Thermal Property Measurement of Semiconductor Melt using Modified Laser Flash Method

NASA Technical Reports Server (NTRS)

Lin, Bochuan; Zhu, Shen; Ban, Heng; Li, Chao; Scripa, Rosalla N.; Su, Ching-Hua; Lehoczky, Sandor L.

2003-01-01

This study further developed standard laser flash method to measure multiple thermal properties of semiconductor melts. The modified method can determine thermal diffusivity, thermal conductivity, and specific heat capacity of the melt simultaneously. The transient heat transfer process in the melt and its quartz container was numerically studied in detail. A fitting procedure based on numerical simulation results and the least root-mean-square error fitting to the experimental data was used to extract the values of specific heat capacity, thermal conductivity and thermal diffusivity. This modified method is a step forward from the standard laser flash method, which is usually used to measure thermal diffusivity of solids. The result for tellurium (Te) at 873 K: specific heat capacity 300.2 Joules per kilogram K, thermal conductivity 3.50 Watts per meter K, thermal diffusivity 2.04 x 10(exp -6) square meters per second, are within the range reported in literature. The uncertainty analysis showed the quantitative effect of sample geometry, transient temperature measured, and the energy of the laser pulse.

Thermal Diffusivity Measurement for Thermal Spray Coating Attached to Substrate Using Laser Flash Method

NASA Astrophysics Data System (ADS)

Akoshima, Megumi; Tanaka, Takashi; Endo, Satoshi; Baba, Tetsuya; Harada, Yoshio; Kojima, Yoshitaka; Kawasaki, Akira; Ono, Fumio

2011-11-01

Ceramic-based thermal barrier coatings are used as heat and wear shields of gas turbine blades. There is a strong need to evaluate the thermal conductivity of coating for thermal design and use. The thermal conductivity of a bulk material is obtained as the product of thermal diffusivity, specific heat capacity, and density above room temperature in many cases. Thermal diffusivity and thermal conductivity are unique for a given material because they are sensitive to the structure of the material. Therefore, it is important to measure them in each sample. However it is difficult to measure the thermal diffusivity and thermal conductivity of coatings because coatings are attached to substrates. In order to evaluate the thermal diffusivity of a coating attached to the substrate, we have examined the laser flash method with the multilayer model on the basis of the response function method. We carried out laser flash measurements in layered samples composed of a CoNiCrAlY bond coating and a 8YSZ top coating by thermal spraying on a Ni-based superalloy substrate. It was found that the procedure using laser flash method with the multilayer model is useful for the thermal diffusivity evaluation of a coating attached to a substrate.

Lidar Systems for Precision Navigation and Safe Landing on Planetary Bodies

NASA Technical Reports Server (NTRS)

Amzajerdian, Farzin; Pierrottet, Diego F.; Petway, Larry B.; Hines, Glenn D.; Roback, Vincent E.

2011-01-01

The ability of lidar technology to provide three-dimensional elevation maps of the terrain, high precision distance to the ground, and approach velocity can enable safe landing of robotic and manned vehicles with a high degree of precision. Currently, NASA is developing novel lidar sensors aimed at needs of future planetary landing missions. These lidar sensors are a 3-Dimensional Imaging Flash Lidar, a Doppler Lidar, and a Laser Altimeter. The Flash Lidar is capable of generating elevation maps of the terrain that indicate hazardous features such as rocks, craters, and steep slopes. The elevation maps collected during the approach phase of a landing vehicle, at about 1 km above the ground, can be used to determine the most suitable safe landing site. The Doppler Lidar provides highly accurate ground relative velocity and distance data allowing for precision navigation to the landing site. Our Doppler lidar utilizes three laser beams pointed to different directions to measure line of sight velocities and ranges to the ground from altitudes of over 2 km. Throughout the landing trajectory starting at altitudes of about 20 km, the Laser Altimeter can provide very accurate ground relative altitude measurements that are used to improve the vehicle position knowledge obtained from the vehicle navigation system. At altitudes from approximately 15 km to 10 km, either the Laser Altimeter or the Flash Lidar can be used to generate contour maps of the terrain, identifying known surface features such as craters, to perform Terrain relative Navigation thus further reducing the vehicle s relative position error. This paper describes the operational capabilities of each lidar sensor and provides a status of their development. Keywords: Laser Remote Sensing, Laser Radar, Doppler Lidar, Flash Lidar, 3-D Imaging, Laser Altimeter, Precession Landing, Hazard Detection

Recent advance to 3 × 10(-5) rad near diffraction-limited beam divergence of dye laser with transverse-discharge flash-lamp pumping.

PubMed

Trusov, K K

1994-02-20

A new experimental setup of a Rhodamine 6G dye laser with a transverse-discharge flash-lamp-pumping system is presented. It differs from a previous setup [Sov. J. Quantum Electron. 16, 468-471 (1989)] in that it has a larger laser beam aperture (32 mm) and higher pumping energy (1 kJ), which made it possible to test the scalability and reach near diffraction-limited laser beam divergence of 3 × 10(-5) rad FWHM at beam energy 1.4 J. The effect of spectral dispersion in the active medium and of other optical elements on the beam divergence is also discussed.

Modified Laser Flash Method for Thermal Properties Measurements and the Influence of Heat Convection

NASA Technical Reports Server (NTRS)

Lin, Bochuan; Zhu, Shen; Ban, Heng; Li, Chao; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

2003-01-01

The study examined the effect of natural convection in applying the modified laser flash method to measure thermal properties of semiconductor melts. Common laser flash method uses a laser pulse to heat one side of a thin circular sample and measures the temperature response of the other side. Thermal diffusivity can be calculations based on a heat conduction analysis. For semiconductor melt, the sample is contained in a specially designed quartz cell with optical windows on both sides. When laser heats the vertical melt surface, the resulting natural convection can introduce errors in calculation based on heat conduction model alone. The effect of natural convection was studied by CFD simulations with experimental verification by temperature measurement. The CFD results indicated that natural convection would decrease the time needed for the rear side to reach its peak temperature, and also decrease the peak temperature slightly in our experimental configuration. Using the experimental data, the calculation using only heat conduction model resulted in a thermal diffusivity value is about 7.7% lower than that from the model with natural convection. Specific heat capacity was about the same, and the difference is within 1.6%, regardless of heat transfer models.

Novel short-pulse laser diode source for high-resolution 3D flash lidar

NASA Astrophysics Data System (ADS)

Canal, Celine; Laugustin, Arnaud; Kohl, Andreas; Rabot, Olivier

2017-06-01

Imaging based on laser illumination is present in various fields of applications such as medicine, security, defense, civil engineering and in the automotive sector. In this last domain, research and development to bring autonomous vehicles on the roads has been intensified the recent years. Among the various technologies currently studied, automotive lidars are a fast-growing one due to their accuracy to detect a wide range of objects at distances up to a few hundreds of meters in various weather conditions. First commercialized devices for ADAS were laser scanners. Since then, new architectures have recently appeared such as solid-state lidar and flash lidar that offer a higher compactness, robustness and a cost reduction. Flash lidars are based on time-of-flight measurements, with the particularity that they do not require beam scanners because only one short laser pulse with a large divergence is used to enlighten the whole scene. Depth of encountered objects can then be recovered from measurement of echoed light at once, hence enabling real-time 3D mapping of the environment. This paper will bring into the picture a cutting edge laser diode source that can deliver millijoule pulses as short as 12 ns, which makes them highly suitable for integration in flash lidars. They provide a 100-kW peak power highly divergent beam in a footprint of 4x5 cm2 (including both the laser diode and driver) and with a 30-% electrical-to-optical efficiency, making them suitable for integration in environments in which compactness and power consumption are a priority. Their emission in the range of 800-1000 nm is considered to be eye safe when taking into account the high divergence of the output beam. An overview of architecture of these state-of-the-art pulsed laser diode sources will be given together with some solutions for their integration in 3D mapping systems. Future work leads will be discussed for miniaturization of the laser diode and drastic cost reduction.

Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy

PubMed Central

Zhou, Shengqiang; Liu, Fang; Prucnal, S.; Gao, Kun; Khalid, M.; Baehtz, C.; Posselt, M.; Skorupa, W.; Helm, M.

2015-01-01

Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability. PMID:25660096

Flash/crazing effects on simulator pursuit tracking performance

NASA Astrophysics Data System (ADS)

Stamper, D. A.; Lund, D. J.; Levine, R. R.; Molchany, J. W.; Best, P.

1986-03-01

Day sights which are purposefully or inadvertently irradiated with laser radiation may become nonfunctional due to cracking or crazing of the optical glass. The degree of performance degradation may be related to the amount of damage to the glass and possible flash blindness from reradiation. Thirty-two male enlisted men and officers tracked a scale model tank through a constant arc at a simulated distance of 1 km, using a laboratory constructed viscous-damped tracking device. There were four crazing groups (4 men/group) under bright and dim ambient light conditions for a total of eight groups. Each man tracked the target during three flash/crazing and three crazing only trials, which were randomly presented during 30 trials. The simulated countermeasure which included the flash and crazing had dramatic effects on tracking performance, even under daylight conditions. Under the most severe degree of crazing, tracking performance was not possible under either ambient light condition. The relatively small amounts of laser radiation used to craze the BK-7 glass used in this study, which lead to significant performance decrements, demonstrates the potential impact of flash/crazing effects on operators of day sights.

Investigation of Current Spike Phenomena During Heavy Ion Irradiation of NAND Flash Memories

NASA Technical Reports Server (NTRS)

Oldham, Timothy R.; Berg, Melanie; Friendlich, Mark; Wilcox, Ted; Seidleck, Christina; LaBel, Kenneth A.; Irom, Farokh; Buchner, Steven P.; McMorrow, Dale; Mavis, David G.;

Analysis of multibunch free electron laser operation

NASA Astrophysics Data System (ADS)

Hellert, Thorsten; Decking, Winfried; Branlard, Julien

2017-09-01

At the SASE-FEL user facilities FLASH and European XFEL, superconducting TESLA type cavities are used for acceleration of the driving electron bunches. The high achievable duty cycle allows for operating with long bunch trains, hence considerably increasing the efficiency of the machine. However, multibunch free electron lasers (FEL) operation requires longitudinal and transverse stability within the bunch train. The purpose of this work is to investigate the intra-bunch-train transverse dynamics at FLASH and European XFEL. Key relationships of superconducting rf cavity operation and the resulting impact on the intrabunch-train trajectory variation are described. The observed trajectory variation during multibunch user runs at FLASH is analyzed and related to both, intrabunch-train variations of the rf and the following impact on the multibunch FEL performance.

Hemangiomas

MedlinePlus

... grow. The flash-lamp pulse dye, pump dye, diode, and sclero-laser are the primary lasers used ... go through several trials of dosing-tapering. The current protocol is to put them on the initial ...

Investigation of 2.1-micron lasing properties of Ho:Tm:Cr:YAG crystals under flash-lamp pumping at various operating conditions

NASA Technical Reports Server (NTRS)

Kim, Kyong H.; Choi, Young S.; Barnes, Norman P.; Hess, Robert V.; Bair, Clayton H.; Brockman, Philip

1993-01-01

Flash-lamp-pumped normal-mode and Q-switched 2.1-micron laser operations of Ho:Tm:Cr:YAG crystals have been evaluated under a wide variety of experimental conditions in order to determine an optimum lasing condition and to characterize the laser outputs. Q-switched laser-output energies equal to, or in some cases exceeding the normal-mode laser energies, were obtained in the form of a strong single spike through an optimization of the opening time of a lithium niobate Q switch. The increase of the normal-mode laser slope efficiency was observed with the increase of the Tm concentration from 2.5 to 4.5 at. pct at operating temperatures from 120 K to near room temperature. Laser transitions were observed only at 2.098 and 2.091 microns under various conditions. The 2.091-micron laser transition appeared to be dominant at high-temperature operations with low-reflective-output couplers.

Opacplot2: Enabling tabulated EoS and opacity compatibility for HEDLP simulations with the FLASH code

NASA Astrophysics Data System (ADS)

Laune, Jordan; Tzeferacos, Petros; Feister, Scott; Fatenejad, Milad; Yurchak, Roman; Flocke, Norbert; Weide, Klaus; Lamb, Donald

2017-10-01

Thermodynamic and opacity properties of materials are necessary to accurately simulate laser-driven laboratory experiments. Such data are compiled in tabular format since the thermodynamic range that needs to be covered cannot be described with one single theoretical model. Moreover, tabulated data can be made available prior to runtime, reducing both compute cost and code complexity. This approach is employed by the FLASH code. Equation of state (EoS) and opacity data comes in various formats, matrix-layouts, and file-structures. We discuss recent developments on opacplot2, an open-source Python module that manipulates tabulated EoS and opacity data. We present software that builds upon opacplot2 and enables easy-to-use conversion of different table formats into the IONMIX format, the native tabular input used by FLASH. Our work enables FLASH users to take advantage of a wider range of accurate EoS and opacity tables in simulating HELP experiments at the National Laser User Facilities.

FLASH2: Operation, beamlines, and photon diagnostics

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

Plönjes, Elke, E-mail: elke.ploenjes@desy.de; Faatz, Bart; Kuhlmann, Marion

2016-07-27

FLASH2, a major extension of the soft X-ray free-electron laser FLASH at DESY, turns FLASH into a multi-user FEL facility. A new undulator line is located in a separate accelerator tunnel and driven additionally by the FLASH linear accelerator. First lasing of FLASH2 was achieved in August 2014 with simultaneous user operation at FLASH1. The new FLASH2 experimental hall offers space for up to six experimental end stations, some of which will be installed permanently. The wide wavelength range spans from 4-60 nm and 0.8 nm in the 5{sup th} harmonic and in the future deep into the water windowmore » in the fundamental. While this is of high interest to users, it is challenging from the beamline instrumentation point of view. Online diagnostics - which are mostly pulse resolved - for beam intensity, position, wavelength, wave front, and pulse length have been to a large extent developed at FLASH(1) and have now been optimized for FLASH2. Pump-probe facilities for XUV-XUV, XUV optical and XUV-THz experiments will complete the FLASH2 user facility.« less

Ultra-bright γ-ray flashes and dense attosecond positron bunches from two counter-propagating laser pulses irradiating a micro-wire target.

PubMed

Li, Han-Zhen; Yu, Tong-Pu; Hu, Li-Xiang; Yin, Yan; Zou, De-Bin; Liu, Jian-Xun; Wang, Wei-Quan; Hu, Shun; Shao, Fu-Qiu

2017-09-04

We propose a novel scheme to generate ultra-bright ultra-short γ-ray flashes and high-energy-density attosecond positron bunches by using multi-dimensional particle-in-cell simulations with quantum electrodynamics effects incorporated. By irradiating a 10 PW laser pulse with an intensity of 10 23 W/cm 2 onto a micro-wire target, surface electrons are dragged-out of the micro-wire and are effectively accelerated to several GeV energies by the laser ponderomotive force, forming relativistic attosecond electron bunches. When these electrons interact with the probe pulse from the other side, ultra-short γ-ray flashes are emitted with an ultra-high peak brightness of 1.8 × 10 24 photons s -1 mm -2 mrad -2 per 0.1%BW at 24 MeV. These photons propagate with a low divergence and collide with the probe pulse, triggering the Breit-Wheeler process. Dense attosecond e - e + pair bunches are produced with the positron energy density as high as 10 17 J/m 3 and number of 10 9 . Such ultra-bright ultra-short γ-ray flashes and secondary positron beams may have potential applications in fundamental physics, high-energy-density physics, applied science and laboratory astrophysics.

Higher-order mode-based cavity misalignment measurements at the free-electron laser FLASH

NASA Astrophysics Data System (ADS)

Hellert, Thorsten; Baboi, Nicoleta; Shi, Liangliang

2017-12-01

At the Free-Electron Laser in Hamburg (FLASH) and the European X-Ray Free-Electron Laser, superconducting TeV-energy superconducting linear accelerator (TESLA)-type cavities are used for the acceleration of electron bunches, generating intense free-electron laser (FEL) beams. A long rf pulse structure allows one to accelerate long bunch trains, which considerably increases the efficiency of the machine. However, intrabunch-train variations of rf parameters and misalignments of rf structures induce significant trajectory variations that may decrease the FEL performance. The accelerating cavities are housed inside cryomodules, which restricts the ability for direct alignment measurements. In order to determine the transverse cavity position, we use a method based on beam-excited dipole modes in the cavities. We have developed an efficient measurement and signal processing routine and present its application to multiple accelerating modules at FLASH. The measured rms cavity offset agrees with the specification of the TESLA modules. For the first time, the tilt of a TESLA cavity inside a cryomodule is measured. The preliminary result agrees well with the ratio between the offset and angle dependence of the dipole mode which we calculated with eigenmode simulations.

Reconstruction of Axial Energy Deposition in Magnetic Liner Inertial Fusion Based on PECOS Shadowgraph Unfolds Using the AMR Code FLASH

NASA Astrophysics Data System (ADS)

Adams, Marissa; Jennings, Christopher; Slutz, Stephen; Peterson, Kyle; Gourdain, Pierre; U. Rochester-Sandia Collaboration

2017-10-01

Magnetic Liner Inertial Fusion (MagLIF) experiments incorporate a laser to preheat a deuterium filled capsule before compression via a magnetically imploding liner. In this work, we focus on the blast wave formed in the fuel during the laser preheat component of MagLIF, where approximately 1kJ of energy is deposited in 3ns into the capsule axially before implosion. To model blast waves directly relevant to experiments such as MagLIF, we inferred deposited energy from shadowgraphy of laser-only experiments preformed at the PECOS target chamber using the Z-Beamlet laser. These energy profiles were used to initialize 2-dimensional simulations using by the adaptive mesh refinement code FLASH. Gradients or asymmetries in the energy deposition may seed instabilities that alter the fuel's distribution, or promote mix, as the blast wave interacts with the liner wall. The AMR capabilities of FLASH allow us to study the development and dynamics of these instabilities within the fuel and their effect on the liner before implosion. Sandia Natl Labs is managed by NTES of Sandia, LLC., a subsidiary of Honeywell International, Inc, for the U.S. DOEs NNSA under contract DE-NA0003525.

Generation of cavitation luminescence by laser-induced exothermic chemical reaction

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

Jung Park, Han; Diebold, Gerald J.

2013-08-14

Absorption of high power laser radiation by aqueous carbon suspensions is known to result in the formation of highly compressed bubbles of hydrogen and carbon monoxide through the endothermic carbon-steam reaction. The bubbles expand rapidly, overreaching their equilibrium diameter, and then collapse tens to hundreds of microseconds after formation to give a flash of radiation. Here we report on the effects of laser-initiated exothermic chemical reaction on cavitation luminescence. Experiments with hydrogen peroxide added to colloidal carbon suspensions show that both the time of the light flash following the laser pulse and the intensity of luminescence increase with hydrogen peroxidemore » concentration, indicating that large, highly energetic gas bubbles are produced. Additional experiments with colloidal carbon suspensions show the effects of high pressure on the luminescent intensity and its time of appearance following firing of the laser.« less

High-Fidelity Flash Lidar Model Development

NASA Technical Reports Server (NTRS)

Hines, Glenn D.; Pierrottet, Diego F.; Amzajerdian, Farzin

2014-01-01

NASA's Autonomous Landing and Hazard Avoidance Technologies (ALHAT) project is currently developing the critical technologies to safely and precisely navigate and land crew, cargo and robotic spacecraft vehicles on and around planetary bodies. One key element of this project is a high-fidelity Flash Lidar sensor that can generate three-dimensional (3-D) images of the planetary surface. These images are processed with hazard detection and avoidance and hazard relative navigation algorithms, and then are subsequently used by the Guidance, Navigation and Control subsystem to generate an optimal navigation solution. A complex, high-fidelity model of the Flash Lidar was developed in order to evaluate the performance of the sensor and its interaction with the interfacing ALHAT components on vehicles with different configurations and under different flight trajectories. The model contains a parameterized, general approach to Flash Lidar detection and reflects physical attributes such as range and electronic noise sources, and laser pulse temporal and spatial profiles. It also provides the realistic interaction of the laser pulse with terrain features that include varying albedo, boulders, craters slopes and shadows. This paper gives a description of the Flash Lidar model and presents results from the Lidar operating under different scenarios.

How MLA Works

NASA Image and Video Library

2012-12-03

NASA Mercury Laser Altimeter MLA is shown ranging to Mercury surface from orbit. In this animation, yellow flashes represent near-infrared laser pulses that can reflect off terrain in shadow as well as in sunlight.

European X-Ray Free Electron Laser (EXFEL): local implications

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2013-10-01

European X-Ray FEL - free electron laser is under construction in DESY Hamburg. It is scheduled to be operational at 2015/16 at a cost more than 1 billion Euro. The laser uses SASE method to generate x-ray light. It is propelled by an electron linac of 17,5GeV energy and more than 2km in length. The linac uses superconducting SRF TESLA technology working at 1,3 GHz in frequency. The prototype of EXFEL is FLASH Laser (200 m in length), where the "proof of principle" was checked, and from the technologies were transferred to the bigger machine. The project was stared in the nineties by building a TTF Laboratory -Tesla Test Facility. The EXFEL laser is a child of a much bigger teraelectronovolt collider project TESLA (now abandoned in Germany but undertaken by international community in a form the ILC). A number of experts and young researchers from Poland participate in the design, construction and research of the FLASH and EXFEL lasers.

Photochemistry of transition-metal phthalocyanines. Mechanistic aspects of the photochemistry of the acido(phthalocyanine)rhodium(III) complexes investigated by continuous, flash, and laser flash photolysis

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

Muralidharan, S.; Ferraudi, G.; Schmatz, K.

1982-08-01

Rh(ph)(CH/sub 3/OH)X, X = Cl, Br, or I, has been prepared and characterized. Continuous-wave irradiations of these phthalocyanines in the ultraviolet region of the spectrum, in acetonitrile and acetonitrile-isopropyl alcohol mixtures, result in the redox-induced substitution of the axially coordinated halide ions by the solvent. Even though the overall reaction was photosubstitution, the intermediates observed by conventional and laser flash photolysis were found to be rhodium(II) phthalocyanine and rhodium(III) phthalocyanine ligand radicals. The photoredox processes were attributed to the population of (n..pi..*) ligand-centered excited states that involve the lone electron pair from the bridge nitrogens of the phthalocyanine ligand. 9more » figures, 3 tables.« less

Laser emission from flash ignition of Zr/Al nanoparticles.

PubMed

Yang, Fan; Kang, Xiaoli; Luo, Jiangshan; Sun, Laixi; Xia, Handing; Yi, Zao; Tang, Yongjian

2017-10-02

We report the first laser emission from flash ignition of Zr/Al nanoparticles with the addition of strong oxidizer KClO 4 using Nd: YAG as a laser medium. The mixture Zr/Al/Kp-45 (mass ratio = 33%Zr: 33%Al: 34%KClO 4 ) has the highest brightness temperature Tb = 4615 K and the adiabatic flame temperature Tf = 4194 K with the duration of 20 ms. At 1064 nm we measured a maximum output energy of 702.5 mJ with the duration of nearly 10 ms by using only 100 mg mixture with an output coupler (transmission T = 10%). Further optimizing the concentration cavity and increasing the mixture content will yield much higher efficiency and output energy.

Synchronizing flash-melting in a diamond cell with synchrotron X ray diffraction (XRD)

NASA Astrophysics Data System (ADS)

Karandikar, Amol; Boehler, Reinhard; Meng, Yue; Rod, Eric; Shen, Guoyin

2013-06-01

The major challenges in measuring melting temperatures in laser heated diamond cells are sample instability, thermal runaway and chemical reactions. To circumvent these problems, we developed a ``flash heating'' method using a modulated CW fiber laser and fast X ray detection capability at APS (Pilatus 1M detector). As an example, Pt spheres of 5 micron diameter were loaded in a single crystal sapphire encapsulation in the diamond cell at 65 GPa and heated in a single flash heating event for 20 ms to reach a desired temperature. A CCD spectrometer and the Pilatus were synchronized to measure the temperature and the XRD signal, respectively, when the sample reached the thermal steady state. Each successive flash heating was done at a higher temperature. The integrated XRD pattern, collected during and after (300 K) each heating, showed no chemical reaction up to 3639 K, the highest temperature reached in the experiment. Pt111 and 200 peak intensity variation showed gradual recrystalization and complete diminishing at about 3600 K, indicating melting. Thus, synchronized flash heating with novel sample encapsulation circumvents previous notorious problems and enables accurate melting temperature measurement in the diamond cell using synchrotron XRD probe. Affiliation 2: Geowissenschaeften, Goethe-Universitaet, Altenhoeferallee 1, D-60438 Frankfurt a.M., Germany.

Modeling Studies of Inhomogeneity Effects during Laser Flash Photolysis Experiments: A Reaction-Diffusion Approach.

PubMed

Dóka, Éva; Lente, Gábor

2017-04-13

This work presents a rigorous mathematical study of the effect of unavoidable inhomogeneities in laser flash photolysis experiments. There are two different kinds of inhomegenities: the first arises from diffusion, whereas the second one has geometric origins (the shapes of the excitation and detection light beams). Both of these are taken into account in our reported model, which gives rise to a set of reaction-diffusion type partial differential equations. These equations are solved by a specially developed finite volume method. As an example, the aqueous reaction between the sulfate ion radical and iodide ion is used, for which sufficiently detailed experimental data are available from an earlier publication. The results showed that diffusion itself is in general too slow to influence the kinetic curves on the usual time scales of laser flash photolysis experiments. However, the use of the absorbances measured (e.g., to calculate the molar absorption coefficients of transient species) requires very detailed mathematical consideration and full knowledge of the geometrical shapes of the excitation laser beam and the separate detection light beam. It is also noted that the usual pseudo-first-order approach to evaluating the kinetic traces can be used successfully even if the usual large excess condition is not rigorously met in the reaction cell locally.

Laser induced photoluminiscence studies of primary photochemical production processes of cometary radicals

NASA Technical Reports Server (NTRS)

Jackson, W. M.

1977-01-01

A tunable vacuum ultraviolet flash lamp was constructed. This unique flash lamp was coupled with a tunable dye laser detector and permits the experimenter to measure the production rates of ground state radicals as a function of wavelength. A new technique for producing fluorescent radicals was discovered. This technique called multiphoton ultraviolet photodissociation is currently being applied to several problems of both cometary and stratospheric interest. It was demonstrated that NO2 will dissociate to produce an excited fragment and the radiation can possibly be used for remote detection of this species.

Thermal diffusivity of UO2 up to the melting point

NASA Astrophysics Data System (ADS)

Vlahovic, L.; Staicu, D.; Küst, A.; Konings, R. J. M.

2018-02-01

The thermal diffusivity of uranium dioxide was measured from 500 to 3060 K with two different set-ups, both based on the laser-flash technique. Above 1600 K the measurements were performed with an advanced laser-flash technique, which was slightly improved in comparison with a former work. In the temperature range 500-2000 K the thermal diffusivity is decreasing, then relatively constant up to 2700 K, and tends to increase by approaching the melting point. The measurements of the thermal diffusivity in the vicinity of the melting point are possible under certain conditions, and are discussed in this paper.

Transient spectra study on photo-dynamics of curcumin

NASA Astrophysics Data System (ADS)

Qian, Tingting; Wang, Mei; Wang, Jiao; Zhu, Rongrong; He, Xiaolie; Sun, Xiaoyu; Sun, Dongmei; Wang, Qingxiu; Wang, ShiLong

2016-09-01

A novel mechanism of DNA damage induced by photosensitized curcumin (Cur) was explored using laser flash photolysis, pulse radiolysis and gel electrophoresis. Cur neutral radical (Currad) was confirmed as an identical product in photo-sensitization of Cur by laser flash photolysis and pulse radiolysis. A series of reaction rate constants between Currad and nucleic acid bases/nucleotides were determined by pulse radiolysis. Gel electrophoresis was carried out to investigate damage induced by photosensitized Cur to biologically active DNA. The results indicate that the damage to DNA may be caused by Currad produced from the photosensitization of Cur.

Simulation of medical Q-switch flash-pumped Er:YAG laser

NASA Astrophysics Data System (ADS)

-Yan-lin, Wang; Huang-Chuyun; Yao-Yucheng; Xiaolin, Zou

2011-01-01

Er: YAG laser, the wavelength is 2940nm, can be absorbed strongly by water. The absorption coefficient is as high as 13000 cm-1. As the water strong absorption, Erbium laser can bring shallow penetration depth and smaller surrounding tissue injury in most soft tissue and hard tissue. At the same time, the interaction between 2940nm radiation and biological tissue saturated with water is equivalent to instantaneous heating within limited volume, thus resulting in the phenomenon of micro-explosion to removal organization. Different parameters can be set up to cut enamel, dentin, caries and soft tissue. For the development and optimization of laser system, it is a practical choice to use laser modeling to predict the influence of various parameters for laser performance. Aim at the status of low Erbium laser output power, flash-pumped Er: YAG laser performance was simulated to obtain optical output in theory. the rate equation model was obtained and used to predict the change of population densities in various manifolds and use the technology of Q-switch the simulate laser output for different design parameters and results showed that Er: YAG laser output energy can achieve the maximum average output power of 9.8W under the given parameters. The model can be used to find the potential laser systems that meet application requirements.

Shock compression and flash-heating of molecular adsorbates on the picosecond time scale

NASA Astrophysics Data System (ADS)

Berg, Christopher Michael

An ultrafast nonlinear coherent laser spectroscopy termed broadband multiplex vibrational sum-frequency generation (SFG) with nonresonant suppression was employed to monitor vibrational transitions of molecular adsorbates on metallic substrates during laser-driven shock compression and flash-heating. Adsorbates were in the form of well-ordered self-assembled monolayers (SAMs) and included molecular explosive simulants, such as nitroaromatics, and long chain-length alkanethiols. Based on reflectance measurements of the metallic substrates, femtosecond flash-heating pulses were capable of producing large-amplitude temperature jumps with DeltaT = 500 K. Laser-driven shock compression of SAMs produced pressures up to 2 GPa, where 1 GPa ≈ 1 x 104 atm. Shock pressures were estimated via comparison with frequency shifts observed in the monolayer vibrational transitions during hydrostatic pressure measurements in a SiC anvil cell. Molecular dynamics during flash-heating and shock loading were probed with vibrational SFG spectroscopy with picosecond temporal resolution and sub-nanometer spatial resolution. Flash-heating studies of 4-nitrobenzenethiolate (NBT) on Au provided insight into effects from hot-electron excitation of the molecular adsorbates at early pump-probe delay times. At longer delay times, effects from the excitation of SAM lattice modes and lower-energy NBT vibrations were shown. In addition, flash-heating studies of alkanethiolates demonstrated chain disordering behaviors as well as interface thermal conductances across the Au-SAM junction, which was of specific interest within the context of molecular electronics. Shock compression studies of molecular explosive simulants, such as 4-nitrobenzoate (NBA), demonstrated the proficiency of this technique to observe shock-induced molecular dynamics, in this case orientational dynamics, on the picosecond time scale. Results validated the utilization of these refined shock loading techniques to probe the shock initiation or first bond-breaking reactions in molecular explosives such as delta-HMX: a necessary study for the development of safer and more effective energetic materials.

Single-particle coherent diffractive imaging with a soft x-ray free electron laser: towards soot aerosol morphology

NASA Astrophysics Data System (ADS)

Bogan, Michael J.; Starodub, Dmitri; Hampton, Christina Y.; Sierra, Raymond G.

2010-10-01

The first of its kind, the Free electron LASer facility in Hamburg, FLASH, produces soft x-ray pulses with unprecedented properties (10 fs, 6.8-47 nm, 1012 photons per pulse, 20 µm diameter). One of the seminal FLASH experiments is single-pulse coherent x-ray diffractive imaging (CXDI). CXDI utilizes the ultrafast and ultrabright pulses to overcome resolution limitations in x-ray microscopy imposed by x-ray-induced damage to the sample by 'diffracting before destroying' the sample on sub-picosecond timescales. For many lensless imaging algorithms used for CXDI it is convenient when the data satisfy an oversampling constraint that requires the sample to be an isolated object, i.e. an individual 'free-standing' portion of disordered matter delivered to the centre of the x-ray focus. By definition, this type of matter is an aerosol. This paper will describe the role of aerosol science methodologies used for the validation of the 'diffract before destroy' hypothesis and the execution of the first single-particle CXDI experiments being developed for biological imaging. FLASH CXDI now enables the highest resolution imaging of single micron-sized or smaller airborne particulate matter to date while preserving the native substrate-free state of the aerosol. Electron microscopy offers higher resolution for single-particle analysis but the aerosol must be captured on a substrate, potentially modifying the particle morphology. Thus, FLASH is poised to contribute significant advancements in our knowledge of aerosol morphology and dynamics. As an example, we simulate CXDI of combustion particle (soot) morphology and introduce the concept of extracting radius of gyration of fractal aggregates from single-pulse x-ray diffraction data. Future upgrades to FLASH will enable higher spatially and temporally resolved single-particle aerosol dynamics studies, filling a critical technological need in aerosol science and nanotechnology. Many of the methodologies described for FLASH will directly translate to use at hard x-ray free electron lasers.

Time-diagnostics for improved dynamics experiments at XUV FELs

NASA Astrophysics Data System (ADS)

Drescher, Markus; Frühling, Ulrike; Krikunova, Maria; Maltezopoulos, Theophilos; Wieland, Marek

2010-10-01

Significantly structured and fluctuating temporal profiles of pulses from self-amplified spontaneous emission free electron lasers as well as their unstable timing require time diagnostics on a single-shot basis. The duration and structure of extreme-ultraviolet (XUV) pulses from the Free Electron Laser (FEL) in Hamburg (FLASH) are becoming accessible using a variation of the streak camera principle, where photoemitted electrons are energetically streaked in the electric field component of a terahertz electromagnetic wave. The timing with respect to an independently generated laser pulse can be measured in an XUV/laser cross-correlator, based on a non-collinear superposition of both pulses on a solid state surface and detection of XUV-induced modulations of its reflectivity for visible light. Sorting of data according to the measured timing dramatically improves the temporal resolution of an experiment sampling the relaxation of transient electronic states in xenon after linear- as well as nonlinear excitation with intense XUV pulses from FLASH.

Porosity Measurement in Laminated Composites by Thermography and FEA

NASA Technical Reports Server (NTRS)

Chu, Tsuchin Philip; Russell, Samuel S.; Walker, James L.; Munafo, Paul M. (Technical Monitor)

2001-01-01

This paper presents the correlation between the through-thickness thermal diffusivity and the porosity of composites. Finite element analysis (FEA) was used to determine the transient thermal response of composites that were subjected to laser heating. A series of finite element models were built and thermal responses for isotropic and orthographic materials with various thermal diffusivities subjected to different heating conditions were investigated. Experiments were conducted to verify the models and to estimate the unknown parameters such as the amount of heat flux. The analysis and experimental results show good correlation between thermal diffusivity and porosity in the composite materials. They also show that both laser and flash heating can be used effectively to obtain thermal diffusivity. The current infrared thermography system is developed for use with flash heating. The laser heating models and the FEA results can provide useful tools to develop practical thermal diffusivity measurement scheme using laser heat.

Small SWAP 3D imaging flash ladar for small tactical unmanned air systems

NASA Astrophysics Data System (ADS)

Bird, Alan; Anderson, Scott A.; Wojcik, Michael; Budge, Scott E.

2015-05-01

The Space Dynamics Laboratory (SDL), working with Naval Research Laboratory (NRL) and industry leaders Advanced Scientific Concepts (ASC) and Hood Technology Corporation, has developed a small SWAP (size, weight, and power) 3D imaging flash ladar (LAser Detection And Ranging) sensor system concept design for small tactical unmanned air systems (STUAS). The design utilizes an ASC 3D flash ladar camera and laser in a Hood Technology gyro-stabilized gimbal system. The design is an autonomous, intelligent, geo-aware sensor system that supplies real-time 3D terrain and target images. Flash ladar and visible camera data are processed at the sensor using a custom digitizer/frame grabber with compression. Mounted in the aft housing are power, controls, processing computers, and GPS/INS. The onboard processor controls pointing and handles image data, detection algorithms and queuing. The small SWAP 3D imaging flash ladar sensor system generates georeferenced terrain and target images with a low probability of false return and <10 cm range accuracy through foliage in real-time. The 3D imaging flash ladar is designed for a STUAS with a complete system SWAP estimate of <9 kg, <0.2 m3 and <350 W power. The system is modeled using LadarSIM, a MATLAB® and Simulink®- based ladar system simulator designed and developed by the Center for Advanced Imaging Ladar (CAIL) at Utah State University. We will present the concept design and modeled performance predictions.

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

NASA Astrophysics Data System (ADS)

Faatz, B.; Plönjes, E.; Ackermann, S.; Agababyan, A.; Asgekar, V.; Ayvazyan, V.; Baark, S.; Baboi, N.; Balandin, V.; von Bargen, N.; Bican, Y.; Bilani, O.; Bödewadt, J.; Böhnert, M.; Böspflug, R.; Bonfigt, S.; Bolz, H.; Borges, F.; Borkenhagen, O.; Brachmanski, M.; Braune, M.; Brinkmann, A.; Brovko, O.; Bruns, T.; Castro, P.; Chen, J.; Czwalinna, M. K.; Damker, H.; Decking, W.; Degenhardt, M.; Delfs, A.; Delfs, T.; Deng, H.; Dressel, M.; Duhme, H.-T.; Düsterer, S.; Eckoldt, H.; Eislage, A.; Felber, M.; Feldhaus, J.; Gessler, P.; Gibau, M.; Golubeva, N.; Golz, T.; Gonschior, J.; Grebentsov, A.; Grecki, M.; Grün, C.; Grunewald, S.; Hacker, K.; Hänisch, L.; Hage, A.; Hans, T.; Hass, E.; Hauberg, A.; Hensler, O.; Hesse, M.; Heuck, K.; Hidvegi, A.; Holz, M.; Honkavaara, K.; Höppner, H.; Ignatenko, A.; Jäger, J.; Jastrow, U.; Kammering, R.; Karstensen, S.; Kaukher, A.; Kay, H.; Keil, B.; Klose, K.; Kocharyan, V.; Köpke, M.; Körfer, M.; Kook, W.; Krause, B.; Krebs, O.; Kreis, S.; Krivan, F.; Kuhlmann, J.; Kuhlmann, M.; Kube, G.; Laarmann, T.; Lechner, C.; Lederer, S.; Leuschner, A.; Liebertz, D.; Liebing, J.; Liedtke, A.; Lilje, L.; Limberg, T.; Lipka, D.; Liu, B.; Lorbeer, B.; Ludwig, K.; Mahn, H.; Marinkovic, G.; Martens, C.; Marutzky, F.; Maslocv, M.; Meissner, D.; Mildner, N.; Miltchev, V.; Molnar, S.; Mross, D.; Müller, F.; Neumann, R.; Neumann, P.; Nölle, D.; Obier, F.; Pelzer, M.; Peters, H.-B.; Petersen, K.; Petrosyan, A.; Petrosyan, G.; Petrosyan, L.; Petrosyan, V.; Petrov, A.; Pfeiffer, S.; Piotrowski, A.; Pisarov, Z.; Plath, T.; Pototzki, P.; Prandolini, M. J.; Prenting, J.; Priebe, G.; Racky, B.; Ramm, T.; Rehlich, K.; Riedel, R.; Roggli, M.; Röhling, M.; Rönsch-Schulenburg, J.; Rossbach, J.; Rybnikov, V.; Schäfer, J.; Schaffran, J.; Schlarb, H.; Schlesselmann, G.; Schlösser, M.; Schmid, P.; Schmidt, C.; Schmidt-Föhre, F.; Schmitz, M.; Schneidmiller, E.; Schöps, A.; Scholz, M.; Schreiber, S.; Schütt, K.; Schütz, U.; Schulte-Schrepping, H.; Schulz, M.; Shabunov, A.; Smirnov, P.; Sombrowski, E.; Sorokin, A.; Sparr, B.; Spengler, J.; Staack, M.; Stadler, M.; Stechmann, C.; Steffen, B.; Stojanovic, N.; Sychev, V.; Syresin, E.; Tanikawa, T.; Tavella, F.; Tesch, N.; Tiedtke, K.; Tischer, M.; Treusch, R.; Tripathi, S.; Vagin, P.; Vetrov, P.; Vilcins, S.; Vogt, M.; de Zubiaurre Wagner, A.; Wamsat, T.; Weddig, H.; Weichert, G.; Weigelt, H.; Wentowski, N.; Wiebers, C.; Wilksen, T.; Willner, A.; Wittenburg, K.; Wohlenberg, T.; Wortmann, J.; Wurth, W.; Yurkov, M.; Zagorodnov, I.; Zemella, J.

2016-06-01

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.

[Physical treatment methods for acne. Light, laser, photodynamic therapy and peeling].

PubMed

Borelli, C; Korting, H C

2010-02-01

The medical treatment of acne is generally sufficient to meet the expectations of acne patients. However, in a number of situations additional therapeutic approaches may be advisable. There are a wide variety of useful physical methods. They range from electromagnetic waves, usually light, to peeling and manual therapy. Phototherapy of acne includes not just visible light but also laser and flash lamp therapy. The present review provides an overview on the evidence. Visible light, in particular blue light, provides an effective option for treatment of inflammatory acne. Photodynamic therapy also is efficacious; however, it should not be used because of an unfavorable risk-benefit ratio. UV treatment of acne is obsolete. Newer studies on the use of a variety of laser systems and flash lamps have demonstrated in part rewarding results.

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

Savelyev, Evgeny; Boll, Rebecca; Bomme, Cedric

In pump-probe experiments employing a free-electron laser (FEL) in combination with a synchronized optical femtosecond laser, the arrival-time jitter between the FEL pulse and the optical laser pulse often severely limits the temporal resolution that can be achieved. Here, we present a pump-probe experiment on the UV-induced dissociation of 2,6-difluoroiodobenzene C 6H 3F 2I) molecules performed at the FLASH FEL that takes advantage of recent upgrades of the FLASH timing and synchronization system to obtain high-quality data that are not limited by the FEL arrival-time jitter. Here, we discuss in detail the necessary data analysis steps and describe the originmore » of the time-dependent effects in the yields and kinetic energies of the fragment ions that we observe in the experiment.« less

Comparative laser-tissue interaction effects at 1.96 and 2.01 um of Cr; Tm:YAG laser

NASA Astrophysics Data System (ADS)

Pankratov, Michail M.; Perrault, Donald F., Jr.; Shapshay, Stanley M.; Pinto, Joseph F.; Esterowitz, Dina; Aretz, H. Thomas

1992-08-01

A pulsed spiking and nonspiking Cr; thulium (Tm):YAG flash lamp pumped laser operating at 1.96 and 2.01 μm was investigated in vitro in the clinically relevant power range for its basic laser-tissue interaction with soft, cartilaginous, and bone tissues. Some explanations of the differences and possible medical applications are discussed.

Magnetic Field Effect: An Efficient Tool To Investigate The Mechanism Of Reactions Using Laser Flash Photolysis Technique

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

Basu, Samita; Bose, Adity; Dey, Debarati

2008-04-24

Magnetic field effect combined with laser flash photolysis technique have been used to study the mechanism of interactions between two drug-like quinone molecules, Menadione (1,4-naphthoquinone, MQ) and 9, 10 Anthraquinone (AQ) with one of the DNA bases, Adenine in homogeneous acetonitrile/water and heterogeneous micellar media. A switchover in reaction mode from electron transfer to hydrogen abstraction is observed with MQ on changing the solvent from acetonitrile/water to micelle; whereas, AQ retains its mode of interaction towards Adenine as electron transfer in both the media due to its bulky structure compared to MQ.

Magnetic Field Effect: An Efficient Tool To Investigate The Mechanism Of Reactions Using Laser Flash Photolysis Technique

NASA Astrophysics Data System (ADS)

Basu, Samita; Bose, Adity; Dey, Debarati

2008-04-01

Magnetic field effect combined with laser flash photolysis technique have been used to study the mechanism of interactions between two drug-like quinone molecules, Menadione (1,4-naphthoquinone, MQ) and 9, 10 Anthraquinone (AQ) with one of the DNA bases, Adenine in homogeneous acetonitrile/water and heterogeneous micellar media. A switchover in reaction mode from electron transfer to hydrogen abstraction is observed with MQ on changing the solvent from acetonitrile/water to micelle; whereas, AQ retains its mode of interaction towards Adenine as electron transfer in both the media due to its bulky structure compared to MQ.

Laser flash-photolysis and gas discharge in N2O-containing mixture: kinetic mechanism

NASA Astrophysics Data System (ADS)

Kosarev, Ilya; Popov, Nikolay; Starikovskaia, Svetlana; Starikovskiy, Andrey; mipt Team

2011-10-01

The paper is devoted to further experimental and theoretical analysis of ignition by ArF laser flash-photolysis and nanosecond discharge in N2O-containing mixture has been done. Additional experiments have been made to assure that laser emission is distributed uniformly throughout the cross-section. The series of experiments was proposed and carried out to check validity of O(1D) determination in experiments on plasma assisted ignition initiated by flash-photolysis. In these experiments, ozone density in the given mixture (mixture composition and kinetics has been preliminary analyzed) was measured using UV light absorption in Hartley band. Good coincidence between experimental data and results of calculations have been obtained Temporal behavior of energy input, electric field and electric current has been measured and analyzed. These data are considered as initial conditions for numerical modeling of the discharge in O2:N2O:H2:Ar = 0.3:1:3:5 mixture. Ion-molecular reactions and reactions of active species production in Ar:H2:O2:N2O mixture were analyzed. The set of reactions to describe chemical transformation in the system due to the discharge action has been selected.

Spark Generated by ChemCam Laser During Tests

NASA Image and Video Library

2010-09-21

The ChemCam instrument for NASA Mars Science Laboratory mission uses a pulsed laser beam to vaporize a pinhead-size target, producing a flash of light from the ionized material plasma that can be analyzed to identify chemical elements in the target.

Comprehensive study of electro-optic and passive Q-switching in solid state lasers for altimeter applications

NASA Astrophysics Data System (ADS)

Bhardwaj, Atul; Agrawal, Lalita; Pal, Suranjan; Kumar, Anil

2006-12-01

Laser Science and Technology Center (LASTEC), Delhi, is developing a space qualified diode pumped Nd: YAG laser transmitter capable of generating 10 ns pulses of 30 mJ energy @ 10 pps. This paper presents the results of experiments for comparative studies between electro-optic and passively Q-switched Nd: YAG laser in a crossed porro prism based laser resonator. Experimental studies have been performed by developing an economical bench model of flash lamp pumped Nd: YAG laser (rod dimension, \

Brilliant GeV gamma-ray flash from inverse Compton scattering in the QED regime

NASA Astrophysics Data System (ADS)

Gong, Z.; Hu, R. H.; Lu, H. Y.; Yu, J. Q.; Wang, D. H.; Fu, E. G.; Chen, C. E.; He, X. T.; Yan, X. Q.

2018-04-01

An all-optical scheme is proposed for studying laser plasma based incoherent photon emission from inverse Compton scattering in the quantum electrodynamic regime. A theoretical model is presented to explain the coupling effects among radiation reaction trapping, the self-generated magnetic field and the spiral attractor in phase space, which guarantees the transfer of energy and angular momentum from electromagnetic fields to particles. Taking advantage of a prospective ˜ 1023 W cm-2 laser facility, 3D particle-in-cell simulations show a gamma-ray flash with unprecedented multi-petawatt power and brightness of 1.7 × 1023 photons s-1 mm-2 mrad-2/0.1% bandwidth (at 1 GeV). These results bode well for new research directions in particle physics and laboratory astrophysics exploring laser plasma interactions.

Reviews Equipment: Chameleon Nano Flakes Book: Requiem for a Species Equipment: Laser Sound System Equipment: EasySense VISION Equipment: UV Flash Kit Book: The Demon-Haunted World Book: Nonsense on Stilts Book: How to Think about Weird Things Web Watch

NASA Astrophysics Data System (ADS)

2011-03-01

WE RECOMMEND Requiem for a Species This book delivers a sober message about climate change Laser Sound System Sound kit is useful for laser demonstrations EasySense VISION Data Harvest produces another easy-to-use data logger UV Flash Kit Useful equipment captures shadows on film The Demon-Haunted World World-famous astronomer attacks pseudoscience in this book Nonsense on Stilts A thought-provoking analysis of hard and soft sciences How to Think about Weird Things This book explores the credibility of astrologers and their ilk WORTH A LOOK Chameleon Nano Flakes Product lacks good instructions and guidelines WEB WATCH Amateur scientists help out researchers with a variety of online projects

Viewing Spark Generated by ChemCam Laser for Mars Rover

NASA Image and Video Library

2010-09-21

The ChemCam instrument for NASA Mars Science Laboratory mission uses a pulsed laser beam to vaporize a pinhead-size target, producing a flash of light from the ionized material plasma that can be analyzed to identify chemical elements in the target.

High-Accuracy Multisensor Geolocation Technology to Support Geophysical Data Collection at MEC Sites

DTIC Science & Technology

2012-12-01

image with intensity data in a single step. Flash LiDAR can use both basic solutions to emit laser , either a single pulse with large aperture will...45 6. LASER SENSOR DEVELOPMENTS...and a terrestrial laser scanner (TLS). State-of-the-art GPS navigation allows for cm- accurate positioning in open areas where a sufficient number

Physics Flash August 2016

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

Kippen, Karen Elizabeth

Physics Flash is the newsletter for the Physics Division at Los Alamos National Laboratory. This newsletter is for August 2016. The following topics are covered: "Accomplishments in the Trident Laser Facility", "David Meyerhofer elected as chair-elect APS Nominating Committee", "HAWC searches for gamma rays from dark matter", "Proton Radiography Facility commissions electromagnetic magnifier", and "Cosmic ray muon computed tomography of spent nuclear fuel in dry storage casks."

Non-invasive online wavelength measurements at FLASH2 and present benchmark

PubMed Central

Braune, Markus; Buck, Jens; Kuhlmann, Marion; Grunewald, Sören; Düsterer, Stefan; Viefhaus, Jens; Tiedtke, Kai

2018-01-01

At FLASH2, the free-electron laser radiation wavelength is routinely measured by an online spectrometer based on photoionization of gas targets. Photoelectrons are detected with time-of-flight spectrometers and the wavelength is determined by means of well known binding energies of the target species. The wavelength measurement is non-invasive and transparent with respect to running user experiments due to the low gas pressure applied. Sophisticated controls for setting the OPIS operation parameters have been created and integrated into the distributed object-oriented control system at FLASH2. Raw and processed data can be stored on request in the FLASH data acquisition system for later correlation with data from user experiments or re-analysis. In this paper, the commissioning of the instrument at FLASH2 and the challenges of space charge effects on wavelength determination are reported. Furthermore, strategies for fast data reduction and online data processing are presented. PMID:29271744

Radiation measurement in the environment of FLASH using passive dosimeters

NASA Astrophysics Data System (ADS)

Mukherjee, B.; Rybka, D.; Makowski, D.; Lipka, T.; Simrock, S.

2007-08-01

Sophisticated electronic devices comprising sensitive microelectronic components have been installed in the close proximity of the 720 MeV superconducting electron linear accelerator (linac) driving the FLASH (Free Electron Laser in Hamburg), presently in operation at DESY in Hamburg. Microelectronic chips are inherently vulnerable to ionizing radiation, usually generated during routine operation of high-energy particle accelerator facilities like the FLASH. Hence, in order to assess the radiation effect on microelectronic chips and to develop suitable mitigation strategy, it becomes imperative to characterize the radiation field in the FLASH environment. We have evaluated the neutron and gamma energy (spectra) and dose distributions at critical locations in the FLASH tunnel using superheated emulsion (bubble) detectors, GaAs light emitting diodes (LED), LiF-thermoluminescence dosimeters (TLD) and radiochromic (Gafchromic EBT) films. This paper highlights the application of passive dosimeters for an accurate analysis of the radiation field produced by high-energy electron linear accelerators.

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

DOE PAGES

Faatz, B.; Plönjes, E.; Ackermann, S.; ...

2016-06-20

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated inmore » both FELs simultaneously. Here, FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.« less

Photonic Modulation Using Bi-Directional Diamond Shaped Ring Lasers at 1550 NM

DTIC Science & Technology

2007-04-01

modes for (a) 1% of the relaxation running oscillation frequency and (b) just below free running relaxation oscillation frequency ... List of Tables Table 1. Power requirements needed for a ring laser based flash architecture. Table 2. Achievable bits using 10 mW and

Generating circularly polarized radiation in the extreme ultraviolet spectral range at the free-electron laser FLASH

NASA Astrophysics Data System (ADS)

von Korff Schmising, Clemens; Weder, David; Noll, Tino; Pfau, Bastian; Hennecke, Martin; Strüber, Christian; Radu, Ilie; Schneider, Michael; Staeck, Steffen; Günther, Christian M.; Lüning, Jan; Merhe, Alaa el dine; Buck, Jens; Hartmann, Gregor; Viefhaus, Jens; Treusch, Rolf; Eisebitt, Stefan

2017-05-01

A new device for polarization control at the free electron laser facility FLASH1 at DESY has been commissioned for user operation. The polarizer is based on phase retardation upon reflection off metallic mirrors. Its performance is characterized in three independent measurements and confirms the theoretical predictions of efficient and broadband generation of circularly polarized radiation in the extreme ultraviolet spectral range from 35 eV to 90 eV. The degree of circular polarization reaches up to 90% while maintaining high total transmission values exceeding 30%. The simple design of the device allows straightforward alignment for user operation and rapid switching between left and right circularly polarized radiation.

Laser shocking of materials: Toward the national ignition facility

DOE PAGES

Meyers, M. A.; Remington, B. A.; Maddox, B.; ...

2010-01-16

In recent years a powerful experimental tool has been added to the arsenal at the disposal of the materials scientist investigating materials response at extreme regimes of strain rates, temperatures, and pressures: laser compression. In this paper, this technique has been applied successfully to mono-, poly-, and nanocrystalline metals and the results have been compared with predictions from analytical models and molecular dynamics simulations. Special flash x-ray radiography and flash x-ray diffraction, combined with laser shock propagation, are yielding the strength of metals at strain rates on the order of 10 7–10 8 s -1 and resolving details of themore » kinetics of phase transitions. A puzzling result is that experiments, analysis, and simulations predict dislocation densities that are off by orders of magnitude. Finally, other surprises undoubtedly await us as we explore even higher pressure/strain rate/temperature regimes enabled by the National Ignition Facility.« less

Laser High-Speed Photography System Used To Take Pictures Of The Attitudes Of Flying Projectile At The Muzzle Of Heavy Calibre Gun

NASA Astrophysics Data System (ADS)

Yuren, Wang; Fang, Shao; Weiping, Sun; Xioujuan, Li; Suning, Tian; Hongyan, Li

1989-06-01

When a heavy-calibre gun is fired and a projectite is flying near the gun muzzle, velocity of the projectile is very high and firing process is accompanying with strong muzzle flash. So taking the picture of the attitudes of flying projectile at the gun muzzle is very difficult. "YDS speed Photography System" developed by our group can take the framing pictures of the attitudes of the projectile and prevent them from flash confusing at the muzzle. Since framing depends on sequential pulse of the laser and the width of the putse is very narrow, therefore the exposure time is very short and photos of high-velocity flying body taken are very clear. This paper Introduces configuration and operation principle of "YDS laser High-speed Photography System" and the fuctions of the devices in this system In addition, some experimental results are briefly introduced.

Compact X-ray sources: X-rays from self-reflection

NASA Astrophysics Data System (ADS)

Mangles, Stuart P. D.

2012-05-01

Laser-based particle acceleration offers a way to reduce the size of hard-X-ray sources. Scientists have now developed a simple scheme that produces a bright flash of hard X-rays by using a single laser pulse both to generate and to scatter an electron beam.

Improving Range Estimation of a 3-Dimensional Flash Ladar via Blind Deconvolution

DTIC Science & Technology

2010-09-01

12 2.1.4 Optical Imaging as a Linear and Nonlinear System 15 2.1.5 Coherence Theory and Laser Light Statistics . . . 16 2.2 Deconvolution...rather than deconvolution. 2.1.5 Coherence Theory and Laser Light Statistics. Using [24] and [25], this section serves as background on coherence theory...the laser light incident on the detector surface. The image intensity related to different types of coherence is governed by the laser light’s spatial

ManPortable and UGV LIVAR: advances in sensor suite integration bring improvements to target observation and identification for the electronic battlefield

NASA Astrophysics Data System (ADS)

Lynam, Jeff R.

2001-09-01

A more highly integrated, electro-optical sensor suite using Laser Illuminated Viewing and Ranging (LIVAR) techniques is being developed under the Army Advanced Concept Technology- II (ACT-II) program for enhanced manportable target surveillance and identification. The ManPortable LIVAR system currently in development employs a wide-array of sensor technologies that provides the foot-bound soldier and UGV significant advantages and capabilities in lightweight, fieldable, target location, ranging and imaging systems. The unit incorporates a wide field-of-view, 5DEG x 3DEG, uncooled LWIR passive sensor for primary target location. Laser range finding and active illumination is done with a triggered, flash-lamp pumped, eyesafe micro-laser operating in the 1.5 micron region, and is used in conjunction with a range-gated, electron-bombarded CCD digital camera to then image the target objective in a more- narrow, 0.3$DEG, field-of-view. Target range determination is acquired using the integrated LRF and a target position is calculated using data from other onboard devices providing GPS coordinates, tilt, bank and corrected magnetic azimuth. Range gate timing and coordinated receiver optics focus control allow for target imaging operations to be optimized. The onboard control electronics provide power efficient, system operations for extended field use periods from the internal, rechargeable battery packs. Image data storage, transmission, and processing performance capabilities are also being incorporated to provide the best all-around support, for the electronic battlefield, in this type of system. The paper will describe flash laser illumination technology, EBCCD camera technology with flash laser detection system, and image resolution improvement through frame averaging.

Laser-induced pressure-wave and barocaloric effect during flash diffusivity measurements

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

Wang, Hsin; Porter, Wallace D.; Dinwiddie, Ralph Barton

We report laser-induced pressure-wave and barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 ms) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. Standard thermal diffusivity analysis only focuses the longer time scale thermal transient measured from the back surface due to thermal conduction. These negative spikes are filtered out and ignored as noise or anomaly from instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansionmore » and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (< 100 microsecond) is also known as thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about one millisecond. The pressure-wave induced thermal signal was systematically studied and analyzed. In conclusion, the underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.« less

Laser-induced pressure-wave and barocaloric effect during flash diffusivity measurements

DOE PAGES

Wang, Hsin; Porter, Wallace D.; Dinwiddie, Ralph Barton

2017-08-01

We report laser-induced pressure-wave and barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 ms) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. Standard thermal diffusivity analysis only focuses the longer time scale thermal transient measured from the back surface due to thermal conduction. These negative spikes are filtered out and ignored as noise or anomaly from instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansionmore » and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (< 100 microsecond) is also known as thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about one millisecond. The pressure-wave induced thermal signal was systematically studied and analyzed. In conclusion, the underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.« less

The examination of berberine excited state by laser flash photolysis

NASA Astrophysics Data System (ADS)

Cheng, Lingli; Wang, Mei; Zhao, Ping; Zhu, Hui; Zhu, Rongrong; Sun, Xiaoyu; Yao, Side; Wang, Shilong

2009-07-01

The property of the excited triplet state of berberine (BBR) was investigated by using time-resolved laser flash photolysis of 355 nm in acetonitrile. The transient absorption spectra of the excited triplet BBR were obtained in acetonitrile, which have an absorption maximum at 420 nm. And the ratio of excitation to ionization of BBR in acetonitrile solvent was calculated. The self-decay and self-quenching rate constants, and the absorption coefficient of 3BBR* were investigated and the excited state quantum yield was determined. Furthermore utilizing the benzophenone (BEN) as a triplet sensitizer, and the β-carotene (Car) as an excited energy transfer acceptor, the assignment of 3BBR* was further confirmed and the related energy transfer rate constants were also determined.

Characterization of the transient species generated by the photoionization of Berberine: A laser flash photolysis study

NASA Astrophysics Data System (ADS)

Cheng, Ling-Li; Wang, Mei; Zhu, Hui; Li, Kun; Zhu, Rong-Rong; Sun, Xiao-Yu; Yao, Si-De; Wu, Qing-Sheng; Wang, Shi-Long

2009-09-01

Using 266 nm laser flash photolysis it has been demonstrated that Berberine (BBR) in aqueous solution is ionized via a mono-photonic process giving a hydrated electron, anion radical that formed by hydrated electron react with steady state of BBR, and neutral radical that formed from rapid deprotonation of the radical cation of BBR. The quantum yield of photoionization is determined to be 0.03 at room temperature with KI solution used as a reference. Furthermore utilizing pH changing method and the SO 4rad - radical oxidation method, the assignment of radical cation of BBR was further confirmed, the p Ka value of it was calculated, and the related set up rate constant was also determined.

Laser flash photolysis studies of atmospheric free radical chemistry using optical diagnostic techniques

NASA Technical Reports Server (NTRS)

Wine, Paul H.; Nicovich, J. M.; Hynes, Anthony J.; Stickel, Robert E.; Thorn, R. P.; Chin, Mian; Cronkhite, Jeffrey A.; Shackelford, Christie J.; Zhao, Zhizhong; Daykin, Edward P.

1993-01-01

Some recent studies carried out in our laboratory are described where laser flash photolytic production of reactant free radicals has been combined with reactant and/or product detection using time-resolved optical techniques to investigate the kinetics and mechanisms of important atmospheric chemical reactions. Discussed are (1) a study of the radical-radical reaction O + BrO yields Br + O2 where two photolysis lasers are employed to prepare the reaction mixture and where the reactants O and BrO are monitored simultaneously using atomic resonance fluorescence to detect O and multipass UV absorption to detect BrO; (2) a study of the reaction of atomic chlorine with dimethylsulfide (CH3SCH3) where atomic resonance fluorescence detection of Cl is employed to elucidate the kinetics and tunable diode laser absorption spectroscopy is employed to investigate the HCl product yield; and (3) a study of the aqueous phase chemistry of Cl2(-) radicals where longpath UV absorption spectroscopy is employed to investigate the kinetics of the Cl2(-) + H2O reaction.

Laser photolysis studies of ω-bond dissociation in aromatic carbonyls with a C-C triple bond stimulated by triplet sensitization.

PubMed

Yamaji, Minoru; Horimoto, Ami; Marciniak, Bronislaw

2017-07-14

We have prepared three types of carbonyl compounds, benzoylethynylmethyl phenyl sulfide (2@SPh), (p-benzoyl)phenylethynylmethyl phenyl sulfide (3@SPh) and p-(benzoylethynyl)benzyl phenyl sulfide (4@SPh) with benzoyl and phenylthiylmethyl groups, which are interconnected with a C-C triple bond and a phenyl ring. Laser flash photolysis of 3@SPh and 4@SPh in acetonitrile provided the transient absorption spectra of the corresponding triplet states where no chemical reactions were recognized. Upon laser flash photolysis of 2@SPh, the absorption band due to the phenylthiyl radical (PTR) was obtained, indicating that the C-S bond cleaved in the excited state. Triplet sensitization of these carbonyl compounds using acetone and xanthone was conducted using laser photolysis techniques. The formation of triplet 3@SPh was seen in the transient absorption, whereas the PTR formation was observed for 2@SPh and 4@SPh, indicating that the triplet states were reactive for the C-S bond dissociation. The C-S bond dissociation mechanism for 4@SPh upon triplet sensitization is discussed in comparison with those for 2@SPh and 3@SPh.

Pressure Studies of Protein Dynamics

DTIC Science & Technology

1989-02-26

infrared flash photolysis system with the monitoring light produced by a Spectra-Physics/ Laser Analytics tunable- diode laser and detected by a liquid...refrigerator. Time range extends from about 100 ms to 100 s. The diode laser current is modulated at 10 kHz and the signal is amplified with a PAR 5101...Photolysis is obtained with a Phase-R D 121OOC dye laser using rhodamine 6G (pulse 4 width 500 ns, 0.3 J). Kinetic spectra are obtained from about 10

Taking Snapshots of Photosynthetic Water Oxidation Using Femtosecond X-ray Diffraction and Spectroscopy

PubMed Central

Kern, Jan; Tran, Rosalie; Alonso-Mori, Roberto; Koroidov, Sergey; Echols, Nathaniel; Hattne, Johan; Ibrahim, Mohamed; Gul, Sheraz; Laksmono, Hartawan; Sierra, Raymond G.; Gildea, Richard J.; Han, Guangye; Hellmich, Julia; Lassalle-Kaiser, Benedikt; Chatterjee, Ruchira; Brewster, Aaron S.; Stan, Claudiu A.; Glöckner, Carina; Lampe, Alyssa; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R.; Seibert, M. Marvin; Koglin, Jason E.; Gallo, Erik; Uhlig, Jens; Sokaras, Dimosthenis; Weng, Tsu-Chien; Zwart, Petrus H.; Skinner, David E.; Bogan, Michael J.; Messerschmidt, Marc; Glatzel, Pieter; Williams, Garth J.; Boutet, Sébastien; Adams, Paul D.; Zouni, Athina; Messinger, Johannes; Sauter, Nicholas K.; Bergmann, Uwe; Yano, Junko; Yachandra, Vittal K.

2014-01-01

The dioxygen we breathe is formed from water by its light-induced oxidation in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction center is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2 flash (2F) and 3 flash (3F) photosystem II samples, and of a transient 3F′ state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn-reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II. PMID:25006873

Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy

NASA Astrophysics Data System (ADS)

Kern, Jan; Tran, Rosalie; Alonso-Mori, Roberto; Koroidov, Sergey; Echols, Nathaniel; Hattne, Johan; Ibrahim, Mohamed; Gul, Sheraz; Laksmono, Hartawan; Sierra, Raymond G.; Gildea, Richard J.; Han, Guangye; Hellmich, Julia; Lassalle-Kaiser, Benedikt; Chatterjee, Ruchira; Brewster, Aaron S.; Stan, Claudiu A.; Glöckner, Carina; Lampe, Alyssa; Difiore, Dörte; Milathianaki, Despina; Fry, Alan R.; Seibert, M. Marvin; Koglin, Jason E.; Gallo, Erik; Uhlig, Jens; Sokaras, Dimosthenis; Weng, Tsu-Chien; Zwart, Petrus H.; Skinner, David E.; Bogan, Michael J.; Messerschmidt, Marc; Glatzel, Pieter; Williams, Garth J.; Boutet, Sébastien; Adams, Paul D.; Zouni, Athina; Messinger, Johannes; Sauter, Nicholas K.; Bergmann, Uwe; Yano, Junko; Yachandra, Vittal K.

2014-07-01

The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F’ state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

Bright half-cycle optical radiation from relativistic wavebreaking

NASA Astrophysics Data System (ADS)

Miao, Bo; Goers, Andy; Hine, George; Feder, Linus; Salehi, Fatholah; Wahlstrand, Jared; Milchberg, Howard

2015-11-01

Wavebreaking injection of electrons into relativistic plasma wakes generated in near-critical density hydrogen plasmas by sub-terawatt laser pulses is observed to generate an extremely energetic and ultra-broadband radiation flash. The flash is coherent, with a bandwidth of Δλ / λ ~ 0 . 7 consistent with half-cycle optical emission of duration ~ 1 fs from violent unidirectional acceleration of electrons to light speed from rest over a distance much less than the radiated wavelength. We studied the temporal duration and coherence of the flash by interfering it in the frequency domain with a well-characterized Xe supercontinuum pulse. Fringes across the full flash spectrum were observed with high visibility, and the extracted flash spectral phase supports it being a nearly transform-limited pulse. To our knowledge, this is the first evidence of bright half-cycle optical emission. This research is supported by the Defense Threat Reduction Agency, the US Department of Energy, and the Air Force Office of Scientific Research.

Development and performance characteristics of flash lamp pumped Yb:YAG, Cr:Tm:Ho:YAG, Er:Tm:Ho:YLF laser sources and investigation of their potential biological applications

NASA Astrophysics Data System (ADS)

Karadimitriou, N.; Klinkenberg, B.; Papadopoulos, D. N.; Serafetinides, A. A.

