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| 6. |
- Maranghino-Singer, B., et al.
(författare)
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An information system supporting cap and trade in organizations
- 2015
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Ingår i: ICT Innovations for Sustainability. - Cham : Springer. - 9783319092270 - 9783319092287 ; , s. 285-299
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Bokkapitel (refereegranskat)abstract
- We present a software system to create and implement internal markets in organizations that want to limit the CO2 emissions or the use of scarce resources by their employees. This system can be applied to domains such as business travel by distributing a limited number of permits for business travel-related CO2 emissions at the beginning of a period and then allowing the permits to be traded inside the organization. The system calculates the CO2 emissions caused byplanned trips and provides the market mechanisms to trade the permits. The approach can be generalized from emission permits to any scarce good that is assigned by the management to units or individual members of the organization, such as parking spaces. Both cases are described by way of detailed examples.
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| 7. |
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| 8. |
- Hilty, F. M., et al.
(författare)
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Development and optimization of iron- and zinc-containing nanostructured powders for nutritional applications
- 2009
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 20:47
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Tidskriftsartikel (refereegranskat)abstract
- Reducing the size of low-solubility iron (Fe)-containing compounds to nanoscale has the potential to improve their bioavailability. Because Fe and zinc (Zn) deficiencies often coexist in populations, combined Fe/Zn-containing nanostructured compounds may be useful for nutritional applications. Such compounds are developed here and their solubility in dilute acid, a reliable indicator of iron bioavailability in humans, and sensory qualities in sensitive food matrices are investigated. Phosphates and oxides of Fe and atomically mixed Fe/Zn-containing (primarily ZnFe(2)O(4))nanostructured powders were produced by flame spray pyrolysis (FSP). Chemical composition and surface area were systematically controlled by varying precursor concentration and feed rate during powder synthesis to increase solubility to the level of ferrous sulfate at maximum Fe and Zn content. Solubility of the nanostructured compounds was dependent on their particle size and crystallinity. The new nanostructured powders produced minimal color changes when added to dairy products containing chocolate or fruit compared to the changes produced when ferrous sulfate or ferrous fumarate were added to these foods. Flame-made Fe- and Fe/Zn-containing nanostructured powders have solubilities comparable to ferrous and Zn sulfate but may produce fewer color changes when added to difficult-to-fortify foods. Thus, these powders are promising for food fortification and other nutritional applications.
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| 9. |
- Huber, M. Z., et al.
(författare)
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Gamification and sustainable consumption : Overcoming the limitations of persuasive technologies
- 2014
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Ingår i: ICT Innovations for Sustainability. - Cham : Springer. - 9783319092270 - 9783319092287 ; , s. 367-385
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Bokkapitel (refereegranskat)abstract
- The current patterns of production and consumption in the industrialized world are not sustainable. The goods and services we consume cause resource extractions, greenhouse gas emissions and other environmental impacts that are already affecting the conditions of living on Earth. To support the transition toward sustainable consumption patterns, ICT applications that persuade consumers to change their behavior into a ‘‘green’’ direction have been developed in the field of Persuasive Technology (PT). Such persuasive systems, however, have been criticized for two reasons. First, they are often based on the assumption that information (e.g., information on individual energy consumption) causes behavior change, or a change in awareness and attitude that then changes behavior. Second, PT approaches assume that the designer of the system starts from objective criteria for ‘‘sustainable’’ behavior and is able to operationalize them in the context of the application. In this chapter, we are exploring the potential of gamification to overcome the limitations of persuasive systems. Gamification, the process of using game elements in a non-game context, opens up a broader design space for ICT applications created to support sustainable consumption. In particular, a gamifi- cation-based approach may give the user more autonomy in selecting goals and relating individual action to social interaction. The idea of gamification may also help designers to view the user’s actions in a broader context and to recognize the relevance of different motivational aspects of social interaction, such as competition and cooperation. Based on this discussion we define basic requirements to be used as guidance in gamification-based motivation design for sustainable consumption.
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| 10. |
- Santarius, T., et al.
(författare)
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Digital sufficiency : conceptual considerations for ICTs on a finite planet
- 2022
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Ingår i: Annales des télécommunications. - : Springer Nature. - 0003-4347 .- 1958-9395.
