Picosecond rotationally resolved stimulated emission pumping spectroscopy of nitric oxide

International Nuclear Information System (INIS)

Tanjaroon, Chakree; Reeve, Scott W.; Ford, Alan; Murry, W. Dean; Lyon, Kevin; Yount, Bret; Britton, Dan; Burns, William A.; Allen, Susan D.; Bruce Johnson, J.

2012-01-01

Highlights: ► Stimulated emission pumping for nitric oxide was studied using picosecond lasers. ► Weak and tightly focused pulses provide sufficient energy for population transfer. ► Selective excitation at the bandhead yields strong fluorescence depletion signals. ► We observe 19% population transfer to v″ = 2 of the X 2 Π 1/2 ground electronic state. - Abstract: Stimulated emission pumping (SEP) experiments were performed on the nitric oxide molecule in a flow cell environment using lasers with pulse widths of 17–25 ps. A lambda excitation scheme, or ‘‘pump–dump” arrangement, was employed with the pump laser tuned to the T 00 vibronic band origin (λ pump =226.35(1)nm) of the A 2 Σ + (v′ = 0, J′) ← X 2 Π 1/2 (v″ = 0, J″) and the dump laser scanned from 246–248 nm within the A 2 Σ + (v′ = 0, J′) → X 2 Π 1/2 (v″ = 2, J″) transition. The rotationally resolved SEP spectra were measured by observing the total fluorescence within the A 2 Σ + (v′ = 0, J′) → X 2 Π 1/2 (v″ = 1, J″) transition between 235 nm and 237.2 nm while scanning the dump laser wavelengths. Multiple rotational states were excited due to the broad laser bandwidth. Measurements showed that the resolved rotational structure depended on the energy and bandwidth of the applied pump and dump laser pulses. Analysis of the observed fluorescence depletion signals yielded an average percent fluorescence depletion of about 19% when λ pump =226.35(1)nm and λ dump =247.91(1)nm. This value reflects the percent transfer of the NO population from the A 2 Σ + (V′ = 0, J′) excited electronic state to the X 2 Π 1/2 (v″ = 2, J″) ground electronic state. The maximum expected depletion is 50% in the limit of dump saturation. Selective excitation of NO at the bandhead provides good spectral discrimination from the background emission and noise and unambiguously confirms the identity of the emitter.

Induced absorption and stimulated emission in a driven two-level atom

International Nuclear Information System (INIS)

Mavroyannis, C.

1992-01-01

We have considered the induced processes that occur in a driven two-level atom, where a laser photon is absorbed and emitted by the ground and by the excited states of the atom, respectively. In the low-intensity limit of the laser field, the induced spectra arising when a laser photon is absorbed by the ground state of the atom consist of two peaks describing induced absorption and stimulated-emission processes, respectively, where the former prevails over the latter. Asymmetry of the spectral lines occurs at off-resonance and its extent depends on the detuning of the laser field. The physical. process where a laser photon is emitted by the excited state is the reverse of that arising from the absorption of a laser photon by the ground state of the atom. The former differs from the latter in that the emission of a laser photon by the excited state occurs in the low frequency regime and that the stimulated-emission process prevails over that of the induced absorption. In this case, amplification of ultrashort pulses is likely to occur without the need of population inversion between the optical transitions. The computed spectra are graphically presented and discussed. (author)

single photon emission tomography and positron emission tomography - Part 1 (October 2012), Part 2 (October 2010)

International Nuclear Information System (INIS)

Buvat, Irene

2010-10-01

The objective of this lecture is to present the single photon emission computed tomography (SPECT) and the positron emission tomography (PET) imaging techniques. Part 1 Content: 1 - Introduction: anatomic, functional and molecular imaging; 2 - Radiotracers: chemical and physical constraints, gamma photon emitters, positon emitters, radioisotopes production, emitters type and imaging techniques; 3 - Gamma cameras; 4 - Quantification in emission tomography: attenuation, scattering, un-stationary spatial resolution; 5 - Synthesis and conclusion. Part 2 content: 1 - Positon emitters; 2 - Positons detection: Coincidence detection (electronic collimation, PET detectors with gamma cameras, dedicated PET detectors, spectrometry); PET detectors type; time-of-flight PET; 2D PET; 3D PET; 3 - Quantification in emission tomography: detected events, attenuation, scattering, fortuitous coincidences, standardisation; 4 - Common SPECT and PET problems: partial volume effect, movement, tomographic reconstruction, calibration, dead time; 5 - Synthesis and conclusion

Conversion of the luminescence of laser dyes in opal matrices to stimulated emission

International Nuclear Information System (INIS)

Alimov, O K; Basiev, T T; Orlovskii, Yu V; Osiko, V V; Samoilovich, M I

2008-01-01

The luminescence and laser characteristics of a synthetic opal matrix filled with organic dyes are studied upon excitation by nanosecond laser pulses. The appearance of stimulated emission in a partially ordered scattering medium is investigated. It is shown that if the luminescence spectrum of a dye (oxazine-17) is located far outside the photonic bandgap of the opal matrix, stimulated emission along a preferential direction in the (111) plane is observed when pumping exceeds a threshold even without an external optical cavity. The stimulated emission spectrum is considerably narrower than the luminescence spectrum and consists of several narrow lines located within the dye luminescence band. If the luminescence spectrum of a dye (rhodamine 6G) overlaps with the photonic bandgap of the opal matrix, a different picture is observed. The loss of radiation in the matrix leads to the red shift of the luminescence spectrum, while the stimulated emission as in the case of oxazine-17 lies is observed within the luminescence band. (active media, lasers, and amplifiers)

Two-photon resonant, stimulated processes in krypton and xenon

International Nuclear Information System (INIS)

Miller, J.C.

1988-11-01

Both on-axis and conical emissions have been observed following two-photon pumping of the 5p states of krypton and the 6p', 7p, 8p, and 4f states of xenon. In the former case, coherent emissions from the 5p states to the 5s are observed, and in the latter case, many p→s, d→p, and f→d cascade emissions are observed. By analogy to the well-studied alkali and alkaline earth examples, the emissions are discussed in terms of amplified spontaneous emission (ASE), stimulated hyper-Raman scattering, and parametric four-wave mixing. The physical processes responsible for the conical emission and for intensity anomalies in the xenon p→s emissions are not understood at present. Interference effects due to coherent cancellation between competing excitation pathways may be occurring. 4 refs., 3 figs

Discovery of pulsed OH maser emission stimulated by a pulsar.

Science.gov (United States)

Weisberg, Joel M; Johnston, Simon; Koribalski, Bärbel; Stanimirovic, Snezana

2005-07-01

Stimulated emission of radiation has not been directly observed in astrophysical situations up to this time. Here we demonstrate that photons from pulsar B1641-45 stimulate pulses of excess 1720-megahertz line emission in an interstellar hydroxyl (OH) cloud. As this stimulated emission is driven by the pulsar, it varies on a few-millisecond time scale, which is orders of magnitude shorter than the quickest OH maser variations previously detected. Our 1612-megahertz spectra are inverted copies of the 1720-megahertz spectra. This "conjugate line" phenomenon enables us to constrain the properties of the interstellar OH line-producing gas. We also show that pulsar signals undergo significantly deeper OH absorption than do other background sources, which confirms earlier tentative findings that OH clouds are clumpier on small scales than are neutral hydrogen clouds.

Microscopic theory of cavity-enhanced single-photon emission from optical two-photon Raman processes

Science.gov (United States)

Breddermann, Dominik; Praschan, Tom; Heinze, Dirk; Binder, Rolf; Schumacher, Stefan

2018-03-01

We consider cavity-enhanced single-photon generation from stimulated two-photon Raman processes in three-level systems. We compare four fundamental system configurations, one Λ -, one V-, and two ladder (Ξ -) configurations. These can be realized as subsystems of a single quantum dot or of quantum-dot molecules. For a new microscopic understanding of the Raman process, we analyze the Heisenberg equation of motion applying the cluster-expansion scheme. Within this formalism an exact and rigorous definition of a cavity-enhanced Raman photon via its corresponding Raman correlation is possible. This definition for example enables us to systematically investigate the on-demand potential of Raman-transition-based single-photon sources. The four system arrangements can be divided into two subclasses, Λ -type and V-type, which exhibit strongly different Raman-emission characteristics and Raman-emission probabilities. Moreover, our approach reveals whether the Raman path generates a single photon or just induces destructive quantum interference with other excitation paths. Based on our findings and as a first application, we gain a more detailed understanding of experimental data from the literature. Our analysis and results are also transferable to the case of atomic three-level-resonator systems and can be extended to more complicated multilevel schemes.

Two-photon stimulated emission and pulse amplification

International Nuclear Information System (INIS)

Yuen, H.P.

1975-01-01

Threshold conditions are given for the sustained operation of standing-wave and long-pulse traveling-wave two-photon lasers. Pulse shortening in long-pulse two-photon amplification, a behavior absent in the one-photon case, is also demonstrated analytically. (U.S.)

Experimental assessment of fluorescence microscopy signal enhancement by stimulated emission

Science.gov (United States)

Dake, Fumihiro; Yazawa, Hiroki

2017-10-01

The quantity of photons generated during fluorescence microscopy is principally determined by the quantum yield of the fluorescence dyes and the optical power of the excitation beam. However, even though low quantum yields can produce poor images, it is challenging to tune this parameter, while increasing the power of the excitation beam often results in photodamage. Here, we propose the use of stimulated emission (SE) as a means of enhancing both the signal intensity and signal-to-noise ratio during confocal fluorescence microscopy. This work experimentally confirmed that both these factors can be enhanced by SE radiation, through generating a greater number of photons than are associated with the standard fluorescence signal. We also propose the concept of stimulated emission enhancing fluorescence (SEEF) microscopy, which employs both the SE and fluorescence signals, and demonstrate that the intensity of an SEEF signal is greater than those of the individual SE and fluorescence signals.

Physical injury stimulates aerobic methane emissions from terrestrial plants

Directory of Open Access Journals (Sweden)

Z.-P. Wang

2009-04-01

Full Text Available Physical injury is common in terrestrial plants as a result of grazing, harvesting, trampling, and extreme weather events. Previous studies demonstrated enhanced emission of non-microbial CH₄ under aerobic conditions from plant tissues when they were exposed to increasing UV radiation and temperature. Since physical injury is also a form of environmental stress, we sought to determine whether it would also affect CH₄ emissions from plants. Physical injury (cutting stimulated CH₄ emission from fresh twigs of Artemisia species under aerobic conditions. More cutting resulted in more CH₄ emissions. Hypoxia also enhanced CH₄ emission from both uncut and cut Artemisia frigida twigs. Physical injury typically results in cell wall degradation, which may either stimulate formation of reactive oxygen species (ROS or decrease scavenging of them. Increased ROS activity might explain increased CH₄ emission in response to physical injury and other forms of stress. There were significant differences in CH₄ emissions among 10 species of Artemisia, with some species emitting no detectable CH₄ under any circumstances. Consequently, CH₄ emissions may be species-dependent and therefore difficult to estimate in nature based on total plant biomass. Our results and those of previous studies suggest that a variety of environmental stresses stimulate CH₄ emission from a wide variety of plant species. Global change processes, including climate change, depletion of stratospheric ozone, increasing ground-level ozone, spread of plant pests, and land-use changes, could cause more stress in plants on a global scale, potentially stimulating more CH₄ emission globally.

Picosecond rotationally resolved stimulated emission pumping spectroscopy of nitric oxide

Science.gov (United States)

Tanjaroon, Chakree; Reeve, Scott W.; Ford, Alan; Murry, W. Dean; Lyon, Kevin; Yount, Bret; Britton, Dan; Burns, William A.; Allen, Susan D.; Bruce Johnson, J.

2012-01-01

Stimulated emission pumping (SEP) experiments were performed on the nitric oxide molecule in a flow cell environment using lasers with pulse widths of 17-25 ps. A lambda excitation scheme, or ''pump-dump" arrangement, was employed with the pump laser tuned to the T 00 vibronic band origin ( λ=226.35(1)nm) of the A2Σ+( v' = 0, J') ← X2Π1/2( v″ = 0, J″) and the dump laser scanned from 246-248 nm within the A2Σ+( v' = 0, J') → X2Π1/2( v″ = 2, J″) transition. The rotationally resolved SEP spectra were measured by observing the total fluorescence within the A2Σ+( v' = 0, J') → X2Π1/2( v″ = 1, J″) transition between 235 nm and 237.2 nm while scanning the dump laser wavelengths. Multiple rotational states were excited due to the broad laser bandwidth. Measurements showed that the resolved rotational structure depended on the energy and bandwidth of the applied pump and dump laser pulses. Analysis of the observed fluorescence depletion signals yielded an average percent fluorescence depletion of about 19% when λ=226.35(1)nm and λ=247.91(1)nm. This value reflects the percent transfer of the NO population from the A2Σ+( V' = 0, J') excited electronic state to the X2Π1/2( v″ = 2, J″) ground electronic state. The maximum expected depletion is 50% in the limit of dump saturation. Selective excitation of NO at the bandhead provides good spectral discrimination from the background emission and noise and unambiguously confirms the identity of the emitter.

Reliability of low-frequency auditory stimulation studies associated with technetium-99m hexamethylpropylene amine oxime single-photon emission tomography

Energy Technology Data Exchange (ETDEWEB)

Le Saco, Y.; Turzo, A.; Guias, B.; Morin, P.P. (Centre Hospitalier Universitaire, 29 - Brest (France). Dept. of Nuclear Medicine); Jezequel, J. (Centre Hospitalier Universitaire, 29 - Brest (France). Dept. of Otorhinolaryngology); Robier, A. (Centre Hospitalier Universitaire, 37 - Tours (France). Dept. of Otorhinolaryngology); Baulieu, J.L. (Centre Hospitalier Universitaire, 37 - Tours (France). Dept. of Nuclear Medicine)

1993-05-01

Development of auditory stimulation tests associated with single-photon emission tomography (SPET) shows evidence of variations in perfusion related to the stimuli. Three brain SPET examinations with technetium-99m hexamethylpropylene amine oxime were performed on eight right-handed adults with normal hearing, the first one without stimulation and the other two associated with a 500-Hz/30-dB stimulation of the right ear. Temporal regions of interest covering auditory areas, as well as parietal ones (internal control), were drawn on three successive coronal slices. A cortico-cerebellar index R was calculated, and the variation in activity was defined for each subject using the ratio R[sub poststimulation] - R[sub prestimulation]/R[sub prest]u[sub mulation]. A significant increase in the temporal cortex count occurred in all subjects. This increase was bilateral, except for one subject in whom it was not significant on the right side. This result recurred during the second stimulation study. Overall the response of the left temporal cortex was stronger, although the asymmetry was not significant. The asymmetry repeated itself after each stimulation. The perfursion response is globally reliable in our study. We must ascertainhow sensitive this test is with regard to deaf adults and adults with normal hearing before extending its use to children. (orig.).

Reliability of low-frequency auditory stimulation studies associated with technetium-99m hexamethylpropylene amine oxime single-photon emission tomography

International Nuclear Information System (INIS)

Le Saco, Y.; Turzo, A.; Guias, B.; Morin, P.P.; Jezequel, J.; Robier, A.; Baulieu, J.L.

1993-01-01

Development of auditory stimulation tests associated with single-photon emission tomography (SPET) shows evidence of variations in perfusion related to the stimuli. Three brain SPET examinations with technetium-99m hexamethylpropylene amine oxime were performed on eight right-handed adults with normal hearing, the first one without stimulation and the other two associated with a 500-Hz/30-dB stimulation of the right ear. Temporal regions of interest covering auditory areas, as well as parietal ones (internal control), were drawn on three successive coronal slices. A cortico-cerebellar index R was calculated, and the variation in activity was defined for each subject using the ratio R poststimulation - R prestimulation /R prest u mulation . A significant increase in the temporal cortex count occurred in all subjects. This increase was bilateral, except for one subject in whom it was not significant on the right side. This result recurred during the second stimulation study. Overall the response of the left temporal cortex was stronger, although the asymmetry was not significant. The asymmetry repeated itself after each stimulation. The perfursion response is globally reliable in our study. We must ascertainhow sensitive this test is with regard to deaf adults and adults with normal hearing before extending its use to children. (orig.)

Effect of greenhouse gas emissions on stratospheric ozone depletion

NARCIS (Netherlands)

Velders GJM; LLO

1997-01-01

The depletion of the ozone layer is caused mainly by the increase in emissions of chlorine- and bromine-containing compounds like CFCs, halons, carbon tetrachloride, methyl chloroform and methyl bromide. Emissions of greenhouse gases can affect the depletion of the ozone layer through atmospheric

Electron and photon emissions from gold nanoparticles irradiated by X-ray photons

Energy Technology Data Exchange (ETDEWEB)

Casta, R., E-mail: castaromain@gmail.com, E-mail: romain.casta@irsamc.ups-tlse.fr; Champeaux, J.-P.; Moretto-Capelle, P.; Sence, M.; Cafarelli, P. [Université de Toulouse, UPS, Laboratoire Collisions Agrégats Réactivité, IRSAMC, CNRS, UMR 5589 (France)

2015-01-15

In this paper, we develop a totally new probabilistic model for the electron and photon emission of gold nanoparticles irradiated by X-ray photons. This model allows direct applications to recent researches about the radiotherapy enhancement by gold nanoparticles in the context of cancer treatment. Our model uses, in a complete original way, simulated Auger cascade and stopping power to compute electron emission spectra, photon emission spectra and released energy inside the material of gold nanoparticles. It allows us to present new results about the electron and photon emission of gold nanoparticle irradiated by hard X-rays.

Measurement of L x-ray emission from elements in 64 ≤ Z ≤ 73 interval stimulated by 59.54 keV photons

International Nuclear Information System (INIS)

Baraldi, C; Casnati, E; Tartari, A; Singh, B

2005-01-01

Accurate measurements (mostly within 5%) of L α , L β and L γ x-ray emission cross sections were carried out on thick foils of elements lying in 64 ≤ Z ≤ 73 interval, stimulated by 59.54 keV photons. They can be of help as an overall reference to compare the theoretical and semi-empirical approaches by which the atomic parameters included in the expressions of L emission cross sections are evaluated. An appropriate extension of the expression linking the cross section to the counting rate measured in reflection geometry on thick targets makes it possible to overcome the difficulties arising from the width in energy of the L β and L γ groups and from the jump present in the attenuation coefficients of the target elements within the energy interval of their L γ emission lines

Stimulated emission within the exciplex band by plasmonic-nanostructured polymeric heterojunctions

Science.gov (United States)

Zhang, Xinping; Li, Hongwei; Wang, Yimeng; Liu, Feifei

2015-03-01

Organic heterojunctions have been extensively employed in the design of light-emitting diodes, photovoltaic devices, and thin-film field-effect transistors, which can be achieved by constructing a bilayer or a multi-layered thin-film deposition, or by blending two or more organic semiconductors with different charge-transport performances. Charge transfer excited states or exciplex may form on the heterointerfaces. Efficient light-emitting diodes have been demonstrated using exciplex emission. However, lasing or stimulated emission processes have not been observed with exciplex formation at organic heterojunctions. In this work, we demonstrate strong coherent interaction between photons and exciplex formation in the blends of poly-9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4-phenylenediamine (PFB) and poly-9,9'-dioctylfluorene-co-benzothiadiazole (F8BT), leading to transient stimulated exciplex emission. The responsible mechanisms involve plasmonic local-field enhancement and plasmonic feedback in a three-dimensional gold-nanoparticle matrix.Organic heterojunctions have been extensively employed in the design of light-emitting diodes, photovoltaic devices, and thin-film field-effect transistors, which can be achieved by constructing a bilayer or a multi-layered thin-film deposition, or by blending two or more organic semiconductors with different charge-transport performances. Charge transfer excited states or exciplex may form on the heterointerfaces. Efficient light-emitting diodes have been demonstrated using exciplex emission. However, lasing or stimulated emission processes have not been observed with exciplex formation at organic heterojunctions. In this work, we demonstrate strong coherent interaction between photons and exciplex formation in the blends of poly-9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4-phenylenediamine (PFB) and poly-9,9'-dioctylfluorene-co-benzothiadiazole (F8BT), leading to transient

Ultrafast photon counting applied to resonant scanning STED microscopy.

Science.gov (United States)

Wu, Xundong; Toro, Ligia; Stefani, Enrico; Wu, Yong

2015-01-01

To take full advantage of fast resonant scanning in super-resolution stimulated emission depletion (STED) microscopy, we have developed an ultrafast photon counting system based on a multigiga sample per second analogue-to-digital conversion chip that delivers an unprecedented 450 MHz pixel clock (2.2 ns pixel dwell time in each scan). The system achieves a large field of view (∼50 × 50 μm) with fast scanning that reduces photobleaching, and advances the time-gated continuous wave STED technology to the usage of resonant scanning with hardware-based time-gating. The assembled system provides superb signal-to-noise ratio and highly linear quantification of light that result in superior image quality. Also, the system design allows great flexibility in processing photon signals to further improve the dynamic range. In conclusion, we have constructed a frontier photon counting image acquisition system with ultrafast readout rate, excellent counting linearity, and with the capacity of realizing resonant-scanning continuous wave STED microscopy with online time-gated detection. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Cooling atoms with extraresonant stimulated emission below the Doppler limit

International Nuclear Information System (INIS)

Shevy, Y.

1989-01-01

The process of cooling atoms with radiation pressure is well understood in terms of absorption and spontaneous emission of fluorescence photons. This process imposes a lower limit on the minimum equilibrium temperature of laser cooled two level atoms of K b T = ℎΓ 21 /2 (the Doppler limit), where Γ 21 is the excited state decay rate to the ground state. At high laser intensity, it has been demonstrated that the stimulated emission process changes the sign of the force to a heating force at the red side of the atomic resonance and to a cooling force at blue detunings. Although this stimulated force is more efficient than the radiation pressure force, it has been generally accepted that this force cannot lead to lower equilibrium temperatures due to the large heating caused by diffusion of momentum at high intensity. These conclusions are valid only when the sole damping mechanism is the excited state decay to the ground state by spontaneous emission. However, when the atomic system is opened, i.e., is allowed to decay to other levels, or the dipole decay rate is altered by dephasing events, the stimulated force is dramatically modified. Under this conditions the stimulated force can occur at lower laser intensity and can even reverse sign to provide damping at the red side of resonance. These phenomena originate from extraresonances in the stimulated emission process between the two counterpropagating waves. These resonances appear as a dispersive feature in pump probe spectra (Two Wave Mixing) and are closely related to the extraresonances in four wave mixing studied originally by Bloembergen and co-workers. This paper establishes this connection and the potential of these phenomena for laser cooling. The implications of these results to the recently observed ultra-cold Na and Cs atoms are also discussed

Stimulated light emission in a dielectrically disordered composite porous matrix

Science.gov (United States)

Gross, E.; Künzner, N.; Diener, J.; Fujii, Minoru; Timoshenko, V. Yu.; Kovalev, D.

2005-06-01

We report on a medium exhibiting extremely efficient light scattering properties: a liquid network formed in a porous matrix. Liquid fragments confined in the solid matrix result in a random fluctuation of the dielectric function and act as scattering objects for photons. The optical scattering efficiency is defined by the filling factor of the liquid in the pores and its dielectric constant. The spectral dependence of the scattering length of photons indicates that the phenomenon is governed by a Mie-type scattering mechanism. The degree of the dielectric disorder of the medium, i.e. the level of opacity is tunable by the ambient vapor pressure of the dielectric substance. In the strongest scattering regime the scattering length of photons is found to be in the micrometer range. By incorporation of dye molecules in the voids of the porous layer a system exhibiting optical gain is realized. In the multiple scattering regime the optical path of diffusively propagating photons is enhanced and light amplification through stimulated emission occurs: a strong intensity enhancement of the dye emission accompanied by significant spectral narrowing is observed above the excitation threshold for a layer being in the opalescence state.

Stimulated Emission Computed Tomography (NSECT) images enhancement using a linear filter in the frequency domain

Energy Technology Data Exchange (ETDEWEB)

Viana, Rodrigo S.S.; Tardelli, Tiago C.; Yoriyaz, Helio, E-mail: hyoriyaz@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Jackowski, Marcel P., E-mail: mjack@ime.usp.b [University of Sao Paulo (USP), SP (Brazil). Dept. of Computer Science

2011-07-01

In recent years, a new technique for in vivo spectrographic imaging of stable isotopes was presented as Neutron Stimulated Emission Computed Tomography (NSECT). In this technique, a fast neutrons beam stimulates stable nuclei in a sample, which emit characteristic gamma radiation. The photon energy is unique and is used to identify the emitting nuclei. The emitted gamma energy spectra can be used for reconstruction of the target tissue image and for determination of the tissue elemental composition. Due to the stochastic nature of photon emission process by irradiated tissue, one of the most suitable algorithms for tomographic reconstruction is the Expectation-Maximization (E-M) algorithm, once on its formulation are considered simultaneously the probabilities of photons emission and detection. However, a disadvantage of this algorithm is the introduction of noise in the reconstructed image as the number of iterations increases. This increase can be caused either by features of the algorithm itself or by the low sampling rate of projections used for tomographic reconstruction. In this work, a linear filter in the frequency domain was used in order to improve the quality of the reconstructed images. (author)

Stimulated Emission Computed Tomography (NSECT) images enhancement using a linear filter in the frequency domain

International Nuclear Information System (INIS)

Viana, Rodrigo S.S.; Tardelli, Tiago C.; Yoriyaz, Helio; Jackowski, Marcel P.

2011-01-01

In recent years, a new technique for in vivo spectrographic imaging of stable isotopes was presented as Neutron Stimulated Emission Computed Tomography (NSECT). In this technique, a fast neutrons beam stimulates stable nuclei in a sample, which emit characteristic gamma radiation. The photon energy is unique and is used to identify the emitting nuclei. The emitted gamma energy spectra can be used for reconstruction of the target tissue image and for determination of the tissue elemental composition. Due to the stochastic nature of photon emission process by irradiated tissue, one of the most suitable algorithms for tomographic reconstruction is the Expectation-Maximization (E-M) algorithm, once on its formulation are considered simultaneously the probabilities of photons emission and detection. However, a disadvantage of this algorithm is the introduction of noise in the reconstructed image as the number of iterations increases. This increase can be caused either by features of the algorithm itself or by the low sampling rate of projections used for tomographic reconstruction. In this work, a linear filter in the frequency domain was used in order to improve the quality of the reconstructed images. (author)

Picosecond buildup and relaxation of intense stimulated emission in GaAs

International Nuclear Information System (INIS)

Ageeva, N. N.; Bronevoi, I. L.; Zabegaev, D. N.; Krivonosov, A. N.

2013-01-01

In support of the idea developed previously based on circumstantial evidence, we have found that stimulated emission emerges in GaAs and its intensity increases with a picosecond delay relative to the front of powerful picosecond optical pumping that produced a dense electron-hole plasma. The emission intensity relaxes with decreasing pumping with a characteristic time of ∼10 ps. We have derived the dependences of the delay time, the relaxation time, and the duration of the picosecond emission pulse on its photon energy. The estimates based on the fact that the relaxation of emission is determined by electron-hole plasma cooling correspond to the measured relaxation time.

Enhanced two-photon emission from a dressed biexciton

International Nuclear Information System (INIS)

Sánchez Muñoz, Carlos; Laussy, Fabrice P; Tejedor, Carlos; Valle, Elena del

2015-01-01

Radiative two-photon cascades from biexcitons in semiconductor quantum dots under resonant two-photon excitation are promising candidates for the generation of photon pairs. In this work, we propose a scheme to obtain two-photon emission that allows us to operate under very intense driving fields. This approach relies on the Purcell enhancement of two-photon virtual transitions between states of the biexciton dressed by the laser. The richness provided by the biexcitonic level structure allows to reach a variety of regimes, from antibunched and bunched photon pairs with polarization orthogonal to the driving field, to polarization entangled two-photon emission. This provides evidence that the general paradigm of two-photon emission from a ladder of dressed states can find interesting, particular implementations in a variety of systems. (paper)

Photon emission from massive projectile impacts on solids.

Science.gov (United States)

Fernandez-Lima, F A; Pinnick, V T; Della-Negra, S; Schweikert, E A

2011-01-01

First evidence of photon emission from individual impacts of massive gold projectiles on solids for a number of projectile-target combinations is reported. Photon emission from individual impacts of massive Au(n) (+q) (1 ≤ n ≤ 400; q = 1-4) projectiles with impact energies in the range of 28-136 keV occurs in less than 10 ns after the projectile impact. Experimental observations show an increase in the photon yield from individual impacts with the projectile size and velocity. Concurrently with the photon emission, electron emission from the impact area has been observed below the kinetic emission threshold and under unlikely conditions for potential electron emission. We interpret the puzzling electron emission and correlated luminescence observation as evidence of the electronic excitation resulting from the high-energy density deposited by massive cluster projectiles during the impact.

Optically stimulated exoelectron emission processes in quartz: comparison of experiment and theory

DEFF Research Database (Denmark)

Pagonis, V.; Ankjærgaard, Christina; Murray, A.S.

2009-01-01

Recent experiments have demonstrated that it is possible to measure optically stimulated exoelectron emission (OSE) signals simultaneously with optically stimulated luminescence (OSL) from quartz samples. These experiments provide valuable information on the charge movement in quartz grains. Two...... data yield a value of χ1.2 eV for the work function of quartz. The experimental temperature dependence of the OSE signals is interpreted on the basis of a photo-thermostimulated (PTSEE) process involving the main OSL trap at 320 °C; this process takes place with a thermal assistance energy estimated...... at W(0.29±0.02) eV. Good quantitative agreement is obtained between theory and experiment by assuming a thermal broadening of the thermal depletion factor for the OSL traps, described by a Gaussian distribution of energies....

Photon emission spectroscopy of ion-atom collisions

International Nuclear Information System (INIS)

Nystroem, B.

1995-10-01

Emission cross sections for the 1snp 1 P 1 -levels have been measured by photon emission spectroscopy for the collision systems He + + He at 10 keV and He 2+ + He at 10-35 keV. Photon spectra of Krypton (Kr VIII) and Xenon (Xe V - IX) have also been obtained using 10q keV beams of Kr q+ (q=7-9) and Xe q+ (q=5-9) colliding with Helium and Argon. The Lifetimes of 3p 2 P-levels in Na-like Nb are reported together with lifetime for the 3s3p 3 P 1 -level in Mg-like Ni, Kr, Y, Zr and Nb where this level has an intercombination transition to the ground state. 45 refs, 20 figs

Zn doped GaN for single-photon emission

Energy Technology Data Exchange (ETDEWEB)

Behrends, Arne; Ledig, Johannes; Al-Suleiman, Mohamed Aid Mansur; Bakin, Andrey; Waag, Andreas [Institute of Semiconductor Technology, University of Technology Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig (Germany); Peters, Silke; Racu, Ana Maria; Schmunk, Waldemar; Hofer, Helmut; Kueck, Stefan [Physikalisch Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig (Germany)

2012-03-15

In this work we report on the optical investigation of Zn doped GaN films fabricated by metal organic chemical vapor deposition. The samples show bright emission in the blue spectral range around 2.9 eV when Si codoping is provided. This emission is suggested to be used for single-photon emission, thus the density of the Zn-Si pairs was drastically reduced leading to a decrease of the blue luminescence. For electrically excited single-photon sources these Zn-Si pairs have to be incorporated into LEDs, therefore we fabricated GaN-based nano-LEDs which show electroluminescence at 430 nm (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Photon emission spectroscopy of ion-atom collisions

Energy Technology Data Exchange (ETDEWEB)

Nystroem, B

1995-10-01

Emission cross sections for the 1snp{sup 1}P{sub 1}-levels have been measured by photon emission spectroscopy for the collision systems He{sup +} + He at 10 keV and He{sup 2+} + He at 10-35 keV. Photon spectra of Krypton (Kr VIII) and Xenon (Xe V - IX) have also been obtained using 10q keV beams of Kr{sup q+} (q=7-9) and Xe{sup q+} (q=5-9) colliding with Helium and Argon. The Lifetimes of 3p{sup 2}P-levels in Na-like Nb are reported together with lifetime for the 3s3p{sup 3}P{sub 1}-level in Mg-like Ni, Kr, Y, Zr and Nb where this level has an intercombination transition to the ground state. 45 refs, 20 figs.

Super-resolution imaging of ciliary microdomains in isolated olfactory sensory neurons using a custom two-color stimulated emission depletion microscope

Science.gov (United States)

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.

Controlling spontaneous emission of light by photonic crystals

DEFF Research Database (Denmark)

Lodahl, Peter

2005-01-01

Photonic bandgap crystals were proposed almost two decades ago as a unique tool for controlling propagation and emission of light. Since then the research field of photonic crystals has exploded and many beautiful demonstrations of the use of photonic crystals and fibers for molding light...... propagation have appeared that hold great promises for integrated optics. These major achievements solidly demonstrate the ability to control propagation of light. In contrast, an experimental demonstration of the use of photonic crystals for timing the emission of light has so far lacked. In a recent...... publication in Nature, we have demonstrated experimentally that both the direction and time of spontaneous emission can be controlled, thereby confirming the original proposal by Eli Yablonovich that founded the field of photonic crystals. We believe that this work opens new opportunities for solid...

Neutron stimulated emission computed tomography: Background corrections

International Nuclear Information System (INIS)

Floyd, Carey E.; Sharma, Amy C.; Bender, Janelle E.; Kapadia, Anuj J.; Xia, Jessie Q.; Harrawood, Brian P.; Tourassi, Georgia D.; Lo, Joseph Y.; Kiser, Matthew R.; Crowell, Alexander S.; Pedroni, Ronald S.; Macri, Robert A.; Tajima, Shigeyuki; Howell, Calvin R.

2007-01-01

Neutron stimulated emission computed tomography (NSECT) is an imaging technique that provides an in-vivo tomographic spectroscopic image of the distribution of elements in a body. To achieve this, a neutron beam illuminates the body. Nuclei in the body along the path of the beam are stimulated by inelastic scattering of the neutrons in the beam and emit characteristic gamma photons whose unique energy identifies the element. The emitted gammas are collected in a spectrometer and form a projection intensity for each spectral line at the projection orientation of the neutron beam. Rotating and translating either the body or the beam will allow a tomographic projection set to be acquired. Images are reconstructed to represent the spatial distribution of elements in the body. Critical to this process is the appropriate removal of background gamma events from the spectrum. Here we demonstrate the equivalence of two background correction techniques and discuss the appropriate application of each

Ozone Depletion in Tropospheric Volcanic Plumes: From Halogen-Poor to Halogen-Rich Emissions

Directory of Open Access Journals (Sweden)

Tjarda J. Roberts

2018-02-01

Full Text Available Volcanic halogen emissions to the troposphere undergo a rapid plume chemistry that destroys ozone. Quantifying the impact of volcanic halogens on tropospheric ozone is challenging, only a few observations exist. This study presents measurements of ozone in volcanic plumes from Kīlauea (HI, USA, a low halogen emitter. The results are combined with published data from high halogen emitters (Mt Etna, Italy; Mt Redoubt, AK, USA to identify controls on plume processes. Ozone was measured during periods of relatively sustained Kīlauea plume exposure, using an Aeroqual instrument deployed alongside Multi-Gas SO2 and H2S sensors. Interferences were accounted for in data post-processing. The volcanic H2S/SO2 molar ratio was quantified as 0.03. At Halema‘uma‘u crater-rim, ozone was close to ambient in the emission plume (at 10 ppmv SO2. Measurements in grounding plume (at 5 ppmv SO2 about 10 km downwind of Pu‘u ‘Ō‘ō showed just slight ozone depletion. These Kīlauea observations contrast with substantial ozone depletion reported at Mt Etna and Mt Redoubt. Analysis of the combined data from these three volcanoes identifies the emitted Br/S as a strong but non-linear control on the rate of ozone depletion. Model simulations of the volcanic plume chemistry highlight that the proportion of HBr converted into reactive bromine is a key control on the efficiency of ozone depletion. This underlines the importance of chemistry in the very near-source plume on the fate and atmospheric impacts of volcanic emissions to the troposphere.

Deciphering excited state evolution in halorhodopsin with stimulated emission pumping.

Science.gov (United States)

Bismuth, Oshrat; Komm, Pavel; Friedman, Noga; Eliash, Tamar; Sheves, Mordechai; Ruhman, Sanford

2010-03-04

The primary photochemical dynamics of Hb. pharaonis Halorhodopsin (pHR) are investigated by femtosecond visible pump-near IR dump-hyperspectral probe spectroscopy. The efficiency of excited state depletion is deduced from transient changes in absorption, recorded with and without stimulated emission pumping (SEP), as a function of the dump delay. The concomitant reduction of photocycle population is assessed by probing the "K" intermediate difference spectrum. Results show that the cross section for stimulating emission is nearly constant throughout the fluorescent state lifetime. Probing "K" demonstrates that dumping produces a proportionate reduction in photocycle yields. We conclude that, despite its nonexponential internal conversion (IC) kinetics, the fluorescent state in pHR constitutes a single intermediate in the photocycle. This contrasts with conclusions drawn from the study of primary events in the related chloride pump from Hb. salinarum (sHR), believed to produce the "K" intermediate from a distinct short-lived subpopulation in the excited state. Our discoveries concerning internal conversion dynamics in pHR are discussed in light of recent expectations for similar excited state dynamics in both proteins.

Mycobacterial antigens stimulate rheumatoid mononuclear cells to cartilage proteoglycan depletion

NARCIS (Netherlands)

Wilbrink, B.; Bijlsma, J. W.; Huber-Bruning, O.; van Roy, J. L.; den Otter, W.; van Eden, W.

1990-01-01

In a coculture with porcine articular cartilage explants unstimulated blood mononuclear cells (BMC) from patients with rheumatoid arthritis (RA), but not from healthy controls, induced proteoglycan depletion of dead cartilage. Specific stimulation of the RA BMC with Mycobacterium tuberculosis (MT),

Numerical Investigation into CO Emission, O Depletion, and Thermal Decomposition in a Reacting Slab

Directory of Open Access Journals (Sweden)

O. D. Makinde

2011-01-01

Full Text Available The emission of carbon dioxide (CO2 is closely associated with oxygen (O2 depletion, and thermal decomposition in a reacting stockpile of combustible materials like fossil fuels (e.g., coal, oil, and natural gas. Moreover, it is understood that proper assessment of the emission levels provides a crucial reference point for other assessment tools like climate change indicators and mitigation strategies. In this paper, a nonlinear mathematical model for estimating the CO2 emission, O2 depletion, and thermal stability of a reacting slab is presented and tackled numerically using a semi-implicit finite-difference scheme. It is assumed that the slab surface is subjected to a symmetrical convective heat and mass exchange with the ambient. Both numerical and graphical results are presented and discussed quantitatively with respect to various parameters embedded in the problem.

Towards Quantum Experiments with Human Eyes as Detectors Based on Cloning via Stimulated Emission

Science.gov (United States)

Sekatski, Pavel; Brunner, Nicolas; Branciard, Cyril; Gisin, Nicolas; Simon, Christoph

2009-09-01

We show theoretically that a large Bell inequality violation can be obtained with human eyes as detectors, in a “micro-macro” experiment where one photon from an entangled pair is greatly amplified via stimulated emission. The violation is robust under photon loss. This leads to an apparent paradox, which we resolve by noting that the violation proves the existence of entanglement before the amplification. The same is true for the micro-macro experiments performed so far with conventional detectors. However, we also prove that there is genuine micro-macro entanglement even for high loss.

Search for two-photon emission from 2S states of low-Z muonic atoms

International Nuclear Information System (INIS)

Carter, A.L.; Hincks, E.P.; Cox, C.R.; Dodson, G.W.; Eckhause, M.; Kane, J.R.; Rushton, A.M.; Siegel, R.T.; Welsh, R.E.; Hargrove, C.K.; Mes, H.; Dixit, M.S.; National Research Council of Canada, Ottawa, Ontario)

1983-01-01

A search for two-photon emission from 2S states of low-Z muonic atoms has been made. Intrinsic Ge detectors were positioned around target of Li, Be, B, or their hydrides, or a vessel containing B 2 H 6 , H 2 , or O 2 . Upper limits on the fraction of stopping muons which formed metastable 2S states range from approx.= 10 - 3 to 10 - 5 . (orig.)

Search for two-photon emission from 2S states of low-Z muonic atoms

Energy Technology Data Exchange (ETDEWEB)

Carter, A.L.; Hincks, E.P. (Carleton Univ., Ottawa, Ontario (Canada). Dept. of Physics); Cox, C.R.; Dodson, G.W.; Eckhause, M.; Kane, J.R.; Rushton, A.M.; Siegel, R.T.; Welsh, R.E. (College of William and Mary, Williamsburg, VA (USA). Dept. of Physics); Hargrove, C.K.

1983-05-12

A search for two-photon emission from 2S states of low-Z muonic atoms has been made. Intrinsic Ge detectors were positioned around target of Li, Be, B, or their hydrides, or a vessel containing B/sub 2/H/sub 6/, H/sub 2/, or O/sub 2/. Upper limits on the fraction of stopping muons which formed metastable 2S states range from approximately = 10/sup -3/ to 10/sup -5/.

Photon enhanced thermionic emission

Science.gov (United States)

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.

Single-photon emission tomography and cerebral blood flow

International Nuclear Information System (INIS)

Celsis, P.; Chan, M.; Marc-Vergnes, J.P.; Sveinsdottir, E.; Goldman, T.G.; Henriksen, L.; Paulson, O.B.; Stokely, E.M.; Lassen, N.A.

1982-01-01

This paper illustrates the capabilities of single-photon emission tomography in imaging local cerebral blood flows in man. The results purport the conclusion that a fairly good improvement has been achieved when compared to stationary detectors and that single-photon emission tomography is a well-suited tool for studying cerebral hemodynamics, especially within the framework of clinical studies [fr

Cortical stimulation evokes abnormal responses in the dopamine-depleted rat basal ganglia.

Science.gov (United States)

Kita, Hitoshi; Kita, Takako

2011-07-13

The motor cortex (MC) sends massive projections to the basal ganglia. Motor disabilities in patients and animal models of Parkinson's disease (PD) may be caused by dopamine (DA)-depleted basal ganglia that abnormally process the information originating from MC. To study how DA depletion alters signal transfer in the basal ganglia, MC stimulation-induced (MC-induced) unitary responses were recorded from the basal ganglia of control and 6-hydroxydopamine-treated hemi-parkinsonian rats anesthetized with isoflurane. This report describes new findings about how DA depletion alters MC-induced responses. MC stimulation evokes an excitation in normally quiescent striatal (Str) neurons projecting to the globus pallidus external segment (GPe). After DA-depletion, the spontaneous firing of Str-GPe neurons increases, and MC stimulation evokes a shorter latency excitation followed by a long-lasting inhibition that was invisible under normal conditions. The increased firing activity and the newly exposed long inhibition generate tonic inhibition and a disfacilitation in GPe. The disfacilitation in GPe is then amplified in basal ganglia circuitry and generates a powerful long inhibition in the basal ganglia output nucleus, the globus pallidus internal segment. Intra-Str injections of a behaviorally effective dose of DA precursor l-3,4-dihydroxyphenylalanine effectively reversed these changes. These newly observed mechanisms also support the generation of pauses and burst activity commonly observed in the basal ganglia of parkinsonian subjects. These results suggest that the generation of abnormal response sequences in the basal ganglia contributes to the development of motor disabilities in PD and that intra-Str DA supplements effectively suppress abnormal signal transfer.

Acoustic and photon emissions during mechanical deformation of coloured alkali halide crystals

International Nuclear Information System (INIS)

Chandra, B.P.

