bluuebunny/crossref_metadata_2025 huggingface dataset:
Candida spp./Bacteria Mixed Biofilms
Authors: Rodrigues Maria Elisa , Gomes Fernanda , Rodrigues Célia F.
Published: December 2019

The ability to form biofilms is a common feature of microorganisms, such as bacteria or fungi. These consortiums can colonize a variety of surfaces, such as host tissues, dentures, and catheters, resulting in infections highly resistant to drugs, when compared with their planktonic counterparts. This refractory effect is particularly critical in polymicrobial biofilms involving both fungi and bacteria. This review emphasizes Candida spp.-bacteria biofilms, the epidemiology of this community, the challenges in the eradication of such biofilms, and the most relevant treatments.
A Quantitative Analysis of Risk Premia in the Corporate Bond Market
Authors: Cecchetti Sara
Published: December 2019

Measures of corporate credit risk incorporate compensation for unpredictable future changes in the credit environment and compensation for expected default losses. Since the launch of purchases of government securities and corporate securities by the European Central Bank, it has been discussed whether the observed reduction in corporate credit risk was due to the decrease in risk aversion favored by the monetary easing or by expectations of lower losses due to corporate defaults. This work introduces a new methodology to break down the factors that drive corporate credit risk, namely the premium linked to cyclical and monetary conditions and that linked to the restructuring of the companies. Untangling these two components makes it possible to quantify the drivers of excess returns in the corporate bond market.
Structural Characterisation and Chemical Stability of Commercial Fibrous Carbons in Molten Lithium Salts
Authors: Karakashov Blagoj , Fierro Vanessa , Mathieu Sandrine , Gadonneix Philippe , Medjahdi Ghouti , Celzard Alain
Published: December 2019

The growing trend towards sustainable energy production, while intermittent, can meet all the criteria of energy demand through the use and development of high-performance thermal energy storage (TES). In this context, high-temperature hybrid TES systems, based upon the combination of fibrous carbon hosts and peritectic phase change materials (PCMs), are seen as promising solutions. One of the main conditions for the operational viability of hybrid TES is the chemical inertness between the components of the system. Thus, the chemical stability and compatibility of several commercial carbon felts (CFs) and molten lithium salts are discussed in the present study. Commercial CFs were characterised by elemental analysis, X-ray diffraction (XRD) and Raman spectroscopy before being tested in molten lithium salts: LiOH, LiBr, and the LiOH/LiBr peritectic mixture defined as our PCM of interest. The chemical stability was evaluated by gravimetry, gas adsorption and scanning electron microscopy (SEM). Among the studied CFs, the materials with the highest carbon purity and the most graphitic structure showed improved stability in contact with molten lithium salts, even under the most severe test conditions (750 °C). The application of the Arrhenius law allowed calculating the activation energy (in the range of 116 to 165 kJ mol−1), and estimating the potential stability of CFs at actual application temperatures. These results confirmed the applicability of CFs as porous hosts for stabilising peritectic PCMs based on molten lithium salts.
The Effect of Hot Working on the Mechanical Properties of High Strength Biomedical Ti-Nb-Ta-Zr-O Alloy
Authors: Preisler Dalibor , Janeček Miloš , Harcuba Petr , Džugan Jan , Halmešová Kristýna , Málek Jaroslav , Veverková Anna , Stráský Josef
Published: December 2019

Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt%) was developed as a material intended for the manufacturing of a stem of a hip joint replacement. This alloy contains only biocompatible elements and possesses a very high yield strength already in the cast condition (900 MPa). However, the porosity, large grain size and chemical inhomogeneity reduce the fatigue performance below the limits required for utilization in the desired application. Two methods of hot working, die forging and hot rolling, were used for processing of this alloy. Microstructural evolution, tensile properties and fatigue performance of the hot worked material were investigated and compared to the cast material. Microstructural observations revealed that porosity is removed in all hot-worked conditions and the grain size is significantly reduced when the area reduction exceeds 70%. Static tensile properties were improved by both processing methods and ultimate tensile strength (UTS) of 1200 MPa was achieved. Fatigue results were more reproducible in the hot rolled material due to better microstructural homogeneity, but forging leads to an improved fatigue performance. Fatigue limit of 400 MPa was achieved in the die-forged condition after 70% of area reduction and in the hot rolled condition after 86% of area reduction.
Visible-Light Activated Titania and Its Application to Photoelectrocatalytic Hydrogen Peroxide Production
Authors: Santos Andrade Tatiana , Papagiannis Ioannis , Dracopoulos Vassilios , César Pereira Márcio , Lianos Panagiotis
Published: December 2019

