Thickness Of Water Layer Research Articles

A novel prediction model for the solar radiation absorptivity and reflectivity of cooling photovoltaic panels with water layer

Water cooling of photovoltaic(PV) panels is a cost-effective technique for increasing electrical efficiency. However, there is a lack of a calculation method to accurately predict the solar radiation absorptivity and reflectivity of the double-layer transparent structure consisting of water and glass layers. In this study, based on the analysis of direct radiation light rays in the structure, an equivalent energy model was presented. Thereafter, according to the isotropic radiation within a hemispherical space, the absorptivity and reflectivity of the diffuse radiation were calculated. The effectiveness of the model is verified by the measured transmitted radiation through the horizontal and inclined glass panels in Xiamen city (117°57'E, 24°25'N) of China. The accuracy of simulation is better than that of the calculation methods in the literature. The model is capable of accurately predicting the absorptivity and reflectivity of solar radiation for a diverse range of application contexts and panel types. The simulated results reveal that when the incidence angle exceeds 60°, the absorptivity of PV cell layer decreases markedly. The direct radiation absorptivity of the glass and water layers increases gradually within an incidence angle of 60°, and then decreases as the angle increases. The reflectivity increases slowly when the incidence angle varies from 0° to 50°. The water layer minimally affects the glass layer's solar absorptivity and slightly decreases the reflectivity. But a 1 mm thick water layer can reduce the absorptivity of the PV cell layer by about 0.05, which corresponds to a 7.4 % decrease. The reduction is more pronounced with an increase in the water layer thickness. The prediction model can provide solar radiation absorptivity and reflectivity parameters of PV panels for water cooling simulations.

Evaluating the Influence of Thin Film of Water on the Frequency Dependences of Transmission Line S-Parameters at Positive and Negative Temperatures

Relevance. Provision of reliable and uninterrupted radio communication is critically important under changing climatic conditions of its operation. The combined effect of temperature and humidity can lead to changes in the electrical characteristics of transceiving devices and thereby disrupt the communication channel. In difficult climatic conditions of operation, due to constant temperature changes on the surface of the printed circuit boards, which are part of them, condensation can form, affecting the performance of the entire device. In this regard, the electrical characteristics change, which must be taken into account when designing critical REE. When designing transmission lines on printed circuit boards, it is reasonable to evaluate climatic impacts on it in a wide frequency range, which requires the development of new models and methods that allow taking into account these impacts.Goal of the work: to evaluate the influence of the temperature of a thin film of water on the surface of a microstrip transmission line on its frequency dependences of S-parameters. Finite element methods and laboratory experiment were used.Results. A methodology to account for the effects of ambient temperature and humidity on the electrical characteristics of a microstrip transmission line (MTL) is presented, which allows evaluating the variation of the S-parameters of the line over wide ranges of frequencies, air temperature and humidity, as well as the chemical composition of the environment. The S-parameters of water in a container placed inside a coaxial chamber are measured over the frequency and temperature ranges of 10 MHz to 12 GHz and minus 50 to 100℃, respectively. Using the presented model, the frequency dependences of the electrical conductivity of water at different temperatures are calculated. It is shown that at positive temperature, the electrical conductivity can reach 6.5 Sm/m and at negative temperature it can reach 1.3 Sm/m. Using the developed methodology, the influence of different water electrical conductivity on the S-parameters of MTLs is evaluated. The influence of water and ice layer thickness on the S-parameters of MTLs was shown. It is found that models describing the electrical conductivity of water have an excellent influence on the electrical parameters of the transmission line. Novelty. A method of accounting for the influence of ambient temperature and humidity on the S-parameters of the transmission line is presented, which is characterized by the use of a model of water conductivity based on insertion losses calculated from the measured S-parameters of a coaxial chamber with water in the container when its temperature is changed. Practical significance: a model and a methodology for taking into account the impact of temperature and humidity of the environment on the MTL characteristics are presented, allowing estimating the S-parameters of the line in a wide range of frequencies, air temperature and humidity, as well as the chemical composition of the environment.

Imaging Dissolution Dynamics of Individual NaCl Nanoparticles during Deliquescence with In Situ Transmission Electron Microscopy.

