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| 8. |
- Albinsson, Bo, 1963, et al.
(författare)
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Matrix-isolation IR and UV spectra of Si3H8 and Si4H10: Isomers and conformers of oligosilanes
- 1996
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Ingår i: Journal of Physical Chemistry. - 0022-3654. ; 100:21, s. 8681-8691
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Tidskriftsartikel (refereegranskat)abstract
- Matrix-isolation IR and UV spectra of Si3H8, i-Si4H10, and the two conformers of n-Si4H10 have been recorded. A quantitative separation of the IR spectrum of n-Si4H10 into contributions from the anti and gauche forms was accomplished by a combination of matrix annealing and selective monochromatic photodestruction experiments. A qualitative separation of their UV spectra was achieved as well. The IR spectra of Si3H8, i-Si4H10, and the two conformers of n-Si4H10 have been assigned by comparison with results of ab initio calculations, which reproduce the frequencies and even the relative intensities quite well. The calculations predict dihedral angles omega of 180 degrees and 57 degrees for the anti and the gauche conformer of n-Si4H10, respectively, and confirm earlier predictions of nearly equal stability for an isolated molecule. In the matrix, the anti conformer is more stable, The conformational effects on the UV spectrum of n-Si4H10 are not those anticipated from simple models of the Sandorfy or ladder C type, in that it is primarily not the energy but the intensity of the low-energy excited singlet states that depends strongly on the SiSiSiSi dihedral angle omega. This result is interpreted in terms of data from 6-in-8 CASSCF 6-31G* calculations, which predict an avoided crossing between a strongly allowed sigma sigma* B state and a very weakly allowed sigma pi* B state as omega changes, with the former lower in energy at 180 degrees and the latter lower at 0 degrees. Consequences for attempts to understand the effects of conformation on optical spectra of polysilanes are noted.
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- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 14. |
- Chum, H., et al.
(författare)
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Sustainability indicators - A review of the literature
- 2011
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Ingår i: 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings. 11AIChE, Chicago, IL, 13 - 17 March 2011. - 9780816910670 ; , s. 3 (p)-
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Konferensbidrag (refereegranskat)abstract
- Biomass for energy is an issue that crosses many sectors including climate, energy, land-use, and development policies. A discussion on sustainability indicators covers variables that define the extent to which land- and biomass-based energy can contribute to climate change mitigation; complexities associated with biomass resources; impact indicators of bioenergy performance; policy approaches seeking to facilitate choices of technologies, products, and locations to reduce greenhouse gas emissions; environmental impacts of bioenergy systems; the displacement factor; roundtable groups seeking to establish accreditation systems based on indicator systems; Fischer-Tropsch diesel production; and contextual issues and conditions that characterize large-scale biomass energy as an essential part of informed decision making. This is an abstract of a paper presented at the 2011 AIChE Spring Meeting & 7th Global Congress on Process Safety (Chicago, IL 3/13-17/2011).
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| 15. |
- Dale, Virginia H., et al.
(författare)
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Status and prospects for renewable energy using wood pellets from the southeastern United States
- 2017
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Ingår i: Global Change Biology Bioenergy. - : Wiley-Blackwell. - 1757-1693 .- 1757-1707. ; 9:8, s. 1296-1305
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Tidskriftsartikel (refereegranskat)abstract
- The ongoing debate about costs and benefits of wood-pellet based bioenergy production in the southeastern United States (SE USA) requires an understanding of the science and context influencing market decisions associated with its sustainability. Production of pellets has garnered much attention as US exports have grown from negligible amounts in the early 2000s to 4.6 million metric tonnes in 2015. Currently, 98% of these pellet exports are shipped to Europe to displace coal in power plants. We ask, 'How is the production of wood pellets in the SE USA affecting forest systems and the ecosystem services they provide?' To address this question, we review current forest conditions and the status of the wood products industry, how pellet production affects ecosystem services and biodiversity, and what methods are in place to monitor changes and protect vulnerable systems. Scientific studies provide evidence that wood pellets in the SE USA are a fraction of total forestry operations and can be produced while maintaining or improving forest ecosystem services. Ecosystem services are protected by the requirement to utilize loggers trained to apply scientifically based best management practices in planning and implementing harvest for the export market. Bioenergy markets supplement incomes to private rural landholders and provide an incentive for forest management practices that simultaneously benefit water quality and wildlife and reduce risk of fire and insect outbreaks. Bioenergy also increases the value of forest land to landowners, thereby decreasing likelihood of conversion to nonforest uses. Monitoring and evaluation are essential to verify that regulations and good practices are achieving goals and to enable timely responses if problems arise. Conducting rigorous research to understand how conditions change in response to management choices requires baseline data, monitoring, and appropriate reference scenarios. Long-term monitoring data on forest conditions should be publicly accessible and utilized to inform adaptive management.
