bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Carbon Content and Boronizing Parameters on Growth Kinetics of Boride Layers Obtained on Carbon Steels
Authors: Milinović Andrijana , Marušić Vlatko , Konjatić Pejo , Berić Nikolina
Published: March 2022

Boronizing is a thermochemical treatment performed to produce hard and wear-resistant surface layers. In order to control the process and obtain boride layers with the desired properties, it is very important to know how the boronizing parameters and the chemical composition of the treated steel affect the boronizing. The aim of the present study is to investigate the influence of carbon content in carbon steels, boronizing temperature, and boronizing duration on the growth kinetics of boride layers. For this purpose, three carbon steels (C1y5, C45, and C70W2) were boronized in solid medium. The experimental results show that there is a linear relationship between the carbon content and the activation energy values, and between the carbon content and the frequency factors. In addition, a statistical analysis was performed to determine the contribution of each factor. The ANOVA showed that boronizing temperature has the highest effect on the boride layer thickness, followed by the boronizing duration, while the carbon content of the steel has the least effect on the boride layer thickness. Based on a regression model, an empirical equation was derived to estimate the thickness of the boride layer on carbon steels as a function of carbon content, boronizing temperature, and duration.
TiO2-Modified Magnetic Nanoparticles (Fe3O4) with Antibacterial Properties
Authors: Wojciechowska Agnieszka , Markowska-Szczupak Agata , Lendzion-Bieluń Zofia
Published: March 2022

This paper presents the synthesis and characteristics of Fe3O4/C/TiO2 hybrid magnetic nanomaterials with antibacterial properties. The materials used were obtained using a microwave-assisted two-stage precipitation method. In the first stage, magnetite nanoparticles (Fe3O4) were prepared with the precipitation method, during which an additional glucose layer was placed on them. Next, the surface of Fe3O4 nanoparticles was covered by TiO2. It was observed that the addition of carbon and titanium dioxide caused a decrease in the average size of magnetite crystallites from 15.6 to 9.2 nm. Materials with varying contents of anatase phase were obtained. They were characterized in terms of phase composition, crystallite size, specific surface area, surface charge and the kinds of function groups on the surface. The results show a successful method of synthesizing hybrid magnetic nanoparticles, stable in a solution, with antibacterial properties under direct solar light irradiation. Compared to classical materials based on TiO2 and used for water disinfection, the obtained photocatalytic nanomaterials have magnetic properties. Owing to this fact, they can be easily removed from water once their activity under direct irradiance in a given process has completed.
Electrical Contact Performance of Cu Alloy under Vibration Condition and Acetal Glue Environment
Authors: Cao Zhongqing , Yu Yanqing , He Liping , Nie Yuchen , Gong Congyu , Liu Xiaohong
Published: March 2022

In view of the serious sliding electrical contact performance caused by external vibration and environmental contaminant, a study on the tribological characteristic and contact resistance of Cu alloy was conducted using a self-developed micro-load reciprocating electric contact device. Various glue concentrations (0%, 10%, 30%, and 50%) were prepared with anhydrous ethanol and deposited on the surface of a pure copper block via the deposition method. An external vibration source was installed on the sliding module to achieve vertical vibration. The results indicate that the final contact resistance and coefficient of friction (COF) in direct metal contact are about 0.01 Ω and 0.3, respectively. At this time, the wear volume is 2 to 3 orders of magnitude higher than the condition with glue residual. As glue concentration is above 10%, residual glue on the surface of Cu alloy hinders efficient contact between friction pairs, resulting in higher contact resistance. Glue exhibits lubrication, anti-wear, and insulation properties. External vibration causes friction pairs to briefly separate, leading to a lower glue removal capacity than that under non-vibration conditions. The contact resistance with glue addition under vibration conditions is higher than that under non-vibration conditions at 3 × 104 cycles. The dominant oxide product is CuO, which has a limited effect on contact resistance.
Correlation Analysis between Mechanical Properties and Fractions Composition of Oil-Rejuvenated Asphalt
Authors: Tian Rongyan , Luo Haoyuan , Huang Xiaoming , Zheng Yangzezhi , Zhu Leyi , Liu Fengyang
Published: March 2022

To clarify the intrinsic relationship between the mechanical properties of asphalt and its fraction composition, the SARA fraction composition and six macroscopic mechanical properties (critical cracking temperature (TCR), fatigue life (Nf), non-recoverable creep (Jnr3.2), penetration, ductility, and softening point) were investigated for 16 asphalt samples. Fraction contents of asphaltene and aromatic are strongly correlated with TCR and ductility (R2 > 0.92) that characterize the ability of asphalt to adapt to deformation at low and medium temperatures. Heavy fraction (asphaltene and resins) content is also strongly correlated with (R2 > 0.90) penetration and Jnr3.2 that characterize the resistance of the asphalt to overall deformation at medium and high temperatures. To express the changes in the four fractions simultaneously with one indicator, a statistic, average deviation of the fractions between the given asphalt and its original (marked σ), is introduced in this study to characterize the degree of asphalt aging based on the fraction changes. It normalizes the four simultaneous change indicators (percentage of SARA fractions) during asphalt aging into one indicator. This new indicator has a strong correlation with several mechanical performance indicators of asphalt, where it is strongly correlated with TCR (R2 > 0.90), ductility, and penetration, which are also well correlated with Jnr3.2 (R2 > 0.85), Nf (R2 > 0.75), and softening point (R2 > 0.75).
Magnetic Measurement of Zn Layer Heterogeneity on the Flange of the Steel Road Barrier
Authors: Pitoňák Martin , Ondruš Ján , Minárik Peter , Kubjatko Tibor , Neslušan Miroslav
Published: March 2022

