Winter 1976

Lawn Fertilization (3) Turf Conference Reminder (4) Perennial Ryegrass Variety Trial--Performance in 1976 (5) Red Fescue Variety Tiral--Performance in 1976 (7) University of Massachusetts Turfgrass Research Fund (10) Will Congress Control the Chemical Industry? (11) Kentucky Bluegrass Variety Trial 1973--Performance in 1976 (14) Kentucky Bluegrass Variety Trial 1974--Performance in 1976 (18

Summer 1976

The Superintendents\u27s Obligation (page 3) Farm Machinery Noise can Damage Hearing (9) Back and Beyond (10) Tolerance to Benzimidazole-Derivative Fungacides by Fusarium Roseum on Kentucky Bluegrass Turf (13) Biological Pest Control Gaining Acceptance (16) Compare Fertilizer Values Before Buying (18) UMass Turfgrass Research Fund (19

Influence of Humidity on Ultraviolet Injury

High humidity enhances the injurious effect of ultraviolet radiation. This was demonstrated in experiments in which hairless mice were irradiated with Westinghouse FS-40-T-12 sunlamps while maintained in an environmental chamber allowing controlled conditions of relative humidity and temperature. Hairless mice given 10 MED (minimal erythemal dose) while maintained at 80% relative humidity had markedly greater exfoliation, crusting, and erosion of skin than did mice maintained at 5% and 10% relative humidity. Animals kept at 50% humidity had damage intermediate to those kept at high and low humidity. These morphologic observations were confirmed histologically.Additionally, water immersion enhances ultraviolet injury. Animals immersed in water for 6 hr prior to irradiation with 3 MED had more damage than animals irradiated but not immersed. Similarly, albino rabbits irradiated with 300 nm radiation from a xenon arc grating monochrometer had lower erythemal energy requirements on that part of their skin that had been hydrated with wet packs compared to nonhydrated skin

Summer 1974

The Fertilizer Fight (page 3) Ammonia Production Must Receive Top Priority (4) Back and Beyond (9) Herbicides--Are They Safe? (10) Maintenane of Poa Annua (17) A Responsible Neighbor (19) University of Massachusetts Turfgrass Research Fun (20

Fall 1972

Ecological Effects of Herbicides (3) Turf Management (6) For the Homeowner--How to Handle Those Tough Shady Spots (7) Crownvetch--One answer to Those Problem Maintenance Areas (8) Kentucky Bluegrass Variety Trails (10) Grass, an Endangered Species (15) Turf Grass Research (16) Have Times Changed? Caring for Trees on the Golf Course (1929) (19) Lime...350 Million Years in the Making (19) 1972--A Tough Season (20

Scattering map for two black holes

We study the motion of light in the gravitational field of two Schwarzschild black holes, making the approximation that they are far apart, so that the motion of light rays in the neighborhood of one black hole can be considered to be the result of the action of each black hole separately. Using this approximation, the dynamics is reduced to a 2-dimensional map, which we study both numerically and analytically. The map is found to be chaotic, with a fractal basin boundary separating the possible outcomes of the orbits (escape or falling into one of the black holes). In the limit of large separation distances, the basin boundary becomes a self-similar Cantor set, and we find that the box-counting dimension decays slowly with the separation distance, following a logarithmic decay law.Comment: 20 pages, 5 figures, uses REVTE