Biomass materials can serve as a good alternative source of renewable energy that will help decrease reliance on fossil fuels and will help decrease environmental pollution. Charcoal specifically burns more efficiently and generates less smoke emissions than raw biomass, leading to minimal greenhouse gas emissions. The biomass to charcoal briquettes provide a combined solution to energy insecurity, waste management, and environmental sustainability. This study examines the fuel and environmental characteristics of charcoal briquettes made using rice straw, sugarcane leaves, sawdust, maize cobs, and forest residues. It sought to assess their relevance as clean solid fuels in domestic and small-scale energy usages. The agricultural and forest residues were subjected to controlled carbonization and then briquette formation was carried out through low compaction pressure (no more than 7 MPa) and starch as a natural binder. All the experimental analyses were carried out in accordance with the standard procedures and generally accepted tests. Proximate analysis showed a percentage of water content, volatile matter, ash content, and fixed carbon. The resulting briquettes also showed a calorific value ranging between 16.6 and 22 MJ kg -1, which means that the energy density of these briquettes is favorable and is comparable to those of solid fuels in common use. A comparative evaluation against the locally available coal revealed that the resulting charcoal briquettes had much lower concentrations of nitrogen and sulfur, and this implied that there was less promise of harmful emissions like NOx and SOx during combustion. All these attributes affirm the environmental benefits of charcoal produced through biomass against traditional coal fuels. Moreover, briquettes made of biocomposites of agricultural residues had a better fuel consistency and burning efficacy than the ones made up of single constituents. The results indicate that biocomposite charcoal briquettes show promise as an environmentally friendly and sustainable substitute of firewood and coal. This strategy is the way to offer a viable avenue of transforming agricultural wastes into clean energy sources that will serve the decentralized power facilities and help achieve the sustainable energy transition and resource efficiency.

Introduction

Energy transitions in developing economies lie at the intersection of social justice, public health, and climate action. Over 80% of the world’s 2.3 billion people without access to clean cooking solutions live in Sub-Saharan Africa, where continued reliance on traditional biomass fuels such as wood, charcoal, and agricultural residues contributes to more than 800,000 premature deaths annually, disproportionately affecting women and children. This study examines the relationship between energy transitions and health equity in developing economies, with particular attention to Bangladesh, South Asia, and Sub-Saharan Africa. It explores how the adoption of clean energy influences health outcomes, household medical costs, and gender equity. For low- and middle-income countries, transitioning from fossil-based and traditional biomass energy systems to renewable and clean energy sources presents both opportunities to reduce health disparities and challenges related to affordability, infrastructure, and policy implementation.

Methods

A systematic review methodology was employed, integrating qualitative assessments of policy interventions with quantitative analysis of empirical studies published between 2020 and 2025. Peer-reviewed literature focusing on household energy transitions in China, Bangladesh, Kenya, and broader Sub-Saharan African contexts was analyzed. Data sources included longitudinal household surveys, geospatial modeling studies, and difference-in-differences (DID) analyses. Key outcome measures were: (1) household medical expenditures before and after clean energy adoption; (2) health outcomes measured through respiratory disease incidence, mortality rates, and disability-adjusted life years; (3) gender-specific impacts on time use, income generation, and household decision-making; and (4) rural–urban disparities in energy access and health equity. Case studies were selected based on geographical diversity, empirical rigor, and representation of diverse clean energy technologies, including liquefied petroleum gas (LPG), solar home systems, biogas digesters, improved cookstoves, and micro-hydropower. The analysis also incorporated policy framework evaluations, infrastructure requirements, and cost–benefit considerations to identify scalable and context-specific solutions.

Results

The findings demonstrate that clean energy transitions yield significant health and economic benefits, with notable heterogeneity across populations. In China, household adoption of clean energy was associated with a 16.1% reduction in medical expenditures, with stronger effects observed among rural households, individuals with lower educational attainment, and medium-sized families. These reductions were mediated by improvements in income and health status. In Bangladesh, more than 6 million solar home systems had been installed by 2021, generating 489 MW of electricity and substantially expanding energy access. However, high upfront costs and infrastructure limitations constrained broader impacts, with renewables accounting for only 3.5% of total energy consumption.

