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461.
Fungus-growing termites are associated with genus-specific fungal symbionts, which they acquire via horizontal transmission. Selection of specific symbionts may be explained by the provisioning of specific, optimal cultivar growth substrates by termite farmers. We tested whether differences in in vitro performance of Termitomyces cultivars from nests of three termite species on various substrates are correlated with the interaction specificity of their hosts. We performed single-factor growth assays (varying carbon sources), and a two-factor geometric framework experiment (simultaneously varying carbohydrate and protein availability). Although we did not find qualitative differences between Termitomyces strains in carbon-source use, there were quantitative differences, which we analysed using principal component analysis. This showed that growth of Termitomyces on different carbon sources was correlated with termite host genus, rather than host species, while growth on different ratios and concentrations of protein and carbohydrate was correlated with termite host species. Our findings corroborate the interaction specificity between fungus-growing termites and Termitomyces cultivars and indicate that specificity between termite hosts and fungi is reflected both nutritionally and physiologically. However, it remains to be demonstrated whether those differences contribute to selection of specific fungal cultivars by termites at the onset of colony foundation.  相似文献   
462.
Intensive land use by humans has led to severe degradation of streams and rivers, especially in highly industrialised countries and in lowland agricultural areas. Restorations have been conducted with the aim to improve hydromorphological conditions in modified streams. However, success has often been limited, partly because the restorations have been conducted without due regard to river-type-specific characteristics. The aim of this study was to evaluate restorations of Danish lowland streams by applying a type-specific approach. We compared the physical condition of restored streams with that of near-natural streams (least disturbed condition) and channelized streams. We stratified the data according to different stream types and included also reference sites from a less impacted country (Lithuania) in the evaluation. Our results revealed that restorations have created physical conditions that do not resemble river-type-specific LDCs, primarily due to the addition of large amounts of coarse substrate. This may have implications for the ecological communities and for biodiversity and consequently for the implementation of the Water Framework Directive in restored lowland streams. We also found that observations of physical condition in nearby reference streams may be used to advantage in future restoration planning, thereby assuring a higher degree of physical integrity in restored streams.  相似文献   
463.
The geometric framework provides a way for understanding the multi‐dimensional nutritional relationships between consumers and their food. We use this approach to further our understanding of the feeding and nutritional ecology of a ubiquitous mixed‐feeding insect herbivore that consumes a variety of host plants spanning a wide range of nutritional composition. Our overall objective was to examine feeding decisions, resulting performance, and post‐ingestive consequences in a common mixed‐feeding insect herbivore, Melanoplus bivittatus (Say) (Orthoptera: Acrididae), when presented with paired diets differing in protein:carbohydrate (p:c) ratio. Intake p:c of M. bivittatus differed among all but two treatments and in many cases was farther than expected from the previously identified p:c intake target for this species. Despite this variability in intake of protein and carbohydrate, we found few effects of the diet treatments on performance or post‐ingestive processing. However, our results suggest that when feeding on high‐quality diets, nutrients consumed in excess may be stored rather than excreted.  相似文献   
464.
K‐ion batteries (KIBs) are promising for large‐scale energy storage owing to various advantages like the high abundance of potassium resources in the Earth's crust, high operational potentials, and high power due to fast diffusion of K+ ions. However, to realize the practical application of KIBs, electrode materials are needed with high operational voltage, good capacity, long cycle life, and low‐cost. This work reports a layered open framework material, K2[(VOHPO4)2(C2O4)], composited with reduced graphene oxide (rGO) as a 4 V positive electrode material for KIBs. The material is prepared by a simple precipitation reaction at room temperature. The material demonstrates reversible K‐extraction/insertion with conventional carbonate ester KPF6 solutions; however, with low specific capacity and low Coulombic efficiency. A high discharge capacity of >100 mAh g?1 with good cycling stability and higher Coulombic efficiency is achieved in a highly concentrated electrolyte, 7 mol kg?1 of potassium bis(fluorosulfonyl)amide (KFSA) in dimethoxyethane (DME) at 0.1 C rate. Due to the facile migration of K+ ions in the framework, the material exhibits excellent rate capability with a discharge capacity of 80 mAh g?1 at 10 C rate, and a good capacity retention of 67% after 500 cycles at 2 C rate.  相似文献   
465.
The oxygen evolution reaction (OER) is a bottleneck process for water splitting and finding highly efficient, durable, low‐cost, and earth‐abundant electrocatalysts is still a major challenge. Here a sulfur‐treated Fe‐based metal–organic‐framework is reported as a promising electrocatalyst for the OER, which shows a low overpotential of 218 mV at the current density of 10 mA cm?2 and exhibits a very low Tafel slope of 36.2 mV dec?1 at room temperature. It can work on high current densities of 500 and 1000 mA cm?2 at low overpotentials of 298 and 330 mV, respectively, by keeping 97% of its initial activity after 100 h. Notably, it can achieve 1000 mA cm?2 at 296 mV with a good stability at 50 °C, fully fitting the requirements for large‐scale industrial water electrolysis. The high catalytic performance can be attributed to the thermocatalytic processes of H+ capture by –SO3 groups from *OH or *OOH species, which cascades to the electrocatalytic pathway and then significantly reduces the OER overpotentials.  相似文献   
466.
