bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Treatment-Induced Microstructure and Property Evolution of Mg/Al Intermetallic Compound Coatings Prepared by Al Electrodeposition on Mg Alloy from Molten Salt Electrolytes
Authors: Yao Tianyu , Wang Kui , Yang Haiyan , Jiang Haiyan , Wei Jie , Wu Weiping , Liu Hezhou , Wang Qudong , Ding Wenjiang
Published: March 2021

A method of forming an Mg/Al intermetallic compound coating enriched with Mg17Al12 and Mg2Al3 was developed by heat treatment of electrodeposition Al coatings on Mg alloy at 350 °C. The composition of the Mg/Al intermetallic compounds could be tuned by changing the thickness of the Zn immersion layer. The morphology and composition of the Mg/Al intermetallic compound coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscattered diffraction (EBSD). Nanomechanical properties were investigated via nano-hardness (nHV) and the elastic modulus (EIT), and the corrosion behavior was studied through hydrogen evolution and potentiodynamic (PD) polarization. The compact and uniform Al coating was electrodeposited on the Zn-immersed AZ91D substrate. After heat treatment, Mg2Al3 and Mg17Al12 phases formed, and as the thickness of the Zn layer increased from 0.2 to 1.8 μm, the ratio of Mg2Al3 and Mg17Al12 varied from 1:1 to 4:1. The nano-hardness increased to 2.4 ± 0.5 GPa and further improved to 3.5 ± 0.1 GPa. The Mg/Al intermetallic compound coating exhibited excellent corrosion resistance and had a prominent effect on the protection of the Mg alloy matrix. The control over the ratio of intermetallic compounds by varying the thickness of the Zn immersion layer can be an effective approach to achieve the optimal comprehensive performance. As the Zn immersion time was 4 min, the obtained intermetallic compounds had relatively excellent comprehensive properties.
Failure Evaluation of Bridge Deck Based on Parallel Connection Bayesian Network: Analytical Model
Authors: Ding Yang , Dong Jingliang , Yang Tonglin , Zhou Shuangxi , Wei Yongqi
Published: March 2021

Failure is a major element that causes deterioration, which in turn affects the serviceability of long span bridges. Currently, the Bayesian network, which relates to probability statistics, is widely used for evaluating fatigue failure reliability. In particular, Bayesian network can not only calculate the fatigue failure at the system level, but also deduce the fatigue failure at the weld level. In this study, a system-level fatigue reliability evaluation model of a bridge deck (BD), which is seen as a parallel system, is proposed based on the Bayesian network. A fatigue probability reliability model of the BD was derived using the master S-N curve. In addition, the Monte Carlo (MC) method was applied to solve the multi-dimensional and complex analytical expressions in the Bayesian network. The applicability of the proposed model was demonstrated by three numerical case studies.
Recycling of Waste Solution after Hydrothermal Conversion of Fly Ash on a Semi-Technical Scale for Zeolite Synthesis
Authors: Panek Rafał , Madej Jarosław , Bandura Lidia , Słowik Grzegorz
Published: March 2021

Nowadays, using fly ash for zeolites production has become a well-known strategy aimed on sustainable development. During zeolite synthesis in a hydrothermal conversion large amount of post-reaction solution is generated. In this work, the solution was used as a substrate for Na-A and Na-X zeolites synthesis at laboratory and technical scale. Obtained materials were characterized using particle size analysis, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), and nitrogen adsorption/desorption isotherm. Produced zeolites revealed high purity (>98%) and monomineral zeolitic phase composition. The SiO2 content was in the range 39–42% and 40–38%, whereas Al2O3 content was 23–22% and 25–26% for Na-X and Na-A, respectively. TEM and BET analyses revealed Na-X zeolite pores were almost identical to commercial 13X with SBET in the range 671–734 m2/g. FTIR indicated slight differences between materials obtained at laboratory and technical scale in Si-O-(Si/Al) bridges of the zeolitic skeleton. The results showed good replicability of the laboratory process in the larger scale. The proposed method allows for waste solution reusability with a view to highly pure zeolites production in line with circular economy assumptions.
Thermal Energy Storage by the Encapsulation of Phase Change Materials in Building Elements—A Review
Authors: Reyez-Araiza José Luis , Pineda-Piñón Jorge , López-Romero José M. , Gasca-Tirado José Ramón , Arroyo Contreras Moises , Jáuregui Correa Juan Carlos , Apátiga-Castro Luis Miguel , Rivera-Muñoz Eric Mauricio , Velazquez-Castillo Rodrigo Rafael , Pérez Bueno José de Jesús , Manzano-Ramirez Alejandro
Published: March 2021

The energy sector is one of the fields of interest for different nations around the world. Due to the current fossil fuel crisis, the scientific community develops new energy-saving experiences to address this concern. Buildings are one of the elements of higher energy consumption, so the generation of knowledge and technological development may offer solutions to this energy demand, which are more than welcome. Phase change materials (PCMs) included in building elements such as wall panels, blocks, panels or coatings, for heating and cooling applications have been shown, when heating, to increase the heat storage capacity by absorbing heat as latent heat. Therefore, the use of latent heat storage systems using phase change materials (PCMs) has been investigated within the last two decades. In the present review, the macro and micro encapsulation methods for construction materials are reviewed, the former being the most viable method of inclusion of PCMs in construction elements. In addition, based on the analysis of the existing papers on the encapsulation process of PCMs, the importance to pay more attention to the bio-based PCMs is shown, since more research is needed to process such PCMs. To determine its thermophysical and mechanical behavior at the micro and macro levels, in order to see the feasibility of substituting petroleum-based PCMs with a more environmentally friendly bio-based one, a section devoted to the excellent PCM with lightweight aggregate (PCM-LWA concrete) is presented due to the lack of description given in other reviews.
Fatigue Life Improvement of Cracked Aluminum 6061-T6 Plates Repaired by Composite Patches
Authors: Yousefi Armin , Jolaiy Saman , Hedayati Reza , Serjouei Ahmad , Bodaghi Mahdi
Published: March 2021

