bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and Characterization of Two New Metabolites from the Sponge-Derived Fungus Aspergillus sp. LS34 by OSMAC Approach
Authors: Li Wei , Ding Lijian , Wang Ning , Xu Jianzhou , Zhang Weiyan , Zhang Bin , He Shan , Wu Bin , Jin Haixiao
Published: May 2019

The application of an OSMAC (One Strain-Many Compounds) approach on the sponge-derived fungus Aspergillus sp. LS34, using two different media including solid rice medium and potato dextrose broth (PDB) resulted in the isolation and identification of two new compounds, named asperspin A (1) and asperther A (2) along with seven known compounds 3–9. Compounds 1–5 were detected in fungal extracts from rice medium, while compounds 6–9 were isolated from PDB medium. Their structures were unambiguously characterized by HRESIMS and NMR spectroscopic data. The growth inhibitory activity of these compounds against four pathogenic bacteria (Vibrio parahaemolyticus, Vibrio harveyi, Escherichia coli, and Staphylococcus aureus) were evaluated. All the compounds were also tested for their cytotoxicity against seven cancer cell lines, including CCRF-CEM, K562, BGC823, AGS, HCT-116, MDA-MB-453, and COR-L23. Among them, compound 9 showed strong activity against CCRF-CEM and K562 cells with IC50 values of 1.22 ± 0.05 µM and 10.58 ± 0.19 µM, respectively. Notably, compound 7 also showed pronounced activity against S. aureus with an MIC value of 3.54 µM.
Protective Effect of Pyropia yezoensis Peptide on Dexamethasone-Induced Myotube Atrophy in C2C12 Myotubes
Authors: Lee Min-Kyeong , Choi Jeong-Wook , Choi Youn Hee , Nam Taek-Jeong
Published: May 2019

Dexamethasone (DEX), a synthetic glucocorticoid, causes skeletal muscle atrophy. This study examined the protective effects of Pyropia yezoensis peptide (PYP15) against DEX-induced myotube atrophy and its association with insulin-like growth factor-I (IGF-I) and the Akt/mammalian target of rapamycin (mTOR)-forkhead box O (FoxO) signaling pathway. To elucidate the molecular mechanisms underlying the effects of PYP15 on DEX-induced myotube atrophy, C2C12 myotubes were treated for 24 h with 100 μM DEX in the presence or absence of 500 ng/mL PYP15. Cell viability assays revealed no PYP15 toxicity in C2C12 myotubes. PYP15 activated the insulin-like growth factor-I receptor (IGF-IR) and Akt-mTORC1 signaling pathway in DEX-induced myotube atrophy. In addition, PYP15 markedly downregulated the nuclear translocation of transcription factors FoxO1 and FoxO3a, and inhibited 20S proteasome activity. Furthermore, PYP15 inhibited the autophagy-lysosomal pathway in DEX-stimulated myotube atrophy. Our findings suggest that PYP15 treatment protected against myotube atrophy by regulating IGF-I and the Akt-mTORC1-FoxO signaling pathway in skeletal muscle. Therefore, PYP15 treatment appears to exert protective effects against skeletal muscle atrophy.
Antihypertensive Effect in Vivo of QAGLSPVR and Its Transepithelial Transport Through the Caco-2 Cell Monolayer
Authors: Sun Liping , Wu Beiyi , Yan Mingyan , Hou Hu , Zhuang Yongliang
Published: May 2019

The peptide QAGLSPVR, which features high angiotensin-I-converting enzyme (ACE) inhibitory activity, was identified in our previous study. In this study, the in vivo antihypertensive effect of QAGLSPVR was evaluated. Results showed that QAGLSPVR exerts a clear antihypertensive effect on spontaneously hypertensive rats (SHRs), and the systolic and diastolic blood pressures of the rats remarkably decreased by 41.86 and 40.40 mm Hg, respectively, 3 h after peptide administration. The serum ACE activities of SHRs were determined at different times, and QAGLSPVR was found to decrease ACE activities in serum; specifically, minimal ACE activity was found 3 h after administration. QAGLSPVR could be completely absorbed by the Caco-2 cell monolayer, and its transport percentage was 3.5% after 2 h. The transport route results of QAGLSPVR showed that Gly-Sar and wortmannin exert minimal effects on the transport percentage of the peptide (p> 0.05), thus indicating that QAGLSPVR transport through the Caco-2 cell monolayer is not mediated by peptide transporter 1 or transcytosis. By contrast, cytochalasin D significantly increased QAGLSPVR transport (p< 0.05); thus, QAGLSPVR may be transported through the Caco-2 cell monolayer via the paracellular pathway.
Genotype–Phenotype Correlation in a New Fabry-Disease-Causing Mutation
Authors: Čerkauskaitė Agnė , Čerkauskienė Rimantė , Miglinas Marius , Laurinavičius Arvydas , Ding Can , Rolfs Arndt , Vencevičienė Lina , Barysienė Jūratė , Kazėnaitė Edita , Sadauskienė Eglė
Published: May 2019

