Numerical Simulation on the Driftwood Behavior in Open-Channel Flows by Using the Distinct Element Method

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

Oxy-trifluoromethylation of alkenes and its application to the synthesis of β-trifluoromethylstyrene derivatives

AbstractOxy-trifluoromethylation of di-substituted styrenes and dienes was achieved by using Cu/Togni's reagent system. Not only gem-di-substituted styrenes, but also a β-methylstyrene derivative were transformed to the corresponding oxy-trifluoromethylation products. 1,4-Addition products were obtained selectively in the reaction of mono-substituted dienes. These reactions provide a new approach for the synthesis of β-trifluoromethyl styrene derivatives

Does blended problem-based learning make Asian medical students active learners?:A prospective comparative study

Background: Asian educators have struggled to implement problem-based learning (PBL) because students rarely discuss their work actively and are not sufficiently engaged in self-directed learning. Supplementing PBL with additional e-learning, i.e. 'blended' PBL (bPBL), could stimulate students' learning process. Methods: We investigated the effects of bPBL on tutorial group functioning (discussion, self-efficacy, self-directed learning, active participation, and tutor's perceived authority) and students' level of acceptance of the e-learning elements. We compared PBL and bPBL in a medical university in Japan. In the bPBL condition, the tutor's instructions were replaced with online materials and short quizzes. After the course, a 13-item questionnaire using a 5-point Likert scale was distributed regarding the tutorial group functioning of the tutorial group (influence of discussion, self-efficacy, self-directed learning, active participation, and tutors' authority). The mean scores of subscales were compared with analysis of covariance. Knowledge levels were measured using a pre-test post-test design. A multiple regression analysis was performed to explore the association between e-learning acceptance and the subscales related to PBL. Results: Ninety-six students participated in the study (PBL: n = 24, bPBL: n = 72). Self-efficacy and motivation for learning triggered by group discussions was significantly higher for students in bPBL (p = 0.032 and 0.007, respectively). Knowledge gain in test scores was also significantly better in the bPBL condition (p = 0.026), and self-directed learning related positively to the acceptance of blended learning (p = 0.044). Conclusions: bPBL seemed more effective in promoting active learning and improving knowledge, without affecting tutors' authority. Implementing e-learning into PBL is suggested to be an effective strategy in the Asian context

Crystal Chemistry and Magnetic Properties of Manganese Zinc Alloy "YMn2Zn20" Comprising a Mn Pyrochlore Lattice

The chemical composition, crystal structure, and magnetic properties of a manganese zinc alloy with an ideal composition of YMn2Zn20, which comprises a pyrochlore lattice made of Mn atoms, are reported. The compound is stable only when In or Al is partially substituted for Zn. We have determined the actual chemical formula as YMn2+dZn20-x-dMx, with M = In or Al, and have identified the characteristic preferences with which the incorporated M and excess Mn atoms occupy the three crystallographic sites for Zn atoms. The Mn atoms in the pyrochlore lattice possess small magnetic moments that interact with each other antiferromagnetically but exhibit no long-range order above 0.4 K, probably owing to the geometrical frustration of the pyrochlore lattice. As a result, the effective mass of the conduction electrons is considerably enhanced, as observed in the related pyrochlore-lattice compounds (Y,Sc)Mn2 and LiV2O4. However, the presence of excess Mn atoms with large localized magnetic moments comparable to spin 5/2 tends to mask the inherent magnetism of the pyrochlore Mn atoms. It is suggested that "YMn2Zn18In2" with neither excess Mn atoms nor site disorder would be an ideal compound for further study.Comment: 19 pages, 18 figures, accepted for publication in J. Solid State Che

Structure Effect on Antioxidant Activity of Catecholamines toward Singlet Oxygen and Other Reactive Oxygen Species in vitro

