bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Physical and Chemical Modification of Pure Iron by Using Atmospheric Pressure Plasma Treatment
Authors: Kong Jinxing , Du Dongxing , Song Aisheng , Zhang Fan , Huang Wen
Published: October 2020

To investigate the mechanism of surface modification of pure iron by atmospheric pressure plasma treatment (APPT), the surface wettability of pure iron was characterized by using a contact-angle measuring instrument, and the mechanical properties of pure iron were measured by a tensile testing machine and nanoindentation instrument. Molecular dynamics simulations were used to explain the modification mechanism of the surface wettability and the mechanical behavior of pure iron by APPT. The experimental results show that pure iron treated by APPT is superhydrophilic, with reduced tensile strength and surface hardness. This result agrees with the molecular dynamics simulation, which shows that the pure iron material hydrophilicity improved after APPT. The behavior was attributed to the formation of hydrogen bonds on the surface of the pure iron after APPT. The surface binding energy of the pure iron material increased between the water molecule and the residual N atom that was induced by APPT. The N atom that was introduced by the APPT led to Fe bond fracture, and the N atom reduced the Fe bond strength, which resulted in a reduction of material yield strength and microhardness.
Effect of Graphene Nanoplatelets on the Structure, the Morphology, and the Dielectric Behavior of Low-Density Polyethylene Nanocomposites
Authors: Maniadi Athena , Vamvakaki Maria , Suchea Mirela , Tudose Ioan Valentin , Popescu Marian , Romanitan Cosmin , Pachiu Cristina , Ionescu Octavian N. , Viskadourakis Zaharias , Kenanakis George , Koudoumas Emmanouel
Published: October 2020

The incorporation of graphene nanoplatelets (GnPs) within a polymer matrix can play an important role in the physical properties and the functionality of the composite material. Composites consisting of low-density polyethylene (LDPE) and GnPs of different concentrations were developed by mixing GnPs with a molten form of the polymeric matrix. The effect of the GnPs content on the morphological, structural, and electrical properties of the composites were investigated. As shown, graphene presence and its concentration significantly modified the polymer matrix properties, a behavior that can be employed for tailoring its applicability in electrical applications. It was found that the increase of the graphene platelets concentration seems to promote the formation of graphene agglomerates, air gaps, and inhomogeneities, while higher dielectric constant/lower dielectric losses can be achieved.
Interlayer Reinforcement Combined with Fiber Reinforcement for Extruded Lightweight Mortar Elements
Authors: Matthäus Carla , Kofler Nadine , Kränkel Thomas , Weger Daniel , Gehlen Christoph
Published: October 2020

Lightweight mortar extrusion enables the production of monolithic exterior wall components with improved thermal insulation by installing air chambers and reduced material demand compared to conventional construction techniques. However, without reinforcement, the systems are not capable of bearing high flexural forces and, thus, the application possibilities are limited. Furthermore, the layer bonding is a weak spot in the system. We investigate a reinforcement strategy combining fibers in the mortar matrix with vertically inserted elements to compensate the layer bonding. By implementing fibers in the extruded matrix, the flexural strength can be increased almost threefold parallel to the layers. However, there is still an anisotropy between the layers as fibers are oriented during deposition and the layer bond is still mainly depending on hydration processes. This can be compensated by the vertical insertion of reinforcement elements in the freshly deposited layers. Corrugated wire fibers as well as short steel reinforcement elements were suitable to increase the flexural strength between the layers. As shown, the potential increase in flexural strength could be of a factor six compared to the reference (12 N/mm2 instead of 1.9 N/mm2). Thus, the presented methods reduce anisotropy in flexural strength due to layered production.
A Facile Method for the Generation of Fe3C Nanoparticle and Fe-Nx Active Site in Carbon Matrix to Achieve Good Oxygen Reduction Reaction Electrochemical Performances
Authors: Wu Yuzhe , Li Yuntong , Yuan Conghui , Dai Lizong
Published: October 2020

Introduction of both nitrogen and transition metal elements into the carbon materials has demonstrated to be a promising strategy to construct highly active electrode materials for energy shortage. In this work, through the coordination reaction between Fe3+ and 1,3,5–tris(4–aminophenyl)benzene, metallosupramolecular polymer precursors are designed for the preparation of carbon flakes co-doped with both Fe and N elements. The as-prepared carbon flakes display wrinkled edges and comprise Fe3C nanoparticle and active site of Fe–Nx. These carbon materials exhibit excellent electrocatalytic performance. Towards oxygen reduction reaction (ORR), the optimized sample has Eonset and Ehalf-wave of 0.93 V and 0.83 V in alkaline system, respectively, which are very close to that of Pt/C. This approach may offer a new way to high performance and low-cost electrochemical catalysts.
Effect of H2O Activity on Zeolite Formation
Authors: Belviso Claudia , Cavalcante Francesco
Published: October 2020

