867 research outputs found

    TEM observation of void-like defect structures in matrix-and isolated-olivine grains in Allende (CV3)

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    Olivine grains in the Allende CV3 carbonaceous chondrite matrix were examined mainly by TEM. Compositional data of olivine by EPMA are also given. It was revealed that void-like defects were observed occurring in iron enriched portions of both matrix olivine and rims of isolated olivine grains. Detailed observations of these void-like defects suggest that the void structure was formed during thermal metamorphism and that the thermal metamorphism was also related to some chemical reaction to form fayalitic olivine either in the pre-solar nebula or on a parent body

    Evaluation of Removal Condition of Invasive Plant 'Eragrostis Curvula' by Considering Erosion Rate

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    Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

    NScluster: An R Package for Maximum Palm Likelihood Estimation for Cluster Point Process Models Using OpenMP

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    NScluster is an R package used for simulation and parameter estimation for NeymanScott cluster point process models and their extensions. For parameter estimation, NScluster uses the maximum Palm likelihood estimation procedure. As some estimation procedures proposed herein require heavy calculation, NScluster can use parallel computation via OpenMP and achieve significant speedup in some cases. In this paper, we discuss results obtained using a laptop PC and a shared memory supercomputer. In addition, we examine the performance characteristics of parallel computation via OpenMP

    Establishment of a new method for precisely determining the functions of individual mitochondrial genes, using Dictyostelium cells

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    <p>Abstract</p> <p>Background</p> <p>Disruption of mitochondrial genes may become a powerful tool for elucidating precisely the functions of individual mitochondrial genes. However, it is generally difficult to manipulate genetically mitochondrial genes, because 1) a mitochondrion is surrounded by inner and outer membranes, and 2) there are a large number of mtDNA copies in a single cell. This is the reason why we tried to establish a novel method for disrupting a certain mitochondrial gene (<it>rps4</it>), using <it>Dictyostelium </it>cells.</p> <p>Results</p> <p>Here, we have developed a new method for specifically disrupting a mitochondrial gene (<it>rps4 </it>; ribosomal protein subunit S4), by a combination of homologous recombination and delivery of an appropriate restriction endonuclease (<it>Sfo</it>I) into mitochondria. First, mitochondrially targeted <it>Sfo</it>I whose expression is under control of the tetracycline (Tet)-regulated gene expression system was introduced into cells heteroplasmic with respect to the <it>rps4 </it>gene. Then, the heteroplasmic cells were produced by homologous recombination by use of the construct in which the unique <it>Sfo</it>I site and the 5'-half of the <it>rps4 </it>coding region were deleted not to be digested by <it>Sfo</it>I, and therefore their mitochondria have both the wild-type mtDNA and the mutant mtDNA with the disrupted <it>rps4 </it>gene. In response to removal of Tet from growth medium, <it>Sfo</it>I was selectively delivered into mitochondria and digested only the wild-type mtDNA but not the mutated <it>rps4</it>. Thus one can gain <it>rps4</it>-null cells with only the mutated mtDNA, under the Tet-minus condition.</p> <p>Conclusion</p> <p>The mitochondrial gene-disruption method presented here must be widely useful for precisely determining the functions of individual mitochondrial genes. This is the first report to demonstrate complete and specific mitochondrial gene disruption.</p

    Synthesis and conformational studies of chiral macrocyclic [1.1.1]metacyclophanes containing benzofuran rings

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    Macrocyclic [1.1.1]metacyclophanes (MCPs) containing benzene and benzofuran rings linked by methylene bridges and which can be viewed as calixarene analogues, have been synthesized by demethylation of [3.3.1]MCP-diones with trimethylsilyl iodide (TMSI) in MeCN. The [3.3.1]MCP-diones are synthesized by using (p-tolylsulfonyl)methyl isocyanide (TosMIC) as the cyclization reagent in N,N-dimethylformamide (DMF) with an excess of sodium hydride. ¹H NMR spectroscopy revealed that the remaining hydroxyl group on the phenyl ring is involved in intramolecular hydrogen bonding with the oxygen of one of the benzofuran rings. O-Methylation at the lower rim of monohydroxy[1.1.1]MCP in the presence of K₂CO₃ in acetone afforded a novel and inherently chiral calixarene analogue, namely the macrocyclic [1.1.1]MCP, possessing C₁ symmetry. The inherent chirality of the two conformers was characterized by ¹H NMR spectroscopy by addition of an excess of Pirkle's chiral shift reagent, which caused a splitting of the corresponding methylene protons to AB patterns. Single crystal X-ray analysis revealed the adoptation of a hemisphere-shaped cone isomer. DFT calculations were carried out to investigate the energy-minimized structures and the hydrogen bonds of the synthesized MCPs

    Synthesis and conformations of [2.n]metacyclophan-1-ene epoxides and their conversion to [n.1]metacyclophanes

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    A series of syn- and anti-[2.n]metacyclophan-1-enes have been prepared in good yields by McMurry cyclizations of 1,n-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)alkanes. Significantly, acid catalyzed rearrangements of [2.n]metacyclophan-1-enes afforded [n.1]metacyclophanes in good yield. The ratios of the products are strongly regulated by the number of methylene bridges present. The percentages of the rearrangement products increase with increasing length of the carbon bridges. Characterization and the conformational studies of these products are described. Single crystal X-ray analysis revealed the adoption of syn- and anti-conformations. DFT calculations were carried out to estimate the energy-minimized structures of the synthesized metacyclophanes

    Approximate Optimization Algorithms in Markov Random Field Model Based on Statistical-Mechanical Techniques

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    An image restoration can be often formulated as an energy minimization problem. When an energy function is expressed by using the hamiltonian of a classical spin system only with finite range interactions, the probabilistic model, which is described in the form of Gibbs distribution for the energy function, can be regarded as a Markov random field (MRF) model. Some approximate optimization algorithms for the energy minimization problem were proposed in the standpoint of statistical-mechanics. In this paper, the approximate optimization algorithms are summarized and are applied to the image restoration for natural image.特集 : 「産業におけるソフトコンピューティングに関する国際会議\u2799」発表論文選

    Forest structure and the unevenness of seed dispersal by birds

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    本研究は, 森林構造と鳥類による種子散布の関係を明らかにすることを目的とする. 季節によって鳥類による種子散布が集中する場所が異なり, 秋においては年によっても異なる分布を示した. これらのことから, 季節や年ごとの結実個体の生育分布の違いが鳥散布種子の集中分布に影響していると考えられる. しかし春においては, 結実個体のない場所でも鳥散布種子数が多くなる場所がみられたため, そのような場所では結実個体とは別の要因が鳥類の行動に影響したと考えられる. 1年を通して確認頻度の高かったヒヨドリが種子散布者として最も貢献していると考えられる. 春に採餌が観察されたヒヨドリはほとんどの個体が亜高木層と高木層で観察された. したがって, 春の鳥類の行動は亜高木層や高木層の密度の違いに影響を受けると考えられる. 草本層から高木層の密度と自然落下種子数を説明変数, 鳥散布種子数を目的変数とし, 重回帰分析を行った結果, 春において高木層の密度が高い場所で鳥散布種子数が多くなる正の相関が認められた. これは, 繁殖期の鳥類がソングポストになり得る高木を好むためだと考えられる. 森林の鳥散布種子の分布に最も影響を与える要因は, どの季節においても結実個体の生育場所の違いであり, 鳥類の繁殖期にあたる春においては, 森林構造の違いが鳥類による種子散布の不均一性に影響を与えることが示唆された
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