bluuebunny/crossref_metadata_2025 huggingface dataset:
REDD1 Is Involved in Amyloid β-Induced Synaptic Dysfunction and Memory Impairment
Authors: Yi Jee Hyun , Kwon Huiyoung , Cho Eunbi , Jeon Jieun , Lee Jeongwon , Lee Young Choon , Cho Jong Hyun , Jun Mira , Moon Minho , Ryu Jong Hoon , Kim Ji-Su , Choi Ji Woong , Park Se Jin , Lee Seungheon , Kim Dong Hyun
Published: December 2020

Alzheimer’s disease (AD) is a neurodegenerative disease characterized by neurological dysfunction, including memory impairment, attributed to the accumulation of amyloid β (Aβ) in the brain. Although several studies reported possible mechanisms involved in Aβ pathology, much remains unknown. Previous findings suggested that a protein regulated in development and DNA damage response 1 (REDD1), a stress-coping regulator, is an Aβ-responsive gene involved in Aβ cytotoxicity. However, we still do not know how Aβ increases the level of REDD1 and whether REDD1 mediates Aβ-induced synaptic dysfunction. To elucidate this, we examined the effect of Aβ on REDD1-expression using acute hippocampal slices from mice, and the effect of REDD1 short hairpin RNA (shRNA) on Aβ-induced synaptic dysfunction. Lastly, we observed the effect of REDD1 shRNA on memory deficit in an AD-like mouse model. Through the experiments, we found that Aβ-incubated acute hippocampal slices showed increased REDD1 levels. Moreover, Aβ injection into the lateral ventricle increased REDD1 levels in the hippocampus. Anisomycin, but not actinomycin D, blocked Aβ-induced increase in REDD1 levels in the acute hippocampal slices, suggesting that Aβ may increase REDD1 translation rather than transcription. Aβ activated Fyn/ERK/S6 cascade, and inhibitors for Fyn/ERK/S6 or mGluR5 blocked Aβ-induced REDD1 upregulation. REDD1 inducer, a transcriptional activator, and Aβ blocked synaptic plasticity in the acute hippocampal slices. REDD1 inducer inhibited mTOR/Akt signaling. REDD1 shRNA blocked Aβ-induced synaptic deficits. REDD1 shRNA also blocked Aβ-induced memory deficits in passive-avoidance and object-recognition tests. Collectively, these results demonstrate that REDD1 participates in Aβ pathology and could be a target for AD therapy.
Low Repair Capacity of DNA Double-Strand Breaks Induced by Laser-Driven Ultrashort Electron Beams in Cancer Cells
Authors: Babayan Nelly , Vorobyeva Natalia , Grigoryan Bagrat , Grekhova Anna , Pustovalova Margarita , Rodneva Sofya , Fedotov Yuriy , Tsakanova Gohar , Aroutiounian Rouben , Osipov Andreyan
Published: December 2020

Laser-driven accelerators allow to generate ultrashort (from femto- to picoseconds) high peak dose-rate (up to tens of GGy/s) accelerated particle beams. However, the radiobiological effects of ultrashort pulsed irradiation are still poorly studied. The aim of this work was to compare the formation and elimination of γH2AX and 53BP1 foci (well known markers for DNA double-strand breaks (DSBs)) in Hela cells exposed to ultrashort pulsed electron beams generated by Advanced Research Electron Accelerator Laboratory (AREAL) accelerator (electron energy 3.6 MeV, pulse duration 450 fs, pulse repetition rates 2 or 20 Hz) and quasi-continuous radiation generated by Varian accelerator (electron energy 4 MeV) at doses of 250–1000 mGy. Additionally, a study on the dose–response relationships of changes in the number of residual γH2AX foci in HeLa and A549 cells 24 h after irradiation at doses of 500–10,000 mGy were performed. We found no statistically significant differences in γH2AX and 53BP1 foci yields at 1 h after exposure to 2 Hz ultrashort pulse vs. quasi-continuous radiations. In contrast, 20 Hz ultrashort pulse irradiation resulted in 1.27-fold higher foci yields as compared to the quasi-continuous one. After 24 h of pulse irradiation at doses of 500–10,000 mGy the number of residual γH2AX foci in Hela and A549 cells was 1.7–2.9 times higher compared to that of quasi-continuous irradiation. Overall, the obtained results suggest the slower repair rate for DSBs induced by ultrashort pulse irradiation in comparison to DSBs induced by quasi-continuous irradiation.
Release of the Fourth Season of Money Heist: Analysis of Its Social Audience on Twitter during Lockdown in Spain
Authors: Cristófol Rodríguez Carmen , Meliveo Nogués Paula , Cristòfol Francisco Javier
Published: December 2020

