Line Source Research Articles

Experimental and GEANT4 Simulated FEPE of NaI(Tl) Detector for Linear Sources.

The current study investigated the geometry, design and solid angle impacts on full energy peak efficiency (FEPE) of NaI(Tl) detectors for a line source. A line source is fabricated using 99mTc solution filled in a borosilicate glass tube of inner diameter 3 mm, tube wall thickness 2.5 mm and length 12.7 cm. The FEPE is measured for the fabricated linear source using 2''⨯2'' NaI(Tl) cylindrical detector at various source-detector distances. The experimental setup is simulated in GEANT4 and the computed FEPE values are compared with experimental values. The absolute error of 5% is observed between computed and measured FEPE values. Utilizing the advantages of MC simulations, the impact of numerous source parameters such as source length, diameter, source-detector distance, glass tube thickness and lead shield effects on FEPE are investigated to optimize the fabrication process of linear sources. A case study for current investigation has been analyzed by considering absolute FEPE of the NaI(Tl) system for a syringe filled with radioactive solution. This study provides an insight for the fabrication of standard linear sources by analyzing different source parameters and hence, may serve as a guideline to prepare standard linear sources for the calibration of radiation detectors.

Realistic total-body J-PET geometry optimization: Monte Carlo study.

Total-body (TB) Positron Emission Tomography (PET) is one of the most promising medical diagnostics modalities, opening new perspectives for personalized medicine, low-dose imaging, multi-organ dynamic imaging or kinetic modeling. The high sensitivity provided by total-body technology can be advantageous for novel tomography methods like positronium imaging, demanding the registration of triple coincidences. Currently, state-of-the-art PET scanners use inorganic scintillators. However, the high acquisition cost reduces the accessibility of TB PET technology. Several efforts are ongoing to mitigate this problem. Among the alternatives, the Jagiellonian PET (J-PET) technology, based on axially arranged plastic scintillator strips, offers a low-cost alternative solution for TBPET. The work aimed to compare five total-body J-PET geometries with plastic scintillators suitable for multi-organ and positronium tomography as a possible next-generation J-PET scannerdesign. We present comparative studies of performance characteristics of the cost-effective total-body PET scanners using J-PET technology. We investigated in silico five TB scanner geometries, varying the number of rings, scanner radii, and other parameters. Monte Carlo simulations of the anthropomorphic XCAT phantom, the extended 2-m sensitivity line source and positronium sensitivity phantoms were used to assess the performance of the geometries. Two hot spheres were placed in the lungs and in the liver of the XCAT phantom to mimic the pathological changes. We compared the sensitivity profiles and performed quantitative analysis of the reconstructed images by using quality metrics such as contrast recovery coefficient, background variability and root mean squared error. The studies are complemented by the determination of sensitivity for the positronium lifetime tomography and the relative cost analysis of the studiedsetups. The analysis of the reconstructed XCAT images reveals the superiority of the seven-ring scanners over the three-ring setups. However, the three-ring scanners would be approximately 2-3 times cheaper. The peak sensitivity values for two-gamma vary from 20 to 34cps/kBq and are dominated by the differences in geometrical acceptance of the scanners. The sensitivity curves for the positronium tomography have a similar shape to the two-gamma sensitivity profiles. The peak values are lower compared to the two-gamma cases, from about 20-28 times, with a maximum value of 1.66 cps/kBq. This can be contrasted with the 50-cm one-layer J-PET modular scanner used to perform the first in-vivo positronium imaging with a sensitivity of 0.06 cps/kBq. The results show the feasibility of multi-organ imaging of all the systems to be considered for the next generation of TB J-PET designs. Among the scanner parameters, the most important ones are related to the axial field-of-view coverage. The two-gamma sensitivity and XCAT image reconstruction analyzes show the advantage of seven-ring scanners. However, the cost of the scintillator materials and SiPMs is more than two times higher for the longer modalities compared to the three-ring solutions. Nevertheless, the relative cost for all the scanners is about 10-4 times lower compared to the cost of the uExplorer. These properties coupled together with J-PET cost-effectiveness and triggerless acquisition mode enabling three-gamma positronium imaging, make the J-PET technology an attractive solution for broad application inclinics.

