Transmission Coefficients Research Articles

Improved Oxygen Barrier Properties of Polypropylene/Polyvinyl Alcohol Blends Through Reactive Compatibilization

ABSTRACT The relatively poor oxygen barrier property limits broad application of polypropylene (PP) as packaging materials, pipes, etc. while incorporation of nanoparticles, EVOH etc. faces problems of poor compatibility and dispersion, and high price. In this work, in light of polyvinyl alcohol (PVA) with polyhydroxy structure and excellent barrier properties, PP was blended with PVA through reactive compatibilization by using polypropylene grafted maleic anhydride (PgM) as compatibilizer. A strong intermolecular interaction and entanglement between the two phases formed, leading to an increase of interfacial transition area, and the phase size decreased, changing from “sea-island” to “co-continuous” structure, while a relatively high PVA polymerization degree would lead to a decrease of intermolecular entanglement. In addition, the hydrogen bonding in the system was enhanced, although the crystallinity of the two phases decreased by blending. As a result, the oxygen transmission coefficient of the PP/PVA/PgM blends reached as low as 6.48 × 10−14 cm3·cm/(cm2·s·Pa), which was 48.1% lower than that of PP, while the impact toughness was improved by 56.5%. This work provides a feasible and economic method for enhancing the oxygen barrier ability of PP.

Spectra and transport of probability and energy densities in a PT-symmetric square well with a delta-function potential

Abstract We study the spectrum, eigenstates and transport properties of a simple $\mathcal{PT}$-symmetric model consisting in a finite, complex, square well potential with a delta potential at the origin. We show that as the strength of the delta potential increases, the system exhibits exceptional points accompanied by an accumulation of density associated with the break in the PT-symmetry. We also obtain the density and energy density fluxes and analyze their transport properties. We find that in the $\mathcal{PT}$-symmetric phase transport is efficient, in the sense that all the density that flows into the system at the source, flows out at the sink, which is sufficient to derive a generalized unitary relation for the transmission and reflection coefficients.

Experimental study of different oxides in B2O3–ZnO–BaO glass system for gamma-ray shielding

Glass system of 45B2O3–20ZnO–30BaO–5X, (where X represents CaO, MgO, Al2O3, TiO2, CuO and Fe2O3) in mole percentage was investigated for gamma ray radiation shielding experimentally. Six glass composites were fabricated and the density was measured experimentally and the BZBCa glass sample has the least density with a value of 3.932 g cm−3 and this is due to the presence of CaO in it, and the sample BZBFe has the highest density with a value of 4.031 g cm−3. Through comparing the linear attenuation coefficient (LAC) data (experimental and Phy-X) for the BZBX glass samples, the LAC values for glass samples obtained experimentally and using Phy-X are in a very close range. All the glass samples have the greatest LAC values at 0.0595 MeV, the lowest energy value. Sample BZBCu has a LAC value of 16.203 1/cm, which is also the highest LAC value among all the studied glasses, this is as a result of the high density of this glass and due to the high atomic number of Cu. The glasses’ transmission factor (TF) at 1 cm thickness against energy was determined. The TF values of all the glasses were almost zero. The TF values increased significantly for all the glasses when the energy was increased to 0.662 MeV, and for sample BZBCa its TF value increases 74.08%, which was the highest TF value increase. The half-value layer and other shielding parameters have been determined experimentally.

Roles of Whole-Genome Sequencing in Determining Transmission and Risk Factors Associated with Carbapenem-Resistant Organisms at a Vietnam HealthCare Center of Orphan Children

Roles of Whole-Genome Sequencing in Determining Transmission and Risk Factors Associated with Carbapenem-Resistant Organisms at a Vietnam HealthCare Center of Orphan Children

Beam steering of Fabry Pérot antenna by using hybrid metasurfaces

This paper presents a new approach for designing a superstrate for the Fabry Pérot antenna, to achieve beam steering over the full azimuthal plane. The superstrate of the proposed antenna consists of a linearly graded metasurface (LgMS) and a constant phase partially reflecting surface (PRS). The hybrid metasurfaces offer gradual changes in the magnitude and phase of the reflection and transmission coefficient characteristics, which causes tilting of the main lobe direction.Further, the mechanical rotation of the superstrate structure in the azimuthal plane causes the main lobe direction to steer in the same plane. The proposed antenna operates from 4.33 GHz to 5.1 GHz with a maximum directivity of about 11 dBi and offers beam steering over complete azimuthal plane for frequencies below 4.8 GHz. The proposed structure can be used as a beam steering antenna for applications like air traffic control, satellite communication, shipboard communication, etc.

