bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Treatment of Zn-Mn-Mg Alloys by Micro-Arc Oxidation in Silicate-Based Solutions with Different NaF Concentrations
Authors: Sun Shineng , Ye Guo , Lu Ziting , Weng Yuming , Ma Guofeng , Liu Jiatao
Published: August 2021

Newly developed Zn-Mn-Mg alloys can be invoked as biomedical materials because of their excellent mechanical properties. However, the corrosion behavior of Zn-Mn-Mg alloys was still lacking in research. It had grown to be a hot research topic to improve the corrosion behavior of Zn alloys by surface treatment to meet the application of degradable Zn alloys in biomedical applications. Micro arc oxidation (MAO) is a simple and effective method to improve the corrosion behavior of the alloy. MAO coatings were successfully prepared on the surface of Zn-Mn-Mg alloys by MAO in silicate-based solutions with different NaF concentrations. The microstructure and phase composition of MAO coatings prepared on Zn-Mn-Mg alloys with different NaF concentrations in the electrolyte was examined by a scanning electron microscope and X-ray diffraction. The results showed that the MAO coatings are porous and mainly composed of ZnO. With the increasing NaF concentration in the electrolyte, the average thickness increases. The distribution of the micro/nanopores was uniform, and the pore size ranged from the submicron scale to several micrometers after MAO treatment in the electrolyte containing different concentrations of NaF. Potential dynamic polarization curves and electrochemical impedance spectroscopy were employed to assess the corrosion behavior of MAO coatings in Hank’s solution. The highest corrosion rate can be achieved after MAO treatment, with an electrolyte concentration of 1.5 g/L NaF in Hank’s solution. These results indicated that MAO coating can accelerate the corrosion resistance of a Zn-Mn-Mg alloy.
A Study on the Effect of Adhesive Cavities on the Scuffing Initiation in a Sliding Contact
Authors: Kaczor Grzegorz , Machno Magdalena
Published: August 2021

Scuffing is a particularly problematic wear phenomenon in sliding contact that has not yet been fully elucidated. The complicated mechanism of the development of this phenomenon results from the simultaneous influence of many factors. There is a continuous need for new research to gain a deeper understanding of the complex frictional processes that scuffing is. Components such as cams, tappets, piston rings and gears are extremely susceptible to scuffing. The idea of the research on the scuffing wear development is the study of the formation of adhesive cavities as the effects of the destruction of adhesive bonds at various operating parameters. The goal of the presented work is the analysis of the influence of the oscillation frequency on the formation of adhesive cavities leading to scuffing. The tests carried out with the use of S235 steel showed that the adhesive cavities on the surfaces of the tested components appear regardless of the adopted values of the oscillation frequency. The surfaces of the specimen and counter-specimen were analyzed before and after wear tests on the block-on-ring test stand at the different values of the oscillation frequency. The conducted research revealed that the greatest change in the values of the friction coefficient occurs with an increase in frequency from 2 to 5 Hz, and the largest change in the number of scuffing initiating cycles occurs with an increase in the oscillation frequency from 1 to 2 Hz.
Benzimidazole-Based N,O Boron Complexes as Deep Blue Solid-State Fluorophores
Authors: Vaz Patrícia A. A. M. , Rocha João , Silva Artur M. S. , Guieu Samuel
Published: August 2021

Benzimidazole-based boranils were designed and synthesized in order to assess the influence of halogen substituents on their optoelectronic properties. All compounds are photoluminescent in solution and solid state. Compared to the free ligands, the new boranils emit at a lower wavelength, by elimination of the excited-state intramolecular proton transfer observed with the ligands. In the solid state, some of the boranils exhibit a deep blue emission, presenting Commission Internationale de l’Éclairage (CIE) coordinates with an x-component of less than 0.16 and a y-component smaller than 0.04, highly desired values for the development of blue emitting materials.
Materials for Production of High and Ultra-High Performance Concrete: Review and Perspective of Possible Novel Materials
Authors: Marvila Markssuel Teixeira , de Azevedo Afonso Rangel Garcez , de Matos Paulo R. , Monteiro Sergio Neves , Vieira Carlos Maurício Fontes
Published: August 2021

This review article proposes the identification and basic concepts of materials that might be used for the production of high-performance concrete (HPC) and ultra-high-performance concrete (UHPC). Although other reviews have addressed this topic, the present work differs by presenting relevant aspects on possible materials applied in the production of HPC and UHPC. The main innovation of this review article is to identify the perspectives for new materials that can be considered in the production of novel special concretes. After consulting different bibliographic databases, some information related to ordinary Portland cement (OPC), mineral additions, aggregates, and chemical additives used for the production of HPC and UHPC were highlighted. Relevant information on the application of synthetic and natural fibers is also highlighted in association with a cement matrix of HPC and UHPC, forming composites with properties superior to conventional concrete used in civil construction. The article also presents some relevant characteristics for the application of HPC and UHPC produced with alkali-activated cement, an alternative binder to OPC produced through the reaction between two essential components: precursors and activators. Some information about the main types of precursors, subdivided into materials rich in aluminosilicates and rich in calcium, were also highlighted. Finally, suggestions for future work related to the application of HPC and UHPC are highlighted, guiding future research on this topic.
Effect of Laser Energy Density on the Microstructure and Texture Evolution of Hastelloy-X Alloy Fabricated by Laser Powder Bed Fusion
Authors: Zhang Shuzhe , Lei Yunpei , Chen Zhen , Wei Pei , Liu Wenjie , Yao Sen , Lu Bingheng
Published: August 2021

