Science.gov

Sample records for photon emission microscope

  1. Ion photon emission microscope

    DOEpatents

    Doyle, Barney L.

    2003-04-22

    An ion beam analysis system that creates microscopic multidimensional image maps of the effects of high energy ions from an unfocussed source upon a sample by correlating the exact entry point of an ion into a sample by projection imaging of the ion-induced photons emitted at that point with a signal from a detector that measures the interaction of that ion within the sample. The emitted photons are collected in the lens system of a conventional optical microscope, and projected on the image plane of a high resolution single photon position sensitive detector. Position signals from this photon detector are then correlated in time with electrical effects, including the malfunction of digital circuits, detected within the sample that were caused by the individual ion that created these photons initially.

  2. Improved Photon-Emission-Microscope System

    NASA Technical Reports Server (NTRS)

    Vu, Duc

    2006-01-01

    An improved photon-emission-microscope (PEM) instrumentation system has been developed for use in diagnosing failure conditions in semiconductor devices, including complex integrated circuits. This system is designed primarily to image areas that emit photons, at wavelengths from 400 to 1,100 nm, associated with device failures caused by leakage of electric current through SiO2 and other dielectric materials used in multilayer semiconductor structures. In addition, the system is sensitive enough to image areas that emit photons during normal operation.

  3. Design and Feasibility Study of a Single Photon Emission Microscope System for Small Animal I-125 Imaging

    PubMed Central

    Meng, L. J.; Clinthorne, N. H.; Skinner, S.; Hay, R. V.; Gross, M.

    2016-01-01

    This paper presents a design study of a single photon emission microscope (SPEM) system for small animal imaging using I-125 labelled radiotracers. This system is based on the use of a very-high resolution gamma camera coupled to a converging non-multiplexing multiple pinhole collimator. This enables one to “zoom” into a small local region inside the object to extract imaging information with a very high spatial resolution and a reasonable sensitivity for gamma rays emitted from this local region. The SPEM system also includes a pinhole (or multiple pinhole) gamma camera that has a full angular coverage of the entire object. The designed imaging spatial resolution for the SPEM system is between 250 μm to 500 μm FWHM.

  4. Stimulated Parametric Emission Microscope Systems

    NASA Astrophysics Data System (ADS)

    Itoh, Kazuyoshi; Isobe, Keisuke

    2006-10-01

    We present a novel microscopy technique based on the fourwave mixing (FWM) process that is enhanced by two-photon electronic resonance induced by a pump pulse along with stimulated emission induced by a dump pulse. A Ti:sapphire laser and an optical parametric oscillator are used as light sources for the pump and dump pulses, respectively. We demonstrate that our FWM technique can be used to obtain two-dimensional microscopic images of an unstained leaf of Camellia sinensis and an unlabeled tobacco BY2 Cell.

  5. Ion photon emission microscopy

    NASA Astrophysics Data System (ADS)

    Rossi, P.; Doyle, B. L.; Banks, J. C.; Battistella, A.; Gennaro, G.; McDaniel, F. D.; Mellon, M.; Vittone, E.; Vizkelethy, G.; Wing, N. D.

    2003-09-01

    A new ion-induced emission microscopy has been invented and demonstrated, which is called ion photon emission microscopy (IPEM). It employs a low current, broad ion beam impinging on a sample, previously coated or simply covered with a few microns of a fast, highly efficient phosphor layer. The light produced at the single ion impact point is collected with an optical microscope and projected at high magnification onto a single photon position sensitive detector (PSD). This allows maps of the ion strike effects to be produced, effectively removing the need for a microbeam. Irradiation in air and even the use of alpha particle sources with no accelerator are possible. Potential applications include ion beam induced charge collection studies of semiconducting and insulating materials, single event upset studies on microchips and even biological cells in radiobiological effectiveness experiments. We describe the IPEM setup, including a 60× OM-40 microscope with a 1.5 mm hole for the beam transmission and a Quantar PSD with 60 μm pixel. Bicron plastic scintillator blades of 10 μm were chosen as a phosphor for their nanosecond time resolution, homogeneity, utility and commercial availability. The results given in this paper are for a prototype IPEM system. They indicate a resolution of ˜12 μm, the presence of a spatial halo and a He-ion efficiency of ˜20%. This marks the first time that nuclear microscopy has been performed with a radioactive source.

  6. Non-Uniform Object-Space Pixelation (NUOP) for Penalized Maximum-Likelihood Image Reconstruction for a Single Photon Emission Microscope System

    PubMed Central

    Meng, L. J.; Li, Nan

    2016-01-01

    This paper presents a non-uniform object-space pixelation (NUOP) approach for image reconstruction using the penalized maximum likelihood methods. This method was developed for use with a single photon emission microscope (SPEM) system that offers an ultrahigh spatial resolution for a targeted local region inside mouse brain. In this approach, the object-space is divided with non-uniform pixel sizes, which are chosen adaptively based on object-dependent criteria. These include (a) some known characteristics of a target-region, (b) the associated Fisher Information that measures the weighted correlation between the responses of the system to gamma ray emissions occurred at different spatial locations, and (c) the linear distance from a given location to the target-region. In order to quantify the impact of this non-uniform pixelation approach on image quality, we used the Modified Uniform Cramer-Rao bound (MUCRB) to evaluate the local resolution-variance and bias-variance tradeoffs achievable with different pixelation strategies. As demonstrated in this paper, an efficient object-space pixelation could improve the speed of computation by 1–2 orders of magnitude, whilst maintaining an excellent reconstruction for the target-region. This improvement is crucial for making the SPEM system a practical imaging tool for mouse brain studies. The proposed method also allows rapid computation of the first and second order statistics of reconstructed images using analytical approximations, which is the key for the evaluation of several analytical system performance indices for system design and optimization.

  7. Photon enhanced thermionic emission

    SciTech Connect

    Schwede, Jared; Melosh, Nicholas; Shen, Zhixun

    2014-10-07

    Photon Enhanced Thermionic Emission (PETE) is exploited to provide improved efficiency for radiant energy conversion. A hot (greater than 200.degree. C.) semiconductor cathode is illuminated such that it emits electrons. Because the cathode is hot, significantly more electrons are emitted than would be emitted from a room temperature (or colder) cathode under the same illumination conditions. As a result of this increased electron emission, the energy conversion efficiency can be significantly increased relative to a conventional photovoltaic device. In PETE, the cathode electrons can be (and typically are) thermalized with respect to the cathode. As a result, PETE does not rely on emission of non-thermalized electrons, and is significantly easier to implement than hot-carrier emission approaches.

  8. Thermodynamic Laws of Neutrino and Photon Emission.

    ERIC Educational Resources Information Center

    Walsh, P. J.; Gallo, C. F.

    1980-01-01

    Compares neutrino and photon emissions, develops the thermodynamic blackbody laws of neutrino emission analogous to laws governing photon emission, points out that combined radiation from a "true blackbody" consists of both photon and neutrino emissions of comparable magnitude, and speculates upon the existence of blackbody neutrino…

  9. Photon upconversion with directed emission

    NASA Astrophysics Data System (ADS)

    Börjesson, K.; Rudquist, P.; Gray, V.; Moth-Poulsen, K.

    2016-08-01

    Photon upconversion has the potential to increase the efficiency of single bandgap solar cells beyond the Shockley Queisser limit. Efficient light management is an important point in this context. Here we demonstrate that the direction of upconverted emission can be controlled in a reversible way, by embedding anthracene derivatives together with palladium porphyrin in a liquid crystalline matrix. The system is employed in a triplet-triplet annihilation photon upconversion scheme demonstrating controlled switching of directional anti Stokes emission. Using this approach an emission ratio of 0.37 between the axial and longitudinal emission directions and a directivity of 1.52 is achieved, reasonably close to the theoretical maximal value of 2 obtained from a perfectly oriented sample. The system can be switched for multiple cycles without any visible degradation and the speed of switching is only limited by the intrinsic rate of alignment of the liquid crystalline matrix.

  10. Photon upconversion with directed emission

    PubMed Central

    Börjesson, K.; Rudquist, P.; Gray, V.; Moth-Poulsen, K.

    2016-01-01

    Photon upconversion has the potential to increase the efficiency of single bandgap solar cells beyond the Shockley Queisser limit. Efficient light management is an important point in this context. Here we demonstrate that the direction of upconverted emission can be controlled in a reversible way, by embedding anthracene derivatives together with palladium porphyrin in a liquid crystalline matrix. The system is employed in a triplet-triplet annihilation photon upconversion scheme demonstrating controlled switching of directional anti Stokes emission. Using this approach an emission ratio of 0.37 between the axial and longitudinal emission directions and a directivity of 1.52 is achieved, reasonably close to the theoretical maximal value of 2 obtained from a perfectly oriented sample. The system can be switched for multiple cycles without any visible degradation and the speed of switching is only limited by the intrinsic rate of alignment of the liquid crystalline matrix. PMID:27573539

  11. Photon emission from gold surfaces in air using scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Gallagher, Mark J.; Howells, Sam; Yi, Leon; Chen, Ting; Sarid, Dror

    1992-11-01

    Photon emission was observed at the tunnel junction of a scanning tunneling microscope while scanning Au structures in air. Emission levels of about 4000 counts per second (cps) were routinely achieved with Au tips, allowing photon maps to be produced. The similarity between these photon maps and the topographic images of the Au samples are discussed.

  12. Single photon emission computed tomography

    SciTech Connect

    Piez, C.W. Jr.; Holman, B.L.

    1985-07-01

    Single photon emission computed tomography (SPECT) is becoming an increasingly important part of routine clinical nuclear medicine. By providing tomographic reconstructions in multiple planes through the patient, SPECT expands the clinical applications in nuclear medicine as well as providing better contrast, edge definition and separation of target from background activities. Imaging techniques have been developed for the evaluation of regional cerebral blood flow using radiolabeled amines. Thus, cerebral functional imaging can be used in the diagnosis of acute cerebral infarction, cerebral vascular disease, dementia and epilepsy. SPECT plays a complementary role in the evaluation of coronary artery disease, particularly when it is coupled with thallium-201 and exercise testing. SPECT extends our diagnostic capabilities in additional areas, such as liver and bone scintigraphy as well as tumor imaging with gallium-67.

  13. Two-Photon Fluorescence Microscope for Microgravity Research

    NASA Technical Reports Server (NTRS)

    Fischer, David G.; Zimmerli, Gregory A.; Asipauskas, Marius

    2005-01-01

    A two-photon fluorescence microscope has been developed for the study of biophysical phenomena. Two-photon microscopy is a novel form of laser-based scanning microscopy that enables three-dimensional imaging without many of the problems inherent in confocal microscopy. Unlike one-photon optical microscopy, two-photon microscopy utilizes the simultaneous nonlinear absorption of two near-infrared photons. However, the efficiency of two-photon absorption is much lower than that of one-photon absorption, so an ultra-fast pulsed laser source is typically employed. On the other hand, the critical energy threshold for two-photon absorption leads to fluorophore excitation that is intrinsically localized to the focal volume. Consequently, two-photon microscopy enables optical sectioning and confocal performance without the need for a signal-limiting pinhole. In addition, there is a reduction (relative to one-photon optical microscopy) in photon-induced damage because of the longer excitation wavelength. This reduction is especially advantageous for in vivo studies. Relative to confocal microscopy, there is also a reduction in background fluorescence, and, because of a reduction in Rayleigh scattering, there is a 4 increase of penetration depth. The prohibitive cost of a commercial two-photon fluorescence-microscope system, as well as a need for modularity, has led to the construction of a custom-built system (see Figure 1). This system includes a coherent mode-locked titanium: sapphire laser emitting 120-fs-duration pulses at a repetition rate of 80 MHz. The pulsed laser has an average output power of 800 mW and a wavelength tuning range of 700 to 980 nm, enabling the excitation of a variety of targeted fluorophores. The output from the laser is attenuated, spatially filtered, and then directed into a confocal scanning head that has been modified to provide for side entry of the laser beam. The laser output coupler has been replaced with a dichroic filter that reflects the

  14. Mobile laser lithography station for microscopic two-photon polymerization

    NASA Astrophysics Data System (ADS)

    Leinenbach, F.; Breunig, H. G.; König, K.

    2015-03-01

    We present a mobile laser lithography station for 3D structuring by microscopic two-photon polymerization. For structuring the Coherent Vitara UBB titanium:sapphire femtosecond laser is used, which has a power output of 500mW and generates pulses with a central wavelength of 810nm. The laser pulses have a tunable bandwidth from 50nm to 250nm. The pulses are temporally compressed using chirped mirrors to a minimum duration of less than 15fs at the sample. The laser power reaching the sample can be motionless controlled by a combination of a liquid crystal retarder and a polarizer within milliseconds. The sample is placed onto a microscope stage which has a movement range of 300µm in the X, Y and Z direction with an accuracy of 2nm. Sample imaging is possible with a microscope camera simultaneous to the structuring. The pulses are focused by a 40X microscope objective (1.3NA) onto the sample. To operate the lithography station, we developed a LabVIEW-based software which controls sample position, laser power and objective height and as well as the microscope camera. Furthermore, CAD data can be read and converted into sample position data. By combining all these components, a fully automatic structuring of a sample with sub-micrometer precision is possible.

  15. An ultrafast electron microscope gun driven by two-photon photoemission from a nanotip cathode

    SciTech Connect

    Bormann, Reiner; Strauch, Stefanie; Schäfer, Sascha Ropers, Claus

    2015-11-07

    We experimentally and numerically investigate the performance of an advanced ultrafast electron source, based on two-photon photoemission from a tungsten needle cathode incorporated in an electron microscope gun geometry. Emission properties are characterized as a function of the electrostatic gun settings, and operating conditions leading to laser-triggered electron beams of very low emittance (below 20 nm mrad) are identified. The results highlight the excellent suitability of optically driven nano-cathodes for the further development of ultrafast transmission electron microscopy.

  16. The mechanism of light emission from a scanning tunnelling microscope operating in air

    NASA Astrophysics Data System (ADS)

    Rogez, B.; Cao, S.; Dujardin, G.; Comtet, G.; Le Moal, E.; Mayne, A.; Boer-Duchemin, E.

    2016-11-01

    The scanning tunnelling microscope (STM) may be used as a low-energy, electrical nanosource of surface plasmon polaritons and light. In this article, we demonstrate that the optimum mode of operation of the STM for maximum photon emission is completely different in air than in vacuum. To this end, we investigate the emission of photons, the variation in the relative tip-sample distance and the measured current as a function of time for an STM operating in air. Contrary to the case of an STM operating in vacuum, the measured current between the tip and sample for an STM in air is very unstable (rapidly fluctuating in time) when the applied voltage between the tip and sample is in the ˜1.5-3 V range (i.e., in the energy range of visible photons). The photon emission occurs in short (50 μs) bursts when the STM tip is closest to the sample. The current instabilities are shown to be a key ingredient for producing intense light emission from an STM operating in air (photon emission rate several orders of magnitude higher than for stable current). These results are explained in terms of the interplay between the tunnel current and the electrochemical current in the ubiquitous thin water layer that exists when working in air.

  17. Compact scanning transmission x-ray microscope at the photon factory

    SciTech Connect

    Takeichi, Yasuo Inami, Nobuhito; Ono, Kanta; Suga, Hiroki; Takahashi, Yoshio

    2016-01-28

    We report the design and performance of a compact scanning transmission X-ray microscope developed at the Photon Factory. Piezo-driven linear stages are used as coarse stages of the microscope to realize excellent compactness, mobility, and vibrational and thermal stability. An X-ray beam with an intensity of ∼10{sup 7} photons/s was focused to a diameter of ∼40 nm at the sample. At the soft X-ray undulator beamline used with the microscope, a wide range of photon energies (250–1600 eV) is available. The microscope has been used to research energy materials and in environmental sciences.

  18. Secondary photon emission in plasma processing

    SciTech Connect

    Moshkalyov, S.; Machida, M.; Campos, D.; Dulkin, A.

    1997-05-01

    Optical emission spectroscopy with high spatial resolution was applied for the study of plasma{endash}material interaction in low-pressure reactive ion etching. Atomic and molecular emission by sputtered material has been found to be strongly localized near the surface. Excited particles are produced during sputtering by energetic ions, with the mechanisms being different for atoms and molecules. In atomic secondary photon emission, a cascade from highly excited levels is shown to be important. This method can be used as a probe during plasma processing. {copyright} {ital 1997 American Institute of Physics.}

  19. Measuring calcium levels in Saprolegnia ferax using the two-photon laser scanning microscope

    NASA Astrophysics Data System (ADS)

    Lilje, Osu

    2003-07-01

    xThe genus Saprolegnia in the phylum Oomycetes contains a number of parasitic species that can cause a range of important animal diseases. The aim of this study was to measure the calcium gradient, one of the growth regulating mechanisms, in Saprolegnia ferax. The two-photon laser scanning microscope allowed for detailed physiological measurements of calcium levels along the fungus-like hyphae of S.ferax. Calcium concentration was determined by making ratiometric calculation of emission levels of the calcium-sensitive fluorochrome Indo-1 at 485nm to 405nm. The calculated values were compared to the intracellular calibration values. The advantage of the two-photon laser scanning microscope is that it allows minor changes in concentration to be detected in highly localized regions of the hyphae. The technique used in this study minimized background and autofluorescence and therefore allowed for more accurate changes in intracellular Ca2+ concentration to be detected. The calcium concentration at the hyphal tip and 5, 10 and 40μm distal to the tip were calculated to be 65, 17, 38 and 20nM respectively, confirming other studies that suggest a tip-high calcium gradient.

  20. Applications of 1 MV field-emission transmission electron microscope.

    PubMed

    Tonomura, Akira

    2003-01-01

    A newly developed 1 MV field-emission transmission electron microscope has recently been applied to the field of superconductivity by utilizing its bright and monochromatic field-emission electron beam. This microscope allows individual magnetic vortices inside high-Tc superconductors to be observed, thus, opening the way to investigate the unusual behaviour of vortices, which reflects the anisotropic layered structure of these superconducting materials. One example is the observation of the arrangements of chain vortex lines that are formed when a magnetic field is applied obliquely to the layer plane of the materials.

  1. Optical microscope using an interferometric source of two-color, two-beam entangled photons

    DOEpatents

    Dress, William B.; Kisner, Roger A.; Richards, Roger K.

    2004-07-13

    Systems and methods are described for an optical microscope using an interferometric source of multi-color, multi-beam entangled photons. A method includes: downconverting a beam of coherent energy to provide a beam of multi-color entangled photons; converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; transforming at least a portion of the converged multi-color entangled photon beam by interaction with a sample to generate an entangled photon specimen beam; and combining the entangled photon specimen beam with an entangled photon reference beam within a single beamsplitter. An apparatus includes: a multi-refringent device providing a beam of multi-color entangled photons; a condenser device optically coupled to the multi-refringent device, the condenser device converging two spatially resolved portions of the beam of multi-color entangled photons into a converged multi-color entangled photon beam; a beam probe director and specimen assembly optically coupled to the condenser device; and a beam splitter optically coupled to the beam probe director and specimen assembly, the beam splitter combining an entangled photon specimen beam from the beam probe director and specimen assembly with an entangled photon reference beam.

  2. Atlas of solar hidden photon emission

    SciTech Connect

    Redondo, Javier

    2015-07-01

    Hidden photons, gauge bosons of a U(1) symmetry of a hidden sector, can constitute the dark matter of the universe and a smoking gun for large volume compactifications of string theory. In the sub-eV mass range, a possible discovery experiment consists on searching the copious flux of these particles emitted from the Sun in a helioscope setup à la Sikivie. In this paper, we compute in great detail the flux of HPs from the Sun, a necessary ingredient for interpreting such experiments. We provide a detailed exposition of transverse photon-HP oscillations in inhomogenous media, with special focus on resonance oscillations, which play a leading role in many cases. The region of the Sun emitting HPs resonantly is a thin spherical shell for which we justify an averaged-emission formula and which implies a distinctive morphology of the angular distribution of HPs on Earth in many cases. Low mass HPs with energies in the visible and IR have resonances very close to the photosphere where the solar plasma is not fully ionised and requires building a detailed model of solar refraction and absorption. We present results for a broad range of HP masses (from 0–1 keV) and energies (from the IR to the X-ray range), the most complete atlas of solar HP emission to date.

  3. Atlas of solar hidden photon emission

    SciTech Connect

    Redondo, Javier

    2015-07-20

    Hidden photons, gauge bosons of a U(1) symmetry of a hidden sector, can constitute the dark matter of the universe and a smoking gun for large volume compactifications of string theory. In the sub-eV mass range, a possible discovery experiment consists on searching the copious flux of these particles emitted from the Sun in a helioscope setup à la Sikivie. In this paper, we compute in great detail the flux of HPs from the Sun, a necessary ingredient for interpreting such experiments. We provide a detailed exposition of transverse photon-HP oscillations in inhomogenous media, with special focus on resonance oscillations, which play a leading role in many cases. The region of the Sun emitting HPs resonantly is a thin spherical shell for which we justify an averaged-emission formula and which implies a distinctive morphology of the angular distribution of HPs on Earth in many cases. Low mass HPs with energies in the visible and IR have resonances very close to the photosphere where the solar plasma is not fully ionised and requires building a detailed model of solar refraction and absorption. We present results for a broad range of HP masses (from 0–1 keV) and energies (from the IR to the X-ray range), the most complete atlas of solar HP emission to date.

  4. Ultraweak photon emission from herbivory-injured maize plants

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Naoko; Kato, Kimihiko; Kageyama, Chizuko; Fujisaki, Kenji; Nishida, Ritsuo; Mori, Naoki

    2006-01-01

    Following perception of herbivory or infection, plants exhibit a wide range of inducible responses. In this study, we found ultraweak photon emissions from maize leaves damaged by Helicoverpa armigera (Noctuidae). Interestingly, mechanically damaged maize leaves treated with caterpillar regurgitants emitted the same intensity and pattern of photon emissions as those from maize leaves damaged by caterpillars. Furthermore, two-dimensional imaging of the leaf section treated with the oral secretions clearly shows that photon emissions were observed specifically at the lip of the wound exposed to the secretions. These results suggest that the direct interaction between maize leaf cells and chemicals contained in caterpillar regurgitants triggers these photon emissions.

  5. Single photon emission from diamond nanocrystals in an opal photonic crystal.

    PubMed

    Stewart, L A; Zhai, Y; Dawes, J M; Steel, M J; Rabeau, J R; Withford, M J

    2009-09-28

    We present the first optical measurement of a single nitrogen-vacancy (NV) center in a three-dimensional photonic crystal. The photonic crystal, fabricated by self-assembly of polystyrene microspheres, exhibits a photonic stopband that overlaps the NV photoluminescence spectrum. A modified emission spectrum and photon antibunching were measured from the NV centers. Time-resolved fluorescence measurements revealed a 30% increase in the source lifetime. Encapsulation of single NV centers in a three-dimensional photonic crystal is a step towards controlling emission properties of a single photon source.

  6. Application and development of a spectrally-resolved confocal microscope: A study of lipofuscin emission properties

    NASA Astrophysics Data System (ADS)

    Haralampus-Grynaviski, Nicole Marie

    A unique spectrally-resolved confocal microscope is developed for use in biophysical applications. This microscope enables the rapid collection of the complete emission spectra for every pixel in a fluorescence image. The basic optical design and function of the device are assessed through examination of fluorescently labeled beads, using both one- and two-photon excitation. The spatial resolution of the device is found to approach the diffraction limit in the lateral plane and ˜2 mum in the axial plane. This device can readily distinguish between overlapping emissions which are not easily differentiated using standard filter techniques. The potential of this device to be used as a detection method in DNA sequence experiments is demonstrated. Images of a human skin tissue section and a mouse kidney section are presented which demonstrate the structure and spectra of biologic samples can be resolved. The emission properties of human ocular lipofuscin, LF, a heterogeneous auto-fluorescent material associated with age-related macular degeneration is investigated in detail. Isolated LF granules show substantial variation in emission spectra. Near-field scanning microscopy experiments find the emissive regions on a single LF granule are homogeneous on the ˜150 nm scale and confirm results obtained on the microscope developed here. For ˜100 studied LF deposits, the histogram of the measured peak emission is centered around 18,000 cm-1 (555 nm). The average emission spectra for large LF aggregates (peak 17,150 cm-1) is red-shifted compared to the average emission from small individual granules (peak 17,600 cm-1). The average LF granule emission observed here is similar to previously reported bulk LF emission and the emission of a previously identified LF chromophore, A2E. Individual LF granules show a broad range in emission maximum whether the LF is isolated from multiple donors or examined within the cells of a single donor. Multiple as yet unidentified chromophores

  7. Stimulated photon emission and two-photon Raman scattering in a coupled-cavity QED system

    PubMed Central

    Li, C.; Song, Z.

    2016-01-01

    We study the scattering problem of photon and polariton in a one-dimensional coupled-cavity system. Analytical approximate analysis and numerical simulation show that a photon can stimulate the photon emission from a polariton through polariton-photon collisions. This observation opens the possibility of photon-stimulated transition from insulating to radiative phase in a coupled-cavity QED system. Inversely, we also find that a polariton can be generated by a two-photon Raman scattering process. This paves the way towards single photon storage by the aid of atom-cavity interaction. PMID:26877252

  8. Stimulated photon emission and two-photon Raman scattering in a coupled-cavity QED system.

    PubMed

    Li, C; Song, Z

    2016-02-15

    We study the scattering problem of photon and polariton in a one-dimensional coupled-cavity system. Analytical approximate analysis and numerical simulation show that a photon can stimulate the photon emission from a polariton through polariton-photon collisions. This observation opens the possibility of photon-stimulated transition from insulating to radiative phase in a coupled-cavity QED system. Inversely, we also find that a polariton can be generated by a two-photon Raman scattering process. This paves the way towards single photon storage by the aid of atom-cavity interaction.

  9. Engineering photonic and plasmonic light emission enhancement

    NASA Astrophysics Data System (ADS)

    Lawrence, Nathaniel

    Semiconductor photonic devices are a rapidly maturing technology which currently occupy multi-billion dollar markets in the areas of LED lighting and optical data communication. LEDs currently demonstrate the highest luminous efficiency of any light source for general lighting. Long-haul optical data communication currently forms the backbone of the global communication network. Proper design of light management is required for photonic devices, which can increase the overall efficiency or add new device functionality. In this thesis, novel methods for the control of light propagation and confinement are developed for the use in integrated photonic devices. The first part of this work focuses on the engineering of field confinement within deep subwavelength plasmonic resonators for the enhancement of light-matter interaction. In this section, plasmonic ring nanocavities are shown to form gap plasmon modes confined to the dielectric region between two metal layers. The scattering properties, near-field enhancement and photonic density of states of nanocavity devices are studied using analytic theory and 3D finite difference time domain simulations. Plasmonic ring nanocavities are fabricated and characterized using photoluminescence intensity and decay rate measurements. A 25 times increase in the radiative decay rate of Er:Si02 is demonstrated in nanocavities where light is confined to volumes as small as 0.01( ln )3. The potential to achieve lasing, due to the enhancement of stimulated emission rate in ring nanocavities, is studied as a route to Si-compatible plasmon-enhanced nanolasers. The second part of this work focuses on the manipulation of light generated in planar semiconductor devices using arrays of dielectric nanopillars. In particular, aperiodic arrays of nanopillars are engineered for omnidirectional light extraction enhancement. Arrays of Er:SiNx, nanopillars are fabricated and a ten times increase in light extraction is experimentally demonstrated

  10. Multi-photon microscope driven by novel green laser pump

    NASA Astrophysics Data System (ADS)

    Marti, Dominik; Djurhuus, Martin; Jensen, Ole Bjarlin; Andersen, Peter E.

    2016-03-01

    Multi-photon microscopy is extensively used in research due to its superior possibilities when compared to other microscopy modalities. The technique also has the possibility to advance diagnostics in clinical applications, due to its capabilities complementing existing technology in a multimodal system. However, translation is hindered due to the high cost, high training demand and large footprint of a standard setup. We show in this article that minification of the setup, while also reducing cost and complexity, is indeed possible without compromising on image quality, by using a novel diode laser replacing the commonly used conventional solid state laser as the pump for the femtosecond system driving the imaging.

  11. Predicting vehicular emissions in high spatial resolution using pervasively measured transportation data and microscopic emissions model

    NASA Astrophysics Data System (ADS)

    Nyhan, Marguerite; Sobolevsky, Stanislav; Kang, Chaogui; Robinson, Prudence; Corti, Andrea; Szell, Michael; Streets, David; Lu, Zifeng; Britter, Rex; Barrett, Steven R. H.; Ratti, Carlo

    2016-09-01

    Air pollution related to traffic emissions pose an especially significant problem in cities; this is due to its adverse impact on human health and well-being. Previous studies which have aimed to quantify emissions from the transportation sector have been limited by either simulated or coarsely resolved traffic volume data. Emissions inventories form the basis of urban pollution models, therefore in this study, Global Positioning System (GPS) trajectory data from a taxi fleet of over 15,000 vehicles were analyzed with the aim of predicting air pollution emissions for Singapore. This novel approach enabled the quantification of instantaneous drive cycle parameters in high spatio-temporal resolution, which provided the basis for a microscopic emissions model. Carbon dioxide (CO2), nitrogen oxides (NOx), volatile organic compounds (VOCs) and particulate matter (PM) emissions were thus estimated. Highly localized areas of elevated emissions levels were identified, with a spatio-temporal precision not possible with previously used methods for estimating emissions. Relatively higher emissions areas were mainly concentrated in a few districts that were the Singapore Downtown Core area, to the north of the central urban region and to the east of it. Daily emissions quantified for the total motor vehicle population of Singapore were found to be comparable to another emissions dataset. Results demonstrated that high-resolution spatio-temporal vehicle traces detected using GPS in large taxi fleets could be used to infer highly localized areas of elevated acceleration and air pollution emissions in cities, and may become a complement to traditional emission estimates, especially in emerging cities and countries where reliable fine-grained urban air quality data is not easily available. This is the first study of its kind to investigate measured microscopic vehicle movement in tandem with microscopic emissions modeling for a substantial study domain.

  12. Development of a two photon microscope for tracking Drosophila larvae

    NASA Astrophysics Data System (ADS)

    Karagyozov, Doycho; Mihovilovic Skanata, Mirna; Gershow, Marc

    Current in vivo methods for measuring neural activity in Drosophila larva require immobilization of the animal. Although we can record neural signals while stimulating the sensory organs, we cannot read the behavioral output because we have prevented the animal from moving. Many research questions cannot be answered without observation of neural activity in behaving (freely-moving) animals. Our project aims to develop a tracking microscope that maintains the neurons of interest in the field of view and in focus during the rapid three dimensional motion of a free larva.

  13. Development and design of advanced two-photon microscope used in neuroscience

    NASA Astrophysics Data System (ADS)

    Doronin, M. S.; Popov, A. V.

    2016-08-01

    This work represents the real steps to development and design advanced two-photon microscope by efforts of laboratory staff. Self-developed microscopy system provides possibility to service it and modify the structure of microscope depending on highly specialized experimental design and scientific goals. We are presenting here module-based microscopy system which provides an opportunity to looking for new applications of this setup depending on laboratories needs using with galvo and resonant scanners.

  14. Single-photon emission computed tomography (SPECT): Applications and potential

    SciTech Connect

    Holman, B.L.; Tumeh, S.S. )

    1990-01-26

    Single-photon emission computed tomography has received increasing attention as radiopharmaceuticals that reflect perfusion, metabolism, and receptor and cellular function have become widely available. Perfusion single-photon emission computed tomography of the brain provides functional information useful for the diagnosis and management of stroke, dementia, and epilepsy. Single-photon emission computed tomography has been applied to myocardial, skeletal, hepatic, and tumor scintigraphy, resulting in increased diagnostic accuracy over planar imaging because background activity and overlapping tissues interfere far less with activity from the target structure when tomographic techniques are used. Single-photon emission computed tomography is substantially less expensive and far more accessible than positron emission tomography and will become an increasingly attractive alternative for transferring the positron emission tomography technology to routine clinical use.

  15. Deep two-photon microscopic imaging through brain tissue using the second singlet state from fluorescent agent chlorophyll α in spinach leaf.

    PubMed

    Shi, Lingyan; Rodríguez-Contreras, Adrián; Budansky, Yury; Pu, Yang; Nguyen, Thien An; Alfano, Robert R

    2014-06-01

    Two-photon (2P) excitation of the second singlet (S₂) state was studied to achieve deep optical microscopic imaging in brain tissue when both the excitation (800 nm) and emission (685 nm) wavelengths lie in the "tissue optical window" (650 to 950 nm). S₂ state technique was used to investigate chlorophyll α (Chl α) fluorescence inside a spinach leaf under a thick layer of freshly sliced rat brain tissue in combination with 2P microscopic imaging. Strong emission at the peak wavelength of 685 nm under the 2P S₂ state of Chl α enabled the imaging depth up to 450 μm through rat brain tissue.

  16. Deep two-photon microscopic imaging through brain tissue using the second singlet state from fluorescent agent chlorophyll α in spinach leaf

    NASA Astrophysics Data System (ADS)

    Shi, Lingyan; Rodríguez-Contreras, Adrián; Budansky, Yury; Pu, Yang; An Nguyen, Thien; Alfano, Robert R.

    2014-06-01

    Two-photon (2P) excitation of the second singlet (S) state was studied to achieve deep optical microscopic imaging in brain tissue when both the excitation (800 nm) and emission (685 nm) wavelengths lie in the "tissue optical window" (650 to 950 nm). S2 state technique was used to investigate chlorophyll α (Chl α) fluorescence inside a spinach leaf under a thick layer of freshly sliced rat brain tissue in combination with 2P microscopic imaging. Strong emission at the peak wavelength of 685 nm under the 2P S state of Chl α enabled the imaging depth up to 450 μm through rat brain tissue.

  17. A modular two-photon microscope for simultaneous imaging of distant cortical areas in vivo

    NASA Astrophysics Data System (ADS)

    Voigt, Fabian F.; Chen, Jerry L.; Krueppel, Roland; Helmchen, Fritjof

    2015-03-01

    We have designed and built a two-photon microscope which allows calcium imaging in awake, behaving animals across field-of-views (FOV) of up to 1.7 × 1.7 mm. A special scan system enables independent x,y, and z-positioning of two smaller sub-areas within this FOV for simultaneous functional recordings. This microscope enables us to optically record neuronal activity with cellular resolution across much larger spatial scales than previously possible and should help in deciphering the behavior-dependent flow of information within the neocortex. The microscope hard- and software are modular and can be extended to other imaging and photostimulation modalities.

  18. Single photon emission from ZnO nanoparticles

    SciTech Connect

    Choi, Sumin; Ton-That, Cuong; Phillips, Matthew R.; Aharonovich, Igor; Johnson, Brett C.; Castelletto, Stefania

    2014-06-30

    Room temperature single photon emitters are very important resources for photonics and emerging quantum technologies. In this work, we study single photon emission from defect centers in 20 nm zinc oxide (ZnO) nanoparticles. The emitters exhibit bright broadband fluorescence in the red spectral range centered at 640 nm with polarized excitation and emission. The studied emitters showed continuous blinking; however, bleaching can be suppressed using a polymethyl methacrylate coating. Furthermore, hydrogen termination increased the density of single photon emitters. Our results will contribute to the identification of quantum systems in ZnO.

  19. Absorption and emission properties of photonic crystals and metamaterials

    SciTech Connect

    Peng, Lili

    2007-01-01

    We study the emission and absorption properties of photonic crystals and metamaterials using Comsol Multiphysics and Ansoft HFSS as simulation tools. We calculate the emission properties of metallic designs using drude model and the results illustrate that an appropriate termination of the surface of the metallic structure can significantly increase the absorption and therefore the thermal emissivity. We investigate the spontaneous emission rate modifications that occur for emitters inside two-dimensional photonic crystals and find the isotropic and directional emissions with respect to different frequencies as we have expected.

  20. Spectroscopy of Light Emission from a Scanning Tunneling Microscope in Air

    NASA Astrophysics Data System (ADS)

    Péchou, R.; Coratger, R.; Girardin, C.; Ajustron, F.; Beauvillain, J.

    1996-11-01

    Light emission has been detected at the tip-sample junction of a Scanning Tunneling Microscope (S.T.M.) in air on noble metallic surfaces. A spectroscopic study of emitted photons for Au-Au and PtIr-Au tunneling junctions is presented. The general aspect of the spectra depends on the materials used in the junctions; a study of the spectra as a function of tunneling current and surface bias voltage reveals similar and reproducible characteristics. Une émission de lumière a été détectée au niveau de la jonction pointe-surface d'un microscope à effet tunnel dans l'air sur des surfaces de métaux nobles. Une étude spectroscopique des photons émis par des jonctions tunnel Au-Au et PtIr-Au est présentée. L'aspect général des spectres dépend des matériaux utilisés ; une étude en fonction du courant tunnel et de la tension de polarisation de la jonction révéle des caractéristiques similaires et reproductibles.

  1. COMPACT NON-CONTACT TOTAL EMISSION DETECTION FOR IN-VIVO MULTI-PHOTON EXCITATION MICROSCOPY

    PubMed Central

    Glancy, Brian; Karamzadeh, Nader S.; Gandjbakhche, Amir H.; Redford, Glen; Kilborn, Karl; Knutson, Jay R.; Balaban, Robert S.

    2014-01-01

    Summary We describe a compact, non-contact design for a Total Emission Detection (c-TED) system for intra-vital multi-photon imaging. To conform to a standard upright two-photon microscope design, this system uses a parabolic mirror surrounding a standard microscope objective in concert with an optical path that does not interfere with normal microscope operation. The non-contact design of this device allows for maximal light collection without disrupting the physiology of the specimen being examined. Tests were conducted on exposed tissues in live animals to examine the emission collection enhancement of the c-TED device compared to heavily optimized objective-based emission collection. The best light collection enhancement was seen from murine fat (5×-2× gains as a function of depth), while murine skeletal muscle and rat kidney showed gains of over two and just under two-fold near the surface, respectively. Gains decreased with imaging depth (particularly in the kidney). Zebrafish imaging on a reflective substrate showed close to a two-fold gain throughout the entire volume of an intact embryo (approximately 150 μm deep). Direct measurement of bleaching rates confirmed that the lower laser powers (enabled by greater light collection efficiency) yielded reduced photobleaching in vivo. The potential benefits of increased light collection in terms of speed of imaging and reduced photo-damage, as well as the applicability of this device to other multi-photon imaging methods is discussed. PMID:24251437

  2. Highly charged ion based time of flight emission microscope

    DOEpatents

    Barnes, Alan V.; Schenkel, Thomas; Hamza, Alex V.; Schneider, Dieter H.; Doyle, Barney

    2001-01-01

    A highly charged ion based time-of-flight emission microscope has been designed, which improves the surface sensitivity of static SIMS measurements because of the higher ionization probability of highly charged ions. Slow, highly charged ions are produced in an electron beam ion trap and are directed to the sample surface. The sputtered secondary ions and electrons pass through a specially designed objective lens to a microchannel plate detector. This new instrument permits high surface sensitivity (10.sup.10 atoms/cm.sup.2), high spatial resolution (100 nm), and chemical structural information due to the high molecular ion yields. The high secondary ion yield permits coincidence counting, which can be used to enhance determination of chemical and topological structure and to correlate specific molecular species.

  3. Virtual photon emission from a quark-gluon plasma

    NASA Astrophysics Data System (ADS)

    Suryanarayana, S. V.

    2007-10-01

    We present phenomenological formulas for virtual photon emission rates from a thermalized quark-gluon plasma (QGP) that include bremsstrahlung and annihilation with scattering (AWS) mechanisms along with the Landau-Pomeranchuk-Migdal (LPM) effects. For this purpose we follow the approach of generalized emission functions (GEF) for virtual photon emission, we showed earlier for a fixed temperature and strong coupling constant. In the present work, we extend the LPM calculations for several temperatures and strong coupling strengths, photon energies (q0), photon mass (Q2), and quark energies (p0). We generalize the dynamical scaling variables, xT,xL, for bremsstrahlung and AWS processes that are now functions of variables p0,q0,Q2,T,αs. The GEF introduced earlier, gTb,gTa,gLb,gLa, are also generalized for any temperatures and coupling strengths. From this, the imaginary part of the photon polarization tensor as a function of photon mass and energy has been calculated as a one-dimensional integral over these GEF and parton distribution functions in the plasma. By fitting these polarization tensors obtained from GEF method, we obtained a phenomenological formula for virtual photon emission rates as a function of {q0,Q2,T,αs} that includes bremsstrahlung and AWS mechanisms with LPM effects.

  4. Dirac directional emission in anisotropic zero refractive index photonic crystals.

    PubMed

    He, Xin-Tao; Zhong, Yao-Nan; Zhou, You; Zhong, Zhi-Chao; Dong, Jian-Wen

    2015-08-14

    A certain class of photonic crystals with conical dispersion is known to behave as isotropic zero-refractive-index medium. However, the discrete building blocks in such photonic crystals are limited to construct multidirectional devices, even for high-symmetric photonic crystals. Here, we show multidirectional emission from low-symmetric photonic crystals with semi-Dirac dispersion at the zone center. We demonstrate that such low-symmetric photonic crystal can be considered as an effective anisotropic zero-refractive-index medium, as long as there is only one propagation mode near Dirac frequency. Four kinds of Dirac multidirectional emitters are achieved with the channel numbers of five, seven, eleven, and thirteen, respectively. Spatial power combination for such kind of Dirac directional emitter is also verified even when multiple sources are randomly placed in the anisotropic zero-refractive-index photonic crystal.

  5. Spontaneous emission and nonlinear effects in photonic bandgap materials

    NASA Astrophysics Data System (ADS)

    Fogel, Ishella S.; Bendickson, Jon M.; Tocci, Michael D.; Bloemer, Mark J.; Scalora, Michael; Bowden, Charles M.; Dowling, Jonathan P.

    1998-03-01

    We summarize and review our theoretical and experimental work on spontaneous emission and nonlinear effects in one-dimensional, photonic bandgap (PBG) structures. We present a new result: a method for calculating the normal-mode solutions - and hence the spontaneous emission of embedded emitters - in an arbitrary, linear, lossless, one-dimensional, PBG structure.

  6. Compact two-photon laser-scanning microscope made from minimally modified commercial components

    NASA Astrophysics Data System (ADS)

    Iyer, Vijay; Hoogland, Tycho; Losavio, Bradley E.; McQuiston, A. R.; Saggau, Peter

    2002-06-01

    A compact two-photon laser-scanning microscope (TPLSM) was constructed using a diode-pumped, mode-locked Nd:YLF laser (Biolight 1000, Coherent Laser Group) and a small confocal laser scan-head (PCM2000, Nikon Bioscience). The laser emits at 1047nm and is fiber-coupled to a compact compressor unit producing a pulse-width of ~175fsec. Both the pulse compressor and confocal scan head were interfaced on a small optical breadboard that was directly attached to an upright research microscope (Eclipse E600FN, Nikon Bioscience). Two-photon fluorescence emitted from the specimen was collected into a multimode fiber and transmitted directly to an external PMT supplied with the Nikon confocal system. The modifications to the scanhead were minimal (a single mirror replacement) and did not interfere with its confocal function. The resulting system offers several advantages: compact size, turnkey operation, and the ability to translate the microscope rather than an often delicate specimen. In addition, it is possible to switch between confocal and two-photon operation, allowing for straightforward comparison. Using this compact TPLSM, we obtained structural and functional images from hippocampal neurons in living brain slices using commonly available fluorophores.

  7. Magnetic two-photon scattering and two-photon emission - Cross sections and redistribution functions

    NASA Technical Reports Server (NTRS)

    Alexander, S. G.; Meszaros, P.

    1991-01-01

    The magnetic two-photon scattering cross section is discussed within the framework of QED, and the corresponding scattering redistribution function for this process and its inverse, as well as the scattering source function are calculated explicitly. In a similar way, the magnetic two-photon emission process which follows the radiative excitation of Landau levels above ground is calculated. The two-photon scattering and two-photon emission are of the same order as the single-photon magnetic scattering. All three of these processes, and in optically thick cases also their inverses, are included in radiative transport calculations modeling accreting pulsars and gamma-ray bursters. These processes play a prominent role in determining the relative strength of the first two cyclotron harmonics, and their effects extend also to the higher harmonics.

  8. Multiple photon emission in heavy particle decays

    NASA Technical Reports Server (NTRS)

    Asakimori, K.; Burnett, T. H.; Cherry, M. L.; Christl, M. J.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.; Gregory, J. C.; Hayashi, T.

    1994-01-01

    Cosmic ray interactions, at energies above 1 TeV/nucleon, in emulsion chambers flown on high altitude balloons have yielded two events showing apparent decays of a heavy particle into one charged particle and four photons. The photons converted into electron pairs very close to the decay vertex. Attempts to explain this decay topology with known particle decays are presented. Unless both events represent a b yields u transition, which is statistically unlikely, then other known decay modes for charmed or bottom particles do not account satisfactorily for these observations. This could indicate, possibly, a new decay channel.

  9. Photon and neutrino-pair emission from circulating quantum ions

    NASA Astrophysics Data System (ADS)

    Yoshimura, M.; Sasao, N.

    2016-06-01

    The recent proposal of a photon and a neutrino-pair beam is investigated in detail. Production rates, both differential and total, of a single photon, two photons, and a neutrino pair emitted from quantum ions in circular motion are given for any velocity of ion. This part is an extension of our previous calculations at highest energies to lower energies of circulating ions, and hopefully helps to identify the new process of quantum ion circulation at a low energy ring. We clarify how to utilize the circulating ion for a new source of coherent neutrino beam despite much stronger background photons. Once one verifies that the coherence is maintained in the initial phases of time evolution after laser irradiation, large background photon emission rates are not an obstacle against utilizing the extracted neutrino-pair beam.

  10. Diagnosis of dementia with single photon emission computed tomography

    SciTech Connect

    Jagust, W.J.; Budinger, T.F.; Reed, B.R.

    1987-03-01

    Single photon emission computed tomography is a practical modality for the study of physiologic cerebral activity in vivo. We utilized single photon emission computed tomography and N-isopropyl-p-iodoamphetamine iodine 123 to evaluate regional cerebral blood flow in nine patients with Alzheimer's disease (AD), five healthy elderly control subjects, and two patients with multi-infarct dementia. We found that all subjects with AD demonstrated flow deficits in temporoparietal cortex bilaterally, and that the ratio of activity in bilateral temporoparietal cortex to activity in the whole slice allowed the differentiation of all patients with AD from both the controls and from the patients with multi-infarct dementia. Furthermore, this ratio showed a strong correlation with disease severity in the AD group. Single photon emission computed tomography appears to be useful in the differential diagnosis of dementia and reflects clinical features of the disease.

  11. Adapting a compact confocal microscope system to a two-photon excitation fluorescence imaging architecture.

    PubMed

    Diaspro, A; Corosu, M; Ramoino, P; Robello, M

    1999-11-01

    Within the framework of a national National Institute of Physics of Matter (INFM) project, we have realised a two-photon excitation (TPE) fluorescence microscope based on a new generation commercial confocal scanning head. The core of the architecture is a mode-locked Ti:Sapphire laser (Tsunami 3960, Spectra Physics Inc., Mountain View, CA) pumped by a high-power (5 W, 532 nm) laser (Millennia V, Spectra Physics Inc.) and an ultracompact confocal scanning head, Nikon PCM2000 (Nikon Instruments, Florence, Italy) using a single-pinhole design. Three-dimensional point-spread function has been measured to define spatial resolution performances. The TPE microscope has been used with a wide range of excitable fluorescent molecules (DAPI, Fura-2, Indo-1, DiOC(6)(3), fluoresceine, Texas red) covering a single photon spectral range from UV to green. An example is reported on 3D imaging of the helical structure of the sperm head of the Octopus Eledone cirrhosa labelled with an UV excitable dye, i.e., DAPI. The system can be easily switched for operating both in conventional and two-photon mode.

  12. Wide-band acousto-optic deflectors for large field of view two-photon microscope.

    PubMed

    Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2012-04-01

    Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV.

  13. Thermodynamics of photon-enhanced thermionic emission solar cells

    SciTech Connect

    Reck, Kasper; Hansen, Ole

    2014-01-13

    Photon-enhanced thermionic emission (PETE) cells in which direct photon energy as well as thermal energy can be harvested have recently been suggested as a new candidate for high efficiency solar cells. Here, we present an analytic thermodynamical model for evaluation of the efficiency of PETE solar cells including an analysis of the entropy production due to thermionic emission of general validity. The model is applied to find the maximum efficiency of a PETE cell for given cathode and anode work functions and temperatures.

  14. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    NASA Astrophysics Data System (ADS)

    See, Gloria G.; Xu, Lu; Sutanto, Erick; Alleyne, Andrew G.; Nuzzo, Ralph G.; Cunningham, Brian T.

    2015-08-01

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure.

  15. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    SciTech Connect

    See, Gloria G.; Xu, Lu; Nuzzo, Ralph G.; Sutanto, Erick; Alleyne, Andrew G.; Cunningham, Brian T.

    2015-08-03

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure.

  16. Manipulating light propagation and emission using photonic crystals

    SciTech Connect

    Nair, Rajesh V.; Jagatap, B. N.

    2014-03-31

    We discuss the synthesis and characterization of self-assembled photonic crystals using polymer colloids having sub-micron diameters. The angle resolved optical reflectivity measurements indicate the hybridization between stop gaps in the multiple Bragg diffraction regimes. Each diffraction resonances in the multiple Bragg diffraction regimes are assigned to respective crystal planes. We also discuss laser-induced studies of spontaneous emission in self-assembled photonic crystals having Rhodamine-B dye doped colloids. Our experimental results reveal more than 51% inhibition in emission intensity within the stop gap as compared to a proper reference sample.

  17. Single-wavelength two-photon excitation–stimulated emission depletion (SW2PE-STED) superresolution imaging

    PubMed Central

    Bianchini, Paolo; Harke, Benjamin; Galiani, Silvia; Vicidomini, Giuseppe; Diaspro, Alberto

    2012-01-01

    We developed a new class of two-photon excitation–stimulated emission depletion (2PE-STED) optical microscope. In this work, we show the opportunity to perform superresolved fluorescence imaging, exciting and stimulating the emission of a fluorophore by means of a single wavelength. We show that a widely used red-emitting fluorophore, ATTO647N, can be two-photon excited at a wavelength allowing both 2PE and STED using the very same laser source. This fact opens the possibility to perform 2PE microscopy at four to five times STED-improved resolution, while exploiting the intrinsic advantages of nonlinear excitation. PMID:22493221

  18. Improving z-tracking accuracy in the two-photon single-particle tracking microscope

    NASA Astrophysics Data System (ADS)

    Liu, C.; Liu, Y.-L.; Perillo, E. P.; Jiang, N.; Dunn, A. K.; Yeh, H.-C.

    2015-10-01

    Here, we present a method that can improve the z-tracking accuracy of the recently invented TSUNAMI (Tracking of Single particles Using Nonlinear And Multiplexed Illumination) microscope. This method utilizes a maximum likelihood estimator (MLE) to determine the particle's 3D position that maximizes the likelihood of the observed time-correlated photon count distribution. Our Monte Carlo simulations show that the MLE-based tracking scheme can improve the z-tracking accuracy of TSUNAMI microscope by 1.7 fold. In addition, MLE is also found to reduce the temporal correlation of the z-tracking error. Taking advantage of the smaller and less temporally correlated z-tracking error, we have precisely recovered the hybridization-melting kinetics of a DNA model system from thousands of short single-particle trajectories in silico. Our method can be generally applied to other 3D single-particle tracking techniques.

  19. Two-photon microscope for multisite microphotolysis of caged neurotransmitters in acute brain slices

    PubMed Central

    Losavio, Bradley E.; Iyer, Vijay; Saggau, Peter

    2009-01-01

    We developed a two-photon microscope optimized for physiologically manipulating single neurons through their postsynaptic receptors. The optical layout fulfills the stringent design criteria required for high-speed, high-resolution imaging in scattering brain tissue with minimal photodamage. We detail the practical compensation of spectral and temporal dispersion inherent in fast laser beam scanning with acousto-optic deflectors, as well as a set of biological protocols for visualizing nearly diffraction-limited structures and delivering physiological synaptic stimuli. The microscope clearly resolves dendritic spines and evokes electrophysiological transients in single neurons that are similar to endogenous responses. This system enables the study of multisynaptic integration and will assist our understanding of single neuron function and dendritic computation. PMID:20059271

  20. Improving z-tracking accuracy in the two-photon single-particle tracking microscope

    SciTech Connect

    Liu, C.; Liu, Y.-L.; Perillo, E. P.; Jiang, N.; Dunn, A. K. E-mail: tim.yeh@austin.utexas.edu; Yeh, H.-C. E-mail: tim.yeh@austin.utexas.edu

    2015-10-12

    Here, we present a method that can improve the z-tracking accuracy of the recently invented TSUNAMI (Tracking of Single particles Using Nonlinear And Multiplexed Illumination) microscope. This method utilizes a maximum likelihood estimator (MLE) to determine the particle's 3D position that maximizes the likelihood of the observed time-correlated photon count distribution. Our Monte Carlo simulations show that the MLE-based tracking scheme can improve the z-tracking accuracy of TSUNAMI microscope by 1.7 fold. In addition, MLE is also found to reduce the temporal correlation of the z-tracking error. Taking advantage of the smaller and less temporally correlated z-tracking error, we have precisely recovered the hybridization-melting kinetics of a DNA model system from thousands of short single-particle trajectories in silico. Our method can be generally applied to other 3D single-particle tracking techniques.

  1. Controlling the Two-Photon-Induced Photon Cascade Emission in a Gd3+/Tb3+-Codoped Glass for Multicolor Display

    PubMed Central

    Yuan, Mao-Hui; Fan, Hai-Hua; Li, Hui; Lan, Sheng; Tie, Shao-Long; Yang, Zhong-Min

    2016-01-01

    We reported the first observation of the two-photon-induced quantum cutting phenomenon in a Gd3+/Tb3+-codoped glass in which two photons at ~400 nm are simultaneously absorbed, leading to the cascade emission of three photons in the visible spectral region. The two-photon absorption induced by femtosecond laser pulses allows the excitation of the energy states in Gd3+ which are inactive for single-photon excitation and enables the observation of many new electric transitions which are invisible in the single-photon-induced luminescence. The competition between the two-photon-induced photon cascade emission and the single-photon-induced emission was manipulated to control the luminescence color of the glass. We demonstrated the change of the luminescence color from red to yellow and eventually to green by varying either the excitation wavelength or the excitation power density. PMID:26899189

  2. Photonic band-edge-induced enhancement in absorption and emission

    NASA Astrophysics Data System (ADS)

    Ummer, Karikkuzhi Variyath; Vijaya, Ramarao

    2015-01-01

    An enhancement in photonic band-edge-induced absorption and emission from rhodamine-B dye doped polystyrene pseudo gap photonic crystals is studied. The band-edge-induced enhancement in absorption is achieved by selecting the incident angle of the excitation beam so that the absorption spectrum of the emitter overlaps the photonic band edge. The band-edge-induced enhancement in emission, on the other hand, is possible with and without an enhancement in band-edge-induced absorption, depending on the collection angle of emission. Through a simple set of measurements with suitably chosen angles for excitation and emission, we achieve a maximum enhancement of 70% in emission intensity with band-edge-induced effects over and above the intrinsic emission in the case of self-assembled opals. This is a comprehensive effort to interpret tunable lasing in opals as well as to predict the wavelength of lasing arising as a result of band-edge-induced distributed feedback effects.

  3. Cavity-induced backaction in Purcell-enhanced photon emission of a single ion in an ultraviolet fiber cavity

    NASA Astrophysics Data System (ADS)

    Ballance, T. G.; Meyer, H. M.; Kobel, P.; Ott, K.; Reichel, J.; Köhl, M.

    2017-03-01

    We study the behavior of a single laser-driven trapped ion inside a microscopic optical Fabry-Perot cavity. In particular, we demonstrate a fiber Fabry-Perot cavity operating on the principal S1 /2→P1 /2 electric dipole transition of an Yb+ ion at 369 nm with an ion-cavity coupling strength of g =2 π ×67 (1 ) MHz. We employ the cavity to study the generation of single photons and observe cavity-induced backaction in the Purcell-enhanced emission of photons. Tuning of the amplitude and phase between the driving field and the cavity field built up from photons scattered into the cavity mode by the ion allows us to enhance or suppress the total rate of photon emission from the ion-cavity system.

  4. Reassignment of scattered emission photons in multifocal multiphoton microscopy.

    PubMed

    Cha, Jae Won; Singh, Vijay Raj; Kim, Ki Hean; Subramanian, Jaichandar; Peng, Qiwen; Yu, Hanry; Nedivi, Elly; So, Peter T C

    2014-06-05

    Multifocal multiphoton microscopy (MMM) achieves fast imaging by simultaneously scanning multiple foci across different regions of specimen. The use of imaging detectors in MMM, such as CCD or CMOS, results in degradation of image signal-to-noise-ratio (SNR) due to the scattering of emitted photons. SNR can be partly recovered using multianode photomultiplier tubes (MAPMT). In this design, however, emission photons scattered to neighbor anodes are encoded by the foci scan location resulting in ghost images. The crosstalk between different anodes is currently measured a priori, which is cumbersome as it depends specimen properties. Here, we present the photon reassignment method for MMM, established based on the maximum likelihood (ML) estimation, for quantification of crosstalk between the anodes of MAPMT without a priori measurement. The method provides the reassignment of the photons generated by the ghost images to the original spatial location thus increases the SNR of the final reconstructed image.

  5. Sum rules and photon emission in hadronic matter

    NASA Astrophysics Data System (ADS)

    Holt, Nathan Prescott Montgomery

    In this work, we examine properties of quantum chromodynamics (QCD) at moderate temperatures and density. These conditions are reached in the later stages of ultra-relativistic heavy-ion collisions after the matter has cooled sufficiently to re-hadronize from a quark-gluon plasma. The properties of matter in this stage are expected to change smoothly with temperature. We explore this behavior in two ways. First, we use finite-temperature sum rules to analyze the properties of vector and axial-vector spectral functions at low temperatures. Previous models used in sum rule analyses frequently led to ambiguous applications. Here we avoid such ambiguities by using an improved vacuum spectral function model together with a strict leading-order-in-temperature expansion. This results in well-defined finite temperature spectral functions. Additionally, we incorporate a finite pion mass, which we show induces an analytical violation of the sum rules. We then proceed to numerically measure that violation. Second, we calculate thermal photon emissivities of QCD matter from interactions involving both mesons and baryons. We identify a novel source of thermal photons from a system composed of pi, rho, and o mesons, then calculate photon emission rates from this system using both relativistic kinetic theory and thermal field theory. These rates are compared to existing calculations and found to be significant. We then calculate thermal photon emission rates from baryon interactions, using an exhaustive set of both strange and non-strange particles. We again find novel sources of photons from this system, compare the total rates to calculations of current state-of-the-art photon emission rates, and find them to be comparable.

  6. Coherent fluorescence emission by using hybrid photonic-plasmonic crystals.

    PubMed

    Shi, Lei; Yuan, Xiaowen; Zhang, Yafeng; Hakala, Tommi; Yin, Shaoyu; Han, Dezhuan; Zhu, Xiaolong; Zhang, Bo; Liu, Xiaohan; Törmä, Päivi; Lu, Wei; Zi, Jian

    2014-09-01

    The spatial and temporal coherence of the fluorescence emission controlled by a quasi-two-dimensional hybrid photonic-plasmonic crystal structure covered with a thin fluorescent-molecular-doped dielectric film is investigated experimentally. A simple theoretical model to describe how a confined quasi-two-dimensional optical mode may induce coherent fluorescence emission is also presented. Concerning the spatial coherence, it is experimentally observed that the coherence area in the plane of the light source is in excess of 49 μm(2), which results in enhanced directional fluorescence emission. Concerning temporal coherence, the obtained coherence time is 4 times longer than that of the normal fluorescence emission in vacuum. Moreover, a Young's double-slit interference experiment is performed to directly confirm the spatially coherent emission. This smoking gun proof of spatial coherence is reported here for the first time for the optical-mode-modified emission.

  7. Spontaneous heavy cluster emission rates using microscopic potentials

    NASA Astrophysics Data System (ADS)

    Basu, D. N.

    2002-08-01

    The nuclear cluster radioactivities have been studied theoretically in the framework of a microscopic superasymmetric fission model (MSAFM). The nuclear interaction potentials required for binary cold fission processes are calculated by folding in the density distribution functions of the two fragments with a realistic effective interaction. The microscopic nuclear potential thus obtained has been used to calculate the action integral within the WKB approximation. The calculated half-lives of the present MSAFM calculations are found to be in good agreement over a wide range of observed experimental data.

  8. Photon emission near extreme Kerr black holes

    NASA Astrophysics Data System (ADS)

    Porfyriadis, Achilleas P.; Shi, Yichen; Strominger, Andrew

    2017-03-01

    Ongoing astronomical efforts extract physical properties of black holes from electromagnetic emissions in their near-vicinity. This requires finding the null geodesics which extend from the near-horizon region out to a distant observatory. In general these are given by elliptic integrals which are often studied numerically. In this paper, for the interesting special case of extremally spinning Kerr black holes, we use an emergent near-horizon conformal symmetry to find near-superradiant geodesics analytically in terms of elementary functions.

  9. Ultra-weak photon emission of hands in aging prediction.

    PubMed

    Zhao, Xin; van Wijk, Eduard; Yan, Yu; van Wijk, Roeland; Yang, Huanming; Zhang, Yan; Wang, Jian

    2016-09-01

    Aging has been one of the several topics intensely investigated during recent decades. More scientists have been scrutinizing mechanisms behind the human aging process. Ultra-weak photon emission is known as one type of spontaneous photon emission that can be detected with a highly sensitive single photon counting photomultiplier tube (PMT) from the surface of human bodies. It may reflect the body's oxidative damage. Our aim was to examine whether ultra-weak photon emission from a human hand is able to predict one's chronological age. Sixty subjects were recruited and grouped by age. We examined four areas of each hand: palm side of fingers, palm side of hand, dorsum side of fingers, and dorsum side of hand. Left and right hand were measured synchronously with two independent PMTs. Mean strength and Fano factor values of photon counts were utilized to compare the UPE patterns of males and females of different age groups. Subsequently, we utilized UPE data from the most sensitive PMT to develop an age prediction model. We randomly picked 49 subjects to construct the model, whereas the remaining 11 subjects were utilized for validation. The results demonstrated that the model was a good regression compared to the observed values (Pearson's r=0.6, adjusted R square=0.4, p=9.4E-7, accuracy=49/60). Further analysis revealed that the average difference between the chronological age and predicted age was only 7.6±0.8years. It was concluded that this fast and non-invasive photon technology is sufficiently promising to be developed for the estimation of biological aging.

  10. Photonic Crystals-Inhibited Spontaneous Emission: Optical Antennas-Enhanced Spontaneous Emission

    NASA Astrophysics Data System (ADS)

    Yablonovitch, Eli

    Photonic crystals are also part of everyday technological life in opto-electronic telecommunication devices that provide us with internet, cloud storage, and email. But photonic crystals have also been identified in nature, in the coloration of peacocks, parrots, chameleons, butterflies and many other species.In spite of its broad applicability, the original motivation of photonic crystals was to create a ``bandgap'' in which the spontaneous emission of light would be inhibited. Conversely, the opposite is now possible. The ``optical antenna'' can accelerate spontaneous emission. Over 100 years after the radio antenna, we finally have tiny ``optical antennas'' which can act on molecules and quantum dots. Employing optical antennas, spontaneous light emission can become faster than stimulated emission.

  11. High-performance imaging of stem cells using single-photon emissions

    NASA Astrophysics Data System (ADS)

    Wagenaar, Douglas J.; Moats, Rex A.; Hartsough, Neal E.; Meier, Dirk; Hugg, James W.; Yang, Tang; Gazit, Dan; Pelled, Gadi; Patt, Bradley E.

    2011-10-01

    Radiolabeled cells have been imaged for decades in the field of autoradiography. Recent advances in detector and microelectronics technologies have enabled the new field of "digital autoradiography" which remains limited to ex vivo specimens of thin tissue slices. The 3D field-of-view (FOV) of single cell imaging can be extended to millimeters if the low energy (10-30 keV) photon emissions of radionuclides are used for single-photon nuclear imaging. This new microscope uses a coded aperture foil made of highly attenuating elements such as gold or platinum to form the image as a kind of "lens". The detectors used for single-photon emission microscopy are typically silicon detectors with a pixel pitch less than 60 μm. The goal of this work is to image radiolabeled mesenchymal stem cells in vivo in an animal model of tendon repair processes. Single-photon nuclear imaging is an attractive modality for translational medicine since the labeled cells can be imaged simultaneously with the reparative processes by using the dual-isotope imaging technique. The details our microscope's two-layer gold aperture and the operation of the energy-dispersive, pixellated silicon detector are presented along with the first demonstration of energy discrimination with a 57Co source. Cell labeling techniques have been augmented by genetic engineering with the sodium-iodide symporter, a type of reporter gene imaging method that enables in vivo uptake of free 99mTc or an iodine isotope at a time point days or weeks after the insertion of the genetically modified stem cells into the animal model. This microscopy work in animal research may expand to the imaging of reporter-enabled stem cells simultaneously with the expected biological repair process in human clinical trials of stem cell therapies.

  12. Enhanced trion emission from colloidal quantum dots with photonic crystals by two-photon excitation.

    PubMed

    Xu, Xingsheng

    2013-11-15

    For colloidal quantum dots, the ongoing biggest problem is their fluorescence blinking. Until now, there is no generally accepted model for this fluorescence blinking. Here, two-photon excited fluorescence from CdSe/ZnS nanocrystals on silicon nitride photonic crystals is studied using a femtosecond laser. From analysis of the spectra and decay processes, most of the relative trion efficiency is larger than 10%, and the largest relative trion efficiency reaches 46.7%. The photonic crystals enhance the trion emission of CdSe/ZnS nanocrystals, where the enhancement is due to the coupling of the trion emission to the leaky mode of the photonic crystal slab. Moreover, the photonic crystals enhance the Auger-assisted trapping efficiency of electrons/holes to surface states, and then enhance the efficiency of the generations of charge separation and DC electric field, which modifies the trion spectrum. Therefore, a model is present for explaining the mechanism of fluorescence blinking including the effect of the environment.

  13. Two-photon spectral fluorescence lifetime and second-harmonic generation imaging of the porcine cornea with a 12-femtosecond laser microscope.

    PubMed

    Batista, Ana; Breunig, Hans Georg; Uchugonova, Aisada; Morgado, António Miguel; König, Karsten

    2016-03-01

    Five dimensional microscopy with a 12-fs laser scanning microscope based on spectrally resolved two-photon autofluorescence lifetime and second-harmonic generation (SHG) imaging was used to characterize all layers of the porcine cornea. This setup allowed the simultaneous excitation of both metabolic cofactors, NAD(P)H and flavins, and their discrimination based on their spectral emission properties and fluorescence decay characteristics. Furthermore, the architecture of the stromal collagen fibrils was assessed by SHG imaging in both forward and backward directions. Information on the metabolic state and the tissue architecture of the porcine cornea were obtained with subcellular resolution, and high temporal and spectral resolutions.

  14. Two-photon spectral fluorescence lifetime and second-harmonic generation imaging of the porcine cornea with a 12-femtosecond laser microscope

    NASA Astrophysics Data System (ADS)

    Batista, Ana; Breunig, Hans Georg; Uchugonova, Aisada; Morgado, António Miguel; König, Karsten

    2016-03-01

    Five dimensional microscopy with a 12-fs laser scanning microscope based on spectrally resolved two-photon autofluorescence lifetime and second-harmonic generation (SHG) imaging was used to characterize all layers of the porcine cornea. This setup allowed the simultaneous excitation of both metabolic cofactors, NAD(P)H and flavins, and their discrimination based on their spectral emission properties and fluorescence decay characteristics. Furthermore, the architecture of the stromal collagen fibrils was assessed by SHG imaging in both forward and backward directions. Information on the metabolic state and the tissue architecture of the porcine cornea were obtained with subcellular resolution, and high temporal and spectral resolutions.

  15. Microscopic probabilistic model for the simulation of secondary electron emission

    SciTech Connect

    Furman, M.A.; Pivi, M.T.F.

    2002-07-29

    We provide a detailed description of a model and its computational algorithm for the secondary electron emission process. The model is based on a broad phenomenological fit to data for the secondary emission yield (SEY) and the emitted-energy spectrum. We provide two sets of values for the parameters by fitting our model to two particular data sets, one for copper and the other one for stainless steel.

  16. A photonic microscope for observing real-time vibrations of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Barnard, Arthur W.; Zhang, Mian; Wiederhecker, Gustavo; Lipson, Michal; McEuen, Paul L.

