bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the Infill Design on the Tensile Response of 3D Printed Polylactic Acid Polymer
Authors: Harpool Tanner David , Alarifi Ibrahim Mohammed , Alshammari Basheer A. , Aabid Abdul , Baig Muneer , Malik Rizwan Ahmed , Mohamed Sayed Ahmed , Asmatulu Ramazan , EL-Bagory Tarek Mohamed Ahmed Ali
Published: April 2021

The current study explores the effects of geometrical shapes of the infills on the 3D printed polylactic acid (PLA) plastic on the tensile properties. For this purpose, by utilizing an accessible supply desktop printer, specimens of diamond, rectangular, and hexagonal infill patterns were produced using the fused filament fabrication (FFF) 3D printing technique. Additionally, solid samples were printed for comparison. The printed tensile test specimens were conducted at environmental temperature, Ta of 23 °C and crosshead speed, VC.H of 5 mm/min. Mainly, this study focuses on investigating the percentage infill with respect to the cross-sectional area of the investigated samples. The mechanical properties, i.e., modulus of toughness, ultimate tensile stress, yield stress, and percent elongation, were explored for each sample having a different geometrical infill design. The test outcomes for each pattern were systematically compared. To further validate the experimental results, a computer simulation using finite element analysis was also performed and contrasted with the experimental tensile tests. The experimental results mainly suggested a brittle behavior for solidly infilled specimen, while rectangular, diamond, and hexagonal infill patterns showed ductile-like behavior (fine size and texture of infills). This brittleness may be due to the relatively higher infill density results that led to the high bonding adhesion of the printed layers, and the size and thickness effects of the solid substrate. It made the solidly infilled specimen structure denser and brittle. Among all structures, hexagon geometrical infill showed relative improvement in the mechanical properties (highest ultimate tensile stress and modulus values 1759.4 MPa and 57.74 MPa, respectively) compared with other geometrical infills. Therefore, the geometrical infill effects play an important role in selecting the suitable mechanical property’s values in industrial applications.
Investigation of Photonic-Crystal-Structured p-GaN Nanorods Fabricated by Polystyrene Nanosphere Lithography Method to Improve the Light Extraction Efficiency of InGaN/GaN Green Light-Emitting Diodes
Authors: Lei Po-Hsun , Yang Po-Chun , Huang Po-Chun
Published: April 2021

We fabricated the photonic-crystal-structured p-GaN (PC-structured p-GaN) nanorods using the modified polystyrene nanosphere (PS NS) lithography method for InGaN/GaN green light-emitting diodes (LEDs) to enhance the light extraction efficiency (LEE). A modified PS NS lithography method including two-times spin-coating processes and the post-spin-coating heating treatment was used to obtain a self-assembly close-packed PS NS array of monolayer as a mask and then a partially dry etching process was applied to PS NS, SiO2, and p-GaN to form PC-structured p-GaN nanorods on the InGaN/GaN green LEDs. The light output intensity and LEE of InGaN/GaN green LEDs with the PC-structured p-GaN nanorods depend on the period, diameter, and height of PC-structured p-GaN nanorods. RSoft FullWAVE software based on the three-dimension finite-difference time-domain (FDTD) algorithm was used to calculate the LEE of InGaN/GaN green LEDs with PC-structured p-GaN nanorods of the varied period, diameter, and height. The optimal period, diameter, and height of PC-structured p-GaN nanorods are 150, 350, and 110 nm. The InGaN/GaN green LEDs with optimal PC-structured p-GaN nanorods exhibit an enhancement of 41% of emission intensity under the driving current of 20 mA as compared to conventional LED.
Stochastic Process-Based Inversion of Electromagnetic Data for Hydrocarbon Resistivity Estimation in Seabed Logging
Authors: Mohd Aris Muhammad Naeim , Daud Hanita , Mohd Noh Khairul Arifin , Dass Sarat Chandra
Published: April 2021

This work proposes a stochastic process-based inversion to estimate hydrocarbon resistivity based on multifrequency electromagnetic (EM) data. Currently, mesh-based algorithms are used for processing the EM responses which cause high time-consuming and unable to quantify uncertainty. Gaussian process (GP) is utilized as the alternative forward modeling approach to evaluate the EM profiles with uncertainty quantification. For the optimization, gradient descent is used to find the optimum by minimizing its loss function. The prior EM profiles are evaluated using finite element (FE) through computer simulation technology (CST) software. For validation purposes, mean squared deviation and its root between EM profiles evaluated by the GP and FE at the unobserved resistivities are computed. Time taken for the GP and CST to evaluate the EM profiles is compared, and absolute error between the estimate and its simulation input is also computed. All the resulting deviations were significantly small, and the GP took lesser time to evaluate the EM profiles compared to the software. The observational datasets also lied within the 95% confidence interval (CI) where the resistivity inputs were estimated by the proposed inversion. This indicates the stochastic process-based inversion can effectively estimate the hydrocarbon resistivity in the seabed logging.
Resolution of Fuzzy Relational Inequalities with Boolean Semi-Tensor Product Composition
Authors: Wang Shuling , Li Haitao
Published: April 2021