Assessment of AERMOD and ADMS for NOx dispersion modeling with a combination of line and point sources

Assessment of AERMOD and ADMS for NOx dispersion modeling with a combination of line and point sources

Systematical Theoretical Study of the Nonpoint Source Effects in Nuclear Medicine Shielding Calculation

Abstract The objective of this note was to systematically study the effects from nonpoint radiation sources on the nuclear medicine imaging room or uptake room shielding design. The dose from a nonpoint source to a location at a certain distance to the center of the source was calculated. A correction factor could be applied to the dose calculated using a point source model with the same distance to compensate the nonpoint source effects. The correction factor was a function only depending on the source relative dimension, the ratio of the source’s geometric dimension to the distance. Theoretical and numerical calculation were performed to calculate the correction factor on a one-dimensional line source, two-dimensional circular disc source, three-dimensional sphere, and cylinder sources. Our study indicated that for large nuclear medicine imaging rooms, the point source model was a good approximation for shielding design. For a small uptake room, a nonpoint source correction may be considered to calculate the barrier thickness.

Quantum mode-locked Faraday laser

We report an external-cavity mode-locked semiconductor laser that uses a Faraday atomic filter as a saturable absorber (SA), termed as the quantum mode-locked Faraday laser. The unique SA exhibits nonlinear transmission characteristics exclusively in the vicinity of the atomic quantum transition frequency, which narrows down the spectral bandwidth of the mode-locked pulses to the gigahertz level and results in a central wavelength of the mode-locked pulses corresponding to the 87Rb (F=2) component of the D2 quantum transition line. Simultaneously, influenced by the slow-light effect of rubidium-dispersive vapor in the SA configuration, the fundamental repetition rate of the mode locking can vary between 261 and 228 MHz. Pulse delay tests conducted outside the resonator provide conclusive evidence of a gigahertz-bandwidth slow light within the Faraday laser. The mode-locking technique presented here can be applied to pulsed light sources of other quantum transition lines by setting appropriate atomic filter parameters. In addition, this narrow-spectrum mode-locked laser, with a tunable repetition rate and a central wavelength corresponding to a quantum transition line, has potential applications in the fields of atomic precision spectroscopy and quantum precision metrology.

Design of an adjustable low-temperature linear microwave plasma source for atmospheric pressure applications

Linear plasmas, compared to small-area low-temperature plasma jets, offer a larger single-treatment area with a brush-like pattern, making them highly promising for various applications. This paper introduces the design of an adjustable low-temperature linear plasma source that operates under atmospheric pressure at 2.45 GHz. The design integrated microwave theory with dielectric barrier discharge principles, utilizing a resonant structure based on a microstrip power divider with one end open and the other shorted. The ground plane of the microstrip structure was replaced by a metal plate featuring a large groove. Argon gas was introduced from the short-circuited end and exited through the groove at the open end, where plasma excitation occurred. Experimental results demonstrated that the device, operating at atmospheric pressure, can achieve adjustable linear plasma widths ranging from 10 mm to 50 mm by varying the incident power between 30 and 100 W. Optical emission measurements confirmed the uniformity of the linear plasma, and the gas temperature 5 mm away from the discharge area remained at only 65 °C, even with a microwave incident power of 100 W. This study offers a novel approach to designing linear atmospheric pressure microwave plasma sources, with significant potential for diverse material treatment applications.

Performance Characteristics of a New Generation 148-cm Axial Field-of-View uMI Panorama GS PET/CT System with Extended NEMA NU 2-2018 and EARL Standards.

