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Photons

Distribution by Scientific Domains

Physics and Astronomy	54%
Chemistry	19%
Medical Sciences	10%
Polymers and Materials Science	5%
Life Sciences	5%
4 Other Domains	7%

Distribution within Physics and Astronomy

Astronomy & Astrophysics	42%
General & Introductory Physics	31%
Solid State Physics	18%

Kinds of Photons

incident photon

single photon

Terms modified by Photons

photon absorption

photon correlation spectroscopy

photon counting

photon emission

photon emission tomography

Selected Abstracts

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 5 2010
Rev. 4(5)/2010
50 years after its invention the Laser seems to have a brighter future than ever. In this picture the invention is celebrating itself with a breathtaking laser show. (Picture: courtesy of LOBO Laser- und Multimediasysteme, Aalen, Germany) [source]

Contents: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 5 2010
Rev.: 4(5)/2010
First page of article [source]

Front Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 4 2010
Rev. 4(4)/2010
Illustration of local deformation in an isolated carbon nanotube due to the pressure applied through the apex of a nano-tip. By sensing this local deformation by means of Raman shift in TERS, the sample can be imaged with extremely high spatial resolution.(Picture: P. Verma et al., pp. 548,561, in this issue) [source]

Front Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 3 2010
Rev. 4(3)/2010
The ultra-low timing jitter of optical pulse trains from femtosecond mode-locked lasers can be used for the attosecond-precision generation, distribution, measurement, and synchronization of optical and microwave signals. (Picture: Jungwon Kim and Franz X. Kärtner, pp. 432 in this issue) [source]

Front Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 2 2010
Rev. 4(2)/2010
Schematic of resonant transmission through nanohole array using electron microscope image of as-fabricated sample. With applications ranging from linear and nonlinear optics to sensing and spectroscopy, nanohole arrays are promising for compact device integration. (Picture: R. Gordon et al., pp. 311,335, in this issue) [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 1 2010
Rev. 4(1)/2010
When a laser pulse propagates through a pair of diffraction gratings, its carrier-envelope phase depends strongly on the separation of gratings. This effect has been used to stabilize the carrier-envelope phase in chirped pulse laser amplifiers. (Picture: E. Moon et al., pp. 160,177, in this issue) [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 6 2009
Rev. 3(6)/200
White light diffraction from waveguide Bragg gratings fabricated in doped phosphate glass using the femtosecond laser direct-write technique. Such a waveguide Bragg grating was instrumental to the first demonstration of a monolithic waveguide laser using this technique. (Picture: M. Ams et al., pp. 535,544, in this issue) [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 5 2009
Rev. 3(5)/200
Ablation impact of a spherical polystyrene particle on a silicon surface irradiated with single femtosecond pulses. The anisotropy is a result of the near-field-enhanced sub-threshold ablation process. (Picture: A. Plech, P. Leiderer, J. Boneberg, pp. 435,451, in this issue) [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 4 2009
Rev. 3(4)/200
Schematic of a 40 GHz mode locked silicon evanescent laser. (Picture: B. R. Koch et al., pp. 355,369, in this issue) [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 3 2009
Rev. 3(3)/200
Micro-structuring techniques in lithium niobate crystals can lead to unprecedented performance in integrated Mach-Zehnder modulators, including ultra-low voltage and large bandwidth operation. (Picture: D. Janner et al., pp. 301,313, in this issue) [source]

Front Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 1-2 2009
Rev. 3(1-2)/200
A train of optical pulses are injected into a quantum dot semiconductor optical waveguide, where the velocity is slowed down and the pulsewidth is reduced. [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 6 2008
Rev. 2(6)/200
Cross section of a PCF with inner and outer cladding where an LPG has been impressed in the core. Cover picture: O. Frazão et al., pp. 449,459, in this issue. [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 5 2008
Rev. 2(5)/200
An artist's conception of laser tweezers Raman spectroscopy: A single laser beam is focused through a high power microscope objective to create a tight, diffraction-limited spot, which results in a single-beam optical trap powerful enough to capture and suspend cells up to 30 microns in diameter. Photons from the same laser beam scatter off molecular bonds in the sample and are used to construct a full Raman spectrum of the sample (see inset).(Cover picture: J. Chan, S. Fore, S. Wachsmann-Hogiu, and T. Huser, pp. 325-349, in this issue). [source]

