A Benzaldehyde Derivative as a Chelating Ligand: Helical Manganese(II) Coordination Polymers Assembling into a Porous Solid

A molecular, porous crystalline material constructed from neutral helical coordination polymers incorporating manganese(II) ions and two types of bridging ligands, namely the deprotonated form of 2-hydroxy-5-methoxy-3-nitrobenzaldehyde (HL) and isobutyrate (iB−), has been obtained and structurally characterized. Structural analysis reveals that within the coordination polymer each benzaldehyde derivative ligates two manganese ions in 6-membered chelating rings, and the isobutyrate ligands cooperatively chelate either two or three manganese ions. The solid state assembly of the resulting polymeric chains of formula [Mn4(L)2(iB)6]n (1), described in the polar space group R3c, is associated with tubular channels occupied by MeCN solvent molecules (1·xMeCN; x ≤ 9). TGA profiles and PXRD measurements demonstrate that the crystallinity of the solid remains intact in its fully desolvated form, and its stability and crystallinity are ensured up to a temperature of 190 °C. Gas adsorption properties of desolvated crystals were probed, but no remarkable sorption capacity of N2 and only a limited one for CO2 could be observed. Magnetic susceptibility data reveal an antiferromagnetic type of coupling between adjacent manganese(II) ions along the helical chains with energy parameters J1 = −5.9(6) cm−1 and J2 = −1.8(9) cm−1.

Synthesis of bone-like micro-porous calcium phosphate/iota-carrageenan composites by gel diffusion

Brushite and octacalcium phosphate (OCP) crystals are well-known precursors of hydroxylapatite (HAp), the main mineral found in bone. In this report, we present a new method for biomimicking brushite and OCP using single and double diffusion techniques. Brushite and OCP crystals were grown in an iota-carrageenan gel. The aggregates were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and thermal gravimetric analysis (TGA). SEM revealed different morphologies of brushite crystals from highly porous aggregates to plate-shaped forms. OCP crystals grown in iota-carrageenan showed a porous spherical shape different from brushite growth forms. The XRD method demonstrated that the single-diffusion method favors the formation of monoclinic brushite. In contrast, the double diffusion method was found to promote the formation of the triclinic octacalcium phosphate OCP phase. By combining the different parameters for crystal growth in carrageenan, such as ion concentration, gel pH and gel density, it is possible to modify the morphology of composite crystals, change the phase of calcium phosphate and modulate the amount of carrageenan inclusion in crystals. This study suggests that iota-carrageenan is a high-molecular-weight polysaccharide that is potentially applicable for controlling calcium phosphate crystallization.

Upscaling of anisotropy in unsaturated Miller-similar porous media

Geological and pedological processes rarely form isotropic media as is usually assumed in transport studies. Anisotropy at the Darcy or field scale may be detected directly by measuring flow parameters or may become indirectly evident from movement and shape of solute plumes. Anisotropic behavior of a soil at one scale may, in many cases, be related to the presence of lower-scale directional structures. Miller similitude with different pore-scale geometries of the basic element is used to model macroscopic flow and transport behavior. Analytical expressions for the anisotropic conductivity tensor are derived based on the dynamic law that governs the flow problem at the pore scale. The effects of anisotropy on transport parameters are estimated by numerical modeling.

Development of light-responsive porous polycarbonate membranes for controlled caffeine delivery

For controlled caffeine release, light-responsive membranes were developed. It was possible to produce membranes that reduced their caffeine permeability resistance by about 97% when irradiated with UV-light compared to measurements at daylight. This was achieved by grafting polymers possessing photochromic units onto track-edged polycarbonate membranes. Covalently linked coatings on porous polycarbonate membranes were obtained by plasma activation of the membrane surface followed by plasma-induced graft polymerization. Copolymerization of spiro-compounds during the coating process as well as postmodification of preformed coatings with spiropyran resulted in photochromic membranes. For the copolymerization process, the synthesis of five photochromic methacrylic and acrylic spiropyrans and spirooxazines was successfully performed. Additionally, a spiropyran with carboxylic acid functionality was synthesized for the postmodification process. This enabled us to postmodify polymeric materials containing alcohol or amine groups to obtain photochromic materials. UV-irradiation of these light-responsive membranes resulted in a strong colouration of the membrane, in a reduction of surface tension, which resulted in a decreased caffeine permeability resistance. The membranes were characterized using XPS for the elemental composition of the coating, contact angle measurements for the surface tension, solid-state UV/VIS measurements for the determination of the kinetic and stability properties, and two-photon microscopy for the localisation of the photochromic substance in the porous membrane.

