2,325 research outputs found
A Novel Longitudinal Mode in the Coupled Quantum Chain Compound KCuF3
Inelastic neutron scattering measurements are reported that show a new
longitudinal mode in the antiferromagnetically ordered phase of the spin-1/2
quasi-one-dimensional antiferromagnet KCuF3. This mode signals the cross-over
from one-dimensional to three-dimensional behavior and indicates a reduction in
the ordered spin moment of a spin-1/2 antiferromagnet. The measurements are
compared with recent quantum field theory results and are found to be in
excellent agreement. A feature of the data not predicted by theory is a damping
of the mode by decay processes to the transverse spin-wave branches.Comment: 9 pages of text plus 4 postscript figures (1 color
Use of soil water measurements to assist crop management in low rainfall areas.
Trial 90M9
Trial summary.
Location: Merredin Research Station.
90M9 was established as part of the long term monitoring system to obtain base information on water use from several different soils. A simple rotation experiment was established in T3 on the Merredin Research Station.
Trial 89ME32
Rowspacing summary.
Location: Merredin Research Station.
89ME32 was monitored as part of the long term monitoring system. Previous to 1990 two years of continued measurements had been done on the same soil type. Located on the CSIRO lease block above the Merredin Research Station on Crook\u27s property.
Trial 87M71
Heavyload rowspacing summary.
Location: Merredin Research Station.
The changes in the soil moisture down the profile were monitored in 87M71 as part of the long term monitoring network.
Trial 88ME83
Trial summary.
As part of the baseline monitoring system access tubes were inserted in 88ME83 on existing trial on sandy clay loam on Robartson\u27s farm, Merredin.
82M47
Trial summary
Location: Merredin Research Station.
Tubes were inserted in 82M47 an existing clover:wheat rotation to monitor the changes in the soil water balance. 82M47 is one of the trials in the long turn monitoring system.
Trial 86M79
Trial summary.
The long term moisture monitoring network was established in 1990. 86M79 was monitored as part of this network
Internal construct validity of the Warwick-Edinburgh Mental Well-being Scale (WEMWBS): a Rasch analysis using data from the Scottish Health Education Population Survey
Background: The Warwick-Edinburgh Mental Well-Being Scale (WEMWBS) was developed to meet demand for instruments
to measure mental well-being. It comprises 14 positively phrased Likert-style items and fulfils classic criteria for scale development. We report here the internal construct validity of WEMWBS from the perspective of the Rasch measurement model.
Methods: The model was applied to data collected from 779 respondents in Wave 12 (Autumn 2006) of the Scottish Health
Education Population Survey. Respondents were aged 16–74 (average 41.9) yrs.
Results: Initial fit to model expectations was poor. The items 'I've been feeling good about myself', 'I've been interested in new things' and 'I've been feeling cheerful' all showed significant misfit to model expectations, and were deleted. This led to a marginal improvement in fit to the model. After further analysis, more items were deleted and a strict unidimensional seven item scale (the Short Warwick Edinburgh Mental Well-Being Scale (SWEMWBS)) was resolved. Many items deleted because of misfit with
model expectations showed considerable bias for gender. Two retained items also demonstrated bias for gender but, at the
scale level, cancelled out. One further retained item 'I've been feeling optimistic about the future' showed bias for age. The correlation between the 14 item and 7 item versions was 0.954. Given fit to the Rasch model, and strict unidimensionality, SWEMWBS provides an interval scale estimate of mental well-being.
Conclusion: A short 7 item version of WEMWBS was found to satisfy the strict unidimensionality expectations of the Rasch model, and be largely free of bias. This scale, SWEMWBS, provides a raw score-interval scale transformation for use in parametric procedures. In terms of face validity, SWEMWBS presents a more restricted view of mental well-being than the 14 item WEMWBS, with most items representing aspects of psychological and eudemonic well-being, and few covering hedonic well-being or affect. However, robust measurement properties combined with brevity make SWEMWBS preferable to WEMWBS at present for monitoring mental well-being in populations. Where face validity is an issue there remain arguments for continuing to collect data on the full 14 item WEMWBS
Fabrication technologies for quantum cascade photonic-crystal microlasers
In this paper we describe the technological and fabrication methods necessary to incorporate both photonic and electronic-band engineering in order to create novel surface-emitting quantum cascade microcavity laser sources. This technology offers the promise of several innovative applications such as the miniaturization of QC lasers, and multi-wavelength two-dimensional laser arrays for spectroscopy, gas-sensing and imaging. This approach is not limited to light-emitting devices, and may be efficiently applied to the development of mid- and far-infrared normal-incidence detectors
Fabrication methods for a quantum cascade photonic crystal surface emitting laser
Conventional quantum cascade (QC) lasers are intrinsically edge-emitting devices with mode confinement achieved via a standard mesa stripe configuration. Surface emission in edge emitting QC lasers has therefore necessitated redirecting the waveguided laser emission using a second order grating. This paper describes the methods used to fabricate a 2D photonic crystal (PC) structure with or without a central defect superimposed on an electrically pumped QC laser structure with the goal of achieving direct surface emission. A successful systematic study of PC hole radius and spacing was performed using e-beam lithography. This PC method offers the promise of a number of interesting applications, including miniaturization and integration of QC lasers
Quantum cascade photonic crystal surface emitting injection laser
A surface emitting quantum cascade injection laser is presented. Direct surface emission is obtained by using a 2D photonic-band-gap structure that simultaneously acts as a microcavity. The approach may allow miniaturization and on-chip-integration of the devices
Exact two-spinon dynamical correlation function of the Heisenberg model
We derive the exact contribution of two spinons to the dynamical correlation
function of the spin-1/2 Heisenberg model. For this, we use the isotropic
limits of the exact form factors that have been recently computed through the
quantum affine symmetry of the anisotropic Heisenberg model Comment: 9 pages, Latex, 2 corrections of coefficient
Water use of wheatbelt crop and pasture species
Water use of wheatbelt crop and pasture species Location: 83WH29 - Wongan Hills Research Station, Wongan Hills Abstract. A comprehensive experiment to investigate the productivity and water use of important wheatbelt crop and pasture species was undertaken in 1983. The experiment has provided important information on potential crop and pasture productivity and the role of alternate crop and pasture species in managing groundwater recharge and the development of secondary salinity. Contents 1. Background and industry significance 2. Aims of the experiment 3. Personnel 4. Site characterisation 5. Experimental detail 6. Results i) Meterological data ii) Dry matter, leaf area and grain yield iii) Soil Water iv) Root growth and water extraction v) Infra-red Thermometr
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