2007-07-01

Laser ablation for the formation of apodized patterns on intraocular lenses, as an alternative of the conventional injection molding, has been proved to be a very promising new technique. For the precise lenses ablation, the use of suitable laser wavelength and pulse duration, resulting in a small optical penetration depth in the lens and in confinement of the energy deposition in a small volume, as well as the reduced thermal damage to the surrounding tissue, is essential. Mid-infrared laser wavelengths, at which the organic biological simulators absorption coefficient is large, meet well the above conditions. Towards the complete understanding of the intraocular lens ablation procedure and therefore the choice of the optimum laser beam characteristics for the most accurate, efficient and safe surgical application, the comparative study of various mid-infrared laser sources is of great interest. In this work we investigate the potential of the development of three different mid-infrared laser sources, namely the Yb:YAG, the Cr:Tm:Ho:YAG and the Er:Tm:Ho:YLF laser, operating at 1029 nm, 2060 nm and 2080 nm respectively and their ability in forming patterns on biomaterials. Pumping was achieved with conventional Xe flash lamps in a double elliptical pump chamber. A properly designed Pulse-Forming- Network capable of delivering energy up to 800 J, in variable lamp illumination durations is used. Several hundreds of mJoules were achieved from the Yb:YAG laser oscillator and several Joules from the Ho:YAG and Ho:YLF laser oscillators. Free running and Q-switched laser operation studies and preliminary experiments on laser and biomaterials (biopolymers and animal tissues) interactions will be reported.

Research on the liquid coolant applied in the high repetition rate slab amplifier

NASA Astrophysics Data System (ADS)

Wang, Bingyan; Li, Yangshuai; Zhang, Panzheng; Wang, Li; Zhang, Yanli; Feng, Tao; Zhou, Qiong; Liu, Qiang; Li, Haiyuan; Zhang, Xu; Zhou, Shenlei; Ma, Weixin; Zhu, Jian; Zhu, Jianqiang

2018-03-01

High repetition rate slab amplifier (HRRSA) is extraordinarily indispensable for the future fusion power plant, ultra-short laser, laser weapon, and so on. Thermal controlling is the decisive factor for the repetition rate and the output energy of the slab amplifier. For larger clear aperture HRRSA, flash-lamp pumped slab amplifier based on neodymium phosphate glass (Nd:glass) is chosen with the liquid cooling. The liquid coolant circulates across the Nd:glass and takes off the thermal induced in the pumping process. A novel liquid coolant (Series A) whose refractive index is the same with Nd:glass is proposed to alleviate the wavefront distortion induced by thermal. The chemical stability of the liquid coolant under high energy flash-lamp irradiation with 200 shots and under the irradiation of a 1053nm laser with 19 hours and 37 hours are experimented. The results show that the chemical stability of the liquid coolant is stable under irradiation.

A photochemical study of the kinetics of the reactions of NH2 with phosphine, ethylene, and acetylene using flash photolysis-laser induced fluorescence. Ph.D. Thesis Catholic Univ. of America; [ammonia in the atmosphere of Jupiter

NASA Technical Reports Server (NTRS)

Bosco, S. R.

1982-01-01

The photochemistry of the reactions of NH2 was investigated in an attempt to explain the existence of an abundance of ammonia in the Jovian atmosphere. The production of ammonia reservoirs from the coupling of ammonia with other atmospheric constituents was considered. The rate constants for the reactions of NH2 radicals with phosphine, acetylene, and ethylene were measured. Flash photolysis was used for the production of NH2 radicals and laser induced fluorescence was employed for radical detection. It was determined that the rates of the reactions were too slow to be significant as a source of ammonia reservoirs in the Jovian atmosphere.

Primary photochemical processes for Pt(iv) diazido complexes prospective in photodynamic therapy of tumors.

PubMed

Shushakov, Anton A; Pozdnyakov, Ivan P; Grivin, Vjacheslav P; Plyusnin, Victor F; Vasilchenko, Danila B; Zadesenets, Andrei V; Melnikov, Alexei A; Chekalin, Sergey V; Glebov, Evgeni M

2017-07-25

Diazide diamino complexes of Pt(iv) are considered as prospective prodrugs in oxygen-free photodynamic therapy (PDT). Primary photophysical and photochemical processes for cis,trans,cis-[Pt(N 3 ) 2 (OH) 2 (NH 3 ) 2 ] and trans,trans,trans-[Pt(N 3 ) 2 (OH) 2 (NH 3 ) 2 ] complexes were studied by means of stationary photolysis, nanosecond laser flash photolysis and ultrafast kinetic spectroscopy. The process of photolysis is multistage. The first stage is the photosubstitution of an azide ligand to a water molecule. This process was shown to be a chain reaction involving redox stages. Pt(iv) and Pt(iii) intermediates responsible for the chain propagation were recorded using ultrafast kinetic spectroscopy and nanosecond laser flash photolysis. The mechanism of photosubstitution is proposed.

Nitric oxide synthase inhibition attenuates cutaneous vasodilation during the post-menopausal hot flash

PubMed Central

Hubing, Kimberly A.; Wingo, Jonathan E.; Brothers, R. Matthew; Coso, Juan Del; Low, David A.; Crandall, Craig G.

2010-01-01

Objective The purpose of this study was to test the hypothesis that local inhibition of nitric oxide and prostaglandin synthesis attenuates cutaneous vasodilator responses during post-menopausal hot flashes. Methods Four microdialysis membranes were inserted into forearm skin (dorsal surface) of 8 post-menopausal women (mean ± SD, 51±7 y). Ringers solution (control), 10mM Ketorolac (Keto) to inhibit prostaglandin synthesis, 10mM NG-L-arginine methyl ester (L-NAME) to inhibit nitric oxide synthase, and a combination of 10mM Keto + 10mM L-NAME were each infused at the separate sites. Skin blood flow at each site was indexed using laser-Doppler flowmetry. Cutaneous vascular conductance (CVC) was calculated as laser-Doppler flux/mean arterial blood pressure and was expressed as a percentage of the maximal calculated CVC (CVCmax) obtained following infusion of 50mM sodium nitropruside at all sites at the end of the study. Data from 13 hot flashes were analyzed. Results At the control site, the mean ± SD peak increase in CVC was 15.5±6% CVCmax units. This value was not different relative to the peak increase in CVC at the Keto site (13.0±5 % CVCmax units, P = 0.09). However, the peak increase in CVC during the flash was attenuated at the L-NAME and L-NAME + Keto sites (7.4±4 % CVCmax units and 8.7±7 % CVCmax units, respectively) relative to both the control and the Keto sites (P<0.05 for both comparisons). There were no significant differences in the peak increases in sweat rate between any of the sites (P = 0.24). Conclusions These data demonstrate that cutaneous vasodilation during a hot flash has a nitric oxide component. Increases in CVC despite the inhibition of prostaglandin synthesis suggest prostaglandins do not contribute to cutaneous vasodilation during a hot flash. PMID:20505548

Vacuum suppression of acousto-optic self-modulation in a broad-area Nd-doped yttrium-aluminum-garnet single-shot laser

NASA Astrophysics Data System (ADS)

Rus, M. Odín Soler; Cabrera-Granado, E.; Guerra Pérez, J. M.

2013-07-01

We report on the origin of an acousto-optic Raman-Nath self-modulation found in a broad-area Nd:YAG single-shot laser. Operating the laser device under vacuum conditions suppresses the spectral splitting associated with acousto-optic modulation by the shock waves produced by the discharge of the pumping flash lamps. This splitting is reproduced by a general class B laser model that takes into account the dynamical density grating generated by a stationary acoustic radial wave.

Observation of nanosecond laser induced fluorescence of in vitro seawater phytoplankton

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

Bensky, Thomas J.; Clemo, Lisa; Gilbert, Chris

2008-08-01

Seawater has been irradiated using a train of 70 ns flashes from a 440 nm laser source. This wavelength is on resonance with the blue absorption peak of Chlorophyll pigment associated with the photosystem of in vitro phytoplankton. The resulting fluorescence at 685 nm is instantaneously recorded during each laser pulse using a streak camera. Delayed fluorescence is observed, yielding clues about initiation of the photosynthetic process on a nanosecond time scale. Further data processing allows for determination of the functional absorption cross section, found to be 0.0095 ?{sup 2}, which is the first reporting of this number for inmore » vitro phytoplankton. Unlike other flash-pump studies of Chlorophyll, using a LED or flashlamp-based sources, the short laser pulse used here does not reveal any pulse-to-pulse hysteresis (i.e., variable fluorescence), indicating that the laser pulses used here are not able to drive the photosynthetic process to completion. This is attributed to competition from a back reaction between the photoexcited photosystem II and the intermediate electron acceptor. The significance of this work as a new type of deployable ocean fluorimeter is discussed, and it is believed the apparatus will have applications in thin-layer phytoplankton research.« less

Flash melting of tantalum in a diamond cell to 85 GPa

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

Karandikar, Amol; Boehler, Reinhard

2016-02-09

Here, we demonstrate a new level of precision in measuring melting temperatures at high pressure using laser flash-heating followed by Scanning Electron Microscopy and Focused Ion Beam Milling. Furthermore, the new measurements on tantalum put unprecedented constraints on its highly debated melting slope, calling for a reevaluation of theoretical, shock compression and diamond cell approaches to determine melting at high pressure. X-ray analysis of the recovered samples confirmed the absence of chemical reactions, which likely played a significant role in previous experiments.

Voltage Dependence of Proton Pumping by Bacteriorhodopsin Mutants with Altered Lifetime of the M Intermediate

PubMed Central

Geibel, Sven; Lörinczi, Èva; Bamberg, Ernst; Friedrich, Thomas

2013-01-01

The light-driven proton pump bacteriorhodopsin (BR) from Halobacterium salinarum is tightly regulated by the [H+] gradient and transmembrane potential. BR exhibits optoelectric properties, since spectral changes during the photocycle are kinetically controlled by voltage, which predestines BR for optical storage or processing devices. BR mutants with prolonged lifetime of the blue-shifted M intermediate would be advantageous, but the optoelectric properties of such mutants are still elusive. Using expression in Xenopus oocytes and two-electrode voltage-clamping, we analyzed photocurrents of BR mutants with kinetically destabilized (F171C, F219L) or stabilized (D96N, D96G) M intermediate in response to green light (to probe H+ pumping) and blue laser flashes (to probe accumulation/decay of M). These mutants have divergent M lifetimes. As for BR-WT, this strictly correlates with the voltage dependence of H+ pumping. BR-F171C and BR-F219L showed photocurrents similar to BR-WT. Yet, BR-F171C showed a weaker voltage dependence of proton pumping. For both mutants, blue laser flashes applied during and after green-light illumination showed reduced M accumulation and shorter M lifetime. In contrast, BR-D96G and BR-D96N exhibited small photocurrents, with nonlinear current-voltage curves, which increased strongly in the presence of azide. Blue laser flashes showed heavy M accumulation and prolonged M lifetime, which accounts for the strongly reduced H+ pumping rate. Hyperpolarizing potentials augmented these effects. The combination of M-stabilizing and -destabilizing mutations in BR-D96G/F171C/F219L (BR-tri) shows that disruption of the primary proton donor Asp-96 is fatal for BR as a proton pump. Mechanistically, M destabilizing mutations cannot compensate for the disruption of Asp-96. Accordingly, BR-tri and BR-D96G photocurrents were similar. However, BR-tri showed negative blue laser flash-induced currents even without actinic green light, indicating that Schiff base deprotonation in BR-tri exists in the dark, in line with previous spectroscopic investigations. Thus, M-stabilizing mutations, including the triple mutation, drastically interfere with electrochemical H+ gradient generation. PMID:24019918

Infrared Absorption Spectroscopy and Chemical Kinetics of Free Radicals. Final Performance Report, August 1, 1985--July 31, 1994

DOE R&D Accomplishments Database

Curl, R. F.; Glass, G. P.

1995-06-01

This research was directed at the detection, monitoring, and study (by infrared absorption spectroscopy) of the chemical kinetic behavior of small free radical species thought to be important intermediates in combustion. The work typically progressed from the detection and analysis of the infrared spectrum of combustion radical to the utilization of the infrared spectrum thus obtained in the investigation of chemical kinetics of the radical species. The methodology employed was infrared kinetic spectroscopy. In this technique the radical is produced by UV flash photolysis using an excimer laser and then its transient infrared absorption is observed using a single frequency cw laser as the source of the infrared probe light. When the probe laser frequency is near the center of an absorption line of the radical produced by the flash, the transient infrared absorption rises rapidly and then decays as the radical reacts with the precursor or with substances introduced for the purpose of studying the reaction kinetics or with itself. The decay times observed in these studies varied from less than one microsecond to more than one millisecond. By choosing appropriate time windows after the flash and the average infrared detector signal in a window as data channels, the infrared spectrum of the radical may be obtained. By locking the infrared probe laser to the center of the absorption line and measuring the rate of decay of the transient infrared absorption signal as the chemical composition of the gas mixture is varied, the chemical kinetics of the radical may be investigated. In what follows the systems investigated and the results obtained are outlined.

Hartmann wavefront sensors and their application at FLASH.

PubMed

Keitel, Barbara; Plönjes, Elke; Kreis, Svea; Kuhlmann, Marion; Tiedtke, Kai; Mey, Tobias; Schäfer, Bernd; Mann, Klaus

2016-01-01

Different types of Hartmann wavefront sensors are presented which are usable for a variety of applications in the soft X-ray spectral region at FLASH, the free-electron laser (FEL) in Hamburg. As a typical application, online measurements of photon beam parameters during mirror alignment are reported on. A compact Hartmann sensor, operating in the wavelength range from 4 to 38 nm, was used to determine the wavefront quality as well as aberrations of individual FEL pulses during the alignment procedure. Beam characterization and alignment of the focusing optics of the FLASH beamline BL3 were performed with λ(13.5 nm)/116 accuracy for wavefront r.m.s. (w(rms)) repeatability, resulting in a reduction of w(rms) by 33% during alignment.

Coherent Doppler lidar for automated space vehicle, rendezvous, station-keeping and capture

NASA Technical Reports Server (NTRS)

Dunkin, James A.

1991-01-01

Recent advances in eye-safe, short wavelength solid-state lasers offer real potential for the development of compact, reliable, light-weight, efficient coherent lidar. Laser diode pumping of these devices has been demonstrated, thereby eliminating the need for flash lamp pumping, which has been a major drawback to the use of these lasers in space based applications. Also these lasers now have the frequency stability required to make them useful in coherent lidar, which offers all of the advantages of non-coherent lidar, but with the additional advantage that direct determination of target velocity is possible by measurement of the Doppler shift. By combining the Doppler velocity measurement capability with the inherent high angular resolution and range accuracy of lidar it is possible to construct Doppler images of targets for target motion assessment. A coherent lidar based on a Tm,Ho:YAG 2-micrometer wavelength laser was constructed and successfully field tested on atmospheric targets in 1990. This lidar incorporated an all solid state (laser diode pumped) master oscillator, in conjunction with a flash lamp pumped slave oscillator. Solid-state laser technology is rapidly advancing, and with the advent of high efficiency, high power, semiconductor laser diodes as pump sources, all-solid-state, coherent lidars are a real possibility in the near future. MSFC currently has a feasibility demonstration effort under way which will involve component testing, and preliminary design of an all-solid-state, coherent lidar for automatic rendezvous, and capture. This two year effort, funded by the Director's Discretionary Fund is due for completion in 1992.

Temporal characterization of the wave-breaking flash in a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Miao, Bo; Feder, Linus; Goers, Andrew; Hine, George; Salehi, Fatholah; Wahlstrand, Jared; Woodbury, Daniel; Milchberg, Howard

2017-10-01

Wave-breaking injection of electrons into a relativistic plasma wake generated in near-critical density plasma by sub-terawatt laser pulses generates an intense ( 1 μJ) and ultra-broadband (Δλ 300 nm) radiation flash. In this work we demonstrate the spectral coherence of this radiation and measure its temporal width using single-shot supercontinuum spectral interferometry (SSSI). The measured temporal width is limited by measurement resolution to 50 fs. Spectral coherence is corroborated by PIC simulations which show that the spatial extent of the acceleration trajectory at the trapping region is small compared to the radiation center wavelength. To our knowledge, this is the first temporal and coherence characterization of wave-breaking radiation. This work is supported by the US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research.

Evidence for the load-dependent mechanical efficiency of individual myosin heads in skeletal muscle fibers activated by laser flash photolysis of caged calcium in the presence of a limited amount of ATP.

PubMed

Sugi, H; Iwamoto, H; Akimoto, T; Ushitani, H

1998-03-03

Although a contracting muscle regulates its energy output depending on the load imposed on it ("Fenn effect"), the mechanism underlying the load-dependent energy output remains obscure. To explore the possibility that the mechanical efficiency, with which chemical energy derived from ATP hydrolysis is converted into mechanical work, of individual myosin heads changes in a load-dependent manner, we examined the auxotonic shortening of glycerinated rabbit psoas muscle fibers, containing ATP molecules almost equal in number to the myosin heads, after laser-flash photolysis of caged calcium. Immediately before laser-flash activation, almost all of the myosin heads in the fiber are in the state M.ADP.Pi, and can undergo only one ATP hydrolysis cycle after activation. When the fibers were activated to shorten under various auxotonic loads, the length, force, and power output changes were found to be scaled according to the auxotonic load. Both the power and energy outputs were maximal under a moderate auxotonic load. The amount of M.ADP.Pi utilized at a time after activation was estimated from the amount of isometric force developed after interruption of fiber shortening. This amount was minimal in the isometric condition and increased nearly in proportion to the distance of fiber shortening. These results are taken as evidence that the efficiency of chemomechanical energy conversion in individual myosin heads changes in a load-dependent manner.

Load-dependent mechanical efficiency of individual myosin heads in skeletal muscle fibers activated by laser flash photolysis of caged calcium in the presence of a limited amount of ATP.

PubMed

Sugi, H; Iwamoto, H; Akimoto, T; Ushitani, H

1998-01-01

Although a contracting muscle regulates its energy output depending on the load imposed on it ("Fenn effect"), the mechanism underlying the load-dependent energy output remains obscure. To explore the possibility that the mechanical efficiency, with which chemical energy derived from ATP hydrolysis is converted into mechanical work, of individual myosin heads changes in a load-dependent manner, we examined the auxotonic shortening of glycerinated rabbit psoas muscle fibers, containing ATP molecules almost equal in number to the myosin heads, following laser flash photolysis of caged calcium. Immediately before laser flash activation, almost all of the myosin heads in the fiber are in the state, M.ADP.Pi, and can undergo only one ATP hydrolysis cycle after activation. When the fibers were activated to shorten under various auxotonic loads, the length, force and power output changes were found to be scaled according to the auxotonic load. Both the power and energy outputs were maximal under a moderate auxotonic load. The amount of M.ADP.Pi utilized at a time after activation was estimated from the amount of isometric force developed after interruption of fiber shortening. This amount was minimal in the isometric condition, and increased nearly in proportion to the distance of fiber shortening. These results are taken as evidence that the efficiency of chemo-mechanical energy conversion in individual myosin heads changes in a load-dependent manner.

Combined hostile fire and optics detection

NASA Astrophysics Data System (ADS)

Brännlund, Carl; Tidström, Jonas; Henriksson, Markus; Sjöqvist, Lars

2013-10-01

Snipers and other optically guided weapon systems are serious threats in military operations. We have studied a SWIR (Short Wave Infrared) camera-based system with capability to detect and locate snipers both before and after shot over a large field-of-view. The high frame rate SWIR-camera allows resolution of the temporal profile of muzzle flashes which is the infrared signature associated with the ejection of the bullet from the rifle. The capability to detect and discriminate sniper muzzle flashes with this system has been verified by FOI in earlier studies. In this work we have extended the system by adding a laser channel for optics detection. A laser diode with slit-shaped beam profile is scanned over the camera field-of-view to detect retro reflection from optical sights. The optics detection system has been tested at various distances up to 1.15 km showing the feasibility to detect rifle scopes in full daylight. The high speed camera gives the possibility to discriminate false alarms by analyzing the temporal data. The intensity variation, caused by atmospheric turbulence, enables discrimination of small sights from larger reflectors due to aperture averaging, although the targets only cover a single pixel. It is shown that optics detection can be integrated in combination with muzzle flash detection by adding a scanning rectangular laser slit. The overall optics detection capability by continuous surveillance of a relatively large field-of-view looks promising. This type of multifunctional system may become an important tool to detect snipers before and after shot.

White light velocity interferometer

DOEpatents

Erskine, D.J.

1999-06-08

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s. 41 figs.

White light velocity interferometer

DOEpatents

Erskine, David J.

1997-01-01

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.

White light velocity interferometer

DOEpatents

Erskine, David J.

1999-01-01

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.

White light velocity interferometer

DOEpatents

Erskine, D.J.

1997-06-24

The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s. 41 figs.

Optical countermeasures against CLOS weapon systems

NASA Astrophysics Data System (ADS)

Toet, Alexander; Benoist, Koen W.; van Lingen, Joost N. J.; Schleijpen, H. Ric M. A.

2013-10-01

There are many weapon systems in which a human operator acquires a target, tracks it and designates it. Optical countermeasures against this type of systems deny the operator the possibility to fulfill this visual task. We describe the different effects that result from stimulation of the human visual system with high intensity (visible) light, and the associated potential operational impact. Of practical use are flash blindness, where an intense flash of light produces a temporary "blind-spot" in (part of) the visual field, flicker distraction, where strong intensity and/or color changes at a discomfortable frequency are produced, and disability glare where a source of light leads to contrast reduction. Hence there are three possibilities to disrupt the visual task of an operator with optical countermeasures such as flares or lasers or a combination of these; namely, by an intense flash of light, by an annoying light flicker or by a glare source. A variety of flares for this purpose is now available or under development: high intensity flash flares, continuous burning flares or strobe flares which have an oscillating intensity. The use of flare arrays seems particularly promising as an optical countermeasure. Lasers are particularly suited to interfere with human vision, because they can easily be varied in intensity, color and size, but they have to be directed at the (human) target, and issues like pointing and eye-safety have to be taken into account. Here we discuss the design issues and the operational impact of optical countermeasures against human operators.

New counter-countermeasure techniques for laser anti-dazzling spectacles

NASA Astrophysics Data System (ADS)

Donval, Ariela; Partouche, Eran; Lipman, Ofir; Gross, Noam; Fisher, Tali; Oron, Moshe

2016-05-01

Aviation, commercial and military, is new area in optics that is suffering from laser threats in the last years. Dazzling and damage to pilot's eyes by laser pointers is a common threat lately. Under certain conditions, laser light, directed at aircraft can be hazardous. The most likely scenario is when bright visible laser light causes distraction and/or temporary flash blindness to the pilot, during a critical phase of flight like landing or takeoff. It is also possible, that a visible or invisible beam could cause permanent damage to a pilot's eyes. This paper presents a novel technology for protection of the human eye against laser threats in the visible range.

Nanosecond laser photolysis studies of vitamin K 3 in aqueous solution

NASA Astrophysics Data System (ADS)

Chen, J. F.; Ge, X. W.; Chu, G. S.; Zhang, Z. C.; Zhang, M. W.; Yao, S. D.; Lin, N. Y.

1999-06-01

Vitamin K 3 in aqueous solution was investigated by 248 nm laser flash photolysis. Laser-induced transient species were characterized according to kinetic analysis and quenching experiments by Mn 2+ and O 2. In neutral solutions, the intermediates recorded were assigned to excited triplet states and dehydrogenated radicals of vitamin K 3. In comparison with the results of pulse radiolytical experiment, vitamin K 3 not only has strong electron affinity but could also could be photoionized by UV laser light. All this shows that vitamin K 3 acts as an effective electron carrier and electron transfer agent.

Lasers' spectral and temporal profile can affect visual glare disability.

PubMed

Beer, Jeremy M A; Freeman, David A

2012-12-01

Experiments measured the effects of laser glare on visual orientation and motion perception. Laser stimuli were varied according to spectral composition and temporal presentation as subjects identified targets' tilt (Experiment 1) and movement (Experiment 2). The objective was to determine whether the glare parameters would alter visual disruption. Three spectral profiles (monochromatic Green vs. polychromatic White vs. alternating Red-Green) were used to produce a ring of laser glare surrounding a target. Two experiments were performed to measure the minimum contrast required to report target orientation or motion direction. The temporal glare profile was also varied: the ring was illuminated either continuously or discontinuously. Time-averaged luminance of the glare stimuli was matched across all conditions. In both experiments, threshold (deltaL) values were approximately 0.15 log units higher in monochromatic Green than in polychromatic White conditions. In Experiment 2 (motion identification), thresholds were approximately 0.17 log units higher in rapidly flashing (6, 10, or 14 Hz) than in continuous exposure conditions. Monochromatic extended-source laser glare disrupted orientation and motion identification more than polychromatic glare. In the motion task, pulse trains faster than 6 Hz (but below flicker fusion) elevated thresholds more than continuous glare with the same time-averaged luminance. Under these conditions, alternating the wavelength of monochromatic glare over time did not aggravate disability relative to green-only glare. Repetitively flashing monochromatic laser glare induced occasional episodes of impaired motion identification, perhaps resulting from cognitive interference. Interference speckle might play a role in aggravating monochromatic glare effects.

Nonvolatile Memory Technology for Space Applications

NASA Technical Reports Server (NTRS)

Oldham, Timothy R.; Irom, Farokh; Friendlich, Mark; Nguyen, Duc; Kim, Hak; Berg, Melanie; LaBel, Kenneth A.

2010-01-01

This slide presentation reviews several forms of nonvolatile memory for use in space applications. The intent is to: (1) Determine inherent radiation tolerance and sensitivities, (2) Identify challenges for future radiation hardening efforts, (3) Investigate new failure modes and effects, and technology modeling programs. Testing includes total dose, single event (proton, laser, heavy ion), and proton damage (where appropriate). Test vehicles are expected to be a variety of non-volatile memory devices as available including Flash (NAND and NOR), Charge Trap, Nanocrystal Flash, Magnetic Memory (MRAM), Phase Change--Chalcogenide, (CRAM), Ferroelectric (FRAM), CNT, and Resistive RAM.

Flash Photolysis and Its Applications: Meeting in Honour of Sir George Porter, P.R.S. held in London, England on 14-16 July 1986,

DTIC Science & Technology

1986-07-16

present the design and results from the current flash spectroscopic system at the R.I. A hybrid mode-locked, cavity dumped dye laser is used to seed a...date require a HE sum of at least three exponentials to achieve an acceptable fit. Lettuce chloroplasts exhibit decay times of 100 psec., 500-600 psec...other lettuce preparations. A PS1 preparation from the cyanobacterium Chlorogloea Fritschii, which has been thoroughly characterised previously [2

Energetic Materials Laboratory

DTIC Science & Technology

2015-04-30

regolith simulants mixed with magnesium, supported by NASA. It has also been used for studies on combustion synthesis of magnesium silicide , a...ammonium dinitramide based monopropellant.  The laser flash apparatus has been used for thermal diffusivities measurements for magnesium silicide and

Kinetic determinations of accurate relative oxidation potentials of amines with reactive radical cations.

PubMed

Gould, Ian R; Wosinska, Zofia M; Farid, Samir

2006-01-01

Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials.

Numerical design of a magnetized turbulence experiment at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Feister, Scott; Tzeferacos, Petros; Meinecke, Jena; Bott, Archie; Caprioli, Damiano; Laune, Jt; Bell, Tony; Casner, Alexis; Koenig, Michel; Li, Chikang; Miniati, Francesco; Petrasso, Richard; Remington, Bruce; Reville, Brian; Ross, J. Steven; Ryu, Dongsu; Ryutov, Dmitri; Sio, Hong; Turnbull, David; Zylstra, Alex; Schekochihin, Alexander; Froula, Dustin; Park, Hye-Sook; Lamb, Don; Gregori, Gianluca

2017-10-01

The origin and amplification of magnetic fields remains an active astrophysical research topic. We discuss design (using three-dimensional FLASH simulations) of a magnetized turbulence experiment at the National Ignition Facility (NIF). NIF lasers drive together two counter-propagating plasma flows to form a hot, turbulent plasma at the center. In the simulations, plasma temperatures are high enough to reach super-critical values of magnetic Reynolds number (Rm). Biermann battery seed magnetic fields (generated during laser-target interaction) are advected into the turbulent region and amplified by fluctuation dynamo in the above-unity Prandtl number regime. Plasma diagnostics are modeled with FLASH for planning and direct comparison with NIF experimental data. This work was supported in part at the University of Chicago by the DOE NNSA, the DOE Office of Science, and the NSF. The numerical simulations were conducted at ALCF's Mira under the auspices of the DOE Office of Science ALCC program.

Process research of non-Cz material

NASA Astrophysics Data System (ADS)

Campbell, R. B.

1985-06-01

Efforts were aimed at achieving a simultaneous front and back junction. Lasers and other heat sources were tried. Successful results were gained by two different methods: laser and flash lamp. Polymer dopants were applied to both sides of dendritic web cells. Rapid heating and cooling avoided any cross contamination between two junctions after removal of the dendrites. Both methods required subsequent thermal annealing in an oven to produce maximum efficiency cells.

Laser induced photoluminescence spectroscopy of cometary radicals

NASA Technical Reports Server (NTRS)

Jackson, W. M.; Cody, R. J.; Sabety-Dzvonik, M.

1976-01-01

Flash photolysis together with laser excitation of the product fragments was used in laboratory studies of cometary radicals. The LIPS method has been applied to the CN radical to determine: (1) Radiative lifetimes of individual rotational levels in the zeroth vibrational level of the B state; (2) energy partitioning during photodissociation of C2N2; and (3) vibrational and rotational excitation during formation of CN radicals in the photodissociation of dicyanoacetylene.

Research on the Ocular Effects of Laser Radiation. Executive Summary

DTIC Science & Technology

1988-09-01

safety standards and identify- ing the need for additional safety criteria. 7he Execulive Summ~ary is przsanted in seven parts dealing with the effects...laser safety standards and in identifying the need for additional safety criteria. The Executive Summary is divided into seven parts, dealing with...to coherent and noncoherent light flashes at flashblinding intensities, only limited studies have been made of the functional effects of lesion

Selective removal of natural caries lesions from dentin and tooth occlusal surfaces using a diode-pumped Er:YAG laser

NASA Astrophysics Data System (ADS)

Jew, Jamison; Chan, Kenneth H.; Darling, Cynthia L.; Fried, Daniel

2017-02-01

Selective removal of caries lesions with high precision is best accomplished using lasers operating at high pulse repetition rates utilizing small spot sizes. Conventional flash-lamp pumped Er:YAG lasers are poorly suited for this purpose, but new diode-pumped solid-state (DPSS) Er:YAG lasers have become available operating at high pulse repetition rates. Microradiography was used to determine the mineral content of the demineralized dentin of 200-μm thick sections with natural caries lesions prior to laser ablation. The purpose of this study was to explore the use of a DPSS Er:YAG laser for the selective removal of demineralized dentin and natural occlusal lesions on extracted teeth.

Kinetic studies of the reaction between pesticides and hydroxyl radical generated by laser flash photolysis.

PubMed

Gozzi, Fábio; Oliveira, Silvio C; Dantas, Renato F; Silva, Volnir O; Quina, Frank H; Machulek, Amilcar

2016-03-30

Due to contamination of the environment by pesticides and their mishandling, there is the need for treatment of contaminated sites and correct disposal of materials containing them. Thus, studies with advanced oxidation processes are expanding and can determine the rate constant of the hydroxyl radical with organic compounds of great importance in environmental contamination. In this context, the use of laser flash photolysis has been shown to be viable for the determination of these constants. The reaction rate constants of different pesticides with HO(•) in degassed acetonitrile have been determined. They were 1.6 × 10(9)  M(-1)  s(-1), 0.6 × 10(9)  M(-1)  s(-1), 1.2 × 10(9)  M(-1)  s(-1), 2.4 × 10(9)  M(-1)  s(-1) and 2.2 × 10(9)  M(-1)  s(-1) for the pesticides carbaryl, propoxur, fenoxycarb, ethoxysulfuron and chlorimuron-ethyl, respectively. These values are about an order of magnitude smaller than the diffusion controlled rate and correlate with the relative rates of disappearance of the pesticides in the photo-Fenton reaction in water. The correlation of the relative rate constants determined by laser flash photolysis with the relative rates of photo-Fenton degradation of the pesticides is compelling evidence for the participation of the hydroxyl radical in the degradation of these pesticides in the latter system. © 2015 Society of Chemical Industry.

Novel approach to real-time flash photolysis and confocal [Ca2+] imaging

PubMed Central

Sobie, Eric A.; Kao, Joseph P.Y.; Lederer, W. J.

2008-01-01

Flash photolysis of “caged” compounds using ultraviolet light is a powerful experimental technique for producing rapid changes in concentrations of bioactive signaling molecules. Studies that employ this technique have used diverse strategies for controlling the spatial and temporal application of light to the specimen. Here we describe a new system for flash photolysis that delivers light from a pulsed, adjustable intensity laser through an optical fiber coupled into the epifluorescence port of a commercial confocal microscope. Photolysis is achieved with extremely brief (5 ns) pulses of ultraviolet light (355 nm) that can be synchronized with respect to confocal laser scanning. The system described also localizes the UV intensity spatially so that uncaging only occurs in defined sub-cellular regions; moreover, since the microscope optics are used in localization, the photolysis volume can be easily adjusted. Experiments performed on rat ventricular myocytes loaded with the Ca2+ indicator fluo-3 and the Ca2+ cage NP-EGTA demonstrate the system's capabilities. Localized intracellular increases in [Ca2+] can trigger sarcoplasmic reticular Ca2+ release events such as Ca2+ sparks and, under certain conditions, regenerative Ca2+ waves. This relatively simple and inexpensive system is therefore a useful tool for examining local signaling in heart and other tissues. PMID:17323075

Structure-Kinetics Correlations in Isostructural Crystals of α-(ortho-Tolyl)-acetophenones: Pinning Down Electronic Effects Using Laser-Flash Photolysis in the Solid State.

PubMed

Ayitou, Anoklase J-L; Flynn, Kristen; Jockusch, Steffen; Khan, Saeed I; Garcia-Garibay, Miguel A

2016-03-02

Aqueous suspensions of nanocrystals in the 200-500 nm size range of isostructural α-(ortho-tolyl)-acetophenone (1a) and α-(ortho-tolyl)-para-methylacetophenone (1b) displayed good absorption characteristics for flash photolysis experiments in a flow system, with transient spectra and decay kinetics with a quality that is similar to that recorded in solution. In contrast to solution measurements, reactions in the solid state were characterized by a rate limiting hydrogen transfer reaction from the triplet excited state and a very short-lived biradical intermediate, which does not accumulate. Notably, the rate for δ-hydrogen atom transfer of 1a (2.7 × 10(7) s(-1)) in the crystalline phase is 18-fold larger than that of 1b (1.5 × 10(6) s(-1)). With nearly identical molecular and crystal structures, this decrease in the rate of δ-hydrogen abstraction can be assigned unambiguously to an electronic effect by the para-methyl group in 1b, which increases the contribution of the (3)π,π* configuration relative to the reactive (3)n,π* configuration in the lowest triplet excited state. These results highlight the potential of relating single crystal X-ray structural data with absolute kinetics from laser flash photolysis.

Sensitized and heavy atom induced production of acenaphthylene triplet: A laser flash photolysis study

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

Samanta, A.; Fessenden, R.W.

1989-07-27

The triplet state of acenaphthylene has been examined by nanosecond laser flash photolysis using sensitization and heavy atom perturbation techniques. Although acenaphthylene does not form any observable triplet upon direct flash excitation, a transient with microsecond lifetime ({lambda}{sub max} = 315 nm) is observable when a solution of the sample is excited by sensitizers (benzophenone, thioxanthone, benzil). This transient is ascribed to the triplet of acenaphthylene on the basis of its quenching behavior toward oxygen, ferrocene, azulene, and {beta}-carotene. Quantitative data concerning the triplet-triplet absorption and quenching constants are presented. The triplet energy is estimated to lie between 46 andmore » 47 kcal/mol. The triplet can also be produced by direct excitation in solvents containing heavy atoms (ethyl bromide, ethyl iodide). The triplet yield is found to increase with an increase of the amount of the heavy atom containing solvent. No saturation limit is obtained. These facts together with the effect of heavy atoms on the T{sub 1} {yields} S{sub 0} process allow the differing behavior of ethyl bromide and ethyl iodide on the photodimerization process of acenaphthylene to be explained. Triplet-state parameters (extinction coefficient and triplet yield) have been estimated in these solvents by the energy-transfer technique and actinometry.« less

Time-resolved measurements of statistics for a Nd:YAG laser.

PubMed

Hubschmid, W; Bombach, R; Gerber, T

1994-08-20

Time-resolved measurements of the fluctuating intensity of a multimode frequency-doubled Nd:YAG laser have been performed. For various operating conditions the enhancement factors in nonlinear optical processes that use a fluctuating instead of a single-mode laser have been determined up to the sixth order. In the case of reduced flash-lamp excitation and a switched-off laser amplifier, the intensity fluctuations agree with the normalized Gaussian model for the fluctuations of the fundamental frequency, whereas strong deviations are found under usual operating conditions. The frequencydoubled light has in the latter case enhancement factors not so far from values of Gaussian statistics.

Ocular dynamics and visual tracking performance after Q-switched laser exposure

NASA Astrophysics Data System (ADS)

Zwick, Harry; Stuck, Bruce E.; Lund, David J.; Nawim, Maqsood

2001-05-01

In previous investigations of q-switched laser retinal exposure in awake task oriented non-human primates (NHPs), the threshold for retinal damage occurred well below that of the threshold for permanent visual function loss. Visual function measures used in these studies involved measures of visual acuity and contrast sensitivity. In the present study, we examine the same relationship for q-switched laser exposure using a visual performance task, where task dependency involves more parafoveal than foveal retina. NHPs were trained on a visual pursuit motor tracking performance task that required maintaining a small HeNe laser spot (0.3 degrees) centered in a slowly moving (0.5deg/sec) annulus. When NHPs reliably produced visual target tracking efficiencies > 80%, single q-switched laser exposures (7 nsec) were made coaxially with the line of sight of the moving target. An infrared camera imaged the pupil during exposure to obtain the pupillary response to the laser flash. Retinal images were obtained with a scanning laser ophthalmoscope 3 days post exposure under ketamine and nembutol anesthesia. Q-switched visible laser exposures at twice the damage threshold produced small (about 50mm) retinal lesions temporal to the fovea; deficits in NHP visual pursuit tracking were transient, demonstrating full recovery to baseline within a single tracking session. Post exposure analysis of the pupillary response demonstrated that the exposure flash entered the pupil, followed by 90 msec refractory period and than a 12 % pupillary contraction within 1.5 sec from the onset of laser exposure. At 6 times the morphological threshold damage level for 532 nm q-switched exposure, longer term losses in NHP pursuit tracking performance were observed. In summary, q-switched laser exposure appears to have a higher threshold for permanent visual performance loss than the corresponding threshold to produce retinal threshold injury. Mechanisms of neural plasticity within the retina and at higher visual brain centers may mediat

Energy transfer dynamics in strongly inhomogeneous hot-dense-matter systems

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

Stillman, C. R.; Nilson, P. M.; Sefkow, A. B.

Direct measurements of energy transfer across steep density and temperature gradients in a hot-dense-matter system are presented. Hot dense plasma conditions were generated by high-intensity laser irradiation of a thin-foil target containing a buried metal layer. Energy transfer to the layer was measured using picosecond time-resolved x-ray emission spectroscopy. Here, the data show two x-ray flashes in time. Fully explicit, coupled particle-in-cell and collisional-radiative atomic kinetics model predictions reproduce these observations, connecting the two x-ray flashes with staged radial energy transfer within the target.

Energy transfer dynamics in strongly inhomogeneous hot-dense-matter systems

DOE PAGES

Stillman, C. R.; Nilson, P. M.; Sefkow, A. B.; ...

2018-06-25

Direct measurements of energy transfer across steep density and temperature gradients in a hot-dense-matter system are presented. Hot dense plasma conditions were generated by high-intensity laser irradiation of a thin-foil target containing a buried metal layer. Energy transfer to the layer was measured using picosecond time-resolved x-ray emission spectroscopy. Here, the data show two x-ray flashes in time. Fully explicit, coupled particle-in-cell and collisional-radiative atomic kinetics model predictions reproduce these observations, connecting the two x-ray flashes with staged radial energy transfer within the target.

Time-Space Position of Warm Dense Matter in Laser Plasma Interaction Process

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

Cao, L F; Uschmann, I; Forster, E

2006-09-25

Laser plasma interaction experiments have been perform performed using an fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. Electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were cautiously compared with relevant 1D numerical simulation. Finally these results provide a first experience of searching for the time-space position of the so-called warm dense plasma in an ultra fast laser target interaction process. These experiments aim to prepare nearmore » solid-density plasmas for Thomson scattering experiments using the short wavelength free-electron laser FLASH, DESY Hamburg.« less

Eye injuries from laser exposure: a review.

PubMed

Hudson, S J

1998-05-01

Lasers pose a significant threat to vision in modern military operations. Anti-personnel lasers have been designed that can cause intentional blindness in large numbers of personnel. Although the use of blinding laser weapons during combat has been prohibited by international legislation, research and development of these weapons have not been prohibited, and significant controversy remains. Unintentional blinding can also result from other types of lasers used on the battlefield, such as range-finders and anti-material lasers. Lasers that are capable of producing blindness operate within specific wavelength parameters and include visible and near infrared lasers. Patients who suffer from laser eye injuries usually complain of flash blindness, followed by transient or permanent visual loss. Laser retinal damage should be suspected in any patient with visual complaints in an operational setting. The treatment for laser retinal injuries is extremely limited, and prevention is essential. Improved protective eyeware and other countermeasures to laser eye injury are necessary as long as the threat remains.

Magnetic field effect corroborated with docking study to explore photoinduced electron transfer in drug-protein interaction.

PubMed

Chakraborty, Brotati; Roy, Atanu Singha; Dasgupta, Swagata; Basu, Samita

2010-12-30

Conventional spectroscopic tools such as absorption, fluorescence, and circular dichroism spectroscopy used in the study of photoinduced drug-protein interactions can yield useful information about ground-state and excited-state phenomena. However, photoinduced electron transfer (PET) may be a possible phenomenon in the drug-protein interaction, which may go unnoticed if only conventional spectroscopic observations are taken into account. Laser flash photolysis coupled with an external magnetic field can be utilized to confirm the occurrence of PET and authenticate the spin states of the radicals/radical ions formed. In the study of interaction of the model protein human serum albumin (HSA) with acridine derivatives, acridine yellow (AY) and proflavin (PF(+)), conventional spectroscopic tools along with docking study have been used to decipher the binding mechanism, and laser flash photolysis technique with an associated magnetic field (MF) has been used to explore PET. The results of fluorescence study indicate that fluorescence resonance energy transfer takes place from the protein to the acridine-based drugs. Docking study unveils the crucial role of Ser 232 residue of HSA in explaining the differential behavior of the two drugs towards the model protein. Laser flash photolysis experiments help to identify the radicals/radical ions formed in the due course of PET (PF(•), AY(•-), TrpH(•+), Trp(•)), and the application of an external MF has been used to characterize their initial spin-state. Owing to its distance dependence, MF effect gives an idea about the proximity of the radicals/radical ions during interaction in the system and also helps to elucidate the reaction mechanisms. A prominent MF effect is observed in homogeneous buffer medium owing to the pseudoconfinement of the radicals/radical ions provided by the complex structure of the protein.

Development of LIDAR sensor systems for autonomous safe landing on planetary bodies

NASA Astrophysics Data System (ADS)

Amzajerdian, F.; Pierrottet, D.; Petway, L.; Vanek, M.

2017-11-01

Future NASA exploratory missions to the Moon and Mars will require safe soft-landings at the designated sites with a high degree of precision. These sites may include areas of high scientific value with relatively rough terrain with little or no solar illumination and possibly areas near pre-deployed assets. The ability of lidar technology to provide three-dimensional elevation maps of the terrain, high precision distance to the ground, and approach velocity can enable safe landing of large robotic and manned vehicles with a high degree of precision. Currently, NASA-LaRC is developing novel lidar sensors aimed at meeting NASA's objectives for future planetary landing missions under the Autonomous Landing and Hazard Avoidance (ALHAT) project. These lidar sensors are 3-Dimensional Imaging Flash Lidar, Doppler Lidar, and Laser Altimeter. The Flash Lidar is capable of generating elevation maps of the terrain identifying hazardous features such as rocks, craters, and steep slopes. The elevation maps collected during the approach phase between 1000 m to 500 m above the ground can be used to determine the most suitable safe landing site. The Doppler Lidar provides highly accurate ground velocity and distance data allowing for precision navigation to the selected landing site. Prior to the approach phase at altitudes of over 15 km, the Laser Altimeter can provide sufficient data for updating the vehicle position and attitude data from the Inertial Measurement Unit. At these higher altitudes, either the Laser Altimeter or the Flash Lidar can be used for generating a contour map of the terrain below for identifying known surface features such as craters for further reducing the vehicle relative position error.

Development of lidar sensor systems for autonomous safe landing on planetary bodies

NASA Astrophysics Data System (ADS)

Amzajerdian, F.; Pierrottet, D.; Petway, L.; Vanek, M.

2017-11-01

Future NASA exploratory missions to the Moon and Mars will require safe soft-landings at the designated sites with a high degree of precision. These sites may include areas of high scientific value with relatively rough terrain with little or no solar illumination and possibly areas near pre-deployed assets. The ability of lidar technology to provide three-dimensional elevation maps of the terrain, high precision distance to the ground, and approach velocity can enable safe landing of large robotic and manned vehicles with a high degree of precision. Currently, NASA-LaRC is developing novel lidar sensors aimed at meeting NASA's objectives for future planetary landing missions under the Autonomous Landing and Hazard Avoidance (ALHAT) project [1]. These lidar sensors are 3-Dimensional Imaging Flash Lidar, Doppler Lidar, and Laser Altimeter. The Flash Lidar is capable of generating elevation maps of the terrain identifying hazardous features such as rocks, craters, and steep slopes. The elevation maps collected during the approach phase between 1000 m to 500 m above the ground can be used to determine the most suitable safe landing site. The Doppler Lidar provides highly accurate ground velocity and distance data allowing for precision navigation to the selected landing site. Prior to the approach phase at altitudes of over 15 km, the Laser Altimeter can provide sufficient data for updating the vehicle position and attitude data from the Inertial Measurement Unit. At these higher altitudes, either the Laser Altimeter or the Flash Lidar can be used for generating a contour map of the terrain below for identifying known surface features such as craters for further reducing the vehicle relative position error.

Radiation Chemistry in Organized Assemblies.

ERIC Educational Resources Information Center

Thomas, J. K.; Chen, T. S.

1981-01-01

Expands the basic concepts regarding the radiation chemistry of simple aqueous systems to more complex, but well defined, organized assemblies. Discusses the differences in behavior in comparison to simple systems. Reviews these techniques: pulse radiolysis, laser flash, photolysis, and steady state irradiation by gamma rays or light. (CS)

Laser flash photolysis and magnetic-field-effect studies on interaction of thymine and thymidine with menadione: role of sugar in controlling reaction pattern

NASA Astrophysics Data System (ADS)

Bose, Adity; Dey, Debarati; Basu, Samita

2008-04-01

The magnetic field effect (MFE) in conjunction with laser flash photolysis has been used for the study of the interaction of one of the small drug like quinone molecules, 2-methyl, 1,4-naphthoquinone, commonly known as menadione (MQ), with one of the DNA bases, thymine (THN), and its corresponding nucleoside, thymidine (THDN), in acetonitrile (ACN) and sodium dodecylsulfate (SDS) micelles. It has been observed that THN undergoes electron transfer (ET) and hydrogen (H) abstraction with MQ, while THDN undergoes only H abstraction in both the media. However, our earlier studies showed that a purine base, adenine (ADN), and its nucleoside, 2'-deoxyadenosine (ADS), undergo ET in ACN and H abstraction in SDS. Here we have attempted to explain the differences in the reactions of these DNA bases with MQ. We also reveal the crucial role of a sugar unit in altering the behavior of purine and pyrimidine bases with respect to ET and H abstraction.

Synthesis and characterization of TiO₂ and TiO₂/Ag for use in photodegradation of methylviologen, with kinetic study by laser flash photolysis.

PubMed

Ramos, Dayana Doffinger; Bezerra, Paula C S; Quina, Frank H; Dantas, Renato F; Casagrande, Gleison A; Oliveira, Silvio C; Oliveira, Márcio R S; Oliveira, Lincoln C S; Ferreira, Valdir S; Oliveira, Samuel L; Machulek, Amilcar

2015-01-01

This paper reports the synthesis, characterization, and application of TiO2 and TiO2/Ag nanoparticles for use in photocatalysis, employing the herbicide methylviologen (MV) as a substrate for photocatalytic activity testing. At suitable metal to oxide ratios, increases in silver surface coating on TiO2 enhanced the efficiency of heterogeneous photocatalysis by increasing the electron transfer constant. The sol-gel method was used for TiO2 synthesis. P25 TiO2 was the control material. Both oxides were subjected to the same silver incorporation process. The materials were characterized by conventional spectroscopy, SEM micrography, X-ray diffraction, calculation of surface area per mass of catalyst, and thermogravimetry. Also, electron transfers between TiO2 or TiO2/Ag and MV in the absence and presence of sodium formate were investigated using laser flash photolysis. Oxides synthesized with 2.0 % silver exhibited superior photocatalytic activity for MV degradation.

Hydrogen bonding effects on the reorganization energy for photoinduced charge separation reaction between porphyrin and quinone studied by nanosecond laser flash photolysis.

PubMed

Yago, Tomoaki; Gohdo, Masao; Wakasa, Masanobu

2010-02-25

Alcohol concentration dependences of photoinduced charge separation (CS) reaction of zinc tetraphenyl-porphyrin (ZnTPP) and duroquinone (DQ) were investigated in benzonitrile by a nanosecond laser flash photolysis technique. The photoinduced CS reaction was accelerated by the addition of alcohols, whereas the addition of acetonitrile caused little effect on the CS reactions. The simple theory was developed to calculate an increase in reorganization energies induced by the hydrogen bonding interactions between DQ and alcohols using the chemical equilibrium constants for the hydrogen bonding complexes through the concerted pathway and the stepwise one. The experimental results were analyzed by using the Marcus equation where we took into account the hydrogen bonding effects on the reorganization energy and the reaction free energy for the CS reaction. The observed alcohol concentration dependence of the CS reaction rates was well explained by the formation of the hydrogen bonding complexes through the concerted pathway, demonstrating the increase in the reorganization energy by the hydrogen bonding interactions.

Thermal ring closure in Mo(CO){sub 5}L (L = bpy, dmbpy, dpbpy) transients generated by pulsed laser flash photolysis. Mechanistic information from high-pressure effects

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

Reddy, K.B.; Hoffmann, R.; Konya, G.

1992-06-01

The kinetics of the ring-closure reactions of Mo(CO){sub 5}L, produced during the laser flash photolysis of Mo(CO){sub 6} and L where L = 2,2{prime}-bipyridine (bpy), 4,4{prime}-dimethyl-2,2{prime}-bipyridine (dpbpy) and 4,4{prime}-dephenyl-2,2{prime}-bipyridine (dpbpy) were studied as a function of temperature and pressure. The values of the activation parameters and pressure. The values of the activation parameters {Delta}S and {Delta}V are small and negative for L = bpy and dmbpy supporting an associative interchange mechanism (I{sub a}) for CO extrusion. For L = dpbpy, {Delta}V is small and positive in line with a dissociative interchange mechanism (I{sub d}). The results demonstrate a changeover inmore » mechanism from I{sub a} to I{sub d} with increasing steric hindrance on the bidentate ligand L. 36 refs., 1 fig., 2 tabs.« less

PS II model based analysis of transient fluorescence yield measured on whole leaves of Arabidopsis thaliana after excitation with light flashes of different energies.

PubMed

Belyaeva, N E; Schmitt, F-J; Paschenko, V Z; Riznichenko, G Yu; Rubin, A B; Renger, G

2011-02-01

Our recently presented PS II model (Belyaeva et al., 2008) was improved in order to permit a consistent simulation of Single Flash Induced Transient Fluorescence Yield (SFITFY) traces that were earlier measured by Steffen et al. (2005) on whole leaves of Arabidopsis (A.) thaliana at four different energies of the actinic flash. As the essential modification, the shape of the actinic flash was explicitly taken into account assuming that an exponentially decaying rate simulates the time dependent excitation of PS II by the 10 ns actinic flash. The maximum amplitude of this excitation exceeds that of the measuring light by 9 orders of magnitude. A very good fit of the SFITFY data was achieved in the time domain from 100 ns to 10s for all actinic flash energies (the maximum energy of 7.5 × 10¹⁶ photons/(cm²flash) is set to 100%, the relative energies of weaker actinic flashes were of ∼8%, 4%, ∼1%). Our model allows the calculation and visualization of the transient PS II redox state populations ranging from the dark adapted state, via excitation energy and electron transfer steps induced by pulse excitation, followed by final relaxation into the stationary state eventually attained under the measuring light. It turned out that the rate constants of electron transfer steps are invariant to intensity of the actinic laser flash. In marked contrast, an increase of the actinic flash energy by more than two orders of magnitude from 5.4×10¹⁴ photons/(cm²flash) to 7.5×10¹⁶ photons/(cm²flash), leads to an increase of the extent of fluorescence quenching due to carotenoid triplet (³Car) formation by a factor of 14 and of the recombination reaction between reduced primary pheophytin (Phe(-)) and P680(+) by a factor of 3 while the heat dissipation in the antenna complex remains virtually constant. The modified PS II model offers new opportunities to compare electron transfer and dissipative parameters for different species (e.g. for the green algae and the higher plant) under varying illumination conditions. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Femtosecond all-optical synchronization of an X-ray free-electron laser

DOE PAGES

Schulz, S.; Grguraš, I.; Behrens, C.; ...

2015-01-20

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30 fs r.m.s. for 90 fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarilymore » by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses.« less

Femtosecond all-optical synchronization of an X-ray free-electron laser

PubMed Central

Schulz, S.; Grguraš, I.; Behrens, C.; Bromberger, H.; Costello, J. T.; Czwalinna, M. K.; Felber, M.; Hoffmann, M. C.; Ilchen, M.; Liu, H. Y.; Mazza, T.; Meyer, M.; Pfeiffer, S.; Prędki, P.; Schefer, S.; Schmidt, C.; Wegner, U.; Schlarb, H.; Cavalieri, A. L.

2015-01-01

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30 fs r.m.s. for 90 fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses. PMID:25600823

Longitudinal space charge assisted echo seeding of a free-electron laser with laser-spoiler noise suppression

NASA Astrophysics Data System (ADS)

Hacker, Kirsten

2014-09-01

Seed lasers are employed to improve the temporal coherence of free-electron laser (FEL) light. However, when these seed pulses are short relative to the particle bunch, the noisy, temporally incoherent radiation from the unseeded electrons can overwhelm the coherent, seeded radiation. In this paper, a technique to seed a particle bunch with an external laser is presented in which a new mechanism to improve the contrast between coherent and incoherent free electron laser radiation is employed together with a novel, simplified echo-seeding method. The concept relies on a combination of longitudinal space charge wakes and an echo-seeding technique to make a short, coherent pulse of FEL light together with noise background suppression. Several different simulation codes are used to illustrate the concept with conditions at the soft x-ray free-electron laser in Hamburg, FLASH.

High-energy, high-average-power laser with Nd:YLF rods corrected by magnetorheological finishing.

PubMed

Bagnoud, Vincent; Guardalben, Mark J; Puth, Jason; Zuegel, Jonathan D; Mooney, Ted; Dumas, Paul

2005-01-10

A high-energy, high-average-power laser system, optimized to efficiently pump a high-performance optical parametric chirped-pulse amplifier at 527 nm, has been demonstrated. The crystal large-aperture ring amplifier employs two flash-lamp-pumped, 25.4-mm-diameter Nd:YLF rods. The transmitted wave front of these rods is corrected by magnetorheological finishing to achieve nearly diffraction-limited output performance with frequency-doubled pulse energies up to 1.8 J at 5 Hz.

[Nondestructive Evaluation (NDE) Capabilities

NASA Technical Reports Server (NTRS)

Born, Martin

2010-01-01

These poster boards display the United Space Alliance's (USA) systems and equipment used for Nondestructive Evaluation. These include: (1) the Robotic Inspection Facility, (2) CAT-Scan and Laminography, (3) Laser Surface Profilometry, (4) Remote Eddy Current, (5) Ultrasonic Phased Array, (7) Infrared Flash Thermography, and (8) Backscatter X-Ray (BSX)

Development of Ultrafast Indirect Flash Heating Methods for RDX

DTIC Science & Technology

2014-02-01

8 1 1. Introduction The mission of the Multiscale Response of Energetic Materials program is to establish...vinyl nitrate ) Films. J. Phys. Chem. A 2004, 108 (43), 9342–9347. 11 12. Gottfried, J. L.; de Lucia, F. C., Jr.; Piraino, S. M. Ultrafast Laser

The role of hot electrons in the dynamics of a laser-driven strong converging shock

DOE PAGES

Llor Aisa, E.; Ribeyre, X.; Duchateau, G.; ...

2017-11-30

Experiments on strong shock excitation in spherical plastic targets conducted at the Omega Laser Facility are interpreted with the radiation–hydrodynamics code CHIC to account for parametric instabilities excitation and hot-electron generation. The effects of hot electrons on the shock-pressure amplification and upstream preheat are analyzed. In this study, it is demonstrated that both effects contribute to an increase in shock velocity. Comparison of the measured laser reflectivity and shock flash time with numerical simulations make it possible to reconstitute the time history of the ablation and shock pressures. Finally, consequences of this analysis for the shock-ignition target design are discussed.

The role of hot electrons in the dynamics of a laser-driven strong converging shock

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

Llor Aisa, E.; Ribeyre, X.; Duchateau, G.

Experiments on strong shock excitation in spherical plastic targets conducted at the Omega Laser Facility are interpreted with the radiation–hydrodynamics code CHIC to account for parametric instabilities excitation and hot-electron generation. The effects of hot electrons on the shock-pressure amplification and upstream preheat are analyzed. In this study, it is demonstrated that both effects contribute to an increase in shock velocity. Comparison of the measured laser reflectivity and shock flash time with numerical simulations make it possible to reconstitute the time history of the ablation and shock pressures. Finally, consequences of this analysis for the shock-ignition target design are discussed.

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

DOE PAGES

Zastrau, U.; Rodel, C.; Nakatsutsumi, M.; ...

2018-02-05

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Here, imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense mattermore » studies of micrometer-sized samples in laser-plasma experiments.« less

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

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

Zastrau, U.; Rodel, C.; Nakatsutsumi, M.

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Here, imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense mattermore » studies of micrometer-sized samples in laser-plasma experiments.« less

Feasibility Analysis and Demonstration of High-Speed Digital Imaging Using Micro-Arrays of Vertical Cavity Surface-Emitting Lasers

DTIC Science & Technology

2011-04-01

Proceedings, Bristol, UK (2006). 5. M. A. Mentzer, Applied Optics Fundamentals and Device Applications: Nano, MOEMS , and Biotechnology, CRC Taylor...ballistic sensing, flash x-ray cineradiography, digital image correlation, image processing al- gorithms, and applications of MOEMS to nano- and

Light-induced structural changes and the site of O=O bond formation in PSII caught by XFEL.

PubMed

Suga, Michihiro; Akita, Fusamichi; Sugahara, Michihiro; Kubo, Minoru; Nakajima, Yoshiki; Nakane, Takanori; Yamashita, Keitaro; Umena, Yasufumi; Nakabayashi, Makoto; Yamane, Takahiro; Nakano, Takamitsu; Suzuki, Mamoru; Masuda, Tetsuya; Inoue, Shigeyuki; Kimura, Tetsunari; Nomura, Takashi; Yonekura, Shinichiro; Yu, Long-Jiang; Sakamoto, Tomohiro; Motomura, Taiki; Chen, Jing-Hua; Kato, Yuki; Noguchi, Takumi; Tono, Kensuke; Joti, Yasumasa; Kameshima, Takashi; Hatsui, Takaki; Nango, Eriko; Tanaka, Rie; Naitow, Hisashi; Matsuura, Yoshinori; Yamashita, Ayumi; Yamamoto, Masaki; Nureki, Osamu; Yabashi, Makina; Ishikawa, Tetsuya; Iwata, So; Shen, Jian-Ren

2017-03-02

Photosystem II (PSII) is a huge membrane-protein complex consisting of 20 different subunits with a total molecular mass of 350 kDa for a monomer. It catalyses light-driven water oxidation at its catalytic centre, the oxygen-evolving complex (OEC). The structure of PSII has been analysed at 1.9 Å resolution by synchrotron radiation X-rays, which revealed that the OEC is a Mn 4 CaO 5 cluster organized in an asymmetric, 'distorted-chair' form. This structure was further analysed with femtosecond X-ray free electron lasers (XFEL), providing the 'radiation damage-free' structure. The mechanism of O=O bond formation, however, remains obscure owing to the lack of intermediate-state structures. Here we describe the structural changes in PSII induced by two-flash illumination at room temperature at a resolution of 2.35 Å using time-resolved serial femtosecond crystallography with an XFEL provided by the SPring-8 ångström compact free-electron laser. An isomorphous difference Fourier map between the two-flash and dark-adapted states revealed two areas of apparent changes: around the Q B /non-haem iron and the Mn 4 CaO 5 cluster. The changes around the Q B /non-haem iron region reflected the electron and proton transfers induced by the two-flash illumination. In the region around the OEC, a water molecule located 3.5 Å from the Mn 4 CaO 5 cluster disappeared from the map upon two-flash illumination. This reduced the distance between another water molecule and the oxygen atom O4, suggesting that proton transfer also occurred. Importantly, the two-flash-minus-dark isomorphous difference Fourier map showed an apparent positive peak around O5, a unique μ 4 -oxo-bridge located in the quasi-centre of Mn1 and Mn4 (refs 4,5). This suggests the insertion of a new oxygen atom (O6) close to O5, providing an O=O distance of 1.5 Å between these two oxygen atoms. This provides a mechanism for the O=O bond formation consistent with that proposed previously.

Experimental study of flash boiling spray vaporization through quantitative vapor concentration and liquid temperature measurements

NASA Astrophysics Data System (ADS)

Zhang, Gaoming; Hung, David L. S.; Xu, Min

2014-08-01

Flash boiling sprays of liquid injection under superheated conditions provide the novel solutions of fast vaporization and better air-fuel mixture formation for internal combustion engines. However, the physical mechanisms of flash boiling spray vaporization are more complicated than the droplet surface vaporization due to the unique bubble generation and boiling process inside a superheated bulk liquid, which are not well understood. In this study, the vaporization of flash boiling sprays was investigated experimentally through the quantitative measurements of vapor concentration and liquid temperature. Specifically, the laser-induced exciplex fluorescence technique was applied to distinguish the liquid and vapor distributions. Quantitative vapor concentration was obtained by correlating the intensity of vapor-phase fluorescence with vapor concentration through systematic corrections and calibrations. The intensities of two wavelengths were captured simultaneously from the liquid-phase fluorescence spectra, and their intensity ratios were correlated with liquid temperature. The results show that both liquid and vapor phase of multi-hole sprays collapse toward the centerline of the spray with different mass distributions under the flash boiling conditions. Large amount of vapor aggregates along the centerline of the spray to form a "gas jet" structure, whereas the liquid distributes more uniformly with large vortexes formed in the vicinity of the spray tip. The vaporization process under the flash boiling condition is greatly enhanced due to the intense bubble generation and burst. The liquid temperature measurements show strong temperature variations inside the flash boiling sprays with hot zones present in the "gas jet" structure and vortex region. In addition, high vapor concentration and closed vortex motion seem to have inhibited the heat and mass transfer in these regions. In summary, the vapor concentration and liquid temperature provide detailed information concerning the heat and mass transfer inside flash boiling sprays, which is important for the understanding of its unique vaporization process.

Blast-Wave Generation and Propagation in Rapidly Heated Laser-Irradiated Targets

NASA Astrophysics Data System (ADS)

Ivancic, S. T.; Stillman, C. R.; Nilson, P. M.; Solodov, A. A.; Froula, D. H.

2017-10-01

Time-resolved extreme ultraviolet (XUV) spectroscopy was used to study the creation and propagation of a >100-Mbar blast wave in a target irradiated by an intense (>1018WWcm2 cm2) laser pulse. Blast waves provide a platform to generate immense pressures in the laboratory. A temporal double flash of XUV radiation was observed when viewing the rear side of the target, which is attributed to the emergence of a blast wave following rapid heating by a fast-electron beam generated from the laser pulse. The time-history of XUV emission in the photon energy range of 50 to 200 eV was recorded with an x-ray streak camera with 7-ps temporal resolution. The heating and expansion of the target was simulated with an electron transport code coupled to 1-D radiation-hydrodynamics simulations. The temporal delay between the two flashes measured in a systematic study of target thickness and composition was found to evolve in good agreement with a Sedov-Taylor blast-wave solution. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and Department of Energy Office of Science Award Number DE-SC-0012317.

Space-Time Characterization of Laser Plasma Interactions in the Warm Dense Matter Regime

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

Cao, L F; Uschmann, I; Forster, E

2008-04-30

Laser plasma interaction experiments have been performed using a fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. The electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were compared with hydrodynamic simulation. First results to characterize the plasma density and temperature as a function of space and time are obtained. This work aims to generate plasmas in the warm dense matter (WDM) regime at near solid-density in anmore » ultra-fast laser target interaction process. Plasmas under these conditions can serve as targets to develop x-ray Thomson scattering as a plasma diagnostic tool, e.g., using the VUV free-electron laser (FLASH) at DESY Hamburg.« less

Flash scanning the CO2 laser: a revival of the CO2 laser in plastic surgery

NASA Astrophysics Data System (ADS)

Lach, Elliot

1994-09-01

The CO2 laser has broad clinical application yet also presents a number of practical disadvantages. These drawbacks have limited the success and utilization of this laser in plastic surgery. Flashscanner technology has recently been used for char-free CO2 laser surgery of the oropharynx, the external female genital tract, and perirectal mucosa. A commercially available optomechanical flashscanner unit `Swiftlase,' was adapted to a CO2 laser and used for treatment in numerous plastic surgical applications. Conditions and situations that were treated in this study included generalized neurofibromatosis, tuberous sclerosis, rhinophyma, viral warts, breast reconstruction, and deepithelialization prior to microsurgery or local flap transfer and/or skin graft placement. There were no significant wound healing complications. Some patients previously sustained undue scarring from conventional CO2 laser surgery. Conservative, primarily ablative CO2 laser surgery with the Swiftlase has usefulness for treatment of patients in plastic surgery including those that were previously unsuccessfully treated.

Synchronous Phase-Resolving Flash Range Imaging

NASA Technical Reports Server (NTRS)

Pain, Bedabrata; Hancock, Bruce

2007-01-01

An apparatus, now undergoing development, for range imaging based on measurement of the round-trip phase delay of a pulsed laser beam is described. The apparatus would operate in a staring mode. A pulsed laser would illuminate a target. Laser light reflected from the target would be imaged on a verylarge- scale integrated (VLSI)-circuit image detector, each pixel of which would contain a photodetector and a phase-measuring circuit. The round-trip travel time for the reflected laser light incident on each pixel, and thus the distance to the portion of the target imaged in that pixel, would be measured in terms of the phase difference between (1) the photodetector output pulse and (2) a local-oscillator signal that would have a frequency between 10 and 20 MHz and that would be synchronized with the laser-pulse-triggering signal.

longitudinal space charge assisted echo seeding of a free electron laser

NASA Astrophysics Data System (ADS)

Hacker, Kirsten

2015-05-01

Seed lasers are employed to improve the temporal coherence of free-electron laser light. However, when seed pulses are short relative to the particle bunch, the noisy, temporally incoherent radiation from the un-seeded electrons can overwhelm the coherent, seeded radiation. In this paper a new seeding mechanism to improve the contrast between coherent and incoherent free electron laser radiation is employed together with a novel, simplified echo-seeding method. The concept relies on a combination of longitudinal space charge wakes and an echo-seeding technique to make a short, coherent pulse of FEL light together with noise background suppression. Several different simulation codes are used to illustrate the concept with conditions at the soft x-ray Free-electron LASer in Hamburg, FLASH. The impacts of coherent synchrotron radiation, intra beam scattering, and high peak current operation are investigated.