This study deals with monitoring of Zn layer heterogeneity on the flange of steel road barriers using magnetic measurements. The Barkhausen noise technique is employed for such purpose, and parameters extracted from Barkhausen noise signals are correlated with the true thickness of the Zn layer. The true values of the Zn layer were obtained from the metallographic images, as well as the thickness gauge CM-8825FN (Guangzhou Landtek Instruments Co. Ltd., Guangzhou, China) device. It was observed that the diffusion region lies below the Zn protective layer, which makes the thickness of the Zn layer obtained from the CM-8825FN device thicker than that measured on the metallographic images. For this reason, the chemical gradient of Zn below the Zn layer can be reported, and it affects Barkhausen noise emission. Barkhausen noise decreases along with increasing thickness of the Zn layer, and Barkhausen noise envelopes are shifted to stronger magnetic fields. The number of strong MBN pulses drops down with the increasing thickness of Zn coating at the expense of the increasing number of the weak MBN pulses. The thickness of Zn coating can be polluted by the solidification of Zn melt after galvanizing. The presence of the diffusion layer dims the contrast between ferromagnetic and paramagnetic phases.
RPEOD: A Real-Time Pose Estimation and Object Detection System for Aerial Robot Target Tracking
Authors: Zhang Chi , Yang Zhong , Liao Luwei , You Yulong , Sui Yaoyu , Zhu Tang
Published: March 2022

Pose estimation and environmental perception are the fundamental capabilities of autonomous robots. In this paper, a novel real-time pose estimation and object detection (RPEOD) strategy for aerial robot target tracking is presented. The aerial robot is equipped with a binocular fisheye camera for pose estimation and a depth camera to capture the spatial position of the tracked target. The RPEOD system uses a sparse optical flow algorithm to track image corner features, and the local bundle adjustment is restricted in a sliding window. Ulteriorly, we proposed YZNet, a lightweight neural inference structure, and took it as the backbone in YOLOV5 (the state-of-the-art real-time object detector). The RPEOD system can dramatically reduce the computational complexity in reprojection error minimization and the neural network inference process; Thus, it can calculate real-time on the onboard computer carried by the aerial robot. The RPEOD system is evaluated using both simulated and real-world experiments, demonstrating clear advantages over state-of-the-art approaches, and is significantly more fast.
Experimental Research on the Coupling Relationship between Fishtail Stiffness and Undulatory Frequency
Authors: Zhang Yuanhao , Kang Rongjie , Romano Donato , Dario Paolo , Song Zhibin
Published: March 2022

Fish can swim in a variety of states. For example, they look flexible and perform low-frequency undulatory locomotion when cruising, but they seem very powerful and stiff and perform high-frequency undulatory when hunting. In the process of changing the motion state, the stiffness of the fish body affects the swimming performance of the fish. In this article, we imitated the change of stiffness by superimposing rubber sheets and used experimental methods to test its swimming performance under different swing frequencies. A series of rubber fish tails were made according to the analysis of the swimming movement of real fish, providing different stiffness values and changing the curves of the body. In the prototype experiments, the base of the fish tail was fixed to a platform via a force sensor, which can oscillate at various speeds, so that the fish tail was able to swing and the thrust could be tested at different frequencies. According to the experimental results, we found that with the change of the swing frequency, there were different optimal stiffnesses that could make the thrust reach the maximum value, and with the increase of stiffness, the envelope interval of the swing curve gradually widened, the amplitude increased, and the hysteresis of the tail fin relative to the end decreased.
Fast Computation of Optimal Damping Parameters for Linear Vibrational Systems
Authors: Jakovčević Stor Nevena , Slapničar Ivan , Tomljanović Zoran
Published: March 2022

We propose a fast algorithm for computing optimal viscosities of dampers of a linear vibrational system. We are using a standard approach where the vibrational system is first modeled using the second-order structure. This structure yields a quadratic eigenvalue problem which is then linearized. Optimal viscosities are those for which the trace of the solution of the Lyapunov equation with the linearized matrix is minimal. Here, the free term of the Lyapunov equation is a low-rank matrix that depends on the eigenfrequencies that need to be damped. The optimization process in the standard approach requires O(n3) floating-point operations. In our approach, we transform the linearized matrix into an eigenvalue problem of a diagonal-plus-low-rank matrix whose eigenvectors have a Cauchy-like structure. Our algorithm is based on a new fast eigensolver for complex symmetric diagonal-plus-rank-one matrices and fast multiplication of linked Cauchy-like matrices, yielding computation of optimal viscosities for each choice of external dampers in O(kn2) operations, k being the number of dampers. The accuracy of our algorithm is compatible with the accuracy of the standard approach.
Design Plan for an Evolution Study of Related Characteristics of a Population
Authors: Rodríguez-Díaz Juan M. , Pruneda Rosa E. , Rodríguez-Hernández Mercedes
Published: March 2022

