Moiré patterns observed in bi layer graphene irradiated with high energetic protons

Customarily, it is likely that irradiated graphene yield indication of per- turbations induced by irradiation. High Resolution Transmission Electron Micros- copy (HRTEM) analysis has been performed on proton irradiated graphene. The analysis indicates the existence of Moiré patterns produced by the rotations induced by the irradiation in between planes. The rotations measured fluctuate between 3 and 5 degrees respectively. These rotations may influence the electronic properties of the material under investigation. In order to explain the observed rotations in between planes, theoretical analysis were performed under the scheme of extended Hückel tight-binding method. Average total energy of the system was careful ana- lyzed throughout the experiment composed of two graphene layers with two carbon vacancies and then the replaced carbons were intercalated in between the two lay- ers. The results obtained indicate that the system remain semi metallic. Moreover, the theoretical results yielded that the 3 degree rotation is favored, although the 5 degree rotation is not discarded. Furthermore, energy bands as well as total and projected DOS were performed in order to provide more information about the electronic changes induced by the rotations applied to the system

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Characterization of mass transfer of lower chlorinated benzenes from contaminated sediment into water

Mass transport of chlorinated benzenes as found at the Petro-Processors of Louisiana, Inc. (PPI) Superfund site was characterized for a range of flow rates in small streams. At this site hazardous waste was historically disposed of in unengineered pits. Hexachlorobenzene and lesser chlorinated degradation products were found among other compounds. As waste was being disposed into unengineered pits, it seeped to lagoons and sediments of Baton Rouge Bayou (BRB), which flows through and nearby the former disposal areas. Characterization of the transport and fate of chlorobenzenes at PPI is an integral part of the Monitored Natural Attenuation (MNA) remedy currently underway. Laboratory experimental results and mathematical model predictions of the flux of 1,3-dichlorobenzene (1,3-DCB) from sediments into water are presented. 1,3-DCB was studied as individually and as part of a mixture of four contaminants with 1,2-DCB, chlorobenzene (MCB) and trichlorobenzene (TCB). Surficial sediments were collected, spiked with contaminants and leached to determine flux over time. Two advection-dispersion models were tested and the effect of low, cycling and fast stream flow on the contaminant flux was assessed. Model results suggest that tortuosity and effective diffusivity are related effective system predictors and descriptors. Statistical analysis supports the models\u27 predictive capabilities

The role of ad-atoms in the coalescence of alkanethiol-passivated gold nanoparticles

In the present work we show how the role of ad-atoms and surface imperfections play a key role during the coalescence of thiol-passivated Au nanoparticles (NPs) below 4 nm in diameter. Using spherical aberration corrected scanning transmission electron microscopy (STEM) with ultra-high resolution and computer simulations we reveal the main structural and energetic changes throughout the diffusion/migration of surface atoms during coalescence of monolayer-protected NPs. The sintering process of nanoparticles with similar size (diameter) follows a neck-formation mechanism. However, in the case of thiol-protected Au NPs with different size (i.e. with dissimilar surface curvature) the Ostwald ripening mechanism has been detected with atomic resolution in situ STEM measurements for the first time. In particular we have observed how the larger particles grow in size at the expense of the smaller ones, until the latter completely disappear. The experimental findings have been supported with the aid of state-of-the-art computer simulations.Fil: Gutierrez Wing, C.. Instituto Nacional de Investigaciones Nucleares Ciencias Aplicadas-Tecnología de Materiales; MéxicoFil: Olmos Asar, Jimena Anahí. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Esparza, R.. Universidad Nacional Autónoma de México; México. University of Texas; Estados UnidosFil: Mariscal, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Yacaman, M. J.. University of Texas; Estados Unido