bluuebunny/crossref_metadata_2025 huggingface dataset:
The Optical and Thermo-Optical Properties of Non-Stoichiometric Silicon Nitride Layers Obtained by the PECVD Method with Varying Levels of Nitrogen Content
Authors: Kluska Stanisława , Jurzecka-Szymacha Maria , Nosidlak Natalia , Dulian Piotr , Jaglarz Janusz
Published: March 2022

In this paper, we investigated the optical and thermo-optical properties of a-SiNx:H layers obtained using the PECVD technique. SiNx:H layers with different refractive indices were obtained from silane and ammonia as precursor gases. Surface morphology and chemical composition studies were investigated using atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectrometry methods. Spectroscopic ellipsometry was used to determine the optical indexes, thicknesses and optical bandgap of the films. The main purpose was to identify the thermo-optical characteristics of layers with different refractive indexes. Thermo-optical studies were performed to determine the temperature hysteresis of optical parameters. These measurements showed that after annealing up to 300 °C and subsequent cooling, the value of optical parameters returned to the initial values.
Calculation of Thermal Expansion Coefficient of Rare Earth Zirconate System at High Temperature by First Principles
Authors: Wang Xingqi , Bai Xue , Xiao Wei , Liu Yuyang , Li Xiaoning , Wang Jianwei , Peng Cheng , Wang Lijun , Wang Xingming
Published: March 2022

Compounds of rare earth zirconates with pyrochlore structure are candidates for the application of thermal barrier coatings of next generation. In order to modify the mechanic properties and maintain the low thermal conductivity, other trivalent rare-earth element substitution is commonly used. Presently, investigation on the evaluation of the property of thermal expansion is attracting more attention. In this paper, a feature parameter of thermal expansion coefficient at high temperature (α∞) was proposed by combining Grüneisen’s equation and the Debye heat capacity model. Using α∞ model, the thermal expansion property of different compounds can be easily figured out by first principles. Firstly, α∞ of ZrO2, HfO2, were calculated, and results are in good agreement with the experimental data from the literature. Moreover, α∞ of La2Zr2O7, Pr2Zr2O7, Gd2Zr2O7, and Dy2Zr2O7 were calculated, and results demonstrated that the model of α∞ is a useful tool to predict the thermal expansion coefficient at high temperature. Finally, Gd2Zr2O7 with 4 different Yb dopant concentrations (Gd1-xYbx)2Zr2O7 (x = 0, 0.125, 0.3125, 0.5) were calculated. Comparing with the experimental data from the literature, the calculation results showed the same tendency with the increasing of Yb concentration.
Praseodymium Orthoniobate and Praseodymium Substituted Lanthanum Orthoniobate: Electrical and Structural Properties
Authors: Dzierzgowski Kacper , Wachowski Sebastian , Łapiński Marcin , Mielewczyk-Gryń Aleksandra , Gazda Maria
Published: March 2022

In this paper, the structural properties and the electrical conductivity of La1−xPrxNbO4+δ (x = 0.00, 0.05, 0.1, 0.15, 0.2, 0.3) and PrNbO4+δ are presented and discussed. All synthesized samples crystallized in a monoclinic structure with similar thermal expansion coefficients. The phase transition temperature between the monoclinic and tetragonal structure increases with increasing praseodymium content from 500 °C for undoped LaNbO4+δ to 700 °C for PrNbO4+δ. Thermogravimetry, along with X-ray photoelectron spectroscopy, confirmed a mixed 3+/4+ oxidation state of praseodymium. All studied materials, in humid air, exhibited mixed protonic, oxygen ionic and hole conductivity. The highest total conductivity was measured in dry air at 700 °C for PrNbO4+δ, and its value was 1.4 × 10−3 S/cm.
Estimate of Coffin–Manson Curve Shift for the Porous Alloy AlSi9Cu3 Based on Numerical Simulations of a Porous Material Carried Out by Using the Taguchi Array
Authors: Tomažinčič Dejan , Klemenc Jernej
Published: March 2022

In real engineering applications, machine parts are rarely completely homogeneous; in most cases, there are at least some minor notch effects or even more extensive inhomogeneities, which cause critical local stress concentrations from which fatigue fractures develop. In the present research, a shift of the Coffin–Manson εa–N material curve in a structure with random porosity subjected to dynamic LCF loads was studied. This allows the rest of the fatigue life prediction process to remain the same as if it were a homogeneous material. Apart from the cyclic σ–ε curve, which is relatively easy to obtain experimentally, the εa–N curve is the second most important curve to describe the correlation between the fatigue life N and the strain level εa. Therefore, the correct shift of the εa–N curve of the homogeneous material to a position corresponding to the porous state of the material is crucial. We have found that the curve shift can be efficiently performed on the basis of numerical simulations of a combination of five porosity-specific geometric influences and the associated regression analysis. To model the modified synthetic εa–N curve, five geometric influences of porosity by X-ray or μ-CT analysis are quantified, and then the porosity-adjusted coefficients of the Coffin–Manson equation are calculated. The proposed approach has been successfully applied to standard specimens with different porosity topography.
Effective Viscoplastic-Softening Model Suitable for Brain Impact Modelling
Authors: Dyniewicz Bartłomiej , Bajkowski Jacek M. , Bajer Czesław I.
Published: March 2022