Dissolution-Precipitation in Porous Media: Experiments and Modelling

The evolution of porosity due to dissolution/precipitation processes of minerals and the associated change of transport parameters are of major interest for natural geological environments and engineered underground structures. We designed a reproducible and fast to conduct 2D experiment, which is flexible enough to investigate several process couplings implemented in the numerical code OpenGeosys-GEM (OGS-GEM). We investigated advective-diffusive transport of solutes, effect of liquid phase density on advective transport, and kinetically controlled dissolution/precipitation reactions causing porosity changes. In addition, the system allowed to investigate the influence of microscopic (pore scale) processes on macroscopic (continuum scale) transport. A Plexiglas tank of dimension 10 × 10 cm was filled with a 1 cm thick reactive layer consisting of a bimodal grain size distribution of celestite (SrSO4) crystals, sandwiched between two layers of sand. A barium chloride solution was injected into the tank causing an asymmetric flow field to develop. As the barium chloride reached the celestite region, dissolution of celestite was initiated and barite precipitated. Due to the higher molar volume of barite, its precipitation caused a porosity decrease and thus also a decrease in the permeability of the porous medium. The change of flow in space and time was observed via injection of conservative tracers and analysis of effluents. In addition, an extensive post-mortem analysis of the reacted medium was conducted. We could successfully model the flow (with and without fluid density effects) and the transport of conservative tracers with a (continuum scale) reactive transport model. The prediction of the reactive experiments initially failed. Only the inclusion of information from post-mortem analysis gave a satisfactory match for the case where the flow field changed due to dissolution/precipitation reactions. We concentrated on the refinement of post-mortem analysis and the investigation of the dissolution/precipitation mechanisms at the pore scale. Our analytical techniques combined scanning electron microscopy (SEM) and synchrotron X-ray micro-diffraction/micro-fluorescence performed at the XAS beamline (Swiss Light Source). The newly formed phases include an epitaxial growth of barite micro-crystals on large celestite crystals (epitaxial growth) and a nano-crystalline barite phase (resulting from the dissolution of small celestite crystals) with residues of celestite crystals in the pore interstices. Classical nucleation theory, using well-established and estimated parameters describing barite precipitation, was applied to explain the mineralogical changes occurring in our system. Our pore scale investigation showed limits of the continuum scale reactive transport model. Although kinetic effects were implemented by fixing two distinct rates for the dissolution of large and small celestite crystals, instantaneous precipitation of barite was assumed as soon as oversaturation occurred. Precipitation kinetics, passivation of large celestite crystals and metastability of supersaturated solutions, i.e. the conditions under which nucleation cannot occur despite high supersaturation, were neglected. These results will be used to develop a pore scale model that describes precipitation and dissolution of crystals at the pore scale for various transport and chemical conditions. Pore scale modelling can be used to parameterize constitutive equations to introduce pore-scale corrections into macroscopic (continuum) reactive transport models. Microscopic understanding of the system is fundamental for modelling from the pore to the continuum scale.

Permittivity measurements of porous matter in support of investigations of the surface and interior of 67P/Churyumov-Gerasimenko

Aims. Permittivity measurements on porous samples of volcanic origin have been performed in the 0.05-190 GHz range under laboratory conditions in support of the Rosetta mission to comet 67P/Churyumov-Gerasimenko, specifically with the MIRO radiometric experiment and CONSERT radar experiment. Methods. The samples were split into several subsamples with different size ranges covering a few mu m to 500 mu m. Bulk densities of the subsamples were estimated to be in the 800 to 1500 kg/m(3) range. The porosities were in the range of 48% to 65%. From 50 MHz to 6 GHz and at 190 GHz, permittivity has been determined with a coaxial cell and with a quasi-optical bench, respectively. Results. Without taking into account the volume-scattering effect at 190 GHz, the real part of the permittivity, normalized by the bulk density, is in the range of 2.1 to 2.6. The results suggest that the real part of the permittivity of an ice-free dust mantle covering the nucleus is in the 1.5-2.2 range at 190 GHz. From these values, a lower limit for the absorption length for the millimeter receiver of MIRO has been estimated to be between 0.6 and 2 cm, in agreement with results obtained from MIRO in September 2014. At frequencies of interest for CONSERT experiment, the real part of the permittivity of a suspected ice-free dust mantle should be below 2.2. It may be in the range of 1.2 to 1.7 for the nucleus, in agreement with first CONSERT results, taking into account a mean temperature of 110 K and different values for the dust-to-ice volumetric ratio. Estimations of contributions of the different parameters to the permittivity variation may indicate that the porosity is the main parameter.

