Search

We elaborate on the nature of the prompt core confinement improvement observed at the L–H transition in DIII-D, which is a long-standing issue unsolved for more than two decades and can impact future fusion reactor performance. Dynamic transport analysis suggests the essential role of the profile stiffness for understanding the mechanism of the prompt core confinement improvement. Beam emission spectroscopy shows that transport reduction at the core cannot be explained only by the ion scale turbulence density fluctuation suppression. Properties of nonlocal confinement improvement across the L–H transition are experimentally assessed in hydrogen (H) and deuterium (D) plasmas. Prompt core confinement improvement is found to be more rapid in the lighter hydrogen isotope.

The edge-harmonic oscillations (EHOs) in standard quiescent H-mode (QH-mode) plasmas in DIII-D are consistent with edge-localized neoclassical tearing modes (NTMs) based on nonlinear two-fluid MHD simulations. Using kinetic equilibria constrained by edge profile measurements, the MHD simulations show that the n = 1 NTM and its harmonics can be destabilized at the pedestal top of QH-mode plasma by the edge bootstrap current. The simulations further show that the unstable NTMs can saturate either at small (N) or large (>4% ψN) island width depending on the magnitude of the edge bootstrap current, where ψN is the normalized radius in poloidal flux. The onset of the EHO also results in a prompt decrease in the pedestal width and height, consistent with simulation results for the onset of the NTM at the top of the QH-mode pedestal. This suggests that the avoidance of edge-localized modes (ELMs) in QH-mode can be attributed to the enhanced local transport induced by the NTM that is sufficient to prevent the expansion of the pedestal to an unstable width, analogous to the mechanism explored for ELM suppression by resonant magnetic perturbations. Nonlinear MHD simulations scanning the E × B frequency and the ratio of parallel and perpendicular thermal diffusivity ( χǁ/ χ⊥) at the pedestal top show that edge-localized NTMs are destabilized for conditions of high E × B frequency, high pedestal temperature, and low pedestal density, qualitatively consistent with experimental conditions required for observing the EHO.

DIII-D research is addressing critical challenges in preparation for ITER and the next generation of fusion devices through focusing on plasma physics fundamentals that underpin key fusion goals, understanding the interaction of disparate core and boundary plasma physics, and developing integrated scenarios for achieving high performance fusion regimes. Fundamental investigations into fusion energy science find that anomalous dissipation of runaway electrons (RE) that arise following a disruption is likely due to interactions with RE-driven kinetic instabilities, some of which have been directly observed, opening a new avenue for RE energy dissipation using naturally excited waves. Dimensionless parameter scaling of intrinsic rotation and gyrokinetic simulations give a predicted ITER rotation profile with significant turbulence stabilization. Coherence imaging spectroscopy confirms near sonic flow throughout the divertor towards the target, which may account for the convection-dominated parallel heat flux. Core-boundary integration studies show that the small angle slot divertor achieves detachment at lower density and extends plasma cooling across the divertor target plate, which is essential for controlling heat flux and erosion. The Super H-mode regime has been extended to high plasma current (2.0 MA) and density to achieve very high pedestal pressures (~30 kPa) and stored energy (3.2 MJ) with H 98y2 ≈ 1.6–2.4. In scenario work, the ITER baseline Q = 10 scenario with zero injected torque is found to have a fusion gain metric independent of current between q 95 = 2.8–3.7, and a lower limit of pedestal rotation for RMP ELM suppression has been found. In the wide pedestal QH-mode regime that exhibits improved performance and no ELMs, the start-up counter torque has been eliminated so that the entire discharge uses ≈0 injected torque and the operating space is more ITER-relevant. Finally, the high- (⩽3.8) hybrid scenario has been extended to the high-density levels necessary for radiating divertor operation, achieving ~40% divertor heat flux reduction using either argon or neon with P tot up to 15 MW.

