Homogeneous Irradiation Research Articles

Plasma Spraying of a Microwave Absorber Coating for an RF Dummy Load

The European fusion reactor research facility, called International Thermonuclear Experimental Reactor (ITER), is one of the most challenging projects that involves design and testing of hundreds of separately designed reactor elements and peripheric modules. One of the core elements involved in plasma heating are gyrotrons. They are used as a microwave source in electron–cyclotron resonance heating systems (ECRH) for variable injection of RF power into the plasma ring. In this work, the development and application of an alumina-titania 60/40 mixed oxide ceramic absorber coating on a copper cylinder is described. The cylinder is part of a dummy load used in gyrotron testing and its purpose is to absorb microwave radiation generated by gyrotrons during testing phase. The coating is applied by means of atmospheric plasma spraying (APS). The absorber coating is deposited on the inner diameter of a one-meter cylindrical tube. To ensure homogeneous radiation absorption when the incoming microwave beam is repeatedly scattered along the inner tube surface, the coating shows a varying thickness as a function of the tube length. By this it is ensured that the thermal power is distributed homogeneously on the entire inner tube surface. This paper describes a modeling approach of the coating thickness distribution, the manufacturing concept for the internal plasma spray coating and the coating characterization with regard to coating microstructure and microwave absorption characteristics.

Light delivery device modelling for homogenous irradiation distribution in photodynamic therapy of non-spherical hollow organs

SignificancePhotodynamic therapy (PDT) is a useful treatment for select cancers. Homogeneous illumination is a key factor in the successful application of PDT treatment of tumours in hollow organs. Over illumination may damage normal tissue while under illumination may not ablate the target. BackgroundThere have been many approaches to provide homogeneous irradiation for PDT treatment of hollow organs, including light-scattering medium and isotropic emitter to diffuse light, a balloon filled with solution to expand the organ wall, and shaped fibres. In most studies, the organ is assumed to be spherical. However, many hollow organs treated by PDT are non-spherical, and the uniformity of azimuthal irradiation remains an unsolved problem for cylindrical light sources. ObjectiveFind a design principle for homogeneous irradiation in a non-spherical cavity for PDT treatment. MethodA PDT light delivery device is modeled by a series of sub light sources placed along the longitudinal axis of an ellipsoid. In order to achieve a homogeneous azimuthal irradiation distribution on the elliptical arc, a cost function is solved by adding modulation coefficient to the emission profile. The coefficient of variation of uniformity (Ucov) describes the statistical dispersion of the variation in irradiation over the ellipsoid to the average value. Ucov is used to evaluate the homogeneity of the azimuthal irradiation distribution. ResultBy minimizing the cost function, we found that the truncated Gaussian function can be chosen as the emission profile to generate homogeneous irradiation profile within an ellipsoid cavity model. The emission profile can be tailored to generate Ucov of 96.7 %. Further discussion shows that the light distribution could be generated practically by a side-emitting optical fibre, a LED array, or moving an isotropic emitter successively. The impact of emission angle of light sub-source is analysed and the irradiation profile from discrete longitudinal emissions is calculated. ConclusionTheory analysis and simulation indicate that a cylindrical emitter with a non-uniform longitudinal emission profile (truncated Gaussian functions) results in an approximate homogeneous irradiance profile within an ellipsoidal cavity.

Cellular Radiosensitivity of Soft Tissue Sarcoma.

