Improved integrated waveguide absorbance optodes for ion-selective sensing

The first prototype of a technologically improved integrated waveguide absorbance optode (IWAO) was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a cadmium ionophore. It was designed with curved instead of rectilinear planar waveguides. Results demonstrated the suitability of the new IWAOs to be employed as sensing platforms, which confer versatility, robustness, and mass production capabilities besides high sensitivity on conventional bulk optodes, as well as the usefulness of such dyes in developing ion-selective membranes in combination with a selective ionophore. The sensor integration as a detector in a flow injection system (FIA) was proposed to obtain an automated, simple, and sufficiently reproducible (RSD <5%) analytical methodology with a sample throughput of 55 h(-1). Very sensitive optodes were obtained, and detection limits on the order of 20 ppb were achieved. Because of the ionophore employed, the optode system showed excellent selectivity over alkali and alkaline-earth metals with the exception of samples containing lead and cadmium ions, where the membrane responded to both analytes. The proposed procedure combines all the advantages of the FIA systems, the simplicity of optical detection, ion recognition selectivity, and sensitivity of ketocyanine dyes, and the features achieved using the integrated device, which comprise an improved sensitivity and short response times as well as robustness, easy handling, and mass production.     

Aligned Immobilization of Proteins Using AC Electric Fields

Protein molecules are aligned and immobilized from solution by AC electric fields. In a single‐step experiment, the enhanced green fluorescent proteins are immobilized on the surface as well as at the edges of planar nanoelectrodes. Alignment is found to follow the molecules' geometrical shape with their longitudinal axes parallel to the electric field. Simultaneous dielectrophoretic attraction and AC electroosmotic flow are identified as the dominant forces causing protein movement and alignment. Molecular orientation is determined by fluorescence microscopy based on polarized excitation of the proteins' chromophores. The chromophores' orientation with respect to the whole molecule supports X‐ray crystal data.     

Locking and Unlocking the Molecular Spin Crossover Transition

The Fe(II) spin crossover complex [Fe{H₂B(pz)₂}₂(bipy)] (pz = pyrazol‐1‐yl, bipy = 2,2′‐bipyridine) can be locked in a largely low‐spin‐state configuration over a temperature range that includes temperatures well above the thermal spin crossover temperature of 160 K. This locking of the spin state is achieved for nanometer thin films of this complex in two distinct ways: through substrate interactions with dielectric substrates such as SiO₂ and Al₂O₃, or in powder samples by mixing with the strongly dipolar zwitterionic p ‐benzoquinonemonoimine C₆H₂(—? NH₂)₂(—? O)₂. Remarkably, it is found in both cases that incident X‐ray fluences then restore the [Fe{H₂B(pz)₂}₂(bipy)] moiety to an electronic state characteristic of the high spin state at temperatures of 200 K to above room temperature; that is, well above the spin crossover transition temperature for the pristine powder, and well above the temperatures characteristic of light‐ or X‐ray‐induced excited‐spin‐state trapping. Heating slightly above room temperature allows the initial locked state to be restored. These findings, supported by theory, show how the spin crossover transition can be manipulated reversibly around room temperature by appropriate design of the electrostatic and chemical environment.     

Encapsulation,Visualization and Expression of Genes with Biomimetically Mineralized Zeolitic Imidazolate Framework‐8 (ZIF‐8)

Recent work in biomolecule‐metal–organic framework (MOF) composites has proven to be an effective strategy for the protection of proteins. However, for other biomacromolecules such as nucleic acids, the encapsulation into nano MOFs and the related characterizations are in their infancy. Herein, encapsulation of a complete gene‐set in zeolitic imidazolate framework‐8 (ZIF‐8) MOFs and cellular expression of the gene delivered by the nano MOF composites are reported. Using a green fluorescent protein (GFP) plasmid (plGFP) as a proof‐of‐concept genetic macromolecule, successful transfection of mammalian cancer cells with plGFP for up to 4 days is shown. Cell transfection assays and soft X‐ray cryo‐tomography (cryo‐SXT) demonstrate the feasibility of DNA@MOF biocomposites as intracellular gene delivery vehicles. Expression occurs over relatively prolonged time points where the cargo nucleic acid is released gradually in order to maintain sustained expression.     