Sub-Saharan Africa faces the most severe challenges: in 2022, approximately 990 million people lacked access to clean cooking, a figure increasing annually due to population growth outpacing infrastructure expansion. Geospatial analyses indicate that traditional biomass yields the lowest social net benefits, reflecting significant market failures. Gender impacts were particularly pronounced, as women in rural areas spend an average of 20 hours per week collecting firewood—time that could otherwise be allocated to education or income-generating activities. Clean cooking initiatives, such as biogas programs in East Africa, benefited approximately 0.5 million people and enabled participating women to save $150–$300 annually in fuel costs. Health gains extended beyond reductions in mortality to lower incidences of chronic obstructive pulmonary disease, lung cancer, and ischemic heart disease. Projections suggest that universal access to clean cooking could avert 2.5 million premature deaths globally by 2030.

Conclusion

Energy transitions in developing economies offer substantial potential to advance health equity, gender equality, and climate objectives, particularly for vulnerable populations such as women, low-income households, and rural communities. Clean energy adoption reduces household medical costs, improves health outcomes, and redistributes time and economic opportunities more equitably. Nonetheless, achieving universal access requires addressing persistent barriers, including inadequate infrastructure, affordability constraints, and limited financing mechanisms. The global annual financing gap of approximately $8 billion represents a small fraction of existing energy subsidies, underscoring that political commitment rather than resource scarcity remains the principal obstacle. Successful transitions demand gender-inclusive policies, innovative financing, strengthened local governance, and context-specific strategies grounded in energy justice. As climate change is projected to affect billions of people in coming decades, accelerating clean energy access constitutes essential infrastructure for sustainable development, public health protection, and social equity.

The recovery of residual oil from mature and non-producing reservoirs remains a major challenge owing to unfavourable mobility ratios and persistent rock fluid interactions. Although polymer flooding is a developed chemical enhanced oil recovery (cEOR) technique, the long-term performance of both synthetic and natural polymers is often limited by thermal degradation, salinity sensitivity, and shear-induced instability under reservoir conditions. These limitations highlight the development of polymer systems with modified molecular structures capable of enhancing mobility control and interfacial interactions. In this study, a chemically modified guar gum-based biopolymer was developed to overcome the limitations of conventional polymer flooding. The polymer structure was modified through a chemo-selective approach involving graft copolymerization, esterification, gel modification, crosslinking, and nanocomposite functionalization to achieve improved rheological stability and interfacial performance. Structural modification was confirmed by spectroscopic characterization, and the polymer system was systematically evaluated under reservoir-simulated conditions. Rheological investigations showed a significant enhancement in dynamic viscosity compared to native guar gum, along with stable pseudoplastic behaviour over a temperature range of 30-70 °C, showing improved resistance to gravitational flow and enhanced sweep efficiency. Interfacial studies showed a significant reduction in oil–water interfacial tension to 27 dyne/cm, accompanied by a decrease in surface tension, facilitating improved oil mobilization. Wettability alteration experiments on oil-aged carbonate rocks showed a clear transition from oil-wet to water-wet conditions. These findings were confirmed by flotation and qualitative wettability tests, including flotation and two-phase separation experiments, where polymer-treated carbonate powders migrated to the aqueous phase. The modified polymer also exhibited enhanced emulsifying activity with the formation of finer and more stable oil water droplets. The displacement efficiency of the developed polymer was further validated through oil reservoir simulating bioreactor (ORSB) flooding experiments conducted at 70 °C. Polymer flooding resulted in an additional oil recovery of more than 10% original oil in place (OOIP). The enhanced recovery performance results from the synergistic effects of viscosity enhancement, viscoelastic flow behaviour, interfacial tension reduction, wettability alteration, and stable emulsion formation. Overall, this study demonstrates that rational chemo-selective modification of natural polymers provides a sustainable and cost-effective pathway for developing high-performance EOR agents. The developed biopolymer system shows strong potential for deployment in mature and non-producing reservoirs under harsh reservoir conditions.

“Next-Generation Biopolymer Systems for Sustainable and Energy-Efficient Oil Recovery”

Introduction:

South Africa’s energy supply remains heavily reliant on coal, which provides about three-quarters of the country's national electricity and sustains nearly 90,000 jobs in coal-dependent provinces, such as Mpumalanga. While this reliance has historically ensured energy security and economic activity, it has also placed South Africa among the world’s leading carbon emitters, undermining climate commitments and contributing to environmental degradation and public health risks. At the same time, renewable energy initiatives, notably the Renewable Energy Independent Power Producer Procurement Programme (REIPPPP), have added over six gigawatts of solar and wind power to the grid, now supplying roughly a quarter of electricity. However, the transition is constrained by challenges such as grid integration, funding shortages, and uneven policy enforcement.

