Photon Penetration Depth Research Articles

A study of the energy absorption and exposure buildup factors of some anti-inflammatory drugs

Human radiation exposure is increasing due to radiation development in science and technology. The development of radioprotective agents is important for protecting patients from the side effects of radiotherapy and for protecting the public from unwanted irradiation. Radioprotective agents are used to reduce the damage caused by radiation in healthy tissues. There are several classes of radioprotective compounds that are under investigation. Analgesics and anti-inflammatory compounds are being considered for treating or preventing the effects of damage due to radiation exposure, or for increasing the chance of survival after exposure to a high dose of radiation. In this study, we investigated the radioprotective effects of some analgesic and anti-inflammatory compounds by evaluating buildup factors. The gamma ray energy absorption (EABF) and exposure buildup factors (EBF) were calculated to select compounds in a 0.015–15MeV energy region up to a penetration depth of 40mfp (mean free path). Variations of EABF and EBF with incident photon energy and penetration depth elements were also investigated. Significant variations in both EABF and EBF values were observed for several compounds at the moderate energy region. At energies below 0.15MeV, EABF and EBF values increased with decreasing equivalent atomic number (Zeq) of the samples. In addition, EABF and EBF were the largest for ibuprofen, aspirin, paracetamol, naproxen and ketoprofen at 0.05 and 0.06MeV, respectively, and the EABF value was 0.1MeV for aceclofenac. From these results, we concluded that the buildup of photons is less for aceclofenac compared to other materials.

Study on γ-ray exposure buildup factors and fast neutron-shielding properties of some building materials

We have computed γ-ray exposure buildup factors (EBF) of some building materials; glass, marble, flyash, cement, limestone, brick, plaster of paris (POP) and gypsum for energy 0.015–15 MeV up to 40 mfp (mfp, mean free path) penetration depth. Also, the macroscopic effective removal cross-sections (ΣR) for fast neutron were calculated. We discussed the dependency of EBF values on photon energy, penetration depth and chemical elements. The half-value layer and kinetic energy per unit mass relative to air of building materials were calculated for assessment of shielding effectiveness. Shielding thicknesses for glass, marble, flyash, cement, limestone and gypsum plaster (or Plaster of Paris, POP) were found comparable with ordinary concrete. Among the studied materials limestone and POP showed superior shielding properties for γ-ray and neutron, respectively. Radiation safety inside houses, schools and primary health centers for sheltering and annual dose can be assessed by the determination of shielding parameters of common building materials.

Large penetration depth of near-field heat flux in hyperbolic media

We compare super-Planckian thermal radiation between phonon-polaritonic media and hyperbolic metamaterials. In particular, we determine the penetration depth of thermal photons inside the absorbing medium for three different structures: two semi-infinite phonon-polaritonic media supporting surface modes, two multilayer hyperbolic metamaterials and two nanowire hyperbolic metamaterials. We show that for hyperbolic modes the penetration depth can be orders of magnitude larger than for surface modes suggesting that hyperbolic materials are much more preferable for near-field thermophotovoltaic applications than pure phonon-polaritonic materials.

IPhone 4s Photoplethysmography: Which Light Color Yields the Most Accurate Heart Rate and Normalized Pulse Volume Using the iPhysioMeter Application in the Presence of Motion Artifact?

Recent progress in information and communication technologies has made it possible to measure heart rate (HR) and normalized pulse volume (NPV), which are important physiological indices, using only a smartphone. This has been achieved with reflection mode photoplethysmography (PPG), by using a smartphone’s embedded flash as a light source and the camera as a light sensor. Despite its widespread use, the method of PPG is susceptible to motion artifacts as physical displacements influence photon propagation phenomena and, thereby, the effective optical path length. Further, it is known that the wavelength of light used for PPG influences the photon penetration depth and we therefore hypothesized that influences of motion artifact could be wavelength-dependant. To test this hypothesis, we made measurements in 12 healthy volunteers of HR and NPV derived from reflection mode plethysmograms recorded simultaneously at three different spectral regions (red, green and blue) at the same physical location with a smartphone. We then assessed the accuracy of the HR and NPV measurements under the influence of motion artifacts. The analyses revealed that the accuracy of HR was acceptably high with all three wavelengths (all rs > 0.996, fixed biases: −0.12 to 0.10 beats per minute, proportional biases: r = −0.29 to 0.03), but that of NPV was the best with green light (r = 0.791, fixed biases: −0.01 arbitrary units, proportional bias: r = 0.11). Moreover, the signal-to-noise ratio obtained with green and blue light PPG was higher than that of red light PPG. These findings suggest that green is the most suitable color for measuring HR and NPV from the reflection mode photoplethysmogram under motion artifact conditions. We conclude that the use of green light PPG could be of particular benefit in ambulatory monitoring where motion artifacts are a significant issue.

