Detecting animals in African Savanna with UAVs and the crowds

Unmanned aerial vehicles (UAVs) offer new opportunities for wildlife monitoring, with several advantages over traditional field-based methods. They have readily been used to count birds, marine mammals and large herbivores in different environments, tasks which are routinely performed through manual counting in large collections of images. In this paper, we propose a semi-automatic system able to detect large mammals in semi-arid Savanna. It relies on an animal-detection system based on machine learning, trained with crowd-sourced annotations provided by volunteers who manually interpreted sub-decimeter resolution color images. The system achieves a high recall rate and a human operator can then eliminate false detections with limited effort. Our system provides good perspectives for the development of data-driven management practices in wildlife conservation. It shows that the detection of large mammals in semi-arid Savanna can be approached by processing data provided by standard RGB cameras mounted on affordable fixed wings UAVs

Exorbitant Privilege and Exorbitant Duty

We update and improve the Gourinchas and Rey (2007a) dataset of the historical evolution of US external assets and liabilities at market value since 1952 to include the recent crisis period. We find strong evidence of a sizeable excess return of gross assets over gross liabilities. The center country of the International Monetary System enjoys an gexorbitant privilegeh that significantly weakens its external constraint. In exchange for this gexorbitant privilegeh we document that the US provides insurance to the rest of the world, especially in times of global stress. This gexorbitant dutyh is the other side of the coin. During the 2007-2009 global financial crisis, payments from the US to the rest of the world amounted to 19 percent of US GDP. We present a stylized model that accounts for these facts.

Diagrammatic Analysis of Charmless Three-Body B Decays

We express the amplitudes for charmless three-body B decays in terms of diagrams. In addition, we show how to use Dalitz-plot analyses to obtain decay amplitudes which are symmetric or antisymmetric under the exchange of two of the final-state particles. When annihilation-type diagrams are neglected, as in two-body decays, many of the exact, purely isospin-based results are modified, leading to new tests of the standard model (SM). Some of the tests can be performed now, and we find that present data agree with the predictions of the SM. Furthermore, contrary to what was thought previously, it is possible to cleanly extract weak-phase information from three-body decays, and we discuss methods for B -> K pi pi, K K Kbar, K Kbar pi and pi pi pi.Comment: 30 pages, 10 figures, reference updated, sentences added regarding indirect CP violation and CP of the final state. Significant text added describing how to obtain symmetric/antisymmetric decay amplitudes, results of the comparison of the predictions of the SM with present data for several decays, and the momentum dependence of the diagram

First-principles study of lithium-doped carbon clathrates under pressure

We present a theoretical study on the behavior under pressure of the two hypothetical C$_{46}$ and Li$_8$C$_{46}$ type-I carbon clathrates in order to bring new informations concerning their synthesis. Using \textit{ab initio} calculations, we have explored the energetic and structural properties under pressure of these two carbon based cage-like materials. These low-density meta-stable phases show large negative pressure transitions compared to diamond which represent a serious obstacle for their synthesis. However, we evidence that a minimum energy barrier can be reached close to 40 GPa, suggesting that the synthesis of the Li-clathrate under extreme conditions of pressure and temperature may be possible. Electronic band structure with related density of states behavior under pressure as well as the dependence of the active Raman modes with pressure are also examined

Home bias in open economy financial macroeconomics

Home bias is a perennial feature of international capital markets. We review various explanations of this puzzling phenomenon highlighting recent developments in macroeconomic modelling that incorporate international portfolio choices in standard two-country general equilibrium models. We refer to this new literature as Open Economy Financial Macroeconomics. We focus on three broad classes of explanations: (i) hedging motives in frictionless financial markets (real exchange rate and non-tradable income risk), (ii) asset trade costs in international financial markets (such as transaction costs or differences in tax treatments between national and foreign assets), (iii) informational frictions and behavioural biases. Recent theories call for new portfolio facts beyond equity home bias. We present new evidence on crossborder asset holdings across different types of assets: equities, bonds and bank lending and new micro data on institutional holdings of equity at the fund level. These data should inform macroeconomic modelling of the open economy and a growing literature of models of delegated investment

