Relevant bibliographies by topics / Photons migration

Academic literature on the topic 'Photons migration'

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Published: 10 March 2023

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Journal articles on the topic "Photons migration"

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Chen, Yan Ping, Xiong Ma, Chun Bin Li, and Song Qing Chen. "Research on the Near-Infrared (NIR) Photon Migration in the Knee." Advanced Materials Research 760-762 (September 2013): 388–91. http://dx.doi.org/10.4028/www.scientific.net/amr.760-762.388.

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To study the phenomena of photon migration in the knee joint is very important in the field of non-invasive near-infrared optical early diagnosis of osteoarthritis of the knee (KOA). In this paper, a photon propagation model of the knee layered structure based on Monte Carlo method is proposed. The migration trace and distribution rule of the photons in knee layered structure are simulated by the Monte Carlo modeling. The proportion of photons which collide with bone tissue then migrate out of the muscle tissue and photons directly migrate out of muscle tissue is calculated and analyzed. The conclusion is that the MC method provided in this study is useful to analyze the photon migration in knee layered structure and to place the detector in a suitable position.
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Perelman, Lev T., Joshua Winn, Jun Wu, Ramachandra R. Dasari, and Michael S. Feld. "Photon migration of near-diffusive photons in turbid media: a Lagrangian-based approach." Journal of the Optical Society of America A 14, no. 1 (January 1, 1997): 224. http://dx.doi.org/10.1364/josaa.14.000224.

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Lakowicz, Joseph R., Ignacy Gryczynski, and Zygmunt Gryczynski. "High Throughput Screening with Multiphoton Excitation." Journal of Biomolecular Screening 4, no. 6 (December 1999): 355–61. http://dx.doi.org/10.1177/108705719900400610.

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Fluorescence detection is extensively used in high throughput screening. In HTS there is a continuous migration toward higher density plates and smaller sample volumes. In the present report we describe the advantages of two-photon or multiphoton excitation for HTS. Multiphoton excitation (MPE) is the simultaneous absorption of two long-wavelength photons to excite the lowest singlet state of the fluorophore. MPE is typically accomplished with short but high-intensity laser pulses, which allows simultaneous absorption of two or more photons. The intensity of the multiphoton-induced fluorescence is proportional to the square, cube, or higher power of the instantneous photon flux. Consequently, two-photon or multiphoton excitation only occurs at the focal point of the incident beam. This property of two-photon excitation allows the excited volume to be very small and to be localized in the center of each well in the HTS plate. We show that two-photon-induced fluorescence of fluorescein can be reliably measured in microwell plates. We also show the use of 6-carboxy fluorescein as a pH probe with two-photon excitation, and measure 4′-6-diamidino-2-phenylindole (DAPI) binding and two-photon-induced fluorescence. In further studies we measure the time-dependent intensity decays of DAPI bound to DNA and of calcium-dependent fluorophores. Finally, we demonstrate the possibility of three-photon excitation of several fluorophores, including indole, in the HTS plate. These results suggest that MPE can be used in high-density multiwell plates.
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Baranyai, László, and Manuela Zude. "Analysis of laser light migration in apple tissue by Monte Carlo simulation." Progress in Agricultural Engineering Sciences 4, no. 1 (December 1, 2008): 45–59. http://dx.doi.org/10.1556/progress.4.2008.3.

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The distribution of laser light in the tissue of Golden Delicious and Idared apples was measured with backscattering imaging and simulated with Monte Carlo (MC) method. The settings of the vision system (sensitivity and resolution) and the parameters of the laser modules (wavelength, power and beam diameter) were used in a time resolved MC model to optimize the computation. The 1 ns pulse containing 1.42 × 10 7 (at 670 nm) and 2.49 × 10 8 (at 785 nm) photons was selected for the simulation of backscattering on the fruit surface. The statistical effect of the scattering coefficient (µ s ), absorption coefficient (μ a ), and anisotropy factor ( g ) on photon flux and shape of the backscattering profile was evaluated within ±20 % range relative to expected mean values for apple tissue (µ a = 0.63 cm −1 , µ s = 30.0 cm −1 and g = 0.8). The multi-factor ANOVA test pointed out the highest importance (p<0.001) of the anisotropy factor compared to the scattering and absorption coefficients. Decreasing value of anisotropy factor enhanced the maximum intensity and increased the decline of the gradient resulting in a rotation of the intensity profiles. The measured backscattering profiles for Golden Delicious apples responded to bruising (p<0.05) already after one day storage.
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Du, Fei, Wenzhi Chang, Jiangang Bi, Shuai Yuan, Xinghui Zhang, and Yanpeng Gong. "Evolution mechanism of ultraviolet and electrical phenomena induced by protrusion discharge in GIS." Journal of Electrical Engineering 71, no. 4 (August 1, 2020): 268–73. http://dx.doi.org/10.2478/jee-2020-0036.

