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Journal articles on the topic 'Resistance fluctuation spectroscopy'
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Biswas, Sangram, R. K. Gopal, Sourabh Singh, Raushan Kant, Chiranjib Mitra, and Aveek Bid. "Resistance fluctuation spectroscopy of thin films of 3D topological insulator BiSbTeSe1.6." Applied Physics Letters 115, no. 13 (September 23, 2019): 131601. http://dx.doi.org/10.1063/1.5119288.
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Gomri, S., J. Seguin, T. Contaret, T. Fiorido, and K. Aguir. "A Noise Spectroscopy-Based Selective Gas Sensing with MOX Gas Sensors." Fluctuation and Noise Letters 17, no. 02 (May 2, 2018): 1850016. http://dx.doi.org/10.1142/s0219477518500165.
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We propose a new method for obtaining a fluctuation-enhanced sensing (FES) signature of a gas using a single metal oxide (MOX) gas micro sensor. Starting from our model of adsorption–desorption (A–D) noise previously developed, we show theoretically that the product of frequency by the power spectrum density (PSD) of the gas sensing layer resistance fluctuations often has a maximum which is characteristic of the gas. This property was experimentally confirmed in the case of the detection of NO2 and O3 using a WO3 sensing layer. This method could be useful for classifying gases. Furthermore, our noise measurements confirm our previous model showing that PSD of the A–Dnoise in MOX gas sensor is a combination of Lorentzians having a low frequency magnitude and a cut-off frequency which depends on the nature of the detected gas.
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Nagarajan, Ramya, Ranjan Kumar Patel, and Aveek Bid. "Resistance fluctuation spectroscopy of phase transitions in ( La0.2Pr0.2Nd0.2Sm0.2Eu0.2)NiO3 thin films." Applied Physics Letters 122, no. 10 (March 6, 2023): 102404. http://dx.doi.org/10.1063/5.0139995.
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The study of phase transitions is crucial to understanding the physics of materials and utilizing them for technological applications. This article presents a detailed analysis of the electronic transport properties of high entropy oxide thin films. We observe an increase in resistance fluctuations across a first-order phase transition. We show that the noise arises from an electronic phase separation accompanying the spin ordering due to the formation of domains of localized and delocalized charges. We conclude that due to charge disproportionation, the charge carriers form domains of localized and delocalized electrons in this system. Our study establishes the existence of multiple states with near equal energy in such complex oxide thin films.
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Sita, Zdenek, Vlasta Sedlakova, Jiri Majzner, Petr Sedlak, Josef Sikula, and Lubomir Grmela. "Analysis of Noise and Non-Linearity of I-V Characteristics of Positive Temperature Coefficient Chip Thermistors." Metrology and Measurement Systems 20, no. 4 (December 1, 2013): 635–44. http://dx.doi.org/10.2478/mms-2013-0054.
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Abstract Noise spectroscopy and I-V characteristic non-linearity measurement were applied as diagnostic tools in order to characterize the volume and contact quality of positive temperature coefficient (PTC) chip sensors and to predict possible contact failure. Correctly made and stable contacts are crucial for proper sensing. I-V characteristics and time dependences of resistance were measured for studied sensors and, besides the samples with stable resistance value, spike type resistance fluctuation was observed for some samples. These spikes often disappear after about 24 hours of voltage application. Linear I-V characteristics were measured for the samples with stable resistance. The resistance fluctuation of burst noise type was observed for some samples showing the I-V characteristic dependent on the electric field orientation. We have found that the thermistors with high quality contacts had a linear I-V characteristic, the noise spectral density is of 1/f type and the third harmonic index is lower than 60 dB. The samples with poor quality contacts show non-linear I-V characteristics and excess noise is given by superposition of g-r and 1/fn type noises, and the third harmonic index is higher than 60 dB.
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Zhao, Qi, Zhang, Li, and Li. "Electrochemical Impedance Spectroscopy Investigation on the Corrosive Behaviour of Waterborne Silicate Micaceous Iron Oxide Coatings in Seawater." Coatings 9, no. 7 (June 28, 2019): 415. http://dx.doi.org/10.3390/coatings9070415.
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The anticorrosive composite coatings based on waterborne silicate were prepared to replace existing solvent-based coatings suitable for ships. A series of composite coatings were prepared by adding zinc powder and micaceous iron oxide to the waterborne silicate resin. The adhesion, pencil hardness and impact resistance of the coatings were investigated and corrosion performance in seawater is characterized by electrochemical impedance spectroscopy (EIS). The results show that coatings have excellent adhesion and impact resistance and their pencil hardness can reach up to 4H. During the immersion of composite coatings in seawater for 8 h, only one time constant appears in the Bode plot, coating capacitance (Qc) gradually increases but dispersion coefficient (n) and coating resistance (Rc) gradually decrease. The breakpoint frequency formula was deduced, considering the dispersion effect. With the increase of micaceous iron oxide, the fluctuation of breakpoint frequency with immersion time is weakened. It can be used to evaluate the corrosion resistance of inorganic anticorrosive coatings in seawater. In addition, different penetration models of corrosive media were proposed for the coatings with low or high content of micaceous iron oxide.
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Mollaamin, Fatemeh. "Increasing corrosion resistance of binary Al-Alloy through implanting with some transition elements and heteroatom organic compounds." Acta Chimica Asiana 6, no. 2 (June 23, 2023): 328–42. http://dx.doi.org/10.29303/aca.v6i2.166.
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Decorating of Transition metals (TMs) on the "AlMg" nanoalloy has been studied on the basis of Langmuir adsorption applying "ONIOM" model with three levels of «high, medium and low» by using "LANL2DZ /6-31+G(d,p)/EPR-III", "semi-empirical" and "MM2" functions. The fluctuation of "NQR" has estimated the inhibiting role of pyridine and alkylpyridines containing 2-picoline (2Pic), 3-picoline (3Pic) ,4-picoline (4Pic), and 2,4-lutidine (24Lut) for (Sc, Ti, Cr, Ni, Cu, Zn)-doped AlMg alloy nanosheet due to "N" atom in the benzene cycle of heterocyclic carbenes being near the monolayer surface of ternary "TM–(Al–Mg)" (TM= Sc, Ti, Cr, Ni, Cu, Zn) nanoalloys. The "NMR" spectroscopy has remarked In fact, the NMR results of the adsorption of pyridine and alkylpyridines of 2Pic, 3Pic, 4Pic and 24Lut molecules represent spin polarization on the TM (Sc, Ti, Cr, Ni, Cu, Zn)-doped Al–Mg nanoalloy surfaces that these surfaces can be employed as the magnetic N-heterocyclic carbene sensors. In fact, "TM" sites in "TM–(Al–Mg)" nanoalloy surfaces have bigger interaction energy amount from "Van der Waals’ forces" with pyridine and its nitrogen heterocyclic family that might cause them large stable towards coating data on the nanosurface. It has been estimated that the criterion for choosing the surface linkage of "N" atom in pyridine and alkylpyridines in adsorption sites can be impacted by the existence of close atoms of aluminum and magnesium in the "TM–(AlMg)" surfaces. Moreover, "IR" spectroscopy has exhibited that (Sc, Ti, Cr, Ni, Cu, Zn)-doped AlMg alloy nanosheet with the fluctuation in the frequency of intra-atomic interaction leads us to the most considerable influence in the vicinage elements generated due to inter-atomic interaction. Comparison to amounts versus dipole moment has illustrated a proper accord among measured parameters based on the rightness of the chosen isotherm for the adsorption steps of the formation of Py@Sc–(Al–Mg), Py@Ti–(Al–Mg), Py@Cr–(Al–Mg), Py@Ni–(Al–Mg), Py@Cu–(Al–Mg), and Py@Zn–(Al–Mg) complexes. Thus, the interval between nitrogen atom in pyridine during interaction with transition metals of "Sc, Ti, Cr, Ni, Cu, Zn" in "TM–(Al–Mg)" nanoalloys, (N→TM), has been estimated with relation coefficient of R² = 0.9284. Thus, the present has exhibit the influence of "TMs" doped on the "Al–Mg" surface for adsorption of N-heterocyclic carbenes of pyridine and alkylpyridines by using theoretical methods.
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Cao, Qizheng, Li Fan, Haiyan Chen, Yue Hou, Lihua Dong, and Zhiwei Ni. "Wear and corrosion mechanisms of Ni–WC coatings modified with different Y2O3 by laser cladding on AISI 4145H steel." Science and Engineering of Composite Materials 29, no. 1 (January 1, 2022): 364–77. http://dx.doi.org/10.1515/secm-2022-0163.
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Abstract In order to evaluate the effect of rare earth Y2O3 on the wear and corrosion properties of WC–Ni composite coatings, X-ray diffraction, scanning electron microscopy(SEM), electrochemical polarization curve, electrochemical impedance spectroscopy (EIS), and friction and wear tests were used to analyze the metallographic structure, corrosion characteristics in simulated seawater and friction and wear principle of the composite coatings. Results of SEM revealed that the microstructure of the Y2O3 added coatings was refined with the grains changing smaller and the impurity disappearing. The EIS results proved that the addition of Y2O3 brought a positive influence on the corrosion resistance by reducing the capacitance and increasing the R f and R c. The hardness of the coatings with Y2O3 addition tends to be smooth without wild fluctuation, and the coating with 0.5 wt% Y2O3 owned the hardness values reaching 850 HV. With the addition of rare earth elements, the coefficient of fiction values decreased, reaching the lowest (0.3418) at the content of Y2O3 of 0.5 wt%. The surface of the coating without Y2O3 appears grooved due to the abrasive wear; the coatings with Y2O3 did not suffer serious wear and tear. The coating with 0.5 wt% Y2O3 exhibited the best corrosion resistance and wear resistance properties in all the specimens.
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Lui, Ashley, Robert Sparks, Rekha Patel, and Niketa A. Patel. "Identification of Sortilin Alternatively Spliced Variants in Mouse 3T3L1 Adipocytes." International Journal of Molecular Sciences 22, no. 3 (January 20, 2021): 983. http://dx.doi.org/10.3390/ijms22030983.
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Type 2 diabetes mellitus is a metabolic disorder defined by systemic insulin resistance. Insulin resistance in adipocytes, an important regulator of glucose metabolism, results in impaired glucose uptake. The trafficking protein, sortilin, regulates major glucose transporter 4 (Glut4) movement, thereby promoting glucose uptake in adipocytes. Here, we demonstrate the presence of an alternatively spliced sortilin variant (Sort17b), whose levels increase with insulin resistance in mouse 3T3L1 adipocytes. Using a splicing minigene, we show that inclusion of alternative exon 17b results in the expression of Sort17b splice variant. Bioinformatic analysis indicated a novel intrinsic disorder region (IDR) encoded by exon 17b of Sort17b. Root mean square deviation (RMSD) and root mean square fluctuation (RMSF) measurements using molecular dynamics demonstrated increased flexibility of the protein backbone within the IDR. Using protein–protein docking and co-immunoprecipitation assays, we show robust binding of Glut4 to Sort17b. Further, results demonstrate that over-expression of Sort17b correlates with reduced Glut4 translocation and decreased glucose uptake in adipocytes. The study demonstrates that insulin resistance in 3T3L1 adipocytes promotes expression of a novel sortilin splice variant with thus far unknown implications in glucose metabolism. This knowledge may be used to develop therapeutics targeting sortilin variants in the management of type 2 diabetes and metabolic syndrome.