The objective is to study the evolution of different characteristics of a population through time. These response variables may be related for each experimental unit, and in addition, the observations for each response may as well be correlated with time, producing a complex correlation structure. The number of responses that can be observed is usually limited for budget, resources, or time reasons, and thus the selection of the most informative time points when data must be taken is quite convenient. This will be performed by using the optimal design of experiments techniques. Some analytical results will be shown, and the results will be applied to obtain the most convenient points when tests about two variables related with the capability of the resolution of mathematical problems in primary school students should be performed.
Special Type Routing Problems in Plane Graphs
Authors: Makarovskikh Tatiana , Panyukov Anatoly
Published: March 2022

We considered routing problems for plane graphs to solve control problems of cutting machines in the industry. According to the cutting plan, we form its homeomorphic image in the form of a plane graph G. We determine the appropriate type of route for the given graph: OE-route represents an ordered sequence of chains satisfying the requirement that the part of the route that is not passed does not intersect the interior of its passed part, AOE-chain represents OE-chain consecutive edges which are incident to vertex v and they are neighbours in the cyclic order O±(v), NOE-route represents the non-intersecting OE-route, PPOE-route represents the Pierce Point NOE-route with allowable pierce points that are start points of OE-chains forming this route. We analyse the solvability of the listed routing problems in graph G. We developed the polynomial algorithms for obtaining listed routes with the minimum number of covering paths and the minimum length of transitions between the ending of the current path and the beginning of the next path. The solutions proposed in the article can improve the quality of technological preparation of cutting processes in CAD/CAM systems.
SVseg: Stacked Sparse Autoencoder-Based Patch Classification Modeling for Vertebrae Segmentation
Authors: Qadri Syed Furqan , Shen Linlin , Ahmad Mubashir , Qadri Salman , Zareen Syeda Shamaila , Akbar Muhammad Azeem
Published: March 2022

Precise vertebrae segmentation is essential for the image-related analysis of spine pathologies such as vertebral compression fractures and other abnormalities, as well as for clinical diagnostic treatment and surgical planning. An automatic and objective system for vertebra segmentation is required, but its development is likely to run into difficulties such as low segmentation accuracy and the requirement of prior knowledge or human intervention. Recently, vertebral segmentation methods have focused on deep learning-based techniques. To mitigate the challenges involved, we propose deep learning primitives and stacked Sparse autoencoder-based patch classification modeling for Vertebrae segmentation (SVseg) from Computed Tomography (CT) images. After data preprocessing, we extract overlapping patches from CT images as input to train the model. The stacked sparse autoencoder learns high-level features from unlabeled image patches in an unsupervised way. Furthermore, we employ supervised learning to refine the feature representation to improve the discriminability of learned features. These high-level features are fed into a logistic regression classifier to fine-tune the model. A sigmoid classifier is added to the network to discriminate the vertebrae patches from non-vertebrae patches by selecting the class with the highest probabilities. We validated our proposed SVseg model on the publicly available MICCAI Computational Spine Imaging (CSI) dataset. After configuration optimization, our proposed SVseg model achieved impressive performance, with 87.39% in Dice Similarity Coefficient (DSC), 77.60% in Jaccard Similarity Coefficient (JSC), 91.53% in precision (PRE), and 90.88% in sensitivity (SEN). The experimental results demonstrated the method’s efficiency and significant potential for diagnosing and treating clinical spinal diseases.
Bipolar Dissimilarity and Similarity Correlations of Numbers
Authors: Batyrshin Ildar Z. , Tóth-Laufer Edit
Published: March 2022

Many papers on fuzzy risk analysis calculate the similarity between fuzzy numbers. Usually, they use symmetric and reflexive similarity measures between parameters of fuzzy sets or “centers of gravity” of generalized fuzzy numbers represented by real numbers. This paper studies bipolar similarity functions (fuzzy relations) defined on a domain with involutive (negation) operation. The bipolarity property reflects a structure of the domain with involutive operation, and bipolar similarity functions are more suitable for calculating a similarity between elements of such domain. On the set of real numbers, similarity measures should take into account symmetry between positive and negative numbers given by involutive negation of numbers. Another reason to consider bipolar similarity functions is that these functions define measures of correlation (association) between elements of the domain. The paper gives a short introduction to the theory of correlation functions defined on sets with an involutive operation. It shows that the dissimilarity function generating Pearson’s correlation coefficient is bipolar. Further, it proposes new normalized similarity and dissimilarity functions on the set of real numbers. It shows that non-bipolar similarity functions have drawbacks in comparison with bipolar similarity functions. For this reason, bipolar similarity measures can be recommended for use in fuzzy risk analysis. Finally, the correlation functions between numbers corresponding to bipolar similarity functions are proposed.
Machining Parameters Optimization Based on Objective Function Linearization
Authors: Gavrus Cristina , Ivan Nicolae-Valentin , Oancea Gheorghe
Published: March 2022

