255 research outputs found
Comments on the ecology of grass grub and porina caterpillar
The object of this paper is to discuss the ecology of grass
grub, Costelytra zealandica White, and porina, Wiseana
cervinata (Walker), New Zealand’s most important
pastoral insect pests, and to survey what has been achieved
in ecological understanding of these insects. The biology
and ecology of either or both insects have previously been
reviewed by Dumbleton (1942), Miller (1945), Kelsey
(1951a, b) and Hoy (1963). The lack of fundamental
biological information on grass grub (and this is equally
applicable to porina caterpillar) and the need for longterm
team studies were stressed, although little sustained,
co-ordinated research has since eventuated.
Examination of the literature clearly indicates that the
lack of fundamental ecological research on these pasture
pests is directly due to the introduction of organochlorine
insecticides, particularly DDT, to control both porina and
grass grub. These insecticides proved cheap, persistent
in soil, relatively safe to handle and easy to apply (Kelsey
and Hay., 1950; Kelsey 1951a, b, 1952, 1959). DDT was
so effective that it led to complacency, in spite of the
warning by Miller (1945) that in his view no single control
would suffice. There was failure to anticipate:
(1) Development of insect resistance. to insecticides.
(2) Possible alteration of tolerance limits for insecticides
in foodstuffs, by countries importing New Zealand
produce.
(3) Failure of DDT to be effective in certain soils.
(4) The need for fundamental knowledge, in case the
efficacy of DDT and related insecticides diminished,
and new methods had to be found
Rapid bioconcentration of steroids in the plasma of three-spined stickleback Gasterosteus aculeatus exposed to waterborne testosterone and 17β-oestradiol
The relationship over time between the concentrations of two steroids, singly and in combination, in a static exposure system and in the blood of three-spined stickleback Gasterosteus aculeatus, held within the exposure system was investigated. Groups of three-spined stickleback were exposed (nominally) to either 1000 ng l1 17β-oestradiol (E2), testosterone (T) or E2 and T in combination at the same concentrations for 6 days. Both water and fish were sampled at intervals and steroid concentrations in both compartments were determined. The plasma steroid time profile revealed a rapid bioconcentration within the first 6 h of exposure. The plasma steroid levels attained at this time point (20–90 ng ml1) were up to 50-fold (E2) and 200-fold (T) greater than the actual levels of steroid measured in the exposure water, while levels in the blood of control fish did not exceed 4 ng ml1. The substantial elevation of plasma steroid levels relative to the concentrations of steroid to which the fish were exposed in the ambient water gives scope for delivery of the steroids to target endocrine tissues at levels far in excess of what might be predicted on the basis of passive branchial uptake alone. These results are discussed in relation to endocrine disruption, and in particular the occurrence of effects in fish exposed to levels of endocrine active substances that are seemingly physiologically irrelevant
Direct thrust measurement of a permanent magnet helicon double layer thruster
Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure
Characterising strongly normalising intuitionistic sequent terms
This paper gives a characterisation, via intersection types, of the strongly normalising terms of an intuitionistic sequent calculus (where LJ easily embeds). The soundness of the typing
system is reduced to that of a well known typing system with intersection types for the ordinary lambda-calculus. The completeness of the typing system is obtained from subject expansion at root position. This paper's sequent term calculus integrates smoothly the lambda-terms with generalised application or explicit substitution. Strong normalisability of these terms as
sequent terms characterises their typeability in certain "natural'' typing systems with intersection types. The latter are in the natural deduction format, like systems previously studied by Matthes and Lengrand et al., except that they do not contain any extra, exceptional rules for typing generalised applications or substitution
Secular Trends in Nosocomial Bloodstream Infections: Antibiotic-Resistant Bacteria Increase the Total Burden of Infection
In this international study, we demonstrate that increasing rates of nosocomial bloodstream infections caused by antibiotic-resistant bacteria do not replace infections caused by antibiotic-susceptible bacteria, but occur in addition to these infections, thereby increasing the total burden of diseas
VIS: the visible imager for Euclid
Euclid-VIS is the large format visible imager for the ESA Euclid space mission in their Cosmic Vision program, scheduled for launch in 2020. Together with the near infrared imaging within the NISP instrument, it forms the basis of the weak lensing measurements of Euclid. VIS will image in a single r+i+z band from 550-900 nm over a field of view of ~0.5 deg2. By combining 4 exposures with a total of 2260 sec, VIS will reach to V=24.5 (10σ) for sources with extent ~0.3 arcsec. The image sampling is 0.1 arcsec. VIS will provide deep imaging with a tightly controlled and stable point spread function (PSF) over a wide survey area of 15000 deg2 to measure the cosmic shear from nearly 1.5 billion galaxies to high levels of accuracy, from which the cosmological parameters will be measured. In addition, VIS will also provide a legacy dataset with an unprecedented combination of spatial resolution, depth and area covering most of the extra-Galactic sky. Here we will present the results of the study carried out by the Euclid Consortium during the period up to the Preliminary Design Review. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
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