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Shmidt, Natalia M., Evgeniya I. Shabunina, Ekaterina V. Gushchina, Vasiliy N. Petrov, Ilya A. Eliseyev, Sergey P. Lebedev, Sergei Iu Priobrazhenskii, et al. "Quality Assessment of Processed Graphene Chips for Biosensor Application." Materials 16, no. 16 (August 15, 2023): 5628. http://dx.doi.org/10.3390/ma16165628.
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The quality of graphene intended for use in biosensors was assessed on manufactured chips using a set of methods including atomic force microscopy (AFM), Raman spectroscopy, and low-frequency noise investigation. It is shown that local areas of residues on the graphene surface, formed as a result of the interaction of graphene with a photoresist at the initial stage of chip development, led to a spread of chip resistance (R) in the range of 1–10 kOhm and to an increase in the root mean square (RMS) roughness up to 10 times, which can significantly worsen the reproducibility of the parameters of graphene chips for biosensor applications. It was observed that the control of the photoresist residues after photolithography (PLG) using AFM and subsequent additional cleaning reduced the spread of R values in chips to 1–1.6 kOhm and obtained an RMS roughness similar to the roughness in the graphene film before PLG. Monitoring of the spectral density of low-frequency voltage fluctuation (SU), which provides integral information about the system of defects and quality of the material, makes it possible to identify chips with low graphene quality and with inhomogeneously distributed areas of compressive stresses by the type of frequency dependence SU(f).
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Kubasova, Tereza, Zuzana Seidlerova, and Ivan Rychlik. "Ecological Adaptations of Gut Microbiota Members and Their Consequences for Use as a New Generation of Probiotics." International Journal of Molecular Sciences 22, no. 11 (May 22, 2021): 5471. http://dx.doi.org/10.3390/ijms22115471.
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In this review, we link ecological adaptations of different gut microbiota members with their potential for use as a new generation of probiotics. Gut microbiota members differ in their adaptations to survival in aerobic environments. Interestingly, there is an inverse relationship between aerobic survival and abundance or potential for prolonged colonization of the intestinal tract. Facultative anaerobes, aerotolerant Lactobacilli and endospore-forming Firmicutes exhibit high fluctuation, and if such bacteria are to be used as probiotics, they must be continuously administered to mimic their permanent supply from the environment. On the other hand, species not expressing any form of aerobic resistance, such as those from phylum Bacteroidetes, commonly represent host-adapted microbiota members characterized by vertical transmission from mothers to offspring, capable of long-term colonization following a single dose administration. To achieve maximal probiotic efficacy, the mode of their administration should thus reflect their natural ecology.
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Lin, Xiu Zhou, Min Hao Zhu, Zhen Bing Cai, J. F. Zheng, and Jin Fang Peng. "Microstructure and Reciprocating Sliding Tribological Performance of Micro-Arc Oxidation Coating Prepared on Al-Si Alloy." Advanced Materials Research 97-101 (March 2010): 1518–26. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.1518.
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Micro-arc oxidation coatings were prepared on Al-Si alloys surface by using a self-made micro-arc oxidation equipment. Its characterizations were systematically detected by Vickers hardness tester, profilometer, scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDX), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). Reciprocating sliding tribological tests without lubricant of the micro-arc oxidation coating and its substrate alloy have been carried out under normal load of 5 N and displacement amplitudes of 2 mm. Dynamic analyses in combination with microscopic examinations were performed in detail through optical microscope (OM), SEM and EDX. The experimental results indicated that the MAO coating, with rough surface, high hardness and typical porous ceramic structure, is mainly consist of Al2O3, SiO2 and Al2SiO5 phases. The elementary substance Si and Al are not presented nearly on surface of coatings since the alloy is oxidated adequately during the micro arc oxidation process. Three stages can be observed in the friction coefficient curves both for the MAO coating and its substrate. The COF of the substrate was very low in initial stage, then a rapid ascend to a higher level and fluctuated in a larger range. But for the MAO coating, since its higher hardness and rough surface, the COF was higher than its substrate in initial stage. After a gradually ascent stage, the COF reached a steady state with a small range fluctuation and higher values. The wear mechanism for Al-Si alloy was main adhesive wear, abrasive wear, delamination and slight oxidative wear. After the micro-arc oxidation, the wear resistance of Al-Si alloy was greatly improved, and the wear mechanism of the MAO coating was the combination of delamination, abrasive wear, slight oxidative wear and some material transferred from the ball specimen.
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Mezzalira, Silvia, Elena De Mattia, Michela Guardascione, Chiara Dalle Fratte, Erika Cecchin, and Giuseppe Toffoli. "Circulating-Free DNA Analysis in Hepatocellular Carcinoma: A Promising Strategy to Improve Patients’ Management and Therapy Outcomes." International Journal of Molecular Sciences 20, no. 21 (November 5, 2019): 5498. http://dx.doi.org/10.3390/ijms20215498.
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Hepatocellular carcinoma (HCC) is the sixth most common malignancy worldwide, representing the third leading cause of cancer-related deaths. HCC genetic characterization at the tumor level has been recently completed, highlighting how a number of genes are frequently mutated in this pathology. Actionable somatic mutations found in a HCC tumor may represent targets for innovative drugs as well as prognostic/predictive markers. Nonetheless, surgical or bioptic tissue is hardly accessible in HCC and a single tumor sample is poorly representative of the tumor genetic heterogeneity. In this context, analyzing the circulating cell-free DNA (ccfDNA) and its tumor-derived fraction (ctDNA) could represent a promising strategy of liquid biopsy. Recent data suggested that the fluctuation of the ccfDNA quantity in the plasma of HCC patients could anticipate the detection of tumor progression. The presence of somatic mutations in p53 signaling, Wnt/β-catenin, chromatin remodeling, response to oxidative stress and telomerase maintenance pathways can also be studied in ccfDNA bypassing the need to perform a tumor biopsy. The profiling of ccfDNA fragmentation and the methylation pattern could further improve the clinical management of HCC patients. Performing a dynamic monitoring in the course of systemic treatment with sorafenib or regorafenib is a possible way to provide insights into the resistance mechanism, and to identify predictive and prognostic genetic alterations, helping the clinicians in terms of treatment decision making. This review will discuss the most recent literature data about the use of ccfDNA to monitor and improve the treatment of HCC.
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Guo, Dong, Wu Shuai Zheng, Teng Long Huang, Shu Ling Zhang, and Feng Guo. "Friction and Wear Properties of Multilayer Films Designed on Tantalum Substrate." Materials Science Forum 1078 (December 22, 2022): 121–35. http://dx.doi.org/10.4028/p-l75xgh.
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In this paper, a titanium nitride film (TiN) monolayer film was deposited on a pure Tantalum (Ta) substrate with Ti as an intermediate layer by magnetron sputtering technique, and a Ta/Ti/DLC (diamond-like carbon)/Ti/TiN/DLC multilayer film was designed. Raman spectroscopy and scanning electron microscopy were used to observe the film structure and morphology. Friction and wear properties of Ta/Ti/TiN monolayer film and Ta/Ti/DLC/Ti/TiN/DLC multilayer film were analyzed by UMT-3 tester. The results show that the surface of multilayer film is denser and better bonded than TiN monolayer film. Under dry friction conditions, the friction coefficient of TiN monolayer film is stable at about 0.45. In contrast, the friction coefficient of DLC multilayer film remains around 0.15 with very small fluctuation during the whole friction process. This is determined by the inherent characteristics of DLC film, which is composed of sp2-C graphite structure and sp3-C diamond structure. From the analysis of the wear mechanism, the Ta substrate mainly undergoes adhesive wear and abrasive wear, however, the TiN monolayer film and Ta/Ti/DLC/Ti/TiN/DLC multilayer films mainly undergo abrasive wear mechanism. The friction coefficient of TiN monolayer fluctuates more than that of dry friction conditions in the body-liquid environment, and finally stabilize at about 0.5. The friction coefficient of DLC multilayer films does not differ much from those of dry friction conditions. This is because the TiN monolayer film generates a large amount of abrasive chips to fill the scratches in the body fluid environment, accompanied by the peeling and flaking of the compacted abrasive chips, thus the friction coefficient fluctuates greatly. The DLC multilayer films also undergoes graphitization transfer. In addition, the free hanging bonds of DLC film are passivated, which reduces the degree of adhesive wear. In summary, the DLC multilayer film has better biocompatibility, wear resistance, and stronger bonding.
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Stadler, Adam, and Andrzej Dziedzic. "Virtual instruments in low-frequency noise spectroscopy experiments." Facta universitatis - series: Electronics and Energetics 28, no. 1 (2015): 17–28. http://dx.doi.org/10.2298/fuee1501017s.
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Low-frequency noise spectroscopy (LFNS) is an experimental technique to study noise spectra, typically below 10 kHz, as a function of temperature. Results of LFNS may be presented as the ?so-called? noise maps, giving a detailed insight into fluctuating phenomena in electronic devices and materials. The authors show the usefulness of virtual instrument concept in developing and controlling the measurement setup for LFNS experiments. An example of a noise map obtained for polymer thick-film resistors (PTFRs), made of commercial compositions, for temperature range 77 K - 300 K has been shown. The experiments proved that 1/f noise caused by resistance fluctuations is the dominant noise component in the studied samples. However, the obtained noise map revealed also thermally activated noise sources. Furthermore, parameters describing noise properties of resistive materials and components have been introduced and calculated using data from LFNS. The results of the work may be useful for comparison of noise properties of different resistive materials, giving also directions for improvement of thick-film technology in order to manufacture reliable, low-noise and stable PTFRs.
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Wang, Yun, and Xiao Xi Hu. "The Influence of AC Perturbations on EIS Measurement of Copper/LDPE Composite with High Resistance." Advanced Materials Research 690-693 (May 2013): 355–58. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.355.
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Copper/LDPE composites are novel materials for intrauterine devices and they are the dispersion-type composites with high resistances. When the electrochemical impedance spectroscopy was used to evaluate the properties of materials with high resistances, in order to reduce the fluctuations in the measured data, the AC perturbation should be optimized. In this paper, the effects of the AC perturbations on the electrochemical impedance spectroscopy of copper/LDPE were discussed and the optimal AC perturbation was confirmed. The results have shown that the optimal perturbation of the electrochemical impedance spectroscopy of copper/LDPE composite, in the earlier period was 50mV, after achieving the saturation point the perturbation would change to 5mV.
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Stadler, Adam Witold, Zbigniew Zawiślak, Andrzej Dziedzic, and Damian Nowak. "NOISE SPECTROSCOPY OF RESISTIVE COMPONENTS AT ELEVATED TEMPERATURE." Metrology and Measurement Systems 21, no. 1 (March 1, 2014): 15–26. http://dx.doi.org/10.2478/mms-2014-0002.