It is of great importance to study the microstructure and textural evolution of laser powder bed fusion (LPBF) formed Hastelloy-X alloys, in order to establish a close relationship between the process, microstructure, and properties through the regulation of the Hastelloy-X formation process parameters. In this paper, components of a Hastelloy-X alloy were formed with different laser energy densities (also known as the volume energy density VED). The densification mechanism of Hastelloy-X was studied, and the causes of defects, such as pores and cracks, were analyzed. The influence of different energy densities on grain size, texture, and orientation was investigated using an electron backscatter diffraction technique. The results show that the average grain size, primary dendrite arm spacing, and number of low angle grain boundaries increased with the increase of energy density. At the same time, the VED can strengthen the texture. The textural intensity increases with the increase of energy density. The best mechanical properties were obtained at the VED of 96 J·mm−3.
Synthesis, Characterization and Filtration Properties of Ecofriendly Fe3O4 Nanoparticles Derived from Olive Leaves Extract
Authors: Boudouh Djahida , Ikram Rabia , Mohamed Jan Badrul , Simon Cornelis Metselaar Hendrik , Hamana Djamel , Kenanakis George
Published: August 2021

Recently, value-added nanomaterials including nanoparticles or nanofluids have been significantly used in designing drilling fluids with tunable rheological properties to meet specific downhole and environmental requirements. In this work, we report novel water-based drilling fluids (WBDF) containing eco-friendly Fe3O4 nanoparticles (Fe3O4-NPs) prepared by using olive leaves extract (OLE) as a reducing and capping agent. A series of economical and excellent performance of WBDF was obtained by introducing low, medium, and high concentrations of Fe3O4-NPs into the conventional WBDF. The synthesis of Fe3O4-NPs was accomplished through the thermal decomposition of iron precursors in an organic medium. NPs were added to the based fluid at concentrations of 0.01, 0.1, and 0.5 wt%. Emission scanning microscopy (FESEM), field- and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Energy-dispersive X-ray analysis (EDX) were used for Fe3O4-NPs analysis. Compared to the conventional WBDF, the addition of Fe3O4-NPs as an additive in the based fluids has been investigated to help increasing viscosity and yield point, which is advantageous for hole cleaning, as well as decreasing fluid loss and mud cake thickness.
The Influence of pH on Complexation Process of Copper(II) Phosphoethanolamine to Pyrimidine Nucleosides
Authors: Gabryel-Skrodzka Malwina , Nowak Martyna , Stachowiak Klaudia , Zabiszak Michal , Ogawa Kazuma , Jastrzab Renata
Published: August 2021

The influence of pH on the complex formation of phosphoethanolamine and pyrimidine nucleosides (uridine, cytidine and thymidine) with copper(II) ions was studied. All investigations were performed in aqueous solution. The overall stability constants of the complexes and non-covalent compounds were obtained using the potentiometric method with computer calculation of the data. Moreover, equilibrium constants of the reaction were determined. The mode of coordination was obtained using spectroscopic methods. Analysis of the potentiometric and spectroscopic data confirmed the involvement and effectiveness of phosphate groups in species formation as well as the influence of pH on the mode of coordination of the investigated biomaterials. In the next step, studied complexes will be applied as potential biomaterials with biological applications.
Flexible and Stretchable Liquid Metal Electrodes Working at Sub-Zero Temperature and Their Applications
Authors: Xiao Peng , Kim Ju-Hyung , Seo Soonmin
Published: August 2021

We investigated characteristics of highly flexible and stretchable electrodes consisting of Galinstan (i.e., a gallium-based liquid metal alloy) under various conditions including sub-zero temperature (i.e., <0 °C) and demonstrated solar-blind photodetection via the spontaneous oxidation of Galinstan. For this work, a simple and rapid method was introduced to fabricate the Galinstan electrodes with precise patterns and to exfoliate their surface oxide layers. Thin conductive films possessing flexibility and stretchability can be easily prepared on flexible substrates with large areas through compression of a dried suspension of Galinstan microdroplets. Furthermore, a laser marking machine was employed to facilitate patterning of the Galinstan films at a high resolution of 20 μm. The patterned Galinstan films were used as flexible and stretchable electrodes. The electrical conductivity of these electrodes was measured to be ~1.3 × 106 S m−1, which were still electrically conductive even if the stretching ratio increased up to 130% below 0 °C. In addition, the surface oxide (i.e., Ga2O3) layers possessing photo-responsive properties were spontaneously formed on the Galinstan surfaces under ambient conditions, which could be solely exfoliated using elastomeric stamps. By combining Galinstan and its surface oxide layers, solar-blind photodetectors were successfully fabricated on flexible substrates, exhibiting a distinct increase of up to 14.7% in output current under deep ultraviolet irradiation (254 nm wavelength) with an extremely low light intensity of 0.1 mW cm−2, whereas no significant change was observed under visible light irradiation.
Additive Manufacturing of Ti-Based Intermetallic Alloys: A Review and Conceptualization of a Next-Generation Machine
Authors: Dzogbewu Thywill Cephas , du Preez Willie Bouwer
Published: August 2021

