Transfer Coefficient Research Articles

Electrochemical Extraction of Fission Element Samarium from Molten NaCl-2CsCl Eutectic Salt Using the Liquid Gallium Cathode

The effective extraction of neutron poison samarium from nuclear waste to prevent reactions with metallic uranium is crucial for the sustainable development of nuclear energy. The electrochemical recovery of samarium on the liquid gallium cathode from the NaCl-2CsCl molten salts has been investigated by a variety of electrochemical techniques, and its electrochemical reduction properties and kinetic parameters have been provided. It was revealed that the reduction reaction on the Mo cathode of Ga(III) to Ga(0) and Sm(III) to Sm(II) is a two-step and one-step reaction process, respectively, and both reactions are reversible. The diffusion coefficients of Ga(III)/Ga(II) and Sm(III)/Sm(II) were identified, and the activation energies were 20.07 and 42.96 kJ mol–1, respectively. Simultaneously, the codeposition mechanism of Ga(III) and Sm(III) on the Mo cathode was systematically investigated, and the potential and types of formation of binary intermetallic compounds were explored. Subsequently, it was determined that there are two main reaction processes for Sm(III) on the liquid Ga cathode, and the deposition potential of Sm becomes more positive due to the formation of the alloy. The exchange current density values of Sm(III)/Sm(Ga) obtained by both linear polarity (LP) and Tafel techniques increased with temperature, meanwhile the charge transfer resistance decreased, as well as the transfer coefficient. In addition, the apparent electrode potential of Sm(III)/Sm(Ga) was also calculated. Based on the electrochemical analysis, the fission element Sm was deposited on the liquid Ga cathode by potentiostatic electrolysis at a suitable potential, and the alloy products were verified by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Ultimately, the highest separation efficiency of Sm on the liquid Ga cathode reached 92.43% according to the analysis of inductively coupled plasma atomic emission spectrometry (ICP-AES) results.

Introducing Hybrid Defects of Silicon Doping and Oxygen Vacancies into MOF-Derived TiO2-X @Carbon Nanotablets Toward High-Performance Sodium-Ion Storage.

Titanium dioxide (TiO2 ) is a promising anode material for sodium-ion batteries (SIBs), which suffer from the intrinsic sluggish ion transferability and poor conductivity. To overcome these drawbacks, a facile strategy is developed to synergistically engineer the lattice defects (i.e., heteroatom doping and oxygen vacancy generation) and the fine microstructure (i.e., carbon hybridization and porous structure) of TiO2 -based anode, which efficiently enhances the sodium storage performance. Herein, it is successfully realized that the Si-doping into the MIL-125 metal-organic framework structure, which can be easily converted to SiO2 /TiO2-x @C nanotablets by annealing under inert atmosphere. After NaOH etching SiO2 /TiO2-x @C which contains unbonded SiO2 and chemically bonded SiOTi, thus the lattice Si-doped TiO2-x @C (Si-TiO2-x @C) nanotablets with rich Ti3+ /oxygen vacancies and abundant inner pores are developed. When examined as an anode for SIB, the Si-TiO2-x @C exhibits a high sodium storage capacity (285mAhg-1 at 0.2Ag-1 ), excellent long-term cycling, and high-rate performances (190mAhg-1 at 2Ag-1 after 2500 cycles with 95.1% capacity retention). Theoretical calculations indicate that the rich Ti3+ /oxygen vacancies and Si-doping synergistically contribute to a narrowed bandgap and lower sodiation barrier, which thus lead to fast electron/ion transfer coefficients and the predominant pseudocapacitive sodium storage behavior.

