Amorphous interface layer in thin graphite films grown on the carbon face of SiC

Cross-sectional transmission electron microscopy (TEM) is used to characterize an amorphous layer observed at the interface in graphite and graphene films grown via thermal decomposition of C-face 4H-SiC. The amorphous layer does not to cover the entire interface, but uniform contiguous regions span microns of cross-sectional interface. Annular dark field scanning transmission electron microscopy (ADF-STEM) images and electron energy loss spectroscopy (EELS) demonstrate that the amorphous layer is a carbon-rich composition of Si/C. The amorphous layer is clearly observed in samples grown at 1600{\deg}C for a range of growth pressures in argon, but not at 1500{\deg}C, suggesting a temperature-dependent formation mechanism

Multi-mode photonic crystal fibers for VCSEL based data transmission

Quasi error-free 10 Gbit/s data transmission is demonstrated over a novel type of 50 micron core diameter photonic crystal fiber with as much as 100 m length. Combined with 850$ nm VCSEL sources, this fiber is an attractive alternative to graded-index multi-mode fibers for datacom applications. A comparison to numerical simulations suggests that the high bit-rate may be partly explained by inter-modal diffusion.Comment: Accepted for Optics Expres

Towards understanding balancing in exertion games

Playing exertion games with others can be engaging. However, players with different physical skill levels competing against each other can experience reduced engagement because they are either not challenged enough, or challenged too much. Balancing methods can address this; however, there is only limited understanding of balancing in exertion games. In this paper, we identify two distinct dimensional balancing techniques: "internal adjustment" and "external adjustment". We report results from a study where we measured player engagement after applying these adjustments to a digital table tennis game and the traditional table tennis game, finding two disengagement factors: "unexpected physical challenges" and "unacceptable competitive advantage". Based on these factors we derived a set of exertion game design considerations. We conclude that applying digital technology to a physical game can change the required skill level to play the game, and this can affect the impact of these adjustments on player engagement. These results enhances our understanding of balancing in exertion games, supporting the benefits of playing exertion games with others

Development of an electrochemical immunosensor for Phakopsora pachyrhizi detection in the early diagnosis of soybean rust

Soybean rust is a disease that occurs on soybean leaves and is considered very aggressive, reducing product quality. Early identification of fungus in the plants prevents severe farming losses as well as spreading to neighboring cultures. In this paper, a label-free immunosensor was developed based on impedance measurements to detect Asian rust on soybean leaf extract at the early stages of the disease. The antibody anti-mycelium of Phakopsora pachyrhizi fungus (disease agent) was immobilized on a gold substrate via a self-assembled monolayer (SAM) of thiols using covalent cysteamine coupling. This immunosensor presents a limit of detection of 385 ng mL-1. The optimization of experimental conditions and surface blocking to minimize non-specific adsorption on the immunosensor response were evaluated. These studies, based on electrochemical impedance spectroscopy (EIS), provide new perspectives on using this method for early diagnosis of soybean rust

Efficiency determination of resistive plate chambers for fast quasi-monoenergetic neutrons

Composite detectors made of stainless steel converters and multigap resistive plate chambers have been irradiated with quasi-monoenergetic neutrons with a peak energy of 175MeV. The neutron detection efficiency has been determined using two different methods. The data are in agreement with the output of Monte Carlo simulations. The simulations are then extended to study the response of a hypothetical array made of these detectors to energetic neutrons from a radioactive ion beam experiment.Comment: Submitted to Eur.Phys.J. A; upgraded version correcting some typos and updating ref.

A numerical test of differential equations for one- and two-loop sunrise diagrams using configuration space techniques

We use configuration space methods to write down one-dimensional integral representations for one- and two-loop sunrise diagrams (also called Bessel moments) which we use to numerically check on the correctness of the second order differential equations for one- and two-loop sunrise diagrams that have recently been discussed in the literature.Comment: 11 pages, no figures, published versio

The role of interparticle heterogeneities in the selenization pathway of Cu Zn Sn S nanoparticle thin films a real time study

Real time energy dispersive X ray diffraction EDXRD analysis has been utilized to observe the selenization of Cu Zn Sn S nanoparticle films coated from three nanoparticle populations Cu and Sn rich particles roughly 5 nm in size, Zn rich nanoparticles ranging from 10 to 20 nm in diameter, and a mixture of both types of nanoparticles roughly 1 1 by mass , which corresponds to a synthesis recipe yielding CZTSSe solar cells with reported total area efficiencies as high as 7.9 . The EDXRD studies presented herein show that the formation of copper selenide intermediates during the selenization of mixed particle films can be primarily attributed to the small, Cu and Sn rich particles. Moreover, the formation of these copper selenide phases represents the first stage of the CZTSSe grain growth mechanism. The large, Zn rich particles subsequently contribute their composition to form micrometer sized CZTSSe grains. These findings enable further development of a previously proposed selenization pathway to account for the roles of interparticle heterogeneities, which in turn provides a valuable guide for future optimization of processes to synthesize high quality CZTSSe absorber layer

The Catalytic Mechanism of a Natural Diels-Alderase Revealed in Molecular Detail

The Diels-Alder reaction, a [4 + 2] cycloaddition of a conjugated diene to a dienophile, is one of the most powerful reactions in synthetic chemistry. Biocatalysts capable of unlocking new and efficient Diels-Alder reactions would have major impact. Here we present a molecular-level description of the reaction mechanism of the spirotetronate cyclase AbyU, an enzyme shown here to be a bona fide natural Diels-Alderase. Using enzyme assays, X-ray crystal structures, and simulations of the reaction in the enzyme, we reveal how linear substrate chains are contorted within the AbyU active site to facilitate a transannular pericyclic reaction. This study provides compelling evidence for the existence of a natural enzyme evolved to catalyze a Diels-Alder reaction and shows how catalysis is achieved