2023 - present: Research Fellow, TAEDA Tech Project, Centre for Environment and Sustainability, University of Surrey
2023 - present: Fellow of the Institute for Sustainability, University of Surrey
2020 - present: Research Fellow, SWEET Project, Centre for Environment and Sustainability, University of Surrey
2019 - 2020: Research Fellow, EnergyREV Project, Centre for Environment and Sustainability, University of Surrey
2019 - 2019: Research Fellow, Food Waste Recycling Using Black Soldier Fly Larvae, Department of Chemical and Process Engineering, University of Surrey
2015 - 2019: Research Fellow, Stepping Up, Centre for Environment and Sustainability, University of Surrey.
2014 - 2015: Research Fellow, CLEVER Project, Centre for Environment and Sustainability, University of Surrey.
2007 - 2013: Senior Researcher, Sharp Laboratories of Europe, Oxford. SLE is part of Sharp Corporation. Developed novel optical systems for use in consumer electronics, including LCDTV, mobile phone, luminaires and a laser headlight.
2005 - 2006: Post Doctoral Researcher, University of Exeter.
2002 - 2005: PhD, University of Exeter.
- Replacement of added sugar in food and drink with high intensity sweeteners.
- Insects for sustainable food and feed.
- Innovation at Water-Energy-Food Nexus with potential to create step change in sustainability.
- Resource efficiency in mobile electronic devices.
- Product service systems.
- Life cycle assessment.
- Replacement of added sugar in food and drink with high intensity sweeteners.
- Insects for sustainable food and feed.
- Innovation at Water-Energy-Food Nexus with potential to create step change in sustainability.
- Resource efficiency in mobile electronic devices.
- Product service systems.
- Life cycle assessment.
Recognizing that there are multiple environmental limits within which humanity can safely operate, it is essential that potential negative outcomes of seemingly positive actions are accounted for. This alertness to unintended consequences underscores the importance of so called ‘nexus’ research, which recognizes the integrated and interactive nature of water, energy and food systems, and aims to understand the broader implications of developments in any one of these systems. This article presents a novel framework for categorizing such detrimental unintended consequences, based upon how much is known about the system in question and the scope for avoiding any such unintended consequences. The framework comprises four categories (Knowable and Avoidable; Knowable and Unavoidable; Unknowable and Avoidable, and Unknowable and Unavoidable). The categories are explored with reference to examples in both the water-energy-food nexus and planetary boundary frameworks. The examples highlight the potential for the unexpected to happen and explore dynamic nature of the situations that give rise to the unexpected. The article concludes with guidance on how the framework can be used to increase confidence that best efforts have been made to navigate our way towards secure and sustainable water, energy and food systems, avoiding and/or managing unintended consequences along the way.
Mobile phones offer many potential social benefits throughout their lifetime, but this life is often much shorter than design intent. Reuse of the phone in a developing country allows these social benefits to be fully realized. Unfortunately, under the current state of development of recycling infrastructure, recovery rates of phones after reuse are very low in those markets, which may lead to an environmental burden due to loss of materials to landfill. In order to recover those materials most effectively, recycling in developed countries may be the best option, but at a cost of the ability to reuse the phones. The issues facing integration of social and environmental concerns into a single life cycle assessment and resulting challenges of identifying the disposal option with the most sustainable outcome are explored using mobile phones as a case study. These include obtaining sufficient geographical and temporal detail of the end of life options, the collation and analysis of the large amounts of data generated and the weighting of the disparate environmental and social impact categories. The numerous challenges may mount up to make performing life cycle assessment of mobile phones unwieldy. Instead of trying to encompass every aspect in full, it is proposed that focus is given to answering a question which takes into account the resources available: it is important to ask the question which has the best chance of being answered.
Selective transmission of radiation through a two-dimensional array of subwavelength slits in an otherwise opaque thin metal film is presented at microwave frequencies. Individual slits are modified with the addition of perpendicular cuts, which interestingly and perhaps counterintuitively leads to resonant transmission when the incident radiation is polarized parallel to the slits. Finite element modeling of the structure shows the transmission of radiation polarized parallel to the slit direction to be a result of induced surface currents exciting a zeroth-order Fabry-Ṕrot mode. © 2007 American Institute of Physics.
