On the spectrum of the magnetohydrodynamic mean-field alpha^2-dynamo operator

The existence of magnetohydrodynamic mean-field alpha^2-dynamos with spherically symmetric, isotropic helical turbulence function alpha is related to a non-self-adjoint spectral problem for a coupled system of two singular second order ordinary differential equations. We establish global estimates for the eigenvalues of this system in terms of the turbulence function alpha and its derivative alpha'. They allow us to formulate an anti-dynamo theorem and a non-oscillation theorem. The conditions of these theorems, which again involve alpha and alpha', must be violated in order to reach supercritical or oscillatory regimes.Comment: 35 pages, 4 figures, to be published in SIAM J. Math. Anal

Join optimization in distributed database systems based on a complete search space

In the context of the project HEaD (Heterogeneous Extensibleand Distributed DBMS) we present a technology to distributejoin queries over distributed relational DBMSs in a heterogeneous workstation network. Special aspects are the optimization of multi-way joins and the optimal parallel execution based on data flow control involving CPU, I/O, memory allocation and network load. We focus our attention on spanning a complete search space without invalid elements to optimize multi-way joins with help of an approximative search algorithm and a complex cost function

Thermodynamically consistent description of the hydrodynamics of free surfaces covered by insoluble surfactants of high concentration

In this paper we propose several models that describe the dynamics of liquid films which are covered by a high concentration layer of insoluble surfactant. First, we briefly review the 'classical' hydrodynamic form of the coupled evolution equations for the film height and surfactant concentration that are well established for small concentrations. Then we re-formulate the basic model as a gradient dynamics based on an underlying free energy functional that accounts for wettability and capillarity. Based on this re-formulation in the framework of nonequilibrium thermodynamics, we propose extensions of the basic hydrodynamic model that account for (i) nonlinear equations of state, (ii) surfactant-dependent wettability, (iii) surfactant phase transitions, and (iv) substrate-mediated condensation. In passing, we discuss important differences to most of the models found in the literature.Comment: 31 pages, 2 figure

Mushroom-Like Skin Tumours: Report of Three Cases

Mushroom like the growth of skin tumour is a rare phenomenon although described already in 1806 by Alibert, who focused on mycosis fungicides. We identified only four case reports in PUBMED database using the terms "mushroom-like growth" and "skin tumour". We analysed our files and identified three elderly female patients (69 to 94 years old). Histological diagnosis was melanoma, Merkel cell carcinoma and basal cell carcinoma. All tumours could be completely removed by wide excision or delayed Mohs surgery. No metastatic spread was noted

Registration of phase contrast images in propagation-based X-ray phase tomography

International audienceX-ray phase tomography aims at reconstructing the 3D electron density distribution of an object. It offers enhanced sensitivity compared to attenuation-based X-ray absorption tomography. In propagation-based methods, phase contrast is achieved by letting the beam propagate after interaction with the object. The phase shift is then retrieved at each projection angle, and subsequently used in tomographic reconstruction to obtain the refractive index decrement distribution, which is proportional to the electron density. Accurate phase retrieval is achieved by combining images at different propagation distances. For reconstructions of good quality, the phase-contrast images recorded at different distances need to be accurately aligned. In this work, we characterise the artefacts related to misalignment of the phase-contrast images, and investigate the use of different registration algorithms for aligning in-line phase-contrast images. The characterisation of artefacts is done by a simulation study and comparison with experimental data. Loss in resolution due to vibrations is found to be comparable to attenuation-based computed tomography. Further, it is shown that registration of phase-contrast images is nontrivial due to the difference in contrast between the different images, and the often periodical artefacts present in the phase-contrast images if multilayer X-ray optics are used. To address this, we compared two registration algorithms for aligning phase-contrast images acquired by magnified X-ray nanotomography: one based on cross-correlation and one based on mutual information. We found that the mutual information-based registration algorithm was more robust than a correlation-based method

Кластер как инструмент повышения качества высшего образования

В статье рассматривается место и роль университета при его вхождении в инновационный кластер на базе научно-исследовательского университета. Представлены основные преимущества данной форы интеграции образования и бизнеса, а также доказано, что кластер является инструментом повышения качества высшего образования

Biogeochemie von Quecksilber in zeitweise überfluteten Böden

We have assessed the effect of various factors on the mobility of total mercury (Hg) as well as on the methylation of Hg in two floodplain soils with different Hg loads using an automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions. The experiment was conducted under stepwise variation from reducing (approximately -240 mV at pH 5) to oxidizing (approximately 600 mV at pH 5) conditions. Generally it is known that sulphate (SO42-) reduction is mainly catalyzed by sulfate reducing bacteria (SRB) and iron (Fe) reducing bacteria, which promote the Hg methylation. However, the specific linking mechanisms between Hg methylation and microorganisms are still a black box. Analysis of phospholipid fatty acids (PLFA) indicate the occurrence of sulphate reducing bacteria such as Desulfovibrio or Desulfobulbus species, which are considered to promote Hg methylation. A direct impact of EH and pH could not be detected, instead, EH and pH indirectly affected Hg dynamics and methylation rate. Dissolved organic carbon (DOC) is an important factor controlling the dynamics and methylation of Hg. Both, Hg and methyl mercury (MeHg) in the solution increased with raising DOC. The lnMeHg/Hg ratio as the net production of MeHg normalized to the Hg concentration increases with increasing lnDOC/Hg ratio under changing EH

CXCL13 and CXCL9 CSF Levels in Central Nervous System Lymphoma-Diagnostic, Therapeutic, and Prognostic Relevance

Background: Diagnostic delay and neurologic deterioration are still a problem for the treatment of rapidly progressing CNS lymphoma (CNSL); there is an unmet need for a diagnostic test with a high diagnostic yield and limited risk, minimizing the time to the initiation of effective treatment. Methods: In this prospective monocentric study, we analyzed the utility of CXCL13 and CXCL9 as diagnostic, therapeutic and prognostic biomarkers for CNSL. Cerebrospinal fluid (CSF) from 155 consecutive patients admitted with brain lesions of various origins was collected. Levels of CXCL13 and CXCL9 were analyzed by ELISA. Additionally, CSF was analyzed during CNSL disease course (relapse, remission, progress) in 17 patients. Results: CXCL13 and CXCL9 CSF levels were significantly increased in patients with CNSL compared to control patients with lesions of other origin. Using logistic regression and a minimal-p-value approach, a cut-off value of 80 pg/ml for CXCL13 shows high sensitivity (90.7%) and specificity (90.1%) for the diagnosis of active CNSL. CXCL9 at a cut-off value of 84 pg/ml is less sensitive (61.5%) and specific (87.1%). Both cytokines correlate with the clinical course and response to therapy. Conclusions: Our results confirm the excellent diagnostic potential of CXCL13 and introduce CXCL9 as a novel albeit less powerful marker for PCNSL