Scale-free switching of polarization in the layered ferroelectric material CuInP2_2S6_6

Using first-principles calculations we model the out-of-plane switching of local dipoles in CuInP$_2$S$_6$ (CIPS) that are largely induced by Cu off-centering. Previously, a coherent switching of polarization via a quadruple-well potential was proposed for these materials. In the super-cells we considered, we find multiple structures with similar energies but with different local polar order. Our results suggest that the individual dipoles are weakly coupled in-plane and under an electric field at very low temperatures these dipoles in CIPS should undergo incoherent disordered switching. The barrier for switching is determined by the single Cu-ion switching barrier. This in turn suggests a scale-free polarization with a switching barrier of $\sim$ 203.6-258.0 meV, a factor of five smaller than that of HfO$_2$ (1380 meV) a prototypical scale-free ferroelectric. The mechanism of polarization switching in CIPS is mediated by the switching of each weakly interacting dipole rather than the macroscopic polarization itself as previously hypothesized. These findings reconcile prior observations of a quadruple well with sloping hysteresis loops, large ionic conductivity even at 250~K well below the Curie temperature (315~K), and a significant wake-up effects where the macroscopic polarization is slow to order and set-in under an applied electric field. We also find that computed piezoelectric response and the polarization show a linear dependence on the local dipolar order. This is consistent with having scale-free polarization and other polarization-dependent properties and opens doors for engineering tunable metastability by-design in CIPS (and related family of materials) for neuromorphic applications

Application of remote sensing techniques for locating pelagic fish concentrations along the Kerala Coast (SW Coast of India) and Minicoy waters

Intensive validation programme on Potential Fishing Zone (PPZ) forecasts carried out by the MARSIS Centre of Central Marine Fisheries Research Institute, Cochin, at 17 selected fish landing centres along the Kerala coast and around Minicoy Island between November 1995 and May 1997 revealed positive relationship between PPZ and occurrence / abundance of commercially important pelagic tlshes, An attempt is made to identify possible reasons for the above, based on results of oceanographic investigations undertaken in the area and also taking into consideration their behaviour in relation to environment based on past data

Heavy landing of tuna by multiday deep sea ringseiners at Cuddalore.

In Tamil Nadu, Cuddalore fishing harbour is known for ringseine operation and in February 2018, the fishermen introduced multiday deep sea ringseine for oceanic tunas and the result was encouraging ( Sivadas et al., 2018. Mar. Fish. Infor. Ser. T & E Ser. No.235). Now the fishermen from neighbouring areas like Pazhayar, Kalpakkam etc also started practising this fishing. In 2019 since July, there were good landings by this gear. A brief account of the landings during July and August is given below to highlight their role in exploitation of both inshore and oceanic tunas. In a boat the catch varied from 5 t to 30 t. Initially the catch was comprised by yellowfin tuna and skipjack tuna

Stock assessment of skipjack tuna, Katsuwonus pelamis from Minicoy, Lakshadweep

Analysis of the past six years data on skipjack tuna fishery by pole and line at Minicoy showed tremendous improvement as from 412.6 t in 2000-01 the catch rose to 1776.9 t in 2002-03. The CPUE was also highest being 370 kg during this year. ?he size of skipjack ranged from 12 to 74 cm Bulk of the catch is comprised of the size group 48 to 64 c

Stock assessment of Indian squid, Uroteuthis (Photololigo) duvaucelii (d'Orbigny [in Férussac & d'Orbigny], 1835) from south-western Bay of Bengal

Stock assessment of the Indian squid Uroteuthis (Photololigo) duvaucelii off north Tamil Nadu coast from commercial trawl landings was studied during the period 2012-2016. The species is mainly caught by trawl net and the annual average landing of the species was 563.3 t contributing to 2 % to the total trawl landing along north Tamil Nadu coast. L∞, K and t0 were estimated as 260 mm, 0.84 yr-1 and -0.105 yr, respectively. Total mortality rate (Z), Natural mortality rate (M), and Fishing mortality rate (F) were 4.43 yr-1, 1.67 yr-1 and 2.78 yr-1, respectively. tmax was estimated to be 3.47 yr. The length atfirst capture (Lc50 = 62 mm) estimated by Length converted catch curve method was found to be lower than Length at first maturity (Lm50 = 80 mm). Furthermore, Ecurr (current exploitation rate) was found be on higher side than the Emax (0.48) and E0.1 (0.40) which indicates that the fishery is in overexploited stage. Thompson and Bell prediction model showed that a marginal decrease (20 %) in current level of exploitation would help in regeneration of stock for long term sustainability of the resources as well as in achieving maximized economic return