Nowadays we are witnessing a significant change in content consumption. This, together with the global health situation, has caused some behaviors to accelerate. This research focuses on the specific case of the lockdown in Spain and the coincidence with the launch of the fourth season of Money Heist compared to the launch of season three. Starting with a review of the theoretical framework, in which the related concepts of coronavirus, television, and Video on Demand (VOD) platforms are presented, the importance of transmedia communication is also introduced. The methodological aspect is developed through content analysis and in-depth interviews. The tool used on the first methodology has been Twlets. With regard to the sources, the specific bibliography of the audiovisual sector, the official profile of the series on Twitter and personal interviews with professionals from the communication department of the production company, Vancouver Media, and from the series directing were taken into account. The methodology used to carry out this work has been the analysis of quantitative–qualitative content of the various sources consulted. The results of the study are presented in graphs, crossing the data from the different sources to detect the strategies of marketing and communication used for the release of the fourth season of the series. These results reflect the change in the communication strategy, the behavior of the social audience of the Twitter account of Money Heist (La Casa de Papel) and its relationship with the period of lockdown in Spain.
A Model for the Frequency Distribution of Multi-Scale Phenomena
Authors: Favati Paola , Lotti Grazia , Menchi Ornella , Romani Francesco
Published: December 2020

Frequency analysis is often used to investigate the structure of systems representing multi-scale real-world phenomena. In many different environments, functional relationships characterized by a power law have been recognized, but, in many cases this simple model has turned out to be absolutely inadequate and other models have been proposed. In this paper, we propose a general abstract model which constitutes a unifying framework, including many models found in literature, like the mixed model, the exponential cut-off and the log-normal. It is based on a discrete-time stochastic process, which leads to a recurrence relation describing the temporal evolution of the system. The steady state solution of the system highlights the probability distribution, which underlies the frequency behavior. A particular instance of the general model, called cubic-cut-off, was analyzed and tested in a number of experiments, producing good answers in difficult cases, even in the presence of peculiar behaviors.
Design Corrections in Spanish Office Buildings to Improve Energy Efficiency in the Face of Climate Change
Authors: Orosa José A. , Vergara Diego , Fraguela Feliciano , Fernández-Arias Pablo
Published: December 2020

The majority of buildings in Europe are at present naturally ventilated and do not use heating or cooling equipment throughout the summer. However, this idea is changing and as a result heating ventilation air conditioning (HVAC) related energy consumption has been rising in the recent years. On the other hand, predictions published by the intergovernmental Panel on Climate Change (IPCC) indicate an annual warming rate ranging between 0.1 and 0.4 °C. In the present study, the ISO 13790:2011 standard has been employed to analyze the effect of building design corrections over the energy saving of a real building during its mean life and under climatic change predictions. In this sense, the effect of climate change, ventilation rate and its energetic and carbon dioxide emissions implications are obtained for the next 15 years. The results obtained indicate that an increment in the air changes by natural ventilation will be more effective than changing the wall structure and, in consequence, the thermal inertia. In particular, it was obtained that an increase of natural ventilation will always reduce the energy consumption and that this consumption will be lower with time due to an increment of an average outdoor air temperature. This modification will allow reduced cooling energy peak demands during the summer season and improve indoor ambiences in mild regions and the energy efficiency.
Preliminary Evaluation of a Granite Rock Dust Product for Pest Herbivore Management in Field Conditions
Authors: Faraone Nicoletta , Hillier N. Kirk
Published: December 2020

The effects of granite rock dust in dry and aqueous formulations were evaluated under field conditions for control of insect pests in different crop systems and ornamental plants. We tested efficacy of crop protection following foliar applications on lily, squash, and cabbage plants by evaluating subsequent pest damage, overall plant health, and quantity of crops produced over one season. Lily plants treated with dry and aqueous formulations of rock dust were subject to lower herbivore damage (>1% and 11% herbivory damage, respectively) when compared to the controls (30% herbivory damage). Treatment on cabbage was less effective to protect plants against herbivory damage, and no statistically significant differences were reported within treatments. The foliar applications (dry and aqueous formulations) had positive impacts on growth of squash fruit resulting in a 2.5-fold increase in size relative to the control squash fruit. These results support the potential field application of granite dust to protect ornamental plants against herbivory attack, and reveal an alternative positive effect of the silica-based product on plant growth and development.
Correction: Nguyen T.L., et al. Role of Prokineticin Receptor-1 in Epicardial Progenitor Cells. J. Dev. Biol. 2013, 1, 20–31
Authors: Nguyen Thu Lan , Gasser Adeline , Nebigil Canan G.
Published: December 2020

The authors wish to make the following corrections to this paper [...]
Probing Magnetic Pulse Welding of Thin-Walled Tubes
Authors: Faes Koen , Shotri Rishabh , De Amitava
Published: December 2020

Magnetic pulse welding is a solid-state joining technology, based on the use of electromagnetic forces to deform and to weld workpieces. Since no external heat sources are used during the magnetic pulse welding process, it offers important advantages for the joining of dissimilar material combinations. Although magnetic pulse welding has emerged as a novel technique to join metallic tubes, the dimensional consistency of the joint assembly due to the strong impact of the flyer tube onto the target tube and the resulting plastic deformation is a major concern. Often, an internal support inside the target tube is considered as a solution to improve the stiffness of the joint assembly. A detailed investigation of magnetic pulse welding of Cu-DHP flyer tubes and 11SMnPb30 steel target tubes is performed, with and without an internal support inside the target tubes, and using a range of experimental conditions. The influence of the key process conditions on the evolution of the joint between the tubes with progress in time has been determined using experimental investigations and numerical modelling. As the process is extremely fast, real-time monitoring of the process conditions and evolution of important responses such as impact velocity and angle, and collision velocity, which determine the formation of a metallic bond, is impossible. Therefore, an integrated approach using a computational model using a finite-element method is developed to predict the progress of the impact of the flyer onto the target, the resulting flyer impact velocity and angle, the collision velocity between the flyer and the target, and the evolution of the welded joint, which are usually impossible to measure using experimental observations.
Long-Term and Seasonal Trends in Global Wave Height Extremes Derived from ERA-5 Reanalysis Data
Authors: Takbash Alicia , Young Ian
Published: December 2020

