Evaluating regional patterns in nitrate sources to watersheds in National Parks of the Rocky Mountains using nitrate isotopes

In the Rocky Mountains, there is uncertainty about the source areas and emission types that contribute to nitrate (NO3) deposition, which can adversely affect sensitive aquatic habitats of high-elevation watersheds. Regional patterns in NO3 deposition sources were evaluated using NO3 isotopes in five National Parks, including 37 lakes and 7 precipitation sites. Results indicate that lake NO3 ranged from detection limit to 38 microeq/L, delta18O (NO3) ranged from -5.7 to +21.3% per thousand, and delta15N (NO3) ranged from -6.6 to +4.6 per thousand. delta18O (NO3) in precipitation ranged from +71 to +78% per thousand. delta15N (NO3) in precipitation and lakes overlap; however, delta15N (NO3) in precipitation is more depleted than delta15N (NO3) in lakes, ranging from -5.5 to -2.0 per thousand. delta15N (NO3) values are significantly related (p < 0.05) to wet deposition of inorganic N, sulfate, and acidity, suggesting that spatial variability of delta15N (NO3) over the Rocky Mountains may be related to source areas of these solutes. Regional patterns show that NO3 and delta15N (NO3) are more enriched in lakes and precipitation from the southern Rockies and at higher elevations compared to the northern Rockies. The correspondence of high NO3 and enriched delta15N (NO3) in precipitation with high NO3 and enriched delta15N (NO3) in lakes, suggests that deposition of inorganic N in wetfall may affect the amount of NO3 in lakes through a combination of direct and indirect processes such as enhanced nitrification.     

Eutectic Gallium‐Indium (EGaIn): A Liquid Metal Alloy for the Formation of Stable Structures in Microchannels at Room Temperature

This paper describes the rheological behavior of the liquid metal eutectic gallium‐indium (EGaIn) as it is injected into microfluidic channels to form stable microstructures of liquid metal. EGaIn is well‐ ;suited for this application because of its rheological properties at room temperature: it behaves like an elastic material until it experiences a critical surface stress, at which point it yields and flows readily. These properties allow EGaIn to fill microchannels rapidly when sufficient pressure is applied to the inlet of the channels, yet maintain structural stability within the channels once ambient pressure is restored. Experiments conducted in microfluidic channels, and in a parallel‐plate rheometer, suggest that EGaIn's behavior is dictated by the properties of its surface (predominantly gallium oxide, as determined by Auger measurement s); these two experiments both yield approximately the same number for the critical surface stress required to induce EGaIn to flow (～0 .5 N/m). This analysis–which shows that the pressure that must be exceeded for EGaIn to flow through a microchannel is inversely proportional to the critical (i.e., smallest) dimension of the channel–is useful to guide future fabrication of microfluidic channels to mold EGaIn into functional microstructures.     

Economics of compressed air energy storage to integrate wind power: A case study in ERCOT

Compressed air energy storage (CAES) could be paired with a wind farm to provide firm, dispatchable baseload power, or serve as a peaking plant and capture upswings in electricity prices. We present a firm-level engineering-economic analysis of a wind/CAES system with a wind farm in central Texas, load in either Dallas or Houston, and a CAES plant whose location is profit-optimized. With 2008 hourly prices and load in Houston, the economically optimal CAES expander capacity is unrealistically large – 24 GW – and dispatches for only a few hours per week when prices are highest; a price cap and capacity payment likewise results in a large (17 GW) profit-maximizing CAES expander. Under all other scenarios considered the CAES plant is unprofitable. Using 2008 data, a baseload wind/CAES system is less profitable than a natural gas combined cycle (NGCC) plant at carbon prices less than $56/tCO₂ ($15/MMBTU gas) to $230/tCO₂ ($5/MMBTU gas). Entering regulation markets raises profit only slightly. Social benefits of CAES paired with wind include avoided construction of new generation capacity, improved air quality during peak times, and increased economic surplus, but may not outweigh the private cost of the CAES system nor justify a subsidy.     

Randomized controlled trial of a family cognitive-behavioral preventive intervention for children of depressed parents.

A family cognitive-behavioral preventive intervention for parents with a history of depression and their 9–15-year-old children was compared with a self-study written information condition in a randomized clinical trial (n = 111 families). Outcomes were assessed at postintervention (2 months), after completion of 4 monthly booster sessions (6 months), and at 12-month follow-up. Children were assessed by child reports on depressive symptoms, internalizing problems, and externalizing problems; by parent reports on internalizing and externalizing problems; and by child and parent reports on a standardized diagnostic interview. Parent depressive symptoms and parent episodes of major depression also were assessed. Evidence emerged for significant differences favoring the family group intervention on both child and parent outcomes; strongest effects for child outcomes were found at the 12-month assessment with medium effect sizes on most measures. Implications for the prevention of adverse outcomes in children of depressed parents are highlighted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The variability of interconnected wind plants