TiAl-based intermetallic alloys have come to the fore as the preferred alloys for high-temperature applications. Conventional methods (casting, forging, sheet forming, extrusion, etc.) have been applied to produce TiAl intermetallic alloys. However, the inherent limitations of conventional methods do not permit the production of the TiAl alloys with intricate geometries. Additive manufacturing technologies such as electron beam melting (EBM) and laser powder bed fusion (LPBF), were used to produce TiAl alloys with complex geometries. EBM technology can produce crack-free TiAl components but lacks geometrical accuracy. LPBF technology has great geometrical precision that could be used to produce TiAl alloys with tailored complex geometries, but cannot produce crack-free TiAl components. To satisfy the current industrial requirement of producing crack-free TiAl alloys with tailored geometries, the paper proposes a new heating model for the LPBF manufacturing process. The model could maintain even temperature between the solidified and subsequent layers, reducing temperature gradients (residual stress), which could eliminate crack formation. The new conceptualized model also opens a window for in situ heat treatment of the built samples to obtain the desired TiAl (γ-phase) and Ti3Al (α2-phase) intermetallic phases for high-temperature operations. In situ heat treatment would also improve the homogeneity of the microstructure of LPBF manufactured samples.
Redox Activity as a Powerful Strategy to Tune Magnetic and/or Conducting Properties in Benzoquinone-Based Metal-Organic Frameworks
Authors: Monni Noemi , Oggianu Mariangela , Ashoka Sahadevan Suchithra , Mercuri Maria Laura
Published: August 2021

Multifunctional molecular materials have attracted material scientists for several years as they are promising materials for the future generation of electronic devices. Careful selection of their molecular building blocks allows for the combination and/or even interplay of different physical properties in the same crystal lattice. Incorporation of redox activity in these networks is one of the most appealing and recent synthetic strategies used to enhance magnetic and/or conducting and/or optical properties. Quinone derivatives are excellent redox-active linkers, widely used for various applications such as electrode materials, flow batteries, pseudo-capacitors, etc. Quinones undergo a reversible two-electron redox reaction to form hydroquinone dianions via intermediate semiquinone radical formation. Moreover, the possibility to functionalize the six-membered ring of the quinone by various substituents/functional groups make them excellent molecular building blocks for the construction of multifunctional tunable metal-organic frameworks (MOFs). An overview of the recent advances on benzoquinone-based MOFs, with a particular focus on key examples where magnetic and/or conducting properties are tuned/switched, even simultaneously, by playing with redox activity, is herein envisioned.
Genome Mining and Metabolic Profiling Uncover Polycyclic Tetramate Macrolactams from Streptomyces koyangensis SCSIO 5802
Authors: Ding Wenjuan , Tu Jiajia , Zhang Huaran , Wei Xiaoyi , Ju Jianhua , Li Qinglian
Published: August 2021

We have previously shown deep-sea-derived Streptomyces koyangensis SCSIO 5802 to produce two types of active secondary metabolites, abyssomicins and candicidins. Here, we report the complete genome sequence of S. koyangensis SCSIO 5802 employing bioinformatics to highlight its potential to produce at least 21 categories of natural products. In order to mine novel natural products, the production of two polycyclic tetramate macrolactams (PTMs), the known 10-epi-HSAF (1) and a new compound, koyanamide A (2), was stimulated via inactivation of the abyssomicin and candicidin biosynthetic machineries. Detailed bioinformatics analyses revealed a PKS/NRPS gene cluster, containing 6 open reading frames (ORFs) and spanning ~16 kb of contiguous genomic DNA, as the putative PTM biosynthetic gene cluster (BGC) (termed herein sko). We furthermore demonstrate, via gene disruption experiments, that the sko cluster encodes the biosynthesis of 10-epi-HSAF and koyanamide A. Finally, we propose a plausible biosynthetic pathway to 10-epi-HSAF and koyanamide A. In total, this study demonstrates an effective approach to cryptic BGC activation enabling the discovery of new bioactive metabolites; genome mining and metabolic profiling methods play key roles in this strategy.
Effect of Phlorofucofuroeckol A and Dieckol Extracted from Ecklonia cava on Noise-induced Hearing Loss in a Mouse Model
Authors: Woo Hyunjun , Kim Min-Kyung , Park Sohyeon , Han Seung-Hee , Shin Hyeon-Cheol , Kim Byeong-gon , Oh Seung-Ha , Suh Myung-Whan , Lee Jun-Ho , Park Moo-Kyun
Published: August 2021

One of the well-known causes of hearing loss is noise. Approximately 31.1% of Americans between the ages of 20 and 69 years (61.1 million people) have high-frequency hearing loss associated with noise exposure. In addition, recurrent noise exposure can accelerate age-related hearing loss. Phlorofucofuroeckol A (PFF-A) and dieckol, polyphenols extracted from the brown alga Ecklonia cava, are potent antioxidant agents. In this study, we investigated the effect of PFF-A and dieckol on the consequences of noise exposure in mice. In 1,1-diphenyl-2-picrylhydrazyl assay, dieckol and PFF-A both showed significant radical-scavenging activity. The mice were exposed to 115 dB SPL of noise one single time for 2 h. Auditory brainstem response(ABR) threshold shifts 4 h after 4 kHz noise exposure in mice that received dieckol were significantly lower than those in the saline with noise group. The high-PFF-A group showed a lower threshold shift at click and 16 kHz 1 day after noise exposure than the control group. The high-PFF-A group also showed higher hair cell survival than in the control at 3 days after exposure in the apical turn. These results suggest that noise-induced hair cell damage in cochlear and the ABR threshold shift can be alleviated by dieckol and PFF-A in the mouse. Derivatives of these compounds may be applied to individuals who are inevitably exposed to noise, contributing to the prevention of noise-induced hearing loss with a low probability of adverse effects.
Perspectives and Values of Dental Medicine Students Regarding Domestic Violence
Authors: Isailă Oana-Maria , Hostiuc Sorin , Curcă George-Cristian
Published: August 2021

