70 resultados para Structural Constraints of Kind (Min, Max)
Resumo:
The flexibility of the metal-organic framework Cu-2(OH)(C8H3O7S)(H2O)center dot 2H(2)O (Cu-SIP-3) toward reversible single-crystal to single-crystal transformations is demonstrated using in situ diffraction methods at variable temperature. At temperatures below a dehydration-induced phase transition (T < 370 K) the structure is confirmed as being hydrated. In the temperature range where the transition takes place (370 K < T < 405 K) no discrete, sharp Bragg peaks can be seen in the single-crystal X-ray diffraction pattern, indicating significant loss of long-range order. At temperatures higher than 405 K, the Bragg peaks return and the structure can be refined as dehydrated Cu-SIP-3. The loss of guest water molecules can be followed at temperatures below the phase transition giving insight into the mechanism of the dehydration. Addition of nitric oxide gas to the material above the gating opening pressure of 275 mbar also leads to loss of Bragg scattering in the diffraction pattern.
Resumo:
In situ EXAFS has been used to examine the hydrogen effect on the selective catalytic reduction of NOx over silver/alumina catalysts. For all SCR conditions used, with or without co-reductant (H-2 or CO), the catalyst structure remained the same. Significant changes in the catalyst were only found under reducing conditions. The enhanced activity found in the presence of hydrogen is thought to be due to a chemical effect and not the result of a change in the structure of the active site.
Resumo:
A solid-phase radioimmunoassay was used to determine the specificity of IgG antibodies from normal sera, sera and CSF from patients with SSPE for the structural polypeptides of measles virus. The polypeptide specificity of antibodies from these sources were qualitatively similar; these results indicate antigenic cross-reactivity between SSPE-derived (Mantooth) and non-SSPE-derived strains of measles virus and stimulation of antibody formation by comparable antigens.
Resumo:
We demonstrate a method for tailoring local mechanical properties near channel surfaces of vascular structural polymers in order to achieve high structural performance in microvascular systems. While synthetic vascularized materials have been created by a variety of manufacturing techniques, unreinforced microchannels act as stress concentrators and lead to the initiation of premature failure. Taking inspiration from biological tissues such as dentin and bone, these mechanical deficiencies can be mitigated by complex hierarchical structural features near to channel surfaces. By employing electrostatic layer-by-layer assembly (ELbL) to deposit films containing halloysite nanotubes onto scaffold surfaces followed by matrix infiltration and scaffold removal, we are able to controllably deposit nanoscale reinforcement onto 200 micron diameter channel surface interiors in microvascular networks. High resolution strain measurements on reinforced networks under load verify that the halloysite reduces strain concentrations and improves mechanical performance.
Resumo:
University incubators (UI) are generally believed to be important in the successful commercialisation of university spin-outs (USO) with over half of all UK Universities having established an on-campus UI. In this chapter we examine the value of UIs in the spin-out process, focusing on the structural networks of USOs located in a UI as compared to USOs in a University with no access to a UI. Our primary research question is therefore: to what extent does the structural network of USOs with access to an on-campus UI differ from USOs without? The research therefore con-tributes to a growing critique of the effectiveness of UIs in commercialis-ing academic research and the recognition of positive direct and indirect externalities from participation in networks. Through network mapping of all USOs from two research intensive universities, we profile and ana-lyse the formal and informal network ties of USOs to various partners in-ternal and external to the host university. Through interviews we also consider how these networks enhance the resources and capabilities of USOs. Our findings highlight significant differences, with USOs located in a UI having more informal but fewer formal ties, both to other USOs as well as within the host University. In contrast, location in an incuba-tor was not found to affect the extent and nature of ties with external or-ganisations. Reasons for these differences are examined through inter-views with the USOs and point to various factors including the proactive brokering role of incubator and university staff, university bureaucracy, the hidden networks of executive board members across USOs, university equity investment policy and complementary technologies.
Resumo:
This paper describes the problems in experimentally obtaining hydrodynamic loads on an oscillating wave surge converter during slamming events, with the aim of furthering understanding of full scale hydrodynamic loads that flap type devices must be designed to withstand. Including how hydro-elastic effects and structural response are linked and why they are essential to the measurement of impulsive hydrodynamic loads. A combined experimental and numerical structural response study carried out on a 40th scale Oyster model drew conclusions on the structural vibration observed in the strain gauge load cell measurement. A further structural response study on a piezo electric load measurement device gave an insight into the advantages it could bring to reducing hydro-elastic effects.