Compression of ultrashort UV pulses in a self-defocusing gas

Compression of UV femtosecond laser pulses focused into a gas cell filled with xenon is reported numerically. With a large negative Kerr index and normal dispersion, xenon promotes temporal modulational instability (MI) which can be monitored to shorten ~ 100 fs pulses to robust, singly-peaked waveforms exhibiting a fourfold compression factor. Combining standard MI theory with a variational approach allows us to predict the beam parameters suitable for efficient compression. At powers < 30 MW, nonlinear dispersion is shown to shift the pulse temporal profile to the rear zone.Comment: 4 pages, 4 figure

Observations of Galactic Gamma-Ray Sources with H.E.S.S

H.E.S.S. results from the first three years of nominal operation are presented. Among the many exciting measurements that have been made, most gamma-ray sources are of Galactic origin. I will concentrate here on an overview of Galactic observations and summarise and discuss observations of selected objects of the different source types.Comment: 13 pages, 10 figures, based on a talk presented at the workshop 'Energy Budget in the High Energy Universe', Kashiwa, Japan 22 - 24 February 200

Feed the crop or feed the soil? A case study in leek (Allium porrum L.)

The purpose of our study was to assess the role of soil quality parameters in leek production and to assess their importance relative to nitrogen (N) applied as fertilizer. We selected seven (2004) and seven (2005) fields on leek farms in the southern sand district of the Netherlands and measured physical and chemical soil properties. Three N rates (0, 90 and 360 kg N ha-1 as calcium ammonium nitrate; denoted as N0, N90, N360) were given at each site. Leek (Allium porrum L. ‘Kenton’) was planted in June-July and harvested next spring. Measured response variables were shoot biomass yield (gross and net, fresh and dry) and shoot N-yield (gross, net) at harvest. Pooled data from both years were analyzed by linear regression. N uptake from unfertilized soil (U0), and topsoil properties soluble organic N (Nso), soil organic matter content (SOM), total nitrogen (Ntot) and water content at field capacity (Wfc) all had large and significant impacts on biomass yield and N yield. These five properties (Xi) were correlated and were therefore used alternately in regression models. Effects of soil properties found by regression refer to a shift in the regressor from its 25% to its 75% percentile value, and are expressed here relative to mean yields (both years, all treatments). This normalization facilitates direct comparison with fertilizer effects. Normalized effects of Xi variables on biomass yield and N yield were between +0.10 and +0.20. Effects of fertilizer application at N90 were about +0.10 (biomass yield) and +0.20 (N yield). At N360 effects were +0.10 to +0.20 (biomass yield) and +0.30 to +0.40 (N-yield). So while N fertilizer strongly promoted N-uptake relative to growth, soil properties Xi affected growth and N yield more evenly. With shifts in Xi variables, dry matter produced per kg additional N uptake was 1.49 to 1.77 times larger than with extra N uptake resulting from fertilizer application at N90. This indicates that soil properties Xi promoted yield not only via enhanced N supply. Besides effects of Xi properties and N fertilizer, we found significant effects of year, soil texture, pH and inorganic soil N at planting, on biomass yield. Texture parameters Fsfine (50-210 µm) and M50 (median of particle size in 50-2000 µm fraction) had large and additive positive effects on net fresh yield. Apparent recovery of fertilizer N (ANR) averaged 0.35 at N90, and 0.17 at N360. ANR decreased with higher Nso and increased with higher Wfc

Challenges and possibilities in telecare: Realist evaluation of a Norwegian telecare project

This thesis reports from a telecare evaluation in a Norwegian municipality (2012-2016). The project was established to provide domestic results from a hitherto new field in the country to underpin future policy. This evaluation includes pre- and post-implementation data collection, which has been scarce in telecare. The methodological approach was realist evaluation that seeks to explore how telecare works, for whom, why and in which circumstances – or why it does not work. The research aimed to explore the hypothesis elicited from national policy documents: ‘If telecare is used, then people are enabled to remain safe in their own home for longer’. Various methods were used to gather data from multiple stakeholders as they have different knowledge about how the implementation developed. The methods in this evaluation included literature reviews, observations, and sequential interviews with users and relatives in addition to sequential focus groups with frontline staff. Realist evaluation was particularly suitable in demonstrating how and why telecare is useful to some users but not to others. Telecare had to match users’ abilities and needs for them to benefit from it. Telecare operates in a dynamic context, and therefore requires adjustment according to the user’s current situation, taking into account changes as they occur. This appears to have been often underestimated. Telecare holds a different position from other devices and technologies in people’s everyday life, which also needs to be acknowledged. Correct assessment is significant for users to obtain the intended effect from telecare. When telecare is correctly adjusted to users, it increases safety, which is essential for enabling older people to remain living at home. Several challenges in establishing telecare projects are identified and alternative ways to understand multi-disciplinary partnerships are suggested. By using realist evaluation the findings are nuanced and point to elements that are significant for achieving the intended outcomes