Manufacturing process optimization is an ever-actual goal. Within this goal, machining parameters optimization is a very important task. Machining parameters strongly influence the manufacturing costs, process productivity and piece quality. Literature presents a series of optimization methods. The results supplied by these methods are comparable and it is difficult to establish which method is the best. For machining parameters optimization, this paper proposes a novel, simple and efficient method, without additional costs related to new software packages. This approach is based on linear mathematical programming. The optimization mathematical models are, however, nonlinear. Therefore, mathematical model linearization is required. The major and difficult problem is the linearization of the objective function. This represents the key element of the proposed optimization method. In this respect, the paper proposes an original mathematical procedure for calculating the part of the objective function that refers to the analytical integration of the tool life into the model. This calculus procedure was transposed into an original software tool. For demonstrating the validity of the method, a comparison is presented among the results obtained by certain optimization techniques. It results that the proposed method is simple and as good as those presented by the literature.
The Cost-Balanced Path Problem: A Mathematical Formulation and Complexity Analysis
Authors: Ambrosino Daniela , Cerrone Carmine
Published: March 2022

This paper introduces a new variant of the Shortest Path Problem (SPP) called the Cost-Balanced Path Problem (CBPP). Various real problems can either be modeled as BCPP or include BCPP as a sub-problem. We prove several properties related to the complexity of the CBPP problem. In particular, we demonstrate that the problem is NP-hard in its general version, but it becomes solvable in polynomial time in a specific family of instances. Moreover, a mathematical formulation of the CBPP, as a mixed-integer programming model, is proposed, and some additional constraints for modeling real requirements are given. This paper validates the proposed model and its extensions with experimental tests based on random instances. The analysis of the results of the computational experiments shows that the proposed model and its extension can be used to model many real applications. Obviously, due to the problem complexity, the main limitation of the proposed approach is related to the size of the instances. A heuristic solution approach should be required for larger-sized and more complex instances.
The Replicated Core under Multi-Choice Non-Transferable- Utility Situations: Converse Reduction Axiomatic Enlargements
Authors: Hwang Yan-An , Liao Yu-Hsien
Published: March 2022

Since the replicated core counters the (inferior) converse reduction axiom under multi-choice non-transferable-utility (NTU) situations, two converse reduction axiomatic enlargements of the replicated core are generated. These two enlargements are the smallest (inferior) converse reduction axiomatic solutions that contain the replicated core. Finally, relative axiomatic results are also provided.
Peristaltic Transport of Carreau Nanofluid in Presence of Triple Diffusion in an Asymmetric Channel by Multi-Step Differential Transformation Method
Authors: Kotnurkar Asha S. , Beleri Joonabi , Badruddin Irfan Anjum , Kamangar Sarfaraz , Ahammad Nandalur Ameer
Published: March 2022

The present work investigates the influence of triple diffusion on Carreau nanoliquid in peristaltic flow through an asymmetric channel. By using appropriate non-dimensional parameters, governing equations are transformed to conventional non-linear partial differential equations. The Ms-DTM is used to find solutions to developing equations. Because of the buoyancy force that prevails inside the boundary layer, velocity is impacted by the buoyancy ratio. The current investigation found that as the varied values of the modified Dufour parameter were increased, the temperature profile increased. The thermal conductivity increases as thermal diffusivity increases. It has also been discovered that the existence of triple-diffusing components with low diffusivity might alter the type of convection in the system. Graphs depict the influence of several parameters on velocity, salt1 and salt2 concentrations, solute concentration, and temperature.
Risk Evaluation: Brief Review and Innovation Model Based on Fuzzy Logic and MCDM
Authors: Djenadic Stevan , Tanasijevic Milos , Jovancic Predrag , Ignjatovic Dragan , Petrovic Dejan , Bugaric Ugljesa
Published: March 2022

The risk assessment of engineering systems represents an important part of the quality of service and dependability. The existing methods for risk evaluation use crisp sets for rating partial indicators’ proposition and their cumulative products as an overall indicator. In this paper, existing FMEA and FMECA methods have been improved using the fuzzy expert system for calculating the risk priority number. The application of fuzzy logic allows the use of linguistic descriptions for risk analysis. In this way, the state of the system in terms of risks and consequences is better described. The settings of the fuzzy systems are based on the application of two multi-criteria decision-making methods. The AHP method was used to define the mutual relationship of the impact of partial indicators (occurrence, severity, and detectability) on risk. In this way, subjectivity in risk assessment is reduced. In the composition of the fuzzy model, the TOPSIS method is introduced to reduce the dissipation of results, which contributes to the accuracy of the outcome. This contributes to the accuracy of the results. The results were verified through a case study of a complex engineering system—bucket-wheel excavators. The risk was observed from the aspect of the danger of damage and the danger of downtime. The initial information for weak points of ES is defined according to historical damage events and statistics of downtime. Expert knowledge was used for weak points grading in the model. Additional model verification was performed using similar methods, using the same input data. The innovative model, presented in the paper, shows that it is possible to correct different weights of risk indicators. The obtained results show less dispersion compared with other existing methods. Weak points with increased risk have been located, and an algorithm has been proposed for risk-based maintenance application and implementation.
Percutaneous Chevron Osteotomy: A Prospective Randomized Controlled Trial
Authors: Dragosloveanu Serban , Popov Viola Maria , Cotor Dragoș-Corneliu , Dragosloveanu Christiana , Stoica Cristian Ioan
Published: March 2022