An analysis of the sequences of scyllatoxin and charybdotoxin suggested that it would be possible to design a core peptide sequence which would still fold to give the β-hairpin and helix seen in the toxins, but which would eliminate one disulfide and connecting residues. The core sequence was modeled, then synthesized and purified. The cysteines oxidize in air to give the same disulfide pairings as seen in the parent toxins as the major product. The three-dimensional structure of the core sequence peptide, termed Max, was determined using proton NMR spectroscopy and found to be identical in secondary structure to the toxins. However differences were found in the relative orientation of the β-hairpin and helix. The use of this structural motif, found in many insect toxins, as a disulfide framework for exploring sequence/structure/activity relationships is discussed. © 1994 John Wiley & Sons, Inc.  相似文献   
467.
In this work, molecular dynamics simulations were performed to investigate the gas diffusion mechanism in catenated metal–organic frameworks (MOFs), for which methane was adopted as a probe and two catenated IRMOFs with interwoven structure, IRMOF-11 and IRMOF-13, were considered. This work reveals that the diffusion pathways of methane molecules in catenated MOFs are mainly governed by the strong confinement in catenation regions, leading to a 3D diffusion along the sheets formed by the A-regions (xy-direction) as well as from one A-region to another by crossing a B-region (z-direction). In addition, the present work shows that the effect of catenation on methane diffusivity is very large, much larger than that on hydrogen diffusivity at room temperature, and that both adsorption selectivity and dynamic selectivity of gas mixtures may be enhanced largely in catenated MOFs, indicating that catenation is a good strategy to improve the overall performance of a material as a membrane in separation applications.  相似文献   
468.
《Endocrine practice》2021,27(9):912-917
ObjectiveActive surveillance (AS) is a management alternative for patients with low-risk papillary thyroid microcarcinoma (PTMC). To decide the best candidates for AS, clinicians can use a framework to classify PTMC patients as ideal, appropriate, or inappropriate. This study aimed to explore the correlation between the framework categories and surgical pathology.MethodsThis multicenter retrospective study was conducted between 2014 and 2016. We included 1997 patients who underwent thyroid surgery for the first time due to suspected PTMC and were confirmed as PTMC by postoperative pathology. The consistency of modified preoperative risk stratification and the pathologic condition were evaluated using a consistency ratio and the Kappa coefficient. Stratified analysis was also performed to test consistency in different age groups.ResultsBased on the decision-making framework, 558 (27.9%) patients could receive AS while 810 (40.6%) patients did not require immediate surgery according to the actual postoperative pathology. The sensitivity, false-positive rate, specificity, false-negative rate, and consistency rate were 82.39%, 56.91%, 43.09%, 17.61%, and 66.45%, respectively. The Kappa value was 0.268. Stratified analysis showed that the sensitivity was 87.7% among patients aged 18 to 59 years. In the group aged ≥60 years, the specificity was up to 87.5%, but the sensitivity was low.ConclusionThe results of the modified risk-stratified clinical decision-making framework did not have a high consistency with the postoperative results. However, the framework showed a good effect in selecting patients for immediate surgery in the younger group and patients for AS in the older group.  相似文献   
469.
Goal, Scope and Background To enhance the use of life cycle assessment (LCA) as a tool in business decision-making, a methodology for Social life cycle impact assessment (LCIA) is being developed. Social LCA aims at facilitating companies to conduct business in a socially responsible manner by providing information about the potential social impacts on people caused by the activities in the life cycle of their product. The development of the methodology has been guided by a business perspective accepting that companies, on the one hand, have responsibility for the people affected by their business activities, but, on the other hand, must also be able to compete and make profit in order to survive in the marketplace. Methods A combined, bottom-up and top-down approach has been taken in the development of the Social LCIA. Universal consensus documents regarding social issues as well as consideration for the specific business context of companies has guided the determination of damage categories, impact categories and category indicators. Results Discussion, and Conclusion. The main results are the following: (1) Impacts on people are naturally related to the conduct of the companies engaged in the life cycle rather than to the individual industrial processes, as is the case in Environmental LCA. Inventory analysis is therefore focused on the conduct of the companies engaged in the life cycle. A consequence of this view is that a key must be determined for relating the social profiles of the companies along the life cycle to the product. This need is not present in Environmental LCA, where we base the connection on the physical link which exists between process and product. (2) Boundaries of the product system are determined with respect to the influence that the product manufacturer exerts over the activities in the product chain. (3) A two-layer Social LCA method with an optional and an obligatory set of impact categories is suggested to ensure both societal and company relevance of the method. The obligatory set of impact categories encompasses the minimum expectations to a company conducting responsible business. (4) A new area of protection, Human dignity and Well-being, is defined and used to guide the modelling of impact chains. (5) The Universal Declaration of Human Rights serves as normative basis for Social LCA, together with local or country norms based on socio-economic development goals of individual countries. The International Labour Organisation's Conventions and Recommendations, and the Tripartite Declaration of Principles concerning Multinational Enterprises and Social Policy, support development of the impact pathway top-down, starting from the normative basis. (6) The obligatory part of Social LCA addresses the main stakeholder groups, employees, local community and society. Recommendations and Outlook Social LCA is still in its infancy and a number of further research tasks within this new area are identified.  相似文献   
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