Potential Difference Measurements Research Articles

Rectal organoid morphology analysis (ROMA) as a novel physiological assay for diagnostic classification in cystic fibrosis

BackgroundDiagnosing cystic fibrosis (CF) is not always straightforward, in particular when sweat chloride concentration (SCC) is intermediate and <2 CF-causing CFTR variants are identified. The physiological CFTR assays proposed in...

Topography and localized charge of steps on CeO2(111) investigated by AFM/KPFM

The configuration of step edges on metal oxide surface is significant for understanding fundamental reactivity and predicting the performance in catalysis. In this work, the topography feature and charge of steps on CeO2(111) are investigated by atomic force microscopy /kelvin probe force microscopy combined with density functional theory. Hexagonal islands and pits containing step I edge and step II edge have been observed at annealing 1100 K. The irregular structures with the addition of step III edge have been found at 1200 K. The measurement of contact potential difference reveals that step II displays the strongest localized charge state, followed by step III, and step I with the weakest localized charge state. The calculations of density functional theory have confirmed that step II possesses a stronger localized charge state. In addition, the Ce atoms at the step II edge exhibit greater positive and negative charge accumulation. These results provide the surface structure and electrical potential of three step edges on the CeO2(111), and establish both experimental and theoretical foundations for subsequent investigations on adsorption and catalysis.

Calcium-sensing receptor (CaSR) modulates ocular surface chloride transport and its inhibition promotes ocular surface hydration

PurposeOcular surface hydration is critical for eye health and its impairment can lead to dry eye disease. Extracellular calcium-sensing receptor (CaSR) is regulator of ion transport in epithelial cells expressing cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel. CFTR is also a major ion channel in ocular surface epithelia, however the roles of CaSR in ocular surface are not well studied. This study aims to investigate expression and functional roles of CaSR in ocular surface. MethodsCaSR immunostaining was performed in mouse and human cornea and conjunctiva. Ocular surface potential difference (OSPD) and tear fluid volume measurements were performed in mice with topically applied cinacalcet (CaSR activator) and NPS-2143 (CaSR inhibitor). ResultsCaSR is expressed in corneal and conjunctival epithelia of mice and humans. Topically administered CaSR activator cinacalcet inhibits cAMP agonist forskolin-induced Cl− secretion and CFTR activity up to 90 %. CaSR inhibitor NPS-2143 stimulates CFTR-mediated Cl− secretion in mouse ocular surface, after which cAMP agonist forskolin had minimal additional secretory effects. Single dose NPS-2143 treatment (as an eye drop) increases tear fluid volume in mice by ∼60 % compared to vehicle treatment. NPS-2143 effect on tear volume lasts at least 8 h after single dose. ConclusionsCaSR is a key regulator of ocular surface ion transport and CaSR inhibition promotes Cl− and tear secretion in the ocular surface. If they are found to be effective in in dry eye models, CaSR inhibitors (currently in clinical development) can potentially be repurposed as novel prosecretory treatments for dry eye disease.

Atomic force microscopy observation of surface morphologies and measurements of local contact potential differences of amorphous solid water samples deposited at 15 and 100 K.

We use an ultra-high vacuum cryogenic atomic force microscope to investigate the surface morphology of amorphous solid water (ASW) prepared by oblique deposition of water vapor onto Si(111)7 × 7 substrates at temperatures of 15 and 100 K. Height-height correlation function analysis of topographic images suggests that ASW at 15 K has a columnar structure and that the typical diameter of the column is 5-10 nm. At 100 K, the typical diameter is 10-30 nm, although columnar features are less prominent. The surface roughness (i.e., deviation of the height) is greater at 15 K than at 100 K, indicating that the surface at 100 K exhibits a relatively flat morphology. This result implies that transient diffusion of deposited water molecules affects the surface morphology at 100 K. In addition, measurements of the local contact potential difference between the tip and the ASW surface suggest that the magnitude of the negative surface potential at the microscopic scale, which is attributed to spontaneous polarisation, cannot simply be scaled by the thickness of ASW as predicted in previous experiments with Kelvin probes.