Advanced tokamak (AT) research seeks to develop steady-state operating scenarios for ITER and other future devices from a demonstrated scientific basis. Normalized target parameters for steady-state operation on ITER are 100% non-inductive current operation with a bootstrap current fraction f BS ≥ 60%, q 95 ∼ 4-5 and G ≡ β N H scaling /q 2 95 ≥ 0.3. Progress in realizing such plasmas is considered in terms of the development of plasma control capabilities and scientific understanding, leading to improved AT performance. NSTX has demonstrated active resistive wall mode stabilization with low, ITER-relevant, rotation rates below the critical value required for passive stabilization. On DIII-D, experimental observations and GYRO simulations indicate that ion internal transport barrier (ITB) formation at rational-q surfaces is due to equilibrium zonal flows generating high local E x B shear levels. In addition, stability modelling for DIII-D indicates a path to operation at β N ≥ 4 with q min ≥ 2, using broad, hollow current profiles to increase the ideal wall stability limit. Both NSTX and DIII-D have optimized plasma performance and expanded AT operational limits. NSTX now has long-pulse, high performance discharges meeting the normalized targets for an spherical torus-based component test facility. DIII-D has developed sustained discharges combining high beta and ITBs, with performance approaching levels required for AT reactor concepts, e.g. β N = 4, H 89 = 2.5, with f BS > 60%. Most importantly, DIII-D has developed ITER steady-state demonstration discharges, simultaneously meeting the targets for steady-state Q ≥ 5 operation on ITER set out above, substantially increasing confidence in ITER meeting its steady-state performance objective.

The advanced tokamak programme on DIII-D is to develop the scientific basis for steady state, high performance operation in future devices. We report on experiments attempting to demonstrate sustainment of 100% noninductive current for several seconds at high beta, using up to 2.5 MW of off-axis electron cyclotron current drive and up to 15 MW of neutral beam injection with q95 ≈ 5. A 100% noninductive condition was achieved with βT = 3.6%, βN = 3.5, H89 = 2.4 and improved current drive alignment. However, the duration of this phase was limited by the pressure profile evolution leading to magnetohydrodynamic instabilities after about 0.7 s. In a separate discharge, a nearly (~90%) noninductive, stationary condition was maintained for one current relaxation time (1.8 s) only limited by the duration of the hardware system. These experiments have achieved normalized fusion performance with bootstrap current fraction fBS ≈ 60%, consistent with requirements for the ITER Q = 5 steady-state scenarios. The modelling tools that were successfully employed to devise experiments in DIII-D are applied to ITER, indicating that full noninductive operation is plausible for an ITER steady-state scenario with Q ≈ 5.

A field study was initiated in mid-July, 1988, to investigate the effects of removing growth taller than one meter on half from one side each within 2 years (half-hedging) in summer and winter on total yield, marketable yield, and fruit size of mature rabbiteye blueberry (Vaccinium ashei Reade) cv. Tifblue. Each plant was fully hedged in 2 years. In 1990, yields on summer-hedged plants were reduced 75% and on winter-hedged plants about 92% when compared with nonhedged plants. Fruit size increased 13% and 26% for summer- and winter-hedged plants in 1990, respectively. Total yields did not differ among treatments during 1991-1993 harvest. However, yields were lower in 1991 and 1992 than in 1989 and 1993. These lower yields were attributed to adverse weather conditions during vegetative bud break, growth, and flowering. Hedged plants did not yield more than nonhedged plants over the 5-year experimental period. However, winter hedging significantly decreased total yield. Although no significant diffe...

