Permeation of CO₂ and N₂ through glassy poly(dimethyl phenylene) oxide under steady- and presteady-state conditions

Glassy polymers are often used for gas separations because of their high selectivity. Although the dual‐mode permeation model correctly fits their sorption and permeation isotherms, its physical interpretation is disputed, and it does not describe permeation far from steady state, a condition expected when separations involve intermittent renewable energy sources. To develop a more comprehensive permeation model, we combine experiment, molecular dynamics, and multiscale reaction–diffusion modeling to characterize the time‐dependent permeation of N₂ and CO₂ through a glassy poly(dimethyl phenylene oxide) membrane, a model system. Simulations of experimental time‐dependent permeation data for both gases in the presteady‐state and steady‐state regimes show that both single‐ and dual‐mode reaction–diffusion models reproduce the experimental observations, and that sorbed gas concentrations lag the external pressure rise. The results point to environment‐sensitive diffusion coefficients as a vital characteristic of transport in glassy polymers

Predictive simulation of non-steady-state transport of gases through rubbery polymer membranes

A multiscale, physically-based, reaction-diffusion kinetics model is developed for non-steady-state transport of simple gases through a rubbery polymer. Experimental data from the literature, new measurements of non-steady-state permeation and a molecular dynamics simulation of a gas-polymer sticking probability for a typical system are used to construct and validate the model framework. Using no adjustable parameters, the model successfully reproduces time-dependent experimental data for two distinct systems: (1) O_2 quenching of a phosphorescent dye embedded in poly(n-butyl(amino) thionylphosphazene), and (2) O_2, N_2, CH_4 and CO_2 transport through poly(dimethyl siloxane). The calculations show that in the pre-steady-state regime, permeation is only correctly described if the sorbed gas concentration in the polymer is dynamically determined by the rise in pressure. The framework is used to predict selectivity targets for two applications involving rubbery membranes: CO_2 capture from air and blocking of methane cross-over in an aged solar fuels device

Challenges in implementing system thinking in agricultural sustainable intensification: A methodological note

System thinking is relevant to solve complex problems and deliver solutions for sustainable intensification of agricultural systems. Successful implementation of System Thinking in Sustainable Intensification of Agricultural Systems has faced conceptual hurdles that hinder its practical application. This methodological note addressed these challenges by emphasizing on the complexity and difficulty in conceptualizing STIBs and considering the absence of standardized approaches. These issues significantly impact the authentic integration of system thinking into agricultural systems. Key impediments include the identification of stakeholders and the determination of objective functions for STIBs implementation. Moreover, the spatial scale, spanning from the plot to the national level, poses a crucial consideration, as all issues across these scales contribute to effective system thinking. The temporal scale is equally important, encompassing events and phenomena over both short and extended periods. While efforts have been made to develop tools and approaches for guiding STIBs implementation within specific components or sectors, there is a notable gap in tools that facilitate a comprehensive system approach. Existing tools designed for this purpose are limited in their implementation and are not widely adopted. Alternatively, a critical approach involves selecting tools across scales and chaining them together to address these challenges. In this context, we designed an example of how tools at the plot, household (HH), landscape, and national scales can be strategically chained to tackle some of the aforementioned challenges, using Ethiopia as a case study. However, it is important to acknowledge the limitations associated with coupling and utilizing these processes effectively. By exploring the integration of tools across different scales and systematically chaining them, there is potential to overcome the current challenges in STIBs implementation. This methodological exploration aims to contribute to the development of a more holistic and widely applicable framework for successful system thinking in the context of sustainable agricultural intensification

Predictive simulation of non-steady-state transport of gases through rubbery polymer membranes

A multiscale, physically-based, reaction-diffusion kinetics model is developed for non-steady-state transport of simple gases through a rubbery polymer. Experimental data from the literature, new measurements of non-steady-state permeation and a molecular dynamics simulation of a gas-polymer sticking probability for a typical system are used to construct and validate the model framework. Using no adjustable parameters, the model successfully reproduces time-dependent experimental data for two distinct systems: (1) O_2 quenching of a phosphorescent dye embedded in poly(n-butyl(amino) thionylphosphazene), and (2) O_2, N_2, CH_4 and CO_2 transport through poly(dimethyl siloxane). The calculations show that in the pre-steady-state regime, permeation is only correctly described if the sorbed gas concentration in the polymer is dynamically determined by the rise in pressure. The framework is used to predict selectivity targets for two applications involving rubbery membranes: CO_2 capture from air and blocking of methane cross-over in an aged solar fuels device

Antenatal care utilization and nutrition counseling are strongly associated with infant and young child feeding knowledge among rural/semi-urban women in Harari region, Eastern Ethiopia

