bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk Factors Associated with the Prevalence of Upper and Lower Back Pain in Male Underground Coal Miners in Punjab, Pakistan
Authors: Ijaz Madiha , Akram Muhammad , Ahmad Sajid Rashid , Mirza Kamran , Ali Nadeem Falaq , Thygerson Steven M.
Published: June 2020

There is not enough data available on occupational health and safety issues of underground coal miners in Pakistan. This study focuses on spinal disorders in association with personal and occupational factors. The Nordic Musculoskeletal Questionnaire was used for a cross-sectional study of 260 workers of 20 mines located in four districts of Punjab, Pakistan. Regression models were created for upper back pain and lower back pain of workers whose mean age is 19.8 years (±SD 1.47). Results identify the coal cutting as the most harmful work with odds ratios (ORs) 13.06 (95% confidence interval (CI) 13.7–21.5) for lower back pain and 11.2 (95% CI 3.5–19.4) for upper back pain in participants. Those with greater years of work experience had higher odds of upper back pain (2.4, 95% CI 1.4–3.5) and lower back pain (3.3, 95% CI 1.1–4.4). Number of repetitions (mean value 25.85/minute with ±SD 9.48) are also significant for spinal disorder with ORs of 4.3 (95% CI 3.2–7.4) for lower back and 1.3 (95% CI 1.0–2.4) for upper back. Many other occupational and personal factors are positively associated with the back pain in underground coal mines workers, requiring immediate ergonomic intervention.
Immediate Effects of Tibialis Anterior and Calf Muscle Taping on Center of Pressure Excursion in Chronic Stroke Patients: A Cross-Over Study
Authors: Park Shin Jun , Kim Tae-Hyun , Oh Seunghue
Published: June 2020

Stroke patients often have muscles spasticity, difficulty with posture control, and tend to fall. This study investigated the use of kinesiology tape for patients with spasticity of ankle muscles after stroke. This study had a randomized, repeated measures design, and evaluated the immediate effect of kinesiology tape on the center of pressure (COP) excursion when applied to the calf and tibialis anterior muscles in stroke survivors. We determined that the taping attachment direction affects the COP movement. Twenty subjects were randomly assigned to the tibialis anterior taping condition, calf taping condition, or nontaping condition. Condition excursion was assessed. The measured variables included the paretic side area, nonparetic side area, forward area, and backward area of COP. All evaluations were conducted immediately after taping. COP excursion for chronic stroke survivors improved after tibialis anterior and calf taping (p < 0.05). Calf taping conditions increased significantly in the forward area (p < 0.05), and tibialis anterior taping conditions increased significantly in the backward area (p < 0.05). Kinesiology tape immediately increased the forward and backward COP excursion for patients with stroke.
Exploring the Underlying Causes of Chinese Eastern Star, Korean Sewol, and Thai Phoenix Ferry Accidents by Employing the HFACS-MA
Authors: Wang Xiaolong , Zhang Boling , Zhao Xu , Wang Lulu , Tong Ruipeng
Published: June 2020

Maritime safety is a significant topic in the maritime industry since the numerous dangers at sea could lead to loss of property, environmental pollution, and even casualties. Existing research illustrates that human factors are the primary reasons of maritime accidents. Indeed, numerous maritime accidents can be classified into different types of human factors. In this context, the Human Factors Analysis and Classification System for Maritime Accidents (HFACS-MA) model is introduced in this paper. The HFACS-MA framework consists of five levels, complying with the core concepts of HFACS and the guiding principles of the International Maritime Organization (IMO). Based on the five levels of the framework, this research explores the underlying causes of Chinese Eastern Star, Korean Sewol, and Thai Phoenix accidents, and a comparative analysis is conducted. The analysis demonstrates the utility of applying the HFACS-MA model to the maritime industry, and the results emphasize the importance of the following categories: legislation gaps, organizational process, inadequate supervision, communication (ships and VTS), decision errors, and so on. Consequently, the research enables increased support for HFACS-MA and its application and provides valuable information for safety management and policy development in the maritime industry at different levels.
Air Quality Variation in Wuhan, Daegu, and Tokyo during the Explosive Outbreak of COVID-19 and Its Health Effects
Authors: Ma Chang-Jin , Kang Gong-Unn
Published: June 2020

This study was designed to assess the variation of the air quality actually measured from the air pollution monitoring stations (AQMS) in three cities (Wuhan, Daegu, and Tokyo), in Asian countries experiencing the explosive outbreak of COVID-19, in a short period of time. In addition, we made a new attempt to calculate the reduced DosePM2.5 (μg) at the bronchiolar (Br.) and alveolar-interstitial (AI) regions of the 10-year-old children after the city lockdown/self-reflection of each city. A comparison of the average PM2.5 of a month before and after the lockdown (Wuhan) and self-reflection (Daegu and Tokyo) clearly shows that the PM2.5 concentration was decreased by 29.9, 20.9, and 3.6% in Wuhan, Daegu and Tokyo, respectively. Wuhan, Daegu and Tokyo also recorded 53.2, 19.0, and 10.4% falls of NO2 concentration, respectively. Wuhan, which had the largest decrease of PM2.5 concentration due to COVID-19, also marked the largest reduced DosePM2.5 10-year-old children (μg) (3660 μg at Br. and 6222 μg at AI), followed by Daegu (445 μg at Br. and 1287 μg at AI), and Tokyo (18 μg at Br. and 52 μg at AI), over two months after the city lockdown/self-reflection. Our results suggest that the city lockdown/self-reflection had the effect of lowering the concentration of PM2.5, resulting in an extension of the period it took to the acute allergic airway inflammation (AAI) for the 10-year-old children.
Gadolinium Complexes as Contrast Agent for Cellular NMR Spectroscopy
Authors: Sakol Nat , Egawa Ayako , Fujiwara Toshimichi
Published: June 2020