Resolution of fuzzy relational inequalities (FRIs) plays a significant role in decision-making, image compression and fuzzy control. This paper studies the resolution of a kind of FRIs with Boolean semi-tensor product composition. First, by resorting to the column stacking technique, the equivalent form of FRIs with Boolean semi-tensor product composition is obtained, which is a system of FRIs (SFRIs) with max–min composition. Second, based on the semi-tensor product method, all the solutions to FRIs with Boolean semi-tensor product composition are obtained by finding all possible parameter set solutions. Finally, a general procedure is developed for the resolution of FRIs with Boolean semi-tensor product composition. Two illustrative examples are worked out to show the effectiveness of the obtained new results.
Visualization Method for Decision-Making: A Case Study in Bibliometric Analysis
Authors: Haghnazar Koochaksaraei Roozbeh , Gadelha Guimarães Frederico , Hamidzadeh Babak , Hashemkhani Zolfani Sarfaraz
Published: April 2021

Data and information visualization have drawn an increasingly wide range of interest from several academic fields and industries. Concurrently, exploring a huge set of data to support feasible decisions needs an organized method of Multi-Criteria Decision Making (MCDM). The dramatic increasing of data producing during the past decade makes visualization necessary as a presentation layer on the top of MCDM process. This study aims to propose an integrated strategy to rank the alternatives in the dataset, by combining data, MCDM methods, and visualization layers. In fact, the well designed combination of Information Visualization and MCDM provides a more user-friendly approach than the traditional methods. We investigate a case study in bibliometric analyses, which have become an important dimension and tool for evaluating the impact and performance of researchers, departments, and universities. Hence, finding the best and most reliable papers, authors, and publishers considering diverse criteria is one of the important challenges in science world. Therefore, this text is presenting a new strategy on the bibliometric dataset as a case study and it demonstrates that this strategy can be more meaningful for the end users than the current tools. Finally, the presented simulations illustrate the performance and utilization of this combination. In other words, the researchers of this study could design and implement a tool that overcomes the biggest challenges of data analyzing and ranking via a combination of MCDM and visualization methodologies that can provide a tremendous amount of insight and information from a massive dataset in an efficient way.
Three Authentication Schemes without Secrecy over Finite Fields and Galois Rings
Authors: Ku-Cauich Juan Carlos , Márquez-Hidalgo Miguel Angel
Published: April 2021

We provide three new authentication schemes without secrecy. The first two on finite fields and Galois rings, using Gray map for this link. The third construction is based on Galois rings. The main achievement in this work is to obtain optimal impersonation and substitution probabilities in the schemes. Additionally, in the first and second scheme, we simplify the source space and obtain a better relationship between the size of the message space and the key space than the one given in a recent paper. Finally, we provide a third scheme on Galois rings.
Optimal Software Feature-Limited Freemium Model Design: A New Consumer Learning Theoretical Framework
Authors: Li Kang , Zhang Jingwei , Zhang Lunchuan
Published: April 2021

The software industry is increasingly adopting a feature-limited freemium business model that combines “free” and “premium” contents in one product, to sell its products. How to determine the optimal product quality differences between the free and premium versions of software is a central business problem facing many software vendors. In this paper, we study the optimal feature-limited freemium software strategy design, as well as the associated pricing strategies based on consumer learning and network externality effects. We propose a new consumer learning framework induced by cross-module synergies that contains both direct and indirect learning processes. By employing a two-stage mathematical theoretical model and a numerical analysis method, we gained some insights regarding the feature-limited free trial strategy design and associated pricing strategies while considering the associated trade-off between the benefits and costs of the free trial strategy. In our modeling and numerical results, consumers’ prior beliefs about the quality of premium content before the free trial, network effect intensity, and indirect learning intensity were found to be three conditions that need to be studied to examine software vendors’ management decisions. For the software industry, the quality difference between free and premium functionality or the service and price strategy for a feature-limited free trial model can be designed while considering these factors, which will provide some useful guidelines for the industry.
Adaptive Stepsize Control for Extrapolation Semi-Implicit Multistep ODE Solvers
Authors: Butusov Denis
Published: April 2021

Developing new and efficient numerical integration techniques is of great importance in applied mathematics and computer science. Among the variety of available methods, multistep ODE solvers are broadly used in simulation software. Recently, semi-implicit integration proved to be an efficient compromise between implicit and explicit ODE solvers, and multiple high-performance semi-implicit methods were proposed. However, the computational efficiency of any ODE solver can be significantly increased through the introduction of an adaptive integration stepsize, but it requires the estimation of local truncation error. It is known that recently proposed extrapolation semi-implicit multistep methods (ESIMM) cannot operate with existing local truncation error (LTE) estimators, e.g., embedded methods approach, due to their specific right-hand side calculation algorithm. In this paper, we propose two different techniques for local truncation error estimation and study the performance of ESIMM methods with adaptive stepsize control. The first considered approach is based on two parallel semi-implicit solutions with different commutation orders. The second estimator, called the “double extrapolation” method, is a modification of the embedded method approach. The introduction of the double extrapolation LTE estimator allowed us to additionally increase the precision of the ESIMM solver. Using several known nonlinear systems, including stiff van der Pol oscillator, as the testbench, we explicitly show that ESIMM solvers can outperform both implicit and explicit linear multistep methods when implemented with an adaptive stepsize.
Investigation of X and Y Configuration Modal and Dynamic Response to Velocity Excitation of the Nanometer Resolution Linear Servo Motor Stage with Quasi-Industrial Guiding System in Quasi-Stable State
Authors: Piščalov Artur , Urbonas Edgaras , Vainorius Darius , Matijošius Jonas , Kilikevičius Artūras
Published: April 2021

