Site Analysis for Seismic Soil Liquefaction Potential

Field penetration data and cyclic laboratory test data are presented for evaluating the seismically induced soil liquefaction potential at a waterfront site. Dynamic split-spoon penetration recordings and three types of quasistatic friction cone probings were made. The friction cones were the standard mechanical cone, the electric cone, and the piezometric cone. The latter penetrometer has a porous element near the tip which permits measurement of pore water pressures generated during penetration. By interrupting penetration, the rate of pore pressure dissipation can be recorded, so an estimate of soil permeability can also be derived. Undisturbed samples were taken using an Osterberg piston sampler, and the specimens were subjected to cyclic triaxial testing in the laboratory. The field sounding techniques were in agreement; however, they indicated a recently deposited sensitive silty sand to have a liquefaction resistance approximately one-half that based upon cyclic triaxial testing. The question arises as to whether the liquefaction resistance as determined by laboratory testing is more appropriate herein, or whether behavior suggested by the penetration test results more realistically predicts the response of this type of soil to an actual earthquake

Effects of Litter on Aquatic Macrophyte Germination and Growth

In Arkansas, during seasonal drought periods, lake water levels drop leaving exposed mudflats which are primary sites for seedling establishment. Commonly, these exposed mudflats are partially covered with decomposing litter from previous stands of aquatic plants. In this study, aqueous leachates from the litter of four macrophytes, Eleocharis quadrangulata, Justicia americana, Polygonum lapathifolium, and Potamogeton nodosus, were used to test for chemical interference with germination and seedling growth. Only Justicia americana leachate was found to affect the growth of several of the test species. The potential for chemical interference by Justicia litter was evaluated further using extracts of acidified leachate. Resulting bioassays demonstrated significant effects on growth but not on seed germination. Bioassays of chromatographically separated fractions again revealed significant effects on seedling growth. These results suggest that interference by Justicia americana leachate on growth of seedlings is in part allelochemic

State Department of Agriculture Participation in Fresh Produce Marketing in Georgia, Kentucky, North Carolina, and Tennessee

Agricultural and Food Policy,

Removing Distribution Barriers Confronting Small-Volume Fruit and Vegetable Growers: Results of the Tennessee Extension Service Survey

Crop Production/Industries, Teaching/Communication/Extension/Profession,

Produce Growers and Market Development: A Four-State Comparison

Crop Production/Industries,

COMPTEL observations of gamma‐ray flares in October 1991

The COMPTEL experiment on GRO images 0.75–30 MeV celestial gamma‐radiation that falls within its 1 steradian field of view. During observation 12 (primary target Cen A) in October 1991 the sun had been in the fov and several solar flares associated with the active region 6891 had been observed. Time profile and energy spectra had been produced, using COMPTEL’s primary mode of operation (the telescope mode). Additionally the number of counts received in the D2‐single burst detector (the secondary mode of operation) are given. We summarize the preliminary results on all of these flares

COMPTEL gamma ray and neutron measurements of solar flares

COMPTEL on the Compton Gamma Ray Observatory has measured the flux of x‐rays and neutrons from several solar flares. These data have also been used to image the Sun in both forms of radiation. Unusually intense flares occurred during June 1991 yielding data sets that offer some new insight into of how energetic protons and electrons are accelerated and behave in the solar environment. We summarize here some of the essential features in the solar flare data as obtained by COMPTEL during June 1991

Neutron and gamma‐ray measurements of the solar flare of 1991 June 9

The COMPTEL Imaging Compton Telescope on‐board the Compton Gamma Ray Observatory measured significant neutron and γ‐ray fluxes from the solar flare of 9 June 1991. The γ‐ray flux had an integrated intensity (≳1 MeV) of ∼30 cm−2, extending in time from 0136 UT to 0143 UT, while the time of energetic neutron emission extended approximately 10 minutes longer, indicating either extended proton acceleration to high energies or trapping and precipitation of energetic protons. The production of neutrons without accompanying γ‐rays in the proper proportion indicates a significant hardening of the precipitating proton spectrum through either the trapping or extended acceleration process

Observations of the 1991 June 11 solar flare with COMPTEL

The COMPTEL instrument onboard of the Compton Gamma‐Ray Observatory (CGRO) is sensitive to γ‐rays in the energy range from 0.75 to 30 MeV and to neutrons in the energy range from 10 to 100 MeV. During the period of unexpectedly high solar activity in June 1991, several flares from active region 6659 were observed by COMPTEL. For the flare on June 11, we have analyzed the COMPTEL telescope data, finding strong 2.223 MeV line emission, that declines with a time constant of 11.8 minutes during the satellite orbit in which the flare occurs. It remains visible for at least 4 hours. We obtained preliminary values for the 2.2 MeV and 4–7 MeV fluences. Neutrons with energies above 20 MeV have been detected and their arrival time at the Earth is consistent with the γ‐ray emission during the impulsive phase

Desensitization of Gonadotropin-releasing Hormone Action in αT3-1 Cells Due to Uncoupling of Inositol 1,4,5-Trisphosphate Generation and Ca 2+ Mobilization

Gonadotropin-releasing hormone (GnRH) acts via a G-protein coupled receptor on gonadotropes to increase cytosolic Ca2+ and stimulate gonadotropin secretion. Sustained exposure causes desensitization of these effects, but the GnRH receptor has no C-terminal tail and does not undergo rapid (<5 min) desensitization. Nevertheless, pretreatment of alphaT3-1 cells with GnRH reduced the spike Ca2+ response to GnRH and decreased the GnRH effect on inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) by 30-50%. Ca2+-free medium with or without thapsigargin also decreased GnRH-stimulated Ins(1,4,5)P3 generation, implying that attenuation of the Ca2+ response underlies the Ins(1,4,5)P3 reduction rather than vice versa. Intracellular Ca2+ pool depletion cannot explain desensitization of the Ca2+ response because pool depletion and repletion were faster (half-times, <1 min) than the onset of and recovery from desensitization (half-times 10-20 min and 4-6 h). Moreover, 1-h GnRH pre-treatment attenuated the spike Ca2+ response to GnRH but not that to ionomycin, and brief GnRH exposure in Ca2+-free medium reduced the response to ionomycin more effectively in controls than in desensitized cells. GnRH pretreatment also attenuated the Ca2+ response to PACAP38. This novel form of desensitization does not reflect uncoupling of GnRH receptors from their immediate effector system but rather a reduced efficiency of mobilization by Ins(1,4,5)P3 of Ca2+ from an intact intracellular pool