Resonant transmission of microwaves through a hexagonal array of holes in a very thin aluminium layer is studied. The array of holes, with diameter much less than the incident wavelength, leads to a strong transmission peak at a frequency just lower than the diffraction limit of the array. The results are well-modelled using a finite element package. The effect of metal depth on transmission intensity and the maximum efficiency of the hole array is also explored. Further experimental data are presented for the transmission of microwaves as a function of angle of incidence. It is shown that strong transmission occurs at frequencies just lower than the diffraction edges of the array. Incidentally, it is also shown that less than 0.01% of normally incident microwave radiation is transmitted through a continuous metal layer of thickness only 40% of the skin depth. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
The water-energy-food (WEF) nexus has become a popular, and potentially powerful, frame through which to analyse interactions and interdependencies between these three systems. Though the case for transdisciplinary research in this space has been made, the extent of stakeholder engagement in research remains limited with stakeholders most commonly incorporated in research as end-users. Yet stakeholders interact with nexus issues in a variety of ways, consequently there is much that collaboration might offer to develop nexus research and enhance its application. This paper outlines four aspects of nexus research and considers the value and potential challenges for transdisciplinary research in each. We focus on assessing and visualising nexus systems; understanding governance and capacity building; the importance of scale; and the implications of future change. The paper then proceeds to describe a novel mixed-method study that deeply integrates stakeholder knowledge with insights from multiple disciplines. We argue that mixed-method research designs – in this case orientated around a number of cases studies – are best suited to understanding and addressing real-world nexus challenges, with their inevitable complex, non-linear system characteristics. Moreover, integrating multiple forms of knowledge in the manner described in this paper enables research to assess the potential for, and processes of, scaling up innovations in the nexus space, in order to contribute insights to policy and decision making.
Fabry-Perot-like resonant transmission of microwave radiation through a single subwavelength slit in a thick aluminum plate is quantified for a range of slit widths. Surprisingly, and in contrast to previous studies [e.g., Phys. Rev. Lett. 86, 5601 (2001)]], the resonant frequency exhibits a maximum as a function of slit width, decreasing as the slit width is reduced to less than 2% of the incident wavelength. This result accords with a new model based on coupled surface plasmon theory taking into account the finite conductivity, and hence permittivity, of the metal. This is contrary to a common assumption that metals can be treated as infinitely conducting in this regime.
Hibernation, the dead storage period when a mobile phone is still retained by the user at its end-of-life, is both a common and a significant barrier to the effective flow of time-sensitive stock value within a circular economic model. In this paper we present the findings of a survey of 181 mobile phone owners, aged between 18–25 years old, living and studying in the UK, which explored mobile phone ownership, reasons for hibernation, and replacement motives. This paper also outlines and implements a novel mechanism for quantifying the mean hibernation period based on the survey findings. The results show that only 33.70% of previously owned mobile phones were returned back into the system. The average duration of ownership of mobile phones kept and still in hibernation was 4 years 11 months, with average use and hibernation durations of 1 year 11 months, and 3 years respectively; on average, mobile phones that are kept by the user are hibernated for longer than they are ever actually used as primary devices. The results also indicate that mobile phone replacement is driven primarily by physical (technological, functional and absolute) obsolescence, with economic obsolescence, partly in response to the notion of being ‘due an upgrade’, also featuring significantly. We also identify in this paper the concept of a secondary phone, a recently replaced phone that holds a different function for the user than their primary phone but is still valued and intentionally retained by the user, and which, we conclude, should be accounted for in any reverse logistics strategy.
A slit in a thick metal plate that is extremely subwavelength will not transmit microwaves polarized parallel to it. It is shown here that cuts perpendicular to the slit allow parallel polarized radiation to resonantly transmit. Furthermore, a zero-order mode may be excited within the slit, the frequency of which, to first order, is independent of the plate depth. Remarkably, for this novel type of resonance, the field in the slit oscillates with a constant phase and little amplitude variation throughout the plate depth, while the resonant wavelength tends to infinity as the slit width approaches zero.
