Greenhouse experiments were conducted to evaluate the effect of the fungus Dactylaria higginsii on the interference of Cyperus rotundus (purple nutsedge) with Lycopersicon esculentum (tomato ‘Agroset'). Cyperus rotundus plants established from tubers were planted at initial densities equivalent to 40, 80, 160, and 320 tubers m−2 with L. esculentum in 35-cm-diam pots. Cyperus rotundus plants were inoculated by spraying with a spore suspension of D. higginsii containing 0.5% Metamucil as a carrier. The treatments were Metamucil only, 104 conidia ml−1 + Metamucil, or 106 conidia ml−1 + Metamucil. In the absence of D. higginsii, C. rotundus at densities of 80, 160, and 320 tubers m−2 reduced L. esculentum yield by 14, 68, and 70%, respectively. In contrast, yield of L. esculentum treated with D. higginsii at 106 conidia ml−1 was equal to that in the weed-free control. The rate of disease increase (r G) was higher in treatments with 106 conidia ml−1 (r G = 0.126 to 0.136) compared to 104 conidia ml−1 (r G = 0.046 to 0.050). At 106 conidia ml−1D. higginsii reduced the interference from C. rotundus, controlled C. rotundus better, and increased L. esculentum yield compared to the weedy checks.

Greenhouse and field experiments were conducted to identify alternative herbicide treatments for the control of a biotype of American black nightshade which has been shown to tolerate paraquat. In greenhouse experiments the combination of paraquat and the metal chelator diethyldithiocarbamate at either 1% w/v or 3% w/v, and diquat alone significantly lowered I50 values, based on dry weight, when compared with paraquat alone. None of these treatments provided acceptable control (>90%) in field experiments. Treatments that controlled American black nightshade under field conditions were: monocarbamide dihydrogensulfate at 9 kg ai ha-1, monocarbamide dihydrogensulfate at 9 kg ha-1 + paraquat at 0.6 kg ha-1, lactofen at 0.6 kg ha-1, oxyfluorfen at 0.6 kg ha-1, and acifluorfen at 0.6 kg ha-1. Addition of tridiphane at 1.7 kg ha-1 to paraquat at 0.6 kg ha-1 did not improve control of American black nightshade under field conditions.

Experiments were conducted to determine the interaction between cupric hydroxide and paraquat on the control of American black nightshade. Three cupric hydroxide applications lowered paraquat toxicity with no further decrease in toxicity with six or nine cupric hydroxide applications when paraquat was applied 3 days after the last cupric hydroxide application. The interval between the last cupric hydroxide application and paraquat application was more important in decreasing paraquat toxicity than the number of cupric hydroxide applications. Three cupric hydroxide applications with a 10-day interval before paraquat application decreased paraquat toxicity less than three cupric hydroxide applications with a 3-day interval before paraquat application. Plants collected from three American black nightshade populations (Naples, Bradenton, and Gainesville) differed in their sensitivity to paraquat. I50 values, based on dry weight, showed Naples plants to be 12 times more tolerant to paraquat than Gainesville plants without cupric hydroxide, and 14 times more tolerant when cupric hydroxide was applied. More plants of the Naples biotype regrew from apical buds after paraquat treatment following cupric hydroxide application, and from axillary buds with paraquat but not cupric hydroxide treatment, than did the Bradenton biotype. Plants of the Gainesville biotype did not regrow after paraquat application, regardless of cupric hydroxide treatment.

An isolate of the fungus Dactylaria higginsii obtained from purple nutsedge in Florida was highly pathogenic to Cyperus spp. The potential of this isolate as a bioherbicide was field tested in natural populations of purple nutsedge in Gainesville and Jay, FL. The fungus was applied in 0.5% Metamucil® as a carrier, and the treatments were: carrier only, 105 conidia/ml + carrier, and 106 conidia/ml + carrier. Treatments were applied as single, double, or triple postemergence (POST) sprays at biweekly intervals. The disease and secondary infections developed in about 5 and 15 d after inoculation, respectively, killing most of the infected leaves. All weed growth parameters and disease progress rates were affected by inoculum dosage and inoculation frequencies. Three inoculations, each at 106 conidia/ml, provided effective control of purple nutsedge compared to a single inoculation, as measured by shoot dry weight, tuber numbers, and tuber dry weight. Higher rates of disease progress and disease levels, defined by the area under the disease progress curve (AUDPC), occurred with three inoculations at 106 conidia/ml. Disease progress was slower and the level of weed control was lower at 105 conidia/ml compared to the higher inoculum level. Three applications of 106 conidia/ml provided >90% nutsedge control. Dactylaria higginsii appears to be an effective bioherbicide candidate deserving further development for commercial use.