Mechanism of Fe(II) Chemisorption on Hematite(001) Revealed by Reactive Neural Network Potential Molecular Dynamics.

Atomic-scale understanding of important geochemical processes including sorption, dissolution, nucleation, and crystal growth is difficult to obtain from experimental measurements alone and would benefit from strong continuous progress in molecular simulation. To this end, we present a reactive neural network potential-based molecular dynamics approach to simulate the interaction of aqueous ions on mineral surfaces in contact with liquid water, taking Fe(II) on hematite(001) as a model system. We show that a single neural network potential predicts rate constants for water exchange for aqueous Fe(II) and for the exergonic chemisorption of aqueous Fe(II) on hematite(001) in good agreement with experimental observations. The neural network potential developed herein allows one to converge free energy profiles and transmission coefficients at density functional theory-level accuracy outperforming state-of-the-art classical force field potentials. This suggests that machine learning potential molecular dynamics should become the method of choice for atomistic studies of geochemical processes.

Influence of Proton Irradiation on Thin Films of AZO and ITO Transparent Conductive Oxides—Simulation of Space Environment

Transparent conductive oxides are essential materials for many optoelectronic applications. For new devices for aerospace and space applications, it is crucial to know how they respond to the space environment. The most important issue in commonly used low-Earth orbits is proton radiation. This study examines the effects of high-energy proton irradiation (226.5 MeV) on thin films of aluminium-doped zinc oxide (AZO) and indium tin oxide (ITO). We use X-ray diffraction and electron microscopy observations to see the changes in the structure and microstructure of the films. The optical properties and homogeneity of the materials are determined by spectrophotometry and spectroscopic ellipsometry (SE). Analysis of the chemical states of the elements with X-ray photoelectron spectroscopy (XPS) gives insight into what proton irradiation changes at the surface of the oxides. All measurements show that ITO is less influenced than AZO. The proton energy and fluence used in this study simulate about a hundred years in low Earth orbit. This research demonstrates that both transparent conductive oxide thin films can function under simulated space conditions, with ITO showing superior resilience. The ITO film was more homogenous in terms of the total thickness measured with SE, had fewer defects and adsorbates present on the surface, as XPS analysis proved, and did not show a difference after irradiation regarding its optical properties, transmission, refractive index, or extinction coefficient.

Approximation for reflection and transmission at a thin isotropic poroelastic bed between two isotropic elastic half‐spaces

AbstractSeismic responses from a horizontal poroelastic layer provide chances to detect fluids and characterize reservoirs. The poroelastic layer can be considered a thin poroelastic bed if the layer's thickness is less than about one‐eighth of the P‐wave wavelength. Most previous theoretical studies on the reflection and transmission of waves in a model containing a thin poroelastic bed employ fluid or poroelastic medium as the overlying media. Existing approximate formulas of PP‐wave reflection coefficients are given for P‐wave normal‐incidence. Thus, this paper derived the wave reflection and transmission approximate formulas of a thin poroelastic bed between two elastic half‐spaces with P‐wave oblique incident. First, we illustrated the exact reflection and transmission matrix equations for P‐wave incidents based on poroelasticity theory and the boundary conditions. Assuming the poroelastic bed's thickness is far less than wavelengths of S‐ and P‐waves, approximate reflection and transmission formulas are expanded in Taylor series centred at value of the parameter defined as the product of angular frequency, thickness and slowness. Numerical results show that the thinner the poroelastic layer, the closer the approximate reflection and transmission coefficients are to the exact ones. The approximate formulas are valid for small and medium angles. Approximated PP‐wave reflection and transmission coefficients are closer to the exact values than those of the converted waves, which is caused by the fact that P‐wave has a lower slowness than S‐wave.

Wearable Displacement Sensor Using Inductive Coupling of Printed RFID Tag with Metallic Strip

This paper presents a passive displacement sensor based on the inductive coupling between a printed UHF RFID tag and a metallic strip. The sensor operates by exploiting variations in mutual inductive coupling, which modulate the tag impedance and transmission coefficient, thereby altering the backscattered signal strength and the maximum read range of the RFID tag. The performance of the sensor is validated through simulations and experiments, which demonstrate a sensitivity characterized by an approximately 9 dB reduction in the received signal strength indicator (RSSI) and a 2.3 m decrease in the read range within the first 12 mm of displacement. Furthermore, its potential for wearable applications is showcased through respiratory monitoring, where RSSI variations of approximately 5 dB are observed between the inspiration and expiration phases when positioned on the abdominal region of a volunteer. Thus, the proposed displacement sensing approach offers a cost-effective and battery-free solution for wearable applications with remote monitoring capabilities.

