bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural specialization for hovering in hummingbirds: Hypertrophy of the pretectal nucleus lentiformis mesencephali
Authors: Iwaniuk Andrew N. , Wylie Douglas R.W. 
Published: November 2006

AbstractHummingbirds possess an array of morphological and physiological specializations that allow them hover such that they maintain a stable position in space for extended periods. Among birds, this sustained hovering is unique to hummingbirds, but possible neural specializations underlying this behavior have not been investigated. The optokinetic response (OKR) is one of several behaviors that facilitates stabilization. In birds, the OKR is generated by the nucleus of the basal optic root (nBOR) and pretectal nucleus lentiformis mesencephali (LM). Because stabilization during hovering is dependent on the OKR, we predicted that nBOR and LM would be significantly enlarged in hummingbirds. We examined the relative size of nBOR, LM, and other visual nuclei of 37 species of birds from 13 orders, including nine hummingbird species. Also included were three species that hover for short periods of time (transient hoverers; a kingfisher, a kestrel, and a nectarivorous songbird). Our results demonstrate that, relative to brain volume, LM is significantly hypertrophied in hummingbirds compared with other birds. In the transient hoverers, there is a moderate enlargement of the LM, but not to the extent found in the hummingbirds. The same degree of hypertrophy is not, however, present in nBOR or the other visual nuclei measured: nucleus geniculatus lateralis, pars ventralis, and optic tectum. This selective hypertrophy of LM and not other visual nuclei suggests that the direction‐selective optokinetic neurons in LM are critical for sustained hovering flight because of their prominent role in the OKR and gaze stabilization. J. Comp. Neurol. 500:211–221, 2007. © 2006 Wiley‐Liss, Inc.
Epidermal growth factor receptor in adult retinal neurons of rat, mouse, and human
Authors: Chen Huiyi , Liu Bin , Neufeld Arthur H. 
Published: November 2006

AbstractDuring development, the epidermal growth factor receptor (EGFR) regulates proliferation and differentiation of many types of cells, including precursors of neurons and glia. In the adult, EGFR continues to drive the growth and differentiation of epithelial cells but is absent from glia in the CNS. However, the localization and functions of EGFR in adult neurons are not well defined. By using immunohistochemistry and Western blotting, we have identified EGFR and its ligands in adult retinal ganglion cells in the normal rat, mouse, and human retina. EGFR and its ligands were also present in certain other adult retinal neurons, for example, horizontal cells and amacrine cells, and had different distribution patterns among these species. In addition, we found that EGFR was expressed in the rat retinal ganglion cell line RGC‐5. One of the EGFR ligands, EGF, caused a cell shape change and increased neurofilament phosphorylation in RGC‐5 cells. The expression of EGFR in postmitotic, terminally differentiated adult retinal neurons suggests that EGFR has pleiotropic functions. In addition to the conventional mitogenic role in adult epithelial cells, EGFR must serve a different, nonmitogenic function in adult neurons. Our work localizes EGFR and its ligands in the adult retinas of several species as a step toward investigating the nonmitogenic functions of EGFR in adult neurons. J. Comp. Neurol. 500:299–310, 2007. © 2006 Wiley‐Liss, Inc.
Callosal axon arbors in the limb representations of the somatosensory cortex (SI) in the agouti (Dasyprocta primnolopha)
Authors: Rocha E.G. , Santiago L.F. , Freire M.A.M. , Gomes‐Leal W. , Dias I.A. , Lent R. , Houzel J.C. , Franca J.G. , Pereira A. , Picanço‐Diniz C.W. 
Published: November 2006

