437 research outputs found
Refined forest land use classification with implications for United States national carbon accounting
The United States provides annual estimates of carbon sources and sinks as part of its National Green-house Gas Inventory (NGHGI). Within this effort, carbon stocks and fluxes are reported for six land use categories that are relevant to economic sectors and land use policy. The goal of this study is to develop methodologies that will allow the US to align with an internationally agreed upon forest land use definition which requires forest to be able to reach 5 m in height at maturity. Models to assess height potential are available for a majority of US forests except for woodland ecosystems. We develop a set of models to assess height potential in these systems. Our results suggest that âŒ13.5 million ha of forests are unlikely to meet the international definition of forests due to environmental limitations to maximum attainable height. The incorporation of this height criteria in the NGHGI results in a carbon stock transfer of âŒ848 Tg from the forest land use to woodland land use (a sub-category of grasslands) with minimal effect on sequestration rates. The development of a forest land use definition sensitive to climatic factors in this study enables a land use classification system that can be responsive to climate change effects on land uses themselves while being more consistent across a host of international and domestic carbon reporting efforts
Estimating carbon storage in windbreak trees on U.S. agricultural lands
Assessing carbon (C) capture and storage potential by the agroforestry practice of windbreaks has been limited. This is due, in part, to a lack of suitable data and associated models for estimating tree biomass and C for species growing under more opengrown conditions such as windbreaks in the Central Plains region of the United States (U.S.). We evaluated 15 allometric models using destructively sampled Pinus ponderosa (Lawson & C. Lawson) data from field windbreaks in Nebraska and Montana. Several goodness-of-fit metrics were used to select the optimal model. The Jenkinsâ et al. model was then used to estimate biomass for 16 tree species in windbreaks projected over a 50 year time horizon in nine continental U.S. regions. Carbon storage potential in the windbreak scenarios ranged from 1.07 ± 0.21 to 3.84 ± 0.04 Mg C ha-1 year-1 for conifer species and from 0.99 ± 0.16 to 13.6 ± 7.72 Mg C ha-1 year-1 for broadleaved deciduous species during the 50 year period. Estimated mean C storage potentials across species and regions were 2.45 ± 0.42 and 4.39 ± 1.74 Mg C ha-1 year-1 for conifer and broadleaved deciduous species, respectively. Such information enhances our capacity to better predict the C sequestration potential of windbreaks associated with whole farm/ranch operations in the U.S
Estimating carbon storage in windbreak trees on U.S. agricultural lands
Assessing carbon (C) capture and storage potential by the agroforestry practice of windbreaks has been limited. This is due, in part, to a lack of suitable data and associated models for estimating tree biomass and C for species growing under more opengrown conditions such as windbreaks in the Central Plains region of the United States (U.S.). We evaluated 15 allometric models using destructively sampled Pinus ponderosa (Lawson & C. Lawson) data from field windbreaks in Nebraska and Montana. Several goodness-of-fit metrics were used to select the optimal model. The Jenkinsâ et al. model was then used to estimate biomass for 16 tree species in windbreaks projected over a 50 year time horizon in nine continental U.S. regions. Carbon storage potential in the windbreak scenarios ranged from 1.07 ± 0.21 to 3.84 ± 0.04 Mg C ha-1 year-1 for conifer species and from 0.99 ± 0.16 to 13.6 ± 7.72 Mg C ha-1 year-1 for broadleaved deciduous species during the 50 year period. Estimated mean C storage potentials across species and regions were 2.45 ± 0.42 and 4.39 ± 1.74 Mg C ha-1 year-1 for conifer and broadleaved deciduous species, respectively. Such information enhances our capacity to better predict the C sequestration potential of windbreaks associated with whole farm/ranch operations in the U.S
Intermanifold similarities in partial photoionization cross sections of helium
Using the eigenchannel R-matrix method we calculate partial photoionization
cross sections from the ground state of the helium atom for incident photon
energies up to the N=9 manifold. The wide energy range covered by our
calculations permits a thorough investigation of general patterns in the cross
sections which were first discussed by Menzel and co-workers [Phys. Rev. A {\bf
54}, 2080 (1996)]. The existence of these patterns can easily be understood in
terms of propensity rules for autoionization. As the photon energy is increased
the regular patterns are locally interrupted by perturber states until they
fade out indicating the progressive break-down of the propensity rules and the
underlying approximate quantum numbers. We demonstrate that the destructive
influence of isolated perturbers can be compensated with an energy-dependent
quantum defect.Comment: 10 pages, 10 figures, replacement with some typos correcte
The cell-cell junctions of mammalian testes: I. The adhering junctions of the seminiferous epithelium represent special differentiation structures