Photoelectrochemical cells have been constructed with photoanodes based on mesoporous titania deposited on transparent electrodes and sensitized in the Visible by nanoparticulate CdS or CdS combined with CdSe. The cathode electrode was an air–breathing carbon cloth carrying nanoparticulate carbon. These cells functioned in the Photo Fuel Cell mode, i.e., without bias, simply by shining light on the photoanode. The cathode functionality was governed by a two-electron oxygen reduction, which led to formation of hydrogen peroxide. Thus, these devices were employed for photoelectrocatalytic hydrogen peroxide production. Two-compartment cells have been used, carrying different electrolytes in the photoanode and cathode compartments. Hydrogen peroxide production has been monitored by using various electrolytes in the cathode compartment. In the presence of NaHCO3, the Faradaic efficiency for hydrogen peroxide production exceeded 100% due to a catalytic effect induced by this electrolyte. Photocurrent has been generated by either a CdS/TiO2 or a CdSe/CdS/TiO2 combination, both functioning in the presence of sacrificial agents. Thus, in the first case ethanol was used as fuel, while in the second case a mixture of Na2S with Na2SO3 has been employed.
HPMC- and PLGA-Based Nanoparticles for the Mucoadhesive Delivery of Sitagliptin: Optimization and In Vivo Evaluation in Rats
Authors: Nair Anroop B. , Sreeharsha Nagaraja , Al-Dhubiab Bandar E. , Hiremath Jagadeesh G. , Shinu Pottathil , Attimarad Mahesh , Venugopala Katharigatta N. , Mutahar Mohamed
Published: December 2019

Mucoadhesive nanoparticles represent a potential drug delivery strategy to enhance the therapeutic efficacy in oral therapy. This study assessed the prospective of developing HPMC- and PLGA-based nanoparticles using a nanospray drier as a mucoadhesive extended release drug delivery system for sitagliptin and evaluated their potential in an animal model. Nanoparticles were prepared using a Buchi® B-90 nanospray drier. Optimization of particle size was performed using response surface methodology by examining the influence of spray-drying process variables (inlet temperature, feed flow, and polymer concentration) on the particle size. The prepared nanoparticles were characterized for various physicochemical characteristics (yield, drug content, morphology, particle size, thermal, and crystallographic properties) and assessed for drug release, stability, and mucoadhesive efficacy by ex vivo and in vivo studies in rats. A linear model was suggested by the design of the experiments to be the best fit for the generated design and values. The yield was 77 ± 4%, and the drug content was 90.5 ± 3.5%. Prepared nanoparticles showed an average particle size of 448.8 nm, with a narrow particle size distribution, and were wrinkled. Thermal and crystallographic characteristics showed that the drug present in the nanoparticles is in amorphous dispersion. Nanoparticles exhibited a biphasic drug release with an initial rapid release (24.9 ± 2.7% at 30 min) and a prolonged release (98.9 ± 1.8% up to 12 h). The ex vivo mucoadhesive studies confirmed the adherence of nanoparticles in stomach mucosa for a long period. Histopathological assessment showed that the formulation is safe for oral drug delivery. Nanoparticles showed a significantly higher (p < 0.05) amount of sitagliptin retention in the GIT (gastrointestinal tract) as compared to control. The data observed in this study indicate that the prepared mucoadhesive nanoparticles can be an effective alternative delivery system for the oral therapy of sitagliptin.
Effect of Trace Zn Addition on Interfacial Evolution in Sn-10Bi/Cu Solder Joints during Aging Condition
Authors: Wang Qingfeng , Chen Hong , Wang Fengjiang
Published: December 2019

Excessive growth of intermetallic compounds (IMCs) during service affects the reliability of solder joints, so how to suppress the growth of IMC thickness at the interface in solder joints becomes a widespread concern. In this work, the interfacial reaction between Sn-10Bi solder and Cu substrate after thermal aging was investigated. Moreover, to depress the IMC growth at the interface, trace amounts of Zn was added into the Sn-10Bi solder, and the interfacial reactions of Sn-10Bi-xZn solders (x = 0.2, 0.5) and Cu substrate after thermal aging were studied in this paper. Compounds such as Cu6(Sn, Zn)5 and Cu5Zn8 were formed at the interface after adding trace amounts of Zn. The addition of 0.2 and 0.5 wt% Zn significantly inhibited the thickness growth of IMCs and the formation of Cu3Sn IMC at the interface of Sn-10Bi-0.2Zn/Cu and Sn-10Bi-0.5Zn/Cu during thermal aging. Therefore, the addition of trace Zn had an obvious effect on the interfacial reaction of Sn-10Bi/Cu solder joint. Interestingly, the evolution of IMC thickness in Sn-10Bi-0.5Zn/Cu solder joints was completely different from that in Sn-10Bi or Sn-10Bi-0.2Zn solder joints, in which the spalling of IMCs occurred. In order to explore the mechanisms on the depressing effect from the addition of trace Zn, the activation energy Q in solder joints during aging was calculated.
Micro–Macro Relationships in the Simulation of Wave Propagation Phenomenon Using the Discrete Element Method
Authors: Rojek Jerzy , Madan Nikhil , Nosewicz Szymon
Published: December 2019

The present work is aimed to investigate the capability of the discrete element method (DEM) to model properly wave propagation in solid materials, with special focus on the determination of elastic properties through wave velocities. Reference micro–macro relationships for elastic constitutive parameters have been based on the kinematic hypothesis as well as obtained numerically by simulation of a quasistatic uniaxial compression test. The validity of these relationships in the dynamic analysis of the wave propagation has been checked. Propagation of the longitudinal and shear wave pulse in rectangular sample discretized with discs has been analysed. Wave propagation velocities obtained in the analysis have been used to determine elastic properties. Elastic properties obtained in the dynamic analysis have been compared with those determined by simulation of the quasistatic compression test.
Methods of Gold and Silver Nanoparticles Preparation
Authors: Slepička Petr , Slepičková Kasálková Nikola , Siegel Jakub , Kolská Zdeňka , Švorčík Václav
Published: December 2019

