Small Dimensions Research Articles

The challenge of transseptal access for catheter ablation of left-sided arrhythmia substrate in infants and small children under 6 years of age

Abstract Background Young age and small cardiac dimensions are increased risk factors for catheter ablation (CA), therefore ablation below 15 kg should be recommended only in selected drug-refractory cases. The need for a transseptal puncture (TSP) may be an additional risk factor. Persistent foramen ovale (PFO) in infants can mitigate this risk and paradoxically, decrease the complication rate in the very young. Purpose This study aimed to compare the results of left-sided CA in infants under 1 year and in children between 1-6 years of age. Methods Between January 2010 and September 2023, 1703 pediatric CAs were performed, of which 17 left-sided ablations in children under 6 years without structural heart disease were retrospectively evaluated. CA results below 1 year and between 1-6 years of age were compared in terms of body size, procedural parameters, left atrial (LA) access, complication, and success rate. Results The patient group below 1 year (Group 1, n=5) has a mean age=0.13±0.03 years, mean body weight=3.6±1.1 kg, mean height=52.3±3.6 cm. Patients between 1-6 years (Group 2, n=12) have mean age=5.0±1.1 years, mean body weight=17.9±2.2 kg, mean height=111.2±7.4 cm. The arrhythmia substrate was an overt pathway in 3 pts (17.6%), concealed accessory pathway in 7 pts (41.2%), and focal LA tachycardia in 7 pts (41.2%). Foramen ovale was persistent in all 5 children in Group 1 and TSP was not required. In Group 2, only 2 pts (16.7%) had PFO, and, all other procedures required TSP. TSP was successful in 9/10 cases (90%). No complications related to LA access or other adverse events occurred in Group 1. In Group 2, there was one case of pericardial effusion that spontaneously regressed and one case of mechanical-induced advanced AV block that resolved after six days. There were no significant differences in procedure time, fluoroscopic time, and radiation dose between the two groups (Group 1: 126.4±47.0 min, 6.4±4.5 min, 4.0±5.3 cGycm2 vs. Group 2: 162.6±49.2 min, 7.9±9.4 min, 9.0±12.4 cGycm2, p>0.05). All CAs were performed with RF energy. The acute success rate of the procedures was 100%. Conclusion CA of left-sided arrhythmias in infants and small children may offer a safe and effective therapeutic option in selected cases. The high prevalence of PFO may explain the paradoxically less complication under 1 year of age.

Magnetic and Thermal Behavior of a Planar Toroidal Transformer

This paper presents a study on the magnetic and thermal behaviors of a planar toroidal transformer, comprising two planar toroidal coils. In our configuration, the primary coil consists of twenty turns, while the secondary coil consists of ten turns. This design combines the advantages of both toroidal and planar transformers: it employs flat coils, akin to those utilized in planar transformers, while retaining a toroidal shape for its magnetic core. This combination enables leveraging the distinctive characteristics of both transformer types. This study delves into electromagnetic and thermal behaviors. Electromagnetic behavior is elucidated through Maxwell’s equations, offering insights into the distribution of magnetic fields, potentials, and electric current densities. Fluid flow is modeled via the Navier–Stokes equations. By coupling these equation sets, a more comprehensive and accurate portrayal of the thermal phenomena surrounding electrical equipment is attained. Such research is invaluable in the design and optimization of electrical systems, empowering engineers to forecast and manage thermal effects more efficiently. Consequently, this aids in enhancing the reliability, durability, and performance optimization of electrical equipment. The mathematical model was solved using the finite element method integrated into the COMSOL Multiphysics software v. 6.0. The COMSOL Multiphysics simulation showed correct behavior of potential, electric field, current density, and uniformly distributed temperature. In addition, this planar toroidal coil transformer model offers many advantages, such as small dimensions, high resonance frequency, and high operating reliability. This study made it possible to identify the range of its optimal functioning.

Selected Nonorthogonal Configuration Interaction with Compressed Single and Double Excitations.

