324 research outputs found
Fact sheet: Field considerations for measuring evapotranspiration with the Eddy Covariance Method.
In semi-arid ponderosa pine forests of the southwestern US, up to 90% of the annual water budget is re-turned to the atmosphere through evapotranspiration (ET). Accurate measurements of this component of the water budget are, therefore, critical to assess hydrological responses to planned forest restoration. The eddy covariance (EC) method is an atmospheric measurement technique that yields accurate ET measurements. The EC method calculates vertical turbulent fluxes within an atmospheric boundary layer over natural ecosystems and agricultural systems to determine gas exchange rates (e.g., water vapor concentration, carbon dioxide (CO2) concentration) (Burba 2013). Both natural and human-mediated processes affect forest gas exchange. Recent studies of both wildfire and forest restoration treatments in stands of ponderosa pine show a reduction of ET compared to an undisturbed forest site (Dore et al. 2010). Application of EC to investigate CO2 and water fluxes in ponderosa pine forest improves understanding of CO2 and water flux exchange patterns. This fact sheet describes installation of an EC system, including flux tower placement requirements and maintenance of scientific instruments
An econometric analysis of the impact of forest restoration on agriculture in the Verde River Watershed, Arizona: Working paper series--14-04
Known as the Four Forest Restoration Initiative (4FRI), the US Forest Service is planning a large-scale restoration of ponderosa pine forests in the Verde River watershed in central Arizona. This paper uses a reduced-form econometric regression model with 1969-2010 time-series data to estimate the economic benefits of the increased water yield due to planned forest restoration of the first phase of 4FRI. We split data sample into 1969-1989 and 1990-2010 time periods, and conclude that during the second time period, water use is statistically and economically significant. This is consistent with the reality that the Verde River watershed has been in drought since the early 1990s. Our central finding is that, if water use increases by 1%, the farm income will increase by 1.33%. If a 5-10% increase in water yield caused by the first phase of the 4FRI is all used by agriculture, agricultural income will increase by 6.65-13.3% annually
Accurate first-principle equation of state for the One-Component Plasma
Accurate "first-principle" expressions for the excess free energy
and internal energy of the classical one-component plasma (OCP) are
obtained. We use the Hubbard-Schofield transformation that maps the OCP
Hamiltonian onto the Ising-like Hamiltonian, with coefficients expressed in
terms of equilibrium correlation functions of a reference system. We use the
ideal gas as a reference system for which all the correlation functions are
known. Explicit calculations are performed with the high-order terms in the
Ising-like Hamiltonian omitted. For small values of the plasma parameter
the Debye-Huckel result for and is recovered. For
large these depend linearly on in accordance with the Monte
Carlo findings for the OCP. The MC data for the internal energy are reproduced
fairly well by the obtained analytical expression.Comment: 15 pages, 2 figures, to appear in Contrib. Plasma Phys., v.38 N4,
(1998
SU(3) Predictions for Weak Decays of Doubly Heavy Baryons -- including SU(3) breaking terms
We find expressions for the weak decay amplitudes of baryons containing two b
quarks (or one b and one c quark -- many relationship are the same) in terms of
unknown reduced matrix elements. This project was originally motivated by the
request of the FNAL Run II b Physics Workshop organizers for a guide to
experimentalists in their search for as yet unobserved hadrons. We include an
analysis of linear SU(3) breaking terms in addition to relationships generated
by unbroken SU(3) symmetry, and relate these to expressions in terms of the
complete set of possible reduced matrix elements.Comment: 49 page
Fibroblasts from different sites may promote or inhibit recruitment of flowing lymphocytes by endothelial cells
We examined the hypothesis that stromal fibroblasts modulate the ability of endothelial cells (EC) to recruit lymphocytes in a site-specific manner. PBL were perfused over HUVEC that had been cultured with fibroblasts isolated from the inflamed synovium or the skin of patients with rheumatoid arthritis or osteoarthritis, or from normal synovium, with or without exposure to the inflammatory cytokines TNF-a+IFN-c. Fibroblasts from inflamed synovium, but no others, caused unstimulated HUVEC to bind flowing lymphocytes. This adhesion was supported by a4b1-VCAM-1 interaction and stabilised by activation of PBL through CXCR4–CXCL12. Antibody neutralisation of IL-6 during co-culture effectively
abolished the ability of EC to bind lymphocytes. Cytokine-stimulated EC supported high levels of lymphocyte adhesion, through the presentation of VCAM-1, E-selectin and chemokine(s) acting through CXCR3. Interestingly, co-culture with dermal fibroblasts caused a marked reduction in cytokine-induced adhesion, while synovial fibroblasts had variable effects depending on their source. In the dermal co-cultures, neutralisation of IL-6 or TGF-b caused partial recovery of cytokine-induced lymphocyte adhesion; this was complete when both were neutralised. Exogenous IL-6 was also found to inhibit response to TNF-a+IFN-c. Normal stromal fibroblasts appear to regulate the cytokine-sensitivity of vascular endothelium, while fibroblasts associated with chronic inflammation bypass this and develop a directly inflammatory phenotype. Actions of IL-6 might be pro-inflammatory or anti-inflammatory, depending on the local milieu
New Physics and CP Violation in Hyperon Nonleptonic Decays
The sum of the CP-violating asymmetries A(Lambda_-^0) and A(Xi_-^-) in
hyperon nonleptonic decays is presently being measured by the E871 experiment.