Introduction: Minimally invasive surgical techniques for hallux valgus have gained popularity, showing good results characterized by smaller postoperative scars, less pain, lower infection risk, and fewer wound complications. Given the lack of evidence available in our country regarding this subject, especially about this type of surgical technique, our paper aims to compare open and MIS approaches for chevron osteotomy. We evaluated the outcome and complications after 12 months. Materials and Methods: We undertook a prospective, randomized, controlled, single-center study between October 2017 and December 2020. The patients were randomized into two groups: one group that received percutaneous chevron osteotomy (MIS), and the other, open chevron osteotomy (OC). For clinical assessment, we determined the function and the level of pain using the Visual Analogue Scale (VAS) and The American Orthopaedic Foot and Ankle Surgery score (AOFAS). The VAS scale was measured before the surgical procedure, at discharge, and at 3 weeks, 6 weeks, 6 months, and 12 months after surgery. The AOFAS score was calculated preoperatively and after 6 months. The hallux angle (HVA) and intramedullary angle (IMA) were measured preoperatively, and at 6 weeks, 6 months and 12 months. Results: We included 26 cases in the open chevron osteotomy group (24 female, 2 male) and 24 in the MIS group (24 female, 0 male). Both groups demonstrated improvements regarding the IMA and HVA at the last follow-up without any significant differences between the groups at the final assessment. The VAS showed significantly better post-operative results for the MIS group at discharge (p < 0.001) and 3 weeks (p < 0.001), 6 weeks (p < 0.001), and 6 months (p = 0.004) post-surgery. The AOFAS showed no significant differences either before or after surgery. Four cases with screw prominence were reported, three of which belonged to the MIS group. Only one case with metatarsalgia was found in the OC group. Conclusions: This paper demonstrates that minimally invasive chevron osteotomy has comparable results with open chevron osteotomy, even though surgical time and radiological exposure are significantly longer. More studies are required to evaluate the complications and the risk of recurrences.
Comparison of Navigated Expandable Vertebral Cage with Conventional Expandable Vertebral Cage for Minimally Invasive Lumbar/Thoracolumbar Corpectomy
Authors: Tanaka Masato , Singh Mahendra , Fujiwara Yoshihiro , Uotani Koji , Oda Yoshiaki , Arataki Shinya , Yamauchi Taro , Takigawa Tomoyuki , Ito Yasuo
Published: March 2022

Background and Objectives: The thoracolumbar burst fracture is one of the most common spinal injuries. If the patient has severe symptoms, corpectomy is indicated. Currently, minimally invasive corpectomy with a navigated expandable vertebral cage is available thanks to spinal surgical technology. The aim of this study is to retrospectively compare clinical and radiographic outcomes of conventional and navigational minimally invasive corpectomy techniques. Materials and Methods: We retrospectively evaluated 21 patients who underwent thoracolumbar minimally invasive corpectomy between October 2016 and January 2021. Eleven patients had a navigated expandable cage (group N) and 10 patients had a conventional expandable cage (group C). Mean follow-up period was 31.9 months for group N and 34.7 months for group C, ranging from 12 to 42 months in both groups. Clinical and radiographic outcomes are assessed using values including visual analogue scale (VAS) for back pain and Oswestry disability index (ODI). This data was collected preoperatively and at 6, 12, and 24 months postoperatively. Results: Surgical time and intraoperative blood loss of both groups were not significantly different (234 min vs. 267 min, 656 mL vs. 786 mL). Changes in VAS and ODI were similar in both groups. However, lateral cage mal-position ratio in group N was lower than that of group C (relative risk 1.64, Odds ratio 4.5) and postoperative cage sinking was significantly lower in group N (p = 0.033). Conclusions: Clinical outcomes are not significantly different, but radiographic outcomes of lateral cage mal-position and postoperative cage sinking were significantly lower in the navigation group.
Trends in Participation, Sex Differences and Age of Peak Performance in Time-Limited Ultramarathon Events: A Secular Analysis
Authors: Thuany Mabliny , Gomes Thayse Natacha , Villiger Elias , Weiss Katja , Scheer Volker , Nikolaidis Pantelis T. , Knechtle Beat
Published: March 2022