The uMI Panorama GS PET/CT system is a new long-axial-field-of-view scanner featuring high sensitivity, time-of-flight (TOF) resolution, spatial resolution, and count rate performance. The aim of this study is to assess the PET system on the basis of the National Electrical Manufacturers Association (NEMA) NU 2-2018 and European Association of Nuclear Medicine Research Limited (EARL) standards. Methods: Spatial resolution, count rate performance, sensitivity, accuracy, image quality, TOF resolution, and coregistration accuracy were evaluated following the NEMA NU 2-2018 standard. Additional experiments included energy resolution, 200-cm-long line sources for sensitivity, a 175-cm-long scatter phantom for count rate and TOF resolution, as well as the compliance with the EARL guideline. Moreover, an 18F-FDG PET patient study was reconstructed with various frame durations. Results: The PET system achieved sub-3-mm transaxial and axial spatial resolutions at a 1-cm radial offset. The sensitivities with the 70-cm-long and 200-cm-long line sources were observed to be 176.3 and 90.8 kcps/MBq, respectively, at the center of the field of view. The noise-equivalent count rates (NECRs) of the 70-cm-long and 175-cm-long scatter phantoms were measured to be 3.35 Mcps at 57.57 kBq/mL and 2.24 Mcps at 33.27 kBq/mL, respectively. The TOF resolutions for both phantoms were approximately 189 ps at 5.3 kBq/mL and lower than 200 ps below the NECR peaks. The absolute count rate errors of all 34 acquisitions were less than 3% below the NECR peak for the 70-cm-long scatter phantom. With the standard NEMA image quality phantom experiment, the contrast recovery coefficient varied from 68.17% to 94.20% and the background variabilities were all below 2%. The maximum PET/CT coregistration error was 1.33 mm. Regarding EARL compliance, the gaussian filter of 5-mm full width at half maximum could produce acceptable images. The patient data demonstrate visually satisfactory image quality with short frames (less than 1 min). Conclusion: The uMI Panorama GS exhibits spatial resolution and TOF resolution similar to those of the uMI Panorama system (35-cm axial field of view), despite the extended axial field of view. The 148-cm axial coverage, sub-200-ps TOF resolution, high sensitivity, and count rate performances are expected to yield superior image quality and offer new opportunities for various clinical applications.

Free-surface flow due to a line source near a vertical barrier

The unsteady flow generated by a line source that is located at an arbitrary location beneath the free surface of a fluid of finite depth is considered when there is vertical barrier located nearby. The surface may have surface tension. The barrier is shown to have a significant effect on the wave height generated at the barrier and the outward travelling bore generated by the initiation of the flow. Simulations of free surface flows are very difficult due to the formation of curvature singularities on the surface. The method employed in this work does not appear to have these difficulties and the solutions can be computed almost up until the moment the wave breaks, including in some cases a significant spill at the front. A linearized solution and a fully nonlinear solution are presented and the results compared and discussed.

Effect of surface tension on the propagation of water waves by a line source in the presence of a nearly vertical cliff

Effect of surface tension on the propagation of water waves by a line source in the presence of a nearly vertical cliff

Long-term Evaluation of Mature-line and Juvenile-line ‘Valencia’ and ‘Vernia’ Sweet Orange Budlines on ‘Carrizo’ Rootstock

Field trials are critically important to the citrus industry because they provide scientific data from replicated plantings that can be used to determine which rootstock-scion combinations to plant. The field trial reported here was a semi-commercial-scale scion trial involving several selections of ‘Valencia’ and one ‘Vernia’ selection on the ‘Carrizo’ citrange rootstock. The purpose of this trial was to evaluate ‘Valencia’ and ‘Vernia’ scion selections from various sources to identify accessions that could complement the existing scion cultivar range and provide a wider harvest window. The scions consisted of advanced seedless somaclonal ‘Valencia’ selections, irradiated material, and an assortment of other selections, including accessions from Australia, Brazil, and California. Of special interest were young (juvenile line) sources. A secondary objective was to assess the relative response of the selections to huanglongbing (HLB), which was discovered in Florida during this trial. The location of this trial was Lake County, FL, USA, and the trees were planted in Mar 2000. A randomized complete block design was used with four replications of multiple tree plots. Data collected included total soluble solids, titratable acidity, sugar-to-acid ratio, pounds-solids per box, number of boxes per tree, pounds-solids per acre, cumulative pounds-solids per acre, and HLB rating. There were significant differences among the scions for several variables, including boxes of fruit per tree, pounds-solids per acre, HLB rating, and others. The findings of this research suggest that there are differences in performance among scion selections for a variety of horticultural traits important to citrus growers and processors.

