Distribution and Seasonal Abundance of Macro Benthos of Gangavali Estuary, Uttar Kannada, West Coast of India

Distribution and seasonal abundance of Gangavali estuary was studied for one year from September 2007 to August 2008. The diversity, abundance and biomass of macro-benthos were observed selecting four stations along the Gangavali estuary and eleven benthic organisms were encountered in the present study. Polycheates were observed at all four stations with maximum faunal distribution. The diversity of macro benthos was at maximum numbers towards lower reaches of the estuary. The benthic faunal components exhibit bimodal pattern of distribution with monsoon as a period of minimum density and post-monsoon and early pre-mansion with maximum density

External respiratory function in a patient after removal of the middle and lower lobes of the right lung (pulmonary compensatory possibilities of ventilation lung function)

Scientific advisers: ass. prof. M. I. Shevchuk, ass. prof. E. P. Medved, assoc. prof. N. I. Skokova, prof. M. I. Yabluchansk

Quantum-fluctuation-induced repelling interaction of quantum string between walls

Quantum string, which was brought into discussion recently as a model for the stripe phase in doped cuprates, is simulated by means of the density-matrix-renormalization-group method. String collides with adjacent neighbors, as it wonders, owing to quantum zero-point fluctuations. The energy cost due to the collisions is our main concern. Embedding a quantum string between rigid walls with separation d, we found that for sufficiently large d, collision-induced energy cost obeys the formula \sim exp (- A d^alpha) with alpha=0.808(1), and string's mean fluctuation width grows logarithmically \sim log d. Those results are not understood in terms of conventional picture that the string is `disordered,' and only the short-wave-length fluctuations contribute to collisions. Rather, our results support a recent proposal that owing to collisions, short-wave-length fluctuations are suppressed, but instead, long-wave-length fluctuations become significant. This mechanism would be responsible for stabilizing the stripe phase

DDW Order and its Role in the Phase Diagram of Extended Hubbard Models

We show in a mean-field calculation that phase diagrams remarkably similar to those recently proposed for the cuprates arise in simple microscopic models of interacting electrons near half-filling. The models are extended Hubbard models with nearest neighbor interaction and correlated hopping. The underdoped region of the phase diagram features $d_{{x^2}-{y^2}}$ density-wave (DDW) order. In a certain regime of temperature and doping, DDW order coexists with antiferromagnetic (AF) order. For larger doping, it coexists with $d_{{x^2}-{y^2}}$ superconductivity (DSC). While phase diagrams of this form are robust, they are not inevitable. For other reasonable values of the coupling constants, drastically different phase diagrams are obtained. We comment on implications for the cuprates.Comment: 7 pages, 3 figure

Spin and charge order in the vortex lattice of the cuprates: experiment and theory

I summarize recent results, obtained with E. Demler, K. Park, A. Polkovnikov, M. Vojta, and Y. Zhang, on spin and charge correlations near a magnetic quantum phase transition in the cuprates. STM experiments on slightly overdoped BSCCO (J.E. Hoffman et al., Science 295, 466 (2002)) are consistent with the nucleation of static charge order coexisting with dynamic spin correlations around vortices, and neutron scattering experiments have measured the magnetic field dependence of static spin order in the underdoped regime in LSCO (B. Lake et al., Nature 415, 299 (2002)) and LaCuO_4+y (B. Khaykovich et al., Phys. Rev. B 66, 014528 (2002)). Our predictions provide a semi-quantitative description of these observations, with only a single parameter measuring distance from the quantum critical point changing with doping level. These results suggest that a common theory of competing spin, charge and superconducting orders provides a unified description of all the cuprates.Comment: 18 pages, 7 figures; Proceedings of the Mexican Meeting on Mathematical and Experimental Physics, Mexico City, September 2001, to be published by Kluwer Academic/Plenum Press; (v2) added clarifications and updated reference

Scaling approach to itinerant quantum critical points

Based on phase space arguments, we develop a simple approach to metallic quantum critical points, designed to study the problem without integrating the fermions out of the partition function. The method is applied to the spin-fermion model of a T=0 ferromagnetic transition. Stability criteria for the conduction and the spin fluids are derived by scaling at the tree level. We conclude that anomalous exponents may be generated for the fermion self-energy and the spin-spin correlation functions below $d=3$, in spite of the spin fluid being above its upper critical dimension.Comment: 3 pages, 2 figures; discussion of the phase space restriction modified and, for illustrative purposes, restricted to the tree-level analysis of the ferromagnetic transitio

Holons on a meandering stripe: quantum numbers

We attempt to access the regime of strong coupling between charge carriers and transverse dynamics of an isolated conducting ``stripe'', such as those found in cuprate superconductors. A stripe is modeled as a partially doped domain wall in an antiferromagnet (AF), introduced in the context of two different models: the t-J model with strong Ising anisotropy, and the Hubbard model in the Hartree-Fock approximation. The domain walls with a given linear charge density are supported artificially by boundary conditions. In both models we find a regime of parameters where doped holes lose their spin and become holons (charge Q=1, spin S_z=0), which can move along the stripe without frustrating AF environment. One aspect in which the holons on the AF domain wall differ from those in an ordinary one-dimensional electron gas is their transverse degree of freedom: a mobile holon always resides on a transverse kink (or antikink) of the domain wall. This gives rise to two holon flavors and to a strong coupling between doped charges and transverse fluctuations of a stripe.Comment: Minor revisions: references update

Transmission-electron-microscopy study of charge-stripe order in La(1.725)Sr(0.275)NiO(4)

We characterize the local structure and correlations of charge stripes in La(1.725)Sr(0.275)NiO(4) using transmission-electron microscopy. We present direct evidence that the stripe modulation is indeed one-dimensional within each NiO(2) plane. Furthermore, we show that individual stripes tend to be either site-centered or bond-centered, with a bias towards the former. The spacing between stripes often fluctuates about the mean, contributing to a certain degree of frustration of the approximate body-centered stacking along the c-axis. These results confirm ideas inferred from previous neutron-diffraction measurements on doped nickelates, and demonstrate that charge-stripe order is quite different from the conventional concept of charge-density-wave order.Comment: 5 pages, 6 figures, submitted to PR

Phase Diagram of a Spin Ladder with Cyclic Four Spin Exchange

We present the phase diagram of the $S=1/2$ Heisenberg model on the two leg ladder with cyclic four spin exchange, determined by a combination of Exact Diagonalization and Density Matrix Renormalization Group techniques. We find six different phases and regimes: the rung singlet phase, a ferromagnetic phase, two symmetry broken phases with staggered dimers and staggered scalar chiralities, and a gapped region with dominant vector chirality or collinear spin correlations. We localize the phase transitions and investigate their nature.Comment: 4 pages, 6 figures, REVTeX 4, published versio

Stability of metallic stripes in the extended one-band Hubbard model

Based on an unrestricted Gutzwiller approximation (GA) we investigate the stripe orientation and periodicity in an extended one-band Hubbard model. A negative ratio between next-nearest and nearest neighbor hopping t'/t, as appropriate for cuprates, favors partially filled (metallic) stripes for both vertical and diagonal configurations. At around optimal doping diagonal stripes, site centered (SC) and bond centered (BC) vertical stripes become degenerate suggesting strong lateral and orientational fluctuations. We find that within the GA the resulting phase diagram is in agreement with experiment whereas it is not in the Hartree-Fock approximation due to a strong overestimation of the stripe filling. Results are in agreement with previous calculations within the three-band Hubbard model but with the role of SC and BC stripes interchanged.Comment: 10 pages, 8 figure