Research institutions and industrial enterprises demand high accuracy and precision positioning systems to fulfil cutting edge requirements of up-to-date technological processes in the field of metrology and optical fabrication. Linear motor system design with high performance mechanical guiding system and optical encoder ensures nanometer scale precision and constant static error, which can be calibrated by optical instruments. Mechanical guiding systems has its benefits in case of control theory and its stability; unfortunately, on the other hand, there exists high influence of structure geometry and tribological effects such as friction and modal response. The aforementioned effect cannot be straightforwardly identified during the assembly process. Degradation of dynamic units can be detected only after certain operating time. Single degree of freedom systems are well investigated and the effect of degradation can be predicted, but there exists a gap in the analysis of nanometer scale multi degree of freedom dynamic systems; therefore, novel diagnostic tools need to be proposed. In this particular paper, dual axes dynamic system analysis will be presented. The main idea is to decouple standard stacked XY stage and analyse X and Y configuration as two different configurations of the same object, while imitators of corresponding axes are absolutely solid and stationary. As storage and analysis of time domain data is not efficient, main attention will be concentrated on frequency domain data, while, of course, statistical and graphical representation of dynamic response will be presented. Transfer function, dynamic response, spectral analysis of dynamic response, and modal analysis will be presented and discussed. Based on the collected data and its analysis, comparison of X and Y responses to different velocity excitation will be presented. Finally, conclusions and recommendations of novel diagnostic way will be presented.
Modeling Political Corruption in Spain
Authors: de la Poza Elena , Jódar Lucas , Merello Paloma
Published: April 2021

Political corruption is a universal phenomenon. Even though it is a cross-country reality, its level of intensity and the manner of its effect vary worldwide. In Spain, the demonstrated political corruption cases that have been echoed by the media in recent years for their economic, judicial and social significance are merely the tip of the iceberg as regards a problem hidden by many interested parties, plus the shortage of the means to fight against it. This study models and quantifies the population at risk of committing political corruption in Spain by identifying and quantifying the drivers that explain political corruption. Having quantified the problem, the model allows changes to be made in parameters, as well as fiscal, economic and legal measures being simulated, to quantify and better understand their impact on Spanish citizenship. Our results suggest increasing women’s leadership positions to mitigate this problem, plus changes in the political Parties’ Law in Spain and increasing the judiciary system’s budget.
On Certain Properties and Applications of the Perturbed Meixner–Pollaczek Weight
Authors: Kelil Abey S. , Jooste Alta S. , Appadu Appanah R.
Published: April 2021

This paper deals with monic orthogonal polynomials orthogonal with a perturbation of classical Meixner–Pollaczek measure. These polynomials, called Perturbed Meixner–Pollaczek polynomials, are described by their weight function emanating from an exponential deformation of the classical Meixner–Pollaczek measure. In this contribution, we investigate certain properties such as moments of finite order, some new recursive relations, concise formulations, differential-recurrence relations, integral representation and some properties of the zeros (quasi-orthogonality, monotonicity and convexity of the extreme zeros) of the corresponding perturbed polynomials. Some auxiliary results for Meixner–Pollaczek polynomials are revisited. Some applications such as Fisher’s information, Toda-type relations associated with these polynomials, Gauss–Meixner–Pollaczek quadrature as well as their role in quantum oscillators are also reproduced.
Herpes Simplex Keratitis in Patients with SARS-CoV-2 Infection: A Series of Five Cases
Authors: Majtanova Nora , Kriskova Petra , Keri Petra , Fellner Zlatica , Majtan Juraj , Kolar Petr
Published: April 2021

Herpes simplex virus type 1 (HSV-1) is a leading cause of infectious blindness worldwide. Most of the initial infection cases manifest as acute epithelial keratitis. Reactivation of herpesviruses is common in critically ill patients, including patients with severe Coronavirus disease (COVID-19). However, the data on COVID-19-related ocular infections is sparse, despite recent observations that more than 30% of COVID-19-infected patients had ocular manifestations. We report five cases of HSV-1 keratitis in COVID-19 patients. In total, five COVID-19 patients underwent ophthalmic examination, showing similar symptoms, including photophobia, tearing, decreased vision, eye redness, and pain. After initial assessment, tests of visual acuity and corneal sensitivity, a fluorescein staining test, and complete anterior and posterior segment examinations were performed. A diagnosis of HSV-1 keratitis was confirmed in all cases. Therapy was initiated using a local and systemic antiviral approach together with local antibiotic and mydriatic therapy. The complete reduction of keratitis symptoms and a clear cornea was achieved in all patients within 2 weeks. SARS-CoV-2 infection may be a risk factor for developing HSV-1 keratitis, or it may act as a potential activator of this ocular disease.
Antidepressants and Risk of Sudden Cardiac Death: A Network Meta-Analysis and Systematic Review
Authors: Prasitlumkum Narut , Cheungpasitporn Wisit , Tokavanich Nithi , Ding Kimberly R. , Kewcharoen Jakrin , Thongprayoon Charat , Kaewput Wisit , Bathini Tarun , Vallabhajosyula Saraschandra , Chokesuwattanaskul Ronpichai
Published: April 2021