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Abstract Studies of electrical properties, including noise properties, of thick-film resistors prepared from various resistive and conductive materials on LTCC substrates have been described. Experiments have been carried out in the temperature range from 300 K up to 650 K using two methods, i.e. measuring (i) spectra of voltage fluctuations observed on the studied samples and (ii) the current noise index by a standard meter, both at constant temperature and during a temperature sweep with a slow rate. The 1/f noise component caused by resistance fluctuations occurred to be dominant in the entire range of temperature. The dependence of the noise intensity on temperature revealed that a temperature change from 300 K to 650 K causes a rise in magnitude of the noise intensity approximately one order of magnitude. Using the experimental data, the parameters describing noise properties of the used materials have been calculated and compared to the properties of other previously studied thick-film materials.
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Stenclova, Pavla, Simon Freisinger, Holger Barth, Alexander Kromka, and Boris Mizaikoff. "Cyclic Changes in the Amide Bands Within Escherichia coli Biofilms Monitored Using Real-Time Infrared Attenuated Total Reflection Spectroscopy (IR-ATR)." Applied Spectroscopy 73, no. 4 (February 20, 2019): 424–32. http://dx.doi.org/10.1177/0003702819829081.
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Contrary to the planktonic state of bacteria, their biofilm form represents severe complications in areas such as human medicine or food industry due to the increasing resistance against harsh conditions and treatment. In the present study, infrared attenuated total reflection (IR-ATR) spectroscopy has been applied as an analytic tool studying Escherichia coli ( E. coli) biofilm formation close to real time. We report on IR spectroscopic investigations on the biofilm formation via ATR waveguides probing the biofilm in the spectral window of 1800–900 cm−1 at dynamic flow conditions, which facilitated monitoring the growth dynamics during several days. Key IR bands are in the range 1700–1590 cm−1 (amide I), 1580–1490 cm−1 (amide II), and 1141–1006 cm−1 extracellular polymeric substances (EPS), which were evaluated as a function of time. Cyclic fluctuations of the amide I and amide II bands and a continuous increase of the EPS band were related to the starvation of bottom-layered bacteria caused by the nutrient gradient. Potential death of bacteria may then result in cannibalistic behavior known for E. coli colonies. Observing this behavior via IR spectroscopy allows revealing these cyclical changes in bottom-layered bacteria within the biofilm under continuous nutrient flow, in molecular detail, and during extended periods for the first time.
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Sugano, Nobuhiko, and Giuseppe Pezzotti. "Role of Grain Size Fluctuations on the Environmental Resistance of Alumina-Zirconia Composite in Comparison with Commercially Available Monolithic Zirconia Femoral Head." Advances in Science and Technology 76 (October 2010): 235–39. http://dx.doi.org/10.4028/www.scientific.net/ast.76.235.
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Raman microprobe spectroscopy and atomic force microscopy (AFM) were systematically used to characterize the surface of an advanced alumina/zirconia composite (henceforth also referred to as zirconia toughened alumina, ZTA), in comparison with a commercially available femoral head made of monolithic zirconia. Experiments were conducted before and after in vitro exposure in water moist environment up to 100 h. Both materials contained zirconia partly stabilized with yttria. Tetragonal-to-monoclinic phase transformation, which was quantitatively characterized by confocal Raman spectroscopy as a function of grain size, showed significant difference between the investigated samples. Such difference was similarly found with respect to both roughness level and time needed for such topologic changes to occur. Variation of phase fractions and of topologic surface parameters were plotted as a function of in vitro exposure time and compared.
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Zi, Hai, Yuan Yao, Ming-Chong He, Di Ke, Hong-Xing Zhan, Yu-Qing Zhao, Hai-Hu Wen, and Cong Ren. "Resistance fluctuations in superconducting K x Fe2 – y Se2 single crystals studied by low-frequency noise spectroscopy*." Chinese Physics B 30, no. 4 (April 1, 2021): 047402. http://dx.doi.org/10.1088/1674-1056/abf103.
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Tahri, Amina, Mohsine Bouya, Mokhtar Ghazouani, Ouafae Achak, Tarik Chafik, Khalid El Azdi, and Sanae Boughanbour. "Impact of Solar Energy Integration on the Rheological and Chemical Properties of Bitumen." Energies 16, no. 1 (December 20, 2022): 14. http://dx.doi.org/10.3390/en16010014.
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The use of solar energy to partially satisfy the demand for heat in the bitumen industry constitutes an enormous step towards industrial decarbonization. This paper investigates the effect of thermal fluctuations caused by solar energy usage in bitumen storage in the region of Rabat, Morocco. We studied different temperature ranges and storage periods, covering the most common scenarios in this region. This work inspected the impact of these studied conditions on the performance of 35/50 bitumen. After the simulation of fluctuations through thermal storage, we simulated short-term and long-term aging using RTFO and PAV tests, respectively. In addition to the needle penetration at 25 °C and the determination of softening point tests, we used a dynamic shear rheometer (DSR) and Fourier-transform infrared spectroscopy (FTIR) to assess the rheological and chemical evolutions of the samples. We found that thermal fluctuations enhanced the rheological performance of the binders by improving their rutting and fatigue cracking resistance. We observed that longer storage durations (three months) under thermal fluctuations made bitumen more prone to oxidation in the long term. We conclude that solar energy usage in bitumen storage is not detrimental as long as we avoid long storage periods (more than one month), especially when the maximum storage temperature is higher than 165 °C.
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Raigorodskaya, M. R., and D. A. Sakharov. "Transcriptome analysis of signaling pathways involved in the formation of intestinal villi in Caco-2 cells." Biotekhnologiya 36, no. 1 (2020): 25–29. http://dx.doi.org/10.21519/0234-2758-2020-36-1-25-29.
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Caco-2 cells are traditionally used to construct in vitro models of the intestinal barrier. One of the characteristics of the mature intestine is the presence of villi, outgrowths of connective tissue covered with epithelial cells. Recently it has been shown that during prolonged cultivation Caco-2 cells form structures resembling intestinal villi. Here, using transcriptome analysis, we showed that BMP and PDGF signaling involved in the formation of villi in vivo significantly altered during the differentiation of Caco-2 cells and, thus, can participate in the formation of similar structures in vitro. In particular, a significant decrease in the expression of the BMP4, BMP7, and BMP8A genes in differentiated cells compared to undifferentiated ones was found. Periodic fluctuations in transepithelial resistance during the differentiation of Caco-2 cells have been discovered for the first time. The period of observed fluctuations indicates that they can arise in the result of cell proliferation during the formation of villi. According to the period of observed fluctuations, one can suppose that they arise in the result of cell proliferation during the formation of villi. impedance spectroscopy, intestine, villi, TEER, BMP, PDGF The study was funded by the Russian Science Foundation (project 16-19-10597).
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Денисов, Е. С. "SMALL-SIGNAL ELECTRICAL MODEL OF A PEM FUEL CELL." Южно-Сибирский научный вестник, no. 3(49) (June 30, 2023): 152–58. http://dx.doi.org/10.25699/sssb.2023.49.3.012.
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Твердополимерные топливные элементы (ТТЭ)являются одними из наиболее перспективных средств получения электрической энергии быстро развивающейся водородной энергетики. Для поддержания высоких удельных энергетических характеристик ТТЭ требуются эффективные системы управления и диагностики с возможностью обнаружения неисправностей и некорректных режимов работы на ранних этапах развития. Для этой цели лучше всего подходят методы, позволяющие проводить диагностику в процессе функционирования, такие как анализ импедансных,релаксационных и флуктуационно-шумовых характеристик. Применение таких методов подразумевает использование малосигнальных электрических моделей, среди которых наибольшее распространение получила эквивалентная схема Эршлера-Рэндлса. Наиболее сложным для моделирования и идентификации по экспериментальным данным элементом этой схемы является диффузионный импеданс. В рамках данной работы решается задача аппроксимации импеданса Варбурга на основе цепей Кауэра и минимизации их параметрического описания таким образом, чтобы обеспечить возможность эффективного определения параметров диффузионного импеданса при идентификации по экспериментальным данным. В работе показана возможность описания короткозамкнутого импеданса Варбурга в широком диапазоне частот цепями Кауэра второго-пятого порядка, описываемыми только двумя независимыми параметрами: постоянной времени и сопротивлением. При этом достигаются среднеквадратические погрешности аппроксимации 0,5% и менее. В работе рекомендуется использовать модели второго и третьего порядков, поскольку модель первого порядка не обеспечивает достаточную точность, а использование моделей более высоких порядков приводит к росту сложности вычислительных процедур. Кроме того, погрешность в основном обусловлена высокочастотным диапазоном, ее вклад в реальных приложениях будет уменьшаться, поскольку полный импеданс ТТЭ в этом диапазоне определяется другими элементами эквивалентной схемы. Предложенные подходы к описанию малосигнальной электрической модели позволят повысить эффективность процедур обработки сигналов для методов диагностики и моделирования режимов работы ТТЭ и других электрохимических источников электрической энергии. Proton exchange membrane fuel cell (PEMFC) is one of the most promising means for generating electrical energy in the rapidly developing hydrogen energy industry. To maintain high specific energy characteristics of PEMFC, effective control and diagnostic systems designed to detect faults and incorrect operating modes at early stages of development are required. For this purpose, methods are best suited that allow diagnostics during the process of operation, such as impedance spectroscopy, analysis of relaxations and fluctuation-noise characteristics. Such methods use small-signal electrical models, among which the Ershler-Randles equivalent circuit is most widely used. The most difficult for modelling and identifying from experimental data element here is the diffusion impedance. Within the framework of this work, the problem of approximating the diffusion (Warburg) impedance based on Cauer circuits and minimizing their parametric description in such a way as to provide the possibility of effectively determining the diffusion impedance parameters during identification from experimental data is solved. The paper shows the possibility of describing the short-circuited Warburg impedance in a wide frequency range by Cauer circuits of the second-fifth order, described by only two independent parameters: time constant and resistance. In this case, root-mean-square approximation errors of 0.5% or less are achieved. It is recommended to use models of the second and third orders in the work, since the first order model does not provide sufficient accuracy, and the use of higher order models leads to an increase in the complexity of computational procedures. In addition, the error are concentrated within the high-frequency range, therefore its contribution in real applications will decrease, since the total impedance of PEMFC in this range is determined by other elements of the electrical model. The proposed approaches to the description of a small-signal electrical model will improve the efficiency of signal processing procedures for methods of diagnostics and simulation of operating modes of PEMFC and other types of electrochemical power source.
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Vinogradova, S. S., and Ye V. Pleshkova. "Staged Local Dissolution of Stainless Steel in Chloride Solutions." Solid State Phenomena 299 (January 2020): 711–15. http://dx.doi.org/10.4028/www.scientific.net/ssp.299.711.
