The role of extraterrestrial particles in the formation of the ozone hole. Part I: The concentration of extraterrestrial particles at ozone hole formation

The object of Part I of this paper is to estimate the concentration of extraterrestrial particles in the ozone layer over South Pole, Antarctica, during ozone hole formation. This estimate is based on an analysis of microscopic magnetic spherules collected in an extended program of atmospheric sampling. Spherules are shown to be of extraterrestrial origin and serve as markers for the larger class of less distinguished extraterrestrial particles. These particles settle to ground level as aggregates formed in a stratospheric ice crystal coalescence process. Specific spherule arrivals at ground level are strongly associated with apparent ozone depletion episodes during formation of the ozone hole. The origin of these spherules is a major stream of extraterrestrial particles independent of known meteor showers. The variability in its intensity from year to year corresponds to the variability in ozone depletion in the ozone hole itself. A quantitative theory based on these spherule arrivals and this coalescence process implies that the concentration of extraterrestrial particles at ozone hole formation lies between500 and 2000 / m3. A mechanism is proposed in Part II of this paper by which particle concentrations in this range are sufficient to produce the ozone hole

The role of extraterrestrial particles in the formation of the ozone hole. Part II: The action of extraterrestrial particles at ozone hole formation

The object of this paper is to assess the possibility that particles of extraterrestrial origin play a significant role in the formation of the ozone hole. Preliminary analysis shows that air in the ozone layer over South Pole tends to be stable, saturated, and essentially particle-free just prior to ozone hole formation. Further, gas-phase reactions generally responsible for ozone loss in the atmosphere are unrelated to ozone hole formation. According to Part I of this paper, a massive influx of extraterrestrial particles invades the ozone layer over South Pole precisely at ozone hole formation. We hypothesize that ozone diffuses to the surfaces of these particles, where it is adsorbed and enters into a series of reactions leading to its net loss in the atmosphere. To test this hypothesis, we have constructed a mathematical model of this process. We have also identified principal features in ozone hole formation in field data for 1986. These include the start of ozone hole formation three weeks before sunrise, a spike in ozone concentration at sunrise, and cessation in ozone depletion before disintegration of the circumpolar vortex. Projections of the model are in good agreement with these features. To conclude, this analysis has developed strong evidence that the ozone hole is primarily a natural phenomenon caused by the depletion of ozone in reactions on the surfaces of extraterrestrial particles

Two-axis bend measurement with Bragg gratings in multicore optical fiber

We describe what is to our knowledge the first use of fiber Bragg gratings written into three separate cores of a multicore fiber for two-axis curvature measurement. The gratings act as independent, but isothermal, fiber strain gauges for which local curvature determines the difference in strain between cores, permitting temperature-independent bend measurement. (C) 2003 Optical Society of America

Top-down and bottom-up approach to competence management implementation: A case of two central banks Abordagem top-down (de cima para baixo) e bottom-up (de baixo para cima) para a implementação de gestão de competências: O caso de dois bancos centrais

Abstract The primary aim of this paper is to evaluate the contribution that competence based approaches to staff management can and ought to make to the overall effectiveness of organisations. The importance of competencies and their proper management is broadly acknowledged in the literature, and the first part of the paper is a literature review. This is followed with a comparison of the design and implementation of two competence management projects that were introduced in two central banks, one of a western European nation, and the other of a central European nation. There is a brief presentation of two fundamental approaches to competence management implementation in organization (top-down (directive) and bottom-up (participative)), and this is juxtaposed with the actual implementation of competence management model that took place in two central banks. What ensues from the comparison is the identification of potential threats to the implementation of competence management models in organizations, accompanied by suggestions on how to counteract them. Keywords: Strategic HRM, competencies, competence management, organisation development, HR development strategies. Resumo O objetivo principal deste trabalho é avaliar o contributo que as abordagens baseadas nas competências na gestão do pessoal pode e deve dar para a eficácia global das organizações. A primeira parte do artigo faz uma revisão da literatura, na qual a importância das competências e da sua correta gestão é amplamente reconhecida. Segue-se uma comparação entre o desenho e implementação de dois projetos de gestão de competências que foram introduzidas em dois bancos centrais, um de um país da Europa Ocidental e outro de um país da Europa Central. Há uma breve apresentação de duas abordagens fundamentais para a implementação da gestão de competências numa organização (topdown (diretiva) e bottom-up (participativa)), sendo isto justaposto com a implementação do modelo de gestão de competências que ocorreu em dois bancos centrais

Protons accelerated in the target normal sheath acceleration regime by a femtosecond laser

Advanced targets based on thin films of graphene oxide covered by metallic layers have been irradiated at high laser intensity (∼1019 W/cm2) with 40 fs laser pulses to investigate the forward ion acceleration in the target normal sheath acceleration regime. A time-of-flight technique was employed with silicon-carbide detectors and ion collectors as fast on-line plasma diagnostics. At the optimized conditions of the laser focus position with respect to the target surface was measured the maximum proton energy using Au metallic films. A maximum proton energy of 2.85 MeV was measured using the Au metallization of 200 nm. The presence of graphene oxide facilitates the electron crossing of the foil minimizing the electron scattering and increasing the electric field driving the ion acceleration. The effect of plasma electron density control using the graphene oxide is presented and discussed