Plants of ‘Delite’ and ‘Tifblue’ rabbiteye blueberries were planted 3 m × 1.8 m at Plains, Georgia in 1981 in a Greenville sandy clay loam (clayey, kaolimitic, thermic, Rhodic Paleuduit). Total fruit weight, fruit size at the first harvest, and percent marketable yield were recorded. Soil and leaf samples were taken immediately after the last harvest for chemical analysis and ranged in soil water pH from 4.3 to 5.1. Soil pH did not affect soil P, K, or Fe but soil Ca, Mg, Mn, and Cu were highest levels when the soil pH was 6.5. The only effect of soil pH on leaf mineral concentration occurring in 1989 when increasing pH increased leaf Mg. ‘Delite’ yield and plant volume (m3) decreased linearly as the soil pH increased. The percent marketable yield was maximum at soil pH 4.7 to 4.8. Maximum plant growth of ‘Tifblue’ occurred around pH 4.3 to 4.4, then decreased when soil pH increased to 4.8 to 4.9. However, maximum yield and percent marketable yield of ‘Tifblue’ were the highest at soil pH 5.0 to ...

Thomson scattering produces ne profiles from measurement of scattered laser beam intensity. Rayleigh scattering provides a first calibration of the relation ne ∝ ITS, which depends on many factors (e.g., laser alignment and power, optics, and measurement systems). On DIII-D, the ne calibration is adjusted against an absolute ne from the density-driven cutoff of the 48 channel 2nd harmonic X-mode electron cyclotron emission system. This method has been used to calibrate Thomson ne from the edge to near the core (r/a > 0.15). Application of core electron cyclotron heating improves the quality of cutoff and depth of its penetration into the core, and also changes underlying MHD activity, minimizing crashes which confound calibration. Less fueling is needed as “ECH pump-out” generates a plasma ready to take up gas. On removal of gyrotron power, cutoff penetrates into the core as channels fall successively and smoothly into cutoff.

Repetitive bursting instabilities with strong frequency chirping occur in highbeta, beam-heated plasmas with safety factor q > 1 in the DIII-D tokamak. Although the mode structures differ, in many ways, the off-axis fishbones are similar to the q = 1 fishbones first observed on the Poloidal Divertor Experiment (PDX). The modes are driven by energetic trapped ions at the fastion precession frequency. During a burst, the frequency changes most rapidly as the mode reaches its maximum amplitude. Larger amplitude bursts have larger growth rates and frequency chirps. Unlike PDX fishbones, the decay phase is highly variable and is usually shorter than the growth phase. Also, the waveform is highly distorted by higher harmonics during the latter portion of a burst. The radial mode structure alters its shape during the burst. Like PDX fishbones, the modes expel trapped ions in a ‘beacon’ with a definite phase relationship relative to the mode. Seven types of loss detectors measure the beacon. The losses scale linearly with mode amplitude. The neutron rate changes most rapidly at maximum mode amplitude but, depending on the loss diagnostic, the losses often peak a few cycles later. The non-ambipolar fast-ion losses cause a sudden change in toroidal rotation frequency across the entire plasma. In addition to an overall drop, the neutron signal oscillates in response to the wave. Unlike the beacon of lost particles, which maintains a fixed phase relative to the mode, the phase of the neutron oscillations steadily increases throughout the burst, with the greatest phase slippage occurring in the highly nonlinear phase near maximum mode amplitude US Department of Energy SC-G903402, DE-FC02-04ER54698, DE-FG02-07ER54917

The effects of soil pH on yield and average berry weight of rabbiteye blueberry cvs Delite and Tifblue were investigated. Over a three year period, the higher soil pH decreased from 6.5 to 5.9, but the total yield of both cultivars decreased more than 60% as soil pH increased from 4.5 to 6.5 in the first two years and to 5.9 during the last year. Percent marketable yield was less influenced by the change in soil pH than was total yield. ‘Tifblue’ produced more fruit and had higher marketable yields, but the fruit size determined by average berry weight was smaller than ‘Delite’. When the soil pH was at a more desirable range for maximum yield (4.5 to 5.3), ripening was more uniform for both cultivars. This study illustrated that: (a) two rabbiteye blueberry cultivars differed in tolerance to alkaline growing conditions, (b) the response of the two cultivars to the change in soil pH varied from year to year, and (c) total yield of both cultivars was maximized when soil pH was below 5.0.

