Totally normal cellular stratified spaces and applications to the configuration space of graphs

The notion of regular cell complexes plays a central role in topological combinatorics because of its close relationship with posets. A generalization, called totally normal cellular stratified spaces, was introduced by the third author by relaxing two conditions; face posets are replaced by acyclic categories and cells with incomplete boundaries are allowed. The aim of this article is to demonstrate the usefulness of totally normal cellular stratified spaces by constructing a combinatorial model for the configuration space of graphs. As an application, we obtain a simpler proof of Ghrist's theorem on the homotopy dimension of the configuration space of graphs. We also make sample calculations of the fundamental group of ordered and unordered configuration spaces of two points for small graphs.Comment: 44 pages. v2. Typos fixed. Accepted for publication by Topological Methods in Nonlinear Analysi

Peripheral nerve-derived VEGF promotes arterial differentiation via neuropilin 1-mediated positive feedback

In developing limb skin, peripheral nerves are required for arterial differentiation, and guide the pattern of arterial branching. In vitro experiments suggest that nerve-derived VEGF may be important for arteriogenesis, but its role in vivo remains unclear. Using a series of nerve-specific Cre lines, we show that VEGF derived from sensory neurons, motoneurons and/or Schwann cells is required for arteriogenesis in vivo. Arteriogenesis also requires endothelial expression of NRP1, an artery-specific coreceptor for VEGF^(164) that is itself induced by VEGF. Our results provide the first evidence that VEGF is necessary for arteriogenesis from a primitive capillary plexus in vivo, and show that in limb skin the nerve is indeed the principal source of this signal. They also suggest a model in which a `winner-takes-all' competition for VEGF may control arterial differentiation, with the outcome biased by a VEGF^(164)-NRP1 positive-feedback loop. Our results also demonstrate that nerve-vessel alignment is a necessary, but not sufficient, condition for nerve-induced arteriogenesis. Different mechanisms therefore probably underlie these endothelial patterning and differentiation processes

Low-temperature formation of alpha-alumina from various polyhydroxoaluminum-hydroxy acid composite gels

Low-temperature alpha-alumina formation was attempted using various polyhydroxoaluminum (PHA)-hydroxy acid composite gels, which were prepared from PHA solutions containing different amounts of hydroxy acids, such as lactic acid, glycolic acid, malic acid, citric acid or mandelic acid. The composite gels began to transform into alpha-alumina when heated at lower temperatures of around 500 degrees C and the alpha-alumina fraction of the heat-treated products increased with increasing temperature. The alpha-alumina fraction was also dependent on both the type and amount of hydroxy acid additive. Among the composite gels studied, significant low-temperature alpha-alumina formation was observed for the PHA-mandelic acid, PHA-citric acid and PHA-lactic acid series. Low-temperature alpha-alumina formation was further promoted by employing a two-step heat-treatment method. The interaction between the functional groups of PHA and hydroxy acid and the seeding effect appear to play important roles in the course of the gelation and calcination processes for low-temperature alpha-alumina formation.ArticleCERAMICS INTERNATIONAL. 37(1):201-206 (2011)journal articl

Neural crest stem cells undergo multilineage differentiation in developing peripheral nerves to generate endoneurial fibroblasts in addition to Schwann cells

Neural crest stem cells (NCSCs) persist in peripheral nerves throughout late gestation but their function is unknown. Current models of nerve development only consider the generation of Schwann cells from neural crest, but the presence of NCSCs raises the possibility of multilineage differentiation. We performed Cre-recombinase fate mapping to determine which nerve cells are neural crest derived. Endoneurial fibroblasts, in addition to myelinating and non-myelinating Schwann cells, were neural crest derived, whereas perineurial cells, pericytes and endothelial cells were not. This identified endoneurial fibroblasts as a novel neural crest derivative, and demonstrated that trunk neural crest does give rise to fibroblasts in vivo, consistent with previous studies of trunk NCSCs in culture. The multilineage differentiation of NCSCs into glial and non-glial derivatives in the developing nerve appears to be regulated by neuregulin, notch ligands, and bone morphogenic proteins, as these factors are expressed in the developing nerve, and cause nerve NCSCs to generate Schwann cells and fibroblasts, but not neurons, in culture. Nerve development is thus more complex than was previously thought, involving NCSC self-renewal, lineage commitment and multilineage differentiation