Addressing both dynamic and static correlations accurately is a primary goal in electronic structure theory. Nonorthogonal configuration interaction (NOCI) is a versatile tool for treating static correlation, offering chemical insights by combining diverse reference states. Nevertheless, achieving quantitative accuracy requires the inclusion of the missing dynamic correlation. This work introduces a framework for compressing orthogonal single and double excitations into a NOCI of a much smaller dimension. This compression is repeated with each Slater determinant in a reference NOCI, resulting in another NOCI that includes all of its single and double excitations (NOCISD), effectively recovering the missing dynamic correlations from the reference. This compressed NOCISD is further refined through a selection process using metric and energy tests (SNOCISD). We validate the effectiveness of SNOCISD through its application to the dissociation of the nitrogen molecule and the hole-doped two-dimensional Hubbard model at various interaction strengths.

Finite dimensional Frobenius–Perron algebras

Motivated by the Frobenius–Perron (FP) theory of endofunctors of a [Formula: see text]-linear category, we introduce the notion of a FP algebra. This notion can be seen as a generalization of a fusion algebra, and is related to the PP theory of endofunctors of the categories of finite dimensional representations of Taft algebras. Our main result is to classify such algebras with small dimensions according to their FP dimension vectors. Moreover, we introduce the notion of a FP Hopf algebra which can be used to categorify a FP algebra via the Green ring of the Hopf algebra.

End-effector with winding and scooping functions for folding and transporting various cloth parts after cutting

In this study, we propose a novel end-effector that combines the characteristics of winding and scooping fabrics to grasp and categorically place various cloth parts cut by a cutting machine. In addition, we introduce a method for folding the fabric front and back into smaller dimensions, thereby reducing the space required for categorizing, placing, and packaging various clothes, which, to the best of our knowledge, is unique. Subsequently, we develop a method that autonomously determines folding strategies based on the different dimensions of cloth parts, allowing targeted processing of various cloth parts. This approach reduces the height demands of the robot and improves its capability to simultaneously handle multiple types of clothes. Finally, we evaluate the proposed end-effector and folding method in a simulated factory environment using T-shirt parts made of different materials.

Transient Temperature at Tool-Chip Interface during Initial Period of Chip Formation in Orthogonal Cutting of Inconel 718.

Machining nickel-based super alloys such as Inconel 718 generates a high thermal load induced via friction and plastic deformation, causing these alloys to be among most difficult-to-cut materials. Localized heat generation occurring in machining induces high temperature gradients. Experimental techniques for determining cutting tool temperature are challenging due to the small dimensions of the heat source and the chips produced, making it difficult to observe the tool-chip interface. Therefore, theoretical analysis of cutting temperatures is crucial for understanding heat generation and temperature distribution during cutting operations. Periodic heating and cooling occurring during cutting and interruption, respectively, are modeled using a hybrid analytical and finite element (FE) transient thermal model. In addition to identifying a transition distance associated with initial period of chip formation (IPCF) from apparent coefficient of friction results using a sigmoid function, the transition temperature is also identified using the thermal model. The model is validated experimentally by measuring the tool-chip interface temperature using a two-color pyrometer at a specific cutting distance. Due to the cyclic behavior in interrupted cutting, where a steady-state condition may or may not be achieved, transient thermal modeling is required in this case. Input parameters required to identify the heat flux for the transient thermal model are obtained experimentally and the definitions of heat-flux-reducing factors along the cutting path are associated with interruptions and the repeating IPCF. The thermal model consists of two main parts: one is related to identifying the heat flux, and the other part involves the determination of the temperature field within the tool using a partial differential equation (PDE) solved numerically via a 2D finite element method.