A non-stationary extreme value analysis of 41 years (1979–2019) of global ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis) significant wave height data is undertaken to investigate trends in the values of 100-year significant wave height, Hs100. The analysis shows that there has been a statistically significant increase in the value of Hs100 over large regions of the Southern Hemisphere. There have also been smaller decreases in Hs100 in the Northern Hemisphere, although the related trends are generally not statistically significant. The increases in the Southern Hemisphere are a result of an increase in either the frequency or intensity of winter storms, particularly in the Southern Ocean.
Seaports and Economic Growth: Panel Data Analysis of EU Port Regions
Authors: Mudronja Gorana , Jugović Alen , Škalamera-Alilović Dunja
Published: December 2020

Seaports are an important factor in regional economies since their operations create positive effects on the economy. The application of new technologies and innovations is important for the successful operation of seaports; their use reduces costs, facilitates business, increases transparency, and attracts new business entities. This paper analyses the impact of seaports on the growth of regional economies within the endogenous growth theory based on research and development (R&D) for a sample of 107 European Union’s (EU) port regions observed over the period from 2005 to 2015. The model was tested by using the two-step generalized method of moments. The results of the research indicate that seaports have a significant impact on the economic growth of the EU port regions, yet it is necessary to consider other factors that affect the growth of regional economies such as investments in R&D and human capital. These factors are often underestimated in relation to investment in transport infrastructure; therefore, the guidelines for partial diversion of funds might follow such a path.
Immunoproteomic Analysis Reveals Novel Candidate Antigens for the Diagnosis of Paracoccidioidomycosis Due to Paracoccidioides lutzii
Authors: Rodrigues Anderson Messias , Kubitschek-Barreira Paula Helena , Pinheiro Breno Gonçalves , Teixeira-Ferreira André , Hahn Rosane Christine , de Camargo Zoilo Pires
Published: December 2020

Paracoccidioidomycosis (PCM) is a life-threatening systemic infection caused by the fungal pathogen Paracoccidioides brasiliensis and related species. Whole-genome sequencing and stage-specific proteomic analysis of Paracoccidioides offer the opportunity to profile humoral immune responses against P. lutzii and P. brasiliensis s. str. infection using innovative screening approaches. Here, an immunoproteomic approach was used to identify PCM-associated antigens that elicit immune responses by combining 2-D electrophoresis of P. lutzii and P. brasiliensis proteomes, immunological detection using a gold-standard serum, and mass spectrometry analysis. A total of 16 and 25 highly immunoreactive proteins were identified in P. lutzii and P. brasiliensis, respectively, and 29 were shown to be the novel antigens for Paracoccidioides species, including seven uncharacterized proteins. Among the panel of proteins identified, most are involved in metabolic pathways, carbon metabolism, and biosynthesis of secondary metabolites in both immunoproteomes. Remarkably, six isoforms of the surface-associated enolase in the range of 54 kDa were identified as the major antigens in human PCM due to P. lutzii. These novel immunoproteomes of Paracoccidioides will be employed to develop a sensitive and affordable point-of-care diagnostic assay and an effective vaccine to identify infected hosts and prevent infection and development of human PCM. These findings provide a unique opportunity for the refinement of diagnostic tools of this important neglected systemic mycosis, which is usually associated with poverty.
Examining the Impacts of CO2 Concentration and Genetic Compatibility on Perennial Ryegrass—Epichloë festucae var lolii Interactions
Authors: Geddes-McAlister Jennifer , Sukumaran Arjun , Patchett Aurora , Hager Heather A. , Dale Jenna C. M. , Roloson Jennifer L. , Prudhomme Nicholas , Bolton Kim , Muselius Benjamin , Powers Jacqueline , Newman Jonathan A.
Published: December 2020

