314 research outputs found

    The nature of the observed free-electron-like state in a PTCDA monolayer on Ag(111)

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    A free-electron like band has recently been observed in a monolayer of PTCDA (3,4,9,10-perylene tetracarboxylic dianhydride) molecules on Ag(111) by two-photon photoemission [Schwalb et al., Phys. Rev. Lett. 101, 146801 (2008)] and scanning tunneling spectroscopy [Temirov et al., Nature 444, 350 (2006)]. Using density functional theory calculations, we find that the observed free-electron like band originates from the Shockley surface state band being dramatically shifted up in energy by the interaction with the adsorbed molecules while it acquires also a substantial admixture with a molecular band

    The nature of highly anisotropic free-electron-like states in a glycinate monolayer on Cu(100)

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    The free-electron-like state observed in a scanning tunneling spectroscopy study of a chiral p(2x4) monolayer of glycinate ions on the Cu(100) surface [K. Kanazawa et al, J. Am. Chem. Soc. 129, 740 (2007)] is shown from density functional theory calculations to originate from a Cu Shockley surface state at the surface Brillouin zone boundary of the clean surface with highly anisotropic dispersion. The presence of the glycinate ions on the surface causes a dramatically enhanced tunneling into this surface state that is otherwise not observed in tunneling on the bare surface

    Cost-effectiveness of a European preventive cardiology programme in primary care: A Markov modelling approach

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    This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license.OBJECTIVE: To investigate the longer-term cost-effectiveness of a nurse-coordinated preventive cardiology programme for primary prevention of cardiovascular disease (CVD) compared to routine practice from a health service perspective. DESIGN: A matched, paired cluster-randomised controlled trial. SETTING: Six pairs of general practices in six countries. PARTICIPANTS: 1019 patients were randomised to the EUROACTION intervention programme and 1005 patients to usual care (UC) and who completed the 1-year follow-up. OUTCOME MEASURES: Evidence on health outcomes and costs was based on patient-level data from the study, which had a 1-year follow-up period. Future risk of CVD events was modelled, using published risk models based on patient characteristics. An individual-level Markov model for each patient was used to extrapolate beyond the end of the trial, which was populated with data from published sources. We used an 11-year time horizon and investigated the impact on the cost-effectiveness of varying the duration of the effect of the intervention beyond the end of the trial. Results are expressed as incremental cost per quality-adjusted life-year gained. RESULTS: Unadjusted results found the intervention to be more costly and also more effective than UC. However, after adjusting for differences in age, gender, country and baseline risk factors, the intervention was dominated by UC, but this analysis was not able to take into account the lifestyle changes in terms of diet and physical activity. CONCLUSIONS: Although the EUROACTION study achieved healthier lifestyle changes and improvements in management of blood pressure and lipids for patients at high risk of CVD, compared to UC, it was not possible to show, using available risk equations which do not incorporate diet and physical activity, that the intervention reduced longer-term cardiovascular risk cost-effectively. Whether or not an intervention such as that offered by EUROACTION is cost-effective requires a longer-term trial with major cardiovascular events as the outcome.This study is sponsored solely by AstraZeneca through the provision of an unconditional educational grant

    Inferring energy-composition relationships with Bayesian optimization enhances exploration of inorganic materials

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    Computational exploration of the compositional spaces of materials can provide guidance for synthetic research and thus accelerate the discovery of novel materials. Most approaches employ high-throughput sampling and focus on reducing the time for energy evaluation for individual compositions, often at the cost of accuracy. Here, we present an alternative approach focusing on effective sampling of the compositional space. The learning algorithm PhaseBO optimizes the stoichiometry of the potential target material while improving the probability of and accelerating its discovery without compromising the accuracy of energy evaluation

    Visible Light Photo-oxidation of Model Pollutants Using CaCu3Ti4O12: An Experimental and Theoretical Study of Optical Properties, Electronic Structure, and Selectivity

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    [Image: see text] Charge transfer between metal ions occupying distinct crystallographic sublattices in an ordered material is a strategy to confer visible light absorption on complex oxides to generate potentially catalytically active electron and hole charge carriers. CaCu(3)Ti(4)O(12) has distinct octahedral Ti(4+) and square planar Cu(2+) sites and is thus a candidate material for this approach. The sol‚ąígel synthesis of high surface area CaCu(3)Ti(4)O(12) and investigation of its optical absorption and photocatalytic reactivity with model pollutants are reported. Two gaps of 2.21 and 1.39 eV are observed in the visible region. These absorptions are explained by LSDA+U electronic structure calculations, including electron correlation on the Cu sites, as arising from transitions from a Cu-hybridized O 2p-derived valence band to localized empty states on Cu (attributed to the isolation of CuO(4) units within the structure of CaCu(3)Ti(4)O(12)) and to a Ti-based conduction band. The resulting charge carriers produce selective visible light photodegradation of 4-chlorophenol (monitored by mass spectrometry) by Pt-loaded CaCu(3)Ti(4)O(12) which is attributed to the chemical nature of the photogenerated charge carriers and has a quantum yield comparable with commercial visible light photocatalysts

    Conformational control of structure and guest uptake by a tripeptide-based porous material