Background: Fabry disease (FD) is a rare X-linked inherited lysosomal storage disorder caused by α-galactosidase A deficiency leading to intracellular glycosphingolipid accumulation. FD manifestation is multisystem, and can differ depending on disease-related genetic variants. Currently, more than 700 different FD-causing mutations have been identified in the human GLA gene. We identified a novel mutation in a Lithuanian family with classical manifestations of Fabry disease, revealing severe effects to the cardiovascular systems of heterozygous women. Case presentation: A 49-year-old woman underwent echocardiography due to progressive dyspnea that lasted seven years, reduced physical activity, and periodic cardiac arrhythmia. Echocardiography revealed left ventricular hypertrophy with normal diastolic function. The patient had experienced acroparesthesia in her upper limbs and abdominal pain since childhood, and in the last decade had experienced mild proteinuria without renal failure. Her renal biopsy was typical for Fabry disease. The patient’s brain magnetic resonance imaging (MRI) (T2 flair) showed white matter hyperintensities lesions. DNA sequencing of the proband, her mother and one of her sons showed a novel GLA gene exon 2 mutation, c.270C>G (p.Cys90Trp). All three patients had decreased α-galactosidase A activity and specific FD manifestations. Conclusions: A novel GLA mutation, c.270C>G (p.Cys90Trp), was found in a Lithuanian family with a classical form of Fabry disease in heterozygous women with predominant cardiac involvement. However, the exact manifestation of this mutation is still unclear as it is newly reported and further research must be done.
Neutrophil-to-Lymphocyte Ratio, Platelet-to-Lymphocyte Ratio, and Routine Complete Blood Count Components in HELLP Syndrome: A Matched Case Control Study
Authors: Sisti Giovanni , Faraci Andrea , Silva Jessica , Upadhyay Ruchi
Published: May 2019

Background and objective: Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are new readily available inflammatory markers that have been analyzed in pregnancy-induced hypertensive disorders such as preeclampsia. Studies on the NLR/PLR ratio in hemolysis, elevated liver enzymes, low-platelet count (HELLP) syndrome are limited in the current literature. We compared NLR/PLR and other complete blood count (CBC) components between women with HELLP syndrome and women with healthy pregnancies. Methods: We conducted a retrospective matched case–control study at a tertiary care hospital in NY (USA) in the time frame between January 2016 and December 2018. The study compared pregnant women with HELLP syndrome (cases) to women with healthy pregnancies in the third trimester (controls), matched by age, body mass index (BMI), parity, and race. Patient with preeclampsia, infection, and fever were excluded. Venous blood samples were obtained as part of the routine work-up at admission for delivery, which included a CBC. The main outcomes were NLR and PLR. The secondary outcomes were hemoglobin, red cell distribution width (RDW), platelet count, mean platelet volume (MPV), neutrophils, lymphocytes. Results: There were 14 patients in each group. They were matched by age, race, BMI, and parity. NLR (5.8 vs. 3.6, p-value = 0.002) and neutrophil count (10.7 vs. 6.8, p-value = 0.001) were higher in women with HELLP compared to controls. PLR (34 vs. 130.2, p-value < 0.001) and platelet count (71 vs. 223, p-value < 0.001) were lower in the study group compared to controls. Conclusions: NLR was higher, and PLR was lower in women with HELLP syndrome. These inflammatory markers can be incorporated into the diagnostic algorithm for HELLP syndrome. Future studies are needed to evaluate their ability to predict HELLP syndrome.
Trends in Cigarette Smoking among Middle-Aged Lithuanian Subjects Participating in the Primary Prevention Program between 2009 and 2016
Authors: Rinkūnienė Egidija , Petrulionienė Žaneta , Dženkevičiūtė Vilma , Gimžauskaitė Silvija , Mainelis Antanas , Puronaitė Roma , Jucevičienė Agnė , Gargalskaitė Urtė , Laucevičius Aleksandras
Published: May 2019

Background and Objectives: The aim of the study was to evaluate trends in smoking among middle-aged men and women based on the data from the Lithuanian High Cardiovascular Risk (LitHiR) primary prevention program between 2009 and 2016. Materials and Methods: A community-based cross-sectional study comprised 92373 Lithuanian adults (41.6% men and 58.4% women). We compared the prevalence of smoking, smoking cessation activity and smoking intensity by gender and age groups. Results: There was a statistically significant upward trend in the number of smoking subjects (average annual percent change (AAPC) 2.99%, p < 0.001). The number of smoking male subjects remained much higher than the number of smoking female subjects during the 2009–2016 period. The study showed a significant increase in the percentage of smoking quitters in the whole group (AAPC 7.22%, p < 0.001) and among men and women separately. There was no significant change in smoking intensity in groups of male and female smokers separately. Conclusions: The analysis showed that the prevalence of smoking in Lithuania is still increasing due to women smoking despite all the governmental tobacco control efforts to reduce it.
Immunomodulatory Changes Following Isolated RF Ablation in Colorectal Liver Metastases: A Case Report
Authors: Janikashvili Nona , Jayant Kumar , Kikodze Nino , Mazmishvili Ketevan , Pantsulaia Ia , Sandhu Bynvant , Podda Mauro , Iobadze Manana , Azrumelashvili Tamta , Mizandari Malkhaz , Habib Nagy , Chikovani Tinatin
Published: May 2019

