Mean Energy Loss Research Articles

Proton straggling in thick silicon detectors

Straggling functions for protons in thick silicon radiation detectors are computed by Monte Carlo simulation. Mean energy loss is constrained by the silicon stopping power, providing higher straggling at low energy and probabilities for stopping within the detector volume. By matching the first four moments of simulated energy-loss distributions, straggling functions are approximated by a log-normal distribution that is accurate for Vavilov κ≳0.3. They are verified by comparison to experimental proton data from a charged particle telescope.

A comparative study of inelastic scattering models at energy levels ranging from 0.5 keV to 10 keV

Six models, including a single-scattering model, four hybrid models, and one dielectric function model, were evaluated using Monte Carlo simulations for aluminum and copper at incident beam energies ranging from 0.5keV to 10keV. The inelastic mean free path, mean energy loss per unit path length, and backscattering coefficients obtained by these models are compared and discussed to understand the merits of the various models. ANOVA (analysis of variance) statistical models were used to quantify the effects of inelastic cross section and energy loss models on the basis of the simulated results deviation from the experimental data for the inelastic mean free path, the mean energy loss per unit path length, and the backscattering coefficient, as well as their correlations. This work in this study is believed to be the first application of ANOVA models towards evaluating inelastic electron beam scattering models. This approach is an improvement over the traditional approach which involves only visual estimation of the difference between the experimental data and simulated results. The data suggests that the optimization of the effective electron number per atom, binding energy, and cut-off energy of an inelastic model for different materials at different beam energies is more important than the selection of inelastic models for Monte Carlo electron scattering simulation. During the simulations, parameters in the equations should be tuned according to different materials for different beam energies rather than merely employing default parameters for an arbitrary material. Energy loss models and cross-section formulas are not the main factors influencing energy loss. Comparison of the deviation of the simulated results from the experimental data shows a significant correlation (p<0.05) between the backscattering coefficient and energy loss per unit path length. The inclusion of backscattering electrons generated by both primary and secondary electrons for backscattering coefficient simulation is recommended for elements with high atomic numbers. In hybrid models, introducing the inner shell ionization model improves the accuracy of simulated results.

Comparison of the Performance of a Sutureless Bioprosthesis With Two Pericardial Stented Valves on Small Annuli: An In Vitro Study

Aortic valve replacement has evolved recently with the development of the sutureless bioprosthesis. One such valve is the Perceval bioprosthesis, which is built by mounting leaflets of bovine pericardium to a thin stent; this approach has the potential to provide an excellent fluid dynamic performance. We undertook an invitro study to compare the hydrodynamic performance of the sutureless bioprosthesis with two standard pericardial stented bioprostheses (Crown and Magna). Tests were conducted using a mock loop, testing on two sizes of the three prostheses. The prosthesis sizes were chosen to house the valves in porcine aortic roots with a native annulus diameter of 19 mm (n= 6) or 21 mm (n= 6). The stroke volume ranged from 25 mL to 105 mL at a simulated heart rate of 70 beats per minute. Mean pressure drop and energy loss rose with increasing stroke volume in all of the valves tested (p<0.001), with the sutureless valve showing the lowest values for both variables (p < 0.001). Effective orifice area values were stable across the stroke volume intervals and were larger in the sutureless valves (p < 0.001). All of the valves tested provided good fluid dynamic performances. The sutureless bioprosthesis provided the best performance with the least hindrance to flow behavior. From the hydrodynamic perspective, the sutureless prosthesis may present an advance in the evolution of bioprostheses, ensuring low gradients and potential for low incidence of patient-prosthesis mismatch even in small annuli.

Measurement of Energy Loss Straggling of Relativistic Electrons in Thin Aluminum Foils

The mean energy loss straggling per unit path length of relativistic electrons in aluminum has been determined by recording electrons with a Si(Li) detector coupled to 8K multi channel analyzer. The energy loss straggling is determined by measuring the full width at half maximum of the spectrum of the incident and transmitted internal conversion electrons of energies 942 keV and 1016 keV from Bi source. Measured values have been compared with theoretical values indicating that the present method can be used for measuring mean energy loss straggling.

Suppression in p-A collisions from charm quark energy loss in cold nuclear matter

The energy loss effect of charm quarks in cold nuclear matter on suppression in p-A collisions is studied. By means of two parametrizations of quark energy loss, the leading-order computations for production cross section ratios are presented and compared with the selected E866 experimental data, with the remaining colored on its entire path in the medium. It is found that the energy loss of the color octet is an important effect in suppression; however, whether it is linear or quadratic with the path length cannot be determined. The successful description of suppression in gives the charm quark mean energy loss per unit path length /fm. Using the same quark energy loss model, we further give the phenomenological analysis at the leading order for production cross section ratios as a function of y for the Large Hadron Collider experimental data.