Development of trench-shaped microstructure thermal neutron detector using α-Al2O3:C based on optically stimulated luminescence

Optical stimulated luminescence technique is increasingly used in neutron personal dosimetry, due to its capability of fast readout and potential for re-estimation of absorbed dose. The design configuration and performance of the microstructure optically stimulated luminescence neutron detector (MOSLND) using α-Al2O3:C was reported. To improve thermal neutron response, the MOSLND is structured with a matrix of microstructure trenches into the α-Al2O3:C substrate and backfilled with 6LiF. To obtain an optimum trench geometric parameter, several Monte Carlo simulations were performed using Geant4 code. The simulation results show that relatively high energy deposition can be realized for small cell dimensions with deep trenches, and is significantly increased compared with that of simple planar designs. Based on the results of calculation and practical limitation, the device was produced and tested using D2O-modrated 252Cf. The optimized minimal detectable dose (MDD) corresponding to signal integration time of 2 s is 7.2 μSv. The experimental results indicate that MOSLND can be a potential solution for personal neutron dosimetry.

MR-Neurography of the facial nerve in parotid tumors: intra-parotid nerve visualization and surgical correlation.

One of the most severe complications in surgery of parotid tumors is facial palsy. Imaging of the intra-parotid facial nerve is challenging due to small dimensions. Our aim was to assess, in patients with parotid tumors, the ability of high-resolution 3D double-echo steady-state sequence with water excitation (DE3D-WE) (1) to visualize the extracranial facial nerve and its tracts, (2) to evaluate their relationship to the parotid lesion and (3) to compare MRI and surgical findings. A retrospective study was conducted including all patients with parotid tumors, who underwent MRI from April 2022 to December 2023.Two radiologists independently reviewed DE3D-WE images, assessing quality of visualization of the facial nerve bilaterally and localizing the nerve's divisions in relation to the tumor. MRI data were compared with surgical findings. Forty consecutive patients were included (M:F = 22:18; mean age 56.3 ± 17.4years). DE3D-WE could excellently visualize the nerve main trunk and the temporofacial division in all cases. The cervicofacial branch was visible in 99% of cases and visibility was good. Distal divisions were displayed in 34% of cases with a higher visibility on the tumor side (p < 0.05). Interrater agreement was high (weighted kappa 0.94 ± 0.01 [95% CI 0.92-0.97]). Compared to surgery accuracy of MRI in localizing the nerve was 100% for the main trunk, 96% for the temporofacial and 89% for the cervicofacial branches. Facial nerve MR-neurography represents a reliable tool. DE3D-WE can play an important role in surgical planning of patients with parotid tumors, reducing the risk of nerve injury.

Revisiting the Pathophysiology of Intracranial Hemorrhage in Fetuses with Chiari II Malformation: Novel Imaging Biomarkers of Disease Severity?

Intracranial hemorrhage (ICH) has emerged as a notable concern in Chiari II malformation (CM II), yet its origins and clinical implications remain elusive. This study aims to validate the in utero prevalence of ICH in CM II and investigate contributing factors, and visualize the findings in a network format. A single-center retrospective review of fetal MRI scans obtained in fetuses with CM II (presenting January 2007 to December 2022) was performed for ICH utilizing EPI-T2* blood-sensitive sequence. Fetuses with aqueduct stenosis (AS) were included as a control group. The incidence of ICH and corresponding gestational ages were compared between CM II and AS cases, and morphometric measurements (inner/outer CSF spaces, posterior fossa, venous structure) were compared among the 4 1:1 age-matched groups: CM II+ICH, CM II-ICH, AS+ICH, and AS-ICH. Additionally, a co-occurrence network was constructed to visualize associations between phenotypic features in ICH cases. A total of 101 fetuses with CM II and 90 controls with AS at a median gestational age of 24.4 weeks and 22.8 weeks (P = .138) were included. Prevalence of ICH in fetuses with CM II was higher compared with the AS cases (28.7% versus 18.9%, P = .023), accompanied by congested veins (deep vein congestion mainly in young fetuses, and cortical veins may also be affected in older fetuses). ICH was notably correlated with specific anatomic features, essentially characterized by reduced outer CSF spaces and clivus-supraocciput angle. The co-occurrence network analysis reveals complex connections including bony defects, small posterior fossa dimensions, vermis ectopia, reduced CSF spaces, as well as venous congestion and venous sinus stenosis as pivotal components within the network. The high prevalence of ICH-detected by fetal MRI-among fetuses with CM emphasizes the pathophysiologic importance of venous congestion, ICH, and vasogenic edema. As indicators of disease severity, these features may serve as helpful additional imaging biomarkers for the identification of potential candidates for fetal surgery.

