Trajectory dependence of electronic energy-loss straggling at keV ion energies

We have measured the electronic energy-loss straggling of protons, helium, boron and silicon ions in silicon using a transmission time-of-flight approach. Ions with velocities between 0.25 and 1.6 times the Bohr velocity were transmitted through single-crystalline Si(100) nanomembranes in either channelling or random geometry to study the impact parameter dependence of energy-loss straggling. Nuclear and path length contributions to the straggling were determined with the help of Monte Carlo simulations. Our results exhibit an increase in straggling with increasing ion velocity for channelled trajectories for all projectiles as well as for protons and helium in random geometry. In contrast for heavier ions, electronic straggling at low velocities does not decrease further but plateaus and even seems to increase again. We compare our experimental results with transport cross section calculations. The satisfying agreement for helium shows that electronic stopping for light ions is dominated by electron-hole pair excitations, and that the previously observed trajectory dependence can indeed be attributed to a higher mean charge state for random trajectories. No agreement is found for boron and silicon indicating that local electron-promotion and charge-exchange events significantly contribute to energy loss at low velocities

Lift devices in the flight of Archaeopteryx

Archaeopteryx has played a central role in the debates on the origins of avian (and dinosaurian) flight, even though as a flier it probably represents a relatively late stage in the beginnings of fl ight. We report on aerodynamic tests using a life-sized model of Archaeopteryx performing in a low turbulence wind tunnel. Our results indicate that tail deflection significantly decreased take-off velocity and power consumption, and that the first manual digit could have functioned as the structural precursor of the alula. Such results demonstrate that Archaeopteryx had already evolved high-lift devices, which are functional analogues of those present in today's birds

Thermal behaviour of Cu and Au nanoparticles grown on CeO2 thin films

RM and FG acknowledge funding from EPSRC grants (RM: EP/506631/1; FG: EP/M029077/1). JAvdB and AKR acknowledge the EPSRC funding for the use of the MEIS facility at the University of Huddersfield within grant EP/M029077/1. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -Brasil (CAPES) - Finance Code 001, by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and PRONEX-FAPERGS16/2551-0000479-0.Bimetallic catalysts are often more active and/or selective than their monometallic counterparts. The behaviour of such catalysts is frequently strongly dependent on the molar ratio of the two elements as well as nanoparticle size and the interaction with the support material. X-ray photoelectron spectroscopy (XPS) is an excellent surface analytical technique for probing the electronic properties of catalytic systems. When a mixture of pure and alloyed particles is present, it is more difficult to extract information from XPS given that it is a spatial averaging technique. Recently, the technique of medium energy ion scattering (MEIS) has been exploited to investigate the depth-dependent composition of nanoparticles on planar surfaces. Herein, we combine the two techniques to investigate the nature of Cu and Au nanoparticles deposited onto ultrathin CeO2 films on Si(111) examining their morphology and chemical composition as a function of annealing temperature for samples that have been maintained in an ultrahigh vacuum environment and exposed to air. The Cu/Au/CeO2/Si(111) is chosen as a model system in order to provide insight into how the catalytic properties of Cu/Au/CeO2 depend on the presence of discrete Cu and Au particles versus fully intermixed Cu/Au systems.PostprintPeer reviewe

Best standards for data collection and reporting requirements on FOBs: towards a science-based FOB fishery management.

A major concern for tropical tunas, on these last years, has been the worldwide increasing use of drifting FOBs by purse seiners, which are equipped with satellite buoys and echo-sounders. The use of these floating objects has contributed to increase the catch of skipjack tuna, but also of juveniles of yellowfin and bigeye tunas. Moreover, it has increased the amount of by-catch (including some species classified as vulnerable or endangered) and has likely resulted in adverse effects on the ecology of fish and on vulnerable areas (e.g. beaching events on coral reef areas). Despite the increasing FOB use and concerns, little information is available on FOB use worldwide for an appropriate monitoring and management. Thus, FOB monitoring has become a priority in all tuna t-RFMOs. However, the data collection and reporting requirements around FOBs are not standardized and there are significant data gaps. The aim of this document is to review current requirements and procedures in place and propose standards for data collection and submission on FOBs to tRFMOs. The proposals included in this document are the result of a collaborative work between scientists and the fishing industry

Control de capa limite en el vuelo a bajos números de Reynolds

Estudio y comprobación experimental de los efectos de los bajos números de Reynolds

Biodegradable DFADs: Current status and prospects

Until recently, dFAD structure, materials and designs have remained quite rudimentary and virtually the same since their discovery, characterized by the increase of the dimensions and prevailing heavy use of plastic components. Biodegradable materials are called to be an important part of the solution, as they can faster degrade in the environment, free of toxins and heavy metals, reducing their lifespan, and preventing them from accumulating in sensitive areas once they are abandoned, lost or discarded. During last decades, regulatory measures at tRFMOs have advanced in the gradual implementation of biodegradable materials in dFAD constructions together with other measures limiting the number of active dFADs and the use of netting materials. However, more clarity is needed starting with a standardised definition of biodegradable dFADs among tRFMOs, to provide operational guidance. Research with those natural and synthetic materials is required, along with updated data collection for monitoring standards, as well as alternative and complementary actions need to be explored to contribute to minimising dFAD adverse effects on environment. Acknowledging the current difficulties for the implementation of fully biodegradable dFADs a stepwise process towards the implementation of fully biodegradable dFADs should be considered.Postprin

Peeling graphite layer by layer reveals the charge exchange dynamics of ions inside a solid

Over seventy years ago, Niels Bohr described how the charge state of an atomic ion moving through a solid changes dynamically as a result of electron capture and loss processes, eventually resulting in an equilibrium charge state. Although obvious, this process has so far eluded direct experimental observation. By peeling a solid, such as graphite, layer by layer, and studying the transmission of highly charged ions through single-, bi- and trilayer graphene, we can now observe dynamical changes in ion charge states with monolayer precision. In addition we present a first-principles approach based on the virtual photon model for interparticle energy transfer to corroborate our findings. Our model that uses a Gaussian shaped dynamic polarisability rather than a spatial delta function is a major step in providing a self-consistent description for interparticle de-excitation processes at the limit of small separations

The Spanish Infrared Camera onboard the EUSO-BALLOON (CNES) flight on August 24, 2014

The EUSO-Balloon (CNES) campaign was held during Summer 2014 with a launch on August 24. In the gondola, next to the Photo Detector Module (PDM), a completely isolated Infrared camera was allocated. Also, a helicopter which shooted flashers flew below the balloon. We have retrieved the Cloud Top Height (CTH) with the IR camera, and also the optical depth of the nonclear atmosphere have been inferred with two approaches: The first one is with the comparison of the brightness temperature of the cloud and the real temperature obtained after the pertinent corrections. The second one is by measuring the detected signal from the helicopter flashers by the IR Camera, considering the energy of the flashers and the location of the helicopter

The atmospheric science of JEM-EUSO

An Atmospheric Monitoring System (AMS) is critical suite of instruments for JEM-EUSO whose aim is to detect Ultra-High Energy Cosmic Rays (UHECR) and (EHECR) from Space. The AMS comprises an advanced space qualified infrared camera and a LIDAR with cross checks provided by a ground-based and airborne Global Light System Stations. Moreover the Slow Data Mode of JEM-EUSO has been proven crucial for the UV background analysis by comparing the UV and IR images. It will also contribute to the investigation of atmospheric effects seen in the data from the GLS or even to our understanding of Space Weather