AbstractThe present report compares the morphology of callosal axon arbors projecting from and to the hind‐ or forelimb representations in the primary somatosensory cortex (SI) of the agouti (Dasyprocta primnolopha), a large, lisencephlic Brazilian rodent that uses forelimb coordination for feeding. Callosal axons were labeled after single pressure (n = 6) or iontophoretic injections (n = 2) of the neuronal tracer biotinylated dextran amine (BDA, 10 kD), either into the hind‐ (n = 4) or forelimb (n = 4) representations of SI, as identified by electrophysiological recording. Sixty‐nine labeled axon fragments located across all layers of contralateral SI representations of the hindlimb (n = 35) and forelimb (n = 34) were analyzed. Quantitative morphometric features such as densities of branching points and boutons, segments length, branching angles, and terminal field areas were measured. Cluster analysis of these values revealed the existence of two types of axon terminals: Type I (46.4%), less branched and more widespread, and Type II (53.6%), more branched and compact. Both axon types were asymmetrically distributed; Type I axonal fragments being more frequent in hindlimb (71.9%) vs. forelimb (28.13%) representation, while most of Type II axonal arbors were found in the forelimb representation (67.56%). We concluded that the sets of callosal axon connecting fore‐ and hindlimb regions in SI are morphometrically distinct from each other. As callosal projections in somatosensory and motor cortices seem to be essential for bimanual interaction, we suggest that the morphological specialization of callosal axons in SI of the agouti may be correlated with this particular function. J. Comp. Neurol. 500:255–266, 2007. © 2006 Wiley‐Liss, Inc.
Polarized distribution of ion channels within microdomains of the axon initial segment
Authors: Van Wart Audra , Trimmer James S. , Matthews Gary 
Published: November 2006

AbstractVoltage‐gated sodium (Nav) channels accumulate at the axon initial segment (IS), where their high density supports spike initiation. Maintenance of this high density of Nav channels involves a macromolecular complex that includes the cytoskeletal linker protein ankyrin‐G, the only protein known to bind Nav channels and localize them at the IS. We found previously that Nav1.6 is the predominant Nav channel isoform at IS of adult rodent retinal ganglion cells. However, here we report that Nav1.6 immunostaining is consistently reduced or absent in short regions of the IS proximal to the soma, although both ankyrin‐G and pan‐Nav antibodies stain this region. We show that this proximal IS subregion is a unique axonal microdomain, containing an accumulation of Nav1.1 channels that are spatially segregated from the Nav1.6 channels of the distal IS. Additionally, we find that axonal Kv1.2 potassium channels are present within the distal IS, but are also excluded from the Nav1.1‐enriched proximal IS microdomain. Because ankyrin‐G was prominent in both proximal and distal subcompartments of the IS, where it colocalized with either Nav1.1 or Nav1.6, respectively, mechanisms other than association with ankyrin‐G must mediate differential targeting of Nav channel subtypes to achieve the spatial precision observed within the IS. This precise arrangement of ion channels within the axon initial segment is likely an important determinant of the firing properties of ganglion cells and other mammalian neurons. J. Comp. Neurol. 500:339–352, 2007. © 2006 Wiley‐Liss, Inc.
Vibration analysis of conical panels using the method of discrete singular convolution
Authors: Civalek Ömer 
Published: November 2006

AbstractA discrete singular convolution (DSC) free vibration analysis of conical panels is presented. Regularized Shannon's delta kernel (RSK) is selected as singular convolution to illustrate the present algorithm. In the proposed approach, the derivatives in both the governing equations and the boundary conditions are discretized by the method of DSC. Effects of boundary conditions, vertex and subtended angle on the frequencies of conical panel are investigated. The effect of the circumferential node number on the vibrational behaviour of the panel is also analysed. The obtained results are compared with those of other numerical methods. Numerical results indicate that the DSC is a simple and reliable method for vibration analysis of conical panels. Copyright © 2006 John Wiley & Sons, Ltd.
Parallel computing comes of age: Supercomputer level parallel computations at Caltech
Authors: Fox Geoffrey C. 
Published: November 2006