Grand societal challenges such as climate change, poverty and biodiversity loss call for rapid and radical changes to systems of production and consumption. Consequently, there is a growing interest in the dynamics of innovation, both social and technical, to accelerate innovation diffusion so as increase the possibility of a step-change or large-scale transition. Research on the water-energy-food nexus adds an additional dimension to existing discussions, calling for transitions that recognise the sustainability challenges facing three major resource domains, and the synergies and tensions involved in their management. This paper examines Anaerobic Digestion (AD) – an example of innovation with potential benefits across the water-energy-food nexus – to understand the conditions that influence the rate of AD implementation and the achievement of its potential multi-sectoral benefits across the water-energy-food nexus. Interview data regarding 15 AD plants are examined alongside complementary data from interviews and workshops using the Technological Innovation Systems framework. This framework provides an analytical structure through which the processes that enable and constrain the implementation of AD in the UK can be examined, enabling the identification of potential mechanisms to support AD’s wider and more effective deployment. The findings call for recognition of the unintended consequences of sectoral support mechanisms for technological adaptation, and consequent performance of AD in other resource domains and call for greater integration between policy mechanisms to enable AD to perform across the nexus. They also highlight a need to assimilate knowledge from multiple sources (including site-specific understanding gained from experimentation) to enhance the base on which policy and decision-making occurs. These findings contribute to existing literature on sustainable transitions by examining the complexities of multi-sectoral resource management in the context of nexus research.
The mobile phone industry is based upon the rapid development of handsets and the high turnover of devices in order to drive sales. Phones are often used for shorter periods of time than their designed life, and when discarded it is often through channels that result in lost resource. This unsustainable business model places strain on resources and creates adverse environmental and social impacts. Through interrogation of a stock and flow model, a product-service system (PSS) for a small consumer electronic device, a mobile telephone, is proposed. The points at which value may be extracted from the PSS are identified. A quantitative measure of value is proposed in order to allow the evaluation of the most appropriate time to extract it. This value is not solely monetary, but is derived from the combination of indicators which encompass environmental, economic, and technological factors. A worked example is presented, in which it is found that the precious metals within the phone are the main determinants for value extraction. These metals are found in the printed circuit board, leading to a requirement to design phones for ease of extraction of these components in order to access the value within.
We solve the problem of identifying one or more optimal patterns of anaerobic digestion (AD) installation across the UK, by considering existing installations, the current feedstock potential and the project growth of the potential via population, demography and urbanization. We test several scenarios for the level of adoption of the AD operations in the community under varying amounts of feedstock supply, which may arise from change in food waste or energy crops generation via other policies and incentives. For the most resilient scales of solutions, we demonstrate for the UK the net energy production (bio-gas and electricity) from AD (and so the avoided emissions from grid energy), the mass of bio-waste processed (and avoided land-fill), and the quantum of digestate produced (as a proxy for avoided irrigation and fertilizer production). In order to simulate the AD innovation within WEF nexus we use agent based modelling (ABM) owing to its bottom-up approach and capability of modelling complex systems with relatively low level data and information.
The Planetary Boundaries (PB) framework represents a significant advance in specifying the ecological constraints on human development. However, to enable decision-makers in business and public policy to respect these constraints in strategic planning, the PB framework needs to be developed to generate practical tools. With this objective in mind, we analyse the recent literature and highlight three major scientific and technical challenges in operationalizing the PB approach in decision-making: first, identification of thresholds or boundaries with associated metrics for different geographical scales; second, the need to frame approaches to allocate fair shares in the ‘safe operating space’ bounded by the PBs across the value chain and; third, the need for international bodies to co-ordinate the implementation of the measures needed to respect the Planetary Boundaries. For the first two of these challenges, we consider how they might be addressed for four PBs: climate change, freshwater use, biosphere integrity and chemical pollution and other novel entities. Four key opportunities are identified: (1) development of a common system of metrics that can be applied consistently at and across different scales; (2) setting ‘distance from boundary’ measures that can be applied at different scales; (3) development of global, preferably open-source, databases and models; and (4) advancing understanding of the interactions between the different PBs. Addressing the scientific and technical challenges in operationalizing the planetary boundaries needs be complemented with progress in addressing the equity and ethical issues in allocating the safe operating space between companies and sectors.
We studied the spectral evolution of plasmon modes associated with silver nanotriangles as a function of dielectric overlayer thickness in the range of 5-300 nm. A substantial red-shift of the resonance is observed that oscillates with increasing over-layer thickness. We explain this previously unreported oscillation through the cavity quantum electrodynamical effect of the array of triangles combined with the dielectric overlayer. The red-shift, though substantial, is less than expected. Comparison with numerical models indicates that this discrepancy is due to very tight field confinement around the tips of the triangles.
