Theoretical fabrication of subwavelength structures by surface plasmon interference based on complementary grating

This paper presents a surface plasmon interference lithography technique based on the complementary grating, which comprises silicon gratings and complementary aluminum grating masks, for fabricating subwavelength structures. In this theoretical study, the optimal parameters of the complementary grating structure were determined using the reflectance spectrum. The optical field distributions of one- and two-dimensional subwavelength structures were obtained using the finite-difference time-domain method and rotation-related formulas. The results of numerical evaluations show that a one-dimensional periodic structure with a half-pitch resolution of 60.5 nm (approximately [Formula: see text]/6.7) can be fabricated. In addition, subwavelength structures can be diversified using different rotation methods to expose the photolithography samples, such as square dot arrays and quasi-hexagonal closely packed structures. The proposed method combines surface plasmon interference with sample rotation, thereby enabling fabrication of abundant subwavelength structures.

DETERMINATION OF WOOD COMPOSITION USING SOLID-STATE 13C NMR SPECTROSCOPY

In recent years, solid-state 13C NMR spectroscopy using the technique of cross-polarization (CP) and sample rotation at a magic angle (MAS) has been widely used in the analysis of plant materials, including wood. Knowledge of the composition, structure and behavior of wood components under various conditions is of great importance, since the properties of wood materials depend on this. In this work, differences in the composition of wood belonging to various tree species growing in central Russia (spruce, aspen, birch, oak, linden, pine, poplar and larch) were revealed using CP MAS 13C NMR spectroscopy. The assignment of various peaks in CP MAS 13C NMR spectra to the main components of wood was carried out. It was shown that cellulose is present in its amorphous and crystalline forms, the presence of lignin was unambiguously confirmed by the signals of aromatic carbon atoms, and hemicelluloses were detected by the signals from the carbon atoms of methyl groups of acetylxylose and L-rhamnose. According to the integral intensities, the total ratio of cellulose and hemicelluloses to lignin was determined: the largest amount of lignin was found in coniferous wood (spruce, larch and pine), and the smallest amount of lignin was detected in deciduous species (aspen, oak, linden, birch and poplar).

Direct cross-sectional imaging using X-ray Compton scattering: application to commercial batteries

A synchrotron-based technique using Compton scattering imaging is presented. This technique has been applied to a coin battery (CR2023), and the cross-sectional image has been obtained in 34 ms without sample rotation. A three-dimensional image of the whole structure has been reconstructed from 74 cross-sectional images taken consecutively by scanning the incident, wide X-ray beam along one direction. This work demonstrates that quick cross-sectional imaging of regions of interest and three-dimensional image reconstruction without sample rotation are feasible using Compton scattering imaging.

CP MAS 13C NMR SPECTROSCOPY IN DETERMINATION OF SPECIFIC DIFFERENCES IN COMPOSITION OF WOOD

In recent years solid-state 13C NMR spectroscopy using the technique of cross-polarization (CP) and sample rotation at a magic angle (MAS) has been used in the analysis of plant materials, including wood. Knowledge of the composition, structure and behavior of wood components in different conditions is of great importance, since the properties of wood materials depend on this. In this work differences in the composition of various tree species wood in central Russia (birch, aspen, spruce, and larch) were revealed using CP MAS 13C NMR spectroscopy. Assignment of various peaks in CP MAS 13C NMR spectra with the main components of wood was carried out. It was shown that cellulose is presented in amorphous and crystalline forms, the presence of lignin is unambiguously confirmed by signals of aromatic carbon atoms, and hemicellulose is detected by signals from carbon atoms of methyl groups of acetylxylose and L-rhamnose. According to the integral intensities, the total proportion of cellulose and hemicellulose in relation to lignin was determined: the largest amount of lignin was found in coniferous wood (spruce, larch), and the smallest amount of lignin was detected in deciduous species (aspen and birch).

Orthopaedic Residency Program Website Content and Accessibility During the COVID-19 Pandemic: Observational Study (Preprint)

BACKGROUND The exceptional competitiveness of the orthopaedic surgery specialty, combined with the unclear impact of the COVID-19 pandemic on residency recruitment, has presented significant challenges to applicants and residency program directors.1 With limited in-person opportunities in the 2020-2021 application cycle, applicants have been pressed to gauge chances and best fit by browsing program websites. OBJECTIVE The objective of the study was to assess the accessibility and content of accredited orthopaedic surgery residency program websites during the COVID-19 pandemic. METHODS Using the online database of the Electronic Residency Application Series (ERAS), we compiled a list of accredited orthopaedic residency programs in the United States. Program websites were evaluated across four domains: program overview, education, research opportunities, and application details. Each website was assessed twice in July, during a period of adjustment to the COVID-19 pandemic, and twice in November, following the October ERAS application deadline. RESULTS 189 accredited orthopaedic surgery residency programs were identified through ERAS. Three programs did not have a website and were not evaluated for content. Data analysis of content in each domain revealed that most websites included program details, a description of the didactic curriculum, and sample rotation schedules. Between the two evaluation periods in July and November, the percentage of program websites containing informative videos and virtual tours rose from 12% to 48% and 1% to 13%, respectively (p<0.005). However, the number of programs that included information about a virtual sub-internship or virtual interview to their websites did not change. CONCLUSIONS Most residency program websites offered program details and an overview of educational and research opportunities; however, few addressed the virtual transition of interviews and sub-internships during the COVID-19 pandemic.