Face stability of shallowly buried large-section EPB box jacking crossing the Beijing-Hangzhou Grand Canal

The mechanical response of conditioned soil in an earth chamber is crucial for maintaining the face stability of earth pressure balance (EPB) box jacking. This study presents the project of a shallowly buried large-section box jacking crossing the Beijing-Hangzhou Grand Canal in Suzhou, China. The characteristics of tunneling parameters, such as the earth chamber pressure pe, total jacking force Pf and frictional force Ffric, were revealed by field measurements. A refined three-dimensional finite difference model was developed using the fluid–solid coupling analysis mode to evaluate the tunnel face stability, in which the geometric configurations of box jacking machine and the contact interfaces between different components were considered explicitly. In addition, the differences between driving and stoppage of box jacking machine were also considered. Upon the successful calibration of the numerical model, the transfer mechanism and the face support efficacy of conditioned soil are evaluated. In the end, a parametric study was conducted to discuss the influences of conditioned soil permeability, shear strength and thickness. The results indicate that the permeability of conditioned soil has no significant influence on its mechanical response, and a larger shear strength can obviously enhance the stress level at the lower part of the earth chamber. In addition, a larger thickness of conditioned soil can reduce its transfer coefficient and the fluctuation of earth chamber pressure.

Imaging concentration fields in microfluidic fuel cells as a mass transfer characterization platform

Microfluidic fuel cells (MFCs) are microfluidic electrochemical conversion devices that are used to power electrical equipment. Their performance relies on improving reactant mass transfer at the electrode interface. In this work, a MFC is developed to implement a novel imaging technique that allows the measurement of reactant concentration fields, featuring formic acid as the fuel and potassium permanganate as the oxidant. The concentration fields were imaged based on transmitted visible spectroscopy, which links the light intensity passing through the MFC to its local reactant concentration. An analytical model was developed to estimate the mass diffusivity and kinetic reaction rate coefficient. For the first time, mass transport and transfer coefficient were simultaneously measured during operation. These parameters estimated using the proposed technique can be implemented in a numerical model to predict the MFC performance and concentration distribution. This work paves the way towards advanced imaging tools for operando mass transfer characterizations in microfluidics and Tafel kinetic characterization in many electrochemical devices.

Phytoremediation potential depends on the degree of soil pollution: a case study in an urban brownfield

Phytoremediation is a cost-effective nature-based solution for brownfield reclamation. The choice of phytoextraction or phytostabilization strategies is highly relevant when planning full-scale treatments. A suitable approach to identify such species involves the evaluation of plants that grow spontaneously on the contaminated sites. Here, we sought to determine the phytoremediation potential of three spontaneous plant species, namely the trees Acer pseudoplatanus L (A. pseudoplatanus) and Betula celtiberica Rothm. & Vasc (B. celtiberica), and the shrub Buddleja davidii Franch (B. davidii), for the recovery of an urban brownfield. To determine the response of the species to the degree of contamination, we conducted soil and vegetation sampling inside and outside the site. The concentrations of As, Cu, and Zn in soil and plant samples were measured, and then various indexes related to phytoremediation were calculated. The translocation factor and transfer coefficient indicated that vegetation outside the brownfield had phytoextraction capacity while the same plants inside the brownfield revealed phytostabilization properties. Given our results, we propose that the selected species are suitable for phytostabilization strategies in areas with high concentrations of contaminants, whereas they could be used for phytoextraction only in soils with low or moderate levels of pollution.Graphical

Enhancement of phytoextraction efficiency coupling Pteris vittata with low-dose biochar in arsenic-contaminated soil

Phytoremediation of arsenic (As) by Pteris vittata (P. vittata) is a cost-effective and environmentally friendly method for restoring As-contaminated sites. However, the phytoextraction efficiency is low in some cases, such as clay soil, thus biochar was applied to enhance the efficiency of As extraction. The paper investigated the effect of biochar on soil characteristic, As mobility, and As uptake in P. vittata with a 90-day greenhouse experiment. Biochar derived from rice straw was added at rates of 0.5, 1.5, and 4% (w/w). The results showed that, under biochar amendment, soil pH raised from 5.24 to 6.03 and 4.91 to 5.85, soil dissolved organic carbon (DOC) increased 11.1–46.1% and 2.8–11.2%, respectively, in rhizosphere and bulk soils. Biochar also increased soil catalase (CAT) activity significantly, especially for the rhizosphere soil. Besides, biochar increased the labile As in the soils and transfer coefficient from roots to aboveground, thereby enhancing As accumulation by P. vittata tissues. The accumulation of As in fronds of P. vittata was up to 350 mg kg−1 in 1.5% biochar, which was more than twice the control and far beyond other biochar treatments. The results indicate that biochar addition is favorable to improve phytoremediation of P. vittata in As-contaminated soil and 1.5% (w/w) biochar may be a reasonable application ratio, thus providing an effective solution to enhance the efficiency of As phytoextraction.

