Showing papers by "Johannes Kepler University of Linz published in 2003"

Effects of Postproduction Treatment on Plastic Solar Cells

Abstract: Efficiencies of organic solar cells based on an interpenetrating network of a conjugated polymer and a fullerene as donor and acceptor materials still need to be improved for commercial use. We have developed a postproduction treatment that improves the performance of solar cells based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) by means of a tempering cycle at elevated temperatures in which an external voltage is simultaneously applied, resulting in a significant increase of the short-circuit current. Using this postproduction treatment, an enhancement of the short-circuit current density, Isc, to 8.5 mA cm–2 under illumination with white light at an illumination intensity of 800 W m–2 and an increase in external quantum efficiency (IPCE, incident photon to collected electron efficiency) to 70 % are demonstrated.

A Meta-Analysis of the International Gender Wage Gap

Abstract: Since the early 1970s, a number of authors have calculated gender wage differentials between women and men of equal productivity. This meta-study provides a new quantitative review of this vast amount of empirical literature on gender wage differentials as it concerns not only differences in methodology, data, and time periods, but also different countries. We place particular emphasis on a proper consideration of the quality of the underlying study which is done by a weighting with quality indicators. The results show that data restrictions - i.e. the limitation of the analysis to new entrants, never-marrieds, or one narrow occupation only - have the biggest impact on the resulting gender wage gap. Moreover, we are able to show what effect a misspecification of the underlying wage equation - like the frequent use of potential experience - has on the calculated gender wage gap. Over time, raw wage differentials worldwide have fallen substantially; however, most of this decrease is due to better labor market endowments of females.

The Shadow Economy: An International Survey

Abstract: List of figures List of tables Foreword Vito Tanzi 1. The shadow economy: a challenge for economic and social policy 2. Defining the shadow economy 3. Methods to estimate the size of the shadow economy 4. Size of shadow economies around the world 5. The size of the shadow economy labour force 6. An integrated approach to explain deviant behaviour 7. Analysing the causes and measures of economic policy 8. Effects of the increasing shadow economy 9. The 'two-pillar strategy' 10. Conclusion and outlook List of references Index.

Context-awareness on mobile devices - the hydrogen approach

Abstract: Information about the user's environment offers new opportunities and exposes new challenges in terms of time-aware, location-aware, device-aware and personalized applications. Such applications constantly need to monitor the environment - called context - to allow the application to react accordingly to this context. Context-awareness is especially interesting in mobile scenarios where the context of the application is highly dynamic and allows the application to deal with the constraints of mobile devices in terms of presentation and interaction abilities and communication restrictions. Current context-aware applications often realize sensing of context information in an ad hoc manner. The application programmer needs to deal with the supply of the context information including the sensing of the environment, its interpretation and its disposal for further processing in addition to the primary purpose of the application. The close interweavement of device specific context handling with the application obstructs its reuse with other hardware configurations. Recently, architectures providing support for context-aware applications have been developed. Up to now such architectures are not trimmed to the special requirements of mobile devices regarding particularly the limitations of network connections, limited computing power and the characteristics of mobile users. This paper proposes an architecture and a software framework - the hydrogen context framework -which support context-awareness for considering these constraints. It is extensible to consider all kind of context information and comprises a layered architecture. To prove the feasibility the framework has been implemented to run on mobile devices. A context-aware postbox is realized to demonstrate the capabilities of the framework.

Hybrid Solar Cells Based on Nanoparticles of CuInS2 in Organic Matrices

Abstract: We report on solution-processed hybrid solar cells consisting of a nanocrystalline inorganic semiconductor, CuInS2, and organic materials. Synthesis of quantized CuInS2 nanoparticles was performed using a colloidal route, where the particle surface was shielded by an organic surfactant. First attempts were made to use nanocrystalline CuInS2 with fullerene derivatives to form flat-interface donor–acceptor heterojunction solar cells. We investigated also bulk heterojunctions by replacing the CuInS2 single layer by a blend of CuInS2 and p-type polymer (PEDOT:PSS; poly(3,4-ethylenedioxythiophene:poly(styrene sulfonic acid) in the same cell configuration. Bulk heterojunction solar cells show better photovoltaic response with external quantum efficiencies up to 20 %.

