certain carrier-envelope phase (CEP) values of the driving pulse. For 6 fs incident laser pulses, single attosecond pulses are produced for all values of the CEP (the intensity of the attosecond pulse still depends on the actual value of the CEP). If implemented with state-of-the-art 5 fs laser pulses, this technique can even lead to the production of sub-100 as pulses. (letter to the editor)

  16. Groups of bats improve sonar efficiency through mutual suppression of pulse emissions.

    Directory of Open Access Journals (Sweden)

    Jenna eJarvis

    2013-06-01

    Full Text Available How bats adapt their sonar behavior to accommodate the noisiness of a crowded day roost is a mystery. Some bats change their pulse acoustics to enhance the distinction between theirs and another bat’s echoes, but additional mechanisms are needed to explain the bat sonar system’s exceptional resilience to jamming by conspecifics. Variable pulse repetition rate strategies offer one potential solution to this dynamic problem, but precisely how changes in pulse rate could improve sonar performance in social settings is unclear. Here we show that bats decrease their emission rates as population density increases, following a pattern that reflects a cumulative mutual suppression of each other’s pulse emissions. Playback of artificially-generated echolocation pulses similarly slowed emission rates, demonstrating that suppression was mediated by hearing the pulses of other bats. Slower emission rates did not support an antiphonal emission strategy but did reduce the relative proportion of emitted pulses that overlapped with another bat’s emissions, reducing the relative rate of mutual interference. The prevalence of acoustic interferences occurring amongst bats was empirically determined to be a linear function of population density and mean emission rates. Consequently as group size increased, small reductions in emission rates spread across the group partially mitigated the increase in interference rate. Drawing on lessons learned from communications networking theory we show how modest decreases in pulse emission rates can significantly increase the net information throughput of the shared acoustic space, thereby improving sonar efficiency for all individuals in a group. We propose that an automated acoustic suppression of pulse emissions triggered by bats hearing each other's emissions dynamically optimizes sonar efficiency for the entire group.

  17. Hybrid Pulsed Nd:YAG Laser

    Science.gov (United States)

    Miller, Sawyer; Trujillo, Skyler; Fort Lewis College Laser Group Team

    This work concerns the novel design of an inexpensive pulsed Nd:YAG laser, consisting of a hybrid Kerr Mode Lock (KLM) and Q-switch pulse. The two pulse generation systems work independently, non simultaneously of each other, thus generating the ability for the user to easily switch between ultra-short pulse widths or large energy density pulses. Traditionally, SF57 glass has been used as the Kerr medium. In this work, novel Kerr mode-locking mediums are being investigated including: tellurite compound glass (TeO2), carbon disulfide (CS2), and chalcogenide glass. These materials have a nonlinear index of refraction orders of magnitude,(n2), larger than SF57 glass. The Q-switched pulse will utilize a Pockels cell. As the two pulse generation systems cannot be operated simultaneously, the Pockels cell and Kerr medium are attached to kinematic mounts, allowing for quick interchange between systems. Pulse widths and repetition rates will vary between the two systems. A goal of 100 picosecond pulse widths are desired for the mode-locked system. A goal of 10 nanosecond pulse widths are desired for the Q-switch system, with a desired repetition rate of 50 Hz. As designed, the laser will be useful in imaging applications.

  18. Nonlinear reflection of a spherically divergent N-wave from a plane surface: Optical interferometry measurements in air

    Energy Technology Data Exchange (ETDEWEB)

    Karzova, M., E-mail: masha@acs366.phys.msu.ru [Laboratoire de Mécanique des Fluides et d’Acoustique, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Yuldashev, P.; Khokhlova, V. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Ollivier, S.; Blanc-Benon, Ph. [Laboratoire de Mécanique des Fluides et d’Acoustique, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France)

    2015-10-28

    Mach stem is a well-known structure typically observed in the process of strong (acoustic Mach numbers greater than 0.4) step-shock waves reflection from a rigid boundary. However, this phenomenon has been much less studied for weak shocks in nonlinear acoustic fields where Mach numbers are in the range from 0.001 to 0.01 and pressure waveforms have more complicated waveforms than step shocks. The goal of this work was to demonstrate experimentally how nonlinear reflection occurs in air for very weak spherically divergent acoustic spark-generated pulses resembling an N-wave. Measurements of reflection patterns were performed using a Mach-Zehnder interferometer. A thin laser beam with sub-millimeter cross-section was used to obtain the time resolution of 0.4 µs, which is 6 times higher than the time resolution of the condenser microphones. Pressure waveforms were reconstructed using the inverse Abel transform applied to the phase of the signal measured by the interferometer. The Mach stem formation was observed experimentally as a result of collision of the incident and reflected shock pulses. It was shown that irregular reflection of the pulse occurred in a dynamic way and the length of the Mach stem increased linearly while the pulse propagated along the surface. Since the front shock of the spark-generated pulse was steeper than the rear shock, irregular type of reflection was observed only for the front shock of the pulse while the rear shock reflection occurred in a regular regime.

  19. Temporal pulse shaping: a key parameter for the laser welding of dental alloys.

    Science.gov (United States)

    Bertrand, Caroline; Poulon-Quintin, Angeline

    2015-07-01

    This study aims to describe the effect of pulse shaping on the prevention of internal defects during laser welding for two dental alloys mainly used in prosthetic dentistry. Single spot, weld beads, and welds with 80 % overlapping were performed on Co-Cr-Mo and Pd-Ag-Sn cast plates with a pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. A specific welding procedure using adapted parameters to each alloy was completed. All the possibilities for pulse shaping were tested: (1) the square pulse shape as a default setting, (2) a rising edge slope for gradual heating, (3) a falling edge slope to slow the cooling process, and (4) a combination of rising and falling edges. The optimization of the pulse shape is supposed to produce defect-free welds (crack, pores, voids). Cross-section SEM observations and Vickers microhardness measurements were made. Pd-Ag-Sn was highly sensitive to hot cracking, and Co-Cr-Mo was more sensitive to voids and small porosities (sometimes combined with cracks). Using a slow cooling ramp allowed a better control on the solidification process for those two alloys always preventing internal defects. A rapid slope should be preferred for Co-Cr-Mo alloys due to its low-laser beam reflectivity. On the opposite, for Pd-Ag-Sn alloy, a slow rising slope should be preferred because this alloy has a high-laser beam reflectivity.

  20. Pulse-Flow Microencapsulation System

    Science.gov (United States)

    Morrison, Dennis R.

    2006-01-01

    The pulse-flow microencapsulation system (PFMS) is an automated system that continuously produces a stream of liquid-filled microcapsules for delivery of therapeutic agents to target tissues. Prior microencapsulation systems have relied on batch processes that involve transfer of batches between different apparatuses for different stages of production followed by sampling for acquisition of quality-control data, including measurements of size. In contrast, the PFMS is a single, microprocessor-controlled system that performs all processing steps, including acquisition of quality-control data. The quality-control data can be used as real-time feedback to ensure the production of large quantities of uniform microcapsules.

  1. Pulsed Terahertz Spectroscopy of Biomolecules

    Science.gov (United States)

    Markelz, A. G.; Heilweil, E. J.

    1998-03-01

    Measurements of the collective vibrational modes associated with the 3D tertiary structure of biomolecules were undertaken using pulse terahertz spectroscopy. Transmission measurements of calf thymus DNA (CT-DNA), bovine serum albumin (BSA), and collagen were made for 2 cm-1 to 45 cm-1. For all three biomolecules, low frequency absorption bands could be distinguished from a broadband absorption increasing with frequency. For lyophilized powder samples, features appear at 15 cm-1 and 22 cm-1 for CT-DNA, 10 cm-1 for BSA, and 8 cm-1 and 12 cm-1 for collagen. Measurements were performed as a function of hydration and conformation.

  2. Flexible Bistable Cholesteric Reflective Displays

    Science.gov (United States)

    Yang, Deng-Ke

    2006-03-01

    Cholesteric liquid crystals (ChLCs) exhibit two stable states at zero field condition-the reflecting planar state and the nonreflecting focal conic state. ChLCs are an excellent candidate for inexpensive and rugged electronic books and papers. This paper will review the display cell structure,materials and drive schemes for flexible bistable cholesteric (Ch) reflective displays.

  3. Ethical Reflections on Becoming Teachers

    Science.gov (United States)

    Joseph, Pamela Bolotin

    2016-01-01

    This study analyzes narratives written in a culminating graduate seminar on reflective practice by 36 new secondary teachers who were asked to consider their moral beliefs, moral values and system of ethics as they reflected on their recent student teaching experiences. The findings explore how the participants depicted their constructed moral…

  4. Pulse-to-pulse intensity modulation and drifting subpulses in recycled pulsars

    OpenAIRE

    Edwards, R; Stappers, B. W.

    2003-01-01

    We report the detection of pulse-to-pulse periodic intensity modulations, in observations of recycled pulsars. Even though the detection of individual pulses was generally not possible due to their low flux density and short duration, through the accumulation of statistics over sequences of 10^5--10^6 pulses we were able to determine the presence and properties of the pulse-to-pulse intensity variations of six pulsars. In most cases we found that the modulation included a weak, broadly quasi-...

  5. Storytelling: A Guided Reflection Activity.

    Science.gov (United States)

    Wheeler, Pamela L; Butell, Sue S; Epeneter, Beverly Jean; Langford, Cheryl Anne; Taylor, Jana Doughty

    2016-03-01

    Reflective practice is a mode of inquiry in the authors' baccalaureate nursing program. To increase students' ability to "think like a nurse," the Reflective Practice Storytelling Guide was developed to facilitate discussion during weekly clinical seminars in the students' final clinical course. To evaluate the effectiveness of this guided activity, students were asked to provide feedback to specific questions following each seminar when the reflective presence activity was utilized. Common themes emerged from the storytellers and the members of the group. Themes identified in the responses of the storytellers included role development and formation and the value of team support. Learning themes that emerged from the participants included communication, teamwork, clinical judgment, patient-centered care, use of resources, ethical and legal parameters in practice, and patient safety. Utilizing a guided reflection activity resulted in the students experiencing a broader, deeper understanding of reflective professional practice. Copyright 2016, SLACK Incorporated.

  6. [Concept analysis of reflective thinking].

    Science.gov (United States)

    Van Vuuren, M; Botes, A

    1999-09-01

    The nursing practice is described as a scientific practice, but also as a practice where caring is important. The purpose of nursing education is to provide competent nursing practitioners. This implies that future practitioners must have both critical analytical thinking abilities, as well as empathy and moral values. Reflective thinking could probably accommodate these thinking skills. It seems that the facilitation of reflective thinking skills is essential in nursing education. The research question that is relevant in this context is: "What is reflective thinking?" The purpose of this article is to report on the concept analysis of reflective thinking and in particular on the connotative meaning (critical attributes) thereof. The method used to perform the concept analysis is based on the original method of Wilson (1987) as described by Walker & Avant (1995). As part of the concept analysis the connotations (critical attributes) are identified, reduced and organized into three categories, namely pre-requisites, processes and outcomes. A model case is described which confirms the essential critical attributes of reflective thinking. Finally a theoretical definition of reflective thinking is derived and reads as follows: Reflective thinking is a cyclic, hierarchical and interactive construction process. It is initiated, extended and continued because of personal cognitive-affective interaction (individual dimension) as well as interaction with the social environment (social dimension). to realize reflective thinking, a level of internalization on the cognitive and affective domain is required. The result of reflective thinking is a integrated framework of knowledge (meaningful learning) and a internalized value system providing a new perspective on and better understanding of a problem. Reflective thinking further leads to more effective decision making- and problem solving skills.

  7. 25 years of pulsed laser deposition

    Science.gov (United States)

    Lorenz, Michael; Ramachandra Rao, M. S.

    2014-01-01

    decade, large-area PLD grown YBa2Cu3O7-δ thin films became a reality for applications in microwave filters for satellite and mobile communication. The material systems that could be covered under the PLD gamut extended to almost all oxides, nitrides and even organics. A second textbook exclusively dedicated to PLD was edited by Rob Eason in 2007 [4], reviewing many possible modifications and extensions of the method. To celebrate 25 years of pulsed laser deposition, Venkatesan organized a symposium on 'Recent Advances in the Pulsed Laser Deposition of Thin Films and Nanostructures' in 2013 [5]. Besides dielectric, ferroelectric and magnetic oxides, the wide-bandgap group II-VI semiconductor ZnO is among the most intensively researched compounds during the last decade. Therefore, this material has become the subject of two introductory reviews in this issue by Opel et al and Tsukazaki et al , to show the state-of-the-art work carried out on ZnO thin films to 2013. The detailed insights into growth parameter control and their impact on the ZnO film performance make both reviews highly instructional not only for specialists, but also for beginners in PLD. The perspective of PLD towards industrial applications largely depends, first, on the ability of the excimer laser suppliers to further increase the laser power and, second, on the deposition schemes to distribute the ablated material homogeneously on technologically relevant substrate areas (8-inch diameter). These developments are explained here by the leading companies dealing with high-power excimer lasers and large-area PLD equipment, such as Coherent Laser Systems GmbH, PVD Products, Inc., and SolMateS B.V. It is also important to note the efforts made by Blank and Rijnders for atomic layer control of PLD by in situ high-pressure reflection high-energy electron diffraction (RHEED), which is now adopted by many groups worldwide. The potential of multi-beam PLD for advanced optical waveguides and of advanced design

  8. Laser-Material Interaction of Powerful Ultrashort Laser Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Komashko, A

    2003-01-06

    biological tissue) and laser-induced pressure waves. Simulations on the basis of the nonlinear ionization equation were used to examine effects of the laser created surface plasma on light absorption, reflection and transmission. Laser pulse energy conversion efficiency into pressure waves was studied experimentally and theoretically.