In an effort to understand the effects of H2O activity on zeolite formation, we have synthesized LTA zeolite using a combination of freezing processes and varying drying temperatures. Sodium aluminate and sodium silicate were used to form LTA zeolite, according to the IZA (International Zeolite Association) protocol. The synthesis steps were modified by adding the precursor frozen process by a rapid liquid nitrogen (−196 °C) treatment or slow conventional freezer treatment (−20 °C). The samples were subsequently sonicated and then dried at 80 °C or 40 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed on the samples immediately after the drying process as well as after 2 weeks and 1 month of aging the solid products. The results indicated that LTA zeolite does not form. The silica-alumina precursor after both freezing processes and after being dried at 80 °C showed the presence of sodalite displaying stable behavior over time. Both sets of samples dried at 40 °C and did not show the presence of zeolite immediately after the drying process. However, after 2 weeks, the liquid nitrogen–frozen precursor was characterized by the presence of EMT whereas zeolites never formed in the −20 °C samples. These results suggest that freezing processes differently control the H2O activity during the drying and aging processes in the solid state. Thus, although the precursor chemical composition is the same, the type of zeolite formed is different.
Reliability of Metal 3D Printing with Respect to the Marginal Fit of Fixed Dental Prostheses: A Systematic Review and Meta-Analysis
Authors: Bae Soohyun , Hong Min-Ho , Lee Hyunwoo , Lee Cheong-Hee , Hong Mihee , Lee Jaesik , Lee Du-Hyeong
Published: October 2020

Three-dimensional (3D) printing technologies have been widely used to manufacture crowns and frameworks for fixed dental prostheses. This systematic review and meta-analysis aimed to assess the reliability of the marginal fit of 3D-printed cobalt-chromium-based fixed dental prostheses in comparison to conventional casting methods. Articles published until 25 June 2020, reporting the marginal fit of fixed prostheses fabricated with metal 3D printing, were searched using electronic literature databases. After the screening and quality assessment, 21 eligible peer-reviewed articles were selected. Meta-analysis revealed that the marginal gap of the prostheses manufactured using 3D printing was significantly smaller compared to that manufactured using casting methods (standard mean difference (95% CI): −0.92 (−1.45, −0.38); Z = −3.37; p = 0.0008). The estimated difference between the single and multi-unit types did not differ significantly (p = 0.3573). In the subgroup analysis for the measurement methods, the tendency of marginal discrepancy between the 3D printing and casting groups was significantly different between articles that used direct observation and those that used the silicone replica technique (p < 0.001). Metal 3D printing technologies appear reliable as an alternative to casting methods in terms of the fit of the fixed dental prostheses. In order to analyze the factors influencing manufacturing and confirm the results of this review, further controlled laboratory and clinical studies are required.
The Effect of Particle Shell on Cooling Rates in Oil-in-Oil Magnetic Pickering Emulsions
Authors: Bielas Rafał , Józefczak Arkadiusz
Published: October 2020

Pickering emulsions (particle-stabilized emulsions) are usually considered because of their unique properties compared to surfactant-stabilized emulsions including better stability against emulsion aging. However, the interesting feature of particle-stabilized emulsions could be revealed during their magnetic heating. When magnetic particles constitute a shell around droplets and the sample is placed in an alternating magnetic field, a temperature increase appears due to energy dissipation from magnetic relaxation and hysteresis within magnetic particles. We hypothesize that the solidity of the magnetic particle shell around droplets can influence the process of heat transfer from inside the droplet to the surrounding medium. In this way, particle-stabilized emulsions can be considered as materials with changeable heat transfer. We investigated macroscopically heating and cooling of oil-in-oil magnetic Pickering emulsions with merely packed particle layers and these with a stable particle shell. The change in stability of the shell was obtained here by using the coalescence of droplets under the electric field. The results from calorimetric measurements show that the presence of a stable particle shell caused a slower temperature decrease in samples, especially for lower intensities of the magnetic field. The retarded heat transfer from magnetic Pickering droplets can be utilized in further potential applications where delayed heat transfer is desirable.
Polysiloxanes Grafted with Mono(alkenyl)Silsesquioxanes—Particular Concept for Their Connection
Authors: Mituła Katarzyna , Duszczak Julia , Rzonsowska Monika , Żak Patrycja , Dudziec Beata
Published: October 2020

Herein, a facile and efficient synthetic route to unique hybrid materials containing polysiloxanes and mono(alkyl)silsesquioxanes as their pendant modifiers (T8@PS) was demonstrated. The idea of this work was to apply the hydrosilylation reaction as a tool for the efficient and selective attachment of mono(alkenyl)substituted silsesquioxanes (differing in the alkenyl chain length, from -vinyl to -dec-9-enyl and types of inert groups iBu, Ph at the inorganic core) onto two polysiloxanes containing various amount of Si-H units. The synthetic protocol, determined and confirmed by FT-IR in situ and NMR analyses, was optimized to ensure complete Si-H consumption along with the avoidance of side-products. A series of 20 new compounds with high yields and complete β-addition selectivity was obtained and characterized by spectroscopic methods.
Corrosion of High-Strength Steel Wires under Tensile Stress
Authors: Lv Shanglin , Li Kefei , Chen Jie , Li Xiaobin
Published: October 2020

The stress corrosion cracking is the central issue for high-strength wires under high tensile stress used in civil engineering. This paper explores the resistance of stress corrosion cracking of three typical steel wires of high-strength carbon through a laboratory test, combining the actions of tensile stress and corrosive solution. Besides, the impact of tensile stress and immersion time are also investigated. During the tests, the wires were subject to electrochemical measurements of potentiodynamic polarization and electrochemical impedance spectroscopy, and the microstructure analysis was performed on the fractured cross sections. The obtained results show the following: the high-strength wire, conforming to GB/T 5224, has higher resistance to the combined actions of tensile stress and corrosive solution; tensile stress of 70% fracture strength and longer loading-immersion time make the film of corrosion products on steel surface unstable and weaken the corrosion resistance; the surface film consisted of the iron oxide film and the corrosion products film whose components are mainly iron thiocyanate and iron sulphide.
Effect of Zn and Mg Content on Crashworthiness of Al-Zn-Mg Alloy Thin-Walled Square Extrusions
Authors: Guo Hui , Wang Cheng , Zhang Jin , Deng Yunlai
Published: October 2020