The seminiferous tubules and the excurrent ducts of the mammalian testis are physiologically separated from the mesenchymal tissues and the blood and lymph system by a special structural barrier to paracellular translocations of molecules and particles: the âbloodâtestis barrierâ, formed by junctions connecting Sertoli cells with each other and with spermatogonial cells. In combined biochemical as well as light and electron microscopical studies we systematically determine the molecules located in the adhering junctions of adult mammalian (human, bovine, porcine, murine, i.e., rat and mouse) testis. We show that the seminiferous epithelium does not contain desmosomes, or âdesmosome-likeâ junctions, nor any of the desmosome-specific marker molecules and that the adhering junctions of tubules and ductules are fundamentally different. While the ductules contain classical epithelial cell layers with E-cadherin-based adherens junctions (AJs) and typical desmosomes, the Sertoli cells of the tubules lack desmosomes and âdesmosome-likeâ junctions but are connected by morphologically different forms of AJs. These junctions are based on N-cadherin anchored in cytoplasmic plaques, which in some subforms appear thick and dense but in other subforms contain only scarce and loosely arranged plaque structures formed by α- and ÎČ-catenin, proteins p120, p0071 and plakoglobin, together with a member of the striatin family and also, in rodents, the proteins ZO-1 and myozap. These N-cadherin-based AJs also include two novel types of junctions: the âareae adhaerentesâ, i.e., variously-sized, often very large cell-cell contacts and small sieve-plate-like AJs perforated by cytoplasm-to-cytoplasm channels of 5â7 nm internal diameter (âcribelliform junctionsâ). We emphasize the unique character of this epithelium that totally lacks major epithelial marker molecules and structures such as keratin filaments and desmosomal elements as well as EpCAM- and PERP-containing junctions. We also discuss the nature, development and possible functions of these junctions.German-Israeli Foundation for Scientific Research and Development (GIF grant I-1098-43.11/2010
Analytical and clinical evaluation of an electrochemiluminescence immunoassay for the determination of CA 125
The CA 125 II assay on the Elecsys(R) 2010 analyzer was evaluated in an
international multicenter trial. Imprecision studies yielded within-run
CVs of 0.8-3.3% and between-day CVs of 2.4-10.9%; CVs for total
imprecision in the manufacturer's laboratory were 2.4-7.8%. The linear
range of the assay extended to at least 4500 kilounits/L (three decades).
Interference from triglycerides (10.3 mmol/L), bilirubin (850 micromol/L),
hemoglobin (1.1 mmol/L), anticoagulants (plasma), and several widely used
drugs was undetectable. Method comparisons with five other CA 125 II
assays showed good correlation but differences in standardization. A 95th
percentile cutoff value of 35 kilounits/L was calculated from values
measured in 593 apparently healthy (pre- and postmenopausal) women. In 95%
of patients with benign gynecological diseases CA 125 was </=190
kilounits/L; 63% of patients with newly diagnosed ovarian carcinoma had
values >190 kilounits/L. A comparison of CA 125 values obtained with the
Elecsys test and with other common CA 125 tests in monitored patients
being treated for ovarian cancer showed identical patterns. In conclusion,
the Elecsys CA 125 II assay is linear over a broad range, yields precise
and accurate results, is free from interferences, and compares well with
other assays
Mirror Position Determination for the Alignment of Cherenkov Telescopes
Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with
large apertures to map the faint Cherenkov light emitted in extensive air
showers onto their image sensors. Segmented reflectors fulfill these needs
using mass produced and light weight mirror facets. However, as the overall
image is the sum of the individual mirror facet images, alignment is important.
Here we present a method to determine the mirror facet positions on a segmented
reflector in a very direct way. Our method reconstructs the mirror facet
positions from photographs and a laser distance meter measurement which goes
from the center of the image sensor plane to the center of each mirror facet.
We use our method to both align the mirror facet positions and to feed the
measured positions into our IACT simulation. We demonstrate our implementation
on the 4 m First Geiger-mode Avalanche Cherenkov Telescope (FACT).Comment: 11 figures, small ray tracing performance simulation, and
implementation demonstratio
FACT -- the First Cherenkov Telescope using a G-APD Camera for TeV Gamma-ray Astronomy (HEAD 2010)
Geiger-mode Avalanche Photodiodes (G-APD) bear the potential to significantly
improve the sensitivity of Imaging Air Cherenkov Telescopes (IACT). We are
currently building the First G-APD Cherenkov Telescope (FACT) by refurbishing
an old IACT with a mirror area of 9.5 square meters and construct a new, fine
pixelized camera using novel G-APDs. The main goal is to evaluate the
performance of a complete system by observing very high energy gamma-rays from
the Crab Nebula. This is an important field test to check the feasibility of
G-APD-based cameras to replace at some time the PMT-based cameras of planned
future IACTs like AGIS and CTA. In this article, we present the basic design of
such a camera as well as some important details to be taken into account.Comment: Poster shown at HEAD 2010, Big Island, Hawaii, March 1-4, 201
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