Water vapor condensation on hygroscopic aerosol particles plays an important role in cloud formation, climate change, secondary aerosol formation, and aerosol aging. Conventional understanding considers deliquescence of nanosized hygroscopic aerosol particles a nearly instantaneous solid to liquid phase transition. However, the nanoscale dynamics of water condensation and aerosol particle dissolution prior to and during deliquescence remain obscure due to a lack of high spatial and temporal resolution single particle measurements. Here we use real time in situ transmission electron microscopy (TEM) imaging of individual sodium chloride (NaCl) nanoparticles to demonstrate that water adsorption and aerosol particle dissolution prior to and during deliquescence is a multistep dynamic process. Water condensation and aerosol particle dissolution was investigated for lab generated NaCl aerosols and found to occur in three distinct stages as a function of increasing relative humidity (RH). First, a < 100 nm water layer adsorbed on the NaCl cubes and caused sharp corners to dissolve and truncate. The water layer grew to several hundred nanometers with increasing RH and was rapidly saturated with solute, as evidenced by halting of particle dissolution. Adjacent cube corners displayed second-scale curvature fluctuations with no net particle dissolution or water layer thickness change. We propose that droplet solute concentration fluctuations drove NaCl transport from regions of high local curvature to regions of low curvature. Finally, we observed coexistence of a liquid water droplet and aerosol particle immediately prior to deliquescence. Particles dissolved discretely along single crystallographic directions, separated by few second lag times with no dissolution. This work demonstrates that deliquescence of simple pure salt particles with sizes in the range of 100 nm to several microns is not an instantaneous phase transition and instead involves a range of complex dissolution and water condensation dynamics.

Mechanisms of water layer thickness and ullage height on crude oil boilover: a theoretical model coupling the effects of multiple physical fields

Boilover is one of the most destructive tank fire scenarios. A series of experiments were conducted using eight different depths of oil pans (ranging from internal depths of 4 to 20 cm) to vary the water layer thickness and ullage height. The results indicate that the water layer effectively cools the sidewalls, reduces the burning rate, inhibits the development of hot zones, and delays the onset of boilover in small and medium-scale experiments. Conversely, the ullage height affects the burning rate, formation of hot zones, intensity of the boilover, and boilover onset time. Utilizing experimental data and thermodynamic analysis, both water layer thickness and fuel layer thickness were considered as variables to predict sidewall temperature at the fuel surface. These results were then introduced into the burning rate prediction model. A prediction model for the boilover onset time was also developed using the water layer thickness as a variable, and a thermodynamic analysis revealed the existence of a limit to the effect of water layer thickness on the boilover onset time. Bubble dynamics was introduced to analyze the boilover process at the oil-water interface, clarifying that the influence of water layer thickness and ullage height on boilover intensity primarily lies in factors such as the degree of superheat at the fuel-water interface. The study’s findings hold significant implications for predicting and assessing fire accidents in storage tanks.

Effect of aqueous layer thickness on nano-scratching of single-crystal γ-TiAl alloys

ABSTRACT The study of nano-scratching under water lubrication is helpful to understand the role of lubrication mechanism in the machining of single crystal γ-TiAl alloy. In this paper, through the comparative analysis of nano-scratching under different thicknesses of water layers, it was found that under a water layer thickness of 1 nm, nano-scratching not only improves the surface quality but also achieves multiple reductions in scratch force, stress, temperature and subsurface structural damage. In order to deeply reveal the internal mechanism of workpiece temperature variation under different thicknesses of water layer lubrication, a fitting formula was innovatively adopted to conduct quantitative analysis. In addition, with the increase of the thickness of the water layer, it was observed that the water film effect was continuously enhanced, and this change caused the matrix stress to gradually increase, which hindered the forward motion of the nanoscratch, ultimately resulting in an increase in the friction coefficient. These findings provide valuable insights into the nanoscratching mechanism of monocrystalline γ-TiAl alloy in the presence of water film, and provide a new perspective for understanding the complex mechanism of nanoscratch behaviour under water lubrication, thus promoting the understanding of nanoscale lubrication effects.

