0022]FIG. 2 is a basic block diagram of an embodiment of the pulse oximeter system 10 that is capable of transmission mode photon density wave emission and detection. The configuration and operation of the system 10 in transmission mode may enable deep penetration of the photon density waves into a region of interest in a patients tissue. As in FIG. 1, the system 10 illustrated in FIG. 2 includes the monitor 12 and the sensor 14. In FIG. 2, the monitor 12 and the sensor 14 include features capable of cooperating to transmit photon density waves into one side of a patients tissue and out of a generally opposite side for detection. Specifically, in FIG. 2, the monitor 12 is illustrated as including various functional components that facilitate transmission of photon density waves through an emitter-side fiber optic cable 22 to the sensor 14. The sensor 14 is physically configured such that, when properly attached to a patients tissue 24, the photon density waves from the emitter-side fiber ...
Two-photon absorption spectra of Al|sub>0.4|/sub>Ga|sub>0.6|/sub>As/GaAs quantum wells in static electric fields are investigated experimentally. A drastic field-induced increase in the absorption peaks at energies close to |i>half|/i> the bandgap energy is reported for the first time. In particular, we observed the rise and red-shift of a peak corresponding to |i>half|/i>the lowest light-hole exciton energy not seen in non-biased quantum wells. For moderate fields, the results agree with a theory based on a zero-bias infinite- level model, whereas the large peak value at stronger fields is explained by a two-level model. Contrary to bulk GaAs, a large value of the third order optical susceptibility is predicted |i>just below|/i> the two-photon absorption edge at which the biased quantum wells are highly transparent. This gives a large figure of merit for ultrafast optical nonlinearities. |p> We have also theoretically and experimentally investigated time-resolved two-photon absorption in bulk GaAs and
Treatment Planning for Photon Radiotherapy will be performed using the Planning Systems available at the Department of Radiation Oncology in Heidelberg, Germany (including Masterplan/Nucletron, Virtuos-Konrad/Siemens, or Precisis/STP/Stryker-Leibinger, or the Tomotherapy Software). Carbon ion and proton RT planning is performed using the treatment planning software PT-Planning (Siemens, Erlangen, Germany) including biologic plan optimization. Biologically effective dose distributions will be calculated using the a/ß ratio for meningioma as well as for the endpoint late toxicity to the brain. Patient positioning prior to radiotherapy will be evaluated by comparison of x-rays to the DRRs. Set up deviations ,3mm are corrected prior to radiotherapy.. To the target volume defined for photon treatment, a total dose of 52.2 Gy E - 57.6 Gy E is applied in single fractions of 1.8Gy E. In the 3Gy E Photon arm, photon radiotherapy will be delivered to a total dose of 45 Gy E in 15 fractions. ...
© The Author(s). Published by IOP Publishing Ltd. Probing the diffusion of molecules has become a routine measurement across the life sciences, chemistry and physics. It provides valuable insights into reaction dynamics, oligomerisation, molecular (re-)organisation or cellular heterogeneities. Fluorescence correlation spectroscopy (FCS) is one of the widely applied techniques to determine diffusion dynamics in two and three dimensions. This technique relies on the temporal autocorrelation of intensity fluctuations but recording these fluctuations has thus far been limited by the detection electronics, which could not efficiently and accurately time-tag photons at high count rates. This has until now restricted the range of measurable dye concentrations, as well as the data quality of the FCS recordings, especially in combination with super-resolution stimulated emission depletion (STED) nanoscopy. Here, we investigate the applicability and reliability of (STED-)FCS at high photon count rates (average
We present the first study of two-photon absorption (TPA) of solvated molecules based on direct evaluation of TPA cross sections from the quadratic response of time-dependent perturbations. A set of prototypical two-photon (TP) chromophores has been selected and analyzed: a pure pi system (t-stilbene) and its substituted homologs obtained employing a donor (D) and an acceptor (A) group to probe the solvent effects along the series pi, D-pi-D, A-pi-D, and A-pi-A. For the selected systems we have calculated the TPA cross sections in different environments by means of the polarizable continuum model. The data have been analyzed to evaluate how the structural and environmental parameters contribute to the final two-photon absorption cross section. These include molecular structure, geometry relaxation in solution, polarity, and refractive index of the solvent. The performances of the three common functionals SVWN, BLYP, and B3LYP have been compared. The results show a significant solvent dependence ...
Due to the large transmural variation in transmembrane potential following the application of strong electric shocks, it is thought that fluorescent photon scattering from depth plays a significant role in optical signal modulation at shock-end. For the first time, a model of photon scattering is used to accurately synthesize fluorescent signals over the irregular geometry of the rabbit ventricles following the application of such strong shocks. A bidomain representation of electrical activity is combined with finite element solutions to the photon diffusion equation, simulating both the excitation and emission processes, over an anatomically-based model of rabbit ventricular geometry and fiber orientation. Photon scattering from within a 3D volume beneath the epicardial optical recording site is shown to transduce differences in transmembrane potential within this volume through the myocardial wall. This leads directly to a significantly modulated optical signal response with respect to that predicted
Abstract: An extensive series of pyrazole aluminum compounds containing an Al2N4 center as a pseudoconjugated system were theoretically investigated for their one-photon absorption and two-photon absorption (OPA and TPA) properties by density functional theory (DFT) and Zerners intermediate neglect of differential overlap (ZINDO) methods. The results indicate that pyrazole aluminum compounds are good TPA materials and that the TPA maximal absorption cross-section (δmax) can reach 2860.1 GM (1 GM=10-50 cm4·s·photon-1). By incorporating electron-acceptors in the central core, a π-conjugated bridge and terminal groups, the OPA and TPA properties can be modulated. This research provides strategies for the enhancement of molecular TPA in the target region. The origin of the large δmax of some of the studied molecules was determined using a three-level energy model. We conclude that an increase in the intramolecular charge transfer can enhance δmax. Moreover, the pyrazole aluminum compounds ...
