Comment on "Scaling of atmosphere and ocean temperature correlations in observations and climate models"

In a recent letter [K. Fraedrich and R. Blender, Phys. Rev. Lett. 90, 108501 (2003)], Fraedrich and Blender studied the scaling of atmosphere and ocean temperature. They analyzed the fluctuation functions F(s) ~ s^alpha of monthly temperature records (mostly from grid data) by using the detrended fluctuation analysis (DFA2) and claim that the scaling exponent alpha over the inner continents is equal to 0.5, being characteristic of uncorrelated random sequences. Here we show that this statement is (i) not supported by their own analysis and (ii) disagrees with the analysis of the daily observational data from which the grid monthly data have been derived. We conclude that also for the inner continents, the exponent is between 0.6 and 0.7, similar as for the coastline-stations.Comment: 1 page with 2 figure

Planar Waveguide from PPV Derivatives

Abstract. We report in this paper the result of thin film fabrication of MEH-PPV and MEH-PPB having good optical transparency and low surface roughness suitable for planar waveguide application. The linear optical properties of the polymers were characterized using reflectometry and prism coupling, while the non-linear optical property was measured by means of optical third harmonic generation (THG). The waveguide attenuation of the polymer films was determined by employing prism coupling set-up equipped with a photodiode array detector. The MEH-PPV waveguide film was shown to have a very low attenuation of 0.5 dB cm-1 at 1064 nm yielding an unprecedentedly high figure of merits of 11 at 1 GW/cm2. Pandu Gelombang Planar dari Turunan PPVSari. Dalam tulisan ini dilaporkan fabrikasi film tipis polimer MEH-PPV dan MEH-PPB yang mempunyai transparansi optik tinggi dan permukaan yang halus sehingga cocok untuk aplikasi pandu gelombang planar. Sifat optic linier dari polimer yang bersangkutan diukur dengan teknik reflektometri dan kopling prisma dan sifat optic nonlinier diukur dengan metoda third harmonic generation (THG). Selanjutnya, atenuasi pandu gelombang dari film polimer yang bersangkutan diukur dengan konfigurasi kopling prisma dan detector diode arrat. Film pandu gelombang yang dihasilkan dalam eksperimen ini memiliki atenuasi rendah sebesar 0.5 dB cm-1 pada panjang gelombang 1064 nm dan menghasilkan "figure of merits" (FOM) sebesar 11 pada intensitas 1 GW/cm2 yang merupakan nilai tertinggi sejauh ini

Design considerations for table-top, laser-based VUV and X-ray free electron lasers

A recent breakthrough in laser-plasma accelerators, based upon ultrashort high-intensity lasers, demonstrated the generation of quasi-monoenergetic GeV-electrons. With future Petawatt lasers ultra-high beam currents of ~100 kA in ~10 fs can be expected, allowing for drastic reduction in the undulator length of free-electron-lasers (FELs). We present a discussion of the key aspects of a table-top FEL design, including energy loss and chirps induced by space-charge and wakefields. These effects become important for an optimized table-top FEL operation. A first proof-of-principle VUV case is considered as well as a table-top X-ray-FEL which may open a brilliant light source also for new ways in clinical diagnostics.Comment: 6 pages, 4 figures; accepted for publication in Appl. Phys.

Competition for inorganic and organic forms of nitrogen and phosphorous between phytoplankton and bacteria during an <i>Emiliania huxleyi</i> spring bloom

Using ¹⁵N and ³³P, we measured the turnover of organic and inorganic nitrogen (N) and phosphorus (P) substrates, and the partitioning of N and P from these sources into two size fractions of marine osmotrophs during the course of a phytoplankton bloom in a nutrient manipulated mesocosm. The larger size fraction (&gt;0.8 μm), mainly consisting of the coccolithophorid <i>Emiliania huxleyi</i>, but also including an increasing amount of large particle-associated bacteria as the bloom proceeded, dominated uptake of the inorganic forms NH₄⁺, NO₃^&minus;, and PO₄^3&minus;. The uptake of N from leucine, and P from ATP and dissolved DNA, was initially dominated by the 0.8&ndash;0.2 μm size fraction, but shifted towards dominance by the &gt;0.8 μm size fraction as the system turned to an increasing degree of N-deficiency. Normalizing uptake to biomass of phytoplankton and heterotrophic bacteria revealed that organisms in the 0.8&ndash;0.2 μm size fraction had higher specific affinity for leucine-N than those in the &gt;0.8 μm size fraction when N was deficient, whereas the opposite was the case for NH₄⁺. There was no such difference regarding the specific affinity for P substrates. Since heterotrophic bacteria seem to acquire N from organic compounds like leucine more efficiently than phytoplankton, our results suggest different structuring of the microbial food chain in N-limited relative to P-limited environments

Power-law persistence and trends in the atmosphere: A detailed study of long temperature records

We use several variants of the detrended fluctuation analysis to study the appearance of long-term persistence in temperature records, obtained at 95 stations all over the globe. Our results basically confirm earlier studies. We find that the persistence, characterized by the correlation C(s) of temperature variations separated by s days, decays for large s as a power law, C(s) ~ s^(-gamma). For continental stations, including stations along the coastlines, we find that gamma is always close to 0.7. For stations on islands, we find that gamma ranges between 0.3 and 0.7, with a maximum at gamma = 0.4. This is consistent with earlier studies of the persistence in sea surface temperature records where gamma is close to 0.4. In all cases, the exponent gamma does not depend on the distance of the stations to the continental coastlines. By varying the degree of detrending in the fluctuation analysis we obtain also information about trends in the temperature records.Comment: 5 pages, 4 including eps figure