Chitosan-coated liposomal systems for delivery of antibacterial peptide LL17-32 to Porphyromonas gingivalis

Periodontal disease is triggered by surface bacterial biofilms where bacteria are less susceptible to antibiotic treatment. The development of liposome-based delivery mechanisms for the therapeutic use of antimicrobial peptides is an attractive alternative in this regard. The cationic antimicrobial peptide LL-37 (human cathelicidin) is well-known to exert antibacterial activity against Porphyromonasgingivalis, a keystone oral pathogen. However, the antibacterial activity of the 16-amino acid fragment (LL17-32) of LL-37, is unknown. In addition, there are still gaps in studies using liposomal formulations as delivery vehicles of antibacterial peptides against this pathogen. This study was designed to examine the influence of the different types of liposomal formulations to associate and deliver LL17-32 to act against P. gingivalis. Chitosans of varying Mw and degree of acetylation (DA) were adsorbed at the surface of soya lecithin (SL) liposomes. Their bulk (average hydrodynamic size, ζ-potential and membrane fluidity) and ultrastructural (d-spacing, half-bilayer thickness and the water layer thickness) biophysical properties were investigated by a panel of techniques (DLS, SAXS, M3-PALS, fluorescence spectroscopy and TEM imaging). Their association efficiency, in vitro release, stability, and efficacy in killing the periodontal pathogen P. gingivalis were also investigated. All liposomal systems possessed spherical morphologies and good shelf-life stabilities. Under physiological conditions, chitosan formulations with a high DA demonstrated enhanced stability in comparison to low DA-chitosan formulations. Chitosans and LL17-32 both decreased SL-liposomal membrane fluidity. LL17-32 exhibited a high degree of association with SL-liposomes without in vitro release. In biological studies, free LL17-32 or chitosans alone, demonstrated microbicidal activity against P. gingivalis, however this was attenuated when LL17-32 was loaded onto the SL-liposome delivery system, presumably due to the restrained release of the peptide. A property that could be harnessed in future studies (e.g., oral mucoadhesive slow-release formulations).

Changes in the Thickness of the Sublens Water Layer in Patients Using Scleral Lenses

Purpose of the study. To analyze the change in the thickness of the sub­lens water layer depending on the time of wearing lenses in patients using scleral lenses using the SkyOptix Laboratory lenses as an example.Patients and methods. To determine the thickness of the sublens water layer in the vertical and horizontal meridians, a study was performed in 33 people in 46 eyes. Among the patients there were 25 men and 8 women, from 18 to 59 years old (mean 37.3 ± 9.5 years). The main indication for the use of scleral lenses was the ineffectiveness of other methods of vision correction.Results. The mean sublens water layer thickness reduction in the total group of examined patients using scleral lenses was 9.3 % or 37.73 μm after 1 hour of wear and 20.8 % or 84.48 μm after 4 hours of wear compared to initial values.Conclusions. The largest and clinically significant changes in the thickness of the sublens water layer occur during the first hour of lens wear, which, according to our study, is approximately 40 microns. Considering the temporal dynamics of changes in the thickness of the sublens water layer, the final calculation of the parameters must be made no earlier than after 1 hour of wearing the scleral lens. The thickness of the sublens water layer should be assessed in relation to the time spent in the scleral lens. According to our survey, over the entire period of observation in all patients using scleral lenses, there is a decrease in the thickness of the sublens water layer over time of wearing, which requires further additional research to determine identifying the exact causes and factors underlying this process.

Interfacial adhesion features of high-viscosity asphalt and aggregate under water conditioning: Micro perspective and molecular simulation

Interface properties between asphalt and aggregate intimately affect the service performance and long-term durability of asphalt pavement. This study seeks to explore the interfacial adhesion features of high-viscosity asphalt (HVA)-aggregate under water conditioning to provide the understanding for the moisture damage of HVA-aggregate interface and asphalt pavement. To this end, the HVA was initially suffered from different durations of water conditioning, and atomic force microscopy (AFM) test was employed to gather the microscopic phase structure and adhesion force of water-conditioned HVA and aggregate, to analyze the adhesion variations of HVA-aggregate interface. Further, molecular dynamics method was used to simulate the changing process and influencing mechanism of adhesion effect at the HVA-aggregate interface under water immersion. The findings indicated that with the increasing water immersion, Catana phase of HVAs vanished, and concave and convex structures appeared on the surface, along with pit groove dispersion phase structures. Longer immersion time resulted in augmented surface roughness of HVA and a more dispersed height distribution in the area domain, most notably during the initial stages of water immersion. Aging increased sensitivity to immersion duration in terms of surface roughness, mechanical properties and adhesion ability of HVAs. Water immersion had a diminishing effect on the mechanical properties of HVA at different aging degrees, although it increased the micro-mechanical modulus of HVAs and impaired the interface adhesion with aggregates. Under water immersion, the phase structure and mechanical properties of HVAs and the interface adhesion indexes all distinguished a prominent negative Pearson correlation (correlation coefficient |R| > 0.7000), and these factors were critical for HVA-aggregate interface adhesion, as alterations in surface phase structure and micro-mechanical traits of HVAs triggered variations in the HVA-aggregate interface adhesion. In addition, water content in the interface layer, simulation temperature and mineral anisotropy significantly affected the interfacial adhesion of HVA and aggregate in water environment. The introduction of water and the rise of temperature considerably weakened the interfacial adhesion effect of asphalt-aggregate system, and the interface adhesion failure occurred once the water layer thickness surpassed 5 Å. Comparatively, the HVA-calcite system demonstrated better interfacial adhesion competence than the HVA-α-quartz system, and the HVA-calcite {1 0 4} system showed the optimal interfacial adhesion.