Aqua Gd3+ and Gd-DOTA (gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacete) complexes were studied as a contrast agent in cellular NMR (nuclear magnetic resonance) spectroscopy for distinguishing between intracellular and extracellular spaces. The contrast agents for this purpose should provide strong paramagnetic relaxation enhancement and localize in the extracellular space without disturbing biological functions. Cell membrane permeability to Gd complexes was evaluated from the concentrations of gadolinium complexes in the inside and outside of E. coli cells measured by the 1H-NMR relaxation. The site-specific binding of the complexes to E. coli cells was also analyzed by high-resolution solid-state 13C-NMR. The aqua Gd3+ complex did not enhance T1 relaxation in proportion to the amount of added Gd3+. This Gd3+ concentration dependence and the 13C-NMR indicated that its strong cytotoxicity should be due to the binding of the paramagnetic ions to cellular components especially at the lipid membranes. In contrast, Gd-DOTA stayed in the solution states and enhanced relaxation in proportion to the added amount. This agent exhibited strong T1 contrast between the intra- and extracellular spaces by a factor of ten at high concentrations under which the cells were viable over a long experimental time of days. These properties make Gd-DOTA suitable for selectively contrasting the living cellular space in NMR spectroscopy primarily owing to its weak interaction with cellular components.
Embryonic Program Activated during Blast Crisis of Chronic Myelogenous Leukemia (CML) Implicates a TCF7L2 and MYC Cooperative Chromatin Binding
Authors: Desterke Christophe , Hugues Patricia , Hwang Jin Wook , Bennaceur-Griscelli Annelise , Turhan Ali G.
Published: June 2020

Chronic myeloid leukemia (CML) is characterized by an inherent genetic instability, which contributes to the progression of the disease towards an accelerated phase (AP) and blast crisis (BC). Several cytogenetic and genomic alterations have been reported in the progression towards BC, but the precise molecular mechanisms of this event are undetermined. Transcription Factor 7 like 2 (TFC7L2) is a member of the TCF family of proteins that are known to activate WNT target genes such as Cyclin D1. TCF7L2 has been shown to be overexpressed in acute myeloid leukemia (AML) and represents a druggable target. We report here that TCF7L2 transcription factor expression was found to be correlated to blast cell numbers during the progression of the disease. In these cells, TCF7L2 CHIP-sequencing highlighted distal cis active enhancer, such as elements in SMAD3, ATF5, and PRMT1 genomic regions and a proximal active transcriptional program of 144 genes. The analysis of CHIP-sequencing of MYC revealed a significant overlapping of TCF7L2 epigenetic program with MYC. The β-catenin activator lithium chloride and the MYC-MAX dimerization inhibitor 10058-F4 significantly modified the expression of three epigenetic targets in the BC cell line K562. These results suggest for the first time the cooperative role of TCF7L2 and MYC during CML-BC and they strengthen previous data showing a possible involvement of embryonic genes in this process.
Apolipoprotein A-I Supports MSCs Survival under Stress Conditions
Authors: Miroshnichenko Svetlana , Usynin Ivan , Dudarev Alexey , Nimaev Vadim , Solovieva Anastasiya
Published: June 2020

Clinical trials have shown the safety of mesenchymal stem/stromal cells (MSCs) transplantation, but the effectiveness of these treatments is limited. Since, transplanted MSCs will undergo metabolic disturbances in the bloodstream, we investigated the influence of blood plasmas of type 2 diabetes (T2D) patients on MSCs viability and examined whether apolipoprotein A-I (apoA-I) could protect cells from stressful conditions of serum deprivation (SD), hypoxia, and elevated concentrations of reactive oxygen species (ROS). ApoA-I exhibits anti-inflammatory, immune activities, improves glycemic control, and is suitable for T2D patients but its influence on MSCs remains unknown. For the first time we have shown that apoA-I decreases intracellular ROS and supports proliferative rate of MSCs, thereby increasing cell count in oxidation conditions. ApoA-I did not influence cell cycle when MSCs were predominantly in the G0/G1 phases under conditions of SD/hypoxia, activated proliferation rapidly, and reduced apoptosis during MSCs transition to the oxygenation or oxidation conditions. Finally, it was found that the blood plasma of T2D individuals had a cytotoxic effect on MSCs in 39% of cases and had a wide variability of antioxidant properties. ApoA-I protects cells under all adverse conditions and can increase the efficiency of MSCs transplantation in T2D patients.
Regulation of Epithelial-to-Mesenchymal Transition by Alternative Translation Initiation Mechanisms and Its Implications for Cancer Metastasis
Authors: Bera Amit , Lewis Stephen M.
Published: June 2020

