17,197 research outputs found
Rotary antenna attenuator
Radio frequency attenuator, having negligible insertion loss at minimum attenuation, can be used for making precise antenna gain measurements. It is small in size compared to a rotary-vane attenuator
The Nature of the Peculiar Virgo Cluster Galaxies NGC 4064 and NGC 4424
We present a detailed study of the peculiar HI-deficient Virgo cluster spiral
galaxies NGC 4064 and NGC 4424, using CO 1-0 interferometry, optical
imaging and integral-field spectroscopic observations, in order to learn what
type of environmental interactions have afected these galaxies. Optical imaging
reveals that NGC 4424 has a strongly disturbed stellar disk, with banana-shaped
isophotes and shells. NGC 4064, which lies in the cluster outskirts, possesses
a relatively undisturbed outer stellar disk and a central bar. In both galaxies
H-alpha emission is confined to the central kiloparsec. CO observations reveal
bilobal molecular gas morphologies, with H-alpha emission peaking inside the CO
lobes, implying a time sequence in the star formation process.Gas kinematics
reveals strong bar-like non-circular motions in the molecular gas in both
galaxies, suggesting that the material is radially infalling. In NGC 4064 the
stellar kinematics reveal strong bar-like non-circular motions in the central 1
kpc. On the other hand, NGC 4424 has extremely modest stellar rotation
velocities (Vmax ~ 30 km s-1), and stars are supported by random motions as far
out as we can measure it. The observations suggest that the peculiarities of
NGC 4424 are the result of an intermediate-mass merger plus ram pressure
stripping. In the case of NGC 4064, the evidence suggests an already stripped
"truncated/normal" galaxy that recently suffered a minor merger or tidal
interaction with another galaxy. We propose that galaxies with
"truncated/compact" H-alpha morphologies such as these are the result of the
independent effects of ram pressure stripping, which removes gas from the outer
disk, and gravitational interactions such as mergers, which heat stellar disks,
drive gas to the central kpc and increase the central mass concentrations.Comment: 42 pages, 21 figure
Upgraded demonstration vehicle task report
Vehicle/battery performance capabilities and interface problems that occurred when upgraded developmental batteries were integrated with upgraded versions of comercially available electric vehicles were investigated. Developmental batteries used included nickel zinc batteries, a nickel iron battery, and an improved lead acid battery. Testing of the electric vehicles and upgraded batteries was performed in the complete vehicle system environment to characterize performance and identify problems unique to the vehicle/battery system. Constant speed tests and driving schedule range tests were performed on a chassis dynamometer. The results from these tests of the upgraded batteries and vehicles were compared to performance capabilities for the same vehicles equipped with standard batteries
Detection of moisture and moisture related phenomena from Skylab
There are no author-identified significant results in this report
New insights into the supression of plant pathogenic fungus (Phytophthora cinnamomi) by compost leachates
Use of compost as a soil conditioner and low-grade fertiliser is gaining popularity worldwide (Epstein, 1997). Compost not only adds plant nutrients to the soil, but also improves physical properties of soil such as buffering capacity, cation exchange capacity and water holding capacity. In addition to these benefits, compost can also suppress plant diseases caused by Phytophthora cinnamomi (Hoitink et al., 1977), Pythium aphanidermatum (Mandelbaum and Hadar, 1990), Rhizoctonia solani and Sclerotium rolfoii (Gorodecki and Hadar, 1990).
Irwin et al., (1995) reported that the diseases caused by P. cinnamomi are directly responsible for considerable economic losses in many horticultural, ornamental and forestry industries throughout Australia. Phytophthora spp. continue to be the focus of attention of many researchers due to the diversity of P. cinnamomi-host interactions and their potential economic impact on a wide range of industries.
The practise of using methyl bromide and other chemicals for disinfection of soil is widespread (Trill as et al., 2002). However, the use of methyl bromide and other chemicals is phased out in the USA and Europe. The suppression of soil-borne plant fungus by composts produced from tree barks (Spencer et al., 1982) and municipal solid wastes is well documented (Trill as et al., 2002).