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Tidskriftsartikel (refereegranskat)abstract
- ICT hold significant potential to increase resource and energy efficiencies and contribute to a circular economy. Yet unresolved is whether the aggregated net effect of ICT overall mitigates or aggravates environmental burdens. While the savings potentials have been explored, drivers that prevent these and possible counter measures have not been researched thoroughly. The concept digital sufficiency constitutes a basis to understand how ICT can become part of the essential environmental transformation. Digital sufficiency consists of four dimensions, each suggesting a set of strategies and policy proposals: (a) hardware sufficiency, which aims for fewer devices needing to be produced and their absolute energy demand being kept to the lowest level possible to perform the desired tasks; (b) software sufficiency, which covers ensuring that data traffic and hardware utilization during application are kept as low as possible; (c) user sufficiency, which strives for users applying digital devices frugally and using ICT in a way that promotes sustainable lifestyles; and (d) economic sufficiency, which aspires to digitalization supporting a transition to an economy characterized not by economic growth as the primary goal but by sufficient production and consumption within planetary boundaries. The policies for hardware and software sufficiency are relatively easily conceivable and executable. Policies for user and economic sufficiency are politically more difficult to implement and relate strongly to policies for environmental transformation in general. This article argues for comprehensive policies for digital sufficiency, which are indispensible if ICT are to play a beneficial role in overall environmental transformation.
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| 11. |
- Santarius, T., et al.
(författare)
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Digitalization and Sustainability : A Call for a Digital Green Deal
- 2023
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Ingår i: Environmental Science and Policy. - : Elsevier BV. - 1462-9011 .- 1873-6416. ; 147, s. 11-14
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Tidskriftsartikel (refereegranskat)abstract
- The relation between digitalization and environmental sustainability is ambiguous. There is potential of various digital technologies to slow down the transgression of planetary boundaries. Yet resource and energy demand for digital hardware production and use of data-intensive applications is of substantial size. The world over, there is no comprehensive regulation that addresses opportunities and risks of digital technology for sustainability. In this perspective article, we call for a Digital Green Deal that includes strong, cross-sectoral green digitalization policies on all levels of governance. We argue that a Digital Green Deal should first and foremost aim at greater policy coherence: Current digital policy initiatives should include measures that service environmental goals, and environmental policies must address risks and advance opportunities of digital technologies to spur sustainability transformations.
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| 12. |
- Siebenmann, C, et al.
(författare)
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Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454-m altitude
- 2015
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 119:10, s. 1194-1201
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Tidskriftsartikel (refereegranskat)abstract
- Siebenmann C, Cathomen A, Hug M, Keiser S, Lundby AK, Hilty MP, Goetze JP, Rasmussen P, Lundby C. Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454 m altitude. J Appl Physiol 119: 1194-1201, 2015. First published March 6, 2015; doi:10.1152/japplphysiol.01121.2014.-High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements, and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV was estimated by carbon monoxide rebreathing at SL, on every 4th day at HA, and 1 and 2 wk upon return to SL. Four weeks at HA increased Hbmass by 5.26% (range 2.5-11.1%; P < 0.001). The individual Hbmass increases commenced with up to 12 days of delay and reached a maximal rate of 4.04±1.02 g/day after 14.9±5.2 days. The probability for Hbmass to plateau increased steeply after 20-24 days. Upon return to SL Hbmass decayed by-2.46 ± 2.3 g/day, reaching values similar to baseline after 2 wk. PV, aldosterone concentration, and renin activity were reduced at HA (P < 0.001) while the total circulating protein mass remained unaffected. In summary, the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ∼3 wk. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data support that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure. © 2015 The American Physiological Society.
