bluuebunny/crossref_metadata_2025 huggingface dataset:
An Immunogenicity Report for the Comparison between Heterologous and Homologous Prime-Boost Schedules with ChAdOx1-S and BNT162b2 Vaccines
Authors: Vallée Alexandre , Vasse Marc , Mazaux Laurence , Bonan Brigitte , Amiel Carline , Zia-Chahabi Sara , Chan-Hew-Wai Aurélie , Farfour Eric , Camps Eve , Touche Pauline , Barret Flavie , Parquin François , Zucman David , Fourn Erwan
Published: August 2021

Background: There is a small amount of immunological data on COVID-19 heterologous vaccination schedules in humans. We assessed the immunogenicity of BNT162b2 (Pfizer/BioNTech) administered as a second dose in healthcare workers primed with ChAdOx1-S (Vaxzevria, AstraZeneca). Methods: 197 healthcare workers were included in a monocentric observational study in Foch hospital, France, between June and July 2021. The main outcome was the immunogenicity measured by serum SARS-CoV-2 IgG antibodies. Results: 130 participants received the ChAdOx1-S/BNT vaccine and 67 received the BNT/BNT vaccine. The geometric mean of IgG antibodies was significantly higher in the BNT/BNT vaccine group compared to the ChAdOx1-S/BNT vaccine group, namely 10,734.9, 95% CI (9141.1–12,589.3) vs. 7268.6, 95% CI (6501.3–8128.3), respectively (p < 0.001). However, after adjustment for time duration between the prime and second vaccinations, no significant difference was observed (p = 0.181). A negative correlation between antibody levels and time duration between second dose and serology test was observed for the BNT/BNT vaccine (p < 0.001), which remained significant after adjustment for all covariates (p < 0.001), but not for the ChAdOx1-S/BNT vaccine (p = 0.467). Conclusions: Heterologous and homologous schedules of ChAdOx1-S and BNT vaccines present robust immune responses after the second vaccination. The results observed were equivalent after adjustment for covariates and emphasize the importance of flexibility in deploying mRNA and viral vectored vaccines. Nevertheless, applying the ChAdOx1-S schedule vaccination for the heterologous second dose of BNT was associated with decreased IgG antibody levels compared to the homologous BNT/BNT vaccination.
Recent Advances in the Management of Acute Variceal Hemorrhage
Authors: Zanetto Alberto , Shalaby Sarah , Feltracco Paolo , Gambato Martina , Germani Giacomo , Russo Francesco Paolo , Burra Patrizia , Senzolo Marco
Published: August 2021

Gastrointestinal bleeding is one of the most relevant causes of death in patients with cirrhosis and clinically significant portal hypertension, with gastroesophageal varices being the most frequent source of hemorrhage. Despite survival has improved thanks to the standardization on medical treatment aiming to decrease portal hypertension and prevent infections, mortality remains significant. In this review, our goal is to discuss the most recent advances in the management of esophageal variceal hemorrhage in cirrhosis with specific attention to the treatment algorithms involving the use of indirect measurement of portal pressure (HVPG) and transjugular intrahepatic portosystemic shunt (TIPS), which aim to further reduce mortality in high-risk patients after acute variceal hemorrhage and in the setting of secondary prophylaxis.
Usefulness of Clinical and Laboratory Criteria for Diagnosing Autoimmune Liver Disease among Patients with Systemic Lupus Erythematosus: An Observational Study
Authors: Heijke Rebecca , Ahmad Awais , Frodlund Martina , Wirestam Lina , Dahlström Örjan , Dahle Charlotte , Kechagias Stergios , Sjöwall Christopher
Published: August 2021

Abnormal liver function tests are frequently observed during follow-up of patients with systemic lupus erythematosus (SLE) but data on co-existence with autoimmune liver diseases (AILD) are scarce. This retrospective study aimed to describe the prevalence of autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) among well-characterized subjects with SLE. We also evaluated whether the presence of autoantibodies to complement protein 1q (C1q) and/or ribosomal P protein (anti-ribP) are, directly or inversely, associated with AIH, as proposed in some reports. The number of screened patients was 287 (86% females), and all cases were included in a regional Swedish cohort. Each subject of the study population met the 1982 American College of Rheumatology classification criteria and/or the Fries’ diagnostic principle. By applying the simplified diagnostic AIH criteria combined with persistent transaminasemia, 40 (13.9%) cases reached at least “probable AIH”. However, merely 8 of these had been diagnosed with AIH (overall AIH prevalence 2.8%). Neither anti-C1q nor anti-ribP associated significantly with AIH. By applying the recent PBC guidelines, 6 (2.1%) cases were found, but only 3 of them had actually been diagnosed with PBC and one additional subject was not identified by the guidelines (overall PBC prevalence 1.4%). Compared to prevalence data from the general Swedish population, both AIH and PBC were highly overrepresented in our study population. The sensitivity of the diagnostic AIH criteria was impeccable but the specificity was less impressive, mainly due to positive ANA and hypergammaglobulinemia. Based on our findings, among subjects with SLE, the AIH criteria are less useful and liver biopsy combined with detection of other AILD-associated autoantibodies should be performed.
Effects of Non-Pharmacological Treatment on Pain, Flexibility, Balance and Quality of Life in Women with Fibromyalgia: A Randomised Clinical Trial
Authors: Rodríguez-Mansilla Juan , Mejías-Gil Abel , Garrido-Ardila Elisa María , Jiménez-Palomares María , Montanero-Fernández Jesús , González-López-Arza María Victoria
Published: August 2021