Translation initiation plays a critical role in the regulation of gene expression for development and disease conditions. During the processes of development and disease, cells select specific mRNAs to be translated by controlling the use of diverse translation initiation mechanisms. Cells often switch translation initiation from a cap-dependent to a cap-independent mechanism during epithelial-to-mesenchymal transition (EMT), a process that plays an important role in both development and disease. EMT is involved in tumor metastasis because it leads to cancer cell migration and invasion, and is also associated with chemoresistance. In this review we will provide an overview of both the internal ribosome entry site (IRES)-dependent and N6-methyladenosine (m6A)-mediated translation initiation mechanisms and discuss how cap-independent translation enables cells from primary epithelial tumors to achieve a motile mesenchymal-like phenotype, which in turn drives tumor metastasis.
Magnetic β-Cyclodextrin Nanosponges for Potential Application in the Removal of the Neonicotinoid Dinotefuran from Wastewater
Authors: Salazar Sebastián , Yutronic Nicolás , Jara Paul
Published: June 2020

This article describes the use of β-cyclodextrin-based carbonate nanosponges (NSs) decorated with superparamagnetic Fe3O4 nanoparticles to study and investigate the potential removal of dinotefuran (DTF) from wastewater. The NS-DTF inclusion compound was characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), UV-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD) and proton nuclear magnetic resonance (1H-NMR). The adsorption efficiency of NSs was evaluated as function of different contact times. The results confirmed that the NSs have a favourable sorption capacity for the chosen guest, as the polymers exhibited a maximum adsorption of 4.53 × 10−3 mmol/g for DTF. We also found that magnetic NSs show good reusability as they maintain their efficiency after eight adsorption and desorption cycles. Our studies and characterization by means of SEM, TEM, EDS, vibrating sample magnetometer (VSM) and UV-VIS also show that NSs with magnetic properties are excellent tools for insecticide removal from aqueous environments.
Evaluation of Different Adiposity Indices and Association with Metabolic Syndrome Risk in Obese Children: Is there a Winner?
Authors: Leone Alessandro , Vizzuso Sara , Brambilla Paolo , Mameli Chiara , Ravella Simone , De Amicis Ramona , Battezzati Alberto , Zuccotti Gianvincenzo , Bertoli Simona , Verduci Elvira
Published: June 2020

Body shape index (ABSI) and triponderal mass index (TMI) have been recently associated with cardiovascular risk in adults. A cross-sectional study was conducted to evaluate the relationship between different anthropometric adiposity indexes and metabolic syndrome (MetS) in Caucasian obese children and adolescents. Consecutive obese children aged ≥7 years have been enrolled. Anthropometric parameters, body composition (by bioelectrical impedance), and systolic and diastolic blood pressure have been measured. Fasting blood samples have been analyzed for lipids, insulin, glucose. A multivariate logistic regression analyses, with body mass index z-score, waist to height ratio, ABSI z-score, TMI, conicity index as predictors for MetS (IDEFICS and IDF criteria according to age) has been performed. Four hundred and three (179 boys and 224 girls) obese children, aged 7–20 years, have been evaluated. When we explored the joint contribution of each anthropometric and adiposity index of interest and BMIz on the risk of MetS, we found that the inclusion of ABSIz improved the prediction of MetS compared to BMIz alone. ABSI-BMI can be a useful index for evaluating the relative contribution of central obesity to cardiometabolic risk in clinical management of obese children and adolescents.
Mutant p53 as an Antigen in Cancer Immunotherapy
Authors: Sobhani Navid , D’Angelo Alberto , Wang Xu , Young Ken H. , Generali Daniele , Li Yong
Published: June 2020

The p53 tumor suppressor plays a pivotal role in cancer and infectious disease. Many oncology treatments are now calling on immunotherapy approaches, and scores of studies have investigated the role of p53 antibodies in cancer diagnosis and therapy. This review summarizes the current knowledge from the preliminary evidence that suggests a potential role of p53 as an antigen in the adaptive immune response and as a key monitor of the innate immune system, thereby speculating on the idea that mutant p53 antigens serve as a druggable targets in immunotherapy. Except in a few cases, the vast majority of published work on p53 antibodies in cancer patients use wild-type p53 as the antigen to detect these antibodies and it is unclear whether they can recognize p53 mutants carried by cancer patients at all. We envision that an antibody targeting a specific mutant p53 will be effective therapeutically against a cancer carrying the exact same mutant p53. To corroborate such a possibility, a recent study showed that a T cell receptor-like (TCLR) antibody, initially made for a wild-type antigen, was capable of discriminating between mutant p53 and wild-type p53, specifically killing more cancer cells expressing mutant p53 than wild-type p53 in vitro and inhibiting the tumour growth of mice injected with mutant p53 cancer cells than mice with wild-type p53 cancer cells. Thus, novel antibodies targeting mutant p53, but not the wild-type isoform, should be pursued in preclinical and clinical studies.
The Role of ERα36 in Development and Tumor Malignancy
Authors: Thiebaut Charlène , Konan Henri-Philippe , Guerquin Marie-Justine , Chesnel Amand , Livera Gabriel , Le Romancer Muriel , Dumond Hélène
Published: June 2020