Background: Antidepressants are one of the most prescribed medications, particularly for patients with mental disorders. Nevertheless, there are still limited data regarding the risk of ventricular arrhythmia (VA) and sudden cardiac death (SCD) associated with these medications. Thus, we performed systemic review and meta-analysis to characterize the risks of VA and SCD among patients who used common antidepressants. Methods: A literature search for studies that reported risk of ventricular arrhythmias and sudden cardiac death in antidepressant use from MEDLINE, EMBASE, and Cochrane Database from inception through September 2020. A random-effects model network meta-analysis model was used to analyze the relation between antidepressants and VA/SCD. Surface Under Cumulative Ranking Curve (SUCRA) was used to rank the treatment for each outcome. Results: The mean study sample size was 355,158 subjects. Tricyclic antidepressant (TCA) patients were the least likely to develop ventricular arrhythmia events/sudden cardiac deaths at OR 0.24, 0.028–1.2, OR 0.32 (95% CI 0.038–1.6) for serotonin and norepinephrine reuptake inhibitors (SNRI), and OR 0.36 (95% CI 0.043, 1.8) for selective serotonin reuptake inhibitors (SSRI), respectively. According to SUCRA analysis, TCA was on a higher rank compared to SNRI and SSRI considering the risk of VA/SCD. Conclusion: Our network meta-analysis demonstrated the low risk of VA/SCD among patients using antidepressants for SNRI, SSRI and especially, TCA. Despite the relatively lowest VA/SCD in TCA, drug efficacy and other adverse effects should be taken into account in patients with mental disorders.
Biofunctionalization of Porous Ti Substrates Coated with Ag Nanoparticles for Potential Antibacterial Behavior
Authors: Gaviria Juliana , Alcudia Ana , Begines Belén , Beltrán Ana María , Rodríguez-Ortiz José Antonio , Trueba Paloma , Villarraga Junes , Torres Yadir
Published: April 2021

Ti prosthesis have shown better biological compatibility, mechanical performance, and resistance to corrosion in cases of bone replacements. Nevertheless, fully dense Ti in connection with bone-host tissues show stress-shielding phenomenon that, together with the development of frequent undesirable microbial infections, may lead to implant failures. To overcome these issues, the present study aimed at the development of a novel combination of a chemically functionalized porous Ti substrate with a potentially therapeutic AgNPs coating. Fully dense and porous Ti substrates (30 and 60 vol.%, 100–200 and 355–500 μm, as spacer particles) were studied. Ti surface was treated with acid or basic medium followed by silanization and deposition of AgNPs by “submerged” and “in situ” methods. In general, for similar porosity, mechanical resistance decreased as pore size increased. Acidic reagent and submerged methodology were the best combination for fully dense Ti substrates. Hence, they were also employed for porous Ti substrates. Depending on the porosity of the substrates, variations can be observed both in the size and degree of agglomeration of the deposited AgNPs, entailing differences in the antibacterial behavior of the samples.
Characteristics of Ternary Metal (Cu-Ni-TiN) Electrodes Used in an Electrical Discharge Machining Process
Authors: Saodaen Rattikorn , Janmanee Pichai , Rodchanarowan Aphichart
Published: April 2021

In the industrial field, electric discharge machining (EDM) is the most commonly used non-traditional machining process because it has the potential to machine electrically conductive materials of high hardness. To satisfy the need for rapid and economical fabrication of EDM electrodes, techniques that use the addition of more metal in the manufacturing process are gaining in popularity. This study presents an investigation of the characterization of ternary metals (Cu–Ni–TiN) for EDM electrodes by using powder metallurgy, which leads to enhancement of the mechanical properties, such as the hardness, electrical properties, and other properties, for the formation of Cu in Ni-TiN electrodes using a cold press at pressures of 18, 20, and 22 MPa. The influences of the parameters of this process were identified for the betterment of Cu–Ni–TiN on the surface. The specimens were calcined in a furnace at 1100 °C for 1 h, with a mixture of argon and hydrogen gas as a controlled gas in the ratio of 95:5. The specimens were investigated in terms of hardness, electric resistivity, apparent density, and porosity. The results show that the 80% Cu–3% Ni–17% TiN electrode at 18 MPa had the highest hardness (124.38 HV) and the lowest electric resistivity (0.39188 cm), while the specimen increased Cu with a ratio of 85% Cu–3% Ni–12% TiN, and a pressure of 20 MPa was found to have the highest density (8.5472 g/cm3) and the lowest porosity (6.2922%). As a further confirmation of the above results, the X-ray diffraction (XRD) patterns of the surfaces of the specimens exhibited major phases that supported the ternary Cu–Ni–TiN phase. However, we also achieved the successful use of Cu–Ni–TiN electrodes as a titanium source (as an alternative to the conventional metal powder) to provide a novel approach to fabricating composite electrodes through the EDM process.
Microstructural Features and Surface Hardening of Ultrafine-Grained Ti-6Al-4V Alloy through Plasma Electrolytic Polishing and Nitrogen Ion Implantation
Authors: Smyslova Marina K. , Valiev Roman R. , Smyslov Anatoliy M. , Modina Iuliia M. , Sitdikov Vil D. , Semenova Irina P.
Published: April 2021

This work studies a near-surface layer microstructure in Ti-6Al-4V alloy samples subjected to plasma electrolytic polishing (PEP) and subsequent high-energy ion implantation with nitrogen (II). Samples with a conventional coarse-grained (CG) structure with an average α-phase size of 8 μm and an ultrafine-grained (UFG) structure (α-phase size up to 0.35 μm) produced by equal channel angular pressing were used in the studies. Features of phase composition and substructure in the thin surface layers are shown after sequential processing by PEP and II of both substrates with CG and UFG structures. Irrespective of a substrate structure, the so-called “long-range effect” was observed, which manifested itself in enhanced microhardness to a depth of surface layer up to 40 μm, exceeding the penetration distance of an implanted ion he. The effect of a UFG structure on depth and degree of surface hardening after PEP and ion-implantation is discussed.
316L(N) Creep Modeling with Phenomenological Approach and Artificial Intelligence Based Methods
Authors: Baraldi Daniele , Holmström Stefan , Nilsson Karl-Fredrik , Bruchhausen Matthias , Simonovski Igor
Published: April 2021