Failure assessment of corroded offshore pipelines using code-based approaches and a combination of numerical analysis and artificial neural network

The main purpose of the present paper is to investigate the failure pressure and the remaining life of the corroded offshore pipelines utilizing code-based methods such as ASME B31G, modified ASME B31G, DNV RP-F101 and FFS Level-1. Besides, the results of these approaches are compared with the responses of Finite Element Method (FEM) using Artificial Neural Network (ANN) model. To this purpose, the probability distribution of the corrosion defect length and depth as well as the corrosion rate values are obtained from an In-Line Inspection (ILI) survey of an offshore pipeline project in the Persian Gulf. In addition, a 3D verified numerical model of a corroded pipeline is constructed to conduct the numerical analyses. Using the numerical analysis data, a Multi-Layer Perceptron (MLP) model is created to estimate the failure pressure of the pipeline with arbitrary defect dimensions. Moreover, the remaining life of the corroded pipeline is quantified in order to prevent the catastrophic consequences of the pipeline failure. The results show that the MLP model is capable of estimating the failure pressure of the corroded offshore pipeline with quite acceptable accuracy compared with the mentioned code-based methods. Furthermore, the calculated failure pressure of the corroded pipeline can be sorted in ascending order as: (1) FFS-Level 1 (2) ASME modified B31G (3 & 4) ASME B31G & DNV RP-F101 (5) FEM + MLP. In fact, the failure pressure and the remaining life calculated by DNV RP-F101 are closer to the FEM + MLP results for the defects with small and medium dimensions. Diversely, the DNV RP-F101 method underestimates the failure pressure of the corroded pipeline when the defect dimensions become larger.

Nonlinear dynamics of dissipative water conveying SWCNT/MWCNT/Ferro nanofluid subject to radiation: Thermal analysis by linear slope regression

Carbon nanotubes have gained significant attention due to their unique properties like small dimensions, high thermal conductivity, and unique architecture. These nanotubes have enormous potential in various fields such as nanomedicine, mechanical compound materials, sensor devices, bio-sensors, and many other applications. The present study investigates the impact of adding nanoparticles such as iron oxide (Fe3O4), single-walled carbon nanotubes (SWCNT), and multi-walled carbon nanotubes (MWCNT) on magnetohydrodynamics (MHD) oscillatory water-based flow over a porous medium. The aim is to examine the effect of heat and mass transfer rate and radiative viscous dissipation that interacts with Fe3O4 nanoparticles and carbon nanotubes. The governing equations of the dynamic nanofluid systems are transformed into a set of coupled nonlinear partial differential equations through suitable dimensionless transformations and further converted into ordinary differential equations by taking appropriate solutions for oscillatory-type nanofluid flow. The homotopy perturbation method is applied to solve the governing equations with oscillatory boundary conditions and the solution is also compared with the numerical solver bvp4c. The rate of increase in the temperature and Heat Transfer are computed by the linear slope regression method and results are computed for nanoparticles SWCNT, MWCNT, and Ferro. Also, Skin friction and rate of heat transfer are computed and compared for the nanoparticles with varying Peclet and Eckert numbers. The velocity profile and temperature profile of SWCNT/MWCNT/Ferro nanofluids are being compared. The heat transfer rate is observed to be high for Ferro nanoparticles compared to SWCNT and MWCNT.

Accurate Description of Coulombic Interactions in Organic Field‐Effect Transistors Enabled by Efficient 3D Poisson's Equation Solver with Mixed Boundary Conditions

AbstractThe rational development of organic electronic devices can greatly benefit from a molecular‐level description, where an accurate description of the Coulombic interactions among charge carriers holds paramount importance. However, the molecular‐level organic field‐effect transistor (OFET) simulations do not fully include the short‐range charge‐carrier Coulombic interactions, thus limiting their accuracy. Here, an efficient solution is demonstrated to the 3D Poisson's equation with mixed boundary conditions, optimized for integration into the simulations of organic electronic devices. It leverages the finite difference method for discretization, the Krylov subspace iterative methods for solving the linear system, the algebraic multigrid algorithm for preconditioning, and OpenMP and CUDA parallelization for acceleration. For the organic field‐effect transistors of micrometer sizes or smaller dimensions, obtaining the electric potential within the device takes less than 0.1 s, which is sufficiently efficient for molecular‐level modeling. As a result, both short‐ and long‐range electrostatic interactions are successfully incorporated in the molecular‐level modeling of OFET devices. This integration significantly enhances the robustness of OFET modeling for future applications.

