bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Analysis of Friction and Wear of Self-Lubricating Composites Used for Dry Lubrication of Ball Bearing for Space Applications
Authors: Colas Guillaume , Saulot Aurélien , Michel Yann , Filleter Tobin , Merstallinger Andreas
Published: April 2021

Lubricating space mechanisms are a challenge. Lubrication must be sustained in different environments, for a very long period of time, and without any maintenance possible. This study focuses on the self-lubricating composite used in the double transfer lubrication of ball bearing. Ball/races contacts are lubricated via the transfer of materials from the cage that is made of the composite. A dedicated tribometer has been designed for the study. A specificity of the tribometer is to not fully constrain the composite sample but to let it move, as the cage would do in the bearing. Four composites (PTFE, MoS2, glass or mineral fibers) where tested in ultrahigh vacuum and humid air environments. Transfer was achieved with morphologies and composition similar to what is observed on real bearings. Adhesion measurements performed on composite materials before and after friction allowed one to explain the differences in tribological behaviors observed (transfer quality and contact instabilities). Beyond strengthening the composites, fibers are shown to be critical in trapping mechanically and chemically the transferred material to lubricate and prevent instabilities. Equilibrium between internal cohesion of transferred material, and adhesion to counterparts must be satisfied. Mass spectrometry showed that water appears also critical in the establishment of stable transfer film, even in vacuum.
Mechanical Properties of Al Matrix Composite Enhanced by In Situ Formed SiC, MgAl2O4, and MgO via Casting Process
Authors: Jiao Yuhong , Zhu Jianfeng , Li Xuelin , Shi Chunjie , Lu Bo , Wang Fen , Abdul Waras
Published: April 2021

Al matrix composite, reinforced with the in situ synthesized 3C–SiC, MgAl2O4, and MgO grains, was produced via the casting process using phenolic resin pyrolysis products in flash mode. The contents and microstructure of the composites’ fracture characteristics were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties were tested by universal testing machine. Owing to the strong propulsion formed in turbulent flow in the pyrolysis process, nano-ceramic grains were formed in the resin pyrolysis process and simultaneously were homogeneously scattered in the alloy matrix. Thermodynamic calculation supported that the gas products, as carbon and oxygen sources, had a different chemical activity on in situ growth. In addition, ceramic (3C–SiC, MgAl2O4, and MgO) grains have discrepant contents. Resin pyrolysis in the molten alloy decreased oxide slag but increased pores in the alloy matrix. Tensile strength (142.6 ± 3.5 MPa) had no change due to the cooperative action of increased pores and fine grains; the bending and compression strength was increasing under increased contents of ceramic grains; the maximum bending strength was 378.2 MPa in 1.5% resin-added samples; and the maximum compression strength was 299.4 MPa. Lath-shaped Si was the primary effect factor of mechanical properties. The failure mechanism was controlled by transcrystalline rupture mechanism. We explain that the effects of the ceramic grains formed in the hot process at the condition of the resin exist in mold or other accessory materials. Meanwhile, a novel ceramic-reinforced Al matrix was provided. The organic gas was an excellent source of carbon, nitrogen, and oxygen to in situ ceramic grains in Al alloy.
An In Vivo Spectrophotometric Analysis of Gingival Acrylic Shade Guide
Authors: Grieco Peter C. , Da Silva John D. , Ishida Yoshiki , Ishikawa-Nagai Shigemi
Published: April 2021

Selecting shades of acrylic gingival restorative material is challenging. This study examined the shade appropriateness of five acrylic gingival restorative materials. The color was analyzed using an intraoral spectrophotometer (Crystaleye®, Olympus). The gingival color of maxillary incisors for eighty-nine patients was measured. CIELAB color coordinates (L*, a* and b*) were obtained, and the color difference ∆E (Coverage Error: CE) between shade tabs and natural gingival color of patient samples for each shade guide system were compared. Repeated ANOVA and post hoc analyses with Tukey′s HSD were performed. There was a significant difference among the mean minimum CEs of the tab sets (p < 0.01). GC Acrylic (CE = 5.89 ∆E ± 2.97) and Lucitone 199® (CE = 6.55 ± 3.33) groups exhibited CEs significantly lower than all other groups (all p < 0.001). The IvoCap® system exhibited the highest CE (10.78 ± 3.80), significantly greater than all other groups (p < 0.001). No significant differences were observed based on sex (p = 0.055) or ethnicity (p = 0.327). The GC Acrylic and Lucitone 199® shade guides showed the lowest CEs. All guides had coverage errors above 5.89 ∆E, which is larger than ∆E thresholds of acceptability. Of the materials evaluated in this study, GC Acrylic and Lucitione 199® are best able to reproduce the clinical appearance of the gingival tissue. Many patients have tissue that cannot be reproduced accurately with currently available materials.
Reduction of Load Capacity of Fiber Cement Board Facade Cladding under the Influence of Fire
Authors: Schabowicz Krzysztof , Sulik Paweł , Zawiślak Łukasz
Published: April 2021