Dynamic Plastics Flow Analysis for Korea between 1982-2020

Objectives : This study analyzed Korea’s plastic flows and stocks over the past 40 years to provide a quantitative basis for the nation’s plastic management and circular economy.Methods : Dynamic material flow analysis was conducted to quantify plastic flows across lifecycle stages and to estimate the size of in-use stocks. Focusing on 10 resins and 7 products, the analysis was conducted between 1982 and 2020 and at a national level. Production and trade flows were mainly quantified based on statistical and literature data, while consumption and waste flows were estimated using transfer coefficients. Different from static material flow analysis, waste flows were calculated based on the products’ lifetime distribution functions, and the changes in in-use stocks were estimated.Results and Discussion : Between 1982 and 2020, Korea produced 237 million tons of resins and provided 242 million tons of primary plastic products after the trade. Approximately 207 million tons of final products were consumed, 71% of which was generated as post-consumption waste and additional 3.8 million tons of waste was generated from the manufacturing stage. The amount of in-use stock of plastics was estimated to be 60 million tons. Of the 151 million tons of plastic waste, 24% was landfilled, 29% was incinerated and 47% was entered into sorting and recycling facilities. After sorting and recycling, 27 million tons were estimated to be recycled into products. From 1982 to 2020, per-capita plastic consumption increased from 15 kg to 150 kg, and per-capita waste generation increased from 2 kg to 139 kg. Packaging and containers, or PP and PE represented a major share of plastic consumption as well as waste generation. On the other hand, about half of the plastic stock was used for buildings and more than 50% of the building plastic stock was PVC.Conclusion : This study used a dynamic material flow analysis to quantify plastic flows over time, identify the composition of plastic waste flows according to resins or products, and estimate the size of in-use stocks. Such information on the waste composition and in-use stocks would be useful to improve recycling systems and estimate future waste flows.

Detection of bisphenol A in thermal paper receipts and assessment of human exposure: A case study from Sharjah, United Arab Emirates.

Bisphenol A (BPA) is an industrial chemical that is widely used in various industrial applications. It has concerns in its use as a color developer in thermal paper receipts since it is identified as an endocrine disruptor and causes hormonal disturbances. In this study, thirty thermal paper receipt samples were randomly collected from various locations in Sharjah, United Arab Emirates and analyzed using high performance liquid chromatography-mass spectrometry. Sixty percent (60%) of receipt samples showed BPA levels above the acceptable limit (200 ng/mg) set by the European Union (EU) for thermal papers. On the other hand, 40% of the samples reported very low BPA levels (< 0.02 ng/mg). However, estimated weight adjusted daily intakes (EDI) ranged between 8.22 ×10-11 and 0.000812 μg/kg bw/day for the general population, and between 7.89×10-9 and 0.0681 μg/kg bw/day for the occupationally exposed cashiers. Thus, all calculated EDIs were below the European Food Safety Authority Tolerable Daily Intake (4 μg/kg·bw/day) and the provisional Health Canada Tolerable Daily Intake (25 ug/kg bw/day) under varying paper-to-skin transfer coefficients and absorption fractions. Nevertheless, due to its health effects and recent legal restrictions by EU, the occurrence of co-exposure to dietary and non-dietary sources should be considered in the health risk assessment of Bisphenol A, mainly for people with frequent occupational exposure to thermal paper, and especially with the increased use of sanitizers. The current study is a first within the UAE context in relation to BPA in thermal paper receipts, thus its significance especially with the recent EU enforcement of BPA limits in paper receipts. The study highlights that proper policies as well as education and awareness may assist in limiting transdermal BPA exposure for the general and occupationally exposed populations.

Semi-microscopic Theory for the Current Rectification Phenomenon in Nanogap Molecular Devices.

