Supersaturating silicon with transition metals by ion implantation and pulsed laser melting

We investigate the possibility of creating an intermediate band semiconductor by supersaturating Si with a range of transition metals (Au, Co, Cr, Cu, Fe, Pd, Pt, W, and Zn) using ion implantation followed by pulsed laser melting (PLM). Structural characterization shows evidence of either surface segregation or cellular breakdown in all transition metals investigated, preventing the formation of high supersaturations. However, concentration-depth profiling reveals that regions of Si supersaturated with Au and Zn are formed below the regions of cellular breakdown. Fits to the concentration-depth profile are used to estimate the diffusive speeds, v [subscript D], of Au and Zn, and put lower bounds on v [subscript D] of the other metals ranging from 10[superscript 2] to 10[superscript 4] m/s. Knowledge of v [subscript D] is used to tailor the irradiation conditions and synthesize single-crystal Si supersaturated with 10[superscript 19] Au/cm[superscript 3] without cellular breakdown. Values of v [subscript D] are compared to those for other elements in Si. Two independent thermophysical properties, the solute diffusivity at the melting temperature, D [subscript s](T [subscript m]), and the equilibrium partition coefficient, k [subscript e], are shown to simultaneously affect v [subscript D]. We demonstrate a correlation between v [subscript D] and the ratio D [subscript s](T [subscript m])/k [subscript e] [superscript 0.67], which is exhibited for Group III, IV, and V solutes but not for the transition metals investigated. Nevertheless, comparison with experimental results suggests that D [subscript s](T [subscript m])/k [subscript e] [superscript 0.67] might serve as a metric for evaluating the potential to supersaturate Si with transition metals by PLM.National Science Foundation (U.S.) (Faculty Early Career Development Program ECCS-1150878)Chesonis Family FoundationUnited States. Army Research Laboratory (United States. Army Research Office Grant W911NF-10-1-0442)National Science Foundation (U.S.) (United States. Dept. of Energy NSF CA EEC-1041895

Atomistic Mechanisms for the Thermal Relaxation of Au -hyperdoped Si

Au-hyperdoped Si produced by ion implantation and pulsed laser melting exhibits sub-band-gap absorption in the near infrared, a property that is interesting for Si photonics. However, the sub-band-gap absorption has previously been shown to be thermally metastable. In this work, we study the atomistic processes that occur during the thermal relaxation of Au-hyperdoped Si. We show that the first step in thermal relaxation is the release of substitutional Au from lattice sites. This process is characterized by an activation energy of around 1.6 eV, a value similar to that associated with Au diffusion in Si, suggesting that both processes could be rate limited by the exchange of substitutional and interstitial Au atoms. As the system further relaxes, Au is found to locally diffuse and become trapped at nearby lattice defects, notably vacancies and vacancy complexes. In fact, density-functional theory results suggest that the formation of Au dimers is energetically favourable after the Au becomes locally trapped. The dimers could subsequently evolve into trimers, etc., as other diffusing Au atoms become trapped at the dimer. At low Au concentrations, this clustering process does not form visible precipitation after annealing at 750 ◦C for 3 min. In contrast, spherical Au precipitates are found in samples with higher Au concentrations (>0.14 at. %), where the Au atoms and the associated lattice defect distributions are laterally inhomogeneous.Funding from the U.S. Army under Contract No. FA5209-16-P-0104 is acknowledged for partial support of this work. This work was performed in part at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Coordinated Infrastructure Network (NNCI), which is supported by the National Science Foundation under NSF Grant No. 1541959. CNS is part of Harvard University

Multifaceted study of the interactions between CPO-27-Ni and polyurethane and their impact on nitric oxide release performance