Bonded patches are widely used in several industry sectors for repairing damaged plates, cracks in metallic structures, and reinforcement of damaged structures. Composite patches have optimal properties such as high strength-to-weight ratio, easiness in being applied, and high flexibility. Due to recent rapid growth in the aerospace industry, analyses of adhesively bonded patches applicable to repairing cracked structures have become of great significance. In the present study, the fatigue behavior of the aluminum alloy, repaired by a double-sided glass/epoxy composite patch, is studied numerically. More specifically, the effect of applying a double-sided composite patch on the fatigue life improvement of a damaged aluminum 6061-T6 is analyzed. 3D finite element numerical modeling is performed to analyze the fatigue performance of both repaired and unrepaired aluminum plates using the Abaqus package. To determine the fatigue life of the aluminum 6061-T6 plate, first, the hysteresis loop is determined, and afterward, the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted and validated against the available experimental data from the literature. Results reveal that composite patches increase the fatigue life of cracked structures significantly, ranging from 55% to 100% for different applied stresses.
Simple Model for Alkali Leaching from Geopolymers: Effects of Raw Materials and Acetic Acid Concentration on Apparent Diffusion Coefficient
Authors: Ukrainczyk Neven
Published: March 2021

This paper investigates alkali leaching from geopolymers under various concentrations of acetic acid solutions. The effects of the raw metakaolin purity as well as fly ash-based geopolymer mortars and pastes are considered. A new methodology for (acetic) acid attack is proposed, adapting standard approaches, where the concentration of the leached alkali in the exposure solution is measured over time. The applicability of a simple diffusion-based mathematical model to determine the apparent diffusion coefficient (Dapp) for geopolymer pastes and mortars was validated. At the end of the paste tests, microstructural alterations of the specimens’ cross-sections were analyzed microscopically, revealing occurrence of degradation across the outermost surface parts and, especially under acid attack, the formation of long cracks that connect the surface with the intact inner zone. Drastically different Dapp are discussed in terms of the differences in the mix designs, principally resulting in different alkali-binding capacities of the geopolymers, while the acid promoted dissolution and increased porosity. As a result of this interpretation, it was concluded that Dapp is governed mainly by the chemistry of the alkali release from the gel, as it overruled the effects of porosity and cracks.
Study of a Gate-Engineered Vertical TFET with GaSb/GaAs0.5Sb0.5 Heterojunction
Authors: Xie Haiwu , Chen Yanning , Liu Hongxia , Guo Dan
Published: March 2021

It is well known that the vertical tunnel field effect transistor (TFET) is easier to fabricate than the conventional lateral TFETs in technology. Meanwhile, a lightly doped pocket under the source region can improve the subthreshold performance of the vertical TFETs. This paper demonstrates a dual material gate heterogeneous dielectric vertical TFET (DMG-HD-VTFET) with a lightly doped source-pocket. The proposed structure adopts a GaSb/GaAs0.5Sb0.5 heterojunction at the source and pocket to improve the band-to-band tunneling (BTBT) rate; at the same time, the gate electrode is divided into two parts, namely a tunnel gate (M1) and control gate (M2) with work functions ΦM1 and ΦM2, where ΦM1 > ΦM2. In addition, further performance enhancement in the proposed device is realized by a heterogeneous dielectric corresponding to a dual material gate. Simulation results indicate that DMG-HD-VTFET and HD-VTFET possess superior metrics in terms of DC (Direct Current) and RF (Radio Frequency) performance as compared with conventional VTFET. As a result, the ON-state current of 2.92 × 10−4 A/μm, transconductance of 6.46 × 10−4 S/μm, and average subthreshold swing (SSave) of 18.1 mV/Dec at low drain voltage can be obtained. At the same time, DMG-HD-VTFET could achieve a maximum fT of 459 GHz at 0.72 V gate-to-source voltage (Vgs) and a maximum gain bandwidth (GBW) of 35 GHz at Vgs = 0.6 V, respectively. So, the proposed structure will have a great potential to boost the device performance of traditional vertical TFETs.
Aeroelastic Response of Aircraft Wings to External Store Separation Using Flexible Multibody Dynamics
Authors: Tamer Aykut
Published: March 2021

In aviation, using external stores under the wings is a common method of carrying payload or fuel. In some cases, the payload can be rigidly attached to the wing. However, stores must often be ejected during flight for aircraft, such as military type, which carry drop tanks and missiles. This may cause the wing to respond dynamically with increasing amplitudes, due to the impulsive load of ejection and the change of total mass. This is especially critical in aircraft with highly flexible wings, such as those with high aspect ratios. In this case, it is crucial to evaluate the wing response to store separation, which requires a suitable simulation environment that is able to support nonlinear and multidisciplinary analysis. To address such a need, this work presents the use of flexible multibody dynamics in the simulation of wing response to store separation. To demonstrate, a highly compliant wing was selected with a rigid body that was mounted on the wing to represent an external store. The time marching simulation of the wing before and after the store separation was presented to show the features and benefits of the method.
The Simulation of Heat Supply System with a Scale Formation Factor to Enable Automation of Greenhouse Geothermal Heat Supply System
Authors: Korzhakov Alexey , Oskin Sergei , Korzhakov Valery , Korzhakova Svetlana
Published: March 2021