第二言語習得において学習者の適性が学習成果に与える影響 : 言語分析能力・音韻的短期記憶・ワーキングメモリに焦点を当てて

武蔵野大学Musashino University本研究は学習者の適性として言語分析能力,音韻的短期記憶,ワーキングメモリを取り上げ,それらが第二言語としての日本語学習に与える影響を縦断的に検証することを目的とする。初級から学習を開始した中国人日本語学習者37名を対象として,(1)学習開始前に適性を測定する3つのタスク(2)学習開始後から15ヶ月後までの間に,3ヶ月ごとに計5回,学習成果を測定する文法(筆記産出),読解,聴解テストを実施し,適性と学習成果との関連を相関と重回帰分析によって検討した。分析の結果,音韻的短期記憶は初期に重要,言語分析能力は一貫して重要,ワーキングメモリは学習が進んだ段階で重要であることが示された。また,学習成果の測定方法,測定時期によって異なるが,学習成果は言語分析能力,音韻的短期記憶によって説明された。これらの結果から,学習成果に関与する適性は学習段階,スキルによって異なることが示された。The study investigated the contribution by language aptitudes to learning Japanese as a second language (L2). The language aptitudes in the study were defined as follows: (1) language analytic ability; (2) phonological short-term memory; and (3) working memory. The participants were 37 adults with Chinese L1 background with the introductory level of L2 proficiency at the beginning of the study. The study administered two types of tasks: (1) three tasks to measure aptitudes; and (2) three written tests to measure the outcome of L2 learning. The aptitude tasks were administered at the beginning of the study, and the L2 tests were administered five times, i.e. at the third-, sixth-, ninth-, twelfth-, and fifteenth- months of instruction. The study conducted correlation and regression analyses between the aptitude tasks and the L2 tests. The data indicated that: (1) phonological short-term memory was critical at the early stages of the instruction; (2) language analytic ability was critical throughout the fifteen months; and (3) working memory became critical later in the study. The data also showed that the aptitude tasks exhibited varying degrees of explanatory power toward the outcome of L2 learning, depending on the measures of L2 learning and at the time of data collection. In sum, these results generally indicate that language aptitudes contribute to L2 learning, however, further research is necessary to identify specifically which aspects of aptitudes contribute to which L2 skills. Future research also needs to examine when aptitudes are critical the most in different stages of L2 learning

Lymphatic vasculature in the central nervous system

The central nervous system (CNS) is considered as an immune privilege organ, based on experiments in the mid 20th century showing that the brain fails to mount an efficient immune response against an allogeneic graft. This suggests that in addition to the presence of the blood-brain barrier (BBB), the apparent absence of classical lymphatic vasculature in the CNS parenchyma limits the capacity for an immune response. Although this view is partially overturned by the recent discovery of the lymphatic-like hybrid vessels in the Schlemm’s canal in the eye and the lymphatic vasculature in the outmost layer of the meninges, the existence of lymphatic vessels in the CNS parenchyma has not been reported. Two potential mechanisms by which lymphatic vasculature may arise in the organs are: 1) sprouting and invasion of lymphatic vessels from the surrounding tissues into the parenchyma and 2) differentiation of blood endothelial cells into lymphatic endothelial cells in the parenchyma. Considering these mechanisms, we here discuss what causes the dearth of lymphatic vessels specifically in the CNS parenchyma

文法学習に関する信念・態度，学習ストラテジー，学習成果の関連 : 暗示的帰納的指導のコンテクストの中で

お茶の水女子大学本研究は文法説明をしない暗示的帰納的指導の中で,学習者の文法学習に関する信念,及び指導方法に対する態度,学習ストラテジー,学習成果との関連を解明することを目的とする。初級中国人学習者161人の5件法質問紙調査データの因子得点とテスト得点との相関を分析した結果,「文法知識の役割の肯定的受け止め」の信念,指導方法に対する「学習困難感」と学習成果に負の相関があること,指導方法に対する態度によって使用する学習ストラテジーが異なることが示された。これらのことから信念・態度,ストラテジー,学習成果は相互に関連すること,学習者の個人差と指導方法が適合しないと指導効果が現れにくいことが示唆された。The purpose of this survey is to investigate the relationship between learners\u27 beliefs about grammar learning, attitude toward grammar instruction, learning strategies, and learning outcomes in the context of implicit inductive teaching where no explicit grammar explanation was given. A five-point Likert scale questionnaire was administered to 161 beginning-level Chinese learners in a Japanese school where implicit inductive teaching is employed. A factor analysis was run, and the correlation coefficients between the factor scores and the scores of the examination were analyzed. The results indicate that learning outcomes have a negative correlation with the positive acceptance of the role of grammatical knowledge; and the difficulty felt during implicit inductive instruction. They also show that the strategies used by learners vary depending on their attitudes toward the instruction. These findings imply that beliefs about grammar learning, attitudes toward instruction, learning strategies, and learning outcomes are interrelated, and that instruction cannot be effective when it is not matched to learners\u27 beliefs, attitudes, and learning strategies