2,039 research outputs found
Millettia pseudoracemosa Thothathri & Ravikumar 1997
No full textIdentities of <i>Millettia pseudoracemosa</i> and <p> <b> <i>Millettia pseudoracemosa</i> Thothathri & Ravikumar (1997: 239) was described on the basis of a single collection (<i>S. Ravikumar 334</i>, Fig. 1: A–B), which was collected on 21 April 1995 from Anamalai Hills, Tamil Nadu, South India. The new species was considered to be similar to <i>M. racemosa</i> (Roxburgh 1832: 329) Bentham (1852: 249) in habit, shape, number and hairiness of leaflets, floral color, and pod shape. The latter species was first described based on specimens also from India, but it has been treated as a monospecific genus <i>Endosamara</i> Geesink (1984: 93) belonging to the tribe Wisterieae because of its true panicles with ebracteole flowers and very peculiar fruits with a lomented endocarp around each seed (Compton <i>et al.</i> 2019). Thothathri & Ravikumar (1997) also pointed out that their new species has a unique character in the genus, i.e. the large sized (2.5–3.0 cm long) and violet flowers.</b> </p>Published as part of <i>Song, Zhu-Qiu, 2023, The identities of Millettia pseudoracemosa and M. pulchra var. munnarensis (Fabaceae: Millettieae) from South India, pp. 55-63 in Phytotaxa 591 (1)</i> on page 56, DOI: 10.11646/phytotaxa.591.1.5, <a href="http://zenodo.org/record/7784270">http://zenodo.org/record/7784270</a>
Bauhinia bassacensis var. nicobarica Tiwari U. L., K. Ravikumar & N. Balachandran 2013, var. nov.
No full textBauhinia bassacensis var. nicobarica Tiwari U.L., K. Ravikumar & N. Balachandran, var. nov. (Figs. 1 & 2) Differs from the typical variety in having exstipulate leaves, lobes of leaves obtuse at apex, bract rusty tomentose and ovate, bracteoles 2, lanceolate, rusty tomentose; fertile stamens always 2; filaments hairy, anther lobes brown. Type:— INDIA. Great Nicobar Island: Near Army land, Campbell Bay, 20 February 2013, N- 71 o 2’ 2.9’’, E 93 o 55’ 2.9’’, 16 m ASL, K . Ravikumar, N. Balachandran and Umeshkumar Tiwari 115533 (holotype FRLH!; isotypes FRLH!, PBL!). Large, woody, climbers; tendrils coiled stout, glabrous; young branches rusty tomentose, mature grooved and lenticellate. Leaves exstipulate; petioles glabrescent, 2 7 cm long; lamina ovate-cordate, ca. 19 × 13 cm, 9 13-nerved, bifid, down to 3.5 4.8 cm length with narrow sinus, apex of lobes obtuse, base cordate, upper surface glabrous, lower brownish tomentose to glabrescent, base of the lamina with two distinct glands expanding up to pulvinous base. Inflorescences lateral or terminal, many-flowered, racemes or panicles; peduncles rusty tomentose; pedicels ca. 3.5 cm long in flower and ca. 7 cm long in fruit; bracts ovate, rusty tomentose, ca. 0.5 mm long; bracteoles 2, lanceolate, inserted near the middle of the pedicels, rusty tomentose, 1–1.5 mm long. Buds ovoid, rusty tomentose, 4–6 mm long. Hypanthium c. 1 mm long. Calyx during anthesis splitting into 2 segments forming right angles with the pedicels, 5–7 mm long, sometime persistent with fruit. Petals 2 above and three below, pubescent, creamish with purplish-red veins prominent on both sides, blade deltoid, crumpled, subequal, narrowly ovate to suborbicular with undulate margin, ca. 6 × 5 mm; claw 1.5–2 cm long, soft hairy. Stamens 9 (2 + 7); fertile stamens 2, staminodes absent sometime 1; filaments 1.2–1.6cm long, hairy; anthers 1–2 mm long, lobes brown; reduced stamens 7 in number, unequal, 3–9 mm long, filiform, white. Carpels densely brownish pilose, distinctly stalked, styles 6-8 mm, hairy with a small capitate stigma. Pods rusty tomentose, 8–13 × 3–4 cm with persistent