S.M.V. would like to thank the EPSRC for funding opportunities under grant agreement EP/K005499/1. S.M.V. and D.N.M. would further like to acknowledge the EPSRC Capital for Great Technologies grant (EP/L017008/1) and the EPSRC Strategic Equipment Resource grant (EP/R023751) for funding and supporting electron microscopy facilities at the University of St Andrews. M.J.D. and S.J.W. would like to acknowledge the ProDIA project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 685727.A multifaceted study involving focused ion beam scanning electron microscopy techniques, mechanical analysis, water adsorption measurements, and molecular simulations is employed to rationalize the nitric oxide release performance of polyurethane films containing 5, 10, 20, and 40 wt % of the metal-organic framework (MOF) CPO-27-Ni. The polymer and the MOF are first demonstrated to exhibit excellent compatibility. This is reflected in the even distribution and encapsulation of large wt % MOF loadings throughout the full thickness of the films and by the rather minimal influence of the MOF on the mechanical properties of the polymer at low wt %. The NO release efficiency of the MOF is attenuated by the polymer and found to depend on wt % of MOF loading. The formation of a fully connected network of MOF agglomerates within the films at higher wt % is proposed to contribute to a more complex guest transport in these formulations, resulting in a reduction of NO release efficiency and film ductility. An optimum MOF loading of 10 wt % is identified for maximizing NO release without adversely impacting the polymer properties. Bactericidal efficacy of released NO from the films is demonstrated against Pseudomonas aeruginosa, with a >8 log10 reduction in cell density observed after a contact period of 24 h.Publisher PDFPeer reviewe

Integrated respiratory and palliative care may improve outcomes in advanced lung disease

The unaddressed palliative care needs of patients with advanced, nonmalignant, lung disease highlight the urgent requirement for new models of care. This study describes a new integrated respiratory and palliative care service and examines outcomes from this service. The Advanced Lung Disease Service (ALDS) is a long-term, multidisciplinary, integrated service. In this single-group cohort study, demographic and prospective outcome data were collected over 4 years, with retrospective evaluation of unscheduled healthcare usage. Of 171 patients included, 97 (56.7%) were male with mean age 75.9 years and 142 (83.0%) had chronic obstructive pulmonary disease. ALDS patients had severely reduced pulmonary function (median (interquartile range (IQR)) forced expiratory volume in 1 s 0.8 (0.6-1.1) L and diffusing capacity of the lung for carbon monoxide 37.5 (29.0-48.0) % pred) and severe breathlessness. All patients received nonpharmacological breathlessness management education and 74 (43.3%) were prescribed morphine for breathlessness (median dose 9 mg·day-1). There was a 52.4% reduction in the mean number of emergency department respiratory presentations in the year after ALDS care commenced (p=0.007). 145 patients (84.8%) discussed and/or completed an advance care plan. 61 patients died, of whom only 15 (24.6%) died in an acute hospital bed. While this was a single-group cohort study, integrated respiratory and palliative care was associated with improved end-of-life care and reduced unscheduled healthcare usage

Inverse bicontinuous cubic phases in fatty acid/phosphatidylcholine mixtures: the effects of pressure and lipid composition

We report on the effect of hydrostatic pressure on the structure and phase behaviour of symmetric 2:1 (mol/mol) fatty acid/phosphatidylcholine (FA/PC) mixtures. In addition, the effect of changing the fatty acid/phospholipid composition has been explored. The working hypothesis we have used, was that increasing pressure, or reducing the fatty acid composition will reduce the desire for interfacial curvature towards the water and so may favour the formation of inverse bicontinuous cubic phases. We have recorded the excess water, pressure–temperature phase diagrams of 2:1 FA/PC mixtures of chain length C12, C14, C16 and C18, over the range 1–1000 bar and approximately 0–100°C. There is no evidence in the data of the appearance of new bicontinuous cubic phases under the application of pressure. However, we have been able to induce cubic phases by reducing the FA/PC ratio from 2:1 to 1:1. We then find that we induce an Im3m cubic phase, believed to be based on the P minimal surface, in the C16 system. In the C18 system we induce a Pn3m cubic phase, which we believe corresponds to the D minimal surface, which co-exists with an inverse hexagonal phase