    Vibrational modes in suspended carbon nanotubes (CNTs) are incredibly responsive to small forces, which makes them a prime candidate as nano-mechanical sensors. However, transducing this mechanical motion into detectable signals is a considerable challenge. Electrical detection, which has been the prevailing method thus far, suffers a significant impedance mismatch to macroscopic electronics and is thus susceptible to noise. We demonstrate an alternative: optical readout of CNT vibrations in real-time. By combining a unique CNT microtweezer platform with a high-finesse optical microdisk resonator, we dramatically enhance the naturally small optical cross-section of CNTs and thereby achieve unprecedented detection sensitivity. With this novel photonic microscope, we directly measure the thermal Brownian motion of CNTs and observe marked spectral diffusion at room temperature, shedding light on CNTs unique thermal physics. By further enhancing the optical coupling, we demonstrate optical amplification of CNT vibrations and directly observe period-doubling in the amplified state.

  17. Photon-enhanced thermionic emission for solar concentrator systems.

    PubMed

    Schwede, Jared W; Bargatin, Igor; Riley, Daniel C; Hardin, Brian E; Rosenthal, Samuel J; Sun, Yun; Schmitt, Felix; Pianetta, Piero; Howe, Roger T; Shen, Zhi-Xun; Melosh, Nicholas A

    2010-09-01

    Solar-energy conversion usually takes one of two forms: the 'quantum' approach, which uses the large per-photon energy of solar radiation to excite electrons, as in photovoltaic cells, or the 'thermal' approach, which uses concentrated sunlight as a thermal-energy source to indirectly produce electricity using a heat engine. Here we present a new concept for solar electricity generation, photon-enhanced thermionic emission, which combines quantum and thermal mechanisms into a single physical process. The device is based on thermionic emission of photoexcited electrons from a semiconductor cathode at high temperature. Temperature-dependent photoemission-yield measurements from GaN show strong evidence for photon-enhanced thermionic emission, and calculated efficiencies for idealized devices can exceed the theoretical limits of single-junction photovoltaic cells. The proposed solar converter would operate at temperatures exceeding 200 degrees C, enabling its waste heat to be used to power a secondary thermal engine, boosting theoretical combined conversion efficiencies above 50%.

  18. Spatial frequencies from human periosteum at different depths using two-photon microscopic images

    NASA Astrophysics Data System (ADS)

    Sordillo, Laura A.; Shi, Lingyan; Bhagroo, Stephen; Nguyen, Theinan; Lubicz, Stephanie; Pu, Yang; Budansky, Yuri; Hatak, Noella; Alfano, R. R.

    2014-03-01

    The outer layer of human bone, the periosteum, was studied using two-photon (2P) fluorescence microscopy. This layer of the periosteum is composed mostly of fibrous collagen. The inner cambium layer has less collagen and contains osteoblasts necessary for bone remodeling. The spatial frequencies from the layers of the periosteum of human bone at different depths were investigated using images acquired with two-photon excitation microscopy. This 2P spectroscopic method offers deeper depth penetration into samples, high fluorescence collection efficiency, and a reduction in photobleaching and photodamage. Using 130 femtosecond pulses with an 800 nm wavelength excitation, a 40× microscope objective, and a photomultiplier tube (PMT) detector, high contrast images of the collagen present in the periosteum at various micrometers depths from the surface were obtained. Fourier transform analysis of the 2P images was used to assess the structure of the periosteum at different depths in terms of spatial frequencies. The spatial frequency spectra from the outer and inner periosteal regions show significant spectral peak differences which can provide information on the structure of the layers of the periosteum. One may be able to use spatial frequency spectra for optical detection of abnormalities of the periosteum which can occur in disease.

  19. Novel failure analysis techniques using photon probing with a scanning optical microscope

    SciTech Connect

    Cole, E.I. Jr.; Soden, J.M.; Rife, J.L.; Barton, D.L.; Henderson, C.L.

    1993-12-31

    Three new failure analysis techniques for integrated circuits (ICs) have been developed using localized photon probing with a scanning optical microscope (SOM). The first two are light-induced voltage alteration (LIVA) imaging techniques that (1) localize open-circuited and damaged junctions and (2) image transistor logic states. The third technique uses the SOM to control logic states optically from the IC backside. LIVA images are produced by monitoring the voltage fluctuations of a constant current power supply as a laser beam is scanned over the IC. High selectivity for localizing defects has been demonstrated using the LIVA approach. Logic state mapping results, similar to previous work using biased optical beam induced current (OBIC) and laser probing approaches have also been produced using LIVA. Application of the two LIVA based techniques to backside failure analysis has been demonstrated using an infrared laser source. Optical logic state control is based upon earlier work examining transistor response to photon injection. The physics of each method and their applications for failure analysis are described.

  20. Disorder in Stimuli-responsive Microgel Photonic Crystals: A Confocal Microscopic Study

    NASA Astrophysics Data System (ADS)

    Gupta, Deepak Kumar; Tata, B. V. R.; Brijitta, J.; Joshi, R. G.

    2011-10-01

    Crystalline arrays of sub-micron sized particles have lattice constants in the visible range and serve as photonic crystals. Highly diffracting photonic crystals (PCs) can be prepared through colloidal route by self-assembly of monodisperse particles. Size polydispersity (SPD) is known to induce second type disorder in these crystals.SPD is inherent to hard-sphere as well as charged colloidal suspensions and cannot be tailored through external conditions. We employ a confocal laser scanning microscope (CLSM) to study the disorder in PCs of poly(N-isopropylacrylamide-co-Acrylic acid) (PNIPAM-co-AAc) stimuli-responsive microgel suspensions and show here for the first time, that osmotic pressure reduces the SPD; hence the second type disorder in these crystals. Different samples with varying particle concentrations have been prepared by subjecting the dilute suspensions to different amounts of osmotic pressure. The crystallized samples were investigated for their structure and disorder using CLSM. (111) planes of single crystalline domains have been imaged and real-space coordinates of the particles and the SPD have been determined by image analysis. Different types of disorder present in these crystals are investigated by analyzing the diffraction peaks computed from the particle coordinates. The analysis revealed presence of second-type disorder in these crystals. Our results indicate that second type disorder in these crystals arises due to SPD which is found to decrease with increase in osmotic pressure.

  1. Photon assisted processes: Probability amplitudes for the absorption and emission of photons and dc-photocurrents

    SciTech Connect

    Micu, C.; Racolta, D.; Papp, E.

    2014-11-24

    In this paper one deals with the derivation of probability amplitudes characterizing the photon assisted injection of electrons in a two-terminal quantum conductor. For this purpose one accounts for spatially constant but time dependent periodic voltages applied on an Ohmic contact. Resorting to the discrete Fourier transform provides the probability amplitudes for the emission and absorption of photons in terms of squared Bessel functions of the first kind and integer order. Several kinds of ac-pulses like sinusoidal and dc+sinusoidal are assumed. Mean square values concerning photon numbers have been discussed in some more detail. Time averages of squared time dependent classical currents and leading corrections to the rescaled dc-photocurrent have also been accounted for.

  2. Modification of Thermal Emission via Metallic Photonic Crystals

    SciTech Connect

    Norris, David J.; Stein, Andreas; George, Steven M.

    2012-07-30

    Photonic crystals are materials that are periodically structured on an optical length scale. It was previously demonstrated that the glow, or thermal emission, of tungsten photonic crystals that have a specific structure - known as the 'woodpile structure' - could be modified to reduce the amount of infrared radiation from the material. This ability has implications for improving the efficiency of thermal emission sources and for thermophotovoltaic devices. The study of this effect had been limited because the fabrication of metallic woodpile structures had previously required a complex fabrication process. In this project we pursued several approaches to simplify the fabrication of metallic photonic crystals that are useful for modification of thermal emission. First, we used the self-assembly of micrometer-scale spheres into colloidal crystals known as synthetic opals. These opals can then be infiltrated with a metal and the spheres removed to obtain a structure, known as an inverse opal, in which a three-dimensional array of bubbles is embedded in a film. Second, we used direct laser writing, in which the focus of an infrared laser is moved through a thin film of photoresist to form lines by multiphoton polymerization. Proper layering of such lines can lead to a scaffold with the woodpile structure, which can be coated with a refractory metal. Third, we explored a completely new approach to modified thermal emission - thin metal foils that contain a simple periodic surface pattern, as shown in Fig. 1. When such a foil is heated, surface plasmons are excited that propagate along the metal interface. If these waves strike the pattern, they can be converted into thermal emission with specific properties.

  3. Two-photon excited fluorescence emission from hemoglobin

    NASA Astrophysics Data System (ADS)

    Sun, Qiqi; Zeng, Yan; Zhang, Wei; Zheng, Wei; Luo, Yi; Qu, Jianan Y.

    2015-03-01

    Hemoglobin, one of the most important proteins in blood, is responsible for oxygen transportation in almost all vertebrates. Recently, we discovered two-photon excited hemoglobin fluorescence and achieved label-free microvascular imaging based on the hemoglobin fluorescence. However, the mechanism of its fluorescence emission still remains unknown. In this work, we studied the two-photon excited fluorescence properties of the hemoglobin subunits, heme/hemin (iron (II)/(III) protoporphyrin IX) and globin. We first studied the properties of heme and the similar spectral and temporal characteristics of heme and hemoglobin fluorescence provide strong evidence that heme is the fluorophore in hemoglobin. Then we studied the fluorescence properties of hemin, globin and methemoglobin, and found that the hemin may have the main effect on the methemoglobin fluorescence and that globin has tryptophan fluorescence like other proteins. Finally, since heme is a centrosymmetric molecule, that the Soret band fluorescence of heme and hemoglobin was not observed in the single photon process in the previous study may be due to the parity selection rule. The discovery of heme two-photon excited fluorescence may open a new window for heme biology research, since heme as a cofactor of hemoprotein has many functions, including chemical catalysis, electron transfer and diatomic gases transportation.

  4. Brain single-photon emission CT physics principles.

    PubMed

    Accorsi, R

    2008-08-01

    The basic principles of scintigraphy are reviewed and extended to 3D imaging. Single-photon emission computed tomography (SPECT) is a sensitive and specific 3D technique to monitor in vivo functional processes in both clinical and preclinical studies. SPECT/CT systems are becoming increasingly common and can provide accurately registered anatomic information as well. In general, SPECT is affected by low photon-collection efficiency, but in brain imaging, not all of the large FOV of clinical gamma cameras is needed: The use of fan- and cone-beam collimation trades off the unused FOV for increased sensitivity and resolution. The design of dedicated cameras aims at increased angular coverage and resolution by minimizing the distance from the patient. The corrections needed for quantitative imaging are challenging but can take advantage of the relative spatial uniformity of attenuation and scatter. Preclinical systems can provide submillimeter resolution in small animal brain imaging with workable sensitivity.

  5. Single-Photon Emission of a Hydrogenlike Atom

    NASA Astrophysics Data System (ADS)

    Skobelev, V. V.

    2016-11-01

    Implementing a previously obtained, original solution of the Dirac equation for an electron in the field of a nucleus ( Ze) expressed in terms of the wave function of the corresponding Schrödinger equation and its derivatives in spherical coordinates and the spin projection operator Σ3 associated with the eigenfunction, taking into account in each component of the spinor the leading term of the expansion in the small parameter ( Zα), α = e 2 / ħc ≈ 1 / 137, the partial probabilities W of emission of a photon ( Zα)* → ( Zα) + γ have been calculated. Here two orthogonal states of the linear polarization of the photon, and also the spin states of the electron, which previously had not been taken into consideration, have been taken into account in the transverse gauge. It turns out that the probabilities W of emission of a photon per unit time for any allowed transitions are proportional to (Zα)4, as was previously accepted, and the selection rules for the quantum number m have the usual form ∆ m = 0,±1. It was found that a spin flip does not take place during emission. In contrast to the customary situation with the selection rules for the quantum number l being of the form ∆ l = ±1, for ∆ m = ±1 there also exist integrals over dcosθ which are not equal to zero for undetermined odd values of ∆ l. In this, and also in a fundamentally different dependence of the amplitude on the quantum numbers consist the differences from the traditional approach to the problem. Necessary conditions are formulated, under the fulfillment of which the selection rules for l are not changed, having values ∆ l = ±1 for arbitrary ∆ m, but it was not possible, however, to give a complete proof of these rules.

  6. Quantitative analysis of directional spontaneous emission spectra from light sources in photonic crystals

    SciTech Connect

    Nikolaev, Ivan S.; Lodahl, Peter; Vos, Willem L.

    2005-05-15

    We have performed angle-resolved measurements of spontaneous-emission spectra from laser dyes and quantum dots in opal and inverse opal photonic crystals. Pronounced directional dependencies of the emission spectra are observed: angular ranges of strongly reduced emission adjoin with angular ranges of enhanced emission. It appears that emission from embedded light sources is affected both by the periodicity and by the structural imperfections of the crystals: the photons are Bragg diffracted by lattice planes and scattered by unavoidable structural disorder. Using a model comprising diffuse light transport and photonic band structure, we quantitatively explain the directional emission spectra. This work provides detailed understanding of the transport of spontaneously emitted light in real photonic crystals, which is essential in the interpretation of quantum optics in photonic-band-gap crystals and for applications wherein directional emission and total emission power are controlled.

  7. Photon event distribution sampling: an image formation technique for scanning microscopes that permits tracking of sub-diffraction particles with high spatial and temporal resolutions.

    PubMed

    Larkin, J D; Publicover, N G; Sutko, J L

    2011-01-01

    In photon event distribution sampling, an image formation technique for scanning microscopes, the maximum likelihood position of origin of each detected photon is acquired as a data set rather than binning photons in pixels. Subsequently, an intensity-related probability density function describing the uncertainty associated with the photon position measurement is applied to each position and individual photon intensity distributions are summed to form an image. Compared to pixel-based images, photon event distribution sampling images exhibit increased signal-to-noise and comparable spatial resolution. Photon event distribution sampling is superior to pixel-based image formation in recognizing the presence of structured (non-random) photon distributions at low photon counts and permits use of non-raster scanning patterns. A photon event distribution sampling based method for localizing single particles derived from a multi-variate normal distribution is more precise than statistical (Gaussian) fitting to pixel-based images. Using the multi-variate normal distribution method, non-raster scanning and a typical confocal microscope, localizations with 8 nm precision were achieved at 10 ms sampling rates with acquisition of ~200 photons per frame. Single nanometre precision was obtained with a greater number of photons per frame. In summary, photon event distribution sampling provides an efficient way to form images when low numbers of photons are involved and permits particle tracking with confocal point-scanning microscopes with nanometre precision deep within specimens.

  8. Spontaneous emission control in a tunable hybrid photonic system.

    PubMed

    Frimmer, Martin; Koenderink, A Femius

    2013-05-24

    We experimentally demonstrate control of the rate of spontaneous emission in a tunable hybrid photonic system that consists of two canonical building blocks for spontaneous emission control, an optical antenna and a mirror, each providing a modification of the local density of optical states (LDOS). We couple fluorophores to a plasmonic antenna to create a superemitter with an enhanced decay rate. In a superemitter analog of the seminal Drexhage experiment we probe the LDOS of a nanomechanically approached mirror. Because of the electrodynamic interaction of the antenna with its own mirror image, the superemitter traces the inverse of the LDOS enhancement provided by the mirror, in stark contrast to a bare source, whose decay rate is proportional to the mirror LDOS.

  9. Application of ultra-weak photon emission measurements in agriculture.

    PubMed

    Kato, Kimihiko; Iyozumi, Hiroyuki; Kageyama, Chizuko; Inagaki, Hidehiro; Yamaguchi, Akira; Nukui, Hideki

    2014-10-05

    Here we report our two applications of ultra-weak photon emission (UPE) measurements in agriculture. One is to find new types of agrochemicals that potentiate plants' defense, so-called "plant activator". We first analyzed the relation between plant defense and Elicitor-Responsive Photon Emission (ERPE) using a combination of rice cells and a chitin elicitor. Pharmacological analyses clarified that ERPE was generated as a part of the chitin elicitor-responsive defense in close relation with the generation of reactive oxygen species (ROS). Then we successfully detected the activity of plant activators as the potentiation of ERPE, and developed a new screening system for plant activators based on this principle. Another UPE application is to distinguish herbicide-resistant weeds from susceptible ones by measuring UPE in weeds. In our study, it was revealed that the weed biotypes resistant to sulfonylurea (SU) herbicides, one of the major herbicide groups, showed stronger UPE than susceptible ones after an SU herbicide treatment. By further analysis with a pharmacological and RNAi study, we found that the detoxifying enzyme P450s contributed to the UPE increase in SU herbicide resistant weeds. It is considered that weeds resistant to herbicides other than SU might also be able to be distinguished from susceptible ones by UPE measurement, as long as the herbicides are subject to detoxification by P450s.

  10. Nonlinear Shock Acceleration and Photon Emission in Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Ellison, Donald C.; Berezhko, Evgeny G.; Baring, Matthew G.

    2000-01-01

    We have extended a simple model of nonlinear diffusive shock acceleration (Berezhko & Ellison 1999: Ellison &, Berezhko 1999a) to include the injection and acceleration of electrons and the production of photons from bremsstrahlung, synchrotron, inverse Compton, and pion-decay processes. We argue that, the results of this model, which is simpler to use than more elaborate ones, offer a significant improvement, over test-particle, power-law spectra which are often used in astrophysical applications of diffusive shock acceleration. With an evolutionary supernova remnant (SNR) model to obtain shock parameters as functions of ambient interstellar medium parameters and time, we predict broad-band continuum photon emission from supernova remnants in general, and SN1006 in particular, showing that our results compare well with the more complete time-dependent and spherically symmetric nonlinear model of Berezhko, Ksenofontov, & Petukhov (1999a). We discuss the implications nonlinear shock acceleration has for X-ray line emission, and use our model to describe how ambient conditions determine the TeV/radio flux ratio, an important parameter for gamma-ray observations of radio SNRs.

  11. Photon-enhanced thermionic emission from heterostructures with low interface recombination

    NASA Astrophysics Data System (ADS)

    Schwede, J. W.; Sarmiento, T.; Narasimhan, V. K.; Rosenthal, S. J.; Riley, D. C.; Schmitt, F.; Bargatin, I.; Sahasrabuddhe, K.; Howe, R. T.; Harris, J. S.; Melosh, N. A.; Shen, Z.-X.

    2013-03-01

    Photon-enhanced thermionic emission is a method of solar-energy conversion that promises to combine photon and thermal processes into a single mechanism, overcoming fundamental limits on the efficiency of photovoltaic cells. Photon-enhanced thermionic emission relies on vacuum emission of photoexcited electrons that are in thermal equilibrium with a semiconductor lattice, avoiding challenging non-equilibrium requirements and exotic material properties. However, although previous work demonstrated the photon-enhanced thermionic emission effect, efficiency has until now remained very low. Here we describe electron-emission measurements on a GaAs/AlGaAs heterostructure that introduces an internal interface, decoupling the basic physics of photon-enhanced thermionic emission from the vacuum emission process. Quantum efficiencies are dramatically higher than in previous experiments because of low interface recombination and are projected to increase another order of magnitude with more stable, low work-function coatings. The results highlight the effectiveness of the photon-enhanced thermionic emission process and demonstrate that efficient photon-enhanced thermionic emission is achievable, a key step towards realistic photon-enhanced thermionic emission based energy conversion.

  12. The investigation of Alzheimer's disease with single photon emission tomography.

    PubMed Central

    Burns, A; Philpot, M P; Costa, D C; Ell, P J; Levy, R

    1989-01-01

    Twenty patients satisfying standard clinical criteria for Alzheimer's disease (AD) and six age-matched normal controls were studied using 99mTc hexamethyl-propyleneamine oxime and single photon emission tomography. The AD patients had lower regional cerebral blood flow (rCBF) in the temporal and posterior parietal lobes compared to controls. AD patients with apraxia and aphasia had lower rCBF in the lateral temporal and posterior parietal lobes than AD patients without these features. Within the AD group, correlations were found between neuropsychological tests and rCBF: praxis correlated with posterior parietal activity, memory with left temporal lobe activity and language with activity throughout the left hemisphere. Images PMID:2467967

  13. Photon emission and quantum signalling in biological systems

    NASA Astrophysics Data System (ADS)

    Mayburov, S. N.

    2015-05-01

    Ultra-weak, non-termal photon emission is universal feature of living organisms and plants. In our experiment the fine structure of optical radiation emitted by the loach fish eggs is studied. It was shown earlier that such radiation performs the signaling between the distant fish egg samples, which result in significant correlations of their growth. The optical radiation of biological sample was measured by the cooled photomultiplier in photocurrent regime, it was found that the main bulk of radiation is produced in form of short-time quasi-periodic bursts. The analysis of radiation temporal structure indicates that the information about egg age and growth is encoded via the values of time intervals between neighbor bursts with the height higher than some fixed level. The applications of such biological radiation in medical diagnostics and biotechnology are considered.

  14. Single photon emission computed tomography (SPECT) in epilepsy

    SciTech Connect

    Leroy, R.F.

    1991-12-31

    Epilepsy is a common neurologic disorder which has just begun to be studied with single photon emission computerized tomography (SPECT). Epilepsy usually is studied with electroencephalographic (EEG) techniques that demonstrate the physiologic changes that occur during seizures, and with neuroimaging techniques that show the brain structures where seizures originate. Neither method alone has been adequate to describe the pathophysiology of the patient with epilepsy. EEG techniques lack anatomic sensitivity, and there are no structural abnormalities shown by neuroimaging which are specific for epilepsy. Functional imaging (FI) has developed as a physiologic tool with anatomic sensitivity, and SPECT has been promoted as a FI technique because of its potentially wide availability. However, SPECT is early in its development and its clinical utility for epilepsy still has to be demonstrated. To understand this role of SPECT, consideration must be given to the pathophysiology of epilepsy, brain physiology, types of seizure, epileptic syndromes, and the SPECT technique itself. 44 refs., 2 tabs.

  15. Single photon emission computed tomography in seizure disorders.

    PubMed Central

    Denays, R; Rubinstein, M; Ham, H; Piepsz, A; Noël, P

    1988-01-01

    Fourteen children with various seizure disorders were studied using a cerebral blood flow tracer, 123I iodoamphetamine (0.05 mCi/kg), and single photon emission computed tomography (SPECT). In the five patients with radiological lesions, SPECT showed congruent or more extensive abnormalities. Five of the nine children with a normal scan on computed tomography had abnormal SPECT studies consisting of focal hypoperfusion, diffuse hemispheric hypoperfusion, multifocal and bilateral hypoperfusion, or focal hyperperfusion. A focal lesion seen on SPECT has been found in children with tonic-clonic seizures suggesting secondarily generalised seizures. Moreover the pattern seen on SPECT seemed to be related to the clinical status. An extensive impairment found on SPECT was associated with a poor evolution in terms of intellectual performance and seizure frequency. Conversely all children with a normal result on SPECT had less than two seizures per year and normal neurological and intellectual development. Images Figure PMID:3264135

  16. Single photon emission computed tomography in AIDS dementia complex

    SciTech Connect

    Pohl, P.; Vogl, G.; Fill, H.; Roessler, H.Z.; Zangerle, R.; Gerstenbrand, F.

    1988-08-01

    Single photon emission computed tomography (SPECT) studies were performed in AIDS dementia complex using IMP in 12 patients (and HM-PAO in four of these same patients). In all patients, SPECT revealed either multiple or focal uptake defects, the latter corresponding with focal signs or symptoms in all but one case. Computerized tomography showed a diffuse cerebral atrophy in eight of 12 patients, magnetic resonance imaging exhibited changes like atrophy and/or leukoencephalopathy in two of five cases. Our data indicate that both disturbance of cerebral amine metabolism and alteration of local perfusion share in the pathogenesis of AIDS dementia complex. SPECT is an important aid in the diagnosis of AIDS dementia complex and contributes to the understanding of the pathophysiological mechanisms of this disorder.

  17. Heavy Ion Radiation Effects Studies With Ion Photon Emission Microscopy

    SciTech Connect

    Branson, J. V.; Hattar, K.; Vizkelethy, G.; Powell, C. J.; Doyle, B. L.; Rossi, P.

    2011-06-01

    The development of a new radiation effects microscopy (REM) technique is crucial as emerging semiconductor technologies demonstrate smaller feature sizes and thicker back end of line (BEOL) layers. To penetrate these materials and still deposit sufficient energy into the device to induce single event effects, high energy heavy ions are required. Ion photon emission microscopy (IPEM) is a technique that utilizes coincident photons, which are emitted from the location of each ion impact to map out regions of radiation sensitivity in integrated circuits and devices, circumventing the obstacle of focusing high-energy heavy ions. Several versions of the IPEM have been developed and implemented at Sandia National Laboratories (SNL). One such instrument has been utilized on the microbeam line of the 6 MV tandem accelerator at SNL. Another IPEM was designed for ex-vacu use at the 88'' cyclotron at Lawrence Berkeley National Laboratory (LBNL). Extensive engineering is involved in the development of these IPEM systems, including resolving issues with electronics, event timing, optics, phosphor selection, and mechanics. The various versions of the IPEM and the obstacles, as well as benefits associated with each will be presented. In addition, the current stage of IPEM development as a user instrument will be discussed in the context of recent results.

  18. A custom-built two-photon microscope based on a mode-locked Yb3+ doped fiber laser

    NASA Astrophysics Data System (ADS)

    Kim, Dong Uk; Song, Hoseong; Song, Woosub, III; Kwon, Hyuk-Sang; Kim, Dug Yong

    2012-03-01

    Two-photon microscopy is a very attractive tool for the study of the three-dimensional (3D) and dynamic processes in cells and tissues. One of the feasible constructions of two-photon microscopy is the combination a confocal laser scanning microscope and a mode-locked Ti:sapphire laser. Even though this approach is the simplest and fastest implementation, this system is highly cost-intensive and considerably difficult in modification. Many researcher therefore decide to build a more cost-effective and flexible system with a self-developed software for operation and data acquisition. We present a custom-built two-photon microscope based on a mode-locked Yb3+ doped fiber laser and demonstrate two-photon fluorescence imaging of biological specimens. The mode-locked fiber laser at 1060 nm delivers 320 fs laser pulses at a frequency of 36 MHz up to average power of 80 mW. The excitation at 1060 nm can be more suitable in thick, turbid samples for 3D image construction as well as cell viability. The system can simply accomplish confocal and two-photon mode by an additional optical coupler that allows conventional laser source to transfer to the scanning head. The normal frame rate is 1 frames/s for 400 x 400 pixel images. The measured full width at half maximum resolutions were about 0.44 μm laterally and 1.34 μm axially. A multi-color stained convallaria, rat basophilic leukemia cells and a rat brain tissue were observed by two-photon fluorescence imaging in our system.

  19. Spectral narrowing of emission in self-assembled colloidal photonic superlattices

    NASA Astrophysics Data System (ADS)

    Baert, Kasper; Song, Kai; Vallée, Renaud A. L.; Van der Auweraer, Mark; Clays, Koen

    2006-12-01

    We report on the influence of a well-designed passband in the stop band of a suitably engineered self-assembled colloidal photonic crystal superlattice on the steady-state emission properties of infiltrated fluorophores. The photonic superlattice was built by convective self-assembly of slabs of silica spheres of two different sizes. Transmission experiments on the engineered photonic crystal structure show two stop bands with an effective passband in between. The presence of this passband results in a narrow spectral range of increased density of states for photon modes. This shows up as a decrease in the emission suppression (enhancement of the emission) in the narrow effective passband spectral region. These experiments indicate that the threshold for lasing can possibly be lowered by spectrally narrowing the emission of fluorophores infiltrated in suitably engineered self-assembled photonic crystal superlattices, and are therefore important towards the realization of efficient all-optical integrated circuits from functionalized photonic superlattices and heterostructures.

  20. Comparison between laser terahertz emission microscope and conventional methods for analysis of polycrystalline silicon solar cell

    SciTech Connect

    Nakanishi, Hidetoshi Ito, Akira; Takayama, Kazuhisa Kawayama, Iwao Murakami, Hironaru Tonouchi, Masayoshi

    2015-11-15

    A laser terahertz emission microscope (LTEM) can be used for noncontact inspection to detect the waveforms of photoinduced terahertz emissions from material devices. In this study, we experimentally compared the performance of LTEM with conventional analysis methods, e.g., electroluminescence (EL), photoluminescence (PL), and laser beam induced current (LBIC), as an inspection method for solar cells. The results showed that LTEM was more sensitive to the characteristics of the depletion layer of the polycrystalline solar cell compared with EL, PL, and LBIC and that it could be used as a complementary tool to the conventional analysis methods for a solar cell.

  1. Direct calculation of thermal emission for three-dimensionally periodic photonic crystal slabs.

    PubMed

    Chan, David L C; Soljacić, Marin; Joannopoulos, J D

    2006-09-01

    We perform direct thermal emission calculations for three-dimensionally periodic photonic crystal slabs using stochastic electrodynamics following the Langevin approach, implemented via a finite-difference time-domain algorithm. We demonstrate that emissivity and absorptivity are equal, by showing that such photonic crystal systems emit as much radiation as they absorb, for every frequency, up to statistical fluctuations. We also study the effect of surface termination on absorption and emission spectra from these systems.

  2. Direct calculation of thermal emission for three-dimensionally periodic photonic crystal slabs

    NASA Astrophysics Data System (ADS)

    Chan, David L. C.; Soljačić, Marin; Joannopoulos, J. D.

    2006-09-01

    We perform direct thermal emission calculations for three-dimensionally periodic photonic crystal slabs using stochastic electrodynamics following the Langevin approach, implemented via a finite-difference time-domain algorithm. We demonstrate that emissivity and absorptivity are equal, by showing that such photonic crystal systems emit as much radiation as they absorb, for every frequency, up to statistical fluctuations. We also study the effect of surface termination on absorption and emission spectra from these systems.

  3. Two-Photon Emission of a Hydrogenlike Atom with Photon Polarization and Electron Spin States Taken into Account

    NASA Astrophysics Data System (ADS)

    Skobelev, V. V.

    2017-02-01

    The process of two-photon emission ( Ze)* → ( Ze) + 2 γ of a hydrogenlike atom is considered with spin states of the electron and polarization of the photons taken into account, which had not been done before. A general expression for the probability of the process per unit time has been obtained for different polarization states of the photons with a formulation of hard and soft selection rules for the quantum numbers m and l. It is shown that by virtue of the established specifics of the properties of the two-photon emission process (absence of a Zeeman effect and dependence of the probability on the polarization states of the photons), it can in principle be identified against the background of single-photon emission ( Ze)* → ( Ze) + γ, despite the presence of additional small factors: 1) α = e 2/ ћc ≈ 1/137 of the perturbation theory in e, and 2) the square of the atomic expansion parameter ( Zα)2 in the expression for the probability.

  4. Study of photon emission by electron capture during solar nuclei acceleration. 3: Photon production evaluations

    NASA Technical Reports Server (NTRS)

    Perez-Peraza, J.; Alvarez, M.; Gallegos, A.

    1985-01-01

    Lower limits of photon fluxes were evaluated from electron capture during acceleration in solar flares, because the arbitrary q sub c asterisk assumed in this work evolves very slow with velocity, probably much more slowly than the physical actual situation: in fact, more emission is expected toward the IR region. Nevertheless the authors claim to show that the factibility of sounding acceleration processes, charge evolution processes and physical parameters of the source itself, by the observational analysis of this kind of emissions. For instance, it would be interesting to search observationally, for the predicted flux and energy drift of F sub e ions interacting with the atomic 0 and F sub e of the source matter, or, even more feasible for the X-ray lines at 4.2 keV and 2.624 + 0.003 KeV from Fe and S ions in ionized Fe at T = 10 to the 7th power K respectively, the 418 + or - 2 eV and 20 + or - 4 eV lines of Fe and S in ionized Fe at 5 x 10 to the 6th power K, which are predicted from Fermi acceleration.

  5. Photon path distribution and optical responses of turbid media: theoretical analysis based on the microscopic Beer-Lambert law.

    PubMed

    Tsuchiya, Y

    2001-08-01

    A concise theoretical treatment has been developed to describe the optical responses of a highly scattering inhomogeneous medium using functions of the photon path distribution (PPD). The treatment is based on the microscopic Beer-Lambert law and has been found to yield a complete set of optical responses by time- and frequency-domain measurements. The PPD is defined for possible photons having a total zigzag pathlength of l between the points of light input and detection. Such a distribution is independent of the absorption properties of the medium and can be uniquely determined for the medium under quantification. Therefore, the PPD can be calculated with an imaginary reference medium having the same optical properties as the medium under quantification except for the absence of absorption. One of the advantages of this method is that the optical responses, the total attenuation, the mean pathlength, etc are expressed by functions of the PPD and the absorption distribution.

  6. In-plane emission of indistinguishable photons generated by an integrated quantum emitter

    SciTech Connect

    Kalliakos, Sokratis Bennett, Anthony J.; Ward, Martin B.; Ellis, David J. P.; Skiba-Szymanska, Joanna; Shields, Andrew J.; Brody, Yarden; Schwagmann, Andre; Farrer, Ian; Griffiths, Jonathan P.; Jones, Geb A. C.; Ritchie, David A.

    2014-06-02

    We demonstrate the emission of indistinguishable photons along a semiconductor chip originating from carrier recombination in an InAs quantum dot. The emitter is integrated in the waveguiding region of a photonic crystal structure, allowing for on-chip light propagation. We perform a Hong-Ou-Mandel-type of experiment with photons collected from the exit of the waveguide, and we observe two-photon interference under continuous wave excitation. Our results pave the way for the integration of quantum emitters in advanced photonic quantum circuits.

  7. Analysis of photon-scanning tunneling microscope images of inhomogeneous samples: determination of the local refractive index of channel waveguides

    NASA Astrophysics Data System (ADS)

    Bourillot, E.; de Fornel, F.; Goudonnet, J. P.; Persegol, D.; Kevorkian, A.; Delacourt, D.

    1995-01-01

    Channel waveguides are imaged by a photon-scanning tunneling microscope (PSTM). The polarization of the light and its orientation with respect to the guide axis are shown to be very important parameters in the analysis of the images of such samples. We simulated image formation for the plane of incidence parallel to the axis of the guide. Our theoretical results are qualitatively in agreement with our measurements. These results show the ability of the PSTM to give information about the local refractive-index variations of a sample.

  8. Positron emission tomography and single-photon emission computed tomography in substance abuse research.

    PubMed

    Volkow, Nora D; Fowler, Joanna S; Wang, Gene-Jack

    2003-04-01

    Many advances in the conceptualization of addiction as a disease of the brain have come from the application of imaging technologies directly in the human drug abuser. New knowledge has been driven by advances in radiotracer design and chemistry and positron emission tomography (PET) and single-photon emission computed tomography (SPECT) instrumentation and the integration of these scientific tools with the tools of biochemistry, pharmacology, and medicine. This topic cuts across the medical specialties of neurology, psychiatry, oncology, and cardiology because of the high medical, social, and economic toll that drugs of abuse, including the legal drugs, cigarettes and alcohol, take on society. This article highlights recent advances in the use of PET and SPECT imaging to measure the pharmacokinetic and pharmacodynamic effects of drugs of abuse on the human brain.

  9. Imaging of ultraweak spontaneous photon emission from human body displaying diurnal rhythm.

    PubMed

    Kobayashi, Masaki; Kikuchi, Daisuke; Okamura, Hitoshi

    2009-07-16

    The human body literally glimmers. The intensity of the light emitted by the body is 1000 times lower than the sensitivity of our naked eyes. Ultraweak photon emission is known as the energy released as light through the changes in energy metabolism. We successfully imaged the diurnal change of this ultraweak photon emission with an improved highly sensitive imaging system using cryogenic charge-coupled device (CCD) camera. We found that the human body directly and rhythmically emits light. The diurnal changes in photon emission might be linked to changes in energy metabolism.

  10. Photon shielding for a positron emission tomography suite.

    PubMed

    Courtney, J C; Mendez, P; Hidalgo-Salvatierra, O; Bujenovic, S

    2001-08-01

    This paper provides information on the effects of distance and attenuation in lead sheet and gypsum board of the 0.511 MeV photon produced by positron annihilation. Exposure rates are projected external to an adult injected with 185 MBq (5 mCi) of 18F in a fluorodeoxyglucose solution and for the same activity in a small unshielded container. These data have been applied to estimate the shielding requirements for the Positron Emission Tomography (PET) suite operated by the Nuclear Medicine Department of Our Lady of the Lake Regional Medical Center. To assure that exposures are as low as reasonably achievable, lead was added to the walls of the room where the 18F is stored, handled, and injected into the patients. The PET scanner is installed in a room that formerly contained a Computerized Axial Tomography scanner; the existing 1.6 mm of lead sheet was left in place even though it is not required for personnel protection. During the initial phase of operation, a shield test program was conducted to estimate annual exposures to personnel inside and outside the suite. Projection of measured rates over a year of operation demonstrate that whole body doses are well below regulatory limits.

  11. Brain single photon emission computed tomography in neonates

    SciTech Connect

    Denays, R.; Van Pachterbeke, T.; Tondeur, M.; Spehl, M.; Toppet, V.; Ham, H.; Piepsz, A.; Rubinstein, M.; Nol, P.H.; Haumont, D. )

    1989-08-01

    This study was designed to rate the clinical value of ({sup 123}I)iodoamphetamine (IMP) or ({sup 99m}Tc) hexamethyl propylene amine oxyme (HM-PAO) brain single photon emission computed tomography (SPECT) in neonates, especially in those likely to develop cerebral palsy. The results showed that SPECT abnormalities were congruent in most cases with structural lesions demonstrated by ultrasonography. However, mild bilateral ventricular dilatation and bilateral subependymal porencephalic cysts diagnosed by ultrasound were not associated with an abnormal SPECT finding. In contrast, some cortical periventricular and sylvian lesions and all the parasagittal lesions well visualized in SPECT studies were not diagnosed by ultrasound scans. In neonates with subependymal and/or intraventricular hemorrhage the existence of a parenchymal abnormality was only diagnosed by SPECT. These results indicate that ({sup 123}I)IMP or ({sup 99m}Tc)HM-PAO brain SPECT shows a potential clinical value as the neurodevelopmental outcome is clearly related to the site, the extent, and the number of cerebral lesions. Long-term clinical follow-up is, however, mandatory in order to define which SPECT abnormality is associated with neurologic deficit.

  12. Stress-first single photon emission computed myocardial perfusion imaging

    PubMed Central

    Aquino, C I; Scarano, M; Squame, F; Casaburi, G; Nori, S L; Pace, L

    2016-01-01

    Background Myocardial perfusion imaging (MPI) with single photon emission tomography (SPET) is widely used in coronary artery disease evaluation. Recently major dosimetric concerns have arisen. The aim of this study was to evaluate if a pre-test scoring system could predict the results of stress SPET MPI, thus avoiding two radionuclide injections. Methods All consecutive patients (n=309) undergoing SPET MPI during the first 6 months of 2014 constituted the study group. The scoring system is based on these characteristics: age >65 years (1 point), diabetes (2 points), typical chest pain (2 points), congestive heart failure (3 points), abnormal ECG (4 points), male gender (4 points), and documented previous CAD (5 points). The patients were divided on the basis of the prediction score into 3 classes of risk for an abnormal stress-first protocol. Results An abnormal stress SPET MPI was present in 7/31 patients (23%) with a low risk score, in 24/90 (27%) with an intermediate score risk, and in 124/188 (66%) with an high score risk. ROC curve analysis showed good prediction of abnormal stress MPI. Conclusions Our results suggest an appropriate use of a pre-test clinical prediction formula of abnormal stress MPI in a routine clinical setting. PMID:27896227

  13. Proceedings of clinical SPECT (single photon emission computed tomography) symposium

    SciTech Connect

    Not Available

    1986-09-01

    It has been five years since the last in-depth American College of Nuclear Physicians/Society of Nuclear Medicine Symposium on the subject of single photon emission computed tomography (SPECT) was held. Because this subject was nominated as the single most desired topic we have selected SPECT imaging as the basis for this year's program. The objectives of this symposium are to survey the progress of SPECT clinical applications that have taken place over the last five years and to provide practical and timely guidelines to users of SPECT so that this exciting imaging modality can be fully integrated into the evaluation of pathologic processes. The first half was devoted to a consideration of technical factors important in SPECT acquisition and the second half was devoted to those organ systems about which sufficient clinical SPECT imaging data are available. With respect to the technical aspect of the program we have selected the key areas which demand awareness and attention in order to make SPECT operational in clinical practice. These include selection of equipment, details of uniformity correction, utilization of phantoms for equipment acceptance and quality assurance, the major aspect of algorithms, an understanding of filtered back projection and appropriate choice of filters and an awareness of the most commonly generated artifacts and how to recognize them. With respect to the acquisition and interpretation of organ images, the faculty will present information on the major aspects of hepatic, brain, cardiac, skeletal, and immunologic imaging techniques. Individual papers are processed separately for the data base. (TEM)

  14. Using AIE Luminogen for Long-term and Low-background Three-Photon Microscopic Functional Bioimaging

    NASA Astrophysics Data System (ADS)

    Zhu, Zhenfeng; Leung, Chris W. T.; Zhao, Xinyuan; Wang, Yalun; Qian, Jun; Tang, Ben Zhong; He, Sailing

    2015-10-01

    Fluorescent probes are one of the most popularly used bioimaging markers to monitor metabolic processes of living cells. However, long-term light excitation always leads to photobleaching of fluorescent probes, unavoidable autofluorescence as well as photodamage of cells. To overcome these limitations, we synthesized a type of photostable luminogen named TPE-TPP with an aggregation induced emission (AIE) characteristic, and achieved its three-photon imaging with femtosecond laser excitation of 1020 nm. By using TPE-TPP as fluorescent probes, three-photon microscopy under 1020 nm excitation showed little photo-damage, as well as low autofluorescence to HeLa cells. Due to the AIE effect, the TPE-TPP nanoaggregates uptaken by cells were resistant to photobleaching under three-photon excitation for an extended period of time. Furthermore, we demonstrated that for the present TPE-TPP AIE the three-photon microscopy (with 1020 nm excitation) had a better signal to noise ratio than the two-photon microscopy (with 810 nm excitation) in tissue imaging.

  15. Fabrication and characterization of solid-state nanopores using a field emission scanning electron microscope

    SciTech Connect

    Chang Hung; Iqbal, Samir M.; Stach, Eric A.; King, Alexander H.; Zaluzec, Nestor J.; Bashir, Rashid

    2006-03-06

    The fabrication of solid-state nanopores using the electron beam of a transmission electron microscope (TEM) has been reported in the past. Here, we report a similar method to fabricate solid-state nanopores using the electron source of a conventional field-emission scanning electron microscope (FESEM) instead. Micromachining was used to create initial pore diameters between 50 nm and 200 nm, and controlled pore shrinking to sub 10 nm diameters was performed subsequently during in situ processing in the FESEM. Noticeably, different shrinking behavior was observed when using irradiation from the electron source of the FESEM than the TEM. Unlike previous reports of TEM mediated pore shrinkage, the mechanism of pore shrinkage when using the FESEM could be a result of surface defects generated by radiolysis and subsequent motion of silicon atoms to the pore periphery.

  16. Estimation of Photon Effects on Townsend Discharges for SecondaryElectronEmission Coefficient Measurements

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Tomokazu; Akashi, Haruaki

    2015-09-01

    A Monte Carlo simulation (MCS) is applied to investigate the secondary electron emission in Argon Townsend discharges. The influxes of ions, photons and metastable species onto the cathode surface are estimated simply from the number of inelastic collisions. The effect of photons becomes significant especially under higher pd conditions since the photon influx increases. This suggests the possibility of the estimation of the secondary electron emission coefficient of photons by examining breakdown voltage characteristics (Paschen curves). The effect of metastable species is much smaller than those of ions and photons and is negligible. The Paschen curves evaluated with MCS agrees well with the results of one-dimensional fluid model simulation when the photon effect is neglected, showing the necessity of further improvement. Supported by JSPS KAKENHI Grant Number 26820108.

  17. Design of rare-earth-ion doped chalcogenide photonic crystals for enhancing the fluorescence emission

    NASA Astrophysics Data System (ADS)

    Zhang, Peiqing; Dai, Shixun; Niu, Xueke; Xu, Yinsheng; Zhang, Wei; Wu, Yuehao; Xu, Tiefeng; Nie, Qiuhua

    2014-07-01

    Rare-earth-ion doped chalcogenide glass is a promising material for developing mid-infrared light sources. In this work, Tm3+-doped chalcogenide glass was prepared and photonic crystal structures were designed to enhance its fluorescence emission at approximately 3.8 μm. By employing the finite-difference time-domain (FDTD) simulation, the emission characteristics of the luminescent centers in the bulk material and in the photonic crystals were worked out. Utilizing analysis of the photon excitation inside the sample and the photon extraction on the sample surface, it was found that fluorescence emission can be significantly enhanced 260-fold with the designed photonic crystal structure. The results of this work can be used to realize high-efficiency mid-infrared light sources.

  18. Single-photon emission of two-level system via rapid adiabatic passage

    NASA Astrophysics Data System (ADS)

    Miao, Qiang; Zheng, Yujun

    2016-09-01

    In this paper, we present a high quality single-photon source based on the two-level system undergoing rapid adiabatic passage (RAP). A trigger strategy (sweet region) is suggested to optimize the single-photon emission and explain a counter-intuitive phenomenon on the optimal parameters. The RAP strategy of single-photon source is robust against control error and environmental fluctuation.

  19. Single-photon emission of two-level system via rapid adiabatic passage

    PubMed Central

    Miao, Qiang; Zheng, Yujun

    2016-01-01

    In this paper, we present a high quality single-photon source based on the two-level system undergoing rapid adiabatic passage (RAP). A trigger strategy (sweet region) is suggested to optimize the single-photon emission and explain a counter-intuitive phenomenon on the optimal parameters. The RAP strategy of single-photon source is robust against control error and environmental fluctuation. PMID:27601295

  20. Use of emission electron microscope for potential mapping in semiconductor microelectronics.

    PubMed

    Nepijko, S A; Sedov, N N; Schönhense, G; Escher, M

    2002-05-01

    An emission electron microscope was used for visualization and measurement of the distribution of electric fields and potentials on the surface under study. The contrast of microfields is caused by the fact that slow-moving electrons emitted from the object surface are deflected by these fields. The measurements were performed on a p-n junction to which a voltage was applied. It is shown that the type of contrast from the p-n junction can be reversed depending on the position of the contrast aperture restricting the electron beam. The same result was obtained by means of a computer simulation.

  1. PHOTONIC CRYSTAL SURFACE ENHANCED UPCONVERSION EMISSION OF YF3:Yb3+, Er3+ NANOPARTICLES

    NASA Astrophysics Data System (ADS)

    Shao, Bo; Yang, Zhengwen; Li, Jun; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo; Yang, Yong; Zhou, Dacheng

    2015-11-01

    The opal photonic crystals made of polystyrene microspheres with 155, 230, 270 or 410 nm in diameter were used to enhance upconversion (UC) emission of YF3:Yb3+, Er3+ nanoparticles, respectively. The red or green UC emission of YF3:Yb3+, Er3+ nanoparticles can be selectively enhanced when the red or green UC emission wavelength overlapped with the photonic bandgaps of opals, which is attributed to Bragg reflection of photonic bandgap. In addition, when the 980 nm excitation light wavelength was in the region of the photonic bandgap, red and green UC emissions of YF3:Yb3+, Er3+ nanoparticles were enhanced due to the enhancement of excitation field.

  2. 3D Orbital Tracking in a Modified Two-photon Microscope: An Application to the Tracking of Intracellular Vesicles

    PubMed Central

    Gratton, Enrico

    2014-01-01

    The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a modified two-photon microscope1. As opposed to conventional approaches (raster scan or wide field based on a stack of frames), the 3D orbital tracking allows to localize and follow with a high spatial (10 nm accuracy) and temporal resolution (50 Hz frequency response) the 3D displacement of a moving fluorescent particle on length-scales of hundreds of microns2. The method is based on a feedback algorithm that controls the hardware of a two-photon laser scanning microscope in order to perform a circular orbit around the object to be tracked: the feedback mechanism will maintain the fluorescent object in the center by controlling the displacement of the scanning beam3-5. To demonstrate the advantages of this technique, we followed a fast moving organelle, the lysosome, within a living cell6,7. Cells were plated according to standard protocols, and stained using a commercially lysosome dye. We discuss briefly the hardware configuration and in more detail the control software, to perform a 3D orbital tracking experiment inside living cells. We discuss in detail the parameters required in order to control the scanning microscope and enable the motion of the beam in a closed orbit around the particle. We conclude by demonstrating how this method can be effectively used to track the fast motion of a labeled lysosome along microtubules in 3D within a live cell. Lysosomes can move with speeds in the range of 0.4-0.5 µm/sec, typically displaying a directed motion along the microtubule network8. PMID:25350070

  3. 3D orbital tracking in a modified two-photon microscope: an application to the tracking of intracellular vesicles.

    PubMed

    Anzalone, Andrea; Annibale, Paolo; Gratton, Enrico

    2014-10-01

    The objective of this video protocol is to discuss how to perform and analyze a three-dimensional fluorescent orbital particle tracking experiment using a modified two-photon microscope(1). As opposed to conventional approaches (raster scan or wide field based on a stack of frames), the 3D orbital tracking allows to localize and follow with a high spatial (10 nm accuracy) and temporal resolution (50 Hz frequency response) the 3D displacement of a moving fluorescent particle on length-scales of hundreds of microns(2). The method is based on a feedback algorithm that controls the hardware of a two-photon laser scanning microscope in order to perform a circular orbit around the object to be tracked: the feedback mechanism will maintain the fluorescent object in the center by controlling the displacement of the scanning beam(3-5). To demonstrate the advantages of this technique, we followed a fast moving organelle, the lysosome, within a living cell(6,7). Cells were plated according to standard protocols, and stained using a commercially lysosome dye. We discuss briefly the hardware configuration and in more detail the control software, to perform a 3D orbital tracking experiment inside living cells. We discuss in detail the parameters required in order to control the scanning microscope and enable the motion of the beam in a closed orbit around the particle. We conclude by demonstrating how this method can be effectively used to track the fast motion of a labeled lysosome along microtubules in 3D within a live cell. Lysosomes can move with speeds in the range of 0.4-0.5 µm/sec, typically displaying a directed motion along the microtubule network(8).

  4. Deep, high contrast microscopic cell imaging using three-photon luminescence of β-(NaYF4:Er3+/NaYF4) nanoprobe excited by 1480-nm CW laser of only 1.5-mW

    PubMed Central

    Liu, Jing; Wu, Ruitao; Li, Nana; Zhang, Xin; Zhan, Qiuqiang; He, Sailing

    2015-01-01

    It is challenging to achieve deep microscopic imaging for the strong scattering in biotissue. An efficient three-photon luminescence can effectively increase the penetration depth. Here we report that β-NaYF4: Er3+/NaYF4 UCNPs were excited by a 1480-nm CW-laser and emitted 543/653-nm light through a three-photon process. With the merit of the hexagonal crystal phase, sub-milliwatt laser power was utilized to excite the UCNP-probed cells to minimize the heating effect. The polymer-coated UCNPs were shown to be harmless to cells. The deep, high contrast in vitro microscopic imaging was implemented through an artificial phantom. Imaging depth of 800 μm was achieved using only 1.5 mW excitation and a 0.7 NA objective. The green/red emission intensities ratio after penetrating the phantom was studied, indicating that longer emission wavelength is preferred for deep multiphoton microscopy. The proposed and demonstrated β-UCNPs would have great potential in three-photon microscopy. PMID:26137385

  5. Deep, high contrast microscopic cell imaging using three-photon luminescence of β-(NaYF4:Er(3+)/NaYF4) nanoprobe excited by 1480-nm CW laser of only 1.5-mW.

    PubMed

    Liu, Jing; Wu, Ruitao; Li, Nana; Zhang, Xin; Zhan, Qiuqiang; He, Sailing

    2015-05-01

    It is challenging to achieve deep microscopic imaging for the strong scattering in biotissue. An efficient three-photon luminescence can effectively increase the penetration depth. Here we report that β-NaYF4: Er(3+)/NaYF4 UCNPs were excited by a 1480-nm CW-laser and emitted 543/653-nm light through a three-photon process. With the merit of the hexagonal crystal phase, sub-milliwatt laser power was utilized to excite the UCNP-probed cells to minimize the heating effect. The polymer-coated UCNPs were shown to be harmless to cells. The deep, high contrast in vitro microscopic imaging was implemented through an artificial phantom. Imaging depth of 800 μm was achieved using only 1.5 mW excitation and a 0.7 NA objective. The green/red emission intensities ratio after penetrating the phantom was studied, indicating that longer emission wavelength is preferred for deep multiphoton microscopy. The proposed and demonstrated β-UCNPs would have great potential in three-photon microscopy.

  6. Fully kinetic simulations of collisionless, mesothermal plasma emission: Macroscopic plume structure and microscopic electron characteristics

    NASA Astrophysics Data System (ADS)

    Hu, Yuan; Wang, Joseph

    2017-03-01

    This paper presents a fully kinetic particle particle-in-cell simulation study on the emission of a collisionless plasma plume consisting of cold beam ions and thermal electrons. Results are presented for both the two-dimensional macroscopic plume structure and the microscopic electron kinetic characteristics. We find that the macroscopic plume structure exhibits several distinctive regions, including an undisturbed core region, an electron cooling expansion region, and an electron isothermal expansion region. The properties of each region are determined by microscopic electron kinetic characteristics. The division between the undisturbed region and the cooling expansion region approximately matches the Mach line generated at the edge of the emission surface, and that between the cooling expansion region and the isothermal expansion region approximately matches the potential well established in the beam. The interactions between electrons and the potential well lead to a new, near-equilibrium state different from the initial distribution for the electrons in the isothermal expansion region. The electron kinetic characteristics in the plume are also very anisotropic. As the electron expansion process is mostly non-equilibrium and anisotropic, the commonly used assumption that the electrons in a collisionless, mesothermal plasma plume may be treated as a single equilibrium fluid in general is not valid.

  7. [Ventricular volumes determined by single-photon emission computed tomography].

    PubMed

    Katohno, E; Ono, K; Owada, K; Fujino, A; Watanabe, N; Sato, M; Konno, I; Yaoita, H; Tsuda, F; Kariyone, S

    1987-06-01

    To determine right (RV) and left ventricular (LV) volumes, a new technique was developed using ECG-gated single-photon emission computed tomography (SPECT). RV volumes of nine patients and LV volumes of 22 patients measured by SPECT and biplane contrast cineangiography were compared. In addition, volume and ejection fraction (EF) of the RV and LV were obtained by SPECT for 10 normal controls, 21 patients with old myocardial infarction (OMI), eight patients with hypertrophic cardiomyopathy (HCM) and 12 patients with dilated cardiomyopathy (DCM), and these results were compared. The intracardiac blood pool was labeled with Tc-99m sodium pertechnetate and 32 images were recorded through 180 degrees by a rotating gamma-camera. End-diastolic and end-systolic counts during 50 msec were recorded during 50 or 60 cardiac cycles. These counting data were reconstructed as tomographic images of vertical long-axial slices with thickness of a pixel without any attenuation correction. The numbers of voxels within the % cut-off level were summed, and the sum was multiplied by the one voxel volume. The cut-off level for ventricular delineation was determined as 45% by phantom studies. 1. The values obtained from SPECT and contrast angiography correlated well. 2. In normal controls, LV end-diastolic and end-systolic volumes were significantly less than those of the RV (p less than 0.05, p less than 0.001) and LVEF was significantly greater than the RVEF (p less than 0.001). 3. In OMI (single vessel disease), both end-diastolic and end-systolic volumes of the LV were significantly greater than those of normals (p less than 0.01, p less than 0.001) and LVEF was significantly less. In HCM end-systolic volumes of the RV were significantly less (p less than 0.05) than those of the normals. 4. LV volume was greater and LVEF was extremely low both in DCM and in OMI (multivessel disease) compared to that of the normals. In DCM, RV end-systolic volumes was greater and RVEF was lower than

  8. Emission in a SnS{sub 2} inverted opaline photonic crystal

    SciTech Connect

    Romanov, S. G.; Maka, T.; Sotomayor Torres, C. M.; Mueller, M.; Zentel, R.

    2001-08-06

    The photoluminescence of a dye embedded in the three-dimensional SnS{sub 2} inverted opal has been studied. Changes of the emission spectrum compared with the free-space dye emission was observed in the stop-band frequency range in accord with reflectance/transmission spectra of this photonic crystal. The angular-dependent component, due to the Bragg stop band, and the angular-independent component, which is, possibly, related to the minimum in the density of photon states, have been distinguished in the dye emission spectrum. {copyright} 2001 American Institute of Physics.

  9. Low-cost two-photon microscope with fully customized trajectories

    NASA Astrophysics Data System (ADS)

    Lodo, Stefano; Tomaselli, Alessandra; Vacchi, Carla; Ugolotti, Elena

    2010-02-01

    A modular and efficient nonlinear scanning microscope using an ultrashort pulse laser has been developed. The system is fully supervised by with an ad-hoc electronic system based on FPGA (Field Programmable Gate Array). A closed-loop control allows the compensation of scanning system non-idealities. Fully customizable trajectories can be used, in order to find best performances of the mechanical system. The electronic system is also characterized by the management of the target focusing on different focal planes and automatic research of the best focal plane. An ad-hoc software controls the system by a standard USB interface and processes images.

  10. Simulation of multi-photon emission isotopes using time-resolved SimSET multiple photon history generator

    SciTech Connect

    Chiang, Chih-Chieh; Lin, Hsin-Hon; Lin, Chang-Shiun; Chuang, Keh-Shih; Jan, Meei-Ling

    2015-07-01

    Abstract-Multiple-photon emitters, such as In-111 or Se-75, have enormous potential in the field of nuclear medicine imaging. For example, Se-75 can be used to investigate the bile acid malabsorption and measure the bile acid pool loss. The simulation system for emission tomography (SimSET) is a well-known Monte Carlo simulation (MCS) code in nuclear medicine for its high computational efficiency. However, current SimSET cannot simulate these isotopes due to the lack of modeling of complex decay scheme and the time-dependent decay process. To extend the versatility of SimSET for simulation of those multi-photon emission isotopes, a time-resolved multiple photon history generator based on SimSET codes is developed in present study. For developing the time-resolved SimSET (trSimSET) with radionuclide decay process, the new MCS model introduce new features, including decay time information and photon time-of-flight information, into this new code. The half-life of energy states were tabulated from the Evaluated Nuclear Structure Data File (ENSDF) database. The MCS results indicate that the overall percent difference is less than 8.5% for all simulation trials as compared to GATE. To sum up, we demonstrated that time-resolved SimSET multiple photon history generator can have comparable accuracy with GATE and keeping better computational efficiency. The new MCS code is very useful to study the multi-photon imaging of novel isotopes that needs the simulation of lifetime and the time-of-fight measurements. (authors)

  11. Quantifying distortions in two-photon remote focussing microscope images using a volumetric calibration specimen

    PubMed Central

    Corbett, Alexander D.; Burton, Rebecca A. B.; Bub, Gil; Salter, Patrick S.; Tuohy, Simon; Booth, Martin J.; Wilson, Tony

    2014-01-01

    Remote focussing microscopy allows sharp, in-focus images to be acquired at high speed from outside of the focal plane of an objective lens without any agitation of the specimen. However, without careful optical alignment, the advantages of remote focussing microscopy could be compromised by the introduction of depth-dependent scaling artifacts. To achieve an ideal alignment in a point-scanning remote focussing microscope, the lateral (XY) scan mirror pair must be imaged onto the back focal plane of both the reference and imaging objectives, in a telecentric arrangement. However, for many commercial objective lenses, it can be difficult to accurately locate the position of the back focal plane. This paper investigates the impact of this limitation on the fidelity of three-dimensional data sets of living cardiac tissue, specifically the introduction of distortions. These distortions limit the accuracy of sarcomere measurements taken directly from raw volumetric data. The origin of the distortion is first identified through simulation of a remote focussing microscope. Using a novel three-dimensional calibration specimen it was then possible to quantify experimentally the size of the distortion as a function of objective misalignment. Finally, by first approximating and then compensating the distortion in imaging data from whole heart rodent studies, the variance of sarcomere length (SL) measurements was reduced by almost 50%. PMID:25339910

  12. Ultra-weak photon emission from biological samples: definition, mechanisms, properties, detection and applications.

    PubMed

    Cifra, Michal; Pospíšil, Pavel

    2014-10-05

    This review attempts to summarize molecular mechanisms, spectral and intensity properties, detection techniques and applications of ultra-weak photon emission. Ultra-weak photon emission is the chemiluminescence from biological systems where electronically excited species are formed during oxidative metabolic or oxidative stress processes. It is generally accepted that photons are emitted (1) at near UVA, visible, and near IR spectral ranges from 350 to 1300nm and (2) at the intensity of photon emission in the range of several units to several hundreds (oxidative metabolic process) and several hundreds to several thousands (oxidative stress process) photons s(-1)cm(-2). Current development in detection using low-noise photomultiplier tubes and imaging using highly sensitive charge coupled device cameras allows temporal and spatial visualization of oxidative metabolic or oxidative stress processes, respectively. As the phenomenon of ultra-weak photon emission reflects oxidative metabolic or oxidative stress processes, it can be widely used as a non-invasive tool for monitoring of the physiological state of biological systems.

  13. Method to quantify accuracy of position feedback signals of a three-dimensional two-photon laser-scanning microscope

    PubMed Central

    Kummer, Michael; Kirmse, Knut; Witte, Otto W.; Haueisen, Jens; Holthoff, Knut

    2015-01-01

    Two-photon laser-scanning microscopy enables to record neuronal network activity in three-dimensional space while maintaining single-cellular resolution. One of the proposed approaches combines galvanometric x-y scanning with piezo-driven objective movements and employs hardware feedback signals for position monitoring. However, readily applicable methods to quantify the accuracy of those feedback signals are currently lacking. Here we provide techniques based on contact-free laser reflection and laser triangulation for the quantification of positioning accuracy of each spatial axis. We found that the lateral feedback signals are sufficiently accurate (defined as <2.5 µm) for a wide range of scan trajectories and frequencies. We further show that axial positioning accuracy does not only depend on objective acceleration and mass but also its geometry. We conclude that the introduced methods allow a reliable quantification of position feedback signals in a cost-efficient, easy-to-install manner and should be applicable for a wide range of two-photon laser scanning microscopes. PMID:26504620

  14. Single-photon pulse propagation in and into a medium of two-level atoms: Microscopic Fresnel equations

    SciTech Connect

    Berman, P. R.; Ooi, C. H. Raymond

    2011-12-15

    The propagation of an off-resonant, single-photon pulse in and into a medium of two-level atoms is considered. When the pulse is launched from within the medium, there are two propagation speeds, neither of which is the normal group velocity. For densities as small as 10{sup 11} atoms/cm{sup 3} and detunings of order 10{sup 11} s{sup -1}, both propagation speeds approach one half the speed of light in vacuum. Moreover, rather remarkably, there are Rabi oscillations between the field and atomic excitation, even for this single-photon pulse. In contrast, for a pulse sent into the medium, the atom-field system remains adiabatically in a dressed state that propagates with the normal group velocity. In the limit that the index of refraction is approximately equal to unity, we obtain the Fresnel equations for the reflection and transmission coefficients based on this microscopic model. The transmission coefficient differs from the conventional result owing to the fact that we quantize the field in free space.

  15. Modulation of the pupil function of microscope objective lens for multifocal multi-photon microscopy using a spatial light modulator

    NASA Astrophysics Data System (ADS)

    Matsumoto, Naoya; Okazaki, Shigetoshi; Takamoto, Hisayoshi; Inoue, Takashi; Terakawa, Susumu

    2014-02-01

    We propose a method for high precision modulation of the pupil function of a microscope objective lens to improve the performance of multifocal multi-photon microscopy (MMM). To modulate the pupil function, we adopt a spatial light modulator (SLM) and place it at the conjugate position of the objective lens. The SLM can generate an arbitrary number of spots to excite the multiple fluorescence spots (MFS) at the desired positions and intensities by applying an appropriate computer-generated hologram (CGH). This flexibility allows us to control the MFS according to the photobleaching level of a fluorescent protein and phototoxicity of a specimen. However, when a large number of excitation spots are generated, the intensity distribution of the MFS is significantly different from the one originally designed due to misalignment of the optical setup and characteristics of the SLM. As a result, the image of a specimen obtained using laser scanning for the MFS has block noise segments because the SLM could not generate a uniform MFS. To improve the intensity distribution of the MFS, we adaptively redesigned the CGH based on the observed MFS. We experimentally demonstrate an improvement in the uniformity of a 10 × 10 MFS grid using a dye solution. The simplicity of the proposed method will allow it to be applied for calibration of MMM before observing living tissue. After the MMM calibration, we performed laser scanning with two-photon excitation to observe a real specimen without detecting block noise segments.

  16. Method to quantify accuracy of position feedback signals of a three-dimensional two-photon laser-scanning microscope.

    PubMed

    Kummer, Michael; Kirmse, Knut; Witte, Otto W; Haueisen, Jens; Holthoff, Knut

    2015-10-01

    Two-photon laser-scanning microscopy enables to record neuronal network activity in three-dimensional space while maintaining single-cellular resolution. One of the proposed approaches combines galvanometric x-y scanning with piezo-driven objective movements and employs hardware feedback signals for position monitoring. However, readily applicable methods to quantify the accuracy of those feedback signals are currently lacking. Here we provide techniques based on contact-free laser reflection and laser triangulation for the quantification of positioning accuracy of each spatial axis. We found that the lateral feedback signals are sufficiently accurate (defined as <2.5 µm) for a wide range of scan trajectories and frequencies. We further show that axial positioning accuracy does not only depend on objective acceleration and mass but also its geometry. We conclude that the introduced methods allow a reliable quantification of position feedback signals in a cost-efficient, easy-to-install manner and should be applicable for a wide range of two-photon laser scanning microscopes.

  17. Dynamic performance of microelectromechanical systems deformable mirrors for use in an active/adaptive two-photon microscope

    NASA Astrophysics Data System (ADS)

    Archer-Zhang, Christian Chunzi; Foster, Warren B.; Downey, Ryan D.; Arrasmith, Christopher L.; Dickensheets, David L.

    2016-12-01

    Active optics such as deformable mirrors can be used to control both focal depth and aberrations during scanning laser microscopy. If the focal depth can be changed dynamically during scanning, then imaging of oblique surfaces becomes possible. If aberrations can be corrected dynamically during scanning, an image can be optimized throughout the field of view. Here, we characterize the speed and dynamic precision of a Boston Micromachines Corporation Multi-DM 140 element aberration correction mirror and a Revibro Optics 4-zone focus control mirror to assess suitability for use in an active and adaptive two-photon microscope. Tests for the multi-DM include both step response and sinusoidal frequency sweeps of specific Zernike modes (defocus, spherical aberration, coma, astigmatism, and trefoil). We find wavefront error settling times for mode amplitude steps as large as 400 nm to be less than 52 μs, with 3 dB frequencies ranging from 6.5 to 10 kHz. The Revibro Optics mirror was tested for step response only, with wavefront error settling time less than 80 μs for defocus steps up to 3000 nm, and less than 45 μs for spherical aberration steps up to 600 nm. These response speeds are sufficient for intrascan correction at scan rates typical of two-photon microscopy.

  18. Broadband enhancement of spontaneous emission in a photonic-plasmonic structure.

    PubMed

    Zhu, Xiaolong; Xie, Fengxian; Shi, Lei; Liu, Xiaohan; Mortensen, N Asger; Xiao, Sanshui; Zi, Jian; Choy, Wallace

    2012-06-01

    We demonstrate that a broadband enhancement of spontaneous emission can be achieved within a photonic-plasmonic structure. The structure can strongly modify the spontaneous emission by exciting plasmonic modes. Because of the excited plasmonic modes, an enhancement up to 30 times is observed, leading to a 4 times broader emission spectrum. The reflectance measurement and the finite-difference time-domain simulation are carried out to support these results.

  19. Intracellular nanomanipulation by a photonic-force microscope with real-time acquisition of a 3D stiffness matrix

    NASA Astrophysics Data System (ADS)

    Bertseva, E.; Singh, A. S. G.; Lekki, J.; Thévenaz, P.; Lekka, M.; Jeney, S.; Gremaud, G.; Puttini, S.; Nowak, W.; Dietler, G.; Forró, L.; Unser, M.; Kulik, A. J.

    2009-07-01

    A traditional photonic-force microscope (PFM) results in huge sets of data, which requires tedious numerical analysis. In this paper, we propose instead an analog signal processor to attain real-time capabilities while retaining the richness of the traditional PFM data. Our system is devoted to intracellular measurements and is fully interactive through the use of a haptic joystick. Using our specialized analog hardware along with a dedicated algorithm, we can extract the full 3D stiffness matrix of the optical trap in real time, including the off-diagonal cross-terms. Our system is also capable of simultaneously recording data for subsequent offline analysis. This allows us to check that a good correlation exists between the classical analysis of stiffness and our real-time measurements. We monitor the PFM beads using an optical microscope. The force-feedback mechanism of the haptic joystick helps us in interactively guiding the bead inside living cells and collecting information from its (possibly anisotropic) environment. The instantaneous stiffness measurements are also displayed in real time on a graphical user interface. The whole system has been built and is operational; here we present early results that confirm the consistency of the real-time measurements with offline computations.