  9. Conditions for effects of radiation pulsing

    CERN Document Server

    Trinkaus, H

    2002-01-01

    The possibility of pulsing effects on radiation damage is due to differences in the delay times of relevant defect reactions and/or to the non-linear dependence of such reactions on defect production rates. Thus, significant pulsing effects require (1) proper relationships of the internal time scales of defect production and reaction to the time scales of pulsing and (2) sufficiently large pulsing induced fluctuations in relevant microstructural variables. We show that the first condition, which we quantify by a 'relative dynamic bias', is indeed fulfilled in wide ranges of the main irradiation parameters. The second condition, quantified by an 'absolute dynamic bias', is, however, found to restrict the parameter ranges of possible pulsing effects substantially. For planned spallation neutron sources and similar accelerator driven systems facilities we find, for instance, that, in the temperature range of interest, the defect yield of one pulse (controlling the absolute dynamic bias) is much too small to allo...

  10. VCSEL based, wearable, continuously monitoring pulse oximeter.

    Science.gov (United States)

    Kollmann, Daniel; Hogan, William K; Steidl, Charles; Hibbs-Brenner, Mary K; Hedin, Daniel S; Lichter, Patrick A

    2013-01-01

    We present the development of a novel pulse oximeter based on low power, low cost, Vertical Cavity Surface Emitting Laser (VCSEL) technology. This new design will help address a need to perform regular measurements of pulse oximetry for patients with chronic obstructive pulmonary disease. VCSELs with wavelengths suitable for pulse oximetry were developed and packaged in a PLCC package for a low cost solution that is easy to integrate into a pulse oximeter design. The VCSELs were integrated into a prototype pulse oximeter that is unobtrusive and suitable for long term wearable use. The prototype achieved good performance compared the Nonin Onyx II pulse oximeter at less than one fifth the weight in a design that can be worn behind the ear like a hearing aid.

  11. Cryogenic pulsed inductive microwave magnetometer

    Science.gov (United States)

    Kos, A. B.; Nibarger, J. P.; Lopusnik, R.; Silva, T. J.; Celinski, Z.

    2003-05-01

    A cryogenic pulsed inductive microwave magnetometer is used to characterize the switching dynamics in thin-film magnetic materials at low temperatures and microwave frequencies. The system is contained inside a 20-cm-diam ultrahigh vacuum chamber and cooled by a cryopump that allows measurements between 20 and 350 K. A temperature controller regulates the sample temperature using two silicon diodes as sensors. Applied magnetic fields of up to 36 kA/m (450 Oe) are generated by a four-pole, water-cooled electromagnet with independent control of each axis. Magnetic switching in the sample is driven by high-speed current step pulses in a coplanar waveguide structure with the sample placed in a flip-chip configuration. A 20 GHz sampling oscilloscope is used to record the dynamics of the magnetic reorientation. The switching dynamics are given for a 10-nm-thick Ni-Fe film at 30 K in response to a 1 kA/m field step.

  12. Pulsed Power Bibliography. Volume 2. Annotated Bibliography.

    Science.gov (United States)

    1983-08-01

    inoestigated at different pressures and generating signal nacimum peak pouer; One flow rote and sturate volume detereine amplitudes. 22 Refs. mauimumrunn...and Local Thermodyvasic Equilibrium INTERUPTION (LTE) of the arc planna. .srical solutions for the field variables T.E. Browne Jr. are obtained by...complete high current pulse amplifier were fabricated and teste forSwpplTss. Pulse Ognerater; S inductsr DiOedes; diode sturation charsctettcs and pulse

  13. New pulse modulator with low switching frequency

    Directory of Open Access Journals (Sweden)

    Golub V. S.

    2014-12-01

    Full Text Available The author presents an integrating pulse modulator (analog signal converter with the pulse frequency and duration modulation similar to sigma-delta modulation (with low switching frequency, without quantization. The modulator is characterized by the absence of the quantization noise inherent in sigma-delta modulator, and a low switching frequency, unlike the pulse-frequency modulator. The modulator is recommended, in particular, to convert signals at the input of the class D power amplifier.

  14. Femtosecond Laser Pulses Principles and Experiments

    CERN Document Server

    Rullière, Claude

    2005-01-01

    This smooth introduction for advanced undergraduates starts with the fundamentals of lasers and pulsed optics. Thus prepared, the student is introduced to short and ultrashort laser pulses, and learns how to generate, manipulate, and measure them. Spectroscopic implications are also discussed. The second edition has been completely revised and includes two new chapters on some of the most promising and fast-developing applications in ultrafast phenomena: coherent control and attosecond pulses.

  15. Pulsed-Power Burnout of Integrated Circuits

    Science.gov (United States)

    Results of pulsed-power burnout testing the Fairchild 9046 quad dual-input nand gate and the Amelco 6041 three-input nand gate showed the circuits to...be vulnerable to junction burnout for pulses of less than 100 V and pulse widths on the order of 100 nsec. Calculations based on Wunsch-Bell junction... burnout theory showed good agreement with the experimental results. Sample calculations applying Wunsch-Bell theory to integrated circuits are given.

  16. Dark pulse quantum dot diode laser.

    Science.gov (United States)

    Feng, Mingming; Silverman, Kevin L; Mirin, Richard P; Cundiff, Steven T

    2010-06-21

    We describe an operating regime for passively mode-locked quantum dot diode laser where the output consists of a train of dark pulses, i.e., intensity dips on a continuous background. We show that a dark pulse train is a solution to the master equation for mode-locked lasers. Using simulations, we study stability of the dark pulses and show they are consistent with the experimental results.

  17. Radiation spectroscopy by digital pulse height analysis

    Energy Technology Data Exchange (ETDEWEB)

    Los Arcos, J.M. (Metrologia de Radiaciones, Instituto de Investigacion Basica, CIEMAT, Avda. Complutense 22, Madrid 28040 (Spain)); Garcia-Torano, E. (Metrologia de Radiaciones, Instituto de Investigacion Basica, CIEMAT, Avda. Complutense 22, Madrid 28040 (Spain)); Olmos, P. (Tecnologias Avanzadas de Sensores, Direccion de Tecnologia, CIEMAT, Avda. Complutense 22, Madrid 28040 (Spain)); Marin, J. (Tecnologias Avanzadas de Sensores, Direccion de Tecnologia, CIEMAT, Avda. Complutense 22, Madrid 28040 (Spain))

    1994-12-30

    This paper presents a new version of the Digital Pulse-Height Analysis (DPHA) method described in a previous paper, which is based on data acquisition through a personal computer using a flash-ADC card followed by numerical processing of pulses in the same computer. Performance tests carried out with a pulse generator and gamma-ray spectra have been carried out and their results are discussed. ((orig.))

  18. Pulsed writing of solid state holograms.

    Science.gov (United States)

    Gaylord, T. K.; Rabson, T. A.; Tittel, F. K.; Quick, C. R.

    1973-01-01

    The pulsed writing of volume holograms in lithium niobate is reported, both with 200-nsec and 20-nsec duration pulses. This information is of particular interest in high capacity information storage applications since it indicates that writing times at least as short as 20-nsec are readily possible. A series of pulses was used in each case, and the diffraction efficiency was monitored using a He-Ne laser operating at 6328 A and aligned to its corresponding Bragg angle.

  19. PULSE DRYING EXPERIMENT AND BURNER CONSTRUCTION

    Energy Technology Data Exchange (ETDEWEB)

    Robert States

    2006-07-15

    Non steady impingement heat transfer is measured. Impingement heating consumes 130 T-BTU/Yr in paper drying, but is only 25% thermally efficient. Pulse impingement is experimentally shown to enhance heat transfer by 2.8, and may deliver thermal efficiencies near 85%. Experimental results uncovered heat transfer deviations from steady theory and from previous investigators, indicating the need for further study and a better theoretical framework. The pulse burner is described, and its roll in pulse impingement is analyzed.

  20. Pulsed-N2 assisted growth of 5-20 nm thick β-W films

    Directory of Open Access Journals (Sweden)

    Avyaya J. Narasimham

    2015-11-01

    Full Text Available A technique to deposit 5-20 nm thick β-phase W using a 2-second periodic pulse of 1 sccm-N2 gas on Si(001 and SiN(5 nm/Si(001 substrates is reported. Resistivity, X-ray photoelectron spectroscopy and X-ray reflectivity were utilized to determine phase, bonding and thickness, respectively. X-ray diffraction patterns were utilized to determine the crystal structure, lattice constant and crystal size using the LeBail method. The flow rate of Nitrogen gas (continuous vs. pulsing had significant impact upon the crystallinity and formation of β-phase W.

  1. Effect of a target on the stimulated emission of microsecond CO2-laser pulses

    Science.gov (United States)

    Baranov, V. Iu.; Dolgov, V. A.; Maliuta, D. D.; Mezhevov, V. S.; Semak, V. V.

    1987-12-01

    The paper reports a change in the pulse shape of a TEA CO2 laser with an unstable cavity under the interaction between the laser radiation and a metal surface in the presence of a breakdown plasma. It is shown that a continuous change in the phase difference between the wave reflected in the cavity and the principal cavity wave gives rise to changes in the pulse shape and the appearance of power fluctuations. The possible effect of these phenomena on the laser treatment of materials is considered.

  2. Pulse wave reflection is associated with diabetes duration, albuminuria and cardiovascular disease in type 1 diabetes

    DEFF Research Database (Denmark)

    Theilade, Simone; Lajer, Maria; Hansen, Tine Willum

    2014-01-01

    , and smoking. RESULTS: AP and AI75 measurements were available in 636 (94.1 %) patients and were 9.9 ± 7.6 mmHg and 16.9 ± 12.0, respectively. After adjustment, AP and AI75 were independently associated with diabetes duration and albuminuria (p ≤ 0.001). Furthermore, higher AP and AI75 were associated...... with diabetes duration, albuminuria, and CVD, independently of conventional risk factors. ClinicalTrials.gov:NCT01171248....

  3. Reflection of Microwave Pulses From Acoustic Waves: Summary of Experimental and Computational Studies

    National Research Council Canada - National Science Library

    Kepler, G. M; Albanese, R. A; Banks, H. T; Bokil, V. A

    2005-01-01

    .... The response of atomic electrons to an applied electrical field in a material medium results in a material polarization with a concomitant index of refraction that is a function of the local density in the material...

  4. Synergies in Critical Reflective Practice and Science: Science as Reflection and Reflection as Science

    Science.gov (United States)

    Mathieson, Luke

    2016-01-01

    The conceptions of reflective practice in education have their roots at least partly in the work of Dewey, who describes reflection as "the active, persistent, and careful consideration of any belief or supposed form of knowledge in the light of the grounds that support it and the further conclusions to which it tends" (Dewey 1933, p.9).…

  5. Pulsed Single Frequency MOPA Laser Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Latest advances in semiconductor optoelectronics makes it possible to develop compact light weight robust sources of coherent optical pulses, demanded for numerous...

  6. Pulse reversal plating of nickel alloys

    DEFF Research Database (Denmark)

    Tang, Peter Torben

    2007-01-01

    Pulse plating has previously been reported to improve the properties of nickel and nickel alloy deposits. Typically, focus has been on properties such as grain size, hardness and smoothness. When pulse plating is to be utilised for microtechnologies such as microelectromechanical systems (MEMS......), internal stress and material distribution are even more important. With baths based upon nickel chloride, and nickel and cobalt chlorides, pulse reversal plating of both pure nickel and nickel-cobalt alloys has been used to fabricate tools for microinjection moulding. Pulse reversal plating of ternary soft...

