Radar inference of the bulk properties of glacier beds, most notably identifying basal melting, is, in general, derived from the basal reflection coefficient. On the scale of an ice sheet, ...unambiguous determination of basal reflection is primarily limited by uncertainty in the englacial attenuation of the radio wave, which is an Arrhenius function of temperature. Existing bed-returned power algorithms for deriving attenuation assume that the attenuation rate is regionally constant, which is not feasible at an ice-sheet-wide scale. Here we introduce a new semi-empirical framework for deriving englacial attenuation, and, to demonstrate its efficacy, we apply it to the Greenland Ice Sheet. A central feature is the use of a prior Arrhenius temperature model to estimate the spatial variation in englacial attenuation as a first guess input for the radar algorithm. We demonstrate regions of solution convergence for two input temperature fields and for independently analysed field campaigns. The coverage achieved is a trade-off with uncertainty and we propose that the algorithm can be "tuned" for discrimination of basal melt (attenuation loss uncertainty ∼ 5 dB). This is supported by our physically realistic ( ∼ 20 dB) range for the basal reflection coefficient. Finally, we show that the attenuation solution can be used to predict the temperature bias of thermomechanical ice sheet models and is in agreement with known model temperature biases at the Dye 3 ice core.
Loss of nitrogen in deep drainage from agriculture is an important issue for environmental and economic reasons, but limited field data is available for tropical crops. In this study, nitrogen (N) ...loads leaving the root zone of two major humid tropical crops in Australia, sugarcane and bananas, were measured. The two field sites, 57km apart, had a similar soil type (a well drained Dermosol) and rainfall (∼2700mmyear−1) but contrasting crops and management. A sugarcane crop in a commercial field received 136–148kgNha−1year−1 applied in one application each year and was monitored for 3 years (first to third ratoon crops). N treatments of 0–600kgha−1year−1 were applied to a plant and following ratoon crop of bananas. N was applied as urea throughout the growing season in irrigation water through mini-sprinklers. Low-suction lysimeters were installed at a depth of 1m under both crops to monitor loads of N in deep drainage. Drainage at 1m depth in the sugarcane crops was 22–37% of rainfall. Under bananas, drainage in the row was 65% of rainfall plus irrigation for the plant crop, and 37% for the ratoon. Nitrogen leaching loads were low under sugarcane (<1–9kgha−1year−1) possibly reflecting the N fertiliser applications being reasonably matched to crop requirements and at least 26 days between fertiliser application and deep drainage. Under bananas, there were large loads of N in deep drainage when N application rates were in excess of plant demand, even when applied fortnightly. The deep drainage loss of N attributable to N fertiliser, calculated by subtracting the loss from unfertilised plots, was 246 and 641kgha−1 over 2 crop cycles, which was equivalent to 37 and 63% of the fertiliser application for treatments receiving 710 and 1065kgha−1, respectively. Those rates of fertiliser application resulted in soil acidification to a depth of 0.6m by as much as 0.6 of a unit at 0.1–0.2m depth. The higher leaching losses from bananas indicated that they should be a priority for improved N management.
Objective: To formulate diagnostic criteria for exercise dependence. Method: Fifty six adult female exercisers were interviewed about their exercise behaviour and attitudes. The eating disorders ...examination, a semistructured clinical interview, was used to diagnose eating disorders. Interviews were taped, transcribed verbatim, and analysed from a social constructionist perspective using QSR NUD*IST. Participants also completed the exercise dependence questionnaire. Results: Two diagnostic criteria emerged from analysis of the interview data: impaired functioning and withdrawal. Impaired functioning was manifest in four areas: psychological, social and occupational, physical, and behavioural. Impairment in at least two areas was considered necessary for diagnosis. Withdrawal was evident as either an adverse reaction to the interruption of exercise or unsuccessful attempts at exercise control. Either sufficed for diagnosis. The absence or presence of an eating disorder was used to distinguish between primary and secondary exercise dependence. Ten women met these criteria for exercise dependence. All 10 also exhibited eating disorders and, accordingly, should be regarded as showing secondary, rather than primary, exercise dependence. Exercise dependent women had significantly higher scores on the exercise dependence questionnaire than non-dependent women. Conclusion: These new diagnostic criteria should now be adopted and explored further, particularly among men and individuals with possible primary exercise dependence.
Adenovirus infection in red squirrels Shuttleworth, C M; Everest, D J; Stidworthy, M F ...
Veterinary record,
12/2021, Letnik:
189, Številka:
11
Journal Article
There is widespread, but often indirect, evidence that a significant fraction of the bed beneath the Greenland Ice Sheet is thawed (at or above the pressure melting point for ice). This includes the ...beds of major outlet glaciers and their tributaries and a large area around the NorthGRIP borehole in the ice-sheet interior. The ice-sheet-scale distribution of basal water is, however, poorly constrained by existing observations. In principle, airborne radio-echo sounding (RES) enables the detection of basal water from bed-echo reflectivity, but unambiguous mapping is limited by uncertainty in signal attenuation within the ice. Here we introduce a new, RES diagnostic for basal water that is associated with wet-dry transitions in bed material: bed-echo reflectivity variability. This technique acts as a form of edge detector and is a sufficient, but not necessary, criteria for basal water. However, the technique has the advantage of being attenuation insensitive and suited to combined analysis of over a decade of Operation IceBridge survey data.
Current treatment for pulmonary tuberculosis (TB) might be shortened by the incorporation of fluoroquinolones (FQs).
A Phase II study aimed to assess the sterilising activities of three novel ...regimens containing FQs before a Phase III trial of a 4-month regimen containing gatifloxacin (GFX).
