Asymmetric Field Research Articles

Ionizing Radiation Synthesis of Hydrogel Nanoparticles of Gelatin and Polyethylene Glycol at High Temperature.

Nanohydrogel particles of polyethylene glycol (PEG), gelatin (GEL), and PEG-GEL mixtures (MIXs) were synthesized with a high electron beam and 60Co gamma-ray radiation. The relatively novel technique of Asymmetrical Flow Field Flow Fractionation (AF4 or AFFFF) coupled to a Multi-Angle Laser Light Scattering (MALLS) detector was mainly used to determine the hydrodynamic diameter (Dh) of the radiation-synthesized PEG, GEL, and PEG-GEL nanohydrogel particles. Our approach to achieving nanohydrogel particles is to enhance the intracrosslinking reactions and decrease the intercrosslinking reactions of the C-centered radicals of the PEG and GEL. The intracrosslinking reactions of these free radicals were enhanced via irradiation at temperatures of 77-80 °C and using a high dose rate and pulsed irradiation. The shorter average distance between the C-centered free radicals on the backbone of the thermally collapsed PEG and GEL chain, due to the destruction of hydrogen bonds, enhances the intracrosslinking reactions. It was observed that increasing the dose and dose rate decreased the Dh. DLS results lined up with AF4 measurements. This study provides researchers with a clean method to produce GEL-PEG hydrogels without the use of toxic reagents. Particle size can be tuned with dose, dose rate, and temperature as demonstrated in this work. This is ideal for medical applications as the use of ionizing radiation eliminates toxicity concerns and provides simultaneous sterilization of the material.

Dielectrophoretic Movement of Cell Passing Between Surface Electrodes in Flow Channel

Abstract In this study, cell behavior in a microchannel was tracked for the application of dielectrophoresis to biological cell sorting. A pair of titanium surface electrodes was fabricated inside the microchannel by photolithographic techniques: a triangular electrode with a tip angle of 0.26 rad and a rectangular electrode. A periodic alternating current of square wave with a period of 1 μs was introduced between the electrodes to induce an asymmetric electric field perpendicular to the mainstream direction. The behavior of mouse myoblasts (C2C12: mouse myoblast cell line) was measured in vitro while the suspension was flowing. The relationship between cell shift motion near the electrode and cell shape on the two-dimensional projection plane was investigated. Experimental results showed that cell movement in the direction perpendicular to the mainstream increased with geometries away from the circle in the two-dimensional projection plane. This method can be applied to sort cells according to their degree of shape deviation from a sphere. The dielectrophoretic effect can be applied to sort cells not only by cell size but also by cell deformation.

Multilevel asymmetric coupler MAC field rotator for LP11 mode in few mode fiber

In this work, we present a new design for an integrated optical field rotator for the mode LP11a to the mode LP11b and vice versa using planar Silica over silicon technology. The structure is designed using a Multilayer Asymmetric Coupler. The coupling efficiency of the coupler could be as high as 99% when its length is about 1 mm. For a shorter coupler of length 550 microns and a coupling efficiency of 91%, a complete structure is designed to couple 2 few mode fibers of diameters 15.4 microns through an inverted taper from one side and a Y junction with two inverted tapers from the other side. The fiber to fiber insertion loss of the proposed structure is less than 3 dB over about 190 nm spectral range around 1550 nm. The 3 dB bandwidth of the structure is greater than 360 nm as demonstrated by the Beam Propagation Method BPM simulation.

