bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Multidrug Resistance in Cancer Chemotherapy
Authors: Bukowski Karol , Kciuk Mateusz , Kontek Renata
Published: May 2020

Cancer is one of the main causes of death worldwide. Despite the significant development of methods of cancer healing during the past decades, chemotherapy still remains the main method for cancer treatment. Depending on the mechanism of action, commonly used chemotherapeutic agents can be divided into several classes (antimetabolites, alkylating agents, mitotic spindle inhibitors, topoisomerase inhibitors, and others). Multidrug resistance (MDR) is responsible for over 90% of deaths in cancer patients receiving traditional chemotherapeutics or novel targeted drugs. The mechanisms of MDR include elevated metabolism of xenobiotics, enhanced efflux of drugs, growth factors, increased DNA repair capacity, and genetic factors (gene mutations, amplifications, and epigenetic alterations). Rapidly increasing numbers of biomedical studies are focused on designing chemotherapeutics that are able to evade or reverse MDR. The aim of this review is not only to demonstrate the latest data on the mechanisms of cellular resistance to anticancer agents currently used in clinical treatment but also to present the mechanisms of action of novel potential antitumor drugs which have been designed to overcome these resistance mechanisms. Better understanding of the mechanisms of MDR and targets of novel chemotherapy agents should provide guidance for future research concerning new effective strategies in cancer treatment.
HVCN1 Channels Are Relevant for the Maintenance of Sperm Motility During In Vitro Capacitation of Pig Spermatozoa
Authors: Yeste Marc , Llavanera Marc , Mateo-Otero Yentel , Catalán Jaime , Bonet Sergi , Pinart Elisabeth
Published: May 2020

The objective of the present study was to determine the physiological role of voltage-gated hydrogen channels 1 (HVCN1 channels) during in vitro capacitation of pig spermatozoa. Sperm samples from 20 boars were incubated in capacitating medium for 300 minutes (min) in the presence of 2-guanidino benzimidazole (2-GBI), a specific HVCN1-channel blocker, added either at 0 min or after 240 min of incubation. Control samples were incubated in capacitating medium without the inhibitor. In all samples, acrosomal exocytosis was triggered with progesterone after 240 min of incubation. Sperm viability, sperm motility and kinematics, acrosomal exocytosis, membrane lipid disorder, intracellular calcium levels and mitochondrial membrane potential were evaluated after 0, 60, 120, 180, 240, 250, 270 and 300 min of incubation. While HVCN1-blockage resulted in altered sperm viability, sperm motility and kinematics and reduced mitochondrial membrane potential as compared to control samples, at any blocker concentration and incubation time, it had a non-significant effect on intracellular Ca2+ levels determined through Fluo3-staining. The effects on acrosomal exocytosis were only significant in blocked samples at 0 min, and were associated with increased membrane lipid disorder and Ca2+ levels of the sperm head determined through Rhod5-staining. In conclusion, HVCN1 channels play a crucial role in the modulation of sperm motility and kinematics, and in Ca2+ entrance to the sperm head.
TwiFly: A Data Analysis Framework for Twitter
Authors: Chatziadam Panagiotis , Dimitriadis Aftantil , Gikas Stefanos , Logothetis Ilias , Michalodimitrakis Manolis , Neratzoulakis Manolis , Papadakis Alexandros , Kontoulis Vasileios , Siganos Nikolaos , Theodoropoulos Dimitrios , Vougioukalos Giannis , Hatzakis Ilias , Gerakis George , Papadakis Nikolaos , Kondylakis Haridimos
Published: May 2020

Over the last decade, there have been many changes in the field of political analysis at a global level. Through social networking platforms, millions of people have the opportunity to express their opinion and capture their thoughts at any time, leaving their digital footprint. As such, massive datasets are now available, which can be used by analysts to gain useful insights on the current political climate and identify political tendencies. In this paper, we present TwiFly, a framework built for analyzing Twitter data. TwiFly accepts a number of accounts to be monitored for a specific time-frame and visualizes in real time useful extracted information. As a proof of concept, we present the application of our platform to the most recent elections of Greece, gaining useful insights on the election results.
Effect of Modification with Helium Atmospheric-Pressure Plasma and Deep-Ultraviolet Light on Adhesive Shear Strength of Fiber-Reinforced Poly(ether-ether-ketone) Polymer
Authors: Okawa Seigo , Taka Norimasa , Aoyagi Yujin
Published: May 2020

We investigated the effect of helium atmospheric-pressure plasma (PL) and deep-ultraviolet (UV) light treatments on the adhesive properties of fiber-reinforced poly(ether-ether-ketone) polymer (PEEK). PEEK disks reinforced with carbon (CPEEK) or glass (GPEEK) fibers were polished, modified with PL and UV for 60 s, and the surface energy was calculated by measuring the contact angles. The disk surfaces were analyzed by X-ray photoemission spectroscopy. Shear bond strength testing was performed using a universal testing machine, and the fracture surfaces were observed by electron probe microanalyzer. Data were analyzed with one and two-way ANOVA and Tukey’s post-hoc test (p < 0.05). The surface energies were increased by the modifications, which created OH functional groups on the surfaces. The bond strengths of CPEEK were increased by PL, and those of GPEEK were increased by PL and UV, owing to chemical bonding at the interface.
Revisiting the Determinants of Pro-Environmental Behaviour to Inform Land Management Policy: A Meta-Analytic Structural Equation Model Application
Authors: Okumah Murat , Martin-Ortega Julia , Novo Paula , J. Chapman Pippa
Published: May 2020

