Revised phase diagram for the Pt-Ti system from 30 to 60 at.% platinum

Alloys of the Ti-Pt system between 30 and 61 at.% Pt were studied using metallography with optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential thermal analysis (DTA). A phase of nominal composition Ti4Pt3, in the range 41.7-43.4 at.% Pt was found in samples containing between 30 and 47 at.% Pt, and was apparently formed by a peritectoid reaction between β-TiPt and Ti3Pt at 1205±10°C. The eutectic reaction between Ti3Pt and β-TiPt was found to be at ∼35 at.% Pt and 1424±10°C, and the Ti3Pt phase melted at circa 1500°C. The other phase boundaries agreed with the published literature, except that a slightly wider range was found at 1200°C for β-TiPt. © 2004 Elsevier B.V. All rights reserved

The effect of nickel on the martensitic-type transformations Of Pt3Al and TiPt

The effect of nickel on two classes of martensitic-type transformations in platinum systems has been studied. The first transformation is Ll2 to DO'c in the Pt3Al system and the second is B2 to B19 in the TiPt system. The microstructures after transformation in the two systems are very different. The product of the Pt3Al transformation has a twinned microstructure, typical of cubic-to-tetragonal transformations. The product of the TiPt transformation is lath-like, although the morphology can be altered using heat treatments. The parent phase in the TiPt system is not retained at room temperature, whereas the parent phase in the Pt3Al transformation can be stabilised to room temperature. A great variation in hardness and transformation temperature is seen in each system as the composition is varied about the stoichiometric ratio, which has the lowest hardness. The Pt3Al transformation temperature has been reported to range from around room temperature to 1000°C. The TiPt transformation temperature can range from 1000 to 1080°C. The effect of nickel additions on these alloys also has a marked effect on the parent and product phase stability, and hence the microstructure and resulting hardness. The effect on the Pt3Al phase is complex, as nickel appears to stabilise the parent phase. The hardness varied in the region of 350 to 500 HV10. For the TiPt phase, the hardness values were generally found to increase with the nickel additions increasing from 250 to about 600 HV10. The addition of 20 at.% nickel decreases the transformation temperature from around 1000°C to about 600°C

Energy landscapes of a pair of adsorbed peptides

The wide relevance of peptide adsorption in natural and synthetic contexts means it has attracted much attention. Molecular dynamics (MD) simulation has been widely used in these endeavors. Much of this has focused on single peptides due to the computational effort required to capture the rare events that characterize their adsorption. This focus is, however, of limited practical relevance as in reality, most systems of interest operate in the nondilute regime where peptides will interact with other adsorbed peptides. As an alternative to MD simulation, we have used energy landscape mapping (ELM) to investigate two met-enkephalin molecules adsorbed at a gas/graphite interface. Major conformations of the adsorbed peptides and the connecting transition states are elucidated along with the associated energy barriers and rates of exchange. The last of these makes clear that MD simulations are currently of limited use in probing the co-adsorption of two peptides, let alone more. The constant volume heat capacity as a function of temperature is also presented. Overall, this study represents a significant step toward characterizing peptide adsorption beyond the dilute limit

Energy landscape mapping and replica exchange molecular dynamics of an adsorbed peptide

Adsorption of peptides at the interface between a fluid and a solid occurs widely in both nature and applications. Knowing the dominant conformations of adsorbed peptides and the energy barriers between them is of interest for a variety of reasons. Molecular dynamics (MD) simulation is a widely used technique that can yield such understanding. However, the complexity of the energy landscapes of adsorbed peptides means that comprehensive exploration of the energy landscape by MD simulation is challenging. An alternative approach is energy landscape mapping (ELM), which involves the location of stationary points on the potential energy surface, and its analysis to determine, for example, the pathways and energy barriers between them. In the study reported here, a comparison is made between this technique and replica exchange molecular dynamics (REMD) for met-enkephalin adsorbed at the interface between graphite and the gas phase: the first ever direct comparison of these techniques for adsorbed peptides. Both methods yield the dominant adsorbed peptide conformations. Unlike REMD, however, ELM readily allows the identification of the connectivity and energy barriers between the favored conformations, transition paths, and structures between these conformations and the impact of entropy. It also permits the calculation of the constant volume heat capacity although the accuracy of this is limited by the sampling of high-energy minima. Overall, compared to REMD, ELM provides additional insights into the adsorbed peptide system provided sufficient care is taken to ensure that key parts of the landscape are adequately sampled