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AbstractTo improve the sensitive and reliability of condition monitoring in gas insulated switchgear (GIS), discharge perception system applied to GIS insulators protrusion discharge based on single ultraviolet photon is built. Step method is used to inspire the discharges of different severity, based on which, the regression relationship of ultraviolet (UV) signal and electrical signal are studied, and the perception mechanism of UV signal in different severity of discharges is analyzed. The study indicates that, the development of protrusion discharge in GIS can be divided into four stages, and there is no positive correlation between the number of ultraviolet photons caused by discharge radiation and insulation deterioration level, but related to the diffusion, migration and recombination of charged particles, then UV optical method for quantitative monitoring of discharge in each stage is provided, which provide a new method for quantitative measurement of GIS insulator discharge.
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Gratton, Gabriele, Monica Fabiani, David Friedman, Maria Angela Franceschini, Sergio Fantini, Paul Corballis, and Enrico Gratton. "Rapid Changes of Optical Parameters in the Human Brain During a Tapping Task." Journal of Cognitive Neuroscience 7, no. 4 (October 1995): 446–56. http://dx.doi.org/10.1162/jocn.1995.7.4.446.

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Measures of parameters of the migration of near-infrared photons through the head (attenuation, or intensity, and time-of-flight, or delay) have been proposed as a way of assessing noninvasively and in a quasicontinuous fashion changes in the scattering and absorption properties of brain tissue. These, in turn, may reflect functional changes associated with behavioral tasks. To test this hypothesis, we measured changes of photon migration parameters from scalp locations proximal to the motor cortex from four human subjects, tapping at a rate of 0.8 Hz with their left or right hand, or with their left or right foot. Tapping produced both slow effects (requiring several seconds) and fast effects (tracking the tapping frequency). Slow effects were characterized by increase and delay of the light passing through the hemisphere contralateral to the tapping hand. Fast effects consisted of changes in the light delay during hand tapping. Monte Carlo simulations based on layer models of the brain indicated that fast effects are consistent with changes in deep layers of the head (presumably in the cortex), and that slow effects are consistent with either a shift of absorbing material toward deeper layers or a reduction in scattering. These results suggest that optical parameters can monitor rapid changes of brain activity, matching the contralateral organization of the motor cortex.
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Raja-Mogan, Tharishinny, Bunsho Ohtani, and Ewa Kowalska. "Photonic Crystals for Plasmonic Photocatalysis." Catalysts 10, no. 8 (July 23, 2020): 827. http://dx.doi.org/10.3390/catal10080827.

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Noble metal (NM)-modified wide-bandgap semiconductors with activity under visible light (Vis) irradiation, due to localized surface plasmon resonance (LSPR), known as plasmonic photocatalysts, have been intensively studied over the last few years. Despite the novelty of the topic, a large number of reports have already been published, discussing the optimal properties, synthesis methods and mechanism clarification. It has been proposed that both efficient light harvesting and charge carriers’ migration are detrimental for high and stable activity under Vis irradiation. Accordingly, photonic crystals (PCs) with photonic bandgap (PBG) and slow photon effects seem to be highly attractive for efficient use of incident photons. Therefore, the study on PCs-based plasmonic photocatalysts has been conducted, mainly on titania inverse opal (IO) modified with nanoparticles (NPs) of NM. Although, the research is quite new and only several reports have been published, it might be concluded that the matching between LSPR and PBG (especially at red edge) by tuning of NMNPs size and IO-void diameter, respectively, is the most crucial for the photocatalytic activity.
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Ebel, Horst, Robert Svagera, Maria F. Ebel, Norbert Zagler, Wolfgang S. M. Wemer, Herbert Stön, and Martin Gröschl. "On the Sampling Depth of Total Electron Yield (Tey) Measurements." Advances in X-ray Analysis 39 (1995): 665–74. http://dx.doi.org/10.1154/s0376030800023107.

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Photoabsorption of x-rays in solids causes primary and secondary photo and Auger electrons. The latter are from self absorption of characteristic radiations which have been produced in the solid by radiative de-excitation of photoionized atoms. Whereas the energy of the electrons at the origin is described by discrete values of a few eV up to nearly the energy of the photoabsorbed photons, we observe after the escape of the electrons from the solid a continuous energy distribution with a superposition of the original line spectrum. This is explained by inelastic collisions of the electrons in the course of their migration through the solid and the subsequent loss of kinetic energy. Since the electron range decreases with decreasing kinetic energy, only a relatively small amount of electrons is able to reach the surface and to escape from there.
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Zhong, Yi, Jinhui Xu, Xinyu Zhao, Tongfei Qu, Chen Guan, Chengzong Hou, Xuexi Tang, and Ying Wang. "Balancing Damage via Non-Photochemical Quenching, Phenolic Compounds and Photorespiration in Ulva prolifera Induced by Low-Dose and Short-Term UV-B Radiation." International Journal of Molecular Sciences 23, no. 5 (February 28, 2022): 2693. http://dx.doi.org/10.3390/ijms23052693.