Environmental policies in the realm of land management are increasingly focussing on inducing behavioural change to improve environmental management outcomes. This is based, implicitly or explicitly, on theories that suggest that pro-environmental behaviour can be understood, predicted and altered based on certain factors (referred to as determinants of pro-environmental behaviour). However, studies examining the determinants of pro-environmental behaviour have found mixed evidence. It is therefore important that we revisit these theories to assess if the evidence supports their postulations so that a more robust knowledge base can be established to inform land management policies. In this study, we do this using meta-analytic structural equation modelling (MASEM) to explore whether the evidence on determinants of pro-environmental behaviour supports the postulations of some predominantly applied theories of behaviour and/or behaviour change. The study analyses research in four environmental policy areas to identify implications for land management. Evidence from these related environmental areas is expected to provide insights relevant to the land management literature and to allow us to identify the extent to which lessons on pro-environmental behaviour from these other areas can be transferred to the land management context. Our findings suggest a strong evidence base for the Theories of Planned Behaviour and Reasoned Action, Attitude-Behaviour-Context Model, and the Persuasion Theory, but a weak evidence base for the Value-Belief-Norm Theory and the Norm Activation Model. We also found that type of environmental policy area moderates the relationship between different variables. This has key policy implications since, while lessons can be learnt from other environmental policy areas, land management policies aimed at influencing behaviours will need to be tailored to the specific context rather than simply ‘imported’ from other fields. Such context-specific policies may encourage pro-environmental behaviours, and potentially contribute towards improving environmental management outcomes.
Quarries: From Abandoned to Renewed Places
Authors: Talento Katia , Amado Miguel , Kullberg José Carlos
Published: May 2020

Numerous industrial pits are discarded after their exploitation in every part of the world. Humanity both transforms the original morphology of the landscape, due to industrial activity in the territory, and, at the same time, rejects this "new" situation. This is to the detriment of the landscape, which is witness to this transfiguration, degradation, and abandonment. What is the future of these impersonal and empty areas? In this article, we present a general survey concerning the notion of quarry reuse to highlight the importance of this current and common problem. Our work approached the topic through a combination of the main concepts and a description of selected cases of study of quarry reconversions, sensitive to the environmental issues, climate changes, and sustainability. According to this premise, the research also provides an innovative matrix of schemes to classify the existing fundamental methods of recovery. For this effect, the investigation was proposed to be an instrument to improve the knowledge in the scientific and theoretical sectors, flanking the practical understanding, which has already started to move in this direction of reconversion, as the paper shows.
Maximum Fraction Images Derived from Year-Based Project for On-Board Autonomy-Vegetation (PROBA-V) Data for the Rapid Assessment of Land Use and Land Cover Areas in Mato Grosso State, Brazil
Authors: Godinho Cassol Henrique Luis , Arai Egidio , Eyji Sano Edson , Dutra Andeise Cerqueira , Hoffmann Tânia Beatriz , Shimabukuro Yosio Edemir
Published: May 2020

This paper presents a new approach for rapidly assessing the extent of land use and land cover (LULC) areas in Mato Grosso state, Brazil. The novel idea is the use of an annual time series of fraction images derived from the linear spectral mixing model (LSMM) instead of original bands. The LSMM was applied to the Project for On-Board Autonomy-Vegetation (PROBA-V) 100-m data composites from 2015 (~73 scenes/year, cloud-free images, in theory), generating vegetation, soil, and shade fraction images. These fraction images highlight the LULC components inside the pixels. The other new idea is to reduce these time series to only six single bands representing the maximum and standard deviation values of these fraction images in an annual composite, reducing the volume of data to classify the main LULC classes. The whole image classification process was conducted in the Google Earth Engine platform using the pixel-based random forest algorithm. A set of 622 samples of each LULC class was collected by visual inspection of PROBA-V and Landsat-8 Operational Land Imager (OLI) images and divided into training and validation datasets. The performance of the method was evaluated by the overall accuracy and confusion matrix. The overall accuracy was 92.4%, with the lowest misclassification found for cropland and forestland (<9% error). The same validation data set showed 88% agreement with the LULC map made available by the Landsat-based MapBiomas project. This proposed method has the potential to be used operationally to accurately map the main LULC areas and to rapidly use the PROBA-V dataset at regional or national levels.
Characterizing Micromechanical Properties of Friction Welding Interface between TiAl Alloy and GH3039 Superalloy
Authors: Du Suigeng , Wang Songlin , Xu Wanting
Published: May 2020

