3,222 research outputs found
The rise of peri-urban aquaculture in Nigeria
The paper traced aquacultural development in Nigeria to the colonial period in 1950s with fish farming in tilapias during which more than 200 small scale subsistence level ponds were built with some growth continuing in the rural areas. There was a bloom in farming of catfishes in 2000. The interest shown by private fish farmers has been identified as a propelling factor for aquacultural development in Nigeria. The development of private fish hatcheries has been another factor leading to the growth of aquaculture. The paper noted that social capital and its development either directly or indirectly can be identified as contributing to the success of the sectors. The increasing profit from aquaculture has led to fish farmers increasing beyond 5000 tonnes in 2009. The paper highlighted the numerous advantages which led to the expansion of the industry in Nigerian villages
Assessment of Gerio Lake Fishery for Enhanced Management and Improved Fish Production
The highlights of the Fisheries Assessment Survey conducted on Gerio
Lake, Yola in Adamawa State, North-eastern Nigeria in February, 2005 is
presented in this paper. There were 22 fish species found in
fishermen\u2019s landings during the survey period. About 30 fishermen
were found using undersized nets to catch the juveniles of these
species. Fishing pressure was found to be very high. For an optimum
catch, about 10 fishermen ought to have engaged in full time fishing
activities if, the fisheries of the lake is to be managed on a
sustainable basis. However, a surplus of over 80 fishermen was recorded
actively fishing during the period of the assessment. All these have a
depleting effect on the abundance and sizes of fish harvested from the
lake. A community based fisheries management system, which establishes
a participatory involvement of fishermen in the conservation and
rational exploitation of fisheries resources for the well being of the
stakeholders is recommended for the Lake
NEUTRON LOSSES TO Pa IN THE AQUEOUS HOMOGENEOUS BREEDER REACTOR
Neutron losses to Pa/sup 2//sup 3//sup 3/ in the blanket of the AHBR were computed and compared for two cases: (1) concentration of Pa/sup 2//sup 3// sup 3/ is maintained uniform by continuous mixing, and (2) batches of fertile material are shifted periodically from high- to low-flux regions of blanket. It was found that, if the fertile material is cycled through three radial positions in three days, the loss of neutrons to Pa/sup 2//sup 3//sup 3/ is no more than one per cent greater than if it is mixed continuously. (auth
A molecular phylogenetic reappraisal of the Hysteriaceae, Mytilinidiaceae and Gloniaceae (Pleosporomycetidae, Dothideomycetes) with keys to world species
A reappraisal of the phylogenetic integrity of bitunicate ascomycete fungi
belonging to or previously affiliated with the Hysteriaceae,
Mytilinidiaceae, Gloniaceae and Patellariaceae is
presented, based on an analysis of 121 isolates and four nuclear genes, the
ribosomal large and small subunits, transcription elongation factor 1 and the
second largest RNA polymerase II subunit. A geographically diverse and high
density taxon sampling strategy was employed, including multiple
isolates/species from the following genera: Anteaglonium (6/4),
Encephalographa (1/1), Farlowiella (3/1),
Gloniopsis (8/4), Glonium (4/2), Hysterium (12/5),
Hysterobrevium (14/3), Hysterographium (2/1),
Hysteropatella (2/2), Lophium (4/2), Mytilinidion
(13/10), Oedohysterium (5/3), Ostreichnion (2/2),
Patellaria (1/1), Psiloglonium (11/3), Quasiconcha
(1/1), Rhytidhysteron (8/3), and 24 outgroup taxa. Sequence data
indicate that although the Hysteriales are closely related to the
Pleosporales, sufficient branch support exists for their separation
into separate orders within the Pleosporomycetidae. The
Mytilinidiales are more distantly related within the subclass and
show a close association with the Gloniaceae. Although there are
examples of concordance between morphological and molecular data, these are
few. Molecular data instead support the premise of a large number of
convergent evolutionary lineages, which do not correspond to previously held
assumptions of synapomorphy relating to spore morphology. Thus, within the
Hysteriaceae, the genera Gloniopsis, Glonium,
Hysterium and Hysterographium are highly polyphyletic. This
necessitated the transfer of two species of Hysterium to
Oedohysterium gen. nov. (Od. insidens comb.