The gamma-ray and neutron shielding factors of fly-ash brick materials

A comprehensive study of gamma-ray exposure build-up factors (EBFs) of fly-ash brick materials has been carried out for photon energies of 0.015–15 MeV up to a penetration depth of 40 mfp (mean free path) by a geometrical progression (GP) fitting method. The EBF values of the fly-ash brick materials were found to be dependent upon the photon energy, penetration depth and chemical composition, and were found to be higher than the values for mud bricks and common bricks. Above a photon energy of 3 MeV for large penetration depths (>10 mfp), the EBF becomes directly proportional to Zeq. EBFs of fly-ashes were found to be less than or equal to those of concrete for low penetration depths (<10 mfp) for intermediate photon energies up to 1.5 MeV. The EBF values of fly-ash materials were found to be almost independent of Si concentration. The fast neutron removal cross sections of the fly-ash brick materials, mud bricks and common bricks were also calculated to understand their shielding effectiveness. The shielding effectiveness of the fly-ash materials against gamma-ray radiation was lower than that of common and mud bricks.

Epidural catheter with integrated light guides for spectroscopic tissue characterization

Epidural catheters are used to deliver anesthetics and opioids for managing pain in many clinical scenarios. Currently, epidural catheter insertion is performed without information about the tissues that are directly ahead of the catheter. As a result, the catheter can be incorrectly positioned within a blood vessel, which can cause toxicity. Recent studies have shown that optical reflectance spectroscopy could be beneficial for guiding needles that are used to insert catheters. In this study, we investigate the whether this technique could benefit the placement of catheters within the epidural space. We present a novel optical epidural catheter with integrated polymer light guides that allows for optical spectra to be acquired from tissues at the distal tip. To obtain an initial indication of the information that could be obtained, reflectance values and photon penetration depth were estimated using Monte Carlo simulations, and optical reflectance spectra were acquired during a laminectomy of a swine ex vivo. Large differences between the spectra acquired from epidural adipose tissue and from venous blood were observed. The optical catheter has the potential to provide real-time detection of intravascular catheter placement that could reduce the risk of complications.

Modeling of InGaN p-n junction solar cells

InGaN p-n junction solar cells with various indium composition and thickness of upper p-InGaN and lower n-InGaN junctions are investigated theoretically. The physical properties of InGaN p-n junction solar cells, such as the short circuit current density (JSC), open circuit voltage (Voc), fill factor (FF), and conversion efficiency (η), are theoretically calculated and simulated by varying the device structures, position of the depletion region, indium content, and photon penetration depth. The results indicate that an In0.6Ga0.4N solar cell, with optimal device parameters, can have a JSC ~31.8 mA/cm2, Voc ~0.874 volt, FF ~0.775, and η ~21.5%. It clearly demonstrates that medium-indium-content InGaN materials have the potential to realize high efficiency solar cells. Furthermore, the simulation results, with various thicknesses of the p-InGaN junction but a fixed thickness of the n-InGaN junction, shows that the performance of InGaN solar cells is determined by the upper p-InGaN junction rather than the n-InGaN substrate. This is attributed to the different amount of light absorption in the depletion region and the variation of the collection efficiency of minority carriers.

Gamma-ray exposure build-up factors of some brick materials in the state of Punjab

The gamma-ray exposure build-up factors of raw materials of bricks (soils and fly-ashes) in the state of Punjab were investigated for the photon energy range 0.015 to 15 MeV up to 40 mfp penetration depth by the geometrical progression (GP) method. Appreciable variations in the exposure build-up factor (EBF) are noted for the raw materials. The EBFs of the raw materials of bricks change depending on the photon energy, penetration depth and chemical composition. The build-up factors are low at low and high photon energies, whereas they are very high in the medium-energy region. The peak energy of the EBF for soils is 0.3 MeV and 0.2 MeV for fly ashes. The EBFs of the raw materials of bricks are also compared with those of bricks of red mud and common brick materials. Common bricks were found to have the lowest gamma-ray EBF. This study should be useful for emergency preparedness planning and emergency dose estimation for future planned nuclear power plants in the state of Punjab.

