Polymethylmethacrylate Plates Research Articles

Effects of multiple reflected P waves on crack-tip stress and crack propagation in directional fracturing blasting

Directional fracturing blasting is effective for rock engineering, but it is inevitably disturbed by multiple reflected waves from different directions in natural rock mass due to discontinuous boundaries. Reflected waves affect both crack-tip stress and crack propagation, hence affect the results of directional fracturing blasting. In this paper, with the aid of high-speed photography, an optical caustics method is used to study effects of multiple reflected P waves on a directional blast-induced crack in a polymethyl methacrylate (PMMA) plate, specifically on crack path, crack fracturing mode, crack-tip stress and crack velocity. Crack-tip stress field is indicated by the shape of caustics pattern. Before the loading of reflected P waves, the mode I directional crack driven by blast-induced gases propagates in a straight path; crack-tip stress field is K-dominated, and crack-tip caustics pattern is consistent with classical caustics theory. On the contrary, under the loading of reflected P waves, the directional crack changes to be mixed-mode I + II and propagates in a curved path; Crack-tip stress field is non-K-dominated due to transient stress superposition of reflected P waves, and crack-tip caustics pattern is consistent with modified caustics theory. Transient stress superposition is not obvious for reflected P waves with a longer reflection distance. The tension loading of reflected P waves plays a more important role than the compression loading, which increases crack-tip stress intensity factors and crack velocity. This study provides a comprehensive understanding of effects of multiple reflected P waves from different directions on directional fracturing blasting.

Evolution Characteristics of Strain and Displacement Fields in Double-Hole Short-Delay Blasting Based on DIC

In the process of porous blasting excavation in engineering projects such as mining, hydropower stations, and tunnels, the delay time between adjacent blast holes significantly influences the characteristics of rock fracture and fragmentation. In order to visually explore the changing characteristics of strain and displacement between adjacent blast holes under different delay times, polymethyl methacrylate (PMMA) plates were used to simulate rock materials, and 2D digital image correlation (2D-DIC) testing methods were employed to measure the explosive strain field with different delay times (0 µs, 5 µs, 15 µs, 40 µs, 70 µs) for dual holes. Full-field principal strain cloud maps and displacement fields of PMMA boards in two-dimensional spatial coordinates were obtained, and the representative monitoring points were analyzed. The experimental results show that the maximum values of the first compressive principal strain peak and the first tensile principal strain peak at the connecting center of the two holes exist at a delay time of 0~40 µs under blasting conditions with the same hole distance and single hole charge. At the center point of the connection between the two holes, the interval time between the two principal strain peaks decreases with the increase in delay time. The maximum principal strain on the central vertical line of the connection line decreases exponentially with the increase in hole distance, and the attenuation trend increases first and then decreases with the delay time between 0 and 40 µs. At the peak of strain, the maximum average displacement of the connecting center of the two holes exists in the delay time between 0 and 40 µs. With the increase in delay time, the displacement trend between the two explosion holes gradually changes from shear to tension, and the vulnerable damage area increases, which makes the communication between the two explosion holes easier. This study can provide a basis for the precise selection of delay times between blasting holes in engineering.

Determining the refractive index of transparent materials using total internal reflection in teaching experiment

In this paper, we introduce a three-dimensional demonstration for the refraction and reflection based on total internal reflection of light in transparent media, and discuss the reasons for the formation of circular bright areas and circular shadows, respectively. Then, according to the relationship between the diameter of circular shadows and bright areas, the depth of water, and the thickness of the polymethyl methacrylate plate, we described a teaching experiment based on total internal reflection of light to achieve refractive index measurement of transparent liquids and solids. The refractive index of transparent media measured using this method is in good agreement with reported data.

Image Quality and Radiation Exposure in Abdominal Angiography: A Head-to-Head Comparison of Conventional Detector-Dose-Driven Versus Contrast-to-Noise Ratio-Driven Exposure Control at Various Source-to-Image Receptor Distances and Collimations in a Pilot Phantom and Animal Study.