Composts that suppress plant disease have been extensively described and are used in greenhouse production systems (Lazarovitis et aI, 2001). However, most studies have focused on compo sting different types of materials and their effect on fungal pathogens inhibition rather than compo sting conditions that may produce suppressive composts. An objective of this study was to investigate the role of moisture, aeration and compost maturity in enhancing the inhibition effect of compost on the plant pathogen P. cinnamomi. A further objective was to generate an increased understanding of the mechanism of growth inhibition
The use of thematic mapper data for land cover discrimination: Preliminary results from the UK SATMaP programme
The principal objectives of the UK SATMaP program are to determine thematic mapper (TM) performance with particular reference to spatial resolution properties and geometric characteristics of the data. So far, analysis is restricted to images from the U.S. and concentrates on spectra and radiometric properties. The results indicate that the data are inherently three dimensional compared with the two dimensional character of MSS data. Preliminary classification results indicate the importance of the near infrared band (TM 4), at least one middle infrared band (TM 5 or TM 6) and at least one of the visible bands (preferably either TM 3 or TM 1). The thermal infrared also appears to have discriminatory ability despite its coarser spatial resolution. For band 4 the forward and reverse scans show somewhat different spectral responses in one scene but this effect is absent in the other analyzed. From examination of the histograms it would appear that the full 8-bit quantization is not being effectively utilized for all the bands
Measurement of the half-life of 198Au in a non-metal: High-precision measurement shows no host-material dependence
We have measured the half-life of the beta decay of 198Au to be 2.6948(9) d,
with the nuclide sited in an insulating environment. Comparing this result with
the half-life we measured previously with a metallic environment, we find the
half-lives in both environments to be the same within 0.04%, thus contradicting
a prediction that screening from a "plasma" of quasi-free electrons in a metal
increases the half-life by as much as 7%
Towards Quantum Gravity: A Framework for Probabilistic Theories with Non-Fixed Causal Structure
General relativity is a deterministic theory with non-fixed causal structure.
Quantum theory is a probabilistic theory with fixed causal structure. In this
paper we build a framework for probabilistic theories with non-fixed causal
structure. This combines the radical elements of general relativity and quantum
theory. The key idea in the construction is physical compression. A physical
theory relates quantities. Thus, if we specify a sufficiently large set of
quantities (this is the compressed set), we can calculate all the others. We
apply three levels of physical compression. First, we apply it locally to
quantities (actually probabilities) that might be measured in a particular
region of spacetime. Then we consider composite regions. We find that there is
a second level of physical compression for the composite region over and above
the first level physical compression for the component regions. Each
application of first and second level physical compression is quantified by a
matrix. We find that these matrices themselves are related by the physical
theory and can therefore be subject to compression. This is the third level of
physical compression. This third level of physical compression gives rise to a
new mathematical object which we call the causaloid. From the causaloid for a
particular physical theory we can calculate verything the physical theory can
calculate. This approach allows us to set up a framework for calculating
probabilistic correlations in data without imposing a fixed causal structure
(such as a background time). We show how to put quantum theory in this
framework (thus providing a new formulation of this theory). We indicate how
general relativity might be put into this framework and how the framework might
be used to construct a theory of quantum gravity.Comment: 23 pages. For special issue of Journal of Physics A entitled "The
quantum universe" in honour of Giancarlo Ghirard
Flight evaluation of the STOL flare and landing during night operations
Simulated instrument approaches were made to Category 1 minimums followed by a visual landing on a 100 x 1700 ft STOL runway. Data were obtained for variations in the aircraft's flare response characteristics and control techniques and for different combinations of aircraft and runway lighting and a visual approach slope indication. With the complete aircraft and runway lighting and visual guidance no degradation in flying qualities or landing performance was observed compared to daylight operations. elimination of the touchdown zone floodlights or the aircraft landing lights led to somewhat greater pilot workload; however, the landing could still be accomplished successfully. Loss of both touchdown zone and aircraft landing lights led to a high workload situation and only a marginally adequate to inadequate landing capability
Distributional versions of Littlewood's Tauberian theorem
We provide several general versions of Littlewood's Tauberian theorem. These
versions are applicable to Laplace transforms of Schwartz distributions. We
apply these Tauberian results to deduce a number of Tauberian theorems for
power series where Ces\`{a}ro summability follows from Abel summability. We
also use our general results to give a new simple proof of the classical
Littlewood one-sided Tauberian theorem for power series.Comment: 15 page
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