The paper analyzes the issue of the reduction of load capacity in fiber cement board during a fire. Fiber cement boards were put under the influence of fire by using a large-scale facade model. Such a model is a reliable source of knowledge about the behavior of facade cladding and the way fire spreads. One technical solution for external walls—a ventilated facade—is gaining popularity and is used more and more often. However, the problem of the destruction during a fire of a range of different materials used in external facade cladding is insufficiently recognized. For this study, the authors used fiber cement boards as the facade cladding. Fiber cement boards are fiber-reinforced composite materials, mainly used for facade cladding, but also used as roof cladding, drywall, drywall ceiling and floorboards. This paper analyzes the effect of fire temperatures on facade cladding using a large-scale facade model. Samples were taken from external facade cladding materials that were mounted on the model at specific locations above the combustion chamber. Subsequently, three-point bending flexural tests were performed and the effects of temperature and the integrals of temperature and time functions on the samples were evaluated. The three-point bending flexural test was chosen because it is a universal method for assessing fiber cement boards, cited in Standard EN 12467. It also allows easy reference to results in other literature.
Third-Order Theory for the Bending Analysis of Laminated Thin and Thick Plates Including the Strain Gradient Effect
Authors: Bacciocchi Michele , Tarantino Angelo Marcello
Published: April 2021

The aim of the paper is the development of a third-order theory for laminated composite plates that is able to accurately investigate their bending behavior in terms of displacements and stresses. The starting point is given by the corresponding Reddy’s Third-order Shear Deformation Theory (TSDT). This model is then generalized to consider simultaneously the Classical Laminated Plate Theory (CLPT), as well as the First-order Shear Deformation Theory (FSDT). The constitutive laws are modified according to the principles of the nonlocal strain gradient approach. The fundamental equations are solved analytically by means of the Navier methodology taking into account cross-ply and angle-ply lamination schemes. The numerical applications are presented to highlight the nonlocal effects on static behavior.
Vegetable Fillers and Rapeseed Oil-Based Polyol as Natural Raw Materials for the Production of Rigid Polyurethane Foams
Authors: Leszczyńska Milena , Malewska Elżbieta , Ryszkowska Joanna , Kurańska Maria , Gloc Michał , Leszczyński Michał K. , Prociak Aleksander
Published: April 2021

The reported study concerns the introduction of renewable raw materials into the formulation of rigid polyurethane foams in the quest for the sustainable development of polymer composites. In this study, rigid polyurethane foam composites were prepared using 75 wt.% of rapeseed oil-based polyol and 15 parts per hundred parts of polyol (php) of natural fillers such as chokeberry pomace, raspberry seeds, as well as hazelnut and walnut shells. The influence of the used raw materials on the foaming process, structure, and properties of foams was investigated using a FOAMAT analyzer and a wide selection of characterization techniques. The introduction of renewable raw materials limited reactivity of the system, which reduced maximum temperature of the foaming process. Moreover, foams prepared using renewable raw materials were characterized by a more regular cell structure, a higher share of closed cells, lower apparent density, lower compressive strength and glass transition temperature, low friability (<2%), low water absorption (<1%), high dimensional stability (<±0.5%) and increased thermal stability. The proper selection and preparation of the renewable raw materials and the rational development of the polyurethane recipe composition allow for the preparation of environmentally-friendly foam products with beneficial application properties considering the demands of the circular economy in the synthesis of rigid foams.
Effect of Tensile Deformation on Residual Stress of GH4169 Alloy
Authors: Zhu Wenxiang , Zhao Fei , Yin Sheng , Liu Yuan , Yang Ronggui
Published: April 2021

In order to reduce the residual stress of the GH4169 alloy, the effect and micro-mechanism of the tensile deformation were studied. The residual stress, dislocation density, and distribution of the GH4169 alloy were analyzed by X-ray residual stress tester, X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD). The results show that: with the increase of tensile deformation, the residual stress relief first increases and then decreases. When the tensile deformation is 3%, the reduction rate of residual stress reaches the maximum, which is 90%. The mechanism of residual stress relief by the tensile treatment is that the dislocation group in the alloy is activated by tensile treatment, and the dislocation distribution in the alloy is more uniform by dislocation movement, multiplication, and annihilation so that the residual stress can be eliminated.
Tuning the Photoelectrochemical Properties of Narrow Band Gap Nanoporous Anodic SnOx Films by Simple Soaking in Water
Authors: Gurgul Magdalena , Kozieł Marcin , Zaraska Leszek
Published: April 2021

Nanoporous tin oxide layers obtained via anodic oxidation of metallic tin at the potential of 4 V in the alkaline electrolyte (1 M NaOH) were soaked in distilled water for various durations (from 2 h to 120 h) to verify the influence of water-enabled crystallization on the morphology, composition, and related optical and photoelectrochemical properties of such kind of anodic SnOx. Although water soaking generally contributes to more stoichiometric and crystalline tin oxide, it was confirmed that at the initial stages of the water-induced dissolution–redeposition process, material exhibits enhanced photoelectrochemical performance under simulated sunlight irradiation. However, long-time exposure to water results in a gradual widening of the material’s band gap, shifting of the photoelectrochemical spectra towards higher energies, and almost complete deterioration of the photoelectrochemical activity under sunlight irradiation.
Proportional Integral Derivative Control in Spark Plasma Sintering Simulations
Authors: Jiang Runjian , Torresani Elisa , Cui Guodong , Olevsky Eugene A.
Published: April 2021

