Absorption Correction Research Articles

Charmonia suppression in heavy ion collisions: Hot versus cold matter effects

In this paper we study charmonium suppression in heavy ion collisions and develop a joint microscopic description of the initial- and final-state interactions. In the cold phase, we consider a conventional mechanism of nuclear suppression due to inelastic absorptive interactions. We also take into account a novel production mechanism via fusion of three gluons from different nucleons, which partially compensates the strong suppression of the first term expected in the Large Hadron Collider (LHC) kinematics. In the hot phase, we take into account both the Debye screening and the absorptive correction due to color-exchange interactions with the medium. We found that the latter mechanism becomes dominant for large transverse momenta $\ensuremath{\langle}{p}_{T}\ensuremath{\rangle}\ensuremath{\gtrsim}10\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$. The evaluated suppression ${R}_{AA}$ in our approach is in reasonable agreement with recent experimental data for $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$ in the LHC kinematics.

Self‐consistent absorption correction for quantifying very noisy X‐ray maps: group III nitride nanowires as an example

Energy-dispersive X-ray mapping in a scanning transmission electron microscope is a method to visualize the spatial distribution of chemical elements in a sample. Quantification of the signal intensities depends on proper background elimination and correction of the self-absorption of X-ray lines in the sample. Here we show that our previously developed method of self-consistent effective absorption factors works well even with extremely noise elemental maps of a few net counts only where the human eye can hardly discern any pattern and the background signal is typically less than a single count in each spectrum channel. Correcting the background intensity to sub-pixel accuracy is then necessary for reliable quantification.

I179] SPECT/CT quantitative reconstruction techniques

The last years, the clinical interest in quantitative SPECT/CT imaging is increasing. Especially in the rapidly growing field of radionuclide therapy, quantitative imaging is essential to provide nuclear medicine physicians with accurate dosimetric data. As a result, manufacturers now focus on producing SPECT/CT systems that are intrinsically quantitative. SPECT quantification is more challenging than PET quantification. In fact, the correction for photon absorption is relatively straightforward to apply in PET. In addition, in SPECT, we need to consider a variety of radionuclides with different photon energies and energy windows, different collimators and the potential for drifts in performance due to the greater number of moving parts in a SPECT system. With SPECT/CT, the coregistered CT data provide accurate information on the density of the body tissues, which can be used in algorithms that correct for photons that have been Compton-scattered or attenuated within the body. State-of-the-art reconstruction techniques are based on statistical iterative methods such as the ordered-subset maximum-likelihood expectation maximization algorithm (OSEM). In this approach, the physical characteristics of the acquisition process can be completely modeled in the reconstruction. In this presentation, an overview of all factors affecting SPECT image quantification will be presented. The latest developments to achieve quantitative SPECT/CT reconstruction will be discussed, together with calibration issues to finally obtain radioactivity concentrations per unit volume (kBq/ml).

Mechanism of Li3PS4 Liquid Phase Synthesis By Total X-Ray Scattering Measurement Coupled to Pair Distribution Function Analysis

