3,416 research outputs found
A possible observational bias in the estimation of the virial parameter in virialized clumps
The dynamics of massive clumps, the environment where massive stars
originate, is still unclear. Many theories predict that these regions are in a
state of near-virial equilibrium, or near energy equi-partition, while others
predict that clumps are in a sub-virial state. Observationally, the majority of
the massive clumps are in a sub-virial state with a clear anti-correlation
between the virial parameter and the mass of the clumps ,
which suggests that the more massive objects are also the more gravitationally
bound. Although this trend is observed at all scales, from massive clouds down
to star-forming cores, theories do not predict it. In this work we show how,
starting from virialized clumps, an observational bias is introduced in the
specific case where the kinetic and the gravitational energies are estimated in
different volumes within clumps and how it can contribute to the spurious
anti-correlation in these data. As a result, the observed
effective virial parameter , and in some
circumstances it might not be representative of the virial state of the
observed clumps.Comment: A&A letter, accepte
Interpretation of fish shoal indications in the Arabian Sea
Availability of resources is perhaps
one of the most important factors which
determines the success of any industry.
In the case of the fishing industry, at the
basic production level the availability
of fishable concentrations of fishes and
other marine life is the decisive factor
which controls the economy of the whole
system
The Indian oil sardine
The Indian oil sardine, Sardinella longiceps Val, supports a neritic
pelagic fishery contributing 2 to 33 % of the annual marine fish
production in India. Though distributed all along the Indian coast
the species sustains a commercial fishery of high magnitude along
the coasts of Kerala, Karnataka , Goa and southern part oJ
Maharashtra. During the last fifty years the annual all India production
oscillated between 14.000 t in 1952 to 3 lakh t during 1968.
Presently the west coast indicates a declining trend compared to an
ascending pattern along the east coasl. The production from east
coast surpassed that of the west coast contributing 52% of the all
India production of 2.03 lakh t in 1998. The fishery along the west
coast is known for its fiuctuating nature. Further, the species
indicates a cyclic pattern of abundance. A variety of traditional gears
were engaged in exploiting the resource till the introduction of
modern and sophisticated gear like the purse seines in the late
seventies and the ring seines in the late eighties. In fact oil sardine
is one among the few species that have ever remained a subject
matter of intensive research. The focus of this compilation is to
present a comprehensive picture of the Indian oil sardine, its fishery,
biology, stock, future prospects of exploitation and management
measures needed for yield optimisation
Fishery and biology of yellowfin tuna occurring in the coastal fishery in Indian seas
In the recently convened Workshop on "Stock assessment of yellowfin tuna in the Indian Ocean" (FAO/IPTP, 1991) the present status of the fishery, biology and stock structure of yellawfiil tuna taken by different countries bordering the Indian Ocean have been discussed, and recommednations on the development of the fishery for this species made
Ultrafast switching time and third order nonlinear coefficients of microwave treated single walled carbon nanotube suspensions
Microwave treated water soluble and amide functionalized single walled carbon
nanotubes have been investigated using femtosecond degenerate pump-probe and
nonlinear transmission experiments. The time resolved differential transmission
using 75 femtosecond pulse with the central wavelength of 790 nm shows a
bi-exponential ultrafast photo-bleaching with time constants of of 160 fs (130
fs) and 920 fs (300 fs) for water soluble (amide functionalized) nanotubes.
Open and closed aperture z-scans show saturation absorption and positive
(negative) nonlinear refraction for water soluble (amide functionalized)
nanotubes. Two photon absorption coefficient,beata ~250 cm/GW (650 cm/GW) and
nonlinear index, gamma ~ 15 cm^2/pW (-30 cm^2/pW) are obtained from the
theoretical fit in the saturation limit to the data for two types of nanotubes.Comment: 15 pages, 4 figure
Status and scope of research on pelagic fisheries of India
Extensive and indiscriminate exploitation of marine natural resources,
during the last three decades is leading to a situation where no more
commercial fish stocks may be left in the sea by year 2050 unless ecosystems
are protected and the biodiversity is revived, warns a new study cataloging
the global collapse of marine ecosystems (Worm et al., 2006). The task of
understanding the dynamics of large marine ecosystems to offer effective
and relevant scientific advice to develop management interventions is a
difficult, complex, expensive and lengthy process. This is especially true in
the Indian context where the country has an EEZ of 2.02 million km2, which
contributes nearly 40% of the total fish production from the Indian Ocean.