Three-Dimensional Super-Resolution: Theory, Modeling, and Field Tests Results

NASA Technical Reports Server (NTRS)

Bulyshev, Alexander; Amzajerdian, Farzin; Roback, Vincent E.; Hines, Glenn; Pierrottet, Diego; Reisse, Robert

2014-01-01

Many flash lidar applications continue to demand higher three-dimensional image resolution beyond the current state-of-the-art technology of the detector arrays and their associated readout circuits. Even with the available number of focal plane pixels, the required number of photons for illuminating all the pixels may impose impractical requirements on the laser pulse energy or the receiver aperture size. Therefore, image resolution enhancement by means of a super-resolution algorithm in near real time presents a very attractive solution for a wide range of flash lidar applications. This paper describes a superresolution technique and illustrates its performance and merits for generating three-dimensional image frames at a video rate.

Carbenes and Nitrenes: Recent Developments in Fundamental Chemistry.

PubMed

Wentrup, Curt

2018-05-29

There has been significant progress in the direct observation of carbenes, nitrenes, and many other reactive intermediates in recent years due to the application of matrix photolysis and flash vacuum pyrolysis linked with matrix isolation at cryogenic temperatures. Our understanding of singlet and triplet states has improved through the interplay of spectroscopy and computations. Bistable carbenes and nitrenes as well as many examples of tunneling have been discovered. Numerous rearrangements and fragmentations have been documented. This minireview aims to give an overview of some of these developments but will not generally cover laser flash photolysis and chemical reactions in liquid solution. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser based spot weld characterization

NASA Astrophysics Data System (ADS)

Jonietz, Florian; Myrach, Philipp; Rethmeier, Michael; Suwala, Hubert; Ziegler, Mathias

2016-02-01

Spot welding is one of the most important joining technologies, especially in the automotive industry. Hitherto, the quality of spot welded joints is tested mainly by random destructive tests. A nondestructive testing technique offers the benefit of cost reduction of the testing procedure and optimization of the fabrication process, because every joint could be examined. This would lead to a reduced number of spot welded joints, as redundancies could be avoided. In the procedure described here, the spot welded joint between two zinc-coated steel sheets (HX340LAD+Z100MB or HC340LA+ZE 50/50) is heated optically on one side. Laser radiation and flash light are used as heat sources. The melted zone, the so called "weld nugget" provides the mechanical stability of the connection, but also constitutes a thermal bridge between the sheets. Due to the better thermal contact, the spot welded joint reveals a thermal behavior different from the surrounding material, where the heat transfer between the two sheets is much lower. The difference in the transient thermal behavior is measured with time resolved thermography. Hence, the size of the thermal contact between the two sheets is determined, which is directly correlated to the size of the weld nugget, indicating the quality of the spot weld. The method performs well in transmission with laser radiation and flash light. With laser radiation, it works even in reflection geometry, thus offering the possibility of testing with just one-sided accessibility. By using heating with collimated laser radiation, not only contact-free, but also remote testing is feasible. A further convenience compared to similar thermographic approaches is the applicability on bare steel sheets without any optical coating for emissivity correction. For this purpose, a proper way of emissivity correction was established.

2.79 μm high peak power LGS electro-optically Q-switched Cr,Er:YSGG laser.

PubMed

Wang, Li; Wang, Jintao; Yang, Jingwei; Wu, Xianyou; Sun, Dunlu; Yin, Shaotang; Jiang, Haihe; Wang, Jiyang; Xu, Changqing

2013-06-15

A flash lamp pumped Cr,Er:YSGG laser utilizing a langasite (LGS) crystal as an electro-optic Q-switch is proposed and demonstrated. It is proved that a LGS crystal with relatively high damage threshold can be used as the electro-optic Q-switch at 2.79 μm, and 216 mJ pulse energy with 14.36 ns pulse width is achieved. Its corresponding peak power of pulse can reach 15 MW, to our knowledge the best result at a 2.79 μm wavelength.

Laser stimulation can activate autophagy in HeLa cells

NASA Astrophysics Data System (ADS)

Wang, Yisen; Lan, Bei; He, Hao; Hu, Minglie; Cao, Youjia; Wang, Chingyue

2014-10-01

For decades, lasers have been a daily tool in most biological research for fluorescent excitation by confocal or multiphoton microscopy. More than 20 years ago, cell photodamage caused by intense laser stimulation was noticed by generating reactive oxygen species, which was then thought as the main damage effect by photons. In this study, we show that laser stimulation can induce autophagy, an important cell lysosomal pathway responding to immune stimulation and starvation, without any biochemical treatment. Two different types of laser stimulations are found to be capable of activating autophagy: continuous scanning by continuous-wave visible lasers and a short-time flash of femtosecond laser irradiation. The autophagy generation is independent from wavelength, power, and scanning duration of the visible lasers. In contrast, the power of femtosecond laser is very critical to autophagy because the multiphoton excited Ca2+ dominates autophagy signaling. In general, we show here the different mechanisms of autophagy generation by such laser stimulation, which correspond to confocal microscopy and cell surgery, respectively. Those results can help further understanding of photodamage and autophagy signaling.

Research Studies on Radiative Collision Lasers

DTIC Science & Technology

1980-06-01

34Branching Ratios for TlBr Photodissocia- tion with 2660 X Radiation." Abstract: Selective molecular photodi:ssociation as a pumping mechanism to invert...following the flash photolysis of CF I. In the present work we examine the selective 3 photodissociation of TlBr into the Tl(6p 2 P3 / 2 ) metastable state

Improving Multiple Surface Range Estimation of a 3-Dimensional FLASH LADAR in the Presence of Atmospheric Turbulence

DTIC Science & Technology

2013-06-01

during the design process. For instance, the detector could be calibrated with incoherent il- lumination and a separate calibration could be performed...Poisson dis- tribution is often employed as a statistical distribution for the detected images. How- ever, due to the highly coherent nature of laser

Spectrometer for shot-to-shot photon energy characterization in the multi-bunch mode of the free electron laser at Hamburg

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

Palutke, S., E-mail: steffen.palutke@desy.de; Wurth, W.; Deutsches Elekronen Synchrotron

The setup and first results from commissioning of a fast online photon energy spectrometer for the vacuum ultraviolet free electron laser at Hamburg (FLASH) at DESY are presented. With the use of the latest advances in detector development, the presented spectrometer reaches readout frequencies up to 1 MHz. In this paper, we demonstrate the ability to record online photon energy spectra on a shot-to-shot base in the multi-bunch mode of FLASH. Clearly resolved shifts in the mean wavelength over the pulse train as well as shot-to-shot wavelength fluctuations arising from the statistical nature of the photon generating self-amplified spontaneous emissionmore » process have been observed. In addition to an online tool for beam calibration and photon diagnostics, the spectrometer enables the determination and selection of spectral data taken with a transparent experiment up front over the photon energy of every shot. This leads to higher spectral resolutions without the loss of efficiency or photon flux by using single-bunch mode or monochromators.« less

Design of a laser system for instantaneous location of a longwall shearer

NASA Technical Reports Server (NTRS)

Stein, R.

1981-01-01

Calculations and measurements for the design of a laser system for instantaneous location of a longwall shearer were made. The designs determine shearer location to approximately one foot. The roll, pitch, and yaw angles of the shearer track are determined to approximately two degrees. The first technique uses the water target system. A single silicon sensor system and three gallium arsenide laser beams are used in this technique. The second technique is based on an arrangement similar to that employed in aircraft omnidirectional position finding. The angle between two points is determined by combining information in an onmidirectional flash with a scanned, narrow beam beacon. It is concluded that this approach maximizes the signal levels.

International Congress on High-Speed Photography and Photonics, 19th, Cambridge, England, Sept. 16-21, 1990, Proceedings

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

Garfield, B.R.; Rendell, J.T.

1991-01-01

The present conference discusses the application of schlieren photography in industry, laser fiber-optic high speed photography, holographic visualization of hypervelocity explosions, sub-100-picosec X-ray grating cameras, flash soft X-radiography, a novel approach to synchroballistic photography, a programmable image converter framing camera, high speed readout CCDs, an ultrafast optomechanical camera, a femtosec streak tube, a modular streak camera for laser ranging, and human-movement analysis with real-time imaging. Also discussed are high-speed photography of high-resolution moire patterns, a 2D electron-bombarded CCD readout for picosec electrooptical data, laser-generated plasma X-ray diagnostics, 3D shape restoration with virtual grating phase detection, Cu vapor lasers for highmore » speed photography, a two-frequency picosec laser with electrooptical feedback, the conversion of schlieren systems to high speed interferometers, laser-induced cavitation bubbles, stereo holographic cinematography, a gatable photonic detector, and laser generation of Stoneley waves at liquid-solid boundaries.« less

Electro-optically Q-switched dual-wavelength Nd:YLF laser emitting at 1047 nm and 1053 nm

NASA Astrophysics Data System (ADS)

Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Li, Yongfu; Zhang, Xingyu

2015-05-01

A flash-lamp pumped electro-optically Q-switched dual-wavelength Nd:YLF laser is demonstrated. Two Nd:YLF crystals placed in two cavities are employed to generate orthogonally polarized 1047 nm and 1053 nm radiations, respectively. The two cavities are jointed together by a polarizer and share the same electro-optical Q-switch. Two narrow-band pass filters are used to block unexpected oscillations at the hold-off state of the electro-optical Q-switch. In this case, electro-optical Q-switching is able to operate successfully. With pulse synchronization realized, the maximum output energy of 66.2 mJ and 83.9 mJ are obtained for 1047 nm and 1053 nm lasers, respectively. Correspondingly, the minimum pulse width is both 17 ns for 1047 nm and 1053 nm lasers. Sum frequency generation is realized. This demonstrates the potential of this laser in difference-frequency generations to obtain terahertz wave.

Suppressing the cellular breakdown in silicon supersaturated with titanium

NASA Astrophysics Data System (ADS)

Liu, Fang; Prucnal, S.; Hübner, R.; Yuan, Ye; Skorupa, W.; Helm, M.; Zhou, Shengqiang

2016-06-01

Hyper doping Si with up to 6 at.% Ti in solid solution was performed by ion implantation followed by pulsed laser annealing and flash lamp annealing. In both cases, the implanted Si layer can be well recrystallized by liquid phase epitaxy and solid phase epitaxy, respectively. Cross-sectional transmission electron microscopy of Ti-implanted Si after liquid phase epitaxy shows the so-called growth interface breakdown or cellular breakdown owing to the occurrence of constitutional supercooling in the melt. The appearance of cellular breakdown prevents further recrystallization. However, the out-diffusion and cellular breakdown can be effectively suppressed by solid phase epitaxy during flash lamp annealing due to the high velocity of amorphous-crystalline interface and the low diffusion velocity for Ti in the solid phase.

Formation of tryptophan radicals in irradiated aqueous solutions of hexachloroplatinate(IV): a flash photolysis study.

PubMed

Zang, L; Rodgers, M A

1999-10-01

The oxidation of tryptophan photosensitized by PtCl6(2-) has been investigated in aqueous solutions at different pH using nanosecond laser flash photolysis. Cationic and neutral radicals of tryptophan were detected at pH 2.8 and 8.5, respectively. The generation of the radical was attributed to oxidation by Cl2- that was formed from the homolytic bond cleavage in the excited state of PtCl6(2-). The bimolecular rate constant derived from the kinetics analysis, 2.8 +/- 0.2 x 10(9) M-1 s-1, is in good agreement with the value obtained in earlier pulse radiolysis studies. Both the cationic and neutral radicals decayed by second-order kinetics, consistent with the dimerization process.

Optical Pumping of Molecular Gases

DTIC Science & Technology

1976-04-01

ser emission ott a The typical experimental apparatus is shown i.- Fig. *series of green and yellow molecular B-X’-basnd transi- 2. For B-bantd optical...with A, at 0. 473 pim and that Na2 may operate as a flash -lamp -pumped laser X,... at 0. 54 umn the Doppler widths are AwD - 12.42 source with buffer

Laser Flash Photolysis Studies of Radical-Radical Reaction Kinetics: The O((sup 3)P(sub J)) + BrO Reaction

NASA Technical Reports Server (NTRS)

Thorn, R. P.; Cronkhite, J. M.; Nicovich, J. M.; Wine, P. H.

1997-01-01

A novel dual laser flash photolysis-long path absorption-resonance fluorescence technique has been employed to study the kinetics of the important stratospheric reaction 0((sup 3)P(sub j)) + Br yields(k1) BrO((sup 2)P(sub J)) + O2 as a function of temperature (231-328 K) and pressure (25-150 Torr) in N2 buffer gas. The experimental approach preserves the principal advantages of the flash photolysis method, i.e., complete absence of surface reactions and a wide range of accessible pressures, but also employs techniques which are characteristic of the discharge flow method, namely chemical titration as a means for deducing the absolute concentration of a radical reactant and use of multiple detection axes. We find that k1 is independent of pressure, and that the temperature dependence of k1 is adequately described by the Arrhenius expression k1(T) = 1.91 x 10(exp -11)(230/J) cu cm/ molecule.s; the absolute accuracy of measured values for k1 is estimated to vary from +/- 20 percent at at T approximately 230 K to +/- 30 percent at T approximately 330 K. Our results demonstrate that the O((sup 3)P(sub j)) + BrO rate coefficient is significantly faster than previously 'guesstimated,' and suggest that the catalytic cycle with the O((sup 3)P(sub j)) + BrO reaction as its rate-limiting step is the dominant stratospheric BrO(x), odd-oxygen destruction cycle at altitudes above 24 km.

Semiconductor cylinder fiber laser

NASA Astrophysics Data System (ADS)

Sandupatla, Abhinay; Flattery, James; Kornreich, Philipp

2015-12-01

We fabricated a fiber laser that uses a thin semiconductor layer surrounding the glass core as the gain medium. This is a completely new type of laser. The In2Te3 semiconductor layer is about 15-nm thick. The fiber laser has a core diameter of 14.2 μm, an outside diameter of 126 μm, and it is 25-mm long. The laser mirrors consist of a thick vacuum-deposited aluminum layer at one end and a thin semitransparent aluminum layer deposited at the other end of the fiber. The laser is pumped from the side with either light from a halogen tungsten incandescent lamp or a blue light emitting diode flash light. Both the In2Te3 gain medium and the aluminum mirrors have a wide bandwidth. Therefore, the output spectrum consists of a pedestal from a wavelength of about 454 to 623 nm with several peaks. There is a main peak at 545 nm. The main peak has an amplitude of 16.5 dB above the noise level of -73 dB.

Evaluation of a commercially available passively Q-switched Nd:YAG laser with LiF: F2- saturable absorber for laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Carson, Cantwell G.; Goueguel, Christian L.; Sanghapi, Hervé; Jain, Jinesh; McIntyre, Dustin

2016-05-01

Interest in passively Q-switched microchip lasers as a means for miniaturization of laser-induced breakdown spectroscopy (LIBS) apparatus has rapidly grown in the last years. To explore the possibility of using a comparatively UV-vis transparent absorber, we herein present the first report on the evaluation of a commercially available flash lamp-pumped passively Q-switched Nd:YAG laser with LiF: F2- saturable absorber as an excitation source in LIBS. Quantitative measurements of barium, strontium, rubidium and lithium in granite, rhyolite, basalt and syenite whole-rock glass samples were performed. Using a gated intensified benchtop spectrometer, limits of detection of 0.97, 23, 37, and 144 ppm were obtained for Li, Sr, Rb, and Ba, respectively. Finally, we discuss the advantages of using such a laser unit for LIBS applications in terms of ablation efficiency, analytical performances, output energy, and standoff capabilities.

Multistep Ionization of Argon Clusters in Intense Femtosecond Extreme Ultraviolet Pulses

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

Bostedt, C.; Thomas, H.; Hoener, M.

The interaction of intense extreme ultraviolet femtosecond laser pulses ({lambda}=32.8 nm) from the FLASH free electron laser (FEL) with clusters has been investigated by means of photoelectron spectroscopy and modeled by Monte Carlo simulations. For laser intensities up to 5x10{sup 13} W/cm{sup 2}, we find that the cluster ionization process is a sequence of direct electron emission events in a developing Coulomb field. A nanoplasma is formed only at the highest investigated power densities where ionization is frustrated due to the deep cluster potential. In contrast with earlier studies in the IR and vacuum ultraviolet spectral regime, we find nomore » evidence for electron emission from plasma heating processes.« less

Investigating the interaction of x-ray free electron laser radiation with grating structure.

PubMed

Gaudin, Jérôme; Ozkan, Cigdem; Chalupský, Jaromír; Bajt, Saša; Burian, Tomáš; Vyšín, Ludek; Coppola, Nicola; Farahani, Shafagh Dastjani; Chapman, Henry N; Galasso, Germano; Hájková, Vera; Harmand, Marion; Juha, Libor; Jurek, Marek; Loch, Rolf A; Möller, Stefan; Nagasono, Mitsuru; Störmer, Michael; Sinn, Harald; Saksl, Karel; Sobierajski, Ryszard; Schulz, Joachim; Sovak, Pavol; Toleikis, Sven; Tiedtke, Kai; Tschentscher, Thomas; Krzywinski, Jacek

2012-08-01

The interaction of free electron laser pulses with grating structure is investigated using 4.6±0.1 nm radiation at the FLASH facility in Hamburg. For fluences above 63.7±8.7 mJ/cm2, the interaction triggers a damage process starting at the edge of the grating structure as evidenced by optical and atomic force microscopy. Simulations based on solution of the Helmholtz equation demonstrate an enhancement of the electric field intensity distribution at the edge of the grating structure. A procedure is finally deduced to evaluate damage threshold.

Anti-dazzling protection for Air Force pilots

NASA Astrophysics Data System (ADS)

Donval, Ariela; Fisher, Tali; Lipman, Ofir; Oron, Moshe

2012-06-01

Under certain conditions, laser directed at aircraft can be a hazard. The most likely scenario is when a bright visible laser causes distraction or temporary flash blindness to a pilot, during a critical phase of flight such as landing or takeoff. It is also possible, that a visible or invisible beam could cause permanent harm to a pilot's eyes. We present a non-linear, solid-state dynamic filter solutions protecting from dazzling and damage in a passive way. Our filters limit the transmission, only if the power exceeds a certain threshold as opposed to spectral filters that block a certain wavelength permanently.

Preventing kinetic roughening in physical vapor-phase-deposited films.

PubMed

Vasco, E; Polop, C; Sacedón, J L

2008-01-11

The growth kinetics of the mostly used physical vapor-phase deposition techniques -molecular beam epitaxy, sputtering, flash evaporation, and pulsed laser deposition-is investigated by rate equations with the aim of testing their suitability for the preparation of ultraflat ultrathin films. The techniques are studied in regard to the roughness and morphology during early stages of growth. We demonstrate that pulsed laser deposition is the best technique for preparing the flattest films due to two key features [use of (i) a supersaturated pulsed flux of (ii) hyperthermal species] that promote a kinetically limited Ostwald ripening mechanism.

Lidar Sensor Performance in Closed-Loop Flight Testing of the Morpheus Rocket-Propelled Lander to a Lunar-Like Hazard Field

NASA Technical Reports Server (NTRS)

Roback, Vincent E.; Pierrottet, Diego F.; Amzajerdian, Farzin; Barnes, Bruce W.; Hines, Glenn D.; Petway, Larry B.; Brewster, Paul F.; Kempton, Kevin S.; Bulyshev, Alexander E.

2015-01-01

For the first time, a suite of three lidar sensors have been used in flight to scan a lunar-like hazard field, identify a safe landing site, and, in concert with an experimental Guidance, Navigation, and Control (GN&C) system, guide the Morpheus autonomous, rocket-propelled, free-flying test bed to a safe landing on the hazard field. The lidar sensors and GN&C system are part of the Autonomous Precision Landing and Hazard Detection and Avoidance Technology (ALHAT) project which has been seeking to develop a system capable of enabling safe, precise crewed or robotic landings in challenging terrain on planetary bodies under any ambient lighting conditions. The 3-D imaging flash lidar is a second generation, compact, real-time, air-cooled instrument developed from a number of cutting-edge components from industry and NASA and is used as part of the ALHAT Hazard Detection System (HDS) to scan the hazard field and build a 3-D Digital Elevation Map (DEM) in near-real time for identifying safe sites. The flash lidar is capable of identifying a 30 cm hazard from a slant range of 1 km with its 8 cm range precision at 1 sigma. The flash lidar is also used in Hazard Relative Navigation (HRN) to provide position updates down to a 250m slant range to the ALHAT navigation filter as it guides Morpheus to the safe site. The Doppler Lidar system has been developed within NASA to provide velocity measurements with an accuracy of 0.2 cm/sec and range measurements with an accuracy of 17 cm both from a maximum range of 2,200 m to a minimum range of several meters above the ground. The Doppler Lidar's measurements are fed into the ALHAT navigation filter to provide lander guidance to the safe site. The Laser Altimeter, also developed within NASA, provides range measurements with an accuracy of 5 cm from a maximum operational range of 30 km down to 1 m and, being a separate sensor from the flash lidar, can provide range along a separate vector. The Laser Altimeter measurements are also fed into the ALHAT navigation filter to provide lander guidance to the safe site. The flight tests served as the culmination of the TRL 6 journey for the lidar suite and included launch from a pad situated at the NASA-Kennedy Space Center Shuttle Landing Facility (SLF) runway, a lunar-like descent trajectory from an altitude of 250m, and landing on a lunar-like hazard field of rocks, craters, hazardous slopes, and safe sites 400m down-range just off the North end of the runway. The tests both confirmed the expected performance and also revealed several challenges present in the flight-like environment which will feed into future TRL advancement of the sensors. The flash lidar identified hazards as small as 30 cm from the maximum slant range of 450 m which Morpheus could provide, however, it was occasionally susceptible to an increase in range noise due to heated air from the Morpheus rocket plume which entered its Field-of-View (FOV). The flash lidar was also susceptible to pre-triggering on dust during the HRN phase which was created during launch and transported by the wind. The Doppler Lidar provided velocity and range measurements to the expected accuracy levels yet it was also susceptible to signal degradation due to air heated by the rocket engine. The Laser Altimeter, operating with a degraded transmitter laser, also showed signal attenuation over a few seconds at a specific phase of the flight due to the heat plume generated by the rocket engine.

Investigation of thermal transport in polymer composites with percolating networks of silver thin films by the flash diffusivity method

NASA Astrophysics Data System (ADS)

Pettersen, Sigurd R.; Nagao, Shijo; Kristiansen, Helge; Helland, Susanne; Njagi, John; Suganuma, Katsuaki; Zhang, Zhiliang; He, Jianying

2017-01-01

The flash diffusivity method, also known as laser flash analysis (LFA), is commonly used to obtain the thermal diffusivity (α) and thermal conductivity (κ) of materials, due to its relative simplicity, rapid measurements, small sample size requirement, and standardized commercially available instruments. In this work, an epoxy adhesive was filled with a large fraction of homogeneous micron-sized polymethylmethacrylate spheres coated with thin silver films, such that a percolating metallic network that dominated the electric and thermal transport formed through the polymer at <3 vol. % silver. Specific heat capacity (Cp) was measured from the LFA measurements by a comparative method and from the total and reversible heat flow signals of modulated differential scanning calorimetry (MDSC). κ was estimated as the product of α, Cp, and density (ρ) and was found to vary significantly with the method to find Cp. The electron contribution was found from the electrical conductivity by the Wiedemann-Franz law and was used to elucidate the thermal transport mechanisms in the composite. A theoretical background for the various methods is included.

Developing Photoacoustic Tomography Devices for Translational Medicine and Basic Science Research

NASA Astrophysics Data System (ADS)

Wong, Terence Tsz Wai

Photoacoustic (PA) tomography (PAT) provides volumetric images of biological tissue with scalable spatial resolutions and imaging depths, while preserving the same imaging contrast--optical absorption. Taking the advantage of its 100% sensitivity to optical absorption, PAT has been widely applied in structural, functional, and molecular imaging, with both endogenous and exogenous contrasts, at superior depths than pure optical methods. Intuitively, hemoglobin has been the most commonly studied biomolecule in PAT due to its strong absorption in the visible wavelength regime. One of the main focuses of this dissertation is to investigate an underexplored wavelength regime--ultraviolet (UV), which allows us to image cell nuclei without labels and generate histology-like images naturally from unprocessed biological tissue. These preparation-free and easy-to-interpret characteristics open up new possibilities for PAT to become readily applicable to other important biomedical problems (e.g., surgical margin analysis, Chapter 2) or basic science studies (e.g., whole-organ imaging, Chapter 3). For instance, we developed and optimized a PA microscopy system with UV laser illumination (UV-PAM) to achieve fast, label-free, multilayered, and histology-like imaging of human breast cancer in Chapter 2. These imaging abilities are essential to intraoperative surgical margin analysis, which enables promptly directed re-excision and reduces the number of repeat surgeries. We have incorporated the Gruneisen relaxation (GR) effect with UV-PAM to improve the performance of our UV-PAM system (e.g., the axial resolution), thus providing more accurate three-dimensional (3D) information (Chapter 4). The nonlinear PA signals caused by the GR effect enable optical sectioning capability, revealing important 3D cell nuclear distributions and internal structures for cancer diagnosis. In the final focus of this dissertation, we have implemented a low-cost PA computed tomography (PACT) system with a single xenon flash lamp as the illumination source (Chapter 5). Lasers have been commonly used as illumination light sources in PACT. However, lasers are usually expensive and bulky, limiting their applicability in many clinical usages. Therefore, the use of a single xenon flash lamp as an alternative light source was explored. We found that PACT images acquired with flash lamp illumination were comparable to those acquired with laser illumination. This low-cost and portable PACT system opens up new potentials, such as low-cost skin melanoma imaging in undeveloped countries.

Groundwater demand management at local scale in rural areas of India: a strategy to ensure water well sustainability based on aquifer diffusivity and community participation

NASA Astrophysics Data System (ADS)

Kulkarni, Himanshu; Vijay Shankar, P. S.; Deolankar, S. B.; Shah, Mihir

Watershed development programmes provide an opportunity for sustainable management strategies, although currently, they remain largely `supply-side' mechanisms of water resources development. Hydrogeological conditions, community participation and status of groundwater usage are important in evolving strategies on `demand-side' groundwater management. Neemkheda aquifer is a typical low-storage, low-hydraulic conductivity aquifer from a watershed in the dryland regions of Madhya Pradesh State of central India. A shallow unconfined aquifer, it consists of an upper coarse, calcareous sandstone unit underlain by a fine-grained sandstone unit. A `well commune' of seven wells is poised to test the concept of joint groundwater management, wherein wells are mechanisms of tapping a common water source, the Neemkheda aquifer. The strategy for systematic groundwater management in the Neemkheda well commune is based upon the relationship between Transmissivity (T) and Storage coefficient (S), i.e. aquifer diffusivity, and its variation within the aquifer. Wells within a high diffusivity domain tend to dewater more quickly than wells within a low diffusivity domain. A well-use schedule during the dry season, based upon aquifer diffusivity forms the basis of the groundwater management concept. The distribution of local aquifer diffusivities governs the relationship between local and regional aquifer depletion times and forms the basis of the groundwater management exercise being proposed for the Neemkheda aquifer. Los programas de desarrollo de una cuenca hídrica son una oportunidad para el uso de estrategias de gestión sostenible, aunque hoy en día estas siguen siendo principalmente mecanismos para el desarrollo de recursos hídricos con énfasis en la ``oferta''. Las condiciones hidrogeológicas, la participación comunitaria y la condición de utilización del agua subterránea, son importantes en el desarrollo de estrategias para la gestión del agua subterránea, desde el punto de vista de la ``demanda''. El acuífero de Neemkheda es un acuífero típico de almacenamiento bajo y conductividad hidráulica baja, perteneciente a una cuenca hídrica ubicada en las regiones secas del Estado de Madhya Pradesh, en la parte central de India. Un acuífero de tipo libre, somero, formado por una unidad superior de arenisca calcárea de grano grueso, subyacida por una unidad de arenisca de grano fino. Un campo de pozos comunitario compuesto por siete pozos, pone a prueba el concepto de gestión conjunta del agua subterránea, dentro del cual los pozos son mecanismos para usar una fuente de agua común: El acuífero de Neemkheda. La estrategia usada para la gestión sistemática del agua subterránea, en el campo de pozos comunitario de Neemkheda, se basa en la relación existente entre Transmisividad (T) y Coeficiente de Almacenamiento (S), es decir en la Difusividad del Acuífero y en su variación observada dentro del mismo acuífero. Los pozos cuya difusividad esta dentro de un rango alto, tienden a experimentar un descenso en su nivel mas rápidamente que aquellos pozos con una difusividad baja. El concepto de gestión de agua subterránea se basa en un programa especial de operación para cada pozo durante la estación seca, el cual a su vez se basa en la difusividad del acuífero. La distribución de difusividades locales del acuífero rige las relaciones entre las épocas de descensos de nivel en el acuífero a escala regional y local, y además constituyen la base del ejercicio de la gestión del agua subterránea que se esta proponiendo para el acuífero de Neemkheda. Les programmes de développement des bassins versants offrent une occasion de développer des stratégies pour une gestion durable, bien qu' à présent elles restent en grande mesure `le terme source' dans le mécanisme de développement de la ressource en eau. Les conditions hydrogéologiques, la participation de la communauté et l'usage des eaux souterraines sont importants pour le `terme demande' dans les stratégies de gestion des eaux souterraines. L'aquifère de Neemkheda presents des caractéristiques typiques pour un bassin versant dans les régions arides de l'état Madhya Pradesh de l'Inde centrale en ce qui concerne les faible valeurs de la conductivité hydraulique et du coéfficient d'emmagasinement. Il s'agit d'un aquifère phrèatique dont la partie supérieure est constitué par des grès calcaire qui restent sur des grés plus fins. Afin d'essayer le concept de gestion integrée, on a réalisé dans l'aquifère de Neemkheda un captage ayant sept forages qui forment la ressource en eau communale. La stratégie de la gestion systématique du captage est basée sur la relation entre la transmissivité (T), le coéfficient d'emmagasinement (S), donc la diffusivité hydraulique ainsi que sa variation spatiale. Les puits forés dans les zones à grande diffusivité tendent à s'assècher plus vite que ceux creusés dans des zones à faible diffusivité. Le concept de la gestion des eaux souterraines est donc basé sur la distribution spatiale des diffusivités. À partir de ce concept on a développé un programme d'exploitation des forages pendant les saisons sèches. La relation entre les temps d' épuissment locaux et régionaux est determiné par la distribution spatiale de la diffusivitée et forme la base de l'exercice sur la gestion des eaux proposée pour l'aquifère de Neemkheda.

Is [Co4(H2O)2(α-PW9O34)2](10-) a genuine molecular catalyst in photochemical water oxidation? Answers from time-resolved hole scavenging experiments.

PubMed

Natali, Mirco; Berardi, Serena; Sartorel, Andrea; Bonchio, Marcella; Campagna, Sebastiano; Scandola, Franco

2012-09-11

Water oxidation catalysts: evolution of [Co(4)(H(2)O)(2)(α-PW(9)O(34))(2)](10-) to catalytically active species is assessed by laser flash photolysis in sacrificial photocatalytic cycles with Ru(bpy)(3)(2+) as a photosensitizer.

Acquisition of a Nanosecond Laser Flash Photolysis Spectrometer to Enhance Understanding of Photochemistry and Reaction Kinetics in Undergraduate Research/Curriculum

DTIC Science & Technology

2016-03-31

photolysis # Compound # Compound 1 1,4-Dinitrobenzene 9 Azulene 2 1,2-Dinitrobenzene 10 4-Cyanophenol 3 Ferrocene 11 2-Nitrotoluene 4 4-Phenylphenol 12...Anthracene 4-Hydroxy-3-methoxybenzoic acid Cyclohexane Dithieno[3,2-b:2’,3’-d] thiophene Ferrocene Dimthylaniline Benzene 1,4- Diazabicyclo[2.2.2

Solving Kinetic Equations for the Laser Flash Photolysis Experiment on Nitric Oxide Synthases: Effect of Conformational Dynamics on the Interdomain Electron Transfer.

PubMed

Astashkin, Andrei V; Feng, Changjian

2015-11-12

The production of nitric oxide by the nitric oxide synthase (NOS) enzyme depends on the interdomain electron transfer (IET) between the flavin mononucleotide (FMN) and heme domains. Although the rate of this IET has been measured by laser flash photolysis (LFP) for various NOS proteins, no rigorous analysis of the relevant kinetic equations was performed so far. In this work, we provide an analytical solution of the kinetic equations underlying the LFP approach. The derived expressions reveal that the bulk IET rate is significantly affected by the conformational dynamics that determines the formation and dissociation rates of the docking complex between the FMN and heme domains. We show that in order to informatively study the electron transfer across the NOS enzyme, LFP should be used in combination with other spectroscopic methods that could directly probe the docking equilibrium and the conformational change rate constants. The implications of the obtained analytical expressions for the interpretation of the LFP results from various native and modified NOS proteins are discussed. The mathematical formulas derived in this work should also be applicable for interpreting the IET kinetics in other modular redox enzymes.

Photochemical reactions of metal nitrosyl complexes. Mechanisms of NO reactions with biologically relevant metal centers

DOE PAGES

Ford, Peter C.

2001-01-01

Tmore » he discoveries that nitric oxide (a.k.a. nitrogen monoxide) serves important roles in mammalian bioregulation and immunology have stimulated intense interest in the chemistry and biochemistry of NO and derivatives such as metal nitrosyl complexes. Also of interest are strategies to deliver NO to biological targets on demand. One such strategy would be to employ a precursor which displays relatively low thermal reactivity but is photochemically active to release NO. his proposition led us to investigate laser flash and continuous photolysis kinetics of nitrosyl complexes such as the Roussin's iron-sulfur-nitrosyl cluster anions Fe 2 S 2 ( NO ) 4 2 − and Fe 4 S 3 ( NO ) 7 − and several ruthenium salen and porphyrin nitrosyls. hese include studies using metal-nitrosyl photochemistry as a vehicle for delivering NO to hypoxic cell cultures in order to sensitize γ -radiation damage. Also studied were the rates and mechanisms of NO “on” reactions with model water soluble heme compounds, the ferriheme protein met-myoglobin and various ruthenium complexes using ns laser flash photolysis techniques. An overview of these studies is presented.« less

Reaction kinetics and mechanisms of organosilicon fungicide flusilazole with sulfate and hydroxyl radicals.

PubMed

Mercado, D Fabio; Bracco, Larisa L B; Arques, Antonio; Gonzalez, Mónica C; Caregnato, Paula

2018-01-01

Flusilazole is an organosilane fungicide used for treatments in agriculture and horticulture for control of diseases. The reaction kinetics and mechanism of flusilazole with sulfate and hydroxyl radicals were studied. The rate constant of the radicals with the fungicide were determined by laser flash photolysis of peroxodisulfate and hydrogen peroxide. The results were 2.0 × 10 9 s -1 M -1 for the reaction of the fungicide with HO and 4.6 × 10 8  s -1  M -1 for the same reaction with SO 4 - radicals. The absorption spectra of organic intermediates detected by laser flash photolysis of S 2 O 8 2- with flusilazole, were identified as α-aminoalkyl and siloxyl radicals and agree very well with those estimated employing the time-dependent density functional theory with explicit account for bulk solvent effects. In the continuous photolysis experiments, performed by photo-Fenton reaction of the fungicide, the main degradation products were: (bis(4-fluorophenyl)-hydroxy-methylsilane) and the non-toxic silicic acid, diethyl bis(trimethylsilyl) ester, in ten and twenty minutes of reaction, respectively. Copyright © 2017. Published by Elsevier Ltd.

Laser flash photolysis and CIDNP studies of steric effects on coupling rate constants of imidazolidine nitroxide with carbon-centered radicals, methyl isobutyrate-2-yl and tert-butyl propionate-2-yl.

PubMed

Zubenko, Dmitry; Tsentalovich, Yuri; Lebedeva, Nataly; Kirilyuk, Igor; Roshchupkina, Galina; Zhurko, Irina; Reznikov, Vladimir; Marque, Sylvain R A; Bagryanskaya, Elena

2006-08-04

Time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) and laser flash photolysis (LFP) techniques have been used to measure rate constants for coupling between acrylate-type radicals and a series of newly synthesized stable imidazolidine N-oxyl radicals. The carbon-centered radicals under investigation were generated by photolysis of their corresponding ketone precursors RC(O)R (R = C(CH3)2-C(O)OCH3 and CH(CH3)-C(O)-OtBu) in the presence of stable nitroxides. The coupling rate constants kc for modeling studies of nitroxide-mediated polymerization (NMP) experiments were determined, and the influence of steric and electronic factors on kc values was addressed by using a Hammett linear free energy relationship. The systematic changes in kc due to the varied steric (Es,n) and electronic (sigmaL,n) characters of the substituents are well-described by the biparameter equation log(kc/M- 1s(-1)) = 3.52sigmaL,n + 0.47Es,n + 10.62. Hence, kc decreases with the increasing steric demand and increases with the increasing electron-withdrawing character of the substituents on the nitroxide.

Performance of a reentrant cavity beam position monitor

NASA Astrophysics Data System (ADS)

Simon, Claire; Luong, Michel; Chel, Stéphane; Napoly, Olivier; Novo, Jorge; Roudier, Dominique; Rouvière, Nelly; Baboi, Nicoleta; Mildner, Nils; Nölle, Dirk

2008-08-01

The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs). In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryomodule, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10μm and has the possibility to perform bunch to bunch measurements for the x-ray free electron laser (X-FEL) and the International Linear Collider (ILC). Its other features are a small size of the rf cavity, a large aperture (78 mm), and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH), at Deutsches Elektronen-Synchrotron (DESY) and demonstrated its operation at cryogenic temperature inside a cryomodule. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4μm over a dynamic range ±5mm in single bunch.

Spin dynamics of light-induced charge separation in composites of semiconducting polymers and PC60BM revealed using Q-band pulse EPR.

PubMed

Lukina, E A; Suturina, E; Reijerse, E; Lubitz, W; Kulik, L V

2017-08-23

Light-induced processes in composites of semiconducting polymers and fullerene derivatives have been widely studied due to their usage as active layers of organic solar cells. However the process of charge separation under light illumination - the key process of an organic solar cell is not well understood yet. Here we report a Q-band pulse electron paramagnetic resonance study of composites of the fullerene derivative PC 60 BM ([6,6]-phenyl-C 61 -butyric acid methyl ester) with different p-type semiconducting polymers regioregular and regiorandom P3HT (poly(3-hexylthiophene-2,5-diyl), MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]), PCDTBT (poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]), PTB7 (poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}))), resulting in a detailed description of the in-phase laser flash-induced electron spin echo (ESE) signal. We found that in organic donor-acceptor composites the laser flash simultaneously induces species of two types: a polymer˙ + /fullerene˙ - spin-correlated polaron pair (SCPP) with an initial singlet spin state and (nearly) free polymer˙ + and fullerene˙ - species with non-equilibrium spin polarization. Species of the first type (SCPP) are well-known for polymer/fullerene blends and are usually associated with a charge-separated state. Also, spin polarization of long-living free species (polarons in deep traps) is affected by the laser flash, which is the third contribution to the flash-induced ESE signal. A protocol for extracting the in-phase ESE signal of the SCPP based on the dependence of the microwave nutation frequency on the strength of the spin coupling within the polaron pair was developed. Nutation experiments revealed an unusual pattern of the SCPP in RR-P3HT/PC 60 BM composites, from which the strength of the exchange interaction between the polymer˙ + and fullerene˙ - was extracted. In composites with low-efficient polymers the contribution of the SCPP to the in-phase ESE signal is high, while in composites with high-efficient polymers it is low. This finding can be used as a selection criterion of charge separation efficiency in the polymer/fullerene composites.

Low laser power micro-Raman study of Co{sub (1−x)}Mn{sub (x)}Fe{sub 2}O{sub 4} prepared by flash combustion method

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

Baraliya, J. D.

2016-05-23

Manganese substituted Cobalt ferrites of composition with nominal formula Co{sub (1−x)}Mn{sub (x)}Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) prepared by the Flash Combustion Method(FCM). The single phase spinel formation of nano ferrites was confirmed by X-ray diffraction techniques and micro - Raman spectroscopy. The particle size calculated from the Scherrer formula varied within 13 to 17 nm. Lattice parameter, nano particle size, and cation distribution were quantified as a function of the Mn-content in the range x = 0.0 to 1.0. Micro-Raman spectroscopic studies yielded convincing evidence for a transformation of the structure.

Super-resolution depth information from a short-wave infrared laser gated-viewing system by using correlated double sampling

NASA Astrophysics Data System (ADS)

Göhler, Benjamin; Lutzmann, Peter

2017-10-01

Primarily, a laser gated-viewing (GV) system provides range-gated 2D images without any range resolution within the range gate. By combining two GV images with slightly different gate positions, 3D information within a part of the range gate can be obtained. The depth resolution is higher (super-resolution) than the minimal gate shift step size in a tomographic sequence of the scene. For a state-of-the-art system with a typical frame rate of 20 Hz, the time difference between the two required GV images is 50 ms which may be too long in a dynamic scenario with moving objects. Therefore, we have applied this approach to the reset and signal level images of a new short-wave infrared (SWIR) GV camera whose read-out integrated circuit supports correlated double sampling (CDS) actually intended for the reduction of kTC noise (reset noise). These images are extracted from only one single laser pulse with a marginal time difference in between. The SWIR GV camera consists of 640 x 512 avalanche photodiodes based on mercury cadmium telluride with a pixel pitch of 15 μm. A Q-switched, flash lamp pumped solid-state laser with 1.57 μm wavelength (OPO), 52 mJ pulse energy after beam shaping, 7 ns pulse length and 20 Hz pulse repetition frequency is used for flash illumination. In this paper, the experimental set-up is described and the operating principle of CDS is explained. The method of deriving super-resolution depth information from a GV system by using CDS is introduced and optimized. Further, the range accuracy is estimated from measured image data.

Thermal wave interference with high-power VCSEL arrays for locating vertically oriented subsurface defects

NASA Astrophysics Data System (ADS)

Thiel, Erik; Kreutzbruck, Marc; Studemund, Taarna; Ziegler, Mathias

2018-04-01

Among the photothermal methods, full-field thermal imaging is used to characterize materials, to determine thicknesses of layers, or to find inhomogeneities such as voids or cracks. The use of classical light sources such as flash lamps (impulse heating) or halogen lamps (modulated heating) led to a variety of nondestructive testing methods, in particular, lock-in and flash-thermography. In vertical-cavity surface-emitting lasers (VCSELs), laser light is emitted perpendicularly to the surface with a symmetrical beam profile. Due to the vertical structure, they can be arranged in large arrays of many thousands of individual lasers, which allows power scaling into the kilowatt range. Recently, a high-power yet very compact version of such a VCSEL-array became available that offers both the fast timing behavior of a laser as well as the large illumination area of a lamp. Moreover, it allows a spatial and temporal control of the heating because individual parts of the array can be controlled arbitrarily in frequency, amplitude, and phase. In conjunction with a fast infrared camera, such structured heating opens up a field of novel thermal imaging and testing methods. As a first demonstration of this approach, we chose a testing problem very challenging to conventional thermal infrared testing: The detection of very thin subsurface defects perpendicularly oriented to the surface of metallic samples. First, we generate destructively interfering thermal wave fields, which are then affected by the presence of defects within their reach. It turned out that this technique allows highly sensitive detection of subsurface defects down to depths in excess of the usual thermographic rule of thumb, with no need for a reference or surface preparation.

Drug delivery with microsecond laser pulses into gelatin

NASA Astrophysics Data System (ADS)

Shangguan, Hanqun; Casperson, Lee W.; Shearin, Alan; Gregory, Kenton W.; Prahl, Scott A.

1996-07-01

Photoacoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 mu m when the gelatin structure was not fractured. localized drug delivery, cavitation bubble, laser thrombolysis.

Nd- And Er-Doped Phosphate Glass For Fiber Laser.

NASA Astrophysics Data System (ADS)

Yamashita, Toshiharu T.

1990-02-01

Laser fibers prepared from Nd- and Er-doped phosphate glass possessing a large stimulated emission cross section have been investigated both in a single fiber and in a fiber bundle. In the single fiber, continuous wave oscillations were successfully obtained at 1.054 p.m and 1.366 µm on a high Nd-doped single-mode fiber of 10 mm in length and also at 1.535 pm in a Er-doped single-mode fiber, sensitized by Nd, Yb. Especially, a low threshold of 1 mw and a high slope-efficiency of 50% were achieved in 1.054 pm laser oscillation on a Nd-doped fiber, end-pumped with a laser diode. A fiber bundle of phosphate glass doped with 8 wt% Nd2O3 yielded an average output power of 100 W at 50 pps where the bundle was 4.6 mm in diameter and was side-pumped with flash lamps.

Direct measurement of the pulse duration and frequency chirp of seeded XUV free electron laser pulses

NASA Astrophysics Data System (ADS)

Azima, Armin; Bödewadt, Jörn; Becker, Oliver; Düsterer, Stefan; Ekanayake, Nagitha; Ivanov, Rosen; Kazemi, Mehdi M.; Lamberto Lazzarino, Leslie; Lechner, Christoph; Maltezopoulos, Theophilos; Manschwetus, Bastian; Miltchev, Velizar; Müller, Jost; Plath, Tim; Przystawik, Andreas; Wieland, Marek; Assmann, Ralph; Hartl, Ingmar; Laarmann, Tim; Rossbach, Jörg; Wurth, Wilfried; Drescher, Markus

2018-01-01

We report on a direct time-domain measurement of the temporal properties of a seeded free-electron laser pulse in the extreme ultraviolet spectral range. Utilizing the oscillating electromagnetic field of terahertz radiation, a single-shot THz streak-camera was applied for measuring the duration as well as spectral phase of the generated intense XUV pulses. The experiment was conducted at FLASH, the free electron laser user facility at DESY in Hamburg, Germany. In contrast to indirect methods, this approach directly resolves and visualizes the frequency chirp of a seeded free-electron laser (FEL) pulse. The reported diagnostic capability is a prerequisite to tailor amplitude, phase and frequency distributions of FEL beams on demand. In particular, it opens up a new window of opportunities for advanced coherent spectroscopic studies making use of the high degree of temporal coherence expected from a seeded FEL pulse.

Wavefront correction by target-phase-locking technology in a 500 TW laser facility

NASA Astrophysics Data System (ADS)

Wang, D. E.; Dai, W. J.; Zhou, K. N.; Su, J. Q.; Xue, Q.; Yuan, Q.; Zhang, X.; Deng, X. W.; Yang, Y.; Wang, Y. C.; Xie, N.; Sun, L.; Hu, D. X.; Zhu, Q. H.

2017-03-01

We demonstrate a novel approach termed target-phase-locking that could improve the entire beam wavefront quality of a 500 TW Nd3+:phosphate glass laser facility. The thermal and static wavefront from front-end to target is corrected by using one deformable mirror that receives feedback from both the focal-spot sensor and wavefront sensor, and only the main laser of the laser system is employed in the correction process, with auxiliary calibration light no longer necessary. As a result, a static focal spot with full width at half maximum of 8.87  ×  5.74 µm is achieved, the thermal wavefront induced by flash-lamp-pumped Nd3+:phosphate glass is compensated with PV from 3.54-0.43 µm, and a dynamic focal spot with intensity exceeding 1020 W cm-2 is precisely predicted at the target with such an approach.

Laboratory-scale photoredox catalysis using hydrated electrons sustainably generated with a single green laser.

PubMed

Naumann, Robert; Kerzig, Christoph; Goez, Martin

2017-11-01

The ruthenium-tris-bipyridyl dication as catalyst combined with the ascorbate dianion as bioavailable sacrificial donor provides the first regenerative source of hydrated electrons for chemical syntheses on millimolar scales. This electron generator is operated simply by illumination with a frequency-doubled Nd:YAG laser (532 nm) running at its normal repetition rate. Much more detailed information than by product studies alone was obtained by photokinetical characterization from submicroseconds (time-resolved laser flash photolysis) up to one hour (preparative photolysis). The experiments on short timescales established a reaction mechanism more complex than previously thought, and proved the catalytic action by unchanged concentration traces of the key transients over a number of flashes so large that the accumulated electron total surpassed the catalyst concentration many times. Preparative photolyses revealed that the sacrificial donor greatly enhances the catalyst stability through quenching the initial metal-to-ligand charge-transfer state before destructive dd states can be populated from it, such that the efficiency of this electron generator is no longer limited by catalyst decomposition but by electron scavenging by the accumulating oxidation products of the ascorbate. Applications covered dechlorinations of selected aliphatic and aromatic chlorides and the reduction of a model ketone. All these substrates are impervious to photoredox catalysts exhibiting lower reducing power than the hydrated electron, but the combination of an extremely negative standard potential and a long unquenched life allowed turnover numbers up to 1400 with our method.

High Energy, Single-Mode, All-Solid-State and Tunable UV Laser Transmitter

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Hovis, FLoyd

2007-01-01

A high energy, single mode, all solid-state Nd:YAG laser primarily for pumping an UV converter is developed. Greater than 1 J/pulse at 50 HZ PRF and pulse widths around 22 ns have been demonstrated. Higher energy, greater efficiency may be possible. Refinements are known and practical to implement. Technology Demonstration of a highly efficient, high-pulse-energy, single mode UV wavelength generation using flash lamp pumped laser has been achieved. Greater than 90% pump depletion is observed. 190 mJ extra-cavity SFG; IR to UV efficiency > 21% (> 27% for 1 mJ seed). 160 mJ intra-cavity SFG; IR to UV efficiency up to 24% Fluence < 1 J/sq cm for most beams. The pump beam quality of the Nd:YAG pump laser is being refined to match or exceed the above UV converter results. Currently the Nd:YAG pump laser development is a technology demonstration. System can be engineered for compact packaging.

Clusters in intense x-ray pulses

NASA Astrophysics Data System (ADS)

Bostedt, Christoph

2012-06-01

Free-electron lasers can deliver extremely intense, coherent x-ray flashes with femtosecond pulse length, opening the door for imaging single nanoscale objects in a single shot. All matter irradiated by these intense x-ray pulses, however, will be transformed into a highly-excited non-equilibrium plasma within femtoseconds. During the x-ray pulse complex electron dynamics and the onset of atomic disorder will be induced, leading to a time-varying sample. We have performed first experiments about x-ray laser pulse -- cluster interaction with a combined spectroscopy and imaging approach at both, the FLASH free electron laser in Hamburg (Germany) and the LCLS x-ray free-electron laser in Stanford (California). Atomic clusters are ideal for investigating the light - matter interaction because their size can be tuned from the molecular to the bulk regime, thus allowing to distinguish between intra and inter atomic processes. Imaging experiments with xenon clusters show power-density dependent changes in the scattering patterns. Modeling the scattering data indicates that the optical constants of the clusters change during the femtosecond pulse due to the transient creation of high charge states. The results show that ultra fast scattering is a promising approach to study transient states of matter on a femtosecond time scale. Coincident recording of time-of-flight spectra and scattering patterns allows the deconvolution of focal volume and particle size distribution effects. Single-shot single-particle experiments with keV x-rays reveal that for the highest power densities an highly excited and hot cluster plasma is formed for which recombination is suppressed. Time resolved infrared pump -- x-ray probe experiments have started. Here, the clusters are pumped into a nanoplasma state and their time evolution is probed with femtosecond x-ray scattering. The data show strong variations in the scattering patterns stemming from electronic reconfigurations in the cluster plasma. The results will be compared to theoretical predictions and discussed in light of current developments at free-electron laser sources.

Coherence properties of the radiation from FLASH

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2016-02-01

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.

Electron transfer reactions of excited dyes with metal complexes. Progress report, May 1, 1976--January 31, 1977. [Fe(III)--thionine reaction

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

Lichtin, N.N.

1977-02-01

A study was initiated of the factors which determine quantum efficiency of transfer of reducing equivalents between excited dye molecules and metal complexes in their ground state and composition and dynamics of formation and decay of related photostationary states. A ruby laser capable of delivering a 3.6 J, 19 nsec flash was acquired and assembly of an apparatus for laser flash photolysis begun. At the same time, conventional flash photolysis was used to pursue investigation of the dependence upon solvent, anions, pH, and ionic strength of the kinetics of the spontaneous dark reaction of Fe(H/sub 2/O)/sup 3 +//sub 6/ withmore » leucothionine and with semithionine, reactions which contribute to the composition and dynamics of formation and decay of the photostationary state of the iron-thionine photoredox reaction. Results are consistent with formation of an intermediate complex between leucothionine and Fe(III), K/sub A/ = 380 M/sup -1/ and k(elec. transfer) = 0.88 s/sup -1/ at approximately 22/sup 0/ in water solution at pH2, with sulfate as anion and ..mu.. = .05 - .1 M. Under similar conditions in 50 v/v percent aqueous CH/sub 3/CN, K/sub A/ = 780 M/sup -1/, k(elec. transfer) = 0.55 s/sup -1/. In both solvents, sulfate produces a large positive salt effect. Intermediacy of a complex was not established for the faster reaction of Fe(III) with semithionine under similar conditions: K/sub A/ . k(elec. transfer) approximately 3.5 x 10/sup 5/ M/sup -1/s/sup -1/ in H/sub 2/O, approximately 1.0 x 10/sup 4/ in 50 v/v percent aqueous CH/sub 3/CN.« less

A laser flash photolysis kinetics study of the reaction OH + H2O2 yields HO2 + H2O

NASA Technical Reports Server (NTRS)

Wine, P. H.; Semmes, D. H.; Ravishankara, A. R.

1981-01-01

Absolute rate constants for the reaction are reported as a function of temperature over the range 273-410 K. OH radicals are produced by 266 nm laser photolysis of H2O2 and detected by resonance fluorescence. H2O2 concentrations are determined in situ in the slow flow system by UV photometry. The results confirm the findings of two recent discharge flow-resonance fluorescence studies that the title reaction is considerably faster, particularly at temperatures below 300 K, than all earlier studies had indicated. A table giving kinetic data from the reaction is included.

Photothermally Activated Motion and Ignition Using Aluminum Nanoparticles

DTIC Science & Technology

2013-01-17

In comparison with alternative sources such as spark ignition,19 laser igni- tion,20 plasma ignition,21 plasma -assisted combustion,22 and combustion...energy-dispersive X-ray spectroscopy measurements of motion-only and afterignition products confirm significant Al oxidation occurs through sintering ...significant Al oxidation occurs through sintering and bursting after the flash exposure. Simulations suggest local heat generation is enhanced by LSPR. The

Distinguished Lectureship Award on the Applications of Physics: Illuminating My Career - From Flash Gordon to Laser Surgery

NASA Astrophysics Data System (ADS)

Wynne, James

2015-03-01

As a child, I was fascinated by television programs about Flash Gordon. His partner in conquering the universe was Dr. Alexis Zarkov, a physicist, who had invented, among other things, a death ray gun. My personal ``death ray'' was a magnifying glass, focusing sunlight on unsuspecting insects, like crawling ants. I also practiced sneaking up on resting, flying, stinging insects and burning their wings before they could take off and attack me. So I understood something about the power of sunlight. In my senior year of high school, I had a fabulous physics teacher, Lewis E. Love, and I knew after one week that I wanted to be a physicist, not a medical doctor, which is the career my parents wanted me to pursue. It turns out that the first laser functioned on May 16, 1960, just one month before I graduated from high school, and it was inevitable that I would pursue a career working with lasers. My first job as a physicist, during the summer of 1963, was working with lasers at TRG, Inc. a small company whose guru was Gordon Gould, now recognized as the inventor of the laser. After three summers at TRG, I spent three years working on nonlinear optics for my PhD thesis, under the guidance of Prof. Nicolaas Bloembergen, who later won the Nobel Prize in Physics for codifying nonlinear optics. Following completion of my PhD research in 1969, I joined IBM Research, where I have worked ever since. Upon joining the Quantum Electronics group in the Physical Sciences Dept. of the T.J. Watson Research Center, my management told me to ``do something great'' with lasers. After working on atomic spectroscopy with dye lasers through the 1970s, I had the inspiration to acquire an excimer laser for the Laser Physics and Chemistry group. Using this laser, my colleagues and I discovered excimer laser surgery, capable of removing human and animal tissue with great precision, while leaving the underlying and adjacent tissue free of collateral damage. This discovery laid the foundation for the laser refractive surgical procedures of PRK and LASIK, which have been used to improve the visual acuity of nearly 30 million people. Today, I am working on validating my concept that the argon fluoride excimer laser can serve as a ``smart scalpel,'' capable of debriding necrotic lesions of the skin without damaging the underlying and adjacent viable tissue, leading to faster healing, reduced pain, reduced probability of infection, and minimal scarring. To quote Louis Pasteur, ``Chance favors the prepared mind!''

High power diode lasers for solid-state laser pumps

NASA Technical Reports Server (NTRS)

Linden, Kurt J.; Mcdonnell, Patrick N.

1994-01-01

The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

Vibrational energy on surfaces: Ultrafast flash-thermal conductance of molecular monolayers

NASA Astrophysics Data System (ADS)

Dlott, Dana

2008-03-01

Vibrational energy flow through molecules remains a perennial problem in chemical physics. Usually vibrational energy dynamics are viewed through the lens of time-dependent level populations. This is natural because lasers naturally pump and probe vibrational transitions, but it is also useful to think of vibrational energy as being conducted from one location in a molecule to another. We have developed a new technique where energy is driven into a specific part of molecules adsorbed on a metal surface, and ultrafast nonlinear coherent vibrational spectroscopy is used to watch the energy arrive at another part. This technique is the analog of a flash thermal conductance apparatus, except it probes energy flow with angstrom spatial and femtosecond temporal resolution. Specific examples to be presented include energy flow along alkane chains, and energy flow into substituted benzenes. Ref: Z. Wang, J. A. Carter, A. Lagutchev, Y. K. Koh, N.-H. Seong, D. G. Cahill, and D. D. Dlott, Ultrafast flash thermal conductance of molecular chains, Science 317, 787-790 (2007). This material is based upon work supported by the National Science Foundation under award DMR 0504038 and the Air Force Office of Scientific Research under award FA9550-06-1-0235.

Pump-probe imaging of nanosecond laser-induced bubbles in agar gel.

PubMed

Evans, R; Camacho-López, S; Pérez-Gutiérrez, F G; Aguilar, G

2008-05-12

In this paper we show results of Nd:YAG laser-induced bubbles formed in a one millimeter thick agar gel slab. The nine nanosecond duration pulse with a wave length of 532 nm was tightly focused inside the bulk of the gel sample. We present for the first time a pump-probe laser-flash shadowgraphy system that uses two electronically delayed Nd:YAG lasers to image the the bubble formation and shock wave fronts with nanosecond temporal resolution and up to nine seconds of temporal range. The shock waves generated by the laser are shown to begin at an earlier times within the laser pulse as the pulse energy increases. The shock wave velocity is used to infer a shocked to unshocked material pressure difference of up to 500 MPa. The bubble created settles to a quasi-stable size that has a linear relation to the maximum bubble size. The energy stored in the bubble is shown to increase nonlinearly with applied laser energy, and corresponds in form to the energy transmission in the agar gel. We show that the interaction is highly nonlinear, and most likely is plasma-mediated.

Drug delivery with microsecond laser pulses into gelatin.

PubMed

Shangguan, H; Casperson, L W; Shearin, A; Gregory, K W; Prahl, S A

1996-07-01

Photo acoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 µm when the gelatin structure was not fractured.

Flash Photolysis Experiment of o-Methyl Red as a Function of pH: A Low-Cost Experiment for the Undergraduate Physical Chemistry Lab

ERIC Educational Resources Information Center

Larsen, Molly C.; Perkins, Russell J.

2016-01-01

A low-cost, time-resolved spectroscopy experiment appropriate for third year physical chemistry students is presented. Students excite o-methyl red in basic solutions with a laser pointer and use a modular spectrometer with a CCD array detector to monitor the transient spectra as the higher-energy cis conformer of the molecule converts back to the…

USAF Summer Research Program - 1993 Summer Research Extension Program Final Reports, Volume 1B, Armstrong Laboratory

DTIC Science & Technology

1994-11-01

For example, the Collimating scotopic components of the ERG flash response are significantly attenuated by retinitis pigmentosa [7]. It is possible... RETINAL DAMAGE Bernard S. Gerstman Associate Professor Department of Physics Florida International University University Park Miami, FL 33199 Final...and Florida International University April 1994 6-1 A COMPUTATIONAL THERMAL MODEL AND THEORETICAL THERMODYNAMIC MODEL OF LASER INDUCED RETINAL DAMAGE

Three-dimensional FLASH Laser Radar Range Estimation via Blind Deconvolution

DTIC Science & Technology

2009-10-01

scene can result in errors due to several factors including the optical spatial impulse response, detector blurring, photon noise , timing jitter, and...estimation error include spatial blur, detector blurring, noise , timing jitter, and inter-sample targets. Unlike previous research, this paper ac- counts...for pixel coupling by defining the range image mathematical model as a 2D convolution between the system spatial impulse response and the object (target

Beam Research Program

DTIC Science & Technology

1984-04-01

wavelengths. A direct application of such a laser is isotope separation. 2. For a brief status report of the Laboratory’s high- explosive flash...operation in the fall of 1982. in a 50-MeV Advanced Test Accelerator Facility (the ATA)1 that we are con- structing at our high- explosives test loca...chemical explosives in target-damage studies. Potential hazards associated with the ATA experiments were considered in choosing our site. LLNL’s

Photophysical properties of C60 colloids suspended in water with Triton X-100 surfactant: excited-state properties with femtosecond resolution.

PubMed

Clements, Andrew F; Haley, Joy E; Urbas, Augustine M; Kost, Alan; Rauh, R David; Bertone, Jane F; Wang, Fei; Wiers, Brian M; Gao, De; Stefanik, Todd S; Mott, Andrew G; Mackie, David M

2009-06-11

We examine the photophysics of a colloidal suspension of C(60) particles in a micellar solution of Triton X-100 and water, prepared via a new synthesis which allows high-concentration suspensions. The particle sizes are characterized by transmission electron microscopy and dynamic light scattering and found to be somewhat polydisperse in the range of 10-100 nm. The suspension is characterized optically by UV-vis spectroscopy, femtosecond transient absorption spectroscopy, laser flash photolysis, and z-scan. The ground-state absorbance spectrum shows a broad absorbance feature centered near 450 nm which is indicative of colloidal C(60). The transient absorption dynamics, presented for the first time with femtosecond resolution, are very similar to that of thin films of C(60) and indicate a strong quenching of the singlet excited state on short time scales and evidence of little intersystem crossing to a triplet excited state. Laser flash photolysis reveals that a triplet excited-state absorption spectrum, which is essentially identical in shape to that of molecular C(60) solutions, does indeed arise, but with much lower magnitude and somewhat shorter lifetime. Z-scan analysis confirms that the optical response of this material is dominated by nonlinear scattering.

Laser photolysis studies of the phenolic H-atom transfer mechanism for a triplet π,π ∗ ketone in solution revisited

NASA Astrophysics Data System (ADS)

Yamaji, Minoru; Aoyama, Yutaka; Furukawa, Takashi; Itoh, Takao; Tobita, Seiji

2006-03-01

The mechanism of the H-atom transfer from phenols or thiophenols to triplet π,π ∗ 5,12-naphthacenequinone (5,12-NQ) has been examined by means of laser flash photolysis at 295 K. Based on the Hammett plots and the Rehm-Weller equation for the quenching rate constants, the phenolic H-atom transfer from phenols or thiophenols to triplet π,π ∗ 5,12-NQ is shown to proceed via the electron transfer followed by proton transfer. The previously proposed mechanism for H-atom transfer of π,π ∗ triplets, that proton transfer is followed by electron transfer, was not verified in the present systems.

Active lamp pulse driver circuit. [optical pumping of laser media

NASA Technical Reports Server (NTRS)

Logan, K. E. (Inventor)

1983-01-01

A flashlamp drive circuit is described which uses an unsaturated transistor as a current mode switch to periodically subject a partially ionized gaseous laser excitation flashlamp to a stable, rectangular pulse of current from an incomplete discharge of an energy storage capacitor. A monostable multivibrator sets the pulse interval, initiating the pulse in response to a flash command by providing a reference voltage to a non-inverting terminal of a base drive amplifier; a tap on an emitter resistor provides a feedback signal sensitive to the current amplitude to an inverting terminal of amplifier, thereby controlling the pulse amplitude. The circuit drives the flashlamp to provide a squarewave current flashlamp discharge.

Compact Fast Ignition experiments using Joule-class tailored drive pulses under counterbeam configuration

NASA Astrophysics Data System (ADS)

Mori, Yoshitaka; Hanayama, Ryohei; Ishii, Katsuhiro; Kitagawa, Yoneyoshi; Sekine, Takashi; Takeuchi, Yasuki; Kurita, Takashi; Katoh, Yoshinori; Satoh, Nakahiro; Kurita, Norio; Kawashima, Toshiyuki; Komeda, Osamu; Hioki, Tatsumi; Motohiro, Tomoyoshi; Sunahara, Atsushi; Sentoku, Yasuhiko; Miura, Eisuke; Iwamoto, Akifumi; Sakagami, Hitoshi

2017-10-01

Fast ignition (FI) is a form of inertial confinement fusion in which the ignition step and the compression step are separate processes resulting in a reduction of the symmetry requirement for hot spot generation. One of the problems of FI so far are the accessibility of an ignition laser pulse into the assembled core in which the driver energy is converted into relativistic electrons produced in the laser-plasma interaction. We have experimentally demonstrated that a tailored-pulse-assembled core with a diameter of 70 μ m, originally a deuterated polystyrene spherical shell of 500 μ m diameter, is flashed by directly counter irradiating 0.8 J/110 fs laser pulses [Y. MORI et al., PRL 2016]. This result indicates that once the assembled core is squeezed into the target center, the heating lasers can access the core's; edges and deposit their energy into the core. In this talk, we will discuss the heating effects in relation to formation of the assembled core.

Fast neutron production from lithium converters and laser driven protons

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

Storm, M.; Jiang, S.; Wertepny, D.

2013-05-15

Experiments to generate neutrons from the {sup 7}Li(p,n){sup 7}Be reaction with 60 J, 180 fs laser pulses have been performed at the Texas Petawatt Laser Facility at the University of Texas at Austin. The protons were accelerated from the rear surface of a thin target membrane using the target-normal-sheath-acceleration mechanism. The neutrons were generated in nuclear reactions caused by the subsequent proton bombardment of a pure lithium foil of natural isotopic abundance. The neutron energy ranged up to 2.9 MeV. The total yield was estimated to be 1.6 × 10{sup 7} neutrons per steradian. An extreme ultra-violet light camera, usedmore » to image the target rear surface, correlated variations in the proton yield and peak energy to target rear surface ablation. Calculations using the hydrodynamics code FLASH indicated that the ablation resulted from a laser pre-pulse of prolonged intensity. The ablation severely limited the proton acceleration and neutron yield.« less

Laser cleaning of works of art: evaluation of the thermal stress induced by Er:YAG laser

NASA Astrophysics Data System (ADS)

De Cruz, A.; Andreotti, A.; Ceccarini, A.; Colombini, M. P.