A model that describes creep behavior is essential in the design or life assessment of components and systems that operate at high temperatures. Using the RCC-MRx data and the LCSP (logistic creep strain prediction) model, processed design data were generated over the whole creep regime of 316L(N) steel—i.e., primary, secondary, and tertiary creep. The processed design data were used to develop three models with different approaches for the creep rate: a phenomenological approach; an artificial neural network; and an artificial intelligence method based on symbolic regression and genetic programming. It was shown that all three models are capable of describing the true creep rate as a function of true creep strain and true stress over a wide range of engineering stresses and temperatures without the need of additional micro-structural information. Furthermore, the results of finite element simulations reproduce the trends of experimental data from the literature.
A Comparative Study of Acicular Ferrite Transformation Behavior between Surface and Interior in a Low C–Mn Steel by HT-LSCM
Authors: Liu Xiaojin , Yuan Guo , Misra Raja. Devesh Kumar , Wang Guodong
Published: April 2021

In this study, the acicular ferrite transformation behavior of a Ti–Ca deoxidized low carbon steel was studied using a high-temperature laser scanning confocal microscopy (HT-LSCM). The in situ observation of the transformation behavior on the sample surface with different cooling rates was achieved by HT-LSCM. The microstructure between the surface and interior of the HT-LSCM sample was compared. The results showed that Ti–Ca oxide particles were effective sites for acicular ferrite (AF) nucleation. The start transformation temperature at grain boundaries and intragranular particles decreased with an increase in cooling rate, but the AF nucleation rate increased and the surface microstructure was more interlocked. The sample surface microstructure obtained at 3 °C/s was dominated by ferrite side plates, while the ferrite nucleating sites transferred from grain boundaries to intragranular particles when the cooling rate was 15 °C/s. Moreover, it was interesting that the microstructure and microhardness of the sample surface and interior were different. The AF dominating microstructure, obtained in the sample interior, was much finer than the sample surface, and the microhardness of the sample surface was much lower than the sample interior. The combined factors led to a coarse size of AF on the sample surface. AF formed at a higher temperature resulted in the coarse size. The available particles for AF nucleation on the sample surface were quite limited, such that hard impingement between AF plates was much weaker than that in the sample interior. In addition, the transformation stress in austenite on the sample surface could be largely released, which contributed to a coarser AF plate size. The coarse grain size, low dislocation concentration and low carbon content led to lower hardness on the sample surface.
A Comprehensive Assessment of the Safety of Blautia producta DSM 2950
Authors: Liu Xuemei , Guo Weiling , Cui Shumao , Tang Xin , Zhao Jianxin , Zhang Hao , Mao Bingyong , Chen Wei
Published: April 2021

In recent years, Blautia has attracted attention for its role in ameliorating host diseases. In particular, Blautia producta DSM 2950 has been considered a potential probiotic due to its ability to mitigate inflammation in poly(I:C) induced HT-29 cells. Thus, to promote the development of indigenous intestinal microorganisms with potential probiotic function, we conducted a comprehensive experimental analysis of DSM 2950 to determine its safety. This comprised a study of its potential virulence genes, antibiotic resistance genes, genomic islands, antibiotic resistance, and hemolytic activity and a 14-day test of its acute oral toxicity in mice. The results indicated no toxin-related virulence genes in the DSM 2950 genome. Most of the genomic islands in DSM 2950 were related to metabolism, rather than virulence expression. DSM 2950 was sensitive to most of the tested antibiotics but was tolerant of treatment with kanamycin, neomycin, clindamycin, or ciprofloxacin, probably because it possessed the corresponding antibiotic resistance genes. Oral acute toxicity tests indicated that the consumption of DSM 2950 does not cause toxic side effects in mice. Overall, the safety profile of DSM 2950 confirmed that it could be a candidate probiotic for use in food and pharmaceutical preparations.
The First Insight into Polyhydroxyalkanoates Accumulation in Multi-Extremophilic Rubrobacter xylanophilus and Rubrobacter spartanus
Authors: Kouřilová Xenie , Schwarzerová Jana , Pernicová Iva , Sedlář Karel , Mrázová Kateřina , Krzyžánek Vladislav , Nebesářová Jana , Obruča Stanislav
Published: April 2021

Actinobacteria belonging to the genus Rubrobacter are known for their multi-extremophilic growth conditions—they are highly radiation-resistant, halotolerant, thermotolerant or even thermophilic. This work demonstrates that the members of the genus are capable of accumulating polyhydroxyalkanoates (PHA) since PHA-related genes are widely distributed among Rubrobacter spp. whose complete genome sequences are available in public databases. Interestingly, all Rubrobacter strains possess both class I and class III synthases (PhaC). We have experimentally investigated the PHA accumulation in two thermophilic species, R. xylanophilus and R. spartanus. The PHA content in both strains reached up to 50% of the cell dry mass, both bacteria were able to accumulate PHA consisting of 3-hydroxybutyrate and 3-hydroxyvalerate monomeric units, none other monomers were incorporated into the polymer chain. The capability of PHA accumulation likely contributes to the multi-extremophilic characteristics since it is known that PHA substantially enhances the stress robustness of bacteria. Hence, PHA can be considered as extremolytes enabling adaptation to extreme conditions. Furthermore, due to the high PHA content in biomass, a wide range of utilizable substrates, Gram-stain positivity, and thermophilic features, the Rubrobacter species, in particular Rubrobacter xylanophilus, could be also interesting candidates for industrial production of PHA within the concept of Next-Generation Industrial Biotechnology.
Response of Key Metabolites during a UV-A Exposure Time-Series in the Cyanobacterium Chlorogloeopsis fritschii PCC 6912
Authors: Kultschar Bethan , Dudley Ed , Wilson Steve , Llewellyn Carole Anne
Published: April 2021

