Добірка наукової літератури з теми "Resistance fluctuation spectroscopy"

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.

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.

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.

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.

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.

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.

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.

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).

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.

In condensed matter physics, the concepts of topology and symmetry are of paramount importance, particularly in understanding quantum phase transitions. Topology classifies objects based on their topological properties, which are properties that are preserved under continuous deformation. This is relevant to a wide range of phenomena, such as topological insulators and the quantum Hall effect. On the other hand, symmetry is used to understand phase transitions, where a higher symmetry group is broken into a lower symmetry subgroup. The study of quantum phases and phase transitions is a fundamental theme in condensed matter physics, and topology and symmetry play a critical role in comprehending these phenomena. This field of research is vital in understanding the behavior of matter at the quantum level and has potential applications in quantum computing and other technologies This thesis mainly explored the quantum phase transitions through resistance fluctuation spectroscopy. The first part of the thesis focused on uncovering the electronic phases in 1T-TaS2 . The presence of a low temperature insulating phase in 1T-TaS2 has been a matter of debate among researchers, with recent theoretical calculations suggesting that it is a result of out-of-plane stacking rather than a Mott insulator Our findings suggest that out-of-plane stacking might be responsible for the observed insulating phase at low temperatures. Our study showed that the device exhibited metallic behavior at low temperatures, but an insulating phase was restored over a narrow range as the temperature increased. The system also exhibited signs of electrical phase separation prior to the restoration of the insulating phase, as seen through quantized jumps in conductance between two well-defined levels. These jumps were speculated to result from metallic domain walls separating insulating regions. In the second part of the thesis, we studied the resistance fluctuations near the Lifshitz transition in WTe2 using electrical and thermal transport studies. The presence of two holes and two electron pockets in the band structure at low temperatures and the disappearance of the hole pockets above the transition temperature could be related to a topological phase transition in the material. An electrical noise peak was observed at the transition temperature, which was attributed to inter-band scattering at Weyl points. The study emphasized the importance of high-quality samples for detecting the unique properties of Weyl semi-metals. In the final section of the thesis, the behavior of charge dynamics in a quasi-two-dimensional electron gas (q2DEG) at the LaScO3/SrTiO3 interface was studied through resistance fluctuation spectroscopy. Despite persistent efforts, the source of charge carriers at the oxide interface remains elusive. [7, 8, 9]. Our study indicated that the role of oxygen vacancies in transport properties at the oxide interface requires further exploration. The q2DEG at the LaScO3/SrTiO3 interface was found to exhibit random telegraphic noise (RTN) at high temperatures, which disappeared below 40 K, indicating a temperature-dependent behavior of the charge dynamics. Based on these observations, we posit that the RTN is likely the result of charge exchange between mid-gap defect states in the bulk and the q2DEG.