Noncontact rotation of a small object using an asymmetric ultrasonic field

Noncontact manipulation techniques using airborne high-intensity ultrasound can be applied in various industrial fields such as pharmaceutical industry and future space industry. This paper discusses a method to rotate a small object in the air without physical contact using ultrasound. The experimental system consists of a vibrating disc with four bolt-clamped Langevin-type ultrasound transducers and two semicircular reflectors. The flexural vibration of the disc generates an acoustic standing wave between them, and a small object can be levitated at the nodal position. By inclining one of the two reflectors, an asymmetric acoustic field and an acoustic traveling wave in the circumferential direction are generated where the object can be rotated in the clockwise or counterclockwise direction. Vector flows of the acoustic intensity in the air between the vibrator and reflectors were calculated. When the tilt angle of the reflector was 0.32°, the object was rotated without contact, and the rotation direction corresponded with the direction of the vector flows of the acoustic intensity. A greater input current gave a greater rotation speed; the maximum rotation speed of the object was 6.84 rps in the case of 1.14 A.

Different Behaviors of Outer Radiation Belt keV and MeV Electrons During Two Sequential Geomagnetic Storms

AbstractElectron flux dropout is an extraordinary phenomenon in the outer radiation belt, which is characterized by a drastic depletion in trapped electron populations over a broad range of energies, pitch angles, and L‐shells. Using data from multiple satellites, we study a 5‐day dropout of MeV electrons and a several‐hour dropout of keV electrons in geostationary Earth orbit (GEO) during two sequential geomagnetic storms. Outward radial diffusion caused real loss of MeV electrons, while asymmetric and depressed magnetic fields led to adiabatic variations in keV electron fluxes. In addition to time scale differences, low‐energy keV, medium‐energy keV and high‐energy MeV electron fluxes behaved differently, involving an increasing trend, an initial decreasing trend followed by an increasing trend, and a decreasing trend, respectively, as observed by Radiation Belt Storm Probes (RBSPs) and low‐altitude satellites during the first storm. Substorm injections accompanied by inward radial diffusion initially produced an enhanced flux of electrons with energies up to ∼100 keV. Chorus waves generated in morning side of magnetosphere were responsible for scattering part of this seed population into the atmosphere. In turn, these enhanced but short‐lived chorus waves accelerated lower‐energy keV electrons to achieve a moderate energy level of hundreds of keV within one day. Additionally, the initial slow outward radial diffusion was associated with MeV electron loss, and there was insufficient time for acceleration by chorus waves, so only MeV electrons could maintain long‐term dropout. Competition between energy‐ and L‐shell‐dependent acceleration and loss mechanisms caused different keV and MeV electron behaviors.

Derivatives of linseed oil and camelina oil as monomers for emulsion polymerization

Acrylated methyl esters of higher fatty acids derived from camelina oil and linseed oil were synthesized through transesterification, epoxidation, and subsequent acrylation. Methyl methacrylate and butyl acrylate were copolymerized with various amounts of bio-based derivatives (5 – 30 wt% in monomer mixture) to obtain polymeric latexes for coating applications. Successful emulsion polymerizations with up to 25 wt% of the bio-based derivatives were performed with low coagulum (below 2%) and high monomer conversion (around 95%). The incorporation of bio-based derivatives into polymeric latexes was confirmed with infrared spectroscopy. Asymmetric flow field flow fractionation coupled with a multi-angle light scattering was used to analyze the synthesized copolymers in terms of their molar mass distribution. The results revealed that copolymerizing the bio-based derivatives resulted in ultra-high molar mass nanogel fractions formed because of multi-acrylated ingredients derived from polyunsaturated fatty acids. The phenomenon of nanogel formation became more pronounced for the linseed oil-based derivative. Evaluated coating properties showed that latexes comprising the bio-based derivatives provided increased water repellence (about 10° higher water contact angles were achieved for all bio-based coating compositions in contrast to a reference latex). Moreover, latexes comprising chemically modified oils in the content of 25 and 30 wt% provided water whitening-resistant coatings, making the bio-based derivatives promising candidates for replacing petroleum-based monomers in the production of sustainable latex coatings.Graphical abstract

Analysis of rotor fatigue characteristics of permanent magnet synchronous motor spindle in eccentric state

In this paper, the distribution of the air gap magnetic field in the motorized spindle is obtained through theoretical derivation, which is verified by comparing with the finite element simulation results. Based on the original calculation of air gap magnetic field, the rotor eccentricity theory is added, and the distribution of air gap magnetic field after rotor eccentricity is obtained. The correctness of the calculation theory of eccentric air gap magnetic field is verified by the finite element simulation results. Through the electromagnetic force calculation and finite element simulation of asymmetric magnetic field in eccentric state, the influence law of unbalanced electromagnetic force on the fatigue life of motorized spindle rotor is summarized.