The versatile family of nanoparticles is considered to have a huge impact on the different fields of materials research, mostly nanoelectronics, catalytic chemistry and in study of cytocompatibility, targeted drug delivery and tissue engineering. Different approaches for nanoparticle preparation have been developed, not only based on “bottom up” and “top down” techniques, but also several procedures of effective nanoparticle modifications have been successfully used. This paper is focused on different techniques of nanoparticles’ preparation, with primary focus on metal nanoparticles. Dispergation methods such as laser ablation and vacuum sputtering are introduced. Condensation methods such as reduction with sodium citrate, the Brust–Schiffrin method and approaches based on ultraviolet light or biosynthesis of silver and gold are also discussed. Basic properties of colloidal solutions are described. Also a historical overview of nanoparticles are briefly introduced together with short introduction to specific properties of nanoparticles and their solutions.
The Effect of the Parameters of T-RTM on the Properties of Polyamide 6 Prepared by in Situ Polymerization
Authors: Semperger Orsolya Viktória , Suplicz András
Published: December 2019

With the rapid development of the automotive industry, there is also a significant need to improve the raw materials used. Therefore, the demand is increasing for polymer composites with a focus on mass reduction and recyclability. Thermoplastic polymers are preferred because of their recyclability. As the automotive industry requires mass production, they require a thermoplastic raw material that can impregnate the reinforcement in a short cycle time. The most suitable monomer for this purpose is caprolactam. It can be most efficiently processed with T-RTM (thermoplastic resin transfer molding) technology, during which polyamide 6 is produced from the low-viscosity monomer by anionic ring-opening (in situ) polymerization in a tempered mold with a sufficiently short cycle time. Manufacturing parameters, such as polymerization time and mold temperature, highly influence the morphological and mechanical properties of the product. In this paper, the properties of polyamide 6 produced by T-RTM are analyzed as a function of the production parameters. We determine the crystallinity and the residual monomer content of the samples and their effect on mechanical properties.
Fabrication of High Temperature Oxidation Resistance Nanocomposite Coatings on PEO Treated TC21 Alloy
Authors: Zhou Kai , Xie Faqin , Wu Xiangqing , Wang Shaoqing
Published: December 2019

The effects of ZrO2 nanoparticles in a NaAlO2 electrolyte on the thickness, morphology, composition, structure, and high temperature oxidation resistance of plasma electrolytic oxidation (PEO) coatings on a TC21 titanium alloy were investigated. The coating thickness increased with increasing concentration of ZrO2 nanoparticles in the electrolyte, accompanied by a decrease in the porosity of the coating surface. The PEO coatings formed in the ZrO2 nanoparticle-free electrolyte were composed of Al2TiO5. ZrTiO4, m-ZrO2, and t-ZrO2 were detected in the PEO coatings produced by the electrolyte that contained ZrO2 nanoparticles, which indicated that the deposition mechanism of the nanoparticles was partly reactive incorporation. The high temperature oxidation resistance of the TC21 titanium alloy at 650 °C and 750 °C was improved by 3–5 times after PEO treatment. The oxidation mechanism involved oxygen diffusing inward to form an oxide layer at the interface of the PEO coating and substrate.
In-situ Deposition of Graphene Oxide Catalyst for Efficient Photoelectrochemical Hydrogen Evolution Reaction Using Atmospheric Plasma
Authors: Alam Khurshed , Sim Yelyn , Yu Ji-Hun , Gnanaprakasam Janani , Choi Hyeonuk , Chae Yujin , Sim Uk , Cho Hoonsung
Published: December 2019

The vacuum deposition method requires high energy and temperature. Hydrophobic reduced graphene oxide (rGO) can be obtained by plasma-enhanced chemical vapor deposition under atmospheric pressure, which shows the hydrophobic surface property. Further, to compare the effect of hydrophobic and the hydrophilic nature of catalysts in the photoelectrochemical cell (PEC), the prepared rGO was additionally treated with plasma that attaches oxygen functional groups effectively to obtain hydrophilic graphene oxide (GO). The hydrogen evolution reaction (HER) electrocatalytic activity of the hydrophobic rGO and hydrophilic GO deposited on the p-type Si wafer was analyzed. Herein, we have proposed a facile way to directly deposit the surface property engineered GO.
One-Pot Sonochemical Synthesis of ZnO Nanoparticles for Photocatalytic Applications, Modelling and Optimization
Authors: Noman Muhammad Tayyab , Petru Michal , Militký Jiří , Azeem Musaddaq , Ashraf Muhammad Azeem
Published: December 2019

This present study proposed a successful one pot synthesis of zinc oxide nanoparticles (ZnO NPs) and their optimisation for photocatalytic applications. Zinc chloride (ZnCl2) and sodium hydroxide (NaOH) were selected as chemical reagents for the proposed study. The design of this experiment was based on the reagents’ amounts and the ultrasonic irradiations’ time. The results regarding scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy confirmed the presence of ZnO NPs with pure hexagonal wurtzite crystalline structure in all synthesised samples. Photocatalytic activity of the developed samples was evaluated against methylene blue dye solution. The rapid removal of methylene blue dye indicated the higher photocatalytic activity of the developed samples than untreated samples. Moreover, central composite design was utilised for statistical analysis regarding the obtained results. A mathematical model for the optimisation of input conditions was designed to predict the results at any given point. The role of crystallisation on the photocatalytic performance of developed samples was discussed in detail in this novel study.
Deformation Analysis of Reinforced Beams Made of Lightweight Aggregate Concrete
Authors: Bacinskas Darius , Rumsys Deividas , Sokolov Aleksandr , Kaklauskas Gintaris
Published: December 2019