In this paper, we address the numerical aspects and implementation of a nonlinear viscoplastic model of the mechanical behaviour of brain tissue to simulate the dynamic responses related to impact loads which may cause traumatic injury. Among the various viscoelastic models available, we deliberately considered modifying the Norton–Hoff model in order to introduce non-typical viscoplastic softening behaviour that imitates a brain’s response just several milliseconds after a rapid impact. We describe the discretisation and three dimensional implementation of the model, with the aim of obtaining accurate numerical results in a reasonable computational time. Due to the large scale and complexity of the problem, a parallel computation technique, using a space–time finite element method, was used to facilitate the computation boost. It is proven that, after calibrating, the introduced viscoplastic-softening model is better suited for modelling brain tissue behaviour for the specific case of rapid impact loading rather than the commonly used viscoelastic models.
Feasibility Study on the Steel-Plastic Geogrid Instead of Wire Mesh for Bolt Mesh Supporting
Authors: Wang Qingbiao , Wang Dong , Li Yue , Liu Wenxia , Tian Chenglin , Shi Zhenyue , Wang Keyong , Song Hongxu , Hu Zhongjing , Zhang Xu , Liang Xunmei , Tang Fei , Tang Xingquan , Liu Zhengyin , Zhang Mingjing
Published: March 2022

Wire mesh is a common material for bolt mesh supporting structures, but its application in engineering has revealed many defects. At the same time, with the development of new materials for civil engineering, the new material mesh performance and cost show outstanding advantages over wire mesh. In this paper, the feasibility of replacing wire mesh with steel-plastic geogrid as an alternative material is carefully studied through indoor tests and field applications. The following conclusions were drawn from a comparative analysis with wire mesh, mainly in terms of mechanical properties, engineering characteristics, and construction techniques: (1) in terms of mesh wire strength, wire mesh is slightly better than steel-plastic geogrid, but in the case of similar tensile strength, the amount of steel used per unit length of steel geogrid bars is only 36.75% of that of steel-plastic geogrid, while the tensile strength of the high-strength steel wire attached to the steel-plastic geogrid belt is about 3.3 times that of steel bars; (2) in terms of junction peel strength, both values are similar, with the injection-moulded junction being 1154.56–1224.38 N and the welded junction of 4 mm mesh being 988.35 N; (3) in terms of the strength of the mesh, steel-plastic geogrid is better than wire mesh, and with the same mesh wire strength, the bearing capacity of steel-plastic geogrid is increased by about 63.17% and the contribution of the mesh wire bearing capacity is increased by 83.66%, with the damage mainly being in the form of wire breakage in the ribbon causing ribbon failure, leading to further damage to the mesh; (4) in terms of the engineering application of steel-plastic geogrid compared to wire mesh, the utilization rate of mesh increases by about 24.99%, the construction efficiency increases by about 14.10%, and the economic benefit increases by about 45.31%. In practical application, the steel-plastic geogrid has good adhesion with surrounding rock and strong corrosion resistance. According to the above research analysis, the steel-plastic geogrid is feasible to replace the wire mesh for bolt mesh supporting.
Influence of ZnF2 and WO3 on Radiation Attenuation Features of Oxyfluoride Tellurite WO3-ZnF2-TeO2 Glasses Using Phy-X/PSD Software
Authors: Almuqrin Aljawhara H. , Sayyed M. I.
Published: March 2022

The radiation shielding features of the ternary oxyfluoride tellurite glasses were studied by calculating different shielding factors. The effect of the TeO2, WO3, and ZnF2 on the tested glass system’s attenuating performance was predicted from the examination. The mass attenuation coefficient (µ/ρ) values for the oxyfluoride tellurite glasses depend highly on the concentration of WO3, as well as ZnF2. All the present ZnFWTe1-ZnFWTe5 samples have higher µ/ρ values than that of the pure TeO2 glass at all energies. For the samples with a fixed content of WO3, the replacement of TeO2 by ZnF2 increases the µ/ρ, while for the glasses with a fixed content of TeO2, the replacement of WO3 by ZnF2 results in a decline in the µ/ρ values. The results revealed that ZnFWTe4 has the lowest linear attenuation coefficient (µ) among the oxyfluoride tellurite glasses, whereby it has a slightly higher value than pure TeO2 glass. The maximum effective atomic number (Zeff) is found at 0.284 MeV and varied between 31.75 and 34.30 for the tested glasses; it equaled to 30.29 for the pure TeO2 glass. The half-value layer (HVL) of the glasses showed a gradual decline with increasing density. The pure TeO2 was revealed to have thicker HVL than the selected oxyfluoride tellurite glasses. A 1.901-cm thickness of the sample, ZnFWTe1, is required to decrease the intensity of a photon with an energy of 0.284 MeV to one-tenth of its original, whereas 1.936, 1.956, 2.212, and 2.079 cm are required for glasses ZnFWTe2, ZnFWTe3, ZnFWTe4, and ZnFWTe5, respectively.
Multilayer Nonwoven Inserts with Aerogel/PCMs for the Improvement of Thermophysiological Comfort in Protective Clothing against the Cold
Authors: Greszta Agnieszka , Bartkowiak Grażyna , Dąbrowska Anna , Gliścińska Eulalia , Machnowski Waldemar , Kozikowski Paweł
Published: March 2022