The effects of Zn and Mg content in thin-walled square extrusions of Al-Zn-Mg alloys on its crashworthiness were investigated, and the correlation between the crushing properties, mechanical properties, and microstructures of the profiles were investigated. The results showed that the strength and the compression properties were gradually increased with a decrease in the Zn/Mg ratios (from 12.48 to 4.57). When the Zn/Mg ratio is lower (less than 6.29), an increase in the Mg content simultaneously improves the alloy strength and the compression properties. An increase in Zn content (from 5.07 to 6.77) can improve the strength of the alloy however, it does not affect the compression properties. However, the higher Zn contents (6.77%) would lead to cracking in advance during the compressing, which reduces the compression energy absorption capacities of the product. Therefore, in order to obtain higher strength and excellent compression properties, the Zn/Mg ratio should be reduced. For the upper limit, the Zn content should not be too high (less than 6.77), as this may lead to early cracking and failure. For the lower limit, the Mg content should be higher (more than 0.91) to make sure that the alloy has excellent compression properties and higher strength.
Third-Generation Cephalosporin-Loaded Chitosan Used to Limit Microorganisms Resistance
Authors: Duceac Letiția Doina , Calin Gabriela , Eva Lucian , Marcu Constantin , Bogdan Goroftei Elena Roxana , Dabija Marius Gabriel , Mitrea Geta , Luca Alina Costina , Hanganu Elena , Gutu Cristian , Stafie Liviu , Banu Elena Ariela , Grierosu Carmen , Iordache Alin Constantin
Published: October 2020

From their discovery, antibiotics have significantly improved clinical treatments of infections, thus leading to diminishing morbidity and mortality in critical care patients, as well as surgical, transplant and other types of medical procedures. In contemporary medicine, a significant debate regarding the development of multi-drug resistance involves all types of pathogens, especially in acute care hospitals due to suboptimal or inappropriate therapy. The possibility of nanotechnology using nanoparticles as matrices to encapsulate a lot of active molecules should increase drug efficacy, limit adverse effects and be an alternative helping to combat antibiotic resistance. The major aim of this study was to obtain and to analyze physico-chemical features of chitosan used as a drug-delivery system in order to stop the antibiotic resistance of different pathogens. It is well known that World Health Organization stated that multidrug resistance is one of the most important health threats worldwide. In last few years, nano-medicine emerged as an improved therapy to combat antibiotic-resistant infections agents. This work relies on enhancement of the antimicrobial efficiency of ceftriaxone against gram(+) and gram(−) bacteria by antibiotic encapsulation into chitosan nanoparticles. Physicochemical features of ceftriaxone-loaded polymer nanoparticles were investigated by particle size distribution and zeta potential, Fourier-transform infrared spectroscopy (FTIR), Thermal Gravimetric Analysis (TG/TGA), Scanning Electron Microscopy (SEM) characteristics techniques. The obtained results revealed an average particle size of 250 nm and a zeta potential value of 38.5 mV. The release profile indicates an incipient drug deliverance of almost 15%, after 2 h of approximately 83%, followed by a slowed drug release up to 24 h. Characteristics peaks of chitosan were confirmed by FTIR spectra indicating a similar structure in the case of ceftriaxone-loaded chitosan nanoparticles. A good encapsulation of the antibiotic into chitosan nanoparticles was also provided by thermo-gravimetric analysis. Morphological characteristics shown by SEM micrographs exhibit spherical nanoparticles of 30–250 nm in size with agglomerated architectures. Chitosan, a natural polymer which is used to load different drugs, provides sustained and prolonged release of antibiotics at a specific target by possessing antimicrobial activity against gram(+) and gram(−) bacteria. In this research, ceftriaxone-loaded chitosan nanoparticles were investigated as a carrier in antibiotic delivery.
In Situ and Ex Situ Designed Hydroxyapatite: Bacterial Cellulose Materials with Biomedical Applications
Authors: Nicoara Adrian Ionut , Stoica Alexandra Elena , Ene Denisa-Ionela , Vasile Bogdan Stefan , Holban Alina Maria , Neacsu Ionela Andreea
Published: October 2020

Hydroxyapatite (HAp) and bacterial cellulose (BC) composite materials represent a promising approach for tissue engineering due to their excellent biocompatibility and bioactivity. This paper presents the synthesis and characterization of two types of materials based on HAp and BC, with antibacterial properties provided by silver nanoparticles (AgNPs). The composite materials were obtained following two routes: (1) HAp was obtained in situ directly in the BC matrix containing different amounts of AgNPs by the coprecipitation method, and (2) HAp was first obtained separately using the coprecipitation method, then combined with BC containing different amounts of AgNPs by ultrasound exposure. The obtained materials were characterized by means of XRD, SEM, and FT-IR, while their antimicrobial effect was evaluated against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and yeast (Candida albicans). The results demonstrated that the obtained composite materials were characterized by a homogenous porous structure and high water absorption capacity (more than 1000% w/w). These materials also possessed low degradation rates (<5% in simulated body fluid (SBF) at 37 °C) and considerable antimicrobial effect due to silver nanoparticles (10–70 nm) embedded in the polymer matrix. These properties could be finetuned by adjusting the content of AgNPs and the synthesis route. The samples prepared using the in situ route had a wider porosity range and better homogeneity.
Exploring Macroporosity of Additively Manufactured Titanium Metamaterials for Bone Regeneration with Quality by Design: A Systematic Literature Review
Authors: Martinez-Marquez Daniel , Delmar Ylva , Sun Shoujin , Stewart Rodney A.
Published: October 2020