Biocompatible nanoparticles for metals removal from fresh water with potential for rare earth extraction applications

Freshwater contamination by metals can come from a variety of sources and be damaging to wildlife, alter landscapes, and impact human health. Metals removal is desirable not only for improving water quality and preventing adverse effects but also for metals collection and recycling. Nanoadsorption of metals is economically feasible and nanoscale materials exhibit a high surface-area-to-volume ratio that is promising for high adsorption and reactivity. However, the extraordinarily small dimensions of these materials allow them to maneuver biological systems, and combined with high reactivity, this translocation can result in toxicity. In this work, nanoparticles (NPs) composed of a magnetite core coated in hydroxyapatite (HA) and functionalized for adsorption with titanium dioxide (TiHAMNPs) were synthesized. The magnetic core enabled NP retrieval, while HA enhanced adsorption and minimized toxicity. Here, synthesis and characterization are presented, revealing a stable NP structure exhibiting a near neutral surface charge. Results of adsorption studies showed that as compared to silica-coated magnetite nanoparticles (SiMNPs), traditionally used for this application, TiHAMNPs exhibited significantly higher adsorption (43.28% more Cu removal) after 24 h. The equilibrium rate constant for the adsorption of Cu by TiHAMNPs was 0.0003 g/(min*mg) and TiHAMNP adsorption data indicated that TiHAMNPs adsorb metals in a monolayer at the particle surface with a maximum capacity of 2.8 mmol/g. Metabolic and toxicity assays showed TiHAMNPs were highly biocompatible as compared to SiMNPs. This work also explores rare earth element (REE) separation applications of TiHAMNPs, finding that TiHAMNPs may provide a promising alternative for REE retrieval and/or separation.

Design of UWB Wearable Conformal Antenna for Body Area Networks

In this paper, a wearable ultra-wideband (UWB) micro-strip antenna is designed to meet the demand for Wireless Body Area Network (WBAN). This is a wearable textile antenna, which was formed on a jeans fabric substrate to reduce surface-wave losses. The single-fed circular strip monopole antenna provides good impedance matching over the entire UWB frequency range of 2.9∼10.6 GHz. The dielectric constant εr 2.2, and the loss tangent tan δ 0.04 of the jean substrates are measured by using the coaxial ring method. The proposed antenna consists of an improved circular radiation patch with the defective ground structure to expand the frequency band of the antenna and improve the radiation characteristics of the antenna with small dimensions of 20 × 30 × 1.4 mm3. In addition, structural deformation of the proposed antenna is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit, making it most suitable for wearable applications. Key Words: Antenna, S-Parameters, Far Field Directivity, Applications of Antenna, HFSS.

Fabrication of Perfluoropolyether Microfluidic Devices Using Laser Engraving for Uniform Droplet Production.

A perfluoropolyether (PFPE)-based microfluidic device with cross-junction microchannels was fabricated with the purpose of producing uniform droplets. The microchannels were developed using CO2 laser engraving. PFPE was chosen as the main material because of its excellent solvent resistance. Polyethylene glycol diacrylate (PEGDA) was mixed with PFPE to improve the hydrophilic properties of the inner surface of the microchannels. The microchannels of the polydimethylsiloxane microfluidic device had a blackened and rough surface after laser engraving. By contrast, the inner surface of the microchannels of the PFPE-PEGDA microfluidic device exhibited a smooth surface. The lower power and faster speed of the laser engraving resulted in the development of microchannels with smaller dimensions, less than 30 μm in depth. The PFPE and PFPE-PEGDA microfluidic devices were used to produce uniform water and oil droplets, respectively. We believe that such a PFPE-based microfluidic device with CO2-laser-engraved microchannels can be used as a microfluidic platform for applications in various fields, such as biological and chemical analysis, extraction, and synthesis.

