Μm Radius Research Articles

Influence of waste foundry sand on microstructural and mechanical behavior of self consolidated concrete filled steel columns

The impacts of leftover foundry sand on steel sections filled with high strength Self-Consolidated Concrete (SCC) were investigated and addressed in this study. 24 steel sections were examined under progressive axial pressure to establish the optimal proportion of leftover foundry sand, a byproduct. 24 samples were divided into 12 columns with eight circular cross sections of 50 mm in radius and 500 mm in length, and eight additional specimens with square sections of 500 mm in length and 100 mm on each side. Additional 12 columns with eight circular specimens measuring 50 mm in radius and 1000 mm in height and eight square specimens measuring 100 mm on each side and 1000 mm in length. The twelve sections can be divided into hollow steel sections and SCC filled sections. The predicted outcome from the studies show that the capability of carrying axial loads and ductility of the SCC-filled steel sections are affected by the use of leftover foundry sand. Additionally, the steel section parts serve as external reinforcement to promote lateral stability and decrease local buckling. The square sections use 25% less steel than the circular sections. By substituting leftover foundry sand for some of the cement, SCC mixes are made. In this project, steel sections filled with self-consolidated concrete were made using varying amounts of leftover foundry sand, including 0%, 4%, 8%, 12%, 16% and 20%. According to the analysis, steel columns with leftover foundry sand have a higher ultimate load than standard concrete, which results in a 12% reduction in construction costs. The work offers a remedy for efficient byproduct management that lessens environmental risk and creates an atmosphere that is eco-friendly.

Genomic capacities for Reactive Oxygen Species metabolism across marine phytoplankton.

Marine phytoplankton produce and scavenge Reactive Oxygen Species, to support cellular processes, while limiting damaging reactions. Some prokaryotic picophytoplankton have, however, lost all genes encoding scavenging of hydrogen peroxide. Such losses of metabolic function can only apply to Reactive Oxygen Species which potentially traverse the cell membrane outwards, before provoking damaging intracellular reactions. We hypothesized that cell radius influences which elements of Reactive Oxygen Species metabolism are partially or fully dispensable from a cell. We therefore investigated genomes and transcriptomes from diverse marine eukaryotic phytoplankton, ranging from 0.4 to 44 μm radius, to analyze the genomic allocations encoding enzymes metabolizing Reactive Oxygen Species. Superoxide has high reactivity, short lifetimes and limited membrane permeability. Genes encoding superoxide scavenging are ubiquitous across phytoplankton, but the fractional gene allocation decreased with increasing cell radius, consistent with a nearly fixed set of core genes for scavenging superoxide pools. Hydrogen peroxide has lower reactivity, longer intracellular and extracellular lifetimes and readily crosses cell membranes. Genomic allocations to both hydrogen peroxide production and scavenging decrease with increasing cell radius. Nitric Oxide has low reactivity, long intracellular and extracellular lifetimes and readily crosses cell membranes. Neither Nitric Oxide production nor scavenging genomic allocations changed with increasing cell radius. Many taxa, however, lack the genomic capacity for nitric oxide production or scavenging. The probability of presence of capacity to produce nitric oxide decreases with increasing cell size, and is influenced by flagella and colony formation. In contrast, the probability of presence of capacity to scavenge nitric oxide increases with increasing cell size, and is again influenced by flagella and colony formation.

Quasi-simultaneous photometric, polarimetric, and spectral observations of distant comet C/2014 B1 (Schwartz)

