Two tone response of radiofrequency signals using the voltage output of a Superconducting Quantum Interference Filter

In the presence of weak time harmonic electromagnetic fields, Superconducting Quantum Interference Filters (SQIFs) show the typical behavior of non linear mixers. The SQIFs are manufactured from high-T_c grain boundary Josephson junctions and operated in active microcooler. The dependence of dc voltage output V_dc vs. static external magnetic field B is non-periodic and consists of a well pronounced unique dip at zero field, with marginal side modulations at higher fields. We have successfully exploited the parabolic shape of the voltage dip around B=0 to mix quadratically two external time harmonic rf-signals, at frequencies f_1 and f_2 below the Josephson frequency f_J, and detect the corresponding mixing signal at f_1-f_2. When the mixing takes place on the SQIF current-voltage characteristics the component at 2f_2 - f_1 is present. The experiments suggest potential applications of a SQIF as a non-linear mixing device, capable to operate at frequencies from dc to few GHz with a large dynamic range.Comment: 10 pages, 3 Figures, submitted to J. Supercond. (as proceeding of the HTSHFF Symposium, June 2006, Cardiff

Scale morphology and specialized dorsal scales of a new teleosteomorph fish from the Aptian of West Gondwana

Scales of a new species of Teleosteomorpha from the continental Aptian of the south of South America are studied. These neopterygians are from the La Cantera Formation in central Argentina, and were previously identified as Pholidophoriformes. They present ganoid scales; most of them are rhombic with well-developed peg-and-socket articulations and possessing a smooth surface. They have a straight posterior margin, but occasionally, some scales of the flank have a sinuous posterior margin with one or two serrations. The shape of the scales varies along the body from large, rectangular and deeper than long scales behind the head to the preanal region to smaller and rhomboidal scales in the caudal region. There are a few horizontal rows along the flank and about 32 lateral line scales. Thick, round ganoid scales are present in the prepelvic region close to the ventral margin. The round and rhombic scales present growth lines, which form concentric ridges on the external side. A characteristic row of deep scales forms the dorsal margin on each side of the body; a row of median ridge scales is not present. This is a unique feature of the studied fishes. Scutes covered with unornamented ganoine precede the pelvic, dorsal, and anal fins, as well as the dorsal and ventral margins of the caudal fin. The posterior margin of the dorsal lobe of the caudal fin is formed by a single line of scales, which continues and covers the base of the first principal caudal ray. Histological studies reveal a lepisosteoid-scale type with multiple ganoine layers, lack of dentine, and the presence of canaliculi of Williamson. The macro- and micromorphology of the scales shows features that are found in other teleosteomorphs, but also in other neopterygians

Enhancement of the ferromagnetic order of graphite after sulphuric acid treatment

We have studied the changes in the ferromagnetic behavior of graphite powder and graphite flakes after treatment with diluted sulphuric acid. We show that this kind of acid treatment enhances substantially the ferromagnetic magnetization of virgin graphite micrometer size powder as well as in graphite flakes. The anisotropic magnetoresistance (AMR) amplitude at 300 K measured in a micrometer size thin graphite flake after acid treatment reaches values comparable to polycrystalline cobalt.Comment: 3.2 pages, 4 figure

A Porolepiform Rhipidistian from the Lower Devonian of the Canadian Arctic

A holoptychiid fish is described from the Lower Devonian of Arctic Canada. The new form is distinct from other holoptychiids by the presence of a large supraorbital bone and a boomerang-shaped tabular. Nasogaluakus n. gen. is the oldest and most primitive holoptychiid based on a phylogenetic analysis of porolepiforms and their closest relatives. The sequence of the genera corresponds to their stratigraphic appearance. Ein Holoptychiide aus dem Unterdevon der kanadischen Arktis wird beschrieben. Er unterscheidet sich durch ein großes Supraorbitale und die Bumerang-Form des Tabulare von allen übrigen Holoptychiiden. Nasogaluakus n. gen. ist der älteste und primitivste Holoptychiide, was durch eine phylogenetische Analyse der Porolepiformes belegt wird. Die Abfolge der Gattungen in diesem Verwandtschaftsschema stimmt mit ihrem zeitlichen Auftreten überein. doi:10.1002/mmng.20000030106</a

Adsorptionsuntersuchungen an Organokieselsäurepolymeren

BET-Oberflächen und Isothermen von n-Hexan, Benzen, Wasser und Stickstoff wurden an vier Organokieselsäurepolymeren vermessen, die sich im Vernetzungsgrad der Doppelvierring-Kieselsäureeinheiten Si8O20 und in der Struktur der Brücken unterscheiden. Ein Polymer ist mikroporös, die anderen sind makroporös. Alle Polymere verhalten sich hydrophob. Neben der Adsorption tritt Quellung bei der Einwirkung organischer Adsorptive auf. Die Zusammenhänge zwischen der Länge der Brücken und der Porosität werden diskutiert

The effectiveness of imperfect weighting in advice taking

We investigate decision-making in the Judge-Advisor-System where one person, the "judge", wants to estimate the number of a certain entity and is given advice by another person. The question is how to combine the judge's initial estimate and that of the advisor in order to get the optimal expected outcome. A previous approach compared two frequently applied strategies, taking the average or choosing the better estimate. In most situations, averaging produced the better estimates. However, this approach neglected a third strategy that judges frequently use, namely a weighted mean of the judges' initial estimate and the advice. We compare the performance of averaging and choosing to weighting in a theoretical analysis. If the judge can, without error, detect ability differences between judge and advisor, a straight-forward calculation shows that weighting outperforms both of these strategies. More interestingly, after introducing errors in the perception of the ability differences, we show that such emph{imperfect} weighting may or may not be the optimal strategy. The relative performance of imperfect weighting compared to averaging or choosing depends on the size of the actual ability differences as well as the magnitude of the error. However, for a sizeable range of ability differences and errors, weighting is preferable to averaging and more so to choosing. Our analysis expands previous research by showing that weighting, even when imperfect, is an appropriate advice taking strategy and under which circumsances judges benefit most from applying it

The Influence of Length of Storage of Bovine Semen on Conception Rate under Field Conditions

It is the purpose of this study to determine whether under conditions of routine handling in artificial breeding associations there is a decline in semen fertility from day to day and also to determine the magnitude of this decline. Tabulation of such data will not only be of value in determining the effect of frequent semen collection on the over-all artificial breeding results but will also serve as a basis of comparison in investigational work directed toward increasing the efficiency of artificial breeding