To explore the macro-fracture mechanism of a friction welded joint between TiAl alloy and GH3039 superalloy, the micromechanical properties of intermediate phases at the joint interface are characterized and the relationship between the macro-fracture and micro-fracture of the joint is established. The indentation technique has been employed to calculate the nano-hardness and fracture toughness of the intermediate phases. The dynamic in-situ tensile test in SEM has been applied to observe the initiation and propagation process of cracks at the interface. It has been found that Al3NiTi2 and AlNi2Ti have the highest nano-hardness and elastic recovery rates, while TiAl and GH3039 base metals have the lowest nano-hardness and elastic recovery rates. This indicates that the harder the materials, the more prone they are to elastic deformation. Nevertheless, the fracture toughness of Al3NiTi2 and AlNi2Ti are the two lowest, which were 1.7 MPa·m1/2 and 2.7 MPa·m1/2, respectively. The cracks sprouted from Al3NiTi2 and AlNi2Ti and then spread throughout the entire intermediate phase zone. In other words, the fracture mainly happened in these two phase layers. It has been concluded that Al3NiTi2 and AlNi2Ti were the two weakest phases at the interface and their poor fracture toughness results in low joint strength.
Recent Advances in Anodes for Microbial Fuel Cells: An Overview
Authors: Yaqoob Asim Ali , Mohamad Ibrahim Mohamad Nasir , Rafatullah Mohd , Chua Yong Shen , Ahmad Akil , Umar Khalid
Published: May 2020

The recycling and treatment of wastewater using microbial fuel cells (MFCs) has been attracting significant attention as a way to control energy crises and water pollution simultaneously. Despite all efforts, MFCs are unable to produce high energy or efficiently treat pollutants due to several issues, one being the anode’s material. The anode is one of the most important parts of an MFC. Recently, different types of anode materials have been developed to improve the removal rate of pollutants and the efficiency of energy production. In MFCs, carbon-based materials have been employed as the most commonly preferred anode material. An extensive range of potentials are presently available for use in the fabrication of anode materials and can considerably minimize the current challenges, such as the need for high quality materials and their costs. The fabrication of an anode using biomass waste is an ideal approach to address the present issues and increase the working efficiency of MFCs. Furthermore, the current challenges and future perspectives of anode materials are briefly discussed.
Portland Cement/Acrocomia Aculeata Endocarp Bricks: Thermal Insulation and Mechanical Properties
Authors: Calvani Camila C. , Goncalves Além-Mar B. , Silva Michael J. , Oliveira Samuel L. , Marangoni Bruno S. , Reis Diogo D. dos , Cena Cicero
Published: May 2020

In the last few decades, Portland/residue composites have been researched due to their technological and environmental advantages. In this study, residues of Acrocomia aculeata (Jacq.) Lodd endocarp (AE) were introduced in the Portland cement–soil (PC) matrix in different concentrations (0, 5, 10, 15, 20, and 50 wt%) to produce PC/AE bricks. The characterization of the microstructures of the bricks indicate agglomerates of AE particles with increased humidity in small regions distributed throughout the matrix. Mid-infrared and laser-induced breakdown spectroscopy, along with thermogravimetry, indicated that AE contained mainly lignin and cellulose, as well as inorganic chemical elements such as Mg and Si. X-ray studies revealed that AE did not affect the crystallographic properties of the Portland/AE bricks. The findings indicate that the use of AE improved the thermal insulation capability of the composites with a small impact on the compressive strength.
Red and Near-Infrared Absorbing Dicyanomethylene Squaraine Cyanine Dyes: Photophysicochemical Properties and Anti-Tumor Photosensitizing Effects
Authors: D. Martins Tiago , Lima Eurico , E. Boto Renato , Ferreira Diana , R. Fernandes José , Almeida Paulo , F. V. Ferreira Luis , Silva Amélia M. , V. Reis Lucinda
Published: May 2020

Photodynamic therapy is a medical modality developed for the treatment of several diseases of oncological and non-oncological etiology that requires the presence of a photosensitizer, light and molecular oxygen, which combined will trigger physicochemical reactions responsible for reactive oxygen species production. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties and the photobiological activity of several dicyanomethylene squaraine cyanine dyes. Thus, herein, the study of their aggregation character, photobleaching and singlet oxygen production ability, and the further application of the previously synthesized dyes in Caco-2 and HepG2 cancer cell lines, to evaluate their phototherapeutic effects, are described. Dicyanomethylene squaraine dyes exhibited moderate light-stability and, despite the low singlet oxygen quantum yields, were a core of dyes that exhibited relevant in vitro photodynamic activity, as there was an evident increase in the toxicity of some of the tested dyes exclusive to radiation treatments.
Mastering Yield Stress Evolution and Formwork Friction for Smart Dynamic Casting
Authors: Szabo Anna , Reiter Lex , Lloret-Fritschi Ena , Gramazio Fabio , Kohler Matthias , Flatt Robert J.
Published: May 2020

