bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypoxic Melanoma Cells Deliver microRNAs to Dendritic Cells and Cytotoxic T Lymphocytes through Connexin-43 Channels
Authors: Tittarelli Andrés , Navarrete Mariela , Lizana Marcelo , Hofmann-Vega Francisca , Salazar-Onfray Flavio
Published: October 2020

Alterations in microRNA (miRNA) profiles, induced by tumor microenvironment stressors, like hypoxia, allow cancer cells to acquire immune-resistance phenotypes. Indeed, hypoxia-induced miRNAs have been implicated in cancer progression through numerous cancer cell non-autonomous mechanisms, including the direct transfer of hypoxia-responsive miRNA from cancer to immune cells via extracellular vesicles. Connexin-43 (Cx43)-constituted gap junctions (GJs) have also been involved in miRNA intercellular mobilization, in other biological processes. In this report, we aimed to evaluate the involvement of Cx43-GJs in the shift of miRNAs induced by hypoxia, from hypoxic melanoma cells to dendritic cells and melanoma-specific cytotoxic T lymphocytes (CTLs). Using qRT-PCR arrays, we identified that miR-192-5p was strongly induced in hypoxic melanoma cells. Immune cells acquired this miRNA after co-culture with hypoxic melanoma cells. The transfer of miR-192-5p was inhibited when hypoxic melanoma cells expressed a dominant negative Cx43 mutant or when Cx43 expression was silenced using specific short-hairpin RNAs. Interestingly, miR-192-5p levels on CTLs after co-culture with hypoxic melanoma cells were inversely correlated with the cytotoxic activity of T cells and with ZEB2 mRNA expression, a validated immune-related target of miR-192-5p, which is also observed in vivo. Altogether, our data suggest that hypoxic melanoma cells may suppress CTLs cytotoxic activity by transferring hypoxia-induced miR-192-5p through a Cx43-GJs driven mechanism, constituting a resistance strategy for immunological tumor escape.
The Heavy Chain 4F2hc Modulates the Substrate Affinity and Specificity of the Light Chains LAT1 and LAT2
Authors: Kantipudi Satish , Jeckelmann Jean-Marc , Ucurum Zöhre , Bosshart Patrick D. , Fotiadis Dimitrios
Published: October 2020

The human L-type amino acid transporters LAT1 and LAT2 mediate the transport of amino acids and amino acid derivatives across plasma membranes in a sodium-independent, obligatory antiport mode. In mammalian cells, LAT1 and LAT2 associate with the type-II membrane N-glycoprotein 4F2hc to form heteromeric amino acid transporters (HATs). The glycosylated ancillary protein 4F2hc is known to be important for successful trafficking of the unglycosylated transporters to the plasma membrane. The heavy (i.e., 4F2hc) and light (i.e., LAT1 and LAT2) chains belong to the solute carrier (SLC) families SLC3 and SLC7, and are covalently linked by a conserved disulfide bridge. Overexpression, absence, or malfunction of certain HATs is associated with human diseases and HATs are therefore considered therapeutic targets. Here, we present a comparative, functional characterization of the HATs 4F2hc-LAT1 and 4F2hc-LAT2, and their light chains LAT1 and LAT2. For this purpose, the HATs and the light chains were expressed in the methylotrophic yeast Pichia pastoris and a radiolabel transport assay was established. Importantly and in contrast to mammalian cells, P. pastoris has proven useful as eukaryotic expression system to successfully express human LAT1 and LAT2 in the plasma membrane without the requirement of co-expressed trafficking chaperone 4F2hc. Our results show a novel function of the heavy chain 4F2hc that impacts transport by modulating the substrate affinity and specificity of corresponding LATs. In addition, the presented data confirm that the light chains LAT1 and LAT2 constitute the substrate-transporting subunits of the HATs, and that light chains are also functional in the absence of the ancillary protein 4F2hc.
Mechanism and Function of the Catch State in Molluscan Smooth Muscle: A Historical Perspective
Authors: Sugi Haruo , Ohno Tetsuo , Moriya Masamichi
Published: October 2020

Molluscan smooth muscles exhibit the catch state, in which both tension and resistance to stretch are maintained with very low rates of energy consumption. The catch state is studied mainly on the anterior byssus retractor muscle (ABRM) of a bivalve molluscan animal, Mytilus, which can easily be split into small bundles consisting of parallel fibers. The ABRM contracts actively with an increase in the intracellular free Ca ion concentration, [Ca2+]i, as with all other types of muscle. Meanwhile, the catch state is established after the reduction of [Ca2+]i to the resting level. Despite extensive studies, the mechanism underlying the catch state is not yet fully understood. This article briefly deals with (1) anatomical and ultrastructural aspects of the ABRM, (2) mechanical studies on the transition from the active to the catch state in the isotonic condition, (3) electron microscopic and histochemical studies on the intracellular translocation of Ca ions during the transition from the active to the catch state, and (4) biochemical studies on the catch state, with special reference to a high molecular mass protein, twitchin, which is known to occur in molluscan catch muscles.
Regulation of Platelet Production and Life Span: Role of Bcl-xL and Potential Implications for Human Platelet Diseases
Authors: Josefsson Emma C. , Vainchenker William , James Chloe
Published: October 2020