Introduction All-solid-state batteries are one of the most promising candidates for next generation batteries because of their safety property and high power density1. The sulfur solid electrolyte is prepared conventionally by hand-mixing in the all-solid-state batteries. The ball-milling method is not suitable for large-scale preparation. Therefore it is important to develop the large-scale synthesis method of solid electrolyte. Recently, some research groups have reported on the synthesis of Li3PS4 electrolyte via liquid phase by dissolving the starting sulfide materials such as Li2S and P2S5 in organic solvents2. However, the formation mechanism has not been clearly understood. In this study, we evaluate a local structure change of Li3PS4 (LPS) in the liquid phase synthesis process by total X-ray scattering measurement coupled with pair distribution function (PDF) analysis to clarify the formation mechanism. Experimental Li3PS4 was prepared by liquid-phase shaking method as previously reported2. Li2S (Sigma-Aldrich), P2S5(Sigma-Aldrich), dehydrated ethyl propionate (Sigma-Aldrich) and zirconia balls were added in centrifugation tube and shaken under Ar atmosphere from 0 min to 360 min at 1500 rpm. The tube was centrifuged at 10000 rpm for 5 min. The supernatant was decanted and the residual solvent was evacuated at room temperature. Then the precursor was annealed at 170 ºC in low pressure for 2 h. The high-energy X-ray diffraction experiments were carried out at the beamline BL08W using a two-dimensional detector in SPring-8, Japan. The incident X-ray energy was 115 keV. The diffraction patterns of the samples and an empty tube were measured in the transmission geometry. The obtained data of each sample was corrected for background, absorption correction, multiple scattering and inelastic scattering. Results and discussion Figure 1 shows that reduced pair distribution functions, G(r), obtained from a Fourier transformation of total structure factors for each liquid phase sample. In the initial stage of the synthesis process, peaks were attributed to the starting materials of P2S5 and Li2S. In the middle stage of the synthesis process, although the intensity of the peak from Li2S decrease, intensity of the first peak from P-S bond of PS4 tetrahedral anion increased. In the end stage of the synthesis process, two peaks, which were observed in Li3PS4 obtained by subsequent annealing treatment, appeared around 3.3 Å, 4.0 Å. These results indicate that the locally ordered structure of Li2S is broken while the locally ordered structure at short range is grown in the middle stage of the synthesis process. In the end stage of the synthesis process, locally ordered structure at middle range of Li3PS4 forms with keeping locally ordered structure at the short range. Acknowledgement This research was financially supported by the Japan Science and Technology Agency (JST), Advanced Low Carbon Technology Research and Development Program (ALCA), Specially Promoted Research for Innovative Next Generation Batteries (SPRING) Project. Figure 1

Accurate data processing for neutron Laue diffractometers

The factors affecting the accuracy of structural refinements from image-plate neutron Laue diffractometers are analysed. From this analysis, an improved data-processing method is developed which optimizes the intensity corrections for exposure scaling, wavelength distribution, absorption and extinction corrections, and the wavelength/spatial/time dependence of the image-plate detector efficiencies. Of equal importance is an analysis of the sources of uncertainty in the final corrected intensities, without which bias of the merged intensities occurs, due to the dominance of measurements with small statistical errors though potentially large systematic errors. A new aspect of the impact of detector crosstalk on the counting statistics of area detectors is reported and shown to be significant for the case of neutron Laue diffraction. These methods have been implemented in software which processes data from the KOALA instrument at ANSTO and the now decommissioned VIVALDI instrument at ILL (Grenoble, France). A comparison with earlier data-analysis methods shows a significant improvement in accuracy of the refined structures.

Relative L3 transition probabilities of titanium compounds as a function of the oxidation state using high-resolution X-ray emission spectrometry

The relative transition probabilities of the L3-fluorescence lines from different titanium oxides were determined using high-resolution X-ray emission spectrometry. A reliable deconvolution of the X-ray emission spectra, by means of both experimentally determined response functions and absorption correction, reduces the relative uncertainties of the relative transition probabilities to 10% for titanium and 15% for titanium dioxide. The relative L3 transition probability of metallic titanium amounts to 0.66 ± 0.07 for the Ll fluorescence line and 0.34 ± 0.07 for the Lα fluorescence line, respectively. Respective database values from existing literature vary up to a factor of 3, which shows that a determination of the fundamental parameters in the soft X-ray range with low uncertainties is needed in particular with respect to surface sensitive X-ray spectrometer methods. The relative L3 transition probability for titanium dioxide is slightly changed to 0.56 ± 0.08 for the Ll fluorescence line and 0.44 ± 0.08 for the group of fluorescence lines associated to the L3 transition of titanium dioxide that can be considered equivalent to the metal Lα fluorescence line.