2014-06-01

The Er:YAG laser has proven particularly efficient in cleaning procedures of works of art. The removal of the superficial deposits is achieved through melting, thermal decomposition and evaporation. However, the energy absorbed by vibrational modes is dissipated as heat, increasing the temperature of the surface coating that could cause damage on the object. The aim of this study was to evaluate the temperature increase induced by a Er:YAG MonaLaser (LLC., Orlando, FL, USA). To that purpose, we designed a dedicated device to perform the tests in an inert atmosphere or with a wetting agent, to measure the radiant energy per laser pulse. Tests were carried out both on graphite, which absorbs IR radiation and showed a very intense flash emission, and on different kind of samples representative of materials with different levels of conductivity and thermal diffusivity. Results obtained showed that the temperature increase in the irradiated surface depends on the substrate but never causes the damage of the organic and inorganic material. The use of a solvent as wetting agent has been also tested.

Bubble formation during pulsed laser ablation: mechanism and implications

NASA Astrophysics Data System (ADS)

van Leeuwen, Ton G. J. M.; Jansen, E. Duco; Motamedi, Massoud; Welch, Ashley J.; Borst, Cornelius

1993-07-01

Holmium ((lambda) equals 2.09 micrometers ) and excimer ((lambda) equals 308 nm) lasers are used for ablation of tissue. In a previous study it was demonstrated that both excimer and holmium laser pulses produce fast expanding and collapsing vapor bubbles. To investigate whether the excimer induced bubble is caused by vaporization of water, the threshold fluence for bubble formation at a bare fiber tip in water was compared between the excimer laser (pulse length 115 ns) and the Q-switched and free-running holmium lasers (pulse length 1 microsecond(s) to 250 microsecond(s) , respectively). To induce bubble formation by excimer laser light in water, the absorber oxybuprocaine-hydrochloride (OBP-HCl) was added to the water. Fast flash photography was used to measure the threshold fluence as a function of the water temperature (6 - 90 degree(s)C) at environmental pressure. The ultraviolet excimer laser light is strongly absorbed by blood. Therefore, to document the implications of bubble formation at fluences above the tissue ablation threshold, excimer laser pulses were delivered in vitro in hemoglobin solution and in vivo in the femoral artery of the rabbit. We conclude that the principal content of the fast bubble induced by a 308 nm excimer laser pulse is water vapor. Therefore, delivery of excimer laser pulses in a water or blood environment will cause fast expanding water vapor bubbles, which may induce mechanical damage to adjacent tissue.

Development of all-solid-state flash x-ray generator with photoconductive semiconductor switches.

PubMed

Xun, Ma; Jianjun, Deng; Hongwei, Liu; Jianqiang, Yuan; Jinfeng, Liu; Bing, Wei; Yanling, Qing; Wenhui, Han; Lingyun, Wang; Pin, Jiang; Hongtao, Li

2014-09-01

A compact, low-jitter, and high repetitive rate all-solid-state flash x-ray generator making use of photo conductive semiconductor switches was developed recently for the diagnostic purpose of some hydrokinetical experiments. The generator consisted of twelve stages of Blumlein pulse forming networks, and an industrial cold cathode diode was used to generate intense x-ray radiations with photon energy up to 220 keV. Test experiments showed that the generator could produce >1 kA electron beam currents and x-ray pulses with ~40 ns duration under 100 Hz repetitive rates at least (limited by the triggering laser on hand), also found was that the delay time of the cathode explosive emission is crucial to the energy transfer efficiency of the whole system. In addition, factors affecting the diode impedance, how the switching synchronization and diode impedance determining the allowable operation voltage were discussed.

A non-invasive online photoionization spectrometer for FLASH2.

PubMed

Braune, Markus; Brenner, Günter; Dziarzhytski, Siarhei; Juranić, Pavle; Sorokin, Andrey; Tiedtke, Kai

2016-01-01

The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon-matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real-time feedback of these properties for each individual photon bunch for interpretation of the experimental data. Furthermore, any device developed to deliver the according information should not significantly interfere with or degrade the FEL beam. Regarding the spectral properties, a device for online monitoring of FEL wavelengths has been developed for FLASH2, which is based on photoionization of gaseous targets and the measurements of the corresponding electron and ion time-of-flight spectra. This paper presents experimental studies and cross-calibration measurements demonstrating the viability of this online photoionization spectrometer.

A non-invasive online photoionization spectrometer for FLASH2

PubMed Central

Braune, Markus; Brenner, Günter; Dziarzhytski, Siarhei; Juranić, Pavle; Sorokin, Andrey; Tiedtke, Kai

2016-01-01

The stochastic nature of the self-amplified spontaneous emission (SASE) process of free-electron lasers (FELs) effects pulse-to-pulse fluctuations of the radiation properties, such as the photon energy, which are determinative for processes of photon–matter interactions. Hence, SASE FEL sources pose a great challenge for scientific investigations, since experimenters need to obtain precise real-time feedback of these properties for each individual photon bunch for interpretation of the experimental data. Furthermore, any device developed to deliver the according information should not significantly interfere with or degrade the FEL beam. Regarding the spectral properties, a device for online monitoring of FEL wavelengths has been developed for FLASH2, which is based on photoionization of gaseous targets and the measurements of the corresponding electron and ion time-of-flight spectra. This paper presents experimental studies and cross-calibration measurements demonstrating the viability of this online photoionization spectrometer. PMID:26698040

Resolution Studies at Beam Position Monitors at the FLASH Facility at DESY

NASA Astrophysics Data System (ADS)

Baboi, N.; Lund-Nielsen, J.; Noelle, D.; Riesch, W.; Traber, T.; Kruse, J.; Wendt, M.

2006-11-01

More than 60 beam position monitors (BPM) are installed along about 350m of beamline of the Free Electron LASer in Hamburg (FLASH) at DESY. The room-temperature part of the accelerator is equipped mainly with stripline position monitors. In the accelerating cryo-modules there are cavity and re-entrant cavity BPMs, which will not be discussed here. In the undulator part of the machine button BPMs are used. This area requires a single bunch resolution of 10μm. The electronics is based on the AM/PM normalization principle and is externally triggered. Single-bunch position is measured. This paper presents the methods used to determine the resolution of the BPMs. The results based on correlations between different BPMs along the machine are compared to noise measurements in the RF lab. The performance and difficulties with the BPM design and the current electronics as well as its development are discussed.

Functional Assessment of Laser Irradiation.

DTIC Science & Technology

1988-03-01

shock altogether. Following shaping, threshold acuity testing was derived using a modification of the von Bekesy tracking technique (14). In this...burns produced by atomic flash. AMA Arch. Ophthal 53: 351-364 (1955) 2. Hawerth, R.S. and Sperling , H.G. Prolonged color blindness induced by intense...Swinnen, M.E.T., Brady, J.V. & Powell, M.G. A new device for the application of shock. Behav. Meth. & Instrum 1: 184 (1969) 14. Bekesy, G. von . A new

Suppressing the memory state of floating gate transistors with repeated femtosecond laser backside irradiations

NASA Astrophysics Data System (ADS)

Chambonneau, Maxime; Souiki-Figuigui, Sarra; Chiquet, Philippe; Della Marca, Vincenzo; Postel-Pellerin, Jérémy; Canet, Pierre; Portal, Jean-Michel; Grojo, David

2017-04-01

We demonstrate that infrared femtosecond laser pulses with intensity above the two-photon ionization threshold of crystalline silicon induce charge transport through the tunnel oxide in floating gate Metal-Oxide-Semiconductor transistor devices. With repeated irradiations of Flash memory cells, we show how the laser-produced free-electrons naturally redistribute on both sides of the tunnel oxide until the electric field of the transistor is suppressed. This ability enables us to determine in a nondestructive, rapid and contactless way the flat band and the neutral threshold voltages of the tested device. The physical mechanisms including nonlinear ionization, quantum tunneling of free-carriers, and flattening of the band diagram are discussed for interpreting the experiments. The possibility to control the carriers in memory transistors with ultrashort pulses holds promises for fast and remote device analyses (reliability, security, and defectivity) and for considerable developments in the growing field of ultrafast microelectronics.

Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds.

PubMed

Ghezzi, Diego; Vazquez, Rebeca Martinez; Osellame, Roberto; Valtorta, Flavia; Pedrocchi, Alessandra; Valle, Giuseppe Della; Ramponi, Roberta; Ferrigno, Giancarlo; Cerullo, Giulio

2008-10-23

Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged.

Science and technology in the stockpile stewardship program, S & TR reprints

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

Storm, E

This document reports on these topics: Computer Simulations in Support of National Security; Enhanced Surveillance of Aging Weapons; A New Precision Cutting Tool: The Femtosecond Laser; Superlasers as a Tool of Stockpile Stewardship; Nova Laser Experiments and Stockpile Stewardship; Transforming Explosive Art into Science; Better Flash Radiography Using the FXR; Preserving Nuclear Weapons Information; Site 300Õs New Contained Firing Facility; The Linear Electric Motor: Instability at 1,000 gÕs; A Powerful New Tool to Detect Clandestine Nuclear Tests; High Explosives in Stockpile Surveillance Indicate Constancy; Addressing a Cold War Legacy with a New Way to Produce TATB; JumpinÕ Jupiter! Metallic Hydrogen;more » Keeping the Nuclear Stockpile Safe, Secure, and Reliable; The Multibeam FabryÐPerot Velocimeter: Efficient Measurements of High Velocities; Theory and Modeling in Material Science; The Diamond Anvil Cell; Gamma-Ray Imaging Spectrometry; X-Ray Lasers and High-Density Plasma« less

Conceptual design of sub-exa-watt system by using optical parametric chirped pulse amplification

NASA Astrophysics Data System (ADS)

Kawanaka, J.; Tsubakimoto, K.; Yoshida, H.; Fujioka, K.; Fujimoto, Y.; Tokita, S.; Jitsuno, T.; Miyanaga, N.; Gekko-EXA Design Team

2016-03-01

A 50 PW ultrahigh-peak-power laser has been conceptually designed, which is based on optical parametric chirped pulse amplification (OPCPA). A 250 J DPSSL and a flash- lamp-pumped kJ laser are adopted as new repeatable pump source. The existed LFEX-laser with more than ten kilo joules are used in the final amplifier stage and the OPCPA with the 2x2 tiled pump beams in random phase has been proposed with several ten centimeter aperture. A pulse duration of amplified pulses is set at less than 10 fs. A broadband OPCPA with ∼500 nm of the gain spectral width near 1 μm is required. A partially deuterated KDP (p-DKDP) crystal is one of the most promising nonlinear crystals and our numerical calculation ensured such ultra-broad gain width. p-DKDP crystals with several deuteration ratio have been successfully grown.

H2/O2 three-body rates at high temperatures

NASA Technical Reports Server (NTRS)

Marinelli, William J.; Kessler, William J.; Piper, Lawrence G.; Rawlins, W. Terry

1990-01-01

The extraction of thrust from air breathing hypersonic propulsion systems is critically dependent on the degree to which chemical equilibrium is reached in the combustion process. In the combustion of H2/Air mixtures, slow three-body chemical reactions involving H-atoms, O-atoms, and the OH radical play an important role in energy extraction. A first-generation high temperature and pressure flash-photolysis/laser-induced fluorescence reactor was designed and constructed to measure these important three-body rates. The system employs a high power excimer laser to produce these radicals via the photolysis of stable precursors. A novel two-photon laser-induced fluorescence technique is employed to detect H-atoms without optical thickness or O2 absorption problems. To demonstrate the feasibility of the technique the apparatus in the program is designed to perform preliminary measurements on the H + O2 + M reaction at temperatures from 300 to 835 K.

Laser photolysis study of the exciplex between triplet benzil and triethylamine

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

Encinas, M.V.; Scaiano, J.C.

1979-12-19

Nanosecond laser flash photolysis techniques have been used to examine the triplet decay and radical-ion formation in the triethylamine (TEA) - benzil system in wet acetonitrile. Under conditions of high TEA concentrations yielding short triplet lifetime, the formation of the benzil radical anion was found to be considerably slower than the decay of the triplet state. This effect is attributed to the intermediacy of a relatively stable exciplex whose properties are reported here. Results of a study of optical density of the system with time following laser excitation led to the assignment of a lifetime of 55ns to the exciplexmore » formed between the triplet benzil and TEA. A structure is suggested for the exciplex. Results of experiments with the non-polar medium n-heptane indicated a shorter lifetime exciplex or one with very different properties from the species identified in the polar medium, wet acetonitrile. (BLM)« less

Detailed Balance Limit of Efficiency of Broadband-Pumped Lasers.

PubMed

Nechayev, Sergey; Rotschild, Carmel

2017-09-13

Broadband light sources are a wide class of pumping schemes for lasers including LEDs, sunlight and flash lamps. Recently, efficient coupling of broadband light to high-quality micro-cavities has been demonstrated for on-chip applications and low-threshold solar-pumped lasers via cascade energy transfer. However, the conversion of incoherent to coherent light comes with an inherent price of reduced efficiency, which has yet to be assessed. In this paper, we derive the detailed balance limit of efficiency of broadband-pumped lasers and discuss how it is affected by the need to maintain a threshold population inversion and thermodynamically dictated minimal Stokes' shift. We show that lasers' slope efficiency is analogous to the nominal efficiency of solar cells, limited by thermalisation losses and additional unavoidable Stokes' shift. The lasers' power efficiency is analogous to the detailed balance limit of efficiency of solar cells, affected by the cavity mirrors and impedance matching factor, respectively. As an example we analyze the specific case of solar-pumped sensitized Nd 3+ :YAG-like lasers and define the conditions to reach their thermodynamic limit of efficiency. Our work establishes an upper theoretical limit for the efficiency of broadband-pumped lasers. Our general, yet flexible model also provides a way to incorporate other optical and thermodynamic losses and, hence, to estimate the efficiency of non-ideal broadband-pumped lasers.

Helicopter flight test of 3D imaging flash LIDAR technology for safe, autonomous, and precise planetary landing

NASA Astrophysics Data System (ADS)

Roback, Vincent; Bulyshev, Alexander; Amzajerdian, Farzin; Reisse, Robert

2013-05-01

Two flash lidars, integrated from a number of cutting-edge components from industry and NASA, are lab characterized and flight tested for determination of maximum operational range under the Autonomous Landing and Hazard Avoidance Technology (ALHAT) project (in its fourth development and field test cycle) which is seeking to develop a guidance, navigation, and control (GNC) and sensing system based on lidar technology capable of enabling safe, precise crewed or robotic landings in challenging terrain on planetary bodies under any ambient lighting conditions. The flash lidars incorporate pioneering 3-D imaging cameras based on Indium-Gallium-Arsenide Avalanche Photo Diode (InGaAs APD) and novel micro-electronic technology for a 128 x 128 pixel array operating at 30 Hz, high pulse-energy 1.06 μm Nd:YAG lasers, and high performance transmitter and receiver fixed and zoom optics. The two flash lidars are characterized on the NASA-Langley Research Center (LaRC) Sensor Test Range, integrated with other portions of the ALHAT GNC system from partner organizations into an instrument pod at NASA-JPL, integrated onto an Erickson Aircrane Helicopter at NASA-Dryden, and flight tested at the Edwards AFB Rogers dry lakebed over a field of humanmade geometric hazards during the summer of 2010. Results show that the maximum operational range goal of 1 km is met and exceeded up to a value of 1.2 km. In addition, calibrated 3-D images of several hazards are acquired in realtime for later reconstruction into Digital Elevation Maps (DEM's).

All-digital full waveform recording photon counting flash lidar

NASA Astrophysics Data System (ADS)

Grund, Christian J.; Harwit, Alex

2010-08-01

Current generation analog and photon counting flash lidar approaches suffer from limitation in waveform depth, dynamic range, sensitivity, false alarm rates, optical acceptance angle (f/#), optical and electronic cross talk, and pixel density. To address these issues Ball Aerospace is developing a new approach to flash lidar that employs direct coupling of a photocathode and microchannel plate front end to a high-speed, pipelined, all-digital Read Out Integrated Circuit (ROIC) to achieve photon-counting temporal waveform capture in each pixel on each laser return pulse. A unique characteristic is the absence of performance-limiting analog or mixed signal components. When implemented in 65nm CMOS technology, the Ball Intensified Imaging Photon Counting (I2PC) flash lidar FPA technology can record up to 300 photon arrivals in each pixel with 100 ps resolution on each photon return, with up to 6000 range bins in each pixel. The architecture supports near 100% fill factor and fast optical system designs (f/#<1), and array sizes to 3000×3000 pixels. Compared to existing technologies, >60 dB ultimate dynamic range improvement, and >104 reductions in false alarm rates are anticipated, while achieving single photon range precision better than 1cm. I2PC significantly extends long-range and low-power hard target imaging capabilities useful for autonomous hazard avoidance (ALHAT), navigation, imaging vibrometry, and inspection applications, and enables scannerless 3D imaging for distributed target applications such as range-resolved atmospheric remote sensing, vegetation canopies, and camouflage penetration from terrestrial, airborne, GEO, and LEO platforms. We discuss the I2PC architecture, development status, anticipated performance advantages, and limitations.

Helicopter Flight Test of 3-D Imaging Flash LIDAR Technology for Safe, Autonomous, and Precise Planetary Landing

NASA Technical Reports Server (NTRS)

Roback, Vincent; Bulyshev, Alexander; Amzajerdian, Farzin; Reisse, Robert

2013-01-01

Two flash lidars, integrated from a number of cutting-edge components from industry and NASA, are lab characterized and flight tested for determination of maximum operational range under the Autonomous Landing and Hazard Avoidance Technology (ALHAT) project (in its fourth development and field test cycle) which is seeking to develop a guidance, navigation, and control (GN&C) and sensing system based on lidar technology capable of enabling safe, precise crewed or robotic landings in challenging terrain on planetary bodies under any ambient lighting conditions. The flash lidars incorporate pioneering 3-D imaging cameras based on Indium-Gallium-Arsenide Avalanche Photo Diode (InGaAs APD) and novel micro-electronic technology for a 128 x 128 pixel array operating at 30 Hz, high pulse-energy 1.06 micrometer Nd:YAG lasers, and high performance transmitter and receiver fixed and zoom optics. The two flash lidars are characterized on the NASA-Langley Research Center (LaRC) Sensor Test Range, integrated with other portions of the ALHAT GN&C system from partner organizations into an instrument pod at NASA-JPL, integrated onto an Erickson Aircrane Helicopter at NASA-Dryden, and flight tested at the Edwards AFB Rogers dry lakebed over a field of human-made geometric hazards during the summer of 2010. Results show that the maximum operational range goal of 1 km is met and exceeded up to a value of 1.2 km. In addition, calibrated 3-D images of several hazards are acquired in real-time for later reconstruction into Digital Elevation Maps (DEM's).

Growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal.

PubMed

Luo, Jianqiao; Sun, Dunlu; Zhang, Huili; Guo, Qiang; Fang, Zhongqing; Zhao, Xuyao; Cheng, Maojie; Zhang, Qingli; Yin, Shaotang

2015-09-15

We demonstrate the growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal. The lifetimes for the upper laser level (4)I(11/2) and lower laser level (4)I(13/2) are 0.59 and 0.84 ms, respectively, which are due to the doping of the Pr(3+) ions. A maximum pulse energy of 278 mJ operated at 10 Hz and 2.79 μm is obtained when pumped with a flash lamp, which corresponds to the electrical-to-optical efficiency of 0.6% and a slope efficiency of 0.7%. A maximum average power of 2.9 W at 60 Hz is achieved, which corresponds to the electrical-to-optical efficiency of 0.4% and slope efficiency of 0.8%. Compared with a Cr,Er:YSGG crystal, the Cr,Er,Pr:GYSGG crystal can be operated at a higher pulse repetition rate. These results suggest that doping deactivator Pr(3+) ions can effectively decrease the lower laser level lifetime and improve the laser repetition rate. Therefore, the application fields and range of the Cr,Er,Pr:GYSGG laser can be extended greatly due to its properties of radiation resistance and high repetition frequency.

Nicotinic acetylcholine receptor probed with a photoactivatable agonist: improved labeling specificity by addition of CeIV/glutathione. Extension to laser flash photolabeling.

PubMed

Grutter, T; Goeldner, M; Kotzyba-Hibert, F

1999-06-08

The molecular structure of Torpedo marmorata acetylcholine binding sites has been investigated previously by photoaffinity labeling. However, besides the nicotine molecule [Middleton et al. (1991) Biochemistry 30, 6987-6997], all other photosensitive probes used for this purpose interacted only with closed receptor states. In the perspective of mapping the functional activated state, we synthesized and developed a new photoactivatable agonist of nAChR capable of alkylation of the acetylcholine (ACh) binding sites, as reported previously [Kotzyba-Hibert et al. (1997) Bioconjugate Chem. 8, 472-480]. Here, we describe the setup of experimental conditions that were made in order to optimize the photolabeling reaction and in particular its specificity. We found that subsequent addition of the oxidant ceric ion (CeIV) and reduced glutathione before the photolabeling step lowered considerably nonspecific labeling (over 90% protection with d-tubocurarine) without affecting the binding properties of the ACh binding sites. As a consequence, irradiation at 360 nm for 20 min in these new conditions gave satisfactory coupling yields (7.5%). A general mechanism was proposed to explain the successive reactions occurring and their drastic effect on the specificity of the labeling reaction. Last, these incubation conditions can be extended to nanosecond pulsed laser photolysis leading to the same specific photoincorporation as for usual irradiations (8.5% coupling yield of ACh binding sites, 77% protection with carbamylcholine). Laser flash photocoupling of a diazocyclohexadienoyl probe on nAChR was achieved for the first time. Taken together, these data indicate that future investigation of the molecular dynamics of allosteric transitions occurring at the activated ACh binding sites should be possible.

Helicopter Flight Test of a Compact, Real-Time 3-D Flash Lidar for Imaging Hazardous Terrain During Planetary Landing

NASA Technical Reports Server (NTRS)

Roback, VIncent E.; Amzajerdian, Farzin; Brewster, Paul F.; Barnes, Bruce W.; Kempton, Kevin S.; Reisse, Robert A.; Bulyshev, Alexander E.

2013-01-01

A second generation, compact, real-time, air-cooled 3-D imaging Flash Lidar sensor system, developed from a number of cutting-edge components from industry and NASA, is lab characterized and helicopter flight tested under the Autonomous Precision Landing and Hazard Detection and Avoidance Technology (ALHAT) project. The ALHAT project is seeking to develop a guidance, navigation, and control (GN&C) and sensing system based on lidar technology capable of enabling safe, precise crewed or robotic landings in challenging terrain on planetary bodies under any ambient lighting conditions. The Flash Lidar incorporates a 3-D imaging video camera based on Indium-Gallium-Arsenide Avalanche Photo Diode and novel micro-electronic technology for a 128 x 128 pixel array operating at a video rate of 20 Hz, a high pulse-energy 1.06 µm Neodymium-doped: Yttrium Aluminum Garnet (Nd:YAG) laser, a remote laser safety termination system, high performance transmitter and receiver optics with one and five degrees field-of-view (FOV), enhanced onboard thermal control, as well as a compact and self-contained suite of support electronics housed in a single box and built around a PC-104 architecture to enable autonomous operations. The Flash Lidar was developed and then characterized at two NASA-Langley Research Center (LaRC) outdoor laser test range facilities both statically and dynamically, integrated with other ALHAT GN&C subsystems from partner organizations, and installed onto a Bell UH-1H Iroquois "Huey" helicopter at LaRC. The integrated system was flight tested at the NASA-Kennedy Space Center (KSC) on simulated lunar approach to a custom hazard field consisting of rocks, craters, hazardous slopes, and safe-sites near the Shuttle Landing Facility runway starting at slant ranges of 750 m. In order to evaluate different methods of achieving hazard detection, the lidar, in conjunction with the ALHAT hazard detection and GN&C system, operates in both a narrow 1deg FOV raster-scanning mode in which successive, gimbaled images of the hazard field are mosaicked together as well as in a wider, 4.85deg FOV staring mode in which digital magnification, via a novel 3-D superresolution technique, is used to effectively achieve the same spatial precision attained with the more narrow FOV optics. The lidar generates calibrated and corrected 3-D range images of the hazard field in real-time and passes them to the ALHAT Hazard Detection System (HDS) which stitches the images together to generate on-the-fly Digital Elevation Maps (DEM's) and identifies hazards and safe-landing sites which the ALHAT GN&C system can then use to guide the host vehicle to a safe landing on the selected site. Results indicate that, for the KSC hazard field, the lidar operational range extends from 100m to 1.35 km for a 30 degree line-of-sight angle and a range precision as low as 8 cm which permits hazards as small as 25 cm to be identified. Based on the Flash Lidar images, the HDS correctly found and reported safe sites in near-real-time during several of the flights. A follow-on field test, planned for 2013, seeks to complete the closing of the GN&C loop for fully-autonomous operations on-board the Morpheus robotic, rocket-powered, free-flyer test bed in which the ALHAT system would scan the KSC hazard field (which was vetted during the present testing) and command the vehicle to landing on one of the selected safe sites.

Flash lamp-excited time-resolved fluorescence microscope suppresses autofluorescence in water concentrates to deliver an 11-fold increase in signal-to-noise ratio.

PubMed

Connally, Russell; Veal, Duncan; Piper, James

2004-01-01

The ubiquity of naturally fluorescing components (autofluorophores) encountered in most biological samples hinders the detection and identification of labeled targets through fluorescence-based techniques. Time-resolved fluorescence (TRF) is a technique by which the effects of autofluorescence are reduced by using specific fluorescent labels with long fluorescence lifetimes (compared with autofluorophores) in conjunction with time-gated detection. A time-resolved fluorescence microscope (TRFM) is described that is based on a standard epifluorescence microscope modified by the addition of a pulsed excitation source and an image-intensified time-gateable CCD camera. The choice of pulsed excitation source for TRFM has a large impact on the price and performance of the instrument. A flash lamp with rapid discharge characteristics was selected for our instrument because of the high spectral energy in the UV region and short pulse length. However, the flash output decayed with an approximate lifetime of 18 micros and the TRFM required a long-lived lanthanide chelate label to ensure that probe fluorescence was visible after decay of the flash plasma. We synthesized a recently reported fluorescent chelate (BHHCT) and conjugated it to a monoclonal antibody directed against the waterborne parasite Giardia lamblia. For a 600-nm bandpass filter set and a gate delay of 60 micros, the TRFM provided an 11.3-fold improvement in the signal-to-noise ratio (S/N) of labeled Giardia over background. A smaller gain in an SNR of 9.69-fold was achieved with a 420-nm longpass filter set; however, the final contrast ratio between labeled cyst and background was higher (11.3 versus 8.5). Despite the decay characteristics of the light pulse, flash lamps have many practical advantages compared with optical chopper wheels and modulated lasers for applications in TRFM.

Effects of malicious ocular laser exposure in commercial airline pilots.

PubMed

Palakkamanil, Mathew M; Fielden, Michael P

2015-12-01

Intentional malicious laser strikes on commercial pilots are committed by individuals who target a laser into airplane cockpits during takeoff and landing. Because laser exposure to pilots is a relatively new but growing occurrence, our study investigates the ocular effect of this laser exposure in pilots. Retrospective chart review by a single ophthalmologist. All commercial airline pilots (58 male, 3 female) who experienced a laser strike while flying between April 2012 and November 2014 who presented to our clinic were included. A retrospective chart review was performed in a retinal specialist's practice. Ocular assessment was performed within 3 days of laser exposure. A complete ophthalmic evaluation was conducted, including Early Treatment Diabetic Retinopathy Study visual acuity, colour vision, visual fields, intraocular pressure, slit-lamp examination, dilated fundus examination, colour fundus photographs, and ocular coherence tomography. Sixty-four laser strike incidents involving commercial pilots were included. All pilots in the study experienced some degree of immediate ocular irritation or light sensitivity. No definite cases of ocular damage were attributed to laser strikes. No pilot had any functional ocular deficits. Our study revealed that laser strikes on aircraft did not result in permanent visual functional or structural deficits. However, laser strikes cause immediate visual effects, including glare, flash blindness, and ocular irritation that can interfere with a pilot's visual function. Given the widespread accessibility of high-power lasers and the rapid increase in incidents, laser strikes threaten to jeopardize aviation safety unless effective preventative measures are put in place. Copyright © 2015 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.

Cephalopod-INspired Adaptive Photonic SystEms (CINAPSE)

DTIC Science & Technology

2013-09-13

2013 19.00 L. M. Mathger, G. R. R. Bell, A. M. Kuzirian, J. J. Allen, R. T. Hanlon. How does the blue - ringed octopus (Hapalochlaena lunulata) flash...its blue rings ?, Journal of Experimental Biology, (10 2012): 3752. doi: 10.1242/jeb.076869 08/28/2013 20.00 T. J. Wardill, P. T. Gonzalez-Bellido, R...distinct fluorescent emission spectrum shift into the near-red wavelengths (610-630 ¿) when excited by a 514 ¿ ( blue -green) laser beam. The

Multiple ionization of neon by soft x-rays at ultrahigh intensity

NASA Astrophysics Data System (ADS)

Guichard, R.; Richter, M.; Rost, J.-M.; Saalmann, U.; Sorokin, A. A.; Tiedtke, K.

2013-08-01

At the free-electron laser FLASH, multiple ionization of neon atoms was quantitatively investigated at photon energies of 93.0 and 90.5 eV. For ion charge states up to 6+, we compare the respective absolute photoionization yields with results from a minimal model and an elaborate description including standard sequential and direct photoionization channels. Both approaches are based on rate equations and take into account a Gaussian spatial intensity distribution of the laser beam. From the comparison we conclude that photoionization up to a charge of 5+ can be described by the minimal model which we interpret as sequential photoionization assisted by electron shake-up processes. For higher charges, the experimental ionization yields systematically exceed the elaborate rate-based prediction.

An Experimental and Master Equation Study of the Kinetics of OH/OD + SO2: The Limiting High-Pressure Rate Coefficients.

PubMed

Blitz, Mark A; Salter, Robert J; Heard, Dwayne E; Seakins, Paul W

2017-05-04

The kinetics of the reaction OH/OD + SO 2 were studied using a laser flash photolysis/laser-induced fluorescence technique. Evidence for two-photon photolysis of SO 2 at 248 nm is presented and quantified, and which appears to have been evident to some extent in most previous photolysis studies, potentially leading to values for the rate coefficient k 1 that are too large. The kinetics of the reaction OH(v = 0) + SO 2 (T = 295 K, p = 25-300 torr) were measured under conditions where SO 2 photolysis was taken into account. These results, together with literature data, were modeled using a master equation analysis. This analysis highlighted problems with the literature data: the rate coefficients derived from flash photolysis data were generally too high and from the flow tube data too low. Our best estimate of the high-pressure limiting rate coefficient k 1 ∞ was obtained from selected data and gives a value of (7.8 ± 2.2) × 10 -13 cm 3 molecule -1 s -1 , which is lower than that recommended in the literature. A parametrized form of k 1 ([N 2 ],T) is provided. The OD(v = 0) + SO 2 (T = 295 K, p = 25-300 torr) data are reported for the first time, and master equation analysis reinforces our assignment of k 1 ∞ .

A highly efficient and compact long pulse Nd:YAG rod laser with 540 J of pulse energy for welding application.

PubMed

Choubey, Ambar; Vishwakarma, S C; Misra, Pushkar; Jain, R K; Agrawal, D K; Arya, R; Upadhyaya, B N; Oak, S M

2013-07-01

We have developed an efficient and high average power flash lamp pumped long pulse Nd:YAG laser capable of generating 1 kW of average output power with maximum 540 J of single pulse energy and 20 kW of peak power. The laser pulse duration can be varied from 1 to 40 ms and repetition rate from 1 to 100 Hz. A compact and robust laser pump chamber and resonator was designed to achieve this high average and peak power. It was found that this laser system provides highest single pulse energy as compared to other long pulsed Nd:YAG laser systems of similar rating. A slope efficiency of 5.4% has been achieved, which is on higher side for typical lamp pumped solid-state lasers. This system will be highly useful in laser welding of materials such as aluminium and titanium. We have achieved 4 mm deep penetration welding of these metals under optimized conditions of output power, pulse energy, and pulse duration. The laser resonator was optimized to provide stable operation from single shot to 100 Hz of repetition rate. The beam quality factor was measured to be M(2) ~ 91 and pulse-to-pulse stability of ±3% for the multimode operation. The laser beam was efficiently coupled through an optical fiber of 600 μm core diameter and 0.22 numerical aperture with power transmission of 90%.

Blue Laser Induced Retinal Injury in a Commercial Pilot at 1300 ft.

PubMed

Gosling, Daniel B; O'Hagan, John B; Quhill, Fahd M

2016-01-01

We report what may be the first evidence-based report of a retinal laser injury to a pilot during commercial flight from a laser device on the ground. Given the significant subjective (blind spot) and objective evidence of focal retinal damage, coupled with the distance involved, we suspect the laser had a radiant power of several watts, known to be injurious to the human retina. An airline pilot presented to our department complaining of a blind spot in the upper left area of his visual field in the right eye (right supero-nasal scotoma) following exposure to a laser beam while performing a landing maneuver of a commercial aircraft. At around 1300 ft (396 m), a blue laser beam from the ground directly entered his right eye, with immediate flash blindness and pain. Spectral domain ocular coherence tomography highlighted a localized area of photoreceptor disruption corresponding to a well demarcated area of hypofluorescence on fundus autofluorescence, representing a focal outer retinal laser injury. Fundus examination a fortnight later revealed a clinically identifiable lesion in the pilot's right eye commensurate with a retinal-laser burn. The case reports highlights the growing threat to the ocular health of airline crew and, potentially, passenger safety due to the lack of regulatory oversight of high powered laser devices obtained from the internet. We strongly believe high powered handheld laser devices should not be in the possession of the general public.

Perfluorocarbon compounds: transmitting liquids for infrared laser tissue ablation

NASA Astrophysics Data System (ADS)

Frenz, Martin; Pratisto, Hans S.; Toth, Cynthia A.; Jansen, E. Duco; Altermatt, Hans J.; Welch, Ashley J.; Weber, Heinz P.

1996-05-01

One concern during IR-laser ablation of tissue under water is the mechanical injury that may be induced in tissue due to rapid bubble expansion and collapse or due to strong laser-induced pressure waves. The objective of this study was to evaluate the feasibility of using a liquid which is transparent to the IR-region of the spectrum in order to minimize these undesired mechanical side-effects. As transmitting medium perfluorocarbon liquid was used. Free- running Er:YAG and Ho:YAG laser pulses were delivered into the liquid via a 400 micrometers fiber. Bubble formation during the ablation process was recorded with fast flash photography while pressure transients were measured with a needle hydrophone. The effect of the surrounding material (air, water, perfluorooctane) on the tissue response of chicken breast was evaluated in vitro using histology. It was observed that a large bubble (up to 6 mm in diameter) was formed under perfluorooctane driven by the ablation products. This bubble, however, does not generate a pressure wave when collapsing. Although perfluorooctane only shows a weak absorption for infrared radiation, laser-induced thermal lensing in the liquid strongly decreases the radiant exposure and therefore the ablation efficiency.

Effect of aerobic exercises versus laser acupuncture in treatment of postmenopausal hot flushes: a randomized controlled trial.

PubMed

Elhosary, Eman Abdelfatah Mohamed; Ewidea, Mahmoud Mohamed; Ahmed, Hamada Ahmed Hamada; El Khatib, Ayman

2018-02-01

[Purpose] To compare the effect of aerobic exercises versus laser acupuncture in treatment of postmenopausal hot flushes. [Subjects and Methods] This study was designed as single blind randomized controlled trial. A total of 48 postmenopausal women complained of hot flushes. Their ages ranged between 45 to 55 years and were randomly assigned into 2 equal groups: group (A), which received an aerobic exercises, and group (B), which received laser acupuncture. Both groups recieved 3 sessions per week for two months. The level of follicular stimulating hormone, lutelizing hormone, and hot flushes dairy card were assessed the severity of hot flahes before and after treatment program. [Results] There were Significant reduction in FSH, LH, and menopausal daily hot flush scale in group A compared with group B at the post treatment. [Conclusion] Eight week program of an aerobic exercises yields improvement in FSH, LH, and decrease in severity of hot flushes assessed by hot flush dairy card than laser acupuncture in the treatment of postmenopausal hot flashes.

Fully vectorial laser resonator modeling of continuous-wave solid-state lasers including rate equations, thermal lensing and stress-induced birefringence.

PubMed

Asoubar, Daniel; Wyrowski, Frank

2015-07-27

The computer-aided design of high quality mono-mode, continuous-wave solid-state lasers requires fast, flexible and accurate simulation algorithms. Therefore in this work a model for the calculation of the transversal dominant mode structure is introduced. It is based on the generalization of the scalar Fox and Li algorithm to a fully-vectorial light representation. To provide a flexible modeling concept of different resonator geometries containing various optical elements, rigorous and approximative solutions of Maxwell's equations are combined in different subdomains of the resonator. This approach allows the simulation of plenty of different passive intracavity components as well as active media. For the numerically efficient simulation of nonlinear gain, thermal lensing and stress-induced birefringence effects in solid-state active crystals a semi-analytical vectorial beam propagation method is discussed in detail. As a numerical example the beam quality and output power of a flash-lamp-pumped Nd:YAG laser are improved. To that end we compensate the influence of stress-induced birefringence and thermal lensing by an aspherical mirror and a 90° quartz polarization rotator.

Dynamics and detection of laser induced microbubbles in the retinal pigment epithelium (RPE)

NASA Astrophysics Data System (ADS)

Fritz, Andreas; Ptaszynski, Lars; Stoehr, Hardo; Brinkmann, Ralf

2007-07-01

Selective Retina Treatment (SRT) is a new method to treat eye diseases associated with disorders of the RPE. Selective RPE cell damage is achieved by applying a train of 1.7 μs laser pulses at 527 nm. The treatment of retinal diseases as e.g. diabetic maculopathy (DMP), is currently investigated within clinical studies, however 200 ns pulse durations are under investigation. Transient micro bubbles in the retinal pigment epithelium (RPE) are expected to be the origin of cell damage due to irradiation with laser pulses shorter than 50 μs. The bubbles emerge at the strongly absorbing RPE melanosomes. Cell membrane disruption caused by the transient associated volume increase is expected to be the origin of the angiographically observed RPE leakage. We investigate micro bubble formation and dynamics in porcine RPE using pulse durations of 150 ns. A laser interferometry system at 830 nm with the aim of an online dosimetry control for SRT was developed. Bubble formation was detected interferometrically and by fast flash photography. A correlation to cell damage observed with a vitality stain is found. A bubble detection algorithm is presented.

Combining Raman and laser induced breakdown spectroscopy by double pulse lasing.

PubMed

Lednev, Vasily N; Pershin, Sergey M; Sdvizhenskii, Pavel A; Grishin, Mikhail Ya; Fedorov, Alexander N; Bukin, Vladimir V; Oshurko, Vadim B; Shchegolikhin, Alexander N

2018-01-01

A new approach combining Raman spectrometry and laser induced breakdown spectrometry (LIBS) within a single laser event was suggested. A pulsed solid state Nd:YAG laser running in double pulse mode (two frequency-doubled sequential nanosecond laser pulses with dozens microseconds delay) was used to combine two spectrometry methods within a single instrument (Raman/LIBS spectrometer). First, a low-energy laser pulse (power density far below ablation threshold) was used for Raman measurements while a second powerful laser pulse created the plasma suitable for LIBS analysis. A short time delay between two successive pulses allows measuring LIBS and Raman spectra at different moments but within a single laser flash-lamp pumping. Principal advantages of the developed instrument include high quality Raman/LIBS spectra acquisition (due to optimal gating for Raman/LIBS independently) and absence of target thermal alteration during Raman measurements. A series of high quality Raman and LIBS spectra were acquired for inorganic salts (gypsum, anhydrite) as well as for pharmaceutical samples (acetylsalicylic acid). To the best of our knowledge, the quantitative analysis feasibility by combined Raman/LIBS instrument was demonstrated for the first time by calibration curves construction for acetylsalicylic acid (Raman) and copper (LIBS) in gypsum matrix. Combining ablation pulses and Raman measurements (LIBS/Raman measurements) within a single instrument makes it an efficient tool for identification of samples hidden by non-transparent covering or performing depth profiling analysis including remote sensing. Graphical abstract Combining Raman and laser induced breakdown spectroscopy by double pulse lasing.

Influence of Interfacial Carbide Layer Characteristics on Thermal Properties of Copper-Diamond Composites (Postprint)

DTIC Science & Technology

2014-04-01

wettability of diamond is not an issue. Moreover, the solid-state processing can, in principle , be carried out at relatively low temperatures even for non...capacity. q was mea- sured using Archimedes ’ method, and D was measured with laser flash technique per ASTM E1461. The speci- mens for D measurement... principle , attainable by changing the interfacial Cr3C2 layer characteristics. In an earlier study [3], for a given diamond particle size and volume

Conference on Singlet Molecular Oxygen (COSMO 84) Held at Clearwater, Beach, Florida on 4-7 January 1984. Program and Abstracts.

DTIC Science & Technology

1984-09-24

BREAKS will be announced by the SESSION CHAIRMAN. 6. LOCAL INFORMATION may be obtained at the HILTON REGISTRATION DESK or the LOBBY REGISTRATION DESK...carotene and laser flash photolysis experiments to determine the rates of quenching of 3 BChl a by oxygen, $-carotene#,3 tetracene and pentacene . References...with the tumor localizing and photosensitizing constituent of HPD strongly suggests that the in situ "’ * tumor sensitizer in photoradiation therapy is

Photochemistry and photooxidation of tetraphenyl-p-dioxin

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

George, M.V.; Kumar, C.V.; Scaiano, J.C.

1979-09-20

Laser flash photolysis studies of tetraphenyl-p-dioxin have led to the characterization of its triplet state. The T-T absorption spectra shows maxima at 350 and 545 nm; the triplet has a lifetime of 535 ns in methanol and can be quenched by di-tert-butyl nitroxide, paraquat dications, oxygen, and di-tert-butyl selenoketone. The interaction of the triplet with oxygen leads to the formation of singlet oxygen which in turn reacts with the title compound to yield benzil.

Photophysics and Photochemistry of 2-Aminobenzoic Acid Anion in Aqueous Solution

NASA Astrophysics Data System (ADS)

Pozdnyakov, Ivan P.; Plyusnin, Victor F.; Grivin, Vjacheslav P.

2009-11-01

Nanosecond laser flash photolysis and absorption and fluorescence spectroscopy were used to study photochemical processes of 2-aminobenzoic acid anion (ABA-) in aqueous solutions. Excitation of this species gives rise to the ABA- triplet state to the ABA• radical and to the hydrated electron (eaq-). The last two species result from two-photon processes. In a neutral medium, the main decay channels of ABA- triplet state, the ABA• radical, and eaq- are T-T annihilation, recombination, and capture by the ABA- anion, respectively.

Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

NASA Astrophysics Data System (ADS)

Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

1994-12-01

The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

Patterning of wound-induced intercellular Ca2+ flashes in a developing epithelium

NASA Astrophysics Data System (ADS)

Narciso, Cody; Wu, Qinfeng; Brodskiy, Pavel; Garston, George; Baker, Ruth; Fletcher, Alexander; Zartman, Jeremiah

2015-10-01

Differential mechanical force distributions are increasingly recognized to provide important feedback into the control of an organ’s final size and shape. As a second messenger that integrates and relays mechanical information to the cell, calcium ions (Ca2+) are a prime candidate for providing important information on both the overall mechanical state of the tissue and resulting behavior at the individual-cell level during development. Still, how the spatiotemporal properties of Ca2+ transients reflect the underlying mechanical characteristics of tissues is still poorly understood. Here we use an established model system of an epithelial tissue, the Drosophila wing imaginal disc, to investigate how tissue properties impact the propagation of Ca2+ transients induced by laser ablation. The resulting intercellular Ca2+ flash is found to be mediated by inositol 1,4,5-trisphosphate and depends on gap junction communication. Further, we find that intercellular Ca2+ transients show spatially non-uniform characteristics across the proximal-distal axis of the larval wing imaginal disc, which exhibit a gradient in cell size and anisotropy. A computational model of Ca2+ transients is employed to identify the principle factors explaining the spatiotemporal patterning dynamics of intercellular Ca2+ flashes. The relative Ca2+ flash anisotropy is principally explained by local cell shape anisotropy. Further, Ca2+ velocities are relatively uniform throughout the wing disc, irrespective of cell size or anisotropy. This can be explained by the opposing effects of cell diameter and cell elongation on intercellular Ca2+ propagation. Thus, intercellular Ca2+ transients follow lines of mechanical tension at velocities that are largely independent of tissue heterogeneity and reflect the mechanical state of the underlying tissue.

THz pulse doubler at FLASH: double pulses for pump–probe experiments at X-ray FELs

PubMed Central

Zapolnova, Ekaterina; Golz, Torsten; Pan, Rui; Klose, Karsten; Stojanovic, Nikola

2018-01-01

FLASH, the X-ray free-electron laser in Hamburg, Germany, employs a narrowband high-field accelerator THz source for unique THz pump X-ray probe experiments. However, the large difference in optical paths of the THz and X-ray beamlines prevents utilization of the machine’s full potential (e.g. extreme pulse energies in the soft X-ray range). To solve this issue, lasing of double electron bunches, separated by 28 periods of the driving radiofrequency (at 1.3 GHz), timed for the temporal overlap of THz and X-ray pulses at the experimental station has been employed. In order to optimize conditions for a typical THz pump X-ray probe experiment, X-ray lasing of the first bunch to one-sixth of that of the second has been suppressed. Finally, synchronization of THz radiation pulses was measured to be ∼20 fs (r.m.s.), and a solution for monitoring the arrival time for achieving higher temporal resolution is presented. PMID:29271749

THz pulse doubler at FLASH: double pulses for pump-probe experiments at X-ray FELs.

PubMed

Zapolnova, Ekaterina; Golz, Torsten; Pan, Rui; Klose, Karsten; Schreiber, Siegfried; Stojanovic, Nikola

2018-01-01

FLASH, the X-ray free-electron laser in Hamburg, Germany, employs a narrowband high-field accelerator THz source for unique THz pump X-ray probe experiments. However, the large difference in optical paths of the THz and X-ray beamlines prevents utilization of the machine's full potential (e.g. extreme pulse energies in the soft X-ray range). To solve this issue, lasing of double electron bunches, separated by 28 periods of the driving radiofrequency (at 1.3 GHz), timed for the temporal overlap of THz and X-ray pulses at the experimental station has been employed. In order to optimize conditions for a typical THz pump X-ray probe experiment, X-ray lasing of the first bunch to one-sixth of that of the second has been suppressed. Finally, synchronization of THz radiation pulses was measured to be ∼20 fs (r.m.s.), and a solution for monitoring the arrival time for achieving higher temporal resolution is presented.

Defining the unknowns of sonoluminescence

NASA Astrophysics Data System (ADS)

Barber, Bradley P.; Hiller, Robert A.; Löfstedt, Ritva; Putterman, Seth J.; Weninger, Keith R.

1997-03-01

As the intensity of a standing sound wave is increased the pulsations of a bubble of gas trapped at a velocity node attain sufficient amplitude so as to emit picosecond flashes of light with a broadband spectrum that increases into the ultraviolet. The acoustic resonator can be tuned so that the flashes of light occur with a clocklike regularity: one flash for each cycle of sound with a jitter in the time between flashes that is also measured in picoseconds. This phenomenon (sonoluminescence or “SL”) is remarkable because it is the only means of generating picosecond flashes of light that does not use a laser and the input acoustic energy density must be concentrated by twelve orders of magnitude in order to produce light. Light scattering measurements indicate that the bubble wall is collapsing at more than 4 times the ambient speed of sound in the gas just prior to the light emitting moment when the gas has been compressed to a density determined by its van der Waals hard core. Experiments indicate that the collapse is remarkably spherical, water is the best fluid for SL, some noble gas is essential for stable SL, and that the light intensity increases as the ambient temperature is lowered. In the extremely stable experimental configuration consisting of an air bubble in water, measurements indicate that the bubble chooses an ambient radius that is not explained by mass diffusion. Experiments have not yet been able to map out the complete spectrum because above 6 eV it is obscured by the cutoff imposed by water, and furthermore experiments have only determined an upper bound on the flash widths. In addition to the above puzzles, the theory for the light emitting mechanism is still open. The scenario of a supersonic bubble collapse launching an imploding shock wave which ionizes the bubble contents so as to cause it to emit Bremsstrahlung radiation is the best candidate theory but it has not been shown how to extract from it the richness of this phenomenon. Most exciting is the issue of whether SL is a classical effect or whether Planck's constant should be invoked to explain how energy which enters a medium at the macroscopic scale holds together and focuses so as to be emitted at the microscopic scale.

Versatile illumination platform and fast optical switch to give standard observation camera gated active imaging capacity

NASA Astrophysics Data System (ADS)

Grasser, R.; Peyronneaudi, Benjamin; Yon, Kevin; Aubry, Marie

2015-10-01

CILAS, subsidiary of Airbus Defense and Space, develops, manufactures and sales laser-based optronics equipment for defense and homeland security applications. Part of its activity is related to active systems for threat detection, recognition and identification. Active surveillance and active imaging systems are often required to achieve identification capacity in case for long range observation in adverse conditions. In order to ease the deployment of active imaging systems often complex and expensive, CILAS suggests a new concept. It consists on the association of two apparatus working together. On one side, a patented versatile laser platform enables high peak power laser illumination for long range observation. On the other side, a small camera add-on works as a fast optical switch to select photons with specific time of flight only. The association of the versatile illumination platform and the fast optical switch presents itself as an independent body, so called "flash module", giving to virtually any passive observation systems gated active imaging capacity in NIR and SWIR.

All-Solid-State UV Transmitter Development for Ozone Sensing Applications

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Armstrong, Darrell Jr.

2009-01-01

In this paper, recent progress made in the development of an all-solid-state UV transmitter suitable for ozone sensing applications from space based platforms is discussed. A nonlinear optics based UV setup based on Rotated Image Singly Resonant Twisted Rectangle (RISTRA) optical parametric oscillator (OPO) module was effectively coupled to a diode pumped, single longitudinal mode, conductively cooled, short-pulsed, high-energy Nd:YAG laser operating at 1064 nm with 50 Hz PRF. An estimated 10 mJ/pulse with 10% conversion efficiency at 320 nm has been demonstrated limited only by the pump pulse spatial profile. The current arrangement has the potential for obtaining greater than 200 mJ/pulse. Previously, using a flash-lamp pumped Nd:YAG laser with round, top-hat profile, up to 24% IR-UV conversion efficiency was achieved with the same UV module. Efforts are underway to increase the IR-UV conversion efficiency of the all solid-state setup by modifying the pump laser spatial profile along with incorporating improved OPO crystals.

Femtosecond Laser Microfabrication of an Integrated Device for Optical Release and Sensing of Bioactive Compounds

PubMed Central

Ghezzi, Diego; Vazquez, Rebeca Martinez; Osellame, Roberto; Valtorta, Flavia; Pedrocchi, Alessandra; Valle, Giuseppe Della; Ramponi, Roberta; Ferrigno, Giancarlo; Cerullo, Giulio

2008-01-01

Flash photolysis of caged compounds is one of the most powerful approaches to investigate the dynamic response of living cells. Monolithically integrated devices suitable for optical uncaging are in great demand since they greatly simplify the experiments and allow their automation. Here we demonstrate the fabrication of an integrated bio-photonic device for the optical release of caged compounds. Such a device is fabricated using femtosecond laser micromachining of a glass substrate. More in detail, femtosecond lasers are used both to cut the substrate in order to create a pit for cell growth and to inscribe optical waveguides for spatially selective uncaging of the compounds present in the culture medium. The operation of this monolithic bio-photonic device is tested using both free and caged fluorescent compounds to probe its capability of multipoint release and optical sensing. Application of this device to the study of neuronal network activity can be envisaged. PMID:27873888

The European XFEL Free Electron Laser at DESY

ScienceCinema

Weise, Hans [Deutsches Elektronen-Synchrotron, Germany

2017-12-09

The European X-ray Free-Electron laser Facility (XFEL) is going to be built in an international collaboration at the Deutsches Elektronen-Synchrotron (DESY), Germany, and the Technical Design Report was published in 2006. The official project is expected for summer 2007. This new facility will offer photon beams at wavelengths as short as 1 angstrom with highest peak brilliance being more than 100 million times higher than present day synchrotron radiation sources. The radiation has a high degree of transverse coherence and the pulse duration is reduced from {approx}100 picoseconds (typ. for SR light sources) down to the {approx}10 femtosecond time domain. The overall layout of the XFEL will be described. This includes the envisaged operation parameters for the linear accelerator using superconducting TESLA technology. The complete design is based on the actually operated FLASH free-electron laser at DESY. Experience with the operation during first long user runs at wavelengths from 30 to 13 nm will be described in detail.

Prospects for compact high-intensity laser synchrotron x-ray and gamma sources

NASA Astrophysics Data System (ADS)

Pogorelsky, I. V.

1997-03-01

A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power CO2 laser may be used for prototype LSS demonstration. In a feasible demonstration experiment, 10-GW, 100-ps CO2 laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 Å) x-rays of 10-ps pulse duration, with a flux of ˜1019photons/sec, will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to the e-beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 1022 photons/sec level, after the ongoing ATF CO2 laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact "table-top" LSS of monochromatic gamma radiation may become feasible.

Investigations on the potential of a low power diode pumped Er:YAG laser system for oral surgery

NASA Astrophysics Data System (ADS)

Stock, Karl; Wurm, Holger; Hausladen, Florian; Wagner, Sophia; Hibst, Raimund

2015-02-01

Flash lamp pumped Er:YAG-lasers are used in clinical practice for dental applications successfully. As an alternative, several diode pumped Er:YAG laser systems (Pantec Engineering AG) become available, with mean laser power of 2W, 15W, and 30W. The aim of the presented study is to investigate the potential of the 2W Er:YAG laser system for oral surgery. At first an appropriate experimental set-up was realized with a beam delivery and both, a focusing unit for non-contact tissue cutting and a fiber tip for tissue cutting in contact mode. In order to produce reproducible cuts, the samples (porcine gingiva) were moved by a computer controlled translation stage. On the fresh samples cutting depth and quality were determined by light microscopy. Afterwards histological sections were prepared and microscopically analyzed regarding cutting depth and thermal damage zone. The experiments show that low laser power ≤ 2W is sufficient to perform efficient oral soft tissue cutting with cut depth up to 2mm (sample movement 2mm/s). The width of the thermal damage zone can be controlled by the irradiation parameters within a range of about 50μm to 110μm. In general, thermal injury is more pronounced using fiber tips in contact mode compared to the focused laser beam. In conclusion the results reveal that even the low power diode pumped Er:YAG laser is an appropriate tool for oral surgery.

A laser flash photolysis-resonance fluorescence kinetics study of the reaction Cl/2P/ + CH4 yields CH3 + HCl

NASA Technical Reports Server (NTRS)

Ravishankara, A. R.; Wine, P. H.

1980-01-01

The technique of laser flash photolysis-resonance fluorescence is employed to study the kinetics of the reaction Cl(2P) + CH4 yields CH3 + HCl over the temperature range 221-375 K. At temperatures less than or equal to 241 K the apparent bimolecular rate constant is found to be dependent upon the identity of the chemically inert gases in the reaction mixture. For Cl2/CH4/He reaction mixtures (total pressure = 50 torr) different bimolecular rate constants are measured at low and high methane concentrations. For Cl2/CH4/CCl/He and Cl2/CH4/Ar reaction mixtures, the bimolecular rate constant is independent of methane concentration, being approximately equal to the rate constant measured at low methane concentrations for Cl2/CH4/He mixtures. These rate constants are in good agreement with previous results obtained using the discharge flow-resonance fluorescence and competitive chlorination techniques. At 298 K the measured bimolecular rate constant is independent of the identity of the chemically inert gases in the reaction mixture and in good agreement with all previous investigations. The low-temperature results obtained in this investigation and all previous investigations can be rationalized in terms of a model which assumes that the Cl(2P 1/2) state reacts with CH4 much faster than the Cl(2P 3/2) state. Extrapolation of this model to higher temperatures, however, is not straightforward.

Photoionization of oxidized coenzyme Q in microemulsion: laser flash photolysis study in biomembrane-like system.

PubMed

Li, Kun; Wang, Mei; Wang, Jin; Zhu, Rongrong; Sun, Dongmei; Sun, Xiaoyu; Wang, Shi-Long

2013-01-01

Photoexcitation to generate triplet state has been proved to be the main photoreaction in homogeneous system for many benzoquinone derivatives, including oxidized coenzyme Q (CoQ) and its analogs. In the present study, microemulsion of CoQ, a heterogeneous system, is employed to mimic the distribution of CoQ in biomembrane. The photochemistry of CoQ(10) in microemulsion and cyclohexane is investigated and compared using laser flash photolysis and results show that CoQ(10) undergoes photoionization via a monophotonic process to generate radical cation of CoQ(10) in microemulsion and photoexcitation to generate excited triplet state in cyclohexane. Meanwhile, photoreactions of duroquinone (DQ) and CoQ(0) in microemulsion are also investigated to analyze the influence of molecular structure on the photochemistry of benzoquinone derivatives in microemulsion. Results suggest that photoexcitation, which is followed by excited state-involved hydrogen-abstraction reaction, is the main photoreaction for DQ and CoQ(0) in microemulsion. However, photoexcited CoQ(0) also leads to the formation of hydrated electrons. The isoprenoid side chain-involved high resonance stabilization is proposed to explain the difference in photoreactions of CoQ(0) and CoQ(10) in microemulsion. Considering that microemulsion is close to biomembrane system, its photoionization in microemulsion may be helpful to understand the real photochemistry of biological quinones in biomembrane system. © 2012 Tongji University. Photochemistry and Photobiology © 2012 The American Society of Photobiology.

Study of the chemistry of ortho- and para-biphenylnitrenes by laser flash photolysis and time-resolved IR experiments and by B3LYP and CASPT2 calculations.

PubMed

Tsao, Meng-Lin; Gritsan, Nina; James, Tammi R; Platz, Matthew S; Hrovat, David A; Borden, Weston Thatcher

2003-08-06

The photochemistry of ortho-biphenyl azide (1a) has been studied by laser flash photolysis (LFP), with UV-vis and IR detection of the transient intermediates formed. LFP (266 nm) of 1a in glassy 3-methylpentane at 77 K releases singlet ortho-biphenylnitrene (1b) (lambda(max) = 410 nm, tau = 59 +/- 6 ns), which under these conditions decays cleanly to the lower energy triplet state. In fluid solution at 298 K, 1b rapidly (tau < 10 ns) partitions between formation of isocarbazole (4) (lambda(max) = 430 nm, tau = 70 ns) and benzazirine (1e) (lambda(max) = 305 nm, tau = 12 ns). Isocarbazole 4 undergoes a 1,5-hydrogen shift, with k(H)/k(D) = 3.4 at 298 K to form carbazole 9 and smaller amounts of two other isocarbazoles (7 and 8). Benzazirine 1e ring-opens reversibly to azacycloheptatetraene (1f), which serves as a reservoir for singlet nitrene 1b. Azacycloheptatetraene 1f ultimately forms carbazole 9 on the millisecond time scale by the pathway 1f --> 1e --> 1b --> 4 --> 9. The energies of the transient intermediates and of the transition structures connecting them were successfully predicted by CASPT2/6-31G calculations. The electronic and vibrational spectra of the intermediates, computed by density functional theory, support the assignment of the transient spectra, observed in the formation of 9 from 1a.

Studies on photoinduced H-atom and electron transfer reactions of o-naphthoquinones by laser flash photolysis.

PubMed

Pan, Yang; Fu, Yao; Liu, Shaoxiong; Yu, Haizhu; Gao, Yuhe; Guo, Qingxiang; Yu, Shuqin

2006-06-15

The quenching of the triplets of 1,2-naphthoquinone (NQ) and 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS) by various electron and H-atom donors was investigated by laser flash photolysis measurement in acetonitrile and benzene. The results showed that the reactivities and configurations of 3NQ* (3NQS*) are governed by solvent polarity. All the quenching rate constants (kq) measured in benzene are larger than those in acetonitrile. The SO3Na substituent at the C-4 position of NQS makes 3NQS* more reactive than 3NQ* in electron/H-atom transfer reactions. Large differences of kq values were discovered in H-atom transfer reactions for alcohols and phenols, which can be explained by different H-abstraction mechanisms. Detection of radical cations of amines/anilines in time-resolved transient absorption spectra confirms an electron transfer mechanism. Triplets are identified as precursors of formed radical anions of NQ and NQS in photoinduced reactions. The dependence of electron transfer rate constants on the free energy changes (DeltaG) was treated by using the Rehm-Weller equation. For the four anilines with different substituents on the para or meta position of amidocyanogen, good correlation between log kq values with Hammett sigma constants testifies the correctness of empirical Hammett equation. Charge density distributions, adiabatic ionization/affinity potentials and redox potentials of NQ (NQS) and some quenchers were studied by quantum chemistry calculation.

Medium-dependent interactions of quinones with cytosine and cytidine: a laser flash photolysis study with magnetic field effect.

PubMed

Bose, Adity; Basu, Samita

2009-03-01

Laser flash photolysis and an external magnetic field have been used for the study of the interaction of two quinone molecules, namely, 9,10-anthraquinone (AQ) and 2-methyl 1,4-naphthoquinone (or menadione, MQ) with a DNA base, cytosine (C) and its nucleoside cytidine (dC) in two media, a homogeneous one composed of acetonitrile/water (ACN/H(2)O, 9:1, v/v) and a SDS micellar heterogeneous one. We have applied an external magnetic field for the proper identification of the transients formed during the interactions in micellar media. Cytosine exhibits electron transfer (ET) followed by hydrogen abstraction (HA) while dC reveals a reduced ET compared to C, with both quinones in organic homogeneous medium (ACN/H(2)O). Due to a higher electron affinity, AQ supports more faciler ET than MQ with dC in ACN/H(2)O but observations in SDS have been just the reverse. In SDS, ET from dC is completely quenched and a dominant HA is all that could be discerned. This work reveals two main findings: first, a drop in ET on addition of a ribose unit to C, which has been attributed to a role of keto-enol tautomerism in inducing ET from electron-rich nucleus and second, the effect of medium in controlling reaction mechanism by favoring HA with AQ although it is intrinsically more prone towards ET.

High efficient bone ablation with diode pumped Erbium and Thulium lasers including different delivery fibers: a comparative in vitro study

NASA Astrophysics Data System (ADS)

Stock, Karl; Hausladen, Florian; Stegmayer, Thomas; Wurm, Holger

2018-02-01

Er:YAG lasers (3μm) allow efficient bone ablation caused by the strong absorption in water. Unfortunately, there are only a few and comparable expensive fiber materials for this wavelength available which are suitable for high laser power. The bone ablation efficiency of the Tm:YAG laser is minor (2μm) but inexpensive silica fibers can be used. The aim of this study was to investigate the bone ablation, using novel diode pumped high power Er:YAG (laser power 40W) and Tm:YAG laser system (60W) and adaptive fiber delivery systems. Expected advantage of these lasers is the longer lifetime of the fibers because of the high repetition rate and low pulse energy compared to the flash lamp pumped laser systems. The bare fiber output ends of a sapphire fiber (Er:YAG laser) and of a silica fiber (Tm:YAG laser) were attached under water and a water filled container including the fixed sample (bovine bone slices) was moved by a computer controlled translation stage. In a second set-up we provided a focusing unit and appropriate water spray unit. The generated cut kerfs were analyzed by light microcopy and laser scanning microscopy. The results show that with the diode pumped Er:YAG laser and sapphire fiber a particular high efficient bone ablation (> 0.16mm2/J) is possible both with bare fiber under water and focusing unit with water spray. The higher power of the Tm:YAG laser also results in high ablation rates but causes enlarged thermal damages. In conclusion, this study demonstrates that efficient bone ablation is possible with both diode pumped laser systems. In terms of efficiency the Er:YAG laser is outstanding. The Tm:YAG laser also allows fast bone ablation, provided that the thermal impact is limited by effective cooling and high movement velocity of the laser spot, for example by using an automatic scanner.

Primary investigations on the potential of a novel diode pumped Er:YAG laser system for middle ear surgery

NASA Astrophysics Data System (ADS)

Stock, Karl; Wurm, Holger; Hausladen, Florian

2016-02-01

Flashlamp pumped Er:YAG lasers are successfully used clinically for both precise soft and hard tissue ablation. Since several years a novel diode pumped Er:YAG laser system (Pantec Engineering AG) is available, with mean laser power up to 40 W and pulse repetition rate up to 1 kHz. The aim of the study was to investigate the suitability of the laser system specifically for stapedotomy. Firstly an experimental setup was realized with a beam focusing unit and a computer controlled translation stage to move the samples (slices of porcine bone) with a defined velocity while irradiation with various laser parameters. A microphone was positioned in a defined distance to the ablation point and the resulting acoustic signal of the ablation process was recorded. For comparison, measurements were also performed with a flash lamp pumped Er:YAG laser system. After irradiation the resulting ablation quality and efficacy were determined using light microscopy. Using a high speed camera and "Töpler-Schlierentechnik" the cavitation bubble in water after perforation of a bone slice was investigated. The results show efficient bone ablation using the diode pumped Er:YAG laser system. Also a decrease of the sound level and of the cavitation bubble volume was observed with decreasing pulse duration. Higher repetition rates lead to a slightly increase of thermal side effects but have no influence on the ablation efficiency. In conclusion, these first experiments demonstrate the high potential of the diode pumped Er:YAG laser system for use in middle ear surgery.

Los Alamos Laser Eye Investigation.

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

Odom, C. R.

2005-01-01

A student working in a laser laboratory at Los Alamos National Laboratory sustained a serious retinal injury to her left eye when she attempted to view suspended particles in a partially evacuated target chamber. The principle investigator was using the white light from the flash lamp of a Class 4 Nd:YAG laser to illuminate the particles. Since the Q-switch was thought to be disabled at the time of the accident, the principal investigator assumed it would be safe to view the particles without wearing laser eye protection. The Laboratory Director appointed a team to investigate the accident and to reportmore » back to him the events and conditions leading up to the accident, equipment malfunctions, safety management causal factors, supervisory and management action/inaction, adequacy of institutional processes and procedures, emergency and notification response, effectiveness of corrective actions and lessons learned from previous similar events, and recommendations for human and institutional safety improvements. The team interviewed personnel, reviewed documents, and characterized systems and conditions in the laser laboratory during an intense six week investigation. The team determined that the direct and primary failures leading to this accident were, respectively, the principle investigator's unsafe work practices and the institution's inadequate monitoring of worker performance. This paper describes the details of the investigation, the human and institutional failures, and the recommendations for improving the laser safety program.« less

Recent Progress Made in the Development of High-Energy UV Transmitter

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Armstrong, Darrell J.

2007-01-01

In this paper, the status of an all-solid-state UV converter development for ozone sensing applications is discussed. A high energy Nd:YAG laser for pumping the UV converter arrangement was recently reported. The pump is an all-solid-state, single longitudinal mode, and conductively cooled Nd:YAG laser operating at 1064 nm wavelength. Currently, this pump laser provides an output pulse energy of greater than 1J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of approx. 2. The spatial profile of the output beam is a rectangular super Gaussian. This Nd:YAG pump laser has been developed to pump the nonlinear optics based UV converter arrangement to generate 320 nm and 308 nm wavelengths by means of 532 nm wavelength. Previously, this UV converter arrangement has demonstrated IR-to-UV conversion efficiency of 24% using a flash lamp pumped laser providing a round, flat top spatial profile. Recently, the UV converter was assembled and tested at NASA LaRC for pumping with the diode pumped Nd:YAG laser. With current spatial profile, the UV converter was made operational. Current efforts to maximize the nonlinear conversion efficiency by refining its spatial profile to match RISTRA OPO requirements are progressing.

Acoustic transient generation in pulsed holmium laser ablation under water

NASA Astrophysics Data System (ADS)

Asshauer, Thomas; Rink, Klaus; Delacretaz, Guy P.; Salathe, Rene-Paul; Gerber, Bruno E.; Frenz, Martin; Pratisto, Hans; Ith, Michael; Romano, Valerio; Weber, Heinz P.