And this is how they know which slit the photon went through? Exactly. They use a small optical fiber to collect only the top or bottom lobe of one photon from the pair, and send the other one onto the double-slit, aligned so that the top lobe hits the top slit only, and the bottom lobe hits the bottom slit only. If they put a similar detector behind the slits, they can confirm that when they look for a photon arriving behind the slits at the same time that one hits the top/bottom detector, they only see photons in the appropriate slit, as seen in the figure at right. In this case, theyre looking in the near field, which means that the fibers to detect the photons are right behind the slit, too close to see an interference pattern.. So, how does this not destroy the interference? Well, it does while theyre doing this measurement. Having used this measurement to show that the top/bottom correlation works, though, they move the detector behind the slits into the far field, which means more ...
Hello, Two questions about the test image attached here. * Why the beam circled in black is dimmer than the others ? They are all in the same media. In the general settings, the parameters for the photons are : photons { count 320000 max_trace_level 10 media 500, 2 } Im not sure they are all good Render Statistics give : --------------------------------------- Number of photons shot: 170798 Surface photons stored: 173 Media photons stored: 44288 Gather function called: 2634991 --------------------------------------- * Where does the difference between the number of photons requested (320000) and the number of photons shoted (170798). Its about half Merci -- Kurtz le pirate Compagnie de la Banquise ...
Though silicon photodetectors are usually insensitive to near infrared light of the wavelength longer than 1100 nm, they become sensitive to it with high intensity, producing photocurrent in proportion to the square of the intensity. This is due to two-photon absorption (TPA) process. So far, the TPA process in silicon photodetectors has mainly been applied to measuring the waveform of optical short pulses, since it can give the intensity correlation of incident light signals. In this paper, as a new application of the TPA process in photodetectors, we propose a novel profilometry based on Michelson interferometer with optical microwave as a light source and avalanche photodiode as a two-photon absorber. In contrast to the classical heterodyne profilometer that measures the optical path length difference from the phase of the modulated optical signal, the dynamic range of the TPA method is not limited by the bandwidth of a photodetector and attached electronic devices. The TPA method can realize ...
We propose photon energy qubits and schemes for photon energy entanglement characterization. Bell inequality violation for energy qubits and complete Bell state analysis are demonstrated theoretically. Photon energy superposition state detection is performed by a two-photon absorption interferometer based on electron transition path interference. The scheme can be realized at room-temperature by two-level systems and semiconductor devices.. ©2009 Optical Society of America. Full Article , PDF Article ...
We use cookies to ensure that we give you the best experience on our website. If you click Continue well assume that you are happy to receive all cookies and you wont see this message again. Click Find out more for information on how to change your cookie settings ...
Integrated optics has emerged as a promising solution to the electronic interconnect bottleneck, enabling high bandwidth density and low power consumption. Recently, confining photochemical and physical reactions in a micro-volume has given an extra dimension to optical interconnection using glass or polymer. Three-dimensional waveguides can then connect, combine, or split the optical signal among any blocks in all dimensions. However, the refractive index increase is still a challenge to fabricate free-form, stable and single-mode three-dimensional buried waveguides.. This paper presents a new concept to tackle this challenge using the combination of femtosecond direct laser writing (FsDLW) in polymer and external diffusion of a gaseous monomer. FsDLW with two-photon absorption was used to initiate cross-linking following a programmed trajectory to form the waveguide core. A thermal treatment was then needed to complete cross-linking. Afterwards, a low-index monomer from a gas atmosphere was ...
We demonstrate an all-optical intensity noise reduction technique by using two-photon absorption of ZnSe in a Z-scan configuration. We measure the nonlinear transmission and the shot-to-shot energy fluctuations of 860-nm intense femtosecond laser pulses. At a 40% nonlinear transmission level the noise in the pulse train is reduced to 24%. This yields an additional 40% reduction in the relative pulse energy fluctuation. A realistic theoretical treatment is presented and is found to be in good agreement with experimental results.. © 2003 Optical Society of America. Full Article , PDF Article ...
New insight in boron chemistry: Application in two-photon absorption Optical Materials Elsevier 0925-3467 10.1016/J.OPTMAT.2011.02.035
Extreme photon localization is applicable to constructing building blocks in photonic systems and quantum information systems. A finding fact that photon localization in small space modifies the radiation process was reported in 1944 by Purcell, and advances in fabrication technology enable such structures to be constructed at optical frequencies. Many demands of building compact photonic systems and quantum information systems have enhanced activities in this field. The photonic crystal cavity has potential in providing a cavity that supports only the fundamental mode of (lambda/2n)^3 together with good confinement of light within a resonator. This thesis addresses experimental and theoretical aspects of building such photon localization blocks embedding active quantum nanostructures in a planar photonic crystal platform. Examples given in this thesis are (1) quantum dot photonic crystal nanolasers, (2) high-speed photonic crystal nanolasers, and (3) light-matter coupling in a single quantum ...
A photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). The photon has zero rest mass and always moves at the speed of light within a vacuum.. Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave-particle duality, exhibiting properties of both waves and particles. For example, a single photon may be refracted by a lens and exhibit wave interference with itself, and it can behave as a particle with definite and finite measurable position or momentum, though not both at the same time. The photons wave and quanta qualities are two observable aspects of a single phenomenon, and cannot be described by any mechanical model;[2] a representation of this dual property of light, which assumes certain points on the wavefront to be the seat of the energy, is not possible. The quanta ...
Pump-probe spectroscopy has long been useful in the elucidating ultrafast molecular phenomena. We developed a variation of time-resolved, pump-probe methodology using cross-correlation principles of the frequency-domain. An unique feature of our technique is that the low-frequency, cross correlation signal and its harmonics which contain lifetime information at high excitation frequencies can be simultaneously acquired and analyzed by a frequency spectrum analyzer. The result is that high frequency spectral information can be acquired without a fast optical detector and simultaneous acquisition of multiple harmonics reduce data acquisition time. A second key feature of this technique is that the cross-correlation signal comes primarily from the focal volume and hence microscopic imaging using this technique results in axial depth discrimination and improved spatial resolution similar in two-photon excitation microscopy. Using this technique, spectroscopic data measuring the lifetime and ...