Purpose: To explore the literature surrounding the environmental impact of mobile phones and the implications of moving from the current business model of selling, using and discarding phones to a product service system based upon a cloud service. The exploration of the impacts relating to this shift and subsequent change in scope is explored in relation to the life cycle profile of a typical smartphone. Methods: A literature study is conducted into the existing literature in order to define the characteristics of a “typical” smartphone. Focus is given to greenhouse gas (GHG) emissions in different life cycle phases in line with that reported in the majority of literature. Usage patterns from literature are presented in order to show how a smartphone is increasingly responsible for not only data consumption, but also data generation. The subsequent consequences of this for the balance of the life cycle phases are explored with the inclusion of wider elements in the potential expanded mobile infrastructure, such as servers and the network. Result & Discussions: From the available literature the manufacturing phase is shown to dominate the life cycle of a “typical” smartphone for GHG emissions. Smartphone users are shown to be increasingly reliant upon the internet for provision of their communications. Adding a server into the scope of a smartphone is shown to increase the use phase impact from 8.5 kgCO2-eq to 18.0 kgCO2-eq, other phases are less affected. Addition of the network increases the use phase by another 24.7 kgCO2-eq. In addition, it is shown that take-back of mobile phones is not effective at present and that prompt return of the phones could result in reduction in impact by best reuse potential and further reduction in toxic emissions through inappropriate disposal. Conclusions: The way in which consumers interact with their phones is changing, leading to a system which is far more integrated with the internet. A product service system based upon a cloud service highlights the need for improved energy efficiency to make greatest reduction in GHG emissions in the use phase, and gives a mechanism to exploit residual value of the handsets by timely return of the phones, their components and recovery of materials.
The resonant transmission of microwaves polarized perpendicular to a single subwavelength slit of finite length is presented in detail. It is shown that the resonant frequency rises monotonically as slit length is reduced. Increasing confinement of the resonant fields within the slit is shown to cause the frequency rise. Angle dependence of the transmission is also presented. The results show clearly Fabry-Perot-like standing waves in the direction of propagation with waveguide mode behaviour in the orthogonal direction.
Purpose: Rearing crickets in the UK for the live pet food market is already a well-established industry. However, there is interest in also producing food for human consumption. This paper presents a life cycle assessment (LCA) of a current live pet food business. Using results from this LCA, the papers explores how current business practices could be improved to reduce environmental impacts, and discusses the potential benefits of a hybrid live pet food/human consumption business model. Methods: An attributional, cradle-to-farm-gate life cycle assessment was conducted on rearing crickets for the live pet food market, with data collected on-site at a case study business. Results are reported in multiple impact categories from the ILCD 2011 Midpoint+ method. Comparison is made to the only other similar study: an LCA of rearing crickets in Thailand for human consumption (Halloran et al. 2017). The sources of the different environmental impacts between the two studies are explored and inefficiencies in the live pet food rearing process identified. Subsequently, scenarios are used to explore how the inefficiencies may be mitigated, and environmental impact of the live pet food production process reduced through adoption of a hybrid live pet food/human food production model. Results and Discussions: The environmental impact was found to be larger across all impact categories than the only known comparable study, which is for rearing crickets in Thailand for human consumption (Halloran et al. 2017). Some of this difference is due to the heating required for rearing crickets in a climate such as the UK, and some is due to the requirements of the live pet food market being much more demanding on resources than the human food model. The current study identifies improvements in practices that would make this contrast less stark, such as optimizing feeding practices, and the benefits of moving to a hybrid live pet food/human consumption business model. Conclusions: This is the first LCA of crickets reared in the UK. The results highlight inefficiencies in the rearing process that are now being addressed by the case study business. The study also shows the potential co-benefits of a hybrid business model, in which crickets for human consumption are produced alongside crickets for the live pet food market.