Perennial ryegrass (Lolium perenne) is the most cultivated cool-season grass worldwide with crucial roles in carbon fixation, turfgrass applications, and fodder for livestock. Lolium perenne forms a mutualism with the strictly vertically transmitted fungal endophyte, Epichloë festucae var lolii. The fungus produces alkaloids that protect the grass from herbivory, as well as conferring protection from drought and nutrient stress. The rising concentration of atmospheric CO2, a proximate cause of climatic change, is known to have many direct and indirect effects on plant growth. There is keen interest in how the nature of this plant–fungal interaction will change with climate change. Lolium perenne is an obligately outcrossing species, meaning that the genetic profile of the host is constantly being reshuffled. Meanwhile, the fungus is asexual implying both a relatively constant genetic profile and the potential for incompatible grass–fungus pairings. In this study, we used a single cultivar, “Alto”, of L. perenne. Each plant was infected with one of four strains of the endophyte: AR1, AR37, NEA2, and Lp19 (the “common strain”). We outcrossed the Alto mothers with pollen from a number of individuals from different ryegrass cultivars to create more genetic diversity in the hosts. We collected seed such that we had replicate maternal half-sib families. Seed from each family was randomly allocated into the two levels of the CO2 treatment, 400 and 800 ppm. Elevated CO2 resulted in an c. 18% increase in plant biomass. AR37 produced higher fungal concentrations than other strains; NEA2 produced the lowest fungal concentrations. We did not find evidence of genetic incompatibility between the host plants and the fungal strains. We conducted untargeted metabolomics and quantitative proteomics to investigate the grass-fungus interactions between and within family and treatment groups. We identified a number of changes in both the proteome and metabalome. Taken together, our data set provides new understanding into the intricacy of the interaction between endophyte and host from multiple molecular levels and suggests opportunity to promote plant robustness and survivability in rising CO2 environmental conditions through application of bioprotective epichloid strains.
Inhibition of Phenolics Uptake by Ligninolytic Fungal Cells and Its Potential as a Tool for the Production of Lignin-Derived Aromatic Building Blocks
Authors: Leriche-Grandchamp Mathilde , Flourat Amandine , Shen Hangchen , Picard Flavien , Giordana Heloïse , Allais Florent , Fayeulle Antoine
Published: December 2020

Lignin is the principal natural source of phenolics but its structural complexity and variability make it difficult to valorize through chemical depolymerization approaches. White rots are one of the rare groups of organisms that are able to degrade lignin in ecosystems. This biodegradation starts through extracellular enzymes producing oxidizing agents to depolymerize lignin and continue with the uptake of the generated oligomers by fungal cells for further degradation. Phanerochaete chrysosporium is one of the most studied species for the elucidation of these biodegradation mechanisms. Although the extracellular depolymerization step appears interesting for phenolics production from lignin, the uptake and intracellular degradation of oligomers occurring in the course of the depolymerization limits its potential. In this study, we aimed at inhibiting the phenolics uptake mechanism through metabolic inhibitors to favor extracellular oligomers accumulation without preventing the ligninases production that is necessary for extracellular depolymerization. The use of sodium azide confirmed that an active transportation phenomenon is involved in the phenolics uptake in P. chrysosporium. A protocol based on carbonyl cyanide m-chlorophenyl hydrazone enabled reaching 85% inhibition for vanillin uptake. This protocol was shown not to inhibit, but on the contrary, to stimulate the depolymerization of both dehydrogenation polymers (DHPs) and industrial purified lignins.
Tweets That Matter: Reconsidering Journalistic Sourcing and Framing Processes in the Context of the #Grexit Debate
Authors: Kollias Andreas , Kountouri Fani
Published: December 2020

This study explores the news media Twitter messaging on the issue of Grexit, as an exemplary case of transmediatisation of problems in highly polarized contexts. Our analysis focuses on media tweets (in English, French, Italian, and Greek) using the Grexit hashtag between March and July 2015. There are three main questions on the potential reshaping of journalistic sourcing and framing on Twitter. The first focuses on the milieu of actors used by media outlets as sources in the #Grexit debate, the second on the types of news frames that dominated #Grexit media tweets, and the third on how sourcing and news frames interact to construct a space of power positions. The above processes took shape within a close information system, which included politicians, media elites, and economic experts that marginalized alternative voices and critical perspectives. These findings indicate that mainstream news media normalized Twitter to fit their traditional sourcing and framing norms and practices. More specifically, our findings indicate the following: first, traditional sources and powerful economic actors get easier access to online media reporting on Twitter; second, the negative and episodic media-driven frames take the lead in the frame-building process; and third, the non-elite political and socially-driven frames are marginalized in the framing building process. The Twitter affordances were essentially normalized by media to fit into their understandings of the negotiation process as a high-stakes international politics and economic game with predetermined winners and losers. It is also likely that this normalization reflects the normalization of Twitter by powerful political and economic elites aiming to offer journalists on Twitter easy and instant access to their narratives.
Agricultural Resources and Trade Strategies: Response to Falling Land-to-Labor Ratios in Malawi
Authors: Tione Sarah Ephrida
Published: December 2020

This study assesses how growing land scarcity relative to family labor is influencing farm household decisions to trade in agricultural land and labor markets to improve their livelihood. Using the farm household model, I analyze decisions to rent-in land or hire out labor among smallholders in Malawi. I use data from two rounds of a nationally representative balanced-household panel and apply a systems approach to jointly estimate land rental and labor market decisions while controlling for simultaneity and unobserved heterogeneity. The results indicate that the falling owned-land-to-labor-endowment ratio can push households to participate in either land rental or seasonal agricultural labor markets. However, the probability of hiring out labor for casual work and short-term gains decreases when potential tenant households rent-in land. Based on asset-wealth-to-labor-endowment ratios, wealthier households are more likely to rent-in land while poorer households, including most smallholder households, are more likely to hire out labor. These results suggest higher friction in the land rental market compared to the agricultural labor markets and liquidity constraints dictating what is necessary to support agricultural operations and household needs. Accordingly, agricultural policy in Malawi should aim to reduce friction in factor markets.
Assessment of Gradient-Based Algorithm for Surface Determination in Multi-Material Gap Measurements by X ray Computed Tomography
Authors: Jiménez-Pacheco Roberto , Ontiveros Sinué , Yagüe-Fabra José A. , Zanini Filippo , Carmignato Simone , Albajez José Antonio
Published: December 2020