Blood platelets have important roles in haemostasis, where they quickly stop bleeding in response to vascular damage. They have also recognised functions in thrombosis, immunity, antimicrobal defense, cancer growth and metastasis, tumour angiogenesis, lymphangiogenesis, inflammatory diseases, wound healing, liver regeneration and neurodegeneration. Their brief life span in circulation is strictly controlled by intrinsic apoptosis, where the prosurvival Bcl-2 family protein, Bcl-xL, has a major role. Blood platelets are produced by large polyploid precursor cells, megakaryocytes, residing mainly in the bone marrow. Together with Mcl-1, Bcl-xL regulates megakaryocyte survival. This review describes megakaryocyte maturation and survival, platelet production, platelet life span and diseases of abnormal platelet number with a focus on the role of Bcl-xL during these processes.
Multiple Endocrine Neoplasia Type 1: The Potential Role of microRNAs in the Management of the Syndrome
Authors: Donati Simone , Ciuffi Simone , Marini Francesca , Palmini Gaia , Miglietta Francesca , Aurilia Cinzia , Brandi Maria Luisa
Published: October 2020

Multiple endocrine neoplasia type 1 (MEN1) is a rare inherited tumor syndrome, characterized by the development of multiple neuroendocrine tumors (NETs) in a single patient. Major manifestations include primary hyperparathyroidism, gastro-entero-pancreatic neuroendocrine tumors, and pituitary adenomas. In addition to these main NETs, various combinations of more than 20 endocrine and non-endocrine tumors have been described in MEN1 patients. Despite advances in diagnostic techniques and treatment options, which are generally similar to those of sporadic tumors, patients with MEN1 have a poor life expectancy, and the need for targeted therapies is strongly felt. MEN1 is caused by germline heterozygous inactivating mutations of the MEN1 gene, which encodes menin, a tumor suppressor protein. The lack of a direct genotype–phenotype correlation does not permit the determination of the exact clinical course of the syndrome. One of the possible causes of this lack of association could be ascribed to epigenetic factors, including microRNAs (miRNAs), single-stranded non-coding small RNAs that negatively regulate post-transcriptional gene expression. Some miRNAs, and their deregulation, have been associated with MEN1 tumorigenesis. Recently, an extracellular class of miRNAs has also been identified (c-miRNAs); variations in their levels showed association with various human diseases, including tumors. The aim of this review is to provide a general overview on the involvement of miRNAs in MEN1 tumor development, to be used as possible targets for novel molecular therapies. The potential role of c-miRNAs as future non-invasive diagnostic and prognostic biomarkers of MEN1 will be discussed as well.
New Insights into Cockroach Control: Using Functional Diversity of Blattella germanica Symbionts
Authors: Pan Xiaoyuan , Wang Xuejun , Zhang Fan
Published: October 2020

Insects have close symbiotic relationships with several microbes, which extends the limited metabolic networks of most insects. Using symbiotic microorganisms for the biological control of pests and insect-borne diseases has become a promising direction. Blattella germanica (L.) (Blattaria: Blattidae) is a public health pest worldwide, which is difficult to control because of its strong reproductive ability, adaptability, and resistance to insecticides. In this paper, the diverse biological functions (nutrition, reproductive regulation, insecticide resistance, defense, and behavior) of symbionts were reviewed, and new biological control strategies on the basis of insect–symbiont interaction were proposed. We highlight new directions in B. germanica control, such as suppressing cockroach population using Wolbachia or paratransgenes, and combining fungal insecticides with synergistic agents to enhance insecticidal efficacy.
One Step Is Not Enough: A Multi-Step Procedure for Building the Training Set of a Query by String Keyword Spotting System to Assist the Transcription of Historical Document
Authors: Parziale Antonio , Capriolo Giuliana , Marcelli Angelo
Published: October 2020

Digital libraries offer access to a large number of handwritten historical documents. These documents are available as raw images and therefore their content is not searchable. A fully manual transcription is time-consuming and expensive while a fully automatic transcription is cheaper but not comparable in terms of accuracy. The performance of automatic transcription systems is strictly related to the composition of the training set. We propose a multi-step procedure that exploits a Keyword Spotting system and human validation for building up a training set in a time shorter than the one required by a fully manual procedure. The multi-step procedure was tested on a data set made up of 50 pages extracted from the Bentham collection. The palaeographer that transcribed the data set with the multi-step procedure instead of the fully manual procedure had a time gain of 52.54%. Moreover, a small size training set that allowed the keyword spotting system to show a precision value greater than the recall value was built with the multi-step procedure in a time equal to 35.25% of the time required for annotating the whole data set.
Development of GMDH-Based Storm Surge Forecast Models for Sakaiminato, Tottori, Japan
Authors: Kim Sooyoul , Mase Hajime , Thuy Nguyen Ba , Takeda Masahide , Tran Cao Truong , Dang Vu Hai
Published: October 2020

The current study developed storm surge hindcast/forecast models with lead times of 5, 12, and 24 h at the Sakaiminato port, Tottori, Japan, using the group method of data handling (GMDH) algorithm. For training, local meteorological and hydrodynamic data observed in Sakaiminato during Typhoons Maemi (2003), Songda (2004), and Megi (2004) were collected at six stations. In the forecast experiments, the two typhoons, Maemi and Megi, as well as the typhoon Songda, were used for training and testing, respectively. It was found that the essential input parameters varied with the lead time of the forecasts, and many types of input parameters relevant to training were necessary for near–far forecasting time-series of storm surge levels. In addition, it was seen that the inclusion of the storm surge level at the input layer was critical to the accuracy of the forecast model.
Bottlenecks to Financial Development, Financial Inclusion, and Microfinance: A Case Study of Mauritania
Authors: Bouasria Mohamedou , Ashta Arvind , Ratsimalahelo Zaka
Published: October 2020