The construction industry is a slow adopter of new technologies and materials. However, interdisciplinary research efforts in digital fabrication methods with concrete aim to make a real impact on the way we build by showing faster production, higher quality and enlarged freedom of design. In this paper, the potential and constraints of a specific digital slip-forming process, smart dynamic casting (SDC), are investigated with a material-focused approach in the complex task of producing thin folded structures. Firstly, the workability and the strength evolution of different material compositions are studied to achieve the constant processing rate for SDC. Secondly, friction between the formwork walls and the concrete, a key aspect in slip-casting, is studied with a simplified experimental setup to identify if any of these mixes would provide an advantage for processing. Finally, a theoretical framework is constructed to link the material properties, the process conditions and the designed geometry. This framework introduces the ‘SDC number’ as a simplified approach to formulate the process window, the suitable conditions for slip-forming. The experimental results prove the assumption of the model that friction is proportional to yield stress for all base compositions and acceleration methods regardless of the filling history. The results are evaluated in the context of the narrow process window of thin folded structures as well as the wider process window of columns. The necessity of consistent strength evolution is underlined for narrow windows. Further, friction is shown to be the highest initially, thus with both narrow and wide process windows, after a successful start-up the continuation of slipping is less prone to failure. The proposed theoretical model could provide material and geometry-specific slipping strategy for start time and slipping rate during production.
Crystal and Supramolecular Structure of Bacterial Cellulose Hydrolyzed by Cellobiohydrolase from Scytalidium Candidum 3C: A Basis for Development of Biodegradable Wound Dressings
Authors: Ivanova Lyubov A. , Ustinovich Konstantin B. , Khamova Tamara V. , Eneyskaya Elena V. , Gorshkova Yulia E. , Tsvigun Natalia V. , Burdakov Vladimir S. , Verlov Nikolay A. , Zinovev Evgenii V. , Asadulaev Marat S. , Shabunin Anton S. , Fedyk Andrey M. , Baranchikov Alexander Ye. , Kopitsa Gennady P. , Kulminskaya Anna A.
Published: May 2020

The crystal and supramolecular structure of the bacterial cellulose (BC) has been studied at different stages of cellobiohydrolase hydrolysis using various physical and microscopic methods. Enzymatic hydrolysis significantly affected the crystal and supramolecular structure of native BC, in which the 3D polymer network consisted of nanoribbons with a thickness T ≈ 8 nm and a width W ≈ 50 nm, and with a developed specific surface SBET ≈ 260 m2·g−1. Biodegradation for 24 h led to a ten percent decrease in the mean crystal size Dhkl of BC, to two-fold increase in the sizes of nanoribbons, and in the specific surface area SBET up to ≈ 100 m2·g−1. Atomic force and scanning electron microscopy images showed BC microstructure “loosening“after enzymatic treatment, as well as the formation and accumulation of submicron particles in the cells of the 3D polymer network. Experiments in vitro and in vivo did not reveal cytotoxic effect by the enzyme addition to BC dressings and showed a generally positive influence on the treatment of extensive III-degree burns, significantly accelerating wound healing in rats. Thus, in our opinion, the results obtained can serve as a basis for further development of effective biodegradable dressings for wound healing.
Characterization of Wood and Graphene Nanoplatelets (GNPs) Reinforced Polymer Composites
Authors: Al-Maqdasi Zainab , Gong Guan , Nyström Birgitha , Emami Nazanin , Joffe Roberts
Published: May 2020

This paper investigates the utilization of commercial masterbatches of graphene nanoplatelets to improve the properties of neat polymer and wood fiber composites manufactured by conventional processing methods. The effect of aspect ratio of the graphene platelets (represented by the different number of layers in the nanoplatelet) on the properties of high-density polyethylene (HDPE) is discussed. The composites were characterized for their mechanical properties (tensile, flexural, impact) and physical characteristics (morphology, crystallization, and thermal stability). The effect of the addition of nanoplatelets on the thermal conductivity and diffusivity of the reinforced polymer with different contents of reinforcement was also investigated. In general, the mechanical performance of the polymer was enhanced at the presence of either of the reinforcements (graphene or wood fiber). The improvement in mechanical properties of the nanocomposite was notable considering that no compatibilizer was used in the manufacturing. The use of a masterbatch can promote utilization of nano-modified polymer composites on an industrial scale without modification of the currently employed processing methods and facilities.
Effect of Mineral Aggregates and Chemical Admixtures as Internal Curing Agents on the Mechanical Properties and Durability of High-Performance Concrete
Authors: Vázquez-Rodríguez Francisco Javier , Elizondo-Villareal Nora , Verástegui Luz Hypatia , Arato Tovar Ana Maria , López-Perales Jesus Fernando , Contreras de León José Eulalio , Gómez-Rodríguez Cristian , Fernández-González Daniel , Verdeja Luis Felipe , García-Quiñonez Linda Viviana , Rodríguez Castellanos Edén Amaral
Published: May 2020

In the present work, the effect of mineral aggregates (pumice stone and expanded clay aggregates) and chemical admixtures (superplasticizers and shrinkage reducing additives) as an alternative internal curing technique was investigated, to improve the properties of high-performance concrete. In the fresh and hardened state, concretes with partial replacements of Portland cement (CPC30R and OPC40C) by pulverized fly ash in combination with the addition of mineral aggregates and chemical admixtures were studied. The physical, mechanical, and durability properties in terms of slump, density, porosity, compressive strength, and permeability to chloride ions were respectively determined. The microstructural analysis was carried out by scanning electronic microscopy. The results highlight the effect of the addition of expanded clay aggregate on the internal curing of the concrete, which allowed developing the maximum compressive strength at 28 days (61 MPa). Meanwhile, the replacement of fine aggregate by 20% of pumice stone allowed developing the maximum compressive strength (52 MPa) in an OPC-based concrete at 180 days. The effectiveness of internal curing to develop higher strength is attributed to control in the porosity and a high water release at a later age. Finally, the lowest permeability value at 90 days (945 C) was found by the substitutions of fine aggregate by 20% of pumice stone saturated with shrinkage reducing admixture into pores and OPC40C by 15% of pulverized fly ash. It might be due to impeded diffusion of chloride ions into cement paste in the vicinity of pulverized fly ash, where the pozzolanic reaction has occurred. The proposed internal curing technology can be considered a real alternative to achieve the expected performance of a high-performance concrete since a concrete with a compressive strength range from 45 to 67 MPa, density range from 2130 to 2310 kg/m3, and exceptional durability (< 2000 C) was effectively developed.
Properties and Microstructure Distribution of High-Performance Thermal Insulation Concrete
Authors: Mohammad Malek , Masad Eyad , Seers Thomas , Al-Ghamdi Sami G.
Published: May 2020

