Comparison of Direct and Adjoint k and α-Eigenfunctions

Modal expansions based on k-eigenvalues and α-eigenvalues are commonly used in order to investigate the reactor behaviour, each with a distinct point of view: the former is related to fission generations, whereas the latter is related to time. Well-known Monte Carlo methods exist to compute the direct k or α fundamental eigenmodes, based on variants of the power iteration. The possibility of computing adjoint eigenfunctions in continuous-energy transport has been recently implemented and tested in the development version of TRIPOLI-4®, using a modified version of the Iterated Fission Probability (IFP) method for the adjoint α calculation. In this work we present a preliminary comparison of direct and adjoint k and α eigenmodes by Monte Carlo methods, for small deviations from criticality. When the reactor is exactly critical, i.e., for k0 = 1 or equivalently α0 = 0, the fundamental modes of both eigenfunction bases coincide, as expected on physical grounds. However, for non-critical systems the fundamental k and α eigenmodes show significant discrepancies.

A Novel Low-Cost Method for Fabrication of 2D Multi-Electrode Array (MEA) to Evaluate Functionality of Neuronal Cells

In this paper, a fabrication method for two-dimensional multi-electrode arrays (MEAs) using inexpensive material and method is proposed. The focus in this work is on the design and fabrication of 2D Microelectrode arrays using metallic electrodes on a silica substrate. Titanium/gold multi-electrode arrays containing 60 electrodes with optimized metal thicknesses and 30 μm diameter, covered with thin modified SU-8 insulator layer as biocompatible material have been designed and manufactured using the standard photolithography-based microfabrication method. The utilization of affordable and more accessible materials and simpler techniques can be mentioned as the distinct point of the proposed fabrication method. Using these multi-electrode arrays, it is possible to either record or stimulate cells by accessing multiple sites of cell tissues and collect signals from the sources around each electrode simultaneously. Precisely adjusting the size, distance, and number of microelectrodes causes high measurement selectivity and reliability which has been taken into account in the design of the microelectrodes. In this study, we manufactured a preliminary representative MEA and the bio-compatibility of the manufactured MEA is going to be evaluated by neural cells, obtained from rat cortices. The main aim of this study is to compare our inexpensive strategy with other approaches.

Novel insights into Entamoeba cyst wall formation and the importance of actin cytoskeleton

The cyst wall of Entamoeba histolytica, the causative agent of the amoebiasis, is a potential target for new drugs. The “Wattle and Daub” model of cyst wall formation of Entamoeba invadens had already been reported. In this study, we demonstrate in more detail the morphological stages of chitin wall formation in E. invadens using fluorescent chitin-binding dyes and immunolocalization of the cyst wall proteins. Here, the expression and localization of chitin synthase and the importance of actin cytoskeleton dynamics at cellular level, during encystations have been demonstrated for the first time. Chitin deposition was found to be initiated on the cell surface mostly from one distinct point, though multipoint initiation was also observed sometimes. From these points, the wall grew outwards and gradually covered the entire cyst surface with time. The initiation of chitin deposition was guided by the localization of chitin synthase 1 on the plasma membrane. The gradual formation of the cyst wall follows the Wattle and daub model. The chitin deposition occurred on the foundation of Jacob lectin at the cell membrane, and the other cyst wall components, like chitinase, and Jessie were also found to be present in the growing incomplete walls. In contrary to the Wattle and daub model, Jessie was found to be expressed and localized in the growing wall at the early hours of encystations. During encystation, F-actin was reorganized into the cortical region within an hour encystation initiation and remained intact until the completion of the chitin wall. Disruption of cortical actin polymerization with 2, 3-Butanedione monoxime inhibited proper wall formation but produced wall-less cysts or cysts with defective chitin wall. Malformations of cyst-walls were mainly due to improper localization and activity of chitin synthases, which indicates the indispensability of cortical actin cytoskeleton for the proper cyst wall formation.Author SummaryEntamoeba parasites reach new hosts using the resistant cyst form, so preventing its formation can stop the spread of amoebiasis. The resistant nature of the cyst is due to the chitin wall, and thus identifying the critical steps of wall formation could provide targets for designing new drugs. Here we studied the morphological stages of the cyst wall formation by observing how the chitin and other cell wall components were deposited on the cell surface using fluorescent chitin-binding dyes and antibodies against cyst wall proteins. In most cases, the chitin wall was found to start from one distinct point from which it spread all over the cell surface, guided by chitin synthase. The composition of these incomplete walls was the same as a mature cyst wall indicating that the wall may be a result of extracellular self-assembly of its constituents from one starting point. We have also observed that F-actin polymerized in the cortex of encysting cells and its disruption resulted in wall-less cysts or cysts with aberrant walls showing the importance of actin cytoskeleton in proper chitin deposition.