Background and Objectives: The purpose of this study is to evaluate dental medical students’ opinions concerning domestic violence from a social and medical standpoint and from the perspective of the moral values of the physician–patient relationship. Materials and Methods: We performed an observational study with 4- and 5-year dental medical students at the UMF “Carol Davila” in Bucharest from October 2020–May 2021, using a questionnaire containing 20 items on domestic violence (DV). The questionnaire was uploaded online on the e-learning platform where the students have access. To collect the data, we used Microsoft Excel 365, and the statistical analysis was performed using Jamovi. Results: Of the 600 students enrolled, 415 answered the questionnaire, the answering rate being 69.16%. A total of 215 (53.1%) personally knew victims of DV, 4 (1.0%) considered that violence within a couple is necessary for certain situations, 401 (99.0%) considered that domestic violence is a fundamental problem in today’s society, and 170 (41.5%) felt that in domestic violence situations, the blame lies solely with the partner who resorts to physical violence. Regarding the role of the physician, 220 (56%) considered that the physician should breach confidentiality and report cases when patients state they are a victim of DV, 337 (88.2%) thought that free medical treatment should be provided for DV victims who have a dire financial situation, and 212 (56.7%) considered that victims of DV are non-compliant patients. Conclusions: Domestic violence is a phenomenon well-known to stomatology students, which creates the premise of an excellent physician–patient relationship with them, aiding in proper management of ethical issues such as a potential need to breach confidentiality or evaluate the potential conflicts between autonomy and beneficence.
Post-Treatment Status of Impacted Maxillary Central Incisors following Surgical-Orthodontic Treatment: A Systematic Review
Authors: Žarovienė Alvyda , Grinkevičienė Dominyka , Trakinienė Giedrė , Smailienė Dalia
Published: August 2021

Background and Objectives: The aim of this systematic review was to summarize currently available data of published articles that have investigated the post-treatment status of impacted maxillary central incisors (ICI) treated by the surgical-orthodontic approach. Materials and Methods: MEDLINE, Scopus, Cochrane Oral Health Group’s Trials Register, and ScienceDirect electronic databases were systematically searched with no publication date restrictions up to January 2021. Data assessing the status of ICI after combined surgical-orthodontic treatment and forced eruption duration were extracted, and the quality of the studies was evaluated. Results: In total, 7074 studies were identified, of which 42 articles were assessed for eligibility through full-text evaluation. Seven included studies (five retrospective studies, one randomized clinical trial, and one prospective clinical trial) met the inclusion criteria, representing 211 patients with unilaterally impacted maxillary incisors. The risk of bias ranged from moderate to high. The results show that the root length of immature ICIs increased significantly but remained shorter than that of homonym teeth at post-treatment. Periodontal parameters of treated ICIs were in a clinically acceptable range. Measurements of the alveolar bone showed a reduction of bone thickness and support. The average forced eruption duration ranged from 8.0 ± 4.5 to 14.41 ± 4.03 months. Conclusions: Based on existing evidence, it is reasonable to conclude that the surgical-orthodontic treatment affected the post-treatment status of ICI; however, the current literature is insufficient to draw concrete conclusions. Further well-conducted multi-center randomized studies with a large sample are needed to confirm this statement.
An In Vitro Anti-Cancer Activity of Ocimum tenuiflorum Essential Oil by Inducing Apoptosis in Human Gastric Cancer Cell Line
Authors: Boonyanugomol Wongwarut , Rukseree Kamolchanok , Prapatpong Pornpan , Reamtong Onrapak , Baik Seung-Chul , Jung Myunghwan , Shin Min-Kyoung , Kang Hyung-Lyun , Lee Woo-Kon
Published: August 2021

Background and Objectives: The effects of Ocimum tenuiflorum essential oil (OTEO) against gastric cancer remain unknown and merit investigation. Materials and Methods: In the present study, the anti-cancer activity of OTEO was examined in a human gastric cancer cell line (AGS). After OTEO treatment, AGS cell viability was determined by an MTT assay, and inhibition of metastasis was determined by cell migration and invasion assays. The expression of apoptosis-related genes in treated AGS cells was determined by qRT-PCR. Results: OTEO significantly decreased AGS cell viability in a dose-dependent manner (IC50 163.42 µg/mL) and effectively inhibited cell migration and invasion. Morphological examination demonstrated that OTEO induced cell shrinkage, chromatin condensation, and fragmentation, which are considered typical morphologies of apoptotic cell death. Pro-apoptotic genes (TP53, BAX, and BAK) were significantly up-regulated, while anti-apoptotic genes (BCL-2 and BCL-xL) were significantly down-regulated after treatment with OTEO. In addition, significantly increased gene expression was detected for CASP8, CASP9, and CASP3 in AGS cells exposed to OTEO. GC-MS analysis demonstrated that the major compound of OTEO was caryophyllene (25.85%) and α-pinene (11.66%). Conclusions: This in vitro study demonstrates for the first time that OTEO has potential anti-gastric cancer activity and may induce apoptosis in AGS cells through extrinsic and intrinsic pathways.
A Retrospective Analysis of Pain Etiology in Middle-Aged Patients with Peripheral Neuropathy
Authors: Szewczyk Anna K. , Jamroz-Wiśniewska Anna , Rejdak Konrad
Published: August 2021