Additive manufacturing facilitates the design of porous metal implants with detailed internal architecture. A rationally designed porous structure can provide to biocompatible titanium alloys biomimetic mechanical and biological properties for bone regeneration. However, increased porosity results in decreased material strength. The porosity and pore sizes that are ideal for porous implants are still controversial in the literature, complicating the justification of a design decision. Recently, metallic porous biomaterials have been proposed for load-bearing applications beyond surface coatings. This recent science lacks standards, but the Quality by Design (QbD) system can assist the design process in a systematic way. This study used the QbD system to explore the Quality Target Product Profile and Ideal Quality Attributes of additively manufactured titanium porous scaffolds for bone regeneration with a biomimetic approach. For this purpose, a total of 807 experimental results extracted from 50 different studies were benchmarked against proposed target values based on bone properties, governmental regulations, and scientific research relevant to bone implants. The scaffold properties such as unit cell geometry, pore size, porosity, compressive strength, and fatigue strength were studied. The results of this study may help future research to effectively direct the design process under the QbD system.
Magnetorheological Elastomer Stress Relaxation Behaviour during Compression: Experiment and Modelling
Authors: Kukla Mateusz , Warguła Łukasz , Talaśka Krzysztof , Wojtkowiak Dominik
Published: October 2020

Materials characterized by magnetorheological properties are non-classic engineering materials. A significant increase in the interest of the scientific community about this group of materials could be observed over the recent years. The results of research presented in this article are oriented on the examination of the said materials’ mechanical properties. Stress relaxation tests were carried out on cylindrical samples of magnetorheological elastomers loaded with compressive stress, for various values of magnetic induction (B1 = 0 mT, B2 = 32 mT, B3 = 48 mT, and B4 = 64 mT) and temperature (T1 = 25 °C, T2 = 30 °C, and T3 = 40 °C). The results of these tests indicate that the stiffness of the examined samples increased along with the increase of magnetic field induction, and decreased along with the increase of temperature. On this basis, it has been determined that: the biggest stress amplitude change, caused by the influence of magnetic field, was σ0ΔB = 12.7%, and the biggest stress amplitude change, caused by the influence of temperature, was σ0ΔT = 11.3%. As a result of applying a mathematical model, it was indicated that the stress relaxation in the examined magnetorheological elastomer, for the adopted time range (t = 3600 s), had a hyperbolic decline nature. The collected test results point to the examined materials being characterized by extensive rheological properties, which leads to the conclusion that it is necessary to conduct further tests in this area.
Preliminary Interpretation of the Induction Period in Hydration of Sodium Hydroxide/Silicate Activated Slag
Authors: Zuo Yibing , Ye Guang
Published: October 2020

Many calorimetric studies have been carried out to investigate the reaction process of alkali-activated slag paste. However, the origin of the induction period and action mechanism of soluble Si in the dissolution of slag are still not clear. Moreover, the mechanisms behind different reaction periods are not well described. In this study, the reaction kinetics of alkali-activated slag paste was monitored by isothermal calorimetry and the effect of soluble Si was investigated through a dissolution test. The results showed that occurrence of the induction period in hydration of alkali-activated slag paste depended on the presence of soluble Si in alkaline activator and the soluble Si slowed down the dissolution of slag. A dissolution theory-based mechanism was introduced and applied to the dissolution of slag, showing good interpretation of the action mechanism of soluble Si. With this dissolution theory-based mechanism, origin of the induction period in hydration of alkali-activated slag was explicitly interpreted.
Solutions of the Two-Wave Interactions in Quadratic Nonlinear Media
Authors: Bougoffa Lazhar , Bougouffa Smail
Published: October 2020

In this paper, we propose a reliable treatment for studying the two-wave (symbiotic) solitons of interactions in nonlinear quadratic media. We investigate the Schauder’s fixed point theorem for proving the existence theorem. Additionally, the uniqueness solution for this system is proved. Also, a highly accurate approximate solution is presented via an iteration algorithm.
The Most Refined Axiom for a Digital Covering Space and Its Utilities
Authors: Han Sang-Eon
Published: October 2020

