Diffusive Loss Research Articles

Investigation of the afterpeaks in pulsed microwave argon plasma at atmospheric pressure

We studied the energy transport process in pulsed microwave argon plasmas at atmospheric pressure, focusing on the optical emission burst during the pulse-off time called the afterpeak. Guided by experimental observations using nanosecond time resolution imaging and spectroscopic diagnostics, we developed a global simulation model considering time-varying reaction rate coefficients and non-thermal electron energy distribution. Experimental and simulation results show that the afterpeak can be maximized by choosing an appropriate pulse period. Our analysis of the generation and consumption of excited argon species reveals that the rapid drop in electron temperature during the inter-pulse time reduces the diffusive loss of ions and enhances the recombination reactions, which produce the afterpeak. We also reveal that the radiation trapping and high energy level argon must be considered to simulate the afterpeak in atmospheric conditions. The improved understanding of the afterpeak dynamics can be utilized to optimize the power coupling and/or generation of reactive species.

Flame stability under flow-induced anisotropic diffusion and heat loss

A two-dimensional model for premixed flames accounting for flow-enhanced diffusion or Taylor dispersion and heat loss is investigated. This is the first analytical study addressing the effect of Taylor dispersion on the thermo-diffusive instabilities of non-adiabatic flames. It is also the first numerical study coupling flame instability with Taylor dispersion. A linear stability analysis is carried out in the limit of infinite Zeldovich number β. This leads to a dispersion relation, generalising classical relations in the literature, and involving three parameters, l (the reduced Lewis number), p (the Taylor-dispersion coefficient which is proportional to the Peclet number), and κ (the heat loss coefficient). Stability diagrams are determined and their implications on the cellular and oscillatory instabilities are discussed. A Kuramoto–Sivashinsky type equation incorporating the parameters l, p and κ and characterising the flame dynamics in the weakly non-linear regime near the onset of the cellular instability is derived. The theoretical results demonstrate the ability of Taylor dispersion and heat loss to significantly affect the flame stability. In particular, the oscillatory instability is found to be promoted by an increase in κ and hampered by an increase in p. On the other hand, both p and κ have a destabilising effect in connection with the cellular instability. Also, the theory provides a formula predicting the typical size of cells first emerging from the cellular instability which is found to be a decreasing function of p.Numerical simulations are carried out illustrating and significantly extending the analytical findings. Particular attention is devoted to the influence of β. In particular, we reconcile apparent quantitative and sometimes qualitative discrepancies between the numerical and theoretical predictions, which are found to be more pronounced for larger values of p. Luckily, the asymptotic theory is found to be robust in the sense that its predictions are recovered numerically if β is taken large enough, although such predictions may be questionable for realistic values of β. In general, the effect of β on flame stability is found to be opposite to that of p: an increase in p or a decrease in β have a destabilising effect in connection with the cellular instability, and a stabilizing effect in connection with the oscillatory instability; both instabilities are promoted by an increase in κ.

High-loading polysulfide/cement cathode for the manufacture of dynamically and statically stable lean-electrolyte lithium–sulfur batteries

In order to design lithium-sulfur cells for practical viability in the high-density energy storage, the exploitation of the effective contribution of the large amount of active-material mass to the high specific capacity at a lean-electrolyte condition must be considered. However, this is limited by the insulating nature of solid-state sulfur/sulfide, and the diffusion loss of the liquid-state polysulfides. In this study, Portland cement is adopted as a reinforcement material to design a high-loading polysulfide/cement cathode with sulfur loading and content of 8.64 mg cm−2 and 60 wt%, respectively. The nonporous cement exhibits a high polysulfide-trapping capability and low electrolyte consumption, which enable the high-sulfur-loading cathode to achieve record low electrolyte-to-sulfur ratios of 7–3 μL mg−1, with high gravimetric capacity and areal capacity of the cathode (i.e., 768 mA h g−1 and 11.06 mA h cm−2, respectively) and dynamically/statically electrochemical stability with 90% capacity retention after 100 cycles and a 1-month rest.