Experiments on DIII‐D have measured the electron cyclotron current drive (ECCD) efficiency for co‐ and counter‐injection in low density plasmas with radiation temperatures from electron cyclotron emission (ECE) above 20 keV. The radiation temperature is generally higher than the Thomson scattering temperature, indicating that there is a significant population of non‐thermal electrons. The experimental ECCD profile measured with motional Stark effect (MSE) polarimetry is found to agree with quasi‐linear theory except for the highest power density cases (QEC/ne2≫1). Radial transport of the energetic electrons with diffusion coefficients of ∼0.4 m2/s is needed to model the broadened ECCD profile at high power density.

Advanced Tokamak research in DIII-D seeks to develop a scientific basis for steady-state high-performance tokamak operation. Fully noninductive (fNI≈ 100%) in-principle steady-state discharges have been maintained for several confinement times. These plasmas have weak negative central shear with qmin≈ 1.5-2, βN≈ 3.5, and large, well-aligned bootstrap current. The loop voltage is near zero across the entire profile. The remaining current is provided by neutral beam current drive (NBCD) and electron cyclotron current drive (ECCD). Similar plasmas are stationary with fNI≈ 90-95% and duration up to 2 s, limited only by hardware. In other experiments, βN≈ 4 is maintained for 2 s with internal transport barriers, exceeding previously achieved performance under similar conditions. This is allowed by broadened profiles and active magnetohydrodynamic instability control. Modifications now underway on DIII-D are expected to allow extension of these results to higher performance and longer duration. A new pumped divertor will allow density control in high triangularity double-null divertor configurations, facilitating access to similar in-principle steady-state regimes with βN> 4. Additional current drive capabilities, both off-axis ECCD and on-axis fast wave current drive (FWCD), will increase the magnitude, duration, and flexibility of externally driven current. © 2006 Elsevier B.V. All rights reserved.

Extensive studies to date of edge localized modes (ELMs) have sought their origin inside the separatrix, i.e., MHD instability from steep gradients in the plasma edge, and examined their consequences outside the separatrix, i.e., transport of heat and particles in the scrape-off-layer (SOL) and divertors. Recent measurement by a high-speed scrape-off-layer current (SOLC) diagnostic may indicate that the ELM trigger process lies, in part, in the SOL. Thermoelectrically driven SOLC precedes, or co-evolves with, other parameters of the ELM process, and thus can potentially play a causal role: error field generated by non-axisymmetric SOLC, flowing in the immediate vicinity (approximately 1 cm) of the plasma edge, may contribute toward destabilizing MHD modes. The SOLC, observed concurrently with MHD activity, including ELMs, has been reported elsewhere.

The photodegradation behavior of a propylene/ethylene copolymer has been investigated and compared to the degradation of a polypropylene homopolymer. The materials contained small amounts of thermal stabilizers, but no photo-stabilizers. The development of carbonyl and hydroxyl oxidation species was followed by infrared spectroscopy, but this was not a sensitive detection method in the early stages of degradation. Mechanical measurements indicated that the performance of the copolymer deteriorated after only brief exposures to ultraviolet irradiation in an accelerated weathering cabinet. In contrast, the homopolymer showed no signs of mechanical degradation during a short induction period, but then degraded very rapidly. The induction period corresponded to the disappearance of the thermal stabilizers. Outdoor weathering results confirmed the trends predicted by artificial weathering; however, the predicted service lifetimes were underestimated by about 50%. >

The first of three MW-level 110 GHz gyrotrons was operated into the DIII-D tokamak in late 1996. Two additional units will be commissioned during 1997. Each gyrotron is connected to the tokamak by a low loss, windowless, evacuated transmission line using circular corrugated waveguide carrying the HE11 mode. The microwave beam spot is well focused with a spot size of approximately 6 cm and can be steered poloidally from the center to the outer edge of the plasma. The initial operation with about 0.5 MW delivered to a low density plasma for 0.5 s showed good central electron heating, with peak temperature in excess of 10 keV. The injection was 19° off perpendicular for current drive.