Context. We analyze the results of our comprehensive observations of the high-perihelion comet C/2014 B1 (Schwartz) with stable disk-shaped coma and jets in order to study its nature. Aims. The main objective of our study is to obtain new observational results for a unique disk-like comet C/2014 B1 (Schwartz) with a perihelion distance of 9.56 au. Methods. Quasi-simultaneous long-slit spectra, as well as photometric and polarimetric images with g-sdss and r-sdss filters, were acquired with the 6 m telescope of the Special Astrophysical Observatory on 2017 January 23. The BVR-band photometry of the comet was also performed at the 2m telescope of the Peak Terskol Observatory on 2017 January 31. We modeled the dynamics of the jets and the behavior of the color and polarization in the coma considering the dust as aggregated large particles. Results. We did not reveal any emissions in the spectra. The positions of two jets oriented along the position angles of 179° and 350° and the disk-like shape of the coma have remained unchanged for more than 4 yr. The most realistic model able to explain jets of such stable orientation includes the existence of two active sources located near the north and south poles of the rotating nucleus whose diameter was determined to be between 7.6 and 12.2 km depending on the albedo, of namely between 0.1 and 0.04, respectively. The high activity of the comet is characterized by the high dust production Afρ which varied from 4440 to 3357 cm between 2017 January 23 and 31. A significant difference between the radial surface brightness profiles of the jets and the ambient (undisturbed by the jets) coma is found. The color of the jet structures is much redder than that of the ambient coma, and the nucleus has a very red color, V − R=0.93m±0.19m. There are spatial variations of the color and polarization over the coma and jets. Conclusions. The observed trends in color and polarization, as well as the brightness profiles, can be explained by the fragmentation of aggregated particles formed by CO2/H2O ices, silicates, and organics, which are of ~1 mm in radius near the nucleus and ~10 μm in radius at the periphery of the coma.

Enhancement of faradaic current in an electrochemical cell integrated into silicon microfluidic channels

Implantable electrochemical sensors enable fast and sensitive detection of analytes in biological tissue, but are hampered by bio-foulant attack and are unable to be recalibrated in-situ. Herein, an electrochemical sensor integrated into ultra-low flow (nL/min) silicon microfluidic channels for protection from foulants and in-situ calibration is demonstrated. The small footprint (5 µm radius channel cross-section) of the device allows its integration into implantable sampling probes for monitoring chemical concentrations in biological tissues. The device is designed for fast scan cyclic voltammetry (FSCV) in the thin-layer regime when analyte depletion at the electrode is efficiently compensated by microfluidic flow. A 3X enhancement of faradaic peak currents is observed due to the increased flux of analytes towards the electrodes. Numerical analysis of in-channel analyte concentration confirmed near complete electrolysis in the thin-layer regime below 10 nL/min. The manufacturing approach is highly scalable and reproducible as it utilizes standard silicon microfabrication technologies.

Post-explant profiling of subcellular-scale carbon fiber intracortical electrodes and surrounding neurons enables modeling of recorded electrophysiology

Objective. Characterizing the relationship between neuron spiking and the signals that electrodes record is vital to defining the neural circuits driving brain function and informing clinical brain-machine interface design. However, high electrode biocompatibility and precisely localizing neurons around the electrodes are critical to defining this relationship. Approach. Here, we demonstrate consistent localization of the recording site tips of subcellular-scale (6.8 µm diameter) carbon fiber electrodes and the positions of surrounding neurons. We implanted male rats with carbon fiber electrode arrays for 6 or 12+ weeks targeting layer V motor cortex. After explanting the arrays, we immunostained the implant site and localized putative recording site tips with subcellular-cellular resolution. We then 3D segmented neuron somata within a 50 µm radius from implanted tips to measure neuron positions and health and compare to healthy cortex with symmetric stereotaxic coordinates. Main results. Immunostaining of astrocyte, microglia, and neuron markers confirmed that overall tissue health was indicative of high biocompatibility near the tips. While neurons near implanted carbon fibers were stretched, their number and distribution were similar to hypothetical fibers placed in healthy contralateral brain. Such similar neuron distributions suggest that these minimally invasive electrodes demonstrate the potential to sample naturalistic neural populations. This motivated the prediction of spikes produced by nearby neurons using a simple point source model fit using recorded electrophysiology and the mean positions of the nearest neurons observed in histology. Comparing spike amplitudes suggests that the radius at which single units can be distinguished from others is near the fourth closest neuron (30.7 ± 4.6 µm, ± S) in layer V motor cortex. Significance. Collectively, these data and simulations provide the first direct evidence that neuron placement in the immediate vicinity of the recording site influences how many spike clusters can be reliably identified by spike sorting.