Aspects of Assembly and Cascaded Aspects of Assembly: Logical and Temporal Properties

Highly dynamic computing environments, like ubiquitous and pervasive computing environments, require frequent adaptation of applications. This has to be done in a timely fashion, and the adaptation process must be as fast as possible and mastered. Moreover the adaptation process has to ensure a consistent result when finished whereas adaptations to be implemented cannot be anticipated at design time. In this paper we present our mechanism for self-adaptation based on the aspect oriented programming paradigm called Aspect of Assembly (AAs). Using AAs: (1) the adaptations process is fast and its duration is mastered; (2) adaptations' entities are independent of each other thanks to the weaver logical merging mechanism; and (3) the high variability of the software infrastructure can be managed using a mono or multi-cycle weaving approach.Comment: 14 pages, published in International Journal of Computer Science, Volume 8, issue 4, Jul 2011, ISSN 1694-081

Biomimetic apatite-based biomaterials: on the critical impact of synthesis and post-synthesis parameters

Nanocrystalline apatites are major constituents of hard tissues, and attempts are made worldwide to prepare synthetic analogs. However the impact of synthesis/ postsynthesis parameters is often disregarded. Based on an updated knowledge on such compounds, we inspected the effects of synthesis parameters (maturation time, temperature,pH, nature of counter-ions) and post-treatments (re-immersion in aqueous media, thermal treatment) on physicochemical characteristics. Great modifications were noticed during the 3 first days of maturation, where a progressive evolution of the apatite phase (localized in the core of the nanocrystals) toward stoichiometry was observed at the expense of the non-apatitic surface layer which progressively disappears. Similar trends were also evidenced for maturation run under increasing temperatures, studied here in the range 20–100 °C. pH impacted more specifically the chemical composition. The nature of the counter-ion in the starting phosphate salt influenced composition and nonstoichiometry, depending on its (in)ability to be incorporated in the lattice. Freeze-drying allowed to preserve a high surface reactivity, although further evolutions were noticed after re-immersion. Effects of a thermal treatment of dried samples were unveiled, suggesting a denaturation of the hydrated layer on the nanocrystals. This work underlines the necessity of a good control of synthesis/postsynthesis parameters for the production of biomimetic apatites

Stimuli-responsive behavior of PNiPAm microgels under interfacial confinement

The volume phase transition of microgels is one of the most paradigmatic examples of stimuli-responsiveness, enabling a collapse from a highly swollen microgel state into a densely coiled state by an external stimulus. Although well characterized in bulk, it remains unclear how the phase transition is affected by the presence of a confining interface. Here, we demonstrate that the temperature-induced volume phase transition of poly(N-isopropylacrylamide) microgels, conventionally considered an intrinsic molecular property of the polymer, is in fact largely suppressed when the microgel is adsorbed to an air/liquid interface. We further observe a hysteresis in core morphology and interfacial pressure between heating and cooling cycles. Our results, supported by molecular dynamics simulations, reveal that the dangling polymer chains of microgel particles, spread at the interface under the influence of surface tension, do not undergo any volume phase transition, demonstrating that the balance in free energy responsible for the volume phase transition is fundamentally altered by interfacial confinement. These results imply that important technological properties of such systems, including the temperature-induced destabilization of emulsions does not occur via a decrease in interfacial coverage of the microgels

A deep subaqueous fan depositional model for the Palaeoarchaean (3.46 Ga) Marble Bar Cherts, Warrawoona Group, Western Australia

International audienceThe 3.46 Ga Marble Bar Chert Member of the East Pilbara Craton, Western Australia, is one of the earliest and best-preserved sedimentary successions on Earth. Here, we interpret the finely laminated thin-bedded cherts, mixed conglomeratic beds, chert breccia beds and chert folded beds of the Marble Bar Chert Member as the product of low-density turbidity currents, high-density turbidity currents, mass transport complexes and slumps, respectively. Integrated into a channel-levee depositional model, the Marble Bar Chert Member constitutes the oldest documented deep-sea fan on Earth, with thin-bedded cherts, breccia beds and slumps composing the outer levee facies tracts, and scours and conglomeratic beds representing the channel systems