  20. Apertureless scanning microscope probe as a detector of semiconductor laser emission

    SciTech Connect

    Dunaevskiy, Mikhail; Dontsov, Anton; Monakhov, Andrei; Alekseev, Prokhor; Titkov, Alexander; Baranov, Alexei; Girard, Paul; Arinero, Richard; Teissier, Roland

    2015-04-27

    An operating semiconductor laser has been studied using a scanning probe microscope. A shift of the resonance frequency of probe that is due to its heating by laser radiation has been analyzed. The observed shift is proportional to the absorbed radiation and can be used to measure the laser near field or its output power. A periodical dependence of the measured signal has been observed as a function of distance between the probe and the surface of the laser due to the interference of the outgoing and cantilever-reflected waves. Due to the multiple reflections resulting in the interference, the light absorption by the probe cantilever is greatly enhanced compared with a single pass case. Interaction of infrared emission of a diode laser with different probes has been studied.

  1. Acquisition of a High Resolution Field Emission Scanning Electron Microscope for the Analysis of Returned Samples

    NASA Technical Reports Server (NTRS)

    Nittler, Larry R.

    2003-01-01

    This grant furnished funds to purchase a state-of-the-art scanning electron microscope (SEM) to support our analytical facilities for extraterrestrial samples. After evaluating several instruments, we purchased a JEOL 6500F thermal field emission SEM with the following analytical accessories: EDAX energy-dispersive x-ray analysis system with fully automated control of instrument and sample stage; EDAX LEXS wavelength-dispersive x-ray spectrometer for high sensitivity light-element analysis; EDAX/TSL electron backscatter diffraction (EBSD) system with software for phase identification and crystal orientation mapping; Robinson backscatter electron detector; and an in situ micro-manipulator (Kleindiek). The total price was $550,000 (with $150,000 of the purchase supported by Carnegie institution matching funds). The microscope was delivered in October 2002, and most of the analytical accessories were installed by January 2003. With the exception of the wavelength spectrometer (which has been undergoing design changes) everything is working well and the SEM is in routine use in our laboratory.

  2. Femtosecond photoelectron point projection microscope

    SciTech Connect

    Quinonez, Erik; Handali, Jonathan; Barwick, Brett

    2013-10-15

    By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron microscope. These models show a significant increase in temporal resolution when comparing to ultrafast electron microscopes based on conventional designs. We also model the microscopes spectroscopic abilities to capture ultrafast phenomena such as the photon induced near field effect.

  3. Factors affecting ultraviolet-A photon emission from β-irradiated human keratinocyte cells.

    PubMed

    Le, M; Mothersill, C E; Seymour, C B; Ahmad, S B; Armstrong, A; Rainbow, A J; McNeill, F E

    2015-08-21

    The luminescence intensity of 340±5 nm photons emitted from HaCaT (human keratinocyte) cells was investigated using a single-photon-counting system during cellular exposure to (90)Y β-particles. Multiple factors were assessed to determine their influence upon the quantity and pattern of photon emission from β-irradiated cells. Exposure of 1 x 10(4) cells/5 mL to 703 μCi resulted in maximum UVA photoemission at 44.8 x 10(3)±2.5 x 10(3) counts per second (cps) from live HaCaT cells (background: 1-5 cps); a 16-fold increase above cell-free controls. Significant biophoton emission was achieved only upon stimulation and was also dependent upon presence of cells. UVA luminescence was measured for (90)Y activities 14 to 703 μCi where a positive relationship between photoemission and (90)Y activity was observed. Irradiation of live HaCaT cells plated at various densities produced a distinct pattern of emission whereby luminescence increased up to a maximum at 1 x 10(4) cells/5 mL and thereafter decreased. However, this result was not observed in the dead cell population. Both live and dead HaCaT cells were irradiated and were found to demonstrate different rates of photon emission at low β activities (⩽400 μCi). Dead cells exhibited greater photon emission rates than live cells which may be attributable to metabolic processes taking place to modulate the photoemissive effect. The results indicate that photon emission from HaCaT cells is perturbed by external stimulation, is dependent upon the activity of radiation delivered, the density of irradiated cells, and cell viability. It is postulated that biophoton emission may be modulated by a biological or metabolic process.

  4. Factors affecting ultraviolet-A photon emission from β-irradiated human keratinocyte cells

    NASA Astrophysics Data System (ADS)

    Le, M.; Mothersill, C. E.; Seymour, C. B.; Ahmad, S. B.; Armstrong, A.; Rainbow, A. J.; McNeill, F. E.

    2015-08-01

    The luminescence intensity of 340+/- 5 nm photons emitted from HaCaT (human keratinocyte) cells was investigated using a single-photon-counting system during cellular exposure to 90Y β-particles. Multiple factors were assessed to determine their influence upon the quantity and pattern of photon emission from β-irradiated cells. Exposure of 1× {{10}4} cells/5 mL to 703 μCi resulted in maximum UVA photoemission at 44.8× {{10}3}+/- 2.5× {{10}3} counts per second (cps) from live HaCaT cells (background: 1-5 cps); a 16-fold increase above cell-free controls. Significant biophoton emission was achieved only upon stimulation and was also dependent upon presence of cells. UVA luminescence was measured for 90Y activities 14 to 703 μCi where a positive relationship between photoemission and 90Y activity was observed. Irradiation of live HaCaT cells plated at various densities produced a distinct pattern of emission whereby luminescence increased up to a maximum at 1× {{10}4} cells/5 mL and thereafter decreased. However, this result was not observed in the dead cell population. Both live and dead HaCaT cells were irradiated and were found to demonstrate different rates of photon emission at low β activities (⩽400 μCi). Dead cells exhibited greater photon emission rates than live cells which may be attributable to metabolic processes taking place to modulate the photoemissive effect. The results indicate that photon emission from HaCaT cells is perturbed by external stimulation, is dependent upon the activity of radiation delivered, the density of irradiated cells, and cell viability. It is postulated that biophoton emission may be modulated by a biological or metabolic process.

  5. Spontaneous ultraweak photon emission imaging of oxidative metabolic processes in human skin: effect of molecular oxygen and antioxidant defense system

    NASA Astrophysics Data System (ADS)

    Rastogi, Anshu; Pospíšil, Pavel

    2011-09-01

    All living organisms emit spontaneous ultraweak photon emission as a result of cellular metabolic processes. In this study, the involvement of reactive oxygen species (ROS) formed as the byproduct of oxidative metabolic processes in spontaneous ultraweak photon emission was studied in human hand skin. The effect of molecular oxygen and ROS scavengers on spontaneous ultraweak photon emission from human skin was monitored using a highly sensitive photomultiplier tube and charged coupled device camera. When spontaneous ultraweak photon emission was measured under anaerobic conditions, the photon emission was decreased, whereas under hyperaerobic condition the enhancement in photon emission was observed. Spontaneous ultraweak photon emission measured after topical application of glutathione, α-tocopherol, ascorbate, and coenzyme Q10 was observed to be decreased. These results reveal that ROS formed during the cellular metabolic processes in the epidermal cells play a significant role in the spontaneous ultraweak photon emission. It is proposed that spontaneous ultraweak photon emission can be used as a noninvasive tool for the temporal and spatial monitoring of the oxidative metabolic processes and intrinsic antioxidant system in human skin.

  6. Detection efficiency and spatial resolution of the SIRAD ion electron emission microscope

    NASA Astrophysics Data System (ADS)

    Bisello, D.; Giubilato, P.; Kaminsky, A.; Mattiazzo, S.; Nigro, M.; Pantano, D.; Silvestrin, L.; Tessaro, M.; Wyss, J.; Bertazzoni, S.; Mongiardo, L.; Salmeri, M.; Salsano, A.

    2009-06-01

    An axial ion electron emission microscope (IEEM) has been built at the SIRAD irradiation facility at the 15 MV Tandem accelerator of INFN Legnaro National Laboratory (Padova, Italy) to obtain a micrometric sensitivity map to single event effects (SEE) of electronic devices. In this contribution we report on two experiments performed with the IEEM. Si 3N 4 ultra-thin membranes with a gold deposition were placed on the device under test (DUT) to ensure a uniform and abundant secondary electron emission In the first experiment we measured an IEEM ion detection efficiency of 83% with a 58Ni (220 MeV) beam, in good agreement with the expected value. The second experiment allowed us to estimate the lateral resolution of the IEEM. The positions of ion induced single event upsets (SEU) in a synchronous dynamic random access memory (SDRAM), used as a reference target, were compared with the corresponding ion impact points reconstructed by the IEEM. The result (FWHM ˜4.4 μm with a 79Br beam of 214 MeV) is encouraging because of the residual presence of distortions of the image and mechanical vibrations.

  7. Broadband Enhancement of Spontaneous Emission in Two-Dimensional Semiconductors Using Photonic Hypercrystals.

    PubMed

    Galfsky, Tal; Sun, Zheng; Considine, Christopher R; Chou, Cheng-Tse; Ko, Wei-Chun; Lee, Yi-Hsien; Narimanov, Evgenii E; Menon, Vinod M

    2016-08-10

    The low quantum yield observed in two-dimensional semiconductors of transition metal dichalcogenides (TMDs) has motivated the quest for approaches that can enhance the light emission from these systems. Here, we demonstrate broadband enhancement of spontaneous emission and increase in Raman signature from archetype two-dimensional semiconductors: molybdenum disulfide (MoS2) and tungsten disulfide (WS2) by placing the monolayers in the near field of a photonic hypercrystal having hyperbolic dispersion. Hypercrystals are characterized by a large broadband photonic density of states due to hyperbolic dispersion while having enhanced light in/out coupling by a subwavelength photonic crystal lattice. This dual advantage is exploited here to enhance the light emission from the 2D TMDs and can be utilized for developing light emitters and solar cells using two-dimensional semiconductors.

  8. Quantum-confined single photon emission at room temperature from SiC tetrapods.

    PubMed

    Castelletto, Stefania; Bodrog, Zoltán; Magyar, Andrew P; Gentle, Angus; Gali, Adam; Aharonovich, Igor

    2014-09-07

    Controlled engineering of isolated solid state quantum systems is one of the most prominent goals in modern nanotechnology. In this letter we demonstrate a previously unknown quantum system namely silicon carbide tetrapods. The tetrapods have a cubic polytype core (3C) and hexagonal polytype legs (4H)--a geometry that creates spontaneous polarization within a single tetrapod. Modeling of the tetrapod structures predicts that a bound exciton should exist at the 3C-4H interface. The simulations are confirmed by the observation of fully polarized and narrowband single photon emission from the tetrapods at room temperature. The single photon emission provides important insights into understanding the quantum confinement effects in non-spherical nanostructures. Our results pave the way to a new class of crystal phase nanomaterials that exhibit single photon emission at room temperature and therefore are suitable for sensing, quantum information and nanophotonics.

  9. Design of highly efficient metallo-dielectric patch antennas for single-photon emission.

    PubMed

    Bigourdan, F; Marquier, F; Hugonin, J-P; Greffet, J-J

    2014-02-10

    Quantum emitters such as NV-centers or quantum dots can be used as single-photon sources. To improve their performance, they can be coupled to microcavities or nano-antennas. Plasmonic antennas offer an appealing solution as they can be used with broadband emitters. When properly designed, these antennas funnel light into useful modes, increasing the emission rate and the collection of single-photons. Yet, their inherent metallic losses are responsible for very low radiative efficiencies. Here, we introduce a new design of directional, metallo-dielectric, optical antennas with a Purcell factor of 150, a total efficiency of 74% and a collection efficiency of emitted photons of 99%.

  10. Surface acoustic wave regulated single photon emission from a coupled quantum dot-nanocavity system

    NASA Astrophysics Data System (ADS)

    Weiß, M.; Kapfinger, S.; Reichert, T.; Finley, J. J.; Wixforth, A.; Kaniber, M.; Krenner, H. J.

    2016-07-01

    A coupled quantum dot-nanocavity system in the weak coupling regime of cavity-quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a fSAW ≃ 800 MHz surface acoustic wave. When the system is brought to resonance by the sound wave, light-matter interaction is strongly increased by the Purcell effect. This leads to a precisely timed single photon emission as confirmed by the second order photon correlation function, g(2). All relevant frequencies of our experiment are faithfully identified in the Fourier transform of g(2), demonstrating high fidelity regulation of the stream of single photons emitted by the system.

  11. A High Performance, Cost-Effective, Open-Source Microscope for Scanning Two-Photon Microscopy that Is Modular and Readily Adaptable

    PubMed Central

    Rosenegger, David G.; Tran, Cam Ha T.; LeDue, Jeffery; Zhou, Ning; Gordon, Grant R.

    2014-01-01

    Two-photon laser scanning microscopy has revolutionized the ability to delineate cellular and physiological function in acutely isolated tissue and in vivo. However, there exist barriers for many laboratories to acquire two-photon microscopes. Additionally, if owned, typical systems are difficult to modify to rapidly evolving methodologies. A potential solution to these problems is to enable scientists to build their own high-performance and adaptable system by overcoming a resource insufficiency. Here we present a detailed hardware resource and protocol for building an upright, highly modular and adaptable two-photon laser scanning fluorescence microscope that can be used for in vitro or in vivo applications. The microscope is comprised of high-end componentry on a skeleton of off-the-shelf compatible opto-mechanical parts. The dedicated design enabled imaging depths close to 1 mm into mouse brain tissue and a signal-to-noise ratio that exceeded all commercial two-photon systems tested. In addition to a detailed parts list, instructions for assembly, testing and troubleshooting, our plan includes complete three dimensional computer models that greatly reduce the knowledge base required for the non-expert user. This open-source resource lowers barriers in order to equip more laboratories with high-performance two-photon imaging and to help progress our understanding of the cellular and physiological function of living systems. PMID:25333934

  12. Quantum-confined single photon emission at room temperature from SiC tetrapods

    NASA Astrophysics Data System (ADS)

    Castelletto, Stefania; Bodrog, Zoltán; Magyar, Andrew P.; Gentle, Angus; Gali, Adam; Aharonovich, Igor

    2014-08-01

    Controlled engineering of isolated solid state quantum systems is one of the most prominent goals in modern nanotechnology. In this letter we demonstrate a previously unknown quantum system namely silicon carbide tetrapods. The tetrapods have a cubic polytype core (3C) and hexagonal polytype legs (4H) - a geometry that creates spontaneous polarization within a single tetrapod. Modeling of the tetrapod structures predicts that a bound exciton should exist at the 3C-4H interface. The simulations are confirmed by the observation of fully polarized and narrowband single photon emission from the tetrapods at room temperature. The single photon emission provides important insights into understanding the quantum confinement effects in non-spherical nanostructures. Our results pave the way to a new class of crystal phase nanomaterials that exhibit single photon emission at room temperature and therefore are suitable for sensing, quantum information and nanophotonics.Controlled engineering of isolated solid state quantum systems is one of the most prominent goals in modern nanotechnology. In this letter we demonstrate a previously unknown quantum system namely silicon carbide tetrapods. The tetrapods have a cubic polytype core (3C) and hexagonal polytype legs (4H) - a geometry that creates spontaneous polarization within a single tetrapod. Modeling of the tetrapod structures predicts that a bound exciton should exist at the 3C-4H interface. The simulations are confirmed by the observation of fully polarized and narrowband single photon emission from the tetrapods at room temperature. The single photon emission provides important insights into understanding the quantum confinement effects in non-spherical nanostructures. Our results pave the way to a new class of crystal phase nanomaterials that exhibit single photon emission at room temperature and therefore are suitable for sensing, quantum information and nanophotonics. Electronic supplementary information (ESI) available

  13. Three-dimensional image cytometer based on a high-speed two-photon scanning microscope

    NASA Astrophysics Data System (ADS)

    Kim, Ki H.; Stitt, Molly S.; Hendricks, Carrie A.; Almeida, Karen H.; Engelward, Bevin P.; So, Peter T. C.

    2001-04-01

    We developed a 3-D image cytometer based on two-photon scanning microscopy. The system keeps the inherent advantages from two-photon scanning microscopy: (1) The ability of imaging thick tissue samples up to a few hundred micrometers, (2) The ability to study tissue structures with subcellular resolution, (3) The ability to monitor tissue biochemistry and metabolism, and (4) The reduction of specimen photobleaching and photodamage. Therefore, 3-D image cytometer has the ability to characterize multiple cell layer specimens, in contrast with 2-D image cytometer where only single cell layer samples can be imaged. 3-D image cytometry increases its frame rate by adapting a polygonal mirror scanner and high-speed photomultiplier tubes. The current frame rate is 13 frames per second. High throughput rate is achieved by imaging multiple cell layer specimens in 3-D at a high frame rate. The throughput rate of this system is dependent on the choice of objective lenses, specimen properties, and the speed of computer-controlled specimen stage. It can be up to approximately 100 cells per second which is comparable with that of 2-D image cytometers. With the high throughput rate and deep tissue imaging capability, 3-D image cytometer has the potential for the detection of rare cellular events inside living, intact tissues. A promising application of this 3-D image cytometer is the study of mitotic recombination in tissues. Mitotic recombination is a mechanism for genetic change. Therefore it is one of causes for carcinogenesis. However, the study of this process is difficult because recombination event is rare and it occurs at a rate of one cell in 105 cells. The new method for the study is (1) to engineer transgenic mice whose cells will express fluorescence in the presence of mitotic recombination, (2) to detect cells which have undergone mitotic recombination with 3-D image cytometry. The estimated time required to quantify spontaneous recombination rate is approximately

  14. Emission of Photons and Relativistic Axions from Axion stars

    NASA Astrophysics Data System (ADS)

    Mohapatra, Abhishek; Braaten, Eric; Zhang, Hong

    2017-01-01

    The number of nonrelativistic axions can be changed by inelastic reactions that produce relativistic axions or photons. Any even number of nonrelativistic axions can scatter inelastically into two relativistic axions. Any odd number of axions can annihilate into two photons. This reaction produces a monochromatic radio-frequency signal at an odd-integer harmonic of the fundamental frequency set by the axion mass. The loss rates of axions from axion stars through these inelastic relations are calculated using the framework of a nonrelativistic effective field theory. Odd-integer harmonics of a fundamental radio-frequency signal provide a unique signature for collapsing axion stars or any dense configuration of axions. Supported by NSF and the DOE.

  15. Photon scattering from /sup 90/Zr below neutron emission threshold

    SciTech Connect

    Alarcon, R.; Laszewski, R.M.; Nathan, A.M.; Hoblit, S.D.

    1987-09-01

    Cross sections for elastic and inelastic scattering of monochromatic photons from /sup 90/Zr have been measured for excitations between 8.1 and 10.5 MeV. The observed inelastic cross sections sigma/sub el//sub el//sub i/ correspond to transitions to the 02 , 21 , 22 , and 23 states. A simple theoretical description using the Brink-Axel hypothesis and estimates of the level density and of the total photon interaction cross section sigma/sub el//sub T/ gives predictions for the individual cross sections that are in very good agreement with data. The E1 strength corresponding to the inferred sigma/sub el//sub T/ amounts to about B(E1up-arrow)--0.5 eS fmS for the energy range under consideration.

  16. Spectral discrimination between healthy people and cold patients using spontaneous photon emission

    PubMed Central

    Yang, Meina; Pang, Jiangxiang; Liu, Junyan; Liu, Yanli; Fan, Hua; Han, Jinxiang

    2015-01-01

    In this paper, ultra-weak photon emission (UPE) was used to distinguish cold patients from healthy subjects. The UPE intensity of fingertips of two hands from healthy subjects and cold patients was measured using a two-hand UPE detecting system and a group of cut-off filters. We found a significant difference in the maximum spectral peak and photon emission ratio between the filter of 550nm and 495nm, which can be used in distinguish cold patients from healthy people. Methods and results in this work could be useful for developing a new optical diagnostic tool for early disease diagnosis in the future. PMID:25909016

  17. Emission polarization control in semiconductor quantum dots coupled to a photonic crystal microcavity.

    PubMed

    Gallardo, E; Martínez, L J; Nowak, A K; van der Meulen, H P; Calleja, J M; Tejedor, C; Prieto, I; Granados, D; Taboada, A G; García, J M; Postigo, P A

    2010-06-07

    We study the optical emission of single semiconductor quantum dots weakly coupled to a photonic-crystal micro-cavity. The linearly polarized emission of a selected quantum dot changes continuously its polarization angle, from nearly perpendicular to the cavity mode polarization at large detuning, to parallel at zero detuning, and reversing sign for negative detuning. The linear polarization rotation is qualitatively interpreted in terms of the detuning dependent mixing of the quantum dot and cavity states. The present result is relevant to achieve continuous control of the linear polarization in single photon emitters.

  18. Plasmonic Structures for CMOS Photonics and Control of Spontaneous Emission

    DTIC Science & Technology

    2013-04-01

    record low coupling loss from silicon-on-insulator waveguides to dielectrically-loaded surface plasmon polariton waveguides with 1 dB/transition...loaded surface plasmon polariton waveguides with < 1 dB/transition insertion loss, iii. efficient coupling from silicon-on-insulator waveguides to...Plasmonic  and  Silicon  Photonic  Waveguides In this work, we demonstrate dielectric-loaded surface plasmon polariton (DLSPP) waveguides

  19. Photon emission of extremal Kerr-Newman black holes

    NASA Astrophysics Data System (ADS)

    Wei, Shao-Wen; Gu, Bao-Min; Wang, Yong-Qiang; Liu, Yu-Xiao

    2017-02-01

    In this paper, we deal with the null geodesics extending from the near-horizon region out to a distant observatory in an extremal Kerr-Newman black hole background. In particular, using the matched asymptotic expansion method, we analytically solve the null geodesics near the superradiant bound in the form of algebraic equations. For the case that the photon trajectories are limited in the equatorial plane, the shifts in the azimuthal angle and time are obtained.

  20. 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.

  1. Optical spectral analysis of ultra-weak photon emission from tissue culture and yeast cells

    NASA Astrophysics Data System (ADS)

    Nerudová, Michaela; Červinková, Kateřina; Hašek, Jiří; Cifra, Michal

    2015-01-01

    Optical spectral analysis of the ultra-weak photon emission (UPE) could be utilized for non-invasive diagnostic of state of biological systems and for elucidation of underlying mechanisms of UPE generation. Optical spectra of UPE from differentiated HL-60 cells and yeast cells (Saccharomyces cerevisiae) were investigated. Induced photon emission of neutrophil-like cells and spontaneous photon emission of yeast cells were measured using highly sensitive photomultiplier module Hamamatsu H7360-01 in a thermally regulated light-tight chamber. The respiratory burst of neutrophil-like HL-60 cells was induced with the PMA (phorbol 12-myristate, 13-acetate). PMA activates an assembly of NADPH oxidase, which induces a rapid formation of reactive oxygen species (ROS). Long-pass edge filters (wavelength 350, from 400 to 600 with 25 nm resolution and 650 nm) were used for optical spectral analysis. Propagation of error of indirect measurements and standard deviation were used to assess reliability of the measured spectra. Results indicate that the photon emission from both cell cultures is detectable in the six from eight examined wavelength ranges with different percentage distribution of cell suspensions, particularly 450-475, 475-500, 500-525, 525-550, 550-575 and 575-600 nm. The wavelength range of spectra from 450 to 550 nm coincides with the range of photon emission from triplet excited carbonyls (350-550 nm). The both cells cultures emitted photons in wavelength range from 550 to 600 nm but this range does not correspond with any known emitter. To summarize, we have demonstrated a clear difference in the UPE spectra between two organisms using rigorous methodology and error analysis.

  2. Biocompatible and photostable AIE dots with red emission for in vivo two-photon bioimaging.

    PubMed

    Wang, Dan; Qian, Jun; Qin, Wei; Qin, Anjun; Tang, Ben Zhong; He, Sailing

    2014-03-17

    Bioimaging systems with cytocompatibility, photostability, red fluorescence, and optical nonlinearity are in great demand. Herein we report such a bioimaging system. Integration of tetraphenylethene (T), triphenylamine (T), and fumaronitrile (F) units yielded adduct TTF with aggregation-induced emission (AIE). Nanodots of the AIE fluorogen with efficient red emission were fabricated by encapsulating TTF with phospholipid. The AIE dots enabled three-dimensional dynamic imaging with high resolution in blood vessels of mouse brain under two-photon excitation.

  3. Biocompatible and Photostable AIE Dots with Red Emission for In Vivo Two-Photon Bioimaging

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Qian, Jun; Qin, Wei; Qin, Anjun; Tang, Ben Zhong; He, Sailing

    2014-03-01

    Bioimaging systems with cytocompatibility, photostability, red fluorescence, and optical nonlinearity are in great demand. Herein we report such a bioimaging system. Integration of tetraphenylethene (T), triphenylamine (T), and fumaronitrile (F) units yielded adduct TTF with aggregation-induced emission (AIE). Nanodots of the AIE fluorogen with efficient red emission were fabricated by encapsulating TTF with phospholipid. The AIE dots enabled three-dimensional dynamic imaging with high resolution in blood vessels of mouse brain under two-photon excitation.

  4. Spontaneous emission enhancement and saturable absorption of colloidal quantum dots coupled to photonic crystal cavity.

    PubMed

    Gupta, Shilpi; Waks, Edo

    2013-12-02

    We demonstrate spontaneous emission rate enhancement and saturable absorption of cadmium selenide colloidal quantum dots coupled to a nanobeam photonic crystal cavity. We perform time-resolved lifetime measurements and observe an average enhancement of 4.6 for the spontaneous emission rate of quantum dots located at the cavity as compared to those located on an unpatterned surface. We also demonstrate that the cavity linewidth narrows with increasing pump intensity due to quantum dot saturable absorption.

  5. Classical microscopic theory of dispersion, emission and absorption of light in dielectrics. Classical microscopic theory of dielectric susceptibility

    NASA Astrophysics Data System (ADS)

    Carati, Andrea; Galgani, Luigi

    2014-10-01

    This paper is a continuation of a recent one in which, apparently for the first time, the existence of polaritons in ionic crystals was proven in a microscopic electrodynamic theory. This was obtained through an explicit computation of the dispersion curves. Here the main further contribution consists in studying electric susceptibility, from which the spectrum can be inferred. We show how susceptibility is obtained by the Green-Kubo methods of Hamiltonian statistical mechanics, and give for it a concrete expression in terms of time-correlation functions. As in the previous paper, here too we work in a completely classical framework, in which the electrodynamic forces acting on the charges are all taken into account, both the retarded forces and the radiation reaction ones. So, in order to apply the methods of statistical mechanics, the system has to be previously reduced to a Hamiltonian one. This is made possible in virtue of two global properties of classical electrodynamics, namely, the Wheeler-Feynman identity and the Ewald resummation properties, the proofs of which were already given for ordered system. The second contribution consists in formulating the theory in a completely general way, so that in principle it applies also to disordered systems such as glasses, or liquids or gases, provided the two general properties mentioned above continue to hold. A first step in this direction is made here by providing a completely general proof of the Wheeler-Feynman identity, which is shown to be the counterpart of a general causality property of classical electrodynamics. Finally it is shown how a line spectrum can appear at all in classical systems, as a counterpart of suitable stability properties of the motions, with a broadening due to a coexistence of chaoticity. The relevance of some recent results of the theory of dynamical systems in this connection is also pointed out.

  6. Ultrafast Room-Temperature Single Photon Emission from Quantum Dots Coupled to Plasmonic Nanocavities.

    PubMed

    Hoang, Thang B; Akselrod, Gleb M; Mikkelsen, Maiken H

    2016-01-13

    Efficient and bright single photon sources at room temperature are critical components for quantum information systems such as quantum key distribution, quantum state teleportation, and quantum computation. However, the intrinsic radiative lifetime of quantum emitters is typically ∼10 ns, which severely limits the maximum single photon emission rate and thus entanglement rates. Here, we demonstrate the regime of ultrafast spontaneous emission (∼10 ps) from a single quantum emitter coupled to a plasmonic nanocavity at room temperature. The nanocavity integrated with a single colloidal semiconductor quantum dot produces a 540-fold decrease in the emission lifetime and a simultaneous 1900-fold increase in the total emission intensity. At the same time, the nanocavity acts as a highly efficient optical antenna directing the emission into a single lobe normal to the surface. This plasmonic platform is a versatile geometry into which a variety of other quantum emitters, such as crystal color centers, can be integrated for directional, room-temperature single photon emission rates exceeding 80 GHz.

  7. Continuous-Wave Stimulated Emission Depletion Microscope for Imaging Actin Cytoskeleton in Fixed and Live Cells

    PubMed Central

    Neupane, Bhanu; Jin, Tao; Mellor, Liliana F.; Loboa, Elizabeth G.; Ligler, Frances S.; Wang, Gufeng

    2015-01-01

    Stimulated emission depletion (STED) microscopy provides a new opportunity to study fine sub-cellular structures and highly dynamic cellular processes, which are challenging to observe using conventional optical microscopy. Using actin as an example, we explored the feasibility of using a continuous wave (CW)-STED microscope to study the fine structure and dynamics in fixed and live cells. Actin plays an important role in cellular processes, whose functioning involves dynamic formation and reorganization of fine structures of actin filaments. Frequently used confocal fluorescence and STED microscopy dyes were employed to image fixed PC-12 cells (dyed with phalloidin- fluorescein isothiocyante) and live rat chondrosarcoma cells (RCS) transfected with actin-green fluorescent protein (GFP). Compared to conventional confocal fluorescence microscopy, CW-STED microscopy shows improved spatial resolution in both fixed and live cells. We were able to monitor cell morphology changes continuously; however, the number of repetitive analyses were limited primarily by the dyes used in these experiments and could be improved with the use of dyes less susceptible to photobleaching. In conclusion, CW-STED may disclose new information for biological systems with a proper characteristic length scale. The challenges of using CW-STED microscopy to study cell structures are discussed. PMID:26393614

  8. Photon-splitting limits to the hardness of emission in strongly magnetized soft gamma repeaters

    NASA Technical Reports Server (NTRS)

    Baring, Matthew G.

    1995-01-01

    Soft gamma repeaters are characterized by recurrent activity consisting of short-duration outbursts of high-energy emission that is typically of temperature less than 40 keV. One recent model of repeaters is that they originate in the environs of neutron stars with superstrong magnetic fields, perhaps greater than 10(exp 14) G. In such fields, the exotic process of magnetic photon splitting gamma yields gamma gamma acts very effectively to reprocess gamma-ray radiation down to hard X-ray energies. In this Letter, the action of photon splitting is considered in some detail, via the solution of photon kinetic equations, determining how it limits the hardness of emission in strongly magnetized repeaters, and thereby obtaining observational constraints to the field in SGR 1806-20.

  9. Frequency-upconverted stimulated emission by simultaneous five-photon absorption

    NASA Astrophysics Data System (ADS)

    Zheng, Qingdong; Zhu, Haomiao; Chen, Shan-Ci; Tang, Changquan; Ma, En; Chen, Xueyuan

    2013-03-01

    Since the invention of the laser in 1960, multiphoton effects have become useful in techniques for real applications as well as conceptual predictions. Here, we report the first experimental observation of frequency-upconverted stimulated emission from a novel fluorophore through simultaneous five-photon absorption. Compared to lower-order nonlinear absorption, the fifth-order dependence on input light intensity of the five-photon absorption process will provide much stronger spatial confinement, allowing the achievement of a much higher contrast in imaging. Stimulated emission has also been achieved by the absorption of two to four photons under near-infrared laser excitation, making this gain medium a promising multiphoton imaging probe with attractive features, including the absence of autofluorescence from biological samples, large penetration depth, and improved sensitivity and resolution.

  10. Multi-photon excited coherent random laser emission in ZnO powders.

    PubMed

    Tolentino Dominguez, Christian; Gomes, Maria de A; Macedo, Zélia S; de Araújo, Cid B; Gomes, Anderson S L

    2015-01-07

    We report the observation and analysis of anti-Stokes coherent random laser (RL) emission from zinc oxide (ZnO) powders excited by one-, two- or three-photon femtosecond laser radiation. The ZnO powders were produced via a novel proteic sol-gel, low-cost and environmentally friendly route using coconut water in the polymerization step of the metal precursor. One- and two-photon excitation at 354 nm and 710 nm, respectively, generated single-band emissions centred at about 387 nm. For three-photon excitation, the emission spectra showed a strong ultraviolet (UV) band (380-396 nm) attributed to direct three-photon absorption from the valence band to the conduction band. The presence of an intensity threshold and a bandwidth narrowing of the UV band from about 20 to 4 nm are clear evidence of RL action. The observation of multiple sub-nanometre narrow peaks in the emission spectra for excitation above the RL threshold is consistent with random lasing by coherent feedback.

  11. Multi-photon excited coherent random laser emission in ZnO powders

    NASA Astrophysics Data System (ADS)

    Tolentino Dominguez, Christian; Gomes, Maria De A.; Macedo, Zélia S.; de Araújo, Cid B.; Gomes, Anderson S. L.

    2014-11-01

    We report the observation and analysis of anti-Stokes coherent random laser (RL) emission from zinc oxide (ZnO) powders excited by one-, two- or three-photon femtosecond laser radiation. The ZnO powders were produced via a novel proteic sol-gel, low-cost and environmentally friendly route using coconut water in the polymerization step of the metal precursor. One- and two-photon excitation at 354 nm and 710 nm, respectively, generated single-band emissions centred at about 387 nm. For three-photon excitation, the emission spectra showed a strong ultraviolet (UV) band (380-396 nm) attributed to direct three-photon absorption from the valence band to the conduction band. The presence of an intensity threshold and a bandwidth narrowing of the UV band from about 20 to 4 nm are clear evidence of RL action. The observation of multiple sub-nanometre narrow peaks in the emission spectra for excitation above the RL threshold is consistent with random lasing by coherent feedback.

  12. Final LDRD report : enhanced spontaneous emission rate in visible III-nitride LEDs using 3D photonic crystal cavities.

    SciTech Connect

    Fischer, Arthur Joseph; Subramania, Ganapathi S.; Coley, Anthony J.; Lee, Yun-Ju; Li, Qiming; Wang, George T.; Luk, Ting Shan; Koleske, Daniel David; Fullmer, Kristine Wanta

    2009-09-01

    The fundamental spontaneous emission rate for a photon source can be modified by placing the emitter inside a periodic dielectric structure allowing the emission to be dramatically enhanced or suppressed depending on the intended application. We have investigated the relatively unexplored realm of interaction between semiconductor emitters and three dimensional photonic crystals in the visible spectrum. Although this interaction has been investigated at longer wavelengths, very little work has been done in the visible spectrum. During the course of this LDRD, we have fabricated TiO{sub 2} logpile photonic crystal structures with the shortest wavelength band gap ever demonstrated. A variety of different emitters with emission between 365 nm and 700 nm were incorporated into photonic crystal structures. Time-integrated and time-resolved photoluminescence measurements were performed to measure changes to the spontaneous emission rate. Both enhanced and suppressed emission were demonstrated and attributed to changes to the photonic density of states.

  13. A quantum dot single-photon source with on-the-fly all-optical polarization control and timed emission

    PubMed Central

    Heinze, Dirk; Breddermann, Dominik; Zrenner, Artur; Schumacher, Stefan

    2015-01-01

    Sources of single photons are key elements for applications in quantum information science. Among the different sources available, semiconductor quantum dots excel with their integrability in semiconductor on-chip solutions and the potential that photon emission can be triggered on demand. Usually, the photon is emitted from a single-exciton ground state. Polarization of the photon and time of emission are either probabilistic or pre-determined by electronic properties of the system. Here, we study the direct two-photon emission from the biexciton. The two-photon emission is enabled by a laser pulse driving the system into a virtual state inside the band gap. From this intermediate state, the single photon of interest is then spontaneously emitted. We show that emission through this higher-order transition provides a versatile approach to generate a single photon. Through the driving laser pulse, polarization state, frequency and emission time of the photon can be controlled on-the-fly. PMID:26436776

  14. Measurement of direct photon emission in the K(L) ---> pi+ pi- gamma decay mode

    SciTech Connect

    Abouzaid, E.; Arenton, M.; Barker, A.R.; Bellantoni, L.; Bellavance, A.; Blucher, E.; Bock, G.J.; Cheu, E.; Coleman, R.; Corcoran, M.D.; Corti, G.; /Virginia U. /Wisconsin U., Madison

    2006-04-01

    In this paper the KTeV collaboration reports the analysis of 112.1 x 10{sup 3} candidate K{sub L} {yields} {pi}{sup +}{pi}{sup -}{gamma} decays including a background of 671 {+-} 41 events with the objective of determining the photon production mechanisms intrinsic to the decay process. These decays have been analyzed to extract the relative contributions of the Cp violating bremsstrahlung process and the CP conserving M1 and CP violating E1 direct photon emission processes. The M1 direct photon emission amplitude and its associated vector form factor parameterized as |{bar g}{sub M1}|(1 + a{sub 1}/a{sub 2}/(M{sub {rho}}{sup 2}-M{sub K}{sup 2}) + 2M{sub K}E{sub {gamma}}) have been measured to be |{bar g}{sub M1}| = 1.198 {+-} 0.035(stat) {+-} 0.086(syst) and a{sub 1}/a{sub 2} = =0.738 {+-} 0.007(stat) {+-} 0.018(syst) GeV{sup 2}/c{sup 2} respectively. An upper limit for the CP violating E1 direct emission amplitude |g{sub E1}| {le} 0.1 (90%CL) has been found. The overall ratio of direct photon emission (DE) to total photon emission including the bremsstrahlung process (IB) has been determined to be DE/(DE + IB) = 0.689 {+-} 0.021 for E{sub {gamma}} {ge} 20 MeV.

  15. Probing the intrinsic optical Bloch-mode emission from a 3D photonic crystal

    NASA Astrophysics Data System (ADS)

    Hsieh, Mei-Li; Bur, James A.; Du, Qingguo; John, Sajeev; Lin, Shawn-Yu

    2016-10-01

    We report experimental observation of intrinsic Bloch-mode emission from a 3D tungsten photonic crystal at low thermal excitation. After the successful removal of conventional metallic emission (normal emission), it is possible to make an accurate comparison of the Bloch-mode and the normal emission. For all biases, we found that the emission intensity of the Bloch-mode is higher than that of the normal emission. The Bloch-mode emission also exhibits a slower dependence on (\\hslash ω /{k}bT) than that of the normal emission. The observed higher emission intensity and a different T-dependence is attributed to Bloch-mode assisted emission where emitters have been located into a medium having local density of states different than the isotropic case. Furthermore, our finite-difference time-domain (FDTD) simulation shows the presence of localized spots at metal-air boundaries and corners, having intense electric field. The enhanced plasmonic field and local non-equilibrium could induce a strong thermally stimulated emission and may be the cause of our unusual observation.

  16. Cascaded emission of single photons from the biexciton in monolayered WSe2

    PubMed Central

    He, Yu-Ming; Iff, Oliver; Lundt, Nils; Baumann, Vasilij; Davanco, Marcelo; Srinivasan, Kartik; Höfling, Sven; Schneider, Christian

    2016-01-01

    Monolayers of transition metal dichalcogenide materials emerged as a new material class to study excitonic effects in solid state, as they benefit from enormous Coulomb correlations between electrons and holes. Especially in WSe2, sharp emission features have been observed at cryogenic temperatures, which act as single photon sources. Tight exciton localization has been assumed to induce an anharmonic excitation spectrum; however, the evidence of the hypothesis, namely the demonstration of a localized biexciton, is elusive. Here we unambiguously demonstrate the existence of a localized biexciton in a monolayer of WSe2, which triggers an emission cascade of single photons. The biexciton is identified by its time-resolved photoluminescence, superlinearity and distinct polarization in micro-photoluminescence experiments. We evidence the cascaded nature of the emission process in a cross-correlation experiment, which yields a strong bunching behaviour. Our work paves the way to a new generation of quantum optics experiments with two-dimensional semiconductors. PMID:27830703

  17. Photon Emission and Reabsorption Processes in CH3NH3PbBr3 Single Crystals Revealed by Time-Resolved Two-Photon-Excitation Photoluminescence Microscopy

    NASA Astrophysics Data System (ADS)

    Yamada, Takumi; Yamada, Yasuhiro; Nakaike, Yumi; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2017-01-01

    The dynamical processes of radiative recombination of photocarriers and reabsorption of emitted photons in CH3NH3PbBr3 single crystals are studied using time-resolved two-photon-excitation photoluminescence (PL) microscopy. We find that the PL spectrum and its decay dynamics depend on the excitation-depth profile. As the excitation depth increases, the PL spectrum becomes asymmetric, the peak energy redshifts, and the PL decay time becomes longer. These observations can be well explained by a simple model including photon recycling (photon emission and reabsorption) in thick samples with strong band-to-band transitions and high radiative recombination efficiencies.

  18. Time-resolved photon emission from layered turbid media

    SciTech Connect

    Hielscher, A.H.; Liu, H.; Chance, B.; Tittel, F.K.; Jacques, S.L.

    1996-02-01

    We present numerical and experimental results of time-resolved emission profiles from various layered turbid media. Numerical solutions determined by time-resolved Monte Carlo simulations are compared with measurements on layered-tissue phantoms made from gelatin. In particular, we show that in certain cases the effects of the upper layers can be eliminated. As a practical example, these results are used to analyze {ital in} {ital vivo} measurements on the human head. This demonstrates the influence of skin, skull, and meninges on the determination of the blood oxygenation in the brain. {copyright} {ital 1996 Optical Society of America.}

  19. Collective Evidence for Inverse Compton Emission from External Photons in High-Power Blazars

    NASA Technical Reports Server (NTRS)

    Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

    2012-01-01

    We present the first collective evidence that Fermi-detected jets of high kinetic power (L(sub kin)) are dominated by inverse Compton emission from upscattered external photons. Using a sample with a broad range in orientation angle, including radio galaxies and blazars, we find that very high power sources (L(sub kin) > 10(exp 45.5) erg/s) show a significant increase in the ratio of inverse Compton to synchrotron power (Compton dominance) with decreasing orientation angle, as measured by the radio core dominance and confirmed by the distribution of superluminal speeds. This increase is consistent with beaming expectations for external Compton (EC) emission, but not for synchrotron self Compton (SSC) emission. For the lowest power jets (L(sub kin) < 10(exp 43.5) erg /s), no trend between Compton and radio core dominance is found, consistent with SSC. Importantly, the EC trend is not seen for moderately high power flat spectrum radio quasars with strong external photon fields. Coupled with the evidence that jet power is linked to the jet speed, this finding suggests that external photon fields become the dominant source of seed photons in the jet comoving frame only for the faster and therefore more powerful jets.

  20. Collective Evidence for Inverse Compton Emission from External Photons in High-power Blazars

    NASA Astrophysics Data System (ADS)

    Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

    2012-06-01

    We present the first collective evidence that Fermi-detected jets of high kinetic power (L kin) are dominated by inverse Compton emission from upscattered external photons. Using a sample with a broad range in orientation angle, including radio galaxies and blazars, we find that very high power sources (L kin > 1045.5 erg s-1) show a significant increase in the ratio of inverse Compton to synchrotron power (Compton dominance) with decreasing orientation angle, as measured by the radio core dominance and confirmed by the distribution of superluminal speeds. This increase is consistent with beaming expectations for external Compton (EC) emission, but not for synchrotron self-Compton (SSC) emission. For the lowest power jets (L kin < 1043.5 erg s-1), no trend between Compton and radio core dominance is found, consistent with SSC. Importantly, the EC trend is not seen for moderately high power flat spectrum radio quasars with strong external photon fields. Coupled with the evidence that jet power is linked to the jet speed, this finding suggests that external photon fields become the dominant source of seed photons in the jet comoving frame only for the faster and therefore more powerful jets.

  1. Relative-phase and time-delay maps all over the emission cone of hyperentangled photon source

    NASA Astrophysics Data System (ADS)

    Hegazy, Salem F.; Badr, Yahia A.; Obayya, Salah S. A.

    2017-02-01

    Realizing high flux of hyperentangled photons requires collecting photon pairs simultaneously entangled in multiple degrees of freedom over relatively wide spectral and angular emission ranges. We consider the hyperentangled photons produced by superimposing noncollinear spontaneous parametric down conversion (SPDC) emissions of two crossed and coherently pumped nonlinear crystals. We present an approach for determining the directional-spectral relative-phase and time-delay maps of hyperentangled photons all over the SPDC emission cone. A vectorial representation is adopted for all parameters of concern. This enables us to examine unconventional arrangements such as the autocompensation of relative-phase and time-delay via oblique pump incidence. While prior works often adopt first-order approximation, it is shown that the actual directional relative-phase map is very well approximated by a quadratic function of the polar angle of the two-photon emission while negligibly varying with the azimuthal angle.

  2. Ultraweak photon emission and proteomics analyses in soybean under abiotic stress.

    PubMed

    Komatsu, Setsuko; Kamal, Abu Hena Mostafa; Makino, Takahiro; Hossain, Zahed

    2014-07-01

    Biophotons are ultraweak photon emissions that are closely related to various biological activities and processes. In mammals, biophoton emissions originate from oxidative bursts in immunocytes during immunological responses. Biophotons emitted from plant organs provide novel information about the physiological state of plant under in vivo condition. In this review, the principles and recent advances in the measurement of biophoton emissions in plants are described. Furthermore, examples of biophoton emission and proteomics in soybean under abiotic stress are reviewed and discussed. Finally, this review suggests that the application of proteomics should provide a better interpretation of plant response to biophoton emission and allow the identification of genes that will allow the screening of crops able to produce maximal yields, even in stressful environments.

  3. Aberration corrected 1.2-MV cold field-emission transmission electron microscope with a sub-50-pm resolution

    SciTech Connect

    Akashi, Tetsuya; Takahashi, Yoshio; Tanigaki, Toshiaki Shimakura, Tomokazu; Kawasaki, Takeshi; Furutsu, Tadao; Shinada, Hiroyuki; Osakabe, Nobuyuki; Müller, Heiko; Haider, Maximilian; Tonomura, Akira

    2015-02-16

    Atomic-resolution electromagnetic field observation is critical to the development of advanced materials and to the unveiling of their fundamental physics. For this purpose, a spherical-aberration corrected 1.2-MV cold field-emission transmission electron microscope has been developed. The microscope has the following superior properties: stabilized accelerating voltage, minimized electrical and mechanical fluctuation, and coherent electron emission. These properties have enabled to obtain 43-pm information transfer. On the bases of these performances, a 43-pm resolution has been obtained by correcting lens aberrations up to the third order. Observations of GaN [411] thin crystal showed a projected atomic locations with a separation of 44 pm.

  4. Lorentz microscopy observation of vortices in high-Tc superconductors using a 1-MV field emission transmission electron microscope.

    PubMed

    Harada, Ken

    2013-06-01

    Lorentz microscopy has opened the door to observing a single quantized magnetic flux line (i.e. a vortex) and its dynamic behavior inside a superconductor in real time. It resulted from the efforts of Dr Akira Tonomura and his collaborators, who developed a field emission electron microscope and advanced the technologies used for visualizing vortices (e.g. a low-temperature specimen stage and a magnetic-field application system). They used a 1-MV field emission transmission electron microscope with an electron beam that can penetrate thick specimens of high-temperature superconductors (Bi2Sr2CaCu2O8+δ and YB2C3O7-δ) to reveal the flux-line features inside materials and their interactions with defects. This memorial paper reviews the results of research in the area of vortex matter physics.

  5. Tamm plasmon- and surface plasmon-coupled emission from hybrid plasmonic–photonic structures

    PubMed Central

    Chen, Yikai; Zhang, Douguo; Zhu, Liangfu; Wang, Ruxue; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

    2015-01-01

    Photonic and plasmon-coupled emissions present new opportunities for control on light emission from fluorophores, and have many applications in the physical and biological sciences. The mechanism of and the influencing factors for the coupling between the fluorescent molecules and plasmon and/or photonic modes are active areas of research. In this paper, we describe a hybrid photonic–plasmonic structure that simultaneously contains two plasmon modes: surface plasmons (SPs) and Tamm plasmons (TPs), both of which can modulate fluorescence emission. Experimental results show that both SP-coupled emission (SPCE) and TP-coupled emission (TPCE) can be observed simultaneously with this hybrid structure. Due to the different resonant angles of the TP and SP modes, the TPCE and SPCE can be beamed in different directions and can be separated easily. Back focal plane images of the fluorescence emission show that the relative intensities of the SPCE and TPCE can be changed if the probes are at different locations inside the hybrid structure, which reveals the probe location-dependent different coupling strengths of the fluorescent molecules with SPs and TPs. The different coupling strengths are ascribed to the electric field distribution of the two modes in the structure. Here, we present an understanding of these factors influencing mode coupling with probes, which is vital for structure design for suitable applications in sensing and diagnostics. PMID:26526929

  6. Spontaneous emission from a microwave-driven four-level atom in an anisotropic photonic crystal

    NASA Astrophysics Data System (ADS)

    Jiang, Li; Wan, Ren-Gang; Yao, Zhi-Hai

    2016-10-01

    The spontaneous emission from a microwave-driven four-level atom embedded in an anisotropic photonic crystal is studied. Due to the modified density of state (DOS) in the anisotropic photonic band gap (PBG) and the coherent control induced by the coupling fields, spontaneous emission can be significantly enhanced when the position of the spontaneous emission peak gets close to the band gap edge. As a result of the closed-loop interaction between the fields and the atom, the spontaneous emission depends on the dynamically induced Autler-Townes splitting and its position relative to the PBG. Interesting phenomena, such as spectral-line suppression, enhancement and narrowing, and fluorescence quenching, appear in the spontaneous emission spectra, which are modulated by amplitudes and phases of the coherently driven fields and the effect of PBG. This theoretical study can provide us with more efficient methods to manipulate the atomic spontaneous emission. Project supported by the National Natural Science Foundation of China (Grant Nos. 11447232, 11204367, 11447157, and 11305020).

  7. Information transfer of 25.5 nm-1 in a 1-MV field-emission transmission electron microscope.

    PubMed

    Akashi, Tetsuya; Takahashi, Yoshio; Onai, Toshio; Kasai, Hiroto; Shinada, Hiroyuki; Osakabe, Nobuyuki; Tonomura, Akira

    2016-08-01

    Information transfer of a 1-MV field-emission transmission electron microscope (TEM) was improved by reducing mechanical vibrations and improving the stability of an acceleration voltage. The resulting mechanical stability was estimated from lattice fringes with an obtained spacing of 19.6 pm under achromatic conditions. This value corresponds to a vibration amplitude of <19.6 pm. The stability of the acceleration voltage was improved by reducing thermal noises in the power supply. As a result, 39.2-pm-spacing linear lattice fringes were obtained under chromatic conditions. This indicates that 25.5 nm(-1) information transfer was accomplished in the 1 MV field-emission TEM.

  8. Photon and dilepton production at the Facility for Proton and Anti-Proton Research and beam-energy scan at the Relativistic Heavy-Ion Collider using coarse-grained microscopic transport simulations

    NASA Astrophysics Data System (ADS)

    Endres, Stephan; van Hees, Hendrik; Bleicher, Marcus

    2016-05-01

    We present calculations of dilepton and photon spectra for the energy range Elab=2 A to35 A GeV which will be available for the Compressed Baryonic Matter (CBM) experiment at the future Facility for Proton and Anti-Proton Research (FAIR). The same energy regime will also be covered by phase II of the beam-energy scan at the Relativistic Heavy-Ion Collider (RHIC-BES). Coarse-grained dynamics from microscopic transport calculations of the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model is used to determine temperature and chemical potentials, which allows for the use of dilepton and photon-emission rates from equilibrium quantum-field-theory calculations. The results indicate that nonequilibrium effects, the presence of baryonic matter, and the creation of a deconfined phase might show up in specific manners in the measurable dilepton invariant-mass spectra and in the photon transverse-momentum spectra. However, as the many influences are difficult to disentangle, we argue that the challenge for future measurements of electromagnetic probes will be to provide a high precision with uncertainties much lower than in previous experiments. Furthermore, a systematic study of the whole energy range covered by CBM at FAIR and RHIC-BES is necessary to discriminate between different effects, which influence the spectra, and to identify possible signatures of a phase transition.

  9. Enhancement of molecular sensitivity in positron emission tomography with quantum correlation of γ-ray photons

    NASA Astrophysics Data System (ADS)

    Sato, K.; Kobayashi, Y.

    2015-05-01

    Enhancement of molecular sensitivity in positron emission tomography (PET) has long been discussed with respect to imaging instrumentation and algorithms for data treatment. Here, the molecular sensitivity in PET is discussed on the basis of 2-dimensional coincident measurements of 511 keV γ ray photons resultant from two-photon annihilation. Introduction of an additional selection window based on the energy sum and difference of the coincidently measured γ ray photons, without any significant instrumental and algorithmic changes, showed an improvement in the signal-to-noise ratio (SNR) by an order of magnitude. Improvement of performance characteristics in the PET imaging system was demonstrated by an increase in the noise equivalent count rate (NECR) which takes both the SNR and the detection efficiency into consideration. A further improvement of both the SNR and the NECR is expected for the present system in real clinical and in-vivo environments, where much stronger positron sources are employed.

  10. Enhancement of molecular sensitivity in positron emission tomography with quantum correlation of γ-ray photons.

    PubMed

    Sato, K; Kobayashi, Y

    2015-05-01

    Enhancement of molecular sensitivity in positron emission tomography (PET) has long been discussed with respect to imaging instrumentation and algorithms for data treatment. Here, the molecular sensitivity in PET is discussed on the basis of 2-dimensional coincident measurements of 511 keV γ ray photons resultant from two-photon annihilation. Introduction of an additional selection window based on the energy sum and difference of the coincidently measured γ ray photons, without any significant instrumental and algorithmic changes, showed an improvement in the signal-to-noise ratio (SNR) by an order of magnitude. Improvement of performance characteristics in the PET imaging system was demonstrated by an increase in the noise equivalent count rate (NECR) which takes both the SNR and the detection efficiency into consideration. A further improvement of both the SNR and the NECR is expected for the present system in real clinical and in-vivo environments, where much stronger positron sources are employed.

  11. The Number of Accumulated Photons and the Quality of Stimulated Emission Depletion Lifetime Images

    SciTech Connect

    Syed, Aleem; Lesoine, Michael D; Bhattacharjee, Ujjal; Petrich, Jacob W; Smith, Emily A

    2014-03-03

    Time binning is used to increase the number of photon counts in the peak channel of stimulated emission depletion (STED) fluorescence lifetime decay curves to determine how it affects the resulting lifetime image. The fluorescence lifetime of the fluorophore, Alexa Fluor 594 phalloidin, bound to F-actin is probed in cultured S2 cells at a spatial resolution of ~40 nm. This corresponds to a tenfold smaller probe volume compared to confocal imaging, and a reduced number of photons contributing to the signal. Pixel-by-pixel fluorescence lifetime measurements and error analysis show that an average of 40 ± 30 photon counts in the peak channel with a signal-to-noise ratio of 20 is enough to calculate a reliable fluorescence lifetime from a single exponential fluorescence decay. No heterogeneity in the actin cytoskeleton in different regions of the cultured cells was measured in the 40- to 400-nm spatial regime.

  12. NIR to VUV: Seven-Photon Upconversion Emissions from Gd(3+) Ions in Fluoride Nanocrystals.

    PubMed

    Zheng, Kezhi; Qin, Weiping; Cao, Chunyan; Zhao, Dan; Wang, Lili

    2015-02-05

    Here we show that a near-infrared (NIR) diode laser is capable of generating vacuum ultraviolet (VUV) emissions in fluoride nanocrystals through photon upconversion (UC) processes. By using Yb(3+) and Tm(3+) as sensitizers, we successfully obtained the VUV photons with the energy exceeding 6 eV in YF3: Yb, Tm, and Gd nanocrystals. The seven photon UC fluorescence from the (6)GJ → (8)S7/2 transitions of Gd(3+) ions and the possible VUV UC mechanism were reported along with the calculation of the branching ratio under different pumping power excitation. Practically, it offers a promising solution for VUV light generation without cryogens and expensive instrumentations. Fundamentally, the extremely high-order UC processes will intrigue great interest in exploring unusual high-energy radiative transitions in rare earth ions.

  13. Enhancement of molecular sensitivity in positron emission tomography with quantum correlation of γ-ray photons

    SciTech Connect

    Sato, K.; Kobayashi, Y.

    2015-05-15

    Enhancement of molecular sensitivity in positron emission tomography (PET) has long been discussed with respect to imaging instrumentation and algorithms for data treatment. Here, the molecular sensitivity in PET is discussed on the basis of 2-dimensional coincident measurements of 511 keV γ ray photons resultant from two-photon annihilation. Introduction of an additional selection window based on the energy sum and difference of the coincidently measured γ ray photons, without any significant instrumental and algorithmic changes, showed an improvement in the signal-to-noise ratio (SNR) by an order of magnitude. Improvement of performance characteristics in the PET imaging system was demonstrated by an increase in the noise equivalent count rate (NECR) which takes both the SNR and the detection efficiency into consideration. A further improvement of both the SNR and the NECR is expected for the present system in real clinical and in-vivo environments, where much stronger positron sources are employed.

  14. Single photon infrared emission spectroscopy: a study of IR emission from UV laser excited PAHs between 3 and 15 micrometers

    NASA Technical Reports Server (NTRS)

    Cook, D. J.; Schlemmer, S.; Balucani, N.; Wagner, D. R.; Harrison, J. A.; Steiner, B.; Saykally, R. J.

    1998-01-01

    Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-micrometers (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs. Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.

  15. FAINT HIGH-ENERGY GAMMA-RAY PHOTON EMISSION OF GRB 081006A FROM FERMI OBSERVATIONS

    SciTech Connect

    Zheng Weikang; Akerlof, Carl W.; Pandey, Shashi B.; McKay, Timothy A.; Zhang Binbin; Zhang Bing

    2012-01-20

    Since the launch of the Fermi Gamma-ray Space Telescope on 2008 June 11, the Large Area Telescope (LAT) instrument has firmly detected more than 20 gamma-ray bursts (GRBs) with high-energy photon emission above 100 MeV. Using the matched filter technique, three more GRBs have also shown evidence of correlation with high-energy photon emission as demonstrated by Akerlof et al. In this paper, we present another GRB, GRB 081006A, unambiguously detected by the matched filter technique. This event is associated with more than 13 high-energy photons above 100 MeV. The likelihood analysis code provided by the Fermi Science Support Center generated an independent verification of this detection using a comparison of the test statistics value with similar calculations for random LAT data fields. We have performed detailed temporal and spectral analysis of photons from 8 keV up to 0.8 GeV from the Gamma-ray Burst Monitor and the LAT. The properties of GRB 081006A can be compared to those of the other two long-duration GRBs detected at similar significance, GRB 080825C and GRB 090217A. We find that GRB 081006A is more similar to GRB 080825C with comparable appearances of late high-energy photon emission. As demonstrated previously, there appears to be a surprising dearth of faint LAT GRBs, with only one additional GRB identified in a sample of 74. In this unique period when both Swift and Fermi are operational, there is some urgency to explore this aspect of GRBs as fully as possible.

  16. Upconversion emission properties of CeO2: Tm3+, Yb3+ inverse opal photonic crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Gong; Wu, Hangjun; Yang, Zhengwen; Liao, Jiayan; Lai, Shenfeng; Qiu, Jianbei; Song, Zhiguo

    2014-10-01

    The ordered and disordered templates were assembled by vertical deposition of polystyrene microspheres. The CeO2: Tm3+, Yb3+ precursor solution was used to infiltrate into the voids of the ordered and disordered templates, respectively. Then the ordered and disordered templates were calcined at 950°C in an air furnace, and the CeO2: Tm3+, Yb3+ inverse opals were obtained. The upconversion emissions from CeO2: Tm3+, Yb3+ inverse opals were suppressed due to the photon trapping caused by Bragg reflection of lattice planes when the upconversion emission band was in the range of the photonic band gaps in the inverse opals.

  17. Photon and radiowave emission from peeling pressure sensitive adhesives in air

    NASA Technical Reports Server (NTRS)

    Donaldson, E. E.; Shen, X. A.; Dickinson, J. T.

    1985-01-01

    During separation of an adhesive from a polymer substrate in air, intense bursts of photons ('phE', for photon emission) and long wavelength electromagnetic radiation ('RE', for radiowave emission), similar to those reported earlier by Deryagin, et al. (1978) have been observed. In this paper, careful measurements of the phE time distributions, as well as time correlations between bursts of phE and RE, are reported. These results support the view that patches of electrical charge produced by charge separation between dissimilar materials lead to microdischarges in and near the crack tip. The role of these discharges in producing sustained phE after the discharge has been extinguished is also discussed.

  18. Inhibition of light emission in a 2.5D photonic structure

    SciTech Connect

    Peretti, Romain; Seassal, Christian; Viktorovich, Pierre; Letartre, Xavier

    2014-07-14

    We analyse inhibition of emission in a 2.5D photonic structures made up of a photonic crystal (PhC) and Bragg mirrors using Finite Differences Time Domaine (FDTD) simulations. A comparison is made between an isolated PhC membrane and the same PhC suspended onto a Bragg mirror or sandwiched between 2 Bragg mirrors. Strong inhibition of the Purcell factor is observed in a broad spectral range, whatever the in-plane orientation and location of the emitting dipole. We analysed these results numerically and theoretically by simulating the experimentally observed lifetime of a collection of randomly distributed emitters, showing that their average emission rate is decreased by more than one decade, both for coupled or isolated emitters.

  19. Analytic treatment of source photon emission times to reduce noise in implicit Monte Carlo calculations

    SciTech Connect

    Trahan, Travis J.; Gentile, Nicholas A.

    2012-09-10

    Statistical uncertainty is inherent to any Monte Carlo simulation of radiation transport problems. In space-angle-frequency independent radiative transfer calculations, the uncertainty in the solution is entirely due to random sampling of source photon emission times. We have developed a modification to the Implicit Monte Carlo algorithm that eliminates noise due to sampling of the emission time of source photons. In problems that are independent of space, angle, and energy, the new algorithm generates a smooth solution, while a standard implicit Monte Carlo solution is noisy. For space- and angle-dependent problems, the new algorithm exhibits reduced noise relative to standard implicit Monte Carlo in some cases, and comparable noise in all other cases. In conclusion, the improvements are limited to short time scales; over long time scales, noise due to random sampling of spatial and angular variables tends to dominate the noise reduction from the new algorithm.

  20. Single photon emission computed tomography in Alzheimer's disease. Abnormal iofetamine I 123 uptake reflects dementia severity

    SciTech Connect

    Johnson, K.A.; Holman, B.L.; Mueller, S.P.; Rosen, T.J.; English, R.; Nagel, J.S.; Growdon, J.H.

    1988-04-01

    To determine whether abnormalities in regional cerebral functional activity estimated by iofetamine hydrochloride I 123 and single photon emission computed tomography can be detected in mild or moderate as well as severe cases of Alzheimer's disease (AD), we performed iofetamine I 123-single photon emission computed tomography in 37 patients with probable AD (nine patients with mild, 18 patients with moderate, and ten patients with severe dementia) and nine age-matched control subjects. Iofetamine I 123 uptake was measured in right and left frontal, temporal, parietal, and occipital cortices. Mean (right and left) iofetamine I 123 activity was lowest in the parietal region of patients with AD and was significantly reduced in the other three regions compared with control subjects. Only in the parietal region was lower relative iofetamine I 123 activity associated with an impaired level of patient function and with cognitive deficit.

  1. Photon-assisted field emission from a Si tip at addition of an AC low voltage

    NASA Astrophysics Data System (ADS)

    Zaporozhchenko, A. V.; Chernov, S. V.; Odnodvorets, L. V.; Stetsenko, B. V.; Nepijko, S. A.; Elmers, H. J.; Schönhense, G.

    2015-07-01

    We investigated the field emission current from a p-type silicon tip with large resistivity of 4 × 103 Ω cm for light illumination with a photon energy of 1.3 eV and tip-anode voltages of 0.7-5.0 kV. Additional AC voltage with amplitude 30-60 V and frequency varying in the range of 10-107 Hz was applied to the tip which resulted in variations of emission current. We investigated the dependence of this phenomenon on the AC signal parameters, light intensity and temperature. The resonant-like frequency dependence of the emission current is because the tip acts as a driven plasmonic resonator. The results represent an important step forward for the development of high-frequency display systems based on electron field emission.

  2. Monitoring CBF in clinical routine by dynamic single photon emission tomography (SPECT) of inhaled xenon-133

    SciTech Connect

    Sugiyama, H.; Christensen, J.; Skyhoj Olsen, T.; Lassen, N.A.

    1986-11-01

    A very simple and low-cost brain dedicated, rapidly rotating Single Photon Emission Tomograph SPECT is described. Its use in following patients with ischemic stroke is illustrated by two middle cerebral artery occlusion cases, one with persistent occlusion and low CBF in MCA territory, and one with early lysis of the occlusion having high CBF (massive luxury perfusion) for some weeks. Evidence of this kind may be essential in the evaluation of therapeutic measures in ischemic stroke.

  3. Ultraweak Photon Emission as a Non-Invasive Health Assessment: A Systematic Review

    PubMed Central

    Ives, John A.; van Wijk, Eduard P. A.; Bat, Namuun; Crawford, Cindy; Walter, Avi; Jonas, Wayne B.; van Wijk, Roeland; van der Greef, Jan

    2014-01-01

    We conducted a systematic review (SR) of the peer reviewed scientific literature on ultraweak photon emissions (UPE) from humans. The question was: Can ultraweak photon emissions from humans be used as a non-invasive health assessment? A systematic search was conducted across eight relevant databases: PubMed/MEDLINE, BIOSIS, CINAHL, PSYCHINFO, All of Cochrane EBM databases, GIDEON, DoD Biomedical Research, and clinicaltrials.gov from database inception to October 2011. Of the 1315 studies captured by the search strategy, 56 met the inclusion criteria, out of which 1 was a RCT, 27 were CCT, and 28 were observational and descriptive studies. There were no systematic reviews/meta-analyses that fit the inclusion criteria. In this report, the authors provide an assessment of the quality of the RCT included; describe the characteristics of all the included studies, the outcomes assessed, and the effectiveness of photon emission as a potential health assessment tool. This report demonstrates that the peer reviewed literature on UPE and human UPE measurement in particular is surprisingly large. Most of the human UPE literature is of good to high quality based on our systematic evaluation. However, an evaluation tool for systematically evaluating this type of “bio-evaluation” methodology is not currently available and would be worth developing. Publications in the peer reviewed literature over the last 50 years demonstrate that the use of “off-the-shelf” technologies and well described methodologies for the detection of human photon emissions are being used on a regular basis in medical and research settings. The overall quality of this literature is good and the use of this approach for determining inflammatory and oxidative states of patients indicate the growing use and value of this approach as both a medical and research tool. PMID:24586274

  4. Advances in Single-Photon Emission Computed Tomography Hardware and Software.

    PubMed

    Piccinelli, Marina; Garcia, Ernest V

    2016-02-01

    Nuclear imaging techniques remain today's most reliable modality for the assessment and quantification of myocardial perfusion. In recent years, the field has experienced tremendous progress both in terms of dedicated cameras for cardiac applications and software techniques for image reconstruction. The most recent advances in single-photon emission computed tomography hardware and software are reviewed, focusing on how these improvements have resulted in an even more powerful diagnostic tool with reduced injected radiation dose and acquisition time.

  5. Iofetamine I 123 single photon emission computed tomography is accurate in the diagnosis of Alzheimer's disease

    SciTech Connect

    Johnson, K.A.; Holman, B.L.; Rosen, T.J.; Nagel, J.S.; English, R.J.; Growdon, J.H. )

    1990-04-01

    To determine the diagnostic accuracy of iofetamine hydrochloride I 123 (IMP) with single photon emission computed tomography in Alzheimer's disease, we studied 58 patients with AD and 15 age-matched healthy control subjects. We used a qualitative method to assess regional IMP uptake in the entire brain and to rate image data sets as normal or abnormal without knowledge of subjects'clinical classification. The sensitivity and specificity of IMP with single photon emission computed tomography in AD were 88% and 87%, respectively. In 15 patients with mild cognitive deficits (Blessed Dementia Scale score, less than or equal to 10), sensitivity was 80%. With the use of a semiquantitative measure of regional cortical IMP uptake, the parietal lobes were the most functionally impaired in AD and the most strongly associated with the patients' Blessed Dementia Scale scores. These results indicated that IMP with single photon emission computed tomography may be a useful adjunct in the clinical diagnosis of AD in early, mild disease.

