44,033 research outputs found
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
FIGURE 2. Aristolochia gurinderii K in Aristolochia gurinderii (Aristolochiaceae): a new species from Great Nicobar Island, India
No full textFIGURE 2. Aristolochia gurinderii K. Ravikumar, Umeshkumar Tiwari and N. Balachandran, sp. nov.: A. Leaf with fruit; B. Inflorescence; C. Flower patterns; D. Close up of Flower; E. Dry Fruits and F. Green Fruit (Type: FRLH).Published as part of Ravikumar, K., Tiwari, Umeshkumar & Balachandran, N., 2014, Aristolochia gurinderii (Aristolochiaceae): a new species from Great Nicobar Island, India, pp. 117-122 in Phytotaxa 172 (2) on page 120, DOI: 10.11646/phytotaxa.172.2.7, http://zenodo.org/record/514244
Spectroscopic Fingerprints of sp1 Hybridized C in Surface-Grown Molecular Assemblies
No full textThe advent of on-surface chemistry and molecular self-assembly opened the way to the realization of organic materials whose lack of stability in vacuo would otherwise forbid their synthesis. Recently the on-surface coupling of the precursors has also been used to synthesize adsorbed organic systems with chemically vulnerable linear carbon chains with sp 1 hybridization [1]. A notable advantage of on-surface synthesis is that the full realm of the experimental and theoretical surface science toolbox is available for the investigation. While the method of choice for surface-supported architectures is the scanning tunneling microscope and ultimate resolution is achieved by low-T non-contact atomic force microscopy, electron core-level spectroscopy can provide an even more local probe of the electronic properties of the material. In particular, polarized near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is here suggested to discriminate sp 1 /sp 2 character in the structures. We present an ab initio study of the polarized NEXAFS spectrum of model and real sp 1 /sp 2 materials. Calculations are performed within density functional theory with plane waves and pseudopotentials, and spectra are computed by core-excited C potentials as validated by previous studies [2,3]. We evaluate the dichroism in the spectrum for ideal carbynes and highlight the main differences relative to typical sp 2 systems. We then consider a mixed polymer alternating sp 1 C 4 units with sp 2 biphenyl groups, recently synthesized on Au(111) [4], as well as other linear structures and two-dimensional networks, pointing out a spectral line shape specifically due to the the presence of linear C chains [5]. Our study suggests that the measurements of polarized NEXAFS spectra could be used to distinctly fingerprint the presence of sp 1 hybridization in surface-grown C structures. [1] Q. Sun, R. Zhang, J. Qiu, R. Liu, and W. Xu, Adv. Mater. 2018, 30, 1705630 [2] G. Fratesi, V. Lanzilotto, L. Floreano, and G. P. Brivio, J. Phys. Chem. C 2013, 117, 6632 [3] G. Fratesi, V. Lanzilotto, S. Stranges, M. Alagia, G. P. Brivio, and L. Floreano, Phys. Chem. Chem. Phys. 2014, 16, 14834 [4] Q. Sun, L. Cai, H. Ma, C. Yuan, and W. Xu, ACS Nano 2016, 10, 7023 [5] G. Fratesi, S. Achilli, N. Manini, G. Onida, A. Baby, A. Ravikumar, A. Ugolotti, G.P. Brivio, A. Milani, and C.S. Casari, Materials 2018, 11, 255
Rhodium Catalyzed Stereoselective Mono-alkenylation of Aryl sp2 C-H Bond via C-N Bond Cleavage: N-allylbenzimidazole as Strategic Alkenylating Agent
No full textA Rh-catalyzed C(sp2)-H alkenylation has been achieved by taking N-allylbenzimidazole as an allylamine congener. This distinctive transformation has been observed for the first time which is attributed to the rigid benzimidazole unit. Lewis acid assisted cleavage of C(sp3)-N bond by coordinating to the N3 of N-allylbenzimidazole has been established. Thus, herein we have demonstrated an unprecedented protocol of domino C-N bond cleavage followed by aryl C(sp2)-H alkenylation. Further, detailed mechanistic studies, control experiments have been conducted to understand the mechanism. The rhodacycle-intermediates involved in the reaction have been isolated and characterized through NMR, HRMS, and single crystal X-ray
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Acid/Base Controlled Size Modulation of Capsular Phosphates, Hydroxide Encapsulation, Quantitative and Clean Extraction of Sulfate with Carbonate Capsules of a Tripodal Urea Receptor
No full textA simple tris-(2-aminoethyl) amine based pentafluorophenyl substituted tripodal urea receptor L has been extensively studied as a versatile receptor for various anions. Combined H-1-NMR, Isothermal Titration Calorimetry (ITC) and single crystal X-ray diffraction studies reveal that mononegative anions like F-, OH- and H2PO4- are encapsulated into the pseudocapsular dimeric assemblies of L with 1 : 1 stoichiometry whereas dinegative anions like CO32-, SO42- and HPO42- form tight capsular dimeric assemblies of L with 1 : 2 stoichiometries. Single crystal X-ray diffraction study clearly depicts that the size of the dimer of H2PO4- encapsulated pseudocapsule is 13.8 angstrom whereas the size of the tight HPO42- encapsulated capsular assembly is only 9.9 angstrom. The charge dependent anion encapsulated capsular size modulation of phosphates has been demonstrated by