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Determination of the gas diffusion coefficient of a peat grassland soil
Peatland habitats are important carbon stocks that also have the potential to be significant sources of greenhouse gases, particularly when subject to changes such as artificial drainage and application of fertilizer. Models aiming to estimate greenhouse gas release from peatlands require an accurate estimate of the diffusion coefficient of gas transport through soil (Ds). The availability of specific measurements for peatland soils is currently limited. This study measured Ds for a peat soil with an overlying clay horizon and compared values with those from widely available models. The Ds value of a sandy loam reference soil was measured for comparison. Using the Currie (1960) method, Ds was measured between an air-filled porosity (ϵ) range of 0 and 0.5 cm3 cm−3. Values of Ds for the peat cores ranged between 3.2 × 10−4 and 4.4 × 10−3 m2 hour−1, for loamy clay cores between 0 and 4.7 × 10−3 m2 hour−1 and for the sandy reference soil they were between 5.4 × 10−4 and 3.4 × 10−3 m2 hour−1. The agreement of measured and modelled values of relative diffusivity (Ds/D0, with D0 the diffusion coefficient through free air) varied with soil type; however, the Campbell (1985) model provided the best replication of measured values for all soils. This research therefore suggests that the use of the Campbell model in the absence of accurately measured Ds and porosity values for a study soil would be appropriate. Future research into methods to reduce shrinkage of peat during measurement and therefore allow measurement of Ds for a greater range of ϵ would be beneficial
Limb reconstruction in Ollier's disease.
We present our experience of lengthening and correction of complex deformities in the management of patients with Ollier's dysplasia (multiple enchondromatosis) from 1985 and 2002. All patients were under 18 years with a minimum follow-up time of 2 years (mean 9.6 years, range 2-15 years). There were a total of ten patients of which seven were male and three female. The mean age at presentation was 10.7 years (range 5-17 years; SD 3.7 years). The total length gain was 42.3 mm (range 30-110 mm; SD 28.9 mm). The number of days in external fixation was 164.8 days (range 76-244 days; SD 42.9 days). The bone healing index was 32.5 days/cm (18-50 days/cm; SD 10.3 days/cm). Patients with Ollier's disease have limb length inequality and angular deformities and require multiple reconstructive procedures owing to a high incidence of recurrence. We identified a tendency for the osteotomy to prematurely consolidate and advise the latency period after surgery to be 4-5 days and for distraction to proceed at a faster rate
Degenerative mitral valve disease: Survival of dogs attending primary-care practice in england
Linear-scaling first-principles study of a quasicrystalline molecular material
Accepted versio
In situ light dosimetry during photodynamic therapy of Barrett's esophagus with 5-aminolevulinic acid
Background and Objectives: Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronchi have shown that due to scattering and reflection, the actually delivered fluence rate on the surface in a hollow organ can be significantly higher than expected. In this pilot study, we investigated the differences between the primary calculated and the actual measured fluence rate during PDT of Barrett's Esophagus (BE) using 23 independent clinical measurements in 15 patients. Study Design/Materials and Methods: A KTP-dye module laser at 630 nm was used as light source. Light delivery was performed using a cylindrical light diffuser inserted in the center of an inflatable transparent balloon with a length corresponding to the length of the Barrett's epithelium. The total light output power of the cylindrical diffuser was calibrated using an integrating sphere to deliver a primary fluence rate of 100 mW cm-2. Two fiber-optic pseudo sphere isotropic detectors were placed on the balloon and were used to measure fluence rate at the surface of the esophageal wall during PDT. Results and Conclusions: The actual fluence rate measured was 1.5-3.9 times higher than the primary fluence rate for 630 nm. In general, the fluence rate amplification factor decreased with increasing redness of the tissue and was less for shorter diffusers. Fluence rate variations in time were observed which coincided with patients coughing, movement, and esophageal spasms. These factors combined with inter patient variability of the fluence rate measured appears to justify the routine application of this technique in PDT of BE