1984-01-01

Acoustic and photon emissions take place in the elastic and plastic as well as the fracture region of x-irradiated KBr, KCl and NaCl crystals. The rate of photon emission is linear with the strain rate: however, the RMS value of the acoustic emission is proportional to the square root of the strain rate. The acoustic emission is maximum for x-irradiated NaCl crystals; however, the photon emission is maximum for x-irradiated KBr crystals. From the similarity between the acoustic emission and the photon emission, it seems that mobile dislocations are responsible for the acoustic emission in coloured alkali halide crystals. (author)

Coherent effects on two-photon correlation and directional emission of two two-level atoms

International Nuclear Information System (INIS)

Ooi, C. H. Raymond; Kim, Byung-Gyu; Lee, Hai-Woong

2007-01-01

Sub- and superradiant dynamics of spontaneously decaying atoms are manifestations of collective many-body systems. We study the internal dynamics and the radiation properties of two atoms in free space. Interesting results are obtained when the atoms are separated by less than half a wavelength of the atomic transition, where the dipole-dipole interaction gives rise to new coherent effects, such as (a) coherence between two intermediate collective states, (b) oscillations in the two-photon correlation G (2) , (c) emission of two photons by one atom, and (d) the loss of directional correlation. We compare the population dynamics during the two-photon emission process with the dynamics of single-photon emission in the cases of a Λ and a V scheme. We compute the temporal correlation and angular correlation of two successively emitted photons using the G (2) for different values of atomic separation. We find antibunching when the atomic separation is a quarter wavelength λ/4. Oscillations in the temporal correlation provide a useful feature for measuring subwavelength atomic separation. Strong directional correlation between two emitted photons is found for atomic separation larger than a wavelength. We also compare the directionality of a photon spontaneously emitted by the two atoms prepared in phased-symmetric and phased-antisymmetric entangled states vertical bar ±> k 0 =e ik 0 ·r 1 vertical bar a 1 ,b 2 >±e ik 0 ·r 2 vertical bar b 1 ,a 2 > by a laser pulse with wave vector k 0 . Photon emission is directionally suppressed along k 0 for the phased-antisymmetric state. The directionality ceases for interatomic distances less than λ/2

Absorption and emission properties of photonic crystals and metamaterials

International Nuclear Information System (INIS)

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.

Direct measurements of neutral density depletion by two-photon absorption laser-induced fluorescence spectroscopy

International Nuclear Information System (INIS)

Aanesland, A.; Liard, L.; Leray, G.; Jolly, J.; Chabert, P.

2007-01-01

The ground state density of xenon atoms has been measured by spatially resolved laser-induced fluorescence spectroscopy with two-photon excitation in the diffusion chamber of a magnetized Helicon plasma. This technique allows the authors to directly measure the relative variations of the xenon atom density without any assumptions. A significant neutral gas density depletion was measured in the core of the magnetized plasma, in agreement with previous theoretical and experimental works. It was also found that the neutral gas density was depleted near the radial walls

Studies in dosimetry using stimulated exoelectron emission

International Nuclear Information System (INIS)

Petel, Maurice.

1976-06-01

Some applications of the stimulated exoelectron emission in radiation dosimetry are discussed. The principles which govern the phenomenon are presented. The apparatus, in particular the counter, used to monitor the emission is discussed with reference to both optical and thermal stimulation. The correlation existing between thermoluminescence and thermally stimulated exoelectron emission were studied in both lithium fluoride and aluminium oxide. Furthermore, aluminium oxides from different sources were examined, and one of these, chosen to investigate the dosimetric properties of this material using both methods of stimulation [fr

EUV stimulated emission from MgO pumped by FEL pulses

Directory of Open Access Journals (Sweden)

Philippe Jonnard

2017-09-01

Full Text Available Stimulated emission is a fundamental process in nature that deserves to be investigated and understood in the extreme ultra-violet (EUV and x-ray regimes. Today, this is definitely possible through high energy density free electron laser (FEL beams. In this context, we give evidence for soft-x-ray stimulated emission from a magnesium oxide solid target pumped by EUV FEL pulses formed in the regime of travelling-wave amplified spontaneous emission in backward geometry. Our results combine two effects separately reported in previous works: emission in a privileged direction and existence of a material-dependent threshold for the stimulated emission. We develop a novel theoretical framework, based on coupled rate and transport equations taking into account the solid-density plasma state of the target. Our model accounts for both observed mechanisms that are the privileged direction for the stimulated emission of the Mg L2,3 characteristic emission and the pumping threshold.

Photons emission processes in electron scattering

International Nuclear Information System (INIS)

Soto Vargas, C.W.

1996-01-01

The investigations involving the scattering sections arising in virtual an real photon emission processes of electron and positron scattering by an atomic nucleus, have the need for thorough and complete calculations of the virtual photon spectrum and then introduce the distorted wave formulation, which is mathematically involved an numerically elaborated, but accessible to its use in experimental electron scattering facilities. (author) [es

An all-silicon laser by coupling between electronic localized states and defect states of photonic crystal

Energy Technology Data Exchange (ETDEWEB)

Huang Weiqi, E-mail: WQHuang2001@yahoo.com [Institute of Nanophotonic Physics, Key Laboratory of Photoelectron Technology and Application, Guizhou University, Guiyang 550025 (China); Huang Zhongmei; Miao Xinjiang; Cai Chenlan; Liu Jiaxin; Lue Quan [Institute of Nanophotonic Physics, Key Laboratory of Photoelectron Technology and Application, Guizhou University, Guiyang 550025 (China); Liu Shirong, E-mail: Shirong@yahoo.com [State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550003 (China); Qin Chaojian [State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550003 (China)

2012-01-15

In a nano-laser of Si quantum dots (QD), the smaller QD fabricated by nanosecond pulse laser can form the pumping level tuned by the quantum confinement (QC) effect. Coupling between the active centers formed by localized states of surface bonds and the two-dimensional (2D) photonic crystal is used to select model in the nano-laser. The experimental demonstration is reported in which the peaks of stimulated emission at about 600 nm and 700 nm were observed on the Si QD prepared in oxygen after annealing which improves the stimulated emission. It is interesting to make a comparison between the localized electronic states in gap due to defect formed by surface bonds and the localized photonic states in gap of photonic band due to defect of 2D photonic crystal.

Spontaneous and light-induced photon emission from intact brains of chick embryos

Institute of Scientific and Technical Information of China (English)

张锦珠; 于文斗; 孙彤

1997-01-01

Photon emission (PE) and light-induced photon emission(LPE) of intact brains isolated from chick embryos have been measured by using the single photon counting device. Experimental results showed that the intensi-ty level of photon emission was detected to be higher from intact brain than from the medium in which the brain was immerged during measuring, and the emission intensity was related to the developmental stages, the healthy situation of the measured embryos, and the freshness of isolated brains as well. After white light illumination, a short-life de-layed emission from intact brains was observed, and its relaxation behavior followed a hyperbolic rather than an expo-nential law. According to the hypothesis of biophoton emission originating from a delocalized coherent electromagnetic field and Frohlich’s idea of coherent long-range interactions in biological systems, discussions were made on the signifi-cance of photon emission in studying cell communication, biological regulation, living system’

Zero photon dissociation of CS2+ in intense ultrashort laser pulses

Science.gov (United States)

Severt, Travis; Betsch, K. J.; Zohrabi, M.; Ablikim, U.; Jochim, Bethany; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

2013-05-01

We measured the dissociation of a CS2+ molecular ion beam in intense laser pulses ( C+ + S+. We speculate that a pump-dump process occurs whereby the vibrational wavepacket in the electronic ground state of CS2+ is pumped into the electronic first excited state's continuum by a single photon during the laser pulse. Once this continuum vibrational wavepacket passes the potential barrier in the ground electronic potential, the emission of a second photon is stimulated by the same laser pulse, most likely when the wavepacket moves through the internuclear distance where the two electronic states are in resonance with the driving field. A comparison is made to ZPD and ATD in the isovalent CO2+ species. Curiously, ATD is the favored mechanism in CO2+. The underlying molecular structure and dynamics determining this preference will be discussed. Supported by Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Simulating three-dimensional nonthermal high-energy photon emission in colliding-wind binaries

Energy Technology Data Exchange (ETDEWEB)

Reitberger, K.; Kissmann, R.; Reimer, A.; Reimer, O., E-mail: klaus.reitberger@uibk.ac.at [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria)

2014-07-01

Massive stars in binary systems have long been regarded as potential sources of high-energy γ rays. The emission is principally thought to arise in the region where the stellar winds collide and accelerate relativistic particles which subsequently emit γ rays. On the basis of a three-dimensional distribution function of high-energy particles in the wind collision region—as obtained by a numerical hydrodynamics and particle transport model—we present the computation of the three-dimensional nonthermal photon emission for a given line of sight. Anisotropic inverse Compton emission is modeled using the target radiation field of both stars. Photons from relativistic bremsstrahlung and neutral pion decay are computed on the basis of local wind plasma densities. We also consider photon-photon opacity effects due to the dense radiation fields of the stars. Results are shown for different stellar separations of a given binary system comprising of a B star and a Wolf-Rayet star. The influence of orbital orientation with respect to the line of sight is also studied by using different orbital viewing angles. For the chosen electron-proton injection ratio of 10{sup –2}, we present the ensuing photon emission in terms of two-dimensional projections maps, spectral energy distributions, and integrated photon flux values in various energy bands. Here, we find a transition from hadron-dominated to lepton-dominated high-energy emission with increasing stellar separations. In addition, we confirm findings from previous analytic modeling that the spectral energy distribution varies significantly with orbital orientation.

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Single-photon emission computed tomography

International Nuclear Information System (INIS)

Budinger, T.F.

1986-01-01

Single photon tomography dates from the early 1960's when the idea of emission transverse section tomography was presented by Kuhl and Edwards. They used a rectilinear scanner and analogue back-projection methods to detect emissions from a series of sequential positions transverse to the cephaldcaudad axis of the body. This chapter presents an explanation of emission tomography by describing longitudinal and transverse section tomography. In principle all modes of tomography can be considered under the general topic of coded apertures wherein the code ranges from translation of a pinhole collimator to rotation of a parallel hole or focused collimator array

N2O emission from plant surfaces - light stimulated and a global phenomenon.

Science.gov (United States)

Mikkelsen, Teis; Bruhn, Dan; Ambus, Per

2017-04-01

Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2 h-1, mostly due to the UV component. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed. Literature: Mikkelsen TN, Bruhn D & Ambus P. (2016). Solar UV Irradiation-Induced Production of Greenhouse Gases from Plant Surfaces: From Leaf to Earth. Progress in Botany, DOI 10.1007/124_2016_10. Bruhn D, Albert KR, Mikkelsen TN & Ambus P. (2014). UV-induced N2O emission from plants. Atmospheric Environment 99, 206-214.

Future emission scenarios for chemicals that may deplete stratospheric ozone

International Nuclear Information System (INIS)

Hammitt, J.K; Camm, Frank; Mooz, W.E.; Wolf, K.A.; Bamezai, Anil; Connel, P.S.; Wuebbles, D.J.

1990-01-01

Scenarios are developed for long-term future emissions of seven of the most important manmade chemicals that may deplete ozone and the corresponding effect on stratospheric ozone concentrations is calculated using a one-dimensional atmospheric model. The scenarios are based on detailed analysis of the markets for products that use these chemicals and span a central 90% probability interval for the chemicals joint effect on calculated ozone abundance, assuming no additional regulations. (author). 22 refs., 2 figs., 5 tabs

Quantification in single photon emission computed tomography (SPECT)

International Nuclear Information System (INIS)

Buvat, Irene

2005-01-01

The objective of this lecture is to understand the possibilities and limitations of the quantitative analysis of single photon emission computed tomography (SPECT) images. It is also to identify the conditions to be fulfilled to obtain reliable quantitative measurements from images. Content: 1 - Introduction: Quantification in emission tomography - definition and challenges; quantification biasing phenomena; 2 - quantification in SPECT, problems and correction methods: Attenuation, scattering, un-stationary spatial resolution, partial volume effect, movement, tomographic reconstruction, calibration; 3 - Synthesis: actual quantification accuracy; 4 - Beyond the activity concentration measurement

Greenhouse gas impacts of declining hydrocarbon resource quality: Depletion, dynamics, and process emissions

Science.gov (United States)

Brandt, Adam Robert

This dissertation explores the environmental and economic impacts of the transition to hydrocarbon substitutes for conventional petroleum (SCPs). First, mathematical models of oil depletion are reviewed, including the Hubbert model, curve-fitting methods, simulation models, and economic models. The benefits and drawbacks of each method are outlined. I discuss the predictive value of the models and our ability to determine if one model type works best. I argue that forecasting oil depletion without also including substitution with SCPs results in unrealistic projections of future energy supply. I next use information theoretic techniques to test the Hubbert model of oil depletion against five other asymmetric and symmetric curve-fitting models using data from 139 oil producing regions. I also test the assumptions that production curves are symmetric and that production is more bell-shaped in larger regions. Results show that if symmetry is enforced, Gaussian production curves perform best, while if asymmetry is allowed, asymmetric exponential models prove most useful. I also find strong evidence for asymmetry: production declines are consistently less steep than inclines. In order to understand the impacts of oil depletion on GHG emissions, I developed the Regional Optimization Model for Emissions from Oil Substitutes (ROMEO). ROMEO is an economic optimization model of investment and production of fuels. Results indicate that incremental emissions (with demand held constant) from SCPs could be 5-20 GtC over the next 50 years. These results are sensitive to the endowment of conventional oil and not sensitive to a carbon tax. If demand can vary, total emissions could decline under a transition because the higher cost of SCPs lessens overall fuel consumption. Lastly, I study the energetic and environmental characteristics of the in situ conversion process, which utilizes electricity to generate liquid hydrocarbons from oil shale. I model the energy inputs and outputs

Thermodynamics of photon-enhanced thermionic emission solar cells

International Nuclear Information System (INIS)

Reck, Kasper; Hansen, Ole

2014-01-01

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

The High Energy Photons Emission from Solar Flares Observed by SZ2-XD

Science.gov (United States)

Wang, Huanyu; Li, Xinqiao; Ma, Yuqian; Zhang, Chengmo; Xu, Yupeng; Wang, Jingzhou; Chen, Guoming

The spectra and light curve of near a hundred Solar X-ray Flare events, which were observed by SZ2/XD in the energy band of 10-800 keV during 2001, have been investigated. The events covered from C to X-class flares, which are shown different characters of high energy photons emission. The results will be presented in this paper. The discussions will be made especially for 3 of the brightest X-class solar flares SF010402(X20),SF010406(X5.6) and SF010415 (X14.4, a GLE event).

Frequency dependence of coherently amplified two-photon emission from hydrogen molecules

Science.gov (United States)

Hara, Hideaki; Miyamoto, Yuki; Hiraki, Takahiro; Masuda, Takahiko; Sasao, Noboru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko

2017-12-01

We investigate how the efficiency of coherently amplified two-photon emission depends on the frequency of one of the two emitted photons, namely the signal photon. This is done over the wavelength range of 5.048-10.21 μ m by using the vibrational transition of parahydrogen. The efficiency increases with the frequency of the signal photon. Considering experimental errors, our results are consistent with the theoretical prediction for the present experimental conditions. This study is an experimental demonstration of the frequency dependence of coherently amplified two-photon emission, and also presents its potential as a light source.

Photon emission produced by Kr+ ions bombardment of Cr and Cr2O3 targets

International Nuclear Information System (INIS)

Boujlaidi, A. El; Hammoum, K.; Jadoual, L.; Jourdani, R.; Ait El Fqih, M.; Aouchiche, H.; Kaddouri, A.

2015-01-01

The sputter induced photon spectroscopy technique was used to study the luminescence spectra of the species sputtered from chromium powder and its oxide Cr 2 O 3 , during 5 keV Kr + ions bombardment in vacuum better than 10 −7 torr. The optical spectra recorded between 350 and 470 nm exhibit discrete lines which are attributed to neutral excited atoms of chromium (Cr I lines). The experiments are also performed under 10 −5 torr ultra pure oxygen partial pressure. The results demonstrate that the measured intensities of the emitted photons are always higher in the presence of oxygen and even higher than those obtained for Cr 2 O 3 target. In the presence of oxygen vapor we assume that an oxide film is formed on the chromium surface which is responsible of the increase of photon emission. This variation in the intensities is correctly explained in the model of electron transfer processes between the excited sputtered atom and the bombarded surface. This model suggests that the structure formed on the Cr surface in the case of oxygenated chromium is closer to that of Cr 2 O 3 oxide

Thermodynamics of photon-enhanced thermionic emission solar cells

DEFF Research Database (Denmark)

Reck, Kasper; Hansen, Ole

2014-01-01

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...

Students' Understanding of the Greenhouse Effect, the Societal Consequences of Reducing CO2 Emissions and the Problem of Ozone Layer Depletion.

Science.gov (United States)

Andersson, Bjorn; Wallin, Anita

2000-01-01

Contributes to the growing body of knowledge about students' conceptions and views of environmental and natural resource issues. Questions 9th and 12th grade Swedish students' understandings of the greenhouse effect, reduction of CO2 emissions, and the depletion of the ozone layer. Observes five models of the greenhouse effect that appear among…

Diagnosis of dementia with single photon emission computed tomography

International Nuclear Information System (INIS)

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

1987-01-01

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

Two-photon cooperative emission in the presence of athermal electromagnetic field

International Nuclear Information System (INIS)

Enaki, N.A.; Mihalache, D.

1997-01-01

The possibility of cooperative spontaneous two-photon emission of an extended radiators system and the influence of the external thermal electromagnetic field on the spontaneous emission rate, in such a system, are investigated. It is concluded that, in an external electromagnetic field, the two-photon cooperative emission rate increases significantly. The importance of this effect on the emission of gamma rays from inverted long-lived isomers triggered by X-ray thermal fields, is emphasized

An advanced technique of the search for the stimulated gamma-ray emission

International Nuclear Information System (INIS)

Strilchuk, N.V.; Kirischuk, V.I.

1999-01-01

An experiment which is not based on the assumption that the stimulating and stimulated photons are time-coincident, is proposed. The idea is to compare, for the source in the form of a long filament, the number of simple pulses, corresponding to the isomeric transition energy, counted in the axial direction with the number seen off-axis by the same detector. It is interesting that if the stimulating and stimulated photons are time-coincident, such techniques has essential advantages as well. (authors)

Non-scanning fiber-optic near-infrared beam led to two-photon optogenetic stimulation in-vivo.

Directory of Open Access Journals (Sweden)

Kamal R Dhakal

Full Text Available Stimulation of specific neurons expressing opsins in a targeted region to manipulate brain function has proved to be a powerful tool in neuroscience. However, the use of visible light for optogenetic stimulation is invasive due to low penetration depth and tissue damage owing to larger absorption and scattering. Here, we report, for the first time, in-depth non-scanning fiber-optic two-photon optogenetic stimulation (FO-TPOS of neurons in-vivo in transgenic mouse models. In order to optimize the deep-brain stimulation strategy, we characterized two-photon activation efficacy at different near-infrared laser parameters. The significantly-enhanced in-depth stimulation efficiency of FO-TPOS as compared to conventional single-photon beam was demonstrated both by experiments and Monte Carlo simulation. The non-scanning FO-TPOS technology will lead to better understanding of the in-vivo neural circuitry because this technology permits more precise and less invasive anatomical delivery of stimulation.

Ultraviolet Stimulated Emission from Sol-Gel Spin Coated ZnO Thin Films

Directory of Open Access Journals (Sweden)

Ahmed S. Razeen

2017-01-01

Full Text Available Low cost ultraviolet stimulated emission has been generated using optical excitation of ZnO thin films deposited by sol-gel spin coating on n+ As-doped 100 Si-substrate. The number of deposited layers and the heat treatment have been investigated to obtain a film that can generate stimulated emission under optical excitation. The optimum condition for preparation of the film has been presented. X-ray diffraction and scanning electron microscope have been used for structural and morphological investigations. Input-output intensity dependence and spectral width, peak emission wavelength, and the quantum efficiency versus the pump intensity have been presented. A quantum efficiency of about 24.2% has been reported, a power exponent higher than 8 has been obtained in input-output intensity dependence, and a threshold of about 23 Mw/cm2 has been evaluated for the samples. The mechanism by which stimulated emission occurs has been discussed. The results show that sol-gel spin coating is a promising method for generating ultraviolet stimulated emission from ZnO thin films.

Excitation enhancement and extraction enhancement with photonic crystals

Science.gov (United States)

Shapira, Ofer; Soljacic, Marin; Zhen, Bo; Chua, Song-Liang; Lee, Jeongwon; Joannopoulos, John

2015-03-03

Disclosed herein is a system for stimulating emission from at least one an emitter, such as a quantum dot or organic molecule, on the surface of a photonic crystal comprising a patterned dielectric substrate. Embodiments of this system include a laser or other source that illuminates the emitter and the photonic crystal, which is characterized by an energy band structure exhibiting a Fano resonance, from a first angle so as to stimulate the emission from the emitter at a second angle. The coupling between the photonic crystal and the emitter may result in spectral and angular enhancement of the emission through excitation and extraction enhancement. These enhancement mechanisms also reduce the emitter's lasing threshold. For instance, these enhancement mechanisms enable lasing of a 100 nm thick layer of diluted organic molecules solution with reduced threshold intensity. This reduction in lasing threshold enables more efficient organic light emitting devices and more sensitive molecular sensing.

Room-Temperature Single-Photon Emission from Micrometer-Long Air-Suspended Carbon Nanotubes

Science.gov (United States)

Ishii, A.; Uda, T.; Kato, Y. K.

2017-11-01

Statistics of photons emitted by mobile excitons in individual carbon nanotubes are investigated. Photoluminescence spectroscopy is used to identify the chiralities and suspended lengths of air-suspended nanotubes, and photon-correlation measurements are performed at room temperature on telecommunication-wavelength nanotube emission with a Hanbury-Brown-Twiss setup. We obtain zero-delay second-order correlation g(2 )(0 ) less than 0.5, indicating single-photon generation. Excitation power dependence of the photon antibunching characteristics is examined for nanotubes with various chiralities and suspended lengths, where we find that the minimum value of g(2 )(0 ) is obtained at the lowest power. The influence of exciton diffusion and end quenching is studied by Monte Carlo simulations, and we derive an analytical expression for the minimum value of g(2 )(0 ). Our results indicate that mobile excitons in micrometer-long nanotubes can in principle produce high-purity single photons, leading to new design strategies for quantum photon sources.

Development of uncoupling between D1- and D2-mediated motor behavior in rats depleted of dopamine as neonates.

Science.gov (United States)

Byrnes, E M; Bruno, J P

1994-09-01

The D1- and D2-mediation of stimulated motor behavior was studied in pups (Days 10-11) and weanlings (Days 20-21) that had been depleted of dopamine (DA) on postnatal Day 3. Administration of the D1-like agonist SKF 38393 (30.0 mg/kg) or the D2-like agonist quinpirole (3.0 mg/kg) increased the incidence of sniffing and locomotion in intact and DA-depleted animals tested at either age. However, the ability of selective DA antagonists to reduce these stimulated responses interacted with both the depletion and the age at the time of testing. When tested as pups, both the D1 antagonist SCH 23390 (0.2 or 0.4 mg/kg) and the D2 antagonist clebopride (10.0 mg/kg) suppressed the behaviors induced by either class of DA agonist. When tested as weanlings, intact animals exhibited the profile of pups (i.e., either antagonist blocked each agonist). In DA-depleted weanlings, however, only the D1 antagonist blocked the D1 agonist-induced responses and only the D2 antagonist blocked the D2 agonist-induced responses. These data demonstrate that the interactions between D1 and D2 receptors in the expression of stimulated motor behaviors are altered following DA depletions in neonates. Moreover, this change in receptor function occurs sometime between 7 and 13 days after the DA depletion.

Effect of composition on the spontaneous emission probabilities, stimulated emission cross-sections and local environment of Tm{sup 3+} in TeO{sub 2}-WO{sub 3} glass

Energy Technology Data Exchange (ETDEWEB)

Oezen, G. E-mail: gozenl@itu.edu.tr; Aydinli, A.; Cenk, S.; Sennaroglu, A

2003-04-01

Effect of composition on the structure, spontaneous and stimulated emission probabilities of various 1.0 mol% Tm{sub 2}O{sub 3} doped (1-x)TeO{sub 2}+(x)WO{sub 3} glasses were investigated using Raman spectroscopy, ultraviolet-visible-near-infrared (UV/VIS/NIR) absorption and luminescence measurements. Absorption measurements in the UV/VIS/NIR region were used to determine spontaneous emission probabilities for the 4f-4f transitions of Tm{sup 3+} ions. Six absorption bands corresponding to the absorption of the {sup 1}G{sub 4}, {sup 3}F{sub 2}, {sup 3}F{sub 3} and {sup 3}F{sub 4}, {sup 3}H{sub 5} and {sup 3}H{sub 4} levels from the {sup 3}H{sub 6} ground level were observed. Integrated absorption cross-section of each band except that of {sup 3}H{sub 5} level was found to vary with the glass composition. Luminescence spectra of the samples were measured upon 457.9 nm excitation. Three emission bands centered at 476 nm ({sup 1}G{sub 4}{yields}{sup 3}H{sub 6} transition), 651 nm ({sup 1}G{sub 4}{yields}{sup 3}H{sub 4} transition) and 800 nm ({sup 1}G{sub 4}{yields}{sup 3}H{sub 5} transition) were observed. Spontaneous emission cross-sections together with the luminescence spectra measured upon 457.9 nm excitation were used to determine the stimulated emission cross-sections of these emissions. The effect of glass composition on the Judd-Ofelt parameters and therefore on the spontaneous and the stimulated emission cross-sections for the metastable levels of Tm{sup 3+} ions were discussed in detail. The effect of temperature on the stimulated emission cross-sections for the emissions observed upon 457.9 nm excitation was also discussed.

Room-temperature light-emission from Ge quantum dots in photonic crystals

Energy Technology Data Exchange (ETDEWEB)

Xia Jinsong [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)], E-mail: jxia@sc.musashi-tech.ac.jp; Nemoto, Koudai; Ikegami, Yuta [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan); Usami, Noritaka [Institute of Materials Research, Tohoku University, 2-2-1 Katahira, Aoba-ku, Sendai Japan (Japan)], E-mail: usa@imr.tohoku.ac.jp; Nakata, Yasushi [Horiba, Ltd., 1-7-8 Higashi-Kanda, Chiyoda-ku, Tokyo 101-0031 (Japan)], E-mail: yasushi.nakata@horiba.com; Shiraki, Yasuhiro [Advanced Research Laboratories, Musashi Institute of Technolgy, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)

2008-11-03

Multiple layers of Ge self-assembled quantum dots were embedded into two-dimensional silicon photonic crystal microcavities fabricated on silicon-on-insulator substrates. Microphotoluminescence was used to study the light-emission characteristic of the Ge quantum dots in the microcavities. Strong resonant room-temperature light-emission was observed in the telecommunication wavelength region. Significant enhancement of the luminescence from Ge dots was obtained due to the resonance in the cavities. Multiple sharp resonant peaks dominated the spectrum, showing strong optical resonance inside the cavity. By changing the lattice constant of photonic crystal structure, the wavelengths of the resonant peaks are tuned in the wide wavelength range from 1.2 to 1.6 {mu}m.

Linear Gain and Gain Saturation in a Photonic Free-Electron Laser

NARCIS (Netherlands)

Denis, T.; Boller, Klaus J.; Lee, J.H.H.; van der Slot, P.J.M.; van Dijk, Marc

2012-01-01

Photonic crystals are used to manipulate the generation of light, for example, stimulated emission can be enhanced. A photonic free-electron laser (pFEL) applies this enhancement to generate widely tunable coherent Cerenkov radiation from low energy electrons (keV) streaming through the photonic

Ultraweak photon emission as a non-invasive health assessment: A systematic review

NARCIS (Netherlands)

Ives, J.A.; Wijk, E.P.A. van; Bat, N.; Crawford, C.; Walter, A.; Jonas, W.B.; Wijk, R. van; Greef, J. van der

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

Stimulated-emission effects in particle creation near black holes

International Nuclear Information System (INIS)

Wald, R.M.

1976-01-01

It has recently been shown that if a black hole is formed by gravitational collapse, spontaneous particle creation will occur and a thermal spectrum of all species of particles will be emitted to infinity if the quantum matter was initially in the vacuum state. In this paper we investigate the stimulated-emission effects which occur if particles are present initially. We show in general that for a Hermitian scalar field in an external potential or in curved, asymptotically flat spacetime, stimulated-emission effects can occur precisely in those modes for which there is spontaneous particle creation from the vacuum. For the case of a Schwarzschild black hole, this result appears paradoxical, since spontaneous emission occurs at late times but there is no classical analog of stimulated emission at late times. The resolution of this paradox is that in order to induce emission of particles which emerge at late times one must send in particles at early times, so that they reach the black hole very near the instant of its formation. However, enormous energy is required of these incoming particles in order to stimulate emission of particles which emerge at late times. Thus, for a Schwarzschild black hole, even if particles are initially present (with limited energy) they will induce emission only at early times; at late times one will see only the spontaneously emitted blackbody thermal radiation. For the case of a Kerr black hole stimulated emission can be induced by particles sent in at late times with the appropriate frequencies and angular dependence. If the number of incoming particles is large, this quantum stimulated emission just gives the classical superradiant scattering

Engineering photonic and plasmonic light emission enhancement

Science.gov (United States)

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

Dynamics of Spontaneous Emission Controlled by Local Density of States in Photonic Crystals

DEFF Research Database (Denmark)

Lodahl, Peter; Nikolaev, Ivan S.; van Driel, A. Floris

2006-01-01

We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter.......We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter....

Photonic engineering of highly linearly polarized quantum dot emission at telecommunication wavelengths

Science.gov (United States)

Mrowiński, P.; Emmerling, M.; Schneider, C.; Reithmaier, J. P.; Misiewicz, J.; Höfling, S.; Sek, G.

2018-04-01

In this work, we discuss a method to control the polarization anisotropy of spontaneous emission from neutral excitons confined in quantum-dot-like nanostructures, namely single epitaxial InAs quantum dashes emitting at telecom wavelengths. The nanostructures are embedded inside lithographically defined, in-plane asymmetric photonic mesa structures, which generate polarization-dependent photonic confinement. First, we study the influence of the photonic confinement on the polarization anisotropy of the emission by photoluminescence spectroscopy, and we find evidence of different contributions to a degree of linear polarization (DOLP), i.e., from the quantum dash and the photonic mesa, in total giving rise to DOLP =0.85 . Then, we perform finite-difference time-domain simulations of photonic confinement, and we calculate the DOLP in a dipole approximation showing well-matched results for the established model. Furthermore, by using numerical calculations, we demonstrate several types of photonic confinements where highly linearly polarized emission with DOLP of about 0.9 is possible by controlling the position of a quantum emitter inside the photonic structure. Then, we elaborate on anisotropic quantum emitters allowing for exceeding DOLP =0.95 in an optimized case, and we discuss the ways towards efficient linearly polarized single photon source at telecom bands.

Simulation of Halocarbon Production and Emissions and Effects on Ozone Depletion

Science.gov (United States)

Holmes; Ellis

1997-09-01

/ This paper describes an integrated model that simulates future halocarbon production/emissions and potential ozone depletion. Applications and historical production levels for various halocarbons are discussed first. A framework is then presented for modeling future halocarbon impacts incorporating differences in underlying demands, applications, regulatory mandates, and environmental characteristics. The model is used to simulate the potential impacts of several prominent issues relating to halocarbon production, regulation, and environmental interactions, notably: changes in agricultural methyl bromide use, increases in effectiveness of bromine for ozone depletion, modifications to the elimination schedule for HCFCs, short-term expansion of CFC demand in low use compliance countries, and delays in Russian Federation compliance. Individually, each issue does not unequivocally represent a significant likely increase in long-term atmospheric halogen loading and stratospheric ozone depletion. In combination, however, these impacts could increase peak halogen concentrations and long-term integral halogen loading, resulting in higher levels of stratospheric ozone depletion and longer exposure to increased levels of UV radiation.KEY WORDS: Halocarbons; Ozone depletion; Montreal Protocol; Integrated assessment

Stimulated emission at 2.8 μm from Hg-based quantum well structures grown by photoassisted molecular beam epitaxy

International Nuclear Information System (INIS)

Giles, N.C.; Yang, Z.; Han, J.W.; Cook, J.W. Jr.; Schetzina, J.F.

1990-01-01

We report the first observation of stimulated emission from Hg-based quantum well structures in which the active region is a HgCdTe superlattice. The laser structures were grown on (100) CdZnTe substrates by photoassisted molecular beam epitaxy. Cleaved laser cavities were optically pumped using the 1.06 μm output from a continuous wave Nd:YAG laser. Stimulated emission cavity modes were seen at cw laser power densities as low as 3.4 kW/cm 2 and at temperatures ≥60 K

Measurement and model of the infrared two-photon emission spectrum of GaAs.

Science.gov (United States)

Hayat, Alex; Ginzburg, Pavel; Orenstein, Meir

2009-07-10

Two-photon emission from semiconductors was recently observed, but not fully interpreted. We develop a dressed-state model incorporating intraband scattering-related level broadening, yielding nondivergent emission rates. The spectrum calculations for high carrier concentrations including the time dependence of the screening buildup correspond well to our measured two-photon emission spectrum from GaAs.

Modification of Thermal Emission via Metallic Photonic Crystals

International Nuclear Information System (INIS)

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

2012-01-01

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.

Spontaneous emission control in a tunable hybrid photonic system

NARCIS (Netherlands)

Frimmer, M.; Koenderink, A.F.

2013-01-01

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).

CdSe quantum dot in vertical ZnSe nanowire and photonic wire for efficient single-photon emission

DEFF Research Database (Denmark)

Cremel, Thibault; Bellet-Amalric, Edith; Cagnon, Laurent

conformal dielectric coating of Al2O3 on the NW-QDs using Atomic Layer Deposition so that a photonic wire is formed with the CdSe QD deterministically positioned on its axis. The collection enhancement effect is studied by measuring the emission (with pulse excitation, at saturation intensity) of single...

Tracking biochemical changes correlated with ultra-weak photon emission using metabolomics

Czech Academy of Sciences Publication Activity Database

Burgos, R.C.R.; Červinková, Kateřina; van der Laan, T.; Ramautar, R.; van Wijk, E.P.A.; Cifra, Michal; Koval, S.; Berger, R.; Hankemeier, T.; van der Greef, J.

-, č. 163 (2016), s. 237-245 ISSN 1011-1344 R&D Projects: GA ČR GA13-29294S Institutional support: RVO:67985882 Keywords : Ultra-weak photon emission * Capillary electrophoresis-mass spectrometry * HL-60 cells Subject RIV: BO - Biophysics Impact factor: 2.673, year: 2016

Spontaneous emission of quantum dots in disordered photonic crystal waveguides

DEFF Research Database (Denmark)

Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren

2010-01-01

We report on the enhancement of the spontaneous emission rate of single semiconductor quantum dots embedded in a photonic crystal waveguide with engineered disorder. Random high-Q cavities, that are signature of Anderson localization, are measured in photoluminescence experiments and appear...... in the slow light regime of the waveguide mode. Time resolved experiments show a 15-fold enhancement of the spontaneous emission rate, with coupling efficiencies of single photons into Anderson localized cavity modes of 94%. These results show that the performances of Anderson-localized cavities...

Photon emission statistics and photon tracking in single-molecule spectroscopy of molecular aggregates : Dimers and trimers

NARCIS (Netherlands)

Bloemsma, E. A.; Knoester, J.

2012-01-01

Based on the generating function formalism, we investigate broadband photon statistics of emission for single dimers and trimers driven by a continuous monochromatic laser field. In particular, we study the first and second moments of the emission statistics, which are the fluorescence excitation

Broadband transient absorption spectroscopy with 1- and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution

Energy Technology Data Exchange (ETDEWEB)

Moreno, J.; Dobryakov, A. L.; Hecht, S., E-mail: sh@chemie.hu-berlin.de, E-mail: skovale@chemie.hu-berlin.de; Kovalenko, S. A., E-mail: sh@chemie.hu-berlin.de, E-mail: skovale@chemie.hu-berlin.de [Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-St. 2, 12489 Berlin (Germany); Ioffe, I. N. [Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Granovsky, A. A. [Firefly Project, 117593 Moscow (Russian Federation)

2015-07-14

1-photon (382 nm) and 2-photon (752 nm) excitations to the S{sub 1} state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S{sub 1} → S{sub n} due to resonant absorption of a third pump photon. Subsequent S{sub n} → S{sub 1} internal conversion (with τ{sub 1} = 1 ps) prepares a very hot S{sub 1} state which cools down with τ{sub 2} = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections σ{sup (2)} = 32 ⋅ 10{sup −50} cm{sup 4} s at 752 nm are evaluated from the bleach signal.

Photon distribution function for stocks wave for stimulated Raman scattering

International Nuclear Information System (INIS)

Man'ko, O.V.; Tcherniega, N.V.

1997-04-01

New time-dependent integrals of motion are found for stimulated Raman scattering. Explicit formula for the photon-number probability distribution as a function of the laser-field intensity and the medium parameters is obtained in terms of Hermite polynomials of two variables. (author). 29 refs

Directional emission of single photons from small atomic samples

DEFF Research Database (Denmark)

Miroshnychenko, Yevhen; V. Poulsen, Uffe; Mølmer, Klaus

2013-01-01

We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state i...... is coupled by a classical laser field to an optically excited state which rapidly decays to the ground atomic state. Our model accounts for the different field polarization components via re-absorption and emission of light by the Zeeman manifold of optically excited states.......We provide a formalism to describe deterministic emission of single photons with tailored spatial and temporal profiles from a regular array of multi-level atoms. We assume that a single collective excitation is initially shared by all the atoms in a metastable atomic state, and that this state...

Dose response of commercially available optically stimulated luminescent detector, Al2O3:C for megavoltage photons and electrons.

Science.gov (United States)

Kim, Dong Wook; Chung, Weon Kuu; Shin, Dong Oh; Yoon, Myonggeun; Hwang, Ui-Jung; Rah, Jeong-Eun; Jeong, Hojin; Lee, Sang Yeob; Shin, Dongho; Lee, Se Byeong; Park, Sung Yong

2012-04-01

This study examined the dose response of an optically stimulated luminescence dosemeter (OSLD) to megavoltage photon and electron beams. A nanoDot™ dosemeter was used to measure the dose response of the OSLD. Photons of 6-15 MV and electrons of 9-20 MeV were delivered by a Varian 21iX machine (Varian Medical System, Inc. Milpitas, CA, USA). The energy dependency was dose was linear until 200 cGy. The superficial dose measurements revealed photon irradiation to have an angular dependency. The nanoDot™ dosemeter has potential use as an in vivo dosimetric tool that is independent of the energy, has dose linearity and a rapid response compared with normal in vivo dosimetric tools, such as thermoluminescence detectors. However, the OSLD must be treated very carefully due to the high angular dependency of the photon beam.

Ozone Depletion Caused by Rocket Engine Emissions: A Fundamental Limit on the Scale and Viability of Space-Based Geoengineering Schemes

Science.gov (United States)

Ross, M. N.; Toohey, D.

2008-12-01

Emissions from solid and liquid propellant rocket engines reduce global stratospheric ozone levels. Currently ~ one kiloton of payloads are launched into earth orbit annually by the global space industry. Stratospheric ozone depletion from present day launches is a small fraction of the ~ 4% globally averaged ozone loss caused by halogen gases. Thus rocket engine emissions are currently considered a minor, if poorly understood, contributor to ozone depletion. Proposed space-based geoengineering projects designed to mitigate climate change would require order of magnitude increases in the amount of material launched into earth orbit. The increased launches would result in comparable increases in the global ozone depletion caused by rocket emissions. We estimate global ozone loss caused by three space-based geoengineering proposals to mitigate climate change: (1) mirrors, (2) sunshade, and (3) space-based solar power (SSP). The SSP concept does not directly engineer climate, but is touted as a mitigation strategy in that SSP would reduce CO2 emissions. We show that launching the mirrors or sunshade would cause global ozone loss between 2% and 20%. Ozone loss associated with an economically viable SSP system would be at least 0.4% and possibly as large as 3%. It is not clear which, if any, of these levels of ozone loss would be acceptable under the Montreal Protocol. The large uncertainties are mainly caused by a lack of data or validated models regarding liquid propellant rocket engine emissions. Our results offer four main conclusions. (1) The viability of space-based geoengineering schemes could well be undermined by the relatively large ozone depletion that would be caused by the required rocket launches. (2) Analysis of space- based geoengineering schemes should include the difficult tradeoff between the gain of long-term (~ decades) climate control and the loss of short-term (~ years) deep ozone loss. (3) The trade can be properly evaluated only if our

LETTER TO THE EDITOR: Green emission and bandgap narrowing due to two-photon excitation in thin film CdS formed by spray pyrolysis

Science.gov (United States)

Ullrich, B.; Schroeder, R.

2001-08-01

Thin (10 µm) film CdS on Pyrex® formed by spray pyrolysis is excited below the gap at 804 nm with 200 fs laser pulses at room temperature. Excitation intensities up to 250 GW cm-2 evoke green bandgap emission due to two-photon transitions. This two-photon photoluminescence does not show a red emission contribution in contrast to the single-photon excited emission, which is dominated by broad emission in the red spectral range. It is demonstrated that two-photon excitation causes photo-induced bandgap narrowing due to Debye screening. At 250 GW cm-2 bandgap narrowing of 47 meV is observed, which corresponds to an excited electron density of 1.6×1018 cm-3.

The use of angle resolved electron and photon stimulated desorption for the determination of molecular structure at surfaces

International Nuclear Information System (INIS)

Madey, T.E.; Stockbauer, R.

1983-01-01

A brief review of recent data related to the use of angle-resolved electron stimulated desorption and photon stimulated desorption in determining the structures of molecules at surfaces is made. Examples include a variety of structural assignments based on ESIAD (electron stimulated desorption ion angular distributions), the observation of short-range local ordering effects induced in adsorbed molecules by surface impurities, and the application of photon stimulated desorption to both ionic and covalent adsorbate systems. (Author) [pt

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

Energy Technology Data Exchange (ETDEWEB)

Chiang, Chih-Chieh; Lin, Hsin-Hon; Lin, Chang-Shiun; Chuang, Keh-Shih [Department of Biomedical Engineering and Environmental Sciences, National Tsing-HuaUniversity, Hsinchu, Taiwan (China); Jan, Meei-Ling [Health Physics Division, Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan, Taiwan (China)

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)

Photocount statistics of ultra-weak photon emission from germinating mung bean

Czech Academy of Sciences Publication Activity Database

Rafieiolhosseini, N.; Poplová, Michaela; Sasanpour, P.; Rafii-Tabar, H.; Alhossaini, M.R.; Cifra, Michal

2016-01-01

Roč. 162, September (2016), s. 50-55 ISSN 1011-1344 R&D Projects: GA ČR GA13-29294S Institutional support: RVO:67985882 Keywords : Mung bean * PMT photomultiplier tube * Abbreviations UPE ultra-weak photon emission Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.673, year: 2016

Quantum Optics with Photonic Nanowires and Photonic Trumpets: Basics and Applications

DEFF Research Database (Denmark)

Gerard, J.; Claudon, J.; Munsch, M.

, the node of future quantum networks. Besides optical microcavities [1], photonic wires have recently demonstrated in this context an appealing potential [2, 3]. For instance, single photon sources (SPS) based on a single quantum dot in a vertical photonic wire with integrated bottom mirror and tapered tip...... have enabled for the ¯rst time to achieve simultaneously a very high e±ciency (0.72 photon per pulse) and a very pure single photon emission (g(2)(0) control of the spontaneous emission of embedded emitters [4...

Correlated Photon Emission from Multiatom Rydberg Dark States

DEFF Research Database (Denmark)

Pritchard, J.D.; Adams, C.S.; Mølmer, Klaus

2012-01-01

We consider three-level atoms driven by two resonant light fields in a ladder scheme where the upper level is a highly excited Rydberg state. We show that the dipole-dipole interactions between Rydberg excited atoms prevents the formation of single particle dark states and leads to strongly corre...... correlated photon pairs from atoms separated by distances large compared to the emission wavelength. For a pair of atoms, this enables realization of an efficient photon-pair source with on average one pair every 30 μs....

Reliability Study of Mechatronic Power Components Using Spectral Photon Emission Microscopy

Directory of Open Access Journals (Sweden)

N. Moultif

2016-11-01

Full Text Available In this paper, we present one of the most important failure analysis tools that permits the localizing and the identification of the failure mechanisms. It is a new spectral photon emission system, enabling to localize the failure, and quickly get the photon emission spectra that characterize the failure with high resolution. A diffraction grating is used as a spectrometer in the system. Application results on mechatronic power devices such as HEMT AlGaN/GAN and SiC MOSFETs are reported.

Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

International Nuclear Information System (INIS)

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

2015-01-01

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

High multi-photon visible upconversion emissions of Er3+ singly doped BiOCl microcrystals: A photon avalanche of Er3+ induced by 980 nm excitation

International Nuclear Information System (INIS)

Li, Yongjin; Song, Zhiguo; Li, Chen; Wan, Ronghua; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Yang, Yong; Zhou, Dacheng; Wang, Qi

2013-01-01

Under 980 nm excitation, high multi-photon upconversion (UC) emission from the 2 H 11/2 / 4 S 3/2 (green) and 4 F 9/2 (red) levels of Er 3+ ions were observed from Er 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 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 3+ ions doping

Measuring mouse retina response near the detection threshold to direct stimulation of photons with sub-poisson statistics

Science.gov (United States)

Tavala, Amir; Dovzhik, Krishna; Schicker, Klaus; Koschak, Alexandra; Zeilinger, Anton

Probing the visual system of human and animals at very low photon rate regime has recently attracted the quantum optics community. In an experiment on the isolated photoreceptor cells of Xenopus, the cell output signal was measured while stimulating it by pulses with sub-poisson distributed photons. The results showed single photon detection efficiency of 29 +/-4.7% [1]. Another behavioral experiment on human suggests a less detection capability at perception level with the chance of 0.516 +/-0.01 (i.e. slightly better than random guess) [2]. Although the species are different, both biological models and experimental observations with classical light stimuli expect that a fraction of single photon responses is filtered somewhere within the retina network and/or during the neural processes in the brain. In this ongoing experiment, we look for a quantitative answer to this question by measuring the output signals of the last neural layer of WT mouse retina using microelectrode arrays. We use a heralded downconversion single-photon source. We stimulate the retina directly since the eye lens (responsible for 20-50% of optical loss and scattering [2]) is being removed. Here, we demonstrate our first results that confirms the response to the sub-poisson distributied pulses. This project was supported by Austrian Academy of Sciences, SFB FoQuS F 4007-N23 funded by FWF and ERC QIT4QAD 227844 funded by EU Commission.

Measurement of multilayer mirror reflectivity and stimulated emission in the XUV spectral region

International Nuclear Information System (INIS)

Keane, C.; Nam, C.H.; Meixler, L.; Milchberg, H.; Skinner, C.H.; Suckewer, S.; Voorhees, D.; Barbee, T.

1986-03-01

We present measurements of multilayer mirror reflectivity and stimulated emission in the XUV spectral region. A molybdenum-silicon multilayer mirror with 12% measured reflectivity at 182 A was found to produce a 120% enhancement of the C VI 182 A line (3 → 2 transition) in a strongly recombining plasma. No such enhancement of the CV 186.7 A line was seen, demonstrating amplification of stimulated emission at 182 A

Ultra-weak photon emission as a non-invasive tool for monitoring of oxidative processes in the epidermal cells of human skin: comparative study on the dorsal and the palm side of the hand.

Science.gov (United States)

Rastogi, Anshu; Pospísil, Pavel

2010-08-01

All living organisms emit spontaneous ultra-weak photon emission as a result of cellular metabolic processes. Exposure of living organisms to exogenous factors results in oxidative processes and enhancement in ultra-weak photon emission. Here, hydrogen peroxide (H(2)O(2)), as a strongly oxidizing molecule, was used to induce oxidative processes and enhance ultra-weak photon emission in human hand skin. The presented work intends to compare both spontaneous and peroxide-induced ultra-weak photon emission from the epidermal cells on the dorsal and the palm side of the hand. A highly sensitive photomultiplier tube and a charge-coupled device camera were used to detect ultra-weak photon emission from human hand skin. Spontaneous ultra-weak photon emission from the epidermal cells on the dorsal side of the hand was 4 counts/s. Topical application of 500 mM H(2)O(2) to the dorsal side of the hand caused enhancement in ultra-weak photon emission to 40 counts/s. Interestingly, both spontaneous and peroxide-induced ultra-weak photon emission from the epidermal cells on the palm side of the hand were observed to increase twice their values, i.e. 8 and 80 counts/s, respectively. Similarly, the two-dimensional image of ultra-weak photon emission observed after topical application of H(2)O(2) to human skin reveals that photon emission from the palm side exceeds the photon emission from the dorsal side of the hand. The results presented indicate that the ultra-weak photon emission originating from the epidermal cells on the dorsal and the palm side of the hand is related to the histological structure of the human hand skin. Ultra-weak photon emission is shown as a non-destructive technique for monitoring of oxidative processes in the epidermal cells of the human hand skin and as a diagnostic tool for skin diseases.

Auger decay mechanism in photon-stimulated desorption of ions from surfaces

International Nuclear Information System (INIS)

Parks, C.C.

1983-11-01

Photon-stimulated desorption (PSD) of positive ions was studied with synchrotron radiation using an angle-integrating time-of-flight mass spectrometer. Ion yields as functions of photon energy near core levels were measured from condensed gases, alkali fluorides, and other alkali and alkaline earth halides. These results are compared to bulk photoabsorption measurements with emphasis on understanding fundamental desorption mechanisms. The applicability of the Auger decay mechanism, in which ion desorption is strictly proportional to surface absorption, is discussed in detail. The Auger decay model is developed in detail to describe Na + and F + desorption from NaF following Na(1s) excitation. The major decay pathways of the Na(1s) hole leading to desorption are described and equations for the energetics of ion desorption are developed. Ion desorption spectra of H + , Li + , and F + are compared to bulk photoabsorption near the F(2s) and Li(1s) edges of LiF. A strong photon beam exposure dependence of ion yields from alkali fluorides is revealed, which may indicate the predominance of metal ion desorption from defect sites. The large role of indirect mechanisms in ion desorption condensed N 2 -O 2 multilayers is demonstrated and discussed. Ion desorption spectra from several alkali halides and alkaline earth halides are compared to bulk photoabsorption spectra. Relative ion yields from BaF 2 and a series of alkali halides are discussed in terms of desorption mechanisms

Dirac directional emission in anisotropic zero refractive index photonic crystals.

Science.gov (United States)

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.

Quantitative single-photon emission tomography for cerebral flow and receptor distribution imaging

International Nuclear Information System (INIS)

Budinger, T.F.

1985-01-01

Recently there has been renewed interest in single-photon emission tomography for two major reasons. First, correction methods have been devised for attenuation compensation, nonuniform resolution, and scattered radiation. Second, new radiopharmaceuticals with 1-5% uptake in the brain provide adequate statistics for quantitative imaging of flow using properly designed single-photon tomographic instruments. The lack of commercially available instruments designed specifically to optimize sensitivity for a resolution finer than 15 mm full width at half maximum (FWHM) seems now to be the major deterrent to the widespread use of single-photon emission tomography. But it appears now that some development in this respect also might lead to a widespread renewed interest in single-photon tomography of the brain. Major activities of the past few years can be placed in three distinct categories of instrumentation and methodology

Broadband enhancement of spontaneous emission in a photonic-plasmonic structure

DEFF Research Database (Denmark)

Zhu, Xiaolong; Xie, Fengxian; Shi, Lei

2012-01-01

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, lea......, 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....

Design of Slow and Fast Light Photonic Crystal Waveguides for Single-photon Emission Using a Bloch Mode Expansion Technique

DEFF Research Database (Denmark)

de Lasson, Jakob Rosenkrantz; Rigal, B.; Kapon, E.

We design slow and fast light photonic crystal waveguides for single-photon emission using a Bloch mode expansion and scattering matrix technique. We propose slow light designs that increase the group index-waveguide mode volume ratio for larger Purcell enhancement, and address efficient slow-to-...

Half-life measurements and photon emission probabilities of frequently applied radioisotopes

International Nuclear Information System (INIS)

Schoetzig, U.; Schrader, H.

1998-09-01

It belongs to the duties of the PTB department for 'Radioactivity' to determine the radioactivity emitted by radioactive radiation sources and publish their specific decay data, also called ''standards'', so that appliers of such sources may calibrate their equipment accordingly, as e.g. photon detectors. Further data required for proper calibration are those defining the photon emission probability per decay, P(E), at the relevant photon energy E. The emission rate R(E) is derived from the activity A, by the calculus R(E)=A x P(E), and the half-lives of decay, T 1 /2, together with the standards are used for determining the time of measurement. The calibration quality essentially is determined by those two parameters and the incertainties involved. The PTB 'Radioactivity' department therefore publishes for users recommended decay data elaborated and used by the experts at PTB. The tabulated data are either measured at PTB, or critically selected from data compilations of other publication sources. The tabulated decay data presented here are intended to serve as a source of reference for laboratory work and should be used in combination with the comprehensive data collections available (see the bibliography of this document: 86BRFI, 91TECD, 96FI, Nuclear Data Sheets, e.g. 98ND84). (orig./CB) [de

Cortical perfusion response to an electrical stimulation of the auditory nerve in profoundly deaf patients: Study with technetium-99m hexamethylpropylene amine oxime single photon emission tomography

International Nuclear Information System (INIS)

Le Scao, Y.; Robier, A.; Beuter, P.; Baulieu, J.L.; Pourcelot, L.

1992-01-01

Brain activation procedures associated with single photon emission tomography (SPET) have recently been developed in healthy controls and diseased patients in order to help in their diagnosis and treatment. We investigated the effects of a promontory test (PT) on the cerebral distribution of technetium-99m hexamethyl-propylene amine oxime ( 99m Tc-HMPAO) in 7 profoundly deaf patients, 6 PT+ and PT-. The count variation in the temporal lobe was calculated on 6 coronal slices using the ratio (R stimulation -R deprivation )/R deprivation where R=counts in the temporal lobe was observed in all patients and was higher in all patients with PT+ than in the patient with PT-. The problems of head positioning and resolution of the system were taken into account, and we considered that the maximal count increment was related to the auditory cortex response to the stimulus. Further clinical investigations with high-resolution systems have to be performed in order to validate this presurgery test in cochlear implant assessment. (orig.)

Multiphoton STED and FRET in human skin: Resolving the skin barrier

DEFF Research Database (Denmark)

Antonescu, Irina; Dreier, Jes; Brewer, Jonathan R.

intercellular spaces. Characterization of the structural and dynamical processes occurring across the skin barrier is essential for understanding healthy and diseased skin and for designing successful transdermal drug delivery strategies. In this study we use Stimulated emission depletion (STED), two photon...

Interactions of low-power photons with natural opals—PBG materials, photonic control, natural metamaterials, spontaneous laser emissions, and band-gap boundary responses

International Nuclear Information System (INIS)

Stem, Michelle R.

2012-01-01

Four views of each of the opal research specimens in white light (for in-article or cover), in the same order as the specimens depicted in Fig. 3 of the main manuscript. A.On the left: 1.5 carat oval cabochon precious fire opal. B.In the center: 2.5 carats faceted fancy shield precious fire contra luz with mild adularescence. C.On the right: 5.0 carats round cabochon precious crystal opal with blue adularescence. Highlights: ► Emission of micro-lasers from microspheroid cluster boundary zones (quantum dots). ► Lasers illuminated or fluoresced the intra-opal structures of microspheroid photonic glass clusters. ► Microspheroid boundaries are durable to low power light sources. ► Display of previously unknown low power photonic optic properties. ► The research specimens are natural metamaterials. - Abstract: One overall goal of this research was to examine types of naturally-occurring opals that exhibit photonic control to learn about previously-unknown properties of naturally occurring photonic control that may be developed for broader applications. Three different photon sources were applied consecutively to three different types of natural, flawless, gem-quality precious opals. Two photon sources were lasers (green and red) and one was simulated daylight tungsten white. As each type of precious opal was exposed to each of the photon sources, the respective refractions, reflections, and transmissions were studied. This research is the first to show that applying various pleochroic and laser photon sources to these types of opals revealed significant information regarding naturally occurring photonic control, metamaterials, spontaneous laser emissions, and microspheroid cluster (inter-PBG zone) boundary effects. Plus, minimizing ambient light and the use of low power photon sources were critical to observing the properties regarding this photonic materials research. This research yielded information applicable to the development of materials to advance

Atlas of solar hidden photon emission

Energy Technology Data Exchange (ETDEWEB)

Redondo, Javier [Departamento de Física Teórica, Universidad de Zaragoza,Pedro Cerbuna 12, E-50009, Zaragoza (Spain); Max-Planck-Institut für Physik, Werner-Heisenberg-Institut,Föhringer Ring 6, 80805 München (Germany)

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.

Atlas of solar hidden photon emission

Energy Technology Data Exchange (ETDEWEB)

Redondo, Javier, E-mail: redondo@mpp.mpg.de [Departamento de Física Teórica, Universidad de Zaragoza, Pedro Cerbuna 12, E-50009, Zaragoza, España (Spain)

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.

Stimulated secondary emission from semiconductor microcavities

DEFF Research Database (Denmark)

Østergaard, John Erland; Mizeikis, V.; Langbein, Wolfgang Werner

2001-01-01

We find strong influence of final-state stimulation on the time-resolved light emission dynamics from semiconductor microcavities after pulsed excitation allowing angle-resonant polariton-polariton scattering on the lower-polariton branch. The polariton dynamics can be controlled by injection...

Single photon detection and signal analysis for high sensitivity dosimetry based on optically stimulated luminescence with beryllium oxide

Science.gov (United States)

Radtke, J.; Sponner, J.; Jakobi, C.; Schneider, J.; Sommer, M.; Teichmann, T.; Ullrich, W.; Henniger, J.; Kormoll, T.

2018-01-01

Single photon detection applied to optically stimulated luminescence (OSL) dosimetry is a promising approach due to the low level of luminescence light and the known statistical behavior of single photon events. Time resolved detection allows to apply a variety of different and independent data analysis methods. Furthermore, using amplitude modulated stimulation impresses time- and frequency information into the OSL light and therefore allows for additional means of analysis. Considering the impressed frequency information, data analysis by using Fourier transform algorithms or other digital filters can be used for separating the OSL signal from unwanted light or events generated by other phenomena. This potentially lowers the detection limits of low dose measurements and might improve the reproducibility and stability of obtained data. In this work, an OSL system based on a single photon detector, a fast and accurate stimulation unit and an FPGA is presented. Different analysis algorithms which are applied to the single photon data are discussed.

Si light-emitting device in integrated photonic CMOS ICs

Science.gov (United States)

Xu, Kaikai; Snyman, Lukas W.; Aharoni, Herzl

2017-07-01

The motivation for integrated Si optoelectronics is the creation of low-cost photonics for mass-market applications. Especially, the growing demand for sensitive biochemical sensors in the environmental control or medicine leads to the development of integrated high resolution sensors. Here CMOS-compatible Si light-emitting device structures are presented for investigating the effect of various depletion layer profiles and defect engineering on the photonic transition in the 1.4-2.8 eV. A novel Si device is proposed to realize both a two-terminal Si-diode light-emitting device and a three-terminal Si gate-controlled diode light-emitting device in the same device structure. In addition to the spectral analysis, differences between two-terminal and three-terminal devices are discussed, showing the light emission efficiency change. The proposed Si optical source may find potential applications in micro-photonic systems and micro-optoelectro-mechanical systems (MOEMS) in CMOS integrated circuitry.

First observations of stimulated emission and of stimulated Raman scattering in acentric cubic Nd3+:Bi12SiO20 crystals

International Nuclear Information System (INIS)

Kaminskii, Alexandr A; Bagayev, S N; Garsia, Sole J; Jaque, D; Eichler, H J; Findeisen, J; Fernandez, J; Balda, R; Agullo, Rueda F

1999-01-01

Laser action (in the 4 F 3/2 - 4 I 11/2 channel) and stimulated Raman scattering were excited for the first time in an Nd 3+ :Bi 12 SiO 20 single crystal at room temperature. All the observed stimulated emission and multiple Stokes and anti-Stokes lines were identified. (letters to the editor)

Effect of Ag doping on the properties of ZnO thin films for UV stimulated emission

Science.gov (United States)

Razeen, Ahmed S.; Gadallah, A.-S.; El-Nahass, M. M.

2018-06-01

Ag doped ZnO thin films have been prepared using sol-gel spin coating method, with different doping concentrations. Structural and morphological properties of the films have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Thin films have been optically pumped and stimulated emission has been observed with strong peaks in the UV region. The UV stimulated emission is found to be due to exciton-exciton scattering, and Ag doping promoted this process by increasing the excitons concentrations in the ZnO lattice. Output-input intensity relation and peak emission, FWHM, and quantum efficiency relations with pump intensity have been reported. The threshold for which stimulated emission started has been evaluated to be about 18 MW/cm2 with quantum efficiency of about 58.7%. Mechanisms explaining the role of Ag in enhancement of stimulated emission from ZnO thin films have been proposed.

Nonclassical photon streams using rephased amplified spontaneous emission

International Nuclear Information System (INIS)

Ledingham, Patrick M.; Naylor, William R.; Longdell, Jevon J.; Beavan, Sarah E.; Sellars, Matthew J.

2010-01-01

We present a fully quantum mechanical treatment of optically rephased photon echoes. These echoes exhibit noise due to amplified spontaneous emission; however, this noise can be seen as a consequence of the entanglement between the atoms and the output light. With a rephasing pulse one can get an 'echo' of the amplified spontaneous emission, leading to light with nonclassical correlations at points separated in time, which is of interest in the context of building wide bandwith quantum repeaters. We also suggest a wideband version of DLCZ protocol based on the same ideas.

Two-photon excited fluorescence emission from hemoglobin

Science.gov (United States)

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.

Stimulated X-Ray Emission Spectroscopy in Transition Metal Complexes

Science.gov (United States)

Kroll, Thomas; Weninger, Clemens; Alonso-Mori, Roberto; Sokaras, Dimosthenis; Zhu, Diling; Mercadier, Laurent; Majety, Vinay P.; Marinelli, Agostino; Lutman, Alberto; Guetg, Marc W.; Decker, Franz-Josef; Boutet, Sébastien; Aquila, Andy; Koglin, Jason; Koralek, Jake; DePonte, Daniel P.; Kern, Jan; Fuller, Franklin D.; Pastor, Ernest; Fransson, Thomas; Zhang, Yu; Yano, Junko; Yachandra, Vittal K.; Rohringer, Nina; Bergmann, Uwe

2018-03-01

We report the observation and analysis of the gain curve of amplified K α x-ray emission from solutions of Mn(II) and Mn(VII) complexes using an x-ray free electron laser to create the 1 s core-hole population inversion. We find spectra at amplification levels extending over 4 orders of magnitude until saturation. We observe bandwidths below the Mn 1 s core-hole lifetime broadening in the onset of the stimulated emission. In the exponential amplification regime the resolution corrected spectral width of ˜1.7 eV FWHM is constant over 3 orders of magnitude, pointing to the buildup of transform limited pulses of ˜1 fs duration. Driving the amplification into saturation leads to broadening and a shift of the line. Importantly, the chemical sensitivity of the stimulated x-ray emission to the Mn oxidation state is preserved at power densities of ˜1020 W /cm2 for the incoming x-ray pulses. Differences in signal sensitivity and spectral information compared to conventional (spontaneous) x-ray emission spectroscopy are discussed. Our findings build a baseline for nonlinear x-ray spectroscopy for a wide range of transition metal complexes in inorganic chemistry, catalysis, and materials science.

Stimulation of autophagy by the p53 target gene Sestrin2.

Science.gov (United States)

Maiuri, Maria Chiara; Malik, Shoaib Ahmad; Morselli, Eugenia; Kepp, Oliver; Criollo, Alfredo; Mouchel, Pierre-Luc; Carnuccio, Rosa; Kroemer, Guido

2009-05-15

The oncosuppressor protein p53 regulates autophagy in a dual fashion. The pool of cytoplasmic p53 protein represses autophagy in a transcription-independent fashion, while the pool of nuclear p53 stimulates autophagy through the transactivation of specific genes. Here we report the discovery that Sestrin2, a novel p53 target gene, is involved in the induction of autophagy. Depletion of Sestrin2 by RNA interference reduced the level of autophagy in a panel of p53-sufficient human cancer cell lines responding to distinct autophagy inducers. In quantitative terms, Sestrin2 depletion was as efficient in preventing autophagy induction as was the depletion of Dram, another p53 target gene. Knockout of either Sestrin2 or Dram reduced autophagy elicited by nutrient depletion, rapamycin, lithium or thapsigargin. Moreover, autophagy induction by nutrient depletion or pharmacological stimuli led to an increase in Sestrin2 expression levels in p53-proficient cells. In strict contrast, the depletion of Sestrin2 or Dram failed to affect autophagy in p53-deficient cells and did not modulate the inhibition of baseline autophagy by a cytoplasmic p53 mutant that was reintroduced into p53-deficient cells. We conclude that Sestrin2 acts as a positive regulator of autophagy in p53-proficient cells.

High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two Photon Absorption process (TPA-eTCT)

CERN Document Server

García, Marcos Fernández; Echeverría, Richard Jaramillo; Moll, Michael; Santos, Raúl Montero; Moya, David; Pinto, Rogelio Palomo; Vila, Iván

2016-01-01

For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample.

High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two Photon Absorption process (TPA-eTCT)

Energy Technology Data Exchange (ETDEWEB)

García, Marcos Fernández; Sánchez, Javier González; Echeverría, Richard Jaramillo [Instituto de Física de Cantabria (CSIC-UC), Avda. los Castros s/n, E-39005 Santander (Spain); Moll, Michael [CERN, Organisation europénne pour la recherche nucléaire, CH-1211 Genéve 23 (Switzerland); Santos, Raúl Montero [SGIker Laser Facility, UPV/EHU, Sarriena, s/n - 48940 Leioa-Bizkaia (Spain); Moya, David [Instituto de Física de Cantabria (CSIC-UC), Avda. los Castros s/n, E-39005 Santander (Spain); Pinto, Rogelio Palomo [Departamento de Ingeniería Electrónica, Escuela Superior de Ingenieros Universidad de Sevilla (Spain); Vila, Iván [Instituto de Física de Cantabria (CSIC-UC), Avda. los Castros s/n, E-39005 Santander (Spain)

2017-02-11

For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample.

Broadband enhancement of single photon emission and polarization dependent coupling in silicon nitride waveguides.

Science.gov (United States)

Bisschop, Suzanne; Guille, Antoine; Van Thourhout, Dries; Hens, Zeger; Brainis, Edouard

2015-06-01

Single-photon (SP) sources are important for a number of optical quantum information processing applications. We study the possibility to integrate triggered solid-state SP emitters directly on a photonic chip. A major challenge consists in efficiently extracting their emission into a single guided mode. Using 3D finite-difference time-domain simulations, we investigate the SP emission from dipole-like nanometer-sized inclusions embedded into different silicon nitride (SiNx) photonic nanowire waveguide designs. We elucidate the effect of the geometry on the emission lifetime and the polarization of the emitted SP. The results show that highly efficient and polarized SP sources can be realized using suspended SiNx slot-waveguides. Combining this with the well-established CMOS-compatible processing technology, fully integrated and complex optical circuits for quantum optics experiments can be developed.

Three-beam double stimulated Raman scatterings: Cascading configuration

Science.gov (United States)

Rao, B. Jayachander; Cho, Minhaeng

2018-03-01

Two-beam stimulated Raman scattering (SRS) has been used in diverse label-free spectroscopy and imaging applications of live cells, biological tissues, and functional materials. Recently, we developed a theoretical framework for the three-beam double SRS processes that involve pump, Stokes, and depletion beams, where the pump-Stokes and pump-depletion SRS processes compete with each other. It was shown that the net Stokes gain signal can be suppressed by increasing the depletion beam intensity. The theoretical prediction has been experimentally confirmed recently. In the previous scheme for a selective suppression of one SRS by making it compete with another SRS, the two SRS processes occur in a parallel manner. However, there is another possibility of three-beam double SRS scheme that can be of use to suppress either Raman gain of the Stokes beam or Raman loss of the pump beam by depleting the Stokes photons with yet another SRS process induced by the pair of Stokes and another (second) Stokes beam. This three-beam double SRS process resembles a cascading energy transfer process from the pump beam to the first Stokes beam (SRS-1) and subsequently from the first Stokes beam to the second Stokes beam (SRS-2). Here, the two stimulated Raman gain-loss processes are associated with two different Raman-active vibrational modes of solute molecule. In the present theory, both the radiation and the molecules are treated quantum mechanically. We then show that the cascading-type three-beam double SRS can be described by coupled differential equations for the photon numbers of the pump and Stokes beams. From the approximate solutions as well as exact numerical calculation results for the coupled differential equations, a possibility of efficiently suppressing the stimulated Raman loss of the pump beam by increasing the second Stokes beam intensity is shown and discussed. To further prove a potential use of this scheme for developing a super-resolution SRS microscopy, we

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

Energy Technology Data Exchange (ETDEWEB)

Schlehahn, A.; Gschrey, M.; Schnauber, P.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Heindel, T., E-mail: tobias.heindel@tu-berlin.de; Reitzenstein, S. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin 10623 (Germany); Gaafar, M.; Vaupel, M.; Stolz, W.; Rahimi-Iman, A.; Koch, M. [Department of Physics and Materials Science Center, Philipps-Universität Marburg, 35032 Marburg (Germany)

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.

Quantum photonics

CERN Document Server

Pearsall, Thomas P

2017-01-01

This textbook employs a pedagogical approach that facilitates access to the fundamentals of Quantum Photonics. It contains an introductory description of the quantum properties of photons through the second quantization of the electromagnetic field, introducing stimulated and spontaneous emission of photons at the quantum level. Schrödinger’s equation is used to describe the behavior of electrons in a one-dimensional potential. Tunneling through a barrier is used to introduce the concept of non­locality of an electron at the quantum level, which is closely-related to quantum confinement tunneling, resonant tunneling, and the origin of energy bands in both periodic (crystalline) and aperiodic (non-crystalline) materials. Introducing the concepts of reciprocal space, Brillouin zones, and Bloch’s theorem, the determination of electronic band structure using the pseudopotential method is presented, allowing direct computation of the band structures of most group IV, group III-V, and group II-VI semiconducto...

Ozone-depleting substances and the greenhouse gases HFCs, PFCs and SF{sub 6}. Danish consumption and emissions, 2005

Energy Technology Data Exchange (ETDEWEB)

Sander Poulsen, T. [PlanMiljoe (Denmark)

2007-06-15

An evaluation of Danish consumption and emissions of ozone-depleting substances and industrial greenhouse gases has been carried out in continuation of previous evaluations, partly to fulfil Denmark's international obligations to provide information within this area and partly to follow the trend in consumption of ozone-depleting substances as well as the consumption and emissions of HFCs, PFCs and SF{sub 6}. The evaluation includes a calculation of actual emissions of HFCs, PFCs, and SF{sub 6} for 2006. In this calculation the release from stock of greenhouse gases in products has been taken into account, and adjustments have been made for imports and exports of the greenhouse gases in products. (BA)

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

Energy Technology Data Exchange (ETDEWEB)

Li, Yongjin; Song, Zhiguo, E-mail: songzg@kmust.edu.cn; Li, Chen; Wan, Ronghua; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Yang, Yong; Zhou, Dacheng; Wang, Qi [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

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.

Wigner functions and tomograms of the photon-depleted even and odd coherent states

International Nuclear Information System (INIS)

Wang Jisuo; Meng Xiangguo

2008-01-01

Using the coherent state representation of Wigner operator and the technique of integration within an ordered product (IWOP) of operators, this paper derives the Wigner functions for the photon-depleted even and odd coherent states (PDEOCSs). Moreover, in terms of the Wigner functions with respect to the complex parameter α the nonclassical properties of the PDEOCSs are discussed. The results show that the nonclassicality for the state |β, m) o (or |β, m) e ) is more pronounced when m is even (or odd). According to the marginal distributions of the Wigner functions, the physical meaning of the Wigner functions is given. Further, the tomograms of the PDEOCSs are calculated with the aid of newly introduced intermediate coordinate-momentum representation in quantum optics

The first demonstration of room temperature stimulated emission from metal halides －its evidence in CsPbBr3 films

OpenAIRE

中西, 貴之; 高橋, 一彰; 斎藤, 忠昭; 近藤, 新一

2005-01-01

Photoluminescence from CsPbBr3 films prepared by crystallization from the amorphous phase is measured under N2 laser excitation. Stimulated emission due to free exaction-free exaction inelastic collision occurs not only at cryogenic temperature but also elevated temperatures. The intensity of the stimulated emission more rapidly increases with pumping intensity at room temperature than at 77K. The temperature dependence of the stimulated emission measured under 1100kW cm-2 pumping shows th...

Tailorable stimulated Brillouin scattering in nanoscale silicon waveguides.

Science.gov (United States)

Shin, Heedeuk; Qiu, Wenjun; Jarecki, Robert; Cox, Jonathan A; Olsson, Roy H; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T

2013-01-01

Nanoscale modal confinement is known to radically enhance the effect of intrinsic Kerr and Raman nonlinearities within nanophotonic silicon waveguides. By contrast, stimulated Brillouin-scattering nonlinearities, which involve coherent coupling between guided photon and phonon modes, are stifled in conventional nanophotonics, preventing the realization of a host of Brillouin-based signal-processing technologies in silicon. Here we demonstrate stimulated Brillouin scattering in silicon waveguides, for the first time, through a new class of hybrid photonic-phononic waveguides. Tailorable travelling-wave forward-stimulated Brillouin scattering is realized-with over 1,000 times larger nonlinearity than reported in previous systems-yielding strong Brillouin coupling to phonons from 1 to 18 GHz. Experiments show that radiation pressures, produced by subwavelength modal confinement, yield enhancement of Brillouin nonlinearity beyond those of material nonlinearity alone. In addition, such enhanced and wideband coherent phonon emission paves the way towards the hybridization of silicon photonics, microelectromechanical systems and CMOS signal-processing technologies on chip.

Coupled Photonic Crystal Cavity Array Laser

DEFF Research Database (Denmark)

Schubert, Martin

in the quadratic lattice. Processing techniques are developed and optimized in order fabricate photonic crystals membranes in gallium arsenide with quantum dots as gain medium and in indium gallium arsenide phosphide with quantum wells as gain medium. Several key issues in process to ensure good quality....... The results are in good agreement with standard coupled mode theory. Also a novel type of photonic crystal structure is proposed called lambda shifted cavity which is a twodimensional photonic crystal laser analog of a VCSEL laser. Detailed measurements of the coupled modes in the photonic crystals...... with quantum dots are carried out. In agreement with a simple gain model the structures do not show stimulated emission. The spectral splitting due to the coupling between single cavities as well as arrays of cavities is studied theoretically and experimentally. Lasing is observed for photonic crystal cavity...

Single photon emission and quantum ring-cavity coupling in InAs/GaAs quantum rings

International Nuclear Information System (INIS)

Gallardo, E; Nowak, A K; Sanvitto, D; Meulen, H P van der; Calleja, J M; MartInez, L J; Prieto, I; Alija, A R; Granados, D; Taboada, A G; GarcIa, J M; Postigo, P A; Sarkar, D

2010-01-01

Different InAs/GaAs quantum rings embedded in a photonic crystal microcavity are studied by quantum correlation measurements. Single photon emission, with g (2) (0) values around 0.3, is demonstrated for a quantum ring not coupled to the microcavity. Characteristic rise-times are found to be longer for excitons than for biexcitons, resulting in the time asymmetry of the exciton-biexciton cross-correlation. No antibunching is observed in another quantum ring weakly coupled to the microcavity.

Establishing personal dosimetry procedure using optically stimulated luminescence dosimeters in photon and mixed photon-neutron radiation fields

International Nuclear Information System (INIS)

Le Ngoc Thiem; Bui Duc Ky; Trinh Van Giap; Nguyen Huu Quyet; Ho Quang Tuan; Vu Manh Khoi; Chu Vu Long

2017-01-01

According to Vietnamese Law on Atomic Energy, personal dosimetry (PD) for radiation workers is required periodically in order to fulfil the national legal requirements on occupational radiation dose management. Since the radiation applications have become popular in Vietnamese society, the thermal luminescence dosimeters (TLDs) have been used as passive dosimeters for occupational monitoring in the nation. Together with the quick increase in radiation applications and the number of personnel working in radiation fields, the Optically Stimulated Luminescence Dosimeters (OSLDs) have been first introduced since 2015. This work presents the establishment of PD measuring procedure using OSLDs which are used for measuring photons and betas known as Inlight model 2 OSL (OSLDs-p,e) and for measuring mixed radiations of neutrons, photons and betas known as Inlight LDR model 2 (OSLDs-n,p,e). Such following features of OSLDs are investigated: detection limit, energy response, linearity, reproducibility, angular dependency and fading with both types of OSLDs-p,e and OSLDs-n,p,e. The result of an intercomparison in PD using OSLDs is also presented in the work. The research work also indicates that OSL dosimetry can be an alternative method applied in PD and possibly become one of the most popular personal dosimetry method in the future. (author)

Cortical perfusion response to an electrical stimulation of the auditory nerve in profoundly deaf patients: Study with technetium-99m hexamethylpropylene amine oxime single photon emission tomography

Energy Technology Data Exchange (ETDEWEB)

Le Scao, Y.; Robier, A.; Beuter, P. (Centre Hospitalier Universitaire, 37 - Tours (France). Dept. of Otorhinolaryngology); Baulieu, J.L.; Pourcelot, L. (Centre Hospitalier Universitaire, 37 - Tours (France). Dept. of Nuclear Medicine)

1992-04-01

Brain activation procedures associated with single photon emission tomography (SPET) have recently been developed in healthy controls and diseased patients in order to help in their diagnosis and treatment. We investigated the effects of a promontory test (PT) on the cerebral distribution of technetium-99m hexamethyl-propylene amine oxime ({sup 99m}Tc-HMPAO) in 7 profoundly deaf patients, 6 PT+ and PT-. The count variation in the temporal lobe was calculated on 6 coronal slices using the ratio (R{sub stimulation}-R{sub deprivation})/R{sub deprivation} where R=counts in the temporal lobe was observed in all patients and was higher in all patients with PT+ than in the patient with PT-. The problems of head positioning and resolution of the system were taken into account, and we considered that the maximal count increment was related to the auditory cortex response to the stimulus. Further clinical investigations with high-resolution systems have to be performed in order to validate this presurgery test in cochlear implant assessment. (orig.).

Enhanced single-photon emission from a diamond–silver aperture

KAUST Repository

Choy, Jennifer T.

2011-10-09

Solid-state quantum emitters, such as the nitrogen-vacancy centre in diamond, are robust systems for practical realizations of various quantum information processing protocols2-5 and nanoscale magnetometry schemes6,7 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 resonators8-13, 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 emitterg-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. © 2011 Macmillan Publishers Limited. All rights reserved.

Enhanced single-photon emission from a diamond–silver aperture

KAUST Repository

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

2011-01-01

Solid-state quantum emitters, such as the nitrogen-vacancy centre in diamond, are robust systems for practical realizations of various quantum information processing protocols2-5 and nanoscale magnetometry schemes6,7 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 resonators8-13, 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 emitterg-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. © 2011 Macmillan Publishers Limited. All rights reserved.

Mercury depletion as a way of changing the emission spectrum of a fluorescent lamp

NARCIS (Netherlands)

Bakker, L.P.; Kroesen, G.M.W.

2000-01-01

We present a promising option for changing the emission spectrum of a fluorescent lamp. In a neon/mercury discharge, neon radiation is produced when the mercury density is sufficiently low. Under certain discharge conditions, radial cathaphoresis causes depletion of mercury atoms in the center of

Multiple photon emission and b-quark asymmetries

International Nuclear Information System (INIS)

Jadach, S.; Ward, B.F.L.

1991-01-01

Recently the authors have introduced methods at the level of an event-by-event simulator, the effects of multiple photon emission in Z o physics scenarios relevant to the SLC and LEP. And, indeed, the respective Monte-Carlo Fortran programs for the processes e + e - → f bar f + n(γ), f ≠ e, and e + e - → e + e - + n(γ) are, in fact available from the authors, for example, for the interested reader. The authors have illustrated the respective multiple-photon effects in the case that f = μ and in the Bhabha scattering case (the latter case is dealt with only at the low-angle scattering regime relevant to luminosity simulations). Here, the authors focus on the case e + e - → b bar b + n(γ) in the high-precision regime. Such high-precision considerations may be relevant to a high-luminosity upgrade of the LEP collider, for example. Such a high-luminosity upgrade of the SLC appears more remote at this time, according to the lore. In this paper, the authors review the elements of the methods they shall employ in the next section. The authors then discuss in the third section, the multiple-photon emission effects on the b-quark asymmetries of interest to the authors here. The interplay of the radiative effects and the detector cuts is realized by applying Mark II-type detector cuts. Here, in order to make the comparison with their earlier work on μ bar μ + nγ final states immediate, the authors impose the same μ like cuts on their b-quark. The authors realize that, in doing this, some of what the authors gain in immediacy the authors may lose in the proximity to reality. In any event, we do not lose contact with the effects of interest to the authors. Finally, the authors conclude with some summary remarks

Brain Single Photon Emission Computed Tomography in Anosmic Subjects Ater Closed Head Trauma

Directory of Open Access Journals (Sweden)

Roozbeh Banan

2011-01-01

Full Text Available Anosmia following head trauma is relatively common and in many cases is persistent and irreversible. The ability to objectively measure such a decline in smelling, for both clinical and medicolegal goals, is very important. The aim of this study was to find results of brain Single Photon Emission Computed Tomography (SPECT in anosmic subjects after closed head trauma. This case-control cross sectional study was conducted in a tertiary referral University Hospital. The brain perfusion state of nineteen anosmic patients and thirteen normal controls was evaluated by means of the SPECT with 99mtc- ECD infusion- before and after olfactory stimulation. The orbitofrontal lobe of the brain was assumed as the region of interest and changes in perfusion of this area before and after the stimulations were compared in two groups. The mean of brain perfusion in controls before and after the stimulation was 8.26% ± 0.19% and 9.89% ± 0.54%, respectively (P < 0.0001. Among patients group, these quantities were 7.97% ± 1.05% and 8.49% ± 1.5%, respectively (P < 0.004. The difference between all the measures in cases and controls were statistically significant (P < 0.0001. There were no differences in age and sex between two groups. The brain SPECT is an objective technique suitable for evaluating anosmia following the head trauma and it may be used with other diagnostic modalities

Applications of anomalous diffraction systems, generation of attosecond electron and photon pulses and Raman amplification by stimulated emission of radiation

Science.gov (United States)

Vartak, Sameer Dinkar

1998-10-01

efficient delivery of this power to the screen. We describe a method based on optical rectification to create an electron acceleration process which can act simultaneously on a femtosecond photo-electron pulse as well as cancel space-charge effects. This method can be used to produce attosecond electron and photon pulses. Narrow linewidth high intensity tunable light pulses are very useful for applications such as spectroscopic studies and remote sensing. Tunable lasers and stimulated Raman scattering (SRS) process are commonly used for this purpose. SRS process has high threshold because of small spontaneous Raman scattering cross-sections. We combined amplified spontaneous emission (ASE) from dye molecules with SRS process in solvent molecules in which dye molecules are dissolved. ASE seeds SRS process and SRS peak is further amplified by stimulated emission gain. We got amplifications ~100 over SRS from pure solvent. This peak can be tuned over gain bandwidth of dye molecules.

Depletion of intracellular calcium stores facilitates the influx of extracellular calcium in platelet derived growth factor stimulated A172 glioblastoma cells.

Science.gov (United States)

Vereb, G; Szöllösi, J; Mátyus, L; Balázs, M; Hyun, W C; Feuerstein, B G

1996-05-01

Calcium signaling in non-excitable cells is the consequence of calcium release from intracellular stores, at times followed by entry of extracellular calcium through the plasma membrane. To study whether entry of calcium depends upon the level of saturation of intracellular stores, we measured calcium channel opening in the plasma membrane of single confluent A172 glioblastoma cells stimulated with platelet derived growth factor (PDGF) and/or bradykinin (BK). We monitored the entry of extracellular calcium by measuring manganese quenching of Indo-1 fluorescence. PDGF raised intracellular calcium concentration ([Ca2+]i) after a dose-dependent delay (tdel) and then opened calcium channels after a dose-independent delay (tch). At higher doses (> 3 nM), BK increased [Ca2+]i after a tdel approximately 0 s, and tch decreased inversely with both dose and peak [Ca2+]i. Experiments with thapsigargin (TG), BK, and PDGF indicated that BK and PDGF share intracellular Ca2+ pools that are sensitive to TG. When these stores were depleted by treatment with BK and intracellular BAPTA, tdel did not change, but tch fell to almost 0 s in PDGF stimulated cells, indicating that depletion of calcium stores affects calcium channel opening in the plasma membrane. Our data support the capacitative model for calcium channel opening and the steady-state model describing quantal Ca2+ release from intracellular stores.

Photon and neutrino emission from active galactic nuclei

Energy Technology Data Exchange (ETDEWEB)

Biermann, Peter L. [MPI for Radioastronomy, Bonn (Germany); Becker, Julia K. [Inst. for Phys., Univ. Bochum, Bochum (Germany); Caramete, Laurentiu I. [MPI for Radioastronomy, Bonn (Germany); Fraschetti, Federico [Inst. for Phys., Univ. Bochum, Bochum (Germany); Kneiske, Tanja [Inst. fuer Exp.Physik, Univ. Hamburg, Hamburg (Germany); Meli, Athina [Erlangen Center for Astroparticle Physics, University Erlangen-Nuremberg (Germany); Stanev, Todor [Bartol Research Inst., Univ. of Delaware, Newark, DE (United States)

2011-08-15

Supermassive black holes in the centers of galaxies are very common. They are known to rotate, accrete, spin down and eject highly relativistic jets; those jets pointed at us all seem to show a spectrum with two strong bumps, one in the TeV photon range, and one in X-rays - ordered by the emission frequency of the first bump this constitutes the blazar sequence. Here we wish to explain this sequence as primary synchrotron emission of energetic electrons and protons, and secondary emission from interactions at the first strong shockwave pattern in the relativistic jet. With two key assumptions on particle scattering, this concept predicts that the two basic maximum peak frequencies {nu}{sub syn,e,p} scale with the mass of the central black hole as {nu}{sub e,p{approx}}M{sub BH}{sup -1/2}, of {nu}{sub syn,p}/{nu}{sub syn,e}=(m{sub p}/m{sub e}){sup 3}, and the luminosities with the mass itself L{sub e,p{approx}}M{sub BH}. Due to strong losses of the leptons, the peak luminosities are generally the same, but with large variations around equality. This model predicts large fluxes in ultra high energy cosmic rays, and also large neutrino luminosities.

UV photon and low-energy (5--150 eV) electron-stimulated processes at environmental interfaces

International Nuclear Information System (INIS)

Orlando, T.M.

1997-01-01

Irradiation of surfaces and interfaces with low-energy (5--150 eV) electrons and ultraviolet photons occurs during the storage of ''mixed'' (chemical/radioactive) waste forms and during processing steps which involve the use of low temperature plasmas. It is well known that electron- and photon-stimulated desorption (ESD and PSD) from wide band-gap materials and interfaces can be initiated by Auger decay of deep valence and shallow core holes. This process consists of hole production, Auger decay, reversal of the Madelung potential, and ion expulsion due to the Coulomb repulsion. ESD and PSD of neutrals also occurs and involves production of electron-hole pairs and excitons. Generally, neutral yields dominate ESD and PSD cross sections, which typically vary between ∼10 -16 and 10 -22 cm 2 . The authors present results on the ESD and PSD of environmentally relevant substrates such as ZrO 2 (100), soda-glass, and NaNO 3 . The major cation thresholds and yields indicate that ESD and PSD from these complex materials involves Auger stimulated events. In particular, desorption thresholds correlate with ionization of the O(2s), Zr(4p), Si(2p) and Na(2s) levels. The near band-gap threshold energy (∼5--7 eV) for the desorption of neutrals (i.e., atomic oxygen, NO, etc) demonstrate the overall importance of self-trapped and localized excitons in both ESD and PSD of typical ceramics and oxides

Suppression of two-photon resonantly enhanced nonlinear processes in extended media

International Nuclear Information System (INIS)

Garrett, W.R.; Moore, M.A.; Payne, M.G.; Wunderlich, R.K.

1988-11-01

On the basis of combined experimental and theoretical studies of nonlinear processes associated with two-photon excitations near 3d and 4d states in Na, we show how resonantly enhanced stimulated hyper-Raman emission, parametric four-wave mixing processes and total resonant two-photon absorption can become severely suppressed through the actions of internally generated fields on the total atomic response in extended media. 7 refs., 3 figs

Radiation dosimetry by optically stimulated phosphorescence of CaF2:Mn

International Nuclear Information System (INIS)

Bernhardt, R.