A replacement series study was conducted to describe the aggressivity between cucumber, smooth pigweed, and livid amaranth. Cucumber was three times more competitive than smooth pigweed or livid amaranth, under the conditions of this study. However, there was equal competition and no antagonism between smooth pigweed and livid amaranth. Where cucumbers were planted in mixture with either of the two weeds, the relative yield total values were approximately 10 to 20% higher than the monocultures. Cucumber was a superior competitor when grown in mixture with smooth pigweed or livid amaranth, and the following aggressivity hierarchy exists: cucumber > livid amaranth = smooth pigweed. Results from the additive field study indicated that amaranth dry weights were significantly affected by smooth pigweed and livid amaranth density. Dry weight of amaranth was decreased by 48% at Gainesville and 25% at Live Oak, at 18 plants/m2. Despite differences between the Gainesville and Live Oak results, the dry weight data were similar for both smooth pigweed and livid amaranth at each location.

Field studies were conducted to determine the effect of season-long interference of smooth pigweed or livid amaranth on the shoot dry weight and fruit yield of cucumber. Smooth pigweed or livid amaranth densities as low as 1 to 2 weeds per m2 caused a 10% yield reduction in cucumber. The biological threshold of smooth pigweed or livid amaranth with cucumber is between 6 to 8 weeds per m2. Consequently, weed interference resulted in a reduction in cucumber fruit yield. Smooth pigweed, livid amaranth, and cucumber plant dry weight decreased as weed density increased. Evaluation of smooth pigweed, livid amaranth, and cucumber mean dry weights in interspecific competition studies indicated that cucumber reduced the dry weight of both species of amaranths.

This giant race of the species freija Thun. was collected along the Alaska Military Highway in British Columbia. In size and wing shape this would appear to be a race of frigga Thun. rather than of freija, and we have no doubt but that those who depend on external characters only will insist that we are in error; nevertheless gentalic study leaves no doubt as to its true relationship with freija.

TPL has developed a method and instrumentation system for characterizing the surface area and pore size distribution of a thin-film or coating in its as-deposited state. Errors associated with destructive removal of the film are avoided and small sample sizes can be utilized with high-fidelity results.

Traditional coil-based eddy-current sensors are severely limited in their ability to detect small buried defects, defects under fasteners and deeply buried cracks and corrosion. TPL has developed eddy-current sensors and arrays based on the use of Giant Magnetoresistance (GMR) sensor elements. GMR offers high sensitivity, very wide bandwidth and low noise from DC to over 1 GHz. Coupled with the ability to fabricate GMR sensors with micron-level dimensions, these new eddy-current sensors offer an ideal technology for inspections requiring high spatial resolution and low-frequency, deeply-penetrating fields.

Electrically switchable volume reflection holograms were written by inhomogeneous illumination of a prepolymer syrup containing a nematic liquid crystal and a multifunctional acrylate monomer. Switchable holograms are diffractive optics structures and the diffraction efficiency can be controlled by the application of an electric field. Reflection gratings with grating spacing varying between 0.16-0.27 µm were made during the phase separation of liquid crystals from the fast curing prepolymer syrup. The reflection efficiency of the holograms were electrically modulated with the applied field of ∼10-15V/µm. Real time study of the grating formation revealed that the maximum efficiency is reached in ∼15 seconds. The shrinkage of the host polymer during grating formation resulted in the blue shift of the reflection notch. The response time of the grating in an electric field is ∼50 µs. Low voltage scanning electron microscope studies showed the presence of discrete nematic droplet domains of sizes 30-60 nm in liquid crystal rich region.