This phantom and animal pilot study aimed to compare image quality and radiation exposure between detector-dose-driven exposure control (DEC) and contrast-to-noise ratio (CNR)-driven exposure control (CEC) as functions of source-to-image receptor distance (SID) and collimation. First, an iron foil simulated a guide wire in a stack of polymethyl methacrylate and aluminum plates representing patient thicknesses of 15, 25, and 35 cm. Fluoroscopic images were acquired using 5 SIDs ranging from 100 to 130 cm and 2 collimations (full field of view, collimated field of view: 6 × 6 cm). The iron foil CNRs were calculated, and radiation doses in terms of air kerma rate were obtained and assessed using a multivariate regression. Second, 5 angiographic scenarios were created in 2 anesthetized pigs. Fluoroscopic images were acquired at 2 SIDs (110 and 130 cm) and both collimations. Two blinded experienced readers compared image quality to the reference image using full field of view at an SID of 110 cm. Air kerma rate was obtained and compared using t tests. Using DEC, both CNR and air kerma rate increased significantly at longer SID and collimation below the air kerma rate limit. When using CEC, CNR was significantly less dependent of SID, collimation, and patient thickness. Air kerma rate decreased at longer SID and tighter collimation. After reaching the air kerma rate limit, CEC behaved similarly to DEC. In the animal study using DEC, image quality and air kerma rate increased with longer SID and collimation ( P < 0.005). Using CEC, image quality was not significantly different than using longer SID or tighter collimation. Air kerma rate was not significantly different at longer SID but lower using collimation ( P = 0.012). CEC maintains the image quality with varying SID and collimation stricter than DEC, does not increase the air kerma rate at longer SID and reduces it with tighter collimation. After reaching the air kerma rate limit, CEC and DEC perform similarly.

Use of reconstructed skin model to assess the photoprotection afforded by three sunscreen products having different SPF values against DNA lesions and cellular alterations

IntroductionBoth UVB and UVA rays induce biological damages in the epidermis and the dermis that contribute to photo-carcinogenesis and photoaging. In the present study, the photoprotective effect of 2 ISO standard sunscreens, P3 (Sun Protection Factor [SPF]15) and P6 (SPF40) and of an SPF50+ labeled commercial sunscreen product was tested in reconstructed skin tissues exposed to increasing doses of UV Solar Simulated Radiation (UV-SSR). UV-induced damages were evaluated using several biological markers, including DNA lesions in the presence or absence of sunscreen protection. MethodT-Skin™ model samples (EPISKIN), composed of a fibroblast-populated dermal equivalent and a fully differentiated epidermis, were protected with the test sunscreens (1.3 mg/cm² topically applied on molded polymethyl methacrylate plate) before being exposed to increasing UV doses (0 – 2.5 – 5 - 25 – 40 J/cm²). Twenty-four hours after exposure, tissues with and without sunscreen protection, were analyzed for skin viability and morphology, DNA lesions (cyclobutane pyrimidine dimer) and inflammatory mediator quantification. Results were compared to untreated exposed tissues using a Wilcoxon non-parametric test. ResultsFor untreated tissues, UV-SSR exposure induced a dose-dependent decrease in epidermal and dermal viabilities, an increase in release of proinflammatory cytokines and matrix metalloproteinases and were associated with morphological damages at doses as low as 5 J/cm2. DNA lesions were even detected at the lowest dose of 2.5 J/cm2, and their number increased with the UV-SSR dose. In the samples protected with sunscreens, these abnormalities were partially or totally prevented with P6 providing a better protection compared to P3, and the SPF50+ sunscreen showing a trend for better protection than P6, for example against DNA damage. ConclusionsThis study demonstrates that photoprotective effects of different sunscreens can be discriminated and ranked on reconstructed skin tissues (T-Skin™ model) exposed to UV-SSR. Showing significant differences between the reference products P3 and P6 in line with their respective SPF values, such study allows the evaluation of epidermal and dermal damages at the tissue, cellular and molecular levels. It thus opens the way to a new model of integrated assessment of sunscreens. In line with its labeled 50+ SPF, the commercial test product confirmed its improved protection especially on DNA damage prevention.

