Structure and Composition of Tree Islands and Krummholz within the Forest-Tundra Ecotone in Central and Eastern Canada

The forest-tundra ecotone is expected to experience some of the initial effects of climate change. At the forefront of this transition zone, we find clonal growth forms of stunted and deformed trees with and without taller erect trees, called tree islands and krummholz, respectively. We sought to assess the potential effects of expansion of these clonal growth forms on tundra plant species at two Canadian locations, one in the Mealy Mountains of Labrador and the other near Churchill, Manitoba. Our objectives were 1) to analyze the structure (height distribution and shape) of these clonal growth forms to determine whether they are expanding; 2) to compare tree cover on the leeward and windward sides of clonal growths and 3) to assess patterns in individual plant species across these growth forms. Cover of trees and other plant species was measured at both locations, while tree stems were mapped near Churchill only. The presence of seedlings and symmetric patterns of tree height suggest that half of the tree islands near Churchill may be expanding. The edges of tree islands and krummholz may harbour safe sites for tundra plant species, as shown by peaks in cover of individual species at these edges. Our results suggest that expansion of tree islands and krummholz would affect the abundance of tundra plant species, which could lead to changes in species composition and biodiversity.On s’attend à ce que l’écotone de la toundra forestière subisse dans une certaine mesure les premiers effets du changement climatique. À l’avant-plan de cette zone de transition se trouvent des formes de croissance clonales d’arbres rabougris et difformes parfois assortis ou non assortis de plus grands arbres dressés, ce que l’on appelle des îlots boisés et des krummholz, respectivement. Nous avons cherché à évaluer les effets potentiels de l’expansion de ces formes de croissance clonales sur les espèces végétales de la toundra à deux emplacements situés au Canada, un aux monts Mealy du Labrador et l’autre près de Churchill, au Manitoba. Nos objectifs étaient les suivants : 1) analyser la structure (répartition des hauteurs et formes) de ces formes de croissance clonales afin de déterminer si elles prennent de l’expansion; 2) comparer la couverture arborescente en aval et en amont des croissances clonales; et 3) évaluer les modèles se dessinant chez les diverses espèces végétales individuelles au sein de ces formes de croissance. Les couvertures arborescentes et d’autres espèces végétales ont été mesurées aux deux endroits, tandis que les tiges d’arbres n’ont été relevées qu’à l’emplacement de Churchill. La présence de semis et de modèles symétriques en ce qui a trait à la hauteur des arbres suggère que la moitié des îlots boisés près de Churchill pourraient être en expansion. Le bord des îlots boisés et des krummholz pourrait constituer des lieux sûrs pour les espèces végétales de la toundra, comme l’indiquent les crêtes caractérisant la couverture des espèces individuelles situées en bordure. Nos résultats laissent entendre que l’expansion des îlots boisés et des krummholz aurait des incidences sur l’abondance des espèces végétales de la toundra, ce qui pourrait entraîner des changements sur le plan de la composition et de la biodiversité des espèces

Inverted Echo Sounder Data Processing Report

The Inverted Echo Sounder (IES) is an instrument that acoustically monitors the depth of the main thermocline from a moored position one meter above the ocean floor. Additionally, the IESs can be equipped to measure both pressure and temperature. The standard steps for processing IES data are documented here. The effect and purpose of each step are discussed followed by a description of how to apply the computer programs that constitute the step. The FORTRAN and MATLAB codes are also supplied

Double layer charging driven carbon dioxide adsorption limits the rate of electrochemical carbon dioxide reduction on Gold.

Electrochemical CO[Formula: see text] reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO[Formula: see text] reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO[Formula: see text] adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO[Formula: see text] adsorption at intermediate ones, and CO[Formula: see text] mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO[Formula: see text] and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport

A Future with Fusion

The world's energy resources are facing depletion. The resources which are presently used in energy production are nonrenewable and therefore, are increasing in price as they become more scarce. As a result of the increasing expense, these materials are becoming economically less attractive. This necessitates a change in technology which will enable energy production from alternative resources. Nuclear fusion is currently undergoing research as a possible solution to the world's growing demand for electricity. In order to determine if fusion power is feasible, the economic efficiency as well as the technical efficiency must be compared with that of conventional resources. This comparison will involve such factors as spillover costs, construction and fuel costs, thermal efficiencies and availability

Effects of airgun discharges used in seismic surveys on development and mortality in nauplii of the copepod Acartia tonsa

Seismic surveys are conducted worldwide to explore for oil and gas deposits and to map subsea formations. The airguns used in these surveys emit low-frequency sound waves. Studies on zooplankton responses to airguns report a range of effects, from none to substantial mortality. A field experiment was conducted to assess mortality and naupliar body length of the calanoid copepod Acartia tonsa when exposed to the discharge of two 40-inch airguns. Nauplii were placed in plastic bags and attached to a line at a depth of 6 m. For each treatment, three bags of nauplii were exposed to one of three treatments for 2.5 h: Airgun array discharge, a boat control, or a silent control. After exposure, nauplii were kept in filtered seawater in the laboratory without food. Immediate mortality in the nauplii was approximately 14% compared to less than 4% in the silent and boat control. Similarly, there was higher mortality in the airgun exposed nauplii up to six days after exposure compared to the control treatments. Nearly all of the airgun exposed nauplii were dead after four days, while >50% of the nauplii in the control treatments were alive at six days post-exposure. There was an interaction between treatment and time on naupliar body length, indicating lower growth in the nauplii exposed to the airgun discharge (growth rates after 4 days: 1.7, 5.4, and 6.1 μm d−1 in the airgun exposed, silent control, and boat control, respectively). These experiments indicate that the output of two small airguns affected mortality and growth of the naupliar stages of Acartia tonsa in close vicinity to the array.publishedVersio