This study aimed to assess the developed nonwoven inserts with aerogel/PCM (phase change material) microcapsules for use in protective clothing against cold in terms of properties related to thermophysiological comfort. These inserts were obtained by the thermal bonding of a multilayer system consisting of needled-punched nonwovens and silica aerogel particles and/or PCM microcapsules evenly distributed between them. The influence of aerogel and PCM microcapsules on the basic physical properties of inserts, their microstructure, air permeability, and water vapor resistance was investigated and analyzed. The thermal insulation properties of inserts were assessed based on thermal conductivity results. The inserts with PCMs were also tested for their ability to regulate the temperature in the undergarment microclimate using the differential scanning calorimeter (DSC) and the “skin model” device. The research showed that the use of aerogel allowed for reducing the thermal conductivity of the insert by approximately 13% compared to the insert without additives. The high values obtained of the melting and crystallization enthalpy of inserts with PCMs confirmed their high efficiency in the heat absorption and release. Thus, the use of aerogel and PCMs in protective clothing against cold seems to be an effective solution for improving its protective properties and actively adapting its thermal insulation to the changing temperature conditions and the activity level of employees.
Sealing Contact Transient Thermal-Structural Coupling Analysis of the Subsea Connector
Authors: Liu Dong , Yun Feihong , Wang Wuchao , Jiao Kefeng , Wang Liquan , Yan Zheping , Jia Peng , Wang Xiangyu , Liu Weifeng , Sun Haiting , Xu Xiujun
Published: March 2022

Taking the subsea collect connector as an example, the sealing characteristics of the sealing structure of the subsea connector under transient thermal–structural coupling were studied. Based on Airy’s thermal stress function, the mathematical model was established, the complex stress function was used to solve the problem, and a three-dimensional transient thermal stress model of the core sealing parts was obtained. The transient thermal–structural coupling stress model of the core seal was obtained by linear superposition principle. The transient temperature field of the subsea collet connector under different working conditions was analyzed. It was found that the larger the temperature difference between the components was, the greater the difference of expansion rate was, and the greater the impact on the sealing performance of LSG was in the process of temperature variation from transient to steady distribution. Numerical simulations of various working conditions under the transient temperature field were carried out. The results showed that sudden change of the temperature and oil–gas pressure will bring about large fluctuations of the maximum contact stress and equivalent stress of the seal, which was easy to fatigue wear, and thus affect the reliability of the sealing performance. Finally, the experiment proves that the sealing ring can maintain sealing performance under the conditions of temperature-cyclic loading. The coupled mathematical model proposed in this paper could be used for the transient thermal–structural coupling theoretical analysis of similar subsea equipment.
The Relativistic Electrodynamics of Classical Charged Particles
Authors: Kidd Braden
Published: March 2022

Maxwell’s equations and the Lorentz force equation form the foundation of classical electromagnetic theory and their discovery led to the development of special relativity. Despite this achievement, their universal compatibility with the conservation of momentum and relativistic energy transformations is still debated. Incorporating effects of hidden momentum with the Lorentz force equation or using the Einstein–Laub formula are two common approaches to address some of these concerns. Which method to use, or if a change to classical electromagnetism is even required, remains controversial. A new theoretical approach is presented in this paper to address this using relativistic electromagnetic energy inertial frame transformations. These transformations identify a situation where an apparent violation of conservation laws could occur and how to consolidate this with electromagnetic theory. An explanation regarding the elementary nature of magnetism and the relationship between inertia and electromagnetic energy is also commented on.
Electroviscous Effect of Water-Base Nanofluid Flow between Two Parallel Disks with Suction/Injection Effect
Authors: Khan Muhammad Sohail , Mei Sun , Shabnam  , Fernandez-Gamiz Unai , Noeiaghdam Samad , Khan Aamir , Shah Said Anwar
Published: March 2022

This article, investigates the behaviour of an ionized nanoliquid motion regarding heat transmission between two parallel discs. In the proposed model, the squeezing flow of Cu-water nanofluid with electrical potential force is analysed for studying the flow properties and an uniform magnetic field is applied to that fluid, by taking the surface of the bottom disc porous. We have also studied the effects of different nanomaterials on the transmission of heat through nanofluids. Furthermore, the influence of various physical parameters in the proposed model of nanofluids flow like volume fraction of nanomaterials, squeezing number, Hartmann number, Eckert number, and Prandtl number are analysed and discussed quantitatively through various tables and graphs. The system of nonlinear partial differential equations (PDE’s) has been used to formulate the proposed flow model and later converted to a set of nonlinear ODE’s by mean similarity transformation. Further, the reduced form of ODEs has been solved by Parametric Continuation Method (PCM), which is a stable numerical scheme. The outcomes obtained from the proposed model could also be used to analyse nanofluid flow in several fields, such as polymer processing, power transfer and hydraulic lifts.
New Operated Polynomial Identities and Gröbner-Shirshov Bases
Authors: Wang Jinwei , Zhu Zhicheng , Gao Xing
Published: March 2022

Twenty years ago, Rota posed the problem of finding all possible algebraic identities that can be satisfied by a linear operator on an algebra, named Rota’s Classification Problem later. Rota’s Classification Problem has proceeded two steps to understand it and has been studied actively recently. In particular, the method of Gröbner-Shirshov bases has been used successfully in the study of Rota’s Classification Problem. Quite recently, a new approach introduced to Rota’s Classification Problem and classified some (new) operated polynomial identities. In this paper, we prove that all operated polynomial identities classified via this new approach are Gröbner-Shirshov. This gives a partial answer of Rota’s Classification Problem.
Non-Isolated Resolving Sets of Corona Graphs with Some Regular Graphs
Authors: Abidin Wahyuni , Salman Anm , Saputro Suhadi Wido
Published: March 2022

