"WissensWert - Wert des Wissens": Kooperativer Bericht von der ODOK 2012 - 14. Österreichisches Online-Informationstreffen und 15. Österreichischer Dokumentartag in Wels (12.-14. September 2012)

cooperative report of the Austrian library conference ODOK "worth knowing - the worth of knowledge", September 201

Nontunneling high-order harmonics from ultra-intense laser-driven tightly bound systems

High-order harmonic emission is investigated by numerical solution of the weakly relativistic, two-dimensional Schrödinger equation for the case of ultra-intense laser-driven tightly bound systems (for example, multiply charged ions such as O7+ exposed to laser fields of the order of 1018 W cm-2 at 248 nm). In contrast to their usual substantial decrease, the low-order harmonics having an energy less than the ionization potential exhibit a high efficiency (i.e. intense) plateau with a well defined cutoff. The shape of this plateau is found to depend on the shape of the binding potential. A classical “surfing” mechanism for the generation of these harmonics is proposed that does not involve tunneling and that nevertheless explains the observed cutoff. Thus we call them “nontunneling harmonics.” The significance of relativistic effects for these harmonics is investigated and found to be small, despite the high laser intensity, because of the absence of tunneling

Demonstration of a hybrid collisional soft-x-ray laser

Includes bibliographical references (pages 033803-4-033803-5).We report on a demonstration of x-ray-ultraviolet amplification following collisional excitation in a discharge-created plasma waveguide irradiated by a picosecond optical laser pulse. A capillary discharge was used to generate a sulfur plasma column with a large concentration of Ne-like ions and a radially concave electron density profile. The intense short laser pulse rapidly heated the electrons, producing amplification in the 3p 1S0-3s 1P1 transition of Ne-like S at 60.8 nm. The integrated gain-length product obtained exciting a 3-cm-long capillary with a 0.46-J short laser pulse is 6.8. The beam divergence was observed to decrease as a function of plasma column length, reaching 2.5 mrad for 30-mm-long capillaries. This hybrid laser pumping scheme could lead to a new generation of efficient tabletop soft-x-ray lasers

Laser Induced Non-Sequential Double Ionization Investigated at and Below the Threshold for Electron Impact Ionization

We use correlated electron–ion momentum measurements to investigate laserinduced non-sequential double ionization of Ar and Ne. Light intensities are chosen in a regime at and below the threshold where, within the rescattering model, electron impact ionization of the singly charged ion core is expected to become energetically forbidden. Yet we find Ar2+ ion momentum distributions and an electron–electron momentum correlation indicative of direct impactionization. Within the quasistatic model this may be understood by assuming that the electric field of the light wave reduces the ionization potential of the singly charged ion core at the instant of scattering. The width of the projection of the ion momentum distribution onto an axis perpendicular to the light beam polarization vector is found to scalewiththe square root of the peak electric field strength in the light pulse. A scaling like this is not expected from the phase space available after electron impact ionization. It may indicate that the electric field at the instant of scattering is usually different fromzero and determines the transverse momentum distribution. A comparison of our experimental results with several theoretical results is give

Fast capillary discharge plasma as a preformed medium for longitudinally pumped collisional x-ray lasers

Includes bibliographical references (pages 219-220).Simulations of plasma dynamics in a fast capillary discharge are presented. The temporal dependence of the plasma column's resistance validates the one-dimensional model that was used in the numerical simulations. Numerical analysis of the laser absorption determines the pump parameter range for efficient excitation of longitudinally pumped transient collisional x-ray lasers

COPERNICUS SENTINEL-2 DATA FOR THE DETERMINATION OF GROUNDWATER WITHDRAWAL IN THE MAGHREB REGION

Agriculture plays an important role in the economy of the Maghreb region. Most of the water needed for irrigation comes from pumping of the aquifers. A controlled pumping of the groundwater resources does not exist yet, thus, estimating the total water consumption for agricultural use only with in situ data is nearly impossible. In order to overcome this lack of information, Copernicus data are used for determining the groundwater withdrawal through agriculture in the Maghreb region. This paper presents an approach for estimating and monitoring crop water requirements in Tunisia based on multitemporal Sentinel-2 data. Using this multitemporal information, a thorough analysis of the different culture types over time is possible, from which a set of additional multitemporal features is deduced for crop type classification. In this paper, the contribution of those features is analyzed, showing a classification accuracy enhanced by 10 % with the multitemporal features. Furthermore, relying on existing methods and FAO standards for the estimation of crop water needs, the methodology aims to estimate the specific crop water consumption. The results of the water estimates are validated against delimited areas where estimates of the water consumption are available from the authorities. Finally, as the study is conducted within the framework of an international technical cooperation, the methodology aims to be reproducible and sustainable for local authorities. The particularity of the results presented here is that they are achieved through automatic processing and using exclusively Open Source solutions, deployable on simple workstations

Retrospective, observational study in patients receiving a dexamethasone intravitreal implant 0.7 mg for macular oedema secondary to retinal vein occlusion

PURPOSE To retrospectively evaluate the re-injection interval, efficacy and safety of dexamethasone (DEX) intravitreal implant 0.7 mg in the treatment of macular oedema (ME) due to retinal vein occlusion (RVO) in Germany in 2009-2012. METHODS Retrospective, multicentre, anonymised observational study of data collected from the first DEX implant 0.7 mg injection through 3-6 months following the last injection. Data were included if the patient was \textgreater18 years old, had a diagnosis of ME secondary to branch or central RVO, and received at least 2 DEX implant 0.7 mg injections during routine practice. RESULTS Data from 87 patients were analysed. Mean time to re-injection between first and second treatments was 5.03 months in the total RVO population, and 5.46 and 4.52 months for the branch and central RVO subpopulations, respectively. An intraocular pressure increase of \textgreater25 mm Hg was recorded in 20% of patients, and 34% of patients began treatment with anti-glaucoma medication, but surgery was not needed for this condition. CONCLUSIONS DEX implant 0.7 mg was found to be well tolerated and effective with repeat treatments in clinical practice

Stable laser-ion acceleration in the light sail regime

We present experimental results on ion acceleration with circularly polarized, ultrahigh contrast laser pulses focused to peak intensities of 5×1019 W cm-2 onto polymer targets of a few 10 nanometer thickness. We observed spatially and energetically separated protons and carbon ions that accumulate to pronounced peaks around 2 MeV containing as much as 6.5% of the laser energy. Based on particle-in-cell simulation, we illustrate that an early separation of heavier carbon ions and lighter protons creates a stable interface that is maintained beyond the end of the radiation pressure dominated acceleration process