This paper is devoted to establishing the most refined axiom for a digital covering space which remains open. The crucial step in making our approach is to simplify the notions of several types of earlier versions of local (k0,k1)-isomorphisms and use the most simplified local (k0,k1)-isomorphism. This approach is indeed a key step to make the axioms for a digital covering space very refined. In this paper, the most refined local (k0,k1)-isomorphism is proved to be a (k0,k1)-covering map, which implies that the earlier axioms for a digital covering space are significantly simplified with one axiom. This finding facilitates the calculations of digital fundamental groups of digital images using the unique lifting property and the homotopy lifting theorem. In addition, consider a simple closed k:=k(t,n)-curve with five elements in Zn, denoted by SCkn,5. After introducing the notion of digital topological imbedding, we investigate some properties of SCkn,5, where k:=k(t,n),3≤t≤n. Since SCkn,5 is the minimal and simple closed k-curve with odd elements in Zn which is not k-contractible, we strongly study some properties of it associated with generalized digital wedges from the viewpoint of fixed point theory. Finally, after introducing the notion of generalized digital wedge, we further address some issues which remain open. The present paper only deals with k-connected digital images.
Antioxidant and Cytotoxic Effects on Tumor Cells of Exopolysaccharides from Tetraselmis suecica (Kylin) Butcher Grown Under Autotrophic and Heterotrophic Conditions
Authors: Parra-Riofrío Geovanna , García-Márquez Jorge , Casas-Arrojo Virginia , Uribe-Tapia Eduardo , Abdala-Díaz Roberto Teófilo
Published: October 2020

Marine microalgae produce extracellular metabolites such as exopolysaccharides (EPS) with potentially beneficial biological applications to human health, especially antioxidant and antitumor properties, which can be increased with changes in crop trophic conditions. This study aimed to develop the autotrophic and heterotrophic culture of Tetraselmis suecica (Kylin) Butcher in order to increase EPS production and to characterize its antioxidant activity and cytotoxic effects on tumor cells. The adaptation of autotrophic to heterotrophic culture was carried out by progressively reducing the photoperiod and adding glucose. EPS extraction and purification were performed. EPS were characterized by Fourier-transform infrared spectroscopy and gas chromatography-mass spectrometry. The antioxidant capacity of EPS was analyzed by the 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) method, and the antitumor capacity was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, showing high activity on human leukemia, breast and lung cancer cell lines. Although total EPS showed no cytotoxicity, acidic EPS showed cytotoxicity over the gingival fibroblasts cell line. Heterotrophic culture has advantages over autotrophic, such as increasing EPS yield, higher antioxidant capacity of the EPS and, to the best of our knowledge, this is the first probe that T. suecica EPS have cytotoxic effects on tumor cells; therefore, they could offer greater advantages as possible natural nutraceuticals for the pharmaceutical industry.
Human Peripheral Blood Dendritic Cell and T Cell Activation by Codium fragile Polysaccharide
Authors: Zhang Wei , Hwang Juyoung , Park Hae-Bin , Lim Seong-Min , Go Seulgi , Kim Jihoe , Choi Inho , You Sangguan , Jin Jun-O
Published: October 2020

Natural polysaccharides exhibit an immunostimulatory effect with low toxicity in humans and animals. It has shown that polysaccharide extracted from Codium fragile (CFP) induces anti-cancer immunity by dendritic cell (DC) activation, while the effect of CFP has not examined in the human immune cells. In this study, we found that CFP promoted the upregulation of CD80, CD83 and CD86 and major histocompatibility complex (MHC) class I and II in human monocyte-derived dendritic cells (MDDCs). In addition, CFP induced the production of proinflammatory cytokines in MDDCs. Moreover, CFP directly induced the activation of Blood Dendritic Cell Antigen (BDCA)1+ and BDCA3+ subsets of human peripheral blood DCs (PBDCs). The CFP-stimulated BDCA1+ PBDCs further promoted activation and proliferation of syngeneic CD4 T cells. The CFP-activated BDCA3+ PBDCs activated syngeneic CD8 T cells, which produced cytotoxic mediators, namely, cytotoxic T lymphocytes. These results suggest that CFP may be a candidate molecule for enhancing immune activation in humans.
Quaternary Ammonium-Bearing Perfluorinated Polymers for Anion Exchange Membrane Applications
Authors: Lee Seunghyun , Lee Hyejin , Yang Tae-Hyun , Bae Byungchan , Tran Nguyen Anh Thu , Cho Younghyun , Jung Namgee , Shin Dongwon
Published: October 2020

Perfluorinated polymers are widely used in polymer electrolyte membranes because of their excellent ion conductivity, which are attributed to the well-defined morphologies resulting from their extremely hydrophobic main-chains and flexible hydrophilic side-chains. Perfluorinated polymers containing quaternary ammonium groups were prepared from Nafion- and Aquivion-based sulfonyl fluoride precursors by the Menshutkin reaction to give anion exchange membranes. Perfluorinated polymers tend to exhibit poor solubility in organic solvents; however, clear polymer dispersions and transparent membranes were successfully prepared using N-methyl-2-pyrrolidone at high temperatures and pressures. Both perfluorinated polymer-based membranes exhibited distinct hydrophilic-hydrophobic phase-separated morphologies, resulting in high ion conductivity despite their low ion exchange capacities and limited water uptake properties. Moreover, it was found that the capacitive deionization performances and stabilities of the perfluorinated polymer membranes were superior to those of the commercial Fumatech membrane.
Effect of Oxygen in the Structure, Microstructure and Mechanical Properties of Ti-xNi (x = 5, 10, 15 and 20 wt%) Alloys
Authors: Cascadan Daniela , Grandini Carlos Roberto
Published: October 2020

