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point sources for digital lensless holographic microscopy: comparative assessment

OPTICAL ENGINEERING 2024年第11期63卷 111808-111808页

作者： Buitrago-Duque, Carlos Patino-Jurado, Brayan Garcia-Sucerquia, Jorge Univ Nacl Colombia Sede Medellin Dept Phys Medellin Colombia

The light source in digital lensless holographic microscopy (DLHM) plays a key role in the optical performance of this microscopy methodology. The underlying physics that support DLHM rely on having an outward propagating spherical wavefront illuminating the sample to record on the surface of a digital camera the intensity of the diffracted wavefield that is magnified by free-space propagation;this first stage constitutes the recording. The information of the sample is numerically retrieved by computing the diffraction that an inward propagating spherical wavefront undergoes in the recorded intensity in a stage known as reconstruction. In both stages of this lensless microscopy method, it is assumed that perfect spherical wavefronts are utilized;hence, the closer the illumination light sources to exp[+/- ikr]/|r| are, the better the performance of the microscope. For the recovery of the information of the sample, the accuracy of the inward propagating spherical wavefront exp[-ikr]/|r| is guaranteed by its correct sampling in the numerical computation of the diffraction process;thus, the main challenge is the physical production of light sources to illuminate the sample whose amplitude profile is accurately described by exp[ikr]/|r|. In this work, the different approaches that our research group has explored to produce illuminating point sources for DLHM are evaluated. point sources based on pinholes, coned-shaped optical fibers, optical pick-up units, and aspheric lenses are evaluated by rating their robustness, compactness, reliability, cost and easiness of production, and their performance on imaging test targets and biosamples. Some additional DLHM light sources reported in the literature are also briefly reviewed based on their available data.

关键词： digital lensless holographic microscopy illumination quality point sources

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Cooperative concurrent targeting for planar arrays of point sources

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AUTOMATICA 2024年 159卷

作者： Ramazi, Pouria Zhang, Fan Cao, Ming Brock Univ Dept Math & Stat Brock ON Canada Sun Yat Sen Univ Sch Aeronaut & Astronaut Shenzhen Peoples R China Univ Groningen Fac Sci & Engn ENTEG Groningen Netherlands

Motivated by practical applications in satellite formations and directional antenna arrays, the problem of targeting a planar array of point sources at one common object of interest is proposed and then solved using novel distributed coordination strategies. These point sources are arbitrarily located on the x-y plane and the boundary point sources, whose either x or y coordinate is extremal, already orient to the non-coplanar target point. The only global information shared among the remaining point sources is the positive directions of the global coordinate axes x and y, and hence, they have to rely on sensing the changes of the orientation angles of their nearest neighbors to adjust their own orientation. We prove that under our control law, the orientation lines will asymptotically intersect at the same point of concurrency as the boundary point sources. The main idea behind the designed control law is the intuitive argument from Euclidean geometry that reducing the differences between the distances to the x-y plane of the pairwise intersection points of the orientation lines leads to realizing concurrent targeting. We further show the boundedness and exponential convergence speed of the orientation angles.(c) 2023 Elsevier Ltd. All rights reserved.

关键词： Multi-agent systems point sources Concurrent targeting Distributed coordination

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GENERALIZED OPTICAL THEOREM AND point sources

LIGHT & ENGINEERING

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LIGHT & ENGINEERING 2021年第5期29卷 4-11页

作者： Apresyan, Leon A. Russian Acad Sci Prokhorov Inst Gen Phys Moscow Russia

A simple derivation of the general form of the optical theorem (GOT) is given for the case of a conservative scatterer in a homogeneous lossless medium, suitable for describing point sources and an observation region close to the scatterer. The presentation is based on the use of the operator approach and scalar wave equation in the limit of vanishingly small absorption. This approach does not require asymptotic estimates of rapidly oscillating integrals, does not use the integration of fluxes, which leads to the loss of information about the energy conservation law, and allows a natural generalization to the case of polarized radiation, as well as more complex multi-part fields. Such GOT generalizes the results known in the mathematical literature for models to the case of any conservative ( real) scattering potential and arbitrary sources.

