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Sample records for active photon flux

  1. Accuracy of quantum sensors measuring yield photon flux and photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Barnes, C.; Tibbitts, T.; Sager, J.; Deitzer, G.; Bubenheim, D.; Koerner, G.; Bugbee, B.; Knott, W. M. (Principal Investigator)

    1993-01-01

    Photosynthesis is fundamentally driven by photon flux rather than energy flux, but not all absorbed photons yield equal amounts of photosynthesis. Thus, two measures of photosynthetically active radiation have emerged: photosynthetic photon flux (PPF), which values all photons from 400 to 700 nm equally, and yield photon flux (YPF), which weights photons in the range from 360 to 760 nm according to plant photosynthetic response. We selected seven common radiation sources and measured YPF and PPF from each source with a spectroradiometer. We then compared these measurements with measurements from three quantum sensors designed to measure YPF, and from six quantum sensors designed to measure PPF. There were few differences among sensors within a group (usually <5%), but YPF values from sensors were consistently lower (3% to 20%) than YPF values calculated from spectroradiometric measurements. Quantum sensor measurements of PPF also were consistently lower than PPF values calculated from spectroradiometric measurements, but the differences were <7% for all sources, except red-light-emitting diodes. The sensors were most accurate for broad-band sources and least accurate for narrow-band sources. According to spectroradiometric measurements, YPF sensors were significantly less accurate (>9% difference) than PPF sensors under metal halide, high-pressure sodium, and low-pressure sodium lamps. Both sensor types were inaccurate (>18% error) under red-light-emitting diodes. Because both YPF and PPF sensors are imperfect integrators, and because spectroradiometers can measure photosynthetically active radiation much more accurately, researchers should consider developing calibration factors from spectroradiometric data for some specific radiation sources to improve the accuracy of integrating sensors.

  2. High precision photon flux determination for photon tagging experiments

    SciTech Connect

    Teymurazyan, A; Ahmidouch, A; Ambrozewicz, P; Asratyan, A; Baker, K; Benton, L; Burkert, V; Clinton, E; Cole, P; Collins, P; Dale, D; Danagoulian, S; Davidenko, G; Demirchyan, R; Deur, A; Dolgolenko, A; Dzyubenko, G; Ent, R; Evdokimov, A; Feng, J; Gabrielyan, M; Gan, L; Gasparian, A; Glamazdin, A; Goryachev, V; Hardy, K; He, J; Ito, M; Jiang, L; Kashy, D; Khandaker, M; Kolarkar, A; Konchatnyi, M; Korchin, A; Korsch, W; Kosinov, O; Kowalski, S; Kubantsev, M; Kubarovsky, V; Larin, I; Lawrence, D; Li, X; Martel, P; Matveev, V; McNulty, D; Mecking, B; Milbrath, B; Minehart, R; Miskimen, R; Mochalov, V; Nakagawa, I; Overby, S; Pasyuk, E; Payen, M; Pedroni, R; Prok, Y; Ritchie, B; Salgado, C; Shahinyan, A; Sitnikov, A; Sober, D; Stepanyan, S; Stevens, W; Underwood, J; Vasiliev, A; Vishnyakov, V; Wood, M; Zhou, S

    2014-07-01

    The Jefferson Laboratory PrimEx Collaboration has developed and implemented a method to control the tagged photon flux in photoproduction experiments at the 1% level over the photon energy range from 4.9 to 5.5 GeV. This method has been successfully implemented in a high precision measurement of the neutral pion lifetime. Here, we outline the experimental equipment and the analysis techniques used to accomplish this. These include the use of a total absorption counter for absolute flux calibration, a pair spectrometer for online relative flux monitoring, and a new method for post-bremsstrahlung electron counting.

  3. High precision photon flux determination for photon tagging experiments

    NASA Astrophysics Data System (ADS)

    Teymurazyan, A.; Ahmidouch, A.; Ambrozewicz, P.; Asratyan, A.; Baker, K.; Benton, L.; Burkert, V.; Clinton, E.; Cole, P.; Collins, P.; Dale, D.; Danagoulian, S.; Davidenko, G.; Demirchyan, R.; Deur, A.; Dolgolenko, A.; Dzyubenko, G.; Ent, R.; Evdokimov, A.; Feng, J.; Gabrielyan, M.; Gan, L.; Gasparian, A.; Glamazdin, A.; Goryachev, V.; Hardy, K.; He, J.; Ito, M.; Jiang, L.; Kashy, D.; Khandaker, M.; Kolarkar, A.; Konchatnyi, M.; Korchin, A.; Korsch, W.; Kosinov, O.; Kowalski, S.; Kubantsev, M.; Kubarovsky, V.; Larin, I.; Lawrence, D.; Li, X.; Martel, P.; Matveev, V.; McNulty, D.; Mecking, B.; Milbrath, B.; Minehart, R.; Miskimen, R.; Mochalov, V.; Nakagawa, I.; Overby, S.; Pasyuk, E.; Payen, M.; Pedroni, R.; Prok, Y.; Ritchie, B.; Salgado, C.; Shahinyan, A.; Sitnikov, A.; Sober, D.; Stepanyan, S.; Stevens, W.; Underwood, J.; Vasiliev, A.; Vishnyakov, V.; Wood, M.; Zhou, S.

    2014-12-01

    The Jefferson Laboratory PrimEx Collaboration has developed and implemented a method to control the tagged photon flux in photoproduction experiments at the 1% level over the photon energy range from 4.9 to 5.5 GeV. This method has been successfully implemented in a high precision measurement of the neutral pion lifetime. Here, we outline the experimental equipment and the analysis techniques used to accomplish this. These include the use of a total absorption counter for absolute flux calibration, a pair spectrometer for online relative flux monitoring, and a new method for post-bremsstrahlung electron counting.

  4. High flux photon beam monitor

    SciTech Connect

    Mortazavi, P.; Woodle, M.; Rarback, H.; Shu, D.; Howells, M.

    1985-01-01

    We have designed two photon beam position monitors for use on our x-ray storage ring beam lines. In both designs, a pair of tungsten blades, separated by a pre-determined gap, intercepts a small fraction of the incoming beam. Due to photoemission, an electrical signal is generated which is proportional to the amount of beam intercepted. The thermal load deposited in the blade is transferred by a heat pipe to a heat exchanger outside the vacuum chamber. A prototype monitor with gap adjustment capability was fabricated and tested at a uv beam line. The results show that the generated electrical signal is a good measurement of the photon beam position. In the following sections, design features and test results are discussed.

  5. Contactless heat flux control with photonic devices

    SciTech Connect

    Ben-Abdallah, Philippe; Biehs, Svend-Age

    2015-05-15

    The ability to control electric currents in solids using diodes and transistors is undoubtedly at the origin of the main developments in modern electronics which have revolutionized the daily life in the second half of 20th century. Surprisingly, until the year 2000 no thermal counterpart for such a control had been proposed. Since then, based on pioneering works on the control of phononic heat currents new devices were proposed which allow for the control of heat fluxes carried by photons rather than phonons or electrons. The goal of the present paper is to summarize the main advances achieved recently in the field of thermal energy control with photons.

  6. Photon Flux Amplification for Enhancing Photonic Laser Propulsive Forces

    NASA Technical Reports Server (NTRS)

    Gray, Perry A.; Carruth, M. Ralph, Jr.; Edwards, David L.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    An enhancement to the available force from a solar/laser sail is being investigated. This enhancement involves the use of a high power laser as the main source of propulsion or as a supplement to a solar sail. The enhancement utilizes a high power laser and multiple photon reflections to amplify the laser photon flux impinging on a sail. It is thus possible to amplify the force by as much as a factor of 50 or more. This paper explores the use of a stable optical cavity and will illustrate the optics involved in producing a stable cavity. A breadboard of the optical system was constructed and a stable cavity was demonstrated. Once the breadboard system was complete and a stable cavity achieved, the system was placed in vacuum and photon force amplification was measured using a vacuum compatible microbalance.

  7. Photon-activation therapy

    SciTech Connect

    Fairchild, R.G.; Bond, V.P.

    1982-01-01

    Photon Activation Therapy (PAT) is a technique in which radiation dose to tumor is enhanced via introduction of stable /sup 127/I in the form of iodinated deoxyuridine (IdUrd). Stimulation of cytotoxic effects from IdUrd is accomplished by activation with external (or implanted) radiation sources. Thus, accumulations of this nucleoside in actively competing cellpools do not preclude therapy in so far as such tissues can be excluded from the radiation field. Calculations show that 5% replacement of thymidine (Tyd) in tumor DNA should enhance the biological effectiveness of a given photon radiotherapy dose by a factor of approx. 3. Proportionally higher gains would result from higher replacements of Tyd and IdUrd. In addition, biological response is enhanced by chemical sensitization with IdUrd. The data indicate that damage from photon activation as well as chemical sensitization does not repair. Thus, at low dose rates, a further increase in therapeutic gain should accrue as normal tissues are allowed to repair and regenerate. A samarium-145 source has been developed for PAT, with activating x-ray energies of from 38 to 45 keV. Favorable clinical results can be expected through the use of IdUrd and protracted irradiations with low energy x-rays. In particular, PAT may provide unique advantages at selected sites such as brain, or head and neck tumors. (ERB)

  8. High-flux solar photon processes

    SciTech Connect

    Lorents, D C; Narang, S; Huestis, D C; Mooney, J L; Mill, T; Song, H K; Ventura, S

    1992-06-01

    This study was commissioned by the National Renewable Energy Laboratory (NREL) for the purpose of identifying high-flux photoprocesses that would lead to beneficial national and commercial applications. The specific focus on high-flux photoprocesses is based on the recent development by NREL of solar concentrator technology capable of delivering record flux levels. We examined photolytic and photocatalytic chemical processes as well as photothermal processes in the search for processes where concentrated solar flux would offer a unique advantage. 37 refs.

  9. Absolute photon-flux measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Haddad, G. N.

    1974-01-01

    Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

  10. Vorticity flux from active dimples

    NASA Astrophysics Data System (ADS)

    McKeon, Beverley; Sherwin, Spencer; Morrison, Jonathan

    2004-11-01

    The effect of surface depressions, or dimples, in reducing drag on golf balls is well-known. Here this concept is extended to using ``active" dimples to manipulate vorticity flux at the wall. Surface vorticity flux is governed by surface accelerations, pressure and shear stress gradients, and surface curvature. ``Active" (or vibrating) dimples may generate vorticity flux by each of these terms, making them an excellent candidate for a basic study of flux manipulation, by which flow control may be achieved. Flow over an active dimple in fully-developed laminar channel flow is simulated with velocity boundary conditions developed from a linearized perturbation method imposed at the wall. This simple model cannot capture flow separation, but gives insight into the most straightforward means of flux generation from the concave surface. Vorticity flux due to dimple geometry and motion is quantified, and enhancements of two to three orders of magnitude in peak vorticity over the static dimple case are observed.

  11. High-flux solar photon processes: Opportunities for applications

    SciTech Connect

    Steinfeld, J.I.; Coy, S.L.; Herzog, H.; Shorter, J.A.; Schlamp, M.; Tester, J.W.; Peters, W.A.

    1992-06-01

    The overall goal of this study was to identify new high-flux solar photon (HFSP) processes that show promise of being feasible and in the national interest. Electric power generation and hazardous waste destruction were excluded from this study at sponsor request. Our overall conclusion is that there is promise for new applications of concentrated solar photons, especially in certain aspects of materials processing and premium materials synthesis. Evaluation of the full potential of these and other possible applications, including opportunities for commercialization, requires further research and testing. 100 refs.

  12. VUV Photon Fluxes from Microwave Excited Microplasmas at Low Pressure

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Denning, Mark; Urdhal, Randall; Kushner, Mark J.

    2013-09-01

    Microplasmas in rare gases and rare gases mixtures can provide efficient and discretely tunable sources of VUV light. Microwave excited microplasma sources excited by a split-ring resonator antenna in rare gas mixtures operated in ceramic cavities with sub-mm dimensions have been developed as discretely tunable VUV sources for chemical analysis. Controlling wavelengths and the ratio of ion to VUV fluxes are important to achieving chemical selectivity. In this paper, we will discuss results from an investigation of scaling laws for the efficiency of VUV photon production in rare gas mixtures. The investigation was performed using a hydrodynamics model where the electron energy distribution and radiation transport are addressed by Monte Carlo simulations. Plasma density, VUV photon production and fluxes from the cavities will be discussed for mixtures of Ar, He, Xe, Kr, and as a function of power format (pulsing, cw), pressure and cavity sizes.

  13. Testing the quasi-absolute method in photon activation analysis

    SciTech Connect

    Sun, Z. J.; Wells, D.; Starovoitova, V.; Segebade, C.

    2013-04-19

    In photon activation analysis (PAA), relative methods are widely used because of their accuracy and precision. Absolute methods, which are conducted without any assistance from calibration materials, are seldom applied for the difficulty in obtaining photon flux in measurements. This research is an attempt to perform a new absolute approach in PAA - quasi-absolute method - by retrieving photon flux in the sample through Monte Carlo simulation. With simulated photon flux and database of experimental cross sections, it is possible to calculate the concentration of target elements in the sample directly. The QA/QC procedures to solidify the research are discussed in detail. Our results show that the accuracy of the method for certain elements is close to a useful level in practice. Furthermore, the future results from the quasi-absolute method can also serve as a validation technique for experimental data on cross sections. The quasi-absolute method looks promising.

  14. Seismic stress responses of soybean to different photosynthetic photon flux

    NASA Technical Reports Server (NTRS)

    Jones, R. S.; Coe, L. L.; Montgomery, L.; Mitchell, C. A.

    1990-01-01

    Physical agitation applied as periodic seismic stress (shaking) reduced stem elongation, leaf expansion, and biomass accumulation by vegetative soybeans. Level of photon flux (PPF) influenced the type and extent of plant response to mechanical stress. Plant parts responded differently as PPF varied between 135 and 592 micromoles m-2 s-1. Stem length was significantly reduced by seismic stress at 135 micromoles m-2 s-1 but this effect was insignificant at higher PPFs. Reduced stem length resulted from an inhibition of internode elongation. Stem diameter was unaffected by stress at the PPFs tested. In contrast to effects on stem elongation, leaf area was insensitive to stress treatments at 135 micromoles m-2 s-1 but was progressively inhibited by stress as PPF increased. Statistically significant reductions in shoot f. wt and d. wt by seismic stress occurred only at 295 micromoles m-2 s-1. Root biomass accumulation was not affected by seismic stress at any PPF used in this study.

  15. Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor

    NASA Astrophysics Data System (ADS)

    Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

    2013-10-01

    Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18 W g-1 and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

  16. Controlling Ion and UV/VUV Photon Fluxes in Pulsed Low Pressure Plasmas for Materials Processing

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2012-10-01

    UV/VUV photon fluxes in plasma materials processing have a variety of effects ranging from damaging to synergistic. To optimize these processes, it is desirable to have separate control over the fluxes of ions and photons, or at least be able to control their relative fluxes or overlap in time. Pulsed plasmas may provide such control as the rates at which ion and photon fluxes respond to the pulse power deposition are different. Results from a computational investigation of pulsed plasmas will be discussed to determine methods to control the ratio of ion to photon fluxes. Simulations were performed using a 2-dimensional plasma hydrodynamics model which addresses radiation transport using a Monte Carlo Simulation. Radiation transport is frequency resolved using partial-frequency-redistribution algorithms. Results for low pressure (10s of mTorr) inductively and capacitively coupled plasmas in Ar/Cl2 mixtures will be discussed while varying duty cycle, reactor geometry, gas mixture and pressure. We found that the time averaged ratio of VUV photon-to-ion fluxes in ICPs can be controlled with duty cycle of the pulsed power. Even with radiation trapping, photon fluxes tend to follow the power pulse whereas due to their finite response times, fluxes of ions tend to average the power pulse. Due to the overshoot in electron temperature that occurs at the start of low-duty-cycle pulses, disproportionately large photon fluxes (compared to ion fluxes) can be generated.

  17. Effect of CO sub 2 enrichment and high photosynthetic photon flux densities (PPFD) on rubisco and PEP-case activities of in vitro cultured strawberry plants

    SciTech Connect

    Desjardins, Y.; Beeson, R.; Gosselin, A. )

    1989-04-01

    Standard growing conditions in vitro (low light and CO{sub 2}) are not conducive to autotrophy. An experiment was conducted to improve photosynthesis in vitro in the hope of increasing survival in acclimatization. A factorial experiment was elaborated where CO{sub 2} and PPFD were supplied to in vitro cultured strawberry plants in the rooting stage. Activities of carboxylating enzymes were determined after 4 weeks of culture. The activities of non-activated and activated rubisco and PEP-Case were measured after extraction of the enzymes and a reaction with NaH{sup 14}CO{sub 3} followed by scintillation counting spectroscopy. High CO{sub 2} concentration significantly increased net assimilation rates (NAR) by 165% over the control for both 1650 and 3000 ppm CO{sub 2}. High PPFD only increased NAR by 12 and 35% for 150 and 250 {mu}mol{center dot}m{sup {minus}2}{center dot}s{sup {minus}1} respectively over the control. Plants grown at 3000 ppm CO{sub 2} had the highest level of chlorophyll/g FW with 97% more than the control. The activity of PEP-Case was the highest at high light levels and high CO{sub 2} with rates of 1.65 for 1650 ppm versus 1.22 mmol CO{sub 2} mg{sup {minus}1} chl. h{sup {minus}1} at 250 {mu}mol{center dot}m{sup {minus}2}{center dot}s{sup {minus}1}. There was no difference in PEP activity at low light levels. The rubisco activity was lower at 1650 and 3000 ppm CO{sub 2}. Increases in NAR correlate more closely to the PEP-Case than to Rubisco activity. Physiological significance of high activity of PEP-Case over rubisco will be discussed.

  18. Controlling VUV photon fluxes in low-pressure inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Tian, Peng; Kushner, Mark J.

    2015-06-01

    Low-pressure (a few to hundreds of millitorrs) inductively coupled plasmas (ICPs), as typically used in microelectronics fabrication, often produce vacuum-ultraviolet (VUV) photon fluxes onto surfaces comparable to or exceeding the magnitude of ion fluxes. These VUV photon fluxes are desirable in applications such as sterilization of medical equipment but are unwanted in many materials fabrication processes due to damage to the devices by the high-energy photons. Under specific conditions, VUV fluxes may stimulate etching or synergistically combine with ion fluxes to modify polymeric materials. In this regard, it is desirable to control the magnitude of VUV fluxes or the ratio of VUV fluxes to those of other reactive species, such as ions, or to discretely control the VUV spectrum. In this paper, we discuss results from a computational investigation of VUV fluxes from low-pressure ICPs sustained in rare gas mixtures. The control of VUV fluxes through the use of pressure, pulsed power, and gas mixture is discussed. We found that the ratio, β, of VUV photon to ion fluxes onto surfaces generally increases with increasing pressure. When using pulsed plasmas, the instantaneous value of β can vary by a factor of 4 or more during the pulse cycle due to the VUV flux more closely following the pulsed power.

  19. Emerging flux in active regions. [of sun

    NASA Technical Reports Server (NTRS)

    Liggett, M.; Zirin, H.

    1985-01-01

    The rates at which flux emerges in active and quiet solar regions within the sunspot belts are compared. The emerging flux regions (EFRs) were identified by the appearance of arch filament structures in H-alpha. All EFRs in high resolution films of active regions made at Big Bear in 1978 were counted. The comparable rate of flux emergence in quiet regions was obtained from SGD data and independently from EFRs detected outside the active region perimeter on the same films. The rate of flux emergence is 10 times higher in active regions than in quiet regions. A sample of all active regions in 31 days of 1983 gave a ratio of 7.5. Possible mechanisms which might funnel new magnetic flux to regions of strong magnetic field are discussed.

  20. Dual active surface heat flux gage probe

    NASA Astrophysics Data System (ADS)

    Liebert, Curt H.; Kolodziej, Paul

    1995-02-01

    A unique plug-type heat flux gage probe was tested in the NASA Ames Research Center 2x9 turbulent flow duct facility. The probe was fabricated by welding a miniature dual active surface heat flux gage body to the end of a hollow metal cylindrical bolt containing a metal inner tube. Cooling air flows through the inner tube, impinges onto the back of the gage body and then flows out through the annulus formed between the inner tube and the hollow bolt wall. Heat flux was generated in the duct facility with a Huels arc heater. The duct had a rectangular cross section and one wall was fabricated from 2.54 centimeter thick thermal insulation rigid surface material mounted onto an aluminum plate. To measure heat flux, the probe was inserted through the plate and insulating materials with the from of the gage located flush with the hot gas-side insulation surface. Absorbed heat fluxes measured with the probe were compared with absorbed heat fluxes measured with six water-cooled reference calorimeters. These calorimeters were located in a water-cooled metal duct wall which was located across from the probe position. Correspondence of transient and steady heat fluxes measured with the reference calorimeters and heat flux gage probe was generally within a satisfactory plus or minus 10 percent. This good correspondence was achieved even though the much cooler probe caused a large surface temperature disruption of 1000K between the metal gage and the insulation. However, this temperature disruption did not seriously effect the accuracy of the heat flux measurement. A current application for dual active surface heat flux gages is for transient and steady absorbed heat flux, surface temperature and heat transfer coefficient measurements on the surface of an oxidizer turbine inlet deflector operating in a space shuttle test bed engine.

  1. Combined analysis of neutron and photon flux measurements for the Jules Horowitz reactor core mapping

    SciTech Connect

    Fourmentel, D.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Bignan, G.; Chauvin, J. P.; Gonnier, C.; Guimbal, P.; Malo, J. Y.; Carette, M.; Janulyte, A.; Merroun, O.; Brun, J.; Zerega, Y.; Andre, J.

    2011-07-01

    We study the combined analysis of nuclear measurements to improve the knowledge of the irradiation conditions in the experimental locations of the future Jules Horowitz Reactor (JHR). The goal of the present work is to measure more accurately neutron flux, photon flux and nuclear heating in the reactor. In a Material Testing Reactor (MTR), nuclear heating is a crucial parameter to design the experimental devices to be irradiated in harsh nuclear conditions. This parameter drives the temperature of the devices and of the samples. The numerical codes can predict this parameter but in-situ measurements are necessary to reach the expected accuracy. For this reason, one objective of the IN-CORE program [1] is to study the combined measurements of neutron and photon flux and their cross advanced interpretation. It should be reminded that both neutron and photon sensors are not totally selective as their signals are due to neutron and photon interactions. We intend to measure the neutron flux by three different kinds of sensors (Uranium Fission chamber, Plutonium Fission chamber and Self Powered Neutron Detector), the photon flux by two different sensors (Ionization chamber and Self Powered Gamma Detector) and the nuclear heating by two different ones (Differential calorimeter and Gamma Thermometer). For the same parameter, we expect that the use of different kinds of sensors will allow a better estimation of the aimed parameter by mixing different spectrum responses and different neutron and gamma contributions. An experimental test called CARMEN-1 is scheduled in OSIRIS reactor (CEA Saclay - France) at the end of 2011, with the goal to map irradiation locations in the reactor reflector to get a first validation of the analysis model. This article focuses on the sensor selection for CARMEN-1 experiment and to the way to link neutron and photon flux measurements in view to reduce their uncertainties but also to better assess the neutron and photon contributions to nuclear

  2. PHOTON FLUX DENSITY INFLUENCES GRASS RESPONSES TO EXTENDED PHOTOPERIOD

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant sensitivity to extended photoperiod has been well documented, with little attention to the possibility that quantum flux density used to extend photoperiod has an influence on the expression of photoperiod response. This study was undertaken with 4 grass species under field conditions to exami...

  3. Fluxes and spectra of quasimonochromatic annihilation photons for studying E1 giant resonances in nuclei

    SciTech Connect

    Dzhilavyan, L. Z.

    2014-12-15

    The fluxes and spectra of quasimonochromatic photons originating from the in-flight annihilation of positrons interacting with electrons of targets are analyzed in the energy region characteristic of the excitation of E1 giant resonances in nuclei. Targets of small thickness and low atomic number are used. The dependences of the spectra on the energy and angle (and their scatter) for positrons incident to the target, on the collimation angle for photons, and on the target thickness are studied.

  4. Photonic crystals with active organic materials

    NASA Astrophysics Data System (ADS)

    Wu, Yeheng

    The concept of photonic crystals, which involves periodically arranged dielectrics that form a new type of material having novel photonic properties, was first proposed about two decades ago. Since then, a number of applications in photonic technology have been explored. Specifically, organic and hybrid photonic crystals are promising because of the unique advantages of the organic materials. A one-dimensional (1D) photonic crystal (multilayer) has high reflectance across a certain wavelength range. We report on studies of 1D multilayer polymer films that were fabricated using spin-coating, free film stacking, and co-extrusion techniques. For example, a stack fabricated by placing a laser dye-doped gain medium between two multilayer reflecting polymer films forms a micro-resonator laser or distributed Bragg laser. The resulting laser system is made entirely of plastic and is only several tens of micrometers in thickness. When the gain, a dye-doped medium, comprises one type of a two-type multilayer film, it results a laser exhibiting distributed feedback. At the edge of the photonic band, the group velocity becomes small and the density of photon states becomes high, which leads to laser emission. Such distributed feedback lasers were fabricated using the co-extrusion technique. The refractive indices and the photonic lattice determine the photonic band gap, which can be tuned by changing these parameters. Materials with Kerr nonlinearity exhibit a change in refractive index depending on the incident intensity of the light. To demonstrate such switching, electrochemical etching techniques on silicon wafers were used to form two-dimensional (2D) photonic crystals. By incorporating the nonlinear organic material into the 2D structure, we have made all-optical switches. The reflection of a beam from the 2D photonic crystal can be controlled by another beam because it induces a refractive index change in the active material by altering the reflection band. A mid

  5. Signal photon flux generated by high-frequency relic gravitational waves

    NASA Astrophysics Data System (ADS)

    Li, Xin; Wang, Sai; Wen, Hao

    2016-08-01

    The power spectrum of primordial tensor perturbations increases rapidly in the high frequency region if the spectral index n t > 0. It is shown that the amplitude of relic gravitational waves h t(5 × 109 Hz) varies from 10‑36 to 10‑25 while n t varies from ‑6.25 × 10‑3 to 0.87. A high frequency gravitational wave detector proposed by F.-Y. Li detects gravitational waves through observing the perturbed photon flux that is generated by interaction between relic gravitational waves and electromagnetic field. It is shown that the perturbative photon flux (5 × 109 Hz) varies from 1.40 × 10‑4 s‑1 to 2.85 × 107 s‑1 while n t varies from ‑6.25 × 10‑3 to 0.87. Correspondingly, the ratio of the transverse perturbative photon flux to the background photon flux varies from 10‑28 to 10‑16. Supported by National Natural Science Foundation of China (11305181,11322545,11335012) and Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y5KF181CJ1)

  6. A scheme for two-photon lasing with two coupled flux qubits in circuit quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Huang, Wen; Zou, Xu-Bo; Guo, Guang-Can

    2015-06-01

    We theoretically study the system of a superconducting transmission line resonator coupled to two interacting superconducting flux qubits. It is shown that under certain conditions the resonator mode can be tuned to two-photon resonance between the ground state and the highest excited state while the middle excited states are far-off resonance. Furthermore, we study the steady-state properties of the flux qubits and resonator, such as the photon statistics, the spectrum and squeezing of the resonator, and demonstrate that two-photon laser can be implemented with current experimental technology. Project supported by the National Fundamental Research Program of China (Grant No. 2011cba00200), the National Natural Science Foundation of China (Grant No. 11274295), and the Doctor Foundation of Education Ministry of China (Grant No. 20113402110059).

  7. Photon flux requirements for EUV reticle imaging microscopy in the 22 and 16 nm nodes

    SciTech Connect

    Wintz, D.; Goldberg, K. A.; Mochi, I.; Huh, S.

    2010-03-12

    EUV-wavelength actinic microscopy yields detailed information about EUV mask patterns, architectures, defects, and the performance of defect repair strategies, without the complications of photoresist imaging. The measured aerial image intensity profiles provide valuable feedback to improve mask and lithography system modeling methods. In order to understand the photon-flux-dependent pattern measurement limits of EUV mask-imaging microscopy, we have investigated the effects of shot noise on aerial image linewidth measurements for lines in the 22 and 16-nm generations. Using a simple model of image formation near the resolution limit, we probe the influence of photon shot noise on the measured, apparent line roughness. With this methodology, we arrive at general flux density requirements independent of the specific EUV microscope configurations. Analytical and statistical analysis of aerial image simulations in the 22 and 16-nm generations reveal the trade-offs between photon energy density (controllable with exposure time), effective pixel dimension on the CCO (controlled by the microscope's magnification ratio), and image log slope (ILS). We find that shot-noise-induced linewidth roughness (LWR) varies imersely with the square root of the photon energy density, and is proportional to the imaging magnification ratio. While high magnification is necessary for adequate spatial resolution, for a given flux density, higher magnification ratios have diminishing benefits. With practical imaging parameters, we find that in order to achieve an LWR (3{sigma}) value of 5% of linewidth for dense, 88-nm mask features with 80% aerial image contrast and 13.5-nm effective pixel width (1000x magnification ratio), a peak photon flux of approximately 1400 photons per pixel per exposure is required.

  8. Photochemistry of solutes in/on ice: reaction rate dependence on sample orientation and photon flux

    NASA Astrophysics Data System (ADS)

    Hullar, T.; Anastasio, C.

    2015-12-01

    Particularly in polar regions, photochemical reactions in snowpacks can be an important mechanism for transforming organic and inorganic compounds. Chemicals within snow and ice are found in three different compartments: distributed in the bulk ice, concentrated in liquid-like regions (LLRs) within the ice matrix (such as at grain boundaries), or present in quasi-liquid layers (QLLs) at the air-ice interface. While some previous work suggested reaction rates may vary in these different compartments, our preliminary experiments found similar reaction rates in all three compartments, as well as in aqueous solution. Previous work also suggested reaction rate constants may be independent of photon flux under certain illumination conditions. Here, we extend our investigations to measure reaction rate constants in ice samples with different orientations to the illumination source, which our work thus far suggests may impact the measured rate constants. Polycyclic aromatic hydrocarbons (PAHs) are common pollutants in snow and ice. We first prepared aqueous solutions of a single PAH. We then froze these samples using various methods previously shown to segregate the solute into known locations in the ice matrix. With simulated polar sunlight, we illuminated these samples and measured photon flux (using 2-nitrobenzaldehyde as a chemical actinometer) and photodecay of the PAH. Using this information, we normalized the rate of PAH loss to the photon flux and calculated the rate constants for PAH photodegradation under various freezing conditions, photon fluxes, and sample orientations. We will report on the impact of these variables on PAH photodegradation as well as the effect of varying the photon flux.

  9. The PHOTON explorations: sixteen activities, many uses

    NASA Astrophysics Data System (ADS)

    Donnelly, Judith; Amatrudo, Kathryn; Robinson, Kathleen; Hanes, Fenna

    2014-07-01

    The PHOTON Explorations were adapted from favorite demonstrations of teacher participants in the PHOTON projects of the New England Board of Higher Education as well as Hands-on-Optics activities and interesting demonstrations found on the web. Since the end of project PHOTON2 in 2006, the sixteen inquiry-based activities have formed the basis for a hands-on "home lab" distance- learning course that has been used for college students, teacher professional development and corporate training. With the support of OSA, they have been brought to life in a series of sixteen short videos aimed at a middle school audience. The Explorations are regularly used as activities in outreach activities for middle and high school students and are introduced yearly to an international audience at an outreach workshop at SPIE's Optics and Photonics meeting. In this paper we will demonstrate the Explorations, trace their origins and explain the content. We will also provide details on the development of the Exploration videos, the online course, and outreach materials and give statistics on their use in each format. Links to online resources will be provided.

  10. Generation of high-photon flux-coherent soft x-ray radiation with few-cycle pulses.

    PubMed

    Demmler, Stefan; Rothhardt, Jan; Hädrich, Steffen; Krebs, Manuel; Hage, Arvid; Limpert, Jens; Tünnermann, Andreas

    2013-12-01

    We present a tabletop source of coherent soft x-ray radiation with high-photon flux. Two-cycle pulses delivered by a fiber-laser-pumped optical parametric chirped-pulse amplifier operating at 180 kHz repetition rate are upconverted via high harmonic generation in neon to photon energies beyond 200 eV. A maximum photon flux of 1.3·10(8) photons/s is achieved within a 1% bandwidth at 125 eV photon energy. This corresponds to a conversion efficiency of ~10(-9), which can be reached due to a gas jet simultaneously providing a high target density and phase matching. Further scaling potential toward higher photon flux as well as higher photon energies are discussed. PMID:24281507

  11. Method for photon activation positron annihilation analysis

    DOEpatents

    Akers, Douglas W.

    2006-06-06

    A non-destructive testing method comprises providing a specimen having at least one positron emitter therein; determining a threshold energy for activating the positron emitter; and determining whether a half-life of the positron emitter is less than a selected half-life. If the half-life of the positron emitter is greater than or equal to the selected half-life, then activating the positron emitter by bombarding the specimen with photons having energies greater than the threshold energy and detecting gamma rays produced by annihilation of positrons in the specimen. If the half-life of the positron emitter is less then the selected half-life, then alternately activating the positron emitter by bombarding the specimen with photons having energies greater then the threshold energy and detecting gamma rays produced by positron annihilation within the specimen.

  12. Macroscopic response in active nonlinear photonic crystals.

    PubMed

    Alagappan, Gandhi; John, Sajeev; Li, Er Ping

    2013-09-15

    We derive macroscopic equations of motion for the slowly varying electric field amplitude in three-dimensional active nonlinear optical nanostructures. We show that the microscopic Maxwell equations and polarization dynamics can be simplified to a macroscopic one-dimensional problem in the direction of group velocity. For a three-level active material, we derive the steady-state equations for normal mode frequency, threshold pumping, nonlinear Bloch mode amplitude, and lasing in photonic crystals. Our analytical results accurately recapture the results of exact numerical methods. PMID:24104802

  13. Microsystem for remote sensing of high energy radiation with associated extremely low photon flux densities

    NASA Astrophysics Data System (ADS)

    Otten, A.; Jain, V. K.

    2015-08-01

    This paper presents a microsystem for remote sensing of high energy radiation in extremely low flux density conditions. With wide deployment in mind, potential applications range from nuclear non-proliferation, to hospital radiation-safety. The daunting challenge is the low level of photon flux densities - emerging from a Scintillation Crystal (SC) on to a ~1 mm-square detector, which are a factor of 10000 or so lower than those acceptable to recently reported photonic chips (including `single-photon detection' chips), due to a combination of low Lux, small detector size, and short duration SC output pulses - on the order of 1 μs. These challenges are attempted to be overcome by the design of an innovative `System on a Chip' type microchip, with high detector sensitivity, and effective coupling from the SC to the photodetector. The microchip houses a tiny n+ diff p-epi photodiode (PD) as well as the associated analog amplification and other related circuitry, all fabricated in 0.5micron, 3-metal 2-poly CMOS technology. The amplification, together with pulse-shaping of the photocurrent-induced voltage signal, is achieved through a tandem of two capacitively coupled, double-cascode amplifiers. Included in the paper are theoretical estimates and experimental results.

  14. Workshop on photon activation therapy: proceedings

    SciTech Connect

    Fairchild, R.G.

    1985-04-18

    This Workshop was held concurrently with an IAEA Research Coordination Meeting on Exploration of the Possibility of High-LET Radiation for Non-conventional Radiotherapy in Cancer. The Workshop on Photon Activation Therapy (PAT) was given as a special session on April 18, as it was thoght PAT might eventually be found to be attractive to developing countries, which is a major concern of the IAEA. An effort was made to bring together representatives of the various groups known to be actively working on PAT; these included investigators from Sweden and Japan as well as the US. It is hoped that this compendium of papers will be of use to those currently active in this developing field, as well as to those who might join this area of endeavor in the future.

  15. Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California

    NASA Astrophysics Data System (ADS)

    Ge, Shaokui; Smith, Richard G.; Jacovides, Constantinos P.; Kramer, Marc G.; Carruthers, Raymond I.

    2011-08-01

    Plants require solar radiation for photosynthesis and their growth is directly related to the amount received, assuming that other environmental parameters are not limiting. Therefore, precise estimation of photosynthetically active radiation (PAR) is necessary to enhance overall accuracies of plant growth models. This study aimed to explore the PAR radiant flux in the San Francisco Bay Area of northern California. During the growing season (March through August) for 2 years 2007-2008, the on-site magnitudes of photosynthetic photon flux densities (PPFD) were investigated and then processed at both the hourly and daily time scales. Combined with global solar radiation ( R S) and simulated extraterrestrial solar radiation, five PAR-related values were developed, i.e., flux density-based PAR (PPFD), energy-based PAR (PARE), from-flux-to-energy conversion efficiency (fFEC), and the fraction of PAR energy in the global solar radiation (fE), and a new developed indicator—lost PARE percentages (LPR)—when solar radiation penetrates from the extraterrestrial system to the ground. These PAR-related values indicated significant diurnal variation, high values occurring at midday, with the low values occurring in the morning and afternoon hours. During the entire experimental season, the overall mean hourly value of fFEC was found to be 2.17 μmol J-1, while the respective fE value was 0.49. The monthly averages of hourly fFEC and fE at the solar noon time ranged from 2.15 in March to 2.39 μmol J-1 in August and from 0.47 in March to 0.52 in July, respectively. However, the monthly average daily values were relatively constant, and they exhibited a weak seasonal variation, ranging from 2.02 mol MJ-1 and 0.45 (March) to 2.19 mol MJ-1 and 0.48 (June). The mean daily values of fFEC and fE at the solar noon were 2.16 mol MJ-1 and 0.47 across the entire growing season, respectively. Both PPFD and the ever first reported LPR showed strong diurnal patterns. However, they had

  16. Apparatus for photon activation positron annihilation analysis

    DOEpatents

    Akers, Douglas W.

    2007-06-12

    Non-destructive testing apparatus according to one embodiment of the invention comprises a photon source. The photon source produces photons having predetermined energies and directs the photons toward a specimen being tested. The photons from the photon source result in the creation of positrons within the specimen being tested. A detector positioned adjacent the specimen being tested detects gamma rays produced by annihilation of positrons with electrons. A data processing system operatively associated with the detector produces output data indicative of a lattice characteristic of the specimen being tested.

  17. Dynamic control of photosynthetic photon flux for lettuce production in CELSS

    NASA Technical Reports Server (NTRS)

    Chun, C.; Mitchell, C. A.

    1996-01-01

    A new dynamic control of photosynthetic photon flux (PPF) was tested using lettuce canopies growing in the Minitron II plant-growth/canopy gas-exchange system. Canopy photosynthetic rates (Pn) were measured in real time and fedback for further environment control. Pn can be manipulated by changing PPF, which is a good environmental parameter for dynamic control of crop production in a Controlled Ecological Life-Support Systems CELSS. Decision making that combines empirical mathematical models with rule sets developed from recent experimental data was tested. With comparable yield indices and potential for energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.

  18. A miniature closed-circle flow cell for high photon flux X-ray scattering experiments.

    PubMed

    Sahle, Ch J; Henriquet, C; Schroer, M A; Juurinen, I; Niskanen, J; Krisch, M

    2015-11-01

    A closed-circle miniature flow cell for high X-ray photon flux experiments on radiation-sensitive liquid samples is presented. The compact cell is made from highly inert material and the flow is induced by a rotating magnetic stir bar, which acts as a centrifugal pump inside the cell. The cell is ideal for radiation-sensitive yet precious or hazardous liquid samples, such as concentrated acids or bases. As a demonstration of the cell's capabilities, X-ray Raman scattering spectroscopy data on the oxygen K-edge of liquid water under ambient conditions are presented. PMID:26524322

  19. Signal photon flux and background noise in a coupling electromagnetic detecting system for high-frequency gravitational waves

    NASA Astrophysics Data System (ADS)

    Li, Fangyu; Yang, Nan; Fang, Zhenyun; Baker, Robert M. L., Jr.; Stephenson, Gary V.; Wen, Hao

    2009-09-01

    A coupling system among Gaussian-type microwave photon flux, a static magnetic field, and fractal membranes (or other equivalent microwave lenses) can be used to detect high-frequency gravitational waves (HFGWs) in the microwave band. We study the signal photon flux, background photon flux, and the requisite minimal accumulation time of the signal in the coupling system. Unlike the pure inverse Gertsenshtein effect (G effect) caused by the HFGWs in the gigahertz band, the electromagnetic (EM) detecting scheme proposed by China and the U.S. HFGW groups is based on the composite effect of the synchroresonance effect and the inverse G effect. The key parameter in the scheme is the first-order perturbative photon flux (PPF) and not the second-order PPF; the distinguishable signal is the transverse first-order PPF and not the longitudinal PPF; the photon flux focused by the fractal membranes or other equivalent microwave lenses is not only the transverse first-order PPF but the total transverse photon flux, and these photon fluxes have different signal-to-noise ratios at the different receiving surfaces. Theoretical analysis and numerical estimation show that the requisite minimal accumulation time of the signal at the special receiving surfaces and in the background noise fluctuation would be ˜103-105 seconds for the typical laboratory condition and parameters of hrms˜10-26-10-30/Hz at 5 GHz with bandwidth ˜1Hz. In addition, we review the inverse G effect in the EM detection of the HFGWs, and it is shown that the EM detecting scheme based only on the pure inverse G effect in the laboratory condition would not be useful to detect HFGWs in the microwave band.

  20. Arrangement Analysis of Leaves Optimized on Photon Flux Density or Photosynthetic Rate

    NASA Astrophysics Data System (ADS)

    Obara, Shin'ya; Tanno, Itaru

    By clarifying a plant evolutive process, useful information may be obtained on engineering. Consequently, an analysis algorithm that investigates the optimal arrangement of plant leaves was developed. In the developed algorithm, the Monte Carlo method is introduced and sunlight is simulated. Moreover, the arrangement optimization of leaves is analyzed using a Genetic Algorithm (GA). The number of light quanta (photon flux density) that reaches leaves, or the average photosynthetic rate of the same was set as the objective function, and leaf models of a dogwood and a ginkgo tree were analyzed. The number of leaf models was set between two to four, and the position of the leaf was expressed in terms of the angle of direction, elevation angle, rotation angle, and the representative length of the branch of a leaf. The chromosome model introduced into GA consists of information concerning the position of the leaf. Based on the analysis results, the characteristics of the leaf of an actual plant could be simulated by ensuring the algorithm had multiple constrained conditions. The optimal arrangement of leaves differs in maximization of the photon flux density, and that of the average value of a photosynthetic rate. Furthermore, the leaf form affecting the optimal arrangement of leave and also having a significant influence also on a photosynthetic rate was shown.

  1. A solid-state amorphous selenium avalanche technology for low photon flux imaging applications

    PubMed Central

    Wronski, M. M.; Zhao, W.; Reznik, A.; Tanioka, K.; DeCrescenzo, G.; Rowlands, J. A.

    2010-01-01

    Purpose: The feasibility of a practical solid-state technology for low photon flux imaging applications was investigated. The technology is based on an amorphous selenium photoreceptor with a voltage-controlled avalanche multiplication gain. If this photoreceptor can provide sufficient internal gain, it will be useful for an extensive range of diagnostic imaging systems. Methods: The avalanche photoreceptor under investigation is referred to as HARP-DRL. This is a novel concept in which a high-gain avalanche rushing photoconductor (HARP) is integrated with a distributed resistance layer (DRL) and sandwiched between two electrodes. The avalanche gain and leakage current characteristics of this photoreceptor were measured. Results: HARP-DRL has been found to sustain very high electric field strengths without electrical breakdown. It has shown avalanche multiplication gains as high as 104 and a very low leakage current (≤20 pA∕mm2). Conclusions: This is the first experimental demonstration of a solid-state amorphous photoreceptor which provides sufficient internal avalanche gain for photon counting and photon starved imaging applications. PMID:20964217

  2. Self-Adjoint Angular Flux Equation for Coupled Electron-Photon Transport

    SciTech Connect

    Liscum-Powell, J.L.; Lorence, L.J. Jr.; Morel, J.E.; Prinja, A.K.

    1999-07-08

    Recently, Morel and McGhee described an alternate second-order form of the transport equation called the self adjoint angular flux (SAAF) equation that has the angular flux as its unknown. The SAAF formulation has all the advantages of the traditional even- and odd-parity self-adjoint equations, with the added advantages that it yields the full angular flux when it is numerically solved, it is significantly easier to implement reflective and reflective-like boundary conditions, and in the appropriate form it can be solved in void regions. The SAAF equation has the disadvantage that the angular domain is the full unit sphere and, like the even- and odd- parity form, S{sub n} source iteration cannot be implemented using the standard sweeping algorithm. Also, problems arise in pure scattering media. Morel and McGhee demonstrated the efficacy of the SAAF formulation for neutral particle transport. Here we apply the SAAF formulation to coupled electron-photon transport problems using multigroup cross-sections from the CEPXS code and S{sub n} discretization.

  3. Experimental generation of single photons via active multiplexing

    SciTech Connect

    Ma Xiaosong; Zotter, Stefan; Kofler, Johannes; Jennewein, Thomas; Zeilinger, Anton

    2011-04-15

    An on-demand single-photon source is a fundamental building block in quantum science and technology. We experimentally demonstrate the proof of concept for a scheme to generate on-demand single photons via actively multiplexing several heralded photons probabilistically produced from pulsed spontaneous parametric down-conversions (SPDCs). By utilizing a four-photon-pair source, an active feed-forward technique, and an ultrafast single-photon router, we show a fourfold enhancement of the output photon rate. Simultaneously, we maintain the quality of the output single-photon states, confirmed by correlation measurements. We also experimentally verify, via Hong-Ou-Mandel interference, that the router does not affect the indistinguishability of the single photons. Furthermore, we give numerical simulations, which indicate that photons based on multiplexing of four SPDC sources can outperform the heralding based on highly advanced photon-number-resolving detectors. Our results show a route for on-demand single-photon generation and the practical realization of scalable linear optical quantum-information processing.

  4. Early capillary flux homogenization in response to neural activation.

    PubMed

    Lee, Jonghwan; Wu, Weicheng; Boas, David A

    2016-02-01

    This Brief Communication reports early homogenization of capillary network flow during somatosensory activation in the rat cerebral cortex. We used optical coherence tomography and statistical intensity variation analysis for tracing changes in the red blood cell flux over hundreds of capillaries nearly at the same time with 1-s resolution. We observed that while the mean capillary flux exhibited a typical increase during activation, the standard deviation of the capillary flux exhibited an early decrease that happened before the mean flux increase. This network-level data is consistent with the theoretical hypothesis that capillary flow homogenizes during activation to improve oxygen delivery. PMID:26661145

  5. The relevance of particle flux monitors in accelerator-based activation analysis

    SciTech Connect

    Segebade, Chr.; Maimaitimin, M.; Sun Zaijing

    2013-04-19

    One of the most critical parameters in activation analysis is the flux density of the activating radiation, its spatial distribution in particular. The validity of the basic equation for calculating the activity induced to the exposed item depends upon the fulfilment of several conditions, the most relevant of them being equal doses of incident activating radiation received by the unknown sample, the calibration material and the reference material, respectively. This requirement is most problematic if accelerator-produced radiation is used for activation. Whilst nuclear research reactors usually are equipped with exposure positions that provide fairly homogenous activation fields for thermal neutron activation analysis accelerator-generated particle beams (neutrons, photons, charged particles) usually exhibit axial and, in particular, sharp radial flux gradients. Different experimental procedures have been developed to fulfil the condition mentioned above. In this paper, three variants of the application of flux monitors in photon activation analysis are discussed (external monitor, additive and inherent internal monitor). Experiments have indicated that the latter technique yields highest quality of the analytical results.

  6. The relevance of particle flux monitors in accelerator-based activation analysis

    NASA Astrophysics Data System (ADS)

    Segebade, Chr.; Maimaitimin, M.; Zaijing, Sun

    2013-04-01

    One of the most critical parameters in activation analysis is the flux density of the activating radiation, its spatial distribution in particular. The validity of the basic equation for calculating the activity induced to the exposed item depends upon the fulfilment of several conditions, the most relevant of them being equal doses of incident activating radiation received by the unknown sample, the calibration material and the reference material, respectively. This requirement is most problematic if accelerator-produced radiation is used for activation. Whilst nuclear research reactors usually are equipped with exposure positions that provide fairly homogenous activation fields for thermal neutron activation analysis accelerator-generated particle beams (neutrons, photons, charged particles) usually exhibit axial and, in particular, sharp radial flux gradients. Different experimental procedures have been developed to fulfil the condition mentioned above. In this paper, three variants of the application of flux monitors in photon activation analysis are discussed (external monitor, additive and inherent internal monitor). Experiments have indicated that the latter technique yields highest quality of the analytical results.

  7. Active temporal multiplexing of indistinguishable heralded single photons.

    PubMed

    Xiong, C; Zhang, X; Liu, Z; Collins, M J; Mahendra, A; Helt, L G; Steel, M J; Choi, D-Y; Chae, C J; Leong, P H W; Eggleton, B J

    2016-01-01

    It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Actively multiplexing photons generated in many temporal modes can decouple these probabilities, but key issues are to minimize resource requirements to allow scalability, and to ensure indistinguishability of the generated photons. Here we demonstrate the multiplexing of photons from four temporal modes solely using fibre-integrated optics and off-the-shelf electronic components. We show a 100% enhancement to the single-photon output probability without introducing additional multi-photon noise. Photon indistinguishability is confirmed by a fourfold Hong-Ou-Mandel quantum interference with a 91±16% visibility after subtracting multi-photon noise due to high pump power. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies. PMID:26996317

  8. Active temporal multiplexing of indistinguishable heralded single photons

    NASA Astrophysics Data System (ADS)

    Xiong, C.; Zhang, X.; Liu, Z.; Collins, M. J.; Mahendra, A.; Helt, L. G.; Steel, M. J.; Choi, D.-Y.; Chae, C. J.; Leong, P. H. W.; Eggleton, B. J.

    2016-03-01

    It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Actively multiplexing photons generated in many temporal modes can decouple these probabilities, but key issues are to minimize resource requirements to allow scalability, and to ensure indistinguishability of the generated photons. Here we demonstrate the multiplexing of photons from four temporal modes solely using fibre-integrated optics and off-the-shelf electronic components. We show a 100% enhancement to the single-photon output probability without introducing additional multi-photon noise. Photon indistinguishability is confirmed by a fourfold Hong-Ou-Mandel quantum interference with a 91+/-16% visibility after subtracting multi-photon noise due to high pump power. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies.

  9. Active temporal multiplexing of indistinguishable heralded single photons

    PubMed Central

    Xiong, C.; Zhang, X.; Liu, Z.; Collins, M. J.; Mahendra, A.; Helt, L. G.; Steel, M. J.; Choi, D. -Y.; Chae, C. J.; Leong, P. H. W.; Eggleton, B. J.

    2016-01-01

    It is a fundamental challenge in quantum optics to deterministically generate indistinguishable single photons through non-deterministic nonlinear optical processes, due to the intrinsic coupling of single- and multi-photon-generation probabilities in these processes. Actively multiplexing photons generated in many temporal modes can decouple these probabilities, but key issues are to minimize resource requirements to allow scalability, and to ensure indistinguishability of the generated photons. Here we demonstrate the multiplexing of photons from four temporal modes solely using fibre-integrated optics and off-the-shelf electronic components. We show a 100% enhancement to the single-photon output probability without introducing additional multi-photon noise. Photon indistinguishability is confirmed by a fourfold Hong–Ou–Mandel quantum interference with a 91±16% visibility after subtracting multi-photon noise due to high pump power. Our demonstration paves the way for scalable multiplexing of many non-deterministic photon sources to a single near-deterministic source, which will be of benefit to future quantum photonic technologies. PMID:26996317

  10. Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The seasonal trends and diurnal patterns of Photosynthetically Active Radiation (PAR) were investigated in the San Francisco Bay Area of Northern California from March through August in 2007 and 2008. During these periods, the daily values of PAR flux density (PFD), energy loading with PAR (PARE), a...

  11. Leaf photosynthetic and solar-tracking responses of mallow, Malva parviflora, to photon flux density.

    PubMed

    Greer, Dennis H; Thorpe, Michael R

    2009-10-01

    Malva parviflora L. (mallow) is a species that occupies high-light habitats as a weedy invader in orchards and vineyards. Species of the Malvaceae are known to solar track and anecdotal evidence suggests this species may also. How M. parviflora responds physiologically to light in comparison with other species within the Malvaceae remains unknown. Tracking and photosynthetic responses to photon flux density (PFD) were evaluated on plants grown in greenhouse conditions. Tracking ability was assessed in the growth conditions and by exposing leaves to specific light intensities and measuring changes in the angle of the leaf plane. Light responses were also determined by photosynthesis and chlorophyll fluorescence. Leaves followed a heliotropic response which was highly PFD-dependent, with tracking rates increasing in a curvilinear pattern. Maximum tracking rates were up to 20 degrees h(-1) and saturated for light above 1,300 micromol (photons) m(-2) s(-1). This high-light saturation, both for tracking (much higher than the other species), and for photosynthesis, confirmed mallow as a high-light demanding species. Further, because there was no photoinhibition, the leaves could capture the potential of an increased carbon gain in higher irradiance by resorting to solar tracking. Modelling suggested the tracking response could increase the annual carbon gain by as much as 25% compared with leaves that do not track the sun. The various leaf attributes associated with solar tracking, therefore, help to account for the success of this species as a weed in many locations worldwide. PMID:19576789

  12. Variability of the Lyman alpha flux with solar activity

    SciTech Connect

    Lean, J.L.; Skumanich, A.

    1983-07-01

    A three-component model of the solar chromosphere, developed from ground based observations of the Ca II K chromospheric emission, is used to calculate the variability of the Lyman alpha flux between 1969 and 1980. The Lyman alpha flux at solar minimum is required in the model and is taken as 2.32 x 10/sup 11/ photons/cm/sup 2//s. This value occurred during 1975 as well as in 1976 near the commencement of solar cycle 21. The model predicts that the Lyman alpha flux increases to as much as 5 x 10/sup 11/ photons/cm/sup 2//s at the maximum of the solar cycle. The ratio of the average fluxes for December 1979 (cycle maximum) and July 1976 (cycle minimum) is 1.9. During solar maximum the 27-day solar rotation is shown to cause the Lyman alpha flux to vary by as much as 40% or as little as 5%. The model also shows that the Lyman alpha flux varies over intermediate time periods of 2 to 3 years, as well as over the 11-year sunspot cycle. We conclude that, unlike the sunspot number and the 10.7-cm radio flux, the Lyman alpha flux had a variability that was approximately the same during each of the past three cycles. Lyman alpha fluxes calculated by the model are consistent with measurements of the Lyman alpha flux made by 11 of a total of 14 rocket experiments conducted during the period 1969--1980. The model explains satisfactorily the absolute magnitude, long-term trends, and the cycle variability seen in the Lyman alpha irradiances by the OSO 5 satellite experiment. The 27-day variability observed by the AE-E satellite experiment is well reproduced. However, the magntidue of the AE-E 1 Lyman alpha irradiances are higher than the model calculations by between 40% and 80%. We suggest that the assumed calibration of the AE-E irradiances is in error.

  13. Photosynthetic photon flux density, carbon dioxide concentration, and vapor pressure deficit effects on photosynthesis in cacao seedlings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cacao (Theobroma cacao) is a shade plant, native to the under-story of the evergreen rain forest of the Amazon basin and adapted to low levels of photosynthetic photon flux density (PPFD). The influence of PPFD, leaf to air water vapor pressure deficit (VPD) and external carbon dioxide concentration...

  14. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  15. Explosive Flux Compression: 50 Years of Los Alamos Activities

    SciTech Connect

    Fowler, C.M.; Thomson, D.B.; Garn, W.B.

    1998-10-18

    Los Alamos flux compression activities are surveyed, mainly through references in view of space limitations. However, two plasma physics programs done with Sandia National Laboratory are discussed in more detail.

  16. Photon damping in cosmic-ray acceleration in active galactic nuclei

    SciTech Connect

    Colgate, S.A.

    1983-04-07

    The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 15/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultra high energy. Hence, it is unlikely that any reasonable configuration of acceleration can void disastrous photon energy loss. A different site for ultra high energy cosmic ray acceleration must be found.

  17. Integral window/photon beam position monitor and beam flux detectors for x-ray beams

    DOEpatents

    Shu, Deming; Kuzay, Tuncer M.

    1995-01-01

    A monitor/detector assembly in a synchrotron for either monitoring the position of a photon beam or detecting beam flux may additionally function as a vacuum barrier between the front end and downstream segment of the beamline in the synchrotron. A base flange of the monitor/detector assembly is formed of oxygen free copper with a central opening covered by a window foil that is fused thereon. The window foil is made of man-made materials, such as chemical vapor deposition diamond or cubic boron nitrate and in certain configurations includes a central opening through which the beams are transmitted. Sensors of low atomic number materials, such as aluminum or beryllium, are laid on the window foil. The configuration of the sensors on the window foil may be varied depending on the function to be performed. A contact plate of insulating material, such as aluminum oxide, is secured to the base flange and is thereby clamped against the sensor on the window foil. The sensor is coupled to external electronic signal processing devices via a gold or silver lead printed onto the contact plate and a copper post screw or alternatively via a copper screw and a copper spring that can be inserted through the contact plate and coupled to the sensors. In an alternate embodiment of the monitor/detector assembly, the sensors are sandwiched between the window foil of chemical vapor deposition diamond or cubic boron nitrate and a front foil made of similar material.

  18. FLUX AND PHOTON SPECTRAL INDEX DISTRIBUTIONS OF FERMI-LAT BLAZARS AND CONTRIBUTION TO THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

    SciTech Connect

    Singal, J.; Petrosian, V.; Ajello, M.

    2012-07-01

    We present a determination of the distributions of the photon spectral index and gamma-ray flux-the so-called log N-log S relation-for the 352 blazars detected with a greater than approximately 7{sigma} detection threshold and located above {+-}20 Degree-Sign Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true log N-log S counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation between the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law with high and low indices of -2.37 {+-} 0.13 and -1.70 {+-} 0.26, respectively, and the intrinsic photon index distribution can be represented by a Gaussian with mean of 2.41 {+-} 0.13 and width of 0.25 {+-} 0.03. We also find the intrinsic distributions for the sub-populations of BL Lac and flat spectrum radio quasar type blazars separately. We then calculate the contribution of Fermi blazars to the diffuse extragalactic gamma-ray background radiation. Under the assumption that the flux distribution of blazars continues to arbitrarily low fluxes, we calculate the best-fit contribution of all blazars to the total extragalactic gamma-ray output to be 60%, with a large uncertainty.

  19. Standardizing Activation Analysis: New Software for Photon Activation Analysis

    SciTech Connect

    Sun, Z. J.; Wells, D.; Green, J.; Segebade, C.

    2011-06-01

    Photon Activation Analysis (PAA) of environmental, archaeological and industrial samples requires extensive data analysis that is susceptible to error. For the purpose of saving time, manpower and minimizing error, a computer program was designed, built and implemented using SQL, Access 2007 and asp.net technology to automate this process. Based on the peak information of the spectrum and assisted by its PAA library, the program automatically identifies elements in the samples and calculates their concentrations and respective uncertainties. The software also could be operated in browser/server mode, which gives the possibility to use it anywhere the internet is accessible. By switching the nuclide library and the related formula behind, the new software can be easily expanded to neutron activation analysis (NAA), charged particle activation analysis (CPAA) or proton-induced X-ray emission (PIXE). Implementation of this would standardize the analysis of nuclear activation data. Results from this software were compared to standard PAA analysis with excellent agreement. With minimum input from the user, the software has proven to be fast, user-friendly and reliable.

  20. Quiet time particle fluxes and active phenomena on the Sun

    NASA Astrophysics Data System (ADS)

    Ishkov, Vitaly; Zeldovich, Mariya; Logachev, Yurii; Kecskemety, Karoly

    Using ACE, SOHO and STEREO data the connection of quiet time particle fluxes with active processes on the Sun is examined in the 23rd SC. Investigation of the intervals selected in the conditions of low solar activity supports our assumption that the active structures on the Sun arising during minimum solar activity are mostly responsible for background particle fluxes. Sources on the Sun of charged particles with energies 0.3-8 MeV/nucleon have been determined during quiet time periods over all solar cycle by comparison with solar wind fluxes. It is shown that at the solar maximum a part of background fluxes with abundances of C and Fe corresponding to mean values in solar corona resulted from equatorial coronal holes. Bipolar structures arising in the hole area (bright X-ray points) were accompanied in most cases by the ejection of solar plasma according to HINOTORI satellite. The speed of a part of such emissions and open magnetic field lines above coronal holes can allow energetic particles to escape into the interplanetary space. During solar minimum abundances of C and Fe in majority of quiet time fluxes corresponded to solar wind values possibly indicating the common origin of energetic particle and solar wind fluxes.

  1. Estimating ROI activity concentration with photon-processing and photon-counting SPECT imaging systems

    NASA Astrophysics Data System (ADS)

    Jha, Abhinav K.; Frey, Eric C.

    2015-03-01

    Recently a new class of imaging systems, referred to as photon-processing (PP) systems, are being developed that uses real-time maximum-likelihood (ML) methods to estimate multiple attributes per detected photon and store these attributes in a list format. PP systems could have a number of potential advantages compared to systems that bin photons based on attributes such as energy, projection angle, and position, referred to as photon-counting (PC) systems. For example, PP systems do not suffer from binning-related information loss and provide the potential to extract information from attributes such as energy deposited by the detected photon. To quantify the effects of this advantage on task performance, objective evaluation studies are required. We performed this study in the context of quantitative 2-dimensional single-photon emission computed tomography (SPECT) imaging with the end task of estimating the mean activity concentration within a region of interest (ROI). We first theoretically outline the effect of null space on estimating the mean activity concentration, and argue that due to this effect, PP systems could have better estimation performance compared to PC systems with noise-free data. To evaluate the performance of PP and PC systems with noisy data, we developed a singular value decomposition (SVD)-based analytic method to estimate the activity concentration from PP systems. Using simulations, we studied the accuracy and precision of this technique in estimating the activity concentration. We used this framework to objectively compare PP and PC systems on the activity concentration estimation task. We investigated the effects of varying the size of the ROI and varying the number of bins for the attribute corresponding to the angular orientation of the detector in a continuously rotating SPECT system. The results indicate that in several cases, PP systems offer improved estimation performance compared to PC systems.

  2. Crassulacean Acid Metabolism and Photochemical Efficiency of Photosystem II in the Adaxial and Abaxial Parts of the Succulent Leaves of Kalanchoë daigremontiana Grown at Four Photon Flux Densities.

    PubMed

    Winter, K; Awender, G

    1989-07-01

    Kalanchoë daigremontiana, a species possessing crassulacean acid metabolism, was grown at four photon flux densities (1300, 400, 60, and 25 micromole photons per square meter per second). In leaves which had developed at 1300 and 400 micromole photons per square meter per second, CO(2) was mainly incorporated through the lower, shaded leaf surfaces, and the chlorenchyma adjacent to the lower surfaces showed a higher degree of nocturnal acid synthesis than the chlorenchyma adjacent to the upper surfaces. In leaves acclimated to 60 and 25 micromole photons per square meter per second, the gradient in CAM activity was reversed, i.e. more CO(2) was taken up through the upper than through the lower surfaces and nocturnal acidification was higher in the tissue next to the upper surfaces. Total net carbon gain and total nocturnal acid synthesis were highest in leaves which had developed at 400 micromole photons per square meter per second. Chlorophyll content was markedly reduced in leaves which had developed at 1300 micromole photons per square meter per second, especially in the exposed adaxial parts. There was also a sustained reduction in photosystem II photochemical efficiency as indicated by measurements of the ratio of variable over maximum chlorophyll a fluorescence. These findings suggest that, at high growth photon flux densities, the reduced activity of the exposed portions of these succulent leaves is caused by (a) the adverse effects of excess light, (b) together with a genotypic component which favors CO(2) uptake and acid synthesis in the abaxial (lower) leaf parts even when light is not or only marginally excessive. This latter component is predominant at medium photon flux densities, e.g. at 400 micromole photons per square meter per second. It becomes overridden, however, under conditions of deep shade when strongly reduced light levels in the abaxial parts of the leaf chlorenchyma severely limit photosynthesis. PMID:16666903

  3. Growth and yield characteristics of 'Waldmann's Green' leaf lettuce under different photon fluxes from metal halide or incandescent + fluorescent radiation

    NASA Technical Reports Server (NTRS)

    Knight, Sharon L.; Mitchell, Cary A.

    1988-01-01

    Growth of 'Waldmann's Green' leaf lettuce under metal halide radiation was compared with that under In = Fl at the same photosynthetic photon flux (920 micromol/s/sq m) to evaluate the influence of lamp type on growth. No differences in leaf dry weight, leaf area, relative growth rate or photosynthesis occurred after 8 days of exposure to these radiation treatments for 20 h/day.

  4. Analysis of the relationship between photosynthetic photon flux density and natural Taxus baccata seedlings occurrence

    NASA Astrophysics Data System (ADS)

    Iszkuło, Grzegorz; Boratyński, Adam

    2006-01-01

    The aim of the present work was to analyse the relationship of seedlings and saplings of Taxus baccata to the photosynthetic photon flux density (PPFD) reaching the forest floor under natural conditions. Two permanent plots, subdivided into 1 × 1 m square plots, were established in a naturally regenerating population of T. baccata formed during last decades in the Kórnik Arboretum, Poland. All seedlings in every 1 × 1 m plots were counted. Relative PPFD was measured for every plot at the canopy height of the yew seedlings. The dependence of seedling density upon PPFD was examined. We found, that the frequency of the smallest seedlings (to 6.0 cm tall) was highest in the most shaded plots and decreased in plots with increasing PPFD. Thus, the youngest yew seedlings can germinate and grow in very shady conditions. However, the older seedlings (6.1-25.0 and 25.1-100.0 classes) were observed most frequently in 2-7% PPFD. The small numbers of older, taller seedlings in deep shade likely indicate a higher mortality rate of seedlings less than 6 cm in height without promotion to the next height class. Probably the low value of PPFD under the canopy of the stand significantly reduces the competition of other plants with the youngest yew seedlings. At higher light levels they may not be able to compete with more light-demanding plants, such as herbs and seedlings of broad-leaved trees. The seedlings of the second (6.1-25.0 cm) and third (25.1-100.0 cm) height classes were observed most frequently in the plots with 2-7% PPFD ( Fig. 1b and c).

  5. Photon-photon absorption and the uniqueness of the spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    1984-01-01

    The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon-photon absorption of its own radiation was examined. Under the assumption of continuous electron injection with a power law spectrum E to the minus gamma power and Compton losses only, it is shown that for gamma 2 the steady state electron distribution function has a unique form independent of the primary injection spectrum. This electron distribution function can, by synchrotron emission, reproduce the general characteristics of the observed radio to optical active galactic nuclei spectra. Inverse Compton scattering of the synchrotron photons by the same electron distribution can account for their X-ray spectra, and also implies gamma ray emission from these objects. This result is invoked to account for the similarity of these spectra, and it is consistent with observations of the diffuse gamma ray background.

  6. Photon-axion mixing within the jets of active galactic nuclei and prospects for detection

    SciTech Connect

    Harris, J.; Chadwick, P.M. E-mail: p.m.chadwick@durham.ac.uk

    2014-10-01

    Very high energy γ-ray observations of distant active galactic nuclei (AGN) generally result in higher fluxes and harder spectra than expected, resulting in some tension with the level of the extragalactic background light (EBL). If hypothetical axions or axion-like particles (ALPs) were to exist, this tension could be relieved since the oscillation of photons to ALPs would mitigate the effects of EBL absorption and lead to softer inferred intrinsic AGN spectra. In this paper we consider the effect of photon-ALP mixing on observed spectra, including the photon-ALP mixing that would occur within AGN jets. We then simulate observations of three AGN with the Cherenkov Telescope Array (CTA), a next generation γ-ray telescope, to determine its prospects for detecting the signatures of photon-ALP mixing on the spectra. We conclude that prospects for CTA detecting these signatures or else setting limits on the ALP parameter space are quite promising. We find that prospects are improved if photon-ALP mixing within the jet is properly considered and that the best target for observations is PKS 2155-304.

  7. Inverse relationship between photon flux densities and nanotesla magnetic fields over cell aggregates: Quantitative evidence for energetic conservation

    PubMed Central

    Persinger, Michael A.; Dotta, Blake T.; Karbowski, Lukasz M.; Murugan, Nirosha J.

    2015-01-01

    The quantitative relationship between local changes in magnetic fields and photon emissions within ∼2 mm of aggregates of 105–106 cells was explored experimentally. The vertical component of the earth’s magnetic field as measured by different magnetometers was ∼15 nT higher when plates of cells removed from incubation were measured compared to plates containing only medium. Additional experiments indicated an inverse relationship over the first ∼45 min between changes in photon counts (∼10−12 W·m−2) following removal from incubation and similar changes in magnetic field intensity. Calculations indicated that the energy within the aqueous volume containing the cells was equivalent for that associated with the flux densities of the magnetic fields and the photon emissions. For every approximately 1 nT increase in magnetic field intensity value there was a decrease of ∼2 photons (equivalent of 10−18 J). These results complement correlation studies and suggest there may be a conservation of energy between expression as magnetic fields that are subtracted or added to the adjacent geomagnetic field and reciprocal changes in photon emissions when aggregates of cells within a specific volume of medium (water) adapt to new environments. PMID:26005634

  8. SNS Sample Activation Calculator Flux Recommendations and Validation

    SciTech Connect

    McClanahan, Tucker C.; Gallmeier, Franz X.; Iverson, Erik B.; Lu, Wei

    2015-02-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) uses the Sample Activation Calculator (SAC) to calculate the activation of a sample after the sample has been exposed to the neutron beam in one of the SNS beamlines. The SAC webpage takes user inputs (choice of beamline, the mass, composition and area of the sample, irradiation time, decay time, etc.) and calculates the activation for the sample. In recent years, the SAC has been incorporated into the user proposal and sample handling process, and instrument teams and users have noticed discrepancies in the predicted activation of their samples. The Neutronics Analysis Team validated SAC by performing measurements on select beamlines and confirmed the discrepancies seen by the instrument teams and users. The conclusions were that the discrepancies were a result of a combination of faulty neutron flux spectra for the instruments, improper inputs supplied by SAC (1.12), and a mishandling of cross section data in the Sample Activation Program for Easy Use (SAPEU) (1.1.2). This report focuses on the conclusion that the SAPEU (1.1.2) beamline neutron flux spectra have errors and are a significant contributor to the activation discrepancies. The results of the analysis of the SAPEU (1.1.2) flux spectra for all beamlines will be discussed in detail. The recommendations for the implementation of improved neutron flux spectra in SAPEU (1.1.3) are also discussed.

  9. Simulation of Active-Region-Scale Flux Emergence

    NASA Astrophysics Data System (ADS)

    Manchester, W.; van der Holst, B.

    2015-12-01

    Shear flows long observed in solar active regions are now understood to be a consequence of the Lorentz force that develops from a complex interaction between magnetic fields and the thermal pressure of the Sun's gravitationally stratified atmosphere. The shearing motions transport magnetic flux and energy from the submerged portion of the field to the corona providing the necessary energy for flares, filament eruptions and CMEs. To further examine this shearing process, we simulate flux emergence on the scale of active regions with a large-scale model of the near surface convection zone constructed on an adaptive spherical grid. This model is designed to simulate flux emerging on the scale of active regions from a depth of 30 Mm. Here, we show results of a twisted flux rope emerging through the hierarchy of granular convection, and examine the flow patterns that arise as the flux approaches the photosphere. We show how these organized flows driven by the Lorentz force cause the coronal field evolve to a highly non-potential configuration capable of driving solar eruptions such as CMEs and flares.

  10. Non-line-of-sight active imaging of scattered photons

    NASA Astrophysics Data System (ADS)

    Laurenzis, Martin; Velten, Andreas

    2013-10-01

    Laser Gated Viewing is a prominent sensing technology for optical imaging in harsh environments and can be applied to the vision through fog, smoke and other degraded environmental conditions as well as to the vision through sea water in submarine operation. A direct imaging of non-scattered photons (or ballistic photons) is limited in range and performance by the free optical path length i.e. the length in which a photon can propagate without interaction with scattering particles or object surfaces. The imaging and analysis of scattered photons can overcome these classical limitations and it is possible to realize a non-line-of-sight imaging. The spatial and temporal distribution of scattered photons can be analyzed by means of computational optics and their information of the scenario can be restored. In the case of Lambertian scattering sources the scattered photons carry information of the complete environment. Especial the information outside the line of sight or outside the visibility range is of high interest. Here, we discuss approaches for non line of sight active imaging with different indirect and direct illumination concepts (point, surface and volume scattering sources).

  11. Flux and Photon Spectral Index Distributions of Fermi-LAT Blazars and Contribution to the Extragalactic Gamma-ray Background

    SciTech Connect

    Singal, J.; Petrosian, V.; Ajello, M.; /KIPAC, Menlo Park /SLAC /Stanford U.

    2011-12-09

    We present a determination of the distributions of gamma-ray flux - the so called LogN-LogS relation - and photon spectral index for the 352 blazars detected with a greater than approximately seven sigma detection threshold and located above {+-} 20{sup o} Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true LogN-LogS counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation among the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law of slopes -2.37 {+-} 0.13 and -1.70 {+-} 0.26, and the intrinsic photon index distribution can be represented by a Gaussian with mean 2.41 {+-} 0.13 and 1{sigma} width of 0.25 {+-} 0.03. We also find the intrinsic distributions for the sub-populations of BL Lac and FSRQs type blazars separately. We then calculate the contribution of blazars to the diffuse cosmic gamma-ray background radiation to be 28% {+-} 19%.

