Diode laser 87Rb optical pumping in an evacuated wall-coated cell

The evacuated wall coated sealed cell coupled with diode laser optical pumping offers a number of attractive potential advantages for use in Rb or Cs atomic frequency standards. An investigation of systematic effects is required to explore possible limitations of the technique. The use of diode laser optical pumping of 87 Rb in an evacuated wall coated sealed cell is presented. Experimental results/discussion to be presented include the signal strength and line broadening of the 0 - 0 hyperfine resonance as a function of light intensity for the D1 optical transitions (F - F prime) - (2 1 prime) and (2 - 2 prime), shift of the 0 - 0 hyperfine frequency as a function of laser intensity and de-tuning from optical resonance, and diode laser frequency stabilization techniques

A 128K-bit CCD buffer memory system

A prototype system was implemented to demonstrate that CCD's can be applied advantageously to the problem of low power digital storage and particularly to the problem of interfacing widely varying data rates. 8K-bit CCD shift register memories were used to construct a feasibility model 128K-bit buffer memory system. Peak power dissipation during a data transfer is less than 7 W., while idle power is approximately 5.4 W. The system features automatic data input synchronization with the recirculating CCD memory block start address. Descriptions are provided of both the buffer memory system and a custom tester that was used to exercise the memory. The testing procedures and testing results are discussed. Suggestions are provided for further development with regards to the utilization of advanced versions of CCD memory devices to both simplified and expanded memory system applications

On electrons and hydrogen-bond connectivity in liquid water

The network connectivity in liquid water is revised in terms of electronic signatures of hydrogen bonds (HBs) instead of geometric criteria, in view of recent X-ray absorption studies. The analysis is based on ab initio molecular-dynamics simulations at ambient conditions. Even if instantaneous thread-like structures are observed in the electronic network, they continuously reshape in oscillations reminiscent of the r and t modes in ice (tau~170 fs). However, two water molecules initially joint by a HB remain effectively bound over many periods regardless of its electronic signature.Comment: 4 pages, 4 figure

Revisiting the Concept of the Planning Region in Settings with Dynamic Spatial-Temporal Conditions: Lessons from Land Use Planning in Pastoral Areas of Kenya, Ethiopia and Tanzania

Pastoralist rangeland systems often provide prime examples of scale mismatch—the challenge that arises when the scale and geographic extent of decision-making institutions do not correspond to the scale and geographic extent of problems that need to be addressed. Pastoralist resource use and traditional governance systems operate at multiple levels, and are often characterized by multiple, overlapping claims, rights, and management territories. Scholarship on pastoralist systems suggests that their fuzziness, flexibility, and overlap in territories and rights mean that there is no single scale or level that is optimal for effective resource governance. These characteristics stymie attempts to implement conventional land governance systems in pastoralist areas. Land use planning represents an approach to land governance with the potential to address some of the challenges of pastoral systems, but only if the challenge of scale can be addressed. Land use planning is a process that has to be applied over a set of particular—usually clearly-defined—spaces: planning units and regions. An essential step in the land use planning process is interpreting the site to delimit the planning area and determine the appropriate planning units. This paper considers the question of how to apply the concept of a planning region in land use planning in pastoral settings. Land use planning interventions that make use of simplistic delineations of planning units and planning regions run the risk of fragmenting pastoral systems and compounding scale mismatch. The paper describes how frameworks for land use planning in pastoral areas now being rolled out in three different countries in East Africa address this problem. Among the strategies adopted are explicitly planning at multiple levels with cross-level linkages, and planning with multiple, overlapping kinds of planning units

PLASIM: A computer code for simulating charge exchange plasma propagation

The propagation of the charge exchange plasma for an electrostatic ion thruster is crucial in determining the interaction of that plasma with the associated spacecraft. A model that describes this plasma and its propagation is described, together with a computer code based on this model. The structure and calling sequence of the code, named PLASIM, is described. An explanation of the program's input and output is included, together with samples of both. The code is written in ANSI Standard FORTRAN