bluuebunny/crossref_metadata_2025 huggingface dataset:
Research Progress on the Collaborative Drag Reduction Effect of Polymers and Surfactants
Authors: Gu Yunqing , Yu Songwei , Mou Jiegang , Wu Denghao , Zheng Shuihua
Published: January 2020

Polymer additives and surfactants as drag reduction agents have been widely used in the field of fluid drag reduction. Polymer additives can reduce drag effectively with only a small amount, but they degrade easily. Surfactants have an anti-degradation ability. This paper categorizes the mechanism of drag reducing agents and the influencing factors of drag reduction characteristics. The factors affecting the degradation of polymer additives and the anti-degradation properties of surfactants are discussed. A mixture of polymer additive and surfactant has the characteristics of high shear resistance, a lower critical micelle concentration (CMC), and a good drag reduction effect at higher Reynolds numbers. Therefore, this paper focuses more on a drag reducing agent mixed with a polymer and a surfactant, including the mechanism model, drag reduction characteristics, and anti-degradation ability.
High-Performance Temperature Sensors Based on Dual 4H-SiC JBS and SBD Devices
Authors: Min Seong-Ji , Shin Myeong Cheol , Thi Nguyen Ngoc , Oh Jong-Min , Koo Sang-Mo
Published: January 2020

Schottky diode-based temperature sensors are the most common commercially available temperature sensors, and they are attracting increasing interest owing to their higher Schottky barrier height compared to their silicon counterparts. Therefore, this paper presents a comparison of the thermal sensitivity variation trend in temperature sensors, based on dual 4H-SiC junction barrier Schottky (JBS) diodes and Schottky barrier diodes (SBDs). The forward bias current–voltage characteristics were acquired by sweeping the DC bias voltage from 0 to 3 V. The dual JBS sensor exhibited a higher peak sensitivity (4.32 mV/K) than the sensitivity exhibited by the SBD sensor (2.85 mV/K), at temperatures ranging from 298 to 573 K. The JBS sensor exhibited a higher ideality factor and barrier height owing to the p–n junction in JBS devices. The developed sensor showed good repeatability, maintaining a stable output over several cycles of measurements on different days. It is worth noting that the ideality factor and barrier height influenced the forward biased voltage, leading to a higher sensitivity for the JBS device compared to the SBD device. This allows the JBS device to be suitably integrated with SiC power management and control circuitry to create a sensing module capable of working at high temperatures.
Micro-Structure Modelling and Electrical Properties Analysis of PZT Matrix Ferroelectric Composites
Authors: Zhou Weibin , Fan Jinbo , Xin Zhenchao , You Guodong
Published: January 2020

PZT matrix ferroelectric composite is an important research topic in material science because of its many practical, industrial, and scientific applications. Materials with high dielectric permittivity are used to manufacture electronic devices, particularly capacitors and dynamic random access memory (DRAM). Therefore, the development of reliable and efficient micro models to be utilized in analyzing electrical properties can be of great value in accelerating research in this field. In this paper, a 3D microstructure model for PZT matrix ferroelectric composites has been developed and adopted the finite element method (FEM) to calculate the dielectric constant. The microscopy parameters of developed microstructure model are acquired based on the real composites from X-ray (micro-) diffraction and stereological method. The dielectric constant of different volume ratios of PZT matrix ferroelectric composites can be calculated by accurately controlling the volume of Ferrite particles. At the point of validation, the proposed approach makes visual and numeric comparisons between the morphology of the real microstructure and the model generated by the proposed technique. The simulation results by our method was essentially in agreement with experimental results in other literature. Simulation Experimental results also demonstrate that the dielectric constant of PZT matrix ferroelectric composites is significantly changed while the volume ratio of high dielectric phase particles was below 20%. PZT matrix ferroelectric composites Consequently, this method can be easily extended to composites preparation.
Strategy of Residual Stress Determination on Selective Laser Melted Al Alloy Using XRD
Authors: Chen Yujiong , Sun Hua , Li Zechen , Wu Yi , Xiao Yakai , Chen Zhe , Zhong Shengyi , Wang Haowei
Published: January 2020

Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in the residual stress values reported in the literature. On the basis of studying the influence of surface roughness on residual stress measured using X-ray diffraction (XRD), we propose a procedure coupling XRD technique with pretreatment consisting of mechanical polishing and chemical etching. The results highlight that residual stresses measured using XRD on as-built SLM-produced samples with high surface roughness are significantly lower than those measured on samples with finished surface, which is due to the stress relaxation on the spiked surface of as-built samples. Surface distribution of residual stresses and the effect of scanning strategy were systematically investigated for SLM-produced AlSi10Mg samples. Microstructural morphology was observed at the interface between sample and building platform and was linked to the surface distribution of residual stresses. This procedure can help us accurately measure the residual stresses in SLM-produced samples and thus better understand its build-up mechanism during the SLM process.
Cytotoxicity of Self-Etch Versus Etch-and-Rinse Dentin Adhesives: A Screening Study
Authors: Fröb Luisa , Rüttermann Stefan , Romanos Georgios E. , Herrmann Eva , Gerhardt-Szép Susanne
Published: January 2020