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The paper defines galvanostatic polarization parameters (current density and test duration) to simulate self-dissolution conditions; the results are confirmed by potentiostatic tests. It is shown that under the conditions of self-dissolution simulation, increasing the solution concentration reduces the nucleation rate, while prolonging the pitting development time. Spectral analysis of chronopotentiograpms reveals low-frequency potential fluctuations that characterize the nucleation and passivation of pits at the onset of pitting corrosion. The paper describes the basic regularities observed in the alteration of surface electrochemistry by impedance spectroscopy; such alteration corresponds to the transition from the passive area to the pitting area. The researchers propose optimal electric equivalent circuits to reflect the surface conditions in early nucleation of pits. The paper also proposes an additional pitting resistance criterion, that is, cumulative electric-charge density.
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Vinogradova, S. S., and Ye V. Pleshkova. "Staged Local Dissolution of Stainless Steel in Chloride Solutions." Materials Science Forum 989 (May 2020): 74–78. http://dx.doi.org/10.4028/www.scientific.net/msf.989.74.
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The paper defines galvanostatic polarization parameters (current density and test duration), to simulate self-dissolution conditions; the results are confirmed by potentiostatic tests. It is shown that under the conditions of self-dissolution simulation, increasing the solution concentration reduces the nucleation rate, while prolonging the pitting development time. Spectral analysis of chronopotentiograms reveals low-frequency potential fluctuations that characterize the nucleation and passivation of pits at the onset of pitting corrosion. The paper describes the basic regularities, observed in the alteration of surface electrochemistry by impedance spectroscopy; such alteration corresponds to the transition from the passive area to the pitting area. The researchers propose optimal electric equivalent circuits to reflect the surface conditions in early nucleation of pits. The paper also proposes an additional pitting resistance criterion, that is, cumulative electric-charge density.
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Briandet, R., P. Lacroix-Gueu, M. Renault, S. Lecart, T. Meylheuc, E. Bidnenko, K. Steenkeste, M. N. Bellon-Fontaine, and M. P. Fontaine-Aupart. "Fluorescence Correlation Spectroscopy To Study Diffusion and Reaction of Bacteriophages inside Biofilms." Applied and Environmental Microbiology 74, no. 7 (February 1, 2008): 2135–43. http://dx.doi.org/10.1128/aem.02304-07.
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ABSTRACT In the natural environment, most of the phages that target bacteria are thought to exist in biofilm ecosystems. The purpose of this study was to gain a clearer understanding of the reactivity of these viral particles when they come into contact with bacteria embedded in biofilms. Experimentally, we quantified lactococcal c2 phage diffusion and reaction through model biofilms using in situ fluorescence correlation spectroscopy with two-photon excitation. Correlation curves for fluorescently labeled c2 phage in nonreacting Stenotrophomonas maltophilia biofilms indicated that extracellular polymeric substances did not provide significant resistance to phage penetration and diffusion, even though penetration and diffusion were sometimes restricted because of the noncontractile tail of the viral particle. Fluctuations in the fluorescence intensity of the labeled phage were detected throughout the thickness of biofilms formed by c2-sensitive and c2-resistant strains of Lactococcus lactis but could never be correlated with time, revealing that the phage was immobile. This finding confirmed that recognition binding receptors for the viral particles were present on the resistant bacterial cell wall. Taken together, our results suggest that biofilms may act as “active” phage reservoirs that can entrap and amplify viral particles and protect them from harsh environments.
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Sun, Yongjie, Pengpeng Wang, Tingting Zhang, Kun Li, Feng Peng, and Cunguang Zhu. "Principle and Performance Analysis of the Levenberg–Marquardt Algorithm in WMS Spectral Line Fitting." Photonics 9, no. 12 (December 18, 2022): 999. http://dx.doi.org/10.3390/photonics9120999.
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Calibration-free wavelength modulation spectroscopy (WMS) is an efficient technique for trace gas monitoring. It is widely used due to its resistance to light intensity fluctuations, strong suppression of low-frequency noise, fast response time, and excellent environmental adaptability. The calibration-free WMS often employs the Levenberg–Marquardt algorithm for spectral fitting to retrieve gas characteristics. However, to the best of our knowledge, an analysis of the main factors affecting the operational effectiveness of the Levenberg–Marquardt algorithm in calibration-free WMS has merely been reported. In this paper, we have systematically analyzed the Levenberg–Marquardt algorithm’s operating mechanism in WMS-2f/1f. The results show that the number of parameters and the estimation errors of the initial parameters are the main factors limiting the retrieval accuracy of the algorithm, which provides some important guidelines for the subsequent optimization of the spectral fitting scheme.
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Ivanič, Andrej, Gregor Kravanja, Wadie Kidess, Rebeka Rudolf, and Samo Lubej. "The Influences of Moisture on the Mechanical, Morphological and Thermogravimetric Properties of Mineral Wool Made from Basalt Glass Fibers." Materials 13, no. 10 (May 22, 2020): 2392. http://dx.doi.org/10.3390/ma13102392.
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Mineral wool made from basalt fibers is frequently used as an insulating material in construction systems. In this study, both unused mineral wool and wool obtained from the softened roofing area were comprehensively analyzed in a laboratory using different characterization techniques. Firstly, the initial water content and compressive strength at 10% deformation were determined. Secondly, microstructure and surface chemical composition were analyzed by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX). To study heterogeneities near the fiber surface and to examine cross-sectional composition, a scanning transmission electron microscope (STEM) was used. Finally, to verify possible reasons for resin degradation, thermogravimetric analysis and differential scanning colometry (TGA-DSC) were simultaneously carried out. The results show that natural aging under high humidity and thermal fluctuations greatly affected the surface morphology and chemical composition of the fibrous composite. Phenol-formaldehyde and other hydrophobic compounds that protect fibers against moisture and give compressive resistance were found to be degraded.
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Mukhin, V. V., Natalia N. Petrova, V. V. Portnyagina, A. L. Fedorov, and A. V. Baisheva. "Investigation of the Plasticizer Content Effects on the Operability of the Epichlorohydrin Rubber Based Elastomeric Material during Full-Scale Test under Cold Climate Conditions and Hydrocarbon Medium Influence." Materials Science Forum 945 (February 2019): 417–21. http://dx.doi.org/10.4028/www.scientific.net/msf.945.417.
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Sealing rubbers used in the climatic conditions of the Far North and the Arctic, based on butadiene-nitrile rubbers contain significant amounts of plasticizers, which increase their frost resistance. They lose low-temperature and operational properties when they contact with the hydrocarbon medium due to intensive plasticizer washing out. Zeon Hydrin T6000 epichlorohydrin rubber, has a low glass transition temperature (Tg = -60 °C) and resistance to aggressive media. The model rubber was developed that minimally meets the requirements for sealing rubbers. Samples were exposed in oil, for 2 years, in climate of Yakutsk, the Republic of Sakha (Yakutia), Russia. The climate is characterized by significant average daily temperature fluctuations with a transition through the 0 °C and low temperatures below-60 °C. For comparison, simultaneously rubbers based on butadiene-nitrile rubbers was investigated. Every two months, the main parameters were measured: swelling degree, tensile strength, elongation, frost resistance coefficient for elastic recovery after compression at-50 °C and-30 °C, compression set and plasticizer content by means of IR spectroscopy. Model rubber showed excellent frost resistance while retaining the other properties, regardless of the plasticizer content, while rubber based on butadiene-nitrile rubber irreversibly lost low-temperature properties in the first months. Similar results were obtained earlier in the study propylene oxide rubber produced in Russia (Tg = -74°C). During full-scale exposure, a small dependence of its low-temperature characteristics on the amount of plasticizer in the elastomeric material was also revealed. Thus, epichlorohydrin rubber Hydrin T6000 can be used as a sealing rubber.
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Caliskan, Halil, Emre Altas, and Peter Panjan. "Study of Nanolayer AlTiN/TiN Coating Deposition on Cemented Carbide and its Performance as a Cutting Tool." Journal of Nano Research 47 (May 2017): 1–10. http://dx.doi.org/10.4028/www.scientific.net/jnanor.47.1.
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Titanium and its alloys are widely used in aerospace and aviation industries because of their high strength-to-weight ratio, high fracture resistance and corrosion resistance at elevated temperatures. However, chemical reactivity and low thermal conductivity of these alloys lead to adhesion and diffusion wears on carbide tools, respectively. In addition, fluctuations in cutting forces occur during the cutting process due to chip shear band formation; and chipping wear is observed at the tool cutting edge as a result. Therefore, machining of these alloys is a challenge for researchers. A common method to increase the lifetime of carbide tools is to coat them with a thin hard coating. In this study, a nanolayer AlTiN/TiN coating was deposited on carbide cutting tools using an industrial magnetron sputtering system in order to enhance their wear resistance and lifetime in milling of Ti6Al4V. The cutting tests with the coated tools were performed at a cutting speed of 50 m/min, feed rate of 0.1 mm/tooth and depth of cut of 1 mm under dry conditions. Tool wear and surface roughness on the workpiece were measured and recorded as a function of cutting distance. Wear mechanisms and types were revealed using optical and scanning electron microscopy and energy dispersive spectroscopy. It was found that the nanolayer AlTiN/TiN coated tools provide higher wear resistance and 4 times longer lifetime when compared to uncoated ones. The main observed wear types are notch wear and build-up edge formation on the cutting edge. A slight improvement in surface roughness of the workpiece was observed with the nanolayered coating.
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Potyrailo, Radislav A., Brian Scherer, Baokai Cheng, Majid Nayeri, Shiyao Shan, Janell Crowder, Richard St-Pierre, Joleyn Brewer, and Renner Ruffalo. "First-Order Individual Gas Sensors as Next Generation Reliable Analytical Instruments." Applied Spectroscopy 77, no. 8 (August 2023): 860–72. http://dx.doi.org/10.1177/00037028231186821.
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It is conventionally expected that the performance of existing gas sensors may degrade in the field compared to laboratory conditions because (i) a sensor may lose its accuracy in the presence of chemical interferences and (ii) variations of ambient conditions over time may induce sensor-response fluctuations (i.e., drift). Breaking this status quo in poor sensor performance requires understanding the origins of design principles of existing sensors and bringing new principles to sensor designs. Existing gas sensors are single-output (e.g., resistance, electrical current, light intensity, etc.) sensors, also known as zero-order sensors (Karl Booksh and Bruce R. Kowalski, Analytical Chemistry, DOI: 10.1021/ac00087a718). Any zero-order sensor is undesirably affected by variable chemical background and sensor drift that cannot be distinguished from the response to an analyte. To address these limitations, we are developing multivariable gas sensors with independent responses, which are first-order analytical instruments. Here, we demonstrate self-correction against drift in two types of first-order gas sensors that operate in different portions of the electromagnetic spectrum. Our radiofrequency sensors utilize dielectric excitation of semiconducting metal oxide materials on the shoulder of their dielectric relaxation peak and achieve self-correction of the baseline drift by operation at several frequencies. Our photonic sensors utilize nanostructured sensing materials inspired by Morpho butterflies and achieve self-correction of the baseline drift by operation at several wavelengths. These principles of self-correction for drift effects in first-order sensors open opportunities for diverse emerging monitoring applications that cannot afford frequent periodic maintenance that is typical of traditional analytical instruments.