Energetic investigation of the fatigue of wood

Abstract There are gaps in our knowledge regarding temporal changes in wood stability and mechanical properties in the context of wood durability. Energetic analyses have been performed in this study based on experimental results on the bending fatigue of wood under multiple loading conditions. New findings regarding the fatigue limit and fatigue life (N f) are presented. The strain energy (SE) obtained from stress-strain envelopes until wood reaches its N f is a value specific to wood species and static strength regardless of the loading conditions. This value is about 50% higher than the SE in static tests. The relationship between mean energy loss (EL) and stress level (SL) to the point of fatigue failure is bilinear, and the mean EL is closely related to N f. Moreover, the SL – when mean EL approaches a specific value (∼1.10 kJ m-3 per cycle) as N f approaches infinity – is considered to be the fatigue limit; the latter is estimated to be about 20–30% of static strength.

Impact of Obesity and Nonobesity on Grading the Severity of Aortic Valve Stenosis

We tested the hypothesis that the disproportionate increase of body surface area in obesity may lead to the overestimation of aortic stenosis (AS) severity when the aortic valve area (AVA) is indexed (AVAI) for body surface area in 1,524 patients enrolled in the Simvastatin and Ezetimibe in AS study. Obesity was defined as a body mass index of ≥30kg/m(2). Peak aortic jet velocity, mean aortic gradient, AVA, and energy loss (EL) did not differ, although AVAI and EL indexed (ELI) for body surface area were significantly smaller in the obese group (n= 321) compared with the nonobese (n= 1,203) group (both p <0.05). Severe AS by AVAI (<0.6cm(2)/m(2)) but nonsevere by AVA (>1.0cm(2); AVAI/AVA discordance) was found in 15% of the patients, whereas severe AS by ELI (<0.6cm(2)/m(2)) but nonsevere by EL (>1.0cm(2); ELI/EL discordance) was found in 9% of the patients. Obesity was associated with a 2.4-fold higher prevalence of AVAI/AVA discordance and a 1.6-fold higher prevalence of ELI/EL discordance. Discordant grading was also associated with male gender, larger body size, higher mean aortic gradient, and stroke volume (all p <0.05). During a median follow-up of 4.3years, 419 patients were referred for aortic valve replacement and 177 patients died or were hospitalized because of heart failure. In the Cox regression analyses, AVAI/AVA discordance was associated with a 28% higher rate of aortic valve replacement (p <0.05) but did not predict the rate of combined death and hospitalization for heart failure. In conclusion, using AVAI and ELI for the grading of stenosis in patients with obesity may lead to overestimation of true AS severity.

Stopping of a relativistic electron beam in a plasma irradiated by an intense laser field

AbstractThe effects of a radiation field (RF) on the interaction process of a relativistic electron beam (REB) with an electron plasma are investigated. The stopping power of the test electron averaged with a period of the RF has been calculated assuming an underdense plasma, ω0 &gt; ωp, where ω0is the frequency of the RF and ωpis the plasma frequency. In order to highlight the effect of the radiation field we present a comparison of our analytical and numerical results obtained for nonzero RF with those for vanishing RF. In particular, it has been shown that the weak RF increases the mean energy loss for small angles between the velocity of the REB and the direction of polarization of the RF while decreasing it at large angles. Furthermore, the relative deviation of the energy loss from the field-free value is strongly reduced with increasing the beam energy. Special case of the parallel orientation of the polarization of the RF with respect to the beam velocity has been also considered. At high-intensities of the RF two extreme regimes have been distinguished when the excited harmonics cancel effectively each other reducing strongly the energy loss or increasing it due to the constructive interference. Moreover, it has been demonstrated that the energy loss of the ultrarelativistic electron beam increases systematically with the intensity of the RF exceeding essentially the field-free value.