Problem Statement: The central problem, which is South Africa’s dependence on coal, creates a dual crisis: (1) escalating carbon emissions and climate vulnerability, and (2) socio-economic risks for communities reliant on coal mining and power generation. A rapid coal phase-out without safeguards could devastate livelihoods, while a slow transition undermines environmental and health objectives. The adverse impact is felt both globally (through emissions) and locally (through job insecurity, pollution, and unreliable electricity supply). The problem to be solved is how to balance emission reduction with social protection and energy reliability.

Why the Problem Must Be Solved: Failure to act deepens climate risks, worsens air quality, and jeopardizes South Africa’s international commitments under frameworks such as the Paris Agreement. At the same time, inaction prolongs economic dependence on a declining industry, leaving coal communities vulnerable to unemployment and poverty. Solving this problem is essential to secure a sustainable, inclusive energy future that protects both people and the planet.

Research Methodology: This study will adopt a mixed-methods approach. Quantitative analysis will assess energy production, emissions data, and job trends across fossil and renewable sectors. Qualitative research, including policy analysis, stakeholder interviews, and case studies of REIPPPP projects, will explore governance challenges, community perspectives, and opportunities for just transition strategies. Comparative analysis with international energy transitions will provide lessons adaptable to South Africa’s context.

Collaborators: The research will engage with government agencies (e.g., Department of Mineral Resources and Energy, Eskom), renewable energy developers, labor unions representing coal workers, and civil society organizations advocating for environmental justice. Academic institutions and international partners (such as climate finance bodies and technical experts from the International Renewable Energy Agency) will provide additional expertise and comparative insights.

By integrating technical, social, and policy dimensions, this research aims to propose pathways for a just and inclusive energy transition that safeguards livelihoods while advancing renewable innovation.

Perovskite solar cells have evolved as a revolutionary photovoltaic technology in just over a decade, with power conversion efficiencies that have been proven to be higher than 26%. The exceptional performance of these materials can be attributed to the exceptional optoelectronic properties of ABX3-structured materials. These properties include the long diffusion lengths of charge carriers and high absorption coefficients. A substantial amount of research has been conducted on non-toxic, all-inorganic alternatives as a result of concerns with the long-term stability of high-performance formulations and the toxicity of lead.

This computational study aims to employ SCAPS-1D device modelling to predict novel lead-free photovoltaic absorbers utilising copper(I) perovskite chlorides (CuMClₜ, where M = Fe, Cr, Zn) with a target power conversion efficiency (PCE) of 23%. CuMCl₃ compounds are selected due to their lower total energies compared to caesium-based alternatives and their direct, tuneable bandgaps ranging from 1.4 to 1.6 eV, which closely approach the optimal Shockley-Queisser limit for single-junction cells. These compounds exhibit enhanced projected electron and hole mobilities by diminishing their carrier effective masses in comparison to CsPbCl₃. The A-site cation not only contributes to structural stability but also, due to its distinctive hybridisation of Cu⁺ and MCl₆ orbitals, plays an active role in the electronic structure, influencing electrical characteristics.

Detailed SCAPS-1D simulations of a conventional n-i-p architecture (FTO/TiO₂/CuFeCl₃/Spiro-OMeTAD/Au) demonstrated that CuFeCl₃ had an exceptional capability characterised by a bandgap of 1.45 eV. Through the precise optimisation of layer thickness, doping density, and interface characteristics, a simulated device achieved a peak power conversion efficiency of 23.2%. The performance of the device is characterised by an open-circuit voltage (VOC) of 1.12 V, a short-circuit current density (JSC) of 26.8 mA/cm², and a fill factor of 77.4%. A key benefit is the improved volatile organic compound (VOC), which signifies a minimal voltage deficit and implies a decrease in non-radiative recombination. Notwithstanding defect densities of 10⁴ cm⁻³, the material demonstrated exceptional defect tolerance inside the absorber bulk, maintaining an efficiency above 20%. The performance exhibited significant sensitivity to the quality of the interface. To limit recombination losses, it is crucial that the defect concentrations at the interfaces of the charge transport layer remain below 10 cm⁻².