style, stalks c. 3 mm long; styles persistent in fruit. Seeds, 2–5, dark brown, flattened, oblong-orbicular, c. 1.5 × 2 cm, smooth, glabrous. Flowering & Fruiting:— From February to March. Distribution:— India: Campbell Bay, Great Nicobar Island, Andaman and Nicobar Islands. Habitat:— Liana in mixed semi-evergreen forests. Ecological status:— About three individuals confined to an area of 1 km 2 were observed during field survey. Though it qualifies to be kept under Critically Endangered (CR) category, further studies and explorations in adjacent areas are required to ascertain its actual status. Etymology:— The varietal epithet refers to the place of its collection. This new variety is allied to typical var. bassacensis and var. backeri, but differs from both markedly in having exstipulate leaves, lobes of leaves obtuse at apex, bract rusty tomentose and ovate, bracteoles 2, lanceolate, rusty tomentose; fertile stamens always 2; filaments hairy, anther lobes brown (see table 1).Published as part of Tiwari, Umeshkumar, Ravikumar, Kaliamoorthy & Balachandran, Natesan, 2013, A new variety of Bauhinia bassacensis (Leguminosae: Caesalpinioideae) from Great Nicobar Island, India, pp. 12-18 in Phytotaxa 149 (1) on pages 13-16, DOI: 10.11646/phytotaxa.149.1.2, http://zenodo.org/record/510042
Electron transfer with core-level excitations at hybrid interfaces
No full textElectron core-level spectroscopies have emerged as effective tools to investigate several aspects of the hybrid interface between organic molecules and a substrate. In particular, resonant photoemission spectroscopy can measure interfacial electron transfer times down to the femtosecond timescale. Furthermore, the strong perturbation induced by the core hole opens up the several questions on how the properties of the interface are modified, calling for a theoretical description of the core-excited system.
We adopt a theoretical framework based on density-functional theory (DFT), where the excitation is introduced explicitly in the core-level occupation of an atom in a molecule, to investigate the electronic structure and electron transfer from/to organic molecules adsorbed on metal, semimetal, and semiconducting substrates.
The perturbing potential lowers the energy of the molecular orbitals. Focusing on the lowest-unoccupied (LUMO), a filling of the core-excited LUMO* by substrate electrons may occur within the core-hole lifetime, as found for molecules on metals where the adsorption angle is also shown to influence the electron transfer rate [1,2]. In the case of a semimetal graphene substrate, a spin-polarized LUMO* pinned at the Fermi level can be determined for physisorbed molecules. In that case electron transfer would be suppressed given the low density of states of unsupported graphene at that energy, but still possible for graphene supported on a metal [3]. For molecules adsorbed on a semiconductor, the LUMO* may form a bound exciton in the gap [4]. Here, we found especially interesting to consider the influence of thermal motion on the energy-level alignment and the absorption coefficient [5,6].
References
[1] D. Cvetko, G. Fratesi, G. Kladnik, A. Cossaro, G.P. Brivio, L. Venkataraman, and A. Morgante, submitted.
[2] A. Baby, G. Fratesi, S.R. Vaidya, L.L. Patera, C. Africh, L. Floreano, G.P. Brivio, J. Phys. Chem. C 119 (2015) 3624.
[3] A. Ravikumar, A. Baby, H. Lin, G.P. Brivio, and G. Fratesi, Scientific Reports 6 (2016) 24603.
[4] G. Fratesi, C. Motta, M. I. Trioni, G. P. Brivio, and D. Sánchez-Portal, J. Phys. Chem. C 118 (2014) 8775
[5] H. Lin, G. Fratesi, S. Selçuk, G.P. Brivio, and A. Selloni, J. Phys. Chem. C, 120 (2016) 3899.