AbstractParallel supercomputers are now in regular use at Caltech for several major scientific calculations. We use this experience to abstract a set of lessons for applications, decomposition, performance, hardware and software. We consider hypercubes, transputer arrays and the SIMD Connection Machine CM‐2 and AMT DAP. These are contrasted, where possible, with CRAY and other high performance conventional computers. Applications covered are lattice gauge theory, plasma physics, statistical and condensed matter physics, astronomical data analysis, quantum chemistry, graphics ray tracing, string dynamics, grain dynamics, astrophysical particle dynamics, computer chess and Kalman filters.
Experiments with multicomputer LU‐decomposition
Authors: van de Velde Eric F. 
Published: November 2006

AbstractWe present a new concurrent LU‐decomposition algorithm based on implicit pivoting of both rows and columns. This algorithm is, to a large extent, independent of the distribution of the matrix over the concurrent processes. As a result, it can be used in programs with dynamically varying data distributions. Another advantage is that most pivoting strategies are easily incorporated. We also introduce two new, intrinsically concurrent, pivoting strategies: multirow and multicolumn pivoting.With this program, we study the performance of concurrent LU‐decomposition as a function of data distribution and pivoting strategy. We show that LU‐decomposition with some pivoting strategies is both faster and numerically more stable than LU‐decomposition without pivoting. Experimental evidence on the Symult 2010 and the iPSC/2 shows that, for performance considerations, pivoting is equivalent to randomizing the data distribution.
The schedule parallel programming package with recycling job queues and iterated dependency graphs
Authors: Hanson F. B. , Sorensen D. C. 
Published: November 2006

AbstractThe SCHEDULE parallel programming package has been modified so that many more total processes may be spawned as long as the number of currently active processes satisfy the former limits of the package rather than the cumulative total number. This has been accomplished principally by changing the queueing system for both the job parameter queue and the ready jobs queue. The original linear queues are converted to circular queues, in that finished places in the queues are reused for new jobs and that the physical end of the queue is logically connected to the physical beginning of the queue. Two additional features facilitate the change in queues. The first is the implementation of a third queue, a free list, which keeps a list of the currently free slots on the job parameter queue. The second new feature is the use of SCHEDULE generated job tags rather than user‐generated job tags within the package. The user program now gets a job tag number from SCHEDULE with a subroutine call. Another improvement permits the iteration of dependency graphs, with minimal restoration of dependency data. This improvement facilitates the application of the SCHEDULE package to iterations and time‐stepping problems, by saving and reusing the iterated part of the dependency graph. This feature can result in a significant reduction in the number of newly spawned processes that would otherwise be needed for iterations.
Construction of a large‐scale neural network: Simulation of handwritten Japanese character recognition on NCUBE
Authors: Joe Kazuki , Mori Yoshihiro , Miyake Sei 
Published: November 2006

AbstractThis paper describes how new learning methods may make it possible for a large‐scale, hierarchical neural network to recognize most Japanese handwritten characters. This is a very large and complex task, as the Japanese character set consists of about 3000 categories which can be written in many different ways. Such a difficult task can lead a neural network to converge very slowly and to yield recognition rates that are uneven between categories. To address these problems we here propose five learning methods as modifications of the conventional back‐propagation learning rule. These methods produce fast convergence, even recognition rates over all categories, and adequate recognition of test samples. We also describe how a large‐scale neural network can be built by dividing the recognition task into several subtasks, with networks for each subtask, and then integrating these subnetworks in a large network with a hierarchical structure. In a hierarchical network, the upper level network directly integrates outputs from each lower level network. Application of that network to handwritten Japanese character recognition has resulted in poor recognition, because lower level networks do not know about unknown input patterns, and the direct integration of ambiguous outputs from many lower level networks confuses the upper level network. We propose a new integration method which provides each subnetwork with more information as to how close an input pattern is to the categories of that subnetwork. This method resulted in high recognition performance for character recognition. We here described the above methods, and report the performance of our implementation of a neural network for the recognition of 71 Hiragana characters, and describe our implementation of this network on a hypercube concurrent computer.
A real‐time distributed algorithm for an aircraft longitudinal optimal autopilot
Authors: Tahir Jamel M. , Virk Gurvinder S. 
Published: November 2006