This article presents the results of the simulation of an automatic control system for the heat supply of a greenhouse complex with a geothermal heat source, conducted in order to study the possibility of geothermal heat supply system automation. Scilab version 6.1 was used for simulation. Based on the results of the simulation, the optimal mode of the automation system function of the heat exchanger primary circuit was developed and implemented. Reagentless treatment of geothermal water in the heat supply system with an acoustic–magnetic device (designed and patented by the authors of this paper) can significantly reduce the intensity of scale formation in the heat exchanger and geothermal heat supply system equipment. It provides conditions for the automation of geothermal heat supply systems of greenhouses with a surface heat exchanger. Using an automation system allows greater accuracy and reliability in maintaining the required temperature regime (18–20 °C) in the greenhouse, reduces the frequency of system shutdown for unplanned cleaning of the heat exchanger and equipment, reduces the complexity of manual operations of heat exchanger and equipment maintenance (removal of sludge, scale) and reduces the economic costs of transportation and heat consumption.
Effects of Perpendicular Magnetic Field Annealing on the Structural and Magnetic Properties of [Co/Ni]2/PtMn Thin Films
Authors: Yadav Roshni , Wu Chun-Hsien , Huang I-Fen , Li Xu , Wu Te-Ho , Lin Ko-Wei
Published: March 2021

In this study, [Co/Ni]2/PtMn thin films with different PtMn thicknesses (2.7 to 32.4 nm) were prepared on Si/SiO2 substrates. The post-deposition perpendicular magnetic field annealing (MFA) processes were carried out to modify the structures and magnetic properties. The MFA process also induced strong interlayer diffusion, rendering a less sharp interface between Co and Ni and PtMn layers. The transmission electron microscopy (TEM) lattice image analysis has shown that the films consisted of face-centered tetragonal (fct) PtMn (ordered by MFA), body-centered cubic (bcc) NiMn (due to intermixing), in addition to face-centered cubic (fcc) Co, Ni, and PtMn phases. The peak shift (2-theta from 39.9° to 40.3°) in X-ray diffraction spectra also confirmed the structural transition from fcc PtMn to fct PtMn after MFA, in agreement with those obtained by lattice images in TEM. The interdiffusion induced by MFA was also evidenced by the depth profile of X-ray photoelectron spectroscopy (XPS). Further, the magnetic properties measured by vibrating sample magnetometry (VSM) have shown an increased coercivity in MFA-treated samples. This is attributed to the presence of ordered fct PtMn, and NiMn phases exchange coupled to the ferromagnetic [Co/Ni]2 layers. The vertical shift (Mshift = −0.03 memu) of the hysteresis loops is ascribed to the pinned spins resulting from perpendicular MFA processes.
Structures and Properties of 4-phpy, pyz, and 4,4′-bpy Adducts of Lantern-Type Dirhodium Complexes with µ-Formamidinato and µ-Carboxylato Bridges
Authors: Handa Makoto , Nishiura Satoshi , Kano Makoto , Yano Natsumi , Akashi Haruo , Mikuriya Masahiro , Tanaka Hidekazu , Kawamoto Tatsuya , Kataoka Yusuke
Published: March 2021

Dinuclear and polymer complexes of 4-phenylpyridine (4-phpy), pyazine (pyz), and 4,4′-bipyridine (4,4′-bpy) were prepared by using cis-[Rh2(4-Me-pf)2(O2CR)2] (4-Me-pf- =N,N’-bis(4-methylphenyl)formamidinate anion; R = CF3 and CMe3) as precursor dinuclear units. The dinuclear structures of cis-[Rh2II,II(4-Me-pf)2(O2CR)2(4-phpy)2] and cis-[Rh2II,III(4-Me-pf)2(O2CCMe3)2(4-phpy)2]BF4 and polymer structures of [Rh2II,II(4-Me-pf)2(O2CR)2(L)]n (L = pyz and 4,4′-bpy) were confirmed by X-ray crystal structure analyses. In these complexes, the lantern-type dinuclear core structures with cis-(2:2) arrangement of formamidinato (4-Me-pf-) and carboxylato ligands are preserved with Rh–Rh distances of 2.44–2.47 Å, regardless of the difference in the axial ligand and oxidation state Rh2II,II or Rh2II,III. In the cyclic voltammograms (CVs) in CH2Cl2, the redox potentials for Rh2II,III/Rh2II,II were estimated as E1/2 = 0.07 V and −0.28 V (vs. Fc+/Fc) for cis-[Rh2(4-Me-pf)2(O2CCF3)2(4-phpy)2] and cis-[Rh2(4-Me-pf)2(O2CCMe3)2(4-phpy)2], respectively, negatively shifted by 0.16 and 0.12 V compared with those of corresponding parent dinuclear complexes. The results were interpreted that the axial interaction with 4-phpy ligands makes the Rh2II,II core oxidized easily. The oxidized complex cis-[Rh2(4-Me-pf)2(O2CCMe3)2(4-phpy)2]BF4 is paramagnetic, which was confirmed by effective magnetic moment value μeff = 1.90 μB at 300 K per Rh2II,III unit (S = 1/2). The polymer complexes [Rh2(4-Me-pf)2(O2CR)2(L)]n (L = pyz and 4,4′-bpy) showed Type II gas-adsorption properties for N2.
Motor Imagery Classification Based on a Recurrent-Convolutional Architecture to Control a Hexapod Robot
Authors: Mwata-Velu Tat’y , Ruiz-Pinales Jose , Rostro-Gonzalez Horacio , Ibarra-Manzano Mario Alberto , Cruz-Duarte Jorge Mario , Avina-Cervantes Juan Gabriel
Published: March 2021