The aim of this experimental study is to develop high strength and lightweight concrete mixture suitable for structural applications. This work investigates the effect of replacing normal aggregate either partially or totally with expanded perlite aggregate. This material allows for better thermal insulation properties, thus decreasing the energy usage within the life cycle of the concrete structure. Expanded perlite aggregate was used in concrete by 20%, 40%, 60%, 80%, and 100% in replacement of the natural aggregate. Material characterization tests of compressive strength, flexural strength, and thermal conductivity were carried out for six concrete mixtures. In addition, microstructure analysis was performed with the aid of a micro-computed tomography system to investigate the effects and relation of microstructure quantities on material properties. The proposed concrete mixture, which has 100% of expanded perlite aggregate, has a unit weight of 1703 kg/m3 and achieved reduction percentage of thermal conductivity around 62% (1.81 to 0.69 W·m−1·K−1) and a compressive strength of 42 MPa at 28 days; and thus is ideal for structural applications with enhanced properties.
Effect of Ultrasonic Surface Impact on the Fatigue Properties of Ti3Zr2Sn3Mo25Nb
Authors: Cheng Zhangjianing , Cao Xiaojian , Xu Xiaoli , Shen Qiangru , Yu Tianchong , Jin Jiang
Published: May 2020

The effect of nano grain surface layer generated by ultrasonic impact on the fatigue behaviors of a titanium alloy Ti3Zr2Sn3Mo25Nb (TLM) was investigated. Three vibration strike-numbers of 24,000 times, 36,000 times and 48,000 times per unit are chosen to treat the surface of TLM specimens. Nanocrystals with an average size of 30 nm are generated. The dislocation motion plays an important role in the transformation of nanograins. Ultrasonic surface impact improves the mechanical properties of TLM, such as hardness, surface residual stress, tensile strength and fatigue strength. More vibration strike numbers will cause a higher enhancement. With a vibration strike number of 48,000 times per square millimeter the rotating-bending fatigue strength of TLM at 107 cycles is improved by 23.7%. All the fatigue cracks initiate from the surface of untreated specimens, while inner cracks appear after the fatigue life of 106 cycles with the ultrasonic surface impact. The crystal slip in the crack initiation zone is the main way of growth for microcracks. Crack cores are usually formed at the junction of crystals. The stress intensity factor of TLM titanium alloy is approximately 7.0 MPa·m1/2.
Eumelanin Precursor 2-Carboxy-5,6-Dihydroxyindole (DHICA) as Doping Factor in Ternary (PEDOT:PSS/Eumelanin) Thin Films for Conductivity Enhancement
Authors: Migliaccio Ludovico , Gesuele Felice , Manini Paola , Maglione Maria Grazia , Tassini Paolo , Pezzella Alessandro
Published: May 2020

The integration of the pristine not-doped commercial poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) PH1000 with eumelanin, the brown to black kind of melanin pigment, was achieved by dissolving the melanogenic precursors 2-carboxy-5,6-dihydroxyindole (DHICA) in the PH1000 suspension. Solid state oxidative polymerization of the catecholic indole allowed obtaining the ternary blend PEDOT:PSS/eumelanin. The introduction of DHICA into PH1000 produced a noticeable increase in the conductivity of PEDOT thin films akin to that produced by dimethyl sulfoxide (DMSO) treatment, opening up novel strategies for the simultaneous integration of eumelanin polymer and conductivity enhancement of PEDOT containing coatings, as well as the long term goal of replacing PSS by DHICA eumelanin for PEDOT pairing.
Early-Age Properties of Concrete Based on Numerical Hydration Modelling: A Parametric Analysis
Authors: Pepe Marco , Lima Carmine , Martinelli Enzo
Published: May 2020

The early-age performances of cement-based mixtures are governed by cement hydration reactions. As a matter of fact, the heat generated during the setting and hardening phases due to the hydration processes increases the temperatures within the concrete elements while it starts developing its mechanical properties. These thermal stresses can cause the premature cracking of the cementitious matrix and undermine the long-term durability of the whole concrete element, especially in the case of massive structures where the dissipation of generated heat is more difficult. It is worth highlighting that the kinetics of cement hydration is mainly governed by the mixture composition; on the other hand, the heat generated during the setting and hardening is also influenced by the geometry of the element and/or its curing conditions. In this context, this study presents a numerical procedure intended to simulate the hydration reactions, and hence scrutinize the development of concrete properties at the early-age. Specifically, considering the variation of several factors, such as concrete strength class, element size and curing conditions, a comprehensive parametric analysis is presented herein, leading to the proposal of a simplified approach for both predicting the time evolution of the concrete mechanical performances at the early-age and mitigating the risk of premature cracking.
Structure Zone Investigation of Multiple Principle Element Alloy Thin Films as Optimization for Nanoindentation Measurements
Authors: Savan Alan , Allermann Timo , Wang Xiao , Grochla Dario , Banko Lars , Kalchev Yordan , Kostka Aleksander , Pfetzing-Micklich Janine , Ludwig Alfred
Published: May 2020