The prediction of microstructure evolution and densification behavior during the spark plasma sintering (SPS) process largely depends on accurate temperature regulation. A loop feedback control algorithm called proportional integral derivative (PID) control is a practical simulation tool, but its coefficients are often determined by an inefficient “trial and error” method. This paper is devoted to proposing a numerical method based on the principles of variable coefficients to construct an optimal linear PID controller in SPS electro-thermal simulations. Different types of temperature profiles were applied to evaluate the feasibility of the proposed method. Simulation results showed that, for temperature profiles conventionally used in SPS cycles, the PID output keeps pace with the desired profile. Characterized by an imperfect time delay and overshoot/undershoot, the constructed PID controller needs further advancement to provide a more satisfactory temperature regulation for non-continuous temperature profiles. The first step towards a numerical rule for the optimal PID controller design was undertaken in this work. It is expected to provide a valuable reference for the advanced electro-thermal modeling of SPS.
On the Scale Invariance in State of the Art CNNs Trained on ImageNet
Authors: Graziani Mara , Lompech Thomas , Müller Henning , Depeursinge Adrien , Andrearczyk Vincent
Published: April 2021

The diffused practice of pre-training Convolutional Neural Networks (CNNs) on large natural image datasets such as ImageNet causes the automatic learning of invariance to object scale variations. This, however, can be detrimental in medical imaging, where pixel spacing has a known physical correspondence and size is crucial to the diagnosis, for example, the size of lesions, tumors or cell nuclei. In this paper, we use deep learning interpretability to identify at what intermediate layers such invariance is learned. We train and evaluate different regression models on the PASCAL-VOC (Pattern Analysis, Statistical modeling and ComputAtional Learning-Visual Object Classes) annotated data to (i) separate the effects of the closely related yet different notions of image size and object scale, (ii) quantify the presence of scale information in the CNN in terms of the layer-wise correlation between input scale and feature maps in InceptionV3 and ResNet50, and (iii) develop a pruning strategy that reduces the invariance to object scale of the learned features. Results indicate that scale information peaks at central CNN layers and drops close to the softmax, where the invariance is reached. Our pruning strategy uses this to obtain features that preserve scale information. We show that the pruning significantly improves the performance on medical tasks where scale is a relevant factor, for example for the regression of breast histology image magnification. These results show that the presence of scale information at intermediate layers legitimates transfer learning in applications that require scale covariance rather than invariance and that the performance on these tasks can be improved by pruning off the layers where the invariance is learned. All experiments are performed on publicly available data and the code is available on GitHub.
Molecular Mechanisms of Astaxanthin as a Potential Neurotherapeutic Agent
Authors: Bahbah Eshak I. , Ghozy Sherief , Attia Mohamed S. , Negida Ahmed , Emran Talha Bin , Mitra Saikat , Albadrani Ghadeer M. , Abdel-Daim Mohamed M. , Uddin Md. Sahab , Simal-Gandara Jesus
Published: April 2021

Neurological disorders are diseases of the central and peripheral nervous system that affect millions of people, and the numbers are rising gradually. In the pathogenesis of neurodegenerative diseases, the roles of many signaling pathways were elucidated; however, the exact pathophysiology of neurological disorders and possible effective therapeutics have not yet been precisely identified. This necessitates developing multi-target treatments, which would simultaneously modulate neuroinflammation, apoptosis, and oxidative stress. The present review aims to explore the potential therapeutic use of astaxanthin (ASX) in neurological and neuroinflammatory diseases. ASX, a member of the xanthophyll group, was found to be a promising therapeutic anti-inflammatory agent for many neurological disorders, including cerebral ischemia, Parkinson’s disease, Alzheimer’s disease, autism, and neuropathic pain. An effective drug delivery system of ASX should be developed and further tested by appropriate clinical trials.
Glycosaminoglycans from Litopenaeus vannamei Inhibit the Alzheimer’s Disease β Secretase, BACE1
Authors: Mycroft-West Courtney J. , Devlin Anthony J. , Cooper Lynsay C. , Guimond Scott E. , Procter Patricia , Guerrini Marco , Miller Gavin J. , Fernig David G. , Yates Edwin A. , Lima Marcelo A. , Skidmore Mark A.
Published: April 2021

Only palliative therapeutic options exist for the treatment of Alzheimer’s Disease; no new successful drug candidates have been developed in over 15 years. The widely used clinical anticoagulant heparin has been reported to exert beneficial effects through multiple pathophysiological pathways involved in the aetiology of Alzheimer’s Disease, for example, amyloid peptide production and clearance, tau phosphorylation, inflammation and oxidative stress. Despite the therapeutic potential of heparin as a multi-target drug for Alzheimer’s disease, the repurposing of pharmaceutical heparin is proscribed owing to the potent anticoagulant activity of this drug. Here, a heterogenous non-anticoagulant glycosaminoglycan extract, obtained from the shrimp Litopenaeus vannamei, was found to inhibit the key neuronal β-secretase, BACE1, displaying a more favorable therapeutic ratio compared to pharmaceutical heparin when anticoagulant activity is considered.
Vitamin D and VDR Gene Polymorphisms’ Association with Rheumatoid Arthritis in Lithuanian Population
Authors: Punceviciene Egle , Gaizevska Justina , Sabaliauskaite Rasa , Venceviciene Lina , Puriene Alina , Vitkus Dalius , Jarmalaite Sonata , Butrimiene Irena
Published: April 2021