Fishery, biology and dynamics of dogtooth tuna, Gymnosarda unicolor (Rüppell, 1838) exploited from Indian seas

Dogtooth tuna, Gymnosarda unicolor (Rüppell, 1838) (Fig. 1) is a pelagic tuna preferring waters of temperature between 21 and 26 oC. It is one of the principal species exploited by hook and line (recreational as well as commercial fishery) operated in the oceanic region. Meat of dogtooth tuna is white and so it has great demand and fetch high price (IUCN, 2011). However, occasional ciguatera fish poisoning in humans has been reported on consumption of dogtooth tuna. It is exported in fresh and frozen state and is used for the production of sashimi, canned tuna, and pouch products. Most of the world landings of dogtooth tuna during 1963 -2006 was from the Indian Ocean. Small scale tuna long lines for the species operating in the Indian Ocean belong to Taiwan, Srilanka, Maldives, Japan or Pakista

Analysis on the relativistic electron precipitation in the midnight sector

We analyze the precipitation of relativistic electrons occurring in the midnight sector, defined over 22–02 MLT. In the nightside, electron precipitation is primarily driven either by pitch angle scattering from interactions between electrons and plasma waves or by pitch angle scattering due to the stretching of magnetic field lines (also called “current sheet scattering”). We identified ~400 relativistic electron precipitation events and separated them into wave-driven (REPs) and CSS-driven (CSSs) events. Although REPs tend to occur at slightly lower L shells and CSSs are found at marginally higher L shells, there is not a clear separation in location between these two precipitation types. Furthermore, we show that REPs occur on smaller L shell scales at post-midnight and on wider L shell scales at pre-midnight, suggesting that the wave driver characteristics vary across midnight.First author draf

Length weight relationship, relative condition, size at first maturity and sex ratio of Indian mackerel Rastrelliger kanagurta from Calicut

Length weight relationship, relative condition, size at first maturity and sex ratio of Indian mackerel Rastrelliger kanagurta was studied based on the data collected from the ring net and trawl net catches landed at Puthiappa in Calicut during the period July 2001 to December 2004.The length weight relationship for the pooled male and female was W = 0.0000014 L3.3a8n d that of indeterminate category was W = .000044 L2.".T he condition factor per length group the highest value was at 145 mm and in the monthly values, the lowest in May in the samples from both ring net and trawl net. Sex ratio showed deviation from'1:l in certain months. The size at first maturity was estimated to be 173 mm for both the sexes

Distribution and abundance of carangids along the EEZ India

Distribution and abundance of carangid groups of fish along the EEZ of India based on the data collected during 80 cruises undertaken by FORV Sagar Sampada is presented here. East coast of India showed maximum concentration of ctrangids with a catch rate of 64 kg/hr along the northeast coast. The least distribution was noticed along the northwest coast ( 5 kg/hr). Carangids formed up to a maximum of 19 % of the total bottom trawl catch along the northwest coast. With more than 20 species of carangids reported to be caught in various cruises, Decapterus spp formed the most dominant group, followed by species like Atule mate, Selar crumenophthalmus, Carangoides malabaricus etc. Depthwise distribution showed higher density in the 60-80 m range all along the coast excepting the Andaman-Nicobar archipelago. Areawise, higher densities of carangids were noticed at latitude-longitude 7°N - 77°E, 1TN - 75°E, 1TN - 79°E, 14°N - 80°E , 18°N - 72°E, 19°N -85°E and 19°N -86°E. Seasonally, carangids were represented in the catch more during the monsoon especially along the northeast and southwest coasts. Potential yield of carangids along the EEZ of India is estimated to be 94971 tonne