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Chakraborty, Saptarshi, Milka Doktorova, Trivikram R. Molugu, Frederick A. Heberle, Haden L. Scott, Boris Dzikovski, Michihiro Nagao, et al. "How cholesterol stiffens unsaturated lipid membranes." Proceedings of the National Academy of Sciences 117, no. 36 (August 25, 2020): 21896–905. http://dx.doi.org/10.1073/pnas.2004807117.
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Cholesterol is an integral component of eukaryotic cell membranes and a key molecule in controlling membrane fluidity, organization, and other physicochemical parameters. It also plays a regulatory function in antibiotic drug resistance and the immune response of cells against viruses, by stabilizing the membrane against structural damage. While it is well understood that, structurally, cholesterol exhibits a densification effect on fluid lipid membranes, its effects on membrane bending rigidity are assumed to be nonuniversal; i.e., cholesterol stiffens saturated lipid membranes, but has no stiffening effect on membranes populated by unsaturated lipids, such as 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). This observation presents a clear challenge to structure–property relationships and to our understanding of cholesterol-mediated biological functions. Here, using a comprehensive approach—combining neutron spin-echo (NSE) spectroscopy, solid-state deuterium NMR (2H NMR) spectroscopy, and molecular dynamics (MD) simulations—we report that cholesterol locally increases the bending rigidity of DOPC membranes, similar to saturated membranes, by increasing the bilayer’s packing density. All three techniques, inherently sensitive to mesoscale bending fluctuations, show up to a threefold increase in effective bending rigidity with increasing cholesterol content approaching a mole fraction of 50%. Our observations are in good agreement with the known effects of cholesterol on the area-compressibility modulus and membrane structure, reaffirming membrane structure–property relationships. The current findings point to a scale-dependent manifestation of membrane properties, highlighting the need to reassess cholesterol’s role in controlling membrane bending rigidity over mesoscopic length and time scales of important biological functions, such as viral budding and lipid–protein interactions.
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Ganguly, Antra, Paul Rice, Kai-Chun Lin, Sriram Muthukumar, and Shalini Prasad. "A Combinatorial Electrochemical Biosensor for Sweat Biomarker Benchmarking." SLAS TECHNOLOGY: Translating Life Sciences Innovation 25, no. 1 (October 16, 2019): 25–32. http://dx.doi.org/10.1177/2472630319882003.
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Misclassification of an acute disease condition as chronic and vice versa by electrochemical sweat biomarker sensors can cause significant psychological, emotional, and financial stress among patients. To achieve higher accuracy in distinguishing between a chronic condition and an acute condition, there is a need to establish a reference biomarker to index the actual chronic disease biomarker of interest by combinatorial sensing. This work provides the first technological proof of leveraging the chloride ion content in sweat for a combinatorial sweat biomarker benchmarking scheme. In this scheme, the sweat chloride ion has been demonstrated as the reference/indexing biomarker, while sweat cortisol has been studied as the disease biomarker of interest. Label-free affinity biosensing is achieved by using a two-electrode electrochemical system on a flexible substrate suitable for wearable applications. The electrochemical stability of the fabricated electrodes for biosensing applications was studied by open-circuit potential measurements. Attenuated total reflectance–Fourier transform infrared spectroscopy spectra validate the crosslinker–antibody binding chemistry. Concentration-dependent analyte–capture probe binding induces a modulation in the electrical properties (charge transfer resistance and double-layer capacitance) at the electrode–sweat buffer interface, which are transduced by nonfaradaic electrochemical impedance spectroscopy (EIS). Calibration dose responses for the sensor for cortisol (5–200 ng/mL) and chloride (10–100 mM) detection were evaluated in synthetic (pH 6) and pooled human sweat ( R2 > 0.95). The variation in the cortisol sensor response due to fluctuations in sweat chloride levels and the significance of reporting normalized biomarker levels were demonstrated to further emphasize the need for biomarker benchmarking in electrochemical sensors.
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Szenajch, Jolanta, Alicja Szabelska-Beręsewicz, Aleksandra Świercz, Joanna Zyprych-Walczak, Idzi Siatkowski, Michał Góralski, Agnieszka Synowiec, and Luiza Handschuh. "Transcriptome Remodeling in Gradual Development of Inverse Resistance between Paclitaxel and Cisplatin in Ovarian Cancer Cells." International Journal of Molecular Sciences 21, no. 23 (December 3, 2020): 9218. http://dx.doi.org/10.3390/ijms21239218.
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Resistance to anti-cancer drugs is the main challenge in oncology. In pre-clinical studies, established cancer cell lines are primary tools in deciphering molecular mechanisms of this phenomenon. In this study, we proposed a new, transcriptome-focused approach, utilizing a model of isogenic cancer cell lines with gradually changing resistance. We analyzed trends in gene expression in the aim to find out a scaffold of resistance development process. The ovarian cancer cell line A2780 was treated with stepwise increased concentrations of paclitaxel (PTX) to generate a series of drug resistant sublines. To monitor transcriptome changes we submitted them to mRNA-sequencing, followed by the identification of differentially expressed genes (DEGs), principal component analysis (PCA), and hierarchical clustering. Functional interactions of proteins, encoded by DEGs, were analyzed by building protein-protein interaction (PPI) networks. We obtained human ovarian cancer cell lines with gradually developed resistance to PTX and collateral sensitivity to cisplatin (CDDP) (inverse resistance). In their transcriptomes, we identified two groups of DEGs: (1) With fluctuations in expression in the course of resistance acquiring; and (2) with a consistently changed expression at each stage of resistance development, constituting a scaffold of the process. In the scaffold PPI network, the cell cycle regulator—polo-like kinase 2 (PLK2); proteins belonging to the tumor necrosis factor (TNF) ligand and receptor family, as well as to the ephrin receptor family were found, and moreover, proteins linked to osteo- and chondrogenesis and the nervous system development. Our cellular model of drug resistance allowed for keeping track of trends in gene expression and studying this phenomenon as a process of evolution, reflected by global transcriptome remodeling. This approach enabled us to explore novel candidate genes and surmise that abrogation of the osteomimic phenotype in ovarian cancer cells might occur during the development of inverse resistance between PTX and CDDP.
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Bacelis, Ángel, Lucien Veleva, and Mario A. Alpuche-Avilés. "Copper Corrosion Behavior in Simulated Concrete-Pore Solutions." Metals 10, no. 4 (April 4, 2020): 474. http://dx.doi.org/10.3390/met10040474.
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The copper corrosion was studied for 30 days in two alkaline electrolytes: saturated Ca(OH)2 and cement extract, employed to simulate concrete-pore environments. Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry were carried out at the open circuit potential (OCP), and potentiodynamic polarization (PDP) curves were performed for comparative purposes. Electrochemical current fluctuations, considered as electrochemical noise (EN), were employed as non-destructive methods. The tests revealed that sat. Ca(OH)2 is the less aggressive to the Cu surface, mainly because of the lower in one order pH. In consequence, the OCP values of Cu were more positive, the polarization resistance values were higher by one order of magnitude, and the anodic currents of Cu were lower than those in the cement extract. The analyzed EN indicated that the initial corrosion attacks on the Cu surface are quasi-uniform, resulting from the stationary persistent corrosion process occurring in both model solutions. XPS analysis and X-ray diffraction (XRD) patterns revealed that in sat. Ca(OH)2, a Cu2O/CuO corrosion layer was formed, which effectively protects the metallic Cu-surface. We present evidence for the sequential oxidation of Cu to the (+1) and (+2) species, its impact on the corrosion layer, and also its protective properties.
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Chávez, Luis, Lucien Veleva, Sebastián Feliu, Danai Giannopoulou, and Hajo Dieringa. "Corrosion Behavior of Extruded AM60-AlN Metal Matrix Nanocomposite and AM60 Alloy Exposed to Simulated Acid Rain Environment." Metals 11, no. 6 (June 21, 2021): 990. http://dx.doi.org/10.3390/met11060990.
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The present work compared the initial stages of corrosion process development on the AM60-AlN metal matrix nanocomposite surface and on AM60, during their exposure for 30 days to simulated acid rain solution (SAR). The AlN nanoparticles were observed as “attached” to those of Mn-rich AlMn intermetallic particles, forming clusters. The introduction of 1.0 wt.% AlN (≈ 80 nm) in the AM60 alloy carried a slight grain refinement and favored the formation of a denser and more protective corrosion layer, suggested by the electrochemical impedance spectroscopy (EIS) values of higher charge transfer resistance (R2) and capacitance, characteristic of the double layer in the presence of corrosion products, and also suggested by Rn (EN) values, compared to those of the AM60 alloy. Thus, the concentration of the released Mg-ions from the composite surface was lower. Due to the increase in time of the SAR solution pH, Al de-alloying may occur, as well as Al(OH)3 formation, as confirmed by XPS analysis. Due to the presence of Cl-ions in SAR solution, localized corrosion was observed, suggested as fractional Gaussian noise of a stationary and persistent process in time, according to the PSD of the corrosion current fluctuations (EN).
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Williams, Rhys, Sivakkumaran Sukumaran, Qaisar Abbas, and Michael Hunt. "Few-Layer Graphene As an Electrode, Electrode Additive and an Interfacial Layer in Aqueous Supercapacitors." ECS Meeting Abstracts MA2022-02, no. 8 (October 9, 2022): 660. http://dx.doi.org/10.1149/ma2022-028660mtgabs.