Let G be a connected, simple, and finite graph. For an ordered set W={w1,w2,…,wk}⊆V(G) and a vertex v of G, the representation of v with respect to W is the k-vector r(v|W)=(dG(v,w1),…,dG(v,wk)). The set W is called a resolving set of G, if every two vertices of G has a different representation. A resolving set containing a minimum number of vertices is called a basis of H. The number of elements in a basis of G is called the metric dimension of G and denoted by dim(G). In this paper, we considered a resolving set W of G where the induced subgraph of G by W does not contain an isolated vertex. Such a resolving set is called a non-isolated resolving set. A non-isolated resolving set of G with minimum cardinality is called an nr-set of G. The cardinality of an nr-set of G is called the non-isolated resolving number of G, denoted by nr(G). Let H be a graph. The corona product graph of G with H, denoted by G⊙H, is a graph obtained by taking one copy of G and |V(G)| copies of H, namely H1,H2,…,H|V(G)|, such that the i-th vertex of G is adjacent to every vertex of Hi. If the degree of every vertex of H is k, then H is called a k-regular graph. In this paper, we determined nr(G⊙H) where G is an arbitrary connected graph of order n at least two and H is a k-regular graph of order t with k∈{t−2,t−3}.
Global Existence for an Implicit Hybrid Differential Equation of Arbitrary Orders with a Delay
Authors: El-Sayed Ahmed M. A. , Abd El-Salam Sheren A. , Hashem Hind H. G.
Published: March 2022

In this paper, we present a qualitative study of an implicit fractional differential equation involving Riemann–Liouville fractional derivative with delay and its corresponding integral equation. Under some sufficient conditions, we establish the global and local existence results for that problem by applying some fixed point theorems. In addition, we have investigated the continuous and integrable solutions for that problem. Moreover, we discuss the continuous dependence of the solution on the delay function and on some data. Finally, further results and particular cases are presented.
Tuning of PID Control for the Double Integrator Plus Dead Time Model by Modified Real Dominant Pole and Performance Portrait Methods
Authors: Huba Mikulas , Vrancic Damir
Published: March 2022

The paper discusses the proportional-integral-derivative (PID) controller from the viewpoint of (a) the analytical tuning of the PID controller for the double integrator plus dead time (DIPDT) model and (b) the numerical tuning using the performance portrait method (PPM). In the first case, the already published tuning with multiple real dominant pole, extended by integrated tuning procedures, which incorporate the inevitable low-pass filters by delay equivalences, is elaborated for modified sets of real poles. By considering several such modified sets of real poles, resulting in several new sets of controller parameters, the design can be better adapted to the requirements of the control tasks solved and to the limitations of the existing control loop hardware. In a noisy and uncertain environment, the balance between speed of setpoint and disturbance responses and acceptable excessive controller effort can thus be improved. The effectiveness of the analytical design can be evaluated using the numerical performance portrait method (PPM). For an already generated performance portrait (PP), it can offer a broad spectrum of controller settings that satisfy various design constraints. However, the results of the analytical design are still important as they facilitate the initial steps in the elaboration of the PPM and in explaining the nature of PID control. The developed controller tuning are compared using a new interpretation of PID controller as an extension of the stabilising PD controller by disturbance observer (DOB). The input disturbances reconstructed by DOB by evaluating the controller output of an integral process model in steady-state, can be estimated by a low-pass filter with a sufficiently long (integral) time constant. All analysed results are in full agreement with the proposed DOB interpretation, which furthermore contributes significantly to the explanation of the problems related to the optimal design of PID controllers.
On a New Generalization of Bernstein-Type Rational Functions and Its Approximation
Authors: Özkan Esma Yıldız , Aksoy Gözde
Published: March 2022

In this study, we introduce a new generalization of a Bernstein-type rational function possessing better estimates than the classical Bernstein-type rational function. We investigate its error of approximation globally and locally in terms of the first and second modulus of continuity and a class of Lipschitz-type functions. We present graphical comparisons of its approximation with illustrative examples.
Uniform Persistence and Global Attractivity in a Delayed Virus Dynamic Model with Apoptosis and Both Virus-to-Cell and Cell-to-Cell Infections
Authors: Li Meng , Guo Ke , Ma Wanbiao
Published: March 2022

In this paper, we study the global dynamics of a delayed virus dynamics model with apoptosis and both virus-to-cell and cell-to-cell infections. When the basic reproduction number R0>1, we obtain the uniform persistence of the model, and give some explicit expressions of the ultimate upper and lower bounds of any positive solution of the model. In addition, by constructing the appropriate Lyapunov functionals, we obtain some sufficient conditions for the global attractivity of the disease-free equilibrium and the chronic infection equilibrium of the model. Our results extend existing related works.
IoT Analytics and Agile Optimization for Solving Dynamic Team Orienteering Problems with Mandatory Visits
Authors: Li Yuda , Peyman Mohammad , Panadero Javier , Juan Angel A. , Xhafa Fatos
Published: March 2022