There is a gap in evidence linking antenatal care (ANC) utilization, nutrition counseling, and knowledge of pregnant women about infant and young child feeding (IYCF), particularly in low-income settings. Therefore, this study aimed to identify the association between ANC follow-up and nutrition counseling with IYCF knowledge. A cross-sectional study was conducted among 390 pregnant women in the rural kebeles of the Harari region from January to June 2019. Data were collected using face-to-face interviews on tablet computers. Bivariate and multivariate logistic regression were employed. An adjusted odds ratio (with 95% CI) was used to determine the strength of association between IYCF knowledge with ANC follow-up and nutrition counseling by adjusting for educational status, occupation, gravida, and distance to the nearest health center. Overall, 54.4% [95% CI 49.2, 59.2] of currently pregnant women were knowledgeable about IYCF of which only 20% started ANC follow-up and 24.4% received nutrition counseling. Out of 288 multigravida women, only 51.4% had ANC follow-up during their last pregnancy. In the adjusted model, ANC follow-up during the current pregnancy (AOR 1.85, 95% CI 1.07–3.22), those who received nutrition counseling (AOR 1.92, 95% CI 1.09–3.38), literate in education (AOR 1.71, 95% CI 1.07–2.73), multigravida (AOR 1.96, 95% CI 1.12–3.43), and far from the nearest health center (AOR 0.95, 95% CI 0.93–0.97) were significantly associated with the mothers IYCF knowledge. Thus, health care providers should encourage mothers to attend ANC during pregnancy and provide nutrition counseling about the IYCF

Understanding the Impact of Confinement on Ionomer Thin Film Transport Properties

Existing state-of-the-art electrochemical devices like polymer-electrolyte fuel cells (PEFCs) and other growing applications like separation membranes, protective coatings, photonics, nanocomposites, and microelectronics utilize polymers of thicknesses less than 100 nm. These thin and ultra-thin polymer films provide ease of processing, application-specific tunable properties, and reduction in material cost. Nano-confined polymer thin films, however, often display surface and thickness-dependent behavior that results in deviation from well-characterized bulk properties. As a result, they pose significant challenges to predictability, optimization, and performance. In PEFCs, thin film ion-conducting polymers (ionomers) of thickness < 100 nm serve as functional binder in the catalyst layers (CLs), aiding proton conduction and extending the reaction zone of the CL porous electrode. Unfortunately, these same ionomer thin films contribute to large proton- and gas-transport losses in PEFCs, thereby considerably limiting commercialization of affordable, low precious-metal catalyst-loaded fuel cells. Remediation of this phenomenon requires fundamental understanding of thin film behavior near interfaces and surfaces and quantification of an ionomer’s thickness-dependent properties. Furthermore, design improvements circumventing the losses aforementioned will require establishment of correlations between tunable variables and ionomer thin-film properties under a range of operating conditions. This dissertation aims to carry this out in three interconnected ways. First, model systems are used to develop fundamental understanding of dimensional swellability and thermal relaxation of ionomer thin films proximal to supports and dynamic interfaces that mimic phenomena in CLs. Second, ionomer thin film structure-property relationships are established through exploring and exploiting ionomer counterion identity and thickness variation. Third, properties like ionomer thin-film gas transport are quantified as a function of thickness to create a direct link between losses observed in the CL to local alterations in thin-film properties. Understanding pairwise interactions between gas/ionomer thin film, ionomer/substrate, and gas/substrate are critical for decoupling the impact of substrate and interface from intrinsic ionomer thin-film properties driven by a finite-size effect. Swelling and thermal relaxation of ionomer thin films on different supports are explored in Chapters 2 and 3 to provide meaningful insights that may also occur at interfaces in the electrode. Swelling behavior, morphology, and mechanical properties of ionomer thin films (~50 nm) spin coated onto the platinum (Pt) support were exposed to both H2 and Air as experimental systems that mimic anode and cathode CLs and their Pt/ionomer system. Findings indicate lower uptake, increased densification of ionomer matrix, and increased rate in relative humidity-induced aging in a reducing environment as compared to an oxidizing and/or inert environment. Intrinsic mobility of ionomer chains anchored by strong interaction with substrate were additionally explored via thermal relaxation. The change in thermal transition temperature is a key marker of stiffness and polymer-chain mobility and has direct implications on ease of water and gas transport through polymer films. An increase in thermal transition temperature in ionomers supported on silicon (Si/SiO2) is observed with decrease in thickness. Thermal relaxation dynamics observed result from the positive effect of increased chain mobility at the free surface and the hindered motion at the strongly interacting substrate interface. Monitoring of swellability in alternative gas-environment experiments demonstrated that substrate/ionomer interface can dictate water distribution through the thin film. Absent a dynamic interface and hydration, anchoring of ionomer chains at the substrate interface creates a distributed degree of chain mobility across the thickness that is overpowered by the influence of substrate interaction with further reduction in thickness. Water uptake and chain mobility findings from these model systems have implications that translate to ion conductivity and gas transport in PEFCs. This correlation is established through structure-property relationships, notably altering cation as a proxy of tuning the nature of ionomer with no additional synthesis as explored in Chapter 4. Alteration of intermolecular forces in the conventional, proton conducting, acid-form ionomer was conducted via exchange with metal cations. Water-uptake capacity, mechanical property, and thermal transition were explored for these exchange ionomers. For monovalent cations with varying cation size and Lewis acid strength, water content showed an inverse relationship with the former and direct relationship with the latter. Hydration is reduced by the increase in mechanical strength upon cation exchange, which is a result of solvation and thermodynamic energy equilibrium in the ionomer matrix. Similar insight was gained for thermal expansivity; an increase in thermal transition temperature was observed in cation exchanged ionomers with a minimal dependence on ionomer thickness. Upon confinement, the interplay between chain mobility at the free surface and near the substrate is dominated by internal hindered motion of ionomer chains tethered to the strong cation. Findings also provide awareness to the impact of ionic contamination in operating PEFCs. Lastly, links from property measurements in well-defined model systems to real PEFC performance metrics must be established. In this work, quantification of ionomer gas-transport property is carried out in three separate methods to account for variable pertinent conditions for operation (temperature, humidity, and potential). Constant-volume-permeation method showed that unsupported films under dry concentration gradients demonstrated a slight increase in gas permeability with reduction in thickness. However, this data suffered from various sources of inaccuracies due to the fragile nature of thin films under high concentration gradients. Oxygen permeation via luminescent quenching method overcomes this challenge by employing supported thin film system that maintains integrity of thin films during experiment. Additionally, humidity- and potential-dependent microelectrode method was also utilized. Both methods reflect an order of magnitude reduction in gas permeability for thin films of thickness 260 to 440 nm relative to the bulk ionomer membrane counterparts. However, more work is needed to ensure confidence in these findings and explore wide range of thicknesses under variable conditions essential to PEFC CLs. Electrodes in electrochemical devices are somewhat of a black box with minimal direct insights and predictions. Improved understanding of confinement related performance losses at surfaces and interfaces can help expand ionomer thin-film functionality and affordability of energy-conversion devices by providing critical design metrics and research directions. It is therefore essential to employ model systems and investigate properties of ionomer thin films with perturbations similar to those in operating devices. Such insights are not only useful for PEFCs, but also extend fundamental insights into thin functional polymer films employed in various applications

