Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma

Boron carbide (B4C) is one of the few materials that is expected to be mostly resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at modern light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. These contaminations represent a serious issue for the operation of high performance FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same IBSS GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude from these comparative plasma processes that pure O2 feedstock plasma only exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coating.Comment: 27 pages, 15 figure

Influence of temperature on extreme rainfall intensity in Sicily (Italy)

Some climate model experiments suggest an intensification of short-duration extreme precipitation in many parts of the world associated with a warming climate. This behavior could have a physical motivation due to the fact that warmer air has the potential to hold more atmospheric moisture and, then, to provide more water to rainfall events. The theoretical basis of the relationship that links air temperature and atmospheric humidity is provided by the Clausius-Clapeyron relation, according to which, if the relative humidity remains constant, then atmospheric humidity will increase with temperature at a rate (often referred to as CC-rate) in the order of 6-7% C-1, following the saturation vapour pressure curve as a function of temperature. The study of the relationship between extreme rainfall events and surface temperature could be of capital importance for evaluating the effects of global warming on future precipitation, since it may have important impacts on society with relevant fallouts on several aspects (e.g. flooding, risk protection, etc.). Different approaches have been proposed for the study at different locations of the scaling relationship between extreme rainfall intensity and surface temperature. In some cases, it has been observed a rate consistent with the thermodynamic Clausius-Clapeyron relation (CC-rate). Nevertheless, in many cases, the existence of scaling rate between temperature and extreme precipitation has been demonstrated with significantly different values with respect to the theoretical CC-rate, being in some cases sensibly higher (super-CC) and in other relevantly lower (sub-CC). In this work, an analysis of the scaling relationship between sub-daily extreme rainfall and surface temperature in a semi-arid region (Sicily, Italy) is carried out, also investigating the role of different factors, such as the duration of maximum rainfall depths for fixed duration (i.e. 10, 30 and 60 minutes), the type of adopted regression models (exponential regression, two-segments piecewise regression and LOESS - Locally-weighted scatterplot smoothing - regression), and the climate seasonality (unique season for the entire hydrological year; dry season from April to September and wet season for the remaining part of the year). The original dataset is constituted by hourly temperature and 10-minutes rainfall data collected from 2003 to 2015 by the regional agency SIAS (Servizio Informativo Agrometeorologico Siciliano) through 107 weather stations spread over the region. The results demonstrate that in Sicily the scaling rates are generally lower than the CC-rate; however, the observed tendency towards sub-CC rates is smoothed by the consideration of shorter duration for rainfall maximum depths (higher rates for 10-minutes durations) and under wetter periods (higher rates considering only wet season values), demonstrating how such factors play a fundamental role

Singular points in N=2 SQCD

We revisit the study of singular points in N=2 SQCD with classical gauge groups. Using a technique proposed recently by Gaiotto, Seiberg and Tachikawa we find that the low-energy physics at the maximally singular point involves two superconformal sectors coupled to an infrared free SU(2) gauge group. When one softly breaks extended supersymmetry to N=1 adding a mass term for the chiral multiplet in the adjoint representation, a finite number of vacua remain and the theory becomes confining. Our analysis allows to identify the low-energy physics at these distinguished points in the moduli space. In some cases, which we will describe in detail, two sectors coupled to an infrared free SU(2) gauge group emerge as before. For USp and SO gauge groups one of these sectors is always free, contrary to the SU case.Comment: 22 pages, 2 figure

Modulating Thermal Properties of Polymers through Crystal Engineering

Crystal engineering has exclusively focused on the development of advanced materials based on small organic molecules. We now demonstrate how the cocrystallization of a polymer yields a material with significantly enhanced thermal stability but equivalent mechanical flexibility. Isomorphous replacement of one of the cocrystal components enables the formation of solid solutions with melting points that can be readily fine-tuned over a usefully wide temperature range. The results of this study credibly extend the scope of crystal engineering and cocrystallization from small molecules to polymers

EXPLORING JITTERING AND ROUTING OPTIONS FOR CONVERTING ORIGIN-DESTINATION DATA INTO ROUTE NETWORKS: TOWARDS ACCURATE ESTIMATES OF MOVEMENT AT THE STREET LEVEL

Origin-Destination (OD) datasets provide vital information on how people travel between areas in many cities, regions and countries worldwide. OD datasets are usually represented geographically with straight lines or routes between zone centroids. For active travel, this geographic representation has substantial limitations, especially when zone origins and centroids are large: only using a single centroid origin/destination for each large zone results in sparse route networks covering only a small fraction of likely walking and cycling routes. This paper implements and explores the use of jittering and different routing options to overcome this limitation, thereby adding value to aggregate OD data to support investment in sustainable transport infrastructure. The route network results — generated from on an open dataset representing cycling trips in Lisbon, Portugal — were compared with a ground-truth dataset from 67 count locations distributed throughout the city. This approach enabled exploration of which jittering parameters and routing options lead to the most accurate route network results approximating the real geographic distribution of cycling trips in the study area. We found that jittering and disaggregating OD data, combined with routing using low level of traffic stress (quieter) preferences resulted in the most accurate route networks. We conclude that a combined approach involving 1) jittering with intermediate levels of disaggregation and 2) careful selection of routing options can lead to much more realistic route networks than using established OD processing techniques. The methods can be deployed to support evidence-based investment in strategic cycling and other sustainable transport networks in cities worldwide. </jats:p