Transport activities and citizen mobility have a deep impact on enlarged smart cities. By analyzing Big Data streams generated through Internet of Things (IoT) devices, this paper aims to show the efficiency of using IoT analytics, as an agile optimization input for solving real-time problems in smart cities. IoT analytics has become the main core of large-scale Internet applications, however, its utilization in optimization approaches for real-time configuration and dynamic conditions of a smart city has been less discussed. The challenging research topic is how to reach real-time IoT analytics for use in optimization approaches. In this paper, we consider integrating IoT analytics into agile optimization problems. A realistic waste collection problem is modeled as a dynamic team orienteering problem with mandatory visits. Open data repositories from smart cities are used for extracting the IoT analytics to achieve maximum advantage under the city environment condition. Our developed methodology allows us to process real-time information gathered from IoT systems in order to optimize the vehicle routing decision under dynamic changes of the traffic environments. A series of computational experiments is provided in order to illustrate our approach and discuss its effectiveness. In these experiments, a traditional static approach is compared against a dynamic one. In the former, the solution is calculated only once at the beginning, while in the latter, the solution is re-calculated periodically as new data are obtained. The results of the experiments clearly show that our proposed dynamic approach outperforms the static one in terms of rewards.
Pyranodipyran Derivatives with Tyrosyl DNA Phosphodiesterase 1 Inhibitory Activities and Fluorescent Properties from Aspergillus sp. EGF 15-0-3
Authors: Wei Xia , Wang Fang-Ting , Si-Tu Mei-Xia , Fan Hao , Hu Jin-Shan , Yang Hao , Guan Shan-Yue , An Lin-Kun , Zhang Cui-Xian
Published: March 2022

Four new benzodipyran racemates, namely (±)-aspergiletals A–D (3–6), representing a rare pyrano[4,3-h]chromene scaffold were isolated together with eurotiumide G (1) and eurotiumide F (2) from the soft-coral-derived fungus Aspergillus sp. EGF 15-0-3. All the corresponding optically pure enantiomers were successfully separated by a chiral HPLC column. The structures and configurations of all the compounds were elucidated based on the combination of NMR and HRESIMS data, chiral separation, single-crystal X-ray diffraction, quantum chemical 13C NMR, and electronic circular dichroism calculations. Meanwhile, the structure of eurotiumide G was also revised. The TDP1 inhibitor activities and photophysical properties of the obtained compounds were evaluated. In the TDP1 inhibition assay, as a result of synergy between (+)-6 and (−)-6, (±)-6 displayed strong inhibitory activity to TDP1 with IC50 values of 6.50 ± 0.73 μM. All compounds had a large Stokes shift and could be utilized for elucidating the mode of bioactivities by fluorescence imaging.
Ximaoornatins A–C, Polyoxygenated Diterpenoids from the Hainan Soft Coral Sinularia ornata
Authors: Sun Li-Li , Li Xu-Wen , Guo Yue-Wei
Published: March 2022

Three complex polyoxygenated diterpenoids possessing uncommon tetradecahydro-2,13:6,9-diepoxybenzo[10]annulene scaffold, namely ximaoornatins A–C (1–3), one new eunicellin-type diterpene, litophynin K (4), and a related known compound, litophynol B (5) were isolated from the South China Sea soft coral Sinularia ornata. The structures and absolute configurations of 1–4 were established by extensive spectroscopic analysis, X-ray diffraction analysis, and/or modified Mosher’s method. A plausible biosynthetic relationship of 1 and its potential precursor 4 was proposed. In a bioassay, none of the isolated compounds showed obvious anti-inflammatory activity on LPS-induced TNF-α release in RAW264.7 macrophages and PTP1B inhibitory effects.
Effects of Non-Invasive Radiofrequency Diathermy in Pelvic Floor Disorders: A Systematic Review
Authors: González-Gutiérrez María Dolores , López-Garrido Álvaro , Cortés-Pérez Irene , Obrero-Gaitán Esteban , León-Morillas Felipe , Ibáñez-Vera Alfonso Javier
Published: March 2022

Background and Objectives: In recent years, the use of radiofrequency diathermy in pelvic floor disorders has grown proportionally to the interest in this specialty. Despite the common use of this therapy among pelvic floor physiotherapists, little is known about its effects and effectiveness in pelvic floor disorders. For this reason, the aim of the present review is to assess the effects of non-invasive 300 kHz–1 MHz radiofrequency diathermy in the treatment of pelvic floor disorders. Materials and Methods: A literature search was performed in PubMed, Scopus and Web of Science, searching for any type of study that included pelvic floor disorder participants and an experimental group treated with non-invasive nor ablative radiofrequency diathermy. Results: There were a total of 578 studies after removing duplicates. The inclusion and exclusion criteria were applied, resulting in a total of 15 studies, which were methodologically assessed with PEDro and the Newcastle and Ottawa scale. Conclusions: Despite the low quality of most of them, the studies showed improvements in urinary incontinence, pelvic pain conditions, pelvic floor muscles strength and sexual function. These findings must be considered with caution until more randomized clinical trials are performed to solve the biases detected.
Muscle-MRI and Functional Levels for the Evaluation of Upper Limbs in Duchenne Muscular Dystrophy: A Critical Review of the Literature
Authors: Cristiano Lara , Brogna Claudia , Tasca Giorgio , Verdolotti Tommaso , Pane Marika , Mercuri Eugenio
Published: March 2022