Background: Colorectal cancer (CRC) is the third most common cancer worldwide and the second leading cause of cancer-related deaths in developed countries. The liver is the most prevalent site of metastasis from CRC. Currently, the gold-standard treatment for colorectal liver metastases (CLMs) is surgical resection. However, depending on the pattern of the disease, a significant number of patients may require different approaches alone or in combination with surgery, including thermal ablation (radiofrequency (RFA) or microwave (MWA) ablation) or transarterial liver-directed therapies, although the latter is not yet part of the standard treatment for CRC liver metastases. Methods and Results: We present the case of a 63-yearold man with bilobar CLM who was treated with transarterial embolization (TAE) and RFA followed by chemotherapy. A post-RFA study of immune parameters revealed the downregulation of CD39 expression in the circulating CD4+ T cell population and a reduction of the serum levels of cytokines IL-10, TGF-β, IFN-gamma and IL-17, which positively correlated with the diminished serum level of gamma-glutamyl transferase (GGT) and the subdued inflammatory markers: the neutrophil/lymphocyte ratio (NLR) and platelet/lymphocyte ratio (PLR). Later, the patient underwent chemotherapy. Liver failure developed within two years and nine months following tumour ablation, leading to the death of the patient. Conclusions: However, the denial of adjuvant chemotherapy by the patient gave us the opportunity to assess the immunomodulatory changes following RFA in the absence of any other therapeutic modalities.
Triple-Layer Nanofiber Membranes for Treating High Salinity Brines Using Direct Contact Membrane Distillation
Authors: Al-Furaiji Mustafa , Arena Jason T. , Ren Jian , Benes Nieck , Nijmeijer Arian , McCutcheon Jeffrey R.
Published: May 2019

A composite, three-layered membrane for membrane distillation was prepared from electrospun polyvinylidene fluoride (PVDF) nanofibers supported by commercial polyethersulfone (PES) nanofiber based nonwoven from E.I. duPont de Nemours company (DuPont). The membranes were tested in direct contact membrane distillation (DCMD) using a 5.0 M sodium chloride brine as a feed solution. The triple layer membrane combines the hydrophobicity of PVDF and the robustness of the PES. The triple layer membrane demonstrated excellent performance in DCMD (i.e., relatively high water flux compared to the commercial PVDF membrane and a complete salt rejection of the brine) with mechanical properties imparted by the PES layer. This work is the first to demonstrate the use of a commercially produced nanofiber nonwoven for membrane distillation.
Hybrid Forward Osmosis–Nanofiltration for Wastewater Reuse: System Design
Authors: Giagnorio Mattia , Ricceri Francesco , Tagliabue Marco , Zaninetta Luciano , Tiraferri Alberto
Published: May 2019

The design of a hybrid forward osmosis–nanofiltration (FO–NF) system for the extraction of high-quality water from wastewater is presented here. Simulations were performed based on experimental results obtained in a previous study using real wastewater as the feed solution. A sensitivity analysis, conducted to evaluate the influence of different process parameters, showed that an optimum configuration can be designed with (i) an influent draw solution osmotic pressure equal to 15 bar and (ii) a ratio of influent draw solution to feed solution flow rate equal to 1.5:1. With this configuration, the simulations suggested that the overall FO–NF system can achieve up to 85% water recovery using Na2SO4 or MgCl2 as the draw solute. The modular configuration and the size of the NF stage, accommodating approximately 7000 m2 of active membrane area, was a function of the properties of the membranes selected to separate the draw solutes and water, while detailed simulations indicated that the size of the FO unit might be reduced by adopting a counter-current configuration. Experimental tests with samples of the relevant wastewater showed that Cl−- and Mg2+-based draw solutes would be associated with larger membrane fouling, possibly due to their interaction with the other substances present in the feed solution. However, the results suggest that fouling would not significantly decrease the performance of the designed system. This study contributes to the further evaluation and potential implementation of FO in water reuse systems.
Compressive Properties of Additively Manufactured Functionally Graded Kagome Lattice Structure
Authors: Gautam Rinoj , Idapalapati Sridhar
Published: May 2019

Cellular lattice structures have important applications in aerospace, automobile and defense industries due to their high specific strength, modulus and energy absorption. Additive manufacturing provides the design freedom to fabricate complex cellular structures. This study investigates the compressive properties and deformation behavior of a Ti-6Al-4V unit Kagome structure fabricated by selective laser melting. Further, the mechanical performance of multi-unit and multi-layer Kagome structure of acrylonitrile butadiene styrene (ABS) ABS-M30™ manufactured by fused deposition modeling is explored. The effect of a number of layers of Kagome structure on the compressive properties is investigated. This paper also explores the mechanical properties of functionally graded and uniform density Kagome structure. The stiffness of the structure decreased with the increase in the number of layers whereas no change in peak load was observed. The functionally graded Kagome structure provided 35% more energy absorption than the uniform density structure.
Erosive Wear Resistance Regarding Different Destabilization Heat Treatments of Austenite in High Chromium White Cast Iron, Alloyed with Mo
Authors: Gonzalez-Pociño Alejandro , Alvarez-Antolin Florentino , Asensio-Lozano Juan
Published: May 2019

With the aim of improving erosive wear resistance in hypoeutectic white cast irons with 18% Cr and 2% Mo, several samples of this grade were subjected to different heat treatments at 1000 °C to destabilize the austenite. The dwell times at this temperature varied from 4 to 24 h and the samples were cooled in air or oil. The existing phases were identified and quantified by applying the Rietveld structural refinement method. The results were correlated with the hardness of the material and with the microhardness of the matrix constituent. The greatest resistance to erosive wear was achieved in those samples that had a higher percentage of secondary carbides. The longer the dwell time at the destabilization temperature of austenite, the greater the amount of precipitated secondary carbides. However, the percentage of dissolved eutectic carbides is also higher. These eutectic carbides were formed as a result of non-equilibrium solidification. Low cooling rates (in still air) can offset this solution of eutectic carbides via the additional precipitation of secondary carbides in the 600–400 °C temperature range. A sharp decrease is observed in the percentage of retained austenite in those treatments with dwell times at 1000 °C equal to or greater than 12 h, reaching minimum values of around 2% volume. The percentage of retained austenite was always lower after oil quenching and the hardness of oil quenched samples was observed to be greater than those quenched in air. In these samples, the maximum hardness value obtained was 993 HV after a 12 h dwell, which result from the optimum balance between the percentages of retained austenite and of precipitated carbides.
Microstructural Characterization and Formation Mechanism of Nitrided Layers on Aluminum Substrates by Thermal Plasma Nitriding
Authors: Li Xin , Xin Weida , Zheng Xiaoyi , Ren Zhen’an , Sun Daqian , Lu Wanli
Published: May 2019