Background and Objectives: Rheumatoid arthritis (RA) is a chronic, inflammatory, autoimmune, multi-factorial disease, in which environmental and genetic factors play a major role. RA is possibly linked to vitamin D deficiency and vitamin D receptor (VDR) gene polymorphisms, and research demonstrates that FokI variant susceptibility is associated with increased disease risk among Caucasians. The aim of this study was to evaluate vitamin D deficiency prevalence and its correlation to RA clinical parameters, and to determine the possible association of VDR gene polymorphisms and RA susceptibility in the Lithuanian population. Materials and Methods: Overall, 206 RA patients and 180 age- and sex-matched healthy controls were enrolled at Vilnius University Hospital Santaros Klinikos after informed consent was obtained. The disease activity score 28 C-reactive protein (DAS28 CRP), rheumatoid arthritis impact of disease (RAID) score, and health assessment questionnaire (HAQ) were recorded in RA patients, and 25(OH)D serum levels were evaluated by chemiluminescent microparticle immunoassay for all subjects. Four VDR gene polymorphisms, BsmI, FokI, ApaI, and TaqI, were assessed using real-time PCR instruments and genotyping assays in both groups. Results: The study registered a high prevalence of 25(OH)D deficiency (<50 nmol/L) in RA patients (61.55% (n = 127)). The mean serum concentration in RA patients (44.96 ± 21.92 (nmol/L)) was significantly lower than in the healthy controls (54.90 ± 22.82 (nmol/L)), p < 0.0001. A significant inverse correlation between vitamin D level, DAS28 CRP, and HAQ scores was confirmed in RA patients, with p < 0.05. Still, there was no significant association between the overall risk of RA disease for any allele or genotype of the four VDR loci tested. Conclusions: The study confirmed that vitamin D deficiency is prevalent among RA patients and the 25(OH)D level is significantly lower compared with healthy controls. Lower vitamin D concentration was related with increased disease activity and disability scores. However, genetic analysis of four VDR polymorphisms did not confer the susceptibility to RA in Lithuanian population.
Microstructures and Properties of V-Modified A380 Aluminum Alloy Produced by High Pressure Rheo-Squeeze Casting with Compound Field Treatment
Authors: Lin Chong , Chen Hanxin , Zeng Li , Wu Shusen , Fang Xiaogang
Published: April 2021

The melt of V-modified A380 alloy aluminum alloy was treated by compound field of ultrasonic vibration (UV) and electromagnetic stirring (ES) around liquidus temperatures. Then the high pressure rheo-squeeze casting (HPRSC) process was used to produce an ingot with the alloy melt obtained. The results indicate that the polygonal Si2V phase is precipitated after adding vanadium to the alloy. With the increasing of V content from 0 to 1.05%, the average length and volume fraction of β-Al5FeSi phase is decreased to 30 μm and 1.44%, respectively. The refinement effects of UV, ES, and UV-ES compound field on the microstructure of the gravity casting alloy are as follows: UV-ES > UV > ES. When the pressure is increased from 0 to 400 MPa, the size of primary α-Al is decreased gradually, the morphology of β-Al5FeSi phase is changed from an acicular to a fine fibrous-like one, and the polygonal Si2V phase is refined to fine particle with an average grain diameter of about 8 μm. The ultimate tensile strength (UTS), yield strength (YS), and elongation of the alloy without V are lower than that of the alloy with 0.7% V under the same pressure. When the pressure is 400 MPa, the UTS, YS, and elongation of T6 heat-treated HPRSC alloy with 0.7% V are 301 MPa, 182 MPa, and 3.3%, respectively. With the decrease in the length of β-Al5FeSi phase, the quality index of the HPRSC alloy is increased.
Laser Defocusing Effect on the Microstructure and Defects of 17-4PH Parts Additively Manufactured by SLM at a Low Energy Input
Authors: Leo Paola , Cabibbo Marcello , Del Prete Antonio , Giganto Sara , Martínez-Pellitero Susana , Barreiro Joaquin
Published: April 2021

In this paper, the microstructure, defects, hardness, and tensile strength of the 17-4PH specimens manufactured additively using the selective laser melting (SLM) technique were studied. The analyzed parts (10 mm size cubic specimens and tensile specimens) were manufactured with different defocus parameter values (−1, 0, +1 mm) in order to evaluate this effect with a low power laser (38 W). The study was carried out on three different sections of each cubic specimen, one perpendicular to the laser beam or SLM manufacturing direction (transversal section), and another two parallel to the laser beam direction (longitudinal sections). The specimens microstructures were analyzed with an X-ray diffraction technique, as well as optical, scanning electron, and transmission electron microscopes. Image J software was used to characterize the defects and phase ratio. In addition, hardness and tensile tests were performed according to the corresponding standards. The results show that the amount of austenitic phase and the average grain size varied with defocusing. The percentage of defective area was less than 0.25%. The analyzed defocus distance did not affect the number and average size of the defects. Adjusting the defocusing SLM parameter is important for manufacturing parts with good mechanical properties.
Comprehensive Literature Review of Hyperpolarized Carbon-13 MRI: The Road to Clinical Application
Authors: Vaeggemose Michael , F. Schulte Rolf , Laustsen Christoffer
Published: April 2021

This review provides a comprehensive assessment of the development of hyperpolarized (HP) carbon-13 metabolic MRI from the early days to the present with a focus on clinical applications. The status and upcoming challenges of translating HP carbon-13 into clinical application are reviewed, along with the complexity, technical advancements, and future directions. The road to clinical application is discussed regarding clinical needs and technological advancements, highlighting the most recent successes of metabolic imaging with hyperpolarized carbon-13 MRI. Given the current state of hyperpolarized carbon-13 MRI, the conclusion of this review is that the workflow for hyperpolarized carbon-13 MRI is the limiting factor.
An RFID-Based Self-Biased 40 nm Low Power LDO Regulator for IoT Applications
Authors: Bahramali Asghar , Lopez-Vallejo Marisa
Published: April 2021