Experiments to study the effect of plasma shape on performance show that the high performance levels characteristic of VH-mode plasmas are only obtained for high triangularity ({delta}). A characteristic difference in central heating efficiency is observed when high and low {delta} plasmas are compared. The authors find this difference to correlate well with the attainment of Mercier stability. The core plasma for the high {delta} cases achieves Mercier stability when q{sub 0} rises above a critical value which depends on {delta}, providing direct access to the second-stable regime. Other attributes of the VH-mode commence after a delay. The rise in q{sub 0} is attributable to the radial gradients in the neutral beam and bootstrap current sources. Simulation indicates that such plasmas would persist for many seconds if the rise in density could be controlled, maintaining a centrally peaked neutral beam deposition profile.

The DIII-D Advanced Tokamak (AT) program in the DIII-D tokamak [J. L. Luxon, Plasma Physics and Controlled Fusion Research, 1986, Vol. I (International Atomic Energy Agency, Vienna, 1987), p. 159] is aimed at developing a scientific basis for steady-state, high-performance operation in future devices. This requires simultaneously achieving 100% noninductive operation with high self-driven bootstrap current fraction and toroidal beta. Recent progress in this area includes demonstration of 100% noninductive conditions with toroidal beta, βT=3.6%, normalized beta, βN=3.5, and confinement factor, H89=2.4 with the plasma current driven completely by bootstrap, neutral beam current drive, and electron cyclotron current drive (ECCD). The equilibrium reconstructions indicate that the noninductive current profile is well aligned, with little inductively driven current remaining anywhere in the plasma. The current balance calculation improved with beam ion redistribution that was supported by recent fast ion diagno...

The response of rabbiteye blueberry (Vaccinium ashei Reade, cv. Tifblue) to 3 plant spacings and 3 fertilizer levels was compared for 6 years. Tifblue did not respond to fertilizer levels during the first 5 years, but beginning the 3rd year in the field, higher yields were obtained with higher plant population (2315 plants/ha). Increasing fertilizer levels increased unmarketable fruit, the amount of pruned wood and the time required to grade fruit. The best combination of spacing and fertilizer were 1.8 m in-the-row spacing and 67-30-40 kg/ha of N-P-K, respectively.

Blueberry seeds (Vaccinium ashei Reade cv. Tifblue) were aspirated into several terminal velocity (TV) grades in an elutriation column. Different light and temperature environments were used to germinate the seeds. In all tests, germination was best at TV grades 2.23 and 2.45. Seed remaining in the air columns after aspiration did not germinate. Light was necessary for germination.

Rabbiteye blueberries (Vaccinium ashei Reade, cvs. Tifblue and Woodard) were fertilized with various ratios of nutrients for 6 years. ‘Tifblue’ responded to 4–8–8 (4.0 N–3.5 P–6.6 K), 5–10–10 (5.0 N–4.4 P–8.3 K), and cottonseed meal 7–2–2 (7.0N–0.9P–1.7K). ‘Woodard’ did not respond to any fertilizer.

SummaryFour Ipomoea batatas cultivars were observed to develop measurable storage roots at the 6-to 8-leaf stage approximately 3 weeks from planting. The increase in sweet potato storage root weight followed a linear growth pattern with time. It was seen that the attainment of the highest vegetative growth weight preceded the largest storage root weight increase by several weeks, and this time interval was dependent upon the cultivar and the condition of growth. A high degree of correlation existed in each year between the development of the tops and the storage root weight.

Chemical and mechanical treatments were applied to 3 cultivars of field grown sweet potatoes, Ipomoea batatas (Lam.), in an attempt to reduce the amount of skinning injury from harvest and handling. Treatments that destroyed the leaves and vines, i.e. sodium arsenite, paraquat, and mowing at soil level, reduced skinning of fleshy roots later during harvest. The reduction in fleshy root skinning from harvest treatments was significant but not visually apparent in field containers. Thickness of periderm of the sweet potatoes was not influenced by chemical or mechanical treatments but dates of application and time of harvest influenced periderm development. Skinning was most severe when the periderm was thickest. There appeared to be an association between low soil temperature (60° F) and skinning. Changes in carbohydrate composition of ‘Nemagold’ roots were partly associated with changes in soil temperature. Accumulation of carbohydrates in roots varied with cultivar and season, and there was no relationship between the carbohydrate composition and severity of skinning. Yield of roots was reduced in most plots where vines were killed or stunted by treatments, especially those made early in the harvest season and in treatments applied 2 weeks prior to harvest.

