154 research outputs found
Scale-free switching of polarization in the layered ferroelectric material CuInPS
Using first-principles calculations we model the out-of-plane switching of
local dipoles in CuInPS (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 203.6-258.0 meV, a factor of five smaller than that
of HfO (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
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