Background and Objectives: Increases in the number of participants in time-limited ultra-marathons have been reported. However, no information is available regarding the trends in participation, performance and age in 12 h and 24 h time-limited events. The aim of the study was to describe the trends in runners’ participation, performance and age in 12 h and 24 h ultra-marathons for both sexes and to identify the age of peak performance, taking into account the ranking position and age categories. Materials and Methods: The sample comprised 210,455 runners in time-limited ultra-marathons (female 12 h = 23,706; female 24 h = 28,585; male 12 h = 61,594; male 24 h = 96,570) competing between 1876 and 2020 and aged 18 to 86 years. The age of peak performance was tested according to their ranking position (first–third; fourth–tenth and >tenth position) and taking into account their running speed in different age categories (<30 years; 31–40 years; 41–50 years; 51–60 years; >60 years), using the Kruskal–Wallis test, followed by the Bonferroni adjustment. Results: An increase in the number of participants and a decrease in running speed were observed across the years. For both events, the sex differences in performance decreased over time. The sex differences showed that male runners performed better than female runners, but the lowest differences in recent years were observed in the 24 h ultra-marathons. A positive trend in age across the years was found with an increase in mean age (“before 1989” = 40.33 ± 10.07 years; “1990–1999” = 44.16 ± 10.37 years; “2000–2009” = 45.99 ± 10.33 years; “2010–2020” = 45.62 ± 10.80 years). Male runners in 24 h races were the oldest (46.13 ± 10.83 years), while female runners in 12 h races were the youngest (43.46 ± 10.16 years). Athletes ranked first–third position were the youngest (female 12 h = 41.19 ± 8.87 years; female 24 h = 42.19 ± 8.50 years; male 12 h = 42.03 ± 9.40 years; male 24 h = 43.55 ± 9.03 years). When age categories were considered, the best performance was found for athletes aged between 41 and 50 years (female 12 h 6.48 ± 1.74 km/h; female 24 h 5.64 ± 1.68 km/h; male 12 h 7.19 ± 1.90 km/h; male 24 h 6.03 ± 1.78 km/h). Conclusion: A positive trend in participation in 12 h and 24 h ultra-marathons was shown across the years; however, athletes were becoming slower and older. The fastest athletes were the youngest ones, but when age intervals were considered, the age of peak performance was between 41 and 50 years.
Effect of Aeration Intensity on Performance of Lab-Scale Quorum-Quenching Membrane Bioreactor
Authors: Islam Zia Ul , Ayub Mariam , Chung Shinho , Oh Heekyong
Published: March 2022

Biofouling is one of the main drawbacks of membrane bioreactors (MBRs). Among the different methods, the quorum-quenching (QQ) technique is a novel method as it delays biofilm formation on the membrane surface through disruption of bacterial cell-to-cell communication and thus effectively mitigates membrane biofouling. QQ bacteria require a certain concentration of dissolved oxygen to show their best activities. Despite the importance of the amount of aeration, there have not been enough studies on aeration condition utilizing the separate determination of pure QQ effect and physical cleaning effect. This research aimed to find the optimum aeration intensity by separation of the two effects from QQ and physical cleaning. Three bead type conditions (no bead, vacant bead, and QQ beads) at three aeration intensities (1.5, 2.5, and 3.5 L/min representing low, medium, and high aeration intensity) were applied. From the results, no QQ effect and small QQ effect were observed at low and high aeration, while the greatest QQ effect (48.2% of 737 h improvement) was observed at medium aeration. The best performance was observed at high aeration with QQ beads having a 1536 h operational duration (303% improvement compared to the no bead condition); however, this excellent performance was attributed more to the physical cleaning effect than to the QQ effect.
Microstructure Characterization and Small Punch Test Analysis in Nickel-Based Alloy 617 by High Energy Neon Implantation
Authors: Shen Yuanhua , Lv Shasha , Zhou Qin , Shi Li , Sun Libin , Li Zhengcao
Published: March 2022

Nickel-based alloys are good candidate structural materials for ultra-high temperature gas-cooled reactors due to their excellent mechanical properties under high-temperature conditions. The operating environment in the compact high-temperature gas-cooled reactor proposes more stringent requirements with higher displacement and temperatures higher than 700 °C. The irradiation resistance of nickel-based alloy 617 is evaluated by 120 MeV neon ion irradiation. The neon ion fluence is set with reference to the number of helium atoms generated by the reaction of (n, α) in nickel-based alloy under actual service conditions. With the application of an energy gradient degrader, the irradiation damage area is more uniform with increasing depth. The neon ion irradiation causes no significant surface damage to alloy 617 while the evolution of defects such as inherent dislocation lines is affected, thus leading to the deterioration of mechanical properties. By using the small punch test to analyze the irradiation effects, it is found that the neon ion irradiation results in the tendency of irradiation softening and does not lead to changes in the basic fracture characteristics under different annealing conditions. After annealing at 700 and 800 °C for 2 h, the irradiation embrittlement trend is intensified, with the fracture characteristic values of irradiated samples showing a more obvious decreasing trend.
Hydrogen-Related Fracture Behavior under Constant Loading Tensile Test in As-Quenched Low-Carbon Martensitic Steel
Authors: Shibata Akinobu , Takeda Yasunari , Kimura Yuuji , Tsuji Nobuhiro
Published: March 2022