Six dentin adhesives were tested in vitro regarding their cytotoxicity on human fibroblasts. The adhesives Hybrid Bond, One-up Bond F Plus, AdheSE, Clearfil SE Bond, Optibond Solo Plus and Syntac were eluted with culture medium as single or sequentially applied adhesive part for 24 h. 75 Petri dishes were produced per group. They were evaluated triangulated, comprising the quantitative evaluation (105 ones) to determine “viable”, “dead” and “debris” cells with the use of a cell-counter and the reactivity index was also identified based on the qualitative assessment (420 ones). One-up Bond F Plus, AdheSE and Clearfil SE Bond showed a statistical difference of viable cells to the cell control. For One-up Bond F Plus, statistically, differences compared to hybrid bond and Syntac were also found. All the adhesives except One-up Bond F Plus showed significant differences between single and sequentially applied adhesive part regarding the quantitative evaluation. The test material showed a moderate grade of cytotoxicity. As a result, a statistically significant difference of the cytotoxicity between the self-etch and etch-and-rinse adhesives cannot be demonstrated regarding the qualitative evaluation and the reactivity index, but the differences between sequentially applied and single applied components can be proved.
Material Analysis and Molecular Dynamics Simulation for Cavitation Erosion and Corrosion Suppression in Water Hydraulic Valves
Authors: Mlela Masoud Kamoleka , Xu He , Sun Feng , Wang Haihang , Madenge Gabriel Donald
Published: January 2020

In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the appropriate selection, we conflicted properties that are vital for erosion and corrosion inhibitors, as well as the tribology in the sense of coefficient of friction. This article aimed to choose the best alternative polymer for coating on the selected substrate, that is, Cr2O3, Al2O3, Ti2O3. By applying PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations), the best polymer obtained with an analyzed performance attribute is Polytetrafluoroethylene (PTFE) that comes up with higher outranking (0.5932052). A Molecular Dynamics (MD) simulation was conducted to identify the stronger bonding with the regards of the better cleave plane between Polytetrafluoroethylene (PTFE) and the selected substrate. Polytetrafluoroethylene (PTFE)/Al2O3 cleaved in (010) plane was observed to be the strongest bond in terms of binding energy (3188 kJ/mol) suitable for further studies.
Magnetic Nanoparticles
Authors: Katz Evgeny
Published: January 2020

Magnetic nanoparticles are a class of nanoparticle that can be manipulated using magnetic fields [...]
Dynamic Modelling of Interactions between Microglia and Endogenous Neural Stem Cells in the Brain during a Stroke
Authors: Alqarni Awatif Jahman , Rambely Azmin Sham , Hashim Ishak
Published: January 2020

In this paper, we study the interactions between microglia and neural stem cells and the impact of these interactions on the brain cells during a stroke. Microglia cells, neural stem cells, the damage on brain cells from the stroke and the impacts these interactions have on living brain cells are considered in the design of mathematical models. The models consist of ordinary differential equations describing the effects of microglia on brain cells and the interactions between microglia and neural stem cells in the case of a stroke. Variables considered include: resident microglia, classically activated microglia, alternatively activated microglia, neural stem cells, tissue damage on cells in the brain, and the impacts these interactions have on living brain cells. The first model describes what happens in the brain at the stroke onset during the first three days without the generation of any neural stem cells. The second model studies the dynamic effect of microglia and neural stem cells on the brain cells following the generation of neural stem cells and potential recovery after this stage. We look at the stability and the instability of the models which are both studied analytically. The results show that the immune cells can help the brain by cleaning dead cells and stimulating the generation of neural stem cells; however, excessive activation may cause damage and affect the injured region. Microglia have beneficial and harmful functions after ischemic stroke. The microglia stimulate neural stem cells to generate new cells that substitute dead cells during the recovery stage but sometimes the endogenous neural stem cells are highly sensitive to inflammatory in the brain.
Parameter and State Estimation of One-Dimensional Infiltration Processes: A Simultaneous Approach
Authors: Bo Song , Sahoo Soumya R. , Yin Xunyuan , Liu Jinfeng , Shah Sirish L.
Published: January 2020

The Richards equation plays an important role in the study of agro-hydrological systems. It models the water movement in soil in the vadose zone, which is driven by capillary and gravitational forces. Its states (capillary potential) and parameters (hydraulic conductivity, saturated and residual soil moistures and van Genuchten-Mualem parameters) are essential for the accuracy of mathematical modeling, yet difficult to obtain experimentally. In this work, an estimation approach is developed to estimate the parameters and states of Richards equation simultaneously. In the proposed approach, parameter identifiability and sensitivity analysis are used to determine the most important parameters for estimation purpose. Three common estimation schemes (extended Kalman filter, ensemble Kalman filter and moving horizon estimation) are investigated. The estimation performance is compared and analyzed based on extensive simulations.
Evaluation of Maternal and Neonatal Outcomes of Assisted Reproduction Technology: A Retrospective Cohort Study
Authors: Tanaka Hiroaki , Tanaka Kayo , Osato Kazuhiro , Kusaka Hideto , Maegawa Yuka , Taniguchi Haruki , Ikeda Tomoaki
Published: January 2020