The objective of the study was to enhance our knowledge on institutional bottlenecks for financial development, financial inclusion, and microfinance, using Mauritania as a case study. We used a mixed-methods’ methodology that combines analysis of secondary data and an expert interview. First, a logit model with dummy independent variables was used to investigate the factors that impact the households’ access to credit, the main advantage of this model being to avoid confounding effects by analyzing the association of all variables together. Our study found that access to financial services is equal in Mauritania between men and women, but that access to credit is higher for public sector employees, educated people, and households with smaller families. Second, using principal components’ analysis, we found that the different regions of Mauritania can be divided based on unemployment, income, literacy, financial inclusion, and population density into two main dimensions, yielding four quadrants: Attractive, industrious, moderate, and resource cursed. We expected that sparsely populated countries would have less access to credit. Counterintuitively, we found that within a low-density country, people in the lowest-density regions have higher odds of getting credit. Third, based on an interview with an expert, we noted the key challenges that microfinance is facing in Mauritania and provided recommendations to overcome these. As in most case studies, external validity was limited.
Tax Loss Amortization of Companies in Slovakia
Authors: Bánociová Anna , Ťahlová Slavomíra
Published: October 2020

The purpose of this article is to research how companies optimize income tax with the ambition to maintain the achieved sales and profits at the highest possible level. Its purpose is to find out whether companies in Slovakia compensate for higher tax liability by tax loss amortization to reduce their income tax payable. Based on the review of literature from the field of legislation concerning the tax loss amortization by using the descriptive statistics of selected corporate and tax indicators, the companies are monitored in order to capture their behavior in paying income tax. The methods of deduction and synthesis are used in this article. The observed corporate and tax indicators are focusing on the relationship between the tax liability arising from corporate income tax, amortized tax losses, and the amount of tax payable in Slovakia in the period from 2015 to 2018. Tax loss can be considered as a tool for tax optimization, which is used by companies in all countries of the European Union, while the scope of its applicability is often limited by a time horizon. The amortization of tax losses has an impact on the amount of tax levied and the subsequent income tax payable, while the possibility to use this tool of tax optimization is influenced by the changing legislation in the period under review.
Electroacupuncture on the Scalp over the Motor Cortex Ameliorates Behavioral Deficits Following Neonatal Hypoxia-Ischemia in Rats via the Activation of Neural Stem Cells
Authors: Jung Da Hee , Pak Malk Eun , Lee Hong Ju , Ahn Sung Min , Yun Young Ju , Shin Yong-Il , Shin Hwa Kyoung , Lee Seo-Yeon , Choi Byung Tae
Published: October 2020

Electroacupuncture (EA) therapy via alternating current stimulation on the scalp over the motor cortex is used for the treatment of brain disorders. Perinatal hypoxia-ischemia (HI), a brain injury in newborns, leads to long-term neurologic complications. Here, we investigated whether EA could promote functional improvements and neurogenesis in a neonatal HI rat model. A neonatal HI rat model was induced by permanent ligation of the left carotid artery in postnatal day 7 pups. EA for neonatal HI rats was performed at 2 Hz (1, 3, or 5 mA; 20 min) from 4–6 weeks after birth. HI rats undergoing EA had improved motor and memory function, with the greatest improvement after 3 mA EA. The corpus callosum was significantly thicker and showed a significant increase in proliferating astrocytes in the 3 mA EA group. We observed proliferating cells and a greater number of newly developed neurons and astrocytes in the subventricular zone and dentate gyrus of the 3 mA EA group than in those of the HI group. These results suggest that EA promotes functional improvements following neonatal HI assault via the proliferation and differentiation of neural stem cells. This effect was the strongest after 3 mA EA, suggesting that this is the optimal treatment dose.
Di(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)dimethylsilane
Authors: Levchenko Konstantin S. , Adamov Gregory E. , Demin Dmitri Yu. , Chicheva Polina A. , Chudov Konstantin A. , Shmelin Pavel S. , Grebennikov Evgeny P.
Published: October 2020

Di(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)dimethylsilane (DiBCB-DMS) was synthesized as a promising monomer for polymer coating production with good dielectric properties for electronics. DiBCB-DMS was characterized by 1H, 13C NMR, IR, UV/VIS, and HRMS analysis.
Effects of Methyl Terminal and Carbon Bridging Groups Ratio on Critical Properties of Porous Organosilicate Glass Films
Authors: Vishnevskiy Alexey S. , Naumov Sergej , Seregin Dmitry S. , Wu Yu-Hsuan , Chuang Wei-Tsung , Rasadujjaman Md , Zhang Jing , Leu Jihperng , Vorotilov Konstantin A. , Baklanov Mikhail R.
Published: October 2020

