An effective method to read out large scintillator areas with precise timing

Using scintillator tile technology several square meters of plastic scintillator are read out by only two photomultiplier with a time precision of about 1.5 nsec. Two examples are discussed to build a detector based on this technology to search for cosmic muons and neutrinos.Comment: 8 pages, 9 figures. Contributed to Workshop on Scintillating Fiber Detectors (SCIFI97), Notre Dame, IN, 2-6 Nov 199

Silicon Waveguides and Ring Resonators at 5.5 {\mu}m

We demonstrate low loss ridge waveguides and the first ring resonators for the mid-infrared, for wavelengths ranging from 5.4 to 5.6 {\mu}m. Structures were fabricated using electron-beam lithography on the silicon-on-sapphire material system. Waveguide losses of 4.0 +/- 0.7 dB/cm are achieved, as well as Q-values of 3.0 k.Comment: 4 pages, 4 figures, includes supplemental material

Integrable Discretizations of Chiral Models

A construction of conservation laws for chiral models (generalized sigma-models on a two-dimensional space-time continuum using differential forms is extended in such a way that it also comprises corresponding discrete versions. This is achieved via a deformation of the ordinary differential calculus. In particular, the nonlinear Toda lattice results in this way from the linear (continuum) wave equation. The method is applied to several further examples. We also construct Lax pairs and B\"acklund transformations for the class of models considered in this work.Comment: 14 pages, Late

Functional and Molecular Aspects of Xenobiotic Transport in Choroid Plexus

The choroid plexus (CP) epithelium forms the blood-cerebrospinal fluid (CSF) barrier, which along with the blood-brain barrier (BBB) capillary endothelium maintains the fluid environment of the brain. The CP not only secretes CSF, but also transports potentially toxic xenobiotics and waste products of neural metabolism to the blood for eventual clearance in kidney and liver. For several decades it has been known that the CP is actively involved in removing organic anions and other organic compounds from the extra-cellular fluid (Pappenheimer et al., 1961; Villalobos et al., 2002; Miller et al., 2002; Breen et al., 2004; Baehr et al., in press). However, studying CP is difficult, due to complex morphology, anatomical location and small size of the tissue and little is known about the molecular mechanisms, functional complexity and hormonal regulation of organic anion secretion. To further elucidate the underlying mechanisms of organic anion transport across CP epithelium, a primary porcine CP cell culture model was established and characterized on a molecular and functional basis. All cultures were free of contaminating cells, developed intact monolayers and were fully differentiated. Expression of marker protein prealbumin was demonstrated in isolated CP epithelial cells (CPEC) using RT-PCR, immunostaining and Western blot analyses. Alkaline phosphatase and -glutamyl transferase were quantified and cerebrospinal fluid secretion was measured. In addition, two active transport proteins, the MDR1 gene product P-glycoprotein (Pgp) and the multidrug-resistance associated protein 1, were assessed by RT-PCR, immunohistological staining and in Western blots of isolated membrane fractions. Integrity of fully differentiated monolayers was ensured by TEER measurements as well as permeability analyses using marker compounds. Further, functional analyses of Pgp were carried out. Organic anion transport was studied in a mammalian (rat), a comparative elasmobranch and in the in vitro porcine CPEC culture model, using the model compound fluorescein-methotrexate (FL-MTX). FL-MTX transport was shown to be a specific and concentrative, Na+-dependent and metabolism-dependent two-step process. Finally, for the first time, these studies demonstrate that organic anion transport is regulated by protein kinase C (PKC) and PKA. Responsible hormones remain to be identified

Testrun results from prototype fiber detectors for high rate particle tracking

A fiber detector concept has been realized allowing to registrate particles within less than 100 nsec with a space point precision of about 0.1 mm at low occupancy. Three full size prototypes have been build by different producers and tested at a 3 GeV electron beam at DESY. After 3 m of light guides 8-10 photoelectrons were registrated by multichannel photomultipliers providing an efficiency of more than 99%. Using all available data a resolution of 0.086 mm was measured.Comment: 18 pages, 17 figure

Differential Calculi on Commutative Algebras

A differential calculus on an associative algebra A is an algebraic analogue of the calculus of differential forms on a smooth manifold. It supplies A with a structure on which dynamics and field theory can be formulated to some extent in very much the same way we are used to from the geometrical arena underlying classical physical theories and models. In previous work, certain differential calculi on a commutative algebra exhibited relations with lattice structures, stochastics, and parametrized quantum theories. This motivated the present systematic investigation of differential calculi on commutative and associative algebras. Various results about their structure are obtained. In particular, it is shown that there is a correspondence between first order differential calculi on such an algebra and commutative and associative products in the space of 1-forms. An example of such a product is provided by the Ito calculus of stochastic differentials. For the case where the algebra A is freely generated by `coordinates' x^i, i=1,...,n, we study calculi for which the differentials dx^i constitute a basis of the space of 1-forms (as a left A-module). These may be regarded as `deformations' of the ordinary differential calculus on R^n. For n < 4 a classification of all (orbits under the general linear group of) such calculi with `constant structure functions' is presented. We analyse whether these calculi are reducible (i.e., a skew tensor product of lower-dimensional calculi) or whether they are the extension (as defined in this article) of a one dimension lower calculus. Furthermore, generalizations to arbitrary n are obtained for all these calculi.Comment: 33 pages, LaTeX. Revision: A remark about a quasilattice and Penrose tiling was incorrect in the first version of the paper (p. 14

Oceanic Rossby waves drive inter-annual predictability of net primary production in the central tropical Pacific

In the Pacific Ocean, off-equatorial Rossby waves (RWs), initiated by atmosphere-ocean interaction, modulate the inter-annual variability of the thermocline. In this study, we explore the resulting potential gain in predictability of central tropical Pacific primary production, which in this region strongly depends on the supply of macronutrients from below the thermocline. We use a decadal prediction system based on the Max Planck Institute Earth system model to demonstrate that for the time period 1998-2014 properly initialized RWs explain an increase in predictability of net primary productivity (NPP) in the off-equatorial central tropical Pacific. We show that, for up to 5 years in advance, predictability of NPP derived from the decadal prediction system is significantly larger than that derived from persistence alone, or an uninitialized historical simulation. The predicted signal can be explained by the following mechanism: off-equatorial RWs are initiated in the eastern Pacific and travel towards the central tropical Pacific on a time scale of 2-6 years. On their arrival the RWs modify the depths of both thermocline and nutricline, which is fundamental to the availability of nutrients in the euphotic layer. Local upwelling transports nutrients from below the nutricline into the euphotic zone, effectively transferring the RW signal to the near-surface ocean. While we show that skillful prediction of central off-equatorial tropical Pacific NPP is possible, we open the door for establishing predictive systems for food web and ecosystem services in that region