Currently, all soft tissue sarcomas (STS) are irradiated by the same regimen, disregarding possible subtype-specific radiosensitivities. To gain further insight, cellular radiosensitivity was investigated in a panel of sarcoma cell lines. Fourteen sarcoma cell lines, derived from synovial sarcoma, leiomyosarcoma, fibrosarcoma and liposarcoma origin, were submitted to clonogenic survival assays. Cells were irradiated with single doses from 1-8 Gy and surviving fraction (SF) was calculated from the resulting response data. Alpha/beta (α/β) ratios were inferred from radiation-response curves using the linear-quadratic (LQ)-model. Cellular radiosensitivities varied largely in this panel, indicating a considerable degree of heterogeneity. Surviving fraction after 2 Gy (SF2) ranged from 0.27 to 0.76 with evidence of a particular radiosensitive phenotype in only few cell lines. D37% on the mean data was 3.4 Gy and the median SF2 was 0.52. The median α/β was 4.9 Gy and in six cell lines the α/β was below 4 Gy. A fairly homogeneous radiation response was observed in myxoid liposarcoma cell lines with SF2 between 0.64 and 0.67. Further comparing sarcomas of different origin, synovial sarcomas, as a group, showed the lowest SF2 values (mean 0.35) and was significantly more radiosensitive than myxoid liposarcomas and leiomyosarcomas (P = 0.0084 and 0.024, respectively). This study demonstrates a broad spectrum of radiosensitivities across STS cell lines and reveals subtype-specific radiation responses. The particular cellular radiosensitivity of synovial sarcoma cells supports consideration of the different sarcoma entities in clinical studies that aim to optimize sarcoma radiotherapy.

Design of a uniform irradiance source based on light emitting diodes

Many applications in various fields require uniform illumination from light sources, for example, in medical imaging in the biophotonics area. In this work, the design and application of an annular light-emitting diode array capable of producing a homogeneous irradiance pattern is presented. As part of the design process, software that allows the simulation of the irradiance pattern as a function of the LED’s radiant intensity distribution, and the position and inclination angle of the LEDs, was developed and validated. Based on the simulation results, a source that produces homogeneous illumination over an area of 20 mm in diameter, where the lowest irradiance is more than 94% of the maximum irradiance, was constructed and tested in real conditions. The simulation method and theoretical calculations on which the array is based can be applied to the design of sources for other applications where a homogeneous irradiance is required.

Optimizing proton minibeam radiotherapy by interlacing and heterogeneous tumor dose on the basis of calculated clonogenic cell survival

Proton minibeam radiotherapy (pMBRT) is a spatial fractionation method using sub-millimeter beams at center-to-center (ctc) distances of a few millimeters to widen the therapeutic index by reduction of side effects in normal tissues. Interlaced minibeams from two opposing or four orthogonal directions are calculated to minimize side effects. In particular, heterogeneous dose distributions applied to the tumor are investigated to evaluate optimized sparing capabilities of normal tissues at the close tumor surrounding. A 5 cm thick tumor is considered at 10 cm depth within a 25 cm thick water phantom. Pencil and planar minibeams are interlaced from two (opposing) directions as well as planar beams from four directions. An initial beam size of σ0 = 0.2 mm (standard deviation) is assumed in all cases. Tissue sparing potential is evaluated by calculating mean clonogenic cell survival using a linear-quadratic model on the calculated dose distributions. Interlacing proton minibeams for homogeneous irradiation of the tumor has only minor benefits for the mean clonogenic cell survival compared to unidirectional minibeam irradiation modes. Enhanced mean cell survival, however, is obtained when a heterogeneous dose distribution within the tumor is permitted. The benefits hold true even for an elevated mean tumor dose, which is necessary to avoid cold spots within the tumor in concerns of a prescribed dose. The heterogeneous irradiation of the tumor allows for larger ctc distances. Thus, a high mean cell survival of up to 47% is maintained even close to the tumor edges for single fraction doses in the tumor of at least 10 Gy. Similar benefits would result for heavy ion minibeams with the advantage of smaller minibeams in deep tissue potentially offering even increased tissue sparing. The enhanced mean clonogenic cell survival through large ctc distances for interlaced pMBRT with heterogeneous tumor dose distribution results in optimum tissue sparing potential. The calculations show the largest enhancement of the mean cell survival in normal tissue for high-dose fractions. Thus, hypo-fractionation or even single dose fractions become possible for tumor irradiation. A widened therapeutic index at big cost reductions is offered by interlaced proton or heavy ion minibeam therapy.