X-ray computed tomography is one of the most promising measurement techniques for the dimensional evaluation of industrial components. However, the inherent complexity of this technology also involves important challenges. One of them is to develop surface determination algorithms capable of providing measurement results with better accuracy in any situation—for example, for single and multi-material parts, inner and outer geometries, with and without image artefacts, etc.—and reducing user influence. The surface determination is particularly complex in the case of multi-material parts, especially when they are separated by small air gaps. In previous works, two gradient-based algorithms were presented, that showed less measurement variability throughout the whole part, and reduced the computational cost and operator influence compared to threshold-based algorithms. This work focuses on the evaluation of the performance of these algorithms when used in a scenario so complex that parts of it are made of one or more materials (metal–metal and polymer–metal) with gaps inside. For this purpose, a set of multi-material reference standards is used. The presented gradient-based algorithms show measurement errors comparable to commercial threshold-based algorithms, but with the capability of obtaining accurate measurements in smaller gaps, apart from reducing the user influence on the measurement process.
New Experimental Installation to Determine Adsorptive Properties of Magnesium Sulphate
Authors: Banos Oscar , Ohmann Sven , Breitkopf Cornelia
Published: December 2020

Adsorption processes are of great interest in catalysis, material separation, and thermal management. In recent decades, adsorbents have been further investigated because of their applications in adsorption refrigeration, heat pumps, and thermal energy storage. Thus, there is an increasing need to determine the macroscopic properties of the adsorbent, specifically their adsorption/desorption capacity and speed, because these two factors determine the power and size of the corresponding adsorber. Many designs have been proposed, but there is still not a generally adopted technology for the analysis of those properties. In this paper, a novel instrument is described, which is capable of determining the macrokinetic properties of an adsorbent composite, with better control and higher accuracy than gravimetric, volumetric, or barometric installations, and lower price and complexity than spectroscopic installations. The design of the installation is detailed, highlighting the main challenges and critical factors. The two working modes of the installation are described, and one example is provided and analyzed for each of them.
Experimental and Analytical Study on Residual Stiffness/Strength of CFRP Tendons under Cyclic Loading
Authors: Wang Chao , Zhang Jiwen
Published: December 2020

Based on tension–tension fatigue tests, this paper investigated the mechanical property degradation of carbon fiber reinforced polymer (CFRP) tendons from a macroscopic perspective. According to the degradation regularity, this paper proposed a normalized phenomenological fatigue model based on the residual stiffness/strength of CFRP tendons during the fatigue loading process. In this paper, the residual stiffness of CFRP tendons were tested at five stress ranges, while the residual strength was tested at four stress ranges. In order to validate the reliability and applicability of proposed fatigue damage model, the predictions of proposed model and cited models from the literature are discussed and compared. Furthermore, experimental results from literatures were adopted to verify the accuracy of the proposed model. The results showed that the proposed model is applicable to predict both residual stiffness and residual strength throughout fatigue life cycle and has a better accuracy than models from the literature. Moreover, the three-stage degradation can be observed from the degradation processes of stiffness and strength at each stress level.
Effect of Finishing Systems on Surface Roughness and Gloss of Full-Body Bulk-Fill Resin Composites
Authors: Paolone Gaetano , Moratti Eugenio , Goracci Cecilia , Gherlone Enrico , Vichi Alessandro
Published: December 2020

Background: In this study, we assess the effect produced on roughness and gloss of full-body bulk-fill materials by different finishing and polishing systems. Methods: Four full-body bulk-fill materials were tested: SonicFill2 (SF), Filtek Bulk Fill Posterior Restorative (FB), Tetric EvoCeram bulk-fill (EC), and Fill-Up! (FU). Sixty discs per material (2 mm in thickness and 7 mm in diameter) were obtained and randomly assigned (n = 15) to four finishing and polishing methods: Sof-Lex Spiral Wheels (SW), HiLusterPLUS (HL), Astropol (AP), and Opti1Step (OS). Surface roughness and gloss were then measured. Results: For roughness, material and surface treatment were significant factors (p < 0.001) with SF = FB = EC < FU and AP < SW < HL = OS. Material and surface treatment had a significant effect also on gloss (p < 0.001), with SF > FB = EC > FU and SW > AP > HL > OS. Conclusions: The tested combinations of bulk-fill and polishing systems provided clinically acceptable results with regard to roughness, while the outcome was poor for gloss. Multistep finishing/polishing systems were able to produce smoother surfaces on full-body bulk-fill materials compared to simplified ones.
Joining of Hypereutectic Al-50Si Alloys Using Lead-Free Brazing Filler Glass in Air
Authors: Wang Zhenjiang , Gao Zeng , Ba Xianli , Chu Junlong , He Peng , Niu Jitai
Published: December 2020