  6. Selective two-photon fluorescence suppression by ultrafast pulse-pair excitation: control by selective one-color stimulated emission.

    PubMed

    Kumar De, Arijit; Roy, Debjit; Goswami, Debabrata

    2011-10-01

    Controlling two-photon molecular fluorescence leading to selective fluorophore excitation has been a long sought after goal in fluorescence microscopy. In this letter, we thoroughly explore selective fluorescence suppression through simultaneous two-photon absorption by two different fluorophores followed by selective one-photon stimulated emission for one particular fluorophore. We achieve this by precisely controlling the time delay between two identical ultrafast near infrared laser pulses.

  7. Comparison of HORACE and PHOTOS Algorithms for Multi-Photon Emission in the Context of the W Boson Mass Measurement

    SciTech Connect

    Kotwal, Ashutosh V.; Jayatilaka, Bodhitha

    2016-01-01

    W boson mass measurement is sensitive to QED radiative corrections due to virtual photon loops and real photon emission. The largest shift in the measured mass, which depends on the transverse momentum spectrum of the charged lepton from the boson decay, is caused by the emission of real photons from the final-state lepton. There are a number of calculations and codes available to model the final-state photon emission. We perform a detailed study, comparing the results from HORACE and PHOTOS implementations of the final-state multiphoton emission in the context of a direct measurement ofW boson mass at Tevatron. Mass fits are performed using a simulation of the CDF II detector.

  8. Comparison of HORACE and PHOTOS Algorithms for Multi-Photon Emission in the Context of the W Boson Mass Measurement

    DOE PAGES

    Kotwal, Ashutosh V.; Jayatilaka, Bodhitha

    2016-01-01

    W boson mass measurement is sensitive to QED radiative corrections due to virtual photon loops and real photon emission. The largest shift in the measured mass, which depends on the transverse momentum spectrum of the charged lepton from the boson decay, is caused by the emission of real photons from the final-state lepton. There are a number of calculations and codes available to model the final-state photon emission. We perform a detailed study, comparing the results from HORACE and PHOTOS implementations of the final-state multiphoton emission in the context of a direct measurement ofW boson mass at Tevatron. Mass fitsmore » are performed using a simulation of the CDF II detector.« less

  9. Direct evidence of single quantum dot emission from GaN islands formed at threading dislocations using nanoscale cathodoluminescence: A source of single photons in the ultraviolet

    SciTech Connect

    Schmidt, Gordon Berger, Christoph; Veit, Peter; Metzner, Sebastian; Bertram, Frank; Bläsing, Jürgen; Dadgar, Armin; Strittmatter, André; Christen, Jürgen; Callsen, Gordon; Kalinowski, Stefan; Hoffmann, Axel

    2015-06-22

    Intense emission from GaN islands embedded in AlN resulting from GaN/AlN quantum well growth is directly resolved by performing cathodoluminescence spectroscopy in a scanning transmission electron microscope. Line widths down to 440 μeV are measured in a wavelength region between 220 and 310 nm confirming quantum dot like electronic properties in the islands. These quantum dot states can be structurally correlated to islands of slightly enlarged thicknesses of the GaN/AlN quantum well layer preferentially formed in vicinity to dislocations. The quantum dot states exhibit single photon emission in Hanbury Brown-Twiss experiments with a clear antibunching in the second order correlation function at zero time delay.

  10. Anisotropic emission and photon-recycling in strain-balanced quantum well solar cells

    SciTech Connect

    Cabrera, C. I.; Enciso, A.; Contreras-Solorio, D. A.; Hernandez, L.; Connolly, J. P.

    2014-04-28

    Strain-balanced quantum well solar cells (SB-QWSCs) extend the photon absorption edge beyond that of bulk GaAs by incorporation of quantum wells in the i-region of a p–i–n device. Anisotropy arises from a splitting of the valence band due to compressive strain in the quantum wells, suppressing a transition which contributes to emission from the edge of the quantum wells. We have studied both the emission light polarized in the plane perpendicular (TM) to the quantum well which couples exclusively to the light hole transition and the emission polarized in the plane of the quantum wells (TE) which couples mainly to the heavy hole transition. It was found that the spontaneous emission rates TM and TE increase when the quantum wells are deeper. The addition of a distributed Bragg reflector can substantially increase the photocurrent while decreasing the radiative recombination current. We have examined the impact of the photon recycling effect on SB-QWSC performance. We have optimized SB-QWSC design to achieve single junction efficiencies above 30%.

  11. Observation of upconversion fluorescence and stimulated emission based on three-photon absorption

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Lin, S.; Xu, L.; Yang, F.; Yang, Y.; Pan, L.; Sun, C.; Li, Y.; Sun, G.; Jiang, Z.

    2005-06-01

    The observations of three-photon-induced frequency-upconversion fluorescence and the highly directional stimulated visible emission in two dyes, 4-[p-(dicyanoethylamino) styryl]-N-methylpyridinium iodide (abbreviated as CEASP) and the complex of CEASP and Ce(NO3) (abbreviated as CEASP-Ce), are reported. The photographs of the forward amplified spontaneous emissions spots, pumped by an optical parametric oscillator idler with a pulse width of 8 ns and a wavelength of 1.3 μ m, are shown. The upconversion fluorescence produced both in dimethyl formamide solution and 2-hydroxyethyl methacrylate (HEMA) polymer spans from green to red, with a cubic dependence on the pump light intensity. The experimental results imply that the existence of the lanthanide ion Ce3 + sensitizes the nonlinear absorption and emission.

  12. On-chip time resolved detection of quantum dot emission using integrated superconducting single photon detectors.

    PubMed

    Reithmaier, G; Lichtmannecker, S; Reichert, T; Hasch, P; Müller, K; Bichler, M; Gross, R; Finley, J J

    2013-01-01

    We report the routing of quantum light emitted by self-assembled InGaAs quantum dots (QDs) into the optical modes of a GaAs ridge waveguide and its efficient detection on-chip via evanescent coupling to NbN superconducting nanowire single photon detectors (SSPDs). The waveguide coupled SSPDs primarily detect QD luminescence, with scattered photons from the excitation laser onto the proximal detector being negligible by comparison. The SSPD detection efficiency from the evanescently coupled waveguide modes is shown to be two orders of magnitude larger when compared with operation under normal incidence illumination, due to the much longer optical interaction length. Furthermore, in-situ time resolved measurements performed using the integrated detector show an average QD spontaneous emission lifetime of 0.95 ns, measured with a timing jitter of only 72 ps. The performance metrics of the SSPD integrated directly onto GaAs nano-photonic hardware confirms the strong potential for on-chip few-photon quantum optics using such semiconductor-superconductor hybrid systems.

  13. Region specific enhancement of quantum dot emission using interleaved two-dimensional photonic crystals.

    PubMed

    See, Gloria G; Xu, Lu; Naughton, Matt S; Tang, Tiantian; Bonita, Yolanda; Joo, Jake; Trefonas, Peter; Deshpande, Kishori; Kenis, Paul J A; Nuzzo, Ralph G; Cunningham, Brian T

    2015-03-20

    The power efficiency, spectral characteristics, and output directionality of light emitting diodes (LEDs) used for lighting and video display may be tailored by integrating nanostructures that interact with photon emitters. In this work, we demonstrate an approach in which visible-wavelength-emitting quantum dots (QDs) are integrated within a polymer-based photonic crystal (PC) and excited by an ultraviolet-emitting LED. The PC design incorporates two interleaved regions, each with distinct periods in orthogonal directions. The structure enables simultaneous resonant coupling of ultraviolet excitation photons to the QDs and visible QD emission at two different wavelengths to efficiently extract photons normal to the PC surface. The combined excitation and extraction enhancements result in a 5.8X increase in the QD output intensity. Further, we demonstrate multiple QD-doped PCs combined on a single surface to optimally couple with distinct populations of QDs, offering a means for blending color output and directionality of multiple wavelengths. Devices are fabricated upon flexible plastic surfaces by a manufacturable replica molding approach.

  14. Microscopic emission and reflectance thermal infrared spectroscopy: instrumentation for quantitative in situ mineralogy of complex planetary surfaces.

    PubMed

    Edwards, C S; Christensen, P R

    2013-04-10

    The diversity of investigations of planetary surfaces, especially Mars, using in situ instrumentation over the last decade is unprecedented in the exploration history of our solar system. The style of instrumentation that landed spacecraft can support is dependent on several parameters, including mass, power consumption, instrument complexity, cost, and desired measurement type (e.g., chemistry, mineralogy, petrology, morphology, etc.), all of which must be evaluated when deciding an appropriate spacecraft payload. We present a laboratory technique for a microscopic emission and reflectance spectrometer for the analysis of martian analog materials as a strong candidate for the next generation of in situ instruments designed to definitively assess sample mineralogy and petrology while preserving geologic context. We discuss the instrument capabilities, signal and noise, and overall system performance. We evaluate the ability of this instrument to quantitatively determine sample mineralogy, including bulk mineral abundances. This capability is greatly enhanced. Whereas the number of mineral components observed from existing emission spectrometers is high (often >5 to 10 depending on the number of accessory and alteration phases present), the number of mineral components at any microscopic measurement spot is low (typically <2 to 3). Since this style of instrument is based on a long heritage of thermal infrared emission spectrometers sent to orbit (the thermal emission spectrometer), sent to planetary surfaces [the mini-thermal emission spectrometers (mini-TES)], and evaluated in laboratory environments (e.g., the Arizona State University emission spectrometer laboratory), direct comparisons to existing data are uniquely possible with this style of instrument. The ability to obtain bulk mineralogy and atmospheric data, much in the same manner as the mini-TESs, is of significant additional value and maintains the long history of atmospheric monitoring for Mars

  15. Measurements of wavelength-dependent double photoelectron emission from single photons in VUV-sensitive photomultiplier tubes

    NASA Astrophysics Data System (ADS)

    Faham, C. H.; Gehman, V. M.; Currie, A.; Dobi, A.; Sorensen, P.; Gaitskell, R. J.

    2015-09-01

    Measurements of double photoelectron emission (DPE) probabilities as a function of wavelength are reported for Hamamatsu R8778, R8520, and R11410 VUV-sensitive photomultiplier tubes (PMTs). In DPE, a single photon strikes the PMT photocathode and produces two photoelectrons instead of a single one. It was found that the fraction of detected photons that result in DPE emission is a function of the incident photon wavelength, and manifests itself below ~250 nm. For the xenon scintillation wavelength of 175 nm, a DPE probability of 18-24% was measured depending on the tube and measurement method. This wavelength-dependent single photon response has implications for the energy calibration and photon counting of current and future liquid xenon detectors such as LUX, LZ, XENON100/1T, Panda-X and XMASS.

  16. Single-photon and photon pair emission from MOVPE-grown In(Ga)As quantum dots: shifting the emission wavelength from 1.0 to 1.3 μm

    NASA Astrophysics Data System (ADS)

    Kettler, Jan; Paul, Matthias; Olbrich, Fabian; Zeuner, Katharina; Jetter, Michael; Michler, Peter

    2016-03-01

    InAs quantum dots grown on a GaAs substrate have been one of the most successful semiconductor material systems to demonstrate single-photon-based quantum optical phenomena. In this context, we present the feasibility to extend the low-temperature photoluminescence emission range of In(Ga)As/GaAs quantum dots grown by metal-organic vapor-phase epitaxy from the typical window between 880 and 960 nm to wavelengths above 1.3 μm. A low quantum dot density can be obtained throughout this range, enabling the demonstration of single- and cascaded photon emission. We further analyze polarization-resolved micro-photoluminescence from a large number of individual quantum dots with respect to anisotropy and size of the underlying fine-structure splittings in the emission spectra. For samples with elevated emission wavelengths, we observe an increasing tendency of the emitted photons to be polarized along the main crystal axes.

  17. Multicolor upconversion emissions in Tm 3+/Er3+ codoped tellurite photonic microwire between silica fiber tapers.

    PubMed

    Chen, Nan-Kuang; Kuan, Pei-Wen; Zhang, Junjie; Zhang, Liyan; Hu, Lili; Lin, Chinlon; Tong, Limin

    2010-12-06

    We report multicolor upconversion emissions including the blue-violet, green, and red lights in a Tm 3+/Er3+codoped tellurite glass photonic microwire between two silica fiber tapers. A silica fiber is tapered until its evanescent field is exposed and then angled-cleaved at the tapered center to divide the tapered fibers into two parts. A tellurite glass is melted by a gas flame to cluster into a sphere at the tip of one tapered fiber. The other angled-cleaved tapered fiber is blended into the melted tellurite glass. When the tellurite glass is melted, the two silica fiber tapers are simultaneously moving outwards to draw the tellurite glass into a microwire in between. The advantage of angled-cleaving on fiber tapers is to avoid cavity resonances in high index photonic microwire. Thus, the broadband white light can be transmitted between silica fibers and a special optical property like high intensity upconversion emission can be achieved. A cw 1064 nm Nd:YAG laser light is launched into the Tm 3+/Er3+ codoped tellurite microwire through a silica fiber taper to generate the multicolor upconversion emissions, including the blue-violet, green, and red lights, simultaneously.

  18. Radiative Decay Engineering 7: Tamm State-Coupled Emission Using a Hybrid Plasmonic-Photonic Structure

    PubMed Central

    Badugu, Ramachandram; Descrovi, Emiliano; Lakowicz, Joseph R.

    2014-01-01

    and display Tamm state-coupled emission (TSCE). In contrast to SPCE, the Tamm states can display either S- or P-polarization. The TSCE angle is highly sensitive to wavelength which suggests the use of Tamm structures to provide both directional emission and wavelength dispersion. Metallic structures can modify fluorophore decay rates but also have high losses. Photonic crystals have low losses, but may lack the enhanced light-induced fields near metals. The combination of plasmonic and photonic structures offers the opportunity for radiative decay engineering to design new formats for clinical testing and other fluorescence-based applications. PMID:24135654

  19. Diamond photonic crystal slab: leaky modes and modified photoluminescence emission of surface-deposited quantum dots.

    PubMed

    Ondič, Lukáš; Babchenko, Oleg; Varga, Marián; Kromka, Alexander; Ctyroký, Jiří; Pelant, Ivan

    2012-01-01

    Detailed analysis of a band diagram of a photonic crystal (PhC) slab prepared on a nano-diamond layer is presented. Even though the PhC is structurally imperfect, the existence of leaky modes, determined both theoretically and experimentally in the broad spectral region, implies that an efficient light interaction with a material periodicity occurs in the sample. It is shown that the luminescence emission spectrum of a light source placed directly on the PhC surface can be modified by employing the optical modes of the studied structure. We stress also the impact of intrinsic optical losses of the nano-diamond on this modification.

  20. Painful spondylolysis or spondylolisthesis studied by radiography and single-photon emission computed tomography

    SciTech Connect

    Collier, B.D.; Johnson, R.P.; Carrera, G.F.; Meyer, G.A.; Schwab, J.P.; Flatley, T.J.; Isitman, A.T.; Hellman, R.S.; Zielonka, J.S.; Knobel, J.

    1985-01-01

    Planar bone scintigraphy (PBS) and single-photon emission computed tomography (SPECT) were compared in 19 adults with radiographic evidence of spondylolysis and/or spondylolisthesis. SPECT was more sensitive than PBS when used to identify symptomatic patients and sites of painful defects in the pars interarticularis. In addition, SPECT allowed more accurate localization than PBS. In 6 patients, spondylolysis or spondylolisthesis was unrealted to low back pain, and SPECT images of the posterior neural arch were normal. The authors conclude that when spondylolysis or spondylolisthesis is the cause of low back pain, pars defects are frequently heralded by increased scintigraphic activity which is best detected and localized by SPECT.

  1. Electron microscopic study of soot particulate matter emissions from aircraft turbine engines.

    PubMed

    Liati, Anthi; Brem, Benjamin T; Durdina, Lukas; Vögtli, Melanie; Dasilva, Yadira Arroyo Rojas; Eggenschwiler, Panayotis Dimopoulos; Wang, Jing

    2014-09-16

    The microscopic characteristics of soot particulate matter (PM) in gas turbine exhaust are critical for an accurate assessment of the potential impacts of the aviation industry on the environment and human health. The morphology and internal structure of soot particles emitted from a CFM 56-7B26/3 turbofan engine were analyzed in an electron microscopic study, down to the nanoscale, for ∼ 100%, ∼ 65%, and ∼ 7% static engine thrust as a proxy for takeoff, cruising, and taxiing, respectively. Sampling was performed directly on transmission electron microscopy (TEM) grids with a state-of-the-art sampling system designed for nonvolatile particulate matter. The electron microscopy results reveal that ∼ 100% thrust produces the highest amount of soot, the highest soot particle volume, and the largest and most crystalline primary soot particles with the lowest oxidative reactivity. The opposite is the case for soot produced during taxiing, where primary soot particles are smallest and most reactive and the soot amount and volume are lowest. The microscopic characteristics of cruising condition soot resemble the ones of the ∼ 100% thrust conditions, but they are more moderate. Real time online measurements of number and mass concentration show also a clear correlation with engine thrust level, comparable with the TEM study. The results of the present work, in particular the small size of primary soot particles present in the exhaust (modes of 24, 20, and 13 nm in diameter for ∼ 100%, ∼ 65% and ∼ 7% engine thrust, respectively) could be a concern for human health and the environment and merit further study. This work further emphasizes the significance of the detailed morphological characteristics of soot for assessing environmental impacts.

  2. Quantification of re-absorption and re-emission processes to determine photon recycling efficiency in perovskite single crystals

    PubMed Central

    Fang, Yanjun; Wei, Haotong; Dong, Qingfeng; Huang, Jinsong

    2017-01-01

    Photon recycling, that is, iterative self-absorption and re-emission by the photoactive layer itself, has been speculated to contribute to the high open-circuit voltage in several types of high efficiency solar cells. For organic–inorganic halide perovskites that have yielded highly efficient photovoltaic devices, however, it remains unclear whether the photon recycling effect is significant enough to improve solar cell efficiency. Here we quantitatively evaluate the re-absorption and re-emission processes to determine photon recycling efficiency in hybrid perovskite with its single crystals by measuring the ratio of the re-emitted photons to the initially excited photons, which is realized by modulating their polarization to differentiate them. The photon recycling efficiencies are revealed to be less than 0.5% in CH3NH3PbI3 and CH3NH3PbBr3 single crystals under excitation intensity close to one sun, highlighting the intrinsically long carrier recombination lifetime instead of the photon-recycling-induced photon propagation as the origin of their long carrier diffusion length. PMID:28220791

  3. Quantification of re-absorption and re-emission processes to determine photon recycling efficiency in perovskite single crystals

    NASA Astrophysics Data System (ADS)

    Fang, Yanjun; Wei, Haotong; Dong, Qingfeng; Huang, Jinsong

    2017-02-01

    Photon recycling, that is, iterative self-absorption and re-emission by the photoactive layer itself, has been speculated to contribute to the high open-circuit voltage in several types of high efficiency solar cells. For organic-inorganic halide perovskites that have yielded highly efficient photovoltaic devices, however, it remains unclear whether the photon recycling effect is significant enough to improve solar cell efficiency. Here we quantitatively evaluate the re-absorption and re-emission processes to determine photon recycling efficiency in hybrid perovskite with its single crystals by measuring the ratio of the re-emitted photons to the initially excited photons, which is realized by modulating their polarization to differentiate them. The photon recycling efficiencies are revealed to be less than 0.5% in CH3NH3PbI3 and CH3NH3PbBr3 single crystals under excitation intensity close to one sun, highlighting the intrinsically long carrier recombination lifetime instead of the photon-recycling-induced photon propagation as the origin of their long carrier diffusion length.

  4. The microscopic approach to the rates of radioactive decay by emission of heavy clusters

    NASA Astrophysics Data System (ADS)

    Ivaşcu, M.; Silişteanu, I.

    1988-08-01

    We have applied a simple microscopic decay theory to the analysis of the rare decay modes. The absolute decay rates are estimated by using the shell model and resonance formation factors and optical model penetrabilities. The resonance formation factors are deduced from the strong interaction form of the theory where the wave function in the internal region is represented in terms of compound nucleus decay. In order to account fully for the data, the implication of internal degrees of freedom was found to be necessary, but no adjustment of Gamow factor was needed. The results have been discussed in the light of the previously reported results and data.

  5. Microscopic calculation for α and heavier cluster emissions from proton rich Ba and Ce isotopes

    NASA Astrophysics Data System (ADS)

    Florescu, A.; Insolia, A.

    1995-08-01

    We present a completely microscopic approach for obtaining the preformation factors and the decay widths of α, 12Ca, and 16O cluster decays. We start from realistic single particle Woods-Saxon wave functions and include a large space BCS-type configuration mixing. A pairing interaction acting among valence particles, placed above a double magic core, was considered. The penetrability is evaluated within the WKB approximation. The model predictions are also checked for some well-known α and 14C decays from even-even nuclei.

  6. Imaging in breast cancer: Single-photon computed tomography and positron-emission tomography

    PubMed Central

    Bénard, François; Turcotte, Éric

    2005-01-01

    Although mammography remains a key imaging method for the early detection and screening of breast cancer, the overall accuracy of this test remains low. Several radiopharmaceuticals have been proposed as adjunct imaging methods to characterize breast masses by single-photon-emission computed tomography (SPECT) and positron-emission tomography (PET). Useful in characterizing indeterminate palpable masses and in the detection of axillary metastases, these techniques are insufficiently sensitive to detect subcentimetric tumor deposits. Their role in staging nodal involvement of the axillary areas therefore currently remains limited. Several enzymes and receptors have been targeted for imaging breast cancers with PET. [18F]Fluorodeoxyglucose is particularly useful in the detection and staging of recurrent breast cancer and in assessing the response to chemotherapy. Several other ligands targeting proliferative activity, protein synthesis, and hormone and cell-membrane receptors may complement this approach by providing unique information about biological characteristics of breast cancer across primary and metastatic tumor sites. PMID:15987467

  7. Development of radioiodinated receptor ligands for cerebral single photon emission tomography

    SciTech Connect

    Knapp, F.F. Jr.; McPherson, D.W.

    1992-01-01

    In the last decade the use of radiolabeled ligands for the imaging of cerebral receptors by emission computed tomography (ECT) has seen rapid growth. The opportunity to routinely perform cerebral single photon emission tomography (SPET) with iodine-123-labeled ligands depends on the availability of receptor ligands into which iodine can be introduced without decreasing the required high target receptor specificity. The use of iodine-123-labeled receptor-specific ligands also depends on the availability of high purity iodine-123 at reasonable costs and the necessary imaging instrumentation. In this paper, the development and current stage of evaluation of various iodine-123-labeled ligands for SPET imaging of dopaminergic, serotonergic and muscarinic acetylcholinergic receptor classes are discussed.

  8. 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.

  9. Development of radioiodinated receptor ligands for cerebral single photon emission tomography

    SciTech Connect

    Knapp, F.F. Jr.; McPherson, D.W.

    1992-03-01

    In the last decade the use of radiolabeled ligands for the imaging of cerebral receptors by emission computed tomography (ECT) has seen rapid growth. The opportunity to routinely perform cerebral single photon emission tomography (SPET) with iodine-123-labeled ligands depends on the availability of receptor ligands into which iodine can be introduced without decreasing the required high target receptor specificity. The use of iodine-123-labeled receptor-specific ligands also depends on the availability of high purity iodine-123 at reasonable costs and the necessary imaging instrumentation. In this paper, the development and current stage of evaluation of various iodine-123-labeled ligands for SPET imaging of dopaminergic, serotonergic and muscarinic acetylcholinergic receptor classes are discussed.

  10. Dementias appear to have individual profiles in single photon emission computed tomography

    SciTech Connect

    Not Available

    1989-02-17

    A number of researchers are seeking clinical applications for single photon emission computed tomographic (SPECT) images of demented patients. They have found that dementias have somewhat individual SPECT profiles. The challenge now, they say, is to determine if the SPECT information is meaningful to the clinician and to develop more specific radiotracers, such as tracers for individual neuroreceptors. The initial work was done with positron emission tomography (PET), a sometimes more sensitive, but much more expensive technique. Recently, a number of centers began trying to duplicate the PET findings using SPECT. Developing SPECT could actually make dementia scanning fairly available, they say. Radiologists estimate that three fourths of the nation's nuclear medicine departments have SPECT scanning machines-either rotating or multiaperature gamma cameras.

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

    PubMed

    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.

  12. Saturation behaviour of colloidal PbSe quantum dot exciton emission coupled into silicon photonic circuits.

    PubMed

    Foell, Charles A; Schelew, Ellen; Qiao, Haijun; Abel, Keith A; Hughes, Stephen; van Veggel, Frank C J M; Young, Jeff F

    2012-05-07

    We report coupling of the excitonic photon emission from photoexcited PbSe colloidal quantum dots (QDs) into an optical circuit that was fabricated in a silicon-on-insulator wafer using a CMOS-compatible process. The coupling between excitons and sub-μm sized silicon channel waveguides was mediated by a photonic crystal microcavity. The intensity of the coupled light saturates rapidly with the optical excitation power. The saturation behaviour was quantitatively studied using an isolated photonic crystal cavity with PbSe QDs site-selectively located at the cavity mode antinode position. Saturation occurs when a few μW of continuous wave HeNe pump power excites the QDs with a Gaussian spot size of 2 μm. By comparing the results with a master equation analysis that rigorously accounts for the complex dielectric environment of the QD excitons, the saturation is attributed to ground state depletion due to a non-radiative exciton decay channel with a trap state lifetime ~ 3 μs.

  13. The photon emission, ATP level and motility of boar spermatozoa during liquid storage.

    PubMed

    Gogol, Piotr; Szcześniak-Fabiańczyk, Barbara; Wierzchoś-Hilczer, Agnieszka

    2009-03-01

    Changes were studied in induced photon emission (as an indicator of oxidative stress), ATP level and sperm motility during seven day-storage of boar semen at 15 degrees C extended with the use of BTS extender. Photon emission was measured using a luminometer equipped with a cooled photomultiplier with a spectral response range from 370 to 620 nm. The time of storage had a significant effect on luminescence parameters (integral and peak max), intracellular ATP level and percentage of motile spermatozoa. The increase in luminescence parameters was paralleled by a decrease in ATP level and sperm motility. A significant correlation was found between the percentage of motile spermatozoa and integral (r=-0.27) and peak max (r=-0.31). ATP level was correlated with integral (r=-0.25) but not with peak max. Our results suggest that reactive oxygen species and products of cell membrane lipid peroxidation have a negative effect on ATP level and sperm motility. Induced luminescence assessment in combination with sperm motility and ATP level can give valuable information about the status and function of spermatozoa which may be relevant for predicting the fertilizing potential of the semen.

  14. Tip-geometry effects in circularly polarized light emission from a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Anisimovas, Egidijus; Johansson, Peter

    1999-02-01

    We present a calculation of the degree of circular polarization ρ, of the light emitted from a scanning tunneling microscope due to tip asymmetry. In order to take into account the essential geometrical features of an imperfect tip its shape is approximated by a tilted spheroid. We work in the nonretarded limit and use experimentally measured dielectric functions to describe the electromagnetic properties of the tip (W and Ir) and sample (noble metals) materials. The results show that the polarization can reach 20-30 % for what we think are moderately asymmetric tips. This result, as well as the strong dependence of ρ on the azimuthal observation angle, is in reasonable agreement with experimental findings [A. L. Vázquez de Parga and S. F. Alvarado, Europhys. Lett. 36, 577 (1996)].

  15. Photon emission by nanocavity-enhanced quantum anti-Zeno effect in solid-state cavity quantum-electrodynamics.

    PubMed

    Yamaguchi, Makoto; Asano, Takashi; Noda, Susumu

    2008-10-27

    Solid-state cavity quantum-electrodynamics (QED) has great potential owing to advances such as coupled systems combining a nanocavity and a quantum dot (QD). These systems involve two photon-emission mechanisms: the Purcell effect in the weak coupling regime and vacuum Rabi-splitting in the strong coupling regime. In this paper, we describe a third emission mechanism based on the quantum anti-Zeno effect (AZE) induced by the pure-dephasing in a QD. This is significantly enhanced by the inherent characteristics of the nanocavity. This mechanism explains the origin of strong photon emission at a cavity mode largely detuned from a QD, previously considered a counterintuitive, prima facie non-energy-conserving, light-emission phenomenon. These findings could help in controlling the decay and emission characteristics of solid-state cavity QED, and developing solid-state quantum devices.

  16. CO2BOLD assessment of moyamoya syndrome: Validation with single photon emission computed tomography and positron emission tomography imaging

    PubMed Central

    Pellaton, Alain; Bijlenga, Philippe; Bouchez, Laurie; Cuvinciuc, Victor; Barnaure, Isabelle; Garibotto, Valentina; Lövblad, Karl-Olof; Haller, Sven

    2016-01-01

    AIM To compare the assessment of cerebrovascular reserve (CVR) using CO2BOLD magnetic resonance imaging (MRI) vs positron emission tomography (PET) and single photon emission computed tomography (SPECT) as reference standard. METHODS Ten consecutive patients (8 women, mean age of 41 ± 26 years) with moyamoya syndrome underwent 14 pre-surgical evaluations for external-internal carotid artery bypass surgery. CVR was assessed using CO2BOLD and PET (4)/SPECT (11) with a maximum interval of 36 d, and evaluated by two experienced neuroradiologists. RESULTS The inter-rater agreement was 0.81 for SPECT (excellent), 0.43 for PET (fair) and 0.7 for CO2BOLD (good). In 9/14 cases, there was a correspondence between CO2BOLD and PET/SPECT. In 4/14 cases, CVR was over-estimated in CO2BOLD, while in 1/14 case, CVR was underestimated in CO2BOLD. The sensitivity of CO2BOLD was 86% and a specificity of 43%. CONCLUSION CO2BOLD can be used for pre-surgical assessment of CVR in patients with moyamoya syndrome and combines the advantages of absent irradiation, high availability of MRI and assessment of brain parenchyma, cerebral vessels and surrogate CVR in one stop. PMID:27928470

  17. Cascaded emission of linearly polarized single photons from positioned InP/GaInP quantum dots

    SciTech Connect

    Braun, T.; Unsleber, S.; Baumann, V.; Schneider, C.; Höfling, S.; Kamp, M.; Gschrey, M.; Rodt, S.; Reitzenstein, S.

    2013-11-04

    We report on the optical characterization of site-controlled InP/GaInP quantum dots (QDs). Spatially resolved low temperature cathodoluminescence proves the long-range ordering of the buried emitters, revealing a yield of ∼90% of optically active, positioned QDs and a strong suppression of emitters on interstitial positions. The emission of single QDs shows a pronounced degree of linear polarization along the [0,−1,1] crystal axis with an average degree of polarization of 94%. Photon correlation measurements of the emission from a single QD indicate the single-photon character of the exciton and biexciton emission lines as well as the cascaded nature of the photon pair.

  18. Nonlinear theory of a two-photon correlated-spontaneous-emission laser: A coherently pumped two-level--two-photon laser

    SciTech Connect

    Lu, N.; Zhao, F.; Bergou, J.

    1989-05-15

    We develop a nonlinear theory of a two-photon correlated-spontaneous-emission laser (CEL) by using an effective interaction Hamiltonian for a two-level system coupled by a two-photon transition. Assuming that the active atoms are prepared initially in a coherent superposition of two atomic levels involved in the two-photon transition, we derive a master equation for the field-density operator by using our quantum theory for coherently pumped lasers. The steady-state properties of the two-photon CEL are studied by converting the field master equation into a Fokker-Planck equation for the antinormal-ordering Q representation of the field-density operator. Because of the injected atomic coherence, the drift and diffusion coefficients become phase sensitive. This leads to laser phase locking and an extra two-photon CEL gain. The laser field can build up from a vacuum in the no-population-inversion region, in contrast to an ordinary two-photon laser for which triggering is needed. We find an approximate steady-state solution of the Q representation for the laser field, which consists of two identical peaks of elliptical type. We calculate the phase variance and, for any given mean photon number, obtain the minimum variance in the phase quadrature as a function of the initial atomic variables. Squeezing of the quantum noise in the phase quadrature is found and it exhibits the following features: (1) it is possible only when the laser intensity is smaller than a certain value; (2) it becomes most significant for small mean photon number, which is achievable in the no-population-inversion region; and (3) a maximum of 50% squeezing can be asymptotically approached in the small laser intensity limit.

  19. Quantitative and Qualitative Imaging in Single Photon Emission Tomography for Nuclear Medicine Applications.

    NASA Astrophysics Data System (ADS)

    Masoomi, Mojtaba (Arash).

    Available from UMI in association with The British Library. An important goal of single photon emission tomography (SPECT) is the determination of absolute regional radionuclide concentration as a function of time. Quantitative and qualitative studies of SPECT with regard to clinical application is the object of this work. Three basic approaches for image reconstruction and factors which affect the choice of a reconstruction algorithm have been reviewed, discussed and the reconstruction techniques, GRADY and CBP evaluated, based on computer modelling. A sophisticated package of computational subroutines, RECLBL, for image reconstruction and for generation of phantoms, which was fully implemented on PRIME was used throughout this study. Two different systems, a rotating gamma-camera and a prototype scanning-rig have been used to carry out tomography experiments with different phantoms in emission and transmission mode. Performance assessment and reproducibility of the gamma-camera was tested prior to the experimental work. SPECT studies are generally hampered for a number of reasons, the most severe being attenuation and scattering. The effect of scattered photons on image quality was discussed, three distinct techniques were utilised to correct the images and results were compared. Determination of the depth of the source, Am-241 and Tc-99m in the attenuating media, water and TEMEX by analysing the spectroscopic data base on the SPR and spatial resolution was studied, results revealed that both techniques had the same range of depth sensitivity. A method of simultaneous emission and transmission tomography was developed to correct the images for attenuation. The reproducibility of the technique was examined. Results showed that the technique is able to present a promising and a practical approach to more accurate quantitative SPECT imaging. A procedure to evaluate images, under certain conditions has been defined, its properties were evaluated using computer

  20. Morphology and chemical composition analysis of inorganic nanosheets by the field-emission scanning electron microscope system.

    PubMed

    Li, Qinghui; Ono, Yuki; Homma, Yoshikazu; Nakai, Izumi; Fukuda, Katsutoshi; Sasaki, Takayoshi; Tanaka, Keiichi; Nakayama, Satoshi

    2009-01-01

    Nanosheets can be used as building blocks to fabricate versatile nanostructured materials. In this paper, morphology of the Cs(4)W(11)O(36) and Nb(3)O(8) and TaO(3) sheets with different layers are analyzed by different field-emission scanning electron microscopes (FE-SEMs). Chemical composition of the single-layered Cs(4)W(11)O(36) with thickness of about 2 nm, and multilayered Nb(3)O(8) nanosheets with thickness of less than 14 nm are analyzed by both the Si(Li) solid-state detector and transition edge sensor (TES) microcalorimeter, successfully. The effects of energy resolution, accelerating voltage and substrate on the quantitative analysis are discussed briefly.

  1. Single-photon emission from InAsP quantum dots embedded in density-controlled InP nanowires

    NASA Astrophysics Data System (ADS)

    Yanase, Shougo; Sasakura, Hirotaka; Hara, Shinjiro; Motohisa, Junichi

    2017-04-01

    We attempted to control the density and size of InP-based nanowires (NWs) and nanowire quantum dots (NW-QDs) during selective-area metalorganic vapor phase epitaxy. InP nanowire arrays with a 5 µm pitch and an average NW diameter d of 67 nm were successfully grown by optimization of growth conditions. InAsP quantum dots were embedded in these density-controlled InP NW arrays, and clear single-photon emission and exciton-biexciton cascaded emission were confirmed by excitation-dependent photoluminescence and photon correlation measurements.

  2. Emission FTIR analyses of thin microscopic patches of jet fuel residue deposited on heated metal surface

    NASA Technical Reports Server (NTRS)

    Lauer, J. L.; Vogel, P.

    1984-01-01

    Deposits laid down in patches on metal strips in a high pressure/high temperature fuel system simulator operated with aerated fuel at varying flow rates were analyzed by emission FTIR in terms of functional groups. Significant differences were found in the spectra and amounts of deposits derived from fuels to which small concentrations of oxygen-, nitrogen-, or sulfur-containing heterocyclics or metal naphthenates were added. The spectra of deposits generated on strips by heating fuels and air in a closed container were very different from those of the flowing fluid deposits. One such closed-container dodecane deposit on silver gave a strong surface-enhanced Raman spectrum.

  3. Scanning tunneling microscope light emission: Effect of the strong dc field on junction plasmons

    NASA Astrophysics Data System (ADS)

    Kalathingal, Vijith; Dawson, Paul; Mitra, J.

    2016-07-01

    The observed energies of the localized surface plasmons (LSPs) excited at the tip-sample junction of a scanning tunneling microscope, as identified by spectral peaks in the light output, are very significantly redshifted with respect to calculations that use standard optical data for the tip and sample material, gold in this case. We argue that this anomaly depends on the extreme field in the sub-nm tunneling proximity of the tip and the sample, across which a dc bias (1-2 V) is applied. Finite element modeling analysis is presented of a gold nanosphere-plane (NS-P) combination in tunneling proximity and, crucially, in the presence of a high static electric field (˜109V /m ). It is argued that the strong dc field induces nonlinear corrections to the dielectric function of the gold via the effect of a large background polarizability through the nonlinear, χ(3 ) susceptibility contribution. When fed into the model system the modified optical data alters the LSP cavity modes of the NS-P system to indeed reveal a large redshift in energy compared to those of the virgin gold NS-P system. The net outcome may be regarded as equivalent to lowering the bulk plasmon energy, the physical interpretation being that the intense field of the tunneling environment leads to surface charge screening, effectively reducing the density of free electrons available to participate in the plasmon oscillations.

  4. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

    SciTech Connect

    Tretiak, Sergei

    2009-01-01

    The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D{prime} or A{prime} units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted

  5. Enhanced single-photon emission from a diamond-silver aperture

    NASA Astrophysics Data System (ADS)

    Choy, Jennifer T.; Hausmann, Birgit J. M.; Babinec, Thomas M.; Bulu, Irfan; Khan, Mughees; Maletinsky, Patrick; Yacoby, Amir; Lončar, Marko

    2011-12-01

    Solid-state quantum emitters, such as the nitrogen-vacancy centre in diamond, are robust systems for practical realizations of various quantum information processing protocols and nanoscale magnetometry schemes at room temperature. Such applications benefit from the high emission efficiency and flux of single photons, which can be achieved by engineering the electromagnetic environment of the emitter. One attractive approach is based on plasmonic resonators, in which sub-wavelength confinement of optical fields can strongly modify the spontaneous emission of a suitably embedded dipole despite having only modest quality factors. Meanwhile, the scalability of solid-state quantum systems critically depends on the ability to control such emitter-cavity interaction in a number of devices arranged in parallel. Here, we demonstrate a method to enhance the radiative emission rate of single nitrogen-vacancy centres in ordered arrays of plasmonic apertures that promises greater scalability over the previously demonstrated bottom-up approaches for the realization of on-chip quantum networks.

  6. Active Mediation of Plasmon Enhanced Localized Exciton Generation, Carrier Diffusion and Enhanced Photon Emission.

    PubMed

    Haq, Sharmin; Addamane, Sadhvikas; Kafle, Bijesh; Huang, Danhong; Balakrishnan, Ganesh; Habteyes, Terefe G

    2017-04-13

    Understanding the enhancement of charge carrier generation and their diffusion is imperative for improving the efficiency of optoelectronic devices particularly infrared photodetectors that are less developed than their visible counterpart. Here, using gold nanorods as model plasmonic systems, InAs quantum dots (QDs) embedded in an InGaAs quantum well as an emitter, and GaAs as an active mediator of surface plasmons for enhancing carrier generation and photon emission, the distance dependence of energy transfer and carrier diffusion have been investigated both experimentally and theoretically. Analysis of the QD emission enhancement as a function of distance reveals a Förster radius of 3.85 ± 0.15 nm, a near-field decay length of 4.8 ± 0.1 nm and an effective carrier diffusion length of 64.0 ± 3.0 nm. Theoretical study of the temporal-evolution of the electron-hole occupation number of the excited states of the QDs indicates that the emission enhancement trend is determined by the carrier diffusion and capture rates.

  7. Polychromatic spectral pattern analysis of ultra-weak photon emissions from a human body.

    PubMed

    Kobayashi, Masaki; Iwasa, Torai; Tada, Mika

    2016-06-01

    Ultra-weak photon emission (UPE), often designated as biophoton emission, is generally observed in a wide range of living organisms, including human beings. This phenomenon is closely associated with reactive oxygen species (ROS) generated during normal metabolic processes and pathological states induced by oxidative stress. Application of UPE extracting the pathophysiological information has long been anticipated because of its potential non-invasiveness, facilitating its diagnostic use. Nevertheless, its weak intensity and UPE mechanism complexity hinder its use for practical applications. Spectroscopy is crucially important for UPE analysis. However, filter-type spectroscopy technique, used as a conventional method for UPE analysis, intrinsically limits its performance because of its monochromatic scheme. To overcome the shortcomings of conventional methods, the authors developed a polychromatic spectroscopy system for UPE spectral pattern analysis. It is based on a highly efficient lens systems and a transmission-type diffraction grating with a highly sensitive, cooled, charge-coupled-device (CCD) camera. Spectral pattern analysis of the human body was done for a fingertip using the developed system. The UPE spectrum covers the spectral range of 450-750nm, with a dominant emission region of 570-670nm. The primary peak is located in the 600-650nm region. Furthermore, application of UPE source exploration was demonstrated with the chemiluminescence spectrum of melanin and coexistence with oxidized linoleic acid.

  8. Local detection efficiency of a NbN superconducting single photon detector explored by a scattering scanning near-field optical microscope.

    PubMed

    Wang, Qiang; Renema, Jelmer J; Engel, Andreas; van Exter, Martin P; de Dood, Michiel J A

    2015-09-21

    We propose an experiment to directly probe the local response of a superconducting single photon detector using a sharp metal tip in a scattering scanning near-field optical microscope. The optical absorption is obtained by simulating the tip-detector system, where the tip-detector is illuminated from the side, with the tip functioning as an optical antenna. The local detection efficiency is calculated by considering the recently introduced position-dependent threshold current in the detector. The calculated response for a 150 nm wide detector shows a peak close to the edge that can be spatially resolved with an estimated resolution of ∼ 20 nm, using a tip with parameters that are experimentally accessible.

  9. Emission FTIR analyses of thin microscopic patches of jet fuel residues deposited on heated metal surfaces

    NASA Technical Reports Server (NTRS)

    Lauer, J. L.; Vogel, P.

    1986-01-01

    The relationship of fuel stability to fuel composition and the development of mechanisms for deposit formation were investigated. Fuel deposits reduce heat transfer efficiency and increase resistance to fuel flow and are highly detrimental to aircraft performance. Infrared emission Fourier transform spectroscopy was chosen as the primary method of analysis because it was sensitive enough to be used in-situ on tiny patches of monolayers or of only a few molecular layers of deposits which generally proved completely insoluble in any nondestructive solvents. Deposits of four base fuels were compared; dodecane, a dodecane/tetralin blend, commercial Jet A fuel, and a broadened-properties jet fuel particularly rich in polynuclear aromatics. Every fuel in turn was provided with and without small additions of such additives as thiophene, furan, pyrrole, and copper and iron naphthenates.

  10. Single photon emission computerized tomography (SPECT) in detecting neurodegeneration in Huntington's disease.

    PubMed

    Reynolds, N C; Hellman, R S; Tikofsky, R S; Prost, R W; Mark, L P; Elejalde, B R; Lebel, R; Hamsher, K S; Swanson, S; Benezra, E E

    2002-01-01

    Single photon emission computerized tomography (SPECT) studies were performed on 34 manifest Huntington's disease (HD) patients at various stages of clinical pathology ranging from early chorea to late dystonia with or without signs of dementia and 12 pre-symptomatic patients with abnormal terminal CAG expansions. Thirty HD patients with obvious clinical signs and seven pre-symptomatic patients without signs or symptoms of HD displayed selective caudate hypoperfusion by direct visual inspection. Such qualitative, selective striatal hypoperfusion patterns can be indicative of early and persistent metabolic changes in striatal neuropathology. SPECT studies can be useful in documenting early pre-clinical changes in patients with abnormal terminal CAG expansions and in confirming the presence of caudate pathology in patients with clinical signs of HD.

  11. Detection of avascular necrosis in adults by single photon emission computed tomography

    SciTech Connect

    Collier, B.D.; Johnston, R.P.; Carrera, G.; Isitman, A.T.; Hellman, R.S.; Zielonka, J.S.

    1984-01-01

    Twenty-one adult patients with the clinical diagnosis of avascular necrosis (AVN) of the femoral head were examined with planar bone scintigraphy (high resolution collimator) and single photon emission computed tomography (SPECT). The duration of hip pain ranged from 1 day to 18 months. Risk factors (including steroids, renal transplantation, alcoholism, and trauma) were present in 17 cases. A final diagnosis of AVN (20 hips), osteochondral facture, or stress fracture, was established for 17 patients. The 4 remaining patients, who were radiographically normal and did not complain of pain 3 months later, were thought to have no significant bone pathology. SPECT and planar bone scintigraphy were reported as positive for AVN only if a photopenic bony defect could be identified. In particular, uniformly increased activity throughout the femoral head was not considered to be diagnostic of AVN. The authors conclude that by identifying a photopenic defect which is not evident on planar bone scintigraphy, SPECT can contribute to accurate diagnosis of AVN.

  12. High-energy two-electron capture with emission of a single photon

    SciTech Connect

    Drukarev, E. G.; Mikhailov, A. I.; Mikhailov, I. A.; Scheid, W.

    2007-12-15

    We investigate the two-electron capture with emission of a single photon to the ground state in the Coulomb field of a heavy nucleus in its collision with a light atom. Describing electron-electron interactions in the bound state perturbatively, we obtained an analytical formula for the high-energy limit of the cross section. In combination with previous results obtained in the same approach we calculated the cross section in a broad interval of energies of the collision. We show that the amplitude of the process at high energy depends on the behavior of the bound state wave function near the triple coalescence point. We analyze the properties of the approximate wave functions which are necessary for the description of the high-energy limit.

  13. Brain perfusion single photon emission computed tomography in major psychiatric disorders: From basics to clinical practice

    PubMed Central

    Santra, Amburanjan; Kumar, Rakesh

    2014-01-01

    Brain single photon emission computed tomography (SPECT) is a well-established and reliable method to assess brain function through measurement of regional cerebral blood flow (rCBF). It can be used to define a patient's pathophysiological status when neurological or psychiatric symptoms cannot be explained by anatomical neuroimaging findings. Though there is ample evidence validating brain SPECT as a technique to track human behavior and correlating psychiatric disorders with dysfunction of specific brain regions, only few psychiatrists have adopted brain SPECT in routine clinical practice. It can be utilized to evaluate the involvement of brain regions in a particular patient, to individualize treatment on basis of SPECT findings, to monitor the treatment response and modify treatment, if necessary. In this article, we have reviewed the available studies in this regard from existing literature and tried to present the evidence for establishing the clinical role of brain SPECT in major psychiatric illnesses. PMID:25400359

  14. Myocardial stunning in hypertrophic cardiomyopathy: recovery predicted by single photon emission computed tomographic thallium-201 scintigraphy

    SciTech Connect

    Fine, D.G.; Clements, I.P.; Callahan, M.J.

    1989-05-01

    A young woman with hypertrophic cardiomyopathy confirmed by echocardiography and cardiac catheterization presented with chest pain and features of a large left ventricular aneurysm. The initial diagnosis was myocardial ischemia with either an evolving or an ancient myocardial infarction. Subsequently, verapamil therapy was associated with complete resolution of the extensive left ventricular wall motion abnormalities, normalization of left ventricular ejection fraction and a minimal myocardial infarction. Normal thallium uptake on single photon emission computed tomographic scintigraphy early in the hospital course predicted myocardial viability in the region of the aneurysm. Thus, orally administered verapamil may reverse spontaneous extensive myocardial ischemia in hypertrophic cardiomyopathy and possibly limit the extent of myocardial infarction in such circumstances.

  15. Novel cone lasing emission in a non-uniform one-dimensional photonic crystal

    NASA Astrophysics Data System (ADS)

    Li, Yi; Zhou, Wen-Yuan; Ying, Cui-Feng; Yang, Na; Chen, Shao-Jie; Ye, Qing; Tian, Jian-Guo

    2015-06-01

    Novel cone lasing emission is observed from a photonic crystal (PC) with graded layers, which is fabricated by two-beam holographic interference in dichromated gelatin. The cone lasing is composed of one lasing spot and one concentric lasing ring. The good agreement between the experimental results and a numerical simulation performed using the transfer matrix method demonstrates that this lasing ring is induced by the coupling between the band edge and minigap, which is represented as some oscillations near the band edge in the passband of the reflection spectrum. The cone lasing may be useful for multi-wavelength fluorescence detection since the dual-colour directional enhanced fluorescence can be achieved without the mutual interference of lasing modes. Moreover, this readily observable cone lasing provides a direct visualization of the dispersion relation of non-uniform PCs.

  16. Diagnosis of partial and total physeal arrest by bone single-photon emission computed tomography.

    PubMed

    Wioland, M; Bonnerot, V

    1993-09-01

    Bone single-photon emission computed tomography (SPECT), capable of creating maps of the distribution of osteoblastic activity in every spatial plane of a physis, should provide images of diagnostic value in the case of patients suffering from growth arrests (epiphysiodeses). Seventy-five bone SPECT scans were obtained in 64 children suspected to have developed physeal arrests. The transaxial slices of the physis, in the case of partial epiphysiodeses: (a) indicated the percentage of the remaining normal physis, (b) located the bony bridge within the physis and (c) showed the slowdown of the growth of the remaining normal physis induced by the bony bridge in some children. Misdiagnosis occurred in six patients. For total epiphysiodeses, the radionuclide diagnosis was confirmed in 20 of 21 patients. Radionuclide, x-ray and MRI examinations in the study of growth disturbances were found to be complementary.

  17. 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

  18. Enhancement and Inhibition of Spontaneous Photon Emission by Resonant Silicon Nanoantennas

    NASA Astrophysics Data System (ADS)

    Bouchet, Dorian; Mivelle, Mathieu; Proust, Julien; Gallas, Bruno; Ozerov, Igor; Garcia-Parajo, Maria F.; Gulinatti, Angelo; Rech, Ivan; De Wilde, Yannick; Bonod, Nicolas; Krachmalnicoff, Valentina; Bidault, Sébastien

    2016-12-01

    Substituting noble metals for high-index dielectrics has recently been proposed as an alternative strategy in nanophotonics to design broadband optical resonators and circumvent the Ohmic losses of plasmonic materials. In this paper, we demonstrate that subwavelength silicon nanoantennas can manipulate the photon emission dynamics of fluorescent molecules. In practice, we show that dielectric nanoantennas can both increase and decrease the local density of optical states at room temperature, a process that is inaccessible with noble metals at the nanoscale. Using scanning probe microscopy, we analyze quantitatively, in three dimensions, the near-field interaction between a 100-nm fluorescent nanosphere and silicon nanoantennas with diameters ranging between 170 and 250 nm. Associated with numerical simulations, these measurements indicate increased or decreased total spontaneous decay rates by up to 15% and a gain in the collection efficiency of emitted photons by up to 85%. Our study demonstrates the potential of silicon-based nanoantennas for the low-loss manipulation of solid-state emitters at the nanoscale and at room temperature.

  19. Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions

    NASA Astrophysics Data System (ADS)

    Parzefall, M.; Bharadwaj, P.; Jain, A.; Taniguchi, T.; Watanabe, K.; Novotny, L.

    2015-12-01

    The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.

  20. Increased light extraction and directional emission control in gallium nitride photonic crystal light emitting diodes

    NASA Astrophysics Data System (ADS)

    McGroddy, Kelly C.

    GaN has become the prominent material for blue-green light emitting diodes (LEDs) and efficient white light sources. Advancements in LED efficiency for lighting has the potential to dramatically impact energy consumption world wide. A limiting factor to achieving high efficiencies in GaN LEDs is the light extraction efficiency. This work addresses many key issues pertaining to the use of PhCs to increase the extraction efficiency and emission directionality of GaN LEDs. Limitations in extraction efficiency of GaN photonic crystal light emitting diodes (LEDs) are addressed by implementing an LED design using both 2D photonic crystals (PhCs) in-plane and index guiding layers (IGLs) in the vertical direction. The effects of PhCs on light extraction and emission directionality from GaN LEDs are studied experimentally. Angular resolved electroluminescence clearly shows the combined effect of controlling the vertical mode profile with the IGLs and tailoring the emission profile with the periodicity of the PhC lattice. Various materials are used to increase the index contrast of the IGL and the effects are measured. Increases in vertical emission as high as 3.5x are achieved for PhC LEDs with an Al0.12Ga0.88N IGL over non-PhC LEDs with a ˜30% improvement attributed to the incorporation of the AlGaN IGL. This enhancement is achieved by tailoring both the directionality and guided mode control. The impact of incorporating PhCs and IGLs on LED device design and performance are addressed. Effects of etching the PhCs near the QWs have been observed and explanations for this behavior will be discussed. It will be shown that an un-doped IGL can severely limit current spreading in the n-type side of the device and have a detrimental impact on device performance. Finally, a method of patterning PhCs with periodicities as small as 230nm by laser interference lithography and imprint lithography has been developed to provide a fast, inexpensive method of pattering PhCs over large

  1. Suppression of single-cesium-atom heating in a microscopic optical dipole trap for demonstration of an 852-nm triggered single-photon source

    NASA Astrophysics Data System (ADS)

    Liu, Bei; Jin, Gang; He, Jun; Wang, Junmin

    2016-07-01

    We investigate single-cesium-atom heating owing to the momentum accumulation process induced by the resonant pulsed excitation in a microscopic optical dipole trap formed by a strongly focused 1064-nm laser beam. The heating depends on the trap frequency, which restricts the maximum repetition rate of the pulsed excitation. We experimentally verify the heating of a single atom and then demonstrate how to suppress it with an optimized pulsed excitation and cooling method. The typical trap lifetime of a single cesium atom is extended from 108 ±6 μ s to 2536 ±31 ms , and the corresponding number of excitations increases from ˜108 to ˜360 000 . In applying this faster cooling method, we use the trapped single cesium atom as a triggered single-photon source at an excitation repetition rate of 10 MHz. The second-order intensity correlations of the emitted single photons are characterized by implementing a Hanbury Brown and Twiss setup, and a clear antibunching effect has been observed.

  2. Two-color single-photon emission from InAs quantum dots: toward logic information management using quantum light.

    PubMed

    Rivas, David; Muñoz-Matutano, Guillermo; Canet-Ferrer, Josep; García-Calzada, Raúl; Trevisi, Giovanna; Seravalli, Luca; Frigeri, Paola; Martínez-Pastor, Juan P

    2014-02-12

    In this work, we propose the use of the Hanbury-Brown and Twiss interferometric technique and a switchable two-color excitation method for evaluating the exciton and noncorrelated electron-hole dynamics associated with single photon emission from indium arsenide (InAs) self-assembled quantum dots (QDs). Using a microstate master equation model we demonstrate that our single QDs are described by nonlinear exciton dynamics. The simultaneous detection of two-color, single photon emission from InAs QDs using these nonlinear dynamics was used to design a NOT AND logic transference function. This computational functionality combines the advantages of working with light/photons as input/output device parameters (all-optical system) and that of a nanodevice (QD size of ∼ 20 nm) while also providing high optical sensitivity (ultralow optical power operational requirements). These system features represent an important and interesting step toward the development of new prototypes for the incoming quantum information technologies.

  3. Electric-Field-Induced Energy Tuning of On-Demand Entangled-Photon Emission from Self-Assembled Quantum Dots.

    PubMed

    Zhang, Jiaxiang; Zallo, Eugenio; Höfer, Bianca; Chen, Yan; Keil, Robert; Zopf, Michael; Böttner, Stefan; Ding, Fei; Schmidt, Oliver G

    2017-01-11

    We explore a method to achieve electrical control over the energy of on-demand entangled-photon emission from self-assembled quantum dots (QDs). The device used in our work consists of an electrically tunable diode-like membrane integrated onto a piezoactuator, which is capable of exerting a uniaxial stress on QDs. We theoretically reveal that, through application of the quantum-confined Stark effect to QDs by a vertical electric field, the critical uniaxial stress used to eliminate the fine structure splitting of QDs can be linearly tuned. This feature allows experimental realization of a triggered source of energy-tunable entangled-photon emission. Our demonstration represents an important step toward realization of a solid-state quantum repeater using indistinguishable entangled photons in Bell state measurements.

  4. Microscopic imaging of glyceraldehyde-induced tissue glycation with intrinsic second harmonic generation and two-photon fluorescence contrasts

    NASA Astrophysics Data System (ADS)

    Hwang, Yu Jer; Granelli, Joseph; Tirumalasetty, Manasa; Lyubovitsky, Julia

    2013-02-01

    The bioinspired approaches to tissue strengthening and preservation rely on non-toxic cross-linking agents one of which is glyceraldehyde. In this study we used multiphoton microscopy that employs second harmonic generation (SHG) contrast to evaluate collagen microstructures and two-photon fluorescence (TPF) contrast to monitor progression of cross-linking upon treatment of tissues with glyceraldehyde. We examined collagen hydrogels assembled at 37 °C and 27 °C, bovine scleral and corneal tissues, skin as well as rat tail tendons. The results show a different effect of glyceraldehyde on collagen microstructures within the above tissues. This effect depends on the original microstructural assembly of collagen within a specific tissue. Our data suggests that epidermis (in skin and cornea) will protect collagen from cross-linking with glyceraldehyde. The work highlights benefits of monitoring progression of collagen cross-linking and effects of cross-linking on fiber microstructures as imaged with SHG and TPF signals.

  5. Accuracy of coregistration of single-photon emission CT with MR via a brain surface matching technique.

    PubMed

    Hogan, R E; Cook, M J; Kilpatrick, C J; Binns, D W; Desmond, P M; Morris, K

    1996-04-01

    We describe a technique of brain surface matching of single-photon emission CT and MR images in human subjects and document the accuracy of this technique with the use of fiduciary markers. This mismatch averaged 4.3 mm as measured by the fiduciary markers and 2.1 mm as measured by the root mean square distance.

  6. Analysis of photon emission from 50--350-keV proton impact on H2O

    NASA Astrophysics Data System (ADS)

    Goldman, Benjamin D.; Timpone, Stephanie A.; Monce, Michael N.; Mitchell, Laurel; Griffin, Brian

    2011-04-01

    We have measured photon emission cross sections from neutral fragments produced by collisions of 50-350 keV protons with H2O molecules. Balmer α-δ emissions from both the target and projectile were recorded. We also analyzed A2Σ+-X2Π (0,0) and (1,0) emission from the excited OH fragment produced during target dissociation. Trends in the cross sections revealed two key properties of the collision process: (1) The Bethe theory accurately describes target emission from both H and OH fragments and (2) the ratio of any two Balmer emission cross sections for both the target and projectile can be approximated by simple functions of the respective optical oscillator strengths. Finally, we provide the Bethe fit parameters necessary to calculate the target emission cross sections at all nonrelativistic impact energies.

  7. Extended calibration range for prompt photon emission in ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Bellini, F.; Boehlen, T. T.; Chin, M. P. W.; Collamati, F.; De Lucia, E.; Faccini, R.; Ferrari, A.; Lanza, L.; Mancini-Terracciano, C.; Marafini, M.; Mattei, I.; Morganti, S.; Ortega, P. G.; Patera, V.; Piersanti, L.; Russomando, A.; Sala, P. R.; Sarti, A.; Sciubba, A.; Solfaroli Camillocci, E.; Voena, C.

    2014-05-01

    Monitoring the dose delivered during proton and carbon ion therapy is still a matter of research. Among the possible solutions, several exploit the measurement of the single photon emission from nuclear decays induced by the irradiation. To fully characterize such emission the detectors need development, since the energy spectrum spans the range above the MeV that is not traditionally used in medical applications. On the other hand, a deeper understanding of the reactions involving gamma production is needed in order to improve the physic models of Monte Carlo codes, relevant for an accurate prediction of the prompt-gamma energy spectrum. This paper describes a calibration technique tailored for the range of energy of interest and reanalyzes the data of the interaction of a 80 MeV/u fully stripped carbon ion beam with a Poly-methyl methacrylate target. By adopting the FLUKA simulation with the appropriate calibration and resolution a significant improvement in the agreement between data and simulation is reported.

  8. Effects of nanoscale vacuum gap on photon-enhanced thermionic emission devices

    SciTech Connect

    Wang, Yuan; Liao, Tianjun; Zhang, Yanchao; Chen, Xiaohang E-mail: jcchen@xmu.edu.cn; Su, Shanhe; Chen, Jincan E-mail: jcchen@xmu.edu.cn

    2016-01-28

    A new model of the photon-enhanced thermionic emission (PETE) device with a nanoscale vacuum gap is established by introducing the quantum tunneling effect and the image force correction. Analytic expressions for both the thermionic emission and tunneling currents are derived. The electron concentration and the temperature of the cathode are determined by the particle conservation and energy balance equations. The effects of the operating voltage on the maximum potential barrier, cathode temperature, electron concentration and equilibrium electron concentration of the conduction band, and efficiency of the PETE device are discussed in detail for different given values of the vacuum gap length. The influence of the band gap of the cathode and flux concentration on the efficiency is further analyzed. The maximum efficiency of the PETE and the corresponding optimum values of the band gap and the operating voltage are determined. The results obtained here show that the efficiency of the PETE device can be significantly improved by employing a nanoscale vacuum gap.

  9. Negative space charge effects in photon-enhanced thermionic emission solar converters

    SciTech Connect

    Segev, G.; Weisman, D.; Rosenwaks, Y.; Kribus, A.

    2015-07-06

    In thermionic energy converters, electrons in the gap between electrodes form a negative space charge and inhibit the emission of additional electrons, causing a significant reduction in conversion efficiency. However, in Photon Enhanced Thermionic Emission (PETE) solar energy converters, electrons that are reflected by the electric field in the gap return to the cathode with energy above the conduction band minimum. These electrons first occupy the conduction band from which they can be reemitted. This form of electron recycling makes PETE converters less susceptible to negative space charge loss. While the negative space charge effect was studied extensively in thermionic converters, modeling its effect in PETE converters does not account for important issues such as this form of electron recycling, nor the cathode thermal energy balance. Here, we investigate the space charge effect in PETE solar converters accounting for electron recycling, with full coupling of the cathode and gap models, and addressing conservation of both electric and thermal energy. The analysis shows that the negative space charge loss is lower than previously reported, allowing somewhat larger gaps compared to previous predictions. For a converter with a specific gap, there is an optimal solar flux concentration. The optimal solar flux concentration, the cathode temperature, and the efficiency all increase with smaller gaps. For example, for a gap of 3 μm the maximum efficiency is 38% and the optimal flux concentration is 628, while for a gap of 5 μm the maximum efficiency is 31% and optimal flux concentration is 163.

  10. Single Cesium Lead Halide Perovskite Nanocrystals at Low Temperature: Fast Single-Photon Emission, Reduced Blinking, and Exciton Fine Structure

    PubMed Central

    2016-01-01

    Metal-halide semiconductors with perovskite crystal structure are attractive due to their facile solution processability, and have recently been harnessed very successfully for high-efficiency photovoltaics and bright light sources. Here, we show that at low temperature single colloidal cesium lead halide (CsPbX3, where X = Cl/Br) nanocrystals exhibit stable, narrow-band emission with suppressed blinking and small spectral diffusion. Photon antibunching demonstrates unambiguously nonclassical single-photon emission with radiative decay on the order of 250 ps, representing a significant acceleration compared to other common quantum emitters. High-resolution spectroscopy provides insight into the complex nature of the emission process such as the fine structure and charged exciton dynamics. PMID:26771336

  11. Measurement of spontaneous-emission enhancement near the one-dimensional photonic band edge of semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Tocci, Michael D.; Scalora, Michael; Bloemer, Mark J.; Dowling, Jonathan P.; Bowden, Charles M.

    1996-04-01

    We present results of an experimental investigation into alteration of the spontaneous emission spectrum of GaAs from within one-dimensional photonic band gap (PBG) structures. The PBG samples are multilayer AlAs/Al0.2Ga0.8As/GaAs p-i-n light-emitting diodes, with layers arranged as a distributed Bragg reflector. The emission spectra normal to the layers are measured, and we use a simple method to model the power spectrum of spontaneous emission from within the structures. We find that the emitted power is enhanced by a factor of 3.5 at the frequencies near the photonic band edge.

  12. Spontaneous emission intensity and anisotropy of quantum dot films in proximity to nanoscale photonic-plasmonic templates

    NASA Astrophysics Data System (ADS)

    Indukuri, Chaitanya; Basu, J. K.

    2016-07-01

    We discuss results on spontaneous emission intensity and lifetime anisotropy of cadmium selenide quantum dot monolayer films placed in close proximity to a porous block copolymer based photonic-plasmonic two dimensional array. The porous block copolymer cylinders can be filled with metal nanoparticles and the concentration of these nanoparticles is varied to control both the photoluminescence intensity and lifetime of a layer of quantum dots placed above the template. Significant emission enhancement is achieved even for the quantum dot layer whose core lies about 1 nm above the template surface. Interestingly, polarised decay lifetime analysis indicates considerable emission anisotropy, as well for these quantum dots. Our results thus demonstrates how such hybrid optical materials can be created with controlled optical properties and suggests extension of this method to other novel two dimensional materials in combination with the photonic-plasmonic template.

  13. Room Temperature Single-Photon Emission from Individual Perovskite Quantum Dots.

    PubMed

    Park, Young-Shin; Guo, Shaojun; Makarov, Nikolay S; Klimov, Victor I

    2015-10-27

    Lead-halide-based perovskites have been the subject of numerous recent studies largely motivated by their exceptional performance in solar cells. Electronic and optical properties of these materials have been commonly controlled by varying the composition (e.g., the halide component) and/or crystal structure. Use of nanostructured forms of perovskites can provide additional means for tailoring their functionalities via effects of quantum confinement and wave function engineering. Furthermore, it may enable applications that explicitly rely on the quantum nature of electronic excitations. Here, we demonstrate that CsPbX3 quantum dots (X = I, Br) can serve as room-temperature sources of quantum light, as indicated by strong photon antibunching detected in single-dot photoluminescence measurements. We explain this observation by the presence of fast nonradiative Auger recombination, which renders multiexciton states virtually nonemissive and limits the fraction of photon coincidence events to ∼6% on average. We analyze limitations of these quantum dots associated with irreversible photodegradation and fluctuations ("blinking") of the photoluminescence intensity. On the basis of emission intensity-lifetime correlations, we assign the "blinking" behavior to random charging/discharging of the quantum dot driven by photoassisted ionization. This study suggests that perovskite quantum dots hold significant promise for applications such as quantum emitters; however, to realize this goal, one must resolve the problems of photochemical stability and photocharging. These problems are largely similar to those of more traditional quantum dots and, hopefully, can be successfully resolved using advanced methodologies developed over the years in the field of colloidal nanostructures.

  14. Low-noise cold-field emission current obtained between two opposed carbon cone nanotips during in situ transmission electron microscope biasing

    SciTech Connect

    Knoop, L. de; Gatel, C.; Houdellier, F.; Monthioux, M.; Masseboeuf, A.; Snoeck, E.; Hÿtch, M. J.

    2015-06-29

    A dedicated transmission electron microscope sample holder has been used to study in situ the cold-field emission process of carbon cone nanotips (CCnTs). We show that when using a CCnT instead of a Au plate-anode, the standard deviation of the emission current noise can be decreased from the 10 nA range to the 1 nA range under vacuum conditions of 10{sup −5 }Pa. This shows the strong influence of the anode on the cold-field emission current noise.

  15. Design of a 300-kV gas environmental transmission electron microscope equipped with a cold field emission gun.

    PubMed

    Isakozawa, Shigeto; Nagaoki, Isao; Watabe, Akira; Nagakubo, Yasuhira; Saito, Nobuhiro; Matsumoto, Hiroaki; Zhang, Xiao Feng; Taniguchi, Yoshifumi; Baba, Norio

    2016-08-01

    A new in situ environmental transmission electron microscope (ETEM) was developed based on a 300 kV TEM with a cold field emission gun (CFEG). Particular caution was taken in the ETEM design to assure uncompromised imaging and analytical performance of the TEM. Because of the improved pumping system between the gun and column, the vacuum of CFEG was largely improved and the probe current was sufficiently stabilized to operate without tip flashing for 2-3 h or longer. A high brightness of 2.5 × 10(9) A/cm(2) sr was measured at 300 kV, verifying the high quality of the CFEG electron beam. A specially designed gas injection-heating holder was used in the in situ TEM study at elevated temperatures with or without gas around the TEM specimen. Using this holder in a 10 Pa gas atmosphere and specimen temperatures up to 1000°C, high-resolution ETEM performance and analysis were achieved.