Replacing added sugar with non-nutritive sweeteners and sweetness enhancers is of increasing interest due to the negative health effects of excess sugar consumption. Much has been done to understand health and safety of such sweetening additives, but little on their sustainability. This study, part of the Horizon 2020 SWEET project, presents results from the first life cycle assessment of the sweetness enhancer thaumatin, produced from Thaumatococcus daniellii fruit, from forests in West Africa and extracted in the United Kingdom. Thaumatin is used in formulations to increase perceived sweetness of added sugar, allowing some to be removed. Environmental impact is reported for multiple impact categories from the ReCiPe 2016 (H) method, focusing on global warming potential, land use, water consumption, and freshwater eutrophication. Impacts are expressed in terms of product mass and sweetness equivalence. Global warming potential for production of thaumatin is found to be 719.2 kgCO2-eq/kg. When thaumatin replaces 20% of added sugar, environmental impact for a given sweetness is found to reduce by an average of 19.4% across all impact categories. International transport is a major contributor to global warming potential, as is aril removal from the fruit to freshwater eutrophication and water use, and fruit foraging to land use. However, land use is identified as a key area of future research to improve uncertainty in the data. Results show that thaumatin can be used to reduce the environmental impact of providing sweet taste in food and beverage products.
Purpose There is an increasing interest in the use of non-nutritive sweeteners to replace added sugar in food and beverage products for reasons of improving consumer health. Much work has been done to understand safety of sweeteners, but very little on sustainability. To address that gap, this study presents the results of a life cycle assessment (LCA) of production of rebaudioside A 60%, 95% pure (RA60) steviol glycoside mix from Stevia rebaudiana leaf grown in Europe. Methods An attributional cradle-to-factory-gate life cycle assessment was conducted on growing of stevia leaves and extraction of steviol glycosides in Europe. Primary data were used from a case study supply chain. Results are reported in impact categories from the ReCiPe 2016 (H) method, with focus given to global warming potential, freshwater eutrophication, water consumption, and land use. Impacts are expressed both in terms of production mass and sweetness equivalence, a common metric for understanding high intensity sweetener potency. Sweetness equivalence of RA60 is typically 200 to 300 times that of sugar. Comparison of environmental impact is made to sugar (sucrose) produced from both cane and beets. The research is part of the EU project SWEET (sweeteners and sweetness enhancers: impact on health, obesity, safety, and sustainability). Results and discussion Global warming potential for production of RA60 was found to be 20.25 kgCO2-eq/kgRA60 on a mass basis and 0.081 kgCO2-eq/kgSE on a sweetness equivalence basis. Field production of stevia leaves was found to be the main source of impact for most impact categories, and for all four focus categories. Extraction of the RA60 was the main source of impact for the others. Leaf processing and seedling propagation were minor contributors to life cycle impact. Removal of international transport from the supply chain reduced global warming potential by 18.8%. Compared with sugar on a sweetness equivalence basis, RA60 has approximately 5.7% to 10.2% the impact for global warming potential, 5.6% to 7.2% the impact for land use, and is lower across most other impact categories. Conclusion This is the first LCA of steviol glycoside mix RA60 produced from leaf in Europe. The results indicate that RA60 can be used to reduce environmental impact of providing a sweet taste by replacing sugar across all impact categories. However, it is important to note that specific formulations in which RA60 is used will have a bearing on the final environmental impact of any food or beverage products. For solid foods, this requires further research.
The human food supply chain is placing great strain upon the environment. This is compounded by the creation of wastes at all points along the supply chain. Yet many of these “wastes” are instead surplus foodstuffs that may yet have the potential to be used. Recapturing the value in these surplus foodstuffs is essential in reducing environmental impact of the food supply chain. Insect bioconversion of such surplus foodstuffs back into animal feed is one promising way of doing this. In this study an optimization-based decision support tool is developed to inform bioconversion businesses what locations to source surplus foodstuffs from, where to locate processing facilities and what business model to pursue. A case study business is presented, which utilizes Hermetia illucens (black soldier fly larvae, BSFL) in small bioconversion units which have flexible location options, i.e. close to individual sources of surplus foodstuffs. Spent brewer's grains (SBG) are used as a case study surplus foodstuff. The quantities and locations of SBG are identified within the South East UK. Three business models are evaluated, one using the live BSFL to feed local poultry and two based upon dried BSFL-meal used in aquaculture feeds. The live BSFL business model is shown to be most viable at present with the best margins, and greatest resilience to model perturbations. The novelty of this study is the application of optimization understand the reality of how insect bioconversion may operate within current supply chains, as opposed to the technical or social aspects more usually studied.