  7. MEDEA II two-pulse generator development

    Energy Technology Data Exchange (ETDEWEB)

    Bieniosek, F.M.; Honig, J.; Theby, E.A. (McDonnell Douglas Research Laboratories, P. O. Box 516, St. Louis, Missouri 63166 (USA))

    1990-06-01

    This article discusses improvements in the efficiency, output power, and operational flexibility of MEDEA II, a double-pulse electron beam accelerator at McDonnell Douglas Research Laboratories. A modified charging circuit, based on the triple-resonance pulse transformer concept, was implemented on both of MEDEA II's two stages. The output switches were modified to increase maximum output voltages, and a new, second output switch with asymmetric breakdown characteristics was developed. To avoid degradation of the second-pulse output waveform at the diode, a keep-alive circuit was installed. The effects of diode closure on double-pulse operation are also discussed.

  8. MEDEA II two-pulse generator development

    Science.gov (United States)

    Bieniosek, F. M.; Honig, J.; Theby, E. A.

    1990-06-01

    This article discusses improvements in the efficiency, output power, and operational flexibility of MEDEA II, a double-pulse electron beam accelerator at McDonnell Douglas Research Laboratories. A modified charging circuit, based on the triple-resonance pulse transformer concept, was implemented on both of MEDEA II's two stages. The output switches were modified to increase maximum output voltages, and a new, second output switch with asymmetric breakdown characteristics was developed. To avoid degradation of the second-pulse output waveform at the diode, a keep-alive circuit was installed. The effects of diode closure on double-pulse operation are also discussed.

  9. Pulsed Laser Spectroscopy: An Inexpensive Approach

    Science.gov (United States)

    Daly, J. G.; Hastings, R.; Schmidt, J. A.

    1982-10-01

    The assembly of a pulsed laser spectroscopy laboratory is presented. The authors describe how they constructed pulsed lasers, fast photodetectors, a boxcar signal averager, and associated equipment. A molecular nitrogen laser operating up to 50 Hz with an ultraviolet (337.1 nm) 700 kW pulse was used to optically pump an organic dye laser. The resulting output could be tuned from 360.0 to 680.0 nm. This pulse was typically 30 kW and 8 nsec, which makes it ideally suited to selective excitation and fluorescence studies. By constructing this equipment, it is estimated that the investment was one-tenth the cost of commercial components.

  10. Ultrashort Laser Pulses in Biology and Medicine

    CERN Document Server

    Braun, Markus; Zinth, Wolfgang

    2008-01-01

    Sources of ultrashort laser pulses are nowadays commercially available and have entered many areas of research and development. This book gives an overview of biological and medical applications of these laser pulses. The briefness of these laser pulses permits the tracing of the fastest processes in photo-active bio-systems, which is one focus of the book. The other focus is applications that rely on the high peak intensity of ultrashort laser pulses. Examples covered span non-linear imaging techniques, optical tomography, and laser surgery.

  11. Synthesis of Nanosecond Ultrawideband Radiation Pulses

    Science.gov (United States)

    Koshelev, V. I.; Plisko, V. V.; Sevostyanov, E. A.

    2017-12-01

    The synthesis of electromagnetic pulses with an extended spectrum by summing pulses of different duration in free space has been studied. The radiation spectrum has been estimated analytically for a 4-element array of combined antennas excited by bipolar voltage pulses of duration 0.5, 1, 2, and 3 ns. It has been shown experimentally that radiation with a spectral width of more than three octaves can be produced using a 2×2 array of combined antennas excited by bipolar pulses of duration 2 and 3 ns.

  12. A Chaotic Pulse-Time Modulation Method for Digital Communication

    OpenAIRE

    Nguyen Xuan Quyen; Vu Van Yem; Thang Manh Hoang

    2012-01-01

    We present and investigate a method of chaotic pulse-time modulation (PTM) named chaotic pulse-width-position modulation (CPWPM) which is the combination of pulse-position-modulation (PPM) and pulse-width modulation (PWM) with the inclusion of chaos technique for digital communications. CPWPM signal is in the pulse train format, in which binary information is modulated onto chaotically-varied intervals of position and width of pulses, and therefore two bits are encoded on a single pulse. The ...

  13. A novel programmable pulse generator with nanosecond resolution for pulsed electron paramagnetic resonance applications.

    Science.gov (United States)

    Devasahayam, N; Subramanian, S; Krishna, M C

    2008-02-01

    A pulse programmer with nanosecond time resolution needed for time-domain electron paramagnetic resonance (EPR) spectroscopic applications is described. This unit uses commercially available timing and input-output port modules and control software developed in our laboratory. The pulse programmer is operated through a personal computer front panel graphic user interface (GUI) inputs to control pulse widths, delays, and the associated acquisition trigger timings. Based on these parameters, all other associated gate and trigger timings are internally generated automatically without the need to enter them explicitly. The excitation pulse widths were of nanosecond resolution while all other gate pulses can be incremented in steps of 20 ns without compromising spectrometer performance. In the current configuration, the pulse programmer permits generation of a single pulse or multiple pulse sequences for EPR imaging with minimal data entry via the front panel GUI.

  14. Group velocity and pulse lengthening of mismatched laser pulses in plasma channels

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl; Benedetti, Carlo; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim

    2011-07-07

    Analytic solutions are presented to the non-paraxial wave equation describing an ultra-short, low-power, laser pulse propagating in aplasma channel. Expressions for the laser pulse centroid motion and laser group velocity are derived, valid for matched and mismatchedpropagation in a parabolic plasma channel, as well as in vacuum, for an arbitrary Laguerre-Gaussian laser mode. The group velocity of amismatched laser pulse, for which the laser spot size is strongly oscillating, is found to be independent of propagation distance andsignificantly less than that of a matched pulse. Laser pulse lengthening of a mismatched pulse owing to laser mode slippage isexamined and found to dominate over that due to dispersive pulse spreading for sufficiently long pulses. Analytic results are shown tobe in excellent agreement with numerical solutions of the full Maxwell equations coupled to the plasma response. Implications for plasmachannel diagnostics are discussed.

  15. Enhancement effects of flat-mirror reflection on plasma radiation.

    Science.gov (United States)

    Chen, Jin-zhong; Bai, Jin-ning; Song, Guang-ju; Sun, Jiang; Deng, Ze-chao; Wang, Ying-long

    2013-09-01

    Laser-induced breakdown spectroscopy quality can be improved by using a nanosecond Nd:YAG laser pulse to excite soil samples. To investigate how flat-mirror reflection affects the radiation characteristics of laser-induced plasma, emission spectra of sample elements were recorded using a grating spectrometer and photoelectric detection system. Placing a planar mirror vertically on the sample surface (10 mm mirror to plasma-center axis distance) for flat-mirror reflection increased spectral line intensities of Mg, Al, Fe, and Ba by 93.06%, 159.63%, 93.43%, and 94.61%, respectively. Signal-to-noise ratio increased by 17.56%, 40.21%, 31.29%, and 30%. The radiation enhancement mechanism was clarified using measured plasma parameters.

  16. Laser-induced retinal damage threshold for repetitive-pulse exposure to 100-microsecs pulses

    Science.gov (United States)

    2014-10-07

    and 1000 Hz (Fig. 3). In Fig. 4, PS model predictions based on the experimentally determined single pulse ED50 and probit slope are compared to the...pulse repetition frequencies. The variation of the ED50 with the number of pulses is described well by the probability summation model , in which each...summation (PS) model of Menendez et al.15–17 For this injury mechanism, the cumulative threshold is depen dent only on the number of pulses in the exposure

  17. Efficient chirped-pulse amplification of sub-20 fs laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, Shinichi; Yamakawa, Koichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    We have developed a model for ultrabroadband and ultrashort pulse amplification including the effects of a pulse shaper for regenerative pulse shaping, gain narrowing and gain saturation in the amplifiers. Thin solid etalons are used to control both gain narrowing and gain saturation during amplification. This model has been used to design an optimized Ti:sapphire amplifier system for producing efficiently pulses of < 20-fs duration with approaching peak and average powers of 100 TW and 20 W. (author)

  18. Fiber Optical Parametric Chirped Pulse Amplification of Sub-Picosecond Pulses

    DEFF Research Database (Denmark)

    Cristofori, Valentina; Lali-Dastjerdi, Zohreh; Da Ros, Francesco

    2013-01-01

    We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs.......We demonstrate experimentally, for the first time to our knowledge, fiber optical parametric chirped pulse amplification of 400-fs pulses. The 400-fs signal is stretched, amplified by 26 dB and compressed back to 500 fs....

  19. Pulse pressure reduction and cardiovascular protection.

    Science.gov (United States)

    Laurent, Stéphane; Tropeano, Anne-Isabelle; Boutouyrie, Pierre

    2006-05-01

    Brachial pulse pressure (PP) is now a well-established cardiovascular risk factor. Central rather than peripheral PP should be measured to determine the 'true' haemodynamic effects of antihypertensive agents on target organs. Peripheral PP, measured at the brachial artery, does not reflect central PP (either carotid or ascending aorta), because their determinants are different and pathophysiological conditions and drugs may change central PP without changing peripheral PP. Central PP (i.e. carotid artery or ascending aorta) has shown an independent predictive value for all-cause mortality in patients with end-stage renal disease and in the hypertensive patients of the CAFE study. Antihypertensive treatment has repeatedly demonstrated its ability to prevent cardiovascular events. Whether the effect on cardiovascular events in clinical trials comparing two pharmacological classes or two therapeutic strategies is, at least partly, the result of differential effects on PP remains to be demonstrated. It is therefore of major importance to determine which therapeutic strategies may differentially lower central PP, and in turn reduce cardiovascular events. In clinical practice, lowering PP is often a difficult task, particularly in diabetic hypertensive individuals. In the PARADIS study, we aimed to determine, in a population of hypertensive patients with both type 2 diabetes and PP greater than 60 mmHg, which clinical characteristics predict the fall in PP on treatment and a reduction in cardiovascular events. The reinforcement of therapeutic measures, including a fixed low-dose perindopril/indapamide combination, made possible the effective lowering of PP and cardiovascular events in type 2 diabetic hypertensive patients, under conditions of usual care by general practitioners and specialists.

  20. The effects of scattering and mirror reflectivity on the performance of a ruby laser.

    Science.gov (United States)

    Edwards, J G

    1967-06-01

    The output energy expected from a conventional ruby laser generator with plane parallel mirrors is calculated for a range of excitation energies, pulse lengths, mirror reflectivities and absorption, scattering and reflection losses. A linear dependence of output energy on excitation energy is expected only for a vanishingly small pulse length. The effects of localized losses such as those from reflections at the ends of the crystal are similar to scattering losses distributed through the crystal. The output mirror reflectivity giving maximum output energy falls as the excitation energy and scattering increase but is typically 50-60%. The reduction in output caused by scattering is less for lower reflectivities. The angular distribution of light scattered from the ruby when lasing is measured by varying the resonator length to assess the scattering. The predictions of output energy are in good agreement with experiment for all the excitation energies, introduced scattering losses, and mirror reflectivities tri d, except that above 70% reflectivity the prediction is up to 60% low. Possible reasons for this discrepancy are discussed. It was also found experimentally that the resonances between the ends of the ruby are suppressed when lasing, probably due to the optical inhomogeneities produced by the refractive index changes associated with the population changes during a laser spike. The output energy is thus reduced when the ends are not aligned in the resonator. These dynamic inhomogeneities are thought to override any static inhomogeneities already present in the crystal and are a major source of resonator loss.

  1. Pulse consumption, satiety, and weight management.

    Science.gov (United States)

    McCrory, Megan A; Hamaker, Bruce R; Lovejoy, Jennifer C; Eichelsdoerfer, Petra E

    2010-11-01

    The prevalence of obesity has reached epidemic proportions, making finding effective solutions to reduce obesity a public health priority. One part of the solution could be for individuals to increase consumption of nonoilseed pulses (dry beans, peas, chickpeas, and lentils), because they have nutritional attributes thought to benefit weight control, including slowly digestible carbohydrates, high fiber and protein contents, and moderate energy density. Observational studies consistently show an inverse relationship between pulse consumption and BMI or risk for obesity, but many do not control for potentially confounding dietary and other lifestyle factors. Short-term (≤1 d) experimental studies using meals controlled for energy, but not those controlled for available carbohydrate, show that pulse consumption increases satiety over 2-4 h, suggesting that at least part of the effect of pulses on satiety is mediated by available carbohydrate amount or composition. Randomized controlled trials generally support a beneficial effect of pulses on weight loss when pulse consumption is coupled with energy restriction, but not without energy restriction. However, few randomized trials have been conducted and most were short term (3-8 wk for whole pulses and 4-12 wk for pulse extracts). Overall, there is some indication of a beneficial effect of pulses on short-term satiety and weight loss during intentional energy restriction, but more studies are needed in this area, particularly those that are longer term (≥1 y), investigate the optimal amount of pulses to consume for weight control, and include behavioral elements to help overcome barriers to pulse consumption.