Testing And Data Recovery Excavations At The Jayroe Site (41HM51), Hamilton County, Texas

In 2003–2004, Prewitt and Associates, Inc., performed National Register of Historic Places testing and subsequent data recovery excavations at the Jayroe site (41HM51) in Hamilton County for the Texas Department of Transportation, Environmental Affairs Division, under Texas Antiquities Permit Nos. 3211 and 3405. The investigations were prompted by the planned replacement of the County Road 294 bridge at the Leon River (CSJ No. 0909-29-030), in compliance with Section 106 of the National Historic Preservation Act and its implementing regulations (36 CFR Part 800) and the Antiquities Code of Texas. Testing consisted of the excavation of 6 backhoe trenches and 19 test units, and the data recovery work consisted mainly of hand excavation of 153 contiguous 1x1-m units within a single block, with 2 backhoe trenches and 2 manual units apart from the block excavation. Combined, the testing and data recovery identified 16 cultural features interpreted as 3 open hearths, 4 shallow earth ovens or surface hearths, 8 scatters of various kinds of debris, and 1 knapping station. The excavations recovered 322 chipped stone tools, 26 cores, 6,589 pieces of unmodified debitage, 21 ground or battered stone tools, 38 potential pigment sources, 43 ceramic sherds, 15 modified bone artifacts, 7,649 animal bones, 1,200 mussel shells, and macrobotanical remains. Four analytical units are defined for the site, only one of which—the Toyah phase component— has much interpretive potential. It is interpreted as a campsite used at least several times, mostly in the a.d. 1470s, at which butchering of mostly bison and deer, late-stage lithic tool manufacture and repair, and other maintenance tasks figured prominently in the site activities. The artifacts recovered and records generated by the project are curated at the Center for Archaeological Studies, Texas State University

Associations between Health Effects and Particulate Matter and Black Carbon in Subjects with Respiratory Disease

We measured fractional exhaled nitric oxide (FE(NO)), spirometry, blood pressure, oxygen saturation of the blood (SaO(2)), and pulse rate in 16 older subjects with asthma or chronic obstructive pulmonary disease (COPD) in Seattle, Washington. Data were collected daily for 12 days. We simultaneously collected PM(10) and PM(2.5) (particulate matter ≤10 μm or ≤2.5 μm, respectively) filter samples at a central outdoor site, as well as outside and inside the subjects’ homes. Personal PM(10) filter samples were also collected. All filters were analyzed for mass and light absorbance. We analyzed within-subject associations between health outcomes and air pollution metrics using a linear mixed-effects model with random intercept, controlling for age, ambient relative humidity, and ambient temperature. For the 7 subjects with asthma, a 10 μg/m(3) increase in 24-hr average outdoor PM(10) and PM(2.5) was associated with a 5.9 [95% confidence interval (CI), 2.9–8.9] and 4.2 ppb (95% CI, 1.3–7.1) increase in FE(NO), respectively. A 1 μg/m(3) increase in outdoor, indoor, and personal black carbon (BC) was associated with increases in FE(NO) of 2.3 ppb (95% CI, 1.1–3.6), 4.0 ppb (95% CI, 2.0–5.9), and 1.2 ppb (95% CI, 0.2–2.2), respectively. No significant association was found between PM or BC measures and changes in spirometry, blood pressure, pulse rate, or SaO(2) in these subjects. Results from this study indicate that FE(NO) may be a more sensitive marker of PM exposure than traditional health outcomes and that particle-associated BC is useful for examining associations between primary combustion constituents of PM and health outcomes

Learning hand in hand: Engaging in research-practice partnerships to advance developmental science.

Developmental science research often involves research questions developed by academic teams, which are tested within community or educational settings. In this piece, we outline the importance of research-practice partnerships, which involve both research and practice-based partners collaborating at each stage of the research process. We articulate challenges and benefits of these partnerships for developmental science research, identify relevant research frameworks that may inform these partnerships, and provide an example of an ongoing research-practice partnership

Interest and learning in informal science learning sites: Differences in experiences with different types of educators.

This study explored topic interest, perceived learning and actual recall of exhibit content in 979 children and adolescents and 1,184 adults who visited informal science learning sites and interacted with an adult or youth educator or just the exhibit itself as part of family visits to the sites. Children in early childhood reported greater topic interest and perceived learning, but actually recalled less content, than participants in middle childhood or adolescence. Youth visitors reported greater interest after interacting with a youth educator than just the exhibit, and perceived that they learn more if they interact with an educator (youth or adult). Participants in middle childhood recall more when they encounter a youth educator. Adult visitors reported greater interest after interaction with a youth educator than with the exhibit alone or an adult educator. They also perceived that they learn more if they interact with an educator (youth or adult) than just the exhibit and perceived that they learned more if they interacted with a youth educator than an adult educator. Results highlight the benefits of educators in informal science learning sites and document the importance of attention to developmental needs