A lamp comprises a thin layer of phosphor which is irradiated, for example by ultraviolet radiation, by a source which typically comprises a laser diode and a condenser. This causes the phosphor to emit visible light with a Lambertian-type emission pattern. An optical system such as a reflector concentrates the light form the phosphor. The phosphor is thermally connected to a heatsink, of example by a plate of sapphire glass, so as to dissipate the heat produced by the phosphor. The phosphor may be mounted on a plane reflector disposed on or comprising a heatsink and facing a curved reflector and the radiation source. Alternatively, the optical system may have an optical axis and the phosphor may be substantially flat and inclined with the respect to the optical axis.
A display device for detecting light includes a display surface, at least one light sensitive element arranged behind the display surface, and a liquid Crystal element arranged between the display Surface and the at least one light Sensitive element. The liquid crystal element is operative to polarization shift light incident on the at least one light sensitive element based on an orientation of the plurality of molecules. The display device further includes at least one electrode operative to change an orientation of the plurality of molecules. The at least one electrode is patterned to define a geometry of at least one field of view of the at least one light sensitive element. A controller is electrically coupled to the at least one electrode, wherein the controller is configured to apply a voltage to the at least one electrode to effect selection of the at least one field of view.
A light projection unit capable of improving light use efficiency is provided. This light projection unit includes: a fluorescent member that includes an illuminated surface to which laser light is directed, converts at least part of the laser light into fluorescent light and outputs the fluorescent light from chiefly the illuminated surface; and a reflection member that includes a first reflection surface which reflects the fluorescent light output from the fluorescent member. The illuminated surface of the fluorescent member is inclined with respect to the predetermined direction in such a way that the illuminated surface faces in a direction opposite to a light projection direction.
The rapid turnover in consumer electronics, fuelled by increased global consumption, has resulted in negative environmental and social consequences. Consumer electronics are typically disposed of into UK landfills; exported to developing countries; incinerated; retained in households in a redundant state; or otherwise 'lost' with very few being recycled. As a result, the high value metals they contain are not effectively recovered and new raw materials must be extracted to produce more goods. To assist in a transition from the current throw-away society towards a circular economy, the Closed Loop Emotionally Valuable E-waste Recovery (CLEVER) project is developing a novel Product-Service System (PSS). In the proposed PSS, component parts with 'low-emotional value', but requiring regular technical upgrade (such as circuit boards, chips and other electronic components) will be owned by manufacturers and leased to customers, and potentially ‘high-emotional value’ components (such as the outer casing) will be owned and valued by the customer so that they become products that are kept for longer periods of time. This research conceptualizes a consumer electronic device as comprising a 'skin' - the outer casing, or the part that the user interacts with directly; a 'skeleton' - the critical support components inside the device; and 'organs' - the high-tech electronics that deliver the product’s core functionality. Each of these has different longevity requirements and value-chain lifetimes, engendering different levels of stakeholder interaction. This paper contributes to academic debate by exploring the feasibility of creating a PSS which addresses conflicting issues for different components within the same device with different optimal lifetimes and end-of-life fates.
A headlamp of an embodiment of this invention includes a laser element, a light emitting section and a parabolic mirror. A part of the parabolic mirror is provided so as to face an upper surface of the light emitting section, which upper surface has a larger area than that of a side surface of the light emitting section. The light emitting section emits fluorescence in such a manner that distribution of the fluorescence corresponds to the Lambertian distribution.
A headlamp of one embodiment of this invention includes a laser element for emitting a laser beam, a light emitting section for generating fluorescence upon receiving the laser beam, and a reflecting mirror for projecting the fluorescence. Distribution of the fluorescence emitted by the light emitting section corresponds to Lambertian distribution, and an incident angle of the laser beam with respect to an excitation light irradiated surface, which is a surface of the light emitting section irradiated with the laser beam, is set so that use efficiency of the fluorescence emitting by the light emitting section in increased.
Wilson GT, Bridgens B, Hobson K, Lee J, Lilley D, Scott JL, Suckling JR
Product Lifetimes and the Environment, Nottingham, UK, 17 Jun 2015 - 19 Jun 2015. Editors: Cooper T, Braithwaite N, Moreno M, Salvia G. http://www.ntu.ac.uk/plate_conference/proceedings/index.html. Pages 394-400.