Background: To evaluate maternal and neonatal outcomes of assisted reproductive technology (ART). Materials and Methods: Pregnant women registered from 2015 through 2017 (n = 6994) at five perinatal centers that managed high-risk pregnancies in Mie, Japan, retrospectively. Rates of preterm birth (<37 gestational weeks), early onset preeclampsia (<34 gestational weeks), late onset preeclampsia (≥34 gestational weeks), low-lying placenta, placenta previa, placenta accreta, placental abruption, atonic bleeding, uterine rupture, and amniotic fluid embolism after ART were evaluated. ART was defined as in vitro fertilization and micro-fertilization. Fisher’s exact test, Mann–Whitney’s U test, and logistic regression analysis were used to analyze the data. Results: Rates of obstetrical complications including low-lying placenta, placenta previa, placenta accreta, and atonic bleeding were increased with ART compared to those with the control. Particularly, ART was associated with a significantly increased rate of placenta accreta (adjusted odds ratio: 7.35, 95% confidence interval (CI): 3.20–16.6) and significantly decreased rate of placental abruption (adjusted odds ratio: 0.24, 95% CI: 0.07–0.61). Conclusions: This study showed that ART may reduce placental abruption and increase placenta previa. There is a possibility that the placenta attaches deeper in the myometrium because of ART.
The Presence of Immature GV− Stage Oocytes during IVF/ICSI Is a Marker of Poor Oocyte Quality: A Pilot Study
Authors: Astbury Pia , Subramanian Goutham N. , Greaney Jessica , Roling Chris , Irving Jacqui , Homer Hayden A.
Published: January 2020

Here we investigate whether the presence of germinal vesicle-stage oocytes (GV− oocytes) reflects poor oocyte developmental competence (or quality). This was a prospective, non-randomised, cohort pilot-study involving 60 patients undergoing in vitro fertilization/ intracytoplasmic sperm injection for whom complete pregnancy outcome data were available. Patients in whom GV− oocytes were retrieved (GV+) at transvaginal oocyte retrieval (TVOR) were compared with those from whom no GVs were retrieved (GV−). We found that GV+ (n = 29) and GV− (n = 31) patients were similarly aged (35.4 vs. 36.4 years; p = 0.446). GV+ patients had a mean of 2.41 ± 2.03 GVs and comparable yields of MII oocytes to GV− patients (11 ± 6.88 vs. 8.26 ± 4.84; p = 0.077). Compared with GV− patients, GV+ patients had markedly lower implantation rates (11.8% vs. 30.2%; p = 0.022) as well as oocyte utilisation rates for clinical pregnancy (2.3% vs. 6.8%; p = 0.018) and live-birth (1.9% vs. 5.7%; p = 0.029). DNA damage levels measured using γH2AX immunostaining were not different in oocytes from women <36 years versus those ≥36 years (p = 0.606). Thus, patients who have GV− stage oocytes at TVOR exhibit poor oocyte quality reflected in reduced per-oocyte pregnancy success rates and uniformly high levels of oocyte DNA damage.
Nanoindentation Properties of 18CrNiMo7-6 Steel after Carburizing and Quenching Determined by Continuous Stiffness Measurement Method
Authors: Zhou Guiyuan , Guo Jian , Zhao Junyu , Tang Qian , Hu Zhaonan
Published: January 2020

In this work, the nanomechanical properties involving the indentation size effect (ISE) and yield strength of a surface-modified layer of 18CrNiMo7-6 steel after case hardening were investigated via nanoindentation experiments. The experimental results showed that the hardness increased with an increase in strain rate; the contact stiffness versus indentation depth curves take the form of upper convexity due to residual compressive stress relaxation. On the basis of the Ruiz-Moreno model, a modified model considering the cutoff parameter as a function of indentation depth was proposed. This model was able to better describe the ISE of the surface-modified layer. With the Hough transform error angle of 0.1° as the critical value (h0.1° is the corresponding depth), when h > h0.1°, the yield strength calculated by the Ma model started to disperse at the depth of h0.1°. These results provide useful insight into the local mechanical properties of 18CrNiMo7-6 steel after carburizing and quenching treatment.
Research on Laser-TIG Hybrid Welding of 6061-T6 Aluminum Alloys Joint and Post Heat Treatment
Authors: Wang Hongyang , Liu Xiaohong , Liu Liming
Published: January 2020

The 6061-T6 aluminum (Al) alloys was joined by the laser induced tungsten inert gas (TIG) hybrid welding technique. It mainly studied the influences of welding parameters, solution, and aging (STA) treatment on the microstructure and tensile properties of Al alloy hybrid welding joints. Microstructures of the joints were also analyzed by optical microscopy and transmission electron microscopy. Results showed that the laser induced arc hybrid welding source changed the microstructure of the fusion zone and heat effect zone. STA treatment effectively improved the mechanical properties of the softening area in the hybrid welding joint, whose values of the tensile strength and elongation were on average 286 MPa and 20.5%. The distribution of the reinforcement phases and dislocations distributed were more uniform, which improved the property of STA treated joint.
Self-Reduction Behavior of Bio-Coal Containing Iron Ore Composites
Authors: El-Tawil Asmaa A. , Ahmed Hesham M. , Ökvist Lena Sundqvist , Björkman Bo
Published: January 2020