ADAPTIVE DIFFUSION OF SENSITIVE INFORMATION IN ONLINE PUBLIC NETWORKS

The Pouncing of Delicate Information like Private Data or Rumours is a serious issue in Online social media Now-a-days. One Solution for stopping the Pouncing of Delicate Data is Limiting the spreading among social media users. However, the spreading of Limiting measures also stops the spreading of Non-Delicate Data which will result in worst experience for the user. To handle this situation, in our paper, we will study the problem of how to reduce the Delicate data while storing the non-Delicate data as same without effecting it. In our study we use known Diffusion credentials of all users for Completely-Known Networks and unknown Diffusion credentials of some users for Partially-Known Networks in Prior. For this we use Bandit Framework to Combinedly design the Result with Polynomial Convolution in both situations. Finally, we can say that our solution ensures that non-Delicate Diffusion loss will be 40% less compared to four baseline Algorithm.

A revised alpha-ejection correction calculation for (U–Th) ∕ He thermochronology dates of broken apatite crystals

Abstract. Accurate corrections for the effects of alpha ejection (the loss of daughter He near grain or crystal surfaces due to long alpha stopping distances) are central to (U-Th)/He thermochronometry. In the case of apatite (U-Th)/He dating, alpha-ejection correction is complicated by the fact that crystals are often broken perpendicular to the c axis. In such cases, the correction should account for the fact that only some parts of the crystal are affected by alpha ejection. A common current practice to account for such broken crystals is to modify measured lengths of broken crystals missing one termination by a factor of 1.5, and those missing both terminations by a factor of 2. This alpha-ejection “correction correction” systematically overestimates the actual fraction of helium lost to alpha ejection, and thus overcorrects the measured date relative to that determined for an otherwise equivalent unbroken crystal. The ratio of the alpha-ejection-affected surface area to the volume of a fragmented crystal is equivalent to the surface-area-to-volume ratio of an unbroken crystal that is either twice as long (for fragments with one termination) or infinitely long (for fragments with no termination). We suggest that it is appropriate to revise the fragmentation correction to multiply the lengths of crystals missing one c-axis termination by 2, and those missing both c-axis terminations by some large number ≳20. We examine the effect of this revised correction and demonstrate the accuracy of the new method using synthetic datasets. Taking into account alpha ejection, the rounding of the He concentration profile due to diffusive loss, and the accumulation of radiation damage over a range of thermal histories, we show that the revised fragmentation alpha-ejection correction proposed here accurately approximates the corrected date of an unbroken crystal (“true” date) to within <0.7 % on average (±4.2 %, 1σ), whereas the former method overcorrects dates to be ∼3 % older than the “true” date on average. For individual grains, the former method can result in dates that are older by a few percent in most cases, and by as much as 12 % for grains with aspect ratios of up to 1:1. The revised alpha-ejection correction proposed here is both more accurate and more precise than the previous correction, and does not introduce any significant systematic bias into the apparent dates from a sample.

Temperature-Dependent Decay of Quasi-Two-Dimensional Vortices across the BCS-BEC Crossover.

We systematically study the decay of quasi-two-dimensional vortices in an oblate strongly interacting Fermi gas over a wide interaction range and observe that, as the system temperature is lowered, the vortex lifetime increases in the Bose-Einstein condensate (BEC) regime but decreases at unitarity and in the Bardeen-Cooper-Schrieffer (BCS) regime. The observations can be qualitatively captured by a phenomenological model simply involving diffusion and two-body collisional loss, in which the vortex lifetime is mostly determined by the slower process of the two. In particular, the counterintuitive vortex decay in the BCS regime can be interpreted by considering the competition between the temperature dependence of the vortex annihilation rate and that of unpaired fermions. Our results suggest a competing mechanism for the complex vortex decay dynamics in the BCS-BEC crossover for the fermionic superfluids.

Effect of shock strength on the radiation of focusing shock wave

High temperature radiating Air is produced experimentally by focusing a shock wave with the help of a spherically converging test section attached to a shock tube. The converging section concentrates the shock to a point with minimum diffusion losses. A shift in radiation towards the UV region was observed with an increase in the strength of the focusing shock wave. The atomic and molecular emission was observed from the radiation spectrum. Along with the emission from molecules of Air, emissions from contaminations were also observed. The temperature of the radiating gas was estimated using the blackbody radiation curve and was observed to be 13000 K.

