Narrow Structure Research Articles

Acoustic Startle Reflex In Adolescents With And Without A Concussion History: A Preliminary Investigation

Due to its narrow structure and sensitivity to rotational forces, the brainstem is particularly vulnerable to injury from head impacts. The acoustic startle reflex is a brainstem-mediated, cross-species reflex that may serve as a sensitive marker for concussion-related brainstem injury. PURPOSE: To examine the acoustic startle reflex in adolescent athletes with a concussion history compared to healthy controls. METHODS: We conducted a cross-sectional study on twenty adolescent athletes with (n = 13, age: 14.8 ± 2.0 years; 46% female) and without (n = 7; age: 13.9 ± 3.1 years; 43% female) a concussion history. Acoustic startle probes were administered to participants through noise-canceling headphones while sitting upright with eyes fixed on a target. The eye blink component of the startle reflex was recorded via electromyography activity of the orbicularis oculi muscle using electrodes placed under the right eye. Measurement sessions began with a one-minute acclimatization period of white noise, followed by twelve 103 decibel acoustic startle probes approximately 50 milliseconds in duration delivered 15-25 seconds apart. The primary dependent variable was mean startle magnitude (μV), and group was the primary independent variable. We analyzed mean startle magnitude with group (concussion history vs healthy control) as a between subjects factor and participant age as a covariate. RESULTS: Mean startle magnitude was markedly lower in adolescents with a concussion history (70.8 ± 25.6 μV) compared to healthy controls (164.1 ± 35.0 μV, t = 2.15, p = 0.047). CONCLUSIONS: These preliminary results provide novel evidence for a distinct attenuation of acoustic startle magnitude in adolescent athletes with a concussion history. This suggests potential for use of the startle reflex to detect lingering physiological dysfunction beyond traditional clinical assessment of recovery. Supported by Thrasher Research Fund Early Career Award

1,8‐Octanedithiol as an Effective Intermediate Layer for Deposition of Cu Electrodes via Inkjet Printing and Laser Sintering on III–V Triple‐Junction Solar Cells

This research study combines surface modification techniques with back‐end‐of‐line (BEOL) methods for cost‐effective, scalable front contact electrode deposition on III–V solar cells. Copper nanoparticle grids are deposited by inkjet printing on surface‐modified III–V solar cells. The deposition of a self‐assembled monolayer (such as 1,8‐octanedithiol) as an intermediate layer is a proven method for surface modification to improve the wettability of the substrate surface and the adhesion of the printed copper nanoparticle structures on the substrate to perform inkjet printing of coherent and narrow electrode structures. Then, the printed copper ink is converted to a conductive copper grid by a picosecond pulsed laser with optimized settings and an additional galvanic plating step is required for the thickening of inkjet‐printed and laser‐sintered seeding layer for solar cell applications. As a result, an ohmic copper contact on III–V layer with low contact resistivity (5 mΩ cm2) is realized successfully. The processed solar cell shows a functioning behavior with 20% conversion efficiency.

87. Sacroiliac joint fusion: review of adverse events and strategies to improve patient safety

87. Sacroiliac joint fusion: review of adverse events and strategies to improve patient safety

Liquefaction mitigation methods for existing shallow-founded elongated structures on horizontal or mildly-inclined ground

This numerical study investigates the effectiveness of selected ground improvement methods for existing elongated structures that are shallow-founded on horizontal or mildly-inclined liquefiable ground. It employs non-linear dynamic fully coupled 2D ground response analyses performed with the finite-difference method. When the mildly-inclined ground remains unimproved, narrow structures prove more susceptible to horizontal displacement and rotation than wide structures with the same load. However, settlements develop regardless of the width of the structure and the (mild) inclination angle of the ground. Focusing on the improvement of existing structures, the paper studies prefabricated vertical drains or stiff containment walls implemented solely at their perimeter. Reinforced concrete walls (diaphragm or secant pile walls) prove much more effective in reducing structural settlements, horizontal displacements and rotations than prefabricated vertical drains, provided that their tip reaches the bottom of the liquefiable layer. Constructing these walls with deep soil-cement mixing proves a viable (less costly) alternative, at least for horizontal ground conditions.