Interfacial debonds of layered anisotropic materials using a quasi-static interface damage model with Coulomb friction

The resistance to mode I failure of rubbers is studied by submitting single edge notch samples to uniaxial tension. Reproducing the seminal work of Rivlin and Thomas (J Polym Sci 10:291–318, 1953), single edge notch tension specimens, presenting notches of various lengths, are stretched until break. A styrene butadiene rubber, unfilled and filled with carbon-black, and an unfilled rubber from the latter mentioned work, were considered. When the notch is smaller than one fifth of the sample width, mode I crack opening is observed, leading to catastrophic failure that creates smooth mirror-like crack surfaces. Nonetheless, the experimental force-elongation responses show that the mode I critical energy release rate cannot be calculated by a classical Griffith elastic failure analysis. When notches are longer, the SENT samples are not submitted to pure uniaxial tension only. Structural bending leads to uncontrolled mixed mode crack propagation. The surfaces created when the long notches propagate are rough and bifurcations are witnessed for the filled rubbers.     

Influence of the length of the internal sleeve valve on the release of powdery substances from the closures of valved bags for dangerous goods

In practice, checks on dangerous goods transports often detect leaks of powdered dangerous goods from valved bags. In this work, the influence factors of a sudden release of powdery substances from the valves of valved bags were investigated. Drop tests were performed on paper bags of UN design type 5M2 with internal sleeve valve using 2 different powdery substances (Esplas H130 and zinc oxide “Rotsiegel”). The internal sleeve valves of all test samples were not sift‐proof with respect to both filling substances. For almost all test samples, the Esplas H130 powder already leaked out of pasted joints during manual filling. This is a contradiction to the requirement in UN 6.1.4.18.1, according to which closures and joints of paper bags 5M2 should be sift‐proof. In the drop tests, longer valve lengths had a greater sealing effect for both filling substances (for filling degrees of at least 95% and for test samples which had already been mechanically loaded). As an extreme example, at the drop height of 1.20 m and a filling degree of 100%, the released amount of zinc oxide powder from a 10‐cm‐long valve was about 16 times higher than from a valve length of 12.5 cm. The valve length is therefore a safety‐relevant parameter and should be specified by the manufacturer. To ensure that only filling goods with similar physical properties in comparison with the test substance are used for valved bags, the user must be informed of the particle size of the test substance.     

Tunable Magnetism in Nanoporous CuNi Alloys by Reversible Voltage‐Driven Element‐Selective Redox Processes

Voltage‐driven manipulation of magnetism in electrodeposited 200 nm thick nanoporous single‐phase solid solution Cu₂₀Ni₈₀ (at%) alloy films (with sub 10 nm pore size) is accomplished by controlled reduction‐oxidation (i.e., redox) processes in a protic solvent, namely 1 m NaOH aqueous solution. Owing to the selectivity of the electrochemical processes, the oxidation of the CuNi film mainly occurs on the Cu counterpart of the solid solution, resulting in a Ni‐enriched alloy. As a consequence, the magnetic moment at saturation significantly increases (up to 33% enhancement with respect to the as‐prepared sample), while only slight changes in coercivity are observed. Conversely, the reduction process brings Cu back to its metallic state and, remarkably, it becomes alloyed to Ni again. The reported phenomenon is fully reversible, thus allowing for the precise adjustment of the magnetic properties of this system through the sign and amplitude of the applied voltage.     

Atomic Structures of Precipitates in Al–Mg–Si Alloys with Small Additions of Other Elements

In Al–Mg–Si alloys, additions of only a few weight percent of Mg and Si enable formation of hardening precipitates during heat treatment. The precipitation is complex and is influenced by chemical compositions and thermo‐mechanical treatment. Structural analysis at the atomic scale has played an important role for understanding the Al–Mg–Si system. This review paper gives a summary of the influence of elements on the precipitate structures of Al–Mg–Si alloys at the atomic scale. The structures are modified by small additions of different elements, but all the encountered precipitates are structurally connected with the Si network, except for the main hardening phase which exhibit a partially discontinuous Si network. The influence of the selected elements (Li, Cu, Zn, Ge, Ag, Ni, Co, and Au) is discussed in detail.

     

An adaptive solver for the spherical shallow water equations

The shallow water equations (SWE), which describe the flow of a thin layer of fluid in two dimensions have been used by the atmospheric modelling community as a vehicle for testing promising numerical methods for solving atmospheric and oceanic problems. The SWE are important for the study of the dynamics of large-scale flows, as well for the development of new numerical schemes that are applied to more complex models. In this paper we present a finite difference p-adaptive method based on high order finite differences that is applied using an error indicator for solving the SWE on the sphere. A standard test set is used to evaluate the accuracy of the new method. The results obtained are compared with the pseudo-spectral method.