  12. ASYMMETRY OF HELICITY INJECTION FLUX IN EMERGING ACTIVE REGIONS

    SciTech Connect

    Tian Lirong; Alexander, David

    2009-04-20

    Observational and modeling results indicate that typically the leading magnetic field of bipolar active regions (ARs) is often spatially more compact, while more dispersed and fragmented in following polarity. In this paper, we address the origin of this morphological asymmetry, which is not well understood. Although it may be assumed that, in an emerging {omega}-shaped flux tube, those portions of the flux tube in which the magnetic field has a higher twist may maintain its coherence more readily, this has not been tested observationally. To assess this possibility, it is important to characterize the nature of the fragmentation and asymmetry in solar ARs and this provides the motivation for this paper. We separately calculate the distribution of the helicity flux injected in the leading and following polarities of 15 emerging bipolar ARs, using the Michelson Doppler Image 96 minute line-of-sight magnetograms and a local correlation tracking technique. We find from this statistical study that the leading (compact) polarity injects several times more helicity flux than the following (fragmented) one (typically 3-10 times). This result suggests that the leading polarity of the {omega}-shaped flux tube possesses a much larger amount of twist than the following field prior to emergence. We argue that the helicity asymmetry between the leading and following magnetic field for the ARs studied here results in the observed magnetic field asymmetry of the two polarities due to an imbalance in the magnetic tension of the emerging flux tube. We suggest that the observed imbalance in the helicity distribution results from a difference in the speed of emergence between the leading and following legs of an inclined {omega}-shaped flux tube. In addition, there is also the effect of magnetic flux imbalance between the two polarities with the fragmented following polarity displaying spatial fluctuation in both the magnitude and sign of helicity measured.

  13. Carbon Gain and Photosynthetic Response of Chrysanthemum to Photosynthetic Photon Flux Density Cycles 1

    PubMed Central

    Stoop, Johan M. H.; Willits, Dan H.; Peet, Mary M.; Nelson, Paul V.

    1991-01-01

    Most models of carbon gain as a function of photosynthetic irradiance assume an instantaneous response to increases and decreases in irradiance. High- and low-light-grown plants differ, however, in the time required to adjust to increases and decreases in irradiance. In this study the response to a series of increases and decreases in irradiance was observed in Chrysanthemum × morifolium Ramat. “Fiesta” and compared with calculated values assuming an instantaneous response. There were significant differences between high- and low-light-grown plants in their photosynthetic response to four sequential photosynthetic photon flux density (PPFD) cycles consisting of 5-minute exposures to 200 and 400 micromoles per square meter per second (μmol m−2s−1). The CO2 assimilation rate of high-light-grown plants at the cycle peak increased throughout the PPFD sequence, but the rate of increase was similar to the increase in CO2 assimilation rate observed under continuous high-light conditions. Low-light leaves showed more variability in their response to light cycles with no significant increase in CO2 assimilation rate at the cycle peak during sequential cycles. Carbon gain and deviations from actual values (percentage carbon gain over- or underestimation) based on assumptions of instantaneous response were compared under continuous and cyclic light conditions. The percentage carbon gain overestimation depended on the PPFD step size and growth light level of the leaf. When leaves were exposed to a large PPFD increase, the carbon gain was overestimated by 16 to 26%. The photosynthetic response to 100 μmol m−2 s−1 PPFD increases and decreases was rapid, and the small overestimation of the predicted carbon gain, observed during photosynthetic induction, was almost entirely negated by the carbon gain underestimation observed after a decrease. If the PPFD cycle was 200 or 400 μmol m−2 s−1, high- and low-light leaves showed a carbon gain overestimation of 25

  14. Active Integrated Filters for RF-Photonic Channelizers

    PubMed Central

    Nagdi, Amr El; Liu, Ke; LaFave, Tim P.; Hunt, Louis R.; Ramakrishna, Viswanath; Dabkowski, Mieczyslaw; MacFarlane, Duncan L.; Christensen, Marc P.

    2011-01-01

    A theoretical study of RF-photonic channelizers using four architectures formed by active integrated filters with tunable gains is presented. The integrated filters are enabled by two- and four-port nano-photonic couplers (NPCs). Lossless and three individual manufacturing cases with high transmission, high reflection, and symmetric couplers are assumed in the work. NPCs behavior is dependent upon the phenomenon of frustrated total internal reflection. Experimentally, photonic channelizers are fabricated in one single semiconductor chip on multi-quantum well epitaxial InP wafers using conventional microelectronics processing techniques. A state space modeling approach is used to derive the transfer functions and analyze the stability of these filters. The ability of adapting using the gains is demonstrated. Our simulation results indicate that the characteristic bandpass and notch filter responses of each structure are the basis of channelizer architectures, and optical gain may be used to adjust filter parameters to obtain a desired frequency magnitude response, especially in the range of 1–5 GHz for the chip with a coupler separation of ∼9 mm. Preliminarily, the measurement of spectral response shows enhancement of quality factor by using higher optical gains. The present compact active filters on an InP-based integrated photonic circuit hold the potential for a variety of channelizer applications. Compared to a pure RF channelizer, photonic channelizers may perform both channelization and down-conversion in an optical domain. PMID:22319352

  15. Advanced active quenching circuits for single-photon avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Stipčević, M.; Christensen, B. G.; Kwiat, P. G.; Gauthier, D. J.

    2016-05-01

    Commercial photon-counting modules, often based on actively quenched solid-state avalanche photodiode sensors, are used in wide variety of applications. Manufacturers characterize their detectors by specifying a small set of parameters, such as detection efficiency, dead time, dark counts rate, afterpulsing probability and single photon arrival time resolution (jitter), however they usually do not specify the conditions under which these parameters are constant or present a sufficient description. In this work, we present an in-depth analysis of the active quenching process and identify intrinsic limitations and engineering challenges. Based on that, we investigate the range of validity of the typical parameters used by two commercial detectors. We identify an additional set of imperfections that must be specified in order to sufficiently characterize the behavior of single-photon counting detectors in realistic applications. The additional imperfections include rate-dependence of the dead time, jitter, detection delay shift, and "twilighting." Also, the temporal distribution of afterpulsing and various artifacts of the electronics are important. We find that these additional non-ideal behaviors can lead to unexpected effects or strong deterioration of the system's performance. Specifically, we discuss implications of these new findings in a few applications in which single-photon detectors play a major role: the security of a quantum cryptographic protocol, the quality of single-photon-based random number generators and a few other applications. Finally, we describe an example of an optimized avalanche quenching circuit for a high-rate quantum key distribution system based on time-bin entangled photons.

  16. A Direct Comparison Between EUV Coronal Flux and Helium Resonance Line Photon Flux from SOHO/CDS Data

    NASA Technical Reports Server (NTRS)

    Andretta, V.; Landi, Enrico; DelZanna, Giulio; Jordan, Stuart D.

    1999-01-01

    In the wealth of EUV spectroscopic and imaging data gathered by the SOHO and TRACE missions, a prominent role is played by the helium resonance emission. For example, He I lines are among the most intense features in CDS/NIS spectra, while the EIT 304 waveband (dominated by He II emission) is routinely employed to map the structure of the solar chromosphere and transition region. However, no 'standard' model has emerged so far that is able to interpret observed He spectra/images to a satisfactory degree of self-consistency. Recent research on the problem of the formation of the solar helium spectrum tends to rule out a dominant role of coronal radiation in exciting He resonance lines. However, while evidence for this result is strong, it is based on indirect tests. Here we present a preliminary assessment of this issue based on a more direct approach, which involves a measure with CDS/GIS of the photoionizing EUV radiation. This measure can be directly compared with the observed flux in the main He I and He II resonance lines observed with CDS/NIS2.

  17. Fluctuations in the electron system of a superconductor exposed to a photon flux

    PubMed Central

    de Visser, P. J.; Baselmans, J. J. A.; Bueno, J.; Llombart, N.; Klapwijk, T. M.

    2014-01-01

    In a superconductor, in which electrons are paired, the density of unpaired electrons should become zero when approaching zero temperature. Therefore, radiation detectors based on breaking of pairs promise supreme sensitivity, which we demonstrate using an aluminium superconducting microwave resonator. Here we show that the resonator also enables the study of the response of the electron system of the superconductor to pair-breaking photons, microwave photons and varying temperatures. A large range in radiation power (at 1.54 THz) can be chosen by carefully filtering the radiation from a blackbody source. We identify two regimes. At high radiation power, fluctuations in the electron system caused by the random arrival rate of the photons are resolved, giving a straightforward measure of the optical efficiency (48±8%) and showing an unprecedented detector sensitivity. At low radiation power, fluctuations are dominated by excess quasiparticles, the number of which is measured through their recombination lifetime. PMID:24496036

  18. Fluctuations in the electron system of a superconductor exposed to a photon flux.

    PubMed

    de Visser, P J; Baselmans, J J A; Bueno, J; Llombart, N; Klapwijk, T M

    2014-01-01

    In a superconductor, in which electrons are paired, the density of unpaired electrons should become zero when approaching zero temperature. Therefore, radiation detectors based on breaking of pairs promise supreme sensitivity, which we demonstrate using an aluminium superconducting microwave resonator. Here we show that the resonator also enables the study of the response of the electron system of the superconductor to pair-breaking photons, microwave photons and varying temperatures. A large range in radiation power (at 1.54 THz) can be chosen by carefully filtering the radiation from a blackbody source. We identify two regimes. At high radiation power, fluctuations in the electron system caused by the random arrival rate of the photons are resolved, giving a straightforward measure of the optical efficiency (48 ± 8%) and showing an unprecedented detector sensitivity. At low radiation power, fluctuations are dominated by excess quasiparticles, the number of which is measured through their recombination lifetime. PMID:24496036

  19. A rare gas optics-free absolute photon flux and energy analyzer for solar and planetary observations

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    We have developed a prototype spectrometer for space applications requiring long term absolute EUV photon flux measurements. In this recently developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  20. GPS as a solar observational instrument: Real-time estimation of EUV photons flux rate during strong, medium, and weak solar flares

    NASA Astrophysics Data System (ADS)

    Singh, Talwinder; Hernandez-Pajares, Manuel; Monte, Enric; Garcia-Rigo, Alberto; Olivares-Pulido, Germán.

    2015-12-01

    In this manuscript, the authors show how the Global Navigation Satellite Systems, GNSS (exemplified in the Global Positioning System, GPS), can be efficiently used for a very different purpose from that for which it was designed as an accurate Solar observational tool, already operational from the open global GPS measurements available in real-time, and with some advantages regarding dedicated instruments onboard spacecraft. The very high correlation of the solar extreme ultraviolet (EUV) photon flux rate in the 26-34 mm spectral band, obtained from the solar EUV monitor instrument onboard the SOHO spacecraft during Solar flares, is shown with the GNSS solar flare activity indicator (GSFLAI). The GSFLAI is defined as the gradient of the ionospheric vertical total electron content rate versus the cosine of the Solar zenith angle in the day hemisphere (which filters out nonsolar over ionization), and it is measured from data collected by a global network of dual frequency GPS receivers (giving in this way continuous coverage). GSFLAI for 60 X class flares, 320 M class flares, and 300 C class flares, occurred since 2001, were directly compared with the EUV solar flux rate data to show existing correlations. It was found that the GSFLAI and EUV flux rate present the same linear relationship for all classes of flares, not only the strong and medium intensity ones, X and M class, as in previous works, but also for the weakest C class solar flares, which is a remarkable result.

  1. Photonic network R and D activities in Japan

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-ichi; Miki, Tetsuya; Morioka, Toshio; Tsushima, Hideaki; Koga, Masafumi; Mori, Kazuyuki; Araki, Soichiro; Sato, Ken-ichi; Onaka, Hiroshi; Namiki, Shu; Aovama, Tomonori

    2005-11-01

    R and D activities on photonic networks in Japan are presented. First, milestones in current, ongoing R and D programs supported by Japanese government agencies are introduced, including long-distance and WDM fiber transmission, wavelength routing, optical burst switching, and control plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP over WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R and D programs for photonic networks over the next five years until 2010, by focusing on the report which has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R and D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis through the customer's initiative, to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

  2. Evidence for long-term variability in the ultra high energy photon flux from Cygnus X-3

    NASA Technical Reports Server (NTRS)

    Bhat, C. L.; Rannot, R. C.; Rawat, H. S.; Razdan, H.; Sanecha, V. K.; Sapru, M.

    1985-01-01

    A time-correlation analysis of atmospheric Cerenkov pulses by a wide-angle photomultiplier system was previously shown to have present in it a nonrandom component which seemed associated with the Right Ascension (RA) range approx. 20+or-04h. A recent examination of multi-muon events recorded by a photon-decay detector shows a similar time-dependent effect, closely matching the previous results, supporting the suggestion that the effect is of cosmic origin. However, even though Cyg. X-3 lies well inside the region of peak intensity, it does not seem possible to ascribe to it the whole effect, for the implied photon flux appears too large to be reconciled to various gamma-ray measurements of Cyg. X-3. The original data were subjected to a phase-histogram analysis and it as found that only 2.5% of overall recorded data are compatible with a phase-dependent emission from Cyg. X-3. Assuming these events to be gamma rays yields a detected flux of (2.6 + or - 0.3) x 10 to the minus 12th power gamma cm -2s-1 above 5 x 10 to the 14th power eV. Comparing this value with more recent ultra high energy (UHE) photon data from the same source, it is suggested that the available data generally favor a long-term reduction in the Cyg. X-3 inferred luminosity ( 10 to the 13th power eV) by a factor of (1.8 + or - 0.3) per year.

  3. Polarization rotator-splitters in standard active silicon photonics platforms.

    PubMed

    Sacher, Wesley D; Barwicz, Tymon; Taylor, Benjamin J F; Poon, Joyce K S

    2014-02-24

    We demonstrate various silicon-on-insulator polarization management structures based on a polarization rotator-splitter that uses a bi-level taper TM0-TE1 mode converter. The designs are fully compatible with standard active silicon photonics platforms with no new levels required and were implemented in the IME baseline and IME-OpSIS silicon photonics processes. We demonstrate a polarization rotator-splitter with polarization crosstalk < -13 dB over a bandwidth of 50 nm. Then, we improve the crosstalk to < -22 dB over a bandwidth of 80 nm by integrating the polarization rotator-splitter with directional coupler polarization filters. Finally, we demonstrate a polarization controller by integrating the polarization rotator-splitters with directional couplers, thermal tuners, and PIN diode phase shifters. PMID:24663698

  4. The activity of calcium in calcium-metal-fluoride fluxes

    NASA Astrophysics Data System (ADS)

    Ochifuji, Yuichiro; Tsukihashi, Fumitaka; Sano, Nobuo

    1995-08-01

    The standard Gibbs energy of reaction Ca (1) + O (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: Δ G° = -64,300(±700) + 19.8(±3.5) T J/mol (1373 to 1623 K) The activities of calcium in the CaOsatd-Ca- MF2 ( M: Ca, Ba, Mg) and CaOsatd-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF2, BaF2, and MgF2 at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed.

  5. The activity of calcium in calcium-metal-fluoride fluxes

    SciTech Connect

    Ochifuji, Yuichiro; Tsukihashi, Fumitaka; Sano, Nobuo

    1995-08-01

    The standard Gibbs energy of reaction Ca (1) + {und O} (mass pct, in Zr) = CaO (s) has been determined as follows by equilibrating molten calcium with solid zirconium in a CaO crucible: {Delta}G{degree} = {minus}64,300({+-}700) + 19.8({+-}3.5)T J/mol (1,373 to 1,623 K). The activities of calcium in the CaO{sub satd.}-Ca-MF{sub 2} (M: Ca, Ba, Mg) and CaO{sub satd.}-Ca-NaF systems were measured as a function of calcium composition at high calcium contents at 1,473 K on the basis of the standard Gibbs energy. The activities of calcium increase in the order of CaF{sub 2}, BaF{sub 2}, and MgF{sub 2} at the same calcium fraction of these fluxes. The observed activities are compared with those estimated by using the Temkin model for ionic solutions. Furthermore, the possibility of the removal of tramp elements such as tin, arsenic, antimony, bismuth, and lead from carbon-saturated iron by using calcium-metal-fluoride fluxes is discussed.

  6. A determination of the gamma-ray flux and photon spectral index distributions of blazars from the Fermi-LAT 3LAC

    NASA Astrophysics Data System (ADS)

    Singal, J.

    2015-11-01

    We present a determination of the distributions of gamma-ray photon flux - the so-called LogN-LogS relation - and photon spectral index for blazars, based on the third extragalactic source catalogue of the Fermi Gamma-ray Space Telescope's Large Area Telescope, and considering the photon energy range from 100 MeV to 100 GeV. The data set consists of the 774 blazars in the so-called Clean sample detected with a greater than approximately 7σ detection threshold and located above ±20° Galactic latitude. We use non-parametric methods verified in previous works to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation between the flux and photon index. The intrinsic flux distribution can be represented by a broken power law with a high-flux power-law index of -2.43 ± 0.08 and a low-flux power-law index of -1.87 ± 0.10. The intrinsic photon index distribution can be represented by a Gaussian with mean of 2.62 ± 0.05 and width of 0.17 ± 0.02. We also report the intrinsic distributions for the subpopulations of BL Lac and FSRQ (Flat Spectrum Radio Quasar)-type blazars separately and these differ substantially. We then estimate the contribution of FSRQs and BL Lacs to the diffuse extragalactic gamma-ray background radiation. Under the simplistic assumption that the flux distributions probed in this analysis continue to arbitrary low flux, we calculate that the best-fitting contribution of FSRQs is 35 per cent and BL Lacs 17 per cent of the total gamma-ray output of the Universe in this energy range.

  7. High-flux source of polarization-entangled photons from a periodically poled KTiOPO{sub 4} parametric down-converter

    SciTech Connect

    Kuklewicz, Christopher E.; Fiorentino, Marco; Messin, Gaetan; Wong, Franco N.C.; Shapiro, Jeffrey H.

    2004-01-01

    We have demonstrated a high-flux source of polarization-entangled photons using a type-II phase-matched periodically poled KTiOPO{sub 4} parametric down-converter in a collinearly propagating configuration. We have observed quantum interference between the single-beam down-converted photons with a visibility of 99% together with a measured coincidence flux of 300 s{sup -1}/mW of pump. The Clauser-Horne-Shimony-Holt version of Bell's inequality was violated with a value of 2.711{+-}0.017.

  8. Transition region fluxes in A-F Dwarfs: Basal fluxes and dynamo activity

    NASA Technical Reports Server (NTRS)

    Walter, Frederick M.; Schrijver, Carolus J.; Boyd, William

    1988-01-01

    The transition region spectra of 87 late A and early F dwarfs and subgiants were analyzed. The emission line fluxes are uniformly strong in the early F stars, and drop off rapidly among the late A stars. The basal flux level in the F stars is consistent with an extrapolation of that observed among the G stars, while the magnetic component displays the same flux-flux relations seen among solar-like stars. Despite the steep decrease in transition region emission flux for B-V less than 0.28, C II emission is detected in alpha Aql (B-V = 0.22). The dropoff in emission is inconsistent with models of the mechanically generated acoustic flux available. It is concluded that, although the nonmagnetic basal heating is an increasingly important source of atmospheric heating among the early F stars, magnetic heating occurs in any star which has a sufficiently thick convective zone to generate acoustic heating.

  9. Strong optical activity from twisted-cross photonic metamaterials.

    PubMed

    Decker, M; Ruther, M; Kriegler, C E; Zhou, J; Soukoulis, C M; Linden, S; Wegener, M

    2009-08-15

    Following a recent theoretical suggestion and microwave experiments, we fabricate photonic metamaterials composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric. The resulting two effective resonances of the coupled system lie in the 1-2 microm wavelength regime and exhibit pronounced circular dichroism, while the circular polarization conversion is very small. In between the two resonances, we find a fairly broad spectral regime with strong optical activity, i.e., with a pure rotation of incident linear polarization. The measured optical transmittance spectra agree well with theory. PMID:19684829

  10. Using Photon Activation Analysis To Determine Concentrations Of Unknown Components In Reference Materials

    SciTech Connect

    Green, Jaromy; Sun, Zaijing; Wells, Doug; Maschner, Herb

    2011-06-01

    Using certified multi-element reference materials for instrumental analyses one frequently is confronted with the embarrassing fact that the concentration of some desired elements are not given in the respective certificate, nonetheless are detectable, e.g. by photon activation analysis (PAA). However, these elements might be determinable with sufficient quality of the results using scaling parameters and the well-known quantities of a reference element within the reference material itself. Scaling parameters include: activation threshold energy, Giant Dipole Resonance (GDR) peak and endpoint energy of the bremsstrahlung continuum; integrated photo-nuclear cross sections for the isotopes of the reference element; bremsstrahlung continuum integral; target thickness; photon flux density. Photo-nuclear cross sections from the unreferenced elements must be known, too. With these quantities, the integral was obtained for both the known and unknown elements resulting in an inference of the concentration of the unreported element based upon the reported value, thus also the concentration of the unreferenced element in the reference material. A similar method to determine elements using the basic nuclear and experimental data has been developed for thermal neutron activation analysis some time ago (k{sub 0} Method).

  11. Longitudinal photons in a relativistic magneto-active plasma

    SciTech Connect

    Tsintsadze, N. L.; Rehman, Ayesha; Murtaza, G.; Shah, H. A.

    2007-10-15

    This paper presents some aspects of interaction of superstrong high-frequency electromagnetic waves with strongly magnetized plasmas. The case in which the photon-photon interaction dominates the photon-plasma particle interaction is considered. Strictly speaking, the photon and photon bunch interaction leads to the self-modulation of the photon gas. Assuming that the density of the plasma does not change, the dispersion relation, which includes relativistic self-modulation, is investigated. The existence of longitudinal photons in a strong magnetic field has the well-known Bogoliubov-type energy spectrum. The stability of the photon flow is investigated and an expression for Landau damping of the photons is obtained. Finally, it has been shown that the interaction of even a very strong electromagnetic radiation with a plasma does not always lead to instability, but causes only a change in plasma properties, whereby the plasma remains stable.

  12. FEC coding for QKD at higher photon flux levels based on spatial entanglement of twin beams in PDC

    NASA Astrophysics Data System (ADS)

    Daneshgaran, Fred; Mondin, Marina; Bari, Inam

    2014-10-01

    A major problem with conventional QKD techniques is the raw key transmission rate which for acceptable level of security is generally low. One way to overcome this problem is to create either directly or indirectly a number of parallel QKD transmission channels thus achieving a rate multiplicity equal to the number of parallel channels. This paper explores how a number of parallel Discrete Memoryless Channels (DMCs) can be created from imaging twin beams from a Parametric Down Conversion (PDC) process and examines the performance of FEC coding for information reconciliation over the resulting parallel channels. Twin beams exhibit quantum correlations that has been effectively used as a tool for many applications including calibration of single photon detectors. By now, detection of multimode spatial correlations is a mature field and in principle, only depends on the transmission and detection efficiency of the devices and the channel. In,1-3 the authors utilized their know-how on almost perfect selection of modes of pairwise correlated entangled beams and the optimization of the noise reduction to below the shot-noise level, for absolute calibration of Charge Coupled Device (CCD) cameras. The same basic principle is currently being considered by the same authors for possible use in Quantum Key Distribution (QKD). The main advantage in such an approach would be the ability to work with much higher photon fluxes than that of a single photon regime that is theoretically required for discrete variable QKD applications (in practice, very weak laser pulses with mean photon count below one are used), and the fact that the QKD data rate is increased significantly since multiple equivalent parallel channels result from quantization of symmetric regions into super-pixels. The natural setup of quantization of CCD detection area and subsequent measurement of the correlation statistic needed to detect the presence of the eavesdropper Eve, leads to a number of parallel QKD

  13. EFFECTS OF ULTRAVIOLET-B IRRADIANCE ON SOYBEAN. V. THE DEPENDENCE OF PLANT SENSITIVITY ON THE PHOTOSYNTHETIC PHOTON FLUX DENSITY DURING AND AFTER LEAF EXPANSION

    EPA Science Inventory

    Soybeans (Glycine max (L.) Merr. cv Essex) were grown in a green house, and the first trifoliate leaf was either allowed to expand under a high photosynthetic photon flux density (PPFD) (1.4 millimoled per square meter per second) or a low PPFD (0.8 Millimoles per square meter pe...

  14. Directed motion of electrons in gases under the action of photon flux

    NASA Astrophysics Data System (ADS)

    Amusia, M. Ya.; Baltenkov, A. S.; Chernysheva, L. V.; Felfli, Z.; Msezane, A. Z.; Nordgren, J.

    2001-05-01

    The phenomenon of directed motion of electrons and ions in gases under the action of ionizing radiation pressure is investigated. It is shown that for photon energies from the thresholds of atomic photoionization to several keV the photoionization process is the main mechanism for the transfer of electromagnetic radiation momentum to an atom. Expressions for the drag currents that appear under the action of ionizing radiation in atomic gases and their mixtures are obtained. The connection between the drag currents and one of the nondipole asymmetry parameters is established. Experimental investigation of the drag currents for use in precision measurement of the asymmetry parameters is discussed, particularly for small photoelectron energies where it is difficult to apply the traditional experimental schemes to measure the differential cross sections for photoionization. Nondipole parameters for the Ne 2s, Ne 2p, and Ar 1s subshell photoionization are calculated and compared with measurements and other calculations. Partial drag currents for the Ne 2s, Ne 2p, and Ar 1s subshells are also presented.

  15. Enhanced efficiencies in thin and semi-transparent dye-sensitized solar cells under low photon flux conditions using TiO2 nanotube photonic crystal

    NASA Astrophysics Data System (ADS)

    Xie, Keyu; Guo, Min; Liu, Xiaolin; Huang, Haitao

    2015-10-01

    The photovoltaic output of dye-sensitized solar cells (DSSCs) are greatly dependent on the amount of absorbed photons, which is limited by the thickness of active layer of DSSCs and the illumination conditions. To improve the cell performance under low irradiance condition, a photoanode was designed by attaching a TiO2 nanotube photonic crystal (NTPC) onto the thin TiO2 nanoparticle (NP) layer for applications in thin and semi-transparent DSSCs. It is found that the introduction of the TiO2 NTPC significantly increases the light harvesting and hence the power conversion efficiency (PCE) of the respective DSSCs. The TiO2 NTPC provides multi-functionalities, such as Bragg reflection, light scatting and additional light harvesting from its nanotube structure, leading to more significant light harvesting enhancement in these thin and semi-transparent DSSCs. Compared with the single-layer TiO2 NP based reference DSSCs, the above-mentioned synergic effects in a cell incoporated with a ∼2.3-μm-thick TiO2 NTPC yield PCE enhancements up to 99.1% and 130%, under 1 and 0.5 Sun conditions, respectively. Meanwhile, an obvious compensation effect of TiO2 NTPC to reduce the output power drop of these cells under tilted incient light is also demonstrated. The work will boost the practical applications of PC in irradiance sensitive devices.

  16. Photonic crystal lasers using wavelength-scale embedded active region

    NASA Astrophysics Data System (ADS)

    Matsuo, Shinji; Sato, Tomonari; Takeda, Koji; Shinya, Akihiko; Nozaki, Kengo; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya; Fujii, Takuro; Hasebe, Koichi; Kakitsuka, Takaaki

    2014-01-01

    Lasers with ultra-low operating energy are desired for use in chip-to-chip and on-chip optical interconnects. If we are to reduce the operating energy, we must reduce the active volume. Therefore, a photonic crystal (PhC) laser with a wavelength-scale cavity has attracted a lot of attention because a PhC provides a large Q-factor with a small volume. To improve this device's performance, we employ an embedded active region structure in which the wavelength-scale active region is buried with an InP PhC slab. This structure enables us to achieve effective confinement of both carriers and photons, and to improve the thermal resistance of the device. Thus, we have obtained a large external differential quantum efficiency of 55% and an output power of -10 dBm by optical pumping. For electrical pumping, we use a lateral p-i-n structure that employs Zn diffusion and Si ion implantation for p-type and n-type doping, respectively. We have achieved room-temperature continuous-wave operation with a threshold current of 7.8 µA and a maximum 3 dB bandwidth of 16.2 GHz. The results of an experimental bit error rate measurement with a 10 Gbit s-1 NRZ signal reveal the minimum operating energy for transferring a single bit of 5.5 fJ. These results show the potential of this laser to be used for very short reach interconnects. We also describe the optimal design of cavity quality (Q) factor in terms of achieving a large output power with a low operating energy using a calculation based on rate equations. When we assume an internal absorption loss of 20 cm-1, the optimized coupling Q-factor is 2000.

  17. Photonic crystals cause active colour change in chameleons

    PubMed Central

    Teyssier, Jérémie; Saenko, Suzanne V.; van der Marel, Dirk; Milinkovitch, Michel C.

    2015-01-01

    Many chameleons, and panther chameleons in particular, have the remarkable ability to exhibit complex and rapid colour changes during social interactions such as male contests or courtship. It is generally interpreted that these changes are due to dispersion/aggregation of pigment-containing organelles within dermal chromatophores. Here, combining microscopy, photometric videography and photonic band-gap modelling, we show that chameleons shift colour through active tuning of a lattice of guanine nanocrystals within a superficial thick layer of dermal iridophores. In addition, we show that a deeper population of iridophores with larger crystals reflects a substantial proportion of sunlight especially in the near-infrared range. The organization of iridophores into two superposed layers constitutes an evolutionary novelty for chameleons, which allows some species to combine efficient camouflage with spectacular display, while potentially providing passive thermal protection. PMID:25757068

  18. Photonic crystals cause active colour change in chameleons.

    PubMed

    Teyssier, Jérémie; Saenko, Suzanne V; van der Marel, Dirk; Milinkovitch, Michel C

    2015-01-01

    Many chameleons, and panther chameleons in particular, have the remarkable ability to exhibit complex and rapid colour changes during social interactions such as male contests or courtship. It is generally interpreted that these changes are due to dispersion/aggregation of pigment-containing organelles within dermal chromatophores. Here, combining microscopy, photometric videography and photonic band-gap modelling, we show that chameleons shift colour through active tuning of a lattice of guanine nanocrystals within a superficial thick layer of dermal iridophores. In addition, we show that a deeper population of iridophores with larger crystals reflects a substantial proportion of sunlight especially in the near-infrared range. The organization of iridophores into two superposed layers constitutes an evolutionary novelty for chameleons, which allows some species to combine efficient camouflage with spectacular display, while potentially providing passive thermal protection. PMID:25757068

  19. Active learning in optics and photonics: Fraunhofer diffraction

    NASA Astrophysics Data System (ADS)

    Ghalila, H.; Ben Lakhdar, Z.; Lahmar, S.; Dhouaidi, Z.; Majdi, Y.

    2014-07-01

    "Active Learning in Optics and Photonics" (ALOP), funded by UNESCO within its Physics Program framework with the support of ICTP (Abdus Salam International Centre for Theoretical Physics) and SPIE (Society of Photo-Optical Instrumentation Engineers), aimed to helps and promotes a friendly and interactive method in teaching optics using simple and inexpensive equipment. Many workshops were organized since 2005 the year when Z. BenLakhdar, whom is part of the creators of ALOP, proposed this project to STO (Société Tunisienne d'Optique). These workshops address several issues in optics, covering geometrical optics, wave optics, optical communication and they are dedicated to both teachers and students. We focus this lecture on Fraunhofer diffraction emphasizing the facility to achieve this mechanism in classroom, using small laser and operating a slit in a sheet of paper. We accompany this demonstration using mobile phone and numerical modeling to assist in the analysis of the diffraction pattern figure.

  20. Photonic crystals cause active colour change in chameleons

    NASA Astrophysics Data System (ADS)

    Teyssier, Jérémie; Saenko, Suzanne V.; van der Marel, Dirk; Milinkovitch, Michel C.

    2015-03-01

    Many chameleons, and panther chameleons in particular, have the remarkable ability to exhibit complex and rapid colour changes during social interactions such as male contests or courtship. It is generally interpreted that these changes are due to dispersion/aggregation of pigment-containing organelles within dermal chromatophores. Here, combining microscopy, photometric videography and photonic band-gap modelling, we show that chameleons shift colour through active tuning of a lattice of guanine nanocrystals within a superficial thick layer of dermal iridophores. In addition, we show that a deeper population of iridophores with larger crystals reflects a substantial proportion of sunlight especially in the near-infrared range. The organization of iridophores into two superposed layers constitutes an evolutionary novelty for chameleons, which allows some species to combine efficient camouflage with spectacular display, while potentially providing passive thermal protection.

  1. Bayesian calibration of reactor neutron flux spectrum using activation detectors measurements: Application to CALIBAN reactor

    SciTech Connect

    Cartier, J.; Casoli, P.; Chappert, F.

    2013-07-01

    In this paper, we present calibration methods in order to estimate reactor neutron flux spectrum and its uncertainties by using integral activation measurements. These techniques are performed using Bayesian and MCMC framework. These methods are applied to integral activation experiments in the cavity of the CALIBAN reactor. We estimate the neutron flux and its related uncertainties. The originality of this work is that these uncertainties take into account measurements uncertainties, cross-sections uncertainties and model error. In particular, our results give a very good approximation of the total flux and indicate that neutron flux from MCNP simulation for energies above about 5 MeV seems to overestimate the 'real flux'. (authors)

  2. Photonic Activation of Plasminogen Induced by Low Dose UVB

    PubMed Central

    Correia, Manuel; Snabe, Torben; Thiagarajan, Viruthachalam; Petersen, Steffen Bjørn; Campos, Sara R. R.; Baptista, António M.; Neves-Petersen, Maria Teresa

    2015-01-01

    Activation of plasminogen to its active form plasmin is essential for several key mechanisms, including the dissolution of blood clots. Activation occurs naturally via enzymatic proteolysis. We report that activation can be achieved with 280 nm light. A 2.6 fold increase in proteolytic activity was observed after 10 min illumination of human plasminogen. Irradiance levels used are in the same order of magnitude of the UVB solar irradiance. Activation is correlated with light induced disruption of disulphide bridges upon UVB excitation of the aromatic residues and with the formation of photochemical products, e.g. dityrosine and N-formylkynurenine. Most of the protein fold is maintained after 10 min illumination since no major changes are observed in the near-UV CD spectrum. Far-UV CD shows loss of secondary structure after illumination (33.4% signal loss at 206 nm). Thermal unfolding CD studies show that plasminogen retains a native like cooperative transition at ~70 ºC after UV-illumination. We propose that UVB activation of plasminogen occurs upon photo-cleavage of a functional allosteric disulphide bond, Cys737-Cys765, located in the catalytic domain and in van der Waals contact with Trp761 (4.3 Å). Such proximity makes its disruption very likely, which may occur upon electron transfer from excited Trp761. Reduction of Cys737-Cys765 will result in likely conformational changes in the catalytic site. Molecular dynamics simulations reveal that reduction of Cys737-Cys765 in plasminogen leads to an increase of the fluctuations of loop 760–765, the S1-entrance frame located close to the active site. These fluctuations affect the range of solvent exposure of the catalytic triad, particularly of Asp646 and Ser74, which acquire an exposure profile similar to the values in plasmin. The presented photonic mechanism of plasminogen activation has the potential to be used in clinical applications, possibly together with other enzymatic treatments for the elimination of

  3. Magnetic flux cancellation and Doppler shifts in flaring active regions

    NASA Astrophysics Data System (ADS)

    Burtseva, Olga; Petrie, Gordon

    2016-05-01

    Flux cancellation plays an important role in some theories of solar eruptions. The mechanism of flux cancellation is suggested by many models to be a necessary condition of flare initiation as a part of slow reconnection processes in the lower atmosphere. In our earlier work we analyzed flux cancellation events during major flares using GONG line-of-sight magnetograms. In this work we use vector magnetic field data from SDO/HMI for better interpretation of the longitudinal field changes. We also compute Doppler velocity shifts at the cancellation sites in attempt to distinguish between the three physical processes that could stand behind flux removal from the photosphere: submergence of U-shaped loops, emergence of Ω-shaped loops and magnetic reconnection.

  4. Plant lighting system with five wavelength-band light-emitting diodes providing photon flux density and mixing ratio control

    PubMed Central

    2012-01-01

    Background Plant growth and development depend on the availability of light. Lighting systems therefore play crucial roles in plant studies. Recent advancements of light-emitting diode (LED) technologies provide abundant opportunities to study various plant light responses. The LED merits include solidity, longevity, small element volume, radiant flux controllability, and monochromaticity. To apply these merits in plant light response studies, a lighting system must provide precisely controlled light spectra that are useful for inducing various plant responses. Results We have developed a plant lighting system that irradiated a 0.18 m2 area with a highly uniform distribution of photon flux density (PFD). The average photosynthetic PFD (PPFD) in the irradiated area was 438 micro-mol m–2 s–1 (coefficient of variation 9.6%), which is appropriate for growing leafy vegetables. The irradiated light includes violet, blue, orange-red, red, and far-red wavelength bands created by LEDs of five types. The PFD and mixing ratio of the five wavelength-band lights are controllable using a computer and drive circuits. The phototropic response of oat coleoptiles was investigated to evaluate plant sensitivity to the light control quality of the lighting system. Oat coleoptiles irradiated for 23 h with a uniformly distributed spectral PFD (SPFD) of 1 micro-mol m–2 s–1 nm–1 at every peak wavelength (405, 460, 630, 660, and 735 nm) grew almost straight upwards. When they were irradiated with an SPFD gradient of blue light (460 nm peak wavelength), the coleoptiles showed a phototropic curvature in the direction of the greater SPFD of blue light. The greater SPFD gradient induced the greater curvature of coleoptiles. The relation between the phototropic curvature (deg) and the blue-light SPFD gradient (micro-mol m–2 s–1 nm–1 m–1) was 2 deg per 1 micro-mol m–2 s–1 nm–1 m–1. Conclusions The plant lighting system, with a computer with a graphical user interface

  5. Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions.

    PubMed

    Chandra, Suman; Lata, Hemant; Khan, Ikhlas A; Elsohly, Mahmoud A

    2008-10-01

    Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m(-2)s(-1)), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol(-1)) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m(-2)s(-1) PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m(-2)s(-1) and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m(-2)s(-1). In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol(-1)) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10

  6. Interacting effects of photoperiod and photosynthetic photon flux on net carbon assimilation and starch accumulation in potato leaves

    NASA Technical Reports Server (NTRS)

    Stutte, G. W.; Yorio, N. C.; Wheeler, R. M.

    1996-01-01

    The effect of photoperiod (PP) on net carbon assimilation rate (Anet) and starch accumulation in newly mature canopy leaves of 'Norland' potato (Solanum tuberosum L.) was determined under high (412 varies as mol m-2s-1) and low (263 varies as mol m-2s-1) photosynthetic photon flux (PPF) conditions. The Anet decreased from 13.9 to 11.6 and 9.3 micromoles m-2s-1, and leaf starch increased from 70 to 129 and 118 mg g-1 drymass (DM) as photoperiod (PP) was increased from 12/12 to 18/6, and 24/0, respectively. Longer PP had a greater effect with high PPF conditions than with low PPF treatments, with high PPF showing greater decline in Anet. Photoperiod did not affect either the CO2 compensation point (50 micromoles mol-1) or CO2 saturation point (1100-1200 micromoles mol-1) for Anet. These results show an apparent limit to the amount of starch that can be stored (approximately 15% DM) in potato leaves. An apparent feedback mechanism exists for regulating Anet under high PPF, high CO2, and long PP, but there was no correlation between Anet and starch concentration in individual leaves. This suggests that maximum Anet cannot be sustained with elevated CO2 conditions under long PP (> or = 12 hours) and high PPF conditions. If a physiological limit exists for the fixation and transport of carbon,then increasing photoperiod and light intensity under high CO2 conditions is not the most appropriate means to maximize the yield of potatoes.

  7. Improved mesh based photon sampling techniques for neutron activation analysis

    SciTech Connect

    Relson, E.; Wilson, P. P. H.; Biondo, E. D.

    2013-07-01

    The design of fusion power systems requires analysis of neutron activation of large, complex volumes, and the resulting particles emitted from these volumes. Structured mesh-based discretization of these problems allows for improved modeling in these activation analysis problems. Finer discretization of these problems results in large computational costs, which drives the investigation of more efficient methods. Within an ad hoc subroutine of the Monte Carlo transport code MCNP, we implement sampling of voxels and photon energies for volumetric sources using the alias method. The alias method enables efficient sampling of a discrete probability distribution, and operates in 0(1) time, whereas the simpler direct discrete method requires 0(log(n)) time. By using the alias method, voxel sampling becomes a viable alternative to sampling space with the 0(1) approach of uniformly sampling the problem volume. Additionally, with voxel sampling it is straightforward to introduce biasing of volumetric sources, and we implement this biasing of voxels as an additional variance reduction technique that can be applied. We verify our implementation and compare the alias method, with and without biasing, to direct discrete sampling of voxels, and to uniform sampling. We study the behavior of source biasing in a second set of tests and find trends between improvements and source shape, material, and material density. Overall, however, the magnitude of improvements from source biasing appears to be limited. Future work will benefit from the implementation of efficient voxel sampling - particularly with conformal unstructured meshes where the uniform sampling approach cannot be applied. (authors)

  8. Photonic Network R&D Activities in Japan-Current Activities and Future Perspectives

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-Ichi; Miki, Tetsuya; Morioka, Toshio; Tsushima, Hideaki; Koga, Masafumi; Mori, Kazuyuki; Araki, Soichiro; Sato, Ken-Ichi; Onaka, Hiroshi; Namiki, Shu; Aoyama, Tomonori

    2005-10-01

    R&D activities on photonic networks in Japan are presented. First, milestones in current ongoing R&D programs supported by Japanese government agencies are introduced, including long-distance and wavelength division multiplexing (WDM) fiber transmission, wavelength routing, optical burst switching (OBS), and control-plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP-over-WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R&D programs for photonic networks over the next 5 years until 2010, by focusing on the report that has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R&D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis, through the customer's initiative to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

  9. Active stabilization of a fiber-optic two-photon interferometer using continuous optical length control.

    PubMed

    Cho, Seok-Beom; Kim, Heonoh

    2016-05-16

    The practical realization of long-distance entanglement-based quantum communication systems strongly rely on the observation of highly stable quantum interference between correlated single photons. This task must accompany active stabilization of the optical path lengths within the single-photon coherence length. Here, we provide two-step interferometer stabilization methods employing continuous optical length control and experimentally demonstrate two-photon quantum interference using an actively stabilized 6-km-long fiber-optic Hong-Ou-Mandel interferometer. The two-step active control techniques are applied for measuring highly stable two-photon interference fringes by scanning the optical path-length difference. The obtained two-photon interference visibilities with and without accidental subtraction are found to be approximately 90.7% and 65.4%, respectively. PMID:27409920

  10. Monte Carlo based method for conversion of in-situ gamma ray spectra obtained with a portable Ge detector to an incident photon flux energy distribution.

    PubMed

    Clouvas, A; Xanthos, S; Antonopoulos-Domis, M; Silva, J

    1998-02-01

    A Monte Carlo based method for the conversion of an in-situ gamma-ray spectrum obtained with a portable Ge detector to photon flux energy distribution is proposed. The spectrum is first stripped of the partial absorption and cosmic-ray events leaving only the events corresponding to the full absorption of a gamma ray. Applying to the resulting spectrum the full absorption efficiency curve of the detector determined by calibrated point sources and Monte Carlo simulations, the photon flux energy distribution is deduced. The events corresponding to partial absorption in the detector are determined by Monte Carlo simulations for different incident photon energies and angles using the CERN's GEANT library. Using the detector's characteristics given by the manufacturer as input it is impossible to reproduce experimental spectra obtained with point sources. A transition zone of increasing charge collection efficiency has to be introduced in the simulation geometry, after the inactive Ge layer, in order to obtain good agreement between the simulated and experimental spectra. The functional form of the charge collection efficiency is deduced from a diffusion model. PMID:9450590

  11. Neutron Unfolding Code System for Calculating Neutron Flux Spectra from Activation Data of Dosimeter Foils.

    1982-04-30

    Version 00 As a part of the measurement and analysis plan for the Dosimetry Experiment at the "JOYO" experimental fast reactor, neutron flux spectral analysis is performed using the NEUPAC (Neutron Unfolding Code Package) code system. NEUPAC calculates the neutron flux spectra and other integral quantities from the activation data of the dosimeter foils.

  12. High energy photon and particle luminosity from active nuclei

    NASA Technical Reports Server (NTRS)

    Eilek, J. A.; Caroff, L. J.; Noerdlinger, P. D.; Dove, M. E.

    1986-01-01

    This paper describes a numerical calculation which follows the evolution of an initial photon and particle spectrum in an expanding, relativistic wind or jet, describes in particular the quasi-equilibrium distribution found for initial optical depths above 100 or so, and points out that this calculation may be relevant for the situation in luminous, compact nuclear sources.

  13. W-band active imaging by photonics-based synthesizer

    NASA Astrophysics Data System (ADS)

    Kanno, Atsushi; Sekine, Norihiko; Kasamatsu, Akifumi; Yamamoto, Naokatsu

    2016-05-01

    We demonstrate a nondestructive electromagnetic-wave imaging system with a photonics-based W-band synthe- sizer, traveling-wave tube amplifier and focal-plane transistor array in real time manner. High-power amplifier with multi-watts output will enhance the quality of obtained images under transmission and reflection imaging configurations.

  14. Active photonic crystal devices in self-assembled electro-optic polymeric materials

    NASA Astrophysics Data System (ADS)

    Li, J.; Neyman, P. J.; Vercellino, M.; Heflin, J. R.; Duncan, R.; Evoy, S.

    2004-03-01

    Photonic crystals (PC) offer novel and potent approaches for the control of light compared to traditional technologies. The development of a photonic crystal technology in electro-optic (EO) materials would now provide a novel approach for the development and integration of important "active devices" such as switch, interferometers, etc. We report the development of an active photonic crystal technology that uses ionically self-assembled multilayer (ISAM) as materials platform. Specifically, we concentrate on ISAM film grown from the alternate deposition of individual monolayers of Procion Red MX-5B (PR) and poly(allylamine hydrochloride) (PAH). Films grown with this method show a second harmonic generation (SHG) factor (2) as high as 11 x 10-9 esu, and a r33 coefficient of 3 pm/V. Active photonic crystal are designed and demonstrated in this material using the FEMLAB software. In a first design, a simple switch is implemented by simple shift of the photonic crystal bandgap of a waveguiding structure. A Mach-Zehnder photonic crystal interferometer structure is also demonstrated, in which a 1800 phase shift is obtained between the two arms. We will report on the preliminary realization of active photonic devices using this material self-assembly and nanofabrication platform.

  15. High-repetition-rate and high-photon-flux 70 eV high-harmonic source for coincidence ion imaging of gas-phase molecules.

    PubMed

    Rothhardt, Jan; Hädrich, Steffen; Shamir, Yariv; Tschnernajew, Maxim; Klas, Robert; Hoffmann, Armin; Tadesse, Getnet K; Klenke, Arno; Gottschall, Thomas; Eidam, Tino; Limpert, Jens; Tünnermann, Andreas; Boll, Rebecca; Bomme, Cedric; Dachraoui, Hatem; Erk, Benjamin; Di Fraia, Michele; Horke, Daniel A; Kierspel, Thomas; Mullins, Terence; Przystawik, Andreas; Savelyev, Evgeny; Wiese, Joss; Laarmann, Tim; Küpper, Jochen; Rolles, Daniel

    2016-08-01

    Unraveling and controlling chemical dynamics requires techniques to image structural changes of molecules with femtosecond temporal and picometer spatial resolution. Ultrashort-pulse x-ray free-electron lasers have significantly advanced the field by enabling advanced pump-probe schemes. There is an increasing interest in using table-top photon sources enabled by high-harmonic generation of ultrashort-pulse lasers for such studies. We present a novel high-harmonic source driven by a 100 kHz fiber laser system, which delivers 1011 photons/s in a single 1.3 eV bandwidth harmonic at 68.6 eV. The combination of record-high photon flux and high repetition rate paves the way for time-resolved studies of the dissociation dynamics of inner-shell ionized molecules in a coincidence detection scheme. First coincidence measurements on CH3I are shown and it is outlined how the anticipated advancement of fiber laser technology and improved sample delivery will, in the next step, allow pump-probe studies of ultrafast molecular dynamics with table-top XUV-photon sources. These table-top sources can provide significantly higher repetition rates than the currently operating free-electron lasers and they offer very high temporal resolution due to the intrinsically small timing jitter between pump and probe pulses. PMID:27505779

  16. Enzymatically active high-flux selectively gas-permeable membranes

    DOEpatents

    Jiang, Ying-Bing; Cecchi, Joseph L.; Rempe, Susan; FU, Yaqin; Brinker, C. Jeffrey

    2016-01-26

    An ultra-thin, catalyzed liquid transport medium-based membrane structure fabricated with a porous supporting substrate may be used for separating an object species such as a carbon dioxide object species. Carbon dioxide flux through this membrane structures may be several orders of magnitude higher than traditional polymer membranes with a high selectivity to carbon dioxide. Other gases such as molecular oxygen, molecular hydrogen, and other species including non-gaseous species, for example ionic materials, may be separated using variations to the membrane discussed.

  17. Microbial Activity and Volatile Fluxes in Seafloor Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Corrigan, R. S.; Lowell, R. P.

    2013-12-01

    Understanding geographically and biologically the production or utilization of volatile chemical species such as CO2, CH4, and H2 is crucial not only for understanding hydrothermal processes but also for understanding life processes in the oceanic crust. To estimate the microbial effect on the transport of these volatiles, we consider a double-loop single pass model as shown in Figure 1 to estimate the mass fluxes shown. We then use a simple mixing formulation: C4Q4 = C3 (Q1 -Q3)+ C2Q2, where C2 is the concentration of the chemical in seawater, C3 is the average concentration of the chemical in high temperature focused flow, C4 is the expected concentration of the chemical as a result of mixing, and the relevant mass flows are as shown in Figure 1. Finally, we compare the calculated values of CO2, CH4, and H2 in diffuse flow fluids to those observed. The required data are available for both the Main Endeavour Field on the Juan de Fuca Ridge and the East Pacific Rise 9°50' N systems. In both cases we find that, although individual diffuse flow sites have observed concentrations of some elements that are greater than average, the average concentration of these volatiles is smaller in all cases than the concentration that would be expected from simple mixing. This indicates that subsurface microbes are net utilizers of these chemical constituents at the Main Endeavour Field and at EPR 9°50' N on the vent field scale. Figure 1. Schematic of a 'double-loop' single-pass model above a convecting, crystallizing, replenished AMC (not to scale). Heat transfer from the vigorously convecting, cooling, and replenished AMC across the conductive boundary layer δ drives the overlying hydrothermal system. The deep circulation represented by mass flux Q1 and black smoker temperature T3 induces shallow circulation noted by Q2. Some black smoker fluid mixes with seawater resulting in diffuse discharge Q4, T4, while the direct black smoker mass flux with temperature T3 is reduced

  18. Detection of TeV photons from the active galaxy Markarian 421

    NASA Technical Reports Server (NTRS)

    Punch, M.; Akerlof, C. W.; Cawley, M. F.; Chantell, M.; Fegan, D. J.; Fennell, S.; Gaidos, J. A.; Hagan, J.; Hillas, A. M.; Jiang, Y.

    1992-01-01

    The detection of TeV energy photons from the giant elliptical galaxy Markarian 421 using the Whipple Observatory gamma-ray telescope is reported. The signal has a statistical significance of 6 sigma above background and the flux above 0.5 TeV is 0.3 of that from the Crab Nebula. The source location agrees with the position of Mk 421 within the angular uncertainty of the Whipple instrument.

  19. NEW VACUUM SOLAR TELESCOPE OBSERVATIONS OF A FLUX ROPE TRACKED BY A FILAMENT ACTIVATION

    SciTech Connect

    Yang, Shuhong; Zhang, Jun; Liu, Zhong; Xiang, Yongyuan E-mail: zjun@nao.cas.cn

    2014-04-01

    One main goal of the New Vacuum Solar Telescope (NVST) which is located at the Fuxian Solar Observatory is to image the Sun at high resolution. Based on the high spatial and temporal resolution NVST Hα data and combined with the simultaneous observations from the Solar Dynamics Observatory for the first time, we investigate a flux rope tracked by filament activation. The filament material is initially located at one end of the flux rope and fills in a section of the rope; the filament is then activated by magnetic field cancellation. The activated filament rises and flows along helical threads, tracking the twisted flux rope structure. The length of the flux rope is about 75 Mm, the average width of its individual threads is 1.11 Mm, and the estimated twist is 1π. The flux rope appears as a dark structure in Hα images, a partial dark and partial bright structure in 304 Å, and as a bright structure in 171 Å and 131 Å images. During this process, the overlying coronal loops are quite steady since the filament is confined within the flux rope and does not erupt successfully. It seems that, for the event in this study, the filament is located and confined within the flux rope threads, instead of being suspended in the dips of twisted magnetic flux.

  20. Demonstration of HNO3 Eddy Flux Measurements at the Boulder Atmospheric Observatory Using Active Passivation

    NASA Astrophysics Data System (ADS)

    Roscioli, J. R.; Herndon, S. C.; Zahniser, M. S.; Nelson, D. D.; Zaragoza, J.; Pollack, I. B.; Fischer, E. V.

    2015-12-01

    Eddy flux measurements of "sticky" molecules have historically proven difficult due to strong interactions with instrument surfaces. A novel approach has been developed to improve these response times, enabling flux measurements of nitric acid (HNO3) and and ammonia (NH3). Deliberate addition of the vapor of perfluorinated acids and bases into a sample stream serves to eject existing surface-bound sample molecules and passivate instrument surfaces. HNO3 response times for an Aerodyne quantum cascade laser absorption spectrometer (QCLAS) improve by a factor of 60-fold when actively passivating. This approach was used during field measurements of HNO3 fluxes at the Boulder Atmospheric Observatory, where an actively passivated inertial inlet at 8 m height yielded HNO3 deposition fluxes of 0.5 - 2 nmol/m2/sec. The dependence of the deposition flux upon urban vs rural outflow is discussed.

  1. Photosynthetic photon flux, photoperiod, and temperature effects on emissions of (Z)-3-hexenal, (Z)-3-hexenol, and (Z)-3-hexenyl acetate from lettuce

    NASA Technical Reports Server (NTRS)

    Charron, C. S.; Cantliffe, D. J.; Wheeler, R. M.; Manukian, A.; Heath, R. R.

    1996-01-01

    To investigate the effects of environment on plant volatile emissions, 'Waldmann's Green' leaf lettuce was cultivated under different levels of photosynthetic photon flux (PPF), photoperiod, and temperature. A modified growth chamber was used to sample plant volatile emissions nondestructively, over time, and under controlled conditions. Total volatile emission rates were significantly higher from lettuce cultivated under PPF of 360 or 200 micromoles m-2 s-1 compared to 105 micromoles m-2 s-1, and significantly higher under a 16-h photoperiod than an 8-h photoperiod. No differences were detected among emission rates from different temperature treatments. In controlled environments, emissions could be regulated by adjusting environmental conditions accordingly.

  2. Heat-flux control and solid-state cooling by regulating chemical potential of photons in near-field electromagnetic heat transfer

    NASA Astrophysics Data System (ADS)

    Chen, Kaifeng; Santhanam, Parthiban; Sandhu, Sunil; Zhu, Linxiao; Fan, Shanhui

    2015-04-01

    We consider near-field heat transfer with nonzero chemical potential for photons, as can occur between two semiconductor bodies, held at different temperatures with at least one of the bodies under external bias. We show that the dependence of radiative heat flux on chemical potential enables electronic control of both the direction and magnitude of near-field heat transfer between the two bodies. Moreover such a configuration can operate as a solid-state cooling device whose efficiency can approach the Carnot limit in the ideal case. Significant cooling can also be achieved in the presence of inherent nonidealities including Auger recombination and parasitic phonon-polariton heat transfer.

  3. Testing of actively cooled high heat flux mock-ups

    NASA Astrophysics Data System (ADS)

    Rödig, M.; Duwe, R.; Kühnlein, W.; Linke, J.; Scheerer, M.; Smid, I.; Wiechers, B.

    1998-10-01

    Several un-irradiated CFC monoblock mock-ups have been loaded in thermal fatigue tests up to 1000 cycles at power densities <25 MW/m 2. No indication of failure was observed for these loading conditions. Two of the mock-ups were inspected by ultra-sonic methods before thermal cycling. It could be proved that the voids found in the post-mortem metallography existed before and had no effect on the integrity of the mock-up. For the first time, neutron-irradiated CFC monoblock mock-ups have been tested in the electron beam facility JUDITH. These mock-ups had been irradiated before in the High Flux Reactor at Petten up to 0.3 dpa at 320°C and 770°C. All samples showed a significant increase of surface temperature, due to the irradiation induced decrease in thermal conductivity of the CFC materials.

  4. Polymer/Perovskite Amplifying Waveguides for Active Hybrid Silicon Photonics.

    PubMed

    Suárez, Isaac; Juárez-Pérez, Emilio J; Bisquert, Juan; Mora-Seró, Iván; Martínez-Pastor, Juan P

    2015-10-28

    The emission properties of hybrid halide perovskites are exploited to implement a stable and very low power operation waveguide optical amplifier integrated in a silicon platform. By optimizing its design with a poly(methyl methacrylate) (PMMA) encapsulation, this novel photonic device presents a net gain of around 10 dB cm(-1) and 3-4 nm linewidth with an energy threshold as low as 2 nJ pulse(-1) and exhibiting no degradation after one year. PMID:26331838

  5. [Spectra and thermal analysis of the arc in activating flux plasma arc welding].

    PubMed

    Chai, Guo-Ming; Zhu, Yi-Feng

    2010-04-01

    In activating flux plasma arc welding the welding arc was analyzed by spectra analysis technique, and the welding arc temperature field was measured by the infrared sensing and computer image technique. The distribution models of welding arc heat flow density of activating flux PAW welding were developed. The composition of welding arc affected by activated flux was studied, and the welding arc temperature field was studied. The results show that the spectral lines of argon atom and ionized argon atom of primary ionization are the main spectra lines of the conventional plasma welding arc. The spectra lines of weld metal are inappreciable in the spectra lines of the conventional plasma welding arc. The gas particle is the main in the conventional plasma welding arc. The conventional plasma welding arc is gas welding arc. The spectra lines of argon atom and ionized argon atom of primary ionization are intensified in the activating flux plasma welding arc, and the spectra lines of Ti, Cr and Fe elements are found in the activating flux plasma welding arc. The welding arc temperature distribution in activating flux plasma arc welding is compact, the outline of the welding arc temperature field is narrow, the range of the welding arc temperature distribution is concentrated, the welding arc radial temperature gradient is large, and the welding arc radial temperature gradient shows normal Gauss distribution. PMID:20545181

  6. Magnetic Flux Transport and the Long-term Evolution of Solar Active Regions

    NASA Astrophysics Data System (ADS)

    Ugarte-Urra, Ignacio; Upton, Lisa; Warren, Harry P.; Hathaway, David H.

    2015-12-01

    With multiple vantage points around the Sun, Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory imaging observations provide a unique opportunity to view the solar surface continuously. We use He ii 304 Å data from these observatories to isolate and track ten active regions and study their long-term evolution. We find that active regions typically follow a standard pattern of emergence over several days followed by a slower decay that is proportional in time to the peak intensity in the region. Since STEREO does not make direct observations of the magnetic field, we employ a flux-luminosity relationship to infer the total unsigned magnetic flux evolution. To investigate this magnetic flux decay over several rotations we use a surface flux transport model, the Advective Flux Transport model, that simulates convective flows using a time-varying velocity field and find that the model provides realistic predictions when information about the active region's magnetic field strength and distribution at peak flux is available. Finally, we illustrate how 304 Å images can be used as a proxy for magnetic flux measurements when magnetic field data is not accessible.

  7. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  8. Flux rope proxies and fan-spine structures in active region NOAA 11897

    NASA Astrophysics Data System (ADS)

    Hou, Y. J.; Li, T.; Zhang, J.

    2016-08-01

    Context. Flux ropes are composed of twisted magnetic fields and are closely connected with coronal mass ejections. The fan-spine magnetic topology is another type of complex magnetic fields. It has been reported by several authors, and is believed to be associated with null-point-type magnetic reconnection. Aims: We try to determine the number of flux rope proxies and reveal fan-spine structures in the complex active region (AR) NOAA 11897. Methods: Employing the high-resolution observations from the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS), we statistically investigated flux rope proxies in NOAA AR 11897 from 14 November 2013 to 19 November 2013 and display two fan-spine structures in this AR. Results: For the first time, we detect flux rope proxies of NOAA 11897 for a total of 30 times in four different locations during this AR's transference from solar east to west on the disk. Moreover, we notice that these flux rope proxies were tracked by active or eruptive material of filaments 12 times, while for the remaining 18 times they appeared as brightenings in the corona. These flux rope proxies were either tracked in both lower and higher temperature wavelengths or only detected in hot channels. None of these flux rope proxies was observed to erupt; they faded away gradually. In addition to these flux rope proxies, we detect for the first time a secondary fan-spine structure. It was covered by dome-shaped magnetic fields that belong to a larger fan-spine topology. Conclusions: These new observations imply that many flux ropes can exist in an AR and that the complexity of AR magnetic configurations is far beyond our imagination. Movies 1-8 are available in electronic form at http://www.aanda.org

  9. Filament Activation in Response to Magnetic Flux Emergence and Cancellation in Filament Channels

    NASA Astrophysics Data System (ADS)

    Li, Ting; Zhang, Jun; Ji, Haisheng

    2015-06-01

    We conducted a comparative analysis of two filaments that showed a quite different activation in response to the flux emergence within the filament channels. The observations from the Solar Dynamics Observatory (SDO) and Global Oscillation Network Group (GONG) were made to analyze the two filaments on 2013 August 17 - 20 (SOL2013-08-17) and September 29 (SOL2013-09-29). The first event showed that the main body of the filament was separated into two parts when an active region (AR) emerged with a maximum magnetic flux of about 6.4×1021 Mx underlying the filament. The close neighborhood and common direction of the bright threads in the filament and the open AR fan loops suggest a similar magnetic connectivity of these two flux systems. The equilibrium of the filament was not destroyed three days after the start of the emergence of the AR. To our knowledge, similar observations have never been reported before. In the second event, the emerging flux occurred nearby a barb of the filament with a maximum magnetic flux of 4.2×1020 Mx, about one order of magnitude lower than that of the first event. Two patches of parasitic polarity in the vicinity of the barb merged, then cancelled with nearby network fields. About 20 hours after the onset of the emergence, the filament erupted. Our findings imply that the location of emerging flux within the filament channel is probably crucial to filament evolution. If the flux emergence appears nearby the barbs, it is highly likely that the emerging flux and the filament magnetic fields will cancel, which may lead to the eruption of the filament. The comparison of the two events shows that the emergence of a small AR may still not be enough to disrupt the stability of a filament system, and the actual eruption only occurs after the flux cancellation sets in.

  10. The role of high energy photons and particles in accretion flows in active nuclei

    NASA Technical Reports Server (NTRS)

    Eilek, Jean A.

    1988-01-01

    The creation of high energy pairs and photons in the conversion of gravitational to thermal energy is a process common to most accretion models for active galactic nuclei. These are two observational methods designed to explore this process: direct observations of the hot photons, through hard X-ray and gamma-ray data, and indirect observations of the energetic pairs, through their polarized, nonthermal low frequency radiation. However, interpretation of these observations in terms of the conditions in the inner accretion flow requires understanding of the various processes which modify the pair and photon distributions within the hot, dense core. These processes include opacity effects within the pair/photon plasma, Compton losses on external photons, further acceleration of the pairs and further radiation by the pairs, and the dynamic interaction of the pair/photon plasma with the surrounding gas. Current observational and theoretical work is reviewed and new directions are considered in a search for constraints on or tests of accretion models of active nuclei.

  11. Identities in flux: cognitive network activation in times of change.

    PubMed

    Menon, Tanya; Smith, Edward Bishop

    2014-05-01

    Using a dynamic cognitive model, we experimentally test two competing hypotheses that link identity and cognitive network activation during times of change. On one hand, affirming people's sense of power might give them confidence to think beyond the densest subsections of their social networks. Alternatively, if such power affirmations conflict with people's more stable status characteristics, this could create tension, deterring people from considering their networks' diversity. We test these competing hypotheses experimentally by priming people at varying levels of status with power (high/low) and asking them to report their social networks. We show that confirming identity-not affirming power-cognitively prepares people to broaden their social networks when the world is changing around them. The emotional signature of having a confirmed identity is feeling comfortable and in control, which mediates network activation. We suggest that stable, confirmed identities are the foundation from which people can exhibit greater network responsiveness. PMID:24576631

  12. Improved thrust calculations of active magnetic bearings considering fringing flux

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Kim, Kwan-Ho; Ko, Kyoung-Jin; Choi, Ji-Hwan; Sung, So-Young; Lee, Yong-Bok

    2012-04-01

    A methodology for deriving fringing permeance in axisymmetric devices such as active thrust magnetic bearings (ATMBs) is presented. The methodology is used to develop an improved equivalent magnetic circuit (EMC) for ATMBs, which considers the fringing effect. This EMC was used to characterize the force between the housing and mover and the dependence of thrust and inductance on the air gap and input current, respectively. These characteristics were validated by comparison with those obtained by the finite element method and in experiments.

  13. Neutron Flux Spectra Determination by Multiple Foil Activation - Iterative Method.

    1994-07-08

    Version 00 Neutron energy spectra are determined by an analysis of experimental activation detector data. As with the original CCC-112/SAND-II program, which was developed at Air Force Weapons Laboratory, this code system consists of four modules, CSTAPE, SLACTS, SLATPE, and SANDII. The first three modules pre-process the dosimetry cross sections and the trial function spectrum library. The last module, SANDII, actually performs the iterative spectrum characterization.

  14. ACTIVE: a program to calculate and plot reaction rates from ANISN calculated fluxes

    SciTech Connect

    Judd, J.L.

    1981-12-01

    The ACTIVE code calculates spatial heating rates, tritium production rates, neutron reaction rates, and energy spectra from particle fluxes calculated by ANISN. ACTIVE has a variety of input options including the capability to plot all calculated spatial distributions. The code was primarily designed for use with fusion first wall/blanket systems, but could be applied to any one-dimensional problem.

  15. Decrease in T Cell Activation and Calcium Flux during Clinorotation

    NASA Technical Reports Server (NTRS)

    Sams, Clarence; Holtzclaw, J. David

    2006-01-01

    We investigated the effect of altered gravitational environments on T cell activation. We isolated human, naive T cells (CD3+CD14-CD19-CD16-CD56-CD25-CD69-CD45RA-) following IRB approved protocols. These purified T cells were then incubated with 6 mm polystyrene beads coated with OKT3 (Ortho Biotech, Raritan, NJ) and antiCD28 (Becton Dickinson (BD), San Jose, CA) at 37 C for 24 hours. Antibodies were at a 1:1 ratio and the bead-to-cell ratio was 2:1. Four incubation conditions existed: 1) static or "1g"; 2) centrifugation at 10 relative centrifugal force (RCF) or "10g"; 3) clinorotation at 25 RPM (functional weightlessness or "0g"); and 4) clinorotation at 80 RPM ("1g" plus net shear force approx.30 dynes/sq cm). Following incubation, T cells were stained for CD25 expression (BD) and intracellular calcium (ratio of Fluo4 to Fura Red, Molecular Probes, Eugene, OR) and analyzed by flow cytometry (Coulter EPICS XL, Miami, FL). Results: Static or "1g" T cells had the highest level of CD25 expression and intracellular calcium. T cells centrifuged at 10 RCF ("10g") had lower CD25 expression and calcium levels compared to the static control. However, cells centrifuged at 10 RCF had higher CD25 expression and calcium levels than those exposed to 24 RPM clinorotation ("0g"). T cells exposed to 24 RPM clinorotation had lower CD25 expression, but the approximately the same calcium levels than T cells exposed to 80 RPM clinorotation. These data suggest that stress-activated calcium channel exist in T cells and may play a role during T cell activation.

  16. Solar Activity and GCR Particle Flux Variations: Assessment and Modeling with Ulysses and ACE/CRIS

    NASA Astrophysics Data System (ADS)

    Saganti, Premkumar

    Galactic Cosmic Ray (GCR) environment during the current and historically known lower solar minimum condition indicate some of the very high anticipated measurements of particle spectral data. Data from the Ulysses spacecraft in the polar orbit about the sun during the years 2004 and 2008 (about 5 AU) provided proton and alpha particle flux data and showed such anticipated high particle flux variations. Also, ACE/CRIS spacecraft data during the years 2007 and 2009 showed some of the high particle flux measurements of several heavy ions such as oxygen and iron. We present Ulysses and ACE/CRIS measured particle flux data and discuss their high density and variations in the context of the current low solar activity for depicting current space radiation environment.

  17. Statistical analysis on activation and photo-bleaching of step-wise multi-photon activation fluorescence of melanin

    NASA Astrophysics Data System (ADS)

    Gu, Zetong; Lai, Zhenhua; Zhang, Xi; Yin, Jihao; DiMarzio, Charles A.

    2015-03-01

    Melanin is regarded as the most enigmatic pigments/biopolymers found in most organisms. We have shown previously that melanin goes through a step-wise multi-photon absorption process after the fluorescence has been activated with high laser intensity. No melanin step-wise multi-photon activation fluorescence (SMPAF) can be obtained without the activation process. The step-wise multi-photon activation fluorescence has been observed to require less laser power than what would be expected from a non-linear optical process. In this paper, we examined the power dependence of the activation process of melanin SMPAF at 830nm and 920nm wavelengths. We have conducted research using varying the laser power to activate the melanin in a point-scanning mode for multi-photon microscopy. We recorded the fluorescence signals and position. A sequence of experiments indicates the relationship of activation to power, energy and time so that we can optimize the power level. Also we explored regional analysis of melanin to study the spatial relationship in SMPAF and define three types of regions which exhibit differences in the activation process.

  18. Active quenching circuit for single-photon detection with Geiger mode avalanche photodiodes.

    PubMed

    Stipcević, Mario

    2009-03-20

    In this paper a novel construction of an active quenching circuit intended for single-photon detection is presented, along with a few original methods for its evaluation. The circuit has been combined with a standard avalanche photodiode C30902S to form a single-photon detector. This detector has a dead time of 39 ns, maximum random counting frequency of 14 MHz, small afterpulsing probability, an estimated peak detection efficiency of over 20%, and a dark count rate of less than 100 Hz. This simple and robust active quenching circuit can be built from off-the-shelf electronic components and is presented with the detailed schematic diagram. PMID:19305468

  19. Lipid-induced NOX2 activation inhibits autophagic flux by impairing lysosomal enzyme activity[S

    PubMed Central

    Jaishy, Bharat; Zhang, Quanjiang; Chung, Heaseung S.; Riehle, Christian; Soto, Jamie; Jenkins, Stephen; Abel, Patrick; Cowart, L. Ashley; Van Eyk, Jennifer E.; Abel, E. Dale

    2015-01-01

    Autophagy is a catabolic process involved in maintaining energy and organelle homeostasis. The relationship between obesity and the regulation of autophagy is cell type specific. Despite adverse consequences of obesity on cardiac structure and function, the contribution of altered cardiac autophagy in response to fatty acid overload is incompletely understood. Here, we report the suppression of autophagosome clearance and the activation of NADPH oxidase (Nox)2 in both high fat-fed murine hearts and palmitate-treated H9C2 cardiomyocytes (CMs). Defective autophagosome clearance is secondary to superoxide-dependent impairment of lysosomal acidification and enzyme activity in palmitate-treated CMs. Inhibition of Nox2 prevented superoxide overproduction, restored lysosome acidification and enzyme activity, and reduced autophagosome accumulation in palmitate-treated CMs. Palmitate-induced Nox2 activation was dependent on the activation of classical protein kinase Cs (PKCs), specifically PKCβII. These findings reveal a novel mechanism linking lipotoxicity with a PKCβ-Nox2-mediated impairment in pH-dependent lysosomal enzyme activity that diminishes autophagic turnover in CMs. PMID:25529920

  20. Heat flux and crustal radio-activity near the Sudbury neutrino observatory, Ontario, Canada

    NASA Astrophysics Data System (ADS)

    Mareschal, J.; Perry, C.; Jaupart, C.

    2009-05-01

    During its next phase, the Sudbury neutrino observatory (SNO) will detect geoneutrinos, antineutrinos produced by the decay of U and Th in the Earth. These observations will provide direct constraints on the contribution of radiogenic heat production in the crust and mantle to the energy budget of the Earth. The geoneutrino flux at SNO depends on the local level of crustal radio-activity. Surface heat flux data record average crustal radio-activity unaffected by small scale heterogeneities. We review all available heat flux data measurements in the Sudbury structure as well as measurements of U, Th, and K concentrations in the main geological units of the area. With all available data, the average heat flux in the Sudbury basin is ~53mW m-2, higher than the mean value of 42mW m-2 for the entire Canadian Shield. The elevated heat flux is due to high heat production in the shallow crust. We estimate that the average heat production of the upper crust near Sudbury is >1.5μ W m-3 compared to an average of 0.95μ W m-3 for the Superior Province. The high crustal radio-activity near Sudbury results in an about 50% increase of the local crustal component of the geoneutrino flux. Crustal radio-activity is highest in the southern part of the structure, near the Creighton mine where SNO is located. High heat flux and heat production values are also found in the Southern Province, on the margin of the Superior Province. An azimuthal variation in the geoneutrino flux with a higher flux from the south than from the north is expected on the basis on the present information. However, we shall need better estimates of the contribution of the rocks in the Superior Province to the North to assess the extent of azimuthal effects. The many available exploration drill holes and core samples provide an opportunity to determine the spatial variations in crustal radioactivity near SNO and improve the interpretation of future measurements of the geoneutrino flux.

  1. Er3+-activated photonic structures fabricated by sol-gel and rf-sputtering techniques

    NASA Astrophysics Data System (ADS)

    Ferrari, M.; Alombert-Goget, G.; Armellini, C.; Berneschi, S.; Bhaktha, S. N. B.; Boulard, B.; Brenci, M.; Chiappini, A.; Chiasera, A.; Duverger-Arfuso, C.; Féron, P.; Gonçalves, R. R.; Jestin, Y.; Minati, L.; Moser, E.; Nunzi Conti, G.; Pelli, S.; Rao, D. N.; Retoux, R.; Righini, G. C.; Speranza, G.