The utilization of CO2 neutral carbon instead of fossil carbon is one way to mitigate CO2 emissions in the steel industry. Using reactive reducing agent, e.g., bio-coal (pre-treated biomass) in iron ore composites for the blast furnace can also enhance the self-reduction. The current study aims at investigating the self-reduction behavior of bio-coal containing iron ore composites under inert conditions and simulated blast furnace thermal profile. Composites with and without 10% bio-coal and sufficient amount of coke breeze to keep the C/O molar ratio equal to one were mixed and Portland cement was used as a binder. The self-reduction of composites was investigated by thermogravimetric analyses under inert atmosphere. To explore the reduction progress in each type of composite vertical tube furnace tests were conducted in nitrogen atmosphere up to temperatures selected based on thermogravimetric results. Bio-coal properties as fixed carbon, volatile matter content and ash composition influence the reduction of iron oxide. The reduction of the bio-coal containing composites begins at about 500 °C, a lower temperature compared to that for the composite with coke as only carbon source. The hematite was successfully reduced to metallic iron at 850 °C by using bio-coal, whereas with coke as a reducing agent temperature up to 1100 °C was required.
Scaling in the Local Strain-Rate Field during Jerky Flow in an Al-3%Mg Alloy
Authors: Lebyodkin Mikhail , Bougherira Youcef , Lebedkina Tatiana , Entemeyer Denis
Published: January 2020

Jerky flow in alloys, or the Portevin-Le Chatelier effect, presents an outstanding example of self-organization phenomena in plasticity. Recent acoustic emission investigations revealed that its microscopic dynamics is governed by scale invariance manifested as power-law statistics of intermittent events. As the macroscopic stress serrations show both scale invariance and characteristic scales, the micro-macro transition is an intricate question requiring an assessment of intermediate behaviors. The first attempt of such an investigation is undertaken in the present paper by virtue of a one-dimensional (1D) local extensometry technique and statistical analysis of time series. The data obtained complete the missing link and bear evidence to a coexistence of characteristic large events and power laws for smaller events. The scale separation is interpreted in terms of the phenomena of self-organized criticality and synchronization in complex systems. Furthermore, it is found that both the stress serrations and local strain-rate bursts agree with the so-called fluctuation scaling related to general mathematical laws and unifying various specific mechanisms proposed to explain scale invariance in diverse systems. Prospects of further investigations including the duality manifested by a wavy spatial organization of the local bursts of plastic deformation are discussed.
Critical Strain for Dynamic Recrystallisation. The Particular Case of Steels
Authors: Varela-Castro Gonzalo , Cabrera José-María , Prado José-Manuel
Published: January 2020

The knowledge of the flow behavior of metallic alloys subjected to hot forming operations has particular interest for metallurgists in the practice of industrial forming processes involving high temperatures (e.g., rolling, forging, and/or extrusion operations). Dynamic recrystallisation (DRX) occurs during high temperature forming over a wide range of metals and alloys, and it is known to be a powerful tool that can be used to control the microstructure and mechanical properties. Therefore, it is important to know, particularly in low stacking fault energy materials, the precise time at which DRX is available to act. Under a constant strain rate condition, and for a given temperature, such a time is defined as a critical strain (εc). Unfortunately, this critical value is not always directly measurable on the flow curve; as a result, different methods have been developed to derive it. Focused on carbon and microalloyed steels subjected to laboratory-scale testing, in the present work, the state of art on the critical strain for the initiation of DRX is reviewed and summarized. A review of the different methods and expressions for assessing the critical strain is also included. The collected data are well suited to feeding constitutive models and computational codes.
Evolution of Phase Transition and Mechanical Properties of Ultra-High Strength Hot-Stamped Steel During Quenching Process
Authors: Liu Shuang , Long Mujun , Ai Songyuan , Zhao Yan , Chen Dengfu , Feng Yi , Duan Huamei , Ma Mingtu
Published: January 2020

Hot stamping process is widely used in the manufacture of the high strength automotive steel, mainly including the stamping and quenching process of the hot-formed steel. In the hot stamping process, the steel is heated above the critical austenitizing temperature, and then it is rapidly stamped in the mold and the quenching phase transition occurs at the same time. The quenching operation in the hot stamping process has a significant influence on the phase transition and mechanical properties of the hot-stamping steel. A proper quenching technique is quite important to control the microstructure and properties of an ultra-high strength hot-stamping steel. In this paper, considering the factors of the austenitizing temperature, the austenitizing time and the cooling rate, a coupled model on the thermal homogenization and phase transition from austenite to martensite in quenching process was established for production of ultra-high strength hot-stamping steel. The temperature variation, the austenite decomposition and martensite formation during quenching process was simulated. At the same time, the microstructure and the properties of the ultra-high strength hot-stamping steel after quenching at different austenitizing temperature were experimental studied. The results show that under the conditions of low cooling rate, the final quenching microstructure of the ultra-high strength hot-stamping steel includes martensite, residual austenite, bainite and ferrite. With the increase of the cooling rate, bainite and ferrite gradually disappear. While austenitizing at 930 °C, the tensile strength, yield strength, elongation and strength-ductility product of the hot-stamping steel are 1770.1 MPa, 1128.2 MPa, 6.72% and 11.9 GPa%, respectively.
Investigations of Graphite Particle Interaction with Metallic Surfaces
Authors: Andris Andreas , Fischer Felix , Herrmann Marion , Lippmann Wolfgang , Hurtado Antonio
Published: January 2020