Sensitivity investigation of open-ended coaxial probe in skin cancer detection

Open-ended coaxial probe method is one of the most common modalities in measuring dielectric properties (DPs) of biological tissues. Due to the significant differences between the tumors and normal tissues in DPs, the technique can be used to detect skin cancer in the early stage. Although various studies have been reported, systematic assessment is in urgent need to advance it to clinical applications, for its parameters interactions and detecting limitations remained unclear. In this study, we aim to provide a comprehensive examination of this method, including the minimum detectable tumor size by using a three-layer skin model via simulation and demonstrated that open-ended coaxial probe method can be used for detection of early-stage skin cancer. The smallest detecting size are subject to different subtypes: for BCC, inside the skin is 0.5mm radius × 0.1mm height; for SCC, inside the skin is 1.4mm × 1.3mm in radius and height; the smallest distinguishing size of BCC is 0.6mm × 0.7mm in radius and height; for SCC is 1.0mm × 1.0mm in radius and height; for MM is 0.7mm × 0.4mm in radius and height. The experiment results showed that sensitivity was affected by tumor dimension, probe size, skin height, and cancer subtype. The probe is more sensitive to cylinder tumor radius than height growing on the surface of the skin while the smallest size probe is the most sensitive among the working probes. We provide a detailed systematic evaluation of the parameters employed in the method for further applications.

Pressure drop measurement in microfluidics channel by the Fabry-Perot diaphragm-based flow sensor

The measurement and control of pressure is an important parameter in optimizing flow rates in microfluidic channels. In this paper, we present simulation and experimental results of measuring pressure drop in a rectangular microfluidics channel by two Fabry-Perot (FP) flow sensors. Sensors include two circular diaphragms made of PDMS (Polydimethylsiloxane) with 50 μm thickness and 200 μm radius, located 2 cm apart which the surface of them create FP cavity with end surface of the fiber optic. Fabry-Pérot interferometers above two diaphragms measure the different deflections of the diaphragms caused by pressure changes in the micro channel. The fluid-structure interaction method is used to solve three-dimensional (3D) Navier-Stokes and continuity equations for selecting appropriate diaphragm thickness and validating experimental results. The experimental and theoretical results are in good agreement and according to the experimental results, these sensors have sensitivities of 30 (nm. (μL/min)-1) and 10 (nm. (μL/min)-1) without hysteresis and the resolution of the sensor is 33 nL/min.

Flexible IrOx neural electrode for mouse vagus nerve stimulation.

Vagus nerve stimulation (VNS) is being actively explored as a treatment for multiple conditions as part of bioelectronic medicine research. Reliable and safe VNS in mouse models is a critical need for understanding mechanisms of these. We report on the development and evaluation of a microfabricated cuff electrode (MouseFlex) constructed of polyimide (PI) and with iridium oxide (IrOx) electrodes that is thermoformed to 86 µm ± 12 µm radius to interface the mouse cervical vagus nerve (r ≈ 50 µm). Innovative bench-top methods were used to evaluate the stimulation stability and electrochemical properties of electrodes. Our aggressive stimulation stability (Stim-Stab) test utilized 1 billion pulses at a 1000 Hz with a current density of 6.28 A/cm2 (1.51 mC/cm2/phase) delivering 3023×103 C/cm2 to evaluate electrode lifetimes, and all electrodes remained functional. We also investigated the effects of thermoforming on their impedance, charge storage capacity (CSC), and charge injection capacity (CIC). The modest changes in electrochemical properties indicate that the thermoforming process was well tolerated. Thermoformed electrode safety and efficacy were evaluated in-vivo by performing acute VNS in mice and monitoring their heart and respiration rate as biomarkers. Their electrochemical properties were also measured before, during and after VNS. Bradycardia and bradypnea were reliably induced at stimulation currents of 100 to 200 µA, well below the in-vivo CIC of ∼1250 µA (∼0.5 mC/cm2), supporting their safety and efficacy. The electrode impedance increased and CIC decreased during in-vivo use, but largely reversed these changes in in-vitro testing after enzymatic cleaning, supporting their tolerance for surgical use. STATEMENT OF SIGNIFICANCE: Vagus nerve stimulation (VNS) is a rapidly growing aspect of healthcare and bioelectronic medicine research. Reliable and safe VNS in mice with small diameter (d ≈ 100 µm) nerves has been a challenge due to achieving intimate contact with the nerve, and the stimulation stability of commonly used electrodes. We demonstrate a microfabricated (MouseFlex) cuff electrode constructed of polyimide with IrOx electrodes that is thermoformed to contact the mouse cervical vagus. Bench studies highlight the stimulation stability exceeded 109 pulses at 6.28 A/cm2 and their electrochemical properties were measured before, during, and after bench and nerve stimulation. Nerve stimulation induced bradycardia and bradypnea at currents below the in-vivo charge injection capacity, supporting their safety, efficacy, and tolerance for surgical handling.

