Electrochemical bioelectronics in drug delivery - effect of the initial gas volume

Implantable bioelectronic devices with drug delivery capabilities have emerged as suitable candidates for biomedical applications focusing on localized drug delivery. These classes of miniaturized bioelectronics offer wireless operation and refillable designs that can be used for repeated animal behavioral studies without restricting their motion. The pumping mechanisms of these bioelectronic devices features soft materials, microfluidics, and electrochemical subsystems that can be scaled from behavioral studies in small animals to delivery of life-saving medication in humans. Here, we study the refillable aspect of these bioelectronic systems using an analytic model for the drug delivery time established from the ideal gas law when an initial gas volume is present in the device electrolyte reservoirs. The effect of the initial gas volume in delaying the drug delivery time is captured via a non-dimensional parameter identified as the normalized initial gas volume. An analytical solution is derived from the perturbation method, which agrees well with the numerical solution. These results have relevance in the reusability aspect of these bioelectronic systems since modifying the amount of initial gas in the device reservoirs for different experiments affects the total delivery time and can serve as a tunable parameter to ensure timely and successful delivery of the drug in the target region.

Gas Laws

Gas Laws summarizes the general laws that describe how the volume of a gas changes in response to changes in pressure (P), temperature (T in Kelvin) or the number of moles (n). The ideal gas law, which combines Boyle’s law, Charles’s law and Avogadro’s law, is presented, with explanations of using it to solve gas-law problems. Mathematical rearrangements of the ideal gas law to determine density and molar mass are described along with the use of Dalton’s law of partial pressures to find the pressure of each gas in a mixture. Finally the chapter presents ideal gas law and reaction stoichiometry, Graham’s law of effusion, and basic notions of real gases and their deviation from the ideal gas laws.

An Ideal yet Highly Accurate Model Correlating Global Average Temperature to Excess CO2-Emissions

The causality of preceding atmospheric excess-to-equilibrium CO₂-amounts and trailing system temperature increase is captured in terms of the ideal gas law, equilibrium thermodynamics and transition state theory for the first time: the model’s performance is excellent, publicly available global mean temperature data from 1880 (13.58 °C / 290.7 ppm) to April 2021 (14.49 °C / 416.2 ppm) are reproduced at less than ±2 % deviation. Eight future global mean temperatures for atmospheric CO₂-levels between 450 ppm and 7000 ppm are extrapolated and an empiric expression of the relation is derived. The model’s ideal nature allows adaption for other greenhouse gases and provides a reference for conclusions about the energetic weighting and the wider significance of the CO₂-based proportion in the total Greenhouse effect.

An Ideal yet Highly Accurate Model Correlating Global Average Temperature to Excess CO2-Emissions

The causality of preceding atmospheric excess-to-equilibrium CO₂-amounts and trailing system temperature increase is captured in terms of the ideal gas law, equilibrium thermodynamics and transition state theory for the first time: the model’s performance is excellent, publicly available global mean temperature data from 1880 (13.58 °C / 290.7 ppm) to April 2021 (14.49 °C / 416.2 ppm) are reproduced at less than ±2 % deviation. Eight future global mean temperatures for atmospheric CO₂-levels between 450 ppm and 7000 ppm are extrapolated and an empiric expression of the relation is derived. The model’s ideal nature allows adaption for other greenhouse gases and provides a reference for conclusions about the energetic weighting and the wider significance of the CO₂-based proportion in the total Greenhouse effect.

The Master Key to the Problem of Reversible Chemical Hydrogen Storage is 12 kJ (mol H2)-1

<p>This article unveils on basis of the ideal gas law, the atomic conception of matter and classic equilibrium thermodynamics the ideal final regularity of reversible hydrogen mass transfer. This result allows to clarify problems of metal hydride chemistry which otherwise are impossible to understand e.g. why the substitution of 4 mol % Na by K in Ti-doped NaAlH₄ raises the reversible hydrogen capacity by 42 % at no substantial change to thermodynamic reaction parameters or how the dopants take effect in (Rb/K)-co-doped Mg(NH₂)₂/2LiH; both cases are discussed in this context. This ideal final regularity is a hitherto missed out superposition of physical chemistry fundamentals and defines the maximum specific energy at distinct conditions: directly for two-phase hydrogen storage methods and indirectly for electrochemical systems due to the normative role of hydrogen electrode potentials.</p>

Novel gas measurement based on pressure triggered release cycles for biochemical methane potential tests

This study aims to present a novel gas counter and to demonstrate its suitability for biochemical methane potential tests. In this system, the gas to be measured is collected in a chamber enclosed with two one-way solenoid valves and the absolute pressure is continuously monitored. After a trigger pressure is reached, a portion of the gas is released and the amount of the released gas is calculated according to ideal gas law and recorded. Three iterations of the supervisory control and data acquisition unit were constructed and tested for BMP measurement. Although it can be further improved and variations are possible, the presented final version works with eight reactors simultaneously and the recommended maximum gas flow is 1.24 mL/min. For those reactors, the measured/theoretical BMP ratio was 65.3% with 4.2% standard uncertainty, which is subjectively acceptable. Therefore, it can be concluded that the concept is valid and applicable to BMP tests.