The results indicate that Cu⁺-based perovskites have considerable promise as next-generation, lead-free photovoltaic materials, accomplished by optimising the all-inorganic composition for improved optoelectronic properties. The research offers a definitive theoretical framework and performance standards for experimental synthesis. Nevertheless, considerable obstacles remain, including the experimental stability of Cu⁺ inside the perovskite lattice to prevent oxidation and the reduction of moderate near-infrared absorption, which requires rather thick active layers. Addressing these issues via sophisticated manufacturing and interface engineering will be essential for converting this promising theoretical prediction into a high-performance, stable, and environmentally friendly solar cell technology.

Energy policy is widely regarded as a primary mechanism for enabling and accelerating energy transitions. Through regulatory frameworks, market interventions, and strategic signalling, policy is expected to shape investment decisions, reorient organisational strategies, and progressively shift energy systems away from carbon-intensive production. Yet, in fossil fuel-dependent economies, the extent to which energy policy materially influences organisational transition trajectories remains an open empirical question. This paper examines how energy policy has shaped, constrained, or enabled transition outcomes within a major fossil fuel organisation, using Woodside Energy as a case study within the Australian energy system.

The study focuses on the period from 2015 to 2025, a decade characterised by intensifying climate commitments, evolving energy security concerns, and the increasing prominence of gas as a so-called “transition fuel” in Australian policy discourse. During this period, successive federal and state governments introduced a range of climate, energy, and gas market policies intended to reduce emissions while maintaining supply reliability and export competitiveness. This paper maps these policy developments against changes in Woodside’s energy mix, specifically examining trends in oil and gas production, project approvals, and investment priorities over time.

Adopting a qualitative longitudinal research design, the analysis draws on publicly available corporate disclosures, including annual reports, sustainability and climate reports, and investor communications, alongside legislative instruments, policy statements, and media coverage. Document analysis is used to trace how policy signals are interpreted, negotiated, and incorporated within corporate strategy, while production data provides a material indicator of transition outcomes. Rather than treating policy as a static constraint, the study conceptualises policy as an evolving and often contested influence that interacts with organisational agency, market conditions, and institutional logics.

The findings suggest that energy policy has exerted an uneven influence on transition outcomes. While policy frameworks have increasingly articulated decarbonisation goals, they have simultaneously reinforced the strategic role of gas in Australia’s transition narrative. This duality appears to have enabled the retention and, in some cases, expansion of gas-related investments, even as organisations publicly align with transition objectives. The persistence of oil and gas production over the decade indicates that policy influence has been more effective in reshaping organisational discourse and justification strategies than in driving substantive changes in the energy mix.

By empirically examining the relationship between policy signals and organisational production outcomes, this paper contributes to transition studies by highlighting the limits of policy-driven change in the absence of clear phase-down or phase-out mechanisms. It underscores the importance of policy coherence, credibility, and enforceability in shaping transition pathways and cautions against over-reliance on transitional narratives that may delay structural change. The paper offers insights for policymakers seeking to design energy policies that more effectively translate transition ambition into measurable transformation within fossil fuel-intensive organisations.

CO2-rich streams generated by acid gas removal units in gas chemical complexes are usually treated as waste, despite their potential value as a technical product. However, conventional separation techniques are frequently only intended for gas purification, which leads to high energy consumption and poor CO2 recovery purity. This study investigates process integration strategies to convert traditional acid gas treatment units into carbon capture systems that generate value in order to recover high-purity CO2 from acid gas mixtures originating from natural gas processing. With a focus on reducing regeneration energy and increasing overall system efficiency, the suggested framework assesses the integration of absorption-based CO2 separation with downstream conditioning, regeneration, and recycling stages. The analysis highlights the role of hybrid chemical loops in improving CO2 selectivity while concurrently lowering solvent degradation, corrosion risks, and utility demand. It takes into account both traditional solvent-based systems and alkaline-assisted capture routes. The relationship between separation units and current plant utilities such as steam, electricity, and waste heat streams is given particular consideration because these factors are crucial in determining overall energy performance. To find critical integration points where heat recovery, material recycling, and process coupling can greatly increase separation efficiency and energy, and mass balance evaluations are used. Reusing low-grade heat from upstream units, optimising solvent regeneration, and carefully conditioning captured CO2 to satisfy purity standards for technical and industrial applications are some of these integration opportunities. The findings show that, in comparison to traditional stand-alone configurations, integrated separation schemes can achieve high CO2 purity appropriate for downstream use while lowering the specific energy consumption of acid gas treatment. Overall, the results show that upgrading current gas purification infrastructure into integrated carbon capture and utilisation platforms is feasible through process-level optimisation. By facilitating circular carbon approaches within gas chemical complexes and promoting more efficient use of fossil-based energy resources, such strategies aid in the shift towards more sustainable and energy-efficient industrial systems.