Multiple principal element alloys, also often referred to as compositionally complex alloys or high entropy alloys, present extreme challenges to characterize. They show a vast, multidimensional composition space that merits detailed investigation and optimization to identify compositions and to map the composition ranges where useful properties are maintained. Combinatorial thin film material libraries are a cost-effective and efficient way to create directly comparable, controlled composition variations. Characterizing them comes with its own challenges, including the need for high-speed, automated measurements of dozens to hundreds or more compositions to be screened. By selecting an appropriate thin film morphology through predictable control of critical deposition parameters, representative measured values can be obtained with less scatter, i.e., requiring fewer measurement repetitions for each particular composition. In the present study, equiatomic CoCrFeNi was grown by magnetron sputtering in different locations in the structure zone diagram applied to multinary element alloys, followed by microstructural and morphological characterizations. Increasing the energy input to the deposition process by increased temperature and adding high-power impulse magnetron sputtering (HiPIMS) plasma generators led to denser, more homogeneous morphologies with smoother surfaces until recrystallization and grain boundary grooving began. Growth at 300 °C, even without the extra particle energy input of HiPIMS generators, led to consistently repeatable nanoindentation load–displacement curves and the resulting hardness and Young’s modulus values.
Improving the Performance of Zn-Air Batteries with N-Doped Electroexfoliated Graphene
Authors: Ilnicka Anna , Skorupska Malgorzata , Romanowski Piotr , Kamedulski Piotr , Lukaszewicz Jerzy P.
Published: May 2020

The constantly growing demand for active, durable, and low-cost electrocatalysts usable in energy storage devices, such as supercapacitors or electrodes in metal-air batteries, has triggered the rapid development of heteroatom-doped carbon materials, which would, among other things, exhibit high catalytic activity in the oxygen reduction reaction (ORR). In this article, a method of synthesizing nitrogen-doped graphene is proposed. Few-layered graphene sheets (FL-graphene) were prepared by electrochemical exfoliation of commercial graphite in a Na2SO4 electrolyte with added calcium carbonate as a separator of newly-exfoliated FL-graphene sheets. Exfoliated FL-graphene was impregnated with a suspension of green algae used as a nitrogen carrier. Impregnated FL-graphene was carbonized at a high temperature under the flow of nitrogen. The N-doped FL-graphene was characterized through instrumental methods: high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Electrochemical performance was determined using cyclic voltamperometry and linear sweep voltamperometry to check catalytic activity in ORR. The N-doped electroexfoliated FL-graphene obeyed the four-electron transfer pathways, leading us to further test these materials as electrode components in rechargeable zinc-air batteries. The obtained results for Zn-air batteries are very important for future development of industry, because the proposed graphene electrode materials do not contain any heavy and noble metals in their composition.
Study on the Influence of Calcined Underground Ant Nest Powder on the Durability of Concrete
Authors: Zhou Wei , Zhu Peng , Qu Wenjun , Yao Wu , Wu Shengji
Published: May 2020

Ants have strict requirements on the building materials of the nest, such as the size, weight, luster and color of soil particles. The soil of underground ant nests is composed of clay particles cemented together to form a hard brick-like material. The ant nest powder shows pozzolanic activity after calcination, which can meet the requirements for active admixture of concrete. Under the standard curing condition, the influence of calcined ant nest clay powder (CANCP) on the durability of concrete is evaluated by chloride penetration resistance, carbonization resistance and freeze–thaw resistance, and the influence of the powder content is investigated. The results show that when the content of CANCP is less than 10%, the chloride penetration resistance of concrete increases with content of CANCP. In the early stage of carbonation, the greater the content of CANCP, the higher the carbonization rate of concrete. In the middle and later stage of carbonation, the carbonation rate of CANCP concrete is significantly lower than that in the early stage, and the carbonation depth is linearly related to the carbonation time. When the content of CANCP is less than 20%, the freeze–thaw resistance of CANCP concrete is better than that of the reference concrete.
Impact Wear of the Protective Cr3C2-Based HVOF-Sprayed Coatings
Authors: Daniel Josef , Grossman Jan , Houdková Šárka , Bystrianský Martin
Published: May 2020

High velocity oxygen-fuel (HVOF) prepared CrC-based hardmetal coatings are generally known for their superior wear, corrosion, and oxidation resistance. These properties make this coating attractive for application in industry. However, under some loading conditions and in aggressive environments, the most commonly used NiCr matrix is not sufficient. The study is focused on the evaluation of dynamic impact wear of the HVOF-sprayed Cr3C2-25%NiCr and Cr3C2-50%NiCrMoNb coatings. Both coatings were tested by an impact tester with a wide range of impact loads. The Wohler-like dependence was determined for both coatings’ materials. It was shown that, due to the different microstructure and higher amount of tough matrix, the impact lifetime of the Cr3C2-50%NiCrMoNb coating was higher than the lifetime of the Cr3C2-25%NiCr coating. Differences in the behavior of the coatings were the most pronounced at high impact loads.
Kineto-Static Analysis of a Wrist Rehabilitation Robot with Compliance and Passive Joints for Joint Misalignment Compensation
Authors: Liu Ying-Chi , Takeda Yukio
Published: May 2020