A semi-microscopic theory is developed for heterogeneous electron transfer (HET) kinetics based on the energy level alignment approach at self-assembled monolayer (SAM) covered metal electrodes. Theory provides the electronic and molecular property-dependent equations for the HET rate constant (k0) and the transfer coefficient (α) for potential. k0 is formulated using the activation free energy as a product of the SAM covered metal work function (WF) and fractional electronic charge exchanged at the transition state (attained through the alignment of the frontier molecular orbital (FMO) energy level of the electroactive group with the WF of metal). k0 is a function of the metal jellium electronic screening length and dielectric and of the molecular self-assembly (through its dipole moment, size, and packing density) and the FMO energies of electroactive groups. The operative potential at the transition state is governed by α, which is a function of molecular spacer length and characteristic electronic-dipolar coupling length. The current rectification phenomenon in nanogap molecular devices is theoretically analyzed using equations for k0 and α for SAM covered source and drain electrodes. Theory unravels the LUMO or HOMO dichotomy for a given metal: (i) for the HOMO assisted ET, the metal with a high WF has a high current rectification ratio (RR), while (ii) for the LUMO assisted ET, the metal with a low WF has a high current RR in asymmetrical devices. Theory predicts the reversal in current rectification by altering the dipole moment of the anchoring molecule, the HOMO/LUMO energy of the electroactive groups, and the nature of the metal. Finally, theory shows qualitative and quantitative coherence with the reported experimental current-potential response of molecular device.

Parametric Investigations of Drying Roselle Calyces Flower

In this research, a new dryer which use halogen lamp must be designed and the drying performance of Roselle is to be investigate. The power of lamp is varied (50, 75, 100, 125, 150, 175, 200, 225) W. The result shows that higher power of lamp produce high temperature and low humidity which shorten the drying time of Roselle. The drying rate of each parameter shows slightly different pattern as temperature does not constant since the power supply does not produce constant voltage or current. The heat of vaporization increase as the power of lamp is increase and quantity of heat energy to raise temperature of Roselle at certain mass also increase. The most suitable parameter is 200W since the colour of Roselle does not degrade very much with short drying time 240mins, heat, transfer coefficient 91.51 W/2K . Maximum has a sour taste and is ordinarily utilized in the readiness of cold and hot drinks and as energy needed to heat Roselle at 62⁰C is 17.02 kJ and heat of vaporization are determined to be 2612.3 kJ/kg.

Lung Function Impairment, Associating Hyperinflation with Impaired Diffusion Capacity and Transfer Coefficient, Is a Risk Factor for Hip Osteoporosis in Patients with Chronic Obstructive Pulmonary Disease.

90 COPD patients underwent dual-energy X-ray absorptiometry (DEXA) and pulmonary function tests. 26% of the COPD patients were osteoporotic. In univariate analysis, each functional parameter associated with emphysema, analyzed separately, was not associated with osteoporosis. In contrast, patients with hyperinflation associated with impaired diffusion capacity and transfer coefficient, defined by the association of the three functional indices (DLCO < 70%, DLCO/AV < 80% and CPT > 115%), had significantly more osteoporosis at the total hip (OR: 5.9, CI: 1.5-23.8, p = 0.013). In multivariate analysis, this phenotype was confirmed as an independent factor associated with hip osteoporosis. In contrast, COPD airway obstruction severity, based on FEV1 (%), was not associated with osteoporosis. A lower BMI, female gender and age were also identified as osteoporosis risk factors. COPD patients with hyperinflation associated with impaired diffusion capacity and transfer coefficient are at higher risk for osteoporosis. Pulmonary function tests associated with emphysema detection can help to identify COPD patients with osteoporosis, in addition to the classical risk factors.