  16. Electrically driven single photon emission from a CdSe/ZnSSe single quantum dot at 200 K

    SciTech Connect

    Quitsch, Wolf; Kümmell, Tilmar; Bacher, Gerd; Gust, Arne; Kruse, Carsten; Hommel, Detlef

    2014-09-01

    High temperature operation of an electrically driven single photon emitter based on a single epitaxial quantum dot is reported. CdSe/ZnSSe/MgS quantum dots are embedded into a p-i-n diode architecture providing almost background free excitonic and biexcitonic electroluminescence from individual quantum dots through apertures in the top contacts. Clear antibunching with g{sup 2}(τ = 0) = 0.28 ± 0.20 can be tracked up to T = 200 K, representing the highest temperature for electrically triggered single photon emission from a single quantum dot device.

  17. Tuning Ag29 nanocluster light emission from red to blue with one and two-photon excitation.

    PubMed

    Russier-Antoine, Isabelle; Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Dugourd, Philippe; Sanader, Željka; Bonačić-Koutecký, Vlasta; Brevet, Pierre-François; Antoine, Rodolphe

    2016-02-07

    We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ∼2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ∼800 nm for Ag29(DHLA)12 is higher than 10(4) GM and the hyperpolarizability is 106 × 10(-30) esu at the same excitation wavelength. The two-photon excited fluorescence spectrum appears strongly blue-shifted as compared to the one-photon excited spectrum, displaying a broad band between 400 and 700 nm. The density functional theory (DFT) provides insight into the structural and electronic properties of Ag29(DHLA)12 as well as into interplay between metallic subunit or core and ligands which is responsible for unique optical properties.

  18. Wide spectral range confocal microscope based on endlessly single-mode fiber.

    PubMed

    Hubbard, R; Ovchinnikov, Yu B; Hayes, J; Richardson, D J; Fu, Y J; Lin, S D; See, P; Sinclair, A G

    2010-08-30

    We report an endlessly single mode, fiber-optic confocal microscope, based on a large mode area photonic crystal fiber. The microscope confines a very broad spectral range of excitation and emission wavelengths to a single spatial mode in the fiber. Single-mode operation over an optical octave is feasible. At a magnification of 10 and λ = 900 nm, its resolution was measured to be 1.0 μm (lateral) and 2.5 μm (axial). The microscope's use is demonstrated by imaging single photons emitted by individual InAs quantum dots in a pillar microcavity.

  19. Endocrine radionuclide scintigraphy with fusion single photon emission computed tomography/computed tomography

    PubMed Central

    Wong, Ka-Kit; Gandhi, Arpit; Viglianti, Benjamin L; Fig, Lorraine M; Rubello, Domenico; Gross, Milton D

    2016-01-01

    AIM: To review the benefits of single photon emission computed tomography (SPECT)/computed tomography (CT) hybrid imaging for diagnosis of various endocrine disorders. METHODS: We performed MEDLINE and PubMed searches using the terms: “SPECT/CT”; “functional anatomic mapping”; “transmission emission tomography”; “parathyroid adenoma”; “thyroid cancer”; “neuroendocrine tumor”; “adrenal”; “pheochromocytoma”; “paraganglioma”; in order to identify relevant articles published in English during the years 2003 to 2015. Reference lists from the articles were reviewed to identify additional pertinent articles. Retrieved manuscripts (case reports, reviews, meta-analyses and abstracts) concerning the application of SPECT/CT to endocrine imaging were analyzed to provide a descriptive synthesis of the utility of this technology. RESULTS: The emergence of hybrid SPECT/CT camera technology now allows simultaneous acquisition of combined multi-modality imaging, with seamless fusion of three-dimensional volume datasets. The usefulness of combining functional information to depict the bio-distribution of radiotracers that map cellular processes of the endocrine system and tumors of endocrine origin, with anatomy derived from CT, has improved the diagnostic capability of scintigraphy for a range of disorders of endocrine gland function. The literature describes benefits of SPECT/CT for 99mTc-sestamibi parathyroid scintigraphy and 99mTc-pertechnetate thyroid scintigraphy, 123I- or 131I-radioiodine for staging of differentiated thyroid carcinoma, 111In- and 99mTc- labeled somatostatin receptor analogues for detection of neuroendocrine tumors, 131I-norcholesterol (NP-59) scans for assessment of adrenal cortical hyperfunction, and 123I- or 131I-metaiodobenzylguanidine imaging for evaluation of pheochromocytoma and paraganglioma. CONCLUSION: SPECT/CT exploits the synergism between the functional information from radiopharmaceutical imaging and anatomy

  20. Single-photon emission computed tomography/computed tomography in brain tumors.

    PubMed

    Schillaci, Orazio; Filippi, Luca; Manni, Carlo; Santoni, Riccardo

    2007-01-01

    Anatomic imaging procedures (computed tomography [CT] and magnetic resonance imaging [MRI]) have become essential tools for brain tumor assessment. Functional images (positron emission tomography [PET] and single-photon emission computed tomography [SPECT]) can provide additional information useful during the diagnostic workup to determine the degree of malignancy and as a substitute or guide for biopsy. After surgery and/or radiotherapy, nuclear medicine examinations are essential to assess persistence of tumor, to differentiate recurrence from radiation necrosis and gliosis, and to monitor the disease. The combination of functional images with anatomic ones is of the utmost importance for a full evaluation of these patients, which can be obtained by means of imaging fusion. Despite the fast-growing diffusion of PET, in most cases of brain tumors, SPECT studies are adequate and provide results that parallel those obtained with PET. The main limitation of SPECT imaging with brain tumor-seeking radiopharmaceuticals is the lack of precise anatomic details; this drawback is overcome by the fusion with morphological studies that provide an anatomic map to scintigraphic data. In the past, software-based fusion of independently performed SPECT and CT or MRI demonstrated usefulness for brain tumor assessment, but this process is often time consuming and not practical for everyday nuclear medicine studies. The recent development of dual-modality integrated imaging systems, which allow the acquisition of SPECT and CT images in the same scanning session, and their co-registration by means of the hardware, has facilitated this process. In SPECT studies of brain tumors with various radiopharmaceuticals, fused images are helpful in providing the precise localization of neoplastic lesions, and in excluding the disease in sites of physiologic tracer uptake. This information is useful for optimizing diagnosis, therapy monitoring, and radiotherapy treatment planning, with a

  1. Spontaneous emission from a two-level atom in anisotropic one-band photonic crystals: A fractional calculus approach

    SciTech Connect

    Wu, J.-N.; Huang, C.-H.; Cheng, S.-C.; Hsieh, W.-F.

    2010-02-15

    Spontaneous emission (SE) from a two-level atom in an anisotropic photonic crystal (PC) is investigated by the fractional calculus. Physical phenomena of the SE are studied analytically by solving the fractional kinetic equations of the SE. There is a dynamical discrepancy between the SE of anisotropic and isotropic PCs. We find that, contrary to the SE phenomenon of the isotropic PC, the SE near the band edge of an anisotropic PC shows no photon-atom bound state. It is consistent with the experimental results of Barth, Schuster, Gruber, and Cichos [Phys. Rev. Lett. 96, 243902 (2006)] that the anisotropic property of the system enhances the SE. We also study effects of dispersion curvatures on the changes of the photonic density of states and the appearance of the diffusion fields in the SE.

  2. Strong enhancement of spontaneous emission in amorphous-silicon-nitride photonic crystal based coupled-microcavity structures

    NASA Astrophysics Data System (ADS)

    Bayindir, M.; Tanriseven, S.; Aydinli, A.; Ozbay, E.

    We investigated photoluminescence (PL) from one-dimensional photonic band gap structures. The photonic crystals, a Fabry-Perot (FP) resonator and a coupled-microcavity (CMC) structure, were fabricated by using alternating hydrogenated amorphous-silicon-nitride and hydrogenated amorphous-silicon-oxide layers. It was observed that these structures strongly modify the PL spectra from optically active amorphous-silicon-nitride thin films. Narrow-band and wide-band PL spectra were achieved in the FP microcavity and the CMC structure, respectively. The angle dependence of PL peak of the FP resonator was also investigated. We also observed that the spontaneous emission increased drastically at the coupled-cavity band edge of the CMC structure due to extremely low group velocity and long photon lifetime. The measurements agree well with the transfer-matrix method results and the prediction of the tight-binding approximation.

  3. Image-Guided Drug Delivery with Single-Photon Emission Computed Tomography: A Review of Literature

    PubMed Central

    Chakravarty, Rubel; Hong, Hao; Cai, Weibo

    2014-01-01

    Tremendous resources are being invested all over the world for prevention, diagnosis, and treatment of various types of cancer. Successful cancer management depends on accurate diagnosis of the disease along with precise therapeutic protocol. The conventional systemic drug delivery approaches generally cannot completely remove the competent cancer cells without surpassing the toxicity limits to normal tissues. Therefore, development of efficient drug delivery systems holds prime importance in medicine and healthcare. Also, molecular imaging can play an increasingly important and revolutionizing role in disease management. Synergistic use of molecular imaging and targeted drug delivery approaches provides unique opportunities in a relatively new area called `image-guided drug delivery' (IGDD). Single-photon emission computed tomography (SPECT) is the most widely used nuclear imaging modality in clinical context and is increasingly being used to guide targeted therapeutics. The innovations in material science have fueled the development of efficient drug carriers based on, polymers, liposomes, micelles, dendrimers, microparticles, nanoparticles, etc. Efficient utilization of these drug carriers along with SPECT imaging technology have the potential to transform patient care by personalizing therapy to the individual patient, lessening the invasiveness of conventional treatment procedures and rapidly monitoring the therapeutic efficacy. SPECT-IGDD is not only effective for treatment of cancer but might also find utility in management of several other diseases. Herein, we provide a concise overview of the latest advances in SPECT-IGDD procedures and discuss the challenges and opportunities for advancement of the field. PMID:25182469

  4. Note: Spectrometer with multichannel photon-counting detector for beam emission spectroscopy in magnetic fusion devices

    SciTech Connect

    Lizunov, A.; Khilchenko, A.; Khilchenko, V.; Kvashnin, A.; Zubarev, P.

    2015-12-15

    A spectrometer based on a linear array photomultiplier tube (PMT) has been developed and calibrated. A 0.635 m focal length Czerny-Turner monochromator combined with a coupling optics provides an image of a narrow 0.5 nm spectral range with a resolution of 0.015 nm/channel on a 32-anode PMT. The system aims at spectroscopy of D{sub α} or H{sub α} lines emitted by a diagnostic atomic beam in a plasma (primarily a motional Stark effect diagnostics). To record a low photon flux of ∼10{sup 6} s{sup −1} per channel with the time resolution of 100 μs, a pulse counting approach has been used. Wideband amplifiers scale single-electron pulses and transmit them to a digital data processing core hardwired in a programmable logic matrix. Calibrations have shown that the aberration-limited instrument function fits to a single detector channel of 1 mm width. Pilot results of passive measurements of D{sub α} light emission from the plasma confined in a magnetic trap are presented.

  5. Brain uptake of iomazenil in cirrhotic patients: a single photon emission tomography study.

    PubMed

    Kapczinski, F; Quevedo, J; Curran, H V; Fleminger, S; Toone, B; Cluckie, A; Lader, M

    1999-01-01

    Brain uptake of 123I-iomazenil was studied in seven cirrhotic patients and eight normal controls using single photon emission computerized tomography. The highest concentration of the ligand was found in the occipital cortex, which corresponds to the brain region with the highest concentration of benzodiazepine receptors. The peak uptake was delayed in patients across all brain regions. The uptake in occipital cortex was higher in low albumin cirrhotics. Patients with low albumin also presented a more delayed peak uptake in occipital cortex and a higher volume of distribution of iomazenil in plasma, compared to patients with normal albumin levels and controls. The changes in brain uptake (delayed peak uptake and increased maximal uptake in occipital cortex) appears to reflect changes in the pharmacokinetics of the ligand, particularly in cirrhotics with low levels of plasma albumin. The curve of brain uptake of the tracer was modelled into a two compartments equation, which seems to provide a practical and reliable method to calculate the slopes of acquisition and decay, time to peak and maximal acquisition.

  6. Fragile X syndrome and cerebral perfusion abnormalities: single-photon emission computed tomographic study.

    PubMed

    Kabakus, Nimet; Aydin, Mustafa; Akin, Haluk; Balci, Tansel Ansal; Kurt, Abdullah; Kekilli, Ersoy

    2006-12-01

    Fragile X syndrome is an inherited disorder caused by a defective gene on the X chromosome. It is associated with developmental or behavioral symptoms and various degrees of mental retardation. Morphologic abnormalities and altered perfusion of various brain areas can underlie these functional disturbances. The aim of this study was to investigate the cerebral perfusion state in patients with fragile X syndrome using single-photon emission computed tomography (SPECT). Structural and functional assessment was also performed by magnetic resonance imaging (MRI) and electroencephalography (EEG). Eight boys with cytogenetically confirmed fragile X syndrome (mean age 8.8 +/- 4.4 years, range 5-18 years), were included. All patients had mental retardation, with a mean IQ of 58.9 +/- 8.8 (range 40-68), and additional neurobehavioral symptoms. SPECT revealed cerebral perfusion abnormalities in six patients (75%), most commonly in the frontoparietotemporal area and prominent in the right hemisphere. The SPECT and EEG findings were concordant: hypoperfused areas in SPECT corresponded to regions of persistent slow-wave paroxysms on EEG. On the other hand, cranial MRI was abnormal qualitatively only in two patients (25%) showing cerebellar and vermal hypoplasia and cerebral hemispheric asymmetry. Our results indicate that cerebral perfusion abnormalities, which are correlated with electrophysiologic findings but not necessarily with anatomic abnormalities, can underlie the pathogenesis of the clinical findings observed in fragile X syndrome.

  7. Cardiac single-photon emission-computed tomography using combinedcone-beam/fan-beam collimation

    SciTech Connect

    Gullberg, Grant T.; Zeng, Gengsheng L.

    2004-12-03

    The objective of this work is to increase system sensitivity in cardiac single-photon emission-computed tomography (SPECT) studies without increasing patient imaging time. For imaging the heart, convergent collimation offers the potential of increased sensitivity over that of parallel-hole collimation. However, if a cone-beam collimated gamma camera is rotated in a planar orbit, the projection data obtained are not complete. Two cone-beam collimators and one fan-beam collimator are used with a three-detector SPECT system. The combined cone-beam/fan-beam collimation provides a complete set of data for image reconstruction. The imaging geometry is evaluated using data acquired from phantom and patient studies. For the Jaszazck cardiac torso phantom experiment, the combined cone-beam/fan-beam collimation provided 1.7 times greater sensitivity than standard parallel-hole collimation (low-energy high-resolution collimators). Also, phantom and patient comparison studies showed improved image quality. The combined cone-beam/fan-beam imaging geometry with appropriate weighting of the two data sets provides improved system sensitivity while measuring sufficient data for artifact free cardiac images.

  8. Note: Spectrometer with multichannel photon-counting detector for beam emission spectroscopy in magnetic fusion devices

    NASA Astrophysics Data System (ADS)

    Lizunov, A.; Khilchenko, A.; Khilchenko, V.; Kvashnin, A.; Zubarev, P.

    2015-12-01

    A spectrometer based on a linear array photomultiplier tube (PMT) has been developed and calibrated. A 0.635 m focal length Czerny-Turner monochromator combined with a coupling optics provides an image of a narrow 0.5 nm spectral range with a resolution of 0.015 nm/channel on a 32-anode PMT. The system aims at spectroscopy of Dα or Hα lines emitted by a diagnostic atomic beam in a plasma (primarily a motional Stark effect diagnostics). To record a low photon flux of ˜106 s-1 per channel with the time resolution of 100 μs, a pulse counting approach has been used. Wideband amplifiers scale single-electron pulses and transmit them to a digital data processing core hardwired in a programmable logic matrix. Calibrations have shown that the aberration-limited instrument function fits to a single detector channel of 1 mm width. Pilot results of passive measurements of Dα light emission from the plasma confined in a magnetic trap are presented.

  9. Imaging-guided two-photon excitation-emission-matrix measurements of human skin tissues

    NASA Astrophysics Data System (ADS)

    Yu, Yingqiu; Lee, Anthony M. D.; Wang, Hequn; Tang, Shuo; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

    2012-07-01

    There are increased interests on using multiphoton imaging and spectroscopy for skin tissue characterization and diagnosis. However, most studies have been done with just a few excitation wavelengths. Our objective is to perform a systematic study of the two-photon fluorescence (TPF) properties of skin fluorophores, normal skin, and diseased skin tissues. A nonlinear excitation-emission-matrix (EEM) spectroscopy system with multiphoton imaging guidance was constructed. A tunable femtosecond laser was used to vary excitation wavelengths from 730 to 920 nm for EEM data acquisition. EEM measurements were performed on excised fresh normal skin tissues, seborrheic keratosis tissue samples, and skin fluorophores including: NADH, FAD, keratin, melanin, collagen, and elastin. We found that in the stratum corneum and upper epidermis of normal skin, the cells have large sizes and the TPF originates from keratin. In the lower epidermis, cells are smaller and TPF is dominated by NADH contributions. In the dermis, TPF is dominated by elastin components. The depth resolved EEM measurements also demonstrated that keratin structure has intruded into the middle sublayers of the epidermal part of the seborrheic keratosis lesion. These results suggest that the imaging guided TPF EEM spectroscopy provides useful information for the development of multiphoton clinical devices for skin disease diagnosis.

  10. Single photon emission computed tomography: An alternative imaging modality in left ventricular evaluation

    PubMed Central

    Yalçin, Hulya; Maza, Sofiane; Yalçin, Fatih

    2008-01-01

    Various diagnostic imaging modalities have been used for quantitative left ventricular (LV) parameters. Because of the suboptimal value of the most widely used technology, two-dimensional (2D) echocardiography, 3D ultrasonographic imaging has improved accuracy for LV volume and function. Single photon emission computed tomography (SPECT) is another diagnostic method where LV volumetric and functional parameters can be accurately provided by gated myocardial perfusion tomographic slices. First pass radionuclide venticulography is another imaging modality which has some practical limitations. Despite lower ejection fraction (EF) values compared with invasive approach, noninvasive techniques are accurate in determination of normal and depressed EF. Noninvasive techniques with 3D approach including gated SPECT are beneficial for not only global but also regional LV evaluation. It has been mentioned that the slight difference between echocardiography and SPECT could be caused by the diverse population studied. The results of diagnostic stress tests support that SPECT is feasible to use in evaluation of LV volume and functional analysis. Magnetic resonance imaging is an expensive modality to use routinely, but it preserves its importance in selected patients for providing precise LV geometric data. PMID:19183754

  11. Comparison of Ga-67 planar imaging and single photon emission computed tomography in malignant chest disease

    SciTech Connect

    Tumeh, S.S.; Rosenthal, D.; Kaplan, W.D.; English, R.E.; Holman, B.L.

    1985-05-01

    To determine the value of Ga-67 single photon emission computed tomography (SPECT) in patients (pts) with malignant chest disease, the authors compared Ga-67 planar scans (ps) and SPECT with the medical records in twenty-five consecutive patients. Twenty-three examinations were performed on 17 pts with Hodgkin's disease (HD) and three pts with non-Hodgkin's lymphoma. Five examinations were performed on 5 pts with bronchogenic carcinoma (BC). The two modalities were evaluated for (1) presence or absence of disease, (2) number of foci of abnormal uptake and (3) extent of disease. In pts with lymphoma, SPECT defined the extent of disease better than planar imaging in eight examinations; it demonstrated para-cardial involvement in one pt, separated hilar from mediastinal disease in 4, and demonstrated posterior mediastinal disease in 3. SPECT clarified suspicious foci on planar images in seven examinations, correctly ruled out disease in two pts with equivocal planar images and did not exchange planar image findings in six examinations. In pts with bronchogenic carcinoma, both medalities correctly ruled out mediastinal involvement in three pts. SPECT detected mediastinal lymph node involvement in one pt with equivocal planar images. Both SPECT and planar imaging missed direct tumor extension to the mediastinum in one pt. They conclude that Ga-67 with SPECT is better than planar images for staging of chest lymphoma and BC. Since it defines different lymph node groups it carries a good potential for staging as well as follow up of those pts.

  12. Scintigraphic appearance of focal fatty infiltration of the liver using single-photon emission computed tomography

    SciTech Connect

    Kudo, M.; Hirasa, M.; Ibuki, Y.; Takakuwa, H.; Fujimi, K.; Veda, S.; Tomita, S.; Komori, H.; Todo, A.; Kitaura, Y.

    1984-01-01

    Fatty infiltration of the liver had been considered to assume a uniform distribution until quite recently. However, the development of X-ray computed tomography (XCT) and the ultrasound (US) has proven that fatty infiltration of the liver may sometimes assume a nonuniform distribution (focal fatty infiltration (FFI)). This investigation was undertaken to evaluate the scintigraphic appearance of FFI using single-photon emission computed tomography (SPECT) with a GE Maxicamera 400T. Radionuclide images including SPECT were evaluated in 12 cases with FFI which were diagnosed by XCT and US. Most of them were histrogically confirmed to be positive fatty infiltration in the liver. The results were as follows. The fatty infiltrated area was visualized as a hot spot in one case, a defect in 2 cases, a low uptake in one case and a normal uptake in 8 cases. Radionuclide imaging of FFI shows a large variety of findings and it suggests that Kupffer cell function varies with the causes or stage of fatty infiltration. And one can understand the pathological state of FFI from a viewpoint of Kupffer cell function only by radionuclide imaging including SPECT, which is very useful to compare the images with XCT images.

  13. Single photon emission computed tomograms of the liver: normal vascular intrahepatic structures.

    PubMed

    Pettigrew, R I; Witztum, K F; Perkins, G C; Johnson, M L; Burks, R N; Verba, J W; Halpern, S E

    1984-01-01

    Because of the high target-to-background contrast obtained with single photon emission computed tomography (SPECT), normal intrahepatic vessels approximately 2 cm in diameter may appear as distinct focal defects in tomographic sections throughout the liver even though normal vessels rarely cause such defects on planar images. To assess this problem, five subjects without evidence of liver disease underwent tomography of the liver with Tc-99m sulfur colloid (TSC) and on a separate occasion tomography of the intrahepatic blood pool with Tc-99m autologous red blood cells (RBC). In each case, well demarcated defects were obvious in contiguous TSC liver tomograms in various planes. Direct comparison with RBC tomograms showed that all of these defects corresponded to intrahepatic veins, typically the right portal vein, its posterior branch, and the left portal vein. Knowledge of the intrahepatic vascular anatomy in a variety of tomographic planes, with examination of each defect in multiple orthogonal planes is necessary to avoid false positive interpretations. In some instances a study with RBC may also be required for more conclusive evaluation of defects seen on TSC liver tomograms.

  14. Regional brain hematocrit in stroke by single photon emission computed tomography imaging

    SciTech Connect

    Loutfi, I.; Frackowiak, R.S.; Myers, M.J.; Lavender, J.P.

    1987-01-01

    Nineteen studies on 18 subjects were performed by single photon emission computed tomography (SPECT) of the head after the successive intravenous administration of a plasma label (/sup 99m/Tc-human serum albumin (HSA)) and /sup 99m/Tc-labeled autologous red blood cells (RBC). Two sets of cerebral tomographic sections were generated: for cerebral /sup 99m/Tc-HSA alone and for combined /sup 99m/Tc-HSA and /sup 99m/Tc-RBC. By relating counts in regions of interest from the cerebral tomograms to counts from blood samples obtained during each tomographic acquisition, regional cerebral haematocrit (Hct) was calculated by the application of a simple formula. Results show 1) lower cerebral Hct than venous Hct (ratio of HCT brain/Hct venous 0.65-0.90) in all subjects, and 2) comparison between right and left hemisphere Hct in 3/3 normal subjects, 6/6 patients with transient ischaemic attacks and 3/8 patients with stroke showed no significant difference. However, in 3/8 patients with stroke (most recent strokes) significant differences were found, the higher Hct value corresponding to the affected side.

  15. Photon-enhanced thermionic emission from p-GaAs with nonequilibrium Cs overlayers

    SciTech Connect

    Zhuravlev, A. G.; Romanov, A. S.; Alperovich, V. L.

    2014-12-22

    Photon-enhanced thermionic emission (PETE), which is promising for increasing the efficiency of solar energy conversion, is studied during cesium deposition on the As- and Ga-rich p-GaAs(001) surfaces and subsequent relaxation in the nonequilibrium Cs overlayer by means of photoemission quantum yield spectroscopy adapted for systems with time-variable parameters. Along with direct photoemission of “hot” electrons excited by light above the vacuum level, the spectra contain PETE contribution of “thermalized” electrons, which are excited below the vacuum level and emit in vacuum due to thermalization up in energy by phonon absorption. Comparing the measured and calculated spectra, the effective electron affinity and escape probabilities of hot and thermalized electrons are obtained as functions of submonolayer Cs coverage. The minima in the affinity and pronounced peaks in the escape probabilities are observed for Cs deposition on both the As- and Ga-rich surfaces. Possible reasons for the low mean values of the electron escape probabilities and for the observed enhancement of the probabilities at certain Cs coverages are discussed, along with the implications for the PETE device realization.

  16. Rapid calculation of detectability in Bayesian single photon emission computed tomography

    NASA Astrophysics Data System (ADS)

    Xing, Yuxiang; Hsiao, Ing-Tsung; Gindi, Gene

    2003-11-01

    We consider the calculation of lesion detectability using a mathematical model observer, the channelized Hotelling observer (CHO), in a signal-known-exactly/background-known-exactly detection task for single photon emission computed tomography (SPECT). We focus on SPECT images reconstructed with Bayesian maximum a posteriori methods. While model observers are designed to replace time-consuming studies using human observers, the calculation of CHO detectability is usually accomplished using a large number of sample images, which is still time consuming. We develop theoretical expressions for a measure of detectability, the signal-to-noise-ratio (SNR) of a CHO observer, that can be very rapidly evaluated. Key to our expressions are approximations to the reconstructed image covariance. In these approximations, we use methods developed in the PET literature, but modify them to reflect the different nature of attenuation and distance-dependent blur in SPECT. We validate our expressions with Monte Carlo methods. We show that reasonably accurate estimates of the SNR can be obtained at a computational expense equivalent to approximately two projection operations, and that evaluating SNR for subsequent lesion locations requires negligible additional computation.

  17. Multicenter evaluation of single-photon emission computed tomography quantification with third-party reconstruction software.

    PubMed

    Kangasmaa, Tuija S; Constable, Chris; Hippeläinen, Eero; Sohlberg, Antti O

    2016-09-01

    Reliable and reproducible quantification is essential in many clinical situations. Previously, single-photon emission computed tomography (SPECT) has not been considered a quantitative imaging modality, but recent advances in reconstruction algorithm development have made SPECT quantitative. In this study, we investigate the reproducibility of SPECT quantification with phantoms in a multicenter setting using novel third-party reconstruction software. A total of five hospitals and eight scanners (three GE scanners and five Siemens scanners) participated in the study. A Jaszczak phantom without inserts was used to calculate counts to activity concentration conversion factors. The quantitative accuracy was tested using the NEMA-IEC phantom with six spherical inserts (diameters from 10 to 37 mm) filled to an 8 : 1 insert-background concentration ratio. Phantom studies were reconstructed at one central location using HERMES HybridRecon applying corrections for attenuation, collimator-detector response, and scatter. Spherical volumes of interest with the same diameter as the inserts were drawn on the images and recovery coefficients for the spheres were calculated. The coefficient of variation (CoV) of the NEMA-IEC phantom recovery coefficients ranged from ∼19 to 5% depending on the insert diameter so that the lowest CoV was obtained with the largest spheres. The intersite CoV was almost equal to intrasite CoV. In conclusion, quantitative SPECT is reproducible in a multicenter setting with third-party reconstruction software.

  18. Microwave response and photon emission of a voltage baised Josephson junction

    NASA Astrophysics Data System (ADS)

    Jebari, Salha; Grimm, Alexander; Hazra, Dibyendu; Hofheinz, Max

    The readout of superconducting qubits requires amplifiers combining noise close to the quantum limit, high gain, large bandwidth, and sufficient dynamic range. Josephson parametric amplifiers using Josephson junctions in the 0-voltage state, driven by a large microwave signals, begin to perform sufficiently well in all 4 of these aspects to be of practical use, but remain difficult to optimize and use. Recent experiments with superconducting circuits consisting of a DC voltage-biased Josephson junction in series with a resonator, showed that a tunneling Cooper pair can emit one or several photons with a total energy of 2e times the applied voltage. We present microwave reflection measurements on this device indicating that amplification is possible with a simple DC voltage-biased Josephson junction. We compare these measurements with the noise power emitted by the junction and show that, for low Josephson energy, transmission and noise emission can be explained within the framework of P(E) theory of inelastic Cooper pair tunneling. Combined with a theoretical model, our results indicate that voltage-biased Josephson junctions might be useful for amplification near the quantum limit, offering simpler design and a different trade-off between gain, bandwidth and dynamic range.

  19. A comparison of two micro-beam X-ray emission techniques for actinide elemental distribution in microscopic particles originating from the hydrogen bombs involved in the Palomares (Spain) and Thule (Greenland) accidents

    NASA Astrophysics Data System (ADS)

    Jimenez-Ramos, M. C.; Eriksson, M.; García-López, J.; Ranebo, Y.; García-Tenorio, R.; Betti, M.; Holm, E.

    2010-09-01

    In order to validate and to gain confidence in two micro-beam techniques: particle induced X-ray emission with nuclear microprobe technique (μ-PIXE) and synchrotron radiation induced X-ray fluorescence in a confocal alignment (confocal SR μ-XRF) for characterization of microscopic particles containing actinide elements (mixed plutonium and uranium) a comparative study has been performed. Inter-comparison of the two techniques is essential as the X-ray production cross-sections for U and Pu are different for protons and photons and not well defined in the open literature, especially for Pu. The particles studied consisted of nuclear weapons material, and originate either in the so called Palomares accident in Spain, 1966 or in the Thule accident in Greenland, 1968. In the determination of the average Pu/U mass ratios (not corrected by self-absorption) in the analysed microscopic particles the results from both techniques show a very good agreement. In addition, the suitability of both techniques for the analysis with good resolution (down to a few μm) of the Pu/U distribution within the particles has been proved. The set of results obtained through both techniques has allowed gaining important information concerning the characterization of the remaining fissile material in the areas affected by the aircraft accidents. This type of information is essential for long-term impact assessments of contaminated sites.

  20. Application of Spontaneous Photon Emission in the Growth Ages and Varieties Screening of Fresh Chinese Herbal Medicines

    PubMed Central

    Zhao, Xiaolei; Fu, Jialei; Van Wijk, Eduard; Liu, Yanli; Fan, Hua; Zhang, Yufeng

    2017-01-01

    Ultraweak photon emission emitted by all living organisms has been confirmed to be a noninvasive indicator for their physiological and pathological characteristics. In this study, we investigated the characteristics of spontaneous photon emission (SPE) and the contents of specific active compounds of roots and flowers buds of several fresh Chinese herbal medicines (natural medicines) with different growth ages and varieties. The results revealed that the contents of specific active compounds from same species herbs with different growth ages and varieties were significantly different, and this difference could be reflected by their SPE. Because the contents of specific bioactive constituents in Chinese herbs are closely related to their quality and curative effect, the SPE measurement technique may contribute to the quality control of Chinese herbal medicine in the future. PMID:28250790

  1. Two-photon emission of an electron in the weak pulsed laser field for the resonant case

    NASA Astrophysics Data System (ADS)

    Nedoreshta, V. N.; Voroshilo, A. I.; Roshchupkin, S. P.; Dubov, V. V.

    2017-02-01

    Resonant two-photon emission of an electron in the weak field of a pulsed laser wave is studied theoretically. The assumption that a laser pulse duration is significantly greater than the characteristic oscillation time is used. It is shown that resonant conditions depend considerably on the energy and the angle of initial-electron incidence. These values determine the possible ranges of emission angles and frequencies of the first and second photon. An analytic expression for the resonant rate of the investigated process was obtained for a range of weak fields. The resonant rate decreases with increasing energy and decreases with the initial-electron incidence angle. It has order of magnitude {{10}-6}~{{\\text{s}}-1}~\\text{Me}{{\\text{V}}-1} for {{E}i}=500~\\text{MeV} and {{10}-5}~{{\\text{s}}-1}~\\text{Me}{{\\text{V}}-1} for {{E}i}=50~\\text{MeV} .

  2. Chemical modulation of the ultra-weak photon emission from Saccharomyces cerevisiae and differentiated HL-60 cells

    NASA Astrophysics Data System (ADS)

    Červinková, Kateřina; Nerudová, Michaela; Hašek, Jiří; Cifra, Michal

    2015-01-01

    The ultra-weak photon emission (UPE) is a universal phenomenon common to all cells with active oxidative metabolism. Generally accepted mechanism of the origin of the ultra-weak photon emission considers reactions of radical or nonradical reactive oxygen species (ROS) with biomolecules such as lipids and proteins which lead to the formation of electron excited species. During the transition to the ground state the excess energy is released as a photon with a wavelength in the visible range of the electromagnetic spectrum. Since the intensity of the light is very low it is possible to be measured only by highly sensitive devices. We used Hamamatsu Photonics PMT module H7360-01 mounted into a light-tight chamber for the purposes of this work. The goal of our research is to delineate an origin of UPE from two model organisms; differentiated HL-60 cells (human promyelocytic leukemia) and yeast cells Saccharomyces cerevisiae. While the UPE from the yeast cells arises spontaneously during the growth without any external stimuli, UPE from HL-60 is induced by phorbol 12-myristate, 13-acetate (PMA). It is possible to modulate the UPE production by certain antioxidants which scavenge ROS formed during the metabolism (yeast cells) or respiratory burst (HL-60 cells). The experiments are focused on the description of effects caused by antioxidants. Several kinds of antioxidants (ascorbic acid, mannitol, glutathione) with different concentration were used and we studied the changes in the UPE intensities of and the temporal developments of the optical signal.

  3. Cavity Photons as a Probe for Charge Relaxation Resistance and Photon Emission in a Quantum Dot Coupled to Normal and Superconducting Continua

    NASA Astrophysics Data System (ADS)

    Bruhat, L. E.; Viennot, J. J.; Dartiailh, M. C.; Desjardins, M. M.; Kontos, T.; Cottet, A.

    2016-04-01

    Microwave cavities have been widely used to investigate the behavior of closed few-level systems. Here, we show that they also represent a powerful probe for the dynamics of charge transfer between a discrete electronic level and fermionic continua. We have combined experiment and theory for a carbon nanotube quantum dot coupled to normal metal and superconducting contacts. In equilibrium conditions, where our device behaves as an effective quantum dot-normal metal junction, we approach a universal photon dissipation regime governed by a quantum charge relaxation effect. We observe how photon dissipation is modified when the dot admittance turns from capacitive to inductive. When the fermionic reservoirs are voltage biased, the dot can even cause photon emission due to inelastic tunneling to/from a Bardeen-Cooper-Schrieffer peak in the density of states of the superconducting contact. We can model these numerous effects quantitatively in terms of the charge susceptibility of the quantum dot circuit. This validates an approach that could be used to study a wide class of mesoscopic QED devices.

  4. Tuning Ag29 nanocluster light emission from red to blue with one and two-photon excitation

    NASA Astrophysics Data System (ADS)

    Russier-Antoine, Isabelle; Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Dugourd, Philippe; Sanader, Željka; Bonačić-Koutecký, Vlasta; Brevet, Pierre-François; Antoine, Rodolphe

    2016-01-01

    We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ~2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ~800 nm for Ag29(DHLA)12 is higher than 104 GM and the hyperpolarizability is 106 × 10-30 esu at the same excitation wavelength. The two-photon excited fluorescence spectrum appears strongly blue-shifted as compared to the one-photon excited spectrum, displaying a broad band between 400 and 700 nm. The density functional theory (DFT) provides insight into the structural and electronic properties of Ag29(DHLA)12 as well as into interplay between metallic subunit or core and ligands which is responsible for unique optical properties.We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ~2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ~800 nm for Ag29(DHLA)12 is higher than 104

  5. Phase-matched emission from an optically thin medium following one-photon pulse excitation: Energy considerations

    SciTech Connect

    Berman, P. R.; Le Goueet, J.-L.

    2011-03-15

    Scully and coworkers [M. O. Scully, E. S. Fry, C. H. R. Oii, and K. Wodkiewicz, Phys. Rev. Lett. 96, 010501 (2006)] demonstrated that there is directional, phase-matched emission following the excitation of an ensemble of atoms by a single-photon pulse. While the phase-matched emission intensity is proportional to the the number of atoms, for optically thin samples the total energy emitted in the phase-matched direction is much less than that radiated in other directions. Moreover, even for optically thin samples, it is necessary to take into account effects related to cooperative decay if energy is to be conserved in the overall emission process. An analytic calculation is presented to show explicitly how cooperative decay reduces the incoherent emission and restores energy conservation in this low-density limit.

  6. Dinuclear Ruthenium(II) Complexes as Two-Photon, Time-Resolved Emission Microscopy Probes for Cellular DNA**

    PubMed Central

    Baggaley, Elizabeth; Gill, Martin R; Green, Nicola H; Turton, David; Sazanovich, Igor V; Botchway, Stanley W; Smythe, Carl; Haycock, John W; Weinstein, Julia A; Thomas, Jim A

    2014-01-01

    The first transition-metal complex-based two-photon absorbing luminescence lifetime probes for cellular DNA are presented. This allows cell imaging of DNA free from endogenous fluorophores and potentially facilitates deep tissue imaging. In this initial study, ruthenium(II) luminophores are used as phosphorescent lifetime imaging microscopy (PLIM) probes for nuclear DNA in both live and fixed cells. The DNA-bound probes display characteristic emission lifetimes of more than 160 ns, while shorter-lived cytoplasmic emission is also observed. These timescales are orders of magnitude longer than conventional FLIM, leading to previously unattainable levels of sensitivity, and autofluorescence-free imaging. PMID:24458590

  7. Organic nanostructure-based probes for two-photon imaging of mitochondria and microbes with emission between 430 nm and 640 nm.

    PubMed

    Yang, Xinglong; Wang, Nuoxin; Zhang, Lingmin; Dai, Luru; Shao, Huawu; Jiang, Xingyu

    2017-03-24

    Multi-photon excitation and versatile fluorescent probes are in high need for biological imaging, since one probe can satisfy many needs as a biosensor. Herein we synthesize a series of two-photon excited probes based on tetraphenylethene (TPE) structures (TPE-Acr, TPE-Py, and TPE-Quino), which can image both mammalian cells and bacteria based on aggregation-induced emission (AIE) without washing them. Because of cationic moieties, the fluorescent molecules can aggregate into nanoscale fluorescent organic nanoscale dots to image mitochondria and bacteria with tunable emissions using both one-photon and two-photon excitation. Our research demonstrates that these AIE-dots expand the functions of luminescent organic dots to construct efficient fluorescent sensors applicable to both one-photon and two-photon excitation for bio-imaging of bacteria and mammalian cells.

  8. Size-dependent one-photon- and two-photon-pumped amplified spontaneous emission from organometal halide CH3NH3PbBr3 perovskite cubic microcrystals.

    PubMed

    Zhang, Zhen-Yu; Wang, Hai-Yu; Zhang, Yan-Xia; Li, Kai-Jiao; Zhan, Xue-Peng; Gao, Bing-Rong; Chen, Qi-Dai; Sun, Hong-Bo

    2017-01-18

    In the past few years, organometal halide light-emitting perovskite thin films and colloidal nanocrystals (NCs) have attracted significant research interest in the field of highly purified illuminating applications. However, knowledge of photoluminescence (PL) characteristics, such as amplified spontaneous emission (ASE) of larger-sized perovskite crystals, is still relatively scarce. Here, we presented room-temperature size-dependent spontaneous emission (SE) and ASE of the organometal halide CH3NH3PbBr3 perovskite cubic microcrystals pumped through one-photon-(1P) and two-photon-(2P) excitation paradigms. The results showed that the optical properties of SE and ASE were sensitively dependent on the sizes of perovskite microcrystals irrespective of whether 1P or 2P excitation was used. Moreover, by comparing the spectral results of 1P- and 2P-pumped experiments, 2P pumping was found to be an effective paradigm to reduce thresholds by one order of magnitude. Finally, we carried out fluences-dependent time-resolved fluorescence dynamics experiments to study the underlying effects of these scale-dependent SE and ASE. We found that the photoluminescence (PL) recombination rates sensitively became faster with increasing carriers' densities, and that the ASE pumped from larger-sized CH3NH3PbBr3 perovskite cubic microcrystals showed faster lifetimes. This work shows that micro-sized perovskite cubic crystals could be the ideal patterns of perovskite materials for realizing ASE applications in the future.

  9. Efficient two-photon fluorescent probe with red emission for imaging of thiophenols in living cells and tissues.

    PubMed

    Liu, Hong-Wen; Zhang, Xiao-Bing; Zhang, Jing; Wang, Qian-Qian; Hu, Xiao-Xiao; Wang, Peng; Tan, Weihong

    2015-09-01

    Thiophenols, a class of highly toxic and pollutant compounds, are widely used in industrial production. Some aliphatic thiols play important roles in living organisms. Therefore, the development of efficient methods to discriminate thiophenols from aliphatic thiols is of great importance. Although several one-photon fluorescent probes have been reported for thiophenols, two-photon fluorescent probes are more favorable for biological imaging due to its low background fluorescence, deep penetration depth, and so on. In this work, a two-photon fluorescent probe for thiophenols, termed NpRb1, has been developed for the first time by employing 2,4-dinitrobenzene-sulfonate (DNBS) as a recognition unit (also a fluorescence quencher) and a naphthalene-BODIPY-based through-bond energy transfer (TBET) cassette as a fluorescent reporter. The TBET system consists of a D-π-A structured two-photon naphthalene fluorophore and a red-emitting BODIPY. It displayed highly energy transfer efficiency (93.5%), large pseudo-Stokes shifts upon one-photon excitation, and red fluorescence emission (λem = 586 nm), which is highly desirable for bioimaging applications. The probe exhibited a 163-fold thiophenol-triggered two-photon excited fluorescence enhancement at 586 nm. It showed a high selectivity and excellent sensitivity to thiophenols, with a detection limit of 4.9 nM. Moreover, it was successfully applied for practical detection of thiophenol in water samples with a good recovery, two-photon imaging of thiophenol in living cells, and tissues with tissue-imaging depths of 90-220 μm, demonstrating its practical application in environmental samples and biological systems.

  10. Quantum theory of two-photon correlated-spontaneous-emission lasers: Exact atom-field interaction Hamiltonian approach

    SciTech Connect

    Lu, N.; Zhu, S. )

    1989-11-15

    A quantum theory of two-photon correlated-spontaneous-emission lasers (CEL's) is developed, starting from the exact atom-field interaction Hamiltonian for cascade three-level atoms interacting with a single-mode radiation field. We consider the situation where the active atoms are prepared initially in a coherent superposition of three atomic levels and derive a master equation for the field-density operator by using a quantum theory for coherently pumped lasers. The master equation is transformed into a Fokker-Planck equation for the antinormal-ordering {ital Q} function. The drift coefficients of the Fokker-Planck equation enable us to study the steady-state operation of the two-photon CEL's analytically. We have studied both resonant two-photon CEL for which there is no threshold, and off-resonant two-photon CEL for which there exists a threshold. In both cases the initial atomic coherences provide phase locking, and squeezing in the phase quadrature of the field is found. The off-resonant two-photon CEL can build up from a vacuum when its linear gain is larger than the cavity loss (even without population inversion). Maximum squeezing is found in the no-population-inversion region with the laser intensities far below saturation in both cases, which are more than 90% for the resonant two-photon CEL and nearly 50% for the off-resonant one. Approximate steady-state {ital Q} functions are obtained for the resonant two-photon CEL and, in certain circumstances, for the off-resonant one.

  11. Stimulated emission and lasing from CdSe/CdS/ZnS core-multi-shell quantum dots by simultaneous three-photon absorption.

    PubMed

    Wang, Yue; Ta, Van Duong; Gao, Yuan; He, Ting Chao; Chen, Rui; Mutlugun, Evren; Demir, Hilmi Volkan; Sun, Han Dong

    2014-05-01

    Three-photon pumped stimulated emission and coherent random lasing from colloidal CdSe/CdS/ZnS core-multishell quantum dots are achieved for the first time. These results can offer new possibilities in biology and photonics, as well as at their intersection of biophotonics.

  12. Abnormal 201Tl myocardial single photon emission computed tomography in energetic male patients with myocardial bridge.

    PubMed

    Huang, W S; Chang, H D; Yang, S P; Tsao, T P; Cheng, C Y; Cherng, S C

    2002-11-01

    Myocardial bridge is a relatively benign condition where a major coronary artery is bridged by a band of muscle and narrows during systole, particularly during rapid heart rates. Its clinical presentation and electrocardiogram (ECG) changes overlap with that of coronary artery disease. 201Tl myocardial perfusion imaging is thus frequently prescribed for further evaluation. This retrospective study was carried out to determine the 201Tl image patterns in patients with myocardial bridge. A total of 17 male patients (aged from 30 to 63 years) who had a positive exercise ECG and angiographic evidence of myocardial bridge in the mid-third of the left anterior descending coronary artery were recruited. Most of them were robust and received routine physical check-ups. They had no known heart disease or medication that affected cardiac function. The patients' clinical presentations, echocardiograph and exercise ECG findings were analysed. 201Tl single photon emission computed tomography (SPECT) was performed by intravenous injection of 201Tl (111 MBq) immediately following stress (treadmill or dipyridamole induced) and 4 h after stress, using a fixed, right angle camera equipped with a low energy, general purpose collimator. The images were interpreted independently by two experienced nuclear medicine physicians. Nine of the 17 patients had anterior chest pain during exercise. All patients had an abnormal ECG during exercise, including ST-T wave depression in leads II, III and aVF, and v4-6. Except for eight patients revealing reversible perfusion defect (R), 16 of the 17 patients also exhibited a partial reversible perfusion defect (PR) or a significant reverse redistribution (RR) scan pattern in the anterior or inferior walls of the left ventricle. Myocardial bridge should be taken into consideration in energetic male patients who had abnormal exercise ECGs and the corresponding patterns of Tl SPECT abnormalities including R, PR and RR.

  13. Prognostic value of single-photon emission tomography in acute ischaemic stroke.

    PubMed

    Weir, C J; Bolster, A A; Tytler, S; Murray, G D; Corrigall, R S; Adams, F G; Lees, K R

    1997-01-01

    Single-photon emission tomography (SPET) is widely used in the investigation of acute stroke. We investigated the relationship between SPET data and functional outcome in a large group of acute stroke patients. One hundred and eight patients underwent cerebral computed tomography (CT) and technetium-99m hexamethylpropylene amine oxime SPET after acute ischaemic stroke. We categorised the clinical presentation according to the Oxford classification of acute stroke. Outcome was measured 1 year after stroke using mortality and the Barthel Index for survivors. SPET scans were interpreted without reference to the clinical data using a semi-automatic technique. Three experienced observers determined the presence of luxury perfusion using suitably scaled SPET images in conjunction with the CT scan. Both SPET volume and severity of deficit were significantly negatively correlated with Barthel Index at 1 year (rs=-0.310, P<0.0001, and rs=-0.316, P<0.0001 respectively). In patients scanned with SPET within 16 h of stroke onset, the correlations were more strongly negative (rs=-0.606, P<0. 001, and rs=-0.492, P<0.005 respectively). Luxury perfusion was not associated (chi2=0.073, df=1, P=0.79) with good functional outcome (Barthel score >/=60). Stepwise logistic regression identified Oxford classification, total deficit volume and patient's age as significant predictors of functional outcome. Overall predictive accuracy was 72%. Predictive accuracy was better in patients who received SPET within 16 h of stroke onset. SPET provides useful information about the functional outcome of acute stroke at 1 year. However, the accuracy of prediction decreases the longer SPET is delayed. Prognostication using SPET in combination with clinical assessment and other investigations may also be considered.

  14. Development of correction methods for variable pinhole single-photon emission computed tomography

    NASA Astrophysics Data System (ADS)

    Bae, S.; Bae, J.; Lee, H.; Lee, K.

    2016-02-01

    We propose a novel pinhole collimator in which the pinhole shape can be changed in real-time, and a new single-photon emission computed tomography (SPECT) system that utilizes this variable pinhole (VP) collimator. The acceptance angle and distance between the collimator and the object of VP SPECT are varied so that the optimum value of the region-of-interest (ROI) can be obtained for each rotation angle. Because of these geometrical variations, new correction methods are required for image reconstruction. In this study, we developed two correction methods. The first is the sensitivity-correction algorithm, which minimizes the variation of a system matrix caused by varying the acceptance angle for each rotation angle. The second is the acquisition-time-correction method, which reduces the variation of uniformity caused by varying the distance between the collimator and the object for each rotation angle. A 3D maximum likelihood expectation maximization (MLEM) algorithm was applied to image reconstruction, and two digital phantoms were studied to evaluate the resolution and sensitivity of the images obtained using the proposed methods. The images obtained by using the proposed correction methods show higher uniformity and resolution than those obtained without using these methods. In particular, the results of the resolution phantom study show that hot rods (0.8-mm-diameter) can be clearly distinguished using the proposed correction methods. A quantitative analysis of the ROI phantom revealed that the mean square error (MSE) was 0.42 without the acquisition-time-correction method, and 0.04 with the acquisition-time-correction method. The MSEs of the resolution phantom without and with the acquisition-time-correction method were calculated as 55.14 and 14.69, respectively.

  15. UK audit of single photon emission computed tomography reconstruction software using software generated phantoms.

    PubMed

    Jarritt, P H; Whalley, D R; Skrypniuk, J V; Houston, A S; Fleming, J S; Cosgriff, P S

    2002-05-01

    The purpose of this study was to undertake an audit of the quantitative characteristics of single photon emission computed tomography software using projection data from an analytically generated software phantom and a measured line source. The phantom consisted of three structures. A uniformly filled cylinder, a series of cylindrical rods of various diameters in a background activity with a rod to background ratio of 2:1 and lastly, a set of three concentric rings of activity in the ratio 1:0:1. The phantom contained no added statistical noise. No attenuation was imposed on the data. The phantom was generated analytically and projections were distributed at six different count densities. A single set of projections from a thin line source was also distributed. These data were distributed to centres throughout the UK. Centres were asked to reconstruct the data using a 'ramp only' reconstruction with no additional smoothing function applied. Data were requested for mean and standard deviation in the uniform cylinder, the maximum counts for each cylindrical rod and the mean counts in regions placed within the concentric rings. For the measured line source, centres were asked to measure the full width at half maximum and peak pixel counts for a profile through the reconstructed line. Results from 115 systems were obtained from 100 centres throughout the UK. These provided data from 12 software providers, 11 of these being commercial companies. Data were compared with the known input values and histograms of the distribution of results obtained. Significant differences in quantitative parameters were noted for the different input count densities as well as between suppliers and revisions of software from single suppliers.

  16. A Study on Determination of an Optimized Detector for Single Photon Emission Computed Tomography

    PubMed Central

    Khoshakhlagh, Mohammad; Islamian, Jalil Pirayesh; Abedi, Mohammad; Mahmoudian, Babak; Mardanshahi, Ali Reza

    2016-01-01

    The detector is a critical component of the single photon emission computed tomography (SPECT) imaging system for giving accurate information from the exact pattern of radionuclide distribution in the target organ. The SIMIND Monte Carlo program was utilized for the simulation of a Siemen's dual head variable angle SPECT imaging system with a low energy high resolution (LEHR) collimator. The Planar and SPECT scans for a 99mTc point source and a Jaszczak Phantom with the both experiment and simulated systems were prepared and after verification and validation of the simulated system, the similar scans of the phantoms were compared (from the point of view of the images’ quality), namely, the simulated system with the detectors including bismuth germanate (BGO), yttrium aluminum garnet (YAG:Ce), Cerium-doped yttrium aluminum garnet (YAG:Ce), yttrium aluminum perovslite (YAP:Ce), lutetium aluminum garnet (LuAG:Ce), cerium activated lanthanum bromide (LaBr3), cadmium zinc telluride (CZT), and sodium iodide activated with thallium [NaI(Tl)]. The parameters of full width at half maximum (FWHM), energy and special resolution, sensitivity, and also the comparison of images’ quality by the structural similarity (SSIM) algorithm with the Zhou Wang and Rouse/Hemami methods were analyzed. FWHMs for the crystals were calculated at 13.895, 14.321, 14.310, 14.322, 14.184, and 14.312 keV and the related energy resolutions obtained 9.854, 10.229, 10.221, 10.230, 10.131, and 10.223 %, respectively. Finally, SSIM indexes for comparison of the phantom images were calculated at 0.22172, 0.16326, 0.18135, 0.17301, 0.18412, and 0.20433 as compared to NaI(Tl). The results showed that BGO and LuAG: Ce crystals have high sensitivity and resolution, and better image quality as compared to other scintillation crystals. PMID:26912973

  17. Quantitative single-photon emission computed tomography/computed tomography for technetium pertechnetate thyroid uptake measurement

    PubMed Central

    Lee, Hyunjong; Kim, Ji Hyun; Kang, Yeon-koo; Moon, Jae Hoon; So, Young; Lee, Won Woo

    2016-01-01

    Abstract Objectives: Technetium pertechnetate (99mTcO4) is a radioactive tracer used to assess thyroid function by thyroid uptake system (TUS). However, the TUS often fails to deliver accurate measurements of the percent of thyroid uptake (%thyroid uptake) of 99mTcO4. Here, we investigated the usefulness of quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) after injection of 99mTcO4 in detecting thyroid function abnormalities. Materials and methods: We retrospectively reviewed data from 50 patients (male:female = 15:35; age, 46.2 ± 16.3 years; 17 Graves disease, 13 thyroiditis, and 20 euthyroid). All patients underwent 99mTcO4 quantitative SPECT/CT (185 MBq = 5 mCi), which yielded %thyroid uptake and standardized uptake value (SUV). Twenty-one (10 Graves disease and 11 thyroiditis) of the 50 patients also underwent conventional %thyroid uptake measurements using a TUS. Results: Quantitative SPECT/CT parameters (%thyroid uptake, SUVmean, and SUVmax) were the highest in Graves disease, second highest in euthyroid, and lowest in thyroiditis (P < 0.0001, Kruskal–Wallis test). TUS significantly overestimated the %thyroid uptake compared with SPECT/CT (P < 0.0001, paired t test) because other 99mTcO4 sources in addition to thyroid, such as salivary glands and saliva, contributed to the %thyroid uptake result by TUS, whereas %thyroid uptake, SUVmean and SUVmax from the SPECT/CT were associated with the functional status of thyroid. Conclusions: Quantitative SPECT/CT is more accurate than conventional TUS for measuring 99mTcO4 %thyroid uptake. Quantitative measurements using SPECT/CT may facilitate more accurate assessment of thyroid tracer uptake. PMID:27399139

  18. Dynamic single photon emission computed tomography—basic principles and cardiac applications

    PubMed Central

    Gullberg, Grant T; Reutter, Bryan W; Sitek, Arkadiusz; Maltz, Jonathan S; Budinger, Thomas F

    2011-01-01

    The very nature of nuclear medicine, the visual representation of injected radiopharmaceuticals, implies imaging of dynamic processes such as the uptake and wash-out of radiotracers from body organs. For years, nuclear medicine has been touted as the modality of choice for evaluating function in health and disease. This evaluation is greatly enhanced using single photon emission computed tomography (SPECT), which permits three-dimensional (3D) visualization of tracer distributions in the body. However, to fully realize the potential of the technique requires the imaging of in vivo dynamic processes of flow and metabolism. Tissue motion and deformation must also be addressed. Absolute quantification of these dynamic processes in the body has the potential to improve diagnosis. This paper presents a review of advancements toward the realization of the potential of dynamic SPECT imaging and a brief history of the development of the instrumentation. A major portion of the paper is devoted to the review of special data processing methods that have been developed for extracting kinetics from dynamic cardiac SPECT data acquired using rotating detector heads that move as radiopharmaceuticals exchange between biological compartments. Recent developments in multi-resolution spatiotemporal methods enable one to estimate kinetic parameters of compartment models of dynamic processes using data acquired from a single camera head with slow gantry rotation. The estimation of kinetic parameters directly from projection measurements improves bias and variance over the conventional method of first reconstructing 3D dynamic images, generating time–activity curves from selected regions of interest and then estimating the kinetic parameters from the generated time–activity curves. Although the potential applications of SPECT for imaging dynamic processes have not been fully realized in the clinic, it is hoped that this review illuminates the potential of SPECT for dynamic imaging

  19. Enhanced Extraction of Silicon-Vacancy Centers Light Emission Using Bottom-Up Engineered Polycrystalline Diamond Photonic Crystal Slabs.

    PubMed

    Ondič, Lukáš; Varga, Marian; Hruška, Karel; Fait, Jan; Kapusta, Peter

    2017-03-03

    Silicon vacancy (SiV) centers are optically active defects in diamond. The SiV centers, in contrast to nitrogen vacancy (NV) centers, possess narrow and efficient luminescence spectrum (centered at ≈738 nm) even at room temperature, which can be utilized for quantum photonics and sensing applications. However, most of light generated in diamond is trapped in the material due to the phenomenon of total internal reflection. In order to overcome this issue, we have prepared two-dimensional photonic crystal slabs from polycrystalline diamond thin layers with high density of SiV centers employing bottom-up growth on quartz templates. We have shown that the spectral overlap between the narrow light emission of the SiV centers and the leaky modes extracting the emission into almost vertical direction (where it can be easily detected) can be obtained by controlling the deposition time. More than 14-fold extraction enhancement of the SiV centers photoluminescence was achieved compared to an uncorrugated sample. Computer simulation confirmed that the extraction enhancement originates from the efficient light-matter interaction between light emitted from the SiV centers and the photonic crystal slab.

  20. The mechanism and properties of bio-photon emission and absorption in protein molecules in living systems

    NASA Astrophysics Data System (ADS)

    Pang, Xiao-feng

    2012-05-01

    The mechanism and properties of bio-photon emission and absorption in bio-tissues were studied using Pang's theory of bio-energy transport, in which the energy spectra of protein molecules are obtained from the discrete dynamic equation. From the energy spectra, it was determined that the protein molecules could both radiate and absorb bio-photons with wavelengths of <3 μm and 5-7 μm, consistent with the energy level transitions of the excitons. These results were consistent with the experimental data; this consisted of infrared absorption data from collagen, bovine serum albumin, the protein-like molecule acetanilide, plasma, and a person's finger, and the laser-Raman spectra of acidity I-type collagen in the lungs of a mouse, and metabolically active Escherichia coli. We further elucidated the mechanism responsible for the non-thermal biological effects produced by the infrared light absorbed by the bio-tissues, using the above results. No temperature rise was observed; instead, the absorbed infrared light promoted the vibrations of amides as well the transport of the bio-energy from one place to other in the protein molecules, which changed their conformations. These experimental results, therefore, not only confirmed the validity of the mechanism of bio-photon emission, and the newly developed theory of bio-energy transport mentioned above, but also explained the mechanism and properties of the non-thermal biological effects produced by the absorption of infrared light by the living systems.

  1. Changes in effective diffusivity for oxygen during neural activation and deactivation estimated from capillary diameter measured by two-photon laser microscope.

    PubMed

    Ito, Hiroshi; Takuwa, Hiroyuki; Tajima, Yosuke; Kawaguchi, Hiroshi; Urushihata, Takuya; Taniguchi, Junko; Ikoma, Yoko; Seki, Chie; Ibaraki, Masanobu; Masamoto, Kazuto; Kanno, Iwao

    2017-03-01

    The relation between cerebral blood flow (CBF) and cerebral oxygen extraction fraction (OEF) can be expressed using the effective diffusivity for oxygen in the capillary bed (D) as OEF = 1 - exp(-D/CBF). The D value is proportional to the microvessel blood volume. In this study, changes in D during neural activation and deactivation were estimated from changes in capillary and arteriole diameter measured by two-photon microscopy in awake mice. Capillary and arteriole vessel diameter in the somatosensory cortex and cerebellum were measured under neural activation (sensory stimulation) and neural deactivation [crossed cerebellar diaschisis (CCD)], respectively. Percentage changes in D during sensory stimulation and CCD were 10.3 ± 7.3 and -17.5 ± 5.3 % for capillary diameter of <6 μm, respectively. These values were closest to the percentage changes in D calculated from previously reported human positron emission tomography data. This may indicate that thinner capillaries might play the greatest role in oxygen transport from blood to brain tissue.

  2. Shifting wavelengths of ultraweak photon emissions from dying melanoma cells: their chemical enhancement and blocking are predicted by Cosic's theory of resonant recognition model for macromolecules

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    During the first 24 h after removal from incubation, melanoma cells in culture displayed reliable increases in emissions of photons of specific wavelengths during discrete portions of this interval. Applications of specific filters revealed marked and protracted increases in infrared (950 nm) photons about 7 h after removal followed 3 h later by marked and protracted increases in near ultraviolet (370 nm) photon emissions. Specific wavelengths within the visible (400 to 800 nm) peaked 12 to 24 h later. Specific activators or inhibitors for specific wavelengths based upon Cosic's resonant recognition model elicited either enhancement or diminishment of photons at the specific wavelength as predicted. Inhibitors or activators predicted for other wavelengths, even within 10 nm, were less or not effective. There is now evidence for quantitative coupling between the wavelength of photon emissions and intrinsic cellular chemistry. The results are consistent with initial activation of signaling molecules associated with infrared followed about 3 h later by growth and protein-structural factors associated with ultraviolet. The greater-than-expected photon counts compared with raw measures through the various filters, which also function as reflective material to other photons, suggest that photons of different wavelengths might be self-stimulatory and could play a significant role in cell-to-cell communication.

  3. Shifting wavelengths of ultraweak photon emissions from dying melanoma cells: their chemical enhancement and blocking are predicted by Cosic's theory of resonant recognition model for macromolecules.

    PubMed

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

    2014-02-01

    During the first 24 h after removal from incubation, melanoma cells in culture displayed reliable increases in emissions of photons of specific wavelengths during discrete portions of this interval. Applications of specific filters revealed marked and protracted increases in infrared (950 nm) photons about 7 h after removal followed 3 h later by marked and protracted increases in near ultraviolet (370 nm) photon emissions. Specific wavelengths within the visible (400 to 800 nm) peaked 12 to 24 h later. Specific activators or inhibitors for specific wavelengths based upon Cosic's resonant recognition model elicited either enhancement or diminishment of photons at the specific wavelength as predicted. Inhibitors or activators predicted for other wavelengths, even within 10 nm, were less or not effective. There is now evidence for quantitative coupling between the wavelength of photon emissions and intrinsic cellular chemistry. The results are consistent with initial activation of signaling molecules associated with infrared followed about 3 h later by growth and protein-structural factors associated with ultraviolet. The greater-than-expected photon counts compared with raw measures through the various filters, which also function as reflective material to other photons, suggest that photons of different wavelengths might be self-stimulatory and could play a significant role in cell-to-cell communication.

  4. Enhanced fluorescence emission using a photonic crystal coupled to an optical cavity

    PubMed Central

    Pokhriyal, Anusha; Lu, Meng; Chaudhery, Vikram; George, Sherine; Cunningham, Brian T.

    2013-01-01

    All fluorescent assays would benefit from greater signal-to-noise ratios (SNRs), which enable detection of disease biomarkers at lower concentrations for earlier disease diagnosis and detection of genes that are expressed at the lowest levels. Here, we report an approach to enhance fluorescence in which surface adsorbed fluorophore-tagged biomolecules are excited on a photonic crystal surface that is coupled to an underlying Fabry-Perot type cavity through a gold mirror reflector beneath the photonic crystal. This approach leads to 6× increase in signal-to-noise ratio of a dye labeled polypeptide compared to ordinary photonic crystal enhanced fluorescence. PMID:23825806

  5. Enhanced fluorescence emission using a photonic crystal coupled to an optical cavity

    NASA Astrophysics Data System (ADS)

    Pokhriyal, Anusha; Lu, Meng; Chaudhery, Vikram; George, Sherine; Cunningham, Brian T.

    2013-06-01

    All fluorescent assays would benefit from greater signal-to-noise ratios (SNRs), which enable detection of disease biomarkers at lower concentrations for earlier disease diagnosis and detection of genes that are expressed at the lowest levels. Here, we report an approach to enhance fluorescence in which surface adsorbed fluorophore-tagged biomolecules are excited on a photonic crystal surface that is coupled to an underlying Fabry-Perot type cavity through a gold mirror reflector beneath the photonic crystal. This approach leads to 6× increase in signal-to-noise ratio of a dye labeled polypeptide compared to ordinary photonic crystal enhanced fluorescence.

  6. Five-element Johann-type x-ray emission spectrometer with a single-photon-counting pixel detector.

    PubMed

    Kleymenov, Evgeny; van Bokhoven, Jeroen A; David, Christian; Glatzel, Pieter; Janousch, Markus; Alonso-Mori, Roberto; Studer, Marco; Willimann, Markus; Bergamaschi, Anna; Henrich, Beat; Nachtegaal, Maarten

    2011-06-01

    A Johann-type spectrometer with five spherically bent crystals and a pixel detector was constructed for a range of hard x-ray photon-in photon-out synchrotron techniques, covering a Bragg-angle range of 60°-88°. The spectrometer provides a sub emission line width energy resolution from sub-eV to a few eV and precise energy calibration, better than 1.5 eV for the full range of Bragg angles. The use of a pixel detector allows fast and easy optimization of the signal-to-background ratio. A concentration detection limit below 0.4 wt% was reached at the Cu Kα(1) line. The spectrometer is designed as a modular mobile device for easy integration in a multi-purpose hard x-ray synchrotron beamline, such as the SuperXAS beamline at the Swiss Light Source.

  7. Five-element Johann-type x-ray emission spectrometer with a single-photon-counting pixel detector

    SciTech Connect

    Kleymenov, Evgeny; Bokhoven, Jeroen A. van; David, Christian; Janousch, Markus; Studer, Marco; Willimann, Markus; Bergamaschi, Anna; Henrich, Beat; Nachtegaal, Maarten; Glatzel, Pieter; Alonso-Mori, Roberto

    2011-06-15

    A Johann-type spectrometer with five spherically bent crystals and a pixel detector was constructed for a range of hard x-ray photon-in photon-out synchrotron techniques, covering a Bragg-angle range of 60 deg. - 88 deg. The spectrometer provides a sub emission line width energy resolution from sub-eV to a few eV and precise energy calibration, better than 1.5 eV for the full range of Bragg angles. The use of a pixel detector allows fast and easy optimization of the signal-to-background ratio. A concentration detection limit below 0.4 wt% was reached at the Cu K{alpha}{sub 1} line. The spectrometer is designed as a modular mobile device for easy integration in a multi-purpose hard x-ray synchrotron beamline, such as the SuperXAS beamline at the Swiss Light Source.

  8. Effective theory of dark matter decay into monochromatic photons and its implications: Constraints from associated cosmic-ray emission

    NASA Astrophysics Data System (ADS)

    Gustafsson, Michael; Hambye, Thomas; Scarnà, Tiziana

    2013-07-01

    We show that there exists only a quite limited number of higher dimensional operators which can naturally lead to a slow decay of dark matter particles into monochromatic photons. As each of these operators inevitably induces decays into particles other than photons, we show that the γ-lines it induces are always accompanied by a continuum flux of cosmic rays. Hence constraints on cosmic-ray fluxes imply constraints on the intensity of γ-lines and vice versa. A comparison with up to date observational bounds shows the possibilities to observe or exclude cosmic rays associated to γ-line emission, so that one could better determine the properties of the DM particle, possibly discriminating between some of the operators.

  9. Central representation of phantom limb phenomenon in amputees studied with single photon emission computerized tomography.