Previous studies on the safety of gas-cooled high-temperature reactors (HTR) have analyzed the corrosion and oxidation behavior of the primary circuit components under normal and accident conditions. Through the use of graphite components, graphite particles can be formed by mechanical and chemical means whose influence on the structural change of metal surfaces must be analyzed in a comprehensive manner. The dust resuspension and deposition in tank geometry (DRESDEN-TANK) test facility was set up to thermally anneal metallic samples (Alloy 800H, Inconel 617) loaded with graphite particles under typical HTR conditions (helium, 750 °C, 6 MPa) for the investigation of interactions over a long-term range. In addition to the carrying out of a description of the processes occurring on the material surface, the gaseous reaction products have been analyzed. The results show that the presence of graphite particles in the near-surface layer has a significant impact on corrosion processes due to thermally-induced interactions. In this case iron and chromium are degraded in the metallic alloys, which leads to a structural change in the near-surface layer. Furthermore, the graphite particles significantly influence the formation of the oxide layers on the alloys; for example, they influence the formation speed of the layer and the layer height. The originally deposited particles thus exhibit a chemically-altered composition and a different geometric shape.
Effects of Magnetic Field on the Residual Stress and Structural Defects of Ti-6Al-4V
Authors: Zhang Xu , Zhao Qian , Cai Zhipeng , Pan Jiluan
Published: January 2020

In this work, the influences of a magnetic field of 2.4 T on the macro residual stress and the status of structural defects, including grain boundaries, dislocations and the Fe-rich clusters of Ti-6Al-4V were investigated by X-ray Diffraction (XRD), Electron Backscatter Diffraction (EBSD) and magnetic measurement. The XRD test results show that the applied magnetic field can cause the relaxation and homogenization of macro residual stress. The maps of Kernel Average Misorientation (KAM) values obtained by EBSD tests present a significant dislocation multiplication caused by a magnetic field, and the rise of dislocation density was estimated to be about 32% by XRD tests. The EBSD test results also show an increase in the fraction of Coincidence Site Lattice (CSL) grain boundaries and a decrease in the fraction of low-angle grain boundaries. The results of magnetic measurement show that Ti-6Al-4V has mixed magnetism consisting of paramagnetism and weak ferromagnetism, and that the ferromagnetic saturation magnetization decreased after exposing the alloy to the magnetic field, which suggests the dissolution of the Fe-rich clusters in the alloy. These magnetically-induced changes are related to magnetoplastic effects, a kind of phenomena on which there have been some research, and the possible mechanism of them is discussed in this paper.
Comparative Analysis of β-Carotene Production by Mucor circinelloides Strains CBS 277.49 and WJ11 under Light and Dark Conditions
Authors: Naz Tahira , Nosheen Shaista , Li Shaoqi , Nazir Yusuf , Mustafa Kiren , Liu Qing , Garre Victoriano , Song Yuanda
Published: January 2020

Carotenoids are natural potent antioxidants and free radical scavengers which are able to modulate the pathogenesis of some cancers and heart diseases in human, indicating their importance in being provided through the diet. Mucor circinelloides accumulates β-carotene as the main carotenoid compound and has been used as a model organism in carotenogenic studies. In the present study, the potential of two M. circinelloides strains to accumulate β-carotene was investigated under light and dark conditions. The results, which were quantitated by HPLC, showed that CBS 277.49 accumulated higher pigment in comparison to WJ11 under both conditions. Continuous illumination triggered the pigment accumulation up to 2.7-fold in strain CBS 277.49 and 2.2-fold in strain WJ11 in comparison to dark. The mRNA analysis of the four key genes involved in isoprenoid pathway by RT-qPCR showed higher transcriptional levels in CBS 277.49 as compared to WJ11, indicating that the pigment production metabolic machinery is more active in CBS 277.49 strain. A new scope for further research was established by this work for improved β-carotene production in the high producing strain CBS 277.49.
Sulfonamide Inhibition Profile of the β-Carbonic Anhydrase from Malassezia restricta, An Opportunistic Pathogen Triggering Scalp Conditions
Authors: Del Prete Sonia , Angeli Andrea , Ghobril Cynthia , Hitce Julien , Clavaud Cécile , Marat Xavier , Supuran Claudiu T. , Capasso Clemente
Published: January 2020