In Vivo Photoadduction of Anesthetic Ligands in Mouse Brain Markedly Extends Sedation and Hypnosis.

Photoaffinity ligands are best known as tools used to identify the specific binding sites of drugs to their molecular targets. However, photoaffinity ligands have the potential to further define critical neuroanatomic targets of drug action. In the brains of WT male mice, we demonstrate the feasibility of using photoaffinity ligands in vivo to prolong anesthesia via targeted yet spatially restricted photoadduction of azi-m-propofol (aziPm), a photoreactive analog of the general anesthetic propofol. Systemic administration of aziPm with bilateral near-ultraviolet photoadduction in the rostral pons, at the border of the parabrachial nucleus and locus coeruleus, produced a 20-fold increase in the duration of sedative and hypnotic effects compared with control mice without UV illumination. Photoadduction that missed the parabrachial-coerulean complex also failed to extend the sedative or hypnotic actions of aziPm and was indistinguishable from nonadducted controls. Paralleling the prolonged behavioral and EEG consequences of on target in vivo photoadduction, we conducted electrophysiologic recordings in rostral pontine brain slices. Using neurons within the locus coeruleus to further highlight the cellular consequences of irreversible aziPm binding, we demonstrate transient slowing of spontaneous action potentials with a brief bath application of aziPm that becomes irreversible on photoadduction. Together, these findings suggest that photochemistry-based strategies are a viable new approach for probing CNS physiology and pathophysiology.SIGNIFICANCE STATEMENT Photoaffinity ligands are drugs capable of light-induced irreversible binding, which have unexploited potential to identify the neuroanatomic sites of drug action. We systemically administer a centrally acting anesthetic photoaffinity ligand in mice, conduct localized photoillumination within the brain to covalently adduct the drug at its in vivo sites of action, and successfully enrich irreversible drug binding within a restricted 250 µm radius. When photoadduction encompassed the pontine parabrachial-coerulean complex, anesthetic sedation and hypnosis was prolonged 20-fold, thus illustrating the power of in vivo photochemistry to help unravel neuronal mechanisms of drug action.

Computational modeling and a Geant4-DNA study of the rejoining of direct and indirect DNA damage induced by low energy electrons and carbon ions

