N ‐Functionalised Imidazoles as Stabilisers for Metal Nanoparticles in Catalysis and Anion Binding

Metal nanoparticles (NPs) have physicochemical properties which are distinct from both the bulk and molecular metal species, and provide opportunities in fields such as catalysis and sensing. NPs typically require protection of their surface to impede aggregation, but these coatings can also block access to the surface which would be required to take advantage of their unusual properties. Here, we show that alkyl imidazoles can stabilise Pd, Pt, Au, and Ag NPs, and delineate the limits of their synthesis. These ligands provide an intermediate level of surface protection, for which we demonstrate proof‐of‐principle in catalysis and anion binding

Are Individuals Fickle-Minded?

Game theory has been used to model large-scale social events — such as constitutional law, democratic stability, standard setting, gender roles, social movements, communication, markets, the selection of officials by means of elections, coalition formation, resource allocation, distribution of goods, and war — as the aggregate result of individual choices in interdependent decision-making. Game theory in this way assumes methodological individualism. The widespread observation that game theory predictions do not in general match observation has led to many attempts to repair game theory by creating behavioral game theory, which adds corrective terms to the game theoretic predictions in the hope of making predictions that better match observations. But for game theory to be useful in making predictions, we must be able to generalize from an individual’s behavior in one situation to that individual’s behavior in very closely similar situations. In other words, behavioral game theory needs individuals to be reasonably consistent in action if the theory is to have predictive power. We argue on the basis of experimental evidence that the assumption of such consistency is unwarranted. More realistic models of individual agents must be developed that acknowledge the variance in behavior for a given individual

Swift heavy-ion irradiation-induced shape and structural transformation in cobalt nanoparticles

The shape and structural evolution of Co nanoparticles embedded in SiO₂ and subjected to swift heavy-ion irradiation have been investigated over a wide energy and fluence range. Modifications of the nanoparticle size and shape were characterized with transmission electron microscopy and small-angle x-ray scattering.Nanoparticles below a threshold diameter remained spherical in shape and progressively decreased in size under irradiation due to dissolution.Nanoparticles above the threshold diameter transformed into nanorods with their major dimension parallel to the incident ion direction. Modifications of the atomic-scale structure of the Co nanoparticles were identified with x-rayabsorption spectroscopy. Analysis of the x-rayabsorption near-edge spectra showed that prior to irradiation all Co atoms were in a metallic state, while after irradiation Co atoms were in both oxidized and metallic environments, the former consistent with dissolution. The evolution of the nanoparticle short-range order was determined from extended x-ray absorption fine structure spectroscopy. Structural changes in the Co nanoparticles as a function of ion fluence included an increase in disorder and asymmetric deviation from a Gaussian interatomic distance distribution coupled with a decrease in bondlength. Such changes resulted from the irradiation-induced decrease in nanoparticle size and subsequent dissolution.This work was financially supported by the Australian Synchrotron and the Australian Research Council with access to equipment provided by the Australian Nanofabrication Facility. ChemMatCARS Sector 15 is principally supported by the NSF/ DOE under Grant No. NSF/CHE–0822838

Amorphization of embedded Cu nanocrystals by ion irradiation

While bulk crystalline elemental metals cannot be amorphized by ion irradiation in the absence of chemical impurities, the authors demonstrate that finite-size effects enable the amorphization of embedded Cu nanocrystals. The authors form and compare the atomic-scale structure of the polycrystalline, nanocrystalline, and amorphous phases, present an explanation for the extreme sensitivity to irradiation exhibited by nanocrystals, and show that low-temperature annealing is sufficient to return amorphized material to the crystalline form

Energy dependent saturation width of swift heavy ion shaped embedded Au nanoparticles

The transformation of Aunanoparticles (NPs) embedded in SiO₂ from spherical to rod-like shapes induced by swift heavy ion irradiation has been studied. Irradiation was performed with ¹⁹⁷Au ions at energies between 54 and 185 MeV. Transmission electron microscopy and small angle x-ray scatteringmeasurements reveal an energy dependent saturation width of the NP rods as well as a minimum size required for the NPs to elongate. The NP saturation width is correlated with the ion track diameter in the SiO₂. NP melting and in-plane strain in the irradiatedSiO₂ are discussed as potential mechanisms for the observed deformation.P.K. and M.C.R. thank the Australian Research Council for support. P.K., R.G., D.J.S., and M.C.R. were supported by the Australian Synchrotron Research Program, funded by the Commonwealth of Australia via the Major National Research Facilities Program

Angoff anchor statements: setting a flawed gold standard?

http://www.mededpublish.org/manuscripts/120

Medical degree apprenticeships: a useful model for the future?