Organosilicate glass-based porous low dielectic constant films with different ratios of terminal methyl to bridging organic (methylene, ethylene and 1,4-phenylene) groups are spin-on deposited by using a mixture of alkylenesiloxane with organic bridges and methyltrimethoxysilane, followed by soft baking at 120–200 °C and curing at 430 °C. The films’ porosity was controlled by using sacrificial template Brij® L4. Changes of the films’ refractive indices, mechanical properties, k-values, porosity and pore structure versus chemical composition of the film’s matrix are evaluated and compared with methyl-terminated low-k materials. The chemical resistance of the films to annealing in oxygen-containing atmosphere is evaluated by using density functional theory (DFT). It is found that the introduction of bridging groups changes their porosity and pore structure, increases Young’s modulus, but the improvement of mechanical properties happens simultaneously with the increase in the refractive index and k-value. The 1,4-phenylene bridging groups have the strongest impact on the films’ properties. Mechanisms of oxidative degradation of carbon bridges are studied and it is shown that 1,4-phenylene-bridged films have the highest stability. Methylene- and ethylene-bridged films are less stable but methylene-bridged films show slightly higher stability than ethylene-bridged films.
Consistent DSC and TGA Methodology as Basis for the Measurement and Comparison of Thermo-Physical Properties of Phase Change Materials
Authors: Müller Lukas , Rubio-Pérez Gabriel , Bach Andreas , Muñoz-Rujas Natalia , Aguilar Fernando , Worlitschek Jörg
Published: October 2020

Measuring thermo-physical properties of phase change materials (PCM) in a consistent and reliable manner is essential for system layout of thermal energy storages and correspondingly material selection. Only if basic properties are assessed in a comparable way a selection process leads to the top candidate for any given application and thus enhances market penetration of renewable energy sources coupled with thermal energy storage. In this study, we focus on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) as basic assessment techniques and develop consistent measurement procedures to create a database with comparable results. We show consistency of the measured results through analysis of coefficient of variation (CV), being in the mean 1.69%, 0.05%, 0.06% and 4.00% for enthalpy, melting onset, melting peak and maximum operating temperature, respectively. Overall, 23 PCM have been measured with the presented methodology, which was mainly possible due to the reduced measurement and preparation time per PCM compared to standard techniques, while achieving similar accuracy and precision.
Analysis of Tortuosity in Compacts of Ternary Mixtures of Spherical Particles
Authors: Zharbossyn Assem , Berkinova Zhazira , Boribayeva Aidana , Yermukhambetova Assiya , Golman Boris
Published: October 2020

Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical Voronoi tessellation. For this purpose, a series of particle compacts geometrically similar to the actual porous electrode were generated using discrete element method; the radical Voronoi tessellation was constructed for each compact to characterize the structural properties; the tortuosity of compact porous structure was simulated by applying the Dijkstra’s shortest path algorithm on radical Voronoi tessellation. Finally, the relationships were established between the tortuosity and the composition of the ternary particle mixture, and between the tortuosity and the radical Voronoi cell parameters. The following correlations between tortuosity values and radical Voronoi cell parameters were found: larger faces and longer edges of radical Voronoi cell leads to the increased fraction of larger values of tortuosity in the distribution, while smaller faces and shorter edges of radical Voronoi cell contribute to the increased fraction of smaller tortuosity values, being the tortuosity values more uniform with narrower distribution. Thus, the compacts with enhanced diffusion properties are expected to be obtained by packing particle mixtures with high volume fraction of small and medium particles. These results will help to design the well-packed particle compacts having improved diffusion properties for various applications including porous electrodes.
Novel Nanocomposites Based on Bacterial Polyester/LDH-SDS Clay for Stem Cells Delivery in Modern Wound Healing Management
Authors: Vasile Eugeniu , Radu Ionut-Cristian , Galateanu Bianca , Rapa Maria , Hudita Ariana , Jianu Dana , Stanescu Paul-Octavian , Cioflan Horia , Zaharia Catalin
Published: October 2020

Nanocomposite materials based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and modified mineral clay layered double hydroxides (LDH-SDS) were explored as novel nanostructured materials for potential tissue engineering applications. The mineral clay inorganic phase was modified with an anionic long-chain structure of carbon atoms, such as sodium dodecyl sulfate, in order to increase the compatibility between the two phases. The melt intercalation method used for nanocomposite fabrication ensures a good dispersion of the modified LDH-SDS within the polymer matrix without using a toxic solvent (chloroform). The nanocomposites were found to have an intercalated/exfoliated structure with an enhanced Young modulus and increased stiffness. This could allow them to be considered for autologous stem cells dressings in the view of efficient wound healing applications.
Reconfigurable Multipoint Forming Using Waffle-Type Elastic Cushion and Variable Loading Profile
Authors: Moheen Mohammed , Abdel-Wahab Adel , Hassanin Hany , Essa Khamis
Published: October 2020

