Comparative Studies on Wine Grapes on Different Trellising Systems: I. Consumptive Water Use

A field trial involving four trellising systems viz.( a) Bush vines, (b) Perold,( c) Lengthened Perold, (d) 1,7 m Slanting trellis, showed differences of the utmost importance with regard to rooting densities, consumptive water use and the incidence of Botrytis rot. Soil physical conditions were dominant in determining root distribution patterns. The slanting trellis had significantlymore roots than the other systems. The consumptive water use, however, was not affected by amount of roots but mainly by the micro-climate. Contrary to expectation, the largest trellising system did not show the highest consumptive water use, but under the experimental conditions the bush vines had the fastest evapotranspiration rate. Average crop factors of 0,313; 0,260; 0,241 and 0,205 were found from bud burst to harvesting for bush vines, slanting trellis, lengthened Perold and Perold systems respectively. The high evapotranspiration rate of the bush vines is attributed to higher ambient air temperatures, more air movement as well as less shading of the soil surface than in the case of the slanting trellis.Crop factors varied according to soil moisture content, indicating the need to determine these parameters for specific irrigation frequencies. The low crop factors determined in this experiment emphasize the high water useefficiency of vineyards and stress the need to adopt existing crop factors to recent findings. Significant differences which cannot be attributed to micro-climate conditions occurred among trellising systems. Grape juice analyses, carried out throughout the growing season, indicated a relationship between total nitrogen and arginine status and Botrytis cinerea determined immediately prior to harvesting. More Botrytis rot was found at lower cropping levels. More investigations as to the relationship among the incidence of Botrytis rot, cropping level and nitrogen status of the plant are needed

Comparative Studies on Wine Grapes on Different Trellising Systems: II. Micro-climatic Studies, Grape Composition and Wine Quality

In a field experiment the micro-climate and grape composition of four trellising systems viz., (a) Bush vines, ( b) Perold system, (c) Lengthened Perold, and (d) Slanting trellis were investigated and compared. Significantly more air movement, higher bunch and ambient air temperature as well as higher soil temperatures at 200 mm depth were recorded in the bush vines compared to the lengthened Perold and slanting trellis. Bunch temperature differences among trellising systems became most pronounced at 12h00 to 14h00

Irrigation Systems - Their Role in Water Requirements and the Performance of Grapevines

Irrigation systems were evaluated in three major viticultural areas in South Africa as regards grapevine performance, must and wine quality and the saving of irrigation water. Furrow irrigation saved more than 50% on irrigation water compared to full surface flooding without affecting grape yield, pruning mass and must composition. The irrigation frequency, however, had to be adapted to the volume of soil wetted. Tricklers gave results comparable to that of furrows. In another viticultural region, tricklers saved 25-30% water and the vines yielded a more favourable sugar/acid ratio compared to micro-jets, sprinklers and flood irrigation. In a third trial on a compact silty soil, tricklers gave results similar to that of flooding. Grape yield was not affected by the irrigation system in any one of the trials. Crop factors to be used for irrigation planning and scheduling are presented

Magnetoplasmon excitations in an array of periodically modulated quantum wires

Motivated by the recent experiment of Hochgraefe et al., we have investigated the magnetoplasmon excitations in a periodic array of quantum wires with a periodic modulation along the wire direction. The equilibrium and dynamic properties of the system are treated self-consistently within the Thomas-Fermi-Dirac-von Weizsaecker approximation. A calculation of the dynamical response of the system to a far-infrared radiation field reveals a resonant anticrossing between the Kohn mode and a finite-wavevector longitudinal excitation which is induced by the density modulation along the wires. Our theoretical calculations are found to be in excellent agreement with experiment.Comment: 9 pages, 8 figure

Vine Response to Water Stress Induced by Polyethylene Glycol

Polyethylene glycol (P E G) was used at different concentrations in glasshouse studies to create a range of solution osmotic potentials in an attempt to simulate the effect of water stress on vines. This was found to be a feasible technique provided that special precautions were taken to prevent P E G uptake and toxicity symptoms caused by mechanical root damage. Vine response in terms of transpiration, shoot elongation rate, stomata! resistance and leaf water potential, was monitored. Significant correlations were found between solution osmotic potential and all these parameters. Shoot growth was more sensitive than stomata! opening to osmotic potential which, in turn, correlated well with transpiration rate

The Effect of Various Supplementary Irrigation Treatments on Plant and Soil Moisture Relationships in a Vineyard (Vitis Vinif era var. Chenin Blanc)

In a field plot trial with grape vines planted on a high potential soil, the soil moisture status on different irrigation treatment plots was compared with that of a dryland control. Soil moisture budgeting was based on physical soil properties and root distribution patterns before treatments commenced. A maximum concentration of roots occurred at the 300-450 mm depth zone, while approximately 90 per cent of the total number of roots was found above 900 mm. Tensiometric readings of soil moisture potential, supplemented by electrometric resistance readings from gypsum blocks, indicated complete depletion between veraison and harvesting of the total available moisture on dryland plots. Despite this severe moisture stress as illustrated by chrono-isopletes, a reasonably good grape yield was still produced by the dryland vines, indicating either exceptional drought resistance or the uptake of water from extraneous sources. Supplementary irrigations greatly improved soil moisture conditions during the important growth stages of (a) flowering and fruit set, (b) green berry stage and (c) veraison. Moisture depletion patterns changed markedly as the season progressed from November to January, and as naturally stored rain water became depleted. In contrast to the absorption pattern in November, the fastest rate of water loss occurred in the deepest root zones during January, because of unsaturated moisture flow into the dry partly decomposed parent material. The apparently unproductive subsoil might act as a large natural reservoir for superfluous winter rain, which in summer becomes available to the vines through unsaturated upward flow into the root zone. Determination of leaf water potential showed unexpectedly high values at night (minima of -283kPa) in plants growing in soil of which the major part was dried below wilting point. Vines were thus able to regain turgidity at night. Crop factors for use with the American Class A-pan for scheduling irrigations were calculated. Crop factors were low (November to February = 0,20-0,30), and again emphasised the ability of vines to use water frugally. Crop factors were strongly dependent upon soil moisture conditions. Empirical coefficients for use in the Blaney-Criddle formula are also presented