Ultraviolet A (UV-A) is the major component of UV radiation reaching the Earth’s surface, causing indirect damage to photosynthetic organisms via the production of reactive oxygen species (ROS). In comparison, UV-B causes both direct damage to biomolecules and indirect damage. UV-B is well studied in cyanobacterial research due to their long evolutionary history and adaptation to high levels of UV, with less work on the effects of UV-A. In this study, the response of key metabolites in Chlorogloeopsis fritschii (C. fritschii) during 48 h of photosynthetically active radiation (PAR, 15 µmol·m−2·s−1) supplemented with UV-A (11 µmol·m−2·s−1) was investigated using gas chromatography- mass spectrometry (GC-MS). Results showed an overall significant increase in metabolite levels up to 24 h of UV-A exposure. Compared with previously reported UV-B (PAR + UV-B) and PAR only results, UV-A showed more similarity compared to PAR only exposure as opposed to supplemented UV-B. The amino acids glutamate, phenylalanine and leucine showed differences in levels between UV (both supplemented UV-A and supplemented UV-B) and PAR only (non-supplemented PAR), hinting to their relevance in UV stress response. The fatty acids, palmitic and stearic acid, showed positive log2 fold-change (FC) in supplemented UV-A and PAR only experiments but negative log2 FC in UV-B, indicating the more harmful effect of UV-B on primary metabolism. Less research has been conducted on UV-A exposure and cyanobacteria, a potential environmental stimuli for the optimisation of metabolites for industrial biotechnology. This study will add to the literature and knowledge on UV-A stress response at the metabolite level in cyanobacteria, especially within the less well-known species C. fritschii.
Elevated Incidences of Antimicrobial Resistance and Multidrug Resistance in the Maumee River (Ohio, USA), a Major Tributary of Lake Erie
Authors: Mukherjee Maitreyee , Marie Leah , Liles Cheyenne , Mustafa Nadia , Bullerjahn George , Gentry Terry J. , Brooks John P.
Published: April 2021

Maumee River, the major tributary in the western basin of Lake Erie, serves as one of major sources of freshwater in the area, supplying potable, recreational, and industrial water. In this study we collected water samples from four sites in the Maumee River Bay between 2016–2017 and E. coli was isolated, enumerated, and analyzed for antimicrobial resistance (AMR) and multidrug resistance (MDR). Strikingly, 95% of the total isolates were found to be resistant to at least one antibiotic. A very high resistance to the drugs cephalothin (95.3%), ampicillin (38.3%), tetracycline (8.8%), gentamicin (8.2%), ciprofloxacin (4.2%), cefoperazone (4%), and sulfamethoxazole (1.5%) was observed within isolates from all four sampling sites. Percentages of AMR and MDR was consistently very high in the summer and fall months, whereas it was observed to be lowest in the winter. A remarkably high number of the isolates were detected to be MDR—95% resistant to ≥1 antibiotic, 43% resistant to ≥2 antibiotics, 15% resistant to ≥3 antibiotics, 4.9% resistant to ≥4 antibiotic and 1.2% resistant to ≥5 antibiotics. This data will serve in better understanding the environmental occurrence and dissemination of AMR/MDR in the area and assist in improving and establishing control measures.
Lactobacillus reuteri Colonisation of Extremely Preterm Infants in a Randomised Placebo-Controlled Trial
Authors: Spreckels Johanne E. , Wejryd Erik , Marchini Giovanna , Jonsson Baldvin , de Vries Dylan H. , Jenmalm Maria C. , Landberg Eva , Sverremark-Ekström Eva , Martí Magalí , Abrahamsson Thomas
Published: April 2021

Lactobacillus reuteri DSM 17938 supplementation reduces morbidities in very low birth weight infants (<1500 g), while the effect on extremely low birth weight infants (ELBW, <1000 g) is still questioned. In a randomised placebo-controlled trial (ClinicalTrials.gov ID NCT01603368), head growth, but not feeding tolerance or morbidities, improved in L. reuteri-supplemented preterm ELBW infants. Here, we investigate colonisation with the probiotic strain in preterm ELBW infants who received L. reuteri DSM 17938 or a placebo from birth to postmenstrual week (PMW) 36. Quantitative PCR was used on 582 faecal DNA samples collected from 132 ELBW infants at one, two, three, and four weeks, at PMW 36, and at two years of age. Human milk oligosaccharides were measured in 31 milk samples at two weeks postpartum. At least 86% of the ELBW infants in the L. reuteri group were colonised with the probiotic strain during the neonatal period, despite low gestational age, high antibiotic pressure, and independent of infant feeding mode. Higher concentrations of lacto-N-tetraose, sialyl-lacto-N-neotetraose c, and 6′-sialyllactose in mother’s milk weakly correlated with lower L. reuteri abundance. Within the L. reuteri group, higher L. reuteri abundance weakly correlated with a shorter time to reach full enteral feeding. Female sex and L. reuteri colonisation improved head growth from birth to four weeks of age. In conclusion, L. reuteri DSM 17938 supplementation leads to successful colonisation in ELBW infants.
Myxococcus xanthus as a Model Organism for Peptidoglycan Assembly and Bacterial Morphogenesis
Authors: Zhang Huan , Venkatesan Srutha , Nan Beiyan
Published: April 2021

