360 research outputs found
Sulfoxides as an intramolecular sulfenylating agent for indoles and diverse applications of the sulfide-sulfoxide redox cycle in organic chemistry
This dissertation involves study of various aspects of sulfoxide chemistry. Specifically designed t-butyl and propanenitrile sulfoxides tethered to indole-2-carboxamide were used as a source of intramolecular sulfenylating agents to synthesize novel indolo[3,2-b]-1-5-benzothiazepinones which are structurally analogous to the other biologically active benzothiazepinones. This study reveals that the intramolecular cyclization of sulfoxide follows an electrophilic sulfenylation (Sulfoxide Electrophilic Sulfenylation, SES) reaction pathway. Evidence of the absence of sulfenic acid as a transient reactive intermediate in such intramolecular cyclization is also provided.
In another study, sulfoxide was used as a “protecting group” of thioether to synthesize 8-membered, indole substituted, thiazocine-2-acetic acid derivative via Ring Closing Metathesis (RCM). Protection (oxidation) of inert (to RCM) sulfide to sulfoxide followed by RCM produced cyclized product in good yields. Deprotection (reduction) of sulfoxide was achieved using Lawessons Reagent (L.R.). Application of the sulfide-sulfoxide redox cycle to solve the existing difficulties in using RCM methodology to thioethers is illustrated.
A new design of a “molecular brake”, based on the sulfide-sulfoxide redox cycle is described. N-Ar rotation in simple isoindolines is controlled by the oxidation state of the proximate sulfur atom. Sulfide [S(II)] shows “free” [brake OFF] N-Ar rotation whereas sulfoxide displayed hindered [brake ON] N-Ar rotation. The semi-empirical molecular orbital (PM3) calculations revealed concerted pyramidalization of amidic nitrogen with N-Ar rotation
Ecology of ficus religiosa accounts for its association with religion
While many plants and trees in specific areas acquire cult significance, very few such as Ficus religiosa L. have acquired a universal status. This hemiepiphyte, Ficus religiosa L., is of dual interest since it venerated by a quarter of the present mankind (Hindus and Buddhists, largely Asian) on one hand and also since these plants are blamed for destruction of buildings due to their ability to grow on buildings. Divergence in views exists whether epiphytic plants exert a destructive influence on buildings. A focused survey of the coastal forts on land and sea has shown uniformly that the naturally growing plants of certain Ficus sp., notably Ficus religiosa L., grow exclusively on the vertical sheer side of rock faces and not either on the ground or on the top surface of these 8-10 centuries old rock structures; also seen on the side of rock piles as recent as 4-5 years as well as in sacred groves of several centuries to millennia old. We could trace the roots through these structures from beginning to the end in many parts of these forts, especially when there are overhanging structures at entrances. The root tips, the point of growth, would be far too insignificant to account for destruction in any of these large rock-and-lime masonry structures while vibration per se was insignificant as the tree was seen in all forts on land or sea. The association with religion of the distinctive Ficus religiosa itself appears to be self-evident from its socio-anthropological association with rock piles, hitherto not visualized for any flora and logically appears to pre-date both Hinduism and Buddhism
Deposition of polymer bilayer configuration by pulsed laser ablation and its use for study of polymer-polymer interface
Thin films of polyphenylene sulphide (PPS) and polyethylene (PE) polymers have been deposited in a bilayer configuration using pulsed excimer laser ablation. Such bilayer specimens have been annealed at different temperatures, up to a maximum of 120°C, and for different time intervals, up to a maximum of 110 min, to investigate the evolution of the interface. By employing the technique of spectroscopic ellipsometry, the nature and the degree of thermally induced polymeric transport across the interface are brought out
Implementation of Classification Technique for Mammogram Image
Abstract: Mammography is an important research field. Mammography Image classification is an area of interest to most of the researchers today. The aim of this paper is to detect the Mammography image for its malignancy. Different methods can be used to detect the malignancy. This paper represents GLDM feature extraction method and SVM classifier. Experiments were conducted on MIAS database. The results show that combination of GLDM feature extractor with SVM classifier is found to give appropriate results
Ring Formation from an Oscillating Black Hole
Massive black hole (BH) mergers can result in the merger remnant receiving a
"kick", of order 200 km s or more, which will cause the remnant to
oscillate about the galaxy centre. Here we analyze the case where the BH
oscillates through the galaxy centre perpendicular or parallel to the plane of
the galaxy for a model galaxy consisting of an exponential disk, a Plummer
model bulge, and an isothermal dark matter halo. For the perpendicular motion
we find that there is a strong resonant forcing of the disk radial motion near
but somewhat less than the "resonant radii" where the BH oscillation
frequency is equal one-half, one-fourth, (1/6, etc.) of the radial epicyclic
frequency in the plane of the disk. Near the resonant radii there can be a
strong enhancement of the radial flow and disk density which can lead to shock
formation. In turn the shock may trigger the formation of a ring of stars near
. As an example, for a BH mass of and a kick velocity of
150 km s, we find that the resonant radii lie between 0.2 and 1 kpc. For
BH motion parallel to the plane of the galaxy we find that the BH leaves behind
it a supersonic wake where star formation may be triggered. The shape of the
wake is calculated as well as the slow-down time of the BH.