There are emerging applications, like bridge structural health monitoring, continuous patient condition and outdoor aiding of the elderly and the disabled, where Internet of things (IoT) nodes are used with very limited accessibility and no connection to the main supply network. They may also be exposed to harsh environmental conditions. These are applications where power and available area constraints are of great concern. In this paper, we design a 1.1 V low dropout (LDO) linear regulator in 40 nm technology to be embedded in IoT nodes. To address these constraints, we used state-of-the-art, variability-aware resistor-less sub-threshold biased CMOS-only ultra low power consumption configurations having low active area. The proposed LDO is internally compensated with embedded 18 pF Miller and 10 pF load capacitances. It can supply 1 mA maximum load current with 0.8 uA quiescent current. The dropout voltage of the regulator is 200 mV with minimum input voltage of 1.3 V. The efficiency of the regulator is 84%, which is about 99% of the maximum achievable efficiency for a 200 mV dropout voltage. The whole circuit, consisting of the embedded voltage reference and the Miller and load capacitances, takes less than 0.007 mm2 of the die size with 1 μW power consumption.
An Empirical Model for the Churning Losses Prediction of Fluid Flow Analysis in Axial Piston Pumps
Authors: Li Ying , Chen Xing , Luo Hao , Zhang Jin
Published: April 2021

The manufacturing development of axial piston pumps usually takes the trend of high speed and miniaturization, and increases power density. Axial piston pumps are usually characterized as high speed to improve the power density; thus, high-speed churning losses caused by the internal rotating components stirring the oil can increase significantly. In order to improve the efficiency, more attention should be given to the churning losses in axial piston pumps, especially in high-speed conditions. Using the method of least-squares curve fitting, this paper establishes a series of formulas based on the churning losses test rig over a wide range of speeds, which enable accurate predictions of churning losses on the cylinder block and pistons. The reduction coefficient of flow resistance of multi-pistons as calculated. The new churning losses formula devoted to the cylinder block and rotating pistons was validated by comparison with experimental evidence in different geometries of axial piston pumps. According to the prediction model of churning losses, some valuable guidance methods are proposed to reduce the energy losses of the axial piston pump, which are the theoretical support for the miniaturization of axial piston pump manufacturing.
Characterization of Soil Bacteria with Potential to Degrade Benzoate and Antagonistic to Fungal and Bacterial Phytopathogens
Authors: Esikova Tatiana Z. , Anokhina Tatiana O. , Abashina Tatiana N. , Suzina Nataliya E. , Solyanikova Inna P.
Published: April 2021

The intensive development of agriculture leads to the depletion of land and a decrease in crop yields and in plant resistances to diseases. A large number of fertilizers and pesticides are currently used to solve these problems. Chemicals can enter the soil and penetrate into the groundwater and agricultural plants. Therefore, the primary task is to intensify agricultural production without causing additional damage to the environment. This problem can be partially solved using microorganisms with target properties. Microorganisms that combine several useful traits are especially valuable. The aim of this work was to search for new microbial strains, which are characterized by the ability to increase the bioavailability of nutrients, phytostimulation, the antifungal effect and the decomposition of some xenobiotics. A few isolated strains of the genera Bacillus and Pseudomonas were characterized by high activity against fungal phytopathogens. One of the bacterial strains identified as Priestiaaryabhattai on the basis of the 16S rRNA gene sequence was characterized by an unusual cellular morphology and development cycle, significantly different from all previously described bacteria of this genus. All isolated bacteria are capable of benzoate degradation as a sign of the ability to degrade aromatic compounds. Isolated strains were shown to be prospective agents in biotechnologies.
A Study of 3CLpros as Promising Targets against SARS-CoV and SARS-CoV-2
Authors: Jo Seri , Kim Suwon , Yoo Jahyun , Kim Mi-Sun , Shin Dong Hae
Published: April 2021

The outbreak of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), results in serious chaos all over the world. In addition to the available vaccines, the development of treatments to cure COVID-19 should be done quickly. One of the fastest strategies is to use a drug-repurposing approach. To provide COVID-19 patients with useful information about medicines currently being used in clinical trials, twenty-four compounds, including antiviral agents, were selected and assayed. These compounds were applied to verify the inhibitory activity for the protein function of 3CLpros (main proteases) of SARS-CoV and SARS-CoV-2. Among them, viral reverse-transcriptase inhibitors abacavir and tenofovir revealed a good inhibitory effect on both 3CLpros. Intriguingly, sildenafil, a cGMP-specific phosphodiesterase type 5 inhibitor also showed significant inhibitory function against them. The in silico docking study suggests that the active-site residues located in the S1 and S2 sites play key roles in the interactions with the inhibitors. The result indicates that 3CLpros are promising targets to cope with SAR-CoV-2 and its variants. The information can be helpful to design treatments to cure patients with COVID-19.
Phylogenomic Insights into Distribution and Adaptation of Bdellovibrionota in Marine Waters
Authors: Li Qing-Mei , Zhou Ying-Li , Wei Zhan-Fei , Wang Yong
Published: April 2021

