Mean geocarposphere temperatures that induce preharvest aflatoxin contamination of peanuts under drought stress

Apparently undamaged peanuts grown under environmental stress in the form of drought and heat become contaminated with Aspergillus flavus and aflatoxin in the soil prior to harvest. The upper mean temperature limit for aflatoxin contamination in undamaged peanut kernels grown under drought stress the latter 4-6 weeks of the growing season was between 29.6-31.3 degrees C. The lower limit was between 25.7-26.3 degrees C. That is, peanuts grown under drought stress with a mean geocarposphere temperature of 29.6 degrees C were highly contaminated while those at 31.3 degrees C were not contaminated. Likewise, those grown under drought stress with a mean geocarposphere temperature of 25.7 degrees C were not contaminated while those subjected to a mean geocarposphere temperature of 26.0 degrees C resulted in some categories becoming contaminated. Increasing the mean temperature up to 29.6 degrees C caused increasing amounts of contamination.

Bioavailability studies with ciglitazone in beagles. I. Effect of a meal on the bioavailability of three ciglitazone dosage forms

Three separate Latin square crossover studies were conducted in beagles to examine the effect of a meal on the bioavailability of a ciglitazone tablet, suspension, and solution. In these studies, drug was administered to fasted animals with either 50 ml water or with 180 g Purina Dog Chow and 20 g butter. The data indicated that the meal significantly increased the AUC by about 40 per cent for both the tablet and the suspension but had no significant effect on the solution treatment. Comparisons across studies indicated low bioavailability in fasted animals from either the tablet or suspension relative to the solution. When drug was co-administered with a meal, however, bioavailability appeared to be independent of dosage form.

Effect of soil temperature and drought on peanut pod and stem temperatures relative to Aspergillus flavus invasion and aflatoxin contamination

Peanut stem and pod temperatures of plants growing in irrigated, drought, drought-heated soil, and drought-cooled soil treatments were determined near the end of the growing season. Mean soil temperatures of the treatments during this period were 21.5 degrees, 25.5 degrees, 30 degrees and 20 degrees C, respectively. Peanut stem temperatures in all drought treatments reached a maximum of ca. 40 degrees C and for 6-7 h each day were as much as 10 degrees C warmer than irrigated peanut stems. Pod temperatures in drought-heated soil and drought treatments were ca. 34 degrees C and 30 degrees C, respectively, for several hours each day. As pod temperatures approached the optimum for A. flavus growth (ca. 35 degrees C), the proportion of kernels colonized and aflatoxin concentrations increased. Increased plant temperature without accompanying pod temperature increases (drought-cooled soil) resulted in colonization percentages and aflatoxin concentrations only slightly higher than those of the irrigated peanuts.

Effect of geocarposphere temperature on pre-harvest colonization of drought-stressed peanuts by Aspergillus flavus and subsequent aflatoxin contamination

Florunner peanuts grown in research plots were subjected to 5 soil temperature and moisture treatment regimes resulting in A. flavus infestation and subsequent aflatoxin contamination in drought-stressed peanuts. Treatments imposed beginning 85 days after planting were drought, drought with heated soil and 3 drought treatments with cooled soil. The incidence of A. flavus in drought-stressed, unshelled , sound mature kernels ( SMK ) decreased with decreases in the mean 5 cm deep soil temperature. The incidence of A. flavus was greater in inedible categories and in damaged kernels than in SMK . The mean, threshold, geocarposphere temperature required for aflatoxin development during the latter part of the peanut growth cycle was found to be between 25.7 degrees C and 27 degrees C.

Viable fungi in corn dust

Numbers of viable fungal propagules in corn dusts in southern Georgia were estimated during various farm and grain elevator operations in 1979, 1980, and 1982. A six-stage Andersen sampler for viable microbial particles was used to sample the dusts with various agar media. The most abundant fungi in corn dusts were species of yeasts: Aspergillus, Penicillium, Cladosporium, Alternaria. Helminthosporium, and Fusarium. However, the relative abundance of these fungi differed between years. There was a greater incidence of the Aspergillus flavus group in the hot, dry year of 1980 compared with the cooler, wetter years of 1979 and 1982. Fungi in the corn dusts sampled numbered between 10(4) and 10(9) viable propagules per m3 of air. By contrast, outdoor air often contained fewer than 10(4) viable fungal propagules per m3. Most A. flavus propagules were deposited at stages three and four of the Andersen sampler, with correspond to the trachea, primary bronchi, and secondary bronchi in the human respiratory system. In an assessment of the air spores by exposing sterile petri dishes, more large-spored fungi, like Alternaria tenuis, and fewer small-spored fungi, such as A. flavus, were detected when compared with colony counts from petri dishes exposed to air in the Anderson sampler.