Article Comprehensive study of energy absorption and exposure build-up factors for concrete shielding in photon energy range 0.015-15 MeV up to 40 mfp penetration depth: dependency of density, chemical elements, photon energy. Gamma ray build-up fact...
Is it possible to create a space void of photons? Or rather free from photon interference? I know single photon emitters have been made to test the behaviour of photons. However it would appear that space...well everything is jam packed with photons in various forms, and therefore observing a single photon seems impossible as its not as easy as turning out the lights. Even darkness is light and space is not the darkness our eyes feebly percieve. I ask this because it would then seem necessary to account for photons as a group or whole regarding motion and behaviour rather than an individual wave particle ...
An imaging device includes first and second photon sensors respectively capture arrival times and locations of individual photons on first and second image planes, while optionally capturing photon colors. A stereoptic distance finder identifies source distance of image elements common to both image planes, while a processor correlates the identified source distances to photons within the image elements. A memory stores the arrival times and locations, the color, and the identified source distances. An orientation sensor captures photon sensor orientation in six degrees of freedom. An image processor selects a time span, identifies photons captured within the time span, defines an image field, divides the image field into virtual pixels, and aggregates the colors of photons arriving within each virtual pixel within the time frame, to determine a color and intensity of the virtual pixel. The image processor also aggregates the virtual pixels to generate an image file.
Abstract: We analyze the second-order photon autocorrelation function $g^{(2)}$ with respect to the photon probability distribution and discuss the generic features of a distribution that result in superthermal photon bunching ($g^{(2)},2$). Superthermal photon bunching has been reported for a number of optical microcavity systems that exhibit processes like superradiance or mode competition. We show that a superthermal photon number distribution cannot be constructed from the principle of maximum entropy, if only the intensity and the second-order autocorrelation are given. However, for bimodal systems an unbiased superthermal distribution can be constructed from second-order correlations and the intensities alone. Our findings suggest modeling superthermal single-mode distributions by a mixture of a thermal and a lasing like state and thus reveal a generic mechanism in the photon probability distribution responsible for creating superthermal photon bunching. We relate our general ...
Now have a look at how one measures indistinguishability. Inthe Hong-Ou-Mandel experiment you take two consecutively emitted photons, insert a delay in the path of the first emitted photon and put the two photons on different entrance ports of a 50/50 beam splitter. If they are indistinguishable, they will leave through the same exit port because of two-photon interference. Otherwise, they will not. Now, the prerequisite for observing two-photon interference is of course that the two photons must overlap at the beam splitter. As a single experiment does not tell you much, you need to repeat the experiment several thousand times. If you revisit the Michelson interferometer experiment I outlined before,it becomes clear that having them overlap is not actually trivial. There is a non-zero probability for detecting a photon only during a time window of the length of the coherence time, so the delay between the two photons must be shorter than the coherence time in order to see two-photon ...
A single photon system consists of an excitation source, for example a laser, a single photon emitter and components collecting the emitted photons and coupling it into an optical fiber. Usually the propagation direction of the single photons is opposite to the propagation direction of the optical pump radiation.,br,,br, ,!--break--,,strong,Technology,/strong,,br, The invention is a ,a name=_GoBack,,/a,very compact single photon system, where the propagation direction of the emitted single photons corresponds to the propagation direction of the optical pump radiation.,br, ,br ...
The method was termed ELLIPSA (elliptical polarization state alteration) and should prove to be of general applicability, being potentially quite sensitive. The fate of two-photon excited neutral molecules and atoms is most easily followed in real time by fluorescence monitoring. In the next sections we show that in spite of the small two-photon absorption crosssection, the method can be used for quantitative kinetic measurements. For some applications, it is more straightforward and leads to less ambiguous interpretation than one-photon excitation. In general, the sodium concentration decreased after the laser pulse, and returned to equilibrium at a slower rate. However, the signals also contained a large sinusoidal modulation, which at high pressures completely obliterated the desired signal. When helium was added to the gas mixture, the sinusoidal frequency increased in accordance with the difference in the velocity of sound. This implies that the modulation is due to changes in the sodium ...
Description: We examine the phenomenology of the production, at the 13 TeV Large Hadron Collider (LHC), of the production of a heavy resonance $X$, which decays via other new on-shell particles $n$ into multi- (i.e.\ three or more) photon final states. In the limit that $n$ is light compared to $X$, the multi-photon final state may dominantly appear as a two photon final state because the $\gamma$s from the $n$ decay are highly collinear and are not resolved. We discuss how to discriminate this scenario from $X \rightarrow \gamma \gamma$: rather than discarding non-isolated photons, it is better to relax the isolation criterion and instead form photon jet substructure variables. The spins of $X$ and $n$ leave their imprint upon the distribution of pseudorapidity gap $\Delta \eta$ between the apparent two photon states. Depending on the total integrated luminosity, this can be used in many cases to claim discrimination, although the case where $X$ and $n$ are both scalar particles cannot be ...
Image acquisition and treatment under deep inspiration breath hold (DIBH) has been demonstrated to reduce treated volumes and doses to organs at risk (OARs) for photon radiotherapy but has not been investigated in the context of proton radiotherapy. The objective of this registry study is to prospectively evaluate deep inspiration breath hold CT scans for use in proton radiotherapy treatment planning and obtain dosimetric data to assess for changes in target volume, planning volumes and doses both to tumor and organs at risk using the SpiroDynrX (SDX) deep inspiration breath hold system as compared to free breathing and 4D CT scans. Patients will be treated with photon therapy. This is a prospective non-randomized, single arm, single institution registry study of patients undergoing definitive external beam photon radiotherapy in our department. Deep inspiration breath hold CT scans will be obtained in our department in the treatment position at the time of CT simulationin addition to the ...