Background: The functional deficits in people with fibromyalgia can be related to the level of physical activity performed. This study investigated the effectiveness of an active exercise programme versus exercise for well-being improving pain, flexibility, static balance, perceived exertion and quality of life of women with fibromyalgia; Methods: A randomised, single-blind, controlled trial was conducted. A total of 141 of women diagnosed with fibromyalgia were enrolled and randomised to an active exercise program group (n = 47), where they performed physical active exercises, an exercise for well-being group (n = 47), which performed the Qi Gong exercises named ‘the twenty Wang Ziping figures for health and longevity’, and a control group (n = 47), which did not receive any intervention, for a period of 4 weeks. Measures were taken at baseline and after the treatment. The primary outcome measures were static balance and centre of gravity (Wii-Fit Nintendo ©), flexibility (test de Wells and Dillon), pain (Visual Analogue Scale) and quality of life (Spanish-Fibromyalgia Impact Questionnaire). The secondary outcome measure was the perceived exertion during activity (BORG Scale). Results: In total, 93 participants completed the study. The mean value of the age was 52.24 ± 6.19. The post intervention results showed statistically significant improvements in the exercise for well-being and the active exercise programme groups vs. the control group in relation to pain (p = 0.006 active exercise programme group, p = 0.001 exercise for well-being group), static balance (p < 0.001 active exercise programme group) and quality of life (p < 0.001 active exercise programme group, p = 0.002 exercise for well-being group). In addition, the mean scores related to perceived fatigue during the sessions were 6.30 ± 1.88 for the active exercise programme group and 5.52 ± 1.55 for the exercise for well-being group. These differences were not significant. Conclusions: The active exercise program and exercise for well-being improved flexibility, static balance, pain and quality of life of women with fibromyalgia. The participants of the active exercise programme achieved better results that those of the exercise for well-being.
FDML versus GMM for Dynamic Panel Models with Roots Near Unity
Authors: Mehic Adrian
Published: August 2021

This paper evaluates the first-differenced maximum likelihood (FDML) and the continuously updating system generalized method of moments (CU-GMM) estimators of dynamic panel models when the data is close to non-stationary. This case is far from trivial, as a high degree of persistence is the norm rather than the exception in economic panels, particularly in financial management. While the CU-GMM is shown to have lower bias and higher power, it suffers from severe size distortions, which are exacerbated when the data approaches non-stationarity.
It’s All about Details. Why the Polish Land Policy Framework Fails to Manage Designation of Developable Land
Authors: Zaborowski Tomasz
Published: August 2021

Since the introduction of the current legal planning system, Polish land policy has failed to manage the designation of developable land. The oversupply of developable land designated in land-use plans and resulting from various weaknesses of auxiliary planning permissions undermines the creation of compact urban settlements. The article argues that, theoretically, the Polish legal framework of developable land designation management conforms with its more effective European counterparts. What makes it not work properly are the detailed regulations and their interpretation. In order to support this argument, the Polish land policy framework will be analysed and assessed by comparing it with the key common features of its German and Spanish counterparts.
A Systematic Comparison of Antiandrogens Identifies Androgen Receptor Protein Stability as an Indicator for Treatment Response
Authors: Siciliano Tiziana , Simons Ingo H. , Beier Alicia-Marie K. , Ebersbach Celina , Aksoy Cem , Seed Robert I. , Stope Matthias B. , Thomas Christian , Erb Holger H. H.
Published: August 2021

Antiandrogen therapy is a primary treatment for patients with metastasized prostate cancer. Whilst the biologic mechanisms of antiandrogens have been extensively studied, the operating protocols used for the characterization of these drugs were not identical, limiting their comparison. Here, the antiandrogens Bicalutamide, Enzalutamide, Apalutamide, and Darolutamide were systematically compared using identical experimental setups. Androgen-dependent LNCaP and LAPC4 cells as well as androgen-independent C4-2 cells were treated with distinct concentrations of antiandrogens. Androgen receptor (AR)-mediated gene transactivation was determined using qPCR. Cell viability was measured by WST1 assay. Protein stability and AR localization were determined using western blot. Response to the tested antiandrogens across cellular backgrounds differed primarily in AR-mediated gene transactivation and cell viability. Antiandrogen treatment in LNCaP and LAPC4 cells resulted in AR protein level reduction, whereas in C4-2 cells marginal decreased AR protein was observed after treatment. In addition, AR downregulation was already detectable after 4 h, whereas reduced AR-mediated gene transactivation was not observed before 6 h. None of the tested antiandrogens displayed an advantage on the tested parameters within one cell line as opposed to the cellular background, which seems to be the primary influence on antiandrogen efficacy. Moreover, the results revealed a prominent role in AR protein stability. It is one of the first events triggered by antiandrogens and correlated with antiandrogen efficiency. Therefore, AR stability may surrogate antiandrogen response and may be a possible target to reverse antiandrogen resistance.
Characteristics of Porous Aluminium Materials Produced by Pressing Sodium Chloride into Their Melts
Authors: Nová Iva , Fraňa Karel , Solfronk Pavel , Sobotka Jiří , Koreček David , Švec Martin
Published: August 2021

