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  • 1
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    Menasha, Wis. : Periodicals Archive Online (PAO)
    The Accounting Review. 43:2 (1968:Apr.) 225 
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  • 2
    Publication Date: 1983-12-01
    Description: Twenty-four specimens of six boreal tree species were excavated: eight Pinusbanksiana Lamb., five Populustremuloides Michx., four Piceaglauca (Moench) Voss, three Piceamariana (Mill.) B.S.P., two Abiesbalsamea (L.) Mills., and two Lara laricina (Du Roi) K. Koch. Root systems were described, and percent biomass determined for above- and below-ground components for half these specimens. Tree ages ranged from 3 to 120 years. Horizontally spreading lateral roots dominated the root systems of all species and occurred within 3– 15 cm of the ground surface. Nutrient and moisture absorption appear to be the principal functions of lateral roots. Maximum vertical root growth occurred near the tree stump as: tap-, heart, sinker, and oblique lateral roots. Vertical root morphology is influenced by site conditions. In addition to providing mechanical support, sinker and taproots may be important adaptations for deep-water utilization on xeric sites. Our data suggest that roots may be important in boreal succession processes through two related mechanisms: (i) nutrient and water deprivation occurring through preemptive growth of tree roots from climax species over roots of serai species, and through interception by mosses; and (ii) niche partitioning occurring below ground between serai and climax, and among climax tree species, by vertical separation of the root systems.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 3
    Publication Date: 1983-08-01
    Description: The root density and depth patterns of four boreal forest age sequences were analyzed for successional trends. Rooting depths increased with age on sandy substrates which supported aspen (Populustremuloides Michx.) and jack pine (Pinusbanksiana Lamb.) communities. Rooting depth did not change in an aspen series on fine-textured substrates or in a black spruce (Piceamariana (Mill.) BSP) series growing on organic substrates. Plant communities growing on mineral soils showed a decrease in near-surface root densities and understory vascular plant cover with increasing age. Maximum rooting was deepest on sandy substrates and shallowest on organic deposits. Roots in all stands were concentrated near the ground surface. In most cases 50% of all roots were located within 15 cm of the forest floor. Root densities in this zone ranged from 11 000 to 30 000 roots m−2 of vertical surface. Densities were approximately 4300 roots m−2 for the overall rooting zone.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 4
    Publication Date: 2016-06-16
    Description: Motivation: Mechanistic models based on ordinary differential equations provide powerful and accurate means to describe the dynamics of molecular machinery which orchestrates gene regulation. When combined with appropriate statistical techniques, mechanistic models can be calibrated using experimental data and, in many cases, also the model structure can be inferred from time–course measurements. However, existing mechanistic models are limited in the sense that they rely on the assumption of static network structure and cannot be applied when transient phenomena affect, or rewire, the network structure. In the context of gene regulatory network inference, network rewiring results from the net impact of possible unobserved transient phenomena such as changes in signaling pathway activities or epigenome, which are generally difficult, but important, to account for. Results: We introduce a novel method that can be used to infer dynamically evolving regulatory networks from time–course data. Our method is based on the notion that all mechanistic ordinary differential equation models can be coupled with a latent process that approximates the network structure rewiring process. We illustrate the performance of the method using simulated data and, further, we apply the method to study the regulatory interactions during T helper 17 (Th17) cell differentiation using time–course RNA sequencing data. The computational experiments with the real data show that our method is capable of capturing the experimentally verified rewiring effects of the core Th17 regulatory network. We predict Th17 lineage specific subnetworks that are activated sequentially and control the differentiation process in an overlapping manner. Availability and Implementation: An implementation of the method is available at http://research.ics.aalto.fi/csb/software/lem/ . Contacts: jukka.intosalmi@aalto.fi or harri.lahdesmaki@aalto.fi
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 5
    Publication Date: 2016-09-17
    Description: The scale dependent distribution of kinetic energy is probed at the surface in the Gulf of Mexico using surface drifters from the Grand Lagrangian Deployment (GLAD) experiment. The second order velocity structure function and its decomposition into rotational and divergent components are examined. The results reveal that the divergent component, compared to the rotational component, dominates at scales below 5 km, and the pattern is reversed at larger scales. The divergent component has a slope near 2/3 below 5 km, similar to an energy cascade range ( k  − 5/3 ). The third order velocity structure function at scales below 5km is negative and implies a forward cascade of energy to smaller scales. The rotational component has a steeper slope, roughly 1.5, from scales of 5km up to the deformation radius. This is similar to a 2D enstrophy cascade, although the slope is shallower than the predicted 2. There is a brief 2/3 range from the deformation radius to 200 km, suggestive of a 2D inverse cascade.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
    Publication Date: 2015-07-11
    Description: Subduction zones exhibit variable degrees of interseismic coupling as resolved by inversions of geodetic data and analyses of seismic energy release. The degree to which a plate boundary fault is coupled can have profound effects on its seismogenic behaviour. Here we use GPS measurements to estimate co- and post-seismic deformation from the 2012 August 27, M w 7.3 megathrust earthquake offshore El Salvador, which was a tsunami earthquake. Inversions of estimated coseismic displacements are in agreement with published seismically derived source models, which indicate shallow (〈20 km depth) rupture of the plate interface. Measured post-seismic deformation in the first year following the earthquake exceeds the coseismic deformation. Our analysis indicates that the post-seismic deformation is dominated by afterslip, as opposed to viscous relaxation, and we estimate a post-seismic moment release one to eight times greater than the coseismic moment during the first 500 d, depending on the relative location of coseismic versus post-seismic slip on the plate interface. We suggest that the excessive post-seismic motion is characteristic for the El Salvador–Nicaragua segment of the Central American margin and may be a characteristic of margins hosting tsunami earthquakes.