关键词： energy conservation generalized optical theorem single scatterer point sources near-and far-field observations

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Determination of actual radiation doses to the fingers when handling Kilo and Mega Becquerel radioactive point sources using VARSKIN

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JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2024年第1期17卷

作者： Tijani, S. A. Oyeyemi, S. M. Sambo, Isa Akerele, O. O. Owoade, L. R. Adeniran, B. M. Alotiby, Mohammed F. Alhuzaymi, Thaqal M. Nigerian Nucl Regulatory Author Natl Inst Radiat Protect & Res Ibadan Nigeria Nigerian Nucl Regulatory Author Dept Radiol Safety Abuja Nigeria King Abdulaziz City Sci & Technol KACST Nucl Technol Inst NTI POB 6086 Riyadh 11442 Saudi Arabia

point sources are used for different activities in a laboratory and for other applications. Some of these activities could involve the calibration of radiation detectors, radiation attenuation measurements etc. During the use of these sources, the laboratory workers use their bare fingers to manipulate these sources or use unsuitable devices to handle these sources. This study aims to estimate the likely radiation doses incurred during the use of Am-241, Cs-137, Co-60, Na-22, and Sr-90 point-sources using VARSKIN computer code. The result of this study shows that handling point sources very close to the hand or skin and holding these point sources with bare hands could give rise to a dose significantly greater than the recommended limit of 500 mSv per cm2 of the skin area meanwhile the use of tong with adequate length can reduce potential radiation doses from point sources to acceptable limit.

关键词： VARSKIN Radiation doses Occupational exposure point sources

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Stormwater impact on water quality of rivers subjected to point sources and urbanization - the case of Addis Ababa, Ethiopia

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WATER AND ENVIRONMENT JOURNAL 2019年第1期33卷 98-110页

作者： Adugna, Dagnachew Lemma, Brook Gebrie, Geremew Sahilu Larsen, Larissa Yeshitela, Kumelachew Jensen, Marina Bergen AAU Ethiopian Inst Architecture Bldg Construct & City Addis Ababa Ethiopia AAU Coll Nat & Computat Sci Addis Ababa Ethiopia AAU Ethiopian Inst Water Resources Addis Ababa Ethiopia Univ Michigan Urban & Reg Planning Ann Arbor MI 48109 USA Univ Copenhagen Dept Geosci & Nat Resource Management Copenhagen Denmark

Urbanization of a catchment often causes degeneration of rivers. We studied the water quality of three rivers in Addis Ababa based on the impact of stormwater and non-point sources, and urbanization. Along these rivers several point sources were registered, with direct discharge of industrial and domestic wastes into them. To distinguish the impact of these year-round point-sources from stormwater, we analysed physicochemical parameters, nutrients and heavy metals sampled from upstream to downstream sections of each river in the dry and wet season. Dissolved oxygen (DO), NO2-N, NH4-N, PO4-P, (Cr(VI) and Cu) exceeded international standards, pointing to a generally poor water quality of the rivers in both seasons. NO3-N, Mn and Zn were problematic in dry season only. Although stormwater improved DO, conductivity, PO4-P, Cr(VI) and Zn, the levels were still critical, pointing to construction sites, agriculture and pit latrines, somewhat offsetting the effect of stormwater dilution. No clear impact of urbanization pressure was found.

关键词： Addis Ababa point sources river water quality stormwater seasons urbanization

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Characterizing pollutant loading from point sources to the Tongqi River of China based on water quality modeling

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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY 2019年第11期16卷 6599-6608页

作者： Yao, H. Ni, T. You, Z. Nantong Univ Sch Geog Nantong 226019 Peoples R China Univ Calif Irvine Program Publ Hlth Irvine CA 92697 USA Nanjing Univ Sch Geog & Oceanog Sci Nanjing 210023 Jiangsu Peoples R China