1974-01-01

In addition to the light emission which occurs in TL, trapped electrons in CaF 2 :Mn can also be released by stimulation with visible and UV light. The measurement of stimulated light emission is disturbed by illumination. But there is an optically-stimulated phosphorescence, which permits to separate measurement of stimulated light emission and illumination. A theory is given. During illumination a part of the released electrons are captured by flat traps, which are emptied at room temperature. A dose dependent signal can be measured at a defined time after the stimulating pulse of visible light. Dosimeters (CaF 2 :Mn teflon disks) were illuminated by the light of a tungsten lamp. The dose response curve was found to be linear from 1 to 10 5 rads. The response curve obtained for optical stimulation was similar to the TL-response curve. Fading of the optically-stimulated signal was higher than TL-fading. Repeated readings of a single sample are possible. The number of readings is dependent on illumination conditions. Accuracy of sample to sample was about 3.5% (standard deviation). There are two background signals. (1) Post-irradiation phosphorescence occurs. Flat traps are also filled after 60 Co gamma excitation. The measurement of the signal is possible after decay of post-irradiation phosphorescence. (2) There is an optically-excited phosphorescence, which also occurs if all trapped electrons are released. The lower limit of dose measurements is given by deviations of optically-excited emission and the dark-current of the photomultiplier tube. (author)

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

International Nuclear Information System (INIS)

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

2014-01-01

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%

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

Energy Technology Data Exchange (ETDEWEB)

Cabrera, C. I.; Enciso, A.; Contreras-Solorio, D. A. [Academic Unit of Physics, Autonomous University of Zacatecas, Czda. Solidaridad y Paseo La Bufa S/N, 98060 Zacatecas, Zac. (Mexico); Rimada, J. C. [Solar Cell Laboratory, Institute of Materials Science and Technology (IMRE), University of Havana, Zapata y G, 10400 La Habana (Cuba); Hernandez, L., E-mail: luisman@fisica.uh.cu [Faculty of Physics, University of Havana, Colina Universitaria. 10400 La Habana (Cuba); Connolly, J. P. [Nanophotonics Technology Center, Universidad Politécnica de Valencia, 46022 Valencia (Spain)

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%.

Luminescent solar concentrators utilizing stimulated emission.

Science.gov (United States)

Kaysir, Md Rejvi; Fleming, Simon; MacQueen, Rowan W; Schmidt, Timothy W; Argyros, Alexander

2016-03-21

Luminescent solar concentrators (LSCs) are an emerging technology that aims primarily to reduce the cost of solar energy, with great potential for building integrated photovoltaic (PV) structures. However, realizing LSCs with commercially viable efficiency is currently hindered by reabsorption losses. Here, we introduce an approach to reducing reabsorption as well as improving directional emission in LSCs by using stimulated emission. Light from a seed laser (potentially an inexpensive laser diode) passes through the entire area of the LSC panel, modifying the emission spectrum of excited dye molecules such that it is spectrally narrower, at wavelengths that minimize reabsorption to allow net gain in the system, and directed towards a small PV cell. A mathematical model, taking into account thermodynamic considerations, of such a system is presented which identifies key parameters and allows evaluation in terms of net effective output power.

Electrothermally Driven Fluorescence Switching by Liquid Crystal Elastomers Based On Dimensional Photonic Crystals.

Science.gov (United States)

Lin, Changxu; Jiang, Yin; Tao, Cheng-An; Yin, Xianpeng; Lan, Yue; Wang, Chen; Wang, Shiqiang; Liu, Xiangyang; Li, Guangtao

2017-04-05

In this article, the fabrication of an active organic-inorganic one-dimensional photonic crystal structure to offer electrothermal fluorescence switching is described. The film is obtained by spin-coating of liquid crystal elastomers (LCEs) and TiO 2 nanoparticles alternatively. By utilizing the property of LCEs that can change their size and shape reversibly under external thermal stimulations, the λ max of the photonic band gap of these films is tuned by voltage through electrothermal conversion. The shifted photonic band gap further changes the matching degree between the photonic band gap of the film and the emission spectrum of organic dye mounting on the film. With rhodamine B as an example, the enhancement factor of its fluorescence emission is controlled by varying the matching degree. Thus, the fluorescence intensity is actively switched by voltage applied on the system, in a fast, adjustable, and reversible manner. The control chain of using the electrothermal stimulus to adjust fluorescence intensity via controlling the photonic band gap is proved by a scanning electron microscope (SEM) and UV-vis reflectance. This mechanism also corresponded to the results from the finite-difference time-domain (FDTD) simulation. The comprehensive usage of photonic crystals and liquid crystal elastomers opened a new possibility for active optical devices.

One- and two-photon spectra of Nd3+ clusters in CaF2 and SrF2 crystals

International Nuclear Information System (INIS)

Basiev, Tasoltan T; Voronov, Valerii V; Glotova, M Yu; Papashvili, A G; Karasik, Aleksandr Ya

2003-01-01

The polarised two-photon (IR) and one-photon (visible) luminescence excitation spectra of Nd 3+ nanoclusters in CaF 2 and SrF 2 crystals are measured at 10 K using a F - 2 :LiF colour centre laser tunable in spectral ranges 1090 - 1230 nm and 545 - 615 nm with an emission linewidth of ∼0.02 - 0.03 cm -1 , an average output power of ∼55 mW, and a pulse repetition rate of 10 Hz. The two-photon excitation spectra at the 4 I 9/2 → 4 G 5/2 transition reveal the structure, which is absent upon one-photon excitation, which can be explained by different selection rules for some Stark - Stark transitions upon one- and two-photon absorption. (special issue devoted to the memory of academician a m prokhorov)

A bioaccumulative cyclometalated platinum(II) complex with two-photon-induced emission for live cell imaging.

Science.gov (United States)

Koo, Chi-Kin; Wong, Ka-Leung; Man, Cornelia Wing-Yin; Lam, Yun-Wah; So, Leo King-Yan; Tam, Hoi-Lam; Tsao, Sai-Wah; Cheah, Kok-Wai; Lau, Kai-Chung; Yang, Yang-Yi; Chen, Jin-Can; Lam, Michael Hon-Wah

2009-02-02

The cyclometalated platinum(II) complex [Pt(L)Cl], where HL is a new cyclometalating ligand 2-phenyl-6-(1H-pyrazol-3-yl)pyridine containing C(phenyl), N(pyridyl), and N(pyrazolyl) donor moieties, was found to possess two-photon-induced luminescent properties. The two-photon-absorption cross section of the complex in N,N-dimethylformamide at room temperature was measured to be 20.8 GM. Upon two-photon excitation at 730 nm from a Ti:sapphire laser, bright-green emission was observed. Besides its two-photon-induced luminescent properties, [Pt(L)Cl] was able to be rapidly accumulated in live HeLa and NIH3T3 cells. The two-photon-induced luminescence of the complex was retained after live cell internalization and can be observed by two-photon confocal microscopy. Its bioaccumulation properties enabled time-lapse imaging of the internalization process of the dye into living cells. Cytotoxicity of [Pt(L)Cl] to both tested cell lines was low, according to MTT assays, even at loadings as high as 20 times the dose concentration for imaging for 6 h.

Fully Depleted Charge-Coupled Devices

International Nuclear Information System (INIS)

Holland, Stephen E.

2006-01-01

We have developed fully depleted, back-illuminated CCDs that build upon earlier research and development efforts directed towards technology development of silicon-strip detectors used in high-energy-physics experiments. The CCDs are fabricated on the same type of high-resistivity, float-zone-refined silicon that is used for strip detectors. The use of high-resistivity substrates allows for thick depletion regions, on the order of 200-300 um, with corresponding high detection efficiency for near-infrared and soft x-ray photons. We compare the fully depleted CCD to the p-i-n diode upon which it is based, and describe the use of fully depleted CCDs in astronomical and x-ray imaging applications

Single photon emission computerized tomography

International Nuclear Information System (INIS)

Hooge, P. de.

1983-01-01

In this thesis two single-photon emission tomographic techniques are presented: (a) longitudinal tomography with a rotating slanting-hole collimator, and (b) transversal tomography with a rotating gamma camera. These methods overcome the disadvantages of conventional scintigraphy. Both detection systems and the image construction methods are explained and comparisons with conventional scintigraphy are drawn. One chapter is dedicated to the determination of system parameters like spatial resolution, contrast, detector uniformity, and size of the object, by phantom studies. In separate chapters the results are presented of detection of tumors and metastases in the liver and the liver hilus; skeletal diseases; various pathological aberrations of the brain; and myocardial perfusion. The possible use of these two ect's for other organs and body areas is discussed in the last chapter. (Auth.)

Preliminary Report on the Evaluation of an Electron-Positron Collider as a source of Monoenergetic Photons

Energy Technology Data Exchange (ETDEWEB)

Fast, James E.; Campbell, Luke W.

2009-11-30

Abstract Active interrogation methods are being investigated to detect shielded special nuclear material (SNM). These approaches utilize either neutron or photon beams to excite the SNM in concert with either neutron or gamma ray detectors to observe the stimulated emissions. The two primary methodologies with photon beams are photofission and nuclear resonance florescence (NRF). Photofission requires photons energies of 7-10 MeV while NRF requires photon energies around 2 MeV. For both techniques, photons that are not in the appropriate energy band, e.g. the low energy tail of a Bremsstrahlung photon beam, contribute unwanted additional radiation dose to cargo. Typically less than 10% of the photons are in the usable energy band. The additional photon production generates a commensurate amount of additional radiation dose in the source and target areas, impacting shielding requirements and/or dose to operators and equipment and at the expense of a similar increase in power consumption. Hence it is highly desirable to produce narrow energy (“monoenergetic”) photon beams with tunable energy in the range of ~2-20 MeV.

Dynamically controlling the emission of single excitons in photonic crystal cavities

NARCIS (Netherlands)

Pagliano, F.; Cho, Y.; Xia, T.; Otten, van F.W.M.; Johne, R.; Fiore, A.

2014-01-01

Single excitons in semiconductor microcavities represent a solid state and scalable platform for cavity quantum electrodynamics, potentially enabling an interface between flying (photon) and static (exciton) quantum bits in future quantum networks. While both singlephoton emission and the strong

Ibuprofen administration attenuates serum TNF-α levels, hepatic glutathione depletion, hepatic apoptosis and mouse mortality after Fas stimulation

International Nuclear Information System (INIS)

Cazanave, Sophie; Vadrot, Nathalie; Tinel, Marina; Berson, Alain; Letteron, Philippe; Larosche, Isabelle; Descatoire, Veronique; Feldmann, Gerard; Robin, Marie-Anne; Pessayre, Dominique

2008-01-01

Fas stimulation recruits neutrophils and activates macrophages that secrete tumor necrosis factor-α (TNF-α), which aggravates Fas-mediated liver injury. To determine whether nonsteroidal anti-inflammatory drugs modify these processes, we challenged 24-hour-fasted mice with the agonistic Jo2 anti-Fas antibody (4 μg/mouse), and treated the animals 1 h later with saline or ibuprofen (250 mg/kg), a dual cyclooxygenase (COX)-1 and COX-2 inhibitor. Ibuprofen attenuated the Jo2-mediated recruitment/activation of myeloperoxidase-secreting neutrophils/macrophages in the liver, and attenuated the surge in serum TNF-α. Ibuprofen also minimized hepatic glutathione depletion, Bid truncation, caspase activation, outer mitochondrial membrane rupture, hepatocyte apoptosis and the increase in serum alanine aminotransferase (ALT) activity 5 h after Jo2 administration, to finally decrease mouse mortality at later times. The concomitant administration of pentoxifylline (decreasing TNF-α secretion) and infliximab (trapping TNF-α) likewise attenuated the Jo2-mediated increase in TNF-α, the decrease in hepatic glutathione, and the increase in serum ALT activity 5 h after Jo2 administration. The concomitant administration of the COX-1 inhibitor, SC-560 (10 mg/kg) and the COX-2 inhibitor, celecoxib (40 mg/kg) 1 h after Jo2 administration, also decreased liver injury 5 h after Jo2 administration. In contrast, SC-560 (10 mg/kg) or celecoxib (40 or 160 mg/kg) given alone had no significant protective effects. In conclusion, secondary TNF-α secretion plays an important role in Jo2-mediated glutathione depletion and liver injury. The combined inhibition of COX-1 and COX-2 by ibuprofen attenuates TNF-α secretion, glutathione depletion, mitochondrial alterations, hepatic apoptosis and mortality in Jo2-treated fasted mice

Yield-scaled N2O emissions in a winter wheat - summer corn double-cropping system

NARCIS (Netherlands)

Qin, S.; Wang, Y.; Hu, C.; Oenema, O.; Li, X.; Zhang, Y.; Dong, W.

2012-01-01

Emissions of nitrous oxide (N2O) from agricultural soils contribute to global warming and stratospheric ozone depletion. Applications of fertilizer nitrogen (N) increase N2O emission, but also increase agricultural production. Here, we report on the responses of crop yield, N2O emission and

Linoleic Acid-Induced Ultra-Weak Photon Emission from Chlamydomonas reinhardtii as a Tool for Monitoring of Lipid Peroxidation in the Cell Membranes

Science.gov (United States)

Prasad, Ankush; Pospíšil, Pavel

2011-01-01

Reactive oxygen species formed as a response to various abiotic and biotic stresses cause an oxidative damage of cellular component such are lipids, proteins and nucleic acids. Lipid peroxidation is considered as one of the major processes responsible for the oxidative damage of the polyunsaturated fatty acid in the cell membranes. Various methods such as a loss of polyunsaturated fatty acids, amount of the primary and the secondary products are used to monitor the level of lipid peroxidation. To investigate the use of ultra-weak photon emission as a non-invasive tool for monitoring of lipid peroxidation, the involvement of lipid peroxidation in ultra-weak photon emission was studied in the unicellular green alga Chlamydomonas reinhardtii. Lipid peroxidation initiated by addition of exogenous linoleic acid to the cells was monitored by ultra-weak photon emission measured with the employment of highly sensitive charged couple device camera and photomultiplier tube. It was found that the addition of linoleic acid to the cells significantly increased the ultra-weak photon emission that correlates with the accumulation of lipid peroxidation product as measured using thiobarbituric acid assay. Scavenging of hydroxyl radical by mannitol, inhibition of intrinsic lipoxygenase by catechol and removal of molecular oxygen considerably suppressed ultra-weak photon emission measured after the addition of linoleic acid. The photon emission dominated at the red region of the spectrum with emission maximum at 680 nm. These observations reveal that the oxidation of linoleic acid by hydroxyl radical and intrinsic lipoxygenase results in the ultra-weak photon emission. Electronically excited species such as excited triplet carbonyls are the likely candidates for the primary excited species formed during the lipid peroxidation, whereas chlorophylls are the final emitters of photons. We propose here that the ultra-weak photon emission can be used as a non-invasive tool for the

Long-wavelength stimulated emission and carrier lifetimes in HgCdTe-based waveguide structures with quantum wells

Energy Technology Data Exchange (ETDEWEB)

Rumyantsev, V. V., E-mail: rumyantsev@ipm.sci-nnov.ru; Fadeev, M. A.; Morozov, S. V.; Dubinov, A. A.; Kudryavtsev, K. E.; Kadykov, A. M. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Tuzov, I. V. [Lobachevsky State University of Nizhny Novgorod (NNSU) (Russian Federation); Dvoretskii, S. A.; Mikhailov, N. N. [Russian Academy of Sciences, Institute for Semiconductor Physics, Siberian Branch (Russian Federation); Gavrilenko, V. I. [Novosibirsk State University (Russian Federation); Teppe, F. [Universite Montpellier II, Laboratoire Charles Coulomb (L2C) (France)

2016-12-15

The interband photoconductivity and photoluminescence in narrow-gap HgCdTe-based waveguide structures with quantum wells (QWs) (designed for long-wavelength stimulated emission under optical pumping) are investigated. The photoconductivity relaxation times in n-type structures reach several microseconds, due to which stimulated emission at a wavelength of 10.2 μm occurs at a low threshold pump intensity (~100 W/cm{sup 2}) at 20 K. In the p-type structures obtained by annealing (to increase the mercury vacancy concentration), even spontaneous emission from the QWs is not detected because of a dramatic decrease in the carrier lifetime with respect to Shockley–Read–Hall nonradiative recombination.

Thermically stimulated exoelectronic emissions and thermoluminescence of MgO

International Nuclear Information System (INIS)

Chubaci, J.F.D.

1987-01-01

In this work, studies were performed on the following topics: i) thermically stimulated exoelectronic emission (TSEE) in pure MgO single crystals ion implanted, submitted to thermal treatment with fast on slow cooling and water adsorption; ii) ultraviolet light effect on TSEE; iii) thermoluminescent emission; iv) crystallization of FeCoB amorphous alloys. (A.C.A.S.) [pt

$\\gamma$-Ray Pulsars: Emission Zones and Viewing Geometries

OpenAIRE

Romani, Roger W.; Yadigaroglu, I. -A.

1994-01-01

There are now a half dozen young pulsars detected in high energy photons by the Compton GRO, showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high energy emission on the sky in a model which posits $\\gamma$-ray production by charge depleted gaps in the outer magnetosphere. This model accounts for the radio to $\\gamma$-ray pulse offsets of the known pulsars, as well as the shape of the high energy pulse profiles. We also show that $...

Spectral distribution of the 2S → 1S two-photon transition in atoms ...

Indian Academy of Sciences (India)

Two-photon decay process was discussed first by Göppert-Mayer [1,2] in the 1930s for hydrogen and later it was described in detail for hydrogen and helium using non- relativistic approach by Breit and Teller [3]. The 2S state decays to ground state primarily by the emission of two electric-dipole photons, i.e. E1E1 or 2E1.

Direct photons in heavy-ion collisions

Energy Technology Data Exchange (ETDEWEB)

Baeuchle, Bjoern

2010-12-13

Direct photon emission from heavy-ion collisions has been calculated and compared to available experimental data. Three different models have been combined to extract direct photons from different environments in a heavy-ion collision: Thermal photons from partonic and hadronic matter have been extracted from relativistic, non-viscous 3+1-dimensional hydrodynamic calculations. Thermal and non-thermal photons from hadronic interactions have been calculated from relativistic transport theory. The impact of different physics assumptions about the thermalized matter has been studied. The models used for the determination of photons from both hydrodynamic and transport calculations have been elucidated and their numerical properties tested. The origin of direct photons, itemised by emission stage, emission time, channel and baryon number density, has been investigated for various systems, as have the transverse momentum spectra and elliptic flow patterns of direct photons. Taking into account the full (vacuum) spectral function of the rho-meson decreases the direct photon emission by approximately 10% at low photon transverse momentum. In all systems that have been considered -- heavy-ion collisions at E{sub lab}=35 AGeV and 158 AGeV, (s{sub NN}){sup 1/2}=62.4 GeV, 130 GeV and 200 GeV -- thermal emission from a system with partonic degrees of freedom is greatly enhanced over that from hadronic systems, while the difference between the direct photon yields from a viscous and a non-viscous hadronic system (transport vs. hydrodynamics) is found to be very small. Predictions for direct photon emission in central U+U-collisions at 35 AGeV have been made. (orig.)

Direct photons in heavy-ion collisions

International Nuclear Information System (INIS)

Baeuchle, Bjoern

2010-01-01

Direct photon emission from heavy-ion collisions has been calculated and compared to available experimental data. Three different models have been combined to extract direct photons from different environments in a heavy-ion collision: Thermal photons from partonic and hadronic matter have been extracted from relativistic, non-viscous 3+1-dimensional hydrodynamic calculations. Thermal and non-thermal photons from hadronic interactions have been calculated from relativistic transport theory. The impact of different physics assumptions about the thermalized matter has been studied. The models used for the determination of photons from both hydrodynamic and transport calculations have been elucidated and their numerical properties tested. The origin of direct photons, itemised by emission stage, emission time, channel and baryon number density, has been investigated for various systems, as have the transverse momentum spectra and elliptic flow patterns of direct photons. Taking into account the full (vacuum) spectral function of the rho-meson decreases the direct photon emission by approximately 10% at low photon transverse momentum. In all systems that have been considered -- heavy-ion collisions at E lab =35 AGeV and 158 AGeV, (s NN ) 1/2 =62.4 GeV, 130 GeV and 200 GeV -- thermal emission from a system with partonic degrees of freedom is greatly enhanced over that from hadronic systems, while the difference between the direct photon yields from a viscous and a non-viscous hadronic system (transport vs. hydrodynamics) is found to be very small. Predictions for direct photon emission in central U+U-collisions at 35 AGeV have been made. (orig.)

Collision-induced stimulated photon echoes in ‘strong’ magnetic field

Science.gov (United States)

Reshetov, V. A.

2018-05-01

Collision-induced stimulated photon echoes formed in a gaseous medium on the transition with the angular momentum change Ja=0 → Jb=1 under the action of ‘strong’ longitudinal magnetic field, when the echo pulse becomes unpolarized, are considered with an account of elastic depolarizing collisions. In the case of narrow spectral line the explicit expressions for the echo polarization density matrix and the degree of polarization are obtained. In the case of broad spectral line the results of the numeric calculations reproduce qualitatively the curve obtained in the experiments with ytterbium vapor.

Frequency-time behavior of artificially stimulated vlf emissions

International Nuclear Information System (INIS)

Stiles, G.S.; Helliwell, R.A.

1975-01-01

Artificially stimulated VLF emissions (ASE's) are emissions triggered in the magnetosphere by the whistler mode signals from VLF transmitters. These emissions may be separated into two classes, rising and falling, depending on whether the final value of df/dt is positive or negative. Several hundred ASE's triggered by three transmitters have been analyzed using the fast Fourier transform with a filter spacing of 25 Hz and an effective filter width of about 45 Hz. The study was limited to the initial frequency-time behavior of ASE's. Averages taken over many events reveal that both rising and falling tones show the same initial behavior. The emissions begin at the frequency of the triggering signal. Both tones initially rise in frequency, falling tones reversing slope at a point 25--300 Hz above the triggering signal. The slope of rising tones, particularly those triggered by NAA, often abruptly levels off in this same frequency range; as a result, a short (approximately 40 ms) plateau is formed that precedes the final rising phase. The initial frequency offset commonly observed in individual events appears to result from the frequent coincidence with this plateau of a peak in amplitude. Emissions stimulated by all three transmitters show essentially the same features; this finding indicates that their frequency behavior does not depend strongly on transmitter power. The process appears to be asymmetric in frequency; no evidence of initial growth below the triggering frequency has been found. (U.S.)

Calcium rubies: a family of red-emitting functionalizable indicators suitable for two-photon Ca2+ imaging.

Science.gov (United States)

Collot, Mayeul; Loukou, Christina; Yakovlev, Aleksey V; Wilms, Christian D; Li, Dongdong; Evrard, Alexis; Zamaleeva, Alsu; Bourdieu, Laurent; Léger, Jean-François; Ropert, Nicole; Eilers, Jens; Oheim, Martin; Feltz, Anne; Mallet, Jean-Maurice

2012-09-12

We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca(2+)) indicators as new tools for biological Ca(2+) imaging. The specificity of this Ca(2+)-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca(2+)-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca(2+) uncaging or optogenetic stimulation with Ca(2+) imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca(2+) transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca(2+)-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca(2+) chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca(2+)-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca(2+) concentrations are feasible.

Single-Photon Emission Computerized Tomography (SPECT in Neuropsychiatry: A Review

Directory of Open Access Journals (Sweden)

B. K. Puri

1992-01-01

Full Text Available Cranial single-photon emission computerized tomography (SPECT or SPET can now give regional cerebral blood flow images with a resolution approaching that of positron emission tomography (PET. In this paper, the use of high resolution SPECT neuroimaging in neuropsychiatric disorders, including Alzheimer's disease, multi-infarct dementia, Pick's disease, progressive supranuclear palsy, Korsakoff's psychosis, Creutzfeld-Jakob disease, Parkinson's disease, Huntington's disease, schizophrenia, mood disorders, obsessive–compulsive disorder, HIV infection and AIDS is reviewed. Finally, further potential research and clinical uses, based on ligand studies, are outlined.

AURORA on MEGSAT 1: a photon counting observatory for the Earth UV night-sky background and Aurora emission

International Nuclear Information System (INIS)

Monfardini, A.; Trampus, P.; Stalio, R.; Mahne, N.; Battiston, R.; Menichelli, M.; Mazzinghi, P.

2001-01-01

A low-mass, low-cost photon-counting scientific payload has been developed and launched on a commercial microsatellite in order to study the near-UV night-sky background emission with a telescope nicknamed 'Notte' and the Aurora emission with 'Alba'. AURORA, this is the name of the experiment, will determine, with the 'Notte' channel, the overall night-side photon background in the 300-400 nm spectral range, together with a particular 2 + N 2 line (λ c =337 nm). The 'Alba' channel, on the other hand, will study the Aurora emissions in four different spectral bands (FWHM=8.4-9.6 nm) centered on: 367 nm (continuum evaluation), 391 nm (1 - N + 2 ), 535 nm (continuum evaluation), 560 nm (OI). The instrument has been launched on the 26 September, 2000 from the Baikonur cosmodrome on a modified SS18 Dnepr-1 'Satan' rocket. The satellite orbit is nearly circular (h apogee =648 km, e=0.0022), and the inclination of the orbital plane is 64.56 deg. An overview of the techniques adopted is given in this paper

Brain receptor single-photon emission computer tomography with 123I Datscan in Parkinson's disease

International Nuclear Information System (INIS)

Minchev, D.; Peshev, N.; Kostadinova, I.; Grigorova, O.; Trindev, P.; Shotekov, P.

2005-01-01

Clinical aspects of Parkinson's disease are not enough for the early diagnosis of the disease. Positron emission tomography and the receptor single - photon emission tomography can be used for imaging functional integrity of nigrostriatal dopaminergic structures. 24 patient (17 men and 7 women) were investigated. 20 of them are with Parkinson's disease and 4 are with essential tremor. The radiopharmaceutical - 123I-Datscan (ioflupane, bind with 123I) represent a cocaine analogue with selective affinity to dopamine transporters, located in the dopaminergic nigrostriatal terminals in the striatum. Single - photon emission computer tomography was performed with SPECT gamma camera (ADAC, SH Epic detector). The scintigraphic study was made 3 to 6 hours after intravenous injection of the radiopharmaceutical - 123I- Datscan in dose 185 MBq. 120 frames are registered with duration of each one 22 seconds and gamma camera rotation 360. After generation of transversal slices we generated two composites pictures. The first composite picture image the striatum, the second - the occipital region. Two ratios were calculated representing the uptake of the radiopharmaceutical in the left and right striatum. Qualitative and quantitative criteria were elaborated for evaluating the scintigraphic patterns. Decreased, nonhomogeneous and asymmetric uptake of the radiopharmaceutical coupled with low quantitative parameters in range from 1.44 to 2.87 represents the characteristic scintigraphic pattern for Parkinson's disease with clear clinical picture. Homogenous with high intensity and symmetric uptake of the radiopharmaceutical in the striatum coupled with his clear frontier and with quantitative parameters up to 4.40 represent the scintigraphic pattern in two patients with essential tremor. Receptor single - photon emission computer tomography with 123I - Datscan represents an accurate nuclear-medicine method for precise diagnosis of Parkinson's disease and for its differentiation from

Dosimetry of Al2O3 optically stimulated luminescent dosimeter at high energy photons and electrons

Science.gov (United States)

Yusof, M. F. Mohd; Joohari, N. A.; Abdullah, R.; Shukor, N. S. Abd; Kadir, A. B. Abd; Isa, N. Mohd

2018-01-01

The linearity of Al2O3 OSL dosimeters (OSLD) were evaluated for dosimetry works in clinical photons and electrons. The measurements were made at a reference depth of Zref according to IAEA TRS 398:2000 codes of practice at 6 and 10 MV photons and 6 and 9 MeV electrons. The measured dose was compared to the thermoluminescence dosimeters (TLD) and ionization chamber commonly used for dosimetry works for higher energy photons and electrons. The results showed that the measured dose in OSL dosimeters were in good agreement with the reported by the ionization chamber in both high energy photons and electrons. A reproducibility test also reported excellent consistency of readings with the OSL at similar energy levels. The overall results confirmed the suitability of OSL dosimeters for dosimetry works involving high energy photons and electrons in radiotherapy.

High brightness single photon sources based on photonic wires

DEFF Research Database (Denmark)

Claudon, J.; Bleuse, J.; Bazin, M.

2009-01-01

We present a novel single-photon-source based on the emission of a semiconductor quantum dot embedded in a single-mode photonic wire. This geometry ensures a very large coupling (> 95%) of the spontaneous emission to the guided mode. Numerical simulations show that a photon collection efficiency...

Photonic band edge assisted spontaneous emission enhancement from all Er3+ 1-D photonic band gap structure

Science.gov (United States)

Chiasera, A.; Meroni, C.; Varas, S.; Valligatla, S.; Scotognella, F.; Boucher, Y. G.; Lukowiak, A.; Zur, L.; Righini, G. C.; Ferrari, M.

2018-06-01

All Er3+ doped dielectric 1-D Photonic Band Gap Structure was fabricated by rf-sputtering technique. The structure was constituted by of twenty pairs of SiO2/TiO2 alternated layers doped with Er3+ ions. The scanning electron microscopy was used to check the morphology of the structure. Transmission measurements put in evidence the stop band in the range 1500 nm-1950 nm. The photoluminescence measurements were obtained by optically exciting the sample and detecting the emitted light in the 1.5 μm region at different detection angles. Luminescence spectra and luminescence decay curves put in evidence that the presence of the stop band modify the emission features of the Er3+ ions.

Neutron stimulated emission computed tomography applied to the assessment of calcium deposition due to the presence of microcalcifications associated with breast cancer; Tomografia computadorizada de emissao estimulada por neutrons aplicada para avaliar a deposicao de calcio devido a presenca de microcalcificacoes associadas ao cancer de mama

Energy Technology Data Exchange (ETDEWEB)

Viana, Rodrigo S.S.; Yoriyaz, Helio [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, (SP) (Brazil)

2011-07-01

In this paper we presented an application of the Neutron Stimulated Emission Computed Tomography (NSECT), which uses a thin beam of fast neutrons to stimulate stable nuclei in a sample, emitting characteristic gamma radiation. The photon energy is unique and it is used to identify the emitting nuclei. This technique was applied for evaluating the calcium isotopic composition changing due to the development of breast microcalcifications. A particular situation was simulated in which clustered microcalcifications were modeled with diameters less than 1.40 mm. In this case, neutron beam breast spectroscopy was successful in detecting the counting changes in the photon emission spectra for energies, which are characteristics of 4{sup 0C}a isotope in a low deposited dose rate. (author)

Basolateral cholesterol depletion alters Aquaporin-2 post-translational modifications and disrupts apical plasma membrane targeting.

Science.gov (United States)

Moeller, Hanne B; Fuglsang, Cecilia Hvitfeldt; Pedersen, Cecilie Nøhr; Fenton, Robert A

2018-01-01

Apical plasma membrane accumulation of the water channel Aquaporin-2 (AQP2) in kidney collecting duct principal cells is critical for body water homeostasis. Posttranslational modification (PTM) of AQP2 is important for regulating AQP2 trafficking. The aim of this study was to determine the role of cholesterol in regulation of AQP2 PTM and in apical plasma membrane targeting of AQP2. Cholesterol depletion from the basolateral plasma membrane of a collecting duct cell line (mpkCCD14) using methyl-beta-cyclodextrin (MBCD) increased AQP2 ubiquitylation. Forskolin, cAMP or dDAVP-mediated AQP2 phosphorylation at Ser269 (pS269-AQP2) was prevented by cholesterol depletion from the basolateral membrane. None of these effects on pS269-AQP2 were observed when cholesterol was depleted from the apical side of cells, or when MBCD was applied subsequent to dDAVP stimulation. Basolateral, but not apical, MBCD application prevented cAMP-induced apical plasma membrane accumulation of AQP2. These studies indicate that manipulation of the cholesterol content of the basolateral plasma membrane interferes with AQP2 PTM and subsequently regulated apical plasma membrane targeting of AQP2. Copyright © 2017 Elsevier Inc. All rights reserved.

Imaging of the dopaminergic neurotransmission system using single-photon emission tomography and positron emission tomography in patients with parkinsonism

International Nuclear Information System (INIS)

Booij, J.; Tissingh, G.; Winogrodzka, A.; Royen, E.A. van

1999-01-01

Parkinsonism is a feature of a number of neurodegenerative diseases, including Parkinson's disease, multiple system atrophy and progressive supranuclear palsy. The results of post-mortem studies point to dysfunction of the dopaminergic neurotransmitter system in patients with parkinsonism. Nowadays, by using single-photon emission tomography (SPET) and positron emission tomography (PET) it is possible to visualise both the nigrostriatal dopaminergic neurons and the striatal dopamine D 2 receptors in vivo. Consequently, SPET and PET imaging of elements of the dopaminergic system can play an important role in the diagnosis of several parkinsonian syndromes. This review concentrates on findings of SPET and PET studies of the dopaminergic neurotransmitter system in various parkinsonian syndromes. (orig.)

Ab initio simulation of stimulated bremsstrahlung in an intense laser field

International Nuclear Information System (INIS)

Volkova, E.A.; Popov, A.M.; Popovicheva, O.B.

1992-01-01

Numerical solution of the time-dependent Schroedinger equation for a quantum system in the field of an electromagnetic wave is used to study a one-dimensional model of stimulated bremsstrahlung (absorption or emission of photons by a field in connection with Coulomb scattering of an electron). The time dependence of the stimulated bremsstrahlung effect is analyzed for various laser radiation intensities. The process of stimulated photorecombination is examined. The results of the calculation are compared with the analytical theory of the stimulated bremsstrahlung effect. 14 refs., 6 figs

Free radicals and low-level photon emission in human pathogenesis: state of the art.

Science.gov (United States)

Van Wijk, Roeland; Van Wijk, Eduard P A; Wiegant, Fred A C; Ives, John

2008-05-01

Convincing evidence supports a role for oxidative stress in the pathogenesis of many chronic diseases. The model includes the formation of radical oxygen species (ROS) and the misassembly and aggregation of proteins when three tiers of cellular defence are insufficient: (a) direct antioxidative systems, (b) molecular damage repairing systems, and (c) compensatory chaperone synthesis. The aim of the present overview is to introduce (a) the basics of free radical and antioxidant metabolism, (b) the role of the protein quality control system in protecting cells from free radical damage and its relation to chronic diseases, (c) the basics of the ultraweak luminescence as marker of the oxidant status of biological systems, and (d) the research in human photon emission as a non-invasive marker of oxidant status in relation to chronic diseases. In considering the role of free radicals in disease, both their generation and their control by the antioxidant system are part of the story. Excessive free radical production leads to the production of heat shock proteins and chaperone proteins as a second line of protection against damage. Chaperones at the molecular level facilitate stress regulation vis-à-vis protein quali y control mechanisms. The manifestation of misfolded proteins and aggregates is a hallmark of a range of neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, amylotrophic lateral sclerosis, polyglutamine (polyQ) diseases, diabetes and many others. Each of these disorders exhibits aging-dependent onset and a progressive, usually fatal clinical course. The second part reviews the current status of human photon emission techniques and protocols for recording the human oxidative status. Sensitive photomultiplier tubes may provide a tool for non-invasive and continuous monitoring of oxidative metabolism. In that respect, recording ultraweak luminescence has been favored compared to other indirect assays. Several biological models have

Linoleic acid-induced ultra-weak photon emission from Chlamydomonas reinhardtii as a tool for monitoring of lipid peroxidation in the cell membranes.

Directory of Open Access Journals (Sweden)

Ankush Prasad

Full Text Available Reactive oxygen species formed as a response to various abiotic and biotic stresses cause an oxidative damage of cellular component such are lipids, proteins and nucleic acids. Lipid peroxidation is considered as one of the major processes responsible for the oxidative damage of the polyunsaturated fatty acid in the cell membranes. Various methods such as a loss of polyunsaturated fatty acids, amount of the primary and the secondary products are used to monitor the level of lipid peroxidation. To investigate the use of ultra-weak photon emission as a non-invasive tool for monitoring of lipid peroxidation, the involvement of lipid peroxidation in ultra-weak photon emission was studied in the unicellular green alga Chlamydomonas reinhardtii. Lipid peroxidation initiated by addition of exogenous linoleic acid to the cells was monitored by ultra-weak photon emission measured with the employment of highly sensitive charged couple device camera and photomultiplier tube. It was found that the addition of linoleic acid to the cells significantly increased the ultra-weak photon emission that correlates with the accumulation of lipid peroxidation product as measured using thiobarbituric acid assay. Scavenging of hydroxyl radical by mannitol, inhibition of intrinsic lipoxygenase by catechol and removal of molecular oxygen considerably suppressed ultra-weak photon emission measured after the addition of linoleic acid. The photon emission dominated at the red region of the spectrum with emission maximum at 680 nm. These observations reveal that the oxidation of linoleic acid by hydroxyl radical and intrinsic lipoxygenase results in the ultra-weak photon emission. Electronically excited species such as excited triplet carbonyls are the likely candidates for the primary excited species formed during the lipid peroxidation, whereas chlorophylls are the final emitters of photons. We propose here that the ultra-weak photon emission can be used as a non

Quantum-dot nano-cavity lasers with Purcell-enhanced stimulated emission

DEFF Research Database (Denmark)

Gregersen, Niels; Skovgård, Troels Suhr; Lorke, Michael

2012-01-01

We present a rate equation model for quantum-dot light-emitting devices that take into account Purcell enhancement of both spontaneous emission and stimulated emission as well as the spectral profile of the optical and electronic density-of-states. We find that below threshold the b-factor in a q...

Barium depletion study on impregnated cathodes and lifetime prediction

International Nuclear Information System (INIS)

Roquais, J.M.; Poret, F.; Doze, R. le; Ricaud, J.L.; Monterrin, A.; Steinbrunn, A.

2003-01-01

In the thermionic cathodes used in cathode ray-tubes (CRTs), barium is the key element for the electronic emission. In the case of the dispenser cathodes made of a porous tungsten pellet impregnated with Ba, Ca aluminates, the evaporation of Ba determines the cathode lifetime with respect to emission performance in the CRT. The Ba evaporation results in progressive depletion of the impregnating material inside the pellet. In the present work, the Ba depletion with time has been extensively characterized over a large range of cathode temperature. Calculations using the depletion data allowed modeling of the depletion as a function of key parameters. The link between measured depletion and emission in tubes has been established, from which an end-of-life criterion was deduced. Taking modeling into account, predicting accelerated life-tests were performed using high-density maximum emission current (MIK)

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

Science.gov (United States)

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.

Depleted Bulk Heterojunction Colloidal Quantum Dot Photovoltaics

KAUST Repository

Barkhouse, D. Aaron R.

2011-05-26

The first solution-processed depleted bulk heterojunction colloidal quantum dot solar cells are presented. The architecture allows for high absorption with full depletion, thereby breaking the photon absorption/carrier extraction compromise inherent in planar devices. A record power conversion of 5.5% under simulated AM 1.5 illumination conditions is reported. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible nanomembrane photonic-crystal cavities for tensilely strained-germanium light emission

Energy Technology Data Exchange (ETDEWEB)

Yin, Jian; Wang, Xiaowei; Paiella, Roberto [Department of Electrical and Computer Engineering and Photonics Center, Boston University, 8 Saint Mary' s Street, Boston, Massachusetts 02215 (United States); Cui, Xiaorui; Sookchoo, Pornsatit; Lagally, Max G. [Department of Materials Science and Engineering, University of Wisconsin – Madison, 1509 University Avenue, Madison, Wisconsin 53706 (United States)

2016-06-13

Flexible photonic-crystal cavities in the form of Si-column arrays embedded in polymeric films are developed on Ge nanomembranes using direct membrane assembly. The resulting devices can sustain large biaxial tensile strain under mechanical stress, as a way to enhance the Ge radiative efficiency. Pronounced emission peaks associated with photonic-crystal cavity resonances are observed in photoluminescence measurements. These results show that ultrathin nanomembrane active layers can be effectively coupled to an optical cavity, while still preserving their mechanical flexibility. Thus, they are promising for the development of strain-enabled Ge lasers, and more generally uniquely flexible optoelectronic devices.

Quantum photonics hybrid integration platform

Energy Technology Data Exchange (ETDEWEB)

Murray, E.; Floether, F. F. [Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Ellis, D. J. P.; Meany, T.; Bennett, A. J., E-mail: anthony.bennet@crl.toshiba.co.uk; Shields, A. J. [Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Lee, J. P. [Cambridge Research Laboratory, Toshiba Research Europe Limited, 208 Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Engineering Department, University of Cambridge, 9 J. J. Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Griffiths, J. P.; Jones, G. A. C.; Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

2015-10-26

Fundamental to integrated photonic quantum computing is an on-chip method for routing and modulating quantum light emission. We demonstrate a hybrid integration platform consisting of arbitrarily designed waveguide circuits and single-photon sources. InAs quantum dots (QD) embedded in GaAs are bonded to a SiON waveguide chip such that the QD emission is coupled to the waveguide mode. The waveguides are SiON core embedded in a SiO{sub 2} cladding. A tuneable Mach Zehnder interferometer (MZI) modulates the emission between two output ports and can act as a path-encoded qubit preparation device. The single-photon nature of the emission was verified using the on-chip MZI as a beamsplitter in a Hanbury Brown and Twiss measurement.

Spectrum of acetylene fluorescence excited by single XUV photons

International Nuclear Information System (INIS)

Schmieder, R.W.

1982-01-01

The spectrum of visible emission from photofragments of acetylene excited by single 16.85 eV photons has been recorded for the first time. The spectrum is dominated by the Swan and Deslandres-d'Azambuja bands of C 2 and the 431.5 nm band of CH. The yields of these emissions are of the order 10 -3 photons per absorbed incident photon. The experimental conditions suggest that the emission results from primary C* 2 and CH* photofragments

Tailorable stimulated Brillouin scattering in nanoscale silicon waveguides

Science.gov (United States)

Shin, Heedeuk; Qiu, Wenjun; Jarecki, Robert; Cox, Jonathan A.; Olsson, Roy H.; Starbuck, Andrew; Wang, Zheng; Rakich, Peter T.

2013-01-01

Nanoscale modal confinement is known to radically enhance the effect of intrinsic Kerr and Raman nonlinearities within nanophotonic silicon waveguides. By contrast, stimulated Brillouin-scattering nonlinearities, which involve coherent coupling between guided photon and phonon modes, are stifled in conventional nanophotonics, preventing the realization of a host of Brillouin-based signal-processing technologies in silicon. Here we demonstrate stimulated Brillouin scattering in silicon waveguides, for the first time, through a new class of hybrid photonic–phononic waveguides. Tailorable travelling-wave forward-stimulated Brillouin scattering is realized—with over 1,000 times larger nonlinearity than reported in previous systems—yielding strong Brillouin coupling to phonons from 1 to 18 GHz. Experiments show that radiation pressures, produced by subwavelength modal confinement, yield enhancement of Brillouin nonlinearity beyond those of material nonlinearity alone. In addition, such enhanced and wideband coherent phonon emission paves the way towards the hybridization of silicon photonics, microelectromechanical systems and CMOS signal-processing technologies on chip. PMID:23739586

Improving the neutron-to-photon discrimination capability of detectors used for neutron dosimetry in high energy photon beam radiotherapy

International Nuclear Information System (INIS)

Irazola, L.; Terrón, J.A.; Bedogni, R; Pola, A.; Lorenzoli, M.; Sánchez-Nieto, B.; Gómez, F.; Sánchez-Doblado, F.

2016-01-01

The increasing interest of the medical community to radioinduced second malignancies due to photoneutrons in patients undergoing high-energy radiotherapy, has stimulated in recent years the study of peripheral doses, including the development of some dedicated active detectors. Although these devices are designed to respond to neutrons only, their parasitic photon response is usually not identically zero and anisotropic. The impact of these facts on measurement accuracy can be important, especially in points close to the photon field-edge. A simple method to estimate the photon contribution to detector readings is to cover it with a thermal neutron absorber with reduced secondary photon emission, such as a borated rubber. This technique was applied to the TNRD (Thermal Neutron Rate Detector), recently validated for thermal neutron measurements in high-energy photon radiotherapy. The positive results, together with the accessibility of the method, encourage its application to other detectors and different clinical scenarios. - Highlights: • Neutron-to-photon discrimination of a thermal neutron detector used in radiotherapy. • Photon and anisotropic response study with distance and beam incidence of thermal neutron detector. • Borated rubber for estimating photon contribution in any thermal neutron detector.