Numerical Simulation of PMMA Impact Based on the J–C Constitutive and Damage Models under Hydrostatic Pressure Loading

Polymethyl methacrylate (PMMA) polymer is widely used in various fields today. In order to reveal the structural impact performance of PMMA materials in underwater engineering thoroughly, this paper firstly proposed a simplified plate model for a spherical shell hull under concentrative impact loading. Then, to simulate the hyper-elastic material properties of PMMA in the impact process, the Johnson–Cook constitutive model and damage failure model were adopted. And the least squares method was used to confirm accurately the J–C constitutive and damage failure model parameters of PMMA through material test data. Moreover, the dynamic process of the steel bullet impacting the PMMA plate structure was analyzed by the finite element software ABAQUS. The calculation results show that the numerical simulation results in this paper have a good convergence, and the residual velocities at different initial velocities and thicknesses of plates are in good agreement with the experimental test data. Therefore, the feasibility and accuracy of the impact analysis of PMMA structures based on J–C constitutive and damage failure models in this paper are verified accordingly. Finally, based on the presented finite element model, the structure response and the variation of residual velocity of the bullet with the PMMA plate thickness was analyzed in depth; that is, the results show that the residual velocity of the bullet has a certain linear relationship with the thickness, even in an underwater environment, and even in an underwater environment will increase both with a thicker structure or a higher pressure.

Predicting impact strength of perforated targets using artificial neural networks trained on FEM-generated datasets

The paper considers application of artificial neural networks (ANNs) for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA (Polymethylmethacrylate) targets. The ANN models were trained using sets of numerical results on impact of PMMA plates obtained via dynamic FEM coupled with incubation time fracture criterion. The developed approach makes it possible to evaluate the impact strength of a particular target configuration without complicated FEM calculations which require considerable computational resources. Moreover, it is shown that the ANN models are able to predict results for the configurations which cannot be processed using the developed FEM routine due to numerical instabilities and errors: the trained neural network uses information from successful computations to obtain results for the problematic cases. A simple static problem of a perforated plate deformation is discussed prior to the impact problem and preferable ANN architectures are presented for both problems. Some insight into the perforation pattern optimization using a genetic algorithm coupled with the ANN is also made and optimized perforation patterns which theoretically enhance the target impact strength are constructed.

Nanosecond laser debonding of strong adhesives

ABSTRACT The goal of this paper is to determine whether laser-induced surface melting can generate adhesive debonding. Commercial cyanoacrylate and acrylic adhesives are used to attach an aluminum (Al) cylinder to a transparent polymethyl(methacrylate) (PMMA) plate, and then a variable force is applied to create an axially loaded butt joint. High energy nanosecond laser pulses at 1064 and 532 nm are directed through the transparent PMMA to be absorbed at the Al surface, causing transient localized heating that leads to joint failure. The dependence of this debonding on both laser fluence (energy per area) and applied force are investigated. Single shot debonding occurs at fluences on the order of 0.47 J/cm2 for 1064 nm and 0.29 J/cm2 for 532 nm pulses with an applied pressure of 0.22 MPa. Characterization of the Al surface before and after laser impact confirms that the debonding arises from surface melting and causes only slight changes to the Al surface. A simple model of the debonding process is developed to explain the dependence of the debonding on the applied load. Single laser pulses can generate instantaneous, relatively clean separation of bonded joints, suggesting that laser debonding may be a promising strategy to initiate deadhesion.

Development and performance of a gelatin-based bio-polysaccharide drag reduction coating

The secreting drag reduction mucus in fish epiderm inspires the manufacturing of five gelatin–polysaccharide drag reduction coatings. First, a mixed solution composed of the gelatin and bio-polysaccharides [guar gum, xanthan gum, locust bean gum, tragacanth gum, or acacia gum] was poured into rectangular grooved polymethyl methacrylate (PMMA) plates, and bionic coatings were obtained after curing. Then, the surface characteristics of the coatings were characterized, and the internal micro-/nanoscale three dimensional (3D) net structures provided releasing access for the polysaccharide molecules. Importantly, a parametric study focusing on the gelatin and polysaccharide proportion affected the drag reduction of the coatings in a turbulent channel flow. Based on a smooth PMMA plate without a coating as a reference, the five developed coatings exhibited considerable drag-reducing effects with the corresponding maximum drag reduction rates that all exceeded 20%. There are three drag reduction mechanisms (polymer drag reduction, slip phenomenon, and wall flexibility) and one drag increase mechanism (surface roughness). Increasing the gelatin proportion affects the release rate of the drag-reducing agents, surface flexibility, and surface slip properties. Meanwhile, increasing the polysaccharide proportion promotes the release of polysaccharides, but increases the surface roughness. Thus, the effects of gelatin and polysaccharide are complicated due to competition between these mechanisms. Future works should focus on clarifying the complex mechanisms to improve the drag reduction efficiency of the gelatin-based bio-polysaccharide coatings. These biomimetic drag-reducing coatings could be further applied to underwater equipment.