Advances in the field of Brain-Computer Interfaces (BCIs) aim, among other applications, to improve the movement capacities of people suffering from the loss of motor skills. The main challenge in this area is to achieve real-time and accurate bio-signal processing for pattern recognition, especially in Motor Imagery (MI). The significant interaction between brain signals and controllable machines requires instantaneous brain data decoding. In this study, an embedded BCI system based on fist MI signals is developed. It uses an Emotiv EPOC+ Brainwear®, an Altera SoCKit® development board, and a hexapod robot for testing locomotion imagery commands. The system is tested to detect the imagined movements of closing and opening the left and right hand to control the robot locomotion. Electroencephalogram (EEG) signals associated with the motion tasks are sensed on the human sensorimotor cortex. Next, the SoCKit processes the data to identify the commands allowing the controlled robot locomotion. The classification of MI-EEG signals from the F3, F4, FC5, and FC6 sensors is performed using a hybrid architecture of Convolutional Neural Networks (CNNs) and Long Short-Term Memory (LSTM) networks. This method takes advantage of the deep learning recognition model to develop a real-time embedded BCI system, where signal processing must be seamless and precise. The proposed method is evaluated using k-fold cross-validation on both created and public Scientific-Data datasets. Our dataset is comprised of 2400 trials obtained from four test subjects, lasting three seconds of closing and opening fist movement imagination. The recognition tasks reach 84.69% and 79.2% accuracy using our data and a state-of-the-art dataset, respectively. Numerical results support that the motor imagery EEG signals can be successfully applied in BCI systems to control mobile robots and related applications such as intelligent vehicles.
Flipped-OCN Method in Mathematics Learning to Analyze the Attitudes of Pre-Service Teachers
Authors: Jeong Jin Su , González-Gómez David
Published: March 2021

Due to the learning difficulties in mathematics education, a new teaching methodology have been proposed for its improvement. Difficulties in mathematics learning indicate that students are not able to properly deal with resolving calculations and/or problems. This research examines the evolution of the attitudes of pre-service teachers’ (PSTs) toward mathematics learning when an open calculation based on numbers (OCN) method was followed in a flipped classroom. It was conducted in a general mathematics course, Primary Education bachelor’s degree during the course of 2019/2020. A total of 143 students participated in the study (230 students enrolled), with a pre- and post-test survey questionnaire. Based on the analysis of survey questionnaires, the obtained results demonstrated that the attitudes (own beliefs and conceptions (OB), positive (ATP), and negative (ATN) attitudes) of PSTs improved positively after completing the flipped-OCN method toward mathematics learning. Regarding the statistical analyses, all questions had a significant difference that showed the influence of the flipped-OCN method, improving the PSTs attitudes toward mathematics learning (p < 0.005). According to the structural equation modeling—partial least squares (SEM-PLS) analysis, it demonstrated that the components relation effects of OB, ATP, and ATN of PSTs toward mathematics learning, and the influence of their educational background. Finally, with the principal component analysis (PCA), it can be found out that the science and technology background were positively correlated after the flipped-OCN method comparing with the rest of PSTs. The influence of the proposed method indicated a significant improvement in these components. Therefore, the results concluded that this study allowed to draw a promising tendency about the PSTs’ attitudes toward mathematics learning with the OCN method in the flipped classroom. Additionally, these outcomes could advance our comprehension of how to help pre-service education for teachers’ enhancement and maturity of positive attitudes about themselves as future teachers. Then, it would be a fundamental piece in building logical and critical thinking and development for children.
GMM Estimation of a Partially Linear Additive Spatial Error Model
Authors: Chen Jianbao , Cheng Suli
Published: March 2021

This article presents a partially linear additive spatial error model (PLASEM) specification and its corresponding generalized method of moments (GMM). It also derives consistency and asymptotic normality of estimators for the case with a single nonparametric term and an arbitrary number of nonparametric additive terms under some regular conditions. In addition, the finite sample performance for our estimates is assessed by Monte Carlo simulations. Lastly, the proposed method is illustrated by analyzing Boston housing data.
Fucoidan and Fucoxanthin Attenuate Hepatic Steatosis and Inflammation of NAFLD through Modulation of Leptin/Adiponectin Axis
Authors: Shih Ping-Hsiao , Shiue Sheng-Jie , Chen Chun-Nan , Cheng Sheng-Wei , Lin Hsin-Yi , Wu Li-Wei , Wu Ming-Shun
Published: March 2021

Non-alcoholic fatty liver disease (NAFLD) is the emerging cause of chronic liver disease globally and lack of approved therapies. Here, we investigated the feasibility of combinatorial effects of low molecular weight fucoidan and high stability fucoxanthin (LMF-HSFx) as a therapeutic approach against NAFLD. We evaluated the inhibitory effects of LMF-HSFx or placebo in 42 NAFLD patients for 24 weeks and related mechanism in high fat diet (HFD) mice model and HepaRGTM cell line. We found that LMF-HSFx reduces the relative values of alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglyceride, fasting blood glucose and hemoglobin A1c in NAFLD patients. For lipid metabolism, LMF-HSFx reduces the scores of controlled attenuation parameter (CAP) and increases adiponectin and leptin expression. Interestingly, it reduces liver fibrosis in NAFLD patients, either. The proinflammatory cytokines interleukin (IL)-6 and interferon-γ are reduced in LMF-HSFx group. In HFD mice, LMF-HSFx attenuates hepatic lipotoxicity and modulates adipogenesis. Additionally, LMF-HSFx modulates SIRI-PGC-1 pathway in HepaRG cells under palmitic acid-induced lipotoxicity environment. Here, we describe that LMF-HSFx ameliorated hepatic steatosis, inflammation, fibrosis and insulin resistance in NAFLD patients. LMF-HSFx may modulate leptin-adiponectin axis in adipocytes and hepatocytes, then regulate lipid and glycogen metabolism, decrease insulin resistance and is against NAFLD.
Can Conventional and Diffusion-Weighted MR Enterography Biomarkers Differentiate Inflammatory from Fibrotic Strictures in Crohn’s Disease?
Authors: Foti Pietro Valerio , Travali Mario , Farina Renato , Palmucci Stefano , Coronella Maria , Spatola Corrado , Puzzo Lidia , Garro Rossella , Inserra Gaetano , Riguccio Gaia , Zanoli Luca , Basile Antonio
Published: March 2021

