When Do Groups Perform Better than Individuals? A Company Takeover Experiment

It is still an open question when groups will perform better than individuals in intellectual tasks. We report that in a company takeover experiment, groups placed better bids than individuals and substantially reduced the winner’s curse. This improvement was mostly due to peer pressure over the minority opinion and to group learning. Learning took place from interacting and negotiating consensus with others, not simply from observing their bids. When there was disagreement within a group, what prevailed was not the best proposal but the one of the majority. Groups underperformed with respect to a “truth wins” benchmark although they outperformed individuals deciding in isolation.

Same process, different outcomes: group performance in an acquiring a company experiment

© 2015, Economic Science Association. It is still an open question when groups perform better than individuals in intellective tasks. We report that in an Acquiring a Company game, what prevailed when there was disagreement among group members was the median proposal and not the best proposal. This aggregation rule explains why groups underperformed with respect to a “truth wins” benchmark and why they performed better than individuals deciding in isolation in a simple version of the task but worse in the more difficult version. Implications are drawn on when to employ groups rather than individuals in decision making

Carbon-atom wires produced by nanosecond pulsed laser deposition in a background gas

Wires of sp-hybridized carbon atoms are attracting interest for both fundamental aspects of carbon science and for their appealing functional properties. The synthesis by physical vapor deposition has been reported to provide sp-rich carbon films but still needs to be further developed and understood in detail. Here the synthesis of carbon-atom wires (CAWs) has been achieved by nanosecond pulsed laser deposition (PLD) expoliting the strong out-of-equilibrium conditions occurring when the ablation plasma is confined in a background gas. Surface Enhnaced Raman scattering (SERS) spectra of deposited films indicates that CAWs are mixed with a mainly $sp^2$ amorphous carbon in a $sp-sp^2$ hybrid material. Optimal conditions for the deposition of sp-carbon phase have been investigated by changing deposition parameters thus suggesting basic mechanisms of carbon wires formation. Our proof-of-concept may open new perspectives for the targeted fabrication of CAWs and $sp-sp^2$ structures.Comment: 15 pages 4 figure

Designing All Graphdiyne Materials as Graphene Derivatives: Topologically Driven Modulation of Electronic Properties

Designing new 2D systems with tunable properties is an important subject for science and technology. Starting from graphene, we developed an algorithm to systematically generate 2D carbon crystals belonging to the family of graphdiynes (GDYs) and having different structures and sp/sp(2) carbon ratios. We analyze how structural and topological effects can tune the relative stability and the electronic behavior, to propose a rationale for the development of new systems with tailored properties. A total of 26 structures have been generated, including the already known polymorphs such as alpha-, beta-, and gamma-GDY. Periodic density functional theory calculations have been employed to optimize the 2D crystal structures and to compute the total energy, the band structure, and the density of states. Relative energies with respect to graphene have been found to increase when the values of the carbon sp/sp(2) ratio increase, following however different trends based on the peculiar topologies present in the crystals. These topologies also influence the band structure, giving rise to semiconductors with a finite band gap, zero-gap semiconductors displaying Dirac cones, or metallic systems. The different trends allow identifying some topological effects as possible guidelines in the design of new 2D carbon materials beyond graphene

Bulk Cr tips for scanning tunneling microscopy and spin-polarized scanning tunneling microscopy

A simple, reliable method for preparation of bulk Cr tips for Scanning Tunneling Microscopy (STM) is proposed and its potentialities in performing high-quality and high-resolution STM and Spin Polarized-STM (SP-STM) are investigated. Cr tips show atomic resolution on ordered surfaces. Contrary to what happens with conventional W tips, rest atoms of the Si(111)-7x7 reconstruction can be routinely observed, probably due to a different electronic structure of the tip apex. SP-STM measurements of the Cr(001) surface showing magnetic contrast are reported. Our results reveal that the peculiar properties of these tips can be suited in a number of STM experimental situations