Nitrided layers on 6082 aluminum alloy substrates and 1060 aluminum substrates are formed at atmospheric pressure using thermal nitrogen plasma, which only takes seconds to form a millimeter-level layer. The nitrided layers are composed of aluminum nitride (AlN) and aluminum solid solution phases. Microstructures in these nitrided layers can be divided into three regions from bottom to top: the transition region, the dendrite region, and the lamella region. These regions are formed in sequence. The formation mechanisms and processes of the three regions are discussed in detail. Furthermore, we found that Al melt is transported upward through the voids and the capillaries in the AlN structures, and reacts with N plasma in the melt surface. The growth of the AlN structures promotes this transport. With the increase of N2 flow rates from 1 L/min to 7.5 L/min, both the hardness and the wear resistance of the nitrided layers are improved, and the nitrided layer becomes thicker.
Influences of Cu Content on the Microstructure and Strengthening Mechanisms of Al-Mg-Si-xCu Alloys
Authors: Chen Yuqiang , Hu Qiang , Pan Suping , Zhang Hao , Liu Huiqun , Zhu Biwu , Liu Xiao , Liu Wenhui
Published: May 2019

The effects of the Cu content on the microstructure and strengthening mechanisms of the Al-Mg-Si-xCu alloys were systematically investigated using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and mechanical tensile tests. The results show that, the strengthening mechanisms change with the Cu content. For as-quenched alloys, solution strengthening (σSS) is predominant when the Cu content ≥2.5 wt.%, and of equivalent importance as grain size strengthening (σH-P) when the Cu content ≤1.0 wt.%. With respect to peak-aged alloys, precipitation strengthening (σppt) is predominant when the Cu content ≥2.5 wt.%, but σSS becomes predominant when the Cu content is 4.5 wt.%. As the Cu content increases from 0.5 to 4.5 wt.%, the main type of precipitates in alloy tends to change from a β″ phase to Q′ phase, and then to a θ′ phase. Among the three types of precipitates, θ′-precipitate causes the largest increase in yield strength (σ0.2) and the largest decrease rate in elongation. β″-precipitate leads to the smallest increase in σ0.2 and the smallest decrease rate in elongation. The increase of Cu content reduces Si solubility in the Al matrix and thus decreases the nucleation rate of β″ phase during subsequent aging.
Investigation on the Corrosion Behavior of Lean Duplex Stainless Steel 2404 after Aging within the 650–850 °C Temperature Range
Authors: Zanotto Federica , Grassi Vincenzo , Balbo Andrea , Zucchi Fabrizio , Monticelli Cecilia
Published: May 2019

This paper reports the effects of thermal aging between 650 and 850 °C on the localized corrosion behavior of lean duplex stainless steel (LDSS 2404). Critical pitting temperature (CPT) and double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were performed. The localization of pitting attack and intergranular corrosion (IGC) attack after DL-EPR was investigated by optical (OM) and scanning electron microscopy (SEM) and by focused ion beam (FIB) coupled to SEM. Thermal aging caused the precipitation of mainly chromium nitrides at grain boundaries. Aging at 650 °C or short aging times (5 min) at 750 °C caused nitride precipitation mainly at α/α grain boundaries as a result of fast diffusion of chromium in this phase. Aging at 850 °C or aging times from 10 to 60 min at 750 °C also allowed the precipitation at the α/γ interface. Nitrides at γ/γ grain boundaries were observed rarely and only after long aging times (60 min) at 850 °C. Electrochemical tests showed that in as-received samples, pitting attack only affected the α phase. Conversely, in aged samples, pitting and IGC attack were detected close to nitrides in correspondence of α/α and α/γ grain boundaries depending on aging temperatures and times.
Automated Continuous Production Line of Parts Made of Metallic Foams
Authors: Duarte Isabel , Vesenjak Matej , Vide Manuel J.
Published: May 2019

The paper presents an automated continuous production line (7 m × 1.5 m × 1 m) of high-quality metallic foams using a powder metallurgical method. This continuous production line was used to obtain metal foam parts and/or components by heating the foamable precursor material at melting temperatures close to the temperature of the metallic matrix and cooling the formed liquid metallic foam (in liquid state), which then results in a solid closed-cell metallic foam. This automated continuous production line is composed of a continuous foaming furnace, a cooling sector and a robotic system. This installation has enabled a technological breakthrough with many improvements solving some technical problems and eliminating the risks and dangers related to the safety of workers due to the high temperatures involved in this process. The whole process becomes automatic without any need for human intervention.
Interface Characterization of Ultrasonic Spot-Welded Mg Alloy Interlayered with Cu Coating
Authors: Badamian Amir , Iwamoto Chihiro , Sato Shigeo , Tashiro Suguru
Published: May 2019