Estrogen nuclear receptors, represented by the canonical forms ERα66 and ERβ1, are the main mediators of the estrogen-dependent pathophysiology in mammals. However, numerous isoforms have been identified, stimulating unconventional estrogen response pathways leading to complex cellular and tissue responses. The estrogen receptor variant, ERα36, was cloned in 2005 and is mainly described in the literature to be involved in the progression of mammary tumors and in the acquired resistance to anti-estrogen drugs, such as tamoxifen. In this review, we will first specify the place that ERα36 currently occupies within the diversity of nuclear and membrane estrogen receptors. We will then report recent data on the impact of ERα36 expression and/or activity in normal breast and testicular cells, but also in different types of tumors including mammary tumors, highlighting why ERα36 can now be considered as a marker of malignancy. Finally, we will explain how studying the regulation of ERα36 expression could provide new clues to counteract resistance to cancer treatments in hormone-sensitive tumors.
Spatial Linear Mixed Effects Modelling for OCT Images: SLME Model
Authors: Zhu Wenyue , Ku Jae Yee , Zheng Yalin , Knox Paul C. , Kolamunnage-Dona Ruwanthi , Czanner Gabriela
Published: June 2020

Much recent research focuses on how to make disease detection more accurate as well as “slimmer”, i.e., allowing analysis with smaller datasets. Explanatory models are a hot research topic because they explain how the data are generated. We propose a spatial explanatory modelling approach that combines Optical Coherence Tomography (OCT) retinal imaging data with clinical information. Our model consists of a spatial linear mixed effects inference framework, which innovatively models the spatial topography of key information via mixed effects and spatial error structures, thus effectively modelling the shape of the thickness map. We show that our spatial linear mixed effects (SLME) model outperforms traditional analysis-of-variance approaches in the analysis of Heidelberg OCT retinal thickness data from a prospective observational study, involving 300 participants with diabetes and 50 age-matched controls. Our SLME model has a higher power for detecting the difference between disease groups, and it shows where the shape of retinal thickness profiles differs between the eyes of participants with diabetes and the eyes of healthy controls. In simulated data, the SLME model demonstrates how incorporating spatial correlations can increase the accuracy of the statistical inferences. This model is crucial in the understanding of the progression of retinal thickness changes in diabetic maculopathy to aid clinicians for early planning of effective treatment. It can be extended to disease monitoring and prognosis in other diseases and with other imaging technologies.
Mechanical Behavior of a Composite Lightweight Slab, Consisting of a Laminated Wooden Joist and Ecological Mortar
Authors: Muñoz-Ruiperez Carmelo , Fiol Oliván Francisco , Calderón Carpintero Verónica , Santamaría-Vicario Isabel , Rodríguez Sáiz Ángel
Published: June 2020

The investigation reported in this paper is an evaluation of the mechanical behavior of full-scale ecological mortar slabs manufactured with a mixture of expanded clay and recycled concrete aggregates. The composite mortars form a compressive layer over laminated wooden joists to form a single construction unit. To do so, full-scale flexural tests are conducted of the composite laminated wood-ecological mortar slabs with different types of mortar designs: reference mortar (MR), lightweight mortar dosed with recycled concrete aggregates (MLC), and lightweight mortar dosed with recycled mixed aggregates (MLM). The test results showed that the mortar forming the compression layer and the laminated wooden joists worked in unison and withstood a higher maximum failure load under flexion than the failure load of the wooden joists in isolation. Moreover, the laboratory test results were compared with the simulated values of the theoretical model, generated in accordance with the technical specifications for structural calculations contained in the Spanish building code, and with the results calculated by a computer software package. From the analysis of the results of the calculation methods and the full-scale laboratory test results, it was concluded that the safety margin yielded by the calculations validated the use of those methods on this type of composite slab. In this way, a strong mixed wood–mortar slab was designed, contributing little dead-load to the building structure and its manufacture with recycled aggregate, also contributes to the circular economy of construction materials.
Evaluation of Equivalent Flexural Strength for Complete Removable Dentures Made of Zirconia-Impregnated PMMA Nanocomposites
Authors: Zidan Saleh , Silikas Nikolaos , Haider Julfikar , Alhotan Abdulaziz , Jahantigh Javad , Yates Julian
Published: June 2020

