476 research outputs found
Temperature sensitivity of Ge-B-SiO<sub>2</sub> waveguide Bragg gratings on a crystallized glass substrate
No full textWaveguide Bragg gratings were fabricated by plasma-enhanced chemical-vapor deposition followed by irradiation with KrF excimer laser light through a phase mask. The period of the Bragg grating was 0.53 µm, and the Bragg wavelength was 1.53 µm. The temperature dependence of the Bragg wavelength was 11 pm/°C for a 10 GeO2 - 90SiO2 (mol.%) core waveguide on a Si substrate, and the Bragg wavelength shift was successfully reduced to 5.0 pm/°C by use of a 14GeO2 - 12B2O3 - 74SiO2 (mol.%) core and a crystallized glass substrate with a thermal-expansion coefficient of -2.0 x 10-6 (/°C)
Hormonal crosstalk in the regulation of meristem activity and the phyllomorph architecture in Streptocarpus (Gesneriaceae): a review
No full textPlants belonging to the family Gesneriaceae exhibit great diversity in shoot architecture. One genus within the family, Streptocarpus, encompasses species with different body plans that do not conform to the standard bauplan of angiosperms. These include features such as ‘anisocotyly’, the unequal cotyledon morphogenesis, and the ‘phyllomorph’ a leaf/shoot
construct of which the development is governed by three meristems (groove meristem, petiolode meristem, basal
meristem). In the extreme case, the plants only consist of one hugely enlarged cotyledon (‘unifoliate’ habit). Modification in the position and activities of the meristem are responsible for the morphological flexibility of the genus. This review summarises the
interactions between hormones and developmental genes and compares these to model plants. Some mechanisms controlled by class 1 KNOX (KNOX1) genes appear to be conserved between plants with
ordinary shoots and the Streptocarpus phyllomorph, while others have diverged. In particular, cytokinins and gibberellins appear to be important for meristem regulation to establish anisocotyly and the development of phyllomorphs in Streptocarpus through KNOX1 regulation. This is supported by expression patterns from hormone metabolism genes. The establishment of anisocotyly is based on an imbalance between cytokinins and gibberellins, causing a shift from apical to lateral dominance that involves the suppression of the microcotyledon and groove meristem and promotion of the basal meristem. We point out future perspectives
in the study of Streptocarpus organogenesis. Streptocarpusmay provide a system to study the functional evolution of plant form in relation to adaptation to diverse environmental conditions
Light as environmental regulator for germination and macrocotyledon development in Streptocarpus rexii
No full textPd-Catalysed synthesis of carborane sulfides from carborane thiols
No full textMinematsu N., Nishii Y., Hirano K.. Pd-Catalysed synthesis of carborane sulfides from carborane thiols. Chemical Communications 60, 13594 (2024); https://doi.org/10.1039/d4cc03934c.Carboranes are an interesting class of aromatic molecules with icosahedral geometry, high stability, and unique electronic effects. We herein report a Pd-catalysed coupling reaction of carborane thiols with aryl halides. This protocol was applicable to the controlled synthesis of di(carboranyl) sulfides, and their catalytic performance for aromatic halogenation was examined
Gibberellin as a suppressor of lateral dominance snd inducer of apical growth in the unifoliate Streptocarpus wendlandii (Gesneriaceae)
No full textWe report on the effects of exogenously applied hormones on the lateral and apical dominance that governs morphogenesis in the unifoliate Streptocarpus wendlandii. In this phenotype, lateral dominance is extreme as the plants only retain a macrocotyledon that develops into a leaf-like phyllomorph by means of a basal meristem and do not show apical growth. Gibberellin applications suppressed the basal meristem activity of the macrocotyledon resulting in an isocotylous seedling with two microcotyledons and caused the formation of a primary phyllomorph, which suggests that the groove meristem, a shoot apical meristem equivalent, is released from apical suppression by the basal meristem. Interestingly, uniconazol, a gibberellin biosynthesis inhibitor, also caused a reduction in basal meristem activity, but without primary phyllomorph formation, suggesting that some gibberellin is required for proper function of the basal meristem. Co-application of gibberellin and cytokinin resulted in two macrocotyledons also without phyllomorph formation, which is similar to previous results for cytokinin-only applications. Thus, cytokinin may act downstream in the regulatory pathway of the basal meristem. Our results suggest that the balance between gibberellin and cytokinin in the cotyledons appears thus as key factor in the regulation of lateral and apical dominance in Streptocarpus. Their interplay may well be the primary explanation for the great diversity in growth form exhibited in species of this genus. Our work shows that small imbalances of hormones in early stages of plant development can have major effects on the final phenotype
Rhodium-catalysed direct formylmethylation using vinylene carbonate and sequential dehydrogenative esterification
No full textKato M., Ghosh K., Nishii Y., et al. Rhodium-catalysed direct formylmethylation using vinylene carbonate and sequential dehydrogenative esterification. Chemical Communications 57, 8280 (2021); https://doi.org/10.1039/D1CC03362J.A rhodium-catalysed direct formylmethylation adopting vinylene carbonate as an ethynol equivalent is reported. The developed catalytic system is further utilised for the oxidant-free production of esters with the liberation of hydrogen gas. Some control experiments are conducted to elucidate the reaction mechanism
Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives
No full textUeno K., Nishii Y., Miura M.. Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives. Organic Letters. 23(9), 3552-3556, (2021), 7 May 2021; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c00970.Herein we disclose a unique directing effect of 9-substituted triptycenes in electrophilic substitution to achieve the regioselective functionalization of the triptycene core. The Hirshfeld population analysis was adopted to predict the selectivity in electrophilic substitution. TMS and t-Bu groups were found to considerably accelerate the reaction at C2 positions to produce C3-symmetric isomers. Correlation between distortion and charge distribution within benzene rings was systematically examined
Rhodium-catalysed direct formylmethylation using vinylene carbonate and sequential dehydrogenative esterification
No full textKato M., Ghosh K., Nishii Y., et al. Rhodium-catalysed direct formylmethylation using vinylene carbonate and sequential dehydrogenative esterification. Chemical Communications 57, 8280 (2021); https://doi.org/10.1039/D1CC03362J.A rhodium-catalysed direct formylmethylation adopting vinylene carbonate as an ethynol equivalent is reported. The developed catalytic system is further utilised for the oxidant-free production of esters with the liberation of hydrogen gas. Some control experiments are conducted to elucidate the reaction mechanism
Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives
No full textUeno K., Nishii Y., Miura M.. Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives. Organic Letters. 23(9), 3552-3556, (2021), 7 May 2021; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c00970.Herein we disclose a unique directing effect of 9-substituted triptycenes in electrophilic substitution to achieve the regioselective functionalization of the triptycene core. The Hirshfeld population analysis was adopted to predict the selectivity in electrophilic substitution. TMS and t-Bu groups were found to considerably accelerate the reaction at C2 positions to produce C3-symmetric isomers. Correlation between distortion and charge distribution within benzene rings was systematically examined
Oreocharis dasyantha var. ferruginosa K. Y. Pan 1987
No full textOreocharis dasyantha var. ferruginosa Pan (1987: 283). Distribution:—As for species.Published as part of Möller, Michael, Middleton, David, Nishii, Kanae, Wei, Yi-Gang, Sontag, Susanne & Weber, Anton, 2011, A new delineation for Oreocharis incorporating an additional ten genera of Chinese Gesneriaceae, pp. 1-36 in Phytotaxa 23 on page 20, DOI: 10.11646/phytotaxa.23.1.1, http://zenodo.org/record/489401
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