Decoding gas-solid interaction effects on adsorption isotherm shape: II. Polar adsorptives

A unique set of 6 polar adsorptives of relatively large dipole moment and of increasing kinetic diameter were used to probe pore volumes available and their mechanism of adsorption on a well-characterized microporous carbon. Multiple adsorption isotherm measurements were made and repeatable results with relatively small standard deviations in amount adsorbed at low relative pressures were obtained. Inconsistencies were observed between calculated Gurvitsch volumes. Sources of these were analysed and identified as contributions from one or more of: (a) molecular sieve effects; (b) molecular packing effects, and; (c) 2D molecular structure formation due to hydrogen bonding. These inconsistencies were further studied by comparison with pore volumes derived via the Dubinin-Radushkevich (DR) equation. Qualitative analyses of the micropore filling processes were proposed, and substantiated by complementary DR analyses. Although most of the isotherms showed Type I character, recasting the relative pressure axis in logarithmic format highlighted clear differences as contributions from fluid-fluid and fluid-solid interactions during pore filling. Overall, the adsorptives were classified into three groups: (a) polar adsorptives with primarily specific interactions adsorbing as a condensation process over a relatively narrow relative pressure range in a medium and late pressure range (iso-PrOH, MeOH, 2-methyl, 2-butanol, H2O); (b) polar adsorptives with potential for non-specific interactions adsorbing as a condensation process over a relatively narrow pressure range in a medium pressure range (pyridine, iso-PrOH, 2-methyl, 2- butanol); and, (c) halogenated adsorptives adsorbing with an S-shaped uptake extending over a broad relative pressure (dichloromethane)

Temporal dynamics of aquatic communities and implications for pond conservation

Conservation through the protection of particular habitats is predicated on the assumption that the conservation value of those habitats is stable. We test this assumption for ponds by investigating temporal variation in macroinvertebrate and macrophyte communities over a 10-year period in northwest England. We surveyed 51 ponds in northern England in 1995/6 and again in 2006, identifying all macrophytes (167 species) and all macroinvertebrates (221 species, excluding Diptera) to species. The alpha-diversity, beta-diversity and conservation value of these ponds were compared between surveys. We find that invertebrate species richness increased from an average of 29. 5 species to 39. 8 species between surveys. Invertebrate gamma-diversity also increased between the two surveys from 181 species to 201 species. However, this increase in diversity was accompanied by a decrease in beta-diversity. Plant alpha-, beta and gamma-diversity remained approximately constant between the two periods. However, increased proportions of grass species and a complete loss of charophytes suggests that the communities are undergoing succession. Conservation value was not correlated between sampling periods in either plants or invertebrates. This was confirmed by comparing ponds that had been disturbed with those that had no history of disturbance to demonstrate that levels of correlation between surveys were approximately equal in each group of ponds. This study has three important conservation implications: (i) a pond with high diversity or high conservation value may not remain that way and so it is unwise to base pond conservation measures upon protecting currently-speciose habitats; (ii) maximising pond gamma-diversity requires a combination of late and early succession ponds, especially for invertebrates; and (iii) invertebrate and plant communities in ponds may require different management strategies if succession occurs at varying rates in the two groups

Carbon nanotubes in TiO2 nanofiber photoelectrodes for high-performance perovskite solar cells

1D semiconducting oxides are unique structures that have been widely used for photovoltaic (PV) devices due to their capability to provide a direct pathway for charge transport. In addition, carbon nanotubes (CNTs) have played multifunctional roles in a range of PV cells because of their fascinating properties. Herein, the influence of CNTs on the PV performance of 1D titanium dioxide nanofiber (TiO2 NF) photoelectrode perovskite solar cells (PSCs) is systematically explored. Among the different types of CNTs, single‐walled CNTs (SWCNTs) incorporated in the TiO2 NF photoelectrode PSCs show a significant enhancement (≈40%) in the power conversion efficiency (PCE) as compared to control cells. SWCNTs incorporated in TiO2 NFs provide a fast electron transfer within the photoelectrode, resulting in an increase in the short‐circuit current (J sc) value. On the basis of our theoretical calculations, the improved open‐circuit voltage (V oc) of the cells can be attributed to a shift in energy level of the photoelectrodes after the introduction of SWCNTs. Furthermore, it is found that the incorporation of SWCNTs into TiO2 NFs reduces the hysteresis effect and improves the stability of the PSC devices. In this study, the best performing PSC device constructed with SWCNT structures achieves a PCE of 14.03%

Non-European Union doctors in the National Health Service: why, when and how do they come to the United Kingdom of Great Britain and Northern Ireland?