In this paper, we present a kineto-static analysis on a wrist rehabilitation robot to compensate for joint misalignment between human and robot joints. Since joint misalignment has proved to generate user–device interaction forces, which reduce the comfort and safety of the wearable devices and limit the user’s willingness to use it. The use of compliance and the addition of passive joints for joint misalignment compensation are discussed. In order to study the effect of the initial offset, we find that the initial offset in the direction perpendicular to the forearm causes a larger unwanted force. In addition, the use of the softest compliance can minimize unwanted force by 38% compared to the case without compliance. Furthermore, the effect of the addition of passive joints to the exoskeleton is investigated. From the analysis results, the soft part of the human being is regarded as a passive joint with the ability to compensate for joint misalignment. Moreover, the influence of the soft characteristics of human limbs should be considered when designing a wearable robot. This soft property, causing the movement of the braces, results in reducing the angular range of the wrist. Through the analysis results, we provide effective ideas for joint misalignment compensation to fulfill a comfortable and safer robot design.
Fixed Point Results for a Selected Class of Multi-Valued Mappings under (θ,ℛ)-Contractions with an Application
Authors: Hasanuzzaman Md , Sessa Salvatore , Imdad Mohammad , Alfaqih Waleed M.
Published: May 2020

In this article, we introduce a relatively new concept of multi-valued ( θ , R ) -contractions and utilize the same to prove some fixed point results for a special class of multi-valued mappings in metric spaces endowed with an amorphous binary relation. Illustrative examples are also provided to exhibit the utility of our results proved herein. Finally, we utilize some of our results to investigate the existence and uniqueness of a positive solution for the integral equation of Volterra type.
Statistical Indicators of the Scientific Publications Importance: A Stochastic Model and Critical Look
Authors: Klebanov Lev B. , Kuvaeva Yulia V. , Volkovich Zeev E.
Published: May 2020

A model of scientific citation distribution is given. We apply it to understand the role of the Hirsch index as an indicator of scientific publication importance in Mathematics and some related fields. The proposed model is based on a generalization of such well-known distributions as geometric and Sibuya laws. Real data analysis of the Hirsch index and corresponding citation numbers is given.
Anti-Tumor Activity vs. Normal Cell Toxicity: Therapeutic Potential of the Bromotyrosines Aerothionin and Homoaerothionin In Vitro
Authors: Drechsel Antje , Helm Jana , Ehrlich Hermann , Pantovic Snezana , Bornstein Stefan R. , Bechmann Nicole
Published: May 2020

Novel strategies to treat cancer effectively without adverse effects on the surrounding normal tissue are urgently needed. Marine sponges provide a natural and renewable source of promising anti-tumor agents. Here, we investigated the anti-tumor activity of Aerothionin and Homoaerothionin, two bromotyrosines isolated from the marine demosponge Aplysina cavernicola, on two mouse pheochromocytoma cells, MPC and MTT. To determine the therapeutic window of these metabolites, we furthermore explored their cytotoxicity on cells of the normal tissue. Both metabolites diminished the viability of the pheochromocytoma cell lines significantly from a concentration of 25 µM under normoxic and hypoxic conditions. Treatment of MPC cells leads moreover to a reduction in the number of proliferating cells. To confirm the anti-tumor activity of these bromotyrosines, 3D-pheochromocytoma cell spheroids were treated with 10 µM of either Aerothionin or Homoaerothionin, resulting in a significant reduction or even complete inhibition of the spheroid growth. Both metabolites reduced viability of normal endothelial cells to a comparable extent at higher micromolar concentration, while the viability of fibroblasts was increased. Our in vitro results show promise for the application of Aerothionin and Homoaerothionin as anti-tumor agents against pheochromocytomas and suggest acceptable toxicity on normal tissue cells.
Clinical Applications of Astaxanthin in the Treatment of Ocular Diseases: Emerging Insights
Authors: Giannaccare Giuseppe , Pellegrini Marco , Senni Carlotta , Bernabei Federico , Scorcia Vincenzo , Cicero Arrigo Francesco Giuseppe
Published: May 2020

Astaxanthin is a naturally occurring red carotenoid pigment belonging to the family of xanthophylls, and is typically found in marine environments, especially in microalgae and seafood such as salmonids, shrimps and lobsters. Due to its unique molecular structure, astaxanthin features some important biologic properties, mostly represented by strong antioxidant, anti-inflammatory and antiapoptotic activities. A growing body of evidence suggests that astaxanthin is efficacious in the prevention and treatment of several ocular diseases, ranging from the anterior to the posterior pole of the eye. Therefore, the present review aimed at providing a comprehensive evaluation of current clinical applications of astaxanthin in the management of ocular diseases. The efficacy of this carotenoid in the setting of retinal diseases, ocular surface disorders, uveitis, cataract and asthenopia is reported in numerous animal and human studies, which highlight its ability of modulating several metabolic pathways, subsequently restoring the cellular homeostatic balance. To maximize its multitarget therapeutic effects, further long-term clinical trials are warranted in order to define appropriate dosage, route of administration and exact composition of the final product.
Effect of Sulfuric Acid Patination Treatment on Atmospheric Corrosion of Weathering Steel
Authors: Crespo Ana , Díaz Iván , Neff Delphine , Llorente Irene , Martínez-Ramírez Sagrario , Cano Emilio
Published: May 2020