Effects of surface and subsurface water/ice on spatial distributions of impact crater ejecta on Mars

Ejecta blankets around craters on a km-scale show stark differences in the ejecta mobility (maximal extent of ejecta divided by the crater radius) with latitude and types of plains on Mars, which has been known for a long time (Barlow and Pollak, 2002; Li et al., 2015) but is not well-understood. Our main goal is to explore the idea that the subsurface rheology drives ejecta dynamics and leaves characteristic, observable imprints in the spatial distributions of ejecta. We conduct numerical simulations of impact cratering into a variety of subsurface models and study the impact of varied subsurface material (porous basalt, water ice, water), as well as structure and layering on impact sites and properties of impact ejecta. Our models consider variations in the depth of water or ice covering basalt; the thickness of buried ice; and the depth of burial of ice. We find that ejection angles and velocities depend on these quantities and configurations, e.g. velocities decrease and angles of ejection increase with increasing water layer thickness, buried ice thickness, or thickness of basaltic debris over an ice sheet. As a result, several ejecta characteristics derived from ejecta thickness profiles carry information about the underlying rheology. Specifically, the ejecta mobility, as well as the radial position of the maximum and the slope of the ejecta thickness profiles are diagnostic. The power-law function of the thickness profile of the ejecta blanket right after formation is a good indicator of ejecta from water- or ice-covered targets but not from more complex multi-layered structures, hence we caution against using scaling relations to describe ejecta from such targets. As any surface water/ice volatile mass is unstable on Mars, we also consider the geomorphology of craters and ejecta after the loss of volatiles. Our main findings include the observation that after the loss of surface volatiles, craters which formed in water-covered targets would appear shallower than those formed in basalt. The ejecta mobilities observed today would also be smaller if craters formed in volatile-covered targets than in basalt. Our findings can aid the interpretation of data returned from cameras onboard multiple spacecraft orbiting Mars such as HiRISE, CaSSIS, or CTX, and constitute a proof of concept of the hypothesis that information on the subsurface, including where ice is or was present, is encoded in the ejecta profile and spatial distribution.

Evaluation of Efficiency of a Finned Corrugation Basin in Inclined Basin-Type Solar Stills in Regulating the Water Supply of the CaspiCement Plant

The need for fresh water production is especially high in hot dry climates without any sources of drinking water but with an abundance of sea and underground water. The solution is water desalination with efficient solar-powered water treatment plants. This article proposes a new modification of a basin made of thin-finned corrugation with 43°-angle-inclined sides, equal to the region’s latitude, which provide strong heating. The experiments were carried out in the hot climate of Aktau city (43°49′ N, 51°1′ E). The study’s outcomes can be useful for regions with drinking water scarcity. To define the level of the corrugated basin’s efficiency, two versions (SS-1, SS-2) of experiments were carried out on a two-slope distiller, complete with two basins. In SS-1, basin-2 was heated by air. By 15:00, basin-2 had heated up to 98.5 °C, and the acrylic cover above had heated up to 101.6 °C, which led to its “deformation”. By 12.00 p.m., the temperature differentials between the glass (40.7 °C), the air–water mixture (57.3 °C), and basin-1 (61.1 °C) were 16.6 °C and 20.4 °C. This resulted from the wind speed increasing up to 5.9 m/s. The large temperature differential contributed to the condensate yield increasing from 0.128 kg at 11 o’clock to 0.293 kg at 12 o’clock. The throughput capability of basin-1 per day was equal to 2.094 kg. Basin-2’s input to the performance in SS-1 was only the thermal effect. In SS-2, basin-2 was used as a regular basin. The plexiglass temperature was lower than the temperatures of the water and basin-2. The temperature differential between the glass and air–water mixture at 10:00 a.m. was 20 °C; at 12:00 p.m. it was 30.6 °C; and a value of 30.6 °C was recorded at 3:00 p.m. The thermal differential between the glass and the air-water mixture provided the highest condensate yield of 1.114 kg at 3.00 p.m. The condensate yield from the basins in SS-2 was 8.72 kg, including 3.5 kg from basin-1, which is 1.7 times more than from basin-1 in SS-1. The experimental results are consistent with the equations coming from the models of Clark J.A. and Dunkle R.V. Tcondensation ≠ Tevaporation is an irreversible process. When the basins are heated, the heat is consumed; when the glass cools down, the heat is given off. Heat losses are minimized due to the “gap” and positive energy is provided. The still’s throughput capability can be made larger by increasing the basin’s area, reducing the water layer thickness, and regulating the flowrate of the desalinated water.