We present the first frequency-dependent analyses of the geographic smoothing of wind power’s variability, analyzing the interconnected measured output of 20 wind plants in Texas. Reductions in variability occur at frequencies corresponding to times shorter than ∼24 h and are quantified by measuring the departure from a Kolmogorov spectrum. At a frequency of 2.8×10⁻⁴ Hz (corresponding to 1 h), an 87% reduction of the variability of a single wind plant is obtained by interconnecting 4 wind plants. Interconnecting the remaining 16 wind plants produces only an additional 8% reduction. We use step change analyses and correlation coefficients to compare our results with previous studies, finding that wind power ramps up faster than it ramps down for each of the step change intervals analyzed and that correlation between the power output of wind plants 200 km away is half that of co-located wind plants. To examine variability at very low frequencies, we estimate yearly wind energy production in the Great Plains region of the United States from automated wind observations at airports covering 36 years. The estimated wind power has significant inter-annual variability and the severity of wind drought years is estimated to be about half that observed nationally for hydroelectric power.     

Nicotine deprivation and trait impulsivity affect smokers' performance on cognitive tasks of inhibition and attention.

Increased nicotine deprivation and impulsivity have been associated with relapse but the degree to which they together influence cognitive processing has not been explored. We examined the effects of increasing levels of nicotine deprivation on cognitive processing, and assessed the relationship of trait impulsivity with these effects in daily smokers (n = 30). Using a within-subject design with three deprivation conditions (nondeprived, 5-hr, 17-hr), volunteers completed the Conners' Continuous Performance Task-II and the Cued Go/No-Go Task. Trait impulsivity was assessed at intake with the Barratt Impulsiveness Scale (Patton et al., 1995). Mixed-model regression analyses revealed deprivation slowed reaction time, increased errors, increased variability in responding, and increased failures of inhibitory control. Performance at 17 hours of deprivation was most likely to be affected. Significant deprivation and impulsivity interactions indicated impulsiveness was negatively correlated with deprivation-associated performance decrements. Less impulsive smokers were more affected by deprivation, demonstrating greater impairment. Research is needed to understand mechanisms by which impulsivity confers greater risk for relapse. Our results suggest deprivation may not increase relapse risk among impulsive smokers by increasing impairment of cognitive processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual kin recognition in nonhuman primates: (Pan troglodytes and Macaca mulatta): Inbreeding avoidance or male distinctiveness?

Faces provide important information about identity, age, and even kinship. A previous study in chimpanzees reported greater similarity between the faces of mothers and sons compared with mothers and daughters, or unrelated individuals. This was interpreted as an inbreeding avoidance mechanism where females, the dispersing gender, should avoid mating with any male that resembles their mother. Alternatively, male faces may be more distinctive than female faces, biasing attention toward males. To test these hypotheses, chimpanzees and rhesus monkeys matched conspecifics' faces of unfamiliar mothers and fathers with their sons and daughters. Results showed no evidence of male distinctiveness, rather a cross-gender effect was found: chimpanzees were better matching moms with sons and fathers with daughters. Rhesus monkeys, however, showed an overwhelming bias toward male-distinctiveness. They were faster to learn male faces, performed better on father–offspring and parent–son trials, and were best matching fathers with sons. This suggests that for the rhesus monkey, inbreeding avoidance involves something other than facial phenotypic matching but that among chimpanzees, the visual recognition of facial similarities may play an important role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some physical drivers of changes in the winter storm tracks over the North Atlantic and Mediterranean during the Holocene

The winter climate of Europe and the Mediterranean is dominated by the weather systems of the mid-latitude storm tracks. The behaviour of the storm tracks is highly variable, particularly in the eastern North Atlantic, and has a profound impact on the hydroclimate of the Mediterranean region. A deeper understanding of the storm tracks and the factors that drive them is therefore crucial for interpreting past changes in Mediterranean climate and the civilizations it has supported over the last 12?000 years (broadly the Holocene period). This paper presents a discussion of how changes in climate forcing (e.g. orbital variations, greenhouse gases, ice sheet cover) may have impacted on the 'basic ingredients' controlling the mid-latitude storm tracks over the North Atlantic and the Mediterranean on intermillennial time scales. Idealized simulations using the HadAM3 atmospheric general circulation model (GCM) are used to explore the basic processes, while a series of timeslice simulations from a similar atmospheric GCM coupled to a thermodynamic slab ocean (HadSM3) are examined to identify the impact these drivers have on the storm track during the Holocene. The results suggest that the North Atlantic storm track has moved northward and strengthened with time since the Early to Mid-Holocene. In contrast, the Mediterranean storm track may have weakened over the same period. It is, however, emphasized that much remains still to be understood about the evolution of the North Atlantic and Mediterranean storm tracks during the Holocene period.