There has been much in the news about the possibility of an alternative route into medicine using medical apprenticeships. In this piece, the authors share their thoughts on the feasibility of apprenticeships, how such a system could be managed and the practicalities that would need to be addressed

Reduction in cytokine production in colorectal cancer patients: association with stage and reversal by resection

The aim of this study was to assess monocyte/macrophage function, as defined by lipopolysaccharide (LPS)-induced production of tumour necrosis factor (TNF)-α, interleukin (IL)-10 and interferon (IFN)-γ by stimulated whole blood cultures in patients with colorectal carcinoma before and after surgical resection. Forty colorectal cancer patients prior to surgery and 31 healthy controls were studied. Heparinized venous blood was taken from colorectal cancer patients prior to surgery and from healthy controls. Serial samples were obtained at least 3–6 weeks post-operatively. Blood was stimulated with LPS for 24 h and supernatants were assayed for TNF-α, IFN-γ and IL-10 by enzyme-linked immunosorbent assay. LPS-induced production of TNF-α and of IFN-γ was reduced in patients with colorectal carcinoma compared to controls (TNF-α, 11 269 pg ml−1{12 598}; IFN-γ, 0.00 pg ml−1{226}; median {IQR}) (TNF-α, 20 576 pg ml−1{11 637}, P< 0.0001; IFN-γ, 1048 {2428}, P = 0.0051, Mann–Whitney U -test). Production in patients after surgery had increased (TNF-α: 17 620 pg ml−1{7986}; IFN-γ: 410 pg ml−1{2696}; mean {s.d.}) and were no longer significantly reduced when compared to controls (TNF-α, P = 0.28; IFN-γ, P = 0.76). Production of TNF-α and IFN-γ prior to surgery were reduced to a greater extent in patients with Dukes' stage C tumours compared to those with Dukes' stage A and B stage. There was no difference in IL-10 production between any group. Monocytes/macrophages from patients with colorectal carcinoma are refractory to LPS stimulation as reflected by reduction in TNF-α and IFN-γ production and this is more pronounced in patients with advanced stage tumours. This suppression is not mediated by IL-10 and disappears following surgical resection of the tumour. This provides evidence for tumour induced suppression of immune function in patients with colorectal cancer and identifies a potential therapeutic avenue. © 2000 Cancer Research Campaig

Visualization and chemical characterization of the cathode electrolyte interphase using He-ion microscopy and in situ time-of-flight secondary ion mass spectrometry

Unstable cathode electrolyte interphase (CEI) formation increases degradation in high voltage Li-ion battery materials. Few techniques couple characterization of nano-scale CEI layers on the macroscale with in situ chemical characterization, and thus, information on how the underlying microstructure affects CEI formation is lost. Here, the process of CEI formation in a high voltage cathode material, LiCoPO4, has been investigated for the first time using helium ion microscopy (HIM) and in situ time-of-flight (ToF) secondary ion mass spectrometry (SIMS). The combination of HIM and Ne-ion ToF-SIMS has been used to correlate the cycle-dependent morphology of the CEI layer on LiCoPO4 with a local cathode microstructure, including position, thickness, and chemistry. HIM imaging identified partial dissolution of the CEI layer on discharge resulting in in-homogenous CEI coverage on larger LiCoPO4 agglomerates. Ne-ion ToF-SIMS characterization identified oxyfluorophosphates from HF attack by the electrolyte and a Li-rich surface region. Variable thickness of the CEI layer coupled with inactive Li on the surface of LiCoPO4 electrodes contributes to severe degradation over the course of 10 cycles. The HIM–SIMS technique has potential to further investigate the effect of microstructures on CEI formation in cathode materials or solid electrolyte interphase formation in anodes, thus aiding future electrode development