Comparison of the RayStation photon Monte Carlo dose calculation algorithm against measured data under homogeneous and heterogeneous irradiation geometries.

This work compares Monte Carlo dose calculations performed using the RayStation treatment planning system against data measured on a Varian Truebeam linear accelerator with 6 MV and 10 MV FFF photon beams. The dosimetric performance of the RayStation Monte Carlo calculations was evaluated in a variety of irradiation geometries employing homogeneous and heterogeneous phantoms. Profile and depth dose comparisons against measurement were carried out in relative mode using the gamma index as a quantitative measure of similarity within the central high dose regions. The results demonstrate that the treatment planning system dose calculation engine agrees with measurement to within 2%/1 mm for more than 95% of the data points in the high dose regions for all test cases. A systematic underestimation was observed at the tail of the profile penumbra and out of field, with mean differences generally<0.5mm or 1% of curve dose maximum respectively. Out of field agreement varied between evaluated beam models. The RayStation implementation of photon Monte Carlo dose calculations show good agreement with measured data for the range of scenarios considered in this work and is deemed sufficiently accurate for introduction into clinical use.

Characterization of the proton pulsed beam at CMAM

In this paper, the technicalities performed to obtain a pulsed beam at the CMAM facility will be explained. The pulsed beam has been characterized with an 8 MeV proton beam, using an existing equipment at CMAM: two pairs of electrostatic plates (RASTER) that deflect the beam, commonly used for homogeneous irradiation of large areas. A pulsed beam is used in many areas such as nuclear physics, material science and, in particular, for proton-therapy medical studies. Rectangular and pyramidal functions have been used to generate different pulses and characterize the response of the RASTER. The results point out that the pulses obtained are suitable for preclinical proton-therapy studies in the FLASH regime, which consists on fractionating the dose in time with short and intense pulses. The set-up for the characterization has been a function generator and a Si-PM outside the chamber.

SOLAR-v: A new solar spectral irradiance dataset based on SOLAR/SOLSPEC observations during solar cycle 24

Context. Solar spectral irradiance (SSI) is the wavelength-dependent energy input to the top of the Earth’s atmosphere. Solar ultraviolet (UV) irradiance represents the primary forcing mechanism for the photochemistry, heating, and dynamics of the Earth’s atmosphere. Hence, both temporal and spectral variations in solar UV irradiance represent crucial inputs to the modeling and understanding of the behavior of the Earth’s atmosphere. Therefore, measuring the long-term solar UV irradiance variations over the 11-year solar activity cycle (and over longer timescales) is fundamental. Thus, each new solar spectral irradiance dataset based on long-term observations represents a major interest and can be used for further investigations of the long-term trend of solar activity and the construction of a homogeneous solar spectral irradiance record. Aims. The main objective of this article is to present a new solar spectral irradiance database (SOLAR-v) with the associated uncertainties. This dataset is based on solar UV irradiance observations (165−300 nm) of the SOLAR/SOLSPEC space-based instrument, which provides measurements of the full-disk SSI during solar cycle 24. Methods. SOLAR/SOLSPEC made solar acquisitions between April 5, 2008 and February 10, 2017. During this period, the instrument was affected by the harsh space environment that introduces instrumental trends (degradation) in the SSI measurements. A new method based on an adaptation of the Multiple Same-Irradiance-Level (MuSIL) technique was used to separate solar variability and any uncorrected instrumental trends in the SOLAR/SOLSPEC UV irradiance measurements. Results. A new method for correcting degradation has been applied to the SOLAR/SOLSPEC UV irradiance records to provide new solar cycle variability results during solar cycle 24. Irradiances are reported at a mean solar distance of 1 astronomical unit (AU). In the 165−242 nm spectral region, the SOLAR/SOLSPEC data agrees with the observations (SORCE/SOLSTICE) and models (SATIRE-S, NRLSSI 2) to within the 1-sigma error envelope. Between 242 and 300 nm, SOLAR/SOLSPEC agrees only with the models.