Dominant geometrical factors of collective cell migration in flexible 3D gelatin tube structures

Collective cell migration is a dynamic and interactive behavior of cell cohorts essential for diverse physiological developments in living organisms. Recent studies have revealed the importance of three-dimensional (3D) topographical confinements to regulate the migration modes of cell cohorts in tubular confinement. However, conventional in vitro assays fail to observe cells’ behavior in response to 3D structural changes, which is necessary for examining the geometric regulation factors of collective migration. Here, we introduce a newly developed assay for fabricating flexible 3D structures of capillary microtunnels to examine the behavior of vascular endothelial cells (ECs) as they progress through the successive transition across wide or narrow tube structures. The microtunnels with altered diameters were formed inside gelatin-gel blocks by photo-thermal etching with micrometer-sized spot heating of the focused infrared laser absorption. The ECs migrated and spread two-dimensionally on the inner surface of gelatin capillary microtunnels as a monolayer instead of filling the entire capillary. In the straight cylindrical topographical constraint, leading ECs exhibited no apparent diameter dependence for the maximum peak migration velocity. However, widening the diameter in the narrow-wide structures caused a decrease in migration velocity following in direct proportion to the diameter increase ratio, whereas narrowing the diameter in wide-narrow microtunnels increased the speed without obvious correlation between velocity change and diameter change. The results demonstrated the ability of the newly developed flexible 3D gelatin tube structures for collective cell migration, and the findings provide insights into the dominant geometric factor of the emerging migratory modes for endothelial migration as asymmetric fluid flow-like behavior in the borderless cylindrical cell sheets.

Edge electron-rich carbon nitride via π-acceptor frame with high-efficient charge separation for photocatalytic hydrogen evolution and environmental remediation

Carbon nitride (g-C3N4) has broad application prospects in photocatalytic hydrogen production, but its photocatalytic efficiency is not ideal because of the rapid recombination of photogenerated electrons and holes. Herein, we developed a green strategy to fabricate hydroxyls and carbon-bridging co-modified g-C3N4 (CCN-OH) through a one-pot copolymerization and hydrothermal treatment. Experiments and density functional theory (DFT) calculations illustrated that carbon substitution of partial bridge nitrogen can improve the degree of electron delocalization to enhance the electron supply capacity of g-C3N4, and the exsitence of the electron-withdrawing OH group induces electron migration from carbon nitride to hydroxyl group, which further improves the efficiency of photogenerated charge separation. In addition, CCN-OH possess narrower band structure, resulting in an increased visible light utilization efficiency. The as-synthesized CCN-OH9 samples displayed an excellent photocatalytic activity for degradation of tetracycline with apparent reaction rate constant (k) of 0.018 min−1 and photocatalytic hydrogen evolution of 1880.3 μmol g-1h−1, which was respectively 2.2 and 9.8 times higher than that of CN.

Thermo-Mechanical Calculation of Printed Circuit Heat Exchanger Using Homogenization

The Finite-Element Method (FEM) is mainly used to design Compact Heat Exchanger structures. However, the narrow channel structures require fine mesh to accurately compute stress and strain. Combined with the dimensions of the overall component, this leads to an excessively large numerical model and therefore long computing time. This is especially true for transient thermal analyses, which require taking into account the full geometry. It is therefore interesting to reduce the size of the mesh. Periodic homogenization is an efficient method for achieving this goal. It can be applied to the core of the structure when periodic patterns (identified on basis of the arrangement of the channels) exist. A method based on this technique, with some improvements, is proposed in this paper for thermal loading without internal pressure. In addition to the Equivalent Homogenous Medium (EHM) replacing the periodic patterns, some explicit channels are interposed between the EHM and the cover plates. This has two advantages. The first is to smooth the transition of stiffness between the cover plates and the homogenized medium. The second one is to be able to directly compute stress and strain on the most critical channels located in this area. This paper assesses the method’s effectiveness for thermal loadings in order to conduct thermal stress analyses. First, the equivalent elastic constants of the EHM are obtained with a numerical Finite Elements Method. Then, two 2D cases using EHM are compared against a 2D explicit model (i.e. explicit geometry for the core channels). These cases are chosen to validate the EHM itself and its effectiveness for a real section of the heat exchanger. Results show very good agreement with a relative difference lower than 1%. In addition, the sensitivity to the number of layers added between the EHM and the cover plates is analysed. It is recommended interposing at least two layers of patterns to obtain converged results for the considered configuration. Finally, a triangular mesh is considered to reduce the size of the model. No difference with a regular quadrangular mesh can be observed whereas the computing time is reduced. This method can be used to perform the design of any CHE under thermal loading as long as the channel arrangement shows periodicity.