Hypereutectic Al-Si alloys are attractive materials in the fields of electronic packaging and aerospace. A Bi2O3-ZnO-B2O3 system lead-free brazing filler glass was employed to braze hypereutectic Al-50Si alloys in air. The hypereutectic Al-50Si alloys were pre-oxidized and the low-temperature glass powder was flake-shaped in the brazing process. The effects of brazing temperature and time on joints microstructure evolution, resulting mechanical strength, and air tightness were systematically investigated. The results indicated that the maximum shear strength of the joint was 34.49 MPa and leakage rate was 1.0 × 10−10 Pa m3/s at a temperature of 495 °C for 30 min. Crystalline phases, including Bi24B2O39 and Bi2O3, were generated in the glass joint. The formation of a diffusion transition layer with a thickness of 3 μm, including elements of Al, Si, Zn, Bi, Na, and B, was the key to form an effective joint. The elements of Al, Si, and Bi had a short diffusion distance while the elements of Zn, Na, and B diffused in a long way under brazing condition.
Influence of Acrylic Acid on Kinetics of UV-Induced Cotelomerization Process and Properties of Obtained Pressure-Sensitive Adhesives
Authors: Kowalczyk Agnieszka , Weisbrodt Mateusz , Schmidt Beata , Gziut Konrad
Published: December 2020

A new environmentally friendly method of photoreactive pressure-sensitive adhesives (PSAs) preparation was demonstrated. PSAs based on n-butyl acrylate (BA), acrylic acid (AA) and 4-acryloyloxy benxophenone (ABP) were prepared via the UV-induced cotelomerization process in the presence of a radical photoinitiator (acylphosphine oxide) and telogen (tetrabromomethane). Hydroxyterminated polybutadiene was used as a crosslinking agent. Influence of AA concentration (0–10 wt %) on kinetics of the cotelomerization process was investigated using a photodifferential scanning calorimetry method, selected physicochemical features of obtained photoreactive BA/AA/ABP cotelomers (molecular masses, polydispersity, monomers conversion and dynamic viscosity) and self-adhesive properties of obtained PSAs (adhesion, tack and cohesion) were studied, as well. It turned out that AA content is the important factor that influences monomers conversion (thereby the volatile parts content in prepolymer) and PSAs’ properties. As the acrylic acid content increases, the reaction rate increases, but the total monomers conversion and the solid content of the prepolymer decreases. Additionally, the adhesion and cohesion of PSAs were grown up, and their tackiness decreased. However, the AA content has no effect on molecular weights (Mw and Mn) and polydispersity (c.a. 1.5) of photoreactive cotelomers. The optimal AA content necessary to obtain a prepolymer with low volatile parts content and good PSA properties was determined.
Dimensional Analysis of Workpieces Machined Using Prototype Machine Tool Integrating 3D Scanning, Milling and Shaped Grinding
Authors: Jaskólski Piotr , Nadolny Krzysztof , Kukiełka Krzysztof , Kapłonek Wojciech , Pimenov Danil Yurievich , Sharma Shubham
Published: December 2020

In the literature, there are a small number of publications regarding the construction and application of machine tools that integrate several machining operations. Additionally, solutions that allow for such integration for complex operations, such as the machining of shape surfaces with complex contours, are relatively rare. The authors of this article carried out dimensional analysis of workpieces machined using a prototype Computerized Numerical Control (CNC) machine tool that integrates the possibilities of 3D scanning, milling operations in three axes, and grinding operations using abrasive discs. The general description of this machine tool with developed methodology and the most interesting results obtained during the experimental studies are given. For a comparative analysis of the influence of the machining method on the geometric accuracy of the test pieces, an Analysis of Variance (ANOVA) was carried out. The obtained results show that for four considered features (deviations of flatness, vertical parallelism, opening dimensions, and opening cylindricality), no statistically significant differences were detected. For the evaluation criteria, the probability level p exceeded the assumed confidence level α = 0.05 and ranged from p = 0.737167 to p = 0.076764. However, such differences were found for two others—a dimensional deviation between flat surfaces (p = 0.010467) and horizontal parallelism deviation (p = 0.0)—as well as for the quality of the machined surface defined by four surface texture parameters: Ra (p = 0.831797), Rt (p = 0.759636), Rq (p = 0.867222), and Rz (p = 0.651896). The information obtained by the ANOVA will be useful for the elimination the weaknesses of the prototype machine tool, further analysis of technological strategies, and to find possible benefits of integrating machining operations.
Features of Electrostatic Fields and Their Force Action When Using Micro- and Nanosized Inter-Electrode Gaps
Authors: Pshchelko Nikolai , Vodkailo Ekaterina
Published: December 2020

The present work is devoted to assessing the influence of discreteness of electric charge distribution in the double electric layer on the characteristics of the electric fields and their force action in capacitor structures with small interelectrode gaps. Due to the fact that modern technologies often use submicron-sized interelectrode gaps, it is no longer possible to consider the electrodes uniformly charged because of the discreteness of the electric charge. The corresponding development of a mathematical and physical model for the study of a non-uniform electric field is suggested. Numerical calculations are carried out, expressions, criteria, and results that are convenient for practical evaluations are obtained. The physical and mathematical model for force characteristics of a non-uniform electric field is developed. With a sufficiently small size of the interelectrode gap, the integral force effect of discretely distributed charges can be significantly higher than with a uniform distribution of the same charge. At reasonable surface charge densities, these phenomena are usually observed at interelectrode gaps less than tenths of a micrometer.
Changes in the Compressive Strength of Concrete in Thin Horizontally Formed Slabs
Authors: Szpetulski Jacek , Stawiski Bohdan
Published: December 2020