The requirements for the formation of a protective patina on conventional weathering steels (WS) are well known in the scientific literature related to civil structures. However, these criteria are not always given due consideration when WS is used in cultural heritage, as in the case of sculptural work. An artificial patina was produced simulating artists’ working procedures using a direct patination technique, applying a solution of 10% H2SO4 on WS specimens. These were exposed for two years in the urban atmosphere of Madrid along with weathering steel specimens without artificial patina, called natural patina. The patinas generated have been analyzed using colorimetry, micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thickness measurements.The artificial patina color formed hardly differs from the color that the natural patina acquires from practically the beginning of its formation in the atmosphere of Madrid. After two years, the atmospheric corrosion rate of patinated WS is lower than 6 µm/year. The sulfuric acid treatment accelerates the protective ability of the patina with respect to the natural patina according to the ratio goethite to lepidocrocite (α/γ). Chromium-rich goethite is located in the inner part of the artificial patina as well as chromium-rich ferrihydrite. Ferrihydrite may act as a precursor of nanophasic goethite.
Effect of Hydrogen on the Deformation Behavior and Localization of Plastic Deformation of the Ultrafine-Grained Zr–1Nb Alloy
Authors: Stepanova Ekaterina , Grabovetskaya Galina , Syrtanov Maxim , Mishin Ivan
Published: May 2020

In this paper, comparison studies of the hydrogen effect on the structural and phase state, deformation behavior, and mechanical properties of the fine- (average grain size 4 µm) and ultrafine-grained (average element size 0.3 and 0.4 µm) Zr–1wt.%Nb (hereinafter Zr–1Nb) alloy under tension at temperatures in the range of 293–873 K were conducted. The formation of an ultrafine-grained structure is established to increase the strength characteristics of the Zr–1Nb alloy by a factor of 1.5–2 with a simultaneous reduction of its resistance to the localization of plastic deformation at the macro level and the value of deformation to failure. The presence of hydrogen in the Zr–1Nb alloy in the form of a solid solution and hydride precipitates increases its resistance to the localization of plastic deformation at the macro level if the alloy has an ultrafine-grained structure and decreases if the structure of the alloy is fine-grained. In the studied temperature range, the Zr–1Nb alloy in the ultrafine-grained state has a higher resistance to hydrogen embrittlement than the alloy in the fine-grained state.
A Bibliometric Analysis of the Publications on In Doped ZnO to be a Guide for Future Studies
Authors: Yilmaz Mehmet , Grilli Maria Luisa , Turgut Guven
Published: May 2020

This study aims to examine the studies regarding In doped ZnO published in the Web of Science database. A total of 777 articles were reached (31 March 2020). The articles were downloaded for the bibliometric analysis and collected in a file. The file was uploaded to VOSViewer programme in order to reveal the most used keywords, words in the abstracts, citation analyses, co-citation and co-authorship and countries analyses of the articles. The results showed that the most used keywords were “ZnO”, “photoluminescence”, “optical properties”, “thin films” and “doping”. These results indicate that the articles mostly focus on some characteristics of In doped ZnO thin films such as structural, optical and electrical features. When the distribution of the number of articles using the keywords by year was searched, it was found that recent articles focus mainly on synthesis of In doped ZnO film via chemical routes such as sol-gel and hydrothermal syntheses, and on ZnO-based device applications such as solar cells and gas sensors. The most used keywords were also found to be films, X-ray, glass substrate, X-ray Diffraction (XRD), spectra and layer. These results indicate that the studies mostly focus on In doped ZnO thin films as transparent conductive oxide (TCO) material used in device applications like solar cells. In this context, it was found that structural, topographical, optical, electrical and magnetic properties of In doped ZnO films were characterized in terms of defected structure or defect type, substrate temperature, film thickness and In doping content. When the distribution of these words is shown on a year-by-year basis, it is evident that more recent articles tend to focus both on efficiency and performance of In doped ZnO films as TCO in solar cells, diodes and photoluminescence applications both on nanostructures, such as nanoparticles, and nanorods for gas sensor applications. The results also indicated that Maldonado and Asomoza were the most cited authors in this field. In addition, Major, Minami and Ozgur were the most cited (co-citation) authors in this field. The most cited journals were found to be Thin Solid Films, Journal of Materials Science Materials in Electronics and Journal of Applied Physics and, more recently, Energy, Ceramics International, Applied Physics-A, Optik, Material Research Express, ACS Applied Materials and Interfaces and Optical Materials. The most co-cited journals were Applied Physics Letters, Thin Solid Films, Journal of Applied Physics, Physical Review B, and Applied Surface Science. Lastly, the countries with the highest number of documents were China, India, South Korea, USA and Japan. Consequently, it is suggested that future research needs to focus more on synthesis and characterization with different growth techniques which make In doped ZnO suitable for device applications, such as solar cells and diodes. In this context, this study may provide valuable information to researchers for future studies on the topic.