Background and Objectives: To retrospectively assess the value of magnetic resonance enterography (MRE) parameters derived from conventional and diffusion weighted imaging (DWI) sequences to differentiate fibrotic strictures from inflammatory ones in adult patients with Crohn’s disease (CD), using surgical specimens as the histopathological reference standard. Material and Methods: Twenty-three patients with CD who had undergone surgical resection of ileal strictures with full-thickness histopathologic analysis within 3 months from preoperative MRE were included. Two radiologists blinded to histopathology in consensus evaluated the following biomarkers on MRE images matched to resected pathological specimens: T1 ratio, T2 ratio, enhancement pattern, mural thickness, pre-stenotic luminal diameter, and apparent diffusion coefficient (ADC). A blinded pathologist graded stricture histological specimens with acute inflammation score (AIS) and fibrosis score (FS). MRE measurements were correlated with the reference standard. Results: Inflammation and fibrosis coexisted in 78.3% of patients. T2 ratio was reduced in patients with severe fibrosis (p = 0.01). Pre-stenotic bowel dilatation positively correlated with FS (p = 0.002). The ADC value negatively correlated with FS (p < 0.001) and was different between FS grades (p < 0.05). The area under the receiver operating characteristic curve for discriminating between none and mild/moderate–severe bowel wall fibrosis was 0.75 for pre-stenotic bowel dilatation (sensitivity 100%, specificity 44.4%) and 0.97 for ADC (sensitivity 80%, specificity 100%). Conclusions: Inflammation and fibrosis often coexist in CD bowel strictures needing surgery. The combination of parameters derived from conventional MR sequences (T2 ratio, pre-stenotic dilatation) and from DWI (ADC) may provide a contribution to detect and grade bowel fibrosis in adult CD patients.
Current Status of the Self-Expandable Metal Stent as a Bridge to Surgery Versus Emergency Surgery in Colorectal Cancer: Results from an Updated Systematic Review and Meta-Analysis of the Literature
Authors: Cirocchi Roberto , Arezzo Alberto , Sapienza Paolo , Crocetti Daniele , Cavaliere Davide , Solaini Leonardo , Ercolani Giorgio , Sterpetti Antonio V. , Mingoli Andrea , Fiori Enrico
Published: March 2021

Background: The current use of endoscopic stenting as a bridge to surgery is not always accepted in standard clinical practice to treat neoplastic colonic obstructions. Objectives: The role of colonic self-expandable metal stent (SEMS) positioning as a bridge to resective surgery versus emergency surgery (ES) for malignant obstruction, using all new data and available variables, was studied and we focused on short- and long-term results. Materials and Methods: A systematic review with meta-analysis was performed. PubMed, SCOPUS and Web of Science databases were included. The search comprised only randomized controlled trials (RCTs) investigating the interventions that included SEMS positioning versus ES. The primary outcomes were the rates of overall postoperative mortality, clinical and technical success. The secondary outcomes were the short- and long-term results. Results: A total of 12 studies were eligible for further analyses. A laparoscopic colectomy was the most common operation performed in the SEMS group, whereas the traditional open approach was commonly used in the ES group. Intraoperative colonic lavage was seldomly performed during ES. There were no differences in mortality rates between the two groups (RR 1.06, 95% CI 0.55 to 2.04; I2 = 0%). In the SEMS group, the rate of successful primary anastomosis was significantly higher in of SEMS (69.75%) than in the ES (55.07%) (RR 1.26, 95% 245 CI 1.01 to 1.57; I2 = 86%). Conversely, the upfront Hartmann procedure was performed more frequently in the ES (39.1%) as compared to the SEMS group (23.4%) (RR 0.61, 95% CI 0.45 to 0.85; I2 = 23%). The overall postoperative complications rate was significantly lower in the SEMS group (32.74%) than in the ES group (48.25%) (RR 0.61, 95% CI 0.41 to 0.91; I2 = 65%). Conclusions: In the presence of malignant colorectal obstruction, SEMS is safe and associated with the same mortality and significantly lower morbidity than the ES group. The rate of successful primary anastomosis was significantly higher than the ES group. Nevertheless, recurrence and survival outcomes are not significantly different between the two groups. The analysis of short- and long-term results can suggest the use of SEMS as a bridge to resective surgery when it is performed by an endoscopist with adequate expertise in both colonoscopy and fluoroscopic techniques and who performed commonly colonic stenting.
Adrenal Cortical Rests in the Fallopian Tube: Report of a Case and Review of the Literature
Authors: Tzigkalidis Theodoros , Skandalou Eleni , Manthou Maria Eleni , Kolovogiannis Nikolaos , Meditskou Soultana
Published: March 2021