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- Englund, Oskar, et al.
(författare)
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Multifunctional perennial production systems for bioenergy: performance and progress
- 2020
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Ingår i: Wiley Interdisciplinary Reviews. - : Wiley. - 2041-8396 .- 2041-840X.
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Tidskriftsartikel (refereegranskat)abstract
- As the global population increases and becomes more affluent, biomass demands for food and biomaterials will increase. Demand growth is further accelerated by the implementation of climate policies and strategies to replace fossil resources with biomass. There are, however, concerns about the size of the prospective biomass demand and the environmental and social consequences of the corresponding resource mobilization, especially concerning impacts from the associated land-use change. Strategically integrating perennials into landscapes dominated by intensive agriculture can, for example, improve biodiversity, reduce soil erosion and nutrient emissions to water, increase soil carbon, enhance pollination, and avoid or mitigate flooding events. Such ?multifunctional perennial production systems? can thus contribute to improving overall land-use sustainability, while maintaining or increasing overall biomass productivity in the landscape. Seven different cases in different world regions are here reviewed to exemplify and evaluate (a) multifunctional production systems that have been established to meet emerging bioenergy demands, and (b) efforts to identify locations where the establishment of perennial crops will be particularly beneficial. An important barrier towards wider implementation of multifunctional systems is the lack of markets, or policies, compensating producers for enhanced ecosystem services and other environmental benefits. This deficiency is particularly important since prices for fossil-based fuels are low relative to bioenergy production costs. Without such compensation, multifunctional perennial production systems will be unlikely to contribute to the development of a sustainable bioeconomy.
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| 21. |
- Janssen, Ralf, 1975-, et al.
(författare)
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The evolution and expression of panarthropod frizzled genes
- 2015
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Wnt signaling regulates many important processes during metazoan development. It has been shown that Wnt ligands represent an ancient diverse family of proteins that likely function in complex signaling landscapes to induce target cells and tissues via receptors including those of the Frizzled family. The four subfamilies of Fz receptors also evolved early in metazoan evolution. To compare with other metazoans and arthropods such as insects, we explored the repertoire of fz genes in three panarthropod species: Parasteatoda tepidariorum, Glomeris marginata and Euperipatoides kanangensis, representing the Chelicerata, Myriapoda and Onychophora respectively. We found that these three diverse panarthropods each have four fz genes with representatives of all four metazoan fz subfamilies found in Glomeris and Euperipatoides while Parasteatoda does not have a fz3 gene but has two fz4 paralogues. Furthermore we characterized the expression patterns of all fz genes in Parasteatoda, Glomeris and Euperipatoides and found both conserved and divergent expression of these genes among these animals and in comparison to insects. Our study provides new insights into the evolution and developmental functions of fz receptors and Wnt signaling more generally.
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| 23. |
- Novak, R., et al.
(författare)
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Robotic fluidic coupling and interrogation of multiple vascularized organ chips
- 2020
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Ingår i: Nature Biomedical Engineering. - : Nature Research. - 2157-846X.
