Slow Transport Processes Research Articles

Shortages, Supply Chains, and Sustainability: Where Does Our Scope of Practice End?

Residents' Review| June 2023 Shortages, Supply Chains, and Sustainability: Where Does Our Scope of Practice End? Federico Ciardi, MA (Oxon), MBBS; Federico Ciardi, MA (Oxon), MBBS Search for other works by this author on: This Site PubMed Google Scholar Briana Kossbiel, MD Briana Kossbiel, MD Search for other works by this author on: This Site PubMed Google Scholar ASA Monitor June 2023, Vol. 87, 35–36. https://doi.org/10.1097/01.ASM.0000938868.62560.20 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn Email Cite Icon Cite Get Permissions Search Site Citation Federico Ciardi, Briana Kossbiel; Shortages, Supply Chains, and Sustainability: Where Does Our Scope of Practice End?. ASA Monitor 2023; 87:35–36 doi: https://doi.org/10.1097/01.ASM.0000938868.62560.20 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll PublicationsASA Monitor Search Advanced Search Topics: scope of practice Extreme climate events from rising temperatures and sea levels are increasing in frequency. Such events are altering complex interdependent pathways – both natural and manmade. While there is direct, acute, and obvious injury to the environment, there are also chronic, indirect effects by the way climate change alters disease patterns. Eventually, the consequences lead to increased costs for an already exasperated medical system, with an inability to meet essential health care needs. Equipment shortages and supply chain interferences are more prevalent as weather events slow production and transport processes, especially for pharmaceuticals. This has been seen recently with Winter Storm Uri in Texas, the drought of the Rhine River, flooding in central China, Hurricane Ida in Louisiana, and Hurricane Maria in Puerto Rico (asamonitor.pub/3Uat9cy; Marit Econ Logist 2022;24:489-506). However, shortages are not just seen in material goods. Climate change has promoted a maldistribution of the health care... You do not currently have access to this content.

New Reduced‐Order Lithium‐Ion Battery Model to Account for the Local Fluctuations in the Porous Electrodes

Numerical simulations of microscopic transport processes in porous electrodes of lithium‐ion batteries demonstrate the presence of spatially localized fluctuations of physical quantities on the microstructure scale. They can influence the macroscopic battery characteristics (for example, the degradation rates). These fluctuations cannot be captured in a straightforward manner by the widely used porous electrode theory by Doyle, Fuller, and Newman (DFN model). The latter treats the porous electrodes as macroscopically homogeneous composite materials; it reduces the computational costs of numerical simulations. Herein, a modification of the DFN model that incorporates the local fluctuations but preserves the computational efficiency is proposed. Numerical simulation examples are presented that test the accuracy of the reproduction of the local fluctuations. The main new feature lies in the mathematical representation of the slow transport processes in the active material and their influence on the macroscopic reaction rates. The model is rooted in the rigorous mathematical analysis of the transition from a microscopic, microstructure‐resolving transport and reaction description to a macroscopic, volume averaging‐based one. The model construction methodology is open for further modifications for the applications in which some of the assumptions should be dropped, or description of new processes, reactions, phases, etc. should be incorporated.

Communication—Identifying and Managing Reversible Capacity Losses that Falsify Cycle Ageing Tests of Lithium-Ion Cells

We report on a cycle ageing study of commercial NCA/Gr+Si cells, in which reversible capacity fluctuations turn a central experimental finding upside down: an upper voltage limit of 4.1 V seems to cause faster degradation than going all the way to 4.2 V. The underlying effect is the reversible loss of lithium inventory into passive anode overhang areas. We demonstrate how the resulting artefact arises from a combination of slow transport processes and the related time periods spent in specific state-of-charge regions. We propose an alternative visualisation tool to identify and manage such artefacts, often neglected in typical ageing studies.

Self-similarity in fate and transport of contaminants in groundwater

Similarity within non-linear geophysical processes under different space and time has been investigated in literature to understand and model the sophisticated nature of these processes. This study deals with the self-similarity of the governing processes of fate and transport of contaminants in groundwater, which include advection, dispersion, sorption, and degradation, either by chemical reaction or microbiological interaction. As such, self-similarity conditions of three-dimensional advective-dispersive-reactive transport (ADR) equation with various initial and boundary conditions are obtained by employing one-parameter Lie group of point scaling transformations. The strength of the proposed scaling approach lies in its ability to handle initial and boundary conditions of the process together with the governing equation. Then, utilizing reported conditions in Borden Field experiment domain, numerical simulations are performed to demonstrate examples of self-similarity when first-order degradation rate constant is zero and nonzero under three sorption conditions. The results of the numerical examples showed the effectiveness of the derived self-similarity conditions and the strength of the proposed approach in handling initial and boundary conditions of the governing transport process. It is possible to obtain both smaller and larger size self-similar (scaled-up or scaled-down) domains, which result in faster and slower transport processes, respectively. The obtained self-similarity criteria can offer further understanding of ADR transport phenomena and can provide spatial, temporal, and economical flexibility in constructing scaled models of field conditions governed by three-dimensional ADR transport process.