1994-08-01

In this study the role of acoustical transients during pulsed holmium laser ablation is addressed. For this the collapse of cavitation bubbles generated by 2.12 micrometers Cr:Tm:Ho:YAG laser pulses delivered via a fiber in water is investigated. Multiple consecutive collapses of a single bubble generating acoustic transients are documented. Pulse durations are varied from 130 - 230 microsecond(s) and pulse energies from 20 - 800 mJ. Fiber diameters of 400 and 600 micrometers are used. The bubble collapse behavior is observed by time resolved fast flash photography with 1 microsecond(s) strobe lamp or 5 ns 1064 nm Nd:YAG laser illumination. A PVDF needle probe transducer is used to observe acoustic transients and measure their pressure amplitudes. Under certain conditions, at the end of the collapse phase the bubbles emit spherical acoustic transients of up to several hundred bars amplitude. After the first collapse up to two rebounds leading to further acoustic transient emissions are observed. Bubbles generated near a solid surface under water are attracted towards the surface during their development. The final phase of the collapse generating the acoustic transients takes place directly on the surface, exposing it to maximum pressure amplitudes. Our results indicate a possible mechanism of unwanted tissue damage during holmium laser application in a liquid environment as in arthroscopy or angioplasty that may set limits to the choice of laser pulse duration and energies.

Why Flash Type Matters: A Statistical Analysis

NASA Astrophysics Data System (ADS)

Mecikalski, Retha M.; Bitzer, Phillip M.; Carey, Lawrence D.

2017-09-01

While the majority of research only differentiates between intracloud (IC) and cloud-to-ground (CG) flashes, there exists a third flash type, known as hybrid flashes. These flashes have extensive IC components as well as return strokes to ground but are misclassified as CG flashes in current flash type analyses due to the presence of a return stroke. In an effort to show that IC, CG, and hybrid flashes should be separately classified, the two-sample Kolmogorov-Smirnov (KS) test was applied to the flash sizes, flash initiation, and flash propagation altitudes for each of the three flash types. The KS test statistically showed that IC, CG, and hybrid flashes do not have the same parent distributions and thus should be separately classified. Separate classification of hybrid flashes will lead to improved lightning-related research, because unambiguously classified hybrid flashes occur on the same order of magnitude as CG flashes for multicellular storms.

Versatile microsecond movie camera

NASA Astrophysics Data System (ADS)

Dreyfus, R. W.

1980-03-01

A laboratory-type movie camera is described which satisfies many requirements in the range 1 microsec to 1 sec. The camera consists of a He-Ne laser and compatible state-of-the-art components; the primary components are an acoustooptic modulator, an electromechanical beam deflector, and a video tape system. The present camera is distinct in its operation in that submicrosecond laser flashes freeze the image motion while still allowing the simplicity of electromechanical image deflection in the millisecond range. The gating and pulse delay circuits of an oscilloscope synchronize the modulator and scanner relative to the subject being photographed. The optical table construction and electronic control enhance the camera's versatility and adaptability. The instant replay video tape recording allows for easy synchronization and immediate viewing of the results. Economy is achieved by using off-the-shelf components, optical table construction, and short assembly time.

Transient Kinetics and Quantum Yield Studies of Nanocrystalline α-Phenyl-Substituted Ketones: Sorting Out Reactions from Singlet and Triplet Excited States.

PubMed

Park, Jin H; Chung, Tim S; Hipwell, Vince M; Rivera, Edris A; Garcia-Garibay, Miguel A

2018-06-11

Recent work has shown that diarylmethyl radicals generated by pulsed laser excitation in nanocrystalline (NC) suspensions of tetraarylacetones constitute a valuable probe for the detailed mechanistic analysis of the solid-state photodecarbonylation reaction. Using a combination of reaction quantum yields and laser flash photolysis in nanocrystalline suspensions of ketones with different substituents on one of the α-carbons we are able to suggest with confidence that a significant fraction of the initial α-cleavage reaction takes place from the ketone singlet excited state, that the originally formed diarylmethyl-acyl radical pair loses CO in the crystal with time constants in the sub-nanosecond regime, and that the secondary bis(diarylmethyl) triplet radical pair has a lifetime limited by the rate of intersystem crossing of ca. 70 ns.

Kinetics of the reactions of alkyl radicals with HBr and DBr

NASA Technical Reports Server (NTRS)

Nicovich, J. M.; Van Dijk, C. A.; Kreutter, K. D.; Wine, P. H.

1991-01-01

The kinetics of the reactions CH3 + HBr, CD3 + HBr, CH3 + DBr, C2H5 + HBr, C2H5 + DBr, t-C4H9 + HBr, and t-C4H9 + DBr is studied as a function of temperature (257-430 K) and pressure (10-300 Torr of N2). Time-resolved resonance fluorescence detection of Br atom appearance following laser flash photolysis of RI was used in the experiments. Results show that the rates of all reactions increased as the temperature decreased.

Photophysics and photochemistry of 2-aminobenzoic acid anion in aqueous solution.

PubMed

Pozdnyakov, Ivan P; Plyusnin, Victor F; Grivin, Vjacheslav P

2009-12-24

Nanosecond laser flash photolysis and absorption and fluorescence spectroscopy were used to study photochemical processes of 2-aminobenzoic acid anion (ABA(-)) in aqueous solutions. Excitation of this species gives rise to the ABA(-) triplet state to the ABA* radical and to the hydrated electron (e(aq)(-)). The last two species result from two-photon processes. In a neutral medium, the main decay channels of ABA(-) triplet state, the ABA* radical, and e(aq)(-) are T-T annihilation, recombination, and capture by the ABA(-) anion, respectively.

Numerical Simulation of Laser Ablative Shock Waves From Aluminum in Presence of Helium Gas At Different Ambient Pressures

NASA Astrophysics Data System (ADS)

Paturi, Prem Kiran; Durvasula, P. S. L. Kameswari; S, Sai Shiva; Acrhem, University Of Hyderabad Team

2017-06-01

A two dimensional comparative study of Laser Ablative Shock Wave into the Aluminum target in the presence of Helium gas at different ambient pressures over a range of 690 - 105 Pa performed using FLASH hydrodynamic codes will be presented. The irradiation of Aluminum target (thickness 2 mm and radius 3 mm) with a 7 ns laser pulse of energy 175 mJ, spot size of 150 µm on the target surface at a wavelength of 532 nm at normal incidence is simulated. Helium gas enclosed in a chamber of height 3 mm and width 3 mm. The electron-ion inverse bremsstrahlung absorption coefficient is considered in the laser energy deposition process. The simulation was performed over a duration of 1 μs. It was observed that an ablative shock is launched into the Helium gas for the pressures of 0.5 atm and above. However, for pressure less than the 0.5 atm the plasma expanded into the He gas upto 12ns and after which due to pressure equilibration with the surroundings and plume splitting shock wave is launched in to Al. Authors acknowledge funding from DRDO, India.

Beam shaping for cosmetic hair removal

NASA Astrophysics Data System (ADS)

Lizotte, Todd E.; Tuttle, Tracie

2007-09-01

Beam shaping has the potential to provide comfort to people who require or seek laser based cosmetic skin procedures. Of immediate interest is the procedure of aesthetic hair removal. Hair removal is performed using a variety of wavelengths from 480 to 1200 nm by means of filtered Xenon flash lamps (pulsed light) or 810 nm diode lasers. These wavelengths are considered the most efficient means available for hair removal applications, but current systems use simple reflector designs and plane filter windows to direct the light to the surface being exposed. Laser hair removal is achieved when these wavelengths at sufficient energy levels are applied to the epidermis. The laser energy is absorbed by the melanin (pigment) in the hair and hair follicle which in turn is transformed into heat. This heat creates the coagulation process, which causes the removal of the hair and prevents growth of new hair [1]. This paper outlines a technique of beam shaping that can be applied to a non-contact based hair removal system. Several features of the beam shaping technique including beam uniformity and heat dispersion across its operational treatment area will be analyzed. A beam shaper design and its fundamental testing will be discussed in detail.

Development of a fluorimeter using laser-induced single-shot fluorescence lifetime spectroscopy

NASA Astrophysics Data System (ADS)

Eisum, Niels H.; Lynggaard-Jensen, Anders

1990-08-01

The developed laboratory prototype fluorimeter is the first step to a new in-situ instrument, and is based on a pulsed nitrogen laser (pumping a color dye laser and the laserbeam passing through a frequency doubler) with a pulse width less than 1 nsec. With such a short excitation pulse it is possible to measure the exponential decay of the fluorescence from the aromatic compounds and thus determine the fluorescence lifetime-curves, which are typically in the region of 5-40 nsec. The emitted fluorescence is collected simultaneously in 35 channels in the wavelength region 250-600 nm. If the fluorescence falls within the transmission areas of the interference filters in each channel the light will be collected by a plastic light guide (doped PMMA) in the actual channel and transmitted to the channels photo multiplier tube (PMT). (The use of the plastic light guide improves the sensitivity). The signal from the PMT is passed on to a 200 MHz 8-bit flash AID-converter connected to a local memory. From this local memory the digital lifetime curves from each channel are transmitted to a computer for presentation of the 3-dimensional spectrum. This spectrum has been obtained with a single laser shot.

Study of laser-generated debris free x-ray sources produced in a high-density linear Ar, Kr, Xe, Kr/Ar and Xe/Kr/Ar mixtures gas jets by 2 ω, sub-ps LLNL Titan laser

NASA Astrophysics Data System (ADS)

Kantsyrev, V. L.; Schultz, K. A.; Shlyaptseva, V. V.; Safronova, A. S.; Cooper, M. C.; Shrestha, I. K.; Petkov, E. E.; Stafford, A.; Moschella, J. J.; Schmidt-Petersen, M. T.; Butcher, C. J.; Kemp, G. E.; Andrews, S. D.; Fournier, K. B.

2016-10-01

The study of laser-generated debris-free x-ray sources in an underdense plasma produced in a high-density linear gas-puff jet was carried out at the LLNL Titan laser (2 ω, 45 J, sub-ps) with an intensity in the 10 um focal spot of 7 x 1019 W/cm2. A linear nozzle with a fast valve was used for the generation of a clusters/gas jet. X-ray diagnostics for the spectral region of 0.7 - 9 keV include: two spectrometers and pinhole cameras, and 3 groups of fast filtered detectors. Electron beams were measured with the EPPS magnetic spectrometer (>1 MeV) and Faraday cups (>72 keV). Spectralon/spectrometer devices were also used to measure absorption of laser radiation in the jets. New results were obtained on: anisotropic generation of x-rays (laser to x-ray conversion coefficient was >1%) and characteristics of laser-generated electron beams; evolution of x-ray generation with the location of the laser focus in a cluster-gas jet, and observations of a strong x-ray flash in some focusing regimes. Non-LTE kinetic modeling was used to estimate plasma parameters. UNR work supported by the DTRA Basic Research Award # HDTRA1-13-1-0033. Work at LLNL was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Lasers in medicine

NASA Astrophysics Data System (ADS)

Peng, Qian; Juzeniene, Asta; Chen, Jiyao; Svaasand, Lars O.; Warloe, Trond; Giercksky, Karl-Erik; Moan, Johan

2008-05-01

It is hard to imagine that a narrow, one-way, coherent, moving, amplified beam of light fired by excited atoms is powerful enough to slice through steel. In 1917, Albert Einstein speculated that under certain conditions atoms could absorb light and be stimulated to shed their borrowed energy. Charles Townes coined the term laser (light amplification by stimulated emission of radiation) in 1951. Theodore Maiman investigated the glare of a flash lamp in a rod of synthetic ruby, creating the first human-made laser in 1960. The laser involves exciting atoms and passing them through a medium such as crystal, gas or liquid. As the cascade of photon energy sweeps through the medium, bouncing off mirrors, it is reflected back and forth, and gains energy to produce a high wattage beam of light. Although lasers are today used by a large variety of professions, one of the most meaningful applications of laser technology has been through its use in medicine. Being faster and less invasive with a high precision, lasers have penetrated into most medical disciplines during the last half century including dermatology, ophthalmology, dentistry, otolaryngology, gastroenterology, urology, gynaecology, cardiology, neurosurgery and orthopaedics. In many ways the laser has revolutionized the diagnosis and treatment of a disease. As a surgical tool the laser is capable of three basic functions. When focused on a point it can cauterize deeply as it cuts, reducing the surgical trauma caused by a knife. It can vaporize the surface of a tissue. Or, through optical fibres, it can permit a doctor to see inside the body. Lasers have also become an indispensable tool in biological applications from high-resolution microscopy to subcellular nanosurgery. Indeed, medical lasers are a prime example of how the movement of an idea can truly change the medical world. This review will survey various applications of lasers in medicine including four major categories: types of lasers, laser-tissue interactions, therapeutics and diagnostics.

A light writable microfluidic "flash memory": optically addressed actuator array with latched operation for microfluidic applications.

PubMed

Hua, Zhishan; Pal, Rohit; Srivannavit, Onnop; Burns, Mark A; Gulari, Erdogan

2008-03-01

This paper presents a novel optically addressed microactuator array (microfluidic "flash memory") with latched operation. Analogous to the address-data bus mediated memory address protocol in electronics, the microactuator array consists of individual phase-change based actuators addressed by localized heating through focused light patterns (address bus), which can be provided by a modified projector or high power laser pointer. A common pressure manifold (data bus) for the entire array is used to generate large deflections of the phase change actuators in the molten phase. The use of phase change material as the working media enables latched operation of the actuator array. After the initial light "writing" during which the phase is temporarily changed to molten, the actuated status is self-maintained by the solid phase of the actuator without power and pressure inputs. The microfluidic flash memory can be re-configured by a new light illumination pattern and common pressure signal. The proposed approach can achieve actuation of arbitrary units in a large-scale array without the need for complex external equipment such as solenoid valves and electrical modules, which leads to significantly simplified system implementation and compact system size. The proposed work therefore provides a flexible, energy-efficient, and low cost multiplexing solution for microfluidic applications based on physical displacements. As an example, the use of the latched microactuator array as "normally closed" or "normally open" microvalves is demonstrated. The phase-change wax is fully encapsulated and thus immune from contamination issues in fluidic environments.

Damage detection in composites using nonlinear ultrasonically modulated thermography

NASA Astrophysics Data System (ADS)

Malfense Fierro, G.-P.; Dionysopoulos, D.; Meo, M.; Ciampa, F.

2018-03-01

This paper proposes a novel nonlinear ultrasonically stimulated thermography technique for a quick and reliable assessment of material damage in carbon fibre reinforced plastic (CFRP) composite materials. The proposed nondestructive evaluation (NDE) method requires narrow sweep ultrasonic excitation using contact piezoelectric transducers in order to identify dual excitation frequencies associated with the damage resonance. High-amplitude signals and higher harmonic generation are necessary conditions for an accurate identification of these two input frequencies. Dual periodic excitation using high- and low-frequency input signals was then performed in order to generate frictional heating at the crack location that was measured by an infrared (IR) camera. To validate this concept, an impact damaged CFRP composite panel was tested and the experimental results were compared with traditional flash thermography. A laser vibrometer was used to investigate the response of the material with dual frequency excitation. The proposed nonlinear ultrasonically modulated thermography successfully detected barely visible impact damage in CFRP composites. Hence, it can be considered as an alternative to traditional flash thermography and thermosonics by allowing repeatable detection of damage in composites.

Double-pulse dichromatic photolysis of fac-CIRe(CO){sub 3}L{sub 2} (L=4-phenylpyridine or 4-cyanopyridine): Photohomolysis of Re-L bonds insuced by irradiation of photochemically unreactive charge transfer states

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

Feliz, M.; Ferraudi, G.

1992-04-02

Photochemical reactions of fac-ClRe(CO){sub 3}L{sub 2} (L=4-phenylpyridine or 4-cyanopyridine), were investigated by sequential biphotonic excitations: one laser flash was used for the preparation of the compounds in the lowest lying MLCT (Re{r_arrow}) state and another flash for the irradiation of the compounds in such excited states. These photolyses led to photodecompostions into CIRe(CO){sub 3}L{sup +} and L{sup .} in a charge transfer state placed 40 Kk above ground state. Quantum yields determined or various excitation energies show that not all the excited state populated in monophotonic excitations can be reached under the sequential biphotonic regime. Therefore, photogeneration of the biradicalmore » intermediate, ClRe(CO){sub 3}L{sup +} and L{sup .}, from ligand-centered states has not been detected in these experiments. Results from monophotonic and biphotonic excitations have been used for a semiquantitative mapping of the excited-state potential surfaces. 41 refs., 6 figs.« less

Flash Vacuum Pyrolysis: Techniques and Reactions.

PubMed

Wentrup, Curt

2017-11-20

Flash vacuum pyrolysis (FVP) had its beginnings in the 1940s and 1950s, mainly through mass spectrometric detection of pyrolytically formed free radicals. In the 1960s many organic chemists started performing FVP experiments with the purpose of isolating new and interesting compounds and understanding pyrolysis processes. Meanwhile, many different types of apparatus and techniques have been developed, and it is the purpose of this review to present the most important methods as well as a survey of typical reactions and observations that can be achieved with the various techniques. This includes preparative FVP, chemical trapping reactions, matrix isolation, and low temperature spectroscopy of reactive intermediates and unstable molecules, the use of online mass, photoelectron, microwave, and millimeterwave spectroscopies, gas-phase laser pyrolysis, pulsed pyrolysis with supersonic jet expansion, very low pressure pyrolysis for kinetic investigations, solution-spray and falling-solid FVP for involatile compounds, and pyrolysis over solid supports and reagents. Moreover, the combination of FVP with matrix isolation and photochemistry is a powerful tool for investigations of reaction mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-intensity fibre laser design for micro-machining applications

NASA Astrophysics Data System (ADS)

Ortiz-Neria, D. I.; Martinez-Piñón, F.; Hernandez-Escamilla, H.; Alvarez-Chavez, J. A.

2010-11-01

This work is focused on the design of a 250W high-intensity continuous-wave fibre optic laser with a 15μm spot size beam and a beam parameter product (BPP) of 1.8 for its use on Laser-assisted Cold Spray process (LCS) in the micro-machining areas. The metal-powder deposition process LCS, is a novel method based on Cold Spray technique (CS) assisted by laser technology. The LCS accelerates metal powders by the use of a high-pressure gas in order to achieve flash welding of particles over substrate. In LCS, the critical velocity of impact is lower with respect with CS while the powder particle is heated before the deposition by a laser beam. Furthermore, LCS does not heat the powder to achieve high temperatures as it happens in plasma processes. This property puts aside cooling problems which normally happen in sintered processes with high oxygen/nitrogen concentration levels. LCS will be used not only in deposition of thin layers. After careful design, proof of concept, experimental data, and prototype development, it should be feasible to perform micro-machining precise work with the use of the highintensity fibre laser presented in this work, and selective deposition of particles, in a similar way to the well-known Direct Metal Laser Sintering process (DMLS). The fibre laser consists on a large-mode area, Yb3+-doped, semi-diffraction limited, 25-m fibre laser cavity, operating in continuous wave regime. The fibre shows an arguably high slope-efficiency with no signs of roll-over. The measured M2 value is 1.8 and doping concentration of 15000ppm. It was made with a slight modification of the traditional MCVD technique. A full optical characterization will be presented.

Self-initiation of UV photopolymerization reactions using tetrahalogenated bisphenol A (meth)acrylates.

PubMed

Pelras, Théophile; Knolle, Wolfgang; Naumov, Sergej; Heymann, Katja; Daikos, Olesya; Scherzer, Tom

2017-05-17

The potential of tetrachlorinated and tetrabrominated bisphenol A diacrylates and dimethacrylates for self-initiation of a radical photopolymerization was investigated. The kinetics of the photopolymerization of an acrylic model varnish containing halogenated monomers was studied by real-time FTIR spectroscopy, whereas the formation of reactive species and secondary products was elucidated by laser flash photolysis and product analysis by GC-MS after steady-state photolysis. The interpretation of the experimental data and the analysis of possible reaction pathways were assisted by quantum chemical calculations. It was shown that all halogenated monomers lead to a significant acceleration of the photopolymerization kinetics at a minimum concentration of 5 wt%. Steady-state and laser flash photolysis measurements as well as quantum chemical calculations showed that brominated and chlorinated samples do not follow the same pathway to generate radical species. Whereas chlorinated (meth)acrylates may cleave only at the C-O bonds of the carboxyl groups resulting in acrolein and oxyl radicals for initiation, brominated monomers may cleave either at the C-O bonds or at the C-Br bonds delivering aryl and bromine radicals. The quantum yields for the photolysis of the halogenated monomers were found to be in the order of 0.1 for acrylates and 0.2 for methacrylates (with an estimated error of 25%), independently of the attached Br and Cl halogens. Finally, the trihalogenated bisphenol A di(meth)acrylate radicals and the acrolein radicals were found to show the highest efficiencies for the reaction with another acrylic double bond leading to the formation of a polymer network.

Biophysical Characterisation of Neuroglobin of the Icefish, a Natural Knockout for Hemoglobin and Myoglobin. Comparison with Human Neuroglobin

PubMed Central

Giordano, Daniela; Boron, Ignacio; Abbruzzetti, Stefania; Van Leuven, Wendy; Nicoletti, Francesco P.; Forti, Flavio; Bruno, Stefano; Cheng, C-H. Christina; Moens, Luc; di Prisco, Guido; Nadra, Alejandro D.; Estrin, Darío; Smulevich, Giulietta; Dewilde, Sylvia; Viappiani, Cristiano; Verde, Cinzia

2012-01-01

The Antarctic icefish Chaenocephalus aceratus lacks the globins common to most vertebrates, hemoglobin and myoglobin, but has retained neuroglobin in the brain. This conserved globin has been cloned, over-expressed and purified. To highlight similarities and differences, the structural features of the neuroglobin of this colourless-blooded fish were compared with those of the well characterised human neuroglobin as well as with the neuroglobin from the retina of the red blooded, hemoglobin and myoglobin-containing, closely related Antarctic notothenioid Dissostichus mawsoni. A detailed structural and functional analysis of the two Antarctic fish neuroglobins was carried out by UV-visible and Resonance Raman spectroscopies, molecular dynamics simulations and laser-flash photolysis. Similar to the human protein, Antarctic fish neuroglobins can reversibly bind oxygen and CO in the Fe2+ form, and show six-coordination by distal His in the absence of exogenous ligands. A very large and structured internal cavity, with discrete docking sites, was identified in the modelled three-dimensional structures of the Antarctic neuroglobins. Estimate of the free-energy barriers from laser-flash photolysis and Implicit Ligand Sampling showed that the cavities are accessible from the solvent in both proteins. Comparison of structural and functional properties suggests that the two Antarctic fish neuroglobins most likely preserved and possibly improved the function recently proposed for human neuroglobin in ligand multichemistry. Despite subtle differences, the adaptation of Antarctic fish neuroglobins does not seem to parallel the dramatic adaptation of the oxygen carrying globins, hemoglobin and myoglobin, in the same organisms. PMID:23226490

Measuring hot flash phenomenonology using ambulatory prospective digital diaries

PubMed Central

Fisher, William I.; Thurston, Rebecca C.

2016-01-01

Objective This study provides the description, protocol, and results from a novel prospective ambulatory digital hot flash phenomenon diary. Methods This study included 152 midlife women with daily hot flashes who completed an ambulatory electronic hot flash diary continuously for the waking hours of 3 consecutive days. In this diary, women recorded their hot flashes and accompanying characteristics and associations as the hot flashes occurred. Results Self-reported hot flash severity on the digital diaries indicated that the majority of hot flashes were rated as mild (41.3%) or moderate (43.7%). Severe (13.1%) and very severe (1.8%) hot flashes were less common. Hot flash bother ratings were rated as mild (43%), or moderate (33.5%), with fewer hot flashes reported bothersome (17.5%) or very bothersome (6%). The majority of hot flashes were reported as occurring on the on the face (78.9%), neck (74.7%), and chest (61.3%). Prickly skin was reported concurrently with 32% of hot flashes, 7% with anxiety and 5% with nausea. A novel finding, 38% of hot flashes were accompanied by a premonitory aura. Conclusion A prospective electronic digital hot flash diary allows for a more precise quantitation of hot flashes while overcoming many of the limitations of commonly employed retrospective questionnaires and paper diaries. Unique insights into the phenomenology, loci and associated characteristics of hot flashes were obtained using this device. The digital hot flash phenomenology diary is recommended for future ambulatory studies of hot flashes as a prospective measure of the hot flash experience. PMID:27404030

Measuring hot flash phenomenonology using ambulatory prospective digital diaries.

PubMed

Fisher, William I; Thurston, Rebecca C

2016-11-01

This study provides the description, protocol, and results from a novel prospective ambulatory digital hot flash phenomenon diary. This study included 152 midlife women with daily hot flashes who completed an ambulatory electronic hot flash diary continuously for the waking hours of three consecutive days. In this diary, women recorded their hot flashes and accompanying characteristics and associations as the hot flashes occurred. Self-reported hot flash severity on the digital diaries indicated that the majority of hot flashes were rated as mild (41.3%) or moderate (43.7%). Severe (13.1%) and very severe (1.8%) hot flashes were less common. Hot flash bother ratings were rated as mild (43%), or moderate (33.5%), with fewer hot flashes reported bothersome (17.5%) or very bothersome (6%). The majority of hot flashes were reported as occurring on the face (78.9%), neck (74.7%), and chest (61.3%). Of all reported hot flashes, 32% occurred concurrently with prickly skin, 7% with anxiety, and 5% with nausea. A novel finding from the study was that 38% of hot flashes were accompanied by a premonitory aura. A prospective electronic digital hot flash diary allows for a more precise quantitation of hot flashes while overcoming many of the limitations of commonly used retrospective questionnaires and paper diaries. Unique insights into the phenomenology, loci, and associated characteristics of hot flashes were obtained using this device. The digital hot flash phenomenology diary is recommended for future ambulatory studies of hot flashes as a prospective measure of the hot flash experience.

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold

PubMed Central

Makhotkin, Igor A.; Sobierajski, Ryszard; Chalupský, Jaromir; Tiedtke, Kai; de Vries, Gosse; Störmer, Michael; Scholze, Frank; Siewert, Frank; van de Kruijs, Robbert W. E.; Milov, Igor; Louis, Eric; Jacyna, Iwanna; Jurek, Marek; Klinger, Dorota; Syryanyy, Yevgen; Juha, Libor; Hájková, Věra; Saksl, Karel; Faatz, Bart; Keitel, Barbara; Plönjes, Elke; Toleikis, Sven; Loch, Rolf; Hermann, Martin; Strobel, Sebastian; Nienhuys, Han-Kwang; Gwalt, Grzegorz; Mey, Tobias; Enkisch, Hartmut

2018-01-01

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface. PMID:29271755

Experimental study of EUV mirror radiation damage resistance under long-term free-electron laser exposures below the single-shot damage threshold.

PubMed

Makhotkin, Igor A; Sobierajski, Ryszard; Chalupský, Jaromir; Tiedtke, Kai; de Vries, Gosse; Störmer, Michael; Scholze, Frank; Siewert, Frank; van de Kruijs, Robbert W E; Milov, Igor; Louis, Eric; Jacyna, Iwanna; Jurek, Marek; Klinger, Dorota; Nittler, Laurent; Syryanyy, Yevgen; Juha, Libor; Hájková, Věra; Vozda, Vojtěch; Burian, Tomáš; Saksl, Karel; Faatz, Bart; Keitel, Barbara; Plönjes, Elke; Schreiber, Siegfried; Toleikis, Sven; Loch, Rolf; Hermann, Martin; Strobel, Sebastian; Nienhuys, Han Kwang; Gwalt, Grzegorz; Mey, Tobias; Enkisch, Hartmut

2018-01-01

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface.

Development of experimental techniques for the characterization of ultrashort photon pulses of extreme ultraviolet free-electron lasers

NASA Astrophysics Data System (ADS)

Düsterer, S.; Rehders, M.; Al-Shemmary, A.; Behrens, C.; Brenner, G.; Brovko, O.; DellAngela, M.; Drescher, M.; Faatz, B.; Feldhaus, J.; Frühling, U.; Gerasimova, N.; Gerken, N.; Gerth, C.; Golz, T.; Grebentsov, A.; Hass, E.; Honkavaara, K.; Kocharian, V.; Kurka, M.; Limberg, Th.; Mitzner, R.; Moshammer, R.; Plönjes, E.; Richter, M.; Rönsch-Schulenburg, J.; Rudenko, A.; Schlarb, H.; Schmidt, B.; Senftleben, A.; Schneidmiller, E. A.; Siemer, B.; Sorgenfrei, F.; Sorokin, A. A.; Stojanovic, N.; Tiedtke, K.; Treusch, R.; Vogt, M.; Wieland, M.; Wurth, W.; Wesch, S.; Yan, M.; Yurkov, M. V.; Zacharias, H.; Schreiber, S.

2014-12-01

One of the most challenging tasks for extreme ultraviolet, soft and hard x-ray free-electron laser photon diagnostics is the precise determination of the photon pulse duration, which is typically in the sub 100 fs range. Nine different methods, able to determine such ultrashort photon pulse durations, were compared experimentally at FLASH, the self-amplified spontaneous emission free-electron laser at DESY in Hamburg, in order to identify advantages and disadvantages of different methods. Radiation pulses at a wavelength of 13.5 and 24.0 nm together with the corresponding electron bunch duration were measured by indirect methods like analyzing spectral correlations, statistical fluctuations, and energy modulations of the electron bunch and also by direct methods like autocorrelation techniques, terahertz streaking, or reflectivity changes of solid state samples. In this paper, we present a comprehensive overview of the various techniques and a comparison of the individual experimental results. The information gained is of utmost importance for the future development of reliable pulse duration monitors indispensable for successful experiments with ultrashort extreme ultraviolet pulses.

Turbulent Dynamo Amplification of Magnetic Fields in Laser-Produced Plasmas: Simulations and Experiments

NASA Astrophysics Data System (ADS)

Tzeferacos, P.; Rigby, A.; Bott, A.; Bell, A.; Bingham, R.; Casner, A.; Cattaneo, F.; Churazov, E.; Forest, C.; Katz, J.; Koenig, M.; Li, C.-K.; Meinecke, J.; Petrasso, R.; Park, H.-S.; Remington, B.; Ross, J.; Ryutov, D.; Ryu, D.; Reville, B.; Miniati, F.; Schekochihin, A.; Froula, D.; Lamb, D.; Gregori, G.

2017-10-01

The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between the filaments of galaxy clusters to several teragauss in black holes and neutron stars. The standard model for cosmological magnetic fields is the nonlinear amplification of seed fields via turbulent dynamo. We have conceived experiments to demonstrate and study the turbulent dynamo mechanism in the laboratory. Here, we describe the design of these experiments through large-scale 3D FLASH simulations on the Mira supercomputer at ANL, and the laser-driven experiments we conducted with the OMEGA laser at LLE. Our results indicate that turbulence is capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. This work was supported in part from the ERC (FP7/2007-2013, No. 256973 and 247039), and the U.S. DOE, Contract No. B591485 to LLNL, FWP 57789 to ANL, Grant No. DE-NA0002724 and DE-SC0016566 to the University of Chicago, and DE-AC02-06CH11357 to ANL.

Optical phase conjugation by four-wave mixing in Nd:YAG laser oscillator for optical energy transfer to a remote target

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

Kawakami, K., E-mail: k.kawakami@al.t.u-tokyo.ac.jp; Komurasaki, K.; Okamura, H.

2015-02-28

A self-starting phase conjugator was designed for optical energy transfer to a remote target. Saturable-gain four-wave mixing in a laser resonator was achieved using a flash-lamp pumped Nd:YAG crystal and phase-conjugate light (PCL) generation were verified. Wavefront correction experimentation revealed that beam wander caused by air turbulence is compensated. Tracking capability was demonstrated in the range of 9 mrad with tracking accuracy of ±0.04 mrad. The maximum field of view was measured to be 4.7°. Dependence of phase-conjugate light energy on reference light energy was investigated. The maximum output of 320 mJ was obtained. The temporal behavior of PCL ismore » discussed based on the four-wave mixing mechanism. Unlike a conventional loop resonator type phase conjugator, this system is applicable for wireless energy transfer to a remote target.« less

High energy chemical laser system

DOEpatents

Gregg, D.W.; Pearson, R.K.

1975-12-23

A high energy chemical laser system is described wherein explosive gaseous mixtures of a reducing agent providing hydrogen isotopes and interhalogen compounds are uniformly ignited by means of an electrical discharge, flash- photolysis or an electron beam. The resulting chemical explosion pumps a lasing chemical species, hydrogen fluoride or deuterium fluoride which is formed in the chemical reaction. The generated lasing pulse has light frequencies in the 3- micron range. Suitable interhalogen compounds include bromine trifluoride (BrF$sub 3$), bromine pentafluoride (BrF$sub 5$), chlorine monofluoride (ClF), chlorine trifluoride (ClF$sub 3$), chlorine pentafluoride (ClF$sub 5$), iodine pentafluoride (IF$sub 5$), and iodine heptafluoride (IF$sub 7$); and suitable reducing agents include hydrogen (H$sub 2$), hydrocarbons such as methane (CH$sub 4$), deuterium (D$sub 2$), and diborane (B$sub 2$H$sub 6$), as well as combinations of the gaseous compound and/or molecular mixtures of the reducing agent.

Direct Determination of the Rate Coefficient for the Reaction of OH Radicals with Monoethanol Amine (MEA) from 296 to 510 K.

PubMed

Onel, L; Blitz, M A; Seakins, P W

2012-04-05

Monoethanol amine (H2NCH2CH2OH, MEA) has been proposed for large-scale use in carbon capture and storage. We present the first absolute, temperature-dependent determination of the rate coefficient for the reaction of OH with MEA using laser flash photolysis for OH generation, monitoring OH removal by laser-induced fluorescence. The room-temperature rate coefficient is determined to be (7.61 ± 0.76) × 10(-11) cm(3) molecule(-1) s(-1), and the rate coefficient decreases by about 40% by 510 K. The temperature dependence of the rate coefficient is given by k1= (7.73 ± 0.24) × 10(-11)(T/295)(-(0.79±0.11)) cm(3) molecule(-1) s(-1). The high rate coefficient shows that gas-phase processing in the atmosphere will be competitive with uptake onto aerosols.

Simultaneous observation solutions for NASA-MOTS and SPEOPT station positions on the North American datum

NASA Technical Reports Server (NTRS)

Reece, J. S.; Marsh, J.

1973-01-01

Simultaneous observations of the GEOS-I and II flashing lamps by the NASA MOTS and SPEOPT cameras on the North American Datum (NAD) were analyzed using geometrical techniques to provide an adjustment of the station coordinates. Two separate adjustments were obtained. An optical data only solution was computed in which the solution scale was provided by the Rosman-Mojave distance obtained from a dynamic station solution. In a second adjustment, scaling was provided by processing simultaneous laser ranging data from Greenbelt and Wallops Island in a combined optical-laser solution. Comparisons of these results with previous GSFC dynamical solutions indicate an rms agreement on the order of 4 meters or better in each coordinate. Comparison with a detailed gravimetric geoid of North America yields agreement of 3 meters or better for mainland U.S. stations and 7 and 3 meters, respectively, for Bermuda and Puerto Rico.

High-order harmonic generation enhanced by XUV light

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

Buth, Christian; Kohler, Markus C.; Ullrich, Joachim

2012-03-19

The combination of high-order harmonic generation (HHG) with resonant XUV excitation of a core electron into the transient valence vacancy that is created in the course of the HHG process is investigated theoretically. In this setup, the first electron performs a HHG three-step process, whereas the second electron Rabi flops between the core and the valence vacancy. The modified HHG spectrum due to recombination with the valence and the core is determined and analyzed for krypton on the 3d {yields} 4p resonance in the ion. We assume an 800 nm laser with an intensity of about 10{sup 14} Wcm{sup 2}more » and XUV radiation from the Free Electron Laser in Hamburg (FLASH) with an intensity in the range 10{sup 13}-10{sup 16} Wcm{sup 2}. Our prediction opens perspectives for nonlinear XUV physics, attosecond x rays, and HHG-based spectroscopy involving core orbitals.« less

Progress toward Kelvin-Helmholtz instabilities in a High-Energy-Density Plasma on the Nike laser

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Gillespie, R. S.; Grosskopf, M. J.; Huntington, C. M.; Aglitskiy, Y.; Weaver, J. L.; Velikovich, A. L.; Plewa, T.; Dwarkadas, V. V.

2008-04-01

In the realm of high-energy-density (HED) plasmas, there exist three primary hydrodynamic instabilities of concern: Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH). Although the RT and the RM instabilities have been readily observed and diagnosed in the laboratory, the KH instability remains relatively unexplored in HED plasmas. Unlike the RT and RM instabilities, the KH instability is driven by a lifting force generated by a strong velocity gradient in a stratified fluid. Understanding the KH instability mechanism in HED plasmas will provide essential insight into oblique shock systems, jets, mass stripping, and detailed RT-spike development. In addition, our KH experiment will help provide the groundwork for future transition to turbulence experiments. We present 2D FLASH simulations and experimental data from our initial attempts to create a pure KH system using the Nike laser at the Naval Research Laboratory.

Evaluation of port-wine stain treatment outcomes using multispectral imaging

NASA Astrophysics Data System (ADS)

Samatham, Ravikant; Choudhury, Niloy; Krol, Alfons L.; Jacques, Steven L.

2012-02-01

Port-wine Stain (PWS) is a vascular malformation characterized by ectasia of superficial dermal capillaries. The flash-lamp pumped pulsed dye laser (PDL) treatment has been the mainstay of PWS for the last decade. Despite the success of the PDL in significantly fading the PWS, the overall cure rate is less than 10%. The precise efficacy of an individual PDL treatment is hard to evaluate and the treatment outcome is measured by visual observation of clinical fading. A hand-held multi-spectral imaging system was developed to image PWS before and after PDL treatment. In an NIH-funded pilot study multi-spectral camera was used to image PWS in children (2- 17 years). Oxygen saturation (S) and blood content (B) of PWS before and after the treatment was determined by analysis of the reflectance spectra. The outcome of the treatment was evaluated during follow up visits of the patients. One of the major causes of failure of laser therapy of port-wine stains (PWS) is reperfusion of the lesion after laser treatment. Oxygen saturation and blood content maps of PWS before and after treatment can predict regions of reperfusion and subsequent failure of the treatment. The ability to measure reperfusion and to predict lesions or areas susceptible to reperfusion, will help in selection of patients/lesions for laser treatment and help to optimize laser dosimetry for maximum effect. The current studies also should provide a basis for monitoring of future alternative therapies or enhancers of laser treatment in resistant cases.

Concurrence of monoenergetic electron beams and bright X-rays from an evolving laser-plasma bubble

PubMed Central

Yan, Wenchao; Chen, Liming; Li, Dazhang; Zhang, Lu; Hafz, Nasr A. M.; Dunn, James; Ma, Yong; Huang, Kai; Su, Luning; Chen, Min; Sheng, Zhengming; Zhang, Jie

2014-01-01

Desktop laser plasma acceleration has proven to be able to generate gigaelectronvolt-level quasi-monoenergetic electron beams. Moreover, such electron beams can oscillate transversely (wiggling motion) in the laser-produced plasma bubble/channel and emit collimated ultrashort X-ray flashes known as betatron radiation with photon energy ranging from kiloelectronvolts to megaelectronvolts. This implies that usually one cannot obtain bright betatron X-rays and high-quality electron beams with low emittance and small energy spread simultaneously in the same accelerating wave bucket. Here, we report the first (to our knowledge) experimental observation of two distinct electron bunches in a single laser shot, one featured with quasi-monoenergetic spectrum and another with continuous spectrum along with large emittance. The latter is able to generate high-flux betatron X-rays. Such is observed only when the laser self-guiding is extended over 4 mm at a fixed plasma density (4 × 1018 cm−3). Numerical simulation reveals that two bunches of electrons are injected at different stages due to the bubble evolution. The first bunch is injected at the beginning to form a stable quasi-monoenergetic electron beam, whereas the second one is injected later due to the oscillation of the bubble size as a result of the change of the laser spot size during the propagation. Due to the inherent temporal synchronization, this unique electron–photon source can be ideal for pump–probe applications with femtosecond time resolution. PMID:24711405

Measurement of thermo-optic properties of Y3Al5O12, Lu3Al5O12, YAIO3, LiYF4, LiLuF4, BaY2F8, KGd(WO4)2, and KY(WO4)2 laser crystals in the 80-300 K temperature range

NASA Astrophysics Data System (ADS)

Aggarwal, R. L.; Ripin, D. J.; Ochoa, J. R.; Fan, T. Y.

2005-11-01

Thermo-optic materials properties of laser host materials have been measured to enable solid-state laser performance modeling. The thermo-optic properties include thermal diffusivity (β), specific heat at constant pressure (Cp), thermal conductivity (κ), coefficient of thermal expansion (α), thermal coefficient of the optical path length (γ) equal to (dO/dT)/L, and thermal coefficient of refractive index (dn/dT) at 1064nm; O denotes the optical path length, which is equal to the product of the refractive index (n) and sample length (L). Thermal diffusivity and specific heat were measured using laser-flash method. Thermal conductivity was deduced using measured values of β, Cp, and the density (ρ ). Thermal expansion was measured using a Michelson laser interferometer. Thermal coefficient of the optical path length was measured at 1064nm, using interference between light reflected from the front and rear facets of the sample. Thermal coefficient of the refractive index was determined, using the measured values of γ, α, and n. β and κ of Y3Al5O12, YAIO3, and LiYF4 were found to decrease, as expected, upon doping with Yb.

Daily Physical Activity and Hot Flashes in the Study of Women's Health Across the Nation FLASHES Study

PubMed Central

Gibson, Carolyn; Matthews, Karen; Thurston, Rebecca

2014-01-01

Objective To examine the role of physical activity in menopausal hot flashes. Competing models conceptualize physical activity as a risk or protective factor for hot flashes. Few studies have examined this relationship prospectively using physiologic measures of hot flashes and physical activity. Design Over two 48 hour-periods, 51 participants wore a physiologic hot flash monitor and activity monitor, and reported their hot flashes in an electronic diary. Physiologic hot flashes, reported hot flashes and reported hot flashes without physiological corroboration were related to activity changes using hierarchical generalized linear modeling, adjusting for potential confounders. Setting Community. Patients Midlife women. Interventions None. Main Outcome Measures Physiologically-detected hot flashes and reported hot flashes with and without physiologic corroboration. Results Hot flash reports without physiologic corroboration were more likely after activity increases (OR 1.04, 95% CI: 1.00-1.10, p=.01), particularly among women with higher levels of depressive symptoms (interaction p=.02). No other types of hot flashes were related to physical activity. Conclusion Acute increases in physical activity were associated with increased reporting of hot flashes lacking physiologic corroboration, particularly among women with depressive symptoms. Clinicians should consider the role of symptom perception and reporting in relations between physical activity and hot flashes. PMID:24491454

Adaptive P300 based control system

PubMed Central

Jin, Jing; Allison, Brendan Z.; Sellers, Eric W.; Brunner, Clemens; Horki, Petar; Wang, Xingyu; Neuper, Christa

2015-01-01

An adaptive P300 brain-computer interface (BCI) using a 12 × 7 matrix explored new paradigms to improve bit rate and accuracy. During online use, the system adaptively selects the number of flashes to average. Five different flash patterns were tested. The 19-flash paradigm represents the typical row/column presentation (i.e., 12 columns and 7 rows). The 9- and 14-flash A & B paradigms present all items of the 12 × 7 matrix three times using either nine or 14 flashes (instead of 19), decreasing the amount of time to present stimuli. Compared to 9-flash A, 9-flash B decreased the likelihood that neighboring items would flash when the target was not flashing, thereby reducing interference from items adjacent to targets. 14-flash A also reduced adjacent item interference and 14-flash B additionally eliminated successive (double) flashes of the same item. Results showed that accuracy and bit rate of the adaptive system were higher than the non-adaptive system. In addition, 9- and 14-flash B produced significantly higher performance than their respective A conditions. The results also show the trend that the 14-flash B paradigm was better than the 19-flash pattern for naïve users. PMID:21474877

Adverse Effects of Induced Hot Flashes on Objectively Recorded and Subjectively Reported Sleep: Results of a Gonadotropin-Releasing Hormone Agonist Experimental Protocol

PubMed Central

Joffe, Hadine; White, David P.; Crawford, Sybil L.; McCurnin, Kristin E.; Economou, Nicole; Connors, Stephanie; Hall, Janet E.

2013-01-01

Objectives The impact of hot flashes on sleep is of great clinical interest, but results are inconsistent, especially when both hot flashes and sleep are measured objectively. Using objective and subjective measurements, we examined the impact of hot flashes on sleep by inducing hot flashes with a gonadotropin-releasing hormone agonist (GnRHa). Methods The GnRHa leuprolide was administered to 20 healthy premenopausal volunteers without hot flashes or sleep disturbances. Induced hot flashes were assessed objectively (skin-conductance monitor) and subjectively (daily diary) during one-month follow-up. Changes from baseline in objective (actigraphy) and subjective sleep quality (Pittsburgh Sleep Quality Index [PSQI]) were compared between women who did and did not develop objective hot flashes, and, in parallel analyses, subjective hot flashes. Results New-onset hot flashes were recorded in 14 (70%) and reported by 14 (70%) women (80% concordance). Estradiol was universally suppressed. Objective sleep efficiency worsened in women with objective hot flashes and improved in women without objective hot flashes (median decrease 2.6%, increase 4.2%, p=0.005). Subjective sleep quality worsened more in those with than without subjective hot flashes (median increase PSQI 2.5 vs. 1.0, p=0.03). Objective hot flashes were not associated with subjective sleep quality, nor were subjective symptoms linked to objective sleep measures. Conclusions This experimental model of induced hot flashes demonstrates a causal relationship between hot flashes and poor sleep quality. Objective hot flashes result in worse objective sleep efficiency, while subjective hot flashes worsen perceived sleep quality. PMID:23481119

Thermophysical properties of plasma sprayed coatings

NASA Technical Reports Server (NTRS)

Wilkes, K. E.; Lagedrost, J. F.

1973-01-01

Thermophysical properties of plasma sprayed materials were determined for the following plasma sprayed materials: CaO - stabilized ZrO2, Y2O3 - stabilized ZerO2, Al2O3, HfO2 Mo, nichrome, NiAl, Mo-ZrO2, and MoAl2O3 mixtures. In all cases the thermal conductivity of the as-sprayed materials was found to be considerably lower than that of the bulk material. The flash-laser thermal diffusivity technique was used both for diffusivity determination of single-layer materials and to determine the thermal contact resistance at the interface of two-layer specimens.

LDEF active optical system components experiment

NASA Technical Reports Server (NTRS)

Blue, M. D.

1992-01-01

A preliminary report on the Active Optical System Components Experiment is presented. This experiment contained 136 components in a six inch deep tray including lasers, infrared detectors and arrays, ultraviolet light detectors, light-emitting diodes, a light modulator, flash lamps, optical filters, glasses, and samples of surface finishes. Thermal, mechanical, and structural considerations leading to the design of the tray hardware are discussed. In general, changes in the retested component characteristics appear as much related to the passage of time as to the effects of the space environment, but organic materials, multilayer optical interference filters, and extreme-infrared reflectivity of black paints show unexpected changes.

Menopausal hot flashes: Randomness or rhythmicity

NASA Astrophysics Data System (ADS)

Kronenberg, Fredi

1991-10-01

Menopausal hot flashes are episodes of flushing, increased heart rate, skin blood flow and skin temperature, and a sensation of heat. The thermoregulatory and cardiovascular concomitants of hot flashes are associated with peaks in the levels of various hormones and neurotransmitters in the peripheral circulation. Although hot flashes affect about 75% of women, and are the primary reason that women at menopause seek medical attention, the mechanism of hot flashes is still not understood. Hot flashes vary in frequency and intensity both within and between individuals, and have been thought of as occurring randomly. Yet, some women report that their hot flashes are worse at a particular time of day or year. Initial examination of subjects' recordings of their hot flashes showed diurnal patterns of hot flash occurrence. There also seems to be a diurnal rhythm of hot flash intensity. Continuous physiological monitoring of hot flashes is facilitating the analysis of these patterns, which is revealing circadian and ultradian periodicities. The occurrence of hot flashes can be modulated by external and internal factors, including ambient temperature and fever. Rhythms of thermoregulatory and endocrine functions also may influence hot flash patterns. Examination of the interrelationships between the various systems of the body involved in hot flashes, and a multidisciplinary approach to the analysis of hot flash patterns, will aid our understanding of this complex phenomenon.

Disturbance of visual functions as a result of temporary blinding from low power lasers

NASA Astrophysics Data System (ADS)

Reidenbach, Hans-Dieter

2010-04-01

Although it is well-known that dazzle, flash-blindness and afterimages may be caused by bright optical radiation, only sparse quantitative data are available with regard to the effects arising from low power laser products. Indirect effects like temporary blinding might result in serious incidents or even accidents due to the alteration of visual functions like visual acuity, contrast sensitivity and color discrimination. In order to determine the degree and duration of impairment resulting from dazzle, flash-blindness and afterimages, caused by a laser beam, an investigation has been performed with the goal to improve the current knowledge as far as especially the visual acuity recovery duration is concerned. Two different test set-ups were designed and applied in order to determine the afterimage duration and the recovery time for visual acuity after temporary blinding from a laser, respectively. In order to get the desired information a helium-neon laser was mounted on a movable assembly where the respective beam position and direction could be set up on a semicircle. In addition the mount could be inclined in a vertical plane in order to increase the variability of feasible settings. The power was adjusted in several steps in order to investigate the respective dependence of the afterimage. The investigations were relatively time consuming, since re-adaptation of about half an hour was necessary after every exposure in order not to falsify the results. The trials have been done with several volunteers in the laboratory. After the experimental mapping of the local afterimage duration for the various sites on the retina the foveal afterimage duration taf,fv produced by a red laser beam was determined. The investigations have shown a strong dependence on the angle between the line of sight and the beam direction. Besides a maximum of 300 s the dose relationship taf,fv/s ~ 50.6•ln[(P•texp)/μJ] - 13.4 for laser output powers P between 10 μW and 30 μW with exposure durations texp from 0.25 s up to 10 s was found. The inability to read due to the disturbance produced by afterimages lasts for about 20 s even if the exposure is not more than 0.25 s from a laser with about 0.8 mW optical output power. In addition to the physiological effects of temporary blinding the psychological glare was determined as a function of the angle between line of sight and beam direction. It was found that already at output powers below 30 μW of a He-Nelaser the subjects reported intense glare effects and felt uncomfortable due to the high brightness. Instead of the standard visual acuity measurement used by eye care professionals, a reading test on a computer monitor was applied after laser irradiation. In this case two different lasers were used as a dazzling light source, one with a wavelength of 632.8 nm and the other with 532 nm. The maximum applied optical power in a 7-mm aperture, which is equivalent to the pupil diameter of a dark adapted eye, was 0.783 mW. The exposure durations were chosen as 0.25 s, 0.5 s, 1 s, 5 s, and 20 s.

Femtosecond laser lithotripsy: feasibility and ablation mechanism.

PubMed

Qiu, Jinze; Teichman, Joel M H; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D; Chan, Kin Foong; Milner, Thomas E

2010-01-01

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (lambda=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 microm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 microm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

A Micro-Electrode Array device coupled to a laser-based system for the local stimulation of neurons by optical release of glutamate.

PubMed

Ghezzi, Diego; Menegon, Andrea; Pedrocchi, Alessandra; Valtorta, Flavia; Ferrigno, Giancarlo

2008-10-30

Optical stimulation is a promising approach to investigate the local dynamic responses of cultured neurons. In particular, flash photolysis of caged compounds offers the advantage of allowing the rapid change of concentration of either extracellular or intracellular molecules, such as neurotransmitters or second messengers, for the stimulation or modulation of neuronal activity. We describe here the use of an ultra-violet (UV) laser diode coupled to an optical fibre for the local activation of caged compounds combined with a Micro-Electrode Array (MEA) device. Local uncaging was achieved by UV irradiation through the optical fibre previously positioned by using a red laser diode. The size of the stimulation was determined using caged fluorescein, whereas its efficacy was tested by studying the effect of uncaging the neurotransmitter glutamate. Uncaged glutamate evoked neuronal responses that were recorded using either fluorescence measurements or electrophysiological recordings with MEAs, thus showing the ability of our system to induce local neuronal excitation. This method allows overcoming the limitations of the MEA system related to unfocused electrical stimulation and induction of electrical artefacts. In addition, the coupling of a UV laser diode to an optical fibre allows a precise local stimulation and a quick change of the stimulation point.

Simulations of bremsstrahlung emission in ultra-intense laser interactions with foil targets

NASA Astrophysics Data System (ADS)

Vyskočil, Jiří; Klimo, Ondřej; Weber, Stefan

2018-05-01

Bremsstrahlung emission from interactions of short ultra-intense laser pulses with solid foils is studied using particle-in-cell (PIC) simulations. A module for simulating bremsstrahlung has been implemented in the PIC loop to self-consistently account for the dynamics of the laser–plasma interaction, plasma expansion, and the emission of gamma ray photons. This module made it possible to study emission from thin targets, where refluxing of hot electrons plays an important role. It is shown that the angular distribution of the emitted photons exhibits a four-directional structure with the angle of emission decreasing with the increase of the width of the target. Additionally, a collimated forward flash consisting of high energy photons has been identified in thin targets. The conversion efficiency of the energy of the laser pulse to the energy of the gamma rays rises with both the driving pulse intensity, and the thickness of the target. The amount of gamma rays also increases with the atomic number of the target material, despite a lower absorption of the driving laser pulse. The angular spectrum of the emitted gamma rays is directly related to the increase of hot electron divergence during their refluxing and its measurement can be used in experiments to study this process.

A laser flash photolysis and quantum chemical study of the fluorinated derivatives of singlet phenylnitrene.

PubMed

Gritsan, N P; Gudmundsdóttir, A D; Tigelaar, D; Zhu, Z; Karney, W L; Hadad, C M; Platz, M S

2001-03-07

Laser flash photolysis (LFP, Nd:YAG laser, 35 ps, 266 nm, 10 mJ or KrF excimer laser, 10 ns, 249 nm, 50 mJ) of 2-fluoro, 4-fluoro, 3,5-difluoro, 2,6-difluoro, and 2,3,4,5,6-pentafluorophenyl azides produces the corresponding singlet nitrenes. The singlet nitrenes were detected by transient absorption spectroscopy, and their spectra are characterized by sharp absorption bands with maxima in the range of 300-365 nm. The kinetics of their decay were analyzed as a function of temperature to yield observed decay rate constants, k(OBS). The observed rate constant in inert solvents is the sum of k(R) + k(ISC) where k(R) is the absolute rate constant of rearrangement of singlet nitrene to an azirine and k(ISC) is the absolute rate constant of nitrene intersystem crossing (ISC). Values of k(R) and k(ISC) were deduced after assuming that k(ISC) is independent of temperature. Barriers to cyclization of 4-fluoro-, 3,5-difluoro-, 2-fluoro-, 2,6-difluoro-, and 2,3,4,5,6-pentafluorophenylnitrene in inert solvents are 5.3 +/- 0.3, 5.5 +/- 0.3, 6.7 +/- 0.3, 8.0 +/- 1.5, and 8.8 +/- 0.4 kcal/mol, respectively. The barrier to cyclization of parent singlet phenylnitrene is 5.6 +/- 0.3 kcal/mol. All of these values are in good quantitative agreement with CASPT2 calculations of the relative barrier heights for the conversion of fluoro-substituted singlet aryl nitrenes to benzazirines (Karney, W. L. and Borden, W. T. J. Am. Chem. Soc. 1997, 119, 3347). A single ortho-fluorine substituent exerts a small but significant bystander effect on remote cyclization that is not steric in origin. The influence of two ortho-fluorine substituents on the cyclization is pronounced. In the case of the singlet 2-fluorophenylnitrene system, evidence is presented that the benzazirine is an intermediate and that the corresponding singlet nitrene and benzazirine interconvert. Ab initio calculations at different levels of theory on a series of benzazirines, their isomeric ketenimines, and the transition states converting the benzazirines to ketenimines were performed. The computational results are in good qualitative and quantitative agreement with the experimental findings.

An Analysis of Total Lightning Flash Rates Over Florida

NASA Astrophysics Data System (ADS)

Mazzetti, Thomas O.; Fuelberg, Henry E.

2017-12-01

Although Florida is known as the "Sunshine State", it also contains the greatest lightning flash densities in the United States. Flash density has received considerable attention in the literature, but lightning flash rate has received much less attention. We use data from the Earth Networks Total Lightning Network (ENTLN) to produce a 5 year (2010-2014) set of statistics regarding total flash rates over Florida and adjacent regions. Instead of tracking individual storms, we superimpose a 0.2° × 0.2° grid over the study region and count both cloud-to-ground (CG) and in-cloud (IC) flashes over 5 min intervals. Results show that the distribution of total flash rates is highly skewed toward small values, whereas the greatest rate is 185 flashes min-1. Greatest average annual flash rates ( 3 flashes min-1) are located near Orlando. The southernmost peninsula, North Florida, and the Florida Panhandle exhibit smaller average annual flash rates ( 1.5 flashes min-1). Large flash rates > 100 flashes min-1 can occur during any season, at any time during the 24 h period, and at any location within the domain. However, they are most likely during the afternoon and early evening in East Central Florida during the spring and summer months.

Behavioral weight loss for the management of menopausal hot flashes: a pilot study.

PubMed

Thurston, Rebecca C; Ewing, Linda J; Low, Carissa A; Christie, Aimee J; Levine, Michele D

2015-01-01

Although adiposity has been considered to be protective against hot flashes, newer data suggest positive relationships between hot flashes and adiposity. No studies have been specifically designed to test whether weight loss reduces hot flashes. This pilot study aimed to evaluate the feasibility, acceptability, and initial efficacy of behavioral weight loss in reducing hot flashes. Forty overweight or obese women with hot flashes (≥ 4 hot flashes/d) were randomized to either behavioral weight loss intervention or wait-list control. Hot flashes were assessed before and after intervention via physiologic monitoring, diary, and questionnaire. Comparisons of changes in hot flashes and anthropometrics between conditions were performed via Wilcoxon tests. Study retention (83%) and intervention satisfaction (93.8%) were high. Most women (74.1%) reported that hot flash reduction was a major motivator for losing weight. Women randomized to the weight loss intervention lost more weight (-8.86 kg) than did women randomized to control (+0.23 kg; P < 0.0001). Women randomized to weight loss also showed greater reductions in questionnaire-reported hot flashes (2-wk hot flashes, -63.0) than did women in the control group (-28.0; P = 0.03)-a difference not demonstrated in other hot flash measures. Reductions in weight and hot flashes were significantly correlated (eg, r = 0.47, P = 0.006). This pilot study shows a behavioral weight loss program that is feasible, acceptable, and effective in producing weight loss among overweight or obese women with hot flashes. Findings indicate the importance of a larger study designed to test behavioral weight loss for hot flash reduction. Hot flash management could motivate women to engage in this health-promoting behavior.

Targeting an efficient target-to-target interval for P300 speller brain–computer interfaces

PubMed Central

Sellers, Eric W.; Wang, Xingyu

2013-01-01

Longer target-to-target intervals (TTI) produce greater P300 event-related potential amplitude, which can increase brain–computer interface (BCI) classification accuracy and decrease the number of flashes needed for accurate character classification. However, longer TTIs requires more time for each trial, which will decrease the information transfer rate of BCI. In this paper, a P300 BCI using a 7 × 12 matrix explored new flash patterns (16-, 18- and 21-flash pattern) with different TTIs to assess the effects of TTI on P300 BCI performance. The new flash patterns were designed to minimize TTI, decrease repetition blindness, and examine the temporal relationship between each flash of a given stimulus by placing a minimum of one (16-flash pattern), two (18-flash pattern), or three (21-flash pattern) non-target flashes between each target flashes. Online results showed that the 16-flash pattern yielded the lowest classification accuracy among the three patterns. The results also showed that the 18-flash pattern provides a significantly higher information transfer rate (ITR) than the 21-flash pattern; both patterns provide high ITR and high accuracy for all subjects. PMID:22350331

Spatial-temporal characteristics of lightning flash size in a supercell storm

NASA Astrophysics Data System (ADS)

Zhang, Zhixiao; Zheng, Dong; Zhang, Yijun; Lu, Gaopeng

2017-11-01

The flash sizes of a supercell storm, in New Mexico on October 5, 2004, are studied using the observations from the New Mexico Lightning Mapping Array and the Albuquerque, New Mexico, Doppler radar (KABX). First, during the temporal evolution of the supercell, the mean flash size is anti-correlated with the flash rate, following a unary power function, with a correlation coefficient of - 0.87. In addition, the mean flash size is linearly correlated with the area of reflectivity > 30 dBZ at 5 km normalized by the flash rate, with a correlation coefficient of 0.88. Second, in the horizontal, flash size increases along the direction from the region near the convection zone to the adjacent forward anvil. The region of minimum flash size usually corresponds to the region of maximum flash initiation and extent density. The horizontal correspondence between the mean flash size and the flash extent density can also be fitted by a unary power function, and the correlation coefficient is > 0.5 in 50% of the radar volume scans. Furthermore, the quality of fit is positively correlated to the convective intensity. Third, in the vertical direction, the height of the maximum flash initiation density is close to the height of maximum flash extent density, but corresponds to the height where the mean flash size is relatively small. In the discussion, the distribution of the small and dense charge regions when and where convection is vigorous in the storm, is deduced to be responsible for the relationship that flash size is temporally and spatially anti-correlated with flash rate and density, and the convective intensity.

"Defense-in-Depth" Laser Safety and the National Ignition Facility

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

King, J J

The National Ignition Facility (NIF) is the largest and most energetic laser in the world contained in a complex the size of a football stadium. From the initial laser pulse, provided by telecommunication style infrared nanoJoule pulsed lasers, to the final 192 laser beams (1.8 Mega Joules total energy in the ultraviolet) converging on a target the size of a pencil eraser, laser safety is of paramount concern. In addition to this, there are numerous high-powered (Class 3B and 4) diagnostic lasers in use that can potentially send their laser radiation travelling throughout the facility. With individual beam paths ofmore » up to 1500 meters and a workforce of more than one thousand, the potential for exposure is significant. Simple laser safety practices utilized in typical laser labs just don't apply. To mitigate these hazards, NIF incorporates a multi layered approach to laser safety or 'Defense in Depth.' Most typical high-powered laser operations are contained and controlled within a single room using relatively simplistic controls to protect both the worker and the public. Laser workers are trained, use a standard operating procedure, and are required to wear Personal Protective Equipment (PPE) such as Laser Protective Eyewear (LPE) if the system is not fully enclosed. Non-workers are protected by means of posting the room with a warning sign and a flashing light. In the best of cases, a Safety Interlock System (SIS) will be employed which will 'safe' the laser in the case of unauthorized access. This type of laser operation is relatively easy to employ and manage. As the operation becomes more complex, higher levels of control are required to ensure personnel safety. Examples requiring enhanced controls are outdoor and multi-room laser operations. At the NIF there are 192 beam lines and numerous other Class 4 diagnostic lasers that can potentially deliver their hazardous energy to locations far from the laser source. This presents a serious and complex potential hazard to personnel. Because of this, a multilayered approach to safety is taken. This paper presents the philosophy and approach taken at the NIF in the multi-layered 'defense-in-depth' approach to laser safety.« less

Flash memory management system and method utilizing multiple block list windows

NASA Technical Reports Server (NTRS)

Chow, James (Inventor); Gender, Thomas K. (Inventor)

2005-01-01

The present invention provides a flash memory management system and method with increased performance. The flash memory management system provides the ability to efficiently manage and allocate flash memory use in a way that improves reliability and longevity, while maintaining good performance levels. The flash memory management system includes a free block mechanism, a disk maintenance mechanism, and a bad block detection mechanism. The free block mechanism provides efficient sorting of free blocks to facilitate selecting low use blocks for writing. The disk maintenance mechanism provides for the ability to efficiently clean flash memory blocks during processor idle times. The bad block detection mechanism provides the ability to better detect when a block of flash memory is likely to go bad. The flash status mechanism stores information in fast access memory that describes the content and status of the data in the flash disk. The new bank detection mechanism provides the ability to automatically detect when new banks of flash memory are added to the system. Together, these mechanisms provide a flash memory management system that can improve the operational efficiency of systems that utilize flash memory.

Disruptive laser diode source for embedded LIDAR sensors

NASA Astrophysics Data System (ADS)

Canal, Celine; Laugustin, Arnaud; Kohl, Andreas; Rabot, Olivier

2017-02-01

Active imaging based on laser illumination is used in various fields such as medicine, security, defense, civil engineering and in the automotive sector. In this last domain, research and development to bring autonomous vehicles on the roads has been intensified these last years with an emphasis on lidar technology that is probably the key to achieve full automation level. Based on time-of-flight measurements, the profile of objects can be measured together with their location in various conditions, creating a 3D mapping of the environment. To be embedded on a vehicle as advanced driver assistance systems (ADAS), these sensors require compactness, low-cost and reliability, as it is provided by a flash lidar. An attractive candidate, especially with respect to cost reduction, for the laser source integrated in these devices is certainly laser diodes as long as they can provide sufficiently short pulses with a high energy. A recent breakthrough in laser diode and diode driver technology made by Quantel (Les Ulis, France) now allows laser emission higher than 1 mJ with pulses as short as 12 ns in a footprint of 4x5 cm2 (including both the laser diode and driver) and an electrical-to-optical conversion efficiency of the whole laser diode source higher than 25% at this level of energy. The components used for the laser source presented here can all be manufactured at low cost. In particular, instead of having several individual laser diodes positioned side by side, the laser diodes are monolithically integrated on a single semiconductor chip. The chips are then integrated directly on the driver board in a single assembly step. These laser sources emit in the range of 800-1000 nm and their emission is considered to be eye safe when taking into account the high divergence of the output beam and the aperture of possible macro lenses so that they can be used for end consumer applications. Experimental characterization of these state-of-the-art pulsed laser diode sources will be given. Future work leads will be discussed for miniaturization of the laser diode and drastic cost reduction.

Perceived control and hot flashes in treatment-seeking breast cancer survivors and menopausal women.

PubMed

Carpenter, Janet S; Wu, Jingwei; Burns, Debra S; Yu, Menggang

2012-01-01

Lower perceived control over hot flashes has been linked to fewer coping strategies, more catastrophizing, and greater hot flash severity and distress in midlife women, yet this important concept has not yet been studied in breast cancer survivors. The aim of this study was to explore perceived control over hot flashes and hot flashes in breast cancer survivors compared with midlife women without cancer. Ninety-nine survivors and 138 midlife women completed questionnaires and a prospective, electronic hot flash diary. All data were collected at a baseline assessment before randomization in a behavioral intervention study. Both groups had moderate perceived control over hot flashes. Control was not significantly related to hot flash frequency but was significantly related to hot flash severity, bother, and interference in both groups. A significantly stronger association between control and hot flash interference was found for survivors than for midlife women. Survivors using hot flash treatments perceived less control than did survivors not using hot flash treatments, whereas the opposite was true in midlife women. Findings extend our knowledge of perceived control over hot flashes in both survivors and midlife women. Findings emphasize the importance of continued menopausal symptom assessment and management, support the importance of continuing nursing care even for survivors who are already using hot flash treatment, and suggest that nursing interventions aimed at improving perceived control over hot flashes may be more helpful for survivors than for midlife women.

Electron-transfer and acid-base properties of a two-electron oxidized form of quaterpyrrole that acts as both an electron donor and an acceptor.