Generation of electric potential difference by chromatophores from photosynthetic bacteria in the presence of trehalose under continuous illumination

Measurement of the electrical potential difference (Δψ) in membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides, associated with the surface of a nitrocellulose membrane filter (MF), impregnated with phospholipid solution in decane, as well as immersed inside it, in the presence of exogenous mediators and disaccharide trehalose, demonstrated an increase in the amplitude and stabilization of the signal under continuous illumination. The ascorbate/N,N,N′N′-tetramethyl-p-phenylenediamine pair and ubiquinone-0 were used as mediators (electron donor and acceptor), respectively. Although the stabilization of photoelectric responses under long-term continuous illumination was observed in both cases of immobilization of chromatophores, only when the samples were immersed inside the MF, the functional activity of the reaction centers was maintained for a month when they were stored in the dark at room temperature. Stable photoresponses are probably associated with the preservation of the integrity of chromatophore proteins inside MF pores. The stabilizing effect of the bioprotector trehalose may be due to both its effect on RC proteins and on the phospholipid bilayer membrane. The results obtained will expand modern ideas about the use of semi-synthetic structures based on various intact photosynthetic systems capable of converting solar energy into an electrochemical form.

Flexoelectrically augmented triboelectrification enabled self-power wireless smart home control system

With the rapid development of the Internet of Things and artificial intelligence, smart home has emerged to fulfill the security, convenience, and energy-saving issues of modern life. Self-power, multifunctional, and sensitive sensors are one of the key components for the popularization of smart home systems. Herein, a flexoelectric mica crystal is shown to augment the finger touch-driven triboelectric output enough to operate a wireless and multichannel smart home controller. The smart home controller consists of concave mica films, a hand-grip-type vertical mouse, and an Arduino controller. Strain-gradient-dependent contact potential difference measurement and density functional theory calculation show that flexoelectric charge shifts the workfunction and concave bending reduces the effective electron mass in a mica. A portable hand-grip-type flexoelectrically augmented triboelectric nanogenerator (Flexo-TENG) demonstrates the wireless communication of message in real time and the selective operation of home appliances with various functions via a simple finger touch. This work provides important ingredients for the enhanced triboelectric output via flexoelectricity, and for the realization of a convenient, multifunctional, cost-effective, and adaptable smart home control system without batteries.

Generation of Electric Potential Difference by Chromatophores from Photosynthetic Bacteria in the Presence of Trehalose under Continuous Illumination.

Measurement of electrical potential difference (Δψ) in membrane vesicles (chromatophores) from the purple bacterium Rhodobacter sphaeroides associated with the surface of a nitrocellulose membrane filter (MF) impregnated with a phospholipid solution in decane or immersed into it in the presence of exogenous mediators and disaccharide trehalose demonstrated an increase in the amplitude and stabilization of the signal under continuous illumination. The mediators were the ascorbate/N,N,N'N'-tetramethyl-p-phenylenediamine pair and ubiquinone-0 (electron donor and acceptor, respectively). Although stabilization of photoelectric responses upon long-term continuous illumination was observed for both variants of chromatophore immobilization, only the samples immersed into the MF retained the functional activity of reaction centers (RCs) for a month when stored in the dark at room temperature, which might be due to the preservation of integrity of chromatophore proteins inside the MF pores. The stabilizing effect of the bioprotector trehalose could be related to its effect on both the RC proteins and the phospholipid bilayer membrane. The results obtained will expand current ideas on the use of semi-synthetic structures based on various intact photosynthetic systems capable of converting solar energy into its electrochemical form.

The Use of Thioflavin T for the Estimation and Measurement of the Plasma Membrane Electric Potential Difference in Different Yeast Strains.

The use of the cationic, dye thioflavin T (ThT), to estimate the electric plasma membrane potential difference (PMP) via the fluorescence changes and to obtain its actual values from the accumulation of the dye, considering important correction factors by its binding to the internal components of the cell, was described previously for baker's yeast. However, it was considered important to explore whether the method developed could be applied to other yeast strains. Alternative ways to estimate the PMP by using flow cytometry and a multi-well plate reader are also presented here. The methods were tested with other strains of Saccharomyces cerevisiae (W303-1A and FY833), as well as with non-conventional yeasts: Debaryomyces hansenii, Candida albicans, Meyerozyma guilliermondii, and Rhodotorula mucilaginosa. Results of the estimation of the PMP via the fluorescence changes under different conditions were adequate with all strains. Consistent results were also obtained with several mutants of the main monovalent transporters, validating ThT as a monitor for PMP estimation.