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The Yellow Sea green tide (YSGT) is the world’s largest transregional macroalgal blooms, and the causative species Ulva prolifera (U. prolifera) suffers from ultraviolet-b radiation (UVBR) during the floating migration process. Previous study confirmed that U. prolifera displayed a wide variety of physiological responses characterized as acclimation to UVBR, while the response mechanisms against low-dose and short-term radiation (LDSTR) are not clear. A study with photosynthetically active radiation (PAR) and UVBR was designed: normal light (NL: 72 μmol photons m−2 s−1), NL+0.3 (UVBR: 0.3 W·m−2), and NL+1.6 (UVBR: 1.6 W·m−2). The results showed that high-dose UVBR inhibited photosynthesis in thalli, especially under long-term exposure, while a variety of physiological responses were observed under LDSTR. The inhibition of photosynthesis appeared to be ameliorated by the algae under LDSTR. Further analysis showed that U. prolifera achieved balancing damage by means of non-photochemical quenching (NPQ), accumulation of phenolic compounds coupled with the ASA-GSH cycle involved in the antioxidant process and enhanced photorespiratory metabolism under LDSTR. This study provides new insights into the balancing damage mechanisms of U. prolifera under LDSTR, enabling the thalli to adapt to the light conditions during the long duration and distance involved in floating migration.
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Hossieni, H., and J. M. A. Fatah. "Spooky Birds and Origin of Life: A Quantum Mechanics Description of Bird Migration." Jurnal Pendidikan Fisika Indonesia 15, no. 1 (May 29, 2019): 1–4. http://dx.doi.org/10.15294/jpfi.v15i1.13920.

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In this work we explain a strange quantum phenomenon in biology that the European Robin uses to navigate. The bird’s brain contains a chemical called cryptochromes which has two of its electrons entangled through collision with photons. These two electrons hop between singlet and triplet states. This hopping is sensitive to the earth’s magnetic field causing different signals to be transferred to its brain. It is believed that these birds use quantum entanglement for their navigations. We also discuss the importance of this phenomenon in trying to find the origin of life. We also explain the view of some who believe that quantum field is well entrenched in the origin of life and that we have to look for a quantum self-replicator that can repeat itself.Hasil penelitian ini mencoba menjelaskan fenomena kuantum yang aneh pada ranah biologi dimana burung robin eropa bernavigasi menggunakannya. Otak burung tersebut mengandung material kimia yang disebut dengan cryptochromes yang mempunyai dua buah elektron yang terjebak dalam pengaruh interaksi tumbukan antara elektron tersebut dengan foton. Dua elektron tersebut melompat di antara keadaan singlet dan triplet. Lompatan ini dipengaruhi oleh medan magnetik bumi yang memberikan sinyal berbeda-beda untuk ditransfer ke otaknya. Burung-burung ini diyakini menggunakan prinsip pengaruh kuantum untuk navigasinya. Kami juga mengungkap pentingnya fenomena ini dalam usaha mencari asal mula kehidupan. Kami juga menjelaskan sudut pandang yang mempercayai bahwa medan kuantum diyakini berperan penting dalam penjelasan tentang asal mula kehidupan dan bahwa kita harus mencari tahu tentang pembelahan materi dengan pengaruh kuantum yang dapat berlangsung berulang-ulang dengan sendirinya.
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Dissertations / Theses on the topic "Photons migration"

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Saarela, J. (Juha). "Photon migration in pulp and paper." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514275845.

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Abstract The thesis clearly demonstrates that photon migration measurements allow characterization of pulp and paper properties, especially the fines and filler content of pulp, and the basis weight, thickness and porosity of paper. Pulp and paper are materials with a worldwide significance. Their properties strongly depend on the manufacturing process used. For efficient process control, the employed monitoring and measuring has to be fast. Therefore it is worthwhile to try to develop new approaches and techniques for such measurements. Recent advancements in optics offer new possibilities for such development. If two samples have different optical properties their photon migration distributions are different. The measurement of a photon migration distribution allows some features between two optically slightly dissimilar samples to be distinguished. Some simple measurements, which only yielded the photons' average time of flight, were made with an oscilloscope and a time-of-flight lidar. More precise measurements yielding photon pathway distribution or some selected characteristics like light pulse rise time, broadening, or fall time were measured with a streak camera. Two methods to assess photon path length distribution were introduced: particle determination with simulation, and streak camera with deconvolution. The basic properties for pulp are consistency and fines content and for paper the basic properties are thickness, basis weight and porosity. The influence on photon migration caused by changes in these basic properties was determined. As pulp and paper are rarely very basic, an additional property was demonstrated for both materials. For pulp it was the content of filler talc, and for paper it was the use of beaten pulp as a raw material. These additional properties were also distinguishable.
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Huang, Yingqing. "Characterization of dense suspensions using frequency domain photon migration." Texas A&M University, 2003. http://hdl.handle.net/1969.1/2207.