We report an extremely unusual finding discovered incidentally during a routine pathologic evaluation of a fallopian tube, surgically removed on the grounds of ectopic pregnancy. We came across a minute yellowish nodule situated within the wall of the salpinx, which corresponded to ectopic adrenal cortex, as verified by microscopical examination, and coexisted with salpingitis isthmica nodosa. A research of the available English literature on this subject confirmed the rareness of the entity we encountered. This case is presented because of its uniqueness, aiming to raise awareness of a rare condition which is discussed along with potential diagnostic dilemmas, its prognostic significance, and possible complications.
“Artificial Wood” Lignocellulosic Membranes: Influence of Kraft Lignin on the Properties and Gas Transport in Tunicate-Based Nanocellulose Composites
Authors: Pylypchuk Ievgen , Selyanchyn Roman , Budnyak Tetyana , Zhao Yadong , Lindström Mikael , Fujikawa Shigenori , Sevastyanova Olena
Published: March 2021

Nanocellulose membranes based on tunicate-derived cellulose nanofibers, starch, and ~5% wood-derived lignin were investigated using three different types of lignin. The addition of lignin into cellulose membranes increased the specific surface area (from 5 to ~50 m2/g), however the fine porous geometry of the nanocellulose with characteristic pores below 10 nm in diameter remained similar for all membranes. The permeation of H2, CO2, N2, and O2 through the membranes was investigated and a characteristic Knudsen diffusion through the membranes was observed at a rate proportional to the inverse of their molecular sizes. Permeability values, however, varied significantly between samples containing different lignins, ranging from several to thousands of barrers (10−10 cm3 (STP) cm cm−2 s−1 cmHg−1cm), and were related to the observed morphology and lignin distribution inside the membranes. Additionally, the addition of ~5% lignin resulted in a significant increase in tensile strength from 3 GPa to ~6–7 GPa, but did not change thermal properties (glass transition or thermal stability). Overall, the combination of plant-derived lignin as a filler or binder in cellulose–starch composites with a sea-animal derived nanocellulose presents an interesting new approach for the fabrication of membranes from abundant bio-derived materials. Future studies should focus on the optimization of these types of membranes for the selective and fast transport of gases needed for a variety of industrial separation processes.
Superior Hydrogen Sorption Kinetics of Ti0.20Zr0.20Hf0.20Nb0.40 High-Entropy Alloy
Authors: Zhang Jianwei , Li Pengcheng , Huang Gang , Zhang Weiguang , Hu Jutao , Xiao Haiyan , Zheng Jian , Zhou Xiaosong , Xiang Xia , Yu Jingxia , Shen Huahai , Li Sean , Zu Xiaotao
Published: March 2021

High entropy alloys (HEAs) are composed of multiple main metal elements and have attracted wide attention in various fields. In this study, a novel Ti0.20Zr0.20Hf0.20Nb0.40 HEA was synthesized and its hydrogenation properties were studied, including sorption thermodynamics and hydrogen absorption/desorption kinetics. The maximum hydrogen absorption capacity was 1.5 H/atom at 573 K. X-ray diffraction (XRD) analysis indicated that the crystal structure of Ti0.20Zr0.20Hf0.20Nb0.40 HEA transformed from body-centered cubic (BCC) to body-centered tetragonal (BCT) with increasing hydrogen content, and to face-centered cubic (FCC) after hydrogen absorption to saturation. As a multi-principal element alloy, the Ti0.20Zr0.20Hf0.20Nb0.40 HEA possesses unique hydrogen absorption characteristics. The hydrogen absorption platform pressure rises gradually with the increase of the hydrogen absorption amount, which is caused by multiple kinds of BCT intermediate hydrides with consecutively increasing c/a. The full hydrogen absorption of the Ti0.20Zr0.20Hf0.20Nb0.40 HEA was completed in almost 50 s, which is faster than that of the reported hydrogen storage alloys in the literature. The experimental results demonstrate that the Ti0.20Zr0.20Hf0.20Nb0.40 HEA has excellent kinetic properties, unique thermodynamic hydrogen absorption performance, as well as a low plateau pressure at room temperature.
Development of Universal Mould Geometry for the Teeming of Cylindrical Iron-Base Alloy Ingots
Authors: Odehnal Josef , Ludvík Pavel , Studecký Tomáš , Michálek Pavel
Published: March 2021

The presented work is aimed at developing a mould geometry suitable for casting both low- and high-alloy steel grades into 500 kg experimental ingots. The high Height-to-Diameter (H/D)-ratio mould currently used in COMTES FHT Inc. served as a reference and for finite element method simulations (FEM) of the filling and solidification process. The optimized mould geometry, balancing the porosity and segregations, was determined using MAGMA software. Four different steel grades were defined for the simulation. Case studies were carried out for 34CrNiMo6 (W.Nr. 1.6582), DHQ8, CB2 and borated stainless steel grades ranging from low-alloy steel to high-alloy steel. Extended user-defined criteria and verified boundary conditions were used to predict the formation of A-segregations in cast steel. Both primary (PDAS) and secondary (SDAS) arm spacings were modelled as well. The optimized mould shape and the casting assembly were designed based on the simulation results.
Effect of Normalizing Treatment on Mechanical Properties of AISI 441 Stainless Steel Prepared by Investment Casting
Authors: Hu Yukun , Mao Weimin , Yan Pengyu , Li Naiyong
Published: March 2021