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| 13. |
- Ahmadi Achachlouei, Mohammad, 1981-
(författare)
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Exploring the Effects of ICT on Environmental Sustainability: From Life Cycle Assessment to Complex Systems Modeling
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The production and consumption of information and communication technology (ICT) products and services continue to grow worldwide. This trend is accompanied by a corresponding increase in electricity use by ICT, as well as direct environmental impacts of the technology. Yet a more complicated picture of ICT’s effects is emerging. Positive indirect effects on environmental sustainability can be seen in substitution and optimization (enabling effects), and negative indirect effects can be seen in additional demand due to efficiency improvements (rebound effects).A variety of methods can be employed to model and assess these direct and indirect effects of ICT on environmental sustainability. This doctoral thesis explores methods of modeling and assessing environmental effects of ICT, including electronic media. In a series of five studies, three methods were at times applied in case studies and at others analyzed theoretically. These methods include life cycle assessment (LCA) and complex systems modeling approaches, including System Dynamics (SD) and agent-based (AB) modeling.The first two studies employ the LCA approach in a case study of an ICT application, namely, the tablet edition of a Swedish design magazine. The use of tablets has skyrocketed in recent years, and this phenomenon has been little studied to date. Potential environmental impacts of the magazine’s tablet edition were assessed and compared with those of the print edition. The tablet edition’s emerging version (which is marked by a low number of readers and low reading time per copy) resulted in higher potential environmental impacts per reader than did the print edition. However, the mature tablet edition (with a higher number of readers and greater reading time per copy) yielded lower impacts per reader in half the ten impact categories assessed.While previous studies of electronic media have reported that the main life-cycle contributor to environmental impacts is the use phase (which includes operational electricity use as well as the manufacture of the electronic device), the present study did not support those findings in all scenarios studied in this thesis. Rather, this study found that the number of readers played an important role in determining which life-cycle phase had the greatest impacts. For the emerging version, with few readers, content production was the leading driver of environmental impacts. For the mature version, with a higher number of readers, electronic storage and distribution were the major contributors to environmental impacts. Only when there were many readers but low overall use of the tablet device was the use phase the main contributor to environmental impacts of the tablet edition of the magazine.The third study goes beyond direct effects at product- and service-level LCAs, revisiting an SD simulation study originally conducted in 2002 to model indirect environmental effects of ICT in 15 European countries for the period 2000-2020. In the current study, three scenarios of the 2002 study were validated in light of new empirical data from the period 2000–2012. A new scenario was developed to revisit the quantitative and qualitative results of the original study. The results showed, inter alia, that ICT has a stimulating influence on total passenger transport, for it makes it more cost- and time-efficient (rebound effects).The modeling mechanism used to represent this rebound effect is further investigated in the fourth study, which discusses the feedback loops used to model two types of rebound effects in passenger transport (direct economic rebound and time rebound). Finally, the role of systems thinking and modeling in conceptualizing and communicating the dynamics of rebound effects is examined.The aim of the fifth study was to explore the power of systems modeling and simulation to represent nonlinearities of the complex and dynamic systems examined elsewhere in this thesis. That study reviews previous studies that have compared the SD and AB approaches and models, summarizing their purpose, methodology, and results, based on certain criteria for choosing between SD and AB approaches. The transformation procedure used to develop an AB model for purposes of comparison with an SD model is also explored.In conclusion, first-order or direct environmental effects of ICT production, use, and disposal can be assessed employing an LCA method. This method can also be used to assess second-order or enabling effects by comparing ICT applications with conventional alternatives. However, the assessment of enabling effects can benefit from systems modeling methods, which are able to formally describe the drivers of change, as well as the dynamics of complex social, technical, and environmental systems associated with ICT applications. Such systems methods can also be used to model third-order or rebound effects of efficiency improvements by ICT.
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| 14. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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Modeling the Effects of ICT on Environmental Sustainability : Revisiting a System Dynamics Model Developed for the European Commission
- 2015
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Ingår i: ICT Innovations for Sustainability. - Switzerland : Springer Publishing Company. - 9783319092270 - 9783319092287 ; , s. 449-474
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Bokkapitel (refereegranskat)abstract
- This chapter revisits a System Dynamics model developed in 2002 with the aim of exploring the future impacts of Information and Communication Technology (ICT) on environmental sustainability in the EU, which then consisted of 15 countries. The time horizon of the study was 20 years (2000–2020). We analyze the results in light of empirical data that is now available for 2000–2012. None of the three scenarios that were developed by experts to specify the external factors needed to run the model were realistic from today’s point of view. If the model is re-run with more realistic input data for the first half of the simulation period, however, the main results regarding the impact of ICT remain qualitatively the same; they seem to be relatively robust implications of the causal system structure, as it is represented in the model. Overall, the impacts of ICT for mitigating greenhouse gas emissions and other environmental burdens for 2020 tend to be slightly stronger if the simulation is based on the empirical data now available.
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| 15. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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Modelling Rebound Effects in System Dynamics
- 2014
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Ingår i: Proceedings of the 28th Conference on Environmental Informatics - EnviroInfo 2014 - ICT for Energy Efficiency. - Germany : BIS Oldenburg. - 9783814223179
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Konferensbidrag (refereegranskat)abstract
- The induction of demand by increasing the efficiency of a production or consumption process is known as the rebound effect. Feedback loops in System Dynamics can be used to conceptualize the structure of this complex phenomenon and also for communicating model-based insights. In passenger transport, the rebound effect can be induced through increased cost efficiency (direct economic rebound) and/or increase in speed (time rebound). In this paper we review and compare two models on environmental effects of passenger transport—including a model on the role of information and communication technology. We highlight the feedback mechanisms used to deal with the rebound effect (price, efficiency, and time rebound).
