1,285 research outputs found
The Influence of Age on the Wood Properties of Paulownia tomentosa (Thunb.) Steud
Forests in Portugal are highly dependent on a short number of wood species, and new
species with higher profitability are needed. The Paulownia species has generated great interest due to
its fast-growing and relatively good wood properties. However, environmental factors have shown
that Paulownia grows differently in each case. This study intends to determine the properties of young
Paulownia trees from Portuguese plantations to determine the best age to cut the trees according
to their use. The chemical composition (extractives in dichloromethane, ethanol and water, lignin,
-cellulose, and hemicelluloses), heating value, elemental analysis (CHNO), inorganic elements and
thermogravimetric analyses (TGA), and the most important mechanical and physical properties
(density, MOE, bending strength, water absorption equilibrium, moisture content, and dimensional
changes) were determined for 1-, 3-, and 5-year-old trees. The results show that, chemically, the
extractives increased while hemicelluloses decreased with age, and no trend was found for lignin
and -cellulose. The physical and mechanical properties increased with age, except for the MOE and
bending strength. The 5-year-old samples presented the best features for pellet production, namely,
calorific power, elemental composition CHNO and sulfur, and inorganic elementsinfo:eu-repo/semantics/publishedVersio
The ergogenic effect of beta-alanine combined with sodium bicarbonate on high-intensity swimming performance
We investigated the effect of beta-alanine (BA) alone (study A) and in combination with sodium bicarbonate (SB) (study B) on 100- and 200-m swimming performance. In study A, 16 swimmers were assigned to receive either BA (3.2 g·day−1 for 1 week and 6.4 g·day−1 for 4 weeks) or placebo (PL; dextrose). At baseline and after 5 weeks of supplementation, 100- and 200-m races were completed. In study B, 14 were assigned to receive either BA (3.2 g·day−1 for 1 week and 6.4 g·day−1 for 3 weeks) or PL. Time trials were performed once before and twice after supplementation (with PL and SB), in a crossover fashion, providing 4 conditions: PL-PL, PL-SB, BA-PL, and BA-SB. In study A, BA supplementation improved 100- and 200-m time-trial performance by 2.1% (p = 0.029) and 2.0% (p = 0.0008), respectively. In study B, 200-m time-trial performance improved in all conditions, compared with presupplementation, except the PL-PL condition (PL-SB, +2.3%; BA-PL, +1.5%; BA-SB, +2.13% (p < 0.05)). BA-SB was not different from BA-PL (p = 0.21), but the probability of a positive effect was 78.5%. In the 100-m time-trial, only a within-group effect for SB was observed in the PL-SB (p = 0.022) and BA-SB (p = 0.051) conditions. However, 6 of 7 athletes swam faster after BA supplementation. The probability of BA having a positive effect was 65.2%; when SB was added to BA, the probability was 71.8%. BA and SB supplementation improved 100- and 200-m swimming performance. The coingestion of BA and SB induced a further nonsignificant improvement in performance
Three- and Four-Body Scattering Calculations including the Coulomb Force
The method of screening and renormalization for including the Coulomb
interaction in the framework of momentum-space integral equations is applied to
the three- and four-body nuclear reactions. The Coulomb effect on the
observables and the ability of the present nuclear potential models to describe
the experimental data is discussed.Comment: Proceedings of the Critical Stability workshop, Erice, Sicily,
October 2008, to be published in Few-Body System
Stable and Metastable Structures of Cobalt on Cu(001): An ab initio Study
We report results of density-functional theory calculations on the
structural, magnetic, and electronic properties of (1x1)-structures of Co on
Cu(001) for coverages up to two monolayers. In particular we discuss the
tendency towards phase separation in Co islands and the possibility of
segregation of Cu on top of the Co-film. A sandwich structure consisting of a
bilayer Co-film covered by 1ML of Cu is found to be the lowest-energy
configuration. We also discuss a bilayer c(2x2)-alloy which may form due to
kinetic reasons, or be stabilized at strained surface regions. Furthermore, we
study the influence of magnetism on the various structures and, e.g., find that
Co adlayers induce a weak spin-density wave in the copper substrate.Comment: 11 pages including 4 figures. Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
Indirect search for dark matter: prospects for GLAST
Possible indirect detection of neutralino, through its gamma-ray annihilation
product, by the forthcoming GLAST satellite from our galactic halo, M31, M87
and the dwarf galaxies Draco and Sagittarius is studied. Gamma-ray fluxes are
evaluated for the two representative energy thresholds, 0.1 GeV and 1.0 GeV, at
which the spatial resolution of GLAST varies considerably. Apart from dwarfs
which are described either by a modified Plummer profile or by a
tidally-truncated King profiles, fluxes are compared for halos with central
cusps and cores. It is demonstrated that substructures, irrespective of their
profiles, enhance the gamma-ray emission only marginally. The expected
gamma-ray intensity above 1 GeV at high galactic latitudes is consistent with
the residual emission derived from EGRET data if the density profile has a
central core and the neutralino mass is less than 50 GeV, whereas for a central
cusp only a substantial enhancement would explain the observations. From M31,
the flux can be detected above 0.1 GeV and 1.0 GeV by GLAST only if the
neutralino mass is below 300 GeV and if the density profile has a central cusp,
case in which a significant boost in the gamma-ray emission is produced by the
central black hole. For Sagittarius, the flux above 0.1 GeV is detectable by
GLAST provided the neutralino mass is below 50 GeV. From M87 and Draco the
fluxes are always below the sensitivity limit of GLAST.Comment: 14 Pages, 7 Figures, 3 Tables, version to appear on Physical Review
Numerical modeling and simulation of supersonic flows in propulsion systems by open-source solvers
Two open-source solvers, Eilmer and hyFoam, are here considered for their performance in simulating high-speed flows in different flow conditions and geometric configurations typical of propulsive systems at supersonic speeds. The goal is to identify the open-source platform providing the best compromise between accuracy, flexibility and computational cost to eventually simulate the flow fields inside ramjet and scramjet engines. The differences in terms of discretization and solution methods of the selected solvers are discussed in terms of their impact on solution accuracy and computational efficiency and in view of the aerothermodynamic analysis and design of future trans-atmospheric propulsive systems. In this work steady state problems are considered. Numerical results of two scramjet type engines demonstrated a similar predictive capability of both codes in non-reacting conditions. These results highlight their potential to be considered for further characterization of overall engine performance
A rapid staining technique for the detection of the initiation of germination of bacterial spores
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75645/1/j.1472-765x.2002.01047.x.pd
The Residual Stress Relaxation Behavior of Weldments During Cyclic Loading
Accurate measurement of residual stress is necessary to obtain reliable predictions of fatigue lifetime and enable estimation of time-to-facture for any given stress level. In this article, relaxation of welding residual stresses as a function of cyclic loading was documented on three common steels: AISI 1008, ASTM A572, and AISI 4142. Welded specimens were subjected to cyclic bending (R = 0.1) at different applied stresses, and the residual stress relaxation existing near the welds was measured as a function of cycles. The steels exhibited very different stress relaxation behaviors during cyclic loadings, which can be related to the differences in the microstructures of the specimens. A phenomenological model, which treats dislocation motion during cyclic loading as being analogous to creep of dislocations, is proposed for estimation of the residual stress relaxation
- …