Response Dynamics of Entorhinal Cortex in Awake, Anesthetized, and Bulbotomized Rats. <i>Brain Research</i> <b>911</b>(2)

The generation of oscillatory activity may be crucial to brain function. The coordination of individual neurons into rhythmic and coherently active populations is thought to result from interactions between excitatory and inhibitory cells mediated by local feedback connections. By using extracellular recording wires and silicon microprobes to measure electrically evoked damped oscillatory responses at the level of neural populations in the entorhinal cortex, and by using current-source density analysis to determine the spatial pattern of evoked responses, we show that the propagation of activity through the cortical circuit and consequent oscillations in the local field potential are dependent upon background neural activity. Pharmacological manipulations as well as surgical disconnection of the olfactory bulb serve to quell the background excitatory input incident to entorhinal cortex, resulting in evoked responses without characteristic oscillations and showing no signs of polysynaptic feedback. Electrical stimulation at 200 Hz applied to the lateral olfactory tract provides a substitute for the normal background activity emanating from the bulb and enables the generation of oscillatory responses once again. We conclude that a nonzero background level of activity is necessary and sufficient to sustain normal oscillatory responses and polysynaptic transmission through the entorhinal cortex

Phase changes in 38 atom Lennard-Jones clusters. II: A parallel tempering study of equilibrium and dynamic properties in the molecular dynamics and microcanonical

We study the 38-atom Lennard-Jones cluster with parallel tempering Monte Carlo methods in the microcanonical and molecular dynamics ensembles. A new Monte Carlo algorithm is presented that samples rigorously the molecular dynamics ensemble for a system at constant total energy, linear and angular momenta. By combining the parallel tempering technique with molecular dynamics methods, we develop a hybrid method to overcome quasi-ergodicity and to extract both equilibrium and dynamical properties from Monte Carlo and molecular dynamics simulations. Several thermodynamic, structural and dynamical properties are investigated for LJ$_{38}$, including the caloric curve, the diffusion constant and the largest Lyapunov exponent. The importance of insuring ergodicity in molecular dynamics simulations is illustrated by comparing the results of ergodic simulations with earlier molecular dynamics simulations.Comment: Journal of Chemical Physics, accepte

Controlling Chickweed and Henbit in Alfalfa

Chickweed and henbit weeds are bad in alfalfa this fall. DNBP (premerge or Sinox PE) sprayed on infested fields at rate of 1 to 3 qt in 20 to 40 gallons of water per acre may destroy the weeds without harm to the dormant alfalfa. Use the higher rate if chickweed is matted on the ground or if henbit is heavy in the stand. Spray only when the temperature is 55 to 60 degrees or warmer and fair weather is predicted for 12 hours after treatment. The 1-qt rate applied in early fall when chickweed is very small (not until August seeded alfalfa plants have 2 or more trifoliate leaves) and repeated during a warm spell in March should give good control of chickweed and germinating henbit

Control Annual Weeds in Tobacco Fields with Herbicides

In the years 1957 to 1967 inclusive, many promising herbicides have been used in Kentucky research trials for controlling annual weeds in tobacco fields. Burley tobacco has been used every year at Lexington, for 4 years at Eden Shale farm in Owen county, and 1 year in McCracken county, while dark air-cured tobacco was used for 4 years at the Western Kentucky Substation, Princeton

Controlling Annual Grasses in Spring Seeded Alfalfa with EPTC

Many Kentucky farmers plan to sow alfalfa in early spring on a prepared seed bed. A main objective is to avoid or reduce most of the damage of alfalfa weevil on the first-year crops . Eptam 6 E sprayed on the prepared seed bed at rate of 2 quarts in 10 to 20 gallons of water per acre and disked in 3-4 inches deep right behind the sprayer usually gives good control of annual grass weeds and some control of broadleaf weeds as well. A second disking, crosswise to the first, is needed for thorough mixing of the herbicide with the soil. After smoothing the seedbed, alfalfa may be seeded at once . Grass seed should not be sowed with the alfalfa, as it is likely to be killed by the EPTC. The grass may be drill-seeded in the established alfalfa in early or mid-October. Do not seed a small grain nurse crop with the alfalfa on EPTC treated land

A magnetospheric simulation at the space station

It is proposed that a strong magnet (terrella) be flown at or near the Space Station to create an artificial magnetosphere in a laboratory setting. The relative flow of the ionosphere past the terrella will constitute a plasma wind that will interact with the magnetic field of the terrella to produce a localized magnetosphere. This object could then be extensively studied using diagnostic probes attached to the Space Station, or with free flyers. The space and storage requirements would be minimal, since the experiment would be conducted outside the space station. The total equipment would consist of several terrella (with varying surface conductivities), approximately 3 small magnetometer/plasma diagnostic packages, and several gas canisters for upstream seeding. Power requirements would be approximately 60 watts. Several track mounted tethers, each approximately or 200 m long in length, with track parallel to the orbital motion and 100 m long, are also needed. Astronaut time needed would be minimal in the tethered configuration (approximately 4 man hours/week). A free flying configuration, while not needing the tether track, would require much more human interaction

Enide Recommended for Trial Use on Tobacco Beds

Enide 50W has now been cleared for use on tobacco beds. Treatments with Enide on tobacco beds in mid to late March. at time of seeding have given satisfactory weed control in experimental plots during the past 2 years. No injury or reduction in stand of tobacco plants was observed on plots treated at this time. Reduction in stand of plants did occur in plots treated in late fall. and there are some indications that there may be a reduction in stand from early treatments in February. To insure best results. the chemical should be applied evenly over the treated area. Until additional information is obtained and tobacco growers get more experience with its use, Enide 50W for 1967 is recommended for trial use on only a part of the plant bed