During compaction of a concrete mix, when thin slabs are formed in a horizontal position, the components of this mix become segregated. Heavy components fall to the bottom, and light components (air and water) move to the top. This process may suggest that the upper layers of concrete elements formed in a horizontal position may have lower compressive strength than the remaining part of the element. This problem is recognized and documented in many publications, but there was a publication whose test results indicate a lack of variability in the compressive strength of concrete across the thickness of tested elements. The discrepancies appearing in the evaluation of concrete homogeneity was the reason for conducting destructive tests of the compressive strength of concrete across the thickness of horizontally concreted test elements that imitate thin slabs. The obtained results of the destructive compressive strength confirmed previous results regarding the heterogeneity of concrete. They clearly indicate that there is a differentiation of the compressive strength of concrete across the thickness of a thin element, which remained in a liquefied state for a certain time during its formation. The longer the duration of this state across the entire thickness of the formed element, the greater the differentiation of the compressive strength between the top and bottom layers.
4D In-Situ Microscopy of Aerosol Filtration in a Wall Flow Filter
Authors: Jones Matthew P. , Storm Malte , York Andrew P. E. , Hyde Timothy I. , Hatton Gareth D. , Greenaway Alex G. , Haigh Sarah J. , Eastwood David S.
Published: December 2020

The transient nature of the internal pore structure of particulate wall flow filters, caused by the continuous deposition of particulate matter, makes studying their flow and filtration characteristics challenging. In this article we present a new methodology and first experimental demonstration of time resolved in-situ synchrotron micro X-ray computed tomography (micro-CT) to study aerosol filtration. We directly imaged in 4D (3D plus time) pore scale deposits of TiO2 nanoparticles (nominal mean primary diameter of 25 nm) with a pixel resolution of 1.6 μm. We obtained 3D tomograms at a rate of ∼1 per minute. The combined spatial and temporal resolution allows us to observe pore blocking and filling phenomena as they occur in the filter’s pore space. We quantified the reduction in filter porosity over time, from an initial porosity of 0.60 to a final porosity of 0.56 after 20 min. Furthermore, the penetration depth of particulate deposits and filtration rate was quantified. This novel image-based method offers valuable and statistically relevant insights into how the pore structure and function evolves during particulate filtration. Our data set will allow validation of simulations of automotive wall flow filters. Evolutions of this experimental design have potential for the study of a wide range of dry aerosol filters and could be directly applied to catalysed automotive wall flow filters.
Precision Hard Turning of Ti6Al4V Using Polycrystalline Diamond Inserts: Surface Quality, Cutting Temperature and Productivity in Conventional and High-Speed Machining
Authors: Abdelnasser Elshaimaa , Barakat Azza , Elsanabary Samar , Nassef Ahmed , Elkaseer Ahmed
Published: December 2020

This article presents the results of an experimental investigation into the machinability of Ti6Al4V alloy during hard turning, including both conventional and high-speed machining, using polycrystalline diamond (PCD) inserts. A central composite design of experiment procedure was followed to examine the effects of variable process parameters; feed rate, cutting speed and depth of cut (each at five levels) and their interaction effects on surface roughness and cutting temperature as process responses. The results revealed that cutting temperature increased with increasing cutting speed and decreasing feed rate in both conventional and high-speed machining. It was found that high-speed machining showed an average increase in cutting temperature of 65% compared with conventional machining. Nevertheless, high-speed machining showed better performance in terms of lower surface roughness despite using higher feed rates compared to conventional machining. High-speed machining of Ti6Al4V showed an improvement in surface roughness of 11% compared with conventional machining, with a 207% increase in metal removal rate (MRR) which offered the opportunity to increase productivity. Finally, an inverse relationship was verified between generated cutting temperature and surface roughness. This was attributed mainly to the high cutting temperature generated, softening, and decreasing strength of the material in the vicinity of the cutting zone which in turn enabled smoother machining and reduced surface roughness.
Photocurable Polymeric Blends for Surgical Application
Authors: Cernadas Teresa , Santos Marta , Miguel Sónia , Correia Ilídio , Alves Patrícia , Ferreira Paula
Published: December 2020

The preparation of photocrosslinkable bioadhesives synthesized from oligomers of lactic acid and polycaprolactone (PCL), both functionalized with 2-isocyanoethyl acrylate (AOI), were studied. The obtained modified macromers of LA-AOI (mLA) and PCL-AOI (mCL) were chemically characterized by 1H NMR and used to formulate polymeric blends with different mass proportions, 1:1, 1:2 and 2:1, respectively. Subsequently, the produced blends were crosslinked, considering two UV irradiation times: 30 and 120 s. After their production, the thermal and mechanical properties of bioadhesives were assessed, where upon the rheology, gel content, hydrolytic degradation and dynamic contact angles were determined. Furthermore, the cytotoxic profile of bioadhesives was evaluated in contact with human dermal fibroblasts cells, whereas their antibacterial effect was studied monitoring Escherichia coli and S. aureus growth. Overall, flexible and resistant films were obtained, presenting promising features to be used as surgical bioadhesives.
Tuning the Magnetism in Boron-Doped Strontium Titanate
Authors: Zeng Hui , Wu Meng , Wang Hui-Qiong , Zheng Jin-Cheng , Kang Junyong
Published: December 2020