Minimization of Parallax Error in Dedicated Breast PET

The increase of the detector thickness and the incidence angle of impinging photons permits an enhancement of sensitivity in positron emission tomography (PET) scanners. But also increases the parallax error and leads to a worsening of spatial resolution. Instead of introducing hardware modifications in the readout electronics or in the detector, we propose in this work to model the photon penetration depth in the detector material and to account for this effect during the image reconstruction. The validation of the model was based on experimental measurements with the MAMMI breast dedicated PET. It consists of twelve detector modules of monolithic LYSO scintillators. A point-like source was acquired at several radial positions across the field of view. The performance of the model was analyzed in terms of position accuracy and spatial resolution. Full width at half maximum (FWHM) average improvement values of 1.0 mm (radial), 0.4 mm (tangential), and 0.3 mm (axial) have been measured when the photon penetration depth was taken into account. The use of the model proposed in this work allows us to design PET detectors with improved sensitivity while maintaining the spatial resolution of the scanner.

Studies on energy absorption and exposure buildup factors in some solutions of alkali metal chlorides

Buildup of photons has been investigated through the solutions LiCl, NaCl and KCl with different salt contents in the energy region 0.015-15 MeV up to a penetration depth of 40 mean free paths. Two types of buildup factors, the gamma ray energy absorption () and exposure buildup factors () have been calculated simultaneously using the five parameter geometric progression (G-P) fitting formula. The influence of photon energy, penetration depth and chemical composition on the buildup factors has been studied. Also, a comparison has been made between the values of and if any significant variation occurs between them. Moreover, the Monte Carlo simulation study has been made for the purpose of the comparison. Key words: Gamma ray buildup factor, energy absorption, exposure, solution, Monte Carlo method.

Study of Gamma Ray Exposure Buildup Factor for Some Ceramics with Photon Energy, Penetration Depth and Chemical Composition

Gamma ray exposure buildup factor for some ceramics such as boron nitride (BN), magnesium diboride (MgB2), silicon carbide (SiC), titanium carbide (TiC) and ferrite (Fe3O4) has been computed using five parametric geometric progression (G.P.) fitting method in the energy range of 0.015 to 15.0 MeV, up to the penetration of 40 mean free path (mfp). The variation of exposure buildup factors for all the selected ceramics with incident photon energy, penetration depth, and chemical composition has been studied.

Comparison of thermal shock damages induced by different simulation methods on tungsten

Abstract In this work two simulation methods for transient events on tungsten are compared. ELM-like thermal shock tests were performed with the electron beam device JUDITH 1 and a pulsed Nd:YAG laser on pure tungsten. The major difference between these two simulation methods is the surface near volumetric loading in case of the e-beam while the penetration depth of photons is negligible. Beside the definition of damage threshold values special attention was paid to the analysis of induced damages like surface modifications and crack formation. The obtained results indicate that there are no qualitative differences in the damage behaviour and the damage threshold values of tungsten for both simulation techniques. Slight differences of crack parameters are a result of geometric effects due to differences of the exposed areas. A more distinct impact results from the fast scanning of the sample (e-beam) in contrast to the homogenous loading (laser) which results in different surface modification.