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The intermittent nature of many renewable energy sources such as wind and solar, coupled with fluctuations in energy demand, creates a pressing need for efficient, low-cost energy storage technologies. Supercapacitors are promising candidates to play a role in next-generation energy storage systems. They have a higher power density and better cycle life (although lower energy density) than batteries making them ideal for rapid energy storage and deployment [1]. Activated carbon is a favoured electrode material due to high surface area, although low conductivity requires use of a conductive additive (often carbon black), reducing available surface area for charge storage. In contrast, the high conductivity and specific surface area of graphene has made it a promising material for electrochemical double layer supercapacitors (EDLCs) [2], however, performance is limited by restacking of the graphene sheets, reducing available surface area. In this work, high-shear exfoliated few layer graphene (FLG) [3] is investigated both as an electrode material and as a conductive additive/interfacial layer for EDLCs. FLG suspensions were produced under a variety of exfoliation conditions, with platelet thickness and linear dimension determined from Raman spectroscopy based on metrics developed by Backes et al. [4] and through scanning electron microscopy (SEM). The FLG suspensions were used in three ways: i) to create thin ‘graphene paper’ electrodes; ii) as a conductive additive, mixed into the activated carbon electrode material; iii) deposited onto the back of (and diffused within) activated carbon electrodes. These electrodes were investigated by Raman spectroscopy and Scanning Electron Microscopy, before being assembled into symmetric two-terminal aqueous cells then evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), and their electrochemical performance related to structure and composition. As expected, pure FLG electrodes often showed excellent low series resistance values, however specific capacitance was low, due to restacking. Directly mixing 5% FLG into activated carbon as a conventional conductive additive led to a specific capacitance of 63 F/g (from CV at 10 mV/s), and a series resistance of 19 W (from GCD at 1 A/g) - markedly inferior to those with 5% carbon black as a conductive additive (95 F/g and 2 Ohm) and inferior even to electrodes with no conductive additive (87 F/g and 10 Ohm). However, post fabrication deposition/infusion of FLG offers comparable performance to carbon black (90 F/g and 1 Ohm) at 7% FLG by weight. As the quantity of FLG is increased the specific capacitance decreases sharply. This behaviour is attributed to FLG restacking on the rear of the electrode, so adding mass whilst providing limited additional capacitance, and compression of the electrode. Adding high-shear exfoliated FLG to activated carbon electrodes shows promise for obtaining the benefits of both materials. At present, FLG/activated carbon electrodes can match the performance of those produced from activated carbon with a carbon black conductive additive and, with further optimization, we expect will be able to exceed them. Figure: a) Cross sectional SEM image of activated carbon electrode with graphene interfacial layer; b) magnified cross sectional SEM image of graphene interfacial layer; c) cyclic voltammograms at 10 mV/s of the different electrodes mentioned in the abstract. References: [1] A. Gonzalez, E. Goikolea, J.A. Barrena and R. Mysyk; ‘Review on supercapacitors: Technologies and materials’, Renewable and Sustainable Energy Reviews, 58, 1189-1206 (2016). [2] M.F. El-Kady, Y. Shao, and R.B. Kaner; ‘Graphene for batteries, supercapacitors and beyond’, Nature Reviews Materials 1, 16033 (2016). [3] K.R. Paton et al.; ‘Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids’, Nature Materials, 13, 624-630 (2014). [4] C. Backes et al. ‘Spectroscopic metrics allow in-situ measurement of mean size and thickness of liquid-exfoliated graphene nanosheets’, Nanoscale 8, 4311-4323 (2016). Figure 1
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Muslu, Tugdem, Bala Ani Akpinar, Sezgi Biyiklioglu-Kaya, Meral Yuce, and Hikmet Budak. "Comparative Analysis of Coding and Non-Coding Features within Insect Tolerance Loci in Wheat with Their Homologs in Cereal Genomes." International Journal of Molecular Sciences 22, no. 22 (November 16, 2021): 12349. http://dx.doi.org/10.3390/ijms222212349.
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Food insecurity and malnutrition have reached critical levels with increased human population, climate fluctuations, water shortage; therefore, higher-yielding crops are in the spotlight of numerous studies. Abiotic factors affect the yield of staple food crops; among all, wheat stem sawfly (Cephus cinctus Norton) and orange wheat blossom midge (Sitodiplosis mosellana) are two of the most economically and agronomically harmful insect pests which cause yield loss in cereals, especially in wheat in North America. There is no effective strategy for suppressing this pest damage yet, and only the plants with intrinsic tolerance mechanisms such as solid stem phenotypes for WSS and antixenosis and/or antibiosis mechanisms for OWBM can limit damage. A major QTL and a causal gene for WSS resistance were previously identified in wheat, and 3 major QTLs and a causal gene for OWBM resistance. Here, we present a comparative analysis of coding and non-coding features of these loci of wheat across important cereal crops, barley, rye, oat, and rice. This research paves the way for our cloning and editing of additional WSS and OWBM tolerance gene(s), proteins, and metabolites.
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Giannazzo, Filippo, Emanuela Schilirò, Giuseppe Greco, and Fabrizio Roccaforte. "Conductive Atomic Force Microscopy of Semiconducting Transition Metal Dichalcogenides and Heterostructures." Nanomaterials 10, no. 4 (April 22, 2020): 803. http://dx.doi.org/10.3390/nano10040803.
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Semiconducting transition metal dichalcogenides (TMDs) are promising materials for future electronic and optoelectronic applications. However, their electronic properties are strongly affected by peculiar nanoscale defects/inhomogeneities (point or complex defects, thickness fluctuations, grain boundaries, etc.), which are intrinsic of these materials or introduced during device fabrication processes. This paper reviews recent applications of conductive atomic force microscopy (C-AFM) to the investigation of nanoscale transport properties in TMDs, discussing the implications of the local phenomena in the overall behavior of TMD-based devices. Nanoscale resolution current spectroscopy and mapping by C-AFM provided information on the Schottky barrier uniformity and shed light on the mechanisms responsible for the Fermi level pinning commonly observed at metal/TMD interfaces. Methods for nanoscale tailoring of the Schottky barrier in MoS2 for the realization of ambipolar transistors are also illustrated. Experiments on local conductivity mapping in monolayer MoS2 grown by chemical vapor deposition (CVD) on SiO2 substrates are discussed, providing a direct evidence of the resistance associated to the grain boundaries (GBs) between MoS2 domains. Finally, C-AFM provided an insight into the current transport phenomena in TMD-based heterostructures, including lateral heterojunctions observed within MoxW1–xSe2 alloys, and vertical heterostructures made by van der Waals stacking of different TMDs (e.g., MoS2/WSe2) or by CVD growth of TMDs on bulk semiconductors.
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Oliwa, Jakub, Andrzej Skoczowski, Grzegorz Rut, and Andrzej Kornaś. "Water-Deficit Stress in the Epiphytic Elkhorn Fern: Insight into Photosynthetic Response." International Journal of Molecular Sciences 24, no. 15 (July 27, 2023): 12064. http://dx.doi.org/10.3390/ijms241512064.
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Progressive climate changes cause disturbance of water relations in tropical rainforests, where epiphytic ferns are an important element of biodiversity. In these plants, the efficiency of photosynthesis is closely related to the efficiency of water transport. In addition, due to the lack of contact with the soil, epiphytes are extremely susceptible to water-deficit stress. The aim of this experiment was to determine the response of the photosynthetic apparatus of Platycerium bifurcatum to a 6-week water deficit. The hydration and pigment composition of leaves were determined using reflectance spectroscopy and epifluorescence microscopy. Chlorophyll a fluorescence kinetics parameters, fluorescence induction curves (OJIP), low-temperature fluorescence curves at 77 K and proline concentration were analyzed at seven time points. After a decrease in leaf hydration by 10–15%, there were disturbances in the oxidation–reduction balance, especially in the initial photochemical reactions, a rapid decrease in plant vitality (PI) and significant fluctuations in chlorophyll a fluorescence parameters. The relative size of PSI antenna structures compared to PSII decreased in the following weeks of water deficit. Changes in photochemical reactions were accompanied by a decrease in gross photosynthesis and an increase in proline concentration. Changes in the functioning of photosynthesis light phase and the pigment composition of leaves are related to the resistance of elkhorn fern to long-term water deficit.
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Saeed, Qudsia, Wang Xiukang, Fasih Ullah Haider, Jiří Kučerik, Muhammad Zahid Mumtaz, Jiri Holatko, Munaza Naseem, et al. "Rhizosphere Bacteria in Plant Growth Promotion, Biocontrol, and Bioremediation of Contaminated Sites: A Comprehensive Review of Effects and Mechanisms." International Journal of Molecular Sciences 22, no. 19 (September 29, 2021): 10529. http://dx.doi.org/10.3390/ijms221910529.
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Agriculture in the 21st century is facing multiple challenges, such as those related to soil fertility, climatic fluctuations, environmental degradation, urbanization, and the increase in food demand for the increasing world population. In the meanwhile, the scientific community is facing key challenges in increasing crop production from the existing land base. In this regard, traditional farming has witnessed enhanced per acre crop yields due to irregular and injudicious use of agrochemicals, including pesticides and synthetic fertilizers, but at a substantial environmental cost. Another major concern in modern agriculture is that crop pests are developing pesticide resistance. Therefore, the future of sustainable crop production requires the use of alternative strategies that can enhance crop yields in an environmentally sound manner. The application of rhizobacteria, specifically, plant growth-promoting rhizobacteria (PGPR), as an alternative to chemical pesticides has gained much attention from the scientific community. These rhizobacteria harbor a number of mechanisms through which they promote plant growth, control plant pests, and induce resistance to various abiotic stresses. This review presents a comprehensive overview of the mechanisms of rhizobacteria involved in plant growth promotion, biocontrol of pests, and bioremediation of contaminated soils. It also focuses on the effects of PGPR inoculation on plant growth survival under environmental stress. Furthermore, the pros and cons of rhizobacterial application along with future directions for the sustainable use of rhizobacteria in agriculture are discussed in depth.
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Wu, Han-Yu, Qing-Qing Zou, Wen-Tao Ji, Ying-Wei Wang, Wang-Feng Zhang, and Chuang-Dao Jiang. "A Changing Light Environment Induces Significant Lateral CO2 Diffusion within Maize Leaves." International Journal of Molecular Sciences 23, no. 23 (November 22, 2022): 14530. http://dx.doi.org/10.3390/ijms232314530.
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A leaf structure with high porosity is beneficial for lateral CO2 diffusion inside the leaves. However, the leaf structure of maize is compact, and it has long been considered that lateral CO2 diffusion is restricted. Moreover, lateral CO2 diffusion is closely related to CO2 pressure differences (ΔCO2). Therefore, we speculated that enlarging the ΔCO2 between the adjacent regions inside maize leaves may result in lateral diffusion when the diffusion resistance is kept constant. Thus, the leaf structure and gas exchange of maize (C4), cotton (C3), and other species were explored. The results showed that maize and sorghum leaves had a lower mesophyll porosity than cotton and cucumber leaves. Similar to cotton, the local photosynthetic induction resulted in an increase in the ΔCO2 between the local illuminated and the adjacent unilluminated regions, which significantly reduced the respiration rate of the adjacent unilluminated region. Further analysis showed that when the adjacent region in the maize leaves was maintained under a steady high light, the photosynthesis induction in the local regions not only gradually reduced the ΔCO2 between them but also progressively increased the steady photosynthetic rate in the adjacent region. Under field conditions, the ΔCO2, respiration, and photosynthetic rate of the adjacent region were also markedly changed by fluctuating light in local regions in the maize leaves. Consequently, we proposed that enlarging the ΔCO2 between the adjacent regions inside the maize leaves results in the lateral CO2 diffusion and supports photosynthesis in adjacent regions to a certain extent under fluctuating light.
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Crochiere, Marsha L., Stefan Hannus, Kerrin Hansen, Frank Becker, Joel Ellis, Margaret S. Lee, and Yosef Landesman. "Development of a Pharmacodynamic Assay for XPO1 Occupancy Using Fluorescence Cross Correlation Spectroscopy (FCCS)." Blood 126, no. 23 (December 3, 2015): 2487. http://dx.doi.org/10.1182/blood.v126.23.2487.2487.
