Ultra fast and parsimonious materials screening for polymer solar cells using differentially pumped slot-die coating

We present a technique that enables the probing of the entire parameter space for each parameter with good statistics through a simple roll-to-roll processing method where gradients of donor, acceptor, and solvent are applied by differentially pumped slot-die coating. We thus demonstrate how the optimum donor-acceptor ratio and device film thickness can be determined with improved accuracy by varying the composition in small steps. We give as an example P3HT-PCBM devices and vary the composition between P3HT and PCBM in steps of 0.5-1% giving 100-200 individual solar cells. The coating experiment itself takes less than 4-8 min and requires 15-30 mg each of donor and acceptor material. The optimum donor-acceptor composition of P3HT and PCBM was found to be a broad maximum centered on a 1:1 ratio. We demonstrate how the optimal thickness of the active layer can be found by the same method and materials usage by variation of the layer thickness in small steps of 1.5-4 nm. Contrary to expectation we did not find oscillatory variation of the device performance with device thickness because of optical interference. We ascribe this to the nature of the solar cell type explored in this example that employs nonreflective or semitransparent printed electrodes. We further found that very thick active layers on the order of 1 μm can be prepared without loss in performance and estimate the active layer thickness could easily approach 4-5 μm while maintaining photovoltaic properties.     

FAME--a flexible appearance modeling environment

Combined modeling of pixel intensities and shape has proven to be a very robust and widely applicable approach to interpret images. As such the active appearance model (AAM) framework has been applied to a wide variety of problems within medical image analysis. This paper summarizes AAM applications within medicine and describes a public domain implementation, namely the flexible appearance modeling environment (FAME). We give guidelines for the use of this research platform, and show that the optimization techniques used renders it applicable to interactive medical applications. To increase performance and make models generalize better, we apply parallel analysis to obtain automatic and objective model truncation. Further, two different AAM training methods are compared along with a reference case study carried out on cross-sectional short-axis cardiac magnetic resonance images and face images. Source code and annotated data sets needed to reproduce the results are put in the public domain for further investigation.     

Outsourcing Innovative Capabilities for IT-Enabled Services

IT-enabled innovations are critical for competitive success in a range of industries including financial brokerage. This paper addresses the crucial question: How do capability development strategies differ between first-movers and late-entrants in IT-enabled services. We develop a theory based on two explorative case studies—Charles Schwab and Merrill Lynch. A comparative analysis reveals that governance choices are influenced by a company's attempts to strategically position itself as a first- or late-mover in varying technological regimes.     

In-gel digestion of proteins using a solid-phase extraction microplate

We present a new procedure for in-gel digestion of proteins introducing a combination of two different 96-well microplates. The two plates have incorporated small capillaries with a length of 2.4 mm in each well, one of which has 75-microm-inner diameter capillaries, whereas the second plate has reversed-phase-type capillaries fixed to it. The initial steps of the in-gel digestion process, comprising destaining, reduction/alkylation, dehydration, and digestion, was carried out in the plate containing 75-microm capillaries. Capillaries containing C18 reversed-phase modified monolithic silica rods of a 200-microm diameter were used for the second plate in which extraction and cleanup of peptides were carried out. Peptides were eluted directly from the solid-phase extraction plate onto the MALDI sample support. The separation of the process into two plates led to increased process stability, without compromising sensitivity, i.e. peptide recovery, making it suitable for true high-throughput protein identification. The handling of proteinases could easily be optimized, and no restrictions were made on chosen pH range through the absence of the solid phase in the initial steps of the protocol. Efficient binding of peptides to the solid phase and subsequent direct elution onto the MALDI sample support led to sensitivities in the attomole range. Performance of the process was demonstrated with tryptic digests of proteins stained with colloidal coomassie blue, silver, and the fluorescent stain SYPRO Ruby.     