Relaxation oscillations in stimulated Raman scattering

International Nuclear Information System (INIS)

Kachen, G.I.; Lowdermilk, W.H.

1977-01-01

Light pulses created by stimulated Raman scattering having been found to exhibit a complex time dependence which resembles relaxation oscillations. A focused laser pulse generated both forward and backward Raman emissions which appeared as a series of pulses with durations much shorter than the incident laser pulse. Time dependence of the Raman emission was observed directly by use of a streak camera. The number of observed pulses increased with the intensity of the incident pulse, while separation of the pulses in time depended on the length of the focal region. Beam focusing was incorporated in the coupled wave equations for stimulated Raman scattering. These rate equations were then solved numerically, and the results are in good qualitative agreement with the experimental observations. The short Raman pulses are created by a process associated with depletion of the incident laser pulse. This process occurs under a broad range of conditions

AURORA on MEGSAT 1 a photon counting observatory for the Earth UV night-sky background and Aurora emission

CERN Document Server

Monfardini, A; Stalio, R; Mahne, N; Battiston, R; Menichelli, M; Mazzinghi, P

2001-01-01

A low-mass, low-cost photon-counting scientific payload has been developed and launched on a commercial microsatellite in order to study the near-UV night-sky background emission with a telescope nicknamed 'Notte' and the Aurora emission with 'Alba'. AURORA, this is the name of the experiment, will determine, with the 'Notte' channel, the overall night-side photon background in the 300-400 nm spectral range, together with a particular 2 sup + N sub 2 line (lambda sub c =337 nm). The 'Alba' channel, on the other hand, will study the Aurora emissions in four different spectral bands (FWHM=8.4-9.6 nm) centered on: 367 nm (continuum evaluation), 391 nm (1 sup - N sup + sub 2), 535 nm (continuum evaluation), 560 nm (OI). The instrument has been launched on the 26 September, 2000 from the Baikonur cosmodrome on a modified SS18 Dnepr-1 'Satan' rocket. The satellite orbit is nearly circular (h sub a sub p sub o sub g sub e sub e =648 km, e=0.0022), and the inclination of the orbital plane is 64.56 deg. An overview of...

On spontaneous photon emission in collapse models

International Nuclear Information System (INIS)

Adler, Stephen L; Bassi, Angelo; Donadi, Sandro

2013-01-01

We reanalyze the problem of spontaneous photon emission in collapse models. We show that the extra term found by Bassi and Dürr is present for non-white (colored) noise, but its coefficient is proportional to the zero frequency Fourier component of the noise. This leads one to suspect that the extra term is an artifact. When the calculation is repeated with the final electron in a wave packet and with the noise confined to a bounded region, the extra term vanishes in the limit of continuum state normalization. The result obtained by Fu and by Adler and Ramazanoğlu from application of the Golden Rule is then recovered. (paper)

Optics of globular photonic crystals

International Nuclear Information System (INIS)

Gorelik, V S

2007-01-01

The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter ∼200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported. (review)

AMPT-induced monoamine depletion in humans: evaluation of two alternative [123I]IBZM SPECT procedures

International Nuclear Information System (INIS)

Boot, Erik; Booij, Jan; Hasler, Gregor; Zinkstok, Janneke R.; Haan, Lieuwe de; Linszen, Don H.; Amelsvoort, Therese A. van

2008-01-01

Acute monoamine depletion paradigms using alpha-methyl-para-tyrosine (AMPT) combined with single photon emission computed tomography (SPECT) have been used successfully to evaluate disturbances in central dopaminergic neurotransmission. However, severe side effects due to relatively high doses (4,500 to 8,000 mg) of AMPT have been reasons for study withdrawal. Thus, we assessed the effectiveness and tolerability of two alternative procedures, using lower doses of AMPT. Six healthy subjects underwent three measurements of striatal dopamine D 2 receptor (D 2 R)-binding potential (BP ND ) with SPECT and the selective radiolabeled D 2 R antagonist [ 123 I]IBZM. All subjects were scanned in the absence of pharmacological intervention (baseline) and after two different depletion procedures. In the first depletion session, over 6 h, subjects were administered 1,500 mg of AMPT before scanning. In the second depletion session, over 25 h, subjects were administered 40 mg AMPT/kg body weight. We also administered the Subjective Well-being Under Neuroleptic Treatment Scale, a self-report instrument designed to measure the subjective experience of patients on neuroleptic medication. We found no change of mean D 2 R BP ND after the first and short AMPT challenge compared to the baseline. However, we found a significant increase in striatal D 2 R BP ND binding after the AMPT challenge adjusted for bodyweight compared to both other regimen. Although subjective well-being worsened after the prolonged AMPT challenge, no severe side effects were reported. Our results imply a low-dosage, suitable alternative to the common AMPT procedure. The probability of side effects and study withdrawal can be reduced by this procedure. (orig.)

Detection of carbon monoxide (CO) in sooting hydrocarbon flames using femtosecond two-photon laser-induced fluorescence (fs-TPLIF)

Science.gov (United States)

Wang, Yejun; Kulatilaka, Waruna D.

2018-01-01

Ultrashort-pulse, femtosecond (fs)-duration, two-photon laser-induced fluorescence (fs-TPLIF) measurements of carbon monoxide (CO) are reported in rich, sooting hydrocarbon flames. CO-TPLIF detection using conventional nanosecond or picosecond lasers are often plagued by photochemical interferences, specifically under fuel-rich flames conditions. In the current study, we investigate the commonly used CO two-photon excitation scheme of the B1Σ+ ← X1Σ+ electronic transition, using approximately 100-fs-duration excitation pulses. Fluorescence emission was observed in the Ångström band originating from directly populated B1Σ+ upper state, as well as, in the third positive band from collisionally populated b3Σ+ upper state. The current work was focused on the Ångström band emission. Interference from nascent C2 emissions originating from hot soot particles in the flame could be reduced to a negligible level using a narrower detection gate width. In contrast, avoiding interferences from laser-generated C2 Swan-band emissions required specific narrowband spectral filtering in sooting flame conditions. The observed less than quadratic laser pulse energy dependence of the TPLIF signal suggests the presence of strong three-photon ionization and stimulated emission processes. In a range of CH4/air and C2H4/air premixed flames investigated, the measured CO fluorescence signals agree well with the calculated equilibrium CO number densities. Reduced-interference CO-TPLIF imaging in premixed C2H4/O2/N2 jet flames is also reported.

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

Science.gov (United States)

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.

Searching for illicit materials using nuclear resonance fluorescence stimulated by narrow-band photon sources

Energy Technology Data Exchange (ETDEWEB)

Johnson, M.S., E-mail: johnson329@llnl.gov [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); San Jose State University, San Jose, CA 95192 (United States); Hagmann, C.A.; Hall, J.M.; McNabb, D.P. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Kelley, J.H.; Huibregtse, C. [North Carolina State University, Raleigh, NC 27695 (United States); Kwan, E.; Rusev, G.; Tonchev, A.P. [Duke University, Durham, NC 27708 (United States)

2012-08-15

We report the results of an experimental study of the sensitivity of two distinct classes of systems that exploit nuclear resonance fluorescence (NRF) to search for illicit materials in containers. One class of systems is based on the direct detection of NRF photons emitted from isotopes of interest. The other class infers the presence of a particular isotope by observing the preferential attenuation of resonant photons in the incident beam. We developed a detailed analytical model for both approaches. We performed experiments to test the model using depleted uranium as a surrogate for illicit material and used tungsten as a random choice for shielding. We performed the experiments at Duke University's High Intensity Gamma Source (HIGS). Using the methodology we detail in this paper one can use this model to estimate the performance of potential inspection systems in certifying containers as free of illicit materials and for detecting the presence of those same materials.

Oval cell response is attenuated by depletion of liver resident macrophages in the 2-AAF/partial hepatectomy rat.

Directory of Open Access Journals (Sweden)

Shuai Xiang

Full Text Available BACKGROUND/AIMS: Macrophages are known to play an important role in hepatocyte mediated liver regeneration by secreting inflammatory mediators. However, there is little information available on the role of resident macrophages in oval cell mediated liver regeneration. In the present study we aimed to investigate the role of macrophages in oval cell expansion induced by 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH in rats. METHODOLOGY/PRINCIPAL FINDINGS: We depleted macrophages in the liver of 2-AAF/PH treated rats by injecting liposome encapsulated clodronate 48 hours before PH. Regeneration of remnant liver mass, as well as proliferation and differentiation of oval cells were measured. We found that macrophage-depleted rats suffered higher mortality and liver transaminase levels. We also showed that depletion of macrophages yielded a significant decrease of EPCAM and PCK positive oval cells in immunohistochemical stained liver sections 9 days after PH. Meanwhile, oval cell differentiation was also attenuated as a result of macrophage depletion, as large foci of small basophilic hepatocytes were observed by day 9 following hepatectomy in control rats whereas they were almost absent in macrophage depleted rats. Accordingly, real-time polymerase chain reaction analysis showed lower expression of albumin mRNA in macrophage depleted livers. Then we assessed whether macrophage depletion may affect hepatic production of stimulating cytokines for liver regeneration. We showed that macrophage-depletion significantly inhibited hepatic expression of tumor necrosis factor-α and interleukin-6, along with a lack of signal transducer and activator of transcription 3 phosphorylation during the early period following hepatectomy. CONCLUSIONS: These data indicate that macrophages play an important role in oval cell mediated liver regeneration in the 2-AAF/PH model.

Simulation Study of Single Photon Emission Computed Tomography for Industrial Applications

International Nuclear Information System (INIS)

Roy, Tushar; Sarkar, P. S.; Sinha, Amar

2008-01-01

SPECT (Single Photon Emission Computed Tomography) provides for an invaluable non-invasive technique for the characterization and activity distribution of the gamma-emitting source. For many applications of radioisotopes for medical and industrial application, not only the positional information of the distribution of radioisotopes is needed but also its strength. The well-established X-ray radiography or transmission tomography techniques do not yield sufficient quantitative information about these objects. Emission tomography is one of the important methods for such characterization. Application of parallel beam, fan beam and 3D cone beam emission tomography methods have been discussed in this paper. Simulation studies to test these algorithms have been carried out to validate the technique.

Polarization of the induced THz emission of donors in silicon

Energy Technology Data Exchange (ETDEWEB)

Kovalevsky, K. A., E-mail: atan4@yandex.ru; Zhukavin, R. Kh.; Tsyplenkov, V. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Pavlov, S. G.; Hübers, H.-W. [Humboldt University of Berlin (Germany); Abrosimov, N. V.; Shastin, V. N. [Leibniz Institute for Crystal Growth (Germany)

2016-12-15

The polarization of the terahertz (4.9–6.4 THz) stimulated emission of Group-V (Sb, P, As, Bi) donors in single-crystal silicon under pumping (photoionization) by a CO{sub 2} laser (photon energy 117 meV), depending on the uniaxial compressive deformation of the crystal along the [100] axis, is experimentally investigated. The influence of the field direction of the pump wave on its efficiency is discussed.

The problem of dating quartz 2: Synchrotron generated X-ray excited optical luminescence (XEOL) from quartz

International Nuclear Information System (INIS)

King, G.E.; Finch, A.A.; Robinson, R.A.J.; Taylor, R.P.; Mosselmans, J.F.W.

2011-01-01

The luminescence emission of quartz is used in optically stimulated luminescence dating (OSL), however the precise origins of the emission are unclear. A suite of quartz samples were analysed using X-ray excited optical luminescence (XEOL). Radiation dose effects were observed whereby the UV emissions (3.8 and 3.4 eV) were depleted to the benefit of the red emission (1.9-2.0 eV). Samples were excited at ∼7 keV. Understanding why some quartz emit light more brightly than others will increase the efficiency and precision of OSL analyses. - Highlights: → The X-ray excited optical luminescence (XEOL) emission of quartz is explored. → The XEOL of quartz of different provenances varies. → Radiation dosing causes UV emissions to deplete to the benefit of red emissions. → The 3.8 and 3.4 eV emissions deplete at the same rate. → The quartz luminescence emission exhibits anisotropic effects.

Interictal "patchy" regional cerebral blood flow patterns in migraine patients. A single photon emission computerized tomographic study

DEFF Research Database (Denmark)

Friberg, L; Olesen, J; Iversen, Helle Klingenberg

1994-01-01

In 92 migraine patients and 44 healthy control subjects we recorded regional cerebral blood flow (rCBF) with single photon emission computerized tomography and (133) Xe inhalation or with i.v. (99m) Tc-HMPAO. Migraine patients were studied interictally. A quantitated analysis of right-left asymme......In 92 migraine patients and 44 healthy control subjects we recorded regional cerebral blood flow (rCBF) with single photon emission computerized tomography and (133) Xe inhalation or with i.v. (99m) Tc-HMPAO. Migraine patients were studied interictally. A quantitated analysis of right...... rCBF images is insufficient to pick up abnormalities; (2) almost 50% of the migraine sufferers had abnormal rCBF/asymmetries. However, these are discrete compared with those typically seen during the aura phase of a migraine attack. One explanation to the patchy rCBF patterns might...

Spontaneous and stimulated emission induced by an electron, electron bunch, and electron beam in a plasma

International Nuclear Information System (INIS)

Kuzelev, M V; Rukhadze, A A

2008-01-01

Two fundamental mechanisms - the Cherenkov effect and anomalous Doppler effect - underlying the emission by an electron during its superluminal motion in medium are considered. Cherenkov emission induced by a single electron and a small electron bunch is spontaneous. In the course of spontaneous Cherenkov emission, the translational motion of an electron is slowed down and the radiation energy grows linearly with time. As the number of radiating electrons increases, Cherenkov emission becomes stimulated. Stimulated Cherenkov emission represents a resonance beam instability. This emission process is accompanied by longitudinal electron bunching in the beam or by the breaking of an electron bunch into smaller bunches, in which case the radiation energy grows exponentially with time. In terms of the longitudinal size L e of the electron bunch there is a transition region λ e 0 -1 between the spontaneous and stimulated Cherenkov effects, where λ is the average radiation wavelength, and δ 0 is the dimensionless (in units of the radiation frequency) growth rate of the Cherenkov beam instability. The range to the left of this region is dominated by spontaneous emission, whereas the range to the right of this region is dominated by stimulated emission. In contrast to the Vavilov-Cherenkov effect, the anomalous Doppler effect should always (even for a single electron) be considered as stimulated, because it can only be explained by accounting for the reverse action of the radiation field on the moving electron. During stimulated emission in conditions where anomalous Doppler effect shows itself, an electron is slowed down and spins up; in this case, the radiation energy grows exponentially with time. (reviews of topical problems)

Spontaneous emission near the band edge of a three-dimensional photonic crystal: a fractional calculus approach

International Nuclear Information System (INIS)

Cheng, S-C; Wu, J-N; Tsai, M-R; Hsieh, W-F

2009-01-01

We suggest a better mathematical method, fractional calculus, for studying the behavior of the atom-field interaction in photonic crystals. By studying the spontaneous emission of an atom in a photonic crystal with a one-band isotropic model, we found that the long-time inducing memory of the spontaneous emission is a fractional phenomenon. This behavior could be well described by fractional calculus. The results show no steady photon-atom bound state for the atomic resonant transition frequency lying in the proximity of the allowed band edge which was encountered in a previous study (Woldeyohannes and John 2003 J. Opt. B: Quantum Semiclass. Opt. 5 R43). The correctness of this result is validated by the 'cut-off smoothing' density of photon states (DOS) with fractional calculus. By obtaining a rigorous solution without the multiple-valued problem for the system, we show that the method of fractional calculus has a logically concise property.

Effects of multi-photon interferences from internally generated fields in strongly resonant systems

International Nuclear Information System (INIS)

Deng, Lu; Payne, Marvin G.; Garrett, William R.

2006-01-01

In studies of various nonlinear optical phenomena, strong resonant features in the atomic or molecular response to multi-photon driven processes have been used to greatly enhance the visibility of otherwise weak higher-order processes. However, there are well defined circumstances where a multi-photon-resonant response of a target system leads to the generation of one or more new electromagnetic fields that can drastically change the overall system response from what would be expected from the imposed laser fields alone. New effects can occur and dominate some aspects of the nonlinear optical response because of the constructive or destructive interference between transition amplitudes along multiple excitation pathways between a given set of optically coupled states, where one of the pathways involve internally generated field(s). Under destructive interference some resonant enhancements can become completely canceled (suppressed). This review focuses on the class of optical interference effects associated with internally generated fields, that have been found to be capable of influencing a very significant number of basic physical phenomena in gas or vapor phase systems. It provides a historical overview of experimental and theoretical developments and a modern understanding of the underlying physics and its various manifestations that include: suppression of multi-photon excitation processes, suppression of stimulated emissions (Raman, hyper-Raman, and optically pumped stimulated emissions), saturation of parametric wave-mixing, pressure and beam-geometry dependent shifting of multi-photon-resonant absorption lines, and the suppression of Autler-Townes splitting and ac-stark shifts. Additionally, optical interference effects in some modern contexts, such as achieving multi-photon induced transparency, establishing single-photon self-interference based induced transparency, and generating entangled single photon states, are reviewed

XPS investigation of the photon degradation of Znq{sub 2} green organic phosphor

Energy Technology Data Exchange (ETDEWEB)

Duvenhage, Mart-Mari; Terblans, Jacobus J.; Ntwaeaborwa, Martin; Swart, Hendrik C., E-mail: swarthc@ufs.ac.za

2016-01-01

By substituting Al with Zn to form bis-(8-hydroxyquinoline) zinc (Znq{sub 2}), the device performance of organic light emitting diodes (OLED) can be improved. Znq{sub 2} also has a more closed packed crystal structure that makes it less vulnerable to reactions with atmospheric oxygen and moisture leading to more stable and longer lasting devices. In this work the effect of photon degradation of Znq{sub 2} in air was investigated. Znq{sub 2} powder was synthesized using a co-precipitation method and recrystallized in acetone. The structure of the sample was confirmed to be Znq{sub 2}·2H{sub 2}O by X-ray diffraction. The photoluminescence (PL) emission data also confirmed that the Znq{sub 2}·2H{sub 2}O crystal form of Znq{sub 2} was present. To study the photon degradation, the sample was irradiated with a UV lamp for 400 h. The emission data was collected and the change in PL intensity with time was monitored. X-ray photoelectron spectroscopy was performed on the as prepared and photon-degraded samples. The Zn2p and N1s peaks showed no change after degradation. The O1s and C1s peaks confirmed that the phenoxide ring ruptured and that C=O and C–O species had formed.

Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

Science.gov (United States)

Zhang, Duo; Li, Jiahua; Ding, Chunling; Yang, Xiaoxue

2012-05-01

The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission.

Initial clinical experiences with dopamine D2 receptor imaging by means of 2'-iodospiperone and single-photon emission computed tomography

International Nuclear Information System (INIS)

Yonekura, Yoshiharu; Saji, Hideo; Iwasaki, Yasushi

1995-01-01

Dopamine D 2 receptor imaging was performed with 123 I labeled 2'-iodospiperone (2'-ISP) and single-photon emission computed tomography (SPECT) in 9 patients: 4 with idiopathic Parkinson's disease, 2 with parkinsonism, 1 with Wilson's disease and 2 with pituitary tumor, and the results were compared with the data for 9 normal subjects. Following an intravenous injection of 123 I-2'-ISP, early (within 30 min) and late (between 2 and 4 hr) SPECT images were obtained by means of a multi-detector SPECT scanner or a rotating gamma camera. In normal subjects, early SPECT images demonstrated uniform distribution of radioactivity in the cerebral gray matter and cerebellum reflecting regional cerebral blood flow, whereas late SPECT images showed high radioactivity only in the basal ganglia. All the patients with Parkinson's disease also demonstrated symmetrical basal ganglia uptake in the late SPECT images, but it was diminished in parkinsonism and Wilson's disease. One patient with a growth hormone-producing pituitary tumor had a positive uptake in the tumor. These preliminary clinical data demonstrated that 2'-ISP can be used for SPECT imaging of D 2 dopamine receptors and may be of clinical value for the diagnosis and planning of the treatment of neurological diseases. (author)

Deuterium - depleted water. Achievements and perspectives

International Nuclear Information System (INIS)

Titescu, Gh.; Stefanescu, I.; Saros-Rogobete, I.

2001-01-01

Deuterium - depleted water represents water that has an isotopic content lower than 145 ppm D/(D+H) which is the natural isotopic content of water. The research conducted at ICSI Ramnicu Valcea, regarding deuterium - depleted water were completed by the following patents: - technique and installation for deuterium - depleted water production; - distilled water with low deuterium content; - technique and installation for the production of distilled water with low deuterium content; - mineralized water with low deuterium content and technique to produce it. The gold and silver medals won at international salons for inventions confirmed the novelty of these inventions. Knowing that deuterium content of water has a big influence on living organisms, beginning with 1996, the ICSI Ramnicu Valcea, deuterium - depleted water producer, co-operated with Romanian specialized institutes for biological effects' evaluation of deuterium - depleted water. The role of natural deuterium in living organisms was examined by using deuterium - depleted water instead of natural water. These investigations led to the following conclusions: 1. deuterium - depleted water caused a tendency towards the increase of the basal tone, accompanied by the intensification of the vasoconstrictor effects of phenylefrine, noradrenaline and angiotensin; the increase of the basal tone and vascular reactivity produced by the deuterium - depleted water persists after the removal of the vascular endothelium; -2. animals treated with deuterium - depleted water showed an increase of the resistance both to sublethal and to lethal gamma radiation doses, suggesting a radioprotective action by the stimulation of non-specific immune defence mechanism; 3, deuterium - depleted water stimulates immune defence reactions, represented by the opsonic, bactericidal and phagocyte capacity of the immune system, together with increase in the numbers of polymorphonuclear neutrophils; 4. investigations regarding artificial

DISCOVERY OF TeV GAMMA-RAY EMISSION TOWARD SUPERNOVA REMNANT SNR G78.2+2.1

Energy Technology Data Exchange (ETDEWEB)

Aliu, E. [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States); Archambault, S. [Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada); Arlen, T.; Aune, T. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R. [Department of Physics, Washington University, St. Louis, MO 63130 (United States); Benbow, W. [Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States); Bird, R.; Cannon, A.; Collins-Hughes, E. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Bouvier, A. [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States); Bradbury, S. M. [School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT (United Kingdom); Byrum, K. [Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States); Cesarini, A.; Connolly, M. P. [School of Physics, National University of Ireland Galway, University Road, Galway (Ireland); Ciupik, L. [Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States); Cui, W. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Duke, C., E-mail: amandajw@iastate.edu [Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States); and others

2013-06-20

We report the discovery of an unidentified, extended source of very-high-energy gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hr of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic extent of 0.23 Degree-Sign .23 {+-} 0. Degree-Sign 03{sub stat-0 Degree-Sign .02sys}{sup +0 Degree-Sign .04} and its spectrum is well-characterized by a differential power law (dN/dE = N{sub 0} Multiplication-Sign (E/TeV){sup -{Gamma}}) with a photon index of {Gamma} = 2.37 {+-} 0.14{sub stat} {+-} 0.20{sub sys} and a flux normalization of N{sub 0} = 1.5 {+-} 0.2{sub stat} {+-} 0.4{sub sys} Multiplication-Sign 10{sup -12} photon TeV{sup -1} cm{sup -2} s{sup -1}. This yields an integral flux of 5.2 {+-} 0.8{sub stat} {+-} 1.4{sub sys} Multiplication-Sign 10{sup -12} photon cm{sup -2} s{sup -1} above 320 GeV, corresponding to 3.7% of the Crab Nebula flux. We consider the relationship of the TeV gamma-ray emission with the GeV gamma-ray emission seen from SNR G78.2+2.1 as well as that seen from a nearby cocoon of freshly accelerated cosmic rays. Multiple scenarios are considered as possible origins for the TeV gamma-ray emission, including hadronic particle acceleration at the SNR shock.

Photon-dominated region modeling of the [C I], [C II], and CO Line Emission From A Boundary In The Taurus molecular cloud

Energy Technology Data Exchange (ETDEWEB)

Orr, Matthew E. [Physics and Astronomy Department, University of Southern California, Los Angeles, CA 90089 (United States); Pineda, Jorge L.; Goldsmith, Paul F. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States)

2014-11-01

We present [C I] and [C II] observations of a linear edge region in the Taurus molecular cloud, and model this region as a cylindrically symmetric photon-dominated region (PDR) exposed to a low-intensity UV radiation field. The sharp, long profile of the linear edge makes it an ideal case to test PDR models and determine cloud parameters. We compare observations of the [C I], {sup 3} P {sub 1} → {sup 3} P {sub 0} (492 GHz), [C I] {sup 3} P {sub 2} → {sup 3} P {sub 1} (809 GHz), and [C II] {sup 2} P {sub 3/2} → {sup 2} P {sub 1/2} (1900 GHz) transitions, as well as the lowest rotational transitions of {sup 12}CO and {sup 13}CO, with line intensities produced by the RATRAN radiative transfer code from the results of the Meudon PDR code. We constrain the density structure of the cloud by fitting a cylindrical density function to visual extinction data. We study the effects of variation of the FUV field, {sup 12}C/{sup 13}C isotopic abundance ratio, sulfur depletion, cosmic ray ionization rate, and inclination of the filament relative to the sky-plane on the chemical network of the PDR model and resulting line emission. We also consider the role of suprathermal chemistry and density inhomogeneities. We find good agreement between the model and observations, and that the integrated line intensities can be explained by a PDR model with an external FUV field of 0.05 G {sub 0}, a low ratio of {sup 12}C to {sup 13}C ∼43, a highly depleted sulfur abundance (by a factor of at least 50), a cosmic ray ionization rate (3-6) × 10{sup –17} s{sup –1}, and without significant effects from inclination, clumping or suprathermal chemistry.

AMPT-induced monoamine depletion in humans: evaluation of two alternative [{sup 123}I]IBZM SPECT procedures

Energy Technology Data Exchange (ETDEWEB)

Boot, Erik [Academic Medical Centre (AMC), University of Amsterdam, Department of Psychiatry, Amsterdam (Netherlands); De Bruggen, Centre for People with Intellectual Disability, Zwammerdam (Netherlands); Booij, Jan [AMC, Department of Nuclear Medicine, Amsterdam (Netherlands); Hasler, Gregor [University Hospital, Department of Psychiatry, Zuerich (Switzerland); Zinkstok, Janneke R.; Haan, Lieuwe de; Linszen, Don H.; Amelsvoort, Therese A. van [Academic Medical Centre (AMC), University of Amsterdam, Department of Psychiatry, Amsterdam (Netherlands)

2008-07-15

Acute monoamine depletion paradigms using alpha-methyl-para-tyrosine (AMPT) combined with single photon emission computed tomography (SPECT) have been used successfully to evaluate disturbances in central dopaminergic neurotransmission. However, severe side effects due to relatively high doses (4,500 to 8,000 mg) of AMPT have been reasons for study withdrawal. Thus, we assessed the effectiveness and tolerability of two alternative procedures, using lower doses of AMPT. Six healthy subjects underwent three measurements of striatal dopamine D{sub 2} receptor (D{sub 2}R)-binding potential (BP{sub ND}) with SPECT and the selective radiolabeled D{sub 2}R antagonist [{sup 123}I]IBZM. All subjects were scanned in the absence of pharmacological intervention (baseline) and after two different depletion procedures. In the first depletion session, over 6 h, subjects were administered 1,500 mg of AMPT before scanning. In the second depletion session, over 25 h, subjects were administered 40 mg AMPT/kg body weight. We also administered the Subjective Well-being Under Neuroleptic Treatment Scale, a self-report instrument designed to measure the subjective experience of patients on neuroleptic medication. We found no change of mean D{sub 2}R BP{sub ND} after the first and short AMPT challenge compared to the baseline. However, we found a significant increase in striatal D{sub 2}R BP{sub ND} binding after the AMPT challenge adjusted for bodyweight compared to both other regimen. Although subjective well-being worsened after the prolonged AMPT challenge, no severe side effects were reported. Our results imply a low-dosage, suitable alternative to the common AMPT procedure. The probability of side effects and study withdrawal can be reduced by this procedure. (orig.)

Quantum squeezed state analysis of spontaneous ultra weak light photon emission of practitioners of meditation and control subjects.

Science.gov (United States)

Van Wijk, Eduard P A; Van Wijk, Roeland; Bajpai, Rajendra P

2008-05-01

Research on human ultra-weak photon emission (UPE) has suggested a typical human emission anatomic percentage distribution pattern. It was demonstrated that emission intensities are lower in long-term practitioners of meditation as compared to control subjects. The percent contribution of emission from different anatomic locations was not significantly different for meditation practitioners and control subjects. Recently, a procedure was developed to analyze the fluctuations in the signals by measuring probabilities of detecting different numbers of photons in a bin and correct these for background noise. The procedure was tested utilizing the signal from three different body locations of a single subject, demonstrating that probabilities have non-classical features and are well described by the signal in a coherent state from the three body sites. The values indicate that the quantum state of photon emitted by the subject could be a coherent state in the subject being investigated. The objective in the present study was to systematically quantify, in subjects with long-term meditation experience and subjects without this experience, the photon count distribution of 12 different locations. Data show a variation in quantum state parameters within each individual subject as well as variation in quantum state parameters between the groups.

Long wavelength stimulated emission up to 9.5 μm from HgCdTe quantum well heterostructures

Energy Technology Data Exchange (ETDEWEB)

Morozov, S. V.; Rumyantsev, V. V., E-mail: rumyantsev@ipmras.ru; Dubinov, A. A.; Kudryavtsev, K. E.; Antonov, A. V.; Gavrilenko, V. I. [Institute for Physics of Microstructures of Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod (Russian Federation); Kadykov, A. M. [Institute for Physics of Microstructures of Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); UMR CNRS 5221, GIS-TERALAB, Université Montpellier II, 34095 Montpellier (France); Mikhailov, N. N. [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Dvoretskii, S. A. [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation)

2016-02-29

Stimulated emission from waveguide HgCdTe structures with several quantum wells inside waveguide core is demonstrated at wavelengths up to 9.5 μm. Photoluminescence line narrowing down to kT energy, as well as superlinear rise in its intensity evidence the onset of the stimulated emission, which takes place under optical pumping with intensity as small as ∼0.1 kW/cm{sup 2} at 18 K and 1 kW/cm{sup 2} at 80 K. One can conclude that HgCdTe structures potential for long-wavelength lasers is not exhausted.

Ultrafast electrical control of a resonantly driven single photon source

International Nuclear Information System (INIS)

Cao, Y.; Bennett, A. J.; Ellis, D. J. P.; Shields, A. J.; Farrer, I.; Ritchie, D. A.

2014-01-01

We demonstrate generation of a pulsed stream of electrically triggered single photons in resonance fluorescence, by applying high frequency electrical pulses to a single quantum dot in a p-i-n diode under resonant laser excitation. Single photon emission was verified, with the probability of multiple photon emission reduced to 2.8%. We show that despite the presence of charge noise in the emission spectrum of the dot, resonant excitation acts as a “filter” to generate narrow bandwidth photons

Laser discrimination by stimulated emission of a phosphor

Science.gov (United States)

Mathur, V. K.; Chakrabarti, K.

1991-01-01

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals.

Enhanced stimulated emission in ZnO thin films using microdisk top-down structuring

Energy Technology Data Exchange (ETDEWEB)

Nomenyo, K.; Kostcheev, S.; Lérondel, G. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, CNRS UMR 6281, Université de Technologie de Troyes, 12 rue Marie Curie, CS 42060, 10004 Troyes Cedex (France); Gadallah, A.-S. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, CNRS UMR 6281, Université de Technologie de Troyes, 12 rue Marie Curie, CS 42060, 10004 Troyes Cedex (France); Department of Laser Sciences and Interactions, National Institute of Laser Enhanced Sciences, Cairo University, Giza (Egypt); Rogers, D. J. [Nanovation, 8, route de Chevreuse, 78117 Châteaufort (France)

2014-05-05

Microdisks were fabricated in zinc oxide (ZnO) thin films using a top-down approach combining electron beam lithography and reactive ion etching. These microdisk structured thin films exhibit a stimulated surface emission between 3 and 7 times higher than that from a reference film depending on the excitation power density. Emission peak narrowing, reduction in lasing threshold and blue-shifting of the emission wavelength were observed along with enhancement in the emitted intensity. Results indicate that this enhancement is due to an increase in the internal quantum efficiency combined with an amplification of the stimulated emission. An analysis in terms of waveguiding is presented in order to explain these effects. These results demonstrate that very significant gains in emission can be obtained through conventional microstructuration without the need for more onerous top-down nanostructuration techniques.

A novel phantom design for emission tomography enabling scatter- and attenuation-''free'' single-photon emission tomography imaging

International Nuclear Information System (INIS)

Larsson, S.A.; Johansson, L.; Jonsson, C.; Pagani, M.; Jacobsson, H.

2000-01-01

A newly designed technique for experimental single-photon emission tomography (SPET) and positron emission tomography (PET) data acquisition with minor disturbing effects from scatter and attenuation has been developed. In principle, the method is based on discrete sampling of the radioactivity distribution in 3D objects by means of equidistant 2D planes. The starting point is a set of digitised 2D sections representing the radioactivity distribution of the 3D object. Having a radioactivity-related grey scale, the 2D images are printed on paper sheets using radioactive ink. The radioactive sheets can be shaped to the outline of the object and stacked into a 3D structure with air or some arbitrary dense material in between. For this work, equidistantly spaced transverse images of a uniform cylindrical phantom and of the digitised Hoffman rCBF phantom were selected and printed out on paper sheets. The uniform radioactivity sheets were imaged on the surface of a low-energy ultra-high-resolution collimator (4 mm full-width at half-maximum) of a three-headed SPET camera. The reproducibility was 0.7% and the uniformity was 1.2%. Each rCBF sheet, containing between 8.3 and 80 MBq of 99m TcO 4 - depending on size, was first imaged on the collimator and then stacked into a 3D structure with constant 12 mm air spacing between the slices. SPET was performed with the sheets perpendicular to the central axis of the camera. The total weight of the stacked rCBF phantom in air was 63 g, giving a scatter contribution comparable to that of a point source in air. The overall attenuation losses were <20%. A second SPET study was performed with 12-mm polystyrene plates in between the radioactive sheets. With polystyrene plates, the total phantom weight was 2300 g, giving a scatter and attenuation magnitude similar to that of a patient study. With the proposed technique, it is possible to obtain ''ideal'' experimental images (essentially built up by primary photons) for comparison with

Gamma-ray pulsars: Emission zones and viewing geometries

Science.gov (United States)

Romani, Roger W.; Yadigaroglu, I.-A.

1995-01-01

There are now a half-dozen young pulsars detected in high-energy photons by the Compton Gamma-Ray Observatory (CGRO), showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high-energy emission on the sky in a model which posits gamma-ray production by charge-depleted gaps in the outer magnetosphere. This model accounts for the radio to gamma-ray pulse offsets of the known pulsars, as well as the shape of the high-energy pulse profiles. We also show that about one-third of emitting young radio pulsars will not be detected due to beaming effects, while approximately 2.5 times the number of radio-selected gamma-ray pulsars will be viewed only high energies. Finally we compute the polarization angle variation and find that the previously misunderstood optical polarization sweep of the Crab pulsar arises naturally in this picture. These results strongly support an outer magnetosphere location for the gamma-ray emission.

Transition of lasing modes in polymeric opal photonic crystal resonating cavity.

Science.gov (United States)

Shi, Lan-Ting; Zheng, Mei-Ling; Jin, Feng; Dong, Xian-Zi; Chen, Wei-Qiang; Zhao, Zhen-Sheng; Duan, Xuan-Ming

2016-06-10

We demonstrate the transition of lasing modes in the resonating cavity constructed by polystyrene opal photonic crystals and 7 wt. % tert-butyl Rhodamine B doped polymer film. Both single mode and multiple mode lasing emission are observed from the resonating cavity. The lasing threshold is determined to be 0.81  μJ/pulse for single mode lasing emission and 2.25  μJ/pulse for multiple mode lasing emission. The single mode lasing emission is attributed to photonic lasing resulting from the photonic bandgap effect of the opal photonic crystals, while the multiple mode lasing emission is assigned to random lasing due to the defects in the photonic crystals. The result would benefit the development of low threshold polymeric solid state photonic crystal lasers.

Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

Energy Technology Data Exchange (ETDEWEB)

Zhang, Duo, E-mail: zhangduo10@gmail.com [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Li, Jiahua, E-mail: huajia_li@163.com [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Ding, Chunling; Yang, Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2012-05-21

The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission. -- Highlights: ► Spontaneous emission properties of an atom embedded in PCs are investigated. ► Spectral-line enhancement, suppression and overlapping are observed. ► The results provide more degrees of freedom to control atomic spontaneous emission.

Control of spontaneous emission from a microwave-field-driven four-level atom in an anisotropic photonic crystal

International Nuclear Information System (INIS)

Zhang, Duo; Li, Jiahua; Ding, Chunling; Yang, Xiaoxue

2012-01-01

The spontaneous emission properties of a microwave-field-driven four-level atom embedded in anisotropic double-band photonic crystals (PCs) are investigated. We discuss the influences of the band-edge positions, Rabi frequency and detuning of the microwave field on the emission spectrum. It is found that several interesting features such as spectral-line enhancement, spectral-line suppression, spectral-line overlap, and multi-peak structures can be observed in the spectra. The proposed scheme can be achieved by use of a microwave-coupled field into hyperfine levels in rubidium atom confined in a photonic crystal. These theoretical investigations may provide more degrees of freedom to manipulate the atomic spontaneous emission. -- Highlights: ► Spontaneous emission properties of an atom embedded in PCs are investigated. ► Spectral-line enhancement, suppression and overlapping are observed. ► The results provide more degrees of freedom to control atomic spontaneous emission.

Frequency splitter based on the directional emission from surface modes in dielectric photonic crystal structures.

Science.gov (United States)

Tasolamprou, Anna C; Zhang, Lei; Kafesaki, Maria; Koschny, Thomas; Soukoulis, Costas M

2015-06-01

We demonstrate the numerical design and the experimental validation of frequency dependent directional emission from a dielectric photonic crystal structure. The wave propagates through a photonic crystal line-defect waveguide, while a surface layer at the termination of the photonic crystal enables the excitation of surface modes and a subsequent grating layer transforms the surface energy into outgoing propagating waves of the form of a directional beam. The angle of the beam is controlled by the frequency and the structure operates as a frequency splitter in the intermediate and far field region.

REVIEW: Optics of globular photonic crystals

Science.gov (United States)

Gorelik, V. S.

2007-05-01

The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter ~200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported.

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

Science.gov (United States)

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.

Near infrared emission and multicolor tunability of enhanced upconversion emission from Er{sup 3+}–Yb{sup 3+} co-doped Nb{sub 2}O{sub 5} nanocrystals embedded in silica-based nanocomposite and planar waveguides for photonics

Energy Technology Data Exchange (ETDEWEB)

Aquino, Felipe Thomaz [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo. Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Ferrari, Jefferson Luis [Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo. Av. Bandeirantes, 3900, CEP 14040-901 Ribeirão Preto, SP (Brazil); Grupo de Pesquisa em Química de Materiais – (GPQM), Departamento de Ciências Naturais, Universidade Federal de São João Del Rei, Campus Dom Bosco, Praça Dom Helvécio, 74, 36301-160 São João Del Rei, MG (Brazil); Maia, Lauro June Queiroz [Grupo Física de Materiais, Instituto de Física, Universidade Federal de Goiás, Campus II, C.P. 131, CEP 74001-970, Goiânia, GO (Brazil); Ribeiro, Sidney José Lima [Institute of Chemistry- São Paulo State University- UNESP, Araraquara, SP 14800-900 (Brazil); Ferrier, Alban [PSL Research University, Chimie ParisTech - CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06, 75005 Paris (France); and others

2016-02-15

This work reports on the Yb{sup 3+} ion addition effect on the near infrared emission and infrared-to-visible up conversion from planar waveguides based on Er{sup 3+}–Yb{sup 3+} co-doped Nb{sub 2}O{sub 5} nanocrystals embedded in SiO{sub 2}-based nanocomposite prepared by a sol–gel process with controlled crystallization in situ. Planar waveguides and xerogels containing Si/Nb molar ratio of 90:10 up to 50:50 were prepared. Spherical-like orthorhombic or monoclinic Nb{sub 2}O{sub 5} nanocrystals were grown in the amorphous SiO{sub 2}-based host depending on the niobium content and annealing temperature, resulting in transparent glass ceramics. Crystallization process was intensely affected by rare earth content increase. Enhancement and broadening of the NIR emission has been achieved depending on the rare earth content, niobium content and annealing temperature. Effective Yb{sup 3+}→Er{sup 3+} energy transfer and a high-intensity broad band emission in the near infrared region assigned to the Er{sup 3+} ions {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition, and longer {sup 4}I{sub 13/2} lifetimes were observed for samples containing orthorhombic Nb{sub 2}O{sub 5} nanocrystals. Intense green and red emissions were registered for all Er{sup 3+}–Yb{sup 3+} co-doped waveguides under 980 nm excitation, assigned to {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2} (525 nm),{sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} (545nm) and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} (670 nm) transitions, respectively. Different relative green and red intensities emissions were observed, depending upon niobium oxide content and the laser power. Upconversion dynamics were determined by the photons number, evidencing that ESA or ETU mechanisms are probably occurring. The 1931 CIE chromaticity diagrams indicated interesting color tunability based on the waveguides composition and pump power. The nanocomposite waveguides are promising materials for photonic applications as optical amplifiers and

Nearly Blinking-Free, High-Purity Single-Photon Emission by Colloidal InP/ZnSe Quantum Dots.

Science.gov (United States)

Chandrasekaran, Vigneshwaran; Tessier, Mickaël D; Dupont, Dorian; Geiregat, Pieter; Hens, Zeger; Brainis, Edouard

2017-10-11

Colloidal core/shell InP/ZnSe quantum dots (QDs), recently produced using an improved synthesis method, have a great potential in life-science applications as well as in integrated quantum photonics and quantum information processing as single-photon emitters. Single-particle spectroscopy of 10 nm QDs with 3.2 nm cores reveals strong photon antibunching attributed to fast (70 ps) Auger recombination of multiple excitons. The QDs exhibit very good photostability under strong optical excitation. We demonstrate that the antibunching is preserved when the QDs are excited above the saturation intensity of the fundamental-exciton transition. This result paves the way toward their usage as high-purity on-demand single-photon emitters at room temperature. Unconventionally, despite the strong Auger blockade mechanism, InP/ZnSe QDs also display very little luminescence intermittency ("blinking"), with a simple on/off blinking pattern. The analysis of single-particle luminescence statistics places these InP/ZnSe QDs in the class of nearly blinking-free QDs, with emission stability comparable to state-of-the-art thick-shell and alloyed-interface CdSe/CdS, but with improved single-photon purity.

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

Science.gov (United States)

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.

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

International Nuclear Information System (INIS)

Sato, K.; Kobayashi, Y.

2015-01-01

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

Contribution to the study of stimulated emission in neodymium-doped glass

International Nuclear Information System (INIS)

Jego, J.M.

1969-01-01

In 1917, Einstein discovered the existence of the stimulated emission of electromagnetic waves by atoms. It is caused by the presence of radiating energy of suitable frequency in a material which is in a non equilibrium state. This discovery held the germ of the idea for the fabrication of generators and waves amplifiers for very short, almost monochromatic wavelengths. forty years elapsed however before these were produced for the first time. A maser operating in the field of micrometric waves appeared in 1954. In the optical field, the first 'Laser' was built by MAIMAN in 1960. The active atom was chromium situated in an alumina matrix (ruby). The fluorescent single crystal was placed between two reflectors which maintained in the medium a provoked inversion of the population until the emission conditions were attained. The laser effect has made it possible to produce several hundred line generators covering the optical range for both gaseous and liquid or solid media. Amongst the latter, neodymium has a transition between the 4 F 3/2 and the 4 I 11/2 levels which has made it possible to obtain very high power lasers. A study has been made during the present work of the conditions in which a pulse can be formed, and of its amplification in neodymium-doped glass. By making accurate measurements of the various yields involved in this process, it has been possible to obtain the value for the population inversion obtained in the medium, and to make a detailed study of stimulated emission in neodymium. (author) [fr

On the excess photon noise in single-beam measurements with photo-emissive and photo-conductive cells

NARCIS (Netherlands)

Alkemade, C.T.J.