Cover Picture: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 4 2008
Rev.: 2(4)/200
Light can carry both spin and orbital angular momentum. The orbital angular momentum arises from "twisted" phasefronts which can be made visible in interferograms. Still a young research area, the investigation of orbital angular momentum of light now encompasses areas as diverse as testing of quantum information protocols, manipulation of ultracold atoms and applications in micro-machining. (Cover picture: S. Franke-Arnold, L. Allen, and M. Padgett, pp. 299,313, in this issue) [source]

Contents: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 3 2008
Rev.: 2(3)/200
First page of article [source]

Contents: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 1-2 2008
Rev.: 2(1-2)/200
First page of article [source]

Editorial: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 4 2007
Rev. 1 No. 4 (2007)
No abstract is available for this article. [source]

Editorial: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 3 2007
Rev. 1 No. 3 (2007)
[source]

Editorial: Laser & Photon.

LASER & PHOTONICS REVIEWS, Issue 2 2007
Rev. 1 No. 2 (2007)
No abstract is available for this article. [source]

Visual Signals in the Retina: From Photons to Synapses

EXPERIMENTAL PHYSIOLOGY, Issue 1 2000
Leon Lagnado
The ability to see the world around us is an immediate and striking example of the abilities of the nervous system, and perhaps for this reason, vision is one of the most intensively studied aspects of brain function (Hubel, 1995). This paper examines some of the earliest steps in vision occurring in the retina (Dowling, 1987; Rodieck, 1998). [source]

Molecular Design of Unsymmetrical Squaraine Dyes for High Efficiency Conversion of Low Energy Photons into Electrons Using TiO2 Nanocrystalline Films

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
Thomas Geiger
Abstract An optimized unsymmetrical squaraine dye 5-carboxy-2-[[3-[(2,3-dihydro-1, 1-dimethyl-3-ethyl-1H -benzo[e]indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-3,3-dimethyl-1-octyl-3H -indolium (SQ02) with carboxylic acid as anchoring group is synthesized for dye-sensitized solar cells (DSCs). Although the , -framework of SQ02 is insignificantly extended compared to its antecessor squaraine dye SQ01, photophysical measurements show that the new sensitizer has a much higher overall conversion efficiency , of 5.40% which is improved by 20% when compared to SQ01. UV-vis spectroscopy, cyclic voltammetry and time dependent density functional theory calculations are accomplished to rationalize the higher conversion efficiency of SQ02. A smaller optical band gap including a higher molar absorption coefficient leads to improved light harvesting of the solar cell and a broadened photocurrent spectrum. Furthermore, all excited state orbitals relevant for the ,,,* transition in SQ02 are delocalized over the carboxylic acid anchoring group, ensuring a strong electronic coupling to the conduction band of TiO2 and hence a fast electron transfer. [source]

Cover Picture: Laser & Photon.

Leben und Sterben eines Photons

PHYSIK IN UNSERER ZEIT (PHIUZ), Issue 6 2009
Gerhard Rempe Prof. Dr.
No abstract is available for this article. [source]

Putting Light to Work: Solar,08 Conference

CHEMPHYSCHEM, Issue 8 2008
Sylvie Lacombe Dr.
Photons in, energy out: At the Solar,08 international conference (February 24,28, 2008), 120 scientists from 41 countries gathered to discuss the field of photochemistry, ranging from fundamental photophysical properties of systems to their applications. S. Lacombe presented work on silica xerogel monoliths (see figure) which efficiently produce singlet oxygen when irradiated under visible light. [source]