Robust and Efficient Ray Intersection of Implicit Surfaces

The generation of ray traced images of a variety of surfaces plays a central role in computer graphics. One of the main operations in ray tracing is the calculation of intersections between rays and surfaces. In case of implicitly given surfaces the intersection problem can be formulated as that of finding the smallest non-negative root of an equation in one variable. If the root finding is carried out by means of conventional numerical methods based on point sampling (such as bisection, regula-falsi or Newton) the resulting image can be wrong, e.g. when the surface is thin the ray may "miss" the surface, which may result in an image with background color spots on the surface. To obtain robust intersection detection, methods based either on Lipschitz constants for the function and its derivative or an interval inclusions for the function and its derivative have been suggested. In this paper robust methods are obtained with interval inclusions in a variant of Alefeld-Hansens globally convergent method for computing and bounding all the roots of a single equation. Alefeld-Hansens method has been modified so instead of searching for all roots, a recursive depth-first search is carried out to obtain the smallest non-negative root. When compared to other methods suggested, it is found that this variant of Alefeld-Hansens method is not only robust but also an efficient method for finding the ray intersections.     

New results for Constraint Markov Chains

This paper studies compositional reasoning theories for stochastic systems. A specification theory combines notions of specification and implementation with satisfaction and refinement relations, and a set of operators that together support stepwise design. One of the first behavioral specification theories introduced for stochastic systems is the one of Interval Markov Chains (IMCs), which are Markov Chains whose probability distributions are replaced by a conjunction of intervals. In this paper, we show that IMCs are not closed under conjunction, which gives a formal proof of a conjecture made in several recent works.In order to leverage this problem, we suggested to work with Constraint Markov Chains (CMCs) that is another specification theory where intervals are replaced with general constraints. Contrary to IMCs, one can show that CMCs enjoy the closure properties of a specification theory. In addition, we propose aggressive abstraction procedures for CMCs. Such abstractions can be used either to combat the state-space explosion problem, or to simplify complex constraints. In particular, one can show that, under some assumptions, the behavior of any CMC can be abstracted by an IMC.Finally, we propose an algorithm for counter-example generation, in case a refinement of two CMCs does not hold. We present a tool that implements our results. Implementing CMCs is a complex process and relies on recent advances made in decision procedures for theory of reals.     

A complete process for production of flexible large area polymer solar cells entirely using screen printing—First public demonstration

A complete polymer solar cell module prepared in the ambient atmosphere under industrial conditions is presented. The versatility of the polymer solar cell technology is demonstrated through the use of abstract forms for the active area, a flexible substrate, processing entirely from solution, complete processing in air using commonly available screen printing, and finally, simple mechanical encapsulation using a flexible packaging material and electrical contacting post-production using crimped contacts. We detail the production of more than 2000 modules in one production run and show that the production technique is scalable and well suited for direct transfer to the printing industry employing existing production equipment. The production speed and cost analysis for the individual modules from this batch is discussed and a forecast for the high volume cost based on this method is given. Further, the points where significant cost reductions can be achieved are identified. The use of the solar cell as the power supply for a small radio and other small electronic circuits is demonstrated. Lastly, the operational stability under ambient conditions in the dark and under illumination is discussed.     

Structural determination of ethylene‐propylene‐diene rubber (EPDM) containing high degree of controlled long‐chain branching

This work highlights an attempt to characterize the degree and nature of long‐chain branching (LCB) in an unknown sample of ethylene‐propylene‐diene rubber (EPDM). Two EPDM rubbers selected for this study were comparable in comonomer compositions but significantly different with respect to molar mass and the presence of LCB. Both rubbers contained 5‐ethylidene‐2‐norbornene (ENB) as diene. Solution cast films of pure EPDM samples were used for different characterization techniques. ¹H‐NMR, and ¹³C‐NMR were used for assessing the comonomer ratios and LCB. Size exclusion chromatography (SEC) equipped with triple detector system was used to determine the molar mass (both absolute and relative) and polydispersity index (PDI). Presence of branching was also detected using sec‐viscometry. Rheological analysis has also been used for characterizing LCB. Finally, on the basis of the experimental findings and the available theories, an attempt was made to identify the chemical nature and degree of LCB. This study reveals the possibility of detailed characterization of molecular architecture of EPDM containing LCB by comparing with an essentially linear EPDM in light of an existing theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009