Interactive 3D Time-Integrated Solar Shadow Maps

<p><strong>Abstract.</strong> Urban areas are characterized by a complex topography of buildings, terrain, vegetation and temporary structures, which, depending on their extent, geometry, geographic location and daytime, cast shadow on their surroundings. Given the importance of sunlight for various groups of interest and tasks, we argue that a comprehensive, accessible, usable and intuitive way of predicting its availability for specific usage contexts is surprisingly lacking. In our research, we are investigating how to improve the visual communication of urban solar conditions for various real-world usage scenarios like having a coffee in the sun, parking a car in the shade, or taking a photograph of a particular building in a favorable light. All of these activities take place over a period of time, not in a temporal instant, causing solar shadows to move. Hence, a static representation of the light situation at a distinct point in time, such as offered by available 3D urban maps or GIS systems, is often not sufficient for planning above mentioned recreational or professional activities.</p><p>This factor is incorporated in our system by integrating shadow motion into a shadow map that covers arbitrary timeframes within a given day (Figure 1). Shadows are accumulated by projecting shadow maps from astronomically precise sun positions spanning over the defined timeframe. The number of sampling points directly influences the quality and speed of the rendering. All provided figures currently sample and integrate nine different sun positions.</p><p>Using our system, questions in a manner of “Given a specific point in space, at which time will this point be in sun/shade again” can be answered. E.g., one would like to spend time in the sun at a specific Viennese “Kaffeehaus” (coffee place), from which time on (and for how long) will this space be sunlit (Figure 2). In the future, this process might even be automated.</p>

Gravitational allocation on the sphere

Given a collection L of n points on a sphere Sn2 of surface area n, a fair allocation is a partition of the sphere into n parts each of area 1, and each is associated with a distinct point of L. We show that, if the n points are chosen uniformly at random and if the partition is defined by a certain “gravitational” potential, then the expected distance between a point on the sphere and the associated point of L is O(log⁡n). We use our result to define a matching between two collections of n independent and uniform points on the sphere and prove that the expected distance between a pair of matched points is O(log⁡n), which is optimal by a result of Ajtai, Komlós, and Tusnády.

Language Acquisition: The Influential Factors and Its Connection With Age

The term of language acquisition often leads to a misinterpretation when it deals with English learning. However, there is one distinct point that might be pointed out about language acquisition which differentiates it with the general language learning. Language acquisition is the process of acquire language while language learning is the process of learning the language. This article is meant to give a perspective about language acquisition, factors that influence the acquisition and also the connection of language acquisition with age.

Constrained Point Set Embedding of a Balanced Binary Tree

Given an undirected planar graph G with n vertices and a set S of n points inside a simple polygon P, a point-set embedding of G on S is a planar drawing of G such that each vertex is mapped to a distinct point of S and the edges are polygonal chains surrounded by P. A special case of the embedding problem is that in which G is a balanced binary tree. In this paper, we present a new algorithm for embedding an n-vertex balanced binary tree BBT on a set S of n points inside a simple m-gon P in O(m4/3+ϵ + nlog2 n + m log n) time with at most O(m) bends per edge.

Rakes, Live Deaths and Modified Cassette Players: Three Contemporary Sound Artists from Colombia

Sound art activity in Colombia has proliferated in the last decade, as evidenced by the considerable number of shows focusing on sound works by Colombian artists in recent years. The author presents three artists—Rodrigo Restrepo, Leonel Vásquez and Ícaro Zorbar—each of whom represents a distinct point in the continuum between music and sound art. The artists' individual and distinct approaches to the use of technology and their very personal conceptions of space and time are discussed.

A novel patch assembly domain in Num1 mediates dynein anchoring at the cortex during spindle positioning

During mitosis in budding yeast, cortically anchored dynein generates pulling forces on astral microtubules to position the mitotic spindle across the mother–bud neck. The attachment molecule Num1 is required for dynein anchoring at the cell membrane, but how Num1 assembles into stationary cortical patches and interacts with dynein is unknown. We show that an N-terminal Bin/Amphiphysin/Rvs (BAR)–like domain in Num1 mediates the assembly of morphologically distinct patches and its interaction with dynein for spindle translocation into the bud. We name this domain patch assembly domain (PA; residues 1–303), as it was both necessary and sufficient for the formation of functional dynein-anchoring patches when it was attached to a pleckstrin homology domain or a CAAX motif. Distinct point mutations targeting the predicted BAR-like PA domain differentially disrupted patch assembly, dynein anchoring, and mitochondrial attachment functions of Num1. We also show that the PA domain is an elongated dimer and discuss the mechanism by which it drives patch assembly.