Many qualitative and quantitative Magnetic Resonance Imaging (MRI) techniques have been applied to evaluate muscle fat degeneration in Duchenne muscular dystrophy (DMD) subjects, but only few studies have focused on the upper limbs. We reviewed the literature in order to evaluate the association between muscle MRI findings and motor function levels in the upper limbs of DMD patients. Ten studies with upper limb muscle MRI data were available. Four explored all upper limb segments, while six explored only the forearm. Functional assessments were performed in nine of the ten studies. All of the studies showed a significant correlation between muscle MRI changes and motor function levels in both ambulant and non-ambulant DMD patients.
Burnout Syndrome among Pediatric Nephrologists—Report on Its Prevalence, Severity, and Predisposing Factors
Authors: Pawłowicz-Szlarska Ewa , Skrzypczyk Piotr , Stańczyk Małgorzata , Pańczyk-Tomaszewska Małgorzata , Nowicki Michał
Published: March 2022

Background and Objectives: Burnout is an occupation-related syndrome comprising emotional exhaustion, depersonalization, and reduced feelings of work-related personal accomplishments. There are reports on burnout among adult nephrologists and general pediatricians, but little is known about burnout among pediatric nephrologists. The aim of our study was to assess the prevalence and severity of burnout syndrome among Polish pediatric nephrologists. Materials and Methods: A 25-item study survey consisting of abbreviated Maslach Burnout Inventory and additional self-created questions about work-related factors was completed by 97 physicians affiliated with the Polish Society of Pediatric Nephrology. Women comprised 75.3%, with median time of professional experience in the study group was 15 years. Results: A high level of emotional exhaustion, depersonalization, and reduced feeling of personal accomplishments were observed in 39.2%, 38.1%, and 21.6% of the participants, respectively. At least a medium level of burnout in all three dimensions were observed in 26.8% of the participants and 8.2% of them presented high three-dimensional burnout. About 41.2% of the participants stated that they would like to take part in burnout prevention and support programs. According to the study participants, excessive bureaucracy in healthcare systems, rush at work, and overtime work were the main job-related problems that could influence burnout intensity. Conclusions: Burnout is an important factor in the professional landscape of pediatric nephrology. Actions aimed at reducing the risk of occupational burnout among pediatric nephrologists should be applied, both at the personal and institutional levels.
Fulminant Giant Cell Myocarditis following Heterologous Vaccination of ChAdOx1 nCoV-19 and Pfizer-BioNTech COVID-19
Authors: Kang Dong-Hoon , Na Joo-Young , Yang Jun-Ho , Moon Seong-Ho , Kim Sung-Hwan , Jung Jae-Jun , Cha Ho-Jeong , Ahn Jong-Hwa , Park Yong-Whi , Cho Sang-Yeong , Yu Ho-Kyung , Lee Soo-Hee , Park Mi-Yeong , Kim Jong-Woo , Byun Joung-Hun
Published: March 2022

A 48-year-old female patient underwent a heart transplantation for acute fulminant myocarditis, following heterologous vaccination with the ChAdOx1 nCoV-19 and Pfizer-BioNTech COVID-19. She had no history of severe acute respiratory syndrome coronavirus-2 infection. She did not exhibit clinical signs or have laboratory findings of concomitant infection before or after vaccination. Heart transplantation was performed because her heart failed to recover with venoarterial extracorporeal oxygenation support. Organ autopsy revealed giant cell myocarditis, possibly related to the vaccines. Clinicians may have to consider the possibility of the development of giant cell myocarditis, especially in patients with rapidly deteriorating cardiac function and myocarditis symptoms after COVID-19 vaccination.
Electrospinning of Quaternized Chitosan-Poly(vinyl alcohol) Composite Nanofiber Membrane: Processing Optimization and Antibacterial Efficacy
Authors: Wu Jheng-Yu , Wang Chi-Yun , Chen Kuei-Hsiang , Lai You-Ren , Chiu Chen-Yaw , Lee Hung-Che , Chang Yu-Kaung
Published: March 2022

N-(2-hydroxy) propyl-3-trimethylammonium chitosan chloride (HTCC) is a type of quaternary ammonium chitosan derivative with an antibacterial activity superior to the pristine chitosan, but its electrospinnability is limited. In this study, polyvinyl alcohol (PVA) was blended with HTCC to improve the electrospinnability of nanofibers. The electrospinning of PVA–HTCC nanofiber membranes was optimized in terms of structural stability and antimicrobial performance. Based on scanning electron microscopic analysis, the morphology and diameter of the produced nanofibers were influenced by the applied voltage, flow rate of the feed solution, and weight ratio of the polymer blend. An increase in the HTCC content decreased the average nanofiber diameter. The maximum water solubility of the PVA–HTCC nanofibers reached the maximum value of 70.92% at 12 h and 25 °C. The antibacterial activity of PVA–HTCC nanofiber membranes against Escherichia coli was ~90%, which is significantly higher than that of PVA–chitosan nanofiber membrane. Moreover, the antibacterial efficiency of PVA–HTCC nanofiber membranes remained unaffected after 5 cycles of antibacterial treatment. The good antibacterial performance and biocompatibility of PVA–HTCC nanofiber membrane makes them attractive for biomedical and biochemical applications that necessitate sterile conditions.
New Facility for Membrane Fouling Investigations under Customizable Hydrodynamics: Validation and Preliminary Experiments with Pulsating Cross-Flow
Authors: Bert Roberto , Manes Costantino , Tiraferri Alberto
Published: March 2022