The paper deals with research related to the production of metal cellular aluminium systems, in which production is based on the application of sodium chloride particles. In this paper, the properties of porous aluminium materials that were produced by an unconventional method—by pressing salt particles into the melt of aluminium alloy—are described. The new methodology was developed and verified for the production of these materials. The main feature of this methodology is a hydraulic forming press and a simple-shaped foundry mould. For these purposes, four different groups of sodium chloride particle sizes (1 to 3, 3 to 5, 5 to 7 and 8 to 10 mm) were applied. The preferred aluminium foundry alloy (AlSi12) was used to produce the porous aluminium samples. Based upon this developed methodology, samples of porous aluminium materials were produced and analysed. Their weight and volume were monitored, their density and relative density were calculated, and their porosity was determined. In addition, the porosity of samples and continuity of their air cells were monitored as well. An industrial computed tomograph and a scanning electron microscope were applied for these purposes.
Eco-Friendly Biosorbents Based on Microbial Biomass and Natural Polymers: Synthesis, Characterization and Application for the Removal of Drugs and Dyes from Aqueous Solutions
Authors: Rusu Lăcrămioara , Grigoraș Cristina-Gabriela , Suceveanu Elena Mirela , Simion Andrei-Ionuț , Dediu Botezatu Andreea Veronica , Istrate Bogdan , Doroftei Ioan
Published: August 2021

Pharmaceuticals and dyes are a very important part of the nonbiodegradable or hard biodegradable substances present in wastewater. Microorganisms are already known to be effective biosorbents, but the use of free microbial cells involves difficulties in their separation from effluents and limits their application in wastewater treatment. Thus, this study aimed to develop biosorbents by immobilizing Saccharomyces cerevisiae, Saccharomyces pastorianus and Saccharomyces pastorianus residual biomass on natural polymers (alginate and chitosan) and to evaluate the biosorptive potential for removal of pharmaceuticals and dyes from water. Six types of biosorbents were synthesized and characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy techniques and their biosorptive capacities for three drugs (cephalexin, rifampicin, ethacridine lactate) and two dyes (orange II and indigo carmine) were evaluated. The obtained results show that the removal efficiency depends on the polymer type used for the immobilization. In case of alginate the removal efficiency is between 40.05% and 96.41% for drugs and between 27.83% and 58.29% for dyes, while in the case of chitosan it is between 40.83% and 77.92% for drugs and between 17.17% and 44.77% for dyes. In general, the synthesized biosorbents proved to be promising for the removal of drugs and dyes from aqueous solutions.
Interface Strengthening of PS/aPA Polymer Blend Nanocomposites via In Situ Compatibilization: Enhancement of Electrical and Rheological Properties
Authors: Azubuike Lilian , Sundararaj Uttandaraman
Published: August 2021

The process of strengthening interfaces in polymer blend nanocomposites (PBNs) has been studied extensively, however a corresponding significant enhancement in the electrical and rheological properties is not always achieved. In this work, we exploit the chemical reaction between polystyrene maleic anhydride and the amine group in nylon (polyamide) to achieve an in-situ compatibilization during melt processing. Herein, nanocomposites were made by systematically adding polystyrene maleic anhydride (PSMA) at different compositions (1–10 vol%) in a two-step mixing sequence to a Polystyrene (PS)/Polyamide (aPA) blend with constant composition ratio of 25:75 (PS + PSMA:aPA) and 1.5 vol% carbon nanotube (CNT) loading. The order of addition of the individual components was varied in two-step mixing procedure to investigate the effect of mixing order on morphology and consequently, on the final properties. The electrical and rheological properties of these multiphase nanocomposite materials were investigated. The optical microscope images show that for PS/aPA systems, CNTs preferred the matrix phase aPA, which is the thermodynamically favorable phase according to the wettability parameter calculated using Young’s equation. However, aPA’s great affinity for CNT adversely influenced the electrical properties of our blend. Adding PSMA to PS/aPA changed the structure of the droplet phase significantly. At 1.5 vol% CNT, a more regular and even distribution of the droplet domains was observed, and this produced a better framework to create more CNT networks in the matrix, resulting in a higher conductivity. For example, with only 1.5 vol% CNT in the PBN, at 3 vol% PSMA, the conductivity was 7.4 × 10−2 S/m, which was three and a half orders of magnitude higher than that seen for non-reactive PS/aPA/CNT PBN. The mechanism for the enhanced conductive network formation is delineated and the improved rheological properties due to the interfacial reaction is presented.
Effect of Phase Changes on the Axial Modulus of an FeMnSi-Shape Memory Alloy
Authors: Yang Yajiao , Breveglieri Matteo , Shahverdi Moslem
Published: August 2021

The axial modulus ESMA(κ) of FeMnSi-based shape memory alloys (FeMnSi-SMAs) is a parameter introduced in this study to characterize the relationship between stress and strain behavior at the early stage of tensile loading. ESMA(κ) can be used to correctly estimate and model the interaction forces between FeMnSi-SMAs and other materials. Unlike the conventional Young’s modulus, which is usually given at room temperature, the ESMA(κ) is evaluated at different temperatures and strongly depends on phase transformation and plastic deformation. This study investigated the evolution of ESMA(κ) during and after pre-straining as well as in the course of the activation processes. The effect of different factors (e.g., phase transformation and plastic deformation) on the magnitude of ESMA(κ) is discussed. The result shows that the ESMA(κ) can differ significantly during activation and thus needs to be modified when interaction forces between FeMnSi-SMAs and other substrates materials (e.g., concrete) must be modeled and evaluated.
Determining Johnson-Cook Constitutive Equation for Low-Carbon Steel via Taylor Anvil Test
Authors: Kunčická Lenka , Jopek Miroslav , Kocich Radim , Dvořák Karel
Published: August 2021