Study of shock waves generation, hot electron production and role of parametric instabilities in an intensity regime relevant for the shock ignition

We present experimental results at intensities relevant to Shock Ignition obtained at the sub-ns Prague Asterix Laser System in 2012 . We studied shock waves produced by laser-matter interaction in presence of a pre-plasma. We used a first beam at 1ω (1315 nm) at 7 × 10 13 W/cm 2 to create a pre-plasma on the front side of the target and a second at 3ω (438 nm) at ∼ 10 16 W/cm 2 to create the shock wave. Multilayer targets composed of 25 (or 40 μm) of plastic (doped with Cl), 5 μm of Cu (for Kα diagnostics) and 20 μm of Al for shock measurement were used. We used X-ray spectroscopy of Cl to evaluate the plasma temperature, Kα imaging and spectroscopy to evaluate spatial and spectral properties of the fast electrons and a streak camera for shock breakout measurements. Parametric instabilities (Stimulated Raman Scattering, Stimulated Brillouin Scattering and Two Plasmon Decay) were studied by collecting the back scattered light and analysing its spectrum. Back scattered energy was measured with calorimeters. To evaluate the maximum pressure reached in our experiment we performed hydro simulations with CHIC and DUED codes. The maximum shock pressure generated in our experiment at the front side of the target during laser-interaction is 90 Mbar. The conversion efficiency into hot electrons was estimated to be of the order of ∼ 0.1% and their mean energy in the order ∼50 keV. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributio

Modeling Small Scale Impacts of Multi-Purpose Platforms: An Ecosystem Approach

Aquaculture and marine renewable energy are two expanding sectors of the Blue Economy in Europe. Assessing the long-term environmental impacts in terms of eutrophication and noise is a priority for both the EU Water Framework Directive and the Marine Strategy Framework Directive, and cumulative impacts will be important for the Maritime Spatial Planning under the Integrated Maritime Policy. With the constant expansion of aquaculture production, it is expected that farms might be established further offshore in more remote areas, as high-energy conditions offer an opportunity to generate more power locally using Marine Renewable Energy (MRE) devices. A proposed solution is the co-location of MRE devices and aquaculture systems using Multi-Purpose Platforms (MPPs) comprising offshore wind turbines (OWTs) that will provide energy for farm operations as well as potentially shelter the farm. Disentangling the impacts, conflicts and synergies of MPP elements on the surrounding marine ecosystem is challenging. Here we created a high-resolution spatiotemporal Ecospace model of the West of Scotland, in order to assess impacts of a simple MPP configuration on the surrounding ecosystem and how these impacts can cascade through the food web. The model evaluated the following specific ecosystem responses: (i) top-down control pathways due to distribution changes among top-predators (harbor porpoise, gadoids and seabirds) driven by attraction to the farming sites and/or repulsion/killing due to OWT operations; (ii) bottom-up control pathways due to salmon farm activity providing increasing benthic enrichment predicated by a fish farm particle dispersal model, and sediment nutrient fluxes to the water column by early diagenesis of organic matter (recycled production). Weak responses of the food-web were found for top-down changes, whilst the results showed high sensitivity to increasing changes of bottom-up drivers that cascaded through the food-web from primary producers and detritus to pelagic and benthic consumers, respectively. We assessed the sensitivity of the model to each of these impacts and the cumulative effects on the ecosystem, discuss the capabilities and limitations of the Ecospace modeling approach as a potential tool for marine spatial planning and the impact that these results could have for the Blue Economy and the EU’s New Green Deal

Angular distributions of ions emitted from laser plasma produced at various irradiation angles and laser intensities

AbstractAngular distributions of currents and velocities (energies) of ions produced at various target irradiation angles and laser intensities ranged from 1010 W/cm2 to 1017 W/cm2 were analyzed. It was confirmed that for low laser intensities the ion current distributions are always peaked along the target normal. However, at laser intensities comparable to or higher than 1014 W/cm2, the preferred direction of ion emission strongly depends on the irradiation geometry (laser focus setting, the irradiation angle), and can be off the target normal. This is very likely caused by the non-linear interaction of the laser beam with produced plasma, in particular, by the action of ponderomotive forces and the laser beam self-focusing

Nonlinear excitations in CsNiF3 in magnetic fields perpendicular to the easy plane

Experimental and numerical studies of the magnetic field dependence of the specific heat and magnetization of single crystals of CsNiF3 have been performed at 2.4 K, 2.9 K, and 4.2 K in magnetic fields up to 9 T oriented perpendicular to the easy plane. The experimental results confirm the presence of the theoretically predicted double peak structure in the specific heat arising from the formation of nonlinear spin modes. The demagnetizing effects are found to be negligible, and the overall agreement between the data and numerical predictions is better than reported for the case when the magnetic field was oriented in the easy plane. Demagnetizing effects might play a role in generating the difference observed between theory and experiment in previous work analyzing the excess specific heat using the sine-Gordon model.Comment: 6 pages, 5 figures, submitted to Phys. Rev.