Purpose DNA double-strand breaks (DSBs) created by ionizing radiations are considered as the most detrimental lesion, which could result in the cell death or sterilization. As the empirical evidence gathered from the cellular and molecular radiation biology has demonstrated significant correlations between the initial and lasting levels of DSBs, gaining knowledge into the DSB repair mechanisms proves vital. Much effort has been invested into understanding the mechanisms triggering the repair and processes engaged after irradiation of cells. Given a mechanistic model, we performed – to our knowledge – the first Monte Carlo study of the expected repair kinetics of carbon ions and electrons using on the one hand Geant4-DNA simulations of electrons for benchmarking purposes and on the other hand quantifying the influence of direct and indirect damage. Our objective was to calculate the DSB repair rates using a repair mechanism for G1 and early S phases of the cell cycle in conjunction with simulations of the DNA damage. Materials and Methods Based on Geant4-DNA simulations of DSB damage caused by electrons and carbon ions – using a B-DNA model and a water sphere of 3 μm radius resembling the mean size of human cells – we derived the kinetics of various biochemical repair processes. Results The overall repair times of carbon ions increased with the DSB complexity. Comparison of the DSB complexity (DSBc) and repair times as a function of carbon-ion energy suggested that the repair time of no specific fraction of DSBs could solely be explained as a function of DSB complexity. Conclusion Analysis of the carbon-ion repair kinetics indicated that, given a fraction of DSBs, decreasing the energy would result in an increase of the repair time. The disagreements of the calculated and experimental repair kinetics for electrons could, among others, be due to larger damage complexity predicted by simulations or created actually by electrons of comparable energies to x-rays. They are also due to the employed repair mechanisms, which introduce no inherent dependence on the radiation type but make direct use of the simulated DSBs.

Experimental investigation of effects of indentation depth and probe tip radius on apparent young's modulus of Xenopus laevis oocytes

Throughout their lifespan cells are constantly subjected to mechanical forces. Numerous studies have been conducted to measure mechanical properties of animal cells and understand their effects of the cells’ biological processes. However, the range of the apparent Young's moduli reported in the literature spans three orders of magnitude from 0.1 kPa to 100 kPa, and no clear explanation is given for the source of variation. One of the commonly used experimental techniques to measure material properties at nano- and microscale is nanoindentation. Nanoindentation works by applying a force on a sample via a small probe and recording a force-displacement curve. Probes with different tip shapes and sizes are available. However, there is little guidance on the appropriate choice of probe geometry and size for measurement of properties of animal cells. Eukaryotic cells have a complex structure including a membrane, an actin cortex, a cytoplasm, a nucleus and a cytoskeleton which consists of microfilaments, intermediate filaments and microtubules. These components have different mechanical properties contributing to the overall properties of cells. This work focuses on the effect of tip size and indentation depth on the apparent Young's modulus of Xenopus laevis oocytes measuring approximately 1 mm in diameter. Live cell fluorescent labeling using Lifeact-EGFP and confocal microscopy was used to measure the thickness of the oocyte actin cortex which is expected to have a significant contribution to the cell's stiffness. Apparent mechanical properties were measured using the JPK NanoWizard 4 BioAFM system. Indentations 5, 100 and 400 nm deep using probes with spherical tips of 0.1, 1, and 10 μm radii were performed. Contributions of the membrane and the actin cortex on the overall mechanical properties of the oocytes are analyzed.

On-chip micro-ring resonator array spectrum detection system based on convex optimization algorithm

Abstract We propose an all on-chip micro-ring resonator array spectrum detection system (MRRAS). Micro-ring resonator array as the core is used to construct the transmission matrix of the system. The theoretical analysis of the spectrum detection system is completed with waveguide transmission theory and spectrum construction method based on convex optimization algorithm. In the experiment, we obtain the priori information of the transmission matrix of the system, then detect the output intensity of unknown spectrum through MRRAS, and construct the under-determined matrix equations when the number of micro-rings is much smaller than that of reconstructed wavelengths. Convex optimization algorithm is employed to obtain the least norm solution of the under-determined matrix equations, which enables fast spectrum reconstruction. The experimental results show that the spectrum detection system is constructed using three micro-ring resonators with 4 μm radius, enabling the compact footprint. In addition, the silicon nitride based photonic platform is fully compatible with standard complementary metal oxide semiconductor (CMOS) processes. The system operating bandwidth is more than 12 nm and the resolution is better than 0.17 nm.

Development of a novel cervix-inspired tortuous microfluidic system for efficient, high-quality sperm selection.