The magnetic and electronic properties of boron-doped SrTiO3 have been studied by first-principles calculations. We found that the magnetic ground states of B-doped SrTiO3 strongly depended on the dopant-dopant separation distance. As the dopant–dopant distance varied, the magnetic ground states of B-doped SrTiO3 can have nonmagnetic, ferromagnetic or antiferromagnetic alignment. The structure with the smallest dopant-dopant separation exhibited the lowest total energy among all configurations considered and was characterized by dimer pairs due to strong attraction. Ferromagnetic coupling was observed to be stronger when the two adjacent B atoms aligned linearly along the B-Ti-B axis, which could be associated with their local bonding structures. Therefore, the symmetry of the local structure made an important contribution to the generation of a magnetic moment. Our study also demonstrated that the O-Ti-O unit was easier than the Ti-B-Ti unit to deform. The electronic properties of boron-doped SrTiO3 tended to show semiconducting or insulating features when the dopant–dopant distance was less than 5 Å, which changed to metallic properties when the dopant–dopant distance was beyond 5 Å. Our calculated results indicated that it is possible to manipulate the magnetism and band gap via different dopant–dopant separations.
Anisotropic Response of CoCrFeMnNi High-Entropy Alloy Fabricated by Selective Laser Melting
Authors: Wang Bowen , Sun Miao , Li Bobo , Zhang Lijuan , Lu Bingheng
Published: December 2020

This study investigated the anisotropic characteristics of the microstructural, mechanical and corrosion properties of CoCrFeMnNi high-entropy alloy produced by selective laser melting (SLM) additive manufacturing (AM). Under the extremely high thermal gradient during the SLM process, a columnar solidification structure with a single face-centered cubic (FCC) phase structure was formed. The crystal structure exhibited a regular checkerboard structure in the XOY plane (perpendicular to the building direction), which was composed of {110} direction and a small amount of {100} fiber texture. The cellular-dendritic sub-structures formed in the columnar crystal structure with sizes of about 500 nm in diameter. As for the mechanical properties, the XOY plane exhibited higher ultimate tensile strength and yield strength (σ0.2) but lower elongation to failure compared to the XOZ plane (parallel to building direction), which reflected the anisotropy of the microstructure. The electrochemical test results of the different planes showed that the XOZ plane exhibited better corrosion resistance in comparison with the XOY plane in the 3.5 wt % NaCl solution, which was on account of the selective attack at the Mn-rich inter-cellular regions and the different structures of the cellular-dendritic sub-structures on different planes.
Laser Fabrication of Anti-Icing Surfaces: A Review
Authors: Volpe Annalisa , Gaudiuso Caterina , Ancona Antonio
Published: December 2020

In numerous fields such as aerospace, the environment, and energy supply, ice generation and accretion represent a severe issue. For this reason, numerous methods have been developed for ice formation to be delayed and/or to inhibit ice adhesion to the substrates. Among them, laser micro/nanostructuring of surfaces aiming to obtain superhydrophobic behavior has been taken as a starting point for engineering substrates with anti-icing properties. In this review article, the key concept of surface wettability and its relationship with anti-icing is discussed. Furthermore, a comprehensive overview of the laser strategies to obtain superhydrophobic surfaces with anti-icing behavior is provided, from direct laser writing (DLW) to laser-induced periodic surface structuring (LIPSS), and direct laser interference patterning (DLIP). Micro-/nano-texturing of several materials is reviewed, from aluminum alloys to polymeric substrates.
Histological and Nanomechanical Properties of a New Nanometric Hydroxiapatite Implant Surface. An In Vivo Study in Diabetic Rats
Authors: Oliveira Paula G. F. P. , Coelho Paulo G. , Bergamo Edmara T. P. , Witek Lukasz , Borges Cristine A. , Bezerra Fábio B. , Novaes Arthur B. , Souza Sergio L. S.
Published: December 2020

Implant therapy is a predictable treatment to replace missing teeth. However, the osseointegration process may be negatively influenced by systemic conditions, such as diabetes mellitus (DM). Microtopography and implant surface developments are strategies associated to better bone repair. This study aimed to evaluate, in healthy and diabetic rats, histomorphometric (bone to implant contact = %BIC; and bone area fraction occupancy = %BAFO) and nanomechanical (elastic modulus = EM; and hardness = H) bone parameters, in response to a nanometric hydroxyapatite implant surface. Mini implants (machined = MAC; double acid etched = DAE, and with addition of nano-hydroxyapatite = NANO) were installed in tibias of healthy and diabetic rats. The animals were euthanized at 7 and 30 days. NANO surface presented higher %BIC and %BAFO when compared to MAC and DAE (data evaluated as a function of implant surface). NANO surface presented higher %BIC and %BAFO, with statistically significant differences (data as a function of time and implant surface). NANO surface depicted higher EM and H values, when compared to machined and DAE surfaces (data as a function of time and implant surface). Nano-hydroxyapatite coated implants presented promising biomechanical results and could be an important tool to compensate impaired bone healing reported in diabetics.