A total of 217 newly diagnosed smear-positive patients were randomly allocated to one of four regimens: isoniazid (INH), pyrazinamide and rifampicin (RMP) with either ethambutol, GFX, moxifloxacin (MFX) or ofloxacin (OFX) for 2 months. At the end of the study, RMP and INH were given for 4 months. The rates of elimination of Mycobacterium tuberculosis were compared in the regimens using non-linear mixed effects modelling of the serial sputum colony counts (SSCC) during the first 8 weeks.
After adjustment for covariates, MFX substitution appeared superior during the early phase of a bi-exponential fall in colony counts, but significant and similar acceleration of bacillary elimination during the late phase occurred with both GFX and MFX (P = 0.002). Substitution of OFX had no effect. These findings were supported by estimates of time to conversion, using Cox regression, but there were no significant differences in proportions culture-negative at 8 weeks.
GFX and MFX improve the sterilising activity of regimens and might shorten treatment; their progression into Phase III trials therefore seems warranted.
Suspension plasma spray (SPS) is going through a transition phase from research and development to daily use on production lines. Improving repeatability and reproducibility of coating elements and ...parameters makes SPS a replacement of former well-developed processes. This transition can be achieved by using in-flight particles diagnostic systems to monitor and control key parameters that influence the coating microstructure. Temperature and velocity of the in-flight particles are among the most critical parameters that should be monitored. However, accurately characterizing the in-flight particles in SPS is particularly challenging due to the small particle size of coating materials, harsh spray conditions, considerably shorter spray distances compared to APS, possible interference from the solvent, and limitations of previous measurement systems. In this study, different strategies were investigated to improve the accuracy of temperature measurements of in-flight particles in SPS. For this purpose, two light collection configurations (double-point and single-point measurement) were investigated along with the influence of plasma radiation. The results were evaluated by collecting and studying splats. The size and shape of splats were correlated with the temperature of in-flight particles in order to confirm the accuracy of the sensor’s temperature measurements. In addition, the sensitivity of temperature measurements to the optical filter used for two-color pyrometry, reflection of plasma radiation from surrounding objects, and direct radiation from plasma were investigated. The results showed that the single-point measurement configuration was well adapted for SPS.
Subglacial roughness can be determined at a variety of length scales from radio-echo sounding (RES) data either via statistical analysis of topography or inferred from basal radar scattering. Past ...studies have demonstrated that subglacial terrain exhibits self-affine (power law) roughness scaling behaviour, but existing radar scattering models do not take this into account. Here, using RES data from northern Greenland, we introduce a self-affine statistical framework that enables a consistent integration of topographic-scale roughness with the electromagnetic theory of radar scattering. We demonstrate that the degree of radar scattering, quantified using the waveform abruptness (pulse peakiness), is topographically controlled by the Hurst (roughness power law) exponent. Notably, specular bed reflections are associated with a lower Hurst exponent, with diffuse scattering associated with a higher Hurst exponent. Abrupt waveforms (specular reflections) have previously been used as a RES diagnostic for basal water, and to test this assumption we compare our radar scattering map with a recent prediction for the basal thermal state. We demonstrate that the majority of thawed regions (above pressure melting point) exhibit a diffuse scattering signature, which is in contradiction to the prior approach. Self-affine statistics provide a generalised model for subglacial terrain and can improve our understanding of the relationship between basal properties and ice-sheet dynamics.
This study evaluates the impact of a recent upgrade in the physics package of the regional atmospheric climate model RACMO2 on the simulated surface mass balance (SMB) of the Antarctic ice sheet. The ...modelled SMB increases, in particular over the grounded ice sheet of East Antarctica (+44 Gt a–1), with a small change in West Antarctica. This mainly results from an increase in precipitation, which is explained by changes in the cloud microphysics, including a new parameterization for ice cloud supersaturation, and changes in large-scale circulation patterns, which alter topographically forced precipitation. The spatial changes in SMB are evaluated using 3234 in situ SMB observations and ice-balance velocities, and the temporal variability using GRACE satellite retrievals. The in situ observations and balance velocities show a clear improvement of the spatial representation of the SMB in the interior of East Antarctica, which has become considerably wetter. No improvements are seen for West Antarctica and the coastal regions. A comparison of model SMB temporal variability with GRACE satellite retrievals shows no significant change in performance.
A biophysical model of Sugarcane growth CUADRA, S. V.; COSTA, M. H.; KUCHARIK, C. J. ...
Global change biology. Bioenergy,
01/2012, Letnik:
4, Številka:
1
Journal Article
Odprti dostop
Scientists predict that global agricultural lands will expand over the next few decades due to increasing demands for food production and an exponential increase in crop‐based biofuel production. ...These changes in land use will greatly impact biogeochemical and biogeophysical cycles across the globe. It is therefore important to develop models that can accurately simulate the interactions between the atmosphere and important crops. In this study, we develop and validate a new process‐based sugarcane model (included as a module within the Agro‐IBIS dynamic agro‐ecosystem model) which can be applied at multiple spatial scales. At site level, the model systematically under/overestimated the daily sensible/latent heat flux (by −10.5% and 14.8%, H and λE, respectively) when compared against the micrometeorological observations from southeast Brazil. The model underestimated ET (relative bias between −10.1% and –12.5%) when compared against an agro‐meteorological field experiment from northeast Australia. At the regional level, the model accurately simulated average yield for the four largest mesoregions (clusters of municipalities) in the state of São Paulo, Brazil, over a period of 16 years, with a yield relative bias of −0.68% to 1.08%. Finally, the simulated annual average sugarcane yield over 31 years for the state of Louisiana (US) had a low relative bias (−2.67%), but exhibited a lower interannual variability than the observed yields.
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