    PubMed

    Liaw, M Y; You, D L; Cheng, P T; Kao, P F; Wong, A M

    1998-01-01

    To explore the possible mechanisms of phantom limb discomfort after amputation, three amputees with phantom limb pain were studied. This study examined the change of regional cerebral blood flow using technetium-99m hexamethylpropyleneamine oxime-single photon emission computerized tomography, which was arranged at the time of severe phantom limb discomfort and after the discomfort subsided or was completely relieved. Nine representative transverse slices parallel to the orbitomeatal line were selected for quantification. The cortical ribbon (2-cm thickness) was equally subdivided into 12 symmetrical pairs of sector regions of interest in each slice. The irregularly shaped regions of interest were drawn manually around the right thalamus and basal ganglion and then mirrored to the left thalamus and basal ganglion. The contralateral to ipsilateral ratio of regional cerebral blood flow for each area was calculated. The intensity of phantom limb pain was evaluated on a 0 to 10 visual analog scale. In Cases 1 and 2, the contralateral to ipsilateral regional cerebral blood flow ratios of multiple areas of the frontal, temporal, or parietal lobes were increased at the time of more severe phantom limb pain, and the ratios were normalized or even decreased when the phantom limb pain subsided. In Case 3, increased contralateral to ipsilateral regional cerebral blood flow ratios were also found over the frontal, temporal, and parietal lobe. However, most of the increased regional cerebral blood flow ratios of regions of interest in the first study persisted in the follow-up study. Also, the regional cerebral blood flow ratios of greater number of regions of interest of the same gyrus and new gyrus were increased. There was no significant right-left difference of regional cerebral blood flow over bilateral thalami and basal ganglia in all three cases. The results suggested that phantom limb pain might be associated with cortical activation involving the frontal, temporal, or

  10. Cerebral Hypoperfusion in Hereditary Coproporphyria (HCP): A Single Photon Emission Computed Tomography (SPECT) Study

    PubMed Central

    Valle, Guido; Guida, Claudio Carmine; Nasuto, Michelangelo; Totaro, Manuela; Aucella, Filippo; Frusciante, Vincenzo; Di Mauro, Lazzaro; Potenza, Adele; Savino, Maria; Stanislao, Mario; Popolizio, Teresa; Guglielmi, Giuseppe; Giagulli, Vito Angelo; Guastamacchia, Edoardo; Triggiani, Vincenzo

    2016-01-01

    Background: Hereditary Coproporphyria (HCP) is characterized by abdominal pain, neurologic symptoms and psychiatric disorders, even if it might remain asymptomatic. The pathophysiology of both neurologic and psychiatric symptoms is not fully understood. Therefore, aiming to evaluate a possible role of brain blood flow disorders, we have retrospectively investigated cerebral perfusion patterns in Single Photon Emission Computed Tomography (SPECT) studies in HCP patients. Materials & Methods: We retrospectively evaluated the medical records of patients diagnosed as being affected by HCP. A total of seven HCP patients had been submitted to brain perfusion SPECT study with 99mTc-Exametazime (hexamethylpropyleneamine oxime, HMPAO) or with its functionally equivalent 99mTc-Bicisate (ECD or Neurolite) according with common procedures. In 3 patients the scintigraphic study had been repeated for a second time after the first evaluation at 3, 10 and 20 months, respectively. All the studied subjects had been also submitted to an electromyographic and a Magnetic Resonance Imaging (MRI) study of the brain. Results: Mild to moderate perfusion defects were detected in temporal lobes (all 7 patients), frontal lobes (6 patients) and parietal lobes (4 patients). Occipital lobe, basal ganglia and cerebellar involvement were never observed. In the three subjects in which SPECT study was repeated, some recovery of hypo-perfused areas and appearance of new perfusion defects in other brain regions have been found. In all patients electromyography resulted normal and MRI detected few unspecific gliotic lesions only in one patient. Discussion & Conclusions: Since perfusion abnormalities were usually mild to moderate, this can probably explain the normal pattern observed at MRI studies. Compared to MRI, SPECT with 99mTc showed higher sensitivity in HCP patients. Changes observed in HCP patients who had more than one study suggest that transient perfusion defects might be due to a brain

  11. Super-resolution imaging of ciliary microdomains in isolated olfactory sensory neurons using a custom two-color stimulated emission depletion microscope

    NASA Astrophysics Data System (ADS)

    Meyer, Stephanie A.; Ozbay, Baris N.; Potcoava, Mariana; Salcedo, Ernesto; Restrepo, Diego; Gibson, Emily A.

    2016-06-01

    We performed stimulated emission depletion (STED) imaging of isolated olfactory sensory neurons (OSNs) using a custom-built microscope. The STED microscope uses a single pulsed laser to excite two separate fluorophores, Atto 590 and Atto 647N. A gated timing circuit combined with temporal interleaving of the different color excitation/STED laser pulses filters the two channel detection and greatly minimizes crosstalk. We quantified the instrument resolution to be ˜81 and ˜44 nm, for the Atto 590 and Atto 647N channels. The spatial separation between the two channels was measured to be under 10 nm, well below the resolution limit. The custom-STED microscope is incorporated onto a commercial research microscope allowing brightfield, differential interference contrast, and epifluorescence imaging on the same field of view. We performed immunolabeling of OSNs in mice to image localization of ciliary membrane proteins involved in olfactory transduction. We imaged Ca2+-permeable cyclic nucleotide gated (CNG) channel (Atto 594) and adenylyl cyclase type III (ACIII) (Atto 647N) in distinct cilia. STED imaging resolved well-separated subdiffraction limited clusters for each protein. We quantified the size of each cluster to have a mean value of 88±48 nm and 124±43 nm, for CNG and ACIII, respectively. STED imaging showed separated clusters that were not resolvable in confocal images.

  12. Temperature-dependent spontaneous emission of PbS quantum dots inside photonic nanostructures at telecommunication wavelength

    NASA Astrophysics Data System (ADS)

    Birowosuto, Muhammad Danang; Takiguchi, Masato; Olivier, Aurelien; Tobing, Landobasa Y.; Kuramochi, Eiichi; Yokoo, Atsushi; Hong, Wang; Notomi, Masaya

    2017-01-01

    Spontaneous emission of PbS quantum dots (QDs) in different photonic nanostructures has been studied. We use the temperature-dependent exciton photoluminescence and the classic dipole near interface models to understand the spontaneous emission control at various temperatures. Then, we demonstrate that the enhancement and the inhibition of PbS QDs due to the local density of states (LDOS) inside nanostructures are more efficient at temperature as low as 77 K than the inhibition at 300 K. Largest emission rate enhancement at 77 K of 1.67 ± 0.10 and inhibition factors at 100 K of 2.27 ± 0.15 are reported for the gold (Au) planar mirror and silicon (Si) two-dimensional photonic crystal bandgap, respectively. We attribute those enhancement and inhibition to the large quantum yields Qe at low temperatures, which is much larger than that at 300 K. These results are relevant for application and optimization of PbS QDs in nanophotonics at telecommunication wavelength.

  13. Current Thermal Emission from Photonic Nanostructures Composed of TA, W, GE, and HFO2 Thin Films

    DTIC Science & Technology

    2015-03-01

    AFIT-ENP-MS-12-M-258 Abstract Combining an understanding of thin films and structure/property relationships, photonic nano -structured designs...be used to create selective reflection and absorption for a particular wavelength and direction. Many types of optical nano -structures have been...investigated to engineer unique radiative properties. Those types of nano -structures that have generated the most interest are metamaterials, photonic

  14. Single photon emission tomography in neurological studies: Instrumentation and clinical applications

    NASA Astrophysics Data System (ADS)

    Nikkinen, Paivi Helena

    One triple head and two single head gamma camera systems were used for single photon emission tomography (SPET) imaging of both patients and brain phantoms. Studies with an anatomical brain phantom were performed for evaluation of reconstruction and correction methods in brain perfusion SPET studies. The use of the triple head gamma camera system resulted in a significant increase in image contrast and resolution. This was mainly due to better imaging geometry and the use of a high resolution collimator. The conventional Chang attenuation correction was found suitable for the brain perfusion studies. In the brain perfusion studies region of interest (ROI) based semiquantitation methods were used. A ROI map based on anatomical areas was used in 70 elderly persons (age range 55-85 years) without neurological diseases and in patients suffering from encephalitis or having had a cardiac arrest. Semiquantitative reference values are presented. For the 14 patients with encephalitis the right-to-left side differences were calculated. Defect volume indexes were calculated for 64 patients with brain infarcts. For the 30 cardiac arrest patients the defect percentages and the anteroposterior ratios were used for semiquantitation. It is concluded that different semiquantitation methods are needed for the various patient groups. Age-related reference values will improve the interpretation of SPET data. For validation of the basal ganglia receptor studies measurements were performed using a cylindrical and an anatomical striatal phantom. In these measurements conventional and transmission imaging based non-uniform attenuation corrections were compared. A calibration curve was calculated for the determination of the specific receptor uptake ratio. In the phantom studies using the triple head camera the uptake ratio obtained from simultaneous transmission-emission protocol (STEP) acquisition and iterative reconstruction was closest to the true activity ratio. Conventional

  15. A photon counting dynamic digital lock-in amplifier for background suppression in glow discharge atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Gökmen, Ali; Ulgen, Ahmet; Yalçin, Şerife

    1996-01-01

    A photon counting dynamic digital lock-in amplifier, (PC-DDLIA), has been developed for the suppression of Ar lines in glow discharge lamp atomic emission spectrometry, (GDL-AES). The experimental set-up consists of a Grimm-type GDL, a prism-type scanning monochromator, photon counting electronics, an Apple Ile computer with an interface card and a computer controllable high voltage power supply. The photon counting electronics are designed to convert the photon pulses to logic pulses. A discriminator is used to reject pulses below a threshold level. The high voltage power supply is modulated with a square waveform generated from DAC and photon pulses are counted synchronously by the timer/counter chip, versatile interface adaptor (VIA-6522) on the interface card of computer. The data are analyzed in two steps. In the "learn mode", the GDL is modulated with a square waveform between 370 and 670 V and two spectra consisting of only Ar lines are obtained in a spectral window between 287.1 and 290.0 nm. A new modulation waveform is computed from these spectra which yields two overlapped spectra when the PC-DDLIA is scanned over the same spectral window. In the "analysis mode" of data acquisition, a target material with the analyte element(s) in it is used and the spectrometer is scanned with a dynamically varying rectangular waveform over the same spectral window. The net spectrum consists of pure atomic lines free from any Ar lines. The detection limit for the determination of Si (288.2 nm) in the presence of interfering Ar lines (288.1 and 288.4 nm) is found to be 0.083%, whereas suppression of Ar lines over the same spectral window lowers the detection limit to 0.013%.

  16. Coupling of Ag Nanoparticle with Inverse Opal Photonic Crystals as a Novel Strategy for Upconversion Emission Enhancement of NaYF4: Yb(3+), Er(3+) Nanoparticles.

    PubMed

    Shao, Bo; Yang, Zhengwen; Wang, Yida; Li, Jun; Yang, Jianzhi; Qiu, Jianbei; Song, Zhiguo

    2015-11-18

    Rare-earth-ion-doped upconversion (UC) nanoparticles have generated considerable interest because of their potential application in solar cells, biological labeling, therapeutics, and imaging. However, the applications of UC nanoparticles were still limited because of their low emission efficiency. Photonic crystals and noble metal nanoparticles are applied extensively to enhance the UC emission of rare earth ions. In the present work, a novel substrate consisting of inverse opal photonic crystals and Ag nanoparticles was prepared by the template-assisted method, which was used to enhance the UC emission of NaYF4: Yb(3+), Er(3+) nanoparticles. The red or green UC emissions of NaYF4: Yb(3+), Er(3+) nanoparticles were selectively enhanced on the inverse opal substrates because of the Bragg reflection of the photonic band gap. Additionally, the UC emission enhancement of NaYF4: Yb(3+), Er(3+) nanoparticles induced by the coupling of metal nanoparticle plasmons and photonic crystal effects was realized on the Ag nanoparticles included in the inverse opal substrate. The present results demonstrated that coupling of Ag nanoparticle with inverse opal photonic crystals provides a useful strategy to enhance UC emission of rare-earth-ion-doped nanoparticles.

  17. Diagnosis of sclerosing cholangitis with technetium 99m-labeled iminodiacetic acid planar and single photon emission computed tomographic scintigraphy

    SciTech Connect

    Rodman, C.A.; Keeffe, E.B.; Lieberman, D.A.; Krishnamurthy, S.; Krishnamurthy, G.T.; Gilbert, S.; Eklem, M.J.

    1987-03-01

    The purpose of this study was to determine whether /sup 99m/Tc-iminodiacetic acid planar biliary scintigraphy combined with single photon emission computed tomography could detect sclerosing cholangitis and provide additional information regarding the extent and severity of disease. Thirteen patients with sclerosing cholangitis and 13 normal control subjects were studied. Scintigraphic results were also compared with previously reported studies of patients with isolated common bile duct obstruction and with primary biliary cirrhosis. The planar scintigraphy in patients with sclerosing cholangitis showed beading or bandlike constrictions of the biliary tract corresponding to lesions seen on cholangiography, and the image pattern was distinctly different from images obtained from patients with isolated common bile duct obstruction or primary biliary cirrhosis. The single photon emission computed tomography images of the liver in patients with sclerosing cholangitis demonstrated multiple focal areas of /sup 99m/Tc-iminodiacetic acid retention, representing bile stasis in intrahepatic bile ducts. Compared to controls, the mean hepatic clearance half-time of /sup 99m/Tc-iminodiacetic acid was markedly delayed in patients with sclerosing cholangitis (6-10 times normal). Individual patients with sclerosing cholangitis had wider variation in isotope clearance half-time from three regions of the liver than patients with isolated common bile duct obstruction, consistent with regional difference in disease severity and variable impairment of bile flow. In 4 patients with sclerosing cholangitis with incomplete filling of the right and left hepatic ducts at cholangiography, planar and single photon emission computed tomographic scintigraphy provided evidence of significant intrahepatic sclerosing cholangitis.

  18. Room-temperature single-photon emission from zinc oxide nanoparticle defects and their in vitro photostable intrinsic fluorescence

    NASA Astrophysics Data System (ADS)

    Chung, Kelvin; Karle, Timothy J.; Khalid, Asma; Abraham, Amanda N.; Shukla, Ravi; Gibson, Brant C.; Simpson, David A.; Djurišic, Aleksandra B.; Amekura, Hiroshi; Tomljenovic-Hanic, Snjezana

    2017-01-01

    Zinc oxide (ZnO) is a promising semiconductor that is suitable for bioimaging applications due to its intrinsic defect fluorescence. However, ZnO generally suffers from poor photostability. We report room-temperature single-photon emission from optical defects found in ZnO nanoparticles (NPs) formed by ion implantation followed by thermal oxidation in a silica substrate. We conduct a thorough investigation into the photophysics of a particularly bright defect and identify other single emitters within the NPs. Photostability was observed when the NPs were removed from the growth substrate and taken up by skin cells for in vitro imaging.

  19. Single photon emission photography/magnetic resonance imaging (SPECT/MRI) visualization for frontal-lobe-damaged regions

    NASA Astrophysics Data System (ADS)

    Stokking, Rik; Zuiderveld, Karel J.; Hulshoff Pol, Hilleke E.; Viergever, Max A.

    1994-09-01

    We present multi-modality visualization strategies to convey information contained in registered Single Photon Emission Photography (SPECT) and Magnetic Resonance (MR) images of the brain. Multi-modality visualization provides a means to retrieve valuable information from the data which might otherwise remain obscured. Here we use MRI as an anatomical framework for functional information acquired with SPECT. This is part of clinical research studying the change of functionality caused by a frontal lobe damaged region. A number of known and newly developed techniques for the integrated visualization of SPECT and MR images will be discussed.

  20. Right parietal stroke with Gerstmann's syndrome. Appearance on computed tomography, magnetic resonance imaging, and single-photon emission computed tomography.

    PubMed

    Moore, M R; Saver, J L; Johnson, K A; Romero, J A

    1991-04-01

    We examined a patient who exhibited Gerstmann's syndrome (left-right disorientation, finger agnosia, dyscalculia, and dysgraphia) in association with a perioperative stroke in the right parietal lobe. This is the first description of the Gerstmann tetrad occurring in the setting of discrete right hemisphere pathologic findings. A well-localized vascular lesion was demonstrated by computed tomography, magnetic resonance imaging, and single-photon emission computed tomographic studies. The patient had clinical evidence of reversed functional cerebral dominance and radiologic evidence of reversed anatomic cerebral asymmetries.

  1. Two Cases of Legionella pneumophila Pneumonia with Prolonged Neurologic Symptoms and Brain Hypoperfusion on Single-Photon Emission Computed Tomography

    PubMed Central

    Miura, You; Seto, Akira; Kanazawa, Minoru; Nagata, Makoto

    2016-01-01

    Cerebral and cerebellar symptoms are frequently associated with Legionnaires' disease. However, corresponding brain lesions are difficult to demonstrate using either computed tomography (CT) or magnetic resonance imaging (MRI). We report here two patients with Legionella pneumophila pneumonia accompanied by prolonged neurologic symptoms. In contrast to brain CT and MRI, which failed to detect any abnormalities, single-photon emission computed tomography (SPECT) showed multiple sites of hypoperfusion within the brains of both patients. These cases suggest that vasculopathy, which is detectable by SPECT, might be one of the causes of neurologic symptoms in patients with Legionnaires' disease. PMID:27478660

  2. Domestic Development of Single-Photon Emission Computed Tomography (SPECT) Unit with Detector based on Silicon Photomultipliers

    NASA Astrophysics Data System (ADS)

    Grishakov, S.; Ryzhikova, O.; Sergienko, V.; Ansheles, A.; Novikov, S.

    2017-01-01

    The idea of creating a single-photon emission computed tomography unit with solid-state photomultipliers is not new [1], as the problems of analog-to-digital conversion with a lot of noise and a wide range of values of intrinsic spatial resolution of the detector in a center and relevant fields of view could not be solved by means of gamma-camera detector architectures based on vacuum photomultipliers. This paper offers a new SPECT imaging solution that is free from these problems.

  3. All-Optical Fiber Hanbury Brown &Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot.

    PubMed

    Muñoz-Matutano, G; Barrera, D; Fernández-Pousa, C R; Chulia-Jordan, R; Seravalli, L; Trevisi, G; Frigeri, P; Sales, S; Martínez-Pastor, J

    2016-06-03

    New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure splitting for the neutral exciton transition within our spectral resolution (46 μeV), metamorphic QD single photon emission studied with our all-fiber Hanbury Brown &Twiss interferometer could lead to a more efficient analysis of entangled photon sources at telecom wavelength. This all-optical fiber scheme opens the door to new first and second order interferometers to study photon indistinguishability, entangled photon and photon cross correlation in the more interesting telecom wavelengths.

  4. All-Optical Fiber Hanbury Brown & Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot

    PubMed Central

    Muñoz-Matutano, G.; Barrera, D.; Fernández-Pousa, C.R.; Chulia-Jordan, R.; Seravalli, L.; Trevisi, G.; Frigeri, P.; Sales, S.; Martínez-Pastor, J.

    2016-01-01

    New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure splitting for the neutral exciton transition within our spectral resolution (46 μeV), metamorphic QD single photon emission studied with our all-fiber Hanbury Brown & Twiss interferometer could lead to a more efficient analysis of entangled photon sources at telecom wavelength. This all-optical fiber scheme opens the door to new first and second order interferometers to study photon indistinguishability, entangled photon and photon cross correlation in the more interesting telecom wavelengths. PMID:27257122

  5. All-Optical Fiber Hanbury Brown & Twiss Interferometer to study 1300 nm single photon emission of a metamorphic InAs Quantum Dot

    NASA Astrophysics Data System (ADS)

    Muñoz-Matutano, G.; Barrera, D.; Fernández-Pousa, C. R.; Chulia-Jordan, R.; Seravalli, L.; Trevisi, G.; Frigeri, P.; Sales, S.; Martínez-Pastor, J.

    2016-06-01

    New optical fiber based spectroscopic tools open the possibility to develop more robust and efficient characterization experiments. Spectral filtering and light reflection have been used to produce compact and versatile fiber based optical cavities and sensors. Moreover, these technologies would be also suitable to study N-photon correlations, where high collection efficiency and frequency tunability is desirable. We demonstrated single photon emission of a single quantum dot emitting at 1300 nm, using a Fiber Bragg Grating for wavelength filtering and InGaAs Avalanche Photodiodes operated in Geiger mode for single photon detection. As we do not observe any significant fine structure splitting for the neutral exciton transition within our spectral resolution (46 μeV), metamorphic QD single photon emission studied with our all-fiber Hanbury Brown & Twiss interferometer could lead to a more efficient analysis of entangled photon sources at telecom wavelength. This all-optical fiber scheme opens the door to new first and second order interferometers to study photon indistinguishability, entangled photon and photon cross correlation in the more interesting telecom wavelengths.

  6. Calculation of spontaneous emission from a V-type three-level atom in photonic crystals using fractional calculus

    SciTech Connect

    Huang, Chih-Hsien; Hsieh, Wen-Feng; Wu, Jing-Nuo; Cheng, Szu-Cheng; Li, Yen-Yin

    2011-07-15

    Fractional time derivative, an abstract mathematical operator of fractional calculus, is used to describe the real optical system of a V-type three-level atom embedded in a photonic crystal. A fractional kinetic equation governing the dynamics of the spontaneous emission from this optical system is obtained as a fractional Langevin equation. Solving this fractional kinetic equation by fractional calculus leads to the analytical solutions expressed in terms of fractional exponential functions. The accuracy of the obtained solutions is verified through reducing the system into the special cases whose results are consistent with the experimental observation. With accurate physical results and avoiding the complex integration for solving this optical system, we propose fractional calculus with fractional time derivative as a better mathematical method to study spontaneous emission dynamics from the optical system with non-Markovian dynamics.

  7. Efficient single photon emission from a high-purity hexagonal boron nitride crystal

    NASA Astrophysics Data System (ADS)

    Martínez, L. J.; Pelini, T.; Waselowski, V.; Maze, J. R.; Gil, B.; Cassabois, G.; Jacques, V.

    2016-09-01

    Among a variety of layered materials used as building blocks in van der Waals heterostructures, hexagonal boron nitride (hBN) appears as an ideal platform for hosting optically active defects owing to its large band gap (˜6 eV ). Here we study the optical response of a high-purity hBN crystal under green laser illumination. By means of photon correlation measurements, we identify individual defects emitting a highly photostable fluorescence under ambient conditions. A detailed analysis of the photophysical properties reveals a high quantum efficiency of the radiative transition, leading to a single photon source with very high brightness (˜4 ×106 counts s-1). These results illustrate how the wide range of applications offered by hBN could be further extended to photonic-based quantum information science and metrology.

  8. 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.

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

    PubMed

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

    1996-05-01

    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.

  10. Assessment of cardiac single-photon emission computed tomography performance using a scanning linear observer

    SciTech Connect

    Lee, Chih-Jie; Kupinski, Matthew A.; Volokh, Lana

    2013-01-15

    Purpose: Single-photon emission computed tomography (SPECT) is widely used to detect myocardial ischemia and myocardial infarction. It is important to assess and compare different SPECT system designs in order to achieve the highest detectability of cardiac defects. Methods: Whitaker et al.'s study ['Estimating random signal parameters from noisy images with nuisance parameters: linear and scanning-linear methods,' Opt. Express 16(11), 8150-8173 (2008)] on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than with reconstruction data. Thus, this observer model assesses the overall hardware performance independent of any reconstruction algorithm. In addition, the computation time of image quality studies is significantly reduced. In this study, three systems based on the design of the GE cadmium zinc telluride-based dedicated cardiac SPECT camera Discovery 530c were assessed. This design, which is officially named the Alcyone Technology: Discovery NM 530c, was commercialized in August, 2009. The three systems, GE27, GE19, and GE13, contain 27, 19, and 13 detectors, respectively. Clinically, a human heart can be virtually segmented into three coronary artery territories: the left-anterior descending artery, left-circumflex artery, and right coronary artery. One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can accurately predict in which territory the defect exists [http://www.asnc.org/media/PDFs/PPReporting081511.pdf, Guideline from American Society of Nuclear Cardiology]. A good estimation of the extent of the defect from the projection images is also very helpful for determining the seriousness of the myocardial ischemia. In this study, both the location and extent of defects were estimated by the SLO, and the system performance was assessed by localization

  11. Assessment of cardiac single-photon emission computed tomography performance using a scanning linear observer

    PubMed Central

    Lee, Chih-Jie; Kupinski, Matthew A.; Volokh, Lana

    2013-01-01

    Purpose: Single-photon emission computed tomography (SPECT) is widely used to detect myocardial ischemia and myocardial infarction. It is important to assess and compare different SPECT system designs in order to achieve the highest detectability of cardiac defects. Methods:Whitaker ’s study [“Estimating random signal parameters from noisy images with nuisance parameters: linear and scanning-linear methods,” Opt. Express 16(11), 8150–8173 (2008)]10.1364/OE.16.008150 on the scanning linear observer (SLO) shows that the SLO can be used to estimate the location and size of signals. One major advantage of the SLO is that it can be used with projection data rather than with reconstruction data. Thus, this observer model assesses the overall hardware performance independent of any reconstruction algorithm. In addition, the computation time of image quality studies is significantly reduced. In this study, three systems based on the design of the GE cadmium zinc telluride-based dedicated cardiac SPECT camera Discovery 530c were assessed. This design, which is officially named the Alcyone Technology: Discovery NM 530c, was commercialized in August, 2009. The three systems, GE27, GE19, and GE13, contain 27, 19, and 13 detectors, respectively. Clinically, a human heart can be virtually segmented into three coronary artery territories: the left-anterior descending artery, left-circumflex artery, and right coronary artery. One of the most important functions of a cardiac SPECT system is to produce images from which a radiologist can accurately predict in which territory the defect exists [http://www.asnc.org/media/PDFs/PPReporting081511.pdf, Guideline from American Society of Nuclear Cardiology]. A good estimation of the extent of the defect from the projection images is also very helpful for determining the seriousness of the myocardial ischemia. In this study, both the location and extent of defects were estimated by the SLO, and the system performance was assessed by

  12. Purcell-Enhanced Single-Photon Emission from Nitrogen-Vacancy Centers Coupled to a Tunable Microcavity

    NASA Astrophysics Data System (ADS)

    Kaupp, Hanno; Hümmer, Thomas; Mader, Matthias; Schlederer, Benedikt; Benedikter, Julia; Haeusser, Philip; Chang, Huan-Cheng; Fedder, Helmut; Hänsch, Theodor W.; Hunger, David

    2016-11-01

    Optical microcavities are a powerful tool for enhancing the fluorescence of individual quantum emitters. However, the broad emission spectra encountered in the solid state at room temperature limit the influence of a cavity, calling for an ultrasmall mode volume. We demonstrate Purcell-enhanced single-photon emission from nitrogen-vacancy centers in nanodiamonds coupled to a tunable fiber-based microcavity with a mode volume down to 1.0 λ3. We record cavity-enhanced fluorescence images and study several single emitters with one cavity. The Purcell effect is evidenced by enhanced fluorescence collection and tunable lifetime modification, and we infer an effective Purcell factor of up to 2. Furthermore, we show an alternative regime for light confinement, where a Fabry-Perot mode is combined with additional mode confinement by the nanocrystal itself. Simulations predict effective Purcell factors of up to 11 for nitrogen-vacancy centers and 63 for silicon-vacancy centers, holding promise for bright single-photon sources and efficient spin readout under ambient conditions.

  13. Synthesis of heterodimer radionuclide nanoparticles for magnetic resonance and single-photon emission computed tomography dual-modality imaging

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Zhang, Bin; Tian, Jian; Wang, Jiaqing; Chong, Yu; Wang, Xin; Deng, Yaoyao; Tang, Minghua; Li, Yonggang; Ge, Cuicui; Pan, Yue; Gu, Hongwei

    2015-02-01

    We report a facile synthesis of bifunctional Fe3O4-Ag125I heterodimers for use as dual-modality imaging agents in magnetic resonance (MR) and single-photon emission computed tomography (SPECT). We introduced 125I, which is a clinically used radioisotope, as a SPECT reporter, into Fe3O4-Ag heterodimer nanoparticles to provide a new type of bifunctional contrast agent for MRI and SPECT imaging.We report a facile synthesis of bifunctional Fe3O4-Ag125I heterodimers for use as dual-modality imaging agents in magnetic resonance (MR) and single-photon emission computed tomography (SPECT). We introduced 125I, which is a clinically used radioisotope, as a SPECT reporter, into Fe3O4-Ag heterodimer nanoparticles to provide a new type of bifunctional contrast agent for MRI and SPECT imaging. Electronic supplementary information (ESI) available: Details of general experimental procedures, TEM image. See DOI: 10.1039/c4nr07255c

  14. Electrical stimulation of non-classical photon emission from diamond color centers by means of sub-superficial graphitic electrodes

    PubMed Central

    Forneris, Jacopo; Traina, Paolo; Monticone, Daniele Gatto; Amato, Giampiero; Boarino, Luca; Brida, Giorgio; Degiovanni, Ivo P.; Enrico, Emanuele; Moreva, Ekaterina; Grilj, Veljko; Skukan, Natko; Jakšić, Milko; Genovese, Marco; Olivero, Paolo

    2015-01-01

    Focused MeV ion beams with micrometric resolution are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as already demonstrated for different device applications. In this work we apply this fabrication method to the electrical excitation of color centers in diamond, demonstrating the potential of electrical stimulation in diamond-based single-photon sources. Differently from optically-stimulated light emission from color centers in diamond, electroluminescence (EL) requires a high current flowing in the diamond subgap states between the electrodes. With this purpose, buried graphitic electrode pairs, 10 μm spaced, were fabricated in the bulk of a single-crystal diamond sample using a 6 MeV C microbeam. The electrical characterization of the structure showed a significant current injection above an effective voltage threshold of 150 V, which enabled the stimulation of a stable EL emission. The EL imaging allowed to identify the electroluminescent regions and the residual vacancy distribution associated with the fabrication technique. Measurements evidenced isolated electroluminescent spots where non-classical light emission in the 560–700 nm spectral range was observed. The spectral and auto-correlation features of the EL emission were investigated to qualify the non-classical properties of the color centers. PMID:26510889

  15. Electrical stimulation of non-classical photon emission from diamond color centers by means of sub-superficial graphitic electrodes

    NASA Astrophysics Data System (ADS)

    Forneris, Jacopo; Traina, Paolo; Monticone, Daniele Gatto; Amato, Giampiero; Boarino, Luca; Brida, Giorgio; Degiovanni, Ivo P.; Enrico, Emanuele; Moreva, Ekaterina; Grilj, Veljko; Skukan, Natko; Jakšić, Milko; Genovese, Marco; Olivero, Paolo

    2015-10-01

    Focused MeV ion beams with micrometric resolution are suitable tools for the direct writing of conductive graphitic channels buried in an insulating diamond bulk, as already demonstrated for different device applications. In this work we apply this fabrication method to the electrical excitation of color centers in diamond, demonstrating the potential of electrical stimulation in diamond-based single-photon sources. Differently from optically-stimulated light emission from color centers in diamond, electroluminescence (EL) requires a high current flowing in the diamond subgap states between the electrodes. With this purpose, buried graphitic electrode pairs, 10 μm spaced, were fabricated in the bulk of a single-crystal diamond sample using a 6 MeV C microbeam. The electrical characterization of the structure showed a significant current injection above an effective voltage threshold of 150 V, which enabled the stimulation of a stable EL emission. The EL imaging allowed to identify the electroluminescent regions and the residual vacancy distribution associated with the fabrication technique. Measurements evidenced isolated electroluminescent spots where non-classical light emission in the 560-700 nm spectral range was observed. The spectral and auto-correlation features of the EL emission were investigated to qualify the non-classical properties of the color centers.

  16. Photon emissivity in the vicinity of a critical point - A case study within the quark meson model

    NASA Astrophysics Data System (ADS)

    Wunderlich, F.; Kämpfer, B.

    2017-03-01

    The quark meson (linear sigma) model with linearized fluctuations displays at a critical end point the onset of a curve of first-order phase transitions (FOPTs) located at non-zero chemical potentials and temperatures below a certain cross-over temperature. The model qualifies well for an illustrative example to study the impact of the emerging FOPT, e.g. on photon emissivities. Such a case study unravels the tight interlocking of the phase structure with the emission rates, here calculated according to lowest-order tree level processes by kinetic theory expressions. It is the strong dependence of the rates on the effective masses of the involved degrees of freedom which distinctively vary over the phase diagram thus shaping the emissivity accordingly. At the same time, thermodynamic properties of the medium are linked decisively to these effective masses, i.e. a consistent evaluation of thermodynamics, governing for instance adiabatic expansion paths, and emission rates is maintained within such an approach.

  17. Effects of system geometry and other physical factors on photon sensitivity of high-resolution positron emission tomography.

    PubMed

    Habte, F; Foudray, A M K; Olcott, P D; Levin, C S

    2007-07-07

    We are studying two new detector technologies that directly measure the three-dimensional coordinates of 511 keV photon interactions for high-resolution positron emission tomography (PET) systems designed for small animal and breast imaging. These detectors are based on (1) lutetium oxyorthosilicate (LSO) scintillation crystal arrays coupled to position-sensitive avalanche photodiodes (PSAPD) and (2) cadmium zinc telluride (CZT). The detectors have excellent measured 511 keV photon energy resolutions (photon detection efficiency (referred to as photon sensitivity). To facilitate high photon sensitivity in the proposed PET system designs, the detector arrays are oriented 'edge-on' with respect to incoming 511 keV annihilation photons and arranged to form a compact FOV with detectors very close to, or in contact with, the subject tissues. In this paper, we used Monte Carlo simulation to study various factors that limit the photon sensitivity of a high-resolution PET system dedicated to small animal imaging. To optimize the photon sensitivity, we studied several possible system geometries for a fixed 8 cm transaxial and 8 cm axial FOV. We found that using rectangular-shaped detectors arranged into a cylindrical geometry does not yield the best photon sensitivity. This is due to the fact that forming rectangular-shaped detectors into a ring produces significant wedge-shaped inter-module gaps, through which Compton-scattered photons in the detector can escape. This effect limits the center point source

  18. Effects of system geometry and other physical factors on photon sensitivity of high-resolution positron emission tomography

    PubMed Central

    Foudray, A M K; Olcott, P D

    2013-01-01

    We are studying two new detector technologies that directly measure the three-dimensional coordinates of 511 keV photon interactions for high-resolution positron emission tomography (PET) systems designed for small animal and breast imaging. These detectors are based on (1) lutetium oxyorthosilicate (LSO) scintillation crystal arrays coupled to position-sensitive avalanche photodiodes (PSAPD) and (2) cadmium zinc telluride (CZT). The detectors have excellent measured 511 keV photon energy resolutions (≤12% FWHM for LSO-PSAPD and ≤3% for CZT) and good coincidence time resolutions (2 ns FWHM for LSO-PSAPD and 8 ns for CZT). The goal is to incorporate the detectors into systems that will achieve 1 mm3 spatial resolution (~1 mm3, uniform throughout the field of view (FOV)), with excellent contrast resolution as well. In order to realize 1 mm3 spatial resolution with high signal-to-noise ratio (SNR), it is necessary to significantly boost coincidence photon detection efficiency (referred to as photon sensitivity). To facilitate high photon sensitivity in the proposed PET system designs, the detector arrays are oriented ‘edge-on’ with respect to incoming 511 keV annihilation photons and arranged to form a compact FOV with detectors very close to, or in contact with, the subject tissues. In this paper, we used Monte Carlo simulation to study various factors that limit the photon sensitivity of a high-resolution PET system dedicated to small animal imaging. To optimize the photon sensitivity, we studied several possible system geometries for a fixed 8 cm transaxial and 8 cm axial FOV. We found that using rectangular-shaped detectors arranged into a cylindrical geometry does not yield the best photon sensitivity. This is due to the fact that forming rectangular-shaped detectors into a ring produces significant wedge-shaped inter-module gaps, through which Compton-scattered photons in the detector can escape. This effect limits the center point source photon

  19. Purcell enhancement of fast-dephasing spontaneous emission from electron-hole droplets in high-Q silicon photonic crystal nanocavities

    NASA Astrophysics Data System (ADS)

    Sumikura, Hisashi; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya

    2016-11-01

    We have observed electron-hole droplet emission enhanced by silicon photonic crystal nanocavities with different Q values and simulated their Purcell effect using a semiclassical theory considering the temporal dephasing of the emission. When the photon loss rate of the nanocavities is smaller than the dephasing rate of the emission, the cavity-enhanced integrated photoluminescence (PL) intensity is unchanged by the cavity Q value. This is because the Purcell enhancement of the spontaneous emission rate is saturated in a high-Q region. In contrast, the peak intensity of the cavity-enhanced PL is proportional to the cavity Q value without saturation. These results suggest that a high-Q nanocavity is suitable for fabricating bright narrowband light emitting devices that concentrate the broadband emission energy of fast-dephasing emitters in a narrowband cavity resonance.

  20. GRB 110709A, 111117A, AND 120107A: FAINT HIGH-ENERGY GAMMA-RAY PHOTON EMISSION FROM FERMI-LAT OBSERVATIONS AND DEMOGRAPHIC IMPLICATIONS

    SciTech Connect

    Zheng Weikang; Akerlof, Carl W.; McKay, Timothy A.; Pandey, Shashi B.; Zhang Binbin; Zhang Bing; Sakamoto, Takanori

    2012-09-01

    Launched on 2008 June 11, the Large Area Telescope (LAT) instrument on board the Fermi Gamma-ray Space Telescope has provided a rare opportunity to study high-energy photon emission from gamma-ray bursts (GRBs). Although the majority of such events (27) have been identified by the Fermi-LAT Collaboration, four were uncovered by using more sensitive statistical techniques. In this paper, we continue our earlier work by finding three more GRBs associated with high-energy photon emission, GRB 110709A, 111117A, and 120107A. To systematize our matched filter approach, a pipeline has been developed to identify these objects in nearly real time. GRB 120107A is the first product of this analysis procedure. Despite the reduced threshold for identification, the number of GRB events has not increased significantly. This relative dearth of events with low photon number prompted a study of the apparent photon number distribution. We find an extremely good fit to a simple power law with an exponent of -1.8 {+-} 0.3 for the differential distribution. As might be expected, there is a substantial correlation between the number of lower energy photons detected by the Gamma-ray Burst Monitor (GBM) and the number observed by LAT. Thus, high-energy photon emission is associated with some but not all of the brighter GBM events. Deeper studies of the properties of the small population of high-energy emitting bursts may eventually yield a better understanding of these entire phenomena.

  1. Early Dose Response to Yttrium-90 Microsphere Treatment of Metastatic Liver Cancer by a Patient-Specific Method Using Single Photon Emission Computed Tomography and Positron Emission Tomography

    SciTech Connect

    Campbell, Janice M. Wong, C. Oliver; Muzik, Otto; Marples, Brian; Joiner, Michael; Burmeister, Jay

    2009-05-01

    Purpose: To evaluate a patient-specific single photon emission computed tomography (SPECT)-based method of dose calculation for treatment planning of yttrium-90 ({sup 90}Y) microsphere selective internal radiotherapy (SIRT). Methods and Materials: Fourteen consecutive {sup 90}Y SIRTs for colorectal liver metastasis were retrospectively analyzed. Absorbed dose to tumor and normal liver tissue was calculated by partition methods with two different tumor/normal liver vascularity ratios: an average 3:1 and a patient-specific ratio derived from pretreatment technetium-99m macroaggregated albumin SPECT. Tumor response was quantitatively evaluated from fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography scans. Results: Positron emission tomography showed a significant decrease in total tumor standardized uptake value (average, 52%). There was a significant difference in the tumor absorbed dose between the average and specific methods (p = 0.009). Response vs. dose curves fit by linear and linear-quadratic modeling showed similar results. Linear fit r values increased for all tumor response parameters with the specific method (+0.20 for mean standardized uptake value). Conclusion: Tumor dose calculated with the patient-specific method was more predictive of response in liver-directed {sup 90}Y SIRT.

  2. Topological photon

    NASA Astrophysics Data System (ADS)

    Tiwari, S. C.

    2008-03-01

    We associate intrinsic energy equal to hν /2 with the spin angular momentum of photon, and propose a topological model based on orbifold in space and tifold in time as topological obstructions. The model is substantiated using vector wavefield disclinations. The physical photon is suggested to be a particlelike topological photon and a propagating wave such that the energy hν of photon is equally divided between spin energy and translational energy, corresponding to linear momentum of hν /c. The enigma of wave-particle duality finds natural resolution, and the proposed model gives new insights into the phenomena of interference and emission of radiation.

  3. Formation and stimulated photodissociation of metastable molecules with emission of photon at the collision of two atoms in a laser radiation field

    NASA Astrophysics Data System (ADS)

    Gazazyan, E.; Gazazyan, A.

    2017-04-01

    The formation of metastable molecules (Feshbach resonances) at the collision of two atoms and subsequent stimulated transition to a lower unbound electronic molecular state, with emission of a photon of the laser radiation has been investigated. This can develop, in particular, for Rb 2 molecules due to resonance scattering of two Rb atoms. This process is a basis for the creation of excimer lasers. Expressions have been obtained for the cross sections of elastic and inelastic resonance scattering and the intensity of the stimulated emission of the photons.

  4. Building protection- and building shielding-factors for environmental exposure to radionuclides and monoenergetic photon emissions.

    PubMed

    Dickson, E D; Hamby, D M

    2016-09-01

    We describe a simplified method for calculating both building protection- and shielding-factors for generic one- and two-story housing-unit models that are source-term dependent. Typically, radionuclide-independent factors are applied generically to external dose coefficients to account for the radiation shielding effects of indoor residences. In reality, the shielding effectiveness of each housing-unit would change over time as the radionuclide mixture and gamma-ray energy spectrum change due to physical effects such as deposition, radioactive decay, weathering effects, and decontamination efforts. Thus, it is necessary to develop factors designed for multiple photon energy spectrums to generate a more realistic estimate of the shielding effectiveness of a particular building. It is impractical to develop factors specific to a spectrum of photons emitted by each radionuclide of interest. Therefore, Monte Carlo simulations have been performed for sixteen monoenergetic photon energies from 0.10 to 3.0 MeV to characterize the 3D radiation fluence through each housing-unit produced by two idealized, yet realistic, environmental exposure scenarios. Results of these simulations were then used to develop fitted logarithmic functions (extrapolated to 0.0 MeV) to correlate an estimated factor to any monoenergetic photon energy up to 3.0 MeV. To verify these functions, another series of Monte Carlo simulations were performed for a select set of radionuclides to develop radionuclide-specific building protection- and shielding-factors. Good agreement is achieved between factors estimated using the presented functions and those calculated directly using Monte Carlo methods. Factors predicted by these functions are found to be in general agreement with other study results reported on similar structures which applied various computational methods and source-terms. This study only focuses on generic one- and two-story homes to provide a practical application that can contribute

  5. Effects of Lac operon activation, deletion of the Yhha gene, and the removal of oxygen on the ultra-weak photon emission of Escherichia coli.

    PubMed

    Laager, Frédéric M; Becker, Nicholas M; Park, Sang-Hyun; Soh, Kwang-Sup

    2009-01-01

    We observed a relation between gene activity and ultra-weak photon emission (UPE). By comparing the UPEs of E. coli with the LacI gene present and deleted we found that more gene activity produced higher UPE. This relation was further confirmed by studying the UPE of the E. coli with and without the Yhha gene. We interpreted that a higher aminoacyl t-RNA synthetase activity, which used ATP from the respiratory chain, could increase the emission. Satisfying the increased need of ATP by the E. coli through an increase of respiratory chain activity, which has reactive oxygen species (ROS) as a byproduct, results in a higher rate of photon emission. To ensure that oxygen is at the origin of this emission, we replaced the air by pure nitrogen. After 30 min, it was observed that the emission levels equaled the emission levels of the sterile medium. We could therefore conclude that the source of the photon emission would be affected by genetic activity and is oxygen related.

  6. On the comparison of matrix element calculations of O(ααs) with the measurement of photon emission in hadronic Z 0 decays

    NASA Astrophysics Data System (ADS)

    Mättig, P.; Spiesberger, H.; Zeuner, W.

    1993-12-01

    The uncertainties in interpreting photon bremsstrahlung in the processe^ + e^ - to Z^0 to qbar q with matrix element calculations of O(ααs) are discussed. We address the stability of the calculations with respect to the emission of collinear photons and to higher-order QCD corrections and discuss the bias due to experimental photon isolation cuts. We analyze the resulting uncertainties for various procedures to define an event with a final state photon. Of particular interest are (i) a two-step procedure where first jets are reconstructed from hadrons alone and in a second step the photon is required to be isolated from these jets, and (ii) a ‘democratic’ procedure where the photon is inculded in the jet reconstruction but a certain maximum hadronic energy is allowed in the photon jet. In both cases we estimate that the uncertainties of the theoretical predictions, hadronization effects and the experimental photon isolation are of the order of 4%. To obtain this level of accuracy, however, the democratic procedure requires very hard cuts that reduce the event samples significantly.

  7. Telecommunication Wavelength-Band Single-Photon Emission from Single Large InAs Quantum Dots Nucleated on Low-Density Seed Quantum Dots.

    PubMed

    Chen, Ze-Sheng; Ma, Ben; Shang, Xiang-Jun; He, Yu; Zhang, Li-Chun; Ni, Hai-Qiao; Wang, Jin-Liang; Niu, Zhi-Chuan

    2016-12-01

    Single-photon emission in the telecommunication wavelength band is realized with self-assembled strain-coupled bilayer InAs quantum dots (QDs) embedded in a planar microcavity on GaAs substrate. Low-density large QDs in the upper layer active for ~1.3 μm emission are fabricated by precisely controlling the indium deposition amount and applying a gradient indium flux in both QD layers. Time-resolved photoluminescence (PL) intensity suggested that the radiative lifetime of their exciton emission is 1.5~1.6 ns. The second-order correlation function of g (2)(0) < 0.5 which demonstrates a pure single-photon emission.

  8. Crossing the Boundaries of Our Current Healthcare System by Integrating Ultra-Weak Photon Emissions with Metabolomics

    PubMed Central

    Burgos, Rosilene C. Rossetto; van Wijk, Eduard P. A.; van Wijk, Roeland; He, Min; van der Greef, Jan

    2016-01-01

    The current healthcare system is hampered by a reductionist approach in which diagnostics and interventions focus on a specific target, resulting in medicines that center on generic, static phenomena while excluding inherent dynamic nature of biological processes, let alone psychosocial parameters. In this essay, we present some limitations of the current healthcare system and introduce the novel and potential approach of combining ultra-weak photon emission (UPE) with metabolomics technology in order to provide a dynamic readout of higher organizational systems. We argue that the combination of metabolomics and UPE can bring a new, broader, view of health state and can potentially help to shift healthcare toward more personalized approach that improves patient well-being. PMID:28018239

  9. Enabling enhanced emission and low-threshold lasing of organic molecules using special Fano resonances of macroscopic photonic crystals

    PubMed Central

    Zhen, Bo; Chua, Song-Liang; Lee, Jeongwon; Rodriguez, Alejandro W.; Liang, Xiangdong; Johnson, Steven G.; Joannopoulos, John D.; Soljačić, Marin; Shapira, Ofer

    2013-01-01

    The nature of light interaction with matter can be dramatically altered in optical cavities, often inducing nonclassical behavior. In solid-state systems, excitons need to be spatially incorporated within nanostructured cavities to achieve such behavior. Although fascinating phenomena have been observed with inorganic nanostructures, the incorporation of organic molecules into the typically inorganic cavity is more challenging. Here, we present a unique optofluidic platform comprising organic molecules in solution suspended on a photonic crystal surface, which supports macroscopic Fano resonances and allows strong and tunable interactions with the molecules anywhere along the surface. We develop a theoretical framework of this system and present a rigorous comparison with experimental measurements, showing dramatic spectral and angular enhancement of emission. We then demonstrate that these enhancement mechanisms enable lasing of only a 100-nm thin layer of diluted solution of organic molecules with substantially reduced threshold intensity, which has important implications for organic light-emitting devices and molecular sensing. PMID:23918363

  10. Modal theory of modified spontaneous emission of a quantum emitter in a hybrid plasmonic photonic-crystal cavity system

    NASA Astrophysics Data System (ADS)

    Kamandar Dezfouli, Mohsen; Gordon, Reuven; Hughes, Stephen

    2017-01-01

    We present an intuitive and accurate modal description of the rich optical physics involved for quantum dipole emitters coupled to hybrid plasmonic photonic-cavity structures. A significant frequency dependence for the spontaneous emission decay rate of a quantum dipole emitter coupled to these hybrid structures is found. In particular, it is shown that a Fano-type resonance reported experimentally in hybrid plasmonic systems arises from a large interference between two dominant quasinormal modes of the systems in the frequency range of interest. The presented modal theory forms an efficient basis for modeling quantum light-matter interactions in these complex hybrid systems and also enables the quantitative prediction and understanding of both radiative and nonradiative coupling for a wide range of dipole positions.

  11. Crossing the Boundaries of Our Current Healthcare System by Integrating Ultra-Weak Photon Emissions with Metabolomics.

    PubMed

    Burgos, Rosilene C Rossetto; van Wijk, Eduard P A; van Wijk, Roeland; He, Min; van der Greef, Jan

    2016-01-01

    The current healthcare system is hampered by a reductionist approach in which diagnostics and interventions focus on a specific target, resulting in medicines that center on generic, static phenomena while excluding inherent dynamic nature of biological processes, let alone psychosocial parameters. In this essay, we present some limitations of the current healthcare system and introduce the novel and potential approach of combining ultra-weak photon emission (UPE) with metabolomics technology in order to provide a dynamic readout of higher organizational systems. We argue that the combination of metabolomics and UPE can bring a new, broader, view of health state and can potentially help to shift healthcare toward more personalized approach that improves patient well-being.

  12. Evaluation of extracranial-to-intracranial bypass surgery using iodine 123 iodoamphetamine single-photon emission computed tomography

    SciTech Connect

    Kobayashi, H.; Hayashi, M.; Kawano, H.; Handa, Y.; Kabuto, M.; Maeda, H.; Ishii, Y. )

    1991-06-01

    Eleven patients with occlusive cerebrovascular diseases were imaged with N-isopropyl-p-I-123 iodoamphetamine. Preoperative and postoperative single-photon emission computed tomography was performed in 10 patients undergoing extracranial-to-intracranial bypass procedures. New images were reconstructed from the two images obtained on the different days by superimposition and division in each pixel to get the ratio of cerebral perfusion change. All patients with bypass procedures had an increase in cerebral blood flow in the affected areas, and nine of 10 had an increase in cerebral blood flow in the contralateral cortex. There was no increase in cerebral blood flow in one case with no operation. Neither our procedure nor the results in this small series prove that recovery of function is due to an increase in blood flow, but we believe this is the case.

  13. Enhanced Telecom Emission from Single Group-IV Quantum Dots by Precise CMOS-Compatible Positioning in Photonic Crystal Cavities.

    PubMed

    Schatzl, Magdalena; Hackl, Florian; Glaser, Martin; Rauter, Patrick; Brehm, Moritz; Spindlberger, Lukas; Simbula, Angelica; Galli, Matteo; Fromherz, Thomas; Schäffler, Friedrich

    2017-03-15

    Efficient coupling to integrated high-quality-factor cavities is crucial for the employment of germanium quantum dot (QD) emitters in future monolithic silicon-based optoelectronic platforms. We report on strongly enhanced emission from single Ge QDs into L3 photonic crystal resonator (PCR) modes based on precise positioning of these dots at the maximum of the respective mode field energy density. Perfect site control of Ge QDs grown on prepatterned silicon-on-insulator substrates was exploited to fabricate in one processing run almost 300 PCRs containing single QDs in systematically varying positions within the cavities. Extensive photoluminescence studies on this cavity chip enable a direct evaluation of the position-dependent coupling efficiency between single dots and selected cavity modes. The experimental results demonstrate the great potential of the approach allowing CMOS-compatible parallel fabrication of arrays of spatially matched dot/cavity systems for group-IV-based data transfer or quantum optical systems in the telecom regime.

  14. Long-term noninvasive single photon emission computed tomography monitoring of perfusional changes after EC-IC bypass surgery.

    PubMed Central

    Di Piero, V; Lenzi, G L; Collice, M; Triulzi, F; Gerundini, P; Perani, D; Savi, A R; Fieschi, C; Fazio, F

    1987-01-01

    The rCBF was evaluated using I-123 HIPDM and single photon emission computed tomography (SPECT) on 14 patients undergoing extracranial-intracranial (EC-IC) bypass surgery because of internal carotid artery (ICA) occlusion. Before surgery, all patients showed cortical areas of hypoperfusion over the affected cerebral hemisphere. Shortly after EC-IC bypass a rCBF increase was observed in six patients. However, at the 6 and 12 month follow-ups, with angiographic control of bypass patency, rCBF studies did not show any significant rCBF change. Long-term noninvasive tomographic monitoring of perfusion changes occurring after EC-IC bypass surgery failed to show a long-lasting improvement in perfusion. Images PMID:3498800

  15. Utility of (18)F-choline photon emission tomography/computed tomography in the diagnosis of parathyroid adenoma.

    PubMed

    Damle, Nishikant Avinash; Tripathi, Madhavi; Behera, Abhishek; Aggarwal, Sameer; Bal, Chandrasekhar; Aggarwal, Shipra; Aggarwal, Vivek; Kandasamy, Devasenathipathi; Taywade, Sameer

    2016-01-01

    Recently, the role of (18)F-choline in the detection of parathyroid adenomas has been reported. At our institution, we are currently studying the role of this tracer in comparison to the standard methoxy-isobutyl-isonitrile.(MIBI) scan with single photon emission tomography/computed tomography. Our initial results show that (18)F-choline is at least as good as 99mTc-MIBI scan. We present here a representative case of a 45-year-old woman with multiple skeletal lytic lesions and a high parathyroid hormone.(PTH) who underwent both these imaging techniques with concordant results, further confirmed by histopathology and postoperative fall in serum PTH levels.

  16. Utility of 18F-choline photon emission tomography/computed tomography in the diagnosis of parathyroid adenoma

    PubMed Central

    Damle, Nishikant Avinash; Tripathi, Madhavi; Behera, Abhishek; Aggarwal, Sameer; Bal, Chandrasekhar; Aggarwal, Shipra; Aggarwal, Vivek; Kandasamy, Devasenathipathi; Taywade, Sameer

    2016-01-01

    Recently, the role of 18F-choline in the detection of parathyroid adenomas has been reported. At our institution, we are currently studying the role of this tracer in comparison to the standard methoxy-isobutyl-isonitrile.(MIBI) scan with single photon emission tomography/computed tomography. Our initial results show that 18F-choline is at least as good as 99mTc-MIBI scan. We present here a representative case of a 45-year-old woman with multiple skeletal lytic lesions and a high parathyroid hormone.(PTH) who underwent both these imaging techniques with concordant results, further confirmed by histopathology and postoperative fall in serum PTH levels. PMID:27385893

  17. Muscarinic cholinergic receptor binding: in vivo depiction using single photon emission computed tomography and radioiodinated quinuclidinyl benzilate

    SciTech Connect

    Drayer, B.; Jaszczak, R.; Coleman, E.; Storni, A.; Greer, K.; Petry, N.; Lischko, M.; Flanagan, S.

    1982-06-01

    An attempt was made to characterize, in vivo, specific binding to the muscarinic cholinergic receptor in the calf using the radioiodinated ligand quinuclidinyl benzilate (/sup 123/I-OH-QNB) and single photon detection emission computed tomography (SPECT). The supratentorial brain activity was significantly increased after the intravenous infusion of /sup 123/I-OH-QNB as compared to free /sup 123/I. Scopolamine, a muscarinic cholinergic receptor antagonist, decreased the measured brain activity when infused prior to /sup 123/I-OH-QNB consistent with pharmacologic blockade of specific receptor binding. Quantitative in vitro tissue distribution studies obtained following SPECT imaging were consistent with regionally distinct specific receptor binding in the striatum and cortical gray matter, nonspecific binding in the cerebellum, and pharmacologic blockade of specific binding sites with scopolamine. Although /sup 123/I-OH-QNB is not the ideal radioligand, our limited success will hopefully encourage the development of improved binding probes for SPECT imaging and quantitation.

  18. Effects of high energy photon emissions in laser generated ultra-relativistic plasmas: Real-time synchrotron simulations

    NASA Astrophysics Data System (ADS)

    Wallin, Erik; Gonoskov, Arkady; Marklund, Mattias

    2015-03-01

    We model the emission of high energy photons due to relativistic charged particle motion in intense laser-plasma interactions. This is done within a particle-in-cell code, for which high frequency radiation normally cannot be resolved due to finite time steps and grid size. A simple expression for the synchrotron radiation spectra is used together with a Monte-Carlo method for the emittance. We extend previous work by allowing for arbitrary fields, considering the particles to be in instantaneous circular motion due to an effective magnetic field. Furthermore, we implement noise reduction techniques and present validity estimates of the method. Finally, we perform a rigorous comparison to the mechanism of radiation reaction, and find the emitted energy to be in excellent agreement with the losses calculated using radiation reaction.

  19. Hepatic cavernous hemangioma: diagnosis with /sup 99m/Tc-labeled red cells and single-photon emission CT

    SciTech Connect

    Brodsky, R.I.; Friedman, A.C.; Maurer, A.H.; Radecki, P.D.; Caroline, D.F.

    1987-01-01

    During the performance of high-resolution real-time abdominal sonography, small echogenic hepatic masses are frequently discovered. A second imaging test to confirm the suspected diagnosis of hemangioma is often required. Planar labeled red-cell imaging will often not detect hemangiomas smaller than 3 cm. We studied 14 patients with labeled red-cell scintigraphy and single-photon emission CT (SPECT). Six hemangiomas were diagnosed by SPECT that would have been missed by planar imaging alone. All six were smaller than 2.5 cm. With the addition of SPECT, labeled red-cell scintigraphy has specificity and sensitivity that make it at least as reliable as dynamic CT for the noninvasive diagnosis of hepatic cavernous hemangioma.

  20. Simulation of the 6 MV Elekta Synergy Platform linac photon beam using Geant4 Application for Tomographic Emission.

    PubMed

    Didi, Samir; Moussa, Abdelilah; Yahya, Tayalati; Mustafa, Zerfaoui

    2015-01-01

    The present work validates the Geant4 Application for Tomographic Emission Monte Carlo software for the simulation of a 6 MV photon beam given by Elekta Synergy Platform medical linear accelerator treatment head. The simulation includes the major components of the linear accelerator (LINAC) with multi-leaf collimator and a homogeneous water phantom. Calculations were performed for the photon beam with several treatment field sizes ranging from 5 cm × 5 cm to 30 cm × 30 cm at 100 cm distance from the source. The simulation was successfully validated by comparison with experimental distributions. Good agreement between simulations and measurements was observed, with dose differences of about 0.02% and 2.5% for depth doses and lateral dose profiles, respectively. This agreement was also emphasized by the Kolmogorov-Smirnov goodness-of-fit test and by the gamma-index comparisons where more than 99% of the points for all simulations fulfill the quality assurance criteria of 2 mm/2%.

  1. Simulation of the 6 MV Elekta Synergy Platform linac photon beam using Geant4 Application for Tomographic Emission

    PubMed Central

    Didi, Samir; Moussa, Abdelilah; Yahya, Tayalati; Mustafa, Zerfaoui

    2015-01-01

    The present work validates the Geant4 Application for Tomographic Emission Monte Carlo software for the simulation of a 6 MV photon beam given by Elekta Synergy Platform medical linear accelerator treatment head. The simulation includes the major components of the linear accelerator (LINAC) with multi-leaf collimator and a homogeneous water phantom. Calculations were performed for the photon beam with several treatment field sizes ranging from 5 cm × 5 cm to 30 cm × 30 cm at 100 cm distance from the source. The simulation was successfully validated by comparison with experimental distributions. Good agreement between simulations and measurements was observed, with dose differences of about 0.02% and 2.5% for depth doses and lateral dose profiles, respectively. This agreement was also emphasized by the Kolmogorov–Smirnov goodness-of-fit test and by the gamma-index comparisons where more than 99% of the points for all simulations fulfill the quality assurance criteria of 2 mm/2%. PMID:26500399

  2. Analytical Study of the Effect of the System Geometry on Photon Sensitivity and Depth of Interaction of Positron Emission Mammography

    PubMed Central

    Aguiar, Pablo; Lois, Cristina

    2012-01-01

    Positron emission mammography (PEM) cameras are novel-dedicated PET systems optimized to image the breast. For these cameras it is essential to achieve an optimum trade-off between sensitivity and spatial resolution and therefore the main challenge for the novel cameras is to improve the sensitivity without degrading the spatial resolution. We carry out an analytical study of the effect of the different detector geometries on the photon sensitivity and the angle of incidence of the detected photons which is related to the DOI effect and therefore to the intrinsic spatial resolution. To this end, dual head detectors were compared to box and different polygon-detector configurations. Our results showed that higher sensitivity and uniformity were found for box and polygon-detector configurations compared to dual-head cameras. Thus, the optimal configuration in terms of sensitivity is a PEM scanner based on a polygon of twelve (dodecagon) or more detectors. We have shown that this configuration is clearly superior to dual-head detectors and slightly higher than box, octagon, and hexagon detectors. Nevertheless, DOI effects are increased for this configuration compared to dual head and box scanners and therefore an accurate compensation for this effect is required. PMID:23049553

  3. Two-photon Photo-emission of Ultrathin Film PTCDA Morphologies on Ag(111)

    SciTech Connect

    Yang, Aram; Yang, Aram; Shipman, Steven T.; Garrett-Roe, Sean; Johns, James; Strader, Matt; Szymanski, Paul; Muller, Eric; Harris, Charles B.

    2007-11-29

    Morphology- and layer-dependent electronic structure and dynamics at the PTCDA/Ag(111) interface have been studied with angle-resolved two-photon photoemission. In Stranski-Krastanov growth modes, the exposed wetting layer inhibited the evolution of the vacuum level and valence band to bulk values. For layer-by-layer growth, we observed the transition of electron structure from monolayer to bulk values within eight monolayers. Effective masses and lifetimes of the conduction band and the n=1 image potential state were measured to be larger for disordered layers. The effective mass was interpreted in the context of charge mobility measurements.

  4. Single Photon Emission Computed Tomography-Based Three-Dimensional Conformal Radiotherapy for Hepatocellular Carcinoma With Portal Vein Tumor Thrombus

    SciTech Connect

    Shirai, Shintaro; Sato, Morio Suwa, Kazuhiro; Kishi, Kazushi; Shimono, Chigusa; Kawai, Nobuyuki; Tanihata, Hirohiko; Minamiguchi, Hiroki; Nakai, Motoki

    2009-03-01

    Purpose: To evaluate the safety and efficacy of three-dimensional conformal radiotherapy (3D-CRT) using single photon emission computed tomography (SPECT) in unresectable hepatocellular carcinoma (HCC) with portal vein tumor thrombus (PVTT). Methods and Materials: Patients with HCC with PVTT in the first branch and/or main trunk were selected for this study. The optimal beam directions for 3D-CRT were explored using a Tc-99m-galactosyl human serum albumin SPECT image for guidance. The SPECT image was classified as either wedge type or localized type. The clinical target volume to a total dose of 45 or 50 Gy per 18-20 fractions included the main tumor and PVTT in the wedge type and PVTT alone in the localized type. Results: Twenty-six patients were enrolled: 18 with wedge type and 8 with localized type. Mean tumor size was 7.1 cm (range, 4.4-12.3 cm). Clinical target volumes of wedge type vs. localized type were 111.2 cm{sup 3} vs. 48.4 cm{sup 3} (p = 0.010), respectively. Mean dose to normal liver and mean dose to functional liver were 1185 cGy and 988 cGy (p = 0.001) in wedge type and 1046 cGy and 1043 cGy (p = 0.658) in localized type, respectively. Despite an incidence of Child-Pugh B and C of 57.7%, no patients experienced radiation-induced liver disease. The progression of PVTT was inhibited, with an incidence of 92.2%; survival rates at 1 and 2 years were 44% and 30%, respectively. Conclusion: Single photon emission computed tomography-based 3D-CRT enables irradiation of both the main tumor and PVTT with low toxicity and promising survival.

  5. An Observed Effect of p53 Status on the Bystander Response to Radiation-Induced Cellular Photon Emission.

    PubMed

    Le, M; Mothersill, C E; Seymour, C B; Rainbow, A J; McNeill, F E

    2017-02-01

    In this study, we investigated the potential influence of p53 on ultraviolet (UV) signal generation and response of bystander cells to the UV signals generated by beta-irradiated cells. Five cell lines of various p53 status (HaCaT, mutated; SW48, wild-type; HT29, mutated; HCT116(+/+), wild-type; HCT116(-/-), null) were irradiated with beta particles from tritium. Signal generation (photon emission at 340 ± 5 nm) was quantified from irradiated cells using a photomultiplier tube. Bystander response (clonogenic survival) was assessed by placing reporter cell flasks directly superior to irradiated signal-emitting cells. All cell lines emitted significant quantities of UV after tritium exposure. The magnitudes of HaCaT and HT29 photon emission at 340 nm were similar to each other while they were significantly different from the stronger signals emitted from SW48, HCT116(+/+) and HCT116(-/-) cells. In regard to the bystander responses, HaCaT, HCT116(+/+) and SW48 cells demonstrated significant reductions in survival as a result of exposure to emission signals. HCT116(-/-) and HT29 cells did not exhibit any changes in survival and thus were considered to be lacking the mechanisms or functions required to elicit a response. The survival response was found not to correlate with the observed signal strength for all experimental permutations; this may be attributed to varying emission spectra from cell line to cell line or differences in response sensitivity. Overall, these results suggest that the UV-mediated bystander response is influenced by the p53 status of the cell line. Wild-type p53 cells (HCT116(+/+) and SW48) demonstrated significant responses to UV signals whereas the p53-null cell line (HCT116(-/-)) lacked any response. The two mutated p53 cell lines exhibited contrasting responses, which may be explained by unique modulation of functions by different point mutations. The reduced response (cell death) exhibited by p53-mutated cells compared to p53 wild

  6. Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission

    PubMed Central

    Sapienza, Luca; Davanço, Marcelo; Badolato, Antonio; Srinivasan, Kartik

    2015-01-01

    Self-assembled, epitaxially grown InAs/GaAs quantum dots (QDs) are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of QDs, presenting a challenge in creating devices that exploit the strong interaction of single QDs with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single QDs with respect to alignment features with an average position uncertainty <30 nm (<10 nm when using a solid-immersion lens), which represents an enabling technology for the creation of optimized single QD devices. To that end, we create QD single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48%±5% into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50%), low multiphoton probability (g(2)(0) <1%), and a significant Purcell enhancement factor (≈3). PMID:26211442

  7. Blue single photon emission up to 200 K from an InGaN quantum dot in AlGaN nanowire

    NASA Astrophysics Data System (ADS)

    Deshpande, Saniya; Das, Ayan; Bhattacharya, Pallab

    2013-04-01

    We demonstrate polarized blue single photon emission up to 200 K from an In0.2Ga0.8N quantum dot in a single Al0.1Ga0.9N nanowire. The InGaN/AlGaN dot-in-nanowire heterostructure was grown on (111) silicon by plasma assisted molecular beam epitaxy. Nanowires dispersed on a silicon substrate show sharp exciton and biexciton transitions in the micro-photoluminescence spectra. Second-order correlation measurements performed under pulsed excitation at the biexciton wavelength confirm single photon emission, with a g(2)(0) of 0.43 at 200 K. The emitted photons have a short radiative lifetime of 0.7 ns and are linearly polarized along the c-axis of the nanowire with a degree of polarization of 78%.

  8. Narrow-band single photon emission at room temperature based on a single nitrogen-vacancy center coupled to an all-fiber-cavity

    SciTech Connect

    Albrecht, Roland; Bommer, Alexander; Becher, Christoph; Pauly, Christoph; Mücklich, Frank; Schell, Andreas W.; Engel, Philip; Benson, Oliver; Schröder, Tim; Reichel, Jakob

    2014-08-18

    We report the realization of a device based on a single Nitrogen-Vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and out-put are directly fiber-coupled, and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity, we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work, we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.

  9. Probing the limits of Si:P δ-doped devices patterned by a scanning tunneling microscope in a field-emission mode

    SciTech Connect

    Rudolph, M.; Carr, S. M.; Ten Eyck, G.; Dominguez, J.; Carroll, M. S.; Bussmann, E.; Subramania, G.; Lilly, M. P.; Pluym, T.

    2014-10-20

    Recently, a single atom transistor was deterministically fabricated using phosphorus in Si by H-desorption lithography with a scanning tunneling microscope (STM). This milestone in precision, achieved by operating the STM in the conventional tunneling mode, typically utilizes slow (∼10{sup 2} nm{sup 2}/s) patterning speeds. By contrast, using the STM in a high-voltage (>10 V) field-emission mode, patterning speeds can be increased by orders of magnitude to ≳10{sup 4} nm{sup 2}/s. We show that the rapid patterning negligibly affects the functionality of relatively large micron-sized features, which act as contacting pads for these devices. For nanoscale structures, we show that the resulting electrical transport is consistent with the donor incorporation chemistry constraining the electrical dimensions to a scale of 10 nm even though the pattering spot size is 40 nm.