simple acid/base treatment via solution state P-31-NMR and single crystal X-ray diffraction studies. L is also capable of encapsulating hydroxide in its C-3v-symmetric cavity that is achieved upon treating a DMSO solution of L with tetrabutylammonium (TBA) cyanide and characterized by single crystal X-ray diffraction study. To the best of our knowledge this is the first report on the encapsulation of hydroxide in a neutral synthetic receptor. The excellent property of L to quantitatively capture aerial CO2 in the form of CO32- capsules [L-2(CO3)][N(n-Bu)(4)](2) in basic DMSO solution has been utilized to study the liquid-liquid extraction of SO42- from water via anion exchange. Almost quantitative and clean extraction of SO42- from water (99% from extracted pure mass and > 95% shown gravimetrically) has been unambiguously demonstrated by NMR, FT-IR, EDX, XRD and PXRD studies. Selective SO42- extraction is also demonstrated even in the presence of H2PO4- and NO3-. On the other hand the mixtures of L and TBACl (to solubilize L in CHCl3) results impure sulfate extraction even when 1 : 1 L/TBACl is used. Similar impure SO42- extraction is also observed when organic layers containing [L(Cl)][N(n-Bu)(4)] are used as the extractant, obtained upon precipitating SO42- from the extracted mass, [L-2(SO4)][N(n-Bu)(4)](2) in the carbonate capsules method using aqueous BaCl2 solution.Department of Science and TechnologyCSIR, IndiaChemistr
Recommended from our members
Greedy structure learning of Markov Random Fields
No full texttextProbabilistic graphical models are used in a variety of domains to capture and represent general dependencies in joint probability distributions. In this document we examine the problem of learning the structure of an undirected graphical model, also called a Markov Random Field (MRF), given a set of independent and identically distributed (i.i.d.) samples. Specifically, we introduce an adaptive forward-backward greedy algorithm for learning the structure of a discrete, pairwise MRF given a high dimensional set of i.i.d. samples. The algorithm works by greedily estimating the neighborhood of each node independently through a series of forward and backward steps. By imposing a restricted strong convexity condition on the structure of the learned graph we show that the structure can be fully learned with high probability given samples where is the dimension of the graph and is the number of nodes. This is a significant improvement over existing convex-optimization based algorithms that require a sample complexity of and a stronger irrepresentability condition. We further support these claims with an empirical comparison of the greedy algorithm to node-wise -regularized logistic regression as well as provide a real data analysis of the greedy algorithm using the Audioscrobbler music listener dataset. The results of this document provide an additional representation of work submitted by A. Jalali, C. Johnson, and P. Ravikumar to NIPS 2011.Computer Scienc
Core level spectra of organic molecules adsorbed on graphene
No full textWe perform first principle calculations based on density functional theory to investigate the effect of the adsorption of core-excited organic molecules on graphene. We simulate Near Edge X-ray absorption Fine Structure (NEXAFS) and X-ray Photoemission Spectroscopy (XPS) at the N and C edges for two moieties: pyridine and the pyridine radical on graphene, which exemplify two different adsorption characters. The modifications of molecular and graphene energy levels due to their interplay with the core-level excitation are discussed. We find that upon physisorption of pyridine, the binding energies of graphene close to the adsorption site reduce mildly, and the NEXAFS spectra of the molecule and graphene resemble those of gas phase pyridine and pristine graphene, respectively. However, the chemisorption of the pyridine radical is found to significantly alter these core excited spectra. The C 1s binding energy of the C atom of graphene participating in chemisorption increases by ∼1 eV, and the C atoms of graphene alternate to the adsorption site show a reduction in the binding energy. Analogously, these C atoms also show strong modifications in the NEXAFS spectra. The NEXAFS spectrum of the chemisorbed molecule is also modified as a result of hybridization with and screening by graphene. We eventually explore the electronic properties and magnetism of the system as a core-level excitation is adiabatically switched on
Ambiguity and communication
No full textThe ambiguity of a nondeterministic finite automaton (NFA) N for input size n is the maximal number of accepting computations of N for an input of size n. For all k, r 2 N we construct languages Lr,k which can be recognized by NFA's with size k poly(r) and ambiguity O(nk), but Lr,k has only NFA's with exponential size, if ambiguity o(nk) is required. In particular, a hierarchy for polynomial ambiguity is obtained, solving a long standing open problem (Ravikumar and Ibarra, 1989, Leung, 1998)
Fast implementation of iterative adaptive approach for wideband unambiguous radar detection
No full textAccepted author manuscriptMicrowave Sensing, Signals & System
- …
