Amorphous thin film growth: theory compared with experiment

Experimental results on amorphous ZrAlCu thin film growth and the dynamics of the surface morphology as predicted from a minimal nonlinear stochastic deposition equation are analysed and compared. Key points of this study are (i) an estimation procedure for coefficients entering into the growth equation and (ii) a detailed analysis and interpretation of the time evolution of the correlation length and the surface roughness. The results corroborate the usefulness of the deposition equation as a tool for studying amorphous growth processes.Comment: 7 pages including 5 figure

Plastic deformation of metallic glasses: Size of shear transformation zones from molecular dynamics simulations

Plastic deformation in metallic glasses well below their glass transition temperatures Tg occurs spatially heterogeneously within highly localized regions, termed shear transformation zones (STZs). Yet, their size and the number of atoms involved in a local shear event, remains greatly unclear. With the help of classical molecular dynamics (MD) computer simulations on plastic deformation of the model glass CuTi during pure shearing, we address this issue by evaluating correlations in atomic-scale plastic displacements, viz. the displacement correlation function. From the correlation length, a universal diameter of about 15 Å, or, equivalently, approximately 120 atoms is derived for a variety of conditions, such as variable strains, strain rates, temperatures, and boundary conditions. Our findings are consistent with a recent model proposed by Johnson and Samwer [Phys. Rev. Lett. 95, 195501 (2005)]

Broadband dielectric response of CaCu3Ti4O12: From dc to the electronic transition regime

We report on phonon properties and electronic transitions in CaCu3Ti4O12, a material which reveals a colossal dielectric constant at room temperature without any ferroelectric transition. The results of far- and mid-infrared measurements are compared to those obtained by broadband dielectric and millimeter-wave spectroscopy on the same single crystal. The unusual temperature dependence of phonon eigenfrequencies, dampings and ionic plasma frequencies of low lying phonon modes are analyzed and discussed in detail. Electronic excitations below 4 eV are identified as transitions between full and empty hybridized oxygen-copper bands and between oxygen-copper and unoccupied Ti 3d bands. The unusually small band gap determined from the dc-conductivity (~200 meV) compares well with the optical results.Comment: 7 pages, 8 figure

Association of serum-soluble heat shock protein 60 with carotid atherosclerosis: clinical significance determined in a follow-up study

BACKGROUND AND PURPOSE: Previous work has shown that soluble heat shock protein 60 (HSP60; sHSP60), present in circulating blood, is associated with carotid atherosclerosis. In the current evaluation, we tested the hypothesis that sHSP60 levels are associated with the progression of carotid arteriosclerosis, prospectively. METHODS: The association of sHSP60 with early atherogenesis (5-year development and progression of nonstenotic carotid plaques) was investigated as part of the population-based prospective Bruneck Study. The current study focused on the follow-up period between 1995 and 2000 and, thus, included 684 subjects. RESULTS: sHSP60 levels measured in 1995 and 2000 were highly correlated (r=0.40; P<0.001), indicating consistency over a 5-year period. Circulating HSP60 levels were significantly correlated with antilipopolysaccharide and anti-HSP60 antibodies. It was also elevated in subjects with chronic infection (top quintile group of HSP60, among subjects with and without chronic infection: 23.8% versus 17.0%; P=0.003 after adjustment for age and sex). HSP60 levels were significantly associated with early atherogenesis, both in the entire population (multivariate odds ratio, for a comparison between quintile group V versus I+II: 2.0 [1.2 to 3.5] and the subgroup free of atherosclerosis at the 1995 baseline: 3.8 [1.6 to 8.9]). The risk of early atherogenesis was additionally amplified when high-sHSP60 and chronic infection were present together. CONCLUSIONS: Our study provides the first prospective data confirming an association between high levels of sHSP60 and early carotid atherosclerosis. This possibly indicates an involvement of sHSP60 in activating proinflammatory processes associated with early vessel pathology

Mirror Symmetry and Landau Ginzburg Calabi-Yau Superpotentials in F-theory Compactifications

