Search results for "Length"
showing 10 items of 2188 documents
Exploring Super-Earth Surfaces: Albedo of Near-Airless Magma Ocean Planets and Topography
2021
In this paper we propose an analytic function for the spherical albedo values of airless and near-airless magma ocean planets (AMOPs). We generated 2-D fractal surfaces with varying compositions onto which we individually threw 10,000 light rays. Using an approximate form of the Fresnel equations we measured how much of the incident light was reflected. Having repeated this algorithm on varying surface roughnesses we find the spherical albedo as a function of the Hurst exponent, the geochemical composition of the magma, and the wavelength. As a proof of concept, we used our model on Kepler-10b to demonstrate the applicability of our approach. We present the spherical albedo values produced …
Technical Note: Comparison of Techniques for Evaluating the Relative Preference by Sheep Among Saltbush Clones
2004
This research compared 4 field methods of evaluating the relative preference by sheep of 28 clones of saltbush (Atriplex halimus L.). The methods were as follows. 1) Leaf dots (LD): 8 leaves per shrub were marked on the lower surface with a small dot using a water-resistant, nontoxic ink. 2) Twig marks (TM): 2 current-year twigs per shrub were marked with 3 lines using the same ink approximately in the middle of the basal, median, and apical thirds. 3) Branch length (BL): 2 branches per shrub were marked with ink at the base of the current year's growth. The twigs were measured from the marked point to the top, before and after sheep browsing. 4) Ocular estimation (OE): the percentage of th…
Molecular tools to assess the diversity and density of denitrifying bacteria in their habitats
2007
Publisher Summary This chapter describes the molecular tools to assess the diversity and density of denitrifying bacteria in their habitats. Genome sequencing and metagenomic projects might even provide new denitrification gene sequences, which could aid in designing more broad range primers. Most information is obtained by cloning and sequencing the polymerase chain reaction (PCR) amplicons, but a more rapid analysis is achieved using fingerprinting techniques. As all PCR-based analyses, the fingerprinting techniques are subjected to well-known biases introduced by, e.g., DNA extraction procedures, primer selection, and PCR conditions. For denitrifiers, the PCR-RFLP (restriction fragment l…
Ocean acidification affects fish spawning but not paternity at CO2 seeps
2016
Fish exhibit impaired sensory function and altered behaviour at levels of ocean acidification expected to occur owing to anthropogenic carbon dioxide emissions during this century. We provide the first evidence of the effects of ocean acidification on reproductive behaviour of fish in the wild. Satellite and sneaker male ocellated wrasse (Symphodus ocellatus) compete to fertilize eggs guarded by dominant nesting males. Key mating behaviours such as dominant male courtship and nest defence did not differ between sites with ambient versus elevated CO2 concentrations. Dominant males did, however, experience significantly lower rates of pair spawning at elevated CO2 levels. Despite the higher r…
Quantum field theory of dilute homogeneous Bose-Fermi mixtures at zero temperature: General formalism and beyond mean-field corrections
2002
We consider a dilute homogeneous mixture of bosons and spin-polarized fermions at zero temperature. We first construct the formal scheme for carrying out systematic perturbation theory in terms of single particle Green's functions. We introduce a new relevant object, the renormalized boson-fermion T-matrix which we determine to second order in the boson-fermion s-wave scattering length. We also discuss how to incorporate the usual boson-boson T-matrix in mean-field approximation to obtain the total ground state properties of the system. The next order term beyond mean-field stems from the boson-fermion interaction and is proportional to $a_{\scriptsize BF}k_{\scriptsize F}$. The total groun…
Existence of two time scales in the phase transitions of BaTiO3
1991
Abstract We report new Raman scattering measurements in the tetragonal phase of a single domain BaTiO3 crystal. Data reveal the occurence of a large quasi elastic scattering. The Raman profile is analysed in terms of coexisting soft phonon and Debye relaxation.
Elastic scattering cross sections for 6Li and 7Li scattering by aluminum, silicon and titanium below 12 MeV at angles of 140∘ and 170∘
1999
Abstract Elastic scattering cross sections for 6Li and 7Li scattering by natural aluminum, silicon and titanium have been measured in the energy range of 4–11 MeV. Scattering angles were 140∘ and 170∘ for 6Li and 140∘ for 7Li. The threshold energies above which Rutherford backscattering becomes invalid have been determined. Above this threshold the cross sections decrease rapidly, rendering backscattering analysis impractical. For 7Li scattering by Al and Si the observed threshold values were higher than for 6Li scattering. This behavior was reversed for scattering by Ti. The findings were systematic for both scattering angles. The present cross section and threshold data have been compared…
πNscattering in relativistic baryon chiral perturbation theory reexamined
2011
We have analyzed pion-nucleon scattering using the manifestly relativistic covariant framework of infrared regularization up to $\mathcal{O}({q}^{3})$ in the chiral expansion, where $q$ is a generic small momentum. We describe the low-energy phase shifts with a similar quality as previously achieved with heavy baryon chiral perturbation theory, $\sqrt{s}\ensuremath{\lesssim}1.14$ GeV. New values are provided for the $\mathcal{O}({q}^{2})$ and $\mathcal{O}({q}^{3})$ low-energy constants, which are compared with previous determinations. This is also the case for the scattering lengths and volumes. Finally, we have unitarized the previous amplitudes and as a result the energy range where data …
Proton-Hydrogen Charge Exchange and Elastic Scattering in the Faddeev Approach
2000
Results of the application of Faddeev-type integral equations to proton-hydrogen collisions are reported. The approach, realized in the impact parameter representation, incorporates the exact two-particle off-shell Coulomb T-matrices in all ‘triangle’ contributions to the effective potentials. Calculatedtotal and differential electron-transfer as well as differential elastic scattering cross sections show very good agreement with experiment, over a wide range of incident energies.
Scattering Matrix and Observables in Scattering and Decays
2013
As an interlude in the analysis of canonical field quantization, this section describes important concepts of scattering theory for Lorentz covariant quantum field theories that will be needed for the calculation of observables such as scattering cross sections and decay probabilities.