BACKGROUND: As many as 30% of doctors working for the National Health System (NHS) of the United Kingdom of Great Britain and Northern Ireland (UK) have obtained their primary qualifications from a country outside the European Union. However, factors driving this migration of doctors to the UK merit continuing exploration. Our objective was to obtain training and employment profile of UK doctors who obtained their primary medical qualification outside the European Union (non-European doctors) and to assess self-reported reasons for their migration. METHODS: We conducted an online survey of non-European doctors using a pre-validated questionnaire. RESULTS: One thousand six hundred and nineteen doctors of 26 different nationalities completed the survey. Of the respondents, 90.1% were from India and over three-quarters migrated to the UK mainly for 'training'. Other reasons cited were 'better pay' (7.2%), 'better work environment' (7.1%) and 'having family and friends in the UK' (2.8%). Many of the respondents have been in the UK for more than a year (88.8%), with 31.3% having spent more than 3 years gaining experience of working in the NHS. Most respondents believe they will be affected by recent changes to UK immigration policy (86.6%), few report that they would be unaffected (3.7%) and the rest are unsure (9.8%). CONCLUSION: The primary reason for many non-European doctors to migrate to the UK is for training within the NHS. Secondary reasons like better pay, better work environment and having friends and family in the UK also play a role in attracting these doctors, predominantly from the Indian subcontinent and other British Commonwealth countries

Cobalt(II) tetraaminophthalocyanine‐modified multiwall carbon nanotubes as an efficient sulfur redox catalyst for lithium–sulfur batteries

An efficient Li–S redox catalyst consisting of MWCNTs covalently modified by cobalt(II) tetraaminophthalocyanines (TaPcCo‐MWCNTs) is developed. Effective lithium polysulfide (LiPS) capturing is enabled by the lithiophilic N‐containing phthalocyanine rings and the sulfiphilic Co central atoms. This adsorption geometry utilizes the Co unoccupied d‐orbitals as electron super‐exchange highways. Elevated kinetics of LiPSs reactions in the liquid phase as well as liquid–solid transitions were revealed by electrochemical measurements and density functional theory calculations. Uniform deposition of Li2S films was also observed, which preserves cathode integrity and sulfur utilization during cell cycling. The catalyzed sulfur redox is also significantly facilitated by the fast electron and Li‐ion transport to and from the reaction sites through the conductive MWCNT skeletons and the lithiophilic substituent amino groups on TaPcCo. With 6 wt % addition of TaPcCo‐MWCNT in the cathode coatings, high sulfur utilization is achieved with areal sulfur loadings of up to 7 mg cm−2. Stable long‐term cycling is achieved at 1 C at a sulfur loading of 5 mg cm−2, with an initial areal capacity of 4.4 mAh cm−2 retention of 3.5 mAh cm−2 after 500 cycles. Considering the high structural diversity of phthalocyanines macromolecules, this study provides opportunities for a new class of Li–S catalysts

Surface topography regulates wnt signaling through control of primary cilia structure in mesenchymal stem cells

The primary cilium regulates cellular signalling including influencing wnt sensitivity by sequestering β-catenin within the ciliary compartment. Topographic regulation of intracellular actin-myosin tension can control stem cell fate of which wnt is an important mediator. We hypothesized that topography influences mesenchymal stem cell (MSC) wnt signaling through the regulation of primary cilia structure and function. MSCs cultured on grooves expressed elongated primary cilia, through reduced actin organization. siRNA inhibition of anterograde intraflagellar transport (IFT88) reduced cilia length and increased active nuclear β-catenin. Conversely, increased primary cilia assembly in MSCs cultured on the grooves was associated with decreased levels of nuclear active β-catenin, axin-2 induction and proliferation, in response to wnt3a. This negative regulation, on grooved topography, was reversed by siRNA to IFT88. This indicates that subtle regulation of IFT and associated cilia structure, tunes the wnt response controlling stem cell differentiation.We acknowledge funding from an EPSRC Platform grant which supported McMurray and a Wellcome Trust project grant which supported Wann and McMurray. Wann is now supported on an ARUK project grant. Thompson was funded by a BBSRC PhD studentshi