Temperature distribution characteristics of linear fires in utility tunnels under the influence of sealing ratios and vertical positions of the fire source

This study delves into two key factors affecting fire development process and longitudinal ceiling temperature attenuation characteristics in a utility tunnel: the sealing ratios and the vertical positions of the linear fire source. The evolution process of linear fire is typically divided into five stages. In the stable combustion stage, the flame height at the end of the liner fire source is observed to be higher than that at the center. During the rapid loss stage of mass, the mass loss rate peaks and then stabilizes for a period of time, the maximum peak growth rate is 1.35 (the fire source is located at position 02), the duration shortens as the distance between the liner fire source and the ceiling decreases and the sealing ratio increases. When the sealing ratio is 100 %, the maximum temperature growth rate is 2.25 with the change of fire source position. The ceiling temperature in the upper part of the linear fire zone is lower in the center and higher on both sides, however, the distribution is asymmetric. A mathematical model of longitudinal ceiling temperature attenuation is established. The results may provide guidance for the control of linear fires in long-narrow confined spaces.

A Novel Heat Pulse Method in Determining “Effective” Thermal Properties in Frozen Soil

AbstractAccurate and fast measurements of thermal properties are frequently required for characterizing the heat‐water dynamics in frozen soil. Measuring the thermal properties of frozen soil without inducing ice thaw has proven challenging with conventional heat pulse (HP) methods. In this study, based on an Infinite Line Source (ILS) semi‐analytical model that applies a constant temperature lower than the freezing point at the heat source to prevent the initiation of ice thaw in the frozen soil, we propose a novel HP‐based approach to measure thermal properties, applicable at temperatures below or above 0°C. Laboratory experiments and numerical modeling were utilized to validate the applicability of the approach and optimization strategies of the measurement. We found that the proposed HP‐based approach effectively maintained the maximum spatial temperature below the freezing point and therefore estimated the bulk thermal properties of quartz sand and ice contents. An optimized measurement strategy was proposed to monitor the temperature variations 2–4 cm away from the center of the heat probe after 60 s. This progress can largely facilitate the determination of the thermal properties of multi‐phase and ‐component frozen soil such as thermal conductivity, heat flux, and ice content in cold areas across soil science, hydrology, engineering, and climate science.

On estimating the effective sensitivity of a TOF-PET system for a particular imaging task

Comparing positron emission tomography (PET) systems which have different features is not straightforward. To address this, we propose to image the same object with all considered PET systems using a fixed scan time, and reconstruct from each scan an image at the same predefined spatial resolution. With such resolution matched reconstructions, the images should be identical except for their noise. Therefore, the PET system that produces the image with the lowest variance has the best performance. An analytical model is described to compute this variance, assuming that the PET system is (approximately) cylindrical, the imaged object is a uniform cylinder centered in the field of view, and the variance is only computed at the center of the reconstructed image. The model takes into account the solid angle covered by the detectors, the detector stopping power, the time-of-flight (TOF) resolution, the scatter fraction and the spatial resolution of the system, the attenuation and diameter of the cylinder and the desired spatial resolution of the reconstructed image. The inverse of this variance can be considered as the effective sensitivity of the system. This effective sensitivity can be calibrated based on the NEMA line source sensitivity. As a performance metric for scanning long objects, the minimum sensitivity achieved over the object is computed, with an optimal number of bed positions and optimal overlap between them. The influence of the spatial and TOF resolution on the effective sensitivity is verified with simulations.

Early-stage identification of indoor leakage sources in factories

Identifying the leakage source in industrial factories as soon as an incident happens is crucial for controlling the leak in time and safeguarding lives and property. This study developed a rapid source identification method for factories, aiming to identify the characteristics of leakage sources at the early stage of the leakage event. The approach integrates pollutant diffusion theory, sliding window method, correlation coefficient method, and data fitting method. Based on an experimental cabin, 162 verification conditions were established, encompassing constant sources as well as two time-varying sources: linear and non-linear ones. Additionally, various aspects of the method were evaluated. It was found that considering the error and noise in sensor monitoring data, the method exhibits identification accuracies of 83.3%, 79.6%, and 74.1% for constant sources, linear sources, and non-linear sources, respectively. In the case of non-linear sources, the coefficient “b” must be taken into account when generating the dimensionless concentration vector. A sliding window containing 50 to 60 valid data points can achieve the highest source identification accuracy. This research can provide help in quickly locating leakage sources in factories, help with the timely control of leaks, and protect workers’ health and property safety.

