Evaluation of Waterhyacinth and Paddy Straw Waste for Culture of Oyster Mushrooms

Waterhyacinth ( Eichhornia crassipes (Mart.) Solms.) was evaluated at ratios of 25, 50 and 75% with paddy straw ( Oryza sativa L.) for oyster mushroom ( Pleurotus sajor-caju) cultivation. There was an increase in yield with decreasing ratio waterhyacinth

Length control of microtubules by depolymerizing motor proteins

In many intracellular processes, the length distribution of microtubules is controlled by depolymerizing motor proteins. Experiments have shown that, following non-specific binding to the surface of a microtubule, depolymerizers are transported to the microtubule tip(s) by diffusion or directed walk and, then, depolymerize the microtubule from the tip(s) after accumulating there. We develop a quantitative model to study the depolymerizing action of such a generic motor protein, and its possible effects on the length distribution of microtubules. We show that, when the motor protein concentration in solution exceeds a critical value, a steady state is reached where the length distribution is, in general, non-monotonic with a single peak. However, for highly processive motors and large motor densities, this distribution effectively becomes an exponential decay. Our findings suggest that such motor proteins may be selectively used by the cell to ensure precise control of MT lengths. The model is also used to analyze experimental observations of motor-induced depolymerization.Comment: Added section with figures and significantly expanded text, current version to appear in Europhys. Let

Gas permeation through a polymer network

We study the diffusion of gas molecules through a two-dimensional network of polymers with the help of Monte Carlo simulations. The polymers are modeled as non-interacting random walks on the bonds of a two-dimensional square lattice, while the gas particles occupy the lattice cells. When a particle attempts to jump to a nearest-neighbor empty cell, it has to overcome an energy barrier which is determined by the number of polymer segments on the bond separating the two cells. We investigate the gas current $J$ as a function of the mean segment density $\rho$, the polymer length $\ell$ and the probability $q^{m}$ for hopping across $m$ segments. Whereas $J$ decreases monotonically with $\rho$ for fixed $\ell$, its behavior for fixed $\rho$ and increasing $\ell$ depends strongly on $q$. For small, non-zero $q$, $J$ appears to increase slowly with $\ell$. In contrast, for $q=0$, it is dominated by the underlying percolation problem and can be non-monotonic. We provide heuristic arguments to put these interesting phenomena into context.Comment: Dedicated to Lothar Schaefer on the occasion of his 60th birthday. 11 pages, 3 figure

Interferometric probes of many-body localization

We propose a method for detecting many-body localization (MBL) in disordered spin systems. The method involves pulsed, coherent spin manipulations that probe the dephasing of a given spin due to its entanglement with a set of distant spins. It allows one to distinguish the MBL phase from a non-interacting localized phase and a delocalized phase. In particular, we show that for a properly chosen pulse sequence the MBL phase exhibits a characteristic power-law decay reflecting its slow growth of entanglement. We find that this power-law decay is robust with respect to thermal and disorder averaging, provide numerical simulations supporting our results, and discuss possible experimental realizations in solid-state and cold atom systems.Comment: 5 pages, 4 figure

Stress, heat shock proteins & biotechnological interventions. In: Winter School on Impact of Climate Change on Indian Marine Fisheries held at CMFRI, Cochin 18.1.2008 to 7.2.2008

Fish are exposed to stressors in nature, as well as in artificial conditions such as in aquaculture, or in the laboratory. The increasing contamination of bodies of natural freshwater and marine ecosystem around the world by anthropogenic substances is one category of environmental stressor. Various stressors, such as grading, transportation, and vaccination, are necessary components of modern intensive fish culture. The response of the fish to such stressors involves all levels of organization, from the cell, to the individual organism, to the structure of the population. In as much as the responses of the fish to a stressor is the essence of maintaining homeostasis, it is not surprising that fish respond to a variety of stressors in a generalized way at all these levels of organization. Stress is most often associated with a negative perspective. This is natural as the word and concept in common use is generally associated with a system that is severely challenged, and often fatigued. Experimental biologists are all involved in the practice of systematically imposing some perturbation and measuring a response

Frustration and glassiness in spin models with cavity-mediated interactions

We show that the effective spin-spin interaction between three-level atoms confined in a multimode optical cavity is long-ranged and sign-changing, like the RKKY interaction; therefore, ensembles of such atoms subject to frozen-in positional randomness can realize spin systems having disordered and frustrated interactions. We argue that, whenever the atoms couple to sufficiently many cavity modes, the cavity-mediated interactions give rise to a spin glass. In addition, we show that the quantum dynamics of cavity-confined spin systems is that of a Bose-Hubbard model with strongly disordered hopping but no on-site disorder; this model exhibits a random-singlet glass phase, absent in conventional optical-lattice realizations. We briefly discuss experimental signatures of the realizable phases.Comment: 5 pages, 2 figure

Bopyrid isopods parasitizing on the cultured fresh water prawn, macrobrachium malcolmsonii in South India

The bopyrid isopods are common in wild Macrobrachium spp. but not common in aquaculture condition. This is the first study that reports the parasitizing of bopyrid isopods on the cultured M. malcolmsonii. Bopyrid isopod (Probopyrus buitendijki) was identified in the branchial cavities of the freshwater prawn, M.malcolmsonii fromgrow-out culture pond at Kuriyamangalam, India. Macrobrachium malcolmsonii is a new host for P. buitendijki. A total of 1323 M. malcolmsonii were checked for this study. The overall prevalence of the parasitic infestation was reached 46.2 %. The parasitic infection was higher in female (83 %) than in male (3.4 %). Highest prevalence of infestation was found in the median size group (7–8 cm) (58.7 %). Infected females were not berried unlike uninfected prawns. The parasites cause infertility and does not found any organ deformities due to the infestation. The parasite was inversely attached in the gill chamber with no lesion on the gill but the infected branchial chamber became bulged

Spin-Electron-Phonon Excitation in Re-based Half-Metallic Double Perovskites

A remarkable hardening (~ 30 cm-1) of the normal mode of vibration associated with the symmetric stretching of the oxygen octahedra for the Ba2FeReO6 and Sr2CrReO6 double perovskites is observed below the corresponding magnetic ordering temperatures. The very large magnitude of this effect and its absence for the anti-symmetric stretching mode provide evidence against a conventional spin-phonon coupling mechanism. Our observations are consistent with a collective excitation formed by the combination of the vibrational mode with oscillations of local Fe or Cr 3d and Re 5d occupations and spin magnitudes.Comment: 12 pages, 4 figure

Strong clustering of non-interacting, passive sliders driven by a Kardar-Parisi-Zhang surface

We study the clustering of passive, non-interacting particles moving under the influence of a fluctuating field and random noise, in one dimension. The fluctuating field in our case is provided by a surface governed by the Kardar-Parisi-Zhang (KPZ) equation and the sliding particles follow the local surface slope. As the KPZ equation can be mapped to the noisy Burgers equation, the problem translates to that of passive scalars in a Burgers fluid. We study the case of particles moving in the same direction as the surface, equivalent to advection in fluid language. Monte-Carlo simulations on a discrete lattice model reveal extreme clustering of the passive particles. The resulting Strong Clustering State is defined using the scaling properties of the two point density-density correlation function. Our simulations show that the state is robust against changing the ratio of update speeds of the surface and particles. In the equilibrium limit of a stationary surface and finite noise, one obtains the Sinai model for random walkers on a random landscape. In this limit, we obtain analytic results which allow closed form expressions to be found for the quantities of interest. Surprisingly, these results for the equilibrium problem show good agreement with the results in the non-equilibrium regime.Comment: 14 pages, 9 figure