It is vital to elaborately understand the pollution sources in environmental management. Based on water quality modeling, one procedure was proposed to characterize the pollutant loading from point sources to environmental medium. It included four steps: (1) identifying the pollutants' discharging units (abbreviated as PDUs) according to the outlets distribution along the river;(2) based on the hydraulic characteristics of the river, dividing the river into several segments;(3) introducing the water quality model of the river with calibrated and verified modeling parameters;and (4) estimating and characterizing the pollutant load. The methodology was programmed and applied in characterizing the COD load from point sources to the Tongqi River of China. All point sources along the river were identified to be six PDUs. The temporal variation of the pollutant discharged from point sources could be described by the curves or functions in the procedure. COD load was at the peak of the curve from noon to dusk (about 10:30 a.m. to 8:30 p.m.), and from the midnight to the morning they were stable, at the bottom. This comprehensive understanding for pollution sources could be important in helping decision makers to schedule and control the pollutant load into the river.

关键词： Pollutant load point sources Water quality modeling China

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Assessment of Bacteria Contaminants in Different Zones and point sources of Sandy Beaches in Accra, Ghana

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Microbiology insights 2023年 16卷 11786361231195152-11786361231195152页

作者： Daniel Oduro Stephanie Darko Emmanuel Robert Blankson Gloria Ivy Mensah Department of Animal Biology and Conservation Science University of Ghana Legon Accra Ghana. Department of Bacteriology Noguchi Memorial Institute for Medical Research University of Ghana Legon Accra Ghana.

Background:Bacteria are ubiquitous in the marine environment. Increasing concern for human health has led to growing interest in contamination on public beaches. The presence of pathogenic microorganisms originating from anthropogenic activities such as defecation and disposal of sewage on beaches are of special concern. In this study, presence of pathogenic bacteria and bacterial load in beach zones and point sources were investigated. Methods:Sand core samples from the subtidal zone, intertidal zone, supratidal zone and point sources from 5 beaches in Accra, Ghana, were collected and analysed. Total aerobic, coliform and () counts were determined for each zone in the respective beaches. Bacteria isolates were presumptively identified using biochemical tests and confirmed with MALDI-TOF MS. Results:Mean total aerobic count and total coliform counts ranged from 2.10 to 3.01 log CFU/g and 0.29 to 2.18 log CFU/g respectively while counts ranged from 0.12 to 1.71 log CFU/g for the beaches. Total aerobic count from point sources was 2.4-folds higher than the subtidal zone while total coliform counts were 5-folds higher in the point sources compared to the supratidal zone. point sources had 10 times ( = .0016) more counts as compared to the subtidal zone. Isolates recovered (n = 35) belonged to 10 bacteria genera. These were spp. (25.7%), spp. (14.3%), spp. (14.3%), (14.3%), (8.6%), spp. (8.6%), (5.7%), (2.9%), (2.9%), and (2.9%). Conclusion:point sources are major contributors to contamination on beaches. The presence of potentially pathogenic bacteria in beach sand could be a public health risk. Sensitization on cleanliness in the marine environment including beaches in Ghana is needed to enhance public health and safety.

关键词： Accra Beach zones Ghana MALDITOF bacteria counts contamination point sources

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Awake preclinical brain PET imaging based on point sources 15

Awake preclinical brain PET imaging based on point sources

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15th International Meeting on Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine

作者： Arias-Valcayo, Fernando Herraiz, Joaquin L. Galve, P. Vaquero, J. J. Desco, M. Udias, Jose M. Univ Complutense Madrid Fac Phys Sci Nucl Phys Grp Madrid 28040 Spain CEI Moncloa EMFTEL IPARCOS Madrid 28040 Spain Hosp Clin San Carlos IDISSC Hlth Res Inst Madrid 28040 Spain Univ Carlos III Madrid Dept Bioingn & Ingn Aerosp Madrid Spain Inst Invest Sanitaria Hosp Gregorio Maranon Unidad Med & Cirugia Expt Madrid Spain