Titanium alloys have great potential for use as biomaterials due to good biocompatibility and mechanical properties. The nickel addition to titanium improves the wear, corrosion and mechanical resistance of this element. The objective of this paper was to investigate the effects of oxygen on the structure, microstructure and some selected mechanical properties of this alloy system. The results showed that the samples present the adequate nickel concentration and low concentration of other metals. The alloys exhibit predominantly the α and intermetallic Ti2Ni phases, and the amount of it increases according to the nickel concentration. In the Ti-15Ni and Ti-20Ni alloys, this intermetallic reacted with oxygen forming Ti4Ni2O trioxide. The microstructures varied according to the processing, as well as the microhardness values. Elastic modulus values are slightly above titanium due to the formation of a new intermetallic phase but have not varied significantly with processing and doping with oxygen.
Study on Failure Mechanism and Phase Transformation of 304 Stainless Steel during Erosion Wear
Authors: Ye Youjun , Li Jing , Lv Xingxing , Liu Lin
Published: October 2020

In this paper, the failure mechanism and phase transformation process of 304 stainless steel during the erosion wear process were studied with a rotary erosion wear test device. The surface morphologies of the worn 304 stainless steel were investigated by scanning electron microscopy (SEM). The metallographic structures of the nonworn and worn 304 stainless steel were analyzed by optical microscope (OM) and transmission electron microscopy (TEM). In addition, the surface hardness on different areas of the sample was also measured. The results demonstrated that the failure mechanism of 304 stainless steel during the process of erosion wear was cutting and spalling caused by plastic deformation. The high-density dislocations move along the slip planes between slip lines, which resulted in the formation of martensite phase between the slip lines. Meanwhile, the martensitic transformation on the worn surface caused by severe plastic deformation was the coordination of dislocation martensite and twin martensite.
Solidified Structure Refinement of H13 Tool Steel under a Multi-Rotational Speed Super Gravity Field
Authors: Li Shao-Ying , Qin Shu-Yang , Xi Xiao-Jun , Sun Guan-Yong , Yang Wen-Sheng , Guo Jing , Guo Han-Jie
Published: October 2020

In this paper, the effects of a super-gravity field with multi-rotational speeds on the grain refinement and tensile properties of as-cast H13 steel were investigated systematically. The experimental results showed that compared to the single-rotational speed (conventional) super-gravity field, the as-cast grains of H13 steel can be significantly refined in a multi-rotational speed (speed increased in stages) super-gravity field. In the conventional super-gravity field, with the decrease in rotational radius, the secondary dendrite arm spacing (SDAS) and the prior austenite grain size (PAGS) increase, and the maximum values of SDAS and PAGS are 90 and 55 µm, respectively, while in multi-speed super-gravity fields, at the range of increasing rotational speeds, SDAS and PAGS decrease as the rotational radius decreases. In the three-rotational speed super-gravity field, the maximum values of SDAS and PAGS are 80 µm and 50 µm. In the five-rotational speed super-gravity field, the maximum values of SDAS and PAGS are reduced to 58 µm and 34 µm. Accordingly, both the tensile strength and the plasticity are enhanced when increasing the number of rotational speeds in the super-gravity field, especially for the inner position of the super-gravity sample. The ultimate tensile strengths at outer, middle, and inner positions of H13 steel solidified in the conventional super-gravity field are 1445 MPa, 1378 MPa, and 1023 MPa, corresponding to elongations of 2%, 1.5%, and 0.5%, respectively, while in the five-rotational speed super-gravity field, they are 1408, 1443, and 1453 MPa, corresponding to elongations of 1.8%, 3.9%, and 2.2%, respectively. The mechanism for the grain refinement is that multi-speed super-gravity can reduce the critical nucleation work of austenite and the tangential force produced by increasing the rotational speed break dendrites at the solidification front, refining the solidified structure.
Study on ZrB2-Based Ceramics Reinforced with SiC Fibers or Whiskers Machined by Micro-Electrical Discharge Machining
Authors: Quarto Mariangela , Bissacco Giuliano , D’Urso Gianluca
Published: October 2020

The effects of different reinforcement shapes on stability and repeatability of micro electrical discharge machining were experimentally investigated for ultra-high-temperature ceramics based on zirconium diboride (ZrB2) doped by SiC. Two reinforcement shapes, namely SiC short fibers and SiC whiskers were selected in accordance with their potential effects on mechanical properties and oxidation performance. Specific sets of process parameters were defined minimizing the short circuits in order to identify the best combination for different pulse types. The obtained results were then correlated with the energy per single discharge and the discharges occurred for all the combinations of material and pulse type. The pulse characterization was performed by recording pulses data by means of an oscilloscope, while the surface characteristics were defined by a 3D reconstruction. The results indicated how reinforcement shapes affect the energy efficiency of the process and change the surface aspect.
In-Built N+ Pocket Electrically Doped Tunnel FET With Improved DC and Analog/RF Performance
Authors: Li Jun , Liu Ying , Wei Su-fen , Shan Chan
Published: October 2020

In this paper, we present an in-built N+ pocket electrically doped tunnel FET (ED-TFET) based on the polarity bias concept that enhances the DC and analog/RF performance. The proposed device begins with a MOSFET like structure (n-p-n) with a control gate (CG) and a polarity gate (PG). The PG is biased at −0.7 V to induce a P+ region at the source side, leaving an N+ pocket between the source and the channel. This technique yields an N+ pocket that is realized in the in-built architecture and removes the need for additional chemical doping. Calibrated 2-D simulations have demonstrated that the introduction of the N+ pocket yields a higher ION and a steeper average subthreshold swing when compared to conventional ED-TFET. Further, a local minimum on the conduction band edge (EC) curve at the tunneling junction is observed, leading to a dramatic reduction in the tunneling width. As a result, the in-built N+ pocket ED-TFET significantly improves the DC and analog/RF figure-of-merits and, hence, can serve as a better candidate for low-power applications.
Microneedles: Characteristics, Materials, Production Methods and Commercial Development
Authors: Tucak Amina , Sirbubalo Merima , Hindija Lamija , Rahić Ognjenka , Hadžiabdić Jasmina , Muhamedagić Kenan , Čekić Ahmet , Vranić Edina
Published: October 2020