Establishment of immortalized rabbit bone marrow mesenchymal stem cells and a preliminary study of their osteogenic differentiation capability.

A stable and standardized source of mesenchymal stem cells is a prerequisite for bone repair tissue engineering research and application. We aimed to establish a stable cell line of bone marrow mesenchymal stem cells from New Zealand rabbits and explore their osteogenic differentiation capacity. Primary rabbit bone marrow mesenchymal stem cells (RBMSCs) were isolated and immortalized via retroviral expression of SV40 Large T antigen (LTA). To assess the osteogenic differentiation capacity of the cells invitro, we studied the alkaline phosphatase (ALP) expression level and calcium deposition in bone morphogenetic protein 9 (BMP9)-induced immortalized cells using ALP staining and quantification, as well as alizarin red staining. Ectopic bone formation by the cells was assessed using micro-computed tomography (μCT) and histological examination. The immortalized cell line we established using SV40 LTA, which we termed iRBMSCs, was non-tumorigenic and maintained long-term proliferative activity. We further discovered that BMP9 (MOI = 30) effectively induced the osteogenic differentiation capacity of iRBMSCs invitro, and there was a synergy with GelMA hydrogel in inducing osteogenic differentiation of the iRBMSCs invivo. We confirmed that iRBMSCs are promising as a stable cell line source for bone defect repair engineering.

A MUSE source-blind survey for emission from the circumgalactic medium.

The recent detection of optical emission lines from the circumgalactic medium (CGM) in combined, large samples of low-redshift, normal galaxy spectra hints at the potential to map the cool (∼104 kelvin) CGM in individual, representative galaxies. Using archival data from a forefront instrument (MUSE) on the VLT, we present a source-blind, wide-redshift-range (z ∼ 0 to 5) narrowband imaging survey for CGM emission. Our detected, resolved emission line sources are cataloged and include a 30-kiloparsec-wide Hα source likely tracing the CGM of a low-mass galaxy (stellar mass ∼ 108.78±0.42 solar mass) at z = 0.1723, a 60-kiloparsec-wide Ly α structure associated with a galaxy at z = 3.9076, and a 130-kiloparsec (∼rvir)-wide [O II] feature revealing an interaction between a galaxy pair at z = 1.2480. The Hα velocity field for the low-mass galaxy suggests that the CGM is more chaotic or turbulent than the galaxy disk, while that for the interacting galaxies shows large-scale (∼50 kiloparsec) coherent motions.

Estimation method of soil thermal conductivity distribution of coaxial vertical borehole heat exchanger based on distributed thermal response test

Soil thermal conductivity (λs) is a vital parameter for sizing vertical borehole heat exchanger (VBHE) of ground-source heat pump, which may vary dramatically with the depth. To measure the λs distribution of coaxial VBHE, this study proposes an estimation method based on distributed thermal response test (DTRT). Firstly, a 3D numerical model is built and validated, which is utilized to simulate some DTRTs under various conditions. A 1D model is then developed for any layer of coaxial VBHE, which is discovered to agree better with the 3D model than the traditional infinite line source model. The proposed estimation method utilizes the 1D model to match DTRT data to identify the λs distribution, and then it is compared with the traditional direct method based on the simulated DTRT data. The results show that the traditional method probably has great errors, and that the proposed method could accurately estimate the λs of nearly all the soil layers, the errors of which are basically smaller than 4 %. The precision of the proposed method is slightly affected by the DTRT duration, number of split layers and errors of soil heat capacities. The proposed method is simple and concise, which is convenient for practical application.