A double tangential flow filtration-based microfluidic device for highly efficient separation and enrichment of exosomes

Recently, exosomes have been recognized as important disease biomarkers due to the essential roles they played in disease development. Nevertheless, the highly efficient isolation and enrichment of exosomes from complex body fluids continues to hinder the research and application of exosomes for clinical use. In this work, we developed a double tangential flow filtration-based microfluidic device for exosome isolation from cell supernatants and human serum. The microfluidic device contained two modules. Each module included two polymethylmethacrylate (PMMA) plates with symmetrical serpentine channels and a nanoporous membrane with 200 nm or 30 nm pore diameter and was used to separate larger vesicles, exosomes and free biomolecules. The design of double tangential flow filtration in symmetrical serpentine channels largely increased the contact area between the filtrate and the nanoporous membranes, thus improved the separation efficiency and prevented the clogging of the membrane. Compared with standard separation method, i.e. ultracentrifugation (UC), the microfluidic chip-based separation (Chip) of exosomes showed the advantages of much lower instrumental cost, lower consumable cost, shorter time (<120 min), higher purity (82.8%) and significantly higher recovery rate (77.8%). In addition, due to the label-free separation, the microfluidic device-collected exosomes could be directly used for downstream analysis such as proteomics analysis. The proteomics analysis results of exosomes isolated from the sera of clinical patients with different diseases by the chip revealed richer disease-related information comparing with those exosomes isolated by UC, demonstrating the good practicability of this chip for future clinical research and applications.

Delivery of proton FLASH at the TRIUMF Proton Therapy Research Centre

The TRIUMF particle accelerator center in Vancouver, British Columbia, Canada houses a proton therapy beam line formerly used for the treatment of ocular cancer. This existing Proton Therapy Research Centre (PTRC) was upgraded to deliver protons at ultra-high dose rates which would be required for FLASH radiotherapy treatments. A peak dose rate of 110 Gy/s over an area of 20 mm2 was delivered at a beam energy of 21 MeV. This was achieved by degrading the cyclotron extracted beam energy of 70 MeV using polymethyl methacrylate (PMMA) plates. In addition, a fast, versatile and reliable method for producing static ridge filters has been developed to spread the proton beam to the entirety of the target axially (i.e., in depth). FLASH dose rates were maintained with a spread-out Bragg peak of 0.5 cm.

Toothpaste Abrasion and Abrasive Particle Content: Correlating High-Resolution Profilometric Analysis with Relative Dentin Abrasivity (RDA).

In this in vitro study, the influence of the concentration of abrasive particles on the abrasivity of toothpastes was investigated using laser scan profilometry on polymethyl methacrylate (PMMA) surfaces with the aim of providing an alternative method to developers for screening of new toothpaste formulations. PMMA plates were tested in a toothbrush simulator with distilled water and four model toothpastes with increasing content of hydrated silica (2.5, 5.0, 7.5, 10.0 wt%). The viscosity of the model toothpaste formulations was kept constant by means of varying the content of sodium carboxymethyl cellulose and water. The brushed surfaces were evaluated using laser scan profilometry at micrometer-scale resolutions, and the total volume of the introduced scratches was calculated along with the roughness parameters Ra, Rz and Rv. RDA measurements commissioned for the same toothpaste formulations were used to analyze the correlation between results obtained with the different methods. The same experimental procedure was applied to five commercially available toothpastes, and the results were evaluated against our model system. In addition, we characterize abrasive hydrated silica and discuss their effects on PMMA-sample surfaces. The results show that the abrasiveness of a model toothpaste increases with the weight percentage of hydrated silica. Increasing roughness parameter and volume loss values show good correlation with the likewise increasing corresponding RDA values for all model toothpastes, as well as commercial toothpastes without ingredients that can damage the used substrate PMMA. From our results, we deduce an abrasion classification that corresponds to the RDA classification established for marketed toothpastes.