Charge state of steps on anatase TiO2(1 0 1) at 78 K by AFM/KPFM

Surface steps strongly influence the surface chemistry of metal oxides, a detailed picture of step charge and structure may help to understand reactivity and predict the performance of the overall material in catalysis. In this study, we report the existence of another type of step, step BII, on the anatase TiO2(101) surface using atomic force microscopy/Kelvin probe force microscopy combined with density functional theory (DFT). By in situ measurements of current and contact potential difference (CPD) information, we found that step B II exhibits the highest charge state, followed by step C and D, which have the same structure, and step A with the weakest charge state. This finding challenges the conventional understanding that step C possesses the highest charge state. By incorporating DFT calculations, we confirmed that step B II possesses a higher charge state. This discovery also supports the observation of higher charge states in step C than in step B I. In addition, our results indicate that the valence band is predominantly governed by oxygen atoms, while titanium atoms dominate the conduction band. At the step edge, oxygen atoms act as electron donors, with electrons mainly clustering near the titanium atoms and Ti-O bonds. The present study provides a complete characterization of the charge state of the step edges on the anatase TiO2(101) surface and plays an important role in investigating the molecular adsorption as well as charge transfer in catalytic reactions on metal oxides surface.

A lab-based test of the gravitational redshift with a miniature clock network

Einstein’s theory of general relativity predicts that a clock at a higher gravitational potential will tick faster than an otherwise identical clock at a lower potential, an effect known as the gravitational redshift. Here we perform a laboratory-based, blinded test of the gravitational redshift using differential clock comparisons within an evenly spaced array of 5 atomic ensembles spanning a height difference of 1 cm. We measure a fractional frequency gradient of [ − 12.4 ± 0. 7(stat) ± 2. 5(sys)] × 10−19/cm, consistent with the expected redshift gradient of − 10.9 × 10−19/cm. Our results can also be viewed as relativistic gravitational potential difference measurements with sensitivity to mm scale changes in height on the surface of the Earth. These results highlight the potential of local-oscillator-independent differential clock comparisons for emerging applications of optical atomic clocks including geodesy, searches for new physics, gravitational wave detection, and explorations of the interplay between quantum mechanics and gravity.

Personalized CFTR Modulator Therapy for G85E and N1303K Homozygous Patients with Cystic Fibrosis.

CFTR modulator therapy with elexacaftor/tezacaftor/ivacaftor (ETI) has been approved for people with CF and at least one F508del allele in Europe. In the US, the ETI label has been expanded to 177 rare CFTR mutations responsive in Fischer rat thyroid cells, including G85E, but not N1303K. However, knowledge on the effect of ETI on G85E or N1303K CFTR function remains limited. In vitro effects of ETI were measured in primary human nasal epithelial cultures (pHNECs) of a G85E homozygous patient and an N1303K homozygous patient. Effects of ETI therapy in vivo in these patients were assessed using clinical outcomes, including multiple breath washout and lung MRI, and the CFTR biomarkers sweat chloride concentration (SCC), nasal potential difference (NPD) and intestinal current measurement (ICM), before and after initiation of ETI. ETI increased CFTR-mediated chloride transport in G85E/G85E and N1303K/N1303K pHNECs. In the G85E/G85E and the N1303K/N1303K patient, we observed an improvement in lung function, SCC, and CFTR function in the respiratory and rectal epithelium after initiation of ETI. The approach of combining preclinical in vitro testing with subsequent in vivo verification can facilitate access to CFTR modulator therapy and enhance precision medicine for patients carrying rare CFTR mutations.