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Interparticle interactions determine the microstructure, stability, rheology, and optical properties of concentrated colloidal suspensions involved in paint, paper, cosmetic, and pharmaceutical industries, etc. Frequency domain photon migration (FDPM) involves modeling the photon transport in a multiple scattering medium as a diffusion process in order to simultaneously determine isotropic scattering and absorption coefficients from measured amplitude attenuation and phase shift of the propagating photon density wave. Using FDPM, we investigated the impact of electrostatic interaction upon the optical properties and structure of dense charged suspensions. We demonstrated that electrostatic interactions among charged polystyrene latex may significantly affect the light scattering properties and structure of dense suspensions at low ionic strength (<0.06 mM NaCl equivalent) by actual FDPM measurement. We showed that the structure factor models addressing electrostatic interaction can be used to describe the microstructure of charged suspensions and quenched scattering due to electrostatics, and demonstrated that FDPM has the potential to be a novel structure and surface charge probe for dense suspensions. We also showed that the FDPM measured isotropic scattering coefficients may respond to the change in effective particle surface charge, and displayed the potential of using FDPM for probing particle surface charge in concentrated suspensions. We presented that the interference approximation implies a linear relationship between the absorption coefficient and volume fraction of suspension. We illustrated that FDPM measured absorption coefficient varies linearly with suspension volume fraction and affirmed the interference approximation from a perspective of light absorption. The validation of the interference approximation enables us to develop the methodology for estimating absorption efficiencies and imaginary refractive indices for both particles and suspending fluid simultaneously using FDPM. We further demonstrated a novel application of FDPM measured absorption coefficients in determining pigment absorption spectra, and displayed the potential of using FDPM as a novel analytical tool in pigment and paint industry.
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Xu, Zhoujia. "Migration from electronics to photonics in multicore processor." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45394.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
Includes bibliographical references (leaf 54).
Twenty - first opportunities for Gigascale Integration will be governed in part by a hierarchy of physical limits on interconnect. Microprocessor performance is now limited by the poor delay and bandwidth performance of the on - chip global wiring layer. This thesis is envisioned as a critical showstopper of electronic industry in the near future. The physical reason behind the interconnect bottleneck is the resistive nature of metals. The introduction of copper in place of aluminum has temporarily improved the interconnect performance, but a more disruptive solution will be required in order to keep the current pace of progress, optical interconnect is an intriguing alternative to metallic wires. Many - core microprocessors will push performance per chip from the 10 gigaflop to the 10 teraflop range in the coming decade. Pin limitations, the energy cost of electrical signaling, and the non - scalability of chip - length global wires are significant bandwidth impediments. Silicon nanophotonic based many core architecture are introduced in order to meet the bandwidth requirements at acceptable power levels.
by Zhoujia Xu.
M.Eng.
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Pan, Tianshu. "Application and modeling of near-infrared frequency domain photon migration for monitoring pharmaceutical powder blending operations." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4433.

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Frequency domain photon migration consists of launching an intensitymodulated near-infrared light into the powder medium and measuring the amplitude, mean-intensity, and phase shift of detected intensity modulated light for extracting both the isotropic scattering and absorption coefficients of the powder bed. The dependence of absorption coefficient upon the active pharmaceutical ingredient (API) concentration of powder blend enables FDPM to monitor blending homogeneity. The volume sampled by FDPM in powder blend was investigated through a designed heterogeneity experiments. A model which describes the visitation probability of a local region by migrating photons was developed to theoretically determine the sampled volume of FDPM in terms of signal-to-noise ratio. The applicability of FDPM in monitoring blending homogeneity was directly verified by measuring the API contents in a series of industrial samples, which were retrieved from various locations at various times in an actual pharmaceutical blending process. The FDPM measurement results were consistent with the traditional analysis using high performance liquid chromatography. The homogeneity evolution revealed through FDPM agreed with the well-established first order model of blending. A simulation method was developed which consisted of (i) dynamic simulation for generating the powder structure; (ii) the completely-randommixture model for predicting the spatial distribution of API particles within the powder bed; and (iii) Monte Carlo simulation for tracking photon trajectories within the powder bed. The simulation of photon migration in powder blend revealed that while both the isotropic scattering and absorption coefficients increased with the solid-volume fraction, the ratio of absorption coefficient to the isotropic scattering coefficient is (i) independent of the solid-volume fraction; (ii) linearly dependent upon the API concentration; and (iii) appropriate for monitoring the powder blending homogeneity under simultaneous variations of solid-volume fraction and API content. Finally, a rigorous two-speed diffusion equation for describing photon migration in powders was derived from the two-group radiative transfer equations and the analytical expression of the isotropic scattering coefficient was provided. The theoretical results agreed well with the experimental measurements in resin powder media and resin suspensions.
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Dali, Sarabjyot Singh. "Analysis of dense colloidal dispersions with multiwavelength frequency domain photon migration measurements." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1751.

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Houston, Jessica Perea. "Near infrared optical lymphography for cancer diagnostics." Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/4807.