    2009-05-01

    The realization of photonic structures operating at visible and near infrared frequencies is a highly attractive scientific and technological challenge. Since optical fiber innovation, a huge of activity has been performed leading to interesting results, such as optical waveguides and planar lightwave circuits, microphotonic devices, optical microcavities, nanowires, plasmonic structures, and photonic crystals. These systems have opened new possibilities in the field of both basic and applied physics, in a large area covering Information Communication Technologies, Health and Biology, Structural Engineering, and Environment Monitoring Systems. Several materials and techniques are employed to successfully fabricate photonic structures. Concerning materials, Er3+-activated silica-based glasses still play an important role, although recently interesting results have been published about fluoride glass-ceramic waveguides. As far as regards the fabrication methods sol-gel route and rf sputtering have proved to be versatile and reliable techniques. In this article we will present a review of some Er3+-activated photonic structures fabricated by sol gel route and rf sputtering deposition. In the discussion on the sol-gel approach we focus our attention on the silica-hafnia binary system presenting an overview concerning fabrication protocols and structural, optical and spectroscopic assessment of SiO2-HfO2 waveguides activated by Er3+ ions. In order to put in evidence the reliability and versatility of the sol-gel route for photonics applications four different confined structures are briefly presented: amorphous waveguides, coated microspheres, monolithic waveguide laser, and core-shell nanospheres. As examples of rf sputtering technique, we will discuss Er3+-activated silica-hafnia and silica-germania waveguides, the latter system allowing fabrication of integrated optics structures by UV photo-imprinting. Finally, two examples of photonic crystal structures, one

  2. A Priori Method of Using Photon Activation Analysis to Determine Unknown Trace Element Concentrations in NIST Standards

    SciTech Connect

    Green, Jaromy; Sun Zaijing; Wells, Doug; Benson, Buck; Maschner, Herb

    2009-03-10

    Photon activation analysis detected elements in two NIST standards that did not have reported concentration values. A method is currently being developed to infer these concentrations by using scaling parameters and the appropriate known quantities within the NIST standard itself. Scaling parameters include: threshold, peak and endpoint energies; photo-nuclear cross sections for specific isotopes; Bremstrahlung spectrum; target thickness; and photon flux. Photo-nuclear cross sections and energies from the unknown elements must also be known. With these quantities, the same integral was performed for both the known and unknown elements resulting in an inference of the concentration of the un-reported element based on the reported value. Since Rb and Mn were elements that were reported in the standards, and because they had well-identified peaks, they were used as the standards of inference to determine concentrations of the unreported elements of As, I, Nb, Y, and Zr. This method was tested by choosing other known elements within the standards and inferring a value based on the stated procedure. The reported value of Mn in the first NIST standard was 403{+-}15 ppm and the reported value of Ca in the second NIST standard was 87000 ppm (no reported uncertainty). The inferred concentrations were 370{+-}23 ppm and 80200{+-}8700 ppm respectively.

  3. Development of high flux thermal neutron generator for neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Vainionpaa, Jaakko H.; Chen, Allan X.; Piestrup, Melvin A.; Gary, Charles K.; Jones, Glenn; Pantell, Richard H.

    2015-05-01

    The new model DD110MB neutron generator from Adelphi Technology produces thermal (<0.5 eV) neutron flux that is normally achieved in a nuclear reactor or larger accelerator based systems. Thermal neutron fluxes of 3-5 · 107 n/cm2/s are measured. This flux is achieved using four ion beams arranged concentrically around a target chamber containing a compact moderator with a central sample cylinder. Fast neutron yield of ∼2 · 1010 n/s is created at the titanium surface of the target chamber. The thickness and material of the moderator is selected to maximize the thermal neutron flux at the center. The 2.5 MeV neutrons are quickly thermalized to energies below 0.5 eV and concentrated at the sample cylinder. The maximum flux of thermal neutrons at the target is achieved when approximately half of the neutrons at the sample area are thermalized. In this paper we present simulation results used to characterize performance of the neutron generator. The neutron flux can be used for neutron activation analysis (NAA) prompt gamma neutron activation analysis (PGNAA) for determining the concentrations of elements in many materials. Another envisioned use of the generator is production of radioactive isotopes. DD110MB is small enough for modest-sized laboratories and universities. Compared to nuclear reactors the DD110MB produces comparable thermal flux but provides reduced administrative and safety requirements and it can be run in pulsed mode, which is beneficial in many neutron activation techniques.

  4. Measurement of the light flux density patterns from luminaires proposed as photon sources for photosynthesis during space travel

    NASA Technical Reports Server (NTRS)

    Walker, Paul N.

    1989-01-01

    Two luminaires were evaluated to determine the light flux density pattern on a horizontal plane surface. NASA supplied both luminaires; one was made by NASA and the other is commercially available. Tests were made for three combinations of luminaire height and luminaire lens material using the NASA luminaire; only one configuration of the commercial luminaire was tested. Measurements were made using four sensors with different wavelength range capabilities. The data are presented in graphical and tabular formats.

  5. Advances in the theoretical understanding of photon upconversion in rare-earth activated nanophosphors.

    PubMed

    Liu, Guokui

    2015-03-21

    Photon upconversion in rare earth activated phosphors involves multiple mechanisms of electronic transitions. Stepwise optical excitation, energy transfer, and various nonlinear and collective light-matter interaction processes act together to convert low-energy photons into short-wavelength light emission. Upconversion luminescence from nanomaterials exhibits additional size and surface dependencies. A fundamental understanding of the overall performance of an upconversion system requires basic theories on the spectroscopic properties of solids containing rare earth ions. This review article surveys the recent progress in the theoretical interpretations of the spectroscopic characteristics and luminescence dynamics of photon upconversion in rare earth activated phosphors. The primary aspects of upconversion processes, including energy level splitting, transition probability, line broadening, non-radiative relaxation and energy transfer, are covered with an emphasis on interpreting experimental observations. Theoretical models and methods for analyzing nano-phenomena in upconversion are introduced with detailed discussions on recently reported experimental results. PMID:25286989

  6. Calibration of Cherenkov detectors for monoenergetic photon imaging in active interrogation applications

    NASA Astrophysics Data System (ADS)

    Rose, P. B.; Erickson, A. S.

    2015-11-01

    Active interrogation of cargo containers using monoenergetic photons offers a rapid and low-dose approach to search for shielded special nuclear materials. Cherenkov detectors can be used for imaging of the cargo provided that gamma ray energies used in interrogation are well resolved, as the case in 11B(d,n-γ)12C reaction resulting in 4.4 MeV and 15.1 MeV photons. While an array of Cherenkov threshold detectors reduces low energy background from scatter while providing the ability of high contrast transmission imaging, thus confirming the presence of high-Z materials, these detectors require a special approach to energy calibration due to the lack of resolution. In this paper, we discuss the utility of Cherenkov detectors for active interrogation with monoenergetic photons as well as the results of computational and experimental studies of their energy calibration. The results of the studies with sources emitting monoenergetic photons as well as complex gamma ray spectrum sources, for example 232Th, show that calibration is possible as long as the energies of photons of interest are distinct.

  7. Focusing and photon flux measurements of the 2.88-nm radiation at the sample plane of the soft x-ray microscope, based on capillary discharge source

    NASA Astrophysics Data System (ADS)

    Nawaz, M. Fahad; Jancarek, Alexandr; Nevrkla, Michal; Wachulak, Przemyslaw; Limpouch, Jiri; Pina, Ladislav

    2015-05-01

    Feasibility measurements leading to the development of a Soft X-ray (SXR) microscopy setup, based on capillary discharge XUV source is presented. Here the Z-pinching plasma is acting as a source of XUV radiation, emitting incoherent radiation in the "water-window" (λ = 2.3 - 4.4 nm) region of interest (natural contrast between the carbon and oxygen edges).This soft X-ray microscopy setup will realize imaging of the biological objects with high spatial resolution. The 2.88 nm radiation line is filtered out from the water-window band, and is focused by an axi-symmetric ellipsoidal mirror, coated with nickle. The focussed spot size is measured and reported. Flux measurements for the available number of photons (photons/pulse) at the sample plane has been carried out with AXUV PIN diode at the sample plane (slightly out of focus). For imaging, a fresnel zone plate lens will be used as an objective. The overall compact transmission SXR microscopy setup design is presented.

  8. A novel heat flux study of a geothermally active lake - Lake Rotomahana, New Zealand

    NASA Astrophysics Data System (ADS)

    Tivey, Maurice A.; de Ronde, Cornel E. J.; Tontini, Fabio Caratori; Walker, Sharon L.; Fornari, Daniel J.

    2016-03-01

    A new technique for measuring conductive heat flux in a lake was adapted from the marine environment to allow for multiple measurements to be made in areas where bottom sediment cover is sparse, or even absent. This thermal blanket technique, pioneered in the deep ocean for use in volcanic mid-ocean rift environments, was recently used in the geothermally active Lake Rotomahana, New Zealand. Heat flow from the lake floor propagates into the 0.5 m diameter blanket and establishes a thermal gradient across the known blanket thickness and thereby provides an estimate of the conductive heat flux of the underlying terrain. This approach allows conductive heat flux to be measured over a spatially dense set of stations in a relatively short period of time. We used 10 blankets and deployed them for 1 day each to complete 110 stations over an 11-day program in the 6 × 3 km lake. Results show that Lake Rotomahana has a total conductive heat flux of about 47 MW averaging 6 W/m2 over the geothermally active lake. The western half of the lake has two main areas of high heat flux; 1) a high heat flux area averaging 21.3 W/m2 along the western shoreline, which is likely the location of the pre-existing geothermal system that fed the famous Pink Terraces, mostly destroyed during the 1886 eruption 2) a region southwest of Patiti Island with a heat flux averaging 13.1 W/m2 that appears to be related to the explosive rift that formed the lake in the 1886 Tarawera eruption. A small rise in bottom water temperature over the survey period of 0.01 °C/day suggests the total thermal output of the lake is ~ 112-132 MW and when compared to the conductive heat output suggests that 18-42% of the total thermal energy is by conductive heat transfer.

  9. Correlating two-photon excited fluorescence imaging of breast cancer cellular redox state with seahorse flux analysis of normalized cellular oxygen consumption

    NASA Astrophysics Data System (ADS)

    Hou, Jue; Wright, Heather J.; Chan, Nicole; Tran, Richard; Razorenova, Olga V.; Potma, Eric O.; Tromberg, Bruce J.

    2016-06-01

    Two-photon excited fluorescence (TPEF) imaging of the cellular cofactors nicotinamide adenine dinucleotide and oxidized flavin adenine dinucleotide is widely used to measure cellular metabolism, both in normal and pathological cells and tissues. When dual-wavelength excitation is used, ratiometric TPEF imaging of the intrinsic cofactor fluorescence provides a metabolic index of cells-the "optical redox ratio" (ORR). With increased interest in understanding and controlling cellular metabolism in cancer, there is a need to evaluate the performance of ORR in malignant cells. We compare TPEF metabolic imaging with seahorse flux analysis of cellular oxygen consumption in two different breast cancer cell lines (MCF-7 and MDA-MB-231). We monitor metabolic index in living cells under both normal culture conditions and, for MCF-7, in response to cell respiration inhibitors and uncouplers. We observe a significant correlation between the TPEF-derived ORR and the flux analyzer measurements (R=0.7901, p<0.001). Our results confirm that the ORR is a valid dynamic index of cell metabolism under a range of oxygen consumption conditions relevant for cancer imaging.

  10. Minimum activation martensitic alloys for surface disposal after exposure to neutron flux

    DOEpatents

    Lechtenberg, Thomas

    1985-01-01

    Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

  11. Quantum entanglement distribution with 810 nm photons through active telecommunication fibers.

    PubMed

    Holloway, Catherine; Meyer-Scott, Evan; Erven, Chris; Jennewein, Thomas

    2011-10-10

    We demonstrate the distribution of polarization-entangled photons for the purpose of quantum key distribution (QKD) along active telecom fibers. Entangled photon pairs of 810 nm wavelength generated by a Sagnac interferometer source were coupled into standard telecom single mode fibers. The fibers were either dark or carrying a standardized 1550 nm ethernet signals (1000BASE-ZX) with a nominal speed of 1 GBps from regular media converter devices, without any requirements on the optical power or spectrum transmitted. Our system demonstrates a QKD network covering 6 km in distance with a central service provider for classical and quantum data. PMID:21997067

  12. Quantifying the Sensitivity of Energy Fluxes to Land Surface Parameter Selection Using the Active Subspace Method

    NASA Astrophysics Data System (ADS)

    Jefferson, J.; Gilbert, J. M.; Maxwell, R. M.; Constantine, P. G.

    2015-12-01

    Complex hydrologic models are commonly used as computational tools to assess and quantify fluxes at the land surface and for forecasting and prediction purposes. When estimating water and energy fluxes from vegetated surfaces, the equations solved within these models require that multiple input parameters be specified. Some parameters characterize land cover properties while others are constants used to model physical processes like transpiration. As a result, it becomes important to understand the sensitivity of output flux estimates to uncertain input parameters. The active subspace method identifies the most important direction in the high-dimensional space of model inputs. Perturbations of input parameters in this direction influence output quantities more, on average, than perturbations in other directions. The components of the vector defining this direction quantify the sensitivity of the model output to the corresponding inputs. Discovering whether or not an active subspace exists is computationally efficient compared to several other sensitivity analysis methods. Here, we apply this method to evaluate the sensitivity of latent, sensible and ground heat fluxes from the ParFlow-Common Land Model (PF-CLM). Of the 19 input parameters used to specify properties of a grass covered surface, between three and six parameters are identified as important for heat flux estimates. Furthermore, the 19-dimenision input parameter space is reduced to one active variable and the relationship between the inputs and output fluxes for this case is described by a quadratic polynomial. The input parameter weights and the input-output relationship provide a powerful combination of information that can be used to understand land surface dynamics. Given the success of this proof-of-concept example, extension of this method to identify important parameters within the transpiration computation will be explored.

  13. Two-Photon Activation of p-Hydroxyphenacyl Phototriggers: Toward Spatially Controlled Release of Diethyl Phosphate and ATP.

    PubMed

    Houk, Amanda L; Givens, Richard S; Elles, Christopher G

    2016-03-31

    Two-photon activation of the p-hydroxyphenacyl (pHP) photoactivated protecting group is demonstrated for the first time using visible light at 550 nm from a pulsed laser. Broadband two-photon absorption measurements reveal a strong two-photon transition (>10 GM) near 4.5 eV that closely resembles the lowest-energy band at the same total excitation energy in the one-photon absorption spectrum of the pHP chromophore. The polarization dependence of the two-photon absorption band is consistent with excitation to the same S3 ((1)ππ*) excited state for both one- and two-photon activation. Monitoring the progress of the uncaging reaction under nonresonant excitation at 550 nm confirms a quadratic intensity dependence and that two-photon activation of the uncaging reaction is possible using visible light in the range 500-620 nm. Deprotonation of the pHP chromophore under mildly basic conditions shifts the absorption band to lower energy (3.8 eV) in both the one- and two-photon absorption spectra, suggesting that two-photon activation of the pHP chromophore may be possible using light in the range 550-720 nm. The results of these measurements open the possibility of spatially and temporally selective release of biologically active compounds from the pHP protecting group using visible light from a pulsed laser. PMID:26962676

  14. A universal setup for active control of a single-photon detector

    NASA Astrophysics Data System (ADS)

    Liu, Qin; Lamas-Linares, Antía; Kurtsiefer, Christian; Skaar, Johannes; Makarov, Vadim; Gerhardt, Ilja

    2014-01-01

    The influence of bright light on a single-photon detector has been described in a number of recent publications. The impact on quantum key distribution (QKD) is important, and several hacking experiments have been tailored to fully control single-photon detectors. Special attention has been given to avoid introducing further errors into a QKD system. We describe the design and technical details of an apparatus which allows to attack a quantum-cryptographic connection. This device is capable of controlling free-space and fiber-based systems and of minimizing unwanted clicks in the system. With different control diagrams, we are able to achieve a different level of control. The control was initially targeted to the systems using BB84 protocol, with polarization encoding and basis switching using beamsplitters, but could be extended to other types of systems. We further outline how to characterize the quality of active control of single-photon detectors.

  15. A universal setup for active control of a single-photon detector

    SciTech Connect

    Liu, Qin; Skaar, Johannes; Lamas-Linares, Antía; Kurtsiefer, Christian; Makarov, Vadim; Gerhardt, Ilja

    2014-01-15

    The influence of bright light on a single-photon detector has been described in a number of recent publications. The impact on quantum key distribution (QKD) is important, and several hacking experiments have been tailored to fully control single-photon detectors. Special attention has been given to avoid introducing further errors into a QKD system. We describe the design and technical details of an apparatus which allows to attack a quantum-cryptographic connection. This device is capable of controlling free-space and fiber-based systems and of minimizing unwanted clicks in the system. With different control diagrams, we are able to achieve a different level of control. The control was initially targeted to the systems using BB84 protocol, with polarization encoding and basis switching using beamsplitters, but could be extended to other types of systems. We further outline how to characterize the quality of active control of single-photon detectors.

  16. A universal setup for active control of a single-photon detector.

    PubMed

    Liu, Qin; Lamas-Linares, Antía; Kurtsiefer, Christian; Skaar, Johannes; Makarov, Vadim; Gerhardt, Ilja

    2014-01-01

    The influence of bright light on a single-photon detector has been described in a number of recent publications. The impact on quantum key distribution (QKD) is important, and several hacking experiments have been tailored to fully control single-photon detectors. Special attention has been given to avoid introducing further errors into a QKD system. We describe the design and technical details of an apparatus which allows to attack a quantum-cryptographic connection. This device is capable of controlling free-space and fiber-based systems and of minimizing unwanted clicks in the system. With different control diagrams, we are able to achieve a different level of control. The control was initially targeted to the systems using BB84 protocol, with polarization encoding and basis switching using beamsplitters, but could be extended to other types of systems. We further outline how to characterize the quality of active control of single-photon detectors. PMID:24517746

  17. Gamma-ray-spectroscopy following high-flux 14-MeV neutron activation

    SciTech Connect

    Williams, R.E.

    1981-10-12

    The Rotating Target Neutron Source (RTNS-I), a high-intensity source of 14-MeV neutrons at the Lawrence Livermore National Laboratory (LLNL), has been used for applications in activation analysis, inertial-confinement-fusion diagnostic development, and fission decay-heat studies. The fast-neutron flux from the RTNS-I is at least 50 times the maximum fluxes available from typical neutron generators, making these applications possible. Facilities and procedures necessary for gamma-ray spectroscopy of samples irradiated at the RTNS-I were developed.

  18. Photonic crystals as templates and active devices for cellular and molecular interactions

    NASA Astrophysics Data System (ADS)

    Sonek, G. J.

    2005-04-01

    Photonic crystals are emerging as an important class of engineered nanophotonic devices that possess unique optical properties and which can also provide textured surfaces for the study and control of cellular and molecular interactions. From among the many types of photonic crystal structures, two-dimensional (2D) and planar (slab) photonic crystals are the most attractive because of their ability to support guided-wave and active optical devices in semiconductor and polymer materials, serve as templates for device replication, and interface with colloidal and nanoparticle systems. This paper reports on the results of modeling and design efforts that show how 2d and slab silicon photonic crystals, based on their in-plane optical waveguiding and out-of-plane radiation properties, might be used to probe surface-bound cells and molecules or perform localized spectroscopy. The results of a parametric analysis show that photonic crystals comprised of high-index contrast materials (e.g. Si, air) are sensitive to geometric and material factors, potentially making them an effective medium to study molecular and cellular interactions critical to a number of biotechnological applications

  19. Niacin alleviates TRAIL-mediated colon cancer cell death via autophagy flux activation.

    PubMed

    Kim, Sung-Wook; Lee, Ju-Hee; Moon, Ji-Hong; Nazim, Uddin M D; Lee, You-Jin; Seol, Jae-Won; Hur, Jin; Eo, Seong-Kug; Lee, John-Hwa; Park, Sang-Youel

    2016-01-26

    Niacin, also known as vitamin B3 or nicotinamide is a water-soluble vitamin that is present in black beans and rice among other foods. Niacin is well known as an inhibitor of metastasis in human breast carcinoma cells but the effect of niacin treatment on TRAIL-mediated apoptosis is unknown. Here, we show that niacin plays an important role in the regulation of autophagic flux and protects tumor cells against TRAIL-mediated apoptosis. Our results indicated that niacin activated autophagic flux in human colon cancer cells and the autophagic flux activation protected tumor cells from TRAIL-induced dysfunction of mitochondrial membrane potential and tumor cell death. We also demonstrated that ATG5 siRNA and autophagy inhibitor blocked the niacin-mediated inhibition of TRAIL-induced apoptosis. Taken together, our study is the first report demonstrating that niacin inhibits TRAIL-induced apoptosis through activation of autophagic flux in human colon cancer cells. And our results also suggest that autophagy inhibitors including genetic and pharmacological tools may be a successful therapeutics during anticancer therapy using TRAIL. PMID:26517672

  20. Niacin alleviates TRAIL-mediated colon cancer cell death via autophagy flux activation

    PubMed Central

    Kim, Sung-Wook; Lee, Ju-Hee; Moon, Ji-Hong; Nazim, Uddin M.D.; Lee, You-Jin; Seol, Jae-Won; Hur, Jin; Eo, Seong-Kug; Lee, John-Hwa; Park, Sang-Youel

    2016-01-01

    Niacin, also known as vitamin B3 or nicotinamide is a water-soluble vitamin that is present in black beans and rice among other foods. Niacin is well known as an inhibitor of metastasis in human breast carcinoma cells but the effect of niacin treatment on TRAIL-mediated apoptosis is unknown. Here, we show that niacin plays an important role in the regulation of autophagic flux and protects tumor cells against TRAIL-mediated apoptosis. Our results indicated that niacin activated autophagic flux in human colon cancer cells and the autophagic flux activation protected tumor cells from TRAIL-induced dysfunction of mitochondrial membrane potential and tumor cell death. We also demonstrated that ATG5 siRNA and autophagy inhibitor blocked the niacin-mediated inhibition of TRAIL-induced apoptosis. Taken together, our study is the first report demonstrating that niacin inhibits TRAIL-induced apoptosis through activation of autophagic flux in human colon cancer cells. And our results also suggest that autophagy inhibitors including genetic and pharmacological tools may be a successful therapeutics during anticancer therapy using TRAIL. PMID:26517672

  1. Basic properties of magnetic flux tubes and restrictions on theories of solar activity

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1976-01-01

    It is shown that the mean longitudinal field in a magnetic flux tube is reduced, rather than enhanced, by twisting the tube to form a rope. It is shown that there is no magnetohydrostatic equilibrium when one twisted rope is wound around another. Instead there is rapid line cutting (neutral point annihilation). It is shown that the twisting increases, and the field strength decreases, along a flux tube extending upward through a stratified atmosphere. These facts are at variance with Piddington's (1975) recent suggestion that solar activity is to be understood as the result of flux tubes which are enormously concentrated by twisting, which consist of several twisted ropes wound around each other, and which came untwisted where they emerge through the photosphere.

  2. Above- and below-ground methane fluxes and methanotrophic activity in a landfill-cover soil.

    PubMed

    Schroth, M H; Eugster, W; Gómez, K E; Gonzalez-Gil, G; Niklaus, P A; Oester, P

    2012-05-01

    Landfills are a major anthropogenic source of the greenhouse gas methane (CH(4)). However, much of the CH(4) produced during the anaerobic degradation of organic waste is consumed by methanotrophic microorganisms during passage through the landfill-cover soil. On a section of a closed landfill near Liestal, Switzerland, we performed experiments to compare CH(4) fluxes obtained by different methods at or above the cover-soil surface with below-ground fluxes, and to link methanotrophic activity to estimates of CH(4) ingress (loading) from the waste body at selected locations. Fluxes of CH(4) into or out of the cover soil were quantified by eddy-covariance and static flux-chamber measurements. In addition, CH(4) concentrations at the soil surface were monitored using a field-portable FID detector. Near-surface CH(4) fluxes and CH(4) loading were estimated from soil-gas concentration profiles in conjunction with radon measurements, and gas push-pull tests (GPPTs) were performed to quantify rates of microbial CH(4) oxidation. Eddy-covariance measurements yielded by far the largest and probably most representative estimates of overall CH(4) emissions from the test section (daily mean up to ∼91,500μmolm(-2)d(-1)), whereas flux-chamber measurements and CH(4) concentration profiles indicated that at the majority of locations the cover soil was a net sink for atmospheric CH(4) (uptake up to -380μmolm(-2)d(-1)) during the experimental period. Methane concentration profiles also indicated strong variability in CH(4) loading over short distances in the cover soil, while potential methanotrophic activity derived from GPPTs was high (v(max)∼13mmolL(-1)(soil air)h(-1)) at a location with substantial CH(4) loading. Our results provide a basis to assess spatial and temporal variability of CH(4) dynamics in the complex terrain of a landfill-cover soil. PMID:22143049

  3. High Resolution Simulations of Tearing and Flux-Rope Formation in Active Region Jets

    NASA Astrophysics Data System (ADS)

    Wyper, P. F.; DeVore, C. R.; Karpen, J. T.

    2015-12-01

    Observations of coronal jets increasingly suggest that local fragmentation and the generation of small-scale structure plays an important role in the dynamics of these events. In the magnetically closed corona, jets most often occur near active regions and are associated with an embedded-bipole topology consisting of a 3D magnetic null point atop a domed fan separatrix surface at the base of a coronal loop. Impulsive reconnection in the vicinity of the null point between the magnetic fluxes inside and outside the dome launches the jet along the loop. Wyper & Pontin 2014 showed that the 3D current layers that facilitate such reconnection are explosively unstable to tearing, generating complex flux-rope structures. Utilizing the adaptive mesh capabilities of the Adaptively Refined Magnetohydrodynamics Solver, we investigate the generation of such fine-scale structure in high-resolution simulations of active-region jets. We observe the formation of multiple flux-rope structures forming across the fan separatrix surface and discuss the photospheric signatures of these flux ropes and the associated local topology change. We also introduce a new way of identifying such flux ropes in the magnetic field, based on structures observed in the magnetic squashing factor calculated on the photosphere. By tracking the position and number of new null points produced by the fragmentation, we also show that the formation of flux ropes can occur away from the main null region on the flanks of the separatrix dome and that the jet curtain has a highly complex magnetic structure. This work was funded through an appointment to the NASA Postdoctoral Program and by NASA's Living With a Star TR&T program.

  4. Two-photon, three-photon, and four-photon excellent near-infrared quantum cutting luminescence of Tm3+ ion activator emerged in Tm3+:YNbO4 powder phosphor one material simultaneously

    NASA Astrophysics Data System (ADS)

    Chen, Xiaobo; Salamo, Gregory J.; Li, Song; Wang, Jieliang; Guo, Yuying; Gao, Yan; He, Lizhu; Ma, Hui; Tao, Jingfu; Sun, Ping; Lin, Wei; Liu, Quanlin

    2015-12-01

    In present study, two-photon, three-photon, and four photon near-infrared quantum cutting luminescence of Tm3+ ion activator in YNbO4 powder phosphor is reported. The visible to near-infrared excitation and emission spectra and fluorescence lifetimes of Tm0.038Y0.962NbO4 powder phosphor are measured. Tm0.038Y0.962NbO4 is found to possess intense two-photon, strong three-photon, and moderate four-photon quantum cutting 1820 nm 3F4→3H6 luminescence of the Tm3+ ion simultaneously. The up-limit of the two-, three-, and four-photon near-infrared quantum cutting efficiency are found to be approximately 166%, 198%, and 192%, respectively. These results are expected to be valuable in aiding the probing of new generation environmentally friendly germanium Ge solar cells, currently a popular condensed matter physical topic globally.

  5. Numerical simulations of active region scale flux emergence: From spot formation to decay

    SciTech Connect

    Rempel, M.; Cheung, M. C. M.

    2014-04-20

    We present numerical simulations of active region scale flux emergence covering a time span of up to 6 days. Flux emergence is driven by a bottom boundary condition that advects a semi-torus of magnetic field with 1.7 × 10{sup 22} Mx flux into the computational domain. The simulations show that, even in the absence of twist, the magnetic flux is able the rise through the upper 15.5 Mm of the convection zone and emerge into the photosphere to form spots. We find that spot formation is sensitive to the persistence of upflows at the bottom boundary footpoints, i.e., a continuing upflow would prevent spot formation. In addition, the presence of a torus-aligned flow (such flow into the retrograde direction is expected from angular momentum conservation during the rise of flux ropes through the convection zone) leads to a significant asymmetry between the pair of spots, with the spot corresponding to the leading spot on the Sun being more axisymmetric and coherent, but also forming with a delay relative to the following spot. The spot formation phase transitions directly into a decay phase. Subsurface flows fragment the magnetic field and lead to intrusions of almost field free plasma underneath the photosphere. When such intrusions reach photospheric layers, the spot fragments. The timescale for spot decay is comparable to the longest convective timescales present in the simulation domain. We find that the dispersal of flux from a simulated spot in the first two days of the decay phase is consistent with self-similar decay by turbulent diffusion.

  6. EVOLUTION OF SPINNING AND BRAIDING HELICITY FLUXES IN SOLAR ACTIVE REGION NOAA 10930

    SciTech Connect

    Ravindra, B.; Yoshimura, Keiji; Dasso, Sergio E-mail: yosimura@solar.physics.montana.edu

    2011-12-10

    The line-of-sight magnetograms from Solar Optical Telescope Narrowband Filter Imager observations of NOAA Active Region 10930 have been used to study the evolution of spinning and braiding helicities over a period of five days starting from 2006 December 9. The north (N) polarity sunspot was the follower and the south (S) polarity sunspot was the leader. The N-polarity sunspot in the active region was rotating in the counterclockwise direction. The rate of rotation was small during the first two days of observations and it increased up to 8 Degree-Sign hr{sup -1} on the third day of the observations. On the fourth and fifth days it remained at 4 Degree-Sign hr{sup -1} with small undulations in its magnitude. The sunspot rotated about 260 Degree-Sign in the last three days. The S-polarity sunspot did not complete more than 20 Degree-Sign in five days. However, it changed its direction of rotation five times over a period of five days and injected both the positive and negative type of spin helicity fluxes into the corona. Through the five days, both the positive and negative sunspot regions injected equal amounts of spin helicity. The total injected helicity is predominantly negative in sign. However, the sign of the spin and braiding helicity fluxes computed over all the regions were reversed from negative to positive five times during the five-day period of observations. The reversal in spinning helicity flux was found before the onset of the X3.4-class flare, too. Though, the rotating sunspot has been observed in this active region, the braiding helicity has contributed more to the total accumulated helicity than the spinning helicity. The accumulated helicity is in excess of -7 Multiplication-Sign 10{sup 43} Mx{sup 2} over a period of five days. Before the X3.4-class flare that occurred on 2006 December 13, the rotation speed and spin helicity flux increased in the S-polarity sunspot. Before the flare, the total injected helicity was larger than -6

  7. Magnetic flux transport of decaying active regions and enhanced magnetic network. [of solar supergranulation

    NASA Technical Reports Server (NTRS)

    Wang, Haimin; Zirin, Harold; Ai, Guoxiang

    1991-01-01

    Several series of coordinated observations on decaying active regions and enhanced magnetic network regions on the sun were carried out jointly at Big Bear Solar Observatory and at the Huairou Solar Observing Station of the Bejing Astronomical Observatory in China. The magnetic field evolution in several regions was followed closely for three to seven days. The magnetic flux transport from the remnants of decayed active regions was studied, along with the evolution and lifetime of the magnetic network which defines the boundaries of supergranules. The magnetic flux transport in an enhanced network region was studied in detail and found to be negative. Also briefly described are some properties of moving magnetic features around a sunspot. Results of all of the above studies are presented.

  8. Galactic cosmic ray flux in the mid of 1700 from 44Ti activity of Agen meteorite

    NASA Astrophysics Data System (ADS)

    Taricco, Carla; Sinha, Neeharika; Bhandari, Narendra; Colombetti, Paolo; Mancuso, Salvatore; Rubinetti, Sara; Barghini, Dario

    2016-04-01

    Cosmogenic isotopes produced by galactic cosmic rays (GCR) in meteorites offer the opportunity to reveal the heliospheric magnetic field modulation in the interplanetary space between heliocentric distances of 1 and 3 AU. We present the gamma-activity measurement of Agen meteorite, a H5 chondrite that fell on September 5, 1814 in Aquitaine, France. Its 44Ti activity reflects GCR flux integrated since the mid of 1700 to the time of fall and confirms the decreasing trend of GCR flux that we previously suggested on the basis of measurements of other meteorites which fell in the last 250 years as well as the centennial modulation of GCR due to the Gleissberg solar cycle This result was obtained thanks to the high-efficiency and selective configuration of the gamma-ray spectrometer (HPGe+NaI) operating at the underground Laboratory of Monte dei Cappuccini (OATo, INAF) in Torino, Italy.

  9. Effects of activating fluxes on the weld penetration and corrosion resistant property of laser welded joint of ferritic stainless steel

    NASA Astrophysics Data System (ADS)

    Wang, Yonghui; Hu, Shengsun; Shen, Junqi

    2015-10-01

    This study was based on the ferritic stainless steel SUS430. Under the parallel welding conditions, the critical penetration power values (CPPV) of 3mm steel plates with different surface-coating activating fluxes were tested. Results showed that, after coating with activating fluxes, such as ZrO2, CaCO3, CaF2 and CaO, the CPPV could reduce 100~250 W, which indicating the increases of the weld penetrations (WP). Nevertheless, the variation range of WP with or without activating fluxes was less than 16.7%. Compared with single-component ones, a multi-component activating flux composed of 50% ZrO2, 12.09% CaCO3, 10.43% CaO, and 27.49% MgO was testified to be much more efficient, the WP of which was about 2.3-fold of that without any activating fluxes. Furthermore, a FeCl3 spot corrosion experiment was carried out with samples cut from weld zone to test the effects of different activating fluxes on the corrosion resistant (CR) property of the laser welded joints. It was found that all kinds of activating fluxes could improve the CR of the welded joints. And, it was interesting to find that the effect of the mixed activating fluxes was inferior to those single-component ones. Among all the activating fluxes, the single-component of CaCO3 seemed to be the best in resisting corrosion. By means of Energy Dispersive Spectrometer (EDS) testing, it was found that the use of activating fluxes could effectively restrain the loss of Cr element of weld zone in the process of laser welding, thus greatly improving the CR of welded joints.

  10. Photon-activated electron hopping in a single-electron trap enhanced by Josephson radiation

    NASA Astrophysics Data System (ADS)

    Lotkhov, S. V.; Jalali-Jafari, B.; Zorin, A. B.

    2016-04-01

    Using a Josephson junction interferometer (DC SQUID) as a microwave source for irradiating a single-electron trap, both devices fabricated on the same chip, we study the process of photon-assisted tunneling as an effective mechanism of single photon detection. High sensitivity down to a very small oscillation amplitude v J ˜ 10 nV ≪ E act ≲ h f J and down to low photon absorption rates Γph ˜ (1-50) Hz, as well as a clear threshold type of operation with an activation energy Eact ˜ 400 μeV, is demonstrated for the trap with respect to the microwave photons of frequency fJ ˜ (100-200) GHz. Tunable generation is demonstrated with respect to the power and frequency of the microwave signal produced by the SQUID source biased within the subgap voltage range. A much weaker effect is observed at the higher junction voltages along the quasiparticle branch of the I-V curve; this response mostly appears due to the recombination phonons.

  11. Flux-tube geometry and solar wind speed during an activity cycle

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Brun, A. S.; Rouillard, A. P.

    2016-07-01

    Context. The solar wind speed at 1 AU shows cyclic variations in latitude and in time which reflect the evolution of the global background magnetic field during the activity cycle. It is commonly accepted that the terminal (asymptotic) wind speed in a given magnetic flux-tube is generally anti-correlated with its total expansion ratio, which motivated the definition of widely used semi-empirical scaling laws relating one to the other. In practice, such scaling laws require ad hoc corrections (especially for the slow wind in the vicinities of streamer/coronal hole boundaries) and empirical fits to in situ spacecraft data. A predictive law based solely on physical principles is still missing. Aims: We test whether the flux-tube expansion is the controlling factor of the wind speed at all phases of the cycle and at all latitudes (close to and far from streamer boundaries) using a very large sample of wind-carrying open magnetic flux-tubes. We furthermore search for additional physical parameters based on the geometry of the coronal magnetic field which have an influence on the terminal wind flow speed. Methods: We use numerical magneto-hydrodynamical simulations of the corona and wind coupled to a dynamo model to determine the properties of the coronal magnetic field and of the wind velocity (as a function of time and latitude) during a whole 11-yr activity cycle. These simulations provide a large statistical ensemble of open flux-tubes which we analyse conjointly in order to identify relations of dependence between the wind speed and geometrical parameters of the flux-tubes which are valid globally (for all latitudes and moments of the cycle). Results: Our study confirms that the terminal (asymptotic) speed of the solar wind depends very strongly on the geometry of the open magnetic flux-tubes through which it flows. The total flux-tube expansion is more clearly anti-correlated with the wind speed for fast rather than for slow wind flows, and effectively controls the

  12. Mass flux measurements at active lava lakes: Implications for magma recycling

    NASA Astrophysics Data System (ADS)

    Harris, Andrew J. L.; Flynn, Luke P.; Rothery, David A.; Oppenheimer, Clive; Sherman, Sarah B.

    1999-04-01

    Remotely sensed and field data can be used to estimate heat and mass fluxes at active lava lakes. Here we use a three thermal component pixel model with three bands of Landsat thematic mapper (TM) data to constrain the thermal structure of, and flux from, active lava lakes. Our approach considers that a subpixel lake is surrounded by ground at ambient temperatures and that the surface of the lake is composed of crusted and/or molten material. We then use TM band 6 (10.42-12.42 μm) with bands 3 (0.63-0.69 μm) or 4 (0.76-0.90 μm) and 5 (1.55-1.75 μm) or 7 (2.08-2.35 μm), along with field data (e.g., lava lake area), to place limits on the size and temperature of each thermal component. Previous attempts to achieve this have used two bands of TM data with a two-component thermal model. Using our model results with further field data (e.g., petrological data) for lava lakes at Erebus, Erta 'Ale, and Pu'u 'O'o, we calculate combined radiative and convective fluxes of 11-20, 14-27 and 368-373 MW, respectively. These yield mass fluxes, of 30-76, 44-104 and 1553-2079 kg s-1, respectively. We also identify a hot volcanic feature at Nyiragongo during 1987 from which a combined radiative and convective flux of 0.2-0.6 MW implies a mass flux of 1-2 kg s-1. We use our mass flux estimates to constrain circulation rates in each reservoir-conduit-lake system and consider four models whereby circulation results in intrusion within or beneath the volcano (leading to endogenous or cryptic growth) and/or magma mixing in the reservoir (leading to recycling). We suggest that the presence of lava lakes does not necessarily imply endogenous or cryptic growth: lava lakes could be symptomatic of magma recycling in supraliquidus reservoirs.

  13. HDAC6 activity is not required for basal autophagic flux in metastatic prostate cancer cells.

    PubMed

    Watson, Gregory W; Wickramasekara, Samanthi; Fang, Yufeng; Maier, Claudia S; Williams, David E; Dashwood, Roderick H; Perez, Viviana I; Ho, Emily

    2016-06-01

    Histone deacetylase 6 is a multifunctional lysine deacetylase that is recently emerging as a central facilitator of response to stress and may play an important role in cancer cell proliferation. The histone deacetylase 6-inhibitor tubacin has been shown to slow the growth of metastatic prostate cancer cells and sensitize cancer cells to chemotherapeutic agents. However, the proteins histone deacetylase 6 interacts with, and thus its role in cancer cells, remains poorly characterized. Histone deacetylase 6 deacetylase activity has recently been shown to be required for efficient basal autophagic flux. Autophagy is often dysregulated in cancer cells and may confer stress resistance and allow for cell maintenance and a high proliferation rate. Tubacin may therefore slow cancer cell proliferation by decreasing autophagic flux. We characterized the histone deacetylase 6-interacting proteins in LNCaP metastatic prostate cancer cells and found that histone deacetylase 6 interacts with proteins involved in several cellular processes, including autophagy. Based on our interaction screen, we assessed the impact of the histone deacetylase 6-inhibitor tubacin on autophagic flux in two metastatic prostate cancer cell lines and found that tubacin does not influence autophagic flux. Histone deacetylase 6 therefore influences cell proliferation through an autophagy-independent mechanism. PMID:26643866

  14. Finger heat flux/temperature as an indicator of thermal imbalance with application for extravehicular activity

    NASA Astrophysics Data System (ADS)

    Koscheyev, Victor S.; Leon, Gloria R.; Coca, Aitor

    2005-11-01

    The designation of a simple, non-invasive, and highly precise method to monitor the thermal status of astronauts is important to enhance safety during extravehicular activities (EVA) and onboard emergencies. Finger temperature ( Tfing), finger heat flux, and indices of core temperature ( Tc) [rectal ( Tre), ear canal ( Tec)] were assessed in 3 studies involving different patterns of heat removal/insertion from/to the body by a multi-compartment liquid cooling/warming garment (LCWG). Under both uniform and nonuniform temperature conditions on the body surface, Tfing and finger heat flux were highly correlated with garment heat flux, and also highly correlated with each other. Tc responses did not adequately reflect changes in thermal balance during the ongoing process of heat insertion/removal from the body. Overall, Tfing/finger heat flux adequately reflected the initial destabilization of thermal balance, and therefore appears to have significant potential as a useful index for monitoring and maintaining thermal balance and comfort in extreme conditions in space as well as on Earth.

  15. Measurement of surface mercury fluxes at active industrial gold mines in Nevada (USA).

    PubMed

    Eckley, C S; Gustin, M; Marsik, F; Miller, M B

    2011-01-01

    Mercury (Hg) may be naturally associated with the rock units hosting precious and base metal deposits. Active gold mines are known to have point source releases of Hg associated with ore processing facilities. The nonpoint source release of Hg to the air from the large area (hundreds to thousands of hectares) of disturbed and processed material at industrial open pit gold mines has not been quantified. This paper describes the field data collected as part of a project focused on estimating nonpoint source emissions of Hg from two active mines in Nevada, USA. In situ Hg flux data were collected on diel and seasonal time steps using a dynamic flux chamber from representative mine surfaces. Hg fluxes ranged from <1500 ng m(-2) day(-1) for waste rock piles (0.6-3.5 μg g(-1)) to 684,000 ng m(-2) day(-1) for tailings (2.8-58 μg g(-1)). Releases were positively correlated with material Hg concentrations, surface grain size, and moisture content. Highest Hg releases occurred from materials under active cyanide leaching and from tailings impoundments containing processed high-grade ore. Data collected indicate that as mine sites are reclaimed and material disturbance ceases, emissions will decline. Additionally local cycling of atmospheric Hg (deposition and re-emission) was found to occur. PMID:21078520

  16. High active nitrogen flux growth of GaN by plasma assisted molecular beam epitaxy

    SciTech Connect

    McSkimming, Brian M. Speck, James S.; Chaix, Catherine

    2015-09-15

    In the present study, the authors report on a modified Riber radio frequency (RF) nitrogen plasma source that provides active nitrogen fluxes more than 30 times higher than those commonly used for plasma assisted molecular beam epitaxy (PAMBE) growth of gallium nitride (GaN) and thus a significantly higher growth rate than has been previously reported. GaN films were grown using N{sub 2} gas flow rates between 5 and 25 sccm while varying the plasma source's RF forward power from 200 to 600 W. The highest growth rate, and therefore the highest active nitrogen flux, achieved was ∼7.6 μm/h. For optimized growth conditions, the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 × 3 μm) on the order of 1 nm. Secondary ion mass spectroscopy impurity analysis demonstrates oxygen and hydrogen incorporation of 1 × 10{sup 16} and ∼5 × 10{sup 17}, respectively. In addition, the authors have achieved PAMBE growth of GaN at a substrate temperature more than 150 °C greater than our standard Ga rich GaN growth regime and ∼100 °C greater than any previously reported PAMBE growth of GaN. This growth temperature corresponds to GaN decomposition in vacuum of more than 20 nm/min; a regime previously unattainable with conventional nitrogen plasma sources. Arrhenius analysis of the decomposition rate shows that samples with a flux ratio below stoichiometry have an activation energy greater than decomposition of GaN in vacuum while samples grown at or above stoichiometry have decreased activation energy. The activation energy of decomposition for GaN in vacuum was previously determined to be ∼3.1 eV. For a Ga/N flux ratio of ∼1.5, this activation energy was found to be ∼2.8 eV, while for a Ga/N flux ratio of ∼0.5, it was found to be ∼7.9 eV.

  17. Highly sensitive assay for acetylcholinesterase activity and inhibition based on a specifically reactive photonic nanostructure.

    PubMed

    Tian, Tian; Li, Xuesong; Cui, Jiecheng; Li, Jian; Lan, Yue; Wang, Chen; Zhang, Meng; Wang, Hui; Li, Guangtao

    2014-09-10

    Assays for acetylcholinesterase (AChE) with high sensitivity and high selectivity as well as facile manipulation have been urgently required in various fields. In this work, a reaction-based photonic strategy was developed for the efficient assay of AChE activity and inhibition based on the synergetic combination of the specific thiol-maleimide addition reaction with photonic porous structure. It was found that various applications including detection of AChE activity, measurement of the related enzymatic kinetics, and screening of inhibitors could be efficiently implemented using such strategy. Remarkably, the unique photonic nanostructure endows the constructed sensing platform with high sensitivity with a limit of detection (LOD) of 5 mU/mL for AChE activity, high selectivity, and self-reporting signaling. Moreover, the label-free solid film-based sensing approach described here has advantages of facile manipulation and bare-eye readout, compared with conventional liquid-phase methods, exhibiting promising potential in practical application for the AChE assay. PMID:25130420

  18. YANA – a software tool for analyzing flux modes, gene-expression and enzyme activities

    PubMed Central

    Schwarz, Roland; Musch, Patrick; von Kamp, Axel; Engels, Bernd; Schirmer, Heiner; Schuster, Stefan; Dandekar, Thomas

    2005-01-01

    Background A number of algorithms for steady state analysis of metabolic networks have been developed over the years. Of these, Elementary Mode Analysis (EMA) has proven especially useful. Despite its low user-friendliness, METATOOL as a reliable high-performance implementation of the algorithm has been the instrument of choice up to now. As reported here, the analysis of metabolic networks has been improved by an editor and analyzer of metabolic flux modes. Analysis routines for expression levels and the most central, well connected metabolites and their metabolic connections are of particular interest. Results YANA features a platform-independent, dedicated toolbox for metabolic networks with a graphical user interface to calculate (integrating METATOOL), edit (including support for the SBML format), visualize, centralize, and compare elementary flux modes. Further, YANA calculates expected flux distributions for a given Elementary Mode (EM) activity pattern and vice versa. Moreover, a dissection algorithm, a centralization algorithm, and an average diameter routine can be used to simplify and analyze complex networks. Proteomics or gene expression data give a rough indication of some individual enzyme activities, whereas the complete flux distribution in the network is often not known. As such data are noisy, YANA features a fast evolutionary algorithm (EA) for the prediction of EM activities with minimum error, including alerts for inconsistent experimental data. We offer the possibility to include further known constraints (e.g. growth constraints) in the EA calculation process. The redox metabolism around glutathione reductase serves as an illustration example. All software and documentation are available for download at . Conclusion A graphical toolbox and an editor for METATOOL as well as a series of additional routines for metabolic network analyses constitute a new user-friendly software for such efforts. PMID:15929789

  19. Acute two-photon imaging of the neurovascular unit in the cortex of active mice

    PubMed Central

    Tran, Cam Ha T.; Gordon, Grant R.

    2015-01-01

    In vivo two-photon scanning fluorescence imaging is a powerful technique to observe physiological processes from the millimeter to the micron scale in the intact animal. In neuroscience research, a common approach is to install an acute cranial window and head bar to explore neocortical function under anesthesia before inflammation peaks from the surgery. However, there are few detailed acute protocols for head-restrained and fully awake animal imaging of the neurovascular unit during activity. This is because acutely performed awake experiments are typically untenable when the animal is naïve to the imaging apparatus. Here we detail a method that achieves acute, deep-tissue two-photon imaging of neocortical astrocytes and microvasculature in behaving mice. A week prior to experimentation, implantation of the head bar alone allows mice to train for head-immobilization on an easy-to-learn air-supported ball treadmill. Following just two brief familiarization sessions to the treadmill on separate days, an acute cranial window can subsequently be installed for immediate imaging. We demonstrate how running and whisking data can be captured simultaneously with two-photon fluorescence signals with acceptable movement artifacts during active motion. We also show possible applications of this technique by (1) monitoring dynamic changes to microvascular diameter and red blood cells in response to vibrissa sensory stimulation, (2) examining responses of the cerebral microcirculation to the systemic delivery of pharmacological agents using a tail artery cannula during awake imaging, and (3) measuring Ca2+ signals from synthetic and genetically encoded Ca2+ indicators in astrocytes. This method will facilitate acute two-photon fluorescence imaging in awake, active mice and help link cellular events within the neurovascular unit to behavior. PMID:25698926

  20. Average energetic ion flux variations associated with geomagnetic activity from EPIC/STICS on Geotail

    NASA Technical Reports Server (NTRS)

    Christon, S. P.; Gloeckler, G.; Eastman, T. E.; McEntire, R. W.; Roelef, E. C.; Lui, A. T. Y.; Williams, D. J.; Frank, L. A.; Paterson, W. R.; Kokubun, S.; Matsumoto, H.; Kojima, H.; Mukai, T.; Saito, Y.; Yamamoto, T.

    1996-01-01

    The magnetotail ion flux measurements from the Geotail spacecraft are analyzed both with and without the application of selection criteria that identify the plasma regime in which an observation is obtained. The different results are compared with each other. The initial results on the changes of energetic ion flux and composition correlated to average substorm activity in different magnetotail plasma regimes are discussed. The energetic ions are measured using the energetic particles and ion composition (EPIC) experiment and the suprathermal ion composition spectrometer (STICS). The plasma, wave and field instruments of the Geotail satellite were used to identify the principle magnetotail plasma regimes of plasma sheet, lobe, and magnetospheric boundary layer, as well as the magnetosheath and solar wind. Energetic O and H ions were observed in all the plasma regimes.

  1. All-optical transistor using a photonic-crystal cavity with an active Raman gain medium

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    We propose a design of an all-optical transistor based on a one-dimensional photonic-crystal cavity doped with a four-level N-type active Raman gain medium. The calculated results show that in a photonic-crystal cavity of this kind transmission and reflection of the probe (Raman) beam are strongly dependent on the optical switching power. Transmission and reflection of the probe beam can be greatly amplified or attenuated. Therefore the optical switching field can serve as a gate field of the transistor to effectively control propagation of the weak probe field. It is shown that the group velocity of the probe pulse can be controlled in the range from subluminal (slow light) to superluminal (fast light).

  2. Quasi-biennial modulation of solar neutrino flux: connections with solar activity

    NASA Astrophysics Data System (ADS)

    Vecchio, A.; Laurenza, M.; D'alessi, L.; Carbone, V.; Storini, M.

    2011-12-01

    A quasi-biennial periodicity has been recently found (Vecchio et al., 2010) in the solar neutrino flux, as detected at the Homestake experiment, as well as in the flux of solar energetic protons, by means of the Empirical Modes Decomposition technique. Moreover, both fluxes have been found to be significantly correlated at the quasi-biennial timescale, thus supporting the hypothesis of a connection between solar neutrinos and solar activity. The origin of this connection is investigated, by modeling how the standard Mikheyev-Smirnov-Wolfenstein (MSW) effect (the process for which the well-known neutrino flavor oscillations are modified in passing through the material) could be influenced by matter fluctuations. As proposed by Burgess et al., 2004, by introducing a background magnetic field in the helioseismic model, density fluctuations can be excited in the radiative zone by the resonance between helioseismic g-modes and Alfvén waves. In particular, with reasonable values of the background magnetic field (10-100 kG), the distance between resonant layers could be of the same order of neutrino oscillation length. We study the effect over this distance of a background magnetic field which is variable with a ~2 yr period, in agreement with typical variations of solar activity. Our findings suggest that the quasi-biennial modulation of the neutrino flux is theoretically possible as a consequence of the magnetic field variations in the solar interior. A. Vecchio, M. Laurenza, V. Carbone, M. Storini, The Astrophysical Journal Letters, 709, L1-L5 (2010). C. Burgess, N. S. Dzhalilov, T. I. Rashba, V., B.Semikoz, J. W. F. Valle, Mon. Not. R. Astron. Soc., 348, 609-624 (2004).

  3. Design and testing of an active quenching circuit for an avalanche photodiode photon detector

    NASA Technical Reports Server (NTRS)

    Arbel, D.; Schwartz, J. A.

    1991-01-01

    The photon-detection capabilities of avalanche photodiodes (APDs) operating above their theoretical breakdown voltages are described, with particular attention given to the needs and methods of quenching an avalanche once breakdown has occurred. A brief background on the motives of and previous work with this mode of operation is presented. Finally, a description of the design and testing of an active quenching circuit is given. Although the active quenching circuit did not perform as expected, knowledge was gained as to the signal amplitudes necessary for quenching and the need for a better model for the above-breakdown circuit characteristics of the Geiger-mode APD.

  4. In vivo stepwise multi-photon activation fluorescence imaging of melanin in human skin

    NASA Astrophysics Data System (ADS)

    Lai, Zhenhua; Gu, Zetong; Abbas, Saleh; Lowe, Jared; Sierra, Heidy; Rajadhyaksha, Milind; DiMarzio, Charles

    2014-03-01

    The stepwise multi-photon activated fluorescence (SMPAF) of melanin is a low cost and reliable method of detecting melanin because the activation and excitation can be a continuous-wave (CW) mode near infrared (NIR) laser. Our previous work has demonstrated the melanin SMPAF images in sepia melanin, mouse hair, and mouse skin. In this study, we show the feasibility of using SMPAF to detect melanin in vivo. in vivo melanin SMPAF images of normal skin and benign nevus are demonstrated. SMPAF images add specificity for melanin detection than MPFM images and CRM images. Melanin SMPAF is a promising technology to enable early detection of melanoma for dermatologists.

  5. Erosional flux from tectonically active landscapes: Case studies from Southern Italy

    NASA Astrophysics Data System (ADS)

    Roda-Boluda, Duna; D'Arcy, Mitch; Whittaker, Alex; Allen, Philip; Gheorghiu, Delia; Rodes, Angel

    2016-04-01

    Erosion and sediment supply are fundamentally important controls on landscape evolution, governing the denudation of relief, the stratigraphy deposited in basins, and the ultimate destruction of orogens. However, quantifying the rates, timescales, and predominant processes of erosion remains a major challenge in many tectonically active areas. Here, we use Southern Italy as a case study to demonstrate how these challenges can be overcome. We present 15 new 10Be catchment-averaged erosion rates, for systems distributed along 5 active normal faults for which we have excellent constraints on throw rates along strike and uplift history. These footwall catchments have a total relief of up to 1800 m and throw rates up to 1.4 mm/yr. We show that sediment supply estimates based on the 10Be erosion rates agree well with sediment supply predictions based on the fault throw profiles. Our results suggest that about 80% of the material uplifted by the faults is being eroded at a similar magnitude to the fault throw rates, offering new insights into the topographic balance of uplift and erosion in this area. These findings imply that active normal faulting is the primary control on sediment supply in Southern Italy. Our field observations suggest that landslides are an important source of sediment in our study area, and are largely driven by incision in response to fault activity. Using a field-calibrated landslide inventory, we estimate landslide-derived sediment flux for our sampled catchments. These estimates correlate well with total sediment flux estimates, demonstrating quantitatively that landslides must be a major source of sediment. Their erosional signal is adequately captured by the 10Be analyses most likely because of the high frequency of small landslides and their high spatial density in these catchments (typically >10% of the total area), which ensures sufficient sediment mixing. Finally, we use our results to calibrate the BQART model of sediment supply, enabling

  6. Comprehensive measurement of respiratory activity in permeabilized cells using extracellular flux analysis

    PubMed Central

    Salabei, Joshua K.; Gibb, Andrew A.; Hill, Bradford G.

    2014-01-01

    Extracellular flux (XF) analysis has become a mainstream method to measure bioenergetic function in cells and tissues. While this technique is commonly used to measure energetics in intact cells, we outline here a detailed XF protocol for measuring respiration in permeabilized cells. Cells are permeabilized using saponin, digitonin, or recombinant perfringolysin O (XF PMP reagent) and provided with specific substrates to measure complex I- or II-mediated respiratory activity, Complex III+IV respiratory activity, or Complex IV activity. Medium- and long-chain acylcarnitines or glutamine may also be provided for measuring fatty acid oxidation or glutamine oxidation, respectively. This protocol allows for such measurements using a minimal number of cells compared with other protocols, without the need for mitochondrial isolation. The results are highly reproducible, and mitochondria remain well coupled. Collectively, this protocol provides comprehensive and detailed information regarding mitochondrial activity and efficiency, and, following preparative steps, takes approximately 6 hours to complete. PMID:24457333

  7. Four new two-photon polymerization initiators with varying donor and conjugated bridge: Synthesis and two-photon activity

    NASA Astrophysics Data System (ADS)

    Hao, Fuying; Liu, Zhaodi; Zhang, Mingliang; Liu, Jie; Zhang, Shengyi; Wu, Jieying; Zhou, Hongping; Tian, YuPeng

    2014-01-01

    A specific series of dumbbell-shaped bis-carbazoles or bis-phenothiazines dyes (1, 2, 3 and 4) constructed with styrene or biphenylethyne as the π-bridge have been synthesized and characterized. Detailed spectral properties including linear absorption, one and two-photon fluorescence properties were investigated. The results show that extending conjugated chain and introducing donors have substantial effect on their photophysical properties. Among them, two-photon absorption cross sections (σ) of the four dyes in DMF determined by the Z-scan technique are successively increased from 1 to 4 with enhancing electron-donating ability and extending conjugated chain, but electron-donating ability has larger contribution to the σ values than extending conjugated chain based on the comparison of small molecules (D-π-D). Two-photon initiation polymerization (TPIP) microfabrication experiments have been carried out using compound 4 as an initiator under irradiation of 200 fs, 76 MHz femtosecond laser at 760 nm. The results confirm that the four dyes can be effectively used as organic two-photon photopolymerization initiators.

  8. Two-Photon Enzymatic Probes Visualizing Sub-cellular/Deep-brain Caspase Activities in Neurodegenerative Models

    PubMed Central

    Qian, Linghui; Zhang, Cheng-Wu; Mao, Yanli; Li, Lin; Gao, Nengyue; Lim, Kah-Leong; Xu, Qing-Hua; Yao, Shao Q.

    2016-01-01

    Caspases work as a double-edged sword in maintaining cell homeostasis. Highly regulated caspase activities are essential during animal development, but dysregulation might lead to different diseases, e.g. extreme caspase activation is known to promote neurodegeneration. At present, visualization of caspase activation has mostly remained at the cellular level, in part due to a lack of cell-permeable imaging probes capable of direct, real-time investigations of endogenous caspase activities in deep tissues. Herein, we report a suite of two-photon, small molecule/peptide probes which enable sensitive and dynamic imaging of individual caspase activities in neurodegenerative models under physiological conditions. With no apparent toxicity and the ability of imaging endogenous caspases both in different subcellular organelles of mammalian cells and in brain tissues, these probes serve as complementary tools to conventional histological analysis. They should facilitate future explorations of caspases at molecular, cellular and organism levels and inspire development of novel two-photon probes against other enzymes. PMID:27210613

  9. Two-Photon Enzymatic Probes Visualizing Sub-cellular/Deep-brain Caspase Activities in Neurodegenerative Models.

    PubMed

    Qian, Linghui; Zhang, Cheng-Wu; Mao, Yanli; Li, Lin; Gao, Nengyue; Lim, Kah-Leong; Xu, Qing-Hua; Yao, Shao Q

    2016-01-01

    Caspases work as a double-edged sword in maintaining cell homeostasis. Highly regulated caspase activities are essential during animal development, but dysregulation might lead to different diseases, e.g. extreme caspase activation is known to promote neurodegeneration. At present, visualization of caspase activation has mostly remained at the cellular level, in part due to a lack of cell-permeable imaging probes capable of direct, real-time investigations of endogenous caspase activities in deep tissues. Herein, we report a suite of two-photon, small molecule/peptide probes which enable sensitive and dynamic imaging of individual caspase activities in neurodegenerative models under physiological conditions. With no apparent toxicity and the ability of imaging endogenous caspases both in different subcellular organelles of mammalian cells and in brain tissues, these probes serve as complementary tools to conventional histological analysis. They should facilitate future explorations of caspases at molecular, cellular and organism levels and inspire development of novel two-photon probes against other enzymes. PMID:27210613

  10. Above- and below-ground methane fluxes and methanotrophic activity in a landfill-cover soil

    SciTech Connect

    Schroth, M.H.; Eugster, W.; Gomez, K.E.; Gonzalez-Gil, G.; Niklaus, P.A.; Oester, P.

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer We quantify above- and below-ground CH{sub 4} fluxes in a landfill-cover soil. Black-Right-Pointing-Pointer We link methanotrophic activity to estimates of CH{sub 4} loading from the waste body. Black-Right-Pointing-Pointer Methane loading and emissions are highly variable in space and time. Black-Right-Pointing-Pointer Eddy covariance measurements yield largest estimates of CH{sub 4} emissions. Black-Right-Pointing-Pointer Potential methanotrophic activity is high at a location with substantial CH{sub 4} loading. - Abstract: Landfills are a major anthropogenic source of the greenhouse gas methane (CH{sub 4}). However, much of the CH{sub 4} produced during the anaerobic degradation of organic waste is consumed by methanotrophic microorganisms during passage through the landfill-cover soil. On a section of a closed landfill near Liestal, Switzerland, we performed experiments to compare CH{sub 4} fluxes obtained by different methods at or above the cover-soil surface with below-ground fluxes, and to link methanotrophic activity to estimates of CH{sub 4} ingress (loading) from the waste body at selected locations. Fluxes of CH{sub 4} into or out of the cover soil were quantified by eddy-covariance and static flux-chamber measurements. In addition, CH{sub 4} concentrations at the soil surface were monitored using a field-portable FID detector. Near-surface CH{sub 4} fluxes and CH{sub 4} loading were estimated from soil-gas concentration profiles in conjunction with radon measurements, and gas push-pull tests (GPPTs) were performed to quantify rates of microbial CH{sub 4} oxidation. Eddy-covariance measurements yielded by far the largest and probably most representative estimates of overall CH{sub 4} emissions from the test section (daily mean up to {approx}91,500 {mu}mol m{sup -2} d{sup -1}), whereas flux-chamber measurements and CH{sub 4} concentration profiles indicated that at the majority of locations the cover soil was a

  11. Magnetic quenching of photonic activity in Fe3O4-elastomer composite

    NASA Astrophysics Data System (ADS)

    Ma, Danhao; Hess, Dustin T.; Shetty, Pralav P.; Adu, Kofi W.; Bell, Richard C.; Terrones, Mauricio

    2016-01-01

    We report a quenching phenomenon within the visible region of the electromagnetic spectrum in the photonic response of a passive Fe3O4-silicone elastomer composite film due to magnetically aligned Fe3O4 nanoparticles. We performed systematic studies of the polarization dependence, the effect of particle size, and an in- and out-of-plane particle alignment on the optical response of the Fe3O4-silicone elastomer composites using a UV/vis/NIR spectrometer. We observed systematic redshifts in the response of the out-of-plane composite films with increasing particle alignment and weight that are attributed to dipole-induced effects. There were no observable shifts in the spectra of the in-plane films, suggesting the orientation of the magnetic dipole and the induced electric dipole play a crucial role in the optical response. A dramatic suppression to near quenching of the photonic response occurred in films containing moderate concentrations of the aligned nanoparticles. This is attributed to the interplay between the intra- and the interparticle dipoles. This occurred even when low magnetic fields were used during the curing process, suggesting that particle alignment and particle size limitation are critical in the manipulation of the photonic properties. A dipole approximation model is used to explain the quenching phenomenon. An active system of such a composite has a potential application in magneto-optic switches.

  12. INCLINATION-DEPENDENT ACTIVE GALACTIC NUCLEUS FLUX PROFILES FROM STRONG LENSING OF THE KERR SPACETIME

    SciTech Connect

    Chen, Bin; Dai, Xinyu; Baron, E.

    2013-01-10

    Recent quasar microlensing observations have constrained the X-ray emission sizes of quasars to be about 10 gravitational radii, one order of magnitude smaller than the optical emission sizes. Using a new ray-tracing code for the Kerr spacetime, we find that the observed X-ray flux is strongly influenced by the gravity field of the central black hole, even for observers at moderate inclination angles. We calculate inclination-dependent flux profiles of active galactic nuclei in the optical and X-ray bands by combining the Kerr lensing and projection effects for future reference. We further study the dependence of the X-ray-to-optical flux ratio on the inclination angle caused by differential lensing distortion of the X-ray and optical emission, assuming several corona geometries. The strong lensing X-ray-to-optical magnification ratio can change by a factor of {approx}10 for normal quasars in some cases, and a further factor of {approx}10 for broad absorption line (BAL) quasars and obscured quasars. Comparing our results with the observed distributions in normal and BAL quasars, we find that the inclination angle dependence of the magnification ratios can significantly change the X-ray-to-optical flux ratio distributions. In particular, the mean value of the spectrum slope parameter {alpha}{sub ox}, 0.3838log F {sub 2keV}/F {sub 2500A}, can differ by {approx}0.1-0.2 between normal and BAL quasars, depending on corona geometries, suggesting larger intrinsic absorptions in BAL quasars.

  13. High Active Nitrogen Flux Growth of (Indium) Gallium Nitride by Plasma Assisted Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    McSkimming, Brian Matthew

    Plasma-assisted molecular beam epitaxy (PAMBE) growth of gallium nitride (GaN) has evolved over the past two decades due to progress in growth science and in the active nitrogen plasma source hardware. The transition from electron cyclotron resonance (ECR) microwave plasma sources to radio frequency (RF) plasma sources has enabled higher growth rates, reduced ion damage and improved operation at higher growth chamber pressures. Even with further improvements in RF plasma sources, PAMBE has remained primarily a research tool partially due to limitations in material growth rates. This dissertation presents results based upon two modifications of a commercially available nitrogen plasma source. These modifications have resulted in record active nitrogen fluxes, and therefore record growth rates of more than 7.6 mum/h. For optimized growth conditions in the standard metal-rich growth regime, the surfaces displayed a clear step-terrace structure with an average RMS roughness (3 mumx3 mum) on the order of 1 nm. Secondary ion mass spectroscopy (SIMS) impurity analysis demonstrates unintentional oxygen incorporation of ˜1x1016, comparable to the metal organic chemical vapor deposition (MOCVD) grown template layer. Additionally, a revised universal growth diagram is proposed allowing the rapid determination of the metal flux needed to grow in a specific growth regime for any and all active nitrogen fluxes available. High temperature nitrogen rich PAMBE growth of GaN has been previously demonstrated as a viable alternative to the challenges presented in maintaining the Ga bilayer required by metal rich growth of GaN. This dissertation also present results demonstrating PAMBE growth of GaN at a substrate temperature more than 150 °C greater than our standard Ga rich GaN growth regime and ˜100 °C greater than any previously reported PAMBE growth of GaN. Finally, a revised growth diagram is proposed highlighting a large growth window available at high temperatures.

  14. Calcium flux-independent NMDA receptor activity is required for Aβ oligomer-induced synaptic loss

    PubMed Central

    Birnbaum, J H; Bali, J; Rajendran, L; Nitsch, R M; Tackenberg, C

    2015-01-01

    Synaptic loss is one of the major features of Alzheimer's disease (AD) and correlates with the degree of dementia. N-methyl-d-aspartate receptors (NMDARs) have been shown to mediate downstream effects of the β-amyloid peptide (Aβ) in AD models. NMDARs can trigger intracellular cascades via Ca2+ entry, however, also Ca2+-independent (metabotropic) functions of NMDARs have been described. We aimed to determine whether ionotropic or metabotropic NMDAR signaling is required for the induction of synaptic loss by Aβ. We show that endogenous Aβ as well as exogenously added synthetic Aβ oligomers induced dendritic spine loss and reductions in pre- and postsynaptic protein levels in hippocampal slice cultures. Synaptic alterations were mitigated by blocking glutamate binding to NMDARs using NMDAR antagonist APV, but not by preventing ion flux with Ca2+ chelator BAPTA or open-channel blockers MK-801 or memantine. Aβ increased the activity of p38 MAPK, a kinase involved in long-term depression and inhibition of p38 MAPK abolished the loss of dendritic spines. Aβ-induced increase of p38 MAPK activity was prevented by APV but not by BAPTA, MK-801 or memantine treatment highlighting the role of glutamate binding to NMDARs but not Ca2+ flux for synaptic degeneration by Aβ. We further show that treatment with the G protein inhibitor pertussis toxin (PTX) did not prevent dendritic spine loss in the presence of Aβ oligomers. Our data suggest that Aβ induces the activation of p38 MAPK and subsequent synaptic loss through Ca2+ flux- and G protein-independent mechanisms. PMID:26086964

  15. Calcium flux-independent NMDA receptor activity is required for Aβ oligomer-induced synaptic loss.

    PubMed

    Birnbaum, J H; Bali, J; Rajendran, L; Nitsch, R M; Tackenberg, C

    2015-01-01

    Synaptic loss is one of the major features of Alzheimer's disease (AD) and correlates with the degree of dementia. N-methyl-D-aspartate receptors (NMDARs) have been shown to mediate downstream effects of the β-amyloid peptide (Aβ) in AD models. NMDARs can trigger intracellular cascades via Ca(2+) entry, however, also Ca(2+)-independent (metabotropic) functions of NMDARs have been described. We aimed to determine whether ionotropic or metabotropic NMDAR signaling is required for the induction of synaptic loss by Aβ. We show that endogenous Aβ as well as exogenously added synthetic Aβ oligomers induced dendritic spine loss and reductions in pre- and postsynaptic protein levels in hippocampal slice cultures. Synaptic alterations were mitigated by blocking glutamate binding to NMDARs using NMDAR antagonist APV, but not by preventing ion flux with Ca(2+) chelator BAPTA or open-channel blockers MK-801 or memantine. Aβ increased the activity of p38 MAPK, a kinase involved in long-term depression and inhibition of p38 MAPK abolished the loss of dendritic spines. Aβ-induced increase of p38 MAPK activity was prevented by APV but not by BAPTA, MK-801 or memantine treatment highlighting the role of glutamate binding to NMDARs but not Ca(2+) flux for synaptic degeneration by Aβ. We further show that treatment with the G protein inhibitor pertussis toxin (PTX) did not prevent dendritic spine loss in the presence of Aβ oligomers. Our data suggest that Aβ induces the activation of p38 MAPK and subsequent synaptic loss through Ca(2+) flux- and G protein-independent mechanisms. PMID:26086964

  16. The Physical Mechanism for Retinal Discrete Dark Noise: Thermal Activation or Cellular Ultraweak Photon Emission?

    PubMed Central

    Salari, Vahid; Scholkmann, Felix; Bokkon, Istvan; Shahbazi, Farhad; Tuszynski, Jack

    2016-01-01

    For several decades the physical mechanism underlying discrete dark noise of photoreceptors in the eye has remained highly controversial and poorly understood. It is known that the Arrhenius equation, which is based on the Boltzmann distribution for thermal activation, can model only a part (e.g. half of the activation energy) of the retinal dark noise experimentally observed for vertebrate rod and cone pigments. Using the Hinshelwood distribution instead of the Boltzmann distribution in the Arrhenius equation has been proposed as a solution to the problem. Here, we show that the using the Hinshelwood distribution does not solve the problem completely. As the discrete components of noise are indistinguishable in shape and duration from those produced by real photon induced photo-isomerization, the retinal discrete dark noise is most likely due to ‘internal photons’ inside cells and not due to thermal activation of visual pigments. Indeed, all living cells exhibit spontaneous ultraweak photon emission (UPE), mainly in the optical wavelength range, i.e., 350–700 nm. We show here that the retinal discrete dark noise has a similar rate as UPE and therefore dark noise is most likely due to spontaneous cellular UPE and not due to thermal activation. PMID:26950936

  17. Active photonic sensor communication cable for field application of optical data and power transmission

    NASA Astrophysics Data System (ADS)

    Suthau, Eike; Rieske, Ralf; Zerna, Thomas

    2014-10-01

    Omitting electrically conducting wires for sensor communication and power supply promises protection for sensor systems and monitored structures against lightning or high voltages, prevention of explosion hazards, and reduction of susceptibility to tampering. The ability to photonically power remote systems opens up the full range of electrical sensors. Power-over-fiber is an attractive option in electromagnetically sensitive environments, particularly for longterm, maintenance-free applications. It can deliver uninterrupted power sufficient for elaborate sensors, data processing or even actuators alongside continuous high speed data communication for remote sensor application. This paper proposes an active photonic sensor communication system, which combines the advantages of optical data links in terms of immunity to electromagnetic interference (EMI), high bandwidth, hardiness against tampering or eavesdropping, and low cable weight with the robustness one has come to expect from industrial or military electrical connectors. An application specific integrated circuit (ASIC) is presented that implements a closed-loop regulation of the sensor power supply to guarantee continuous, reliable data communications while maintaining a highly efficient, adaptive sensor supply scheme. It is demonstrated that the resulting novel photonic sensor communication cable can handle sensors and actuators differing orders of magnitude with respect to power consumption. The miniaturization of the electro-optical converters and driving electronics is as important to the presented development as the energy efficiency of the detached, optically powered sensor node. For this reason, a novel photonic packaging technology based on wafer-level assembly of the laser power converters by means of passive alignment will be disclosed in this paper.

  18. Characteristics of fluxes of energetic electrons in the transition region during times of enhanced geophysical activity

    SciTech Connect

    Mineev, Y.V.; Spir'kova, E.S.

    1986-05-01

    In January 1976, the Interplanetary Magnetospheric Study (IMS) began. During the period January-March 1976, geomagnetic disturbances coincided mainly with a recurring sequence of earth passages through sector structures in the interplanetary magnetic field (IMF). In March, unusually large enhancements in energetic electron fluxes were recorded by Prognoz 4. The observations were made during intersections of the flanks of the transition region (TR) in conditions of enhanced geomagnetic activity, and the enhancements were of significant duration. Intense bursts of these particles were also observed in the outer magnetosphere at high latitudes. We discuss possible mechanisms for creating such formations.