Bdellovibrionota is composed of obligate predators that can consume some Gram-negative bacteria inhabiting various environments. However, whether genomic traits influence their distribution and marine adaptation remains to be answered. In this study, we performed phylogenomics and comparative genomics studies using 132 Bdellovibrionota genomes along with five metagenome-assembled genomes (MAGs) from deep sea zones. Four phylogenetic groups, Oligoflexia, Bdello-group1, Bdello-group2 and Bacteriovoracia, were revealed by constructing a phylogenetic tree, of which 53.84% of Bdello-group2 and 48.94% of Bacteriovoracia were derived from the ocean. Bacteriovoracia was more prevalent in deep sea zones, whereas Bdello-group2 was largely distributed in the epipelagic zone. Metabolic reconstruction indicated that genes involved in chemotaxis, flagellar (mobility), type II secretion system, ATP-binding cassette (ABC) transporters and penicillin-binding protein were necessary for the predatory lifestyle of Bdellovibrionota. Genes involved in glycerol metabolism, hydrogen peroxide (H2O2) degradation, cell wall recycling and peptide utilization were ubiquitously present in Bdellovibrionota genomes. Comparative genomics between marine and non-marine Bdellovibrionota demonstrated that betaine as an osmoprotectant is probably widely used by marine Bdellovibrionota, and all the marine genomes have a number of genes for adaptation to marine environments. The genes encoding chitinase and chitin-binding protein were identified for the first time in Oligoflexia, which implied that Oligoflexia may prey on a wider spectrum of microbes. This study expands our knowledge on adaption strategies of Bdellovibrionota inhabiting deep seas and the potential usage of Oligoflexia for biological control.
Control of the Redox Potential by Microcontroller Technology: Researching the Leaching of Chalcopyrite
Authors: Sun Xin , Yuan Wenbing , Jin Kai , Zhang Yansheng
Published: April 2021

The leaching of chalcopyrite under different redox potentials was studied with a redox potential controlling device based on microcontroller technology. The leaching test was carried out in a 500 mL flask with 4 g pure chalcopyrite and 200 mL sulfuric acid. The additional total Fe concentration was 0.1 mol/kg, and the initial pH was 0.7. Chalcopyrite leaching tests with initial redox potential of 400 mV and 600 mV (vs. Ag/AgCl, the same below) and controlled redox potential of 350 mV, 400 mV, 450 mV, 500 mV, and 600 mV were carried out at a temperature of 60 °C and a stirring speed of 300 rpm. The results showed that the dissolution of chalcopyrite could not be hindered until the granular intermediates (S0 and Sn2−) accumulated to a certain amount on the chalcopyrite surface. The main passivating species in chalcopyrite dissolution may be iron-deficient polysulfides. At 400 mV, the chalcopyrite passivation by polysulfides was overcome by the galvanic effect between pyrite and chalcopyrite, and the chalcopyrite was rapidly oxidized with Cu leaching rate reaching up to 32% in 7 h, while it was only 15% in the other experimental groups. However, at 450–500 mV, pyrite was oxidized and the galvanic effect between chalcopyrite and pyrite was destroyed, leading to a significant decrease in Cu leaching rate. When the redox potential was 600 mV, the dissolution of metal-deficient polysulfides was promoted; thus, the passivation was weakened.
Chemical Mapping to Evaluate Post-Depositional Diagenesis among the Earliest Ceramics in the Teotihuacan Valley, Mexico
Authors: Stoner Wesley D. , Shaulis Barry J.
Published: April 2021

Chemical and mineral sourcing techniques are commonly employed in archaeology to reconstruct patterns of ceramic exchange and raw material procurement practices for the past, but the effects of post-depositional diagenesis are still often ignored despite a number of key studies warning that the composition of ceramics from archaeological deposits often diverges greatly from their original composition at the time of production. This current study on diagenesis derives from a large chemical and petrographic analysis of some of the earliest ceramics (1500–100 cal Before Common Era [BCE]) in the Basin of Mexico at a time when the development of ceramic trade networks helped to spread early stylistic canons across Mesoamerica. One important site, Altica, consistently presents ceramics that are high in barium. We use laser ablation-inductively coupled plazma—mass spectrometry (LA-ICP-MS) to map the cross-sections of several samples from this site with the idea that post-depositional intake of mobile cations would appear as enriched at the surfaces of the pottery and around pores. Conversely, cations that leach out of the fabric would exhibit depleted concentrations in those same areas. We find that barium and a suite of other elements (e.g., copper, zinc, lead, tin, arsenic, calcium, strontium, and vanadium) have been chemically altered due to nearly 3000 years of burial in the soil. We explore the implications of those revelations for properly sourcing archaeological ceramics found at the Altica site and provide additional guidance for archaeologists and geochemists who employ ceramic compositional sourcing elsewhere.
Multidimensional Optimization of the Copper Flotation in a Jameson Cell by Means of Taxonomic Methods
Authors: Niedoba Tomasz , Pięta Paulina , Surowiak Agnieszka , Şahbaz Oktay
Published: April 2021

Three factors were measured in the flotation process of copper ore: the copper grade in a concentrate (β), the copper grade in tailings (ϑ), and the recovery of copper in a concentrate (ε). The experiment was conducted by means of a Jameson cell. The factors influencing the quality of the process were the particle size (d), the flotation time (t), the type of collector (k), and the dosage of the collector (s). The considered vector function is then (β(d, t, k, s), ϑ(d, t, k, s), ε(d, t, k, s)). In this work, the optimization was based on determining the values of the adjustable factors (d, t, k, s). The goal was to obtain the possibly highest values of the functions β and ε (maximum) with the possibly lowest values of the function ϑ (minimum). To this end, taxonomic methods were applied. Thanks to the applied method, the optimum—with the adopted assumptions—was found. The presented methodology can be successfully applied in the search for the optima in a variety of technological processes.
Design, Synthesis and Anticancer Activity of New Polycyclic: Imidazole, Thiazine, Oxathiine, Pyrrolo-Quinoxaline and Thienotriazolopyrimidine Derivatives
Authors: Abu-Hashem Ameen Ali , Al-Hussain Sami A. , Zaki Magdi E. A.
Published: April 2021