In the present trend of constructing taller and longer structures, the application of lightweight aggregate concrete is becoming an increasingly important advanced solution in the modern construction industry. In engineering practice, the analysis of lightweight concrete elements is performed using the same algorithms that are applied for normal concrete elements. As an alternative to traditional engineering methods, nonlinear numerical algorithms based on constitutive material models may be used. The paper presents a comparative analysis of curvature calculations for flexural lightweight concrete elements, incorporating analytical code methods EN 1992-1 and ACI 318-19, as well as a numerical analysis using the constitutive model of cracked tensile lightweight concrete recently proposed by the authors. To evaluate the adequacy of the theoretical predictions, experimental data of 51 lightweight concrete beams of five different programs reported in the literature were collected. A comparison of theoretical and experimental results showed that the most accurate predictions are obtained using numerical analysis and the constitutive model proposed by the authors. In the future, the latter algorithm can be used as a reliable tool for improving the design standard methods or numerical modeling of lightweight concrete elements subjected to short-term loading.
Li+ Insertion in Nanostructured TiO2 for Energy Storage
Authors: Serrapede Mara , Savino Umberto , Castellino Micaela , Amici Julia , Bodoardo Silvia , Tresso Elena , Chiodoni Angelica
Published: December 2019

Nanostructured materials possess unique physical-chemical characteristics and have attracted much attention, among others, in the field of energy conversion and storage devices, for the possibility to exploit both their bulk and surface properties, enabling enhanced electron and ion transport, fast diffusion of electrolytes, and consequently high efficiency in the electrochemical processes. In particular, titanium dioxide received great attention, both in the form of amorphous or crystalline material for these applications, due to the large variety of nanostructures in which it can be obtained. In this paper, a comparison of the performance of titanium dioxide prepared through the oxidation of Ti foils in hydrogen peroxide is reported. In particular, two thermal treatments have been compared. One, at 150 °C in Ar, which serves to remove the residual hydrogen peroxide, and the second, at 450 °C in air. The material, after the treatment at 150 °C, results to be not stoichiometric and amorphous, while the treatment at 450 °C provide TiO2 in the anatase form. It turns out that not-stoichiometric TiO2 results to be a highly stable material, being a promising candidate for applications as high power Li-ion batteries, while the anatase TiO2 shows lower cyclability, but it is still promising for energy-storage devices.
Hot Deformation Behavior of a New Al–Mn–Sc Alloy
Authors: Kang Weiqi , Yang Yi , Cao Sheng , Li Lei , Xin Shewei , Wang Hao , Cao Zhiqiang , Liang Enquan , Zhang Xi , Huang Aijun
Published: December 2019

The hot deformation behavior of a new Al–Mn–Sc alloy was investigated by hot compression conducted at temperatures from 330 to 490 °C and strain rates from 0.01 to 10 s−1. The hot deformation behavior and microstructure of the alloy were significantly affected by the deformation temperatures and strain rates. The peak flow stress decreased with increasing deformation temperatures and decreasing strain rates. According to the hot deformation behavior, the constitutive equation was established to describe the steady flow stress, and a hot processing map at 0.4 strain was obtained based on the dynamic material model and the Prasad instability standard, which can be used to evaluate the hot workability of the alloy. The developed hot processing diagram showed that the instability was more likely to occur in the higher Zener–Hollomon parameter region, and the optimal processing range was determined as 420–475 °C and 0.01–0.022 s−1, in which a stable flow and a higher power dissipation were achieved.
Atomic Layer Deposition of GdCoO3 and Gd0.9Ca0.1CoO3
Authors: Duparc Marion , Sønsteby Henrik Hovde , Nilsen Ola , Sjåstad Anja Olafsen , Fjellvåg Helmer
Published: December 2019

Thin films of the catalytically interesting ternary and quaternary perovskites GdCoO3 and Gd0.9Ca0.1CoO3 are fabricated by atomic layer deposition using metal β-diketonates and ozone as precursors. The resulting thin films are amorphous as deposited and become single-oriented crystalline on LaAlO3(100) and YAlO3(100/010) after post-annealing at 650 °C in air. The crystal orientations of the films are tunable by choice and the orientation of the substrate, mitigated through the interface via solid face epitaxy upon annealing. The films exhibit no sign of Co2+. Additionally, high-aspect-ratio Si(100) substrates were used to document the suitability of the developed process for the preparation of coatings on more complex, high-surface-area structures. We believe that coatings of GdCoO3 and Gd1−xCaxCoO3 may find applications within oxidation catalysis.
Surrounding Tissue Response to Surface-Treated Zirconia Implants
Authors: Iinuma Yohei , Hirota Masatsugu , Hayakawa Tohru , Ohkubo Chikahiro
Published: December 2019

Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), which are partially stabilized zirconia, have been used for fabricating dental implants. This study investigated the soft tissue attachment, the collagen fiber orientation to zirconia at different surface conditions, and the bone response using implantation experiments in animals. The zirconia implant surfaces were treated with ultraviolet irradiation (UV), a combination of large-grit sandblasting and hydrofluoric acid etching (blastedHF), and a combination of blastedHF and UV (blastedHF+UV). The surface treated with blastedHF and blastedHF+UV appeared rough and hydrophilic. The surface treated with blastedHF+UV appeared to be superhydrophilic. Subsequently, tapered cylindrical zirconia implants were placed in the alveolar sockets of the maxillary molars of rats. The bone-to-implant contact ratio of blastedHF and blastedHF+UV implants was significantly higher than that of the non-treated controls and UV-treated implants. The four different surface-treated zirconia implants demonstrated tight soft tissue attachments. Perpendicularly oriented collagen fibers towards zirconia implants were more prominent in blastedHF and blastedHF+UV implants compared to the controls and UV-treated implants. The area of the soft tissue attachment was the greatest with the perpendicularly oriented collagen fibers of blastedHF+UV-treated implants. In conclusion, blastedHF+UV treatment could be beneficial for ensuring greater soft-tissue attachment for zirconia implants.
Percussion Drilling Hole in Cu, Al, Ti and Ni Alloys Using Ultra-Short Pulsed Laser Ablation
Authors: Zhao Wanqin , Liu Haodong , Shen Xiaowei , Wang Lingzhi , Mei Xuesong
Published: December 2019

Comparative study on micro-deep hole drilling by picosecond ultra-short pulse laser in four metals, including copper, aluminum alloy, titanium alloy, and nickel alloy, was presented. Destructive testing was performed to measure the depth, shape, and side-wall morphology of micro-deep holes in this study. Diameters and depths of micro-deep holes in four metals ablated using the same processing parameters were compared. The multiple thresholds of metals had been calculated. Relationships between hole dimensions and multiple thresholds (the average ablation threshold, the ablation threshold and the thermal threshold) and physical properties (for example, the heat capacity, the melting temperature, the optical penetration depth and the absorbance, etc.) of the four metals are examined. Furthermore, the surface and side-wall morphologies of the micro-deep holes in four metals were demonstrated. The influence mechanisms, especially the side-wall morphology, were discussed, such as the thresholds, conical emission, self-cleaning effect, physical properties of metals, the energy transmission, the plasma effect, thermochemical reaction, and so on.
Surface-Enhanced Absorption Spectroscopy for Optical Fiber Sensing
Authors: Fuglerud Silje S. , Milenko Karolina , Aksnes Astrid , Hjelme Dag R.
Published: December 2019

Visible and near-infrared spectroscopy are widely used for sensing applications but suffer from poor signal-to-noise ratios for the detection of compounds with low concentrations. Enhancement by surface plasmon resonance is a popular technique that can be utilized to increase the signal of absorption spectroscopy due to the increased near-field created close to the plasmons. Despite interest in surface-enhanced infrared absorption spectroscopy (SEIRAS), the method is usually applied in lab setups rather than real-life sensing situations. This study aimed to achieve enhanced absorption from plasmons on a fiber-optic probe and thus move closer to applications of SEIRAS. A tapered coreless fiber coated with a 100 nm Au film supported signal enhancement at visible wavelengths. An increase in absorption was shown for two dyes spanning concentrations from 5 × 10−8 mol/L to 8 × 10−4 mol/L: Rhodamine 6G and Crystal Violet. In the presence of the Au film, the absorbance signal was 2–3 times higher than from an identically tapered uncoated fiber. The results confirm that the concept of SEIRAS can be implemented on an optical fiber probe, enabling enhanced signal detection in remote sensing applications.
New Proposal for Size and Size-Distribution Evaluation of Nanoparticles Synthesized via Ultrasonic Spray Pyrolysis Using Search Algorithm Based on Image-Processing Technique
Authors: Emil Kaya Elif , Kaya Ozan , Alkan Gözde , Gürmen Sebahattin , Stopic Srecko , Friedrich Bernd
Published: December 2019

Nanoparticle properties are correlated to their size, size distribution, and shape; it is essential to accurately measure these features in the field of nanoscience. In this study, silver nanoparticles (AgNPs) were synthesized with the ultrasonic-spray-pyrolysis (USP) method from a water solution of silver nitrate. The synthesized AgNPs were characterized by Dynamic Light Scattering (DLS) analysis and Scanning Electron Microscopy (SEM) to reveal their size and size distribution. A search algorithm based on an image-processing technique to obtain particle size and particle-size distribution from SEM micrographs is proposed. In order to obtain more quantitative information and data with respect to the morphology of particles synthesized under different process parameters, SEM micrographs with a nonhomogeneous background contrast were examined via image-processing techniques in MATLAB. Due to the inhomogeneous contrast of SEM micrographs, defining an overall threshold value was insufficient in the detection of whole nanoparticles. Thus, subimages were directly created according to the maximum and minimum particle size specified by the user to determine local threshold values. The obtained results were automatically combined to represent both particle dimension and location in the SEM micrographs. We confirmed that the results of our DLS analysis, theoretical calculation, and image-processing technique were correlated with our expected results.
Effect of Different Composition on Voltage Attenuation of Li-Rich Cathode Material for Lithium-Ion Batteries
Authors: Liu Jun , Liu Qiming , Zhu Huali , Lin Feng , Ji Yan , Li Bingjing , Duan Junfei , Li Lingjun , Chen Zhaoyong
Published: December 2019

