Self-Similarity of Friction Laws

The change of the friction law from a mesoscopic level to a macroscopic level is studied in the spring-block models introduced by Burridge-Knopoff. We find that the Coulomb law is always scale invariant. Other proposed scaling laws are only invariant under certain conditions.}Comment: Plain TEX. Figures not include

The walkability of Alvalade neighbourhood for young people: An agent-based model of daily commutes to school

The Alvalade neighbourhood in Lisbon, Portugal, was built in the mid-XX century as low-cost housing for workers, but it has become inhabited by the middle and upper classes. The neighbourhood is home to a large population of young people, including children and teenagers who attend the schools located in the area. We present an agent- based model which aims to investigate the walkability of the neighbourhood for these young people, focusing on the mobility patterns of children and teenagers as they navigate their daily routines of going to school. We simulate the pedestrian movement of these young people, considering factors such as the availability of sidewalks, crosswalks, distance to schools, and the presence of other amenities. Our research reveals the mobility patterns emerging in this area and compares them across the different schools in the area. These results inform both urban policies and interventions that promote safe and accessible routes to school.info:eu-repo/semantics/publishedVersio

Random-walk mobility analysis of Lisbon’s plans for the post-1755 reconstruction

The different options for the reconstruction of the city of Lisbon in the aftermath of the 1755 earthquake are studied with an agent-based model based on randomwalks. This method gives a comparative quantitative measure of mobility of the circulation spaces within the city. The plans proposed for the city of Lisbon signified a departure from the medieval mobility city model. The intricacy of the old city circulation spaces is greatly reduced in the new plans and the mobility between different areas is substantially improved. The simulation results of the random-walk model show that those plans keeping the main force lines of the old city presented less improvement in terms ofmobility. The plans that had greater design freedom were, by contrast, easier to navigate. Lisbon's reconstruction followed a plan that included a shift in the traditional notions of mobility. This affected the daily lives of its citizens by potentiating an easy access to the waterfront, simplifying orientation and navigability. Using the random-walk model it is shown how to quantitatively measure the potential that synthetic plans have in terms of the permeability and navigability of different city public spaces.info:eu-repo/semantics/publishedVersio

Pauli-Lubanski scalar in the Polygon Approach to 2+1-Dimensional Gravity

In this paper we derive an expression for the conserved Pauli-Lubanski scalar in 't Hooft's polygon approach to 2+1-dimensional gravity coupled to point particles. We find that it is represented by an extra spatial shift $\Delta$ in addition to the usual identification rule (being a rotation over the cut). For two particles this invariant is expressed in terms of 't Hooft's phase-space variables and we check its classical limit.Comment: Some errors are corrected and a new introduction and discussion are added. 6 pages Latex, 4 eps-figure

The isotopic composition (d15N, d13C) of agricultural wastes and derived composts.

The aim of this study was to measure variations in the isotopic composition (d13C and d15N) during the composting of different agricultural wastes using bench-scale bioreactors. Four different feedstocks of agricultural wastes (Horse bedding manure + legumes residues; Dairy manure + Jatropha mill cake; Dairy manure + sugarcane residues; Dairy manure) were used for aerobic-thermophilic composting. During composting no significant differences were found between the d13C values of the source material and the compost, except for Dairy manure + sugarcane residues. d15N values increased significantly in composts of Horse bedding manure + legumes residues and Dairy manure + Jatropha mill cake. d15N values of composts may be related to NH3 volatilization during the composting process. Isotopic signatures (d13C, d15N) can be used to differentiate composts from different feedstock sources and d15N values may be a quantitative indicator of NH3 volatilization during composting. Use of bench-scale bioreactors is a promising apparatus to study the dynamics of C and N and stable isotopes signatures during composting, but future adjustments regarding sampling methodology are necessary

Biscoito de gergelim: qualidade nutricional na merenda escolar.

bitstream/CNPA/19927/1/FOLDER_biscoito_gergelim.pdfFolder

Electric-field control of spin waves at room temperature in multiferroic BiFeO3

To face the challenges lying beyond current CMOS-based technology, new paradigms for information processing are required. Magnonics proposes to use spin waves to carry and process information, in analogy with photonics that relies on light waves, with several advantageous features such as potential operation in the THz range and excellent coupling to spintronics. Several magnonic analog and digital logic devices have been proposed, and some demonstrated. Just as for spintronics, a key issue for magnonics is the large power required to control/write information (conventionally achieved through magnetic fields applied by strip lines, or by spin transfer from large spin-polarized currents). Here we show that in BiFeO3, a room-temperature magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned electrically by over 30%, in a non-volatile way and with virtually no power dissipation. Theoretical calculations indicate that this effect originates from a linear magnetoelectric effect related to spin-orbit coupling induced by the applied electric field. We argue that these properties make BiFeO3 a promising medium for spin wave generation, conversion and control in future magnonics architectures.Comment: 3 figure

Understanding social enterprises in the United Kingdom: the case of South Yorkshire

Purpose-- This study analyses the development of social enterprises in the UK, in the context of the increased need for creative solutions to ameliorate deprivation and deliver effective public services. Design/methodology/approach-- The investigation draws on a mixed method approach, using a postal survey of 102 social enterprises complemented by detailed analysis of two selected cases and key informant interviews. Findings-- The results of the study show that there is a paradigm shift in the practice and conceptualisation of social enterprises in South Yorkshire as they are increasingly taking a more corporate approach to achieve their outcomes. Research limitations/implications-- The study is limited to social enterprises in South Yorkshire, UK. Further comparative analysis in other regions and social contexts is required in order to explore if these results are widely applicable. Practical implications-- This study is of potential benefit to researchers and those involved in formulating policies for the development and support of social enterprise. Originality/value-- The study contributes to the extant literature by investigation of the development of social enterprise in competitive markets, which is an area that requires further academic scrutiny. The South Yorkshire region presents an interesting case that extends our understanding of the operations of social enterprises in the UK given the high levels of deprivation due to the steady decline of its industrial base ( Bache and Chapman, 2008)