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A new molecular imaging modality has been developed to detect and locate positive axillary and sentinel lymph nodes non-invasively in breast cancer patients undergoing lymphoscintigraphy. The modality is based on fluorescent photon detection to locate the presence of indocyanine green (ICG) in the lymph subsequent to peritumoral injection of ICG into the breast. The imaging system consists of a gain-modulated intensified charge-coupled device (ICCD) camera, which captures low-intensity, near-infrared, and frequency-modulated photons. A four-fold ‘optical lymphography’ study was conducted to (1) examine fluorescence depth penetration and ICCD system accuracy at clinically relevant depths, (2) compare image quality of the ICCD system vs. conventional gamma imaging, (3) measure ICG pharmacokinetics in vivo, and (4) develop a clinical protocol while examining pre-clinical factors such as the outcome of combining ICG with sulfur colloids used in lymphoscintigraphy. The frequency-domain ICCD system was found to precisely detect modulation amplitude, IAC, and phase, θ, at depths up to 9 cm and with IAC accuracy less than 20% and θ less than 2º using an 80-mW laser incident on phantoms having ranging tissue optical properties. Significant differences in the mean depth of penetration owing to 0.62-ns lifetime and 100-MHz frequency increases were detected. An in vivo optical vs. nuclear image quality comparison demonstrated statistically similar (α=0.05) target-to-background ratios for optical (1.4+/-0.3) and nuclear (1.5+/-0.2). Alternatively, resulting image signal-to-noise ratios (SNR) from the ICCD system were greater than that achieved with a conventional gamma camera (pvalue<<0.01). Analysis of SNR versus contrast showed greater sensitivity of optical over nuclear imaging for subcutaneous tumors. In vivo and rapid detection of ICG in the blood-stream of nude mice was accomplished with a home-built avalanche photodiode dynamic fluorescence measurement system. Intensity data upon i.v. injection were regressed with a pharmacokinetic model describing the partitioning of ICG from the blood to the surrounding tissues. ICG blood-clearance was detected approximately 15 min after injection. Lastly, a human subject protocol was written, practiced, and federally approved for the application of optical lymphography. Furthermore, ICG was unaffected when mixed with sulfur colloids thus supporting the feasibility for combining fluorescence imaging with lymphoscintigraphy in breast cancer patients.
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Wu, Jun 1968. "Photon migration in turbid media : time-resolved optical imaging in tissue-like phantom." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10792.

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Mikaelsson, Therese. "Electronic Energy Migration/Transfer as a Tool to Explore Biomacromolecular Structures." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-86794.

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Fluorescence-based techniques are widely used in bioscience, offering a high sensitivity and versatility. In this work, fluorescence electronic energy migration/ transfer is applied to measure intramolecular distances in two types of systems and under various conditions. The main part of the thesis utilizes the process of donor-acceptor energy transfer to probe distances within the ribosomal protein S16. Proteins are essential to all organisms. Therefore, it is of great interest to study protein structure and function in order to understand and prevent protein malfunction. Moreover, it is also important to try to study the proteins in an environment which resembles its natural habitat. Here two protein homologs were investigated; S16Thermo and S16Meso, isolated from a hyperthemophilic bacterium and a mesophilic bacterium, respectively. It was concluded that the chemically induced unfolded state ensemble of S16Thermo is more compact than the corresponding ensemble of S16Meso. This unfolded state compaction may be one reason for the increased thermal stability of S16Thermo as compared to S16Meso. The unfolded state of S16 was also studied under highly crowded conditions, mimicking the environment found in cells. It appears that a high degree of crowding, induced by 200 mg/mL dextran 20, forces the unfolded state ensemble of S16Thermo to become even more compact. Further, intramolecular distances in the folded state of five S16 mutants were investigated upon increasing amounts of dextran 20. We found that the probed distances in S16Thermo are unaffected by increasing degree of crowding. However, S16Meso shows decreasing intramolecular distances for all three studied variants, up to 100 mg/mL dextran. At higher concentrations, the change in distance becomes anisotropic. This suggests that marginally stable proteins like s16Meso may respond to macromolecular crowding by fine-tuning its structure. More stable proteins like S16Thermo however, show no structural change upon increasing degree of crowding. We also investigated the possibility of local specific interactions between the protein and crowding agent, by means of fluorescence quenching experiments. Upon increasing amounts of a tyrosine labelled dextran, a diverse pattern of fluorescence quantum yield and lifetime suggests that specific, local protein-crowder interactions may occur. In a second studied system, electronic energy migration between two donor-groups, separated by a rigid steroid, was studied by two-photon excitation depolarization experiments. Data were analysed by using recent advances, based on the extended Förster theory, which yield a reasonable value of the distance between the two interacting donor-groups. To the best of our knowledge, this is the first quantitative analysis of energy migration data, obtained from two-photon excited fluorescence.
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Gesta, Emmanuelle. "Study of the interaction and migration mechanisms in the systems polymer/insecticide." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1093.