Background and Objectives: Correct assessment and a multidisciplinary approach appear to be extremely important in preventing peripheral neuropathy and its complications. The purpose of this study was to find the correlations and dissimilarities between different types of peripheral neuropathy, the occurrence of pain, and laboratory results. Materials and Methods: This retrospective study assessed 124 patients who were hospitalized in our neurology department due to various types of sensory or motor disturbances. The patients were eventually diagnosed with peripheral neuropathy, based on the electrophysiological study, anamnesis, physical examination, and laboratory results. The whole group was subjected to statistical analysis. Results: The mean age of patients was over 56 years, with a slight woman predominance. A statistically significant (p < 0.05) relationship between the place of residence and gender was seen, where more men than women live in the rural area, while more women than men live in the urban area. Most often we observed symmetric, sensorimotor, demyelinating, inflammatory, and chronic neuropathy. More than 40% of patients reported pain. A statistically significant correlation between the evolution/severity and the occurrence of pain was seen in subacute type (p < 0.05) and small fibre neuropathy (p < 0.01). Conclusions: A higher incidence of peripheral neuropathy in middle-aged people will become essential in the aging society with lifestyle and chronic disorders. Peripheral neuropathy is slightly more common in women than men and its occurrence may be influenced by work performed or internal and external factors. In the study group, more than 40% of patients reported pain, therefore the pain measurement for each patient should be implemented and repeated at every visit. An assessment of sodium level and, in women, markers of neuroinflammation level in the various types of peripheral neuropathy may be an interesting direction for the future.
Care of Geriatric Patients with Lumbar Spine, Pelvic, and Acetabular Fractures before and after Certification as a Geriatric Trauma Center DGU®: A Retrospective Cohort Study
Authors: Hafner Tobias , Kollmeier Alina , Laubach Markus , Knobe Matthias , Hildebrand Frank , Pishnamaz Miguel
Published: August 2021

Background: More than 750,000 fragility fractures occur in Germany every year, with an expected increase in the following years. Interdisciplinary care pathways for geriatric patients are increasingly established to improve the treatment process and outcome, but there has been only limited evaluation of their use. Objectives: This study aimed to compare patient care before and after the implementation of a geriatric trauma center (GTC) in conformity with the German Society for Trauma Surgery (DGU®). Patients and Methods: We performed a retrospective single-center cohort study, including 361 patients >70 years old with lumbar spine, pelvic, and acetabular fractures, admitted between January 2012 and September 2019. Patients were divided into a usual care cohort (UC, n = 137) before implementation and an ortho-geriatric care cohort (OGC, n = 224) after implementation of the GTC DGU®. We recorded and compared demographic data, fracture type, geriatric assessment and management, therapy, complications, and various clinical parameters, e.g., length of stay, time to surgery, hours admitted to ICU, and change in walking ability. Results: The geriatric assessment revealed significant geriatric co-morbidities and a need for geriatric intervention in 75% of the patients. With orthogeriatric co-management, a significant increase in the detection of urological complications (UC: 25.5% vs. OGC: 37.5%; p = 0.021), earlier postoperative mobilization (UC: 57.1% vs. OGC: 86.3%; p < 0.001), an increased prescription of anti-osteoporotic treatment at discharge (UC: 13.1% vs. OGC: 46.8%; p < 0.001), and lower rates of revision surgery (UC: 5.8% vs. OGC: 3.1%; p = 0.012) could be seen. Conclusions: Our results emphasize the improvement in patient care and clinical outcome by implementing a GTC DGU® and provide opportunities for future improvement in ortho-geriatric patient care.
Optimal Design of the Shape of a Non-Ball Mandrel for Thin-Walled Tube Small Radius Cold Bending
Authors: Bai Lu , Liu Jun , Wang Ziang , Zou Shuanggui
Published: August 2021

In the field of cold bending, it is necessary to use ball mandrels, especially to bend thin-walled tubes with a small radius. However, the bending process with a ball mandrel is complex and expensive, and it is easy to jam the core ball inside the tube. To solve these issues, we designed two kinds of hollow non-ball mandrel schemes with low stiffness that were suitable for the small radius bending of thin-walled tubes. We evaluated the forming quality of cold bending numerically and the influence of the hollow section length and thickness on the forming indices. Our results showed that the thickness of the hollow section has a greater influence on forming quality than the length. As the hollow section’s thickness increased, the wrinkling rate first declined by approximately 40% and then increased by above 50%. When the thickness was 11 mm in scheme 1 and 13 mm in scheme 2, the wrinkling rate reached minimum values of 1.32% and 1.50%, respectively. As the hollow section’s thickness increased, the flattening rate decreased by more than 60% and the thinning rate increased by about 40%. A multi-objective optimization of forming indices was carried out by ideal point method and grey wolf optimizer. By comparing the forming results before and after optimization, the feasibility of using the proposed hollow mandrel was proved, and the hollow mandrel scheme of standard cylinder is therefore recommended.
Optimisation of Lapping Process Parameters for Single-Crystal 4H–SiC Using Orthogonal Experiments and Grey Relational Analysis
Authors: Deng Jiayun , Yan Qiusheng , Lu Jiabin , Xiong Qiang , Pan Jisheng
Published: August 2021