Energy Production Using Microbial Fuel Cell from Sludge Produced from Potable Water Treatment

A microbial fuel cell (MFC) is a type of device which is an electrochemical, after technology that is being to recover electricity from wastewater. This study's objective was to measure the potential difference from sludge collected from El-Sheikh Zayed water purification plant (Egypt in April 2021), isolate and identify bacteria present in sludge: Also, determine the effect of adding some metabolites on such physical and chemical properties. Potential difference measurement showed (192 mV) by using MFC. Pantoea spp., Aeromonas salmonicida, Comamonas testosteroni and Staphylococcus lentus were isolated and identified by biochemical reaction tests. A. salmonicida gave the highest potential difference (13mV). After adding some metabolites separately (albumen, dextrose, gelatin and casein), casein recorded 196Mv, a mixture was done between A. salmonicida and four metabolites measuring 50 mV. Physical and chemical analysis showed that biochemical oxygen demand (BOD) (55.0 P.P.M.), chemical oxygen demand (COD) (112.0 P.P.M.), and many minerals and heavy metals were also detected. Green synthesis of electricity from electrogenic bacteria using wastewater like sludge is a promising way to generate electricity by a cheap method.

Engineering-Physical Method for Determining the Thermal Conductivity of Objects with Micrometric Thickness and a Complex Structure

Introduction. The application of functional coatings on products, the performance properties of which are localized in the surface layer is a trend in modern mechanical engineering and materials science. The issues considered in this regard are relevant, in particular, for thermal-barrier coatings of turbine blades of steam and gas turbine engines. It is worth mentioning the materials that experience significant thermal loads during operation. In this case, the lack of reliable methods for predicting the thermophysical properties of the coating seems to be a problem. The work objective is to create a computational and analytical methodology for determining the thermal conductivity of coatings. This approach is based on experimental data and takes into account structural parameters of the material.Materials and Methods. The experiments were carried out with the blades of a high-speed gas turbine of a locomotive engine made of heat-resistant chromium-nickel alloy Inconel 713LC. An experimental multiphase coating of the Nb-Ti-Al intermetallic system with a thickness of about 80 microns was applied using vacuum ion-plasma technology. The two-beam scanning electron microscope Zeiss CrossBeam 340 was used in the work. The thermal conductivity of the coatings was determined by an experimental technique based on the measurement of the contact potential difference (CPD). Numerical values of this difference were obtained using a mirror galvanometer with high voltage sensitivity. A special signal amplifier and a USB oscilloscope were used to record the readings.Results. The calculation apparatus of the thermal conductivity determination technique is based on the experimental values of ∆φ CPD:– for the base metal (Inconel 713LC) +846 mkV;– for the coating Nb-Ti-Al – 90 mkV.The solution to the problem of the distribution of particles in a force field with a potential difference ∆φ is described by the Boltzmann distribution. Starting from the obtained result, we get:– CPD at the boundary of the contacting metals;– energy and thermal conductivity of the Fermi level;– electron relaxation time.The multidirectional influence that the dimensional differences of the particles of the second phase have on the effective thermal conductivity is considered. For this case, a dimensionless value of the effective thermal conductivity in the direction of each axis and the effective thermal conductivity of the composite are found. Porosity is taken into account according to the Maxwell – Aiken dependence and introduced into the general calculation system. The thermal conductivity of Nb-Ti-Al is established: λNbTiAl = 4,76 W/m.K. Thus, the thermal barrier coating Nb-Ti-Al fully meets its functional purpose.Discussion and Conclusion. The method of determining thermal conductivity described in the article is applicable only to conductive consolidated materials or composites with a continuous conductive matrix. The presented work completes the initial stage of creating a computational and analytical model for predicting the thermal conductivity of materials and coatings. The results of testing the model for materials with a complex structure showed its satisfactory accuracy. This indicates the expediency of using the two considered elements of the model. The first one is the instrumental measurement of the CPD. The second one is taking into account the features of the structural and phase state of the material. With the development of the model, it is expected to overcome its weaknesses:– the impossibility of using non-conductive objects to determine the thermal conductivity;– a significant decrease in the accuracy of determining thermal conductivity for materials and coatings with a gradient structure.

WS04.06 Validation of rectal organoid morphology analysis (ROMA) as a novel physiological CFTR assay for diagnosis of cystic fibrosis

Objectives: When a diagnosis of CF remains inconclusive (intermediate sweat chloride concentration (SCC) and inconclusive genetics), physiological CFTR assays are the next step in the diagnostic algorithm. Nasal potential difference and intestinal current measurement are however not readily available and not feasible at all ages. We propose rectal organoid morphology analysis (ROMA) as a novel diagnostic assay. ROMA quantifies morphological differences between patient-derived rectal organoids (PDRO) from subjects with CF (no visible lumen, irregular shape) and without CF (visible lumen, round shape).