Flux reduction induced by fouling is arguably the most adverse phenomenon in membrane-based separation systems. In this respect, many laboratory-scale filtration studies have shown that an appropriate use of hydrodynamic perturbations can improve both performance and durability of the membrane; however, to fully understand and hence appropriately exploit such effects, it is necessary to understand the underpinning flow processes. Towards this end, in this work we propose and validate a new module-scale laboratory facility with the aim of investigating, at very well-controlled flow conditions, how hydrodynamics affects mass transport phenomena at the feed/membrane interface. The proposed facility was designed to obtain a fully developed and uniform flow inside the test section and to impose both steady and pulsating flow conditions. The walls of the facility were made transparent to grant optical accessibility to the flow. In this paper, we discuss data coming from particle image velocimetry (PIV) measurements and preliminary ultrafiltration tests both under steady and pulsating flow conditions. PIV data indicate that the proposed facility allows for excellent flow control from a purely hydrodynamic standpoint. Results from filtration tests provide promising results pointing towards pulsating flows as a viable technique to reduce fouling in membrane systems.
Permeation Increases Biofilm Development in Nanofiltration Membranes Operated with Varying Feed Water Phosphorous Concentrations
Authors: Javier Luisa , Pulido-Beltran Laura , Vrouwenvelder Johannes S. , Farhat Nadia M.
Published: March 2022

Nutrient limitation has been proposed as a biofouling control strategy for membrane systems. However, the impact of permeation on biofilm development under phosphorus-limited and enriched conditions is poorly understood. This study analyzed biofilm development in membrane fouling simulators (MFSs) with and without permeation supplied with water varying dosed phosphorus concentrations (0 and 25 μg P·L−1). The MFSs operated under permeation conditions were run at a constant flux of 15.6 L·m2·h−1 for 4.7 days. Feed channel pressure drop, transmembrane pressure, and flux were used as performance indicators. Optical coherence tomography (OCT) images and biomass quantification were used to analyze the developed biofilms. The total phosphorus concentration that accumulated on the membrane and spacer was quantified by using microwave digestion and inductively coupled plasma atomic emission spectroscopy (ICP-OES). Results show that permeation impacts biofilm development depending on nutrient condition with a stronger impact at low P concentration (pressure drop increase: 282%; flux decline: 11%) compared to a higher P condition (pressure drop increase: 206%; flux decline: 2%). The biofilm that developed at 0 μg P·L−1 under permeation conditions resulted in a higher performance decline due to biofilm localization and spread in the MFS. A thicker biofilm developed on the membrane for biofilms grown at 0 μg P·L−1 under permeation conditions, causing a stronger effect on flux decline (11%) compared to non-permeation conditions (5%). The difference in the biofilm thickness on the membrane was attributed to a higher phosphorus concentration in the membrane biofilm under permeation conditions. Permeation has an impact on biofilm development and, therefore, should not be excluded in biofouling studies.
Tribological Performance of Diamond Films with Different Roughnesses of Silicon Nitride Substrates and Carbon Source Concentrations
Authors: Lu Feng , Liu Tianwei , Bai Xu , Wu Yuhou , Wang He , Yan Guangyu
Published: March 2022

Diamond films were deposited on silicon nitride (Si3N4) substrates with three different roughnesses using the method of hot-filament chemical vapor deposition (HFCVD). The tribological properties of the film were studied by changing the deposition time, deposition distance, and methane (CH4) concentration. The friction coefficient, delamination threshold load, and wear rate of the diamond films were tested and calculated using the reciprocating friction and wear test under dry friction conditions. The results show that, when the deposition time is 12 h, the bonding force of the film is the lowest and the friction coefficient is the largest (0.175, 0.438, and 0.342); the deposition distance has little effect on the friction performance. The friction coefficients (0.064, 0.107, and 0.093) of nano-diamond films (NCD) prepared at a 40 sccm CH4 concentration are smaller than those of micro-diamond films (MCD) prepared at a 16 sccm CH4 concentration. The load thresholds before delamination of Ra 0.4 μm substrate diamond film are as high as 40 N and 80 N, whereas the diamond films deposited on Ra 0.03 μm substrates have lower wear rates (4.68 × 10−4 mm3/mN, 5.34 × 10−4 mm3/mN) and low friction coefficients (0.119, 0.074, 0.175, and 0.064). Within a certain load range, the deposition of a diamond film on a Ra 0.03 μm Si3N4 substrate significantly reduces the friction coefficient and improves wear resistance. Diamond film can improve the friction performance of a workpiece and prolong its service life.
Chemical Reaction and Internal Heating Effects on the Double Diffusive Convection in Porous Membrane Enclosures Soaked with Maxwell Fluid
Authors: Yadav Dhananjay , Al-Siyabi Maimouna , Awasthi Mukesh Kumar , Al-Nadhairi Salma , Al-Rahbi Amna , Al-Subhi Maryam , Ragoju Ravi , Bhattacharyya Krishnendu
Published: March 2022