Strength comparative analysis of furniture joints made of various materials

The strength comparative analysis of furniture joints made of various materials. The influence of the load on the angular deformation of the furniture joint samples made of various materials was studied. The tests were carried out for six types of furniture materials: chipboard, MDF, hardwood plywood, glued pine wood, glued oak wood and HPL and for three types of fasteners with different ways of fixing in connected elements: shape-thread, expansion-expansion and expansion-thread way of anchoring in material of boards. The joint samples were loaded with a bending moment only (without inducing transverse loadings). The maximum load capacity and load capacity at the 3° (0.052 rad) sample rotation was measured and then the stiffness coefficients were calculated. Considerable differences were found between HPL and others lignocellulosic materials. Expansion fasteners offer incredibly low joint rigidity. This was observed for all tested furniture materials, from soft (chipboard) to very hard (HPL). Expansion connectors work better in soft lignocellulosic materials than in hard materials. The main advantage of expansion fasteners, in comparison to shape-thread fasteners, is its low visibility in the joint and the technological ease of assembly. On the other hand, thread-shaped connectors offer much greater strength and stiffness of joints.

Effect of equal channel angular pressing route and temperature on the mechanical behavior of ZE41 Mg alloy

A commercial ZE41 Mg alloy was processed by equal channel angular pressing (ECAP) using route BC (90o sample rotation after each pass) and route C (180o sample rotation after each pass) at 250, 300 and 350 oC for up to 4 passes. Significant grain refinement from ∼150 μm to ∼33 μm occurred at the higher third and fourth ECAP passes. The most effective process among all routes and temperature combinations was via route C at 250 oC. Nearly 83% increase in yield strength, 58% increase in ultimate tensile strength, and 107% increase in fracture strain were observed after 4 ECAP passes using route C at 250 oC. The increase in the strength of the alloy was attributed to grain refinement during static and dynamic recrystallization. Fractography of tensile samples showed that shallow dimples change to fine dimples at higher passes modifying the failure mode from cleavage to ductile fracture.

Experimental Studies on the Influence of Electrochemical Dimensional Processing on the Surface Fatigue of Rolls in Rolling Machines

The state of surface layer in large part determines the performance characteristics of products, especially those operating at high contact loads, and in particular of rolls in rolling machines. As a rule, grinding is the final processing of rolls, but high specific work and high local heating in the cutting area lead to the appearance of a large variety of defects in the surface layer of the machined part. Subsequent electrochemical dimensional processing can significantly reduce their number. This article presents the results of comparative tests for surface fatigue of samples made of alloy steel 9Cr2MoV. The sequence of samples preparation for experimental studies is considered, they underwent a cycle of heat treatment according to a single standard mode, which made it possible to obtain a martensitic structure in the presence of inclusions of small carbides. Then the samples were ground to the height of irregularities Ra = 0.3-0.2 microns. Some of the ground samples were subjected to electrochemical dimensional processing at rational modes, when 0.2 mm thick metal layer was removed per side in the time equal to 0.5 min. The result was practically flaw-free surface with the microroughness height Ra = 0.25-0.18 microns. The sample tests for surface fatigue were carried out on a two-contact roller machine under rolling conditions with relative slip between the sample surface and pressure rollers at the peripheral speed of sample rotation 1.3 times lower than the circumferential speed of pressure roller rotation. The analysis on the contact stress diagram of the samples showed that higher resistance to fatigue fractures is observed in the samples after electrochemical dimensional processing. The number of cycles at which the limit of material contact endurance occurs for these samples is almost twice as large as for the samples after grinding.

Imaging Mass Spectrometry of Fingermarks on Brass Bullet Casings using Sample Rotation

A rotation stage was developed to allow the surface of bullet casings to be imaged under ultra-high vacuum (UHV) conditions using time-of-flight secondary ion mass spectrometry (ToF -SIMS). Experiments were...

Sample spinning to mitigate polarization artifact and interstitial-vacancy imbalance in ion-beam irradiation

Accelerator-based ion-beam irradiation has been widely used to mimic the effects of neutron radiation damage in nuclear reactors. However, ion radiation is most often monodisperse in the incoming ions’ momentum direction, leading to excessive polarization in defect distribution, while the scattering under neutron irradiation is often more isotropic and has less radiation-induced polarization. Mitigation of the excess-polarization as well as the damage non-uniformity artifact might be crucial for making the simulation of neutron radiation by ion-beam radiation more realistic. In this work, a general radiation polarization theory in treating radiation as external polar stimuli is established to understand the natural material responses in different contexts, and the possibility to correct the defect polarization artifact in ion-beam irradiation. Inspired by Magic Angle Spinning in Nuclear Magnetic Resonance, we present a precise sample spinning strategy to reduce the point-defect imbalance effect in ion-beam irradiation. It can be seen that with optimized surface inclination angle and the axis of sample rotation, the vacancy-interstitial population imbalance, as well as the damage profile non-uniformity in a designated region in the target are both reduced. It is estimated that sample spinning frequency on the order of kHz should be sufficient to scramble the ion momentum monodispersity for commonly taken ion fluxes and dose rates, which is experimentally feasible.