Elevated nitric oxide (NO) levels perform an important pathological role in various inflammatory diseases. Developing NO-activatable theranostic materials with a two-photon excitation (TPE) feature is highly promising for precision imaging and therapy, but constructing such materials is still a tremendous challenge
Coordination coupling induced self-assembly of ZnS microparticles was performed with the help of a π-conjugated sulphur-terminal Zn(ii) complex ZnS2L (L = N-hexyl-3-{2-[4-2,2′:6′,2′′-terpyridin-4′-yl-phenyl]ethenyl}-carbazole). The interactions between ZnS and ZnS2L components at the interface, which were an
The Photon IMU Shield gives the Photon motion-sensing ability by connecting it to an all-in-one 9DOF IMU (a lot like the LSM9DS0). With this shield, the Photon will be able to sense linear acceleration, angular rotation, and magnetic fields. The Photon OLED Shield connects the Photon up to a blue-on-black OLED. The display is small, but its perfect for visualizing IMU data or printing readings from any of the other shields. Finally, no ecosystem is whole without a Prototyping Shield. This simple little board adds some prototyping space in proximity to the Photons I/O pins and power buses. ...
Photon Calc is an iPhone app that displays cross sections for gamma / x-ray photons, fluorescence and edge energies, and allows you to calculate the transmission and attenuation for an arbitrary photon energy
Photon Energy N.V. announced that Photon Energy Solutions HU Kft. - the groupʼs Hungarian subsidiary - has completed and grid-connected two PV power plants, with a combined capacity of 2.8 MWp, near Püspökladány.
Informace o cenn m pap ru Akcie PHOTON ENERGY. Grafy, aktu ln kurzy na BCP a RMS, obchody na RMS/BCPP/SCP, majitel , n zory, inzer ty na n kup a prodej, zam stnanci, portfolio, zpravodajstv k tomuto cenn mu pap ru.
Oligomerization of membrane proteins has received intense research interest because of their importance in cellular signaling and the large pharmacological and clinical potential this offers. Fluorescence imaging methods are emerging as a valid tool to quantify membrane protein oligomerization at high spatial and temporal resolution. Here, we provide a detailed protocol for an image-based method to determine the number and oligomerization state of fluorescently labeled prototypical G-protein-coupled receptors (GPCRs) on the basis of small out-of-equilibrium fluctuations in fluorescence (i.e., molecular brightness) in single cells. The protocol provides a step-by-step procedure that includes instructions for (i) a flexible labeling strategy for the protein of interest (using fluorescent proteins, small self-labeling tags or bio-orthogonal labeling) and the appropriate controls, (ii) performing temporal and spatial brightness image acquisition on a confocal microscope and (iii) analyzing and ...
Two-photon excitation and time-resolved fluorescence: I. The proper response function for analysing single-photon counting experiments ...
Well, as with all things quantum, bizarre is the norm. Recently, particle physicists in Israel have demonstrated the entanglement of two photos that dont exist at the same time. Time-separated entanglement is predicted by standard quantum theory, but has until now never been successfully demonstrated.. Recall that superposition allows a photon to be in two states at once, but once measured, the uncertainty of this superposed waveform (of the particle) collapses into one or the other state (vertically or horizontally polarized). The uncertainty also applies to two-particle systems; each photon in a two photon system can be forced into an uncertain, both-at-once state, but also remain correlated (entangled) despite the uncertain state of either. And, again, once you try to determine the spin state of one photon, its superposed state collapses, and, the other particles state collapses.. We might assume this to be true for even for two entangled pairs of photons (separated by any arbitrary ...
Blue light (400-430 nm) is known to induce lethal effects in some species of fungi by photo-oxidation caused by the excitation of porphyrins but the mechanisms involved remain poorly understood. In this work, we exposed the yeast Saccharomyces cerevisiae to a high density light flux with two-photon excitation (830 nm equivalent to a one-photon excitation around 415 nm) and used quasi real-time visualization with confocal microscopy to study the initiation and dynamics of photo-oxidation in subcellular structures. Our results show that the oxidation generated by light treatments led to the permeabilization of the plasma membrane accompanied by the sudden expulsion of the cellular content, corresponding to cell death by necrosis. Moreover, excitation in the plasma membrane led to very fast oxidation and membrane permeabilization (| 60 s) while excitation at the center of the cell did not induce permeabilization even after a period exceeding 600 s. Finally, our study shows that the relationship between the
TY - JOUR. T1 - Brominated 7-hydroxycoumarin-4-ylmethyls. T2 - Photolabile protecting groups with biologically useful cross-sections for two photon photolysis. AU - Furuta, Toshiaki. AU - Wang, Samuel S.H.. AU - Dantzker, Jami L.. AU - Dore, Timothy M.. AU - Bybee, Wendy J.. AU - Callaway, Edward M.. AU - Denk, Winfried. AU - Tsien, Roger Y.. PY - 1999/2/16. Y1 - 1999/2/16. N2 - Photochemical release (uncaging) of bioactive messengers with three- dimensional spatial resolution in light-scattering media would be greatly facilitated if the photolysis could be powered by pairs of IR photons rather than the customary single UV photons. The quadratic dependence on light intensity would confine the photolysis to the focus point of the laser, and the longer wavelengths would be much less affected by scattering. However, previous caged messengers have had very small cross sections for two-photon excitation in the IR region. We now show that brominated 7-hydroxycoumarin- 4-ylmethyl esters and carbamates ...
Optical parametric oscillation (OPO) and optical parametric generation (OPG) have widely been used for producing tunable radiations. In this paper we prese
Time-correlated photon counting experiments in life and material sciences demand photodetectors with single photon sensitivity, low noise and high time res
TY - JOUR. T1 - Investigation of two-photon excited fluorescence increment via crosslinked bovine serum albumin. AU - Lin, Chun Yu. AU - Lien, Chi Hsiang. AU - Cho, Keng Chi. AU - Chang, Chia Yuan. AU - Chang, Nan Shan. AU - Campagnola, Paul J.. AU - Dong, Chen Yuan. AU - Chen, Shean Jen. PY - 2012/6/18. Y1 - 2012/6/18. N2 - The two-photon excited fluorescence (TPEF) increments of two dyes via bovine serum albumin (BSA) microstructures fabricated by the two-photon crosslinking technique were investigated. One is Rose Bengal (RB) with a high non-radiative decay rate, while the other is Eosin Y with a low non-radiative decay rate. Experimental results demonstrate that the quantum yield and lifetime of RB are both augmented via crosslinked BSA microstructures. Compared with theoretical analysis, this result indicates that the non-radiative decay rate of RB is decreased; hence, the quenched effect induced by BSA solution is suppressed. However, the fluorescence lifetime of Eosin Y is acutely abated ...