Energy Absorption Buildup Factor Studies In Some Soils

An attempt is made to generate effective atomic number, energy absorption buildup factor (EABF) in the energy region 0.015-15.0 MeV up to a penetration depth of 40 mfp for some soils. The five parameters geometrical progression (G-P) fitting approximation has been used to calculate energy absorption build-up factor (EABF). The generated energy absorption buildup factors has been studied as function of incident photon energy & penetration depth and represented graphically. Index Terms: Energy absorption build-up factor (EABF), Mean free path (mfp), Effective atomic number (Zeff ), Equivalent atomic number (Zeq). I. INTRODUCTION Today, to benefit mankind, the radiations are used in basic sciences, medicine, and industry and for generating electricity Gamma radiations occupy the highest energy among the electromagnetic radiations. The exposure to gamma radiations with human body can occur during radiological diagnosis , nuclear reactors & nuclear research establishments .The use of radiations can be biologically hazardous, there is need of restrict and controlled exposure of human beings to these radiations by using shields of proper dimensions and of an appropriate material. The study has been focused on build-up factor which plays major role during interaction of gamma rays with the chosen soils. Nuclear accidents due to natural and manmade disasters cannot be refused in future. To avoid any hazard from day to day exposure of radiation the choice of material is very important for the purpose of shielding of radiations. People involved in industries, institutions & research labs may be the victim of gamma ray exposure. For the safety of people & selection of shielding materials, build-up factors study become important. When gamma radiations interact with material through Compton scattering. The scattering results in accumulation of photons in the interacting material due to which the number of photons buildup in the materials. Two types of build-up factors namely energy absorption build-up factor (EABF) & exposure build-up factor ( EBF). The concept of buildup factor was mutually introduced by White (1) and Fano (2) recognized its importance in attenuation studies.To calculate build-up factor there are different methods like G.P. fitting method. Harima et al. 1986 (3), invariant embedding method, Shimizu, 2002 (4); Shimizu et al., 2004 (5), iterative method, Suteau and Chiron, 2005 (6) and Monte Carlo method, Sardari et al., 2009 (7). Recently American National standards ANSI/ANS-6.4.3(8) has provided buildup factor data for 23 elements, one compound and two mixtures (i.e. air and water) and concrete at energies in the range 0.015-15 MeV up to penetration depths of 40 mfp by using the G.P method. D.Sardari and S. Baradaran 2010 (9) calculated buildup factor of gamma and X-ray photon the energy range of 0.2-2.0 MeV in water and soft tissue using Monte Carlo code MCNP4C. The results are compared with buildup factor data of pure water. In each case very small deviation is observed. There are successful contributions which are based on the buildup factor studies in some soils and ceramic materials available in the literature. For example, Brar et al. (10) have studied the variation of buildup factors of soils with weight fractions of iron and silicon. Sidhu et al. (11) have studied the energy and effective atomic number dependence of the exposure buildup factors in biological samples. Manohara et al. (12) studied the variation of exposure buildup factors for heavy metal oxide glass with photon energy and penetration depth. Singh et al. (13) studied the energy dependence of total photon attenuation coefficients of composite materials Sidhu et al. (14) have studied the energy and effective atomic number dependence of the exposure build-up factors in biological samples J. S. Dhillon et al.(15) have studied Gamma Ray Photon Energy Absorption build-up Factor In Some Soil II.

Photon energy absorption buildup factors of gaseous mixtures used in radiation detectors

Gamma-ray energy absorption buildup factors of gaseous mixtures; neon (95%) + argon (5%), argon (95%) + acetylene (5%), argon (95%) + methane (5%), argon (95%) + carbon dioxide (5%), methane (70%) + pentane (30%) and argon (90%) + methane (10%) were studied by Geometrical Progression (G-P) fitting for the photon energy range 0.015-15 MeV. It was found that the equivalent atomic number, Z eq of the gaseous mixtures sharply reduces after 1 MeV photon energy. The Z eq for the mixture of methane (70%) + pentane (30%) is the minimum, whereas the maximum is for argon (95%) + carbon dioxide (5%) for the photon energies under investigation. The Energy Absorption Buildup Factor (EABF) for methane (70%) + pentane (30%) was found to be the highest among all the selected gaseous mixtures. The chemical composition of the gaseous mixtures has an impact on the EABF values for photon energy and penetration depth. The investigation of the EABF is useful for selection of gaseous mixtures in design consideration of gaseous radiation detectors for gamma radiation.

Vanadium Compounds: As Gamma Rays Shielding Material

Various parameters of dosimetric interest such as mass attenuation coefficient (μm), equivalent atomic number (Zeq), exposure buildup factors (Bex) have been computed for some vanadium compounds (VF3, VF4, VO2 and V2O3) in the photon energy range from 15.0 keV to 15.0 MeV to visualize the feasibility of using these compounds as gamma rays shielding material. The variation of various parameters has been studied as a function of incident photon energy, penetration depth and chemical composition of the selected vanadium compounds. For the better gamma rays shielding material, the equivalent atomic number must be higher and exposure buildup factor must be least. Among the selected vanadium compounds; V2O3 possess such qualities, hence it offers better shielding from gamma rays than the other selected vanadium compounds.

