Distance-dependent fluorescence quenching on gold nanoparticles ensheathed with layer-by-layer assembled polyelectrolytes

We report on the preparation, characterization, and photophysical study of new fluorescent core/shell nanoparticles fabricated by electrostatic layer-by-layer assembly. On the basis of gold cores with a diameter of 13 nm, these nanocolloids possess different fluorescently labeled polymer corona layers at various distances from the surface of the core metal using nonfluorescent polyelectrolytes as spacer layers. UV-visible spectroscopy and transmission electron microscopy confirm that the particle suspensions of fluorescently labeled core/shell nanoparticles are stable at all stages of their construction. Photophysical investigations reveal strongly distance-dependent fluorescence quenching in these particle systems. The contribution of the metal core to this quenching can be assesed precisely after the gentle dissolution of the gold cores by potassium cyanide. The photophysical measurements reveal clearly that the gold nanoparticles decrease the transition probability for radiative transitions.     

Impact of chemical inhomogeneities on local material properties and hydrogen environment embrittlement in AISI 304L steels

This study investigated the influence of segregations on hydrogen environment embrittlement (HEE) of AISI 304L type austenitic stainless steels. The microstructure of tensile specimens, that were fabricated from commercially available AISI 304L steels and tested by means of small strain-rate tensile tests in air as well as hydrogen gas at room temperature, was investigated by means of combined EDS and EBSD measurements. It was shown that two different austenitic stainless steels having the same nominal alloy composition can exhibit different susceptibilities to HEE due to segregation effects resulting from different production routes (continuous casting/electroslag remelting). Local segregation-related variations of the austenite stability were evaluated by thermodynamic and empirical calculations. The alloying element Ni exhibits pronounced segregation bands parallel to the rolling direction of the material, which strongly influences the local austenite stability. The latter was revealed by generating and evaluating two-dimensional distribution maps for the austenite stability. The formation of deformation-induced martensite was shown to be restricted to segregation bands with a low Ni content. Furthermore, it was shown that the formation of hydrogen induced surface cracks is strongly coupled with the existence of surface regions of low Ni content and accordingly low austenite stability. In addition, the growth behavior of hydrogen-induced cracks was linked to the segregation-related local austenite stability.     

Improving neural network models of physical systems through dimensional analysis

The paper presents a technique for generating concise neural network models of physical systems. The neural network models are generated through a two-stage process. The first stage uses information embedded in the dimensions or units in which the data is represented. Dimensional analysis techniques are used initially to make this information explicit, and a limited search in the neural network architecture space is then conducted to determine dimensionless representations of variables/parameters that perform well for a given model complexity. The second stage uses information available in the numerical values of the data to search for high-level dimensionless variables/parameters, generated from simple combinations of dimensionless quantities generated in the first stage and which result in concise neural network models with improved performance characteristics. The search for these high-level dimensionless variables/parameters is conducted in an enhanced representation space using functional link networks with flat or near flat architectures. The use and effectiveness of the technique is demonstrated for three applications. The first is the design and analysis of reinforced concrete beams, which is representative of the class of problems associated with the design and analysis of composites. The second is the classical elastica problem, for predicting non-linear post-buckled behaviour of columns and the third, the analysis of a bent bar under a specified combination of loads.     

Architectural complexity and contradiction: a fuzzy set-theoretic basis and viewpoint

In this paper, the authors examine an essential problem of contemporary architecture, namely, that of complexity and contradiction. The complex and contradictory architecture considered here is that which is based on the richness and ambiguity of modern experience as well as on the perpetual imprecision and fuzziness of human experience. Such an architecture is a valid one which evokes many levels of meaning and combinations of focus, and whose space and elements become readable and workable in many ways at a single instance.The concept of a ‘fuzzy structure’ is developed for the purpose of analysis and synthesis of architectural complexities and contradictions. It is then shown in passing that, under appropriate semantics, the fuzzy algebra of Kandel and the fuzzy system of Zimmermann are ‘components’ — and hence special interpretative realizations — of the fuzzy structure.     