PubMed

Zhang, Min; E, Wenbo; Ohkubo, Kei; Sanchez-Garcia, David; Yoon, Dae-Wi; Sessler, Jonathan L; Fukuzumi, Shunichi; Kadish, Karl M

2008-02-21

Electron-transfer interconversion between the four-electron oxidized form of a quaterpyrrole (abbreviated as P4 for four pyrroles) and the two-electron oxidized form (P4H2) as well as between P4H2 and its fully reduced form (P4H4) bearing analogous substituents in the alpha- and beta-pyrrolic positions was studied by means of cyclic voltammetry and UV-visible spectroelectrochemistry combined with ESR and laser flash photolysis measurements. The two-electron oxidized form, P4H2, acts as both an electron donor and an electron acceptor. The radical cation (P4H2*+) and radical anion (P4H2*-) are both produced by photoinduced electron transfer from dimeric 1-benzyl-1,4-dihydronicotinamide to P4H2, whereas the cation radical form of the compound is also produced by electron-transfer oxidation of P4H2 with [Ru(bpy)3]3+. The ESR spectra of P4H2*+ and P4H2*- were recorded at low temperature and exhibit spin delocalization over all four pyrrole units. Thus, the two-electron oxidized form of the quaterpyrrole (P4H2) displays redox and electronic features analogous to those seen in the case of porphyrins and may be considered as a simple, open-chain model of this well-studied tetrapyrrolic macrocycle. The dynamics of deprotonation from P4H2*+ and disproportionation of P4H2 were examined by laser flash photolysis measurements of photoinduced electron-transfer oxidation and reduction of P4H2, respectively.

Prototype Control System for Compensation of Superconducting Cavities Detuning Using Piezoelectric Actuators

NASA Astrophysics Data System (ADS)

Przygoda, K.; Piotrowski, A.; Jablonski, G.; Makowski, D.; Pozniak, T.; Napieralski, A.

2009-08-01

Pulsed operation of high gradient superconducting radio frequency (SCRF) cavities results in dynamic Lorentz force detuning (LFD) approaching or exceeding the bandwidth of the cavity of order of a few hundreds of Hz. The resulting modulation of the resonance frequency of the cavity is leading to a perturbation of the amplitude and phase of the accelerating field, which can be controlled only at the expense of RF power. Presently, at various labs, a piezoelectric fast tuner based on an active compensation scheme for the resonance frequency control of the cavity is under study. The tests already performed in the Free Electron Laser in Hamburg (FLASH), proved the possibility of Lorentz force detuning compensation by the means of the piezo element excited with the single period of sine wave prior to the RF pulse. The X-Ray Free Electron Laser (X-FEL) accelerator, which is now under development in Deutsche Elektronen-Synchrotron (DESY), will consists of around 800 cavities with a fast tuner fixture including the actuator/sensor configuration. Therefore, it is necessary to design a distributed control system which would be able to supervise around 25 RF stations, each one comprised of 32 cavities. The Advanced Telecomunications Computing Architecture (ATCA) was chosen to design, develop, and build a Low Level Radio Frequency (LLRF) controller for X-FEL. The prototype control system for Lorentz force detuning compensation was designed and developed. The control applications applied in the system were fitted to the main framework of interfaces and communication protocols proposed for the ATCA-based LLRF control system. The paper presents the general view of a designed control system and shows the first experimental results from the tests carried out in FLASH facility. Moreover, the possibilities for integration of the piezo control system to the ATCA standards are discussed.

Lidar Sensor Performance in Closed-Loop Flight Testing of the Morpheus Rocket-Propelled Lander to a Lunar-Like Hazard Field

NASA Technical Reports Server (NTRS)

Roback, V. Eric; Pierrottet, Diego F.; Amzajerdian, Farzin; Barnes, Bruce W.; Bulyshev, Alexander E.; Hines, Glenn D.; Petway, Larry B.; Brewster, Paul F.; Kempton, Kevin S.

2015-01-01

For the first time, a suite of three lidar sensors have been used in flight to scan a lunar-like hazard field, identify a safe landing site, and, in concert with an experimental Guidance, Navigation, and Control (GN&C) system, help to guide the Morpheus autonomous, rocket-propelled, free-flying lander to that safe site on the hazard field. The lidar sensors and GN&C system are part of the Autonomous Precision Landing and Hazard Detection and Avoidance Technology (ALHAT) project which has been seeking to develop a system capable of enabling safe, precise crewed or robotic landings in challenging terrain on planetary bodies under any ambient lighting conditions. The 3-D imaging Flash Lidar is a second generation, compact, real-time, aircooled instrument developed from a number of components from industry and NASA and is used as part of the ALHAT Hazard Detection System (HDS) to scan the hazard field and build a 3-D Digital Elevation Map (DEM) in near-real time for identifying safe sites. The Flash Lidar is capable of identifying a 30 cm hazard from a slant range of 1 km with its 8 cm range precision (1-s). The Flash Lidar is also used in Hazard Relative Navigation (HRN) to provide position updates down to a 250m slant range to the ALHAT navigation filter as it guides Morpheus to the safe site. The Navigation Doppler Lidar (NDL) system has been developed within NASA to provide velocity measurements with an accuracy of 0.2 cm/sec and range measurements with an accuracy of 17 cm both from a maximum range of 2,200 m to a minimum range of several meters above the ground. The NDLâ€"TM"s measurements are fed into the ALHAT navigation filter to provide lander guidance to the safe site. The Laser Altimeter (LA), also developed within NASA, provides range measurements with an accuracy of 5 cm from a maximum operational range of 30 km down to 1 m and, being a separate sensor from the Flash Lidar, can provide range along a separate vector. The LA measurements are also fed into the ALHAT navigation filter to provide lander guidance to the safe site. The flight tests served as the culmination of the TRL 6 journey for the ALHAT system and included launch from a pad situated at the NASA-Kennedy Space Center Shuttle Landing Facility (SLF) runway, a lunar-like descent trajectory from an altitude of 250m, and landing on a lunar-like hazard field of rocks, craters, hazardous slopes, and safe sites 400m down-range just off the North end of the runway. The tests both confirmed the expected performance and also revealed several challenges present in the flight-like environment which will feed into future TRL advancement of the sensors. Guidance provided by the ALHAT system was impeded in portions of the trajectory and intermittent near the end of the trajectory due to optical effects arising from air heated by the rocket engine. The Flash Lidar identified hazards as small as 30 cm from the maximum slant range of 450 m which Morpheus could provide; however, it was occasionally susceptible to an increase in range noise due to scintillation arising from air heated by the Morpheus rocket engine which entered its Field-of-View (FOV). The Flash Lidar was also susceptible to pre-triggering, during the HRN phase, on a dust cloud created during launch and transported down-range by the wind. The NDL provided velocity and range measurements to the expected accuracy levels yet it was also susceptible to signal degradation due to air heated by the rocket engine. The LA, operating with a degraded transmitter laser, also showed signal attenuation over a few seconds at a specific phase of the flight due to the heat plume generated by the rocket engine.

Synoptic-scale atmospheric conditions associated with flash flooding in watersheds of the Catskill Mountains, New York, USA

NASA Astrophysics Data System (ADS)

Teale, N. G.; Quiring, S. M.

2015-12-01

Understanding flash flooding is important in unfiltered watersheds, such as portions of the New York City water supply system (NYCWSS), as water quality is degraded by turbidity associated with flooding. To further understand flash flooding in watersheds of the NYCWSS, synoptic-scale atmospheric conditions most frequently associated with flash flooding between 1987 and 2013 were examined. Flash floods were identified during this time period using USGS 15-minute discharge data at the Esopus Creek near Allaben, NY and Neversink River at Claryville, NY gauges. Overall, 25 flash floods were detected, occurring over 17 separate flash flood days. These flash flood days were compared to the days on which flash flood warnings encompassing the study area was issued by the National Weather Service. The success rate for which the flash flood warnings for Ulster County coincided with flash flood in the study watershed was 0.09, demonstrating the highly localized nature of flash flooding in the Catskill Mountain region. The synoptic-scale atmospheric patterns influencing the study area were characterized by a principal component analysis and k-means clustering of NCEP/NCAR 500 mb geopotential height reanalysis data. This procedure was executed in Spatial Synoptic Typer Tools 4.0. While 17 unique synoptic patterns were identified, only 3 types were strongly associated with flash flooding events. A strong southwesterly flow suggesting advection of moisture from the Atlantic Ocean and Gulf of Mexico is shown in composites of these 3 types. This multiscalar study thereby links flash flooding in the NYCWSS with synoptic-scale atmospheric circulation.Understanding flash flooding is important in unfiltered watersheds, such as portions of the New York City water supply system (NYCWSS), as water quality is degraded by turbidity associated with flooding. To further understand flash flooding in watersheds of the NYCWSS, synoptic-scale atmospheric conditions most frequently associated with flash flooding between 1987 and 2013 were examined. Flash floods were identified during this time period using USGS 15-minute discharge data at the Esopus Creek near Allaben, NY and Neversink River at Claryville, NY gauges. Overall, 25 flash floods were detected, occurring over 17 separate flash flood days. These flash flood days were compared to the days on which flash flood warnings encompassing the study area was issued by the National Weather Service. The success rate for which the flash flood warnings for Ulster County coincided with flash flood in the study watershed was 0.09, demonstrating the highly localized nature of flash flooding in the Catskill Mountain region. The synoptic-scale atmospheric patterns influencing the study area were characterized by a principal component analysis and k-means clustering of NCEP/NCAR 500 mb geopotential height reanalysis data. This procedure was executed in Spatial Synoptic Typer Tools 4.0. While 17 unique synoptic patterns were identified, only 3 types were strongly associated with flash flooding events. A strong southwesterly flow suggesting advection of moisture from the Atlantic Ocean and Gulf of Mexico is shown in composites of these 3 types. This multiscalar study thereby links flash flooding in the NYCWSS with synoptic-scale atmospheric circulation.

Hot Flashes and Quality of Life Among Breast Cancer Patients

DTIC Science & Technology

2006-08-01

hot flashes, 40.7% report at baseline, having used HRT and 26.8% used exercise to control hot flashes. The 12-month data indicates that 26.5% of the...entire sample who are experiencing hot flashes, tried or are using some form of HRT to control hot flashes with exercise still the most frequently...used approach to manage hot flashes with 44.2% of sample currently exercising . 15. SUBJECT TERMS Breast Cancer, Hot Flashes, Quality of Life

Physiologically assessed hot flashes and endothelial function among midlife women.

PubMed

Thurston, Rebecca C; Chang, Yuefang; Barinas-Mitchell, Emma; Jennings, J Richard; von Känel, Roland; Landsittel, Doug P; Matthews, Karen A

2017-08-01

Hot flashes are experienced by most midlife women. Emerging data indicate that they may be associated with endothelial dysfunction. No studies have tested whether hot flashes are associated with endothelial function using physiologic measures of hot flashes. We tested whether physiologically assessed hot flashes were associated with poorer endothelial function. We also considered whether age modified associations. Two hundred seventy-two nonsmoking women reporting either daily hot flashes or no hot flashes, aged 40 to 60 years, and free of clinical cardiovascular disease, underwent ambulatory physiologic hot flash and diary hot flash monitoring; a blood draw; and ultrasound measurement of brachial artery flow-mediated dilation to assess endothelial function. Associations between hot flashes and flow-mediated dilation were tested in linear regression models controlling for lumen diameter, demographics, cardiovascular disease risk factors, and estradiol. In multivariable models incorporating cardiovascular disease risk factors, significant interactions by age (P < 0.05) indicated that among the younger tertile of women in the sample (age 40-53 years), the presence of hot flashes (beta [standard error] = -2.07 [0.79], P = 0.01), and more frequent physiologic hot flashes (for each hot flash: beta [standard error] = -0.10 [0.05], P = 0.03, multivariable) were associated with lower flow-mediated dilation. Associations were not accounted for by estradiol. Associations were not observed among the older women (age 54-60 years) or for self-reported hot flash frequency, severity, or bother. Among the younger women, hot flashes explained more variance in flow-mediated dilation than standard cardiovascular disease risk factors or estradiol. Among younger midlife women, frequent hot flashes were associated with poorer endothelial function and may provide information about women's vascular status beyond cardiovascular disease risk factors and estradiol.

Menopausal Hot Flashes and Carotid Intima Media Thickness Among Midlife Women.

PubMed

Thurston, Rebecca C; Chang, Yuefang; Barinas-Mitchell, Emma; Jennings, J Richard; Landsittel, Doug P; Santoro, Nanette; von Känel, Roland; Matthews, Karen A

2016-12-01

There has been a longstanding interest in the role of menopause and its correlates in the development of cardiovascular disease (CVD) in women. Menopausal hot flashes are experienced by most midlife women; emerging data link hot flashes to CVD risk indicators. We tested whether hot flashes, measured via state-of-the-art physiologic methods, were associated with greater subclinical atherosclerosis as assessed by carotid ultrasound. We considered the role of CVD risk factors and estradiol concentrations in these associations. A total of 295 nonsmoking women free of clinical CVD underwent ambulatory physiologic hot flash assessments; a blood draw; and carotid ultrasound measurement of intima media thickness and plaque. Associations between hot flashes and subclinical atherosclerosis were tested in regression models controlling for CVD risk factors and estradiol. More frequent physiologic hot flashes were associated with higher carotid intima media thickness (for each additional hot flash: β [SE]=0.004 [0.001]; P=0.0001; reported hot flash: β [SE]=0.008 [0.002]; P=0.002, multivariable) and plaque (eg, for each additional hot flash, odds ratio [95% confidence interval] plaque index ≥2=1.07 [1.003-1.14]; P=0.04, relative to no plaque, multivariable] among women reporting daily hot flashes; associations were not accounted for by CVD risk factors or by estradiol. Among women reporting hot flashes, hot flashes accounted for more variance in intima media thickness than most CVD risk factors. Among women reporting daily hot flashes, frequent hot flashes may provide information about a woman's vascular status beyond standard CVD risk factors and estradiol. Frequent hot flashes may mark a vulnerable vascular phenotype among midlife women. © 2016 American Heart Association, Inc.

Menopausal Hot Flashes and Carotid Intima Media Thickness among Midlife Women

PubMed Central

Thurston, Rebecca C.; Chang, Yuefang; Barinas-Mitchell, Emma; Jennings, J. Richard; Landsittel, Doug P.; Santoro, Nanette; von Känel, Roland; Matthews, Karen A.

2016-01-01

Background and Purpose There has been a longstanding interest in the role of menopause and its correlates in the development of cardiovascular disease (CVD) in women. Menopausal hot flashes are experienced by most midlife women; emerging data link hot flashes to CVD risk indicators. We tested whether hot flashes, measured via state-of-the-art physiologic methods, were associated with greater subclinical atherosclerosis as assessed by carotid ultrasound. We considered the role of CVD risk factors and estradiol concentrations in these associations. Methods 295 nonsmoking women free of clinical CVD underwent ambulatory physiologic hot flash assessments; a blood draw; and carotid ultrasound measurement of IMT and plaque. Associations between hot flashes and subclinical atherosclerosis were tested in regression models controlling for CVD risk factors and estradiol. Results More frequent physiologic hot flashes were associated with higher carotid intima media thickness [IMT; for each additional hot flash: beta (standard error)=.004(.001), p=.0001; reported hot flash: beta (standard error)=.008(.002), p=.002, multivariable] and plaque [e.g., for each additional hot flash, odds ratio (95% confidence interval) plaque index ≥2=1.07(1.003–1.14, p=.04), relative to no plaque, multivariable] among women reporting daily hot flashes; associations were not accounted for by CVD risk factors or by estradiol. Among women reporting hot flashes, hot flashes accounted for more variance in IMT than most CVD risk factors. Conclusions Among women reporting daily hot flashes, frequent hot flashes may provide information about a woman’s vascular status beyond standard CVD risk factors and estradiol. Frequent hot flashes may mark a vulnerable vascular phenotype among midlife women. PMID:27834746

Behavioral Weight Loss for the Management of Menopausal Hot Flashes: A Pilot Study

PubMed Central

Thurston, Rebecca C.; Ewing, Linda J.; Low, Carissa A.; Christie, Aimee J.; Levine, Michele D.

2014-01-01

Objective Although adiposity has been considered protective against hot flashes, newer data suggest positive relations between flashes and adiposity. No studies have been specifically designed to test whether weight loss reduces hot flashes. This pilot study aimed to evaluate the feasibility, acceptability, and initial efficacy of behavioral weight loss to reduce hot flashes. Methods Forty overweight/obese women with hot flashes (≥4/day) were randomized to a behavioral weight loss intervention or to wait list control. Hot flashes were assessed pre- and post-intervention via physiologic monitor, diary, and questionnaire. Comparisons of changes in hot flashes and anthropometrics between conditions were tested via Wilcoxon tests. Results Study retention (83%) and intervention satisfaction (93.8%) were high. Most women (74.1%) reported that hot flash reduction was a main motivator to lose weight. Women randomized to the weight loss intervention lost more weight (-8.86 kg) than did women randomized to control (+0.23 kg, p<.0001). Women randomized to weight loss also showed greater reductions in questionnaire-reported hot flashes (2-week hot flashes: −63.0) than did women in the control (−28.0, p=.03), a difference not demonstrated in other hot flash measures. Reductions in weight and hot flashes were significantly correlated (e.g., r=.47, p=.006). Conclusions This pilot study showed a behavioral weight loss program to be feasible, acceptable, and effective in producing weight loss among overweight/obese women with hot flashes. Findings indicate the importance of a larger study designed to test behavioral weight loss for hot flash reduction. Hot flash management could motivate women to engage in this health-promoting behavior. PMID:24977456

Karst flash floods: an example from the Dinaric karst (Croatia)

NASA Astrophysics Data System (ADS)

Bonacci, O.; Ljubenkov, I.; Roje-Bonacci, T.

2006-03-01

Flash floods constitute one of the deadliest and costliest natural disasters worldwide. This paper explains the karst flash flood phenomenon, which represents a special kind of flash flood. As the majority of flash floods karst flash floods are caused by intensive short-term precipitation in an area whose surface rarely exceeds a few square kilometres. The characteristics of all flash floods are their short duration, small areal extent, high flood peaks and rapid flows, and heavy loss of life and property. Karst flash floods have specific characteristics due to special conditions for water circulation, which exist in karst terrains. During karst flash floods a sudden rise of groundwater levels occurs, which causes the appearance of numerous, unexpected, abundant and temporary karst springs. This paper presents in detail an example of a karst flash flood in the Marina bay (Dinaric karst region of Croatia), which occurred in December 2004.

A Comprehensive Study on Energy Efficiency and Performance of Flash-based SSD

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

Park, Seon-Yeon; Kim, Youngjae; Urgaonkar, Bhuvan

2011-01-01

Use of flash memory as a storage medium is becoming popular in diverse computing environments. However, because of differences in interface, flash memory requires a hard-disk-emulation layer, called FTL (flash translation layer). Although the FTL enables flash memory storages to replace conventional hard disks, it induces significant computational and space overhead. Despite the low power consumption of flash memory, this overhead leads to significant power consumption in an overall storage system. In this paper, we analyze the characteristics of flash-based storage devices from the viewpoint of power consumption and energy efficiency by using various methodologies. First, we utilize simulation tomore » investigate the interior operation of flash-based storage of flash-based storages. Subsequently, we measure the performance and energy efficiency of commodity flash-based SSDs by using microbenchmarks to identify the block-device level characteristics and macrobenchmarks to reveal their filesystem level characteristics.« less

Multi- and unisensory visual flash illusions.

PubMed

Courtney, Jon R; Motes, Michael A; Hubbard, Timothy L

2007-01-01

The role of stimulus structure in multisensory and unisensory interactions was examined. When a flash (17 ms) was accompanied by multiple tones (each 7 ms, SOA < or =100 ms) multiple flashes were reported, and this effect has been suggested to reflect the role of stimulus continuity in multisensory interactions. In experiments 1 and 2 we examined if stimulus continuity would affect concurrently presented stimuli. When a relatively longer flash (317 ms) was accompanied by multiple tones (each 7 ms), observers reported perceiving multiple flashes. In experiment 3 we tested whether a flash presented near fixation would induce an illusory flash further in the periphery. One flash (17 ms) presented 5 degrees below fixation was reported as multiple flashes if presented with two flashes (each 17 ms, SOA =100 ms) 2 degrees above fixation. The extent to which these data support a phenomenological continuity principle and whether this principle applies to unisensory perception is discussed.

Interactions of numerical and temporal stimulus characteristics on the control of response location by brief flashes of light.

PubMed

Fetterman, J Gregor; Killeen, P Richard

2011-09-01

Pigeons pecked on three keys, responses to one of which could be reinforced after 3 flashes of the houselight, to a second key after 6, and to a third key after 12. The flashes were arranged according to variable-interval schedules. Response allocation among the keys was a function of the number of flashes. When flashes were omitted, transitions occurred very late. Increasing flash duration produced a leftward shift in the transitions along a number axis. Increasing reinforcement probability produced a leftward shift, and decreasing reinforcement probability produced a rightward shift. Intermixing different flash rates within sessions separated allocations: Faster flash rates shifted the functions sooner in real time, but later in terms of flash count, and conversely for slower flash rates. A model of control by fading memories of number and time was proposed.

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

Yarotski, Dmitry Anatolievitch

On Thursday November 19, 2015, LANL postdoc received an eye injury from a reflected, nonvisible laser beam (Class 4, pulsed, wavelength 800 nanometer). The setup is configured to split the laser output into two work areas in which qualified operators conduct research experiments. During this incident, the laser output beam was being projected to both experimental work areas, although only one experimental area was actively being used. The second laser beam directed to the second work area was blocked by an inappropriate device (Plexiglas, reflective, non-normal incidence) that reflected substantial portion of the beam toward the first setup. In preparationmore » for the measurements, worker stepped on the stepstool and decided to remove the laser goggles to better see the micrometer readings which were difficult to see due to insufficient lighting. Immediately, he noticed a flash of light in his eye. The operator quickly replaced the laser eye-wear and then, using an infrared viewer, located a stray laser beam being reflected from the plexiglas beam block. The operator did not think he had sustained any injury and continued working. Later that day, however, he noticed a blurry spot in the vision of his left eye. He notified his supervisor on Friday morning, November 20, 2015, and was taken by CINT management to Sandia National Laboratories (SNL) medical facility for evaluation. SNL Medical did not find any abnormalities, but referred the operator to a local ophthalmologist for further evaluation. Further evaluations by the ophthalmologist on November 21 and November 23 identified a small spot of inflammation near the fovea on the retina in his left eye. The ophthalmologist stated that this spot would most likely heal on its own and that the blurry spot on the operator's vision would go away. A follow-up visit was scheduled. The employee was released back to work without restrictions.« less

Flash fire propensity of materials

NASA Technical Reports Server (NTRS)

Hilado, C. J.; Cumming, H. J.

1977-01-01

Flash fire test results on 86 materials, evaluated using the USF flash fire screening test, are presented. The materials which appear least prone to flash fires are PVC, polyphenylene oxide and sulfide, and polyether and polyaryl sulfone; these did not produce flash fires under these particular test conditions. The principal value of these screening tests at the present time is in identifying materials which appear prone to flash fires, and in identifying which formulations of a generic material are more or less prone to flash fires.

Hot flash report and measurement among Bangladeshi migrants, their London neighbors, and their community of origin.

PubMed

Sievert, L L; Begum, K; Sharmeen, T; Murphy, L; Whitcomb, B W; Chowdhury, O; Muttukrishna, S; Bentley, G R

2016-12-01

To examine hot flashes in relation to climate and activity patterns, and to compare subjective and objective hot flashes among Bangladeshi immigrants to London, their white London neighbors, and women still living in their community of origin, Sylhet, Bangladesh ("sedentees"). Ninety-five women, aged 40-55, wore the Biolog ambulatory hot flash monitor. Objective measurements and subjective hot flash reports were examined in relation to demographic, reproductive, anthropometric, and lifestyle variables; temperature and humidity at 12:00 and 18:00; and time spent on housework and cooking. Concordance of objective and subjective hot flashes was assessed by Kappa statistics and by sensitivity of hot flash classification. During the study period, Bangladeshi sedentees reported more subjective hot flashes (p < .05), but there was no difference in number of objective hot flashes. White Londoners were more likely to describe hot flashes on their face and neck compared to Bangladeshis (p < .05). Sedentees were more likely to describe hot flashes on their feet (p < .05). Postmenopausal status, increasing parity, and high levels of housework were significant determinants of subjective hot flashes, while ambient temperature and humidity were not. Measures of subjective/objective concordance were low but similar across groups (10-20%). The proportion of objective hot flashes that were also self-reported was lowest among immigrants. Hot flashes were not associated with warmer temperatures, but were associated with housework and with site-specific patterns of cooking. The number of objective hot flash measures did not differ, but differences in subjective experience suggest the influence of culture. © 2016 Wiley Periodicals, Inc.

Phenomenology of the sound-induced flash illusion.

PubMed

Abadi, Richard V; Murphy, Jonathan S

2014-07-01

Past studies, using pairings of auditory tones and visual flashes, which were static and coincident in space but variable in time, demonstrated errors in judging the temporal patterning of the visual flashes-the sound-induced flash illusion. These errors took one of the two forms: under-reporting (sound-induced fusion) or over-reporting (sound-induced fission) of the flash numbers. Our study had three objectives: to examine the robustness of both illusions and to consider the effects of stimulus set and response bias. To this end, we used an extended range of fixed spatial location flash-tone pairings, examined stimuli that were variable in space and time and measured confidence in judging flash numbers. Our results indicated that the sound-induced flash illusion is a robust percept, a finding underpinned by the confidence measures. Sound-induced fusion was found to be more robust than sound-induced fission and a most likely outcome when high numbers of flashes were incorporated within an incongruent flash-tone pairing. Conversely, sound-induced fission was the most likely outcome for the flash-tone pairing which contained two flashes. Fission was also shown to be strongly driven by stimuli confounds such as categorical boundary conditions (e.g. flash-tone pairings with ≤2 flashes) and compressed response options. These findings suggest whilst both fission and fusion are associated with 'auditory driving', the differences in the occurrence and strength of the two illusions not only reflect the separate neuronal mechanisms underlying audio and visual signal processing, but also the test conditions that have been used to investigate the sound-induced flash illusion.

How self-reported hot flashes may relate to affect, cognitive performance and sleep.

PubMed

Regestein, Quentin; Friebely, Joan; Schiff, Isaac

2015-08-01

To explain the controversy about whether midlife women who self-report hot flashes have relatively increased affective symptoms, poor cognitive performance or worse sleep. Retrospective data from 88 women seeking relief from bothersome day and night hot flashes were submitted to mixed linear regression modeling to find if estimated hot flashes, as measured by Women's Health Questionnaire (WHQ) items, or diary-documented hot flashes recorded daily, were associated with each other, or with affective, cognitive or sleep measures. Subjects averaged 6.3 daytime diary-documented hot flashes and 2.4 nighttime diary-documented hot flashes per 24h. Confounder-controlled diary-documented hot flashes but not estimated hot flashes were associated with increased Leeds anxiety scores (F=4.9; t=2.8; p=0.01) and Leeds depression scores (3.4; 2.5; 0.02), decreased Stroop Color-Word test performance (9.4; 3.5; 0.001), increased subjective sleep disturbance (effect size=0.83) and increased objective sleep disturbance (effect size=0.35). Hot flash effects were small to moderate in size. Univariate but not multivariate analyses revealed that all hot flash measures were associated with all affect measures. Different measures of hot flashes associated differently with affect, cognition and sleep. Only nighttime diary-document hot flash consistently correlated with any affect measures in multivariate analyses. The use of differing measures for hot flashes, affect, cognition and sleep may account for the continually reported inconsistencies in menopause study outcomes. This problem impedes forging a consensus on whether hot flashes correlate with neuropsychological symptoms. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Susceptibility to the Flash-Beep Illusion Is Increased in Children Compared to Adults

ERIC Educational Resources Information Center

Innes-Brown, Hamish; Barutchu, Ayla; Shivdasani, Mohit N.; Crewther, David P.; Grayden, David B.; Paolini, Antonio

2011-01-01

Audio-visual integration was studied in children aged 8-17 (N = 30) and adults (N = 22) using the "flash-beep illusion" paradigm, where the presentation of two beeps causes a single flash to be perceived as two flashes ("fission" illusion), and a single beep causes two flashes to be perceived as one flash ("fusion" illusion). Children reported…

Global Patterns of Lightning Properties Derived by OTD and LIS

NASA Technical Reports Server (NTRS)

Beirle, Steffen; Koshak, W.; Blakeslee, R.; Wagner, T.

2014-01-01

The satellite instruments Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) provide unique empirical data about the frequency of lightning flashes around the globe (OTD), and the tropics (LIS), which 5 has been used before to compile a well received global climatology of flash rate densities. Here we present a statistical analysis of various additional lightning properties derived from OTD/LIS, i.e. the number of so-called "events" and "groups" per flash, as well as 10 the mean flash duration, footprint and radiance. These normalized quantities, which can be associated with the flash "strength", show consistent spatial patterns; most strikingly, oceanic flashes show higher values than continental flashes for all properties. Over land, regions with high (Eastern US) 15 and low (India) flash strength can be clearly identified. We discuss possible causes and implications of the observed regional differences. Although a direct quantitative interpretation of the investigated flash properties is difficult, the observed spatial patterns provide valuable information for the 20 interpretation and application of climatological flash rates. Due to the systematic regional variations of physical flash characteristics, viewing conditions, and/or measurement sensitivities, parametrisations of lightning NOx based on total flash rate densities alone are probably affected by regional biases.

Investigations in x-radiation stimulation

NASA Astrophysics Data System (ADS)

Gupta, K. D.

1982-03-01

The objective is to invent a crystal x-ray laser. Investigations in the Radiation Research Lab. at Texas Tech University have established in a very straightforward way the line narrowing associated with a threshold pumping and a nonlinear rise in intensity. Recent work on x-ray Borrmann channeling via monocrystals has demonstrated the existence of a monochromatic x-ray beam without any vertical divergence. This would allow the transport of x-ray energy in space for thousands of miles without any loss of power. Preliminary experiments with a monocrystal excited by pulsed x-rays at Air Force Weapons Laboratory, KAFB, Albuquerque, seem to indicate a gain in intensity of the nondivergent hot spot with a concomitant fading of the regular Laue pattern. Current investigations in this line indicates that with proper doping of the monocrystal the nondivergent beam could be increased in intensity using a flash x-ray tube to pump the doped monocrystal. A concial target double beam flash x-ray line source instrument has been constructed to obtain a beam of nondivergent, stimulated, coherent, and monochromatic x-rays from doped monocrystals. A generation of stimulated x-rays using bunched electrons from pulsed high power klystron striking a monocrystal has been conceived.

Cavitation bubble nucleation induced by shock-bubble interaction in a gelatin gel

NASA Astrophysics Data System (ADS)

Oguri, Ryota; Ando, Keita

2018-05-01

An optical visualization technique is developed to study cavitation bubble nucleation that results from interaction between a laser-induced shock and a preexisting gas bubble in a 10 wt. % gelatin gel; images of the nucleated cavitation bubbles are captured and the cavitation inception pressure is determined based on Euler flow simulation. A spherical gas cavity is generated by focusing an infrared laser pulse into a gas-supersaturated gel and the size of the laser-generated bubble in mechanical equilibrium is tuned via mass transfer of the dissolved gas into the bubble. A spherical shock is then generated, through rapid expansion of plasma induced by the laser focusing, in the vicinity of the gas bubble. The shock-bubble interaction is recorded by a CCD camera with flash illumination of a nanosecond green laser pulse. The observation captures cavitation inception in the gel under tension that results from acoustic impedance mismatching at the bubble interface interacting with the shock. We measure the probability of cavitation inception from a series of the repeated experiments, by varying the bubble radius and the standoff distance. The threshold pressure is defined at the cavitation inception probability equal to one half and is calculated, through comparisons to Euler flow simulation, at -24.4 MPa. This threshold value is similar to that from shock-bubble interaction experiments using water, meaning that viscoelasticity of the 10 wt. % gelatin gel has a limited impact on bubble nucleation dynamics.

Pulsed Laser Techniques to Determine Lattice and Radiative Thermal Conductivity of Deep Planetary Materials at Extreme Pressure-Temperature Conditions

NASA Astrophysics Data System (ADS)

Lobanov, S.; Goncharov, A. F.; Holtgrewe, N.; Konopkova, Z.; McWilliams, R. S.

2017-12-01

Thermal conductivity of deep planetary materials determines the planetary heat transport mode and properties (e.g. magnetic field) and can be used to decipher the planetary thermal history. Due to the lack of direct measurements of the lattice and radiative conductivity of the relevant materials at the planetary conditions, the current geodynamical models use theoretical calculations and extrapolations of the available experimental data. Here we describe our pulsed laser techniques that enable direct measurements of the lattice and radiative lattice conductivity of the Earth's mantle and core materials and also of noble gases and simple molecules present in the interiors of giant planets (e.g. hydrogen). Flash heating laser techniques working in a pump-probe mode that include time resolved two-side radiative and thermoreflection temperature probes employ various laser and photo-detector configurations, which provide a measure of the thermal fluxes propagating through the samples confined in the diamond anvil cell cavity. A supercontinuum ultra-bright broadband laser source empower accurate measurements of the optical properties of planetary materials used to extract the radiative conductivity. Finite element calculations serve to extract the temperature and pressure dependent thermal conductivity and temperature gradients across the sample. We report thermal conductivity measurements of the Earth's minerals (postperovskite, bridgmanite, ferropericlase) and their assemblies (pyrolite) and core materials (Fe and alloys with Si and O) at the realistic deep Earth's pressure temperature conditions. We thank J.-F.Lin, M. Murakami, J. Badro for contributing to this work.

Characteristics of Lightning Within Electrified Snowfall Events Using Lightning Mapping Arrays

NASA Astrophysics Data System (ADS)

Schultz, Christopher J.; Lang, Timothy J.; Bruning, Eric C.; Calhoun, Kristin M.; Harkema, Sebastian; Curtis, Nathan

2018-02-01

This study examined 34 lightning flashes within four separate thundersnow events derived from lightning mapping arrays (LMAs) in northern Alabama, central Oklahoma, and Washington DC. The goals were to characterize the in-cloud component of each lightning flash, as well as the correspondence between the LMA observations and lightning data taken from national lightning networks like the National Lightning Detection Network (NLDN). Individual flashes were examined in detail to highlight several observations within the data set. The study results demonstrated that the structures of these flashes were primarily normal polarity. The mean area encompassed by this set of flashes is 375 km2, with a maximum flash extent of 2,300 km2, a minimum of 3 km2, and a median of 128 km2. An average of 2.29 NLDN flashes were recorded per LMA-derived lightning flash. A maximum of 11 NLDN flashes were recorded in association with a single LMA-derived flash on 10 January 2011. Additionally, seven of the 34 flashes in the study contain zero NLDN-identified flashes. Eleven of the 34 flashes initiated from tall human-made objects (e.g., communication towers). In at least six lightning flashes, the NLDN detected a return stroke from the cloud back to the tower and not the initial upward leader. This study also discusses lightning's interaction with the human-built environment and provides an example of lightning within heavy snowfall observed by Geostationary Operational Environmental Satellite-16's Geostationary Lightning Mapper.

Hot flashes in breast cancer survivors: Frequency, severity and impact.

PubMed

Chang, Hao-Yuan; Jotwani, Aparna C; Lai, Yeur-Hur; Jensen, Mark P; Syrjala, Karen L; Fann, Jesse R; Gralow, Julie

2016-06-01

To (1) determine the frequency and severity of hot flashes, (2) examine the associations between hot flash frequency and severity and quality of life, and (3) identify the predictors of hot flash activity in breast cancer survivors. The study used a cross-sectional design and mailed survey of 253 breast cancer survivors recruited from a cancer wellness clinic. Participants provided information regarding cancer history, hot flashes, pain intensity, sleep problems, physical functioning, and psychological functioning. About half of the survivors reported at least one hot flash in the past 24 h (45%) or past week (52%). The average frequency of hot flashes was 1.9 in the past 24 h and 1.8 in the past week. Hot flash severity was usually mild or asymptomatic. However, participants with hot flashes reported significantly more sleep problems and higher pain severity than those reporting no hot flashes. Moreover, the severity of hot flashes was associated with more sleep problems, higher pain severity, and more psychological dysfunction. History of hormonal suppression therapy and younger age predicted hot flash activity in the study sample. In breast cancer survivors, hot flashes are common and are associated with unpleasant symptoms and poor quality of life. Research is needed to determine if treatments that reduce the frequency and severity of hot flashes in breast cancer survivors also result in improvements in symptoms such as sleep problems, pain, and psychological dysfunction. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hot flashes in breast cancer survivors: Frequency, severity and impact

PubMed Central

Chang, Hao-Yuan; Jotwani, Aparna C.; Lai, Yeur-Hur; Jensen, Mark P.; Syrjala, Karen L.; Fann, Jesse R.; Gralow, Julie

2018-01-01

Purposes To (1) determine the frequency and severity of hot flashes, (2) examine the associations be- tween hot flash frequency and severity and quality of life, and (3) identify the predictors of hot flash activity in breast cancer survivors. Methods The study used a cross-sectional design and mailed survey of 253 breast cancer survivors recruited from a cancer wellness clinic. Participants provided information regarding cancer history, hot flashes, pain intensity, sleep problems, physical functioning, and psychological functioning. Results About half of the survivors reported at least one hot flash in the past 24 h (45%) or past week (52%). The average frequency of hot flashes was 1.9 in the past 24 h and 1.8 in the past week. Hot flash severity was usually mild or asymptomatic. However, participants with hot flashes reported significantly more sleep problems and higher pain severity than those reporting no hot flashes. Moreover, the severity of hot flashes was associated with more sleep problems, higher pain severity, and more psychological dysfunction. History of hormonal suppression therapy and younger age predicted hot flash activity in the study sample. Conclusions In breast cancer survivors, hot flashes are common and are associated with unpleasant symptoms and poor quality of life. Research is needed to determine if treatments that reduce the frequency and severity of hot flashes in breast cancer survivors also result in improvements in symptoms such as sleep problems, pain, and psychological dysfunction. PMID:27065357

Characteristics of Lightning within Electrified Snowfall Events using Lightning Mapping Arrays.

PubMed

Schultz, Christopher J; Lang, Timothy J; Bruning, Eric C; Calhoun, Kristin M; Harkema, Sebastian; Curtis, Nathan

2018-02-27

This study examined 34 lightning flashes within four separate thundersnow events derived from lightning mapping arrays (LMAs) in northern Alabama, central Oklahoma, and Washington DC. The goals were to characterize the in-cloud component of each lightning flash, as well as the correspondence between the LMA observations and lightning data taken from national lightning networks like the National Lightning Detection Network (NLDN). Individual flashes were examined in detail to highlight several observations within the dataset. The study results demonstrated that the structures of these flashes were primarily normal polarity. The mean area encompassed by this set of flashes is 375 km 2 , with a maximum flash extent of 2300 km 2 , a minimum of 3 km 2 , and a median of 128 km 2 . An average of 2.29 NLDN flashes were recorded per LMA-derived lightning flash. A maximum of 11 NLDN flashes were recorded in association with a single LMA-derived flash on 10 January 2011. Additionally, seven of the 34 flashes in the study contain zero NLDN identified flashes. Eleven of the 34 flashes initiated from tall human-made objects (e.g., communication towers). In at least six lightning flashes, the NLDN detected a return stroke from the cloud back to the tower and not the initial upward leader. This study also discusses lightning's interaction with the human built environment and provides an example of lightning within heavy snowfall observed by GOES-16's Geostationary Lightning Mapper.

Cross-bridge kinetics, cooperativity, and negatively strained cross- bridges in vertebrate smooth muscle. A laser-flash photolysis study

PubMed Central

1988-01-01

The effects of laser-flash photolytic release of ATP from caged ATP [P3- 1(2-nitrophenyl)ethyladenosine-5'-triphosphate] on stiffness and tension transients were studied in permeabilized guinea pig protal vein smooth muscle. During rigor, induced by removing ATP from the relaxed or contracting muscles, stiffness was greater than in relaxed muscle, and electron microscopy showed cross-bridges attached to actin filaments at an approximately 45 degree angle. In the absence of Ca2+, liberation of ATP (0.1-1 mM) into muscles in rigor caused relaxation, with kinetics indicating cooperative reattachment of some cross- bridges. Inorganic phosphate (Pi; 20 mM) accelerated relaxation. A rapid phase of force development, accompanied by a decline in stiffness and unaffected by 20 mM Pi, was observed upon liberation of ATP in muscles that were released by 0.5-1.0% just before the laser pulse. This force increment observed upon detachment suggests that the cross- bridges can bear a negative tension. The second-order rate constant for detachment of rigor cross-bridges by ATP, in the absence of Ca2+, was estimated to be 0.1-2.5 X 10(5) M-1s-1, which indicates that this reaction is too fast to limit the rate of ATP hydrolysis during physiological contractions. In the presence of Ca2+, force development occurred at a rate (0.4 s-1) similar to that of intact, electrically stimulated tissue. The rate of force development was an order of magnitude faster in muscles that had been thiophosphorylated with ATP gamma S before the photochemical liberation of ATP, which indicates that under physiological conditions, in non-thiophosphorylated muscles, light-chain phosphorylation, rather than intrinsic properties of the actomyosin cross-bridges, limits the rate of force development. The release of micromolar ATP or CTP from caged ATP or caged CTP caused force development of up to 40% of maximal active tension in the absence of Ca2+, consistent with cooperative attachment of cross-bridges. Cooperative reattachment of dephosphorylated cross-bridges may contribute to force maintenance at low energy cost and low cross-bridge cycling rates in smooth muscle. PMID:3373178

A high-resolution, confocal laser-scanning microscope and flash photolysis system for physiological studies.

PubMed

Parker, I; Callamaras, N; Wier, W G

1997-06-01

We describe the construction of a high-resolution confocal laser-scanning microscope, and illustrate its use for studying elementary Ca2+ signalling events in cells. An avalanche photodiode module and simple optical path provide a high efficiency system for detection of fluorescence signals, allowing use of a small confocal aperture giving near diffraction-limited spatial resolution (< 300 nm lateral and < 400 nm axial). When operated in line-scan mode, the maximum temporal resolution is 1 ms, and the associated computer software allows complete flexibility to record line-scans continuously for long (minutes) periods or to obtain any desired pixel resolution in x-y scans. An independent UV irradiation system permits simultaneous photolysis of caged compounds over either a uniform, wide field (arc lamp source) or at a tightly focussed spot (frequency-tripled Nd:YAG laser). The microscope thus provides a versatile tool for optical studies of dynamic cellular processes, as well as excellent resolution for morphological studies. The confocal scanner can be added to virtually any inverted microscope for a component cost that is only a small fraction of that of comparable commercial instruments, yet offers better performance and greater versatility.

Magnitude of the impact of hot flashes on sleep in perimenopausal women

PubMed Central

de Zambotti, Massimiliano; Colrain, Ian M.; Javitz, Harold S.; Baker, Fiona C.

2014-01-01

Objective To quantify the impact of objectively-recorded hot flashes on objective sleep in perimenopausal women. Design Cross-sectional study. Participants underwent 1–5 laboratory-based polysomnographic recordings for a total of 63 nights, including sternal skin conductance measures, from which 222 hot flashes were identified according to established criteria. Data were analyzed with hierarchical mixed-effect models and Spearman correlations. Setting Sleep laboratory. Patients 34 perimenopausal women (Age±SD:50.4±2.7y). Intervention None. Main Outcome Measures Perceived and polysomnographic sleep measures (sleep quality, amount of wake after sleep onset and number of awakenings). Subjective (frequency and bother) and objective (frequency and amount of hot flash-associated wake time) hot flash measures. Results Women had an average of 3.5 (95%CI:2.8–4.2, range=1– 9) objective hot flashes per night. 69.4% of hot flashes were associated with an awakening. Hot flash-associated wake time per night was, on average, 16.6 min (95%CI:10.8–22.4), which accounted for 27.2% (SD 27.1) of total wakefulness per night. Hot flash-associated wake, but not frequency, was negatively associated with sleep efficiency and positively associated with wake after sleep onset. Also, self-reported wakefulness correlated with hot flash-associated wake, suggesting that women’s estimates of wakefulness are influenced by the amount of time spent awake in association with hot flashes during the night. More perceived and bothersome hot flashes correlated with more perceived wakefulness and awakenings and more objective hot flash-associated wake time and hot flash frequency. Conclusions The presence of physiological hot flashes accounts for a significant proportion of total objective wakefulness during the night in perimenopausal women. PMID:25256933

Adiposity and Hot Flashes in Midlife Women: A Modifying Role of Age

PubMed Central

Santoro, Nanette; Matthews, Karen A.

2011-01-01

Background: The nature of the relationship between adiposity and hot flashes has been debated, but it has not been examined using physiological measures of hot flashes. We examined associations between body size/composition and physiologically assessed hot flashes among women with hot flashes. Methods: A subcohort of women in the Study of Women's Health Across the Nation (n = 52; 25 African-American and 27 non-Hispanic Caucasian; ages, 54 to 63 yr) who reported hot flashes, had their uterus and ovaries, and were not taking medications impacting hot flashes were recruited in 2008–2009. Women completed anthropometric measures [bioimpedance analysis of total percentage of body fat, body mass index (BMI), waist circumference], a blood draw (estradiol, SHBG, FSH, dehydroepiandrosterone sulfate), and 4 d of ambulatory sternal skin conductance monitoring with diary (physiological and reported hot flashes, respectively). Associations between anthropometrics and hot flashes were estimated with generalized estimating equations with covariates age, race, and anxiety. Results: Higher BMI (odds ratio, 0.97; 95% confidence interval, 0.94–0.99; P < 0.05) and waist circumference (odds ratio, 0.98; 95% confidence interval, 0.97–0.99; P < 0.01) were associated with fewer physiological hot flashes. Interactions by age (P < 0.05) indicated that inverse associations of body fat, BMI, and waist circumference with hot flashes were most apparent among the oldest women in the sample. Estradiol and SHBG reduced but did not eliminate age-related variations in relations between body size/composition and hot flashes. Conclusion: Higher adiposity was associated with fewer physiological hot flashes among older women with hot flashes. A modifying role of age must be considered in understanding the role of adiposity in hot flashes. PMID:21778220

Adiposity and hot flashes in midlife women: a modifying role of age.

PubMed

Thurston, Rebecca C; Santoro, Nanette; Matthews, Karen A

2011-10-01

The nature of the relationship between adiposity and hot flashes has been debated, but it has not been examined using physiological measures of hot flashes. We examined associations between body size/composition and physiologically assessed hot flashes among women with hot flashes. A subcohort of women in the Study of Women's Health Across the Nation (n = 52; 25 African-American and 27 non-Hispanic Caucasian; ages, 54 to 63 yr) who reported hot flashes, had their uterus and ovaries, and were not taking medications impacting hot flashes were recruited in 2008-2009. Women completed anthropometric measures [bioimpedance analysis of total percentage of body fat, body mass index (BMI), waist circumference], a blood draw (estradiol, SHBG, FSH, dehydroepiandrosterone sulfate), and 4 d of ambulatory sternal skin conductance monitoring with diary (physiological and reported hot flashes, respectively). Associations between anthropometrics and hot flashes were estimated with generalized estimating equations with covariates age, race, and anxiety. Higher BMI (odds ratio, 0.97; 95% confidence interval, 0.94-0.99; P < 0.05) and waist circumference (odds ratio, 0.98; 95% confidence interval, 0.97-0.99; P < 0.01) were associated with fewer physiological hot flashes. Interactions by age (P < 0.05) indicated that inverse associations of body fat, BMI, and waist circumference with hot flashes were most apparent among the oldest women in the sample. Estradiol and SHBG reduced but did not eliminate age-related variations in relations between body size/composition and hot flashes. Higher adiposity was associated with fewer physiological hot flashes among older women with hot flashes. A modifying role of age must be considered in understanding the role of adiposity in hot flashes.

Initial Breakdown Pulse Amplitudes in Intracloud and Cloud-to-Ground Lightning Flashes

NASA Astrophysics Data System (ADS)

Marshall, T. C.; Smith, E. M.; Stolzenburg, M.; Karunarathne, S.; Siedlecki, R. D., II

2017-12-01

This study analyzes the largest initial breakdown (IB) pulse in flashes from three storms in Florida. The study was motivated in part by the possibility that IB pulses of IC flashes may cause of terrestrial gamma-ray flashes (TGFs). The range-normalized, zero-to-peak amplitude of the largest IB pulse within each flash was determined along with its altitude, duration, and occurrence time in the flash. Appropriate data were available for 40 intracloud (IC) and 32 cloud-to-ground (CG) flashes. Histograms of the magnitude of the largest IB pulse amplitude by flash type were similar, with mean (median) values of 1.49 (1.05) V/m for IC flashes and -1.35 (-0.87) V/m for CG flashes. The mean amplitude of the largest IC IB pulses are substantially smaller (roughly an order of magnitude smaller) than the few known pulse amplitudes of TGF events and TGF candidate events. The largest IB pulse in 30 IC flashes showed a weak inverse relation between pulse amplitude and altitude. Amplitude of the largest IB pulse for 25 CG flashes showed no altitude correlation. Duration of the largest IB pulse in ICs averaged twice as long as in CGs (96 μs versus 46 μs); all of the CG durations were <100 μs. Among the ICs, there is a positive relation between largest IB pulse duration and amplitude; the linear correlation coefficient is 0.385 with outliers excluded. The largest IB pulse in IC flashes typically occurred at a longer time after the first IB pulse (average 4.1 ms) than was the case in CG flashes (average 0.6 ms). In both flash types, the largest IB pulse was the first IB pulse in about 30% of the cases.

SUMO regulates proteasome-dependent degradation of FLASH/Casp8AP2

PubMed Central

Vennemann, Astrid; Hofmann, Thomas G.

2013-01-01

FLASH/Casp8AP2 is a huge multifunctional protein involved in multiple cellular processes, reaching from death receptor signaling to regulation of histone gene transcription and histone mRNA processing. Previous work has shown that FLASH localizes to Cajal bodies and promyelocytic leukemia (PML) bodies. However, the function of its nuclear body association remains unclear. Here we demonstrate that murine FLASH is covalently modified by SUMO at Lys residue 1792. Interestingly, ectopic expression of SUMO results in proteasome-dependent degradation of FLASH. A point mutant of FLASH with a mutated SUMO acceptor lysine residue, FLASHK1792R, is resistant to SUMO-induced degradation. Finally, we show that arsenic trioxide, a drug known to potentiate SUMO modification and degradation of PML, triggers recruitment of FLASH to PML bodies and concomitant loss of FLASH protein. Our data suggest that SUMO targets FLASH for proteasome-dependent degradation, which is associated with recruitment of FLASH to PML bodies. PMID:23673342

The October 2014 United States Treasury bond flash crash and the contributory effect of mini flash crashes

PubMed Central

Levine, Zachary S.; Floridi, Luciano

2017-01-01

We investigate the causal uncertainty surrounding the flash crash in the U.S. Treasury bond market on October 15, 2014, and the unresolved concern that no clear link has been identified between the start of the flash crash at 9:33 and the opening of the U.S. equity market at 9:30. We consider the contributory effect of mini flash crashes in equity markets, and find that the number of equity mini flash crashes in the three-minute window between market open and the Treasury Flash Crash was 2.6 times larger than the number experienced in any other three-minute window in the prior ten weekdays. We argue that (a) this statistically significant finding suggests that mini flash crashes in equity markets both predicted and contributed to the October 2014 U.S. Treasury Bond Flash Crash, and (b) mini-flash crashes are important phenomena with negative externalities that deserve much greater scholarly attention. PMID:29091931

Excited triplet state of N-(9-methylpurin-6-yl)pyridinium cation as an efficient photosensitizer in the oxidation of sulfur-containing amino acids. Laser flash and steady-state photolysis studies

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

Marciniak, B.; Hug, G.L.; Bobrowski, K.

1995-01-11

In this paper, we present and discuss the results of a detailed mechanistic study of the photosensitized oxidation of sulfur-containing amino acids by N-(9-methylpurin-6-yl)pyridinium cations in aqueous solution. The results provide data on the photoreactivity of the pyridinium salts (derived from the purine bases) in the presence of the electron donors such as sulfur-containing organic compounds and give new experimental evidence for the general mechanism of the sensitized photooxidation of thioethers proposed previously. 39 refs., 6 figs., 2 tabs.

Analysis and Testing of a LIDAR-Based Approach to Terrain Relative Navigation for Precise Lunar Landing

NASA Technical Reports Server (NTRS)

Johnson, Andrew E.; Ivanov, Tonislav I.

2011-01-01

To increase safety and land near pre-deployed resources, future NASA missions to the moon will require precision landing. A LIDAR-based terrain relative navigation (TRN) approach can achieve precision landing under any lighting conditions. This paper presents results from processing flash lidar and laser altimeter field test data that show LIDAR TRN can obtain position estimates less than 90m while automatically detecting and eliminating incorrect measurements using internal metrics on terrain relief and data correlation. Sensitivity studies show that the algorithm has no degradation in matching performance with initial position uncertainties up to 1.6 km

The protective effect of salicylic acid on lysozyme against riboflavin-mediated photooxidation

NASA Astrophysics Data System (ADS)

Li, Kun; Wang, Hongbao; Cheng, Lingli; Zhu, Hui; Wang, Mei; Wang, Shi-Long

2011-06-01

As a metabolite of aspirin in vivo, salicylic acid was proved to protect lysozyme from riboflavin-mediated photooxidation in this study. The antioxidative properties of salicylic acid were further studied by using time-resolved laser flash photolysis of 355 nm. It can quench the triplet state of riboflavin via electron transfer from salicylic acid to the triplet state of riboflavin with a reaction constant of 2.25 × 10 9 M -1 s -1. Mechanism of antioxidant activities of salicylic acid on lysozyme oxidation was discussed. Salicylic acid can serve as a potential antioxidant to quench the triplet state of riboflavin and reduce oxidative pressure.

PIAS1 interacts with FLASH and enhances its co-activation of c-Myb

PubMed Central

2011-01-01

Background FLASH is a huge nuclear protein involved in various cellular functions such as apoptosis signalling, NF-κB activation, S-phase regulation, processing of histone pre-mRNAs, and co-regulation of transcription. Recently, we identified FLASH as a co-activator of the transcription factor c-Myb and found FLASH to be tightly associated with active transcription foci. As a huge multifunctional protein, FLASH is expected to have many interaction partners, some which may shed light on its function as a transcriptional regulator. Results To find additional FLASH-associated proteins, we performed a yeast two-hybrid (Y2H) screening with FLASH as bait and identified the SUMO E3 ligase PIAS1 as an interaction partner. The association appears to involve two distinct interaction surfaces in FLASH. We verified the interaction by Y2H-mating, GST pulldowns, co-IP and ChIP. FLASH and PIAS1 were found to co-localize in nuclear speckles. Functional assays revealed that PIAS1 enhances the intrinsic transcriptional activity of FLASH in a RING finger-dependent manner. Furthermore, PIAS1 also augments the specific activity of c-Myb, and cooperates with FLASH to further co-activate c-Myb. The three proteins, FLASH, PIAS1, and c-Myb, are all co-localized with active RNA polymerase II foci, resembling transcription factories. Conclusions We conclude that PIAS1 is a common partner for two cancer-related nuclear factors, c-Myb and FLASH. Our results point to a functional cooperation between FLASH and PIAS1 in the enhancement of c-Myb activity in active nuclear foci. PMID:21338522

"Know What to Do If You Encounter a Flash Flood": Mental Models Analysis for Improving Flash Flood Risk Communication and Public Decision Making.

PubMed

Lazrus, Heather; Morss, Rebecca E; Demuth, Julie L; Lazo, Jeffrey K; Bostrom, Ann

2016-02-01

Understanding how people view flash flood risks can help improve risk communication, ultimately improving outcomes. This article analyzes data from 26 mental models interviews about flash floods with members of the public in Boulder, Colorado, to understand their perspectives on flash flood risks and mitigation. The analysis includes a comparison between public and professional perspectives by referencing a companion mental models study of Boulder-area professionals. A mental models approach can help to diagnose what people already know about flash flood risks and responses, as well as any critical gaps in their knowledge that might be addressed through improved risk communication. A few public interviewees mentioned most of the key concepts discussed by professionals as important for flash flood warning decision making. However, most interviewees exhibited some incomplete understandings and misconceptions about aspects of flash flood development and exposure, effects, or mitigation that may lead to ineffective warning decisions when a flash flood threatens. These include important misunderstandings about the rapid evolution of flash floods, the speed of water in flash floods, the locations and times that pose the greatest flash flood risk in Boulder, the value of situational awareness and environmental cues, and the most appropriate responses when a flash flood threatens. The findings point to recommendations for ways to improve risk communication, over the long term and when an event threatens, to help people quickly recognize and understand threats, obtain needed information, and make informed decisions in complex, rapidly evolving extreme weather events such as flash floods. © 2015 Society for Risk Analysis.

Hot Flashes and Carotid Intima Media Thickness among Midlife Women

PubMed Central

Thurston, Rebecca C.; Sutton-Tyrrell, Kim; Everson-Rose, Susan A.; Hess, Rachel; Powell, Lynda H.; Matthews, Karen A.

2010-01-01

Objective Emerging evidence suggests associations between menopausal hot flashes and cardiovascular risk. Whether hot flashes are associated with intima media thickness (IMT) or IMT changes over time is unknown. We hypothesized that reported hot flashes would be associated with greater IMT cross-sectionally and with greater IMT progression over two years. Methods Participants were 432 women ages 45-58 at baseline participating in SWAN Heart, an ancillary study to the Study of Women's Health Across the Nation. Measures at the SWAN Heart baseline and follow-up visit two years later included a carotid artery ultrasound, reported hot flashes (past two weeks: none, 1-5, ≥6 days), and a blood sample for measurement of estradiol. Results Women reporting hot flashes ≥6 days in the prior two weeks had significantly higher IMT than women without hot flashes at baseline (mean difference(SE), mm =0.02(0.01), p=0.03) and follow-up (mean difference(SE), mm =0.02(0.01), p=0.04) visits, controlling for demographic factors and cardiovascular risk factors. Reporting hot flashes at both study visits was associated with higher follow-up IMT relative to reporting hot flashes at neither visit (mean difference(SE), mm=0.03(0.01), p=0.03). Associations between hot flashes and IMT largely remained after adjusting for estradiol. An interaction between hot flashes and obesity status was observed (p=0.05) such that relations between hot flashes and IMT were observed principally among overweight/obese women. Hot flashes were not associated with IMT progression. Conclusions These findings provided some indication that women reporting hot flashes ≥6 days in the prior two weeks may have higher IMT than women without hot flashes, particularly for women who are overweight or obese. Further work should determine whether hot flashes mark adverse underlying vascular changes. PMID:21242820

50 CFR 600.730 - Facilitation of enforcement.

Code of Federal Regulations, 2011 CFR

2011-10-01

... transmitted by flashing light directed at the vessel signaled. USCG units will normally use the flashing light... your vessel instantly.” (Period (.) means a short flash of light; dash (-) means a long flash of light... authorized officer using loudhailer, radiotelephone, flashing light signal, or other means constitutes prima...

50 CFR 600.730 - Facilitation of enforcement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... transmitted by flashing light directed at the vessel signaled. USCG units will normally use the flashing light... your vessel instantly.” (Period (.) means a short flash of light; dash (-) means a long flash of light... authorized officer using loudhailer, radiotelephone, flashing light signal, or other means constitutes prima...

49 CFR 234.217 - Flashing light units.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Flashing light units. 234.217 Section 234.217..., Inspection, and Testing Maintenance Standards § 234.217 Flashing light units. (a) Each flashing light unit.... (b) Each flashing light unit shall be maintained to prevent dust and moisture from entering the...

49 CFR 234.217 - Flashing light units.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Flashing light units. 234.217 Section 234.217..., Inspection, and Testing Maintenance Standards § 234.217 Flashing light units. (a) Each flashing light unit.... (b) Each flashing light unit shall be maintained to prevent dust and moisture from entering the...

Lunar Impact Flash Locations

NASA Technical Reports Server (NTRS)

Moser, D. E.; Suggs, R. M.; Kupferschmidt, L.; Feldman, J.

2015-01-01

A bright impact flash detected by the NASA Lunar Impact Monitoring Program in March 2013 brought into focus the importance of determining the impact flash location. A process for locating the impact flash, and presumably its associated crater, was developed using commercially available software tools. The process was successfully applied to the March 2013 impact flash and put into production on an additional 300 impact flashes. The goal today: provide a description of the geolocation technique developed.

FLASH Interface; a GUI for managing runtime parameters in FLASH simulations

NASA Astrophysics Data System (ADS)

Walker, Christopher; Tzeferacos, Petros; Weide, Klaus; Lamb, Donald; Flocke, Norbert; Feister, Scott

2017-10-01

We present FLASH Interface, a novel graphical user interface (GUI) for managing runtime parameters in simulations performed with the FLASH code. FLASH Interface supports full text search of available parameters; provides descriptions of each parameter's role and function; allows for the filtering of parameters based on categories; performs input validation; and maintains all comments and non-parameter information already present in existing parameter files. The GUI can be used to edit existing parameter files or generate new ones. FLASH Interface is open source and was implemented with the Electron framework, making it available on Mac OSX, Windows, and Linux operating systems. The new interface lowers the entry barrier for new FLASH users and provides an easy-to-use tool for experienced FLASH simulators. U.S. Department of Energy (DOE), NNSA ASC/Alliances Center for Astrophysical Thermonuclear Flashes, U.S. DOE NNSA ASC through the Argonne Institute for Computing in Science, U.S. National Science Foundation.

OTD Observations of Continental US Ground and Cloud Flashes

NASA Technical Reports Server (NTRS)

Koshak, William

2007-01-01

Lightning optical flash parameters (e.g., radiance, area, duration, number of optical groups, and number of optical events) derived from almost five years of Optical Transient Detector (OTD) data are analyzed. Hundreds of thousands of OTD flashes occurring over the continental US are categorized according to flash type (ground or cloud flash) using US National Lightning Detection Network TM (NLDN) data. The statistics of the optical characteristics of the ground and cloud flashes are inter-compared on an overall basis, and as a function of ground flash polarity. A standard two-distribution hypothesis test is used to inter-compare the population means of a given lightning parameter for the two flash types. Given the differences in the statistics of the optical characteristics, it is suggested that statistical analyses (e.g., Bayesian Inference) of the space-based optical measurements might make it possible to successfully discriminate ground and cloud flashes a reasonable percentage of the time.

Menopausal Hot Flashes and White Matter Hyperintensities

PubMed Central

Thurston, Rebecca C.; Aizenstein, Howard J.; Derby, Carol A.; Sejdić, Ervin; Maki, Pauline M.

2015-01-01

Objective Hot flashes are the classic menopausal symptom. Emerging data links hot flashes to cardiovascular disease (CVD) risk, yet how hot flashes are related to brain health is poorly understood. We examined the relationship between hot flashes - measured via physiologic monitor and self-report - and white matter hyperintensities (WMH) among midlife women. Methods Twenty midlife women ages 40-60 without clinical CVD, with their uterus and both ovaries, and not taking hormone therapy were recruited. Women underwent 24 hours of ambulatory physiologic and diary hot flash monitoring to quantify hot flashes; magnetic resonance imaging to assess WMH burden; 72 hours of actigraphy and questionnaires to quantify sleep; and a blood draw, questionnaires, and physical measures to quantify demographics and CVD risk factors. Test of a priori hypotheses regarding relations between physiologically-monitored and self-reported wake and sleep hot flashes and WMH were conducted in linear regression models. Results More physiologically-monitored hot flashes during sleep were associated with greater WMH, controlling for age, race, and body mass index [beta(standard error)=.0002 (.0001), p=.03]. Findings persisted controlling for sleep characteristics and additional CVD risk factors. No relations were observed for self-reported hot flashes. Conclusions More physiologically-monitored hot flashes during sleep were associated with greater WMH burden among midlife women free of clinical CVD. Results suggest that relations between hot flashes and CVD risk observed in the periphery may extend to the brain. Future work should consider the unique role of sleep hot flashes in brain health. PMID:26057822

Some properties of negative cloud-to-ground flashes from observations of a local thunderstorm based on accurate-stroke-count studies

NASA Astrophysics Data System (ADS)

Zhu, Baoyou; Ma, Ming; Xu, Weiwei; Ma, Dong

2015-12-01

Properties of negative cloud-to-ground (CG) lightning flashes, in terms of number of strokes per flash, inter-stroke intervals and the relative intensity of subsequent and first strokes, were presented by accurate-stroke-count studies based on all 1085 negative flashes from a local thunderstorm. The percentage of single-stroke flashes and stroke multiplicity evolved significantly during the whole life cycle of the study thunderstorm. The occurrence probability of negative CG flashes decreased exponentially with the increasing number of strokes per flash. About 30.5% of negative CG flashes contained only one stroke and number of strokes per flash averaged 3.3. In a subset of 753 negative multiple-stroke flashes, about 41.4% contained at least one subsequent stroke stronger than the corresponding first stroke. Subsequent strokes tended to decrease in strength with their orders and the ratio of subsequent to first stroke peaks presented a geometric mean value of 0.52. Interestingly, negative CG flashes of higher multiplicity tended to have stronger initial strokes. 2525 inter-stroke intervals showed a more or less log-normal distribution and gave a geometric mean value of 62 ms. For CG flashes of particular multiplicity geometric mean inter-stroke intervals tended to decrease with the increasing number of strokes per flash, while those intervals associated with higher order strokes tended to be larger than those associated with low order strokes.

Effect of Escitalopram on Hot Flash Interference: A Randomized, Controlled Trial

PubMed Central

Carpenter, Janet S.; Guthrie, Katherine A.; Larson, Joseph C.; Freeman, Ellen W.; Joffe, Hadine; Reed, Susan D.; Ensrud, Kristine E.; LaCroix, Andrea Z.

2012-01-01

Objectives To estimate the effect of escitalopram 10–20 mg/day versus placebo for reducing hot flash interference in daily life and understand correlates and predictors of reductions in hot flash interference, a key measure of quality of life. Design Multi-site, randomized, double-blind, placebo-controlled clinical trial. Patients 205 midlife women (46% African-American) who met criteria participated. Setting MsFLASH clinical sites in Boston, Indianapolis, Oakland, and Philadelphia. Intervention After baseline, women were randomized to 1 pill of escitalopram 10 mg/day (n=104) or placebo (n=101) with follow-up at 4- and 8-weeks. At week 4, those not achieving 50% fewer hot flashes were increased to 2 pills daily (20 mg/day or 2 placebo pills). Main outcome measures The Hot Flash Related Daily Interference Scale; Correlates were variables from hot flash diaries; Predictors were baseline demographics, clinical variables, depression, anxiety, sleep quality, and hot flashes. Results Compared to placebo, escitalopram significantly reduced hot flash interference by 6.0 points at week 4 and 3.4 points at week 8 more than placebo (p=0.012). Reductions in hot flash interference correlated with changes in hot flash diary variables. However, baseline variables did not significantly predict reductions in hot flash interference. Conclusions Escitalopram 10–20mg/day for 8 weeks improves women’s quality of life and this benefit did not vary by demographic, clinical, mood, sleep, or hot flash variables. PMID:22480818

Improvement in Suppression of Pulsed Nd:YAG Laser Light With Iodine Absorption Cells for Filtered Rayleigh Scattering Measurements

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.; Buggele, Alvin E

1997-01-01

Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10(exp -5) at the 18788.44/cm line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 x 10(exp -3). This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cell and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44/cm are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the cell. Measurements taken with the laser tuned to the center of the iodine absorption line show the light transmitted through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam. A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted laser light. This improvement allows the iodine cell to block significantly more of the stray laser light in filtered Rayleigh scattering experiments. Examples are given of filtered Rayleigh scattering measurements showing the effect of the etalon on measurements taken in a Mach 3 flow in the NASA Lewis 4 inch by 10 inch supersonic wind tunnel.

Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

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

Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno

2013-10-15

The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2–10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., “High power self-pinch diode experiments for radiographic applications” IEEE Trans. Plasma Sci. 35(3), 565–572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567–570]. This generator, made up of a capacitor bank and a Blumlein line, wasmore » initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., “Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV,” Phys. Plasmas 19(9), 093104 (2012)]. The SMP diode which is examined in the present study provides an alternative operating point on the same generator and a different radiographic performance: 142 ± 11 rad at 1 m dose (Al) for a 3.46 ± 0.42 mm spot size (1.4× FWHM of the LSF). This performance is obtained in a reproducible and robust nominal configuration. However, several parametric variations were also tested, such as cathode diameter and anode/cathode gap. They showed that an even better performance is accessible after optimization, in particular, a smaller spot size (<3 mm). Numbers of electrical, optical, and X-ray diagnostics have been implemented in order to gain more insight in the diode physics and to optimize it further. For the first time in France, visible and laser imaging of the SMP diode has been realized, from a radial point of view, thus, providing key information on the electrode plasmas evolution, responsible for the gap closure.« less

Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

NASA Technical Reports Server (NTRS)

Zhao, Z.; Stickel, R. E.; Wine, P. H.

1995-01-01

Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well-known quantum yield for CO production from 248 nm photolysis of phosgene (Cl2CO2). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S((sup 3)P(sub J)) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S((sup 1)D(sub 2)) + OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N2 + N2O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought.

Cardiac autonomic function and hot flashes among perimenopausal and postmenopausal women.

PubMed

Gibson, Carolyn J; Mendes, Wendy Berry; Schembri, Michael; Grady, Deborah; Huang, Alison J

2017-07-01

Abnormalities in autonomic function are posited to play a pathophysiologic role in menopausal hot flashes. We examined relationships between resting cardiac autonomic activity and hot flashes in perimenopausal and postmenopausal women. Autonomic function was assessed at baseline and 12 weeks among perimenopausal and postmenopausal women (n = 121, mean age 53 years) in a randomized trial of slow-paced respiration for hot flashes. Pre-ejection period (PEP), a marker of sympathetic activation, was measured with impedance cardiography. Respiratory sinus arrhythmia (RSA), a marker of parasympathetic activation, was measured with electrocardiography. Participants self-reported hot flash frequency and severity in 7-day symptom diaries. Analysis of covariance models were used to relate autonomic function and hot flash frequency and severity at baseline, and to relate changes in autonomic function to changes in hot flash frequency and severity over 12 weeks, adjusting for age, body mass index, and intervention assignment. PEP was not associated with hot flash frequency or severity at baseline or over 12 weeks (P > 0.05 for all). In contrast, there was a trend toward greater frequency of moderate-to-severe hot flashes with higher RSA at baseline (β = 0.43, P = 0.06), and a positive association between change in RSA and change in frequency of moderate-to-severe hot flashes over 12 weeks (β = 0.63, P = 0.04). Among perimenopausal and postmenopausal women with hot flashes, variations in hot flash frequency and severity were not explained by variations in resting sympathetic activation. Greater parasympathetic activation was associated with more frequent moderate-to-severe hot flashes, which may reflect increased sensitivity to perceiving hot flashes.

Pulsed photoacoustic detection of flash-induced oxygen evolution from intact leaves and its oscillations

PubMed Central

Canaani, Ora; Malkin, Shmuel; Mauzerall, David

1988-01-01

Photoacoustic signals from intact leaves, produced upon excitation with single-turnover flashes, were shown to be dependent on their position in the flash sequence. Compared to the signal obtained from the first flash, all the others were time-shifted and had increased amplitudes. The signal from the third flash had the largest deviation, whereas that from the second flash deviated only minimally. The amplitude difference of the signals relative to that from the first flash was measured at a convenient time point (5 ms) and showed oscillations of period 4, similar to the O2-evolution pattern from algae. These oscillations were strongly damped, tending to a steady state from about the seventh flash on. The extra photoacoustic signal (relative to the first flash) was shown to be inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, heat treatment, or water infiltration. Its change with flash number, its saturation with increasing flash energy, and the above inhibition criteria indicate that it originates in pulsed O2 evolution. The sound wave produced by the first flash, however, arose by a photothermal mechanism only, as shown by its linear dependence on the flash intensity and insensitivity to the above treatments. The above flash pattern demonstrates that the photocycle of the S states (i.e., positive charge accumulation before two water molecules can be oxidized in a concerted way to produce molecular oxygen) occurs in intact leaves. It proves the applicability of the photoacoustic method for mechanistic studies of O2 evolution in leaves under physiological conditions. Water content of leaves is readily measured by this method. Images PMID:16593952

Holmium:YAG laser lithotripsy: A dominant photothermal ablative mechanism with chemical decomposition of urinary calculi.

PubMed

Chan, K F; Vassar, G J; Pfefer, T J; Teichman, J M; Glickman, R D; Weintraub, S T; Welch, A J

1999-01-01

Evidence is presented that the fragmentation process of long-pulse Holmium:YAG (Ho:YAG) lithotripsy is governed by photothermal decomposition of the calculi rather than photomechanical or photoacoustical mechanisms as is widely thought. The clinical Ho:YAG laser lithotriptor (2.12 microm, 250 micros) operates in the free-running mode, producing pulse durations much longer than the time required for a sound wave to propagate beyond the optical penetration depth of this wavelength in water. Hence, it is unlikely that shock waves are produced during bubble formation. In addition, the vapor bubble induced by this laser is not spherical. Thus the magnitude of the pressure wave produced at cavitation collapse does not contribute significantly to lithotripsy. A fast-flash photography setup was used to capture the dynamics of urinary calculus fragmentation at various delay times following the onset of the Ho:YAG laser pulse. These images were concurrently correlated with pressure measurements obtained with a piezoelectric polyvinylidene-fluoride needle-hydrophone. Stone mass-loss measurements for ablation of urinary calculi (1) in air (dehydrated and hydrated) and in water, and (2) at pre-cooled and at room temperatures were compared. Chemical and composition analyses were performed on the ablation products of several types of Ho:YAG laser irradiated urinary calculi, including calcium oxalate monohydrate (COM), calcium hydrogen phosphate dihydrate (CHPD), magnesium ammonium phosphate hexahydrate (MAPH), cystine, and uric acid calculi. When the optical fiber was placed perpendicularly in contact with the surface of the target, fast-flash photography provided visual evidence that ablation occurred approximately 50 micros after the initiation of the Ho:YAG laser pulse (250-350 micros duration; 375-400 mJ per pulse), long before the collapse of the cavitation bubble. The measured peak acoustical pressure upon cavitation collapse was negligible (< 2 bars), indicating that photomechanical forces were not responsible for the observed fragmentation process. When the fiber was placed in parallel to the calculus surface, the pressure peaks occurring at the collapse of the cavitation were on the order of 20 bars, but no fragmentation occurred. Regardless of fiber orientation, no shock waves were recorded at the beginning of bubble formation. Ablation of COM calculi (a total of 150 J; 0.5 J per pulse at an 8-Hz repetition rate) revealed different Ho:YAG efficiencies for dehydrated calculus, hydrated calculus, and submerged calculus. COM and cystine calculi, pre-cooled at -80 degrees C and then placed in water, yielded lower mass-loss during ablation (20 J, 1.0 J per pulse) compared to the mass-loss of calculi at room temperature. Chemical analyses of the ablated calculi revealed products resulting from thermal decomposition. Calcium carbonate was found in samples composed of COM calculi; calcium pyrophosphate was found in CHPD samples; free sulfur and cysteine were discovered in samples composed of cystine samples; and cyanide was found in samples of uric acid calculi. These experimental results provide convincing evidence that long-pulse Ho:YAG laser lithotripsy causes chemical decomposition of urinary calculi as a consequence of a dominant photothermal mechanism. Copyright 1999 Wiley-Liss, Inc.

Understanding the complex relationships underlying hot flashes: a Bayesian network approach.

PubMed

Smith, Rebecca L; Gallicchio, Lisa M; Flaws, Jodi A

2018-02-01

The mechanism underlying hot flashes is not well-understood, primarily because of complex relationships between and among hot flashes and their risk factors. We explored those relationships using a Bayesian network approach based on a 2006 to 2015 cohort study of hot flashes among 776 female residents, 45 to 54 years old, in the Baltimore area. Bayesian networks were fit for each outcome (current hot flashes, hot flashes before the end of the study, hot flash severity, hot flash frequency, and age at first hot flashes) separately and together with a list of risk factors (estrogen, progesterone, testosterone, body mass index and obesity, race, income level, education level, smoking history, drinking history, and activity level). Each fitting was conducted separately on all women and only perimenopausal women, at enrollment and 4 years after enrollment. Hormone levels, almost always interrelated, were the most common variable linked to hot flashes; hormone levels were sometimes related to body mass index, but were not directly related to any other risk factors. Smoking was also frequently associated with increased likelihood of severe symptoms, but not through an antiestrogenic pathway. The age at first hot flashes was related only to race. All other factors were either not related to outcomes or were mediated entirely by race, hormone levels, or smoking. These models can serve as a guide for design of studies into the causal network underlying hot flashes.

Hot Flashes

MedlinePlus

... report menopausal hot flashes than do women of European descent. Hot flashes are less common in women of Japanese and Chinese descent than in white European women. Complications Nighttime hot flashes (night sweats) can ...

Helium shell flashes and evolution of accreting white dwarfs

NASA Astrophysics Data System (ADS)

Fujimoto, M. Y.; Sugimoto, D.

1982-06-01

The evolution of accreting white dwarfs is investigated from the onset of accretion through the helium shell flash. Properties of the helium shell flashes are studied by means of a generalized theory of shell flash and by numerical computations, and it is found that the shell flash grows up to the strength of a supernova explosion when the mass of the helium zone is large enough on a massive white dwarf. Although accretion onto a hot white dwarf causes a weaker shell flash than those onto cool ones, a strong tendency exists for the strength to be determined mainly by the accretion rate. For fast accretion, the shell flashes are weak and triggered recurrently, while for slow accretion the helium shell flash, once triggered, develops into a detonation supernova.

Circulating interleukin-8 and tumor necrosis factor-α are associated with hot flashes in healthy postmenopausal women.

PubMed

Huang, Wan-Yu; Hsin, I-Lun; Chen, Dar-Ren; Chang, Chia-Chu; Kor, Chew-Teng; Chen, Ting-Yu; Wu, Hung-Ming

2017-01-01

Hot flashes have been postulated to be linked to systemic inflammation. This study aimed to investigate the relationship between hot flashes, pro-inflammatory factors, and leukocytes in healthy, non-obese postmenopausal women. In this cross-sectional study, a total of 202 women aged 45-60 years were stratified into one of four groups according to their hot-flash status: never experienced hot flashes (Group N), mild hot flashes (Group m), moderate hot flashes (Group M), and severe hot flashes (Group S). Variables measured in this study included clinical parameters, hot flash experience, leukocytes, and fasting plasma levels of nine circulating cytokines/chemokines measured by using multiplex assays. Multiple linear regression analysis was used to evaluate the associations of hot flashes with these pro-inflammatory factors. The study was performed in a hospital medical center. The mean values of leukocyte number were not different between these four groups. The hot flash status had a positive tendency toward increased levels of circulating IL-6 (P-trend = 0.049), IL-8 (P-trend < 0.001), TNF-α (P-trend = 0.008), and MIP1β (P-trend = 0.04). Multivariate linear regression analysis revealed that hot-flash severity was significantly associated with IL-8 (P-trend < 0.001) and TNFα (P-trend = 0.007) among these nine cytokines/chemokines after adjustment for age, menopausal duration, BMI and FSH. Multivariate analysis further revealed that severe hot flashes were strongly associated with a higher IL-8 (% difference, 37.19%; 95% confidence interval, 14.98,63.69; P < 0.001) and TNFα (51.27%; 6.64,114.57; P < 0.05). The present study provides evidence that hot flashes are associated with circulating IL-8 and TNF-α in healthy postmenopausal women. It suggests that hot flashes might be related to low-grade systemic inflammation.

Expectancy after the first treatment and response to acupuncture for menopausal hot flashes.

PubMed

Ee, Carolyn C; Thuraisingam, Sharmala; Pirotta, Marie V; French, Simon D; Xue, Charlie C; Teede, Helena J

2017-01-01

Evidence on the impact of expectancy on acupuncture treatment response is conflicting. This secondary analysis of a randomized sham-controlled trial on acupuncture for menopausal hot flashes investigated whether treatment expectancy score was associated with hot flash score at end-of-treatment. Secondary analyses investigated whether there were associations between other pre-specified factors and hot flash score. Women experiencing moderately-severe hot flashes were randomized to receive 10 sessions of real or sham acupuncture over eight weeks. Hot flash score was collected using a seven-day hot flash diary, and expectancy using the modified Credibility and Expectancy Questionnaire immediately after the first treatment. Linear mixed-effects models with random intercepts were used to identify associations between expectancy score and hot flash score at end-of-treatment. Regression was also used to identify associations between pre-specified factors of interest and hot flash score. Because there was no difference between real and sham acupuncture for the primary outcome of hot flash score, both arms were combined in the analysis. 285 women returned the Credibility and Expectancy Questionnaire, and 283 women completed both expectancy measures. We found no evidence for an association between expectancy and hot flash score at end-of-treatment for individual cases in either acupuncture or sham group. Hot flash scores at end-of-treatment were 8.1 (95%CI, 3.0 to 13.2; P = 0.002) points lower in regular smokers compared to those who had never smoked, equivalent to four fewer moderate hot flashes a day. In our study of acupuncture for menopausal hot flashes, higher expectancy after the first treatment did not predict better treatment outcomes. Future research may focus on other determinants of outcomes in acupuncture such as therapist attention. The relationship between smoking and hot flashes is poorly understood and needs further exploration.

Circulating interleukin-8 and tumor necrosis factor-α are associated with hot flashes in healthy postmenopausal women

PubMed Central

Huang, Wan-Yu; Hsin, I-Lun; Chen, Dar-Ren; Chang, Chia-Chu; Kor, Chew-Teng; Chen, Ting-Yu

2017-01-01

Introduction Hot flashes have been postulated to be linked to systemic inflammation. This study aimed to investigate the relationship between hot flashes, pro-inflammatory factors, and leukocytes in healthy, non-obese postmenopausal women. Participants and design In this cross-sectional study, a total of 202 women aged 45–60 years were stratified into one of four groups according to their hot-flash status: never experienced hot flashes (Group N), mild hot flashes (Group m), moderate hot flashes (Group M), and severe hot flashes (Group S). Variables measured in this study included clinical parameters, hot flash experience, leukocytes, and fasting plasma levels of nine circulating cytokines/chemokines measured by using multiplex assays. Multiple linear regression analysis was used to evaluate the associations of hot flashes with these pro-inflammatory factors. Settings The study was performed in a hospital medical center. Results The mean values of leukocyte number were not different between these four groups. The hot flash status had a positive tendency toward increased levels of circulating IL-6 (P-trend = 0.049), IL-8 (P-trend < 0.001), TNF-α (P-trend = 0.008), and MIP1β (P-trend = 0.04). Multivariate linear regression analysis revealed that hot-flash severity was significantly associated with IL-8 (P-trend < 0.001) and TNFα (P-trend = 0.007) among these nine cytokines/chemokines after adjustment for age, menopausal duration, BMI and FSH. Multivariate analysis further revealed that severe hot flashes were strongly associated with a higher IL-8 (% difference, 37.19%; 95% confidence interval, 14.98,63.69; P < 0.001) and TNFα (51.27%; 6.64,114.57; P < 0.05). Conclusion The present study provides evidence that hot flashes are associated with circulating IL-8 and TNF-α in healthy postmenopausal women. It suggests that hot flashes might be related to low-grade systemic inflammation. PMID:28846735

A first look at global flash drought: long term change and short term predictability

NASA Astrophysics Data System (ADS)

Yuan, Xing; Wang, Linying; Ji, Peng

2017-04-01

"Flash drought" became popular after the unexpected 2012 central USA drought, mainly due to its rapid development, low predictability and devastating impacts on water resources and crop yields. A pilot study by Mo and Lettenmaier (2015) found that flash drought, based on a definition of concurrent heat extreme, soil moisture deficit and evapotranspiration (ET) enhancement at pentad scale, were in decline over USA during recent 100 years. Meanwhile, a recent work indicated that the occurrence of flash drought in China was doubled during the past 30 years, where a severe flash drought in the summer of 2013 ravaged 13 provinces in southern China. As global warming increases the frequency of heat waves and accelerates the hydrological cycle, the flash drought is expected to increase in general, but its trend might also be affected by interannual to decadal climate oscillations. To consolidate the hotspots of flash drought and the effects of climate change on flash drought, a global inventory is being conducted by using multi-source observations (in-situ, satellite and reanalysis), CMIP5 historical simulations and future projections under different forcing scenarios, as well as global land surface hydrological modeling for key variables including surface air temperature, soil moisture and ET. In particular, a global picture of the flash drought distribution, the contribution of naturalized and anthropogenic forcings to global flash drought change, and the risk of global flash drought in the future, will be presented. Besides investigating the long-term change of flash drought, providing reliable early warning is also essential to developing adaptation strategies. While regional drought early warning systems have been emerging in recent decade, forecasting of flash drought is still at an exploratory stage due to limited understanding of flash drought predictability. Here, a set of sub-seasonal to seasonal (S2S) hindcast datasets are being used to assess the short term predictability of flash drought via a perfect model assumption.

Muzzle flash issues related to the Waco FLIR analysis

NASA Astrophysics Data System (ADS)

Grant, Barbara G.; Hardy, David T.

2001-09-01

The controversy surrounding the origin of flashes on the Mt. Carmel FLIR videotape acquired on April 19, 1993, is introduced. The characteristics of muzzle flash are reviewed. A comparative weapons description is offered. The temporal, spatial, and radiance characteristics of thermal infrared muzzle flash are addressed. Data acquired from a field experiment are presented. The authors conclude that the spatial characteristics of muzzle flash enable its detection by equipment such as the FLIR in use at Mt. Carmel on April 19, 1993; that while flashes obtained in the field appear highly radiant, measurements are necessary to quantify their values; and that the temporal behavior of muzzle flash deserves further study.

Initial Breakdown Pulse Parameters in Intracloud and Cloud-to-Ground Lightning Flashes

NASA Astrophysics Data System (ADS)

Smith, E. M.; Marshall, T. C.; Karunarathne, S.; Siedlecki, R.; Stolzenburg, M.

2018-02-01

This study analyzes the largest initial breakdown (IB) pulse in flashes from four storms in Florida; data from three sensor arrays are used. The range-normalized, zero-to-peak amplitude of the largest IB pulse was determined along with its altitude, duration, and timing within each flash. Appropriate data were available for 40 intracloud (IC) and 32 cloud-to-ground (CG) flashes. Histograms of amplitude of the largest IB pulse by flash type were similar, with mean (median) values of 1.49 (1.05) V/m for IC flashes and -1.35 (-0.87) V/m for CG flashes. The largest IB pulse in 30 IC flashes showed a weak inverse relation between pulse amplitude and altitude. Amplitude of the largest IB pulse for 25 CG flashes showed no altitude correlation. Duration of the largest IB pulse in ICs averaged twice as long as in CGs (96 μs versus 46 μs), and all of the CG durations were <100 μs. Among the ICs, there is a positive relation between largest IB pulse duration and amplitude; the linear correlation coefficient is 0.385 with outliers excluded. The largest IB pulse in IC flashes typically occurred at a longer time after the first IB pulse (average 4.1 ms) than was the case in CG flashes (average 0.6 ms). In both flash types, the largest IB pulse was the first IB pulse in about 30% of the cases. In one storm all 42 IC flashes with triggered data had IB pulses.

Cloud-to-ground lightning and surface rainfall in warm-season Florida thunderstorms

USGS Publications Warehouse

Gungle, B.; Krider, E.P.

2006-01-01

Relationships between cloud-to-ground (CG) lightning and surface rainfall have been examined in nine isolated, warm-season thunderstorms on the east coast of central Florida. CG flashes and the associated rain volumes were measured as a function of time in storm-centered reference frames that followed each storm over a network of rain gauges. Values of the storm-average rain volume per CG flash ranged from 0.70 ?? 104 to 6.4 ?? 104 m3/CG flash, with a mean (and standard deviation) of 2.6 ?? 104 ?? 2.1 ?? 104 m3/CG flash. Values of the rain volume concurrent with CG flashes ranged from 0.11 ?? 104 to 4.9 ?? 104 m3/CG flash with a mean of 2.1 ?? 104 ?? 2.0 ?? 104 m3/CG flash. The lag-time between the peak CG flash rate and the peak rainfall rate (using 5 min bins), and the results of a lag correlation analysis, show that surface rainfall tends to follow the lightning (positive lag) by up to 20 min in six storms. In one storm the rainfall preceded the lightning by 5 min, and two storms had nonsignificant lags. Values of the lagged rain volume concurrent with CG flashes ranged from 0.43 ?? 104 to 4.9 ?? 104 m3/CG flash, and the mean was 1.9 ?? 104 ?? 1.7 ?? 104 m3/CG flash. For the five storms that produced 12 or more flashes and had significant lags, a plot of the optimum lag time versus the total number of CG flashes shows a linear trend (R2 = 0.56). The number of storms is limited, but the lag results do indicate that large storms tend to have longer lags. A linear fit to the lagged rain volume vs. the number of concurrent CG flashes has a slope of 1.9 ?? 104 m3/CG flash (R2 = 0.83). We conclude that warm-season Florida thunderstorms produce a roughly constant rain volume per CG flash and that CG lightning can be used to estimate the location and intensity of convective rainfall in that weather regime. Copyright 2006 by the American Geophysical Union.

Cavity length dependence of mode beating in passively Q-switched Nd-solid state lasers

NASA Astrophysics Data System (ADS)

Zameroski, Nathan D.; Wanke, Michael; Bossert, David

2013-03-01

The temporal intensity profile of pulse(s) from passively Q-switched and passively Q-switched mode locked (QSML) solid-state lasers is known to be dependent on cavity length. In this work, the pulse width, modulation depth, and beat frequencies of a Nd:Cr:GSGG laser using a Cr+4:YAG passive Q-switch are investigated as function cavity length. Measured temporal widths are linearly correlated with cavity length but generally 3-5 ns larger than theoretical predictions. Some cavity lengths exhibit pulse profiles with no modulation while other lengths exhibit complete amplitude modulation. The observed beat frequencies at certain cavity lengths cannot be accounted for with passively QSML models in which the pulse train repetition rate is τRT-1, τRT= round-trip time. They can be explained, however, by including coupled cavity mode-locking effects. A theoretical model developed for a two section coupled cavity semiconductor laser is adapted to a solid-state laser to interpret measured beat frequencies. We also numerically evaluate the temporal criterion required to achieve temporally smooth Q-switched pulses, versus cavity length and pump rate. We show that in flash lamp pumped systems, the difference in buildup time between longitudinal modes is largely dependent on the pump rate. In applications where short pulse delay is important, the pumping rate may limit the ability to achieve temporally smooth pulses in passively Q-switched lasers. Simulations support trends in experimental data. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Brain blood flow and cardiovascular responses to hot flashes in postmenopausal women

PubMed Central

Lucas, Rebekah A. I.; Ganio, Matthew S.; Pearson, James; Crandall, Craig G.

2012-01-01

Objective This study tested two related hypotheses: 1) that brain blood flow is reduced during the postmenopausal hot flash; and, 2) the magnitude of this reduction in brain blood flow is greater during hot flashes where blood pressure is reduced. Methods Eleven healthy, normotensive, postmenopausal women rested in a temperature-controlled laboratory (~25°C) for approximately 120 minutes while waiting for a hot flash to occur. The onset of a hot flash was objectively identified by an abrupt increase in sternal sweat rate (capacitance hygrometry). Middle cerebral artery blood velocity (MCAv, transcranial Doppler) and mean arterial pressure (Finometer®) were measured continuously. Each hot flash was divided into 8 equal segments and the segment with the largest reduction in MCAv and mean arterial pressure identified for each hot flash. Results Twenty-five hot flashes occurred during the experimental sessions (lasting 6.2 ± 2.8 min, 3 ± 1 hot flashes per participant). Seventy-six percent of hot flashes were accompanied by a clear reduction (greater than 5%) in brain blood flow. For all hot flashes, the average maximum decrease in MCAv was 12 ± 9% (7 ± 6 cm.s−1). This value did not correlate with corresponding changes in mean arterial pressure (R=0.36). Conclusion These findings demonstrate that hot flashes are often accompanied by clear reductions in brain blood flow that do not correspond with acute reductions in mean arterial blood pressure. PMID:23435027

Are menopausal hot flashes an evolutionary byproduct of postpartum warming?

PubMed

Sievert, Lynnette Leidy; Masley, Allison

2015-04-01

Hot flashes are commonly associated with menopause, and some researchers have questioned whether the widespread phenomenon may somehow be adaptive. It has been hypothesized that hot flashes were selected to occur during the hypoestrogenic postpartum period as a mechanism to warm infants. The purpose of this study was to test whether postpartum hot flashes are similar to hot flashes associated with menopause and whether postpartum hot flashes are concordant with breast-feeding episodes. Women who gave birth within the past year (n = 20) and a comparison group of women who had not given birth in the past 2 years (n = 14) participated in interviews and anthropometric measures. All wore ambulatory skin conductance monitors for a mean of 6.5 hours during afternoons and early evenings. New mothers also recorded breast-feeding episodes. Objectively measured and subjectively reported hot flashes were compared between groups and in relation to breast-feeding and other variables. Age of infants ranged from 4 days to 11 months. New mothers were more likely to report feeling warmer than the comparison group (100% vs 7%) but were not significantly more likely to demonstrate hot flashes (35% vs 50%) or to report hot flashes (30% vs 21%) during the study period. Of 75 breast-feeding episodes, only 4% were concurrent with an objective hot flash, and only 9% were concurrent with a subjective hot flash. This study does not support the hypothesis that menopausal-like hot flashes evolved to warm infants during the postpartum period.

Laboratory studies of stratospheric bromine chemistry: Kinetics of the reactions of bromine monoxide with nitrogen dioxide and atomic oxygen

NASA Astrophysics Data System (ADS)

Thorn, Robert Peyton

A laser flash photolysis - long path absorption - technique has been employed to study the kinetics of the reaction BrO+NO2+M(k(sub 16)) yields products as a function of temperature (248-346 K), pressure (16-800 Torr), and buffer gas identity (N2, CF4). 351 nm photolysis of NO2/Br2/N2 mixtures generated BrO. The BrO decay in the presence of excess NO2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k(sub 16)(P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k(sub 16)(P,T) for use in modeling stratospheric BrO(x) chemistry. The kinetics of the important stratospheric reaction BrO+O(P-3)(k(sub 14)) yields Br+O2 in N2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25-150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of Br2/O3/N2 mixtures produces O atoms in excess over Br2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolysis a small fraction of the O3 to generate O(P-3). The decay of O(P-3) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resoved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k(sub 14)(T) is k(sub 14)(T) = 1.64 x 10(exp -11) exp(263/T) cm(exp 3) molecule(exp-1)s(exp -1). The absolute accuracy of k(sub 14)(T) at any temperature within the range studied is estimated to be +/- 25%. Possible kinetic interferences from production of vibrationally or electronically excited O2 are discussed. The effect of the faster reaction rate coefficients that are reported for the BrO + NO2 + M and BrO + O(P-3) reactions upon bromine partitioning and ozone depletion in the stratosphere is discussed.

Laboratory Studies of Stratospheric Bromine Chemistry: Kinetics of the Reactions of Bromine Monoxide with Nitrogen Dioxide and Atomic Oxygen.

NASA Astrophysics Data System (ADS)

Thorn, Robert Peyton, Jr.

A laser flash photolysis - long path absorption technique has been employed to study the kinetics of the reaction rm BrO + NO_2 + M{k _{16}atopto} products as a function of temperature (248-346 K), pressure (16 -800 Torr), and buffer gas identity (rm N _2,CF_4). 351 nm photolysis of rm NO_2/Br_2/N_2 mixtures generated BrO. The BrO decay in the presence of excess NO_2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k_{16} (P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k_{16}(P,T) for use in modeling stratospheric BrO_{rm x} chemistry. The kinetics of the important stratospheric reaction rm BrO+O(^3P)_sp{to }{k_{14}}Br+O_2 in N_2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25 -150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of rm Br_2/O _3/N_2 mixtures produces O atoms in excess over Br_2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolyses a small fraction of the O_3 to generate O(^3P). The decay of O(^3P) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resolved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k_{14}(T) is given below.rm k_{14 }(T) = 1.64times 10^{-11} exp (263/T) cm^3 molecule ^{-1} s^{-1} The absolute accuracy of k_{14 }(T) at any temperature within the range studied is estimated to be +/-25%. Possible kinetic interferences from production of vibrationally or electronically excited O_2 are discussed. The effect of the faster reaction rate coefficients that are reported for the rm BrO + NO_2 + M and BrO + O(^3P) reactions upon bromine partitioning and ozone depletion in the stratosphere is discussed.

Post-Flash Validation of the new ACS/WFC Subarrays

NASA Astrophysics Data System (ADS)

Bellini, A.; Grogin, N. A.; Lim, P. L.; Golimowski, D.

2017-05-01

We made use of the new ACS/WFC subarray images of CAL-14410, taken taken with a large range of flash exposure times (0.1-30 seconds), to probe the temporal stability of the reference flash file and to validate the current post-flash correction pipeline of CALACS and ACS DESTRIPE PLUS on the new subarray modes. No statistically-significant deviations are found between the new post-flashed subarray exposures and the flash reference file, indicating that the LED lamp used to post-flash ACS images has been stable over several years. The current calibration pipelines (both CALACS and ACS DESTRIPE PLUS can be successfully used with the new subarray modes.

Flash Platform Examination

DTIC Science & Technology

2011-03-01

than would be performed in software”[108]. Uro Tinic, one of the Flash player’s engineers, further clarifies exactly what Flash player 10 hardware...www.adobe.com/products/flashplayer/features/ (Access date: 28 Sep 2009). [109] Uro , T. What Does GPU Acceleration Mean? (online), http...133] Shorten, A. (2009), Design to Development: Flash Catalyst to Flash Builder, In Proceedings of Adobe Max 2009, Los Angeles, CA. 142 DRDC

The Evolution and Structure of Extreme Optical Lightning Flashes.

PubMed

Peterson, Michael; Rudlosky, Scott; Deierling, Wiebke

2017-12-27

This study documents the composition, morphology, and motion of extreme optical lightning flashes observed by the Lightning Imaging Sensor (LIS). The furthest separation of LIS events (groups) in any flash is 135 km (89 km), the flash with the largest footprint had an illuminated area of 10,604 km 2 , and the most dendritic flash has 234 visible branches. The longest-duration convective LIS flash lasted 28 s and is overgrouped and not physical. The longest-duration convective-to-stratiform propagating flash lasted 7.4 s, while the longest-duration entirely stratiform flash lasted 4.3 s. The longest series of nearly consecutive groups in time lasted 242 ms. The most radiant recorded LIS group (i.e., "superbolt") is 735 times more radiant than the average group. Factors that impact these optical measures of flash morphology and evolution are discussed. While it is apparent that LIS can record the horizontal development of the lightning channel in some cases, radiative transfer within the cloud limits the flash extent and level of detail measured from orbit. These analyses nonetheless suggest that lightning imagers such as LIS and Geostationary Lightning Mapper can complement ground-based lightning locating systems for studying physical lightning phenomena across large geospatial domains.

Hold-up power supply for flash memory

NASA Technical Reports Server (NTRS)

Ott, William E. (Inventor)

2004-01-01

A hold-up power supply for flash memory systems is provided. The hold-up power supply provides the flash memory with the power needed to temporarily operate when a power loss exists. This allows the flash memory system to complete any erasures and writes, and thus allows it to shut down gracefully. The hold-up power supply detects when a power loss on a power supply bus is occurring and supplies the power needed for the flash memory system to temporally operate. The hold-up power supply stores power in at least one capacitor. During normal operation, power from a high voltage supply bus is used to charge the storage capacitors. When a power supply loss is detected, the power supply bus is disconnected from the flash memory system. A hold-up controller controls the power flow from the storage capacitors to the flash memory system. The hold-up controller uses feedback to assure that the proper voltage is provided from the storage capacitors to the flash memory system. This power supplied by the storage capacitors allows the flash memory system to complete any erasures and writes, and thus allows the flash memory system to shut down gracefully.

Determination of flash point in air and pure oxygen using an equilibrium closed bomb apparatus.

PubMed

Kong, Dehong; am Ende, David J; Brenek, Steven J; Weston, Neil P

2003-08-29

The standard closed testers for flash point measurements may not be feasible for measuring flash point in special atmospheres like oxygen because the test atmosphere cannot be maintained due to leakage and the laboratory safety can be compromised. To address these limitations we developed a new "equilibrium closed bomb" (ECB). The ECB generally gives lower flash point values than standard closed cup testers as shown by the results of six flammable liquids. The present results are generally in good agreement with the values calculated from the reported lower flammability limits and the vapor pressures. Our measurements show that increased oxygen concentration had little effect on the flash points of the tested flammable liquids. While generally regarded as non-flammable because of the lack of observed flash point in standard closed cup flash point testers, dichloromethane is known to form flammable mixtures. The flash point of dichloromethane in oxygen measured in the ECB is -7.1 degrees C. The flash point of dichloromethane in air is dependent on the type and energy of the ignition source. Further research is being carried out to establish the relationship between the flash point of dichloromethane and the energy of the ignition source.

Risk Factors for Extended Duration and Timing of Peak Severity of Hot Flashes

PubMed Central

Gallicchio, Lisa; Miller, Susan R.; Zacur, Howard A.; Flaws, Jodi A.

2016-01-01

Objective To identify risk factors associated with the duration of hot flashes and the time of peak hot flash severity in mid-life women. Methods A cohort of 647 women reporting hot flashes were followed for 1–7 years, with survey data and hormone measurements. Survival analysis determined the association of risk factors with the duration of hot flashes. Linear regression determined the association of risk factors with the time of peak severity. Final models were determined through stepwise model selection. Results Average hot flash duration was 2.5 years (range: 1–33), with peak severity on average at 2.96 years (range: 1–20). Duration of hot flashes was associated with race, education, menopause status, smoking history, BMI, alcohol consumption, leisure activity levels, and levels of estradiol and progesterone. In the final model, only race, alcohol consumption, leisure activity, and menopause were retained. White women had significantly shorter hot flash durations than non-white women. Women consuming at least 12 alcoholic drinks in the previous year had a significantly shorter duration of hot flashes with a smaller effect of hot flash duration on increasing in time to peak severity compared to those who consumed less than 12 alcoholic drinks in that year. Higher serum progesterone levels were associated with later peak severity if the duration of the hot flashes was less than 2 years and an earlier peak severity otherwise. Conclusions These results suggest that some behaviors (such as moderate alcohol consumption) are associated with shorter durations of hot flashes, and that progesterone was associated with the dynamics of hot flash severity. PMID:27149066

Metabolic Activity in the Insular Cortex and Hypothalamus Predicts Hot Flashes: An FDG-PET Study

PubMed Central

Deckersbach, Thilo; Lin, Nancy U.; Makris, Nikos; Skaar, Todd C.; Rauch, Scott L.; Dougherty, Darin D.; Hall, Janet E.

2012-01-01

Context: Hot flashes are a common side effect of adjuvant endocrine therapies (AET; leuprolide, tamoxifen, aromatase inhibitors) that reduce quality of life and treatment adherence in breast cancer patients. Because hot flashes affect only some women, preexisting neurobiological traits might predispose to their development. Previous studies have implicated the insula during the perception of hot flashes and the hypothalamus in thermoregulatory dysfunction. Objective: The aim of the study was to understand whether neurobiological factors predict hot flashes. Design: [18F]-Fluorodeoxyglucose (FDG) positron emission tomography (PET) brain scans coregistered with structural magnetic resonance imaging were used to determine whether metabolic activity in the insula and hypothalamic thermoregulatory and estrogen-feedback regions measured before and in response to AET predict hot flashes. Findings were correlated with CYP2D6 genotype because of CYP2D6 polymorphism associations with tamoxifen-induced hot flashes. Outcome Measures: We measured regional cerebral metabolic rate of glucose uptake (rCMRglu) in the insula and hypothalamus on FDG-PET. Results: Of 18 women without hot flashes who began AET, new-onset hot flashes were reported by 10 (55.6%) and were detected objectively in nine (50%) participants. Prior to the use of all AET, rCMRglu in the insula (P ≤ 0.01) and hypothalamic thermoregulatory (P = 0.045) and estrogen-feedback (P = 0.007) regions was lower in women who reported developing hot flashes. In response to AET, rCMRglu was further reduced in the insula in women developing hot flashes (P ≤ 0.02). Insular and hypothalamic rCMRglu levels were lower in intermediate than extensive CYP2D6 metabolizers. Conclusions: Trait neurobiological characteristics predict hot flashes. Genetic variability in CYP2D6 may underlie the neurobiological predisposition to hot flashes induced by AET. PMID:22723326

An unusual characteristic “flower-like” pattern: flash suppressor burns

PubMed Central

Gurcan, Altun

2012-01-01

The case on contact shots from firearms with a flash suppressor is rare. When a rifle fitted with a flash suppressor is fired, the emerging soot-laden gas in the barrel escapes from the slits of the flash suppressor. If the shot is contact or near contact, the flash suppressor will produce a characteristic “flower-like” pattern of seared, blackened zones around the entrance. This paper presents the injury pattern of the flash suppressor in a 29-year-old man who committed suicide with a G3 automatic infantry rifle. PMID:23935280

An unusual characteristic "flower-like" pattern: flash suppressor burns.

PubMed

Gurcan, Altun

2012-04-01

The case on contact shots from firearms with a flash suppressor is rare. When a rifle fitted with a flash suppressor is fired, the emerging soot-laden gas in the barrel escapes from the slits of the flash suppressor. If the shot is contact or near contact, the flash suppressor will produce a characteristic "flower-like" pattern of seared, blackened zones around the entrance. This paper presents the injury pattern of the flash suppressor in a 29-year-old man who committed suicide with a G3 automatic infantry rifle.

Circulating leptin and adiponectin are associated with insulin resistance in healthy postmenopausal women with hot flashes.

PubMed

Huang, Wan-Yu; Chang, Chia-Chu; Chen, Dar-Ren; Kor, Chew-Teng; Chen, Ting-Yu; Wu, Hung-Ming

2017-01-01

Hot flashes have been postulated to be linked to the development of metabolic disorders. This study aimed to evaluate the relationship between hot flashes, adipocyte-derived hormones, and insulin resistance in healthy, non-obese postmenopausal women. In this cross-sectional study, a total of 151 women aged 45-60 years were stratified into one of three groups according to hot-flash status over the past three months: never experienced hot flashes (Group N), mild-to-moderate hot flashes (Group M), and severe hot flashes (Group S). Variables measured in this study included clinical parameters, hot flash experience, fasting levels of circulating glucose, lipid profiles, plasma insulin, and adipocyte-derived hormones. Multiple linear regression analysis was used to evaluate the associations of hot flashes with adipocyte-derived hormones, and with insulin resistance. The study was performed in a hospital medical center. The mean (standard deviation) of body-mass index was 22.8(2.7) for Group N, 22.6(2.6) for Group M, and 23.5(2.4) for Group S, respectively. Women in Group S displayed statistically significantly higher levels of leptin, fasting glucose, and insulin, and lower levels of adiponectin than those in Groups M and N. Multivariate linear regression analysis revealed that hot-flash severity was significantly associated with higher leptin levels, lower adiponectin levels, and higher leptin-to-adiponectin ratio. Univariate linear regression analysis revealed that hot-flash severity was strongly associated with a higher HOMA-IR index (% difference, 58.03%; 95% confidence interval, 31.00-90.64; p < 0.001). The association between hot flashes and HOMA-IR index was attenuated after adjusting for leptin or adiponectin and was no longer significant after simultaneously adjusting for leptin and adiponectin. The present study provides evidence that hot flashes are associated with insulin resistance in postmenopausal women. It further suggests that hot flash association with insulin resistance is dependent on the combination of leptin and adiponectin variables.

Femtosecond X-ray Diffraction: Applications for Laser-Irradiated Materials

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

Wark, Justin S.

2009-09-10

Over the past few years short pulse x-ray diffraction at the nanosecond and picosecond level has become an established technique in many high-power laser laboratories for interrogating the lattice response of laser-perturbed and shocked matter, and is now finding applications in diagnosing the state of crystalline materials subject to quasi-isentropic compression. We review some of the previous results obtained in this area, for example the direct observation of coherent phonons, the first direct confirmation of the alpha-epsilon transition in shocked iron, and recent measurements indicating that the strength of matter can be measured at shock pressures exceeding a Mbar. Themore » majority of sources used to date have been laser-plasma based, with some work being performed using 3{sup rd} generation synchrotron sources. However, the development of 4{sup th} generation x-ray free-electron lasers, such as LCLS, afford many new opportunities, with pulse lengths in the femtosecond regime. The extremely low divergence and monochromatic nature of the LCLS beam make it well suited to study compressed polycrystalline matter, especially samples with small grain sizes. At extremely short pulse lengths, such that the pulse is shorter than an x-ray extinction depth traversal time, the diffraction process itself becomes time-dependent, and in certain cases the full wave-field solution will be required, particularly if the matter itself is being rapidly perturbed, as will occur if the intense x-ray radiation is used to create warm dense matter, as in recent experiments on FLASH at DESY.« less

Optimal flash rate and duty cycle for flashing visual indicators.

NASA Technical Reports Server (NTRS)

Markowitz, J.

1971-01-01

This experiment examined the ability of observers to determine, as quickly as possible, whether a visual indicator was steadily on or flashing. Six flash rates (periods) were combined factorially with three duty cycles (on-off ratios) to define 18 ?types' of intermittent signals. Experimental sessions were divided into six runs of 100 trials, each run utilizing one of the six flash rates. On any given trial in a run, the probability of a steady signal occurring was 0.5 and the probability of a flashing signal occurring was 0.5. A different duty cycle was employed daily for each experimental session. In all, 400 trials were devoted to each of the flash rates at each duty cycle. Accuracy and latency of response were the dependent variables of interest. The results show that the observers view the light for an interval of time appropriate to the expected flash rate and duty cycle; whether they judge the light to be steady or intermittent depends upon whether the light is extinguished during the predetermined waiting period. Adoption of this temporal criterion delays responding in comparison to those tasks involving responses to light onset. The decision or response criteria held by the observers are also sensitive to the parameters of the flashing light: observers become increasingly willing to call a flashing light ?steady' as flash duration increases.

Synchronized Electronic Shutter System (SESS) for Thermal Nondestructive Evaluation

NASA Technical Reports Server (NTRS)

Zalameda, Joseph N.

2001-01-01

The purpose of this paper is to describe a new method for thermal nondestructive evaluation. This method uses a synchronized electronic shutter system (SESS) to remove the heat lamp's influence on the thermal data during and after flash heating. There are two main concerns when using flash heating. The first concern is during the flash when the photons are reflected back into the camera. This tends to saturate the detectors and potentially introduces unknown and uncorrectable errors when curve fitting the data to a model. To address this, an electronically controlled shutter was placed over the infrared camera lens. Before firing the flash lamps, the shutter is opened to acquire the necessary background data for offset calibration. During flash heating, the shutter is closed to prevent the photons from the high intensity flash from saturating the camera's detectors. The second concern is after the flash heating where the lamps radiate heat after firing. This residual cooling introduces an unwanted transient thermal response into the data. To remove this residual effect, a shutter was placed over the flash lamps to block the infrared heat radiating from the flash head after heating. This helped to remove the transient contribution of the flash. The flash lamp shutters were synchronized electronically with the camera shutter. Results are given comparing the use of the thermal inspection with and without the shutter system.

Acupuncture as treatment of hot flashes and the possible role of calcitonin gene-related Peptide.

PubMed

Spetz Holm, Anna-Clara E; Frisk, Jessica; Hammar, Mats L

2012-01-01

The mechanisms behind hot flashes in menopausal women are not fully understood. The flashes in women are probably preceded by and actually initiated by a sudden downward shift in the set point for the core body temperature in the thermoregulatory center that is affected by sex steroids, β-endorphins, and other central neurotransmitters. Treatments that influence these factors may be expected to reduce hot flashes. Since therapy with sex steroids for hot flashes has appeared to cause a number of side effects and risks and women with hot flashes and breast cancer as well as men with prostate cancer and hot flashes are prevented from sex steroid therapy there is a great need for alternative therapies. Acupuncture affecting the opioid system has been suggested as an alternative treatment option for hot flashes in menopausal women and castrated men. The heat loss during hot flashes may be mediated by the potent vasodilator and sweat gland activator calcitonin gene-related peptide (CGRP) the concentration of which increases in plasma during flashes in menopausal women and, according to one study, in castrated men with flushes. There is also evidence for connections between the opioid system and the release of CGRP. In this paper we discuss acupuncture as a treatment alternative for hot flashes and the role of CGRP in this context.

A spatially collocated sound thrusts a flash into awareness

PubMed Central

Aller, Máté; Giani, Anette; Conrad, Verena; Watanabe, Masataka; Noppeney, Uta

2015-01-01

To interact effectively with the environment the brain integrates signals from multiple senses. It is currently unclear to what extent spatial information can be integrated across different senses in the absence of awareness. Combining dynamic continuous flash suppression (CFS) and spatial audiovisual stimulation, the current study investigated whether a sound facilitates a concurrent visual flash to elude flash suppression and enter perceptual awareness depending on audiovisual spatial congruency. Our results demonstrate that a concurrent sound boosts unaware visual signals into perceptual awareness. Critically, this process depended on the spatial congruency of the auditory and visual signals pointing towards low level mechanisms of audiovisual integration. Moreover, the concurrent sound biased the reported location of the flash as a function of flash visibility. The spatial bias of sounds on reported flash location was strongest for flashes that were judged invisible. Our results suggest that multisensory integration is a critical mechanism that enables signals to enter conscious perception. PMID:25774126

Application of adobe flash media to optimize jigsaw learning model on geometry material

NASA Astrophysics Data System (ADS)

Imam, P.; Imam, S.; Ikrar, P.

2018-05-01

This study aims to determine and describe the effectiveness of the application of adobe flash media for jigsaw learning model on geometry material. In this study, the modified jigsaw learning with adobe flash media is called jigsaw-flash model. This research was conducted in Surakarta. The research method used is mix method research with exploratory sequential strategy. The results of this study indicate that students feel more comfortable and interested in studying geometry material taught by jigsaw-flash model. In addition, students taught using the jigsaw-flash model are more active and motivated than the students who were taught using ordinary jigsaw models. This shows that the use of the jigsaw-flash model can increase student participation and motivation. It can be concluded that the adobe flash media can be used as a solution to reduce the level of student abstraction in learning mathematics.

46 CFR 35.20-30 - Flashing the rays of a searchlight or other blinding light-T/ALL.

Code of Federal Regulations, 2012 CFR

2012-10-01

... VESSELS OPERATIONS Navigation § 35.20-30 Flashing the rays of a searchlight or other blinding light—T/ALL. No person shall flash, or cause to be flashed, the rays of a search light or other blinding light... 46 Shipping 1 2012-10-01 2012-10-01 false Flashing the rays of a searchlight or other blinding...

46 CFR 35.20-30 - Flashing the rays of a searchlight or other blinding light-T/ALL.

Code of Federal Regulations, 2010 CFR

2010-10-01

... VESSELS OPERATIONS Navigation § 35.20-30 Flashing the rays of a searchlight or other blinding light—T/ALL. No person shall flash, or cause to be flashed, the rays of a search light or other blinding light... 46 Shipping 1 2010-10-01 2010-10-01 false Flashing the rays of a searchlight or other blinding...

46 CFR 35.20-30 - Flashing the rays of a searchlight or other blinding light-T/ALL.

Code of Federal Regulations, 2014 CFR

2014-10-01

... VESSELS OPERATIONS Navigation § 35.20-30 Flashing the rays of a searchlight or other blinding light—T/ALL. No person shall flash, or cause to be flashed, the rays of a search light or other blinding light... 46 Shipping 1 2014-10-01 2014-10-01 false Flashing the rays of a searchlight or other blinding...

46 CFR 35.20-30 - Flashing the rays of a searchlight or other blinding light-T/ALL.

Code of Federal Regulations, 2013 CFR

2013-10-01

... VESSELS OPERATIONS Navigation § 35.20-30 Flashing the rays of a searchlight or other blinding light—T/ALL. No person shall flash, or cause to be flashed, the rays of a search light or other blinding light... 46 Shipping 1 2013-10-01 2013-10-01 false Flashing the rays of a searchlight or other blinding...

46 CFR 35.20-30 - Flashing the rays of a searchlight or other blinding light-T/ALL.

Code of Federal Regulations, 2011 CFR

2011-10-01

... VESSELS OPERATIONS Navigation § 35.20-30 Flashing the rays of a searchlight or other blinding light—T/ALL. No person shall flash, or cause to be flashed, the rays of a search light or other blinding light... 46 Shipping 1 2011-10-01 2011-10-01 false Flashing the rays of a searchlight or other blinding...

Characteristics of flash initiations in a supercell cluster with tornadoes

NASA Astrophysics Data System (ADS)

Zheng, Dong; MacGorman, Donald R.

2016-01-01

Flash initiations within a supercell cluster during 10-11 May 2010 in Oklahoma were investigated based on observations from the Oklahoma Lightning Mapping Array and the Norman, Oklahoma, polarimetric radar (KOUN). The flash initiations at positions dominated by graupel, dry snow, small hail and crystals accounted for 44.3%, 44.1%, 8.0% and 3.0% of the total flashes, respectively. During the tornadic stage of the southern supercell in the cluster, flash initiations associated with graupel occupied the main body, the right flank and the forward flank of the supercell, while those associated with dry snow dominated the outskirts of the adjacent forward anvil, right anvil and rear anvil. The flash initiations associated with small hail were concentrated around the main updraft, particularly toward its front side. Highly dense flash initiations were located in the regions overlying the differential reflectivity (ZDR) arc and right anvil. The average initial height of the flashes decreased gradually from the rear to the front and from the right to the left flanks, while the height range over which initiations occurred reached a maximum at the front of the updraft. The flashes that were initiated in the adjacent forward anvils were largest on average, followed by those in the regions ahead of the updraft and near the ZDR arc. This study supports the concept of charge pockets and further deduces that the pockets in the right anvil are the most abundant and compact due to the frequent flash initiations, small-sized flashes and thin layers including flash initiations.

Phase II evaluation of S-adenosyl-L-methionine (SAMe) for the treatment of hot flashes.

PubMed

Kadakia, Kunal C; Loprinzi, Charles L; Atherton, Pamela J; Fee-Schroeder, Kelliann C; Sood, Amit; Barton, Debra L

2016-03-01

Hot flashes are a significant source of symptom burden that negatively impacts quality of life (QOL). For women who have contraindications to, or are unwilling to consider, estrogens or antidepressants for bothersome hot flashes, there are limited effective pharmacologic or complementary and alternative medicines. This single-arm phase II trial studied the efficacy of S-adenosyl-L-methionine (SAMe) for the treatment of hot flashes. Eligible women were required to have reported ≥14 hot flashes per week for ≥1 month. The patients were treated with SAMe at a dose of 400 mg twice daily to evaluate whether a reduction in hot flash score appeared to be better than the historical placebo response of approximately 25%. The women kept a daily hot flash diary during a baseline week and then daily during weeks 2-7. The primary endpoint was the change from baseline to week 7 in hot flash score and hot flash frequency. Secondary endpoints included toxicity analyses and the effect of SAMe on QOL. From October 28, 2010 to January 30, 2012, 43 women were treated with SAMe. The decrease in mean percent of baseline hot flash score and frequency was 35.4 and 32.6%, respectively. When compared to the historical placebo response of 25%, the effect of SAMe on hot flash score was not statistically significant (p = 0.09). Treatment was well tolerated with expected grade 1/2 gastrointestinal toxicity and no negative effect on QOL. The use of SAMe does not appear to significantly reduce hot flashes more than would be expected with a placebo.

Two types of flash drought over China and their connections with sub-seasonal to seasonal soil moisture drought

NASA Astrophysics Data System (ADS)

Wang, L.; Yuan, X.; Xie, Z.

2017-12-01

Flash drought has been receiving attention recently due to its rapid development and vast damage on crops in the growing season. Accompanied with heatwave and rainfall deficit, the soil moisture decreased rapidly in a short time and may lead to the failure of root water uptake and large-scale crops wither. There are two types of flash droughts according to the causes (Mo and Lettenmaier, 2016), i.e., heat wave flash drought and rainfall deficit flash drought. Here, based on pentad-mean surface air temperature and precipitation observations from over two thousand meteorological stations as well as soil moisture and ET estimations from three global reanalysis products, the characteristics and evolution of the two types of flash droughts over China are being explored. Heat wave flash drought is more likely to occur in humid and semi-humid areas, such as southern China, while rainfall deficit flash drought is more likely to occur in northern China. Unlike the traditional drought that persists for a few months to decades, the mean durations of both types of flash droughts are very short. We use monthly mean soil moisture to calculate sub-seasonal to seasonal (S2S) soil moisture drought, and compare its characteristics and preferred conditions such as the large-scale atmospheric circulation and oceanic anomaly for both types of flash droughts. The percentages of flash drought in different periods of S2S drought are also being explored to see the potential relationship between flash drought and S2S drought over different regions.

Temporal Binding Window of the Sound-Induced Flash Illusion in Amblyopia.

PubMed

Narinesingh, Cindy; Goltz, Herbert C; Wong, Agnes M F

2017-03-01

Amblyopia is a neurodevelopmental visual disorder caused by abnormal visual experience in childhood. In addition to known visual deficits, there is evidence for changes in audiovisual integration in amblyopia using explicit tasks. We examined audiovisual integration in amblyopia using an implicit task that is more relevant in a real-world context. A total of 11 participants with amblyopia and 16 controls were tested binocularly and monocularly on the sound-induced flash illusion, in which flashes and beeps are presented concurrently and the perceived number of flashes is influenced by the number of beeps. The task used 1 to 2 rapid peripheral flashes presented with 0 to 2 beeps, at 5 stimulus onset asynchronies, that is, beep (-200 milliseconds, -100 milliseconds) or flash leading (100 milliseconds, 200 milliseconds) or simultaneous (0 milliseconds). Participants reported the number of perceived flashes. Susceptibility was indicated by a "2 flashes" response to "fission" (1 flash, 2 beeps) or "1 flash" to "fusion" (2 flashes, 1 beep). For fission with the beep leading during binocular viewing, controls showed an expected decrease in illusion strength as stimulus onset asynchronies increased, whereas the illusion strength remained constant in participants with amblyopia, indicating a wider temporal binding window in amblyopia (P = 0.007). For fusion, participants with amblyopia showed reduced illusion strength during amblyopic eye viewing (P = 0.044) with the flash leading. Amblyopia is associated with the widening of the temporal binding window, specifically for fission when viewing binocularly with the beep leading. This suggests a developmental adaptation to delayed amblyopic eye visual processing to optimize audiovisual integration.

Onset conditions for flash sintering of UO 2

DOE PAGES

Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; ...

2017-06-22

In this paper, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26°C) up to 600°C. The onset conditions for flash sintering were determined for three stoichiometries (UO 2.00, UO 2.08, and UO 2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. Finally, the results from this study highlight the effect of stoichiometry on the flash sintering behavior ofmore » uranium dioxide and will serve as the foundation for future studies on this material.« less

Onset conditions for flash sintering of UO2

NASA Astrophysics Data System (ADS)

Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; Andersson, David A.; Uberuaga, Blas P.; Stanek, Christopher R.; McClellan, Kenneth J.

2017-09-01

In this work, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26 °C) up to 600 °C . The onset conditions for flash sintering were determined for three stoichiometries (UO2.00, UO2.08, and UO2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. The results from this study highlight the effect of stoichiometry on the flash sintering behavior of uranium dioxide and will serve as the foundation for future studies on this material.

Differences in the Optical Characteristics of Continental US Ground and Cloud Flashes as Observed from Space

NASA Technical Reports Server (NTRS)

Koshak, William

2007-01-01

Continental US lightning flashes observed by the Optical Transient Detector (OTD) are categorized according to flash type (ground or cloud flash) using US National Lightning Detection Network (TM) (NLDN) data. The statistics of the ground and cloud flash optical parameters (e.g., radiance, area, duration, number of optical groups, and number of optical events) are inter-compared. On average, the ground flash cloud-top emissions are more radiant, illuminate a larger area, are longer lasting, and have more optical groups and optical events than those cloud-top emissions associated with cloud flashes. Given these differences, it is suggested that the methods of Bayesian Inference could be used to help discriminate between ground and cloud flashes. The ability to discriminate flash type on-orbit is highly desired since such information would help researchers and operational decision makers better assess the intensification, evolutionary state, and severe weather potential of thunderstorms. This work supports risk reduction activities presently underway for the future launch of the GOES-R Geostationary Lightning Mapper (GLM).

Algorithms for Lunar Flash Video Search, Measurement, and Archiving

NASA Technical Reports Server (NTRS)

Swift, Wesley; Suggs, Robert; Cooke, Bill

2007-01-01

Lunar meteoroid impact flashes provide a method to estimate the flux of the large meteoroid flux and thus their hazard to spacecraft. Although meteoroid impacts on the Moon have been detected using video methods for over a decade, the difficulty of manually searching hours of video for the rare, extremely brief impact flashes has discouraged the technique's systematic implementation. A prototype has been developed for the purpose of automatically searching lunar video records for impact flashes, eliminating false detections, editing the returned possible flashes, Z and archiving and documenting the results. The theory and organization of the program is discussed with emphasis on the filtering out of several classes of false detections and retaining the brief portions of the raw video necessary for in depth analysis of the flashes detected. Several utilities for measurement, analysis, and location of the flashes on the moon included in the program are demonstrated. Application of the program to a year's worth of lunar observations is discussed along with examples of impact flashes as well as several classes of false impact flashes.

Algorithms for Lunar Flash Video Search, Measurement, and Archiving

NASA Technical Reports Server (NTRS)

Swift, Wesley; Suggs, Robert; Cooke, William

2007-01-01

Lunar meteoroid impact flashes provide a method to estimate the flux of the large meteoroid flux and thus their hazard to spacecraft. Although meteoroid impacts on the Moon have been detected using video methods for over a decade, the difficulty of manually searching hours of video for the rare, extremely brief impact flashes has discouraged the technique's systematic implementation. A prototype has been developed for the purpose of automatically searching Lunar video records for impact flashes, eliminating false detections, editing the returned possible flashes, and archiving and documenting the results. The theory and organization of the program is discussed with emphasis on the filtering out of several classes of false detections and retaining the brief portions of the raw video necessary for in depth analysis of the flashes detected. Several utilities for measurement, analysis, and location of the flashes on the moon included in the program are demonstrated. Application of the program to a year's worth of Lunar observations is discussed along with examples of impact flashes as well as several classes of false impact flashes.

Lightning Channels of Cloud-to-Ground Flashes Neutralizing Multiple Charge Regions Inside Winter Thunderclouds

NASA Astrophysics Data System (ADS)

Akita, Manabu; Yoshida, Satoru; Nakamura, Yoshitaka; Morimoto, Takeshi; Ushio, Tomoo; Kawasaki, Zen-Ichiro; Wang, Daohong

Lightning Research Group of Osaka University (LRG-OU) has been developing and improving the VHF broadband digital interferometer (DITF) for thunderstorm observations. It enables us to locate the impulsive VHF radiation sources caused by lightning discharges with extremely high resolutions. As a result of the VHF observations during the 2007-2008 winter season in the Japan Sea coastal area, cloud-to-ground (CG) flashes that neutralize multiple charge regions inside thunderclouds are visualized by the VHF broadband DITF. The first flash is the positive CG flash that neutralizes multiple positive charge regions in a flash. The second flash is the bipolar lightning flash that neutralizes both positive and negative charge inside thunderclouds. In the case of bipolar lightning flashes, some tens millisecond after the return strokes, the subsequent negative breakdowns initiate from the proximities of the initiation points of the preceding negative stepped leaders. It was also found that the altitudes of negative charge regions are lower than 2km. The bipolar lightning flashes observed in this campaign neutralize positive charge after lowering the negative charge to the ground.

Two-flash thresholds as a function of flash luminance and area.

DOT National Transportation Integrated Search

1968-09-01

The recent use of strobe lights in aviation suggests the possibility of using temporal patterns of short duration flashes as information-carrying signals. Under night flight conditions, two-flash thresholds were obtained using a two-interval, tempora...

Floods - Multiple Languages

MedlinePlus

... Arabic (العربية) Expand Section Floods and Flash Flooding - English PDF Floods and Flash Flooding - العربية (Arabic) PDF ... Bosnian (bosanski) Expand Section Floods and Flash Flooding - English PDF Floods and Flash Flooding - bosanski (Bosnian) PDF ...

Flashes and Floaters.

PubMed

Sharma, Priya; Sridhar, Jayanth; Mehta, Sonia

2015-09-01

Flashes and floaters are common ocular complaints. Flashes refer to aberrations of light that are seen in a patient's field of gaze. The flashes can be of varying sizes, colors, frequency, and durations, depending on the cause. Floaters are another common visual phenomenon caused by particles or debris in the vitreous gel of the eye that cause shadows and thus visual changes, especially against bright backgrounds and in brightly lit environments. Flashes and floaters can occur individually or together. This article discusses common causes of flashes and floaters to help with the triaging and management of these patients. Copyright © 2015 Elsevier Inc. All rights reserved.

The Evolution and Structure of Extreme Optical Lightning Flashes

PubMed Central

Peterson, Michael; Rudlosky, Scott; Deierling, Wiebke

2018-01-01

This study documents the composition, morphology, and motion of extreme optical lightning flashes observed by the Lightning Imaging Sensor (LIS). The furthest separation of LIS events (groups) in any flash is 135 km (89 km), the flash with the largest footprint had an illuminated area of 10,604 km2, and the most dendritic flash has 234 visible branches. The longest-duration convective LIS flash lasted 28 s and is overgrouped and not physical. The longest-duration convective-to-stratiform propagating flash lasted 7.4 s, while the longest-duration entirely stratiform flash lasted 4.3 s. The longest series of nearly consecutive groups in time lasted 242 ms. The most radiant recorded LIS group (i.e., “superbolt”) is 735 times more radiant than the average group. Factors that impact these optical measures of flash morphology and evolution are discussed. While it is apparent that LIS can record the horizontal development of the lightning channel in some cases, radiative transfer within the cloud limits the flash extent and level of detail measured from orbit. These analyses nonetheless suggest that lightning imagers such as LIS and Geostationary Lightning Mapper can complement ground-based lightning locating systems for studying physical lightning phenomena across large geospatial domains. PMID:29527425

Interaction of proflavin with aromatic amines in homogeneous and micellar media: Photoinduced electron transfer probed by magnetic field effect

NASA Astrophysics Data System (ADS)

Chakraborty, Brotati; Basu, Samita

2010-02-01

Photoinduced electron transfer (PET) between proflavin (PF +) and two aromatic amines viz., dimethylaniline (DMA) and 4,4'-bis(dimethylamino)diphenylmethane (DMDPM) is studied in homogeneous and heterogeneous media using steady-state as well as time-resolved fluorescence spectroscopy and laser flash photolysis with an associated magnetic field. Ionic micelles have been used to study the effect of charge of proflavin on PET with amines. Magnetic field effect on PET reactions reveals that the parent spin-state of precursors of PET for DMA-PF + system is singlet while for DMDPM-PF + system is triplet, implying that the dynamics of PET is influenced by the structure of the donor.

Electron Flow through Proteins

PubMed Central

Gray, Harry B.; Winkler, Jay R.

2009-01-01

Electron transfers in photosynthesis and respiration commonly occur between metal-containing cofactors that are separated by large molecular distances. Employing laser flash-quench triggering methods, we have shown that 20-Å, coupling-limited FeII to RuIII and CuI to RuIII electron tunneling in Ru-modified cytochromes and blue copper proteins can occur on the microsecond timescale both in solutions and crystals. Redox equivalents can be transferred even longer distances by multistep tunneling, often called hopping, through intervening amino acid side chains. Our work has established that 20-Å hole hopping through an intervening tryptophan is two orders of magnitude faster than single-step electron tunneling in a Re-modified blue copper protein. PMID:20161522

Development of minimally invasive surgery for intractable epilepsy

NASA Astrophysics Data System (ADS)

Yamakawa, Takeshi

2009-04-01

Epilepsy is a chronic brain disorder characterized by recurrent seizures. The seizure is shot down by the surgical removal of the region which is so called "epileptogenc focus". However, the accuracy to detect the focus is not good (order of cm). Thus the extirpation of focus with significant margin causes the removal of normal brain and leads to the severe aftereffects such as restricted vision, motor dysfunction, disorder of memory, and so on. To cope with this problem, we should develop the technology of (1) detecting the epileptogenic focus, and (2) necrotizing the epileptogenic focus excluding normal brain by (a) colliquative necrosis with flash freezing and melting or (b) cauterizing by focused laser beam.

Performance Assessment of the Optical Transient Detector and Lightning Imaging Sensor. Part 2; Clustering Algorithm

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Christian, Hugh J.; Blakeslee, Richard; Boccippio, Dennis J.; Goodman, Steve J.; Boeck, William

2006-01-01

We describe the clustering algorithm used by the Lightning Imaging Sensor (LIS) and the Optical Transient Detector (OTD) for combining the lightning pulse data into events, groups, flashes, and areas. Events are single pixels that exceed the LIS/OTD background level during a single frame (2 ms). Groups are clusters of events that occur within the same frame and in adjacent pixels. Flashes are clusters of groups that occur within 330 ms and either 5.5 km (for LIS) or 16.5 km (for OTD) of each other. Areas are clusters of flashes that occur within 16.5 km of each other. Many investigators are utilizing the LIS/OTD flash data; therefore, we test how variations in the algorithms for the event group and group-flash clustering affect the flash count for a subset of the LIS data. We divided the subset into areas with low (1-3), medium (4-15), high (16-63), and very high (64+) flashes to see how changes in the clustering parameters affect the flash rates in these different sizes of areas. We found that as long as the cluster parameters are within about a factor of two of the current values, the flash counts do not change by more than about 20%. Therefore, the flash clustering algorithm used by the LIS and OTD sensors create flash rates that are relatively insensitive to reasonable variations in the clustering algorithms.

How do people perceive, understand, and anticipate responding to flash flood risks and warnings? Results from a public survey in Boulder, Colorado, USA

NASA Astrophysics Data System (ADS)

Morss, Rebecca E.; Mulder, Kelsey J.; Lazo, Jeffrey K.; Demuth, Julie L.

2016-10-01

This study investigates flash flood forecast and warning communication, interpretation, and decision making, using data from a survey of 418 members of the public in Boulder, Colorado, USA. Respondents to the public survey varied in their perceptions and understandings of flash flood risks in Boulder, and some had misconceptions about flash flood risks, such as the safety of crossing fast-flowing water. About 6% of respondents indicated consistent reversals of US watch-warning alert terminology. However, more in-depth analysis illustrates the multi-dimensional, situationally dependent meanings of flash flood alerts, as well as the importance of evaluating interpretation and use of warning information along with alert terminology. Some public respondents estimated low likelihoods of flash flooding given a flash flood warning; these were associated with lower anticipated likelihood of taking protective action given a warning. Protective action intentions were also lower among respondents who had less trust in flash flood warnings, those who had not made prior preparations for flash flooding, and those who believed themselves to be safer from flash flooding. Additional analysis, using open-ended survey questions about responses to warnings, elucidates the complex, contextual nature of protective decision making during flash flood threats. These findings suggest that warnings can play an important role not only by notifying people that there is a threat and helping motivate people to take protective action, but also by helping people evaluate what actions to take given their situation.

NAND FLASH Radiation Tolerant Intelligent Memory Stack (RTIMS FLASH)

NASA Astrophysics Data System (ADS)

Sellier, Charles; Wang, Pierre

2014-08-01

The NAND Flash Radiation Tolerant and Intelligent Memory Stack (RTIMS FLASH) is a User's Friendly, Plug-and- Play and Radiation Protected high density NAND Flash Memory. It provides a very high density, radiation hardened by design and non-volatile memory module suitable for all space applications such as commercial or scientific geo-stationary missions, earth observation, navigation, manned space vehicles and deep space scientific exploration. The Intelligent Memory Module embeds a very high density of non-volatile NAND Flash memory and one Intelligent Flash Memory Controller (FMC). The FMC provides the module with a full protection against the radiation effects such as SEL, SEFI and SEU. It's also granting the module with bad block immunity as well as high level service functions that will benefit to the user's applications.