SummaryDry matter distribution in 3 Ipomoea batatas cultivars was observed in 2 plant populations, 2 locations and 2 seasons. Increases in dry matter were linear with sampling time regardless of spacing, but the final amount produced under 2 populations and 2 locations differed. The cv. Julian was more efficient in accumulating dry matter in its storage roots than cvs. Centennial and Nemagold, and in Julian the relative growth rate of the roots was correlated with the net assimilation rate. The rate at which assimilates move appears to be more important for storage root development than increases in leaf area.

Growth rate of several tomato cultivars, indexed by stem diameter measurements, was not influenced by broadcasting 50–100–100 lb./A fertilizer, by sidedressing 60 to 80 lb N, or by increasing the plant population from 5,800 to 23,200 plants/A in either single or dual rows at 2 locations. Broadcasting 5–10–10 fertilizer prior to planting increased total yields, but the earliest maximum yield of marketable fruit was delayed. Sidedressing N also delayed the earliest maximum yield. Fertilizer application did not influence fruit size, but size was reduced at high plant populations and at later harvests. The once-over maximum yield was increased at a high plant population when spacing between dual rows was 18 or 24 inches.

SummaryThe vegetative growth and flowering patterns of dwarf tomatoes were altered by 10–7 M to 5 x 10–3 M gibberellin A3 concentrations. The six dwarf cultivars studied differed in their sensitivity to the gibberellin as indexed by stem elongation, stem size, change in leaf angles, leaf area expansion, number of leaf nodes, cotyledon abscission, days to first anthesis and flower numbers on the inflorescences. Vegetative growth was more responsive to gibberellin than was flowering.A significant interaction in leaf area was observed between leaf position (or age) and gibberellin A3 concentration. In general, the leaf areas of the older maturing leaves located centrally on the main stem were inhibited, while the younger immature leaves near the growing apex were promoted by high gibberellin concentrations. A possible explanation for this phenomenon is discussed.

SummaryN-(4-chlor-3-trifluormethylphenyl) phthalamic acid (Geigy C-20231) at concentrations of 10−7 to 2 × 10−3 M failed to suppress growth of the sweet potato cultivar Centennial but significantly decreased storage root dry weight at 2 χ 10-3 M in the cultivars Nemagold and Julian without affecting top growth. In contrast, N-(3-trifluormethylphenyl) phthalamic acid (Geigy C-19237) at 10−3 to 2 × 10−3M increased storage root dry weight of Nemagold, while N-(3-methoxyphenyl) phthalamic acid (Geigy C-17273) at the same concentration was without effect. Under long photoperiod C-20231 at 2×10−3M significantly reduced internodal lengths, while under short photoperiod internodal lengths were all reduced by 10−7 to 2 × 10−3M. Petiolar lengths were similarly affected by the chemical and photo-periods. Gibberellin A3 application slightly increased NAR but decreased root RGR. Furthermore, gibberellin A3 significantly enhanced the growth of the petioles of plants grown in Cornell mix (a standard compost) but not in ...

One-wire, 2-wire, and overhead trellis systems of the muscadine grape, Vitis rotundifolia, Mich., cv. Hunt, were compared for 20 bearing years. Initially, plants trained to the 2-wire trellis had the highest yield; but for each of the next 18 years, the highest yield was obtained from the overhead trellis. All training systems exhibited alternate bearing after the 7th crop year. The alternate bearing pattern was the same as the state pecan production.