  2. Pulse Consumption, Satiety, and Weight Management1

    Science.gov (United States)

    McCrory, Megan A.; Hamaker, Bruce R.; Lovejoy, Jennifer C.; Eichelsdoerfer, Petra E.

    2010-01-01

    The prevalence of obesity has reached epidemic proportions, making finding effective solutions to reduce obesity a public health priority. One part of the solution could be for individuals to increase consumption of nonoilseed pulses (dry beans, peas, chickpeas, and lentils), because they have nutritional attributes thought to benefit weight control, including slowly digestible carbohydrates, high fiber and protein contents, and moderate energy density. Observational studies consistently show an inverse relationship between pulse consumption and BMI or risk for obesity, but many do not control for potentially confounding dietary and other lifestyle factors. Short-term (≤1 d) experimental studies using meals controlled for energy, but not those controlled for available carbohydrate, show that pulse consumption increases satiety over 2–4 h, suggesting that at least part of the effect of pulses on satiety is mediated by available carbohydrate amount or composition. Randomized controlled trials generally support a beneficial effect of pulses on weight loss when pulse consumption is coupled with energy restriction, but not without energy restriction. However, few randomized trials have been conducted and most were short term (3–8 wk for whole pulses and 4–12 wk for pulse extracts). Overall, there is some indication of a beneficial effect of pulses on short-term satiety and weight loss during intentional energy restriction, but more studies are needed in this area, particularly those that are longer term (≥1 y), investigate the optimal amount of pulses to consume for weight control, and include behavioral elements to help overcome barriers to pulse consumption. PMID:22043448

  3. Standardization of Rocket Engine Pulse Time Parameters

    Science.gov (United States)

    Larin, Max E.; Lumpkin, Forrest E.; Rauer, Scott J.

    2001-01-01

    Plumes of bipropellant thrusters are a source of contamination. Small bipropellant thrusters are often used for spacecraft attitude control and orbit correction. Such thrusters typically operate in a pulse mode, at various pulse lengths. Quantifying their contamination effects onto spacecraft external surfaces is especially important for long-term complex-geometry vehicles, e.g. International Space Station. Plume contamination tests indicated the presence of liquid phase contaminant in the form of droplets. Their origin is attributed to incomplete combustion. Most of liquid-phase contaminant is generated during the startup and shutdown (unsteady) periods of thruster pulse. These periods are relatively short (typically 10-50 ms), and the amount of contaminant is determined by the thruster design (propellant valve response, combustion chamber size, thruster mass flow rate, film cooling percentage, dribble volume, etc.) and combustion process organization. Steady-state period of pulse is characterized by much lower contamination rates, but may be lengthy enough to significantly conh'ibute to the overall contamination effect. Because there was no standard methodology for thruster pulse time division, plume contamination tests were conducted at various pulse durations, and their results do not allow quantifying contaminant amounts from each portion of the pulse. At present, the ISS plume contamination model uses an assumption that all thrusters operate in a pulse mode with the pulse length being 100 ms. This assumption may lead to a large difference between the actual amounts of contaminant produced by the thruster and the model predictions. This paper suggests a way to standardize thruster startup and shutdown period definitions, and shows the usefulness of this approach to better quantify thruster plume contamination. Use of the suggested thruster pulse time-division technique will ensure methodological consistency of future thruster plume contamination test programs

  4. Ibuanyidanda (Complementary Reflection), Communalism and ...

    African Journals Online (AJOL)

    Fr. Prof. Asouzu

    Complementary Reflection, Communalism and Theory Formulation in African Philosophy 9. Ibuanyidanda (Complementary ...... Metaphysics,. Phenomenology and African Philosophy. Lagos: FADEC Publishers, pp.337-355. Van Steenberghen, Fernand. 1952. Ontology. Flynn, Martin J. trans. London: Joseph F. Wagner.

  5. Worldwide Marine Seismic Reflection Profiles

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NGDC maintains a large volume of both Analog and Digital seismic reflection data. Currently only a limited number of lines are available online. Digital data include...

  6. AMXP Pulse variability wih NICER

    Science.gov (United States)

    Bult, Peter

    2017-08-01

    Accreting millisecond X-ray pulsars show a diverse scope variability, including coherent pulsations from the stellar surface and quasi-periodic oscillations attributed to the accretion flow. Because the pulsations are ultimately powered by accreting material, it may be expected that these periodic and quasi-periodic signals show coupled behavior. Observing and characterizing such coupling then gives a unique view of the flow of matter in the closest vicinity of the neutron star surface. In this contribution I will present recently developed specialized methods that can detect such coupling, and discuss how high quality X-ray observations by NICER may enable pulse amplitude modulation studies, and their potential to constrain the physics of accretion.

  7. Academic Training - Pulsed SC Magnets

    CERN Multimedia

    Françoise Benz

    2006-01-01

    2005-2006 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 2, 3, June 29, 30, 31 May, 1, 2 June 11:00-12:00 - Auditorium, bldg 500 Pulsed SC Magnets by M. Wilson Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mech...

  8. The Body as a Pulse

    Directory of Open Access Journals (Sweden)

    Flavia Liberman

    2010-01-01

    Full Text Available The body is the focus of many studies and interventions. Some paradigms conceptualize the body only in relation to its motor-sensory characteristics, while others prioritize its psychological dimensions. With the aim of contributing towards formulating other perspectives within this field, some aspects of Stanley Keleman and Regina Favre's conceptualization of the body are presented here. Starting from clinical situations during seminar groups, we can take the body to be a multifaceted multimedia pulse that is continually [de]constructed through encounters. Together with the author's clinical experiences as an occupational therapist and teacher or undergraduates, these conceptualizations serve as a guide to clinical practice that is thought out, constructed and balanced by the body, using body approaches to promote encounters molded by affections and events, in an attempt to create bodies capable of sustaining the lived intensity of experiences, and which enable self-observation, closeness to other people and production of singularities.

  9. Ranchero Explosive Pulsed Power Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Goforth, J.H.; Atchison, W.L.; Deninger, W.J.; Fowler, C.M.; Herrera, D.H.; King, J.C.; Lopez, E.A.; Oona, H.; Reinovsky, R.E.; Stokes, J.L.; Sena, F.C.; Tabaka, L.J.; Tasker, D.G.; Torres, D.T.; Lindemuth, I.R.; Faehl, R.J.; Keinigs, R.K.; Taylor, A.J.; Rodriguez, G.; Oro, D.M.; Garcia, O.F.; parker, J.V.; Broste, W.B.

    1999-06-27

    The authors are developing the Ranchero high explosive pulsed power (HEPP) system to power cylindrically imploding solid-density liners for hydrodynamics experiments. The near-term goal is to conduct experiments in the regime pertinent to the Atlas Capacitor bank. That is, they will attempt to implode liners of {approximately}50 g mass at velocities approaching 15 km/sec. The basic building block of the HEPP system is a coaxial generator with a 304.8 mm diameter stator, and an initial armature diameter of 152 mm. The armature is expanded by a high explosive (HE) charge detonated simultaneously along its axis. They have reported a variety of experiments conducted with generator modules 43 cm long and have presented an initial design for hydrodynamic liner experiments. In this paper they give a synopsis of their first system test, and a status report on the development of a generator module that is 1.4 m long.

  10. RANCHERO explosive pulsed power experiments

    CERN Document Server

    Goforth, J H; Armijo, E V; Atchison, W L; Bartos, Yu; Clark, D A; Day, R D; Deninger, W J; Faehl, R J; Fowler, C M; García, F P; García, O F; Herrera, D H; Herrera, T J; Keinigs, R K; King, J C; Lindemuth, I R; López, E; Martínez, E C; Martínez, D; McGuire, J A; Morgan, D; Oona, H; Oro, D M; Parker, J V; Randolph, R B; Reinovsky, R E; Rodríguez, G; Stokes, J L; Sena, F C; Tabaka, L J; Tasker, D G; Taylor, A J; Torres, D T; Anderson, H D; Broste, W B; Johnson, J B; Kirbie, H C

    1999-01-01

    The authors are developing the RANCHERO high explosive pulsed power (HEPP) system to power cylindrically imploding solid-density liners for hydrodynamics experiments. Their near-term goal is to conduct experiments in the regime pertinent to the Atlas capacitor bank. That is, they will attempt to implode liners of ~50 g mass at velocities approaching 15 km/sec. The basic building block of the HEPP system is a coaxial generator with a 304.8 mm diameter stator, and an initial armature diameter of 152 mm. The armature is expanded by a high explosive (HE) charge detonated simultaneously along its axis. The authors have reported a variety of experiments conducted with generator modules 43 cm long and have presented an initial design for hydrodynamic liner experiments. In this paper, they give a synopsis of their first system test, and a status report on the development of a generator module that is 1.4 m long. (6 refs).

  11. Ocular pressure waveform reflects ventricular bigeminy and aortic insufficiency

    Directory of Open Access Journals (Sweden)

    Jean B Kassem

    2015-01-01

    Full Text Available Ocular pulse amplitude (OPA is defined as the difference between maximum and minimum intraocular pressure (IOP during a cardiac cycle. Average values of OPA range from 1 to 4 mmHg. The purpose of this investigation is to determine the source of an irregular IOP waveform with elevated OPA in a 48-year-old male. Ocular pressure waveforms had an unusual shape consistent with early ventricular contraction. With a normal IOP, OPA was 9 mmHg, which is extraordinarily high. The subject was examined by a cardiologist and was determined to be in ventricular bigeminy. In addition, he had bounding carotid pulses and echocardiogram confirmed aortic insufficiency. After replacement of the aortic valve, the bigeminy resolved and the ocular pulse waveform became regular in appearance with an OPA of 1.6-2.0 mmHg. The ocular pressure waveform is a direct reflection of hemodynamics. Evaluating this waveform may provide an additional opportunity for screening subjects for cardiovascular anomalies and arrhythmias.

  12. Aerospace applications of pulsed plasmas

    Science.gov (United States)

    Starikovskiy, Andrey

    2012-10-01

    The use of a thermal equilibrium plasma for combustion control dates back more than a hundred years to the advent of internal combustion (IC) engines and spark ignition systems. The same principles are still applied today to achieve high efficiency in various applications. Recently, the potential use of nonequilibrium plasma for ignition and combustion control has garnered increasing interest due to the possibility of plasma-assisted approaches for ignition and flame stabilization. During the past decade, significant progress has been made toward understanding the mechanisms of plasma chemistry interactions, energy redistribution and the nonequilibrium initiation of combustion. In addition, a wide variety of fuels have been examined using various types of discharge plasmas. Plasma application has been shown to provide additional combustion control, which is necessary for ultra-lean flames, high-speed flows, cold low-pressure conditions of high-altitude gas turbine engine (GTE) relight, detonation initiation in pulsed detonation engines (PDE) and distributed ignition control in homogeneous charge-compression ignition (HCCI) engines, among others. The present paper describes the current understanding of the nonequilibrium excitation of combustible mixtures by electrical discharges and plasma-assisted ignition and combustion. Nonequilibrium plasma demonstrates an ability to control ultra-lean, ultra-fast, low-temperature flames and appears to be an extremely promising technology for a wide range of applications, including aviation GTEs, piston engines, ramjets, scramjets and detonation initiation for pulsed detonation engines. To use nonequilibrium plasma for ignition and combustion in real energetic systems, one must understand the mechanisms of plasma-assisted ignition and combustion and be able to numerically simulate the discharge and combustion processes under various conditions.

  13. Laser system using ultra-short laser pulses

    Science.gov (United States)

    Dantus, Marcos [Okemos, MI; Lozovoy, Vadim V [Okemos, MI; Comstock, Matthew [Milford, MI

    2009-10-27

    A laser system using ultrashort laser pulses is provided. In another aspect of the present invention, the system includes a laser, pulse shaper and detection device. A further aspect of the present invention employs a femtosecond laser and binary pulse shaping (BPS). Still another aspect of the present invention uses a laser beam pulse, a pulse shaper and a SHG crystal.

  14. Generation of synchronized signal and pump pulses for an optical ...

    Indian Academy of Sciences (India)

    Abstract. Synchronized signal (650 ps) and pump (1.3 ns) pulses were generated using. 4-pass geometry in a grating pair based pulse stretcher unit. The pump pulse has been further amplified in a high gain regenerative amplifier. This amplified pulse was used as the pump in an optical parametric chirped pulse ...

  15. Impact of blood volume changes within the human skin on the diffuse reflectance measurements in visible and NIR spectral ranges

    Science.gov (United States)

    Zherebtsov, Evgeny; Bykov, Alexander; Popov, Alexey; Doronin, Alexander; Meglinski, Igor

    2017-03-01

    We consider changes in the volume of blood and oxygen saturation caused by a pulse wave and their influence on the diffuse reflectance spectra in the visible/NIR spectral range. CUDA-based Monte-Carlo model was used for routine simulation of detector depth sensitivity (sampling volume) and skin spectra, and their variations associated with physiological changes in the human skin. The results presented in the form of animated graphs of sampling volume changes for scaling of the parameters of the main human skin layers related to the results of experimental measurements are of particular interest for pulse oximetry, photoplethysmography, Doppler flowmetry, reflectance spectroscopy.