  19. On the area expansion of magnetic flux tubes in solar active regions

    SciTech Connect

    Dudík, Jaroslav; Dzifčáková, Elena; Cirtain, Jonathan W. E-mail: elena@asu.cas.cz

    2014-11-20

    We calculated the three-dimensional (3D) distribution of the area expansion factors in a potential magnetic field, extrapolated from the high-resolution Hinode/SOT magnetogram of the quiescent active region NOAA 11482. Retaining only closed loops within the computational box, we show that the distribution of area expansion factors show significant structure. Loop-like structures characterized by locally lower values of the expansion factor are embedded in a smooth background. These loop-like flux tubes have squashed cross-sections and expand with height. The distribution of the expansion factors show an overall increase with height, allowing an active region core characterized by low values of the expansion factor to be distinguished. The area expansion factors obtained from extrapolation of the Solar Optical Telescope magnetogram are compared to those obtained from an approximation of the observed magnetogram by a series of 134 submerged charges. This approximation retains the general flux distribution in the observed magnetogram, but removes the small-scale structure in both the approximated magnetogram and the 3D distribution of the area expansion factors. We argue that the structuring of the expansion factor can be a significant ingredient in producing the observed structuring of the solar corona. However, due to the potential approximation used, these results may not be applicable to loops exhibiting twist or to active regions producing significant flares.

  20. Sensitivity of quasi-periodic outer rainband activity of tropical cyclones to the surface entropy flux

    NASA Astrophysics Data System (ADS)

    Li, Qingqing; Duan, Yihong

    2013-10-01

    The influence of outer-core surface entropy fluxes (SEFs) on tropical cyclone (TC) outer rainband activity is investigated in this study with a fully compressible, nonhydrostatic model. A control simulation and two sensitivity experiments with the outer-core SEF artificially increased and decreased by 20% respectively were conducted to examine the quasi-periodic outer rainband behavior. Larger negative horizontal advection due to the greater radial wind and the positive contribution by asymmetric eddies leads to a longer period of outerrainband activity in the SEF-enhanced experiment. The well-developed outer rainbands in the control and SEF-reduced simulations significantly limit the TC intensity, whereas such an intensity suppression influence is not pronounced in the SEF-enhanced experiment. As diabatic heating in outer rainbands strengthens the outer-core tangential wind, the quasi-periodic activity of outer rainbands contributes to the quasi-periodic variations of the inner-core size of the TCs.

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

    SciTech Connect

    Fisher, W.A.

    1982-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Fisher, W. A.

    1982-10-01

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

  3. Irradiation system for two-photon induced activation of agents in novel intraocular lenses

    NASA Astrophysics Data System (ADS)

    Klämpfl, Florian; Roth, Stephan; Schmidt, Michael

    This paper presents a newly designed irradiation system for the photochemically triggered two-photon activation of an agent loaded in novel intraocular lenses. After activation, this agent suppresses the formation of after-cataract, a very common disease after the treatment of an eye cataract by implanting an intraocular lens. For this application, intrinsic safety is also important: the laser radiation is applied to one of the most light-sensitive organs: the eye. This has to be taken into account during development of the system. Moreover, the activation uses a two-photon process so a relatively small laser focus is required. To address these issues in combination with economic requirements, a mirror based objective was designed and built, specifically tailored to these needs. Besides the laser beam guidance elements, the irradiation system consists of a camera based monitoring module and an illumination unit. While the first part of the paper shows the design of the system, the second part presents the results of the characterization of the system. The paper closes with a conclusion and an outlook discussing what further development is needed to prepare the system for treatments of human eyes.

  4. Brain single photon emission computed tomography: Newer activation and intervention studies

    SciTech Connect

    Tikofsky, R.S.; Hellman, R.S. )

    1991-01-01

    Single-photon emission computed tomography (SPECT) regional cerebral blood flow (rCBF) findings using non-xenon 133 tracers in combination with activation and intervention techniques are reviewed. Examination of the currently available data indicates that it is possible to detect the effects of a variety of activations and interventional procedures using SPECT rCBF with non-xenon 133 tracers. There are still many issues to be resolved before SPECT can reach the level of sophistication attained by xenon 133 and positron emission tomography in studying rCBF during activation or intervention. However, research to date indicates that SPECT rCBF studied with tracers other than xenon 133 has an excellent potential for increasing the ability to differentiate normal and pathological states. 97 refs.

  5. The dynamic evolution of active-region-scale magnetic flux tubes in the turbulent solar convective envelope

    NASA Astrophysics Data System (ADS)

    Weber, Maria Ann

    2014-12-01

    The Sun exhibits cyclic properties of its large-scale magnetic field on the order of sigma22 years, with a ˜11 year frequency of sunspot occurrence. These sunspots, or active regions, are the centers of magnetically driven phenomena such as flares and coronal mass ejections. Volatile solar magnetic events directed toward the Earth pose a threat to human activities and our increasingly technological society. As such, the origin and nature of solar magnetic flux emergence is a topic of global concern. Sunspots are observable manifestations of solar magnetic fields, thus providing a photospheric link to the deep-seated dynamo mechanism. However, the manner by which bundles of magnetic field, or flux tubes, traverse the convection zone to eventual emergence at the solar surface is not well understood. To provide a connection between dynamo-generated magnetic fields and sunspots, I have performed simulations of magnetic flux emergence through the bulk of a turbulent, solar convective envelope by employing a thin flux tube model subject to interaction with flows taken from a hydrodynamic convection simulation computed through the Anelastic Spherical Harmonic (ASH) code. The convective velocity field interacts with the flux tube through the drag force it experiences as it traverses through the convecting medium. Through performing these simulations, much insight has been gained about the influence of turbulent solar-like convection on the flux emergence process and resulting active region properties. I find that the dynamic evolution of flux tubes change from convection dominated to magnetic buoyancy dominated as the initial field strength of the flux tubes increases from 15 kG to 100 kG. Additionally, active-region-scale flux tubes of 40 kG and greater exhibit properties similar to those of active regions on the Sun, such as: tilt angles, rotation rates, and morphological asymmetries. The joint effect of the Coriolis force and helical motions present in convective

  6. How Phosphorylation and ATPase Activity Regulate Anion Flux though the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR).

    PubMed

    Zwick, Matthias; Esposito, Cinzia; Hellstern, Manuel; Seelig, Anna

    2016-07-01

    The cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), mutations of which cause cystic fibrosis, belongs to the ATP-binding cassette (ABC) transporter family and works as a channel for small anions, such as chloride and bicarbonate. Anion channel activity is known to depend on phosphorylation by cAMP-dependent protein kinase A (PKA) and CFTR-ATPase activity. Whereas anion channel activity has been extensively investigated, phosphorylation and CFTR-ATPase activity are still poorly understood. Here, we show that the two processes can be measured in a label-free and non-invasive manner in real time in live cells, stably transfected with CFTR. This study reveals three key findings. (i) The major contribution (≥90%) to the total CFTR-related ATP hydrolysis rate is due to phosphorylation by PKA and the minor contribution (≤10%) to CFTR-ATPase activity. (ii) The mutant CFTR-E1371S that is still conductive, but defective in ATP hydrolysis, is not phosphorylated, suggesting that phosphorylation requires a functional nucleotide binding domain and occurs in the post-hydrolysis transition state. (iii) CFTR-ATPase activity is inversely related to CFTR anion flux. The present data are consistent with a model in which CFTR is in a closed conformation with two ATPs bound. The open conformation is induced by ATP hydrolysis and corresponds to the post-hydrolysis transition state that is stabilized by phosphorylation and binding of chloride channel potentiators. PMID:27226582

  7. EMERGENCE OF HELICAL FLUX AND THE FORMATION OF AN ACTIVE REGION FILAMENT CHANNEL

    SciTech Connect

    Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K.

    2010-07-20

    We present comprehensive observations of the formation and evolution of a filament channel within NOAA Active Region (AR) 10978 from Hinode/Solar Optical Telescope and TRACE. We employ sequences of Hinode spectro-polarimeter maps of the AR, accompanying Hinode Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode Broadband Filter Instrument filtergrams in the Ca II H line and G-band, Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 A image sequences. The development of the channel resembles qualitatively that presented by Okamoto et al. in that many indicators point to the emergence of a pre-existing sub-surface magnetic flux rope. The consolidation of the filament channel into a coherent structure takes place rapidly during the course of a few hours, and the filament form then gradually shrinks in width over the following two days. Particular to this filament channel is the observation of a segment along its length of horizontal, weak (500 G) flux that, unlike the rest of the filament channel, is not immediately flanked by strong vertical plage fields of opposite polarity on each side of the filament. Because this isolated horizontal field is observed in photospheric lines, we infer that it is unlikely that the channel formed as a result of reconnection in the corona, but the low values of inferred magnetic fill fraction along the entire length of the filament channel suggest that the bulk of the field resides somewhat above the low photosphere. Correlation tracking of granulation in the G band presents no evidence for either systematic flows toward the channel or systematic shear flows along it. The absence of these flows, along with other indications of these data from multiple sources, reinforces (but does not conclusively demonstrate) the picture of an emerging flux rope as the origin of this AR filament channel.

  8. Glycolytic Flux Is Adjusted to Nitrogenase Activity in Nodules of Detopped and Argon-Treated Alfalfa Plants1

    PubMed Central

    Curioni, Paola M.G.; Hartwig, Ueli A.; Nösberger, Josef; Schuller, Kathryn A.

    1999-01-01

    To investigate the short-term (30–240 min) interactions among nitrogenase activity, NH4+ assimilation, and plant glycolysis, we measured the concentrations of selected C and N metabolites in alfalfa (Medicago sativa L.) root nodules after detopping and during continuous exposure of the nodulated roots to Ar:O2 (80:20, v/v). Both treatments caused an increase in the ratios of glucose-6-phosphate to fructose-1,6-bisphosphate, fructose-6-phosphate to fructose-1,6-bisphosphate, phosphoenolpyruvate (PEP) to pyruvate, and PEP to malate. This suggested that glycolytic flux was inhibited at the steps catalyzed by phosphofructokinase, pyruvate kinase, and PEP carboxylase. In the Ar:O2-treated plants the apparent inhibition of glycolytic flux was reversible, whereas in the detopped plants it was not. In both groups of plants the apparent inhibition of glycolytic flux was delayed relative to the decline in nitrogenase activity. The decline in nitrogenase activity was followed by a dramatic increase in the nodular glutamate to glutamine ratio. In the detopped plants this was coincident with the apparent inhibition of glycolytic flux, whereas in the Ar:O2-treated plants it preceded the apparent inhibition of glycolytic flux. We propose that the increase in the nodular glutamate to glutamine ratio, which occurs as a result of the decline in nitrogenase activity, may act as a signal to decrease plant glycolytic flux in legume root nodules. PMID:9952439

  9. LCLS Spectral Flux Viewer

    2005-10-25

    This application (FluxViewer) is a tool for displaying spectral flux data for the Linac Coherent Light Source (LCLS). This tool allows the user to view sliced spatial and energy distributions of the photons selected for specific energies and positions transverse to the beam axis.

  10. Trend of photospheric helicity flux in active regions generating halo CMEs

    NASA Astrophysics Data System (ADS)

    Smyrli, Aimilia; Zuccarello, Francesco; Zuccarello, Francesca; Romano, Paolo; Guglielmino, Salvatore Luigi; Spadaro, Daniele; Hood, Alan; Mackay, Duncan

    Coronal Mass Ejections (CMEs) are very energetic events initiated in the solar atmosphere, re-sulting in the expulsion of magnetized plasma clouds that propagate into interplanetary space. It has been proposed that CMEs can play an important role in shedding magnetic helicity, avoiding its endless accumulation in the corona. We therefore investigated the behavior of magnetic helicity accumulation in sites where the initiation of CMEs occurred, in order to de-termine whether and how changes in magnetic helicity accumulation are temporally correlated with CME occurrence. After identifying the active regions (AR) where the CMEs were ini-tiated by means of a double cross-check based on the flaring-eruptive activity and the use of SOHO/EIT difference images, we used MDI magnetograms to calculate magnetic flux evolu-tion, magnetic helicity injection rate and magnetic helicity injection in 10 active regions that gave rise to 12 halo CMEs observed during the period February 2000 -June 2003. No unique behavior in magnetic helicity injection accompanying halo CME occurrence is found. In fact, in some cases there is an abrupt change in helicity injection timely correlated with the CME event, while in some others no significant variation is recorded. However, our analysis show that the most significant changes in magnetic flux and magnetic helicity injection are associated with impulsive CMEs rather than gradual CMEs. Moreover, the most significant changes in mag-netic helicity are observed when X-class flares or eruptive filaments occur, while the occurrence of flares of class C or M seems not to affect significantly the magnetic helicity accumulation.

  11. Stepwise multi-photon activation fluorescence reveals a new method of melanoma imaging for dermatologists

    NASA Astrophysics Data System (ADS)

    Lai, Zhenhua; Lian, Christine; Ma, Jie; Yu, Jingyi; Gu, Zetong; Rajadhyaksha, Milind; DiMarzio, Charles A.

    2014-02-01

    Previous research has shown that the stepwise multi-photon activated fluorescence (SMPAF) of melanin, activated by a continuous-wave (CW) mode near infrared (NIR) laser, is a low cost and reliable method of detecting melanin. SMPAF images of melanin in a mouse hair and a formalin fixed mouse melanoma were compared with conventional multiphoton fluorescence microscopy (MPFM) images and confocal reflectance microscopy (CRM) images, all of which were acquired at an excitation wavelength of 920 nm, to further prove the effectiveness of SMPAF in detecting melanin. SMPAF images add specificity for melanin detection to MPFM images and CRM images. Melanin SMPAF can be a promising technology to enable melanoma imaging for dermatologists.

  12. The stepwise multi-photon activation fluorescence guided ablation of melanin

    NASA Astrophysics Data System (ADS)

    Lai, Zhenhua; Gu, Zetong; DiMarzio, Charles

    2015-02-01

    Previous research has shown that the stepwise multi-photon activation fluorescence (SMPAF) of melanin, activated and excited by a continuous-wave (CW) mode near infrared (NIR) laser, is a low-cost and reliable method for detecting melanin. We have developed a device utilizing the melanin SMPAF to guide the ablation of melanin with a 975 nm CW laser. This method provides the ability of targeting individual melanin particles with micrometer resolution, and enables localized melanin ablation to be performed without collateral damage. Compared to the traditional selective photothermolysis, which uses pulsed lasers for melanin ablation, this method demonstrates higher precision and lower cost. Therefore, the SMPAF guided selective ablation of melanin is a promising tool of melanin ablation for both medical and cosmetic purposes.

  13. Opportunities for Low Cost Processing of Erbium 8-Quinolinolates for Active Integrated Photonic Applications.

    PubMed

    Penna, Stefano; Mattiello, Leonardo; Di Bartolo, Silvia; Pizzoleo, Angelo; Attanasio, Vincenzo; Beleffi, Giorgio Maria Tosi; Otomo, Akira

    2016-04-01

    Erbium-doped organic emitters are promising active materials for Photonic Integrated Circuits (PICs) due to their emission shown at 1550 nm combined to the potential low cost processing. In particular, Erbium Quinoline (ErQ) gained a strong interest in the last decade for the good emission efficiency. This contribution reports the results derived from the application of ErQ as active core material within a buried optical waveguide, following the development of a purposed optical process to control the refractive index of ErQ and then to define a patterned structure from a single thin film deposition step. The reported results show the potential of Er-doped organic materials for low cost processing and application to planar PICs. PMID:27451632

  14. Flux Tensor Constrained Geodesic Active Contours with Sensor Fusion for Persistent Object Tracking.

    PubMed

    Bunyak, Filiz; Palaniappan, Kannappan; Nath, Sumit Kumar; Seetharaman, Gunasekaran

    2007-08-01

    This paper makes new contributions in motion detection, object segmentation and trajectory estimation to create a successful object tracking system. A new efficient motion detection algorithm referred to as the flux tensor is used to detect moving objects in infrared video without requiring background modeling or contour extraction. The flux tensor-based motion detector when applied to infrared video is more accurate than thresholding "hot-spots", and is insensitive to shadows as well as illumination changes in the visible channel. In real world monitoring tasks fusing scene information from multiple sensors and sources is a useful core mechanism to deal with complex scenes, lighting conditions and environmental variables. The object segmentation algorithm uses level set-based geodesic active contour evolution that incorporates the fusion of visible color and infrared edge informations in a novel manner. Touching or overlapping objects are further refined during the segmentation process using an appropriate shape-based model. Multiple object tracking using correspondence graphs is extended to handle groups of objects and occlusion events by Kalman filter-based cluster trajectory analysis and watershed segmentation. The proposed object tracking algorithm was successfully tested on several difficult outdoor multispectral videos from stationary sensors and is not confounded by shadows or illumination variations. PMID:19096530

  15. Flux Tensor Constrained Geodesic Active Contours with Sensor Fusion for Persistent Object Tracking

    PubMed Central

    Bunyak, Filiz; Palaniappan, Kannappan; Nath, Sumit Kumar; Seetharaman, Gunasekaran

    2007-01-01

    This paper makes new contributions in motion detection, object segmentation and trajectory estimation to create a successful object tracking system. A new efficient motion detection algorithm referred to as the flux tensor is used to detect moving objects in infrared video without requiring background modeling or contour extraction. The flux tensor-based motion detector when applied to infrared video is more accurate than thresholding ”hot-spots”, and is insensitive to shadows as well as illumination changes in the visible channel. In real world monitoring tasks fusing scene information from multiple sensors and sources is a useful core mechanism to deal with complex scenes, lighting conditions and environmental variables. The object segmentation algorithm uses level set-based geodesic active contour evolution that incorporates the fusion of visible color and infrared edge informations in a novel manner. Touching or overlapping objects are further refined during the segmentation process using an appropriate shape-based model. Multiple object tracking using correspondence graphs is extended to handle groups of objects and occlusion events by Kalman filter-based cluster trajectory analysis and watershed segmentation. The proposed object tracking algorithm was successfully tested on several difficult outdoor multispectral videos from stationary sensors and is not confounded by shadows or illumination variations. PMID:19096530

  16. Control of Pitching Airfoil Aerodynamics by Vorticity Flux Modification using Active Bleed

    NASA Astrophysics Data System (ADS)

    Kearney, John; Glezer, Ari

    2014-11-01

    Distributed active bleed driven by pressure differences across a pitching airfoil is used to regulate the vorticity flux over the airfoil's surface and thereby to control aerodynamic loads in wind tunnel experiments. The range of pitch angles is varied beyond the static stall margin of the 2-D VR-7 airfoil at reduced pitching rates up to k = 0.42. Bleed is regulated dynamically using piezoelectric louvers between the model's pressure side near the trailing edge and the suction surface near the leading edge. The time-dependent evolution of vorticity concentrations over the airfoil and in the wake during the pitch cycle is investigated using high-speed PIV and the aerodynamic forces and moments are measured using integrated load cells. The timing of the dynamic stall vorticity flux into the near wake and its effect on the flow field are analyzed in the presence and absence of bleed using proper orthogonal decomposition (POD). It is shown that bleed actuation alters the production, accumulation, and advection of vorticity concentrations near the surface with significant effects on the evolution, and, in particular, the timing of dynamic stall vortices. These changes are manifested by alteration of the lift hysteresis and improvement of pitch stability during the cycle, while maintaining cycle-averaged lift to within 5% of the base flow level with significant implications for improvement of the stability of flexible wings and rotor blades. This work is supported by the Rotorcraft Center (VLRCOE) at Georgia Tech.

  17. Formation of δ-Sunspot in Simulations of Active-Region-Scale Flux Emergence

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Fan, Yuhong

    2015-04-01

    δ-sunspots, with highly complex magnetic structures, are very productive in energetic eruptive events, such as X-class flares and homologous eruptions. We here study the formation of such complex magnetic structures by numerical simulations of magnetic flux emergence from the convection zone into the corona in an active-region-scale domain. In our simulation, two pairs of bipolar sunspots form on the surface, originating from two buoyant segments of a single subsurface twisted flux rope. Expansion and rotation of the emerging fields in the two bipoles drive the two opposite polarities into each other with apparent rotating motion, producing a compact δ-sunspot with a sharp polarity inversion line. The formation of the δ-sunspot in such a realistic-scale domain produces emerging pattherns similar to those formed in observations, e.g. the inverted polarity against Hale’s law, the curvilinear motion of the spot, strong transverse field with highly sheared magnetic and velocity fields at the PIL. Strong current builds up at the PIL, giving rise to reconnection, which produces a complex coronal magnetic connectivity with non-potential fields in the -spot overlaid by more relaxed fields connecting the two polarities at the two ends.

  18. δ-Sunspot Formation in Simulation of Active-region-scale Flux Emergence

    NASA Astrophysics Data System (ADS)

    Fang, Fang; Fan, Yuhong

    2015-06-01

    δ-sunspots, with highly complex magnetic structures, are very productive in energetic eruptive events, such as X-class flares and homologous eruptions. We here study the formation of such complex magnetic structures by numerical simulations of magnetic flux emergence from the convection zone into the corona in an active-region-scale domain. In our simulation, two pairs of bipolar sunspots form on the surface, originating from two buoyant segments of a single subsurface twisted flux rope, following the approach of Toriumi et al. Expansion and rotation of the emerging fields in the two bipoles drive the two opposite polarities into each other with apparent rotating motion, producing a compact δ-sunspot with a sharp polarity inversion line. The formation of the δ-sunspot in such a realistic-scale domain produces emerging patterns similar to those formed in observations, e.g., the inverted polarity against Hale's law, the curvilinear motion of the spot, and strong transverse field with highly sheared magnetic and velocity fields at the polarity inversion line (PIL). Strong current builds up at the PIL, giving rise to reconnection, which produces a complex coronal magnetic connectivity with non-potential fields in the δ-spot overlaid by more relaxed fields connecting the two polarities at the two ends.

  19. Negligible photodesorption of methanol ice and active photon-induced desorption of its irradiation products

    NASA Astrophysics Data System (ADS)

    Cruz-Diaz, G. A.; Martín-Doménech, R.; Muñoz Caro, G. M.; Chen, Y.-J.

    2016-07-01

    Context. Methanol is a common component of interstellar and circumstellar ice mantles and is often used as an evolution indicator in star-forming regions. The observations of gas-phase methanol in the interiors of dense molecular clouds at temperatures as low as 10 K suggest that non-thermal ice desorption must be active. Ice photodesorption has been proposed to explain the abundances of gas-phase molecules toward the coldest regions. Aims: Laboratory experiments were performed to investigate the potential photodesorption of methanol toward the coldest regions. Methods: Solid methanol was deposited at 8 K and UV-irradiated at various temperatures starting from 8 K. The irradiation of the ice was monitored by means of infrared spectroscopy and the molecules in the gas phase were detected using quadrupole mass spectroscopy. Fully deuterated methanol was used for confirmation of the results. Results: The photodesorption of methanol to the gas phase was not observed in the mass spectra at different irradiation temperatures. We estimate an upper limit of 3 × 10-5 molecules per incident photon. On the other hand, photon-induced desorption of the main photoproducts was clearly observed. Conclusions: The negligible photodesorption of methanol could be explained by the ability of UV-photons in the 114-180 nm (10.87-6.88 eV) range to dissociate this molecule efficiently. Therefore, the presence of gas-phase methanol in the absence of thermal desorption remains unexplained. On the other hand, we find CH4 to desorb from irradiated methanol ice, which was not found to desorb in the pure CH4 ice irradiation experiments.

  20. Passive active resonant coupler (PARC): A new platform for monolithic integration of photonic devices

    NASA Astrophysics Data System (ADS)

    Saini, Simarjeet

    The explosive growth of telecommunications and data traffic in recent years has hastened the emergence of optical communication networks. As the volume and complexity of network traffic increases, efficient methods are required for routing and distributing the associated optical signals. This in turn has put pressure on optical device technologies. Not only are new and more complex devices required, but they must also be manufactured and packaged in a cost-efficient way. Soon, there will be a shift in the paradigm from using discrete packaged devices in a module to monolithically integrated photonic circuits where multiple functions are achieved in a single chip. This offers a considerable challenge and a great opportunity for device engineers. It is the goal of this work to continue and expand the sphere of knowledge and applicability of Photonic Integrated circuits (PIC's) by proposing and demonstrating a new platform technology for monolithically integrating various active and passive optical devices. The platform, which has been named the ``Passive Active Resonant Coupler (PARC)'', utilizes single epitaxial growth and conventional fabrication schemes. PARC devices rely on coupling between vertical waveguides where each waveguide is optimized for its specific functionality. The coupling is achieved by using a new proposed scheme of resonance over some specially designed tapers. It has been shown experimentally for the first time that very high coupling efficiencies (less than 1 dB loss) can be achieved over very short lengths, typically less than 100 μm. Coupling between different kinds of active and passive waveguides has been experimentally demonstrated. A few basic PIC's such as the 1 × 2 optical switch and the 2 × 2 cross-point switch have been demonstrated by integrating active and passive waveguides using the PARC platform. The demonstrated integration work is in the 1.55 μm wavelength range using InP as a substrate. However, the PARC platform is

  1. Nematic and blue phase liquid crystals for temperature stabilization and active optical tuning of silicon photonic devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna N.; Khoo, Iam Choon; Fainman, Yeshaiahu

    2015-10-01

    We describe the underlying theories and experimental demonstrations of passive temperature stabilization of silicon photonic devices clad in nematic liquid crystal mixtures, and active optical tuning of silicon photonic resonant structures combined with dye-doped nematic and blue phase liquid crystals. We show how modifications to the resonator device geometry allow for not only enhanced tuning of the resonator response, but also aid in achieving complete athermal operations of silicon photonic circuits. [Ref.: I.C. Khoo, "DC-field-assisted grating formation and nonlinear diffractions in methyl-red dye-doped blue phase liquid crystals," Opt. Lett. 40, 60-63 (2015); J. Ptasinski, I.C. Khoo, and Y. Fainman, "Enhanced optical tuning of modified-geometry resonators clad in blue phase liquid crystals," Opt. Lett. 39, 5435-5438 (2014); J. Ptasinski, I.C. Khoo, and Y. Fainman, "Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals," Materials 7(3), 2229-2241 (2014)].

  2. Active phase drift cancellation for optic-fiber frequency transfer using a photonic radio-frequency phase shifter.

    PubMed

    Shen, Jianguo; Wu, Guiling; Hu, Liang; Zou, Weiwen; Chen, Jianping

    2014-04-15

    We propose an active photonic phase drift cancellation scheme for frequency transfer over optical fiber based on a linear photonic RF phase shifter. The photonic RF phase shifter consists of a dual parallel Mach-Zehnder modulator and optical filter with the assistance of the local microwave signal. The phase drift induced by fiber transmission can be compensated by simply tuning the bias voltage of the modulator. The principle of the phase cancellation scheme based on the photonic phase shifter is demonstrated and validated experimentally by transferring a 0.5 GHz reference signal over a 20 km single-mode fiber with a root mean square jitter of less than 0.5 ps. PMID:24978989

  3. Reactive oxygen species scavenging activity of Jixueteng evaluated by electron spin resonance (ESR) and photon emission.

    PubMed

    Toyama, Toshizo; Wada-Takahashi, Satoko; Takamichi, Maomi; Watanabe, Kiyoko; Yoshida, Ayaka; Yoshino, Fumihiko; Miyamoto, Chihiro; Maehata, Yojiro; Sugiyama, Shuta; Takahashi, Shun-Suke; Todoki, Kazuo; Lee, Masaichi-Chang-Il; Hamada, Nobushiro

    2014-12-01

    Jixueteng, the dried stem of Spatholobus suberectus Dunn (Leguminosae), is a traditional Chinese herbal medicine that is commonly classified as a herb that promotes blood circulation and can be used to treat blood stasis. The aim of this study was to examine the reactive oxygen species (ROS) scavenging activity of Jixueteng and other herbal medicines. The ROS scavenging activities of the water extracts of Jixueteng, Cnidium officinale and Salvia miltiorrhiza were examined using an electron spin resonance (ESR) technique and faint luminescence measurement. The ESR signal intensities of the superoxide anion (O2·) and hydroxyl radical (HO·) were reduced more by Jixueteng than the other herbal medicines we tested. High photon emission intensity to hydrogen peroxide (H202) and HO· was observed in Jixueteng using the XYZ chemiluminescence system that was used as faint luminescence measurement and analysis. The results of the present study revealed that the ROS scavenging activity of 8% Jixueteng was the strongest among the herbal medicines we tested. It has been reported that Jixueteng includes various polyphenols. In the ROS scavenging activity by Jixueteng, it is supposed that the antioxidant activity caused by these polyphenols would contribute greatly. In conclusion, a water extract component of Jixueteng had potent free radical scavenging activity and an antioxidative effect that inhibited the oxidative actions of O2·⁻, H2O2 and HO·. Therefore, Jixueteng represents a promising therapeutic drug for reactive oxygen-associated pathologies. PMID:25632478

  4. Comprehensive measurement of respiratory activity in permeabilized cells using extracellular flux analysis.

    PubMed

    Salabei, Joshua K; Gibb, Andrew A; Hill, Bradford G

    2014-02-01

    Extracellular flux (XF) analysis has become a mainstream method for measuring mitochondrial function in cells and tissues. Although this technique is commonly used to measure bioenergetics in intact cells, we outline here a detailed XF protocol for measuring respiration in permeabilized cells. Cells are permeabilized using saponin (SAP), digitonin (DIG) or recombinant perfringolysin O (rPFO) (XF-plasma membrane permeabilizer (PMP) reagent), and they are provided with specific substrates to measure complex I- or complex II-mediated respiratory activity, complex III+IV respiratory activity or complex IV activity. Medium- and long-chain acylcarnitines or glutamine may also be provided for measuring fatty acid (FA) oxidation or glutamine oxidation, respectively. This protocol uses a minimal number of cells compared with other protocols and does not require isolation of mitochondria. The results are highly reproducible, and mitochondria remain well coupled. Collectively, this protocol provides comprehensive and detailed information regarding mitochondrial activity and efficiency, and, after preparative steps, it takes 6-8 h to complete. PMID:24457333

  5. Nanomaterials for photonic applications: Silica self-assembly and erbium titanate activation

    NASA Astrophysics Data System (ADS)

    Lee, Cheol

    Nanomaterials are typically defined as amorphous or polycrystalline solids with particle diameters or grain sizes of 100 nm or less. Recently, a number of innovative efforts have opened the opportunity to a new class of materials, which allow to control both the flow of light and the dynamics of photons. The nanostructured periodic materials, Photonic Crystals, and waveguides embedded in them have been very attractive subjects of current research. Another attractive approach is to utilize rare earth emission within nanocrystals. The restricted geometry of rare earth ions in nanocrystals may affect luminescence behavior with respect to energy transfer and electron-phonon interactions in a bulk crystal, providing efficient light emission for future integration with optoelectronic devices. Based on such concepts addressed above, this dissertation has focused on two facets of nanomaterials investigation that are applicable to active 1.5 mum emission planar devices. First, the synthetic opaline films, 6 muM in thickness, were fabricated from self-assembly of a monodisperse colloidal suspensions of silica spheres with a diameter of 310 nm. This film showed an optical gap centered around 730 nm with a full width at half maximum (FWHM) of 50 nm, exhibiting 20% of maximum reflectivity. This study showed that the photon bands are the result of interplay between the coherent scattering due to the periodic structure and the non-coherent (diffuse) scattering due to the individual spheres, the latter exhibiting Mie resonance, the scattering coefficient is inversely proportional to lambda2 in regions of optical wavelength. Further, it was indicated that Me resonance remaining in the photon bands should be nearly eliminated to minimize optical loss and maximize band gap strength. This may be possible by organizing uniform features of dielectric structures, whether opal or inverse-opal, with smaller building blocks, the size of which are below theoretical scattering limit. Second

  6. Surface flux transport simulations. Inflows towards active regions and the modulation of the solar cycle.

    NASA Astrophysics Data System (ADS)

    Martin-Belda, David; Cameron, Robert

    2016-07-01

    Aims. We investigate the way near-surface converging flows towards active regions affect the build-up of magnetic field at the Sun's polar caps. In the Babcock-Leighton dynamo framework, this modulation of the polar fields could explain the variability of the solar cycle. Methods. We develop a surface flux transport code incorporating a parametrized model of the inflows and run simulations spanning several cycles. We carry out a parameter study to test how the strength and extension of the inflows affect the amplitude of the polar fields. Results. Inflows are seen to play an important role in the build-up of the polar fields, and can act as the non-linearity feedback mechanism required to limit the strength of the solar cycles in the Babcock-Leighton dynamo framework.

  7. Neutron flux measurements at the TRIGA reactor in Vienna for the prediction of the activation of the biological shield.

    PubMed

    Merz, Stefan; Djuricic, Mile; Villa, Mario; Böck, Helmuth; Steinhauser, Georg

    2011-11-01

    The activation of the biological shield is an important process for waste management considerations of nuclear facilities. The final activity can be estimated by modeling using the neutron flux density rather than the radiometric approach of activity measurements. Measurement series at the TRIGA reactor Vienna reveal that the flux density next to the biological shield is in the order of 10(9)cm(-2)s(-1) at maximum power; but it is strongly influenced by reactor installations. The data allow the estimation of the final waste categorization of the concrete according to the Austrian legislation. PMID:21646026

  8. Active Detection of Shielded Special Nuclear Material in the Presence of Variable High Backgrounds Using a Mixed Photon-Neutron Source

    NASA Astrophysics Data System (ADS)

    Martin, Philip N.; Clemett, Ceri D.; Hill, Cassie; O'Malley, John; Campbell, Ben

    This paper describes and compares two approaches to the analysis of active interrogation data containing high photon backgrounds associated with mixed photon-neutron source flash active interrogation. Results from liquid scintillation detectors (EJ301/EJ309) fielded at the Naval Research Laboratory (NRL), in collaboration with the Atomic Weapons Establishment (AWE), using the NRL Mercury Inductive Voltage Adder (IVA) operating in both a photon and mixed photon-neutron mode at a Depleted Uranium (DU) target are presented. The standard approach applying a Figure of Merit (FOM) consisting of background sigma above background is compared with an approach looking to fit only the time-decaying photon signal with standard delayed photon emission from ∼10-MeV end-point-energy Bremsstrahlung photofission of DU. Examples where each approach does well and less well are presented together with a discussion of the relative limitations of both approaches to the type of mixed photon-neutron flash active interrogation being considered.

  9. Formation of a double-decker magnetic flux rope in the sigmoidal solar active region 11520

    SciTech Connect

    Cheng, X.; Ding, M. D.; Zhang, J.; Guo, Y.; Sun, X. D.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-07-10

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s{sup –1}. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  10. Formation of a Double-decker Magnetic Flux Rope in the Sigmoidal Solar Active Region 11520

    NASA Astrophysics Data System (ADS)

    Cheng, X.; Ding, M. D.; Zhang, J.; Sun, X. D.; Guo, Y.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-07-01

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s-1. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  11. Interplanetary proton flux and solar wind conditions for different solar activities interacting with spacecraft and astronauts in space

    NASA Astrophysics Data System (ADS)

    Nejat, Cyrus

    2014-01-01

    The goal of this research is to determine the interplanetary proton flux and solar wind conditions by using data from several satellites such as Advanced Composition Explorer (ACE), Geostationary Operational Environmental Satellites (GOES) in particular GOES 9, GOES 11, GOES 12, GOES 13, and Solar Heliospheric Observatory (SOHO) to determine proton flux in different solar wind conditions. The data from above satellites were used to determine space weather conditions in which the goals are to evaluate proton fluxes for four periods of solar cycle activity: a solar cycle 23/24 minimum (2008), close to a solar cycle 22/23 minimum (1997), with intermediate activity (2011) and for about maximum activity for the cycle 23 (2003), to compare data of two period of solar cycle in 2003 and 2008 (Max vs. Min), to compare data of two period of solar cycle in 1997 and 2008 (Min vs. Min), to compare soft X-ray flux from SOHO with proton 1-10 MeV flux from GOES 9 for strong flare in 1997. To conclude the above evaluations are being used to determine the interaction between the space weather conditions and the following consequences of these conditions important for astronautics and everyday human activity: 1- Satellite and Spacecraft charging, 2-Dangerous conditions for onboard electronics and astronauts during strong solar flare events, and 3- Total Electron Content (TEC), Global Positioning System (GPS), and radio communication problems related to solar activity.

  12. Multimodal microscopy and the stepwise multi-photon activation fluorescence of melanin

    NASA Astrophysics Data System (ADS)

    Lai, Zhenhua

    The author's work is divided into three aspects: multimodal microscopy, stepwise multi-photon activation fluorescence (SMPAF) of melanin, and customized-profile lenses (CPL) for on-axis laser scanners, which will be introduced respectively. A multimodal microscope provides the ability to image samples with multiple modalities on the same stage, which incorporates the benefits of all modalities. The multimodal microscopes developed in this dissertation are the Keck 3D fusion multimodal microscope 2.0 (3DFM 2.0), upgraded from the old 3DFM with improved performance and flexibility, and the multimodal microscope for targeting small particles (the "Target" system). The control systems developed for both microscopes are low-cost and easy-to-build, with all components off-the-shelf. The control system have not only significantly decreased the complexity and size of the microscope, but also increased the pixel resolution and flexibility. The SMPAF of melanin, activated by a continuous-wave (CW) mode near-infrared (NIR) laser, has potential applications for a low-cost and reliable method of detecting melanin. The photophysics of melanin SMPAF has been studied by theoretical analysis of the excitation process and investigation of the spectra, activation threshold, and photon number absorption of melanin SMPAF. SMPAF images of melanin in mouse hair and skin, mouse melanoma, and human black and white hairs are compared with images taken by conventional multi-photon fluorescence microscopy (MPFM) and confocal reflectance microscopy (CRM). SMPAF images significantly increase specificity and demonstrate the potential to increase sensitivity for melanin detection compared to MPFM images and CRM images. Employing melanin SMPAF imaging to detect melanin inside human skin in vivo has been demonstrated, which proves the effectiveness of melanin detection using SMPAF for medical purposes. Selective melanin ablation with micrometer resolution has been presented using the Target system

  13. Quantifying the Topology and Evolution of a Magnetic Flux Rope Associated with Multi-flare Activities

    NASA Astrophysics Data System (ADS)

    Yang, Kai; Guo, Yang; Ding, M. D.

    2016-06-01

    Magnetic flux ropes (MFRs) play an important role in solar activities. The quantitative assessment of the topology of an MFR and its evolution is crucial for a better understanding of the relationship between the MFR and associated activities. In this paper, we investigate the magnetic field of active region (AR) 12017 from 2014 March 28–29, during which time 12 flares were triggered by intermittent eruptions of a filament (either successful or confined). Using vector magnetic field data from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we calculate the magnetic energy and helicity injection in the AR, and extrapolate the 3D magnetic field with a nonlinear force-free field model. From the extrapolations, we find an MFR that is cospatial with the filament. We further determine the configuration of this MFR from the closed quasi-separatrix layer (QSL) around it. Then, we calculate the twist number and the magnetic helicity for the field lines composing the MFR. The results show that the closed QSL structure surrounding the MFR becomes smaller as a consequence of flare occurrence. We also find that the flares in our sample are mainly triggered by kink instability. Moreover, the twist number varies more sensitively than other parameters with the occurrence of flares.

  14. Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide.

    PubMed

    Fuchs, F; Stender, B; Trupke, M; Simin, D; Pflaum, J; Dyakonov, V; Astakhov, G V

    2015-01-01

    Vacancy-related centres in silicon carbide are attracting growing attention because of their appealing optical and spin properties. These atomic-scale defects can be created using electron or neutron irradiation; however, their precise engineering has not been demonstrated yet. Here, silicon vacancies are generated in a nuclear reactor and their density is controlled over eight orders of magnitude within an accuracy down to a single vacancy level. An isolated silicon vacancy serves as a near-infrared photostable single-photon emitter, operating even at room temperature. The vacancy spins can be manipulated using an optically detected magnetic resonance technique, and we determine the transition rates and absorption cross-section, describing the intensity-dependent photophysics of these emitters. The on-demand engineering of optically active spins in technologically friendly materials is a crucial step toward implementation of both maser amplifiers, requiring high-density spin ensembles, and qubits based on single spins. PMID:26151881

  15. Analysis of marine sediment and lobster hepatopancreas reference materials by instrumental photon activation

    SciTech Connect

    Landsberger, S.; Davidson, W.F.

    1985-01-01

    By use of instrumental photon activation analysis, twelve trace (As, Ba, Cr, Co, Mn, Ni, Pb, Sb, Sr, U, Zn, and Zr) and eight minor (C, Na, Mg, Co, K, Ca, Tl, and Fe) elements were determined in a certified marine sediment standard reference material as well as eight trace (Mn, Ni, Cu, Zn, As, Sr, Cd, and Pb) and four minor (Na, Mg, Cl, and Ca) elements in a certified marine tissue (lobster hepatopancreas) standard reference material. The precision and accuracy of the present results when compared to the accepted values clearly demonstrate the reliability of this nondestructive technique and its applicability to marine environmental or marine geochemical studies. 24 references, 4 figures, 3 tables.

  16. Solid state photon upconversion utilizing thermally activated delayed fluorescence molecules as triplet sensitizer

    SciTech Connect

    Wu, Tony C.; Congreve, Daniel N.; Baldo, Marc A.

    2015-07-20

    The ability to upconvert light is useful for a range of applications, from biological imaging to solar cells. But modern technologies have struggled to upconvert incoherent incident light at low intensities. Here, we report solid state photon upconversion employing triplet-triplet exciton annihilation in an organic semiconductor, sensitized by a thermally activated-delayed fluorescence (TADF) dye. Compared to conventional phosphorescent sensitizers, the TADF dye maximizes the wavelength shift in upconversion due to its small singlet-triplet splitting. The efficiency of energy transfer from the TADF dye is 9.1%, and the conversion yield of sensitizer exciton pairs to singlet excitons in the annihilator is 1.1%. Our results demonstrate upconversion in solid state geometries and with non-heavy metal-based sensitizer materials.

  17. Solid state photon upconversion utilizing thermally activated delayed fluorescence molecules as triplet sensitizer

    NASA Astrophysics Data System (ADS)

    Wu, Tony C.; Congreve, Daniel N.; Baldo, Marc A.

    2015-07-01

    The ability to upconvert light is useful for a range of applications, from biological imaging to solar cells. But modern technologies have struggled to upconvert incoherent incident light at low intensities. Here, we report solid state photon upconversion employing triplet-triplet exciton annihilation in an organic semiconductor, sensitized by a thermally activated-delayed fluorescence (TADF) dye. Compared to conventional phosphorescent sensitizers, the TADF dye maximizes the wavelength shift in upconversion due to its small singlet-triplet splitting. The efficiency of energy transfer from the TADF dye is 9.1%, and the conversion yield of sensitizer exciton pairs to singlet excitons in the annihilator is 1.1%. Our results demonstrate upconversion in solid state geometries and with non-heavy metal-based sensitizer materials.

  18. Packing of Large Two- and Three-Photon Activity Into Smallest Possible Unsymmetrical Fluorene Chromophores.

    PubMed

    Kundi, Varun; Thankachan, Pompozhi Protasis

    2016-05-01

    The quantum chemical study of one-, two-, and three-photon absorption (1PA, 2PA, and 3PA) properties for a set of compact fluorene derivatives (FD) with combination of different donor and acceptor moieties on both sides of fluorene ring system is presented. The main goal of the study is to pack large two-photon (2P) and three-photon (3P) activity into smallest possible chromophore. Linear, quadratic, and cubic response time-dependent density functional theory was used to calculate 1PA, 2PA, and 3PA properties, respectively. We used CAMB3LYP/cc-pVDZ level of theory for all the property calculations. The 2P and 3P transition probabilities were recalculated using two-state model approach and found to be in good agreement with the response theory results for first excited state. To include the contributions from higher states, the three-state model was also employed to recalculate the 2P transition probabilities and found to be in excellent agreement with response theory. The 2P/3P tensor elements were also analyzed to find reasons behind large 2P/3P activities. All the orbitals involved in transition processes were studied in detail by both molecular orbital pictures (qualitatively) and overlap diagnostic Λ-values (quantitatively). The study reveals that the novel fluorene derivatives FD-12 and FD-13 have shown large 2PA cross-section values of 1100 G.M. and 1030 G.M.; and 3PA transition probabilities of 6.10 × 10(10) a.u. and 4.85 × 10(10) a.u., respectively, for transition S0 → S1. The largest 3PA transition probability of 4.04 × 10(11) a.u. was found with FD-12 for S0 → S2 excitation. The linear relationship between Λ-values and 2PA cross-section values was also studied. PMID:27054876

  19. Crosstalk-free operation of multielement superconducting nanowire single-photon detector array integrated with single-flux-quantum circuit in a 0.1 W Gifford-McMahon cryocooler.

    PubMed

    Yamashita, Taro; Miki, Shigehito; Terai, Hirotaka; Makise, Kazumasa; Wang, Zhen

    2012-07-15

    We demonstrate the successful operation of a multielement superconducting nanowire single-photon detector (SSPD) array integrated with a single-flux-quantum (SFQ) readout circuit in a compact 0.1 W Gifford-McMahon cryocooler. A time-resolved readout technique, where output signals from each element enter the SFQ readout circuit with finite time intervals, revealed crosstalk-free operation of the four-element SSPD array connected with the SFQ readout circuit. The timing jitter and the system detection efficiency were measured to be 50 ps and 11.4%, respectively, which were comparable to the performance of practical single-pixel SSPD systems. PMID:22825199

  20. Wide field-of-view, multi-region, two-photon imaging of neuronal activity in the mammalian brain.

    PubMed

    Stirman, Jeffrey N; Smith, Ikuko T; Kudenov, Michael W; Smith, Spencer L

    2016-08-01

    Two-photon calcium imaging provides an optical readout of neuronal activity in populations of neurons with subcellular resolution. However, conventional two-photon imaging systems are limited in their field of view to ∼1 mm(2), precluding the visualization of multiple cortical areas simultaneously. Here, we demonstrate a two-photon microscope with an expanded field of view (>9.5 mm(2)) for rapidly reconfigurable simultaneous scanning of widely separated populations of neurons. We custom designed and assembled an optimized scan engine, objective, and two independently positionable, temporally multiplexed excitation pathways. We used this new microscope to measure activity correlations between two cortical visual areas in mice during visual processing. PMID:27347754

  1. Photospheric Vertical Current Density and Overlying Atmospheric Activity in an Emerging Flux Region

    NASA Astrophysics Data System (ADS)

    Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N.; Schmieder, B.

    2002-05-01

    Using high-resolution vector magnetograms obtained by the balloon-borne Flare Genesis Experiment (FGE), we construct maps of the vertical current density in the emerging flux region NOAA 8844. The vertical current density has been decomposed into components that are field-aligned and perpendicular to the magnetic field, thus allowing a straightforward identification of force-free areas, as well as of areas where the force-free approximation breaks down. Small-scale chromospheric activity, such as H α Ellerman bombs and Ultraviolet bright points in 1600 Åshow a remarkable correlation with areas of strong current density. Simultaneous data of overlying coronal loops, observed by TRACE in the Extreme Ultraviolet (171 Åand 195 Å), have been carefully co-aligned with the FGE photospheric maps. We find that the footpoints of the TRACE loops always coincide with strong vertical currents and enhancements of the current helicity density. We also investigate whether the force-free approximation is valid on the photosphere during various evolutionary stages of the active region.

  2. Evaluation of CETP activity in vivo under non-steady-state conditions: influence of anacetrapib on HDL-TG flux.

    PubMed

    McLaren, David G; Previs, Stephen F; Phair, Robert D; Stout, Steven J; Xie, Dan; Chen, Ying; Salituro, Gino M; Xu, Suoyu S; Castro-Perez, Jose M; Opiteck, Gregory J; Akinsanya, Karen O; Cleary, Michele A; Dansky, Hayes M; Johns, Douglas G; Roddy, Thomas P

    2016-03-01

    Studies in lipoprotein kinetics almost exclusively rely on steady-state approaches to modeling. Herein, we have used a non-steady-state experimental design to examine the role of cholesteryl ester transfer protein (CETP) in mediating HDL-TG flux in vivo in rhesus macaques, and therefore, we developed an alternative strategy to model the data. Two isotopomers ([(2)H11] and [(13)C18]) of oleic acid were administered (orally and intravenously, respectively) to serve as precursors for labeling TGs in apoB-containing lipoproteins. The flux of a specific TG (52:2) from these donor lipoproteins to HDL was used as the measure of CETP activity; calculations are also presented to estimate total HDL-TG flux. Based on our data, we estimate that the peak total postprandial TG flux to HDL via CETP is ∼ 13 mg · h(-1) · kg(-1) and show that this transfer was inhibited by 97% following anacetrapib treatment. Collectively, these data demonstrate that HDL TG flux can be used as a measure of CETP activity in vivo. The fact that the donor lipoproteins can be labeled in situ using well-established stable isotope tracer techniques suggests ways to measure this activity for native lipoproteins in free-living subjects under any physiological conditions. PMID:26658238

  3. High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

    NASA Technical Reports Server (NTRS)

    Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

    1988-01-01

    High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

  4. Determination of Interesting Toxicological Elements in PM2.5 by Neutron and Photon Activation Analysis

    PubMed Central

    Capannesi, Geraldo; Lopez, Francesco

    2013-01-01

    Human activities introduce compounds increasing levels of many dangerous species for environment and population. In this way, trace elements in airborne particulate have a preeminent position due to toxic element presence affecting the biological systems. The main problem is the analytical determination of such species at ultratrace levels: a very specific methodology is necessary with regard to the accuracy and precision and contamination problems. Instrumental Neutron Activation Analysis and Instrumental Photon Activation Analysis assure these requirements. A retrospective element analysis in airborne particulate collected in the last 4 decades has been carried out for studying their trend. The samples were collected in urban location in order to determine only effects due to global aerosol circulation; semiannual samples have been used to characterize the summer/winter behavior of natural and artificial origin. The levels of natural origin element are higher than those in other countries owing to geological and meteorological factors peculiar to Central Italy. The levels of artificial elements are sometimes less than those in other countries, suggesting a less polluted general situation for Central Italy. However, for a few elements (e.g., Pb) the levels measured are only slight lower than those proposed as air ambient standard. PMID:23878525

  5. INITIATION AND ERUPTION PROCESS OF MAGNETIC FLUX ROPE FROM SOLAR ACTIVE REGION NOAA 11719 TO EARTH-DIRECTED CME

    SciTech Connect

    Vemareddy, P.; Zhang, J.

    2014-12-20

    An eruption event launched from the solar active region (AR) NOAA 11719 is investigated based on coronal EUV observations and photospheric magnetic field measurements obtained from the Solar Dynamic Observatory. The AR consists of a filament channel originating from a major sunspot and its south section is associated with an inverse-S sigmoidal system as observed in Atmospheric Imaging Assembly passbands. We regard the sigmoid as the main body of the flux rope (FR). There also exists a twisted flux bundle crossing over this FR. This overlying flux bundle transforms in shape similar to kink-rise evolution, which corresponds with the rise motion of the FR. The emission measure and temperature along the FR exhibits an increasing trend with its rising motion, indicating reconnection in the thinning current sheet underneath the FR. Net magnetic flux of the AR, evaluated at north and south polarities, showed decreasing behavior whereas the net current in these fluxes exhibits an increasing trend. Because the negative (positive) flux has a dominant positive (negative) current, the chirality of AR flux system is likely negative (left handed) in order to be consistent with the chirality of inverse S-sigmoidal FR. This analysis of magnetic fields of the source AR suggests that the cancelling fluxes are prime factors of the monotonous twisting of the FR system, reaching to a critical state to trigger kink instability and rise motion. This rise motion may have led to the onset of the torus instability, resulting in an Earth-directed coronal mass ejection, and the progressive reconnection in the thinning current sheet beneath the rising FR led to the M6.5 flare.

  6. Photon small-field measurements with a CMOS active pixel sensor.

    PubMed

    Spang, F Jiménez; Rosenberg, I; Hedin, E; Royle, G

    2015-06-01

    In this work the dosimetric performance of CMOS active pixel sensors for the measurement of small photon beams is presented. The detector used consisted of an array of 520  × 520 pixels on a 25 µm pitch. Dosimetric parameters measured with this sensor were compared with data collected with an ionization chamber, a film detector and GEANT4 Monte Carlo simulations. The sensor performance for beam profiles measurements was evaluated for field sizes of 0.5  × 0.5 cm(2). The high spatial resolution achieved with this sensor allowed the accurate measurement of profiles, beam penumbrae and field size under lateral electronic disequilibrium. Field size and penumbrae agreed within 5.4% and 2.2% respectively with film measurements. Agreements with ionization chambers better than 1.0% were obtained when measuring tissue-phantom ratios. Output factor measurements were in good agreement with ionization chamber and Monte Carlo simulation. The data obtained from this imaging sensor can be easily analyzed to extract dosimetric information. The results presented in this work are promising for the development and implementation of CMOS active pixel sensors for dosimetry applications. PMID:25985207

  7. Photon small-field measurements with a CMOS active pixel sensor

    NASA Astrophysics Data System (ADS)

    Jiménez Spang, F.; Rosenberg, I.; Hedin, E.; Royle, G.

    2015-06-01

    In this work the dosimetric performance of CMOS active pixel sensors for the measurement of small photon beams is presented. The detector used consisted of an array of 520  × 520 pixels on a 25 µm pitch. Dosimetric parameters measured with this sensor were compared with data collected with an ionization chamber, a film detector and GEANT4 Monte Carlo simulations. The sensor performance for beam profiles measurements was evaluated for field sizes of 0.5  × 0.5 cm2. The high spatial resolution achieved with this sensor allowed the accurate measurement of profiles, beam penumbrae and field size under lateral electronic disequilibrium. Field size and penumbrae agreed within 5.4% and 2.2% respectively with film measurements. Agreements with ionization chambers better than 1.0% were obtained when measuring tissue-phantom ratios. Output factor measurements were in good agreement with ionization chamber and Monte Carlo simulation. The data obtained from this imaging sensor can be easily analyzed to extract dosimetric information. The results presented in this work are promising for the development and implementation of CMOS active pixel sensors for dosimetry applications.

  8. Eruption of the magnetic flux rope in a fast decayed active region

    NASA Astrophysics Data System (ADS)

    Yang, Shangbin

    2012-07-01

    An isolated and fast decayed active region was observed when passing through solar disk. There is only one CME related with it that give us a good opportunity to investigate the whole process of the CME. Filament in this active region rises up rapidly and then hesitates and disintegrates into flare loops. The rising filament from EIT images separates into two parts just before eruption. It is interesting that this filament rises up with positive kink which is opposite to the negative helicity according to the inverse S-shaped X-ray sigmoid and accumulated magnetic helicity. A new filament reforms several hours later after CME and the axis of this new one rotates clockwise about 22° comparing with that of the former one. We also observed a bright transient J-shaped X-ray sigmoid immediately appears after filament eruption. It quickly develops into a soft X-ray cusp and rises up firstly then drops down. We propose that field lines underneath bald-patch sparatrix surface (BPSS) where for the formation of a magnetic tangential discontinuity are locally rooted to the photosphere near the bald-patch (BP) inversion line. Field lines above the surface are detached from the photosphere to form this CME and partially open the field which make the filament loses equilibrium to rise quickly and then be drawn back by the tension force of magnetic field after eruption to form a new filament. Two magnetic cancelation regions have been observed clearly just before filament eruption that reflect the existence of BPs. On the other hand, the values of total magnetic helicity to the corona taken by emergence and differential rotation normalized by the square total magnetic flux implies the possibility of upper bound on the total magnetic helicity that a force-free field can contain.

  9. Modulation of intracellular calcium waves and triggered activities by mitochondrial ca flux in mouse cardiomyocytes.

    PubMed

    Zhao, Zhenghang; Gordan, Richard; Wen, Hairuo; Fefelova, Nadezhda; Zang, Wei-Jin; Xie, Lai-Hua

    2013-01-01

    Recent studies have suggested that mitochondria may play important roles in the Ca(2+) homeostasis of cardiac myocytes. However, it is still unclear if mitochondrial Ca(2+) flux can regulate the generation of Ca(2+) waves (CaWs) and triggered activities in cardiac myocytes. In the present study, intracellular/cytosolic Ca(2+) (Cai (2+)) was imaged in Fluo-4-AM loaded mouse ventricular myocytes. Spontaneous sarcoplasmic reticulum (SR) Ca(2+) release and CaWs were induced in the presence of high (4 mM) external Ca(2+) (Cao (2+)). The protonophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP) reversibly raised basal Cai (2+) levels even after depletion of SR Ca(2+) in the absence of Cao (2+) , suggesting Ca(2+) release from mitochondria. FCCP at 0.01 - 0.1 µM partially depolarized the mitochondrial membrane potential (Δψ m ) and increased the frequency and amplitude of CaWs in a dose-dependent manner. Simultaneous recording of cell membrane potentials showed the augmentation of delayed afterdepolarization amplitudes and frequencies, and induction of triggered action potentials. The effect of FCCP on CaWs was mimicked by antimycin A (an electron transport chain inhibitor disrupting Δψ m ) or Ru360 (a mitochondrial Ca(2+) uniporter inhibitor), but not by oligomycin (an ATP synthase inhibitor) or iodoacetic acid (a glycolytic inhibitor), excluding the contribution of intracellular ATP levels. The effects of FCCP on CaWs were counteracted by the mitochondrial permeability transition pore blocker cyclosporine A, or the mitochondrial Ca(2+) uniporter activator kaempferol. Our results suggest that mitochondrial Ca(2+) release and uptake exquisitely control the local Ca(2+) level in the micro-domain near SR ryanodine receptors and play an important role in regulation of intracellular CaWs and arrhythmogenesis. PMID:24348912

  10. AMPK activation protects cells from oxidative stress-induced senescence via autophagic flux restoration and intracellular NAD(+) elevation.

    PubMed

    Han, Xiaojuan; Tai, Haoran; Wang, Xiaobo; Wang, Zhe; Zhou, Jiao; Wei, Xiawei; Ding, Yi; Gong, Hui; Mo, Chunfen; Zhang, Jie; Qin, Jianqiong; Ma, Yuanji; Huang, Ning; Xiang, Rong; Xiao, Hengyi

    2016-06-01

    AMPK activation is beneficial for cellular homeostasis and senescence prevention. However, the molecular events involved in AMPK activation are not well defined. In this study, we addressed the mechanism underlying the protective effect of AMPK on oxidative stress-induced senescence. The results showed that AMPK was inactivated in senescent cells. However, pharmacological activation of AMPK by metformin and berberine significantly prevented the development of senescence and, accordingly, inhibition of AMPK by Compound C was accelerated. Importantly, AMPK activation prevented hydrogen peroxide-induced impairment of the autophagic flux in senescent cells, evidenced by the decreased p62 degradation, GFP-RFP-LC3 cancellation, and activity of lysosomal hydrolases. We also found that AMPK activation restored the NAD(+) levels in the senescent cells via a mechanism involving mostly the salvage pathway for NAD(+) synthesis. In addition, the mechanistic relationship of autophagic flux and NAD(+) synthesis and the involvement of mTOR and Sirt1 activities were assessed. In summary, our results suggest that AMPK prevents oxidative stress-induced senescence by improving autophagic flux and NAD(+) homeostasis. This study provides a new insight for exploring the mechanisms of aging, autophagy and NAD(+) homeostasis, and it is also valuable in the development of innovative strategies to combat aging. PMID:26890602

  11. Electron-Photon Coincidence Calibration Of Photon Detectors

    NASA Technical Reports Server (NTRS)

    Srivastava, Santosh K.

    1988-01-01

    Absolute and relative detector efficiencies measured. Apparatus uses coincidence-counting techniques to measure efficiency of ultraviolet or vacuum ultraviolet detector at very low radiation intensity. Crossed electron and atomic beams generate photons used to calibrate photon detector. Pulses from electron counter and photon detector(s) processed by standard coincidence-counting techniques. Used to calibrate other detectors or make absolute measurements of incident photon fluxes.

  12. Improved L-lysine production with Corynebacterium glutamicum and systemic insight into citrate synthase flux and activity.

    PubMed

    van Ooyen, Jan; Noack, Stephan; Bott, Michael; Reth, Alexander; Eggeling, Lothar

    2012-08-01

    We here developed a series of Corynebacterium glutamicum strains with gradual decreased specific citrate synthase (CS) activity and quantified in a multifaceted approach the consequences of residual activity on the transcriptome, metabolome, and fluxome level as well as on L-lysine formation and growth. We achieved an intended gradual L-lysine yield increase and recognized and overcame further new limitations in the L-lysine biosynthesis pathway to result in a strain with the highest yield reported so far when assayed under comparable conditions. As a non-intended outcome, a detailed flux analysis revealed an almost constant flux through CS at 10% remaining CS activity, whereas the metabolome data revealed an increase in the oxaloacetate and acetyl-CoA concentrations. Hence reduced CS activity is apparently efficiently buffered by increased concentrations of CS substrates, implying a certain robustness of the central metabolism in response of the imposed gene expressions. PMID:22392073

  13. Design of an actively cooled plate calorimeter for the investigation of pool fire heat fluxes

    SciTech Connect

    Koski, J. A.; Keltner, N. R.; Nicolette, V. F.; Wix, S. D.

    1992-01-01

    For final qualification of shipping containers for transport of hazardous materials, thermal testing in accordance with regulations such as 10CFR71 must be completed. Such tests typically consist of 30 minute exposures with the container fully engulfed in flames from a large, open pool of JP4 jet engine fuel. Despite careful engineering analyses of the container, testing often reveals design problems that must be solved by modification and expensive retesting of the container. One source of this problem is the wide variation in surface heat flux to the container that occurs in pool fires. Average heat fluxes of 50 to 60 kW/m{sup 2} are typical and close the values implied by the radiation model in 10CFR71, but peak fluxes up to 150 kW/m{sup 2} are routinely observed in fires. Heat fluxes in pool fires have been shown to be a function of surface temperature of the container, height above the pool, surface orientation, wind, and other variables. If local variations in the surface heat flux to the container could be better predicted, design analyses would become more accurate, and fewer problems will be uncovered during testing. The objective of the calorimeter design described in this paper is to measure accurately pool fire heat fluxes under controlled conditions, and to provide data for calibration of improved analytical models of local flame-surface interactions.

  14. Formation of sunspots and active regions through the emergence of magnetic flux generated in a solar convective dynamo

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Rempel, Matthias D.; Fan, Yuhong

    2016-05-01

    We present a realistic numerical model of sunspot and active region formation through the emergence of flux tubes generated in a solar convective dynamo. The magnetic and velocity fields in a horizontal layer near the top boundary of the solar convective dynamo simulation are used as a time-dependent bottom boundary to drive the near surface layer radiation MHD simulations of magneto-convection and flux emergence with the MURaM code. The latter code simulates the emergence of the flux tubes through the upper most layer of the convection zone to the photosphere.The emerging flux tubes interact with the convection and break into small scale magnetic elements that further rise to the photosphere. At the photosphere, several bipolar pairs of sunspots are formed through the coalescence of the small scale magnetic elements. The sunspot pairs in the simulation successfully reproduce the fundamental observed properties of solar active regions, including the more coherent leading spots with a stronger field strength, and the correct tilts of the bipolar pairs. These asymmetries come most probably from the intrinsic asymmetries in the emerging fields imposed at the bottom boundary, where the horizontal fields are already tilted and the leading sides of the emerging flux tubes are usually up against the downdraft lanes of the giant cells. It is also found that penumbrae with numerous filamentary structures form in regions of strong horizontal magnetic fields that naturally comes from the ongoing flux emergence. In contrast to previous models, the penumbrae and umbrae are divided by very sharp boarders, which is highly consistent with observations.

  15. Gravity wave activity in the thermosphere inferred from GOCE data, and its dependence on solar flux conditions.

    NASA Astrophysics Data System (ADS)

    Garcia, Raphael F.; Bruinsma, Sean; Doornbos, Eelco; Massarweh, Lotfi

    2016-04-01

    This study is focused on the effect of solar flux conditions on the dynamics of Gravity Waves (GW) in thermosphere. Air density and cross-wind in situ estimates from the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) accelerometers are analyzed for the whole mission duration. The analysis was performed in the Fourier spectral domain averaging spectral results over periods of 2 months close to solstices. First the Amplitude Spectral Density (ASD) and the Magnitude Squared Coherence (MSC) of physical parameters are linked to local gravity waves. Then, a new GW marker (called Cf3) was introduced here to constrain GWs activity under Low, Medium and High solar flux conditions, showing a clear solar dumping effect on GW activity. Most of GW signal has been found in a spectral range above 8 mHz in GOCE data, meaning a maximum horizontal wavelength around 1000 km. The level GW activity at GOCE altitude is strongly decreasing with increasing solar flux. Furthermore, a shift in the dominant frequency with solar flux conditions has been noted, leading to a larger horizontal wavelengths (from 200 to 500 km) during high solar flux conditions. The influence of correlated error sources, between air density and cross-winds, is discussed. Consistency of the spectral domain results has been verified in time-domain with a global mapping of high frequency perturbations along GOCE orbit. This analysis shows a clear dependence with geomagnetic latitude with strong perturbations at magnetic poles, and an extension to lower latitudes favoured by low solar activity conditions. Various possible causes of this spatial trend are discussed.

  16. Gas flux measurements of episodic bimodal eruptive activity at Karymsky volcano (Kamchatka, Russia)

    NASA Astrophysics Data System (ADS)

    Arellano, S.; Galle, B.; Melnikov, D.

    2012-04-01

    Volcanoes of intermediate magmatic composition commonly exhibit episodes of intermittent gas and ash emission of variable duration. Due to the multiple conditions present at each system, different mechanisms have been proposed to account for the observed activity, and without key measurements at hand, a definite understanding of the situation might not be singled out. Karymsky, the most active volcano of Central Kamchatka, has presented a remarkably stable pattern of bimodal eruption since a few weeks after its violent reactivation in 1996. Periods of quasi-periodic explosive emissions with typical recurrence intervals of 3-10 min are alternated with episodes of semi-continuous discharge which intensity has a typical modulation at a frequency of 1 Hz. Geophysical studies at Karymsky have identified the main visual, seismic and acoustic features of these two eruption modalities. From these observations, the time scales of the processes have been defined and relevant models have been formulated, according to which the two modes are controlled by the rheological properties of an intruding gas-saturated magma batch and a shallow gas-depleted magma plug. Explosions are explained as the consequence of the formation of temporary sealing, overpressure buildup and vent clearance. Clearly, direct measurements of the gas emission rate are the key parameter to test such models. In this work, we report on the results of a field campaign for SO2 gas measurements carried out at Karymsky during 10-14 September 2011. We deployed 2 NOVAC-type, scanning DOAS systems as well as 1 rapid wide-Field of View mini-DOAS plume tracker. With this setup, we derived time-resolved SO2 flux, plume height, direction and speed, and detected pulses of increasing emission with high temporal resolution. We observed phases of explosive and quiescent degassing with variable amounts of ash emission and detected intensity changes of the associated acoustic signals. The repose time intervals between these

  17. Impact of seabird activity on nitrous oxide and methane fluxes from High Arctic tundra in Svalbard, Norway

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Chen, Qingqing; Ding, Wei; Xu, Hua

    2012-12-01

    In this study, tundra N2O and CH4 fluxes were measured from one seabird sanctuary (SBT) and two non-seabird colonies (NST-I and NST-II) in Ny-Ålesund (79°55'N, 11°56'E), Svalbard during the summers of 2008 and 2009. N2O and CH4 fluxes from SBT showed large temporal and spatial variations depending on the intensity of seabird activity. High seabird activity sites showed large N2O and CH4 emissions while low N2O and CH4 emissions, even CH4 uptake occurred at medium and low seabird activity sites. Overall the mean fluxes were 18.3 ± 3.6 μg N2O m-2 h-1 and 53.5 ± 20.3 μg CH4 m-2 h-1 from tundra SBT whereas tundra NST-I and NST-II represented a relatively weak N2O source (8.3 ± 13.2 μg N2O m-2 h-1) and strong CH4 sink (-82.8 ± 22.3 μg CH4 m-2 h-1). Seabird activity was the strongest control of N2O and CH4 fluxes compared with soil temperature and moisture, and high N2O and CH4 emissions were created by soil physical and chemical processes (the sufficient supply of nutrients NH4+-N, NO3--N, total nitrogen, total phosphorus and total carbon from seabird guano, seabird tramp and appropriate water content) related to the seabird activity. Our work suggests that tundra ecosystems impacted by seabird activity are the potential "hotspots" for N2O and CH4 emissions although these sources have been largely neglected at present. Furthermore the combination of seabird activity and warming climate will likely further enhance N2O and CH4 emissions from the High Arctic tundra.

  18. On the Photonic Cellular Interaction and the Electric Activity of Neurons in the Human Brain

    NASA Astrophysics Data System (ADS)

    Salari, V.; Tuszynski, J.; Bokkon, I.; Rahnama, M.; Cifra, M.

    2011-12-01

    The subject of Ultraweak Photon Emission (UPE) by biological systems is very fascinating, and both evidence of its effects and applications are growing rapidly due to improvements in experimental techniques. Since the relevant equipment should be ultrasensitive with high quantum efficiencies and very low noise levels, the subject of UPE is still hotly debated and some of the interpretations need stronger empirical evidence to be accepted at face value. In this paper we first review different types of interactions between light and living systems based on recent publications. We then discuss the feasibility of UPE production in the human brain. The subject of UPE in the brain is still in early stages of development and needs more accurate experimental methods for proper analysis. In this work we also discuss a possible role of mitochondria in the production of UPE in the neurons of the brain and the plausibility of their effects on microtubules (MTs). MTs have been implicated as playing an important role in the signal and information processing taking place in the mammalian (especially human) brain. Finally, we provide a short discussion about the feasible effects of MTs on electric neural activity in the human brain.

  19. Remote Maneuver of Space Debris Using Photon Pressure for Active Collision Avoidance

    NASA Astrophysics Data System (ADS)

    Smith, C.

    2014-09-01

    The Space Environment Research Corporation (SERC) is a consortium of companies and research institutions that have joined together to pursue research and development of technologies and capabilities that will help to preserve the orbital space environment. The consortium includes, Electro Optics Systems (Australia), Lockheed Martin Australia, Optus Satellite Systems (Australia), The Australian national University, RMIT University, National Institute of Information and Communications Technology (NICT, Japan) as well as affiliates from NASA Ames and ESA. SERC is also the recipient of and Australian Government Cooperative Research Centre grant. SERC will pursue a wide ranging research program including technologies to improve tracking capability and capacity, orbit determination and propagation algorithms, conjunction analysis and collision avoidance. All of these technologies will contribute to the flagship program to demonstrate active collision avoidance using photon pressure to provide remote maneuver of space debris. This project joins of the proposed NASA Lightforce concept with infrastructure and capabilities provided by SERC. This paper will describe the proposed research and development program to provide an on-orbit demonstration within the next five years for remote maneuver of space debris.

  20. Ultrasensitive and specific measurement of protease activity using functionalized photonic crystals.

    PubMed

    Gupta, Bakul; Mai, Kelly; Lowe, Stuart B; Wakefield, Denis; Di Girolamo, Nick; Gaus, Katharina; Reece, Peter J; Gooding, J Justin

    2015-10-01

    Herein is presented a microsensor technology as a diagnostic tool for detecting specific matrix metalloproteinases (MMPs) at very low concentrations. MMP-2 and MMP-9 are detected using label free porous silicon (PSi) photonic crystals that have been made selective for a given MMP by filling the nanopores with synthetic polymeric substrates containing a peptide sequence for that MMP. Proteolytic cleavage of the peptide sequence results in a shift in wavelength of the main peak in the reflectivity spectrum of the PSi device, which is dependent on the amount of MMP present. The ability to detect picogram amounts of MMP-2 and MMP-9 released by primary retinal pigment epithelial (RPE) cells and iris pigment epithelial (IPE) cells stimulated with lipopolysaccharide (LPS) is demonstrated. It was found that both cell types secrete higher amounts of MMP-2 than MMP-9 in their stimulated state, with RPE cells producing higher amounts of MMPs than IPE cells. The microsensor performance was compared to conventional protease detection systems, including gelatin zymography and enzyme linked immunosorbent assay (ELISA). It was found that the PSi microsensors were more sensitive than gelatin zymography; PSi microsensors detected the presence of both MMP-2 and MMP-9 while zymography could only detect MMP-2. The MMP-2 and MMP-9 quantification correlated well with the ELISA. This new method of detecting protease activity shows superior performance to conventional protease assays and has the potential for translation to high-throughput multiplexed analysis. PMID:26312479

  1. Surveillance photonic fence based on active range-gated imaging for night intrusion detection

    NASA Astrophysics Data System (ADS)

    Wang, Xinwei; Zhou, Yan; He, Jun; Fan, Songtao; Liu, Yuliang

    2011-06-01

    We propose a surveillance photonic fence for night remote intrusion detection, especially in bad environmental conditions. The photonic fence is established by the synchronization of a pulsed infrared laser and a gated imaging sensor. Since the wavelength of the laser is invisible, the photonic fence is also invisible. Only when targets pass the fence, their image information can be collected. Objects and backgrounds out of the fence are all filtered directly which decreases the complexity of image processing about target extraction. For the fence, its location can be easily adjusted by the delay time between the laser pulse and the gate pulse, and its thickness can be set by changing the gate time and the laser pulse width. Furthermore, target space information can also be estimated in terms of the range information of the photonic fence.

  2. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon.

    PubMed

    Kupryianchyk, D; Noori, A; Rakowska, M I; Grotenhuis, J T C; Koelmans, A A

    2013-05-21

    Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column. PMID:23590290

  3. River solute fluxes reflecting active hydrothermal chemical weathering of the Yellowstone Plateau Volcanic Field, USA

    USGS Publications Warehouse

    Hurwitz, S.; Evans, William C.; Lowenstern, J. B.

