1,469 research outputs found
Trajectories of land use change in Europe: a model-based exploration of rural futures
Land use change is characterized by a high diversity of change trajectories depending on the local conditions, regional context and external influences. Policy intervention aims to counteract the negative consequences of these changes and provide incentives for positive developments. Region typologies are a common tool to cluster regions with similar characteristics and possibly similar policy needs. This paper provides a typology of land use change in Europe at a high spatial resolution based on a series of different scenarios of land use change for the period 2000-2030. A series of simulation models ranging from the global to the landscape level are used to translate scenario conditions in terms of demographic, economic and policy change into changes in European land use pattern. A typology developed based on these simulation results identifies the main trajectories of change across Europe: agricultural abandonment, agricultural expansion and urbanization. The results are combined with common typologies of landscape and rurality. The findings indicate that the typologies based on current landscape and ruralities are poor indicators of the land use dynamics simulated for the regions. It is advocated that typologies based on (simulated) future dynamics of land change are more appropriate to identify regions with potentially similar policy need
Understanding the Impact of Different Types of Surface States on Photoelectrochemical Water Oxidation: A Microkinetic Modeling Approach
The oxygen evolution reaction (OER) has been identified as one of the performance-limiting processes in solar water splitting using photoelectrochemical (PEC) cells. One of the reasons for the low OER performance is related to the existence of different types of surface states at the semiconductor–electrolyte interface: recombining surface states (r-SS) and surface states due to intermediate species (i-SS). Since the impact of surface states on OER is still under debate, we investigate how different types of surface states affect PEC water oxidation and how they impact experimental measurements. In a new computational approach, we combine a microkinetic model of the OER on the semiconductor surface with the charge carrier dynamics within the semiconductor. The impact of r-SS and i-SS on the current–voltage curves, hole flux, surface state capacitance, Mott–Schottky plots, and chopped light measurements is systematically investigated. It is found that (a) r-SS results in a capacitance peak below the OER onset potential, while i-SS results in a capacitance peak around the onset potential; (b) r-SS leads to an increase in the OER onset potential and a decrease in the saturation current density; (c) r-SS leads to Fermi-level pinning before the onset potential, while i-SS does not result in Fermi-level pinning; and (d) a smaller capacitance peak of i-SS can be an indication of the lower catalytic performance of the semiconductor surface. Our approach in combination with experimental comparison allows distinguishing the impact of r-SS and i-SS in PEC experiments. We conclude that r-SS reduces the OER performance and i-SS mediates the OER.</p
Automating Agential Reasoning: Proof-Calculi and Syntactic Decidability for STIT Logics
This work provides proof-search algorithms and automated counter-model extraction for a class of STIT logics. With this, we answer an open problem concerning syntactic decision procedures and cut-free calculi for STIT logics. A new class of cut-free complete labelled sequent calculi G3LdmL^m_n, for multi-agent STIT with at most n-many choices, is introduced. We refine the calculi G3LdmL^m_n through the use of propagation rules and demonstrate the admissibility of their structural rules, resulting in auxiliary calculi Ldm^m_nL. In the single-agent case, we show that the refined calculi Ldm^m_nL derive theorems within a restricted class of (forestlike) sequents, allowing us to provide proof-search algorithms that decide single-agent STIT logics. We prove that the proof-search algorithms are correct and terminate
Proline dehydrogenase from Thermus thermophilus does not discriminate between FAD and FMN as cofactor
Flavoenzymes are versatile biocatalysts containing either FAD or FMN as cofactor. FAD often binds to a Rossmann fold, while FMN prefers a TIM-barrel or flavodoxin-like fold. Proline dehydrogenase is denoted as an exception: it possesses a TIM barrel-like fold while binding FAD. Using a riboflavin auxotrophic Escherichia coli strain and maltose-binding protein as solubility tag, we produced the apoprotein of Thermus thermophilus ProDH (MBP-TtProDH). Remarkably, reconstitution with FAD or FMN revealed that MBP-TtProDH has no preference for either of the two prosthetic groups. Kinetic parameters of both holo forms are similar, as are the dissociation constants for FAD and FMN release. Furthermore, we show that the holo form of MBP-TtProDH, as produced in E. coli TOP10 cells, contains about three times more FMN than FAD. In line with this flavin content, the crystal structure of TtProDH variant ÂżABC, which lacks helices aA, aB and aC, shows no electron density for an AMP moiety of the cofactor. To the best of our knowledge, this is the first example of a flavoenzyme that does not discriminate between FAD and FMN as cofactor. Therefore, classification of TtProDH as an FAD-binding enzyme should be reconsidered
The Saccharomyces cerevisiae CWH8 gene is required for full levels of dolichol-linked oligosaccharides in the endoplasmic reticulum and for efficient N-glycosylation