  16. High-Altitude Electromagnetic Pulse (HEMP) Testing

    Science.gov (United States)

    2015-07-09

    Final 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Test Operations Procedure (TOP) 01-2-620A High-Altitude Electromagnetic Pulse ( HEMP ...planning and execution of testing Army/DOD equipment to determine the effects of Horizontal Component High Altitude Electromagnetic Pulse ( HEMP ...5 2.3 HEMP Pre/Post Test Illuminations ..................................................... 7 3. REQUIRED TEST

  17. Fast Heat Pulse Propagation by Turbulence Spreading

    DEFF Research Database (Denmark)

    Naulin, Volker; Juul Rasmussen, Jens; Mantica, Paola

    2009-01-01

    The propagation of a cold pulse initiated by edge cooling in JET is compared to propagation of the heat wave originating from a modulation of the heating source roughly at mid radius. It is found that the propagation of the cold pulse is by far faster than what could be predicted on the basis of ...

  18. Field mapping of ballistic pressure pulse sources

    Directory of Open Access Journals (Sweden)

    Rad Abtin Jamshidi

    2015-09-01

    Full Text Available Ballistic pressure pulse sources are used since late 1990s for the extracorporeal treatment of chronic Enthesitis. Newly indications are found in trigger-point-therapy for the treatment of musculoskeletal disorders. In both applications excellent results without relevant side effects were found in clinical trials. The technical principle of pressure pulse source is based on the same techniques used in air guns. A projectile is accelerated by pressurized air and hits the applicator with high kinetic energy. By this a compression wave travels through the material and induces a fast (4..5μs, almost singular pressure pulse of 2..10 MPa, which is followed by an equally short rarefaction phase of about the same amplitude. It is assumed that the pressure pulse accounts for the biomedical effects of the device. The slower inertial motion of the waveguide is damped by elastic stoppers, but still can be measured several micro seconds after the initial pressure pulse. In order to characterize the pressure pulse devices, field mapping is performed on several radial pressure pulse sources using the fiber optic hydrophone and a polyvinylidenfluorid (PVDF piezoelectric hydrophone. It could be shown that the current standard (IEC 61846 is not appropriate for characterization of ballistic pressure pulse sources.

  19. Pulsed laser deposition: metal versus oxide ablation

    NARCIS (Netherlands)

    Doeswijk, L.M.; Rijnders, Augustinus J.H.M.; Blank, David H.A.

    2004-01-01

    We present experimental results of pulsed laser interaction with metal (Ni, Fe, Nb) and oxide (TiO2, SrTiO3, BaTiO3) targets. The influence of the laser fluence and the number of laser pulses on the resulting target morphology are discussed. Although different responses for metal and oxide targets

  20. Nasal pulse oximetry overestimates oxygen saturation

    DEFF Research Database (Denmark)

    Rosenberg, J; Pedersen, M H

    1990-01-01

    Ten surgical patients were monitored with nasal and finger pulse oximetry (Nellcor N-200) for five study periods with alternating mouth and nasal breathing and switching of cables and sensors. Nasal pulse oximetry was found to overestimate arterial oxygen saturation by 4.7 (SD 1.4%) (bias...

  1. Pulsed electric field inactivation in a microreactor

    NARCIS (Netherlands)

    Fox, M.B.

    2006-01-01

    Pulsed electric fields (PEF) is a novel, non-thermal pasteurization method which uses short, high electric field pulses to inactivate microorganisms. The advantage of a pasteurization method like PEF compared to regular heat pasteurization is that the taste, flavour, texture and nutritional value

  2. High reliability low jitter pulse generator

    Science.gov (United States)

    Savage, Mark E.; Stoltzfus, Brian S.

    2013-01-01

    A method and concomitant apparatus for generating pulses comprising providing a laser light source, disposing a voltage electrode between ground electrodes, generating laser sparks using the laser light source via laser spark gaps between the voltage electrode and the ground electrodes, and outputting pulses via one or more insulated ground connectors connected to the voltage electrode.

  3. Spectral Lag Evolution among -Ray Burst Pulses

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... We analyse the spectral lag evolution of -ray burst (GRB) pulses with observations by CGRO/BATSE. No universal spectral lag evolution feature and pulse luminosity-lag relation within a GRB is observed.Our results suggest that the spectral lag would be due to radiation physics and dynamics of a given ...

  4. Influence of pulse electrodeposition parameters on microhardness ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 5. Influence of ... size rose. The optimum value for pulse frequency was about 25 Hz. Results showed that microhardness of nanocomposite coatings which were produced by pulse current method was higher than that of produced by direct currentmethod.

  5. Development of pulse diagnostic devices in Korea

    Directory of Open Access Journals (Sweden)

    Hyunho Kim

    2013-03-01

    Full Text Available In Korean medicine, pulse diagnosis is one of the important methods for determining the health status of a patient. For over 40 years, electromechanical pulse diagnostic devices have been developed to objectify and quantify pulse diagnoses. In this paper, we review previous research and development for pulse diagnostic devices according to various fields of study: demand analysis and current phase, literature studies, sensors, actuators, systems, physical quantity studies, clinical studies, and the U-health system. We point out some confusing issues that have been naively accepted without strict verification: original pressure pulse waveform and derivative pressure pulse waveform, pressure signals and other signal types, and minutely controlled pressure exertion issues. We then consider some technical and clinical issues to achieve the development of a pulse diagnostic device that is appropriate both technically and in terms of Korean medicine. We hope to show the history of pulse diagnostic device research in Korea and propose a proper method to research and develop these devices.

  6. Estimation of pulse heights and arrival times

    NARCIS (Netherlands)

    Kwakernaak, H.

    1980-01-01

    The problem is studied of estimating the arrival times and heights of pulses of known shape observed with white additive noise. The main difficulty is estimating the number of pulses. When a maximum likelihood formulation is employed for the estimation problem, difficulties similar to the problem of

  7. AN UPDATE ON NIF PULSED POWER

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, P A; James, G F; Petersen, D E; Pendleton, D L; McHale, G B; Barbosa, F; Runtal, A S; Stratton, P L

    2009-06-22

    The National Ignition Facility (NIF) is a 192-beam laser fusion driver operating at Lawrence Livermore National Laboratory. NIF relies on three large-scale pulsed power systems to achieve its goals: the Power Conditioning Unit (PCU), which provides flashlamp excitation for the laser's injection system; the Power Conditioning System (PCS), which provides the multi-megajoule pulsed excitation required to drive flashlamps in the laser's optical amplifiers; and the Plasma Electrode Pockels Cell (PEPC), which enables NIF to take advantage of a fourpass main amplifier. Years of production, installation, and commissioning of the three NIF pulsed power systems are now complete. Seven-day-per-week operation of the laser has commenced, with the three pulsed power systems providing routine support of laser operations. We present the details of the status and operational experience associated with the three systems along with a projection of the future for NIF pulsed power.

  8. The resonant multi-pulse ionization injection

    Science.gov (United States)

    Tomassini, Paolo; De Nicola, Sergio; Labate, Luca; Londrillo, Pasquale; Fedele, Renato; Terzani, Davide; Gizzi, Leonida A.

    2017-10-01

    The production of high-quality electron bunches in Laser Wake Field Acceleration relies on the possibility to inject ultra-low emittance bunches in the plasma wave. In this paper, we present a new bunch injection scheme in which electrons extracted by ionization are trapped by a large-amplitude plasma wave driven by a train of resonant ultrashort pulses. In the Resonant Multi-Pulse Ionization injection scheme, the main portion of a single ultrashort (e.g., Ti:Sa) laser system pulse is temporally shaped as a sequence of resonant sub-pulses, while a minor portion acts as an ionizing pulse. Simulations show that high-quality electron bunches with normalized emittance as low as 0.08 mm × mrad and 0.65% energy spread can be obtained with a single present-day 100TW-class Ti:Sa laser system.

  9. Digital gate pulse generator for cycloconverter control

    Science.gov (United States)

    Klein, Frederick F.; Mutone, Gioacchino A.

    1989-01-01

    The present invention provides a digital gate pulse generator which controls the output of a cycloconverter used for electrical power conversion applications by determining the timing and delivery of the firing pulses to the switching devices in the cycloconverter. Previous gate pulse generators have been built with largely analog or discrete digital circuitry which require many precision components and periodic adjustment. The gate pulse generator of the present invention utilizes digital techniques and a predetermined series of values to develop the necessary timing signals for firing the switching device. Each timing signal is compared with a reference signal to determine the exact firing time. The present invention is significantly more compact than previous gate pulse generators, responds quickly to changes in the output demand and requires only one precision component and no adjustments.

  10. Pulse Shepherding in Nonlinear Fiber Optics

    Science.gov (United States)

    Yeh, C.; Bergman, L.

    1996-01-01

    In a wavelength division multiplexed fiber system, where pulses on different wavelength beams may co-propagate in a single mode fiber, the cross-phase-modulation (CPM) effects caused by the nonlinearity of the optical fiber are unavoidable. In other words, pulses on different wavelength beams can interact with and affect each other through the intensity dependence of the refractive index of the fiber. Although CPM will not cause energy to be exchanged among the beams, the pulse shapes and locations on these beams can be altered significantly. This phenomenon makes possible the manipulation and control of pulses co-propagating on different wavelength beams through the introduction of a shepherd pulse at a separate wavelength. How this can be accomplished is demonstrated in this paper.

  11. Exawatt-Zettawatt Pulse Generation and Applications

    CERN Document Server

    Mourou, G A; Malkin, V M; Toroker, Z; Khazanov, E A; Sergeev, A M; Tajima, T

    2011-01-01

    A new amplification method, weaving the three basic compression techniques, Chirped Pulse Amplification (CPA), Optical Parametric Chirped Pulse Amplification (OPCPA) and Plasma Compression by Backward Raman Amplification (BRA) in plasma, is proposed. It is called C3 for Cascaded Conversion Compression. It has the capability to compress with good efficiency kilojoule to megajoule, nanosecond laser pulses into femtosecond pulses, to produce exawatt and beyond peak power. In the future, C3 could be used at large-scale facilities such as the National Ignition Facility (NIF) or the Laser Megajoule (LMJ) and open the way to zettawatt level pulses. The beam will be focused to a wavelength spot size with a f#1. The very small beam size, i.e. few centimeters, along with the low laser repetition rate laser system will make possible the use of inexpensive, precision, disposable optics. The resulting intensity will approach the Schwinger value, thus opening up new possibilities in fundamental physics.

  12. Methods for High Power EM Pulse Measurement

    Directory of Open Access Journals (Sweden)

    P. Fiala

    2006-12-01

    Full Text Available There are some suitable methods for the measurement of ultra-short solitary electromagnetic pulses that can be generated by high power pulsed generators. The measurement methods properties have to correspond to the fact whether we want to measure pulses of voltage, current or free-space electromagnetic wave. The need for specific measurement methods occurred by the development of high power microwave pulse generator. Applicable methods are presented in this paper. The method utilizing Faraday's induction law allows the measurement of generated current. For the same purpose the magneto-optic method can be utilized, with its advantages. For measurement of output microwave pulse of the generator the calorimetric method was designed and realized.

  13. One laser pulse generates two photoacoustic signals

    CERN Document Server

    Gao, Fei; Zheng, Yuanjin

    2016-01-01

    Photoacoustic sensing and imaging techniques have been studied widely to explore optical absorption contrast based on nanosecond laser illumination. In this paper, we report a long laser pulse induced dual photoacoustic (LDPA) nonlinear effect, which originates from unsatisfied stress and thermal confinements. Being different from conventional short laser pulse illumination, the proposed method utilizes a long square-profile laser pulse to induce dual photoacoustic signals. Without satisfying the stress confinement, the dual photoacoustic signals are generated following the positive and negative edges of the long laser pulse. More interestingly, the first expansion-induced photoacoustic signal exhibits positive waveform due to the initial sharp rising of temperature. On the contrary, the second contraction-induced photoacoustic signal exhibits exactly negative waveform due to the falling of temperature, as well as pulse-width-dependent, signal amplitude which is caused by the concurrent heat accumulation and ...

  14. Description of pulse propagation in a dispersive medium by use of a pulse quality factor.

    Science.gov (United States)

    Rousseau, Guy; McCarthy, Nathalie; Pichãé, Michel

    2002-09-15

    We investigated how the duration of short laser pulses evolves in a dispersive material, using rms widths and a propagation law based on a pulse quality factor. Experiments were carried out with femtosecond pulses (10 to 25fs at the temporal waist) propagating in bulk fused silica. Excellent agreement was found between theory and experiment. This approach does not require complete characterization of laser pulses and eliminates the need for any assumption regarding the interpretation of autocorrelation traces. The method is of general validity, and it can be applied to pulses of arbitrary shape.

