Influence of non‐uniform fine lines in silicon solar cell front metal grid design

While it is well known that the typical printed silver fingers on a silicon solar cell have profile striations, bottle‐necks, and line breaks, the impact of these imperfections have not been assessed in calculations of front grid related power losses. This study uses detailed finite element modeling to show that when the realistic effects of non‐uniform line conductance is accounted for; the simulated cell efficiency can be significantly lower than under the assumption of uniform lines, becoming closer to measured trends. The study also explores the incorporation of additional interconnecting fingers to the parallel grid finger in the H pattern, concluding that they are typically of no benefit to improving the cell efficiency. As an auxiliary observation, it was found that the efficiency calculated by simple ohmic power loss formulae is typically underestimated by 0.1–0.2% absolute, a margin that should be accounted for in cell optimization and analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Rational design of highly active and selective ligands for the alpha5beta1 integrin receptor

The inhibition of integrin function is a major challenge in medicinal chemistry. Potent ligands are currently in different stages of clinical trials for the antiangiogenic therapy of cancer and age-related macula degeneration (AMD). The subtype alpha5beta1 has recently been drawn into the focus of research because of its genuine role in angiogenesis. In our previous work we could demonstrate that the lack of structural information about the receptor could be overcome by a homology model based on the X-ray structure of the alphavbeta3 integrin subtype and the sequence similarities between both receptors. In this work, we describe the rational design and synthesis of high affinity alpha5beta1 binders, and the optimisation of selectivity against alphavbeta3 by means of extensive SAR studies and docking experiments. A first series of compounds based on the tyrosine scaffold resulted in affinities in the low and even subnanomolar range and selectivities of 400-fold against alphavbeta3. The insights about the structure-activity relationship gained from tyrosine-based ligands could be successfully transferred to ligands that bear an aza-glycine scaffold to yield alpha5beta1 ligands with affinities of approximately 1 nm and selectivities that exceed 10(4)-fold. The ligands have already been successfully employed as selective alpha5beta1 ligands in biological research and might serve as lead structures for antiangiogenic cancer therapy.     

Autonomous magnetically actuated continuous flow microimmunofluorocytometry assay

This article presents a microfluidic device which integrates autonomous serial immunofluorocytometry binding reactions of cytometric beads with fluorescence detection and quantification in a continuous flow environment. The microdevice assay is intended to alleviate the extensive benchwork and large sample volumes used when conducting traditional immunoassays, without requiring complex external controls. The technology is based on the miniaturization and automation of the serial processing steps of an antigen sandwich immunoassay, with integrated fluorescence detection using paramagnetic microbeads. The continuous flow design may enable temporal tracking of time-varying protein concentrations in a continuously infused sample for clinical applications, specifically for monitoring inflammation marker proteins in blood produced during cardiac surgeries involving cardiopulmonary bypass (CPB) procedures. The device operation was first validated via a single incubation device which measured the concentration of a fluorescently labeled biotin molecule using streptavidin-coated paramagnetic cytometric beads. Subsequently, a dual incubation device was tested with samples of the anaphylatoxin complement protein C3a, and was shown to be capable of differentiating between samples at typical systemic concentrations of the protein (1–5 μg/ml), with very low sample usage (<6 μl/h). It is believed that this continuous flow, automated microimmunosensor technology will be a platform for high sample rate immunoassays capable of tracking and more thoroughly characterizing the systemic inflammation process, and may aid in the development of better treatment options for systemic inflammation during and after CPB.     

Towards an atomistic understanding of apatite–collagen biomaterials: linking molecular simulation studies of complex-, crystal- and composite-formation to experimental findings

The investigation of the atomistic mechanisms of crystal nucleation constitutes a major challenge to both experiment and theory. Understanding the underlying principles of composite materials formation represents an even harder task. For the investigation of the mechanisms of crystal nucleation a profound knowledge of the ion–solvent and the ion–ion interactions in solution is required. Studying biocomposites like fluorapatite–collagen materials, we must furthermore account for the biomolecules and their effect on the growth process. Molecular simulation approaches directly offer atomistic resolution and hence appear particularly suited for detailed mechanistic analyses. However, the computational effort is typically immense and for a long time the investigation of crystal nucleation from atomistic simulations was considered as impossible. We therefore developed special simulation strategies, which allowed to considerably extent the limitations of computational studies in this field. In combination with advanced experimental investigations this provided new insights into the nucleation of biomimetic apatite–gelatin composites and the mechanisms of hierarchical growth at the micro- and mesoscopic scale. Along this line, molecular simulation studies reflect a powerful tool to achieve a profound understanding of the complex growth processes of apatite/collagen composites. Apart from reviewing related work we outline future directions and discuss the perspectives of simulation studies for the investigation of biomineralization processes in general.     

Size effects on Raman spectra of small CdSe nanoparticles in polymer films

The results of a resonant Raman scattering (RRS) study of polymer-stabilized colloidal CdSe nanoparticles (NPs) are reported. The size-selective nature of the RRS is demonstrated by analysing the NP ensembles with different average size [Formula: see text] and size distribution Δd using a set of excitation wavelengths. The effect of size selection on the estimation of [Formula: see text] and Δd values from the RRS spectra is discussed, as well as some peculiarities of RRS on surface optical phonons. From the experimentally observed small variation of the I(2LO)/I(LO) ratio for 2-5?nm NPs a minor effect of [Formula: see text] on the electron-phonon coupling strength in this [Formula: see text] range is supposed.     

Optimization of multi-wavelength interdigital dielectrometryinstrumentation and algorithms

Interdigital frequency-wavelength dielectrometry can be used to measure the dielectric permittivity and conductivity of insulating materials. The complex dielectric permittivity is directly related to other material properties, such as moisture content, temperature, concentration of impurities and additives, density, aging status, etc. The analysis of spatial and temporal variations of these properties lends valuable insights into physical phenomena which take place in electrical equipment, provides instrumentation for system monitoring and diagnostics, and can be used for optimization of design and performance of electrical apparatus. The optimization of various aspects of this technology is described in this paper. Improvement of performance is achieved through variation of geometrical design, materials, manufacturing processes, and electronic circuitry. Accumulated effects of non-ideal geometry of the experimental setup and the sensor itself are accounted for through empirical measurements, calibration, and use of finite-element calculations. Three distinct operating modes are developed: floating voltage with grounded backplane, floating voltage with guarded backplane, and short circuit current. Measurements reveal that the interfacial contact quality has a strong influence on the sensor's response. Gain/phase measurements over the frequency range 5 mHz to 10 kHz agree well with theoretical calculations on the interfacial contact quality. Full-frequency measurements for several liquid and solid dielectrics are shown to have a good match with theoretical predictions     

Growth and characterization of thin films prepared from perfluoro-isopropyl-substituted perfluorophthalocyanines

Vapor deposition of perfluorinated phthalocyanines with bulky perfluorpropyl groups (F₆₄Pc) yielded intensely colored thin films (20-100 nm) despite the large molecular weight. In situ electrical conduction and optical transmission measurements revealed an almost negligible extent of intermolecular electronic coupling. Such quasi-independent character of molecules in solids was confirmed by detailed spectroscopic ellipsometry. The influence of the bulky peripheral groups on the packing in the films and on the electronic and optical properties of the films as well as potential applications of this class of strong electron acceptors are discussed.