Cleaning of thick viscoplastic soil layers by impinging water jets

The removal of thick (approximately 1–10 mm) layers of three viscoplastic soft-solid food-related materials (a moisturising cream, Biscoff spread and smooth peanut butter) from polymethylmethacrylate plates by turbulent, coherent, 2 mm diameter water jets was studied for jet velocities of 10.6–25.4 m s −1 (10 500 < Re < 25 400). When the layer thickness was smaller than the nozzle diameter, soil removal involved the growth of a circular crater. With thicker layers, the removed soil initially formed a blister which subsequently ruptured, and removal by cratering followed. Blister formation and dynamics were studied for the moisturising cream using 2 mm and 3 mm nozzles, which indicated that this process could be described by simple geometric models. Tests with the moisturising cream on glass and stainless steel substrates indicated little effect of substrate on the removal behaviour. The rate of removal in the cratering regime was quantified by the kinetic model of Glover et al. (2016) and the effect of layer thickness on the kinetic parameters compared with the trend predicted by the model of Fernandes and Wilson (2020): qualitative agreement was evident. The results were used to revisit the study of blister formation by water jets impinging on Carbopol® layers reported by Tuck et al. (2019, 2020) and extract kinetic parameters from their data. • Cleaning of thick soil layers investigated using dual camera arrangement. • Removal mode depends on the ratio of film thickness/nozzle diameter. • Removal of thick layers involves blister formation, rupture and cratering. • Cratering regime exhibits momentum-driven removal, similar to thin layers. • Results from literature were analysed: these follow the expected cratering trends.

Use of Antibiotic-impregnated Polymethylmethacrylate (PMMA) Plates for Prevention of Periprosthetic Infection in Breast Reconstruction.

A retrospective review of patients who underwent immediate breast reconstruction with prepectoral TEs over the span of 5 years performed by two surgeons was completed, revealing a total of 447 patients. Data pertaining to patient demographics, operative details, and postoperative outcomes were recorded. Fifty patients underwent TE reconstruction with the addition of a PMMA plate (Stryker, Kalamazoo, Michigan) impregnated with tobramycin and vancomycin. Antibiotic plates were removed at the time of TE-to-implant exchange. Patient-matching analysis was performed using the 397 patients without PMMA plates to generate a 50-patient nonintervention cohort for statistical analysis. The intervention cohort (n = 50) and 1:1 patient-matched nonintervention cohort (n = 50) demonstrated no statistically significant differences in patient demographics or operative characteristics other than PMMA plate placement. The rate of operative periprosthetic infection was 4% in the intervention group and 14% in the nonintervention group (P = 0.047). The rate of TE explantation was also reduced in the intervention group (6% versus 18%; P = 0.036). Follow-up averaged 9.1 and 8.9 months for the intervention and nonintervention groups, respectively (P = 0.255). Local antibiotic delivery using antibiotic-impregnated PMMA plates can be safely and effectively used for infection prevention with TE-based breast reconstruction.

Thermal behaviour of resin inserts for micro injection moulding: a FEM analysis

One of the future challenges is to satisfy a manufacturing market in which the raw material and its storage are increasingly limited, while the need for product diversification is growing. In this context, the global market, especially in the biomedical sectors, sees a growing interest in the miniaturization of products and features for which micro injection moulding (µIM) seems to be ready. Improvement in mould flexibility in terms of reconfigurability of the cavity mould and features is requested to µIM. A tailored insert approach for the micro mould has been adopted to study different materials and micro manufacturing technologies to produce the inserts with such extreme features. Novel high temperature resins for additive manufacturing, able to withstand temperatures up to 250°C, are used to realize inserts for µIM prototyping and small batches. A numerical simulation of the process to produce a 400µm thick thin plates of polymethylmethacrylate (PMMA), a typical benchmark and polymer for microfluidic applications, has been conducted to evaluate the thermal behavior of the resin insert on the molten polymer with respect to the steel one. The results evidenced an isolating behavior of the resin which reduces the thermal dissipation with consequent lower viscosity also during the packing pressure. To validate the results an experimental campaign, was made using both a steel insert and a high-temperature resistance resin insert. The part produced with the resin insert presented diffused flash, a defect usually correlated to high melt temperature and high injection pressure.

