A Biphasic Approach for the Simulation of Growth Processes in Soft Biological Tissues Incorporating Damage-Induced Stress Softening

In this contribution a coupled material framework is presented, which considers the effects of damage and growth in soft biological tissues. The tissue is described as a porous medium by taking into account a solid and a fluid phase. The fluid phase is assumed to carry nutrients supplying growth of the solid phase. The latter one is described as a fiber-reinforced material, where a damage variable is introduced for the fiber part of the associated free energy function. The performance of the proposed model is demonstrated in a finite element analysis of a simplified human heart model. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A biphasic transverse isotropic FEM model for cartilage

Articular cartilage is a viscoelastic, two-phase and fiber-strengthen tissue; it consists of a solid and a fluid phase. We describe this tissue using the Theory of Porous Media (TPM). Some simulation results are shown. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Deformation induced martensite transformation in a cold-worked forming process of austenitic stainless steel

Within the last years the goal of industrial manufacturing processes – such as tube forming – has shifted towards an optimization of technological as well as mechanical properties of the manufactured structures. For example, during the forming procedure of sheets made of austenitic stainless steel X5CrNi18-10, the content of strain-induced martensite needs to be controlled. In order to achieve optimal structural properties of the manufactured tube with respect to very high-cycle fatigue (VHCF), a martensite ratio of approximately 25% needs to be obtained [1]. On the basis of experimental investigations this contribution deals with the numerical simulation of the tube-forming process with special consideration of the martensite ratio c as a function of temperature and deformation field. For this purpose we extend an existing martensite model on polyaxial states of stress and compare experimental results and numerical simulations for the modified model. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cyclopentadienyl chromium diimine and pyridine-imine complexes: ligand-based radicals and metal-based redox chemistry

Paramagnetic CpCr(III) complexes with antiferromagnetically-coupled anionic radical diimine and pyridine-imine ligands were prepared and characterized. The diimine chloro CpCr[(ArNCR)(2)]Cl complexes (1: Ar = 2,6-iPr(2)C(6)H(3) (Dpp), R = H; 2: Ar = 2,6-Me(2)C(6)H(3) (Xyl), R = Me; 3: Ar = 2,4,6-Me(3)C(6)H(2) (Mes), R = Me) were synthesized by treatment of previously reported Cr(diimine)(THF)(2)Cl(2) precursors with NaCp. Reduction of 1 with Zn gives CpCr[(DppNCH)(2)], 4, resulting from reduction of Cr(III) to Cr(II) with retention of the ligand-based radical. Alkoxide complexes CpCr[(DppNCH)(2)](OCR(2)R') (5: R = Me, R' = Ph; 6: R = iPr, R' = H) were synthesized by protonolysis of Cp(2)Cr with HOCR(2)R' in the presence of the neutral diimine and catalytic base. The corresponding radical pyridine-imine complexes CpCr(PyCHNMes)Cl (9), CpCr(PyCHNMes) (8), and CpCr(PyCHNMes)(OCMe(2)Ph) (11), were prepared by analogous routes. Oxidation of 8 with iodine gives CpCr(PyCHNMes)I (10) where oxidation of Cr(II) to Cr(III) again occurs with retention of the anionic pyridine-imine radical ligand. The molecular structures of complexes 1, 2, 4-8, 10 and 11 were determined by single-crystal X-ray diffraction. Unusual low energy bands were observed in the UV-vis spectra of the reported complexes, with particularly strong transitions observed for the Cr(II) complexes 4 and 8. The electronic structure of pyridine-imine complexes 8 and 10 were investigated by theoretical calculations.     

CAU-3: a new family of porous MOFs with a novel Al-based brick: [Al2(OCH3)4(O2C-X-CO2)] (X = aryl)

A new family of Al-based MOFs denoted as CAU-3 (CAU = Christian-Albrechts-Universit?t) was discovered in the solvothermal system Al(3+)/aryldicarboxylic acid/NaOH/methanol by applying high-throughput-methods. The three compounds reported in this article [Al(2)(OCH(3))(4)BDC], [Al(2)(OCH(3))(4)BDC-NH(2)] and[Al(2)(OCH(3))(4)NDC] (BDC = 1,4-benzenedicarboxylate; NDC = 2,6-naphtalenedicarboxylate) are all based on the same unprecedented inorganic building unit [Al(12)(OCH(3))(24)](12+), which is a dodecameric cyclic aluminium-methanolate-cluster. The material CAU-3-NDC was found to exhibit the highest surface area as well as the highest micropore volume of all Al-based MOFs reported until now.     