Implicit modelling of series-parallel photovoltaic arrays using double-diode model and its solution

As defined, a solar photovoltaic array is internally a power-limited nonlinear current source. They are commonly used to convert electromagnetic radiation from the sun, into electric power. Accurate models of arrays in series–parallel configuration, represent each sub-module with the double-diode model. Nevertheless, most of those models imply a high computational cost because they require the Lambert W-function to obtain approximated explicit equations for the sub-module’s voltage and current. This paper proposes a model of series–parallel photovoltaic arrays, operating under homogeneous and non-homogeneous irradiance conditions, where each sub-module is represented by the implicit expression derived from the double-diode model. The array is divided into strings and a system of implicit nonlinear equations is obtained for each string with the sub-modules’ voltages and string’s current as unknowns. The corresponding systems of implicit equations are solved by using the Trust-Region Dogleg method to obtain all the electrical variables of the array. The results from the proposed model are compared with those obtained with the equivalent electrical circuit of the array, used as a reference. Simulation data for small, medium, and large arrays show that the proposed method yields data akin to those of the reference method obtaining RMSE values below 0.104 A for current-voltage curves in homogeneous and non-homogeneous conditions. Likewise, the model is validated against several experimental conditions, showing a remarkable agreement with RMSE values below 0.161 A for current-voltage curves in each condition. Therefore, the proposed model can be used to represent accurately series-parallel arrays operating in homogeneous and non-homogeneous conditions.

Homogeneously Emitting, Mechanically Stable, and Efficient fs-Laser-Machined Fiber Diffusers for Medical Applications.

Light delivery is an essential part of therapy forms like photodynamic therapy (PDT), laser-induced thermotherapy, and endovenous laser therapy. While there are approaches to the light application for all three therapies, there is no diffuser that can be used for all three approaches. This diffuser must meet the following criteria: Homogeneous radiation profile over a length of 40 mm, efficient light extraction in the diffuser area, mechanical breakage resistance as well as thermal stability when applying high power. An ultrashort pulse laser was used to inscribe inhomogeneities into the core of a fused-silica fiber core while scanning the laser focus within a linear arrangement of cuboids centered around the fiber axis. The manufactured diffuser was optically and mechanically characterized and examined to determine the maximum power that can be applied in a tissue environment. Based on the analysis of all examined diffusers, the manufactured diffuser exhibits an emission efficiency ε = (81.5 ± 5.9)%, an intensity variability of (19 ± 5)% between distal and proximal diffuser end, and a minimum bending radius Rb = (15.4 ± 1.5) mm. It was taken advantage of the fact that the outer areas of the fiber core do not undergo any structural changes due to the machining and therefore do not suffer a major loss of stability. Tissue experiments revealed that a maximal power of 15 W was deliverable from the diffuser without harming the diffuser itself. It could be shown that a diffuser manufactured by ultrafast-laser processing can be used for low power applications as well as for high power applications. Further tests have to show whether the mechanical stability is still maintained after the application of high power in a tissue environment. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Invariance property in inhomogeneous scattering media with refractive-index mismatch

The mean path length invariance property is a very important property of scattering media illuminated by an isotropic and homogeneous radiation. Here we investigate the case of inhomogeneous media with refractive index mismatch between the external environment and also among their subdomains. The invariance property remains valid by the introduction of a correction, dependent on the refractive index, of the mean path length value. It is a consequence of the stationary solution of the radiative transfer equation in a medium subjected to an isotropic and homogeneous radiance. The theoretical results are in agreement with the reported results for numerical simulations for both the three-dimensional and the two-dimensional media.

