ALBERT

Description: Circumpolar expansion of tall shrubs and trees into Arctic tundra is widely thought to be occurring as a result of recent climate warming, but little quantitative evidence exists for northern Siberia, which encompasses the world's largest forest-tundra ecotonal belt. We quantified changes in tall shrub and tree canopy cover in eleven, widely-distributed Siberian ecotonal landscapes by comparing very-high-resolution photography from the Cold War-era “Gambit” and “Corona” satellite surveillance systems (1965-1969) with modern imagery. We also analyzed within-landscape patterns of vegetation change to evaluate the susceptibility of different landscape components to tall shrub and tree increase. The total cover of tall shrubs and trees increased in nine of eleven ecotones. In northwest Siberia, alder ( Alnus ) shrubland cover increased 5.3 – 25.9% in five ecotones. In Taymyr and Yakutia, larch ( Larix ) cover increased 3.0 – 6.7% within three ecotones, but declined 16.8% at a fourth ecotone due to thaw of ice-rich permafrost. In Chukotka, the total cover of alder and dwarf pine ( Pinus ) increased 6.1% within one ecotone and was little-changed at a second ecotone. Within most landscapes, shrub and tree increase was linked to specific geomorphic settings, especially those with active disturbance regimes such as permafrost patterned-ground, floodplains, and colluvial hillslopes. Mean summer temperatures increased at most ecotones since the mid-1960s, but rates of shrub and tree canopy cover expansion were not strongly correlated with temperature trends and were better correlated with mean annual precipitation. We conclude that shrub and tree cover is increasing in tundra ecotones across most of northern Siberia, but rates of increase vary widely regionally and at the landscape-scale. Our results indicate that extensive changes can occur within decades in moist, shrub-dominated ecotones, as in northwest Siberia, while changes are likely to occur much more slowly in the highly continental, larch-dominated ecotones of central and eastern Siberia. This article is protected by copyright. All rights reserved.

Description: Growing season soil CO2 efflux is known to vary laterally by as much as seven fold within small subalpine watersheds (

Description: ABSTRACT Small patterned-ground features (PGFs) in the Arctic have unique soil properties that vary with latitude and may greatly affect tundra biogeochemistry. Because nitrogen availability can strongly limit arctic vegetation growth, we examined how soil nitrogen transformations differ between PGFs and the surrounding inter-PGF tundra along an arctic latitudinal gradient. We collected soils at eight sites from the Alaskan Low Arctic to the Canadian High Arctic. The soils were incubated for 21 days at 9 °C and 15 °C and analysed for changes in total inorganic nitrogen, nitrate and extractable organic nitrogen (EON). We found greater nitrogen immobilisation in the surrounding inter-PGF soils than in the PGF soils. Along the latitudinal gradient, differences in net nitrogen mineralisation and EON cycling between PGF and inter-PGF soils were strongly influenced by the presence of a pH boundary within the Low Arctic and the transition between the High and Low Arctic, with greater immobilisation in the nonacidic and Low Arctic sites, respectively. Incubation temperature affected EON flux but did not affect net nitrogen mineralisation or nitrification. These results show that spatial heterogeneity at several scales can influence soil nitrogen dynamics, and is therefore an important influence on arctic ecosystem function. Copyright © 2012 John Wiley & Sons, Ltd.

Description: The destruction of the Fukushima Daiichi Nuclear Power Plant (NPP) following the March 2011 Tohoku earthquake and tsunami brought into sharp focus the susceptibility of NPPs to natural hazards. This is not a new issue—seismic hazard has affected the development of plants in the United States, and volcanic hazard was among the reasons for not commissioning the Bataan NPP in the Philippines [ Connor et al ., 2009].

Description: Research on the terrestrial C balance focuses largely on measuring and predicting responses of ecosystem-scale production and respiration to changing temperatures and hydrologic regimes. However, landscape morphology can modify the availability of resources from year to year by imposing physical gradients that redistribute soil water and other biophysical variables within ecosystems. This paper demonstrates that the well-established biophysical relationship between soil respiration and soil moisture interacts with topographic structure to create bidirectional (i.e., opposite) responses of soil respiration to soil water availability within the landscape. Based on soil respiration measurements taken at a subalpine forest in central Montana, we found that locations with high drainage areas (i.e., lowlands and wet areas of the forest) had higher cumulative soil respiration in dry years, whereas locations with low drainage areas (i.e., uplands and dry areas of the forest) had higher cumulative soil respiration in wet years. Our results indicate that for 80.9% of the forest soil respiration is likely to increase during wet years, whereas for 19.1% of the forest soil respiration is likely to decrease under the same hydrologic conditions. This emergent, bidirectional behavior is generated from the interaction of three relatively simple elements (parabolic soil biophysics, the relative distribution of landscape positions, and inter-annual climate variability), indicating that terrain complexity is an important mediator of the landscape-scale soil C response to climate. These results highlight that evaluating and predicting ecosystem-scale soil C response to climate fluctuation requires detailed characterization of biophysical-topographic interactions in addition to biophysical-climate interactions.

Description: We present analytical closed-form expressions for the radiation patterns of 2D line sources and 3D point dipoles embedded in a general multi-layered configuration. While the former are simplified model sources, used as a preliminary analytical step toreduce derivation complexity, the latter have been shown experimentally to reproduce the electromagnetic behaviour of many elementary statistical sources. By decomposing the sources to current elements generating pure transverse electric (TE) or transverse magnetic (TM) polarized radiation, we arrive at a unified format for the radiation pattern expression for all sources considered. Analyzing the common 1D (characteristic) Green's function, we show that the normalized TE-polarized emission of model 2D electric line sources reproduces exactly the measured TE-polarized radiation of statistical (3D) dipoles with random in-plane orientation; the connection between the TM-polarized emission of the two species is discussed, and physical interpretation is provided via the unified expression. These results specify the precise relations between the 2D and 3D models, providing intuition as well as guidelines for proper usage of simplified 2D results for analysis of realistic 3D statistical configurations.

Description: Pediatric brain tumors as a group, including medulloblastomas, gliomas and atypical teratoid rhabdoid tumors (ATRT) are the most common solid tumors in children and the leading cause of death from childhood cancer. Brain tumor-derived cell lines are critical for studying the biology of pediatric brain tumors and can be useful for initial screening of new therapies. Use of the appropriate brain tumor cell line for experiments is important, as results may differ depending on tumor properties, and can thus affect the conclusions and applicability as a model. Despite reports in the literature of over 60 pediatric brain tumor cell lines, the majority of published papers utilize only a small number of these cell lines. Here we list the approximately 60 currently-published pediatric brain tumor cell lines and summarize some of their central features as a resource for scientists seeking pediatric brain tumor cell lines for their research. J. Cell. Biochem. © 2014 Wiley Periodicals, Inc.

Description: Valoxy, an alumina-rich waste, was mixed with borosilicate glass (BSG) powder in 10, 20, and 30 wt% concentrations. Sintering was carried out at 850 and 950°C for 30 min. Glass-ceramics (GC) were characterized by X-ray diffraction analysis and scanning electron microscopy. Diametral compression strength (DCS) tests were performed on sintered samples before and after thermal shock. GC samples containing calcined Valoxy showed superior properties in all compositions and processing temperatures compared with samples containing as-received Valoxy. Maximum density of 2.2 g/cm 3 , water absorption below 1 wt% and DCS of ~24MPa were measured for 10 wt% calcined Valoxy + BSG GC composites sintered at 850°C.