Optical Stark effects on pure-spin Raman transitions in molecular oxygen

Fully resolved pure-spin Raman transitions near 2 cm(-1) have been observed in (3)Sigma(g) ground-state molecular oxygen using stimulated Raman techniques. Anomalous differences between polarized and depolarized spectra are fully explained in terms of optical Stark effects.

Effects of soil moisture and temperature on preharvest invasion of peanuts by the Aspergillus flavus group and subsequent aflatoxin development

Four soil temperature and moisture treatment regimens were imposed on Florunner peanuts 94 days after planting in experimental plots in 1980. At harvest (145 days after planting), the incidence of the Aspergillus flavus group and the aflatoxin concentration were greatest in damaged kernels. Extensive colonization of sound mature kernels (SMK) by the A. flavus group occurred with the drought stress treatment (56% kernels colonized); colonization was less in the irrigated plot (7%) and the drought stress plot with cooled soil (11%) and was intermediate in the irrigated plot with heated soil (26%). Aflatoxin was virtually absent from SMK with the last three treatments, but it was found at an average concentration of 244 ppb (ng/g) in drought-stressed SMK. Colonization of SMK by the A. flavus group and aflatoxin production were greater with hot dry conditions. Neither elevated temperature alone nor drought stress alone caused aflatoxin contamination in SMK. When the ratio of SMK colonized by A. flavus compared with A. niger was greater than 19:1, there was aflatoxin contamination, but there was none if this ratio was less than 9:1. Irrigation caused a higher incidence of A. niger than drought did. This may have prevented the aflatoxin contamination of undamaged peanuts.

Isolation of Citreoviridin from Penicillium charlesii Cultures and Molded Pecan Fragments

The extraction and systematic fractionation of Penicillium charlesii Smith cultures and contaminated pecan fragments yielded the yellow mycotoxin citreoviridin. Citreoviridin proved acutely toxic to 1-day-old chickens, with an oral 50% lethal dose of 37.5 mg/kg, and showed plant growth inhibition in wheat coleoptiles even at concentrations as low as 10 −4 M. It was toxic to corn seedlings but did not affect young tobacco seedlings.

Ignition-delay times in laser initiated combustion

A single pulse from a TEA CO(2) laser is used to heat 1:7:14 mixtures of SF(6):CH(4):O(2) to temperatures near 1000 K. A short- or long-duration pulse (one-half the energy deposited in 0.25 or 0.82 microsec, respectively) from a second TEA CO(2) laser is used to ignite the mixture. At comparable values of absorbed energy from the second laser, ignition-delay times for the long-duration secondary pulse are approximately twice those for the short-duration pulse. Ignition of the hot mixture requires about 10% less absorbed energy with the short-duration pulse than with the long-duration pulse. These results indicate the short-duration pulse is more effective in producing a high population density of reactive species that initiate the reactions necessary for ignition.

Holographic interferometry of a large-bore cw high-energy gas-laser medium during laser-power extraction

A holographic interferometer is described that is used in conjunction with a high-speed camera system (10,000 frames/sec) to record the temporal and spatial interactions of the laser gas medium and the resonator mode. In particular, a high-power CO(2) electric discharge convectively cooled laser-gas medium was interferometrically analyzed before, during, and after laser power extraction such that the mode-medium interaction was observed.

Pulsed spontaneous Raman scattering technique for luminous environments

A gated photon counting system, cavity-dumped argon-ion laser, and a multipass retroreflecting light cell have been combined in a system to enhance spontaneous Raman scattering in luminous background situations. Signal-to-background ratio (SBR) has been improved a factor of 450 over a single-pass cw system with cw power equal to the pulsed average power. The improvement attributable to the gating and cavity dumping the laser is a factor of 30. A factor of 15 improvement is due to the retroreflecting light cell. Temperature and density data obtained from N(2)Q-branch spectra of a luminous methane-air flame are presented to illustrate the utility of the system. A passband fitting technique is introduced to analyze the data.

Retroreflecting multipass cell for Raman scattering

A retroreflecting multipass cell consisting of two lenses and both on-axis and off-axis retroreflecting mirror assemblies has been constructed and tested. A gain in Raman scattered signal intensity of 20 has been attained in a focal volume 1.1 mm x 0.3 mm x 0.3 mm. A system employing off-axis paraboloids should provide somewhat higher gain and a diffraction limited focal volume. These systems are applicable to Raman diagnostics of various gas dynamic processes, including flame gases, or the characterization of the gas mixing process in gas-dynamic or chemical laser nozzle arrays.