The effect of Cu coating metallic interlayer on the weldability, joint strength, and interfacial microstructure during high-power ultrasonic spot welding (HP-USW) of AZ31B Mg alloy has been studied. Interlayered samples exhibited good weldability and they resulted in strong sound joints with nearly the same strength as joints without interlayer, with the distinction of lower energy being required. The Cu interlayer affected the thermal and vibrational properties of the interface, as the maximum interface temperature decreased and approached better uniformity across the weld nugget. The base metal grain structure changed to equiaxed larger grains after ultrasonic welding and a chain of parent metal small grains were observed around the interface. A binary intermetallic compound product of Mg-Cu, which was rich in Mg, has been found around the interface that was diffused toward base metal. According to the electron probe micro-analyzer (EPMA) results, alongside temperature measurements and hardness data, the formation of Mg2Cu is suggested in this region. At the interface centerline, a narrow region was identified that was composed of Mg, Cu, and Al. Complementary transmission electron microscopy analysis estimated that Al-containing reaction product is a ternary alloy of the MgCuxAly type. The dispersion of fine grain intermetallic compounds as discrete particles inside Mg substrate in both interfacial regions formed a composite like structure that could participate in joint strengthening.
Mechanical Amorphization and Recrystallization of Mn-Co(Fe)-Ge(Si) Compositions
Authors: Vidal-Crespo Antonio , Ipus Jhon J. , Blázquez Javier S. , Conde Alejandro
Published: May 2019

Mechanical alloying using a planetary ball mill allowed us to obtain two homogeneous systems formed by units with nanometer size and MnCo0.8Fe0.2Ge1−xSix stoichiometry (x = 0 and 0.5). The phase evolution of the systems with the milling time was analyzed using X-ray diffraction. Thermal stability of the final products was studied using differential scanning calorimetry. Room temperature 57Fe Mössbauer spectroscopy was used to follow the changes in the Fe environments. A paramagnetic Co-based amorphous phase developed in both alloys as milling progressed. However, while the presence of Si stabilized the Mn-type phase, mechanical recrystallization was observed in a Si-free composition leading to the formation of a MnCo(Fe)Ge intermetallic (Pnma space group) with a crystal size of 7 ± 1 nm. Mössbauer results indicate that Fe atoms migrate from the initial bcc phase to the amorphous and intermetallic phases.
Creep Buckling of 304 Stainless-Steel Tubes Subjected to External Pressure for Nuclear Power Plant Applications
Authors: Jo Byeongnam , Okamoto Koji , Kasahara Naoto
Published: May 2019

The creep-buckling behaviors of cylindrical stainless-steel tubes subjected to radial external pressure load at elevated temperatures—800, 900, and 1000 °C—were experimentally investigated. Prior to the creep-buckling tests, the buckling pressure was measured under each temperature condition. Then, in creep-buckling experiments, the creep-buckling failure time was measured by reducing the external pressure load for two different tube specimens—representing the first and second buckling modes—to examine the relationship between the external pressure and the creep-buckling failure time. The measured failure time ranged from <1 min to <4 h under 99–41% loading of the buckling pressure. Additionally, an empirical correlation was developed using the Larson–Miller parameter model to predict the long-term buckling time of the stainless-steel tube column according to the experimental results. Moreover, the creep-buckling processes were recorded by two high-speed cameras. Finally, the characteristics of the creep buckling under radial loading were discussed with regard to the geometrical imperfections of the tubes and the material properties of the stainless steel at the high temperatures.
Comparison of Transverse Uniform and Non-Uniform Secondary Cooling Strategies on Heat Transfer and Solidification Structure of Continuous-Casting Billet
Authors: Han Yanshen , Wang Xingyu , Zhang Jiangshan , Zeng Fanzheng , Chen Jun , Guan Min , Liu Qing
Published: May 2019

Water flux distribution largely influences the heat transfer and solidification of continuously-cast steel billets. In this paper, a secondary cooling strategy of transverse non-uniform water flux (i.e., higher flux density on billet center), was established and compared with the uniform cooling strategy using mathematical modeling. Specifically, a heat transfer model and a cellular automaton finite element coupling model were established to simulate the continuous casting of C80D steel billet. The water flux was measured using different nozzle configurations to assist the modeling. The mathematical results were validated by comparing the surface temperature and the solidification structure. It is shown that the non-uniform cooling strategy enables the increase of corner temperature and reduction in surface temperature difference, while a higher reheating rate is found on the surface center of the billet. Moreover, the non-uniform cooling strategy can enhance the cooling effect and refine the solidification structure. Accordingly, the liquid pool length is shortened, and the equiaxed crystal density is increased along with the decreased equiaxed crystal ratio. The uniform cooling strategy contributes to reducing internal cracks of billet, and the non-uniform one is beneficial for surface quality and central segregation. For C80D steel, the non-uniform cooling strategy outperforms the uniform one.
Formation of Large Size Precipitate-Free Zones in β Annealing of the Near-β Ti-55531 Titanium Alloy
Authors: Jiang Xueqi , Shi Xiaoqiang , Fan Xiaoguang , Li Qi
Published: May 2019