Modelling and Experimental Investigation of Luminous Coupling in UVLED Driven Optical Fiber Reactors

Background: Photocatalytic oxidation is a promising tool for waste water treatment and decomposition of biologically non digestible substances. Immersed nanoscale catalyst particles from semiconductor materials such as TiO2 and ZnO can be excited by absorbed UV radiation, leading to hydroxyl-ion formation at the surface of the semiconductor and oxidative degradation of pollutants. Objective: This contribution deals with reactors equipped with catalyst coated light guides to combine the advantages of immobilized catalysts with nearly homogeneous irradiation. With experimental and theoretical methods the coupling and decoupling of radiation were investigated and the performance of catalyst coated light guides was tested by means of methylene-blue degradation. Methods: Radiation models, known from the recent literature, use single ray, parallel ray or multi ray models to approximate the light transmission. These models neglect Fresnel reflection and consider only coupling into the light guide. In this study, the LED was simulated as a Lambertian radiator using 10 4 rays with angle dependent intensities. This well-known model was extended with Fresnelreflection, which predicted the measured coupling efficiencies accurately. The simulations predict the decoupling and catalyst activation at the lateral surface of the light guide for two boundary cases, ideal matt and ideal reflective surfaces. To generate matt surfaces, the light guides were either scratched or coated with TiO2 p25 nanopowder. Sol-gel coating methods were used, to create reflective surfaces. Results: When using matt surfaces, the decoupling rate is very high: 80% of the radiant flux exits the light guide in less than 10 cm. If light guides with reflective surfaces are used, the radiant flux leaving the light guide is low: less than 10% of the radiation exited the light conductor in the first 10 cm. Methyleneblue degradation, seen as a model reaction, was used to determine the reactor performance by comparing the pseudo first order reaction coefficients. Due to the uniform light distribution along the length of the light guides and the resulting even formation of reactive radicals, the quantum yield was increased by a factor of 3, using sol-gel coated light guides, rather than powder coated light guides. Conclusion: The effectiveness of LED driven optical fiber reactors was intensified, if reflective surfaces are used instead of matt surfaces. These surfaces are achieved by sol gel chemistry. However, to use the complete amount of photons, which entered the optical fiber, very long light guides are needed.

Dose Optimization of Electron Arc Treatment Technique in Chest Wall Beams after Mastectomy

In breast cancer, electron energies are preferred over photon energies because they provide minimal lung exposure when conditions allow for thin chest wall irradiation after mastectomy. In patients with irregular chest wall, it is difficult to perform a homogeneous irradiation with fixed electron beam therapy due to reasons such as thickness differences, irregular contour and lack of tissue, long scar and area joint problems. Electron arc therapy is propose as an alternative method in such patients. The study was carried out with electron energies of 6, 9, 12, 13.5 and 16 MeV. First, in order to be able to use it in electron arc planning in the planning system, after determining the dose characteristics of all available electron energies of the electron arc technique, the accuracy of these dose distributions was verified with film and TLD dosimetry. After the suitability was determined, electron arc plans were made on the CT simulation image of 20 patients selected due to the difficulty of homogeneous irradiation with the classical method. While the chosen reference dose of 85% covered the PTV homogeneously, it was found that the dose was decreased by an average of 50% compared to photon and classical electron therapy in the examination performed in terms of radiation dose to which the lung volume was exposed. During the planning, a homogeneous dose and bolus of different thicknesses were required depending on the energy in most patients to regulate the reduction in surface dose depending on the arc angle. Bolus prevents the lung and heart from overdosing while ensuring that the dose in the deeper parts of the target volume is more uniform. The use of tertiary block in electron-arc dose distributions prevented unwanted dose reduction in the field edges and provided a more homogeneous dose distribution at 85% reference isodose. If the structure of the patient's contour is very irregular, the dose distribution is not smooth due to the depth difference. In this context, it has been determined that during optimization, the isocenter depth should be chosen for the homogeneity of the dose distribution and to be as equal as possible from the surface at all beam angles. In addition, in the study, it was determined that more appropriate dose distributions were obtaine when the isocenter depth is greater than the maximum reach of electrons. Even if multiple electron fields of different energies are used, more homogeneous dose distributions have been achieve by eliminating field combination problems with the use of electron arc therapy.