Replica Exchange Light Transport

COMPUTER GRAPHICS FORUM, Issue 8 2009
Shinya Kitaoka
I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism; I.3.3 [Computer Graphics]: Picture/Image Generation Abstract We solve the light transport problem by introducing a novel unbiased Monte Carlo algorithm called replica exchange light transport, inspired by the replica exchange Monte Carlo method in the fields of computational physics and statistical information processing. The replica exchange Monte Carlo method is a sampling technique whose operation resembles simulated annealing in optimization algorithms using a set of sampling distributions. We apply it to the solution of light transport integration by extending the probability density function of an integrand of the integration to a set of distributions. That set of distributions is composed of combinations of the path densities of different path generation types: uniform distributions in the integral domain, explicit and implicit paths in light (particle/photon) tracing, indirect paths in bidirectional path tracing, explicit and implicit paths in path tracing, and implicit caustics paths seen through specular surfaces including the delta function in path tracing. The replica-exchange light transport algorithm generates a sequence of path samples from each distribution and samples the simultaneous distribution of those distributions as a stationary distribution by using the Markov chain Monte Carlo method. Then the algorithm combines the obtained path samples from each distribution using multiple importance sampling. We compare the images generated with our algorithm to those generated with bidirectional path tracing and Metropolis light transport based on the primary sample space. Our proposing algorithm has better convergence property than bidirectional path tracing and the Metropolis light transport, and it is easy to implement by extending the Metropolis light transport. [source]

The implications of solar UV radiation exposure for fish and fisheries

FISH AND FISHERIES, Issue 3 2001
Horacio E Zagarese
Abstract Ultraviolet radiation (UVR) possesses three important properties that combine to make it a potent environmental force. These include the potential to induce damage: UVR carries more energy per photon than any other wavelength reaching the Earth's surface. Such highly energetic photons are known to damage many biological molecules, such as DNA and proteins. In addition, they can initiate a series of redox reactions to form reactive oxygen species (ROS), which cause oxidative stress to cells and tissues. The second property is ubiquity: owing to their dependence on light, primary producers and most visual predators, such as fish, are also necessarily exposed to damaging levels of UVR. Thirdly, the combined effect of UVR and additional environmental factors may result in synergistic effects, such as the photoactivation of organic pollutants and photosensitisation. In natural environments, the concentration of dissolved organic matter (DOM) and habitat depth are the two main factors controlling the degree of UVR exposure experienced by fish. Additional factors include vegetation coverage, particulate materials in suspension, pH and hydrological characteristics, and site location (latitude, elevation). The range of potential effects on fish includes direct DNA damage resulting in embryo and larval mortality, and adult and juvenile sunburn, as well as indirect oxidative stress, phototoxicity and photosensitisation. [source]

Estimating the Maximum Attainable Efficiency in Dye-Sensitized Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2010
Henry J. Snaith
Abstract For an ideal solar cell, a maximum solar-to-electrical power conversion efficiency of just over 30% is achievable by harvesting UV to near IR photons up to 1.1,eV. Dye-sensitized solar cells (DSCs) are, however, not ideal. Here, the electrical and optical losses in the dye-sensitized system are reviewed, and the main losses in potential from the conversion of an absorbed photon at the optical bandgap of the sensitizer to the open-circuit voltage generated by the solar cell are specifically highlighted. In the first instance, the maximum power conversion efficiency attainable as a function of optical bandgap of the sensitizer and the "loss-in-potential" from the optical bandgap to the open-circuit voltage is estimated. For the best performing DSCs with current technology, the loss-in-potential is ,0.75,eV, which leads to a maximum power-conversion efficiency of 13.4% with an optical bandgap of 1.48,eV (840,nm absorption onset). Means by which the loss-in-potential could be reduced to 0.4,eV are discussed; a maximum efficiency of 20.25% with an optical bandgap of 1.31,eV (940,nm) is possible if this is achieved. [source]