AbstractThis paper is concerned with fast and efficient computations for the solution of the two‐point boundary‐value problem that arises in optimal control of an aircraft longitudinal mode. The solution proposed is implemented on a T800 transputer network using parallel C and is shown to be adequate for real‐time control purposes.
Sorting with near linear speed‐up on tightly coupled multiprocessors
Authors: Wheat Mitchell 
Published: November 2006

AbstractA new parallel sorting algorithm, called parsort, suitable for implementation on tightly coupled multiprocessors is presented. The algorithm is based upon quicksort and two‐way merging. An asynchronous parallel partitioning algorithm is used to distribute work evenly during merging to ensure a good load balance amongst processors, which is crucial if we are to achieve high efficiency. The implementation of this parallel sorting algorithm exhibits theoretical and measured near linear speed‐up when compared to sequential quicksort. This is illustrated by the results of experiments carried out on the Sequent Balance 8000 multiprocessor.
Real‐time multi‐scale vision on multi‐computers
Authors: Battiti Roberto 
Published: November 2006

AbstractThis paper investigates the use of large grain size multi‐computers for solving low‐ and intermediate‐level computer vision problems. The realization of a general multi‐resolution framework requiring a two‐dimensional grid of communicating processors is analysed, and the resulting speed‐up and total solution time as a function of software and hardware parameters is presented. The scheme is then specialized for two significant problems: surface reconstruction and optical flow. While the first can be solved with the standard full multigrid approach, the second requires an adaptive grid determined by a local decision: the appropriate resolution for different parts of the image is tuned in order to minimize the error in the coefficients of the differential equations.
Sequence comparison on the connection machine
Authors: Atallah Mikhail J. , McFaddin Scott 
Published: November 2006

AbstractWe give two parallel algorithms for sequence comparison on the Connection Machine 2 (CM‐2). The specific comparison measure we compute is theedit distance: given a finite alphabet ∑ and two input sequencesXϵ ∑+andYϵ ∑+the edit distanced(X,Y)is the minimum cost of transformingXintoYvia a series of weighted insertions, deletions and substitutions of characters. The edit distance comparison measure is equivalent to or subsumes a broad range of well known sequence comparison measures.The CM‐2 is very fast at performing parallel prefix operations. Our contribution consists of casting the problem in terms of these operations. Our first algorithm computesd(X,Y)usingNprocessors andO(M S)time units, whereM= min(|X|,||Y|) + 1,N= max(|X|,|Y|) + 1 andSis the time required for a parallel prefix operation. The second algorithm computesd(X,Y)usingNMprocessors andO((logNlogM)(S+R)) time units, whereRis the time for a ‘router’ communication step—one in which each processor is able to read data, in parallel, from the memory of any other processor. Our algorithms can also be applied to several variants of the problem, such as subsequence comparisons, and one—many and many‐many comparisons on 'sequence databases'.
Tiny: An efficient routing harness for the Inmos transputer
Authors: Clarke Lyndon , Wilson Greg 
Published: November 2006

AbstractMessage‐based MIMD computers that support arbitrary connections over a small number of communications links cannot support parallel applications with complex communication patterns unless the support software includes message routing. This paper describes design issues for such software, using a router for the Inmos T800 transputer called Tiny as an example. Performance figures show that Tiny achieves near optimal routing performance given the hardware limits. Modifications to Tiny to monitor message traffic are also described.
Two approaches to the concurrent implementation of the prime factor algorithm on a hypercube
Authors: Aloisio G. , Lopinto E. , Veneziani N. , Fox G. C. , Kim J. S. 
Published: November 2006

