Self-force: Computational Strategies

Building on substantial foundational progress in understanding the effect of a small body's self-field on its own motion, the past 15 years has seen the emergence of several strategies for explicitly computing self-field corrections to the equations of motion of a small, point-like charge. These approaches broadly fall into three categories: (i) mode-sum regularization, (ii) effective source approaches and (iii) worldline convolution methods. This paper reviews the various approaches and gives details of how each one is implemented in practice, highlighting some of the key features in each case.Comment: Synchronized with final published version. Review to appear in "Equations of Motion in Relativistic Gravity", published as part of the Springer "Fundamental Theories of Physics" series. D. Puetzfeld et al. (eds.), Equations of Motion in Relativistic Gravity, Fundamental Theories of Physics 179, Springer, 201

Primjena i kompozicija individualiziranih zaštitnih elemenata linijske grafike u projektiranju novčanica

Proces stvaranja novčanica je dugotrajan i složen, što rezultira kompleksnim rješenjima koja predstavljaju pravo remek djelo grafike. Novčanice su prožete brojnim detaljima i prenose različite informacije koje se analiziraju u teorijskom dijelu rada. Prvotno se postavljaju kriteriji po kojima se izrađuje detaljna analiza velikog broja zaštitnih i konceptualnih elemenata na primjerima novčanica. Time je prikazan okvirni povijesni pregled razvoja novčanica i utjecaji kojima je bio izložen. Analizira se međuovisnost dizajna o sigurnosnim značajkama, te se ispituje razina informiranosti javnosti o zaštitama na novčanicama. Zaključuje se koje metode zaštite su najučinkovitije, te kako šira javnost najčešće provjerava autentičnost novčanica. U eksperimentalnom dijelu rada se na temelju donesenih zaključaka iz teorijskog dijela izrađuje prototip novčanice koja je u najvećoj mjeri prožeta individualiziranim PostScript programskim rješenjima elemenata linijske grafike (rozete, mikrotekst, zaštitne linije, brojevi apoena), a od ostalih zaštita modeliran je individualizirani raster transformacijom matematičkog izraza u PostScript programski kod. Sve ostale zaštite tipične za novčanice simulirane su alatima za rastersku i vektorsku grafiku. U radu se ispituje utjecaj kompozicije zaštitnih elemenata na prepoznavanje autentičnosti novčanica, te efikasnost samih individualiziranih programskih rješenja

Analysing ‘Super-Participation’ in Online Third Spaces

This chapter focuses on our attempts to overcome the methodological challenges of 'super-participation' in online discussion forums, focusing on the participatory patterns and discursive activity of what we call 'super-participants'. Our principal contribution in this area (Graham and Wright 2013) focuses on the www.moneysavingexpert.com (MSE) discussion forum. It is one of the largest forums in the United Kingdom and has received nearly 30 million posts. Until recently, the forum (and broader website and email list) was owned by the finance guru and campaigner Martin Lewis. We used a large-scale quantitative content analysis that covered all of the users, alongside a detailed qualitative, hand-coded content analysis. While smaller in scale, this still required a large number of posts to be analysed, and this raises its own challenges. In this chapter, we first discuss why active minorities (that is, super-participants) are typically framed negatively by reviewing the normative frameworks commonly used to analyse online political talk. Second, we present a typology for identifying and categorising super-participants, a framework that can be used to conceptualise super-participation in online forums. Third, we explain and describe the methods that we developed for analysing super-participants. As relative novices to the scraping of data, we explain some of the challenges that we faced, as well as how we eventually overcame them. We then outline our qualitative approach and provide some methodological insight for future research on super-participation. Finally, we discuss the methodological implications of our work

Subsurface deposition of Cu-rich massive sulphide underneath a Palaeoproterozoic seafloor hydrothermal system—the Red Bore prospect, Western Australia