Li-rich layered oxide cathode materials have become one of the most promising cathode materials for high specific energy lithium-ion batteries owning to its high theoretical specific capacity, low cost, high operating voltage and environmental friendliness. Yet they suffer from severe capacity and voltage attenuation during prolong cycling, which blocks their commercial application. To clarify these causes, we synthesize Li1.5Mn0.55Ni0.4Co0.05O2.5 (Li1.2Mn0.44Ni0.32Co0.04O2) with high-nickel-content cathode material by a solid-sate complexation method, and it manifests a lot slower capacity and voltage attenuation during prolong cycling compared to Li1.5Mn0.66Ni0.17Co0.17O2.5 (Li1.2Mn0.54Ni0.13Co0.13O2) and Li1.5Mn0.65Ni0.25Co0.1O2.5 (Li1.2Mn0.52Ni0.2Co0.08O2) cathode materials. The capacity retention at 1 C after 100 cycles reaches to 87.5% and the voltage attenuation after 100 cycles is only 0.460 V. Combining X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), it indicates that increasing the nickel content not only stabilizes the structure but also alleviates the attenuation of capacity and voltage. Therefore, it provides a new idea for designing of Li-rich layered oxide cathode materials that suppress voltage and capacity attenuation.
Multiscale Numerical and Experimental Analysis of Tribological Performance of GO Coating on Steel Substrates
Authors: Hildyard Robin , Mohammadpour Mahdi , Saremi-Yarahmadi Sina , Pacella Manuela
Published: December 2019

Herein, nano-tribological behaviour of graphene oxide (GO) coatings is evaluated by a combination of nanoscale frictional performance and adhesion, as well as macroscale numerical modelling. A suite of characterisation techniques including atomic force microscopy (AFM) and optical interferometry are used to characterise the coatings at the asperity level. Numerical modelling is employed to consider the effectiveness of the coatings at the conjunction level. The macroscale numerical model reveals suitable deposition conditions for superior GO coatings, as confirmed by the lowest measured friction values. The proposed macroscale numerical model is developed considering both the surface shear strength of asperities of coatings obtained from AFM and the resultant morphology of the depositions obtained from surface measurements. Such a multi-scale approach, comprising numerical and experimental methods to investigate the tribological behaviour of GO tribological films has not been reported hitherto and can be applied to real-world macroscale applications such as the piston ring/cylinder liner conjunction within the modern internal combustion engine.
Orientation of Electrospun Magnetic Nanofibers Near Conductive Areas
Authors: Storck Jan Lukas , Grothe Timo , Mamun Al , Sabantina Lilia , Klöcker Michaela , Blachowicz Tomasz , Ehrmann Andrea
Published: December 2019

Electrospinning can be used to create nanofibers from diverse polymers in which also other materials can be embedded. Inclusion of magnetic nanoparticles, for example, results in preparation of magnetic nanofibers which are usually isotropically distributed on the substrate. One method to create a preferred direction is using a spinning cylinder as the substrate, which is not always possible, especially in commercial electrospinning machines. Here, another simple technique to partly align magnetic nanofibers is investigated. Since electrospinning works in a strong electric field and the fibers thus carry charges when landing on the substrate, using partly conductive substrates leads to a current flow through the conductive parts of the substrate which, according to Ampère’s right-hand grip rule, creates a magnetic field around it. We observed that this magnetic field, on the other hand, can partly align magnetic nanofibers perpendicular to the borders of the current flow conductor. We report on the first observations of electrospinning magnetic nanofibers on partly conductive substrates with some of the conductive areas additionally being grounded, resulting in partly oriented magnetic nanofibers.
Evaluation of a Zn–2Ag–1.8Au–0.2V Alloy for Absorbable Biocompatible Materials
Authors: Li Ping , Schille Christine , Schweizer Ernst , Kimmerle-Müller Evi , Rupp Frank , Han Xingting , Heiss Alexander , Richter Andreas , Legner Claudia , Klotz Ulrich E. , Geis-Gerstorfer Jürgen , Scheideler Lutz
Published: December 2019

Zinc (Zn) and Zn-based alloys have been proposed as a new generation of absorbable metals mainly owing to the moderate degradation behavior of zinc between magnesium and iron. Nonetheless, mechanical strength of pure Zn is relatively poor, making it insufficient for the majority of clinical applications. In this study, a novel Zn–2Ag–1.8Au–0.2V (wt.%) alloy (Zn–Ag–Au–V) was fabricated and investigated for use as a potential absorbable biocompatible material. Microstructural characterization indicated an effective grain-refining effect on the Zn alloy after a thermomechanical treatment. Compared to pure Zn, the Zn–Ag–Au–V alloy showed significantly enhanced mechanical properties, with a yield strength of 168 MPa, an ultimate tensile strength of 233 MPa, and an elongation of 17%. Immersion test indicated that the degradation rate of the Zn–Ag–Au–V alloy in Dulbecco’s phosphate buffered saline was approximately 7.34 ± 0.64 μm/year, thus being slightly lower than that of pure Zn. Biocompatibility tests with L929 and Saos-2 cells showed a moderate cytotoxicity, alloy extracts at 16.7%, and 10% concentration did not affect metabolic activity and cell proliferation. Plaque formation in vitro was reduced, the Zn–Ag–Au–V surface inhibited adhesion and biofilm formation by the early oral colonizer Streptococcus gordonii, indicating antibacterial properties of the alloy.
How Teacher’s Progressiveness in Using Digital Technologies Influences Levels of Pupils’ Metacognitive Knowledge in Mathematics
Authors: Chytrý Vlastimil , Říčan Jaroslav , Medová Janka
Published: December 2019