Simulation of double resonant excitation of ions in an asymmetric linear ion trap mass analyzer.

Improving the analytical performance of linear ion traps (LITs) is crucial for the advancement of high-performance LIT mass spectrometers. In this study, a double resonant excitation method was employed in an asymmetric LIT to achieve high ion unidirectional ejection efficiency and enhanced mass resolution. The asymmetric trapping field was generated by stretching one x electrode with a distance α. The double resonant excitation was achieved by applying an alternating voltage out of phase and a supplementary alternating voltage in phase to the x and y electrode pairs of the LIT, respectively. Numerical simulations of ion trajectories were performed to validate the effectiveness of this method. The mass resolution of the asymmetric LIT with double resonant excitation could be improved to ~3800, which was over two times compared to that with only dipolar resonant excitation, while both reached ~90% in ion unidirectional ejection efficiency. By employing the double resonant excitation method, the mass resolution could be improved significantly in the asymmetric LIT, while maintaining a considerably high ion unidirectional ejection efficiency. This method might provide a general solution for enhancing ion detection efficiency and mass resolution of LIT mass spectrometers.

Effect of notch location on fatigue crack growth behavior for inhomogeneous material domains in friction stir welded magnesium alloy

The fatigue crack growth behavior of friction stir welded joints of AZ31 Mg alloy is investigated for three different notch locations. The extended finite element method based simulation is developed to capture the effect of stir zone on fatigue crack growth behavior. The notch locations with asymmetric material domain experience an asymmetric stress field, which leads to crack path deviation from the orthogonal direction to the applied force. This leads to a longer crack path. The near-tip stress field from the simulation enhances the understanding of unusual crack path. The experimental results including crack path trajectories from experiments compare well against the numerical predictions.

Isolation of Carbon Black from Soils by Dispersion for Analysis: Quantitation and Characterization by Field Flow Fractionation Techniques.

In the present work, a procedure based on a dispersive medium for carbon black (CB) isolation from soil samples for analysis was proposed for the first time. Polymeric and biological dispersants and a sequential use of both dispersants were assayed. Asymmetrical flow field flow fractionation with dynamic light scattering detector (AF4-DLS) and sedimentation field flow fractionation with multi-angle light scattering detector (SdF3-MALS) were used for CB quantitation and characterization in the achieved dispersions. Soil samples contaminated with CB were processed, and CB isolation depended on the solid size distribution and composition and dispersant nature. More quantitative isolations were achieved for the four soils treated by the biological dispersant. As the organic matter percentage is higher in soil, the CB isolation was better, varying between 75 and 99% with standard deviation (s) ⩽ 2% for all soils. A soil contaminated with a CB-based pigment paste was analyzed, achieving (99 ± 2)% expressed as expanded uncertainty (K = 2) of dispersive isolation by the biological dispersant, and the sampling was scaled to 250 g of soil with positive results. The procedure was completed by CB recovery to obtain a solid residue able to be reused if necessary. For the filter-aided recovery step, different membranes (fiberglass, nylon, and Teflon) with a pore size between 0.1 and 5 μm were tested. The quantitation of the CB retained in the filter was measured by diffuse reflectance spectroscopy. Teflon (0.10 μm) provided better results for CB recovery, and its re-dispersion was also studied with suitable results. Determination of CB from the filters by diffuse reflectance spectrometry provided the same results than AF4 for CB dispersions.