Model of the Impact of Focused Ultrasound on Biological Tissues

To study tissue permeability under extracorporeal exposure to various types of radiation, it is necessary to use multiphysical and mathematical modeling of all stages of the technology being developed, taking into account the dielectric and acoustic properties of human body tissues. The technologies used in medicine with focused ultrasound often have a high level of artifacts in the visualization of diagnostic studies and complications during therapy. When modeling exposure to focused ultrasound, the applied solvers must take into account pressure wave propagation, density changes and jumps, non-linearity and diffusion losses that occur in human tissues, and offer simulation of acoustic propagation in inhomogeneous installations in near real time. The article presents the results of multiphysics and mathematical modeling in the Sim4Life for Science V7.0 package using a full-wave acoustic solver (P-ACOUSTICS) of modern computational acoustics.

Surface passivation in c-Si solar cells via a double-barrier quantum-well structure for ameliorated performance

Modern solar cell technology suffers low surface passivation, high recombination losses at the interface, and dopant diffusion losses that limit solar cell’s efficiency. Therefore, a double-barrier quantum-well (DBQW) structure-based surface passivation contact is introduced here to resolve these shortcomings. In this regard, DBQWs of different thicknesses with stacks of SiOx/ nc-SiOx (3, 5, 8, and 10 nm)/SiOx layers were explored as surface passivation layers and dopant diffusion barriers. Multiple characterizations were utilized to examine DBQW thickness-dependent properties, such as contact resistance, passivation, and recombination current density; the best result was for the 5-nm-thickness QW passivation layer. To justify the obtained result, theoretical calculations were carried out based on the experimental results, which suggested the resonance tunneling of charge carriers across the 5 nm DBQW structure. Furthermore, SIMS was explored to examine the diffusion barrier property of these QWs, which revealed that dopant diffusion was suppressed by the QW with the double SiOx layer. Finally, the nc-SiOx(n) /5-nm QW/c-Si surface passivation structure showed substantial enhancement in a lifetime (τeff) of 3560 μs, an implied open-circuit voltage (iVoc) of 735 mV, and reduced recombination current density (Jo) = 1.5 fA/cm2.

Revealing the radiation damage and Al-content impacts on He diffusion in goethite

Over the past few decades, the (U-Th)/He geochronological method on goethite has been more and more applied to date laterite formation and evolution or ore-deposit formation. However, questions remain on possible He loss by diffusion due to the polycrystalline structure of goethite and associated underestimation of the goethite crystallization date given by the (U-Th)/He age. Prior studies estimated helium loss in goethite to range from 2 to 30%, but no relation or models have been produced to explain such values. To clarify the situation, we firstly performed a complete review of experimental He diffusion data in natural goethite, that reveals the link between activation energy and He loss with the damage dose. To understand He diffusion behavior in goethite and model the He loss, natural defect and alpha damage as well as the chemical composition and growth structure effect on He diffusion have been investigated thanks to a multi-scale study. We used numerical simulations combining the Density Functional Theory (DFT) at the atomic scale and Kinetic Monte Carlo (KMC) simulations at the macroscopic scale. We found that He diffusion is purely anisotropic along the preferential elongated axis (i.e., b-axis) and He leaks out easily in defect-free goethite and Al-goethite. The consequence of this anisotropy is that crystallographic defects and alpha damage strongly lower the He diffusivity in goethite and Al-goethite by obstructing the diffusion channel or trapping He along the b-axis. Defect and damage impact on He diffusion is even larger for Al-goethite. The obtained He diffusion parameters for goethite containing defect and damage are similar to the activation energy and He diffusional loss obtained in natural goethite from the literature. We demonstrate the systematic dependence of the diffusion coefficient with damage dose and the impact of Al on He retention. He atoms are retained only at the favor of obstructions blocking the diffusion and vacancies trapping them in the goethite structure. The consequence of the diffusive behavior is that a part of He diffuses out of the crystal until sufficient damage accumulated along the b-axis. The diffusion domain size is the channel length along the b-axis rather than the whole crystallite size. To correct the He loss this study proposes estimation of the He retention and needed corrections for different types of goethite.