The low efficiency of using appropriate strategies to solve problems in the classroom environment is not due to the lack of knowledge of how to classify concepts, but rather due to the failure to apply this knowledge strategically. Therefore, it is necessary to find a balance between them, i.e., to let the pupils discuss the problems while supporting the teacher’s intervention. The aim of the presented study was to examine the influence of a teacher’s progressiveness on the level of metacognitive knowledge of the pupil. Altogether, 47 teachers and 278 pupils at grade 5 were participating in the study. It is shown that the approach of teachers to innovation itself has an influence on the pupil. When comparing all five groups of innovators, the difference among the categories of teachers was significant ( p = 0.044 ) with the low effect ( d c o h e n = 0.3 ) . When considering only the two almost antagonistic poles of teachers, the innovators and the late majority according to Roger’s innovation diffusion theory, this influence was very strong ( p = 0.009 ) and with medium effect ( d c o h e n = 0.725 ). Our research shows that it is necessary to address the teacher’s innovativeness, affecting the level of metacognitive knowledge of the pupil as an important prediction tool determining school success.
Formulation of Pruning Maps with Rhythmic Neural Firing
Authors: Tsai Feng-Sheng , Shih Yi-Li , Pang Chin-Tzong , Hsu Sheng-Yi
Published: December 2019

Rhythmic neural firing is thought to underlie the operation of neural function. This triggers the construction of dynamical network models to investigate how the rhythms interact with each other. Recently, an approach concerning neural path pruning has been proposed in a dynamical network system, in which critical neuronal connections are identified and adjusted according to the pruning maps, enabling neurons to produce rhythmic, oscillatory activity in simulation. Here, we construct a sort of homomorphic functions based on different rhythms of neural firing in network dynamics. Armed with the homomorphic functions, the pruning maps can be simply expressed in terms of interactive rhythms of neural firing and allow a concrete analysis of coupling operators to control network dynamics. Such formulation of pruning maps is applied to probe the consolidation of rhythmic patterns between layers of neurons in feedforward neural networks.
On the Necessary Conditions for Non-Equivalent Solutions of the Rotlet-Induced Stokes Flow in a Sphere: Towards a Minimal Model for Fluid Flow in the Kupffer’s Vesicle
Authors: Hernández-Pereira Yunay , Guerrero Adán O. , Rendón-Mancha Juan Manuel , Tuval Idan
Published: December 2019

The emergence of left–right (LR) asymmetry in vertebrates is a prime example of a highly conserved fundamental process in developmental biology. Details of how symmetry breaking is established in different organisms are, however, still not fully understood. In the zebrafish (Danio rerio), it is known that a cilia-mediated vortical flow exists within its LR organizer, the so-called Kupffer’s vesicle (KV), and that it is directly involved in early LR determination. However, the flow exhibits spatio-temporal complexity; moreover, its conversion to asymmetric development has proved difficult to resolve despite a number of recent experimental advances and numerical efforts. In this paper, we provide further theoretical insight into the essence of flow generation by putting together a minimal biophysical model which reduces to a set of singular solutions satisfying the imposed boundary conditions; one that is informed by our current understanding of the fluid flow in the KV, that satisfies the requirements for left–right symmetry breaking, but which is also amenable to extensive parametric analysis. Our work is a step forward in this direction. By finding the general conditions for the solution to the fluid mechanics of a singular rotlet within a rigid sphere, we have enlarged the set of available solutions in a way that can be easily extended to more complex configurations. These general conditions define a suitable set for which to apply the superposition principle to the linear Stokes problem and, hence, by which to construct a continuous set of solutions that correspond to spherically constrained vortical flows generated by arbitrarily displaced infinitesimal rotations around any three-dimensional axis.
Generalized Inverses Estimations by Means of Iterative Methods with Memory
Authors: Artidiello Santiago , Cordero Alicia , Torregrosa Juan R. , P. Vassileva María
Published: December 2019

A secant-type method is designed for approximating the inverse and some generalized inverses of a complex matrix A. For a nonsingular matrix, the proposed method gives us an approximation of the inverse and, when the matrix is singular, an approximation of the Moore–Penrose inverse and Drazin inverse are obtained. The convergence and the order of convergence is presented in each case. Some numerical tests allowed us to confirm the theoretical results and to compare the performance of our method with other known ones. With these results, the iterative methods with memory appear for the first time for estimating the solution of a nonlinear matrix equations.
Lattice-Boltzmann Simulations of the Convection-Diffusion Equation with Different Reactive Boundary Conditions
Authors: Du Rui , Wang Jincheng , Sun Dongke
Published: December 2019