Design and performance evaluation of Front glass-covered photovoltaics-thermal hybrid system for enhanced electrical output and hot water production

Proof of concept is established for the thermal management of PV modules for the simultaneous benefit of electrical and thermal efficiency. It was achieved by designing the controlled open-loop water-based hybrid PV-T system and demonstrated for thermal management of 150W photovoltaic panel at natural solar conditions. In this integrated front glass-covered PV-T hybrid (IFG-PV-T) system, the PV panel is clipped between the front glass and rear aluminium collector without causing any permanent changes in the existing panel. The flow of water from the source tank is controlled by automated solenoid valve assembly coupled with thermocouples. The solenoid operational temperature is fixed at 40°C to controlled the PV surface temperature at an optimum range to mitigate the adverse effect on voltage and current output. The water layer thickness in the front glass box is optimized to filter the maximum infrared radiations and the collector's toughened glass feature allows the maximum light transmittance with super safety. The performance of the IFG-PV-T system has been evaluated in terms of variation in open circuit voltage, short circuit current, maximum power output, electric and thermal efficiency under the natural solar insolation for a week. Experimental investigations revealed that the open-circuit voltage is increased by ∼16.1 % with IFG-PV-T as compared to conventional PV panel. The increment can be attributed to the synergy of the front glass collector and solenoid valve operation at 40oC that regulates PV surface temperature and boost the current output. These factors have ameliorated the electrical efficiency of IFG-PV-T compared to conventional PV panel. The average thermal efficiency was 39.4 ​% wherein the IFG-PV-T system provides ∼100 ​L of hot water (38–41 ​°C) per day. The present controlled loop operation system and collector configuration have proven their significance for electrical power increment and concomitantly able to deliver moderate hot water which can be useful for any household or commercial application.

Effects and Mechanism of Hyperbranched Phosphate Polycarboxylate Superplasticizers on Reducing Viscosity of Cement Paste.

The adsorption behavior and dispersing capability of hyperbranched phosphated polycarboxylate superplasticizers (PCEs) containing phosphate monoester and phosphate diester were investigated. The hyperbranched structures were constructed using a special monomer dimethylaminoethyl methacrylate (DMAMEA) to create the branches during the polymerization. Meanwhile, the polymer architectures were tailored by varying the content of phosphate monoester and phosphate diester in the backbone via free radical solution polymerization. In contrast to comb-like PCE, hyperbranched PCEs presented a weaker dispersion capability at w/c = 0.29, but with a lower water-to-cement ratio (w/c), the hyperbranched PCEs exhibited a better dispersion capability than the comb-like PCEs. The dynamic light scattering (DLS) and transmission electron microscope (TEM) analysis showed that the adsorption layer of hyperbranched PCEs were thicker than that of comb-like PCEs. A thicker adsorption layer thickness generated thinner diffusion water layer thickness. The increase of the free water amount due to the thinner water diffusion layer is the key mechanism for improving the dispersibility and decreasing the viscosity of cement paste.