Large size (>10000 μm2) precipitate-free zones in the absence of microsegregation were observed in the near-β Ti-55531 titanium alloy after furnace cooling from high temperature and longtime annealing in the single-β phase field. To reveal the formation mechanism of the large size precipitate-free zone, continuous cooling and isothermal heat treatment were carried out to investigate the β-α phase transformation process. It was found that the large size precipitate free zone is attributed to the heterogeneous nucleation of α phase. The nucleation site evolves in three different modes: I-random nucleation inside the β grain, II-network nucleation inside the β grain and, III-heterogeneous nucleation on the precipitated α phase. Modes I and II lead to homogeneous transformed structure while Mode III results in the large size precipitate-free zone. Both modes II and III are promoted at high annealing temperature, rapid cooling above 600 °C or slow cooling below 600 °C. Mode II is common as it can minimize the strain energy in phase transformation. As a result, the formation of the large size precipitate-free zone is not deterministic.
The Effect of Rapid Heating and Fast Cooling on the Transformation Behavior and Mechanical Properties of an Advanced High Strength Steel (AHSS)
Authors: Pedraza Juan Pablo , Landa-Mejia Rafael , García-Rincon Omar , Garcia C. Isaac
Published: May 2019

The major goal of this work was to study the effect of rapid heating and fast cooling on the transformation behavior of 22MnB5 steel. The effect of the initial microstructure (ferrite + pearlite or fully spheroidized) on the transformation behavior of austenite (during intercritical and supercritical annealing) in terms of heating rates (2.5, 30 & 200 °C/s) and fast cooling, i.e., 300 °C/s rate, were studied. As expected, the kinetics of austenite nucleation and growth were strongly related to the heating rates. Similarly, the carbon content of the austenite was higher at lower intercritical annealing temperatures, particularly when slower heating rates were used. The supercritical temperatures used in this study were similar to those used during commercial hot stamping operations, i.e., 845 and 895 °C, respectively, followed by a fast cooling rate. The prior austenite grain size (PAGS) was not strongly influenced by the nature of the initial microstructure, heating rate, reheating temperatures (845 or 895 °C), at 30 s holding time. The decomposition of austenite using fast cooling rates was examined. The results showed that 100% martensite was not obtained. The observed low temperature transformation products consisted of mixtures of martensite-bainite plus undissolved Fe3C carbides and small amounts of martensite-austenite (M-A). At higher supercritical temperatures, i.e., 1000 °C and 1050 °C, the final microstructure showed an increase in the volume fraction of martensite and a decrease in the volume fraction of bainite. The Fe3C and the M-A microconstituent were not observed. The best combination of tensile properties was obtained on samples reheated in the lower temperature range (845 to 895 °C). Interestingly, when the samples where reheated at the higher temperature range (1000 to 1050 °C) and fast cooled, the results of the mechanical properties did not exhibit significantly higher strength levels independent of heating rate or initial microstructural condition. This can be attributed to the change in the microstructural balance %martensite+%bainite as the reheating temperature increases. The results of this study are presented and discussed.
Texture-Based Metallurgical Phase Identification in Structural Steels: A Supervised Machine Learning Approach
Authors: Naik Dayakar L. , Sajid Hizb Ullah , Kiran Ravi
Published: May 2019

Automatic identification of metallurgical phases based on thresholding methods in microstructural images may not be possible when the pixel intensities associated with the metallurgical phases overlap and, hence, are indistinguishable. To circumvent this problem, additional visual information about the metallurgical phases, referred to as textural features, are considered in this study. Mathematically, textural features are the second order statistics of an image domain and can be distinct for each metallurgical phase. Textural features are evaluated from the gray level co-occurrence matrix (GLCM) of each metallurgical phase (ferrite, pearlite, and martensite) present in heat-treated ASTM A36 steels in this study. The dataset of textural features and pixel intensities generated for the metallurgical phases is used to train supervised machine learning classifiers, which are subsequently employed to predict the metallurgical phases in the microstructure. Naïve Bayes (NB), k-nearest neighbor (K-NN), linear discriminant analysis (LDA), and decision tree (DT) classifiers are the four classifiers employed in this study. The performances of all four classifiers were assessed prior to their deployment, and the classification accuracy was found to be >97%. The proposed technique has two unique advantages: (1) unlike pixel intensity-based methods, the proposed method does not misclassify the grain boundaries as a metallurgical phase, and (2) the proposed method does not require the end-user to input the number of phases present in the microstructure.
The Effect of Hot-Mounting on the Microstructure of an As-Quenched Auto-Tempered Low-Carbon Martensitic Steel
Authors: Ramesh Babu Shashank , Jaskari Matias , Järvenpää Antti , Porter David
Published: May 2019

The effect of hot-mounting for metallographic studies of as-quenched low-carbon martensitic steels has been studied. Hot-mounting is typically carried out at 150–200 °C, i.e., a low-temperature tempering regime. Cold- and hot-mounted specimens from an as-quenched low-carbon auto-tempered steel were examined using a scanning electron microscope and their hardness levels were also compared. It was found that hot-mounting causes additional tempering that manifests as the appearance of new precipitates in those regions that are free of auto-tempered cementite. The observations were rationalized using DICTRA simulations to calculate the potential growth of cementite. Hot-mounting was also shown to cause a small but statistically significant increase in the hardness of the martensite.
Dose Dependence of Micro-Voids Distributions in Low-Temperature Neutron Irradiated Eurofer97 Steel
Authors: Coppola Roberto , Klimenkov Michael
Published: May 2019