Towards a methodology for addressing missingness in datasets, with an application to demographic health datasets

Missing data is a common concern in health datasets, and its impact on good decision-making processes is well documented. Our study's contribution is a methodology for tackling missing data problems using a combination of synthetic dataset generation, missing data imputation and deep learning methods to resolve missing data challenges. Specifically, we conducted a series of experiments with these objectives; $a)$ generating a realistic synthetic dataset, $b)$ simulating data missingness, $c)$ recovering the missing data, and $d)$ analyzing imputation performance. Our methodology used a gaussian mixture model whose parameters were learned from a cleaned subset of a real demographic and health dataset to generate the synthetic data. We simulated various missingness degrees ranging from $10 \%$, $20 \%$, $30 \%$, and $40\%$ under the missing completely at random scheme MCAR. We used an integrated performance analysis framework involving clustering, classification and direct imputation analysis. Our results show that models trained on synthetic and imputed datasets could make predictions with an accuracy of $83 \%$ and $80 \%$ on $a)$ an unseen real dataset and $b)$ an unseen reserved synthetic test dataset, respectively. Moreover, the models that used the DAE method for imputed yielded the lowest log loss an indication of good performance, even though the accuracy measures were slightly lower. In conclusion, our work demonstrates that using our methodology, one can reverse engineer a solution to resolve missingness on an unseen dataset with missingness. Moreover, though we used a health dataset, our methodology can be utilized in other contexts.Comment: 16 pages and references, 5 figures and four tables, Paper accepted for presentation at SACAIR 2022 in Stellenbosch, Westen Cape, South Afric

Theoretical Modeling of the Thermal State of Accreting White Dwarfs Undergoing Classical Novae

White dwarfs experience a thermal renaissance when they receive mass from a stellar companion in a binary. For accretion rates < 10^-8 Msun/yr, the freshly accumulated hydrogen/helium envelope ignites in a thermally unstable manner that results in a classical novae (CN) outburst and ejection of material. We have undertaken a theoretical study of the impact of the accumulating envelope on the thermal state of the underlying white dwarf (WD). This has allowed us to find the equilibrium WD core temperatures (T_c), the classical nova ignition masses (M_ign) and the thermal luminosities for WDs accreting at rates of 10^-11 - 10^-8 Msun/yr. These accretion rates are most appropriate to WDs in cataclysmic variables (CVs) of P_orb <~ 7 hr, many of which accrete sporadically as dwarf novae. We have included ^3He in the accreted material at levels appropriate for CVs and find that it significantly modifies the CN ignition mass. We compare our results with several others from the CN literature and find that the inclusion of ^3He leads to lower M_ign for >~ 10^-10 Msun/yr, and that for below this the particular author's assumption concerning T_c, which we calculate consistently, is a determining factor. Initial comparisons of our CN ignition masses with measured ejected masses find reasonable agreement and point to ejection of material comparable to that accreted.Comment: 14 pages, 11 figures; uses emulateapj; accepted by the Astrophysical Journal; revised for clarity, added short discussion of diffusio

Realistic modeling of leakage and intrusion flows through leak openings in pipes

The hydraulics of leakage and intrusion flows through leak openings in pipes is complicated by variations in the leak areas owing to changes in pressure. This paper argues that the pressure–area relationship can reasonably be assumed to be a linear function, and a modified orifice equation is proposed for more realistic modeling of leakage and intrusion flows. The properties of the modified orifice equation are explored for different classes of leak openings. The implications for the current practice of using a power equation to model leakage and intrusion flows are then investigated. A mathematical proof is proposed for an equation linking the parameters of the modified orifice and power equations using the concept of a dimensionless leakage number. The leakage exponent of a given leak opening is shown to generally not be constant with variations in pressure and to approach infinity when the leakage number approaches a value of minus one. Significant modeling errors may result if the power equation is extrapolated beyond its calibration pressure range or at high exponent values. It is concluded that the modified orifice equation and leakage number provide a more realistic description of leakage and intrusion flows, and it is recommended that this approach be adopted in modeling studies

Stability and correlations in dilute two-dimensional boson systems

The hyperspherical adiabatic expansion method is used to describe correlations in a symmetric boson system rigorously confined to two spatial dimensions. The hyperangular eigenvalue equation turns out to be almost independent of the hyperradius, whereas the solutions are strongly varying with the strength of the attractive two-body potentials. Instability is encountered in hyperangular, hyperradial, and mean-field equations for almost identical strengths inversely proportional to the particle number. The derived conditions for stability are similar to mean-field conditions and closely related to the possible occurrence of the Thomas and Efimov effects. Renormalization in mean-field calculations for two spatial dimensions is probably not needed.Comment: 5 pages, two figures, submitted to Phys. Rev. A, second version contains added discussion, especially of renormalizatio