Entanglement of orbital angular momentum for the signal and idler beams in parametric down-conversion

We calculate the anticipated correlation between measurements of the orbital angular momentum of the signal and idler beams for parametric down-conversion. These calculations apply to the experiments where the orbital angular momentum state is measured by the use of computer-generated holograms. Displacement of these holograms with respect to the beam axis allows the measurement of superpositions of Laguerre—Gaussian modes. The correlations between such superposition modes of the signal and idler beams show their entanglement and could be used for Bell-type tests of nonlocality.     

“GOOD” NEIGHBORHOODS IN PORTLAND,OREGON: FOCUS ON BOTH SOCIAL AND PHYSICAL ENVIRONMENTS

ABSTRACT: We conduct an empirical investigation of the social environment of “good” neighborhoods in physical form in a model of the “compact city,” Portland, Oregon and discuss the implications for design and evaluation of policies inspired by smart growth and new urbanist movements that focus on the urban form and transportation dimensions of neighborhoods, and of housing assistance policies designed to change the economic mix in neighborhoods. We conceptualize the physical and social dimensions of the “good” neighborhood environment and develop an approach to operationalization that uses publicly available data. Our findings indicate that for the most part, Portland has been successful in creating neighborhoods at several economic scales that feature not only the connectivity, accessibility, mixed land use, and access to public transit that characterize “good” neighborhoods from a physical perspective, but also a “good” social environment indicative of strong ties and collective efficacy. However, there are signs that in the process, Portland may be creating poverty areas that lack connectivity, accessibility, and access to public transit and a mix of destinations.     

FACTORS AFFECTING THE COMPARATIVE ADVANTAGES OF SEQUENTIAL AND BATCHED DECISION MAKING

Whether to batch-process data or to randomly update files in real-time is a common design choice faced by information system analysts. A related (but different) problem is whether or not decisions should be batch processed. Though this latter problem is undoubtedly of greater managerial concern it has received less attention. This paper discusses considerations relevant to the optimal batching and timing of decisions and illustrates these by examples. A simple illustrative mathematical model of the problem is developed and optimized. This topic is of interest to MIS designers since their systems may include automated decision making and always support the decision making process.     

Electronic Sensing of Aromatic Volatiles for Quality Sorting of Blueberries

An electronic sniffer using semi-conductor gas sensors that nondestructively measured aromatic volatile gas emissions from fruit was developed to assess blueberry quality. The sniffer detected soft and damaged fruit in packaged containers at a 5% level of damage and distinguished four of five fruit ripeness classes: (1) mature-green and green-pink; (2) blue-pink; (3) blue; and (4) ripe fruit. Sniffer response increased as fruit ripened, as did total concentration of aromatic volatiles. Sniffer response correlated with berry firmness, pH, titratable acidity, and color, and detected differences among 10 cultivars, as did impact response analysis. The electronic sniffer is rapid, nondestructive and may be used to sort and quality check for presence of unripe or damaged fruit in closed packs of fresh berries.     

Maintaining Groundwater Supplies during Drought Conditions in the Brighton Area

The very low level of recharge to the chalk of the South Downs, which provide Brighton with its water supply, has meant that the groundwater levels are very low. Despite this, no restrictions have been necessary since February 1991. This is perhaps due to the instigation of public information campaigns, together with media coverage of the drought, as well as a successful programme of leakage control. This paper looks at how the growth of public water supply has been accommodated operationally while ensuring that groundwater quality is maintained. Options for the future expansion of supply, and their cost-effectiveness, are also considered.     

Strength of Pyrolytic SiC Coatings of Fuel Particles for High-Temperature Gas-Cooled Reactors

Methods for measuring the strength of a hemispherical shell were developed and applied to SiC coatings obtained from reactor fuel particles. These methods allow independent evaluation of the strengths of the inner and outer layers of the coatings. The applied loads are related to the maximum tensile stress using strain-analysis techniques. Coatings from standard SiC fuel particles have a median outer-surface strength of 620 MN m⁻² and a median inner-surface strength of 720 MN m⁻². These strengths relate only to a small region of the tested hemisphere, and statistical analysis is used to obtain strengths for complete spherical shells under internal pressure, the condition relevant to reactor performance. This procedure reduces the median working strength to 105 MN m⁻², with failure occurring preferentially from the outer surface. A second statistical analysis shows that the critical failure stress for 1 particle in 10⁴ (the reactor design requirement) is 22 MN m⁻². A fracture-mechanics analysis of strength indicates that failure occurs by the extension of inherent flaws at the surface. These flaws are associated with surface roughness. Strength was substantially improved by reducing this roughness by controlling the conditions of deposition of the coating and the topography of the underlying pyrocarbon layer. Greatly superior coatings were thus prepared; their median failure stress under internal pressure was 560 MN m⁻² and the 1-in-10⁴ failure stress 195 MN m⁻².     

Characterization and Utilization of Ocean Quahog (Arctica islandica) Clam Juice as a Liquid and Dehydrated Flavoring Agent

Ocean quahog (Arctica islandica) juice produced from mechanical shucking operations was vacuum evaporated, freeze-dried, or spray-dried for use as a natural clam flavoring agent. The flavorings were judged‘equal or superior to several commercially available flavors when used in prepared dishes. Gas chromatographic profiles indicated high volatile concentrations in the effluent from the heat shocking and first washing process. Almost no volatiles were present in successive washings. The use of dextrins was not required since the natural chloride salts of potassium and sodium aided in obtaining powders of acceptable quality.     

Migration during Convective Drying. II–Experimental

In the convective drying of a solution of C. I. Acid Red 1 from the surface of a model capillary system, the concentration of solute has been measured as a function of time and distance from the surface. Analysis of the concentration profiles has shown (i) that they are of the expected form, (ii) that back-diffusion is significant near the surface of evaporation, and (iii) that they can be approximately described by the equation— The practical significance of these observations is discussed briefly.