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| 17. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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System Dynamics vs. agent-based modeling—comparing models and approaches : A literature review and a transformation procedure
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Systems modeling and simulation methods such as System Dynamics (SD) and agent-based (AB) modeling have been used to foster a better understanding of the dynamics and complexity of natural, technical, and social systems. System Dynamics provides an aggregate-level perspective, highlighting thinking in feedback loops and employing differential equations to model the causal relations in a system, exploring the system's dynamics by numerically solving the equations. Agent-based modeling, in a bottom-up method, focuses on constituent units (agents) and their interactions to explore the emerging behavior at a system level by means of simulation. Comparing these modeling methods can help us understand their strengths and weaknesses in order to choose the right approach for a given modeling problem. It may also support the analysis of a given system to build multiple models using the different approaches and comparing them, in particular to treat fundamental uncertainties in systems modeling and simulation. In this paper, we review the existing studies comparing the SD and AB approaches and models, investigating the aims, methodology, and results of such comparative studies. We also highlight lessons learned for future model comparisons by examining how the corresponding SD and AB models are built for the purpose of comparison. A procedure for transforming System Dynamics models into agent-based models is presented and discussed using examples from the literature.
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| 18. |
- Ahmadi Achachlouei, Mohammad, et al.
(författare)
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Using Systems Thinking and System Dynamics Modeling to Understand Rebound Effects
- 2016
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Ingår i: Advances And New Trends In Environmental And Energy Informatics. - Cham, Switzerland : Springer Publishing Company. - 9783319234557 - 9783319234540 ; , s. 237-255
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Bokkapitel (refereegranskat)abstract
- Processes leading to an increase of demand for a resource as a consequence of increasing the efficiency of using this resource in production or consumption are known as (direct) rebound effects. Rebound effects at micro and macro levels tend to offset the reduction in resource consumption enabled by progress in efficiency. Systems thinking and modeling instruments such as causal loop diagrams and System Dynamics can be used to conceptualize the structure of this complex phenomenon and also to communicate model-based insights. In passenger transport, the rebound effect can be invoked by increased cost efficiency (direct economic rebound) and/or increase in speed (time rebound). In this paper we review and compare two existing models on passenger transport—including a model on the role of information and communication technology—with regard to the feedback loops used to conceptualize rebound effects.
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| 19. |
- Bieser, Jan C. T., et al.
(författare)
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Impacts of telecommuting on time use and travel : A case study of a neighborhood telecommuting center in Stockholm
- 2021
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Ingår i: Travel Behaviour & Society. - : Elsevier BV. - 2214-367X .- 2214-3688. ; 23, s. 157-165
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Tidskriftsartikel (refereegranskat)abstract
- While telecommuting (TC) research heavily discusses travel impacts of home-based TC, little is known about impacts of working from a neighborhood TC center on travel and non-travel activities and their energy requirements. We conduct a case study on the impacts of the work location (employer's office, TC center, home) on time use and travel using data collected in a neighborhood TC center in Stockholm. Our results show that telecommuters more frequently replaced working from the TC center for working from the more distant employer's office than for working from home. On TC center and home office days, diarists spent less time traveling, and on home office days more time on chores and leisure than on employer office days. When working from the TC center instead of the employer's office, telecommuters frequently used the same or more energy-efficient commute modes, e.g. biking instead of the car, which was feasible because the TC center is in the local neighborhood. However, when working from home, diarists mainly used the car for private travel. Thus, energy savings of TC can be increased by providing energy-efficient transport options or local access to non-work destinations to telecommuters. TC energy impacts depend also on changes to energy requirements for nontravel activities, for space heating/cooling/lighting at all work locations, and systemic TC effects (e.g. residential relocation), which can only be observed in the long term. Thus, future TC assessments should take an even broader perspective in terms of travel and non-travel activities, their energy requirements, and systemic effects.
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| 20. |
- Bieser, Jan C. T., et al.
(författare)
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Lifetime extension of mobile internet-enabled devices : measures, challenges and environmental implications
- 2021
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Ingår i: Proceedings of the 4th Conference on Product Lifetimes and the Environment (PLATE).