TY - JOUR. T1 - Photon dose calculation incorporating explicit electron transport. AU - Yu, C. X.. AU - Mackie, T. R.. AU - Wong, J. W.. N1 - Copyright: Copyright 2018 Elsevier B.V., All rights reserved.. PY - 1995/7. Y1 - 1995/7. N2 - Significant advances have been made in recent years to improve photon dose calculation. However, accurate prediction of dose perturbation effects near the interfaces of different media, where charged particle equilibrium is not established, remain unsolved. Furthermore, changes in atomic number, which affect the multiple Coulomb scattering of the secondary electrons, are not accounted for by current photon dose calculation algorithms. As local interface effects are mainly due to the perturbation of secondary electrons, a photon-electron cascade model is proposed which incorporates explicit electron transport in the calculation of the primary photon dose component in heterogeneous media. The primary photon beam is treated as the source of many electron pencil ...
Abstract: Two-photon excited fluorescence (TPEF) imaging is a robust and versatile non-invasive, non-destructive, high-resolution technique for studying cell structure and function in 2- and 3-dimensional in vitro systems. This thesis describes three applications of TPEF for studying brain cell structure and function. In the first application, TPEF is used to capture endogenous fluorescence of NAD... read moreH and FAD in 2D cultures of primary rat neurons and astrocytes, as well as in cultures of adult human neural progenitor cells (AHNPs). Analyzing distributions of pixel-wise optical redox ratios, defined as FAD/(FAD+NADH), reveals differences in astrocyte and neuron metabolism consistent with their known tendencies towards glycolysis and oxidative phosphorylation, respectively. Alterations in astrocyte and neuron redox ratio distributions in response to manganese toxicity are consistent with apoptosis and oxidative stress, and are recapitulated in a study with Parkinsons Disease-derived ...
Multiphoton excitation microscopy has revolutionized biomedical research during the last two decades by enabling high resolution fluorescent microscopy in intact tissues. This feature makes two-photon
We report a multifocal multiphoton time-correlated single photon counting (TCSPC) fluorescence lifetime imaging (FLIM) microscope system that uses a 16 channel multi-anode PMT detector. Multiphoton excitation minimizes out-of-focus photobleaching, multifocal excitation reduces non-linear in-plane photobleaching effects and TCSPC electronics provide photon-efficient detection of the fluorescence decay profile. TCSPC detection is less prone to bleaching- and movement-induced artefacts compared to wide-field time-gated or frequency-domain FLIM. This microscope is therefore capable of acquiring 3-D FLIM images at significantly increased speeds compared to single beam multiphoton microscopy and we demonstrate this with live cells expressing a GFP tagged protein. We also apply this system to time-lapse FLIM of NAD(P)H autofluorescence in single live cells and report measurements on the change in the fluorescence decay profile following the application of a known metabolic inhibitor.. ©2007 Optical ...
As recently discussed by K.K. Lehmann in a theoretical analysis of two-photon absorption (TPA) [1], the combination of high circulating power and counterpropagating fields associated with the cavity ring-down spectroscopy (CRDS) technique can yield relatively prominent, two-photon, Doppler-free absorption features for near-resonant, three-level rovibrational systems. Here, we present CRDS measurements of TPA by N$_2$O near $\lambda$ =4.5 $\mu$m. The experiment comprises a quantum cascade laser which is frequency-coupled to a high-finesse optical resonator through controlled optical feedback. Consistent with Lehmanns model, we observe CRDS decay signals that depend upon two characteristic decay rates: a constant single-photon value and an intracavity-power-dependent two-photon absorption rate. The resulting spectra exhibit strong Doppler-free features, saturation effects at low pressure, and TPA cross-section and collisional broadening coefficient consistent with theoretical predictions. 1. K.K. ...
Solvent-induced two-photon absorption cross sections are calculated for a push-pull molecule in solutions using both self-consistent reaction field and internal finite field approaches. It is shown analytically and numerically that the results from the two methods can be connected through induced local reaction field factors. The two-photon cross sections of the studied push-pull polyene are found to be rather insensitive to the choice of cavity shape. The solvent dependence of the two-photon absorption displays a pattern different from that of the first hyperpolarizability.. ...
Low-dose photon irradiation, commonly used in radiotherapy, potentially helps malignant pleural mesothelioma (MPM) cells spread, warns a study by Germanys University of Heidelberg.. The study, Low-dose photon irradiation induces invasiveness through the SDF-1α/CXCR4 pathway in malignant mesothelioma cells, appeared in the journal Oncotarget. It was based on research led by Dr. Stefan Rieken of the universitys departments of thoracic surgery and radiation oncology.. Despite significant research, no definite treatment guidelines have been established for MPM. Multimodality therapy regimens using chemotherapy, radiotherapy or surgery have yielded only minor improvements. In addition, local relapse of MPM often occurs after the multimodality approach.. Radiotherapy routinely uses photon beams. Modern techniques within photon irradiation have enabled specific targeting of tumors while sparing healthy tissues. More recently, a new modality - particle irradiation - has been proposed to replace ...
We have developed a multiphoton microscopy (MPM) system using a 12-fs Ti:sapphire laser with adjustable dispersion precompensation in order to examine the impact of pulse duration on nonlinear optical signals. The efficiencies of two-photon-excited fluorescence (TPEF) and second harmonic generation (SHG) were studied for various pulse durations, measured at the sample, ranging from approximately 400 fs to sub-20 fs. Both TPEF and SHG increased proportionally to the inverse of the pulse duration for the entire tested range. Because of improved signal-to-noise ratio, sub-20-fs pulses were used to enhance MPM imaging depth by approximately 160%, compared to 120-fs pulses, in human skin.. ...