In this paper, the joint impact of the interior heating and chemical reaction on the double diffusive convective flow in porous membrane enclosures soaked by a non-Newtonian Maxwell fluid is investigated applying linear and nonlinear stability techniques. The porous enclosures are square, slender and rectangular. Using the linear stability analysis, the expression for the critical thermal Rayleigh–Darcy number, above which the convective movement occurs, is derived analytically in terms of associated physical parameters. A nonlinear stability examination reliant on the Fourier double series is executed to calculate the convective heat and mass transports of the arrangement. It is observed that the pattern of convective activity is oscillatory only in the occurrence of a relaxation parameter and the threshold value of the relaxation parameter for the occurrence of the oscillatory pattern depends on the other physical parameters. The onset of convective instability accelerates with the increasing chemical reacting parameter, the interior heating parameter, the solute Rayleigh–Darcy number, the Lewis number, the Vadasz number, and the relaxation parameter, while it delays with the heat capacity ratio. The convective heat and mass transfers increase with the solute Rayleigh–Darcy number, the Vadasz number, the relaxation parameter, and the aspect ratio (for rectangular enclosure), while it decreases with the heat capacity ratio and the aspect ratio (for slender enclosure). Additionally, the convective heat transfer enhances with the interior heating parameter, while the convective mass transfer enhances with the chemical reacting parameter and the Lewis number. The effects of Vadasz number, heat capacity ratio, and relaxation parameter are witnessed only on the oscillatory pattern of convection and unsteady convective heat and mass transfers. Further, some existing literature results are compared with the current findings.
Development of Free-Standing Titanium Dioxide Hollow Nanofibers Photocatalyst with Enhanced Recyclability
Authors: Jafri Nurul Natasha Mohammad , Jaafar Juhana , Aziz Farhana , Salleh Wan Norharyati Wan , Yusof Norhaniza , Othman Mohd Hafiz Dzarfan , Rahman Mukhlis A. , Ismail Ahmad Fauzi , Rahman Roshanida A. , Khongnakorn Watsa
Published: March 2022

Titanium dioxide hollow nanofibers (THN) are excellent photocatalysts for the photodegradation of Bisphenol A (BPA) due to their extensive surface area and good optical properties. A template synthesis technique is typically employed to produce titanium dioxide hollow nanofibers. This process, however, involves a calcination procedure at high temperatures that yields powder-form photocatalysts that require post-recovery treatment before recycling. Meanwhile, the immobilization of photocatalysts on/into a membrane has been reported to reduce the active surface area. Novel free-standing TiO2 hollow nanofibers were developed to overcome those shortcomings. The free-standing photocatalyst containing 0.75 g of THN (FS-THN-75) exhibited good adherence and connectivity between the nanofibers. The recyclability of FS-THN-75 outperformed the THN calcined at 600 °C (THN-600), which retained 80% of its original weight while maintaining excellent degradation performance. This study recommends the potential application of free-standing TiO2 hollow nanofibers as high potential novel photocatalysts for the treatment of BPA in wastewater.
Investigating Nanoscale Contact Using AFM-Based Indentation and Molecular Dynamics Simulations
Authors: Roy Shyamal , Wille Sönke , Mordehai Dan , Volkert Cynthia A.
Published: March 2022

In this work we study nanocontact plasticity in Au thin films using an atomic force microscope based indentation method with the goal of relating the changes in surface morphology to the dislocations created by deformation. This provides a rigorous test of our understanding of deformation and dislocation mechanisms in small volumes. A series of indentation experiments with increasing maximum load was performed. Distinct elastic and plastic regimes were identified in the force-displacement curves, and the corresponding residual imprints were measured. Transmission electron microscope based measured dislocation densities appear to be smaller than the densities expected from the measured residual indents. With the help of molecular dynamics simulations we show that dislocation nucleation and glide alone fail to explain the low dislocation density. Increasing the temperature of the simulations accelerates the rate of thermally activated processes and promotes motion and annihilation of dislocations under the indent while transferring material to the upper surface; dislocation density decreases in the plastic zone and material piles up around the indent. Finally, we discuss why a significant number of cross-slip events is expected beneath the indent under experimental conditions and the implications of this for work hardening during wear.
Synthesis of Multiscale Ultrafine Copper Powder via Radio Frequency Induction Coupled Plasma Treatment
Authors: Wu Haibo , Zhang Wei , Gao Shenghan , Li Tiejun , Liu Bin
Published: March 2022

Nano-sized spherical copper powder has important applications in the fields of microelectronic devices, highly efficient catalysts and lubricant additives. In this study, nano-sized and micron-sized spherical copper powders were simultaneously prepared by radio frequency (RF) induction coupled plasma technology. The effects of processing parameters on the powder properties were studied. The results show that by inputting copper powder with D50 = 34.6 μm, nano-sized spherical powder with a particle size of 10–220 nm and micron-sized spherical powder with a particle size of 4.0–144.0 μm were obtained. The ratio of the nano-sized powder reached 86.4 wt.%. The optimal processing parameters are as follows: powder feed rate is 5.5 g/min, carrier gas flow rate is 5–6 L/min and reaction chamber pressure is 15 Psia. When the carrier gas flow rate is 6 L/min, in the plasma zone (>10,000 K), the powder with particle size <42.0 μm is completely vaporized, which forms nano-sized powder during cooling, while the powder with particle size >42.0 μm is melted and partially vaporized, forming a micron-sized powder. The research results provide a new way for engineering the production of copper nano-powder and some other nano-powders with low melting points, such as silver powder, tin powder and so on.