8,363 research outputs found
Seasonal changes in abundance of brown trout (Salmo trutta) and rainbow trout (s. gairdnerii) assessed by drift diving in the Rangitikei river, New Zealand
Numbers and approximate sizes of brown trout (Salmo trutta L.) and rainbow trout (5. gairdnerii Richardson) were estimated by snorkel divers at 6 sites in the middle reaches of the Rangitikei River, North Island, New Zealand, over 14 months. The results showed that different species and sizes of trout varied in abundance with time. The species of fingerling trout (6-12 cm FL) could not be identified because of their small size and shoaling behaviour. Rainbow trout abundance varied seasonally and was greatest in January and April (between 18 and 60 fish per kilometre) when fish between 23 and 38 cm FL were the most abundant size class. Brown trout abundance showed much less variation with time (between 5 and 36 fish per kilometre at most sites). Also in contrast to rainbow trout, the majority of brown trout were > 38 cm FL, and in June, when the greatest density was observed (56 fish per kilometre), 70 redds were seen at the same site. Two sites were dived within a 48 h period to test the variability of the method. Comparisons between the 3 dives at each site revealed no significant differences between the numbers offish in different species and size classes
Quinnat salmon (oncorhynchus tshawytscha) spawning in the Rangitikei river
The occurrence of adult quinnat salmon {Oncorhynchus tshawytscha (Walbaum)) in the Rangitikei River, North Island, New Zealand, has been confirmed on several occasions since 1922, but juvenile salmon have not previously been recorded. In late February 1981 a 79-mm-fork-length smolt was caught in a stranded side channel 180 km upstream from the mouth. This suggests that quinnat salmon can spawn successfully in this river
Quantum Layers over Surfaces Ruled Outside a Compact Set
In this paper, we proved the quantum layer over a surface which is ruled
outside a compact set, asymptotically flat but not totally geodesic admits
ground states
Southern Brazilian indigenous populations and the forest: towards an environmental history
Human societies and economies are inextricably linked to oceans and seas. Eight of the worldās ten largest cities lie adjacent to the ocean (UN Atlas of the Oceans, 2010) and about half of the worldās population lives within 200 km of a coast ā a quarter within 100 km (IPCC, 2007). Oceans and seas provide a range of ecosystem services (including regulating, provisioning and cultural services) that enhance human wellābeing in numerous ways (Millennium Ecosystem Assessment, 2003, 2005; Hicks, 2011). To the extent that climate change affects ecosystems, it will affect fisheries (as discussed in the preceding chapters of this book) and, by extension, human wellābeing. In this chapter, we focus on provisioning and cultural services associated with fisheries. Although important, the oceanās regulating and supporting services, including the fixation of atmospheric carbon, are not further discussed here (for further details, see UNEPāWCMC, 2011). We describe the numerous contributions of marineābased ecosystems to human wellābeing and the ways in which climate change and other confounding factors are likely to disrupt relationships between fishers, fisheries and fishing communities. Our three caseāstudies: smallāscale, artisanal and subsistenceābased fisheries of the western Indian Ocean (WIO), fishing of cultural keystone species in the Torres Strait, and commercial fishing in Australia, serve to highlight the various changes to fisheries likely to be brought about by climate change in three markedly different contexts
Diffusion and Transport Coefficients in Synthetic Opals
Opals are structures composed of the closed packing of spheres in the size
range of nano-to-micro meter. They are sintered to create small necks at the
points of contact. We have solved the diffusion problem in such structures. The
relation between the diffusion coefficient and the termal and electrical
conductivity makes possible to estimate the transport coefficients of opal
structures. We estimate this changes as function of the neck size and the
mean-free path of the carriers. The theory presented is also applicable to the
diffusion problem in other periodic structures.Comment: Submitted to PR
Lipid Rafts and Alzheimerās Disease: Protein-Lipid Interactions and Perturbation of Signaling
Lipid rafts are membrane domains, more ordered than the bulk membrane and enriched in cholesterol and sphingolipids. They represent a platform for protein-lipid and proteināprotein interactions and for cellular signaling events. In addition to their normal functions, including membrane trafficking, ligand binding (including viruses), axonal development and maintenance of synaptic integrity, rafts have also been implicated in the pathogenesis of several neurodegenerative diseases including Alzheimerās disease (AD). Lipid rafts promote interaction of the amyloid precursor protein (APP) with the secretase (BACE-1) responsible for generation of the amyloid Ī² peptide, AĪ². Rafts also regulate cholinergic signaling as well as acetylcholinesterase and AĪ² interaction. In addition, such major lipid raft components as cholesterol and GM1 ganglioside have been directly implicated in pathogenesis of the disease. Perturbation of lipid raft integrity can also affect various signaling pathways leading to cellular death and AD. In this review, we discuss modulation of APP cleavage by lipid rafts and their components, while also looking at more recent findings on the role of lipid rafts in signaling events
The LWA1 Radio Telescope
LWA1 is a new radio telescope operating in the frequency range 10-88 MHz,
located in central New Mexico. The telescope consists of 258 pairs of
dipole-type antennas whose outputs are individually digitized and formed into
beams. Simultaneously, signals from all dipoles can be recorded using one of
the instrument's "all dipoles" modes, facilitating all-sky imaging. Notable
features of the instrument include high intrinsic sensitivity (about 6 kJy
zenith system equivalent flux density), large instantaneous bandwidth (up to 78
MHz), and 4 independently-steerable beams utilizing digital "true time delay"
beamforming. This paper summarizes the design of LWA1 and its performance as
determined in commissioning experiments. We describe the method currently in
use for array calibration, and report on measurements of sensitivity and
beamwidth.Comment: 9 pages, 14 figures, accepted by IEEE Trans. Antennas & Propagation.
Various minor changes from previous versio
- ā¦