The Protection of Traditional Knowledge under International Law: With Particular Emphasis to WIPO Draft Instrument for the Protection of TK

Traditional knowledge consists of is know-how, skills, innovations and practices that are passed on from generation to generation within indigenous peoples or local communities, forming part of its cultural identity and evolving. It contributes to the sustainable use and preservation of biodiversity, environmental and health care. Although the traditional knowledge s of indigenous people has been used to pursue different ends, the owners or holders of the knowledge are not getting benefits from their know-how, innovations, and skills. Currently, there is no international instrument that deals with the protection of traditional knowledge in a comprehensive and holistic manner. Under the auspices of WIPO the Intergovernmental Committee on Intellectual Property and Genetic Resources, Traditional Knowledge and Folklore (IGC) has prepared a draft text for an international regime for the protection of TK. The draft follows a sui generis approach for the protection of TK which combines a wide set of IP and non-IP tools and instruments. However, so far there has been more divergence than convergence on the need and scope of sui generis protection for TK in IGC meetings. Therefore, this thesis is devoted to the discussion on whether sui generis instrument for the protection of traditional knowledge is necessary. It also deals with the elements of effective sui generis instrument for the protection of traditional knowledg

Thermal Transitions in Perfluorosulfonated Ionomer Thin-Films.

Thin perfluorosulfonated ion-conducting polymers (PFSI ionomers) in energy-conversion devices have limitations in functionality attributed to confinement-driven and surface-dependent interactions. This study highlights the effects of confinement and interface-dependent interactions of PFSI thin-films by exploring thin-film thermal transition temperature (TT). Change in TT in polymers is an indicator for chain relaxation and mobility with implications on properties like gas transport. This work demonstrates an increase in TT with decreasing PFSI film thickness in acid (H+) form (from 70 to 130 °C for 400 to 10 nm, respectively). In metal cation (M+) exchanged PFSI, TT remained constant with thickness. Results point to an interplay between increased chain mobility at the free surface and hindered motion near the rigid substrate interface, which is amplified upon further confinement. This balance is additionally impacted by ionomer intermolecular forces, as strong electrostatic networks within the PFSI-M+ matrix raises TT above the mainly hydrogen-bonded PFSI-H+ ionomer