In this article, we showed the synthesis of new polycyclic aromatic compounds, such as thienotriazolopyrimidinones, N-(thienotriazolopyrimidine) acetamide, 2-mercapto-thienotriazolo-pyrimidinones, 2-(((thieno-triazolopyrimidine) methyl) thio) thieno-triazolopyrimidines, thieno-pyrimidotriazolo-thiazines, pyrrolo-triazolo-thienopyrimidines, thienopyrimido-triazolopyrrolo-quinoxalines, thienopyrimido-triazolo-pyrrolo-oxathiino-quinoxalinones, 1,4-oxathiino-pyrrolo- triazolothienopyrimidinones, imidazopyrrolotriazolothienopyrimidines and 1,2,4-triazoloimidazo- pyrrolotriazolothienopyrimidindiones, based on the starting material 2,3-diamino-6-benzoyl-5- methylthieno[2,3-d]pyrimidin-4(3H)-one (3). The chemical structures were confirmed using many spectroscopic ways (IR, 1H, 13C, −NMR and MS) and elemental analyses. A series of thiazine, imidazole, pyrrole, thienotriazolopyrimidine derivatives were synthesized and evaluated for their antiproliferative activity against four human cancer cell lines, i.e., CNE2 (nasopharyngeal), KB (oral), MCF-7 (breast) and MGC-803 (gastric) carcinoma cells. The compounds 20, 19, 17, 16 and 11 showed significant cytotoxicity against types of human cancer cell lines.
Electrophysiological Activity and Survival Rate of Rats Nervous Tissue Cells Depends on D/H Isotopic Composition of Medium
Authors: Kozin Stanislav , Skrebitsky Vladimir , Kondratenko Rodion , Kravtsov Alexander , Butina Elena , Moiseev Arkady , Malyshko Vadim , Baryshev Mikhail , Elkina Anna , Dzhimak Stepan
Published: April 2021

The deuterium content modification in an organism has a neuroprotective effect during the hypoxia model, affecting anxiety, memory and stress resistance. The aim of this work was to elucidate the possible mechanisms of the medium D/H composition modification on nerve cells. We studied the effect of an incubation medium with a 50 ppm deuterium content compared to a medium with 150 ppm on: (1) the activity of Wistar rats’ hippocampus CA1 field neurons, (2) the level of cultured cerebellar neuron death during glucose deprivation and temperature stress, (3) mitochondrial membrane potential (MMP) and the generation of reactive oxygen species in cultures of cerebellar neurons. The results of the analysis showed that the incubation of hippocampal sections in a medium with a 50 ppm deuterium reduced the amplitude of the pop-spike. The restoration of neuron activity was observed when sections were returned to the incubation medium with a 150 ppm deuterium content. An environment with a 50 ppm deuterium did not significantly affect the level of reactive oxygen species in neuron cultures, while MMP decreased by 16–20%. In experiments with glucose deprivation and temperature stress, the medium with 50 ppm increased the death of neurons. Thus, a short exposure of nerve cells in the medium with 50 ppm deuterium acts as an additional stressful factor, which is possibly associated with the violation of the cell energy balance. The decrease in the mitochondrial membrane potential, which is known to be associated with ATP synthesis, indicates that this effect may be associated with the cell energy imbalance. The decrease in the activity of the CA1 field hippocampal neurons may reflect reversible adaptive changes in the operation of fast-reacting ion channels.
Solanum anguivi Lam. Fruits: Their Potential Effects on Type 2 Diabetes Mellitus
Authors: Nakitto Aisha Musaazi Sebunya , Muyonga John H. , Byaruhanga Yusuf Byenkya , Wagner Anika E.
Published: April 2021

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder of glucose homeostasis associated with a status of insulin resistance, impaired insulin signaling, β-cell dysfunction, impaired glucose and lipid metabolism, sub-clinical inflammation, and increased oxidative stress. Consuming fruits and vegetables rich in phytochemicals with potential antidiabetic effects may prevent T2DM and/or support a conservative T2DM treatment while being safer and more affordable for people from low-income countries. Solanum anguivi Lam. fruits (SALF) have been suggested to exhibit antidiabetic properties, potentially due to the presence of various phytochemicals, including saponins, phenolics, alkaloids, ascorbic acid, and flavonoids. For the saponin fraction, antidiabetic effects have already been reported. However, it remains unclear whether this is also true for the other phytochemicals present in SALF. This review article covers information on glucose homeostasis, T2DM pathogenesis, and also the potential antidiabetic effects of phytochemicals present in SALF, including their potential mechanisms of action.
Isolation, Structure Elucidation and In Silico Prediction of Potential Drug-Like Flavonoids from Onosma chitralicum Targeted towards Functionally Important Proteins of Drug-Resistant Bad Bugs
Authors: Khan Shakeel Ahmad , Khan Shafi Ullah , Fozia  , Ullah Najeeb , Shah Mohibullah , Ullah Riaz , Ahmad Ijaz , Alotaibi Amal
Published: April 2021