Tristal steel is low-carbon construction-type steel widely used in the automotive industry, e.g., for braking components. Given the contemporary demands on the high-volume production of such components, these are typically fabricated using automatic sequential machines, which can produce components at strain rates up to 103 s−1. For this reason, characterising the behaviour of the used material at high strain rates is of the utmost importance for successful industrial production. This study focuses on the characterisation of the behaviour of low-carbon steel via developing its material model using the Johnson-Cook constitutive equation. At first, the Taylor anvil test is performed. Subsequently, the acquired data together with the results of observations of structures and properties of the tested specimens are used to fill the necessary parameters into the equation. Finally, the developed equation is used to numerically simulate the Taylor anvil test and the predicted data is correlated with the experimentally acquired one. The results showed a satisfactory correlation of the experimental and predicted data; the deformed specimen region featured increased occurrence of dislocations, as well as higher hardness (its original value of 88 HV increased to more than 200 HV after testing), which corresponded to the predicted distributions of effective imposed strain and compressive stress.
Design of V-Substituted TiFe-Based Alloy for Target Pressure Range and Easy Activation
Authors: Faisal Mohammad , Kim June-Hyung , Cho Young Whan , Jang Jae-il , Suh Jin-Yoo , Shim Jae-Hyeok , Lee Young-Su
Published: August 2021

Titanium iron (TiFe) alloy is a room-temperature hydrogen-storage material, and it absorbs hydrogen via a two-step process to form TiFeH and then TiFeH2. The effect of V addition in TiFe alloy was recently elucidated. The V substitution for Ti sublattice lowers P2/P1 ratio, where P1 and P2 are the equilibrium plateau pressure for TiFe/TiFeH and TiFeH/TiFeH2, respectively, and thus restricts the two-step hydrogenation within a narrow pressure range. The focus of the present investigation was to optimize the V content such that maximum usable storage capacity can be achieved for the target pressure range: 1 MPa for absorption and 0.1 MPa for desorption. The effect of V substitution at selective Ti or Fe sublattices was closely analyzed, and the alloy composition Ti46Fe47.5V6.5 displayed the best performance with ca. 1.5 wt.% of usable capacity within the target pressure range. At the same time, another issue in TiFe-based alloys, which is a difficulty in activation at room temperature, was solved by Ce addition. It was shown that 3 wt.% Ce dispersion in TiFe alloy imparted to it easy room-temperature (RT) activation properties.
Dissolution of Amorphous S53P4 Glass Scaffolds in Dynamic In Vitro Conditions
Authors: Aalto-Setälä Laura , Uppstu Peter , Sinitsyna Polina , Lindfors Nina C. , Hupa Leena
Published: August 2021

The silicate-based bioactive glass S53P4 is clinically used in bone regenerative applications in granule form. However, utilization of the glass in scaffold form has been limited by the high tendency of the glass to crystallize during sintering. Here, careful optimization of sintering parameters enabled the manufacture of porous amorphous S53P4 scaffolds with a strength high enough for surgical procedures in bone applications (5 MPa). Sintering was conducted in a laboratory furnace for times ranging from 25 to 300 min at 630 °C, i.e., narrowly below the commencement of the crystallization. The phase composition of the scaffolds was verified with XRD, and the ion release was tested in vitro and compared with granules in continuous flow of Tris buffer and simulated body fluid (SBF). The amorphous, porous S53P4 scaffolds present the possibility of using the glass composition in a wider range of applications.
Solder Joint Reliability Risk Estimation by AI-Assisted Simulation Framework with Genetic Algorithm to Optimize the Initial Parameters for AI Models
Authors: Yuan Cadmus , Fan Xuejun , Zhang Gouqi
Published: August 2021

Solder joint fatigue is one of the critical failure modes in ball-grid array packaging. Because the reliability test is time-consuming and geometrical/material nonlinearities are required for the physics-driven model, the AI-assisted simulation framework is developed to establish the risk estimation capability against the design and process parameters. Due to the time-dependent and nonlinear characteristics of the solder joint fatigue failure, this research follows the AI-assisted simulation framework and builds the non-sequential artificial neural network (ANN) and sequential recurrent neural network (RNN) architectures. Both are investigated to understand their capability of abstracting the time-dependent solder joint fatigue knowledge from the dataset. Moreover, this research applies the genetic algorithm (GA) optimization to decrease the influence of the initial guessings, including the weightings and bias of the neural network architectures. In this research, two GA optimizers are developed, including the “back-to-original” and “progressing” ones. Moreover, we apply the principal component analysis (PCA) to the GA optimization results to obtain the PCA gene. The prediction error of all neural network models is within 0.15% under GA optimized PCA gene. There is no clear statistical evidence that RNN is better than ANN in the wafer level chip-scaled packaging (WLCSP) solder joint reliability risk estimation when the GA optimizer is applied to minimize the impact of the initial AI model. Hence, a stable optimization with a broad design domain can be realized by an ANN model with a faster training speed than RNN, even though solder fatigue is a time-dependent mechanical behavior.
Stainless Steel Surface Nitriding in Open Atmosphere Cold Plasma: Improved Mechanical, Corrosion and Wear Resistance Properties
Authors: Mateescu Alice O. , Mateescu Gheorghe , Balan Adriana , Ceaus Catalin , Stamatin Ioan , Cristea Daniel , Samoila Cornel , Ursutiu Doru
Published: August 2021