There is an increasing demand for flexible, relatively inexpensive manufacturing techniques that can accommodate frequent changes to part design and production technologies, especially when limited batch sizes are required. Reconfigurable multi-point forming (MPF) is an advanced manufacturing technique which uses a reconfigurable die consisting of a set of moveable pins to shape sheet metal parts easily. This study investigates the use of a novel variable thickness waffle-type elastic cushion and a variable punch-loading profile to either eliminate or minimise defects associated with MPF, namely wrinkling, thickness variation, shape deviation, and dimpling. Finite element modelling (FEM), analysis of variance (ANOVA), and the response surface methodology (RSM) were used to investigate the effect of process parameters pertaining to the cushion dimensions and type of loading profile on the aforementioned defects. The results of this study indicate that the most significant process parameters were maximum cushion thickness, cushion cut-out base radius, and cushion cut-out profile radius. The type of loading profile was found to be insignificant in all responses, but further investigation is required as the rate, and the thermal effects were not considered in the material modelling. Optimal process parameters were found to be a maximum cushion thickness of 3.01 mm, cushion cut-out base radius of 2.37 mm, cushion cut-out profile radius of 10 mm, and a “linear” loading profile. This yielded 0.50 mm, 0.00515 mm, 0.425 mm for peak shape deviation, thickness variation, and wrinkling, respectively.
Micromechanical Model and Thermal Properties of Dry-Friction Hybrid Polymer Composite Clutch Facings
Authors: Biczó Roland , Kalácska Gábor , Mankovits Tamás
Published: October 2020

Fiber-reinforced hybrid composites are the most commonly used dry-friction materials in the automotive industry. On the other hand, the great variety of components utilized these days in such material systems often requires identification investigations for a complex characterization. The development history of clutch materials was reviewed, highlighting and understanding the milestones and efforts leading to the creation of these materials. Investigations were performed to determine mechanical stiffness matrix parameters and thermal properties of a woven fiber yarn (glass fiber with aromatic polyamide, copper, and poly-acrylic-nitrile (PAN) reinforced friction material, revealing and solving challenges faced during identification efforts. This study grants an effective reference and a novel guidance for material identification methods for similar complex materials, and the results provide input parameters for thermomechanical simulation contact model development, which will cover friction material lifetime effects on dry clutch tribology in a future study.
Effect of Post Weld Heat Treatment on the Microstructure and Electrochemical Characteristics of Dissimilar Material Welded by Butter Method
Authors: Masood Chaudry Umer , Ahmad Hafiz Waqar , Tariq Muhammad Rehan , Farooq Ameeq , Khan Muhammad Kashif , Sher Farooq , Zeb Hassan , Hamad Kotiba
Published: October 2020

In the present study, the effect of post weld heat treatment (PWHT) on the microstructure and corrosion kinetics of butter welded Nickel Alloy 617 and 12Cr steel was investigated. Buttering was carried out on the 12Cr side with the Thyssen 617 filler metal. Furthermore, post weld heat treatment (PWHT) was conducted at 730 °C with a holding time of 4 h followed by furnace cooling. Optical Microscopy (OM) was conducted to study the microstructural evolution in dissimilar material welding as a result of PWHT. Moreover, Scanning Electron Microscopy with energy dispersive spectroscopy (SEM-EDS) was employed to determine the elemental concentrations in all important regions of the butter weld before and after the PWHT. In addition, the effect of PWHT on the corrosion kinetics of the butter weld was also investigated by potentiodynamic polarization measurements in 5 wt.% NaCl + 0.5 wt.% CH3COOH electrolyte at room temperature, 30 °C, 50 °C and 70 °C. The corrosion activation parameters were also determined for both the samples by using Arrhenius plots. The results revealed the higher susceptibility of corrosion of the butter weld after PWHT, which was attributed to the reduced Cr content in the heat affected zone of the 12Cr region due to the sensitization effect of the heat treatment, resulting in higher corrosion rates.
Influence of Nanoparticles from Waste Materials on Mechanical Properties, Durability and Microstructure of UHPC
Authors: Mostafa Sahar A. , Faried Ahmed S. , Farghali Ahmed A. , EL-Deeb Mohamed M. , Tawfik Taher A. , Majer Stanisław , Abd Elrahman Mohamed
Published: October 2020

This investigation presents the influence of various types of nanoparticles on the performance of ultra high performance concrete (UHPC). Three nanoparticles from waste materials include nano-crushed glass, nano-metakaolin, nano-rice husk ash were prepared using the milling technique. In addition, nano-silica prepared using chemical method at the laboratory is implemented to compare the performance. Several UHPC mixes incorporating different dosages of nanoparticles up to 5% are prepared and tested. Mechanical properties, durability as well as the microstructure of UHPC mixes have been evaluated in order to study the influence of nanoparticles on the hardened characteristics of UHPC. The experimental results showed that early strength is increased by the incorporation of nanomaterials, as compared to the reference UHPC mix. The incorporation of 3% nano-rice husk ash produced the highest compressive strength at 91 day. Microstructural measurements using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX), and Thermogravimetric Analysis (TGA) confirm the role of nanomaterials in densifying the microstructure, reducing calcium hydroxide content as well as producing more C-S-H, which improves the strength and reduces the absorption of UHPC. Nanoparticles prepared from waste materials by the milling technique are comparable to chemically prepared nanosilica in improving mechanical properties, refining the microstructure and reducing the absorption of UHPC.
3D Printing in Heterogeneous Catalysis—The State of the Art
Authors: Bogdan Elżbieta , Michorczyk Piotr
Published: October 2020

This paper describes the process of additive manufacturing and a selection of three-dimensional (3D) printing methods which have applications in chemical synthesis, specifically for the production of monolithic catalysts. A review was conducted on reference literature for 3D printing applications in the field of catalysis. It was proven that 3D printing is a promising production method for catalysts.
Effects of Groove and Steel Fiber on Shear Properties of Concrete with Recycled Coarse Aggregate
Authors: Gao Danying , Yan Yongming , Pang Yuyang , Tang Jiyu , Yang Lin , Gu Zhiqiang
Published: October 2020