Microfluidic systems have been extensively studied in recent years as potential alternatives for problematic conventional methods of sperm selection. However, despite the widespread use of simple straight channels in these systems, the impact of channel geometry on selected sperm quality has not been thoroughly investigated. To explore this further, we designed and fabricated serpentine microchannels with different radii of curvature, inspired by the tortuous structure of the cervix. Our results showed that in the presence of gentle backflow, microfluidic channels with a 150 μm radius of curvature significantly enhanced the quality of selected sperms when compared to straight channels. Specifically, we observed significant improvements of 7% and 9% in total motility and progressive motility, respectively, as well as 13%, 18%, and 19% improvements in VCL, VAP, and VSL, respectively. Through careful observation of the process, we discovered a unique near-wall sperm migration pattern named boundary detachment-reattachment (BDR), that was observed exclusively in curved microchannels. This pattern, which is a direct consequence of the special serpentine geometry and sperm boundary-following characteristic, contributed to the superior selection performance when combined with a fluid backflow. After determining the best channel design, we fabricated a parallelized chip consisting of 85 microchannels capable of processing 0.5 ml of raw semen within 20 minutes. This chip outperformed conventional methods of swim-up and density gradient centrifugation (DGC) in terms of motility (9% and 25% improvements, respectively), reactive oxygen species (18% and 15% improvements, respectively), and DNA fragmentation index (14% improvement to DGC). Outstanding performance and advantages such as user-friendliness, rapid selection, and independence from centrifugation make our microfluidic system a prospective sperm selection tool in clinical applications.

Miniature Deformable MEMS Mirrors for Ultrafast Optical Focusing.

Here, we introduce ultrafast tunable MEMS mirrors consisting of a miniature circular mirrored membrane, which can be electrostatically actuated to change the mirror curvature at unprecedented speeds. The central deflection zone is a close approximation to a parabolic mirror. The device is fabricated with a minimal membrane diameter, but at least double the size of a focused optical spot. The theory and simulations are used to predict maximum relative focal shifts as a function of membrane size and deflection, beam waist, and incident focal position. These devices are demonstrated to enable fast tuning of the focal wavefront of laser beams at ≈MHz tuning rates, two to three orders of magnitude faster than current optical focusing technologies. The fabricated devices have a silicon membrane with a 30-100 μm radius and a 350 nm gap spacing between the top and bottom electrodes. These devices can change the focal position of a tightly focused beam by ≈1 mm at rates up to 4.9 MHz and with response times smaller than 5 μs.

Development and implementation of a metaphase DNA model for ionizing radiation induced DNA damage calculation

Objective. To develop a metaphase chromosome model representing the complete genome of a human lymphocyte cell to support microscopic Monte Carlo (MMC) simulation-based radiation-induced DNA damage studies. Approach. We first employed coarse-grained polymer physics simulation to obtain a rod-shaped chromatid segment of 730 nm in diameter and 460 nm in height to match Hi–C data. We then voxelized the segment with a voxel size of 11 nm per side and connected the chromatid with 30 types of pre-constructed nucleosomes and 6 types of linker DNAs in base pair (bp) resolutions. Afterward, we piled different numbers of voxelized chromatid segments to create 23 pairs of chromosomes of 1–5 μm long. Finally, we arranged the chromosomes at the cell metaphase plate of 5.5 μm in radius to create the complete set of metaphase chromosomes. We implemented the model in gMicroMC simulation by denoting the DNA structure in a four-level hierarchical tree: nucleotide pairs, nucleosomes and linker DNAs, chromatid segments, and chromosomes. We applied the model to compute DNA damage under different radiation conditions and compared the results to those obtained with G0/G1 model and experimental measurements. We also performed uncertainty analysis for relevant simulation parameters. Main results. The chromatid segment was successfully voxelized and connected in bps resolution, containing 26.8 mega bps (Mbps) of DNA. With 466 segments, we obtained the metaphase chromosome containing 12.5 Gbps of DNA. Applying it to compute the radiation-induced DNA damage, the obtained results were self-consistent and agreed with experimental measurements. Through the parameter uncertainty study, we found that the DNA damage ratio between metaphase and G0/G1 phase models was not sensitive to the chemical simulation time. The damage was also not sensitive to the specific parameter settings in the polymer physics simulation, as long as the produced metaphase model followed a similar contact map distribution. Significance. Experimental data reveal that ionizing radiation induced DNA damage is cell cycle dependent. Yet, DNA chromosome models, except for the G0/G1 phase, are not available in the state-of-the-art MMC simulation. For the first time, we successfully built a metaphase chromosome model and implemented it into MMC simulation for radiation-induced DNA damage computation.

