149 research outputs found
Internal noise driven generalized Langevin equation from a nonlocal continuum model
Starting with a micropolar formulation, known to account for nonlocal
microstructural effects at the continuum level, a generalized Langevin equation
(GLE) for a particle, describing the predominant motion of a localized region
through a single displacement degree-of-freedom (DOF), is derived. The GLE
features a memory dependent multiplicative or internal noise, which appears
upon recognising that the micro-rotation variables possess randomness owing to
an uncertainty principle. Unlike its classical version, the new GLE
qualitatively reproduces the experimentally measured fluctuations in the
steady-state mean square displacement of scattering centers in a polyvinyl
alcohol slab. The origin of the fluctuations is traced to nonlocal spatial
interactions within the continuum. A constraint equation, similar to a
fluctuation dissipation theorem (FDT), is shown to statistically relate the
internal noise to the other parameters in the GLE
Heavy landings of yellowfin tuna Thunnus albacares (Bonnaterre, 1788) by hooks and line off Chennai coast
Tunas are commercially important fish and
widely but sparsely distributed throughout the oceans
of the world, generally in tropical and temperate
waters. They are grouped taxonomically in the family
Scombridae, which includes about 50 species. The
most important of these in commercial and
recreational fisheries are yellowfin (Thunnus
albacares) (Fig. 1), skipjack (Katsuwonus pelamis),
bluefin tuna (T. tonggol), frigate tuna (Auxis thazard)
mackerel tuna (Euthynnus affinis) and striped bonito
(T. orientalis). They are exploited mainly by hooks
and line, mechanised gillnets and trawlnets in India
Heavy landing of juvenile seerfish Scomberomorus commerson (Lacepede, 1800) along Chennai coast
After the fishing ban (15th April - 30th May, 2011),
heavy landings of juvenile seerfish Scomberomorus
commerson (Lacepede, 1800) was observed along
Chennai coast. During the period from April to August
2011, young ones of S. commerson were landed
continuously by gillnet (Pannuvalai). The nets were
operated near the shore in 5-10 m depth. The average
catch per boat was 15-50 kg dail
рдмрдВрдЧрд╛рд▓ рдХреА рдЦрд╛рдбреА рдореЗрдВ рдЪреЗрдиреНрдирдИ рддрдЯ рдкрд░ рдкреЛрдореНрдкрд╛рдиреЛ рдбреЛрд▓реНрдлрд┐рди, рдХреЛрд░рд┐рдлрд╛рдЗрдирд╛ рдЗрдХреНрд╡рд┐рд╕реЗрд▓рд┐рд╕ (рд▓рд┐рдиреНрдирд╕, 1758) рдХреА рдкрд╣рд▓реА рд░рд┐рдХреЛрд░реНрдб
рдХреГрдкрдпрд╛ рдкреВрд░рд╛ рд▓реЗрдЦрд╛ рдкрдв
First record of pompano dolphinfish, Coryphaena equiselis (Linnaeus, 1758) off Chennai coast in Bay of Bengal
On 5.9.2009, a catch comprising 15 specimens
of pompano dolphinfish, Coryphaena equiselis
(Linnaeus, 1758) was landed at Chennai Fisheries
Harbour by mechanised gillnet. The mechanised
gillnets operated usually at a depth between 30 and
50 m at a distance of 30-40 km north of Chennai
towards Andhra Pradesh. Since, trawlnets and
mechanised gillnets are the main fishing gears
operated off Chennai coast, fishes belonging to the
family Coryphaenidae formed part of regular
landings by these two gears. Normally common
dolphinfish, Coryphaena hippurus formed regular
fishery along this coast
Occurrence of a rare species of red crab, Ranina ranina (Linnaeus 1758) along Chennai coast
The red frog crab otherwise called spanner crab
is a coastal water species and single representative
of genus Ranina under family Raninidea. They prefer
to inhabit in bare sandy areas of intertidal and
coastal waters of more than 100m depth. Distribution
of this crab is confined to tropical and sub topical
coastal waters of Indian and Pacific oceans, from
the coast of South Africa to Hawaii and the Great
Barrier Reef. Occurrence of this species is very sparse
in Indian waters and has been recorded once in Gulf
of Mannar (Kasinathan et al., 2007)
рдЪреЗрдиреНрдирдИ рддрдЯ рдореЗрдВ рдХрд╛рдБрдЯрд╛ рдбреЛрд░рд┐рдпреЛрдВ рджреНрд╡рд╛рд░рд╛ рдкреАрдд рдкрдЦ рдЯреВрдпреВрдирд╛ рдердиреНрдирд╕ рдЕрд▓реНрдмрд╛рдХрд╛рд░реЗрд╕ (рдмреЛрдиреНрдирд╛рдЯреЗрд░реЗ, 1788) рдХрд╛ рднрд╛рд░реА рдЕрд╡рд░рдг
рдХреГрдкрдпрд╛ рдкреВрд░рд╛ рд▓реЗрдЦрд╛ рдкрдв
Rare occurrence of deepsea snake mackerel off Nagapattinam coast in the Bay of Bengal
Lepidocybium flavobrunneum (Smith, 1843) has
a wide distribution in tropical and temperate seas of
the world. The species is considered to be
benthopelagic in occurrence between 200 and
1000 m, depth, and probably not reported to occur
in the northern Indian Ocean. Balasubramanian
(2007) reported on the occurrence of this species
during 2004-06 in the landings of large meshed
gillnets operated off Tuticorin coast in the Gulf of
Mannar. A catch of 4 specimens of Lepidocybium
flavobrunneum (Fig. 1) belonging to the family
Gempylidae (snake mackerels) were observed at
Chennai Fisheries Harbour on 5.3.2009
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