In this paper, AISI 441 stainless steel was investigated as a casting steel using the investment casting process (ICP). The microstructure and mechanical properties of the as-cast and normalizing treatment samples were analyzed. The results show that the tensile strength of as-cast AISI 441 prepared by ICP is 458 MPa, and the elongation is 22.7%. Normalizing treatment can improve the mechanical performance of AISI 441 prepared by ICP, but strength and elongation have a slightly decreasing trend with increasing normalizing temperature and time. The suitable normalizing treatment condition is 850 °C for 2 h. It was found that normalizing temperature and time have little effect on grain size and carbonitride. There was an increasing trend in the mean equivalent length (MEL) of the Laves phase as normalizing temperature and time increases. The effect of normalizing treatment on strength increment was mainly related to the change of the Laves phase size.
Advantageous Description of Short Fatigue Crack Growth Rates in Austenitic Stainless Steels with Distinct Properties
Authors: Trávníček Lukáš , Kuběna Ivo , Mazánová Veronika , Vojtek Tomáš , Polák Jaroslav , Hutař Pavel , Šmíd Miroslav
Published: March 2021

In this work two approaches to the description of short fatigue crack growth rate under large-scale yielding condition were comprehensively tested: (i) plastic component of the J-integral and (ii) Polák model of crack propagation. The ability to predict residual fatigue life of bodies with short initial cracks was studied for stainless steels Sanicro 25 and 304L. Despite their coarse microstructure and very different cyclic stress–strain response, the employed continuum mechanics models were found to give satisfactory results. Finite element modeling was used to determine the J-integrals and to simulate the evolution of crack front shapes, which corresponded to the real cracks observed on the fracture surfaces of the specimens. Residual fatigue lives estimated by these models were in good agreement with the number of cycles to failure of individual test specimens strained at various total strain amplitudes. Moreover, the crack growth rates of both investigated materials fell onto the same curve that was previously obtained for other steels with different properties. Such a “master curve” was achieved using the plastic part of J-integral and it has the potential of being an advantageous tool to model the fatigue crack propagation under large-scale yielding regime without a need of any additional experimental data.
Process Condition Diagram Predicting Onset of Microdefects and Fracture in Cold Bar Drawing
Authors: Roh Yong-Hoon , Cho Donghyuk , Choi Hae-Chang , Yang Zhaorui , Lee Youngseog
Published: March 2021

This paper presents a process condition diagram (PCD) that not only identifies conditions under which materials fracture during bar drawing, but also infers the presence or absence of microdefects such as microvoids and microcracks in the drawn material as accumulative damage changes owing to the die semi-angle and reduction ratio. The accumulative damage values were calculated by finite element (FE) analysis. The critical damage values were determined by performing a tensile test using a smooth round bar tensile specimen and performing FE analysis simulating the tensile test. High alloy steel with a 13 mm diameter was used for the draw bench testing in a wide range of drawing conditions. Scanning electron microscopy (SEM) analysis was performed to verify the usefulness of the PCD. SEM images showed that the accumulative damage roughly matched the size of microvoids around the non-metallic inclusions and the creation of microcracks, which eventually led to fractures of material being drawn. Hence, utilizing the proposed PCD, a process designer can design drawing conditions that minimize the occurrence of microdefects in the material being drawn while maximizing the reduction ratio.
Achieving Accuracy Improvements for Single-Point Incremental Forming Process Using a Circumferential Hammering Tool
Authors: Nasulea Daniel , Oancea Gheorghe
Published: March 2021

The paper presents a novel solution for improving the accuracy of the wall area of parts manufactured by single point incremental forming. Thus, a forming tool with a special design that works according to the principle of circumferential hammering is deployed, with a direct improving effect of the forming conditions and consequently of the dimensional accuracy of the part. The research is focused on an experimental study of frustum-of-cone shapes manufactured from sheet metal blanks of DC05 deep drawing steel of 1 mm thickness. A typical customary technological setup is used for the single point incremental forming process, without any additional elements, and two forming tools, a hemispherical and a special one, which use the circumferential hammering effect. Several preliminary tests using both tools were performed in order to prove that part accuracy can be significantly improved by using the circumferential hammering tool. The research was further expanded to investigate the influence on part wall dimensional accuracy of three factors: tool spindle speed, tool feed rate and part dimensional configuration. Using a full factorial plan of experiments the results of 32 test runs were processed. All parts were machined adequately, free of any material fracturing. Based on the achieved machining accuracy of the part walls, precision mathematical models were developed for the prediction of part dimensional accuracy in those areas. The mathematical models were validated by practice, as the predicted accuracies were matched by the experimental results.
Prediction of Fatigue Limit of Spring Steel Considering Surface Defect Size and Stress Ratio
Authors: Ishii Takehiro , Takahashi Koji
Published: March 2021

Surface defects decrease the fatigue limit of metals. In this study, the effects of surface defects on the fatigue limit of high-strength spring steel specimens were investigated. Several equations to predict the fatigue limit of specimens with surface defects were evaluated. Specimens with a semicircular slit with depths ranging from 30 to 400 µm were prepared. The Vickers hardness of the specimen was approximately 470 HV. Bending fatigue tests were performed at stress ratios ranging from −2 to 0.4. The fatigue test results showed that the fatigue limit decreased with an increase in the slit depth. Moreover, the maximum defect size that resulted in a decrease in the fatigue limit was dependent on the stress ratio. On comparing the predicted fatigue limits with the experimental results, it was confirmed that the predictions made based on the modified El-Haddad model were in good agreement with the experimentally obtained data. Thus, this model can be used to evaluate the fatigue limit of high-strength steels containing small surface defects with different stress ratios.
Effect of Mo Element on the Mechanical Properties and Tribological Responses of CoCrFeNiMox High-Entropy Alloys
Authors: Liu Ying , Xie Yongxin , Cui Shaogang , Yi Yanliang , Xing Xuewei , Wang Xiaojian , Li Wei
Published: March 2021