This work presents preliminary results regarding improving the mechanical, wear and protective properties (hardness, coefficient of friction, corrosion resistance) of AISI 304 stainless steel surfaces by open atmosphere cold plasma surface treatment method. Comparative evaluations of the morphological, corrosion resistance, mechanical and tribological properties for different periods of treatment (using N2 gas for cold plasma generation in an open atmosphere) were performed. AFM surface analyses have shown significant surface morphology modifications (average roughness, FWHM, surface skewness and kurtosis coefficient) of the treated samples. An improved corrosion resistance of the N2 treated surfaces in open atmosphere cold plasma could be observed using electrochemical corrosion tests. The mechanical tests have shown that the surface hardness (obtained by instrumented indentation) is higher for the 304 stainless steel samples than it is for the un-treated surface, and it decreases gradually for higher penetration depths. The kinetic coefficient of friction (obtained by ball-on-disk wear tests) is significantly lower for the treated samples and increases gradually to the value of the un-treated surface. The low friction regime length is dependent on the surface treatment period, with a longer cold plasma nitriding process leading to a significantly better wear behavior.
Conductive Polyaniline Patterns on Electrospun Polycaprolactone/Hydroxyapatite Scaffolds for Bone Tissue Engineering
Authors: Rajzer Izabella , Rom Monika , Menaszek Elżbieta , Fabia Janusz , Kwiatkowski Ryszard
Published: August 2021

Currently, the challenge for bone tissue engineering is to design a scaffold that would mimic the structure and biological functions of the extracellular matrix and would be able to direct the appropriate response of cells through electrochemical signals, thus stimulate faster bone formation. The purpose of the presented research was to perform and evaluate PCL/n-HAp scaffolds locally modified with a conductive polymer-polyaniline. The material was obtained using electrospinning, and a simple ink-jet printing method was applied to receive the conductive polyaniline patterns on the surface of the electrospun materials. The samples of scaffolds were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal analysis (DSC, TGA), and infrared spectroscopy (FTIR) before and after immersion of the material in Simulated Body Fluid. The effect of PANI patterns on changes in the SBF mineralization process and cell morphology was evaluated in order to prove that the presented material enables the growth and proliferation of bone cells.
Obtention and Characterization of Ferrous Chloride FeCl2·4H2O from Water Pickling Liquors
Authors: Alcaraz Lorena , Sotillo Belén , Marco José F. , Alguacil Francisco J. , Fernández Paloma , López Félix A.
Published: August 2021

As a hazardous waste, water pickling liquors must be properly treated. An alternative consists of promoting the formation of ferrous salts from this residue due to their higher ferrous content. Since FeCl2·4H2O is widely used in several applications, obtaining pure crystals of this material appears to be an interesting prospect. However, this compound has scarcely been investigated. In the present work, FeCl2·4H2O crystals were obtained from water pickling liquors. Their structural and morphological characteristics were investigated by X-ray diffraction, scanning electron microscopy as well as Mössbauer spectroscopy. In addition, the photoluminescence study of the obtained samples was also assessed. It was observed that after some aging time, the obtained crystals changed in colour from green to more yellowish. As such, the aged sample was also evaluated, and their structural characteristics were compared with the original crystals. Despite this, the obtained crystals exhibit a FeCl2·4H2O structure, which is not modified with the aging of the sample.
Superior Properties through Feedstock Development for Vat Photopolymerization Additive Manufacturing of High-Performance Biobased Feedstocks
Authors: Clay Anthony M. , Mitchell Joshua R. , Boelter Zachary R. , La Scala John J.
Published: August 2021

Vat photopolymerization additive manufacturing (Vat AM) technologies have found niche industrial use being able to produce personalized parts in moderate quantity. However, Vat AM lacks in its ability to produce parts of satisfactory thermal and mechanical properties for structural applications. The purpose of this investigation was to develop high-performance resins with glass transition temperatures (Tg) above 200 °C for Vat AM, evaluate the properties of the produced thermosets and establish a structure–property relationship of the thermosets produced. Herein, we have developed SLA-type resins that feature bio-derived monomer hesperetin trimethacrylate (HTM) synthesized from the flavonone hesperetin. Diluents 4-acryloyl morpholine, styrene, 4-methyl styrene and 4-tert butylstyrene (tbutylsty) were photocured with HTM as the monomer and all produced thermosets with Tg values above 200 °C. Investigations of suitable crosslinkers urethane dimethacrylate, the vinyl ester CN 151 and Ebecryl 4859 (Eb4859) showed that each crosslinker displayed different benefits when formulated with HTM as the monomer and tbutylSty as the diluent (HTM:crosslinker:tbutylSty with mass ratio 2:1:2). The crosslinker CN 151 produced the thermoset of greatest onset of thermal decomposition temperature (T0) of 352 °C. Eb4859 produced the thermoset of highest tensile strength, 19 ± 7 MPa, amongst the set of varied crosslinkers. The formulation featuring UDM (HTM:UDM:tbutysty) offered ease of processing and was seemingly the easiest to print. Investigations of reactive diluent showed that styrene produced the thermoset of the highest extent of cure and the overall highest tensile strength, 25 ± 5 MPa, while tbutylSty produced the thermoset with the greatest Tan-δ Tg, 231 °C. HTM was synthesized, formulated with diluents, crosslinkers and initiators. The HTM resins were then 3D printed to produce thermosets of Tg values greater than 200 °C. The polymer properties were evaluated and a structure–reactivity relationship was discussed.
Oxidation Mechanism of Al-Sn Bearing Alloys
Authors: Guo Qiaoqin , Chen Jihui , Li Jianping , Guo Yongchun , Yang Zhong , Yang Wei , Xu Dapeng , Yang Bo
Published: August 2021