Lapping is one of the standard essential methods to realise the global planarization of SiC and other semiconductor substrates. It is necessary to deeply study the mechanism to obtain SiC lapping process parameters with a strong comprehensive lapping performance (i.e., high material removal rate (MRRm), small surface roughness (Ra), and low total thickness variation (TTV)). The effects of the lapping process parameters and their interactions on lapping performance for SiC were investigated using orthogonal experiments; the effects on the MRRm, Ra, TTV, and optimal parameters under the conditions of a single evaluation index were investigated using intuitive analysis (range analysis, variance analysis, and effect curve analysis). The entropy value method and grey relational analysis were used to transform the multi-evaluation-index optimisation into a single-index optimisation about the grey relational grade (GRG) and to comprehensively evaluate the lapping performance of each process parameter. The results showed that the lapping plate types, abrasive size, and their interaction effect had the most significant effects on MRRm and Ra, with a contribution of over 85%. The interaction between the lapping plate types and abrasive size was also found to have the most significant effect on TTV, with a contribution of up to 51.07%. As the lapping plate’s hardness and abrasive size increased, the MRRm and Ra also gradually increased. As the lapping normal-pressure increased, MRRm increased, Ra gradually decreased, and TTV first decreased and then increased. MRRm, Ra, and TTV first increased and then decreased with increasing abrasive concentration. Compared to the optimisation results obtained by intuitive analysis, the process parameter optimised by the grey relational analysis resulted in a smooth surface with an MRRm of 90.2 μm/h, an Ra of 0.769 nm, and a TTV of 3 μm, with a significant improvement in the comprehensive lapping performance. This study reveals that a combination of orthogonal experiments and grey relational analysis can provide new ideas for optimising the process parameters of SiC.
Towards Fully Integrated Portable Sensing Devices for COVID-19 and Future Global Hazards: Recent Advances, Challenges, and Prospects
Authors: Shaffaf Tina , Forouhi Saghi , Ghafar-Zadeh Ebrahim
Published: August 2021

Since the onset of the coronavirus disease 2019 (COVID-19) pandemic, this fatal disease has been the leading cause of the death of more than 3.9 million people around the world. This tragedy taught us that we should be well-prepared to control the spread of such infectious diseases and prevent future hazards. As a consequence, this pandemic has drawn the attention of many researchers to the development of portable platforms with short hands-on and turnaround time suitable for batch production in urgent pandemic situations such as that of COVID-19. Two main groups of diagnostic assays have been reported for the detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) including nucleic acid-based and protein-based assays. The main focus of this paper is on the latter, which requires a shorter time duration, less skilled technicians, and faces lower contamination. Furthermore, this paper gives an overview of the complementary metal-oxide-semiconductor (CMOS) biosensors, which are potentially useful for implementing point-of-care (PoC) platforms based on such assays. CMOS technology, as a predominant technology for the fabrication of integrated circuits, is a promising candidate for the development of PoC devices by offering the advantages of reliability, accessibility, scalability, low power consumption, and distinct cost.
Micro Satellite Orbital Boost by Electrodynamic Tethers
Authors: Yao Peter , Sands Timothy
Published: August 2021

In this manuscript, a method for maneuvering a spacecraft using electrically charged tethers is explored. The spacecraft’s velocity vector can be modified by interacting with Earth’s magnetic field. Through this method, a spacecraft can maintain an orbit indefinitely by reboosting without the constraint of limited propellant. The spacecraft-tether system dynamics in low Earth orbit are simulated to evaluate the effects of Lorentz force and torques on translational motion. With 500-meter tethers charged with a 1-amp current, a 100-kg spacecraft can gain 250 m of altitude in one orbit. By evaluating the combined effects of Lorenz force and the coupled effects of Lorentz torque propagation through Euler’s moment equation and Newton’s translational motion equations, the simulated spacecraft-tether system can orbit indefinitely at altitudes as low as 275 km. Through a rare evaluation of the nonlinear coupling of the six differential equations of motion, the one finding is that an electrodynamic tether can be used to maintain a spacecraft’s orbit height indefinitely for very low Earth orbits. However, the reboost maneuver is inefficient for high inclination orbits and has high electrical power requirement. To overcome greater aerodynamic drag at lower altitudes, longer tethers with higher power draw are required.
Metal-Free Fabrication of Fused Silica Extended Nanofluidic Channel to Remove Artifacts in Chemical Analysis
Authors: Morikawa Kyojiro , Ohta Ryoichi , Mawatari Kazuma , Kitamori Takehiko
Published: August 2021

In microfluidics, especially in nanofluidics, nanochannels with functionalized surfaces have recently attracted attention for use as a new tool for the investigation of chemical reaction fields. Molecules handled in the reaction field can reach the single–molecule level due to the small size of the nanochannel. In such surroundings, contamination of the channel surface should be removed at the single–molecule level. In this study, it was assumed that metal materials could contaminate the nanochannels during the fabrication processes; therefore, we aimed to develop metal-free fabrication processes. Fused silica channels 1000 nm-deep were conventionally fabricated using a chromium mask. Instead of chromium, electron beam resists more than 1000 nm thick were used and the lithography conditions were optimized. From the results of optimization, channels with 1000 nm scale width and depth were fabricated on fused silica substrates without the use of a chromium mask. In nanofluidic experiments, an oxidation reaction was observed in a device fabricated by conventional fabrication processes using a chromium mask. It was found that Cr6+ remained on the channel surfaces and reacted with chemicals in the liquid phase in the extended nanochannels; this effect occurred at least to the micromolar level. In contrast, the device fabricated with metal-free processes was free of artifacts induced by the presence of chromium. The developed fabrication processes and results of this study will be a significant contribution to the fundamental technologies employed in the fields of microfluidics and nanofluidics.
Study of p-SiC/n-GaN Hetero-Structural Double-Drift Region IMPATT Diode
Authors: Dai Yang , Ye Qingsong , Dang Jiangtao , Lu Zhaoyang , Zhang Weiwei , Lei Xiaoyi , Zhang Yunyao , Zhang Han , Liao Chenguang , Li Yang , Zhao Wu
Published: August 2021