The critical CO2 hydration reaction to bicarbonate and protons is catalyzed by carbonic anhydrases (CAs, EC 4.2.1.1). Their physiological role is to assist the transport of the CO2 and HCO3− at the cellular level, which will not be ensured by the low velocity of the uncatalyzed reaction. CA inhibition may impair the growth of microorganisms. In the yeasts, Candida albicans and Malassezia globosa, the activity of the unique β-CA identified in their genomes was demonstrated to be essential for growth of the pathogen. Here, we decided to investigate the sulfonamide inhibition profile of the homologous β-CA (MreCA) identified in the genome of Malassezia restricta, an opportunistic pathogen triggering dandruff and seborrheic dermatitis. Among 40 investigated derivatives, the best MreCA sulfonamide inhibitors were dorzolamide, brinzolamide, indisulam, valdecoxib, sulthiam, and acetazolamide (KI < 1.0 μM). The MreCA inhibition profile was different from those of the homologous enzyme from Malassezia globosa (MgCA) and the human isoenzymes (hCA I and hCA II). These results might be useful to for designing CA inhibitor scaffolds that may selectively inhibit the dandruff-producing fungi.
Study of the Royal Jelly Free Fatty Acids by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS)
Authors: Kokotou Maroula G. , Mantzourani Christiana , Babaiti Rodalia , Kokotos George
Published: January 2020

The lipidome of royal jelly (RJ) consists of medium-chained (8–12 carbon atoms) free fatty acids. We present herein a liquid chromatography-high resolution mass spectrometry (HRMS) method that permits the determination of RJ fatty acids and at the same time the detection of suspect fatty acids. The method allows for the direct quantification of seven free fatty acids of RJ, avoiding any derivatization step. It was validated and applied in seven RJ samples, where the major RJ fatty acid trans-10-hydroxy-2-decenoic acid (10-HDA) was found to vary from 0.771 ± 0.08 to 0.928 ± 0.04 g/100 g fresh RJ. Four additional suspect fatty acids were simultaneously detected taking advantage of the HRMS detection.
Improving Single-Cell Encapsulation Efficiency and Reliability through Neutral Buoyancy of Suspension
Authors: Liu Hangrui , Li Ming , Wang Yan , Piper Jim , Jiang Lianmei
Published: January 2020

Single-cell analysis is of critical importance in revealing cell-to-cell heterogeneity by characterizing individual cells and identifying minority sub-populations of interest. Droplet-based microfluidics has been widely used in the past decade to achieve high-throughput single-cell analysis. However, to maximize the proportion of single-cell emulsification is challenging due to cell sedimentation and aggregation. The purpose of this study was to investigate the influence of single-cell encapsulation and incubation through the use of neutral buoyancy. As a proof of concept, OptiPrep™ was used to create neutrally buoyant cell suspensions of THP-1, a human monocytic leukemia cell line, for single-cell encapsulation and incubation. We found that using a neutrally buoyant suspension greatly increased the efficiency of single-cell encapsulation in microdroplets and eliminated unnecessary cell loss. Moreover, the presence of OptiPrep™ was shown to not affect cellular viability. This method significantly improved the effectiveness of single-cell study in a non-toxic environment and is expected to broadly facilitate single-cell analysis.
Diagnosis and Improvement of Combustion Characteristics of Methanol Miniature Reciprocating Piston Internal Combustion Engine
Authors: Tang Gangzhi , Wang Shuaibin , Zhang Li , Shang Huichao
Published: January 2020

A micro-reciprocating piston internal combustion engine with liquid hydrocarbon fuel has the potential to supply ultrahigh density energy to micro electro mechanical system because of its high-density energy, simple structure, and mature energy conversion principle. However, the diagnostic test of the combustion characteristics of the micro reciprocating piston internal combustion engine shows that its combustion characteristics are poor, and the combustion rate was lower with the combustion duration of more than 50 °CA. The mean indicated pressure (Pmi) value was only 0.137 MPa, the combustion stability was very poor, and the cycle variation rate of the Pmi was up to 60%. To improve its combustion performance, the method to enhance combustion in micro-space is explored then. Mechanism studies have shown that the pyrolysis reaction of nitromethane and hydrogen peroxide can produce amounts of free radicals OH, with the possibility of improving the combustion of methanol. Therefore, a method for adjusting the composition of methanol fuel to enhance combustion is proposed, and the method is theoretically confirmed. Finally, based on this method, the test was carried out. The results showed that the combustion rate increased and the combustion duration decreased by 6% after adding nitromethane. The power performance was enhanced, and the Pmi value was increased by 30%. The combustion stability was enhanced, and the cycle variation rate of the Pmi was reduced to 16.9%. Nitromethane has a significant effect on improving the combustion characteristics of methanol, and the enhancement of the latter was mainly reflected in the ignition phase of the combustion process. This study indicates that exploring the fuel additive that can increase the concentration of OH radical in the reaction is an effective method to improve the micro-space combustion, which will facilitate the development of micro-piston internal combustion engine to supply energy to a micro electro mechanical system.
Physical-Based Simulation of the GaN-Based Grooved-Anode Planar Gunn Diode
Authors: Wang Ying , Li Liu-An , Ao Jin-Ping , Hao Yue
Published: January 2020