Highly dispersive Cu species constructed in mesoporous silica derived from ZSM-5 for batch and continuous adsorptive desulfurization of thiophene

ZSM-5 zeolite with long narrow pore structure could restrict the adsorption of sulfur compounds from commercial fuels due to their larger molecular dimensions. Herein, ZSM-5 as silica precursor and CTAB as template was successfully employed using dissolution and self-assembly method to synthesize micro-mesoporous silica (MMZ). Compared with ZSM-5, MMZ materials could effectively overcome the diffusion pathway, enhance mesopores and enlarged the BET surface area (830 m2/g). After MMZ crystals were fabricated with 5-20 wt% Cu content by ultrasound facilitated impregnation strategy, the active sites were improved, which promoted thiophene adsorption capacity from 0.9 to 0.44 and 0.48 mmol/g via π-complexation conducted under dynamic (flow) conditions in a fixed bed adsorber and batch stirring tang reactor, respectively. And the desulfurization performances decline in the order 10Cu/MMZ >20Cu/MMZ > 5Cu/MMZ >10Cu/ZSM-5 > MMZ > ZSM-5. The higher adsorption capacity was tentatively linked with well dispersive Cu nanoparticles (NPs) and textural properties of MMZ. Furthermore, the ADS activity of Cu/MMZ towards thiophene can be recovered well without nominal loss.

Magnetic coherence effects in the spectroscopy of transitions between energy levels with total angular momenta J = 1/2 and J = 1 using unidirectional waves

The physical processes that form the spectra of saturated absorption resonances at atomic transitions between energy levels with angular momenta J = 1/2 and J = 1 in the field of two unidirectional linearly polarised laser waves are studied analytically and numerically. It is shown that the specific features of the resonance spectra are formed in the Λ-schemes of transitions and manifest themselves in the form of narrow coherent structures – dips due to the magnetic coherence (optical orientation) of the transition levels induced by the optical fields. In this case, the energy levels of the lower state make the main contribution, and the contribution of the transfer of magnetic coherence from the sublevels of the upper state to the lower ones in the resonance amplitude manifests itself as an additive. Conditions are found under which the nonlinear resonance is exclusively coherent. The effect of the saturating wave field on the shape of coherent resonance structures is studied.

Effect of barrier thickness on photoelectric properties of InGaN/GaN asymmetric multiple-quantum-well structure light-emitting diode

GaN/GaInN asymmetric multiple quantum well light-emitting diodes with varying potential barrier thicknesses (5 and 15 nm) are grown by using metal organic chemical vapor deposition. The narrow barrier structure improves the performance of the device, including the super-linear increase of electroluminescence integral intensity, the mitigation of efficiency droop at high current density, the reduction of wavelength drift, the reduction of forward voltage, and the improvement of wall-plug efficiency. This is due to the narrowing of the thickness of the quantum barrier, which results in the smaller electric field among the quantum well, the weakening of the quantum confinement Stark effect, the more uniform distribution of carriers across the active region of the device, and the suppression of electron leakage.

Zero-phonon Mn2+ luminescence in natural grossular Ca3Al2(SiO4)3

A natural grossular garnet was found to have a luminescence spectrum with a narrow vibrational structure and short decay time that is unusual for minerals. We propose that such emission is generated by Mn2+ accompanied by defect F-centers which both enhance the transition probability and give rise to sensitivity to optical bleaching and reconstitution via irradiation. The elevated Mn concentration in comparison with other potential luminescent impurities was confirmed by LIBS analysis. Such interpretation contradicts the traditional opinion that Mn2+ centers in minerals are characterized only by broadband emission with very long decay times typical of d-d transitions.

Filament dynamics in vertical confined chemical gardens.

When confined to a Hele-Shaw cell, chemical gardens can grow as filaments, narrow structures with an erratic and tortuous trajectory. In this work, the methodology applied to studies with horizontal Hele-Shaw cells is adapted to a vertical configuration, thus introducing the effect of buoyancy into the system. The motion of a single filament tip is modeled by taking into account its internal pressure and the variation of the concentration of precipitate that constitutes the chemical garden membrane. While the model shows good agreement with the results, it also suggests that the concentration of the host solution of sodium silicate also plays a role in the growth of the structures despite being in stoichiometric excess.