Multiple wafer growth of infrared III-V semiconductor materials of InSb and InGaAsP have been produced by metalorganic chemical vapor deposition technology employing a vertical reactor growth configuration with a high speed rotating disk. Three measurement techniques of sheet resistivity, Fourier transform infrared (FTIR) reflectance and photoluminescence have been used to characterize epitaxial films on wafers up to 4″ diameter. Mapping distributions of the film thickness, sheet resistivity, surface morphology, and PL peak wavelength with uniformities better than 1% are illustrated. Data from our 2900 runs are produced. Variations of the characteristic features of the film with the growth conditions are discussed. These whole wafer and non-destructive material characterization techniques tightly coupled with the epitaxial processes are necessary to realize the high quality and high uniformity growth of state-of-art materials in a production environment.

The activation annealing of Si-implanted GaN is reported for temperatures from 1100 to 1400 °C. Although previous work has shown that Si-implanted GaN can be activated by a rapid thermal annealing at ∼1100 °C, it was also shown that significant damage remained in the crystal. Therefore, both AlN-encapsulated and uncapped Si-implanted GaN samples were annealed in a metal organic chemical vapor deposition system in a N2/NH3 ambient to further assess the annealing process. Electrical Hall characterization shows increases in carrier density and mobility for annealing up to 1300 °C before degrading at 1400 °C due to decomposition of the GaN epilayer. Rutherford backscattering spectra show that the high annealing temperatures reduce the implantation induced damage profile but do not completely restore the as-grown crystallinity.

We present results of photoluminescence (PL) studies of GaN, InxGa1-xN and AlxGa1-xN alloys, as well as related thin film heterostructures under hydrostatic pressure using the diamond-anvil-cell technique. The GaN PL spectra are dominated by strong and sharp near-band-edge luminescence associated with annihilations of bound excitons and intrinsic free excitons in the crystals. The spectrally well-resolved emission lines allow us to accurately determine their pressure. The PL spectra of InxGa1-xN and AlxGa1-xN epitaxial films were found to exhibit strong near-band-edge luminescence emissions. By examining the pressure dependence of these spectral features, the pressure coefficients for the PL emissions associated with the direct Γ band gap of InxGa1-xN and AlxGa1-xN were determined for the first time.

There is increasing interest in the epitaxial growth of high quality InSb thin films on GaAs substrates for many device applications such as infrared optoelectronics. The large lattice mismatch (14.6%) between InSb and GaAs has meant that both growth techniques and conditions have a large influence on the interface properties and consequently the film quality. A surface science study, by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) together with Nomarski microscopy, on the surface and interface properties of InSb/GaAs by metalorganic chemical vapor deposition is presented. It is found fromthe XPS data that the ambient surface is composed of InSb, In2O3, Sb2O3 and Sb2O5. The interdiffusion phenomena are studied by AES depth profiling; the width of interdiffusion region is determined to be 50±10 nm for all the samples grown at different V/III ratios. This is narrower than the data previously obtained for InSb/GaAs interfaces produced by metalorganic magnetron sputtering. The results also demonstrate that uniform and stoichiometric InSb films have been obtained, and that the reproducibility of the MOCVD technique is excellent.

Using contactless electroreflectance and surface photovoltage spectroscopy at room temperature we have nondestructively evaluated the band bending (carrier type) at the surface of epitaxial n- and p-type GaN/sapphire samples as well as at both the InGaN surface and the GaN at the InGaN/GaN interface of samples of epitaxial InGaN grown on top of thick GaN epilayers/sapphire, having average n- and p-type character.

The apparent thermal stability of hydrogen passivated Mg acceptors in GaN is a function of the annealing ambient employed, with H2 leading to a reactivation temperature approximately 150°C higher than N2. The dissociation of Mg-H complexes and the loss of hydrogen from GaN are sequential processes, with reactivation occurring at ≤700°C for annealing under N2, while significant concentrations of hydrogen remain in the crystal even at 900°C in implanted samples. The hydrogen is gettered to regions of highest defect density such as the InGaN layer in a GaN/InGaN double heterostructure. The addition of an accelerating potential for 2H+ ions in the plasma did not greatly affect the deuterium profiles.