    2010-01-01

    In the past few decades numerous studies have quantified the load of dissolved solids in large rivers to determine chemical weathering rates in orogenic belts and volcanic areas, mainly motivated by the notion that over timescales greater than ~100kyr, silicate hydrolysis may be the dominant sink for atmospheric CO2, thus creating a feedback between climate and weathering. Here, we report the results of a detailed study during water year 2007 (October 1, 2006 to September 30, 2007) in the major rivers of the Yellowstone Plateau Volcanic Field (YPVF) which hosts Earth's largest "restless" caldera and over 10,000 thermal features. The chemical compositions of rivers that drain thermal areas in the YPVF differ significantly from the compositions of rivers that drain non-thermal areas. There are large seasonal variations in river chemistry and solute flux, which increases with increasing water discharge. The river chemistry and discharge data collected periodically over an entire year allow us to constrain the annual solute fluxes and to distinguish between low-temperature weathering and hydrothermal flux components. The TDS flux from Yellowstone Caldera in water year 2007 was 93t/km2/year. Extensive magma degassing and hydrothermal interaction with rocks accounts for at least 82% of this TDS flux, 83% of the cation flux and 72% of the HCO3- flux. The low-temperature chemical weathering rate (17t/km2/year), calculated on the assumption that all the Cl- is of thermal origin, could include a component from low-temperature hydrolysis reactions induced by CO2 ascending from depth rather than by atmospheric CO2. Although this uncertainty remains, the calculated low-temperature weathering rate of the young rhyolitic rocks in the Yellowstone Caldera is comparable to the world average of large watersheds that drain also more soluble carbonates and evaporates but is slightly lower than calculated rates in other, less-silicic volcanic regions. Long-term average fluxes at

  4. Evidence of flux rope and sigmoid in Active Regions prior eruptions

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho; Bommier, Veronique; Dudik, Jaroslav; Gilchrist, Stuart; Zhao, Jie

    2016-07-01

    In the solar corona, the magnetic field is dominant, and the current density vector is nearly aligned with the magnetic field lines for strong and stressed field regions. Stressed and highly twisted flux ropes are at the origin of eruptive events such as flares and coronal mass ejections, which inject material into the interplanetary medium. The standard three dimensional (3D) flare model predicts the complex evolution of flare loops and the flux rope before the eruption. Flux ropes are not directly observed in the corona, however it has started to be possible to detect their footprints in the photosphere. Recent high spatial and temporal resolution spectro-polarimeters have allowed us to compute the photospheric electric currents and follow their evolution. Characteristics pattern like J-shaped ribbons indicate the presence of a flux rope before the flare. The results confirm the predictions of the 3D MHD standard model of eruptive flares. It is interesting to compare the magnetic helicity of the ejected flux rope with the in situ measurements of the corresponding ICME at L1. We will show some examples (February 15 2011, July 12 2012, Sept 10 2014).

  5. Weak solar flares with a detectable flux of hard X rays: Specific features of microwave radiation in the corresponding active regions

    NASA Astrophysics Data System (ADS)

    Grigor'eva, I. Yu.; Livshits, M. A.

    2014-12-01

    The emission of very weak flares was registered at the Suzaku X-ray observatory in 2005-2009. The photon power spectrum in the 50-110 keV range for a number of these phenomena shows that some electrons accelerate to energies higher than 100 keV. The corresponding flares originate in active regions (ARs) with pronounced sunspots. As in the case of AR 10933 in January 2007 analyzed by us previously (Grigor'eva et al., 2013), the thoroughly studied weak flares in May 2007 are related to the emergence of a new magnetic field in the AR and to the currents that originate in this case. A comparison of the Suzaku data with the RATAN-600 microwave observations indicates that a new polarized source of microwave radiation develops in the AR (or the previously existing source intensifies) one-two days before a weak flare in the emerging flux regions. Arguments in favor of recent views that fields are force-free in the AR corona are put forward. The development of weak flares is related to the fact that the free energy of the currents that flow above the field neutral line at altitudes reaching several thousand kilometers is accumulated and subsequently released.

  6. Two-Photon Semiconducting Polymer Dots with Dual-Emission for Ratiometric Fluorescent Sensing and Bioimaging of Tyrosinase Activity.

    PubMed

    Sun, Junyong; Mei, Han; Wang, Sufan; Gao, Feng

    2016-07-19

    Semiconducting polymer dots (Pdots) with one-, two-photon excitation and dual-emission have been synthesized by coprecipitation of two conjugated polymers including poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylene-1,4-phenylene)] (CN-PPV) and have been further functionalized with l-tyrosine methyl ester (Tyr-OMe) via electrostatic assembly for ratiometric fluorescent sensing and bioimaging of tyrosinase activity. Tyrosinase-catalyzed oxidation of Tyr-OMe effectively modulate the dual-emission fluorescence of PFO/CN-PPV@Tyr-OMe Pdots from orange to blue through a selective photoinduced electron transfer (PET) process. A two-photon ratiometric sensor at almost zero-background interference and bioimaging of tyrosinase activity have been demonstrated, suggesting the potential biomedical applications of the prepared functionalized Pdots. PMID:27322725

  7. Photon-photon collisions

    SciTech Connect

    Burke, D.L.

    1982-10-01

    Studies of photon-photon collisions are reviewed with particular emphasis on new results reported to this conference. These include results on light meson spectroscopy and deep inelastic e..gamma.. scattering. Considerable work has now been accumulated on resonance production by ..gamma gamma.. collisions. Preliminary high statistics studies of the photon structure function F/sub 2//sup ..gamma../(x,Q/sup 2/) are given and comments are made on the problems that remain to be solved.

  8. Thermally Activated Energy and Flux-flow Hall Effect of Fe1+y(Te1+xSx)z

    SciTech Connect

    Petrovic, C.; Lei, H.; Hu, R.; Choi, E.S.

    2010-10-19

    Thermally activated flux flow (TAFF) and flux-flow Hall effect (FFHE) of Fe(Te,S) single crystal in the mixed state are studied in magnetic fields up to 35 T. Thermally activated energy (TAE) is analyzed using conventional Arrhenius relation and modified TAFF theory which is closer to experimental results. The results indicate that there is a crossover from single-vortex pinning region to collective creep pinning region with increasing magnetic field. The temperature dependence of TAE is different for H {parallel} ab and H {parallel} c. On the other hand, the analysis of FFHE in the mixed state indicates that there is no Hall sign reversal. We also observe scaling behavior |{rho}{sub xy}(H)|=A{rho}{sub xx}(H){sup {beta}}.

  9. Synthesis, characterization and preclinical studies of two-photon-activated targeted PDT therapeutic triads

    NASA Astrophysics Data System (ADS)

    Spangler, C. W.; Starkey, J. R.; Rebane, A.; Meng, F.; Gong, A.; Drobizhev, M.

    2006-02-01

    Photodynamic therapy (PDT) continues to evolve into a mature clinical treatment of a variety of cancer types as well as age-related macular degeneration of the eye. However, there are still aspects of PDT that need to be improved in order for greater clinical acceptance. While a number of new PDT photo-sensitizers, sometimes referred to as second- or third- generation therapeutic agents, are currently under clinical investigation, the direct treatment through the skin of subcutaneous tumors deeper than 5 mm remains problematic. Currently approved PDT porphyrin photo-sensitizers, as well as several modified porphyrins (e.g. chlorins, bacteriochlorins, etc.) that are under clinical investigation can be activated at 630-730 nm, but none above 800 nm. It would be highly desirable if new PDT paradigms could be developed that would allow photo-activation deep in the tissue transparency window in the Near-infrared (NIR) above 800 nm to reduce scattering and absorption phenomena that reduce deep tissue PDT efficacy. Rasiris and MPA Technologies have developed new porphyrins that have greatly enhanced two-photon absorption ( P A ) cross-sections and can be activated deep in the NIR (ca. 780-850 nm). These porphyrins can be incorporated into a therapeutic triad that also employs an small molecule targeting agent that directs the triad to over-expressed tumor receptor sites, and a NIR onephoton imaging agent that allows tracking the delivery of the triad to the tumor site, as well as clearance of excess triad from healthy tissue prior to the start of PDT treatment. We are currently using these new triads in efficacy studies with a breast cancer cell line that has been transfected with luciferase genes that allow implanted tumor growth and post- PDT treatment efficacy studies in SCID mouse models by following the rise and decay of the bioluminescence signal. We have also designed highly absorbing and scattering collagen breast cancer phantoms in which we have demonstrated

  10. Sensitive multiplex detection of serological liver cancer biomarkers using SERS-active photonic crystal fiber probe.

    PubMed

    Dinish, U S; Balasundaram, Ghayathri; Chang, Young Tae; Olivo, Malini

    2014-11-01

    Surface-enhanced Raman scattering (SERS) spectroscopy possesses the most promising advantage of multiplex detection for biosensing applications, which is achieved due to the narrow 'fingerprint' Raman spectra from the analyte molecules. We developed an ultrasensitive platform for the multiplex detection of cancer biomarkers by combining the SERS technique with a hollow-core photonic crystal fiber (HCPCF). Axially aligned air channels inside the HCPCF provide an excellent platform for optical sensing using SERS. In addition to the flexibility of optical fibers, HCPCF provides better light confinement and a larger interaction length for the guided light and the analyte, resulting in an improvement in sensitivity to detect low concentrations of bioanalytes in extremely low sample volumes. Herein, for the first time, we demonstrate the sensitive multiplex detection of biomarkers immobilized inside the HCPCF using antibody-conjugated SERS-active nanoparticles (SERS nanotags). As a proof-of-concept for targeted multiplex detection, initially we carried out the sensing of epidermal growth factor receptor (EGFR) biomarker in oral squamous carcinoma cell lysate using three different SERS nanotags. Subsequently, we also achieved simultaneous detection of hepatocellular carcinoma (HCC) biomarkers-alpha fetoprotein (AFP) and alpha-1-antitrypsin (A1AT) secreted in the supernatant from Hep3b cancer cell line. Using a SERS-HCPCF sensing platform, we could successfully demonstrate the multiplex detection in an extremely low sample volume of ∼20 nL. In future, this study may lead to sensitive biosensing platform for the low concentration detection of biomarkers in an extremely low sample volume of body fluids to achieve early diagnosis of multiple diseases. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim). PMID:23963680

  11. Fitting Transporter Activities to Cellular Drug Concentrations and Fluxes: Why the Bumblebee Can Fly

    PubMed Central

    Mendes, Pedro; Oliver, Stephen G.; Kell, Douglas B.

    2015-01-01

    A recent paper in this journal argued that reported expression levels, kcat and Km for drug transporters could be used to estimate the likelihood that drug fluxes through Caco-2 cells could be accounted for solely by protein transporters. It was in fact concluded that if five such transporters contributed ‘randomly’ they could account for the flux of the most permeable drug tested (verapamil) 35% of the time. However, the values of permeability cited for verapamil were unusually high; this and other drugs have much lower permeabilities. Even for the claimed permeabilities, we found that a single ‘random’ transporter could account for the flux 42% of the time, and that two transporters can achieve 10 · 10−6 cm·s−1 90% of the time. Parameter optimisation methods show that even a single transporter can account for Caco-2 drug uptake of the most permeable drug. Overall, the proposal that ‘phospholipid bilayer diffusion (of drugs) is negligible’ is not disproved by the calculations of ‘likely’ transporter-based fluxes. PMID:26538313

  12. Rapid Ca2+ flux through the transverse tubular membrane, activated by individual action potentials in mammalian skeletal muscle

    PubMed Central

    Launikonis, Bradley S; Stephenson, D George; Friedrich, Oliver

    2009-01-01

    Periods of low frequency stimulation are known to increase the net Ca2+ uptake in skeletal muscle but the mechanism responsible for this Ca2+ entry is not known. In this study a novel high-resolution fluorescence microscopy approach allowed the detection of an action potential-induced Ca2+ flux across the tubular (t-) system of rat extensor digitorum longus muscle fibres that appears to be responsible for the net uptake of Ca2+ in working muscle. Action potentials were triggered in the t-system of mechanically skinned fibres from rat by brief field stimulation and t-system [Ca2+] ([Ca2+]t-sys) and cytoplasmic [Ca2+] ([Ca2+]cyto) were simultaneously resolved on a confocal microscope. When initial [Ca2+]t-sys was ≥ 0.2 mm a Ca2+ flux from t-system to the cytoplasm was observed following a single action potential. The action potential-induced Ca2+ flux and associated t-system Ca2+ permeability decayed exponentially and displayed inactivation characteristics such that further Ca2+ entry across the t-system could not be observed after 2–3 action potentials at 10 Hz stimulation rate. When [Ca2+]t-sys was closer to 0.1 mm, a transient rise in [Ca2+]t-sys was observed almost concurrently with the increase in [Ca2+]cyto following the action potential. The change in direction of Ca2+ flux was consistent with changes in the direction of the driving force for Ca2+. This is the first demonstration of a rapid t-system Ca2+ flux associated with a single action potential in mammalian skeletal muscle. The properties of this channel are inconsistent with a flux through the L-type Ca2+ channel suggesting that an as yet unidentified t-system protein is conducting this current. This action potential-activated Ca2+ flux provides an explanation for the previously described Ca2+ entry and accumulation observed with prolonged, intermittent muscle activity. PMID:19332499

  13. CO2 Flux Inversion Error Analyses for Future Active Space CO2 Missions like ASCENDS

    NASA Astrophysics Data System (ADS)

    Baker, D. F.; Kawa, S. R.; Rayner, P. J.; Browell, E. V.; Menzies, R. T.; Abshire, J. B.

    2011-12-01

    We assess the ability of different proposed CO2 lidar measurement approaches to constrain surface CO2 fluxes, as part of the development of science requirements for NASA's ASCENDS mission. Observing system simulation experiments (OSSEs) are performed for different overall measurement uncertainty levels and vertical weightings to determine what designs will yield useful new information on the global carbon cycle. The OSSEs are based on a variational data assimilation method that models the measurements at the time and location they occur with minimal averaging and solves for the surface fluxes at regional spatial scales. Measurements are simulated using the PCTM off-line atmospheric transport model driven by GEOS5 analysis data (winds and vertical mixing parameters) and forced by realistic modeled CO2 fluxes. Both day- and night-side fluxes are estimated in weekly blocks at 4.5°x6° resolution (lat/lon) using a full year of simulated data. Error estimates are computed by direct comparison to the known truth; only random errors in the measurements and assumed flux prior are considered here. Relative measurement uncertainties and vertical averaging kernels have been derived for lidar measurements made using CO2 absorption lines in the 1.57 and 2.06 micron bands using realistic assumptions about clouds, aerosols, and surface reflectivity taken from CALIPSO and MODIS. Two measurement cases are considered for the 1.57 μm band, one using a vertical weighting function weighted to the mid- to lower troposphere, and one combining this with a function peaking near the tropopause. A third case is considered for measurements in the 2.06 μm band, with a vertical weighting peaking strongly near the surface. For each of these cases, three overall measurement uncertainty levels are examined (tied to reference uncertainties of 1.0, 0.5, and 0.2 ppm (1σ) at Railroad Valley, Nevada). OSSEs with simple measurement biases are run to test how the random-error-only findings hold in

  14. CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation

    NASA Astrophysics Data System (ADS)

    Hahn, C.; Weber, G.; Märtin, R.; Höfer, S.; Kämpfer, T.; Stöhlker, Th.

    2016-04-01

    Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays — such as laser-generated plasmas — is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse.

  15. CdTe Timepix detectors for single-photon spectroscopy and linear polarimetry of high-flux hard x-ray radiation.

    PubMed

    Hahn, C; Weber, G; Märtin, R; Höfer, S; Kämpfer, T; Stöhlker, Th

    2016-04-01

    Single-photon spectroscopy of pulsed, high-intensity sources of hard X-rays - such as laser-generated plasmas - is often hampered by the pileup of several photons absorbed by the unsegmented, large-volume sensors routinely used for the detection of high-energy radiation. Detectors based on the Timepix chip, with a segmentation pitch of 55 μm and the possibility to be equipped with high-Z sensor chips, constitute an attractive alternative to commonly used passive solutions such as image plates. In this report, we present energy calibration and characterization measurements of such devices. The achievable energy resolution is comparable to that of scintillators for γ spectroscopy. Moreover, we also introduce a simple two-detector Compton polarimeter setup with a polarimeter quality of (98 ± 1)%. Finally, a proof-of-principle polarimetry experiment is discussed, where we studied the linear polarization of bremsstrahlung emitted by a laser-driven plasma and found an indication of the X-ray polarization direction depending on the polarization state of the incident laser pulse. PMID:27131653

  16. Enhanced Plasmonic Resonance Energy Transfer in Mesoporous Silica-Encased Gold Nanorod for Two-Photon-Activated Photodynamic Therapy

    PubMed Central

    Chen, Nai-Tzu; Tang, Kuo-Chun; Chung, Ming-Fang; Cheng, Shih-Hsun; Huang, Ching-Mao; Chu, Chia-Hui; Chou, Pi-Tai; Souris, Jeffrey S.; Chen, Chin-Tu; Mou, Chung-Yuan; Lo, Leu-Wei

    2014-01-01

    The unique optical properties of gold nanorods (GNRs) have recently drawn considerable interest from those working in in vivo biomolecular sensing and bioimaging. Especially appealing in these applications is the plasmon-enhanced photoluminescence of GNRs induced by two-photon excitation at infrared wavelengths, owing to the significant penetration depth of infrared light in tissue. Unfortunately, many studies have also shown that often the intensity of pulsed coherent irradiation of GNRs needed results in irreversible deformation of GNRs, greatly reducing their two-photon luminescence (TPL) emission intensity. In this work we report the design, synthesis, and evaluation of mesoporous silica-encased gold nanorods (MS-GNRs) that incorporate photosensitizers (PSs) for two-photon-activated photodynamic therapy (TPA-PDT). The PSs, doped into the nano-channels of the mesoporous silica shell, can be efficiently excited via intra-particle plasmonic resonance energy transfer from the encased two-photon excited gold nanorod and further generates cytotoxic singlet oxygen for cancer eradication. In addition, due to the mechanical support provided by encapsulating mesoporous silica matrix against thermal deformation, the two-photon luminescence stability of GNRs was significantly improved; after 100 seconds of 800 nm repetitive laser pulse with the 30 times higher than average power for imaging acquisition, MS-GNR luminescence intensity exhibited ~260% better resistance to deformation than that of the uncoated gold nanorods. These results strongly suggest that MS-GNRs with embedded PSs might provide a promising photodynamic therapy for the treatment of deeply situated cancers via plasmonic resonance energy transfer. PMID:24955141

  17. Photon-photon collisions

    SciTech Connect

    Brodsky, S.J.

    1988-07-01

    Highlights of the VIIIth International Workshop on Photon-Photon Collisions are reviewed. New experimental and theoretical results were reported in virtually every area of ..gamma gamma.. physics, particularly in exotic resonance production and tests of quantum chromodynamics where asymptotic freedom and factorization theorems provide predictions for both inclusive and exclusive ..gamma gamma.. reactions at high momentum transfer. 73 refs., 12 figs.

  18. Photo-redox activated drug delivery systems operating under two photon excitation in the near-IR.

    PubMed

    Guardado-Alvarez, Tania M; Devi, Lekshmi Sudha; Vabre, Jean-Marie; Pecorelli, Travis A; Schwartz, Benjamin J; Durand, Jean-Olivier; Mongin, Olivier; Blanchard-Desce, Mireille; Zink, Jeffrey I

    2014-05-01

    We report the design and synthesis of a nano-container consisting of mesoporous silica nanoparticles with the pore openings covered by "snap-top" caps that are opened by near-IR light. A photo transducer molecule that is a reducing agent in an excited electronic state is covalently attached to the system. Near IR two-photon excitation causes inter-molecular electron transfer that reduces a disulfide bond holding the cap in place, thus allowing the cargo molecules to escape. We describe the operation of the "snap-top" release mechanism by both one- and two-photon activation. This system presents a proof of concept of a near-IR photoredox-induced nanoparticle delivery system that may lead to a new type of photodynamic drug release therapy. PMID:24647752

  19. Highly entangled photons and rapidly responding polarization qubit phase gates in a room-temperature active Raman gain medium

    SciTech Connect

    Hang Chao; Huang Guoxiang

    2010-11-15

    We present a scheme for obtaining entangled photons and quantum phase gates in a room-temperature four-state tripod-type atomic system with two-mode active Raman gain (ARG). We analyze the linear and nonlinear optical responses of this ARG system and show that the scheme is fundamentally different from those based on electromagnetically induced transparency and hence can avoid significant probe-field absorption as well as a temperature-related Doppler effect. We demonstrate that highly entangled photon pairs can be produced and rapidly responding polarization qubit phase gates can be constructed based on the unique features of the enhanced cross-phase-modulation and superluminal probe-field propagation of the system.

  20. Comparing Simulations of Rising Flux Tubes Through the Solar Convection Zone with Observations of Solar Active Regions: Constraining the Dynamo Field Strength

    NASA Astrophysics Data System (ADS)

    Weber, M. A.; Fan, Y.; Miesch, M. S.

    2013-10-01

    We study how active-region-scale flux tubes rise buoyantly from the base of the convection zone to near the solar surface by embedding a thin flux tube model in a rotating spherical shell of solar-like turbulent convection. These toroidal flux tubes that we simulate range in magnetic field strength from 15 kG to 100 kG at initial latitudes of 1∘ to 40∘ in both hemispheres. This article expands upon Weber, Fan, and Miesch ( Astrophys. J. 741, 11, 2011) (Article 1) with the inclusion of tubes with magnetic flux of 1020 Mx and 1021 Mx, and more simulations of the previously investigated case of 1022 Mx, sampling more convective flows than the previous article, greatly improving statistics. Observed properties of active regions are compared to properties of the simulated emerging flux tubes, including: the tilt of active regions in accordance with Joy's Law as in Article 1, and in addition the scatter of tilt angles about the Joy's Law trend, the most commonly occurring tilt angle, the rotation rate of the emerging loops with respect to the surrounding plasma, and the nature of the magnetic field at the flux tube apex. We discuss how these diagnostic properties constrain the initial field strength of the active-region flux tubes at the bottom of the solar convection zone, and suggest that flux tubes of initial magnetic field strengths of ≥ 40 kG are good candidates for the progenitors of large (1021 Mx to 1022 Mx) solar active regions, which agrees with the results from Article 1 for flux tubes of 1022 Mx. With the addition of more magnetic flux values and more simulations, we find that for all magnetic field strengths, the emerging tubes show a positive Joy's Law trend, and that this trend does not show a statistically significant dependence on the magnetic flux.

  1. Measurement of the Total Active 8B Solar Neutrino Flux at the Sudbury Neutrino Observatory with Enhanced Neutral Current Sensitivity

    NASA Astrophysics Data System (ADS)

    Ahmed, S. N.; Anthony, A. E.; Beier, E. W.; Bellerive, A.; Biller, S. D.; Boger, J.; Boulay, M. G.; Bowler, M. G.; Bowles, T. J.; Brice, S. J.; Bullard, T. V.; Chan, Y. D.; Chen, M.; Chen, X.; Cleveland, B. T.; Cox, G. A.; Dai, X.; Dalnoki-Veress, F.; Doe, P. J.; Dosanjh, R. S.; Doucas, G.; Dragowsky, M. R.; Duba, C. A.; Duncan, F. A.; Dunford, M.; Dunmore, J. A.; Earle, E. D.; Elliott, S. R.; Evans, H. C.; Ewan, G. T.; Farine, J.; Fergani, H.; Fleurot, F.; Formaggio, J. A.; Fowler, M. M.; Frame, K.; Fulsom, B. G.; Gagnon, N.; Graham, K.; Grant, D. R.; Hahn, R. L.; Hall, J. C.; Hallin, A. L.; Hallman, E. D.; Hamer, A. S.; Handler, W. B.; Hargrove, C. K.; Harvey, P. J.; Hazama, R.; Heeger, K. M.; Heintzelman, W. J.; Heise, J.; Helmer, R. L.; Hemingway, R. J.; Hime, A.; Howe, M. A.; Jagam, P.; Jelley, N. A.; Klein, J. R.; Kos, M. S.; Krumins, A. V.; Kutter, T.; Kyba, C. C.; Labranche, H.; Lange, R.; Law, J.; Lawson, I. T.; Lesko, K. T.; Leslie, J. R.; Levine, I.; Luoma, S.; MacLellan, R.; Majerus, S.; Mak, H. B.; Maneira, J.; Marino, A. D.; McCauley, N.; McDonald, A. B.; McGee, S.; McGregor, G.; Mifflin, C.; Miknaitis, K. K.; Miller, G. G.; Moffat, B. A.; Nally, C. W.; Nickel, B. G.; Noble, A. J.; Norman, E. B.; Oblath, N. S.; Okada, C. E.; Ollerhead, R. W.; Orrell, J. L.; Oser, S. M.; Ouellet, C.; Peeters, S. J.; Poon, A. W.; Robertson, B. C.; Robertson, R. G.; Rollin, E.; Rosendahl, S. S.; Rusu, V. L.; Schwendener, M. H.; Simard, O.; Simpson, J. J.; Sims, C. J.; Sinclair, D.; Skensved, P.; Smith, M. W.; Starinsky, N.; Stokstad, R. G.; Stonehill, L. C.; Tafirout, R.; Takeuchi, Y.; Tešić, G.; Thomson, M.; Thorman, M.; van Berg, R.; van de Water, R. G.; Virtue, C. J.; Wall, B. L.; Waller, D.; Waltham, C. E.; Tseung, H. Wan; Wark, D. L.; West, N.; Wilhelmy, J. B.; Wilkerson, J. F.; Wilson, J. R.; Wouters, J. M.; Yeh, M.; Zuber, K.

    2004-05-01

    The Sudbury Neutrino Observatory has precisely determined the total active (νx) 8B solar neutrino flux without assumptions about the energy dependence of the νe survival probability. The measurements were made with dissolved NaCl in heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21±0.27(stat)±0.38(syst)×106 cm-2 s-1, in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Δm2=7.1+1.2-0.6×10-5 eV2 and θ=32.5+2.4-2.3 degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations.

  2. NMDA-Receptor Activation but Not Ion Flux Is Required for Amyloid-Beta Induced Synaptic Depression

    PubMed Central

    Tamburri, Albert; Dudilot, Anthony; Licea, Sara; Bourgeois, Catherine; Boehm, Jannic

    2013-01-01

    Alzheimer disease is characterized by a gradual decrease of synaptic function and, ultimately, by neuronal loss. There is considerable evidence supporting the involvement of oligomeric amyloid-beta (Aβ) in the etiology of Alzheimer’s disease. Historically, AD research has mainly focused on the long-term changes caused by Aβ rather than analyzing its immediate effects. Here we show that acute perfusion of hippocampal slice cultures with oligomeric Aβ depresses synaptic transmission within 20 minutes. This depression is dependent on synaptic stimulation and the activation of NMDA-receptors, but not on NMDA-receptor mediated ion flux. It, therefore, appears that Aβ dependent synaptic depression is mediated through a use-dependent metabotropic-like mechanism of the NMDA-receptor, but does not involve NMDA-receptor mediated synaptic transmission, i.e. it is independent of calcium flux through the NMDA-receptor. PMID:23750255

  3. Wide-field and two-photon imaging of brain activity with voltage- and calcium-sensitive dyes

    PubMed Central

    Homma, Ryota; Baker, Bradley J.; Jin, Lei; Garaschuk, Olga; Konnerth, Arthur; Cohen, Lawrence B.; Zecevic, Dejan

    2009-01-01

    This review presents three examples of using voltage- or calcium-sensitive dyes to image the activity of the brain. Our aim is to discuss the advantages and disadvantages of each method with particular reference to its application to the study of the brainstem. Two of the examples use wide-field (one-photon) imaging; the third uses two-photon scanning microscopy. Because the measurements have limited signal-to-noise ratio, the paper also discusses the methodological aspects that are critical for optimizing the signal. The three examples are the following. (i) An intracellularly injected voltage-sensitive dye was used to monitor membrane potential in the dendrites of neurons in in vitro preparations. These experiments were directed at understanding how individual neurons convert complex synaptic inputs into the output spike train. (ii) An extracellular, bath application of a voltage-sensitive dye was used to monitor population signals from different parts of the dorsal brainstem. We describe recordings made during respiratory activity. The population signals indicated four different regions with distinct activity correlated with inspiration. (iii) Calcium-sensitive dyes can be used to label many individual cells in the mammalian brain. This approach, combined with two-photon microscopy, made it possible to follow the spike activity in an in vitro brainstem preparation during fictive respiratory rhythms. The organic voltage- and ion-sensitive dyes used today indiscriminatively stain all of the cell types in the preparation. A major effort is underway to develop fluorescent protein sensors of activity for selectively staining individual cell types. PMID:19651647

  4. A Three-Photon Active Organic Fluorophore for Deep Tissue Ratiometric Imaging of Intracellular Divalent Zinc.

    PubMed

    Philips, Divya Susan; Sreejith, Sivaramapanicker; He, Tingchao; Menon, Nishanth Venugopal; Anees, Palapuravan; Mathew, Jomon; Sajikumar, Sreedharan; Kang, Yuejun; Stuparu, Mihaiela Corina; Sun, Handong; Zhao, Yanli; Ajayaghosh, Ayyappanpillai

    2016-05-20

    Deep tissue bioimaging with three-photon (3P) excitation using near-infrared (NIR) light in the second IR window (1.0-1.4 μm) could provide high resolution images with an improved signal-to-noise ratio. Herein, we report a photostable and nontoxic 3P excitable donor-π-acceptor system (GMP) having 3P cross-section (σ3 ) of 1.78×10(-80)  cm(6)  s(2)  photon(-2) and action cross-section (σ3 η3 ) of 2.31×10(-81)  cm(6)  s(2)  photon(-2) , which provides ratiometric fluorescence response with divalent zinc ions in aqueous conditions. The probe signals the Zn(2+) binding at 530 and 600 nm, respectively, upon 1150 nm excitation with enhanced σ3 of 1.85×10(-80)  cm(6)  s(2)  photon(-2) and σ3 η3 of 3.33×10(-81)  cm(6)  s(2)  photon(-2) . The application of this probe is demonstrated for ratiometric 3P imaging of Zn(2+) in vitro using HuH-7 cell lines. Furthermore, the Zn(2+) concentration in rat hippocampal slices was imaged at 1150 nm excitation after incubation with GMP, illustrating its potential as a 3P ratiometric probe for deep tissue Zn(2+) ion imaging. PMID:26991763

  5. The effects of alkaline earth metal ions and halogen ions on the chromium oxide activities in alkaline earth metal oxide-halide-Cr2O3 system fluxes

    NASA Astrophysics Data System (ADS)

    Li, Lian-Fu; Jiang, Mao-Fa; Wang, Wen-Zhong; Chen, Zhao-Ping

    2000-06-01

    The solid electrolyte cell — Mo|Cr + Cr2O3‖ZrO2(MgO)‖{Cu-Cr}alloy + (Cr2O3)fluxes|Mo+ is used at 1673 K to determine Cr2O3 activities in MO-MX 2-Cr2O3 (M = Ca2+, Ba2-, X = F- or Cl-) ternary fluxes, which are in equilibrium with the copper-chromium binary alloy. The ternary isothermal phase diagrams of CaO-CaF2-Cr2O3 and BaO-BaCl2-Cr2O3 system fluxes are inferred on the basis of the experimental results and binary phase diagrams. The results indicate that Cr2O3 activities in all fluxes always decrease with the increase of the X MO /X MX2 ratio. Partial replacement of BaO in BaO-BaF2-Cr2O3 fluxes by CaO is acceptable for economy and efficiency considerations. At the same time, partial substitution of BaO for CaO in CaO-CaF2-Cr2O3 fluxes is advantageous for phosphorus removal and chromium retention as a result of the increased Cr2O3 activities, increased basicities, and widening of the liquid zones. Compared to those in BaO-BaF2-Cr2O3 fluxes, Cr2O3 activities in CaO-CaF2-Cr2O3 fluxes approximately follow the same curve as the former, although the position and the width of the liquid zones are considerably different, and activities in BaO-BaCl2-Cr2O3 fluxes are higher at the lower Cr2O3 content, or vice versa. The activity coefficients of Cr2O3 in the fluxes decrease with the increase of the X MO /X MX 2 ratios.

  6. Determination of CFTR chloride channel activity and pharmacology using radiotracer flux methods.

    PubMed

    Norez, Caroline; Heda, Ghanshyam D; Jensen, Timothy; Kogan, Ilana; Hughes, Lauren K; Auzanneau, Céline; Dérand, Renaud; Bulteau-Pignoux, Laurence; Li, Canhui; Ramjeesingh, Mohabir; Li, Hongyu; Sheppard, David N; Bear, Christine E; Riordan, John R; Becq, Frédéric

    2004-08-01

    Flux studies using either radioisotopes or ion-selective electrodes are a convenient method to assay the function of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel. Here, we described three different protocols to study the properties, regulation and pharmacology of the CFTR Cl- channel in populations of cells and artificial vesicles. These techniques are widely used to evaluate the function of wild-type and mutant CFTR prior to detailed analyses using the patch-clamp technique. Moreover, they have proved especially valuable in the search for new drugs to treat cystic fibrosis. PMID:15463942

  7. High heat flux test of a HIP-bonded first wall panel of reduced activation ferritic steel F-82H

    NASA Astrophysics Data System (ADS)

    Hatano, T.; Suzuki, S.; Yokoyama, K.; Kuroda, T.; Enoeda, M.

    2000-12-01

    Reduced activation ferritic steel F-82H is a primary candidate structural material of DEMO fusion reactors. In fabrication technology, development of the DEMO blanket in JAERI, a hot isostatic pressing (HIP) bonding method, especially for the first wall structure with built-in cooling tubes has been proposed. A HIP-bonded F-82H first wall panel was successfully fabricated with selected manufacturing parameters. A high heat flux test of the HIP-bonded F-82H first wall panel has been performed to examine the thermo-mechanical performance of the panel including the integrity of the HIP-bonded interfaces and the fatigue behavior. A maximum heat flux of 2.7 MW/m2 was applied to accelerate the fatigue test up to 5000 cycles in test blanket inserted ITER. The maximum temperature of the panel was ∼450°C under this heat flux. Through this test campaign, no damage such as cracks was observed on the surface of the panel, and no degradation in heat removal performance was observed either from the temperature responses. The thermal fatigue lifetime of the panel was found to be longer than the fatigue data obtained by mechanical testing.

  8. The Effects of Severe Hypoxia on Glycolytic Flux and Enzyme Activity in a Model of Solid Tumors.

    PubMed

    Smith, Hannah; Board, Mary; Pellagatti, Andrea; Turley, Helen; Boultwood, Jacqueline; Callaghan, Richard

    2016-08-01

    Solid tumors contend with, and adapt to, a hostile micro-environment that includes limited availability of nutrient fuels and oxygen. The presence of hypoxia (O2 <5%) stabilizes the transcription factor Hif1 and results in numerous cellular adaptations including increased flux of glucose through glycolysis. Increasingly, more sophisticated analysis of tumor oxygenation has revealed large gradients of oxygen tension and significant regions under severe hypoxia (O2 ∼0.1%). The present investigation has demonstrated a significant increase in the glycolytic flux rate when tumor spheroids were exposed to 0.1% O2 . The severe hypoxia was associated with uniform pimonidazole adduct formation and elevated levels of Hif1α and c-Myc. This resulted in elevated expression of GLUT and MCT transporters, in addition to increased activity of PFK1 in comparison to that observed in normoxia. However, the protein expression and enzymatic capacity of HK2, G6PDH, PK, and LDH were all reduced by severe hypoxia. Clearly, the effects of exposure to severe hypoxia lead to a significantly abridged Hif1 response, yet one still able to elevate glycolytic flux and prevent loss of intermediates to anabolism. J. Cell. Biochem. 117: 1890-1901, 2016. © 2016 Wiley Periodicals, Inc. PMID:26755257

  9. Coupling High-Energy Radiography And Photon Activation Analysis (PAA) To Optimize The Characterization Of Nuclear Waste Packages

    SciTech Connect

    Carrel, F.; Agelou, M.; Gmar, M.; Laine, F.; Lamotte, T.; Lazaro, D.; Poumarede, B.; Rattoni, B.

    2009-12-02

    Radiological characterization of nuclear waste packages is an industrial issue in order to select the best mode of storage. The alpha-activity, mainly due to the presence of actinides ({sup 235}U, {sup 238}U, {sup 239}Pu,...) inside the package, is one of the most important parameter to assess during the characterization. Photon Activation Analysis (PAA) is a non-destructive active method (NDA method) based on the photofission process and on the detection of delayed particles (neutrons and gammas). This technique is well-adapted to the characterization of large concrete waste packages. However, PAA methods often require a simulation step which is necessary to analyze experimental results and to quantify the global mass of actinides. The weak point of this approach is that characteristics of the package are often not well-known, these latter having a huge impact on the final simulation result. High-energy radiography, based on the use of a linear electron accelerator (LINAC), allows to visualize the content of the package and is also a performing way to tune simulation models and to optimize the characterization process by PAA. In this article, we present high-energy radiography results obtained for two different large concrete waste packages in the SAPHIR facility (Active Photon and Irradiation System). This facility is dedicated to PAA study and development and setup for a decade in CEA Saclay. We also discuss possibilities offered by the coupling between high-energy radiography and PAA techniques.

  10. Photonic Component Qualification and Implementation Activities at NASA Goddard Space Flight Center

    NASA Technical Reports Server (NTRS)

    Ott, Melanie N.; Jin, Xiaodan Linda; Chuska, Richard F.; LaRocca, Frank V.; MacMurphy, Shawn L.; Matuszeski, Adam J.; Zellar, Ronald S.; Friedberg, Patricia R.; Malenab, Mary C.

    2006-01-01

    The photonics group in Code 562 at NASA Goddard Space Flight Center supports a variety of space flight programs at NASA including the: International Space Station (ISS), Shuttle Return to Flight Mission, Lunar Reconnaissance Orbiter (LRO), Express Logistics Carrier, and the NASA Electronic Parts and Packaging Program (NEPP). Through research, development, and testing of the photonic systems to support these missions much information has been gathered on practical implementations for space environments. Presented here are the highlights and lessons learned as a result of striving to satisfy the project requirements for high performance and reliable commercial optical fiber components for space flight systems. The approach of how to qualify optical fiber components for harsh environmental conditions, the physics of failure and development lessons learned will be discussed.

  11. In vivo imaging of activated microglia in a mouse model of focal cerebral ischemia by two-photon microscopy.

    PubMed

    Bok, Seoyeon; Wang, Taejun; Lee, Chan-Ju; Jeon, Seong-Uk; Kim, Young-Eun; Kim, Jeongwoo; Hong, Beom-Ju; Yoon, Calvin Jinse; Kim, Sungjee; Lee, Seung-Hoon; Kim, Hak Jae; Kim, Il Han; Kim, Ki Hean; Ahn, G-One

    2015-09-01

    Microglia are brain resident macrophages rapidly responding to various stimuli to exert appropriate inflammatory responses. Although they have recently been exploited as an attractive candidate for imaging neuroinflammation, it is still difficult to visualize them at the cellular and molecular levels. Here we imaged activated microglia by establishing intracranial window chamber (ICW) in a mouse model of focal cerebral ischemia by using two-photon microscopy (TPM), in vivo. Intravenous injection of fluorescent antibodies allowed us to detect significantly elevated levels of Iba-1 and CD68 positive activated microglia in the ipsilateral compared to the contralateral side of the infarct. We further observed that indomethacin, a non-steroidal anti-inflammatory drug significantly attenuated CD68-positive microglial activation in ICW, which was further confirmed by qRT-PCR biochemical analyses. In conclusion, we believe that in vivo TPM imaging of ICW would be a useful tool to screen for therapeutic interventions lowering microglial activation hence neuroinflammation. PMID:26417502

  12. In vivo imaging of activated microglia in a mouse model of focal cerebral ischemia by two-photon microscopy

    PubMed Central

    Bok, Seoyeon; Wang, Taejun; Lee, Chan-Ju; Jeon, Seong-Uk; Kim, Young-Eun; Kim, Jeongwoo; Hong, Beom-Ju; Yoon, Calvin Jinse; Kim, Sungjee; Lee, Seung-Hoon; Kim, Hak Jae; Kim, Il Han; Kim, Ki Hean; Ahn, G-One

    2015-01-01

    Microglia are brain resident macrophages rapidly responding to various stimuli to exert appropriate inflammatory responses. Although they have recently been exploited as an attractive candidate for imaging neuroinflammation, it is still difficult to visualize them at the cellular and molecular levels. Here we imaged activated microglia by establishing intracranial window chamber (ICW) in a mouse model of focal cerebral ischemia by using two-photon microscopy (TPM), in vivo. Intravenous injection of fluorescent antibodies allowed us to detect significantly elevated levels of Iba-1 and CD68 positive activated microglia in the ipsilateral compared to the contralateral side of the infarct. We further observed that indomethacin, a non-steroidal anti-inflammatory drug significantly attenuated CD68-positive microglial activation in ICW, which was further confirmed by qRT-PCR biochemical analyses. In conclusion, we believe that in vivo TPM imaging of ICW would be a useful tool to screen for therapeutic interventions lowering microglial activation hence neuroinflammation. PMID:26417502

  13. Validation of the MCNP computational model for neutron flux distribution with the neutron activation analysis measurement

    NASA Astrophysics Data System (ADS)

    Tiyapun, K.; Chimtin, M.; Munsorn, S.; Somchit, S.

    2015-05-01

    The objective of this work is to demonstrate the method for validating the predication of the calculation methods for neutron flux distribution in the irradiation tubes of TRIGA research reactor (TRR-1/M1) using the MCNP computer code model. The reaction rate using in the experiment includes 27Al(n, α)24Na and 197Au(n, γ)198Au reactions. Aluminium (99.9 wt%) and gold (0.1 wt%) foils and the gold foils covered with cadmium were irradiated in 9 locations in the core referred to as CT, C8, C12, F3, F12, F22, F29, G5, and G33. The experimental results were compared to the calculations performed using MCNP which consisted of the detailed geometrical model of the reactor core. The results from the experimental and calculated normalized reaction rates in the reactor core are in good agreement for both reactions showing that the material and geometrical properties of the reactor core are modelled very well. The results indicated that the difference between the experimental measurements and the calculation of the reactor core using the MCNP geometrical model was below 10%. In conclusion the MCNP computational model which was used to calculate the neutron flux and reaction rate distribution in the reactor core can be used for others reactor core parameters including neutron spectra calculation, dose rate calculation, power peaking factors calculation and optimization of research reactor utilization in the future with the confidence in the accuracy and reliability of the calculation.

  14. Mapping fluxes of radicals from the combination of electrochemical activation and optical microscopy.

    PubMed

    Munteanu, Sorin; Roger, Jean Paul; Fedala, Yasmina; Amiot, Fabien; Combellas, Catherine; Tessier, Gilles; Kanoufi, Frédéric

    2013-01-01

    The coating of gold (Au) electrode surfaces with nitrophenyl (NP) layers is studied by combination of electrochemical actuation and optical detection. The electrochemical actuation of the reduction of the nitrobenzenediazonium (NBD) precursor is used to generate NP radicals and therefore initiate the electrografting. The electrografting process is followed in situ and in real time by light reflectivity microscopy imaging, allowing for spatio-temporal imaging with sub-micrometer lateral resolution and sub-nanometer thickness sensitivity of the local growth of a transparent organic coating onto a reflecting Au electrode. The interest of the electrochemical actuation resides in its ability to finely control the grafting rate of the NP layer through the electrode potential. Coupling the electrochemical actuation with microscopic imaging of the electrode surface allows quantitative estimates of the local grafting rates and subsequently a real time and in situ mapping of the reacting fluxes of NP radicals on the surface. Over the 2 orders of magnitude range of grafting rates (from 0.04 to 4 nm s(-1)), it is demonstrated that the edge of Au electrodes are grafted -1.3 times more quickly than their centre, illustrating the manifestation of edge-effects on flux distribution at an electrode. A model is proposed to explain the observed edge-effect, it relies on the short lifetime of the intermediate NP radical species. PMID:24466667

  15. Photons to axion-like particles conversion in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Tavecchio, Fabrizio; Roncadelli, Marco; Galanti, Giorgio

    2015-05-01

    The idea that photons can convert to axion-like particles (ALPs) γ → a in or around an AGN and reconvert back to photons a → γ in the Milky Way magnetic field has been put forward in 2008 and has recently attracted growing interest. Yet, so far nobody has estimated the conversion probability γ → a as carefully as allowed by present-day knowledge. Our aim is to fill this gap. We first remark that AGN which can be detected above 100 GeV are blazars, namely AGN with jets, with one of them pointing towards us. Moreover, blazars fall into two well defined classes: BL Lac objects (BL Lacs) and Flat Spectrum Radio Quasars (FSRQs), with drastically different properties. In this Letter we report a preliminary evaluation of the γ → a conversion probability inside these two classes of blazars. Our findings are surprising. Indeed, while in the case of BL Lacs the conversion probability turns out to be totally unpredictable due to the strong dependence on the values of the somewhat uncertain position of the emission region along the jet and strength of the magnetic field therein, for FSRQs we are able to make a clear-cut prediction. Our results are of paramount importance in view of the planned very-high-energy photon detectors like the CTA, HAWK, GAMMA-400 and HISCORE.

  16. High-flux white neutron source based on p(35)-Be reactions for activation experiments at NPI

    NASA Astrophysics Data System (ADS)

    Stefanik, Milan; Bem, Pavel; Gotz, Miloslav; Katovsky, Karel; Majerle, Mitja; Novak, Jan; Simeckova, Eva

    2014-11-01

    The concept of International Fusion Material Irradiation Facility (IFMIF) is based on the d(40)-Li neutron source reaction which produces the white neutron spectrum with mean energy of 14 MeV, energy range with high intensity of neutron beam up to 35 MeV, and weak tail up to 55 MeV. At the Nuclear Physics Institute of the ASCR in Rez near Prague, the source reaction of p+Be was investigated for proton energy of 35 MeV and beam current intensity of 9.2 μA. The produced white spectrum with neutron flux up to 1011 cm-2 s-1 was determined by the dosimetry foils activation technique at two sample-to-target distances and validated against the Monte Carlo predictions. The neutron field of these high-flux p(35)-Be white neutron source represents the useful tool for experimental simulation of the spectrum of the IFMIF facility, validating the activation cross-section data in the energy range relevant to the IFMIF, studying the radiation hardness of electronics against the high-energy neutron fields, and various activation experiments.

  17. [Effects of brackish water irrigation on soil enzyme activity, soil CO2 flux and organic matter decomposition].

    PubMed

    Zhang, Qian-qian; Wang, Fei; Liu, Tao; Chu, Gui-xin

    2015-09-01

    Brackish water irrigation utilization is an important way to alleviate water resource shortage in arid region. A field-plot experiment was set up to study the impact of the salinity level (0.31, 3.0 or 5.0 g · L(-1) NaCl) of irrigated water on activities of soil catalase, invertase, β-glucosidase, cellulase and polyphenoloxidase in drip irrigation condition, and the responses of soil CO2 flux and organic matter decomposition were also determined by soil carbon dioxide flux instrument (LI-8100) and nylon net bag method. The results showed that in contrast with fresh water irrigation treatment (CK), the activities of invertase, β-glucosidase and cellulase in the brackish water (3.0 g · L(-1)) irrigation treatment declined by 31.7%-32.4%, 29.7%-31.6%, 20.8%-24.3%, respectively, while soil polyphenoloxidase activity was obviously enhanced with increasing the salinity level of irrigated water. Compared to CK, polyphenoloxidase activity increased by 2.4% and 20.5%, respectively, in the brackish water and saline water irrigation treatments. Both soil microbial biomass carbon and microbial quotient decreased with increasing the salinity level, whereas, microbial metabolic quotient showed an increasing tendency with increasing the salinity level. Soil CO2 fluxes in the different treatments were in the order of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) ≥ saline water irrigation (5.0 g · L(-1)). Moreover, CO2 flux from plastic film mulched soil was always much higher than that from no plastic film mulched soil, regardless the salinity of irrigated water. Compared with CK, soil CO2 fluxes in the saline water and brackish water treatments decreased by 29.8% and 28.2% respectively in the boll opening period. The decomposition of either cotton straw or alfalfa straw in the different treatments was in the sequence of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) > saline water treatment (5.0 g · L(-1)). The organic matter

  18. Demonstration of photon–photon resonance peak enhancement by waveguide configuration modification on active multimode interferometer laser diode

    NASA Astrophysics Data System (ADS)

    Kitano, Takuya; Nasir Uddin, Mohammad; Hong, Bingzhou; Tajima, Akio; Jiang, Haisong; Hamamoto, Kiichi

    2016-08-01

    The recent rapid growth of data traffic is leading to high-speed communication for local areas, such as the fiber-to-the-home service. A semiconductor laser is used for such a purpose; however, there is the difficulty that an even higher frequency response occurs in only carrier-photon resonance. For this reason, it is effective to use a second resonance, such as a photon–photon resonance (PPR), for enhancing the frequency response, and the active multimode interferometer laser diode (active-MMI LD) is one of the candidates for achieving a high PPR frequency. In order to obtain an even higher PPR frequency, we have investigated the control scheme of enhancing PPR. In this work, we compared two types of active-MMI waveguide structures to confirm the scheme. As a result, a 3.8 GHz enhancement of the PPR peak, resulting in a 3 dB lower frequency response of 17 GHz, has been successfully achieved by waveguide geometry modification.

  19. Genetically Encoded Optochemical Probes for Simultaneous Fluorescence Reporting and Light Activation of Protein Function with Two-Photon Excitation

    PubMed Central

    2014-01-01

    The site-specific incorporation of three new coumarin lysine analogues into proteins was achieved in bacterial and mammalian cells using an engineered pyrrolysyl-tRNA synthetase system. The genetically encoded coumarin lysines were successfully applied as fluorescent cellular probes for protein localization and for the optical activation of protein function. As a proof-of-principle, photoregulation of firefly luciferase was achieved in live cells by caging a key lysine residue, and excellent OFF to ON light-switching ratios were observed. Furthermore, two-photon and single-photon optochemical control of EGFP maturation was demonstrated, enabling the use of different, potentially orthogonal excitation wavelengths (365, 405, and 760 nm) for the sequential activation of protein function in live cells. These results demonstrate that coumarin lysines are a new and valuable class of optical probes that can be used for the investigation and regulation of protein structure, dynamics, function, and localization in live cells. The small size of coumarin, the site-specific incorporation, the application as both a light-activated caging group and as a fluorescent probe, and the broad range of excitation wavelengths are advantageous over other genetically encoded photocontrol systems and provide a precise and multifunctional tool for cellular biology. PMID:25341086

  20. Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption

    PubMed Central

    Jiang, Chaowei; Wu, S. T.; Feng, Xuesheng; Hu, Qiang

    2016-01-01

    Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling. PMID:27181846

  1. Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption.

    PubMed

    Jiang, Chaowei; Wu, S T; Feng, Xuesheng; Hu, Qiang

    2016-01-01

    Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling. PMID:27181846

  2. Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption

    NASA Astrophysics Data System (ADS)

    Jiang, Chaowei; Wu, S. T.; Feng, Xuesheng; Hu, Qiang

    2016-05-01

    Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling.

  3. Thermally activated flux creep and critical current densities in high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Matsushita, Teruo

    The effect of flux creep is discussed for projected strongly pinned oxide superconductors. It is determined, that if a superconducting wire with a critical current density higher than 10-billion A/sq m at 77 K and 5 T can be produced, the wire will be able to be applied to equipment at high fields; nonzero critical density will be obtained even at 77 K and high fields. The decay of persistent current is expected to be noticeable even in such strongly pinned superconductors, when those are used at 77 K. Although this will be managed in power equipment by lowering the operating current; variation in the magnetic field due to the variation in the current distribution inside superconducting wires appears to be unavoidable. It is suggested that an effort should be made to reduce the variation by reducing the diameter of the superconducting filaments.

  4. Photon beam position monitor

    DOEpatents

    Kuzay, Tuncer M.; Shu, Deming

    1995-01-01

    A photon beam position monitor for use in the front end of a beamline of a high heat flux and high energy photon source such as a synchrotron radiation storage ring detects and measures the position and, when a pair of such monitors are used in tandem, the slope of a photon beam emanating from an insertion device such as a wiggler or an undulator inserted in the straight sections of the ring. The photon beam position monitor includes a plurality of spaced blades for precisely locating the photon beam, with each blade comprised of chemical vapor deposition (CVD) diamond with an outer metal coating of a photon sensitive metal such as tungsten, molybdenum, etc., which combination emits electrons when a high energy photon beam is incident upon the blade. Two such monitors are contemplated for use in the front end of the beamline, with the two monitors having vertically and horizontally offset detector blades to avoid blade "shadowing". Provision is made for aligning the detector blades with the photon beam and limiting detector blade temperature during operation.

  5. Photon beam position monitor

    DOEpatents

    Kuzay, T.M.; Shu, D.

    1995-02-07

    A photon beam position monitor is disclosed for use in the front end of a beamline of a high heat flux and high energy photon source such as a synchrotron radiation storage ring detects and measures the position and, when a pair of such monitors are used in tandem, the slope of a photon beam emanating from an insertion device such as a wiggler or an undulator inserted in the straight sections of the ring. The photon beam position monitor includes a plurality of spaced blades for precisely locating the photon beam, with each blade comprised of chemical vapor deposition (CVD) diamond with an outer metal coating of a photon sensitive metal such as tungsten, molybdenum, etc., which combination emits electrons when a high energy photon beam is incident upon the blade. Two such monitors are contemplated for use in the front end of the beamline, with the two monitors having vertically and horizontally offset detector blades to avoid blade ''shadowing''. Provision is made for aligning the detector blades with the photon beam and limiting detector blade temperature during operation. 18 figs.

  6. Comparison Between the Integrated Ion Outflow Fluxes from the North and South Hemispheres Under Sustained Geomagnetically Active Conditions

    NASA Astrophysics Data System (ADS)

    Barakat, A. R.; Schunk, R. W.; Eccles, J. V.

    2015-12-01

    The Generalized Polar Wind (GPW) model is used to simulate the polar ionosphere during the September/October 2002 storm. The simulation period is near equinox when the north and south hemispheres are similarly exposed to solar radiation. We present a model simulation of the eight day period 2002 September 27 (DOY 270) through October 4 (DOY 277). The first three days have relatively quiet magnetic activity as indicated by low Kp values. The fourth day (270) is moderately active, and over the last four days (1-4 October) a strong magnetic storm takes place where Kp reaches values greater than 7 and Dst reaches values below -170. The GPW model was utilized to simulate the behavior of the plasma outflow from both hemispheres over the eight-day period. This storm differs from idealized storm that was the subject of a number of previous studies by Schunk and coauthors in the following ways. First, the interplanetary magnetic field changed in a complex manner in contrast to the previous studies where the IMF remained in the negative z direction. Second, Kp variation is more complex than the previous investigations. Third, the simulation period of eight days is much longer than the previous simulations (less than 18 hours). Finally, both hemispheres are considered, in contrast to previous simulations that investigated the northern hemisphere only. This investigation focuses on the variation of the integrated flux (from the poles to 45 degrees of latitude). We discuss how the integrated flux depends on the ion species (O+ vs. H+) and on the hemisphere (north vs. south). We also investigated the integrated flux dependence on the physical conditions, e.g., Kp, Dst universal time, etc. This statistical approach helped extract important simple conclusions from the complex behavior of the ion outflow during real a storm.

  7. Ultrafast superconducting single-photon detector with a reduced active area coupled to a tapered lensed single-mode fiber

    NASA Astrophysics Data System (ADS)

    Sidorova, Maria V.; Divochiy, Alexander V.; Vakhtomin, Yury B.; Smirnov, Konstantin V.

    2015-01-01

    This paper presents an ultrafast niobium nitride (NbN) superconducting single-photon detector (SSPD) with an active area of 3×3 μm2 that offers better timing performance metrics than the previous SSPD with an active area of 7×7 μm2. The improved SSPD demonstrates a record timing jitter (<25 ps), an ultrashort recovery time (<2 ns), an extremely low dark count rate, and a high detection efficiency in a wide spectral range from visible part to near infrared. The record parameters were obtained due to the development of a new technique providing effective optical coupling between a detector with a reduced active area and a standard single-mode telecommunication fiber. The advantages of the new approach are experimentally confirmed by taking electro-optical measurements.

  8. Photon Activation Analysis Of Light Elements Using 'Non-Gamma' Radiation Spectroscopy - The Instrumental Determination Of Phosphorus

    SciTech Connect

    Segebade, Christian; Goerner, Wolf

    2011-06-01

    Unlike metal determinations the analysis of light elements (e.g., carbon, oxygen, phosphorus) is frequently problematic, in particular if analysed instrumentally. In photon activation analysis (PAA) the respective activation products do not emit gamma radiation in the most cases. Usually, annihilation quanta counting and subsequent decay curve analysis have been used for determinations of C, N, O, and F. However, radiochemical separation of the respective radioisotopes mostly is indispensable. For several reasons, some of the light elements cannot be analysed following this procedure, e.g. phosphorus. In this contribution the instrumental PAA of phosphorus in organic matrix by activation with bremsstrahlung of an electron linear accelerator and subsequent beta spectroscopy is described. The accuracy of the results was excellent as obtained by analysis of a BCR Reference Material.

  9. Photon-photon collisions

    SciTech Connect

    Brodsky, S.J.

    1985-01-01

    The study of photon-photon collisions has progressed enormously, stimulated by new data and new calculational tools for QCD. In the future we can expect precise determinations of ..cap alpha../sub s/ and ..lambda../sup ms/ from the ..gamma..*..gamma.. ..-->.. ..pi../sup 0/ form factor and the photon structure function, as well as detailed checks of QCD, determination of the shape of the hadron distribution amplitudes from ..gamma gamma.. ..-->.. H anti H, reconstruction of sigma/sub ..gamma gamma../ from exclusive channels at low W/sub ..gamma gamma../, definitive studies of high p/sub T/ hadron and jet production, and studies of threshold production of charmed systems. Photon-photon collisions, along with radiative decays of the psi and UPSILON, are ideal for the study of multiquark and gluonic resonances. We have emphasized the potential for resonance formation near threshold in virtually every hadronic exclusive channel, including heavy quark states c anti c c anti c, c anti c u anti u, etc. At higher energies SLC, LEP, ...) parity-violating electroweak effects and Higgs production due to equivalent Z/sup 0/ and W/sup + -/ beams from e ..-->.. eZ/sup 0/ and e ..-->.. nu W will become important. 44 references.

  10. Superfine powdered activated carbon (S-PAC) coatings on microfiltration membranes: Effects of milling time on contaminant removal and flux.

    PubMed

    Amaral, Pauline; Partlan, Erin; Li, Mengfei; Lapolli, Flavio; Mefford, O Thompson; Karanfil, Tanju; Ladner, David A

    2016-09-01

    In microfiltration processes for drinking water treatment, one method of removing trace contaminants is to add powdered activated carbon (PAC). Recently, a version of PAC called superfine PAC (S-PAC) has been under development. S-PAC has a smaller particle size and thus faster adsorption kinetics than conventionally sized PAC. Membrane coating performance of various S-PAC samples was evaluated by measuring adsorption of atrazine, a model micropollutant. S-PACs were created in-house from PACs of three different materials: coal, wood, and coconut shell. Milling time was varied to produce S-PACs pulverized with different amounts of energy. These had different particles sizes, but other properties (e.g. oxygen content), also differed. In pure water the coal based S-PACs showed superior atrazine adsorption; all milled carbons had over 90% removal while the PAC had only 45% removal. With addition of calcium and/or NOM, removal rates decreased, but milled carbons still removed more atrazine than PAC. Oxygen content and specific external surface area (both of which increased with longer milling times) were the most significant predictors of atrazine removal. S-PAC coatings resulted in loss of filtration flux compared to an uncoated membrane and smaller particles caused more flux decline than larger particles; however, the data suggest that NOM fouling is still more of a concern than S-PAC fouling. The addition of calcium improved the flux, especially for the longer-milled carbons. Overall the data show that when milling S-PAC with different levels of energy there is a tradeoff: smaller particles adsorb contaminants better, but cause greater flux decline. Fortunately, an acceptable balance may be possible; for example, in these experiments the coal-based S-PAC after 30 min of milling achieved a fairly high atrazine removal (overall 80%) with a fairly low flux reduction (under 30%) even in the presence of NOM. This suggests that relatively short duration (low energy

  11. Activity-dependent branching ratios in stocks, solar x-ray flux, and the Bak-Tang-Wiesenfeld sandpile model

    NASA Astrophysics Data System (ADS)

    Martin, Elliot; Shreim, Amer; Paczuski, Maya

    2010-01-01

    We define an activity-dependent branching ratio that allows comparison of different time series Xt . The branching ratio bx is defined as bx=E[ξx/x] . The random variable ξx is the value of the next signal given that the previous one is equal to x , so ξx={Xt+1∣Xt=x} . If bx>1 , the process is on average supercritical when the signal is equal to x , while if bx<1 , it is subcritical. For stock prices we find bx=1 within statistical uncertainty, for all x , consistent with an “efficient market hypothesis.” For stock volumes, solar x-ray flux intensities, and the Bak-Tang-Wiesenfeld (BTW) sandpile model, bx is supercritical for small values of activity and subcritical for the largest ones, indicating a tendency to return to a typical value. For stock volumes this tendency has an approximate power-law behavior. For solar x-ray flux and the BTW model, there is a broad regime of activity where bx≃1 , which we interpret as an indicator of critical behavior. This is true despite different underlying probability distributions for Xt and for ξx . For the BTW model the distribution of ξx is Gaussian, for x sufficiently larger than 1, and its variance grows linearly with x . Hence, the activity in the BTW model obeys a central limit theorem when sampling over past histories. The broad region of activity where bx is close to one disappears once bulk dissipation is introduced in the BTW model—supporting our hypothesis that it is an indicator of criticality.

  12. Activity-dependent branching ratios in stocks, solar x-ray flux, and the Bak-Tang-Wiesenfeld sandpile model.

    PubMed

    Martin, Elliot; Shreim, Amer; Paczuski, Maya

    2010-01-01

    We define an activity-dependent branching ratio that allows comparison of different time series X(t). The branching ratio b(x) is defined as b(x)=E[xi(x)/x]. The random variable xi(x) is the value of the next signal given that the previous one is equal to x, so xi(x)=[X(t+1) | X(t)=x]. If b(x)>1, the process is on average supercritical when the signal is equal to x, while if b(x)<1, it is subcritical. For stock prices we find b(x)=1 within statistical uncertainty, for all x, consistent with an "efficient market hypothesis." For stock volumes, solar x-ray flux intensities, and the Bak-Tang-Wiesenfeld (BTW) sandpile model, b(x) is supercritical for small values of activity and subcritical for the largest ones, indicating a tendency to return to a typical value. For stock volumes this tendency has an approximate power-law behavior. For solar x-ray flux and the BTW model, there is a broad regime of activity where b(x) approximately equal 1, which we interpret as an indicator of critical behavior. This is true despite different underlying probability distributions for X(t) and for xi(x). For the BTW model the distribution of xi(x) is Gaussian, for x sufficiently larger than 1, and its variance grows linearly with x. Hence, the activity in the BTW model obeys a central limit theorem when sampling over past histories. The broad region of activity where b(x) is close to one disappears once bulk dissipation is introduced in the BTW model-supporting our hypothesis that it is an indicator of criticality. PMID:20365434

  13. Demonstration of active feedforward one-way quantum computing with photon-matter hyperentanglement

    NASA Astrophysics Data System (ADS)

    Xu, Xiao-Fan; Bao, Xiao-Hui; Pan, Jian-Wei

    2012-11-01

    We report an optical one-way quantum computing experiment with stationary quantum memory involved. First we create a hybrid four-qubit cluster state with two qubits propagating as photons and the other two stationary and stored in a laser-cooled atomic-ensemble quantum memory, and characterize it with entanglement witnesses and quantum state tomography. Then, by making use of this cluster state and fast operations of electro-optic modulators, we realize memory-assisted feedforward operations and demonstrate deterministic single-qubit rotation as an example.

  14. Manufacturing and thermomechanical testing of actively cooled all beryllium high heat flux test pieces

    SciTech Connect

    Vasiliev, N.N.; Sokolov, Yu.A.; Shatalov, G.E.

    1995-09-01

    One of the problems affiliated to ITER high heat flux elements development is a problem of interface of beryllium protection with heat sink routinely made of copper alloys. To get rid of this problem all beryllium elements could be used as heat receivers in places of enhanced thermal loads. In accordance with this objectives four beryllium test pieces of two types have been manufactured in {open_quotes}Institute of Beryllium{close_quotes} for succeeding thermomechanical testing. Two of them were manufactured in accordance with JET team design; they are round {open_quotes}hypervapotron type{close_quotes} test pieces. Another two ones are rectangular test sections with a twisted tape installed inside of the circular channel. Preliminary stress-strain analysis have been performed for both type of the test pieces. Hypervapotrons have been shipped to JET where they were tested on JET test bed. Thermomechanical testing of pieces of the type of {open_quotes}swirl tape inside of tube{close_quotes} have been performed on Kurchatov Institute test bed. Chosen beryllium grade properties, some details of manufacturing, results of preliminary stress-strain analysis and thermomechanical testing of the test pieces {open_quotes}swirl tape inside of tube{close_quotes} type are given in this report.

  15. Multiple measurement of the coupling between benthic carbon fluxes and bioturbation activity during the spring bloom''

    SciTech Connect

    Aller, R.C.; Aller, J.J.; Cochran, J.K.; Lee, C.

    1992-01-01

    In accordance with the research plan outlined in our original proposal, we began monitoring indicators of plankton production (Chl-a, cell counts) in surface waters of Long Island Sound from the Port Jefferson / Bridgeport Ferry on Dec. 3, 1992. In contrast to past years no dramatic bloom has occurred to date although a significant pattern of increasing chl-a began during the first week of April. We anticipate that the bloom wig be complete by mid to late April. This has been a particularly cold year based on comparison of 1993 bottom water temperatures and previously reported patterns from LIS, possibly reflecting climatic conditions which delayed the bloom. Typical sampling includes: surface and bottom water sampling for suspended matter, cell counts, chlorophyll-a, nutrients; triplicate box cores for macro-, meio-, and microfauna analysis; subcores for O[sub 2] microelectrode profiles; box core for radiochemical analyses ([sup 234]Th, [sup 7]Be); box core subcores for benthic fluxes under aerated and nonaerated conditions (O[sub 2], [Sigma]N, Mn[sup ++], [Sigma]CO[sub 2]); Br[sup [minus

  16. Role of a mitogen-activated protein kinase cascade in ion flux-mediated turgor regulation in fungi.

    PubMed

    Lew, Roger R; Levina, Natalia N; Shabala, Lana; Anderca, Marinela I; Shabala, Sergey N

    2006-03-01

    Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca(2+) influx and the sustained hyperpolarization is due to H(+) efflux by activation of the plasma membrane H(+)-ATPase. Protein synthesis is not required for H(+)-ATPase activation. Net K(+) and Cl(-) uptake occurs at the same time as turgor recovery. The magnitude of the ion uptake is more than sufficient to account for the osmotic gradients required for turgor to return to its original level. Two osmotic mutants, os-1 and os-2, homologs of a two-component histidine kinase sensor and the yeast high osmotic glycerol mitogen-activated protein (MAP) kinase, respectively, have lower turgor than the wild type and do not exhibit the sustained hyperpolarization after hyperosmotic treatment. The os-1 mutant does not exhibit all of the wild-type turgor-adaptive ion fluxes (Cl(-) uptake increases, but net K(+) flux barely changes and net H(+) efflux declines) (os-2 was not examined). Both os mutants are able to regulate turgor but at a lower level than the wild type. Our results demonstrate that a MAP kinase cascade regulates ion transport, activation of the H(+)-ATPase, and net K(+) and Cl(-) uptake during turgor regulation. Other pathways regulating turgor must also exist. PMID:16524903

  17. Role of a Mitogen-Activated Protein Kinase Cascade in Ion Flux-Mediated Turgor Regulation in Fungi

    PubMed Central

    Lew, Roger R.; Levina, Natalia N.; Shabala, Lana; Anderca, Marinela I.; Shabala, Sergey N.

    2006-01-01

    Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca2+ influx and the sustained hyperpolarization is due to H+ efflux by activation of the plasma membrane H+-ATPase. Protein synthesis is not required for H+-ATPase activation. Net K+ and Cl− uptake occurs at the same time as turgor recovery. The magnitude of the ion uptake is more than sufficient to account for the osmotic gradients required for turgor to return to its original level. Two osmotic mutants, os-1 and os-2, homologs of a two-component histidine kinase sensor and the yeast high osmotic glycerol mitogen-activated protein (MAP) kinase, respectively, have lower turgor than the wild type and do not exhibit the sustained hyperpolarization after hyperosmotic treatment. The os-1 mutant does not exhibit all of the wild-type turgor-adaptive ion fluxes (Cl− uptake increases, but net K+ flux barely changes and net H+ efflux declines) (os-2 was not examined). Both os mutants are able to regulate turgor but at a lower level than the wild type. Our results demonstrate that a MAP kinase cascade regulates ion transport, activation of the H+-ATPase, and net K+ and Cl− uptake during turgor regulation. Other pathways regulating turgor must also exist. PMID:16524903

  18. A trial of production of the plant-derived high-value protein in a plant factory: photosynthetic photon fluxes affect the accumulation of recombinant miraculin in transgenic tomato fruits.

    PubMed

    Kato, Kazuhisa; Maruyama, Shinichiro; Hirai, Tadayoshi; Hiwasa-Tanase, Kyoko; Mizoguchi, Tsuyoshi; Goto, Eiji; Ezura, Hiroshi

    2011-08-01

    One of the ultimate goals of plant science is to test a hypothesis obtained by basic science and to apply it to agriculture and industry. A plant factory is one of the ideal systems for this trial. Environmental factors affect both plant yield and the accumulation of recombinant proteins for industrial applications within transgenic plants. However, there have been few reports studying plant productivity for recombinant protein in closed cultivation systems called plant factories. To investigate the effects of photosynthetic photon flux (PPF) on tomato fruit yield and the accumulation of recombinant miraculin, a taste-modifying glycoprotein, in transgenic tomato fruits, plants were cultivated at various PPFs from 100 to 400 (µmol m(-2) s(-)1) in a plant factory. Miraculin production per unit of energy used was highest at PPF100, although miraculin production per unit area was highest at PPF300. The commercial productivity of recombinant miraculin in transgenic tomato fruits largely depended on light conditions in the plant factory. Our trial will be useful to consider the trade-offs between the profits from production of high-value materials in plants and the costs of electricity. PMID:21791976

  19. The spatiotemporal organization of cerebellar network activity resolved by two-photon imaging of multiple single neurons

    PubMed Central

    Gandolfi, Daniela; Pozzi, Paolo; Tognolina, Marialuisa; Chirico, Giuseppe; Mapelli, Jonathan; D'Angelo, Egidio

    2014-01-01

    In order to investigate the spatiotemporal organization of neuronal activity in local microcircuits, techniques allowing the simultaneous recording from multiple single neurons are required. To this end, we implemented an advanced spatial-light modulator two-photon microscope (SLM-2PM). A critical issue for cerebellar theory is the organization of granular layer activity in the cerebellum, which has been predicted by single-cell recordings and computational models. With SLM-2PM, calcium signals could be recorded from different network elements in acute cerebellar slices including granule cells (GrCs), Purkinje cells (PCs) and molecular layer interneurons. By combining WCRs with SLM-2PM, the spike/calcium relationship in GrCs and PCs could be extrapolated toward the detection of single spikes. The SLM-2PM technique made it possible to monitor activity of over tens to hundreds neurons simultaneously. GrC activity depended on the number of spikes in the input mossy fiber bursts. PC and molecular layer interneuron activity paralleled that in the underlying GrC population revealing the spread of activity through the cerebellar cortical network. Moreover, circuit activity was increased by the GABA-A receptor blocker, gabazine, and reduced by the AMPA and NMDA receptor blockers, NBQX and APV. The SLM-2PM analysis of spatiotemporal patterns lent experimental support to the time-window and center-surround organizing principles of the granular layer. PMID:24782707

  20. Relationship between structure of phenothiazine analogues and their activity on platelet calcium fluxes.

    PubMed Central

    Enouf, J.; Lévy-Toledano, S.

    1984-01-01

    Phenothiazine analogues have been tested for their effect on calcium uptake into platelet membrane vesicles and on ionophore-induced platelet activation, both phenomena being Ca2+-dependent. Both calcium uptake into membrane vesicles and ionophore-induced platelet activation were inhibited by the drugs. Evidence for two inhibitors as potent as chlorpromazine and trifluoperazine was found. These drugs are apparently competitive inhibitors of calcium uptake. A structure-activity relationship has been established. The data suggest that the phenothiazines are able to inhibit calmodulin-insensitive calcium uptake of platelet membrane vesicles and that therefore they cannot be assumed to be selective inhibitors of calmodulin interactions under all circumstances. PMID:6697061

  1. Activity of metazoa governs biofilm structure formation and enhances permeate flux during Gravity-Driven Membrane (GDM) filtration.

    PubMed

    Derlon, Nicolas; Koch, Nicolas; Eugster, Bettina; Posch, Thomas; Pernthaler, Jakob; Pronk, Wouter; Morgenroth, Eberhard

    2013-04-15

    The impact of different feed waters in terms of eukaryotic populations and organic carbon content on the biofilm structure formation and permeate flux during Gravity-Driven Membrane (GDM) filtration was investigated in this study. GDM filtration was performed at ultra-low pressure (65 mbar) in dead-end mode without control of the biofilm formation. Different feed waters were tested (River water, pre-treated river water, lake water, and tap water) and varied with regard to their organic substrate content and their predator community. River water was manipulated either by chemically inhibiting all eukaryotes or by filtering out macrozoobenthos (metazoan organisms). The structure of the biofilm was characterized at the meso- and micro-scale using Optical Coherence Tomography (OCT) and Confocal Laser Scanning Microscopy (CLSM), respectively. Based on Total Organic Carbon (TOC) measurements, the river waters provided the highest potential for bacterial growth whereas tap water had the lowest. An increasing content in soluble and particulate organic substrate resulted in increasing biofilm accumulation on membrane surface. However, enhanced biofilm accumulation did not result in lower flux values and permeate flux was mainly influenced by the structure of the biofilm. Metazoan organisms (in particular nematodes and oligochaetes) built-up protective habitats, which resulted in the formation of open and spatially heterogeneous biofilms composed of biomass patches. In the absence of predation by metazoan organisms, a flat and compact biofilm developed. It is concluded that the activity of metazoan organisms in natural river water and its impact on biofilm structure balances the detrimental effect of a high biofilm accumulation, thus allowing for a broader application of GDM filtration. Finally, our results suggest that for surface waters with high particulate organic carbon (POC) content, the use of worms is suitable to enhance POC removal before ultrafiltration units. PMID

  2. Diffuse neutrino intensity from the inner jets of active galactic nuclei: Impacts of external photon fields and the blazar sequence

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Inoue, Yoshiyuki; Dermer, Charles D.