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Le principal objectif des travaux présentés dans ce manuscrit était d’étudier certains paramètres régissant l’efficacité et la durabilité de moustiquaires avec des molécules insecticides incorporées dans les fils de polyéthylène. Pour cela deux axes de travail ont été identifiés : l’étude des phénomènes de migration des molécules insecticide dans les fils de polyéthylène et l’étude des mécanismes de photo-dégradation de l’insecticide étudié : la deltaméthrine.L’étude de l’influence du procédé de fabrication des moustiquaires sur la morphologie du polyéthylène a permis de montrer que l’étape d’étirage à froid était critique dans la définition des propriétés morphologiques (cristallinité et orientation de la structure cristalline) et mécaniques des fils. L’effet du recuit observé est plus modéré (légère augmentation de l’épaisseur des lamelles cristallines). Néanmoins, il a été montré que les modifications induites par le recuit sur la morphologie du polyéthylène ont une influence sur les phénomènes de migration des molécules insecticides dans les fils. En effet, alors qu’un retard est observé dans les courbes de désorption des fils non recuits, ce retard disparaît pour les fils recuits. Il a été également montré que la faible vitesse d’évaporation de la deltaméthrine permet de limiter la migration de la deltaméthrine hors des fils.L’étude de la photo-dégradation de la deltaméthrine a permis de mettre en évidence les principaux mécanismes de dégradation (isomérisation, scission de la fonction ester et de la fonction cyclopropane). L’ajout d’additifs de type antioxydants ou filtres UV permet de limiter la vitesse de dégradation de la deltaméthrine
The main objective of the works presented in this manuscript was to study some of the parameters ruling the efficacy and the durability of the mosquito nets with incorporated insecticide in the polyethylene yarns. To achieve this goal, two lines of research were identified: the study of the insecticide migration phenomena in the yarns and the study of the photodegradation mechanisms of the molecule of interest: the deltamethrin.The study of the influence of the nets fabrication process on the polyethylene morphology showed that the cold-drawing step was critical to define the morphological (crystallinity and orientation of the crystalline structure) and mechanical properties. The observed influence of the heat-setting appeared less important (slight increase of the crystalline lamellae thickness). However, the heat-setting induced modifications which affected the migration of the insecticide molecules in the yarns. Indeed, while a delay is observed in the desorption curves of the non-heat-set yarns, this time-lag disappeared in the heat-set yarns. It was also shown that the low evaporation rate of deltamethrin permits to impede the migration of deltamethrin out of the yarns.The study of the photodegradation of deltamethrin permitted to highlight the main degradation mechanisms (isomerization, ester cleavage and cyclopropane cleavage). Antioxidant and UV absorber additives can be used to reduce the deltamethrin degradation rate
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Rasmussen, John C. "Development of a radiative transport based, fluorescence-enhanced, frequency-domain small animal imaging system." Thesis, [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1067.

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Books on the topic "Photons migration"

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Britton, Chance, ed. Photon migration in tissues. New York: Plenum Press, 1989.

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Chance, Britton, ed. Photon Migration in Tissues. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8.

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Chance, Britton. Photon Migration in Tissues. Boston, MA: Springer US, 1989.

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Winged migration. San Francisco, Calif: Chronicle Books, 2003.

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Ludwig, Museum, ed. Vor Ort: Fotogeschichten zur Migration = In situ : photo stories on migration. Köln: Museum Ludwig, 2021.

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America, Optical Society of, ed. Advances in optical imaging and photon migration: Summaries of papers presented at the topical meeting, advances in optical imaging and photon migration, March 21-23, 1994, Orlando, Florida : technical digest. Washington, DC: The Society, 1994.

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G, Fujimoto James, Patterson Michael S, Optical Society of America, and Laser Institute of America, eds. Advances in optical imaging and photon migration: From the Topical Meeting [sic] Advances in Optical Imaging and Photon Migration, March 8-11, 1998, Orlando, Florida. Washington, DC: Optical Society of America, 1998.

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A, Boas David, Society of Photo-optical Instrumentation Engineers., Optical Society of America, and European Physical Society, eds. Photon migration and diffuse-light imaging: 22-23 June 2003, Munich, Germany. Bellingham, Wash., USA: SPIE, 2003.

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America, Optical Society of, and Laser Institute of America, eds. Advances in optical imaging and photon migration: March 8-11, 1998, Sheraton World Resort Orlando, Orlando, Florida. Washington, DC: The Society, 1998.

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Dündar, A. Merthan. Süyümbike'nin göçyaşları : İdil - Ural türklerinin doğu Asya'ya göçü. Fotoğraflarla bir göç hikâyesi The tears of Süyümbike: Migration of İdil - Ural Turks to east Asia. A migration story in photos. Ankara: Ankara Üniversitesi Yayınları, 2022.

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Book chapters on the topic "Photons migration"

1

Niwayama, Masatsugu, and Yutaka Yamashita. "Photon Migration in Tissue." In Application of Near Infrared Spectroscopy in Biomedicine, 21–35. Boston, MA: Springer US, 2013. http://dx.doi.org/10.1007/978-1-4614-6252-1_2.

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Chance, Britton. "Summary Report of a Workshop on Photon Migration." In Photon Migration in Tissues, 1–8. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_1.

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Chance, B., D. S. Smith, S. Nioka, H. Miyake, G. Holtom, and M. Maris. "Photon Migration in Muscle and Brain." In Photon Migration in Tissues, 121–35. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_10.

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Holtom, Gary R. "Experimental Time Resolved Methods." In Photon Migration in Tissues, 139–46. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_11.

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Greenfeld, Robert Lloyd. "A Tissue Model for Investigating Photon Migration in Trans-Cranial Infrared Imaging." In Photon Migration in Tissues, 147–68. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_12.

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Lakowicz, Joseph R. "Gigahertz Frequency-Domain Fluorometry: Resolution of Complex Intensity Decays, Picosecond Processes and Future Developments." In Photon Migration in Tissues, 169–86. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_13.

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Bonner, Robert F., Ralph Nossal, and George H. Weiss. "A Random Walk Theory of Time-Resolved Optical Absorption Spectroscopy in Tissue." In Photon Migration in Tissues, 11–23. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_2.