Multi-Objective Optimization of Nd: YAG Laser Drilling of Optical-Grade Acrylic Plate Using Taguchi-Based Grey Relational Analysis.

This study proposed an effective method for optimizing laser drilling processing (LDP) by using grey relational analysis (GRA) for multiple performance requirements. First, we developed a system using a Quantel Brilliant Neodymium-doped Yttrium Aluminum Garnet (Nd: YAG) laser with a pulse width of 5-6 ns and F-theta lenses to deliver a focused laser beam with a diameter of 0.2 mm. The developed system was first employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate on a safe window with a high optical density and a grade of OD 7+ @ 950~1085 nm. To avoid errors in the experimental data due to unstable power, a laser power (energy) meter was used to measure the energy stability of the Quantel Brilliant Pulse Laser. Given the stability of 5.6%, this is an effective method for LDP. Four control factors were investigated, including laser pulse energy, repetition rate, focusing position offset, and drilling time. Then, nine experiments were performed using the Taguchi method with orthogonal arrays in L9 (34). The experimental results with multiple quality characteristics were measured and used to optimize the control factors by using GRA with equal weighting of the four qualities (roundness, Hillock ratio, taper, and HAZ). The results show that A1B3C1D1 is the optimal combination of the control factors, and the maximal variation of 0.406 is obtained from the control factor B (focusing position offset) which has the greatest contribution to the drilling time. We then performed confirmation experiment and obtained a better result from the combination of the control factors, A1B3C1D1. GRA helps us determine the best laser drilling parameters to meet the desired multiple drilling qualities.

Comparing image quality of five breast tomosynthesis systems based on radiologists' reviews of phantom data.

Previous studies have shown differences in technical image quality between digital breast tomosynthesis (DBT) systems. However, quantitative image quality measurements may not necessarily fully reflect the clinical performance of DBT. To study the subjective image quality of five DBT systems manufactured by Fujifilm, GE, Hologic, Planmed, and Siemens using phantom images. A TOR MAM test object with polymethyl methacrylate plates was imaged on five DBT systems from different vendors. Three DBT acquisitions were performed at mean glandular doses of 1.0 mGy, 2.0 mGy, and 3.5 mGy while maintaining a constant phantom set-up. Eight DBT acquisitions with different test plate positions and phantom set-up thicknesses were performed at clinically applied dose levels. Additionally, three conventional two-dimensional mammogram images were acquired with different phantom thicknesses. Six radiologists ranked the systems based on the visibilities of the targets seen in the phantom images. In the DBT acquisitions performed at comparable dose levels, one system differed significantly from all other systems in microcalcification scores. When using site-specific DBT protocols, significant differences were found between the devices for microcalcification, filament, and low-contrast targets. A strong correlation was observed between the reviewer scores and radiation doses in DBT acquisitions, whereas no such correlation was observed in the 2D acquisitions. In DBT acquisitions, dose level was found to be a major factor explaining image quality differences between the systems, regardless of other acquisition parameters. Most DBT systems performed equally well at similar dose levels.

An efficient configuration for simultaneous electromembrane extraction of acidic and basic drugs on a chip

• An effective on-chip electromembrane extraction (CEME) was designed and coupled with HPLC. • This design does not require a syringe pump, so the system is simple and easy to handle. • The method was applied for simultaneous extraction and determination of acidic and basic analytes. • Efficient parameters on CEME of ibuprofen, disopyramide and lidocaine were optimized. • The preconcentration factors higher than 7.4 and RSDs% < 3.9% were obtained. In the present study, a new chip was designed for simultaneous electromembrane extraction (EME) of acidic and basic analytes. The method followed by the HPLC-UV analysis, was used for simultaneous extraction and determination of trace amounts of target analytes with different properties. Ibuprofen (IBU), as an acidic model analyte, and disopyramide (DIS) and lidocaine (LID), as basic model analytes, were selected. The chip was composed of three polymethylmethacrylate (PMMA) plates. The chamber for the sample solution was set in the middle plate. Two other chambers were carved on the other plates and they were acted as two acceptor phases’ reservoirs. Two stainless steel electrodes, which were responsible for applying a DC electrical potential on both sides of the supported liquid membranes (SLMs), were placed in the bottom of acceptor phases chambers and connected to a power supply. The two porous polypropylene membrane sheets, which were impregnated with different organic solvents, were used to separate the plates. Effective parameters such as SLM composition (1-octanol for acidic analyte and NPOE+5%DEHP for basic analytes), pH of donor phase and acceptor phases, applied voltage across SLM, and extraction time were optimized. Under the optimized conditions, the calibration curves were linear with coefficient of determinations (R 2 ) higher than 0.991 in the water, urine, and blood plasma samples. The obtained LODs were less than 5.0 µg L −1 and 1 µg L −1 for the basic and acidic analytes, respectively. The results demonstrated that on-chip EME would be used most effectively for extraction and determination of IBU, DIS, and LID in biofluids. Graphical Abstract .