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Konferensbidrag (refereegranskat)abstract
- Increasing the service lifetime of mobile Internet-enabled devices (MIEDs) such as smartphones, tablets and laptops is a promising strategy to reduce the number of devices that need to be produced and reduce environmental impacts associated with device production. A broad spectrum of lifetime-extending measures has been explored in literature and in industry practice. In this article, we present an overview of explored measures, discuss challenges in their implementation and environmental impacts of lifetime extension. We find that measures can be distinguished into measures aiming at (1) the improvement of the device design (e.g. modular or durable design of smartphones), (2) device retention (increasing the time a user keeps a device, e.g. by offering repair services or fostering emotional attachment to devices), and (3) recirculation (creating a second life with a different user and/or in a different context, e.g. by refurbishing and reselling devices). The implementation of measures is challenged by trade-offs faced by organizations in the MIED value chain, which specifically occur when revenues depend on the number of new devices produced and sold. Furthermore, measures are subject to rebound and induction effects (e.g. imperfect substitution, re-spending effects), which can compensate for the (theoretical) environmental gains from service lifetime extension. In particular, it is uncertain to what extent a measure actually leads to lifetime extension and eventually reduces primary production of devices (displacement rate). Thus, more systematic research is needed on the feasibility of measures and the conditions under which they effectively contribute to a net reduction of environmental impacts.
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| 21. |
- Bieser, Jan C. T., et al.
(författare)
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Toward a method for assessing the energy impacts of telecommuting based on time-use data
- 2022
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Ingår i: Travel Behaviour & Society. - : Elsevier BV. - 2214-367X .- 2214-3688. ; 27, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- Most telecommuting (TC) studies focus on travel impacts and do not consider changes in time spent on non-travel activities (e.g. 'leisure') and the energy impacts of these changes. We demonstrate a time-use approach to assess interrelations between changes in commuting time and time spent on travel and non-travel activities and associated energy impacts. Time-use data analysis shows that spending less time on commuting is associated with more time spent on 'sleep', 'leisure', 'personal, household and family care', 'private travel' and 'eating and drinking'. Substituting car commuting with 'sleep', 'eating and drinking', common 'leisure' and 'personal, household and family care' activities is likely to reduce energy requirements as these are associated with less energy requirements than car commuting. This is different for 'private travel', 'meal preparation at home', and energy-intensive or out-of-home 'leisure' activities, which are associated with relatively high energy requirements. The commute modal split is a key variable in energy impacts of TC, because transport modes differ in their energy requirements. While car commuters can realize high energy savings through TC, for people who usually bike or walk to work, direct energy savings through reduced commuting are zero. Thus, any additional energy impact due to substitute activities, increases net direct energy requirements. Future research should further investigate the relationship between TC and time spent on (non-)travel activities and the marginal energy requirements of these activities. If so, the time-use approach can become key for assessing energy impacts of TC and other applications which impact individual time allocation.
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| 22. |
- Coroama, Vlad C., et al.
(författare)
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Assessing Internet energy intensity : A review of methods and results
- 2014
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Ingår i: Environmental impact assessment review. - : Elsevier BV. - 0195-9255 .- 1873-6432. ; 45, s. 63-68
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Forskningsöversikt (refereegranskat)abstract
- Assessing the average energy intensity of Internet transmissions is a complex task that has been a controversial subject of discussion. Estimates published over the last decade diverge by up to four orders of magnitude from 0.0064 kilowatt-hours per gigabyte (kWh/GB) to 136 kWh/GB. This article presents a review of the methodological approaches used so far in such assessments: i) top-down analyses based on estimates of the overall Internet energy consumption and the overall Internet traffic, whereby average energy intensity is calculated by dividing energy by traffic for a given period of time, ii) model-based approaches that model all components needed to sustain an amount of Internet traffic, and iii) bottom-up approaches based on case studies and generalization of the results. Our analysis of the existing studies shows that the large spread of results is mainly caused by two factors: a) the year of reference of the analysis, which has significant influence due to efficiency gains in electronic equipment, and b) whether end devices such as personal computers or servers are included within the system boundary or not. For an overall assessment of the energy needed to perform a specific task involving the Internet, it is necessary to account for the types of end devices needed for the task, while the energy needed for data transmission can be added based on a generic estimate of Internet energy intensity for a given year. Separating the Internet as a data transmission system from the end devices leads to more accurate models and to results that are more informative for decision makers, because end devices and the networking equipment of the Internet usually belong to different spheres of control.
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| 23. |
- Coroama, Vlad C, et al.
(författare)
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Dematerialization Through Electronic Media?