Transfer matrix in graphene-like materials: the case of silicene and transition metal dichalcogenides

The fundamental properties of 1D Dirac-like problems in silicene and transition metal dichalcogenides (TMDs) are derived with the use of the transfer matrix. Analytic expressions for the transmission coefficient and the bound states are obtained for these 2D materials. The continuity between states of perfect transmission and bound states is also addressed in silicene and TMDs. The similarities and differences with respect to the fundamental properties of 1D Dirac-like problems in graphene derived with the transfer matrix (Ibarra-Reyeset al2023J. Phys.: Condens. Matter35395301) are discussed.

Constrained Nuclear-Electronic Orbital Transition State Theory Using Energy Surfaces with Nuclear Quantum Effects.

Hydrogen-atom transfer is crucial in a myriad of chemical and biological processes, yet the accurate and efficient description of hydrogen-atom transfer reactions and kinetic isotope effects remains challenging due to significant quantum effects on hydrogenic motion, especially tunneling and zero-point energy. In this paper, we combine transition state theory (TST) with the recently developed constrained nuclear-electronic orbital (CNEO) theory to propose a new transition state theory denoted CNEO-TST. We use CNEO-TST with CNEO density functional theory (CNEO-DFT) to predict reaction rate constants for two prototypical gas-phase hydrogen-atom transfer reactions and their deuterated isotopologic reactions. CNEO-TST is similar to conventional TST except that it employs constrained minimized energy surfaces to include zero-point energy and shallow tunneling effects in the effective potential. We find that the new theory predicts reaction rates quite accurately at room temperature. The effective potential surface must be generated by CNEO theory rather than by ordinary electronic structure theory, but because of the favorable computational scaling of CNEO-DFT, the cost is economical even for large systems. Our results show that dynamics calculations with this approach achieve accuracy comparable to variational TST with a semiclassical multidimensional tunneling transmission coefficient at and above room temperature. Therefore, CNEO-TST can be a useful tool for rate prediction, even for reactions involving highly quantal motion, such as many chemical and biochemical reactions involving transfers of hydrogen atoms, protons, or hydride ions.

A neural coding method based on feature sensing

AbstractThe novel network contains many sensors, which greatly heightens data transmission burdens. Some networks require the data perceived by sensors for a period to make decisions. Drawing inspiration from the human neural conduction mechanism, a waveform data encoding method called feature sensing neural coding (FSNC) is proposed to enhance network data transmission efficiency. It involves feature decomposition of information and subsequent non‐linear encoding of feature coefficients for data transmission. This approach exploits the unique neuronal responses to diverse stimuli and the inherent non‐linear characteristics of human neural coding. Finally, taking the speech signal and seismic wave signal as examples, the effectiveness of FSNC is verified by simulating the auditory nerve conduction process with frequency as a feature according to the mechanism of travelling wave motion of the basilar membrane in the cochlea. Moreover, experiments on seismic waveform signals have demonstrated the wide applicability of FSNC. Compared with traditional speech coding schemes, the FSNC bit rate is only 6.4 kbps, which greatly reduces the amount of data transmitted. Not only that, FSNC also has a certain fault tolerance, and parallel transmission can also greatly increase the transmission rate. This research provides new ideas for efficient data transmission over new networks.

Mathematical and statistical approaches in epidemiological investigation of hospital infection: A case study of the 2015 Middle East Respiratory Syndrome outbreak in Korea.

Mathematical and statistical methods are invaluable in epidemiological investigations, enhancing our understanding of disease transmission dynamics and informing effective control measures. In this study, we presented a method to estimate transmissibility using patient-level data, with application to the 2015 MERS outbreak at Pyeongtaek St. Mary's Hospital, the Republic of Korea. We developed a stochastic model based on individual case data to derive a likelihood function for disease transmission. Through scenario-based analysis, we explored transmission dynamics, including the role of superspreaders, and investigated how mask-wearing impacted infection control within the hospital. Our findings indicated that the superspreader during the MERS outbreak had approximately 25 times higher transmissibility compared to other patients. Under scenarios of prolonged hospital transmission periods, the number of cases could potentially increase threefold. The impact of mask-wearing in the hospital was significant, with reductions in the epidemic scale ranging from 17% to 77%, depending on the type of mask and intervention intensity. This study quantifies key risk factors in hospital-based transmission, demonstrating the effectiveness of intervention measures. The methodology developed here can be readily adapted to other infectious diseases, providing valuable insights for future outbreak preparedness and response strategies.