Signatures of Primordial non-Gaussianities in the Matter Power-Spectrum and Bispectrum: the Time-RG Approach
We apply the time-renormalization group approach to study the effect of
primordial non-Gaussianities in the non-linear evolution of cosmological dark
matter density perturbations. This method improves the standard perturbation
approach by solving renormalization group-like equations governing the dynamics
of gravitational instability. The primordial bispectra constructed from the
dark matter density contrast and the velocity fields represent initial
conditions for the renormalization group flow. We consider local, equilateral
and folded shapes for the initial non-Gaussianity and analyze as well the case
in which the non-linear parameter f_{NL} parametrizing the strength of the
non-Gaussianity depends on the momenta in Fourier space through a power-law
relation, the so-called running non-Gaussianity. For the local model of
non-Gaussianity we compare our findings for the power-spectrum with those of
recent N-body simulations and find that they accurately fit the N-body data up
to wave-numbers k \sim 0.25 h/Mpc at z=0. We also present predictions for the
(reduced) matter bispectra for the various shapes of non-Gaussianity.Comment: 27 pages, 12 figures. Results and discussion for a particular case
added. One figure and one reference added. Matches with the version accepted
for publication in the JCAP
From Majorana theory of atomic autoionization to Feshbach resonances in high temperature superconductors
The Ettore Majorana paper - Theory of incomplete P triplets- published in
1931, focuses on the role of selection rules for the non-radiative decay of two
electron excitations in atomic spectra, involving the configuration interaction
between discrete and continuum channels. This work is a key step for
understanding the 1935 work of Ugo Fano on the asymmetric lineshape of two
electron excitations and the 1958 Herman Feshbach paper on the shape resonances
in nuclear scattering arising from configuration interaction between many
different scattering channels. The Feshbach resonances are today of high
scientific interest in many different fields and in particular for ultracold
gases and high Tc superconductivity.Comment: 13 pages, 7 figures. Journal of Superconductivity and Novel Magnetism
to be publishe
Chaos in a double driven dissipative nonlinear oscillator
We propose an anharmonic oscillator driven by two periodic forces of
different frequencies as a new time-dependent model for investigating quantum
dissipative chaos. Our analysis is done in the frame of statistical ensemble of
quantum trajectories in quantum state diffusion approach. Quantum dynamical
manifestation of chaotic behavior, including the emergence of chaos, properties
of strange attractors, and quantum entanglement are studied by numerical
simulation of ensemble averaged Wigner function and von Neumann entropy.Comment: 9 pages, 18 figure
Ultrarelativistic black hole in an external electromagnetic field and gravitational waves in the Melvin universe
We investigate the ultrarelativistic boost of a Schwarzschild black hole
immersed in an external electromagnetic field, described by an exact solution
of the Einstein-Maxwell equations found by Ernst (the ``Schwarzschild-Melvin''
metric). Following the classical method of Aichelburg and Sexl, the
gravitational field generated by a black hole moving ``with the speed of
light'' and the transformed electromagnetic field are determined. The
corresponding exact solution describes an impulsive gravitational wave
propagating in the static, cylindrically symmetric, electrovac universe of
Melvin, and for a vanishing electromagnetic field it reduces to the well known
Aichelburg-Sexl pp-wave. In the boosting process, the original Petrov type I of
the Schwarzschild-Melvin solution simplifies to the type II on the impulse, and
to the type D elsewhere. The geometry of the wave front is studied, in
particular its non-constant Gauss curvature. In addition, a more general class
of impulsive waves in the Melvin universe is constructed by means of a
six-dimensional embedding formalism adapted to the background. A coordinate
system is also presented in which all the impulsive metrics take a continuous
form. Finally, it is shown that these solutions are a limiting case of a family
of exact gravitational waves with an arbitrary profile. This family is
identified with a solution previously found by Garfinkle and Melvin. We thus
complement their analysis, in particular demonstrating that such spacetimes are
of type II and belong to the Kundt class.Comment: 11 pages, REVTeX
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