Electron correlation induced transverse delocalization and longitudinal confinement in excited states of phenyl-substituted polyacetylenes

Electron-electron interactions in general lead to both ground state and excited state confinement. We show, however, that in phenyl-substituted polyacetylenes electron-electron interactions cause enhanced delocalization of quasiparticles in the optically excited state from the backbone polyene chain into the phenyl groups, which in turn leads to enhanced confinement in the chain direction. This co-operative delocalization--confinement lowers the energy of the one-photon state and raises the relative energy of the lowest two-photon state. The two-photon state is slightly below the optical state in mono-phenyl substituted polyacetylenes, but above the optical state in di-phenyl substituted polyacetylenes, thereby explaining the strong photoluminescence of the latter class of materials. We present a detailed mechanism of the crossover in the energies of the one- and two-photon states in these systems. In addition, we calculate the optical absorption spectra over a wide wavelength region, and make specific predictions for the polarizations of low and high energy transitions that can be tested on oriented samples. Within existing theories of light emission from $\pi$-conjugated polymers, strong photoluminescence should be restricted to materials whose optical gaps are larger than that of trans-polyacetylene. The present work show that conceptually at least, it is possible to have light emission from systems with smaller optical gaps.Comment: 14 pages, 5 figures, 4 tables included in the tex

Complexity of Scheduling in Synthesizing Hardware from Concurrent Action Oriented Specifications

Concurrent Action Oriented Specifications (CAOS) formalism such as Bluespec Inc.\u27s Bluespec System Verilog (BSV) has been recently shown to be effective for hardware modeling and synthesis. This formalism offers the benefits of automatic handling of concurrency issues in highly concurrent system descriptions, and the associated synthesis algorithms have been shown to produce efficient hardware comparable to those generated from hand-written Verilog/VHDL. These benefits which are inherent in such a synthesis process also aid in faster architectural exploration. This is because CAOS allows a high-level description (above RTL) of a design in terms of atomic transactions, where each transaction corresponds to a collection of operations. Optimal scheduling of such actions in CAOS-based synthesis process is crucial in order to generate hardware that is efficient in terms of area, latency and power. In this paper, we analyze the complexity of the scheduling problems associated with CAOS-based synthesis and discuss several heuristics for meeting the peak power goals of designs generated from CAOS. We also discuss approximability of these problems as appropriate

A review on diversity, conservation and nutrition of wild edible fruits

The United Nations adopted the Millennium Declaration of September 2009 to improve the global living conditions through reducing poverty and hunger. However, considerable numbers of people are still living in utter penury and are deprived of a dignified living. In such tough circumstances nature’s free gift in the form of wild edible foods are benefiting the vulnerable and dependent communities. Wild edible plants (WEPs) are the species those are neither cultivated nor domesticated however are available in their wild natural habitat and used as sources of these plants have played a significant role in the development and civilization of human history throughout the ages and globe. These wild edible plants have played a significant role in supplying food and nutritional requirements of poor communities in many rural parts of the world. These wild edibles can be popularized only when they are comparedfor their nutritional and health benefits with major or widely used cultivated plants. The social, cultural, religious, and belief system of the rural communities are incomplete without these wild edible plants. Domestication of these wild edible plants can increase their use and their conservation as well. The present review paper has described the wild edible plants in context of their diversity, traditional knowledge, conservation practices and nutritional composition from the available secondary literature. Authors feel there is still scope to incorporate more contextual variables for explaining more variations embedded with local people’s perception on values and usage of these wild edible fruits

Desmoid tumour: a rare etiology of intestinal obstruction

Intestinal obstruction is a frequently encountered entity in surgical practice. The signs & symptoms, many a times, are suggestive of the level of obstruction, making the diagnosis of obstruction evident. There are  various causes of intestinal obstruction which diversify to an enormous extent, stamping on the famous  paradigm for the mysterious nature of the abdomen being referred to as the Pandora's Box. In accordance with the above saying, we report a rare case of a desmoid tumour, presenting as intestinal obstruction, which entices us to strongly believe the same.Key words: Intestinal obstruction, pandora´s box, desmoid tumou

Photophysics of charge-transfer excitons in thin films of \pi-conjugated polymers

We develop a theory of the electronic structure and photophysics of interacting chains of \pi- conjugated polymers to understand the differences between solutions and films. While photoexcitation generates only the intrachain exciton in solutions, the optical exciton as well as weakly allowed charge-transfer excitons are generated in films. We extend existing theories of the lowest polaronpair and charge-transfer excitons to obtain descriptions of the excited states of these interchain species, and show that a significant fraction of ultrafast photoinduced absorptions in films originate from the lowest charge-transfer exciton. Our proposed mechanism explains the simultaneous observation of polaronlike induced absorption features peculiar to films in ultrafast spectroscopy and the absence of mobile charge carriers as deduced from other experiments. We also show that there is a 1:1 correspondence between the essential states that describe the photophysics of single chains and of interacting chains that constitute thin films.Comment: 10 pages,4 figures, submitted to Phys Rev

A Rare Case of Primary Mucinous Cystadenoma of Spleen

Mucinous cystadenomas are relatively uncommon benign cystic tumors. Most of them are found in the ovary, pancreas, and appendix. Primary mucinous cystadenoma of spleen is extremely rare and only countable cases have been recorded. These are assumed to arise from heterotopic pancreatic tissue or invaginated spleenic capsular mesothelium. We present a rare case of primary mucinous cystadenoma of spleen without pancreatic tissue in it. Exact tissue of origin could not be determined