In this paper, a series of shear specimens with or without groove were manufactured to mainly analyze the effects of grooves (or shear section height) and steel fibers on the shear properties of concrete with recycled coarse aggregate through double-side direct shear test. In addition, the relationship between the shear strength and the compressive strength and splitting tensile strength of steel fiber reinforced concrete with recycled coarse aggregate (SFRCAC) was also discussed. The experimental results showed that the peak load, deformation corresponding to the peak load and calculated shear strength of the specimens with grooves were lower than those of the specimens without grooves. The steel fiber and recycled coarse aggregate (RCA) had a significant effect on the shear properties of SFRCAC. As the volume content of steel fibers increased, the shear strength of SFRCAC and the corresponding deformation increased gradually. With the replacement ratio of RCA increasing, the shear strength of SFRCAC decreased but the corresponding deformation increased gradually. Finally, the formula for calculating the shear strength of SFRCAC was proposed by analyzing and fitting the test results and the data of related literature.
Microstructure and Porosity Evolution of the Ti–35Zr Biomedical Alloy Produced by Elemental Powder Metallurgy
Authors: Matuła Izabela , Dercz Grzegorz , Zubko Maciej , Maszybrocka Joanna , Jurek-Suliga Justyna , Golba Sylwia , Jendrzejewska Izabela
Published: October 2020

In the present study, the structure and porosity of binary Ti–35Zr (wt.%) alloy were investigated, allowing to consider powder metallurgy as a production method for new metallic materials for potential medical applications. The porous Ti–Zr alloys were obtained by milling, cold isostatic pressing and sintering. The pressure during cold isostatic pressing was a changing parameter and was respectively 250, 500, 750 and 1000 MPa. The X-ray diffraction study revealed only the α phase, which corresponds to the Ti–Zr phase diagram. The microstructure of the Ti–35Zr was observed by optical microscopy and scanning electron microscopy. These observations revealed that the volume fraction of the pores decreased from over 20% to about 7% with increasing pressure during the cold isostatic pressing. The microhardness measurements showed changes from 137 HV0.5 to 225 HV0.5.
Laser Dissimilar Welding of AISI 430F and AISI 304 Stainless Steels
Authors: Pańcikiewicz Krzysztof , Świerczyńska Aleksandra , Hućko Paulina , Tumidajewicz Marek
Published: October 2020

A dissimilar autogenous laser welded joint of AISI 430F (X12CrMoS17) martensitic stainless steel and AISI 304 (X5CrNi18-10) austenitic stainless steel was manufactured. The welded joint was examined by non-destructive visual testing and destructive testing by macro- and microscopic examination and hardness measurements. With reference to the ISO 13919-1 standard the welded joint was characterized by C level, due to the gas pores detected. Microscopic observations of AISI 430F steel revealed a mixture of ferrite and carbides with many type II sulfide inclusions. Detailed analysis showed that they were Cr-rich manganese sulfides. AISI 304 steel was characterized by the expected austenitic microstructure with banded δ-ferrite. Martensitic microstructure with fine, globular sulfide inclusions was observed in the weld metal. The hardness in the heat-affected zone was increased in the martensitic steel in relation to the base metal and decreased in the austenitic steel. The hardness range in the weld metal, caused by chemical inhomogeneity, was 184–416 HV0.3.
On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%)
Authors: Zhao Jiang , Utton Claire , Tsakiropoulos Panos
Published: October 2020

We studied the microstructures and isothermal oxidation of the Nb-silicide-based alloys Nb-11.5Ti-18Si-5Mo-2W-4.9Sn-4.6Ge-4.5Cr-4.7Al-1Hf (JZ4) and Nb-21Ti-18Si-6.7Mo-1.2W-4.4Sn-4.2Ge-4Cr-3.7Al-0.8Hf (JZ5), calculated their average creep rate for the creep goal conditions of T = 1200 °C and σ = 170 MPa, and compared properties of the two alloys with those of other refractory metal (RM) complex concentrated alloys (RCCAs). Both alloys had a density less than 7.3 g/cm3 and lower than the density of multiphase bcc solid solution + M5Si3 silicide RCCAs. There was macrosegregation of Si in both alloys, which had the same phases in their as-cast microstructures, namely βNb5Si3, αNb5Si3, A15-Nb3X (X = Al, Ge, Si, Sn), TM5Sn2X (X = Al, Ge, Si), C14-Cr2Nb, but no solid solution. After heat treatment at 1500 °C for 100 h, a low volume fraction of a W-rich (Nb, W)ss solid solution was observed in both alloys together with βNb5Si3, αNb5Si3 and A15-Nb3X but not the TM5Sn2X, whereas the Laves phase was observed only in JZ4. At 800 °C, both alloys did not pest, and there was no spallation of their scales at 1200 °C. At both temperatures, both alloys followed parabolic oxidation kinetics and their weight changes were lower than those of Ti-rich Nb-silicide-based alloys. The oxidation of both alloys was superior to that of other RCCAs studied to date. For each alloy the Si macrosegregation, volume fraction of solid solution, chemical composition of solid solution and Nb5Si3, and weight changes in isothermal oxidation at 800 and 1200 °C that were calculated using the alloy design methodology NICE agreed well with the experimental results.
Machine Learning-Based Evaluation of Shear Capacity of Recycled Aggregate Concrete Beams
Authors: Yu Yong , Zhao Xinyu , Xu Jinjun , Chen Cheng , Deresa Simret , Zhang Jintuan
Published: October 2020