High-impact (HI) polymethyl methacrylate (PMMA), obtained from modification of conventional PMMA, is commonly used in prosthodontics as a denture base material for improved impact resistance. However, it suffers from poor flexural strength properties. The aim of this study was to investigate the flexural strength of complete removable dentures made of HI heat-polymerised PMMA resin reinforced with zirconia nanoparticles at two different concentrations. The effect of fatigue loading on the flexural strength behaviour of the dentures was also investigated. A total of 30 denture specimens were fabricated from PMMA with different concentrations of zirconia nanoparticles: 0 (control), 3, and 5 wt.%. Ten specimens in each group were divided into two subgroups, with five specimens in each, to conduct both flexural strength and fatigue loading test of each of the subgroups. Fatigue loading was applied on the dentures using a mastication simulator and equivalent flexural strength was calculated with data from bending tests with and without fatigue cyclic loading. One-way analysis of variance (ANOVA) of the test data was conducted with the Bonferroni significant difference post-hoc test at a preset alpha value of 0.05. Paired t-test was employed to identify any difference between the specimens with and without the application of fatigue loading. The fractured surface of the denture specimens was examined with a scanning electron microscope (SEM). The bending tests demonstrated that the mean equivalent flexural strength of reinforced HI PMMA denture specimens with 5 wt.% zirconia nanoparticles increased significantly (134.9 ± 13.9 MPa) compared to the control group (0 wt.%) (106.3 ± 21.3 MPa) without any fatigue loading. The mean strength of the dentures with PMMA +3 wt.% zirconia also increased, but not significantly. Although the mean strength of all specimen groups subjected to fatigue loading slightly decreased compared to that of the specimen groups without any fatigue cyclic loading, this was not statistically significant. Denture specimens made of HI heat-polymerised PMMA reinforced with 5 wt.% zirconia nanoparticles had significantly improved equivalent flexural strength compared to that made of pure PMMA when the specimens were not subjected to any prior fatigue cyclic loading. In addition, the application of fatigue cyclic loading did not significantly improve the equivalent flexural strengths of all denture specimen groups. Within the limitations of this study, it can be concluded that the use of zirconia-impregnated PMMA in the manufacture of dentures does not result in any significant improvement for clinical application.
Additively Manufactured Continuous Cell-Size Gradient Porous Scaffolds: Pore Characteristics, Mechanical Properties and Biological Responses In Vitro
Authors: Liu Fei , Ran Qichun , Zhao Miao , Zhang Tao , Zhang David Z. , Su Zuqiang
Published: June 2020

Porous scaffolds with graded open porosity combining a morphology similar to that of bone with mechanical and biological properties are becoming an attractive candidate for bone grafts. In this work, scaffolds with a continuous cell-size gradient were studied from the aspects of pore properties, mechanical properties and bio-functional properties. Using a mathematical method named triply periodic minimal surfaces (TPMS), uniform and graded scaffolds with Gyroid and Diamond units were manufactured by selective laser melting (SLM) with Ti-6Al-4V, followed by micro-computer tomography (CT) reconstruction, mechanical testing and in vitro evaluation. It was found that gradient scaffolds were preferably replicated by SLM with continuous graded changes in surface area and pore size, but their pore size should be designed to be ≥ 450 μm to ensure good interconnectivity. Both the Gyroid and Diamond structures have superior strength compared to cancellous bones, and their elastic modulus is comparable to the bones. In comparison, Gyroid exhibits better performances than Diamond in terms of the elastic modulus, ultimate strength and ductility. In vitro cell culture experiments show that the gradients provide an ideal growth environment for osteoblast growth in which cells survive well and distribute uniformly due to biocompatibility of the Ti-6Al-4V material, interconnectivity and suitable pore size.
Investigating the Properties of Cetyltrimethylammonium Bromide/Hydroxylated Graphene Quantum Dots Thin Film for Potential Optical Detection of Heavy Metal Ions
Authors: Anas Nur Ain Asyiqin , Fen Yap Wing , Yusof Nor Azah , Omar Nur Alia Sheh , Ramdzan Nur Syahira Md , Daniyal Wan Mohd Ebtisyam Mustaqim Mohd
Published: June 2020

The modification of graphene quantum dots (GQDs) may drastically enhance their properties, therefore resulting in various related applications. This paper reported the preparation of novel cetyltrimethylammonium bromide/hydroxylated graphene quantum dots (CTAB/HGQDs) thin film using the spin coating technique. The properties of the thin film were then investigated and studied. The functional groups existing in CTAB/HGQDs thin film were confirmed by the Fourier transform infrared (FTIR) spectroscopy, while the atomic force microscope (AFM) displayed a homogenous surface of the thin film with an increase in surface roughness upon modification. Optical characterizations using UV-Vis absorption spectroscopy revealed a high absorption with an optical band gap of 4.162 eV. Additionally, the photoluminescence (PL) spectra illustrated the maximum emission peak of CTAB/HGQDs thin film at a wavelength of 444 nm. The sensing properties of the as-prepared CTAB/HGQDs thin film were studied using a surface plasmon resonance technique towards the detection of several heavy metal ions (HMIs) (Zn2+, Ni2+, and Fe3+). This technique generated significant results and showed that CTAB/HGQDs thin film has great potential for HMIs detection.
Metal Matrix Composites Synthesized by Laser-Melting Deposition: A Review
Authors: Mahmood Muhammad Arif , Popescu Andrei C. , Mihailescu Ion N.
Published: June 2020

Metal matrix composites (MMCs) present extraordinary characteristics, including high wear resistance, excellent operational properties at elevated temperature, and better chemical inertness as compared to traditional alloys. These properties make them prospective candidates in the fields of aerospace, automotive, heavy goods vehicles, electrical, and biomedical industries. MMCs are challenging to process via traditional manufacturing techniques, requiring high cost and energy. The laser-melting deposition (LMD) has recently been used to manufacture MMCs via rapid prototyping, thus, solving these drawbacks. Besides the benefits mentioned above, the issues such as lower ultimate tensile strength, yield strength, weak bonding between matrix and reinforcements, and cracking are still prevalent in parts produced by LMD. In this article, a detailed analysis is made on the MMCs manufactured via LMD. An illustration is presented on the LMD working principle, its classification, and dependent and independent process parameters. Moreover, a brief comparison between the wire and powder-based LMDs has been summarized. Ex- and in-situ MMCs and their preparation techniques are discussed. Besides this, various matrices available for MMCs manufacturing, properties of MMCs after printing, possible complications and future research directions are reviewed and summarized.
Anionic Copolymerization of Styrene Sulfide with Elemental Sulfur (S8)
Authors: Wręczycki Jakub , Bieliński Dariusz M. , Kozanecki Marcin , Maczugowska Paulina , Mlostoń Grzegorz
Published: June 2020