Ionization cross section data of nitrogen, methane, and propane for light ions and electrons and their suitability for use in track structure simulations

Track structure Monte Carlo simulations are frequently applied in micro- and nanodosimetry to calculate the radiation transport in detail. The use of a well-validated set of cross section data in such simulation codes ensures accurate calculations of transport parameters, such as ionization yields. These cross section data are, however, scarce and often discrepant when measured by different groups. This work surveys literature data on ionization and charge-transfer cross sections of nitrogen, methane, and propane for electrons, protons, and helium particles, focusing on the energy range between 100 keV and 20 MeV. Based on the evaluated data, different models for the parametrization of the cross section data are implemented in the code ptra, developed for simulating proton and alpha particle transport in an ion-counting nanodosimeter. The suitability of the cross section data is investigated by comparing the calculated mean ionization cluster size and energy loss with experimental results in either nitrogen or propane. For protons, generally good agreement between measured and simulated data is found when the Rudd model is used in ptra. For alpha particles, however, a considerable influence of different parametrizations of cross sections for ionization and charge transfer is observed. The ptra code using the charge-transfer data is, nevertheless, successfully benchmarked by the experimental data for the calculation of nanodosimetric quantities, but remaining discrepancies still have to be further investigated (up to 13% lower energy loss and 19% lower mean ionization cluster size than in the experiment). A continuation of this work should investigate data for the energy loss per interaction as well as differential cross section data of nitrogen and propane. Interpolation models for ionization and charge-transfer data are proposed. The Barkas model, frequently used for a determination of the effective charge in the ionization cross section, significantly underestimates both the energy loss (by up to 19%) and the mean ionization cluster size (up to 65%) for alpha particles. It is, therefore, not recommended for particle-track simulations.

Multiple excitation of Fuchs–Kliewer phonons by Ne+ ions back-scattered by the LiF(100) surface at grazing incidence

An analytic model is developed to describe the inelastic processes occurring when keV Ne+ ions are scattered at grazing incidence by the (100) surface of LiF. The large energy losses (up to 30 eV) of the reflected Ne+ particles reported by Borisov et al (1999 Phys. Rev. Lett. 83 5378) are shown to arise specifically from the long-range coupling between the projectiles and the so-called Fuchs–Kliewer (FK) optical phonons of LiF whose fields extend far outside the surface. The strength of the coupling is estimated, allowing one to compute the average number of excited FK phonon quanta (ħωS = 0.071 eV) and hence the mean energy losses. For emerging, neutralized Ne0, a distinct energy loss mechanism is shown to occur, namely the excitation of FK phonons and other types of surface collective modes associated with the screening of the F0 ‘hole’ left behind by the neutralization process. This mechanism contributes a large fraction of the loss, additional to that suffered by the incident Ne+ ion. The model explains the experimental observations quantitatively (1999 Phys. Rev. Lett. 83 5378). The paper ends with a discussion of the large energy broadening of the observed loss peaks.

Proton impact ionization and a fast calculation method

We present a coupled Monte Carlo and multistream model simulating primary ionization and secondary electron ionization, respectively, from energetic proton precipitation in the Earth's upper atmosphere. Good agreement is obtained with previous model results. It is found that while secondary electrons make a negligible contribution to ionization from low‐energy (≤10 keV) auroral proton precipitation, their importance increases with increasing incident proton energy, confirming earlier findings. It becomes significant or even comparable to primary ionization from protons and generated hydrogen atoms in charge‐changing collisions. Our calculations of the mean energy loss per ion pair production show a nearly monotonic increase with incident proton energy, ranging from about 22 eV to 33 eV when incident energy increases from 100 eV to 1 MeV. To facilitate a fast calculation in large‐scale computations, we develop a parameterization for total (primary plus secondary) ionization from monoenergetic proton precipitation. This is obtained by fitting to a large set of numerical results from the coupled model. The quick method applies to a wide energy range of 100 eV to 1 MeV for incident monoenergetic protons, and its validity has been extensively tested under a variety of background atmospheric conditions. Our new parameterization can be used to rapidly calculate the ionization altitude profile from precipitating protons with any spectral distributions without any significant compromise in accuracy. By considering branching ratios of ionized atmospheric species, the fast calculation method is thus useful for self‐consistently including proton impact effects in large community models.

Estimating energy losses with urine in the cat

Urinary energy losses in cats have to be determined in energy balance trials as well as for the calculation of the metabolizable energy (ME) content of cat food. The aim of the present study was: first, to assess whether the energy content of cat urine quantified by bomb calorimetry differs from that quantified using GE (kJ) urine=33kJ×g C urine+9kJ×g N urine and investigate whether this difference could be attributed to influences of diets. Second, to assess whether the subtraction of 3.1kJ/g of protein intake used for estimation of metabolizable energy content of cat foods is confirmed as usable. Data from 27 energy and protein balance trials from different studies with complete sampling of urine and faeces (29 cats in part A and 35 cats in part B) were used. Gross energy, carbon and nitrogen were determined in food, faeces and urine. Gross energy values in urine tended to be higher when determined with the formula of Hoffman and Klein compared to bomb calorimetry. The average relative difference of gross energy values between the methods was 18.8%. The mean energy loss in kJ/g of protein intake resulted in 3.7kJ/g protein intake, which was not statistically significantly different (p=0.12) from the tested value of 3.1kJ/g of protein intake. In conclusion, the formula of Hoffman and Klein is not appropriate for the estimation of energy in cat urine. In balance studies, it is advisable to quantify the urinary energy content by bomb calorimetry. In the second part of the study, the protein correction factor to determine ME of 3.1kJ/g protein intake for urinary energy losses of Kienzle etal. could be confirmed.

