Evolution of displacements and strains in sheared amorphous solids

The local deformation of two-dimensional Lennard-Jones glasses under imposed shear strain is studied via computer simulations. Both the mean squared displacement and mean squared strain rise linearly with the length of the strain interval $\Delta \gamma$ over which they are measured. However, the increase in displacement does not represent single-particle diffusion. There are long-range spatial correlations in displacement associated with slip lines with an amplitude of order the particle size. Strong dependence on system size is also observed. The probability distributions of displacement and strain are very different. For small $\Delta \gamma$ the distribution of displacement has a plateau followed by an exponential tail. The distribution becomes Gaussian as $\Delta \gamma$ increases to about .03. The strain distributions consist of sharp central peaks associated with elastic regions, and long exponential tails associated with plastic regions. The latter persist to the largest $\Delta \gamma$ studied.Comment: Submitted to J. Phys. Cond. Mat. special volume for PITP Conference on Mechanical Behavior of Glassy Materials. 16 Pages, 8 figure

Radiation-Driven Warping: The Origin of Warps and Precession in Accretion Disks

A geometrically thin, optically thick, warped accretion disk with a central source of luminosity is subject to non-axisymmetric forces due to radiation pressure; the resulting torque acts to modify the warp. In a recent paper, \cite{pri96} used a local analysis to show that initially planar accretion disks are unstable to warping driven by radiation torque. Here we extend this work with a global analysis of the stable and unstable modes. We confirm Pringle's conclusion that thin centrally-illuminated accretion disks are generically unstable to warping via this mechanism; we discuss the time-evolution and likely steady-state of such systems and show specifically that this mechanism can explain the warping of the disk of water masers in NGC 4258 and the 164-day precession period of the accretion disk in SS 433. Radiation-driven warping and precession provides a robust mechanism for producing warped, precessing accretion disks in active galactic nuclei and X-ray binary systems.Comment: 16 pages, latex, 3 figure

The Use of Algal Cultures in Experiments Concerned with Water Supply Problems

Rapid and routine methods for isolating and culturing algae are essential for laboratory studies of those algae which create problems in water supplies and for the development of methods for their control. Just as the bacteriologist must isolate the bacteria in order to study their actions under various conditions, so too, the applied phycologist must now follow essentially the same procedure with the algae. Matheson has emphasized this need in his recent report to the 1952 Congress of the International Water Supply Association

The Use and Legal Significance of the Mean High Water Line in Coastal Boundary Mapping

The effect of unplanned and ill-conceived land use development on the coastal ecology has been well documented in recent years. Recognizing the need for more effective governmental control in this area, a number of state legislatures have enacted statutes to protect the coastal environment and encourage the orderly development of coastal resources. These efforts have received the support of the federal government as well. Determination of coastal boundaries is essential to the development of an effective coastal zone management program. In general such boundaries represent the intersection of the shore with a particular tidal elevation. However, the demarcation of coastal boundaries is complicated by legal uncertainties. Moreover, the unavailability of accurate tidal data or the use of improper survey methods make the accurate location of the physical boundary line a difficult task in many cases. This article will examine a number of physical and legal problems associated with coastal boundary determinations and offer some solutions within the framework of the legislative proposal which accompanies this discussion

The Use and Legal Significance of the Mean High Water Line in Coastal Boundary Mapping

The effect of unplanned and ill-conceived land use development on the coastal ecology has been well documented in recent years. Recognizing the need for more effective governmental control in this area, a number of state legislatures have enacted statutes to protect the coastal environment and encourage the orderly development of coastal resources. These efforts have received the support of the federal government as well. Determination of coastal boundaries is essential to the development of an effective coastal zone management program. In general such boundaries represent the intersection of the shore with a particular tidal elevation. However, the demarcation of coastal boundaries is complicated by legal uncertainties. Moreover, the unavailability of accurate tidal data or the use of improper survey methods make the accurate location of the physical boundary line a difficult task in many cases. This article will examine a number of physical and legal problems associated with coastal boundary determinations and offer some solutions within the framework of the legislative proposal which accompanies this discussion

Administering State Water Resources: The Need for Long-Range Planning

Drastically increased demands upon the nation\u27s water resources are predicted in the coming years as a result of population growth, increased per capita use of water, and the progressive concentration of the population in urban areas. One solution to the water shortage problem is to obtain water from new sources. The boldest and most ambitious proposal is the North American Water and Power Alliance (NAWAPA). This project would result in the damming of various rivers in Alaska and the Canadian Yukon, and transporting the waters of these rivers into a largely man-made five hundred mile long reservoir along the Rocky Mountain Trench. This would involve construction of a series of connecting tunnels, canals, lakes, dams, and lifts. An estimated 70 million to 150 million kilowatts of electric power would also be generated. NAWAPA would provide water to seven provinces of Canada, thirty-three of the United States and to three northern states of Mexico. In all, 110 million acre-feet of water would flow through the system each year with the maximum potential estimated at 250 million acre-feet or about 36 trillion gallons per year. Even if the NAWAPA project is successfully completed, however, additional measures toward more efficient management of water resources must be implemented at all levels of government. This will require a determination of needs and capabilities, and the formulation of long-range plans for the development of all water resources and related land resources within a hydrologic unit. Regulating streams flow, improving water quality, increasing the efficiency of water use, expanding the use of underground storage, and increasing the available water supply by such measures as desalinization, weather modification, and reduction of evaporation losses must be considered in such planning

Water Quality Control: A Modern Approach to State Regulation

The American public of late has shown increasing concern over the quality of the environment. Water pollution has long been recognized as a major threat to a better environment. Municipal, industrial, and agricultural operations all contribute to the pollution problem. Municipalities empty millions of gallons of inadequately-treated sewage into the nation\u27s rivers and streams. Municipal wastes are almost exclusively organic in nature. Currently municipal wastes are estimated to average about ten million tons annually while industrial pollution averages approximately fifteen million tons. Treatment in general is technologically feasible; the primary impediment is financial inability on the part of municipalities to initiate effective abatement measures. Industrial pollution, both organic and inorganic, involves even greater volumes of effluent than municipal operations. The situation is aggravated by the fact that treatment for inorganic industrial wastes is generally more complex and costly than the processes available for treatment of organic matter. Agriculture contributes to the impairment of water quality through confinement livestock feeding operations and the use of chemical fertilizers, pesticides and herbicides. A Model Water Code has been drafted at the University of Florida in an attempt to provide a vehicle for comprehensive state regulation of water resources. The Code consists of six chapters. The first creates a two-tiered administrative system comprised of a State Water Resources Board and a number of regional water management districts administered by governing boards. This chapter also provides for a comprehensive state water plan while chapter two establishes a permit system for the regulation of consumptive uses of water. Chapter three provides for well construction standards and the licensing of the well drilling industry. Chapter four governs the construction of dams, impoundments and appurtenant works. Chapter five is concerned with water quality. Some of the prominent features of this portion of the Code are a water quality plan and the water quality standards contained therein; construction permits for new outlets, disposal systems and treatment works; discharge permits; and the various enforcement powers available to both the state and local agencies. Chapter six is an optional chapter on weather modification. This article introduces chapter five of the proposed Model Water Code as a basis for a state program of water quality control. Although the authors have designed it as part of an overall scheme for the regulation of water use and quality under a comprehensive state water plan, this chapter can be treated in many respects as a self-contained unit and it is on this basis that chapter five is offered in this form