7,375 research outputs found
Wavefront and ray-density plots using seventh-order matrices
The optimization of an optical system benefits greatly from a study of its
aberrations and an identification of each of its elements' contribution to the
overall aberration figures. The matrix formalism developed by one of the
authors was the object of a previous paper and allows the expression of
image-space coordinates as high-order polynomials of object-space coordinates.
In this paper we approach the question of aberrations, both through the
evaluation of the wavefront evolution along the system and its departure from
the ideal spherical shape and the use of ray density plots. Using seventh-order
matrix modeling, we can calculate the optical path between any two points of a
ray as it travels along the optical system and we define the wavefront as the
locus of the points with any given optical path; the results are presented on
the form of traces of the wavefront on the tangential plane, although the
formalism would also permit sagital plane plots. Ray density plots are obtained
by actual derivation of the seventh-order polynomials.Comment: 15 pages, 5 figure
Prevention of vole damage in organic pomiculture
Vole damage is one of the most difficult phytosanitary problems to solve in organic
pomiculture. A survey conducted in 2002 among German fruit growers showed that 90
% of the farms suffered from this damage. The water vole (A. terrestris) revealed to be
the main pest in 80 % of the orchards. 61 % of the farmers announced a high interest in
the development of new preventive and control methods. To stop immigration of voles
into orchards a mechanical barrier system was developed and tested at two study sites
in Baden-Wuerttemberg and Rhineland-Palatinate. At each location barrier systems with
wire mesh (mesh size 10 mm) and polyolefine-foil were installed arround two 0.7 ha
study plots. Two unprotected plots were used as a control. The barriers were anchored
20 cm deep into the soil. 30 cm of the material protruded over the surface. Automatic
gates were installed for the entrance of vehicles. 4 persons needed approximately one
day to install a barrier around a plot with the size of 1 ha. Not only was the wire mesh
cheaper than the foil, it was permeable for wind, water and small beneficial organisms.
After installing the barrier systems, voles were removed from all plots. Snap trap boxes
were ranged along the outside of the barriers to catch migrating voles. A total of 33
water voles and 1263 common voles (M. arvalis) were captured on both study sites from
October 2002 to November 2003. During the study period a total of 5 water voles
immigrated into the first control plot and 6 settled into the other plot. Four water voles
entered two of the barrier protected plots by using fresh mole galleries. The other
protected plots stayed free from water voles. Simultaneous to the field studies, trials in
two enclosures were carried out in Muenster. The barriers kept all water voles outside
the protected plots. The results showed a high efficacy of the developed barrier system
Task-set switching with natural scenes: Measuring the cost of deploying top-down attention
In many everyday situations, we bias our perception from the top down, based on a task or an agenda. Frequently, this entails shifting attention to a specific attribute of a particular object or scene. To explore the cost of shifting top-down attention to a different stimulus attribute, we adopt the task-set switching paradigm, in which switch trials are contrasted with repeat trials in mixed-task blocks and with single-task blocks. Using two tasks that relate to the content of a natural scene in a gray-level photograph and two tasks that relate to the color of the frame around the image, we were able to distinguish switch costs with and without shifts of attention. We found a significant cost in reaction time of 23â31 ms for switches that require shifting attention to other stimulus attributes, but no significant switch cost for switching the task set within an attribute. We conclude that deploying top-down attention to a different attribute incurs a significant cost in reaction time, but that biasing to a different feature value within the same stimulus attribute is effortless
How expensive is vole damage?
Vole species, especially Arvicola terrestris and Microtus arvalis cause significant economical damage in organic pomiculture by gnawing the root system of trees. The importance of voles as pest organisms is well known. Nevertheless, the estimation of financial loss caused by voles is difficult for German fruit growers. We conducted a survey among organic fruit growers to get data on kind and amount of annual damage. Using the available publications and official statistics we calculated economical values of organic apple trees for different types of orchard processing and tree ages. Furthermore we calculated the number of trees lost due to voles in one year
Ensemble versus individual system in quantum optics
Modern techniques allow experiments on a single atom or system, with new
phenomena and new challenges for the theoretician. We discuss what quantum
mechanics has to say about a single system. The quantum jump approach as well
as the role of quantum trajectories are outlined and a rather sophisticated
example is given.Comment: Fundamental problems in quantum theory workshop, invited lecture. 11
pages Latex + 7 figures. To appear in Fortschr. d. Physi
Innovations in spatial planning as a social process â phases, actors, conflicts
The aim of this paper is to understand the social process of the emergence and institutionalization of innovations in spatial planning (which we describe as âsocial innovationsâ). The paper is based on a recently finished empirical and comparative study conducted in four distinct areas of spatial planning in Germany: urban design, neighbourhood development, urban regeneration and regional planning. The empirical cases selected in these areas encompass different topics, historical periods, degrees of maturity and spatial scales of innovation. As a temporal structure of the innovation processes in the different cases we identified five phases: âincubating, generating, formatting, stabilizing, adjustingâ. In a cross-comparison of the case studies and along these phases, we furthermore found typical (groups of) actors, tensions and conflicts. In the focus of our case analyses are the following dimensions: (1) the content of the innovations, (2) actors, networks and communities involved as well as (3) institutions and institutionalization
Quantum bit detector
We propose and analyze an experimental scheme of quantum nondemolition
detection of monophotonic and vacuum states in a superconductive toroidal
cavity by means of Rydberg atoms.Comment: 4 pages, 3 figure
National Endowment for the Arts v. Finley: Sinking Deeper into the Abyss of the Supreme Court\u27s Unintelligible Modern Unconstitutional Conditions Doctrine
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