In this paper the so-called excess photon noise is theoretically considered with regard to noise power measurements with a single, illumined photo-emissive or photo-conductive cell. Starting from a modification of Mandel's stochastic association of the emission of photo-electrons with wave

Slow-light enhancement of spontaneous emission in active photonic crystal waveguides

DEFF Research Database (Denmark)

Ek, Sara; Chen, Yaohui; Semenova, Elizaveta

2012-01-01

Photonic crystal defect waveguides with embedded active layers containing single or multiple quantum wells or quantum dots have been fabricated. Spontaneous emission spectra are enhanced close to the bandedge, consistently with the enhancement of gain by slow light effects. These are promising...... results for future compact devices for terabit/s communication, such as miniaturised semiconductor optical amplifiers and mode-locked lasers....

Photon-phonon laser on crystalline silicon: a feasibility study

International Nuclear Information System (INIS)

Zadernovsky, A A

2015-01-01

We discuss a feasibility of photon-phonon laser action in bulk silicon with electron population inversion. It is well known, that only direct gap semiconductors are used as an active medium in optical lasers. In indirect gap semiconductors, such as crystalline silicon, the near-to-gap radiative electron transitions must be assisted by emission or absorption of phonons to conserve the momentum. The rate of such two-quantum transitions is much less than in direct gap semiconductors, where the similar radiative transitions are single-quantum. As a result, the quantum efficiency of luminescence in silicon is too small to get it as a laser material. Numerous proposals to overcome this problem are aimed at increasing the rate of radiative recombination. We suggest enhancing the quantum efficiency of luminescence in silicon by stimulating the photon part of the two-quantum transitions by light from an appropriate external laser source. This allows us to obtain initially an external-source-assisted lasing in silicon and then a true photon-phonon lasing without any external source of radiation. Performed analysis revealed a number of requirements to the silicon laser medium (temperature, purity and perfection of crystals) and to the intensity of stimulating radiation. We discuss different mechanisms that may hinder the implementation of photon-phonon lasing in silicon

Quantified measurement of brain blood volume: comparative evaluations between the single photon emission computer tomography and the positron computer tomography

International Nuclear Information System (INIS)

Bouvard, G.; Fernandez, Y.; Petit-Taboue, M.C.; Derlon, J.M.; Travere, J.M.; Le Poec, C.

1991-01-01

The quantified measurement of cerebral blood volume is interesting for the brain blood circulation studies. This measurement is often used in positron computed tomography. It's more difficult in single photon emission computed tomography: there are physical problems with the limited resolution of the detector, the Compton effect and the photon attenuation. The objectif of this study is to compare the results between these two techniques. The quantified measurement of brain blood volume is possible with the single photon emission computer tomogragry. However, there is a loss of contrast [fr

Stimulated emission from ZnO nanorods

Energy Technology Data Exchange (ETDEWEB)

Hauschild, R.; Lange, H.; Priller, H.; Klingshirn, C.; Kalt, H. [Institut fuer Angewandte Physik, Universitaet Karlsruhe (T.H.), 76128 Karlsruhe (Germany); Kling, R. [Abteilung Halbleiterphysik, Universitaet Ulm, Albert-Einstein Allee 45, 89081 Ulm (Germany); Waag, A. [Institut fuer Halbleitertechnik, TU-Braunschweig, H.-Sommer-Str. 66, 38106 Braunschweig (Germany); Fan, H.J.; Zacharias, M. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

2006-03-15

By means of time resolved spectroscopy we compare two samples of ZnO nanorods with respect to their suitability as stimulated emitters. In the case of narrow nanorods their wave guiding quality causes a suppression of exciton-exciton scattering whereas no laser emission is detectable. Unlike their narrow counterparts, wide nanorods not only benefit from a larger overlap of the guided mode with the gain medium but a variation in VLS growth results in gold nanoparticles being present at the bottom of nanorods. Consequently, laser emission from single wide rods is evidenced up to 150 K. In addition to experimental studies we carry out 3D numerical simulations of the electric field distribution to evaluate the influence of gold nanoparticles at the nanorod/substrate interface. This finite element analysis confirms that gold leads to an enhancement of confinement within the resonator. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Analysis of borophosphosilicate glass layers on silicon wafers by X-ray emission from photon and electron excitation

International Nuclear Information System (INIS)

Elgersma, O.; Borstrok, J.J.M.

1989-01-01

Phosphorus and oxygen concentrations in the homogeneous layer of borosilicate glass (BPSG) deposited on Si-integrated circuits are determined by X-ray fluorescence from photon excitation. The X-ray emission from electron excitation in an open X-ray tube instrument yields a sufficiently precise determination of the boron content. The thickness of the layer can be derived from silicon Kα-fluorescence. A calibration model is proposed for photon as well as for electron excitation. The experimentally determined parameters in this model well agree with those derived from fundamental parameters for X-ray absorption and emission. The chemical surrounding of silicon affects strongly the peak profile of the silicon Kβ-emission. This enables to distinguish emission from the silicon atoms in the wafer and from the silicon atoms in the silicon oxide complexes of the BPSG-layer. (author)

Efficient 1.9 μm emission in H2-filled hollow core fiber by pure stimulated vibrational Raman scattering

International Nuclear Information System (INIS)

Wang, Zefeng; Yu, Fei; Wadsworth, William J; Knight, Jonathan C

2014-01-01

We report here efficient 1.9 μm emission by pure stimulated vibrational Raman scattering in a hydrogen-filled anti-resonant hollow-core fiber pumped with a 1064 nm microchip laser. A maximum quantum conversion efficiency ∼48% was achieved by using a 6.5 m length of fiber filled with 23 bar hydrogen, with a maximum peak output power >2 kW. By properly designing the transmission bands of the fiber, selecting alternative pump sources and active gases, the emission wavelength could be extended into the mid-infrared. This provides a potential route for generating efficient, compact, broadly tunable, high power, and narrow linewidth mid-infrared fiber gas lasers with broad application in defense, environmental, and medical monitoring. (letter)

Stimulated emission from ZnO nanorod arrays

Energy Technology Data Exchange (ETDEWEB)

Hauschild, R.; Lange, H.; Priller, H.; Klingshirn, C.; Kalt, H. [Institut fuer Angewandte Physik, Universitaet Karlsruhe (TH), 76128 Karlsruhe (Germany); Kling, R. [Abteilung Halbleiterphysik, Universitaet Ulm, Albert-Einstein Allee 45, 89081 Ulm (Germany); Waag, A. [Institut fuer Halbleitertechnik, TU-Braunschweig, H.-Sommer-Str. 66, 38106 Braunschweig (Germany); Fan, H.J.; Zacharias, M. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

2006-08-15

We discuss the time-resolved photoluminescence (PL) spectra of single ZnO nanorods taken at excitation fluences above and below the laser threshold. In the latter case, P-band emission related to polariton-polariton scattering is observed for certain rod geometries while stimulated emission occurs within the electron-hole plasma band. We calculate the intensity distribution of low-order waveguide modes as well as their energy dependence for given nanorod geometries to discuss their relevance with respect to nanorod lasing and polariton propagation. Additional finite-element analysis confirms that a gold layer formed at the nanorod-substrate interface under certain growth conditions leads to an enhancement of confinement within the resonator. (2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Photonic nanowires for quantum optics

DEFF Research Database (Denmark)

Munsch, M.; Claudon, J.; Bleuse, J.

Photonic nanowires (PWs) are simple dielectric structures for which a very efficient and broadband spontaneous emission (SE) control has been predicted [1]. Recently, a single photon source featuring a record high efficiency was demonstrated using this geometry [2]. Using time-resolved micro-phot...

DE-BLURRING SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY IMAGES USING WAVELET DECOMPOSITION

Directory of Open Access Journals (Sweden)

Neethu M. Sasi

2016-02-01

Full Text Available Single photon emission computed tomography imaging is a popular nuclear medicine imaging technique which generates images by detecting radiations emitted by radioactive isotopes injected in the human body. Scattering of these emitted radiations introduces blur in this type of images. This paper proposes an image processing technique to enhance cardiac single photon emission computed tomography images by reducing the blur in the image. The algorithm works in two main stages. In the first stage a maximum likelihood estimate of the point spread function and the true image is obtained. In the second stage Lucy Richardson algorithm is applied on the selected wavelet coefficients of the true image estimate. The significant contribution of this paper is that processing of images is done in the wavelet domain. Pre-filtering is also done as a sub stage to avoid unwanted ringing effects. Real cardiac images are used for the quantitative and qualitative evaluations of the algorithm. Blur metric, peak signal to noise ratio and Tenengrad criterion are used as quantitative measures. Comparison against other existing de-blurring algorithms is also done. The simulation results indicate that the proposed method effectively reduces blur present in the image.

Large current MOSFET on photonic silicon-on-insulator wafers and its monolithic integration with a thermo-optic 2 × 2 Mach-Zehnder switch.

Science.gov (United States)

Cong, G W; Matsukawa, T; Chiba, T; Tadokoro, H; Yanagihara, M; Ohno, M; Kawashima, H; Kuwatsuka, H; Igarashi, Y; Masahara, M; Ishikawa, H

2013-03-25

n-channel body-tied partially depleted metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated for large current applications on a silicon-on-insulator wafer with photonics-oriented specifications. The MOSFET can drive an electrical current as large as 20 mA. We monolithically integrated this MOSFET with a 2 × 2 Mach-Zehnder interferometer optical switch having thermo-optic phase shifters. The static and dynamic performances of the integrated device are experimentally evaluated.

Initial clinical experiences with dopamine D{sub 2} receptor imaging by means of 2`-iodospiperone and single-photon emission computed tomography

Energy Technology Data Exchange (ETDEWEB)

Yonekura, Yoshiharu [Fukui Medical Schoool, Matsuoka (Japan). Biomedical Imaging Research Center; Saji, Hideo; Iwasaki, Yasushi [and others

1995-08-01

Dopamine D{sub 2} receptor imaging was performed with {sup 123}I labeled 2`-iodospiperone (2`-ISP) and single-photon emission computed tomography (SPECT) in 9 patients: 4 with idiopathic Parkinson`s disease, 2 with parkinsonism, 1 with Wilson`s disease and 2 with pituitary tumor, and the results were compared with the data for 9 normal subjects. Following an intravenous injection of {sup 123}I-2`-ISP, early (within 30 min) and late (between 2 and 4 hr) SPECT images were obtained by means of a multi-detector SPECT scanner or a rotating gamma camera. In normal subjects, early SPECT images demonstrated uniform distribution of radioactivity in the cerebral gray matter and cerebellum reflecting regional cerebral blood flow, whereas late SPECT images showed high radioactivity only in the basal ganglia. All the patients with Parkinson`s disease also demonstrated symmetrical basal ganglia uptake in the late SPECT images, but it was diminished in parkinsonism and Wilson`s disease. One patient with a growth hormone-producing pituitary tumor had a positive uptake in the tumor. These preliminary clinical data demonstrated that 2`-ISP can be used for SPECT imaging of D{sub 2} dopamine receptors and may be of clinical value for the diagnosis and planning of the treatment of neurological diseases. (author).

Angiopoietin 2 stimulates TIE2-expressing monocytes to suppress T cell activation and to promote regulatory T cell expansion.

Science.gov (United States)

Coffelt, Seth B; Chen, Yung-Yi; Muthana, Munitta; Welford, Abigail F; Tal, Andrea O; Scholz, Alexander; Plate, Karl H; Reiss, Yvonne; Murdoch, Craig; De Palma, Michele; Lewis, Claire E

2011-04-01

Angiopoietin 2 (ANGPT2) is a proangiogenic cytokine whose expression is often upregulated by endothelial cells in tumors. Expression of its receptor, TIE2, defines a highly proangiogenic subpopulation of myeloid cells in circulation and tumors called TIE2-expressing monocytes/macrophages (TEMs). Genetic depletion of TEMs markedly reduces tumor angiogenesis in various tumor models, emphasizing their essential role in driving tumor progression. Previously, we demonstrated that ANGPT2 augments the expression of various proangiogenic genes, the potent immunosuppressive cytokine, IL-10, and a chemokine for regulatory T cells (Tregs), CCL17 by TEMs in vitro. We now show that TEMs also express higher levels of IL-10 than TIE2(-) macrophages in tumors and that ANGPT2-stimulated release of IL-10 by TEMs suppresses T cell proliferation, increases the ratio of CD4(+) T cells to CD8(+) T cells, and promotes the expansion of CD4(+)CD25(high)FOXP3(+) Tregs. Furthermore, syngeneic murine tumors expressing high levels of ANGPT2 contained not only high numbers of TEMs but also increased numbers of Tregs, whereas genetic depletion of tumor TEMs resulted in a marked reduction in the frequency of Tregs in tumors. Taken together, our data suggest that ANGPT2-stimulated TEMs represent a novel, potent immunosuppressive force in tumors.

Low-frequency-field-induced spontaneous-emission interference in a two-level atom placed in an anisotropic photonic crystal

International Nuclear Information System (INIS)

Li Gaoxiang; Evers, Joerg; Keitel, Christoph H

2005-01-01

We investigate the spontaneous-emission properties of a two-level atom embedded in a three-dimensional anisotropic photonic crystal. In addition to the modified density of states, the atom is driven by a coherent intense low-frequency field (LFF), which creates additional multiphoton decay channels with the exchange of two low-frequency photons and one spontaneous photon during an atomic transition. Due to the low frequency of the applied field, the various transition pathways may interfere with each other and thus give rise to a modified system dynamics. We find that even if all the atomic (bare and induced) transition frequencies are in the conducting band of the photonic crystal, there still may exist a photon-atom bound state in coexistence with propagating modes. The system also allows us to generate narrow lines in the spontaneous-emission spectrum. This spectrum is a function of the distance of the observer from the atom due to the band gap in the photonic crystal. The system properties depend on three characteristic frequencies, which are influenced by quantum interference effects. Thus these results can be attributed to a combination of interference and band-gap effects

Stimulated emission (4F3/2 → 4I11/2 channel) with LD and Xe-flashlamp pumping of tetragonal, incommensurately modulated Ca2MgSi2O7:Nd3+(Na+) – a new disordered laser crystal

International Nuclear Information System (INIS)

Kaminskii, A A; Nakao, H; Ueda, K; Shirakawa, A; Bohatý, L; Becker, P; Liebertz, J; Kleinschrodt, R

2010-01-01

Non-centrosymmetric tetragonal crystal Ca 2 MgSi 2 O 7 :Nd 3+ (Na + ) with incommensurately modulated melilite-type structure is presented as a new laser crystal. By LD and Xe-flashlamp pumping its CW and free-running pulsed stimulated emission of the 4 F 3/2 → 4 I 11/2 generation channel of Nd 3+ lasant ions was excited

Compared studies of natural and artificial deuterium depleted water

International Nuclear Information System (INIS)

Butnaru, Gallia; Mihacea, Sorina; Sirbovan, Alina; Butnariu, H.; Titescu, Gh.

2001-01-01

The biological influence of the deuterium on animals was studied insensitively in the last years. When animal cell cultures were analyzed it turned out an inhibition of the development, due to the reduced deuterium concentration. In the in vivo experiments a decreasing of the number of tumoral cells was pointed out when performing the depleted water treatment. It is obvious that the presence of deuterium in water is necessary for the development, especially for the tumoral cell proliferation. The aim of this work was to establish influence of the natural and artificial deuterium depleted water on the vegetal organisms development. For this purpose, the developmental stages of Lactuca sativa L. growth were followed. The experimental data were compared with the data obtained with distilled water. The birch, wine sap and some fruit juices are considered 'natural depleted' water sources because their deuterium content is smaller in comparison to natural water (D 2 =150 ppm). The effect of artificial deuterium depleted water (29 ppm D 2 ) was analyzed in comparison to three types of wine saps, which also have a reduced deuterium concentration (125-130 ppm D 2 ). If the deuterium depleted water was used, the germination percent and the root and shoot length were higher compared to control in the first stages. In wine sap it had a negative effect on germination and development. After three days the plants were transferred to soil and their development was followed. The foliage area was larger for all of the experimental variants compared to control. The differences were without significance when deuterium depleted water was tested but they were high and very significant in case of wine sap. The experiment pointed out a stimulative effect of the artificial deuterium depleted water. In case of wine sap the effect was negative when the contact was direct, but the growth was stimulated after the stress cessation. The first ontogenetic stages were represented by direct action

Enhanced emission of high-energy photons perpendicular to the reaction plane in α+Th reactions

International Nuclear Information System (INIS)

Tegner, P.; Marianski, B.; Morsch, H.P.; Rogge, M.; Bargholtz, C.; Decowski, P.; Zemlo, L.

1991-01-01

High-energy photon and neutron emission has been measured in coincidence with fission fragments in α+ 232 Th reactions at 170 MeV. From measurements parallel and perpendicular to the fission plane, anisotropies relative to the reaction plane were determined. The in-plane/out-of-plane intensity ratio is 0.72(7) for photons with energies above 20 MeV and 11(3) for neutrons at 35 MeV. The result for high-energy photons can be explained by nucleon-nucleon bremsstrahlung if the initial flow of nucleons has a correlation to the reaction plane similar to the one observed for fast neutrons

PET and Single-Photon Emission Computed Tomography in Brain Concussion.

Science.gov (United States)

Raji, Cyrus A; Henderson, Theodore A

2018-02-01

This article offers an overview of the application of PET and single photon emission computed tomography brain imaging to concussion, a type of mild traumatic brain injury and traumatic brain injury, in general. The article reviews the application of these neuronuclear imaging modalities in cross-sectional and longitudinal studies. Additionally, this article frames the current literature with an overview of the basic physics and radiation exposure risks of each modality. Copyright © 2017 Elsevier Inc. All rights reserved.

Disturbance from Am-241 Photons of the Cellular Dose by Am-241 Alpha Emissions: Am-241 as an alternative source of alpha particles to radon daughters

International Nuclear Information System (INIS)

Lee, Ki-Man; Kim, Eun-Hee

2015-01-01

The Radiation Bioengineering Laboratory (RadBio Lab) at Seoul National University (SNU) has built an Am-241 alpha particle irradiator for study of cellular responses to radiation from radon daughters. The radon daughters of concern that cause internal exposure from inhalation of radon-contaminated air are Po-218, Po-214 and Po-210. In their alpha decay schemes, the yields of photon emissions are negligible. Unfortunately, Am-241, the source of alpha irradiator in RadBio Lab, emits photons at every alpha decay while transforming to Np-237 of long half-life. Employing Am-241 as the source simulating radon daughters, therefore, requires that photon emissions from Am-241 be specified in term of dose contribution. In this study, Monte Carlo calculations have been made to characterize dose contributions of Am-241 photon emissions. This study confirms that disturbance from Am-241 photon emissions of the cellular dose by Am-241 alpha emissions is negligible. Dose contamination fraction from photon emissions was 8.02 .. 10 -6 at 25 mm SSD at maximum. Also, note that LET in tissue-equivalent medium varies within about 20% for alpha particles at energies over 5 MeV

RE-SONANCE--IDec-em--be-r

Indian Academy of Sciences (India)

photon) and the third term corresponds to the decay of population inversion as a result of all the processes other than stimulated emission. In (2), the first term represents the growth rate of the photon number due to stimulated emission and the second term corresponds to the loss of photons within the cavity. When the.

Impact of Wildfire Emissions on Chloride and Bromide Depletion in Marine Aerosol Particles.

Science.gov (United States)

Braun, Rachel A; Dadashazar, Hossein; MacDonald, Alexander B; Aldhaif, Abdulamonam M; Maudlin, Lindsay C; Crosbie, Ewan; Aghdam, Mojtaba Azadi; Hossein Mardi, Ali; Sorooshian, Armin

2017-08-15

This work examines particulate chloride (Cl - ) and bromide (Br - ) depletion in marine aerosol particles influenced by wildfires at a coastal California site in the summers of 2013 and 2016. Chloride exhibited a dominant coarse mode due to sea salt influence, with substantially diminished concentrations during fire periods as compared to nonfire periods. Bromide exhibited a peak in the submicrometer range during fire and nonfire periods, with an additional supermicrometer peak in the latter periods. Chloride and Br - depletions were enhanced during fire periods as compared to nonfire periods. The highest observed %Cl - depletion occurred in the submicrometer range, with maximum values of 98.9% (0.32-0.56 μm) and 85.6% (0.56-1 μm) during fire and nonfire periods, respectively. The highest %Br - depletion occurred in the supermicrometer range during fire and nonfire periods with peak depletion between 1.8-3.2 μm (78.8% and 58.6%, respectively). When accounting for the neutralization of sulfate by ammonium, organic acid particles showed the greatest influence on Cl - depletion in the submicrometer range. These results have implications for aerosol hygroscopicity and radiative forcing in areas with wildfire influence owing to depletion effects on composition.

Reduced dimer production in solar-simulator-pumped continuous wave iodine lasers based on model simulations and scaling and pumping studies

Science.gov (United States)

Costen, Robert C.; Heinbockel, John H.; Miner, Gilda A.; Meador, Willard E., Jr.; Tabibi, Bagher M.; Lee, Ja H.; Williams, Michael D.

1995-01-01

A numerical rate equation model for a continuous wave iodine laser with longitudinally flowing gaseous lasant is validated by approximating two experiments that compare the perfluoroalkyl iodine lasants n-C3F7I and t-C4F9I. The salient feature of the simulations is that the production rate of the dimer (C4F9)2 is reduced by one order of magnitude relative to the dimer (C3F7)2. The model is then used to investigate the kinetic effects of this reduced dimer production, especially how it improves output power. Related parametric and scaling studies are also presented. When dimer production is reduced, more monomer radicals (t-C4F9) are available to combine with iodine ions, thus enhancing depletion of the laser lower level and reducing buildup of the principal quencher, molecular iodine. Fewer iodine molecules result in fewer downward transitions from quenching and more transitions from stimulated emission of lasing photons. Enhanced depletion of the lower level reduces the absorption of lasing photons. The combined result is more lasing photons and proportionally increased output power.

Silicon light-emitting diodes and lasers photon breeding devices using dressed photons

CERN Document Server

Ohtsu, Motoichi

2016-01-01

This book focuses on a novel phenomenon named photon breeding. It is applied to realizing light-emitting diodes and lasers made of indirect-transition-type silicon bulk crystals in which the light-emission principle is based on dressed photons. After presenting physical pictures of dressed photons and dressed-photon phonons, the principle of light emission by using dressed-photon phonons is reviewed. A novel phenomenon named photon breeding is also reviewed. Next, the fabrication and operation of light emitting diodes and lasers are described The role of coherent phonons in these devices is discussed. Finally, light-emitting diodes using other relevant crystals are described and other relevant devices are also reviewed.

Dirac tensor with heavy photon

Energy Technology Data Exchange (ETDEWEB)

Bytev, V.V.; Kuraev, E.A. [Joint Institute of Nuclear Research, Moscow (Russian Federation). Bogoliubov Lab. of Theoretical Physics; Scherbakova, E.S. [Hamburg Univ. (Germany). 1. Inst. fuer Theoretische Physik

2012-01-15

For the large-angles hard photon emission by initial leptons in process of high energy annihilation of e{sup +}e{sup -} {yields} to hadrons the Dirac tensor is obtained, taking into account the lowest order radiative corrections. The case of large-angles emission of two hard photons by initial leptons is considered. This result is being completed by the kinematics case of collinear hard photons emission as well as soft virtual and real photons and can be used for construction of Monte-Carlo generators. (orig.)

Relativistic quantum dynamics in strong fields: Photon emission from heavy, few-electron ions

International Nuclear Information System (INIS)

Fritzsche, S.; Stoehlker, T.

2005-03-01

Recent progress in the study of the photon emission from highly-charged heavy ions is reviewed. These investigations show that high-Z ions provide a unique tool for improving the understanding of the electron-electron and electron-photon interaction in the presence of strong fields. Apart from the bound-state transitions, which are accurately described in the framework of quantum electrodynamics, much information has been obtained also from the radiative capture of (quasi-) free electrons by high-Z ions. Many features in the observed spectra hereby confirm the inherently relativistic behavior of even the simplest compound quantum systems in nature. (orig.)

Highly efficient photonic nanowire single-photon sources for quantum information applications

DEFF Research Database (Denmark)

Gregersen, Niels; Claudon, J.; Munsch, M.

2013-01-01

to a collection efficiency of only 1-2 %, and efficient light extraction thus poses a major challenge in SPS engineering. Initial efforts to improve the efficiency have exploited cavity quantum electrodynamics (cQED) to efficiently couple the emitted photons to the optical cavity mode. An alternative approach......Within the emerging field of optical quantum information processing, the current challenge is to construct the basic building blocks for the quantum computing and communication systems. A key component is the singlephoton source (SPS) capable of emitting single photons on demand. Ideally, the SPS...... must feature near-unity efficiency, where the efficiency is defined as the number of detected photons per trigger, the probability g(2)(τ=0) of multi-photon emission events should be 0 and the emitted photons are required to be indistinguishable. An optically or electrically triggered quantum light...

Ozone-depleting substances and the greenhouse gases HFCs, PFCs and SF{sub 6}. Danish consumption and emissions, 2006

Energy Technology Data Exchange (ETDEWEB)

Sander Poulsen, T. (PlanMiljoe (Denmark))

2007-07-01

The objective of this project was to map the 2006 consumption of newly produced industrial ozone-depleting substances and the consumption and actual emissions of HFCs, PFCs, and SF{sub 6}. The evaluation was made in accordance with the IPCC guidelines and following the method employed in previous evaluations. (BA)

Polychromatic photons

DEFF Research Database (Denmark)

Keller, Ole

2002-01-01

train quantum electrodynamics. A brief description of particle (photon) position operators is given, and it is shown that photons usually are only algebraically confined in an emission process. Finally, it is demonstrated that the profile of the birth domain of a radio-frequency photon emitted...

An electrically driven cavity-enhanced source of indistinguishable photons with 61% overall efficiency

Directory of Open Access Journals (Sweden)

A. Schlehahn

2016-04-01

Full Text Available We report on an electrically driven efficient source of indistinguishable photons operated at pulse-repetition rates f up to 1.2 GHz. The quantum light source is based on a p-i-n-doped micropillar cavity with integrated self-organized quantum dots, which exploits cavity quantum electrodynamics effects in the weak coupling regime to enhance the emission of a single quantum emitter coupled to the cavity mode. We achieve an overall single-photon extraction efficiency of (61 ± 11 % for a device triggered electrically at f = 625 MHz. Analyzing the suppression of multi-photon emission events as a function of excitation repetition rate, we observe single-photon emission associated with g(2HBT(0 values between 0.076 and 0.227 for f ranging from 373 MHz to 1.2 GHz. Hong-Ou-Mandel-type two-photon interference experiments under pulsed current injection at 487 MHz reveal a photon-indistinguishability of (41.1 ± 9.5 % at a single-photon emission rate of (92 ± 23 MHz.

Single photon emission computed tomography and oth selected computer topics

International Nuclear Information System (INIS)

Frey, G.D.

1981-01-01

This book, the proceedings of a meeting in January 1980, contains 21 papers. Thirteen are devoted to aspects of emission tomography, four to nuclear cardiology, and five to other topics. The initial set of papers consists of reviews of the single photon emission tomography process. These include transverse axial tomography using scintillation cameras and other devices, longitudinal section tomography, and pin-hole and slant-hole systems. These reviews are generally well done, but as might be expected, lack any coherence from paper to paper. The papers on nuclear cardiology include several of Fourier analysis in nuclear cardiology and one on shunt quantification. Other clinical papers are on quantifying Tc-99m glucoheptonate uptake in the brain and on iron-59 retention studies. A general criticism of the book is the poor quality of photographic reproductions

Two-photon activation of endogenous store-operated calcium channels without optogenetics

Science.gov (United States)

Cheng, Pan; Tang, Wanyi; He, Hao

2018-02-01

Store-operated calcium (SOC) channels, regulated by intracellular Ca2+ store, are the essential pathway of calcium signaling and participate in a wide variety of cellular activities such as gene expression, secretion and immune response1. However, our understanding and regulation of SOC channels are mainly based on pharmacological methods. Considering the unique advantages of optical control, optogenetic control of SOC channels has been developed2. However, the process of genetic engineering to express exogenous light-sensitive protein is complicated, which arouses concerns about ethic difficulties in some research of animal and applications in human. In this report, we demonstrate rapid, robust and reproducible two-photon activation of endogenous SOC channels by femtosecond laser without optogenetics. We present that the short-duration two-photon scanning on subcellular microregion induces slow Ca2+ influx from extracellular medium, which can be eliminated by removing extracellular Ca2+. Block of SOC channels using various pharmacological inhibitors or knockdown of SOC channels by RNA interference reduce the probability of two-photon activated Ca2+ influx. On the contrary, overexpression of SOC channels can increase the probability of Ca2+ influx by two-photon scanning. These results collectively indicate Ca2+ influx through two-photon activated SOC channels. Different from classical pathway of SOC entry activated by Ca2+ store depletion, STIM1, the sensor protein of Ca2+ level in endoplasmic reticulum, does not show any aggregation or migration in this two-photon activated Ca2+ influx, which rules out the possibility of intracellular Ca2+ store depletion. Thereby, we propose this all-optical method of two-photon activation of SOC channels is of great potential to be widely applied in the research of cell calcium signaling and related biological research.

Single-photon emission computed tomography in the clinical evaluation of dementia

International Nuclear Information System (INIS)

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

1987-01-01

Physiological imaging using positron emission tomography (PET) has been a useful tool in the investigation of dementia. In particular, patterns of cerebral glucose utilization appear to differentiate various types of dementia, with Alzheimer's disease (AD) demonstrating a propensity for hypometabolism to involve the temporoparietal cortex. Single-photon emission computed tomography (SPECT) using new tracers for the measurement of regional cerebral blood flow is a technique with potentially broader clinical availability than PET and thus may provide a practical method of routinely evaluating patients. The authors studied eight patients with AD, four healthy elderly controls, and one patient with multi-infarct dementia (MID) using the tracer 123 I-N-isopropyl-p-iodoamphetamine with SPECT

Development of radioiodinated receptor ligands for cerebral single photon emission tomography

International Nuclear Information System (INIS)

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

Single photon emission computed tomography of the liver

International Nuclear Information System (INIS)

Makler, P.T. Jr.

1988-01-01

Single photon emission computed tomography (SPECT) of the liver has been introduced in order to improve sensitivity and localization of space-occupying lesions. There have been numerous reports on the usefulness of the technique, as well as extensive analyses of its technical drawbacks. In general, SPECT provides a more accurate estimation of defect size than does conventional planar scintigraphy for cases in which one wishes to evaluate changes in lesion size due to therapy. The presence of a superimposed parenchymal disease, however, remains a major problem, which will only be resolved by a scanning technique that specifically detects the disease process of concern (hot spot imaging) rather than displacement of normal tissue (cold spot imaging)

Entangled, guided photon generation in (1+1)-dimensional photonic crystals

International Nuclear Information System (INIS)

Sciscione, L.; Centini, M.; Sibilia, C.; Bertolotti, M.; Scalora, M.

2006-01-01

A scheme based on photonic crystal technology is proposed as an ultrabright source of entangled photons on a miniaturized scale. The geometry consists of a multilayer microcavity, excited by a resonant pump frequency, such that the emitted photons are guided transversally to the direction of the incident pump. The entanglement occurs in direction, frequency, and polarization, and the bandwidth of the emitted photons is of the order of 1 nm. We propose a feasible design based on Al 0.3 Ga 0.7 As/Al 2 O 3 structures and predict an emission rate 10 5 pairs per second with 100 mW pump power. These results are promising for realization of chip and future quantum computer applications

Fast-ICCD photography and gated photon counting measurements of blackbody emission from particulates generated in the KrF-laser ablation of BN and YBCO

Energy Technology Data Exchange (ETDEWEB)

Geohegan, D.B.

1992-11-01

Fast intensified CCD photography and gated photon counting following KrF-laser irradiation of YBCO and BN targets reveals the first observations of very weak emission from slow-moving ejecta up to 2 cm from the target and times extending to {approx}1.5 ms. Time-of-flight velocities inferred from the emission measurements indicate velocities (v {approximately} (0.45--1.2) {times} 10{sup 4} cm s{sup {minus}1}) comparable to those measured for the large particles which often accompany the pulsed laser deposition process. Gated photon counting is employed to obtain temporally resolved spectra of this weak emission. The spectral shape is characteristic of blackbody emission, which shifts to longer wavelengths as the particles cool during flight in vacuum. Estimates of the temperature of the particles are made based on the emissivity of a perfect blackbody and range from 2200 K to 3200 K for both BN and YBCO when irradiated at ({Phi}{sub 248} = 3.5 J cm{sup {minus}2} and 1.5 J cm{sup {minus}2}, respectively. The temperature decrease of the particles in vacuum is compared to a radiative cooling model which gives estimates of the initial surface temperature and radii of the particles.

Stimulated exoelectron emission dosimetry of organic compounds and of ionic crystals

International Nuclear Information System (INIS)

Rocca-Serra nee Chevtchenko, Nathalie

1980-01-01

The purpose of this work is the dosimetric study of stimulated exoelectron emission from various organic compounds (organic acid salts, amino acids) and ionic crystals (sodium chloride, magnesium oxide, calcium sulfate, lithium fluoride and α/β alumina). Experimental results obtained for α/β alumina leads us to determine physical properties of this material such as activation energies and frequency factors of traps involved in the exo-emission process. (author) [fr

Comment on the effect of Cs on photon and secondary ion emission during sputtering

International Nuclear Information System (INIS)

Yu, M.L.

1978-01-01

The effect of Cs on photon and negative ion emission was discussed for the situations where the sputtered atom interacts either very weakly or very strongly with the target surface. The experimental data seem to favor the strong interaction case. 5 references

ORIGEN-ARP 2.00, Isotope Generation and Depletion Code System-Matrix Exponential Method with GUI and Graphics Capability

International Nuclear Information System (INIS)

2002-01-01

1 - Description of program or function: ORIGEN-ARP was developed for the Nuclear Regulatory Commission and the Department of Energy to satisfy a need for an easy-to-use standardized method of isotope depletion/decay analysis for spent fuel, fissile material, and radioactive material. It can be used to solve for spent fuel characterization, isotopic inventory, radiation source terms, and decay heat. This release of ORIGEN-ARP is a standalone code package that contains an updated version of the SCALE-4.4a ORIGEN-S code. It contains a subset of the modules, data libraries, and miscellaneous utilities in SCALE-4.4a. This package is intended for users who do not need the entire SCALE package. ORIGEN-ARP 2.00 (2-12-2002) differs from the previous release ORIGEN-ARP 1.0 (July 2001) in the following ways: 1.The neutron source and energy spectrum routines were replaced with computational algorithms and data from the SOURCES-4B code (RSICC package CCC-661) to provide more accurate spontaneous fission and (alpha,n) neutron sources, and a delayed neutron source capability was added. 2.The printout of the fixed energy group structure photon tables was removed. Gamma sources and spectra are now printed for calculations using the Master Photon Library only. 2 - Methods: ORIGEN-ARP is an automated sequence to perform isotopic depletion / decay calculations using the ARP and ORIGEN-S codes of the SCALE system. The sequence includes the OrigenArp for Windows graphical user interface (GUI) that prepares input for ARP (Automated Rapid Processing) and ORIGEN-S. ARP automatically interpolates cross sections for the ORIGEN-S depletion/decay analysis using enrichment, burnup, and, optionally moderator density, from a set of libraries generated with the SCALE SAS2 depletion sequence. Library sets for four LWR fuel assembly designs (BWR 8 x 8, PWR 14 x 14, 15 x 15, 17 x 17) are included. The libraries span enrichments from 1.5 to 5 wt% U-235 and burnups of 0 to 60,000 MWD/MTU. Other

Selective creation of colour centres and peaks of thermally stimulated luminescence by VUV photons in LiF single crystals

International Nuclear Information System (INIS)

Vasil'chenko, E.; Kudryavtseva, I.; Lushchik, A.; Lushchik, Ch.; Nagirnyi, V.

2005-01-01

Processes of radiation creation and annealing of Frenkel defects as well as electron-hole processes have been studied in LiF single crystals with a various content of impurity ions by means of highly sensitive method of thermally stimulated luminescence (TSL) and other optical methods. In highly pure LiF crystals, X-irradiated at 4.2 K, the TSL peaks connected with the annealing of interstitial fluorine ions (25-40 K) or atoms, i.e. H centres (50-65 K) and self-trapped holes (120-140 K) have been separated. For the first time, the creation spectra of the TSL peaks at 480 and 550 K by 10-33 eV-photon irradiation at 295 K have been measured. The anomalously high creation efficiency of the TSL peak at 480 K by 11.7-12.3 eV and 26-27 eV photons is interpreted as the creation of near-impurity electronic excitations both, directly by photons and by hot conduction electrons. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Enhancement of Spontaneous Erbium Emission near the Photonic Band Edge of Distributed Bragg Reflectors Based on a-Si:H/a-SiOx:H

International Nuclear Information System (INIS)

Medvedev, A.V.; Feoktistov, N.A.; Pevtsov, A.B.; Golubev, V.G.

2005-01-01

Results obtained in an experimental study of spontaneous emission from erbium ions in a spectral range corresponding to the lower photonic band edge of distributed Bragg reflectors (1D photonic crystals) are presented. The photonic crystals were constituted of alternating quarter-wave a-Si:H and a-SiO x :H layers grown by PECVD. Erbium was introduced into the a-Si:H layers by magnetron sputtering of an erbium target in the course of structure growth. The change observed in the intensity of spontaneous emission is due to the nonmonotonic behavior of the density of optical modes near the photonic band edge

Single photon emission tomography (SPET) imaging of dopamine D2 receptors in the course of dopamine replacement therapy in patients with nocturnal myoclonus syndrome (NMS)

International Nuclear Information System (INIS)

Staedt, J.; Stoppe, G.; Riemann, H.; Hajak, G.; Ruether, E.; Koegler, A.; Emrich, D.

1995-01-01

Single photon emission tomography (SPET) permits the in vivo measurements of regional cerebral radioactivity in the human brain following the administration of compounds labeled with photon-emitting isotopes. According to our SPET findings of a reduced binding of [ 123 I]labeled (S)-2-hydroxy-3-iodo-6-methoxy-([1-ethyl-2-pyrrolidinyl]methyl) benzamide (IBZM) (a highly selective CNS D 2 dopamine receptor ligand) to D 2 dopamine receptors in striatal structures in untreated patients with nocturnal myoclonus syndrome (NMS) it seemed to be of interest to investigate whether there are changes in D 2 receptor binding under dopamine replacement therapy or not. We studied the uptake and distribution of [ 123 I]IBZM before and in the course of dopamine replacement therapy in four patients with severe insomnia caused by nocturnal myoclonus syndrome (NMS). We found an increase of the IBZM binding to D 2 receptors in the course of treatment, which was associated with an improvement of sleep quality. Reasons for this are discussed. The [ 123 I]IBZM SPET technique in conclusion offers an interesting tool for in vivo investigations of functional changes in the dopaminergic neurotransmitter system in longitudinal studies. (author)

Enhancement of thermal photon production in event-by-event hydrodynamics

International Nuclear Information System (INIS)

Chatterjee, Rupa; Holopainen, Hannu; Renk, Thorsten; Eskola, Kari J.

2011-01-01

Thermal photon emission is widely believed to reflect properties of the earliest, hottest evolution stage of the medium created in ultrarelativistic heavy-ion collisions. Previous computations of photon emission have been carried out using a hydrodynamical medium description with smooth, averaged initial conditions. Recently, more sophisticated hydrodynamical models that calculate observables by averaging over many evolutions with event-by-event fluctuating initial conditions (ICs) have been developed. Given their direct connection to the early time dynamics, thermal photon emission appears to be an ideal observable to probe fluctuations in the medium initial state. In this work, we demonstrate that including fluctuations in the ICs may lead to an enhancement of the thermal photon yield of about a factor of 2 in the region 2 T <4 GeV/c (where thermal photon production dominates the direct photon yield) compared to a scenario using smooth, averaged ICs. Consequently, a much better agreement with PHENIX data is found. This can be understood in terms of the strong temperature dependence of thermal photon production, translating into a sensitivity to the presence of hotspots in an event and thus establishing thermal photons as a suitable probe to characterize IC fluctuations.

The interplay between SUCLA2, SUCLG2, and mitochondrial DNA depletion

DEFF Research Database (Denmark)

Miller, Chaya; Wang, Liya; Ostergaard, Elsebet

2011-01-01

SUCLA2-related mitochondrial DNA (mtDNA) depletion syndrome is a result of mutations in the β subunit of the ADP-dependent isoform of the Krebs cycle succinyl-CoA synthase (SCS). The mechanism of tissue specificity and mtDNA depletion is elusive but complementation by the GDP-dependent isoform en...

Coupling of Ag Nanoparticle with Inverse Opal Photonic Crystals as a Novel Strategy for Upconversion Emission Enhancement of NaYF4: Yb(3+), Er(3+) Nanoparticles.

Science.gov (United States)

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.

Time-resolved statistics of photon pairs in two-cavity Josephson photonics

Energy Technology Data Exchange (ETDEWEB)

Dambach, Simon; Kubala, Bjoern; Ankerhold, Joachim [Institute for Complex Quantum Systems and IQST, Ulm University (Germany)

2017-06-15

We analyze the creation and emission of pairs of highly nonclassical microwave photons in a setup where a voltage-biased Josephson junction is connected in series to two electromagnetic oscillators. Tuning the external voltage such that the Josephson frequency equals the sum of the two mode frequencies, each tunneling Cooper pair creates one additional photon in both of the two oscillators. The time-resolved statistics of photon emission events from the two oscillators is investigated by means of single- and cross-oscillator variants of the second-order correlation function g{sup (2)}(τ) and the waiting-time distribution w(τ). They provide insight into the strongly correlated quantum dynamics of the two oscillator subsystems and reveal a rich variety of quantum features of light including strong antibunching and the presence of negative values in the Wigner function. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Photon emission from irradiated solids: Proceedings of the Werner Brandt workshop on penetration phenomena

International Nuclear Information System (INIS)

1986-11-01

The workshop was concerned with photon emission from irradiated solids and the present record of the proceedings consists of material solicited from each participant. The results range from detailed and complete manuscripts to skeletal remnants of Vugraph transparencies. Individual papers have been cataloged separately

Interference of Photons from a Weak Laser and a Quantum Dot

Science.gov (United States)

Ritchie, David; Bennett, Anthony; Patel, Raj; Nicoll, Christine; Shields, Andrew

2010-03-01

We demonstrate two-photon interference from two unsynchronized sources operating via different physical processes [1]. One source is spontaneous emission from the X^- state of an electrically-driven InAs/GaAs single quantum dot with μeV linewidth, the other stimulated emission from a laser with a neV linewidth. We mix the emission from these sources on a balanced non-polarising beam splitter and measure correlations in the photons that exit using Si-avalanche photodiodes and a time-correlated counting card. By periodically switching the polarisation state of the weak laser we simultaneously measure the correlation for parallel and orthogonally polarised sources, corresponding to maximum and minimum degrees of interference. When the two sources have the same intensity, a reduction in the correlation function at time zero for the case of parallel photon sources clearly indicates this interference effect. To quantify the degree of interference, we develop a theory that predicts the correlation function. Data and experiment are then compared for a range of intensity ratios. Based on this analysis we infer a wave-function overlap of 91%, which is remarkable given the fundamental differences between the two sources. [1] Bennett A. J et al Nature Physics, 5, 715--717 (2009).

Size dependent emission stimulation in ZnO nanosheets

International Nuclear Information System (INIS)

Torchynska, T.V.; El Filali, B.