The purpose of this paper is to present a method of solving the Gaussian signal in Gaussian noise detection problem when the additive noise influence is not white and the signal and noise strength parameters are unknown to the receiver. This problem has been solved for a finite−dimensional receiver when the channel noise is white. By using a ’’simultaneous diagonalization of covariance matrices,’’ the problem of colored noise can be transformed into the previously considered problem. Furthermore, when the finite−dimensional representation does not apply, a ’’simultaneous orthogonal expansion of covariance kernels’’ will prove to be the medium through which the general problem can be transformed into a white−noise problem. For the restricted case when the finite−dimensional case does apply it will be shown that the same expansion leads to a receiver of the type previously proposed with minor modifications.Subject Classification: 60.XX.

Plants set 6.1, 6.4 and 6.7 m apart in each of 3.0-, 3.7- and 4.3-m rows of the muscadine grape, Vitis rotundifolia, Michx., cv. Hunt, were compared for 25 years. The highest plant density, 477 plants/ha, gave the greatest yield per m2 almost consistently for 25 years. The highest yields per plant were obtained from the wider in-the-row spacings. Alternate bearing was rather consistent from 1949 through 1963, but irregular thereafter.

Seed counts of 2 size grades from 3 fruit sizes were made from 30 fruits each of 21 rabbiteye (Vaccinium ashei Reade) cultivars and selections. Total seeds/berry ranged from 110 for ‘Briteblue’ to 28 for selection T-111. Generally, larger fruit had more total and large seeds than smaller fruit; however, this relationship was not constant for all cultivars. Total seed number and number of large seeds per fruit appear to be heritable.

Fruits of rabbiteye blueberry (Vaccinium ashei Read cv. Tifblue) were harvested by hand and an overrow mechanical harvester for 2 years. Machine harvest increased ground loss of marketable fruit over hand harvest. Hand-harvested fruit were 29 to 37% firmer than machine-harvested fruit. When held for 7-11 days at 15.5°C, machine-harvested fruit had more than twice the amount of soft and unmarketable fruit than hand-harvested fruit. Pruning rabbiteye blueberry plants increased the harvesting efficiency of the machine.

Softwood terminal cuttings of ‘Woodard’ and ‘Tifblue’ blueberry (Vaccinium ashei Reade) rooted best in media containing milled pine bark alone or mixed with equal parts of perlite, compared to sphagnum peatmoss alone or mixed with equal parts of perlite. Percentage rooting, root quality, and percentage marketability of softwood terminal cuttings of Vaccinium ‘Tifton 275’, a complex hybrid of V. corymbosum L. and V. ashei, was unaffected by rooting medium.

Repression of specific growth parameters of Tetragonia tetragonioides (Pall.) Kuntze (syn. Tetragonia expansa Murray) was studied after application of two types of growth regulators. Succinic acid-2,2-dimethylhydrazide (SADH) decreased stem height and dry weight progressively with increased concentration. Ratio of leaf dry weight to stem dry weight increased with concentration. Maleic hydrazide (MH) caused substantial reduction of fruit weight, with fruit number decreasing only at higher concentrations. Whole plant fresh weight and leaf area decreased only with a multiple 500 ppm application of MH. Leaf to fruit fresh weight ratio increased with concentration and number of applications. A formulation C6 to C12 fatty alcohols (Off-Shoot T) had little effect on fruit development and leaf area.

‘Georgiagem’, a new low-chilling cultivar. is the first highbush blueberry (Vacciniwn corymbosum L.) cultivar developed from the cooperative blueberry breeding program of the Georgia Agricultural Experiment Station and the USDA. Although ‘Georgiagem’ originated mostly from tetraploid highbush blueberry parentage, it obtained adaptation to the southern U.S. environment from the diploid species, V. darrowi, selected from the wild in Florida (2). ‘Georgiagem’ is early ripening, moderately productive, and has fruit of medium size with good color, small stem scar, firmness, and pleasant flavor.