Suppression of vortex-induced vibration of an elastically mounted sphere by electromagnetic force

In this paper, electromagnetic force on two degrees of freedom vortex-induced vibration (VIV) of an elastically mounted sphere for vibration suppression is numerically achieved at Re = 300. The relations between the wake structures, velocity and pressure distributions, force coefficients, and sphere displacement are investigated by varying the interaction parameter (N) of electromagnetic force. With the increase in N, the momentum of the fluid near the sphere is enhanced to control the flow separation. Therefore, both the rotation radii of the rear stagnation point (RSP) and the separation line (SL) decrease, causing the spiral vortices to become thinner. This leads to a reduction in the fluctuation amplitude of the lift coefficient and mitigates the VIV. As N exceeds 0.5, the periodic spiral vortices transform into a steady double-thread wake due to the stopping of RSP and SL rotation. Therefore, a constant lift is generated in the z-direction due to the asymmetric flow field in the x–z plane, which is accompanied by the VIV fully suppressed. Moreover, the effect of electromagnetic locations (θm) on vibration suppression is examined. With the increase of θm, the vibration suppression efficiency increases first and then decreases, which achieves the maximum vibration suppression efficiency at θm = 125°. The reason is that the electromagnetic force covers the location of the half-circle-shaped SL, which has a significant effect on the control of the flow separation.

Bound states in the continuum in anisotropic photonic crystal slabs

We investigate the bound states in the continuum (BICs) in photonic crystal slabs composed of alternating anisotropic and isotropic dielectric materials. According to the orientation of optical axis plane, three different configurations are proposed for analyzing various types of BICs, associated with extremely large quality factors and vanishing spectral linewidths. In particular, symmetry-protected (SP) BICs exist at the Brillouin zone center for zero rotation angle of the optical axis, which exhibit antisymmetric field patterns that are decoupled from the symmetric radiating fields. Accidental BICs and Friedrich-Wintgen (FW) BICs also occur at the Brillouin zone center for particular rotation angles of the optical axis. The former emerge on isolated bands with quasi-symmetric or quasi-antisymmetric field patterns, while the latter appear near the avoided crossing between two dispersion bands. At off the Brillouin zone center, SP BICs do not exist while accidental BICs and FW BICs appear at particular optical axis rotation angles, with similar features but somewhat more asymmetric field patterns than those at the Brillouin zone center.

Surface Topographical Engineering of Chiral Au Nanocrystals with Chiral Hot Spots for Plasmon-Enhanced Chiral Discrimination.

Surface roughness in chiral plasmonic nanostructures generates asymmetrical localized electromagnetic fields, which hold great promise for applications in chiral recognition, chiroptical spectroscopic sensing, and enantioselective photocatalysis. In this study, we develop a surface topographical engineering approach to precisely manipulate the surface structures of chiral Au nanocrystals. Through carefully controlling the amounts of l- or d-cystine (Cys) and the seed solution in the growth process, we successfully synthesize chiral Au nanocrystals with highly disordered, ordered, and less ordered wrinkled surfaces. An underlying principle governing the relationship between surface roughness, orderliness, and chiroptical response is also proposed. More importantly, the chiral ordered wrinkles on the surfaces of the nanocrystals generate asymmetrical localized electronic fields with enhanced intensity, which achieve excellent plasmon-enhanced chiral discrimination ability for penicillamine (Pen) enantiomers. This work offers exciting prospects for manipulating the surface structures of chiral nanocrystals and designing highly sensitive plasmon-enhanced enantioselective sensors with chiral hot spots.

Distinguishing shallow from mid-crustal magmatic processes at Soufrière Hills Volcano using Finite Element Modelling and co-analysis of EDM and GPS data

We modelled ground deformation at Soufrière Hills Volcano (SHV), using data collected by the Montserrat Volcano Observatory from 2010–2019. We investigate the combined use of Electronic Distance Measuring (EDM) and Global Positioning System (GPS) to distinguish shallow from mid-crustal magmatic processes and their surface deformation profiles. Our results suggest that the EDM network responds predominantly to changes in the shallow magmatic system, whereas GPS records variation at mid-crustal levels. In addition, we show that the behaviour of the EDM network, and of the GPS site HERM, can be explained by underpressurisation in a shallow dyke conduit orientated NNW–SSE, while the mid-crustal system was still undergoing pressurisation. The modelled dyke may be responding to magma cooling and contraction associated with a previous intrusion. We find that geodetic monitoring coverage of multiple flanks within 1 km of the vent can improve our understanding of shallow magmatic system processes with asymmetric deformation fields.