Nowadays, the immature p-GaN processes cannot meet the manufacturing requirements of GaN impact ionization avalanche transit time (IMPATT) diodes. Against this backdrop, the performance of wide-bandgap p-SiC/n-GaN heterojunction double-drift region (DDR) IMPATT diode is investigated in this paper for the first time. The direct-current (DC) steady-state, small-signal and large-signal characteristics are numerically simulated. The results show that compared with the conventional GaN single-drift region (SDR) IMPATT diode, the performance of the p-SiC/n-GaN DDR IMPATT proposed in this design, such as breakdown voltage, negative conductance, voltage modulation factor, radio frequency (RF) power and DC-RF conversion efficiency have been significantly improved. At the same time, the structure proposed in this design has a larger frequency bandwidth. Due to its greater potential in the RF power density, which is 1.97 MW/cm2 in this study, indicates that the p-SiC/n-GaN heterojunction provides new possibilities for the design and manufacture of IMPATT diode.
An Overview on Target-Based Drug Design against Kinetoplastid Protozoan Infections: Human African Trypanosomiasis, Chagas Disease and Leishmaniases
Authors: Kourbeli Violeta , Chontzopoulou Eleni , Moschovou Kalliopi , Pavlos Dimitrios , Mavromoustakos Thomas , Papanastasiou Ioannis P.
Published: August 2021

The protozoan diseases Human African Trypanosomiasis (HAT), Chagas disease (CD), and leishmaniases span worldwide and therefore their impact is a universal concern. The present regimen against kinetoplastid protozoan infections is poor and insufficient. Target-based design expands the horizon of drug design and development and offers novel chemical entities and potential drug candidates to the therapeutic arsenal against the aforementioned neglected diseases. In this review, we report the most promising targets of the main kinetoplastid parasites, as well as their corresponding inhibitors. This overview is part of the Special Issue, entitled “Advances of Medicinal Chemistry against Kinetoplastid Protozoa (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) Infections: Drug Design, Synthesis and Pharmacology”.
Amber Extract Reduces Lipid Content in Mature 3T3-L1 Adipocytes by Activating the Lipolysis Pathway
Authors: Sogo Erica , Zhou Siqi , Haeiwa Haruna , Takeda Reiko , Okazaki Kazuma , Sekita Marie , Yamamoto Takuya , Yamano Mikio , Sakamoto Kazuichi
Published: August 2021

Amber—the fossilized resin of trees—is rich in terpenoids and rosin acids. The physiological effects, such as antipyretic, sedative, and anti-inflammatory, were used in traditional medicine. This study aims to clarify the physiological effects of amber extract on lipid metabolism in mouse 3T3-L1 cells. Mature adipocytes are used to evaluate the effect of amber extract on lipolysis by measuring the triglyceride content, glucose uptake, glycerol release, and lipolysis-related gene expression. Our results show that the amount of triacylglycerol, which is stored in lipid droplets in mature adipocytes, decreases following 96 h of treatment with different concentrations of amber extract. Amber extract treatment also decreases glucose uptake and increases the release of glycerol from the cells. Moreover, amber extract increases the expression of lipolysis-related genes encoding perilipin and hormone-sensitive lipase (HSL) and promotes the activity of HSL (by increasing HSL phosphorylation). Amber extract treatment also regulates the expression of other adipocytokines in mature adipocytes, such as adiponectin and leptin. Overall, our results indicate that amber extract increases the expression of lipolysis-related genes to induce lipolysis in 3T3-L1 cells, highlighting its potential for treating various obesity-related diseases.
Bioactive Diterpenes from the Brazilian Native Plant (Moquiniastrum pulchrum) and Their Application in Weed Control
Authors: Vela Fátima , Anese Simoni , Varela Rosa M. , Torres Ascensión , Molinillo José M. G. , Macías Francisco A.
Published: August 2021

Even today, weeds continue to be a considerable problem for agriculture. The application of synthetic herbicides produces serious environmental consequences, and crops suffer loss of their activity due to the appearance of new resistant weed biotypes. Our aim is to develop new effective natural herbicides that improve the problem of resistance and do not harm the environment. This work is focused on a bioassay-guided isolation and the characterization of natural products present in Moquiniastrum pulchrum leaves with phytotoxic activity and its preliminary application in weeds. Moquiniastrum pulchrum was selected for two reasons: it is an abundant species in the Cerrado region (the second most important ecosystem in Brazil, after the Amazon)—the explanation behind its being a dominant species is a major focus of interest—and it has traditional employment in folk medicine. Six major compounds were isolated in this plant: one flavone and five diterpenes, two of which are described for the first time in the literature. Four of the six compounds exhibited phytotoxic activity in the bioassays performed. The results confirmed the phytotoxic potential of this plant, which had not been investigated until now.
Pharmacoinformatics and UPLC-QTOF/ESI-MS-Based Phytochemical Screening of Combretum indicum against Oxidative Stress and Alloxan-Induced Diabetes in Long–Evans Rats
Authors: Forid Md. Shaekh , Rahman Md. Atiar , Aluwi Mohd Fadhlizil Fasihi Mohd , Uddin Md. Nazim , Roy Tapashi Ghosh , Mohanta Milon Chandra , Huq AKM Moyeenul , Amiruddin Zakaria Zainul
Published: August 2021