Absolute values of the two-photon absorption cross-sections of Rhodamine 6G, Rhodamine B, Acridine Red, Disodium Fluorescein and DODCI have been obtained by excitation with a neodymium: glass laser (1060 nm). Measurements over eight orders of magnitude of the exciting light flux were carried out by employing the laser both Q-switched and mode-locked. The two-photon fluorescence flux measurements were calibrated by single-photon fluorescence generated by excitation with second-harmonic laser pulses. The experimental results are compared with values predicted by semi-empirical theoretical models and good agreement is obtained. Two-photon amplification of the mode-locked neodymium laser by organic dyes is shown not to be practicable at present. Other possible two-photon oscillators are discussed. ...
Title: Cellular and tissue imaging with multiphoton excitation microscopy Summary: Two-photon microscopy (TPM), sometimes called multiphoton excitation microscopy, is a three dimensional incoherent imaging technique based on the nonlinear excitation of fluorophores. Two-photon excitation occurs only at focal point where the simultaneous absorption from two photons having half of the energy each is needed for the excitation transition. It has several unique features to image cells and tissues, compared with the other 3D imaging microscopes. First, TPM uses high numerical aperture objective with tunable modelocked femtosecond pulsed laser (titanium:sapphire laser), and they enable various biological specimen imaging with sub micrometer resolution down to a depth of a few hundred micrometers using illumination of near infrared (NIR) wavelength light. Second, TPM has a little effect of photodamage on imaging of living specimens, since excitation happens only where the signal is collected without ...
Title: Cellular and tissue imaging with multiphoton excitation microscopy Summary: Two-photon microscopy (TPM), sometimes called multiphoton excitation microscopy, is a three dimensional incoherent imaging technique based on the nonlinear excitation of fluorophores. Two-photon excitation occurs only at focal point where the simultaneous absorption from two photons having half of the energy each is needed for the excitation transition. It has several unique features to image cells and tissues, compared with the other 3D imaging microscopes. First, TPM uses high numerical aperture objective with tunable modelocked femtosecond pulsed laser (titanium:sapphire laser), and they enable various biological specimen imaging with sub micrometer resolution down to a depth of a few hundred micrometers using illumination of near infrared (NIR) wavelength light. Second, TPM has a little effect of photodamage on imaging of living specimens, since excitation happens only where the signal is collected without ...
Kurtz, R.: Bright Solutions to Get Sharp Images: Confocal and Two-Photon Fluorescence Microscopy and the Pros and Cons of New Multifocal Approaches. In: Mendez-Vilas, A. and Diaz, J. (eds.) Modern Research and Educational Topics in Microscopy. Microscopy Series No. 3 Vol. 1. p. 154-163. Formatex (2007 ...
TY - GEN. T1 - Quantum-coherent energy transfer in marine algae at ambient temperature via ultrafast photon echo studies. AU - Wong, Cathy Y.. AU - Hossein-Nejad, Hoda. AU - Curutchet, Carles. AU - Scholes, Gregory D.. PY - 2010/12/1. Y1 - 2010/12/1. N2 - Experiments using two-dimensional photon echo spectroscopy reveal that electronic excitations are coherently coupled in a family of light-harvesting antenna proteins isolated from marine cryptophyte algae, thereby influencing energy transfer.. AB - Experiments using two-dimensional photon echo spectroscopy reveal that electronic excitations are coherently coupled in a family of light-harvesting antenna proteins isolated from marine cryptophyte algae, thereby influencing energy transfer.. UR - http://www.scopus.com/inward/record.url?scp=84897766106&partnerID=8YFLogxK. UR - http://www.scopus.com/inward/citedby.url?scp=84897766106&partnerID=8YFLogxK. M3 - Conference contribution. SN - 9781557528940. T3 - Optics InfoBase Conference Papers. BT - ...
Here, we used time-resolved photoluminescence microscopy to analyze charge carrier transport and recombination in CdTe double heterostructures fabricated by molecular beam epitaxy (MBE). This allowed us to determine the charge carrier mobility in this system, which was found to be 500-625 cm 2/(V s). Charge carrier lifetimes in the 15-100 ns range are limited by the interface recombination, and the data indicate higher interface recombination velocity near extended defects. This study describes a new method to analyze the spatial distribution of the interface recombination velocity and the interface defects in semiconductor heterostructures. ...
A new study from Yale University shows that scientists can create and control a large quantum mechanical system built on photons, suggesting that they might be able to expand the role of photons in quantum information systems.. Light might be able to play a bigger, more versatile role in the future of quantum computing, according to new research by Yale University scientists.. A team of Yale physicists has coaxed an unprecedented number of light particles, or photons, to behave quantum mechanically, or to assume more than one state simultaneously, such as alive and dead. In this case, the light is in the form of trapped microwave photons. Control over a greater number of photons - more than 100 in this case - raises the possibility that such states of light could play the part of several quantum bits (qubits), the building blocks typically found in a quantum computer. This could potentially minimize the physical scale and cost of building one.. The quantum computer, a still embryonic ...
A Monte Carlo study of the transient response of single photon absorption in X-ray pixel detectors is presented. The simulation results have been combined with Monte Carlo simulation of the X-ray photon transport and absorption, and used to estimate the image properties of a detector system, including the pixel array and readout electronics. The study includes several different simulation challenges, such as full band Monte Carlo simulation of charge transport in large devices (300 mu m * 100 mu m), modelling of three-dimensional electrostatic effects using cylindrical coordinates, Monte Carlo simulation of photon transport and absorption, and a system level Monte Carlo simulation of the entire pixel detector and readout. ...
The self mode-locked Ti:sapphire pulsed laser is currently the preferred laser for a majority of multiphoton fluorescence excitation investigations.