  10. Comparison of left ventricular ejection fraction values obtained using invasive contrast left ventriculography, two-dimensional echocardiography, and gated single-photon emission computed tomography

    PubMed Central

    Garg, Nadish; Dresser, Thomas; Aggarwal, Kul; Gupta, Vishal; Mittal, Mayank K; Alpert, Martin A

    2016-01-01

    Objectives: Left ventricular ejection fraction can be measured by a variety of invasive and non-invasive cardiac techniques. This study assesses the relation of three diagnostic modalities to each other in the measurement of left ventricular ejection fraction: invasive contrast left ventriculography, two-dimensional echocardiography, and quantitative gated single-photon emission computed tomography. Methods: Retrospective chart review was conducted on 58 patients hospitalized with chest pain, who underwent left ventricular ejection fraction evaluation using each of the aforementioned modalities within a 3-month period not interrupted by myocardial infarction or revascularization. Results: The mean left ventricular ejection fraction values were as follows: invasive contrast left ventriculography (0.44±0.15), two-dimensional echocardiography (0.46±0.13), and gated single-photon emission computed tomography (0.37±0.10). Correlations coefficients and associated p values were as follows: invasive contrast left ventriculography versus two-dimensional echocardiography (r=0.69, p<0.001), invasive contrast left ventriculography versus gated single-photon emission computed tomography (r=0.80, p<0.0001), and gated single-photon emission computed tomography versus two-dimensional echocardiography (r=0.69, p<0.001). Conclusion: Our results indicate that strong positive correlations exist among the three techniques studied. PMID:27621804

  11. Plasmon-photon conversion to near-infrared emission from Yb3+: (Au/Ag-nanoparticles) in tungsten-tellurite glasses

    PubMed Central

    Rivera, V. A. G.; Ledemi, Yannick; Pereira-da-Silva, Marcelo A.; Messaddeq, Younes; Marega Jr, Euclydes

    2016-01-01

    This manuscript reports on the interaction between 2F5/2→2F7/2 radiative transition from Yb3+ ions and localized surface plasmon resonance (from gold/silver nanoparticles) in a tungsten-tellurite glass. Such an interaction, similar to the down-conversion process, results in the Yb3+ emission in the near-infrared region via resonant and non-resonant energy transfers. We associated such effects with the dynamic coupling described by the variations generated by the Hamiltonian HDC in either the oscillator strength, or the local crystal field, i.e. the line shape changes in the emission band. Here, the Yb3+ ions emission is achieved through plasmon-photon coupling, observable as an enhancement or quenching in the luminescence spectra. Metallic nanoparticles have light-collecting capability in the visible spectrum and can accumulate almost all the photon energy on a nanoscale, which enable the excitation and emission of the Yb3+ ions in the near-infrared region. This plasmon-photon conversion was evaluated from the cavity’s quality factor (Q) and the coupling (g) between the nanoparticles and the Yb3+ ions. We have found samples of low-quality cavities and strong coupling between the nanoparticles and the Yb3+ ions. Our research can be extended towards the understanding of new plasmon-photon converters obtained from interactions between rare-earth ions and localized surface plasmon resonance. PMID:26725938

  12. Self-amplified spontaneous emission saturation at the Advanced Photon Source free-electron laser (abstract) (invited)

    NASA Astrophysics Data System (ADS)

    Moog, E. R.; Milton, S. V.; Arnold, N. D.; Benson, C.; Berg, W.; Biedron, S. G.; Borland, M.; Chae, Y.-C.; Dejus, R. J.; Den Hartog, P. K.; Deriy, B.; Erdmann, M.; Gluskin, E.; Huang, Z.; Kim, K.-J.; Lewellen, J. W.; Li, Y.; Lumpkin, A. H.; Makarov, O.; Nassiri, A.; Sajaev, V.; Soliday, R.; Tieman, B. J.; Trakhtenberg, E. M.; Travish, G.; Vasserman, I. B.; Vinokurov, N. A.; Wiemerslage, G.; Yang, B. X.

    2002-03-01

    Today, many bright photon beams in the ultraviolet and x-ray wavelength range are produced by insertion devices installed in specially designed third-generation storage rings. There is the possibility of producing photon beams that are orders of magnitude brighter than presently achieved at synchrotron sources, by using self-amplified spontaneous emission (SASE). At the Advanced Photon Source (APS), the low-energy undulator test line (LEUTL) free-electron laser (FEL) project was built to explore the SASE process in the visible through vacuum ultraviolet wavelength range. While the understanding gained in these experiments will guide future work to extend SASE FELs to shorter wavelengths, the APS FEL itself will become a continuously tunable, bright light source. Measurements of the SASE process to saturation have been made at 530 and 385 nm. A number of quantities were measured to confirm our understanding of the SASE process and to verify that saturation was reached. The intensity of the FEL light was measured versus distance along the FEL, and was found to flatten out at saturation. The statistical variation of the light intensity was found to be wide in the exponential gain region where the intensity is expected to be noisy, and narrower once saturation was reached. Absolute power measurements compare well with GINGER simulations. The FEL light spectrum at different distances along the undulator line was measured with a high-resolution spectrometer, and the many sharp spectral spikes at the beginning of the SASE process coalesce into a single peak at saturation. The energy spread in the electron beam widens markedly after saturation due to the number of electrons that transfer a significant amount of energy to the photon beam. Coherent transition radiation measurements of the electron beam as it strikes a foil provide additional confirmation of the microbunching of the electron beam. The quantities measured confirm that saturation was indeed reached. Details are

  13. A new sample holder for laser-excited pump-probe magnetic measurements on a Focus photoelectron emission microscope

    SciTech Connect

    Miguel, Jorge; Bernien, Matthias; Kuch, Wolfgang; Bayer, Daniela; Aeschlimann, Martin; Sanchez-Barriga, Jaime; Kronast, Florian; Duerr, Hermann A.

    2008-03-15

    A custom-made Omicron-compatible sample holder for time-resolved photoelectron emission microscopy experiments is presented. It comprises a sample plate with four contacts that hosts a chip carrier where the semiconductor substrate is mounted. Covering the sample holder, a 6 mm diameter mask protects electrostatically the sample from the extractor lens voltage while keeping the imaging quality unperturbed. The improvements are a greater sample lifetime and the ability to withstand much higher currents in the stripline that provides the magnetic pulse to the magnetic microstructure.

  14. Coherent blue emission generated by Rb two-photon excitation using diode and femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Lopez, Jesus P.; Moreno, Marco P.; de Miranda, Marcio H. G.; Vianna, Sandra S.

    2017-04-01

    The coherent blue light generated in rubidium vapor due to the combined action of an ultrashort pulse train and a continuous wave diode laser is investigated. Each step of the two-photon transition 5S–5P{}3/2–5D is excited by one of the lasers, and the induced coherence between the 5S and 6P{}3/2 states is responsible for generating the blue beam. Measurements of the excitation spectrum reveal the frequency comb structure and allow us to identify the resonant modes responsible for inducing the nonlinear process. Further, each resonant mode excites a different group of atoms, making the process selective in atomic velocity. The signal dependency on the atomic density is characterized by a sharp growth and a rapid saturation. We also show that for high intensity of the diode laser, the Stark shift at resonance causes the signal suppression observed at low atomic density.

  15. Microscope basics.

    PubMed

    Sluder, Greenfield; Nordberg, Joshua J

    2013-01-01

    This chapter provides information on how microscopes work and discusses some of the microscope issues to be considered in using a video camera on the microscope. There are two types of microscopes in use today for research in cell biology-the older finite tube-length (typically 160mm mechanical tube length) microscopes and the infinity optics microscopes that are now produced. The objective lens forms a magnified, real image of the specimen at a specific distance from the objective known as the intermediate image plane. All objectives are designed to be used with the specimen at a defined distance from the front lens element of the objective (the working distance) so that the image formed is located at a specific location in the microscope. Infinity optics microscopes differ from the finite tube-length microscopes in that the objectives are designed to project the image of the specimen to infinity and do not, on their own, form a real image of the specimen. Three types of objectives are in common use today-plan achromats, plan apochromats, and plan fluorite lenses. The concept of mounting video cameras on the microscope is also presented in the chapter.

  16. Single-photon property characterization of 1.3 μm emissions from InAs/GaAs quantum dots using silicon avalanche photodiodes

    PubMed Central

    Zhou, P. Y.; Dou, X. M.; Wu, X. F.; Ding, K.; Li, M. F.; Ni, H. Q.; Niu, Z. C.; Jiang, D. S.; Sun, B. Q.

    2014-01-01

    We developed a new approach to test the single-photon emissions of semiconductor quantum dots (QDs) in the optical communication band. A diamond-anvil cell pressure device was used for blue-shifting the 1.3 μm emissions of InAs/GaAs QDs to 0.9 μm for detection by silicon avalanche photodiodes. The obtained g(2)(0) values from the second-order autocorrelation function measurements of several QD emissions at 6.58 GPa were less than 0.3, indicating that this approach provides a convenient and efficient method of characterizing 1.3 μm single-photon source based on semiconductor materials. PMID:24407193

  17. Application of Three-Photon Excitation FCS to the Study of Protein Oligomerization

    PubMed Central

    2015-01-01

    Three-photon excitation fluorescence correlation spectroscopy was used to detect oligomerization equilibria of rat liver phosphofructokinase. The fluorescence intensity produced by the three-photon excitation of tryptophan was collected using the DIVER microscope. In this home-built upright microscope, a large area photomultiplier, placed directly below the sample, is used as the detector. The lack of optical elements in the microscope detection path results in a significantly improved detection efficiency in the UV region down to about 300 nm, which encompasses the fluorescence emission from tryptophan. The three-photon excitation autocorrelation decays obtained for phosphofructokinase in the presence of F6P showed the presence of large oligomers. Substitution of F6P with ATP in the buffer medium results in dissociation of the large oligomers, which is reported by the decreased autocorrelation amplitude. The three-photon excitation process was verified from the slope of the log–log plot of intensity against laser power. PMID:25438088

  18. High multi-photon visible upconversion emissions of Er{sup 3+} singly doped BiOCl microcrystals: A photon avalanche of Er{sup 3+} induced by 980 nm excitation

    SciTech Connect

    Li, Yongjin; Song, Zhiguo Li, Chen; Wan, Ronghua; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Yang, Yong; Zhou, Dacheng; Wang, Qi

    2013-12-02

    Under 980 nm excitation, high multi-photon upconversion (UC) emission from the {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} (green) and {sup 4}F{sub 9/2} (red) levels of Er{sup 3+} ions were observed from Er{sup 3+} singly doped BiOCl microcrystals. These high-energy excited states were populated by a three to ten photon UC process conditionally, which depended on the pump power density and the Er{sup 3+} ion doping concentration, characterizing as a hetero-looping enhanced energy transfer avalanche UC process. UC emission lifetime and Raman analysis suggest that the unusual UC phenomena are initiated by the new and intense phonon vibration modes of BiOCl lattices due to Er{sup 3+} ions doping.

  19. [Microscopic colitis].

    PubMed

    Bohr, Johan

    2002-02-11

    Microscopic colitis is an umbrella term for a newly described group of colitides, belonging to the inflammatory bowel diseases, which are only diagnosable by microscopic evaluation of a macroscopically normal colon mucosa. Collagenous colitis and lymphocytic colitis are the most common of these colitides. Microscopic colitis is characterised clinically by chronic non-bloody watery diarrhoea. Crampy abdominal pain, nocturnal diarrhoea, urgency, and initial weight loss are usual. Concomitant diseases of autoimmune origin and arthralgia are commonly seen. Treatment of microscopic colitis follows the guidelines for treatment of other inflammatory bowel diseases, but a substantial part of the patients with microscopic colitis enter spontaneous remission after some years. A minor part, however, have very troublesome symptoms and are almost refractory to treatment. Microscopic colitis has apparently no malignant potential.

  20. Size-Dependent Photon Emission from Organometal Halide Perovskite Nanocrystals Embedded in an Organic Matrix

    PubMed Central

    2015-01-01

    In recent years, organometal halide perovskite materials have attracted significant research interest in the field of optoelectronics. Here, we introduce a simple and low-temperature route for the formation of self-assembled perovskite nanocrystals in a solid organic matrix. We demonstrate that the size and photoluminescence peak of the perovskite nanocrystals can be tuned by varying the concentration of perovskite in the matrix material. The physical origin of the blue shift of the perovskite nanocrystals’ emission compared to its bulk phase is also discussed. PMID:25949773

  1. Calculation of lung-heart ratios for single-photon emission computed tomography

    SciTech Connect

    Soares, E.J.; King, M.A.; Glick, S.J.; Villegas, B.J.

    1996-06-01

    The authors investigate the effectiveness of simple iterative reconstruction techniques in calculating lung-heart activity ratios (LHRs). The LHR has been shown to be an effective indicator of the severity of coronary artery disease in cardiac SPECT. A study was conducted with a mathematical cardiac torso phantom that modelled uptake of {sup 201}Tl in the heart and lung regions. The projection data included only the effects of nonuniform photon attenuation. The data were first reconstructed with zeroth-order Chang and a variant of the Bellini method, both of which utilize information from the nonuniform attenuation map. This nonuniform (NU) Bellini method compensates exactly for attenuation in the heart region, but is incorrect for other regions in the medium. These reconstructions were then used as the initial estimates in the iterative Chang, variable step-size (VSS) Chang, and Morozumi methods,m for one and five iterations. The average heart count (AHC) and average lung count (ALC) were calculated using region-of-interest (ROI) templates derived from the true activity map. The population mean LHR was tabulated as the ratio of the ALC to AHC. Using the same reconstruction procedure, the authors also calculated the sample mean LHR and standard deviation from 21 noisy 3D reconstructions.

  2. Two-photon decay of excited levels in hydrogen: The ambiguity of the separation of cascades and pure two-photon emission

    SciTech Connect

    Labzowsky, L.; Solovyev, D.; Plunien, G.

    2009-12-15

    The problem of the evaluation of the two-photon decay width of excited states in hydrogen is considered. Two different approaches to the evaluation of the width including cascades channels are employed: the summation of the transition probabilities for various decay channels and the evaluation of the imaginary part of the Lamb shift. As application, the two-photon decay channels for the 3s level of the hydrogen atom are evaluated, including the cascade transition probability 3s-2p-1s. An important role is assigned to the two-photon decays in astrophysics context, since processes of this kind provide a possibility for the decoupling of radiation and matter in the early universe. We demonstrate the ambiguity of separation of the 'pure' two-photon contribution and criticize the existing methods for such a separation.

  3. Design and Preparation of a Functional One-Dimensional Photonic Crystal with Low Emissivity in the Region of 8-14 μm

    NASA Astrophysics Data System (ADS)

    Miao, L.; Shi, J.; Liu, Y.; Wang, J.; Zhao, D.; Cheng, L.; Wang, C.-M.

    2017-01-01

    Low-emissivity materials are widely used in thermal radiation control. They can be made of photonic crystal (PC) characterized by the band gap where the emissivity is low. By introducing a defect (doping), a high emissivity peak can be achieved at a certain wavelength in the band gap to make the PC more composite and multifunctional. In this paper, three commonly-used coating materials, namely, Ge, ZnSe, and Si, are adopted to produce a PC which is poorly emissive in 8-14 μm and highly emissive at 10.6 μm due to a Si doping layer. With such a special spectrum, this kind of PC has the potential of suppressing detection by both far-infrared and CO2 laser radiation. The spectrum of the sample obtained by Fourier transform infrared spectrometer is in satisfactory agreement with the theoretical curve.

  4. GALPROP Code for Galactic Cosmic Ray Propagation and Associated Photon Emissions

    NASA Astrophysics Data System (ADS)

    Moskalenko, Igor; GALPROP Team

    2013-06-01

    Research in many areas of modern physics such as, e.g., indirect searches for dark matter and particle acceleration in supernova remnant shocks rely heavily on studies of cosmic rays (CRs) and associated diffuse emissions (radio, microwave, X-rays, gamma rays). The numerical Galactic CR propagation code GALPROP has been shown to reproduce simultaneously observational data of many kinds related to CR origin and propagation. We report on the latest updates of GALPROP, development of WebRun, a service to the scientific community enabling easy use of the GALPROP code via web browsers, and a library of evaluated isotopic production cross sections. We also report the results of a full Bayesian analysis of propagation parameters using nested sampling and Markov Chain Monte Carlo methods.

  5. 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.

  6. Diagnostic accuracy of exercise thallium-201 single-photon emission computed tomography in patients with left bundle branch block.

    PubMed

    Larcos, G; Gibbons, R J; Brown, M L

    1991-09-15

    Recent reports have proposed that abnormal apical or anterior wall perfusion with exercise thallium-201 imaging may increase diagnostic accuracy for disease of the left anterior descending artery in patients with left bundle branch block (LBBB). To evaluate these suggestions, 83 patients with LBBB who underwent thallium-201 single-photon emission computed tomography and coronary angiography within an interval of 3 months were retrospectively reviewed. There were 59 men and 24 women aged 33 to 84 years (mean 65). Myocardial perfusion to the apex, anterior wall and anterior septum were scored qualitatively by consensus of 2 experienced observers and by quantitative analysis in comparison with a normal data base. The sensitivity, specificity and accuracy of perfusion defects in these segments were then expressed according to angiographic findings. Significant stenosis of vessels within the left anterior descending artery territory was present in 38 patients. By receiver-operator characteristic analysis, a fixed or reversible defect within the apex by the qualitative method was the best criterion for coronary artery disease. However, although highly sensitive (79 and 85% by the qualitative and quantitative methods, respectively), an apical defect was neither specific (38 and 16%, respectively), nor accurate (57 and 46%, respectively). Perfusion abnormalities in the anterior wall and septum were also of limited diagnostic accuracy. Thus, modified interpretative criteria in patients with LBBB are not clinically useful in the assessment of left anterior descending artery disease.

  7. Diagnostic accuracy of exercise thallium-201 single-photon emission computed tomography in patients with left bundle branch block

    SciTech Connect

    Larcos, G.; Gibbons, R.J.; Brown, M.L. )

    1991-09-15

    Recent reports have proposed that abnormal apical or anterior wall perfusion with exercise thallium-201 imaging may increase diagnostic accuracy for disease of the left anterior descending artery in patients with left bundle branch block (LBBB). To evaluate these suggestions, 83 patients with LBBB who underwent thallium-201 single-photon emission computed tomography and coronary angiography within an interval of 3 months were retrospectively reviewed. There were 59 men and 24 women aged 33 to 84 years (mean 65). Myocardial perfusion to the apex, anterior wall and anterior septum were scored qualitatively by consensus of 2 experienced observers and by quantitative analysis in comparison with a normal data base. The sensitivity, specificity and accuracy of perfusion defects in these segments were then expressed according to angiographic findings. Significant stenosis of vessels within the left anterior descending artery territory was present in 38 patients. By receiver-operator characteristic analysis, a fixed or reversible defect within the apex by the qualitative method was the best criterion for coronary artery disease. However, although highly sensitive (79 and 85% by the qualitative and quantitative methods, respectively), an apical defect was neither specific (38 and 16%, respectively), nor accurate (57 and 46%, respectively). Perfusion abnormalities in the anterior wall and septum were also of limited diagnostic accuracy. Thus, modified interpretative criteria in patients with LBBB are not clinically useful in the assessment of left anterior descending artery disease.

  8. Aspects of the application of positron emission tomography to engineering studies: Drawing overlays and correction for photon attenuation

    NASA Astrophysics Data System (ADS)

    O'Dwyer, M. A.; Hawkesworth, M. R.; Walker, J.

    1988-12-01

    Two important aspects of the application of positron emission tomography in engineering are: the creation of accurate but simplified engineering drawings to overlay the radiolabel tomograms as an aid to their interpretation, and the correction of important features in tomograms for attenuation in overlying metal to provide quantitative information. The practical difficulties met in producing overlays and correcting for attenuation are described, and strategies which are proving useful to overcome them are outlined. The essential starting point is the creation in computer memory of a full three-dimensional representation of all the subject of interest. After scaling, any plane through this model can then be extracted to overlay the appropriate plane through the radiolabel distribution, and all acceptable photon trajectories can be traced from each volume element containing positron emitter to give correction factors for attenuation in the materials traversed. It is shown that it is appropriate to use the total attenuation coefficients of materials in the correction and, finally, a gradient-contour routine is described for separating true signal from background prior to correction.

  9. Magnetic Resonance Spectroscopy and Single-Photon Emission Computed Tomography in the Evaluation of Cerebral Tumors: A Case Report

    PubMed Central

    Siasios, Ioannis; Valotassiou, Varvara; Kapsalaki, Eftychia; Tsougos, Ioannis; Georgoulias, Panagiotis; Fotiadou, Aggeliki; Ioannou, Maria; Koukoulis, Georgios; Dimopoulos, Vassilios; Fountas, Kostas

    2017-01-01

    In their daily clinical practice, physicians have to confront diagnostic dilemmas which cannot be resolved by the application of only one imaging technique. In this case report, we present a 66-year-old woman who was admitted to our institution for the surgical resection of a recently diagnosed brain tumor. The patient had a history of epileptic seizures and was hospitalized in the past for anti-phospholipid syndrome related to a non-Hodgkin lymphoma in remission. Magnetic resonance imaging (MRI) examination revealed an enhancing right parasagittal lesion with significant edema suggestive of a high grade glioma. Advanced MRI techniques including proton magnetic resonance spectroscopy (1H-MRS) showed findings compatible of glioma. An additional examination was performed as part of a protocol that we are routinely performing in our institution for all brain tumors including not only the gold standard advanced MRI techniques but also single-photon emission computed tomography (SPECT) with technetium-99m (Tc99m). Brain SPECT indicated the presence of a meningioma which was verified by the histopathology of the resected specimen. In conclusion, a multimodality approach for the pre-surgical assessment of brain tumors has significant advantages not only for the diagnosis but also for the evaluation of intracranial tumors histology. PMID:27924180

  10. A Chinese literature overview on ultra-weak photon emission as promising technology for studying system-based diagnostics.

    PubMed

    He, Min; Sun, Mengmeng; van Wijk, Eduard; van Wietmarschen, Herman; van Wijk, Roeland; Wang, Zhihong; Wang, Mei; Hankemeier, Thomas; van der Greef, Jan

    2016-04-01

    To present the possibilities pertaining to linking ultra-weak photon emission (UPE) with Chinese medicine-based diagnostics principles, we conducted a review of Chinese literature regarding UPE with respect to a systems view of diagnostics. Data were summarized from human clinical studies and animal models published from 1979 through 1998. The research fields can be categorized as follows: (1) human physiological states measured using UPE; (2) characteristics of human UPE in relation to various pathological states; and (3) the relationship between diagnosis (e.g., Chinese syndromes) and the dynamics of UPE in animal models. We conclude that UPE has clear potential in terms of understanding the systems view on health and disease as described using Chinese medicine-based diagnostics, particularly from a biochemistry-based regulatory perspective. Linking UPE with metabolomics can further bridge biochemistry-based Western diagnostics with the phenomenology-based Chinese diagnostics, thus opening new avenues for studying systems diagnostics in the early stage of disease, for prevention-based strategies, as well as for systems-based intervention in chronic disease.

  11. Radiolabeling, whole-body single photon emission computed tomography/computed tomography imaging, and pharmacokinetics of carbon nanohorns in mice

    PubMed Central

    Zhang, Minfang; Jasim, Dhifaf A; Ménard-Moyon, Cécilia; Nunes, Antonio; Iijima, Sumio; Bianco, Alberto; Yudasaka, Masako; Kostarelos, Kostas

    2016-01-01

    In this work, we report that the biodistribution and excretion of carbon nanohorns (CNHs) in mice are dependent on their size and functionalization. Small-sized CNHs (30–50 nm; S-CNHs) and large-sized CNHs (80–100 nm; L-CNHs) were chemically functionalized and radiolabeled with [111In]-diethylenetriaminepentaacetic acid and intravenously injected into mice. Their tissue distribution profiles at different time points were determined by single photon emission computed tomography/computed tomography. The results showed that the S-CNHs circulated longer in blood, while the L-CNHs accumulated faster in major organs like the liver and spleen. Small amounts of S-CNHs- and L-CNHs were excreted in urine within the first few hours postinjection, followed by excretion of smaller quantities within the next 48 hours in both urine and feces. The kinetics of excretion for S-CNHs were more rapid than for L-CNHs. Both S-CNH and L-CNH material accumulated mainly in the liver and spleen; however, S-CNH accumulation in the spleen was more prominent than in the liver. PMID:27524892

  12. Effect of beta blockade on single photon emission computed tomographic (SPECT) thallium-201 images in patients with coronary disease

    SciTech Connect

    Narahara, K.A.; Thompson, C.J.; Hazen, J.F.; Brizendine, M.; Mena, I.

    1989-05-01

    We evaluated the effect of beta blockers on thallium-201 (Tl-201) single photon emission computed tomographic (SPECT) imaging in 12 patients with coronary disease using an automated computer algorithm. Maximal exercise heart rate and blood pressure were reduced and exercise time was increased with beta blockers. Estimated stress defect size decreased from 47 +/- 36.3 gm during placebo treatment to 32 +/- 27.1 gm during beta blocker therapy (-32%; p less than 0.01). The placebo treatment redistribution defect was estimated to be 28 +/- 29.8 gm. It fell to 15 +/- 23.3 gm with beta blockade (-46%; p less than 0.005). All patients had a stress Tl-201 defect during placebo treatment and eight had redistribution defects consistent with residual scar. During beta blocker therapy, 2 of 12 patients had normal stress-redistribution studies and only five patients had redistribution defects. Beta blockade can reduce exercise and redistribution Tl-201 SPECT defect size significantly while simultaneously increasing exercise time and reducing angina. Beta blockers may unmask or may eliminate evidence of redistribution. Tl-201 SPECT imaging may be useful in defining the reduction in ischemia produced by cardiac drugs.

  13. Use of fuzzy edge single-photon emission computed tomography analysis in definite Alzheimer's disease - a retrospective study

    PubMed Central

    2010-01-01

    Background Definite Alzheimer's disease (AD) requires neuropathological confirmation. Single-photon emission computed tomography (SPECT) may enhance diagnostic accuracy, but due to restricted sensitivity and specificity, the role of SPECT is largely limited with regard to this purpose. Methods We propose a new method of SPECT data analysis. The method is based on a combination of parietal lobe selection (as regions-of-interest (ROI)), 3D fuzzy edge detection, and 3D watershed transformation. We applied the algorithm to three-dimensional SPECT images of human brains and compared the number of watershed regions inside the ROI between AD patients and controls. The Student's two-sample t-test was used for testing domain number equity in both groups. Results AD patients had a significantly reduced number of watershed regions compared to controls (p < 0.01). A sensitivity of 94.1% and specificity of 80% was obtained with a threshold value of 57.11 for the watershed domain number. The narrowing of the SPECT analysis to parietal regions leads to a substantial increase in both sensitivity and specificity. Conclusions Our non-invasive, relatively low-cost, and easy method can contribute to a more precise diagnosis of AD. PMID:20809946

  14. Comparison of deconvolution techniques using a distribution mixture parameter estimation: application in single photon emission computed tomography imagery

    NASA Astrophysics Data System (ADS)

    Mignotte, Max; Meunier, Jean; Soucy, Jean-Paul; Janicki, Christian

    2002-01-01

    Thanks to its ability to yield functionally rather than anatomically-based information, the single photon emission computed tomography (SPECT) imagery technique has become a great help in the diagnostic of cerebrovascular diseases which are the third most common cause of death in the USA and Europe. Nevertheless, SPECT images are very blurred and consequently their interpretation is difficult. In order to improve the spatial resolution of these images and then to facilitate their interpretation by the clinician, we propose to implement and to compare the effectiveness of different existing 'blind' or 'supervised' deconvolution methods. To this end, we present an accurate distribution mixture parameter estimation procedure which takes into account the diversity of the laws in the distribution mixture of a SPECT image. In our application, parameters of this distribution mixture are efficiently exploited in order to prevent overfitting of the noisy data for the iterative deconvolution techniques without regularization term, or to determine the exact support of the object to be restored when this one is needed. Recent blind deconvolution techniques such as the NAS--RIF algorithm, combined with this estimation procedure, can be efficiently applied in SPECT imagery and yield promising results.

  15. Enhanced Telecom Emission from Single Group-IV Quantum Dots by Precise CMOS-Compatible Positioning in Photonic Crystal Cavities

    PubMed Central

    2017-01-01

    Efficient coupling to integrated high-quality-factor cavities is crucial for the employment of germanium quantum dot (QD) emitters in future monolithic silicon-based optoelectronic platforms. We report on strongly enhanced emission from single Ge QDs into L3 photonic crystal resonator (PCR) modes based on precise positioning of these dots at the maximum of the respective mode field energy density. Perfect site control of Ge QDs grown on prepatterned silicon-on-insulator substrates was exploited to fabricate in one processing run almost 300 PCRs containing single QDs in systematically varying positions within the cavities. Extensive photoluminescence studies on this cavity chip enable a direct evaluation of the position-dependent coupling efficiency between single dots and selected cavity modes. The experimental results demonstrate the great potential of the approach allowing CMOS-compatible parallel fabrication of arrays of spatially matched dot/cavity systems for group-IV-based data transfer or quantum optical systems in the telecom regime. PMID:28345012

  16. Unusual extracardiac findings detected on myocardial perfusion single photon emission computed tomography studies with Tc-99m sestamibi.

    PubMed

    Gedik, Gonca Kara; Ergün, Eser Lay; Aslan, Mehmet; Caner, Biray

    2007-12-01

    The authors describe the incidence and various uptake patterns of Tc-99m sestamibi (MIBI) in the extracardiac area due to unusual causes on myocardial perfusion single photon emission computed tomography (SPECT) studies. Seven patients are presented in whom incidental extracardiac findings were observed during the interpretation of the raw data besides the routine evaluation of myocardial reconstructed SPECT slices. These 7 patients were detected out of 582 consecutive patients (1.2%) who had myocardial perfusion SPECT with Tc-99m MIBI. The findings on the raw data led to additional reconstruction of thoracic SPECT images and eventually detailed examination of the extracardiac area. Two of the patients underwent surgery because of incidental extracardiac findings (thymoma and multinodular goiter) on cardiac scintigraphy. Other causes of increased extracardiac activity were the intestine protruded through the left hemithorax, uptake in the pulmonary arterial wall, and pulmonary interstitial fibrosis due to sarcoidosis. The reasons for decreased Tc-99m MIBI accumulation in the extracardiac area in the 2 other patients were significantly dilated pulmonary arteries and hydatic cyst, which were not defined before to our knowledge. Familiarity with the normal biodistribution and variable uptake patterns in the raw images becomes necessary during the interpretation of myocardial SPECT in order not to miss very unusual incidental extracardiac uptake or information that could lead to alteration in patient management. Potential underlying mechanisms of extracardiac Tc-99m MIBI accumulation are discussed, and the literature about noncardiac Tc-99m MIBI findings detected on myocardial perfusion SPECT studies was reviewed.

  17. A novel three-dimensional image reconstruction method for near-field coded aperture single photon emission computerized tomography

    PubMed Central

    Mu, Zhiping; Hong, Baoming; Li, Shimin; Liu, Yi-Hwa

    2009-01-01

    Coded aperture imaging for two-dimensional (2D) planar objects has been investigated extensively in the past, whereas little success has been achieved in imaging 3D objects using this technique. In this article, the authors present a novel method of 3D single photon emission computerized tomography (SPECT) reconstruction for near-field coded aperture imaging. Multiangular coded aperture projections are acquired and a stack of 2D images is reconstructed separately from each of the projections. Secondary projections are subsequently generated from the reconstructed image stacks based on the geometry of parallel-hole collimation and the variable magnification of near-field coded aperture imaging. Sinograms of cross-sectional slices of 3D objects are assembled from the secondary projections, and the ordered subset expectation and maximization algorithm is employed to reconstruct the cross-sectional image slices from the sinograms. Experiments were conducted using a customized capillary tube phantom and a micro hot rod phantom. Imaged at approximately 50 cm from the detector, hot rods in the phantom with diameters as small as 2.4 mm could be discerned in the reconstructed SPECT images. These results have demonstrated the feasibility of the authors’ 3D coded aperture image reconstruction algorithm for SPECT, representing an important step in their effort to develop a high sensitivity and high resolution SPECT imaging system. PMID:19544769

  18. The association between heroin expenditure and dopamine transporter availability--a single-photon emission computed tomography study.

    PubMed

    Lin, Shih-Hsien; Chen, Kao Chin; Lee, Sheng-Yu; Chiu, Nan Tsing; Lee, I Hui; Chen, Po See; Yeh, Tzung Lieh; Lu, Ru-Band; Chen, Chia-Chieh; Liao, Mei-Hsiu; Yang, Yen Kuang

    2015-03-30

    One of the consequences of heroin dependency is a huge expenditure on drugs. This underlying economic expense may be a grave burden for heroin users and may lead to criminal behavior, which is a huge cost to society. The neuropsychological mechanism related to heroin purchase remains unclear. Based on recent findings and the established dopamine hypothesis of addiction, we speculated that expenditure on heroin and central dopamine activity may be associated. A total of 21 heroin users were enrolled in this study. The annual expenditure on heroin was assessed, and the availability of the dopamine transporter (DAT) was assessed by single-photon emission computed tomography (SPECT) using [(99m)TC]TRODAT-1. Parametric and nonparametric correlation analyses indicated that annual expenditure on heroin was significantly and negatively correlated with the availability of striatal DAT. After adjustment for potential confounders, the predictive power of DAT availability was significant. Striatal dopamine function may be associated with opioid purchasing behavior among heroin users, and the cycle of spiraling dysfunction in the dopamine reward system could play a role in this association.

  19. Ferrous ion induced photon emission as a method to quantify oxidative stress in stored boar spermatozoa.

    PubMed

    Gogol, Piotr; Pieszka, Marek

    2008-01-01

    The aim of the study was to evaluate the effect of semen storage on ferrous ion induced luminescence of boar spermatozoa and to determine the relationship between parameters of this luminescence and lipid peroxidation as measured by malondialdehyde (MDA) contents. Boar semen samples were diluted in Biosolwens extender and stored for 12 days at 15 degrees C. Luminescence and MDA were measured directly after dilution (day 0) and at 6 and 12 days of semen storage. Luminescence was measured at 20 degrees C using a luminometer equipped with a cooled photomultiplier with a spectral response range from 370 to 620 nm. Emission was induced by adding FeSO4 solution (final concentration 0.05 mM). MDA content was measured by the HPLC method. The day of storage had a significant effect on some luminescence parameters and MDA content in spermatozoa. A significant correlation was observed between luminescence parameters and MDA concentration. The results of the study confirm that induced luminescence is strictly related to lipid peroxidation in spermatozoa that occur during boar semen storage. Parameters of luminescence treated as a holistic response of cells to oxidative stress can be useful for monitoring spermatozoa quality during semen preservation.

  20. Stress scintigraphy using single-photon emission computed tomography in the evaluation of coronary artery disease

    SciTech Connect

    Nohara, R.; Kambara, H.; Suzuki, Y.; Tamaki, S.; Kadota, K.; Kawai, C.; Tamaki, N.; Torizuka, K.

    1984-05-01

    Twenty-seven patients with angina pectoris, 24 with postmyocardial infarction angina and 7 with normal coronary arteries were examined by exercise thallium-201 emission computed tomography (SPECT) and planar scintigraphy. Exercise SPECT was compared with the reperfusion imaging obtained approximately 2 to 3 hours after exercise. The sensitivity and specificity of demonstrating involved coronary arteries by identifying the locations of myocardial perfusion defects were 96 and 87% for right coronary artery, 88 and 89% for left anterior descending artery (LAD) and 78 and 100% for left circumflex artery (LC). These figures are higher than those for planar scintigraphy (85 and 87% for right coronary artery, 73 and 89% for LAD and 39 and 100% for LC arteries). In patients with 3-vessel disease, sensitivity of SPECT (100, 88 and 75% for right coronary artery, LAD and LC, respectively) was higher than planar imaging (88, 63 and 31%, respectively), with a significant difference for LC (p less than 0.05). In 1, 2 and 0-vessel disease the sensitivity and specificity of the 2 techniques were comparable. Multivessel disease was more easily identified as multiple coronary involvement than planar imaging with a significant difference in 3-vessel disease (p less than 0.05). In conclusion, stress SPECT provides useful information for the identification of LC lesions in coronary heart disease, including 3-vessel involvement.

  1. Light-harvesting ytterbium(III)-porphyrinate-BODIPY conjugates: synthesis, excitation-energy transfer, and two-photon-induced near-infrared-emission studies.

    PubMed

    Zhang, Tao; Zhu, Xunjin; Wong, Wai-Kwok; Tam, Hoi-Lam; Wong, Wai-Yeung

    2013-01-07

    Based on a donor-acceptor framework, several conjugates have been designed and prepared in which an electron-donor moiety, ytterbium(III) porphyrinate (YbPor), was linked through an ethynyl bridge to an electron-acceptor moiety, boron dipyrromethene (BODIPY). Photoluminescence studies demonstrated efficient energy transfer from the BODIPY moiety to the YbPor counterpart. When conjugated with the YbPor moiety, the BODIPY moiety served as an antenna to harvest the lower-energy visible light, subsequently transferring its energy to the YbPor counterpart, and, consequently, sensitizing the Yb(III) emission in the near-infrared (NIR) region with a quantum efficiency of up to 0.73% and a lifetime of around 40 μs. Moreover, these conjugates exhibited large two-photon-absorption cross-sections that ranged from 1048-2226 GM and strong two-photon-induced NIR emission.

  2. Combined micro-Raman, micro-infrared, and field emission scanning electron microscope analyses of comet 81P/Wild 2 particles collected by Stardust

    NASA Astrophysics Data System (ADS)

    Rotundi, A.; Baratta, G. A.; Borg, J.; Brucato, J. R.; Busemann, H.; Colangeli, L.; D'Hendecourt, L.; Djouadi, Z.; Ferrini, G.; Franchi, I. A.; Fries, M.; Grossemy, F.; Keller, L. P.; Mennella, V.; Nakamura, K.; Nittler, L. R.; Palumbo, M. E.; Sandford, S. A.; Steele, A.; Wopenka, B.

    2008-02-01

    We report combined micro-infrared, micro-Raman, and field emission scanning electron microscope (FESEM) analyses of particles collected by the Stardust spacecraft during its flyby of comet 81P/Wild 2 on 2 January 2004 and successfully returned back to Earth on 15 January 2006. We present mid-infrared (IR) spectra of six of these particles. The CH2/CH3 ratios inferred from the infrared data are greater than those seen in organics in the diffuse interstellar medium, possibly indicating the presence of longer or less branched aliphatic chains. The micro-Raman data offer insights into the state of the order of the carbonaceous component present in the particles. Raman parameters for most of the particles span a similar range to that observed in interplanetary dust particles (IDPs) and the most primitive meteorites. Both the IR and Raman data imply the presence of a very labile carbonaceous component. Hydrated silicates may be present in two particles of Track 35, one of which may also contain carbonates, but further investigations with other techniques need to be performed to confirm these findings. In some cases, the analyses are difficult to interpret because of the presence of compressed aerogel mixed with the grains.

  3. Contribution of a new generation field-emission scanning electron microscope in the understanding of a 2099 Al-Li alloy.

    PubMed

    Brodusch, Nicolas; Trudeau, Michel; Michaud, Pierre; Rodrigue, Lisa; Boselli, Julien; Gauvin, Raynald

    2012-12-01

    Aluminum-lithium alloys are widespread in the aerospace industry. The new 2099 and 2199 alloys provide improved properties, but their microstructure and texture are not well known. This article describes how state-of-the-art field-emission scanning electron microscopy (FE-SEM) can contribute to the characterization of the 2099 aluminum-lithium alloy and metallic alloys in general. Investigations were carried out on bulk and thinned samples. Backscattered electron imaging at 3 kV and scanning transmission electron microscope imaging at 30 kV along with highly efficient microanalysis permitted correlation of experimental and expected structures. Although our results confirm previous studies, this work points out possible substitutions of Mg and Zn with Li, Al, and Cu in the T1 precipitates. Zinc and magnesium are also present in "rice grain"-shaped precipitates at the grain boundaries. The versatility of the FE-SEM is highlighted as it provides information in the macro- and microscales with relevant details. Its ability to probe the distribution of precipitates from nano- to microsizes throughout the matrix makes FE-SEM an essential technique for the characterization of metallic alloys.

  4. Hepatocellular carcinoma with intra-atrial tumor extension identified on 99mTc-labeled macroaggregated albumin single photon emission computed tomography/computed tomography

    PubMed Central

    Chandra, Piyush; Shah, Sneha; Purandare, Nilendu; Agrawal, Archi; Rangarajan, Venkatesh

    2016-01-01

    99mTc macroaggregated albumin (MAA) scintigraphy is always performed before administration of 90Y--microspheres for the treatment of liver tumors for hepatopulmonary shunt calculation. Tumor thrombus visualization in the hepatic vasculature is an infrequent finding on the 99m Tc--MAA single photon emission computed tomography. We present a rare case of a hepatocellular carcinoma extending as a tumor thrombus through hepatic vein, inferior vena cava into the right atrium. PMID:27833324

  5. 99mTc-methylene diphosphonate single-photon emission computed tomography/computed tomography improves the diagnostic accuracy of osteoid osteoma

    PubMed Central

    Squier, Samuel Brian; Lewis, Jacob Ian; Accurso, Joseph Matthew; Jain, Manoj Kumar

    2016-01-01

    We present a case of a 17-year-old football player who had previously received multiple facet joint injections for presumed secondary osteoarthritis. 99mTc-methylene diphosphonate single-photon emission computed tomography/computed tomography imaging of the cervical spine demonstrated focal increased radiopharmaceutical activity in the right C2 lamina, which was associated with an osteolytic lesion with a central irregular sclerotic nidus. Surgical pathology confirmed an osteoid osteoma. PMID:27833319

  6. ARTICLES: Intermode scattering effects in laser emission spectra of platelet and acicular CdS-type single crystals subjected to one-photon excitation

    NASA Astrophysics Data System (ADS)

    Brodin, M. S.; Vitrikhovskiĭ, N. I.; Kipen', A. A.; Shevel', S. G.; Yanushevskiĭ, N. I.

    1982-12-01

    An investigation was made of the laser emission spectra of platelet CdS, Znx, Cd1-xS, and CdS1-xSex, single crystals and acicular CdS single crystals at T=4.2, 77, and 300 °K. Lasing developed in partial resonators (rectangular insulating microboxes or microprisms) and the emission consisted of total-internal-reflection modes characterized by the highest Q factor. Radiation emerged in vacuum as a result of intermode scattering of photons (without a change in the frequency) out of the total-internal-reflection modes into modes with lower Q factors, which could be emitted.

  7. Determination of photon emission probabilities for the main gamma-rays of ²²³Ra in equilibrium with its progeny.

    PubMed

    Pibida, L; Zimmerman, B; Fitzgerald, R; King, L; Cessna, J T; Bergeron, D E

    2015-07-01

    The currently published (223)Ra gamma-ray emission probabilities display a wide variation in the values depending on the source of the data. The National Institute of Standards and Technology performed activity measurements on a (223)Ra solution that was used to prepare several sources that were used to determine the photon emission probabilities for the main gamma-rays of (223)Ra in equilibrium with its progeny. Several high purity germanium (HPGe) detectors were used to perform the gamma-ray spectrometry measurements.

  8. Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar corona

    SciTech Connect

    Mirzoeva, I. K.

    2013-04-15

    The time profiles of the energy spectra of low-intensity flares and the structure of the thermal background of the soft X-ray component of solar corona emission over the period of January-February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of X-ray emission of the solar flares and the corona thermal background in the 2- to 15-keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball-Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained.

  9. The distribution of cerebral muscarinic acetylcholine receptors in vivo in patients with dementia. A controlled study with 123IQNB and single photon emission computed tomography

    SciTech Connect

    Weinberger, D.R.; Gibson, R.; Coppola, R.; Jones, D.W.; Molchan, S.; Sunderland, T.; Berman, K.F.; Reba, R.C. )

    1991-02-01

    A high-affinity muscarinic receptor antagonist, 123IQNB (3-quinuclidinyl-4-iodobenzilate labeled with iodine 123), was used with single photon emission computed tomography to image muscarinic acetylcholine receptors in 14 patients with dementia and in 11 healthy controls. High-resolution single photon emission computed tomographic scanning was performed 21 hours after the intravenous administration of approximately 5 mCi of IQNB. In normal subjects, the images of retained ligand showed a consistent regional pattern that correlated with postmortem studies of the relative distribution of muscarinic receptors in the normal human brain, having high radioactivity counts in the basal ganglia, occipital cortex, and insular cortex, low counts in the thalamus, and virtually no counts in the cerebellum. Eight of 12 patients with a clinical diagnosis of Alzheimer's disease had obvious focal cortical defects in either frontal or posterior temporal cortex. Both patients with a clinical diagnosis of Pick's disease had obvious frontal and anterior temporal defects. A region of interest statistical analysis of relative regional activity revealed a significant reduction bilaterally in the posterior temporal cortex of the patients with Alzheimer's disease compared with controls. This study demonstrates the practicability of acetylcholine receptor imaging with 123IQNB and single photon emission computed tomography. The data suggest that focal abnormalities in muscarinic binding in vivo may characterize some patients with Alzheimer's disease and Pick's disease, but further studies are needed to address questions about partial volume artifacts and receptor quantification.

  10. Incorporating Quantitative Single Photon Emission Computed Tomography into Radiation Therapy Treatment Planning for Lung Cancer: Impact of Attenuation and Scatter Correction on the Single Photon Emission Computed Tomography-Weighted Mean Dose and Functional Lung Segmentation

    SciTech Connect

    Yin Lingshu; Shcherbinin, Sergey; Celler, Anna

    2010-10-01

    Purpose: To assess the impact of attenuation and scatter corrections on the calculation of single photon emission computed tomography (SPECT)-weighted mean dose (SWMD) and functional volume segmentation as applied to radiation therapy treatment planning for lung cancer. Methods and Materials: Nine patients with lung cancer underwent a SPECT lung perfusion scan. For each scan, four image sets were reconstructed using the ordered subsets expectation maximization method with attenuation and scatter corrections ranging from none to a most comprehensive combination of attenuation corrections and direct scatter modeling. Functional volumes were segmented in each reconstructed image using 10%, 20%, ..., 90% of maximum SPECT intensity as a threshold. Systematic effects of SPECT reconstruction methods on treatment planning using functional volume were studied by calculating size and spatial agreements of functional volumes, and V{sub 20} for functional volume from actual treatment plans. The SWMD was calculated for radiation beams with a variety of possible gantry angles and field sizes. Results: Functional volume segmentation is sensitive to the particular method of SPECT reconstruction used. Large variations in functional volumes, as high as >50%, were observed in SPECT images reconstructed with different attenuation/scatter corrections. However, SWMD was less sensitive to the type of scatter corrections. SWMD was consistent within 2% for all reconstructions as long as computed tomography-based attenuation correction was used. Conclusion: When using perfusion SPECT images during treatment planning optimization/evaluation, the SWMD may be the preferred figure of merit, as it is less affected by reconstruction technique, compared with threshold-based functional volume segmentation.

  11. Two-photon microscopy of cells and tissue.

    PubMed

    Rubart, Michael

    2004-12-10

    Two-photon excitation fluorescence imaging provides thin optical sections from deep within thick, scattering specimens by way of restricting fluorophore excitation (and thus emission) to the focal plane of the microscope. Spatial confinement of two-photon excitation gives rise to several advantages over single-photon confocal microscopy. First, penetration depth of the excitation beam is increased. Second, because out-of-focus fluorescence is never generated, no pinhole is necessary in the detection path of the microscope, resulting in increased fluorescence collection efficiency. Third, two-photon excitation markedly reduces overall photobleaching and photodamage, resulting in extended viability of biological specimens during long-term imaging. Finally, localized excitation can be used for photolysis of caged compounds in femtoliter volumes and for diffusion measurements by two-photon fluorescence photobleaching recovery. This review aims to provide an overview of the use of two-photon excitation microscopy. Selected applications of this technique will illustrate its excellent suitability to assess cellular and subcellular events in intact, strongly scattering tissue. In particular, its capability to resolve differences in calcium dynamics between individual cardiomyocytes deep within intact, buffer-perfused hearts is demonstrated. Potential applications of two-photon laser scanning microscopy as applied to integrative cardiac physiology are pointed out.

  12. Synthesis of novel fluorene-based two-photon absorbing molecules and their applications in optical data storage, microfabrication, and stimulated emission depletion

    NASA Astrophysics Data System (ADS)

    Yanez, Ciceron

    2009-12-01

    Two-photon absorption (2PA) has been used for a number of scientific and technological applications, exploiting the fact that the 2PA probability is directly proportional to the square of the incident light intensity (while one-photon absorption bears a linear relation to the incident light intensity). This intrinsic property of 2PA leads to 3D spatial localization, important in fields such as optical data storage, fluorescence microscopy, and 3D microfabrication. The spatial confinement that 2PA enables has been used to induce photochemical and photophysical events in increasingly smaller volumes and allowed nonlinear, 2PA-based, technologies to reach sub-diffraction limit resolutions. The primary focus of this dissertation is the development of novel, efficient 2PA, fluorene-based molecules to be used either as photoacid generators (PAGs) or fluorophores. A second aim is to develop more effective methods of synthesizing these compounds. As a third and final objective, the new molecules were used to develop a write-once-read many (WORM) optical data storage system, and stimulated emission depletion probes for bioimaging. In Chapter I, the microwave-assisted synthesis of triarylsulfonium salt photoacid generators (PAGs) from their diphenyliodonium counterparts is reported. The microwave-assisted synthesis of these novel sulfonium salts afforded reaction times 90 to 420 times faster than conventional thermal conditions, with photoacid quantum yields of new sulfonium PAGs ranging from 0.01 to 0.4. These PAGs were used to develop a fluorescence readout-based, nonlinear three-dimensional (3D) optical data storage system (Chapter II). In this system, writing was achieved by acid generation upon two-photon absorption (2PA) of a PAG (at 710 or 730 nm). Readout was then performed by interrogating two-photon absorbing dyes, after protonation, at 860 nm. Two-photon recording and readout of voxels was demonstrated in five and eight consecutive, crosstalk-free layers within a

  13. Single-photon emission at a rate of 143 MHz from a deterministic quantum-dot microlens triggered by a mode-locked vertical-external-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Schlehahn, A.; Gaafar, M.; Vaupel, M.; Gschrey, M.; Schnauber, P.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Stolz, W.; Rahimi-Iman, A.; Heindel, T.; Koch, M.; Reitzenstein, S.

    2015-07-01

    We report on the realization of a quantum dot (QD) based single-photon source with a record-high single-photon emission rate. The quantum light source consists of an InGaAs QD which is deterministically integrated within a monolithic microlens with a distributed Bragg reflector as back-side mirror, which is triggered using the frequency-doubled emission of a mode-locked vertical-external-cavity surface-emitting laser (ML-VECSEL). The utilized compact and stable laser system allows us to excite the single-QD microlens at a wavelength of 508 nm with a pulse repetition rate close to 500 MHz at a pulse width of 4.2 ps. Probing the photon statistics of the emission from a single QD state at saturation, we demonstrate single-photon emission of the QD-microlens chip with g(2)(0) < 0.03 at a record-high single-photon flux of (143 ± 16) MHz collected by the first lens of the detection system. Our approach is fully compatible with resonant excitation schemes using wavelength tunable ML-VECSELs, which will optimize the quantum optical properties of the single-photon emission in terms of photon indistinguishability.

  14. Single-photon emission at a rate of 143 MHz from a deterministic quantum-dot microlens triggered by a mode-locked vertical-external-cavity surface-emitting laser

    SciTech Connect

    Schlehahn, A.; Gschrey, M.; Schnauber, P.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Heindel, T. Reitzenstein, S.; Gaafar, M.; Vaupel, M.; Stolz, W.; Rahimi-Iman, A.; Koch, M.

    2015-07-27

    We report on the realization of a quantum dot (QD) based single-photon source with a record-high single-photon emission rate. The quantum light source consists of an InGaAs QD which is deterministically integrated within a monolithic microlens with a distributed Bragg reflector as back-side mirror, which is triggered using the frequency-doubled emission of a mode-locked vertical-external-cavity surface-emitting laser (ML-VECSEL). The utilized compact and stable laser system allows us to excite the single-QD microlens at a wavelength of 508 nm with a pulse repetition rate close to 500 MHz at a pulse width of 4.2 ps. Probing the photon statistics of the emission from a single QD state at saturation, we demonstrate single-photon emission of the QD-microlens chip with g{sup (2)}(0) < 0.03 at a record-high single-photon flux of (143 ± 16) MHz collected by the first lens of the detection system. Our approach is fully compatible with resonant excitation schemes using wavelength tunable ML-VECSELs, which will optimize the quantum optical properties of the single-photon emission in terms of photon indistinguishability.

  15. Factors determining altered perfusion after acute pulmonary embolism assessed by quantified single-photon emission computed tomography-perfusion scan

    PubMed Central

    Meysman, Marc; Everaert, Hendrik; Vincken, Walter

    2017-01-01

    AIM OF THE STUDY: The aim of the study was to analyze the evolution of perfusion (Q)-defects in patients treated for acute pulmonary embolism (PE), correlation with baseline parameters and evaluation of recurrence risk. METHODS: This is a single-center prospective observational cohort study in symptomatic normotensive PE. Comparison of the ventilation/perfusion single-photon emission computed tomography (V/Q-SPECT) acquired at baseline with a quantified SPECT (Q-SPECT) repeated at 1 week and 6 months. The Q-defect extent (percentage of total lung volume affected) was measured semiquantitatively. Data collected at baseline were age, gender, body mass index (BMI), history of previous venous thromboembolism (HVTE), Charlson's Comorbidity Score (CcS), plasma troponin-T and D-dimer levels, PE Severity Index, and tricuspid regurgitation jet (TRJ) velocity. RESULTS: Forty-six patients (22 men/24 women, mean age 61.7 years (± standard deviation 16.3)) completed the study. At 1 week, 13/46 (28.3 %) and at 6 months 22/46 (47.8%) patients had completely normalized Q-SPECT. Persistence of Q-defects was more frequent in female patients in univariate and multivariate analysis. We found no correlation between the persistence of Q-defects on Q-SPECT and HVTE, BMI, plasma troponin-T, and CcS. However, lower TRJ and younger age were statistically significantly linked to normalization of Q-scans after 6 months of treatment only in univariate analysis. There is no difference in the frequency of recurrent PE in relation to the persistence of Q-defects. CONCLUSION: Acute PE patients of female, older age, and higher TRJ in univariate analysis and patients of female in multivariate analysis seem to have a higher risk of persistent Q-defects after 6 months treatment. The presence of residual Q-abnormalities at 6 months was not associated with an increased risk for recurrent PE. PMID:28197219

  16. The value of combining single photon emission computerised tomography and computerised tomography in the investigation of spondylolysis.

    PubMed

    Gregory, P L; Batt, M E; Kerslake, R W; Scammell, B E; Webb, J F

    2004-10-01

    The aim of this study was to assess the diagnostic value of combining single photon emission computerised tomography (SPECT) with reverse gantry computerised tomography (rg-CT) in the investigation of spondylolysis. Patient characteristics and imaging results in 118 patients, aged 8-44 years, with low back pain (LBP) were analysed. SPECT showed increased scintigraphic uptake in 80 patients, and spondylolysis was identified on rg-CT in 53. The Cohen Kappa ratio of 0.362 (95% CI: 0.198-0.526) suggests only fair agreement for the result of increased scintigraphic activity with the finding of spondylolysis on rg-CT. We conclude that these investigations give mutually exclusive information, which leads to four diagnostic categories. When there was increased scintigraphic activity on SPECT, 58.8% (95% CI: 48.0-69.5%) of patients had spondylolysis on rg-CT. With rest from provoking activities, these lesions may heal. We interpret the findings of increased scintigraphic activity, but no spondylolysis demonstrated on rg-CT as indicating a bone stress response. These also require rest from provoking activity to prevent a stress fracture developing. In this study, 84.2% (95% CI: 72.67-95.8%) of those patients without increased activity on SPECT had no spondylolysis identified on rg-CT. These patients may need further investigations such as magnetic resonance imaging (MRI) to diagnose pathology, which typically does not involve the posterior elements--but rest from sport may not be so important. There were five patients in our study, without increased scintigraphic activity, but in whom bilateral chronic-appearing (wide separation, smooth sclerotic bone margins) spondylolyses were identified at L5. These all were anticipated from previous plain radiographs or MRI. This group will almost certainly not heal, and if the spondylolyses are the cause of pain these vertebrae will need stabilisation by surgery if physiotherapy fails.

  17. Quantitative exercise thallium-201 single photon emission computed tomography for the enhanced diagnosis of ischemic heart disease

    SciTech Connect

    Mahmarian, J.J.; Boyce, T.M.; Goldberg, R.K.; Cocanougher, M.K.; Roberts, R.; Verani, M.S. )

    1990-02-01

    The clinical utility of exercise thallium-201 single photon emission computed tomography was investigated in 360 consecutive patients who had concomitant coronary arteriography. Tomographic images were assessed visually and from computer-quantified polar maps. Sensitivity for detecting coronary artery disease was comparably high using quantitative and visual analysis, although specificity tended to improve using the former method (87% versus 76%, p = 0.09). Quantitative analysis was superior to the visual method for identifying left anterior descending (81% versus 68%, p less than 0.05) and circumflex coronary artery (77% versus 60%, p less than 0.05) stenoses and detected most patients (92%) with multivessel coronary artery disease. Multivessel involvement was correctly predicted in 65% of the patients with more than one critically stenosed vessel. Exercise variables in patients with significant coronary artery disease were similar whether the tomographic images were normal or abnormal. However, patients with coronary stenoses and normal versus abnormal tomograms had a trend toward more single vessel disease (79% versus 62%, p = 0.07) and moderate coronary stenosis (66% versus 28%, p less than 0.001), but had less proximal left anterior descending artery involvement (8% versus 34%, p = 0.05). Computer-quantified perfusion defect size was directly related to the extent of coronary artery disease. Intra- and interobserver agreement for quantifying defects were excellent (r = 0.98 and 0.97, respectively). In conclusion, quantitative thallium-201 tomography offers improved detection of coronary artery disease, localization of the anatomic site of coronary stenosis, prediction of multivessel involvement and accurate determination of perfusion defect size, while maintaining a high specificity.

  18. Evaluation of myocardial infarction size with three-dimensional speckle tracking echocardiography: a comparison with single photon emission computed tomography.

    PubMed

    Wang, Qiushuang; Zhang, Chunhong; Huang, Dangsheng; Zhang, Liwei; Yang, Feifei; An, Xiuzhi; Ouyang, Qiaohong; Zhang, Meiqing; Wang, Shuhua; Guo, Jiarui; Ji, Dongdong

    2015-12-01

    To assess whether global and regional myocardial strains from three-dimensional speckle tracking echocardiography (3D-STE) correlate with myocardial infarction size (MIS) detected by single photon emission computed tomography (SPECT). Fifty-seven patients with a history of ST-segment elevation myocardial infarction (MI) within 3-6 months were enrolled, alongside 24 healthy volunteers. Left ventricular (LV) global area strain, global longitudinal strain (GLS), global radial strain, global circumferential strain, left ventricular ejection fraction (LVEF) and wall motion score index (WMSI) were measured and compared with the corresponding SPECT-detected MISs. Patients were sub-grouped into massive MIS group (MIS ≥ 12%) and small MIS group (MIS < 12%). Myocardial strains of all the LV segments were compared with the corresponding MIS. Global myocardial strain parameters, LVEF and WMSI of the patients were significantly different from the control group (all P < 0.05) and correlated well with MISs, most significantly for GLS (r = 0.728, P < 0.01). Significant differences in myocardial strain parameters were found between the massive and small MIS groups (all P < 0.05). Receiver operating characteristic curve analysis indicated that GLS had a highest diagnostic value and when the cutoff was -13.8%, the area under the curve was 0.84, with the 70.6% sensitivity and 87.5% specificity. Significant differences of myocardial strain parameters were observed between segments with and without transmural MIs (P < 0.01). 3D-STE myocardial strain parameters evaluated LV global MIS, 3D GLS had the highest diagnostic value. It also preliminarily gauged the degree of ischemia and necrosis of regional myocardial segments.

  19. Alterations in myocardial thallium-201 distribution in patients with chronic systemic hypertension undergoing single-photon emission computed tomography

    SciTech Connect

    DePuey, E.G.; Guertler-Krawczynska, E.; Perkins, J.V.; Robbins, W.L.; Whelchel, J.D.; Clements, S.D.

    1988-08-01

    To characterize thallium-201 distribution in single-photon emission computed tomography (SPECT) cardiac images and polar bullseye maps, 100 patients with chronic systemic hypertension due to end-stage renal disease were studied and the results compared with those in 35 normotensive control subjects. Thallium-201 SPECT was performed after exercise in all control subjects and 70 hypertensive patients, and after intravenous dipyridamole in 30 patients. A frequent finding in hypertensive patients was a fixed decrease in the normal lateral-to-septal count density ratio in immediate thallium-201 SPECT images (1.02 +/- 0.10 vs 1.17 +/- 0.08 in control subjects, p less than 0.00001) and in 3-hour delayed images (1.02 +/- 0.11 vs 1.11 +/- 0.08 in control subjects, p less than 0.00001). No significant difference in count density ratio was present in patients undergoing treadmill versus diypridamole intervention. In 35 patients the count density ratio was greater than 2.0 standard deviations below the normal mean, creating the false impression of a fixed lateral defect (i.e., myocardial infarction). In 12 patients, myocardial wall thickness was measured at end-diastole by 2-dimensional echocardiography. Wall thickness was increased (greater than 11 mm) in all patients. The mean lateral-to-septal wall thickness ratio was 1.08 +/- 1.11; in no patient was the ratio less than 0.76 to indicate selective septal hypertrophy. The lateral-to-septal wall thickness and lateral-to-septal thallium-201 count density ratios correlated poorly (r = 0.43).

  20. The role of single-photon emission computed tomography/computed tomography in benign and malignant bone disease.

    PubMed

    Horger, Marius; Bares, Roland

    2006-10-01

    Radiological (plain radiographs, computed tomography [CT], magnetic resonance imaging [MRI]) and nuclear medicine methods (bone scan, leukocyte scan) both provide unique information about the status of the skeleton. Both have typical strengths and weaknesses, which often lead to the sequential use of different procedures in daily routine. This use causes the unnecessary loss of time and sometimes money, if redundant information is obtained without establishing a final diagnosis. Recently, new devices for hybrid imaging (single-photon emission computed tomography/computed tomography [SPECT/CT], positron emission tomography/computed tomography [PET/CT]) were introduced, which allow for direct fusion of morphological (CT) and functional (SPECT, PET) data sets. With regard to skeletal abnormalities, this approach appears to be extremely useful because it combines the advantages of both techniques (high-resolution imaging of bone morphology and high sensitivity imaging of bone metabolism). By the accurate correlation of both, a new quality of bone imaging has now become accessible. Although researchers undertaking the initial studies exclusively used low-dose CT equipment, a new generation of SPECT/CT devices has emerged recently. By integrating high-resolution spiral CT, quality of bone imaging may improve once more. Ongoing prospective studies will have to show whether completely new diagnostic algorithms will come up for classification of bone disease as a consequence of this development. Besides, the role of ultrasonography and MRI for bone and soft-tissue imaging also will have to be re-evaluated. Looking at the final aim of all imaging techniques--to achieve correct diagnosis in a fast, noninvasive, comprehensive, and inexpensive way--we are now on the edge of a new era of multimodality imaging that will probably change the paths and structure of medicine in many ways. Presently, hybrid imaging using SPECT/CT has been proven to increase sensitivity and specificity

  1. Imaging of Lactobacillus brevis single cells and microcolonies without a microscope by an ultrasensitive chemiluminescent enzyme immunoassay with a photon-counting television camera.

    PubMed Central

    Yasui, T; Yoda, K

    1997-01-01

    An ultrasensitive chemiluminescent enzyme immunoassay (CLEIA) was developed for the rapid detection and quantification of Lactobacillus brevis contaminants in beer and pitching yeast (Saccharomyces cerevisiae slurry collected for reinoculation). L. brevis cells trapped on a 47-mm nucleopore membrane (0.4-micron pore size) were reacted with a peroxidase-labelled Lactobacillus group E antibody and then subjected to an enhanced CLEIA analysis with 4-iodophenol as the enhancer. The combination of a nucleopore membrane with low background characteristics that enables the antigen-antibody reaction to proceed through the pores of the membrane and a labelled antibody prepared by the maleimide hinge method with minimal nonspecific binding characteristics was essential to minimize background in the detection of single cells. An ultrahigh sensitive charge-coupled device (CCD) camera equipped with a fiber optics image intensifier permitted the imaging of single cells. A clear correlation existed between the number of luminescent spots observed and the plate count [y (CLEIA) = 0.990x (plate count) + 15.9, where n = 7, r = 0.993, and P < 0.001]. Microscopic observation confirmed that the luminescent spots were produced by single cells. This assay could be used to detect approximately 20 L. brevis cells in 633 ml of beer within 4 h. Our ultrasensitive CLEIA could also be used to detect microcolonies approximately 20 microns in diameter which had formed on a membrane after 15 to 18 h of incubation. This method, which we called the microcolony immunoluminescence (MIL) method, increased the signal-to-noise ratio dramatically. The MIL method could be used to detect a 10(0) level of L. brevis contamination in 633 ml of beer and a 1/10(8) level of L. brevis contamination in pitching yeast within 1 day (15 to 18 h to form microcolonies and 2 h for CLEIA). PMID:9361439

  2. Imaging of Lactobacillus brevis single cells and microcolonies without a microscope by an ultrasensitive chemiluminescent enzyme immunoassay with a photon-counting television camera.

    PubMed

    Yasui, T; Yoda, K

    1997-11-01

    An ultrasensitive chemiluminescent enzyme immunoassay (CLEIA) was developed for the rapid detection and quantification of Lactobacillus brevis contaminants in beer and pitching yeast (Saccharomyces cerevisiae slurry collected for reinoculation). L. brevis cells trapped on a 47-mm nucleopore membrane (0.4-micron pore size) were reacted with a peroxidase-labelled Lactobacillus group E antibody and then subjected to an enhanced CLEIA analysis with 4-iodophenol as the enhancer. The combination of a nucleopore membrane with low background characteristics that enables the antigen-antibody reaction to proceed through the pores of the membrane and a labelled antibody prepared by the maleimide hinge method with minimal nonspecific binding characteristics was essential to minimize background in the detection of single cells. An ultrahigh sensitive charge-coupled device (CCD) camera equipped with a fiber optics image intensifier permitted the imaging of single cells. A clear correlation existed between the number of luminescent spots observed and the plate count [y (CLEIA) = 0.990x (plate count) + 15.9, where n = 7, r = 0.993, and P < 0.001]. Microscopic observation confirmed that the luminescent spots were produced by single cells. This assay could be used to detect approximately 20 L. brevis cells in 633 ml of beer within 4 h. Our ultrasensitive CLEIA could also be used to detect microcolonies approximately 20 microns in diameter which had formed on a membrane after 15 to 18 h of incubation. This method, which we called the microcolony immunoluminescence (MIL) method, increased the signal-to-noise ratio dramatically. The MIL method could be used to detect a 10(0) level of L. brevis contamination in 633 ml of beer and a 1/10(8) level of L. brevis contamination in pitching yeast within 1 day (15 to 18 h to form microcolonies and 2 h for CLEIA).

  3. Photonic crystal light source

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Bur, James A.

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  4. Microscopic Polyangiitis

    PubMed Central

    Chung, Sharon A.; Seo, Philip

    2010-01-01

    Synopsis In 1923, Friedrich Wohlwill described two patients with a “microscopic form of periarteritis nodosa”, which was distinct from classical polyarteritis nodosa. This disease, now known as microscopic polyangiitis (MPA), is a primary systemic vasculitis characterized by inflammation of the small-caliber blood vessels and the presence of circulating antineutrophil cytoplasmic antibodies (ANCA). Typically, microscopic polyangiitis presents with glomerulonephritis and pulmonary capillaritis, although involvement of the skin, nerves, and gastrointestinal tract is not uncommon. Treatment of MPA generally requires use of a cytotoxic agent (such as cyclophosphamide) in addition to high-dose glucocorticoids. Recent research has focused on identifying alternate treatment strategies that minimize or eliminate exposure to cytotoxic agents. This article will review the history, pathogenesis, clinical manifestations, and treatment of MPA. PMID:20688249

  5. Exciton-plasmon-photon conversion in silver nanowire: Polarization dependence

    NASA Astrophysics Data System (ADS)

    Wang, Lu-Lu; Zou, Chang-Ling; Ren, Xi-Feng; Liu, Ai-Ping; Lv, Liu; Cai, Yong-Jing; Sun, Fang-Wen; Guo, Guang-Can; Guo, Guo-Ping

    2011-08-01

    Polarization dependence of the exciton-plasmon-photon conversion in silver nanowire-quantum dots structure was investigated using a scanning confocal microscope system. We found that the fluorescence enhancement of the CdSe nanocrystals was correlated with the angle between the excitation light polarization and the silver nanowire direction. The polarization of the emission was also related with the nanowire direction. It was in majority in the direction parallel with nanowire due to the nano-antenna effect.