Modelling Wave Transmission for Transient Flow and Amplitude-Frequency Characteristics of Tubular String in a Water Injection Well

Fluid wave code communication is used in layered water injection intelligent monitoring systems, but a model of fluid transient flow wave signal transmission is still unknown. Impedance and transfer coefficient in power transmission theory were used to describe transient flow waves in the transmission process of a tubular string in a water injection well and a transient flow wave model was built based on the transfer matrix method. The relationship between pressure and discharge was analyzed when the transient flow waves moved along the tubular string, and the influence of terminal impedance and dip angle of the tubular string on the wave transmission was studied. Simulations showed that the transient flow waves were with standing wave distribution when the transient flow wave signals transmitted in the tubular string. Moreover, the transmission volatility under different terminal impedances was analyzed. The communication frequency was selected according to the wave amplitude ratio between the two ends of the water injection tubular string. The relationship between the influence of tubular string parameters and fluid characteristics on the wave velocity and wave amplitude in the signal transmission process was obtained by simulation analysis. The wave velocity tended to decrease as the gas content increased. As the tube diameter–thickness ratio increased, the wave velocity decreased. Taking data from a water injection well in Daqing Oilfield as an example, a two-layer water injection test platform was built to study the fluctuation of discharge and pressure at monitoring points in the tubular string. The experiment condition was that the depth of the injection well was 1400 m. It was verified by the experiments that the pressure and flow changes in the downhole and wellhead had good consistency during the transmission of transient flow waves. Comparing the experimental results with the numerical results, the errors of the wave velocity and wave amplitude were 0.69% and 3.85%, respectively, indicating the verification of the simulation model. This study provides a theoretical support for the transmission of transient flow wave signals in a water injection tubular string.

Chemical process modelling from a micro to a macro approach: Closing the gap

The present study discusses the multiscale modeling of chemical processes. Despite the existence of very good models for chemical processes from a macroscopic point of view, they can be limited due to the use of poorly estimated transport and transfer coefficients that reduce the accuracy needed for good technology development. Even if models are supported by fundamental relations, there is an unclear connection between their transport coefficient and molecular dynamics. The microscopic models can model several phenomena at atomic or molecular sizes with extreme precision. However, creating a link between the micro and the macro scale takes a huge computation time, as the way they link is not direct. We study this in detail here.

3D printed electrodes design and voltammetric response

The limiting aspects in the voltammetric response of 3D printed electrodes is thoroughly investigated with numerical simulations and new 3D printed electrode designs. Severe diffusion limitations, resulting from a recessed electrode geometry, is found in a commonly used 3D printed electrode and electrochemical cell design, impeding the investigation of electron transfer kinetics at these electrodes by classical methods, such as Nicholson's, widely used on this and similarly mass transport-limited designs. A new 3D printed electrode design, an inlaid disk (non-recessed) geometry, is used to investigate the voltammetric response of printed electrodes in bulk solution, i.e., without mass transport limitations. At this condition, it is clear that the voltammetric response is limited by contact resistance, arising from the printed material low electrical conductivity. Gold modified electrodes, deliberately designed with different contact resistances, highlight the resistive behavior, with quasi-reversible voltammetric profiles. This contrasts with the common assumption of a voltammetric response limited by finite electron kinetics. Electron transfer rate constants (k0) and transfer coefficients (α) for electrodes with and without surface modifications are calculated from experimental data using a modified Butler-Volmer equation, incorporating ohmic losses. The reported k0 and α values are independent of electrode geometry or printing parameters, unlike the observable rate constant usually reported for 3D printed electrodes. By accounting for contact resistance and finite electron transfer kinetics, cathodic and anodic peak potentials and currents of voltammograms recorded with 3D printed electrodes are predicted before printing, allowing electrode designs to be optimized in the virtual space.

Changes in plant nutrient status following combined elevated [CO2] and canopy warming in winter wheat.

Projected global climate change is a potential threat to nutrient utilization in agroecosystems. However, the combined effects of elevated [CO2] and canopy warming on plant nutrient concentrations and translocations are not well understood. Here we conducted an open-air field experiment to investigate the impact of factorial elevated [CO2] (up to 500 μmol mol-1) and canopy air warming (+2°C) on nutrient (N, P, and K) status during the wheat growing season in a winter wheat field. Compared to ambient conditions, soil nutrient status was generally unchanged under elevated [CO2] and canopy warming. In contrast, elevated [CO2] decreased K concentrations by 11.0% and 11.5% in plant shoot and root, respectively, but had no impact on N or P concentration. Canopy warming increased shoot N, P and K concentrations by 8.9%, 7.5% and 15.0%, but decreased root N, P, and K concentrations by 12.3%, 9.0% and 31.6%, respectively. Accordingly, canopy warming rather than elevated [CO2] increased respectively N, P and K transfer coefficients (defined as the ratio of nutrient concentrations in the shoot to root) by 22.2%, 27.9% and 84.3%, which illustrated that canopy warming played a more important role in nutrient translocation from belowground to aboveground than elevated [CO2]. These results suggested that the response of nutrient dynamics was more sensitive in plants than in soil under climate change.