Proton Relaxometry of Long-Lived Spin Order.

A study of long-lived spin order in chlorothiophene carboxylates at both high and low magnetic fields is presented. Careful sample preparation (removal of dissolved oxygen in solution, chelating of paramagnetic impurities, reduction of convection) allows one to obtain very long-lived singlet order of the two coupled protons in chlorothiophene derivatives, having lifetimes of about 130 s in D2 O and 240 s in deuterated methanol, which are much longer than the T1 -relaxation times (18 and 30 s, respectively, at a field =9.4 T). In protonated solvents the relaxation times become shorter, but the lifetime is still substantially longer than . In addition, long-lived coherences are shown to have lifetimes as long as 30 s. Thiophene derivatives can be used as molecular tags to study slow transport, slow dynamics and slow chemical processes, as has been shown in recent years.

A characteristic mass fraction difference in absorption chillers

Absorption chillers are considered as heat transfer devices and hence most commonly modeled as heat transfer processes. The absorption of the refrigerant vapor though inherently involves mass transfer into the absorbent, which in comparison to the heat transfer usually is a slow transport process. Modeling absorption chillers, however, usually does not include this mass transfer process. This in fact neglects the dominant process in absorption chillers which is addressed in the present paper.

Light-Driven Chloride Transport Kinetics of Halorhodopsin

Despite growing interest in light-driven ion pumps for use in optogenetics, current estimates of their transport rates span two orders of magnitude due to challenges in measuring slow transport processes and determining protein concentration and/or orientation in membranes in vitro. In this study, we report, to our knowledge, the first direct quantitative measurement of light-driven Cl− transport rates of the anion pump halorohodopsin from Natronomonas pharaonis (NpHR). We used light-interfaced voltage clamp measurements on NpHR-expressing oocytes to obtain a transport rate of 219 (± 98) Cl−/protein/s for a photon flux of 630 photons/protein/s. The measurement is consistent with the literature-reported quantum efficiency of ∼30% for NpHR, i.e., 0.3 isomerizations per photon absorbed. To reconcile our measurements with an earlier-reported 20 ms rate-limiting step, or 35 turnovers/protein/s, we conducted, to our knowledge, novel consecutive single-turnover flash experiments that demonstrate that under continuous illumination, NpHR bypasses this step in the photocycle.

Pore scale study of multiphase multicomponent reactive transport during CO2 dissolution trapping

Abstract Solubility trapping is crucial for permanent CO2 sequestration in deep saline aquifers. For the first time, a pore-scale numerical method is developed to investigate coupled scCO2-water two-phase flow, multicomponent (CO2(aq), H+, HCO3−, CO32− and OH−) mass transport, heterogeneous interfacial dissolution reaction, and homogeneous dissociation reactions. Pore-scale details of evolutions of multiphase distributions and concentration fields are presented and discussed. Time evolutions of several variables including averaged CO2(aq) concentration, scCO2 saturation, and pH value are analyzed. Specific interfacial length, an important variable which cannot be determined but is required by continuum models, is investigated in detail. Mass transport coefficient or efficient dissolution rate is also evaluated. The pore-scale results show strong non-equilibrium characteristics during solubility trapping due to non-uniform distributions of multiphase as well as slow mass transport process. Complicated coupling mechanisms between multiphase flow, mass transport and chemical reactions are also revealed. Finally, effects of wettability are also studied. The pore-scale studies provide deep understanding of non-linear non-equilibrium multiple physicochemical processes during CO2 solubility trapping processes, and also allow to quantitatively predict some important empirical relationships, such as saturation-interfacial surface area, for continuum models.

