Characterization of quantum well structures using a photocathode electron microscope

Present day integrated circuits pose a challenge to conventional electronic and mechanical test methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to facilitate electrical contact to circuits and devices being tested. In addition, microwave operating frequencies require careful attention to distributed effects when considering the electrical signal paths within and external to the device under test. An alternative testing approach which combines the best of electrical and optical time domain testing is presented, namely photocathode electron microscope quantitative voltage contrast (PEMQVC)

The Full Re-Ionization of Helium

Observations of resolved HeII Lyman alpha absorption in spectra of two QSO's suggest that the epoch of helium ionization occurred at z~3. Proximity zones in the spectra of the quasars (z=3.18, 3.285) at 304 A resemble Stromgren spheres, suggesting that the intergalactic medium is only singly ionized in helium. We present models of the proximity effect which include the full physics of the ionization, heating and cooling and an accurately simulated inhomogeneous gas distribution. In these models the underdense intergalactic medium is heated to at least 10,000-20,000 K after cooling to as low as a few 1000 K due to cosmological expansion, with higher temperatures achieved farther away from the quasar due to absorption-hardened ionizing spectra. The quasars turn on for a few times 10^7 years with a fairly steady flux output at 228 A comparable to the 304 A flux output directly observed with HST. The recoveries in the spectra occur naturally due to voids in the IGM and may provide a fairly model-independent probe of the baryon density.Comment: 5 pages, 3 figures, to appear in the proceedings of "After the Dark Ages: When Galaxies were Young (the Universe at 2<z<5)", 9th Annual October Astrophysics Conference in Marylan

Understanding European Union international message telephone services demand

This study provides a contemporary understanding of demand relations in European Union (EU) international message telephone service (IMTS) markets prior to full liberalization at January 1 1998. Point-to-point demand equations that relate IMTS demand to prices, income, population and distance are estimated on bilateral market data for ten EU countries from 1990 to 1995. Model estimates suggest price elasticities of outgoing and incoming demand between 20.175 and 20.456, and 20.215 and 20.674, respectively. These elasticity estimates provide an empirical base from which to calculate welfare gains from the full deregulation of EU IMTS markets after 1998.Elasticity; European Union; International telephone demand

Exotic Annual Plant Invasions and Their Relationships to Roads and Native Perennial Species in the Mojave Desert, Southwestern USA

For the last five years, roadside monitoring for exotic invasive species has been a common practice for documenting distributions in Clark County, Nevada (Abella et al., in press). Yet, studies have shown that weed relationships to road corridors differ depending upon the natural system (Hansen and Clevenger, 2005). In the Mojave Desert, it is unknown whether exotic species are limited to or even predominant along roadsides. Compounding this uncertainty, fertile islands under shrubs are known to enhance conditions for many annuals (Thompson et al., 2005). Thus, a site’s shrub composition could influence exotic invasive plant distributions

The Effects of Nutrition Package Claims, Nutrition Facts Panels, and Motivation to Process Nutrition Information on Consumer Product Evaluations

In a laboratory experiment using a between-subjects design, the authors examine the effects on nutrition and product evaluations of nutrition claims made (e.g., 99% fat free; low in calories ) on a product package, product nutrition value levels, and enduring motivation to process nutrition information. Enduring motivation is shown to moderate the effects of product nutrition value on consumer evaluations. Also, nutrition claims interact with product nutrition value in affecting consumer perceptions of manufacturer credibility. Given the availability of nutrient levels in the Nutrition Facts panel on the back of the mock package, nutrition claims on the front of the package generally did not affect positively consumers\u27 overall product and purchase intention evaluations. The authors discuss some implications of these findings, suggestions for further research, and study limitations

Benefit-Cost Analysis of Green Infrastructure Investments: Application to Small Urban Projects in Hinesville, GA

Small scale urban green infrastructure projects can provide local ecological services that should be accounted for in project assessment. Benefits assessment can be expensive and time consuming; benefit transfer provides an economical alternative, but the quality of the analysis depends upon available data. A best-case scenario for many applications of benefit transfer is to utilize a conforming meta-analysis. In this paper, we use the meta-analysis of Bockarjova, et al. (2020) to predict ecological benefits of small scale urban green infrastructure investments in Hinesville, GA. In doing so, we implement a censoring procedure on the benefit transfer function to permit analysis of small-scale (less than one-hectare) projects. We find evidence of substantial net economic benefits, with estimates ranging from $738,312 to over$5.5 million; positive benefit-to-cost ratios are robust to substantial cost increases (4 times the estimated costs). We provide guidance for how to apply these methods to other contexts

Implications for Management Prioritization of Exotic Annual Weed Monitoring Near Roadsides in the Eastern Mojave Desert, USA

Invasive exotic plants provide an unnatural conduit for fires in the Mojave Desert. For the last five years, roadside monitoring for exotic invasive species has been a common practice for documenting distributions in Clark County, Nevada (Abella et al., in press). Yet, studies have shown that weed relationships to road corridors differ depending upon the natural system (Hansen and Clevenger, 2005). In the Mojave Desert, it is unknown whether exotic species are limited to or even predominant along roadsides. Compounding this uncertainty, fertile islands under shrubs are known to enhance conditions for many annuals (Thompson et al., 2005). Thus, a site’s shrub composition could influence exotic invasive plant distributions

Mapping Low-Density Intergalactic Gas: a Third Helium Lyman-alpha Forest

We present a new HST/STIS spectrum of the z=3.18 quasar PKS 1935-692 and summarize the spectral features shortwards of 304A in the rest frame likely to be caused by foreground HeII Lyman-alpha absorption. In accord with previous results on two other quasars at similar redshifts, we demonstrate a correlation with the HI Lyman-alpha forest absorption, and show that much of the helium absorption is caused by a comparable quantity of more diffuse gas with Omega~0.01, that is not detected in HI. The helium ionization zone around the quasar is detected as well as a void seen in both HI and HeII. The properties of the absorption are in broad agreement with those of the other quasars and with models of the protogalactic gas distribution and ionization at this redshift.Comment: 17 pages including 5 figures. As accepted for publication in The Astronomical Journal (minor revisions