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Spontaneous deamidation prompted backbone isomerization of Asn/Asp residues resulting in – most cases – the insertion of an extra methylene group into the backbone poses a threat to the structural integrity of proteins. Here we present a systematical analysis of how temperature, pH, presence of charged residues, but most importantly backbone conformation and dynamics affect isomerization rates as determined by nuclear magnetic resonance in the case of designed peptide-models. We demonstrate that restricted mobility (such as being part of a secondary structural element) may safeguard against isomerization, but this protective factor is most effective in the case of off-pathway folds which can slow the reaction by several magnitudes compared to their on-pathway counterparts. We show that the geometric descriptors of the initial nucleophilic attack of the isomerization can be used to classify local conformation and contribute to the design of stable protein drugs, antibodies or the assessment of the severity of mutations.
Health technology assessment (HTA) is not simply a mechanistic technical exercise as it takes place within a specific institutional context. Yet, we know little about how this context influences the operation of HTA and its ability to influence policy and practice. We seek to demonstrate the importance of considering institutional context, using a case study of Hungary, a country that has pioneered HTA in Central and Eastern Europe. We conducted 26 in-depth, semi-structured interviews with public- and private-sector stakeholders. We found that while the HTA Department, the Hungarian HTA organisation, fulfilled its formal role envisaged in the legislation, its potential for supporting evidence-based decision-making was not fully realised given the low levels of transparency and stakeholder engagement. Further, the Department’s practical influence throughout the reimbursement process was perceived as being constrained by the payer and policy-makers, as well as its own limited organisational capacity. There was also scepticism as to whether the current operational form of the HTA process delivered ‘good value for money’. Nevertheless, it still had a positive impact on the development of a broader institutional HTA infrastructure in Hungary. Our findings highlight the importance of considering institutional context in analysing the HTA function within health systems.
Fracture-hosted porosity and quartz distribution along with crack-seal texture and fluid inclusion assemblage sequences in isolated, bridging quartz deposits show that open fractures can persist through protracted burial and uplift in foreland basins. Fractures oriented at a high angle to current maximum compressive stress remain open and were weak mechanical discontinuities for millions of years even at great depth. Upper Cretaceous Frontier Formation sandstones in the basement-involved (Laramide) Table Rock anticline, eastern Greater Green River Basin, Wyoming sampled by two horizontal wells (cut parallel or nearly parallel to bedding and at a high angle to steeply dipping fractures) have 41.5 m of rock in four cores at depths of 4538–4547 m. Cores intersect older E-striking Set 1 fractures are abutted by or locally cross-cut by N-striking Set 2 fractures. Both sets contain quartz and porosity. Sequenced using quartz crack-seal cement texture maps, Set 1 fluid inclusion assemblage (FIA) trapping temperatures increase progressively from 140 to 165°C then decrease to c. 150°C, compatible with fracture opening over c. 15 Ma during rapid burial followed by uplift in Eocene–Oligocene time. Set 2 opened at c. 160°C, probably near maximum burial. After a period of quiescence, Set 2 reopened at c. 5 Ma at c. 140°C, on a cooling trajectory. Intermittent Set 2 movement could reflect local basement-involved fault movement, followed after a pause by further Set 2 reactivation in the modern stress field during uplift. Interpretations are sensitive to available burial/thermal histories, which have considerable uncertainty.
A novel cryogenic electrostatic storage device consisting of two ion-beam storage rings with a common straight section for studies of interactions between oppositely charged ions at low and well-defined relative velocities is under construction at Stockholm University. Here we consider the prospect of using this new tool to measure cross-sections and rate coefficients for mutual neutralization reactions of importance in interstellar ion chemistry in general and specifically in cosmic pre-biotic ion chemistry.
This work reports on thermal and electrical conductivities and interface resistances for transport along aligned multiwalled carbon nanotubes (CNT) films grown on a nickel superalloy (Inconel) substrate. The measured specific thermal resistance of the combined Inconel–CNT and indium–CNT interfaces is of the same order as reported for CNT and silicon or SiO2 interfaces but much higher than theoretical predictions considering perfect contact between the tubes and substrate. Imperfect mechanical contact with the substrate and a large contribution caused by indium–CNT interface are thought to be mainly responsible for the high interface resistances and the low effective values of thermal and electrical conductivities. However, reported results represent an incentive for further research on CNT synthesis on metallic substrates for thermal management applications and pave the way for much easier integration of carbon nanotubes in electronic applications.
The preparation of poly(ρ-phenylene vinylene) (PPV) encapsulated in a mesoporous silica, MCM-41, is reported. In situ polymerization of xylylene bis(tetrahydrothiophenium chloride) yields a highly luminescent, yellow powder with a fluorescence spectrum matching that of unencapsulated PPV. Nitrogen adsorption isotherms show that the pore size of the PPVloaded MCM-41 is significantly smaller than that of empty MCM-41 and a polymer loading of ca. 8% by weight is obtained by thermogravimetric analysis. Photoluminescence data for the encapsulated PPV are presented.
The metallurgical and electrical behavior of Au/Zn contacting metallization onp-type InP was investigated as a function of the Zn content in the metallization. It was found that ohmic behavior can be achieved with Zn concentrations as small as 0.05 atomic percent Zn. For Zn concentrations between 0.1 and 36 at.%, the contact resistivity ρc was found to be independent of the Zn content For low Zn concentrations the realization of ohmic behavior was found to require the growth of the compound Au2P3 at the metal-InP interface. The magnitude of ρc is shown to be very sensitive to the growth rate of the interfacial Au2P3 layer. The possibility of exploiting this sensitivity to provide low resistance contacts while avoiding the semiconductor structural damage that is normally attendant to contact formation is discussed.
Systematic relations are shown between the parameters controlling explosive crystallization in silicon (temperature, width of a liquid zone, and gradient of melt undercooling), the kinetics of the crystallization process, the predominance of preferential growth directions, and the crystal structure observed. Three typical regions of crystallization are found: (a) cellular growth of a laminated crystalline layer controlled by the formation of high densities of twins at a nearly plane liquid/solid interface, (b) cellular-dendritic growth of crystal lamellae characterized by branching of a curved interface, and (c) formation of a diffuse “slush zone” due to random nucleation in a-Si and grain growth in the liquid zone.
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