    2014-07-01

    We study high-energy neutrino production in inner jets of radio-loud active galactic nuclei (AGN), taking into account effects of external photon fields and the blazar sequence. We show that the resulting diffuse neutrino intensity is dominated by quasar-hosted blazars, in particular, flat spectrum radio quasars, and that PeV-EeV neutrino production due to photohadronic interactions with broadline and dust radiation is unavoidable if the AGN inner jets are ultrahigh-energy cosmic-ray (UHECR) sources. Their neutrino spectrum has a cutoff feature around PeV energies since target photons are due to Lyα emission. Because of infrared photons provided by the dust torus, neutrino spectra above PeV energies are too hard to be consistent with the IceCube data unless the proton spectral index is steeper than 2.5, or the maximum proton energy is ≲100 PeV. Thus, the simple model has difficulty in explaining the IceCube data. For the cumulative neutrino intensity from blazars to exceed ˜10-8 GeV cm-2 s-1 sr-1, their local cosmic-ray energy generation rate would be ˜10-100 times larger than the local UHECR emissivity but is comparable to the averaged γ-ray blazar emissivity. Interestingly, future detectors such as the Askaryan Radio Array can detect ˜0.1-1 EeV neutrinos even in more conservative cases, allowing us to indirectly test the hypothesis that UHECRs are produced in the inner jets. We find that the diffuse neutrino intensity from radio-loud AGN is dominated by blazars with γ-ray luminosity of ≳1048 erg s-1, and the arrival directions of their ˜1-100 PeV neutrinos correlate with the luminous blazars detected by Fermi.

  3. High-voltage integrated active quenching circuit for single photon count rate up to 80 Mcounts/s.

    PubMed

    Acconcia, Giulia; Rech, Ivan; Gulinatti, Angelo; Ghioni, Massimo

    2016-08-01

    Single photon avalanche diodes (SPADs) have been subject to a fast improvement in recent years. In particular, custom technologies specifically developed to fabricate SPAD devices give the designer the freedom to pursue the best detector performance required by applications. A significant breakthrough in this field is represented by the recent introduction of a red enhanced SPAD (RE-SPAD) technology, capable of attaining a good photon detection efficiency in the near infrared range (e.g. 40% at a wavelength of 800 nm) while maintaining a remarkable timing resolution of about 100ps full width at half maximum. Being planar, the RE-SPAD custom technology opened the way to the development of SPAD arrays particularly suited for demanding applications in the field of life sciences. However, to achieve such excellent performance custom SPAD detectors must be operated with an external active quenching circuit (AQC) designed on purpose. Next steps toward the development of compact and practical multichannel systems will require a new generation of monolithically integrated AQC arrays. In this paper we present a new, fully integrated AQC fabricated in a high-voltage 0.18 µm CMOS technology able to provide quenching pulses up to 50 Volts with fast leading and trailing edges. Although specifically designed for optimal operation of RE-SPAD devices, the new AQC is quite versatile: it can be used with any SPAD detector, regardless its fabrication technology, reaching remarkable count rates up to 80 Mcounts/s and generating a photon detection pulse with a timing jitter as low as 119 ps full width at half maximum. The compact design of our circuit has been specifically laid out to make this IC a suitable building block for monolithically integrated AQC arrays. PMID:27505749

  4. Dynamic Evolution of Active Region Flux Tubes in the Turbulent Convective Envelope of a Young Sun: Solar-like Fast Rotators

    NASA Astrophysics Data System (ADS)

    Weber, Maria A.; Brown, B. P.; Fan, Y.

    2012-05-01

    Our Sun rotated much more rapidly when it was younger, as is suggested by observations of rapidly rotating solar-like stars and the influence of the solar wind, which removes angular momentum from the Sun. By studying how flux emergence may have occurred on the young Sun, we are likely to learn more about the nature of the solar dynamo early in the Sun's history, as well as other solar-like stars. To investigate this, we embed a toroidal flux tube near the base of the convection zone of a rotating spherical shell of turbulent convection performed for solar-like stars that rotate 3, 5, and 10 times the current solar rate. Our objective is to understand how the convective flows of these fast rotators can influence the emergent properties of flux tubes which would rise to create active regions, or starspots, of a variety of magnetic flux strengths, magnetic fields, and initial latitudes. Flux tube properties we will discuss include rise times, latitude of emergence, and tilt angles of the emerging flux tube limbs with respect to the east-west direction. Also of interest is identifying the regimes where dynamics of the flux tube are convection dominated or magnetic buoyancy dominated, as well as attempting to identify active longitudes.

  5. Control of Autophagosome Axonal Retrograde Flux by Presynaptic Activity Unveiled Using Botulinum Neurotoxin Type A

    PubMed Central

    Wang, Tong; Martin, Sally; Papadopulos, Andreas; Harper, Callista B.; Mavlyutov, Timur A.; Niranjan, Dhevahi; Glass, Nick R.; Cooper-White, Justin J.; Sibarita, Jean-Baptiste; Choquet, Daniel; Davletov, Bazbek; Meunier, Frédéric A.

    2015-01-01

    Botulinum neurotoxin type A (BoNT/A) is a highly potent neurotoxin that elicits flaccid paralysis by enzymatic cleavage of the exocytic machinery component SNAP25 in motor nerve terminals. However, recent evidence suggests that the neurotoxic activity of BoNT/A is not restricted to the periphery, but also reaches the CNS after retrograde axonal transport. Because BoNT/A is internalized in recycling synaptic vesicles, it is unclear which compartment facilitates this transport. Using live-cell confocal and single-molecule imaging of rat hippocampal neurons cultured in microfluidic devices, we show that the activity-dependent uptake of the binding domain of the BoNT/A heavy chain (BoNT/A-Hc) is followed by a delayed increase in retrograde axonal transport of BoNT/A-Hc carriers. Consistent with a role of presynaptic activity in initiating transport of the active toxin, activity-dependent uptake of BoNT/A in the terminal led to a significant increase in SNAP25 cleavage detected in the soma chamber compared with nonstimulated neurons. Surprisingly, most endocytosed BoNT/A-Hc was incorporated into LC3-positive autophagosomes generated in the nerve terminals, which then underwent retrograde transport to the cell soma, where they fused with lysosomes both in vitro and in vivo. Blocking autophagosome formation or acidification with wortmannin or bafilomycin A1, respectively, inhibited the activity-dependent retrograde trafficking of BoNT/A-Hc. Our data demonstrate that both the presynaptic formation of autophagosomes and the initiation of their retrograde trafficking are tightly regulated by presynaptic activity. PMID:25878289

  6. Control of autophagosome axonal retrograde flux by presynaptic activity unveiled using botulinum neurotoxin type a.

    PubMed

    Wang, Tong; Martin, Sally; Papadopulos, Andreas; Harper, Callista B; Mavlyutov, Timur A; Niranjan, Dhevahi; Glass, Nick R; Cooper-White, Justin J; Sibarita, Jean-Baptiste; Choquet, Daniel; Davletov, Bazbek; Meunier, Frédéric A

    2015-04-15

    Botulinum neurotoxin type A (BoNT/A) is a highly potent neurotoxin that elicits flaccid paralysis by enzymatic cleavage of the exocytic machinery component SNAP25 in motor nerve terminals. However, recent evidence suggests that the neurotoxic activity of BoNT/A is not restricted to the periphery, but also reaches the CNS after retrograde axonal transport. Because BoNT/A is internalized in recycling synaptic vesicles, it is unclear which compartment facilitates this transport. Using live-cell confocal and single-molecule imaging of rat hippocampal neurons cultured in microfluidic devices, we show that the activity-dependent uptake of the binding domain of the BoNT/A heavy chain (BoNT/A-Hc) is followed by a delayed increase in retrograde axonal transport of BoNT/A-Hc carriers. Consistent with a role of presynaptic activity in initiating transport of the active toxin, activity-dependent uptake of BoNT/A in the terminal led to a significant increase in SNAP25 cleavage detected in the soma chamber compared with nonstimulated neurons. Surprisingly, most endocytosed BoNT/A-Hc was incorporated into LC3-positive autophagosomes generated in the nerve terminals, which then underwent retrograde transport to the cell soma, where they fused with lysosomes both in vitro and in vivo. Blocking autophagosome formation or acidification with wortmannin or bafilomycin A1, respectively, inhibited the activity-dependent retrograde trafficking of BoNT/A-Hc. Our data demonstrate that both the presynaptic formation of autophagosomes and the initiation of their retrograde trafficking are tightly regulated by presynaptic activity. PMID:25878289

  7. A New Way of Sensing: Need-Based Activation of Antibiotic Resistance by a Flux-Sensing Mechanism

    PubMed Central

    Fritz, Georg; Dintner, Sebastian; Treichel, Nicole Simone; Radeck, Jara; Gerland, Ulrich; Gebhard, Susanne

    2015-01-01

    ABSTRACT Sensing of and responding to environmental changes are of vital importance for microbial cells. Consequently, bacteria have evolved a plethora of signaling systems that usually sense biochemical cues either via direct ligand binding acting as “concentration sensors” or by responding to downstream effects on bacterial physiology, such as structural damage to the cell. Here, we describe a novel, alternative signaling mechanism that effectively implements a “flux sensor” to regulate antibiotic resistance. It relies on a sensory complex consisting of a histidine kinase and an ABC transporter, in which the transporter fulfills the dual role of both the sensor of the antibiotic and the mediator of resistance against it. Combining systems biological modeling with in vivo experimentation, we show that these systems in fact respond to changes in activity of individual resistance transporters rather than to changes in the antibiotic concentration. Our model shows that the cell thereby adjusts the rate of de novo transporter synthesis to precisely the level needed for protection. Such a flux-sensing mechanism may serve as a cost-efficient produce-to-demand strategy, controlling a widely conserved class of antibiotic resistance systems. PMID:26199330

  8. Impact of Human Activities on the Flux of Terrestrial Sediments to the Coastal Ocean Offshore Northeastern Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Tzu-Ting; Su, Chih-Chieh; Liu, Char-Shine; Huang, Chen-fen; Hsu, Ho-Han

    2016-04-01

    Land to ocean material fluxes play an important role in global biogeochemical cycles. Changes in sediment supply not only greatly influence the benthic environment of coastal estuaries but also might threaten human lives and properties. Artificial constructions, such as roads and reservoirs, could affect natural environments and change sediment discharges. Due to its high precipitation, steep slopes, small basin areas, and frequent flood events, Taiwan is characterized with rapid erosion rates and extremely high sediment yields. In northeastern Taiwan, the high mean annual precipitation lead to large amounts of sediments being delivered into the ocean through the Lanyang River. Since 1957, the road constructions along the Lanyang River greatly increased terrestrial sediment flux to the coastal ocean. However, its influence on offshore area is not yet clear. In this study, we combine geochemical and geophysical data to evaluate the modern sedimentation history and discuss the impact of human activities on the Ilan Shelf. The preliminary results of grain size and 210Pb analyses from five sediment cores taken from the upper South Guishan Channel indicate the existence of local differences on hydrodynamic conditions. In addition, we also applied similarity index which based on a quantitative analysis algorithm to the chirp sonar data on echo character classification and calculated continuous grain size variations of the seafloor surface sediments. By combining all geochemical and geophysical data, we may reconstruct the holistic picture of human impacts on offshore environment from sedimentology records.

  9. A probabilistic description of the bed load sediment flux: 2. Particle activity and motions

    NASA Astrophysics Data System (ADS)

    Roseberry, John C.; Schmeeckle, Mark W.; Furbish, David Jon

    2012-09-01

    High-speed imaging of coarse sand particles transported as bed load over a planar bed reveals that the particle activity, the solid volume of particles in motion per unit streambed area, fluctuates as particles respond to near-bed fluid turbulence while simultaneously interacting with the bed. The relative magnitude of these fluctuations systematically varies with the size of the sampling area. The particle activity within a specified sampling area is distributed in a manner that is consistent with the existence of an ensemble of configurations of particle positions wherein certain configurations are preferentially selected or excluded by the turbulence structure, manifest as patchiness of active particles. The particle activity increases with increasing bed stress far faster than does the average particle velocity, so changes in the transport rate with changing stress are dominated by changes in the activity, not velocity. The probability density functions of the streamwise and cross-stream particle velocities are exponential-like and lack heavy tails. Plots of the mean squared particle displacement versus time may ostensibly indicate non-Fickian diffusive behavior while actually reflecting effects of correlated random walks associated with intrinsic periodicities in particle motions, not anomalous diffusion. The probability density functions of the particle hop distance (start-to-stop) and the associated travel time are gamma-like, which provides the empirical basis for showing that particle disentrainment rates vary with hop distance and travel time.

  10. 2-Photon Characterization of Optical Proteolytic Beacons for Imaging Changes in Matrix-Metalloprotease Activity in a Mouse Model of Aneurysm

    PubMed Central

    Haskett, Darren G.; Maestas, David; Howerton, Stephen J.; Smith, Tyler; Ardila, D. Catalina; Doetschman, Tom; Utzinger, Urs; McGrath, Dominic; McIntyre, J. Oliver; Vande Geest, Jonathan P.

    2016-01-01

    Abdominal aortic aneurysm is a multifactorial disease that is a leading cause of death in developed countries. Matrix-metalloproteases (MMPs) are part of the disease process, however, assessing their role in disease initiation and progression has been difficult and animal models have become essential. Combining Förster resonance energy transfer (FRET) proteolytic beacons activated in the presence of MMPs with 2-photon microscopy allows for a novel method of evaluating MMP activity within the extracellular matrix (ECM). Single and 2-photon spectra for proteolytic beacons were determined in vitro. Ex vivo experiments using the apolipoprotein E knockout angiotensin II-infused mouse model of aneurysm imaged ECM architecture simultaneously with the MMP-activated FRET beacons. 2-photon spectra of the two-color proteolytic beacons showed peaks for the individual fluorophores that enable imaging of MMP activity through proteolytic cleavage. Ex vivo imaging of the beacons within the ECM revealed both microstructure and MMP activity. 2-photon imaging of the beacons in aneurysmal tissue showed an increase in proteolytic cleavage within the ECM (p < 0.001), thus indicating an increase in MMP activity. Our data suggest that FRET-based proteolytic beacons show promise in assessing MMP activity within the ECM and will therefore allow future studies to identify the heterogeneous distribution of simultaneous ECM remodeling and protease activity in aneurysmal disease. PMID:26903264

  11. 2-Photon Characterization of Optical Proteolytic Beacons for Imaging Changes in Matrix-Metalloprotease Activity in a Mouse Model of Aneurysm.

    PubMed

    Haskett, Darren G; Maestas, David; Howerton, Stephen J; Smith, Tyler; Ardila, D Catalina; Doetschman, Tom; Utzinger, Urs; McGrath, Dominic; McIntyre, J Oliver; Vande Geest, Jonathan P

    2016-04-01

    Abdominal aortic aneurysm is a multifactorial disease that is a leading cause of death in developed countries. Matrix-metalloproteases (MMPs) are part of the disease process, however, assessing their role in disease initiation and progression has been difficult and animal models have become essential. Combining Förster resonance energy transfer (FRET) proteolytic beacons activated in the presence of MMPs with 2-photon microscopy allows for a novel method of evaluating MMP activity within the extracellular matrix (ECM). Single and 2-photon spectra for proteolytic beacons were determined in vitro. Ex vivo experiments using the apolipoprotein E knockout angiotensin II-infused mouse model of aneurysm imaged ECM architecture simultaneously with the MMP-activated FRET beacons. 2-photon spectra of the two-color proteolytic beacons showed peaks for the individual fluorophores that enable imaging of MMP activity through proteolytic cleavage. Ex vivo imaging of the beacons within the ECM revealed both microstructure and MMP activity. 2-photon imaging of the beacons in aneurysmal tissue showed an increase in proteolytic cleavage within the ECM (p<0.001), thus indicating an increase in MMP activity. Our data suggest that FRET-based proteolytic beacons show promise in assessing MMP activity within the ECM and will therefore allow future studies to identify the heterogeneous distribution of simultaneous ECM remodeling and protease activity in aneurysmal disease. PMID:26903264

  12. High heat flux actively cooled honeycomb sandwich structural panel for a hypersonic aircraft

    NASA Technical Reports Server (NTRS)

    Koch, L. C.; Pagel, L. L.

    1978-01-01

    The results of a program to design and fabricate an unshielded actively cooled structural panel for a hypersonic aircraft are presented. The design is an all-aluminum honeycomb sandwich with embedded cooling passages soldered to the inside of the outer moldline skin. The overall finding is that an actively cooled structure appears feasible for application on a hypersonic aircraft, but the fabrication process is complex and some material and manufacturing technology developments are required. Results from the program are summarized and supporting details are presented.

  13. Potential indirect effects of aerosol on tropical cyclone intensity: convective fluxes and cold-pool activity

    NASA Astrophysics Data System (ADS)

    Krall, G. M.; Cottom, W. R.

    2012-01-01

    Observational and model evidence suggest that a 2008 Western Pacific typhoon (NURI) ingested elevated concentrations of aerosol as it neared the Chinese coast. This study uses a regional model with two-moment bin-emulating microphysics to simulate the typhoon as it enters the field of elevated aerosol concentrations. A clean maritime field of cloud condensation nuclei (CCN) was prescribed as marine background CCN concentrations and then based on satellite and global aerosol model output, increased to pollution levels and further enhanced in sensitivity tests. The typhoon was simulated for 96 h beginning 17 August 2008. During the final 60 h CCN concentrations were enhanced as it neared the Philippines and coastal China. The model was initialized with both global reanalysis model data and irregularly spaced dropsonde data from the 2008 T-PARC observational campaign using an objective analysis routine. At 36 h, the internal nudging of the model was switched off and allowed to freely evolve on its own. As the typhoon encountered the elevated CCN in the sensitivity tests, a significant perturbation of windspeed, convective fluxes, and hydrometeor species behavior was simulated. Early during the ingestion of enhanced CCN, precipitation was reduced due to suppressed collision and coalescence, and storm winds increased in strength. Subsequently, owing to reduced fall speeds of the smaller drops, greater amounts of condensate were thrust into supercooled levels where the drops froze releasing greater amounts of latent heat of freezing. Convection thereby intensified which resulted in enhanced rainfall and more vigorous convectively-produced downdrafts. As the convection intensified in the outer rainbands the storm drifted over the developing cold-pools. The enhanced cold-pools blocked the inflow of warm, moist air into the core of the typhoon which led to a weakening of the typhoon with significantly reduced low level wind speeds. The very high amounts of pollution

  14. Cardiac lipoprotein lipase activity in the hypertrophied heart may be regulated by fatty acid flux

    PubMed Central

    Hauton, David; Caldwell, Germaine M.

    2012-01-01

    Cardiac hypertrophy is characterised by an imbalance between lipid uptake and fatty acid β-oxidation leading to an accumulation of lipids, particularly triacylglycerol (TAG). It is unclear whether uptake mechanisms such as lipoprotein lipase (LPL) can be attenuated to diminish this uptake. Rats were cold acclimated to induce cardiac hypertrophy and increase cardiac LPL. Lipid uptake and metabolism were altered by feeding a ‘Western-style’ high fat diet (WSD) or feeding oxfenicine (2 g/L) in the drinking water. Diastolic stiffness (increased volume change/unit pressure change) was induced in hypertrophied hearts for rats fed WSD (P < 0.05) or WSD + oxfenicine (P < 0.01), although absolute performance of cardiac muscle, estimated from stress–strain calculations was unchanged. Cold acclimation increased cardiac endothelial LPL (P < 0.05) but this was diminished following oxfenicine. Following WSD LPL was further decreased below WSD-fed control hearts (P < 0.05) with no further decrease by oxfenicine supplementation. A negative correlation was noted between plasma TAG and endothelial LPL (correlation coefficient = − 0.654; P < 0.001) but not cardiac TAG concentration. Transcript levels of angiopoietin-like protein-4 (ANGPTL4) were increased 6-fold by WSD (P < 0.05) and increased 15-fold following WSD + oxfenicine (P < 0.001). For CA-hearts fed WSD or WSD + oxfenicine ANGPTL4 mRNA levels were preserved at chow-fed levels. VLDLR protein levels were increased 10-fold (P < 0.01) by CA. ANGPTL4 protein levels were increased 2-fold (P < 0.05) by WSD, but restored following oxfenicine. For CA-hearts WSD increased ANGPTL4 protein levels 3-fold (P < 0.01) with WSD + oxfenicine increasing ANGPTL4 protein 4-fold (P < 0.01). These data suggest that endothelial LPL levels in the heart are altered to maintain FA flux and may exploit ANGPTL4. PMID:22226882

  15. Solar activity prediction of sunspot numbers (verification). Predicted solar radio flux; predicted geomagnetic indices Ap and Kp. [space shuttle program: satellite orbital lifetime

    NASA Technical Reports Server (NTRS)

    Newman, S. R.

    1980-01-01

    Efforts to further verify a previously reported technique for predicting monthly sunspot numbers over a period of years (1979 to 1989) involved the application of the technique over the period for the maximum epoch of solar cycle 19. Results obtained are presented. Methods and results for predicting solar flux (F10.7 cm) based on flux/sunspot number models, ascent and descent, and geomagnetic activity indices as a function of sunspot number and solar cycle phase classes are included.

  16. Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

    PubMed

    Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

    2016-11-15

    Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering. PMID:27494632

  17. Exchange diffusion, active transport, and diffusional components of transbranchial Na and cl fluxes.

    PubMed

    Kirschner, L B; Howe, D

    1981-05-01

    Sodium efflux across the gills of the sculpin Leptocottus armatus average about 900 mumol.100 g-1.h-1 in seawater (SW). When external Na+ was replaced by Tris [tris(hydroxymethyl)aminomethane] the efflux dropped about 35% and the voltage across the gill (TEP) decreased from +20.3 to -2.3 mV. The electrical change accounted, almost exactly, for the diminution of efflux, suggesting that most, if not all, of the Na+ efflux in this fish is diffusive. Chloride efflux in SW was about 300 mumol.100 g-1.h-1. When external Cl- was replaced by gluconate, efflux fell to about one-half the SW value. This could not be due to a change in TEP and is therefore attributed to exchange diffusion. Injection of thiocyanate further reduced the efflux to about 15% of the SW rate. This fraction of the total efflux is active extrusion. The remaining efflux (exchange and active transport eliminated) is diffusive. It is also shown that substitution of gluconate for chloride reduces the activity coefficient for Na+. A small decrease in TEP, noted in this substitution, can be explained by the activity change. A few experiments with isethionate suggest that it does not have this effect and hence is a better chloride substitute in single-ion replacement experiments. PMID:7235052

  18. MAGNETIC NON-POTENTIALITY OF SOLAR ACTIVE REGIONS AND PEAK X-RAY FLUX OF THE ASSOCIATED FLARES

    SciTech Connect

    Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay E-mail: sgosain@prl.res.i

    2010-09-20

    Predicting the severity of solar eruptive phenomena such as flares and coronal mass ejections remains a great challenge despite concerted efforts to do so over the past several decades. However, the advent of high-quality vector magnetograms obtained from Hinode (SOT/SP) has increased the possibility of meeting this challenge. In particular, the spatially averaged signed shear angle (SASSA) seems to be a unique parameter for quantifying the non-potentiality of active regions. We demonstrate the usefulness of the SASSA for predicting flare severity. For this purpose, we present case studies of the evolution of magnetic non-potentiality using 115 vector magnetograms of four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963 during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and 2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very active and produced X and M class flares, respectively, along with many smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963 were relatively less active and produced only very small (mostly A- and B-class) flares. For this study, we have used a large number of high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our analysis shows that the peak X-ray flux of the most intense solar flare emanating from the active regions depends on the magnitude of the SASSA at the time of the flare. This finding of the existence of a lower limit of the SASSA for a given class of X-ray flares will be very useful for space weather forecasting. We have also studied another non-potentiality parameter called the mean weighted shear angle (MWSA) of the vector magnetograms along with the SASSA. We find that the MWSA does not show such distinction as the SASSA for upper limits of the GOES X-ray flux of solar flares; however, both the quantities show similar trends during the evolution of all active regions studied.

  19. Improved photon counting efficiency calibration using superconducting single photon detectors

    NASA Astrophysics Data System (ADS)

    Gan, Haiyong; Xu, Nan; Li, Jianwei; Sun, Ruoduan; Feng, Guojin; Wang, Yanfei; Ma, Chong; Lin, Yandong; Zhang, Labao; Kang, Lin; Chen, Jian; Wu, Peiheng

    2015-10-01

    The quantum efficiency of photon counters can be measured with standard uncertainty below 1% level using correlated photon pairs generated through spontaneous parametric down-conversion process. Normally a laser in UV, blue or green wavelength range with sufficient photon energy is applied to produce energy and momentum conserved photon pairs in two channels with desired wavelengths for calibration. One channel is used as the heralding trigger, and the other is used for the calibration of the detector under test. A superconducting nanowire single photon detector with advantages such as high photon counting speed (<20 MHz), low dark count rate (<50 counts per second), and wideband responsivity (UV to near infrared) is used as the trigger detector, enabling correlated photons calibration capabilities into shortwave visible range. For a 355nm single longitudinal mode pump laser, when a superconducting nanowire single photon detector is used as the trigger detector at 1064nm and 1560nm in the near infrared range, the photon counting efficiency calibration capabilities can be realized at 532nm and 460nm. The quantum efficiency measurement on photon counters such as photomultiplier tubes and avalanche photodiodes can be then further extended in a wide wavelength range (e.g. 400-1000nm) using a flat spectral photon flux source to meet the calibration demands in cutting edge low light applications such as time resolved fluorescence and nonlinear optical spectroscopy, super resolution microscopy, deep space observation, and so on.

  20. A sensitive two-photon probe to selectively detect monoamine oxidase B activity in Parkinson’s disease models

    NASA Astrophysics Data System (ADS)

    Li, Lin; Zhang, Cheng-Wu; Chen, Grace Y. J.; Zhu, Biwei; Chai, Chou; Xu, Qing-Hua; Tan, Eng-King; Zhu, Qing; Lim, Kah-Leong; Yao, Shao Q.

    2014-02-01

    The unusually high MAO-B activity consistently observed in Parkinson’s disease (PD) patients has been proposed as a biomarker; however, this has not been realized due to the lack of probes suitable for MAO-B-specific detection in live cells/tissues. Here we report the first two-photon, small molecule fluorogenic probe (U1) that enables highly sensitive/specific and real-time imaging of endogenous MAO-B activities across biological samples. We also used U1 to confirm the reported inverse relationship between parkin and MAO-B in PD models. With no apparent toxicity, U1 may be used to monitor MAO-B activities in small animals during disease development. In clinical samples, we find elevated MAO-B activities only in B lymphocytes (not in fibroblasts), hinting that MAO-B activity in peripheral blood cells might be an accessible biomarker for rapid detection of PD. Our results provide important starting points for using small molecule imaging techniques to explore MAO-B at the organism level.

  1. Gypenoside XVII Enhances Lysosome Biogenesis and Autophagy Flux and Accelerates Autophagic Clearance of Amyloid-β through TFEB Activation.

    PubMed

    Meng, Xiangbao; Luo, Yun; Liang, Tian; Wang, Mengxia; Zhao, Jingyu; Sun, Guibo; Sun, Xiaobo

    2016-04-01

    A strategy for activating transcription factor EB (TFEB) to restore autophagy flux may provide neuroprotection against Alzheimer's disease. Our previous study reported that gypenoside XVII (GP-17), which is a major saponin abundant in ginseng and Panax notoginseng, ameliorated amyloid-β (Aβ)25-35-induced apoptosis in PC12 cells by regulating autophagy. In the present study, we aimed to determine whether GP-17 has neuroprotective effects on PC12 cells expressing the Swedish mutant of APP695 (APP695swe) and APP/PS1 mice. We also investigated the underlying mechanism. We found that GP-17 could significantly increase Atg5 expression and the conversion of LC3-I to LC3-II in APP695 cells, which was associated with a reduction in p62 expression. GP-17 also elevated the number of LC3 puncta in APP695 cells transduced with pCMV-GFP-LC3. GP-17 promoted the autophagy-based elimination of AβPP, Aβ40, and Aβ42 in APP695swe cells and prevented the formation of Aβ plaques in the hippocampus and cortex of APP/PS1 mice. Furthermore, spatial learning and memory deficits were cured. Atg5 knockdown could abrogate the GP-17-mediated removal of AβPP, Aβ40, and Aβ42 in APP695swe cells. GP-17 upregulated LAMP-1, increased LysoTracker staining, and augmented LAMP-1/LC3-II co-localization. GP-17 could release TFEB from TFEB/14-3-3 complexes, which led to TFEB nuclear translocation and the induction of autophagy and lysosome biogenesis and resulted in the amelioration of autophagy flux. The knockdown of TFEB could abolish these effects of GP-17. In summary, these results demonstrated that GP-17 conferred protective effects to the cellular and rodent models of Alzheimer's disease by activating TFEB. PMID:27060963

  2. Ultra-large Angle Curved Reflectors and Their Applications to Passive and Active Photonic Integrated Circuit Devices

    NASA Astrophysics Data System (ADS)

    Hou, Zhenyu

    Nanoscale optical components such as waveguides, resonators are the building blocks of integrated optical networks. With the advent of nano-fabrication technologies we are able to realize such components in strongly confined sub-micron dimensions. A photonic integrated circuit (PIC) that contains these components integrates multiple photonic functions on a single chip. Traditionally, functionality of PIC is realized via modification of waveguide structure. on the contrary, reflective components such as curved reflectors propagate light in two dimensional free space thence have many advantages over their refractive counterparts such as tighter space requirement, more flexibility, and lower loss. In this work, we propose curved reflector as an essential component to realize multiple integrated functions in PICs. These functions include spot size conversion, beam turning, waveguide crossing, etc. Waveguide taper, bended waveguide, direct waveguide crossing are the conventional counterparts to realize such functions. In particular, we proposed and realized photonic integrated interconnections using curved reflectors and curved reflector semiconductor optical amplifier (CR-SOA). In this thesis, theoretically analysis of curved reflectors is introduced and discussed in depth. Gaussian beam analysis, in particular, Hermite-Gaussian beam analysis is used to explain light propagation and distortion in interaction with curved reflectors. Theoretical formulation of beam propagation in presence of curved reflector is verified with Finite-Difference Time-Domain (FDTD) method. General design strategies of curved reflectors are proposed. Multiple applications of curved reflector in passive and active devices are introduced. Distortions induced in light beams by curved reflectors, its original, theoretical description, and compensation methods are discussed in details as well. Photonic integrated interconnection based on silicon-on-insulator (SOI) platform and curved reflector

  3. Qubit dephasing due to photon shot noise from coherent and thermal sources

    NASA Astrophysics Data System (ADS)

    Gustavsson, S.; Yan, F.; Kamal, A.; Orlando, T. P.; Oliver, W. D.; Birenbaum, J.; Sears, A.; Hover, D.; Gudmundsen, T.; Yoder, J.

    We investigate qubit dephasing due to photon shot noise in a superconducting flux qubit transversally coupled to a coplanar microwave resonator. Due to the AC Stark effect, photon fluctuations in the resonator cause frequency shifts of the qubit, which in turn lead to dephasing. While this is universally understood, we have made the first quantitative spectroscopy of this noise for both thermal (i.e., residual photons from higher temperature stages) and coherent photons (residual photons from the readout and control pulses). We find that the bandwidth of the shot noise from thermal and coherent photons differ by approximately a factor of two, which we attribute to differences in the correlation time for the two noise sources. By comparing the results with noise spectra measured without any externally applied photons, we conclude that the qubit coherence times in our setup were limited by photon shot noise from thermal radiation, with an average resonator photon population of 0.006. Equipped with this knowledge, we improved the filtering for thermal noise and thereby improved the qubit coherence times by more than a factor of two, with T2 echo times approaching 100 us. From the measured T2 decay, we determine an upper bound on the residual photon population of 0.0004. This research was funded by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA) via MIT LL under Air Force Contract No. FA8721-05-C-0002.

  4. Active quenching and gating circuit of the photon counting detector for laser time transfer with improved timing resolution and stability

    NASA Astrophysics Data System (ADS)

    Prochazka, Ivan; Blazej, Josef; Kodet, Jan; Michalek, Vojtech

    2015-05-01

    We are presenting the results of research and development of a new active quenching and gating electronics for Single Photon Avalanche Detector (SPAD). The goal of the work was to develop a new SPAD detector package for Laser Time Transfer ground to space with improved timing resolution and stability. The first version of a SPAD detector is operational on board of GNSS navigation satellites. They are based on 25 μm diameter K14 series SPAD chips. They do provide timing resolution of typically 125 ps and stability of the order of 10 ps. The new control electronics provides timing resolution of 25 ps and timing stability and drifts of the order of one picosecond. The device is constructed on a basis of electronics components for which the space qualified equivalents are commercially available. The device construction, tests and results will be presented in detail.

  5. pH Measurement Using Dual-Wavelength Fluorescent Ratio by Two-Photon Excitation for Mitochondrial Activity

    NASA Astrophysics Data System (ADS)

    Kanazashi, Yasuaki; Li, Yongbo; Onojima, Takumi; Iwami, Kentaro; Ohta, Yoshihiro; Umeda, Norihiro

    2012-11-01

    A mitochondrion has a pH gradient between the two sides of its inner membrane in order to produce adenosine triphosphate (ATP). Because ATP depletion causes numerous diseases, the measurement of the pH value around the mitochondrion is expected to clarify the mechanism of these diseases. In this study, a dual-wavelength pH-sensitive dye was excited by two-photon absorption initiated using a femtosecond pulse laser. In addition, fluorescence from the dye was directly collected from the fluorescent point using the collection-mode probe of a scanning near-field optical microscope. By this proposed method, a pH calibration curve was obtained from the fluorescent intensity ratio of the dye solution, and temporal pH variations with 0.1 s time resolution following the addition of acid were observed. Moreover, mitochondrial activity on the basis of the pH changes was successfully observed in three different mitochondrial densities.

  6. Active layer identification of photonic crystal waveguide biosensor chip for the detection of Escherichia coli

    NASA Astrophysics Data System (ADS)

    Painam, Balveer; Kaler, Rajinder S.; Kumar, Mukesh

    2016-07-01

    This work represents experimental and simulation analysis of photonic crystal waveguide (PCW)-based biosensor structures, which is used for detection of the Escherichia coli (E. coli) cell. A method is adopted for E. coli culture to measure length, diameter, and refractive index to finalize the structural design and to verify the suitability of PCW as a biosensor. This method is tested using DH5α strains of E. coli. The typical precisions of measurements are varied in ranges from 1.132 to 1.825 μm and from 0.447 to 0.66 μm for pathogen's length and diameter, respectively. The measured distribution of samples over length and diameter are in correlation with the measurements performed by scanning electron microscope. After obtaining average length and diameter of cylindrical shaped E. coli cell, we consider these values for simulation analysis of designed PCW biosensor. E. coli cell is trapped in the middle of the PCW biosensor having three different types of waveguides, i.e., gallium arsenide/silicon dioxide (GaAs/SiO2), silicon/silicon dioxide (Si/SiO2), or silicon nitride/silicon dioxide (Si3N4/SiO2) to observe the maximum resonance shift and sensitivity. It is observed from the simulation data analysis that GaAs/SiO2 is the preferred PCW biosensor for the identification of E. coli.

  7. Decreased-activity mutants of phosphoglucose isomerase in the cytosol and chloroplast of Clarkia xantiana. Impact on mass-action ratios and fluxes to sucrose and starch, and estimation of Flux Control Coefficients and Elasticity Coefficients.

    PubMed Central

    Kruckeberg, A L; Neuhaus, H E; Feil, R; Gottlieb, L D; Stitt, M

    1989-01-01

    1. Subcellular-compartment-specific decreased-activity mutants of phosphoglucose isomerase in Clarkia xantiana were used to analyse the control of sucrose and starch synthesis during photosynthesis. Mutants were available in which the plastid phosphoglucose isomerase complement is decreased to 75% or 50% of the wild-type level, and the cytosol complement to 64%, 36% or 18% of the wild-type level. 2. The effects on the [product]/[substrate] ratio and on fluxes to sucrose or starch and the rate of photosynthesis were studied with the use of saturating or limiting light intensity to impose a high or low flux through these pathways. 3. Removal of a small fraction of either phosphoglucose isomerase leads to a significant shift of the [product]/[substrate] ratio away, from equilibrium. We conclude that there is no 'excess' of enzyme over that needed to maintain its reactants reasonably close to equilibrium. 4. Decreased phosphoglucose isomerase activity can also alter the fluxes to starch or sucrose. However, the effect on flux does not correlate with the extent of disequilibrium, and also varies depending on the subcellular compartment and on the conditions. 5. The results were used to estimate Flux Control Coefficients for the chloroplast and cytosolic phosphoglucose isomerases. The chloroplast isoenzyme exerts control on the rate of starch synthesis and on photosynthesis in saturating light intensity and CO2, but not at low light intensity. The cytosolic enzyme only exerts significant control when its complement is decreased 3-5-fold, and differs from the plastid isoenzyme in exerting more control in low light intensity. It has a positive Control Coefficient for sucrose synthesis, and a negative Control Coefficient for starch synthesis. 6. The Elasticity Coefficients in vivo of the cytosolic phosphoglucose isomerase were estimated to lie between 5 and 8 in the wild-type. They decrease in mutants with a lowered complement of cytosolic phosphoglucose isomerase. 7. The

  8. Dynamic performance of MEMS deformable mirrors for use in an active/adaptive two-photon microscope

    NASA Astrophysics Data System (ADS)

    Zhang, Christian C.; Foster, Warren B.; Downey, Ryan D.; Arrasmith, Christopher L.; Dickensheets, David L.

    2016-03-01

    Active optics can facilitate two-photon microscopic imaging deep in tissue. We are investigating fast focus control mirrors used in concert with an aberration correction mirror to control the axial position of focus and system aberrations dynamically during scanning. With an adaptive training step, sample-induced aberrations may be compensated as well. If sufficiently fast and precise, active optics may be able to compensate under-corrected imaging optics as well as sample aberrations to maintain diffraction-limited performance throughout the field of view. Toward this end we have measured a Boston Micromachines Corporation Multi-DM 140 element deformable mirror, and a Revibro Optics electrostatic 4-zone focus control mirror to characterize dynamic performance. Tests for the Multi-DM included both step response and sinusoidal frequency sweeps of specific Zernike modes. For the step response we measured 10%-90% rise times for the target Zernike amplitude, and wavefront rms error settling times. Frequency sweeps identified the 3dB bandwidth of the mirror when attempting to follow a sinusoidal amplitude trajectory for a specific Zernike mode. For five tested Zernike modes (defocus, spherical aberration, coma, astigmatism and trefoil) we find error settling times for mode amplitudes up to 400nm to be less than 52 us, and 3 dB frequencies range from 6.5 kHz to 10 kHz. The Revibro Optics mirror was tested for step response only, with error settling time of 80 μs for a large 3 um defocus step, and settling time of only 18 μs for a 400nm spherical aberration step. These response speeds are sufficient for intra-scan correction at scan rates typical of two-photon microscopy.

  9. Energetic solar proton versus terrestrially trapped proton fluxes for the active years 1977 - 1983

    NASA Technical Reports Server (NTRS)

    King, J. H.; Stassinopoulos, E. G.

    1974-01-01

    Ratios of solar to trapped proton fluences were computed for circular-orbit, geocentric space missions to be flown during the active phase of the next solar cycle (1977-1983). The ratios are presented as functions of orbit altitude and inclination, mission duration, proton energy threshold, and the chance the mission planner is willing to take that the actually encountered solar proton fluence will exceed the design fluence provided by the statistical solar proton model. It is shown that the ratio is most sensitively dependent on orbit altitude and inclination, with trapped protons dominant for low inclination, low and mid altitude orbits and for high inclination, mid altitude orbits. Conversely, solar protons are dominant for high inclination, low altitude orbits, and for low and high inclination, high altitude orbits.

  10. Reporting Sodium Channel Activity Using Calcium Flux: Pharmacological Promiscuity of Cardiac Nav1.5

    PubMed Central

    Zhang, Hongkang; Zou, Beiyan; Du, Fang; Xu, Kaiping

    2015-01-01

    Voltage-gated sodium (Nav) channels are essential for membrane excitability and represent therapeutic targets for treating human diseases. Recent reports suggest that these channels, e.g., Nav1.3 and Nav1.5, are inhibited by multiple structurally distinctive small molecule drugs. These studies give reason to wonder whether these drugs collectively target a single site or multiple sites in manifesting such pharmacological promiscuity. We thus investigate the pharmacological profile of Nav1.5 through systemic analysis of its sensitivity to diverse compound collections. Here, we report a dual-color fluorescent method that exploits a customized Nav1.5 [calcium permeable Nav channel, subtype 5 (SoCal5)] with engineered-enhanced calcium permeability. SoCal5 retains wild-type (WT) Nav1.5 pharmacological profiles. WT SoCal5 and SoCal5 with the local anesthetics binding site mutated (F1760A) could be expressed in separate cells, each with a different-colored genetically encoded calcium sensor, which allows a simultaneous report of compound activity and site dependence. The pharmacological profile of SoCal5 reveals a hit rate (>50% inhibition) of around 13% at 10 μM, comparable to that of hERG. The channel activity is susceptible to blockage by known drugs and structurally diverse compounds. The broad inhibition profile is highly dependent on the F1760 residue in the inner cavity, which is a residue conserved among all nine subtypes of Nav channels. Both promiscuity and dependence on F1760 seen in Nav1.5 were replicated in Nav1.4. Our evidence of a broad inhibition profile of Nav channels suggests a need to consider off-target effects on Nav channels. The site-dependent promiscuity forms a foundation to better understand Nav channels and compound interactions. PMID:25422141

  11. Exploring the active galactic nuclei population with extreme X-ray-to-optical flux ratios (fx/fo > 50)

    NASA Astrophysics Data System (ADS)

    Della Ceca, R.; Carrera, F. J.; Caccianiga, A.; Severgnini, P.; Ballo, L.; Braito, V.; Corral, A.; Del Moro, A.; Mateos, S.; Ruiz, A.; Watson, M. G.

    2015-03-01

    The cosmic history of the growth of supermassive black holes in galactic centres parallels that of star formation in the Universe. However, an important fraction of this growth occurs inconspicuously in obscured objects, where ultraviolet/optical/near-infrared emission is heavily obscured by dust. Since the X-ray flux is less attenuated, a high X-ray-to-optical flux ratio (fx/fo) is expected to be an efficient tool to find out these obscured accreting sources. We explore here via optical spectroscopy, X-ray spectroscopy and infrared photometry the most extreme cases of this population (those with fx/fo > 50, EXO50 sources hereafter), using a well-defined sample of seven X-ray sources extracted from the 2XMM catalogue. Five EXO50 sources (˜70 per cent of the sample) in the bright flux regime explored by our survey (f(2-10 keV) ≥ 1.5 × 10-13 erg cm-2 s-1) are associated with obscured AGN (NH > 1022 cm-2), spanning a redshift range between 0.75 and 1 and characterized by 2-10 keV intrinsic luminosities in the QSO regime (e.g. well in excess to 1044 erg s-1). We did not find compelling evidence of Compton thick active galacic nuclei (AGN). Overall, the EXO50 type 2 QSOs do not seem to be different from standard X-ray-selected type 2 QSOs in terms of nuclear absorption; a very high AGN/host galaxy ratio seems to play a major role in explaining their extreme properties. Interestingly, three out of five EXO50 type 2 QSO objects can be classified as extreme dust-obscured galaxies (EDOGs, f24 μm/fR ≥ 2000), suggesting that a very high AGN/host ratios (along with the large amount of dust absorption) could be the natural explanation also for a part of the EDOG population. The remaining two EXO50 sources are classified as BL Lac objects, having rather extreme properties, and which are good candidates for TeV emission.

  12. Monitoring charge flux to quantify unusual ligand-induced ion channel activity for use in biological nanopore-based sensors.

    PubMed

    Macazo, Florika C; White, Ryan J

    2014-06-01

    The utility of biological nanopores for the development of sensors has become a growing area of interest in analytical chemistry. Their emerging use in chemical analysis is a result of several ideal characteristics. First, they provide reproducible control over nanoscale pore sizes with an atomic level of precision. Second, they are amenable to resistive-pulse type measurement systems when embedded into an artificial lipid bilayer. A single binding event causes a change in the flow of millions of ions across the membrane per second that is readily measured as a change in current with excellent signal-to-noise ratio. To date, ion channel-based biosensors have been limited to well-behaved proteins. Most demonstrations of using ion channels as sensors have been limited to proteins that remain in the open, conducting state, unless occupied by an analyte of interest. Furthermore, these proteins are nonspecific, requiring chemical, biochemical, or genetic manipulations to impart chemical specificity. Here, we report on the use of the pore-forming abilities of heat shock cognate 70 (Hsc70) to quantify a specific analyte. Hsc70 reconstitutes into phospholipid membranes and opens to form multiple conductance states specifically in the presence of ATP. We introduce the measurement of "charge flux" to characterize the ATP-regulated multiconductance nature of Hsc70, which enables sensitive quantification of ATP (100 μM-4 mM). We believe that monitoring protein-induced charge flux across a bilayer membrane represents a universal method for quantitatively monitoring ion-channel activity. This measurement has the potential to broaden the library of usable proteins in the development of nanopore-based biosensors. PMID:24794413

  13. Comparison of photon-photon and photon-magnetic field pair production rates. [in neutron stars

    NASA Technical Reports Server (NTRS)

    Burns, M. L.; Harding, A. K.

    1983-01-01

    Neutron stars were proposed as the site of gamma-ray burst activity and the copious supply of MeV photons admits the possibility of electron-positron pair production. If the neutron star magnetic field is sufficiently intense (10 to the 12th power G), both photon-photon (2 gamma) and photon-magnetic field (gamma) pair production should be important mechanisms. Rates for the two processes were calculated using a Maxwellian distribution for the photons. The ratio of 1 gamma to 2 gamma pair production rates was obtained as a function of photon temperature and magnetic field strength.

  14. Comparison of Photon-photon and Photon-magnetic Field Pair Production Rates

    NASA Technical Reports Server (NTRS)

    Burns, M. L.; Harding, A. K.

    1983-01-01

    Neutron stars were proposed as the site of gamma-ray burst activity and the copious supply of MeV photons admits the possibility of electron-positron pair production. If the neutron star magnetic field is sufficiently intense ( 10 to the 12th power G), both photon-photon (2 gamma) and photon-magnetic field ( gamma) pair production should be important mechanisms. Rates for the two processes were calculated using a Maxwellian distribution for the photons. The ratio of 1 gamma to 2 gamma pair production rates was obtained as a function of photon temperature and magnetic field strength.

  15. Low-dose photon irradiation alters cell differentiation via activation of hIK channels.

    PubMed

    Roth, Bastian; Gibhardt, Christine S; Becker, Patrick; Gebhardt, Manuela; Knoop, Jan; Fournier, Claudia; Moroni, Anna; Thiel, Gerhard

    2015-08-01

    To understand the impact of ionizing irradiation from diagnostics and radiotherapy on cells, we examined K(+) channel activity before and immediately after exposing cells to X-rays. Already, low dose in the cGy range caused in adenocarcinoma A549 cells within minutes a hyperpolarization following activation of the human intermediate-conductance Ca(2+)-activated K(+) channel (hIK). The response was specific for cells, which functionally expressed hIK channels and in which hIK activity was low before irradiation. HEK293 cells, which do not respond to X-ray irradiation, accordingly develop a sensitivity to this stress after heterologous expression of hIK channels. The data suggest that hIK activation involves a Ca(2+)-mediated signaling cascade because channel activation is suppressed by a strong cytosolic Ca(2+) buffer. The finding that an elevation of H2O2 causes an increase in the concentration of cytosolic Ca(2+) suggests that radicals, which emerge early in response to irradiation, trigger this Ca(2+) signaling cascade. Inhibition of hIK channels by specific blockers clotrimazole and TRAM-34 slowed cell proliferation and migration in "wound" scratch assays; ionizing irradiation, in turn, stimulated the latter process presumably via its activation of the hIK channels. These data stress an indirect radiosensitivity of hIK channels with an impact on cell differentiation. PMID:25277267

  16. TURBULENT PUMPING OF MAGNETIC FLUX REDUCES SOLAR CYCLE MEMORY AND THUS IMPACTS PREDICTABILITY OF THE SUN'S ACTIVITY

    SciTech Connect

    Karak, Bidya Binay; Nandy, Dibyendu E-mail: dnandi@iiserkol.ac.in

    2012-12-10

    Prediction of the Sun's magnetic activity is important because of its effect on space environment and climate. However, recent efforts to predict the amplitude of the solar cycle have resulted in diverging forecasts with no consensus. Yeates et al. have shown that the dynamical memory of the solar dynamo mechanism governs predictability, and this memory is different for advection- and diffusion-dominated solar convection zones. By utilizing stochastically forced, kinematic dynamo simulations, we demonstrate that the inclusion of downward turbulent pumping of magnetic flux reduces the memory of both advection- and diffusion-dominated solar dynamos to only one cycle; stronger pumping degrades this memory further. Thus, our results reconcile the diverging dynamo-model-based forecasts for the amplitude of solar cycle 24. We conclude that reliable predictions for the maximum of solar activity can be made only at the preceding minimum-allowing about five years of advance planning for space weather. For more accurate predictions, sequential data assimilation would be necessary in forecasting models to account for the Sun's short memory.

  17. Low-Enriched Uranium Fuel Conversion Activities for the High Flux Isotope Reactor, Annual Report for FY 2011

    SciTech Connect

    Renfro, David G; Cook, David Howard; Freels, James D; Griffin, Frederick P; Ilas, Germina; Sease, John D; Chandler, David

    2012-03-01

    This report describes progress made during FY11 in ORNL activities to support converting the High Flux Isotope Reactor (HFIR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Conversion from HEU to LEU will require a change in fuel form from uranium oxide to a uranium-molybdenum (UMo) alloy. With both radial and axial contouring of the fuel foil and an increase in reactor power to 100 MW, calculations indicate that the HFIR can be operated with LEU fuel with no degradation in performance to users from the current levels achieved with HEU fuel. Studies are continuing to demonstrate that the fuel thermal safety margins can be preserved following conversion. Studies are also continuing to update other aspects of the reactor steady state operation and accident response for the effects of fuel conversion. Technical input has been provided to Oregon State University in support of their hydraulic testing program. The HFIR conversion schedule was revised and provided to the GTRI program. In addition to HFIR conversion activities, technical support was provided directly to the Fuel Fabrication Capability program manager.

  18. Dual-tunable multiferroic active ring filter for microwave photonic oscillators

    NASA Astrophysics Data System (ADS)

    Vitko, V. V.; Nikitin, A. A.; Ustinov, A. B.; Kalinikos, B. A.

    2015-12-01

    A theoretical model of a microwave active ring filter based on a ferrite-ferroelectric layered structure serving as a waveguide for spin-electromagnetic waves is developed. An experimental prototype of the device is fabricated and characterized. The device is implemented as an active-ring resonator with a microwave amplifier and a ferrite-ferroelectric delay line. The resonance properties of this system are studied theoretically and experimentally. The results show dual control of central frequency of the filter with magnetic and electric fields. An effective Q-factor of 50 000 and tuning by 5 MHz with an electric field are achieved at 8 GHz.

  19. CH4 Flux Inversion Studies for Future Active Space CH4 Missions like MERLIN

    NASA Astrophysics Data System (ADS)

    Heimann, M.; Marshall, J.

    2011-12-01

    Space based active sensors such as the planned German-French CH4 DIAL MERLIN mission have a very small footprint and therefore see through moderately small cloud holes. This fact, in addition to being independent of reflected sunlight is expected to provide global coverage with a higher number of observations than heretofore possible with passive sensors. How will this impact our ability to infer the different types of CH4 surface sources? Using a global atmospheric inversion system we quantify the resulting error reduction of inferred CH4 source estimates as a function of spatial and temporal resolution given instrument accuracy and other parameters of potential satellite orbits. The methodology is based on the classical Green's function approach on a monthly global 8°x10° resolution (Houweling et al., 2004) extended by using a nested two-step procedure for the investigation of higher temporal and spatial source resolutions (Rödenbeck et al., 2009). We furthermore employ a nested Lagrangian system at very high resolution (down to 1/8° x 1/12°) to quantify the impact on the detection and quantification of point sources such as power plants, landfills, natural gas pipelines, forest fires, geological seeps, and volcanoes. We demonstrate that the current specification of the MERLIN DIAL mission with a nominal breakthrough instrument precision of 18 ppb and bias of 3 ppb over 50km would lead to a substantial improvement of CH4 source quantification in many regions of the world as compared to what is possible with the currently existing observations from the surface network or passive satellite sensors. Houweling, S, FM Breon, I Aben, C Roedenbeck, M Gloor, M Heimann, and P Ciais. 2004. "Inverse modeling of CO2 sources and sinks using satellite data: a synthetic inter-comparison of measurement techniques and their performance as a function of space and time." Atmospheric Chemistry And Physics 4: 523-538. Roedenbeck, C, C Gerbig, K Trusilova, and M Heimann. 2009. "A

  20. A High-Speed, Event-Driven, Active Pixel Sensor Readout for Photon-Counting Microchannel Plate Detectors

    NASA Technical Reports Server (NTRS)

    Kimble, Randy A.; Pain, Bedabrata; Norton, Timothy J.; Haas, J. Patrick; Oegerle, William R. (Technical Monitor)

    2002-01-01

    Silicon array readouts for microchannel plate intensifiers offer several attractive features. In this class of detector, the electron cloud output of the MCP intensifier is converted to visible light by a phosphor; that light is then fiber-optically coupled to the silicon array. In photon-counting mode, the resulting light splashes on the silicon array are recognized and centroided to fractional pixel accuracy by off-chip electronics. This process can result in very high (MCP-limited) spatial resolution while operating at a modest MCP gain (desirable for dynamic range and long term stability). The principal limitation of intensified CCD systems of this type is their severely limited local dynamic range, as accurate photon counting is achieved only if there are not overlapping event splashes within the frame time of the device. This problem can be ameliorated somewhat by processing events only in pre-selected windows of interest of by using an addressable charge injection device (CID) for the readout array. We are currently pursuing the development of an intriguing alternative readout concept based on using an event-driven CMOS Active Pixel Sensor. APS technology permits the incorporation of discriminator circuitry within each pixel. When coupled with suitable CMOS logic outside the array area, the discriminator circuitry can be used to trigger the readout of small sub-array windows only when and where an event splash has been detected, completely eliminating the local dynamic range problem, while achieving a high global count rate capability and maintaining high spatial resolution. We elaborate on this concept and present our progress toward implementing an event-driven APS readout.

  1. A High-Speed, Event-Driven, Active Pixel Sensor Readout for Photon-Counting Microchannel Plate Detectors

    NASA Technical Reports Server (NTRS)

    Kimble, Randy A.; Pain, B.; Norton, T. J.; Haas, P.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Silicon array readouts for microchannel plate intensifiers offer several attractive features. In this class of detector, the electron cloud output of the MCP intensifier is converted to visible light by a phosphor; that light is then fiber-optically coupled to the silicon array. In photon-counting mode, the resulting light splashes on the silicon array are recognized and centroided to fractional pixel accuracy by off-chip electronics. This process can result in very high (MCP-limited) spatial resolution for the readout while operating at a modest MCP gain (desirable for dynamic range and long term stability). The principal limitation of intensified CCD systems of this type is their severely limited local dynamic range, as accurate photon counting is achieved only if there are not overlapping event splashes within the frame time of the device. This problem can be ameliorated somewhat by processing events only in pre-selected windows of interest or by using an addressable charge injection device (CID) for the readout array. We are currently pursuing the development of an intriguing alternative readout concept based on using an event-driven CMOS Active Pixel Sensor. APS technology permits the incorporation of discriminator circuitry within each pixel. When coupled with suitable CMOS logic outside the array area, the discriminator circuitry can be used to trigger the readout of small sub-array windows only when and where an event splash has been detected, completely eliminating the local dynamic range problem, while achieving a high global count rate capability and maintaining high spatial resolution. We elaborate on this concept and present our progress toward implementing an event-driven APS readout.

  2. Twisted split-ring-resonator photonic metamaterial with huge optical activity.

    PubMed

    Decker, M; Zhao, R; Soukoulis, C M; Linden, S; Wegener, M

    2010-05-15

    Coupled split-ring-resonator metamaterials have previously been shown to exhibit large coupling effects, which are a prerequisite for obtaining large effective optical activity. By a suitable lateral arrangement of these building blocks, we completely eliminate linear birefringence and obtain pure optical activity and connected circular optical dichroism. Experiments around a 100 THz frequency and corresponding modeling are in good agreement. Rotation angles of about 30 degrees for 205 nm sample thickness are derived. PMID:20479819

  3. Effect of Activated Flux on the Microstructure, Mechanical Properties, and Residual Stresses of Modified 9Cr-1Mo Steel Weld Joints

    NASA Astrophysics Data System (ADS)

    Maduraimuthu, V.; Vasudevan, M.; Muthupandi, V.; Bhaduri, A. K.; Jayakumar, T.

    2012-02-01

    A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials. The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint.

  4. Analysis of the swimming activity of Pseudomonas aeruginosa by using photonic force microscope

    NASA Astrophysics Data System (ADS)

    Chan, Chia-Han; Chang, Bo-Jui; Huang, Ying-Jung; Fan, Chia-Chieh; Peng, Hwei-Ling; Chi, Sien; Hsu, Long

    2005-08-01

    Swimming activity of flagella is a main factor of the motility of bacteria. Flagella expressed on the surface of bacterial species serve as a primary means of motility including swimming. We propose to use optical tweezers to analyze the swimming activity of bacteria. The sample bacteria in the work is Pseudomonas aeruginosa, and it is a gram-negative bacterium and often causes leading to burn wound infections, urinary-tract infections, and pneumonia. The single polar flagellum of P. aeruginosa has been demonstrated to be important virulence and colonization factor of this opportunistic pathogen. We demonstrate a gene to regulate the bacterial swimming activity in P. aeruginosa PAO1 by biological method. However, the change of flagellar morphology was not observed by electron microscopy analysis, suggesting that the gene regulates the flagellar rotation that could not be detected by biological method. PFM exhibits a spatial resolution of a few nanometers to detect the relative position of the probe at an acquisition rate over 1 MHz. By binding a probe such as a bead or a quantum dot on the flagella, we expect the rotation of the probe due to the flagella could be detected. It is expected that the study of the swimming activity of P. aeruginosa provide potent method for the pathogenic role of the flagella in P. aeruginosa.

  5. Recent developments for an active UF6 gas target for photon-induced fission experiments

    NASA Astrophysics Data System (ADS)

    Freudenberger, M.; Eckardt, C.; Enders, J.; Göök, A.; von Neumann-Cosel, P.; Oberstedt, A.; Oberstedt, S.

    2013-12-01

    Recent developments for an active uranium-hexafluoride-loaded gas target as well as results on the detector gas properties are presented. The gas of choice is a mixture of argon with small amounts of UF6. This contribution presents the experimental setup and focusses on the electron drift velocity with increasing UF6 content. A time-dependent decrease in electron drift velocity is observed in our setup.

  6. Oxide film on 5052 aluminium alloy: Its structure and removal mechanism by activated CsF-AlF3 flux in brazing

    NASA Astrophysics Data System (ADS)

    Xiao, Bing; Wang, Dongpo; Cheng, Fangjie; Wang, Ying

    2015-05-01

    The oxide-film structure on the 5052 Al alloy and the film-removal mechanism by activated CsF-AlF3 flux in brazing were studied. Characterisation of the oxide film shows that thermally activated Mg, segregated from the alloy's interior, was significantly enriched and oxidised during medium-temperature brazing. Thus, the outer oxide surface consisted of the amorphous MgO-like phase, and the interior of the oxide film comprised mainly the amorphous MgO-like phase and dispersely distributed and less-ordered MgAl2O4. The MgO-like phase was the main obstacle to oxide removal in brazing. The activated ZnCl2-containing CsF-AlF3 flux effectively removed the oxide film, and the 5052 Al alloy was successfully brazed by the Zn-Al filler metal and activated flux. When Zn2+ in the molten flux permeated the oxide film through cracks, its chemical reaction with the Al substrate loosened the oxide film, which was eventually pushed out as the filler metal spread over the alloy surface.

  7. Accretion disc dynamo activity in local simulations spanning weak-to-strong net vertical magnetic flux regimes

    NASA Astrophysics Data System (ADS)

    Salvesen, Greg; Simon, Jacob B.; Armitage, Philip J.; Begelman, Mitchell C.

    2016-03-01

    Strongly magnetized accretion discs around black holes have attractive features that may explain enigmatic aspects of X-ray binary behaviour. The structure and evolution of these discs are governed by a dynamo-like mechanism, which channels part of the accretion power liberated by the magnetorotational instability (MRI) into an ordered toroidal magnetic field. To study dynamo activity, we performed three-dimensional, stratified, isothermal, ideal magnetohydrodynamic shearing box simulations. The strength of the self-sustained toroidal magnetic field depends on the net vertical magnetic flux, which we vary across almost the entire range over which the MRI is linearly unstable. We quantify disc structure and dynamo properties as a function of the initial ratio of mid-plane gas pressure to vertical magnetic field pressure, β _0^mid = p_gas / p_B. For 10^5 ≥ β _0^mid ≥ 10 the effective α-viscosity parameter scales as a power law. Dynamo activity persists up to and including β _0^mid = 10^2, at which point the entire vertical column of the disc is magnetic pressure dominated. Still stronger fields result in a highly inhomogeneous disc structure, with large density fluctuations. We show that the turbulent steady state βmid in our simulations is well matched by the analytic model of Begelman et al. describing the creation and buoyant escape of toroidal field, while the vertical structure of the disc can be broadly reproduced using this model. Finally, we discuss the implications of our results for observed properties of X-ray binaries.

  8. UNESCO active learning approach in optics and photonics leads to significant change in Morocco

    NASA Astrophysics Data System (ADS)

    Berrada, K.; Channa, R.; Outzourhit, A.; Azizan, M.; Oueriagli, A.

    2014-07-01

    There are many difficulties in teaching science and technology in developing countries. Several different teaching strategies have to be applied in these cases. More specifically, for developing countries competencies in teaching science in the introductory classroom has attracted much attention. As a specific example we will consider the Moroccan system. In most developing countries everything is moving so slowly that the progress stays static for development. Also, any change needs time, effort and engagement. In our case we discovered that many teachers feel uncomfortable when introducing new teaching methods and evaluation in classes at introductory physics. However, the introduction of an Active Learning in our curricula showed difficulties that students have in understanding physics and especially concepts. Students were interested in having Active Learning courses much more than passive and traditional ones. Changing believes on physical phenomena and reality of the world students become more attractive and their way of thinking Science changed. The main philosophy of fostering modern hands-on learning techniques -adapted to local needs and availability of teaching resources- is elaborated. The Active Learning program provides the teachers with a conceptual evaluation instrument, drawn from relevant physics education research, giving teachers an important tool to measure student learning. We will try to describe the UNESCO Chair project in physics created in 2010 at Cadi Ayyad University since our first experience with UNESCO ALOP program. Many efforts have been done so far and the project helps now to develop more national and international collaborations between universities and Regional Academies of Education and Training. As a new result of these actions and according to our local needs, the translation of the ALOP program into Arabic is now available under the auspice of UNESCO and encouragement of international partners SPIE, ICTP, ICO and OSA.

  9. The AmeriFlux data activity and data system: an evolving collection of data management techniques, tools, products and services

    NASA Astrophysics Data System (ADS)

    Boden, T. A.; Krassovski, M.; Yang, B.

    2013-02-01

    The Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL), USA has provided scientific data management support for the US Department of Energy and international climate change science since 1982. Among the many data archived and available from CDIAC are collections from long-term measurement projects. One current example is the AmeriFlux measurement network. AmeriFlux provides continuous measurements from forests, grasslands, wetlands, and croplands in North, Central, and South America and offers important insight about carbon cycling in terrestrial ecosystems. To successfully manage AmeriFlux data and support climate change research, CDIAC has designed flexible data systems using proven technologies and standards blended with new, evolving technologies and standards. The AmeriFlux data system, comprised primarily of a relational database, a PHP based data-interface and a FTP server, offers a broad suite of AmeriFlux data. The data interface allows users to query the AmeriFlux collection in a variety of ways and then subset, visualize and download the data. From the perspective of data stewardship, on the other hand, this system is designed for CDIAC to easily control database content, automate data movement, track data provenance, manage metadata content, and handle frequent additions and corrections. CDIAC and researchers in the flux community developed data submission guidelines to enhance the AmeriFlux data collection, enable automated data processing, and promote standardization across regional networks. Both continuous flux and meteorological data and irregular biological data collected at AmeriFlux sites are carefully scrutinized by CDIAC using established quality-control algorithms before the data are ingested into the AmeriFlux data system. Other tasks at CDIAC include reformatting and standardizing the diverse and heterogeneous datasets received from individual sites into a uniform and consistent network database

  10. The AmeriFlux data activity and data system: an evolving collection of data management techniques, tools, products and services

    NASA Astrophysics Data System (ADS)

    Boden, T. A.; Krassovski, M.; Yang, B.

    2013-06-01

    The Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL), USA has provided scientific data management support for the US Department of Energy and international climate change science since 1982. Among the many data archived and available from CDIAC are collections from long-term measurement projects. One current example is the AmeriFlux measurement network. AmeriFlux provides continuous measurements from forests, grasslands, wetlands, and croplands in North, Central, and South America and offers important insight about carbon cycling in terrestrial ecosystems. To successfully manage AmeriFlux data and support climate change research, CDIAC has designed flexible data systems using proven technologies and standards blended with new, evolving technologies and standards. The AmeriFlux data system, comprised primarily of a relational database, a PHP-based data interface and a FTP server, offers a broad suite of AmeriFlux data. The data interface allows users to query the AmeriFlux collection in a variety of ways and then subset, visualize and download the data. From the perspective of data stewardship, on the other hand, this system is designed for CDIAC to easily control database content, automate data movement, track data provenance, manage metadata content, and handle frequent additions and corrections. CDIAC and researchers in the flux community developed data submission guidelines to enhance the AmeriFlux data collection, enable automated data processing, and promote standardization across regional networks. Both continuous flux and meteorological data and irregular biological data collected at AmeriFlux sites are carefully scrutinized by CDIAC using established quality-control algorithms before the data are ingested into the AmeriFlux data system. Other tasks at CDIAC include reformatting and standardizing the diverse and heterogeneous datasets received from individual sites into a uniform and consistent network database

  11. Topological photonic crystal with ideal Weyl points

    NASA Astrophysics Data System (ADS)

    Wang, Luyang; Jian, Shao-Kai; Yao, Hong

    Weyl points in three-dimensional photonic crystals behave as monopoles of Berry flux in momentum space. Here, based on symmetry analysis, we show that a minimal number of symmetry-related Weyl points can be realized in time-reversal invariant photonic crystals. We propose to realize these ``ideal'' Weyl points in modified double-gyroid photonic crystals, which is confirmed by our first-principle photonic band-structure calculations. Photonic crystals with ideal Weyl points are qualitatively advantageous in applications such as angular and frequency selectivity, broadband invisibility cloaking, and broadband 3D-imaging.

  12. Topological photonic crystal with equifrequency Weyl points

    NASA Astrophysics Data System (ADS)

    Wang, Luyang; Jian, Shao-Kai; Yao, Hong

    2016-06-01

    Weyl points in three-dimensional photonic crystals behave as monopoles of Berry flux in momentum space. Here, based on general symmetry analysis, we show that a minimal number of four symmetry-related (consequently equifrequency) Weyl points can be realized in time-reversal invariant photonic crystals. We further propose an experimentally feasible way to modify double-gyroid photonic crystals to realize four equifrequency Weyl points, which is explicitly confirmed by our first-principle photonic band-structure calculations. Remarkably, photonic crystals with equifrequency Weyl points are qualitatively advantageous in applications including angular selectivity, frequency selectivity, invisibility cloaking, and three-dimensional imaging.

  13. Carbon Flux and Isotopic Character of Soil and Soil Gas in Stabilized and Active Thaw Slumps in Northwest Alaska

    NASA Astrophysics Data System (ADS)

    Jensen, A.; Crosby, B. T.; Mora, C. I.; Lohse, K. A.

    2012-12-01

    Permafrost soils store nearly half the world's global carbon. Warming of arctic landscape results in permafrost thaw which causes ground subsidence or thermokarst. On hillslopes, these features rapidly and dramatically alter soil structure, temperature, and moisture, as well as the content and quality of soil organic matter. These changes alter both the rate and mechanism of carbon cycling in permafrost soils, making frozen soils available to both anaerobic and aerobic decomposition. In order to improve our predictive capabilities, we use a chronosequence thaw slumps to examine how fluxes from active and stabilized features differ. Our study site is along the Selawik River in northwest Alaska where a retrogressive thaw slump initiated in the spring of 2004. It has grown to a surface area of 50,000 m2. Products of the erosion are stored on the floor of the feature, trapped on a fan or flushed into the Selawik River. North of slump is undisturbed tundra and adjacent to the west is a slump feature that stabilized and is now covered with a second generation of spruce trees. In this 2 year study, we use measurements of CO2 efflux, δC13 in soil profiles and CO2 and CH4 abundance to constrain the response of belowground carbon emissions. We also focused on constraining which environmental factors govern C emissions within each of the above ecosystems. To this end, we measured soil temperature, and moisture, abundance and quality of soil organic carbon (SOC), water content, and bulk carbon compositions. Preliminary data from the summer of 2011 suggest that vegetation composition and soil temperature exert the strong control on CO2 efflux. The floor of the active slump and fan are bare mineral soils and are generally 10 to 15°C warmer than the tundra and stabilized slump. Consistently decreasing δC13 soil gas profiles in the recovered slump confirm that this region is a well-drained soil dominated by C3 vegetation. The δC13 gas profiles for the tundra, active slump

  14. Deep investigation on inorganic fraction of atmospheric PM in Mediterranean area by neutron and photon activation analysis

    PubMed Central

    2013-01-01

    Background Anthropogenic activities introduce materials increasing levels of many dangerous substances for the environmental quality and being hazardous to human health. Major attention has been given to those elements able to alter the environment and endanger human health. The airborne particulate matter pollutant is considered one of the most difficult task in environmental chemistry for its complex composition and implications complicating notably the behavior comprehension. So, for investigating deeply the elemental composition we used two nuclear techniques, Neutron Activation Analysis and Photon Activation Analysis, characterized by high sensitivity, precision and accuracy. An important task has been devoted to the investigation of Quality Control (QC) and Quality Assurance (QA) of the methodology used in this study. This study was therefore extended as far back as possible in time (from 1965 until 2000) in order to analyze the trend of airborne concentration of pollutant elements in connection with the industrial and lifestyle growth during the entire period. Results Almost all the elements may be attributed to long-range transport phenomena from other natural and/or anthropogenic sources: this behavior is common to all the periods studied even if a very light decreasing trend can be evidenced from 1970 to 2002. Finally, in order to investigate a retrospective study of elements in PM10 and their evolution in relationship with the natural or anthropogenic origins, we have investigated the Enrichment Factors. The study shows the EF trends for some elements in PM10 during four decades. Conclusions The two nuclear techniques have allowed to reach elevated sensibility/accuracy levels for determining elements at very low concentrations (trace and ultra-trace levels). The element concentrations determined in this study do not basically show a significant level of attention from a toxicological point of view. PMID:24196275

  15. Assessment of energetic costs of AhR activation by β-naphthoflavone in rainbow trout (Oncorhynchus mykiss) hepatocytes using metabolic flux analysis

    SciTech Connect

    Nault, Rance; Abdul-Fattah, Hiba; Mironov, Gleb G.; Berezovski, Maxim V.; Moon, Thomas W.

    2013-08-15

    Exposure to environmental contaminants such as activators of the aryl hydrocarbon receptor (AhR) leads to the induction of defense and detoxification mechanisms. While these mechanisms allow organisms to metabolize and excrete at least some of these environmental contaminants, it has been proposed that these mechanisms lead to significant energetic challenges. This study tests the hypothesis that activation of the AhR by the model agonist β-naphthoflavone (βNF) results in increased energetic costs in rainbow trout (Oncorhynchus mykiss) hepatocytes. To address this hypothesis, we employed traditional biochemical approaches to examine energy allocation and metabolism including the adenylate energy charge (AEC), protein synthesis rates, Na{sup +}/K{sup +}-ATPase activity, and enzyme activities. Moreover, we have used for the first time in a fish cell preparation, metabolic flux analysis (MFA) an in silico approach for the estimation of intracellular metabolic fluxes. Exposure of trout hepatocytes to 1 μM βNF for 48 h did not alter hepatocyte AEC, protein synthesis, or Na{sup +}/K{sup +}-ATPase activity but did lead to sparing of glycogen reserves and changes in activities of alanine aminotransferase and citrate synthase suggesting altered metabolism. Conversely, MFA did not identify altered metabolic fluxes, although we do show that the dynamic metabolism of isolated trout hepatocytes poses a significant challenge for this type of approach which should be considered in future studies. - Highlights: • Energetic costs of AhR activation by βNF was examined in rainbow trout hepatocytes. • Metabolic flux analysis was performed on a fish cell preparation for the first time. • Exposure to βNF led to sparing of glycogen reserves and altered enzyme activities. • Adenylate energy charge was maintained despite temporal changes in metabolism.

  16. The water fluxes of the Yellow River to the sea in the past 50 years, in response to climate change and human activities.