nov. and Od. sinense comb. nov.), the description of a new
species, Hysterium barrianum sp. nov., and the transfer of
two species of Gloniopsis to Hysterobrevium gen.
nov. (Hb. smilacis comb. nov. and Hb.
constrictum comb. nov.). While Hysterographium, with
the type Hg. fraxini, is removed from the Hysteriaceae, some
of its species remain within the family, transferred here to
Oedohysterium (Od. pulchrum comb. nov.),
Hysterobrevium (Hb. mori comb. nov.) and
Gloniopsis (Gp. subrugosa comb. nov.); the latter
genus, in addition to the type, Gp. praelonga, with two new species,
Gp. arciformis sp. nov. and Gp. kenyensis sp. nov.
The genus Glonium is now divided into Anteaglonium
(Pleosporales), Glonium (Gloniaceae), and
Psiloglonium (Hysteriaceae). The hysterothecium has evolved
convergently no less than five times within the Pleosporomycetidae
(e.g., Anteaglonium, Farlowiella, Glonium,
Hysterographium and the Hysteriaceae). Similarly,
thin-walled mytilinidioid (e.g., Ostreichnion) and patellarioid
(e.g., Rhytidhysteron) genera, previously in the
Mytilinidiaceae and Patellariaceae, respectively,
transferred here to the Hysteriaceae, have also evolved at least
twice within the subclass. As such, character states traditionally considered
to represent synapomorphies among these fungi, whether they relate to spore
septation or the ascomata, in fact, represent symplesiomorphies, and most
likely have arisen multiple times through convergent evolutionary processes in
response to common selective pressures
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A comparative assessment of the economics of plutonium disposition
The US Department of Energy office of Fissile Materials Disposition (DOE/MD) has been evaluating three technologies for the disposition of approximately 50 metric tons of surplus plutonium from defense-related programs: reactors, immobilization, and deep boreholes. As part of the process supporting an early CY 1997 Record of Decision (ROD), a comprehensive assessment of technical viability, cost, and schedule has been conducted by DOE/MD and its national laboratory contractors. Oak Ridge National Laboratory has managed and coordinated the life-cycle cost (LCC) assessment effort for this program. This paper discusses the economic analysis methodology and the results prior to ROD. A secondary intent of the paper is to discuss major technical and economic issues that impact cost and schedule. To evaluate the economics of these technologies on an equitable basis, a set of cost-estimating guidelines and a common cost-estimating format were utilized by all three technology teams. This paper also includes the major economic analysis assumptions and the comparative constant-dollar and discounted-dollar LCCs
Recommended from our members
A comparative assessment of the economics of plutonium disposition including comparison with other nuclear fuel cycles
DOE has been evaluating three technologies for the disposition of approximately 50 metric tons of surplus plutonium from defense-related programs: reactors, immobilization, and deep boreholes. As part of the process supporting an early CY 1997 Record of Decision (ROD), a comprehensive assessment of technical viability, cost, and schedule has been conducted. Oak Ridge National Laboratory has managed and coordinated the life-cycle cost (LCC) assessment effort for this program. This paper discusses the economic analysis methodology and the results prior to ROD. Other objectives of the paper are to discuss major technical and economic issues that impact plutonium disposition cost and schedule. Also to compare the economics of a once-through weapons-derived MOX nuclear fuel cycle to other fuel cycles, such as those utilizing spent fuel reprocessing. To evaluate the economics of these technologies on an equitable basis, a set of cost estimating guidelines and a common cost-estimating format were utilized by all three technology teams. This paper also includes the major economic analysis assumptions and the comparative constant-dollar and discounted-dollar LCCs
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