Structural Instability in Polyacene : A Projector Quantum Monte Carlo Study

We have studied polyacene within the Hubbard model to explore the effect of electron correlations on the Peierls' instability in a system marginally away from one-dimension. We employ the projector quantum Monte Carlo method to obtain ground state estimates of the energy and various correlation functions. We find strong similarities between polyacene and polyacetylene which can be rationalized from the real-space valence-bond arguments of Mazumdar and Dixit. Electron correlations tend to enhance the Peierls' instability in polyacene. This enhancement appears to attain a maximum at $U/t \sim 3.0$ and the maximum shifts to larger values when the alternation parameter is increased. The system shows no tendency to destroy the imposed bond-alternation pattern, as evidenced by the bond-bond correlations. The cis- distortion is seen to be favoured over the trans- distortion. The spin-spin correlations show that undistorted polyacene is susceptible to a SDW distortion for large interaction strength. The charge-charge correlations indicate the absence of a CDW distortion for the parameters studied.Comment: 13 pages, 10 figures available on reques

PHARMACOGNOSTIC STUDY OF MANSOA ALLIACEA LEAF

Mansoa alliacea Lam. (Family: Bignoniaceae) is a native plant from Amazonian basin in South America. Plant derivatives are used as anti-inflammatory, antioxidant, antiseptic and antibacterial agents. The study was aimed to determine the pharmacognostic and phytochemicals present in Mansoa alliacea. Micro and organoleptic characteristics of fresh and dried leaf samples had been examined. Physicochemical variables had been done by using WHO suggested variables; preliminary phytochemical of leaf sample had been performed to identify the presence of alkaloids, flavonoids, tannins and phenols, and quinones using the ethanolic extract of the leaves of M. alliacea

CD imaging of gamma ray burster fields

Gamma Ray Bursts (GRBs) have been known for almost three decades. The nature of the objects producing these bursts is yet unknown and no counterparts have been identified in any other wavelength band so far except for GB970228 recently. In an attempt to identify the optical counterparts of GRBs we obtain deep CCD images of selected, strong GRB fields through broad band filters. From these images we expect to be able to identify any peculiar objects on the basis of photometric colours andlor variability. In this paper we present the preliminary results of the data obtained during our observing run in November 1996 at the UP State Observatory, Nainital

Delocalizing effect of the Hubbard repulsion for electrons on a two-dimensional disordered lattice

We study numerically the ground-state properties of the repulsive Hubbard model for spin-1/2 electrons on two-dimensional lattices with disordered on-site energies. The projector quantum Monte Carlo method is used to obtain very accurate values of the ground-state charge density distributions with $N_p$ and $N_p+1$ particles. The difference in these charge densities allows us to study the localization properties of an added particle. The results obtained at quarter-filling on finite clusters show that the Hubbard repulsion has a strong delocalizing effect on the electrons in disordered 2D lattices. However, numerical restrictions do not allow us to reach a definite conclusion about the existence of a metal-insulator transition in the thermodynamic limit in two-dimensions.Comment: revtex, 7 pages, 7 figure

CCD imaging of gamma ray burster fields

Gamma Ray Bursts (GRBs) have been known for almost three decades. The nature of the objects producing these bursts is yet unknown and no counterparts have been identified in any other wavelength band so far except for GB970228 recently. In an attempt to identify the optical counterparts of GRBs we obtain deep CCD images of selected, strong GRB fields through broad band filters. From these images we expect to be able to identify any peculiar objects on the basis of photometric colours andlor variability. In this paper we present the preliminary results of the data obtained during our observing run in November 1996 at the UP State Observatory, Nainital

Estimation of Channel Performance of Satellite Communication and Frequency Reader

ABSTRACT: National Remote Sensing Center (NRSC) receives data from different remote satellites like IRS-P6, IRS-P5, Cartosat-2, Cartosat-2a, etc., and processes it depending on the user requirements. The satellite data received in X band is in a particular data format. This data has to be frame synchronized using a special hardware. The receiver hardware setup must be ready at any time to make it ready it"s performance is to be tested continuously.The frequency with which satellite data is coming is also continuously tested . In the proposed project VHDL code has been developed for BER reader with differential encoding and decoding and frequency reader. The external frequency and number of errors in satellite data will be displayed on HP display devices. This project has been implemented and tested using the ALTERA EPLDs. This needs crystal oscillators, thumb wheel switches,7 segment display etc., must be programmed as per the requirement. The hardware required for this has been implemented on the wire-warp board

Transition to an Insulating Phase Induced by Attractive Interactions in the Disordered Three-Dimensional Hubbard Model

We study numerically the interplay of disorder and attractive interactions for spin-1/2 fermions in the three-dimensional Hubbard model. The results obtained by projector quantum Monte Carlo simulations show that at moderate disorder, increasing the attractive interaction leads to a transition from delocalized superconducting states to the insulating phase of localized pairs. This transition takes place well within the metallic phase of the single-particle Anderson model.Comment: revtex, 4 pages, 3 figure

Minni Payaru [Vigna stipulacea (Lam.) Kuntz.]: an underutilized ancient legume of India

Minni Payaru [Vigna stipulacea (Lam.) Kuntz] is an underutilized traditional legume species mainly used for food, animal fodder and green manure, particularly in Southern India. In the era of global climate change, this indigenous crop has the ability to survive under harsh environment and also has resistance against various biotic and abiotic stresses. Based on acquired knowledge about this crop, farmers prefer Minni Payaru compared to other commercial kharif pulses. Though Minni Payaru has huge potential to be used as main legume crop, it has not gained popularity in India. Currently, the cultivation of Minni Payaru is restricted to the Southern regions of India. The present review summarises the budding role of Minni Payaru in human nutrition, animal fodder and green manure

Survival, morphological variability, and performance of Opuntia ficus-indica in a semi-arid region of India

Cactus pear (Opuntia ficus-indica (L.) Mill.) can survive extreme environmental condition and is known for its fodder potential in many parts of the world. The morphological diversity of 15 introduced accessions was evaluated at Jhansi, Uttar Pradesh, India. The plants were established in 2013. Survival and nutrient status were evaluated after two years. Above-ground plant height, biomass, primary and secondary cladode numbers, primary and secondary cladode lengths and below-ground root length, weight, and surface area measurements were done six years after cladode planting. Yellow San Cono, White Roccapalumba, and Seedless Roccapalumba survived 100%. The discriminant traits according to principal component analysis were: primary cladodes plant−1 (component loading, 0.87), primary cladodes biomass (0.95), secondary cladodes plant−1 (0.83), canopy width (0.84), and plant biomass (0.92). Hierarchical cluster analysis grouped 15 accessions into two main clusters based on 17 morphological traits. Cluster I showed favorable values for many above- and below-ground morphological traits while Cluster II showed higher performance for root system width, height, and biomass, and primary and secondary cladode numbers. The results indicate that cactus pear accessions have considerable morphological variability and genetic diversity suitable for promotion as alternative fodder resources in semi-arid regions of India