An algorithm for estimating the ultimate speed of vehicles on wet roads

Real-time estimation of a vehicle’s ultimate hydroplaning speed is crucial for ensuring its safety and stability, especially in rainy weather conditions. This paper proposes an algorithm for estimating the ultimate hydroplaning speed of vehicles on wet and slippery road surfaces based on finite element analysis of tire. Using the ABAQUS simulation software, a finite element model of a 205/55 R16 radial tire is established. Subsequently, a fluid-structure coupling model between the tire, water layer, and road surface is developed. The finite element method is employed to simulate and analyze the effects of tire inflation pressure, water layer thickness, vertical load, and tread wear on the vehicle’s ultimate hydroplaning speed. Simulation results indicate that an increase in tire inflation pressure and vertical load leads to an increase in the ultimate hydroplaning speed, while tread wear and an increase in water layer thickness result in a decrease. Finally, based on the simulation analysis data, a BP neural network-based estimation algorithm for the vehicle’s ultimate hydroplaning speed is proposed by combining the relationship between tire inflation pressure, tire vertical load, tread wear, water layer thickness, and ultimate hydroplaning speed. The results show that the estimated ultimate hydroplaning velocity profile has a high degree of overlap with the actual ultimate hydroplaning velocity profile, with a maximum error of no more than 5 km/h and an average percentage error of 2.31416%.

Confined Synthesis of Noble Metal Clusters Assisted by Liquid Film for Photocatalytic CO2 Reduction.

The important concept of confined synthesis is considered a promising strategy for the design and synthesis of definable nanostructured materials with controllable compositions and specific morphology, such as highly loaded single-atom catalysts capable of providing abundant active sites for photocatalytic reactions. In recent years, researchers have been working on developing new confined reaction systems and searching for new confined spaces. Here, we present for the first time the concept of a bubble liquid film as a novel confined space. The liquid film has a typical sandwich structure consisting of a water layer, sandwiched between the upper and lower surfactant layers, with the thickness of the intermediate water layer at the micro- and nanometer scales, which can serve as a good confinement. Based on the above understanding and combined with the photodeposition method, we successfully confined synthesized Ag/TiO2, Au/TiO2, and Pd/TiO2 photocatalysts in liquid film. By HAADF-STEM, it can be seen that the noble metal morphologies are all nanoclusters of about 1 nm and are highly uniformly dispersed on the TiO2 surface. Compared with photodeposition in solution, we believe that the surfactant molecular layer restricts a limited amount of precursor to the liquid film, avoiding the accumulation of noble metals and the formation of large particle size nanoparticles. The liquid film, meanwhile, restricts the migration path of noble metal precursors, allowing for thorough in situ photodeposition and enables the complete and uniform dispersion of noble metal precursors, greatly reducing the photodeposition time. The uniform loading of the three noble metals proved the universality of the method, and the catalysts showed high activity for photocatalytic CO2 reduction. The rates of reduction of CO2 to CO over the Ag/TiO2 photocatalytic reached 230 μmol g-1 h-1.This study provides a new idea for the expansion of the confined reaction system and a reference for the study of liquid film as the confined space.

Terahertz spectroscopy of thick and diluted water solutions.

While bright terahertz sources are used to perform nonlinear experiments, they can be advantageous for high-precision linear measurements of opaque samples. By placing the sample away from the focus, nonlinearities can be suppressed, and sizeable amounts of transmitted radiation detected. Here, this approach is demonstrated for a 0.5 mm thick layer of liquid water in a static sample holder. Variations of the index of refraction as small as (7 ± 2) · 10-4 were detected at 0.58 THz for an aqueous salt solution containing ten millimoles of sodium chloride. To my knowledge, this precision is unprecedented in time-domain spectroscopy studies of diluted aqueous systems or other optically thick and opaque materials.

Inverted Transflection Spectroscopy of Live Cells Using Metallic Grating on Elevated Nanopillars.

Water absorption of mid-infrared (MIR) radiation severely limits the options for vibrational spectroscopy of the analytes-including live biological cells-that must be probed in aqueous environments. While internal reflection elements, such as attenuated total reflection prisms and metasurfaces, partially overcome this limitation, such devices have their own limitations: ATR prisms are difficult to integrate with multiwell cell culture workflows, while metasurfaces suffer from a limited spectral range and small penetration depth into analytes. In this work, we introduce an alternative live cell biosensing platform based on metallic nanogratings fabricated on top of elevated dielectric pillars. For the MIR wavelengths that are significantly longer than the grating period, reflection-based spectroscopy enables broadband sensing of the analytes inside the trenches separating the dielectric pillars. Because the depth of the analyte twice-traversed by the MIR light excludes the highly absorbing thick water layer above the grating, we refer to the technique as inverted transflection spectroscopy (ITS). The analytic power of ITS is established by measuring a wide range of protein concentrations in solution, with the limit of detection in the single-digit mg mL-1. The ability of ITS to interrogate live cells that naturally wrap themselves around the grating is used to characterize their adhesion kinetic.