Solution Combustion Synthesis and Characterization of Magnesium Copper Vanadates.

Magnesium vanadate (MgV2O6) and its alloys with copper vanadate were synthesized via the solution combustion technique. Phase purity and solid solution formation were confirmed by a variety of experimental techniques, supported by electronic structure simulations based on density functional theory (DFT). Powder X-ray diffraction combined with Rietveld refinement, laser Raman spectroscopy, diffuse reflectance spectroscopy, and high-resolution transmission electron microscopy showed single-phase alloy formation despite the MgV2O6 and CuV2O6 end members exhibiting monoclinic and triclinic crystal systems, respectively. DFT-calculated optical band gaps showed close agreement in the computed optical bandgaps with experimentally derived values. Surface photovoltage spectroscopy, ambient-pressure photoemission spectroscopy, and Kelvin probe contact potential difference (work function) measurements confirmed a systematic variation in the optical bandgap modification and band alignment as a function of stoichiometry in the alloy composition. These data indicated n-type semiconductor behavior for all the samples which was confirmed by photoelectrochemical measurements.

High-temperature contact potential difference measurement of surface work function using in vacuo Kelvin probe

Characterization of the work function of emitting surfaces represents an important contribution to thermionic emission research today. This is because materials that exhibit lower work functions are capable of thermionically emitting higher current densities at lower operating temperatures, which ultimately means longer lifetimes for the vacuum electron devices that make use of thermionic emitters. One widely used technique to characterize a material's work function is the measurement of contact potential difference using a Kelvin probe system. When applied in the traditional mode, this technique fails to produce meaningful results in situations where a sufficiently hot sample under inspection and the cooler Kelvin probe are in thermal disequilibrium. However, as this paper will outline, the standard application of a Kelvin probe system can be amended to facilitate meaningful asymmetric contact potential difference measurements, and consequently, obtain values of work function for samples at high temperatures, including relevant operating temperatures for thermionic emitters (>1000 °C).

Hybrid Cathodic/Anodic Electrosynthesis of Phase Pure Ag4V2O7 Thin Films

Here, we demonstrate a two-step electrosynthesis approach for the preparation of silver pyrovanadate, Ag4V2O7 in thin-film form. In the first, cathodic step, polycrystalline Ag was deposited on fluorine doped tin oxide (FTO) substrate from a non-aqueous bath. Aqueous pyrovanadate species were then generated by aging of a CO2-infused sodium orthovanadate (Na3VO4) solution for three weeks. Silver ions were subsequently generated in situ in this medium using anodic stripping of the Ag/ITO films from the first step. Interfacial precipitation of the Ag+ ions with the pyrovanadate species afforded the targeted product in phase pure form. The various stages of the electrosynthesis were monitored in situ via the combined use of voltammetry, electrochemical quartz crystal nanogravimetry (EQCN), and coulometry. The Ag4V2O7 thin films were characterized by a variety of experimental techniques, including X-ray diffraction, laser Raman spectroscopy, diffuse reflectance spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. Surface photovoltage spectroscopy, ambient-pressure photoemission spectroscopy, and Kelvin probe contact potential difference (work function) measurements afforded information on the energy band structure of the p-type Ag4V2O7 semiconductor. Finally, the electrochemical and photoelectrochemical properties of the electrosynthesized Ag4V2O7 thin films were studied in both aqueous and non-aqueous electrolytes.

Differential effects of ELX/TEZ/IVA on organ-specific CFTR function in two patients with the rare CFTR splice mutations c.273+1G>A and c.165-2A>G.