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Wilson, Brian C., Michael S. Patterson, Stephen T. Flock, and Douglas R. Wyman. "Tissue Optical Properties in Relation to Light Propagation Models and in Vivo Dosimetry." In Photon Migration in Tissues, 25–42. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_3.

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Knutson, Jay R. "Some Prospects for Adapting Fluorescence Instrumentation." In Photon Migration in Tissues, 43–51. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_4.

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Yamashita, Y., S. Suzuki, S. Miyaki, and T. Hayakawa. "The Neonate Brain (NIR) and Breast Imaging Using Transillumination." In Photon Migration in Tissues, 55–67. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4757-6178-8_5.

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Conference papers on the topic "Photons migration"

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Polishchuk, A. Ya, Jean Dolne, Feng Liu, M. Zevallos, B. Das, and R. R. Alfano. "Fermat Photons: Paths Propagation and Imaging in Turbid Media." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.pmst14.

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Photon diffusion on the velocity sphere describes photon migration in highly forward scattering media. The non-Euclidean diffusion leads to the concept of the most favorable photon paths described by Generalized Fermat Principle for turbid media. Experimental results are compared to theoretical predictions. Application of Fermat photons to imaging will be discussed.
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Perelman, Lev T., Jun Wu, Kun Chen, Irving Itzkan, Ramachandra R. Dasari, and Michael S. Feld. "Photon Paths in Turbid Media: From Smooth to Random." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.pmst18.

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Wang, Lihong, and Steven L. Jacques. "Application of Probability of n Scatterings of Light Passing through and Idealized Tissue Slab in Breast Imaging." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/aoipm.1994.ncpdir.181.

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Based on the probability of a given number of scatterings for photons transmitted through a tissue slab with a unity anisotropy factor, the minimum number of scatterings required for optical imaging of tissues in the transmission mode was estimated. For breast tissue imaging with visible or near infrared light, ballistic imaging is possible only for thicknesses less than 42 mean free paths, which is 0.14 cm for breast adipose tissue at 700 nm wavelength (scattering coefficient is 300 cm–1). For a 5-cm thickness, at least 1100 scattering events must be allowed to receive on average a single transmitted photon from 10-18 input photons (about 1-J visible light). Monte Carlo simulations have shown that the anisotropy of traveling direction of photons after i scatterings decays exponentially with i. The photons that are launched in the same direction will travel practically isotropically after 3/(1–g) scatterings, where g is the anisotropy factor of the tissue. For the breast adipose tissue with g equal to 0.97, 3/(1–g) is 100.
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Borovoi, A. G. "Analytical Description of Snake Photons." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.pmst69.

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The snake photons are shown to obey the parabolic instead of the more general Maxwell As a result, the snake photons are described by the well-known small-angle approximation of the radiative transfer having a rather simple analytical solutions. Some applications of the solutions for retrieving the parameters of highly scattering media (density inhomogeneities, particle size distributions, etc.) are discussed.
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Nossal, R., and Robert F. Bonner. "Random walk theory of photon migration in biological tissue." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.thd4.

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Mathematical expressions are obtained for various functions (e.g., path length and depth distributions, total reflectance, and its spatial distribution) associated with photon migration in turbid media. The models assume that photons are inserted at a point on the surface of a tissue and detected at another point on this surface (or the parallel lower surface of a slab) at a distance ρ from the point of insertion. For a homogeneous medium characterized by uniform absorption and scattering cross sections, an expression is derived for P(n|ρ), the probability density of photons emerging at surface point ρ whose path length within the media is n, given in units of rms distance between scattering events. The probability density of the corresponding transit times (t = n/c i ) in range-gating applications is also given by this expression. Expressions for spatial distribution of diffuse surface emission, mean path length, and penetration depth of emergent photons at ρ also are derived. Analogous quantities are calculated for photons migrating within a medium having a surface layer whose absorbance differs from that of the lower bulk material. The dependence of these parameters on surface thickness is illustrated.
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Yoo, K. M., B. B. Das, Feng Liu, and R. R. Alfano. "Ultrafast light scattering and photon migration in biomedical media." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.mz3.

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Current femtosecond and picosecond laser technology is used to study forward and backward light scattering and photon migration in biomedical media. One determines, from the pulse transmission experiment using a sensitive streak camera, when the diffusion approximation fails to describe photon migration in tissues, and to study the early-arriving scattered snake photons by temporal gating transillumination technique for improved medical imaging.
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Liu, Feng, K. M. Yoo, and R. R. Alfano. "Early Arriving Transmitted Photon Intensity through Tissues." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/aoipm.1994.trbsdi.170.

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The intensity of transmitted ultrashort laser pulses through thick biological tissue within various arriving time windows were studied. It was found that intensity of the early arriving photons decay exponentially with a factor ≈z/l t , which decay much slower than the first arriving ballistic photons (z/l s ), where z, l t , and l s is thickness, transport mean free path, and scattering mean length of the medium, respectively. This results show that by using near infrared ultrashort laser pulses there may be enough early arriving photons to be used to image through a thick tissue.
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John, Sajeev. "Theory of Multiple-Light-Scattering Spectroscopy." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/aoipm.1994.wpl.58.