  15. On the origin of pulsed emission from the young supernova remnant SN 1987A

    Energy Technology Data Exchange (ETDEWEB)

    Ruderman, M.; Kluzniak, W.; Shaham, J. (Columbia Univ., New York, NY (USA))

    1989-11-01

    To overcome difficulties in understanding the origin of the sub-msec optical pulses from SN 1987A, a model similar to that of Kundt and Krotscheck (1977) for pulsed synchotron emission from the Crab is applied. The interaction of the expected ultrarelativistic electron-positron pulsar wind with pulsar dipole EM wave or wind-carried toroidal magnetic field reflected from the walls of the expected pulsar cavity within the SN 1987A nebula can generate pulsed optical emission with efficiency at most 0.001. The maximum luminosity of the source is reproduced, and other observational constraints can be satisfied for an average wind energy flow of about 10 to the 38th erg/sec sr and for wind electron Lorentz factor gamma of about 100,000. This model applied to the Crab yields pulsations of much lower luminosity and frequency. 17 refs.

  16. Pulsed laser heating of silicon-nitride capped GaAs: Optical properties at high temperature

    Science.gov (United States)

    Bhat, A.; Yao, H. D.; Compaan, A.; Horak, A.; Rys, A.

    1988-09-01

    The optical properties of silicon nitride and gallium arsenide were studied at temperatures up to and beyond the melting point of GaAs by means of laser heating. XeCl excimer and pulsed dye laser pulses, ˜10 ns in duration, were used to heat the semiconductor under nitride capping layers of varying thickness. The transient reflectivity response at 514.5 nm was used together with a multilayer interference analysis to obtain the optical constants of solid and molten GaAs and of solid Si3N4 near the 1513-K melting point of GaAs. In addition, we report the melt duration as a function of laser pulse energy for GaAs with and without capping layers.

  17. Associations between plasma fibulin-1, pulse wave velocity and diabetes in patients with coronary heart disease

    DEFF Research Database (Denmark)

    Hansen, Maria Lyck; Rasmussen, Lars Melholt

    2015-01-01

    BACKGROUND: Diabetes is related to increased risk of cardiovascular disease, and arterial stiffness and its consequences may be the factor connecting the two. Arterial stiffness is often measured by carotid-femoral pulse wave velocity (cf-PWV), but no plasma biomarker reflecting arterial stiffness...... undergoing coronary artery bypass grafting. METHODS: Pulse wave velocity (PWV) and pulse wave analysis including augmentation index (Aix75) was measured in 273 patients, who subsequently underwent a coronary by-pass operation. Plasma samples were drawn and information was gathered on diabetes status, HbA1c...... indices are not directly related in patients with cardiac disease, despite the fact that both measures are increased among patients with diabetes....

  18. Reflections

    Indian Academy of Sciences (India)

    human being - creativity and freedom - presupposing the existence of a human mind. His views, in turn, originate from his thinking about the nature of language which has been exercising his mind from the late. f0I1ies. Chomsky'S prominence as a socio-political thinker has completely overshadowed his professional status ...

  19. Reflections

    Indian Academy of Sciences (India)

    looking back, such a burst of creativity from a single mind in a single year is probably unparalled in our times. The 1905 volume of Annalen de, Physik stands to tell us that all this really happened. Ra;a,am Nityananda. Raman Research Institute, Bangalore 560 080, India. Why does this magnificent applied science, which ...

  20. Reflections

    Indian Academy of Sciences (India)

    Almost single handedly, he tackled all the administrative, infrastructural, and other daily nitty gritty problems of the whole department. From the very beginning, I devoted all my time to whatever work Prof Mitra assigned to me and my dedication came from a sense of gratitude to this great man for giving me an opportunity to ...

  1. Reflections

    Indian Academy of Sciences (India)

    2004-04-01

    Apr 1, 2004 ... climates, for example, those of Greenland, Iceland and the Faroe Islands on the one side and, on the other, the flora of the hot and arid African Sahara near Timbuctoo: regions where the struggle for existence is keenest and 'natural selection' of the hardiest forms takes place. Empetrum hermaphroditum, a ...

  2. Reflections

    Indian Academy of Sciences (India)

    senses - the tactile when we touch keys, the oral when we speak or listen, the visual when we read. Is it not possible that some day the path may be established more directly? We know that when the eye sees, all the consequent information is transmitted to the brain by means of electrical vibrations in the channel of the ...

  3. Reflections

    Indian Academy of Sciences (India)

    The following article by Norbert Wiener makes two points - the first explains the possibility of making computer programs 'human like' by building in learning and adaptfvity in them; the second cautions us on the danger that may arise due to the large difference in time constant between human thinking and action and ...

  4. Reflections

    Indian Academy of Sciences (India)

    (i) strong interactions (ii) electromagnetic interactions (iii) weak interactions (iv) gravitational interaction. As for the basic constituents, ... Further, the electromagnetic and the weak interactions are unified into a single force called the electroweak force. This is reminiscent ... immense problems facing India. It may be noted here ...

  5. REFLECTIONS

    African Journals Online (AJOL)

    Convention, humanitarian law, human rights and codes of conduct with emphasis on humanitarian assistance. Food aid as a development tool is questioned, and what will happen when food aid is drying out. The books provide a comprehensive analysis and are highly recommended. Key words: Food aia'; human security;.

  6. Reflections

    Indian Academy of Sciences (India)

    communication. However, the machine techniques of the present day have invaded the latter fields as well, so that the actual machine oftoday is very different from the image that. Butler held, and we cannot .... losing conflict to which his assumption of the best possible strategy on the part of his enemy would have doomed ...

  7. Reflections

    Indian Academy of Sciences (India)

    but tookno active part and made no speeches. I usually voted for a strike, and considered ..... L S Jacobsen, came to me from the Motor Division, and told me that in the engines of a certain type designed by his department the main ..... California with its warm climate and southern vegetation. We left Ann Arbor without regret.

  8. Reflections

    DEFF Research Database (Denmark)

    du Gay, Paul; Vikkelsø, Signe

    2012-01-01

    The notion of ‘change’ has become pervasive in contemporary organizational discourse. On the one hand, change is represented as an organizational imperative that increasingly appears to trump all other concerns. On the other hand, change is addressed as an abstract, generic entity that can be the...

  9. Reflections

    National Research Council Canada - National Science Library

    Jim Walsh

    2008-01-01

    ....) I imagine that valet parking will become very fashionable at upper end drinking establishments, and at blue collar shot-and-beer joints all across the rust belt, cars will be left idling in parking...

  10. Reflections

    Science.gov (United States)

    Greiner, Walter

    2012-01-01

    This symposium was very special. It was topical: Some of the most outstanding problems in Nuclear Physics were discussed: Superheavy elements; extremely neutron rich elements, as well as nuclei with strangeness and their possible creation in the cosmos and on earth; the nuclear equation of state has to be identified within strongly compressed and hot nuclear matter as it appears in nucleus-nucleus encounters; giant nuclear systems which are short lived (˜ 10-19 - 10-20 seconds) and extremely important for identifying the vacuum decay in overcritical electric fields (this is a very fundamental process - the most fundamental one in Quantum Electrodynamics!); astrophysical centers of extreme high density around which magnificent sun-like objects are Kepler-orbiting are discovered in our Galaxy by R. Genzel and colleagues (these centers are no black holes those don't exist at all because repulsive gravitational forces may play an important role - the pseudocomplex general relativity eliminates the Schwarzschild singularity); network physics for distributing energy (nuclear, wind, sun, tides,...) all over Europe (and over the world) is basic for energy consumption now and even more so in future. We heard wonderful talks and I am grateful to all the friends and speakers (from Russia, America, Europe and India) for coming to Goa. It was a great symposium! Particular thanks go to Professor Bikash Sinha and especially to Professor Debades Bandyopadhyay from Calcutta who had the idea for and organized this Goa-symposium....

  11. Reflections

    Indian Academy of Sciences (India)

    The great Immanuel Kant, the philosopher of the. Enlightenment, set oot to explain why Galilean-Newtonian physics was so successful. At that time there were two contrasting philosophies concerning our knowledge of nature - the rationalist which believed that nature was subordinate to and had to obey reason; and.

  12. Reflections

    Indian Academy of Sciences (India)

    the environment. A very large part of the evolutionary progress, both biologically and culturally, has come from adversity. Life faces environments which are more often niggardly .... by teaching and learning, instead of by genes. The ability ... not even insure the survival of the population or the species when the environment.

  13. First experimental implementation of pulse shaping for neutron diffraction on pulsed sources

    Energy Technology Data Exchange (ETDEWEB)

    Russina, M. [Helmholtz-Zentrum-Berlin, Hahn-Meitner Platz 1, 14109 Berlin (Germany); Kali, Gy.; Santa, Zs. [HAS Research Institute for Solid State Physics, Konkoly Thege ut. 29-33, 1121 Budapest (Hungary); Mezei, F., E-mail: f.mezei@esshungary.eu [HAS Research Institute for Solid State Physics, Konkoly Thege ut. 29-33, 1121 Budapest (Hungary); European Spallation Source ESS AB, P.O. Box 176, 22100 Lund (Sweden)

    2011-10-21

    One of the central issues in the design and the use of pulsed neutron sources is the control of pulse length in elastic scattering experiments, most significantly diffraction on crystalline matter. On the existing short pulse spallation sources the strongly wavelength dependent source pulse length that determines the resolution is permanently fixed on each beam line by the type of the moderator it faces. We have experimentally implemented for the first time the wavelength frame multiplication (WFM) multiplexing chopper method, an earlier proposed variant of the by now fully tested repetition rate multiplication technique for inelastic scattering spectroscopy on pulsed neutron sources. We have operated the time-of-flight diffractometer at the continuous reactor source at BNC in an unconventional multiplexing mode that emulates a pulsed source. As a full proof of principle of the WFM method we have experimentally demonstrated the extraction from each source pulse a series of polychromatic, chopper shaped neutron pulses, which can continuously cover any wavelength band. The achieved 25 {mu}s FWHM pulse length is shorter than that can be obtained at all at short pulse spallation sources for cold neutrons. The method allows us to build efficient, high and variable resolution diffractometers at long pulse spallation sources.

  14. Unstable and Multiple Pulsing Can Be Invisible to Ultrashort Pulse Measurement Techniques

    Directory of Open Access Journals (Sweden)

    Michelle Rhodes

    2016-12-01

    Full Text Available Multiple pulsing occurs in most ultrashort-pulse laser systems when pumped at excessively high powers, and small fluctuations in pump power in certain regimes can cause unusual variations in the temporal separations of sub-pulses. Unfortunately, the ability of modern intensity-and-phase pulse measurement techniques to measure such unstable multi-pulsing has not been studied. Here we report calculations and simulations finding that allowing variations in just the relative phase of a satellite pulse causes the second pulse to completely disappear from a spectral interferometry for direct electric field reconstruction (SPIDER measurement. We find that, although neither frequency-resolved optical gating (FROG nor autocorrelation can determine the precise properties of satellite pulses due to the presence of instability, they always succeed in, at least, seeing the satellite pulses. Also, additional post-processing of the measured FROG trace can determine the correct approximate relative height of the satellite pulse and definitively indicate the presence of unstable multiple-pulsing.

  15. New Assessment Model of Pulse Depth Based on Sensor Displacement in Pulse Diagnostic Devices

    Directory of Open Access Journals (Sweden)

    Jang-Han Bae

    2013-01-01

    Full Text Available An accurate assessment of the pulse depth in pulse diagnosis is vital to determine the floating and sunken pulse qualities (PQs, which are two of the four most basic PQs. In this work, we proposed a novel model of assessing the pulse depth based on sensor displacement (SD normal to the skin surface and compared this model with two previous models which assessed the pulse depth using contact pressure (CP. In contrast to conventional stepwise CP variation tonometry, we applied a continuously evolving tonometric mechanism at a constant velocity and defined the pulse depth index as the optimal SD where the largest pulse amplitude was observed. By calculating the pulse depth index for 18 volunteers, we showed that the pulse was deepest at Cheok (significance level: P<0.01, while no significant difference was found between Chon and Gwan. In contrast, the two CP-based models estimated that the pulse was shallowest at Gwan (P<0.05. For the repeated measures, the new SD-based model showed a smaller coefficient of variation (CV≈7.6% than the two CP-based models (CV≈13.5% and 12.3%, resp.. The SD-based pulse depth assessment is not sensitive to the complex geometry around the palpation locations and temperature variation of contact sensors, which allows cost-effective sensor technology.