Moonlight drives ocean-scale mass vertical migration of zooplankton during the Arctic winter

The creation of the pan-Arctic archive of ADCP data was supported by the UK Natural Environment Research Council (NERC) (Panarchive: NE/H012524/1 and SOFI: NE/F012381/1) as was mooring work in Svalbard (Oceans 2025 and Northern Sea Program). Moorings were also supported by the Research Council of Norway (NFR) projects: Circa (214271), Cleopatra (178766), Cleopatra II (216537), and Marine Night (226471).In extreme high-latitude marine environments that are without solar illumination in winter, light-mediated patterns of biological migration have historically been considered non-existent [1]. However, diel vertical migration (DVM) of zooplankton has been shown to occur even during the darkest part of the polar night, when illumination levels are exceptionally low [2 and 3]. This paradox is, as yet, unexplained. Here, we present evidence of an unexpected uniform behavior across the entire Arctic, in fjord, shelf, slope and open sea, where vertical migrations of zooplankton are driven by lunar illumination. A shift from solar-day (24-hr period) to lunar-day (24.8-hr period) vertical migration takes place in winter when the moon rises above the horizon. Further, mass sinking of zooplankton from the surface waters and accumulation at a depth of ∼50 m occurs every 29.5 days in winter, coincident with the periods of full moon. Moonlight may enable predation of zooplankton by carnivorous zooplankters, fish, and birds now known to feed during the polar night [4]. Although primary production is almost nil at this time, lunar vertical migration (LVM) may facilitate monthly pulses of carbon remineralization, as they occur continuously in illuminated mesopelagic systems [5], due to community respiration of carnivorous and detritivorous zooplankton. The extent of LVM during the winter suggests that the behavior is highly conserved and adaptive and therefore needs to be considered as “baseline” zooplankton activity in a changing Arctic ocean [6, 7, 8 and 9].Publisher PDFPeer reviewe

Prevalence of Rabbit Hemorrhagic Disease (RHD) in wild rabbits (Oryctolagus cuniculus) in Flanders, Belgium, 1999-2002

During the period of July 1999 through June 2002, carcasses of wild rabbits that had been shot or found dead and livers originating from wild rabbits that had been shot for consumption were collected in Flanders. One hundred and twelve carcasses were suitable for necropsy and histological and bacteriological analysis; histological analysis was possible in 41 livers. Considering the 112 rabbit carcasses only, Rabbit Hemorrhagic Disease (RHD) was found to be present in 33.9% of the cases. RHD was the most prevalent wild rabbit pathology detected in this study, before staphylococcosis (12.5%), and myxomatosis (10.7%). None of the liver samples from rabbits shot for consumption were positive for RHD. Of the 38 histologically RHD positive samples, 24 were analyzed with the hemagglutination (HA) technique, yielding 58.3% positive results. Seven samples that were histologically positive for RHD but HA negative were examined by transmission electron microscopy and were found positive for calicivirus. This proves that HA-negative RHD strains are circulating in the Flemish wild rabbit population

Bell's Theorem and Nonlinear Systems

For all Einstein-Podolsky-Rosen-type experiments on deterministic systems the Bell inequality holds, unless non-local interactions exist between certain parts of the setup. Here we show that in nonlinear systems the Bell inequality can be violated by non-local effects that are arbitrarily weak. Then we show that the quantum result of the existing Einstein-Podolsky-Rosen-type experiments can be reproduced within deterministic models that include arbitrarily weak non-local effects.Comment: Accepted for publication in Europhysics Letters. 14 pages, no figures. In the Appendix (not included in the EPL version) the author says what he really thinks about the subjec

Ethnically Biased? Experimental Evidence from Kenya

Ethnicity has been shown to shape political, social, and economic behavior in Africa, but the underlying mechanisms remain contested. We utilize lab experiments to isolate one mechanism - an individual's bias in favor of coethnics and against non-coethnics - that has been central in both theory and in the conventional wisdom about the impact of ethnicity. We employ an unusually rich research design involving a large sample of 1300 participants from Nairobi, Kenya; the collection of multiple rounds of experimental data with varying proximity to national elections; within-lab priming conditions; both standard and novel experimental measures of coethnic bias; and an implicit association test (IAT). We find very little evidence of an ethnic bias in the behavioral games, which runs against the common presumption of extensive coethnic bias among ordinary Africans and suggests that mechanisms other than a coethnic bias in preferences must account for the associations we see in the region between ethnicity and political, social, and economic outcomes