Increased x-ray conversion efficiency from ultra high contrast, relativistic laser pulse irradiation of large aspect ratio, vertically aligned nanowires

NASA Astrophysics Data System (ADS)

Hollinger, R. C.; Bargsten, C.; Shlyaptsev, V. N.; Kaymak, V.; Pukhov, A.; Capeluto, M. G.; Wang, Y.; Wang, S.; Rockwood, A.; Curtis, A.; Rocca, J. J.

2016-10-01

Recent experiments at Colorado State University have shown that the effective trapping of clean, Joule-level fs laser pulses of relativistic intensity in arrays of high aspect ratio aligned nanowire creates multi-kev, near solid density, large scale (>4um deep) plasmas. The drastically decreased radiative life time and increased hydrodynamic cooling time from these plasmas increases the x-ray conversion efficiency. We measured a record conversion efficiency of 10% into hv>1KeV photons (2pi steradians), and of 0.3% for hv>6KeV. The experiments used Au and Ni nanowires of 55nm, 80nm and 100nm in diameter with 12% of solid density irradiated by high contrast (>1012) pulses of 60fs FWHM duration from a frequency doubled Ti:Sa laser at intensities of I =5x1019Wcm-2. We also present preliminary results on x-ray emission from Rhodium nanowires in the 19-22KeV range and demonstrate the potential of this picosecond X-ray source in flash radiography. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy, and by the Defense Threat Reduction Agency Grant HDTRA-1-10-1-0079.

TAKASAGO-6 apparatus for cryogenic coherent X-ray diffraction imaging of biological non-crystalline particles using X-ray free electron laser at SACLA.

PubMed

Kobayashi, Amane; Sekiguchi, Yuki; Takayama, Yuki; Oroguchi, Tomotaka; Shirahama, Keiya; Torizuka, Yasufumi; Manoda, Masahiro; Nakasako, Masayoshi; Yamamoto, Masaki

2016-05-01

Coherent X-ray diffraction imaging (CXDI) is a technique for structure analyses of non-crystalline particles with dimensions ranging from micrometer to sub-micrometer. We have developed a diffraction apparatus named TAKASAGO-6 for use in single-shot CXDI experiments of frozen-hydrated non-crystalline biological particles at cryogenic temperature with X-ray free electron laser pulses provided at a repetition rate of 30 Hz from the SPring-8 Angstrom Compact free-electron LAser. Specimen particles are flash-cooled after being dispersed on thin membranes supported by specially designed disks. The apparatus is equipped with a high-speed translation stage with a cryogenic pot for raster-scanning of the disks at a speed higher than 25 μm/33 ms. In addition, we use devices assisting the easy transfer of cooled specimens from liquid-nitrogen storages to the cryogenic pot. In the current experimental procedure, more than 20 000 diffraction patterns can be collected within 1 h. Here we report the key components and performance of the diffraction apparatus. Based on the efficiency of the diffraction data collection and the structure analyses of metal particles, biological cells, and cellular organelles, we discuss the future application of this diffraction apparatus for structure analyses of biological specimens.

Preparation of Nd-Fe-B/α-Fe nano-composite thick-film magnets on various substrates using PLD with high laser energy density above 10 J/cm2

NASA Astrophysics Data System (ADS)

Nakano, M.; Kondo, H.; Yamashita, A.; Yanai, T.; Itakura, M.; Fukunaga, H.

2018-05-01

PLD (Pulsed Laser Deposition) method with high laser energy density (LED) above 10 J/cm2 followed by a flash annealing enabled us to obtain isotropic nano-composite thick-film magnets with (BH)max ≧ 80 kJ/m3 on polycrystalline Ta substrates. We also have demonstrated that a dispersed structure composed of α-Fe together with Nd2Fe14B phases with the average grain diameter of approximately 20 nm could be formed on the Ta substrates. In this study, we tried to enhance the (BH)max value by controlling the microstructure due to the usage of different metal based substrates with each high melting point such as Ti, Nb, and W. Although it was difficult to vary the microstructure and to improve the magnetic properties of the films deposited on the substrates, we confirmed that isotropic thick-film magnets with (BH)max ≧ 80 kJ/m3 based on the nano-dispersed α-Fe and Nd2Fe14B phases could be obtained on various metal substrates with totally different polycrystalline structure. On the other hand, the use of a glass substrate lead to the deterioration of magnetic properties of a film prepared using the same preparation process.

Capturing Reality at Centre Block

NASA Astrophysics Data System (ADS)

Boulanger, C.; Ouimet, C.; Yeomans, N.

2017-08-01

The Centre Block of Canada's Parliament buildings, National Historic Site of Canada is set to undergo a major rehabilitation project that will take approximately 10 years to complete. In preparation for this work, Heritage Conservation Services (HCS) of Public Services and Procurement Canada has been completing heritage documentation of the entire site which includes laser scanning of all interior rooms and accessible confined spaces such as attics and other similar areas. Other documentation completed includes detailed photogrammetric documentation of rooms and areas of high heritage value. Some of these high heritage value spaces present certain challenges such as accessibility due to the height and the size of the spaces. Another challenge is the poor lighting conditions, requiring the use of flash or strobe lighting to either compliment or completely eliminate the available ambient lighting. All the spaces captured at this higher level of detail were also captured with laser scanning. This allowed the team to validate the information and conduct a quality review of the photogrammetric data. As a result of this exercise, the team realized that in most, if not all cases, the photogrammetric data was more detailed and at a higher quality then the terrestrial laser scanning data. The purpose and motivation of this paper is to present these findings, as well provide the advantages and disadvantages of the two methods and data sets.

Characteristic pulse trains of preliminary breakdown in four isolated small thunderstorms

NASA Astrophysics Data System (ADS)

Ma, Dong

2017-03-01

Using a low-frequency six-station local network, preliminary breakdown (PB) pulses not followed or followed by negative return stroke (RS), which are defined as PB-type and PB cloud-to-ground (PBCG)-type flashes, are analyzed based on four isolated small thunderstorms for the first time. On the basis of 22 PB-type flashes out of totally 2155 flashes, it indicates that the number of PB-type flashes is very small. At the early stage, PB-type flashes are observed in all four thunderstorms. At the active stage, PB-type flashes still can occur; meanwhile, there are few or no negative cloud-to-ground (CG) flashes. However, at the final stage no PB-type flashes occur. At the stage of distinct cell merging or splitting, PB-type flashes are also observed. Based on the 123 PBCG-type flashes, we discuss the percentage of PBCG-type flashes and also analyze the relationship between the electric field (E-field) amplitude of the largest pulse in the PB pulse train normalized to 100 km (PBA), the E-field amplitude of the first return stroke normalized to 100 km (RSA), the time interval between PBA and RSA (PB-RS interval), and the ratio between PBA and RSA (PB-RS ratio). We find that the percentage of PBCG-type flashes is not always dependent on PBA or PB-RS ratio; the type of thunderstorms may also have an impact on this percentage. None of the PB-RS intervals is less than 20 ms; we speculate that such long PB-RS interval is the feature of isolated small thunderstorms, but more observations are needed to further investigate this question.

Anxiogenic CO2 Stimulus Elicits Exacerbated Hot Flash-like Responses in a Rat Menopause Model and Hot Flashes in Menopausal Women

PubMed Central

Federici, Lauren M.; Roth, Sarah Dorsey; Krier, Connie; Fitz, Stephanie D.; Skaar, Todd; Shekhar, Anantha; Carpenter, Janet S.; Johnson, Philip L.

2016-01-01

Objective Since longitudinal studies determined that anxiety is a strong risk factor for hot flashes, we hypothesized that an anxiogenic stimulus that signals air hunger (hypercapnic, normoxic gas) would trigger an exacerbated hot flash-associated increase in tail skin temperature (TST) in a rat ovariectomy (OVEX) model of surgical menopause and hot flashes in symptomatic menopausal women. We also assessed TST responses in OVEX serotonin transporter (SERT)+/− rats that models a common polymorphism that is associated with increased climacteric symptoms in menopausal women and increases in anxiety traits. Methods OVEX and sham-OVEX rats (initial experiment) and wildtype and SERT+/− OVEX rats (subsequent experiment) were exposed to a 5 min infusion of 20%CO2 normoxic gas while measuring TST. Menopausal women were given brief 20% and 35%CO2 challenges, and hot flashes were self-reported and objectively verified. Results Compared to controls, OVEX rats had exacerbated increases in TST, and SERT+/− OVEX rats had prolonged TST increases following CO2. Most women reported mild/moderate hot flashes after CO2 challenges, and the hot flash severity to CO2 was positively correlated with daily hot flash frequency. Conclusions The studies demonstrate that this anxiogenic stimulus is capable of inducing cutaneous vasomotor responses in OVEX rats, and eliciting hot flashes in menopausal women. In rats, the severity of the response was mediated by loss of ovarian function and increased anxiety traits (SERT+/−), and, in women, by daily hot flash frequency. These findings may provide insights into anxiety related triggers and genetic risk factors for hot flashes in thermoneutral environments. PMID:27465717

Continuous transdermal nitroglycerin therapy for menopausal hot flashes: a single-arm, dose-escalation trial.

PubMed

Huang, Alison J; Cummings, Steven R; Schembri, Michael; Vittinghoff, Eric; Ganz, Peter; Grady, Deborah

2016-03-01

To describe the efficacy and tolerability of continuous nitroglycerin for treatment of hot flashes. Perimenopausal and postmenopausal women reporting at least seven hot flashes per day were recruited into a single-arm, dose-escalation trial of continuous transdermal nitroglycerin. Participants were started on a generic 0.1 mg/hour nitroglycerin patch applied daily without patch-free periods. During 4 weeks, participants escalated dosage weekly to 0.2, 0.4, or 0.6 mg/hour as tolerated, then discontinued nitroglycerin during the final week. Changes in hot flash frequency and severity were assessed using symptom diaries. Paired t tests examined change in outcomes between baseline and maximal-dose therapy and after discontinuation of nitroglycerin. Of the 19 participants, mean age was 51.4 (±4.3) years. Women reported an average 10.6 (±3.0) hot flashes and 7.1 (±3.8) moderate-to-severe hot flashes per day at baseline. Eleven women escalated to 0.6 mg/hour, three to 0.4 mg/hour, two to 0.2 mg/hour, and one remained on 0.1 mg/hour nitroglycerin. Two discontinued nitroglycerin before the first outcomes assessment. Among the remaining 17 women, the average daily frequency of hot flashes decreased by 54% and the average frequency of moderate-to-severe hot flashes decreased by 69% from baseline to maximum-dose therapy (P < 0.001 for both). After discontinuing nitroglycerin, participants reported an average 23% increase in frequency of any hot flashes (P = 0.041) and 96% increase in moderate-to-severe hot flashes (P < 0.001). Continuous nitroglycerin may substantially and reversibly decrease hot flash frequency and severity. If confirmed in a randomized blinded trial, it may offer a novel nonhormonal hot flash treatment.

Continuous Transdermal Nitroglycerin Therapy for Menopausal Hot Flashes: A Single-Arm Dose-Escalation Trial

PubMed Central

Huang, Alison J.; Cummings, Steven R.; Schembri, Michael; Vittinghoff, Eric; Ganz, Peter; Grady, Deborah

2015-01-01

Objective To describe the efficacy and tolerability of continuous nitroglycerin for treatment of hot flashes. Methods Peri- and postmenopausal women reporting at least 7 hot flashes per day were recruited into a single-arm, dose-escalation trial of continuous transdermal nitroglycerin. Participants were started on a generic 0.1 mg/hr nitroglycerin patch applied daily without patch-free periods. Over four weeks, participants escalated dosage weekly to 0.2, 0.4, or 0.6 mg/hr as tolerated, then discontinued nitroglycerin during the final week. Changes in hot flash frequency and severity were assessed using symptom diaries. Paired t-tests examined change in outcomes between baseline and maximal-dose therapy as well as after discontinuation of nitroglycerin. Results Of the 19 participants, mean age was 51.4 (±4.3) years. Women reported an average 10.6 (±3.0) hot flashes and 7.1 (±3.8) moderate-to-severe hot flashes per day at baseline. Eleven women escalated to 0.6 mg/hr, three to 0.4 mg/hr, two to 0.2 mg/hr, and one remained on 0.1 mg/hr nitroglycerin. Two discontinued nitroglycerin before the first outcomes assessment. Among the remaining 17 women, the average daily frequency of hot flashes decreased by 54% and the average frequency of moderate-to-severe hot flashes decreased by 69% from baseline to maximum-dose therapy (P<0.001 for both). After discontinuing nitroglycerin, participants reported an average 23% increase in frequency of any hot flashes (P=0.041) and 96% increase in moderate-to-severe hot flashes (P<0.001). Conclusions Continuous nitroglycerin may substantially and reversibly decrease hot flash frequency and severity. If confirmed in a randomized blinded trial, it may offer a novel non-hormonal hot flash treatment. PMID:26263283

Risk of long-term hot flashes after natural menopause: evidence from the Penn Ovarian Aging Study cohort.

PubMed

Freeman, Ellen W; Sammel, Mary D; Sanders, Richard J

2014-09-01

This study aims to estimate the risk of hot flashes relative to natural menopause and to evaluate the associations of hormone levels, behavioral variables, and demographic variables with the risk of hot flashes after menopause. We performed annual assessment of 255 women who were premenopausal at baseline and reached natural menopause within 16 years of follow-up. The prevalence of moderate/severe hot flashes increased in each premenopausal year, reaching a peak of 46% in the first 2 years after the final menstrual period (FMP). Hot flashes decreased slowly after menopause and did not return to premenopausal levels until 9 years after the FMP. The mean (SD) duration of moderate/severe hot flashes after the FMP was 4.6 (2.9) years (for any hot flashes, 4.9 [3.1] y). One third of women at 10 years or more after menopause continued to experience moderate/severe hot flashes. African-American women (obese and nonobese) and obese white women had significantly greater risks of hot flashes compared with nonobese white women (interaction, P = 0.01). In multivariable analysis, increasing follicle-stimulating hormone levels before the FMP (P < 0.001), decreasing estradiol (odds ratio, 0.87; 95% CI, 0.78-0.96; P = 0.008), and increasing anxiety (odds ratio, 1.05; 95% CI, 1.03-1.06; P < 0.001) were significant risk factors for hot flashes, whereas higher education levels were protective (odds ratio, 0.66; 95% CI, 0.47-0.91; P = 0.011). Moderate/severe hot flashes continue, on average, for nearly 5 years after menopause; more than one third of women observed for 10 years or more after menopause have moderate/severe hot flashes. Continuation of hot flashes for more than 5 years after menopause underscores the importance of determining individual risks/benefits when selecting hormone or nonhormone therapy for menopausal symptoms.

RISK OF LONG TERM HOT FLASHES AFTER NATURAL MENOPAUSE: EVIDENCE FROM THE PENN OVARIAN AGING COHORT

PubMed Central

Freeman, Ellen W.; Sammel, Mary D.; Sanders, Richard J.

2015-01-01

Objectives To estimate the risk of hot flashes relative to natural menopause and evaluate associations of hormone levels, behavioral and demographic variables with the risk of hot flashes following menopause. Methods Annual assessments of 255 women who were premenopausal at baseline and reached natural menopause during 16 years of follow-up. Results The prevalence of moderate/severe hot flashes increased in each premenopausal year, reaching a peak of 46% in the first two years after the final menstrual period (FMP). Hot flashes decreased slowly following menopause and did not return to premenopausal levels until 9 years after FMP. The mean duration of moderate/severe hot flashes after FMP was 4.6 (SD2.9) years (4.9, SD3.1 years for any hot flashes). One-third of women at 10 or more years following menopause continued to experience moderate/severe hot flashes. African American women (obese and non-obese) and obese white women had significantly greater risk of hot flashes compared to non-obese white women (interaction P=0.01). In multivariable analysis, increasing FSH levels before FMP (P<0.001), decreasing estradiol (OR 0.87, 95% CI: 0.78–0.96, P=0.008), and increasing anxiety (OR 1.05, 95% CI: 1.03–1.06, P<0.001) were significant risk factors for hot flashes, while higher education levels were protective (OR 0.66, 95% CI: 0.47–0.91, P=0.011). Conclusions Moderate/severe hot flashes continued on average for nearly 5 years following menopause; more than one- third of women observed for 10 or more years following menopause had moderate/severe hot flashes. Continuation of hot flashes for more than 5 years following menopause underscores the importance of determining individual risk/benefit when selecting hormone or non-hormonal therapy for menopausal symptoms. PMID:24473530

FLASH is essential during early embryogenesis and cooperates with p73 to regulate histone gene transcription.

PubMed

De Cola, A; Bongiorno-Borbone, L; Bianchi, E; Barcaroli, D; Carletti, E; Knight, R A; Di Ilio, C; Melino, G; Sette, C; De Laurenzi, V

2012-02-02

Replication-dependent histone gene expression is a fundamental process occurring in S-phase under the control of the cyclin-E/CDK2 complex. This process is regulated by a number of proteins, including Flice-Associated Huge Protein (FLASH) (CASP8AP2), concentrated in specific nuclear organelles known as HLBs. FLASH regulates both histone gene transcription and mRNA maturation, and its downregulation in vitro results in the depletion of the histone pull and cell-cycle arrest in S-phase. Here we show that the transcription factor p73 binds to FLASH and is part of the complex that regulates histone gene transcription. Moreover, we created a novel gene trap to disrupt FLASH in mice, and we show that homozygous deletion of FLASH results in early embryonic lethality, owing to arrest of FLASH(-/-) embryos at the morula stage. These results indicate that FLASH is an essential, non-redundant regulator of histone transcription and cell cycle during embryogenesis.

A pilot study of magnetic therapy for hot flashes after breast cancer.

PubMed

Carpenter, Janet S; Wells, Nancy; Lambert, Beth; Watson, Peggy; Slayton, Tami; Chak, Bapsi; Hepworth, Joseph T; Worthington, W Bradley

2002-04-01

The purpose of this randomized placebo-controlled crossover pilot study was to evaluate the effectiveness and acceptability of magnetic therapy for hot flashes among breast cancer survivors. Participants completed a 24-hour baseline hot-flash monitoring session, wore the magnetic devices or placebo for 3 days, completed an after-treatment hot-flash monitoring session, experienced a 10-day washout period, and then crossed over to the opposite study arm. Magnetic devices and placebos were placed on 6 acupressure sites corresponding to hot-flash relief. Complete data were available from 11 survivors of breast cancer. Results indicated magnetic therapy was no more effective than placebo in decreasing hot-flash severity, and contrary to expectations, placebo was significantly more effective than magnets in decreasing hot-flash frequency, bother, interference with daily activities, and overall quality of life. Implications for clinical practice and future research include the need to explore alternative interventions aimed at alleviating hot flashes in this population.

Obtaining the Grobner Initialization for the Ground Flash Fraction Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Solakiewicz, R.; Attele, R.; Koshak, W.

2011-01-01

At optical wavelengths and from the vantage point of space, the multiple scattering cloud medium obscures one's view and prevents one from easily determining what flashes strike the ground. However, recent investigations have made some progress examining the (easier, but still difficult) problem of estimating the ground flash fraction in a set of N flashes observed from space In the study by Koshak, a Bayesian inversion method was introduced for retrieving the fraction of ground flashes in a set of flashes observed from a (low earth orbiting or geostationary) satellite lightning imager. The method employed a constrained mixed exponential distribution model to describe the lightning optical measurements. To obtain the optimum model parameters, a scalar function of three variables (one of which is the ground flash fraction) was minimized by a numerical method. This method has formed the basis of a Ground Flash Fraction Retrieval Algorithm (GoFFRA) that is being tested as part of GOES-R GLM risk reduction.

Fast repetition rate (FRR) flasher

DOEpatents

Kolber, Zbigniew; Falkowski, Paul

1997-02-11

A fast repetition rate (FRR) flasher suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between Successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz.

Statistical Evolution of the Lightning Flash

NASA Astrophysics Data System (ADS)

Zoghzoghy, F. G.; Cohen, M.; Said, R.; Inan, U. S.

2012-12-01

Natural lightning is one of the most fascinating and powerful electrical processes on Earth. To date, the physics behind this natural phenomenon are not fully understood, due primarily to the difficulty of obtaining measurements inside thunderstorms and to the wide range of timescales involved (from nanoseconds to seconds). Our aim is to use accurate lightning geo-location data from the National Lightning Detection Network (NLDN) to study statistical patterns in lightning, taking advantage of the fact that millions of lightning flashes occur around the globe every day. We present two sets of results, one involving the patterns of flashes in a storm, and a second involving the patterns of strokes in a flash. These patterns can provide a surrogate measure of the timescales and the spatial extents of the underlying physical processes. First, we study the timescales of charge buildup inside thunderstorms. We find that, following a lightning flash, the probability of another neighboring flash decreases and takes tens of seconds to recover. We find that this suppression effect is a function of flash type, stroke peak current, cloud-to-ground (CG) stroke multiplicity, and other lightning and geographical parameters. We find that the probabilities of subsequent flashes are more suppressed following oceanic lightning, or following flashes with higher peak currents and/or higher multiplicities (for CG flashes). Second, we use NLDN data to study the evolution of the strokes within a CG flash. A CG flash typically includes multiple return strokes, which can occur in the same channel or in multiple channels within a few kilometers. We cluster NLDN stroke data into flashes and produce the probability density function of subsequent strokes as a function of distance and time-delays relative to the previous stroke. Using this technique, we investigate processes which occur during the CG lightning flash with nanosecond to millisecond timescales. For instance, our results suggest that subsequent strokes that occur in a newly formed channel follow a pattern that propagates at a speed of ~200 km/s. We present our statistical techniques and discuss more thoroughly our work and results.

Circulating leptin and adiponectin are associated with insulin resistance in healthy postmenopausal women with hot flashes

PubMed Central

Huang, Wan-Yu; Chang, Chia-Chu; Chen, Dar-Ren; Kor, Chew-Teng; Chen, Ting-Yu; Wu, Hung-Ming

2017-01-01

Introduction Hot flashes have been postulated to be linked to the development of metabolic disorders. This study aimed to evaluate the relationship between hot flashes, adipocyte-derived hormones, and insulin resistance in healthy, non-obese postmenopausal women. Participants and design In this cross-sectional study, a total of 151 women aged 45–60 years were stratified into one of three groups according to hot-flash status over the past three months: never experienced hot flashes (Group N), mild-to-moderate hot flashes (Group M), and severe hot flashes (Group S). Variables measured in this study included clinical parameters, hot flash experience, fasting levels of circulating glucose, lipid profiles, plasma insulin, and adipocyte-derived hormones. Multiple linear regression analysis was used to evaluate the associations of hot flashes with adipocyte-derived hormones, and with insulin resistance. Settings The study was performed in a hospital medical center. Results The mean (standard deviation) of body-mass index was 22.8(2.7) for Group N, 22.6(2.6) for Group M, and 23.5(2.4) for Group S, respectively. Women in Group S displayed statistically significantly higher levels of leptin, fasting glucose, and insulin, and lower levels of adiponectin than those in Groups M and N. Multivariate linear regression analysis revealed that hot-flash severity was significantly associated with higher leptin levels, lower adiponectin levels, and higher leptin-to-adiponectin ratio. Univariate linear regression analysis revealed that hot-flash severity was strongly associated with a higher HOMA-IR index (% difference, 58.03%; 95% confidence interval, 31.00–90.64; p < 0.001). The association between hot flashes and HOMA-IR index was attenuated after adjusting for leptin or adiponectin and was no longer significant after simultaneously adjusting for leptin and adiponectin. Conclusion The present study provides evidence that hot flashes are associated with insulin resistance in postmenopausal women. It further suggests that hot flash association with insulin resistance is dependent on the combination of leptin and adiponectin variables. PMID:28448547

Pilot evaluation of hypnosis for the treatment of hot flashes in breast cancer survivors.

PubMed

Elkins, Gary; Marcus, Joel; Stearns, Vered; Hasan Rajab, M

2007-05-01

This single arm, pilot study investigated the use of hypnosis to reduce hot flashes in 16 breast cancer survivors. Each patient provided baseline data and received 4 weekly sessions of hypnosis that followed a standardized transcript. Patients were also instructed in self-hypnosis. Throughout the clinical care, patients completed daily diaries of the frequency and severity of their hot flashes. Patients also completed baseline and post-treatment ratings of the degree to which hot flashes interfered with daily activities and quality of life. Results indicated a 59% decrease in total daily hot flashes and a 70% decrease in weekly hot flash scores from their baselines. There was also a significant decrease in the degree to which hot flashes interfered with daily activities for all measures including work, social activities, leisure activities, sleep, mood, concentration, relations with others, sexuality, enjoyment of life, and overall quality of life. This pilot study suggests that clinical hypnosis may be an effective non-hormonal and non-pharmacological treatment for hot flashes. A randomized, controlled clinical trial is planned to more definitively elucidate the efficacy and applicability of hypnosis for reducing hot flashes.

Management of menopause-associated vasomotor symptoms: Current treatment options, challenges and future directions

PubMed Central

Pachman, Deirdre R; Jones, Jason M; Loprinzi, Charles L

2010-01-01

Hot flashes are one of the most common and distressing symptoms associated with menopause, occurring in more than 75% of postmenopausal women. They are especially problematic in breast cancer patients since some breast cancer therapies can induce hot flashes. For mild hot flashes, it is proposed that behavioral modifications are the first step in management. Hormonal therapies, including estrogens and progestogens, are the most well known effective agents in relieving hot flashes; however, the safety of these agents is controversial. There is an increasing amount of literature on nonhormonal agents for the treatment of hot flashes. The most promising data regard newer antidepressant agents such as venlafaxine, which reduces hot flashes by about 60%. Gabapentin is another nonhormonal agent that is effective in reducing hot flashes. While many complimentary therapies, including phytoestrogens, black cohosh, and dehydroepiandrosterone, have been explored for the treatment of hot flashes; none can be recommended at this time. Furthermore, there is a lack of strong evidence to support exercise, yoga, or relaxation for the treatment of hot flashes. Paced respirations and hypnosis appear to be promising enough to warrant further investigation. Another promising nonpharmacological therapy, currently under investigation, involves a stellate ganglion block. PMID:21072305

GLM Validation Studies in Colorado

NASA Astrophysics Data System (ADS)

Rutledge, S. A.; Reimel, K.; Fuchs, B.; Xu, W.

2017-12-01

On 8 May 2017 the Geostationary Lightning Mapper (GLM) calibration/validation field campaign completed a mission over the domain of the Colorado Lightning Mapping Array (LMA). This "gold mine day" produced a mixture of normal polarity and anomalous storms of varying intensity. A case study analysis has been completed for a portion of three individual storms from this day. By utilizing a cell tracking algorithm and lightning flash attribution program, individual lightning flashes detected by the GLM, LMA, the National Lightning Detection Network (NLDN), and Earth Networks Total Lightning Network (ENTLN) are attributed to individual storm cells. The focus of this analysis is the detection efficiency of GLM. We will discuss how the GLM detection efficiency changes as a result of storm morphology and lightning flash characteristics. Lightning flash size, flash height, and the amount of ice present between the lightning flash altitude and the top of the cloud all appear to play a role in how well GLM detects lightning flashes. Since GLM shares the same concept as its predecessor TRMM LIS (optically-based lightning detection), the evaluation of TRMM LIS against LMA network-detected lightning provides insights into the GLM detection efficiency. We have collected observations by LIS and LMA coincident in time and space during 2008-2014. The sample includes 400 LIS overpasses with both LIS and LMA detecting flashes within 150 km radius of the center of the LMA array during the 120 second LIS observing time period (analysis presently confined to the Alabama LMA network). The overall LIS detection efficiency (DE, defined as the ratio of flash rates between LIS and LMA) is 0.45, with higher DE for lower flash rate cases. LIS showed a DE of nearly 100% for cases with flash rates < 10 fl/min, but had a DE of only 20-30% for high flash rates within intense storms (> 300 fl/min). We further separated the dataset into day and night, and found that the night-time DE (0.6) increased by 20% compared to day-time DE (0.5). LIS DE also increased as a function of LMA-derived flash size, possibly due to stronger radiance from larger flashes. LIS DE was the lowest ( 40%) for flashes with sizes smaller than a single LIS pixel (< 16 km2). These results may be applicable to GLM as well.

Clinical Hypnosis in the Treatment of Post-Menopausal Hot Flashes: A Randomized Controlled Trial

PubMed Central

Elkins, Gary R.; Fisher, William I.; Johnson, Aimee K.; Carpenter, Janet S.; Keith, Timothy Z.

2012-01-01

Objective The use of estrogen and progesterone to manage vasomotor symptoms (i.e., hot flashes, night sweats) has declined due to concerns over their risks and there is an increased interest in alternate, effective, and low-risk treatments. This study reports the results of a randomized, controlled trial of clinical hypnosis in treating vasomotor symptoms among post-menopausal women. Methods Randomized, single-blind, controlled, clinical trial involving 187 post-menopausal women reporting a minimum of seven hot flashes per day, or at least 50 hot flashes a week at baseline between December 2008 and April 2012. Eligible participants received five weekly sessions of either clinical hypnosis or structured-attention control. Primary outcomes were hot flash frequency (subjectively and physiologically recorded) and hot flash score assessed by daily diaries at weeks 2–6, and 12. Secondary outcomes included measures of hot flash related daily interference, sleep quality and treatment satisfaction. Results In a modified intent-to-treat analysis that included all randomized participants that provided data, reported subjective hot flash frequency from baseline to week 12 showed a mean reduction of 55.82 hot flashes for the clinical hypnosis intervention (74.16%), versus a 12.89 hot flash reduction (17.13%) for the control (p<.001, 95% CI, 36.15–49.67). Mean reduction in hot flash score was 18.83 (80.32%) for the clinical hypnosis intervention as compared to 3.53 (15.38%) for the control (p<.001, 95% CI, 12.60–17.54). At 12 week follow-up, the mean reduction in physiologically monitored hot flashes was 5.92 (56.86%) for clinical hypnosis and .88 (9.94%) for the control (p<.001, 95% CI, 2.00–5.46). Secondary outcomes were significantly improved compared to control at 12 week follow-up in hot flash related interference (p<.001, 95% CI, 2.74–4.02), sleep quality (p<.001, 95% CI, 3.65–5.84), and treatment satisfaction (p<.001, 95% CI, 7.79–8.59). Conclusion Compared to a structured attention control, clinical hypnosis resulted in significant reductions in self-reported and physiologically measured hot flashes as well as hot flash scores in post-menopausal women. PMID:23435026

Neutron energy spectra from the laser-induced Dd,n3He reaction.

PubMed

Hilscher, D; Berndt, O; Enke, M; Jahnke, U; Nickles, P V; Ruhl, H; Sandner, W

2001-07-01

Detailed neutron energy spectra were measured for the D(d,n)3He reaction induced in solid (CD2)(n) targets by irradiation with 50-fs 2 x 10(18) W/cm(2) light pulses from a 10-TW Ti:Sapphire laser. The neutrons were observed at two angles 5 degrees and 112 degrees relative to the incident laser beam. The neutron spectra at the two angles are characterized by peaks with large widths of about 700 keV full width at half maximum and a shift of 300 keV between them. Neutron energies of up to about 4 MeV were observed indicating that deuterons are accelerated up to an energy of 1 MeV in the laser produced plasma. Simulation calculations can describe qualitatively the neutron spectra by assuming isotropic deuteron acceleration and a reduction of the reaction probability by a factor of 1/3 for deuterons emitted from the front of the target. These calculations indicate in particular that it is necessary to assume deuterons moving both into and out of the front of the target in order to describe the neutron energy spectra at the two angles. The highest recorded mean neutron yield was about 10(4) neutrons per pulse. The neutron yield increases with the number of electrons emitted from the front of the target and with the intensity of the prompt gamma flash induced by the bremsstrahlung of energetic electrons.

Analyzing and Post-modelling the High Speed Images of a Wavy Laser Induced Boiling Front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

The boiling front in laser materials processing like remote fusion cutting, keyhole welding or drilling can nowadays be recorded by high speed imaging. It was recently observed that bright waves flow down the front. Several complex physical mechanisms are associated with a stable laser-induced boiling front, like beam absorption, shadowing, heating, ablation pressure, fluid flow, etc. The evidence of dynamic phenomena from high speed imaging is closely linked to these phenomena. As a first step, the directly visible phenomena were classified and analyzed. This has led to the insight that the appearance of steady flow of the bright front peaks is a composition of many short flashing events of 20-50 μs duration, though composing a rather constant melt film flow downwards. Five geometrical front shapes of bright and dark domains were categorized, for example long inclined dark valleys. In addition, the special top and bottom regions of the front are distinguished. As a second step, a new method of post-modelling based on the greyscale variation of the images was applied, to approximately reconstruct the topology of the wavy front and subsequently to calculate the absorption across the front. Despite certain simplifications this kind of analysis provides a variety of additional information, including statistical analysis. In particular, the model could show the sensitivity of front waves to the formation of shadow domains and the robustness of fiber lasers to keep most of an irradiated steel surface in an absorptivity window between 35 to 43%.

Safety Evaluation of Discontinuing Late-Night Flash Operations at Signalized Intersections : Summary Report

DOT National Transportation Integrated Search

2013-08-01

During late-night flash (LNF) mode (from late night to early morning hours), traffic signals flash yellow for one road (typically, the major road), requiring caution but no stopping, and flash red for the other road (typically, the minor road), requi...

Flash flood disasters analysis and evaluation: a case study of Yiyang County in China

NASA Astrophysics Data System (ADS)

Li, Haichen; Zhang, Xiaolei; Li, Qing; Qin, Tao; Lei, Xiaohui

2018-03-01

Global climate change leads to the more extreme precipitation and more flash flood disasters, which is a serious threat to the mountain inhabitants. To prevent flash flood disasters, China started flash flood disaster control planning and other projects from 2006. Among those measures, non-engineering measures are effective and economical. This paper introduced the framework of flash flood disaster analysis and evaluation in China, followed by a case study of Yiyang County.

'Flash-forwards' and suicidal ideation: A prospective investigation of mental imagery, entrapment and defeat in a cohort from the Hong Kong Mental Morbidity Survey.

PubMed

Ng, Roger M K; Di Simplicio, Martina; McManus, Freda; Kennerley, Helen; Holmes, Emily A

2016-12-30

'Flash-forwards' - mental images of suicide - have been reported in selected Caucasian samples. Perceptions of defeat and entrapment are considered to be associated with suicidal ideation. We aimed to investigate (1) the presence of suicidal flash-forwards in people with recent suicidal ideation versus those without such ideation in an Asian sample, and (2) associations between suicidal flash-forwards, and perceptions of entrapment accounting for suicidal ideation. Eighty two suicidal and 80 non-suicidal participants from the Hong Kong Mental Morbidity Survey completed questionnaires including suicidal ideation, presence of suicidal flash-forward images, defeat and entrapment, at baseline and seven weeks later. Suicidal 'flash-forwards' were present only in suicidal cases. People with recent suicidal ideation and suicidal flash-forwards had more severe suicidal ideation than those without flash-forwards. Compared to those without suicidal ideation, people with recent suicidal ideation reported higher entrapment and defeat levels. Resolution of suicidal ideation over time was associated with fewer suicidal flash-forwards and reduced entrapment perceptions. At baseline and seven weeks, suicidal ideation was predicted by an interaction between suicidal flash-forwards presence and perceptions of entrapment. Mental imagery of suicide appears to be associated with suicidal ideation, and may represent a novel target in suicidal risk assessment and prevention. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Hot flashes and midlife symptoms in relation to levels of salivary cortisol.

PubMed

Gerber, Linda M; Sievert, Lynnette L; Schwartz, Joseph E

2017-02-01

This study examined the relationship between salivary cortisol levels and hot flashes during midlife. Previous studies have shown that cortisol levels increase with hot flashes in the laboratory, and higher cortisol levels have been associated with more severe hot flashes. Salivary cortisol levels were also examined in relation to total number of midlife symptoms. Women aged 40-60 years (n=109) reported the presence or absence of 23 symptoms, including hot flashes, during the previous 2 weeks. Salivary samples were collected at waking, 30min after waking, 1h before bedtime, and at bedtime. The cortisol awakening response (CAR), cortisol daily decline (CDD), log transformed salivary cortisol levels at each time point, and mean cortisol levels were compared by hot flash report using t-tests. Logistic regression analyses were performed to assess the association between each cortisol measure and the presence or absence of hot flashes, after controlling for potential covariates. Salivary cortisol levels were not significantly associated with hot flashes or sum of symptoms. Hot flash report did not differentiate women who had a positive CAR from those who did not, or women who showed strong CDD from those who did not. Symptomatic women - defined by hot flash report or symptom total - were not found to have higher salivary cortisol levels. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

A parametric multivariate drought index and its application in the attribution and projection of flash drought change in China

NASA Astrophysics Data System (ADS)

Yuan, X.; Wang, L.; Zhang, M.

2017-12-01

Rainfall deficit in the crop growing seasons is usually accompanied by heat waves. Abnormally high temperature increases evapotranspiration and decreases soil moisture rapidly, and ultimately results in a type of drought with a rapid onset, short duration but devastating impact, which is called "Flash drought". With the increase in global temperature, flash drought is expected to occur more frequently. However, there is no consensus on the definition of flash drought so far. Moreover, large uncertainty exists in the estimation of the flash drought and its trend, and the underlying mechanism for its long-term change is not clear. In this presentation, a parametric multivariate drought index that characterizes the joint probability distribution of key variables of flash drought will be developed, and the historical changes in flash drought over China will be analyzed. In addition, a set of land surface model simulations driven by IPCC CMIP5 models with different forcings and future scenarios, will be used for the detection and attribution of flash drought change. This study is targeted at quantifying the influences of natural and anthropogenic climate change on the flash drought change, projecting its future change as well as the corresponding uncertainty, and improving our understanding of the variation of flash drought and its underlying mechanism in a changing climate.

ANXIETY AS A RISK FACTOR FOR MENOPAUSAL HOT FLASHES: EVIDENCE FROM THE PENN OVARIAN AGING COHORT

PubMed Central

Freeman, Ellen W.; Sammel, Mary D.

2016-01-01

Objective The aim of this study was to identify temporal associations of anxiety dimensions with menopausal hot flashes in women progressing through the menopause transition. We hypothesized that associations of both somatic and affective dimensions of anxiety with hot flashes increased in the menopause transition, and that somatic anxiety was an independent risk factor for menopausal hot flashes. Methods Hot flashes, anxiety symptoms, hormone levels and other psychosocial variables were assessed annually for 14 years of follow-up. The 233 women were premenopausal at baseline and continued through one year or more after the final menstrual period. Anxiety dimensions were assessed with the Zung Anxiety Scale (ZAS), a validated measure of affective anxiety and somatic anxiety. Summed item scores were divided by the number of items rated, so that ranges of the two dimensions were comparable. Results Seventy-two percent of the sample reported moderate/severe hot flashes during the 14-year interval. There was no significant interaction between anxiety dimensions and menopausal stages. However, when adjusted for menopausal stage, the magnitude of association between somatic anxiety and hot flashes dramatically increased (OR 3.03, 95% CI: 2.12, 4.32, P<0.001), while the association between affective anxiety and hot flashes increased to a lesser extent (OR 1.27, 95% CI: 1.03, 1.57, P=0.024). Women with high levels of somatic anxiety (top third of the sample) had the greatest risk of hot flashes (P<0.001). When the anxiety dimensions were considered in combination, the additive effect of high affective anxiety symptoms was minimal, with no significant difference between the group with high affective/low somatic symptoms and the low symptom group in incident hot flashes at each menopausal stage (P=0.54). In multivariable analysis, somatic anxiety increased the risk of hot flashes more than 3 times (OR 3.13, 95% CI: 2.16, 4.53, P<0.001), but affective anxiety was not significantly associated with hot flashes after adjustment for other study variables (OR 1.19, 95% CI: 0.96, 1.48, P=0.117). Time-lagged somatic anxiety scores significantly predicted hot flashes, with a 71% increase in risk (OR 1.71, 95% CI: 1.21, 2.41, P=0.002). Time-lagged affective anxiety scores did not predict hot flashes, (OR 1.06, 95% CI: 0.87, 1.31, P=0.58). Conclusions This study showed a strong predictive association of somatic anxiety with the risk of menopausal hot flashes. The temporal associations suggest that somatic anxiety is not simply a redundant measure of hot flashes but predicts the risk of menopausal hot flashes and may be a potential target in clinical management of perimenopausal women. PMID:27433864

Positive cloud-to-ground lightning flashes in severe storms

NASA Technical Reports Server (NTRS)

Rust, W. D.; Macgorman, D. R.; Arnold, R. T.

1981-01-01

The occurrence of cloud-to-ground flashes that effectively lower positive charge to earth (+CG flash) over flat terrain has been documented in the mature stage of severe thunderstorms. Of the 31 documented +CG flashes, most had only one return stroke. Zero-to-peak rise times for the strokes averaged 7 microsec. The +CG flashes averaged 520 ms in duration, with 25 percent lasting more than 800 ms. Many of these had field changes suggestive of continuing current. Positive flashes have been observed to emanate from several regions of severe storms: high on the back of the main storm tower, through the wall cloud, and from the downshear anvil. Visually most of these positive flashes have emanated from high in the storm, and acoustic mapping of two shows thunder sources to a height of about 15 km.

Gun muzzle flash detection using a CMOS single photon avalanche diode

NASA Astrophysics Data System (ADS)

Merhav, Tomer; Savuskan, Vitali; Nemirovsky, Yael

2013-10-01

Si based sensors, in particular CMOS Image sensors, have revolutionized low cost imaging systems but to date have hardly been considered as possible candidates for gun muzzle flash detection, due to performance limitations, and low SNR in the visible spectrum. In this study, a CMOS Single Photon Avalanche Diode (SPAD) module is used to record and sample muzzle flash events in the visible spectrum, from representative weapons, common on the modern battlefield. SPADs possess two crucial properties for muzzle flash imaging - Namely, very high photon detection sensitivity, coupled with a unique ability to convert the optical signal to a digital signal at the source pixel, thus practically eliminating readout noise. This enables high sampling frequencies in the kilohertz range without SNR degradation, in contrast to regular CMOS image sensors. To date, the SPAD has not been utilized for flash detection in an uncontrolled environment, such as gun muzzle flash detection. Gun propellant manufacturers use alkali salts to suppress secondary flashes ignited during the muzzle flash event. Common alkali salts are compounds based on Potassium or Sodium, with spectral emission lines around 769nm and 589nm, respectively. A narrow band filter around the Potassium emission doublet is used in this study to favor the muzzle flash signal over solar radiation. This research will demonstrate the SPAD's ability to accurately sample and reconstruct the temporal behavior of the muzzle flash in the visible wavelength under the specified imaging conditions. The reconstructed signal is clearly distinguishable from background clutter, through exploitation of flash temporal characteristics.

Informing hot flash treatment decisions for breast cancer survivors: a systematic review of randomized trials comparing active interventions.

PubMed

Johns, Claire; Seav, Susan M; Dominick, Sally A; Gorman, Jessica R; Li, Hongying; Natarajan, Loki; Mao, Jun James; Irene Su, H

2016-04-01

Patient-centered decision making about hot flash treatments often incorporates a balance of efficacy and side effects in addition to patient preference. This systematic review examines randomized controlled trials (RCTs) comparing at least two non-hormonal hot flash treatments in breast cancer survivors. In July 2015, PubMed, SCOPUS, CINAHL, Cochrane, and Web of Science databases were searched for RCTs comparing active, non-hormonal hot flash treatments in female breast cancer survivors. Thirteen trials were included after identifying 906 potential studies. Four trials were dose comparison studies of pharmacologic treatments citalopram, venlafaxine, gabapentin, and paroxetine. Hot flash reduction did not differ by tamoxifen or aromatase inhibitor use. Citalopram 10, 20, and 30 mg daily had comparable outcomes. Venlafaxine 75 mg daily improved hot flashes without additional side effects from higher dosing. Gabapentin 900 mg daily improved hot flashes more than 300 mg. Paroxetine 10 mg daily had fewer side effects than 20 mg. Among four trials comparing different pharmacologic treatments, venlafaxine alleviated hot flash symptoms faster than clonidine; participants preferred venlafaxine over gabapentin. Five trials compared pharmacologic to non-pharmacologic treatments. Acupuncture had similar efficacy to venlafaxine and gabapentin but may have longer durability after completing treatment and fewer side effects. We could not perform a pooled meta-analysis because outcomes were not reported in comparable formats. Clinical trial data on non-hormonal hot flash treatments provide comparisons of hot flash efficacy and other patient important outcomes to guide clinical management. Clinicians can use the information to help patients select hot flash interventions.

Abdominal adiposity and hot flashes among midlife women.

PubMed

Thurston, Rebecca C; Sowers, MaryFran R; Sutton-Tyrrell, Kim; Everson-Rose, Susan A; Lewis, Tené T; Edmundowicz, Daniel; Matthews, Karen A

2008-01-01

Two competing hypotheses suggest how adiposity may affect menopausal hot flashes. The "thin hypothesis" asserts that aromatization of androgens to estrogens in body fat should be associated with decreased hot flashes. Conversely, thermoregulatory models argue that body fat should be associated with increased hot flashes. The study objective was to examine associations between abdominal adiposity and hot flashes, including the role of reproductive hormones in these associations. The Study of Women's Health Across the Nation Heart Study (2001-2003) is an ancillary study to the Study of Women's Health Across the Nation, a community-based cohort study. Participants were 461 women (35% African American, 65% white) ages 45 to 58 years with an intact uterus and at least one ovary. Measures included a computed tomography scan to assess abdominal adiposity; reported hot flashes over the previous 2 weeks; and a blood sample for measurement of follicle-stimulating hormone, estradiol, and sex hormone-binding globulin-adjusted estradiol (free estradiol index). Associations were evaluated within multivariable logistic and linear regression models. Every 1-SD increase in total (odds ratio [OR]=1.28; 95% CI: 1.06-1.55) and subcutaneous (OR=1.30; 95% CI: 1.07-1.58) abdominal adiposity was associated with increased odds of hot flashes in age- and site-adjusted models. Visceral adiposity was not associated with hot flashes. Associations were not reduced when models included reproductive hormone concentrations. Increased abdominal adiposity, particularly subcutaneous adiposity, is associated with increased odds of hot flashes, favoring thermoregulatory models of hot flashes. Body fat may not protect women from hot flashes as once thought.

50 CFR 300.5 - Facilitation of enforcement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... transmitted by flashing light directed at the vessel signaled. USCG units will normally use the flashing light..., flashing light, flags, whistle, horn or other means constitutes prima facie evidence of the offense of... International Code of Signals, may be sent by flashing light by an enforcement unit when conditions do not allow...

50 CFR 300.5 - Facilitation of enforcement.

Code of Federal Regulations, 2011 CFR

2011-10-01

... transmitted by flashing light directed at the vessel signaled. USCG units will normally use the flashing light..., flashing light, flags, whistle, horn or other means constitutes prima facie evidence of the offense of... International Code of Signals, may be sent by flashing light by an enforcement unit when conditions do not allow...

33 CFR 117.1007 - Elizabeth River-Eastern Branch.

Code of Federal Regulations, 2013 CFR

2013-07-01

... closing the draw, the channel traffic lights will change from flashing green to flashing red, the horn... down to vessels, the channel traffic lights will continue to flash red. (6) When the rail traffic has... opening to vessel traffic. During the opening swing movement, the channel traffic lights will flash red...

33 CFR 117.1007 - Elizabeth River-Eastern Branch.

Code of Federal Regulations, 2014 CFR

2014-07-01

... closing the draw, the channel traffic lights will change from flashing green to flashing red, the horn... down to vessels, the channel traffic lights will continue to flash red. (6) When the rail traffic has... opening to vessel traffic. During the opening swing movement, the channel traffic lights will flash red...

33 CFR 117.1007 - Elizabeth River-Eastern Branch.

Code of Federal Regulations, 2011 CFR

2011-07-01

... closing the draw, the channel traffic lights will change from flashing green to flashing red, the horn... down to vessels, the channel traffic lights will continue to flash red. (6) When the rail traffic has... opening to vessel traffic. During the opening swing movement, the channel traffic lights will flash red...

33 CFR 117.1007 - Elizabeth River-Eastern Branch.

Code of Federal Regulations, 2012 CFR

2012-07-01

... closing the draw, the channel traffic lights will change from flashing green to flashing red, the horn... down to vessels, the channel traffic lights will continue to flash red. (6) When the rail traffic has... opening to vessel traffic. During the opening swing movement, the channel traffic lights will flash red...

Decision support system for road closures in flash flood emergencies.

DOT National Transportation Integrated Search

2013-06-01

Among all the natural hazards, flash flood ranks as the No. 1 weather-related killer in U.S. More : than half of the deaths in flash flood are due to drowning victims in a traffic environment. So road : closure is critical to save lives from flash fl...

49 CFR 234.253 - Flashing light units and lamp voltage.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 4 2013-10-01 2013-10-01 false Flashing light units and lamp voltage. 234.253....253 Flashing light units and lamp voltage. (a) Each flashing light unit shall be inspected when... with installation specifications. (b) Lamp voltage shall be tested when installed and at least once...

49 CFR 234.253 - Flashing light units and lamp voltage.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Flashing light units and lamp voltage. 234.253....253 Flashing light units and lamp voltage. (a) Each flashing light unit shall be inspected when... with installation specifications. (b) Lamp voltage shall be tested when installed and at least once...

49 CFR 234.253 - Flashing light units and lamp voltage.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Flashing light units and lamp voltage. 234.253... Maintenance, Inspection, and Testing Inspections and Tests § 234.253 Flashing light units and lamp voltage. (a... proper alignment and frequency of flashes in accordance with installation specifications. (b) Lamp...

49 CFR 234.253 - Flashing light units and lamp voltage.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Flashing light units and lamp voltage. 234.253... Maintenance, Inspection, and Testing Inspections and Tests § 234.253 Flashing light units and lamp voltage. (a... proper alignment and frequency of flashes in accordance with installation specifications. (b) Lamp...

49 CFR 234.253 - Flashing light units and lamp voltage.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false Flashing light units and lamp voltage. 234.253....253 Flashing light units and lamp voltage. (a) Each flashing light unit shall be inspected when... with installation specifications. (b) Lamp voltage shall be tested when installed and at least once...

33 CFR 117.903 - Darby Creek.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., nine inches high to indicate the vertical clearance under the closed draw at all stages of the tide... change from flashing green to flashing red anytime the bridge is not in the full open position. (10) During downward span movement, the channel traffic lights will change from flashing green to flashing red...

33 CFR 117.903 - Darby Creek.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., nine inches high to indicate the vertical clearance under the closed draw at all stages of the tide... change from flashing green to flashing red anytime the bridge is not in the full open position. (10) During downward span movement, the channel traffic lights will change from flashing green to flashing red...

33 CFR 117.903 - Darby Creek.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., nine inches high to indicate the vertical clearance under the closed draw at all stages of the tide... change from flashing green to flashing red anytime the bridge is not in the full open position. (10) During downward span movement, the channel traffic lights will change from flashing green to flashing red...

78 FR 48188 - Certain Flash Memory Chips and Products Containing the Same Notice of Receipt of Complaint...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-07

... INTERNATIONAL TRADE COMMISSION [Docket No. 2971] Certain Flash Memory Chips and Products.... International Trade Commission has received a complaint entitled Certain Flash Memory Chips and Products... sale within the United States after importation of certain flash memory chips and products containing...

78 FR 55095 - Certain Flash Memory Chips and Products Containing Same; Institution of Investigation

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-09

... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-893] Certain Flash Memory Chips and... States after importation of certain flash memory chips and products containing the same by reason of... sale within the United States after importation of certain flash memory chips and products containing...

49 CFR 234.217 - Flashing light units.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Flashing light units. 234.217 Section 234.217... light units. (a) Each flashing light unit shall be properly positioned and aligned and shall be visible to a highway user approaching the crossing. (b) Each flashing light unit shall be maintained to...

INRRI-EDM/2016: the first laser retroreflector on the surface of Mars

NASA Astrophysics Data System (ADS)

Dell'Agnello, S.; Delle Monache, G.; Porcelli, L.; Boni, A.; Contessa, S.; Ciocci, E.; Martini, M.; Tibuzzi, M.; Intaglietta, N.; Salvatori, L.; Tuscano, P.; Patrizi, G.; Mondaini, C.; Lops, C.; Vittori, R.; Maiello, M.; Flamini, E.; Marchetti, E.; Bianco, G.; Mugnuolo, R.; Cantone, C.

2017-01-01

During Summer 2015 the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and cube/microsat Characterization Facilities Laboratory, http://www.lnf.infn.it/esperimenti/etrusco, Team of INFN-LNF, with support by ASI, carried out an intense activity of final design, manufacturing and testing in order to construct, space qualify and finally integrate INRRI-EDM/2016 on ESA's ExoMars EDM spacecraft (also dubbed "Schiaparelli"), which was successfully launched on March 14, 2016. INRRI (INstrument for landing-Roving laser Retroreflector Investigation) for the EDM (Entry descent and landing Demonstration Module) 2016 mission is a compact, lightweight, passive, maintenance-free array of eight cube corner laser retroreflectors fixed to an aluminum alloy frame through the use of silicon rubber suitable for space applications. INRRI was installed on the top panel of the EDM Central Bay on October 14, 2015. It will enable the EDM to be laser-located from Mars orbiters, through laser ranging and altimetry, lidar atmospheric observations from orbit, laser flashes emitted by orbiters, and lasercom. One or all of the above means of observation can be supported by INRRI when there is an active, laser-equipped orbiter, especially after EDM end-of-life and for a long time. INRRI goals will cover science (Mars geodesy/geophysics, future Mars test of General Relativity, GR), technology and exploration. Concerning the latter two, INRRI will support mars-georeferencing of the EDM landing site, support potential precision lidar-based landing next to the EDM, support test & diagnostics of lasercom for data exchange among Mars orbit, Mars surface and Earth, and it will be a precursor for additional Mars surface retroreflectors, for example on exploration rovers. This paper describes in detail our innovative payload, hopefully the very first to be deployed safely with the lander Schiaparelli on the Mars surface, and its space qualification for the ExoMars EDM 2016 mission. Despite the fate of the Schiaparelli landing, which is still under the investigation of ESA and the industry, this paper remains a valuable reference for next INRRI-like laser retroreflectors arrays.

Management of a Recurrent Pyogenic Granuloma of the Hard Palate with Diode Laser: A Case Report.

PubMed

Hasanoglu Erbasar, Güzin Neda; Senguven, Burcu; Gultekin, Sibel Elif; Cetiner, Sedat

2016-01-01

Pyogenic granuloma (PG) is a prevalent inflammatory hyperplasia of skin and oral mucosa which is often caused by constant low-grade local irritation, traumatic injury or hormonal factors. In many cases, gingival irritation and inflammation due to poor oral hygiene are precipitating factors. Oral PG occurs predominantly on the gingiva, but it is also encountered on the lips, tongue, buccal mucosa and rarely on the hard palate. Although surgical excision is the first choice of treatment, many other treatment modalities could be counted such as cryosurgery, sodium tetradecyl sulfate sclerotherapy, intralesional steroids, flash lamp pulsed dye laser, neodymium-doped yttrium aluminium garnet (Nd:YAG) laser, carbon dioxide (CO2) laser, erbium-doped yttrium aluminum garnet (Er:YAG) lasers and diode laser have been suggested. After surgical excision recurrence occurs up to 16% of these lesions. It is believed that recurrence ensues as a result of incomplete excision, failure to eliminate etiologic factors or repeated trauma. A 50-year-old female was referred to the Department of Oral Surgery, Gazi University, School of Dentistry, complaining of a swelling and growth on the right side of the hard palate for four months. Patient reported a similar growth in the same area about two years earlier, which had turned out to be a PG by histopathology. The treatment plan included surgical excision of the lesion using diode laser. The patient reported no pain after the surgery. She was discharged with a prescription of chlorhexidine mouthwash and necessary post-operative instructions. At 7 days follow up visit, immediate recurrence of the lesion was observed, and it was excised by diode laser with 2 mm margins at its clinical periphery, to a depth up to the periosteum, by the same operator. No recurrence or scarring was observed in 14 months follow-up. Although diode laser is a secure and efficient technique for the treatment of intraoral PG, in order to minimize its recurrence, the lesion should be excised with a wider margin down to the periosteum or to the causing agent. Also due to its high recurrence rate, long-term follow-up is recommended.

Effect of pulse duration on photomechanical response of soft tissue during Ho:YAG laser ablation

NASA Astrophysics Data System (ADS)

Jansen, E. Duco; Motamedi, Massoud; Pfefer, T. Joshua; Asshauer, Thomas; Frenz, Martin; Delacretaz, Guy P.; Abela, George S.; Welch, Ashley J.

1995-05-01

Mechanical injury during pulsed holmium laser ablation of tissue is caused by rapid bubble expansion and collapse or by laser-induced pressure waves. In this study the effect of pulse duration on the photomechanical response of soft tissue during holmium:YAG laser ablation has been investigated. The dynamics of laser-induced bubble formation was documented in water and in transparent polyacrylamide tissue phantoms with a water concentration of 84%. Holmium:YAG laser radiation ((lambda) equals 2.12 micrometers ) was delivered in water or tissue phantoms via an optical fiber (200 or 400 micrometers ). The laser was operated in either the Q- switched mode ((tau) p equals 500 ns, Qp equals 14 +/- 1 mJ, 200 micrometers fiber, Ho equals 446 mJ/mm2) or the free-running mode ((tau) p equals 100 - 1100 microsecond(s) , Qp equals 200 +/- 5 mJ, 400 micrometers fiber, Ho equals 1592 mJ/mm2). Bubble formation was documented using a fast flash photography setup while simultaneously a PVDP needle hydrophone (40 ns risetime), recorded pressures. The effect of the pulse duration on the photomechanical response of soft biological tissue was evaluated by delivering 5 pulses of 800 mJ to the intimal side of porcine aorta in vitro, followed by histologic evaluation. It was observed that, as the pulse duration was increased the bubble shape changed from almost spherical for Q-switched pulses to a more elongated, cylindrical shape for the longer pulse durations. The bubble expansion velocity was larger for shorter pulse durations. A thermo- elastic expansion wave was measured only during Q-switched pulse delivery. All pulses that induced bubble formation generated pressure waves upon collapse of the bubble in water as well as in the gel. The amplitude of the pressure wave depended strongly on the size and geometry of the laser-induced bubble. The important findings of this study were (1) the magnitude of collapse pressure wave decreased as laser pulse duration increased, and (2) mechanical tissue damage is reduced significantly by using longer pulse durations (> 460 microsecond(s) , for the pulse energy used).

Flash protection controller

DOEpatents

Galbraith, L.K.

1979-12-07

A controller provides a high voltage to maintain an electro-optic shutter in a transparent condition until a flash of light which would be harmful to personnel is sensed by a phototransistor. The controller then shorts the shutter to ground to minimize light transmission to the user and maintains light transmission at the pre-flash level for a predetermined time to allow the flash to subside. A log converter and differential trigger circuit keep the controller from being triggered by other light flashes which are not dangerous.

Flash protection controller

DOEpatents

Galbraith, Lee K.

1981-01-01

A controller provides a high voltage to maintain an electro-optic shutter in a transparent condition until a flash of light which would be harmful to personnel is sensed by a phototransistor. The controller then shorts the shutter to ground to minimize light transmission to the user and maintains light transmission at the pre-flash level for a predetermined time to allow the flash to subside. A log converter and differential trigger circuit keep the controller from being triggered by other light flashes which are not dangerous.

Amino acid residues in Anabaena ferredoxin crucial to interaction with ferredoxin-NADP+ reductase: site-directed mutagenesis and laser flash photolysis.

PubMed

Hurley, J K; Salamon, Z; Meyer, T E; Fitch, J C; Cusanovich, M A; Markley, J L; Cheng, H; Xia, B; Chae, Y K; Medina, M

1993-09-14

Ferredoxin (Fd) functions in photosynthesis to transfer electrons from photosystem I to ferredoxin-NADP+ reductase (FNR). We have made several site-directed mutants of Anabaena 7120 Fd and have used laser flash photolysis to investigate the effects of these mutations on the kinetics of reduction of oxidized Fd by deazariboflavin semiquinone (dRfH.) and the reduction of oxidized Anabaena FNR by reduced Fd. None of the mutations influenced the second-order rate constant for dRfH. reduction by more than a factor of 2, suggesting that the ability of the [2Fe-2S] cluster to participate in electron transfer was not seriously affected. In contrast, a surface charge reversal mutation, E94K, resulted in a 20,000-fold decrease in the second-order rate constant for electron transfer from Fd to FNR, whereas a similar mutation at an adjacent site, E95K, produced little or no change in reaction rate constant compared to wild-type Fd. Such a dramatic difference between contiguous surface mutations suggests a very precise surface complementarity at the protein-protein interface. Mutations introduced at F65 (F65I and F65A) also decreased the rate constant for the Fd/FNR electron transfer reaction by more than 3 orders of magnitude. Spectroscopic and thermodynamic measurements with both the E94 and F65 mutants indicated that the kinetic differences cannot be ascribed to changes in gross conformation, redox potential, or FNR binding constant but rather reflect the protein-protein interactions that control electron transfer. Several mutations at other sites in the vicinity of E94 and F65 (R42, T48, D68, and D69) resulted in little or no perturbation of the Fd/FNR interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Gd-EOB-DTPA-Enhanced MR Guidance in Thermal Ablation of Liver Malignancies

PubMed Central

Rosenberg, Christian; Jahn, Andrea; Pickartz, Tilman; Wahnschaffe, Ulrich; Patrzyk, Maciej; Hosten, Norbert

2014-01-01

Objective To evaluate the potency of Gd-EOB-DTPA to support hepatic catheter placement in laser ablation procedures by quantifying time-dependent delineation effects for instrumentation and target tumor within liver parenchyma. Monitoring potential influence on online MR thermometry during the ablation procedure is a secondary aim. Materials and Methods 30 cases of MR-guided laser ablation were performed after i.v. bolus injection of gadoxetic acid (0.025 mmol/Kg Gd-EOB-DTPA; Bayer Healthcare, Berlin, Germany). T1-weighted GRE sequences were used for applicator guidance (FLASH 3D) in the catheter placement phase and for therapy monitoring (FLASH 2D) in the therapy phase. SNR and consecutive CNR values were measured for elements of interest plotted over time both for catheter placement and therapy phase and compared with a non-contrast control group of 19 earlier cases. Statistical analysis was realized using the paired Wilcoxon test. Results Sustainable signal elevation of liver parenchyma in the contrast-enhanced group was sufficient to silhouette both target tumor and applicator against the liver. Differences in time dependent CNR alteration were highly significant between contrast-enhanced and non-contrast interventions for parenchyma and target on the one hand (p = 0.020) and parenchyma and instrument on the other hand (p = 0.002). Effects lasted for the whole procedure (monitoring up to 60 min) and were specific for the contrast-enhanced group. Contrasting maxima were seen after median 30 (applicator) and 38 (tumor) minutes, in the potential core time of a multineedle procedure. Contrast influence on T1 thermometry for real-time monitoring of thermal impact was not significant (p = 0.068–0.715). Conclusion Results strongly support anticipated promotive effects of Gd-EOB-DTPA for MR-guided percutaneous liver interventions by proving and quantifying the delineating effects for therapy-relevant elements in the procedure. Time benefit, cost effectiveness and oncologic outcome of the described beneficiary effects will have to be part of further investigations. PMID:25541950

An extended laser flash technique for thermal diffusivity measurement of high-temperature materials

NASA Technical Reports Server (NTRS)

Shen, F.; Khodadadi, J. M.

1993-01-01

Knowledge of thermal diffusivity data for high-temperature materials (solids and liquids) is very important in analyzing a number of processes, among them solidification, crystal growth, and welding. However, reliable thermal diffusivity versus temperature data, particularly those for high-temperature liquids, are still far from complete. The main measurement difficulties are due to the presence of convection and the requirement for a container. Fortunately, the availability of levitation techniques has made it possible to solve the containment problem. Based on the feasibility of the levitation technology, a new laser flash technique which is applicable to both levitated liquid and solid samples is being developed. At this point, the analysis for solid samples is near completion and highlights of the technique are presented here. The levitated solid sample which is assumed to be a sphere is subjected to a very short burst of high power radiant energy. The temperature of the irradiated surface area is elevated and a transient heat transfer process takes place within the sample. This containerless process is a two-dimensional unsteady heat conduction problem. Due to the nonlinearity of the radiative plus convective boundary condition, an analytic solution cannot be obtained. Two options are available at this point. Firstly, the radiation boundary condition can be linearized, which then accommodates a closed-form analytic solution. Comparison of the analytic curves for the temperature rise at different points to the experimentally-measured values will then provide the thermal diffusivity values. Secondly, one may set up an inverse conduction problem whereby experimentally obtained surface temperature history is used as the boundary conditions. The thermal diffusivity can then be elevated by minimizing the difference between the real heat flux boundary condition (radiation plus convection) and the measurements. Status of an experimental study directed at measuring the thermal diffusivity of high-temperature solid samples of pure Nickel and Inconel 718 superalloys are presented. Preliminary measurements showing surface temperature histories are discussed.

Gd-EOB-DTPA-enhanced MR guidance in thermal ablation of liver malignancies.

PubMed

Rosenberg, Christian; Jahn, Andrea; Pickartz, Tilman; Wahnschaffe, Ulrich; Patrzyk, Maciej; Hosten, Norbert

2014-01-01

To evaluate the potency of Gd-EOB-DTPA to support hepatic catheter placement in laser ablation procedures by quantifying time-dependent delineation effects for instrumentation and target tumor within liver parenchyma. Monitoring potential influence on online MR thermometry during the ablation procedure is a secondary aim. 30 cases of MR-guided laser ablation were performed after i.v. bolus injection of gadoxetic acid (0.025 mmol/Kg Gd-EOB-DTPA; Bayer Healthcare, Berlin, Germany). T1-weighted GRE sequences were used for applicator guidance (FLASH 3D) in the catheter placement phase and for therapy monitoring (FLASH 2D) in the therapy phase. SNR and consecutive CNR values were measured for elements of interest plotted over time both for catheter placement and therapy phase and compared with a non-contrast control group of 19 earlier cases. Statistical analysis was realized using the paired Wilcoxon test. Sustainable signal elevation of liver parenchyma in the contrast-enhanced group was sufficient to silhouette both target tumor and applicator against the liver. Differences in time dependent CNR alteration were highly significant between contrast-enhanced and non-contrast interventions for parenchyma and target on the one hand (p = 0.020) and parenchyma and instrument on the other hand (p = 0.002). Effects lasted for the whole procedure (monitoring up to 60 min) and were specific for the contrast-enhanced group. Contrasting maxima were seen after median 30 (applicator) and 38 (tumor) minutes, in the potential core time of a multineedle procedure. Contrast influence on T1 thermometry for real-time monitoring of thermal impact was not significant (p = 0.068-0.715). Results strongly support anticipated promotive effects of Gd-EOB-DTPA for MR-guided percutaneous liver interventions by proving and quantifying the delineating effects for therapy-relevant elements in the procedure. Time benefit, cost effectiveness and oncologic outcome of the described beneficiary effects will have to be part of further investigations.

Global optical lightning flash rates determined with the Forte satellite

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

Light, T.; Davis, S. M.; Boeck, W. L.

2003-01-01

Using FORTE photodiode detector (PDD) observations of lightning, we have determined the geographic distribution of nighttime flash rate density. We estimate the PDD flash detection efficiency to be 62% for total lightning through comparison to lightning observations by the TRMM satellite's Lightning Imaging Sensor (LIS), using cases in which FORTE and TRMM viewed the same storm. We present here both seasonal and l,ot,al flash rate maps. We examine some characteristics of the optical emissions of lightning in both high and low flash rate environments, and find that while lightning occurs less frequently over ocean, oceanic lightning flashes are somewhat moremore » powerful, on average, than those over land.« less