The Saccharomyces cerevisiae mutant cwh8 was previously found to have an anomalous cell wall. Here we show that the cwh8 mutant has an N-glycosylation defect. We found that cwh8 cells were resistant to vanadate and sensitive to hygromycin B, and produced glycoforms of invertase and carboxypeptidase Y with a reduced number of N-chains. We have cloned the CWH8 gene. We found that it was nonessential and encoded a putative transmembrane protein of 239 amino acids. Comparison of the in vitro oligosaccharyl transferase activities of membrane preparations from wild type or cwh8Δ cells revealed no differences in enzyme kinetic properties indicating that the oligosaccharyl transferase complex of mutant cells was not affected. cwh8Δ cells also produced normal dolichols and dolichol-linked oligosaccharide intermediates including the full-length form Glc3Man9GlcNAc2. The level of dolichol-linked oligosaccharides in cwh8Δ cells was, however, reduced to about 20% of the wild type. We propose that inefficient N-glycosylation of secretory proteins in cwh8Δ cells is caused by an insufficient supply of dolichol-linked oligosaccharide substrat
Landscape Values and Aesthetic Preferences Across the Front Range
Boulder’s Open Space and Mountain Parks (OSMP) lands are managed to provide a diverse set of benefits valued by Boulder’s residents as well as tourists. Not all OSMP lands provide the same set of benefits however. Understanding how the values associated with OSMP lands vary across the region can provide managers with insights into how best to allocate resources so that they yield the maximum public benefit. In addition to an understanding of the values visitors associate with OSMP lands, management can benefit from knowledge of how different features of the landscape impact user experiences, both positively and negatively
Aesthetic Characteristics of the Front Range: An Analysis of Viewsheds Provided by Boulder OSMP Lands
The city of Boulder’s Open Space and Mountain Parks (OSMP) lands offer residents and visitors a variety of unique recreational, scenic, and cultural experiences that are often captured and shared publicly via social media. Given the diversity of OSMP lands, visitor experiences likely differ based on the aesthetic and biophysical features that can be viewed from these landscapes. For instance, the peaks of the iconic Flatirons provide visitors with different scenic views than the low-lying grasslands in the southeastern area of the city. Furthermore, visitor use and enjoyment of OSMP lands could be directly related to the landscape features that are visible from these different locations. Understanding how visible landscape features vary across OSMP lands can help managers target their planning efforts to improve the quality of outdoor recreation experiences, and potentially identify new locations for outdoor recreation infrastructure (e.g., trails, pavilions, etc.) that offer the ability to see the regions most desirable landscape features. This study: (1) identifies points in the landscape where users are often inspired to take photographs; (2) maps the landscapes most often viewed by visitors; (3) summarizes the types of landscape features viewed from OSMP lands; and (4) determines how these landscape features vary across LCAs
Lens Absorber Coupled MKIDs for Far Infrared Imaging Spectroscopy
Future generation of astronomical imaging spectrometers are targeting the far
infrared wavelengths to close the THz astronomy gap. Similar to lens antenna
coupled Microwave Kinetic Inductance Detectors (MKIDs), lens absorber coupled
MKIDs are a candidate for highly sensitive large format detector arrays.
However, the latter is more robust to misalignment and assembly issues at THz
frequencies due to its incoherent detection mechanism while requiring a less
complex fabrication process. In this work, the performance of such detectors is
investigated. The fabrication and sensitivity measurement of several lens
absorber coupled MKID array prototypes operating at 6.98 and 12 THz central
frequencies is on-going.Comment: 2 pages, 2 figures, IRMMW-THz conference pape
Laboratory-evolved Vanillyl-alcohol Oxidase Produces Natural Vanillin
The flavoenzyme vanillyl-alcohol oxidase was subjected to random mutagenesis to generate mutants with enhanced reactivity to creosol (2-methoxy-4-methylphenol). The vanillyl-alcohol oxidase-mediated conversion of creosol proceeds via a two-step process in which the initially formed vanillyl alcohol (4-hydroxy-3-methoxybenzyl alcohol) is oxidized to the widely used flavor compound vanillin (4-hydroxy-3-methoxybenzaldehyde). The first step of this reaction is extremely slow due to the formation of a covalent FAD N-5-creosol adduct. After a single round of error-prone PCR, seven mutants were generated with increased reactivity to creosol. The single-point mutants I238T, F454Y, E502G, and T505S showed an up to 40-fold increase in catalytic efficiency (k(cat)/K-m) with creosol compared with the wild-type enzyme. This enhanced reactivity was due to a lower stability of the covalent flavin-substrate adduct, thereby promoting vanillin formation. The catalytic efficiencies of the mutants were also enhanced for other ortho-substituted 4-methylphenols, but not for p-cresol (4-methylphenol). The replaced amino acid residues are not located within a distance of direct interaction with the substrate, and the determined three-dimensional structures of the mutant enzymes are highly similar to that of the wild-type enzyme. These results clearly show the importance of remote residues, not readily predicted by rational design, for the substrate specificity of enzymes
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