This study investigated the hydrogen-related fracture behavior in as-quenched low-carbon martensitic steel under a constant loading tensile test with various applied stresses. We found that the fracture time in the constant loading tensile test decreased as the applied stress and hydrogen content increased. The fracture surface topography analysis revealed that when the applied stress was low, the intergranular fracture was initiated around the side surface of the specimen and gradually propagated into the inner part of the specimen. In contrast, several intergranular fractures were separately initiated inside the specimen when the applied stress was high. The mode of hydrogen-related fracture was controlled by the fracture stress and not by the global hydrogen content inside the specimen. Increasing the global hydrogen content caused a decrease in the duration required for the accumulation of critical local hydrogen concentration at the fracture initiation site (prior austenite grain boundary). Accordingly, we propose that the local state at the crack initiation site is constant under a given applied stress, even when the global hydrogen content is different.
Microstructure and Mechanical Properties of Medium-Carbon Si-Rich Steel Processed by Austempering after Intercritical Annealing
Authors: Jia Xin , Wang Yuefeng , Wang Lin , Sun Xiaowen , Zhao Ting , Wang Tiansheng
Published: March 2022

In the present paper, the medium-C Si-rich steel with a quenched martensite microstructure was heated to intercritical annealing temperatures at 750 °C, 760 °C and 770 °C after warm rolling deformation to obtain ferrite with varying volume fractions. Subsequently, bainite/ferrite multiphase microstructures were attained via austempering near Ms temperature. The microstructures of the test steel after different heat treatments were characterized by scanning electron microscopy, transmission electron microscopy and electron backscatter diffraction, and corresponding tensile and impact properties were tested. The results showed that, with the increase of intercritical annealing temperature, the austenite content increased, which limited the growth of ferrite grains, and the grain size decreased from ~1.6 μm to ~1.4 μm. In addition, the degree of ferrite recrystallization was almost complete. At the same intercritical annealing temperature, compared with austempering above Ms, prior athermal martensite (PAM) was obtained after austempering below Ms, which effectively refined the size of bainite ferrite lath. Moreover, with the increase of intercritical annealing temperature, the bainite content of the test steel increased after austempering, resulting in the increase of yield strength, tensile strength and impact energy. In contrast, while the decrease in ferrite content led to a significant decrease in uniform elongation. At constant intercritical annealing temperature, the tensile strength decreased slightly, and the impact property improved after austempering above Ms.
Fe(II) Addition Drives Soil Bacterial Co-Ocurrence Patterns and Functions Mediated by Anaerobic and Chemoautotrophic Taxa
Authors: Zhang Chenyang , Liu Senlin , Hussain Sarfraz , Li Lifeng , Baiome Baiome Abdelmaguid , Xiao Shuiqing , Cao Hui
Published: March 2022

Iron is among the most abundant elements in the soil of paddy fields, and its valence state and partitioning can be transformed by flooding and drainage alternations. However, little is known about the function of soil microbes that interact with Fe(II). In this study, sandy and loamy soils originating from rice fields were treated with Fe(II) at low and high concentrations. The findings demonstrate that additional Fe(II) has various effects on the soil’s microbial community structure and metabolic pathways. We conclude that Fe(II) at high concentrations reduced bacterial abundance and diversity in two textured paddy soils, yet the abundance in loamy soils was higher than it was in sandy soil. Additionally, in environments with high Fe(II) levels, the relative abundance of both anaerobic and chemoautotrophic bacteria increased. The Fe(II) concentration was positively correlated with total reduced substances but negatively correlated with redox potential and pH. Co-occurrence networks revealed that Fe(II) significantly promoted interactions with the most anaerobic and chemoautotrophic bacteria. In addition, adding Fe(II) greatly increased the number of more complex bacterial networks, and an increase in the number of mutually beneficial taxa occurred. We found that Fe(II) promoted the methane pathway, the Calvin cycle, and nitrate reduction to small but significant extents. These pathways involve the growth and interrelation of autotrophic and anaerobic bacteria. These results suggest that changes in the bacterial community structure occur in many dry–wet alternating environments.
Antimicrobial Activity of Ohelo Berry (Vaccinium calycinum) Juice against Listeria monocytogenes and Its Potential for Milk Preservation
Authors: Wu Biyu , Liu Xiaohan , Nakamoto Stuart T. , Wall Marisa , Li Yong
Published: March 2022

Listeria monocytogenes is a foodborne pathogen and causes illnesses with a high mortality rate in susceptible populations. Several dairy-related outbreaks have been attributed to contamination by L. monocytogenes, which requires antimicrobial interventions to enhance the safety of these products. This study aimed to determine the antimicrobial activity of the ohelo berry (Vaccinium calycinum), a Hawaiian wild relative of cranberry, against L. monocytogenes in culture media and milk products. The effect of ohelo berry juice at its sub-inhibitory concentrations on the physicochemical properties, biofilm formation, and gene expression of L. monocytogenes was also investigated. The minimum inhibitory concentration of ohelo berry juice against L. monocytogenes was 12.5%. The sub-inhibitory concentration of ohelo berry juice (6.25%) significantly increased the auto-aggregation and decreased the hydrophobicity, swimming motility, swarming motility, and biofilm formation capability of L. monocytogenes. The relative expression of genes for motility (flaA), biofilm formation and disinfectant resistance (sigB), invasion (iap), listeriolysin (hly), and phospholipase (plcA) was significantly downregulated in L. monocytogenes treated by the 6.25% juice. L. monocytogenes was significantly inhibited in whole and skim milk supplemented with 50% ohelo berry juice, regardless of the fat content. These findings highlight the potential of ohelo berry as a natural preservative and functional food to prevent L. monocytogenes infection.
Metabolism of Aldoximes and Nitriles in Plant-Associated Bacteria and Its Potential in Plant-Bacteria Interactions
Authors: Rädisch Robert , Pátek Miroslav , Křístková Barbora , Winkler Margit , Křen Vladimír , Martínková Ludmila
Published: March 2022