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Tidskriftsartikel (refereegranskat)abstract
- Organ chips can recapitulate organ-level (patho)physiology, yet pharmacokinetic and pharmacodynamic analyses require multi-organ systems linked by vascular perfusion. Here, we describe an ‘interrogator’ that employs liquid-handling robotics, custom software and an integrated mobile microscope for the automated culture, perfusion, medium addition, fluidic linking, sample collection and in situ microscopy imaging of up to ten organ chips inside a standard tissue-culture incubator. The robotic interrogator maintained the viability and organ-specific functions of eight vascularized, two-channel organ chips (intestine, liver, kidney, heart, lung, skin, blood–brain barrier and brain) for 3 weeks in culture when intermittently fluidically coupled via a common blood substitute through their reservoirs of medium and endothelium-lined vascular channels. We used the robotic interrogator and a physiological multicompartmental reduced-order model of the experimental system to quantitatively predict the distribution of an inulin tracer perfused through the multi-organ human-body-on-chips. The automated culture system enables the imaging of cells in the organ chips and the repeated sampling of both the vascular and interstitial compartments without compromising fluidic coupling.
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| 24. |
- Pelkmans, L., et al.
(författare)
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Monitoring the Impact of Sustainability Certification in Relation to Biomass Use for Energy
- 2012
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Ingår i: EUBCE 2012 proceedings. - 9788889407547 ; , s. 2013-2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Since the public has expressed concern about unintended consequences associated with potentially unsustainable biomass production and use for energy (or biofuels), producers of biomass feedstocks in the private sector as well as governmental and non-governmental organisations have initiated many generally unlinked efforts to define 'sustainable' bioenergy production and supply chains. These 'sustainability' standards may be implemented through certification systems involving 3rd party audit, and influence production systems and trade of bioenergy products from producers to consumers of ‘green' energy. At present numerous biomass and biofuel sustainability certification systems are being developed or implemented by a variety of private and public organisations. Systems are applicable to different feedstock production sectors (forests, agricultural crops), different bioenergy products (relatively unprocessed forest residues, ethanol, biodiesel, electricity), and whole or segments of supply chains (production system, chain of custody from growers to energy consumers). It is expected that such a wide range of systems, developed largely without coordination among the organisations involved, could be problematic for all stakeholders along the supply chain in individual sectors and for those involved in deployment of bioenergy systems globally. These are individual feedstock producers, companies and commodity sectors that must comply with these systems either to maintain market access and share or to comply with legislative mandates, and also consumers who prefer to purchase certified green energy, and regulatory agencies and local to national governments that may be involved in enforcing sustainability standards. The potential for confusion among the actors, depression of markets, and unnecessary restrictions on sustainable trade seems high. Within IEA Bioenergy a strategic study was initiated between Task 40, Task 43 and Task 38 to monitor the actual implementation process of sustainability certification of bioenergy, evaluate how stakeholders are affected by certification initiatives, quantify the anticipated impact on worldwide bioenergy trade, assess the level of coordination among schemes, and make recommendations to remove barriers which may depress markets and reduce sustainable trade. Interaction with different stakeholder groups is one of the main objectives of this study, so we anticipate the recommendations being representative of the whole bioenergy certification sector and therefore having high potential to improve an otherwise uncoordinated interest in ensuring bioenergy trade is sustainable.
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| 26. |
- Pinto, H., et al.