Although transdermal drug delivery systems (DDS) offer numerous benefits for patients, including the avoidance of both gastric irritation and first-pass metabolism effect, as well as improved patient compliance, only a limited number of active pharmaceutical ingredients (APIs) can be delivered accordingly. Microneedles (MNs) represent one of the most promising concepts for effective transdermal drug delivery that penetrate the protective skin barrier in a minimally invasive and painless manner. The first MNs were produced in the 90s, and since then, this field has been continually evolving. Therefore, different manufacturing methods, not only for MNs but also MN molds, are introduced, which allows for the cost-effective production of MNs for drug and vaccine delivery and even diagnostic/monitoring purposes. The focus of this review is to give a brief overview of MN characteristics, material composition, as well as the production and commercial development of MN-based systems.
Special Issue “Bifidobacteria: Insights from Ecology to Genomics of a Key Microbial Group of the Mammalian Gut Microbiota”
Authors: Ventura Marco , Turroni Francesca , Milani Christian , Mahony Jennifer , Bottacini Francesca , van Sinderen Douwe
Published: October 2020

In recent years, substantial efforts have been made to dissect the composition of microbial communities that are present in the human gut, and to investigate their interactions with their host [...]
Comparative Genomics Analysis of Vibrio anguillarum Isolated from Lumpfish (Cyclopterus lumpus) in Newfoundland Reveal Novel Chromosomal Organizations
Authors: Vasquez Ignacio , Cao Trung , Chakraborty Setu , Gnanagobal Hajarooba , O’Brien Nicole , Monk Jennifer , Boyce Danny , Westcott Jillian D. , Santander Javier
Published: October 2020

Vibrio anguillarum is a Gram-negative marine pathogen causative agent of vibriosis in a wide range of hosts, including invertebrates and teleosts. Lumpfish (Cyclopterus lumpus), a native fish of the North Atlantic Ocean, is utilized as cleaner fish to control sea lice (Lepeophtheirus salmonis) infestations in the Atlantic salmon (Salmo salar) aquaculture industry. V. anguillarum is one of the most frequent bacterial pathogens affecting lumpfish. Here, we described the phenotype and genomic characteristics of V. anguillarum strain J360 isolated from infected cultured lumpfish in Newfoundland, Canada. Koch’s postulates determined in naïve lumpfish showed lethal acute vibriosis in lumpfish. The V. anguillarum J360 genome was shown to be composed of two chromosomes and two plasmids with a total genome size of 4.56 Mb with 44.85% G + C content. Phylogenetic and comparative analyses showed that V. anguillarum J360 is closely related to V. anguillarum strain VIB43, isolated in Scotland, with a 99.8% genome identity. Differences in the genomic organization were identified and associated with insertion sequence elements (ISs). Additionally, V. anguillarum J360 does not possess a pJM1-like plasmid, typically present in virulent isolates from the Pacific Ocean, suggesting that acquisition of this extrachromosomal element and the virulence of V. anguillarum J360 or other Atlantic isolates could increase.
Effect of the Morphology and Electrical Property of Metal-Deposited ZnO Nanostructures on CO Gas Sensitivity
Authors: Hwang Sung-Ho , Kim Young Kwang , Hong Seong Hui , Lim Sang Kyoo
Published: October 2020

The development of a highly sensitive gas sensor for toxic gases is an important issue in that it can reduce the damage caused by unexpected gas leaks. In this regard, in order to make the sensor accurate and highly responsive, we have investigated which morphology is effective to improve the sensitivity and how the deposited nanoparticle affects the sensitivity by controlling the morphology of semiconductor oxides—either nanorod or nanoplate—and depositing metal nanoparticles on the semiconductor surface. In this study, we compared the CO gas sensitivity for sensors with different morphology (rod and plate) of ZnO nanostructure with metal nanoparticles (gold and copper) photodeposited and investigated the correlation between the gas sensitivity and some factors such as the morphology of ZnO and the properties of the deposited metal. Among the samples, Au/ZnO nanorod showed the best response (~86%) to the exposure of 100 ppm CO gas at 200 °C. The result showed that the electrical properties due to the deposition of metal species also have a strong influence on the sensor properties such as sensor response, working temperature, the response and recovery time, etc., together with the morphology of ZnO.
Synthesis, Physicochemical Characterization, and Cytotoxicity Assessment of Rh Nanoparticles with Different Morphologies-as Potential XFCT Nanoprobes
Authors: Li Yuyang , Saladino Giovanni M. , Shaker Kian , Svenda Martin , Vogt Carmen , Brodin Bertha , Hertz Hans M. , Toprak Muhammet S.
Published: October 2020