The superior ability of thiiranes (episulfides) to undergo ring-opening polymerization (ROP) in the presence of anionic initiators allows the preparation of chemically stable polysulfide homopolymers. Incorporation of elemental sulfur (S8) by copolymerization below the floor temperature of S8 permits the placement of a large quantity of sulfur atoms in the polysulfide mainchain. The utility of styrene sulfide (2-phenylthiirane; StS) for copolymerization with elemental sulfur is reported here. A few polysulfides differing depending on the initial ratio of S8 to StS and copolymerization time were synthesized. Various spectroscopic methods (1H NMR, 13C NMR, Raman spectroscopy and FTIR spectroscopy) were applied to characterize the chemical structure of the copolymers. Additionally, the phase structure and thermal stability of the synthesized polysulfides were investigated using DSC and TGA, respectively. The successful anionic copolymerization of styrene sulfide and elemental sulfur has been demonstrated.
Effect of Filler Alignment on Piezo-Resistive and Mechanical Properties of Carbon Nanotube Composites
Authors: Kim Hyunwoo , Hong Soon-Kook , Ryu Jae-Kwan , Park Sung-Hoon
Published: June 2020

Highly aligned multi-walled carbon nanotube (MWCNT) polymer composites were fabricated via a roll-to-roll milling process; the alignment of the MWCNTs could be controlled by varying the speed of the rotating rolls. The effect of MWCNT alignment on the polymer matrix was morphologically observed and quantitatively characterized using polarized Raman spectroscopy. To provide a more detailed comparison, MWCNT composites with alignment in the transverse direction and random alignment were fabricated and tested. Enhanced mechanical and electrical properties were obtained for the aligned MWCNT composite, which can be attributed to the efficient electrical network and load transfer, respectively. In addition, a cyclic stretching test was conducted to evaluate the piezo-resistive characteristics of the aligned MWCNT composites. The composites with an aligned filler configuration showed an exceptionally high degree of strain sensitivity compared to the other composites.
Structural Instability-Enabled Mechanical Sensors Using Fiber Bragg Grating
Authors: Jiao Pengcheng , Xie Yiwei , Wu Shengnan , Liu Xinyu
Published: June 2020

Structural health monitoring (SHM) has been extensively used in civil infrastructures to assess structural condition and situation. Here, we develop a novel type of mechanical sensing technique using the structural instability of cylindrical cells detected by fiber Bragg grating (FBG). The cylinders are fabricated using a 3D printing technique, which are coiled by the FBG wires to detect the transverse deformation. Structural instability under axial compression is obtained in the experiments and the force–displacement relations are validated by the numerical simulations with satisfactory agreements. The wavelength variation of the FBG, caused by the structural instability, is observed and compared with the predefined threshold. Defining the variation larger than the threshold as “1” and smaller as “0”, the pattern recognition algorithm is used to convert the FBG results into binary data, which can, therefore, be analyzed to indicate the structural conditions. In the end, we envision the potential applications of the reported sensing technique, such as wireless sensors for structural health monitoring (SHM) in civil infrastructures.
Effect of Load on the Corrosion Behavior of Friction Stir Welded AA 7075-T6 Aluminum Alloy
Authors: Cabrini Marina , Bocchi Sara , D’Urso Gianluca , Giardini Claudio , Lorenzi Sergio , Testa Cristian , Pastore Tommaso
Published: June 2020

The paper focuses on the corrosion behavior of aluminum joints made by friction stir welding as a function of loading conditions. A four-points bend-beam test, constant loading test, and slow strain-rate test were carried out on AA 7075-T6 alloy in aerated NaCl 35g/L solution at room temperature monitoring the free corrosion potential. The penetration depth of the intergranular attack was deeper after the four-point bent-beam tests compared to all the other testing techniques. Preferential dissolution along the grain boundaries was found in the heat-affected zone and the attack follows the elongated grains structure along the rolling direction. However, no stress-corrosion cracking phenomena were detected. No relevant stress corrosion cracking (SCC) crack embryos propagation was noticed under uniaxial tensile tests—both constant loading and slow strain-rate tests—manly due to the high dissolution rate occurring at the crack tip which promoted premature shear ruptures.
Efficacy of Bioactive Glass Nanofibers Tested for Oral Mucosal Regeneration in Rabbits with Induced Diabetes
Authors: Elshazly Noha , Khalil Abdelaziz , Saad Manal , Patruno Marco , Chakraborty Jui , Marei Mona
Published: June 2020