    PubMed

    Jiongxin, Xu

    2005-05-01

    Since the 1970s, the water fluxes to the sea of the Yellow River have declined significantly. Based on data of precipitation, air temperature, the measured and "natural" river flow, the water diversion and consumption, and the areas of erosion and sediment control measures over the drainage basin, water fluxes to the sea of the Yellow River are studied in relation with the influences of changing climate and human activities. The Yellow River basin can be divided into different water source areas; multiple regression indicates that the variation in precipitation over different water source areas has different effect on water fluxes to the sea. In the period between 1970 and 1997, averaged air temperature over the whole Yellow River increased by about 1.0 degree C, from 16.5 degrees C to 17.5 degrees C, a factor that is negatively correlated with the water yield of the Yellow River. Water diversion and consumption has sharply increased and resulted in a significant decline in the water fluxes to the sea. Since the 1960s, erosion and sediment control measures have been practiced over the drainage basin. This factor, to a lesser degree, is also responsible for the decrease in water fluxes to the sea. A multiple regression equation has been established to estimate the change in water fluxes to the sea caused by the changes in precipitation, air temperature, water diversion and consumption, erosion, and sediment control measures, indicating that the contribution of water diversion and consumption to the variation in annual water flux to the sea is 41.3%, that of precipitation is 40.8%, that of temperature is 11.4%, and that of erosion and sediment control measures is 6.5%. PMID:15924206

  17. Fluorescence-quenching-based homogeneous caspase-3 activity assay using photon upconversion.

    PubMed

    Vuojola, Johanna; Riuttamäki, Terhi; Kulta, Essi; Arppe, Riikka; Soukka, Tero

    2012-05-01

    Caspase proteases are key mediators in apoptosis and thus of great interest in pharmaceutical industry. Enzyme-activity assays are commonly employed in the screening of protease inhibitors that are potential drug candidates. Conventional homogeneous fluorescence-based assays are susceptible to autofluorescence originating from biological material. This background autofluorescence can be eliminated by using upconverting phosphors (UCPs) that emit visible light upon excitation at near-infrared. In the assay energy was transferred from a UCP-donor to a conventional fluorophore acceptor that resided at one end of a caspase-3-specific substrate peptide. Attached to the other end was a quencher molecule that was used to attenuate the acceptor emission through intramolecular energy transfer in an intact peptide. In non-inhibitory conditions the enzyme reaction separated the fluorophore from the quencher and the emission of the fluorophore was recovered. The method was applied for the detection and characterization of a known caspase-3 inhibitor Z-DEVD-FMK, and the assay gave IC(50) values of approximately 13 nM for this inhibitor. We have demonstrated the applicability of UCPs on a fluorescence-quenching-based homogeneous enzyme-activity assay for the detection of caspase-3 inhibitors. The use of near-infrared excitable UCPs enables inexpensive instrumentation and total elimination of autofluorescence, while the use of an internally quenched substrate molecule diminishes the background resulting from radiatively excited acceptor molecules. The reduction of autofluorescence and radiative background result in high signal-to-background ratios (ratios of approximately 100 were obtained). By further utilizing assay miniaturization and signal enhancement in a white microtitration plate, a significant reduction in the reagent consumption can be achieved rendering the assay applicable for high-throughput screening. PMID:22502613

  18. Photon activation therapy of RG2 glioma carrying Fischer rats using stable thallium and monochromatic synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Ceberg, Crister; Jönsson, Bo-Anders; Prezado, Yolanda; Pommer, Tobias; Nittby, Henrietta; Englund, Elisabet; Grafström, Gustav; Edvardsson, Anneli; Stenvall, Anna; Strömblad, Susanne; Wingårdh, Karin; Persson, Bertil; Elleaume, Hélène; Baldetorp, Bo; Salford, Leif G.; Strand, Sven-Erik

    2012-12-01

    75 RG2 glioma-carrying Fischer rats were treated by photon activation therapy (PAT) with monochromatic synchrotron radiation and stable thallium. Three groups were treated with thallium in combination with radiation at different energy; immediately below and above the thallium K-edge, and at 50 keV. Three control groups were given irradiation only, thallium only, or no treatment at all. For animals receiving thallium in combination with radiation to 15 Gy at 50 keV, the median survival time was 30 days, which was 67% longer than for the untreated controls (p = 0.0020) and 36% longer than for the group treated with radiation alone (not significant). Treatment with thallium and radiation at the higher energy levels were not effective at the given absorbed dose and thallium concentration. In the groups treated at 50 keV and above the K-edge, several animals exhibited extensive and sometimes contra-lateral edema, neuronal death and frank tissue necrosis. No such marked changes were seen in the other groups. The results were discussed with reference to Monte Carlo calculated electron energy spectra and dose enhancement factors.

  19. Nondestructive assay of fluorine in geological and other materials by instrumental photon activation analysis with a microtron

    NASA Astrophysics Data System (ADS)

    Krausová, Ivana; Mizera, Jiří; Řanda, Zdeněk; Chvátil, David; Krist, Pavel

    2015-01-01

    Reliable determination of low concentrations of fluorine in geological and coal samples is difficult. It usually requires tedious decomposition and dissolution of the sample followed by chemical conversion of fluorine into its anionic form. The present paper examines possibilities of non-destructive determination of fluorine, mainly in minerals, rocks and coal, by instrumental photon activation analysis (IPAA) using the MT-25 microtron. The fluorine assay consists of counting the positron-electron annihilation line of 18F at 511 keV, which is a product of the photonuclear reaction 19F(γ, n)18F and a pure positron emitter. The assay is complicated by the simultaneous formation of other positron emitters. The main contributors to interference in geological samples are from 45Ti and 34mCl, whereas those from 44Sc and 89Zr are minor. Optimizing beam energy and irradiation-decay-counting times, together with using interfering element calibration standards, allowed reliable IPAA determination of fluorine in selected USGS and CRPG geochemical reference materials, NIST coal reference materials, and NIST RM 8414 Bovine Muscle. In agreement with the published data obtained by PIGE, the results of the F assay by IPAA have revealed erroneous reference values provided for the NIST reference materials SRM 1632 Bituminous Coal and RM 8414 Bovine Muscle. The detection limits in rock and coal samples are in the range of 10-100 μg g-1.

  20. Photon absorptiometry

    SciTech Connect

    Velchik, M.G.

    1987-01-01

    Recently, there has been a renewed interest in the detection and treatment of osteoporosis. This paper is a review of the merits and limitations of the various noninvasive modalities currently available for the measurement of bone mineral density with special emphasis placed upon the nuclear medicine techniques of single-photon and dual-photon absorptiometry. The clinicians should come away with an understanding of the relative advantages and disadvantages of photon absorptiometry and its optimal clinical application. 49 references.

  1. The effects of environmental parameters on diffuse degassing at Stromboli volcano: Insights from joint monitoring of soil CO2 flux and radon activity

    NASA Astrophysics Data System (ADS)

    Laiolo, M.; Ranaldi, M.; Tarchini, L.; Carapezza, M. L.; Coppola, D.; Ricci, T.; Cigolini, C.

    2016-04-01

    Soil CO2 flux and 222Rn activity measurements may positively contribute to the geochemical monitoring of active volcanoes. The influence of several environmental parameters on the gas signals has been substantially demonstrated. Therefore, the implementation of tools capable of removing (or minimising) the contribution of the atmospheric effects from the acquired time series is a challenge in volcano surveillance. Here, we present 4 years-long continuous monitoring (from April 2007 to September 2011) of radon activity and soil CO2 flux collected on the NE flank of Stromboli volcano. Both gases record higher emissions during fall-winter (up to 2700 Bq * m- 3 for radon and 750 g m- 2 day- 1 for CO2) than during spring-summer seasons. Short-time variations on 222Rn activity are modulated by changes in soil humidity (rainfall), and changes in soil CO2 flux that may be ascribed to variations in wind speed and direction. The spectral analyses reveal diurnal and semi-diurnal cycles on both gases, outlining that atmospheric variations are capable to modify the gas release rate from the soil. The long-term soil CO2 flux shows a slow decreasing trend, not visible in 222Rn activity, suggesting a possible difference in the source depth of the of the gases, CO2 being deeper and likely related to degassing at depth of the magma batch involved in the February-April 2007 effusive eruption. To minimise the effect of the environmental parameters on the 222Rn concentrations and soil CO2 fluxes, two different statistical treatments were applied: the Multiple Linear Regression (MLR) and the Principal Component Regression (PCR). These approaches allow to quantify the weight of each environmental factor on the two gas species and show a strong influence of some parameters on the gas transfer processes through soils. The residual values of radon and CO2 flux, i.e. the values obtained after correction for the environmental influence, were then compared with the eruptive episodes that

  2. Integration of electronics and photonics in active material by femtosecond laser for functional microdevice fabrication

    NASA Astrophysics Data System (ADS)

    Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2010-02-01

    Recently, hybrid integration of multifunctional micro-components for creating complex, intelligent micro/nano systems has attracted significant attention. These micro/nano systems have important applications in a variety of areas, such as healthcare, environment, communication, national security, and so on. Until now, fabrication of micro/nano systems incorporated with different functions is still a challenging issue, which generally requires fabrication of microcomponents beforehand followed by assembly and packaging procedures. Thus, the fabrication process is complex and costly. In recent years, the rapid development of femtosecond laser microfabrication technology has enabled direct fabrication and integration of multifunctional components, such as microfluidics, microoptics, micromechanics, microelectronics, etc., into a substrate. Particularly, in this talk, we show the use of femtosecond laser microfabrication for integrating microelectronics and microphotonics. Both microelectrodes and optical waveguides can be directly embedded in active materials after a femtosecond laser direct writing followed by electroless chemical plating. As examples, electric-optic (EO) modulators were fabricated in lithium niobate (LiNbO3) crystal and their functions were demonstrated.

  3. Measuring Mass Flux, Kinetic Luminosities and Abundances in Outflows from Active Galactic Nuclei using the FUSE Archive

    NASA Astrophysics Data System (ADS)

    Kriss, Gerard

    Previous studies of active galactic nuclei (AGN) show that over half of all AGN show outflows from their nuclear regions as evidenced by blue-shifted absorption lines. Measuring the energetics of outflows is a high priority for NASA's science objective of understanding the effect of energetic processes around supermassive black holes on the surrounding environment in galaxies, clusters and the intergalactic medium. Therefore, the most important goals in the study of these outflows are to measure their mass flux, kinetic luminosity, and chemical abundances in order to assess their importance to AGN feedback on their environment. The broad range of redshifts and the access to short rest wavelengths made possible by Far Ultraviolet Spectroscopic Explorer (FUSE) observations of AGN opens a vast discovery space using the many more diagnostic lines (compared to longer wavelengths) in the 500-1050 A range (rest wavelengths) that show up as absorption troughs in AGN outflows. This is especially true for the density- sensitive excited-state transitions of highly ionized elements (e.g., OIV* 790) that can yield the distance of the outflows from the central source, and the increasingly higher ionization species (O VI, Ne VIII, Na IX and Mg X) that supply the crucial connection between the UV and X-ray (so-called warm absorbers) manifestation of AGN outflows. Over the course of its 10 years of operation, FUSE observed nearly two hundred active galactic nuclei (AGN) at redshifts from less than 0.01 to nearly 3. While a select few of the brightest individual objects have been studied in detail, the surveys of the overall data set done to date examined only the lowest redshift objects (z<0.15), and only using data from the first 6 years or so of the mission. Our preliminary examination of the FUSE archive reveals dozens of AGN with appropriate characteristics for us to carry out our proposed program of study. Many of the best objects also have HST spectra available, and we will

  4. Developmental axon stretch stimulates neuron growth while maintaining normal electrical activity, intracellular calcium flux, and somatic morphology

    PubMed Central

    Loverde, Joseph R.; Pfister, Bryan J.

    2015-01-01

    Elongation of nerve fibers intuitively occurs throughout mammalian development, and is synchronized with expansion of the growing body. While most tissue systems enlarge through mitosis and differentiation, elongation of nerve fibers is remarkably unique. The emerging paradigm suggests that axons undergo stretch as contiguous tissues enlarge between the proximal and distal segments of spanning nerve fibers. While stretch is distinct from growth, tension is a known stimulus which regulates the growth of axons. Here, we hypothesized that the axon stretch-growth process may be a natural form of injury, whereby regenerative processes fortify elongating axons in order to prevent disconnection. Harnessing the live imaging capability of our axon stretch-growth bioreactors, we assessed neurons both during and following stretch for biomarkers associated with injury. Utilizing whole-cell patch clamp recording, we found no evidence of changes in spontaneous action potential activity or degradation of elicited action potentials during real-time axon stretch at strains of up to 18% applied over 5 min. Unlike traumatic axonal injury, functional calcium imaging of the soma revealed no shifts in free intracellular calcium during axon stretch. Finally, the cross-sectional areas of nuclei and cytoplasms were normal, with no evidence of chromatolysis following week-long stretch-growth limited to the lower of 25% strain or 3 mm total daily stretch. The neuronal growth cascade coupled to stretch was concluded to be independent of the changes in membrane potential, action potential generation, or calcium flux associated with traumatic injury. While axon stretch-growth is likely to share overlap with regenerative processes, we conclude that developmental stretch is a distinct stimulus from traumatic axon injury. PMID:26379492

  5. NON-THERMAL RESPONSE OF THE CORONA TO THE MAGNETIC FLUX DISPERSAL IN THE PHOTOSPHERE OF A DECAYING ACTIVE REGION

    SciTech Connect

    Harra, L. K.; Abramenko, V. I.

    2012-11-10

    We analyzed Solar Dynamics Observatory line-of-sight magnetograms for a decaying NOAA active region (AR) 11451 along with co-temporal Extreme-Ultraviolet Imaging Spectrometer (EIS) data from the Hinode spacecraft. The photosphere was studied via time variations of the turbulent magnetic diffusivity coefficient, {eta}(t), and the magnetic power spectrum index, {alpha}, through analysis of magnetogram data from the Helioseismic and Magnetic Imager (HMI). These measure the intensity of the random motions of magnetic elements and the state of turbulence of the magnetic field, respectively. The time changes of the non-thermal energy release in the corona was explored via histogram analysis of the non-thermal velocity, v {sub nt}, in order to highlight the largest values at each time, which may indicate an increase in energy release in the corona. We used the 10% upper range of the histogram of v {sub nt} (which we called V {sup upp} {sub nt}) of the coronal spectral line of Fe XII 195 A. A 2 day time interval was analyzed from HMI data, along with the EIS data for the same field of view. Our main findings are the following. (1) The magnetic turbulent diffusion coefficient, {eta}(t), precedes the upper range of the v {sub nt} with the time lag of approximately 2 hr and the cross-correlation coefficient of 0.76. (2) The power-law index, {alpha}, of the magnetic power spectrum precedes V {sup upp} {sub nt} with a time lag of approximately 3 hr and the cross-correlation coefficient of 0.5. The data show that the magnetic flux dispersal in the photosphere is relevant to non-thermal energy release dynamics in the above corona. The results are consistent with the nanoflare mechanism of the coronal heating, due to the time lags being consistent with the process of heating and cooling the loops heated by nanoflares.

  6. Relating photosynthetic activity of BSCs from spectral indices: a first step to upscale BSC role on carbon fluxes

    NASA Astrophysics Data System (ADS)

    Rodriguez-Caballero, Emilio; Chamizo, Sonia; Miralles, Isabel; Ortega, Raul; Luna, Lourdes; Cantón, Yolanda

    2014-05-01

    Arid and semiarid ecosystems are water limited environments where water availability is the main limiting factor controlling vegetation cover, productivity and ecosystem function. However, bare areas of these systems are usually covered by a thin layer of photoautrophic communities of microorganisms comprising cyanobacteria, algae, microfungi, lichens or bryophytes, so called biological soil crusts (BSCs), which may cover up to 70 % of the soil surface in these areas. These BSCs are capable to survive long drought periods, during which their physiological activity ceases, and become active just after rainfall or even after dew or fog events, thus triggering their photosynthetic activity. So, they play an active role in C storage in arid ecosystems, where they are considered the main agent of nutrient input on bare areas. Moreover, the carbon (C) stored in soils covered by BSCs may constitute an important nutrient surplus for soil microbial communities or vegetation. Thus, having accurate continuous information about C stocks and C fluxes in soils covered by BSCs, at ecosystems scale, constitutes a relevant issue for scientists and researchers from many different disciplines, and is crucial for assessing the impacts of increasing atmospheric CO2 concentration on global environmental change. Remote sensing images and derived vegetation indices are presented as one of the most promising tools to achieve this goal, since they provide spatially explicit information with high temporal resolution. So that, quantifying the photosynthetic activity on BSC areas using remote sensing data constitutes an essential step to advance in the knowledge about the role of arid and semiarid regions in global C balance. In this study we analyzed the potential of the most widely used vegetation indices to estimate gross photosynthesis (GP) in BSCs. To achieve this objective, GP was calculated, after a rainfall event on different BSCs and on bare field plots, as the sum of net primary

  7. On the Predictability Limit of a Chaotic Flux Transport Solar Dynamo Model and its implications for Solar Magnetic Activity Forecasting

    NASA Astrophysics Data System (ADS)

    Sanchez, S. M.; Fournier, A.; Aubert, J.

    2012-12-01

    The Sun's magnetic activity cycle undoubtedly plays a major role on space weather, having a strong impact not only in satellite operation but also probably on the long-term variability of the Earth's climate. It is therefore of great importance to better understand the mechanism underlying the magnetic activity cycle - the solar dynamo. Looking into the past, historical data points both to amplitude and frequency fluctuations of the solar magnetic cycles, displaying even episodes of no sunspot observations such as the Maunder Minimum. This observational constraint together with the intrinsic non-linear turbulent regime in which the solar dynamo operates suggests the chaotic nature of the system, and predictions of solar dynamo activity based on the comprehensive set of equations describing its evolution is currently out of reach. On the other hand, solar dynamo models based on the axisymmetric approximation of the Sun's large-scale magnetic field are able to reproduce some of the fundamental features of the solar magnetic field dynamics. These models often include two main processes to transform poloidal into toroidal fields and vice-versa: first the shearing action of solar differential rotation on an initial poloidal field generates the toroidal field; secondly helical motions due to the Coriolis force on toroidal fields acts as to regenerate the poloidal field. Assuming different strategies for the latter process, these models are currently being used in magnetic activity forecasting for cycle 24. For this purpose, it is of great importance to access the predictability limit of such kind of models and what this information will imply for solar magnetic activity forecasting. In this work we consider the case of an axisymmetric flux-transport dynamo in the kinematic regime, using both Babcock-Leighton effect at the surface and alpha-effect at the base of the convection zone as the mechanisms for poloidal field regeneration in a full meridional plane. Admitting

  8. Photon Colliders

    SciTech Connect

    Gronberg, J

    2002-10-07

    A photon collider interaction region has the possibility of expanding the physics reach of a future TeV scale electron-positron collider. A survey of ongoing efforts to design the required lasers and optics to create a photon collider is presented in this paper.

  9. Analysis of lateritic material from Cerro Impacto by instrumental neutron activation employing a low-energy photon semiconductor and a high-energy Ge(Li) detector

    SciTech Connect

    LaBrecque, J.J.; Beusen, J.M.; Van Grieken, R.E.

    1986-01-01

    Nineteen elements were determined in four different grain size fractions of a bulk geological material from Cerro Impacto for a study of the physical (mechanical) concentration process of different elements based upon the hardness of the different minerals. The analysis was performed by excitation of the sample with a high, slow neutron flux followed by gamma-ray spectroscopy with both a conventional Ge(Li) high-energy detector and a low-energy photon detector (LEPD). The accuracy of this method was studied with the use of two standard reference materials, SY-2 and SY-3, which are similar to the real samples. The values determined were also compared with a secondary target x-ray fluorescence method for all the elements that were suitable to both methods. Actually, the x-ray fluorescence method was found to be more complementary than competitive. 10 refs., 2 figs., 4 tabs.

  10. Application of epithermal neutron activation in multielement analysis of silicate rocks employing both coaxial Ge(Li) and low energy photon detector systems

    USGS Publications Warehouse

    Baedecker, P.A.; Rowe, J.J.; Steinnes, E.

    1977-01-01

    The instrumental activation analysis of silicate rocks using epithermal neutrons has been studied using both high resolution coaxial Ge(Li) detectors and low energy photon detectors, and applied to the determination of 23 elements in eight new U.S.G.S. standard rocks. The analytical use X-ray peaks associated with electron capture or internal conversion processes has been evaluated. Of 28 elements which can be considered to be determinable by instrumental means, the epithermal activation approach is capable of giving improved sensitivity and precision in 16 cases, over the normal INAA procedure. In eleven cases the use of the low energy photon detector is thought to show advantages over convertional coaxial Ge(Li) spectroscopy. ?? 1977 Akade??miai Kiado??.

  11. Room-temperature continuous-wave operation of lateral current injection wavelength-scale embedded active-region photonic-crystal laser.

    PubMed

    Matsuo, Shinji; Takeda, Koji; Sato, Tomonari; Notomi, Masaya; Shinya, Akihiko; Nozaki, Kengo; Taniyama, Hideaki; Hasebe, Koichi; Kakitsuka, Takaaki

    2012-02-13

    We have developed a wavelength-scale embedded active-region photonic-crystal laser using lateral p-i-n structure. Zn diffusion and Si ion implantation are used for p- and n-type doping. Room-temperature continuous-wave lasing behavior is clearly observed from the injection current dependence of the output power, 3dB-bandwidth of the peak, and lasing wavelength. The threshold current is 390 μA and the estimated effective threshold current is 9.4 μA. The output power in output waveguide is 1.82 μW for a 2.0-mA current injection. These results indicate that the embedded active-region structure effectively reduce the thermal resistance. Ultrasmall electrically driven lasers are an important step towards on-chip photonic network applications. PMID:22418134

  12. Nuclear photonics

    SciTech Connect

    Habs, D.; Guenther, M. M.; Jentschel, M.; Thirolf, P. G.

    2012-07-09

    With the planned new {gamma}-beam facilities like MEGa-ray at LLNL (USA) or ELI-NP at Bucharest (Romania) with 10{sup 13}{gamma}/s and a band width of {Delta}E{gamma}/E{gamma} Almost-Equal-To 10{sup -3}, a new era of {gamma} beams with energies up to 20MeV comes into operation, compared to the present world-leading HI{gamma}S facility at Duke University (USA) with 10{sup 8}{gamma}/s and {Delta}E{gamma}/E{gamma} Almost-Equal-To 3 Dot-Operator 10{sup -2}. In the long run even a seeded quantum FEL for {gamma} beams may become possible, with much higher brilliance and spectral flux. At the same time new exciting possibilities open up for focused {gamma} beams. Here we describe a new experiment at the {gamma} beam of the ILL reactor (Grenoble, France), where we observed for the first time that the index of refraction for {gamma} beams is determined by virtual pair creation. Using a combination of refractive and reflective optics, efficient monochromators for {gamma} beams are being developed. Thus, we have to optimize the total system: the {gamma}-beam facility, the {gamma}-beam optics and {gamma} detectors. We can trade {gamma} intensity for band width, going down to {Delta}E{gamma}/E{gamma} Almost-Equal-To 10{sup -6} and address individual nuclear levels. The term 'nuclear photonics' stresses the importance of nuclear applications. We can address with {gamma}-beams individual nuclear isotopes and not just elements like with X-ray beams. Compared to X rays, {gamma} beams can penetrate much deeper into big samples like radioactive waste barrels, motors or batteries. We can perform tomography and microscopy studies by focusing down to {mu}m resolution using Nuclear Resonance Fluorescence (NRF) for detection with eV resolution and high spatial resolution at the same time. We discuss the dominating M1 and E1 excitations like the scissors mode, two-phonon quadrupole octupole excitations, pygmy dipole excitations or giant dipole excitations under the new facet of

  13. The X-ray flux dipole of active galactic nuclei and the peculiar motion of the Local Group

    NASA Technical Reports Server (NTRS)

    Miyaji, Takamitsu; Boldt, Elihu

    1990-01-01

    X-ray emission from 30 resolved AGN's are used to study the dipole moment of their flux distribution on the sky. The data are derived from the Piccinotti et al. (1982) survey. X-ray fluxes are analyzed in terms of the alignment with the direction of the Local Group (LG) of galaxies. It is observed that the direction of the dipole moment of the flux is (313 deg, 38 deg); the dipole direction deviates from the LG velocity by 39 deg. It is detected that the amplitude of the dipole is about 50 percent of the corresponding monopole. Based on a comparison of the data with previous observations it is suggested that the X-ray emission from AGNs traces the underlying mass distribution at least as strongly as optical and IR emission from galaxies.

  14. He, N and C isotopes and fluxes in Aira caldera: Comparative study of hydrothermal activity in Sakurajima volcano and Wakamiko crater, Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Roulleau, Emilie; Sano, Yuji; Takahata, Naoto; Kawagucci, Shinsuke; Takahashi, Hirochi

    2013-05-01

    We investigate the degassing activity of an active submarine crater, Wakamiko, and an active sub-aerial volcano, Sakurajima, both located in Aira caldera, southern Kyushu, Japan. We provide 3He/4He, δ13C-CO2 and δ15N data for 15 hot springs, wells and bubbling gas from Sakurajima volcano, along with 3He/4He from seawater at four different sites for both Kagoshima bay and Wakamiko crater. We find a common magmatic 3He/4He ratio for Sakurajima and Wakamiko, 7.2 ± 0.8 Ra, which is consistent with 1) a mixing between air-saturated water (ASW) and MORB-type He, and 2) a common magmatic source located in the center of Aira caldera. Corrected 3He/4He, δ13C-CO2 and CH4/3He data for Sakurajima are correlated with the distance from the volcanic vent (Showa crater), which we attribute to crustal contamination and biogenic reaction. The low δ13C-CO2 values (- 10.1 ± 0.2‰ to - 13.7 ± 0.3‰) observed at Sakurajima may result from the addition of carbon from organic matter from basement rocks in magmatic source. After correction for air-derived nitrogen, we find δ15Nc values range between - 1.7‰ and + 4.3‰ which indicates that magmatic N is dominated by a sedimentary-derived component (up to 65.8%). We calculate Wakamiko fluxes of 4He (975 ± 228 mol/y), 3He (0.011 ± 0.003 mol/y), CO2 (184 ± 43 t/d), and heat (195 ± 22 MW). Our helium and heat fluxes are the first in situ fluxes ever reported for Wakamiko crater. All these Wakamiko fluxes are at least one order of magnitude lower than those observed for Sakurajima (CO2: 1800 t/d; 3He: 0.71 mol/y; heat: 2100 MW): degassing at Sakurajima volcano is much stronger than that at Wakamiko crater. The variation of Sakurajima CO2 flux with time, source (Minamidake or Showa crater) and eruptive activity, appears not to significantly affect the CO2 flux at Wakamiko crater, which is much more stable (132-307 t/d) during the last 30 years. This indicates that there is no link between Sakurajima and Wakamiko degassing

  15. Multifunctional two-photon active silica-coated Au@MnO Janus particles for selective dual functionalization and imaging.

    PubMed

    Schick, Isabel; Lorenz, Steffen; Gehrig, Dominik; Schilmann, Anna-Maria; Bauer, Heiko; Panthöfer, Martin; Fischer, Karl; Strand, Dennis; Laquai, Frédéric; Tremel, Wolfgang

    2014-02-12

    Monodisperse multifunctional and nontoxic Au@MnO Janus particles with different sizes and morphologies were prepared by a seed-mediated nucleation and growth technique with precise control over domain sizes, surface functionalization, and dye labeling. The metal oxide domain could be coated selectively with a thin silica layer, leaving the metal domain untouched. In particular, size and morphology of the individual (metal and metal oxide) domains could be controlled by adjustment of the synthetic parameters. The SiO2 coating of the oxide domain allows biomolecule conjugation (e.g., antibodies, proteins) in a single step for converting the photoluminescent and superparamagnetic Janus nanoparticles into multifunctional efficient vehicles for theranostics. The Au@MnO@SiO2 Janus particles were characterized using high-resolution transmission electron microscopy (HR-)TEM, powder X-ray diffraction (PXRD), optical (UV-vis) spectroscopy, confocal laser fluorescence scanning microscopy (CLSM), and dynamic light scattering (DLS). The functionalized nanoparticles were stable in buffer solution or serum, showing no indication of aggregation. Biocompatibility and potential biomedical applications of the Au@MnO@SiO2 Janus particles were assayed by a cell viability analysis by coincubating the Au@MnO@SiO2 Janus particles with Caki 1 and HeLa cells. Time-resolved fluorescence spectroscopy in combination with CLSM revealed the silica-coated Au@MnO@SiO2 Janus particles to be highly two-photon active; no indication for an electronic interaction between the dye molecules incorporated in the silica shell surrounding the MnO domains and the attached Au domains was found; fluorescence quenching was observed when dye molecules were bound directly to the Au domains. PMID:24460244

  16. Suspended particulate matter fluxes along with their associated metals, organic matter and carbonates in a coastal Mediterranean area affected by mining activities.

    PubMed

    Helali, Mohamed Amine; Zaaboub, Noureddine; Oueslati, Walid; Added, Ayed; Aleya, Lotfi

    2016-03-15

    A study of suspended particulate matter (SPM) fluxes along with their associated metals, organic matter and carbonates, was conducted off the Mejerda River outlet in May 2011 and in March and July 2012 at depths of 10, 20 and 40 m using sediment traps. SPM fluxes are more significant near the Mejerda outlet, especially in winter, but dissipate further offshore. Normalization reveals that the Mejerda is a major source of Pb, Zn, Cd, Cu, Ni, and Co, all of which are the result of human activities. In contrast, Fe, Mn and N are of authigenic origin. The enrichment factor shows that Pb, Zn and especially Cd are the most highly polluting metals off the Mejerda outlet. This confirms the trend observed on the shores of the Mejerda prodelta and is consistent with the type of mining activities conducted in the Mejerda catchment. PMID:26869095

  17. An investigation of the neutron flux in bone-fluorine phantoms comparing accelerator based in vivo neutron activation analysis and FLUKA simulation data

    NASA Astrophysics Data System (ADS)

    Mostafaei, F.; McNeill, F. E.; Chettle, D. R.; Matysiak, W.; Bhatia, C.; Prestwich, W. V.

    2015-01-01

    We have tested the Monte Carlo code FLUKA for its ability to assist in the development of a better system for the in vivo measurement of fluorine. We used it to create a neutron flux map of the inside of the in vivo neutron activation analysis irradiation cavity at the McMaster Accelerator Laboratory. The cavity is used in a system that has been developed for assessment of fluorine levels in the human hand. This study was undertaken to (i) assess the FLUKA code, (ii) find the optimal hand position inside the cavity and assess the effects on precision of a hand being in a non-optimal position and (iii) to determine the best location for our γ-ray detection system within the accelerator beam hall. Simulation estimates were performed using FLUKA. Experimental measurements of the neutron flux were performed using Mn wires. The activation of the wires was measured inside (1) an empty bottle, (2) a bottle containing water, (3) a bottle covered with cadmium and (4) a dry powder-based fluorine phantom. FLUKA was used to simulate the irradiation cavity, and used to estimate the neutron flux in different positions both inside, and external to, the cavity. The experimental results were found to be consistent with the Monte Carlo simulated neutron flux. Both experiment and simulation showed that there is an optimal position in the cavity, but that the effect on the thermal flux of a hand being in a non-optimal position is less than 20%, which will result in a less than 10% effect on the measurement precision. FLUKA appears to be a code that can be useful for modeling of this type of experimental system.

  18. Conversion from solvent rinsable fluxes to aqueous rinsable fluxes for hot oil solder leveling

    NASA Astrophysics Data System (ADS)

    1992-03-01

    A water rinsable flux was evaluated for hot oil solder leveling of printed wiring boards. The previously used rosin-activated flux required a solvent containing a chlorinated hydrocarbon for removing the flux residues after soldering. The water rinsable flux requires hot water or a solution of hot detergent for removing flux residues after smoldering. The water rinsable flux produced an acceptable soldered surface. Flux residues were removed by either hot water (120 F) or a solution of hot detergent (120 F).

  19. Target-Activated Modulation of Dual-Color and Two-Photon Fluorescence of Graphene Quantum Dots for in Vivo Imaging of Hydrogen Peroxide.

    PubMed

    Zhao, Wenjie; Li, Yinhui; Yang, Sheng; Chen, Yun; Zheng, Jing; Liu, Changhui; Qing, Zhihe; Li, Jishan; Yang, Ronghua

    2016-05-01

    The development of nanoprobes suitable for two-photon microscopy techniques is highly desirable for mapping biological species in living systems. However, at the current stage, the nanoprobes are restricted to single-color fluorescence changes, making it unsuitable for quantitative detection. To circumvent this problem, we report here a rational design of a dual-emission and two-photon (TP) graphene quantum dot (GQD(420)) probe for imaging of hydrogen peroxide (H2O2). For specific recognition of H2O2 and lighting the fluorescence of TPGQD(420), a boronate ester-functionalized merocyanine (BMC) fluorophore was used as both target-activated trigger and the dual-emission fluorescence modulator. Upon two-photon excitation at 740 nm, TPGQD(420)-BMC displays a green-to-blue resolved emission band in response to H2O2 with an emission shift of 110 nm, and the H2O2 can be determined from 0.2 to 40 μM with a detection limit of 0.05 μM. Moreover, the fluorescence response of the TPGQD(420)-BMC toward H2O2 is rapid and extremely specific. The feasibility of the proposed method is demonstrated by two-photon ratiometrically mapping the production of endogenous H2O2 in living cells as well as in deep tissues of murine mode at 0-600 μm. To the best of our knowledge, this is the first paradigm to rationally design a dual-emission and two-photon nanoprobe via fluorescence modulation of GQDs with switchable molecules, which will extend new possibility to design powerful molecular tools for in vivo bioimaging applications. PMID:27072323

  20. Latitudinal distributions of activities in atmospheric aerosols, deposition fluxes, and soil inventories of ⁷Be in the East Asian monsoon zone.

    PubMed

    Gai, N; Pan, J; Yin, X C; Zhu, X H; Yu, H Q; Li, Y; Tan, K Y; Jiao, X C; Yang, Y L

    2015-10-01

    Activities of atmospheric aerosols, bulk deposition fluxes, and undisturbed soil inventories of (7)Be were investigated in China's East Asian monsoon zone at various latitudes ranging from 23.8°N to 43.5°N. The annual latitudinal distributions of (7)Be concentrations in aerosols follow a distribution pattern which looks similar to a normal distribution with the maxima occurring in the mid-latitude region. Simultaneous measurements of (7)Be at various latitudes suggest that atmospheric circulation may play an important role in the latitudinal distributions of (7)Be in surface air. Latitude and wet precipitation are the main factors controlling the bulk (7)Be depositional fluxes. Significant seasonal variations in (7)Be depositional fluxes in Beijing, a mid-latitude city, were observed with the highest flux in summer and the lowest in winter, whereas less seasonality were found in the high- and the low-latitude cities. The highest (7)Be inventory in undisturbed soils in summer also occurred at a mid-latitudinal area in the East Asian monsoon zone. Precipitation is the main factor controlling the (7)Be soil inventory in Qingdao with the highest values occurring in autumn followed by summer. PMID:26114808

  1. Combining active and passive remote sensing from research aircraft with atmospheric models to evaluate NOx emission fluxes and O3 formation in the Los Angeles Megacity

    NASA Astrophysics Data System (ADS)

    Baidar, Sunil; Oetjen, Hilke; Senff, Christoph; Alvarez, Raul, II; Hardesty, Michael; Langford, Andrew; Kim, Si-Wan; Trainer, Michael; Volkamer, Rainer

    2013-04-01

    Ozone (O3) and nitrogen dioxide (NO2) are two important components of air pollution. We have measured vertical column amounts of NO2, and vertical profiles of O3 and wind speed by means of measurements of solar stray light by CU Airborne MAX-DOAS, and active remote sensing using the NOAA TOPAZ lidar, and the University of Leeds Doppler lidar aboard the NOAA Twin Otter research aircraft. A total of 52 flights (up to 4 hours each) were carried out between May 19 and July 19 2010 during the CalNex and CARES field campaigns. These flights cover most of California. The boundary layer height was measured by TOPAZ lidar, and trace gas concentrations of NO2 and O3 were integrated over boundary layer height. These column integrated quantities are then combined with direct wind speed measurements to quantify directly the pollutant flux across the boundary, as defined by the flight track. By tracking the pollution fluxes during transects that are flown upwind and in various distances downwind of a NOx emission source, the NOx emission rate, and the ozone formation rate are quantified. These pollutant fluxes are calculated here for the first time exclusively based on measurements (i.e., without need to infer wind speed from a model). These fluxes provide constraints to quantify localized NOx emissions, and are being compared with WRF-Chem model simulations.

  2. Photon-photon interaction under light localization in a system of conducting nanoparticles

    NASA Astrophysics Data System (ADS)

    Maksimenko, V. V.; Zagaynov, V. A.; Agranovski, I. E.

    2015-09-01

    It is shown that, under conditions of light localization in a system of scatterers, effective photon-photon interaction appears. This interaction is related to neither nonlinearity of medium nor nonlocal interaction of polarization-entangled photon pairs. It is related to the complex topology of photon trajectories. Taking into account this interaction, the scattering cross section of photon pairs is calculated. It is shown that this cross section contains only an extra degree of the small Rayleigh factor in comparison with the classic Rayleigh cross section. The proposed approach could potentially open a gate for controlling light by alternative light fluxes, eliminating the need for slow optoelectronic converters.

  3. Physiological fluxes and antioxidative enzymes activities of immobilized Phanerochaete chrysosporium loaded with TiO2 nanoparticles after exposure to toxic pollutants in solution.

    PubMed

    Tan, Qiong; Chen, Guiqiu; Zeng, Guangming; Chen, Anwei; Guan, Song; Li, Zhongwu; Zuo, Yanan; Huang, Zhenzhen; Guo, Zhi

    2015-06-01

    Immobilized Phanerochaete chrysosporium loaded with TiO2 nanoparticles (PTNs) are novel high-value bioremediation materials for adsorbing cadmium and for degrading 2,4-dichlorophenol (2,4-DCP). The real-time changes in H(+) and O2 fluxes were measured using the noninvasive microtest technique (NMT). The H(+) influx increased after the addition of 2,4-DCP, and shifted to efflux following the addition of Cd(2+). The O2 flux decreased after the addition of both 2,4-DCP and Cd(2+). A larger Cd(2+) flux was immediately observed after exposure to 0.5mM Cd(2+) (-351.25 pmol cm(-2) s(-1)) than to 0.1 mM Cd(2+) (-107.47 pmol cm(-2) s(-1)). The removal of Cd(2+) by the PTNs increased more after treatment with the 0.5 mM exposure solution (27.6 mg g(-1)) than with the 0.1 mM exposure solution (3.49 mg g(-1)). The enzyme activities were analyzed to review the antioxidative defense system of PTNs in a solution containing various concentrations of Cd(2+). The activities of the coenzyme nicotinamide adenine dinucleotide (NADH) oxidase as well as the enzyme catalase (CAT) plateaued at 6.5 U g(-1) FW and 9.7 U g(-1) FW, respectively, after exposure to 0.25 mM Cd(2+). The activity of superoxide dismutase (SOD) increased gradually in solutions containing 0.1-0.6 mM Cd(2+), and eventually reached a maximum (68.86 U g(-1) FW). These results illustrate how the antioxidative defense system and the physiological fluxes of PTNs respond to the stress caused by toxic pollutants. PMID:25638529

  4. Spring geochemistry in an active volcanic environment (São Miguel, Azores): source and fluxes of inorganic solutes.

    PubMed

    Freire, P; Andrade, C; Coutinho, R; Cruz, J V

    2014-01-01

    Mineral waters were monthly sampled in selected springs from Furnas and Fogo trachytic central volcanoes (São Miguel, Azores, Portugal). Water temperatures between 15.1 °C and 90.2 °C, characterize poorly mineralized waters of Na-HCO₃ and Na-HCO₃-Cl types. According to the spring location, two watersheds were selected in each volcano to evaluate solute fluxes and chemical weathering rates (Fogo volcano: Ribeira Grande river - RRG; Furnas volcano: Ribeira Quente river - RRQ). Na, Mg, K and Ca fluxes in groundwater represented 43%, 60%, 46% and 57% of the total (subsurface plus surface fluxes) in RRG, and respectively 43%, 53%, 46% and 49% in RRQ. Average HCO₃ flux is ten times higher in RRQ (130.1 × 10(6) mol/yr) compared to RRG (13.8 × 10(6) mol/yr), reflecting the volcano degassing and the lower ratio between groundwater and river water fluxes. Based on these values, total CO₂-consumption by weathering ranged from 1.5 × 10(6)mol/km(2)/yr (RRG) to 4 × 10(6)mol/km(2)/yr (RRQ). TDS load varied between 3772 t/yr (RRG) and 15388 t/yr (RRQ), and the ratio between values in groundwater and in surface water is respectively equal to 0.72 and 2.04. The associated chemical weathering rates in groundwater were 206 t/km(2)/yr (RRG) and 399 t/km(2)/yr (RRQ). Coupled to river water, these values indicate that total chemical weathering rates are respectively equal to 493 t/km(2)/yr and 594 t/km(2)/yr. A similar approach developed for the entire archipelago showed that the chemical weathering rates due to groundwater are in the range from 33 to 321 t/km(2)/yr, being partially controlled by the age of the islands. Results of the present study point out to the need to consider groundwater solute fluxes due to weathering when establishing geochemical budgets. PMID:23933431

  5. The Study of Electromagnetic Wave Propogation in Photonic Crystals Via Planewave Based Transfer (Scattering) Matrix Method with Active Gain Material Applications

    SciTech Connect

    Ming LI

    2007-12-01

    In this dissertation, a set of numerical simulation tools are developed under previous work to efficiently and accurately study one-dimensional (1D), two-dimensional(2D), 2D slab and three-dimensional (3D) photonic crystal structures and their defects effects by means of spectrum (transmission, reflection, absorption), band structure (dispersion relation), and electric and/or magnetic fields distribution (mode profiles). Furthermore, the lasing property and spontaneous emission behaviors are studied when active gain materials are presented in the photonic crystal structures. Various physical properties such as resonant cavity quality factor, waveguide loss, propagation group velocity of electromagnetic wave and light-current curve (for lasing devices) can be obtained from the developed software package.

  6. Photon generator

    DOEpatents

    Srinivasan-Rao, Triveni

    2002-01-01

    A photon generator includes an electron gun for emitting an electron beam, a laser for emitting a laser beam, and an interaction ring wherein the laser beam repetitively collides with the electron beam for emitting a high energy photon beam therefrom in the exemplary form of x-rays. The interaction ring is a closed loop, sized and configured for circulating the electron beam with a period substantially equal to the period of the laser beam pulses for effecting repetitive collisions.

  7. The study of electromagnetic wave propagation in photonic crystals via planewave based transfer (scattering) matrix method with active gain material applications

    NASA Astrophysics Data System (ADS)

    Li, Ming

    In this dissertation, a set of numerical simulation tools are developed under previous work to efficiently and accurately study one-dimensional (1D), two-dimensional (2D), 2D slab and three-dimensional (3D) photonic crystal structures and their defects effects by means of spectrum (transmission, reflection, absorption), band structure (dispersion relation), and electric and/or magnetic fields distribution (mode profiles). Further more, the lasing property and spontaneous emission behaviors are studied when active gain materials are presented in the photonic crystal structures. First, the planewave based transfer (scattering) matrix method (TMM) is described in every detail along with a brief review of photonic crystal history (Chapter 1 and 2). As a frequency domain method, TMM has the following major advantages over other numerical methods: (1) the planewave basis makes Maxwell's Equations a linear algebra problem and there are mature numerical package to solve linear algebra problem such as Lapack and Scalapack (for parallel computation). (2) Transfer (scattering) matrix method make 3D problem into 2D slices and link all slices together via the scattering matrix (S matrix) which reduces computation time and memory usage dramatically and makes 3D real photonic crystal devices design possible; and this also makes the simulated domain no length limitation along the propagation direction (ideal for waveguide simulation). (3) It is a frequency domain method and calculation results are all for steady state, without the influences of finite time span convolution effects and/or transient effects. (4) TMM can treat dispersive material (such as metal at visible light) naturally without introducing any additional computation; and meanwhile TMM can also deal with anisotropic material and magnetic material (such as perfectly matched layer) naturally from its algorithms. (5) Extension of TMM to deal with active gain material can be done through an iteration procedure with gain

  8. Small-scale and Global Dynamos and the Area and Flux Distributions of Active Regions, Sunspot Groups, and Sunspots: A Multi-database Study

    NASA Astrophysics Data System (ADS)

    Muñoz-Jaramillo, Andrés; Senkpeil, Ryan R.; Windmueller, John C.; Amouzou, Ernest C.; Longcope, Dana W.; Tlatov, Andrey G.; Nagovitsyn, Yury A.; Pevtsov, Alexei A.; Chapman, Gary A.; Cookson, Angela M.; Yeates, Anthony R.; Watson, Fraser T.; Balmaceda, Laura A.; DeLuca, Edward E.; Martens, Petrus C. H.

    2015-02-01

    In this work, we take advantage of 11 different sunspot group, sunspot, and active region databases to characterize the area and flux distributions of photospheric magnetic structures. We find that, when taken separately, different databases are better fitted by different distributions (as has been reported previously in the literature). However, we find that all our databases can be reconciled by the simple application of a proportionality constant, and that, in reality, different databases are sampling different parts of a composite distribution. This composite distribution is made up by linear combination of Weibull and log-normal distributions—where a pure Weibull (log-normal) characterizes the distribution of structures with fluxes below (above) 1021Mx (1022Mx). Additionally, we demonstrate that the Weibull distribution shows the expected linear behavior of a power-law distribution (when extended to smaller fluxes), making our results compatible with the results of Parnell et al. We propose that this is evidence of two separate mechanisms giving rise to visible structures on the photosphere: one directly connected to the global component of the dynamo (and the generation of bipolar active regions), and the other with the small-scale component of the dynamo (and the fragmentation of magnetic structures due to their interaction with turbulent convection).

  9. The CO2 Flux and the Chemistry of the Crater lake in 2013-2015 Evidence for the Enhanced Activity of El Chichon volcano, Mexico.

    NASA Astrophysics Data System (ADS)

    Taran, Y.; Jácome Paz, M. P.; Inguaggiato, S.; Collard, N.

    2015-12-01

    During 2013-2015, four CO2 flux surveys were performed in the El Chichon crater both, from the lake surface and from the soil of the crater. The chemistry of the lake water, as well as its physical parameters (surface area, depth, temperature) were also determined. The CO2 flux in 2014-2015 compared to the 2007-2008 data (Mazot et al., 2011, BV, 73: 423-441) increased almost one order of magnitude (from ~ 140 ton d-1 in 2008 to ~ 840 ton d-1 in 2014). During the last two years the lake became the largest for the whole time of observations with the maximum surface area more than 18 ha covering completely the NE fumarolic field and all thermal springs feeding the lake with mineralized water. Despite the maximum volume of the lake it was characterized in 2015 by the highest since 2007 chloride content (~2500 ppm) and temperature (34°C). A large degassing spot in the middle of the lake for the first time was observed in April 2015 with more than 10,000 g m-2 d-1 of the CO2 flux. These observations evidence that the volcano-hydrothermal system of El Chichon volcano came into a new stage of activity associated most probably with changes in the magmatic activity at depth.

  10. SMALL-SCALE AND GLOBAL DYNAMOS AND THE AREA AND FLUX DISTRIBUTIONS OF ACTIVE REGIONS, SUNSPOT GROUPS, AND SUNSPOTS: A MULTI-DATABASE STUDY

    SciTech Connect

    Muñoz-Jaramillo, Andrés; Windmueller, John C.; Amouzou, Ernest C.; Longcope, Dana W.; Senkpeil, Ryan R.; Tlatov, Andrey G.; Nagovitsyn, Yury A.; Pevtsov, Alexei A.; Chapman, Gary A.; Cookson, Angela M.; Yeates, Anthony R.; Watson, Fraser T.; Balmaceda, Laura A.; DeLuca, Edward E.; Martens, Petrus C. H.

    2015-02-10

    In this work, we take advantage of 11 different sunspot group, sunspot, and active region databases to characterize the area and flux distributions of photospheric magnetic structures. We find that, when taken separately, different databases are better fitted by different distributions (as has been reported previously in the literature). However, we find that all our databases can be reconciled by the simple application of a proportionality constant, and that, in reality, different databases are sampling different parts of a composite distribution. This composite distribution is made up by linear combination of Weibull and log-normal distributions—where a pure Weibull (log-normal) characterizes the distribution of structures with fluxes below (above) 10{sup 21}Mx (10{sup 22}Mx). Additionally, we demonstrate that the Weibull distribution shows the expected linear behavior of a power-law distribution (when extended to smaller fluxes), making our results compatible with the results of Parnell et al. We propose that this is evidence of two separate mechanisms giving rise to visible structures on the photosphere: one directly connected to the global component of the dynamo (and the generation of bipolar active regions), and the other with the small-scale component of the dynamo (and the fragmentation of magnetic structures due to their interaction with turbulent convection)

  11. The CO2 flux and the chemistry of the crater lake in 2013-2015 evidence for the enhanced activity of El Chichon volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Jácome Paz, Mariana Patricia; Taran, Yuri; Inguaggiato, Salvatore; Collard, Nathalie

    2016-04-01

    During 2013-2015, four CO2 flux surveys were performed in the El Chichon crater both, from the lake surface and from the soil of the crater floor. The chemistry of the lake water, as well as its physical parameters (surface area, depth, temperature) were also determined. The CO2 flux in 2014-2015 compared to the 2007-2008 data (Mazot et al., 2011, BV, 73: 423-441) increased almost one order of magnitude (from ~ 140 t/d in 2008 to ~ 840 t/d in 2014). During the last two years the lake became the largest for the whole time of observations with the maximum surface area more than 18 ha covering completely the NE fumarolic field and all thermal springs feeding the lake with mineralized water. Despite the maximum volume of the lake it was characterized in 2015 by the highest since 2007 chloride content (~2500 ppm) and temperature (34°C). A large degassing spot in the middle of the lake for the first time was observed in April 2015 with more than 10,000 g m-2 d-1 of the CO2 flux. These observations evidence that the volcano-hydrothermal system of El Chichon volcano came into a new stage of activity associated most probably with changes in the magmatic activity at depth.

  12. CO2 flux and chemistry of El Chichón crater lake (México) in the period 2013-2015: Evidence for the enhanced volcano activity

    NASA Astrophysics Data System (ADS)

    Jácome Paz, Mariana P.; Taran, Yuri; Inguaggiato, Salvatore; Collard, Nathalie

    2016-01-01

    The CO2 flux from El Chichón crater in the period from 2014 to 2015 increased by a factor of 3 (from ~260 t d-1 to ~800 t d-1) compared to the 2007-2008 data. The mechanism triggering the CO2 flux from the lake surface has changed from being dominantly diffusive to mainly advective (bubbling). The Cl concentration was steadily decreasing during the last two decades in the Na-Cl boiling springs feeding the lake. Since 2013, for both lake and SP springs, the Cl concentration has increased up to the 2005 Cl concentration levels. A large degassing spot in the middle of the lake was found in April 2015 with a CO2 flux of more than 10,000 g m-2 d-1. These observations are the evidence of the onset of a new stage of activity within the volcano-hydrothermal system of El Chichón volcano associated most probably with changes in the magmatic activity at depth.

  13. Seasonal variations in soil carbonic anhydrase activity in a pine forest ecosystem as inferred from soil CO18O flux measurements

    NASA Astrophysics Data System (ADS)

    Ogee, Jerome; Wingate, Lisa; Bosc, Alexandre; Burlett, Régis

    2015-04-01

    Quantifying terrestrial carbon storage and predicting the sensitivity of ecosystems to climate change relies on our ability to obtain observational constraints on photosynthesis and respiration at large scales (ecosystem, regional and global). Photosynthesis (GPP), the largest CO2 flux from the land surface, is currently estimated with considerable uncertainty (1-3). Robust estimates of global GPP can be obtained from an atmospheric budget of the oxygen isotopic composition (δ18O) of atmospheric CO2, provided that we have a good knowledge of the δ18O signatures of the terrestrial CO2 fluxes (1,4). The latter reflect the δ18O of leaf and soil water pools because CO2 exchanges 'isotopically' with water [CO2+H218O⇔H2O+CO18O]. This exchange can be accelerated by the enzyme carbonic anhydrase (CA). In leaves, where CA is present and abundant, this isotopic equilibrium is reached almost instantaneously. As a consequence, and because soil and leaf water pools have different δ18O signatures, CO2 fluxes from leaves and soils carry very distinct δ18O signals and can thus be tracked from the fluctuations in the δ18O of atmospheric CO2 (δa). There is growing evidence that the accelerated isotopic exchange between CO2 and water due to CA activity is a widespread phenomenon in soils as well (4). At the global scale, accounting for soil CA activity dramatically shifts the influence of soil and leaf fluxes on δa, thus changing the estimates of terrestrial gross CO2 fluxes (1,4). In this talk we will briefly present the current state of understanding of the environmental and ecological causes behind the variability in CA activity observed in soils and illustrate, using field data from a temperate pine forest, how soil CA activity varies over a single growing season and how it responds to soil surface environmental variables. References 1. L. R. Welp et al., Interannual variability in the oxygen isotopes of atmospheric CO2 driven by El Niño, Nature 477, 579-582 (2011

  14. Effects of conventional and no-tillage soil management and compost and sludge amendment on soil CO2 fluxes and microbial activities

    NASA Astrophysics Data System (ADS)

    Garcia-Gil, Juan Carlos; Haller, Isabel; Soler-Rovira, Pedro; Polo, Alfredo

    2010-05-01

    Soil management exerts a significant influence on the dynamic of soil organic matter, which is a key issue to enhance soil quality and its ecological functions, but also affects to greenhouse gas emissions and C sequestration processes. The objective of the present research was to determine the influence of soil management (conventional deep-tillage and no-tillage) and the application of two different organic amendment -thermally-dry sewage sludge (TSL) and municipal waste compost (MWC)- on soil CO2 fluxes and microbial activities in a long-term field experiment under semi-arid conditions. Both organic amendments were applied at a rate of 30 t ha-1 prior to sowing a barley crop. The experiment was conducted on an agricultural soil (Calcic Luvisol) from the experimental farm "La Higueruela" (Santa Olalla, Toledo). Unamended soils were used as control in both conventional and no-tillage management. During the course of the experiment, soil CO2 fluxes, microbial biomass C (MBC) and enzyme activities involved in the biogeochemical cycles of C, N and P were monitored during 12 months. The results obtained during the experiment for soil CO2 fluxes showed a great seasonal fluctuation due to semi-arid climate conditions. Overall, conventional deep-tillage soils exhibited higher CO2 fluxes, which was particularly larger during the first hours after deep-tillage was performed, and smaller MBC content and significantly lower dehydrogenase, beta-glucosidase, phosphatase, urease and BAA protease activities than no-tillage soils. Both MWC and TSL amendments provoked a significant increase of CO2 fluxes in both conventional and no-tillage soils, which was larger in TSL amended soils and particularly in no-tillage soils. The application of these organic amendments also enhanced MBC content and the overall enzyme activities in amended soils, which indicate a global revitalization of soil microbial metabolism in response to the fresh input of organic compounds that are energy

  15. Monitoring synaptic and neuronal activity in 3D with synthetic and genetic indicators using a compact acousto-optic lens two-photon microscope☆

    PubMed Central

    Fernández-Alfonso, Tomás; Nadella, K.M. Naga Srinivas; Iacaruso, M. Florencia; Pichler, Bruno; Roš, Hana; Kirkby, Paul A.; Silver, R. Angus

    2014-01-01

    Background Two-photon microscopy is widely used to study brain function, but conventional microscopes are too slow to capture the timing of neuronal signalling and imaging is restricted to one plane. Recent development of acousto-optic-deflector-based random access functional imaging has improved the temporal resolution, but the utility of these technologies for mapping 3D synaptic activity patterns and their performance at the excitation wavelengths required to image genetically encoded indicators have not been investigated. New method Here, we have used a compact acousto-optic lens (AOL) two-photon microscope to make high speed [Ca2+] measurements from spines and dendrites distributed in 3D with different excitation wavelengths (800–920 nm). Results We show simultaneous monitoring of activity from many synaptic inputs distributed over the 3D arborisation of a neuronal dendrite using both synthetic as well as genetically encoded indicators. We confirm the utility of AOL-based imaging for fast in vivo recordings by measuring, simultaneously, visually evoked responses in 100 neurons distributed over a 150 μm focal depth range. Moreover, we explore ways to improve the measurement of timing of neuronal activation by choosing specific regions within the cell soma. Comparison with existing methods These results establish that AOL-based 3D random access two-photon microscopy has a wider range of neuroscience applications than previously shown. Conclusions Our findings show that the compact AOL microscope design has the speed, spatial resolution, sensitivity and wavelength flexibility to measure 3D patterns of synaptic and neuronal activity on individual trials. PMID:24200507

  16. All-photonic quantum repeaters

    PubMed Central

    Azuma, Koji; Tamaki, Kiyoshi; Lo, Hoi-Kwong

    2015-01-01

    Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Photons appear to be the medium of choice for quantum communication. Owing to photon losses, robust quantum communication over long lossy channels requires quantum repeaters. It is widely believed that a necessary and highly demanding requirement for quantum repeaters is the existence of matter quantum memories. Here we show that such a requirement is, in fact, unnecessary by introducing the concept of all-photonic quantum repeaters based on flying qubits. In particular, we present a protocol based on photonic cluster-state machine guns and a loss-tolerant measurement equipped with local high-speed active feedforwards. We show that, with such all-photonic quantum repeaters, the communication efficiency scales polynomially with the channel distance. Our result paves a new route towards quantum repeaters with efficient single-photon sources rather than matter quantum memories. PMID:25873153

  17. All-photonic quantum repeaters

    NASA Astrophysics Data System (ADS)

    Azuma, Koji; Tamaki, Kiyoshi; Lo, Hoi-Kwong

    2015-04-01

    Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Photons appear to be the medium of choice for quantum communication. Owing to photon losses, robust quantum communication over long lossy channels requires quantum repeaters. It is widely believed that a necessary and highly demanding requirement for quantum repeaters is the existence of matter quantum memories. Here we show that such a requirement is, in fact, unnecessary by introducing the concept of all-photonic quantum repeaters based on flying qubits. In particular, we present a protocol based on photonic cluster-state machine guns and a loss-tolerant measurement equipped with local high-speed active feedforwards. We show that, with such all-photonic quantum repeaters, the communication efficiency scales polynomially with the channel distance. Our result paves a new route towards quantum repeaters with efficient single-photon sources rather than matter quantum memories.

  18. All-photonic quantum repeaters.

    PubMed

    Azuma, Koji; Tamaki, Kiyoshi; Lo, Hoi-Kwong

    2015-01-01

    Quantum communication holds promise for unconditionally secure transmission of secret messages and faithful transfer of unknown quantum states. Photons appear to be the medium of choice for quantum communication. Owing to photon losses, robust quantum communication over long lossy channels requires quantum repeaters. It is widely believed that a necessary and highly demanding requirement for quantum repeaters is the existence of matter quantum memories. Here we show that such a requirement is, in fact, unnecessary by introducing the concept of all-photonic quantum repeaters based on flying qubits. In particular, we present a protocol based on photonic cluster-state machine guns and a loss-tolerant measurement equipped with local high-speed active feedforwards. We show that, with such all-photonic quantum repeaters, the communication efficiency scales polynomially with the channel distance. Our result paves a new route towards quantum repeaters with efficient single-photon sources rather than matter quantum memories. PMID:25873153

  19. Flux-creep activation energy for a BaFe1.9Ni0.1As2 single crystal derived from alternating current susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Ge, Jun-Yi; Li, Lin-Jun; Xu, Zhu-An; Moshchalkov, Victor V.

    2016-04-01

    Systematic ac susceptibility measurements have been performed to investigate the vortex dynamics in a BaFe1.9Ni0.1As2 single crystal as a function of temperature, frequency, ac field amplitude, and dc magnetic field. The complex activation energy U ( T , B , j ) is derived in the framework of thermally activated flux creep theory and can be expressed in one simple formula. A power law dependence of U ˜ B α with α = -0.46 is observed. The activation energy reaches 104 K at low fields, suggesting strong pinning in the material. The nonlinear function of the activation energy vs. the current density is determined, which has the expression of U ∝ j - 0.1 .

  20. Optics of globular photonic crystals

    SciTech Connect

    Gorelik, V S

    2007-05-31

    The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter {approx}200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported. (review)

  1. Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr - Part 4: Near-Earth solar wind speed, IMF, and open solar flux

    NASA Astrophysics Data System (ADS)

    Lockwood, M.; Nevanlinna, H.; Barnard, L.; Owens, M. J.; Harrison, R. G.; Rouillard, A. P.; Scott, C. J.

    2014-04-01

    In the concluding paper of this tetralogy, we here use the different geomagnetic activity indices to reconstruct the near-Earth interplanetary magnetic field (IMF) and solar wind flow speed, as well as the open solar flux (OSF) from 1845 to the present day. The differences in how the various indices vary with near-Earth interplanetary parameters, which are here exploited to separate the effects of the IMF and solar wind speed, are shown to be statistically significant at the 93% level or above. Reconstructions are made using four combinations of different indices, compiled using different data and different algorithms, and the results are almost identical for all parameters. The correction to the aa index required is discussed by comparison with the Ap index from a more extensive network of mid-latitude stations. Data from the Helsinki magnetometer station is used to extend the aa index back to 1845 and the results confirmed by comparison with the nearby St Petersburg observatory. The optimum variations, using all available long-term geomagnetic indices, of the near-Earth IMF and solar wind speed, and of the open solar flux, are presented; all with ±2σ uncertainties computed using the Monte Carlo technique outlined in the earlier papers. The open solar flux variation derived is shown to be very similar indeed to that obtained using the method of Lockwood et al. (1999).

  2. Active pixel and photon counting imagers based on poly-Si TFTs: rewriting the rule book on large area flat panel x-ray devices

    NASA Astrophysics Data System (ADS)

    Antonuk, Larry E.; Koniczek, Martin; El-Mohri, Youcef; Zhao, Qihua

    2009-02-01

    The near-ubiquity of large area, active matrix, flat-panel imagers (AMFPIs) in medical x-ray imaging applications is a testament to the usefulness and adaptability of the relatively simple concept of array pixels based on a single amorphous silicon (a-Si:H) TFT coupled to a pixel storage capacitor. Interestingly, the fundamental advantages of a-Si:H thin film electronics (including compatibility with very large area processing, high radiation damage resistance, and continued development driven by interest in mainstream consumer products) are shared by the rapidly advancing technology of polycrystalline silicon (poly-Si) TFTs. Moreover, the far higher mobilities of poly-Si TFTs, compared to those of a- Si:H, facilitate the creation of faster and more complex circuits than are possible with a-Si:H TFTs, leading to the possibility of new classes of large area, flat panel imagers. Given recent progress in the development of initial poly-Si imager prototypes, the creation of increasingly sophisticated active pixel arrays offering pixel-level amplification, variable gain, very high frame rates, and excellent signal-to-noise performance under all fluoroscopic and radiographic conditions (including very low exposures and high spatial frequencies), appears within reach. In addition, it is conceivable that the properties of poly-Si TFTs could allow the development of large area imagers providing single xray photon counting capabilities. In this article, the factors driving the possible realization of clinically practical active pixel and photon counting imagers based on poly-Si TFTs are described and simple calculational estimates related to photon counting imagers are presented. Finally, the prospect for future development of such imagers is discussed.

  3. Multiple measurement of the coupling between benthic carbon fluxes and bioturbation activity during the ``spring bloom``. Progress report 1992

    SciTech Connect

    Aller, R.C.; Aller, J.J.; Cochran, J.K.; Lee, C.

    1992-12-31

    In accordance with the research plan outlined in our original proposal, we began monitoring indicators of plankton production (Chl-a, cell counts) in surface waters of Long Island Sound from the Port Jefferson / Bridgeport Ferry on Dec. 3, 1992. In contrast to past years no dramatic bloom has occurred to date although a significant pattern of increasing chl-a began during the first week of April. We anticipate that the bloom wig be complete by mid to late April. This has been a particularly cold year based on comparison of 1993 bottom water temperatures and previously reported patterns from LIS, possibly reflecting climatic conditions which delayed the bloom. Typical sampling includes: surface and bottom water sampling for suspended matter, cell counts, chlorophyll-a, nutrients; triplicate box cores for macro-, meio-, and microfauna analysis; subcores for O{sub 2} microelectrode profiles; box core for radiochemical analyses ({sup 234}Th, {sup 7}Be); box core subcores for benthic fluxes under aerated and nonaerated conditions (O{sub 2}, {Sigma}N, Mn{sup ++}, {Sigma}CO{sub 2}); Br{sup {minus}} tracer flux core incubation for biogenic irrigation rates; box core for laboratory based luminophore tracer experiments (particle mixing); box core subcores for solid phase and pore water solute profiles (carbonate system, nutrients, Ca, Mg, Sr, F, Mn, Fe) at 0.25 {minus} 1 cm intervals; and box core subcores for chloropigment profiles and reaction rate incubation experiments.

  4. Performance of a high-resolution x-ray microprobe at the Advanced Photon Source.

    SciTech Connect

    Cai, Z.; Lai, B.; Yun, W.; McNulty, I.; Khounsary, A.; Maser, J.; Ilinski, P.; Legnini, D.; Trakhtenberg, E.; Xu, S.; Tieman, B.; Wiemerslage, G.; Gluskin, E.

    1999-12-20

    The authors have developed a x-ray microprobe in the energy region from 6 to 20 keV using undulator radiation and zone-plate optics for microfocusing-based techniques and applications at a beamline at the Advanced Photon Source (APS). The performance of the beamline was shown to meet the design objectives, including preservation of the source brilliance and coherence, selectable transverse coherence length and energy bandwidth, high angular stability, and harmonic suppression of the beam. These objectives were achieved by careful thermal management and use of a novel mirror and crystal monochromator cooling geometry. All beamline optical components are water cooled, and the x-ray beam in the experiment station is stable in beam intensity, energy, and position over many days with no active feedback. Using a double-crystal Si(111) monochromator, they have obtained a focal spot size (FWHM) of 0.15 {micro}m (v) x 1.0 {micro}m (h), and a photon flux of 4 x 10{sup 9} photons/sec at the focal spot, and thus a photon flux density gain of 15,000. A circular beam spot of 0.15 {micro}m in diameter can be achieved by reducing the horizontal source size using a white beam slit located 43.5 meters upstream of the zone plate, with an order of magnitude less flux in the focal spot.

  5. Green photonics

    NASA Astrophysics Data System (ADS)

    Quan, Frederic

    2012-02-01

    Photonics, the broad merger of electronics with the optical sciences, encompasses such a wide swath of technology that its impact is almost universal in our everyday lives. This is a broad overview of some aspects of the industry and their contribution to the ‘green’ or environmental movement. The rationale for energy conservation is briefly discussed and the impact of photonics on our everyday lives and certain industries is described. Some opinions from industry are presented along with market estimates. References are provided to some of the most recent research in these areas.

  6. Photons Revisited

    NASA Astrophysics Data System (ADS)

    Batic, Matej; Begalli, Marcia; Han, Min Cheol; Hauf, Steffen; Hoff, Gabriela; Kim, Chan Hyeong; Kim, Han Sung; Grazia Pia, Maria; Saracco, Paolo; Weidenspointner, Georg

    2014-06-01

    A systematic review of methods and data for the Monte Carlo simulation of photon interactions is in progress: it concerns a wide set of theoretical modeling approaches and data libraries available for this purpose. Models and data libraries are assessed quantitatively with respect to an extensive collection of experimental measurements documented in the literature to determine their accuracy; this evaluation exploits rigorous statistical analysis methods. The computational performance of the associated modeling algorithms is evaluated as well. An overview of the assessment of photon interaction models and results of the experimental validation are presented.

  7. Frequency-tunable optoelectronic oscillator using a dual-mode amplified feedback laser as an electrically controlled active microwave photonic filter.

    PubMed

    Lu, Dan; Pan, Biwei; Chen, Haibo; Zhao, Lingjuan

    2015-09-15

    A widely tunable optoelectronic oscillator (OEO) based on a self-injection-locked monolithic dual-mode amplified feedback laser (DM-AFL) is proposed and experimentally demonstrated. In the proposed OEO structure, the DM-AFL functions as an active tunable microwave photonic filter (MPF). By tuning the injection current applied on the amplifier section of the AFL, tunable microwave outputs ranging from 32 to 41 GHz and single sideband phase noises below -97  dBc/Hz at 10 kHz offset from the carriers were realized. PMID:26371931

  8. Light coupling between vertical III-As nanowires and planar Si photonic waveguides for the monolithic integration of active optoelectronic devices on a Si platform.

    PubMed

    Giuntoni, Ivano; Geelhaar, Lutz; Bruns, Jürgen; Riechert, Henning

    2016-08-01

    We present a new concept for the optical interfacing between vertical III-As nanowires and planar Si waveguides. The nanowires are arranged in a two-dimensional array which forms a grating structure on top of the waveguide. This grating enables light coupling in both directions between the components made from the two different material classes. Numerical simulations show that this concept permits a light extraction efficiency from the waveguide larger than 45% and a light insertion efficiency larger than 35%. This new approach would allow the monolithic integration of nanowire-based active optoelectronics devices, like photodetectors and light sources, on the Si photonics platform. PMID:27505805

  9. Towards an optimum design of a P-MOS radiation detector for use in high-energy medical photon beams and neutron facilities: analysis of activation materials.

    PubMed

    Price, Robert A

    2005-01-01

    The behaviour of packaged and unpackaged ESAPMOS4 RadFET radiation detectors (NMRC Cork, Ireland) was investigated when used in the mixed photon and neutron environment of a medical linear accelerator operating above the nucleon separation energy and in a 14 MeV neutron field provided by a D-T generator. Within the uncertainty of the experimental set-up (4% at 95% confidence level) the unpackaged device was found to have essentially zero activation dose-burden whereas the packaged device exhibits a considerable degree of post irradiation absorbed dose due to deactivation radiation. PMID:16381751

  10. Polyoxymethylene passive samplers to monitor changes in bioavailability and flux of PCBs after activated carbon amendment to sediment in the field.

    PubMed

    Beckingham, B; Ghosh, U

    2013-06-01

    Field and laboratory exposures of polyoxymethylene passive samplers to sediments and the water column were applied to monitor changes in bioavailability and flux of polychlorinated biphenyls (PCBs) following a pilot-scale amendment of activated carbon in Grasse River. Following amendment, reductions in passive sampler uptake tracked reductions in bioaccumulation in a freshwater invertebrate, which supports a biological basis for utilizing passive samplers for in situ site investigations following a remediation. Freely dissolved concentrations of PCBs were reduced in sediment pore waters compared to untreated sediments indicating reduced bioavailability of PCBs after activated carbon amendment. Freely dissolved PCB concentrations in sediment pore water in treated sites were also lower than overlying water concentrations indicating a reversal of the sediment from being a source to a sink of PCBs from the water column. These observations indicate that activated carbon amendment to sediment limits contaminant exposure to both the benthic and pelagic food webs through reductions in bioavailability and flux of PCBs into the water column. PMID:23415491

  11. The AmeriFlux Data Activity and Data System: An Evolving Collection of Data Management Techniques, Tools, Products and Services

    SciTech Connect

    Boden, Thomas A; Krassovski, Misha B; Yang, Bai

    2013-01-01

    support for numerous long-term measurement projects crucial to climate change science. One current example is the AmeriFlux measurement network. AmeriFlux provides continuous measurements from forests, grasslands, wetlands, and croplands in North, Central, and South America and offers important insight about carbon cycling in terrestrial ecosystems. We share our approaches in satisfying the challenges of delivering AmeriFlux data worldwide to benefit others with similar challenges handling climate change data, further heighten awareness and use of an outstanding ecological data resource, and highlight expanded software engineering applications being used for climate change measurement data.

  12. Ultrafast superconducting single-photon detector with reduced-size active area coupled to a tapered lensed single-mode fiber

    NASA Astrophysics Data System (ADS)

    Sidorova, Maria V.; Divochiy, Alexander; Vachtomin, Yury B.; Smirnov, Konstantin V.

    2015-05-01

    We present an ultrafast NbN Superconducting single-photon detector (SSPD) with active area of 3x3 μm2, which reveals better timing performances than a previously developed SSPD with active area of 10x10 μm2. The improved SSPD demonstrates the record timing jitter <25 ps, ultra short recovery time <2 ns, extremely low dark counts level, and high detection efficiency (DE) in a wide spectral range from visible to near-infrared. The record parameters were obtained thanks to the development of a new technique of an effective optical coupling between a detector with reduced-size active area and a standard single-mode telecommunication fiber. The advantages of a new approach are experimentally confirmed by performed electro-optical measurements of the device performances.

  13. Clinical application of in vivo treatment delivery verification based on PET/CT imaging of positron activity induced at high energy photon therapy

    NASA Astrophysics Data System (ADS)

    Janek Strååt, Sara; Andreassen, Björn; Jonsson, Cathrine; Noz, Marilyn E.; Maguire, Gerald Q., Jr.; Näfstadius, Peder; Näslund, Ingemar; Schoenahl, Frederic; Brahme, Anders

    2013-08-01

    The purpose of this study was to investigate in vivo verification of radiation treatment with high energy photon beams using PET/CT to image the induced positron activity. The measurements of the positron activation induced in a preoperative rectal cancer patient and a prostate cancer patient following 50 MV photon treatments are presented. A total dose of 5 and 8 Gy, respectively, were delivered to the tumors. Imaging was performed with a 64-slice PET/CT scanner for 30 min, starting 7 min after the end of the treatment. The CT volume from the PET/CT and the treatment planning CT were coregistered by matching anatomical reference points in the patient. The treatment delivery was imaged in vivo based on the distribution of the induced positron emitters produced by photonuclear reactions in tissue mapped on to the associated dose distribution of the treatment plan. The results showed that spatial distribution of induced activity in both patients agreed well with the delivered beam portals of the treatment plans in the entrance subcutaneous fat regions but less so in blood and oxygen rich soft tissues. For the preoperative rectal cancer patient however, a 2 ± (0.5) cm misalignment was observed in the cranial-caudal direction of the patient between the induced activity distribution and treatment plan, indicating a beam patient setup error. No misalignment of this kind was seen in the prostate cancer patient. However, due to a fast patient setup error in the PET/CT scanner a slight mis-position of the patient in the PET/CT was observed in all three planes, resulting in a deformed activity distribution compared to the treatment plan. The present study indicates that the induced positron emitters by high energy photon beams can be measured quite accurately using PET imaging of subcutaneous fat to allow portal verification of the delivered treatment beams. Measurement of the induced activity in the patient 7 min after receiving 5 Gy involved count rates which were about

  14. Clinical application of in vivo treatment delivery verification based on PET/CT imaging of positron activity induced at high energy photon therapy.