A Unit Pipe Pneumatic model to simulate gas kinetics during measurements of embolism in excised angiosperm xylem

The Pneumatic method has been introduced to quantify embolism resistance in plant xylem of various organs. Despite striking similarity in vulnerability curves between the Pneumatic and hydraulic methods, a modeling approach is highly needed to demonstrate that xylem embolism resistance can be accurately quantified based on gas diffusion kinetics.A Unit Pipe Pneumatic (UPPn) model was developed to estimate gas diffusion from intact conduits, which were axially interconnected by interconduit pit membranes. The physical laws used included Fick’s law for diffusion, Henry’s law for gas concentration partitioning between liquid and gas phases at equilibrium, and the ideal gas law.The UPPn model showed that 91% of the extracted gas came from the first two series of embolized, intact conduits, and only 9% from the aqueous phase after 15 s of simulation. Embolism resistance measured with a Pneumatic apparatus was systematically overestimated by 2 to 17%, corresponding to a typical measuring error of 0.11 MPa for P50 (the water potential equivalent to 50% of the maximum amount of gas extracted).Because results from the UPPn model are supported by experimental evidence, there is a good theoretical and experimental basis for applying the pneumatic method to research on embolism resistance of angiosperms.

The Straightforward Route Towards the Theoretical Specific Free Enthalpy of Electrochemical Reactions

<p></p>This paper outlines a simple yet precise method for identifying the theoretical specific free enthalpy of electrochemical reactions on basis of the ideal gas law, equilibrium thermodynamics and Faraday's law, exploiting the normative role of the standard hydrogen electrode in electrochemistry. The result of this approach are discussed in relation to four battery cell reaction examples: LiCoO₂/C₆, LiFePO₄/C₆, sodium-sulfur (NAS) and NaCl–Ni (ZEBRA). The agreement between calculated and practical values is near-excellent for even stoichiometries which bespeaks the virtually ideal nature of reversible reactions and the quality of the practical optimization efforts alike. These findings highlight the principal nature of intrinsic thermodynamic limitation to equilibrium mass transfer and its key role towards understanding reversible chemical energy storage in a global sense.<br><p></p>

The Master Key to the Problem of Reversible Chemical Hydrogen Storage is 12 kJ (mol H2)-1

<p>This article shows up the intrinsic thermodynamic boundaries to reversible mass transfer on basis of the ideal gas law and classic equilibrium thermodynamics in relation to chemical hydrogen storage. In the event, a global picture of reversible chemical hydrogen storage is unveiled, including an explanation of partial reversibility. The findings of this work help to clarify problems of metal hydride chemistry which otherwise are difficult if not impossible to solve in convergent manner, e.g. why the substitution of 4 mol % Na by K in Ti-doped NaAlH₄ raises the reversible storage capacity by 42 % or the way the dopants take effect in (Rb/K)-co-doped Mg(NH₂)₂/2LiH. This work's result is of a wider significance since based on two cornerstones of physical chemistry and particularly for the normative role of hydrogen electrodes to electrochemistry.</p>

Making sense of sensemaking: using the sensemaking epistemic game to investigate student discourse during a collaborative gas law activity

Beyond students’ ability to manipulate variables and solve problems, chemistry instructors are also interested in students developing a deeper conceptual understanding of chemistry, that is, engaging in the process of sensemaking. The concept of sensemaking transcends problem-solving and focuses on students recognizing a gap in knowledge and working to construct an explanation that resolves this gap, leading them to “make sense” of a concept. Here, we focus on adapting and applying sensemaking as a framework to analyze three groups of students working through a collaborative gas law activity. The activity was designed around the learning cycle to aid students in constructing the ideal gas law using an interactive simulation. For this analysis, we characterized student discourse using the structural components of the sensemaking epistemic game using a deductive coding scheme. Next, we further analyzed students’ epistemic form by assessing features of the activity and student discourse related to sensemaking: whether the question was framed in a real-world context, the extent of student engagement in robust explanation building, and analysis of written scientific explanations. Our work provides further insight regarding the application and use of the sensemaking framework for analyzing students’ problem solving by providing a framework for inferring the depth with which students engage in the process of sensemaking.