The Proterozoic Bryah and Yerrida basins of Western Australia contain important base and precious metal deposits. Here we present microtextural data, trace element and S isotope analyses of massive sulphide mineralisation hosted in Palaeoproterozoic subvolcanic rocks (dolerite) recently discovered at Red Bore. The small-scale high-grade mineralisation, which extends from the sub-surface to at least 95 m down-hole, is dominated by massive chalcopyrite and contains minor pyrite and Bi-Te-(Se) phases. Massive sulphide mineralisation is surrounded by discontinuous brecciated massive magnetite, and a narrow (< 2 m) alteration halo, which suggests very focussed fluid flow. Laser ablation ICP-MS analyses indicate that chalcopyrite contains up to 10 ppm Au and in excess of 100 ppm Ag. Sulphur isotope analyses of pyrite and chalcopyrite indicate a narrow range of δ34SVCD (− 0.2 to + 4.6 ‰), and no significant mass-independent fractionation (− 0.1 < Δ33S < + 0.05 ‰). Re-Os isotope analyses yield scattered values, which suggests secondary remobilisation. Despite the geographical proximity and the common Cu-Au-Ag association, the mineralisation at Red Bore has significant differences with massive sulphide mineralisation at neighbouring DeGrussa, as well as other massive sulphide deposits around the world. These differences include the geometry, sub-volcanic host rocks, extreme Cu enrichment and narrow δ34S ranges. Although a possible explanation for some of these characteristics is leaching of S and metals from the surrounding volcanic rocks, we favour formation as a result of the release of a magmatic fluid phase along very focussed pathways, and we propose that mixing of this fluid with circulating sea water contributed to sea floor mineralisation similar to neighbouring VHMS deposits. Our data are permissive of a genetic association of Red Bore mineralisation with VHMS deposits nearby, thus suggesting a direct connection between magmatism and mineralising fluids responsible for VHMS deposition at surface. Therefore, the Red Bore mineralisation may represent the magmatic roots of a VHMS system

Women and Editorial Leadership of Scientific and Academic Journals: An Explorative Study

The gender balance/imbalance in the governance of academic journals tied to the different scientific areas (i.e., the editorial board composition) represents a rather under investigated topic among the literature stream on diversity in top academic positions. Starting from this premise, the work aims to detect the gender (im)balance within the most prestigious international journals of Accounting. After having traced the theoretical background, the research design includes the empirical investigation focused on the Accounting journals ranked in the list proposed by the Association of Business Schools (ABS) in 2015 and included in the Italian ANVUR list (2017). Results confirm the underrepresentation of women in the editorial team and leadership positions of Accounting journals, as it happens in other fields included among the STEMs (such as Medicine or Math) or non-STEM disciplines (i.e., Management and Marketing). The work has scientific implications since it points out the limited potential of women scholars in covering governing roles and gaining worldwide visibility. Editorial board membership is in fact both a professional honour in recognition of achievements and an opportunity for professional advancement. Under an operational and political perspective, it contributes to nurturing the debate on the presence of an insidious discrimination that is often not easily recognized

Energetic changes throughout early ontogeny of the brooding Antarctic sea star Rhopiella hirsuta (Koehler, 1920)

An unusually high proportion of Antarctic echinoderms brood their young. Protection, reproductive constraints, low temperatures and limited food supply are all suggested motives for this reproductive pattern. This study looks at the reproductive energetics of the Antarctic asteroid Rhopiella hirsuta, and to establish the dynamics of feeding and elemental composition throughout its early juvenile development. Brooding females were analysed in terms of adult size, brood size, and juvenile size with non-significant trends occurring with depth. Four brooding females were frozen straight after sampling and enabled the study of changes in elemental composition throughout embryo and early juvenile development with regard to their feeding mode. Morphological and elemental analyses indicate aseasonality of reproduction and lecithotrophic early ontogeny in this species. The most advanced juveniles found were significantly different of all earlier stages, with an increase in dry weight to 5.87 (± 1.08) mg suggesting growth, but a high C:N ratio of 8.60 (± 0.59) that would indicate lecithotrophy. However, as the increase in DW was attributed to an increase in carbon, but not to an increase in nitrogen, it was not possible for the food source to be of organic origin