    PubMed

    Janek Strååt, Sara; Andreassen, Björn; Jonsson, Cathrine; Noz, Marilyn E; Maguire, Gerald Q; Näfstadius, Peder; Näslund, Ingemar; Schoenahl, Frederic; Brahme, Anders

    2013-08-21

    The purpose of this study was to investigate in vivo verification of radiation treatment with high energy photon beams using PET/CT to image the induced positron activity. The measurements of the positron activation induced in a preoperative rectal cancer patient and a prostate cancer patient following 50 MV photon treatments are presented. A total dose of 5 and 8 Gy, respectively, were delivered to the tumors. Imaging was performed with a 64-slice PET/CT scanner for 30 min, starting 7 min after the end of the treatment. The CT volume from the PET/CT and the treatment planning CT were coregistered by matching anatomical reference points in the patient. The treatment delivery was imaged in vivo based on the distribution of the induced positron emitters produced by photonuclear reactions in tissue mapped on to the associated dose distribution of the treatment plan. The results showed that spatial distribution of induced activity in both patients agreed well with the delivered beam portals of the treatment plans in the entrance subcutaneous fat regions but less so in blood and oxygen rich soft tissues. For the preoperative rectal cancer patient however, a 2 ± (0.5) cm misalignment was observed in the cranial-caudal direction of the patient between the induced activity distribution and treatment plan, indicating a beam patient setup error. No misalignment of this kind was seen in the prostate cancer patient. However, due to a fast patient setup error in the PET/CT scanner a slight mis-position of the patient in the PET/CT was observed in all three planes, resulting in a deformed activity distribution compared to the treatment plan. The present study indicates that the induced positron emitters by high energy photon beams can be measured quite accurately using PET imaging of subcutaneous fat to allow portal verification of the delivered treatment beams. Measurement of the induced activity in the patient 7 min after receiving 5 Gy involved count rates which were about

  15. The influence of cross-sectional channel geometry on rheology and flux estimates for active lava flows

    NASA Astrophysics Data System (ADS)

    Lev, Einat; James, Mike R.

    2014-07-01

    Lava rheology and effusion rate are critical factors in determining the evolution of lava flows. However, direct and accurate field measurements are difficult to carry out, and estimates are usually based on measurements of the flow's surface velocity and assumptions of sub-surface geometry. Using numerical flow models, we show that the potential for error due to geometry uncertainty is minimized if a semi-elliptical cross-sectional channel shape is assumed. Flow is simulated for isothermal Newtonian, temperature-dependent Newtonian, and isothermal power-law rheology lavas. For isothermal Newtonian lava, we find that the error in channel shape alone can make apparent viscosity estimates ˜3.5 times too large (e.g., for inappropriate use of the Jeffreys equation on a narrow semi-elliptical channel). For a temperature-dependent rheology, using an analytical approximation for Newtonian flow in a semi-elliptical geometry yields apparent viscosity and flux values that are more accurate than estimates which assume a rectangular geometry, for all channel shapes considered, including rectangular channels. Viscosity calculations for real channels on Mauna Loa and Mount Etna show that for a Newtonian rheology, a semi-elliptical analytical solution gives an approximation three times closer to the actual viscosity than a rectangle with the same depth while, if the lava is shear-thinning (power law exponent m = 0.6), a rectangular approximation is 15 % more accurate. Our results can be used to bracket possible viscosity and flux estimates when channel topography is poorly constrained.

  16. Response of Venus exospheric temperature measured by neutral mass spectrometer to solar EUV flux measured by Langmuir probe on the Pioneer Venus orbiter

    NASA Technical Reports Server (NTRS)

    Mahajan, K. K.; Kasprzak, W. T.; Brace, L. H.; Niemann, H. B.; Hoegy, W. R.

    1990-01-01

    The photoelectron current from the Pioneer Venus Langmuir probe has provided measurements of the total flux of solar EUV photons at Venus since 1979. The neutral oxygen scale height measured by the orbiter neutral mass spectrometer has permitted the exospheric temperature to be derived during the same mission. In this paper, the EUV observations are used to examine the response of exospheric temperature to changes in solar activity, primarily those related to solar rotation. It is found that the dayside exospheric temperature quite faithfully tracks variations in the EUV flux. Comparison is also made with the earth-based solar activity index F10.7 adjusted to the position of Venus. This index varied from 142 to 249 flux units during the period of measurements. The exospheric temperature is better correlated with EUV flux than with the 10.7-cm solar radio flux.

  17. Photon stimulated desorption from aluminum and stainless steel

    SciTech Connect

    Chou, T.S. )

    1991-05-01

    Photon stimulated desorption of neutral species (PSD) is the major dynamic gas load in electron synchrotron light source. In the National Synchrotron Light Source, (NSLS) PSD presented initial machine commissioning difficulty. Sensitivity to surface contamination on PSD has been experienced during an incident of Fomblin Oil contamination.{sup 1} U10B-photon stimulated desorption experimental station is constructed to investigate: 1---the degree of the contribution to the photon stimulated desorption (PSD) from primary photon flux and scattered secondary photon flux, 2---the underlying mechanism for photon stimulated desorption, 3---criteria to chose the proper beam tube material for future accelerators such as SXLS, FEL, superconducting super collider (SSC), ALS... . In this report, only photon stimulated desorption of neutral species (PSD) from stainless steel and aluminum is reported.

  18. Photon stimulated desorption from aluminum and stainless steel

    SciTech Connect

    Chou, T.S.

    1990-01-01

    Photon Stimulated Desorption of neutral species (PSD) is the major dynamic gas load in electron synchrotron light source. In the National Synchrotron Light Source, (NSLS) PSD presented initial machine commissioning difficulty. Sensitivity to surface contamination on PSD has been experienced during an incident of Fomblin Oil contamination. U1OB-Photon Stimulated Desorption Experimental Station is constructed to investigate: (1) the degree of the contribution to the photon stimulated desorption (PSD) from primary photon flux and scattered secondary photon flux, (2) the underlying mechanism for photon stimulated desorption, (3) criteria to choose the proper beam tube material for future accelerators such as SXLS, FEL, SSC, ALS... In this report, only photon stimulated desorption of neutral species (PSD) from stainless steel and aluminum is reported. 7 refs., 2 figs., 2 tabs.

  19. Photon stimulated desorption of neutral species from aluminum

    SciTech Connect

    Chou, T.S.

    1991-01-01

    Photon Simulated Desorption of neutral species (PSD) is the major dynamic gas load in electron synchrotron light source. In the National Synchrotron Light Source, PSD presented initial machine commissioning difficulty. Sensitivity to surface contamination on PSD had been experienced during an incident of Fomblin Oil contamination. U10B-Photon Stimulated Desorption Experimental Station is constructed to investigate: (1) the degree of the contribution to the photon stimulated desorption (PSD) from primary photon flux and scattered secondary photon flux, (2) the underlying mechanism for photon stimulated desorption, (3) criteria to chose the proper beam tube material for future a accelerator such as the Superconducting X-Ray Lithography Source (SXLS), Free Electron Laser (FEL), Superconducting Super Collider (SSC), Advanced Light Source (ALS) etc. In this report, only photon stimulated desorption of neutral species (PSD) from aluminum with different surface treatments is reported to show the great potential for this station to investigate beam tube material selection. 6 refs., 2 figs., 1 tab.

  20. Photon spectra from WIMP annihilation

    SciTech Connect

    Cembranos, J. A. R.; Cruz-Dombriz, A. de la; Dobado, A.; Maroto, A. L.; Lineros, R. A.

    2011-04-15

    If the present dark matter in the Universe annihilates into standard model particles, it must contribute to the fluxes of cosmic rays that are detected on the Earth and, in particular, to the observed gamma-ray fluxes. The magnitude of such a contribution depends on the particular dark matter candidate, but certain features of the produced photon spectra may be analyzed in a rather model-independent fashion. In this work we provide the complete photon spectra coming from WIMP annihilation into standard model particle-antiparticle pairs obtained by extensive Monte Carlo simulations. We present results for each individual annihilation channel and provide analytical fitting formulas for the different spectra for a wide range of WIMP masses.

  1. Flux control exerted by mitochondrial outer membrane carnitine palmitoyltransferase over beta-oxidation, ketogenesis and tricarboxylic acid cycle activity in hepatocytes isolated from rats in different metabolic states.

    PubMed Central

    Drynan, L; Quant, P A; Zammit, V A

    1996-01-01

    The Flux Control Coefficients of mitochondrial outer membrane carnitine palmitoyltransferase (CPT I) with respect to the overall rates of beta-oxidation, ketogenesis and tricarboxylic acid cycle activity were measured in hepatocytes isolated from rats in different metabolic states (fed, 24 h-starved, starved-refed and starved/insulin-treated). These conditions were chosen because there is controversy as to whether, when significant control ceases to be exerted by CPT I over the rate of fatty oxidation [Moir and Zammit (1994) Trends Biochem. Sci. 19, 313-317], this is transferred to one or more steps proximal to acylcarnitine synthesis (e.g. decreased delivery of fatty acids to the liver) or to the reaction catalysed by mitochondrial 3-hydroxy-3-methyl-glutaryl-CoA synthase [Hegardt (1995) Biochem. Soc. Trans. 23, 486-490]. Therefore isolated hepatocytes were used in the present study to exclude the involvement of changes in the rate of delivery of non-esterified fatty acids (NEFA) to the liver, such as occur in vivo, and to ascertain whether, under conditions of constant supply of NEFA, CPT I retains control over the relevant fluxes of fatty acid oxidation to ketones and carbon dioxide, or whether control is transferred to another (intrahepatocytic) site. The results clearly show that the Flux Control Coefficients of CPT I with respect to overall beta-oxidation and ketogenesis are very high under all conditions investigated, indicating that control is not lost to another intrahepatic site during the metabolic transitions studied. The control of CPT I over tricarboxylic acid cycle activity was always very low. The significance of these findings for the integration of fatty acid and carbohydrate metabolism in the liver is discussed. PMID:8760364

  2. Influence of urban activities on polycyclic aromatic hydrocarbons in precipitation: distribution, sources and depositional flux in a developing metropolis, Fortaleza, Brazil.

    PubMed

    Cavalcante, Rivelino M; Sousa, Francisco W; Nascimento, Ronaldo F; Silveira, Edilberto R; Viana, Rommel B

    2012-01-01

    We measured polycyclic aromatic hydrocarbons (PAHs) in bulk precipitation in the Fortaleza metropolitan area, Ceará, Brazil, for the first time. Because little information is available concerning PAHs in tropical climatic regions, we assessed their spatial distribution and possible sources and the influence of urban activities on the depositional fluxes of PAHs in bulk precipitation. The concentrations of individual and total PAHs (Σ(PAHs)) in bulk precipitation ranged from undetectable to 133.9 ng.L(-1) and from 202.6 to 674.8 ng.L(-1), respectively. The plume of highest concentrations was most intense in a zone with heavy automobile traffic and favorable topography for the concentration of emitted pollutants. The depositional fluxes of PAHs in bulk precipitation calculated in this study (undetectable to 0.87 μg.m(-2).month(-1)) are 4 to 27 times smaller than those reported from tourist sites and industrial and urban areas in the Northern Hemisphere. Diagnostic ratio analyses of PAH samples showed that the major source of emissions is gasoline exhaust, with a small percentage originating from diesel fuel. Contributions from coal and wood combustion were also found. Major economic activities appear to contribute to pollutant emissions. PMID:22134033

  3. Upper critical field, critical current density and thermally activated flux flow in CaFFe0.9Co0.1As superconductor

    NASA Astrophysics Data System (ADS)

    Shekhar, Chandra; Srivastava, Amit; Kumar, Pramod; Srivastava, Pankaj; Srivastava, O. N.

    2012-04-01

    In this paper, we report the synthesis, structure, transition temperature, upper critical field, critical current density and thermally activated flux flow in the CaFFe0.9Co0.1As superconductor. Superconductivity arises at 23 K by Co substitution at the site of Fe atoms and the upper critical field is estimated as 102 T using the Werthamer-Helfand-Hohenberg formula. The flux-flow activation energy (U0/kB) varies from 3230 K and 4190 K in a field of 9 T and 1 T, respectively. At 2 K, the Jc is found to be approximately 4 × 103 A cm-2 and 0.3 × 103 A cm-2 in zero and 6 T field, respectively. Transmission electron microscopy analysis shows an amorphous region surrounding most of the grains which is likely to be present in the form of amorphous and weak link grain boundaries in this compound. It seems that most of the current is hindered by mis-aligned grains, amorphous grain boundaries and impurities, which are invariably found between the grains. The presence of the weakly linked granules and their weakly pinned intergranular Josephson vortices are responsible for both low Jc and the Arrhenius temperature dependence of resistivity.

  4. Measurement of Integrated Low Frequency Flux Noise in Superconducting Flux/Phase Qubits

    SciTech Connect

    Mao Bo; Qiu Wei; Han Siyuan

    2008-11-07

    We measured the integrated low frequency flux noise ({approx}1 m{phi}{sub 0}) of an rf SQUID as a flux qubit by fitting the resonant peaks from photon assistant tunneling (PAT). The energy relaxation time Tl between the ground and first excited states in the same potential well, measured directly in time domain, is 3 ns. From these results we identified low frequency flux noise as the dominant source of decoherence. In addition, we found that the measured values of integrated flux noise in three qubits of various sizes differ more than an order of magnitude.

  5. Estimates of suspended-sediment flux and bedform activity on the inner portion of the Eel continental shelf

    USGS Publications Warehouse

    Cacchione, D.A.; Wiberg, P.L.; Lynch, J.; Irish, J.; Traykovski, P.

    1999-01-01

    Energetic waves, strong bottom currents, and relatively high rates of sediment discharge from the Eel River combined to produce large amounts of suspended-sediment transport on the inner continental shelf near the Eel River during the winter of 1995-1996. Bottom-boundary-layer (BBL) measurements at a depth of ~50 m using the GEOPROBE tripod showed that the strongest near-bottom flows (combined wave and current speeds of over 1 m/s) and highest sediment concentrations (exceeding 2 g/l at ~1.2 m above the bed) occurred during two storms, one in December 1995 and the other in February 1996. Discharge from the Eel River during these storms was estimated at between 2 and 4 x 103 m3/s. Suspended-sediment flux (SSF) was measured 1.2 m above the bed and calculated throughout the BBL, by applying the tripod data to a shelf sediment-transport model. These results showed initially northward along-shelf SSF during the storms, followed by abrupt and persistent southward reversals. Along-shelf flux was more pronounced during and after the December storm than in February. Across-shelf SSF over the entire measurement period was decidedly seaward. This seaward transport could be responsible for surficial deposits of recent sediment on the outer shelf and upper continental slope in this region. Sediment ripples and larger bedforms were observed in the very fine to fine sand at 50-m depth using a sector-scanning sonar mounted on the tripod. Ripple wavelengths estimated from the sonar images were about 9 cm, which compared favorably with photographs of the bottom taken with a camera mounted on the tripod. The ripple patterns were stable during periods of low combined wave-current bottom stresses, but changed significantly during high-stress events, such as the February storm. Two different sonic altimeters recorded changes in bed elevation of 10 to 20 cm during the periods of measurement. These changes are thought to have been caused principally by the migration of low-amplitude, long

  6. Photon Collider Physics with Real Photon Beams

    SciTech Connect

    Gronberg, J; Asztalos, S

    2005-11-03

    Photon-photon interactions have been an important probe into fundamental particle physics. Until recently, the only way to produce photon-photon collisions was parasitically in the collision of charged particles. Recent advances in short-pulse laser technology have made it possible to consider producing high intensity, tightly focused beams of real photons through Compton scattering. A linear e{sup +}e{sup -} collider could thus be transformed into a photon-photon collider with the addition of high power lasers. In this paper they show that it is possible to make a competitive photon-photon collider experiment using the currently mothballed Stanford Linear Collider. This would produce photon-photon collisions in the GeV energy range which would allow the discovery and study of exotic heavy mesons with spin states of zero and two.

  7. A flux of EUV emission measured on-board the “CORONAS” artificial satellites near minimum and maximum of the 23rd cycle of solar activity

    NASA Astrophysics Data System (ADS)

    Nusinov, A. A.; Kazachevskaya, T. V.; Katyushina, V. V.

    The paper presents data on ionizing short-wave UV-emission of the Sun in a wave-range λ ⩽ 130 nm measured on-board the CORONAS-I and CORONAS-F satellites. There were obtained absolute values of solar flux emission in the spectrum range λ ⩽ 130 nm and the band near H Lα hydrogen line on-board both satellites. Measurements on-board the CORONAS-I satellite coincided with a phase near the minimum of solar activity (F10.7 = 80 100). In the period from March to June of 1994 the solar flux was equal on the average to 7.5 erg cm-2 s-1 for λ ⩽ 130 nm and the intensity of emission in H Lα was equal to (5.5 6.1) erg cm-2 s-1. The measurements on-board the CORONAS-F were performed near the maximum of solar activity (F10.7 = 143 279). Emission intensity in H Lα line was about 6.8 8.2 erg cm-2 s-1 and in the wave-range λ ⩽ 130 nm it was equal on the average to 11 13 erg cm-2 s-1. EUV measurements are in agreement with the data obtained on-board UARS satellite and with the results of ionospheric measurement of E-layer critical frequencies. These measurements agree with data of contemporary models as well. A lot of flares including bright ones were observed. The measurement data of a bright flare of X-ray class X5.3 on 25.05.2001 are given. The paper presents the results of comparison between the CORONAS-F data and the X-ray fluxes in waveband 0.1 0.8 nm (GOES). This comparison demonstrated that X-ray emission measured on-board the GOES spacecraft and measured due to SUVR instrument (with filters in wave-range <12 nm) changed almost synchronously in the ranges 0.1 0.8 and 0.1 12 nm. The data measured due to VUSS showed that EUV emission appeared a few minutes (1 13) before X-ray emission. Apparently it evidences that at first a flare begins in the chromosphere and then a heating area is spreading higher. Solar emission increases by ˜20 30% in the range λ < 130 nm, and only by 8 10% in EUV range. Changes of extreme ultraviolet (EUV) solar flux were registered

  8. SAMOS Surface Fluxes

    NASA Astrophysics Data System (ADS)

    Smith, Shawn; Bourassa, Mark

    2014-05-01

    The development of a new surface flux dataset based on underway meteorological observations from research vessels will be presented. The research vessel data center at the Florida State University routinely acquires, quality controls, and distributes underway surface meteorological and oceanographic observations from over 30 oceanographic vessels. These activities are coordinated by the Shipboard Automated Meteorological and Oceanographic System (SAMOS) initiative in partnership with the Rolling Deck to Repository (R2R) project. Recently, the SAMOS data center has used these underway observations to produce bulk flux estimates for each vessel along individual cruise tracks. A description of this new flux product, along with the underlying data quality control procedures applied to SAMOS observations, will be provided. Research vessels provide underway observations at high-temporal frequency (1 min. sampling interval) that include navigational (position, course, heading, and speed), meteorological (air temperature, humidity, wind, surface pressure, radiation, rainfall), and oceanographic (surface sea temperature and salinity) samples. Vessels recruited to the SAMOS initiative collect a high concentration of data within the U.S. continental shelf and also frequently operate well outside routine shipping lanes, capturing observations in extreme ocean environments (Southern, Arctic, South Atlantic, and South Pacific oceans). These observations are atypical for their spatial and temporal sampling, making them very useful for many applications including validation of numerical models and satellite retrievals, as well as local assessments of natural variability. Individual SAMOS observations undergo routine automated quality control and select vessels receive detailed visual data quality inspection. The result is a quality-flagged data set that is ideal for calculating turbulent flux estimates. We will describe the bulk flux algorithms that have been applied to the

  9. Imaging by terahertz photon counting

    NASA Astrophysics Data System (ADS)

    Ikushima, Kenji; Komiyama, Susumu

    2010-08-01

    Photon counting method is indispensable in visible/near-infrared optical measurements for detecting extremely weak radiation. The method, however, has been inaccessible in terahertz region, where the photon energies are more than 100 times smaller and catching individual photons is difficult. Here we review photon counting measurements of terahertz waves, by incorporating a semiconductor quantum-dot terahertz-photon detector into a scanning terahertz microscope. By using a quantum Hall effect detector as well, measurements cover the intensity dynamic range more than six orders of magnitude. Applying the measurement system to the study of semiconductor quantum Hall effect devices, we image extremely weak cyclotron radiation emitted by nonequilibrium electrons. Owing to the unprecedented sensitivity, a variety of new features of electron kinetics are unveiled. Besides semiconductor electric devices studied here, the experimental method will find application in diverse areas of molecular dynamics, microthermography, and cell activities.

  10. Dependence of Cell Survival on Iododeoxyuridine Concentration in 35-keV Photon-Activated Auger Electron Radiotherapy

    SciTech Connect

    Dugas, Joseph P.; Varnes, Marie E.; Sajo, Erno; Welch, Christopher E.; Ham, Kyungmin; Hogstrom, Kenneth R.

    2011-01-01

    Purpose: To measure and compare Chinese hamster ovary cell survival curves using monochromatic 35-keV photons and 4-MV x-rays as a function of concentration of the radiosensitizer iododeoxyuridine (IUdR). Methods and Materials: IUdR was incorporated into Chinese hamster ovary cell DNA at 16.6 {+-} 1.9%, 12.0 {+-} 1.4%, and 9.2 {+-} 1.3% thymidine replacement. Cells were irradiated from 1 to 8 Gy with 35-keV synchrotron-generated photons and conventional radiotherapy 4-MV x-rays. The effects of the radiation were measured via clonogenic survival assays. Surviving fraction was plotted vs. dose and fit to a linear quadratic model. Sensitization enhancement ratios (SER{sub 10}) were calculated as the ratio of doses required to achieve 10% surviving fraction for cells without and with DNA-incorporated IUdR. Results: At 4 MV, SER{sub 10} values were 2.6 {+-} 0.1, 2.2 {+-} 0.1, and 1.5 {+-} 0.1 for 16.6%, 12.0%, and 9.2% thymidine replacement, respectively. At 35 keV, SER{sub 10} values were 4.1 {+-} 0.2, 3.0 {+-} 0.1, and 2.0 {+-} 0.1, respectively, which yielded SER{sub 10} ratios (35 keV:4 MV) of 1.6 {+-} 0.1, 1.4 {+-} 0.1, and 1.3 {+-} 0.1, respectively. Conclusions: SER{sub 10} increases monotonically with percent thymidine replacement by IUdR for both modalities. As compared to 4-MV x-rays, 35-keV photons produce enhanced SER{sub 10} values whose ratios are linear with percent thymidine replacement and assumed to be due to Auger electrons contributing to enhanced dose to DNA. Although this Auger effectiveness factor is less than the radiosensitization factor of IUdR, both could be important for the clinical efficacy of IUdR radiotherapy.

  11. Acute toxicity and sublethal effects of the mixture glyphosate (Roundup Active) and Cosmo-Flux 411F to anuran embryos and tadpoles of four Colombian species.

    PubMed

    Henao Muñoz, Liliana Marcela; Montes Rojas, Claudia Marsela; Bernal Bautista, Manuel Hernando

    2015-03-01

    Glyphosate is the most widely used herbicide in the world with application in agriculture, forestry, industrial weed control, garden and aquatic environments. However, its use is highly controversial for the possible impact on not-target organisms, such as amphibians, which are vanishing at an alarming and rapid rate. Due to the high solubility in water and ionic nature, the glyphosate requires of surfactants to increase activity. In addition, for the control of coca (Erythroxylum coca) and agricultural weeds in Colombia, formulated glyphosate is mixed and sprayed with the adjuvant Cosmo-Flux 411F to increase the penetration and activity of the herbicide. This study evaluates the acute toxic and sublethal effects (embryonic development, tadpole body size, tadpole swimming performance) of the mixture of the formulated glyphosate Roundup Active and Cosmo-Flux 411F to anuran embryos and tadpoles of four Colombian species under 96h laboratory standard tests and microcosms, which are more similar to field conditions as they include soil, sand and macrophytes. In the laboratory, embryos and tadpoles of Engystomops pustulosus were the most tolerant (LC50 = 3904 microg a.e./L; LC50=2 799 pg a.e./L, respectively), while embryos and tadpoles of Hypsiboas crepitans (LC50=2 203 microg a.e./L; LC50=1424 microgg a.e./L, respectively) were the most sensitive. R. humboldti and R. marina presented an intermediate toxicity. Embryos were significantly more tolerant to the mixture than tadpoles, which could be likely attributed to the exclusion of chemicals by the embryonic membranes and the lack of organs, such as gills, which are sensitive to surfactants. Sublethal effects were observed for the tadpole body size, but not for the embryonic development and tadpole swimming performance. In microcosms, no toxicity (LC50 could not be estimated), or sublethal responses were observed at concentrations up to fourfold (14.76 kg glyphosate a.e./ha) the highest field application rate of 3

  12. Characterization of Ca(2+)-activated 86Rb+ fluxes in rat C6 glioma cells: a system for identifying novel IKCa-channel toxins.

    PubMed Central

    de-Allie, F. A.; Bolsover, S. R.; Nowicky, A. V.; Strong, P. N.

    1996-01-01

    1. The pharmacological characteristics of a putative Ca2+ activated K+ channel (IKCa channel) in rat glioma C6 cells were studied in the presence of the Ca2+ ionophore, ionomycin and various K+ channel blockers, 86Rb+ being used as a radioisotopic tracer for K+. 2. The resting 86Rb+ influx into C6 cells was 318 +/- 20 pmol s-1. The threshold for ionomycin activation of 86Rb+ influx was approx. 100 nM. At ionomycin concentrations above the activation threshold, the initial rate of 86Rb+ influx was proportional to ionophore concentration. Ionomycin-activated 86Rb+ flux was saturable (EC50 = 0.62 +/- 0.03 microM) and was not inhibited by ouabain. 3. Intracellular Ca2+ increased within 30 s from a basal level of 42 +/- 2 nM to 233 +/- 17 nM, after addition of 2 microM ionomycin. During this period, intracellular pH fell from 7.03 +/- 0.04 to 6.87 +/- 0.03 and the cell hyperpolarized from -34 +/- 10 mV to -76 +/- 2 mV. 4. Single channel conductance measurements on inside-out patches in physiological K+ solutions identified a 14 +/- 3 pS CA(2+)-activated K+ current between -25 mV and +50 mV. In symmetrical (100 mM) K+, the single channel conductance was 26 pS. 5. Externally applied quinine (IC50 = 0.12 +/- 0.34 mM) and tetraethylammonium chloride (IC50 = 10 +/- 1.9 mM) inhibited 86Rb+ influx into C6 cells in a concentration-dependent manner. Charybdotoxin (IC50 = 0.5 +/- 0.02 nM) and iberiotoxin (IC50 = 800 +/- 150 nM), as well as the crude venoms from the scorpions Leiurus quinquestriatus and Mesobuthus tamulus, also inhibited 86Rb+ influx. In contrast, apamin and toxin I had no inhibitory effects on 86Rb+ flux. A screen of fractions from cation exchange h.p.l.c. of Mesob. tamulus venom revealed the presence of at least four charybdotoxin-like peptides. One of these was iberiotoxin; the other three are novel toxins. 6. The ionomycin-activated 86Rb+ influx into rat C6 glioma cells has proved to be a valuable pharmacological assay for the screening of toxins and crude

  13. Nuclear Resonance Fluorescence Using Different Photon Sources

    SciTech Connect

    Warren, Glen A.; Caggiano, Joseph A.; Ahmed, Mohammad; Bertozzi, William; Hunt, Alan W.; Johnson, James; Jones, James L.; Korbly, Steve; Reedy, Edward; Seipel, Heather; Stave, Sean; Watson, Scott; Weller, Henry

    2008-11-14

    Abstract–Nuclear resonance fluorescence (NRF) is a photon-based active interrogation approach that provides isotope-specific signatures that can be used to detect and characterize samples. As NRF systems are designed to address specific appli¬cations, an obvious first question to address is the type of photon source to be employed for the application. Our collaboration has conducted a series of NRF measurements using different photon sources to begin to examine this issue. The measurements were designed to be as similar as possible to facilitate a straightforward comparison of the different sources. Measurements were conducted with a high-duty factor electron accelerator using bremsstrahlung photons, with a pulsed linear accelerator using bremsstrahlung photons, and with a narrow bandwidth photon source using Compton backscattered photons. We present our observations on the advantages and disadvantages of each photon source type. Issues such as signal rate, the signal-to-noise ratio, and absorbed dose are discussed.

  14. Self-assembly of Terbium(III)-based metal-organic complexes with two-photon absorbing active

    NASA Astrophysics Data System (ADS)

    Li, Dandan; Shao, Nanqi; Sun, Xianshun; Zhang, Guocui; Li, Shengli; Zhou, Hongping; Wu, Jieying; Tian, Yupeng

    2014-12-01

    Hybrid complexes based on D-π-A type dyes p-aminostyryl-pyridinum and Terbium(III) complex anion (1, 2) have been synthesized by ionic exchange reaction. Meanwhile two different alkyl-substituted amino groups were used as electron donors in organic dyes cations. The synthesized complexes were characterized by element analysis. In addition, the structural features of them were systematic studied by single crystal X-ray diffraction analysis. Their linear properties have been systematically investigated by absorption spectra and fluorescence, the results show that the energy transfer takes place from the trans-4-[4‧-(N,N-diethylamino)styryl]-N-methyl pyridinium (2‧) cation to Tb(III). In addition, complex 2 exhibit a large two-photon absorption coefficient β: 0.044 cm/GW at 710 nm.

  15. Quantitative molecular biology and gas flux measurements demonstrate soil treatment and depth affects on the distribution and activity of denitrifiers

    NASA Astrophysics Data System (ADS)

    Barrett, M. M.; Jahangir, M.; Cardenas, L.; Khalil, M.; Richards, K. R.; O'Flaherty, V.

    2010-12-01

    The growing industrialisation of agriculture has led to a dramatic increase in organic and inorganic nitrogen (N) fertiliser inputs to agro-ecosystems. This increase has had negative effects on the quality of water ecosystems and greenhouse gas emissions.The study objective was to quantify denitrification and denitrifying microorganisms, using real-time PCR assays of the nitrite reductase(nir) and nitrous oxide reductase(nos) functional gene copy concentrations (GCC g[soil]-1) in Irish agricultural surface and subsoils. Soil cores from 3 soil horizons (A:0-10 cm; B:45-55 cm; C:120-130cm) were amended with 3 alternate N- and C-source amendments (NO3-; NO3-+glucose-C; NO3-+Dissolved Organic Carbon (DOC). Real-time production of N2O and N2 was recorded by gas chromatography in a specialized He/O2 environment. N2O and Total Denitrification (TDN) (N2O+N2) production was generally greater in surface soil (2.052 mg/kg/d TDN) than in subsoils (0.120 mg/kg/d TDN). The abundance of denitrifying nirS, nirK (nir) and nos genes was higher in the surface soil, decreasing with soil depth, except in incubations amended with NO3- and DOC, where the carbon source directly positively affected gene copy numbers and fluxes of N2O and N2 production. C addition increased soil denitrification rates, and resulted in higher N2O/(N2O+N2) ratios in surface soil (0.39) than subsoils (0.005), indicating that the subsoil had higher potential for complete reduction of N2O to N2. In the subsoils, complete reduction of NO3- due to glucose-C and DOC addition was observed. Interestingly, at all 3 soil depths, lower nirK abundance (2.78 105 GCC) was recorded, compared to nirS (1.45 107 GCC), but the overall abundance of nir (S+K) i.e. (1.54 107GCC), corresponded with N2O emission fluxes (3.34 mg/kg/d) Statistical analysis indicates negative correlation between nirK GCC and N2O production, but a strong positive correlation was observed between nirS GCC and N2O. We therefore hypothesize that the

  16. Measuring the photon fragmentation function at HERA

    NASA Astrophysics Data System (ADS)

    Gehrmann-de Ridder, A.; Gehrmann, T.; Poulsen, E.

    2006-08-01

    The production of final state photons in deep inelastic scattering originates from photon radiation off leptons or quarks involved in the scattering process. Photon radiation off quarks involves a contribution from the quark-to-photon fragmentation function, corresponding to the non-perturbative transition of a hadronic jet into a single, highly energetic photon accompanied by some limited hadronic activity. Up to now, this fragmentation function was measured only in electron positron annihilation at LEP. We demonstrate by a dedicated parton-level calculation that a competitive measurement of the quark-to-photon fragmentation function can be obtained in deep inelastic scattering at HERA. Such a measurement can be obtained by studying the photon energy spectra in γ+(0+1)-jet events, where γ denotes a hadronic jet containing a highly energetic photon (the photon jet). Isolated photons are then defined from the photon jet by imposing a minimal photon energy fraction. For this so-called democratic clustering approach, we study the cross sections for isolated γ+(0+1)-jet and γ+(1+1)-jet production as well as for the inclusive isolated photon production in deep inelastic scattering.

  17. Integrated photonics

    NASA Astrophysics Data System (ADS)

    Gondarenko, Alexander A.

    In 1958 the first integrated circuit was demonstrated to combine transistors, resistors, and capacitors [36]. To this date fabrication technology has been driven by the growing demand for monolithically constructed, densely packed electronic components. The exponentially shrinking device size decreased the feature dimensions from 10 microns to 32 nm and grew transistor count from 2,300 to over 2,000,000,000 in Intel's 4004 and Intel Kentsfield XE microprocessors. The benefits of micro- and nano-fabrication was not limited to just computer chips. MEMs, spintronic, microfluidics, and integrated photonics were all made possible by the ever expanding ability to form complex geometries, on a wide variety of materials, on a micron and submicron scale. This dissertation is part of an effort to design and fabricate novel integrated photonic devices compatible with standard electron beam and photo lithography and utilize a readily available material base. We aim to create devices with a decreased footprint on a chip and operate in the infrared, visible, and UV spectra. We present two general sections, the first is a theoretical effort to find the fundamental design geometries for a variety of optical problems. The second section is an experimental demonstration of techniques and devices for novel optical phenomena in an integrated package. In the theoretical section we develop and apply computational evolutionary algorithms to explore problems of light confinement, coupling, and guiding in two and three dimensional device geometries. Our general aim is to find a global limit to optimal device geometry and performance given a set of constrains. Experimentally, we demonstrate an efficient design and a fabrication process for a short development cycle of photonic devices. For the design part of the workflow, we develop a computational approach to explore device geometries with minimum initial assumptions for a variety of photonic problems. For the fabrication part of the

  18. Evaluation of neutron flux parameters in irradiation sites of research reactor using the Westcott-formalism for the k0 neutron activation analysis method

    NASA Astrophysics Data System (ADS)

    Kasban, H.; Hamid, Ashraf

    2015-12-01

    Instrumental Neutron Activation Analysis using k0 (k0-INAA) method has been used to determine a number of elements in sediment samples collected from El-Manzala Lake in Egypt. k0-INAA according to Westcott's formalism has been implemented using the complete irradiation kit of the fast pneumatic rabbit and some selected manually loaded irradiation sites for short and long irradiation at Egypt Second Research Reactor (ETRR-2). Zr-Au and Co sets as neutron flux monitors are used to determine the neutron flux parameters (f and α) in each irradiation sites. Two reference materials IAEA Soil-7 samples have been inserted and implemented for data validation and an internal monostandard multi monitor used (k0 based IM-NAA). It was given a good agreement between the experimental analyzed values and that obtained of the certified values. The major and trace elements in the sediment samples have been evaluated with the use of Co as an internal and Au as an external monostandard comparators. The concentrations of the elements (Cr, Mn and Zn) in the sediment samples of the present work are discussed regarding to those obtained from other sites.

  19. Advances in photon counting for bioluminescence

    NASA Astrophysics Data System (ADS)

    Ingle, Martin B.; Powell, Ralph

    1998-11-01

    Photon counting systems were originally developed for astronomy, initially by the astronomical community. However, a major application area is in the study of luminescent probes in living plants, fishes and cell cultures. For these applications, it has been necessary to develop camera system capability at very low light levels -- a few photons occasionally -- and also at reasonably high light levels to enable the systems to be focused and to collect quality images of the object under study. The paper presents new data on MTF at extremely low photon flux and conventional ICCD illumination, counting efficiency and dark noise as a function of temperature.

  20. Quantitative Flux Ecoregions for AmeriFlux Using MODIS

    NASA Astrophysics Data System (ADS)

    Hoffman, F. M.; Hargrove, W. W.

    2004-12-01

    Multivariate Geographic Clustering was used with maps of climate, soils, and physiography and MODIS remotely sensed data products to statistically produce a series of the 90 most-different homogeneous flux-relevant ecoregions in the conterminous United States using a parallel supercomputer. Nine separate sets of flux ecoregions were produced; only two will be discussed here. Both the IB and IIIB maps were quantitatively constructed from subsets of the input data integrated during the local growing season (frost-free period) in every 1 km cell. Each map is shown two ways --- once with the 90 flux ecoregions colored randomly, and once using color combinations derived statistically from the first three Principal Component Axes. Although the underlying flux ecoregion polygons are the same in both cases, the statistically derived colors show the similarity of conditions within each flux ecoregion. Coloring the same map in this way shows the continuous gradient of changing flux environments across the US. The IB map, since it considers only abiotic environmental factors, represents flux-ecoregions based on potential vegetation. The IIIB map, since it contains remotely sensed MODIS information about existing vegetation, includes the effects of natural and anthropogenic disturbance, and represents actual or realized flux ecoregions. Thus, differences between the maps are attributable to human activity and natural disturbances. The addition of information on existing vegetation exerts a unifying effect on abiotic-only flux ecoregions. The Mississippi Valley and Corn Belt areas show large differences between the two maps. Map IIIB shows a mosaic of ``speckles'' in areas of intense human land use, ostensibly from disturbances like agriculture, irrigation, fertilization, and clearing. Such ``speckles'' are absent from areas devoid of intense human land use. Major cities are also evident in the IIIB map. We will use the quantitative similarity of the suite of flux

  1. Online coupling of high-resolution chromatography with extreme UV photon activation tandem mass spectrometry: Application to the structural investigation of complex glycans by dissociative photoionization.

    PubMed

    Ropartz, David; Giuliani, Alexandre; Fanuel, Mathieu; Hervé, Cécile; Czjzek, Mirjam; Rogniaux, Hélène

    2016-08-24

    The activation of ions by extreme-energy photons (XUV) produced by a synchrotron radiation beamline is a powerful method for characterizing complex glycans using tandem mass spectrometry (MS). As previously described, this activation method leads to rich fragmentation spectra with many structurally valuable cross-ring cleavages while maintaining labile modifications on the glycan structures. However, until now, the tandem MS event was too long to be compatible with liquid chromatography elution times. In this work, the duty cycle of the activation and detection of fragments was shortened, and the background signal on the spectra was drastically reduced. Both improvements allowed, for the first time, the successful coupling of a UHPLC system to XUV-activated tandem MS. The approach was used to characterize a complex mixture of oligo-porphyrans, which are a class of highly sulfated oligosaccharides, in a fully automated way. Due to an enhanced dynamic range and an increased sensitivity, some hypothetical structures of low abundance have been unequivocally confirmed in this study and others have been revised. Some previously undescribed species of oligo-porphyrans that exhibit lateral branching have been fully resolved. This work contributes to the scarce knowledge of the structure of porphyrans in red algae and pushes the current capacities of XUV-activation tandem MS by demonstrating the possibility of a direct coupling with UHPLC. This study will considerably broaden the applicability and practicality of this method in many fields of analytical biology. PMID:27496992

  2. Photonics applications of nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Kennedy, Scott Ronald

    Using an advanced thin film fabrication technique known as Glancing Angle Deposition (GLAD), it is possible to fabricate unique thin film nanostructures with characteristic dimensions on the order of a wavelength of light. By tailoring the morphologies of the films, they can be designed to exhibit particular optical properties that can be customized through advanced substrate motion and highly oblique flux incidence angles. In applications to photonics, controlling the flow of light for a specified task, GLAD thin films can be fabricated to provide the ability to manipulate incident light through controlled interactions of optical frequency electromagnetic radiation with the thin film nanostructures. Tetragonal square spiral photonic band gap crystals, a new class of periodic dielectric material that is characterized by the elimination of the density of states for frequencies lying in the stop gap of the crystal, can be fabricated using GLAD in a virtual single step process. The design and fabrication of these unique devices has been performed and the resultant crystals characterized in terms of optical response with respect to forbidden propagation modes, material properties, and advanced deposition techniques used to improve the overall structure. Chiral or helical thin films deposited using GLAD were also investigated, and have been shown to exhibit optical activity and circular birefringence due to their inherent structural anisotropy. It has been shown that the addition of nematic liquid crystals (LCs) to chiral thin films enhances the overall device performance due to order induced in the LCs by the film structure. This effect was investigated for a variety of materials and film structures. Finally, by developing a modified GLAD technique whereby the deposited film porosity is controlled through the angle of flux incidence, porous broadband antireflection coatings were produced. Using an appropriate effective medium theory to describe the index of refraction

  3. Photonic Nanojets

    PubMed Central

    Heifetz, Alexander; Kong, Soon-Cheol; Sahakian, Alan V.; Taflove, Allen; Backman, Vadim

    2009-01-01

    This paper reviews the substantial body of literature emerging since 2004 concerning photonic nanojets. The photonic nanojet is a narrow, high-intensity, non-evanescent light beam that can propagate over a distance longer than the wavelength λ after emerging from the shadow-side surface of an illuminated lossless dielectric microcylinder or microsphere of diameter larger than λ. The nanojet’s minimum beamwidth can be smaller than the classical diffraction limit, in fact as small as ~λ/3 for microspheres. It is a nonresonant phenomenon appearing for a wide range of diameters of the microcylinder or microsphere if the refractive index contrast relative to the background is less than about 2:1. Importantly, inserting within a nanojet a nanoparticle of diameter dν perturbs the far-field backscattered power of the illuminated microsphere by an amount that varies as dν3 for a fixed λ. This perturbation is much slower than the dν6 dependence of Rayleigh scattering for the same nanoparticle, if isolated. This leads to a situation where, for example, the measured far-field backscattered power of a 3-μm diameter microsphere could double if a 30-nm diameter nanoparticle were inserted into the nanojet emerging from the microsphere, despite the nanoparticle having only 1/10,000th the cross-section area of the microsphere. In effect, the nanojet serves to project the presence of the nanoparticle to the far field. These properties combine to afford potentially important applications of photonic nanojets for detecting and manipulating nanoscale objects, subdiffraction-resolution nanopatterning and nanolithography, low-loss waveguiding, and ultrahigh-density optical storage. PMID:19946614

  4. Photon calorimeter

    DOEpatents

    Chow, Tze-Show

    1988-04-22

    A photon calorimeter is provided that comprises a laminar substrate that is uniform in density and homogeneous in atomic composition. A plasma-sprayed coating, that is generally uniform in density and homogeneous in atomic composition within the proximity of planes that are parallel to the surfaces of the substrate, is applied to either one or both sides of the laminar substrate. The plasma-sprayed coatings may be very efficiently spectrally tailored in atomic number. Thermocouple measuring junctions, are positioned within the plasma-sprayed coatings. The calorimeter is rugged, inexpensive, and equilibrates in temperature very rapidly. 4 figs.

  5. Photon Calorimeter

    DOEpatents

    Chow, Tze-Show

    1989-01-01

    A photon calorimeter (20, 40) is provided that comprises a laminar substrate (10, 22, 42) that is uniform in density and homogeneous in atomic composition. A plasma-sprayed coating (28, 48, 52), that is generally uniform in density and homogeneous in atomic composition within the proximity of planes that are parallel to the surfaces of the substrate, is applied to either one or both sides of the laminar substrate. The plasma-sprayed coatings may be very efficiently spectrally tailored in atomic number. Thermocouple measuring junctions (30, 50, 54) are positioned within the plasma-sprayed coatings. The calorimeter is rugged, inexpensive, and equilibrates in temperature very rapidly.

  6. Combining urban scale inversions and process-based information from sectors of economic activity in the Indianapolis Flux Experiment (INFLUX) to monitor CO2 emissions

    NASA Astrophysics Data System (ADS)

    Lauvaux, Thomas; Calahan, Bill; Cambaliza, Maria; Davis, Kenneth; Deng, Aijun; Hardesty, Robert; Iraci, Laura; Gurney, Kevin; Karion, Anna; McGowan, Laura; Possolo, Antonio; Razlivanov, Igor; Sarmiento, Daniel; Shepson, Paul; Sweeney, Colm; Turnbull, Jocelyn; Whetstone, James

    2013-04-01

    The Indianapolis Flux Experiment (INFLUX) aims at quantifying emissions of anthropogenic carbon using top-down methods and process-based information (Hestia) at very high resolution over the city of Indianapolis (IN). At present, 9 sensors measuring continuously atmospheric mixing ratios of GHG have been deployed, with additional flask samples of isotopic ratios, one eddy-flux site measuring the surface energy and CO2 fluxes, frequent aircraft flight measurements of GHG, and a column-integrated surface based sensor (FTS-TCCON). Additional meteorological instruments were deployed to assess the accuracy of the modeling system by measuring vertical profiles of several meteorological variables (wind, turbulent mixing height, temperature), from both ground-based and airborne instruments. The inverse modeling system combines the atmospheric transport model WRF in Four-Dimensional Data Assimilation mode with a Lagrangian Particle Dispersion Model to simulate the local atmospheric dynamics over the area. The system was coupled to the high resolution emissions from the Hestia product at the hourly time scale for each individual economic activity sector. We present here the contribution from the different activity sectors as observed by the current atmospheric observation network. The capability of the system to detect and constrain seasonal and spatial signals in the emissions is inferred from sensitivity experiments. Whereas several sectors are widely distributed in space and observed by the whole GHG sensors network, we show that large point sources from industrial and utility sectors are less frequently observed and difficult to simulate correctly in our initial WRF simulations. However, these sectors represent a large fraction of the total emissions in the area. Consequently, seasonal changes in the atmospheric circulation and the sector emissions impact directly the distribution of the final error reduction of the inverse system. We finally estimate the potential of

  7. Solar flux and its variations

    NASA Technical Reports Server (NTRS)

    Smith, E. V. P.; Gottlieb, D. M.

    1975-01-01

    Data are presented on the solar irradiance as derived from a number of sources. An attempt was made to bring these data onto a uniform scale. Summation of fluxes at all wavelengths yields a figure of 1357.826 for the solar constant. Estimates are made of the solar flux variations due to flares, active regions (slowly varying component), 27-day period, and the 11-yr cycle. Solar activity does not produce a significant variation in the value of the solar constant. Variations in the X-ray and EUV portions of the solar flux may be several orders of magnitude during solar activity, especially at times of major flares. It is established that these short wavelength flux enhancements cause significant changes in the terrestrial ionosphere.

  8. SMARTPIX, a photon-counting pixel detector for synchrotron applications based on Medipix3RX readout chip and active edge pixel sensors

    NASA Astrophysics Data System (ADS)

    Ponchut, C.; Collet, E.; Hervé, C.; Le Caer, T.; Cerrai, J.; Siron, L.; Dabin, Y.; Ribois, J. F.

    2015-01-01

    Photon-counting pixel detectors are now routinely used on synchrotron beamlines. Many applications benefit from their noiseless mode of operation, single-pixel point spread function and high frame rates. One of their drawbacks is a discontinuous detection area due to the space-consuming wirebonded connections of the readout chips. Moreover, charge sharing limits their efficiency and their energy discrimination capabilities. In order to overcome these issues the ESRF is developing SMARTPIX,a scalable and versatile pixel detector system with minimized dead areas and with energy resolving capabilities based on the MEDIPIX3RX readout chip. SMARTPIX exploits the through-silicon via technology implemented on MEDIPIX3RX, the active edge sensor processing developed in particular at ADVACAM, and the on-chip analog charge summing feature of MEDIPIX3RX. This article reports on system architecture, unit module structure, data acquisition electronics, target characteristics and applications.

  9. Layered shielding design for an active neutron interrogation system

    NASA Astrophysics Data System (ADS)

    Whetstone, Zachary D.; Kearfott, Kimberlee J.

    2016-08-01

    The use of source and detector shields in active neutron interrogation can improve detector signal. In simulations, a shielded detector with a source rotated π/3 rad relative to the opening decreased neutron flux roughly three orders of magnitude. Several realistic source and detector shield configurations were simulated. A layered design reduced neutron and secondary photon flux in the detector by approximately one order of magnitude for a deuterium-tritium source. The shield arrangement can be adapted for a portable, modular design.

  10. Photon-efficient imaging with a single-photon camera

    NASA Astrophysics Data System (ADS)

    Shin, Dongeek; Xu, Feihu; Venkatraman, Dheera; Lussana, Rudi; Villa, Federica; Zappa, Franco; Goyal, Vivek K.; Wong, Franco N. C.; Shapiro, Jeffrey H.

    2016-06-01

    Reconstructing a scene's 3D structure and reflectivity accurately with an active imaging system operating in low-light-level conditions has wide-ranging applications, spanning biological imaging to remote sensing. Here we propose and experimentally demonstrate a depth and reflectivity imaging system with a single-photon camera that generates high-quality images from ~1 detected signal photon per pixel. Previous achievements of similar photon efficiency have been with conventional raster-scanning data collection using single-pixel photon counters capable of ~10-ps time tagging. In contrast, our camera's detector array requires highly parallelized time-to-digital conversions with photon time-tagging accuracy limited to ~ns. Thus, we develop an array-specific algorithm that converts coarsely time-binned photon detections to highly accurate scene depth and reflectivity by exploiting both the transverse smoothness and longitudinal sparsity of natural scenes. By overcoming the coarse time resolution of the array, our framework uniquely achieves high photon efficiency in a relatively short acquisition time.

  11. Photon-efficient imaging with a single-photon camera

    PubMed Central

    Shin, Dongeek; Xu, Feihu; Venkatraman, Dheera; Lussana, Rudi; Villa, Federica; Zappa, Franco; Goyal, Vivek K.; Wong, Franco N. C.; Shapiro, Jeffrey H.

    2016-01-01

    Reconstructing a scene's 3D structure and reflectivity accurately with an active imaging system operating in low-light-level conditions has wide-ranging applications, spanning biological imaging to remote sensing. Here we propose and experimentally demonstrate a depth and reflectivity imaging system with a single-photon camera that generates high-quality images from ∼1 detected signal photon per pixel. Previous achievements of similar photon efficiency have been with conventional raster-scanning data collection using single-pixel photon counters capable of ∼10-ps time tagging. In contrast, our camera's detector array requires highly parallelized time-to-digital conversions with photon time-tagging accuracy limited to ∼ns. Thus, we develop an array-specific algorithm that converts coarsely time-binned photon detections to highly accurate scene depth and reflectivity by exploiting both the transverse smoothness and longitudinal sparsity of natural scenes. By overcoming the coarse time resolution of the array, our framework uniquely achieves high photon efficiency in a relatively short acquisition time. PMID:27338821

  12. Photon-efficient imaging with a single-photon camera.

    PubMed

    Shin, Dongeek; Xu, Feihu; Venkatraman, Dheera; Lussana, Rudi; Villa, Federica; Zappa, Franco; Goyal, Vivek K; Wong, Franco N C; Shapiro, Jeffrey H

    2016-01-01

    Reconstructing a scene's 3D structure and reflectivity accurately with an active imaging system operating in low-light-level conditions has wide-ranging applications, spanning biological imaging to remote sensing. Here we propose and experimentally demonstrate a depth and reflectivity imaging system with a single-photon camera that generates high-quality images from ∼1 detected signal photon per pixel. Previous achievements of similar photon efficiency have been with conventional raster-scanning data collection using single-pixel photon counters capable of ∼10-ps time tagging. In contrast, our camera's detector array requires highly parallelized time-to-digital conversions with photon time-tagging accuracy limited to ∼ns. Thus, we develop an array-specific algorithm that converts coarsely time-binned photon detections to highly accurate scene depth and reflectivity by exploiting both the transverse smoothness and longitudinal sparsity of natural scenes. By overcoming the coarse time resolution of the array, our framework uniquely achieves high photon efficiency in a relatively short acquisition time. PMID:27338821

  13. Photonics for MS study in radiocommunications

    NASA Astrophysics Data System (ADS)

    Volner, Rudolf; Klima, Milos; Ticha, Dasa

    2002-05-01

    The paper is devoted to an education of Photonics at the Dept. of Telecommunications, Faculty of Electrical Engineering, at the University of Zilina. Originated from the university historical development the photonic subjects are implemented in two basic areas: Telecommunication Technology and Radiocommunication Technology. From the school year 1994/95 the new subject Photonics has been taught and it has attracted numerous students. The subject is focused on both physical principles and system application. The relevant parts can be listed as: interaction photon - matter, photonic receivers and transmitters, modulation and demodulation in Photonics, photonic networks - narrowband and wideband, photonic switches, image sensors and displays. The education of Photonics has been supported by research activities in the field of applied photonic system for signal (data) transmission and selected results have been implemented into the subject structure. The paper listed a detailed content of the subject in two fields: lectures and experimental laboratory exercises. As an integral part of the course we plan to implement selected experiments from the area of 2D photonic (image) processing and to expand the imaging photonic part.

  14. ASP: a new PEP experiment to measure single photons

    SciTech Connect

    Hollebeek, R.

    1984-05-01

    The design and construction of a new experiment for PEP designed to measure the flux of low energy photons unaccompanied by any additional photons, or charged tracks is described. The device consists of arrays of extruded lead glass bars and PWC's in the central region with lead-scintillator shower counters, drift chambers and PWC's in the forward regions. 9 references.

  15. Thermophotovoltaic energy conversion using photonic bandgap selective emitters

    DOEpatents

    Gee, James M.; Lin, Shawn-Yu; Fleming, James G.; Moreno, James B.

    2003-06-24

    A method for thermophotovoltaic generation of electricity comprises heating a metallic photonic crystal to provide selective emission of radiation that is matched to the peak spectral response of a photovoltaic cell that converts the radiation to electricity. The use of a refractory metal, such as tungsten, for the photonic crystal enables high temperature operation for high radiant flux and high dielectric contrast for a full 3D photonic bandgap, preferable for efficient thermophotovoltaic energy conversion.

  16. Topological preparation of Laughlin and Pfaffian states of photons

    NASA Astrophysics Data System (ADS)

    Grusdt, Fabian; Letscher, Fabian; Hafezi, Mohammad; Fleischhauer, Michael

    2014-05-01

    We present a new scheme for the preparation of highly correlated Laughlin and Pfaffian states of photons. In contrast to other proposals we do not start from an N-photon Fock state, but adiabatically introduce photons one by one. As a consequence our scheme only requires a time T ~ N to grow an N-photon Laughlin state. We consider a realistic setup of two-dimensional cavity arrays subject to an effective magnetic field. Moreover we assume strong on-site interactions for photons. Our scheme makes use of the quantization of the Hall current, which is topologically protected, and the ability to manipulate the magnetic flux locally in photonic systems [Hafezi, arXiv:1310.7946]. By adiabatically introducing flux quanta in the center of an N-photon Laughlin state, quasihole excitations can be created. Replenishing the resulting hole with a new photon allows to create an incompressible N + 1 photon Laughlin state. Photon-losses lead to an increasing number of hole-type excitations at the edge of the Laughlin liquid and thus limit the achievable system-sizes. We present numerical simulations for small systems of interacting photons and for an effective model of non-interacting composite fermions, demonstrating the feasibility of our scheme. F.G. thanks his graduate school ``Material Science in MAINZ'' for financial support.

  17. Interpretation of short and long-term oscillations of solar activity by alpha-omega dynamo model with two macro-cells of meridional fluxes

    NASA Astrophysics Data System (ADS)

    Popova, Elena

    2016-04-01

    Solar magnetic activity is related with generation strong magnetic fields in the depths of the Sun and manifested in sunspot occurrence on the solar surface. The amplitude and the spatial configuration of the magnetic field of our star are changing over the years. The most widely known variations of solar magnetic field are 11-years cycles and grand minima. The generation and evolution of the solar magnetic field and other stars is usually related to the dynamo mechanism. This mechanism is based on the consideration of the joint influence of the alpha-effect and differential rotation. Dynamo sources can be located at different depths (active layers) of the convection zone and can have different intensities. Based on such a system, the dynamical system with meridional fluxes in the case of the stellar dynamo with independent active layers has been constructed. We obtained quasi-biennial magnetic field oscillations for middle layer of the convective zone which can account for short term (2.5 years) oscillations often reported for 11 year solar cycles. Magnetic field waves from top and bottom layers of the convective zone are found generated with close frequencies whose interaction leads to beating effects responsible for the grand cycles (350-400 years) superimposed on a standard 22 year cycle. Using our model we made prediction of poloidal and toroidal fields on short (until 2040 year) and long-term timescale (until 3200 year) (V. V. Zharkova, S. J. Shepherd, E. Popova & S. I. Zharkov, Nature SR, 2015).

  18. Bicarbonate-water interactions in the rat proximal convoluted tubule. An effect of volume flux on active proton secretion

    PubMed Central

    1984-01-01

    The effect of volume absorption on bicarbonate absorption was examined in the in vivo perfused rat proximal convoluted tubule. Volume absorption was inhibited by isosmotic replacement of luminal NaCl with raffinose. In tubules perfused with 25 mM bicarbonate, as raffinose was increased from 0 to 55 to 63 mM, volume absorption decreased from 2.18 +/- 0.10 to 0.30 +/- 0.18 to -0.66 +/- 0.30 nl/mm X min, respectively, and bicarbonate absorption decreased from 131 +/- 5 to 106 +/- 8 to 91 +/- 13 pmol/mm X min, respectively. This bicarbonate-water interaction could not be attributed to dilutional changes in luminal or peritubular bulk phase bicarbonate concentrations. Inhibition of active proton secretion by acetazolamide abolished the effect of volume flow on bicarbonate absorption, which implies that the bicarbonate reflection coefficient is close to 1 and eliminates the possibility of solvent drag across the tight junction. When the luminal bicarbonate concentration was varied, the magnitude of the bicarbonate-water interaction increased with increasing luminal bicarbonate concentration. The largest interaction occurred at high luminal bicarbonate concentrations, where the rate of proton secretion has been previously shown to be independent of luminal bicarbonate concentration and pH. The results thus suggest that a peritubular and/or cellular compartment exists that limits bicarbonate diffusion, and where pH changes secondary to bicarbonate-water interactions (solute polarization) alter the rate of active proton secretion. PMID:6096481

  19. Simulated Microgravity Reduces TNF-Alpha Activity, Suppresses Glucose Uptake and Enhances Arginine Flux in Pancreatic Islets of Langerhans

    NASA Technical Reports Server (NTRS)

    Tobin, Brian W.; Leeper-Woodford, Sandra K.; Hashemi, Brian B.; Smith, Scott M.; Sams, Clarence F.; Paloski, W. H. (Technical Monitor)

    2000-01-01

    The present studies were designed to determine effects of microgravity upon lipopolysaccharide (LPS) stimulated tumor necrosis factor alpha (TNF - alpha) activity and indices of insulin and fuel homeostasis of pancreatic islets of Langerhans. Islets (1726+/-117,150 u IEU) from Wistar Furth rats were treated as: 1) HARV (High Aspect Ratio Vessel cell culture) , 2) HARV plus LPS 3) static culture, 4) static culture plus LPS TNF-alpha (L929 cytotoxicity assay) was significantly increased in LPS-induced HARV and static cultures, yet the increase was more pronounced in the static culture group (p<0.05). A decrease in insulin concentration was demonstrated in the LPS stimulated HARV culture (p<0.05). We observed a greater glucose concentration and increased disappearance of arginine in islets cultured in HARVs. While nitrogenous compound analysis indicated a ubiquitous reliance upon glutamine in all experimental groups, arginine was converted to ornithine at a two-fold greater rate in the islets cultured in the HARV microgravity paradigm (p<0.05). These studies demonstrate alterations in LPS induced TNF-alpha production of pancreatic islets of Langerhans, favoring a lesser TNF activity in the HARV paradigm. These alterations in fuel homeostasis may be promulgated by gravity averaged cell culture methods or by three dimensional cell assembly.

  20. Note: Solid state photon counters with sub-picosecond timing stability

    NASA Astrophysics Data System (ADS)

    Prochazka, Ivan; Kodet, Jan; Blazej, Josef

    2013-04-01

    We are reporting on a design, construction, and performance of photon counting detector packages based on solid state sensors. These photon counting devices have been optimized for extremely high stability of their detection delay. The detectors have been designed for applications in fundamental metrology and optical time transfer. The single photon avalanche diode structure manufactured on silicon using the K14 technology is used as a sensor. The active area of the sensor is circular with a diameter of 100 or 200 μm. The sensor is operated in an active quenching and gating mode. The photon detection efficiency exceeds 40% in a wavelength range spanning from 500 to 800 nm. The timing resolution is better than 20 ps rms. Its detection delay is stable within ±600 fs over several days of operation, in a sense of time deviation the detection delay stability of 150 fs has been achieved. The temperature change of the detection delay is as low as 280 fs/K. This timing performance is preserved even under extremely high background photon fluxes exceeding 100 Mc/s. The detectors have been qualified for operation in space missions.

  1. Tevatron direct photon results.

    SciTech Connect

    Kuhlmann, S.

    1999-09-21

    Tevatron direct photon results since DIS98 are reviewed. Two new CDF measurements are discussed, the Run Ib inclusive photon cross section and the photon + Muon cross section. Comparisons with the latest NLO QCD calculations are presented.

  2. Climate, Ice, and Mud: investigating the relationship between glacier activity and sediment flux using varved lake sediments, Iceland

    NASA Astrophysics Data System (ADS)

    Larsen, D. J.; Miller, G. H.; Geirsdottir, A.; Flowers, G. E.; Bjornsson, H.

    2012-12-01

    The worldwide retreat of many glaciers during the 21st century is expected to have profound impacts on local and regional hydrologic cycles. Associated with the forecasted reductions in global ice volume are changes in meltwater runoff and sediment transport in glacially fed drainage systems. Alpine glaciers and small ice caps are particularly sensitive to climate change because their dimensions can respond quickly to changes in glacier mass balance. Records of past glacier fluctuations are important sources of paleoclimate data and also provide a context for current and future changes to glacier hydrologic systems. Annually laminated (varved) sediments from proglacial lake Hvítárvatn, central Iceland, offer a continuous archive of Langjökull ice cap (~925 km2) activity through the late Holocene. A multi-proxy record from this site indicates that Langjökull's size was more variable during the past millennium than during any other multi-centennial interval of the Holocene. Ice growth culminated in the Little Ice Age (LIA), when Langjökull advanced into Hvítárvatn and reached its maximum aerial extent of the past 10 ka. At present, roughly one-third of the ice cap's discharge flows into the lake catchment, constituting ~70% of the total inflow, and lake sedimentation rates are governed by the production and delivery of glacially eroded clastic material transported to the lake by four primary meltwater streams. Glacier fluctuations of the past 1 ka are reconstructed from physical proxies contained in sediment cores retrieved from six locations throughout the main basin. Total sediment yield and distribution during this period are calculated from sediment accumulation rates and from > 100 km of seismic reflection profiles. A tephra-constrained varve chronology provides high chronologic control, with a maximum age uncertainty of ± 10 years. Low and constant sedimentation rates characterize the 11th and 12th centuries, reflecting minimal glacier activity during

  3. Photonic Molecule Lasers Revisited

    NASA Astrophysics Data System (ADS)

    Gagnon, Denis; Dumont, Joey; Déziel, Jean-Luc; Dubé, Louis J.

    2014-05-01

    Photonic molecules (PMs) formed by coupling two or more optical resonators are ideal candidates for the fabrication of integrated microlasers, photonic molecule lasers. Whereas most calculations on PM lasers have been based on cold-cavity (passive) modes, i.e. quasi-bound states, a recently formulated steady-state ab initio laser theory (SALT) offers the possibility to take into account the spectral properties of the underlying gain transition, its position and linewidth, as well as incorporating an arbitrary pump profile. We will combine two theoretical approaches to characterize the lasing properties of PM lasers: for two-dimensional systems, the generalized Lorenz-Mie theory will obtain the resonant modes of the coupled molecules in an active medium described by SALT. Not only is then the theoretical description more complete, the use of an active medium provides additional parameters to control, engineer and harness the lasing properties of PM lasers for ultra-low threshold and directional single-mode emission. We will extend our recent study and present new results for a number of promising geometries. The authors acknowledge financial support from NSERC (Canada) and the CERC in Photonic Innovations of Y. Messaddeq.

  4. Carbon sink activity is stronger under grazing than under mowing: results from a paired eddy flux towers experiment

    NASA Astrophysics Data System (ADS)

    Pintér, Krisztina; Balogh, János; Koncz, Péter; Hidy, Dóra; Cserhalmi, Dóra; Papp, Marianna; Fóti, Szilvia; Nagy, Zoltán

    2014-05-01

    Effect of grazing vs. mowing on carbon balance of a grassland was investigated by a paired eddy towers (one of them measuring the grazed, the another the mowed treatment) experiment at the Bugacpuszta sandy grassland site (HU-Bug, 46.69° N, 19.6° E, 114m asl, 10.4 ° C annual mean temperature, 562 mm annual precipitation sum) located in the Hungarian Plain. Eddy covariance measurements started in July, 2002. The area of the mowed treatment is 1 ha, it is located within the grazed treatment (500 ha). Electric fence was set up around the selected area in spring of 2011. Study years include 2011, 2012 and 2013. The pasture is managed extensively (average grazing pressure of 0.5 cattle per hectare), the cattle herd regularly took several kilometres during a grazing day. Annual net ecosystem exchange (NEE) of the grassland is strongly limited by precipitation, there were 2 source years within the 11 years (2003-2013) of measurements, during which the average annual balance was -109 gCm-2year-1 with standard deviation of 106 gCm-2year-1. Carbon sink activity of the grassland was stronger in the grazed treatment than in the mowed treatment during the three year study period (paired t-test, P=0.058). In the grazed treatment the average sink strength was -142.8 ±40 gCm-2year-1, while in the mowed treatment the average sink strength was -61.5 ±46.5 gCm-2year-1. Differences of carbon balances between the treatments were positively correlated to the annual sum of evapotranspiration (ET), while ETs of the treatments were almost identical (differences within a 10mm year-1 range) in each study year. Water use efficiency in the mowed treatment was 44% of that in the grazed treatment (P=0.045) as a result of the differences in sink capacity. The higher sensitivity to drought by the mowed treatment manifested in decreased sink capacity during summer and in decreased regeneration capacity during autumn rains as shown by the cumulative NEE in the different years. Minor but

  5. Tunable resonant structures for photonic integrated circuits

    NASA Astrophysics Data System (ADS)

    Ptasinski, Joanna Nina

    Photonics is an evolving field allowing for optical devices to be made cost effectively using standard semiconductor fabrication techniques, which in turn enables integration with microelectronic chips. Chip scale photonics will play an increasing role in the future of communications as the demand for bandwidth and reduced power consumption per bit continues to grow. Tunable optical circuit components are one of the essential technologies in the development of photonic analogues for classical electronic devices, where tunable photonic resonant structures allow for altering of their electromagnetic spectrum and find applications in optical switching, filtering, buffering, lasers and biosensors. The scope of this work is focused on tunable resonant structures for photonic integrated circuits. Specifically, this work demonstrates active tuning of silicon photonic resonant structures using the properties of dye doped nematic liquid crystals, temperature stabilization of silicon photonics using the passive properties of liquid crystals, and the effects of low density plasma enhanced chemical vapor deposition (PECVD) claddings on ring resonator device performance.

  6. A Study on the Basic Characteristics of a Novel Design Active Magnetic Bearing with Permanent Magnet Bias Flux

    NASA Astrophysics Data System (ADS)

    Kurita, Nobuyuki; Ohshio, Keisuke; Ishikawa, Takeo

    Advances in the industrial field demand sophisticated electrical motors. However, degradation of traditional ball bearing systems can reduce the efficiency of the motor over time. In addition, bearings require regular maintenance such as lubrication and replacement. Moreover, they cannot be used under some specific environments such as high temperature and vacuum. In order to overcome these problems, this paper proposes a novel active magnetic bearing design. It has only four poles to control the horizontal and vertical suspension, and it is possible to increase the coil winding number without an increase in shaft length. Hence, we can design a high attractive force and stiffness bearing. The stator was initially designed by magnetic field analysis. A simple experimental setup was fabricated in order to confirm the operation principle and attractive force characteristic. The time domain dynamic performance was confirmed by simulation and experimental results. The experimental results verified that the proposed magnetic bearing has sufficient performance for industrial application. Additionally, a small size hydraulic generator was designed for future application.

  7. Resonance formation in photon-photon collisions

    SciTech Connect

    Gidal, G.

    1988-08-01

    Recent experimental progress on resonance formation in photon-photon collisions is reviewed with particular emphasis on the pseudoscalar and tensor nonents and on the ..gamma gamma..* production of spin-one resonances. 37 refs., 17 figs., 5 tabs.

  8. Physics at high energy photon photon colliders

    SciTech Connect

    Chanowitz, M.S.

    1994-06-01

    I review the physic prospects for high energy photon photon colliders, emphasizing results presented at the LBL Gamma Gamma Collider Workshop. Advantages and difficulties are reported for studies of QCD, the electroweak gauge sector, supersymmetry, and electroweak symmetry breaking.

  9. Active mode-locked lasers and other photonic devices using electro-optic whispering gallery mode resonators

    NASA Technical Reports Server (NTRS)

    Matsko, Andrey B. (Inventor); Ilchenko, Vladimir (Inventor); Savchenkov, Anatoliy (Inventor); Maleki, Lutfollah (Inventor)

    2006-01-01

    Techniques and devices using whispering gallery mode (WGM) optical resonators, where the optical materials of the WGM resonators exhibit an electro-optical effect to perform optical modulation. Examples of actively mode-locked lasers and other devices are described.

  10. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  11. The 2005 and 2006 eruptions of Ol Doinyo Lengai: assessing deep and shallow processes at an active carbonatite volcano using volatile chemistry and fluxes

    NASA Astrophysics Data System (ADS)

    Fischer, T.; Burnard, P.; Marty, B.; Palhol, F.; Mangasini, F.; Shaw, A. M.

    2006-12-01

    The African Rift valleys are sites of classical carbonatite volcano complexes. Ol Doinyo Lengai, the spectacular cone that rises to nearly 3000 m above Tanzania's Eastern Rift Valley, is the world's only active carbonatite volcano. High-alkali carbonatite lavas from this volcano were first recognized in the 1960's and the oldest natrocarbonatite tuffs have been dated to 1250 years B.P.. Earlier eruptions produced phonolitic and nephelinitc lavas [1]. Since the 1960's the volcano has erupted frequently producing carbonatite lava flows. Explosive eruptions are much less frequent but have occurred in 1966, 1983 [1] and 1993 [3] producing ash, cones and natrocarbonatite tephra. In July 2005, we launched an expedition to the crater to collect gas and rock samples. On July 4, the volcano began erupting low viscosity, low T (540C) high velocity (2 m/sec) lava flows at a rate of about 0.3 m3/sec. By afternoon, the lava was flowing over the eastern crater rim. During the eruption we sampled gases from nearby hornitos at 120 and 168C, yielding pristine magmatic gases characterized by 75 mol% H2O, 22% CO2, < 1% SO2, H2S, HCl and traces of H2, He, Ar, N2, CH4 and CO. CO2-CH4-CO gas equilibrium temperatures are 580C consistent with lava flow temperatures. N2-He-Ar abundances indicate an upper mantle origin of volatiles, confirmed by isotopes [4]. SO2 flux measured by mini DOAS was low (10 t/day). CO2 fluxes calculated using CO2/SO2 are 3000 to 4000 t/day. Volatiles measured in the carbonatite lavas by SIMS show low H2O (< 0.7 wt%), high S (0.2 to 1 wt%) and Cl (0.6 to 1.4 wt%) and variable F (0.06 to 0.7 wt%). CO2 contents are 30 wt% with major and trace elements typical of natrocarbonatite lavas previously reported in [1]. The release of all CO2 (30 wt% or 20 t/day) from eruption lavas would only produce a small fraction of the measured CO2. In March 2006 eyewitnesses [3] reported the occurrence of an explosive eruption and some of us returned to the volcano on May 12. The

  12. Exclusive photon-photon processes

    SciTech Connect

    Brodsky, S.J.

    1997-07-01

    Exclusive gamma gamma right arrow hadron pairs are among the most fundamental processes in QCD, providing a detailed examination of Compton scattering in the crossed channel. In the high momentum transfer domain (s, t, large, Theta cm for t/s fixed), these processes can be computed from first principles in QCD, yielding important information on the nature of the QCD coupling data and the form of hadron distribution amplitudes. Similarly, the transition form factors gamma star gamma, gamma star gamma right arrow pi(o), Eta (0), Eta`, Eta(c)... provide rigorous tests of QCD and definitive determinations of the meson distribution amplitudes Phi H(x,Q). We show that the assumption of a frozen coupling at low momentum transfers can explain the observed scaling of two-photon exclusive processes.

  13. Photon-Photon Interactions via Rydberg Blockade

    SciTech Connect

    Gorshkov, Alexey V.; Otterbach, Johannes; Fleischhauer, Michael; Pohl, Thomas; Lukin, Mikhail D.

    2011-09-23

    We develop the theory of light propagation under the conditions of electromagnetically induced transparency in systems involving strongly interacting Rydberg states. Taking into account the quantum nature and the spatial propagation of light, we analyze interactions involving few-photon pulses. We show that this system can be used for the generation of nonclassical states of light including trains of single photons with an avoided volume between them, for implementing photon-photon gates, as well as for studying many-body phenomena with strongly correlated photons.

  14. Effective image filtration of pediatric single photon emission tomograms

    SciTech Connect

    Gilday, D.L.; Green, M.D.; Puntillo, R.; Ash, J.M.