Depth of Interaction Measurements Based on Rectangular Light Sharing Window Technology and Nine-Crystals-to-One-SiPM Coupling Method

Depth of interaction (DOI) decoding capability shows great application potential for positron emission tomography (PET), especially for high-resolution small-animal PET or long axial field of view PET systems. On the basis of GATE optical simulation results, we presented a novel $9\times 9$ lutetium–yttrium oxyorthosilicate array with 10-mm rectangular light-sharing windows (RLSWs) and assembly the detector with nine crystals coupled to one silicon photomultiplier (SiPM) method; this caused DOI-related position shifts in the crystal decoding spots of the flood map. Homogeneous radiation was used to establish transfer functions to convert spot shifts into DOI measurements. The conventional collimated radiation experiments were used to assess the accuracy of the DOI measurements. Flood map results show that 81 segmented crystals can be clearly resolved, including 16 crystals adjacent to two RLSW windows (M-type), 40 crystals adjacent to one RLSW window (E-type), and 25 crystals not adjacent to any RLSW window (C-type). The mean absolute error of all DOI-capable crystals, M-type crystals, and E-type crystals are 2.15 ± 0.61, 1.95 ± 0.50, and 2.23 ± 0.63 mm, respectively. The novel nine-crystals-to-one-SiPM coupling technology is a low cost approach for constructing high-performance DOI detector modules. Detectors using nine-crystals-to-one-SiPM coupling technology are good candidates for high-resolution preclinical PET and for total-body PET.

Influence of α-Particle Radiation on Intercellular Communication Networks of Tunneling Nanotubes in U87 Glioblastoma Cells.

Cellular communication plays a crucial role in the coordination and organization of cancer cells. Especially processes such as uncontrolled cell growth, invasion, and therapy resistance (development), which are features of very malignant tumors like glioblastomas, are supported by an efficient cell-to-cell communication in the tumor environment. One powerful way for cells to communicate are tunneling nanotubes (TNTs). These tiny membrane tunnels interconnect cells over long distances and serve as highways for information exchange between distant cells. Here, we study the response of cellular communication via TNTs in U87 glioblastoma cells to homogeneous irradiation with α-particles as a stress factor. We describe the development of TNT networks in certain time steps after irradiation using confocal live-cell imaging and suggest an evaluation method to characterize these communication networks. Our results show that irradiated cells establish their network faster and have more cell-to-cell connections with high TNT content than sham-irradiated controls within the first 24 h. These findings suggest that there is an additional trigger upon radiation damage which results in fast and intensive network formation by TNTs as a radiation damage response mechanism.

Precision Radiotherapy: 18F-FDG PET-based radiotherapy planning in Head and Neck cancers.

Precision medicine is gaining importance in this era of molecular imaging where the molecular features of a disease can be noninvasively assessed and treated with personalized medicine. This is especially suited for head and neck cancers (HNCa). Early stage HNCa are ideally managed with radiotherapy (RT) or surgery. Head and neck (HN) is a complex region and its tumors respond to RT differently due to dissimilar structures and moving organs such as tongue. Radiation oncologists are always in the process of trying and investigating newer RT techniques in order to achieve precise and targetted therapy to tumour/s. One such innovation is Intensity modulated RT (IMRT) using 3 Dimensional conformal RT (3DCRT). This 3DCRT resizes the radiation beams to match the shape of the tumor. Such focused dose escalation may improve local control in HNCa. Image guided RT in conjunction with IMRT is the most advanced form of RT planning being used these days. Simulation computerized tomography (CT) images are usually incorporated into RT planning module. But limitations of CT such as poor soft tissue contrast than magnetic resonance imaging and inability to clearly define solid / cystic / necrotic areas and viable tumour exist. Functional imaging such as Positron Emission Tomography (PET) has established its superiority over CT in delineating the actual site and extent of HN tumors. A combination of IMRT with BTV (Biological Tumour Volume) may be the most ideal technique to deliver a homogeneous radiation boost to tumour. This review shall discuss PET based RT planning, challenges, practical tips, and how to optimize therapy with the least side effects to the normal surrounding tissues.