(författare)
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First-principles studies of the effect of (001) surface terminations on the electronic properties of the negatively charged nitrogen-vacancy defect in diamond
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:4
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Tidskriftsartikel (refereegranskat)abstract
- Density functional calculations have been carried out on (001)-orientated slabs of diamond with different surface terminations. A negatively charged nitrogen-vacancy defect (NV-) is placed in the middle of the slab approximately 1 nm from each surface and the effect of the surface on the internal optical transition in NV- investigated. The calculations show that the chemical nature of the surface is important. We find that although the clean surface does not lead to charge transfer between the defect and the surface, there is a splitting of the empty excited state, the final state in optical absorption, arising from a strong hybridization of the surface and defect bands. This leads to a broadening of the 1.945-eV transition of the NV- defect. OH- and F-terminated surfaces have no surface states in the band gap and again charge transfer between the defect and surface does not occur. The splitting of the e levels responsible for the optical transitions for OH or F termination is similar to that found in periodic boundary condition simulations for bulk diamond where the defects are separated by 1 nm, and thus the calculations show that hydroxylated or fluorinated surfaces give favorable optical properties.
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| 27. |
- Pinto, H., et al.
(författare)
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On the diffusion of NV defects in diamond
- 2012
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 209:9, s. 1765-1768
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Tidskriftsartikel (refereegranskat)abstract
- Besides their importance for quantum information processing, NV defects are crucial agents for the diffusion and aggregation of nitrogen in diamond. In the absence of transition metals, it is thought that the first stage of nitrogen aggregation, where close neighbour nitrogen pairs are formed, is mediated by NV defects. Here we use density functional theory to explore the barriers to NV diffusion. We conclude that the barrier is around 5 eV when there is a ready source of vacancies and that this barrier is weakly dependent on pressure.
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| 28. |
- Pinto, H., et al.
(författare)
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Theory of the surface effects on the luminescence of the NV(-) defect in nanodiamond
- 2011
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 208:9, s. 2045-2050
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Tidskriftsartikel (refereegranskat)abstract
- A vacancy with one of the carbon neighbours replaced by a nitrogen atom in diamond (the NV centre) is a defect of particular interest due to its many potential applications. In the negatively charged state, the defect is paramagnetic with spin 1 and under optical excitation it exhibits an intense luminescence with a zero-phonon line at 1.945eV. This fluorescence is found in nanodiamonds even as small as 5nm and an important question is the effect of the surface of the nanodiamond on the optical emission of NV-.Density functional calculations are used in this work to investigate the effect of the bare (001) and (001)-OH diamond surfaces on the electronic structure of NV-. We show that the (001)-OH diamond surface has the minimum interaction with the defect and is the ideal terminating surface of nanodiamonds, while the bare (001) diamond surface has a strong effect on broadening the emission.
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| 31. |
- Tiwari, Amit K., et al.
(författare)
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Calculated electron affinity and stability of halogen-terminated diamond
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:24
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Tidskriftsartikel (refereegranskat)abstract
- The chemical termination of diamond has a dramatic impact on its electrical and chemical properties, where hydrogen and oxygen termination produce negative and positive electron affinities, respectively. However, the impact of halogen termination is not fully understood. We show that for low-index surfaces, 100% fluorinated surfaces exhibit chemically stable positive electron affinities in the 1.17 to 2.63 eV range, whereas 100% chlorination is energetically unfavorable. At lower coverage the positive electron affinity is smaller, being a combination of halogen-terminated and unterminated sites. For mixed halogen and hydrogen termination, a wide range of negative and positive electron affinities can be achieved by varying the relative concentrations of adsorbed species.
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| 32. |
- Tiwari, Amit K., et al.
(författare)
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Thermodynamic stability and electronic properties of F- and Cl-terminated diamond
- 2012
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 209:9, s. 1709-1714
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Tidskriftsartikel (refereegranskat)abstract
- The chemical termination of diamond has important consequences for its electrical and chemical properties. Despite the impressive potential for various scientific and technological applications, halogen termination of diamond is not fully understood. We find using first principle atomistic simulation that 100% fluorinated diamond (100) surface exhibit a chemically stable positive electron affinity of 2.13 eV, whereas 100% chlorination is energetically unfavourable. The positive electron affinity of halogenated diamond generally increases with increasing surface coverage. For mixed halogen and hydrogen termination, a wide range of negative and positive electron affinities can be achieved theoretically by varying the relative concentrations of adsorbed species.
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