Sulfonyl fluoride-based prosthetic compounds as potential (18) f labelling agents

Nucleophilic incorporation of [(18) F]F(-) under aqueous conditions holds several advantages in radiopharmaceutical development, especially with the advent of complex biological pharmacophores. Sulfonyl fluorides can be prepared in water at room temperature, yet they have not been assayed as a potential means to (18) F-labelled biomarkers for PET chemistry. We developed a general route to prepare bifunctional 4-formyl-, 3-formyl-, 4-maleimido- and 4-oxylalkynl-arylsulfonyl [(18) F]fluorides from their sulfonyl chloride analogues in 1:1 mixtures of acetonitrile, THF, or tBuOH and Cs[(18) F]F/Cs(2) CO(3(aq.)) in a reaction time of 15?min at room temperature. With the exception of 4-N-maleimide-benzenesulfonyl fluoride (3), pyridine could be used to simplify radiotracer purification by selectively degrading the precursor without significantly affecting observed yields. The addition of pyridine at the start of [(18) F]fluorination (1:1:0.8 tBuOH/Cs(2) CO(3(aq.)) /pyridine) did not negatively affect yields of 3-formyl-2,4,6-trimethylbenzenesulfonyl [(18) F]fluoride (2) and dramatically improved the yields of 4-(prop-2-ynyloxy)benzenesulfonyl [(18) F]fluoride (4). The N-arylsulfonyl-4-dimethylaminopyridinium derivative of 4 (14) can be prepared and incorporates (18) F efficiently in solutions of 100?% aqueous Cs(2) CO(3) (10?mg?mL(-1) ). As proof-of-principle, [(18) F]2 was synthesised in a preparative fashion [88(±8)?% decay corrected (n=6) from start-of-synthesis] and used to radioactively label an oxyamino-modified bombesin(6-14) analogue [35(±6)?% decay corrected (n=4) from start-of-synthesis]. Total preparation time was 105-109?min from start-of-synthesis. Although the (18) F-peptide exhibited evidence of proteolytic defluorination and modification, our study is the first step in developing an aqueous, room temperature (18) F labelling strategy.     

Viability of Human Mesenchymal Stem Cells Seeded on Crosslinked Entropy‐Elastic Gelatin‐Based Hydrogels

Biomimetic polymer network systems with tailorable properties based on biopolymers represent a class of degradable hydrogels that provides sequences for protein adsorption and cell adhesion. Such materials show potential for in vitro MSC proliferation as well as in vivo applications and were obtained by crosslinking different concentrations of gelatin using varying amounts of ethyl lysine diisocyanate in the presence of a surfactant in pH 7.4 PBS solution. Material extracts, which were tested for cytotoxic effects using L929 mouse fibroblasts, were non‐toxic. The hydrogels were seeded with human bone marrow‐derived MSCs and supported viable MSCs for the incubation time of 9 d. Preadsorption of fibronectin on materials improved this biofunctionality.

     

A preliminary study of functional abnormalities in aMCI subjects during different episodic memory tasks

Functional magnetic resonance imaging (fMRI) is an important imaging modality to understand the neurodegenerative course of mild cognitive impairment (MCI) and early Alzheimer's disease (AD), because the memory dysfunction may occur before structural degeneration is obvious. In this research, we investigated the functional abnormalities of subjects with amnestic MCI (aMCI) using three episodic memory paradigms that are relevant to different memory domains in both encoding and recognition phases. Both whole-brain analysis and region-of-interest (ROI) analysis of the medial temporal lobes (MTL), which are central to the memory formation and retrieval, were used to compare the efficiency of the different memory paradigms and the functional difference between aMCI subjects and normal control subjects. We also investigated the impact of using different functional activation measurements in ROI analysis. This pilot study could facilitate the use of fMRI activations in the MTL as a marker for early detection and monitoring progression of AD.     

Calculation of dispersion energies

We summarize the theory of van der Waals (dispersion) forces, with emphasis on recent microscopic approaches that permit the prediction of forces between solids and nanostructures right down to intimate contact and binding. Some connections are pointed out between microscopic theory and macroscopic Lifshitz theory.     

Manipulating the nanostructure of organogels generated from molecules with a 3-dimensional truxene core

Two new truxene-based 3-dimensional (3-D) molecules self-assembled in cyclohexane to give organogels with vesicular and fibrillar nano-morphologies governed by the substitution pattern of the peripheral alkyl amido side-chains grafted onto the rigid 3-D core.