The microstructural effects of mixed spectrum neutron irradiation at 250 °C and 300 °C, for 2.7 dpa, 8.4 dpa, and 16.3 dpa doses, have been investigated in standard Eurofer97 (0.12 C, 9 Cr, 0.48 Mn, 0.2 V, 1.08 W, 0.14 Ta wt%) by means of small-angle neutron scattering (SANS) compared with un-irradiated Eurofer97. The observed SANS effects are attributed to the development of micro-voids, also detected by electron microscopy. The micro-voids distributions have been obtained by an improved transformation method of the SANS cross-sections providing consistent results both before and after subtraction of the un-irradiated reference. Mono-disperse micro-voids distributions are found, with average radii increasing with the dose, namely 4.4 Å for irradiation to 2.7 dpa at 300 °C, 6.6 Å for 8.4 dpa at 300 °C, and 12.9 Å for 16.4 dpa at 250 °C; the corresponding volume fractions are 0.001, 0.006, and 0.004, respectively. The differences in such distributions might reflect different damage evolution mechanisms for the different irradiation conditions, as also suggested by the comparison with a Eurofer97 sample irradiated under fast spectrum. A good resistance of Eurofer97 to micro-structural radiation damage, at least under these irradiation conditions, is suggested by the analysis of these experimental results.
Wear and MnS Layer Adhesion in Uncoated Cutting Tools When Dry and Wet Turning Free-Cutting Steels
Authors: Martinez Krahmer D. , Hameed S. , Sánchez Egea A. J. , Pérez D. , Canales J. , López de Lacalle L. N.
Published: May 2019

Free-cutting steels are developed to produce large quantities of parts with low mechanical behavior, mainly for automotive sector. These alloys contain phosphorous, lead, sulfur, and manganese that help to improve the machinability and surface roughness. However, due to the toxicity of lead, steel mills in recent years have been focusing on non-toxic steels to produce minimum environmental pollution and better machinability. The present work investigates the tool wear during dry and wet turning of free-cutting steels (SAE 1212, SAE 12L14, and SAE 1215) by using uncoated hard metal inserts at three cutting speeds. Additionally, a EDS analysis was performed to determine the presence of Mn and S elements at the rake face of the cutting tool that can induce a higher adhesion of manganese sulfide (MnS). The results show that the SAE 12L14 steel has the best performance in terms of tool life at different cutting speeds. This difference is maximum at the lowest cutting speed, which gradually decreases with the increase of the cutting speed. The wear behavior is evaluated in the three steel alloys at each cutting speed and, consequently, the tool wear exhibits a slightly better performance in the dry machining condition for higher cutting speeds (180 and 240 m/min), independent of the steel alloy. Finally, EDS analysis confirms the presence of Mn and S elements at the rake face of the inserts machined in dry condition. Hence, MnS is expected to interpose between the machined surface and cutting tool surface to behave similar to tribofilm by reducing the wear on the cutting edge.
Postprandial Metabolic Effects of Fiber Mixes Revealed by in vivo Stable Isotope Labeling in Humans
Authors: Schlicker Lisa , Boers Hanny M. , Dudek Christian-Alexander , Zhao Gang , Barua Arnab , Trezzi Jean-Pierre , Meyer-Hermann Michael , Jacobs Doris M. , Hiller Karsten
Published: May 2019

Food supplementation with a fiber mix of guar gum and chickpea flour represents a promising approach to reduce the risk of type 2 diabetes mellitus (T2DM) by attenuating postprandial glycemia. To investigate the effects on postprandial metabolic fluxes of glucose-derived metabolites in response to this fiber mix, a randomized, cross-over study was designed. Twelve healthy, male subjects consumed three different flatbreads either supplemented with 2% guar gum or 4% guar gum and 15% chickpea flour or without supplementation (control). The flatbreads were enriched with ~2% of 13C-labeled wheat flour. Blood was collected at 16 intervals over a period of 360 min after bread intake and plasma samples were analyzed by GC-MS based metabolite profiling combined with stable isotope-assisted metabolomics. Although metabolite levels of the downstream metabolites of glucose, specifically lactate and alanine, were not altered in response to the fiber mix, supplementation of 4% guar gum was shown to significantly delay and reduce the exogenous formation of these metabolites. Metabolic modeling and computation of appearance rates revealed that the effects induced by the fiber mix were strongest for glucose and attenuated downstream of glucose. Further investigations to explore the potential of fiber mix supplementation to counteract the development of metabolic diseases are warranted.
Comparison of Bi- and Tri-Linear PLS Models for Variable Selection in Metabolomic Time-Series Experiments
Authors: Gao Qian , Dragsted Lars O. , Ebbels Timothy
Published: May 2019

Metabolomic studies with a time-series design are widely used for discovery and validation of biomarkers. In such studies, changes of metabolic profiles over time under different conditions (e.g., control and intervention) are compared, and metabolites responding differently between the conditions are identified as putative biomarkers. To incorporate time-series information into the variable (biomarker) selection in partial least squares regression (PLS) models, we created PLS models with different combinations of bilinear/trilinear X and group/time response dummy Y. In total, five PLS models were evaluated on two real datasets, and also on simulated datasets with varying characteristics (number of subjects, number of variables, inter-individual variability, intra-individual variability and number of time points). Variables showing specific temporal patterns observed visually and determined statistically were labelled as discriminating variables. Bootstrapped-VIP scores were calculated for variable selection and the variable selection performance of five PLS models were assessed based on their capacity to correctly select the discriminating variables. The results showed that the bilinear PLS model with group × time response as dummy Y provided the highest recall (true positive rate) of 83–95% with high precision, independent of most characteristics of the datasets. Trilinear PLS models tend to select a small number of variables with high precision but relatively high false negative rate (lower power). They are also less affected by the noise compared to bilinear PLS models. In datasets with high inter-individual variability, bilinear PLS models tend to provide higher recall while trilinear models tend to provide higher precision. Overall, we recommend bilinear PLS with group x time response Y for variable selection applications in metabolomics intervention time series studies.
Ovothiol A is the Main Antioxidant in Fish Lens
Authors: Yanshole Vadim V. , Yanshole Lyudmila V. , Zelentsova Ekaterina A. , Tsentalovich Yuri P.
Published: May 2019