  6. Martian Microscope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The microscopic imager (circular device in center) is in clear view above the surface at Meridiani Planum, Mars, in this approximate true-color image taken by the panoramic camera on the Mars Exploration Rover Opportunity. The image was taken on the 9th sol of the rover's journey. The microscopic imager is located on the rover's instrument deployment device, or arm. The arrow is pointing to the lens of the instrument. Note the dust cover, which flips out to the left of the lens, is open. This approximated color image was created using the camera's violet and infrared filters as blue and red.

  7. SU-E-J-09: A Monte Carlo Analysis of the Relationship Between Cherenkov Light Emission and Dose for Electrons, Protons, and X-Ray Photons

    SciTech Connect

    Glaser, A; Zhang, R; Gladstone, D; Pogue, B

    2014-06-01

    Purpose: A number of recent studies have proposed that light emitted by the Cherenkov effect may be used for a number of radiation therapy dosimetry applications. Here we investigate the fundamental nature and accuracy of the technique for the first time by using a theoretical and Monte Carlo based analysis. Methods: Using the GEANT4 architecture for medically-oriented simulations (GAMOS) and BEAMnrc for phase space file generation, the light yield, material variability, field size and energy dependence, and overall agreement between the Cherenkov light emission and dose deposition for electron, proton, and flattened, unflattened, and parallel opposed x-ray photon beams was explored. Results: Due to the exponential attenuation of x-ray photons, Cherenkov light emission and dose deposition were identical for monoenergetic pencil beams. However, polyenergetic beams exhibited errors with depth due to beam hardening, with the error being inversely related to beam energy. For finite field sizes, the error with depth was inversely proportional to field size, and lateral errors in the umbra were greater for larger field sizes. For opposed beams, the technique was most accurate due to an averaging out of beam hardening in a single beam. The technique was found to be not suitable for measuring electron beams, except for relative dosimetry of a plane at a single depth. Due to a lack of light emission, the technique was found to be unsuitable for proton beams. Conclusions: The results from this exploratory study suggest that optical dosimetry by the Cherenkov effect may be most applicable to near monoenergetic x-ray photon beams (e.g. Co-60), dynamic IMRT and VMAT plans, as well as narrow beams used for SRT and SRS. For electron beams, the technique would be best suited for superficial dosimetry, and for protons the technique is not applicable due to a lack of light emission. NIH R01CA109558 and R21EB017559.

  8. Two-Photon Laser Scanning Microscopy

    NASA Astrophysics Data System (ADS)

    Nimmerjahn, A.; Theer, P.; Helmchen, F.

    Since its inception more than 15 years ago, two-photon laser scanning microscopy (2PLSM) has found widespread use in biological and medical research. Two-photon microscopy is based on simultaneous absorption of two photons by fluorophores and subsequent fluorescence emission, a process which under normal illumination conditions is highly improbable. Theoretically described around 1930 by Maria Göppert-Mayer [1], the first experimental demonstration of two-photon excitation had to await the invention of the laser, which produced sufficiently high light intensities to observe two-photon absorption events [2]. Only after the development of ultrafast lasers providing subpicosecond light pulses with high peak power intensities, however, two-photon-excited fluorescence became practical in a laser-scanning microscope [3]. Since then 2PLSM has developed into the method of choice for high-resolution imaging in living animals (reviewed in [4,5]). One of the main reasons is the low sensitivity of 2PLSM to light scattering, which enables imaging relatively deep inside biological tissue and direct observation of the dynamic behavior of cells in their native environment. In this chapter, we introduce the physical principles governing 2PLSM and briefly describe the key instrument components. We give an overview of fluorescence labeling techniques and how they are combined with 2PLSM for functional imaging and photomanipulation in living tissue. Finally, we discuss limitations and provide some future perspectives.

  9. Large area self-assembled masking for photonic applications

    NASA Astrophysics Data System (ADS)

    Nagy, N.; Pap, A. E.; Horváth, E.; Volk, J.; Bársony, I.; Deák, A.; Hórvölgyi, Z.

    2006-08-01

    Ordered porous structures for photonic application were fabricated on p- and n-type silicon by means of masking against ion implantation with Langmuir-Blodgett (LB) films. LB films from Stöber silica spheres [J. Colloid Interface Sci. 26, 62 (1968)] of 350nm diameter were applied in the boron and phosphorus ion-implantation step, thereby offering a laterally periodic doping pattern. Ordered porous silicon structures were obtained after performing an anodic etch and were then removed by alkaline etching resulting in the required two-dimensional photonic arrangement. The LB silica masks and the resulting silicon structures were studied by field emission scanning electron microscope analysis.

  10. Microscopic colitis

    PubMed Central

    Ianiro, Gianluca; Cammarota, Giovanni; Valerio, Luca; Annicchiarico, Brigida Eleonora; Milani, Alessandro; Siciliano, Massimo; Gasbarrini, Antonio

    2012-01-01

    Microscopic colitis may be defined as a clinical syndrome, of unknown etiology, consisting of chronic watery diarrhea, with no alterations in the large bowel at the endoscopic and radiologic evaluation. Therefore, a definitive diagnosis is only possible by histological analysis. The epidemiological impact of this disease has become increasingly clear in the last years, with most data coming from Western countries. Microscopic colitis includes two histological subtypes [collagenous colitis (CC) and lymphocytic colitis (LC)] with no differences in clinical presentation and management. Collagenous colitis is characterized by a thickening of the subepithelial collagen layer that is absent in LC. The main feature of LC is an increase of the density of intra-epithelial lymphocytes in the surface epithelium. A number of pathogenetic theories have been proposed over the years, involving the role of luminal agents, autoimmunity, eosinophils, genetics (human leukocyte antigen), biliary acids, infections, alterations of pericryptal fibroblasts, and drug intake; drugs like ticlopidine, carbamazepine or ranitidine are especially associated with the development of LC, while CC is more frequently linked to cimetidine, non-steroidal antiinflammatory drugs and lansoprazole. Microscopic colitis typically presents as chronic or intermittent watery diarrhea, that may be accompanied by symptoms such as abdominal pain, weight loss and incontinence. Recent evidence has added new pharmacological options for the treatment of microscopic colitis: the role of steroidal therapy, especially oral budesonide, has gained relevance, as well as immunosuppressive agents such as azathioprine and 6-mercaptopurine. The use of anti-tumor necrosis factor-α agents, infliximab and adalimumab, constitutes a new, interesting tool for the treatment of microscopic colitis, but larger, adequately designed studies are needed to confirm existing data. PMID:23180940

  11. Electrically pumped single-photon emission at room temperature from a single InGaN/GaN quantum dot

    SciTech Connect

    Deshpande, Saniya; Frost, Thomas; Hazari, Arnab; Bhattacharya, Pallab

    2014-10-06

    We demonstrate a semiconductor quantum dot based electrically pumped single-photon source operating at room temperature. Single photons emitted in the red spectral range from single In{sub 0.4}Ga{sub 0.6}N/GaN quantum dots exhibit a second-order correlation value g{sup (2)}(0) of 0.29, and fast recombination lifetime ∼1.3 ±0.3 ns at room temperature. The single-photon source can be driven at an excitation repetition rate of 200 MHz.

  12. Ligand-core NLO-phores: a combined experimental and theoretical approach to the two-photon absorption and two-photon excited emission properties of small-ligated silver nanoclusters.

    PubMed

    Russier-Antoine, Isabelle; Bertorelle, Franck; Calin, Nathalie; Sanader, Željka; Krstić, Marjan; Comby-Zerbino, Clothilde; Dugourd, Philippe; Brevet, Pierre-François; Bonačić-Koutecký, Vlasta; Antoine, Rodolphe

    2017-01-19

    We report a combined experimental and theoretical study of the two-photon absorption and excited emission properties of monodisperse ligand stabilized Ag11, Ag15 and Ag31 nanoclusters in aqueous solutions. The nanoclusters were synthesized using a cyclic reduction under oxidative conditions and separated by vertical gel electrophoresis. The two-photon absorption cross-sections of these protected noble metal nanoclusters measured within the biologically attractive 750-900 nm window are several orders of magnitude larger than that reported for commercially available standard organic dyes. The two-photon excited fluorescence spectra are also presented for excitation wavelengths within the same excitation spectral window. They exhibit size-tunability. Because the fundamental photophysical mechanisms underlying these multiphoton processes in ligand protected clusters with only a few metal atoms are not fully understood yet, a theoretical model is proposed to identify the key driving elements. Elements that regulate the dipole moments and the nonlinear optical properties are the nanocluster size, its structure and the charge distribution on both the metal core and the bound ligands. We coined this new class of NLO materials as "Ligand-Core" NLO-phores.

  13. Characterization of [(123)I]IDAM as a novel single-photon emission tomography tracer for serotonin transporters.

    PubMed

    Kung, M P; Hou, C; Oya, S; Mu, M; Acton, P D; Kung, H F

    1999-08-01

    Development of selective serotonin transporter (SERT) tracers for single-photon emission tomography (SPET) is important for studying the underlying pharmacology and interaction of specific serotonin reuptake site inhibitors, commonly used antidepressants, at the SERT sites in the human brain. In search of a new tracer for imaging SERT, IDAM (5-iodo-2-[[2-2-[(dimethylamino)methyl]phenyl]thio]benzyl alcohol) was developed. In vitro characterization of IDAM was carried out with binding studies in cell lines and rat tissue homogenates. In vivo binding of [(125)I]IDAM was evaluated in rats by comparing the uptakes in different brain regions through tissue dissections and ex vivo autoradiography. In vitro binding study showed that IDAM displayed an excellent affinity to SERT sites (K(i)=0.097 nM, using membrane preparations of LLC-PK(1) cells expressing the specific transporter) and showed more than 1000-fold of selectivity for SERT over norepinehrine and dopamine (expressed in the same LLC-PK(1) cells). Scatchard analysis of [(125)I]IDAM binding to frontal cortical membrane homogenates prepared from control or p-chloroamphetamine (PCA)-treated rats was evaluated. As expected, the control membranes showed a K(d) value of 0.25 nM+/-0.05 nM and a B(max) value of 272+/-30 fmol/ mg protein, while the PCA-lesioned membranes displayed a similar K(d), but with a reduced B(max) (20+/-7 fmol/ mg protein). Biodistribution of [(125)I]IDAM (partition coefficient =473; 1-octanol/buffer) in the rat brain showed a high initial uptake (2.44%dose at 2 min after i.v. injection) with the specific binding peaked at 60 min postinjection (hypothalamus-cerebellum/cerebellum =1.75). Ex vivo autoradiographs of rat brain sections (60 min after i.v. injection of [(125)I]IDAM) showed intense labeling in several regions (olfactory tubercle, lateral septal nucleus, hypothalamic and thalamic nuclei, globus pallidus, central gray, superior colliculus, substantia nigra, interpeduncular nucleus, dorsal

  14. Impact of ventilation/perfusion single-photon emission computed tomography on treatment duration of pulmonary embolism

    PubMed Central

    Begic, Amela; Opanković, Emina; Čukić, Vesna; Rustempašić, Medzida; Bašić, Amila; Miniati, Massimo; Jögi, Jonas

    2015-01-01

    Purpose The aim of the study was to establish whether the duration of anticoagulant (AC) therapy can be tailored, on an objective basis, by using ventilation/perfusion single-photon emission computed tomography (V/P SPECT) and to assess the extent of residual perfusion defects over time. In particular, we addressed the following: (a) is the extent of perfusion recovery at 3 months of initial pulmonary embolism (PE) diagnosis a satisfactory criterion for deciding the duration of oral AC? (b) Is it safe to withdraw AC at 3 months if perfusion recovery is complete? Patients and methods Of 269 consecutive patients with suspected PE, 100 patients were diagnosed with PE using V/P SPECT. Sixty-seven patients with acute PE were followed up clinically and with V/P SPECT at 3 months. Sixty-four patients were subject to review and examination using V/P SPECT for a period of 6 months and 33 were followed up only clinically. Therapy was terminated after 3 months if perfusion was normalized, and patients were free of symptoms and the risk of hypercoagulability. Initial extension of PE did not have an impact on decision making. Results PE extension varied from 10 to 70% in the acute stage. After 3 months, complete resolution of PE was found in 48 patients. The treating pulmonologist decided to terminate therapy in 35 (73%) patients and to continue AC in 13 patients because of persistent risk factors. Six months later, at the second control stage, 53 patients had complete recovery of pulmonary perfusion. Eleven patients still had perfusion defects at 6 months. No recurrence was identified at 6 months in the 35 patients whose therapy was terminated after 3 months. No bleeding effects were observed in any of the patients during the 6-month follow-up. Conclusion This study shows that AC therapy can be tailored, on an objective basis, by using V/P SPECT. Normalization of perfusion at 3 months of initial PE diagnosis was a reliable indicator that AC could be safely withdrawn in

  15. Tetrofosmin early time gated post-stress single-photon emission computed tomography imaging: Feasibility and potential benefits

    PubMed Central

    Mérino, Bertrand; Blaire, Tanguy; Bailliez, Alban; Casset-Senon, Danielle; Levy, Maurice; Halley, Arnaud; Divry, Guillaume

    2010-01-01

    Background The purpose of this study is to evaluate the feasibility, the image quality, and the clinical relevance of an early gated post-stress (GPS) single-photon emission computed tomography (SPECT) tetrofosmin (Myoview™—GE Healthcare) acquisition protocol. Time delay between myocardial technetium-labeled tracer administration and SPECT acquisition is usually about 30 minutes after stress, and 45 to 60 minutes at rest: because of the absence of significant redistribution, perfusion images are related to stress even 30 minutes after stress injection, while function and thickening data obtained with gated acquisition 30 minutes after stress are mainly related to rest conditions. Methods 194 patients were prospectively included and analyzed, in a multicenter registry. Three gated-SPECT 99mTc-Tetrofosmin studies were performed per patient: GPS-SPECT, 30 minutes post-stress (GS30), and at rest (GR30). Results GPS image quality was excellent/good (93.9%), and similar to GS30 images (96.6%). The presence of adjacent myocardial sub-diaphragmatic activity on GPS images was similar to GS30 images (24% vs 22%), and less frequent than on GR30 images (31%). For perfusion, thickening, and motion scores, there was no significant difference between early and 30 minute post-stress in the global patient population, but significant differences were observed between GPS and GS30 for LVEF (65% ± 15% vs 63% ± 14%). In the ischemic patients, with the stress-rest protocol, the perfusion score was 14.2 on GPS images and 12.4 on GS30 images (P = .002). Conclusions Tetrofosmin early GPS-SPECT is feasible without impairment of image quality (better count rate). Ischemic defect size on early post-stress images is slightly more pronounced than at 30 minutes: this could modify therapeutic decision. This technique produces reliable function information during early post-stress period, and might be useful for disclosing transient motion abnormalities. PMID:21063927

  16. Deterministic photon-emitter coupling in chiral photonic circuits

    NASA Astrophysics Data System (ADS)

    Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

    2015-09-01

    Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

  17. Deterministic photon-emitter coupling in chiral photonic circuits.

    PubMed

    Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

    2015-09-01

    Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

  18. Inelastic processes in ion/surface collisions: Scattered ion fractions and VUV photon emission for Ne + and Ar + collisions with Mg and Y surfaces

    NASA Astrophysics Data System (ADS)

    Rabalais, J. Wayne; Chen, Jie-Nan; Kumar, R.; Narayana, M.

    1985-12-01

    Time-of-flight (TOF) scattering spectra and vacuum ultraviolet (VUV) photon emission spectra resulting from 1-10 keV Ne+ and Ar+ ions impinging on magnesium and yttrium surfaces and the corresponding oxidized and hydroxylated surfaces have been measured. Measurements of the scattered neutrals plus ions and neutrals only are used to calculate scattered ion fractions Y+ for the single scattering collisions. The Y+ values rise steeply at low ion energies E0 (˜1-2 keV), reaching values of 70% and 38% at 10 keV for Ne+/Mg and Ar+/Y, respectively, and are very sensitive to adsorbate coverage. The dominant photon emission observed from the clean metals in the VUV range 30-200 nm is 1,3P → 1S resonance radiation from the excited neutral projectile atoms; emission was also observed from excited H and O for adsorbate covered surfaces. A model is developed for electronic transitions in keV ion/surface collisions which considers Auger and resonant transitions along the ion trajectory and electron promotions in the quasidiatomic molecule of the close encounter. By making an assumption of equality in the close encounter, the model can be fitted to the experimental data, allowing determination of ionization PI and neutralization PN probabilities as a function of the distance of approach. The results show that electron promotions within MO's of the collision complex formed during encounter are significant, if not dominating, processes in keV ion surface collisions.

  19. Microalgae photonics

    NASA Astrophysics Data System (ADS)

    Floume, Timmy; Coquil, Thomas; Sylvestre, Julien

    2011-05-01

    Due to their metabolic flexibility and fast growth rate, microscopic aquatic phototrophs like algae have a potential to become industrial photochemical converters. Algae photosynthesis could enable the large scale production of clean and renewable liquid fuels and chemicals with major environmental, economic and societal benefits. Capital and operational costs are the main issues to address through optical, process and biochemical engineering improvements. In this perspective, a variety of photonic approaches have been proposed - we introduce them here and describe their potential, limitations and compatibility with separate biotechnology and engineering progresses. We show that only sunlight-based approaches are economically realistic. One of photonics' main goals in the algae field is to dilute light to overcome photosaturation effects that impact upon cultures exposed to full sunlight. Among other approaches, we introduce a widely-compatible broadband spectral adaptation technique called AlgoSun® that uses luminescence to optimize sunlight spectrum in view of the bioconverter's requirements.

  20. Nonadiabatic dynamics in intense continuous wave laser fields and real-time observation of the associated wavepacket bifurcation in terms of spectrogram of induced photon emission

    NASA Astrophysics Data System (ADS)

    Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo

    2016-11-01

    We propose a theoretical principle to directly monitor the bifurcation of quantum wavepackets passing through nonadiabatic regions of a molecule that is placed in intense continuous wave (CW) laser fields. This idea makes use of the phenomenon of laser-driven photon emission from molecules that can undergo nonadiabatic transitions between ionic and covalent potential energy surfaces like Li+ F- and LiF. The resultant photon emission spectra are of anomalous yet characteristic frequency and intensity, if pumped to an energy level in which the nonadiabatic region is accessible and placed in a CW laser field. The proposed method is designed to take the time-frequency spectrogram with an appropriate time-window from this photon emission to detect the time evolution of the frequency and intensity, which depends on the dynamics and location of the relevant nuclear wavepackets. This method is specifically designed for the study of dynamics in intense CW laser fields and is rather limited in scope than other techniques for femtosecond chemical dynamics in vacuum. The following characteristic features of dynamics can be mapped onto the spectrogram: (1) the period of driven vibrational motion (temporally confined vibrational states in otherwise dissociative channels, the period and other states of which dramatically vary depending on the CW driving lasers applied), (2) the existence of multiple nuclear wavepackets running individually on the field-dressed potential energy surfaces, (3) the time scale of coherent interaction between the nuclear wavepackets running on ionic and covalent electronic states after their branching (the so-called coherence time in the terminology of the theory of nonadiabatic interaction), and so on.

  1. Importance of 123I-metaiodobenzylguanidine scintigraphy/single photon emission computed tomography for diagnosis and differential diagnostics of Parkinson syndromes.

    PubMed

    Jost, Wolfgang H; Del Tredici, Kelly; Landvogt, Christian; Braune, Stefan

    2010-01-01

    The goal of Parkinson syndrome diagnostics is twofold: early diagnosis on the one hand, and accurate differentiation among idiopathic and atypical Parkinson syndromes on the other. (123)I-metaiodobenzylguanidine scintigraphy is the only method that can distinguish with a high degree of sensitivity and specificity between atypical Parkinson syndromes and Parkinson's disease or dementia with Lewy bodies. Additional advantages are the method's widespread availability and radioactive exposure dose comparable to that for single photon emission computed tomography imaging with much lower costs. Only a single radiotracer study is necessary. (123)I-metaiodobenzylguanidine scintigraphy is an indispensable tool for purposes of differentiating among the various Parkinson syndromes.

  2. Tc-99m Sulfur Colloid Lymphoscintigraphy with Single-photon Emission Computed Tomography/Computed Tomography in a Case of Acquired Vulval Lymphangiomas

    PubMed Central

    Tulsyan, Shruti; Tripathi, Madhavi; Das, Kalpa; Yadav, Divya; Shamim, Shamim Ahmed; Damle, Nishikant; Bal, Chandrasekhar

    2017-01-01

    We describe the lymphoscintigraphy findings of a 25-year-old female patient who was undergoing presurgical workup for lymphangiomas of the vulva. She had a history of treatment for disseminated tuberculosis 6 years back and presented with herpetiform oozing vesicles in the external genitalia. Single-photon emission computed tomography/computed tomography (SPECT/CT) confirmed cutaneous tracer accumulation in the vulval lesions and demonstrated the presence of densely calcified inguinal nodes secondary to healed tuberculosis as the etiology of secondary lymphangioma. PMID:28242996

  3. Blue and NIR emission from nanostructured Tm3+/  Yb3+ co-doped SiO2-Ta2O5 for photonic applications

    NASA Astrophysics Data System (ADS)

    Cardoso Muscelli, Wesley; de Oliveira Lima, Karmel; Thomaz Aquino, Felipe; Rocha Gonçalves, Rogéria

    2016-05-01

    This paper reports on the synthesis of Tm3+/Yb3+ co-doped SiO2-Ta2O5 nanocomposites prepared by a sol-gel route. XRD analysis revealed initial crystallization of the L-Ta2O5 structure dispersed in the silica host, which depended on lanthanide concentration. Vibrational spectroscopy showed low OH groups content, SiO2-Ta2O5 nanocomposite formation, and controlled phase separation characterized by the presence of Ta2O5 nanoparticles. Emission in the near infrared was evident and also depended on lanthanide concentration and excitation wavelength. Direct excitation on the host promoted NIR luminescence; higher intensity emerged at 980 nm, attributed to Yb3+ ions. Excitation of the Tm3+ excited levels elicited energy transfer between Tm3+ and Yb3+ ions. Excitation of the Tm3+ levels (visible range) and the host (UV) promoted emission in the S telecom band for all the samples. Excitation at 980 nm gave rise to upconversion emissions at 476 nm (blue) and 793 nm (NIR). At higher lanthanide concentration, the presence of a dominant cross-relaxation process reduced the blue emission with respect to the NIR emission. The color coordinates were similar to the coordinates of standard blue. All these luminescent properties make the synthesized materials potential candidates for photonic applications like energy converting devices, solar concentrators, and blue emitters.

  4. Anti-3-[18F]FACBC Positron Emission Tomography-Computerized Tomography and 111In-Capromab Pendetide Single Photon Emission Computerized Tomography-Computerized Tomography for Recurrent Prostate Carcinoma: Results of a Prospective Clinical Trial

    PubMed Central

    Schuster, David M.; Nieh, Peter T.; Jani, Ashesh B.; Amzat, Rianot; Bowman, F. DuBois; Halkar, Raghuveer K.; Master, Viraj A.; Nye, Jonathon A.; Odewole, Oluwaseun A.; Osunkoya, Adeboye O.; Savir-Baruch, Bital; Alaei-Taleghani, Pooneh; Goodman, Mark M.

    2014-01-01

    Purpose We prospectively evaluated the amino acid analogue positron emission tomography radiotracer anti-3-[18F]FACBC compared to ProstaScint® (111In-capromab pendetide) single photon emission computerized tomography-computerized tomography to detect recurrent prostate carcinoma. Materials and Methods A total of 93 patients met study inclusion criteria who underwent anti-3-[18F]FACBC positron emission tomography-computerized tomography plus 111In-capromab pendetide single photon emission computerized tomography-computerized tomography for suspected recurrent prostate carcinoma within 90 days. Reference standards were applied by a multidisciplinary board. We calculated diagnostic performance for detecting disease. Results In the 91 of 93 patients with sufficient data for a consensus on the presence or absence of prostate/bed disease anti-3-[18F]FACBC had 90.2% sensitivity, 40.0% specificity, 73.6% accuracy, 75.3% positive predictive value and 66.7% negative predictive value compared to 111In-capromab pendetide with 67.2%, 56.7%, 63.7%, 75.9% and 45.9%, respectively. In the 70 of 93 patients with a consensus on the presence or absence of extraprostatic disease anti-3-[18F]FACBC had 55.0% sensitivity, 96.7% specificity, 72.9% accuracy, 95.7% positive predictive value and 61.7% negative predictive value compared to 111In-capromabpendetide with10.0%, 86.7%, 42.9%, 50.0% and 41.9%, respectively. Of 77 index lesions used to prove positivity histological proof was obtained in 74 (96.1%). Anti-3-[18F]FACBC identified 14 more positive prostate bed recurrences (55 vs 41) and 18 more patients with extraprostatic involvement (22 vs 4). Anti-3-[18F]FACBC positron emission tomography-computerized tomography correctly up-staged 18 of 70 cases (25.7%) in which there was a consensus on the presence or absence of extraprostatic involvement. Conclusions Better diagnostic performance was noted for anti-3-[18F]FACBC positron emission tomography-computerized tomography than for 111In

  5. Peripherally hydrogenated neutral polycyclic aromatic hydrocarbons as carriers of the 3 micron interstellar infrared emission complex: results from single-photon infrared emission spectroscopy.

    PubMed

    Wagner, D R; Kim, H S; Saykally, R J

    2000-12-20

    Infrared emission spectra of five gas-phase UV laser-excited polycyclic aromatic hydrocarbons (PAHs) containing aliphatic hydrogens are compared with the main 3.3 microns and associated interstellar unidentified infrared emission bands (UIRs). We show that neutral PAHs can account for the majority of the 3 microns emission complex while making little contribution to the other UIR bands; peripherally hydrogenated PAHs produce a better match to astrophysical data than do those containing methyl side groups; 3.4 microns plateau emission is shown to be a general spectral feature of vibrationally excited PAHs containing aliphatic hydrogens, especially those containing methyl groups; and finally, hot-band and overtone emissions arising from aromatic C-H vibrations are not observed in laboratory emission spectra, and therefore, in contrast to current assignments, are not expected to be observed in the UIRs.

  6. Peripherally hydrogenated neutral polycyclic aromatic hydrocarbons as carriers of the 3 micron interstellar infrared emission complex: results from single-photon infrared emission spectroscopy

    NASA Technical Reports Server (NTRS)

    Wagner, D. R.; Kim, H. S.; Saykally, R. J.

    2000-01-01

    Infrared emission spectra of five gas-phase UV laser-excited polycyclic aromatic hydrocarbons (PAHs) containing aliphatic hydrogens are compared with the main 3.3 microns and associated interstellar unidentified infrared emission bands (UIRs). We show that neutral PAHs can account for the majority of the 3 microns emission complex while making little contribution to the other UIR bands; peripherally hydrogenated PAHs produce a better match to astrophysical data than do those containing methyl side groups; 3.4 microns plateau emission is shown to be a general spectral feature of vibrationally excited PAHs containing aliphatic hydrogens, especially those containing methyl groups; and finally, hot-band and overtone emissions arising from aromatic C-H vibrations are not observed in laboratory emission spectra, and therefore, in contrast to current assignments, are not expected to be observed in the UIRs.

  7. A search for 2-photon emission from the 662 keV state in ^137Ba using Gammasphere

    NASA Astrophysics Data System (ADS)

    Lister, C. J.; McCutchan, E. A.; Moran, K.; Zhu, S.; Carpenter, M. P.; Greene, J. P.; Millener, J. D.; Sutter, R. J.; Alburger, D. E.

    2012-10-01

    Two photon decays from excited nuclear states provide an interesting test both of QED and nuclear structure. It has been extensively studied for cases where one photon decay is forbidden [1]. Two photon decay in direct competition with the first order process has never been convincingly demonstrated. Nonetheless, observation of this decay will provide additional challenging tests for experiment and theory. The ^137Ba case is particularly interesting as the decay has high multipolarity, M4, so the 2-photon process can have contributions from both quadrupole-quadrupole and dipole-octupole multipolarities. Gammasphere is the perfect tool for this investigation, having good energy resolution, good efficiency, good coverage of angles, and sufficient granularity to minimize pile-up and count-rate difficulties. A short test experiment showed the power of Gammasphere and the dauntingly high Compton scattering background that need suppression. However, new calculations and new measurements from Brookhaven suggest that the two photon branch is ˜2 x 10-6 and should be measurable. This work was supported by DOE contracts, DE-FG02-94ER40848, DE-AC02-06CH11357 and DE-AC02-98CH10946.[4pt] [1] J. Kramp, et. al, Nucl. Phys. A474 (1987) 412

  8. Emissions in potassium vapour under 4S{sub 1/2}-7S{sub 1/2} two-photon nsec excitation

    SciTech Connect

    Pentaris, D.; Chatzikyriakos, G.; Armyras, A.; Efthimiopoulos, T.

    2010-11-10

    The two-photon excitation of 4S{sub 1/2}-7S{sub 1/2} transition of potassium atoms is studied. Several coherent emissions and processes are possible, such as parametric four-wave (PFWM), parametric six-wave (PSWM) mixing and competition with the stimulated hyper Raman (SHRS) and the amplified spontaneous emission (ASE). The radiations at the transitions 6P{sub 3/2,1/2}-4S{sub 1/2}, 6S{sub 1/2}-4P{sub 3/2,1/2} and 5P{sub 3/2,1/2}-4S{sub 1/2} are emitted only in the forward direction (indicating a parametric process), while the radiation at the transition 4P{sub 3/2,1/2}-4S{sub 1/2} is emitted in the forward and in the backward direction, indicating an ASE process.

  9. In-vivo tissue imaging using a compact mobile nonlinear microscope

    NASA Astrophysics Data System (ADS)

    Cicchi, Riccardo; Kapsokalyvas, Dimitrios; Stampouli, Despoina; De Giorgi, Vincenzo; Massi, Daniela; Lotti, Torello; Pavone, Francesco S.

    2010-02-01

    We have built a compact flexible non-linear microscope equipped with a combination of different non-linear laser imaging techniques including two-photon fluorescence, second-harmonic generation, fluorescence lifetime imaging microscopy, and multispectral two-photon emission detection. The system is composed of a microscope head, containing both scanning and detection system, as well as the electronic and electro-mechanical devices, optically relayed to the laser source with a seven-mirror articulated arm. The particular mirror positioning inside the arm allows to move the microscope head maintaining the optical alignment of the system. The microscope head is composed by two ErGaAl anodized boards, one for laser scanning and the other for signal detection. System performances were characterized by means of point spread function and instrument response function measurements as well as by spatial, temporal, and spectral calibration. The instrument, offering high spatial (up to 300 nm) and temporal (up to 300 ps) resolution, was tested on in-vivo skin imaging of both cellular epidermis and connective dermis. Lifetime and spectral features of fluorescence were used for differentiating epidermal layers by means of fluorescence lifetime and for scoring skin ageing through spectral detection of both second-harmonic and two-photon fluorescence.

  10. Development of confocal laser microscope system for examination of microscopic characteristics of radiophotoluminescence glass dosemeters.

    PubMed

    Maki, Daisuke; Ishii, Tetsuya; Sato, Fuminobu; Kato, Yushi; Yamamoto, Takayoshi; Iida, Toshiyuki

    2011-03-01

    A confocal laser microscope system was developed for the measurement of radiophotoluminescence (RPL) photons emitted from a minute alpha-ray-irradiated area in an RPL glass dosemeter. The system was composed mainly of an inverted-type microscope, an ultraviolet laser, an XY movable stage and photon-counting circuits. The photon-counting circuits were effective in the reduction of the background noise level in the measurement of RPL photons. The performance of this microscope system was examined by the observation of standard RPL glass samples irradiated using (241)Am alpha rays. The spatial resolution of this system was ∼ 3 μm, and with regard to the sensitivity of this system, a hit of more than four to five alpha rays in unit area produced enough amount of RPL photons to construct the image.

  11. Microscopic black holes and cosmic shells

    NASA Astrophysics Data System (ADS)

    Daghigh, Ramin Ghasemzadeh

    In the first part of this thesis the relativistic viscous fluid equations describing the outflow of high temperature matter created via Hawking radiation from microscopic black holes are solved numerically for a realistic equation of state. We focus on black holes with initial temperatures greater than 100 GeV and lifetimes less than 6 days. The spectra of direct photons and photons from π0 decay are calculated for energies greater than 1 GeV. We calculate the diffuse gamma ray spectrum from black holes distributed in our galactic halo. However, the most promising route for their observation is to search for point sources emitting gamma rays of ever-increasing energy. We also calculate the spectra of all three flavors of neutrinos arising from direct emission from the fluid at the neutrino- sphere and from the decay of pions and muons from their decoupling at much larger radii and smaller temperatures for neutrino energies between 1 GeV and the Planck energy. The results for neutrino spectra may be applicable for the last few hours and minutes of the lifetime of a microscopic black hole. In the second part of this thesis the combined field equations of gravity and a scalar field are studied. When a potential for a scalar field has two local minima there arise spherical shell-type solutions of the classical field equations due to gravitational attraction. We establish such solutions numerically in a space which is asymptotically de Sitter. It generically arises when the energy scale characterizing the scalar field potential is much less than the Planck scale. It is shown that the mirror image of the shell appears in the other half of the Penrose diagram. The configuration is smooth everywhere with no physical singularity.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation).

  12. Precise determination of photon emission probabilities for the main X- and gamma-rays of 226Ra in equilibrium with daughters.

    PubMed

    Morel, J; Sepman, S; Rasko, M; Terechtchenko, E; Delgado, J U

    2004-01-01

    Within the context of a joint project between VNIIM (D.I. Mendeleyev Institute for Metrology) and LNHB (Laboratoire National Henri Becquerel), special 226Ra sources were prepared by VNIIM in order to determine as accurately as possible the absolute photon emission probabilities for the main X- and gamma-rays following the decay of 226Ra and daughters. The main purpose of this work was to supplement a previous joint study by Laboratorio Nacional de Metrologia das Radiaçoes Ionizantes (LNMRI) and LNHB to determine their relative values. Some specific point sources were produced for alpha-spectrometry measurements that were undertaken at VNIIM and also for gamma-ray spectrometry studies at VNIIM and LNHB. The 226Ra activity for the gamma-spectrometric sources was measured relative to the alpha-spectrometric sources by comparing the counts of the main gamma-rays. The total uncertainty of the activity for these sources was 0.2% (k = 1). Using calibrated germanium detectors, several X- and gamma-ray spectra were analyzed to determine the absolute photon emission probabilities of 226Ra in radioactive equilibrium with daughters. The results are presented and compared to other published values.

  13. Quantitative thallium-201 single photon emission computed tomography after oral dipyridamole for assessing the presence, anatomic location and severity of coronary artery disease

    SciTech Connect

    Borges-Neto, S.; Mahmarian, J.J.; Jain, A.; Roberts, R.; Verani, M.S.

    1988-05-01

    The objective of this investigation was to determine whether analysis of thallium-201 images as detected by quantitative single photon emission computed tomography after a single high oral dose of dipyridamole (300 mg) would accurately detect the presence of coronary artery disease and the anatomic location of the individual stenosis. Analyses were performed on 100 patients who concomitantly underwent diagnostic coronary arteriography and myocardial imaging. Tomographic myocardial perfusion defects were quantified using computer-generated polar maps. Eighty-four patients had significant coronary artery disease defined as greater than 50% luminal diameter stenosis. The sensitivity for detecting patients with coronary disease was 92% overall, 89% in patients without previous myocardial infarction and 97% in those with prior infarction. The technique had a sensitivity of 80, 87 and 51% for localizing coronary artery stenosis of the left anterior descending, the right coronary and the left circumflex artery, respectively. The corresponding specificity was 84, 92 and 92%. Furthermore, the presence of severe (greater than or equal to 70%) multivessel disease was identified with a sensitivity of 79% and a specificity of 87%. In conclusion, quantitative thallium-201 single photon emission computed tomography after oral dipyridamole has high sensitivity and specificity for diagnosing the presence of coronary disease, ascertaining the location of stenosed vessels and identifying the presence of multivessel disease.

  14. Universal parametrization of thermal photon rates in hadronic matter

    NASA Astrophysics Data System (ADS)

    Heffernan, Matthew; Hohler, Paul; Rapp, Ralf

    2015-02-01

    Electromagnetic (EM) radiation off strongly interacting matter created in high-energy heavy-ion collisions (HICs) encodes information on the high-temperature phases of nuclear matter. Microscopic calculations of thermal EM emission rates are usually rather involved and not readily accessible to broad applications in models of the fireball evolution which are required to compare with experimental data. An accurate and universal parametrization of the microscopic calculations is thus key to honing the theory behind the EM spectra. Here we provide such a parametrization for photon emission rates from hadronic matter, including the contributions from in-medium ρ mesons (which incorporate effects from baryons and antibaryons), as well as bremsstrahlung from π π scattering. Individual parametrizations for each contribution are numerically determined through nested fitting functions for photon energies from 0.2 to 5 GeV in chemically equilibrated matter of temperatures 100-180 MeV and baryon chemical potentials 0-400 MeV. Special care is taken to extent the parametrizations to chemical off-equilibrium as encountered in HICs after chemical freeze-out. This provides a functional description of thermal photon rates within a 20% variation of the microscopically calculated values.

  15. Universal Parametrization of Thermal Photon Production in Hadronic Matter

    NASA Astrophysics Data System (ADS)

    Heffernan, Matthew; Hohler, Paul; Rapp, Ralf

    2014-09-01

    As the production of photons and dileptons from high-energy collisions is able to provide information on the high temperature and high density phases of nuclear matter, an improved and universal parametrization of the rather involved microscopic calculations is key to honing the theory behind this production. We focus on photon emission rates from hadronic many-body calculations of the in-medium rho spectral function, which includes the effects of baryons and antibaryons. Across a range of temperatures from 0.1 to 0.18 GeV and baryon chemical potentials from 0 to 0.4 GeV, a parametrization of thermal photon rates for energies from 0.2 to 5 GeV is numerically determined through the use of nested fitting methods. This provides a fully functional description of thermal photon production largely within an unprecedented 20% of the calculated values from the spectral function, a significant reduction in error from available parametrizations. The contribution of photons and dileptons from pion-pion bremsstrahlung is evaluated for the importance of its contribution. The functional form, coupled with the comparison to the bremsstrahlung production of thermal photons, will provide a baseline for guiding future studies. As the production of photons and dileptons from high-energy collisions is able to provide information on the high temperature and high density phases of nuclear matter, an improved and universal parametrization of the rather involved microscopic calculations is key to honing the theory behind this production. We focus on photon emission rates from hadronic many-body calculations of the in-medium rho spectral function, which includes the effects of baryons and antibaryons. Across a range of temperatures from 0.1 to 0.18 GeV and baryon chemical potentials from 0 to 0.4 GeV, a parametrization of thermal photon rates for energies from 0.2 to 5 GeV is numerically determined through the use of nested fitting methods. This provides a fully functional description of

  16. A perturbation theoretic approach to the Riccati equation for the Floquet energies, spectral intensities, and cutoff energy of harmonic generation in photon emission from nonadiabatic electron-transfer dynamics driven by infrared CW laser fields

    SciTech Connect

    Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo

    2016-01-14

    A complicated yet interesting induced photon emission can take place by a nonadiabatic intramolecular electron transfer system like LiF under an intense CW laser [Y. Arasaki, S. Scheit, and K. Takatsuka, J. Chem. Phys. 138, 161103 (2013)]. Behind this phenomena, the crossing point between two potential energy curves of covalent and ionic natures in diabatic representation is forced to oscillate, since only the ionic potential curve is shifted significantly up and down repeatedly (called the Dynamical Stark effect). The wavepacket pumped initially to the excited covalent potential curve frequently encounters such a dynamically moving crossing point and thereby undergoes very complicated dynamics including wavepacket bifurcation and deformation. Intramolecular electron transfer thus driven by the coupling between nonadiabatic state-mixing and laser fields induces irregular photon emission. Here in this report we discuss the complicated spectral features of this kind of photon emission induced by infrared laser. In the low frequency domain, the photon emission is much more involved than those of ultraviolet/visible driving fields, since many field-dressed states are created on the ionic potential, which have their own classical turning points and crossing points with the covalent counterpart. To analyze the physics behind the phenomena, we develop a perturbation theoretic approach to the Riccati equation that is transformed from coupled first-order linear differential equations with periodic coefficients, which are supposed to produce the so-called Floquet states. We give mathematical expressions for the Floquet energies, frequencies, and intensities of the photon emission spectra, and the cutoff energy of their harmonic generation. Agreement between these approximate quantities and those estimated with full quantum calculations is found to be excellent. Furthermore, the present analysis provides with notions to facilitate deeper understanding for the physical and

  17. A perturbation theoretic approach to the Riccati equation for the Floquet energies, spectral intensities, and cutoff energy of harmonic generation in photon emission from nonadiabatic electron-transfer dynamics driven by infrared CW laser fields.

    PubMed

    Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo

    2016-01-14

    A complicated yet interesting induced photon emission can take place by a nonadiabatic intramolecular electron transfer system like LiF under an intense CW laser [Y. Arasaki, S. Scheit, and K. Takatsuka, J. Chem. Phys. 138, 161103 (2013)]. Behind this phenomena, the crossing point between two potential energy curves of covalent and ionic natures in diabatic representation is forced to oscillate, since only the ionic potential curve is shifted significantly up and down repeatedly (called the Dynamical Stark effect). The wavepacket pumped initially to the excited covalent potential curve frequently encounters such a dynamically moving crossing point and thereby undergoes very complicated dynamics including wavepacket bifurcation and deformation. Intramolecular electron transfer thus driven by the coupling between nonadiabatic state-mixing and laser fields induces irregular photon emission. Here in this report we discuss the complicated spectral features of this kind of photon emission induced by infrared laser. In the low frequency domain, the photon emission is much more involved than those of ultraviolet/visible driving fields, since many field-dressed states are created on the ionic potential, which have their own classical turning points and crossing points with the covalent counterpart. To analyze the physics behind the phenomena, we develop a perturbation theoretic approach to the Riccati equation that is transformed from coupled first-order linear differential equations with periodic coefficients, which are supposed to produce the so-called Floquet states. We give mathematical expressions for the Floquet energies, frequencies, and intensities of the photon emission spectra, and the cutoff energy of their harmonic generation. Agreement between these approximate quantities and those estimated with full quantum calculations is found to be excellent. Furthermore, the present analysis provides with notions to facilitate deeper understanding for the physical and

  18. Observation of enhanced visible and infrared emissions in photonic crystal thin-film light-emitting diodes

    SciTech Connect

    Cheung, Y. F.; Li, K. H.; Hui, R. S. Y.; Choi, H. W.

    2014-08-18

    Photonic crystals, in the form of closed-packed nano-pillar arrays patterned by nanosphere lithography, have been formed on the n-faces of InGaN thin-film vertical light-emitting diodes (LEDs). Through laser lift-off of the sapphire substrate, the thin-film LEDs conduct vertically with reduced dynamic resistances, as well as reduced thermal resistances. The photonic crystal plays a role in enhancing light extraction, not only at visible wavelengths but also at infrared wavelengths boosting heat radiation at high currents, so that heat-induced effects on internal quantum efficiencies are minimized. The observations are consistent with predictions from finite-difference time-domain simulations.

  19. Photon emissions from N2·+ ion beam-target gas collisions in a modified commercial sector mass spectrometer

    NASA Astrophysics Data System (ADS)

    Holmes, H. L.; Mayer, P. M.; Mommers, A. A.

    1994-08-01

    Experiments are reported in which radiative emissions from 8 keV N2·+ projectile ion--target gas (He, N2, O2 and CO2) collisions in the third field-free region of a modified VG ZAB-2F mass spectrometer (BEE geometry) were detected and analyzed using a scanning grating monochromator. The emission spectra between 180 and 680 nm were characterized by the N2·+ (B2[Sigma]u+ --> X2[Sigma]g+) electronic transition and, when N2 and O2 were the targets, the C 3[Pi]u --> B 3[Pi]g second positive system in N2. Fragment N+ emissions were also observed. In addition to the projectile emissions, ionized target gas and even target fragment emissions were present with all targets except helium. Observations made 0.05-0.17 [mu]s after the collision event were similar to those described above, but lacking target gas emissions. Qualitative information concerning the trends in post-collission emission, studied with 18 target gases, was obtained using wavelength cut-off filters. The results were consistent with the above spectral assignments and trends observed in collision induced dissociation mass spectrometry.

  20. Antecedents of two-photon excitation laser scanning microscopy.

    PubMed

    Masters, Barry R; So, Peter T C

    2004-01-01

    In 1931, Maria Göppert-Mayer published her doctoral dissertation on the theory of two-photon quantum transitions (two-photon absorption and emission) in atoms. This report describes and analyzes the theoretical and experimental work on nonlinear optics, in particular two-photon excitation processes, that occurred between 1931 and the experimental implementation of two-photon excitation microscopy by the group of Webb in 1990. In addition to Maria Göppert-Mayer's theoretical work, the invention of the laser has a key role in the development of two-photon microscopy. Nonlinear effects were previously observed in different frequency domains (low-frequency electric and magnetic fields and magnetization), but the high electric field strength afforded by lasers was necessary to demonstrate many nonlinear effects in the optical frequency range. In 1978, the first high-resolution nonlinear microscope with depth resolution was described by the Oxford group. Sheppard and Kompfner published a study in Applied Optics describing microscopic imaging based on second-harmonic generation. In their report, they further proposed that other nonlinear optical effects, such as two-photon fluorescence, could also be applied. However, the developments in the field of nonlinear optical stalled due to a lack of a suitable laser source. This obstacle was removed with the advent of femtosecond lasers in the 1980s. In 1990, the seminal study of Denk, Strickler, and Webb on two-photon laser scanning fluorescence microscopy was published in Science. Their paper clearly demonstrated the capability of two-photon excitation microscopy for biology, and it served to convince a wide audience of scientists of the potential capability of the technique.

  1. X-ray emission around the z = 4.1 radio galaxy TN J1338-1942 and the potential role of far-infrared photons in AGN feedback

    NASA Astrophysics Data System (ADS)

    Smail, Ian; Blundell, Katherine M.

    2013-10-01

    We report the discovery in an 80-ks observation of spatially extended X-ray emission around the high-redshift radio galaxy TN J1388-1942 (z = 4.11) with the Chandra X-ray Observatory. The X-ray emission extends over a ˜30-kpc diameter region and although it is less extended than the GHz-radio lobes, it is roughly aligned with them. We suggest that the X-ray emission arises from inverse-Compton (IC) scattering of photons by relativistic electrons around the radio galaxy. At z = 4.11, this is the highest redshift detection of IC emission around a radio galaxy. We investigate the hypothesis that in this compact source, the cosmic microwave background (CMB), which is ˜700× more intense than at z ˜ 0 is nonetheless not the relevant seed photon field for the bulk of the IC emission. Instead, we find a tentative correlation between the IC emission and far-infrared luminosities of compact, far-infrared luminous high-redshift radio galaxies (those with lobe lengths of ≲100 kpc). Based on these results, we suggest that in the earliest phases of the evolution of radio-loud active galactic nuclei at very high redshift, the far-infrared photons from the co-eval dusty starbursts occurring within these systems may make a significant contribution to their IC X-ray emission and so contribute to the feedback in these massive high-redshift galaxies.

  2. Prevalence and predictors of ischemia and outcomes in outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging.

    PubMed

    Bourque, Jamieson M; Patel, Chetan A; Ali, Mohamed M; Perez, Margarita; Watson, Denny D; Beller, George A

    2013-05-01

    Background- The prevalence of ischemia and its prediction of events are unclear in outpatients with diabetes mellitus in the modern era of intensive medical management. We sought to identify the prevalence of ischemia, subsequent cardiac events, and impact of sex, stress type, and symptom status on these findings in a cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging (MPI). Methods and Results- The study cohort included 575 consecutive outpatients with diabetes mellitus who underwent quantitative, gated single-photon emission computed tomography MPI. Clinical information, stress MPI variables, and cardiac events were prospectively collected and analyzed. The study population was at intermediate risk of coronary artery disease or had known coronary artery disease (40.3%); 29% of patients were asymptomatic at the time of stress testing. Scintigraphic ischemia and significant (≥10%) left ventricular ischemia were present in 126 patients (21.9%) and 29 patients (5.0%), respectively, and <1% of patients had early revascularization. The risk of ischemia was increased >2-fold by male sex (P<0.001), but was not impacted by pharmacological stress (P=0.15) or presence of symptoms (P=0.89). During a median 4.4 years follow-up, the rate of cardiac death/nonfatal myocardial infarction was moderate at 2.6%/y (cardiac death 0.8%/y) in the total cohort, but was 5.7%/y in those with ischemia (P<0.001). Pharmacological stress predicted a higher cardiac event rate (P<0.001) but symptoms did not (P=0.55). Conclusions- This cohort of stable outpatients with diabetes mellitus referred for single-photon emission computed tomography had low rates of significant ischemia and early revascularization; an initially low cardiac event rate increased after 2 years. Independent predictors of cardiac death/nonfatal myocardial infarction were known coronary artery disease, pharmacological stress, and MPI

  3. Room-Temperature Ordered Photon Emission from Multiexciton States in Single CdSe Core-Shell Nanocrystals

    NASA Astrophysics Data System (ADS)

    Fisher, Brent; Caruge, Jean Michel; Zehnder, Don; Bawendi, Moungi

    2005-03-01

    We report room-temperature ordered multiphoton emission from multiexciton states of single CdSe(CdZnS) core(-shell) colloidal nanocrystals (NCs) that are synthesized by wet chemical methods. Spectrally and temporally resolved measurements of biexciton and triexciton emission from single NCs are also presented. A simple four level system models the results accurately and provides estimates for biexciton and triexciton radiative lifetimes and quantum yields.

  4. Room-temperature ordered photon emission from multiexciton states in single CdSe core-shell nanocrystals.

    PubMed

    Fisher, Brent; Caruge, Jean Michel; Zehnder, Don; Bawendi, Moungi

    2005-03-04

    We report room-temperature ordered multiphoton emission from multiexciton states of single CdSe(CdZnS) core(-shell) colloidal nanocrystals (NCs) that are synthesized by wet chemical methods. Spectrally and temporally resolved measurements of biexciton and triexciton emission from single NCs are also presented. A simple four level system models the results accurately and provides estimates for biexciton and triexciton radiative lifetimes and quantum yields.

  5. Red emissive AIE nanodots with high two-photon absorption efficiency at 1040 nm for deep-tissue in vivo imaging.

    PubMed

    Wang, Yalun; Hu, Rongrong; Xi, Wang; Cai, Fuhong; Wang, Shaowei; Zhu, Zhenfeng; Bai, Rongpan; Qian, Jun

    2015-10-01

    Deep-tissue penetration is highly required in in vivo optical bioimaging. We synthesized a type of red emissive fluorophore BT with aggregation-induced emission (AIE) property. BT molecules were then encapsulated with amphiphilic polymers to form nanodots, and a large two-photon absorption (2PA) cross-section of 2.9 × 10(6) GM at 1040 nm was observed from each BT nanodot, which was much larger than those at the wavelengths of 770 to 860 nm. In addition, 1040 nm light was found to have better penetration and focusing capability than 800 nm light in biological tissue, according to the Monte Carlo simulation. The toxicity and tissue distribution of BT nanodots were studied, and they were found to have good biocompatibility. BT nanodots were then utilized for in vivo imaging of mouse ear and brain, and an imaging depth of 700 μm was obtained with the femtosecond (fs) excitation of 1040 nm. The red emissive AIE nanodots with high 2PA efficiency at 1040 nm would be useful for deep-tissue functional bioimaging in the future.

  6. Red emissive AIE nanodots with high two-photon absorption efficiency at 1040 nm for deep-tissue in vivo imaging

    PubMed Central

    Wang, Yalun; Hu, Rongrong; Xi, Wang; Cai, Fuhong; Wang, Shaowei; Zhu, Zhenfeng; Bai, Rongpan; Qian, Jun

    2015-01-01

    Deep-tissue penetration is highly required in in vivo optical bioimaging. We synthesized a type of red emissive fluorophore BT with aggregation-induced emission (AIE) property. BT molecules were then encapsulated with amphiphilic polymers to form nanodots, and a large two-photon absorption (2PA) cross-section of 2.9 × 106 GM at 1040 nm was observed from each BT nanodot, which was much larger than those at the wavelengths of 770 to 860 nm. In addition, 1040 nm light was found to have better penetration and focusing capability than 800 nm light in biological tissue, according to the Monte Carlo simulation. The toxicity and tissue distribution of BT nanodots were studied, and they were found to have good biocompatibility. BT nanodots were then utilized for in vivo imaging of mouse ear and brain, and an imaging depth of 700 μm was obtained with the femtosecond (fs) excitation of 1040 nm. The red emissive AIE nanodots with high 2PA efficiency at 1040 nm would be useful for deep-tissue functional bioimaging in the future. PMID:26504629

  7. Simultaneous and intercontinental tests show synchronism between the local gravimetric tide and the ultra-weak photon emission in seedlings of different plant species.

    PubMed

    Gallep, Cristiano M; Barlow, Peter W; Burgos, Rosilene C R; van Wijk, Eduard P A

    2017-01-01

    In order to corroborate the hypothesis that variations in the rate of spontaneous ultra-weak photon emission (UPE) from germinating seedlings are related to local variations of the lunisolar tidal force, a series of simultaneous tests was performed using the time courses of UPE collected from three plant species-corn, wheat and sunflower-and also from wheat samples whose grains were transported between continents, from Brazil to The Netherlands and vice versa. All tests which were run in parallel showed coincident inflections within the UPE time courses not only between seedlings of the same species but also between the different species. In most cases, the UPE inflections were synchronised with the turning points in the local gravimetric tidal variation. Statistical tests using the local Pearson correlation verified these coincidences in the two time series. The results therefore support the hypothesis of a relationship between UPE emissions and, in the oscillations, the local gravimetric tide. This applies to both the emissions from seedlings of different species and to the seedlings raised from transported grain samples of the same species.

  8. Resonant-scanning dual-color STED microscopy with ultrafast photon counting: a concise guide

    PubMed Central

    Wu, Yong; Wu, Xundong; Toro, Ligia; Stefani, Enrico

    2015-01-01

    STED (stimulated emission depletion) is a popular super-resolution fluorescence microscopy technique. In this paper, we present a concise guide to building a resonant-scanning STED microscope with ultrafast photon-counting acquisition. The STED microscope has two channels, using a pulsed laser and a continuous-wave (CW) laser as the depletion laser source, respectively. The CW STED channel preforms time-gated detection to enhance optical resolution in this channel. We use a resonant mirror to attain high scanning speed and ultrafast photon counting acquisition to scan a large field of view, which help reduce photobleaching. We discuss some practical issues in building a STED microscope, including creating a hollow depletion beam profile, manipulating polarization, and monitoring optical aberration. We also demonstrate a STED image enhancement method using stationary wavelet expansion and image analysis methods to register objects and to quantify colocalization in STED microscopy. PMID:26123183

  9. Enhanced Emission from Single Isolated Gold Quantum Dots Investigated Using Two-Photon-Excited Fluorescence Near-Field Scanning Optical Microscopy.

    PubMed

    Abeyasinghe, Neranga; Kumar, Santosh; Sun, Kai; Mansfield, John F; Jin, Rongchao; Goodson, Theodore

    2016-12-21

    New approaches in molecular nanoscopy are greatly desired for interrogation of biological, organic, and inorganic objects with sizes below the diffraction limit. Our current work investigates emergent monolayer-protected gold quantum dots (nanoclusters, NCs) composed of 25 Au atoms by utilizing two-photon-excited fluorescence (TPEF) near-field scanning optical microscopy (NSOM) at single NC concentrations. Here, we demonstrate an approach to synthesize and isolate single NCs on solid glass substrates. Subsequent investigation of the NCs using TPEF NSOM reveals that, even when they are separated by distances of several tens of nanometers, we can excite and interrogate single NCs individually. Interestingly, we observe an enhanced two-photon absorption (TPA) cross section for single Au25 NCs that can be attributed to few-atom local field effects and to local field-induced microscopic cascading, indicating their potential for use in ultrasensitive sensing, disease diagnostics, cancer cell therapy, and molecular computers. Finally, we report room-temperature aperture-based TPEF NSOM imaging of these NCs for the first time at 30 nm point resolution, which is a ∼5-fold improvement compared to the previous best result for the same technique. This report unveils the unique combination of an unusually large TPA cross section and the high photostability of Au NCs to (non-destructively) investigate stable isolated single NCs using TPEF NSOM. This is the first reported optical study of monolayer-protected single quantum clusters, opening some very promising opportunities in spectroscopy of nanosized objects, bioimaging, ultrasensitive sensing, molecular computers, and high-density data storage.

  10. Differentiation of clear cell ependymoma of the cerebellum from hemangioblastoma by thallium-201 single photon emission computed tomography-case report-.

    PubMed

    Nagamatsu, Ken-ichi; Kumabe, Toshihiro; Watanabe, Mika; Nakazato, Yoichi; Tominaga, Teiji

    2009-12-01

    A 57-year-old man suffered from dizziness for about one year and truncal ataxia for about one month. Magnetic resonance imaging demonstrated a cystic tumor with a homogeneously enhanced mural nodule located in the cerebellar vermis. Computed tomography angiography revealed a hypervascular nodule. These findings were compatible with hemangioblastoma. Thallium-201 single photon emission computed tomography ((201)Tl-SPECT) showed moderately high uptake in the early phase and moderately high retention in the delayed phase, whereas hemangioblastoma shows almost no retention in the delayed phase. The patient underwent total removal of the tumor. The histological diagnosis was clear cell ependymoma (CCE). CCE is a rare subtype of ependymoma, which resembles hemangioblastoma in histological and neuroimaging findings, but is considerably more aggressive. (201)Tl-SPECT can provide useful information for the preoperative differential diagnosis of infratentorial CCE and hemangioblastoma.

  11. Time-resolved measurement of photon emission during fast crack propagation in three-point bending fracture of silica glass and soda lime glass

    SciTech Connect

    Shiota, Tadashi Sato, Yoshitaka; Yasuda, Kouichi

    2014-03-10

    Simultaneous time-resolved measurements of photon emission (PE) and fast crack propagation upon bending fracture were conducted in silica glass and soda lime glass. Observation of fracture surfaces revealed that macroscopic crack propagation behavior was similar between the silica glass and soda lime glass when fracture loads for these specimens were comparable and cracks propagated without branching. However, a large difference in the PE characteristics was found between the two glasses. In silica glass, PE (645–655 nm) was observed during the entire crack propagation process, whereas intense PE (430–490 nm and 500–600 nm) was observed during the initial stages of propagation. In contrast, only weak PE was detected in soda lime glass. These results show that there is a large difference in the atomic processes involved in fast crack propagation between these glasses, and that PE can be used to study brittle fracture on the atomic scale.

  12. Crossed cerebellar diaschisis in ischemic stroke: a study of regional cerebral blood flow by /sup 133/Xe inhalation and single photon emission computerized tomography

    SciTech Connect

    Meneghetti, G.; Vorstrup, S.; Mickey, B.; Lindewald, H.; Lassen, N.A.

    1984-06-01

    Seventy measurements of CBF were performed in 12 stroke patients by /sup 133/Xe inhalation and a rapidly rotating single photon emission computerized tomograph. CBF was measured every other day during the acute phase and at 2- and 6-month follow-up visits. A persistent contralateral cerebellar blood flow depression was evident in five patients with severe hemispheric low flow areas, which correlated with large, hypodense lesions on the computerized tomographic scan. In a sixth patient with a small, deep infarct, a transient crossed cerebellar low flow was observed, while the clinical symptoms persisted. It is concluded from this serial study that crossed cerebellar diaschisis is a common finding in completed stroke. It is probably caused by disconnection of the corticopontine pathways, a disconnection that tends to persist. The phenomenon is in fact less variable than the stroke-related CBF changes in the infarcted hemisphere, in which a period of relative hyperemia is frequently seen.

  13. Method for reducing background artifacts from images in single-photon emission computed tomography with a uniformly redundant array coded aperture

    NASA Astrophysics Data System (ADS)

    Vassilieva, Olga I.; Chaney, Roy C.

    2002-03-01

    Uniformly redundant array coded apertures have proven to be useful in the design of collimators for x-ray astronomy. They were initially expected to be equally successful in single-photon emission computed tomography (SPECT). Unfortunately, the SPECT images produced by this collimator contain artifacts, which mask the true picture and can lead to false diagnosis. Monte Carlo simulation has shown that the formation of a composite image will significantly reduce these artifacts. A simulation of a tumor in a compressed breast phantom has produced a composite image, which clearly indicates the presence of a 5 mm x 5 mm x 5 mm tumor with a 6:1 intensity ratio relative to the background tissue.

  14. Regional cerebral blood flow assessed by single photon emission computed tomography (SPECT) in dogs with congenital portosystemic shunt and hepatic encephalopathy.

    PubMed

    Or, Matan; Peremans, Kathelijne; Martlé, Valentine; Vandermeulen, Eva; Bosmans, Tim; Devriendt, Nausikaa; de Rooster, Hilde

    2017-02-01

    Regional cerebral blood flow (rCBF) in eight dogs with congenital portosystemic shunt (PSS) and hepatic encephalopathy (HE) was compared with rCBF in eight healthy control dogs using single photon emission computed tomography (SPECT) with a (99m)technetium-hexamethylpropylene amine oxime ((99m)Tc-HMPAO) tracer. SPECT scans were abnormal in all PSS dogs. Compared to the control group, rCBF in PSS dogs was significantly decreased in the temporal lobes and increased in the subcortical (thalamic and striatal) area. Brain perfusion imaging alterations observed in the dogs with PSS and HE are similar to those in human patients with HE. These findings suggest that dogs with HE and PSS have altered perfusion of mainly the subcortical and the temporal regions of the brain.

  15. Air-Stable Surface-Passivated Perovskite Quantum Dots for Ultra-Robust, Single- and Two-Photon-Induced Amplified Spontaneous Emission.

    PubMed

    Pan, Jun; Sarmah, Smritakshi P; Murali, Banavoth; Dursun, Ibrahim; Peng, Wei; Parida, Manas R; Liu, Jiakai; Sinatra, Lutfan; Alyami, Noktan; Zhao, Chao; Alarousu, Erkki; Ng, Tien Khee; Ooi, Boon S; Bakr, Osman M; Mohammed, Omar F

    2015-12-17

    We demonstrate ultra-air- and photostable CsPbBr3 quantum dots (QDs) by using an inorganic-organic hybrid ion pair as the capping ligand. This passivation approach to perovskite QDs yields high photoluminescence quantum yield with unprecedented operational stability in ambient conditions (60 ± 5% lab humidity) and high pump fluences, thus overcoming one of the greatest challenges impeding the development of perovskite-based applications. Due to the robustness of passivated perovskite QDs, we were able to induce ultrastable amplified spontaneous emission (ASE) in solution processed QD films not only through one photon but also through two-photon absorption processes. The latter has not been observed before in the family of perovskite materials. More importantly, passivated perovskite QD films showed remarkable photostability under continuous pulsed laser excitation in ambient conditions for at least 34 h (corresponds to 1.2 × 10(8) laser shots), substantially exceeding the stability of other colloidal QD systems in which ASE has been observed.

  16. Coregistration of magnetic resonance and single photon emission computed tomography images for noninvasive localization of stem cells grafted in the infarcted rat myocardium.

    PubMed

    Shen, Dinggang; Liu, Dengfeng; Cao, Zixiong; Acton, Paul D; Zhou, Rong

    2007-01-01

    This paper demonstrates the application of mutual information based coregistration of radionuclide and magnetic resonance imaging (MRI) in an effort to use multimodality imaging for noninvasive localization of stem cells grafted in the infarcted myocardium in rats. Radionuclide imaging such as single photon emission computed tomography (SPECT) or positron emission tomography (PET) inherently has high sensitivity and is suitable for tracking of labeled stem cells, while high-resolution MRI is able to provide detailed anatomical and functional information of myocardium. Thus, coregistration of PET or SPECT images with MRI will map the location and distribution of stem cells on detailed myocardium structures. To validate this coregistration method, SPECT data were simulated by using a Monte Carlo-based projector that modeled the pinhole-imaging physics assuming nonzero diameter and photon penetration at the edge. Translational and rotational errors of the coregistration were examined with respect to various SPECT activities, and they are on average about 0.50 mm and 0.82 degrees , respectively. Only the rotational error is dependent on activity of SPECT data. Stem cells were labeled with (111)Indium oxyquinoline and grafted in the ischemic myocardium of a rat model. Dual-tracer small-animal SPECT images were acquired, which allowed simultaneous detection of (111)In-labeled stem cells and of [(99m)Tc]sestamibi to assess myocardial perfusion deficit. The same animals were subjected to cardiac MRI. A mutual-information-based coregistration method was then applied to the SPECT and MRIs. By coregistration, the (111)In signal from labeled cells was mapped into the akinetic region identified on cine MRIs; the regional perfusion deficit on the SPECT images also coincided with the akinetic region on the MR image.

  17. Variable uptake feature of focal nodular hyperplasia in Tc-99m phytate hepatic scintigraphy/single-photon emission computed tomography-A parametric analysis.

    PubMed

    Hsu, Yu-Ling; Chen, Yu-Wen; Lin, Chia-Yang; Lai, Yun-Chang; Chen, Shinn-Cherng; Lin, Zu-Yau

    2015-12-01

    Tc-99m phytate hepatic scintigraphy remains the standard method for evaluating the functional features of Kupffer cells. In this study, we demonstrate the variable uptake feature of focal nodular hyperplasia (FNH) in Tc-99m phytate scintigraphy. We reviewed all patients who underwent Tc-99m phytate hepatic scintigraphy between 2008 and 2012 in Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. Cases with FNH were diagnosed on the basis of pathology or at least one or more prior imaging with a periodic clinical follow-up. All patients received a standard protocol of dynamic flow study and planar and Tc-99m phytate single-photon emission computed tomography (E. CAM; Siemens). The correlation of variable nodular radioactivity with parameters such as tumor size and localization was analyzed. In total, 15 lesions of 14 patients in the clinic were diagnosed as FNH. The tumor size was approximately 2.9-7.4 cm (mean size 4.6 cm). Four lesions were larger than 5 cm. The major anatomic distribution was in the right hepatic lobe (10 lesions), particularly in the superior segments (7 lesions). Tc-99m phytate single-photon emission computed tomography imaging for determining the functional features of Kupffer cells included cool/cold (8 lesions), isoradioactive/warm (6 lesions), and hot (1 lesion) patterns of uptake. We did not observe any statistically significant correlation between variable nodular radioactivity and tumor size (p=0.68) or localization (p=0.04). Herein, we demonstrate the variable uptake feature of FNH in Tc-99m phytate scintigraphy. In small FNH tumors (< 5 cm), increased or equal uptake still provided specificity for the differential diagnosis of hepatic solid tumors.

  18. Lifetime Reduction and Enhanced Emission of Single Photon Color Centers in Nanodiamond via Surrounding Refractive Index Modification

    PubMed Central

    Khalid, Asma; Chung, Kelvin; Rajasekharan, Ranjith; Lau, Desmond W.M.; Karle, Timothy J.; Gibson, Brant C.; Tomljenovic-Hanic, Snjezana

    2015-01-01

    The negatively-charged nitrogen vacancy (NV−) center in diamond is of great interest for quantum information processing and quantum key distribution applications due to its highly desirable long coherence times at room temperature. One of the challenges for their use in these applications involves the requirement to further optimize the lifetime and emission properties of the centers. Our results demonstrate the reduction of the lifetime of NV− centers, and hence an increase in the emission rate, achieved by modifying the refractive index of the environment surrounding the nanodiamond (ND). By coating the NDs in a polymer film, experimental results and numerical calculations show an average of 63% reduction in the lifetime and an average enhancement in the emission rate by a factor of 1.6. This strategy is also applicable for emitters other than diamond color centers where the particle refractive index is greater than the refractive index of the surrounding media. PMID:26109500

  19. 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.

  20. Design and development of compact multiphoton microscopes

    NASA Astrophysics Data System (ADS)

    Mehravar, SeyedSoroush

    A compact multi-photon microscope (MPM) was designed and developed with the use of low-cost mode-locked fiber lasers operating at 1040nm and 1560nm. The MPM was assembled in-house and the system aberration was investigated using the optical design software: Zemax. A novel characterization methodology based on 'nonlinear knife-edge' technique was also introduced to measure the axial, lateral resolution, and the field curvature of the multi-photon microscope's image plane. The field curvature was then post-corrected using data processing in MATLAB. A customized laser scanning software based on LabVIEW was developed for data acquisition, image display and controlling peripheral electronics. Finally, different modalities of multi-photon excitation such as second- and third harmonic generation, two- and three-photon fluorescence were utilized to study a wide variety of samples from cancerous cells to 2D-layered materials.