Resolution improvement of optoelectronic tweezers using patterned electrodes.

An optoelectronic tweezer (OET) device is presented that exhibits improved trapping resolution for a given optical spot size. The scheme utilizes a pair of patterned physical electrodes to produce an asymmetric electric field gradient. This, in turn, generates an azimuthal force component in addition to the conventional radial gradient force. Stable force equilibrium is achieved along a pair of antipodal points around the optical beam. Unlike conventional OETs where trapping can occur at any point around the beam perimeter, the proposed scheme improves the resolution by limiting trapping to two points. The working principle is analyzed by performing numerical analysis of the electromagnetic fields and corresponding forces. Experimental results are presented that show the trapping and manipulation of micro-particles using the proposed device.

Asymmetric droplet evaporation on inclined surfaces

A computational model based on disjoining pressure is developed to study the asymmetric evaporation of droplets on an inclined substrate. In the proposed formulation, the disjoining pressure is combined with the arbitrary Lagrange-Euler method (ALE) to describe the solid-liquid interaction and investigate the contact angle hysteresis during evaporation. This model can be used to simulate the droplet evaporation modes of constant contact radius (CCR), constant contact angle (CCA) and “Stick-Slip” (mix evaporation mode), while the results are in good agreement with the experimental data. The obtained droplet shape for different inclined angles shows an asymmetric variation in contact angle at the front and rear ends, with the mean contact angle decreasing as the tilt angle increases. The evaporation flux is symmetric in the case of a horizontal substrate, however, when the substrate is tilted, the front and rear contact angles are modified, which leads to a larger evaporation flux on the rear contact line. Moreover, the asymmetric droplet morphology leads to asymmetric temperature field and vortex in the initial stage of evaporation; as evaporation proceeds, however, the flow and temperature fields within the droplet exhibit a gradual convergence towards symmetry. Moreover, when droplets evaporate on a pair of substrates with complementary tilt angles, their lifetimes exhibit a remarkable similarity. From the evaporation rate evolution, it yields that the larger the percentage of pinning time on the contact line, the faster the evaporation rate of the droplet. The evaporation rate of droplets was 14.76% higher at a tilt angle of α=0° than the case of α=45°.

Relationship between Inter-Eye Asymmetries in Corneal Hysteresis and Visual Field Severity in Patients with Primary Open-Angle Glaucoma.

This study investigated the influence of asymmetric corneal hysteresis (CH) on asymmetric visual field impairment between right and left eyes in patients with primary open-angle glaucoma (POAG) without a history of intraocular surgery. CH, corneal resistance factor (CRF), and corneal compensated intraocular pressure (IOPcc) were measured using the Ocular Response Analyzer. Differences between the eyes (right eye-left eye: DIFRL) and CH-based and in target parameters (higher CH eye-lower CH eye: DIFCH) were calculated in the same patient. In 242 phakic eyes of 121 patients, older age (p < 0.001), lower CH (p = 0.001), and lower CRF (p = 0.007) were significantly associated with worse standard automated perimetry (SAP) 24-2 mean deviation (MD). The DIFsRL in axial length (p = 0.003), IOPcc (p = 0.028), and CH (p = 0.001) were significantly associated with the DIFRL in SAP24-2 MD, but not in central corneal thickness (CCT), Goldmann applanation tonometry (GAT) measurement, and CRF. When dividing the patients into two groups based on the median of the CH DIFsCH (0.46), the DIFsCH in CRF (p < 0.001), IOPcc (p < 0.001), CCT (p = 0.004), SAP24-2 MD (p < 0.001), and SAP10-2 MD (p = 0.010) were significantly different between the groups. Large inter-eye asymmetry in CH is an important explanatory factor for disease worsening in patients with POAG.