Towards mass customized interoperability

This paper describes an approach to interoperability in design projects that is based on computational agents customizing the representation of product data to individual design tools. The agents can augment their translator capabilities autonomously at runtime. This has the potential to lessen the need to manually pre-define an appropriate set of tool translators. The process of generating tailored product models uses an approach to organizing agent knowledge that limits computational complexity when large numbers of tools are involved. We report the implementation and evaluation of an agent-based system that demonstrates the fundamental features of mass customized interoperability. Results include an average reduction of manual work by 88% using this approach.     

Impacts of Snowmelt on Peak Flows in a Forest Watershed

Using data of long-term observations at three gauging stations and one climatic station in a forest region in southeast Germany, the impacts of snowmelt on peak flow have been investigated in this paper. Results show that the major climatic feature was found to be a precipitation maximum during the hydrological summer, and the major hydrological feature was a discharge maximum during the hydrological winter. Empirical equations describing snow depth and snow water equivalent for the studied climatic station have been developed for both snow accumulation period and ablation period. Through introducing snowmelt-rainfall depth as a new variable, the present work investigates the simultaneous occurrence of snowmelt and rainfall on snow cover, assesses the characteristics of runoff including peak flows, calculates the runoff from the snowmelt and rainfall. A hydrological model has been applied to generate hydrographs resulted from snowmelt and rainfall-on-snow.     

cAMP and the Fibrous Sheath Protein CABYR (Ca2+-Binding Tyrosine-Phosphorylation-Regulated Protein) Is Required for 4D Sperm Movement

A new life starts with successful fertilization whereby one sperm from a pool of millions fertilizes the oocyte. Sperm motility is one key factor for this selection process, which depends on a coordinated flagellar movement. The flagellar beat cycle is regulated by Ca²⁺ entry via CatSper, cAMP, Mg²⁺, ADP and ATP. This study characterizes the effects of these parameters for 4D sperm motility, especially for flagellar movement and the conserved clockwise (CW) path chirality of murine sperm. Therefore, we use detergent-extracted mouse sperm and digital holographic microscopy (DHM) to show that a balanced ratio of ATP to Mg²⁺ in addition with 18 µM cAMP and 1 mM ADP is necessary for controlled flagellar movement, induction of rolling along the long axis and CW path chirality. Rolling along the sperm’s long axis, a proposed mechanism for sperm selection, is absent in sea urchin sperm, lacking flagellar fibrous sheath (FS) and outer-dense fibers (ODFs). In sperm lacking CABYR, a Ca²⁺-binding tyrosine-phosphorylation regulated protein located in the FS, the swim path chirality is preserved. We conclude that specific concentrations of ATP, ADP, cAMP and Mg²⁺ as well as a functional CABYR play an important role for sperm motility especially for path chirality.     

Immuno-surface-enhanced coherent anti-stokes Raman scattering microscopy: immunohistochemistry with target-specific metallic nanoprobes and nonlinear Raman microscopy

Immunohistochemistry (IHC) is one of the most widely used staining techniques for diagnostic purposes. The selective localization of target proteins in tissue specimens by conventional IHC is achieved with dye- or enzyme-labeled antibodies in combination with light microscopy. In this contribution, we demonstrate the proof-of-principle for IHC based on surface-enhanced coherent Raman scattering for contrast generation. Specifically, antibody-labeled metallic nanoshells in conjunction with surface-enhanced coherent anti-Stokes Raman scattering (SECARS) microscopy are employed for the selective, sensitive, and rapid localization of the basal cell protein p63 in normal prostate tissue. Negative control experiments were performed in order to confirm the selective binding of the target-specific metal nanoprobes and to disentangle the role of plasmonic (metal) and molecular (Raman reporter) resonances in this plasmon-assisted four-wave mixing technique.