  16. Synchronization of picosecond laser pulses to the target X-ray pulses at SPring-8

    CERN Document Server

    Tanaka, Y; Kitamura, H; Ishikawa, T

    2001-01-01

    Synchronization system between an intense picosecond laser and the target X-ray pulses has been developed at SPring-8. The intense laser pulses were obtained by amplification of the pulses picked up from a mode-locked Ti:sapphire laser synchronized with the radio frequency of the storage ring. The repetition rate of amplified laser pulses was controlled to be 1/n of the RF, where n is a multiple of the number of RF buckets in the ring, so that the laser pulses meet the SR pulses originated from a particular electron bunch in partial filling patterns. The temporal overlap of the laser and the target X-ray pulses was achieved as monitored with a streak camera in synchroscan and repetitive single shot operation modes, and was stable with a precision of a few ps for several hours.

  17. Residual stress reduction by combined treatment of pulsed magnetic field and pulsed current

    Energy Technology Data Exchange (ETDEWEB)

    Cai Zhipeng, E-mail: czpdme@gmail.com [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Huang Xinquan [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2011-07-25

    Highlights: {yields} The combination of magnetic field and current releases stress significantly. {yields} Both magneto and electro-plasticity may exit in the combined treatment. {yields} Stress increase caused by current should be studied later. - Abstract: This paper reports a significant decrease on residual stress by combined treatment of a pulsed magnetic field and a pulse current on steel samples with pre-induced residual stress conditions, compared to a separately single treatment by either the pulsed magnetic field or the pulsed current. Briefly, 10% stress decrease by pulsed magnetic field treatment and 20% increase by pulsed current treatment were observed respectively. While 60% stress release is achieved by the combined treatments, in which the same magnetic field and current parameters were applied. It is supposed that the magnetic field facilitates dislocations depinning and pulsed current provides conduction electrons to drive dislocations to move further and faster. The combined effects lead to electro-magneto-plasticity and further residual stress release.

  18. CTS and CZTS for solar cells made by pulsed laser deposition and pulsed electron deposition

    DEFF Research Database (Denmark)

    Ettlinger, Rebecca Bolt

    This thesis concerns the deposition of thin films for solar cells using pulsed laser deposition (PLD) and pulsed electron deposition (PED). The aim was to deposit copper tin sulfide (CTS) and zinc sulfide (ZnS) by pulsed laser deposition to learn about these materials in relation to copper zinc tin......, which make them promising alternatives to the commercially successful solar cell material copper indium gallium diselenide (CIGS). Complementing our group's work on pulsed laser deposition of CZTS, we collaborated with IMEM-CNR in Parma, Italy, to deposit CZTS by pulsed electron deposition for the first...... of using pulsed electron deposition was to make CZTS at a low processing temperature, avoiding the 570 °C annealing step used for our pulsed laser deposited solar cells. Preliminary solar cells had an efficiency of 0.2 % with a 300 °C deposition step without annealing. Further process control is needed...

  19. Single pulse frequency compounding protocol for superharmonic imaging

    Science.gov (United States)

    Danilouchkine, M. G.; van Neer, P. L. M. J.; Verweij, M. D.; Matte, G. M.; Vletter, W. B.; van der Steen, A. F. W.; de Jong, N.

    2013-07-01

    Second harmonic imaging is currently accepted as the standard in commercial echographic systems. A new imaging technique, coined as superharmonic imaging (SHI), combines the third till the fifth harmonics, arising during nonlinear sound propagation. It could further enhance the resolution and quality of echographic images. To meet the bandwidth requirement for SHI a dedicated phased array has been developed: a low frequency subarray, intended for transmission, interleaved with a high frequency subarray, used in reception. As the bandwidth of the elements is limited, the spectral gaps in between the harmonics cause multiple (ghost) reflection artifacts. A dual-pulse frequency compounding method aims at suppressing those artifacts at a price of a reduced frame rate. In this study we explore a possibility of performing frequency compounding within a single transmission. The traditional frequency compounding method suppresses the ripples by consecutively emitting two short Gaussian bursts with a slightly different center frequency. In the newly proposed method, the transmit aperture is divided into two parts: the first half is used to send a pulse at the lower center frequency, while the other half simultaneously transmits at a slightly higher center frequency. The suitability of the protocol for medical imaging applications in terms of the steering capabilities was performed in a simulation study with INCS and the hydrophone measurements. Moreover, an experimental study was carried out to find the optimal parameters for the clinical imaging protocol. The latter was subsequently used to obtain the images of a tissue mimicking phantom containing strongly reflecting wires. Additionally, the images of a human heart in the parasternal projection were acquired. The scanning aperture with the developed protocol amounts to approximately 90°, which is sufficient to capture the cardiac structures in the standard anatomical projections. The theoretically estimated and

  20. Low reflectance radio frequency load

    Science.gov (United States)

    Ives, R. Lawrence; Mizuhara, Yosuke M

    2014-04-01

    A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.

  1. Longitudinally excited CO2 laser with short laser pulse operating at high repetition rate

    Science.gov (United States)

    Li, Jianhui; Uno, Kazuyuki; Akitsu, Tetsuya; Jitsuno, Takahisa

    2016-11-01

    A short-pulse longitudinally excited CO2 laser operating at a high repetition rate was developed. The discharge tube was made of a 45 cm-long or 60 cm-long dielectric tube with an inner diameter of 16 mm and two metallic electrodes at the ends of the tube. The optical cavity was formed by a ZnSe output coupler with a reflectivity of 85% and a high-reflection mirror. Mixed gas (CO2:N2:He = 1:1:2) was flowed into the discharge tube. A high voltage of about 33 kV with a rise time of about 200 ns was applied to the discharge tube. At a repetition rate of 300 Hz and a gas pressure of 3.4 kPa, the 45 cm-long discharge tube produced a short laser pulse with a laser pulse energy of 17.5 mJ, a spike pulse energy of 0.2 mJ, a spike width of 153 ns, and a pulse tail length of 90 μs. The output power was 5.3 W. The laser pulse waveform did not depend on the repetition rate, but the laser beam profile did. At a low repetition rate of less than 50 Hz, the laser beam had a doughnut-like shape. However, at a high repetition rate of more than 150 Hz, the discharge concentrated at the center of the discharge tube, and the intensity at the center of the laser beam was higher. The laser beam profile depended on the distribution of the discharge. An output power of 7.0 W was achieved by using the 60 cm-long tube.

  2. Plasma Mirrors for Cleaning Laser Pulses from the Infrared to the Ultraviolet

    Science.gov (United States)

    Földes, István B.; Gilicze, Barnabás; Kovács, Zsolt; Szatmári, Sándor

    2018-01-01

    Ultrashort laser pulses are generally preceded by prepulses which - in case of high main pulse intensities - may generate preplasmas on solid surfaces, thus making the initial conditions for the interactions ambiguous. Infrared laser systems applied successfully, with high efficiency self-induced plasma mirrors for improving the contrast of the beam. Short wavelength laser beams however have a larger critical density in the plasma, and due to their deeper penetration the absorption is higher, the reflectivity, and the corresponding plasma mirror efficiency is lower. We show herewith that with carefully planned boundary conditions plasma mirrors can reach up to 70% efficiency even for KrF laser radiation. Our observations can be qualitatively explained by the classical Drude model. The high reflectivity allows the use of plasma mirrors even after the final amplification or before the last amplifier. Different arrangement proposals for its integration to our high power KrF laser system are given as well.

  3. Intrasubject variability in power reflectance.

    Science.gov (United States)

    Abur, Defne; Horton, Nicholas J; Voss, Susan E

    2014-05-01

    Power reflectance measurements are an active area of research related to the development of noninvasive middle-ear assessment methods. There are limited data related to test-retest measures of power reflectance. This study investigates test-retest features of power reflectance, including comparisons of intrasubject versus intersubject variability and how ear-canal measurement location affects measurements. Repeated measurements of power reflectance were made at about weekly intervals. The subjects returned for four to eight sessions. Measurements were made at three ear-canal locations: a deep insertion depth (with a foam plug flush at the entrance to the ear canal) and both 3 and 6 mm more lateral to this deep insertion. Repeated measurements on seven subjects are reported. All subjects were female, between 19 and 22 yr old, and enrolled at an undergraduate women's college. Measurements on both the right and left ears were made at three ear-canal locations during each of four to eight measurement sessions. Random-effects regression models were used for the analysis to account for repeated measures within subjects. The mean power reflectance for each position over all sessions was calculated for each subject. The comparison of power reflectance from the left and right ears of an individual subject varied greatly over the seven subjects; the difference between the power reflectance measured on the left and that measured on the right was compared at 248 frequencies, and depending on the subject, the percentage of tested frequencies for which the left and right ears differed significantly ranged from 10% to 93% (some with left values greater than right values and others with the opposite pattern). Although the individual subjects showed left-right differences, the overall population generally did not show significant differences between the left and right ears. The mean power reflectance for each measurement position over all sessions depended on the location of the

  4. Laser-induced damage of multilayer dielectric for broadband pulse compression grating

    Science.gov (United States)

    Kong, Fanyu; Chen, Shunli; Liu, Shijie; Jin, Yunxia; Guan, Heyuan; Du, Ying; Wei, Chaoyang; He, Hongbo; Yi, Kui

    2012-01-01

    The multilayer dielectrics (MLDs) for broad bandwidth 800nm pulse compression gratings were fabricated with optimized design by electron beam evaporation using three different kinds of materials (Ta2O5/SiO2/HfO2), which had more than 99% reflectance with bandwidth larger than 160nm around the center wavelength of 800 nm and high transmission at the exposure wavelength of 413nm. Laser-induced damage behaviors of the mirrors were investigated. It was found that the laser-induced damage threshold (LIDT) of the samples could reach 1.0J/cm2 and 2.0J/cm2 in the normal beam (57 degrees, TE mode) at pulse duration of 50fs and 120fs, respectively. The depth information of the damage sites at these two cases was explored by atomic force microscope (AFM). The reason of the sample having so high LIDT was also discussed in this paper. The MLDs provide a solid base for the high laser threshold 800nm pulse compression gratings and may open a new way for broad bandwidth 800nm reflectance coatings used in the ultrashort pulse laser system.

  5. Laser Spot Welding of Copper-aluminum Joints Using a Pulsed Dual Wavelength Laser at 532 and 1064 nm

    Science.gov (United States)

    Stritt, Peter; Hagenlocher, Christian; Kizler, Christine; Weber, Rudolf; Rüttimann, Christoph; Graf, Thomas

    A modulated pulsed laser source emitting green and infrared laser light is used to join the dissimilar metals copper and aluminum. The resultant dynamic welding process is analyzed using the back reflected laser light and high speed video observations of the interaction zone. Different pulse shapes are applied to influence the melt pool dynamics and thereby the forming grain structure and intermetallic phases. The results of high-speed images and back-reflections prove that a modulation of the pulse shape is transferred to oscillations of the melt pool at the applied frequency. The outcome of the melt pool oscillation is shown by the metallurgically prepared cross-section, which indicates different solidification lines and grain shapes. An energy-dispersivex-ray analysis shows the mixture and the resultant distribution of the two metals, copper and aluminum, within the spot weld. It can be seen that the mixture is homogenized the observed melt pool oscillations.

  6. Phase-coded pulse expander-compressor

    Science.gov (United States)

    Lewis, B. L.

    1985-04-01

    A pulse expansion and compression system, especially useful for radar ranging, comprising a pulse coder for expanding an input pulse and a pulse compressor of the matched-filter type. The coder consists of a plurality of delay stages into which the input pulse is fed, a discrete Fourier transform (DFT) circuit to which the output signals of the delay stages are fed by way of respective phase weights and for which every other frequency port is inverted prior to entry to a time-dispersion-means (TDM) comprising an arrangement of adders interconnected by delay stages for differently delaying the output signals from the DFT. The adders are connected in N/2-fold cyclically permutated order to the frequency ports, where N is the number of frequency ports if that number is even, and N is the number of frequency ports less one if that number is odd. The TDM output is fed to a phase modulator and then to the transmitter. The echo signals are conjugated, time-inverted, and passed through the same DFT as the input pulse signal by way of the phase weights. The outputs of the DFT are then inverted at every other frequency port and passed through the TDM, but this time in time-inverted order. The outputs of the TDM are fed through an envelope detector to provide a cross-correlated facsimile of the original input pulse.

  7. Phase coded pulse expander-compressor

    Science.gov (United States)

    Lewis, B. L.