Recycled aggregate concrete (RAC) is a promising solution to address the challenges raised by concrete production. However, the current lack of pertinent design rules has led to a hesitance to accept structural members made with RAC. It would entail even more difficulties when facing application scenarios where brittle failure is possible (e.g., beam in shear). In this paper, existing major shear design formulae established primarily for conventional concrete beams were assessed for RAC beams. Results showed that when applied to the shear test database compiled for RAC beams, those formulae provided only inaccurate estimations with surprisingly large scatter. To cope with this bias, machine learning (ML) techniques deemed as potential alternative predictors were resorted to. First, a Grey Relational Analysis (GRA) was carried out to rank the importance of the parameters that would affect the shear capacity of RAC beams. Then, two contemporary ML approaches, namely, the artificial neural network (ANN) and the random forest (RF), were leveraged to simulate the beams’ shear strength. It was found that both models produced even better predictions than the evaluated formulae. With this superiority, a parametric study was undertaken to observe the trends of how the parameters played roles in influencing the shear resistance of RAC beams. The findings indicated that, though less influential than the structural parameters such as shear span ratio, the effect of the replacement ratio of recycled aggregate (RA) was still significant. Nevertheless, the value of vc/(fc)1/2 (i.e., the shear contribution from RAC normalized with respect to the square root of its strength) predicted by the ML-based approaches appeared to be insignificantly affected by the replacement level. Given the existing inevitable large experimental scatter, more shear tests are certainly needed and, for safe application of RAC, using partial factors calibrated to consider the uncertainty is feasible when designing the shear strength of RAC beams. Some suggestions for future works are also given at the end of this paper.
Hot Deformation Treatment of Grain-Modified Mg–Li Alloy
Authors: Król Mariusz , Snopiński Przemysław , Pagáč Marek , Hajnyš Jiří , Petrů Jana
Published: October 2020

In this work, a systematic analysis of the hot deformation mechanism and a microstructure characterization of an as-cast single α-phase Mg–4.5 Li–1.5 Al alloy modified with 0.2% TiB addition, as a grain refiner, is presented. The optimized constitutive model and hot working terms of the Mg–Li alloy were also determined. The hot compression procedure of the Mg–4.5 Li–1.5 Al + 0.2 TiB alloy was performed using a DIL 805 A/D dilatometer at deformation temperatures from 250 °C to 400 °C and with strain rates of 0.01–1 s−1. The processing map adapted from a dynamic material model (DMM) of the as-cast alloy was developed through the superposition of the established instability map and power dissipation map. By considering the processing maps and microstructure characteristics, the processing window for the Mg–Li alloy were determined to be at the deformation temperature of 590 K–670 K and with a strain rate range of 0.01–0.02 s−1.
Visible-Light Activation of Photocatalytic for Reduction of Nitrogen to Ammonia by Introducing Impurity Defect Levels into Nanocrystalline Diamond
Authors: Su Rui , Liu Zhangcheng , Abbasi Haris Naeem , Wei Jinjia , Wang Hongxing
Published: October 2020

Nitrogen impurity has been introduced in diamond film to produce a nitrogen vacancy center (NV center) toward the solvated electron-initiated reduction of N2 to NH3 in liquids, giving rise to extend the wavelength region beyond the diamond’s band. Scanning electron microscopy and X-ray diffraction demonstrate the formation of the nanocrystalline nitrogen-doped diamond with an average diameter of ten nanometers. Raman spectroscopy and PhotoLuminescence (PL) spectrum show characteristics of the NV0 and NV− charge states. Measurements of photocatalytic activity using supraband (λ < 225 nm) gap and sub-band gap (λ > 225 nm) excitation show the nitrogen-doped diamond significantly enhanced the ability to reduce N2 to NH3 compared to the polycrystalline diamond and single crystal diamond (SCD). Our results suggest an important process of internal photoemission, in which electrons are excited from negative charge states into conduction band edges, presenting remarkable photoinitiated electrons under ultraviolet and visible light. Other factors, including transitions between defect levels and processes of reaction, are also discussed. This approach can be especially advantageous to such as N2 and CO2 that bind only weakly to most surfaces and high energy conditions.
Frequency Domain Analysis and Precision Realization in Deterministic Figuring of Ultra-Precision Shaft Parts
Authors: Sun Zizhou , Hu Hao , Dai Yifan , Guan Chaoliang , Tie Guipeng , Ou Yang
Published: October 2020