Error-correcting neural networks for semi-Lagrangian advection in the level-set method

We present a machine learning framework that blends image super-resolution technologies with passive, scalar transport in the level-set method. Here, we investigate whether we can compute on-the-fly, data-driven corrections to minimize numerical viscosity in the coarse-mesh evolution of an interface. The proposed system's starting point is the semi-Lagrangian formulation. And, to reduce numerical dissipation, we introduce an error-quantifying multilayer perceptron. The role of this neural network is to improve the numerically estimated surface trajectory. To do so, it processes localized level-set, velocity, and positional data in a single time frame for select vertices near the moving front. Our main contribution is thus a novel machine-learning-augmented transport algorithm that operates alongside selective redistancing and alternates with conventional advection to keep the adjusted interface trajectory smooth. Consequently, our procedure is more efficient than full-scan convolutional-based applications because it concentrates computational effort only around the free boundary. Also, we show through various tests that our strategy is effective at counteracting both numerical diffusion and mass loss. In simple advection problems, for example, our method can achieve the same precision as the baseline scheme at twice the resolution but at a fraction of the cost. Similarly, our hybrid technique can produce feasible solidification fronts for crystallization processes. On the other hand, tangential shear flows and highly deforming simulations can precipitate bias artifacts and inference deterioration. Likewise, stringent design velocity constraints can limit our solver's application to problems involving rapid interface changes. In the latter cases, we have identified several opportunities to enhance robustness without forgoing our approach's basic concept. Despite these circumstances, we believe all the above assets make our framework attractive to parallel level-set algorithms. Its appeal resides in the possibility of avoiding further mesh refinement and decreasing expensive communications between computing nodes.

Modeling of a 43 GHz microplasma within a photonic crystal

The electron density (ne) and argon metastable density (1s5) of a 43GHz microplasma are obtained using the zero-dimensional plasma kinetics solver (ZDPlasKin®) for an incident power of 160 and 1000mW and argon pressures of 10–600Torr (1.3×103 to 8.0×104Pa). These simulations are compared with previously published experimental data. To determine the self-consistent electric field in the modeled plasma, the three-dimensional millimeter wave fields are computed as a function of electron density using ANSYS EM19.2, HFSS®. This electromagnetic field model is coupled to ZDPlasKin such that any increase in the simulated plasma density correctly attenuates the simulated electric field within the microplasma. The electron density is found to be sensitive to argon gas temperature, so a two-zone temperature model was needed to obtain agreement with experimental measurements. The temperature in the central core of the microplasma was determined by a previous experimental study. That temperature was used as an input to the model for the simulation of volume recombination losses. The outer regions of the microplasma are assumed to be in equilibrium with the walls (300K). This second temperature was used in the model to determine diffusion losses. The modeled electron and metastable densities are of the order 1020 and 1018m−3, respectively. This is in good agreement with those measured experimentally as long as the two-zone temperature model is used. In the absence of a hot gas core, the modeled three-body recombination rates are excessive and the simulation severely under-predicts the electron density and over-estimates the metastable density. We conclude that the millimeter wave microplasma has a hot core (2500K at 600Torr) that rarifies the argon gas and effectively reduces three-body recombination. This allows one to achieve high electron density on the order of 1020m−3 with only 100mW of wave power.