Topological semimetal interface resistivity scaling for vertical interconnect applications

In this work, we explore the electron scattering characteristics at interfaces between normal metals and topological semimetals in bulk as well as in thin film structures. We consider Cu/Ta and CoSi/Ta as representative metal/metal and topological semimetal/metal interface structures, respectively. For bulk interface structures, we find that metal/topological semimetal interfaces have roughly 20× higher interfacial resistivity than normal metal/metal interfaces primarily due to the low electronic density of states, the Fermi level in bulk topological semimetals. For thin films, we find that normal metal/metal interfacial resistivity shows a weak dependence on film thickness and is generally close to the corresponding bulk value. Interfaces between surface-conduction dominated topological semimetals, such as CoSi and normal metals in thin films, however, show decreasing interfacial resistivity with decreasing film thickness. This apparent reduction in interface resistivity originates from the surface-dominated transport, where the total transmission across the interface varies little with reduced film thickness, yielding an effective increase in interface conductivity at smaller dimensions. These results suggest that topological semimetals may be attractive candidates for next-generation interconnect materials with critically small dimensions where interfaces with other metals are ubiquitous.

Formulation and Characterization of Chitosan-Based Mixed-Matrix Scaffold for Tissue Engineering

The use of scaffolds, three-dimensional porous, biodegradable and biocompatible structures, that can be produced from natural polymers, synthetics, ceramics and metals is crucial in the tissue engineering field. Chitosan is a polysaccharide of natural origin, found in the exoskeleton of marine arthropods and in the cell wall of fungi, with enormous popularity in the production of three-dimensional materials for Tissue Engineering, in particular bone repair. This polymer has several advantages in the production of these structures in bone regeneration and repair: biodegradability, biocompatibility, non-toxicity and antimicrobial properties. This study aimed to prepare porous scaffolds, for bone repair of degenerative diseases in the spine with better performance and less secondary effects, based on chitosan and another biopolymer (sodium alginate) with the incorporation of calcium phosphates (hydroxyapatite and β-tricalcium phosphate), for tissue engineering application. The obtained scaffolds were object of a detailed characterization, namely with regard to their porosity through the ethanol method, degradation, positron annihilation spectroscopy (PAS), mechanical properties, scanning electronic microscope (SEM), thermal stability through thermogravimetric analysis (TGA), chemical composition through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results obtained showed that the different scaffolds presented pores able to support osteoid matrix growth. The crosslinking of scaffolds was also evaluated and resulted in pores with smaller dimensions and higher regularity in the chitosan-sodium alginate polymer without calcium phosphate scaffold. It was also possible to observe the effect of inorganics on mixed-matrix scaffolds, both morphologically and chemically. These scaffolds showed promising results in terms of mechanical and chemical properties, along with promising porosity for tissue regeneration applications.

Pore structure characterization and its influence on aqueous phase trapping damage in tight gas sandstone reservoirs.