Admittedly, the disastrous emergence of drug resistance in prokaryotic and eukaryotic human pathogens has created an urgent need to develop novel chemotherapeutic agents. Onosma chitralicum is a source of traditional medicine with cooling, laxative, and anthelmintic effects. The objective of the current research was to analyze the biological potential of Onosma chitralicum, and to isolate and characterize the chemical constituents of the plant. The crude extracts of the plant prepared with different solvents, such as aqueous, hexane, chloroform, ethyl acetate, and butanol, were subjected to antimicrobial activities. Results corroborate that crude (methanol), EtoAc, and n-C6H14 fractions were more active against bacterial strains. Among these fractions, the EtoAc fraction was found more potent. The EtoAc fraction was the most active against the selected microbes, which was subjected to successive column chromatography, and the resultant compounds 1 to 7 were isolated. Different techniques, such as UV, IR, and NMR, were used to characterize the structures of the isolated compounds 1–7. All the isolated pure compounds (1–7) were tested for their antimicrobial potential. Compounds 1 (4′,8-dimethoxy-7-hydroxyisoflavone), 6 (5,3′,3-trihydroxy-7,4′-dimethoxyflavanone), and 7 (5′,7,8-trihydroxy-6,3′,4′-trimethoxyflavanone) were found to be more active against Staphylococcus aureus and Salmonella Typhi. Compound 1 inhibited S. typhi and S. aureus to 10 ± 0.21 mm and 10 ± 0.45 mm, whereas compound 6 showed inhibition to 10 ± 0.77 mm and 9 ± 0.20 mm, respectively. Compound 7 inhibited S. aureus to 6 ± 0.36 mm. Compounds 6 and 7 showed significant antibacterial potential, and the structure–activity relationship also justifies their binding to the bacterial enzymes, i.e., beta-hydroxyacyl dehydratase (HadAB complex) and tyrosyl-tRNA synthetase. Both bacterial enzymes are potential drug targets. Further, the isolated compounds were found to be active against the tested fungal strains. Whereas docking identified compound 7, the best binder to the lanosterol 14α-demethylase (an essential fungal cell membrane synthesizing enzyme), reported as an antifungal fluconazole binding enzyme. Based on our isolation-linked preliminary structure-activity relationship (SAR) data, we conclude that O. chitralicum can be a good source of natural compounds for drug development against some potential enzyme targets.
Au@Pt Core-Shell Nanoparticle Bioconjugates for the Therapy of HER2+ Breast Cancer and Hepatocellular Carcinoma. Model Studies on the Applicability of 193mPt and 195mPt Radionuclides in Auger Electron Therapy
Authors: Wawrowicz Kamil , Majkowska-Pilip Agnieszka , Gaweł Damian , Chajduk Ewelina , Pieńkowski Tadeusz , Bilewicz Aleksander
Published: April 2021

193mPt and 195mPt radionuclides are therapeutically attractive Auger electron emitters with notably high Auger electron yield per decay. The present paper summarizes the first step of research on the applications of core-shell (Au@Pt) nanoparticles for electron Auger therapy of HER2+ (human epidermal growth factor receptor 2) breast cancer and hepatocellular carcinoma. Gold nanoparticles (30 nm) were synthesized covered with a platinum shell at high efficiency (>80%) and were further evaluated for in vitro studies such as binding affinity, internalization and cytotoxicity. To find the mechanism(s) responsible for platinum cytotoxicity in HepG2 cells, the platinum concentration in isolated cell nuclei and cytoplasm was determined using ICP-MS (inductively coupled plasma mass spectrometry). Lack of platinum in cell nuclei suggests that the cytotoxic effect is associated with the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Studies carried out on the SKOV-3 cell line with the use of a synthesized targeting bioconjugate (Au@Pt-PEG-trastuzumab) revealed a high affinity of this preparation to HER2+ cells, its internalization, its placement in the perinuclear area and partial intranuclear location. The specific binding for HER2 negative cells, MDA-MB-231, was negligible and Au@Pt-PEG-trastuzumab did not enter these cells. The results obtained are promising and warrant future investigation of Auger electron therapy using 193mPt and 195mPt based radiopharmaceuticals.
Sugar-Based Ionic Liquids: Multifaceted Challenges and Intriguing Potential
Authors: Zullo Valerio , Iuliano Anna , Guazzelli Lorenzo
Published: April 2021

Carbohydrates represent a promising option in transitioning from oil-based chemical resources to renewable ones, with the goal of developing chemistries for a sustainable future. Cellulose, hemicellulose, and largely available monosaccharides already provide useful chemical building blocks, so-called platform chemicals, such as levulinic acid and hydroxymethyl furfural, as well as solvents like cyrene or gamma-valerolactone. Therefore, there is great anticipation for novel applications involving materials and chemicals derived from sugars. In the field of ionic liquids (ILs), sugar-based ILs have been overlooked for a long time, mainly on account of their multistep demanding preparation. However, exploring new strategies for accessing sugar-based ILs, their study, and their exploitation, are attracting increasing interest. This is due to the growing concerns about the negative (eco)toxicity profile of most ILs in conjunction with their non-sustainable nature. In the present review, a literature survey concerning the development of sugar-based ILs since 2011 is presented. Their preparation strategies and thermal behavior analyses, sorted by sugar type, make up the first two sections with the intention to provide the reader with a useful guide. A final overview of the potential applications of sugar-based ILs and their future perspectives complement the present analysis.