An aerostatic spindle is a core component in ultra-precision machine tools. The rotor of the spindle has extremely high manufacturing accuracy, which cannot be directly achieved via traditional machining, but always via manual grinding. The deterministic figuring theory is introduced into the machining of shaft parts, which overcomes many shortcomings of manual grinding. The manufacturing error of the shaft’s surface contains different frequency components, which have different effects on its working performance and the figuring process. Because the deterministic figuring method can only correct the error within a limited frequency range, in order to ensure high efficiency and high precision of the figuring process, we need to use reasonable filtering parameters to filter out the error with unnecessary frequencies. In this paper, the influence of contour error with different frequencies and amplitudes on the air film are analyzed using computational fluid dynamics (CFD) software, and the amplitude–frequency analysis as a function of the power spectral density (PSD) characteristic curve is used to study the filtering parameters of the measured data. After the figuring experiment using the filtering parameters obtained from the analysis, the average roundness of the shaft converged from 0.419 μm to 0.101 μm, and the cylindricity converged from 0.76 μm to 0.35 μm. The precision reached the level of manual grinding, which proves the rationality of the analysis using filtering parameters in a shaft’s deterministic figuring.
Sintering Kinetics of Austenitic Stainless Steel AISI 316L Modified with Nanographite Particles with Highly Developed BET Specific Surface Area
Authors: Kozub Barbara , Kazior Jan , Szewczyk-Nykiel Aneta
Published: October 2020

The subject of this work was the study of processes occurring during sintering of water atomized AISI 316L austenitic stainless steel powder modified by the addition of graphite nanoparticles. The main purpose of the work was to determine the effect of modification of the AISI 316L stainless steel austenitic powder by the addition of graphite nanopowder on the sintering kinetics and oxide reduction mechanism. The phenomena occurring during the sintering process and oxide reduction mechanisms were subjected to detailed characterizations. Mixtures with two types of nanopowder with a high BET (measurement technique of the specific surface area of materials based on Brunauer–Emmett–Teller theory) specific surface area of 350 and 400 m2/g and for comparison with graphite micropowder with a poorly developed BET specific surface area of 15 m2/g were tested. The conducted thermal analysis showed that the samples made of austenitic stainless steel doped with 0.2% and 0.3% by weight graphite nanopowder with a BET specific surface area of 400 m2/g, sintered best the oxide reduction reactions, with a more intensive participation of carbon, for these samples.
Effects of Polyhedral Oligomeric Silsesquioxane (POSS) on Thermal and Mechanical Properties of Polysiloxane Foam
Authors: Zhang Chunling , Zhang Jinrui , Xu Tianlu , Sima Haofei , Hou Jiazi
Published: October 2020

The thermal and mechanical properties of polysiloxane foam are greatly improved by the addition of acrylolsobutyl polyhedral oligomeric silsesquioxane (MA0701, hereinafter referred to as MAPOSS), which has double bonds. The morphologies and properties of the polysiloxane composite foam were characterized. The average cell diameter of the composite foams decreased, while the cell density increased with increasing MAPOSS. Meanwhile, MAPOSS can enhance thermal conductivity and thermal stability. Thermal conductivity increased by 25%, and the temperature at the maximum weight loss rate increased from 556 °C to 599 °C. In addition, MAPOSS also promoted heterogeneous nucleation by functioning as a nucleating agent, which can increase cell density to improve the mechanical properties. The compressive strength of the composite foam increased by 170% compared with that of pure foam. In the composite, MAPOSS increased the cross-linking density by acting as a physical cross-linking point and limited the movement of the segments.
Surface Roughness Investigation of Poly-Jet 3D Printing
Authors: Vidakis Nectarios , Petousis Markos , Vaxevanidis Nikolaos , Kechagias John
Published: October 2020

An experimental investigation of the surface quality of the Poly-Jet 3D printing (PJ-3DP) process is presented. PJ-3DP is an additive manufacturing process, which uses jetted photopolymer droplets, which are immediately cured with ultraviolet lamps, to build physical models, layer-by-layer. This method is fast and accurate due to the mechanism it uses for the deposition of layers as well as the 16 microns of layer thickness used. Τo characterize the surface quality of PJ-3DP printed parts, an experiment was designed and the results were analyzed to identify the impact of the deposition angle and blade mechanism motion onto the surface roughness. First, linear regression models were extracted for the prediction of surface quality parameters, such as the average surface roughness (Ra) and the total height of the profile (Rt) in the X and Y directions. Then, a Feed Forward Back Propagation Neural Network (FFBP-NN) was proposed for increasing the prediction performance of the surface roughness parameters Ra and Rt. These two models were compared with the reported ones in the literature; it was revealed that both performed better, leading to more accurate surface roughness predictions, whilst the NN model resulted in the best predictions, in particular for the Ra parameter.
Sage Revised Reiterative Even Zernike Polynomials Neural Network Control with Modified Fish School Search Applied in SSCCRIM Impelled System
Authors: Lin Chih-Hong
Published: October 2020

In light of fine learning ability in the existing uncertainties, a sage revised reiterative even Zernike polynomials neural network (SRREZPNN) control with modified fish school search (MFSS) method is proposed to control the six-phase squirrel cage copper rotor induction motor (SSCCRIM) impelled continuously variable transmission assembled system for obtaining the brilliant control performance. This control construction can carry out the SRREZPNN control with the cozy learning law, and the indemnified control with an assessed law. In accordance with the Lyapunov stability theorem, the cozy learning law in the revised reiterative even Zernike polynomials neural network (RREZPNN) control can be extracted, and the assessed law of the indemnified control can be elicited. Besides, the MFSS can find two optimal values to adjust two learning rates with raising convergence. In comparison, experimental results are compared to some control systems and are expressed to confirm that the proposed control system can realize fine control performance.