Introduction:
The pressing need for sustainable and energy-efficient construction practices has propelled the exploration of alternative materials in concrete production. One promising avenue is the incorporation of glass waste into green concrete. This approach addresses environmental challenges such as landfill accumulation and natural resource depletion, while also aiming to reduce the carbon footprint associated with cement manufacturing.

Methods: This study systematically analyzes recent advancements in using glass waste—such as glass powder, crushed glass aggregates, expanded glass, and glass fibers—as partial replacements for cement, fine, and coarse aggregates. The study evaluates various forms of glass waste based on particle size, chemical composition, and replacement ratios. Mechanical performance, durability, microstructural behavior, and environmental benefits are assessed through comparative analysis of laboratory experiments and life cycle assessments.

Results and Discussion: Findings reveal that finely ground glass powder (<90 µm) enhances the pozzolanic reaction, leading to improved compressive strength (up to 14%) and reduced water absorption when used at replacement levels of 10–30% for cement. Crushed glass aggregates offer improved packing density and flexural strength at moderate substitution rates (10–25% for sand, ≤10% for coarse aggregate), though excessive use compromises strength due to poor bonding and increased porosity. The integration of glass fibers further boosts tensile and flexural properties by over 20%. Engineered geopolymer composites and mixtures with additives like CNTs and fly ash show promise for high-performance applications. However, challenges such as alkali-silica reaction (ASR), workability reduction, and strength loss at high replacement levels persist. Environmentally, glass waste concrete can lower CO₂ emissions by up to 30% and energy use by 17–20%, supporting circular economy principles and landfill diversion.

Conclusion:
The utilization of glass waste in concrete offers compelling mechanical, durability, and sustainability benefits when applied within optimal replacement thresholds. While current applications are more prevalent in non-structural components (e.g., paver blocks, foam concrete), innovations in processing and mixture optimization are expanding its potential for structural use. Future research should focus on long-term field validation, ASR mitigation strategies, and scaling up implementation to advance the role of glass waste in next-generation green infrastructure.

The increasing global energy demand and environmental concerns associated with conventional fossil fuels have accelerated scientific interest in renewable alternatives. Among the available renewable options, biofuels derived from agricultural waste present a promising pathway to reduce carbon emissions, enhance waste utilization, and support regional energy security. This study focuses on the production efficiency and emission characteristics of biofuel generated from agricultural residues, particularly lignocellulosic biomass such as rice husk, corn stover, palm oil residues, and sugarcane bagasse. The overarching aim is to assess how agricultural waste can be transformed into viable biofuels while maintaining economic and environmental sustainability.

Agricultural waste represents an abundant yet underutilised resource, especially in regions where farming activities dominate national economies. Large quantities of biomass are produced annually and typically subjected to open burning or natural decomposition, leading to methane release, particulate matter formation, and soil nutrient degradation. Converting these waste streams into biofuel offers dual benefits: waste reduction and renewable energy generation. However, key challenges remain in optimising conversion processes, improving energy yield, and minimising emissions during production and end-use combustion. This study examines these challenges by comparing three main conversion pathways—thermochemical, biochemical, and transesterification processes—and evaluating their associated performance indicators.

The experimental component involves conducting controlled pilot-scale production trials using selected agricultural residues. Each biomass sample undergoes pre-treatment and moisture control before being processed through gasification, pyrolysis, or anaerobic digestion, depending on the fuel type produced. Gasification mainly yields syngas, pyrolysis produces bio-oil and biochar, while anaerobic digestion generates biogas rich in methane. Parameters such as reaction temperature, catalyst type, particle size, and oxygen supply are modified to determine the conditions that provide maximum yield. Initial results demonstrate that catalytic pyrolysis using palm kernel shells yields higher bio-oil volume compared to rice husk due to its higher lignin content, which enhances thermal breakdown. Similarly, biogas generation rates from sugarcane bagasse indicate a methane composition exceeding 60%, making it a viable substitute for liquefied petroleum gas.