Stopping power for electrons in pyrimidine in the energy range 20–3000 eV

In this work, we present new experimental electron energy loss distribution functions for pyrimidine (C4H4N2) measured for the incident energy range 30–2000eV. Theoretical total and elastic cross sections for electron scattering from pyrimidine were calculated using the screening-corrected additivity rule (IAM-SCAR) method. Based on the mean energy loss observed in the experiment and the theoretical integral inelastic cross section, the stopping power for electrons in pyrimidine is calculated in the energy range 20–3000eV.

Elastic hysteresis in human eyes is an age‐dependent value

The elastic hysteresis phenomenon is observed when cyclic loading is applied to a viscoelastic system. The purpose of this study was to quantitatively evaluate elastic hysteresis in living human eyes against an external force. Prospective case series. Twenty-four eyes of 24 normal human subjects (mean age: 41.5 ± 10.6 years) were recruited. A non-contact tonometry process was recorded with a high-speed camera. Central corneal thickness, corneal thickness at 4 mm from the centre, corneal curvature and anterior chamber depth were measured. Intraocular pressure was also measured using Goldmann applanation tonometry and dynamic contour tonometer. Energy loss due to elastic hysteresis was calculated and graphed. The mean central corneal thickness was 552.5 ± 36.1 µm, corneal curvature was 7.84 ± 0.26 mm and anterior chamber depth was 2.83 ± 0.29 mm. The mean Goldmann applanation tonometry-intraocular pressure was 14.2 ± 2.7 mmHg and dynamic contour tonometer-intraocular pressure was 16.3 ± 3.5 mmHg. The mean energy loss due to elastic hysteresis was 3.90 × 10(-6) ± 2.49 × 10(-6) Nm. Energy loss due to elastic hysteresis correlated significantly with age (Pearson correlation coefficient = 0.596, P = .0016). There were no significant correlations between energy loss due to elastic hysteresis and other measurements. Energy loss due to elastic hysteresis in the eyes of subjects was found to positively correlate with age, independent of anterior eye structure or intraocular pressure. Therefore, it is believed that the viscosity of the eye increases with age.

Elastic hysteresis in human eyes is age dependent value.

Background: The elastic hysteresis phenomenon is observed when cyclic loading is applied to a viscoelastic system. The purpose of this study was to quantitatively evaluate elastic hysteresis in living human eyes against an external force. Design: Prospective case series. Participants: Twenty-four eyes of 24 normal human subjects (mean age: 41.5 ± 10.6 years) were recruited. Methods: A non-contact tonometry process was recorded with a high-speed camera. Central corneal thickness (CCT), corneal thickness at 4 mm from the center, corneal curvature, and anterior chamber depth (ACD) were measured. Intraocular pressure (IOP) was also measured using Goldmann applanation tonometry (GAT) and dynamic contour tonometer (DCT). Main Outcome Measures: Energy loss due to elastic hysteresis was calculated and graphed. Results: The mean CCT was 552.5 ± 36.1 µm, corneal curvature was 7.84 ± 0.26 mm, and ACD was 2.83 ± 0.29 mm. The mean GAT-IOP was 14.2 ± 2.7 mmHg and DCT-IOP was 16.3 ± 3.5 mmHg. The mean energy loss due to elastic hysteresis was 3.90 × 10(-6) ± 2.49 × 10(-6) Nm. Energy loss due to elastic hysteresis correlated significantly with age (Pearson correlation coefficient = 0.596, p = 0.0016). There were no significant correlations between energy loss due to elastic hysteresis and other measurements. Conclusion: Energy loss due to elastic hysteresis in the eyes of subjects was found to positively correlate with age, independent of anterior eye structure or IOP. Therefore, it is believed that the viscosity of the eye increases with age. © 2010 The Authors. Clinical and Experimental Ophthalmology © 2010 Royal Australian and New Zealand College of Ophthalmologists.