The healing of oral lesions that are associated with diabetes mellitus is a matter of great concern. Bioactive glass is a highly recommended bioceramic scaffold for bone and soft tissue regeneration. In this study, we aimed to assess the efficacy of a novel formula of bioactive glass nanofibers in enhancing oral mucosal wound regeneration in diabetes mellitus. Bioactive glass nanofibres (BGnf) of composition (1–2) mol% of B2O3, (68–69) mol% of SiO2, and (29–30) mol% of CaO were synthesized via the low-temperature sol-gel technique followed by mixing with polymer solution, then electrospinning of the glass sol to produce nanofibers, which were then subjected to heat treatment. X-Ray Diffraction analysis of the prepared nanofibers confirmed its amorphous nature. Microstructure of BGnf simulated that of the fibrin clot with cross-linked nanofibers having a varying range of diameter (500–900 nm). The in-vitro degradation profile of BGnf confirmed its high dissolution rate, which proved the glass bioactivity. Following fibers preparation and characterization, 12 healthy New Zealand male rabbits were successfully subjected to type I diabetic induction using a single dose of intravenous injection of alloxan monohydrate. Two weeks after diabetes confirmation, the rabbits were randomly divided into two groups (control and experimental groups). Bilateral elliptical oral mucosal defects of 10 × 3.5 mm were created in the maxillary mucobuccal fold of both groups. The defects of the experimental group were grafted with BGnf, while the other group of defects considered as a control group. Clinical, histological, and immune-histochemical assessment of both groups of wounds were performed after one, two and three weeks’ time interval. The results of the clinical evaluation of BGnf treated defects showed complete wound closure with the absence of inflammation signs starting from one week postoperative. Control defects, on the other hand, showed an open wound with suppurative exudate. On histological and immunohistochemical level, the BGnf treated defects revealed increasing in cell activity and vascularization with the absence of inflammation signs starting from one week time interval, while the control defects showed signs of suppurative inflammation at one week time interval with diminished vascularization. The results advocated the suitability of BGnf as bioscaffold to be used in a wet environment as the oral cavity that is full of microorganisms and also for an immune-compromised condition as diabetes mellitus.
Morphological Evaluation of Bone by CT to Determine Primary Stability—Clinical Study
Authors: Takechi Masaaki , Ishioka Yasuki , Ninomiya Yoshiaki , Ono Shigehiro , Tada Misato , Nakagawa Takayuki , Sasaki Kazuki , Murodumi Hiroshi , Shigeishi Hideo , Ohta Kouji
Published: June 2020

Background: Primary stability is an important prognostic factor for dental implant therapy. In the present study, we evaluate the relationship between implant stability evaluation findings by the use of an implant stability quotient (ISQ), an index for primary stability, and a morphological evaluation of bone by preoperative computed tomography (CT). Subjects and methods: We analyzed 98 patients who underwent implant placement surgery in this retrospective study. For all 247 implants, the correlations of the ISQ value with cortical bone thickness, cortical bone CT value, cancellous bone CT value, insertion torque value, implant diameter, and implant length were examined. Results: 1. Factors affecting ISQ values in all cases: It was revealed that there were significant associations between the cortical bone thickness and cancellous bone CT values with ISQ by multiple regression analysis. 2. It was revealed that there was a significant correlation between cortical bone thickness and cancellous bone CT values with ISQ by multiple regression analysis in the upper jaw. 3. It was indicated that there was a significant association between cortical bone thickness and implant diameter with ISQ by multiple regression analysis in the lower jaw. Conclusion: We concluded that analysis of the correlation of the ISQ value with cortical bone thickness and values obtained in preoperative CT imaging were useful preoperative evaluations for obtaining implant stability.
Quasi-Monocrystalline Graphene Crystallization on Liquid Copper Matrix
Authors: Kuten Dominika , Dybowski Konrad , Atraszkiewicz Radomir , Kula Piotr
Published: June 2020

To access the properties of theoretical graphene, it is crucial to manufacture layers with a defect-free structure. The imperfections of the structure are the cause of deterioration in both electrical and mechanical properties. Among the most commonly occurring crystalline defects, there are grain boundaries and overlapping zones. Hence, perfect graphene shall be monocrystalline, which is difficult and expensive to obtain. An alternative to monocrystalline structure is a quasi-monocrystalline graphene with low angle-type boundaries without the local overlapping of neighboring flakes. The purpose of this work was to identify factors that directly affect the structure of graphene grown on a surface of a liquid metal. In the article the growth of graphene on a liquid copper is presented. Nucleating graphene flakes are able to move with three degrees of freedom creating low-angle type boundaries when they attach to one another. The structure of graphene grown with the use of this method is almost free of overlapping zones. In addition, the article presents the influence of impurities on the amount of crystallization nuclei formed, and thus the possibility to order the structure, creating a quasi-monocrystalline layer.
Preliminary Analysis of the Ductility and Crack-Control Ability of Engineered Cementitious Composite with Superfine Sand and Polypropylene Fiber (SSPP-ECC)
Authors: Zhu Zhiqing , Tan Guojin , Zhang Weiguang , Wu Chunli
Published: June 2020