AbstractOn sequential computers, the prime factor algorithm (PFA) allows the Computation of the discrete Fourier transform (DFT) with a higher efficiency than the traditional Cooley‐Tukey FFT algorithm (CTA). However, the PFA requires substantial data movement, which poses a challenging problem for distributed‐memory multi‐processor systems. In this paper, two approaches for a concurrent implementation of the PFA on these structures are presented. In the first approach, the concurrent PFA runs on all nodes of the multi‐processor system, which is inefficient on large configurations due to the large communication overhead. A second approach developed to reduce this bottleneck is also presented. These solutions have been benchmarked on Caltech hypercubes, and the performances achieved are reported. In both approaches, thecrystal_routeralgorithm was exploited as a concurrent technique for communicating data among nodes.
Global adaptive quadrature for the approximate computation of multidimensional integrals on a distributed‐memory multiprocessor
Authors: Lapegna Marco 
Published: November 2006

AbstractIn this paper we discuss the problem of computing a multidimensional integral on a MIMD distributed‐memory multiprocessor.Adaptive quadrature is known as a good approach to the problem of achieving accuracy and reliability while attempting to minimize the number of function evaluations. The implementation makes use of dynamical data structures able to manage subinterval partition. On a distributed‐memory multiprocessor, each processor is able to execute code and to manipulate data structures in its own local memory only, and data are sent from one processor to another one by explicit message‐passing. Efficient implementation of an adaptive algorithm for the multidimensional quadrature on a parallel computer is quite difficult, because of the need for continuous information exchange between processors.Our algorithm is based on a global adaptive strategy which dynamically balances the workload and reduces the data communication between processors in order to use the message‐passing environment efficiently.The results and timings for several tests are given.
Sparse iterative algorithm software for large‐scale MIMD machines: An initial discussion and implementation
Authors: Shadid John N. , Tuminaro Ray S. 
Published: November 2006

AbstractThe parallelization of sophisticated applications has dramatically increased in recent years. As machine capabilities rise, greater emphasis on modeling complex phenomena can be expected. Many of these applications require the solution of large sparse matrix equations which approximate systems of partial differential equations (PDEs). Therefore we consider parallel iterative solvers for large sparse non‐symmetric systems and issues related to parallel sparse matrix software. We describe a collection of parallel iterative solvers which use a distributed sparse matrix format that facilitates the interface between specific applications and a variety of Krylov subspace techniques and multigrid methods. These methods have been used to solve a number of linear and non‐linear PDE problems on a 1024‐processor NCUBE 2 hypercube. Over 1 Gflop sustained computation rates are achieved with many of these solvers, demonstrating that high performance can be attained even when using sparse matrix data structures.
Voxel databases: A paradigm for parallelism with spatial structure
Authors: Williams Roy D. 
Published: November 2006

AbstractThis paper concerns parallel, local computations with a data structure such as a graph or mesh, which may be structured or unstructured. The target machine is a distributed‐memory parallel processor with vector or pipeline hardware on the processors, but software based on voxel databases also runs efficiently on shared‐memory and uniprocessor machines with and without vector hardware.A voxel database (VDB) is a distributed shared memory where entities which share memory are those at the same geometric position. A VDB may be thought of as a dictionary of position‐subscript pairs, so that data may be associated with points in space by using the subscript of that point as an index into data arrays. The use of subscripts allows ease of programming and vectorization. The shared memory at each point is weakly coherent and may be either single‐writer, multiple‐reader—also known as the ghost node method—or multiple‐combiner, multiple‐reader memory. The VDB may be sorted to put special points at the beginning or end of the subscript list, and also to reduce cache‐miss inefficiencies. Support is also provided for arbitrary distribution of data entities between processors for load‐balancing.The idea of VDBs and the corresponding software tool provide a clear and efficient way to program a large variety of mesh computations in Fortran or C, such that the execution of the program is independent of the distribution of data to processors, and the mesh may be topologically adapted and load‐balanced.As an example we discuss the implementation of an unstructured finite‐element elliptic solver using a conjugate gradient method. We also discuss the implementations of a finite‐volume flux‐split fluid solver and of local adaptive refinement for meshes of simplices such as triangles or tetrahedra.