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Abstract Introduction: Selinexor, a Selective Inhibitor of Nuclear Export (SINE) compound, is an anti-cancer drug that is currently being evaluated in Phase I and II clinical trials for the treatment of solid and hematological malignancies (clinicaltrials.gov). XPO1 (exportin 1/CRM1), the target of selinexor, is commonly overexpressed in cancer. XPO1 is the main nuclear export protein with over 200 different protein cargos which include tumor suppressor and growth regulatory proteins. Binding of selinexor to XPO1 inhibits the nuclear export of TSPs and GRPs and induces cell cycle arrest followed by cancer cell apoptosis.Certain cancers are more sensitive to selinexor than others. We hypothesized that part of the inherent differences in sensitivities are attributed to different levels of target inactivation upon selinexor binding. To predict patient response to treatment, we developed a binding assay based on Fluorescence Cross Correlation Spectroscopy (FCCS) to measure XPO1 target occupancy in cancer cells. Methods: Cells were treated in culture for 4 hours with 0-10 µM selinexor. Cells were harvested, lysed, and cleared by ultracentrifugation. In vivo, nude mice were inoculated in both flanks with Z-138 tumor cells. Once tumors reached approximately 250 mm3, mice were administered a single dose of 0, 5, 10, 15, or 20 mg/kg selinexor. Tumors were harvested 6 hours post-dose, lysed, and cleared by ultracentrifugation. Cell or tumor supernatants were incubated with a fluorescently labeled antibody (Ab) against XPO1 and fluorescently labeled Leptomycin B (LMB). To allow binding of labeled Ab and LMB to XPO1, samples were measured by FCCS after 15, 120, and 1200 minutes. FCCS measures signal fluctuations induced by fluorescent molecules diffusing through an illuminated microscopic detection spot. The approach allows simultaneous monitoring of 2 different fluorescently labeled molecules and extracts information on particle concentration, size, binding state, and molecular brightness. Interacting particles are scored by codiffusion. FCCS measurements were performed to quantify the concentration of dually labeled XPO1 molecules in prepared lysates. In the absence of selinexor, complexes of XPO1, the labeled antibody (aXPO1ABATTO488), and the red labeled LMB (LMBDY647) are formed and indicate low target occupancy. XPO1 molecules occupied by selinexor cannot bind to the labeled tracer and decrease the number of dually labeled particles. Accordingly, loss of complex formation is a measure of target occupancy in cells and tumor samples. Results: Comparison of cytotoxicity and XPO1 binding in hematological cell lines treated with increasing concentrations of selinexor in vitro indicated that XPO1 occupancy by selinexor occurred to the same extent regardless of drug sensitivity (Table 1). However, there were two observations that distinguished the selinexor-resistant cell line THP-1 from the other 3 sensitive cell lines (Table 1): 1. Untreated THP-1 cells had the highest XPO1 occupancy of fluorescently labeled LMB compared to lower values in more sensitive cells, and 2. Treatment of THP-1 cells with very low dose selinexor (10 nM) demonstrated lower saturation of XPO1 protein, while treatment of MV-4-11, Z-138, and MM.1S with 10 nM selinexor resulted in marked XPO1 occupancy. These results suggest that high levels of XPO1 proteins might lead to resistance to XPO1 inhibition. We are currently testing whether these two observations are general predictors of resistance in other cell lines. Mouse studies showed that XPO1 target occupancy could be measured in tumors and that there was a dose-dependent effect of selinexor on complex formation with >90% target saturation at 10 mg/kg selinexor (estimated Cmax ~2400 ng/ml). Conclusions: For the first time, the FCCS method permits the direct measurement XPO1 occupancy by selinexor in cells and tumors following treatment. Here, we demonstrate XPO1 occupancy saturation at 10 mg/kg (30 mg/m2) in mice, a dose active against xenografts, and consistent with doses of selinexor that show anti-cancer activity in patients with heavily pretreated hematologic and solid tumors. Table 1. Cytotoxicity and FCCS values for cell lines. Cell Line MTT IC50 (nM) FCCS IC50 (nM) FCCS Complex without selinexor (nM) FCCS Complex with 10 nM selinexor (nM) THP-1 1060 35.5 3.95 3.19 MV-4-11 20 56.2 2.55 1.9 Z-138 40 24.0 0.72 0.66 MM.1S 20 20.4 2.25 1.64 Disclosures Crochiere: Karyopharm: Employment. Hannus:Intana: Employment. Hansen:Intana: Employment. Becker:Intana: Employment. Ellis:Karyopharm Therapeutics Inc: Employment. Lee:Karyopharm Therapeutics Inc: Employment. Landesman:Karyopharm: Employment.
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Merle, L., A. Delpoux, A. Mlayah, and J. Grisolia. "Multiscale modeling of the dynamical conductivity of self-assembled nanoparticle networks: Numerical simulations vs analytical models." Journal of Applied Physics 132, no. 1 (July 7, 2022): 015107. http://dx.doi.org/10.1063/5.0097997.
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Impedance spectroscopy experiments are able to reveal the fundamental charge transport properties of a wide variety of complex disordered and nano-structured materials provided that appropriate modeling tools are used. In this paper, we present a numerical simulation-based approach to model the dynamical conductivity of networks formed by self-assembled metal nanoparticles. Inter-particle nano-resistance and nano-capacitance are implemented at the nano-scale assuming inter-particle charge transfer and accumulation mechanisms that can be adapted depending on the nature of the nano-particles and the surrounding medium. The actual positions and spatial arrangements of the nanoparticles within the network are taken into consideration, allowing the attributes of percolating conducting routes to be extracted, classified, and compared in terms of path conductance and statistical distribution of path lengths. Our findings are contrasted to those obtained using analytic models, which are commonly used, but rely on strong assumptions about the electric properties of the conducting paths. We address these assumptions and show that in the case of weakly disordered systems, there is a general agreement between numerical simulations and analytic modeling-based approaches. In the case of disordered networks where the nano-particle size and position fluctuations are included, we show that the path length distribution is frequency-dependent and can differ significantly from the lognormal distribution usually assumed in the analytic models. The impedance of individual pathways may be extracted from the numerical simulations; we discovered that the conductance and susceptance of a specific path are frequency-dependent and inversely proportional to the path length only in ordered networks. Strong scattering of conductance values is caused by disorder effects. The developed numerical approach is generic and applies to most nano-devices where charge transport relies on percolation; it allows to bridge the gap between the nano-scale and micro-scale electric characteristics and, thus, permits a deeper understanding of the charge transport properties of nano-structured materials.
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Maurer, Julian, Thorsten Walles, and Cornelia Wiese-Rischke. "Optimization of Primary Human Bronchial Epithelial 3D Cell Culture with Donor-Matched Fibroblasts and Comparison of Two Different Culture Media." International Journal of Molecular Sciences 24, no. 4 (February 18, 2023): 4113. http://dx.doi.org/10.3390/ijms24044113.
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In vitro airway models are increasingly important for pathomechanistic analyses of respiratory diseases. Existing models are limited in their validity by their incomplete cellular complexity. We therefore aimed to generate a more complex and meaningful three-dimensional (3D) airway model. Primary human bronchial epithelial cells (hbEC) were propagated in airway epithelial cell growth (AECG) or PneumaCult ExPlus medium. Generating 3D models, hbEC were airlifted and cultured on a collagen matrix with donor-matched bronchial fibroblasts for 21 days comparing two media (AECG or PneumaCult ALI (PC ALI)). 3D models were characterized by histology and immunofluorescence staining. The epithelial barrier function was quantified by transepithelial electrical resistance (TEER) measurements. The presence and function of ciliated epithelium were determined by Western blot and microscopy with high-speed camera. In 2D cultures, an increased number of cytokeratin 14-positive hbEC was present with AECG medium. In 3D models, AECG medium accounted for high proliferation, resulting in hypertrophic epithelium and fluctuating TEER values. Models cultured with PC ALI medium developed a functional ciliated epithelium with a stable epithelial barrier. Here, we established a 3D model with high in vivo–in vitro correlation, which has the potential to close the translational gap for investigations of the human respiratory epithelium in pharmacological, infectiological, and inflammatory research.
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Stadler, Adam Witold, Andrzej Kolek, Krzysztof Mleczko, Zbigniew Zawiślak, Andrzej Dziedzic, and Wojciech Stęplewski. "Noise sources in polymer thick-film resistors." Soldering & Surface Mount Technology 27, no. 3 (June 1, 2015): 115–19. http://dx.doi.org/10.1108/ssmt-04-2015-0014.
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Purpose – The paper aims to get the knowledge about electrical properties, including noise, of modern polymer thick-film resistors (TFRs) in a wide range of temperature values, i.e. from 77 K up to room temperature. The sample resistors have been made of different combinations of resistive compositions, either ED7100 or MINICO (M2013, M2010), and conducting pastes (for contacts) Cu- or Au-based, deposited on FR-4 laminate. Design/methodology/approach – The paper opted for an experimental study using either current noise index measurement in room temperature for large batch of samples or noise spectra measurement in temperature range 77-300 K for selected samples. Obtained noise maps, i.e. plots of power spectral density of voltage fluctuations vs frequency and temperature, have been used for evaluation of noise describing parameters like material noise intensity C and figure of merit K, for TFRs made of different combinations of resistive/conductive materials. Comparison of the parameters gives the information about the quality of the technology and matching the conductive/resistive materials. Findings – Experiments confirmed that the main noise component is 1/f resistance noise. However, low-frequency noise spectroscopy revealed that also noise components of Lorentzian shape, associated with thermally activated noise sources exist. Their activation energies have been found to be of a few tenths of eV. Research limitations/implications – The noise intensity of polymer TFRs depends on technology process and/or contacts materials. The use of Au contacts leads to better noise properties of the resistors. The results of the studies might be helpful for further improvement of thick-film technology, especially for manufacturing low-noise, stable and reliable TFRs. Practical implications – The paper includes indications for the materials selection for thick-film technology to manufacture low-noise, reliable and stable TFRs. Originality/value – Experimental studies of electrical properties of polymer TFRs by means of noise spectra measurements in wide range of temperature is rare. They give fundamental knowledge about noise sources in the modern passive electronic components as well as practical indications of selection material for thick-film technology, to obtain high performance components and get technological advantage.
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Grishina, Elena P., Nadezhda O. Kudryakova, Aleksandr N. Predein, and Sergej V. Belyaev. "KINETICS OF CORROSION OF STEEL St3 IN PO-6СT FOAMING AGENT FOR FIRE EXTINGUISHING. ELECTROCHEMICAL INVESTIGATION." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 61, no. 1 (December 21, 2017): 30. http://dx.doi.org/10.6060/tcct.20186101.5666.
