Waseda University

About: Waseda University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Catalysis & Large Hadron Collider. The organization has 24220 authors who have published 46859 publications receiving 837855 citations. The organization is also known as: Waseda daigaku & Sōdai.

Selective adsorption of metal ions on poly(4-vinylpyridine) resins in which the ligand chain is immobilized by crosslinking

Abstract: Chelate forming resins (3) were prepared by crosslinking poly(4-vinylpyridine) (1) with 1,4-dibromobutane (2) and their complexation with metal ions was studied. Stability constants (K) were found to be much higher for the Cu-3 system than for the Cu-1 system, which indicates that 3 uptakes Cu ions with high efficiency. K and the adsorption capacity of Cu decrease largely with increasing degree of crosslinking. Visible and ESR spectra of Cu-3 show that the structure of the Cu complex within 3 is the same as that of the monomeric Cu-pyridine complex. However, the ligand-chain is immobilized in the highly crosslinked 3c and 3d, so that the square planar structure of a stable Cu complex is distorted. The amount of adsorption of Cu, Fe, Cr, Ni, and Zn ions on 3 decreases with the crosslinking, but the adsorption of Hg ions is independent; i.e. 3d selectively adsorbs Hg ions. Metal complexed 1 was crosslinked according to Scheme 1 and the metal ion which was used as template is well adsorbed by the obtained 3. It is considered, therefore, that the ligand chain is maintained at the best conformation for the template ion. Chelatbildende Harze (3) wurden durch Vernetzung von Poly(4-vinylpyridin) (1) mit 1,4-Dibrombutan (2) dargestellt und ihre Komplexbildung mit Metallionen wurde untersucht. Es wurde gefunden, das die Stabilitatskonstanten (K) von Cu-3 groser sind als die von Cu-1, und das 3 Cu-Ionen in hoherer Ausbeute adsorbiert. K und die Adsorptionskapazitat von Cu nehmen mit zunehmendem Vernetzungsgrad ab. Spektren im sichtbaren Bereich und ESR-Spektren von Cu-3 zeigen, das die Struktur der Cu-Komplexe innerhalb von 3 und die eines monomeren Cu-Pyridin-Komplexes gleich sind. Die Ligandenkette in den hoher vernetzten Komplexen 3c und 3d wird jedoch weniger beweglich, wodurch die quadratische flache Struktur eines stabilen Cu-Komplexes verzerrt wird. Der Gehalt an adsorbierten Cu-, Fe-, Cr-, Ni-, und Zn-Ionen an 3 nimmt mit der Vernetzung ab. Die Vernetzung hat jedoch keinen Einflus auf die Adsorption von Hg-Ionen. Die Metallkomplexe von 1 wurden gemas Schema 1 vernetzt, und das als Matrize venvendete Metallion wird vom erhaltenen 3 gut absorbiert, woraus gefolgert wird, das die Ligandenkette in der besten Konformation fur das als Matrize verwendete Ion erhalten bleibt.

Using Listener Judgments to Investigate Linguistic Influences on L2 Comprehensibility and Accentedness: A Validation and Generalization Study

Abstract: The current study investigated linguistic influences on comprehensibility (ease of understanding) and accentedness (linguistic nativelikeness) in second language (L2) learners’ extemporaneous speech. Target materials included picture narratives from 40 native French speakers of English from different proficiency levels. The narratives were subsequently rated by 20 native speakers with or without linguistic and pedagogical experience for comprehensibility, accentedness, and 11 linguistic variables spanning the domains of phonology, lexis, grammar, and discourse structure. Results showed that comprehensibility was associated with several linguistic variables (vowel/consonant errors, word stress, fluency, lexis, grammar), whereas accentedness was chiefly linked to pronunciation (vowel/consonant errors, word stress). Native-speaking listeners thus appear to pay particular attention to pronunciation, rather than lexis and grammar, to evaluate nativelikeness but tend to consider various sources of linguistic information in L2 speech in judging comprehensibility. The use of listener ratings (perceptual measures) in evaluating linguistic aspects of learner speech and their implications for language assessment and pedagogy are discussed.

Hypoxia-inducible factors and their roles in energy metabolism

Abstract: Over the course of evolution, aerobic organisms have developed sophisticated systems for responding to alterations in oxygen concentration, as oxygen acts as a final electron acceptor in oxidative phosphorylation for energy production. Hypoxia-inducible factor (HIF) plays a central role in the adaptive regulation of energy metabolism, by triggering a switch from mitochondrial oxidative phosphorylation to anaerobic glycolysis in hypoxic conditions. HIF also reduces oxygen consumption in mitochondria by inhibiting conversion of pyruvate to acetyl CoA, suppressing mitochondrial biogenesis and activating autophagy of mitochondria concomitantly with reduction in reactive oxygen species production. In addition, metabolic reprogramming in response to hypoxia through HIF activation is not limited to the regulation of carbohydrate metabolism; it occurs in lipid metabolism as well. Recent studies using in vivo gene-targeting technique have revealed unexpected, but novel functions of HIF in energy metabolism in a context- and cell type-specific manner, and shed light on the possibility of pharmaceutical targeting HIF as a new therapy against many diseases, including cancer, diabetes, and fatty liver.

Effects of nano-filler addition on partial discharge resistance and dielectric breakdown strength of Micro-Al 2 O 3 Epoxy composite

Abstract: It is often observed that the insulation structure for an insulated gate bipolar transistor (IGBT) suffers from dielectric failure, when the insulation is made of epoxy resin to which micro fillers with a high thermal conductivity were added. In order to reveal the above phenomena and to clarify the breakdown (BD) mechanism, we have carried out experiments using an MB-PWB (metal-base printed wiring board) insulation simulated structure. As a result, it was clarified that the IGBT insulation breaks down after successive partial discharges (PDs). It was also elucidated that BD strength becomes lower, when epoxy resin was loaded with high content of micro-fillers. A trial was made to raise the once-lowered BD strength by adding nano-Al2O3 fillers. Three kinds of experiments were carried out, i.e. an MB-PWB insulation simulated structure for dielectric failure, a rod-to-plane electrode for PD erosion resistance, and a sphere-to-sphere electrode for BD strength for four kinds of insulation samples, i.e. neat epoxy, 5-wt% nano- Al2O3/epoxy composite, 60-wt% micro-Al2O3/epoxy composite, and combined 2-wt% nano- and 60-wt% micro-Al2O3/epoxy composite. It was clarified that the nano-micro-composite is higher in both BD strength and PD resistance than the micro-composite. It should be noted that the addition of nano-fillers would provide an excellent approach that can increase the dielectric BD strength and time of micro-filled epoxy composites.