Morphologically controllable synthesis of Rh nanoparticles (NPs) was achieved by the use of additives during polyol synthesis. The effect of salts and surfactant additives including PVP, sodium acetate, sodium citrate, CTAB, CTAC, and potassium bromide on Rh NPs morphology was investigated. When PVP was used as the only additive, trigonal NPs were obtained. Additives containing Br− ions (CTAB and KBr) resulted in NPs with a cubic morphology, while those with carboxyl groups (sodium citrate and acetate) formed spheroid NPs. The use of Cl− ions (CTAC) resulted in a mixture of polygon morphologies. Cytotoxicity of these NPs was evaluated on macrophages and ovarian cancer cell lines. Membrane integrity and cellular activity are both influenced to a similar extent, for both the cell lines, with respect to the morphology of Rh NPs. The cells exposed to trigonal Rh NPs showed the highest viability, among the NP series. Particles with a mixed polygon morphology had the highest cytotoxic impact, followed by cubic and spherical NPs. The Rh NPs were further demonstrated as contrast agents for X-ray fluorescence computed tomography (XFCT) in a small-animal imaging setting. This work provides a detailed route for the synthesis, morphology control, and characterization of Rh NPs as viable contrast agents for XFCT bio-imaging.
New Nanostructured Carbon Coating Inhibits Bacterial Growth, but Does Not Influence on Animal Cells
Authors: Barkhudarov Eduard M. , Kossyi Igor A. , Anpilov Andrey M. , Ivashkin Petr I. , Artem’ev Konstantin V. , Moryakov Igor V. , Misakyan Mamikon A. , Christofi Nick , Burmistrov Dmitry E. , Smirnova Veronika V. , Ivanyuk Veronika V. , Bunkin Nikolay F. , Kozlov Valery A. , Penkov Nikita V. , Sharapov Mars G. , Volkov Mikhail Yu. , Sevostyanov Mikhail A. , Lisitsyn Andrey B. , Semenova Anastasia A. , Rebezov Maksim B. , Gudkov Sergey V.
Published: October 2020

An electrospark technology has been developed for obtaining a colloidal solution containing nanosized amorphous carbon. The advantages of the technology are its low cost and high performance. The colloidal solution of nanosized carbon is highly stable. The coatings on its basis are nanostructured. They are characterized by high adhesion and hydrophobicity. It was found that the propagation of microorganisms on nanosized carbon coatings is significantly hindered. At the same time, eukaryotic animal cells grow and develop on nanosized carbon coatings, as well as on the nitinol medical alloy. The use of a colloidal solution as available, cheap and non-toxic nanomaterial for the creation of antibacterial coatings to prevent biofilm formation seems to be very promising for modern medicine, pharmaceutical and food industries.
Enhanced High-Temperature (600 °C) NO2 Response of ZnFe2O4 Nanoparticle-Based Exhaust Gas Sensors
Authors: Afzal Adeel , Mujahid Adnan , Iqbal Naseer , Javaid Rahat , Qazi Umair Yaqub
Published: October 2020

Fabrication of gas sensors to monitor toxic exhaust gases at high working temperatures is a challenging task due to the low sensitivity and narrow long-term stability of the devices under harsh conditions. Herein, the fabrication of a chemiresistor-type gas sensor is reported for the detection of NO2 gas at 600 °C. The sensing element consists of ZnFe2O4 nanoparticles prepared via a high-energy ball milling and annealed at different temperatures (600–1000 °C). The effects of annealing temperature on the crystal structure, morphology, and gas sensing properties of ZnFe2O4 nanoparticles are studied. A mixed spinel structure of ZnFe2O4 nanoparticles with a lattice parameter of 8.445 Å is revealed by X-ray diffraction analysis. The crystallite size and X-ray density of ZnFe2O4 nanoparticles increase with the annealing temperature, whereas the lattice parameter and volume are considerably reduced indicating lattice distortion and defects such as oxygen vacancies. ZnFe2O4 nanoparticles annealed at 1000 °C exhibit the highest sensitivity (0.13% ppm–1), sharp response (τres = 195 s), recovery (τrec = 17 s), and linear response to 100–400 ppm NO2 gas. The annealing temperature and oxygen vacancies play a major role in determining the sensitivity of devices. The plausible sensing mechanism is discussed. ZnFe2O4 nanoparticles show great potential for high-temperature exhaust gas sensing applications.
Effect of Random Nanostructured Metallic Environments on Spontaneous Emission of HITC Dye
Authors: Rout Sangeeta , Qi Zhen , Petrosyan Ludvig S. , Shahbazyan Tigran V. , Biener Monika M. , Bonner Carl E. , Noginov Mikhail A.
Published: October 2020

We have studied emission kinetics of HITC laser dye on top of glass, smooth Au films, and randomly structured porous Au nanofoams. The observed concentration quenching of luminescence of highly concentrated dye on top of glass (energy transfer to acceptors) and the inhibition of the concentration quenching in vicinity of smooth Au films were in accord with our recent findings. Intriguingly, the emission kinetics recorded in different local spots of the Au nanofoam samples had a spread of the decay rates, which was large at low dye concentrations and became narrower with increase of the dye concentration. We infer that in different subvolumes of Au nanofoams, HITC molecules are coupled to the nanofoams weaker or stronger. The inhibition of the concentration quenching in Au nanofoams was stronger than on top of smooth Au films. This was true for all weakly and strongly coupled subvolumes contributing to the spread of the emission kinetics. The experimental observations were explained using theoretical model accounting for change in the Förster radius caused by the strong energy transfer to metal.