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Foaming agents for extinguishing fires are to be stored in a concentrated form. Storage of concentrate in St3 steel containers is allowed. However, this metal can be corroded, which damages the storage tanks, and corrosion products of steel reduce the quality of the foaming agent. The kinetics of metal corrosion depends on the type of foaming agent and the temperature storage conditions. In this study, the corrosion behavior of St3 steel in commercial concentrate of the PO-6CT foam for extinguishing fires was studied by electrochemical methods (potentiometry, voltammetry, electrochemical impedance spectroscopy) at 27±1°С. It was found that during the testing period, which lasted for 6 weeks, the corrosion potential of steel began to undergo sharp fluctuations, but its value was generally negative than the initial value. The greatest changes in the impedance of the steel sample during the corrosion process occur in the first two weeks of contact with the corrosive medium. An equivalent circuit, which takes into account the two time constants was used to interpret the impedance data of the corrosion process which was occurred under the porous layer of corrosion products. It is shown, the charge transfer resistance (Rct) between the corrosive metal and corrosion products, the capacity of the double electrical layer (Cdl) and the electrolyte resistance in the pores of the corrosion products layer (Rpo) highly increase during this period. Subsequently, the Rct is decreased and stabilized at a level 3 times lower than the original value. The properties of the metal/electrolyte interface were stabilized, but the Cdl value and the Rpo values are increased by 5 times and by 10 times, respectively. This indicates a high degree of the surface rust and a stable state of the corrosion products layer. Polarization studies have shown that the anodic and cathodic polarization curves have a Tafel slope equals to 0.147 V and 0.187 V, respectively. This is due to the presence of an oxide-hydroxide film on the electrode surface. The calculated value of the mass index of corrosion rate is 2.46×10-8 kg×m-2×s-1. Thus, the experiment showed that the St3 corrosion proceeds with activation control of the process rate. The corrosive behavior of St3 in the PO-6CT foaming agent for fire extinguishing is a consequence of the physicochemical features of this system. Primary corrosion products of steel St3 (Fe+2 ions) can be readily oxidized to Fe+3 by dissolved oxygen of air, and Fe+3 ions undergo hydrolysis, which leads to an increase in the acidity of the foaming agent and, correspondingly, an increase in its corrosive activity.Forcitation:Grishina E.P., Kudryakova N.O., Predein A.N., Belyaev S.V. Kinetics of corrosion of steel St3 in PO-6СT foaming agent for fire extinguishing. electrochemical investigation. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N1. P. 30-36
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Tvrdá, Eva, Daniel Lovíšek, Eliška Gálová, Marianna Schwarzová, Eva Kováčiková, Simona Kunová, Jana Žiarovská, and Miroslava Kačániová. "Possible Implications of Bacteriospermia on the Sperm Quality, Oxidative Characteristics, and Seminal Cytokine Network in Normozoospermic Men." International Journal of Molecular Sciences 23, no. 15 (August 4, 2022): 8678. http://dx.doi.org/10.3390/ijms23158678.
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This study focused on the identification of bacterial profiles of semen in normozoospermic men and their possible involvement in changes to the sperm structural integrity and functional activity. Furthermore, we studied possible fluctuations of selected cytokines, oxidative markers, and antibacterial proteins as a result of bacterial presence in the ejaculate. Sperm motility was assessed with computer-assisted sperm analysis, while sperm apoptosis, necrosis and acrosome integrity were examined with fluorescent methods. Reactive oxygen species (ROS) generation was quantified via luminometry, sperm DNA fragmentation was evaluated using the TUNEL protocol and chromatin-dispersion test, while the JC-1 assay was applied to evaluate the mitochondrial membrane potential. Cytokine levels were quantified with the biochip assay, whilst selected antibacterial proteins were quantified using the ELISA method. The predominant species identified by the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry were Staphylococcus hominis, Staphylococcus capitis and Micrococcus luteus. The results revealed that the sperm quality decreased proportionally to the increasing bacterial load and occurrence of conditionally pathogenic bacteria, including Enterococcus faecalis, Staphylococcus aureus and Escherichia coli. Antimicrobial susceptibility tests revealed a substantial resistance of randomly selected bacterial strains to ampicillin, vancomycin, tobramycin, and tetracycline. Furthermore, an increased bacterial quantity in semen was accompanied by elevated levels of pro-inflammatory cytokines, including interleukin-1, interleukin-2, interleukin-6, tumor necrosis factor alpha as well as ROS overproduction and lipid peroxidation of the sperm membranes. Our results suggest that semen quality may be notably affected by the bacterial quantity as well as quality. It seems that bacteriospermia may be associated with inflammatory processes, oxidative stress, sperm structural deterioration, and a subsequent risk for the development of subfertility, even in normozoospermic males.
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Simon, Christopher, Tomoko Soga, Nafees Ahemad, Saatheeyavaane Bhuvanendran, and Ishwar Parhar. "Kisspeptin-10 Rescues Cholinergic Differentiated SHSY-5Y Cells from α-Synuclein-Induced Toxicity In Vitro." International Journal of Molecular Sciences 23, no. 9 (May 6, 2022): 5193. http://dx.doi.org/10.3390/ijms23095193.
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The neuropathological substrate of dementia with Lewy bodies (DLB) is defined by the inextricable cross-seeding accretion of amyloid-β (Aβ) and α-synuclein (α-syn)-laden deposits in cholinergic neurons. The recent revelation that neuropeptide kisspeptin-10 (KP-10) is able to mitigate Aβ toxicity via an extracellular binding mechanism may provide a new horizon for innovative drug design endeavors. Considering the sequence similarities between α-syn’s non-amyloid-β component (NAC) and Aβ’s C-terminus, we hypothesized that KP-10 would enhance cholinergic neuronal resistance against α-syn’s deleterious consequences through preferential binding. Here, human cholinergic SH-SY5Y cells were transiently transformed to upsurge the mRNA expression of α-syn while α-syn-mediated cholinergic toxicity was quantified utilizing a standardized viability-based assay. Remarkably, the E46K mutant α-syn displayed elevated α-syn mRNA levels, which subsequently induced more cellular toxicity compared with the wild-type α-syn in choline acetyltransferase (ChAT)-positive cholinergic neurons. Treatment with a high concentration of KP-10 (10 µM) further decreased cholinergic cell viability, while low concentrations of KP-10 (0.01–1 µM) substantially suppressed wild-type and E46K mutant α-syn-mediated toxicity. Correlating with the in vitro observations are approximations from in silico algorithms, which inferred that KP-10 binds favorably to the C-terminal residues of wild-type and E46K mutant α-syn with CDOCKER energy scores of −118.049 kcal/mol and −114.869 kcal/mol, respectively. Over the course of 50 ns simulation time, explicit-solvent molecular dynamics conjointly revealed that the docked complexes were relatively stable despite small-scale fluctuations upon assembly. Taken together, our findings insinuate that KP-10 may serve as a novel therapeutic scaffold with far-reaching implications for the conceptualization of α-syn-based treatments.
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Schefold, Josef, and Hendrik Pöpke. "(Invited) Durability of Electrolyte Supported Solid Oxide Cells for Steam Electrolysis: Results from Cell Testing in the 20,000 h to 50,000 Hours Range." ECS Meeting Abstracts MA2022-01, no. 39 (July 7, 2022): 1738. http://dx.doi.org/10.1149/ma2022-01391738mtgabs.
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There is a current fast development of water/steam electrolysis for the production of hydrogen from renewable energy sources. (Multi) MW power demonstration units using the different (low and high temperature) technologies are, e.g., subject of the R&D project H2Giga funded by the German Federal Ministry of Education and Research /1/. Steam electrolysis with solid oxide cells (SOC) is characterised by a high energy-conversion efficiency, notably if steam is available, such as via a heat source of moderate temperature for steam generation. Approaches for a matching to a fluctuating load, important in the context of operation with renewable energy sources, are also under development with the SOC technology /2/. For the SOC electrolysers, durability analysis of the cells in a time scale appropriate for application remains an important development step. Cell (or short stack) testing allows a rather precise control of the cell temperature which facilitates quantification of degradation for the practically required degradation rates well below 10 mV/1000 h (cf. /3/). In this contribution, our testing results will be updated, with up to about 50,000 h operation using electrolyte supported cells (ESC) with Ni/GDC hydrogen electrodes and different types of electrolyte (10Sc1CeSZ, 6Sc1CeSZ, 3YSZ). As reference for cell durability serves a 23,000 h steam electrolysis test with a cell with 6Sc1CeSZ electrolyte /4/. However, cells with the known robust 3YSZ electrolyte seem to yield a comparably low long-term degradation, together with better initial stability /5/. The use of an electrolyte of high ionic conductivity, 10Sc1CeSZ, allows a relatively low initial temperature (<800°C) for a cell voltage close to the thermal neutral voltage for 0.6 Acm-2 current density. This, in turn, leaves a wide temperature margin for compensation of voltage degradation via a temperature increase (cf. initial period of the test in /3/). The results from the durability tests serve as examples for a large degree of SOFC/SOEC reversibility achievable with the ESC. Moreover, the relatively thick electrolyte layer of the ESC with its large ohmic resistance comes along with a high ohmic contribution in the overall degradation in most tests. The different degradation contributions were separated with in-situ impedance spectroscopy without interrupting the DC current flow. References: /1/ www.wasserstoff-leitprojekte.de/leitprojekte/h2giga. /2/ J. Schefold, A. Brisse, A. Surrey, C. Walter, Int. J. Hydrogen Energy, 45 (2020) 5143-54. /3/ J. Schefold, H. Poepke, A. Brisse, ECS Transactions, 97 (7) (2020) 553-563. /4/ J. Schefold, A. Brisse, H. Poepke, Int. J. Hydrogen Energy, 42 (2017) 13415-26. /5/ A. Brisse, J. Schefold, C. Walter, Proceedings 14th European SOFC & SOE Forum, B0904, 20 - 23 October 2020, Lucerne (Switzerland), pp. 306-314.
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Steppke, Alexander, Sandra Hamann, Markus Koenig, Andrew Mackenzie, Kristin Kliemt, Cornelius Krellner, Marvin Kopp, et al. "Microstructuring YbRh2Si2 for resistance and noise measurements down to ultra-low temperatures." New Journal of Physics, December 5, 2022. http://dx.doi.org/10.1088/1367-2630/aca8c6.
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Abstract he discovery of superconductivity in the quantum critical Kondo-lattice system YbRh2Si2 at an extremely low temperature of 2 mK has inspired efforts to perform high-resolution electrical resistivity measurements down to this temperature range in highly conductive materials. Here we show that control over the sample geometry by microstructuring using focused-ion-beam (FIB) techniques allows to reach ultra-low temperatures and increase signal-to-noise ratios (SNR) tenfold, without adverse effects to sample quality. In five experiments we show four-terminal sensing resistance and magnetoresistance measurements which exhibit sharp phase transitions at the Néel temperature, and Shubnikov-de-Haas (SdH) oscillations between 13 T and 18 T where we identified a new SdH frequency of 0.39 kT. The increased SNR allowed resistance fluctuation (noise) spectroscopy that would not be possible for bulk crystals, and confirmed intrinsic 1/f -type fluctuations. Under controlled strain, two thin microstructured samples exhibited a large increase of TN from 67 mK up to 188 mK while still showing clear signatures of the phase transition and SdH oscillations. SQUID-based thermal noise spectroscopy measurements in a nuclear demagnetisation refrigerator down to 0.95 mK, show a sharp superconducting transition at Tc = 1.2 mK. These experiments demonstrate microstructuring as a powerful tool to investigate the resistance and the noise spectrum of highly conductive correlated metals over wide temperature ranges.