Diphtheria Outbreak in Serang City, Banten, Indonesia, 2024: Epidemiological Investigation and Response

Diphtheria is an infectious disease and often causes outbreak. Despite a significant global decrease in diphtheria cases due to effective vaccines, there's still a risk transmission for individuals who unvaccinated or incompletely vaccinated. A positive culture for Corynebacterium diphtheriae was reported in a diphtheria suspect in Serang City and an outbreak investigation was carried out. This study aimed to investigate the outbreak, identify risk factors, and recommend control measures. Data were collected through interviews and field observations to close contacts consist of household contacts, neighbors and school and we reviewed immunization coverage from the Public Health Center. Based on the investigation, it was shown that a 6 years-old male with signs and symptoms of Fever, Sore Throat, Swollen Neck, Pseudomembrane, difficulty swallowing, mouth ulcers, cough and vomiting, and positive results for toxigenic corynebacterium diphtheriae var intermedius. Risk factors for transmission are low immunization coverage, high population density, and mobilization. No additional cases were identified, but some close contacts were at risk of transmission due to unvaccinated. We recommend implementing Outbreak Response Immunization (ORI) as a critical measure to interrupt transmission.

Simulation of single and double anti-reflective film for solar cell

This work presents the analysis of the Fresnel reflection and transmission coefficients at normal incidence to determine an equation for the reflectivity of single and double thin films that are deposited on the reflective surface of a solar cell. The resulting expressions are simulated in the Matlab software, and it is shown how by having such a thin layer, zero reflection can be achieved at a desired wavelength and the zero reflection bandwidth can increase considerably by having a thin double layer.

Study of autotransformer bridges for measurements of the impedance parameters

The analysis of the existing impedance measurement methods showed that for the establishment of precision comparators that operate in a wide range of values in the audio frequency range, it is best to use transformer and autotransformer bridges. Autotransformer bridges are used for measurements in a wide range of the impedance values. The use of autotransformer bridges allows reducing the measurement error to 10–7–10–9. High metrological characteristics of transformer bridge circuits make it possible to use them in commercial devices and precision measuring equipment. Simple autotransformer bridges do not provide the opportunity to measure the impedance parameters in a wide range of values of the tangent of the loss angle (phase shift). For the synthesis of measuring circuits of bridges and their balancing, it is necessary to have a precision quadrature channel that will ensure high accuracy of the transmission coefficient both by phase and by module. The structures of universal autotransformer comparators and their properties are determined by two main factors: by the method of forming the source of the complex balancing signal and by the types of schemes for replacing the impedances of the compared objects. To determine ways to improve universal precision impedance comparators based on autotransformer bridges, it is necessary to develop and analyze mathematical models of universal comparators. The conducted theoretical analysis showed that in the process of comparison, it is possible to compare impedances with different substitution schemes with a direct reading of reactive and active parameters. By choosing the appropriate transmission direction, with a simple reconstruction of the measuring circuit, it is possible to compare two impedances with a parallel substitution scheme, two impedances with a series substitution scheme, or two impedances with a different substitution scheme. The obtained results made it possible to implement them in a universal autotransformer-comparator bridge.

Photoreconfigurable Metasurface for Independent Full-Space Control of Terahertz Waves.

We present a novel photoreconfigurable metasurface designed for independent and efficient control of electromagnetic waves with identical incident polarization and frequency across the entire spatial domain. The proposed metasurface features a three-layer architecture: a top layer incorporating a gold circular split ring resonator (CSRR) filled with perovskite material and dual C-shaped perovskite resonators; a middle layer of polyimide dielectric; and a bottom layer comprising a perovskite substrate with an oppositely oriented circular split ring resonator filled with gold. By modulating the intensity of a laser beam, we achieve autonomous manipulation of incident circularly polarized terahertz waves in both transmission and reflection modes. Simulation results demonstrate that the metasurface achieves a cross-polarized transmission coefficient of 0.82 without laser illumination and a co-polarization reflection coefficient of 0.8 under laser illumination. Leveraging the geometric phase principle, adjustments to the rotational orientation of the reverse split ring and dual C-shaped perovskite structures enable independent control of transmission and reflection phases. Furthermore, the proposed metasurface induces a +1 order orbital angular momentum in transmission and +2 order in reflection, facilitating beam deflection through metasurface convolution principles. Imaging using metasurface digital imaging technology showcases patterns "NUIST" in reflection and "LOONG" in transmission, illustrating the metasurface design principles via the proposed metasurface. The proposed metasurface's capability for full-space control and reconfigurability presents promising applications in advanced imaging systems, dynamic beam steering, and tunable terahertz devices, highlighting its potential for future technological advancements.

