Has Blending Compromised Cepheid-Based Determinations of the Extragalactic Distance Scale?

We examine the suggestion that half of the HST Key Project- and Sandage/Saha-observed galaxies have had their distances systematically underestimated, by 0.1-0.3 mag in the distance modulus, due to the underappreciated influence of stellar profile blending on the WFC chips. The signature of such an effect would be a systematic trend in (i) the Type Ia supernovae corrected peak luminosity and (ii) the Tully-Fisher residuals, with increasing calibrator distance, and (iii) a differential offset between PC and WFC distance moduli, within the same galaxy. The absence of a trend would be expected if blending were negligible (as has been inherently assumed in the analyses of the aforementioned teams). We adopt a functional form for the predicted influence of blending that is consistent with the models of Mochejska et al. and Stanek & Udalski, and demonstrate that the expected correlation with distance predicted by these studies is not supported by the data. We conclude that the Cepheid-based extragalactic distance scale has not been severely compromised by the neglect of blending.Comment: 14 pages, 2 figures, 1 table, LaTeX, accepted for publication in Astrophysical Journal Letters, also available at http://casa.colorado.edu/~bgibson/publications.htm

Groundwater Recharge Response to Reduced Irrigation Pumping in Western Nebraska

Given current and continued investment in irrigation scheduling technologies, a need exists to better estimate the longevity and magnitude of water savings at watershed level to avoid the paradox of irrigation efficiency. This paradox occurs within a watershed as not all irrigation inefficiencies lead to the system losing water. For example, irrigation pumping rates in excess of crop water demand may lead to enhanced groundwater recharge or surface runoff that migrates to a stream. Thus, increases in efficiency may not lead to similar magnitudes of water savings. I hypothesize that water savings longevities are short given previous work demonstrating rapid responses of groundwater recharge rates to changing surface conditions. To test this hypothesis, I used numerical modeling and hydrogeological field techniques. This work provides localized ranges of: weather, management, soil variability, depth to groundwater, and water fluxes. In chapter two, utilizing a crop modeling and numerical modeling of soil moisture redistribution, I found that irrigation practices within the study area could be reduced by 120 mm yr-1 with impact on yield less than 3% when compared to a long-term dataset of irrigation pumping rates for ~50 fields within the study area. From work in chapter three, I found that sampling locations informed via repeat hydrogeophysical surveys, required only five cores to reduce the cross-validation root mean squared error by an average of 64% as compared to soil parameters predicted by a commonly used benchmark, SSURGO and ROSETTA. This work then informed an intermediate core sampling framework in chapter four to constrain how soil hydraulic fluxes vary on subfield scale. In chapter four, I compared deep drainage outputs of a numerical model parameterized with localized measurements to a chemical tracer analysis and find agreement within 80% despite a wide range of fluxes observed (135-515mm yr-1). Scenario testing informed using the parameterized numerical model and the irrigation reduction potential from chapter two indicated that a 120mm yr-1 reduction of pumping leads to modest water savings (1-3 years; 50-200mm over 10 years). However, when applied over a number of fields, similar irrigation efficiency programs may be competitive with other water resource management programs. Adviser: Trenton E. Fran

STATUTORY ADOPTION OF THE OBJECTIVE TEST FOR ENTRAPMENT AS A SOLUTION TO DUBIOUS TACTICS IN FEDERAL TERRORISM INVESTIGATIONS

Federal investigators and their informants frequently utilize questionable tactics which resemble entrapment in terrorism investigations. Despite the use of such tactics, entrapment has universally failed as an affirmative defense in federal terrorism cases. This is largely as a result of the subjective test for entrapment employed in federal courts which does not allow for a finding of entrapment if the defendant is found to be predisposed to commit the particular offense. This is especially damning for defendants in terrorism cases as they are frequently proponents of fringe political and religious ideologies or mentally ill which easily establishes predisposition for a jury of ordinary citizens. This paper argues that, in response to the dubious tactics of federal terrorism investigators, the federal legislature should replace the subjective test with the objective test for entrapment which does not consider predisposition but considers only whether the government’s conduct created a substantial risk that an ordinary person would commit the offense

WOLVES (\u3ci\u3eCanis lupus\u3c/i\u3e)

Two species of wolves occur in North America, gray wolves (Canis lupus) and red wolves (Canis rufus). During the 1800s, gray wolves ranged over the North American continent as far south as central Mexico. Gray wolves occupy boreal forests and forest/agricultural edge communities in Minnesota, northern Wisconsin, and northern Michigan. Mech (1970) reported that gray wolves prey mainly on large animals including white-tailed deer, mule deer, moose, caribou, elk, Dall sheep, bighorn sheep, and beaver. Gray wolves are highly social, often living in packs of two to eight or more individuals. The ability of wolves to kill cattle, sheep, poultry, and other livestock is well documented (Young and Goldman 1944, Carbyn 1983, Fritts et al. 1992)

WOLVES (\u3ci\u3eCanis lupus\u3c/i\u3e)

Two species of wolves occur in North America, gray wolves (Canis lupus) and red wolves (Canis rufus). During the 1800s, gray wolves ranged over the North American continent as far south as central Mexico. Gray wolves occupy boreal forests and forest/agricultural edge communities in Minnesota, northern Wisconsin, and northern Michigan. Mech (1970) reported that gray wolves prey mainly on large animals including white-tailed deer, mule deer, moose, caribou, elk, Dall sheep, bighorn sheep, and beaver. Gray wolves are highly social, often living in packs of two to eight or more individuals. The ability of wolves to kill cattle, sheep, poultry, and other livestock is well documented (Young and Goldman 1944, Carbyn 1983, Fritts et al. 1992)

