Long-distance navigation in the wandering desert spider Leucorchestris arenicola: can the slope of the dune surface provide a compass cue?

Males of the nocturnal spider Leucorchestris arenicola (Araneae: Sparassidae) wander long distances over seemingly featureless dune surfaces in the Namib Desert searching for females. The spiders live in burrows to which they return after nearly every such excursion. While the outward path of an excursion may be a meandering search, the return path is often a nearly straight line leading towards the burrow. This navigational behaviour resembles that of path integration known from other arthropods, though on a much larger scale (over tens to hundreds of meters). Theoretically, precise navigation by path integration over long distances requires an external compass in order to adjust for inevitable accumulation of navigational errors. As a first step towards identifying any nocturnal compass cues used by the male spiders, a method for detailed 3-D recordings of the spider's paths was developed. The 3-D reconstructions of the paths revealed details about the processes involved in the spiders' nocturnal way of navigation. Analyses of the reconstructed paths suggest that gravity (slope of the dune surface) is an unlikely parameter used in path integration by the L. arenicola spider

Effect of shared information and owner behavior on showing in dogs (Canis familiaris)

Dogs’ production of referential communicative signals, i.e., showing, has gained increasing scientific interest over the last years. In this paper, we investigate whether shared information about the present and the past affects success and form of dog–human interactions. Second, in the context of showing, owners have always been treated as passive receivers of the dog’s signals. Therefore, we examined whether the owner’s behavior can influence the success and form of their dog’s showing behavior. To address these questions, we employed a hidden-object task with knowledgeable dogs and naïve owners. Shared information about the present was varied via the spatial set-up, i.e., position of hiding places, within dog–owner pairs, with two conditions requiring either high or low precision in indicating the target location. Order of conditions varied between pairs, representing differences in shared knowledge about the past (communication history). Results do not support an effect of communication history on either success or showing effort. In contrast, the spatial set-up was found to affect success and choice of showing strategies. However, dogs did not adjust their showing effort according to different spatial set-ups. Our results suggest that the latter could be due to the owner’s influence. Owner behavior generally increased the effort of their dog’s showing behavior which was stronger in the set-up requiring low showing precision. Moreover, our results suggest that owners could influence their dog’s showing accuracy (and thereby success) which, however, tended to be obstructive.Introduction Showing Shared information and the principle of least effort The present study Materials and methods subjects materials and set-up prodedure; pretest test design behavioral coding statistical analysis) Results overall success distribution of showing types effect of correct showing, condition and time on success effect of condition and time on showing effort correlation between showing accuracy and seconds effect of owner behavior on correct showing effect of owner behavior on showing effort) Discussion Communication about the hidden object’s location Sensitivity to spatial set‑up and communication history The principle of least effort and the owner’s influence on it Limitations and implications for future researc

Shouggie Shou, My Bairnie

https://digitalcommons.library.umaine.edu/mmb-vp/6738/thumbnail.jp

Investigation of a direction sensitive sapphire detector stack at the 5 GeV electron beam at DESY-II

Extremely radiation hard sensors are needed in particle physics experiments to instrument the region near the beam pipe. Examples are beam halo and beam loss monitors at the Large Hadron Collider, FLASH or XFEL. Currently artificial diamond sensors are widely used. In this paper single crystal sapphire sensors are considered as a promising alternative. Industrially grown sapphire wafers are available in large sizes, are of low cost and, like diamond sensors, can be operated without cooling. Here we present results of an irradiation study done with sapphire sensors in a high intensity low energy electron beam. Then, a multichannel direction-sensitive sapphire detector stack is described. It comprises 8 sapphire plates of 1 cm^2 size and 525 micro m thickness, metallized on both sides, and apposed to form a stack. Each second metal layer is supplied with a bias voltage, and the layers in between are connected to charge-sensitive preamplifiers. The performance of the detector was studied in a 5 GeV electron beam. The charge collection efficiency measured as a function of the bias voltage rises with the voltage, reaching about 10 % at 950 V. The signal size obtained from electrons crossing the stack at this voltage is about 22000 e, where e is the unit charge. The signal size is measured as a function of the hit position, showing variations of up to 20 % in the direction perpendicular to the beam and to the electric field. The measurement of the signal size as a function of the coordinate parallel to the electric field confirms the prediction that mainly electrons contribute to the signal. Also evidence for the presence of a polarisation field was observed.Comment: 13 pages, 7 figures, 3 table

A Performance Comparison Using HPC Benchmarks: Windows HPC Server 2008 and Red Hat Enterprise Linux 5

This document was developed with support from the National Science Foundation (NSF) under Grant No. 0910812 to Indiana University for ”FutureGrid: An Experimental, High-Performance Grid Test-bed.” Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.A collection of performance benchmarks have been run on an IBM System X iDataPlex cluster using two different operating systems. Windows HPC Server 2008 (WinHPC) and Red Hat Enterprise Linux v5.4 (RHEL5) are compared using SPEC MPI2007 v1.1, the High Performance Computing Challenge (HPCC) and National Science Foundation (NSF) acceptance test benchmark suites. Overall, we find the performance of WinHPC and RHEL5 to be equivalent but significant performance differences exist when analyzing specific applications. We focus on presenting the results from the application benchmarks and include the results of the HPCC microbenchmark for completeness

North-South cooperation through BIOTA: An interdisciplinary monitoring programme in arid and semi-arid southern Africa

Connecting disciplines in a north– South collaboration has many advantages: mutualisms evolve, synergies are created and spin-offs emerge. The BIOTA South (Biodiversity Monitoring Transect Analysis in southern Africa) programme, with its long-term vision to generate knowledge of biodiversity along a north–south transect in southern Africa, is providing opportunities for research, technology transfer and capacity building while focusing on potential solutions for critical challenges that face this environmentally vulnerable part of the subcontinen

Electronically highly cubic conditions for Ru in alpha-RuCl3

We studied the local Ru 4d electronic structure of alpha-RuCl3 by means of polarization dependent x-ray absorption spectroscopy at the Ru-L2,3 edges. We observed a vanishingly small linear dichroism indicating that electronically the Ru 4d local symmetry is highly cubic. Using full multiplet cluster calculations we were able to reproduce the spectra excellently and to extract that the trigonal splitting of the t2g orbitals is -12 $\pm10$ meV, i.e. negligible as compared to the Ru 4d spin-orbit coupling constant. Consistent with our magnetic circular dichroism measurements, we found that the ratio of the orbital and spin moments is 2.0, the value expected for a Jeff = 1/2 ground state. We have thus shown that as far as the Ru 4d local properties are concerned, alpha-RuCl3 is an ideal candidate for the realization of Kitaev physics