Embedded Rough-Neck Helmholtz Resonator Low-Frequency Acoustic Attenuator

In various practical noise control scenarios, such as duct noise mitigation, industrial machinery, architectural acoustics, and underwater applications, it is essential to develop noise absorbers that deliver effective low-frequency attenuation while maintaining compact dimensions. To achieve low-frequency absorption within a limited spatial volume, this study proposes an embedded Helmholtz resonator featuring a roughened neck and establishes a numerical computational model that incorporates thermos viscous effects. A quantitative investigation is conducted on three types of embedded rough-neck geometries (rectangular-grooved, triangular-grooved, and undulated) to elucidate their acoustic performance, with particular attention to differences in acoustic transmission loss and acoustic impedance characteristics. In response to the practical demand for even lower-frequency attenuation, this work further focuses on optimizing the structural parameters of an embedded rectangular-grooved Helmholtz resonator (ERHR). A back-propagation (BP) neural network models and predicts how structural parameters impact the acoustic transmission coefficient, elucidating the effects of geometric variations. Moreover, by coupling the BP network with the Golden Jackal Optimization (GJO) algorithm, a BP-GJO optimization model is developed to refine the structural parameters. The findings reveal that the proposed method significantly improves resonator spatial utilization at a specific noise frequency while preserving acoustic transmission loss performance. This work thereby provides a promising strategy for designing low-frequency, compact Helmholtz resonators suitable for a wide range of noise control applications.

Pre–Human Immunodeficiency Virus (HIV) α4β7hi CD4+ T Cells and HIV Risk Among Heterosexual Individuals in Africa

Abstract Background CD4+ T cells expressing α4β7 are optimal targets for human immunodeficiency virus (HIV) infections, with higher pre-HIV α4β7hi expression linked to increased HIV acquisition and progression in South African women. However, similar associations were not observed in men who have sex with men or people who inject drugs in the Americas, indicating need for further research. Methods This retrospective case-control study enrolled heterosexual men and women from South Africa (HIV Vaccine Trials Network [HVTN] 503) and East Africa (Partners Preexposure Prophylaxis/Couples’ Observational Study [PP/COS]), quantifying α4β7 expression on CD4+ T cells as a predictor of subsequent HIV risk using flow cytometry analyses. Results Associations between α4β7hi expression and HIV acquisition varied across cohorts. In HVTN 503, women had a higher risk estimate compared to men, but this was not significant. In PP/COS, α4β7hi expression was generally protective, particularly in Ugandans. Additionally, α4β7hi expression inversely correlated with peak viral load in PP/COS but not in HVTN 503; in the latter cohort, α4β7hi expression was inversely correlated with the CD4/CD8 ratio and predicted rapid CD4+ T-cell decline, similar to what was observed previously in South Africa. Conclusions These findings suggest that α4β7hi expression on CD4+ T cells may not predict HIV acquisition and progression in all contexts, which may be due to cohort effects, modes of transmission, viral clade, or other factors.

Hydrodynamic analysis of U-shaped OWC with varying bottom profiles integrated with Π-breakwater

In the present study, the fixed U-OWC integrated with Π-shaped breakwater is analysed considering three different bottom profiles (straight, inclined, and curved) of the interior chamber of the U-OWC. The hydrodynamic performance is assessed based on the theoretical maximum efficiency, radiation susceptance and conductance, reflection, transmission and dissipation coefficients and force coefficient on the top lip wall of U-OWC and front face of breakwater. The influence of geometric variations such as width of U-channel, draft of U-OWC, draft and width of breakwater and distance between the two structures on the hydrodynamic performance is analysed using Boundary Element Method (BEM). The study depicts that the presence of a wider U-channel width impairs the energy conversion efficiency of the U-OWC and increasing the draft of the U-OWC improves the efficiency of the device. Further, changing the bottom profile of the internal chamber of U-OWC changes the natural frequency of the device without hampering the efficiency. In addition, as the distance between the two structures is increased, transmission of waves decreases. The influence of wave force on the breakwater is noted to be maximum when the leading U-OWC structure has a curved bottom. The study on the variation of the bottom profile of the fixed U-OWC integrated with breakwater will be helpful in the design and analysis of efficient hybrid floating breakwater system.