Certain amounts of precipitate in CoCrFeNiMox (simplified as Mox) is beneficial to the wear resistance; however, the optimal chemical content of Mo and the anti-wear mechanism behind it remains unclear. The Mox (x = 0, 0.3, 0.5, 1, 1.5 in molar ratio) high entropy alloys (HEAs) were manufactured, the evolution of their microstructure, mechanical, friction, and wear properties with Mo content was studied. The results displayed that the mechanical properties of the FCC solid solution were enhanced from Mo0 to Mo0.3, then kept unchanged till x = 1.5. The volume fraction of the precipitates increased with Mo content. The Mo1 presents the lower average friction coefficient and wear rate, attributed to the desired types, amount, size, distribution of the hard σ and μ phases in the ductile FCC solid solution. The detailed mechanism behind their tribological behaviors were discussed in the manuscript.
Bionic Organs: Shear Forces Reduce Pancreatic Islet and Mammalian Cell Viability during the Process of 3D Bioprinting
Authors: Klak Marta , Kowalska Patrycja , Dobrzański Tomasz , Tymicki Grzegorz , Cywoniuk Piotr , Gomółka Magdalena , Kosowska Katarzyna , Bryniarski Tomasz , Berman Andrzej , Dobrzyń Agnieszka , Sadowski Wojciech , Górecki Bartosz , Wszoła Michał
Published: March 2021

Background: 3D bioprinting is the future of constructing functional organs. Creating a bioactive scaffold with pancreatic islets presents many challenges. The aim of this paper is to assess how the 3D bioprinting process affects islet viability. Methods: The BioX 3D printer (Cellink), 600 μm inner diameter nozzles, and 3% (w/v) alginate cell carrier solution were used with rat, porcine, and human pancreatic islets. Islets were divided into a control group (culture medium) and 6 experimental groups (each subjected to specific pressure between 15 and 100 kPa). FDA/PI staining was performed to assess the viability of islets. Analogous studies were carried out on α-cells, β-cells, fibroblasts, and endothelial cells. Results: Viability of human pancreatic islets was as follows: 92% for alginate-based control and 94%, 90%, 74%, 48%, 61%, and 59% for 15, 25, 30, 50, 75, and 100 kPa, respectively. Statistically significant differences were observed between control and 50, 75, and 100 kPa, respectively. Similar observations were made for porcine and rat islets. Conclusions: Optimal pressure during 3D bioprinting with pancreatic islets by the extrusion method should be lower than 30 kPa while using 3% (w/v) alginate as a carrier.
Small Noncoding RNAs MTS0997 and MTS1338 Affect the Adaptation and Virulence of Mycobacterium tuberculosis
Authors: Shepelkova Galina , Evstifeev Vladimir , Averbakch Jr. Mikhail , Sivokozov Ilya , Ergeshov Atadzhan , Azhikina Tatyana , Yeremeev Vladimir
Published: March 2021

Tuberculosis (TB) is currently the leading cause of death among bacterial infectious diseases. The spectrum of disease manifestations depends on both host immune responses and the ability of Mycobacterium tuberculosis to resist it. Small non-coding RNAs are known to regulate gene expression; however, their functional role in the relationship of M. tuberculosis with the host is poorly understood. Here, we investigated the effect of small non-coding sRNAs MTS1338 and MTS0997 on M. tuberculosis properties by creating knockout strains. We also assessed the effect of small non-coding RNAs on the survival of wild type and mutant mycobacteria in primary cultures of human alveolar macrophages and the virulence of these strains in a mouse infection model. Wild-type and mutants survived differentially in human alveolar macrophages. Infection of I/St mice with KO M. tuberculosis H37RV strains provided beneficial effects onto major TB phenotypes. We observed attenuated tuberculosis-specific inflammatory responses, including reduced cellular infiltration and decreased granuloma formation in the lungs. Infections caused by KO strains were characterized by significantly lower inflammation of mouse lung tissue and increased survival time of infected animals. Thus, the deletion of MTS0997 and MTS1338 lead to a significant decrease in the virulence of M. tuberculosis.
Evaluation of the Estimation Capability of Response Surface Methodology and Artificial Neural Network for the Optimization of Bacteriocin-Like Inhibitory Substances Production by Lactococcus lactis Gh1
Authors: Jawan Roslina , Abbasiliasi Sahar , Tan Joo Shun , Kapri Mohd Rizal , Mustafa Shuhaimi , Halim Murni , Ariff Arbakariya B.
Published: March 2021

Bacteriocin-like inhibitory substances (BLIS) produced by Lactococcus lactis Gh1 had shown antimicrobial activity against Listeria monocytogenes ATCC 15313. Brain Heart Infusion (BHI) broth is used for the cultivation and enumeration of lactic acid bacteria, but there is a need to improve the current medium composition for enhancement of BLIS production, and one of the approaches is to model the optimization process and identify the most appropriate medium formulation. Response surface methodology (RSM) and artificial neural network (ANN) models were employed in this study. In medium optimization, ANN (R2 = 0.98) methodology provided better estimation point and data fitting as compared to RSM (R2 = 0.79). In ANN, the optimal medium consisted of 35.38 g/L soytone, 16 g/L fructose, 3.25 g/L sodium chloride (NaCl) and 5.40 g/L disodium phosphate (Na2HPO4). BLIS production in optimal medium (717.13 ± 0.76 AU/mL) was about 1.40-fold higher than that obtained in nonoptimised (520.56 ± 3.37 AU/mL) medium. BLIS production was further improved by about 1.18 times higher in 2 L stirred tank bioreactor (787.40 ± 1.30 AU/mL) as compared to that obtained in 250 mL shake flask (665.28 ± 14.22 AU/mL) using the optimised medium.