A transient source-function-based embedded discrete fracture model for simulation of multiscale-fractured reservoir: Application in coalbed methane extraction

The classic embedded discrete fracture model (EDFM) may cause certain errors when simulating the transient flow process within the multi-scale fractured system. In this study, the transient transmissibility was derived by using the point (matrix-fracture) and line (fracture-fracture) source functions. The transient source-function-based EDFM (tSEDFM) is established via this method. Then, based on the dual criteria that dNNC is less than a certain distance and its projection point is within the corresponding fracture domain, a 3D fracture meshing method for arbitrary fracture geometry and orientation is established. The finite volume method is used to discrete the fluid flow equations for matrix and fracture systems, considering the multi-deformation-induced permeability evolution. Consequently, the numerical simulation framework of FVM-tSEDFM is proposed to investigate the transient mass transfer characteristics. Compared with the current pEDFM, the pressure drop near fractures of the proposed model is higher and the gap narrows as pressure wave further spreads. Compared with AEDFM, the Tmf of tSEDFM is almost the same, but AEDFM's Tff is substantially higher in the initial stage and the attenuation rate is slower, resulting in an error of nearly 15% at the hydraulic fracture location. As fracture density increases, more transient flow makes AEDFM- and EDFM-calculated BHP values deviate from tSEDFM. History matching using the tSEDFM with only 10000 meshes shows better results where the mismatching rate is larger than 90%. Simulation of CBM extraction indicate that sharp pressure decline occurs near the fractures, resulting in gas desorption enhancement and rapid productivity increment. The tSEDFM demonstrates good practicality in calculating the production and long-term permeability evolution. Results also show that the tSEDFM can correct the underestimation of mass exchange in the early stage and overestimation since the pseudo-steady stage, and can be better applied to the numerical simulation of multi-scale fractured reservoirs. As the dominant factor for gas extraction, sensitivity analyses of fracture properties are also documented.

Knowledge, attitude, and practice regarding tuberculosis in a labor-intensive industrial district.

In China, tuberculosis (TB) is a major contributor to deaths caused by infectious diseases, with a significant number of cases remaining undetected. Lack of knowledge could heighten the chances of infecting TB. Due to the lack of information on the knowledge, attitudes, and practices (KAP) related to TB among labor-intensive businesses, the study aimed to evaluate the TB KAP within this demographic. A descriptive cross-sectional survey was conducted among 1,007 participants from March 1 to 28, 2023. A survey was created for assessing knowledge, attitudes, and practices related to tuberculosis, and was sent to employees within the company. We utilize t-tests, ANOVA, and multiple linear regression to investigate the relationship between TB knowledge, attitudes, and practices and various influencing factors. The mean good scores rate for TB KAP were 43.5, 23.5, and 75.3%, respectively. Native, female, and workers living in their own houses had a higher score in TB knowledge. Native, non-operators, and workers with a history of TB contact had higher scores in TB practice. Regarding the multivariable linear regression analysis, sex, seniority, birthplace, marital status, and sources of information were associated with greater knowledge; monthly income categories were associated with greater attitude; and position, birthplace, and contact history were associated with greater practice. The survey results lead to the assumption that the level of KAP toward TB is not high among manufacturing workers in Songjiang district. Therefore, it is crucial to enhance tuberculosis knowledge, attitudes, and practices within this demographic.

Investigation on the transmission of Love waves due to an impulsive line source in a heterogeneous double porous rock structure

The region around the reservoir sometimes encounters the seismic response of ground. The phenomena of Love waves propagation also caused by seismic activity which can further significantly influenced by an impulsive line source present in the rock structures of ground. The current study elucidates the propagation behavior of Love waves induced by an impulsive line source within the anisotropic layered heterogeneous double porous rock structures commonly found in proximity to the reservoir areas. The expression of the dispersion relation for the Love waves propagation due to an impulsive line source has been derived by using the Fourier transformation and Green’s function technique. The above-mentioned rock composite structure is consisted of two different portions: upper transversely isotropic double porous (TIDP) layer medium and lower heterogeneous isotropic double porous half-space (IDP) medium. In the aforesaid half-space medium, both types of heterogeneities viz. linear and quadratic have been considered. The impacts of heterogeneity parameters associated with the lower heterogeneous IDP half-space, porosity parameter (corresponds to both upper TIDP layer and lower IDP half-space) and anisotropic parameter of TIDP layer on Love waves phase velocity have also been studied. Some special outlines have also been depicted graphically.