Europa’s structural conditions for the existence of subsurface ocean and the absence of metallic core-driven magnetic field

During the Galileo spacecraft’s flyby of Europa, magnetic field measurements detected an inductive signal due to the response of Europa’s interior conductors to temporal fluctuations in the Jovian magnetic field. In contrast, no signatures of intrinsic magnetic field originating from the dynamo motion in the metallic core were acquired. These measurements suggest that a global sub-surface ocean containing electrolytes exists beneath the solid ice shell and that the metallic core lacks convection. Europa’s interior is expected to be divided into the metallic core, rocky mantle and hydrosphere based on the moment of inertia factor estimated from gravity field measurements. Specifically, the thickness of the outermost water layer is 120–170 km, and the radius of the metallic core is 0.12–0.43 times the surface radius. No systematic investigation of Europa’s internal evolution has been conducted to estimate the current state of the subsurface ocean and to explain the absence of a core dynamo field within such uncertainty for internal structure and material properties (especially ice properties). Herein, I performed a numerical simulation of the long-term thermal evolution of Europa’s interior and investigated the temporal changes in the ocean thickness as well as the temperature and heat flow of the metallic core. If the ice reference viscosity is greater than 5 × 1014 Pas, the sub-surface ocean can persist even in the absence of tidal heating. In the case of a tidal heating of 10 mW/m2 and 20 mW/m2, the ice shell thickness is ≤90 km if the ice reference viscosity is ≥1 × 1015 and 1 × 1014 Pas, respectively. Regardless of the ice reference viscosity, if the tidal heating is ≥50 mW/m2, the shell thickness will be ≤40 km. The thermal history of the metallic core is determined by the hydrosphere thickness and the metallic core density, and is unaffected by variations in the ice shell (ocean) thickness. Preferred conditions for the absence of the core dynamo include CI chondritic abundance for the long-lived radioactive isotopes, lower initial core–mantle boundary (CMB) temperature and thicker hydrosphere. The core may be molten without convection if the composition is near the eutectic in a Fe–FeS alloy, or not molten (without convection) if the composition is near the Fe or FeS endmember. Specifically, if the rocky mantle has a CI chondritic radioisotope abundance, any core composition and hydrosphere thickness allow the absence of the core dynamo if the initial temperature at the CMB is lower than 1,250 K. If the rocky mantle has the ordinary chondritic radioisotope abundance, or a higher initial temperature (∼1,500 K) at the CMB, the core density lower than 6,000 kg/m3 is preferred for the absence of the core dynamo. In the case of the core composition near the eutectic one, a hydrosphere thicker than 150 km is required for the lacking core dynamo. The lower pressure of Europa’s rocky mantle due to its thinner hydrosphere compared with that of Ganymede may facilitate heat transfer in the mantle, lowering its temperature and making dynamo motion more challenging.

Accelerating FEM-Based Corrosion Predictions Using Machine Learning

Atmospheric corrosion of metallic parts is a widespread materials degradation phenomena that is challenging to predict given its dependence on many factors (e.g. environmental, physiochemical, and part geometry). For materials with long expected service lives, accurately predicting the degree to which corrosion will degrade part performance is especially difficult due to the stochastic nature of corrosion damage spread across years or decades of service. The Finite Element Method (FEM) is a computational technique capable of providing accurate estimates of corrosion rate by numerically solving complex differential Eqs. characterizing this phenomena. Nevertheless, given the iterative nature of FEM and the computational expense required to solve these complex equations, FEM is ill-equipped for an efficient exploration of the design space to identify factors that accelerate or deter corrosion, despite its accuracy. In this work, a machine learning based surrogate model capable of providing accurate predictions of corrosion with significant computational savings is introduced. Specifically, this work leverages AdaBoosted Decision trees to provide an accurate estimate of corrosion current per width given different values of temperature, water layer thickness, molarity of the solution, and the length of the cathode for a galvanic couple of aluminum and stainless steel.