Superficial and Deep Capillary Plexuses: Potential Biomarkers of Focal Retinal Defects in Eyes Affected by Macular Idiopatic Epiretinal Membranes? A Pilot Study.

Inner macular layers are the most involved in the retinal distortion caused by idiopathic epiretinal membrane (iERM). They represent the anatomical structures in which the superficial (SCP) and deep (DCP) capillary plexus are embedded. We quantified flow signal (FS) in these capillary plexuses using Swept Source OCT angiography to identify possible markers for postoperative outcome. The software ImageJ was used to quantify the FS in a 150 µm radius area around each point analyzed by MAIA microperimeter. In 16 patients with unilateral iERM, focal light sensitivity (FLS) in the para- and perimacular areas was measured to evaluate macular function in 24 points overlapping macular plexuses and compared with normal fellow eyes (FEs). t-Test for independent samples iERM eyes (iERMEs) vs. fellow eyes (FEs) and Pearson correlation coefficient of FS vs. FLS in each point were calculated. A level of p < 0.05 was accepted as statistically significant. As a whole, FLS was significantly higher in FEs vs. ERMEs (p < 0.001); FS in both SCP and DCP was not significantly different between ERMEs and FEs (p = 0.827, p = 0.791). Correlation in focal retinal areas between FLS and FS in ERMEs was significant in SCP (p = 0.002) and not significant in DCP (p = 0.205); in FEs was significant in both SCP (p < 0.001) and DCP (p = 0.022). As previously described, these defective areas were located mainly in sites of distortion of retinal layers; therefore, it can be hypothesized that a focal change in FS, occurring mostly in SCP, could be involved in the onset of the functional defect.

Influence of different heat treatments and temperatures on the cyclic fatigue resistance of endodontic instruments with the same design.

To evaluate the influence of different heat treatments and temperatures on the cyclic fatigue resistance of 2Shape instruments (Micro Mega, Besancon, France) with the same design. A total of 80 2Shape TS1 (#25/.04) and 80 TS2 (#25/.06) files with different heat treatments (no heat-treated, NHT; C-Wire; T-Wire; CM-Wire) were tested at room (25° ± 1°C) and body (37° ± 1°C) temperatures in 16-mm stainless steel artificial canal with a curvature of 60° and 5mm of radius. Files were tested in continuous rotation at 300rpm using a customized device. Cyclic fatigue resistance was expressed in the number of cyclic to fracture (NCF). The phase transformation temperature of each file was determined by differential scanning calorimetry. Data were statistically analyzed using the two-way ANOVA and the Bonferroni post-hoc test with p < 0.05. All CM-Wire TS1 and TS2 files showed higher NCF than the other groups at both temperatures (p < 0.001). C-Wire TS2 showed higher resistance than NHT and T-Wire TS2 (p < 0.001), with no significant differences between the last two. Body temperature significantly decreased NCF of all tested files (p < 0.05) except for NHT and T-Wire TS1. Body temperature negatively affected the cyclic fatigue resistance of C-Wire and CM-Wire TS1 and of all TS2 files compared with room temperature. The CM-Wire instruments exhibited the highest cyclic fatigue resistance of all tested files. Heat-treated nickel-titanium files can differently perform according to environmental temperature and file dimensions. The CM-Wire 2Shape prototypes displayed the highest flexural resistance in all experimental conditions.