In this paper, a novel gallium nitride (GaN)-based heterostructure Gunn diode is proposed for the first time to enhance the output characteristics of Gunn oscillation waveforms. A well-designed grooved anode contact is adopted to separate the long-channel diode into two short-channel diodes in parallel. If the grooved anode contact is positioned in the middle of the device, the output power nearly doubles in the grooved-anode diode compared with the single-channel ones, as does the output frequency. Based on the numerical results, the best output characteristics are obtained at the 2.0-µm symmetrical grooved-anode diode, which produces nearly 5.48 mW of power at the fundamental frequency of 172.81 GHz, with 3.13% efficiency of power conversion. If the grooved anode contact is not positioned in the middle of the diode, the harmonic frequency would be enhanced. The GaN heterostructure grooved-anode Gunn diode has been demonstrated to be an excellent solid-state source of terahertz oscillator.
Subcellular Location of Piscirickettsia salmonis Heat Shock Protein 60 (Hsp60) Chaperone by Using Immunogold Labeling and Proteomic Analysis
Authors: Oliver Cristian , Sánchez Patricio , Valenzuela Karla , Hernández Mauricio , Pontigo Juan Pablo , Rauch Maria C. , Garduño Rafael A. , Avendaño-Herrera Ruben , Yáñez Alejandro J.
Published: January 2020

Piscirickettsia salmonis is the causative bacterial agent of piscirickettsiosis, a systemic fish disease that significantly impacts the Chilean salmon industry. This bacterium possesses a type IV secretion system (T4SS), several proteins of the type III secretion system (T3SS), and a single heat shock protein 60 (Hsp60/GroEL). It has been suggested that due to its high antigenicity, the P. salmonis Hsp60 could be surface-exposed, translocated across the membrane, and (or) secreted into the extracellular matrix. This study tests the hypothesis that P. salmonis Hsp60 could be located on the bacterial surface. Immunogold electron microscopy and proteomic analyses suggested that although P. salmonis Hsp60 was predominantly associated with the bacterial cell cytoplasm, Hsp60-positive spots also exist on the bacterial cell envelope. IgY antibodies against P. salmonis Hsp60 protected SHK-1 cells against infection. Several bioinformatics approaches were used to assess Hsp60 translocation by the T4SS, T3SS, and T6SS, with negative results. These data support the hypothesis that small amounts of Hsp60 must reach the bacterial cell surface in a manner probably not mediated by currently characterized secretion systems, and that they remain biologically active during P. salmonis infection, possibly mediating adherence and (or) invasion.
Modulation of Antibacterial, Antioxidant, and Anti-Inflammatory Properties by Drying of Prunus domestica L. Plum Juice Extracts
Authors: Silvan Jose Manuel , Michalska-Ciechanowska Anna , Martinez-Rodriguez Adolfo J.
Published: January 2020

The consumption of plums in a fresh form is seasonal, therefore the transformation of plum juice extracts into powdered form is a good alternative for its longer availability throughout the year. The drying process can moderate the physical and chemical properties of the plum extracts, thus, this study examined the changes in biological activity, i.e., antibacterial, antioxidant, and anti-inflammatory properties moderated by freeze, vacuum, and spray drying. It was suggested that the drying processes and the applied parameters might moderate the content of polyphenolic compounds in the powders, which influence the different levels of growth inhibition against the foodborne pathogens (17% to 58% of inhibition), demonstrating a strain-dependent effect. These powders could also induce cellular protection against oxidative stress by preventing intracellular reactive oxygen species (ROS) accumulation (23% to 37% of reduction), but the level of antioxidant capacity may be determined by the conditions applied during the drying process. Moreover, plum extract powders exhibited a greater anti-inflammatory capacity (24% to 39% of inhibition), which would be influenced both, by the type of treatment used and by the temperature used in each treatment. The results demonstrate that the selection of the drying method can be an effective tool for modulating the composition, physical, and bioactive properties of plum extracts powders.
Antimicrobial Sensitivity Testing of Mycoplasma bovis Isolates Derived from Western Canadian Feedlot Cattle
Authors: Jelinski Murray , Kinnear Andrea , Gesy Karen , Andrés-Lasheras Sara , Zaheer Rahat , Weese Scott , McAllister Tim A.
Published: January 2020

Mycoplasma bovis is particularly adept at evading the immune system, resulting in chronic infections of the lungs and joints of feedlot cattle. The chronicity of the lesions results in prolonged antimicrobial therapy, possibly exacerbating antimicrobial resistance. This cross-sectional study generated in vitro antimicrobial susceptibility testing (AST) data on 211 M. bovis isolates recovered from 159 healthy, diseased, and dead cattle, spanning the period of 2006–2018. Nine antimicrobials commonly administered to western Canadian feedlot cattle were assessed. The data were analyzed with non-parametric statistical tests with a level of significance of p < 0.05 (two-tailed). Minimum inhibitory concentration (MIC) values tended to increase between the isolates from healthy versus dead cattle and over time (2006–2018). Isolates from dead versus healthy cattle were more likely to be resistant to tulathromycin, gamithromycin, tylosin and enrofloxacin. There was no difference in the distributions of the MICs generated from the isolates recovered from the lungs and joints (p ≥ 0.124) and the lungs and deep nasal passages (p ≥ 0.157) of the same animals.
Detection and Identification of Bacillus anthracis: From Conventional to Molecular Microbiology Methods
Authors: Zasada Aleksandra A.
Published: January 2020