A fundamental question in biology is how cell shapes are genetically encoded and enzymatically generated. Prevalent shapes among walled bacteria include spheres and rods. These shapes are chiefly determined by the peptidoglycan (PG) cell wall. Bacterial division results in two daughter cells, whose shapes are predetermined by the mother. This makes it difficult to explore the origin of cell shapes in healthy bacteria. In this review, we argue that the Gram-negative bacterium Myxococcus xanthus is an ideal model for understanding PG assembly and bacterial morphogenesis, because it forms rods and spheres at different life stages. Rod-shaped vegetative cells of M. xanthus can thoroughly degrade their PG and form spherical spores. As these spores germinate, cells rebuild their PG and reestablish rod shape without preexisting templates. Such a unique sphere-to-rod transition provides a rare opportunity to visualize de novo PG assembly and rod-like morphogenesis in a well-established model organism.
Editorial for the Special Issue: Bacterial Meningitis—Epidemiology and Vaccination
Authors: Stuart James M.
Published: April 2021

Bacterial meningitis has serious health, economic, and social consequences with a high risk of death and lifelong disability [...]
Enterococcus faecalis Endophthalmitis: Clinical Settings, Antibiotic Susceptibility, and Management Outcomes
Authors: Chen Kuan-Jen , Lai Chi-Chun , Chen Hung-Chi , Chong Ying-Jiun , Sun Ming-Hui , Chen Yen-Po , Wang Nan-Kai , Hwang Yih-Shiou , Chao An-Ning , Wu Wei-Chi , Yeung Ling , Sun Chi-Chin , Liu Laura , Chen Yi-Hsing , Chou Hung-Da
Published: April 2021

Enterococcus faecalis is known to cause severe acute endophthalmitis and often leads to poor visual outcomes in most ophthalmic infections. This retrospective study is to report the clinical settings, antimicrobial susceptibility patterns, and visual outcome of E. faecalis endophthalmitis at a tertiary referral institution in Taoyuan, Taiwan. E. faecalis endophthalmitis was diagnosed in 37 eyes of 37 patients. Post-cataract surgery was the most common cause (n = 27, 73%), followed by bleb-associated (n = 3, 8%), endogenous (n = 2, 5%), corneal ulcer-related (n = 2, 5%), post-vitrectomy (n = 1, 3%), post-pterygium excision (n = 1, 3%), and trauma (n = 1, 3%). Visual acuities upon presentation ranged from counting fingers to no light perception. Pars plana vitrectomy with intravitreal antibiotics were performed in 23 eyes (76%) as primary or secondary treatment. All isolates (37/37, 100%) were sensitive to vancomycin, penicillin, ampicillin, and teicoplanin. Six of 22 eyes (27%) were resistant to high-level gentamicin (minimum inhibitory concentration > 500 mg/L). Final visual acuities were better than 20/400 in 11 eyes (30%), 5/200 to hand motions in 4 eyes (11%), and light perception to no light perception in 22 eyes (59%). Three eyes were treated with evisceration. Compared with non-cataract subgroups, the post-cataract subgroup showed a significant difference of better visual prognosis (p = 0.016).
Separation of Fe from Mn in the Cryogenian Sedimentary Mn Deposit, South China: Insights from Ore Mineral Chemistry and S Isotopes from the Dawu Deposit
Authors: Xu Zhiming , Wu Chengquan , Zhang Zhengwei , Xu Jinhong , Li Xiyao , Jin Ziru
Published: April 2021

Manganese and Fe have similar geochemical properties in the supergene environment. Separation of Mn and Fe is an important process for the formation of high-grade sedimentary manganese deposits. Large-scale manganese carbonate deposits (total reserves of approximately 700 Mt) were formed during the interglacial of the Sturtian and Marinoan in South China. The orebodies are hosted in the black rock series at the basal Datangpo Formation of the Cryogenian period. The Fe contents in ores range from 1.15 to 7.18 wt.%, with an average of 2.80 wt.%, and the average Mn/Fe ratio is 8.9, indicating a complete separation of Mn and Fe during the formation of manganese ores. Here, we present element data of manganese carbonates and sulfur isotopes of pyrite from the Dawu deposit, Guizhou, China, aiming to investigate the separation mechanism of Mn and Fe and the ore genesis. The Fe in ores mainly occurs as carbonate (FeCO3) and pyrite (FeS2). The Mn, Ca, Mg and Fe exist in the form of isomorphic substitutions in manganese carbonate. The contents of FeCO3 in manganese carbonates are similar in different deposits, with averages of 2.6–2.8 wt.%. The whole-rock Fe and S contents have an obvious positive correlation (R = 0.69), indicating that the difference of whole-rock Fe content mainly comes from the pyrite content. The δ34SV-CDT of pyrite varies from 40.0 to 48.3‰, indicating that the pyrite formed in a restricted basin where sulfate supply was insufficient and the sulfate concentrations were extremely low. Additionally, the whole-rock Fe content is negatively correlated with the δ34S values of the whole-rock and pyrite, with correlation coefficients of −0.78 and −0.83, respectively. Two stages of separations of Mn and Fe might have occurred during the mineralization processes. The reduced seawater became oxidized gradually after the Sturtian glaciation, and Fe2+ was oxidized and precipitated before Mn2+, which resulted in the first-stage separation of Mn and Fe. The residual Mn-rich and Fe-poor seawater flowed into the restricted rift basin. Mn and Fe were then precipitated in sediments as oxyhydroxide as the seawater was oxidized. At the early stage of diagenesis, organic matter was oxidized, and manganese oxyhydroxide was reduced, forming the manganese carbonate. H2S was insufficient in the restricted basin due to the extremely low sulfate concentration. The Fe2+ was re-released due to the lack of H2S, resulting in the second-stage separation of Mn and Fe. Finally, the manganese carbonate deposit with low Fe and very high δ34S was formed in the restricted basin after the Sturtian glaciation.
Combined In Situ Chemical and Sr Isotopic Compositions and U–Pb Ages of the Mushgai Khudag Alkaline Complex: Implications of Immiscibility, Fractionation, and Alteration
Authors: Yang Fan , Chen Wei , Kynicky Jindrich , Ying Yuancan , Bai Tian
Published: April 2021