Pore scale study of multiphase multicomponent reactive transport during CO2 dissolution trapping

Solubility trapping is crucial for permanent CO2 sequestration in deep saline aquifers. For the first time, a pore-scale numerical method is developed to investigate coupled scCO2-water two-phase flow, multicomponent (CO2(aq), H+, HCO3−, CO32− and OH−) mass transport, heterogeneous interfacial dissolution reaction, and homogeneous dissociation reactions. Pore-scale details of evolutions of multiphase distributions and concentration fields are presented and discussed. Time evolutions of several variables including averaged CO2(aq) concentration, scCO2 saturation, and pH value are analyzed. Specific interfacial length, an important variable which cannot be determined but is required by continuum models, is investigated in detail. Mass transport coefficient or efficient dissolution rate is also evaluated. The pore-scale results show strong non-equilibrium characteristics during solubility trapping due to non-uniform distributions of multiphase as well as slow mass transport process. Complicated coupling mechanisms between multiphase flow, mass transport and chemical reactions are also revealed. Finally, effects of wettability are also studied. The pore-scale studies provide deep understanding of non-linear non-equilibrium multiple physicochemical processes during CO2 solubility trapping processes, and also allow to quantitatively predict some important empirical relationships, such as saturation-interfacial surface area, for continuum models.

Cis Versus trans-Azobenzene: Precise Determination of NMR Parameters and Analysis of Long-Lived States of 15N Spin Pairs

We provide a detailed evaluation of nuclear magnetic resonance (NMR) parameters of the cis- and trans-isomers of azobenzene (AB). For determining the NMR parameters, such as proton–proton and proton–nitrogen J-couplings and chemical shifts, we compared NMR spectra of three different isotopomers of AB: the doubly 15N labeled azobenzene, 15N,15N′-AB, and two partially deuterated AB isotopomers with a single 15N atom. For the total lineshape analysis of NMR spectra, we used the recently developed ANATOLIA software package. The determined NMR parameters allowed us to optimize experiments for investigating singlet long-lived spin states (LLSs) of 15N spin pairs and to measure LLS lifetimes in cis-AB and trans-AB. Magnetization-to-singlet-to-magnetization conversion has been performed using the SLIC and APSOC techniques, providing a degree of conversion up to 17 and 24% of the initial magnetization, respectively. Our approach is useful for optimizing the performance of experiments with singlet LLSs; such LLSs can be exploited for preserving spin hyperpolarization, for probing slow molecular dynamics, slow chemical processes and also slow transport processes.

Drastic sensing enhancement using acoustic bubbles for surface-based microfluidic sensors

There is a high demand for ultrafast biosensors for industrial and public health applications. However, the performance of existing sensors is often limited by the slow mass transport process in traditional pressure-driven microfluidic devices. In this paper, we show for the first time that acoustic microbubbles trapped in prefabricated cavities in a micro-chamber are capable of enhancing fluid sample mixing that results in faster delivery of target species to the sensor surface. We demonstrate a drastic reduction of sensor response time (up to 21.3-fold) for surface-based nanosensors in presence of resonantly actuated microbubbles. The obtained results are valid in a wide pH (4–10) range and agree well with previous studies.

Molybdenum Disulfide‐Based Tubular Microengines: Toward Biomedical Applications

2D molybdenum disulfide (MoS2) is herein explored as an advanced surface material in the fabrication of powerful tubular microengines. The new catalytic self‐propelled open‐tube bilayer microengines have been fabricated using a template electrodeposition and couple the unique properties of sp2 hybridized MoS2 with highly reactive inner granular Pt catalytic structures. The MoS2/metal microengines display extremely efficient bubble propulsion, reflecting the granular structure of the inner catalytic platinum or gold layers (compared to the smooth metal surfaces of common micromotors). The efficient movement of functionalized MoS2 micromotors can address challenges imposed by slow mass transport processes involved in various applications of MoS2. The delocalized electron network of the MoS2 outer layer facilitates π–π stacking interactions and endows the tubular microengines with a diverse array of capabilities. These are demonstrated here for efficient loading and release of the drug doxorubicin, and rapid and sensitive “OFF–ON” fluorescent detection of important nucleic acids (miRNA‐21) and proteins (thrombin) using microengines modified with dye‐labeled single‐stranded DNA and aptamer, respectively. Such coupling of the attractive capabilities of 2D‐MoS2 nanosheets with rapidly moving microengines provides an opportunity to develop multifunctional micromachines for diverse biomedical applications ranging from efficient drug delivery to the detection of important bioanalytes.

A numerical method for the time coarsening of transport processes at the atomistic scale

We propose a novel numerical scheme for the simulation of slow transport processes at the atomistic scale. The scheme is based on a model for non-equilibrium statistical thermodynamics recently proposed by the authors, and extends it by formulating a variational integrator, i.e. a discrete functional whose optimality conditions provide all the governing equations of the problem. The method is employed to study surface segregation of AuAg alloys and its convergence is confirmed numerically.