Aqueous phase trapping (APT), which is one of the most prominent damages, seriously restricts the natural gas production in tight gas sandstone with low permeability. Pore size and microscopic pore structures are the most important factors to determine the water blocking damage. In this paper, 9 core samples from tight gas sandstone with various physical properties were employed, and the pore size distribution (PSD) of the core samples were investigated by high pressure mercury intrusion tests (HPMI). Results showed that the porosity of core samples ranges from 5.68% to 13.7%, and the permeability ranges from 0.00456 to 7.86 mD, which is a typical tight reservoir with strong heterogeneity. According to the HPMI capillary curve, the cores can be divided into two types: Type I and Type II, and the pore sizes of type I are larger than that of type II. Fractal distributions were obtained using HPMI data to further determine the pore structure characteristics of tight reservoirs. The pore structures of tight sandstones display the multifractal fractal feature: D1 corresponding to macro-pores, and D2 corresponding to fractal dimension of micro-pores. Furthermore, APT damage was determined by the permeability recovery ratios (Kr) after gas flooding tests. The correlation of Kr and PSD and fractal dimensions were jointly analyzed in tight gas sandstone. Although positive correlations between pore size parameters and the permeability recovery ratios were observed with relatively weak correlations, for those core samples with very close permeability, pore size parameters (both permeability and PSD) is inadequate in clarifying this damage. The fractal dimension can well describe the complexity and heterogeneity of flow channels in pores, which can become the determining factor to distinguish the flow capacity of tight sandstone. The D2 for samples of type I and type II exhibited a good negative relation with Kr with a correlation coefficient of 0.9878 and 0.7723, respectively. The significance of this finding is that for tight gas sandstone, fractal dimensions, especially the small pore fractal dimension (D2), can be used to predict the possible APT damage very well.

Wet Chemical Engineering of Nanostructured GRIN Lenses

AbstractGradient‐index (GRIN) lenses have long been recognized for their importance in optics as a result of their ability to manipulate light. However, traditional GRIN lenses are limited on a scale of tens of microns, impeding their integration into nanoscale optical devices. This study presents a groundbreaking self‐assembled method that overcomes this limitation, allowing for constructing GRIN lenses at an extremely small dimension. The self‐assembly process offers several advantages, including creating highly precise, scalable, cost‐effective, and complex structures that eliminate the need for intricate and time‐consuming manual assembly. By engineering densely packed arrays of metallic nanoparticles, exceptional control over the local refractive index has been achieved. This is accomplished by layer‐by‐layer assembly of gold nanoparticles of different sizes over silica beads. A GRIN lens light‐sink is built where light is preferentially directed toward the center, which is corroborated by measuring the fluorescence of Rhodamine B (RhB) in the inside. Unlike traditional bulky macroscopic GRIN lenses, light‐sinks boast a size under 2.5 µm. Notably, the self‐focusing effects of this design allowed us to track the growth of single‐nanoparticle layers using SERS (Surface‐Enhanced Raman Spectroscopy). These results pave the way for designing and developing lens‐like devices at the nanoscale, allowing unprecedented light manipulation.

Comparative analysis of installations for heat treatment of non-food pulp raw materials by the influence of electrophysical factors

Relevance. The objectives of the work are to develop radio-hermetic installations and substantiate the effective design of the working chamber, which provides a comprehensive effect of electrophysical factors on non-food pulp raw materials to preserve feed value at reduced operating costs. Scientific tasks: 1) to develop installations with different designs of resonators; 2) to conduct a comparative analysis of the working chambers according to the main parameters; 3) to evaluate the technical and economic indicators of an effective installation in relation to the basic version.Methods. The effect of electrophysical factors on raw materials is realized in resonators with magnetrons and frequency generators of pulse-modeled high-frequency oscillations of 110 kHz, where a bactericidal flux lamp serves as a high-potential electrode.Results. Several continuous-flow radiohermetic installations with ultrahigh-frequency (microwave) power supply to non-standard resonators have been developed, inside which a complex effect of a high-intensity electric field, a bactericidal flow of UV rays and ozone is realized to reduce bacterial contamination of the product and neutralize odor during heat treatment of raw materials, the dimensions of which are consistent with the depth of penetration of the wave. Features of conical and biconic resonators − provide radio leakage in continuous operation by cutting off the tip at the level of the critical section, depending on the angle of inclination of the cone generator, and allow you to keep the standing wave inside the resonator. The combination of magnetron and cylindrical resonators increases the efficiency of the interaction of the electron flux with the microwave field, and an increase in the inductive volume, which is a “reservoir” of energy, increases the intrinsic quality of the resonator. A quasi-toroidal resonator, presented as a conical resonator in a toroidal resonator, having small overall dimensions and metal consumption, provides a traveling wave in the annular space, and a standing wave in the conical space. The high electric field strength in the capacitor part of the resonator and the corona discharge in the torus contribute to the disinfection of raw materials.