In plants, aldoximes per se act as defense compounds and are precursors of complex defense compounds such as cyanogenic glucosides and glucosinolates. Bacteria rarely produce aldoximes, but some are able to transform them by aldoxime dehydratase (Oxd), followed by nitrilase (NLase) or nitrile hydratase (NHase) catalyzed transformations. Oxds are often encoded together with NLases or NHases in a single operon, forming the aldoxime–nitrile pathway. Previous reviews have largely focused on the use of Oxds and NLases or NHases in organic synthesis. In contrast, the focus of this review is on the contribution of these enzymes to plant-bacteria interactions. Therefore, we summarize the substrate specificities of the enzymes for plant compounds. We also analyze the taxonomic and ecological distribution of the enzymes. In addition, we discuss their importance in selected plant symbionts. The data show that Oxds, NLases, and NHases are abundant in Actinobacteria and Proteobacteria. The enzymes seem to be important for breaking through plant defenses and utilizing oximes or nitriles as nutrients. They may also contribute, e.g., to the synthesis of the phytohormone indole-3-acetic acid. We conclude that the bacterial and plant metabolism of aldoximes and nitriles may interfere in several ways. However, further in vitro and in vivo studies are needed to better understand this underexplored aspect of plant-bacteria interactions.
Development of Real-Time Molecular Assays for the Detection of Wesselsbron Virus in Africa
Authors: Faye Martin , Seye Thiané , Patel Pranav , Diagne Cheikh , Diagne Moussa , Dia Moussa , Thiaw Fatou , Sall Amadou , Faye Ousmane
Published: March 2022

Wesselsbron is a neglected, mosquito-borne zoonotic disease endemic to Africa. The virus is mainly transmitted by the mosquitoes of the Aedes genus and primarily affects domestic livestock species with teratogenic effects but can jump to humans. Although no major outbreak or fatal case in humans has been reported as yet worldwide, a total of 31 acute human cases of Wesselsbron infection have been previously described since its first isolation in 1955. However, most of these cases were reported from Sub-Saharan Africa where resources are limited and a lack of diagnostic means exists. We describe here two molecular diagnostic tools suitable for Wesselsbron virus detection. The newly established reverse transcription-quantitative polymerase chain reaction and reverse-transcription-recombinase polymerase amplification assays are highly specific and repeatable, and exhibit good agreement with the reference assay on the samples tested. The validation on clinical and veterinary samples shows that they can be accurately used for Wesselsbron virus detection in public health activities and the veterinary field. Considering the increasing extension of Aedes species worldwide, these new assays could be useful not only in laboratory studies for Wesselsbron virus, but also in routine surveillance activities for zoonotic arboviruses and could be applied in well-equipped central laboratories or in remote areas in Africa, regarding the reverse-transcription-recombinase polymerase amplification assay.
Whole-Genome Sequencing and Comparative Genomic Analysis of Antimicrobial Producing Streptococcus lutetiensis from the Rumen
Authors: de Oliveira Isabela Maria Fernandes , Godoy-Santos Fernanda , Oyama Linda Boniface , Moreira Sofia Magalhães , Dias Rodrigo Gonçalves , Huws Sharon Ann , Creevey Christopher J. , Mantovani Hilário Cuquetto
Published: March 2022

Antimicrobial peptides (AMPs) can efficiently control different microbial pathogens and show the potential to be applied in clinical practice and livestock production. In this work, the aim was to isolate AMP-producing ruminal streptococci and to characterize their genetic features through whole-genome sequencing. We cultured 463 bacterial isolates from the rumen of Nelore bulls, 81 of which were phenotypically classified as being Streptococcaceae. Five isolates with broad-range activity were genome sequenced and confirmed as being Streptococcus lutetiensis. The genetic features linked to their antimicrobial activity or adaptation to the rumen environment were characterized through comparative genomics. The genome of S. lutetiensis UFV80 harbored a putative CRISPR-Cas9 system (Type IIA). Computational tools were used to discover novel biosynthetic clusters linked to the production of bacteriocins. All bacterial genomes harbored genetic clusters related to the biosynthesis of class I and class II bacteriocins. SDS-PAGE confirmed the results obtained in silico and demonstrated that the class II bacteriocins predicted in the genomes of three S. lutetiensis strains had identical molecular mass (5197 Da). These results demonstrate that ruminal bacteria of the Streptococcus bovis/equinus complex represent a promising source of novel antimicrobial peptides.