[6] M. Muller, D. Sànchez-Portal, H. Lin, G. Fratesi, G.P. Brivio, and A. Selloni, in preparation
Public vs Private Schooling in an Endogenous Growth Model
No full textI present an overlapping generations model, with formal education as the engine of growth, close to Glomm and RaviKumar (1992). Contrary to Glomm and Ravikumar, I Show that public schooling, when compared to a private system, may stimulate economic growth.
sj-xlsx-3-pul-10.1177_20458940211031109 - Supplemental material for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension
No full textSupplemental material, sj-xlsx-3-pul-10.1177_20458940211031109 for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension by Ravikumar Sitapara, TuKiet T. Lam, Aneta Gandjeva, Rubin M. Tuder and Lawrence S. Zisman in Pulmonary Circulation</p
sj-pdf-4-pul-10.1177_20458940211031109 - Supplemental material for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension
No full textSupplemental material, sj-pdf-4-pul-10.1177_20458940211031109 for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension by Ravikumar Sitapara, TuKiet T. Lam, Aneta Gandjeva, Rubin M. Tuder and Lawrence S. Zisman in Pulmonary Circulation</p
sj-xlsx-2-pul-10.1177_20458940211031109 - Supplemental material for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension
No full textSupplemental material, sj-xlsx-2-pul-10.1177_20458940211031109 for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension by Ravikumar Sitapara, TuKiet T. Lam, Aneta Gandjeva, Rubin M. Tuder and Lawrence S. Zisman in Pulmonary Circulation</p
sj-pdf-1-pul-10.1177_20458940211031109 - Supplemental material for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension
No full textSupplemental material, sj-pdf-1-pul-10.1177_20458940211031109 for Phosphoproteomic analysis of lung tissue from patients with pulmonary arterial hypertension by Ravikumar Sitapara, TuKiet T. Lam, Aneta Gandjeva, Rubin M. Tuder and Lawrence S. Zisman in Pulmonary Circulation</p
sj-docx-1-pie-10.1177_09544089221112162 - Supplemental material for Study on tribological behaviour of aluminium hybrid composites strengthened with novel groundnut shell ash and boron carbide
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089221112162 for Study on tribological behaviour of aluminium hybrid composites strengthened with novel groundnut shell ash and boron carbide by L. Venkatesh, T.V. Arjunan, M. Arulraj and K. Ravikumar in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
Tuning ultrafast electron injection dynamics at organic-graphene/metal interfaces
No full textThe properties of novel and prospective 2D materials are dramatically influenced by the interaction with a substrate. For example, the electronic hybridization of silicene states on Ag(111) or graphene ones on Ni(111) disrupts the Dirac fermions of the freestanding layers. This calls for efficient approaches to tune the interaction strength at the interface. Here we focus on the case of graphene functionalized by organic molecules and grown on Ni(111) and on the interfacial charge transfer dynamics. This is investigated by X-ray resonant photoemission spectroscopy, that is able to measure electron transfer rates occurring within few femtoseconds, and by a theoretical framework based on density-functional theory [1,2].
We use 4,4’-bipyridine as the prototypical molecule for these explorations as the energy level alignment of core-excited molecular orbitals allows ultrafast injection (τ=4fs) of electrons from the substrate to the molecule adsorbed on epitaxial graphene/Ni(111), which is characterized by a strong hybridization between C and metal states. We demonstrate that this interface can be decoupled by the addition of a second layer of graphene, where the one in contact with the metal acts as a buffer layer and the one in contact with the molecule is less hybridized with Ni underneath. As a result, the ultrafast injection of electrons from the substrate to the molecule is ∼4 times slower on weakly coupled bilayer graphene than on epitaxial graphene. Through our experiments and calculations, we can attribute this to a difference in the density of states close to the Fermi level between graphene and bilayer graphene. We therefore show how graphene coupling with the substrate influences charge transfer dynamics between organic molecules and graphene interfaces.
[1] G. Fratesi, C. Motta, M. I. Trioni, G. P. Brivio, and D. Sánchez-Portal, J. Phys. Chem. C 118, 8775 (2014)
[2] D. Cvetko, G. Fratesi, G. Kladnik, A. Cossaro, G.P. Brivio, L. Venkataraman, and A. Morgante, Phys. Chem. Chem. Phys. 18, 22140 (2016)
[3] A. Ravikumar, G. Kladnik, M. Müller, A. Cossaro, G. Bavdek, L. Patera, D. Sánchez-Portal, L. Venkataraman, A. Morgante, G. P. Brivio, D. Cvetko, and G. Fratesi, Nanoscale 10, 8014 (2018)
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