Osteoblast Response to Commercially Available Ti-6Al-4V and Novel Porous Tantalum. In Vitro Biocompatibility Studies

The response of human osteoblasts to materials is crucial for evaluating biocompatibility of an implant material for bone defects. Previous work in our lab demonstrated that the response of human osteoblasts to orthopaedic and dental materials in vitro varies depending on the sex and age of the patient [1]. Osteoblasts from female patients older than 60 years old, adhered less and produced less matrix proteins and calcification than osteoblasts from younger female patients and all ages of male patients. Recently developed, porous tantalum demonstrates improved biomechanical properties for bone and good biocompatibility in in vivo human studies, however there are few, if any, in vitro biocompatibility studies on this material. In this project, we aimed to compare the phenotypic expression of human osteoblasts from young and old female patients to commercially available Ti-6Al-4V and porous tantalum in a well-developed in vitro system. 1. Zhang H, Lewis CG, Aronow MS, Gronowicz G. The effect of patient age on human osteoblasts’ response to Ti-6Al-4V implants in vitro. J. Orthop. Res. 2004;22(1):30-8.

Heinrich Sauer als Oberon, Annemarie Rothe als Titania, Szenenfoto, in: William Shakespeare: Ein Sommernachtstraum

Signatur des Originals: S 36/F06162

Philine, Mignon {[u.a.], Opernszene, Gruppenbildnis, in: Ambroise Thomas: Mignon, 2. Akt, Polonaise de Titania

Signatur des Originals: S 36/G03813

Theoretical study of band alignment in nano-porous ZnO interacting with substituted Phthalocyanines

The aim of this work is the theoretical study of the band alignment between the two components of a hybrid organic-inorganic solar-cell. The working organic molecules are metal tetra-sulphonated phthalocyanines (M-Pc) and the inorganic material is nano-porous ZnO growth in the 001 direction. The theoretical calculations are being made using the density functional theory (DFT) using a GGA functional with the SIESTA code, which projects electron wave functions and density onto a real space grid and uses as basis set a linear combination of numerical, finite-range localized atomic orbitals. We also used the DFT+U method included in the code that allows a semi-empirical inclusion of electronic correlations in the description of electronic spectra for systems such as zinc oxide.

Community Structure in Soil Porous System

Diffusion controls the gaseous transport process in soils when advective transport is almost null. Knowledge of the soil structure and pore connectivity are critical issues to understand and modelling soil aeration, sequestration or emission of greenhouse gasses, volatilization of volatile organic chemicals among other phenomena. In the last decades these issues increased our attention as scientist have realize that soil is one of the most complex materials on the earth, within which many biological, physical and chemical processes that support life and affect climate change take place. A quantitative and explicit characterization of soil structure is difficult because of the complexity of the pore space. This is the main reason why most theoretical approaches to soil porosity are idealizations to simplify this system. In this work, we proposed a more realistic attempt to capture the complexity of the system developing a model that considers the size and location of pores in order to relate them into a network. In the model we interpret porous soils as heterogeneous networks where pores are represented by nodes, characterized by their size and spatial location, and the links representing flows between them. In this work we perform an analysis of the community structure of porous media of soils represented as networks. For different real soils samples, modelled as heterogeneous complex networks, spatial communities of pores have been detected depending on the values of the parameters of the porous soil model used. These types of models are named as Heterogeneous Preferential Attachment (HPA). Developing an exhaustive analysis of the model, analytical solutions are obtained for the degree densities and degree distribution of the pore networks generated by the model in the thermodynamic limit and shown that the networks exhibit similar properties to those observed in other complex networks. With the aim to study in more detail topological properties of these networks, the presence of soil pore community structures is studied. The detection of communities of pores, as groups densely connected with only sparser connections between groups, could contribute to understand the mechanisms of the diffusion phenomena in soils.