    Keywords: Marine Geosciences and Applied Geophysics
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
    Publication Date: 2012-12-25
    Description: Arctic column ozone reached record low values (∼310 DU) during March of 2011, exposing Arctic ecosystems to enhanced UV-B. We identify the cause of this anomaly using the Oslo CTM2 atmospheric chemistry model driven by ECMWF meteorology to simulate Arctic ozone from 1998 through 2011. CTM2 successfully reproduces the variability in column ozone, from week to week, and from year to year, correctly identifying 2011 as an extreme anomaly over the period. By comparing parallel model simulations, one with all Arctic ozone chemistry turned off on January 1, we find that chemical ozone loss in 2011 is enhanced relative to previous years, but it accounted for only 23% of the anomaly. Weakened transport of ozone from middle latitudes, concurrent with an anomalously strong polar vortex, was the primary cause of the low ozone When the zonal winds relaxed in mid-March 2011, Arctic column ozone quickly recovered.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Publication Date: 2012-06-12
    Description: Biological proteins are known to fold into specific 3D conformations. However, the fundamental question has remained: Do they fold because they are biological, and evolution has selected sequences which fold? Or is folding a common trait, widespread throughout sequence space? To address this question arbitrary, unevolved, random-sequence proteins were examined for structural features found in folded, biological proteins. Libraries of long (71 residue), random-sequence polypeptides, with ensemble amino acid composition near the mean for natural globular proteins, were expressed as cleavable fusions with ubiquitin. The structural properties of both the purified pools and individual isolates were then probed using circular dichroism, fluorescence emission, and fluorescence quenching techniques. Despite this necessarily sparse “sampling” of sequence space, structural properties that define globular biological proteins, namely collapsed conformations, secondary structure, and cooperative unfolding, were found to be prevalent among unevolved sequences. Thus, for polypeptides the size of small proteins, natural selection is not necessary to account for the compact and cooperative folded states observed in nature.
    Electronic ISSN: 2073-4425
    Topics: Biology
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  • 9
    Publication Date: 2012-08-18
    Description: Large-scale budget calculations and numerical model process studies suggest that lateral eddy heat fluxes have an important cooling effect on the Norwegian Atlantic Current (NwAC) as it flows through the Nordic Seas. But observational estimates of such fluxes have been lacking. Here, wintertime surface eddy heat fluxes in the eastern Nordic Seas are estimated from surface drifter data, satellite data and an eddy-permitting numerical model. Maps of the eddy heat flux divergence suggest advective cooling along the path of the NwAC. Integrating the flux divergence over temperature classes yields consistent estimates for the three data sets; the waters warmer than about 6°C are cooled while the cooler waters are warmed. Similar integrations over bottom depth classes show that regions shallower than about 2000 m are cooled while deeper regions are warmed. Finally, integrating the flux divergence along the core of the NwAC suggests that the highest eddy-induced heat loss at the surface is along the steepest part of the continental slope, east of the Lofoten Basin. The model fields indicate that cooling of the current by lateral eddy fluxes is comparable to or larger than the local heat loss to the atmosphere.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
    Publication Date: 2012-06-06
    Description: The response of a two-layer quasigeostrophic ocean model to basin scale stochastic wind forcing is investigated. As found in many previous studies, long Rossby waves are excited at the eastern boundary of the square model basin and the waves are baroclinically unstable. A novel aspect we focus on here is that the instability leads to the generation of zonal jets throughout the domain. The jets are actually wave-like in nature, and result directly from the instability. The “jets” appear when averaging the oceanic zonal velocity field over fixed periods of time. The longer the averaging period, the weaker the jets as the latter are in fact time-varying. The jets occur for a wide range of stratification, strength of stochastic forcing and the presence or not of a time mean circulation. The mechanism of jet generation described here thereby provides an explanation for the recent observations of alternating zonal jets in the mid-latitude oceans.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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