The reactivity of catecholamine neurotransmitters and the related metabolites were precisely investigated toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and reactive oxygen species. Catecholamines reacted immediately with DPPH radicals, their reactivity being stronger than that of ascorbic acid as a reference. Superoxide scavenging activities of catecholamines determined by WST-1 and electron spin resonance (ESR) spin trapping methods were also high. Whereas tyrosine, the dopamine precursor showed no reactivity toward superoxide. The reactivity toward singlet oxygen was evaluated by observing specific photon emission from singlet oxygen. The results revealed that reactivity of catecholamines was markedly higher than that of sodium azide, and catechin as catechol reference. The reaction of catecholamines and singlet oxygen was further studied by ESR using 55-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trapping reagent and rose bengal as photosensitizer. DMPO-OH signal of epinephrine was significantly small compared to other catecholamines, catechin, and 4-methylcatechol as a reference compound and was as small as that of tyrosine. The signal formation was totally dependent on singlet oxygen, and the presence of catechol compounds. These results indicated that epinephrine is the most potent singlet oxygen quencher than other catecholamines, and the secondary amino group in its alkyl side chain could play a role in unique singlet oxygen quenching property of epinephrine

Phospholipase C Produced by Clostridium botulinum Types C and D:Comparison of Gene, Enzymatic, and Biological Activities with Those of Clostridium perfringens Alpha-toxin

Clostridium botulinum type C and D strains recently have been found to produce PLC on egg yolk agar plates. To characterize the gene, enzymatic and biological activities of C. botulinum PLCs (Cb-PLCs), the cb-plc genes from 8 strains were sequenced, and 1 representative gene was cloned and expressed as a recombinant protein. The enzymatic and hemolytic activities of the recombinant Cb-PLC were measured and compared with those of the Clostridium perfringens alpha-toxin. Each of the eight cb-plc genes encoded a 399 amino acid residue protein preceded by a 27 residue signal peptide. The protein consists of 2 domains, the N- and C-domains, and the overall amino acid sequence identity between Cb-PLC and alpha-toxin was greater than 50%, suggesting that Cb-PLC is homologous to the alpha-toxin. The key residues in the N-domain were conserved, whereas those in the C-domain which are important in membrane interaction were different than in the alpha-toxin. As expected, Cb-PLC could hydrolyze egg yolk phospholipid, p-nitrophenylphosphorylcholine, and sphingomyelin, and also exhibited hemolytic activity;however, its activities were about 4- to over 200-fold lower than those of alpha-toxin. Although Cb-PLC showed weak enzymatic and biological activities, it is speculated that Cb-PLC might play a role in the pathogenicity of botulism or for bacterial survival

Dusty ERO Search behind Two Massive Clusters

We performed deep K'-band imaging observations of 2 massive clusters, MS 0451.6-0305 at z = 0.55 and MS 0440.5+0204 at z = 0.19, for searching counterparts of the faint sub-mm sources behind these clusters, which would provide one of the deepest extremely red object(ERO) samples. Comparing our near-infrared images with optical images taken by the Hubble Space Telescope and by the Subaru Telescope, we identified 13 EROs in these fields. The sky distributions of EROs are consistent with the previous results, that there is a sign of strong clustering among detected EROs. Also, the surface density with corrected lensing amplification factors in both clusters are in good agreement with that derived from previous surveys. We found 7 EROs and 3 additional very red objects in a small area (\sim 0.6 arcmin^2) of the MS 0451.6-0305 field around an extended SCUBA source. Many of their optical and near-infrared colors are consistent with dusty star-forming galaxies at high redshifts(z \sim 1.0-4.0), and they may be constituting a cluster of dusty starburst galaxies and/or lensed star-forming galaxies at high redshift. Their red J-K' colors and faint optical magnitudes suggest they are relatively old massive stellar systems with ages(>300 Mega years) suffering from dust obscuration. We also found a surface-density enhancement of EROs around the SCUBA source in the MS 0440.5+0204 field.Comment: 19 pages, 11 figures, Latex(using pasj00.cls). To be published in PASJ vol 55, No. 4(Aug 2003