Diffuse X-Ray-emitting Gas in Major Mergers

Abstract Using archived data from the Chandra X-ray telescope, we have extracted the diffuse X-ray emission from 49 equal-mass interacting/merging galaxy pairs in a merger sequence, from widely separated pairs to merger remnants. After the removal of contributions from unresolved point sources, we compared the diffuse thermal X-ray luminosity from hot gas (L X(gas)) with the global star formation rate (SFR). After correction for absorption within the target galaxy, we do not see a strong trend of L X(gas)/SFR with the SFR or merger stage for galaxies with SFR > 1 M ☉ yr−1. For these galaxies, the median L X(gas)/SFR is 5.5 × 1039 ((erg s−1)/M ☉ yr−1)), similar to that of normal spiral galaxies. These results suggest that stellar feedback in star-forming galaxies reaches an approximately steady-state condition, in which a relatively constant fraction of about 2% of the total energy output from supernovae and stellar winds is converted into X-ray flux. Three late-stage merger remnants with low SFRs and high K-band luminosities (L K ) have enhanced L X(gas)/SFR; their UV/IR/optical colors suggest that they are post-starburst galaxies, perhaps in the process of becoming ellipticals. Systems with L K < 1010 L ☉ have lower L X(gas)/SFR ratios than the other galaxies in our sample, perhaps due to lower gravitational fields or lower metallicities. We see no relation between L X(gas)/SFR and Seyfert activity in this sample, suggesting that feedback from active galactic nuclei is not a major contributor to the hot gas in our sample galaxies.

Nanoscopic X-ray fluorescence imaging and quantification of intracellular key-elements in cryofrozen Friedreich's ataxia fibroblasts.

Synchrotron radiation based nanoscopic X-ray fluorescence (SR nano-XRF) analysis can visualize trace level elemental distribution in a fully quantitative manner within single cells. However, in-air XRF analysis requires chemical fixation modifying the cell’s chemical composition. Here, we describe first nanoscopic XRF analysis upon cryogenically frozen (-150°C) fibroblasts at the ID16A-NI ‘Nano-imaging’ end-station located at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). Fibroblast cells were obtained from skin biopsies from control and Friedreich’s ataxia (FRDA) patients. FRDA is an autosomal recessive disorder with dysregulation of iron metabolism as a key feature. By means of the X-ray Fundamental Parameter (FP) method, including absorption correction of the ice layer deposited onto the fibroblasts, background-corrected mass fraction elemental maps of P, S, Cl, K, Ca, Fe and Zn of entire cryofrozen human fibroblasts were obtained. Despite the presence of diffracting microcrystals in the vitreous ice matrix and minor sample radiation damage effects, clusters of iron-rich hot-spots with similar mass fractions were found in the cytoplasm of both control and FRDA fibroblasts. Interestingly, no significant difference in the mean iron concentration was found in the cytoplasm of FRDA fibroblasts, but a significant decrease in zinc concentration. This finding might underscore metal dysregulation, beyond iron, in cells derived from FRDA patients. In conclusion, although currently having slightly increased limits of detection (LODs) compared to non-cryogenic mode, SR based nanoscopic XRF under cryogenic sample conditions largely obliterates the debate on chemical sample preservation and provides a unique tool for trace level elemental imaging in single cells close to their native state with a superior spatial resolution of 20 nm.

Development and Validation of Absorption Correction Method for Simultaneous Estimation of Paracetamol and Nimesulide in Bulk and Combined Tablet Dosage Form

The present paper describes simple, accurate, rapid, precise and sensitive UV spectrophotometric absorption correction method for the simultaneous determination of paracetamol and nimesulide in combined tablet dosage form. This method is more simple than reported methods and is based on use of 0.1 N NaOH as a solvent. The wavelengths selected for the analysis were 257 nm and 393 nm. Beer's law was obeyed in the concentration range of 4–18 μg/ml and 10–30 μg/ml for paracetamol and nimesulide respectively. The mean percentage drug content for paracetamol and nimesilide were found to be 100.03% w/w and 101% w/w respectively. The % RSD value was found to be less than 2 which shows the precision of method. The high recovery and low coefficients of variation conforms it's suitability for the routine quality control analysis of paracetamol and nimesulide in pure and tablet dosage forms.