Tantalum-specific contrast-to-noise ratio or conventional detector dose-driven exposure control in angiography: radiation dose and image quality evaluation in a porcine model

BackgroundThe aim of this animal study was to compare the fluoroscopic image quality (IQ) and radiation dose between a tantalum (Ta)-specific contrast-to-noise ratio-driven exposure control (Ta-CEC) and a detector dose-driven exposure control (DEC) in abdominal angiography.MethodsNine angiography scenarios were created in seven anaesthetised pigs using Ta-based embolisation material during percutaneous liver and kidney intervention. Fluoroscopic images were acquired using three DEC protocols with different dose levels and Ta-CEC protocols with different IQ levels, sampled in small steps. Polymethyl-methacrylate and aluminium plates were used to simulate attenuation of three water equivalent thicknesses (WET). Three blinded readers evaluated the IQ of DEC and dose equivalent Ta images and selected the Ta-IQ equivalent image corresponding to the DEC image.ResultsInterobserver agreement for the IQ assessment was 0.43 for DEC, 0.56 for Ta-CEC and for the assessment of incident air kerma at the interventional reference point (Ka,r) for the Ta-IQ equivalent image 0.73. The average IQ of the dose equivalent Ta images was superior compared to the DEC images (p < 0.001) and also for every WET (26, 31, or 36 cm) and dose level (p ≤ 0.022). The average Ka,r for the Ta-IQ equivalent images was 59 ± 16% (mean ± standard deviation) lower compared to the DEC images (p < 0.001).ConclusionsCompared to DEC, Ta-CEC significantly improved the fluoroscopic depiction of Ta, while maintaining the Ka,r. Alternatively, the Ka,r can be significantly reduced by using Ta-CEC instead of DEC, while maintaining equivalent IQ.

Effect of electrode separation and electrode backscatter thickness of a parallel plate ionization chamber on the measurement of dose to tissue in beta radiation fields

Plane parallel plate ionization chamber (PPC) is used in dosimetry especially for beta particles and low energy electron beam. The response of the PPC is affected by the electrode separation, thickness and material of backscatterer. The effect of electrode separation arises due to the well-known inscattering effect of electron which causes fluence perturbation inside the chamber cavity. The perturbation is caused due to reduced electron scattering in the chamber cavity compared to an ideal phantom material and it depends on the thickness of the cavity. Furthermore, the response of PPC also gets affected by the material behind the air cavity. Variation in the response depends on the thickness and the atomic number of the material behind collecting electrode of the PPC. The theoretical studies on the effect of collecting electrode backscatter thickness and electrode separation on the response of a PPC used as a transfer standard in ISO 6980 reference beta radiation field from 85Kr, 90Sr–90Y and 106Ru–106Rh radionuclides are presented. Multi-particle transport code FLUKA is used for the studies. The Polymethyl Methacrylate (PMMA) plate having 3.5 mm thickness is found to provide full backscatter for the above beta radionuclides. It is also observed that even for a well-guarded PPC, as the chamber electrode separation increases, the measured depth dose curve deviates from the ideal depth dose curve and the effective point of measurement (EPOM) of the PPC shifts towards downward direction from chamber reference point. It is also observed that the deviation between ideal and measured depth dose curve (related to EPOM shift) depends on the cavity thickness of the PPC. In the present work, optimization of design parameters of a PPC is carried out to establish it as a transfer standard in compliance with ISO 6980 for the standardization of reference beta radiation fields from 85Kr, 90Sr–90Y and 106Ru–106Rh radionuclide.