This research investigated a UPLC-QTOF/ESI-MS-based phytochemical profiling of Combretum indicum leaf extract (CILEx), and explored its in vitro antioxidant and in vivo antidiabetic effects in a Long–Evans rat model. After a one-week intervention, the animals’ blood glucose, lipid profile, and pancreatic architectures were evaluated. UPLC-QTOF/ESI-MS fragmentation of CILEx and its eight docking-guided compounds were further dissected to evaluate their roles using bioinformatics-based network pharmacological tools. Results showed a very promising antioxidative effect of CILEx. Both doses of CILEx were found to significantly (p < 0.05) reduce blood glucose, low-density lipoprotein (LDL), and total cholesterol (TC), and increase high-density lipoprotein (HDL). Pancreatic tissue architectures were much improved compared to the diabetic control group. A computational approach revealed that schizonepetoside E, melianol, leucodelphinidin, and arbutin were highly suitable for further therapeutic assessment. Arbutin, in a Gene Ontology and PPI network study, evolved as the most prospective constituent for 203 target proteins of 48 KEGG pathways regulating immune modulation and insulin secretion to control diabetes. The fragmentation mechanisms of the compounds are consistent with the obtained effects for CILEx. Results show that the natural compounds from CILEx could exert potential antidiabetic effects through in vivo and computational study.
1H-NMR-Based Metabolomics: An Integrated Approach for the Detection of the Adulteration in Chicken, Chevon, Beef and Donkey Meat
Authors: Akhtar Muhammad Tayyab , Samar Muneeba , Shami Anam Amin , Mumtaz Muhammad Waseem , Mukhtar Hamid , Tahir Amna , Shahzad-ul-Hussan Syed , Chaudhary Safee Ullah , Kaka Ubedullah
Published: August 2021

Meat is a rich source of energy that provides high-value animal protein, fats, vitamins, minerals and trace amounts of carbohydrates. Globally, different types of meats are consumed to fulfill nutritional requirements. However, the increasing burden on the livestock industry has triggered the mixing of high-price meat species with low-quality/-price meat. This work aimed to differentiate different meat samples on the basis of metabolites. The metabolic difference between various meat samples was investigated through Nuclear Magnetic Resonance spectroscopy coupled with multivariate data analysis approaches like principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA). In total, 37 metabolites were identified in the gluteal muscle tissues of cow, goat, donkey and chicken using 1H-NMR spectroscopy. PCA was found unable to completely differentiate between meat types, whereas OPLS-DA showed an apparent separation and successfully differentiated samples from all four types of meat. Lactate, creatine, choline, acetate, leucine, isoleucine, valine, formate, carnitine, glutamate, 3-hydroxybutyrate and α-mannose were found as the major discriminating metabolites between white (chicken) and red meat (chevon, beef and donkey). However, inosine, lactate, uracil, carnosine, format, pyruvate, carnitine, creatine and acetate were found responsible for differentiating chevon, beef and donkey meat. The relative quantification of differentiating metabolites was performed using one-way ANOVA and Tukey test. Our results showed that NMR-based metabolomics is a powerful tool for the identification of novel signatures (potential biomarkers) to characterize meats from different sources and could potentially be used for quality control purposes in order to differentiate different meat types.
Germacranolides from Carpesium divaricatum: Some New Data on Cytotoxic and Anti-Inflammatory Activity
Authors: Kłeczek Natalia , Malarz Janusz , Gierlikowska Barbara , Skalniak Łukasz , Galanty Agnieszka , Kiss Anna K. , Stojakowska Anna
Published: August 2021

Carpesium divaricatum Sieb. & Zucc., a traditional medicinal plant used as an inflammation-relieving remedy, is a rich source of terpenoids. At least 40 germacrane-type sesquiterpene lactones, representatives of four different structural groups, were isolated from the plant. Cytotoxicity against cancer cells in vitro is the most frequently described biological activity of the compounds. However, little is known about the selectivity of the cytotoxic effect. The anti-inflammatory activity of the germacranolides is also poorly documented. The objective of the present study was to assess the cytotoxic activity of selected C. divaricatum germacranolides-derivatives of 4,5,8,9-tetrahydroxy-3-oxo-germacran-6,12-olide towards cancer and normal cell lines (including cells of different p53 status). Moreover, to assess the anti-inflammatory effect of the compounds, the release of four proinflammatory cytokines/chemokines (IL-1β, IL-8, TNF-α and CCL2) by lipopolysaccharide-stimulated human neutrophils was measured by ELISA. The investigated sesquiterpene lactones demonstrated nonselective activity towards prostate cancer (Du145 and PC3) and normal prostate epithelial cells (PNT2) as well as against melanoma cells (A375 and HTB140) and keratinocytes (HaCaT). Cytotoxic activity against osteosarcoma cells was independent of their p53 status. In sub-cytotoxic concentrations (0.5–2.5 µM) the studied compounds significantly decreased cytokine/chemokine release by lipopolysaccharide-stimulated human leukocytes.