The differential rotation of the disk stretches the wake into ring-like
segments.Comment: 7 pages, 7 figure
Star cluster formation and star formation: the role of environment and star-formation efficiencies
“The original publication is available at www.springerlink.com”. Copyright Springer. DOI: 10.1007/s10509-009-0088-5By analyzing global starburst properties in various kinds of starburst and post-starburst galaxies and relating them to the properties of the star cluster populations they form, I explore the conditions for the formation of massive, compact, long-lived star clusters. The aim is to determine whether the relative amount of star formation that goes into star cluster formation as opposed to field star formation, and into the formation of massive long-lived clusters in particular, is universal or scales with star-formation rate, burst strength, star-formation efficiency, galaxy or gas mass, and whether or not there are special conditions or some threshold for the formation of star clusters that merit to be called globular clusters a few billion years later.Peer reviewe
Global spiral modes in multi-component disks
We performed two-dimensional non-linear hydrodynamical simulations of
two-component gravitating disks aimed at studying stability properties of these
systems. In agreement with previous analytical and numerical simulations, we
find that the cold gas component strongly affects the growth rates of the
unstable global spiral modes in the disk. Already a five percent admixture of
cold gas increases approximately two-fold the growth rate of the most unstable
global mode while a twenty percent gas admixture enhances the modal growth rate
by a factor of four. The local stability properties of a two-component disk
coupled by self-gravity are governed by a stability criterion similar to
Toomre's Q-parameter derived for one-component systems. Using numerical
simulations, we analyse the applicability of a two-component local stability
criterion for the analysis of the stability properties of global modes. The
comparison of non-linear simulations with the analytical stability criterion
shows that the two-component disks can be globally unstable while being stable
to the local perturbations. The minimum value of the local stability criterion
provides, however, a rough estimate of the global stability properties of
two-component systems. We find that two-component systems with a content of
cold gas of ten percent or less are globally stable, if the minimum value of
the stability parameter exceeds about 2.5.Comment: 7 pages, with 8 postscript figures, accepted for publication by
Astronomy & Astrophysic
Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs
In a composite system of gravitationally coupled stellar and gaseous discs,
we perform linear stability analysis for axisymmetric coplanar perturbations
using the two-fluid formalism. The background stellar and gaseous discs are
taken to be scale-free with all physical variables varying as powers of
cylindrical radius with compatible exponents. The unstable modes set in as
neutral modes or stationary perturbation configurations with angular frequency
.Comment: 7 pages using AAS styl
Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies
New high resolution interferometer data of 10 IR ultraluminous galaxies shows
the molecular gas is in rotating nuclear rings or disks with radii 300 to 800
pc. Most of the CO flux comes from a moderate-density, warm, intercloud medium
rather than self-gravitating clouds. Gas masses of ~ 5 x 10^9 Msun, 5 times
lower than the standard method are derived from a model of the molecular disks.
The ratio of molecular gas to dynamical mass, is M_gas/M_dyn ~ 1/6 with a
maximum ratio of gas to total mass surface density of 1/3. For the galaxies
VIIZw31, Arp193, and IRAS 10565+24, there is good evidence for rotating
molecular rings with a central gap. In addition to the rotating rings a new
class of star formation region is identified which we call an Extreme
Starburst. They have a characteristic size of only 100 pc., about 10^9 Msun of
gas and an IR luminosity of ~3 x 10^11 Lsun. Four extreme starbursts are
identified in the 3 closest galaxies in the sample Arp220, Arp193 and Mrk273.
They are the most prodigious star formation events in the local universe, each
representing about 1000 times as many OB stars as 30 Doradus. In Arp220, the CO
and 1.3 mm continuum maps show the two ``nuclei'' embedded in a central ring or
disk and a fainter structure extending 3 kpc to the east, normal to the nuclear
disk. There is no evidence that these sources really are the pre-merger nuclei.
They are compact, extreme starburst regions containing 10^9 Msun of dense
molecular gas and new stars, but no old stars. Most of the dust emission and
HCN emission arises in the two extreme starbursts. The entire bolometric
luminosity of Arp~220 comes from starbursts, not an AGN. In Mrk231, the disk
geometry shows that the molecular disk cannot be heated by the AGN; the far IR
luminosity of Mrk~231 is powered by a starburst, not the AGN. (Abridged)Comment: 97 pages Latex with aasms.sty, including 29 encapsulated Postscript
figures. Figs 18 and 23 are GIFs. 31 figures total. Text and higher quality
versions of figures available at
http://sbastk.ess.sunysb.edu/www/RINGS_ESB_PREPRINT.html To be published in
Ap. J., 10 Nov. 199
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