The Mushgai Khudag complex consists of numerous silicate volcanic-plutonic rocks including melanephelinites, theralites, trachytes, shonkinites, and syenites and also hosts numerous dykes and stocks of magnetite-apatite-enriched rocks and carbonatites. It hosts the second largest REE–Fe–P–F–Sr–Ba deposit in Mongolia, with REE mineralization associated with magnetite-apatite-enriched rocks and carbonatites. The bulk rock REE content of these two rock types varies from 21,929 to 70,852 ppm, which is much higher than that of syenites (716 ± 241 ppm). Among these, the altered magnetite-apatite-enriched rocks are characterized by the greatest level of REE enrichment (58,036 ± 13,313 ppm). Magmatic apatite from magnetite-apatite-enriched rocks is commonly euhedral with purple luminescence, and altered apatite displays variable purple to blue luminescence and shows fissures and hollows with deposition of fine-grained monazite aggregates. Most magmatic apatite within syenite is prismatic and displays oscillatory zoning with variable purple to yellow luminescence. Both magmatic and altered apatite from magnetite-apatite-enriched rocks were dated using in situ U–Pb dating and found to have ages of 139.7 ± 2.6 and 138.0 ± 1.3 Ma, respectively, which supports the presence of late Mesozoic alkaline magmatism. In situ 87Sr/86Sr ratios obtained for all types of apatite and calcite within carbonatite show limited variation (0.70572–0.70648), which indicates derivation from a common mantle source. All apatite displays steeply fractionated chondrite-normalized REE trends with significant LREE enrichment (46,066 ± 71,391 ppm) and high (La/Yb)N ratios ranging from 72.7 to 256. REE contents and (La/Yb)N values are highly variable among different apatite groups, even within the same apatite grains. The variable REE contents and patterns recorded by magmatic apatite from the core to the rim can be explained by the occurrence of melt differentiation and accompanying fractional crystallization. The Y/Ho ratios of altered apatite deviate from the chondritic values, which reflects alteration by hydrothermal fluids. Altered apatite contains a high level of REE (63,912 ± 31,785 ppm), which are coupled with increased sulfur and/or silica contents, suggesting that sulfate contributes to the mobility and incorporation of REEs into apatite during alteration. Moreover, altered apatite is characterized by higher Zr/Hf, Nb/Ta, and (La/Yb)N ratios (179 ± 48, 19.4 ± 10.3, 241 ± 40, respectively) and a lack of negative Eu anomalies compared with magmatic apatite. The distinct chemical features combined with consistent Sr isotopes and ages for magmatic and altered apatite suggest that pervasive hydrothermal alterations at Mushgai Khudag are most probably being induced by carbonatite-evolved fluids almost simultaneously after the alkaline magmatism.
Chemical Constituents of Cassia abbreviata and Their Anti-HIV-1 Activity
Authors: Yang Xianwen , He Zhihui , Zheng Yue , Wang Ning , Mulinge Martin , Schmit Jean-Claude , Steinmetz André , Seguin-Devaux Carole
Published: April 2021

Three new (1–3) and 25 known compounds were isolated from the crude extract of Cassia abbreviata. The chemical structures of new compounds were established by extensive spectroscopic analyses including 1D and 2D NMR and HRESIMS. Cassiabrevone (1) is the first heterodimer of guibourtinidol and planchol A. Compound 2 was a new chalcane, while 3 was a new naphthalene. Cassiabrevone (1), guibourtinidol-(4α→8)-epiafzelechin (4), taxifolin (8), oleanolic acid (17), piceatannol (22), and palmitic acid (28), exhibited potent anti-HIV-1 activity with IC50 values of 11.89 µM, 15.39 µM, 49.04 µM, 7.95 µM, 3.58 µM, and 15.97 µM, respectively.
Synthesis and Characterization of a Mg2+-Selective Probe Based on Benzoyl Hydrazine Derivative and Its Application in Cell Imaging
Authors: Yu Chunwei , Ji Yuxiang , Wen Shaobai , Zhang Jun
Published: April 2021

A simple benzoyl hydrazine derivative P was successfully synthesized and characterized as Mg2+-selective fluorescent probe. The binding of P with Mg2+ caused an obvious fluorescence enhancement at 482 nm. The fluorescent, UV-vis spectra, 1H-NMR, and IR spectra confirmed the formation of P-Mg2+ complex, and the formation of a 1:1 stoichiometry complex was proved by Job’s plot and mass spectrometry. The recognition mechanism of P to Mg2+ was owing to the photoinduced electron transfer effect (PET). The fluorescent response was linear in the range of 0.9–4.0 µM with the detection limit of 0.3 µM Mg2+ in water–ethanol solution (1:9, v:v, pH10.0, 20 mM HEPES). In addition, the results of cell imaging of Mg2+ in Hl-7701 cells was satisfying.