Gamma-ray inspection of rotating object

We develop a method to diagnose two-dimensional distribution of positron-emitting radioactivity in a rotating object through γ-ray coincidence measurements with two detectors. The principle of this method is same as PET but the measurement system is much simpler. We have constructed a prototype and performed tests with point-like and plate-shaped radioactive sources. The image reconstruction with ML-EM algorithm reproduced the distribution. It can be useful for radiotracer measurements of slow transport processes of materials in a closed system and can find applications in mechanical engineering.

Characterization of Shale Cap-Rock Nano-Pores in Geologic CO2 Containment

Research Article| November 01, 2014 Characterization of Shale Cap-Rock Nano-Pores in Geologic CO2 Containment ABIOLA OLABODE; ABIOLA OLABODE 1 Craft and Hawkins Department of Petroleum Engineering, Louisiana State University, 2129/2131 Patrick F. Taylor Hall, Baton Rouge, LA 70803 1Corresponding author email: aolabo2@lsu.edu. Tel.: 225-921-8309. Search for other works by this author on: GSW Google Scholar MILEVA RADONJIC MILEVA RADONJIC Craft and Hawkins Department of Petroleum Engineering, Louisiana State University, 2129/2131 Patrick F. Taylor Hall, Baton Rouge, LA 70803 Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (2014) 20 (4): 361–370. https://doi.org/10.2113/gseegeosci.20.4.361 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation ABIOLA OLABODE, MILEVA RADONJIC; Characterization of Shale Cap-Rock Nano-Pores in Geologic CO2 Containment. Environmental & Engineering Geoscience 2014;; 20 (4): 361–370. doi: https://doi.org/10.2113/gseegeosci.20.4.361 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Clay-rich cap rocks such as shale should be investigated experimentally for their geomechanical and geochemical behavior when in contact with aqueous CO2 over a long period of time, as can be observed in geologic carbon sequestration. The reactivity of shale cap rock during diffusive transport of CO2-brine needs to be included in the reservoir characterization of potential CO2 sequestration sites because slow reactive transport processes can either strengthen or degrade seal integrity in the long term. This experimental work applied inductively coupled plasma–optical emission spectroscopy (ICP-OES) and the Brunauer-Emmett-Teller (BET) techniques in investigating changes in surface and near-surface properties of crushed shale rocks after exposure (by flooding) to CO2-brine for a time frame ranging from 30 days to 90 days at elevated pressure and fractional flow rate. Flooding of the shale samples with CO2-brine was followed by measurement of changes in internal specific surface area and linear pore-size distribution resulting from aqueous CO2 reactive transport. The intrinsically low hydraulic conductivity of shale may be altered by changes in surface properties because the effective permeability of any porous medium is largely a function of its global specific pore geometry and surface mineralogical properties. Capillary entry pressure for the shale, as well as the average pore throat size were estimated from digitally acquired pressure evolution data. This allowed for the estimation of dimensionless quantities such as Peclet (Pe) and Peclet-Damköhler (PeDa) numbers, which are associated with the geochemical reactivity of rocks and acidic fluid transport through porous media. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Highly Active Nonplatinum Electrodes for Rechargeable Metal-Air Battery

Metal-air batteries have attracted much attention as a promising energy storage system because of their extremely high theoretical energy density. It may also offer the attractive opportunity to utilize inexpensive and environmentally friendly materials. However, it is still hard to meet the high demands such as cycle life or energy efficiency required for electrified transportations like EVs, and needed further understanding of battery science as well as many breakthroughs in material design and system integration.The oxygen reduction reaction (ORR), which proceeds on the air cathode, is believed to be largely responsible for determining the performance of the battery because ORR is intrinsically a demanding reaction due to the sluggish kinetics and slow mass transport process. However, there is still little systematic understanding of what role surface chemistry determines the electron transfer kinetics especially in alkaline media.In this study, mixed metal oxides such as Perovskites and Spinels were prepared with various synthetic concepts and their structural and electrochemical characteristics were investigated. It was found that some Perovskite catalysts prepared by citric acid method show even superior activity than that of Platinum group metal catalyst (Fig. 1). We attribute this excellent ORR activity of the metal oxide-based electrodes to the intimate contact and the specific interaction between metal oxide catalysts and carbon supports which facilitate the efficient electron transfer to adsorbed intermediate peroxide species. This process consequently leads serial reduction of intermediate species to hydroxide, thus the overall process could be viewed as an apparent 4 electrons reduction reaction. It was also found that the facility of ORR was highly dependent on the choice of B site element in Perovskite and the geometrical design of the air electrode tuned by slurry preparation and coating processes.The performance of full cell was evaluated with the air cathode consisted of the Perovskite catalyst and carbon support, various anodes such as originally developed metal hydride and the third electrode specifically used for the oxygen evolution reaction. The battery shows a promising rate capability and capacity retention for extensive cycling test.