Oxidation of Al-Sn bearing alloy occurs during production, processing and use, which reduces both alloy performance and performance of coatings applied to the alloy surface. Therefore, the oxidation mechanism of Al-Sn bearing alloy is studied at 25, 180, 300, and 500 °C. The oxidation morphologies of the alloy were observed by scanning electron microscopy (SEM), and the oxidation products were determined by X-ray diffraction (XRD). The oxidation weight gain curves were obtained by thermogravimetric analysis. The experimental results show that: Al-Sn bearing alloy is oxidized quickly to form Al2O3. As the oxidation temperature increases, Sn phase start to precipitate along the grain boundary and form networked spheroids of Sn on the alloy surface. The amount of precipitation increases with further increase of the oxidation temperature. Cracks and holes are left in the alloy. The oxide layer is mainly composed of Sn, SnO2, and Al2O3. At 25 °C, oxidation rate of Al-Sn alloy approach zero. At 180, 300, and 500 °C, the oxidation rate increases quickly conforming to a power function, and eventually remains stable at about 3 × 10−6 mg·mm−2·s−1.
Effects of TiO2 Nanoparticle Addition on Microstructure and Selected Properties of Ag–xTiO2 Composites
Authors: Wąsik Anna , Leszczyńska-Madej Beata , Madej Marcin
Published: August 2021

The paper presents the results of a study of the microstructure and selected properties of silver-based composites reinforced with TiO2 nanoparticles, produced by the powder metallurgy method. Pure silver powders were mixed with TiO2 reinforcement (5 and 10 wt%) and 5 mm steel balls (100Cr6) for 270 min in a Turbula T2F mixer to produce a homogeneous mixture. The composites were made in a rigid die with a single-action compaction press under a pressure of 400 MPa and 500 MPa and then sintered under nitrogen atmosphere at 900 °C. Additionally, to improve the density and mechanical properties of the obtained sinters, double pressing and double sintering operations were conducted. As a result, compacts with a density of 90–94% were obtained. The microstructure of the sintered compacts consists of uniform grains, and the TiO2 reinforcement phase particles are located on the grain boundaries. There were no discontinuities at the Ag–TiO2 contact boundary, which was confirmed by SEM and TEM analysis. The use of a higher pressure had a positive effect on the hardness and flexural strength of the tested materials. It was found that the composites with 5 wt% TiO2 pressed under 500 MPa are characterized by the highest level of mechanical properties. The hardness of these composites is 57 HB, while the flexural strength is 163 MPa.
An Efficient Approach to the Five-Axis Flank Milling of Non-Ferrous Spiral Bevel Gears
Authors: Xu Hao , Zhou Yuansheng , He Yuhui , Tang Jinyuan
Published: August 2021

Five-axis flank milling has been applied in industry as a relatively new method to cut spiral bevel gears (SBGs) for its flexibility, especially for the applications of small batches and repairs. However, it still has critical inferior aspects compared to the traditional manufacturing ways of SBGs: the efficiency is low, and the machining accuracy may not ensure the qualified meshing performances. To improve the efficiency, especially for cutting non-ferrous metals, this work proposes an approach to simultaneously cut the tooth surface and tooth bottom by a filleted cutter with only one pass. Meanwhile, the machining accuracy of the contact area is considered beforehand for the tool path optimization to ensure the meshing performances, which is further confirmed by FEM (finite element method). For the convenience of the FEM, the tooth surface points are calculated with an even distribution, and the calculation process is efficiently implemented with a closed-form solution. Based on the proposed method, the number (or total length) of the tool path is reduced, and the contact area is qualified. Both the simulation and cutting experiment are implemented to validate the proposed method.
Influence of Sand-Cement Ratio and Polycarboxylate Superplasticizer on the Basic Properties of Mortar Based on Water Film Thickness
Authors: Zhang Zhao , Feng Qingge , Zhu Weiwei , Lin Xianhao , Chen Kao , Yin Wuxiao , Lu Changhai
Published: August 2021