High Temporal Resolution Analyses with GOES-16 Atmospheric Motion Vectors of Mesovortex Rapid Intensification in Subtropical Cyclone Henri (2021)

Abstract Four-dimensional COAMPS dynamic initialization (FCDI) analyses with high temporal and spatial resolution GOES-16 atmospheric motion vectors (AMVs) are utilized to analyze the development and rapid intensification of a mesovortex about 150 km to the south of the center of the subtropical cyclone, Cyclone Henri (2021). During the period of the unusual Henri westward track along 30°N, the FCDI z = 300-m wind vector analyses demonstrate highly asymmetric wind fields and a horseshoe-shaped isotach maximum that is about 75 km from the center, which are characteristics more consistent with the definition of a subtropical cyclone than of a tropical cyclone. Furthermore, the Henri westward track and the vertical wind shear have characteristics resembling a Rossby wave breaking conceptual model. The GOES-16 mesodomain AMVs allow the visualization of a series of outflow bursts in space and time in association with the southern mesovortex development and intensification. Then the FCDI analyses forced by those thousands of AMVs each 15 min depict the z = 13 910-m wind field responses and the subsequent z = 300-m wind field adjustments in the southern mesovortex. A second northern outflow burst displaced to the southeast of the main Henri vortex also led to a strong low-level mesovortex. It was when the two outflow bursts joined to create an eastward radial outflow all along the line between them that the southern mesovortex reached maximum intensity and maximum size. In contrast to the numerical model predictions of intensification, outflow from the mesovortex directed over the main Henri vortex led to a decrease in intensity.

Influence of thermal stresses on the phenomenon of thermal fatigue of rolling cylinders

Hot rolling cylinders are the most important machine parts in plastic deformation equipment. They are taken out of operation due to breakage caused by the predominant action of thermal stresses which cause accidental breakdowns of rolling mills. In view of these aspects, the question arose is to knowing the nature of these stresses, as well as their evaluation. This paper will experimentally determine the mechanical and thermal stresses that arise in the process of plastic deformation of hot rolling cylinders. The purpose of this paper is to evaluate the thermal stresses and compare them with the mechanical ones, as well as to highlight their influence on the thermal fatigue phenomenon. The study shows that the stresses in rolling cylinders are cyclical and occur at each rotation of the cylinders. The thermal stresses are mainly the result of the action of symmetric and asymmetric temperature fields. The overall action of thermal stresses presents an aspect of destruction of the surface layer that characterizes the effect of thermal fatigue phenomenon. The separation of the temperature fields that produce thermal stresses in symmetric and asymmetric and their experimental confirmation represents the originality of the research presented in this paper.

Asymmetrical Flow Field Flow Fractionation for Molar Mass Characterization of Polyethylene Oxide in Abuse-Deterrent Formulations

High molar mass polyethylene oxide (HM-PEO) is commonly used to enhance the mechanical strength of solid oral opioid drug products to deter abuse. Because the properties of PEO depend on molar mass distribution, accurately determining the molar mass distribution is a necessary part of understanding PEO's role in abuse-deterrent formulations (ADF). In this study, an asymmetrical flow field-flow fractionation (AF4) analytical procedure was developed to characterize PEO polymers with nominal molar masses of 1, 4 or 7 MDa as well as those from in-house prepared placebo ADF. The placebo ADF were manufactured using direct compress or hot-melt-extrusion methods, and subjected to physical manipulation, such as heating and grinding before measurement by AF4 were performed. The molar mass distribution characterized by AF4 revealed that PEO was sensitive to thermal stress, exhibiting decreased molar mass with increased heat exposure. The optimized AF4 method was deemed suitable for characterizing HM-PEO, offering adequate dynamic separation range for PEO with molar mass from 100 kDa to approximately 10 MDa.