Light emitting fabrics for photodynamic therapy: Technology, experimental and clinical applications

AbstractA homogeneous and reproducible fluence rate delivery during clinical photodynamic therapy (PDT) plays a determinant role in preventing under‐ or overtreatment. The development of a flexible light source able to generate uniform light on all its surface would considerably improve the homogeneity of light delivery. The integration of plastic optical fibers into textile structures offers an interesting alternative. This article aims to describe briefly the technology used to develop light emitting fabrics (LEF) and their use in vitro (CELL‐LEF), in vivo (VIVO‐LEF) for experimental evaluation of PDT. Finally, the use of LEF for clinical applications is given by three examples. For in vitro applications, the CELL‐LEF device allows the illumination of several 96‐well cell culture plates. For the VIVO‐LEF, the system developed for PDT can treat three mice simultaneously with a homogeneous and high irradiance The medical LEF systems developed for PDT in dermatology for the treatment of actinic keratosis demonstrate their superiority thanks to a uniform light distribution due the flexibility of LEF. Interestingly, the technology used for manufacturing LEF is very well known by the textile industry, leading to very competitive production costs. The fact that optical fibers can transmit light from 400 to 1200 nm allows the connection of LEF to different laser sources covering the light spectrum of all photosensitizers used for medical applications. New developments should allow to use the LEF inside cavities such as the pleural or the peritoneal cavities.

Effect of Cattaneo-Christov Heat Flux on Radiative Hydromagnetic Nanofluid Flow between Parallel Plates using Spectral Quasilinearization Method

In this paper, we numerically solve the equations for hydromagnetic nanofluid flow past semi-infinite parallel plates where thermal radiation and a chemical reaction are assumed to be present and significant. The objective is to give insights on the important mechanisms that influence the flow of an electrically conducting nanofluid between parallel plates, subject to a homogeneous chemical reaction and thermal radiation. These flows have great significance in industrial and engineering applications. The reduced nonlinear model equations are solved using a Newton based spectral quasilinearization method. The accuracy and convergence of the method is established using error analysis. The changes in the fluid properties with various parameters of interest is demonstrated and discussed. The spectral quasilinearization method was found to be rapidly convergent and accuracy is shown through the computation of solution errors.

A Cost-Effective In Situ Zooplankton Monitoring System Based on Novel Illumination Optimization.

A cost-effective and low-power-consumption underwater microscopic imaging system was developed to capture high-resolution zooplankton images in real-time. In this work, dark-field imaging was adopted to reduce backscattering and background noise. To produce an accurate illumination, a novel illumination optimization scheme for the light-emitting diode (LED) array was proposed and applied to design a lighting system for the underwater optical imaging of zooplankton. A multiple objective genetic algorithm was utilized to find the best location of the LED array, which resulted in the specific illumination level and most homogeneous irradiance in the target area. The zooplankton imaging system developed with the optimal configuration of LEDs was tested with Daphnia magna under laboratory conditions. The maximal field of view was 16 mm × 13 mm and the optical resolution was 15 μm. The experimental results showed that the imaging system developed could capture high-resolution and high-definition images of Daphnia. Subsequently, Daphnia individuals were accurately segmented and their geometrical characters were measured by using a classical image processing algorithm. This work provides a cost-effective zooplankton measuring system based on an optimization illumination configuration of an LED array, which has a great potential for minimizing the investment and operating costs associated with long-term in situ monitoring of the physiological state and population conditions of zooplankton.

Comments on the 2013 ICNIRP Laser Guidelines.

Comments on the 2013 ICNIRP Laser Guidelines.