Viking Mars lander 1975 dynamic test model/orbiter developmental test model forced vibration test

The Viking Mars Lander 1975 dynamic test model and orbiter developmental test model were subjected to forced vibration sine tests. Flight acceptance (FA) and type approval (TA) test levels were applied to the spacecraft structure in a longitudinal test configuration using a 133,440-N (30,000-lb) force shaker. Testing in the two lateral axes (X, Y) was performed at lower levels using four 667-N (150-lb) force shakers. Forced vibration qualification (TA) test levels were successfully imposed on the spacecraft at frequencies down to 10 Hz. Measured responses showed the same character as analytical predictions, and correlation was reasonably good. Because of control system test tolerances, orbiter primary structure generally did not reach the design load limits attained in earlier static testing. A post-test examination of critical orbiter structure disclosed no apparent damage to the structure as a result of the test environment

A rapid DNA isolation procedure applicable to many refractory filamentous fungi

Filamentous fungi are notorious for their low DNA and high RNA contents as well as their rigid cell walls

The role of the cytoskeleton in biomineralisation in haptophyte algae

The production of calcium carbonate by coccolithophores (haptophytes) contributes significantly to global biogeochemical cycling. The recent identification of a silicifying haptophyte, Prymnesium neolepis, has provided new insight into the evolution of biomineralisation in this lineage. However, the cellular mechanisms of biomineralisation in both calcifying and silicifying haptophytes remain poorly understood. To look for commonalities between these two biomineralisation systems in haptophytes, we have determined the role of actin and tubulin in the formation of intracellular biomineralised scales in the coccolithophore, Coccolithus braarudii and in P. neolepis. We find that disruption of the actin network interferes with secretion of the biomineralised elements in both C. braarudii and P. neolepis. In contrast, disruption of the microtubule network does not prevent secretion of the silica scales in P. neolepis but results in production of abnormally small silica scales and also results in the increased formation of malformed coccoliths in C. braarudii. We conclude that the cytoskeleton plays a crucial role in biomineralisation in both silicifying and calcifying haptophytes. There are some important similarities in the contribution of the cytoskeleton to these different forms of biomineralisation, suggesting that common cellular mechanisms may have been recruited to perform similar roles in both lineages

Wind electric plants

The foregoing summary is based on the results from several years’ investigation of and one year’s operation,1 under test, of a wind electric plant located at this Station; and from a study2 of the performance of 66 wind electric plants on Iowa farms. The objective of these investigations was to determine as far as practicable the possibilities and limitations of the wind electric plant under Iowa farmstead conditions. The origin of the windmill is obscure. There is some evidence that it was first used in Persia during the early centuries of the Christian era.3 It came into prominent use in Europe during the twelfth century. Murphy4 gives a brief sketch of the early history of the windmill in America, and Barbour5 gives a good description of a large variety of homemade mills used in the Middlewest just following pioneer days

Rubber Tires Lead!

When farm machines are operated in the field or on the road at speeds higher than 2 1/2 to 3 miles per hour they should be equipped with rubber tires. And when these machines are pulled behind rubber-tired tractors the speed should be as high as the operating conditions and the design of the machines permit. In most cases the speed will be higher than 2 1/2 to 3 miles per hour for most efficient use

Life, service and cost of service of pneumatic tractor tires

The experience of Iowa farm users of 199 sets of pneumatic tractor tires indicates satisfactory durability and field performance. These users, selected as a representative sample, were located in 73 counties and represent the equivalent of 381 years of individual observation

Ministerial Entrepreneurship: Reenvisioning Entrepreneurship and Revitalizing the Church

This article considers the marketplace from a Christian perspective, then surveys the nature of an alternative approach to traditional bi-vocational ministry: the ministerial entrepreneur. It then suggests points of future reflection for supervisors as they guide those working as ministerial entrepreneurs as compared to those in bi-vocational ministry

Tractive efficiency of the farm tractor

1. Of the total power used in agriculture, about one-half is used for field work and one-fifth for hauling. 2. Of the total primary power used in Iowa (1930) in farm operations, tractors comprise 39.4 percent and trucks 20 percent. 3. The maximum tractive efficiency of tractors tested under various conditions varied from 40 percent for soft field conditions to 84 percent for smooth hard sod. CONCERNING STEEL TRACTOR WHEELS 4. The rolling resistance of tractors over the tractive surfaces was the principal cause for low efficiency. 5. Lugs or grousers of excessive length used to increase adhesion on a firm surface or turf may cause considerable loss in efficiency. With a wheel tractor weighing 5,620 pounds, the power required to overcome rolling resistance at a speed of 3 miles per hour varied from 2.45 horse power with drive wheels without lugs to 6.3 horse power with drive wheels equipped with 4-inch spade lugs. Because of the lugs, rolling resistance on oat stubble did not differ greatly from that on freshly plowed land. 6. On a loose soil of uniform texture, an increase in length of spade lugs from 4 to 7 inches increasingly lowered tractive efficiency. 7. On a loose soil of uniform texture, an increase in the width of the tire by use of an extension rim gave higher tractive efficiency. 8. On soil with a loose surface, but firm subsurface, a spade lug 9 inches long reaching firm soil resulted in a slightly increased efficiency over 6 and 7-inch lugs but was less than for 4 and 5-inch lugs. 9. Five-inch angle lugs mounted on a wheel 42 inches in diameter with a rim 12-inches wide gave higher tractive efficiency than spade lugs on freshly prepared loose soil. 10. Extension angle iron lugs increased tractive efficiency on loose soil materially, about one-fifth to one-fourth. 11. Angle iron lugs extending over wheel rims were advantageous on sticky soil, because the soil did not pack in between the lugs. 12. Increasing the weight from 1,750 to 2,250 pounds on a 12 x 42-inch traction wheel equipped with spade lugs increased the drawbar pull 75 to 100 pounds at maximum efficiency. The drawbar pull was increased approximately 200 pounds when the wheel was equipped with extension rims and angle lugs. 13. Angle iron lugs gave slightly better results with a 6-inch rim extension than without on freshly prepared loose soil. 14. Open type traction wheels performed practically the same as 12-inch rim wheels with lugs on firm traction surfaces of cinders or sod. The rim did not function, as the weight was carried entirely on the lugs. 15. On loose freshly prepared soil where the space between the lugs did not fill with soil, the rim wheel gave slightly higher tractive efficiency than open wheels. 16. The tractive efficiency of steel drive wheels was progressively raised by increasing the diameter from 38 to 58 inches by 4-inch increments. 17. The effect of wheel diameter is more marked on less firm traction surfaces. CONCERNING LOW PRESSURE PNEUMATIC TIRES 18. The rolling resistance of a wheel tractor. defined herewith as drawbar pull or its equivalent required to move the tractor over a given surface, was materially reduced by low pressure pneumatic tires for all conditions observed. 19. On a smooth hard surface the maximum tractive efficiency of a tractor equipped with pneumatic tires was 84 percent. 20. The maximum drawbar pull of a tractor equipped with low pressure pneumatic tires was materially reduced on stubble and loose soil. 21. The maximum drawbar pull of tractors equipped with low pressure pneumatic tires can be increased by additional weight, chains or lugs. 22. The maximum tractive efficiency was increased progressively with a decrease of inflation pressure from 20 to 16, 12 and 8 pounds per square inch. CONCERNING TRACKS 23. The tractive efficiency of a track tractor as observed is not materially influenced by normal variations of traction surfaces. 24. On freshly prepared loose soil maximum tractive efficiency of a track was lowered by increasing the height of hitch