controlled environment may be adopted for a rapid multiplication of a large number of potato seed tubers. the controlled environment prevents seed tuber degeneration which may occur under field conditions. the objective of this study was to introduce new mini-tuber production system with high multiplication rate and low production cost. to evaluate the performance of culture systems in terms of...

October 1992 nPerils of sand production. At worst, sand production threatens a well. Voids can form behind the pipe, causing formation subsidence and casing collapse. The well may also fill with sand and cease flowing. Or the surface equipment may be catastrophically damaged by erosion or plugging. For help in preparation of this article, thanks to: Bob Elder, Chevron UK Ltd., London, England; ...

Some of the most challenging problems in geomechanics involve the coupling between fluid flow and solid deformation. In this paper we briefly present an overview of existing coupling methods to problems involving fluid flow and deformation and describe testing of a new discrete-based coupling method for problems in porous media. Modeled permeability and porosity distributions are compared to id...

Knowledge of the relationship between stocking rate or grazing intensity and plant production is fundamental to the sustainable management of rangelands. The general management paradigm is that plant production declines as stocking rate increases. Our objective was to determine the impact of stocking rate on herbaceous production of a sand sagebrush (Artemisia filifolia Torr.)grassland. Stockin...

Sod culture is one of the important methods in establishing and repairing of turf grass, especially in sport fields. Nowadays, a mixture of sand and peat are commonly used in sod production in Iran. Because peat media is expensive, it seems necessary to find an alternative medium. Rice hull, tea waste and leaf compost as economical organic material that are available in huge loads in north of I...

An increase in intracellular Ca2+ concentration ([Ca2+]) and morphological were simultaneously observed by epifluorescence and differential interference contrast (DIC) microscopy during fertilization of the sand dollar, Clypeaster japonicus. [Ca2+], which was detected by a Ca2+ indicator, Fluo-3, initially increased just beneath the sperm-attached site on the egg surface 8.6 sec after attachmen...

We summarize information concerning Recent and Pleistocene-Holocene Uruguayan sand dollars (Mellitidae), as well as Miocene taxa (Monophorasteridae). Recent and Pleistocene-Holocene species (Encope emarginata, Mellita quinquiesperforata, and Leodia sexisperforata) are at their southernmost limits of distribution, with only E. emarginata recorded further south than Uruguay. Lower temperatures to...