Optimized diffusion–convection compromise for reversible CO 2 capture on hydroxylated organo-montmorillonite

Carbon dioxide (CO 2 ) was reversibly captured at room temperature and normal pressure by a low cost hybrid absorbent (NaMt-H30) obtained through Na-montmorillonite intercalation with Boltorn dendrimer H30 (1 wt%). Measurements through thermal programmed desorption between 20 °C and 200 °C showed variations of the retention capacities of CO 2 (CRC) and water (WRC) according to the nitrogen stream throughput, contact time and injected CO 2 amount for adsorbent saturation. CRC and WRC modeling as functions of these parameters was achieved using a 3 3 factorial design involving 27 attempts. Model analysis revealed that the retention of CO 2 and water molecules depend not only on the individual effects of each parameters but also on their interactions. High nitrogen throughput and low amount of impregnation resulted in detrimental effects on both CO 2 and moisture retention. This was explained in terms of diffusion and mass loss during impregnation through forced convection. An optimum compromise between these factors in correlation with the contribution of moisture content turned out to be an essential requirement for achieving highest CRC levels that express the effective material affinity towards carbon dioxide. These findings provide a useful tool for rigorously optimizing the reversible capture of CO 2 by hydroxylated adsorbents.

An ant-nest like hierarchical nanoreactor for highly efficient sulfur species redox reactions

The main challenge in the practical exploitation of lithium-sulfur (Li-S) batteries is to resolve the problems of the sluggish liquid-solid conversions and the diffusion loss of liquid polysulfides especially at high sulfur loading. Herein, a novel bio-inspired reactor with ant-nest like architecture was tailored for Li-S electrochemistry, which combines abundant active nickel nanoparticles with hierarchical porous carbon-nanosheets network (HPCN/Ni). The nanoreactor provides multiple functions including strong trapping efficiency with polysulfides, fast transfer of ions/electrons and liquid sulfur species, and sufficient catalytic activity. The cooperative effects could accelerate Li-S redox reactions and improve sulfur utilization. Enhanced by the highly efficient HPCN/Ni naonoreactor, Li-S cells demonstrate a high specific capacity of 1437.9 mAh g−1 at 0.1 C, remarkable rate performances such as 900 mAh g−1 at 2 C, and exellent cycling stability with a high capacity retention of 734.2 mAh g−1 after 300 cycles at 1 C. Even at a high sulfur area loading of 5.63 mg cm−2, a high area capacity of 4.75 mAh cm−2 could be achieved. This contribution affords a fesible approach to design and construct nanoreactors with high efficiency for Li-S batteries and the analogous applications.

Factors that govern sub-3 nm particle measurements in an Airmodus® PSM and a TSI® DEG–SMPS

Measurements of sub-3 nm particles are technically challenging and characterized with significant uncertainties. This study selected two types of widely used commercial instruments: an Airmodus® Particle Size Magnifier (PSM) and a TSI® diethylene glycol-based Scanning Mobility Particle Sizer (DEG–SMPS), and examined factors that govern their abilities on measurements of sub-3 nm particles. Monodisperse standard particles used in the experiments include positively and negatively charged tungsten oxide particles and nickel–chromium (Ni/Cr) oxide particles, positive and negative ions produced in a soft X-ray neutralizer, and positively charged organic particles including tetraheptylammonium bromide (THABr), tetrabutylammonium bromide (TBABr), and polyethylene glycol (PEG) particles. Our results show that both PSM and DEG–SMPS are subject to the influence of particle composition. Negatively charged tungsten oxide particles were detected at higher efficiencies than positively charged ones, whereas opposite results were observed for Ni/Cr particles and background ions produced in the soft X-ray neutralizer. In addition, the concentration accuracy of PSM and DEG–SMPS are explored after calibration using Ni/Cr particles. The inverted total concentrations by DEG–SMPS are usually underestimated because of the overestimation of penetration efficiency through different modules, whereas the inverted total concentrations by PSM can be either overestimated or underestimated, when the properties of analyte particles are significantly different from the calibration particles. A better understanding on the effects of particle chemical composition and charging state, and their diffusion losses in the instruments will help to diminish the uncertainties in the measurements.Copyright © 2022 American Association for Aerosol Research.