Tissue protection from oxidative stress by antioxidants is of vital importance for cellular metabolism. The lens mostly consists of fiber cells lacking nuclei and organelles, having minimal metabolic activity; therefore, the defense of the lens tissue from the oxidative stress strongly relies on metabolites. Protein-free extracts from lenses and gills of freshwater fish, Sander lucioperca and Rutilus rutilus lacustris, were subjected to analysis using high-field 1H NMR spectroscopy and HPLC with optical and high-resolution mass spectrometric detection. It was found that the eye lenses of freshwater fish contain high concentrations of ovothiol A (OSH), i.e., one of the most powerful antioxidants exciting in nature. OSH was identified and quantified in millimolar concentrations. The concentration of OSH in the lens and gills depends on the fish genus and on the season. A possible mechanism of the reactive oxygen species deactivation in fish lenses is discussed. This work is the first to report on the presence of OSH in vertebrates. The presence of ovothiol in the fish tissue implies that it may be a significantly more common antioxidant in freshwater and marine animals than was previously thought.
Inhibitory Effects of Green Tea Polyphenols on Microbial Metabolism of Aromatic Amino Acids in Humans Revealed by Metabolomic Analysis
Authors: Zhou Yuyin , Zhang Ningning , Arikawa Andrea Y. , Chen Chi
Published: May 2019

The bioactivities and potential health benefits of green tea polyphenols (GTP) have been extensively investigated, but the metabolic impact of chronic GTP intake on humans is not well defined. In this study, fecal and urine samples from postmenopausal female subjects taking a GTP supplement or placebo for 12 months were compared by liquid chromatography-mass spectrometry-based metabolomic analysis. The GTP-derived and GTP-responsive metabolites were identified and characterized by structural elucidation and quantitative analysis of the metabolites contributing to the separation of control and treatment samples in the multivariate models. Major GTP and their direct sulfate and glucuronide metabolites were absent in feces and urine. In contrast, GTP-derived phenyl-γ-valerlactone and phenylvaleric acid metabolites were identified as the most abundant GTP-derived metabolites in feces and urine, suggesting extensive microbial biotransformation of GTP in humans. Interestingly, GTP decreased the levels of microbial metabolites of aromatic amino acids (AAA), including indoxyl sulfate, phenylacetylglutamine, and hippuric acid, in urine. However, it did not affect the levels of AAA, as well as other microbial metabolites, including short-chain fatty acids and secondary bile acids, in feces. 16S rRNA gene sequencing indicated that the fecal microbiome was not significantly affected by chronic consumption of GTP. Overall, microbial metabolism is responsible for the formation of GTP metabolites while GTP metabolism may inhibit the formation of AAA metabolites from microbial metabolism. Because these GTP-derived and GTP-responsive metabolites have diverse bioactivities, microbial metabolism of GTP and AAA may play important roles in the beneficial health effects of green tea consumption in humans.
A Flexible Piezoelectric Nanogenerator Based on Aligned P(VDF-TrFE) Nanofibers
Authors: You Sujian , Zhang Lingling , Gui Jinzheng , Cui Heng , Guo Shishang
Published: May 2019

Aligned P(VDF-TrFE) nanofibers are successfully fabricated by advanced electrospinning. The aligned feature of the nanofibers is achieved by using parallel electrodes, which is fabricated by lithography and wet etching, and a rotating drum collector. Scanning electron microscope (SEM) images show that the nanofibers are highly ordered with a smooth surface and uniform diameter. X-ray diffraction (XRD) and Fourier Transform Infrared spectrum (FTIR) tests indicate that the fibers contain high β phase content. The nanogenerator based on aligned P(VDF-TrFE) nanofibers exhibits good electric performance with a maximum output voltage as high as 12 V and peak-peak short circuit current about 150 nA, highlighting the potential application of P(VDF-TrFE) on self-powered and wearable devices.
Fabrication and Hydrodynamic Characterization of a Microfluidic Device for Cell Adhesion Tests in Polymeric Surfaces
Authors: Ponmozhi J. , Moreira J. M. R. , Mergulhão F. J. , Campos J. B. L. M. , Miranda J. M.
Published: May 2019

A fabrication method is developed to produce a microfluidic device to test cell adhesion to polymeric materials. The process is able to produce channels with walls of any spin coatable polymer. The method is a modification of the existing poly-dimethylsiloxane soft lithography method and, therefore, it is compatible with sealing methods and equipment of most microfluidic laboratories. The molds are produced by xurography, simplifying the fabrication in laboratories without sophisticated equipment for photolithography. The fabrication method is tested by determining the effective differences in bacterial adhesion in five different materials. These materials have different surface hydrophobicities and charges. The major drawback of the method is the location of the region of interest in a lowered surface. It is demonstrated by bacterial adhesion experiments that this drawback has a negligible effect on adhesion. The flow in the device was characterized by computational fluid dynamics and it was shown that shear stress in the region of interest can be calculated by numerical methods and by an analytical equation for rectangular channels. The device is therefore validated for adhesion tests.