In addition to production efficiency, this research investigates the emission profile of the produced fuels. Combustion testing is carried out in controlled laboratory burners and small-scale internal combustion engines. Emission factors measured include carbon dioxide, carbon monoxide, nitrogen oxides, particulate matter, and unburned hydrocarbons. Preliminary findings reveal that biofuel combustion generally produces lower net CO₂ emissions compared to fossil diesel, due to the carbon neutrality principle of biomass. However, certain biofuels exhibit higher NOx formation, mainly attributed to elevated combustion temperatures and nitrogen content in the feedstock. Bio-oil derived from pyrolysis shows slightly higher particulate emissions due to incomplete volatilisation, which indicates that post-treatment and upgrading processes may be required to meet strict air-quality regulations.

The study also evaluates lifecycle environmental benefits by comparing greenhouse gas emissions across fuel production, processing, transport, and combustion stages. Results suggest that agricultural waste-based biofuels can reduce total lifecycle emissions by up to 75% relative to fossil fuels, depending on conversion technology and local resource availability. Economic considerations are also explored. Cost modelling indicates that agricultural biomass fuels become financially competitive when feedstock is sourced locally, processing systems are modular, and government incentives support infrastructure development.

In conclusion, this research confirms that agricultural waste has the strong potential to be a sustainable feedstock for renewable biofuel production. With growing agricultural output and rising waste generation, biofuel systems can offer decentralised energy solutions, reduce environmental pollution, and contribute to national decarbonisation efforts. Nonetheless, further refinement in conversion technologies, catalyst improvement, emissions mitigation, and fuel upgrading is required before large-scale implementation. The outcomes of this work provide valuable insight into the interplay between fuel efficiency and emission performance, helping researchers, policymakers, and industries build strategies for scaling up agricultural waste-based bioenergy systems.

Organic solar cells (OSCs) based on π-conjugated small molecules are attracting growing interest as lightweight, flexible, and solution-processable photovoltaic technologies compatible with sustainable energy strategies. Within this class of materials, acceptor–donor–acceptor (A-D-A) chromophores have emerged as a particularly versatile platform, where subtle modifications of donor–acceptor connectivity can substantially alter energy levels, optical gaps, and charge-transport descriptors. Understanding how these intramolecular design choices control key electronic and photophysical properties is therefore essential for the rational development of next-generation OSC active layers.

In this contribution, we present a systematic theoretical investigation of a family of A-D-A small molecules constructed from an electron-rich pentathiophene (PTP) core and electron-deficient trimethylxanthine (TMX) terminal units. By varying only the attachment sites of the two TMX fragments around the PTP ring, four symmetry-distinct isomers are generated within a single chemical platform, allowing us to isolate the effect of donor–acceptor connection pattern without changing the underlying building blocks. Ground-state geometries and electronic structures are obtained through density functional theory (DFT), while excited-state properties are explored using time-dependent DFT (TD-DFT) in an implicit solvent environment. The workflow includes the calculation of frontier orbital energies, density-of-states profiles, chemical reactivity indices, and exciton binding energies, together with simulated absorption and emission spectra and an analysis of charge-transfer character.

Charge-transport descriptors are evaluated within the non-adiabatic Marcus hopping framework from intramolecular reorganization energies, Gibbs free energy differences, and effective electronic couplings extracted from frontier-orbital splittings. In addition, a semi-empirical photovoltaic model is employed to estimate open-circuit voltage, light-harvesting efficiency, fill factor, and normalized power-conversion descriptors based on the computed energetics and oscillator strengths.

The presentation will focus on how this integrated DFT/TD-DFT and Marcus theory framework links donor–acceptor attachment sites to changes in electronic structure, optical response, and charge-transport metrics across the four PTP/TMX isomers. Emphasis will be placed on extracting general structure–property relationships and qualitative design rules that can inform the future synthesis and device integration of A-D-A chromophores for organic solar cells, rather than on reproducing specific experimental devices or quantitative efficiencies.