Marinelli Beaker Measurement and Self Absorption Correction and Application for Various Environmental Samples in Monte Carlo Simulation

Marinelli Beaker Measurement and Self Absorption Correction and Application for Various Environmental Samples in Monte Carlo Simulation

Влияние коррекции поглощения гамма-излучения при исследовании перфузии миокарда методом ОФЭКТ/КТ

Purpose: Assessment of the impact of absorption correction (AC) on quantitative parameters of myocardial perfusion and determination of the extent of stress-induced myocardial microcirculation disorders on SPECT / CT in patients with chest pain and unchanged coronary arteries.
 Material and methods: the study included 35 patients, each of whom was carried a selective coronary angiography and rest/stress SPECT/CT of the myocardium with 99mTc -MIBI with- and without CA.
 Results: In all patients with stress-induced myocardial ischemia was detected both without and with AC images. However, quantitative parameters of myocardial perfusion were lower after the AC: SSS 6.9 ± 1.2 vs. 7.7 ± 1.1; SDS 4.0 ± 0.8 vs. 4.9 ± 0.6; Stress ext. Total 11.2 ± 1.8 vs. 13.0 ± 1.9; Stress TPD total 9.3 ± 1.2 vs.10.9 ± 1.2; TPDi 4.1 ± 1.0 vs.5.9 ± 0.9 (for all p < 0.05). For SRS, Rest ext. Total, and Rest TPD total difference was not significant. The number of hypoperfused segments, according to the segmental analysis, was less after AC and was 126 vs. 153 at rest, 242 vs. 177 under stress.
 In women, significant difference was obtained for all parameters, for men – only for the SSS, SDS, Stress ext. Total, Stress TPD total. In patients with BMI ≥25 significant difference for all parameters was obtained. However, patients with the normal BMI (18,5–24,9;WHO, 2004) significant difference was obtained only for Stress ext. Total, Stress TPD total.
 Conclusion The use of SPECT/CT with AC allow to detect microcirculatory violations of perfusion and myocardial reserve perfusion in patients with pain in the chest with the unchanged CA, as evidenced by indicators of the average values of quantitative parameters of perfusion scintigram. The most significant impact on the quantitative perfusion parameters was observed in women with well-developed breasts and obese patients. The findings give reason to assume the use of AC to avoid revaluation incidence and severity of stress-induced myocardial perfusion disturbances.

Absorptive corrections for vector mesons: matching to complex mass scheme and longitudinal corrections

Unstable spin-1 particles are properly described by including absorptive corrections to the electromagnetic vertex and propagator, without breaking the electromagnetic gauge invariance. We show that the modified propagator can be set in a complex mass form, provided the mass and width parameters, which are properly defined at the pole, are replaced by energy dependent functions fulfilling the same requirements at the pole. We exemplify the case for the vector meson, and find that the mass function deviates around 2 MeV from the threshold to the pole, and that the width function exhibits a different behavior compared to the uncorrected energy dependent width. Considering the decay as dominated by the and vectors and one scalar particle, we exhibit the role of the transversal and longitudinal corrections to the vector propagator by obtaining the modified vector and scalar form factors. The modified vector form factor is found to be the same as in the complex mass form, while the scalar form factor receives a modification from the longitudinal correction to the vector propagator. A fit to the experimental spectrum shows that the phase induced by the presence of this new contribution in the scalar sector improves the description of the experimental data in the troublesome region around 0.7 GeV. Besides that, the correction to the scalar form factor is found to be negligible.

Effective absorption correction for energy dispersive X-ray mapping in a scanning transmission electron microscope: analysing the local indium distribution in rough samples of InGaN alloy layers.

