Fractional vortices in the XY model with π\pi bonds

We define a new set of excitations in the XY model which we call ``fractional vortices''. In the frustrated XY model containing $\pi$ bonds, we make the ansatz that the ground state configurations can be characterized by pairs of oppositely charged fractional vortices. For a chain of $\pi$ bonds, the ground state energy and the phase configurations calculated on the basis of this ansatz agree well with the results from direct numerical simulations. Finally, we discuss the possible connection of these results to some recent experiments by Kirtley {\it et al} [Phys. Rev. B {\bf 51}, R12057 (1995)] on high-T$_c$ superconductors where fractional flux trapping was observed along certain grain boundaries.Comment: 13 pages, 14 figures included (.eps). No essential differences to previous version, however more compact forma

J0041+3224: a new double-double radio galaxy

We report the discovery of a double-double radio galaxy (DDRG), J0041+3224, with the Giant Metrewave Radio Telescope (GMRT) and subsequent high-frequency observations with the Very Large Array (VLA). The inner and outer doubles are aligned within about 4 deg and are reasonably collinear with the parent optical galaxy. The outer double has a steeper radio spectrum compared with the inner one. Using an estimated redshift of 0.45, the projected linear sizes of the outer and inner doubles are 969 and 171 kpc respectively. The time scale of interruption of jet activity has been estimated to be about 20 Myr, similar to other known DDRGs. We have compiled a sample of known DDRGs, and have re-examined the inverse correlation between the ratio of the luminosities of the outer to the inner double and the size of the inner double, l_{in}. Unlike the other DDRGs with l_{in} larger than about 50 kpc, the inner double of J0041+3224 is marginally more luminous than the outer one. The two DDRGs with l_{in} less than about a few kpc have a more luminous inner double than the outer one, possibly due to a higher efficiency of conversion of beam energy as the jets propagate through the dense interstellar medium. We have examined the symmetry parameters and find that the inner doubles appear to be more asymmetric in both its armlength and flux density ratios compared with the outer doubles, although they appear marginally more collinear with the core than the outer double. We discuss briefly possible implications of these trends.Comment: Accepted for publication in MNRAS, 9 pages, 10 figure

Food and feeding habit of a penaeid prawn Metapeneopsis stridulans (Alcock 1905)

Metapeneopsis stridulans feeds on a variety of food items, viz. diatoms, foraminiferans polychaetes, molluscs, crustaceans and detritus consisting of unidentifiable decaying matter along with sand and mud. The species does not show a preference for any particular food item. There is no significant difference in the food habits among the various size groups observed in the prawn. Monthwise feeding intensity for males and females shows males with empty stomach to be prevalent in most months

Analysis of bistable and oscillating reaction systems in presence of an external noise

The paper analyses a bistable and an oscillatory reaction system in the presence of an external noise. The analysis of a bistable system shows that in the normal way the inclusion of noise destroys all the deterministic solutions. In other words, the stochastic system does not admit any solution. With imposition of certain restraints it is possible, however, to get stochastic solutions in a certain region of parameter space, which in general shrinks with the extent of noise. The modality of diminishing the region of solutions is different for white and nonwhite noise and has been discussed The paper also evaluates the influence of white and nonwhite noise on the behavior of an oscillating system and illustrates it by considering two case examples. One example indicates the conflicting role of white and nonwhite noise in bringing about the transitions from the oscillatory behavior while the second example shows no influence of white and nonwhite noise on the oscillating solution The implications of the role of noise in analysing bistable and oscillatory systems is discussed