2014-01-01

Photoluminescence (PL), X ray diffraction (XRD) and Raman scattering have been studied in crystalline ZnO nanosheets (NSs) of different sizes, estimated by scanning electronic microscopy (SEM). ZnO NSs with the size from the range of 60–600 nm were created by the electrochemical (anodization) method and followed thermal annealing at 400 °C for 2 h in ambient air. XRD study confirms the wurtzite structure of ZnO NSs and has revealed that the lattice parameters increase monotonically with decreasing NS sizes. Simultaneously the intensity of a set of Raman peaks increases and Raman peaks shift into the low energy range. The surface phonon has been detected in smallest size ZnO NSs. Two types of PL bands deal with a set of phonon replicas of free excitons and the defect related emission have been detected in ZnO NSs. The intensity enhancement of exciton- and defect-related PL bands with decreasing ZnO NS sizes has been detected. The intensity stimulation of exciton-related PL bands is attributed to the realization of the week confinement and the exciton-light coupling with the formation of polariton in small size ZnO NSs of 67–170 nm. The intensity rising of defect-related PL bands is attributed to the concentration enlargement of surface defects when the surface to volume ration increases at decreasing ZnO NS sizes. Numerical simulations of radiative lifetimes and exciton radiative recombination rates in ZnO NSs for different emission wavelengths have been done using the exciton-light coupling model. Then the experimental and numerically simulated PL results have been compared and discussed. - Highlights: • Optical and structural investigations of the ZnO nanosheets with the sizes 60–600 nm. • The enlargement of interplanar distances in the wurtzite ZnO crystal lattice is detected. • The change of optic phonon energy and surface phonon appearing are reveled. • ZnO emission stimulation at the week confinement and electron-light coupling with the

Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement

International Nuclear Information System (INIS)

Masuda, Takahiko; Hara, Hideaki; Miyamoto, Yuki; Kuma, Susumu; Nakano, Itsuo; Ohae, Chiaki; Sasao, Noboru; Tanaka, Minoru; Uetake, Satoshi; Yoshimi, Akihiro; Yoshimura, Koji; Yoshimura, Motohiko

2015-01-01

We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 10 15 from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect

Rate amplification of the two photon emission from para-hydrogen toward the neutrino mass measurement

Energy Technology Data Exchange (ETDEWEB)

Masuda, Takahiko, E-mail: masuda@okayama-u.ac.jp; Hara, Hideaki; Miyamoto, Yuki [Okayama University, Research Core for Extreme Quantum World (Japan); Kuma, Susumu [Atomic, Molecular and Optical Physics Laboratory, RIKEN (Japan); Nakano, Itsuo [Okayama University, Research Core for Extreme Quantum World (Japan); Ohae, Chiaki [University of Electro-Communications, Department of Engineering Science (Japan); Sasao, Noboru [Okayama University, Research Core for Extreme Quantum World (Japan); Tanaka, Minoru [Osaka University, Department of Physics (Japan); Uetake, Satoshi [Okayama University, Research Center of Quantum Universe (Japan); Yoshimi, Akihiro; Yoshimura, Koji [Okayama University, Research Core for Extreme Quantum World (Japan); Yoshimura, Motohiko [Okayama University, Research Center of Quantum Universe (Japan)

2015-11-15

We recently reported an experiment which focused on demonstrating the macro-coherent amplification mechanism. This mechanism, which was proposed for neutrino mass measurements, indicates that a multi-particle emission rate should be amplified by coherence in a suitable medium. Using a para-hydrogen molecule gas target and the adiabatic Raman excitation method, we observed that the two photon emission rate was amplified by a factor of more than 10{sup 15} from the spontaneous emission rate. This paper briefly summarizes the previous experimental result and presents the current status and the future prospect.

Non-thermal gamma-ray emission from delayed pair breakdown in a magnetized and photon-rich outflow

Energy Technology Data Exchange (ETDEWEB)

Gill, Ramandeep; Thompson, Christopher, E-mail: rgill@cita.utoronto.ca [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)

2014-12-01

We consider delayed, volumetric heating in a magnetized outflow that has broken out of a confining medium and expanded to a high Lorentz factor (Γ ∼ 10{sup 2}-10{sup 3}) and low optical depth to scattering (τ {sub T} ∼ 10{sup –3}-10{sup –2}). The energy flux at breakout is dominated by the magnetic field, with a modest contribution from quasi-thermal gamma rays whose spectrum was calculated in Paper I. We focus on the case of extreme baryon depletion in the magnetized material, but allow for a separate baryonic component that is entrained from a confining medium. Dissipation is driven by relativistic motion between these two components, which develops once the photon compactness drops below 4 × 10{sup 3}(Y{sub e} /0.5){sup –1}. We first calculate the acceleration of the magnetized component following breakout, showing that embedded MHD turbulence provides significant inertia, the neglect of which leads to unrealistically high estimates of flow Lorentz factor. After reheating begins, the pair and photon distributions are evolved self-consistently using a one-zone kinetic code that incorporates an exact treatment of Compton scattering, pair production and annihilation, and Coulomb scattering. Heating leads to a surge in pair creation, and the scattering depth saturates at τ {sub T} ∼ 1-4. The plasma maintains a very low ratio of particle to magnetic pressure, and can support strong anisotropy in the charged particle distribution, with cooling dominated by Compton scattering. High-energy power-law spectra with photon indices in the range observed in gamma-ray bursts (GRBs; –3 < β < –3/2) are obtained by varying the ratio of heat input to the seed energy in quasi-thermal photons. We contrast our results with those for continuous heating across an expanding photosphere, and show that the latter model produces soft-to-hard evolution that is inconsistent with observations of GRBs.

Some general properties of stimulated Raman propagation with pump depletion, transiency and dispersion

International Nuclear Information System (INIS)

Shore, B.W.; Lowder, S.; Johnson, M.A.

1991-01-01

This note considers some of the properties of the Stokes pulse that grows from a specified seed pulse in the presence of a strong pump pulse as it propagates through a dispersive atomic vapor. We first present an generic dimensionless form for the coupled equations that govern the propagation of pump and Stokes fields or collinear plane-wave pulses. By treating the two fields we permit pump depletion. We include transient atomic response (as embodied in the Raman coherence), but neglect changes in atomic populations. (Thus our equations pertain to the regime in which atoms are more numerous than photons). The equations employ a gain length, a dispersion time τ dis , and a Raman coherence time (or memory time) τ R as basic parameters: these two times, together with a single-photon stationary-atom detuning Δ, subsume the details of a particular atomic Raman transition and particular operating conditions. (The effects of Doppler shifts enters the equations through the coherence time). We discuss some general properties of these generic Raman propagation equations, and present illustrations of their solutions in the absence of dispersion. We comment on departures from exponential growth. We than show examples of behavior when dispersion is present and the pump pulse has a bandwidth that exceeds the transform limit. The illustrations presented here do not pertain to any specific atom (i.e. specific wavelengths and oscillator strengths) or to specific experimental conditions (i.e. number densities and pulse intensities). To permit the connection between the present generic results and particular experiments we conclude by providing expressions for the gain length and dispersion time in terms of atomic number density, polarizabilities, oscillator strengths, statistical weights, transition frequencies, and polarization directions. 11 figs

Photon emission induced by brittle fracture of borosilicate glasses

Energy Technology Data Exchange (ETDEWEB)

Shiota, Tadashi, E-mail: tshiota@ceram.titech.ac.jp [Department of Metallurgy and Ceramic Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Sato, Yoshitaka [Department of Metallurgy and Ceramic Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Kishi, Tetsuo [Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Yasuda, Kouichi [Department of Metallurgy and Ceramic Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2016-05-15

Photon emission (PE) at wavelength ranges of 430–490 nm (B-PE), 500–600 nm (G-PE) and 610–680 nm (R-PE) caused by brittle fracture was simultaneously measured in the nanosecond-to-microsecond and millisecond time domains for two types of borosilicate glasses: Pyrex-type Tempax glass and BK7 glass. The results were compared to those for silica and soda lime glasses. The time dependence of the PE of Tempax glass was similar to that of silica glass, while the PE intensity was lower. Because Tempax glass contains both silica-rich and borate-rich amorphous phases, the PE must be mainly produced by the fracture of the silica-rich phase. Moreover, the proportion of B-PE of Tempax glass was higher than that of silica glass. This suggests that the measured B-PE might also include very weak PE caused by the fracture of the borate-rich phase. The PE time dependence of BK7 glass was similar to that of soda lime glass, which was different from the case for Tempax glass. The PE intensity of BK7 glass was slightly higher than that of soda lime glass, but much lower than that of Tempax glass. The result indicates that non-bridging oxygen in the glasses affects crack propagation behavior and reduces the PE. - Highlights: • Photon emission (PE) upon brittle fracture of borosilicate glasses was measured. • Pyrex-type Tempax and BK7 glasses showed different PE characteristics. • The rupture of Si–O bonds produces much stronger PE than that of B–O bonds. • Non-bridging oxygen in glass affects crack propagation behavior and reduces the PE.

Near-infrared emission and upconversion in Er{sup 3+}-doped TeO{sub 2}–ZnO–ZnF{sub 2} glasses

Energy Technology Data Exchange (ETDEWEB)

Miguel, A. [Departamento de Física Aplicada I, Escuela Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alda. Urquijo s/n 48013 Bilbao (Spain); Morea, R.; Gonzalo, J. [Instituto de Optica, Consejo Superior de Investigaciones Científicas CSIC, Serrano 121, 28006 Madrid (Spain); Arriandiaga, M.A. [Departamento de Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, Apartado 644, Bilbao (Spain); Fernandez, J. [Departamento de Física Aplicada I, Escuela Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alda. Urquijo s/n 48013 Bilbao (Spain); Materials Physics Center CSIC-UPV/EHU and Donostia International Physics Center, 20018 San Sebastian (Spain); Balda, R., E-mail: wupbacrr@bi.ehu.es [Departamento de Física Aplicada I, Escuela Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alda. Urquijo s/n 48013 Bilbao (Spain); Materials Physics Center CSIC-UPV/EHU and Donostia International Physics Center, 20018 San Sebastian (Spain)

2013-08-15

We have investigated the near infrared emission and upconversion of Er{sup 3+} ions in two different compositions of glasses based on TeO{sub 2}, ZnO, and ZnF{sub 2} for different ErF{sub 3} concentrations (0.5, 1, 2, and 3 wt%). Judd–Ofelt intensity parameters have been determined and used to calculate the radiative transition probabilities and radiative lifetimes. The infrared emission at around 1532 nm corresponding to the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition is broader by nearly 30 nm if compared to silica based glasses. The stimulated emission cross section is higher for the glass with the lowest content of ZnF{sub 2} which also shows higher values of the figure of merit for bandwidth. On the other hand, the lifetimes of the excited states are longer for the glass with the highest content of ZnF{sub 2}. Green and red emissions corresponding to transitions ({sup 2}H{sub 11/2},{sup 4}S{sub 3/2})→{sup 4}I{sub 15/2} and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} have been observed under excitation at 801 nm and attributed to a two photon process. The temporal evolution of the green emission suggests the presence of excited state absorption and energy transfer upconversion processes to populate the {sup 4}S{sub 3/2} level. In the case of the red emission, its increase as ErF{sub 3} concentration increases together with its temporal behavior indicate that for ErF{sub 3} concentrations higher than 0.5 wt%, level {sup 4}F{sub 9/2} is populated by multiphonon relaxation from level {sup 4}S{sub 3/2} and energy transfer processes. -- Highlights: ► High absorption and emission cross-sections for the {sup 4}I{sub 13/2}↔{sup 4}I{sub 15/2} transition suitable for EDFAs. ► The increase of fluorine content leads to longer lifetimes of excited levels of Er{sup 3+} ions. ► Increase of the red upconversion emission with concentration due to ETU processes.

Stimulated Raman spectroscopy and nanoscopy of molecules using near field photon induced forces without resonant electronic enhancement gain

Energy Technology Data Exchange (ETDEWEB)

Tamma, Venkata Ananth [CaSTL Center, Department of Chemistry, University of California, Irvine, California 92697 (United States); Huang, Fei; Kumar Wickramasinghe, H., E-mail: hkwick@uci.edu [Department of Electrical Engineering and Computer Science, 142 Engineering Tower, University of California, Irvine, California 92697 (United States); Nowak, Derek [Molecular Vista, Inc., 6840 Via Del Oro, San Jose, California 95119 (United States)

2016-06-06

We report on stimulated Raman spectroscopy and nanoscopy of molecules, excited without resonant electronic enhancement gain, and recorded using near field photon induced forces. Photon-induced interaction forces between the sharp metal coated silicon tip of an Atomic Force Microscope (AFM) and a sample resulting from stimulated Raman excitation were detected. We controlled the tip to sample spacing using the higher order flexural eigenmodes of the AFM cantilever, enabling the tip to come very close to the sample. As a result, the detection sensitivity was increased compared with previous work on Raman force microscopy. Raman vibrational spectra of azobenzene thiol and l-phenylalanine were measured and found to agree well with published results. Near-field force detection eliminates the need for far-field optical spectrometer detection. Recorded images show spatial resolution far below the optical diffraction limit. Further optimization and use of ultrafast pulsed lasers could push the detection sensitivity towards the single molecule limit.

A Search for O2 in CO-Depleted Molecular Cloud Cores With Herschel

Science.gov (United States)

Wirstroem, Eva S.; Charnley, Steven B.; Cordiner, Martin; Ceccarelli, Cecilia

2016-01-01

The general lack of molecular oxygen in molecular clouds is an outstanding problem in astrochemistry. Extensive searches with the Submillimeter Astronomical Satellite, Odin, and Herschel have only produced two detections; upper limits to the O2 abundance in the remaining sources observed are about 1000 times lower than predicted by chemical models. Previous atomic oxygen observations and inferences from observations of other molecules indicated that high abundances of O atoms might be present in dense cores exhibiting large amounts of CO depletion. Theoretical arguments concerning the oxygen gas-grain interaction in cold dense cores suggested that, if O atoms could survive in the gas after most of the rest of the heavy molecular material has frozen out onto dust, then O2 could be formed efficiently in the gas. Using Herschel HIFI, we searched a small sample of four depletion cores-L1544, L694-2, L429, and Oph D-for emission in the low excitation O2 N(sub J)?=?3(sub 3)-1(sub 2) line at 487.249 GHz. Molecular oxygen was not detected and we derive upper limits to its abundance in the range of N(O2)/N (H2) approx. = (0.6-1.6) x10(exp -7). We discuss the absence of O2 in the light of recent laboratory and observational studies.

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

Science.gov (United States)

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.

Photonic crystal light source

Science.gov (United States)

Fleming, James G [Albuquerque, NM; Lin, Shawn-Yu [Albuquerque, NM; Bur, James A [Corrales, NM

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.

Engineering a light-emitting planar defect within three-dimensional photonic crystals

Directory of Open Access Journals (Sweden)

Guiqiang Liu, Yan Chen and Zhiqing Ye

2009-01-01

Full Text Available Sandwich structures, constructed from a planar defect of rhodamine-B (RhB-doped titania (TiO2 and two photonic crystals, were synthesized via the self-assembly method combined with spin-coating. The modification of the spontaneous emission of RhB molecules in such structures was investigated experimentally. The spontaneous emission of RhB-doped TiO2 film with photonic crystals was reduced by a factor of 5.5 over a large bandwidth of 13% of the first-order Bragg diffraction frequency when compared with that of RhB-doped TiO2 film without photonic crystals. The angular dependence of the modification and the photoluminescence lifetime of RhB molecules demonstrate that the strong and wide suppression of the spontaneous emission of the RhB molecules is due to the presence of the photonic band gap.

Engineering a light-emitting planar defect within three-dimensional photonic crystals

Science.gov (United States)

Liu, Guiqiang; Chen, Yan; Ye, Zhiqing

2009-01-01

Sandwich structures, constructed from a planar defect of rhodamine-B (RhB)-doped titania (TiO2) and two photonic crystals, were synthesized via the self-assembly method combined with spin-coating. The modification of the spontaneous emission of RhB molecules in such structures was investigated experimentally. The spontaneous emission of RhB-doped TiO2 film with photonic crystals was reduced by a factor of 5.5 over a large bandwidth of 13% of the first-order Bragg diffraction frequency when compared with that of RhB-doped TiO2 film without photonic crystals. The angular dependence of the modification and the photoluminescence lifetime of RhB molecules demonstrate that the strong and wide suppression of the spontaneous emission of the RhB molecules is due to the presence of the photonic band gap. PMID:27877309

Amplified Photon Upconversion by Photonic Shell of Cholesteric Liquid Crystals.

Science.gov (United States)

Kang, Ji-Hwan; Kim, Shin-Hyun; Fernandez-Nieves, Alberto; Reichmanis, Elsa

2017-04-26

As an effective platform to exploit triplet-triplet-annihilation-based photon upconversion (TTA-UC), microcapsules composed of a fluidic UC core and photonic shell are microfluidically prepared using a triple emulsion as the template. The photonic shell consists of cholesteric liquid crystals (CLCs) with a periodic helical structure, exhibiting a photonic band gap. Combined with planar anchoring at the boundaries, the shell serves as a resonance cavity for TTA-UC emission and enables spectral tuning of the UC under low-power-density excitation. The CLC shell can be stabilized by introducing a polymerizable mesogen in the LC host. Because of the microcapsule spherical symmetry, spontaneous emission of the delayed fluorescence is omnidirectionally amplified at the edge of the stop band. These results demonstrate the range of opportunities provided by TTA-UC systems for the future design of low-threshold photonic devices.

Recent Advances for High-Efficiency Sources of Single Photons Based on Photonic Nanowires

DEFF Research Database (Denmark)

Gerard, J. M.; Claudon, J.; Munsch, M.

2012-01-01

Photonic nanowires have recently been used to tailor the spontaneous emission of embedded quantum dots, and to develop record efficiency single-photon sources. We will present recent developments in this field mainly 1) the observation of a strong inhibition of the spontaneous emission of quantum...

Chirped InAs/InP quantum-dash laser with enhanced broad spectrum of stimulated emission

KAUST Repository

Khan, Mohammed Zahed Mustafa

2013-03-01

We report on the demonstration of 50 nm (full-width at half-maximum) broadband stimulated emission from a chirped AlGaInAs barrier thickness multi-stack InAs/InP quantum dash (Qdash) laser. The 2 ?m wide uncoated Fabry-Perot (FP) ridge-waveguide laser exhibits a total power of 0.18 W, corresponding to an average spectral power density of 3.5 mW/nm, under pulsed current conditions. Intentional extended inhomogeneity across the Qdash stacks have been attributed to the enhancement of broadband emission. © 2013 American Institute of Physics.

Chirped InAs/InP quantum-dash laser with enhanced broad spectrum of stimulated emission

KAUST Repository

Khan, Mohammed Zahed Mustafa; Bhattacharya, Pallab K.; Lee, Chi-Sen; Ng, Tien Khee; Ooi, Boon S.

2013-01-01

We report on the demonstration of 50 nm (full-width at half-maximum) broadband stimulated emission from a chirped AlGaInAs barrier thickness multi-stack InAs/InP quantum dash (Qdash) laser. The 2 ?m wide uncoated Fabry-Perot (FP) ridge-waveguide laser exhibits a total power of 0.18 W, corresponding to an average spectral power density of 3.5 mW/nm, under pulsed current conditions. Intentional extended inhomogeneity across the Qdash stacks have been attributed to the enhancement of broadband emission. © 2013 American Institute of Physics.

A bright single-photon source based on a photonic trumpet

DEFF Research Database (Denmark)

Munsch, Mathieu; Malik, Nitin S.; Bleuse, Joël

Fiber-like photonic nanowires, which are optical waveguides made of a high refractive index material n, have recently emerged as non-resonant systems providing an efficient spontaneous emission (SE) control. When they embed a quantum emitter like a quantum dot (QD), they find application to the r......Fiber-like photonic nanowires, which are optical waveguides made of a high refractive index material n, have recently emerged as non-resonant systems providing an efficient spontaneous emission (SE) control. When they embed a quantum emitter like a quantum dot (QD), they find application...... to the realization of bright sources of quantum light and, reversibly, provide an efficient interface between propagating photons and the QD. For a wire diameter ∼ λ/n (λ is the operation wavelength), the fraction of QD SE coupled to the fundamental guided mode exceeds 90%. The collection of the photons can...... be brought close to unity with a proper engineering of the wire ends. In particular, a tapering of the top wire end is necessary to achieve a directive far-field emission pattern [1]. Recently, we have realized a single-photon source featuring a needle-like taper. The source efficiency, though record...

Initial experience with single-photon emission tomography using iodine-123-labelled 2β-carbomethoxy-3β(4-iodophnyl)tropane in human brain

International Nuclear Information System (INIS)

Kuikka, J.T.; Bergstroem, K.A.; Vanninen, E.; Laulumaa, V.; Hartikainen, P.; Laensimies, E.

1993-01-01

The iodinated cocaine analogue 2β-carbomethoxy-3β-(4-iodophenyl)tropane ([ 123 I]β-CIT), a new dopamine transporter, was preliminarily tested in human brain. Two normal volunteers and two patients with Parkinson's disease were imaged with a high-resolution single-photon emission tomography scanner. The specific binding of [ 123 I]β-CIT in the basal ganglia and thalamus was high in normal volunteers. In addition, there was relatively intense uptake in the medial prefrontal area. Patients with Parkinson's disease who were older than controls showed significantly lower specific binding in the basal ganglia and thalamus and no uptake in the medial prefrontal cortex. This decrease in the dopamine transporter may be age related. (orig.)

Initial experience with single-photon emission tomography using iodine-123-labelled 2[beta]-carbomethoxy-3[beta](4-iodophnyl)tropane in human brain

Energy Technology Data Exchange (ETDEWEB)

Kuikka, J T [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology; Bergstroem, K A [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology; Vanninen, E [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology; Laulumaa, V [Kuopio Univ. Hospital (Finland). Dept. of Neurology; Hartikainen, P [Kuopio Univ. Hospital (Finland). Dept. of Neurology; Laensimies, E [Kuopio Univ. Hospital (Finland). Dept. of Clinical Physiology

1993-09-01

The iodinated cocaine analogue 2[beta]-carbomethoxy-3[beta]-(4-iodophenyl)tropane ([sup 123]I[beta]-CIT), a new dopamine transporter, was preliminarily tested in human brain. Two normal volunteers and two patients with Parkinson's disease were imaged with a high-resolution single-photon emission tomography scanner. The specific binding of [sup 123]I[beta]-CIT in the basal ganglia and thalamus was high in normal volunteers. In addition, there was relatively intense uptake in the medial prefrontal area. Patients with Parkinson's disease who were older than controls showed significantly lower specific binding in the basal ganglia and thalamus and no uptake in the medial prefrontal cortex. This decrease in the dopamine transporter may be age related. (orig.)

Upper limit for the emission of monoenergetic photons in Y(1S)- and Y(2S)-meson decays

International Nuclear Information System (INIS)

Albrecht, H.; Binder, U.; Harder, G.; Lembke-Koppitz, I.; Philipp, A.; Schmidt-Parzefall, W.; Schroeder, H.; Schulz, H.D.; Wurth, R.; Drescher, H.; Graewe, B.; Matthiesen, U.; Scheck, H.; Spengler, J.; Wegener, D.; Edwards, K.W.; Kapitza, H.; Yun, J.C.; Frisken, W.R.; Fukunaga, C.; Goddard, M.; Gilkinson, D.J.; Gingrich, D.M.; Kim, P.C.H.; Kutschke, R.; MacFarlane, D.B.; McKenna, J.A.; Orr, R.S.; Padley, P.; Prentice, J.D.; Seywerd, H.C.J.; Stacey, B.J.; Yoon, T.S.; Ammar, R.; Coppage, D.; Davis, R.; Kanekal, S.; Kwak, N.; Kernel, G.; Plesko, M.; Childers, R.; Darden, C.W.; Gennow, H.

1985-08-01

We report the results of a search for monoenergetic photons in the decay of both the Y(1S)- and the Y(2S)-meson. Photons converted in the beam tube or the drift chamber inner wall, and photons detected with the barrel shower counters of the ARGUS detector, respectively, have been used in the analysis. No narrow peak is observed in the energy interval 0.5 GeV<=Esub(γ)<=4.0 GeV. (orig.)

Controlling light emission from single-photon sources using photonic nanowires

DEFF Research Database (Denmark)

Gregersen, Niels; Chen, Yuntian; Mørk, Jesper

2012-01-01

The photonic nanowire has recently emerged as an promising alternative to microcavity-based single-photon source designs. In this simple structure, a geometrical effect ensures a strong coupling between an embedded emitter and the optical mode of interest and a combination of tapers and mirrors a...

Effects of soil water content and grass recycling on N2O emission in an urban lawn under laboratory incubation study

Science.gov (United States)

Nataningtyas, Dilin Rahayu; Morita, Shunsuke; Hatano, Ryusuke

2017-12-01

In the context of global warming, the increase of N2O gas production from the agricultural area has gained enhancing concern due to N2O is a potent greenhouse gas and an ozone depleted substance. While adding clipping grass has been accepted to replace N-fertilizer input in urban law management its effect on soil gas emission still questionable. A laboratory incubation study had been conducted to evaluate the effect of soil water content and grass recycling on greenhouse gas emission from an urban lawn. The soil samples were taken from Yurigahara Park, Sapporo, Hokkaido Japan. The 17 days at 25°C incubation study was started after adjusting soil water content to 35% and 50% with and without adding the clipping grass on soil surfaces. Greenhouse gas emissions were higher with the addition of grass, however, for NO and N2O considerably higher in 35% than 50% water content. The denitrification process was responsible for the N2O increase in this action. Soil chemical and microbial properties, pH, WEOC, NO3--N, NH4+-N and microbial biomass nitrogen (MBN) as well as N-grass content were also measured to know their correlation with N2O emission. The fine-scale heterogeneity occurred in the soil has impact on the variability of soil chemical properties that influenced the N2O emission. In the other hand, the effect of grass recycling appeared to increased soil N-inorganic contents and stimulated the N-gaseous concentration.

Association of Novelty Seeking Scores and Striatal Dopamine D2/D3 Receptor Availability of Healthy Volunteers: Single Photon Emission Computed Tomography With 123I-iodobenzamide

Directory of Open Access Journals (Sweden)

Hsiang Yu Huang

2010-10-01

Full Text Available It has been speculated that novelty seeking (NS behavior is related to the dopaminergic system. Fifty-two subjects completed the Tridimensional Personality Questionnaire and underwent single photon emission computed tomography with 123I-iodobenzamide. A marginally positive correlation was noted between NS and striatal dopamine D2/D3 receptor availability (r = 0.25, p =0.07. A positive association was noted between the NS scores and left striatal D2/D3 receptor availability (r= 0.29, p =0.04. The results suggest that a relationship might exist between NS score and dopaminergic activity.

Deterministic control of the emission from light sources in 1D nanoporous photonic crystals (Conference Presentation)

Science.gov (United States)

Galisteo-López, Juan F.

2017-02-01

Controlling the emission of a light source demands acting on its local photonic environment via the local density of states (LDOS). Approaches to exert such control on large scale samples, commonly relying on self-assembly methods, usually lack from a precise positioning of the emitter within the material. Alternatively expensive and time consuming techniques can be used to produce samples of small dimensions where a deterministic control on emitter position can be achieved. In this work we present a full solution process approach to fabricate photonic architectures containing nano-emitters which position can be controlled with nanometer precision over squared milimiter regions. By a combination of spin and dip coating we fabricate one-dimensional (1D) nanoporous photonic crystals, which potential in different fields such as photovoltaics or sensing has been previously reported, containing monolayers of luminescent polymeric nanospheres. We demonstrate how, by modifying the position of the emitters within the photonic crystal, their emission properties (photoluminescence intensity and angular distribution) can be deterministically modified. Further, the nano-emitters can be used as a probe to study the LDOS distribution within these systems with a spatial resolution of 25 nm (provided by the probe size) carrying out macroscopic measurements over squared milimiter regions. Routes to enhance light-matter interaction in this kind of systems by combining them with metallic surfaces are finally discussed.

The use of stimulated electron emission (SEE) in homeland security applications

Science.gov (United States)

Ing, H.; Andrews, H. R.; Facina, M.; Lee, W. T.; Niu, H. W.

2012-06-01

Certain insulating solids can store a fraction of the absorbed energy when irradiated by ionizing radiation. The stored energy can be released subsequently by heating or optical stimulation. As a result, light may be emitted through Thermoluminescence (TL) or Optically-Stimulated Luminescence (OSL) and electrons may be emitted through Thermally-Stimulated Electron Emission (TSEE) or Optically-Stimulated Electron Emission (OSEE). TL and OSL are widely used in current radiation dosimetry systems. However, despite considerable research effort during the early 1970s, SEE was not commonly adopted for dosimetry applications. One of the main reasons is that SEE is a surface phenomenon, while luminescence is a bulk phenomenon, making SEE more susceptible to humidity, absorption of gases, minor physical defects and handling, both before and after irradiation. Nevertheless, it has been recognized that SEE may be useful for homeland security applications in nuclear forensics, where dose accuracy is not the primary performance metric. In this research, we are investigating the use of SEE for nuclear forensic applications. Many common materials, both natural and man-made, exhibit the phenomenon, providing an opportunity to use the environment itself as an in-situ radiation detector. We have designed and constructed a unique prototype reader for conducting SEE measurements. We have demonstrated that the SEE measurements from a variety of materials are quantitatively reproducible and correlated to radiation exposure. Due to the broad applicability of SEE, significant additional studies are warranted to optimize this novel technique for nuclear forensic and other applications.

Axion-photon conversion in space and in low symmetrical dielectric crystals

International Nuclear Information System (INIS)

Gorelik, V S

2016-01-01

The opportunities of axions detection as the result of axion-photon conversion processes in the space and in low symmetrical dielectric crystals are discussed. In accordance with the modern theory predictions, axions are pseudoscalar vacuum particles having very small (0.001-1.0 meV) rest energy. The possibility of axions conversion into photons and vice-versa processes in vacuum at the presence of outer magnetic field has been analyzed before. Pseudoscalar (axion type) modes are existing in some types of crystals. Polar pseudoscalar lattice and exciton modes in low symmetrical crystals are strongly interacted with axions. In this work, optical excitation of axion-type modes in low symmetrical crystals is proposed for observation of axion - photon conversion processes. Instead of outer magnetic field, the crystalline field of such crystals may be used. The experimental schemes for axion-photon conversion processes observation with recording the secondary emission of luminescence, infrared or Stimulated Raman Scattering in some dielectric crystals are discussed. (paper)

Photon-photon collisions

Energy Technology Data Exchange (ETDEWEB)

Brodsky, S.J.

1985-01-01

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

Photon-photon collisions

International Nuclear Information System (INIS)

Brodsky, S.J.

1985-01-01

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

Measurement of Coherent Emission and Linear Polarization of Photons by Electrons in the Strong Fields of Aligned Crystals

CERN Document Server

Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.

2004-01-01

We present new results regarding the features of high energy photon emission by an electron beam of 178 GeV penetrating a 1.5 cm thick single Si crystal aligned at the Strings-Of-Strings (SOS) orientation. This concerns a special case of coherent bremsstrahlung where the electron interacts with the strong fields of successive atomic strings in a plane and for which the largest enhancement of the highest energy photons is expected. The polarization of the resulting photon beam was measured by the asymmetry of electron-positron pair production in an aligned diamond crystal analyzer. By the selection of a single pair the energy and the polarization of individual photons could be measured in an the environment of multiple photons produced in the radiator crystal. Photons in the high energy region show less than 20% linear polarization at the 90% confidence level.

Improvements in EBR-2 core depletion calculations

International Nuclear Information System (INIS)

Finck, P.J.; Hill, R.N.; Sakamoto, S.

1991-01-01

The need for accurate core depletion calculations in Experimental Breeder Reactor No. 2 (EBR-2) is discussed. Because of the unique physics characteristics of EBR-2, it is difficult to obtain accurate and computationally efficient multigroup flux predictions. This paper describes the effect of various conventional and higher order schemes for group constant generation and for flux computations; results indicate that higher-order methods are required, particularly in the outer regions (i.e. the radial blanket). A methodology based on Nodal Equivalence Theory (N.E.T.) is developed which allows retention of the accuracy of a higher order solution with the computational efficiency of a few group nodal diffusion solution. The application of this methodology to three-dimensional EBR-2 flux predictions is demonstrated; this improved methodology allows accurate core depletion calculations at reasonable cost. 13 refs., 4 figs., 3 tabs

Characteristics of a single photon emission tomography system with a wide field gamma camera

International Nuclear Information System (INIS)

Mathonnat, F.; Soussaline, F.; Todd-Pokropek, A.E.; Kellershohn, C.

1979-01-01

This text summarizes a work study describing the imagery possibilities of a single photon emission tomography system composed of a conventional wide field gamma camera, connected to a computer. The encouraging results achieved on the various phantoms studied suggest a significant development of this technique in clinical work in Nuclear Medicine Departments [fr

Left ventricular volume determination from single-photon emission computed tomography

International Nuclear Information System (INIS)

Bunker, S.R.; Hartshorne, M.F.; Schmidt, W.P.; Cawthon, M.A.; Karl, R.D. Jr.; Bauman, J.M.; Howard, W.H. III; Rubal, B.J.

1985-01-01

To compare the accuracy of single-photon emission computed tomography (SPECT) with that of contrast cineangiography in measuring left ventricular end-diastolic volume, 25 consecutive patients undergoing catheterizaiton for coronary artery or valvular heart disease were first evaluated scintigraphically. SPECT volume values showed a high degree of correlation with those determined by angiography with a standard error of the estimate of 23 ml. SPECT offers a highly accurate and essentially noninvasive method for measuring chamber volumes that is independent of geometric assumptions about ventricular configuration and chest wall attenuation and does not require blood sample counting

Left ventricular volume determination from single-photon emission computed tomography

Energy Technology Data Exchange (ETDEWEB)

Bunker, S.R.; Hartshorne, M.F.; Schmidt, W.P.; Cawthon, M.A.; Karl, R.D. Jr.; Bauman, J.M.; Howard, W.H. III; Rubal, B.J.

1985-02-01

To compare the accuracy of single-photon emission computed tomography (SPECT) with that of contrast cineangiography in measuring left ventricular end-diastolic volume, 25 consecutive patients undergoing catheterizaiton for coronary artery or valvular heart disease were first evaluated scintigraphically. SPECT volume values showed a high degree of correlation with those determined by angiography with a standard error of the estimate of 23 ml. SPECT offers a highly accurate and essentially noninvasive method for measuring chamber volumes that is independent of geometric assumptions about ventricular configuration and chest wall attenuation and does not require blood sample counting.

Omnidirectional photonic band gap in magnetron sputtered TiO{sub 2}/SiO{sub 2} one dimensional photonic crystal

Energy Technology Data Exchange (ETDEWEB)

Jena, S., E-mail: shuvendujena9@gmail.com [Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Tokas, R.B.; Sarkar, P. [Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Misal, J.S.; Maidul Haque, S.; Rao, K.D. [Photonics & Nanotechnology Section, BARC-Vizag, Autonagar, Atomic & Molecular Physics Division, Bhabha Atomic Research Centre facility, Visakhapatnam 530 012 (India); Thakur, S.; Sahoo, N.K. [Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

2016-01-29

One dimensional photonic crystal (1DPC) of TiO{sub 2}/SiO{sub 2} multilayer has been fabricated by sequential asymmetric bipolar pulsed dc magnetron sputtering of TiO{sub 2} and radio frequency magnetron sputtering of SiO{sub 2} to achieve wide omnidirectional photonic band in the visible region. The microstructure and optical response of the TiO{sub 2}/SiO{sub 2} photonic crystal have been characterized by atomic force microscopy, scanning electron microscopy and spectrophotometry respectively. The surface of the photonic crystal is very smooth having surface roughness of 2.6 nm. Reflection and transmission spectra have been measured in the wavelength range 300 to 1000 nm for both transverse electric and transverse magnetic waves. Wide high reflection photonic band gap (∆ λ = 245 nm) in the visible and near infrared regions (592–837 nm) at normal incidence has been achieved. The measured photonic band gap (PBG) is found well matching with the calculated photonic band gap of an infinite 1DPC. The experimentally observed omnidirectional photonic band 592–668 nm (∆ λ = 76 nm) in the visible region with band to mid-band ratio ∆ λ/λ = 12% for reflectivity R > 99% over the incident angle range of 0°–70° is found almost matching with the calculated omnidirectional PBG. The omnidirectional reflection band is found much wider as compared to the values reported in literature so far in the visible region for TiO{sub 2}/SiO{sub 2} periodic photonic crystal. - Highlights: • TiO{sub 2}/SiO{sub 2} 1DPC has been fabricated using magnetron sputtering technique. • Experimental optical response is found good agreement with simulation results. • Wide omnidirectional photonic band in the visible spectrum has been achieved.

Exact analysis of the response of quantum systems to two-photons using a QSDE approach

International Nuclear Information System (INIS)

Pan, Yu; Dong, Daoyi; Zhang, Guofeng

2016-01-01

We introduce the quantum stochastic differential equation (QSDE) approach to exactly analyze the response of quantum systems to a continuous-mode two-photon input. The QSDE description of the two-photon process allows us to integrate the input–output analysis with the quantum network theory, and so the analytical computability of the output state of a general quantum system can be addressed within this framework. We show that the time-domain two-photon output states can be exactly calculated for a large class of quantum systems including passive linear networks, optomechanical oscillators and two-level emitter in waveguide systems. In particular, we propose to utilise the results for the exact simulation of the stimulated emission as well as the study of the scattering of two-mode photon wave packets. (paper)

Squeezing, photon bunching, photon antibunching and nonclassical photon statistics in degenerate hyper Raman processes

International Nuclear Information System (INIS)

Sen, Biswajit; Mandal, Swapan

2007-01-01

An initially prepared coherent state coupled to a second-order nonlinear medium is responsible for stimulated and spontaneous hyper Raman processes. By using an intuitive approach based on perturbation theory, the Hamiltonian corresponding to the hyper Raman processes is analytically solved to obtain the temporal development of the field operators. It is true that these analytical solutions are valid for small coupling constants. However, the interesting part is that these solutions are valid for reasonably large time. Hence, the present analytical solutions are quite general and are fresh compared to those solutions under short-time approximations. By exploiting the analytical solutions of field operators for various modes, we investigate the squeezing, photon antibunching and nonclassical photon statistics for pure modes of the input coherent light responsible for hyper Raman processes. At least in one instance (stimulated hyper Raman processes for vibration phonon mode), we report the simultaneous appearance of classical (photon bunching) and nonclassical (squeezing) effects of the radiation field responsible for hyper Raman processes

Measurement of cerebral blood flow by single photon emission tomography: principles and application to functional studies of the language areas

International Nuclear Information System (INIS)

Tran Dinh, Y.R.; Seylaz, J.

1989-01-01

Quantitative measurement of cerebral blood flow by single photon emission computerized tomography (SPECT) is a new technique which is particularly suitable for routine studies of cerebro-vascular diseases. SPECT can be used to examine the deep structures of the brain and cerebellum. The functional areas of the brain, which have hitherto been only accessible by clinical-anatomical methods, can be imaged by this technique, based on the correlation between cerebral blood flow and metabolism. The demonstration of preferential activation of temporal and frontal zones in the left hemisphere by active speech stimulation confirms the general principles of hemispheric lateralization of cerebral functions. In addition to this role in studying the physiology of normal subjects, the technique has practical pathological applications. Knowledge of hemispheric lateralization of spoken language should be a pre-operative test for cerebral lesion when there is a risk that surgical intervention may produce irreversible neuropsychological lesions [fr

Super-resolution from single photon emission: toward biological application

Science.gov (United States)

Moreva, E.; Traina, P.; Forneris, J.; Ditalia Tchernij, S.; Guarina, L.; Franchino, C.; Picollo, F.; Ruo Berchera, I.; Brida, G.; Degiovanni, I. P.; Carabelli, V.; Olivero, P.; Genovese, M.

2017-08-01

Properties of quantum light represent a tool for overcoming limits of classical optics. Several experiments have demonstrated this advantage ranging from quantum enhanced imaging to quantum illumination. In this work, experimental demonstration of quantum-enhanced resolution in confocal fluorescence microscopy will be presented. This is achieved by exploiting the non-classical photon statistics of fluorescence emission of single nitrogen-vacancy (NV) color centers in diamond. By developing a general model of super-resolution based on the direct sampling of the kth-order autocorrelation function of the photoluminescence signal, we show the possibility to resolve, in principle, arbitrarily close emitting centers. Finally, possible applications of NV-based fluorescent nanodiamonds in biosensing and future developments will be presented.

The Depletion of Water During Dispersal of Planet-forming Disk Regions

Science.gov (United States)

Banzatti, A.; Pontoppidan, K. M.; Salyk, C.; Herczeg, G. J.; van Dishoeck, E. F.; Blake, G. A.

2017-01-01

We present a new velocity-resolved survey of 2.9 μm spectra of hot H2O and OH gas emission from protoplanetary disks, obtained with the Cryogenic Infrared Echelle Spectrometer at the VLT (R ˜ 96,000). With the addition of archival Spitzer-IRS spectra, this is the most comprehensive spectral data set of water vapor emission from disks ever assembled. We provide line fluxes at 2.9-33 μm that probe from the dust sublimation radius at ˜0.05 au out to the region of the water snow line. With a combined data set for 55 disks, we find a new correlation between H2O line fluxes and the radius of CO gas emission, as measured in velocity-resolved 4.7 μm spectra (R {}{co}), which probes molecular gaps in inner disks. We find that H2O emission disappears from 2.9 μm (hotter water) to 33 μm (colder water) as {R}{co} increases and expands out to the snow line radius. These results suggest that the infrared water spectrum is a tracer of inside-out water depletion within the snow line. It also helps clarify an unsolved discrepancy between water observations and models by finding that disks around stars of {M}\\star > 1.5 {M}⊙ generally have inner gaps with depleted molecular gas content. We measure radial trends in H2O, OH, and CO line fluxes that can be used as benchmarks for models to study the chemical composition and evolution of planet-forming disk regions at 0.05-20 au. We propose that JWST spectroscopy of molecular gas may be used as a probe of inner disk gas depletion, complementary to the larger gaps and holes detected by direct imaging and by ALMA.

Multiple photon emission in heavy particle decays

International Nuclear Information System (INIS)

Asakimori, K.; Burnett, T.H.; Cherry, M.L.

1994-03-01

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 → 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. (author). 7 refs, 6 figs, 2 tabs

Anti-3-[(18)F]FACBC positron emission tomography-computerized tomography and (111)In-capromab pendetide single photon emission computerized tomography-computerized tomography for recurrent prostate carcinoma: results of a prospective clinical trial.

Science.gov (United States)

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

2014-05-01

We prospectively evaluated the amino acid analogue positron emission tomography radiotracer anti-3-[(18)F]FACBC compared to ProstaScint® ((111)In-capromab pendetide) single photon emission computerized tomography-computerized tomography to detect recurrent prostate carcinoma. A total of 93 patients met study inclusion criteria who underwent anti-3-[(18)F]FACBC positron emission tomography-computerized tomography plus (111)In-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. In the 91 of 93 patients with sufficient data for a consensus on the presence or absence of prostate/bed disease anti-3-[(18)F]FACBC had 90.2% sensitivity, 40.0% specificity, 73.6% accuracy, 75.3% positive predictive value and 66.7% negative predictive value compared to (111)In-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-[(18)F]FACBC had 55.0% sensitivity, 96.7% specificity, 72.9% accuracy, 95.7% positive predictive value and 61.7% negative predictive value compared to (111)In-capromab pendetide with 10.0%, 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-[(18)F]FACBC identified 14 more positive prostate bed recurrences (55 vs 41) and 18 more patients with extraprostatic involvement (22 vs 4). Anti-3-[(18)F]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. Better diagnostic performance was noted for anti-3-[(18)F]FACBC positron emission tomography-computerized tomography than for (111)In-capromab pendetide single

Mechanisms of ultrafast fluorescence depletion spectroscopy and applications to measure slovation dynamics of coummarin 153 in methanol

International Nuclear Information System (INIS)

Yang Songqiu; Liu Jianyong; Zhou Panwang; Chen Junsheng; Han Keli; He Guozhong

2012-01-01

Subpicosecond fluorescence depletion spectroscopy (FDS) was used to measure the solvation dynamics of coumarin 153 (C153) in methanol. The FDS mechanisms were discussed. A quasi-continuous model was used to describe the solvational relaxation of excited states. The perturbations of the probe pulse on the excited sample system, including up-conversion and stimulated emission, were sufficiently discussed. For a probe molecule used in the FDS experiment, ensuring that the up-conversion perturbation can be negligible is important. FDS was found to be a good technique for measuring the solvation dynamics of C153 in methanol. - Highlights: ► Mechanisms of subpicosecond fluorescence depletion spectroscopy. ► Quasi-continuous model was used to describe the solvational relaxation. ► The solvation dynamics of coumarin 153 in methanol has been measured.