Inversion of time-dependent nuclear well-logging data using neural networks

GEOPHYSICAL PROSPECTING, Issue 1 2008
Laura Carmine
ABSTRACT The purpose of this work was to investigate a new and fast inversion methodology for the prediction of subsurface formation properties such as porosity, salinity and oil saturation, using time-dependent nuclear well logging data. Although the ultimate aim is to apply the technique to real-field data, an initial investigation as described in this paper, was first required; this has been carried out using simulation results from the time-dependent radiation transport problem within a borehole. Simulated neutron and ,-ray fluxes at two sodium iodide (NaI) detectors, one near and one far from a pulsed neutron source emitting at ,14 MeV, were used for the investigation. A total of 67 energy groups from the BUGLE96 cross section library together with 567 property combinations were employed for the original flux response generation, achieved by solving numerically the time-dependent Boltzmann radiation transport equation in its even parity form. Material property combinations (scenarios) and their correspondent teaching outputs (flux response at detectors) are used to train the Artificial Neural Networks (ANNs) and test data is used to assess the accuracy of the ANNs. The trained networks are then used to produce a surrogate model of the expensive, in terms of computational time and resources, forward model with which a simple inversion method is applied to calculate material properties from the time evolution of flux responses at the two detectors. The inversion technique uses a fast surrogate model comprising 8026 artificial neural networks, which consist of an input layer with three input units (neurons) for porosity, salinity and oil saturation; and two hidden layers and one output neuron representing the scalar photon or neutron flux prediction at the detector. This is the first time this technique has been applied to invert pulsed neutron logging tool information and the results produced are very promising. The next step in the procedure is to apply the methodology to real data. [source]

Photosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support Architectures

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2009
David R. Baker
Abstract TiO2 nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO2 nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO2 nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO2 nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons. [source]

Salvage treatment for persistent and recurrent T1,2 nasopharyngeal carcinoma by stereotactic radiosurgery

HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 9 2001
Daniel T. T. Chua FRCR
Abstract Objective To study the efficacy of stereotactic radiosurgery in salvaging early-stage persistent and recurrent nasopharyngeal carcinoma (NPC) after primary radiotherapy. Methods A prospective single-arm study evaluating the response and outcome of patients with rT1,2 NPC treated by stereotactic radiosurgery. Eleven patients with rT1,2 were treated by radiosurgery between March 1998 and March 2000. Four patients were treated for persistent disease occurring within 4 months after primary radiotherapy, six were treated for first recurrence, and one for third recurrence. Six patients had rT1 disease and five had rT2 disease. Most patients had disease not amenable to brachytherapy, surgery, or external re-irradiation. The median target volume was 5.8 cc (range, 3.3,16.9). Radiosurgery was performed with multiple noncoplanar arcs of photon, with a median dose of 12.5 Gy delivered to the 80% isodose line (range, 12,14 Gy). Median follow-up time after radiosurgery was 18 months (range, 9,30). Results Nine patients had complete regression of tumor as assessed by imaging, nasopharyngoscopy, and biopsy; one patient had partial regression of tumor; whereas one patient had static disease. The overall response rate was 91% (10 of 11) and the complete response rate was 82% (9 of 11). Two patients with complete response subsequently had local relapse develop, with one recurrence outside the treated volume 8 months after radiosurgery, and the other within the treated volume 6 months after radiosurgery. One patient with a partial response had neck node recurrence develop. Temporal lobe necrosis occurred in one patient but probably represents sequelae of primary radiation after reviewing the dosimetry. Ten patients are still alive, whereas one patient with local relapse had distant metastases develop and died. The estimated 1-year local control rate after radiosurgery was 82%. Conclusions Our preliminary results indicate that stereotactic radiosurgery is an effective treatment modality for persistent and recurrent T1,T2 NPC, and early control rate seems to be comparable to other salvage treatments. More clinical experiences and longer follow-up are still needed to validate our results and to address fully the role of radiosurgery in salvaging local failures of NPC. © 2001 John Wiley & Sons, Inc. Head Neck 23: 791,798, 2001. [source]