We study Landau Ginzburg (LG) theories mirror to 2D N=2 gauged linear sigma models on toric Calabi-Yau manifolds. We derive and solve new constraint equations for Landau Ginzburg elliptic Calabi-Yau superpotentials, depending on the physical data of dual linear sigma models. In Calabi-Yau threefolds case, we consider two examples. First, we give the mirror symmetry of the canonical line bundle over the Hirzebruch surfaces $\bf F_n$. Second, we find a special geometry with the affine so(8) Lie algebra toric data extending the geometry of elliptically fibered K3. This geometry leads to a pure N=1 six dimensional SO(8) gauge model from the F-theory compactification. For Calabi-Yau fourfolds, we give a new algebraic realization for ADE hypersurfaces.Comment: 27 pages, latex. To appear in Journal of Physics A: Mathematical and Genera

Reciprocal X;1 translocation in a calf

International audienc

A modified Monte Carlo model for the ionospheric heating rates

A Monte Carlo method is adopted as a basis for the derivation of the photoelectron heat input into the ionospheric plasma. This approach is modified in an attempt to minimize the computation time. The heat input distributions are computed for arbitrarily small source elements that are spaced at distances apart corresponding to the photoelectron dissipation range. By means of a nonlinear interpolation procedure their individual heating rate distributions are utilized to produce synthetic ones that fill the gaps between the Monte Carlo generated distributions. By varying these gaps and the corresponding number of Monte Carlo runs the accuracy of the results is tested to verify the validity of this procedure. It is concluded that this model can reduce the computation time by more than a factor of three, thus improving the feasibility of including Monte Carlo calculations in self-consistent ionosphere models

Mechanical spectroscopy of retina explants at the protein level employing nanostructured scaffolds

Development of neuronal tissue, such as folding of the brain, and formation of the fovea centralis in the human retina are intimately connected with the mechanical properties of the underlying cells and the extracellular matrix. In particular for neuronal tissue as complex as the vertebrate retina, mechanical properties are still a matter of debate due to their relation to numerous diseases as well as surgery, where the tension of the retina can result in tissue detachment during cutting. However, measuring the elasticity of adult retina wholemounts is difficult and until now only the mechanical properties at the surface have been characterized with micrometer resolution. Many processes, however, such as pathological changes prone to cause tissue rupture and detachment, respectively, are reflected in variations of retina elasticity at smaller length scales at the protein level. In the present work we demonstrate that freely oscillating cantilevers composed of nanostructured TiO2 scaffolds can be employed to study the frequency-dependent mechanical response of adult mammalian retina explants at the nanoscale. Constituting highly versatile scaffolds with strong tissue attachment for long-term organotypic culture atop, these scaffolds perform damped vibrations as fingerprints of the mechanical tissue properties that are derived using finite element calculations. Since the tissue adheres to the nanostructures via constitutive proteins on the photoreceptor side of the retina, the latter are stretched and compressed during vibration of the underlying scaffold. Probing mechanical response of individual proteins within the tissue, the proposed mechanical spectroscopy approach opens the way for studying tissue mechanics, diseases and the effect of drugs at the protein level

Programing stimuli-responsiveness of gelatin with electron beams: Basic effects and development of a hydration-controlled biocompatible demonstrator

Biomimetic materials with programmable stimuli responsiveness constitute a highly attractive material class for building bioactuators, sensors and active control elements in future biomedical applications. With this background, we demonstrate how energetic electron beams can be utilized to construct tailored stimuli responsive actuators for biomedical applications. Composed of collagen-derived gelatin, they reveal a mechanical response to hydration and changes in pH-value and ion concentration, while maintaining their excellent biocompatibility and biodegradability. While this is explicitly demonstrated by systematic characterizing an electron-beam synthesized gelatin-based actuator of cantilever geometry, the underlying materials processes are also discussed, based on the fundamental physical and chemical principles. When applied within classical electron beam lithography systems, these findings pave the way for a novel class of highly versatile integrated bioactuators from micro-to macroscales