Tomato brown rugose fruit virus: A pathogen that is changing the tomato production worldwide

AbstractTomato (Solanum lycopersicum L., family Solanaceae) represents one of the most cultivated horticultural crops worldwide, with over 5 million hectares of cultivated area and more than 182 million tons of tomato produced globally. Nevertheless, monoculture conditions, intensive selection, domestication throughout the last decades, international trade of infected propagating material and climate changes intensely favoured the establishment of many pathogens and the rapid spread of new diseases, allowing organisms to establish in new and unfavourable environments. Among different biotic agents, viruses are the most dangerous, because of their rapid diffusion and production losses. Here, we review an emerging viral threat to tomato production, tomato brown rugose fruit virus (ToBRFV), a new highly infectious tobamovirus that is currently causing great concern to tomato global production, especially in those areas where mitigation measures are absent or inadequate and which, in recent years, it has considerably increased its diffusion in new tomato cultivation areas. Through a review of all the existing literature, this article highlights the following aspects: (a) main characteristic of tomato species (origin, taxonomy and genome); (b) main diseases that undermine the tomato production, focusing on viral pathogens; (c) ToBRFV main characteristics (origin and spatiotemporal dispersal, taxonomy, genome organisation, host range and symptoms, transmission, spread and epidemiology, and genetic diversity); (d) detection methods developed and disease management; (e) breeding as a new weapon to control the ToBRFV diffusion. Moreover, future perspectives are highlighted, to understand the epidemiology key factors and the ToBRFV‐tomato pathosystem management, in order to develop effective and appropriate control strategies.

Workbench for a Parabolic Trough Solar Collector with a Tracking System.

Solar energy found abundantly in nature is considered a renewable energy source. It is also of great interest as an option for energy generation and CO2 emissions reduction. Several technologies of solar concentrating systems, known internationally as CSP (concentrated solar power), are found in the industrial and scientific environment. One of the most mature and internationally known technologies is the parabolic trough solar collector (PTSC), which has several applications, such as electricity generation, desalination, steam generation, and refrigeration systems, among others. However, more research and development (R&D) has been done to improve its performance, using new materials, absorber tube geometries, solar tracking systems, and work (thermal oils, nanofluids). Thus, the present work describes the development of a low-cost PTSC for academic and research purposes. The PTSC was built with an edge angle of 120°, an opening area of 2.2 m2, and a copper absorber tube of 42 mm in outer diameter without a glass envelope. The gutter structure is composed of wooden sheets cut in a parabolic shape, where a 1.2 mm-thick galvanized steel sheet coated with a reflective film is supported, thus functioning as the reflective surface of the PTSC. The solar tracking system is one of the active types with two axes containing photoresistive sensors, which are used to determine the solar position and electric actuators to correct the positioning of the gutter. The monitoring system was developed through an interactive panel to visualize the operating parameters of the sensing elements, thermocouples that measure the inlet and outlet temperature in the absorber tube, and the flow sensor to measure the flow of the heat transport fluid. Laboratory tests were performed with deionized water as a transport fluid, establishing two testing conditions. The first test condition analyzed the efficiency of the collector at different temperatures. Thus, the inlet temperature varied, between 30 and 70°C, presenting a flow of 0.020 kg/s. The second one evaluated the collector efficiency for different flows, subjecting the collector to flows from 0.002 to 0.030 kg/s. Thus, the proposed collector obtained an efficiency as a function of the temperature represented by the expression η = 0.324–2.47443 c′, where c′ is a parameter that relates the inlet temperature to the ambient temperature as a function of the solar radiation available. Yet, the efficiency in function of the flow became optimal when the flow regime became turbulent. It was concluded that the proposed solar collector obtained lower efficiency when compared with other collectors in the literature, which was assumed to be due to the diffusion losses of the parabolic trough reflector and thermal losses by convection in the parabolic trough absorber tube (optical efficiency, removal factor, and heat loss coefficient).