Carrier transport processes in dye sensitized solar cells based on Zn2SnO4 nanostructures studied by intensity modulated photocurrent/photovoltage spectroscopy

In this work, the electron transport and recombination processes in dye sensitized solar cells (DSSCs) based on Zn2SnO4 nanowires and nanoparticles were studied by intensity modulated photocurrent spectroscopy (IMPS)/photovoltage spectroscopy. Two distinct transport time constants were obtained from the IMPS spectra of Zn2SnO4 nanowire-DSSCs, which were associated with a fast, direct transport through the single crystalline structure of the nanowires and a slow, percolation transport that was assisted by the nanowire surface states, respectively. The charge collection efficiency for the fast transport process was close to unity in all the measurements at different light intensities, indicating that the overall charge collection efficiency of nanowire-DSSCs could be enhanced if the slow transport process could be suppressed.

Revealing and accelerating slow electron transport in amorphous molybdenum sulphide particles for hydrogen evolution reaction

Electrochemical impedance spectroscopy is used to identify a slow electron transport process in hydrogen evolution catalysed by amorphous molybdenum sulphides on glassy carbon. A new chemical synthesis leads to an amorphous molybdenum sulfide catalyst with a higher electronic conductivity.

Experimental Investigations of Caprock Integrity in CO2 Sequestration

The geochemical reactivity of shale caprock during post-injection CO2 diffusive transfer should be included in the reservoir characterization of CO2 sequestration sites as slow reactive transport processes can either improve or degrade seal integrity over the long term. Simulation results reported by various researchers suggested that influx-induced mineral dissolution/precipitation reactions within shale caprocks can continuously close micro-fracture networks, while pressure and effective-stress transformation first rapidly expand then progressively constrict them. This experimental work applied specific analytical techniques in investigating changes in mineralogical and microstructural properties of crushed shale rocks after exposure (by flooding) to CO2-brine for a time frame ranging between 30 days to 92 days at elevated pressure and fractional flow rate. The initial mineralogical composition in the samples showed bulk clay, quartz and feldspar as the major components of the formation. Initial capillary entry parameters for the shale were estimated from digitally acquired injection pressure profile. Flooding of the shale samples with CO2-brine was followed by geochemical characterization of the effluent fluid and bulk shale rock through pH and XRD measurements. Nano-scale measurement of changes in internal specific surface area and cumulative pore size distribution (using the BET Technique) revealed that changes in the shale caprock due to geochemical interaction with aqueous CO2 can affect petrophysical properties. The naturally low permeability in shale may be altered by changes in specific surface area as the effective permeability of any porous medium is largely a function of its total pore geometry/volume, and particularly the pore throat-diameter. The geochemical reactivity of shale caprocks through acidic fluid transport in interconnected pore networks gave insight into the impact of diffusion and reaction rate on shale caprock integrity in CO2 sequestration.

Ionosphere variations at 700 km altitude observed by the DEMETER satellite during the 29 March 2006 solar eclipse

We present an experimental and modeling study of the effects of the 29 March 2006 solar eclipse in the topside ionosphere. Measurements of the densities and temperatures of the thermal electrons and ions were provided by instruments aboard the Centre National d'Etudes Spatiales microsatellite DEMETER, which flew over Europe and Africa near the time of maximum solar obscuration. Data from several orbits, either on the same day or on days encompassing the eclipse day, were available to determine a reference state of the ionosphere along the orbit in absence of eclipse. The comparison between this latter and the actual observations along the eclipse orbit reveal a clear thermal effect with a fast drop of about 200 K of the electron and ion temperatures that follows the variations of the solar UV flux in the F region of the ionosphere conjugate to the satellite position. The plasma density decreases by about 30% but with a significant delay and is better correlated with the solar UV flux averaged over the previous 1 to 2 h in the conjugate F region. This delayed and prolonged decrease of density induces an increase of the electron temperature to be higher than the reference ionosphere. We have also performed a modeling of the ionosphere using the SAMI2 code, after having introduced adequate modifications to reproduce fairly realistic eclipse conditions. Applied to the DEMETER conditions of observation, the model reproduces the observations very well. This work shows that the plasma temperature responds very quickly along the magnetic field lines to the variations of the energy available from the photoelectrons while the plasma density variations are controlled by more complex and slower transport processes.