Aircraft and Satellite Observations of Vortex Evolution and Surface Wind Asymmetry of Concentric Eyewalls in Hurricane Irma

We compare the vortex evolutions of eyewall replacement cycles (ERCs) between the sea-surface and the free-atmosphere levels and investigate the asymmetric structure of concentric eyewalls (CEs) by examining a combination of aircraft observations and surface wind fields derived from C-band spaceborne synthetic aperture radar (SAR) images during Hurricane Irma (2017) from 4 September 2017 to 8 September 2017. A total of 116 radial wind profiles measured by an aircraft were collected and showed that ERCs occur at both the sea-surface and the free-atmosphere levels. The outer eyewall was shown to form at the free atmospheric level (~3 km) with a narrow structure at the sea-surface level and an outward tilt with height in the cross-section. In our study, four ERC events were determined from wind profile parameters fitted by a modified Rankine vortex model, which was validated by 328 radial legs collected from six hurricanes. The outer eyewall did not replace the inner eyewall at the sea-surface level in the third ERC, due to the maintenance of a short duration and intense original eyewall. Additionally, Irma’s intensity weakened during the fourth ERC rather than re-intensified, because of the generation of a third wind maximum outside the secondary eyewall. Comparisons of five SAR-derived surface wind fields in Irma and another two hurricane cases illustrated that the location of the secondary eyewall generation is a key point in the interpretation of anomaly intensity changes in the fourth ERC.

Study of Mask Electrochemical Machining for Ring Narrow Groove under the Action of Multiple Physical Fields

Deep and narrow groove structures are widely used in aviation, aerospace, weapons, and other industries, and play a very important role. In order to solve the problems of machining tool deformation, machining flying edge, burr in traditional Computerized Numerical Control (CNC) milling for deep and narrow grooves, and the problems of serious motor loss and low machining efficiency in non-contact electrical discharge machining (EDM), electrochemical mask machining through the mask treatment of the non-processed part mask processing, and with no loss of the processing cathode tool, was suggested as an efficient way to solve these problems. Considering that the corrosion removal of the anodic workpiece is mainly subject to the multi-physical field coupling action between the electric field, the flow field, and the temperature field, it is necessary to construct a multi-physical field coupling model of electrochemical mask machining and combine this with the numerical simulation analysis to realize the distribution state of the multi-physical field, so as to realize the optimization guidance of the overall processing process.

Insights into the possible existence of a soft dipole mode inHe8

With an extreme neutron-to-proton ratio of N/Z=3, 8He provides an ideal laboratory for the study of a variety of exotic phenomena, such as the emergence of a soft dipole mode that is dominated by transitions into the continuum. In this contribution, a covariant density functional theory (DFT) framework is used to compute ground-state properties and the dipole response of 8He. Although 8He is admittedly too light for DFT to be applicable, the great merit of the approach is that the spurious contamination associated with the center-of-mass motion is guaranteed to decouple from the physical response. Given that a strong mixing between the isoscalar and isovector dipole modes is expected for a system with such a large neutron-proton asymmetry as 8He, the narrow structures that emerged at low energies in the isovector dipole response are attributed to the shift of the spurious strength to zero (or near zero) excitation energy. Thus, the theoretical framework implemented here disfavors the emergence of a soft dipole mode in 8He.

Influence of airfoil trailing edge on blade design and machining of small wind turbine

In the design of small wind turbine, narrow structure is often produced at the trailing edge of airfoil, which brings great difficulties to production and processing. In this paper, the airfoil sd7080 is modified by removing part of the airfoil trailing edge to meet the processing technology. Through the calculation and analysis of the Q blade software, part of the airfoil trailing edge is removed, and the airfoil and wind-wheel aerodynamic characteristics are changed. Results: Under the same angle of attack, after removing part of the airfoil trailing edge, The lift coefficient CL and drag coefficient Cd of the airfoil are reduced, α<8.6°, the lift-to-drag ratio CL/Cd decreases, α>8.6°, the lift-to-drag ratio Cl/Cd slightly increases; After removing the trailing edge of some airfoils, the wind energy utilization coefficient CP, torque and thrust of the wind turbine are slightly reduced, and the aerodynamic performance meets the use requirements. Finally, this paper introduces the blade modeling method, and processes the blade through 3D printing technology. The research provides reference significance for the initial design and processing of small wind turbine blades.