We have applied our previous method of self-consistent k*-factors for absorption correction in energy-dispersive X-ray spectroscopy to quantify the indium content in X-ray maps of thick compound InGaN layers. The method allows us to quantify the indium concentration without measuring the sample thickness, density or beam current, and works even if there is a drastic local thickness change due to sample roughness or preferential thinning. The method is shown to select, point-by-point in a two-dimensional spectrum image or map, the k*-factor from the local Ga K/L intensity ratio that is most appropriate for the corresponding sample geometry, demonstrating it is not the sample thickness measured along the electron beam direction but the optical path length the X-rays have to travel through the sample that is relevant for the absorption correction.

Dust removal from high turbid underwater images using convolutional neural networks

In recent years, underwater image processing has been a focus of many studies. Most underwater image processing technologies are focused on descattering, absorption correction and reflection correction. For a deep sea mining machine, dust seriously affects visual acuity. To correct for this, a two-part dust removal approach is proposed. Underwater red-green minimum channel prior descattering is used to remove fine dust in the first stage. However, the impact of dust streaks on images is always undesirable. Consequently, we propose a further deep convolutional neural-network-based dust removal method. The experimental results show that the proposed method performs better in removing haze-like scatters and dust-like scatters.

Double-ionization satellites in the x-ray emission spectrum of Ni metal

We report measurements of the nonresonant x-ray emission spectroscopy (XES) from Ni metal in an energy range spanning the K_beta, valence-to-core, and double-ionization (DI) satellites that appear beyond the single-particle Fermi level. We make special use of a laboratory-based x-ray spectrometer capable of both x-ray emission and x-ray absorption measurements to accurately align the XES and x-ray absorption spectra to a common energy scale. The careful alignment of energy scales is requisite for correction of the strong sample absorption of DI fluorescence above the Ni K-edge energy. The successful correction of absorption effects allows a determination of the branching ratios for the [1s3d], [1s3p], [1s2p] and [1s2s] satellites with respect to their corresponding diagram lines. We compare our results with other work, finding good agreement with prior experiments and with theoretical calculations in the multi-configuration Dirac-Fock framework.

Interpretation of Raman Spectra of Oxide Materials: The Relevance of Absorption Effects

When using Raman spectra for structural characterization of solid powder materials such as catalysts, the interpretation needs to take into account the possible absorption of radiation. For example, the reduction of oxide materials may result in new UV–vis absorption bands and therefore affect the Raman intensity. In resonance Raman spectroscopy, the absorption correction of Raman intensity based on the Kubelka–Munk theory is widely established. In contrast, in Raman spectroscopy, typically no absorption correction or normalization by a phonon mode is applied. Using a combined approach of Raman and UV–vis spectroscopy, this study examines the effect of absorption on Raman spectra as well as the usefulness of different absorption corrections for Raman spectroscopy. The results show that a change in absorption of about 10% may result in a decrease in Raman intensity of up to one-third. Corrections based on the Kubelka–Munk theory predict large intensity changes for small changes in the low-absorption region...

UV SPECTROPHOTOMETRIC ABSORPTION CORRECTION METHOD FOR SIMULTANEOUS ESTIMATION OF OLMESA RTAN MEDOXOMIL, AMLODIPINE BESYLATE AND HYDROCHLOROTHIAZIDE IN COMBINED TABLET DOSAGE FORM