Three-dimensional photonic crystals are fabricated using inward-growing self-assembly technique from polymethyl methacrylate (PMMA) colloids. Their air voids are infiltrated with zinc oxide (ZnO) by sot-gel method and the PMMA template is removed by the two independent processes of heat treatment and wet chemical method resulting in ZnO inverse photonic crystal. The inversion is confirmed from the structural characterization. In X-ray diffraction (XRD) experiment, the ZnO inverse photonic crystals obtained by both the techniques do not show any signature of single-crystalline ZnO. The inverse photonic crystals obtained by chemical method are further heated at different temperatures and XRD confirms crystalline nature of ZnO for temperature treatment at 400 degrees C. Laser-induced emission studies on ZnO inverse photonic crystals are carried out at two different excitation wavelengths. Excitation with 355 nm enables the observation of the stop band effect for emission at 45 degrees from the ...
A system, apparatus, and method for analyzing photon emission data to discriminate between photons emitted by transistors and photons emitted by background sources. The analysis involves spatial and/or temporal correlation of photon emissions. After correlation, the analysis may further involve obtaining a likelihood that the correlated photons were emitted by a transistor. After correlation, the analysis may also further involve assigning a weight to individual photon emissions as a function of the correlation. The weight, in some instances, reflecting a likelihood that the photons were emitted by a transistor. The analysis may further involve automatically identifying transistors in a photon emission image.
TY - JOUR. T1 - Second harmonic generation imaging analysis of collagen arrangement in human cornea. AU - Park, Choul Yong. AU - Lee, Jimmy K.. AU - Chuck, Roy S.. PY - 2015. Y1 - 2015. N2 - PURPOSE. To describe the horizontal arrangement of human corneal collagen bundles by using second harmonic generation (SHG) imaging. METHODS. Human corneas were imaged with an inverted two photon excitation fluorescence microscope. The excitation laser (Ti:Sapphire) was tuned to 850 nm. Backscatter signals of SHG were collected through a 425/30-nm bandpass emission filter. Multiple, consecutive, and overlapping image stacks (z-stacks) were acquired to generate three dimensional data sets. ImageJ software was used to analyze the arrangement pattern (irregularity) of collagen bundles at each image plane. RESULTS. Collagen bundles in the corneal lamellae demonstrated a complex layout merging and splitting within a single lamellar plane. The patterns were significantly different in the superficial and limbal ...
High quality entangled photon sources are a key requirement for many promising quantum optical technologies. However, the production of multi-photon entangled states with good fidelity is challenging. Current sources of multi-photon entanglement require the use of post-selection, which limits their usefulness for some applications. It has been an open challenge to create a source capable of directly producing three-photon entanglement. An important step in this direction was achieved with the demonstration of photon triplets produced by a new process called cascaded downconversion, but these previous measurements were not sufficient to show whether these photons were in an entangled state and only had detection rates of five triplets per hour. In this thesis, we show the first demonstration of a direct source of three-photon entanglement. Our source is based on cascaded downconversion, and we verify that it produces genuine tripartite entanglement in two degrees of freedom: energy-time and ...
Presentation in the frame of Photonic Crystals course by R. Houdre. Photonic Crystal Fibers. Georgios Violakis. EPFL, Lausanne June 2009. Outline. Introduction to Photonic Crystal Fibers. Fiber types / classification. Common Fabrication Techniques. Slideshow 790887 by muhammed
Hyperspectral AF images (hypercubes) were captured from 66, 40X fields in 11 RPE/BrM flat mounts from human donor eyes using techniques described in detail in the abstract submitted by K. Agarwal. Briefly, for each 40X field, the hypercube has the two spatial dimensions of the field, and at each spatial point the photon counts recorded at each wavelength, hence the third or spectral dimension. For reproducible quantification of these data, exposure times were calibrated so that photon counts per spectral channel fell within the 12-bit linear range of the detector and then were offset by the dark current. Scaled counts-per-second were determined by exposure time (Eqn. 1) and calibrated to a standard fluorescent reference (courtesy of F Delori) to correct for any variation in power of the excitation light, yielding quantified hypercubes with units of photon counts per second at each point and wavelength.. Results ...
Berland, K.M., So, P.T., Gratton, E. 1995. Two-photon fluorescence correlation spectroscopy: method and application to the intracellular environment. Biophys J. 68(2):694-701. PubMed. Chen Y, Müller JD, So PTC, Gratton E. 1999. The photon counting histogram in fluorescence fluctuation spectroscopy. Biophys J. 77: 553-567. PubMed. Elson EL. 2001. Fluorescence correlation spectroscopy measures molecular transport in cells. Traffic 2(11):789-96. PubMed. Elson EL, Magde D. 1974. Fluorescence correlation spectroscopy. I. Conceptual basis and theory. Biopolymers, 13(1):1-27. Kask P, Palo K, Ullmann D and Gall K. 1999. Fluorescence-intensity distribution analysis and its application in biomolecular detection technology. Proc Natl Acad Sci USA 96:13756-13761. PubMed Kis-Petikova K, Chen Y, Müeller JD, Gratton E. 2000. Application of scanning fluorescent correlation spectroscopy for determination of particle shape. Biophys. J., 78(1), 2603. Koppel DE, Axelrod D, Schlessinger J, Elson EL, Webb WW. 1976. ...
Scientists at MIT have developed a new technique that reveals the inner details of photonic crystals, synthetic materials whose exotic optical properties are the subject of widespread research.. Photonic crystals are generally made by drilling millions of closely spaced, minuscule holes in a slab of transparent material, using variations of microchip-fabrication methods. Depending on the exact orientation, size, and spacing of these holes, these materials can exhibit a variety of peculiar optical properties, including superlensing, which allows for magnification that pushes beyond the normal theoretical limits, and negative refraction, in which light is bent in a direction opposite to its path through normal transparent materials.. But to understand exactly how light of various colors and from various directions moves through photonic crystals requires extremely complex calculations. Researchers often use highly simplified approaches; for example they may only calculate the behavior of light ...