A Revolutionary Approach to Study the Hydrogen Electrode Formation on Different Noble Metals Exposed to Monolayer to Sub-Monolayers Range of Water Using Scanning Kelvin Probe

The inadequacy of modern surface analytical tools to probe the electrochemical double layer (EDL) which governs the catalytic reactions at the interface hampers its in-depth investigation. The reason for this is that the EDL is usually buried under the bulk electrolyte. Though great progress was made in computational modeling the EDL [1,2], at the experimental level similar progress is necessary. One approach is to study the EDL of electrodes covered by electrolyte of nano-scale thickness. Till date, such studies of electrodes covered by electrolyte in the monolayer to sub-monolayer range are scarce, although they were at the center of the birth of electrochemical surface science [3]. Recently the “hydrogen electrode in the dry” concept which was established on palladium surface under dry nitrogen conditions could be a novel approach to understand that facet of the electrode interface activities [4]. The amount of water in this case is confined to just 1-2 monolayers to adsorbed water or even below. Similarly, this approach was successful applied for studying the current-potential relationships for oxygen reduction reaction exposed to different amounts of water ranging from micro meter to monolayers of thickness [5]. In this study, this concept was explored to other noble metal systems such as Pd, Au, Pt, and Ir to understand the hydrogen electrode formation.The present study focuses on hydrogen electrode formation on palladium, iridium, gold, and platinum exposed to inert conditions carried out by scanning Kelvin probe method (see fig) at different hydrogen activities. The activities of hydrogen on the surface was defined by electrochemically (entry side from a=0 to a=0.2) cathodic hydrogen charging method. Firstly, the hydrogen activity of 0.2 was defined on the palladium side by increasing the cathodic potential stepwise by potentiostatic hydrogen charging and measuring the corresponding potential on the exit side by Kelvin probe. This potential on palladium in both wet (>95% rh) and dry (<0.1% rh) conditions follows a 1:1 correlation with the applied entry potential, in accordance with the Nernst equation. Iridium samples show 1:1 in humid conditions, but not in dry conditions, i.e. in presence of a much thinner layer of adsorbed water molecules. At intermediate partial pressures of water, a linear response with slope lower than 1 was observed, that increased with increasing humidity. Whereas, gold samples show no correlation in both wet and dry conditions. Additionally, hydrogen electrode formation on emersed surface was checked to understand the effect of an already existing EDL on the formation of the hydrogen electrode. Also, ellipsometry spectroscopy measurements were carried out to determine the water layer thickness at different partial pressures of water. Overall, the current experimental approach of measuring the potential of these different “dry” electrodes gives more insights about hydrogen electrode formation on noble metals at different hydrogen activities, effect of adsorbed anions, and the effect of different amounts of adsorbed water.

Comprehensive analysis of the effective and intra-particle diffusion of weakly retained compounds in silica hydrophilic interaction liquid chromatography columns

A detailed analysis of intra-particle volumes and layer thicknesses and their effect on the diffusion of solutes in hydrophilic interaction liquid chromatography (HILIC) was made. Pycnometric measurements and the retention volume of deuterated mobile phase constituents (water and acetonitrile) were used to estimate the void volume inside the column, including not only the volume of the mobile phase but also part of the enriched water solvent acting as the stationary phase in HILIC. The mobile phase (hold-up) volume accessible to non-retained components was estimated using a homologous series approach. The joint analysis of the different approaches indicated the formation of enriched water layers on the hydrophobic silica mesopore walls with a thickness varying significantly with mobile phase composition. The maximal thickness of the enriched water layers, which corresponded to the minimum void volume accessible to unretained solutes, marked a transition in the retention behavior of the studied analytes. Discrepancies between deuterated solvent measurements and pycnometry were explained by the existence of an irreplaceable water layer adsorbed on the silica surface. Regarding the diffusion behavior in HILIC, peak parking experiments were used to interpret the influence of the acetonitrile content on the effective diffusion coefficient Deff. A systematic decrease in Deff and molecular diffusion Dm was observed with decreasing acetonitrile concentration, primarily attributed to variations in mobile phase viscosity. Notably, Deff/Dm remained nearly unaffected by variations in mobile phase composition. Finally, the effective medium theory was used to make a comprehensive analysis of Dpart/Dm to study the contribution to band broadening when the solute resides in the mesopores. The obtained data unveiled a curvature with a minimum corresponding to conditions of maximum water-layer thickness and retention. For the weakly retained compounds (k’ < 0.5) the Dpart/Dm-values were found to be relatively high (order of 0.35-0.5), which directly reflects the high γsDs/Dm-values that were observed (order 0.35-7).