EFFECT OF BIO-RESIDUES AS HEAVY METAL IMMOBILIZERS IN CUCUMBER AND IRRIGATION WATER AT JAKARA, KANO

Heavy metal contamination is a common problem in areas where industrial effluents are being discharged into the irrigation water. Farmlands along the Jakara River were not exceptions in which high concentrations of heavy metals are reported. This study was intended to evaluate the effect of some selected bio-residues: rice husk, groundnut shell, millet chaff, and sawdust for immobilization of heavy metals on cucumber crops at Jakara irrigated farm. Irrigation water samples were first collected and treated with rice husk and groundnut shell before application to the farm to understand the best treatment material. Similarly, the soil was treated with various quantities of the bio-residues, applied with irrigation water, and allowed for one week to achieve full decomposition of the materials. Thereafter, the cucumber seeds were planted in each treated plot and control plot. The results show that a rice husk of 1.5 g/l is the best bio-residue for water irrigation water treatment. It was found the concentrations of heavy metals in the cucumber yields were reduced by about 34% in the plot treated with 1.5 g/m2 of rice husk bio-residue. Moreover, both the Soil-to-cucumber Transfer Coefficient and Bio-residual Performance Index revealed that there is a highly significant effect of the application of bio-residual materials in managing the concentration of heavy metals in the cucumber yields.

AirSeaFluxCode: Open-source software for calculating turbulent air-sea fluxes from meteorological parameters

The turbulent exchanges, or fluxes, of heat, moisture and momentum between the atmosphere and the ocean play a crucial role in the Earth’s climate system. Direct measurements of turbulent fluxes are very challenging and sparse, and do not span the full range of environmental conditions that exist over the ocean. This means that empirical “bulk formulae” parameterizations that relate direct flux observations to concurrent measurements of the mean meteorological and sea surface variables contain considerable uncertainty. In this paper, we present a Python 3.6 (or higher) open-source software package “AirSeaFluxCode” for the computation of the heat (latent and sensible) and momentum fluxes. Ten different parameterizations are included, each based on published descriptions or code and each derived from a different set of observations, or different assumptions about the turbulent exchange processes. They represent a range of current expert opinion on how the fluxes depend on mean properties and can be used to explore uncertainty in calculated fluxes. AirSeaFluxCode also allows the adjustment of the mean meteorological input parameters (air temperature, humidity and wind speed) from the height at which they are obtained to a user-defined output height. This height adjustment enables the comparison of measurements, or model-derived values, made at different heights above sea-level. The parameterizations calculate the fluxes using input parameters that are relatively easily to measure, or are available as model output: wind speed, air temperature, sea surface temperature, atmospheric pressure and humidity. Where original code is available we have compared its output with that of AirSeaFluxCode. Any changes made to increase consistency across algorithms by standardizing computational methods or calculation of meteorological variables, for example, are discussed and the impacts quantified: these are shown to be insignificant except for a few cases where conditions were extreme, and AirSeaFluxCode is shown to be robust. We also investigate the impact on the fluxes caused by different assumptions about the exchange processes, or the choices inherent in the implementation of the parameterizations. For example, sea surface temperature usually refers to data typically obtained at depths of between 1 and 10 m. However, since some parameterizations require a “skin” sea surface temperature, code that adjusts temperature at depth to skin temperature is included: this has a very significant impact on the fluxes. Selecting a parameterization that is appropriate for the available sea surface temperature will avoid the need to adjust the sea temperature data and the uncertainties associated with that adjustment, and will also avoid the biases due to use of the “wrong” measure of temperature. Significant differences also resulted from assumptions about the size of reduction in sea surface humidity to account for salinity effects: the uncertainty in the reduction factor needs to be quantified in future analyses. Fluxes in extreme conditions are particularly uncertain since the transfer coefficients in the different parameterizations vary most at very high and very low wind speeds. Low wind speeds are also challenging for numerical implementation since choices have to be made regarding: convergence criteria for the iterative calculation, inclusion of a parameterization for convective gustiness, or application of ad hoc limits to various parameters. All of these choices can significantly affect the flux estimates for light winds.