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    Chemical processes often rely on the selective sorting and transformation of molecules according to their size, shape and chemical functionality. For example, porous materials such as zeolites achieve the required selectivity through the constrained pore dimensions of a single structure.1 In contrast, proteins function by navigating between multiple metastable structures using bond rotations of the polypeptide,2,3 where each structure lies in one of the minima of a conformational energy landscape and can be selected according to the chemistry of the molecules interacting with the protein.3 Here we show that rotation about covalent bonds in a peptide linker can change a flexible metal-organic framework (MOF) to afford nine distinct crystal structures, revealing a conformational energy landscape characterised by multiple structural minima. The uptake of small molecule guests by the MOF can be chemically triggered by inducing peptide conformational change. This change transforms the material from a minimum on the landscape that is inactive for guest sorption to an active one. Chemical control of the conformation of a flexible organic linker offers a route to modify the pore geometry and internal surface chemistry and thus the function of open-framework materials

    STM fingerprint of molecule‚Äďadatom interactions in a self-assembled metal‚Äďorganic surface coordination network on Cu(111)

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    7 p√°ginas, 5 figuras, 3 tablas.-- El pdf del art√≠culo es la versi√≥n pre-print.A novel approach of identifying metal atoms within a metal‚Äďorganic surface coordination network using scanning tunnelling microscopy (STM) is presented. The Cu adatoms coordinated in the porous surface network of 1,3,8,10-tetraazaperopyrene (TAPP) molecules on a Cu(111) surface give rise to a characteristic electronic resonance in STM experiments. Using density functional theory calculations, we provide strong evidence that this resonance is a fingerprint of the interaction between the molecules and the Cu adatoms. We also show that the bonding of the Cu adatoms to the organic exodentate ligands is characterised by both the mixing of the nitrogen lone-pair orbitals of TAPP with states on the Cu adatoms and the partial filling of the lowest unoccupied molecular orbital (LUMO) of the TAPP molecule. Furthermore, the key interactions determining the surface unit cell of the network are discussed.This work was financially supported by the European Union through the Marie Curie Research Training Network PRAIRIES (MRTN-CT-2006-035810). Support from the Swiss National Science Foundation, the National Center of Competence in Research (NCCR) ‚Äė‚ÄėNanoscale Science‚Äô‚Äô and the Wolfermann Naegeli Stiftung is also acknowledged. MP is also grateful for support from the Swedish Research Council (VR).Peer reviewe

    SynthoPlate: A platelet-inspired hemostatic nanotechnology for treatment of bleeding complications

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    Platelet transfusions are routinely used in the clinic to treat bleeding complications stemming from trauma, surgery, malignancy-related bone marrow dysfunctions, and congenital or drug-related defects platelet defects. These transfusions primarily use allogeneic platelet concentrates (PCs) that pose issues of limited availability and portability, high risk of bacterial contamination, very short shelf life (~3-5 days), need for antigen matching and several biologic side effects. While robust research is being directed at resolving some of these issues, there is in parallel a significant clinical interest in synthetic platelet substitutes that can render efficient hemostasis by leveraging and amplifying endogenous clotting mechanisms while avoiding the above issues. To this end, we have developed a unique platelet-inspired synthetic hemostat technology called the SynthoPlate¬ģ (US Patent 9107845). Since platelets promote primary hemostasis via adhesion to vWF and collagen at the injury site and concomitant aggregation via fibrinogen binding to integrin GPIIb-IIIa on active platelets, we have mimicked and integrated these key hemostatic mechanisms on the SynthoPlate¬ģ by heteromultivalent surface-engineering of a liposomal platform with vWF-binding peptides (VBP), collagen-binding peptides (CBP) and fibrinogen-mimetic peptides (FMP). These ~150nm diameter SynthoPlate¬ģ vesicles are sterilizable and can be stored as lyophilized powder for long periods of time. We demonstrated, in vitro, that this platelet-mimetic integrative design renders hemostatically relevant functions at levels significantly higher than designs that mimic platelet‚Äôs adhesion function only or aggregation function only. We further demonstrated in vitro that SynthoPlate¬ģ-mediated site-selective amplification of primary hemostatic mechanisms (active platelet recruitment and aggregation) in effect results in site-selective enhancement of secondary hemostatic function (fibrin generation). We also established that SynthoPlate¬ģ does not activate and aggregate resting platelets or trigger coagulation mechanisms in plasma, suggesting that this technology will not have systemic pro-thrombotic and coagulatory risks. The hemostatic efficacy of SynthoPlate¬ģ was tested in appropriate tail-transection and liver bleeding models in mice, as well as, pilot studies in arterial bleeding model in pigs. In tail-transection bleeding model in normal as well as thrombocytopenic mice, prophylactically administered SynthoPlate¬ģ was able to significantly reduce bleeding time by 60-70%. In laparotomy traumatic bleeding model in mice, prophylactically administered SynthoPlate¬ģ was able to reduce blood volume loss by ~30%, reduced hypotension effects and increased survival by \u3e80%. In pilot pig models of arterial bleeding, emergency administration of SynthoPlate¬ģ has shown substantial reduction in blood volume loss. Immunohistological evaluation of tissues from various treated animals have shown marked co-localization of red fluorescent SynthoPlate¬ģ with green fluorescent platelets localized at the clot site. Biodistribution studies in animals indicate that SynthoPlate¬ģ is cleared primarily by liver and spleen, similar to clinically known liposomal technologies. We have also demonstrated that the platelet-mimetic heteromultivalent surface-decoration approach can be adapted to other biomedically relevant particle platforms. Altogether, our studies establish the promise of SynthoPlate¬ģ nanotechnology as a platelet-mimetic intravenous hemostat for treatment of bleeding complications in prophylactic and emergency scenarios. Ongoing studies are focused on evaluating this technology in clinically motivated large animal bleeding models, with a vision for translation
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