넙치 Paralichthys olivaceus 대사율에 미치는 수온과 체중의 영향

The effect of water temperature and body weight on oxygen consumption by the fasted olive flounder Paralichthys olivaceus was investigated in order to assess the metabolic rate of this species under different conditions. The oxygen consumption rate (OCR) was measured at three different water temperatures (15, 20 and <TEX>$25^{\circ}C$</TEX>) and two different body weights [<TEX>$9.1{\pm}1.2$</TEX> g (mean<TEX>${\pm}$</TEX>SD) for the juvenile group and <TEX>$266.4{\pm}29.3$</TEX> g for the immature group] at an interval of 5 minutes for 24 hours using a closed flow-through respirometer. For each treatment condition, three replicates were set up and 135 fish in the juvenile group and 18 fish in the immature group were used. The OCRs exhibited a linear increase described by OCR=-82.06+28.30T (<TEX>$r^2$</TEX>=0.96, p<0.001) in the juvenile group and OCR=-52.52+14.73T (<TEX>$r^2$</TEX>=0.97, p<0.001) in the immature group. The OCRs decreased with increasing body weights at a given water temperature (p<0.001). The metabolic rate was related to the body weight of the fish as a power function with a weight exponent of between 0.77 and 0.82. <TEX>$Q_{10}$</TEX> values ranged 1.67~2.28 when the temperature was between 15 and <TEX>$20^{\circ}C$</TEX>, 1.57~1.93 when the temperature was between 20 and <TEX>$250^{\circ}C$</TEX>, and 1.79~1.89 when the temperature was between 15 and <TEX>$250^{\circ}C$</TEX>. The energy expenditure by respiration increased with increasing water temperature and decreasing body weight (p<0.001). The mean energy loss rates at 15, 20 and <TEX>$25^{\circ}C$</TEX> were 115.9, 149.8 and 208.2 kJ <TEX>$kg^{-1}d^{-1}$</TEX> in the juvenile groups and 53.8, 81.2 and 101.9 kJ <TEX>$kg^{-1}d^{-1}$</TEX> in the immature groups.

Energy Down-Conversion and Thermalization in Metal Absorbers

Absorbers play an important role in all radiation detectors, providing effective energy absorption, fast relaxation and spatial expansion of the excitation volume. A review of the details of energy down-conversion in metal absorbers, both normal metals and superconductors, is given. We discuss the initial absorption of a quantum of energy and ejection of a single photoelectron, followed by fast energy down-conversion via the electron-electron and electron-phonon interactions. We describe the spatial and spectral evolution of the distributions of electronic excitations and phonons, together with the mean energy loss and fluctuations. We also review some recent results regarding thermalization in superconductors at low temperatures, a poorly understood area but one which is crucial for many low temperature devices.

Stopping of ions in a plasma irradiated by an intense laser field

AbstractThe inelastic interaction between heavy ions and an electron plasma in the presence of an intense radiation field (RF) is investigated. The stopping power of the test ion averaged with a period of the RF has been calculated assuming that ω0 &gt; ωp, where ω0 is the frequency of the RF and ωp is the plasma frequency. In order to highlight the effect of the radiation field we present a comparison of our analytical and numerical results obtained for nonzero RF with those for vanishing RF. It has been shown that the RF may strongly reduce the mean energy loss for slow ions while increasing it at high–velocities. Moreover, it has been shown, that acceleration of the projectile ion due to the RF is expected at high–velocities and in the high–intensity limit of the RF, when the quiver velocity of the plasma electrons exceeds the ion velocity.

Evolving distribution of hard partons traversing a hot, strongly interacting plasma

We present results for the evolution of the momentum distribution of a hard parton traversing a brick of quark-gluon plasma, considering both bremsstrahlung and collisional energy loss. The complete leading order transition rates are included. We find a significant modification of the evolving momentum distribution compared to results obtained by employing an approximate implementation of the collisional energy loss that uses the mean energy loss, together with momentum diffusion.

Cherenkov radiation from relativistic heavy ions taking account of their slowing down in radiator

Combining the SRIM’06 computer code and the formula for spectral-angular distribution of radiation from a particle moving in a medium in arbitrary trajectory, we studied numerically the structure of angular distributions of Cherenkov radiation from moderately relativistic heavy ions (RHI) taking into account the decrease of the ion velocity due to stopping in the radiator. The results obtained clearly show that the width and the fine structure of the Cherenkov radiation in the vicinity of the Cherenkov cone depend strongly on several factors, e.g. the mean and total energy losses, the radiator thickness, the square of the ion charge, the emission wavelength and the refractive index of the radiator material. This might be useful for experiments using RICH detectors for relativistic heavy ions.