ISBN: (数字)9781510628380

ISBN: (纸本)9781510628380

The presence of motion during the relatively long PET acquisitions is a very common problem, especially with awake animals, infants and patients with neurological disorders. External motion can be detected based on the optical tracking of markers placed on the skin of the patient, but it needs additional hardware and a somehow complex integration with the PET data. The possibility of motion detection directly from the acquired PET data would overcome these limitations. In this work, we propose the use of the centroid of lines of response to identify long motion free frames (more than 2.5 seconds). In these frames we identify in real-time the location of F-18 markers placed on the head of the rat with the radiotracer labeled with F-18. We evaluated the performance of the proposed method in a preclinical PET/CT scanner with an awake rat injected with 600 mu Ci and four F-18 sources attached in its head. After solid rigid motion compensation, we reconstruct an image that use 70% events of the acquisition, and the resolution is comparable with the motion-free frames.

关键词： Positron Emission Tomography motion correction real-time point sources

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Direct and inverse simulation applied to the identification and quantification of point pollution sources in rivers

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ENVIRONMENTAL MODELLING & SOFTWARE 2022年第0期156卷

作者： Lugao, Bruno C. Knupp, Diego C. Rodriges, Pedro Paulo G. W. Rio Janeiro State Univ Polytech Inst IPRJ UERJ Rua Bonfim 25Vila Amelia BR-28625570 Nova Friburgo RJ Brazil

Concerns about water resource availability and preservation have grown over recent decades due to increased levels of pollution stemming mainly from economic activities and uncontrolled population growth. In this context, the present study seeks to identify and quantify point pollution sources released from river margins. A two-dimensional transient advection-diffusion equation is proposed to model the physical problem, while the inverse problem, for the identification and quantification of pollution sources, is investigated through the definition of an objective function, considering or not the availability of prior information. The objective function then is minimized by applying the differential evolution algorithm. Simulated cases are presented and discussed for distinct release scenarios, including single and multiple point locations. The results obtained were found to be satisfactory even for the most difficult cases, illustrating that the computational approaches presented in this work may yield valuable tools in the management of surface water resources.

关键词： Inverse problem Differential evolution Finite difference Pollutant point sources

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Groundwater contamination from point sources. A hazard index to protect water supply wells in intermediate cities

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GROUNDWATER FOR SUSTAINABLE DEVELOPMENT 2020年 10卷

作者： Barilari, Agustina Quiroz Londono, Mauricio del Carmen Paris, Marta Lourdes Lima, Maria Massone, Hector E. Univ Nacl Mar del Plata Comis Invest Cient Inst Geol Costas & Cuaternario RA-3350 Mar Del Plata Buenos Aires Argentina Consejo Nacl Invest Cient & Tecn Godoy Cruz 2290C1425FQB Buenos Aires DF Argentina Univ Nacl Litoral Fac Ingn & Ciencias Hidr Santa Fe Argentina

Fresh water is of vital importance and therefore, the availability of water in urban areas has been a priority objective in the world for many years. One of the greatest challenges related to any natural resource management process is to achieve the best possible compatibility between the "ideal" and the "possible" situations. Nowadays, urban water management is a key objective particularly in intermediate cities of developing countries where human and economic resources in governmental agencies are limited. So, it is necessary to count with a tool as simple as possible, in order to allow control efforts to be prioritised. The aim of this paper is to develop a hazard index (HI), in order to identify which point sources of groundwater contamination need to be more frequently controlled and to recognise public supply wells that may be threatened. This index was applied in Mar del Plata city, located in the south-east of the Buenos Aires province, Argentina. The HI was defined as a weighted sum of three variables: Potential Contamination Load (PCL), Effluent Disposal mode (ED) and the distance from the point source to groundwater supply wells or Well Protection Areas (WP). HI results for each point source showed that all buried fuel tanks, soil and stone quarries present high HI as well as 2% of the industries. On the other hand, 90% of the inventoried industries and a landfill present the lowest HI values. Some recommendations based on two strategies (mitigation or prevention) are proposed.

关键词： Groundwater contamination Groundwater management point sources Intermediate cities Argentina

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