We evaluate contributions to the asymmetries induced by chromomagnetic-penguin
operators, whose coefficients can be enhanced in certain models of new physics.
Incorporating recent information on the strong phases in Xi->Lambda pi decay,
we show that new-physics contributions to the two asymmetries can be
comparable. We explore how the upcoming results of E871 may constrain the
coefficients of the operators. We find that its preliminary measurement is
already better than the epsilon parameter of K-Kbar mixing in bounding the
parity-conserving contributions.Comment: 12 pages, 2 figure
Montecarlo based quantitative Kramers-Kronig test for PEMFC impedance spectrum validation
Electrochemical Impedance Spectroscopy (EIS) is a very powerful tool to study the behaviour of electrochemical systems. At present, it is widely used in the fuel cell field in order to study challenging cutting edge issues as membrane drying or gas diffusion layer flooding amongst others. The proper analysis of impedance data requires the fulfilment of four fundamental conditions: causality, linearity, stability and finiteness. The non compliance with any of these conditions may lead to biased, or even misguided, conclusions. Therefore it is critical to verify the compliance of these conditions before accepting any analysis performed on an experimental spectrum. This is even more important in a fuel cell experimental spectrum analysis, since fuel cells are markedly non stationary systems. The aim of this work is to establish an impedance spectrum quantitative validation technique to validate the whole experimental spectrum and to identify the individual points within a spectrum that do not comply any of the four conditions, in order to remove these inconsistent points from the analysis. The designed validation method consists in a Kramers Kronig (KK) validation test, by equivalent electrical circuit fitting, coupled with a Montecarlo error propagation method. In a first step, the experimental spectrum is fitted to a particular electrical equivalent circuit, which satisfies the KK relations. Then, in a second step, a statistical Montecarlo method is used in order to propagate the model fitting parameter uncertainty through the model. Using this approach, a consistency region is built for a given confidence level: the experimental points inside this region are considered consistent for the given confidence level, whereas the outside points are rejected. The method was used on PEMFC experimental impedance spectra; and it successfully managed to identify inconsistent points, associated to no stationarities.The authors are very grateful to the Generalitat Valenciana for its economic support in form of Vali+d grant (Ref: ACIF-2013-268).Giner Sanz, JJ.; Ortega Navarro, EM.; Pérez-Herranz, V. (2015). Montecarlo based quantitative Kramers-Kronig test for PEMFC impedance spectrum validation. International Journal of Hydrogen Energy. 40(34):11279-11293. https://doi.org/10.1016/j.ijhydene.2015.03.135S1127911293403
Measurement of the proton-air cross section with Telescope Array's Middle Drum detector and surface array in hybrid mode
In this work we are reporting on the measurement of the proton-air inelastic cross section sigma(inel)(p-air) using the Telescope Array detector. Based on the measurement of the sigma(inel)(p-air), the proton-proton cross section sigma(p-p) value is also determined at root s = 95(-8)(+5) TeV. Detecting cosmic ray events at ultrahigh energies with the Telescope Array enables us to study this fundamental parameter that we are otherwise unable to access with particle accelerators. The data used in this report are the hybrid events observed by the Middle Drum fluorescence detector together with the surface array detector collected over five years. The value of the sigma(inel)(p-air) is found to be equal to 567.0 +/- 70.5[Stat](-25)(+29)[Sys] mb. The total proton-proton cross section is subsequently inferred from Glauber formalism and the Block, Halzen and Stanev QCD inspired fit and is found to be equal to 170(-44)(+48)[Stat](-17)(+19)[Sys] mb.open20
Indications of intermediate-scale anisotropy of cosmic rays with energy greater than 57 EeV in the northern sky measured with the surface detector of the Telescope Array experiment
We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 yr period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20?? radius circles. The hotspot has a Li-Ma statistical significance of 5.1??, and is centered at R.A. = 146.??7, decl. = 43.??2. The position of the hotspot is about 19?? off of the supergalactic plane. The probability of a cluster of events of 5.1?? significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7 ?? 10-4 (3.4??).open2
Milagro limits and HAWC sensitivity for the rate-density of evaporating Primordial Black Holes
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