Engineered cementitious composite (ECC) is a potential cement-based material with the abilities of large deformation and crack width control. However, ECC is difficult to popularize in many developing countries because the costs of silica sand and polyvinyl alcohol (PVA) fiber with a surface coating are too high for practical engineering. Therefore, we proposed an economical ECC with superfine river sand and polypropylene (PP) fiber (SSPP-ECC) to replace PVA fiber and silica sand. The SSPP-ECC proposed in this paper is a sustainable material using local material ingredients, which has considerable adaptability for large-scale engineering applications. The 16 groups of specimens were prepared through a factorial design method, curing for four-point bending tests. The bending strength, deflection, flexural modulus of elasticity, and crack width were measured and calculated during the test. The factor analysis of the test results shows that the contents of fiber and fly ash had significant effects on the ductility of SSPP-ECC with an extra combined effect at the same time, and a response surface model with high accuracy was fitted to predict the yield length of SSPP-ECC. The ductility of SSPP-ECC was positively related to its crack-control ability and it was shown that the crack width of SSPP-ECC increased significantly with a high content of superfine sand. This paper proposed a reasonable way to utilize superfine sand and provided the mix proportion of SSPP-ECC with characteristics of deformation hardening and multi-cracking, which may cater to the demands of many concrete components on ductility and crack resistance.
Stress Corrosion Cracking of Friction Stir-Welded AA-2024 T3 Alloy
Authors: Cabrini Marina , Bocchi Sara , D'Urso Gianluca , Giardini Claudio , Lorenzi Sergio , Testa Cristian , Pastore Tommaso
Published: June 2020

The paper is devoted to the study of stress corrosion cracking phenomena in friction stir welding AA-2024 T3 joints. Constant load (CL) cell and slow strain rate (SSR) tests were carried out in aerated NaCl 35 g/L solution. During the tests, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were measured in the different zones of the welding. The results evidenced initial practical nobilty of the nugget lower compared to both heat-affected zone and the base metal. This effect can be mainly ascribed to the aluminum matrix depletion in copper, which precipitates in form of copper-rich second phases. In this zones, no stress corrosion cracking was noticed, but well-evident stress-enhanced intergranular corrosion occurred. This is due to the uneven distribution of platic deformation during the slow strain rate tests. Higher strain values are localized at the heat affected zone, where softening occurs. On the contrary, stress values at the nugget are not sufficient to favor both the initiation and propagation of stress corrosion cracks. In the range of processing parameter studied in this experimental work, the stress corrosion cracking susceptibility of the friction stir welding (FSW)-ed alloy is then similar to that of the base metal.
Microstructure Evolution and Mechanical Stability of Supersaturated Solid Solution Co-Rich Nanocrystalline Co-Cu Produced by Pulsed Electrodeposition
Authors: Pratama Killang , Barrirero Jenifer , Mücklich Frank , Motz Christian
Published: June 2020

Thick films of supersaturated solid solution nanocrystalline Co-Cu (28 at.% Cu) were synthesized through the pulsed electrodeposition technique. Microstructural changes of nanocrystalline Co-Cu were intensively studied at various annealing temperatures. Annealing at 300 °C results in a spinodal decomposition within the individual grains, with no grain coarsening. On the other hand, distinct phase separation of Co-Cu is detected at annealing temperatures beyond 400 °C. Static micro-bending tests show that the nanocrystalline Co-Cu alloy exhibits a very high yield strength and ductile behavior, with no crack formation. Static micro-bending tests also reported that a large plastic deformation is observed, but no microstructure change is detected. On the other hand, observation on the fatigue resistance of nanocrystalline Co-Cu shows that grain coarsening is observed after conducting the cyclic micro-bending test.
New Constitutive Model for the Size Effect on Flow Stress Based on the Energy Conservation Law
Authors: Wang Chuanjie , Wang Haiyang , Chen Gang , Zhu Qiang , Cui Lingjiang , Zhang Peng , Dong Anping
Published: June 2020

In this study, a new model involving energy is established to characterize the size effect on flow stress. The new model treats the experimental machine and the specimen as an isolated system, and this isolated system satisfies the Energy Conservation Law. The total work performed on the specimen by the experimental machine is nearly equal to the energy consumed by the specimen plastic deformation and the energy consumed by friction (which can be ignored when working without friction). The new model predicts the energy consumption of the specimen deformation by quantifying the total energy input to the specimen by the experimental machine and then obtaining the relevant parameters of the constitutive model. Through uniaxial tensile tests of pure nickel thin sheets with various thickness/average grain sizes (t/d), the new model was used to optimize the parameters of the existing constitutive model that predicts the flow stress of specimens with different t/d. The prediction accuracy of the optimized constitutive model is improved, especially for specimens with a t/d < 1. The new model is established from the perspective of energy input to avoid the analysis of the material deformation mechanism and improve the prediction accuracy.
Removal Mechanism of Oxide Layer on the Surface of Sn-0.4Ti Alloy for Quartz Glass Sealing
Authors: Hao Wanli , Li Fangzi , Ma Yongbo , Zhang Weiguang , Shi Liqun
Published: June 2020

The oxide layer on the surface of Sn-0.4Ti alloy and its removal mechanism were investigated by coalitional analyses, using XPS and TEM technologies. The results show that a compact SnO1.65 oxide layer of less than 4 nm in thickness exists on the surface of Sn-0.4Ti alloy. A large number of TiO2 nanoparticles with scale of several to tens of nanometers were grown in Sn-0.4Ti matrix by depleting SnO1.65 while welding at 800 °C. These nanoparticles were adhered to the interfacial layer between Sn-0.4Ti alloy and quartz glass, which was formed by the reaction of Sn-0.4Ti and SiO2 after SnO1.65 removal from the Sn-0.4Ti. This work may promote further works on Sn-Ti design to further improve the welding quality between Sn-Ti alloy and quartz glass, and also provide a feasible research idea to remove the oxide layer on the surfaces of solders.