Testing turbulent closure models with convection simulations

We compare simple analytical closure models of homogeneous turbulent Boussinesq convection for stellar applications with three-dimensional simulations. We use simple analytical closure models to compute the fluxes of angular momentum and heat as a function of rotation rate measured by the Taylor number. We also investigate cases with varying angles between the angular velocity and gravity vectors, corresponding to locating the computational domain at different latitudes ranging from the pole to the equator of the star. We perform three-dimensional numerical simulations in the same parameter regimes for comparison. The free parameters appearing in the closure models are calibrated by two fitting methods using simulation data. Unique determination of the closure parameters is possible only in the non-rotating case or when the system is placed at the pole. In the other cases the fit procedures yield somewhat differing results. The quality of the closure is tested by substituting the resulting coefficients back into the closure model and comparing with the simulation results. To eliminate the possibilities that the results obtained depend on the aspect ratio of the simulation domain or suffer from too small Rayleigh numbers we performed runs varying these parameters. The simulation data for the Reynolds stress and heat fluxes broadly agree with previous compressible simulations. The closure works fairly well with slow and fast rotation but its quality degrades for intermediate rotation rates. We find that the closure parameters depend not only on rotation rate but also on latitude. The weak dependence on Rayleigh number and the aspect ratio of the domain indicates that our results are generally validComment: 21 pages, 9 figures, submitted to Astron. Nach

Decuplet Baryon Magnetic Moments in the Chiral Quark Model

We present calculations of the decuplet baryon magnetic moments in the chiral quark model. As input we use parameters obtained in qualitatively accurate fits to the octet baryon magnetic moments studied previously. The values found for the magnetic moments of $\Delta^{++}$ and $\Omega^{-}$ are in good agreement with experiments. We finally calculate the total quark spin polarizations of the decuplet baryons and find that they are considerably smaller than what is expected from the non-relativistic quark model

Angular momentum transport in convectively unstable shear flows

Angular momentum transport owing to hydrodynamic turbulent convection is studied using local three dimensional numerical simulations employing the shearing box approximation. We determine the turbulent viscosity from non-rotating runs over a range of values of the shear parameter and use a simple analytical model in order to extract the non-diffusive contribution (Lambda-effect) to the stress in runs where rotation is included. Our results suggest that the turbulent viscosity is of the order of the mixing length estimate and weakly affected by rotation. The Lambda-effect is non-zero and a factor of 2-4 smaller than the turbulent viscosity in the slow rotation regime. We demonstrate that for Keplerian shear, the angular momentum transport can change sign and be outward when the rotation period is greater than the turnover time, i.e. when the Coriolis number is below unity. This result seems to be relatively independent of the value of the Rayleigh number.Comment: 10 pages, 12 figures, published version. Version with higher resolution figures can be found at http://www.helsinki.fi/~kapyla/publ.htm

Mean-field closure parameters for passive scalar turbulence

Peer reviewe

Cutaneous Melanoma Patients Have Normal Repair Kinetics of Ultraviolet-Induced DNA Repair in Skin In Situ

The DNA lesions induced by ultraviolet radiation include cyclobutane pyrimidine dimers and 6–4 photoproducts. We investigated whether cutaneous melanoma patients have an impaired ability to repair their ultraviolet-induced photolesions. Seventeen patients with melanoma and 13 healthy controls took part in this study. Both groups received a dose of 40 mJ per cm2 Commission Internationale de l'Éclairage of solar simulating radiation on previously unexposed buttock skin. Skin biopsies were taken at 0 h, 24 h, and 48 h after ultraviolet exposure. A 32P-postlabeling method was used to measure both cyclobutane pyrimidine dimers and 6–4 photoproducts in skin. Cyclobutane pyrimidine dimers and 6–4 photoproduct levels did not differ in the melanoma patients from those in the control group at any time point post-ultraviolet radiation. The repair rate of cyclobutane dimer TT=C was faster than that for TT=T both at 24 h and 48 h postirradiation in both groups, providing evidence of site-specific repair (p < 0.05). We conclude that patients with melanoma have a normal ultraviolet-induced DNA repair capacity in skin in situ

Magnetic moments of the 3/2 resonances and their quark spin structure

We discuss magnetic moments of the $J=3/2$ baryons based on an earlier model for the baryon magnetic moments, allowing for flavor symmetry breaking in the quark magnetic moments as well as a general quark spin structure. From our earlier analysis of the nucleon-hyperon magnetic moments and the measured values of the magnetic moments of $\Delta^{++}$ and $\Omega^{-}$ we predict the other magnetic moments and deduce the spin structure of the resonance particles. We find from experiment that the total spin polarization of the decuplet baryons, $\Delta\Sigma(3/2)$, is considerably smaller than the non-relativistic quark model value of 3, although the data is still not good enough to give a precise determination.Comment: 13 pages, REVTeX, 2 figures, minor clarifying change

Octet Baryon Magnetic Moments in the Chiral Quark Model with Configuration Mixing

The Coleman-Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman-Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman-Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately.Comment: 22 pages, RevTe

Hexyl aminolevulinate, 5-aminolevulinic acid nanoemulsion, and methyl aminolevulinate in photodynamic therapy of non-aggressive basal cell carcinomas: A non-sponsored, randomized, prospective and double-blinded trial

Abstract Background In the photodynamic therapy (PDT) of non-aggressive basal cell carcinomas (BCCs), 5-aminolevulinic acid nanoemulsion (BF-200ALA) has shown non-inferior efficacy when compared with methyl aminolevulinate (MAL), a widely used photosensitizer. Hexyl aminolevulinate (HAL) is an interesting alternative photosensitizer. To our knowledge, this is the first study using HAL-PDT in the treatment of BCCs. Objectives To compare the histological clearance, tolerability (pain and post-treatment reaction), and cosmetic outcome of MAL, BF-200 ALA, and low-concentration HAL in the PDT of non-aggressive BCCs. Methods Ninety-eight histologically verified non-aggressive BCCs met the inclusion criteria, and 54 patients with 95 lesions completed the study. The lesions were randomized to receive LED-PDT in two repeated treatments with MAL, BF-200 ALA, or HAL. Efficacy was assessed both clinically and confirmed histologically at three months by blinded observers. Furthermore, cosmetic outcome, pain, post-treatment reactions fluorescence, and photobleaching were evaluated. Results According to intention-to-treat analyses, the histologically confirmed lesion clearance was 93.8% (95% confidence interval [CI] = 79.9?98.3) for MAL, 90.9% (95% CI = 76.4?96.9) for BF-200 ALA, and 87.9% (95% CI = 72.7?95.2) for HAL, with no differences between the arms (p=0.84). There were no differences between the arms as regards pain, post-treatment reactions, or cosmetic outcome. Conclusions PDT with low-concentration HAL and BF-200 ALA have a similar efficacy, tolerability, and cosmetic outcome compared to MAL. HAL is an interesting new option in dermatological PDT, since good efficacy is achieved with a low concentration.Peer reviewe

Benign Familial Juvenile Epilepsy in Lagotto Romagnolo Dogs

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