Experimental analysis and numerical simulation of wave overtopping on a fixed vertical cylinder under regular waves

Wave overtopping phenomenon affects relatively narrow offshore marine structures different from shoreline linear structures, where there is not defined a precise prediction methodology as it is the case of the behaviour at long coastal defences. In the present study a combined experimental and numerical approach has been followed to obtain an empirical relation that represents the relative overtopping discharge over a fixed vertical cylinder exposed to non-impulsive wave conditions. The phenomenon follows a Weibull type dependence on the relative freeboard in a similar way as the case of vertical walls but reporting a decreasing overtopping rate at higher freeboards. In addition, a direct linear relationship between the relative mean flow thickness computed at the centre of the circular crest of the cylinder and the relative overtopping discharge has been observed. This methodology may be used as an indirect cost-effective method to characterize experimentally the wave overtopping phenomenon in cylindrical structures of full-scale prototypes without the need of accumulating and characterising huge amounts of overtopped water volumes. The present study contains a systematic analysis of the dispersion obtained in the experimental and computational results to evaluate the performance attributed to the proposed empirical expressions. • Overtopping has been characterized in a fixed vertical cylinder and compared with the behaviour of long shoreline defences. • A RANS-VOF Eulerian numerical model has been validated experimentally with a physical scaled model in a wave flume. • A new Weibull type expression predicts the overtopping discharge in a vertical cylinder for non-impulsive wave conditions. • The flow thickness measured at the crest has been proposed to determine the mean overtopping discharge over the structure.

All Heavy Tetraquarks:The Dynamical Diquark Model and Other Approaches

The 2020 announcement by LHCb of a narrow structure $X(6900)$ in the di-$J/\psi$ spectrum -- a potential $c\bar c c\bar c$ state -- has opened a new era in hadronic spectroscopy. In this talk, we briefly survey theory works preceding this event, examine key features of the observed spectrum, and then discuss how subsequent theory studies (including with the author's own dynamical diquark model) have interpreted these features. We conclude with proposals for experiments capable of distinguishing competing interpretations.

Anisotropic spin dynamics in semiconductor narrow wires from the interplay between spin-orbit interaction and planar magnetic field

The anisotropic spin dynamics in wires based on a [001]-oriented semiconductor quantum well were investigated to determine the effect of applying an in-plane magnetic field both parallel to and perpendicular to the spin-orbit magnetic field, and the interaction between them. In one-dimensional spin motion where the wire width is less than the spin-precession length, it is known that the global spin precession is essentially determined by the spin-orbit induced precession along the wire direction. In this study, our objective is to investigate the nature of anisotropic spin dynamics in such narrow semiconductor wires along various crystal orientations. We proposed an analytic expression for the anisotropic spin-relaxation rates and the Larmor-precession frequencies for the arbitrary magnetic field orientation based on a theoretical understanding of the spin dynamics in the narrow wire structure. This expression describes the interaction between the spin-orbit field and all orientations of the in-plane magnetic field. We experimentally investigated the spin dynamics for lithographically defined 800-nm-width wires oriented along the $[\overline{1}10]$, [100], and [110] crystal orientations using a [001] GaAs/AlGaAs quantum well. Time-resolved Kerr rotation microscopy measurements indicated that the spin-relaxation time was the longest for the in-plane magnetic field perpendicular to the spin-orbit field, whereas the parallel configuration was found to be the shortest among all the directions. The precession frequency was found to have the opposite symmetry. These relations are well explained by the theoretical considerations developed in this work. Because the Rashba and Dresselhaus spin-orbit fields are mutually orthogonal in the [100] crystal orientation, it is possible to evaluate both spin-orbit coefficients from the precession anisotropy. These findings suggest that it is possible to control the spin state in narrow wires approaching the one-dimensional state and evaluate the spin-orbit coefficient. This has the potential to provide a greater understanding of quantum and topological information in semiconductor one-dimensional wires.

On-machine measurement and temperature compensation method of NURBS surface interpolation for semicircular narrow neck thickness based on ultra-precision machine tool

Flexible joint is a typical low-rigidity micro part, which has four narrow neck structures evenly distributed around its central axis. In the ultra-precision machining process, it is crucial to control the dimensional accuracy of the narrow necks to improve stiffness consistency. However, the limited space of the neck structures and the high accuracy requirements bring extremely difficulties to the measuring process. In this paper, a novel on-machine measurement method for the semicircular narrow necks was presented and a measuring device was developed based on the combination of high linearity incremental measurement method and on-machine measurement technology. Moreover, the uncertainty of measurement error was analyzed in detail. In view of the measurement error caused by temperature drift, a compensation method based on non-uniform rational B-spline surface interpolation was used to enhance the measurement accuracy. The experimental results showed that the measurement accuracy enhanced over 30% after compensation, which met the measuring requirement of flexible joint.