    1985-06-01

    A pulse expansion and compression system, especially useful for radar ranging, comprising a pulse coder for expanding an input pulse and a pulse compressor of the matched-filter type. The coder consists of a plurality of delay stages into which the input pulse is fed, a discrete Fourier transform (DFT) circuit to which the output signals of the delay stages are fed by way of respective phase weights and for which every other frequency port is inverted prior to entry to a time-dispersion means (TDM) comprising an arrangement of adders interconnected by delay stages for differently delaying the output signals from the DFT. The TDM output is fed to a phase modulator and then to the transmitter. The echo signals are conjugated, time-inverted, and passed through the same DFT as the input pulse signal by way of the phase weights. The outputs of the DFT are then inverted at every other frequency port and passed through the TDM, but this time in time-inverted order. The outputs of the TDM are fed through an envelope detector to provide a cross-correlated facsimile of the original input pulse.

  8. Decontamination of sugar syrup by pulsed light.

    Science.gov (United States)

    Chaine, Aline; Levy, Caroline; Lacour, Bernard; Riedel, Christophe; Carlin, Frédéric

    2012-05-01

    The pulsed light produced by xenon flash lamps was applied to 65 to 67 °Brix sugar syrups artificially contaminated with suspensions of Saccharomyces cerevisiae and with spores of Bacillus subtilis, Geobacillus stearothermophilus, Alicyclobacillus acidoterrestris, and Aspergillus niger. The emitted pulsed light contained 18.5 % UV radiation. At least 3-log reductions of S. cerevisiae, B. subtilis, G. stearothermophilus, and A. acidoterrestris suspended in 3-mm-deep volumes of sugar syrup were obtained with a fluence of the incident pulsed light equal to or less than 1.8 J/cm(2), and the same results were obtained for B. subtilis and A. acidoterrestris suspended in 10-mm-deep volumes of sugar syrup. A. niger spores would require a more intense treatment; for instance, the maximal log reduction was close to 1 with a fluence of the incident pulsed light of 1.2 J/cm(2). A flowthrough reactor with a flow rate of 320 ml/min and a flow gap of 2.15 mm was designed for pulsed light treatment of sugar syrup. Using this device, a 3-log reduction of A. acidoterrestris spores was obtained with 3 to 4 pulses of incident pulsed light at 0.91 J/cm(2) per sugar syrup volume.

  9. Theoretical spectrum of noisy optical pulse trains.

    Science.gov (United States)

    Lacaze, B; Chabert, M

    2008-06-20

    The intensity of an ideal optical pulse train is often modeled as an exact periodic repetition of a given pulse-shape function with constant amplitude and width. Therefore, the ideal intensity power spectrum is a pure line power spectrum. However, spontaneous-emission noise due to amplification media, electronic noise due to modulators, or even intentional modulations result in period-to-period fluctuations of the pulse amplitude, width, or arrival time. The power spectrum of this so-called noisy optical pulse train is then composed of a line spectrum added to a band spectrum. This study shows that the optical pulse train intensity is cyclostationary under usual assumptions on the fluctuations. This property allows us to derive the exact optical pulse train power spectrum. A general closed-form expression that takes into account the three noise manifestations (jitter, amplitude, and width modulations) is provided. Particular expressions are given for usual cases of interest such as the jitter and amplitude modulation model, for given fluctuation probability distributions, and pulse-shape functions.

  10. Pulse shortening of an ultrafast VECSEL

    Science.gov (United States)

    Waldburger, D.; Alfieri, C. G. E.; Link, S. M.; Gini, E.; Golling, M.; Mangold, M.; Tilma, B. W.; Keller, U.

    2016-03-01

    Ultrafast, optically pumped, passively modelocked vertical external-cavity surface-emitting lasers (VECSELs) are excellent sources for industrial and scientific applications that benefit from compact semiconductor based high-power ultrafast lasers with gigahertz repetition rates and excellent beam quality. Applications such as self-referenced frequency combs and multi-photon imaging require sub-200-fs pulse duration combined with high pulse peak power. Here, we present a semiconductor saturable absorber mirror (SESAM) modelocked VECSEL with a pulse duration of 147 fs and 328 W of pulse peak power. The average output power was 100 mW with a repetition rate of 1.82 GHz at a center wavelength of 1034 nm. The laser has optimal beam quality operating in a fundamental transverse mode with a M2 value of strain-compensated InGaAs quantum wells (QWs). The QWs are placed symmetrical around the antinodes of the standing electric field at a reduced average field enhancement in the QWs of ≈ 0.5 (normalized to 4 outside the structure). These results overcome the trade-off between pulse duration and peak power of the state-of-the-art threshold values of 4.35 kW peak power for a pulse duration of 400 fs and 3.3 W peak power for a pulse duration of 107 fs.

  11. Ultrashort Pulse Propagation in Nonlinear Dispersive Fibers

    Science.gov (United States)

    Agrawal, Govind P.

    Ultrashort optical pulses are often propagated through optical waveguides for a variety of applications including telecommunications and supercontinuum generation [1]. Typically the waveguide is in the form of an optical fiber but it can also be a planar waveguide. The material used to make the waveguide is often silica glass, but other materials such as silicon or chalcogenides have also been used in recent years. What is common to all such materials is they exhibit chromatic dispersion as well as the Kerr nonlinearity. The former makes the refractive index frequency dependent, whereas the latter makes it to depend on the intensity of light propagating through the medium [2]. Both of these effects become more important as optical pulses become shorter and more intense. For pulses not too short (pulse widths > 1 ns) and not too intense (peak powers < 10 mW), the waveguide plays a passive role (except for small optical losses) and acts as a transporter of optical pulses from one place to another, without significantly affecting their shape or spectrum. However, as pulses become shorter and more intense, both the dispersion and the Kerr nonlinearity start to affect the shape and spectrum of an optical pulse during its propagation inside the waveguide. This chapter focuses on silica fibers but similar results are expected for other waveguides made of different materials

  12. Effect of Pulse Polarity on Thresholds and on Non-monotonic Loudness Growth in Cochlear Implant Users.

    Science.gov (United States)

    Macherey, Olivier; Carlyon, Robert P; Chatron, Jacques; Roman, Stéphane

    2017-06-01

    Most cochlear implants (CIs) activate their electrodes non-simultaneously in order to eliminate electrical field interactions. However, the membrane of auditory nerve fibers needs time to return to its resting state, causing the probability of firing to a pulse to be affected by previous pulses. Here, we provide new evidence on the effect of pulse polarity and current level on these interactions. In experiment 1, detection thresholds and most comfortable levels (MCLs) were measured in CI users for 100-Hz pulse trains consisting of two consecutive biphasic pulses of the same or of opposite polarity. All combinations of polarities were studied: anodic-cathodic-anodic-cathodic (ACAC), CACA, ACCA, and CAAC. Thresholds were lower when the adjacent phases of the two pulses had the same polarity (ACCA and CAAC) than when they were different (ACAC and CACA). Some subjects showed a lower threshold for ACCA than for CAAC while others showed the opposite trend demonstrating that polarity sensitivity at threshold is genuine and subject- or electrode-dependent. In contrast, anodic (CAAC) pulses always showed a lower MCL than cathodic (ACCA) pulses, confirming previous reports. In experiments 2 and 3, the subjects compared the loudness of several pulse trains differing in current level separately for ACCA and CAAC. For 40 % of the electrodes tested, loudness grew non-monotonically as a function of current level for ACCA but never for CAAC. This finding may relate to a conduction block of the action potentials along the fibers induced by a strong hyperpolarization of their central processes. Further analysis showed that the electrodes showing a lower threshold for ACCA than for CAAC were more likely to yield a non-monotonic loudness growth. It is proposed that polarity sensitivity at threshold reflects the local neural health and that anodic asymmetric pulses should preferably be used to convey sound information while avoiding abnormal loudness percepts.

  13. On the polyphasic quenching kinetics of chlorophyll a fluorescence in algae after light pulses of variable length

    NARCIS (Netherlands)

    Vredenberg, W.J.; Prasil, O.

    2013-01-01

    This study reports on kinetics of the fluorescence decay in a suspension of the alga Scenedesmus quadricauda after actinic illumination. These are monitored as the variable fluorescence signal in the dark following light pulses of variable intensity and duration. The decay reflects the restoration

  14. Column CO2 Measurement From an Airborne Solid-State Double-Pulsed 2-Micron Integrated Path Differential Absorption Lidar

    Science.gov (United States)

    Singh, U. N.; Yu, J.; Petros, M.; Refaat, T. F.; Remus, R.; Fay, J.; Reithmaier, K.

    2014-01-01

    NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micrometers IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  15. Quasimonoenergetic and low emittance ion bunch generation from ultrathin targets by counterpropagating laser pulses of ultrarelativistic intensities

    CERN Document Server

    Avetissian, H K; Mkrtchian, G F; Sedrakian, Kh V

    2011-01-01

    A new method for generation of quasimonoenergetic and low emittance fast ion/nuclei bunches of solid densities from nanotargets by two counterpropagating laser pulses of ultrarelativistic intensities is proposed, based on the threshold phenomenon of particles "reflection" due to induced nonlinear Compton scattering. Particularly, a setup is considered which provides generation of ion bunches with parameters that are required in hadron therapy.

  16. Reflection of curved shock waves

    Science.gov (United States)

    Mölder, S.

    2017-09-01

    Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.

  17. Beamlet pulsed-power system

    Energy Technology Data Exchange (ETDEWEB)

    Larson, D.

    1996-06-01

    The 13-MJ Beamlet pulsed-power system provides power to the 512 flash lamps in the cavity and booster amplifiers. Since the flash lamps pump all of the apertures in the 2 x 2 amplifier array, the capacitor bank provides roughly four times the energy required to pump the single active beam line. During the 40 s prior to the shot, the capacitors are charged by constant-current power supplies. Ignitron switches transfer the capacitor energy to the flash lamps via coaxial cables. A preionization system triggers the flash lamps and delivers roughly 1 % of the capacitor energy 200 {mu}s prior to the main discharge. This is the first time flash-lamp preionization has been used in a large facility. Preionization improves the amplifier efficiency by roughly 5% and increases the lifetime of the flash lamps. LabVIEW control panels provide an operator interface with the modular controls and diagnostics. To improve the reliability of the system, high-energy-density, self-healing, metallized dielectric capacitors are used. High-frequency, voltage-regulated switching power supplies are integrated into each module on Beamlet, allowing greater independence among the modules and improved charge voltage accuracy, flexibility, and repeatability.

  18. XFEL/Short Pulse Science

    CERN Document Server

    Schneider, Jochen

    2005-01-01

    X-rays are a most powerful tool for 3 dimensional imaging of matter on length scales from mm to nanometer. They allow for highly accurate determination of the position of atoms and their correlated motion in samples with complex structure under extreme temperature or pressure condi-tions, they probe either bulk or surface properties including order-disorder phenomena. With high resolution spectro-microscopy electronic properties of inhomogeneous novel materials are studied in great detail. So far equilibrium states are investigated. The logical next step is to extend our methodology to include the investigation of non-equilibrium, of new states of matter with atomic resolution in space and time. The XFELs provide the necessary very intense flashes of X-rays with wave-lengths down to 0.1 nm with pulse durations of 10 or 100 femtoseconds. Examples of the sug-gested applications of XFELs will be presented. Strategies for performing experiments at LINAC driven light sources will be discussed with emphasis on the ...

  19. [Music, pulse, heart and sport].

    Science.gov (United States)

    Gasenzer, E R; Leischik, R

    2018-02-01

    Music, with its various elements, such as rhythm, sound and melody had the unique ability even in prehistoric, ancient and medieval times to have a special fascination for humans. Nowadays, it is impossible to eliminate music from our daily lives. We are accompanied by music in shopping arcades, on the radio, during sport or leisure time activities and in wellness therapy. Ritualized drumming was used in the medical sense to drive away evil spirits or to undergo holy enlightenment. Today we experience the varied effects of music on all sensory organs and we utilize its impact on cardiovascular and neurological rehabilitation, during invasive cardiovascular procedures or during physical activities, such as training or work. The results of recent studies showed positive effects of music on heart rate and in therapeutic treatment (e. g. music therapy). This article pursues the impact of music on the body and the heart and takes sports medical aspects from the past and the present into consideration; however, not all forms of music and not all types of musical activity are equally suitable and are dependent on the type of intervention, the sports activity or form of movement and also on the underlying disease. This article discusses the influence of music on the body, pulse, on the heart and soul in the past and the present day.

  20. Measurements of UWB Pulse Propagation Along a Wind Turbine Blade at 1 to 20 GHz

    DEFF Research Database (Denmark)

    Hejselbæk, Johannes; Syrytsin, Igor A.; Eggers, Patrick Claus F.

    2018-01-01

    This paper describes propagation measurements of an Ultra Wide Band (UWB) pulse along a full-scale wind turbine blade. The aim is to use the UWB channel characteristics to determine the deflection of the wind turbine blade under different wind loads. The frequency response is measured from 1 to 20...... the reflection originates a ray-tracing study incorporating a model of the curvature of the blade have been conducted. This showed the area causing the reflections depended highly on the placement of the antenna on the wind turbine blade....