Comparing the impact of thermal stresses and bubble pressure on intergranular fracture in UO[formula omitted] using 2D phase field fracture simulations

UO2 fuel fragmentation and pulverization during loss-of-coolant accidents (LOCAs) is an ongoing safety concern that has gained importance due to recent interest in increasing burnup limits for light water reactor fuel. In this work, we investigate the importance of bubble pressure on fragmentation using 2D phase field fracture simulations of UO2 polycrystals. The model includes anisotropic single crystal elastic constants, encourages intergranular fracture, and includes bubble pressure and its impact on crack opening. An external stress is applied that is representative of the internal stresses observed in macroscale BISON simulations of LOCA tests. Cracks do not form under the external applied stress in UO2 polycrystals without porosity. Crack nucleation and propagation do occur under the external applied stress in polycrystals with unpressurized 1 μm radius intergranular voids, and crack propagation accelerates with increasing number of voids. Crack nucleation and propagation also occur in polycrystals without the external applied stress if the intergranular pores are pressurized, and crack propagation is faster with both pressurized pores and the external applied stress. Our 2D results indicate that bubble pressure may not be necessary to initiate fragmentation in polycrystals with intergranular porosity under LOCA conditions, though this should be verified using 3D simulations with fewer assumptions.

An On-Body Matched Differentially Fed Magnetoelectric Dipole Antenna for Head Imaging Systems

An on-body matched differentially fed magnetoelectric (ME) dipole antenna is proposed for the head imaging system to detect intracranial hemorrhage (ICH). The ME dipole with its differential feed achieves a wide impedance bandwidth of 137% from 0.45 to 2.4 GHz. The antenna exhibits unidirectional and symmetrical radiation patterns in the near-field region, leading to a stable main beam toward the 2-D imaging domain inside the human head. The high front-to-back ratio (FBR) above 18 dB is realized in the whole frequency band by this antenna. The values of specific absorption rate (SAR) always remain safe level under 0.82 W/kg in the entire band with an input power of 10 dBm. To validate the detection capability of the proposed antenna, a head imaging system composed of eight antenna elements in a co-polarization state is designed and fabricated. The reconstructed 2-D images of the head interior using a confocal imaging algorithm demonstrate the successful detection and localization of the circular bleeding area as small as 3 mm in radius numerically and 5 mm in radius experimentally, and it has the capability to detect multiple bleeding areas of the human brain, which indicates the head imaging system has the potential to be used in clinical trials.

Quantifying the effects of background concentrations of crude oil pollution on sea ice albedo

Abstract. Sea ice albedo plays an important role in modulating the climate of Earth and is affected by low background concentrations of oil droplets within the ice matrix that absorb solar radiation. In this study, the albedo response of three different types of bare sea ice (melting, first-year, and multi-year sea ice) are calculated at increasing mass ratios (0–1000 ng g−1) of crude oil by using a coupled atmosphere–sea ice radiative-transfer model (TUV-snow; Tropospheric Ultraviolet–Visible) over the optical wavelengths 400–700 nm. The different types of quasi-infinite-thickness sea ice exhibit different albedo responses to oil pollution, with a 1000 ng g−1 mass ratio of oil causing a decrease to 70.9 % in multi-year sea ice, 47.2 % in first-year sea ice, and 22.1 % in melting sea ice relative to the unpolluted albedo at a wavelength of 400 nm. The thickness of the sea ice is also an important factor, with realistic-thickness sea ices exhibiting similar results, albeit with a weaker albedo response for multi-year sea ice to 75.3 %, first-year sea ice to 66.3 %, and melting sea ice to 35.9 %. The type of oil also significantly affects the response of sea ice albedo, with a relatively opaque and heavy crude oil (Romashkino oil) causing a significantly larger decrease in sea ice albedo than a relatively transparent light crude oil (Petrobaltic oil). The size of the oil droplets polluting the oil also plays a minor role in the albedo response, with weathered submicrometre droplets (0.05–0.5 µm radius) of Romashkino oil being the most absorbing across the optical wavelengths considered. Therefore, the work presented here demonstrates that low background concentrations of small submicrometre- to micrometre-sized oil droplets have a significant effect on the albedo of bare sea ice. All three types of sea ice are sensitive to oil pollution; however, first-year sea ice and particularly melting sea ice are very sensitive to oil pollution.