Rapid and reliable identification of Bacillus anthracis is of great importance, especially in the event of suspected deliberate release of anthrax spores. However, the identification of B. anthracis is challenging due to its high similarity to closely related species. Since Amerithrax in 2001, a lot of effort has been made to develop rapid methods for detection and identification of this microorganism with special focus on easy-to-perform rapid tests for first-line responders. This article presents an overview of the evolution of B. anthracis identification methods from the time of the first description of the microorganism until the present day.
Nuclear Gene Transformation in the Dinoflagellate Oxyrrhis marina
Authors: Sprecher Brittany N. , Zhang Huan , Lin Senjie
Published: January 2020

The lack of a robust gene transformation tool that allows proper expression of foreign genes and functional testing for the vast number of nuclear genes in dinoflagellates has greatly hampered our understanding of the fundamental biology in this ecologically important and evolutionarily unique lineage of microeukaryotes. Here, we report the development of a dinoflagellate expression vector containing various DNA elements from phylogenetically separate dinoflagellate lineages, an electroporation protocol, and successful expression of introduced genes in an early branching dinoflagellate, Oxyrrhis marina. This protocol, involving the use of Lonza’s Nucleofector and a codon-optimized antibiotic resistance gene, has been successfully used to produce consistent results in several independent experiments for O. marina. It is anticipated that this protocol will be adaptable for other dinoflagellates and will allow characterization of many novel dinoflagellate genes.
The Impact of Primer Design on Amplicon-Based Metagenomic Profiling Accuracy: Detailed Insights into Bifidobacterial Community Structure
Authors: Mancabelli Leonardo , Milani Christian , Lugli Gabriele Andrea , Fontana Federico , Turroni Francesca , van Sinderen Douwe , Ventura Marco
Published: January 2020

Next Generation Sequencing (NGS) technologies have overcome the limitations of cultivation-dependent approaches and allowed detailed study of bacterial populations that inhabit the human body. The consortium of bacteria residing in the human intestinal tract, also known as the gut microbiota, impacts several physiological processes important for preservation of the health status of the host. The most widespread microbiota profiling method is based on amplification and sequencing of a variable portion of the 16S rRNA gene as a universal taxonomic marker among members of the Bacteria domain. Despite its popularity and obvious advantages, this 16S rRNA gene-based approach comes with some important limitations. In particular, the choice of the primer pair for amplification plays a major role in defining the accuracy of the reconstructed bacterial profiles. In the current study, we performed an in silico PCR using all currently described 16S rRNA gene-targeting primer pairs (PP) in order to assess their efficiency. Our results show that V3, V4, V5, and V6 were the optimal regions on which to design 16S rRNA metagenomic primers. In detail, PP39 (Probio_Uni/Probio_Rev), PP41 (341F/534R), and PP72 (970F/1050R) were the most suitable primer pairs with an amplification efficiency of >98.5%. Furthermore, the Bifidobacterium genus was examined as a test case for accurate evaluation of intra-genus performances at subspecies level. Intriguingly, the in silico analysis revealed that primer pair PP55 (527f/1406r) was unable to amplify the targeted region of any member of this bacterial genus, while several other primer pairs seem to rather inefficiently amplify the target region of the main bifidobacterial taxa. These results highlight that selection of a 16S rRNA gene-based PP should be done with utmost care in order to avoid biases in microbiota profiling results.
Doing More with Less: A Comparison of 16S Hypervariable Regions in Search of Defining the Shrimp Microbiota
Authors: García-López Rodrigo , Cornejo-Granados Fernanda , Lopez-Zavala Alonso A. , Sánchez-López Filiberto , Cota-Huízar Andrés , Sotelo-Mundo Rogerio R. , Guerrero Abraham , Mendoza-Vargas Alfredo , Gómez-Gil Bruno , Ochoa-Leyva Adrian
Published: January 2020

The shrimp has become the most valuable traded marine product in the world, and its microbiota plays an essential role in its development and overall health status. Massive high-throughput sequencing techniques using several hypervariable regions of the 16S rRNA gene are broadly applied in shrimp microbiota studies. However, it is essential to consider that the use of different hypervariable regions can influence the obtained data and the interpretation of the results. The present study compares the shrimp microbiota structure and composition obtained by three types of amplicons: one spanning both the V3 and V4 hypervariable regions (V3V4), one for the V3 region only (V3), and one for the V4 region only (V4) using the same experimental and bioinformatics protocols. Twenty-four samples from hepatopancreas and intestine were sequenced and evaluated using the GreenGenes and silva reference databases for clustering and taxonomic classification. In general, the V3V4 regions resulted in higher richness and diversity, followed by V3 and V4. All three regions establish an apparent clustering effect that discriminates between the two analyzed organs and describe a higher richness for the intestine and a higher diversity for the hepatopancreas samples. Proteobacteria was the most abundant phyla overall, and Cyanobacteria was more common in the intestine, whereas Firmicutes and Actinobacteria were more prevalent in hepatopancreas samples. Also, the genus Vibrio was significantly abundant in the intestine, as well as Acinetobacter and Pseudomonas in the hepatopancreas suggesting these taxa as markers for their respective organs independently of the sequenced region. The use of a single hypervariable region such as V3 may be a low-cost alternative that enables an adequate description of the shrimp microbiota, allowing for the development of strategies to continually monitor the microbial communities and detect changes that could indicate susceptibility to pathogens under real aquaculture conditions while the use of the full V3V4 regions can contribute to a more in-depth characterization of the microbial composition.