Fishes have been mentioned in the ancient literature of India including the
epics such as Ramayana and Mahabaratha. Excavations from Mohenjodaro
and Harappa indicate that fishing with hooks and nets was common as back
as 3000 B.C. and over the years fishing and fisheries in India have evolved at
a rapid pace (Ayyappan et al., 2004). Marine fisheries is basically harnessing
a natural resource and therefore its management must anchor on knowledge-
based interventions generated through close monitoring of their distribution,
abundance, exploitation, population dynamics and fluctuations of fish stocks
in relation to natural factors and anthropogenic interventions. Against a
scenario of an ever-increasing population and stagnant marine fish production
in recent years, per capita seafood availability is a serious concern. The countr
Drift gill net fishery for large pelagics at Cochin - A case study on by-catch of pelagic sharks
In India, the elasmobranchs contributed on an average 60,8(X) t during 1986 to 1999
forming 2.7% of the total marine fish landings. The production varied from 50,000t
in 1990 to a highest of 75,(X)0 t in 1998. The sharks dominated forming 62.4%,
followed by rays (33.5%) and skates the rest. The west coast accounted for 55.5%
and east coast 44.5%. The highest contribution of 30.2% was from Gujarat followed
by Tamilnadu (26.2%). The drift gillnets, sharing 48.5% of the production, was the
major gear, followed by trawls (31.5%) and hooks and line (6.1%). Since the drift
gillnets (DGN), apart from the scombroids, exploit a variety of larger pelagics, a
case study of the shark fishery by the gear at Kochi was made based on the data from
1979 to 1999 and the results are presented her
On the sei whale Balenoptera borealis Lesson stranded along Palk Bay coast near Pamban light house
A Sei whale got entangled in a gill net operated near
Katchathievu on 27-l-'90 at a depth of 8.5 m at about 1900
hrs. Four boats joined together and brought the whale ashore near Pamban Light House on the 28th morning in live
condition. Attempts were made to push the whale back into
the sea but did not succeed. The medium sized female whale
measured 11.4 m in total length and weighed about 7000 kg.
The specimen was identified as Balaenoptera borealis Lesson
(Fig. 1) and it had 47 throat grooves. The morphometric
measurements are give
Hot Core, Outflows and Magnetic Fields in W43-MM1 (G30.79 FIR 10)
We present submillimeter spectral line and dust continuum polarization
observations of a remarkable hot core and multiple outflows in the high-mass
star-forming region W43-MM1 (G30.79 FIR 10), obtained using the Submillimeter
Array (SMA). A temperature of 400 K is estimated for the hot-core using
CHCN (J=19-18) lines, with detections of 11 K-ladder components. The high
temperature and the mass estimates for the outflows indicate high-mass
star-formation. The continuum polarization pattern shows an ordered
distribution, and its orientation over the main outflow appears aligned to the
outflow. The derived magnetic field indicates slightly super-critical
conditions. While the magnetic and outflow energies are comparable, the B-field
orientation appears to have changed from parsec scales to 0.1 pc scales
during the core/star-formation process.Comment: accepted, ApJ Letter
Finfish resources around Andaman and Nicobar islands
The average catch rate of finfishes obtained by FORV Sagar Sampada from the
survey area in the Andaman Sea was 259 kg/hr and the yield ranged from 8.6 to 1260
kg/hr. Silver bellies was the most abundant component (37.5%) with a catch rate of
96.9 kg/hr. Carangids, elasmobranchs and perches accounted for 20.3%, 11.9% and
8.0% of the total catch and the corresponding catch rates were 52.5, 31.1 and 20.8
kg/hr respectively. The highest catch rate of 1260 kg/hr was recorded from 13°10'N
- 92°37'E at a depth of 65m. The catch rate indicated that the depth zone 51-100 m
is productive and yielded 84.7% of the total catch at a catch rate of 501.4 kg/hr.
Although the pelagic trawl was operated at 38 stations, the catch realised was
neghgible (0.83 kg/hr)
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