Plasma Deactivation of Endotoxic Biomolecules: Vacuum Ultraviolet Photon and Radical Beam Effects on Lipid A

AbstractIt is widely accepted that plasma‐generated energetic and reactive species are responsible for plasma‐induced sterilization; however, how these species act alone or synergistically to deactivate endotoxic biomolecules is not completely understood. Using a vacuum beam system, we study the effects of vacuum ultraviolet (VUV) radiation, oxygen and deuterium radicals on lipid A, the immune‐stimulating region of lipopolysaccharide. VUV‐induced photolysis causes bulk modification of exposed lipid A film up to the penetration depth of VUV photons, ≈200 nm. Although radical‐induced etch yield of lipid A is lower than VUV‐induced photolysis, secondary ion mass spectrometry and human whole blood‐based assay suggest that radicals render a higher degree of modification at the film surface. This study contributes to the fundamental understanding of plasma effects on biomolecules for a better deactivation scheme and applications. magnified image

Absorption of acrylates and polysilazanes in the far UVC and the VUV regions

A simple but reliable method was developed for the determination of wavelength-dependent absorption coefficients in the vacuum-UV (VUV) spectral range 160 nm < λ < 195 nm. Absorption coefficients were determined on thin layers of UV curable compounds like acrylates and of polysilazanes, which are subject to photo-induced conversion into SiOx layers. Results were discussed in terms of changing values of the absorption coefficients during irradiation. In case of acrylates polymerization leads to the decrease of the absorption coefficients especially in the wavelength range about 195 nm from about 10 μm−1 to about 1 μm−1. Results of quantum-chemical calculations explain this finding by the depletion of double bonds for which ππ* transitions are characteristic. XPS depth profiles reveal the VUV induced degradation of carboxyl and ether functionalities in a thin surface layer corresponding to the penetration depth of the VUV photons.

Laser beam induced current measurements of Cd1−xZnxS/CdTe solar cells

The role of the window layer in Cd1−xZnxS/CdTe photovoltaic (PV) device structures was investigated using a triple wavelength laser beam induced current (LBIC) technique. Full pn structures were deposited using metal organic chemical vapour deposition (MOCVD). The triple wavelength LBIC technique allowed for the diagnostic analysis of carrier collection uniformity at 3 wavelength dependent photon penetration depths, δp. An assessment of the Cd1−xZnxS window layer film thickness and surface coverage showed a correlation between lateral device performance and window layer thickness distribution. Islands of thick Cd1−xZnxS were shown to increase localised blue absorption, correlating to isolated regions of increased red and IR photoresponse. Overall device open-circuit voltage, Voc is shown to demonstrate a linear dependence on thick (∼300nm) Cd1−xZnxS surface coverage. Voc and shunt resistance Rsh losses attributed to the window layer were found to jointly contribute to the overall cell efficiency losses. A non-uniform pin-hole distribution, leading to Rsh loss, was found to be independent of the overall Cd1−xZnxS thickness distribution; thus the triple wavelength LBIC measurement was able to identify causes for the observed losses in both Voc and Rsh.

Measuring Nanolayer Profiles of Various Materials by Evanescent Light Technique

The evanescent light photon extraction efficiency of insulator, semiconductor and conductor amorphous nanolayers deposited on glass waveguides was evaluated from Differential Evanescent Light Intensity measurements. The Differential Evanescent Light Intensity technique uses the evanescent field scattered by the deposited nanolayer, enabling nanometer thickness profiling due to the high inherent dark background contrast. The results show that the effective evanescent photon penetration depth increases from metal to semiconductor and then to insulating layers, establishing thus the effective photon-material interaction length for the various materials classes.

A Comprehensive Study on Energy Absorption and Exposure Buildup Factors for some Soils and Ceramic Materials

Study of gamma ray energy absorption (EABF) and exposure buildup factors (EBF) for some essential soils, ceramic materials in the energy region 0.015-15 MeV up to a penetration depth of 40 mfp (mean free path). To calculate both EABF and EBF, five parameter geometric progressions (G-P) fitting approximation has been used. Variation of EABF and EBF with incident photon energy, penetration depth and effective atomic number (Zeff) has been studied and presented in the form of graphs. This change results from the dominance of different interaction process in different energy regions. Significant variations were also observed between EABF and EBF which may due to different chemical composition of given materials. Keywords: Cascade silt loam (CSL), Energy absorption buildup factor, Exposure buildup factor, Kaolinite (KLN), Mica, Sand.