Introduction: Evidence for the efficiency of highly-effective triple-CFTR-modulatory therapy with elexacaftor/tezacaftor/ivacaftor (ETI), either demonstrated in clinical trials or by in vitro testing, is lacking for about 10% of people with cystic fibrosis (pwCF) with rare mutations. Comprehensive assessment of CFTR function can provide critical information on the impact of ETI on CFTR function gains for such rare mutations, lending argument of the prescription of ETI. The mutation c.165-2A>G is a rare acceptor splice mutation that has not yet been functionally characterized. We here describe the functional changes induced by ETI in two brothers who are compound heterozygous for the splice mutations c.273+1G>C and c.165-2A>G. Methods: We assessed the effects of ETI on CFTR function by quantitative pilocarpine iontophoresis (QPIT), nasal potential difference measurements (nPD), intestinal current measurements (ICM), β-adrenergic sweat secretion tests (SST) and multiple breath washout (MBW) prior to and 4months after the initiation of ETI. Results: Functional CFTR analysis prior to ETI showed no CFTR function in the respiratory and intestinal epithelia and in the sweat gland reabsorptive duct in either brother. In contrast, β-adrenergic stimulated, CFTR-mediated sweat secretion was detectable in the CF range. Under ETI, both brothers continued to exhibit high sweat chloride concentration in QPIT, evidence of low residual CFTR function in the respiratory epithelia, but normalized β-adrenergically stimulated production of primary sweat. Discussion: Our results are the first to demonstrate that the c.165-2A>G/c.273+1G>C mutation genotype permits mutant CFTR protein expression. We showed organ-specific differences in the expression of CFTR and consecutive responses to ETI of the c.165-2A>G/c.273+1G>C CFTR mutants that are probably accomplished by non-canonical CFTR mRNA isoforms. This showcase tells us that the individual response of rare CFTR mutations to highly-effective CFTR modulation cannot be predicted from assays in standard cell cultures, but requires the personalized multi-organ assessment by CFTR biomarkers.

Electrochemical-Based Sensing Platforms for Detection of Glucose and H2O2 by Porous Metal–Organic Frameworks: A Review of Status and Prospects

Establishing enzyme-free sensing assays with great selectivity and sensitivity for glucose and H2O2 detection has been highly required in biological science. In particular, the exploitation of nanomaterials by using noble metals of high conductivity and surface area has been widely investigated to act as selective catalytic agents for molecular recognition in sensing platforms. Several approaches for a straightforward, speedy, selective, and sensitive recognition of glucose and H2O2 were requested. This paper reviews the current progress in electrochemical detection using metal-organic frameworks (MOFs) for H2O2 and glucose recognition. We have reviewed the latest electrochemical sensing assays for in-place detection with priorities including straightforward procedure and manipulation, high sensitivity, varied linear range, and economic prospects. The mentioned sensing assays apply electrochemical systems through a rapid detection time that enables real-time recognition. In profitable fields, the obstacles that have been associated with sample preparation and tool expense can be solved by applying these sensing means. Some parameters, including the impedance, intensity, and potential difference measurement methods have permitted low limit of detections (LODs) and noticeable durations in agricultural, water, and foodstuff samples with high levels of glucose and H2O2.

Environmental sensitivity of GaN nanofins grown by selective area molecular beam epitaxy

Nanostructures exhibit a large surface-to-volume ratio, which makes them sensitive to their ambient conditions. In particular, GaN nanowires and nanofins react to their environment as adsorbates influence their (opto-) electronic properties. Charge transfer between the semiconductor surface and adsorbed species changes the surface band bending of the nanostructures, and the adsorbates can alter the rate of non-radiative recombination in GaN. Despite the importance of these interactions with the ambient environment, the detailed adsorption mechanisms are still not fully understood. In this article, we present a systematic study concerning the environmental sensitivity of the electrical conductivity of GaN nanofins. We identify oxygen- and water-based adsorbates to be responsible for a quenching of the electrical current through GaN nanofins due to an increased surface band bending. Complementary contact potential difference measurements in controlled atmospheres on bulk m- and c-plane GaN reveal additional complexity with regard to water adsorption, for which surface dipoles might play an important role besides an increased surface depletion width. The sensitive reaction of the electrical parameters to the environment and surface condition underlines the necessity of a reproducible pre-treatment and/or surface passivation. The presented results help to further understand the complex adsorption mechanisms at GaN surfaces. Due to the sensitivity of the nanofin conductivity on the environment, such structures could perform well as sensing devices.