Previous studies demonstrated that water film thickness (WFT) is a key factor that affects the fluidity of mortar. Changes in the sand-cement (S/C) ratio and polycarboxylate superplasticizer (PCE) dosage will affect the WFT. In this study, several mortar samples with different S/C ratios and different PCE dosages were prepared, and the basic properties of the mortar were measured. The results show that as the S/C ratio increases, the packing density of the mortar will decrease, the WFT will decrease, and the cohesiveness will increase, resulting in a decrease in the flow spread and strength of the mortar. When the PCE dosage is increased, the packing density of the mortar will increase, the WFT will increase, and the cohesiveness will decrease, which increases the flow spread of the mortar. When the water-cement (W/C) ratio is low, the S/C ratio has a significant effect on the strength, and the strength will increase with the increasing of the PCE dosage. When the W/C ratio is high, the strength of the mortar will be reduced once the PCE dosage exceeds the saturation value. In the case of different S/C ratios or different PCE dosages, the WFT can be used as a measure of mortar cohesiveness and flow spread.
Impact of Polyethylene Glycol Functionalization of Graphene Oxide on Anticoagulation and Haemolytic Properties of Human Blood
Authors: Kamenska Trayana , Abrashev Miroslav , Georgieva Milena , Krasteva Natalia
Published: August 2021

Graphene oxide (GO) is one of the most explored nanomaterials in recent years. It has numerous biomedical applications as a nanomaterial including drug and gene delivery, contrast imaging, cancer treatment, etc. Since most of these applications need intravenous administration of graphene oxide and derivatives, the evaluation of their haemocompatibility is an essential preliminary step for any of the developed GO applications. Plentiful data show that functionalization of graphene oxide nanoparticles with polyethylene glycol (PEG) increases biocompatibility, thus allowing PEGylated GO to elicit less dramatic blood cell responses than their pristine counterparts. Therefore, in this work, we PEGylated graphene oxide nanoparticles and evaluated the effects of their PEGylation on the structure and function of human blood components, especially on the morphology and the haemolytic potential of red blood cells (RBCs). Further, we studied the effect of PEGylation on some blood coagulation factors, including plasma fibrinogen as well as on the activated partial thromboplastin (aPTT), prothrombin time (PT) and platelet aggregation. Our findings provide important information on the mechanisms through which PEGylation increases GO compatibility with human blood cells. These data are crucial for the molecular design and biomedical applications of PEGylated graphene oxide nanomaterials in the future.
Numerical Study on Surface Roughness Measurement Based on Nonlinear Ultrasonics in Through-Transmission and Pulse-Echo Modes
Authors: Yuan Maodan , Dai Anbang , Liao Lin , Chen Yan , Ji Xuanrong
Published: August 2021

Ultrasonic is one of the well-known methods for surface roughness measurement, but small roughness will only lead to a subtle variation of transmission or reflection. To explore sensitive techniques for surfaces with small roughness, nonlinear ultrasonic measurement in through-transmission and pulse-echo modes was proposed and studied based on an effective unit-cell finite element (FE) model. Higher harmonic generation in solids was realized by applying the Murnaghan hyperelastic material model. This FE model was verified by comparing the absolute value of the nonlinearity parameter with the analytical solution. Then, random surfaces with different roughness values ranging from 0 μm to 200 μm were repeatedly generated and studied in the two modes. The through-transmission mode is very suitable to measure the surfaces with roughness as small as 3% of the wavelength. The pulse-echo mode is sensitive and effective to measure the surface roughness ranging from 0.78% to 5.47% of the wavelength. This study offers a potential nondestructive testing and monitoring method for the interfaces or inner surfaces of the in-service structures.
Effect of Post-Process Curing and Washing Time on Mechanical Properties of mSLA Printouts
Authors: Nowacki Bartłomiej , Kowol Paweł , Kozioł Mateusz , Olesik Piotr , Wieczorek Jakub , Wacławiak Krzysztof
Published: August 2021

The article discusses the influence of the post-process on the mechanical properties of elements produced with the use of the mask stereolithography (mSLA) method. Printed samples were subjected to the following post-process steps: Washing and post-curing, at various times. Then, static tensile and static bending tests were carried out, as well as Shore D hardness measurements for the inner and surface part of the sample, as well as profilographometric analysis of the surface. The post-curing time has been found to strongly affect the tensile and bending strength of printouts, and to improve their surface quality. Washing has an ambiguous effect on the strength of the printouts, but, in the end, it was found that extended washing slightly reduces the strength. Washing significantly affects the quality of the printout surface. A washing time that is too short results in a surface that strongly resembles the printing process, with high roughness. Increasing the washing time to 10 min lowers the roughness by one order of magnitude. Post-curing has also been shown to be beneficial for the cured sample with the application of shielding water. This approach results in an improvement in the flexural strength of the printouts. In general, the obtained research results indicate that, for printouts with cross-sectional dimensions of several mm, the optimal washing time is no more than 10 min and the post-curing time is at least 30 min.
High Performance Valve Seat Materials for CNG Powered Combustion Engines
Authors: Romański Andrzej , Cygan-Bączek Elżbieta
Published: August 2021

The conventional copper infiltrated high speed steel (HSS) valve seats used in gasoline engines are not suitable for CNG combustion because the exhaust gas temperature is at least 80 °C higher, which drastically shortens the service life of the engine valves. Therefore, a proprietary high-alloy HSS-base material was designed to combat hot corrosion and mechanical wear of valve seat faces in CNG fuelled engines. A batch of −100 mesh water atomized HSS powder was commissioned. The powder was vacuum annealed in order to reduce oxygen content and increase its compressibility. To improve the final part machinability, 1.2% MnS was admixed to the HSS powder prior to compaction. The green compacts were sintered at 1135 °C in nitrogen to around 83% TD and subsequently infiltrated with a copper alloy. After installing the valve seat components on a cylinder head, the engine was tested for 100 h according to the automotive industry valve seat wear test procedures. Both the periodic 8-h checks as well as the final examination of the valve seats showed very slow wear, indicating their suitability for CNG powered engines.
RISE-Based Composite Adaptive Control of Electro-Hydrostatic Actuator with Asymptotic Stability
Authors: Ge Yaowen , Yang Xiaowei , Deng Wenxiang , Yao Jianyong
Published: August 2021