Focused, multiple-pass cell for Raman scattering

A simple optical system is described that makes use of a unique property of ellipsoidal mirrors, viz., light brought to one focus will be reflected alternately through the two foci and collapse to the major axis. This system consists of an on-axis ellipsoidal mirror facing a coaxial flat-spherical mirror assembly that is positioned at the minor axis. Calculations indicate that gains of the order of 500 in the light flux at the point of observation should be attainable with low-eccentricity ellipsoids. Raman-scattered light from atmospheric N(2) was obtained with a system employing a 0.2 eccentricity ellipsoid. An experimental gain of 93 was determined by the ratio of the scattering with the system to the scattering obtained with one beam. This result is in good agreement with the theory.

Method for measuring Doppler shifts in arc-heated flows

A novel method of determining both the Doppler and Stark shifts in a single measurement of spectral lines emitted by the arc-heated flow from a plasma jet has been successfully demonstrated. The method uses a spherical mirror arranged with its optical axis coincident with the optical axis of a Fabry-Perot interferometer and with its center of curvature at the center line of the flow. The common optical axis lies at an angle to the flow. With this system, both red-and blue-shifted line profiles are recorded in the same spectral scan. If conditions are such that the red-and blue-shifted profiles are not resolvable, the blue-shifted component is chopped so that the recorded signal consists of the envelopes of both the red-shifted profile and the superimposed red-and blue-shifted profiles. The wavelength difference between the blue-and red-shifted line profiles is exactly twice the Doppler shift integrated along a line of sight through the flow and is independent of a Stark shift. The Stark shift is given by the wavelength difference between the absolute line center and the midpoint of the red-and blue-shifted lines. Abel inversion of integrated line shift data has yielded radial velocity profiles to an accuracy of +/-3% in a supersonic, arc-heated argon flow.

A new plane grating monochromator with off-axis paraboloids and curved slits

A design for a new plane grating monochromator is described. The system employs a symmetrical configuration of off-axis paraboloids for both the collimator and camera mirrors. The entrance and exit slits are mounted on the same side of the grating and are curved in order to eliminate wavelength errors due to spectral line curvature. There is, in fact, a remarkable coincidence between the curvature which is required to avoid wavelength errors and the curvature which is required to obtain equal curvatures in the object and image planes. Ray tracing calculations for a symmetrical configuration of off-axis paraboloids show that the image of a curved slit with a length equal to 0.05 times the focal length of an f/5 mirror is diffraction limited for wavelengths lambda > 0.2 . micro.

Rapid scan spectrometers for the diagnostics of transient plasmas

An observation that a symmetrical configuration of off-axis paraboloidal mirrors produces an excellent image of an extended slit, while an unsymmetrical configuration produces poor images, has led to a modification of the original Sandia rapid scan spectrometer and to the design of a new wide range, rapid scan spectrometer. The new instrument employs a high speed rotating mirror in a Littrow arrangement to obtain a spectral scan speed double that of the original spectrometer; e.g., with a 600-lines/mm grating, a spectral scan speed of ~410 A/microsec is obtained at 1000 rps. Techniques for obtaining an accurate calibration of the spectral scan speed are described, and some examples of spectra which were recorded from a xenon and a hydrogen plasma are shown.

A dual recording, variable range, rapid-scan spectrometer; comparison of simultaneously recorded stark-broadened Halpha and Hbeta line profiles

An ultrarapid scanning spectrometer has been constructed that records spectra at a constant angle of diffraction. The spectral scanning is accomplished by the rotation of a high-speed rotating mirror (7.6 cm diam) that causes a collimated light beam to sweep across a plane grating, changing the angle of incidence. The full-aperture scanning range depends upon the over-all grating width, upon the grating spacing, and upon the orientation of the grating with respect to the high-speed mirror. For example, a 12.5-cm, 1200-lines/mm grating gives a scanning range of approximately 2000 A on each of two separate detector systems, or a total range of 4000 A that can be centered at any wavelength between 4000 A and 8000 A. This grating provides a theoretical resolving power of approximately 85,000 in the first order, a reciprocal dispersion of 17.5 A/mm at f/5, and a spectral scan speed of 115 A/microsec at 1100 rps. This spectrometer has been used to record, simultaneously, Stark-broadened Halpha and Hbeta emission line profiles from a transient plasma generated in the impulse tube. Electron densities calculated from the half-width of the Hbeta profiles are in good agreement with values obtained by fitting the line wings of the self-absorbed Halpha profiles to the theoretical profiles of Griem, Kolb, and Shen.