Multiple CSLs for the body centered cubic lattice

Ordinary Coincidence Site Lattices (CSLs) are defined as the intersection of a lattice $\Gamma$ with a rotated copy $R\Gamma$ of itself. They are useful for classifying grain boundaries and have been studied extensively since the mid sixties. Recently the interests turned to so-called multiple CSLs, i.e. intersections of $n$ rotated copies of a given lattice $\Gamma$, in particular in connection with lattice quantizers. Here we consider multiple CSLs for the 3-dimensional body centered cubic lattice. We discuss the spectrum of coincidence indices and their multiplicity, in particular we show that the latter is a multiplicative function and give an explicit expression of it for some special cases.Comment: 4 pages, SSPCM (31 August - 7 September 2005, Myczkowce, Poland

Coincidence isometries of a shifted square lattice

We consider the coincidence problem for the square lattice that is translated by an arbitrary vector. General results are obtained about the set of coincidence isometries and the coincidence site lattices of a shifted square lattice by identifying the square lattice with the ring of Gaussian integers. To illustrate them, we calculate the set of coincidence isometries, as well as generating functions for the number of coincidence site lattices and coincidence isometries, for specific examples.Comment: 10 pages, 1 figure; paper presented at Aperiodic 2009 (Liverpool

Control of Visually Guided Behavior by Distinct Populations of Spinal Projection Neurons

A basic question in the field of motor control is how different actions are represented by activity in spinal projection neurons. We used a new behavioral assay to identify visual stimuli that specifically drive basic motor patterns in zebrafish. These stimuli evoked consistent patterns of neural activity in the neurons projecting to the spinal cord, which we could map throughout the entire population using in vivo two-photon calcium imaging. We found that stimuli that drive distinct behaviors activated distinct subsets of projection neurons, consisting, in some cases, of just a few cells. This stands in contrast to the distributed activation seen for more complex behaviors. Furthermore, targeted cell by cell ablations of the neurons associated with evoked turns abolished the corresponding behavioral response. This description of the functional organization of the zebrafish motor system provides a framework for identifying the complete circuit underlying a vertebrate behavior.Molecular and Cellular Biolog

Grain boundary energies and cohesive strength as a function of geometry

Cohesive laws are stress-strain curves used in finite element calculations to describe the debonding of interfaces such as grain boundaries. It would be convenient to describe grain boundary cohesive laws as a function of the parameters needed to describe the grain boundary geometry; two parameters in 2D and 5 parameters in 3D. However, we find that the cohesive law is not a smooth function of these parameters. In fact, it is discontinuous at geometries for which the two grains have repeat distances that are rational with respect to one another. Using atomistic simulations, we extract grain boundary energies and cohesive laws of grain boundary fracture in 2D with a Lennard-Jones potential for all possible geometries which can be simulated within periodic boundary conditions with a maximum box size. We introduce a model where grain boundaries are represented as high symmetry boundaries decorated by extra dislocations. Using it, we develop a functional form for the symmetric grain boundary energies, which have cusps at all high symmetry angles. We also find the asymptotic form of the fracture toughness near the discontinuities at high symmetry grain boundaries using our dislocation decoration model.Comment: 12 pages, 19 figures, changed titl

ВИКОРИСТАННЯ ІМПУЛЬСНОГО МЕТОДУ ВИМІРЮВАННЬ ДЛЯ ВИЗНАЧЕННЯ ПОШКОДЖЕННЯ КАБЕЛЬНИХ ЛІНІЙ

В даній роботі розглядаються особливості використання приладу ІКЛ-5 для швидкого визначення точності імпульсних вимірювань в пошкодженнях кабельних ліній і точного знаходження міста пошкодження кабелю. Для досягнення поставленої мети запропонований імпульсний метод, який визначає місце і характер пошкодження кабельних ліній. Обраний у роботі підхід дає можливість вимірювання при будьякому складному характері ушкодження. Завдяки цьому забезпечується зручність, простота і швидкість вимірювань

First results of the air shower experiment KASCADE

The main goals of the KASCADE (KArlsruhe Shower Core and Array DEtector) experiment are the determination of the energy spectrum and elemental composition of the charged cosmic rays in the energy range around the knee at ca. 5 PeV. Due to the large number of measured observables per single shower a variety of different approaches are applied to the data, preferably on an event-by-event basis. First results are presented and the influence of the high-energy interaction models underlying the analyses is discussed.Comment: 3 pages, 3 figures included, to appear in the TAUP 99 Proceedings, Nucl. Phys. B (Proc. Suppl.), ed. by M. Froissart, J. Dumarchez and D. Vignau

A Precision Measurement of pp Elastic Scattering Cross Sections at Intermediate Energies

We have measured differential cross sections for \pp elastic scattering with internal fiber targets in the recirculating beam of the proton synchrotron COSY. Measurements were made continuously during acceleration for projectile kinetic energies between 0.23 and 2.59 GeV in the angular range $30 \leq \theta_{c.m.} \leq 90$ deg. Details of the apparatus and the data analysis are given and the resulting excitation functions and angular distributions presented. The precision of each data point is typically better than 4%, and a relative normalization uncertainty of only 2.5% within an excitation function has been reached. The impact on phase shift analysis as well as upper bounds on possible resonant contributions in lower partial waves are discussed.Comment: 23 pages 29 figure

Electron, Muon, and Hadron Lateral Distributions Measured in Air-Showers by the KASCADE Experiment

Measurements of electron, muon, and hadron lateral distributions of extensive air showers as recorded by the KASCADE experiment are presented. The data cover the energy range from about 5x10^14 eV up to almost 10^17 eV and extend from the inner core region to distances of 200 m. The electron and muon distributions are corrected for mutual contaminations by taking into account the detector properties in the experiment. All distributions are well described by NKG-functions. The scale radii describing the electron and hadron data best are approx. 30 m and 10 m, respectively. We discuss the correlation between scale radii and `age' parameter as well as their dependence on shower size, zenith angle, and particle energy threshold.Comment: 28 pages, 14 figures, Accepted for publication in Astroparticle Physic

A theoretical study of factors influencing calcium-secretion coupling in a presynaptic active zone model

A theoretical analysis of some of the relevant factors influencing the calcium time course and the strength and timing of release probabilities of vesicles evoked by an action potential in a calyx-type active zone is presented in this paper. In particular, our study focus on the comparison of cooperative vs non-cooperative calcium binding by the release site and the effect of the number of Ca2+ binding sites on the calcium sensitivity for release. Regarding the comparison of cooperative and non-cooperative kinetic schemes, our simulations show that quite different results are obtained when considering one or another: a reduction in the release probability of more than a 50% is obtained when considering the cooperative kinetic scheme. Also, a delay in the average time for release appears when using this model for the calcium sensor. Our study also shows that a non-cooperative kinetic binding scheme gives rise to a well defined average calcium level for release assuming that the same kinetic constants are considered for all the sites. Our results also suggest that the central value of the calcium sensitivity for release depends on the number of binding sites N and the dissociation constant KD with a scaling law depending on NKD