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We present an algorithm for determining the dielectric autocorrelation function of a disordered medium from angle resolved multiple light scattering measurements. Photons propagating in a disordered, multiple scattering medium are classified as being either ballistic, “snake-like” or diffusive, depending on the nature of their trajectory between source and detector. Considerable information about the nature of the scattering medium is contained in the early arriving snake-like photons whereas this information is smeared in the late-arriving diffusive photons. We derive from first principle a formal mathematical description which encompasses all three regimes of transport and relates the experimentally observed light intensity correlation functions to the ensemble averaged autocorrelation function B ˜ ( x → , y → ) ≡ 〈 ε * ( x → ) ε ( y → ) 〉 ens for a disordered medium with dielectric constant ε ( x → ) .
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Das, B. B., K. M. Yoo, and R. R. Alfano. "Snake Photon Imaging in Thick Tissues in Visible and Near Infrared Radiation Spectral Region." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/aoipm.1994.trbsdi.166.

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Time-resolved transillumination techniques have been used to image opaque1-6 and partially absorbing7-10 objects hidden in various random media. When ultrashort laser pulses are incident on a slab of scattering medium the transmitted pulses consist of a ballistic (coherent) component11-12, a diffuse component and a snake component1. Using time-resolved detection techniques, the snake photons can be separated from the diffuse component and used to construct the image of an object hidden in a scattering medium with different optical properties. Recently, it has been shown that thick tissue imaging is possible using snake photons in the visible region10.
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Zevallos, M. E., F. Liu, B. B. Das, A. Ya Polishchuck, and R. R. Alfano. "Angular Dependence of The Intensity Temporal Profiles of Scattered Pulses in Diffusive Regime." In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.pmst21.

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In this paper, the angular dependence of intensity temporal profiles for three sample media of different scatterer size are described. Detection angles around a fixed point are varied. Similar detection points in each media have been chosen along two directions: forward - along the light source launching direction, x-axis; and lateral or perpendicular direction, y-axis, for comparison. Measurements show the existence of a strong angular dependence of light traveling in a highly scattering media even for distances as large as 20 transport mean free path. More light is observed in the forward direction than in the lateral direction. The strong angular and spatial dependence indicates the existence of an anisotropic behavior of photons from the source directionality. To describe the high degree of anisotropy of photon migration in the medium, two new anisotropy parameters are introduced.
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Reports on the topic "Photons migration"

1

Jiang, Huabei. Finite Element Based Photon Migration Imaging. Fort Belvoir, VA: Defense Technical Information Center, May 2002. http://dx.doi.org/10.21236/ada405449.

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Jiang, Huabei. Finite Element Based Photon Migration Imaging. Fort Belvoir, VA: Defense Technical Information Center, May 2003. http://dx.doi.org/10.21236/ada416641.

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Jiang, Huabei. Finite Element Based Photon Migration Imaging. Fort Belvoir, VA: Defense Technical Information Center, May 2004. http://dx.doi.org/10.21236/ada424231.

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Jiang, Huabei. Finite Element Based Photon Migration Imaging. Fort Belvoir, VA: Defense Technical Information Center, May 2000. http://dx.doi.org/10.21236/ada391103.

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Leith, Emmett N. Investigator of Coherence Imaging, Photon Migration, and Short-Pulse Image Processing. Fort Belvoir, VA: Defense Technical Information Center, January 2000. http://dx.doi.org/10.21236/ada391597.

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Hsiang, David J. Monitoring the Response of Chemotherapy on Breast Cancer Tumors by Photon Migration Spectroscopy. Fort Belvoir, VA: Defense Technical Information Center, June 2005. http://dx.doi.org/10.21236/ada439237.

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Hsiang, David J. Monitoring the Response of Chemotherapy on Breast Cancer Tumors by Photon Migration Spectroscopy. Fort Belvoir, VA: Defense Technical Information Center, June 2004. http://dx.doi.org/10.21236/ada427179.

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Hsiang, David J. Monitoring the Response of Chemotherapy on Breast Cancer Tumors by Photon Migration Spectroscopy. Fort Belvoir, VA: Defense Technical Information Center, June 2003. http://dx.doi.org/10.21236/ada418087.

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Quinn, Cathy A., Philip K. Hamilton, Scott D. Kraus, and Christopher K. Slay. An assessment of wounds caused by the attachment of remote sensing tags to North Atlantic right whales (Eubalaena Glacialis): 1988 - 1997. New England Aquarium and Woods Hole Oceanographic Institution, February 2023. http://dx.doi.org/10.1575/1912/29702.

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Because of the increase in usage of remote sensing tags to track the migration and movements of cetaceans, it has become increasingly important to assess the impact of such techniques on the target species. Between 1988 and 1997, 55 tags (41 satellite telemetry, 14 VHF or acoustic radio transmitter) were attached to 49 North Atlantic right whales (Eubalaena glacialis). All tags had implantable barbs or were fully implanted below the dermis. Right whales are photographically identifiable and the New England Aquarium curates the North Atlantic catalog, which currently numbers 374 individuals. The photo catalog has made it possible for tagged individuals to be tracked after the tag falls off the whale. Photo documentation during and after tagging provides an opportunity to monitor physiological effects from tags and healing responses to tags.
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