Low-frequency modes in the Raman spectrum of sp-sp2 nanostructured carbon

A novel form of amorphous carbon with sp-sp2 hybridization has been recently produced by supersonic cluster beam deposition showing the presence in the film of both polyynic and cumulenic species [L. Ravagnan et al. Phys. Rev. Lett. 98, 216103 (2007)]. Here we present a in situ Raman characterization of the low frequency vibrational region (400-800 cm-1) of sp-sp2 films at different temperatures. We report the presence of two peaks at 450 cm-1 and 720 cm-1. The lower frequency peak shows an evolution with the variation of the sp content and it can be attributed, with the support of density functional theory (DFT) simulations, to bending modes of sp linear structures. The peak at 720 cm-1 does not vary with the sp content and it can be attributed to a feature in the vibrational density of states activated by the disorder of the sp2 phase.Comment: 15 pages, 5 figures, 1 tabl

Interface coupling in Au-supported MoS2–WS2 heterobilayers grown by pulsed laser deposition

Van der Waals heterostructures of transition metal dichalcogenides (TMDs) are promising systems for engineering functional layered 2D materials with tailored properties. In this work, we study the growth of WS2/MoS2 and MoS2/WS2 heterobilayers by pulsed laser deposition (PLD) under ultra-high vacuum conditions. Using Au(111) as growth substrate, we investigated the heterobilayer morphology and structure at the nanoscale by in-situ scanning tunneling microscopy. Our experiments show that the heterostructure growth can be controlled with high coverage and thickness sensitivity by tuning the number of laser pulses in the PLD process. Raman spectroscopy complemented our investigation, revealing the effect of the interaction with the metallic substrate on the TMD vibrational properties and a strong interlayer coupling between the MoS2 and WS2 layers. The transfer of the heterobilayers on a silica substrate via a wet etching process shows the possibility to decouple them from the native metallic substrate and confirms that the interlayer coupling is not substrate-dependent. This work highlights the potential of the PLD technique as a method to grow TMD heterostructures, opening to new perspectives in the synthesis of complex 2D layered materials

Carbyne: from the elusive allotrope to stable carbon atom wires

Besides graphite and diamond, the solid allotropes of carbon in sp2 and sp3 hybridization, the possible existence of a third allotrope based on the sp-carbon linear chain, the carbyne, has stimulated researchers for a long time. The advent of fullerenes, nanotubes, and graphene has opened new opportunities and nurtured the interest in novel carbon allotropes, including linear structures. The efforts made in this direction produced a number of interesting sp-hybridized carbon molecules and nanostructures in the form of carbon-atom wires. Here we discuss some of the new perspectives opened by the recent advancements in the research on sp-carbon systems

Field cancerization therapy with ingenol mebutate contributes to restoring skin-metabolism to normal-state in patients with actinic keratosis: a metabolomic analysis

Actinic keratosis (AK) is a skin premalignant lesion, which progresses into squamous cell carcinoma (SCC) if left untreated. Ingenol mebutate gel is approved for local treatment of non-hyperkeratotic, non-hypertrophic AK; it also has the potential to act as a field cancerization therapy to prevent the progression of AK to SCC. To gain better insights into the mechanisms of ingenol mebutate beyond the mere clinical assessment, we investigated, for the first time, the metabolome of skin tissues from patients with AK, before and after ingenol mebutate treatment, with high-resolution magic angle spinning nuclear magnetic resonance spectroscopy. The metabolomic profiles were compared with those of tissues from healthy volunteers. Overall, we identified a number of metabolites, the homeostasis of which became altered during the process of tumorigenesis from healthy skin to AK, and was restored, at least partially, by ingenol mebutate therapy. These metabolites may help to attain a better understanding of keratinocyte metabolism and to unmask the metabolic pathways related to cell proliferation. These results provide helpful information to identify biomarkers with prognostic and therapeutic significance in AK, and suggest that field cancerization therapy with ingenol mebutate may contribute to restore skin metabolism to a normal state in patients with AK

Multifocal diffusion of a KPC-3 producing ST512 K. pneumoniae clone in Northern Italy

Sequence Type 258 (ST258) together with its allelic single- and double-locus variants have mostly been associated with the dissemination of KPC-producing Klebsiella pneumoniae in Europe. A total of 56 nonreplicate K. pneumoniae isolates with decreased carbapenem-susceptibility, collected at 7 different hospitals located in Northern Italy were investigated for the occurrence of blaKPC-type genes. PCR and sequencing results highlighted the presence of blaKPC-2 or blaKPC-3 determinants in 10/56 and 5/56 cases respectively. Here we describe the intra- and inter-hospital spread in Northern Italy of a K. pneumoniae ST512 clone harboring the blaKPC-3 gene