Simulation of Photon energy Spectra Using MISC, SOURCES, MCNP and GADRAS

International Nuclear Information System (INIS)

Tucker, Lucas P.; Shores, Erik F.; Myers, Steven C.; Felsher, Paul D.; Garner, Scott E.; Solomon, Clell J. Jr.

2012-01-01

The detector response functions included in the Gamma Detector Response and Analysis Software (GADRAS) are a valuable resource for simulating radioactive source emission spectra. Application of these response functions to the results of three-dimensional transport calculations is a useful modeling capability. Using a 26.2 kg shell of depleted uranium (DU) as a simple test problem, this work illustrates a method for manipulating current tally results from MCNP into the GAM file format necessary for a practical link to GADRAS detector response functions. MISC (MCNP Intrinsic Source Constructor) and SOURCES 4C were used to develop photon and neutron source terms for subsequent MCNP transport, and the resultant spectrum is shown to be in good agreement with that from GADRAS. A 1 kg DU sphere was also modeled with the method described here and showed similarly encouraging results.

Simulation of Photon energy Spectra Using MISC, SOURCES, MCNP and GADRAS

Energy Technology Data Exchange (ETDEWEB)

Tucker, Lucas P. [Los Alamos National Laboratory; Shores, Erik F. [Los Alamos National Laboratory; Myers, Steven C. [Los Alamos National Laboratory; Felsher, Paul D. [Los Alamos National Laboratory; Garner, Scott E. [Los Alamos National Laboratory; Solomon, Clell J. Jr. [Los Alamos National Laboratory

2012-08-14

The detector response functions included in the Gamma Detector Response and Analysis Software (GADRAS) are a valuable resource for simulating radioactive source emission spectra. Application of these response functions to the results of three-dimensional transport calculations is a useful modeling capability. Using a 26.2 kg shell of depleted uranium (DU) as a simple test problem, this work illustrates a method for manipulating current tally results from MCNP into the GAM file format necessary for a practical link to GADRAS detector response functions. MISC (MCNP Intrinsic Source Constructor) and SOURCES 4C were used to develop photon and neutron source terms for subsequent MCNP transport, and the resultant spectrum is shown to be in good agreement with that from GADRAS. A 1 kg DU sphere was also modeled with the method described here and showed similarly encouraging results.

Mid-latitude Narrowband Stimulated Electromagnetic Emissions (NSEE): New Observations and Modeling

Science.gov (United States)

Nossa, E.; Mahmoudian, A.; Isham, B.; Bernhardt, P. A.; Briczinski, S. J., Jr.

2017-12-01

High power electromagnetic waves (EM) transmitted from the ground interact with the local plasma in the ionosphere and can produce Stimulated Electromagnetic Emissions (SEE) through the parametric decay instability (PDI). The classical SEE features known as wideband SEE (WSEE) with frequency offset of 1 kHz up to 100 kHz have been observed and studied in detail in the 1980s and 1990s. A new era of ionospheric remote sensing techniques was begun after the recent update of the HF transmitter at the HAARP. Sideband emissions of unprecedented strength have been reported during recent campaigns at HAARP, reaching up to 10 dB relative to the reflected pump wave which are by far the strongest spectral features of secondary radiation that have been reported. These emissions known as narrowband SEE (NSEE) are shifted by only up to a few tens of Hertz from radio-waves transmitted at several megahertz. One of these new NSEE features are emission lines within 100 Hz of the pump frequency and are produced through magnetized stimulated Brillouin scatter (MSBS) process. Stimulated Brillouin Scatter (SBS) is a strong SEE mode involving a direct parametric decay of the pump wave into an electrostatic wave (ES) and a secondary EM wave that sometimes could be stronger than the HF pump. SBS has been studied in laboratory plasma experiments by the interaction of high power lasers with plasmas. The SBS instability in magnetized ionospheric plasma was observed for the first time at HAARP in 2010. Our recent work at HAARP has shown that MSBS emission lines can be used to asses electron temperature in the heated region, ion mass spectrometry, determine minor ion species and their densities in the ionosphere, study the physics associated with electron acceleration and artificial airglow. Here, we present new observations of narrowband SEE (NSEE) features at the new mid-latitude heating facility at Arecibo. This includes the direct mode conversion of pump wave through MSBS process. Collected

Photon-Enhanced Thermionic Emission in Cesiated p-Type and n-Type Silicon

DEFF Research Database (Denmark)

Reck, Kasper; Dionigi, Fabio; Hansen, Ole

2014-01-01

electrons. Efficiencies above 60% have been predicted theoretically for high solar concentration systems. Silicon is an interesting absorber material for high efficiency PETE solar cells, partly due to its mechanical and thermal properties and partly due to its electrical properties, including a close......Photon-enhanced thermionic emission (PETE) is a relatively new concept for high efficiency solar cells that utilize not only the energy of electrons excited across the band gap by photons, as in conventional photovoltaic solar cells, but also the energy usual lost to thermalization of the excited...... to ideal band gap. The work function of silicon is, however, too high for practical PETE implementations. A well-known method for lowering the work function of silicon (and other materials) is to apply approximately a monolayer of cesium to the silicon surface. We present the first measurements of PETE...

Effect of the temperature, pH and irradiance on the photosynthetic activity by Scenedesmus obtusiusculus under nitrogen replete and deplete conditions.

Science.gov (United States)

Cabello, Juan; Toledo-Cervantes, Alma; Sánchez, León; Revah, Sergio; Morales, Marcia

2015-04-01

This paper evaluates the effect of the irradiance, pH and temperature on the photosynthetic activity (PA) of Scenedesmus obtusiusculus under N-replete and N-deplete conditions through oxygen measurements. The highest PA values were 160 mgO2 gb(-1) h(-1) at 620 μmol m(-2) s(-1), 35 °C and pH of 8 under N-replete conditions and 3.3 mgO2 gb(-1) h(-1) at 100 μmol m(-2) s(-1), 28.5 °C and pH of 5.5 for N-deplete conditions. Those operation conditions were tested in a flat-panel photobioreactor. The biomass productivity was 0.97 gb L(-1) d(-1) under N-replete conditions with a photosynthetic efficiency (PE) of 4.4% yielding 0.85 gb mol photon(-1). Similar biomass productivity was obtained under N-deplete condition; and the lipid productivity was 0.34 gL L(-1) d(-1) with a PE of 7.8% yielding 0.39 gL mol photon(-1). The apparent activation and deactivation energies were 16.1 and 30 kcal mol(-1), and 11.9 and 15.3 kcal mol(-1), for N-replete and N-deplete conditions, respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

N2O emission from plant surfaces – light stimulated and a global phenomenon

DEFF Research Database (Denmark)

Mikkelsen, Teis Nørgaard; Bruhn, Dan; Ambus, Per

2017-01-01

for the first time N2O emission fromterrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurementsto investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and withoutUV-screening. Further laboratory tests were conducted...... with a range of species to study the controls and possibleloci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c.20-50 nmol m-2 h-1, mostly due to the UV component. The emission rate is temperature dependent with a ratherhigh activation energy indicative...

Acute Vagal Nerve Stimulation Lowers α2 Adrenoceptor Availability

DEFF Research Database (Denmark)

Landau, Anne M.; Dyve, Suzan; Jakobsen, Steen

2015-01-01

Background Vagal nerve stimulation (VNS) emerged as an anti-epileptic therapy, and more recently as a potential antidepressant intervention. Objective/hypothesis We hypothesized that salutary effects of VNS are mediated, at least in part, by augmentation of the inhibitory effects of cortical...... monoaminergic neurotransmission at appropriate receptors, specifically adrenoceptors. Our objective was to measure the effect of acute VNS on α2 adrenoceptor binding. Methods Using positron emission tomography (PET), we measured changes in noradrenaline receptor binding associated with acute VNS stimulation...... electrode in minipigs before and within 30 min of the initiation of 1 mA stimulation. Kinetic analysis with the Logan graphical linearization generated tracer volumes of distribution for each condition. We used an averaged value of the distribution volume of non-displaceable ligand (VND), to calculate...

Multi-photon ionization of atoms in intense short-wavelength radiation fields

Science.gov (United States)

Meyer, Michael

2015-05-01

The unprecedented characteristics of XUV and X-ray Free Electron Lasers (FELs) have stimulated numerous investigations focusing on the detailed understanding of fundamental photon-matter interactions in atoms and molecules. In particular, the high intensities (up to 106 W/cm2) giving rise to non-linear phenomena in the short wavelength regime. The basic phenomenology involves the production of highly charged ions via electron emission to which both sequential and direct multi-photon absorption processes contribute. The detailed investigation of the role and relative weight of these processes under different conditions (wavelength, pulse duration, intensity) is the key element for a comprehensive understanding of the ionization dynamics. Here the results of recent investigations are presented, performed at the FELs in Hamburg (FLASH) and Trieste (FERMI) on atomic systems with electronic structures of increasing complexity (Ar, Ne and Xe). Mainly, electron spectroscopy is used to obtain quantitative information about the relevance of various multi-photon ionization processes. For the case of Ar, a variety of processes including above threshold ionization (ATI) from 3p and 3s valence shells, direct 2p two-photon ionization and resonant 2p-4p two-photon excitations were observed and their role was quantitatively determined comparing the experimental ionization yields to ab-initio calculations of the cross sections for the multi-photon processes. Using Ar as a benchmark to prove the reliability of the combined experimental and theoretical approach, the more complex and intriguing case of Xe was studied. Especially, the analysis of the two-photon ATI from the Xe 4d shell reveals new insight into the character of the 4d giant resonance, which was unresolved in the linear one-photon regime. Finally, the influence of intense XUV radiation to the relaxation dynamics of the Ne 2s-3p resonance was investigated by angle-resolved electron spectroscopy, especially be observing

New nonlinear-laser properties of ferroelectric Nd3+:Ba2NaNb5O15 - cw stimulated emission (4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 ), collinear and diffuse self-frequency doubling and summation

International Nuclear Information System (INIS)

Kaminskii, Alexandr A; Jaque, D; Garsia, Sole J; Capmany, J; Bagayev, S N; Ueda, Ken-ichi

1999-01-01

A new cw laser with self-frequency doubling and summation of 1-μm oscillation ( 4 F 3/2 → 4 I 11/2 ) was constructed on the basis of an orthorhombic Nd 3+ :Ba 2 NaNb 5 O 15 crystal. The 4 F 3/2 → 4 I 13/2 inter-Stark transition was used to excite cw 1.3-μm stimulated emission from this ferroelectric. (letters to the editor)

Single photon emission computerized tomography (SPECT)

International Nuclear Information System (INIS)

Ganatra, R.D.

1992-01-01

Tomography in nuclear medicine did not originate after the introduction of X-ray computerized tomography (CT). Even in the days of rectilinear scanner, tomography was attempted with multiple detector heads rotating around the patient, but the counts at each plane were never very high to obtain a satisfactory image. A high resolution focusing collimator can look at different depths but taking several slices in one projection was a time consuming process. Rectilinear scanners lose lot of counts in the collimator to look at one point, at on time, in one plane. It is true that attempts to do tomography with gamma camera really got a boost after the success of CT. By that time, algorithms for doing reconstruction of images also were highly refined and for advanced. Clinical application of SPECT has become widespread now, because of the development of suitable radiopharmaceuticals and improvement in instrumentation. The SPECT provides a direct measure of regional organ function and is performed with nuclides such as 123 I and 99 Tc m that emit a mono-image photon during their decay. SPECT is far less expensive than positron emission tomography

Single photon emission computerized tomography (SPECT)

Energy Technology Data Exchange (ETDEWEB)

Ganatra, R D

1993-12-31

Tomography in nuclear medicine did not originate after the introduction of X-ray computerized tomography (CT). Even in the days of rectilinear scanner, tomography was attempted with multiple detector heads rotating around the patient, but the counts at each plane were never very high to obtain a satisfactory image. A high resolution focusing collimator can look at different depths but taking several slices in one projection was a time consuming process. Rectilinear scanners lose lot of counts in the collimator to look at one point, at on time, in one plane. It is true that attempts to do tomography with gamma camera really got a boost after the success of CT. By that time, algorithms for doing reconstruction of images also were highly refined and for advanced. Clinical application of SPECT has become widespread now, because of the development of suitable radiopharmaceuticals and improvement in instrumentation. The SPECT provides a direct measure of regional organ function and is performed with nuclides such as {sup 123}I and {sup 99}Tc{sup m} that emit a mono-image photon during their decay. SPECT is far less expensive than positron emission tomography

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.

Science.gov (United States)

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.

Degenerative dementia: nosological aspects and results of single photon emission computed tomography

International Nuclear Information System (INIS)

Dubois, B.; Habert, M.O.

1999-01-01

Ten years ago, the diagnosis discussion of a dementia case for the old patient was limited to two pathologies: the Alzheimer illness and the Pick illness. During these last years, the frame of these primary degenerative dementia has fallen into pieces. The different diseases and the results got with single photon emission computed tomography are discussed. for example: fronto-temporal dementia, primary progressive aphasia, progressive apraxia, visio-spatial dysfunction, dementia at Lewy's bodies, or cortico-basal degeneration. (N.C.)

Bronchobiliary Fistula Localized by Cholescintigraphy with Single-Photon Emission Computed Tomography

International Nuclear Information System (INIS)

Artunduaga, Maddy; Patel, Niraj R.; Wendt, Julie A.; Guy, Elizabeth S.; Nachiappan, Arun C.

2015-01-01

Biliptysis is an important clinical feature to recognize as it is associated with bronchobiliary fistula, a rare entity. Bronchobiliary fistulas have been diagnosed with planar cholescintigraphy. However, cholescintigraphy with single-photon emission computed tomography (SPECT) can better spatially localize a bronchobiliary fistula as compared to planar cholescintigraphy alone, and is useful for preoperative planning if surgical treatment is required. Here, we present the case of a 23-year-old male who developed a bronchobiliary fistula in the setting of posttraumatic and postsurgical infection, which was diagnosed and localized by cholescintigraphy with SPECT

Photonic crystal and photonic quasicrystal patterned in PDMS surfaces and their effect on LED radiation properties

Energy Technology Data Exchange (ETDEWEB)

Suslik, Lubos [Dept. of Physics, Faculty of Electrical Engineering, University of Zilina, Univerzitna 1, 010 26, Zilina (Slovakia); Pudis, Dusan, E-mail: pudis@fyzika.uniza.sk [Dept. of Physics, Faculty of Electrical Engineering, University of Zilina, Univerzitna 1, 010 26, Zilina (Slovakia); Goraus, Matej [Dept. of Physics, Faculty of Electrical Engineering, University of Zilina, Univerzitna 1, 010 26, Zilina (Slovakia); Nolte, Rainer [Fakultät für Maschinenbau FG Lichttechnik Ilmenau University of Technology, Ilmenau (Germany); Kovac, Jaroslav [Inst. of Electronics and Photonics, Slovak University of Technology, Ilkovicova 3, 812 19, Bratislava (Slovakia); Durisova, Jana; Gaso, Peter [Dept. of Physics, Faculty of Electrical Engineering, University of Zilina, Univerzitna 1, 010 26, Zilina (Slovakia); Hronec, Pavol [Inst. of Electronics and Photonics, Slovak University of Technology, Ilkovicova 3, 812 19, Bratislava (Slovakia); Schaaf, Peter [Chair Materials for Electronics, Institute of Materials Engineering and Institute of Micro- and Nanotechnologies MacroNano, TU Ilmenau, Gustav-Kirchhoff-Str. 5, 98693 Ilmenau (Germany)

2017-02-15

Graphical abstract: Photonic quasicrystal patterned in the surface of polydimethylsiloxane membrane (left) and radiation pattern of light emitting diode with patterned membrane applied in the surface (right). - Highlights: • We presented fabrication technique of PDMS membranes with patterned surface by photonic crystal (PhC) and photonic quasi-crystal (PQC). • Presented technique is effective for preparation PhC and PQC PDMS membranes easily implementing in the LED chip. • From the goniophotometer measurements, the membranes document effective angular emission due to the diffraction on patterned surfaces. • 12 fold symmetry PQC structure shows homogeneous radiation pattern, while the 2 fold symmetry of square PhC shows evident diffraction lobes. - Abstract: We present results of fabrication and implementation of thin polydimethylsiloxane (PDMS) membranes with patterned surface for the light emitting diode (LED). PDMS membranes were patterned by using the interference lithography in combination with embossing technique. Two-dimensional photonic crystal and photonic quasicrystal structures with different period were patterned in the surface of thin PDMS membranes with depth up to 550 nm. Patterned PDMS membranes placed on the LED chip effectively diffracted light and increased angular emission of LED radiation pattern. We presented effective technique for fabrication of patterned PDMS membranes, which could modify the emission properties of optoelectronic devices and can be applied directly on surface LEDs and small optical devices.

UV-induced N2O emission from plants

Science.gov (United States)

Bruhn, Dan; Albert, Kristian R.; Mikkelsen, Teis N.; Ambus, Per

2014-12-01

Nitrous oxide (N2O) is an important long-lived greenhouse gas and precursor of stratospheric ozone-depleting mono-nitrogen oxides. The atmospheric concentration of N2O is persistently increasing; however, large uncertainties are associated with the distinct source strengths. Here we investigate for the first time N2O emission from terrestrial vegetation in response to natural solar ultra violet radiation. We conducted field site measurements to investigate N2O atmosphere exchange from grass vegetation exposed to solar irradiance with and without UV-screening. Further laboratory tests were conducted with a range of species to study the controls and possible loci of UV-induced N2O emission from plants. Plants released N2O in response to natural sunlight at rates of c. 20-50 nmol m-2h-1, mostly due to the UV component. The emission response to UV-A is of the same magnitude as that to UV-B. Therefore, UV-A is more important than UV-B given the natural UV-spectrum at Earth's surface. Plants also emitted N2O in darkness, although at reduced rates. The emission rate is temperature dependent with a rather high activation energy indicative for an abiotic process. The prevailing zone for the N2O formation appears to be at the very surface of leaves. However, only c. 26% of the UV-induced N2O appears to originate from plant-N. Further, the process is dependent on atmospheric oxygen concentration. Our work demonstrates that ecosystem emission of the important greenhouse gas, N2O, may be up to c. 30% higher than hitherto assumed.

Extreme emission of N2O from tropical wetland soil (Pantanal, South America)

DEFF Research Database (Denmark)

Jensen, Lars Liengård; Nielsen, Lars Peter; Revsbech, Niels Peter

2013-01-01

Nitrous oxide (N(2)O) is an important greenhouse gas and ozone depleter, but the global budget of N(2)O remains unbalanced. Currently, ~25% of the global N(2)O emission is ascribed to uncultivated tropical soils, but the exact locations and controlling mechanisms are not clear. Here we present...... the first study of soil N(2)O emission from the Pantanal indicating that this South American wetland may be a significant natural source of N(2)O. At three sites, we repeatedly measured in situ fluxes of N(2)O and sampled porewater nitrate [Formula: see text] during the low water season in 2008 and 2009....... In 2010, 10 sites were screened for in situ fluxes of N(2)O and soil [Formula: see text] content. The in situ fluxes of N(2)O were comparable to fluxes from heavily fertilized forests or agricultural soils. An important parameter affecting N(2)O emission rate was precipitation, inducing peak emissions...

Whispering gallery mode emission from a composite system of J-aggregates and photonic microcavity

Energy Technology Data Exchange (ETDEWEB)

Melnikau, Dzmitry; Savateeva, Diana [Centro de Física de Materiales (MPC, CSIC-UPV/EHU) and Donostia International Physics Center (DIPC), Po Manuel de Lardizabal 5, Donostia, San Sebastian 20018 (Spain); Rusakov, Konstantin I. [Department of Physics, Brest State Technical University, Brest 224017 (Belarus); Rakovich, Yury P., E-mail: Yury.Rakovich@ehu.es [Centro de Física de Materiales (MPC, CSIC-UPV/EHU) and Donostia International Physics Center (DIPC), Po Manuel de Lardizabal 5, Donostia, San Sebastian 20018 (Spain); IKERBASQUE, Basque Foundation for Science, Bilbao (Spain)

2014-01-15

We report on development and characterization of Whispering Gallery Modes spherical microcavities integrated with organic dye molecules in a J-aggregate state. The microcavities are studied using micro-photoluminescence spectroscopy, and fluorescence lifetime imaging confocal microscopy. Directional emission of light from the microcavity is also experimentally demonstrated and attributed to the photonic jets generated in the microsphere. -- Highlights: • Report on the development and characterization of hybrid system consisting of thin shell of J-aggregates and spherical Whispering Gallery Mode microcavity. • An investigation of spontaneous emission rate in the shell of J-aggregates integrated with a Whispering Gallery Mode cavity. • Demonstration of directional emission from Whispering Gallery Mode cavity with J-aggregates which is highly desirable functionality for both micro- and nano-scale cavities.

Nonlinear time-domain cochlear model for transient stimulation and human otoacoustic emission

DEFF Research Database (Denmark)

Verhulst, Sarah; Dau, Torsten; Shera, Christopher A.

2012-01-01

This paper describes the implementation and performance of a nonlinear time-domain model of the cochlea for transient stimulation and human otoacoustic emission generation. The nonlinearity simulates compressive growth of measured basilar-membrane impulse responses. The model accounts...... for reflection and distortion-source otoacoustic emissions (OAEs) and simulates spontaneous OAEs through manipulation of the middle-ear reflectance. The model was calibrated using human psychoacoustical and otoacoustic tuning parameters. It can be used to investigate time-dependent properties of cochlear...

Hybrid Single Photon Emission Computed Tomography/Computed Tomography Sulphur Colloid Scintigraphy in Focal Nodular Hyperplasia

International Nuclear Information System (INIS)

Bhoil, Amit; Gayana, Shankramurthy; Sood, Ashwani; Bhattacharya, Anish; Mittal, Bhagwant Rai

2013-01-01

It is important to differentiate focal nodular hyperplasia (FNH), a benign condition of liver most commonly affecting women, from other neoplasm such as hepatic adenoma and metastasis. The functional reticuloendothelial features of FNH can be demonstrated by scintigraphy. We present a case of breast cancer in whom fluorodeoxyglucose positron emission tomography/computerized tomography (CT) showed a homogenous hyperdense lesion in liver, which on Tc99m sulfur colloid single-photon emission computed tomography/CT was found to have increased focal tracer uptake suggestive of FNH

Tailoring Nd3+ emission spectrum by a neodymium-doped tellurite all-solid photonic bandgap fiber

Science.gov (United States)

Tong, Hoang Tuan; Demichi, Daisuke; Suzuki, Takenobu; Ohishi, Yasutake

2018-02-01

A tellurite all-solid photonic bandgap fiber (ASPBF) whose cladding consists of 60 high-index rods arranged periodically around a central core was successfully fabricated. The diameter of high-index rod was about 5.0 μm and the distance between the center of two adjacent high-index rods was approximately 8.0 μm. The high-index rod was made of the TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN) glass, the cladding was made of the TeO2-ZnO-Na2O-La2O3 (TZNL) glass as the background glass material and the central core was made of TZNL glass doped with 0.5 wt% of Nd2O3. A supercontinuum light from 0.6 to 2.4 μm was coupled into the core of fiber which is 2.2 cm long to measure its transmission spectrum. High transmission bands were obtained in the vicinity of 0.75 and 1.3 μm but the transmission was suppressed in the wavelength range from 1.0 to 1.06 μm. When a titanium∶Sapphire laser source at 0.75 μm was used, the emission spectrum was obtained with two peaks at 1.06 and 1.33 μm which are attributed to the 4F3/2->4I11/2 and 4F3/2->4I13/2 transitions of Nd3+ ion, respectively. The intensities of those emission peaks were compared with those obtained from a bulk glass having the same doping concentration of Nd3+. The results showed that by using tellurite ASPBF, the intensity of the 1.06-μm emission was suppressed by one-twelfth but the intensity of the 1.33-μm emission was maintained. This feature is very advantageous to filter out the 1.06-μm emission of Nd3+ ion in order to realize practical amplifier devices at 1.3 μm.

Evaluation of scintillators and semiconductor detectors to image three-photon positron annihilation for positron emission tomography

International Nuclear Information System (INIS)

Abuelhia, E.; Spyrou, N.M.; Kacperski, K.; College University, Middlesex Hospital, London

2008-01-01

Positron emission tomography (PET) is rapidly becoming the main nuclear imaging modality of the present century. The future of PET instrumentation relies on semiconductor detectors because of their excellent characteristics. Three-photon positron annihilation has been recently investigated as a novel imaging modality, which demands the crucial high energy resolution of semiconductor detector. In this work the evaluation of the NaI(Tl) scintillator and HPGe and CdZTe semiconductor detectors, to construct a simple three-photon positron annihilation scanner has been explored. The effect of detector and scanner size on spatial resolution (FWHM) is discussed. The characteristics: energy resolution versus count rate and point-spread function of the three-photon positron annihilation image profile from triple coincidence measurements were investigated. (author)

Effects of Biochar Addition on CO2 and N2O Emissions following Fertilizer Application to a Cultivated Grassland Soil.

Science.gov (United States)

Chen, Jingjing; Kim, Hyunjin; Yoo, Gayoung

2015-01-01

Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO2 and N2O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO2 emissions differed according to biochar addition and amendments. CO2 emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO2 emission was observed when biochar and compost were applied together during the summer. Overall N2O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N2O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N2O emission. Two possible mechanisms were proposed to explain the higher N2O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N2O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N2O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N2O emission when applied to soil amended with urea.

Single photon emission computed tomography in AIDS dementia complex

International Nuclear Information System (INIS)

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

1988-01-01

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

Single photon emission computed tomography in children with idiopathic seizures

International Nuclear Information System (INIS)

Hara, Masafumi; Takahashi, Mutsumasa; Kojima, Akihiro; Shimomura, Osamu; Kinoshita, Rumi; Tomiguchi, Seiji; Taku, Keiichi; Miike, Teruhisa

1991-01-01

Single photon emission computed tomography (SPECT) with N-isoprophyl-p [ 123 I]-iodoamphetamine (IMP), X-ray computed tomography (X-CT), and magnetic resonance imaging (MRI) were performed in 20 children with idiopathic seizures. In children with idiopathic seizures, SPECT could detect the abnormal sites at the highest rate (45%) compared with CT (10%) and MRI (12%), but the abnormal sites on SPECT correlated poorly with the foci on electroencephalograph (EEG). Idiopathic epilepsy with hypoperfusion on SPECT was refractory to treatment and was frequently associated with mental and/or developmental retardation. Perfusion defects on SPECT scans probably affect the development and maturation of the brain in children. (author)

A comparative study of attenuation correction algorithms in single photon emission computed tomography (SPECT)

International Nuclear Information System (INIS)

Murase, Kenya; Itoh, Hisao; Mogami, Hiroshi; Ishine, Masashiro; Kawamura, Masashi; Iio, Atsushi; Hamamoto, Ken

1987-01-01

A computer based simulation method was developed to assess the relative effectiveness and availability of various attenuation compensation algorithms in single photon emission computed tomography (SPECT). The effect of the nonuniformity of attenuation coefficient distribution in the body, the errors in determining a body contour and the statistical noise on reconstruction accuracy and the computation time in using the algorithms were studied. The algorithms were classified into three groups: precorrection, post correction and iterative correction methods. Furthermore, a hybrid method was devised by combining several methods. This study will be useful for understanding the characteristics limitations and strengths of the algorithms and searching for a practical correction method for photon attenuation in SPECT. (orig.)

Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal

International Nuclear Information System (INIS)

Bing, Zhang; Xiu-Dong, Sun; Xiang-Qian, Jiang

2010-01-01

We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission. A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal. Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency. It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels. For a zero initial phase, destructive property is presented in the spectra. With the increase of initial phase difference, quantum interference between the two decay channels from upper levels to ground level turns to be constructive. Furthermore, we give an interpretation for the property of these spectra. (atomic and molecular physics)

Gary-scale stimulated acoustic emission: differential diagnosis between hepatocelluar carcinoma and metastastic adenocarcinoma

Energy Technology Data Exchange (ETDEWEB)

Ko, Jang Jae; Yoon, Kwon Ha [Wongwang Univ. School of Medicine, Wonkwang (Korea, Republic of)

2001-01-01

To assess the value of gray-scale stimulated acoustic emission in differential diagnosis between hepatocellular carcinoma and metastatic adenocarcinoma.Twenty-four cases of hepatocellular carcinoma (HCC) in 23 patients and 26 cases of metastatic adenocarcinoma in 14 patients were prospectively examined using the pluse-inversion harmonic technique after intravenous SH U 508A administration. Gray-scale stimulated acoustic emission (SAE) was measured 5 mins after bolus injection of a contrast agent (4g, 400 mg/ml). The presence or absence of SAE signas at internal and marginal areas of the tumor and the appearance (smooth or irregular) of its border were compared. In addition, the SAE index (SAE (parenchyma) - SAE (tumor)/ SAE (parenchyma)) was histographycally determined using a computerized program (PiView{sup TM}; Mediface, Seoul, Korea). The statistics were analysed using student's test. Of the 24 HCC cases, 20 (83%) showed internal SAE signals, while 23 (96%) marginal signals were emitted. Of the 26 cases of metaststic adenocarcinoma, one (4%) showed internal SAE signals, while in five 23 metastatic lesions (88%). For HCC and metastatic tumors, the mean SAE index was 0.38{+-}0.15 and 0.60{+-}0.08, respectively ({rho}< 0.001). Gray-scale stimulated acoustic emission can be a useful tool in differential diagnosis between hepatocellular carcinoma and metastatic adenocarcinoma.

Silicon nanocrystal-based photonic crystal slabs with broadband and efficient directional light emission

Czech Academy of Sciences Publication Activity Database

Ondič, Lukáš; Varga, Marián; Pelant, Ivan; Valenta, J.; Kromka, Alexander; Elliman, R. G.

2017-01-01

Roč. 7, č. 1 (2017), s. 1-8, č. článku 5763. ISSN 2045-2322 R&D Projects: GA ČR GJ16-09692Y; GA MŠk(CZ) LD15003 Institutional support: RVO:68378271 Keywords : photonic crystal slab * silicon nanocrystals * light emission Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 4.259, year: 2016

A simulation method for the rapid screening of potential depleted oil reservoirs for CO2 sequestration

International Nuclear Information System (INIS)

Bossie-Codreanu, D.; Le Gallo, Y.

2004-01-01

The reduction of greenhouse gases emission is a growing concern of many industries. The oil and gas industry has a long commercial practice of gas injection, enhanced oil recovery (EOR) and gas storage. Using a depleted oil or gas reservoir for CO 2 storage has several interesting advantages. The long-term risk analysis of the CO 2 behavior and its impact on the environment is a major concern. That is why the selection of an appropriate reservoir is crucial to the success of a sequestration operation. Our modeling study, based on a synthetic reservoir, quantifies uncertainties due to reservoir parameters in order to establish a set of guidelines to select the most appropriate depleted reservoirs. Several production and sequestration scenarios are investigated in order to quantify key parameter for CO 2 storage. The influence of parameters such as API gravity, heterogeneity (Dykstra-Parson coefficient), pressure support (water injection) and cap rock integrity are analyzed. Estimation of sequestration capacity is proposed through a sequestration factor (SF) estimated for different reservoir production drives. Multiple regression relationships were developed, allowing SF estimation. CO 2 sequestration optimization highlights the best clean oil recovery strategy (CO 2 injection and/or oil production)

Determination of plasma Z-pinch effect by intrinsic stimulated emission

International Nuclear Information System (INIS)

Lue, J.T.; Liang, J.M.

1977-01-01

The plasma Z-pinch behavior has been observed in a relatively small-bore diameter tube and low bank voltage discharge system. The instant of the occurrence of the laser line at 4880 A coincides with the plasma pinch time calculated by using a one-fluid snow-plow model. A determination of plasma pinch parameters by measuring the intrinsic stimulated emission of the ions is described

High-efficiency AlxGa1-xAs/GaAs cathode for photon-enhanced thermionic emission solar energy converters

Science.gov (United States)

Feng, Cheng; Zhang, Yijun; Qian, Yunsheng; Wang, Ziheng; Liu, Jian; Chang, Benkang; Shi, Feng; Jiao, Gangcheng

2018-04-01

A theoretical emission model for AlxGa1-xAs/GaAs cathode with complex structure based on photon-enhanced thermionic emission is developed by utilizing one-dimensional steady-state continuity equations. The cathode structure comprises a graded-composition AlxGa1-xAs window layer and an exponential-doping GaAs absorber layer. In the deduced model, the physical properties changing with the Al composition are taken into consideration. Simulated current-voltage characteristics are presented and some important factors affecting the conversion efficiency are also illustrated. Compared with the graded-composition and uniform-doping cathode structure, and the uniform-composition and uniform-doping cathode structure, the graded-composition and exponential-doping cathode structure can effectively improve the conversion efficiency, which is ascribed to the twofold built-in electric fields. More strikingly, this graded bandgap structure is especially suitable for photon-enhanced thermionic emission devices since a higher conversion efficiency can be achieved at a lower temperature.

Oblique photon expansion of QED structure functions

International Nuclear Information System (INIS)

Chahine, C.

1986-01-01

In the oblique photon expansion, the collinear part of photon emission is summed up to all orders in perturbation theory. The number of oblique or non-collinear photons is the expansion order. Unlike in perturbation theory, every term of the expansion is both infrared finite and gauge invariant. The zero oblique photon contribution to the electromagnetic structure tensor in QED is computed in detail. The behaviors of the structure functions F1 and F2 are discussed in the soft and ultra-soft limits

Modeling of gain saturation effects in active semiconductor photonic crystal waveguides

DEFF Research Database (Denmark)

Chen, Yaohui; Mørk, Jesper

2012-01-01

In this paper, we present a theoretical analysis of slow-light enhanced light amplification in an active semiconductor photonic crystal line defect waveguide. The impact of enhanced light-matter interactions on carrier-depletion-induced modal gain saturation is investigated.......In this paper, we present a theoretical analysis of slow-light enhanced light amplification in an active semiconductor photonic crystal line defect waveguide. The impact of enhanced light-matter interactions on carrier-depletion-induced modal gain saturation is investigated....

Single-photon emission associated with double electron capture in F9+ + C collisions

CERN Document Server

Elkafrawy, Tamer; Tanis, John A; Warczak, Andrzej

2016-01-01

Radiative double electron capture (RDEC), the one-step process occurring in ion-atom collisions, has been investigated for bare fluorine ions colliding with carbon. RDEC is completed when two target electrons are captured to a bound state of a projectile simultaneously with the emission of a single photon. This work is a follow-up to our earlier measurement of RDEC for bare oxygen projectiles, thus providing a recipient system free of electron-related Coulomb fields in both cases and allowing for the comparison between the two collision systems as well as with available theoretical studies. The most significant mechanisms of x-ray emission that may contribute to the RDEC energy region as background processes are also addressed.

Photon stimulated desorption investigations of positive ions of MgO, TiO2, Yb2O3, Nd2O3, H2O/Si(100), CaF2/Si and of H2O, CO and NO on Yb and Nd in the energy range 14 eV up to 800 eV

International Nuclear Information System (INIS)

Senf, F.

1987-01-01

Photon-stimulated desorption of positive ions from surfaces has been studied with synchrotron radiation in the photon energy range 14 -800 eV of the 'FLIPPER'-monochromator using a time-of-flight mass spectrometer. TiO 2 , as a prototype of a maximal valency ionic compound, shows a strong desorption of O +- in the photon energy range of the Ti 3 p → 3d- and Ti 2p → 3d-resonance as well as at the 0 1s-excitation due to intraatomic respectively intraatomic Auger decays, which is in agreement with the Knotek-Feibelman model. The desorption of F + from CaF 2 -covered silicon is found to follow the respective excitation and decay processes in Ca and F. In addition, the very large cross section for the F + desorption causes a radiation damage by photons of more than about 30 eV. The adsorbate system H 2 O/Si (100) needs a multiple electron excitation to show a significant desorption setting in only 30 eV above the 0 1s threshold. The rare earth metals Yb and Nd covered with O 2 , H 2 O, CO or NO exhibit a competitive desorption of O + partly due to intraatomic Auger decays caused by single electron excitations and partly due to multiple electron excitations. The variation of the 0 + yield with regard to the different adsorbates on Yb and Nd is unexpectedly low. A detailed investigation was concerned with thin oxidized Mg-films and differently prepared MgO-single-crystals. Here we found a very efficient desorption of O + and H + resulting from the excitation of O 1s-surface-excitons. In addition, the strong hole-hole-interaction energy of crystalline MgO appears to be responsible for a suppressed O + -signal in the energy range of the Mg 2p-excitation. (orig./BHO)

Ozone-depleting substances and the greenhouse gases HFCs, PFCs and SF6. Danish consumption and emissions, 2004

Energy Technology Data Exchange (ETDEWEB)

Sander Poulsen, T. [PlanMiljoe (Denmark)

2006-05-19

The objective of this project was to map the 2004 consumption of newly produced industrial ozone-depleting substances and the consumption and actual emissions of HFCs, PFCs, and SF6. The evaluation was made in accordance with the IPCC guidelines, and following the method employed in previous evaluations and it covers the net consumption of ozone-depleting substances. The term 'net consumption' is understood as the amount of imported goods in bulk or drums, less any re-export of substances as raw materials. Ozone-depleting substances contained in finished products that are imported and exported are not included in the evaluation. This delimitation is in full compliance with international guidelines. The evaluation does not account for the consumption of ozone-depleting substances used as raw material in the production of other substances, such as tetra chloromethane, and which are not subsequently emitted to the atmosphere. The information on consumption has been gathered from importers, suppliers and enterprise end-users (usually purchasing departments), and Statistics Denmark. This method of data gathering means that the information gathered is about the quantities of substances traded. Purchase and sales figures are used as an expression of consumption. This approach is considered to be suitable and adequate for the present purpose, since experience from previous projects shows that a levelling out occurs with time and that the substances sold/purchased are consumed within a relatively small time horizon. None of the substances covered here are produced in Denmark. Furthermore, ozone-depleting substances are treated at chemical waste processing plants in Denmark. Treatment and destruction data was gathered for the evaluation, but in line with all previous evaluations it has not been accounted for in the consumption figures. (BA)

Deuterium-depleted water. Romanian achievements and perspective

International Nuclear Information System (INIS)

Stefanescu, Ion; Saros-Rogobete, Irina; Titescu, Gheorghe

2001-01-01

Deuterium-depleted water has an isotopic content smaller than 145 ppm D/(D+H) which is the natural isotopic content of water. Beginning with 1996 ICSI Rm. Valcea, deuterium-depleted water producer, co-operated with Romanian specialized institutes for biological effect's evaluation of deuterium-depleted water. These investigations lead to the following conclusions: - Deuterium-depleted water caused a tendency towards the increase of the basal tonus, accompanied by the intensification of the vasoconstrictor effects of phenylefrine, noradrenaline and angiotensin; the increase of the basal tonus and vascular reactivity produced by the deuterium-depleted water persist after the removal of the vascular endothelium; - Animals treated with deuterium-depleted water showed an increase of the resistance both to sublethal and to lethal gamma radiation doses, suggesting a radioprotective action; - Deuterium-depleted water stimulates immune defence reactions and increases the numbers of polymorphonuclear neutrophils; - Investigations regarding artificial reproduction of fish with deuterium-depleted water fecundated solutions confirmed favourable influence in embryo growth stage and resistance in subsequent growth stages; - It was studied germination, growth and quantitative character's variability in plants; one can remark the favourable influence of deuterium-depleted water on biological process in plants in various ontogenetic stages; - The deuterium depletion in seawater produces the diminution of the water spectral energy related to an increased metabolism of Tetraselmis Suecica. (authors)

Nonlinear behavior of photoluminescence from silicon particles under two-photon excitation

International Nuclear Information System (INIS)

Xu Xingsheng; Yokoyama, Shiyoshi

2011-01-01

Two-photon excited fluorescence (TPEF) under continuous-wave excitation from silicon particles produced by a pulsed laser is investigated. Spectra and images of TPEF from silicon particles are studied under different excitation intensities and operation modes (continuous wave or pulse). It is found that the photoluminescence depends superlinearly on the excitation intensity and that the spectral shape and peaks vary with different silicon particles. The above phenomena show the nonlinear behavior of TPEF from silicon particles, and stimulated emission is a possible process.

Ferroelectric Nd3+:SrxBa1-x(NbO3)2-a new nonlinear laser crystal: cw 1-μm stimulated emission (4F3/2→4I11/2) and diffuse self-frequency doubling

International Nuclear Information System (INIS)

Kaminskii, Alexandr A; Garsia, Sole J; Jaque, D; Capmany, J; Bagayev, S N

1998-01-01

Stimulated emission as a result of the inter-Stark transition in the 1-μm 4 F 3/2 → 4 I 11/2 channel of Nd 3+ ions was excited for the first time in an acentric disordered Sr x Ba 1-x (NbO 3 ) 2 (x∼0.6) crystal. The low-threshold lasing of this crystal at the 1.0626 μm wavelength was accompanied by diffuse intracavity generation of the second harmonic. (letters to the editor)

Development of a high energy resolution magnetic bolometer for the determination of photon emission intensities by gamma-ray spectrometry

International Nuclear Information System (INIS)

Rodrigues, M.

2007-12-01

In this research thesis, a first chapter describes the metrological difficulties for the determination of radionuclide photon emission intensities. Then, it discusses the understanding and the required tools for the computing of a magnetic bolometer signal with respect to the different operation parameters and to the sensor geometry. The author describes the implementation of the experimental device and its validation with a first sensor. The new sensor is then optimised for the measurement of photon emission intensities with a good efficiency and a theoretical energy resolution less than 100 eV up to 200 keV. The sensor's detection efficiency and operation have been characterized with a 133 Ba source. The author finally presents the obtained results

Optimum conditions for producing Cs2 molecular condensates by stimulated Raman adiabatic passage

International Nuclear Information System (INIS)

Feng Zhifang; Li Weidong; Wang Lirong; Xiao Liantuan; Jia Suotang

2009-01-01

The optimum conditions for producing Cs 2 molecular condensates from Cs atomic condensates with high transfer efficiency by stimulated Raman adiabatic passage are presented. Under the extended 'two-photon' resonance condition, including the two-photon process, the mean-field correction, and the tunneling coupling between two upper excited molecular levels, a high and stable conversion efficiency is realized. The high conversion efficiency could be achieved by following two methods under experimentally less demanding conditions (relatively small effective Rabi frequency for pump laser pulse). One is adjusting the detuning difference between two laser pulses for same effective Rabi frequencies with up to 87.2% transfer efficiency. Another one is adjusting the effective Rabi frequency, the detuning of dump laser for given effective Rabi frequency, and the detuning of pump laser with up to 80.7% transfer efficiency.

Effects of Biochar Addition on CO2 and N2O Emissions following Fertilizer Application to a Cultivated Grassland Soil.

Directory of Open Access Journals (Sweden)

Jingjing Chen

Full Text Available Carbon (C sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO2 and N2O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N dynamics. Treatments included biochar addition (CHAR, NO CHAR and amendment (COMPOST, UREA, NO FERT. The biochar application rate was 0.3% by weight. The temporal pattern of CO2 emissions differed according to biochar addition and amendments. CO2 emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO2 emission was observed when biochar and compost were applied together during the summer. Overall N2O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N2O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N2O emission. Two possible mechanisms were proposed to explain the higher N2O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N2O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N2O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N2O emission when applied to soil amended with urea.

Spectral, energy, and time parameters of two-photon fluorescence of 2,5-diphenyloxazole polycrystals

International Nuclear Information System (INIS)

Agal'tsov, A.M.; Gorelik, V.S.; Rakhmatullaev, I.A.

1995-01-01

Two-photon fluorescence (TPF) spectra of 2,5-diphenyloxazole polycrystals (known in the literature as PPO) were obtained and studied as a function of the pump power and time delay. The fluorescence spectrum shape observed upon two-photon excitation is shown to be distinctly different from that observed upon electron-beam excitation. It is shown that high pump powers result in stimulated fluorescence. PPO exhibits a high TPF quantum yield, the integrated conversion efficiency of exciting radiation to TPF being 40%. The TPF decay time is measured to be 20 ns. The spectral data obtained for PPO polycrystals can be used in the development of new TPF light sources tunable in the UV region. 10 refs., 4 figs., 1 tab