Search and download thousands of Swedish university dissertations (essays). Full text. Free. Dissertation: A Segmented Silicon Strip Detector for Photon-Counting Spectral Computed Tomography.
The purpose of the present study was to demonstrate an |i|in vitro|/i| proof of principle that spectral photon-counting CT can measure gold-labelled specific antibodies targeted to specific cancer cells. A crossover study was performed with Raji lymphoma cancer cells and HER2-positive SKBR3 breast cancer cells using a MARS spectral CT scanner. Raji cells were incubated with monoclonal antibody-labelled gold, rituximab (specific antibody to Raji cells), and trastuzumab (as a control); HER2-positive SKBR3 breast cancer cells were incubated with monoclonal antibody-labelled gold, trastuzumab (specific antibody to HER2-positive cancer cells), and rituximab (as a control). The calibration vials with multiple concentrations of nonfunctionalised gold nanoparticles were used to calibrate spectral CT. Spectral imaging results showed that the Raji cells-rituximab-gold and HER2-positive cells-trastuzumab-gold had a quantifiable amount of gold, 5.97 mg and 0.78 mg, respectively. In contrast, both cell
article{f1c26851-b0a5-4d22-b574-eb667cd7d2ea, abstract = {Two-photon excited fluorescence spectroscopy has been performed at a microscopic scale in combination with normal, white-light microscopy. This gave simultaneously a spectral resolution of 20 nm and a temporal resolution of 20 ps, from a volume element less than 5 mu m in all three dimensions. The sample was excited with the light from a continuously mode-locked Ti:sapphire laser that was focused on the sample in a fluorescence microscope. A polychromator and a streak-camera were used for detection. The method has been used on tissue, plant and paper samples. It has also been demonstrated how substances naturally occurring in the samples can be identified from their spectroscopic properties and the spatial distribution of these substances can be observed.}, author = {Andersson-Engels, Stefan and Rokahr, I and Carlsson, J}, issn = {0022-2720}, language = {eng}, pages = {195--203}, publisher = {Wiley-Blackwell}, series = {Journal of ...
Many cardiac diseases have been associated with increased fibrosis and changes in the organization of fibrillar collagen. The degree of fibrosis is routinely analyzed with invasive histological and immunohistochemical methods, giving a limited and qualitative understanding of the tissues morphological adaptation to disease. Our aim is to quantitatively evaluate the increase in fibrosis by three-dimensional imaging of the collagen network in the myocardium using the non-linear optical microscopy techniques Two-Photon Excitation microscopy (TPE) and Second Harmonic signal Generation (SHG). No sample staining is needed because numerous endogenous fluorophores are excited by a two-photon mechanism and highly non-centrosymmetric structures such as collagen generate strong second harmonic signals. We propose for the first time a 3D quantitative analysis to carefully evaluate the increased fibrosis in tissue from a rat model of heart failure post myocardial infarction. We show how to measure changes in
The possibilities and implications of photons within the infrared, visible, and ultraviolet behaving as sources of intracellular and intercellular communication and information were investigated experimentally for melanoma cells during the 24 hrs following removal from incubation. Specific wavelengths during different intervals were associated with specific classes of biomolecules that were predicted based on the physical properties associated with their amino acid sequences. Application of a specific intensity and physiologically patterned magnetic field predicted from a model that applied the concept of magnetic moment to the whole cell resulted in photon emissions. They were detected at distances sufficient to allow intercellular communication. The occurrence of macroscopic entanglement or non-locality was shown between two loci of where simple chemically-based photons emissions were generated. Within all three experiments there was marked quantitative congruence between the energies ...
Two-photon fluorescence spectra of (a) melanoma cells, (b) medium before culture, (c) medium after culture, and (d) pure melanin.The narrow peaks around 417 n
The |i|Journal of Biomedical Optics|/i| (JBO) publishes peer-reviewed papers on the use of novel optical systems and techniques for improved health care and biomedical research.
IMRT.Thelatterfindingmightbeparticularlyrelevant inreducingtheriskoflateiatrogenicmalignancyina youngpatient.ConsentWritteninformedconsentwasobtainedfromthepatient forpublicationinthiscasereportandanyaccompanying images.Acopyofthewrittenconsentisavailablefor reviewbytheEditor-in-Chiefofthisjournal.Abbreviations OARs:Organsatrisk;CGE:CobaltGrayequivalent;CTV:Clinicaltarget volume;DT:Desmoidtumor;Gy:Gray;IMRT:Intensity-modulatedradiation therapy;MRI:Magneticresonanceimaging;PT:Protontherapy;RT:Radiation therapy;V18:Targetororganvolumereceiving 18Gy;V30:Targetororgan volumereceiving 30Gy;V4:Targetororganvolumereceiving 4Gy. Competinginterests Theauthorsdeclarethattheyhavenocompetinginterests. Authors contributions WJKanalyzedthetreatmentsanddraftedthemanuscript.RCNplannedand analyzedthetreatmentsandcontributedtothefinaldraftofthemanuscript. JWKperformedthesurgeriesandcontributedtothefinaldraftofthe manuscript.SYHplannedthetreatments,assistedwithanalysis,and ...
Researchers at IMS and their coworkers have shown theoretically and experimentally that a high energy electron in circular/spiral motion radiates vortex photons in the entire wavelength range from the radio-wave to the gamma-rays. This greatly broadens application spectra of the vortex photons in the field of physical science. Moreover, the finding indicates that vortex photons are ubiquitous in the universe. It paves a way to a completely new research field, natural vortex photon science.
Nagoya University researchers have succeeded in developing novel fluorescent compounds that allow users to overcome all current fluorescent dye problems. These novel compounds can be used to stain living cells well (, 500 MW) without any damage using low energy wavelength excitation (561 nm) and they are applicable to the two-photon excitation microscopy assay.. ​. ...
Read independent reviews on NANOPHOX - Photon Cross-correlation Spectroscopy for size and stability analysis of nano-suspensions and emulsions from 1 nm to 10,000 nm from Sympatec GmbH on SelectScience