- 2015
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Ingår i: ICT Innovations for Sustainability. - Cham : Springer. - 9783319092287 ; , s. 405-421
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- While the traditional roles of the computer as a machine for scientific calculations, text editing, and graphic design are still significant, computers are increasingly perceived as means of accessing information and interacting with other people – i.e., as electronic media. The aim of this chapter is to analyze digital electronic media and their effects on environmental sustainability. Two fields of application are addressed: electronic media that may replace or augment traditional print media such as newspapers or magazines, and videoconferencing as a potential substitute for traveling to a face-to-face meeting or conference. In both cases, the environmental costs of the electronic media are compared to those of their conventional counterparts. The examples show that electronic media can represent an energy-efficient alternative to traditional activities such as long-distance travel. But they can also be added on top of existing activities instead of replacing them. In such cases, a net increase in the environmental impact results. The availability of small, energy-efficient devices being used as electronic media does not guarantee dematerialization. The overall resource use and emissions throughout the life cycle of the media product systems and, more importantly, at the macro level of total global production and consumption need to be considered. To achieve the dematerialization potential of new electronic media solutions, their efficiency needs to be combined with sufficiency; thus additional measures are necessary to turn the dematerialization potential of electronic media into environmental relief.
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| 24. |
- Coroama, V. C., et al.
(författare)
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The energy intensity of the internet : Home and access networks
- 2015
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Ingår i: Advances in Intelligent Systems and Computing. - Cham : Springer International Publishing. - 2194-5357 .- 2194-5365. ; 310, s. 137-155
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Tidskriftsartikel (refereegranskat)abstract
- Estimates of the energy intensity of the Internet diverge by several orders of magnitude. We present existing assessments and identify diverging definitions of the system boundary as the main reason for this large spread. The decision of whether or not to include end devices influences the result by 1–2 orders of magnitude. If end devices are excluded, customer premises equipment (CPE) and access networks have a dominant influence. Of less influence is the consideration of cooling equipment and other overhead, redundancy equipment, and the amplifiers in the optical fibers. We argue against the inclusion of end devices when assessing the energy intensity of the Internet, but in favor of including CPE, access networks, redundancy equipment, cooling and other overhead as well as optical fibers. We further show that the intensities of the metro and core network are best modeled as energy per data, while the intensity of CPE and access networks are best modeled as energy per time (i.e., power), making overall assessments challenging. The chapter concludes with a formula for the energy intensity of CPE and access networks. The formula is presented both in generic form as well as with concrete estimates of the average case to be used in quick assessments by practitioners. The next chapter develops a similar formula for the core and edge networks. Taken together, the two chapters provide an assessment method of the Internet’s energy intensity that takes into account different modeling paradigms for different parts of the network.
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| 25. |
- Flück, D., et al.
(författare)
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Age, aerobic fitness, and cerebral perfusion during exercise: Role of carbon dioxide
- 2014
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Ingår i: American Journal of Physiology - Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 307:4
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Tidskriftsartikel (refereegranskat)abstract
- Middle cerebral artery mean velocity (MCAvmean) is attenuated with increasing age both at rest and during exercise. The aim of this study was to determine the influence of the age-dependent reduction in arterial PCO2 (PaCO2) and physical fitness herein. We administered supplemental CO2 (CO2 trial) or no additional gas (control trial) to the inspired air in a blinded and randomized manner, and assessed middle cerebral artery mean flow velocity during graded exercise in 1) 21 young [Y; age 24 ± 3 yr (±SD)] volunteers of whom 11 were trained (YT) and 10 considered untrained (YUT), and 2) 17 old (O; 66 ± 4 yr) volunteers of whom 8 and 9 were considered trained (OT) and untrained (OUT), respectively. A resting hypercapnic reactivity test was also performed. MCAvmean and PaCO2 were lower in O [44.9 ± 3.1 cm/s and 30 ± 1 mmHg (±SE)] compared with Y (59.3 ± 2.3 cm/s and 34 ± 1 mmHg, P < 0.01) at rest, independent of aerobic fitness level. The age-related decreases in MCAvmean and PaCO2 persisted during exercise. Supplemental CO2 reduced the age-associated decline in MCAvmean by 50%, suggesting that PaCO2 is a major component in the decline. On the other hand, relative hypercapnic reactivity was neither influenced by age (P = 0.46) nor aerobic fitness (P = 0.36). Although supplemental CO2 attenuated exercise-induced reduction in cerebral oxygenation (near-infrared spectroscopy), this did not influence exercise performance. In conclusion, PaCO2 contributes to the age-associated decline in MCAvmean at rest and during exercise; however exercise capacity did not diminish this age effect. © 2014 the American Physiological Society.
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