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

Synthetic sustainability index (SSI) based on life cycle assessment approach of low impact development in the Mediterranean area

AbstractClimate change and the processes of urbanization alter the hydrologic and hydraulic regime of runoffs formation in urban areas. Low impact infrastructure development (LID) contributes to achieving conditions of invariance hydrological and hydraulics. The purpose of this work is to identify an index of synthetic sustainability (SSI) based on life cycle assessment (LCA). Such LCA evaluates design alternatives through the comparison of the different values of the SSI. The proposed methodology allows the evaluation of the SSI attributing to the individual layers of the LIDs different weights and taking into account both of the influence that each of them perform on invariance hydrologic and hydraulic both of the LCA normalized output. In this paper is showed a methodological implementation obtained by the analysis of a green roof and a permeable pavement. This green roof has been realized, on real scale, in the Urban Hydrology Experimental Park in University of Calabria (Italy)

Using gravitational waves to distinguish between neutron stars and black holes in compact binary mergers

In August 2017, the first detection of a binary neutron star merger, GW170817, made it possible to study neutron stars in compact binary systems using gravitational waves. Despite being the loudest gravitational wave event detected to date (in terms of signal-to-noise ratio), it was not possible to unequivocally determine that GW170817 was caused by the merger of two neutron stars instead of two black holes from the gravitational-wave data alone. That distinction was primarily due to the accompanying electromagnetic counterpart. This raises the question: under what circumstances can gravitational-wave data alone, in the absence of an electromagnetic signal, be used to distinguish between different types of mergers? Here, we study whether a neutron star-black hole binary merger can be distinguished from a binary black hole merger using gravitational-wave data alone. We build on earlier results using chiral effective field theory to explore whether the data from LIGO and Virgo, LIGO A+, LIGO Voyager, the Einstein Telescope, or Cosmic Explorer could lead to such a distinction. The results suggest that the present LIGO-Virgo detector network will most likely be unable to distinguish between these systems even with the planned near-term upgrades. However, given an event with favorable parameters, third-generation instruments such as Cosmic Explorer will be capable of making this distinction. This result further strengthens the science case for third-generation detectors.Comment: 16 pages, 7 figures, 13 table

Observation of quantum-Hall effect in gated epitaxial graphene grown on SiC (0001)

Epitaxial graphene films were formed on the Si-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. A high-k gate stack on epitaxial graphene is realized by inserting a fully oxidized nanometer thin aluminum film as a seeding layer followed by an atomic-layer deposition process. The electrical properties of epitaxial graphene films are sustained after gate stack formation without significant degradation. At low temperatures, the quantum-Hall effect in Hall resistance is observed along with pronounced Shubnikov-de Hass oscillations in diagonal magneto-resistance of gated epitaxial graphene on SiC (0001).Comment: 2 new references adde

Dealing with the challenges of legitimacy, values, and politics in policy advice

Policy advice has been the subject of ongoing research in the policy sciences as it raises fundamental issues about what constitutes policy knowledge, expertise, and their effects on policymaking. This introduction reviews the existing literature on the subject and introduces the themes motivating the articles in the issue. It highlights the need to consider several key subjects in the topic in the contemporary era: namely the challenge of legitimacy, that of values, and the challenge of politics. The papers in the issue shed light on the ongoing delegitimization of conventional knowledge providers, the problem of the normative basis of experts’ advice, the increasing politicization of expertise in policymaking, and the relevance of political context in influencing not only the role of experts but also whether or not their advice is accepted and implemented. It is argued that these modern challenges, when not addressed, reinforce trends toward the inclusion of antidemocratic values and uninformed ideas in contemporary policymaking

Ab initio Study of Misfit Dislocations at the SiC/Si(001) Interface

The high lattice mismatched SiC/Si(001) interface was investigated by means of combined classical and ab initio molecular dynamics. Among the several configurations analyzed, a dislocation network pinned at the interface was found to be the most efficient mechanism for strain relief. A detailed description of the dislocation core is given, and the related electronic properties are discussed for the most stable geometry: we found interface states localized in the gap that may be a source of failure of electronic devices

Mobilizing Policy (In)Capacity to Fight COVID-19: Understanding Variations in State Responses

The objective of this collection of essays is to gain insights into the different national-level state responses to COVID-19 around the world and the conditions that shaped them. The pandemic offers a natural experiment wherein the policy problem governments faced was the same but the responses they made were different, creating opportunities for comparison of both the kinds of policy tools being used and the factors that accounted for their choice. Accordingly, after surveying on-line databases of policy tools used in the pandemic and subjecting these to topic modelling to reveal the characteristics of a 'standard' national pandemic response, we discuss the similarities and differences found in specific responses. This is done with reference to the nature and level of policy capacity of respective governments, highlighting the critical roles played by (in)adequate preparation and lesson-drawing from past experiences with similar outbreaks or crises. Taken together the articles show how the national responses to the COVID-19 pandemic were shaped by the opportunity and capacity each government had to learn from previous pandemics and their capacity to operationalize and build political support for the standard portfolio of policy measures deployed to deal with the crisis. However, they also show how other factors such as the nature of national leadership, the organization of government and civil society, and blindspots towards the vulnerabilities of certain population segments also helped to shape policy responses to the pandemic

Model systematics in time domain tests of binary black hole evolution

We perform several consistency tests between different phases of binary black hole dynamics; the inspiral, the merger, and the ringdown on the gravitational wave events GW150914 and GW170814. These tests are performed explicitly in the time domain, without any spectral leakage between the different phases. We compute posterior distributions on the mass and spin of the initial black holes and the final black hole. We also compute the initial areas of the two individual black holes and the final area from the parameters describing the remnant black hole. This facilitates a test of Hawking's black hole area theorem. We use different waveform models to quantify systematic waveform uncertainties for the area increase law with the two events. We find that these errors may lead to overstating the confidence with which the area theorem is confirmed. For example, we find $>99\%$ agreement with the area theorem for GW150914 if a damped sinusoid consisting of a single-mode is used at merger to estimate the final area. This is because this model overestimates the final mass. Including an overtone of the dominant mode decreases the confidence to $\sim94\%$; using a full merger-ringdown model further decreases the confidence to $\sim 85-90\%$. We find that comparing the measured change in the area to the expected change in area yields a more robust test, as it also captures over estimates in the change of area. We find good agreement with GR when applying this test to GW150914 and GW170814