Follower Mental Models and Outstanding Leadership

Charismatic, ideological, and pragmatic (CIP) leaders use different mental models to understand and interpret the world. The present study uses this framework to gain a better understanding of how outstanding leaders interact and influence both proximal and distal followers. Participants engaged in a low-fidelity simulation, and their subsequent mental models and performance were analyzed to answer several research questions. First, how does leadership style influence creative outcomes? And second, how does leader-follower congruence of mental models relate to performance? These research questions were tested using a low-fidelity situation calling for creative problem-solving. Results indicate that leadership style does not have differential effects on follower performance but does interact with leader distance such that followers of charismatic leaders perform better with a low leader distance and followers of pragmatic leaders perform better with a higher leader distance. Lastly, mental model congruence may have some effects on the performance of followers. The implications of these findings for theory and practice are discussed

A Chandra View of the Normal SO Galaxy NGC 1332: II: Solar Abundances in the Hot Gas and Implications for SN Enrichment

We present spectral analysis of the diffuse emission in the normal, isolated, moderate-Lx S0 NGC 1332, constraining both the temperature profile and the metal abundances in the ISM. The characteristics of the point source population and the gravitating matter are discussed in two companion papers. The diffuse emission comprises hot gas, with an ~isothermal temperature profile (~0.5 keV), and emission from unresolved point-sources. In contrast with the cool cores of many groups and clusters, we find a small central temperature peak. We obtain emission-weighted abundance contraints within 20 kpc for several key elements: Fe, O, Ne, Mg and Si. The measured iron abundance (Z_Fe=1.1 in solar units; >0.53 at 99% confidence) strongly excludes the very sub-solar values often historically reported for early-type galaxies but agrees with recent observations of brighter galaxies and groups. The abundance ratios, with respect to Fe, of the other elements were also found to be ~solar, although Z_o/Z_Fe was significantly lower (<0.4). Such a low O abundance is not predicted by simple models of ISM enrichment by Type Ia and Type II supernovae, and may indicate a significant contribution from primordial hypernovae. Revisiting Chandra observations of the moderate-Lx, isolated elliptical NGC 720, we obtain similar abundance constraints. Adopting standard SNIa and SNII metal yields, our abundance ratio constraints imply 73+/-5% and 85+/-6% of the Fe enrichment in NGC 1332 and NGC 720, respectively, arises from SNIa. Although these results are sensitive to the considerable systematic uncertainty in the SNe yields, they are in good agreement with observations of more massive systems. These two moderate-Lx early-type galaxies reveal a consistent pattern of metal enrichment from cluster scales to moderate Lx/Lb galaxies. (abridged)Comment: 12 pages, 4 figures, accepted for publication in ApJ. Minor changes to match published versio

Ecophysiological Observations on Lane Mountain Milkvetch, Astragalus Jaegerianus (Fabaceae), a Proposed Endangered Species of the Mojave Desert

Astragalus jaegerianus, the Lane Mountain milkvetch, a perennial herbaceous legume, is a rare and very narrow endemic of the central Mojave Desert in San Bernardino County, California, and currently proposed to be listed as an endangered species. This herb grows in the protection of low shrubs. Anatomical observations revealed that leaflets are amphistomatic and have isolateral mesophyll, typical of full-sun desert leaves, and the green stem is an important photosynthetic organ, having abundant stomata and a cylinder of cortical chlore nchyma. Ecophysiological studies showed that this species requires high PFD (1400-1500 μmol m-2s-1) to achieve maximum photosynthetic rates and, therefore, is probably not utilizing the nurse shrub for shade but, instead, as a trellis for upper shoots to intercept high PFD. A study of δ15N indicated that this legume is a nitrogen fixer, with higher tissue nitrogen content than other associated species (3.1% versus 1.8%). The herb-shrub association is speculated to be mutualistic, in that the shrub may benefit from higher soil nitrogen when it grows with a nitrogen-fixing legume, and A. jaegerianus likely uses the nurse shrub for protection from herbivores

Biotic Regulation of CO2 Uptake–Climate Responses: Links to Vegetation Properties

Identifying the plant traits and patterns of trait distribution in communities that are responsible for biotic regulation of CO2 uptake–climate responses remains a priority for modeling terrestrial C dynamics. We used remotely sensed estimates of gross primary productivity (GPP) from plots planted to different combinations of perennial grassland species in order to determine links between traits and GPP–climate relationships. Climatic variables explained about 50% of the variance in temporal trends in GPP despite large variation in CO2 uptake among seasons, years, and plots of differing composition. GPP was highly correlated with contemporary changes in net radiation (Rn) and precipitation deficit (potential evapotranspiration minus precipitation) but was negatively correlated with precipitation summed over 210 days prior to flux measurements. Plots differed in GPP–Rn and GPP–water (deficit, precipitation) relationships. Accounting for differences in GPP–climate relationships explained an additional 11% of variance in GPP. Plot differences in GPP–Rn and GPP–precipitation slopes were linked to differences in community-level light-use efficiency (GEE*). Plot differences in GPP–deficit slopes were linked to differences in a species abundance-weighted index of specific leaf area (SLA). GEE* and weighted SLA represent vegetation properties that may regulate how CO2 uptake responds to climatic variation in grasslands