The electro-hydrostatic actuator (EHA), the actuator of electric drive and hydraulic transmission, is competitive since it is small in size, light in weight and high in power density. However, the existence of the velocity loop error of servo motors, unmodeled dynamics and highly nonlinear uncertainties restrict the improvement of the tracking accuracy of the EHA system. In order to achieve high-precision motion control of EHAs, a RISE-based composite adaptive control scheme is proposed in this paper. In the proposed composite adaptive control design, a novel parameter adaptive law is synthesized to compensate for the parametric uncertainties and a robust integral of the sign of error (RISE) feedback is utilized to suppress the adverse effects caused by the lumped disturbances, including the velocity loop error of a servo motor and other unmodeled dynamics. The synthesized parameter adaptive law possesses the advantage of fast convergence, which is beneficial to achieve transient tracking performance improvement. In addition, the proposed controller is more suitable for practical applications since it is chattering free. The closed-loop system stability analysis shows that the proposed control scheme guarantees an excellent asymptotic tracking performance. Finally, comparative simulations are conducted to verify the high-performance nature of the proposed controller.
Real-Time Flexibility Assessment for Power Systems with High Wind Energy Penetration
Authors: Glazunova Anna , Semshikov Evgenii , Negnevitsky Michael
Published: August 2021

To reduce the reliance on fossil fuel-based generation, many countries expand the use of renewable energy sources (RES) for electricity production. The stochastic and intermittent nature of such sources (i.e., wind and solar) poses challenges to the stable and reliable operation of the electric power system (EPS) and requires sufficient operational flexibility. With continuous and random changes in the EPS operational conditions, evaluating the system flexibility in a standardized manner may improve the robustness of planning and operating procedures. Therefore, the development of fast algorithms for determining system flexibility is a critical issue. In this paper, the flexibility of the EPS with high wind energy penetration is calculated in real time. In this context, the EPS flexibility is understood as the ability of the system to maintain a balance under irregular and short-term active power variations during a specified time by using the flexibility resources. The EPS flexibility calculation relies on a deterministic method developed to qualitatively and quantitatively assess the EPS readiness to changes in load. Accurate wind power forecasts and the observance of the electric circuit law when solving the optimization problem allow for determining the actual value of the EPS flexibility during a considered time.
Texture Evolution with Different Rolling Parameters of Ferritic Rolled IF Steel
Authors: Li Leilei , Cai Zhen , Wang Shuize , Wu Huibin , Feng Yuhui , Liu Yongqian , Mao Xinping
Published: August 2021

Interstitial free (IF) steel is widely used in the automotive industry, due to its excellent deep drawing performance. In this study, in order to study the influence of different rolling processes on the texture evolution and deep drawing performance of IF steel, we conducted rolling experiments on IF steel with different temperatures, different reduction rates, and different lubrication conditions. The impact of texture on the deep drawing performance of the steel was also analyzed. The microscopic and macroscopic texture analyses were performed using electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), respectively. Deep drawing performance was analyzed by measuring the r-value. The results showed that in non-lubricated rolling, the r-value increased with the decrease in the reduction rate, and the r-value increased with the increase in the deformation temperature. The maximum value of r is 0.85. But in the case of lubricated rolling, the r-value increased significantly from 0.74 to 1.47 compared to non-lubricated (keeping the reduction rate and the rolling temperature constant). The lubrication reduced the shear deformation of the steel surface, resulting in a γ texture on the surface. Texture uniformity along the thickness direction resulted in an increase in the r-value of the steel.
Porous Titanium by Additive Manufacturing: A Focus on Surfaces for Bone Integration
Authors: Ferraris Sara , Spriano Silvia
Published: August 2021

Additive manufacturing (AM) is gaining increasing interest for realization of customized porous titanium constructs for biomedical applications and, in particular, for bone substitution. As first, the present review gives a short introduction on the techniques used for additive manufacturing of Ti/Ti-Alloys (Direct Energy Deposition—DED, Selective Laser Melting—SLM and Electron Beam Melting—EBM) and on the main bulk properties of additively manufactured titanium porous structures. Then, it discusses the main advancements in surface modifications of additively manufactured titanium constructs for bone contact applications. Even if specific surface modifications of constructs from AM are currently not widely explored, it is a critical open issue for application in biomedical implants. Some thermal, chemical, electrochemical, and hydrothermal treatments as well as different coatings are here described. The main aim of these treatments is the development of surface micro/nano textures, specific ion release, and addition of bioactivity to induce bone bonding and antibacterial activity. Physicochemical characterizations, in vitro bioactivity tests, protein absorption, in vitro (cellular/bacterial) and in vivo tests reported in the literature for bare and surface modified AM Ti-based constructs are here reviewed. Future perspectives for development of innovative additively manufactured titanium implants are also discussed.