Tohoku University

About: Tohoku University is a education organization based out in Sendai, Japan. It is known for research contribution in the topics: Magnetization & Population. The organization has 72116 authors who have published 170791 publications receiving 3941714 citations. The organization is also known as: Tōhoku daigaku.

Postcolumn derivatization liquid chromatographic method for paralytic shellfish toxins

Abstract: More than 20 analogues of saxitoxin occur naturally. An accurate analytical method applicable to all saxitoxins is required because of the recent findings that decarbamoyl toxins and C (N- sulfocarbamoyl-11-hydroxysulfate) toxins are metabolites of marine animals or major products of some dinoflagellate species. Almost all the toxins could be determined by ion-interaction chromatography on a silica-based reversed-phase (C 8 ) column with postcolumn periodate oxidation and fluorescence detection. Toxin groups of different net charges were separately determined by isocratic elution using different mobile phases. For determination of the saxitoxin group (net charge, 2+) and the gonyautoxin group (net charge, 1+), use of 1-heptanesulfonate as counterion, with or without acetonitrile in the mobile phase, resulted in resolution of decarbamoyl toxins from their carbamate analogues. C toxins having both N-sulfocarbamoyl and 11-hydroxysulfate moieties on the same molecule were completely resolved using the tetrabutylammonium ion. High sensitivity with detection limits ranging from 20 to 110 fmol were achieved as a result of reduced band broadening and optimized reaction conditions. For applications to biological matrixes, a cleanup procedure using a C 18 solid-phase extraction cartridge was effective in preventing false peaks. When applied to low-toxicity shellfish, the liquid chromatographic method gave higher values than the standard mouse bioassay, because of underestimation by the bioassay

Mechanisms of impulsive pressure generation and damage pit formation by bubble collapse

Abstract: A detailed experimental study has been made to clarify the mechanism of impulsive pressure generation from a single bubble collapsing in a static fluid – this is the most essential and important research task concerned with cavitation damage. First, the general feature of impulsive pressure generation is discussed, and then the impulsive pressure directly contributing to damage is investigated by various means. As a result, it is found that the impulsive pressure causing plastic deformation of material is closely related, directly or indirectly, to the behaviour of a liquid jet. Further more, it is demonstrated that the interaction of a tiny bubble with a shock wave or a pressure wave must be an important effect in producing a local high pressure which causes damage to material. The damage pit caused by the bubble-shock-wave interaction essentially results from the impact pressure from a liquid microjet.

Glucose and fructose decomposition in subcritical and supercritical water: Detailed reaction pathway, mechanisms, and kinetics

Abstract: Experiments were performed on the products of glucose decomposition at short residence times to elucidate the reaction pathways and evaluate kinetics of glucose and fructose decomposition in sub- and supercritical water. The conditions were a temperature of 300−400 °C and pressure of 25−40 MPa for extremely short residence times between 0.02 and 2 s. The products of glucose decomposition were fructose, a product of isomerization, 1,6-anhydroglucose, a product of dehydration, and erythrose and glyceraldehyde, products of C−C bond cleavage. Fructose underwent reactions similar to glucose except that it did not form 1,6-anhydroglucose and isomerization to glucose is negligible. The mechanism for the products formed from C−C bond cleavage could be explained by reverse aldol condensation and the double-bond rule of the respective enediols formed during the Lobry de Bruyn Alberda van Ekenstein transformation. The differential equations resulting from the proposed pathways were fit to experimental results to obt...