We have tested the accuracy and stability of lattice-Boltzmann (LB) simulations of the convection-diffusion equation in a two-dimensional channel flow with reactive-flux boundary conditions. We compared several different implementations of a zero-concentration boundary condition using the Two-Relaxation-Time (TRT) LB model. We found that simulations using an interpolation of the equilibrium distribution were more stable than those based on Multi-Reflection (MR) boundary conditions. We have extended the interpolation method to include mixed boundary conditions, and tested the accuracy and stability of the simulations over a range of Damköhler and Péclet numbers.
Modelling Dependency Structures Produced by the Introduction of a Flipped Classroom
Authors: Maldonado Ana D. , Morales María
Published: December 2019

Teaching processes have been changing in the lasts few decades from a traditional lecture-example-homework format to more active strategies to engage the students in the learning process. One of the most popular methodologies is the flipped classroom, where traditional structure of the course is turned over by moving out of the classroom, most basic knowledge acquisition. However, due to the workload involved in this kind of methodology, an objective analysis of the results should be carried out to assess whether the lecturer’s workload is worth the effort or not. In this paper, we compare the results obtained from two different methodologies: traditional lecturing and flipped classroom methodology, in terms of some performance indicators and an attitudinal survey, in an introductory statistics course for engineering students. Finally, we analysed the changes in the relationships among variables of interest when the traditional teaching was moved to a flipped classroom by using Bayesian networks.
Pattern Formation and Bistability in a Generalist Predator-Prey Model
Authors: Weide Rodrigues Vagner , Cristina Mistro Diomar , Díaz Rodrigues Luiz Alberto
Published: December 2019

Generalist predators have several food sources and do not depend on one prey species to survive. There has been considerable attention paid by modellers to generalist predator-prey interactions in recent years. Erbach and collaborators in 2013 found a complex dynamics with bistability, limit-cycles and bifurcations in a generalist predator-prey system. In this paper we explore the spatio-temporal dynamics of a reaction-diffusion PDE model for the generalist predator-prey dynamics analyzed by Erbach and colleagues. In particular, we study the Turing and Turing-Hopf pattern formation with special attention to the regime of bistability exhibited by the local model. We derive the conditions for Turing instability and find the region of parameters for which Turing and/or Turing-Hopf instability are possible. By means of numerical simulations, we present the main types of patterns observed for parameters in the Turing domain. In the Turing-Hopf range of the parameters, we observed either stable patterns or homogeneous periodic distributions. Our findings reveal that movement can break the effect of hysteresis observed in the local dynamics, what can have important implication in pest management and species conservation.
Twisted Weyl Groups of Compact Lie Groups and Nonabelian Cohomology
Authors: Liu Ming , Zhang Xia
Published: December 2019

Given a compact connected Lie group G with an S 1 -module structure and a maximal compact torus T of G S 1 , we define twisted Weyl group W ( G , S 1 , T ) of G associated to S 1 -module and show that two elements of T are δ -conjugate if and only if they are in one W ( G , S 1 , T ) -orbit. Based on this, we prove that the natural map W ( G , S 1 , T ) \ H 1 ( S 1 , T ) → H 1 ( S 1 , G ) is bijective, which reduces the calculation for the nonabelian cohomology H 1 ( S 1 , G ) .
Glycosaminoglycan from Apostichopus japonicus Improves Glucose Metabolism in the Liver of Insulin Resistant Mice
Authors: Chen Yunmei , Wang Yuanhong , Yang Shuang , Yu Mingming , Jiang Tingfu , Lv Zhihua
Published: December 2019

Holothurian glycosaminoglycan isolated from Apostichopus japonicus (named AHG) can suppress hepatic glucose production in insulin resistant hepatocytes, but its effects on glucose metabolism in vivo are unknown. The present study was conducted to investigate the effects of AHG on hyperglycemia in the liver of insulin resistant mice induced by a high-fat diet (HFD) for 12 weeks. The results demonstrated that AHG supplementation apparently reduced body weight, blood glucose level, and serum insulin content in a dose-dependent manner in HFD-fed mice. The protein levels and gene expression of gluconeogenesis rate-limiting enzymes G6Pase and PEPCK were remarkedly suppressed in the insulin resistant liver. In addition, although the total expression of IRS1, Akt, and AMPK in the insulin resistant liver was not affected by AHG supplementation, the phosphorylation of IRS1, Akt, and AMPK were clearly elevated by AHG treatment. These results suggest that AHG could be a promising natural marine product for the development of an antihyperglycemic agent.
Microalgae with Immunomodulatory Activities
Authors: Riccio Gennaro , Lauritano Chiara
Published: December 2019

Microalgae are photosynthetic microorganisms adapted to live in very different environments and showing an enormous biochemical and genetic diversity, thus representing an excellent source of new natural products with possible applications in several biotechnological sectors. Microalgae-derived compounds have shown several properties, such as anticancer, antimicrobial, anti-inflammatory, and immunomodulatory. In the last decade, compounds stimulating the immune system, both innate immune response and adaptive immune response, have been used to prevent and fight various pathologies, including cancer (cancer immunotherapy). In this review we report the microalgae that have been shown to possess immunomodulatory properties, the cells and the cellular mediators involved in the mechanisms of action and the experimental models used to test immunostimulatory activities. We also report information on fractions or pure compounds from microalgae identified as having immunostimulatory activity. Given the increasing interest in microalgae as new eco-friendly source of bioactive compounds, we also discuss their possible role as source of new classes of promising drugs to treat human pathologies.