A simple, accurate, precise, economical and validated uv spectrometric absorption correction method was developed for olmesartan, medoxomil amlodipine besylate and hydrochlorothiazide in bulk and its dosage form. The stock solutions were prepared in methanol followed by further dilutions with double distilled water. The λmax for olmesartan, amlodipine besylate and hydrochlorothiazide were 256.5 nm, 362 nm and 316 nm, respectively. Beer’s law was obeyed in the concentration range of 3-18 μg/mL, 1- 6μg/mL and 2-12 μg/mL, respectively. The method was validated by following the analytical performance parameters suggested by the ICH Guidelines. The percentage assay in commercial formulation was found to be in the range olmesartan 100.06%, amlodipine 99.17% and hydrochlorothiazide 100.14% by the proposed method. The method was validated with respect to linearity, precision and accuracy. recovery was found to be in the range of olmesartan 99.65%,amlodipine 99.97% and hydrochlorothiazide 99.81% by absorbance corrected method. The high recovery and low coefficients of variation conforms the suitability of the method for simultaneous analysis of three drugs in combined tablets.

Determination of efficiency of an aged HPGe detector for gaseous sources by self absorption correction and point source methods

Methods for the determination of efficiency of an aged high purity germanium (HPGe) detector for gaseous sources have been presented in the paper. X-ray radiography of the detector has been performed to get detector dimensions for computational purposes. The dead layer thickness of HPGe detector has been ascertained from experiments and Monte Carlo computations. Experimental work with standard point and liquid sources in several cylindrical geometries has been undertaken for obtaining energy dependant efficiency. Monte Carlo simulations have been performed for computing efficiencies for point, liquid and gaseous sources. Self absorption correction factors have been obtained using mathematical equations for volume sources and MCNP simulations. Self-absorption correction and point source methods have been used to estimate the efficiency for gaseous sources. The efficiencies determined from the present work have been used to estimate activity of cover gas sample of a fast reactor.

Practical techniques for large-scale Monte Carlo reactor depletion calculatons

This work presents a brief review of numerical methods for nuclide depletion calculations and a summary of several practical techniques for improving computational speed and reducing memory usage in large-scale Monte Carlo reactor depletion calculations. The techniques covered in the paper include: 1) the use of data hierarchy, 2) separation of absorbing and non-absorbing (precursor) nuclides, 3) optimizations for a backward differentiation formula (BDF) numerical solver, 4) the use of simplified (reduced-order) depletion systems, and 5) the use of a residual fission product absorption correction term to account for the cumulative reactivity effect of nuclides that are not explicitly depleted. In addition, the paper describes several implementation and data management strategies used in the MC21 code, which have proven beneficial for large depletion calculations. A description of these various techniques and strategies are presented along with results from scaling studies and representative reactor depletion calculations that demonstrate the effectiveness of these methods. The results from these studies suggest that large-scale MC depletion calculations including tens- to hundreds-of-millions of depletable material compositions are practical on contemporary mid-range computing clusters.

Triple Regge exchange mechanisms of four-pion continuum production in the pp→ppπ+π−π+π− reaction

We consider exclusive multi-peripheral production of four charged pions in proton-proton collisions at high energies with simultaneous exchange of three pomerons/reggeons. The amplitude(s) for the genuine $2 \to 6$ process are written in the Regge approach. The calculation is performed with the help of the GenEx Monte Carlo code. Some corrections at low invariant masses in the two-body subsystems are necessary for application of the Regge formalism. We estimate the corresponding cross section and present differential distributions in rapidity, transverse momenta and two- and four-pion invariant masses. The cross section and the distributions depend on the value of the cut-off parameter of a form factor correcting amplitudes for off-shellness of $t$-channel pions. Rather large cross section is found for the whole phase space ($\sigma \sim$ 1-5 $\mu$b, including absorption corrections). Relatively large four-pion invariant masses are populated in the considered diffractive mechanism compared to other mechanisms discussed so far in the context of four-pion production. We investigate whether the triple Regge exchange processes could be identified with the existing LHC detectors. We consider the case of ATLAS and ALICE cuts. The ATLAS (or CMS) has better chances to identify the process in the region of large invariant masses $M_{4 \pi} > 10$ GeV. In the case of the ALICE experiment the considered mechanism competes with other mechanisms (production of $\sigma \sigma$, $\rho \rho$ pairs or single resonances) and cannot be unambiguously identified.