(2-Chloroethyl)phosphonic acid (ethephon) was applied at 0, 570, 1000 and 2000 ppm to muscadine grapes (Vitis rotundifolia Mich. cv. Hunt), 1, 2, or 3 days before once-over harvest. All ethephon treatments increased berry abscission and reduced skin tear due to harvest when berries were harvested 2 days or 3 days after spraying. Delaying harvest to 3 days after treatment with 2000 ppm ethephon increased berry abscission to 46% and reduced skin tear to 9% in 1977. In 1978, 2000 ppm of ethephon increased berry abscission to 29% and reduced skin rupture to 29%. Taste panels could not detect flavor difference from the ethephon treatments.

The influence of chilling on rabbiteye blueberry (Vaccinium ashei Reade) differed among cultivars studied. Growth measurements made 30 days after chilling indicated that maximum vegetative growth for ‘Climax’ occurred after 450 hours; ‘Bluebelle’ and ‘Delite’, after 500 hr; and ‘Tifblue’, after 650 hr of chilling below 7.2°C. Some ‘Climax’, ‘Bluebelle’, and ‘Delite’ flowered after 150 to 200 chilling hr; however, the latter 3 cultivars studied required at least 650 chilling hr for maximum flower development.

Results of tests to evaluate periderm peeling and failure forces of container-grown roots of sweetpotato (Ipomea batatas, Lam. cv. Nemagold), conditioned to various environments, were erratic. With field-grown roots, peeling and failure forces varied with soil temperature and soil moisture and were generally highest for warm dry conditions. Temperature and moisture had approximately equal effects on periderm peeling resistance within the ranges tested. Periderm thickness decreased and peeling resistance increased as soil temperature increased, but the number of cell layers remained fairly constant.

Prior to 1964 work relating morphological changes of the tomato plant to the occurrence of the earliest once-over maximum yield of ripe fruit had not been reported. In studies of growth and fruiting characteristics of several tomato cultivars to develop an objective method to predict the harvest date, Austin1 determined that the cessation of stem enlargement was the best index. Measuring stems, however, with calipers at 3-and 4-day intervals is laborious.

Ray tracing in a layered atmosphere is accomplished by using a general‐purpose analog computer. Diode function generators are used to simulate the functions V and dV/dy, which are continuous functions defined for all values of range and altitude. It is shows that these diode function generators approximate quite well the speed of sound profiles.

‘Baldwin’ rabbiteye blueberry (Vaccinium ashei Reade) is a new cultivar originating from the cooperative blueberry breeding program of the Georgia Agricultural Experiment Stations and the USDA. It is a very productive, late-ripening cultivar with good flavor and firm, dark-blue fruit. Bacause of its lengthy ripening period ‘Baldwin’ is intended primarily for pick-your-own and backyard planting in areas of the southern United States where rabbiteye blueberries are grown successfully. ‘Baldwin’ is named in honor of Abraham Baldwin, Yale graduate, U.S. Senator, and founder and first president of the Univ. of Georgia,.

Estimates of power spectral densities obtained using time‐compression, swept‐filter spectral analyzers may contain errors due to assumptions regarding normality, randomness and symmetry of the data being processed. This paper considers possible errors in these estimates caused by various effects. The first concern is for hidden periodic components in data records assumed to be entirely random. Expressions describing this error are developed. Also of concern are nonlinear effects in the instrumentation which may result in amplitude‐limiting of data records. Error analysis is performed for several possible amplitude distributions. Finally errors due to asymmetrical data records are considered. Records which are not normally‐distributed in amplitude exhibit some degree of asymmetry and thus the power spectral density estimates obtained from these records will be in error. Expressions for power spectral density estimates of amplitude distributions other than normal are developed. These are compared with estimates obtained under the normal assumption. Also, general relationships regarding power spectral density estimates as a function of the skewness and kurtosis of the data record are discussed.

The Coastal Plain Experiment Station announces the release of ‘Georgia Upright’ Brassica oleracea L. (Acephala group) which is resistant to bolting and has upright leaf petioles.