Determining the noble gas cosmic ray exposure ages of 23 meteorites (8 chondrites and 15 achondrites) from modeling and empirical methods

AbstractWe present He‐Ne‐Ar isotope data for 23 meteorite samples mainly recovered in Antarctica (six ordinary chondrites [OC], two CV chondrites, eight eucrites, one diogenite, and six ureilites), which are used to compute radiogenic gas retention ages and cosmic ray exposure (CRE) ages using both empirical and modeling approaches. For all samples where both 40K‐40Ar and U,Th‐4He retention ages could be derived, we find that U,Th‐4He ages are systematically lower than 40K‐40Ar ages, likely reflecting preferential diffusive loss of He relative to Ar. There is good agreement between empirically derived CRE ages calculated by (22Ne/21Ne)cos‐3Hecos and (22Ne/21Ne)cos‐21Necos approaches; where discrepancies occur, the (22Ne/21Ne)cos‐3Hecos approach systematically yields lower CRE ages, also likely due to 3He loss. Overall, CRE ages derived from the empirical and modeling approaches show excellent agreement, within ∼10%. CRE ages derived for OC (4–24 Myr), CV chondrites (12–26 Myr), eucrites (4–45 Myr), the diogenite (30 Myr), and ureilites (<10 Myr) are in line with previous investigations of these meteorite groups. Some ureilites and one eucrite exhibit remarkably high cosmogenic 22Ne/21Ne > 1.24, as previously observed in various other rare achondrites. These samples likely contain solar cosmic ray‐produced Ne (SCR‐Ne) in addition to the commonly found galactic cosmic ray‐produced Ne (GCR‐Ne), implying low pre‐atmospheric shielding and limited ablation upon atmospheric entry. The presence of SCR‐Ne complicates the determination of the pure GCR‐22Ne/21Ne, hampering its use as a shielding indicator. Nonetheless, we suggest that a first‐order correction for SCR‐Ne contribution can be used to derive a range of potential CRE ages for each sample.

Neurotransmitter Readily Escapes Detection at the Opposing Microelectrode Surface in Typical Amperometric Measurements of Exocytosis at Single Cells.

For decades, carbon-fiber microelectrodes have been used in amperometric measurements of neurotransmitter release at a wide variety of cell types, providing a tremendous amount of valuable information on the mechanisms involved in dense-core vesicle fusion. The electroactive molecules that are released can be detected at the opposing microelectrode surface, allowing for precise quantification as well as detailed kinetic information on the stages of neurotransmitter release. However, it remains unclear how much of the catecholamine that is released into the artificial synapse escapes detection. This work examines two separate mechanisms by which released neurotransmitter goes undetected in a typical amperometric measurement. First, diffusional loss is assessed by monitoring exocytosis at single bovine chromaffin cells using carbon-fiber microelectrodes fabricated in a recessed (cavity) geometry. This creates a microsampling vial that minimizes diffusional loss of analyte prior to detection. More molecules were detected per exocytotic release event when using a recessed cavity sensor as compared to the conventional configuration. In addition, pharmacological inhibition of the norepinephrine transporter (NET), which serves to remove catecholamine from the extracellular space, increased both the size and the time course of individual amperometric events. Overall, this study characterizes distinct physical and biological mechanisms by which released neurotransmitter escapes detection at the opposing microelectrode surface, while also revealing an important role for the NET in "presynaptic" modulation of neurotransmitter release.

A Novel Method for On-Line Characterization of Alkali Release and Thermal Stability of Materials Used in Thermochemical Conversion Processes

Alkali metal compounds are released during the thermal conversion of biofuels and fossil fuels and have a major impact on the efficiency of conversion processes. Herein, we describe a novel method for the simultaneous characterization of alkali release and mass loss from materials used in combustion and gasification processes including solid fuels, fluidized bed materials, and catalysts for gas reforming. The method combines the thermogravimetric analysis of selected samples with the on-line measurement of alkali release using a surface ionization detector. The technique builds on the careful treatment of alkali processes during transport from a sample to the downstream alkali monitor including the losses of alkali in the molecular form to hot walls, the formation of nanometer-sized alkali-containing particles during the cooling of exhaust gases, aerosol particle growth, and diffusion losses in sampling tubes. The performance of the setup was demonstrated using biomass samples and fluidized bed material from an industrial process. The emissions of alkali compounds during sample heating and isothermal conditions were determined and related to the simultaneous thermogravimetric analysis. The methodology was concluded to provide new evidence regarding the behavior of alkali in key processes including biomass pyrolysis and gasification and ash interactions with fluidized beds. The implications and further improvements of the technique are discussed.