Application of nickel-doped graphene nanotubes to modified GCE as a sensitive electrochemical sensor for the antipsychotic drug clozapine in spiked human blood serum samples

Clozapine (CLZ) is one of the most vital medications for managing schizophrenia, and the timely measurement of CLZ levels has been recognized as an obstacle to the wider use of CLZ. Herein, for the first time, nickel-doped graphene nanotubes (Ni@GRNT) were used to construct an electrochemical CLZ sensor by drop coating Ni@GRNT suspension on a glassy carbon electrode. The Ni@GRNT was synthesized and characterized using X‐ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical behavior and influence of different physicochemical factors of sensing electrodes were investigated by using cyclic voltammetry, EIS technique, and differential pulse voltammetry techniques. Also, the catalytic rate constant (kcat) and the transfer coefficient (α) were calculated. The modified electrode illustrated satisfactory linear range, detection limit (LOD), reusability, and reproducibility results. At optimal experimental conditions, measurements can be performed at a broad linear dynamic range of 0.3 nmol L−1–60.0 μmol L−1 CLZ and with a LOD of 0.1 nmol L−1. The sensitivity value was estimated to be 3.06 μA µmol L−1 cm−2. Ultimately, this platform was successfully used for CLZ sensing in spiked human blood serum and tablet samples with an accuracy of > 93%.Graphical abstract

Impact of boron doping on microporous carbon for enhancing the electrochemical sensitivity of vitamin D3

Vitamin D deficiency is becoming a severe burden worldwide, the rapid lifestyle changes are an important cause of that. As a result, rapid, cost-effective, and discriminating sensors for the determination of vitamin D are highly required. Herein, we report, a non-enzymatic sensitive electrochemical method for the determination of vitamin D3 using boron-doped microporous carbon (BMC) as a sensing matrix. The Boron was systematically integrated into the microporous carbon (MC) matrix to increase the electrochemical property. Among the synthesized materials, the MC modified with 5 wt.% boron showed better sensor performance than the others. The kinetics and concentration studies indicate that the rate of electro oxidation on the surface of the modified electrode is significantly faster than that of the unmodified electrode. The scan rate effect and pH studies provide the number of electron transfers, transfer coefficient, and diffusion coefficient of vitamin D3 which are 2, 0.52, and 18.49x10–12 cm2s-1, respectively. The electrolytic pH had a large impact on the oxidation potential, and its activity was significantly closer to that of the previously reported boron-doped diamond electrode. The BMC-5 modified electrode has a great linear range (0.5 μM–42 μM) and a low detection limit (1.45 μM). Hence, from this study, it is concluded that the low-cost and stable BMC is an alternate matrix for the determination of vitamin D3.

Определение значений переносных характеристик в многокомпонентных средах на основе анализа микропроцессов

This paper proposes a two-level approach for mathematical modeling of processes in multicomponent gas mixtures. It involves a combination of the description of conservation laws based on macro-equations and the determination of the corresponding transfer coefficients using the analysis of micro-processes. The main purpose of this work is to develop an algorithm for determining transport characteristics in multicomponent media based on the analysis of inner micro-processes. Hence, the kinetic molecular theory of gases and liquids is used, namely, the collision part of the Boltzmann equation. It includes multiple improper integrals taking into account the effect of micro-processes in the medium on the values of transport coefficients. When integrating the Boltzmann equation by the Chapman-Enskog method, the transport coefficients are expressed through integral brackets of the Sonin polynomials, which represent the linear combinations of molecular collision integrals. Their calculations require the use of efficient mathematically sound ways including the elements of parallel computing.