Tied Down or Room to Move? Investigating the Relationships Between Housing Tenure, Employment Status and Residential Mobility in Britain

Abstract: Using data from the British Household Panel Survey, we investigate the relationships between labour market dynamics, housing tenure and residential mobility. Panel data allow the study of the sequence of household moves and individual labour market status changes, enabling unique analysis of the relationship between job and residential mobility. Our findings suggest that the unemployed are more likely to move than employees. A desire to move motivated by employment reasons has the single largest positive impact on the probability of moving between regions.

A framework for the construction of level set methods for shape optimization and reconstruction

Abstract: The aim of this paper is to develop a functional-analytic framework for the construction of level set methods, when applied to shape optimization and shape reconstruction problems. As a main tool we use a notion of gradient flows for geometric configurations such as used in the modelling of geometric motions in materials science. The analogies to this field lead to a scale of level set evolutions, characterized by the norm used for the choice of the velocity. This scale of methods also includes the standard approach used in previous work on this subject as a special case. Moreover, we apply this framework to some (inverse) model problems for elliptic boundary value problems. In numerical experiments we demonstrate that an appropriate choice of norms (dependent on the problem) yields stable and fast methods.

Flow as an effective promotor of nucleation in polymer melts: a quantitative evaluation

Abstract: An apparatus is presented which enables the application of defined portions of mechanical work to the polymer sample in its state of undercooled melt. For the purpose mainly intermittent shear creep is used. Results are presented for an industrial grade of polypropylene. A three-dimensional picture is presented, in which the resulting numbers of nuclei (per unit volume) are plotted against two responsible parameters: crystallization temperature and mechanical work. With decreasing temperature and with increasing mechanical work the number of nuclei increases by many decades. At sufficiently high mechanical loads a transition to thread-like precursors ("shishs") has been observed previously. Oriented structures (kind of "shish-kebabs") are formed in this way. The periods of shearing applied have always been extremely short compared with the time until crystallization becomes observable. In this way an accumulation of various processes could be avoided. The description of shear induced crystallization, as previously given, is modified in the light of the present results.

Long-lived photoinduced charge separation for solar cell applications in phthalocyanine–fulleropyrrolidine dyad thin films

Abstract: The photophysical properties of a new dyad molecule composed of a covalently linked Zn-phthalocyanine (antenna/donor) and a C60 derivative (acceptor) have been investigated. We report experimental evidence of long-lived charge separation in the solid state with a lifetime several orders of magnitude higher than in solution. Such a long lifetime, unusual for phthalocyanine–fullerene dyads, is the basis for possible photovoltaic applications. A first demonstration of a working solar cell using phthalocyanine–fullerene dyads as the active material is presented. Though the power conversion efficiency under simulated solar illumination of 80 mW cm−2 is found to be moderate (0.02%), it is an encouraging result for application of C60 dyad molecules to photovoltaics.

IgE-mediated immediate-type hypersensitivity to the pyrazolone drug propyphenazone

Abstract: Background: Propyphenazone (1,2–dihydro-1,5-dimethyl-4-(1-methylethyl)-2-phenyl-3H-pyrazol-3-one; PP) is a nonsteroidal anti-inflammatory drug frequently used as mild analgesic medicament. It belongs to the chemical group of pyrazolones. Severe adverse reactions to PP are frequent and have generally been regarded as pseudoallergic or intolerance reactions. Presently, there are no useful in vitro test systems available for the detection of antibodies directed against analgesic drugs. Objective: The purpose of this study was to unequivocally demonstrate that IgE-mediated Type I allergy is the main mechanism leading to immediate-type adverse reactions to the analgesic drug PP. Methods: We investigated 53 young adult patients with adverse reactions to PP. All patients developed symptoms suggestive of IgE-mediated anaphylaxis within 30 minutes after intake of a painkiller containing PP. Patients were subjected to skin tests (prick test and intracutaneous test). In addition, a novel ELISA system was developed to prove the existence of specific IgE antibodies in patients' sera. Results: In 44 of 53 (83%) patients, skin tests showed typical wheal and flare reactions. Significant amounts of PP-specific serum IgE was detected in 31 of 53 (58%) of the serum samples. Moreover, in 7 of 9 patients with skin test negative results, PP-specific IgE could be detected. The assay was PP-specific because only PP, but no other pyrazolone derivative (antipyrine, aminophenazone, or metamizol), was able to inhibit IgE-binding in the system. Conclusion: Propyphenazone is a sensitizing agent in susceptible individuals and can elicit IgE-mediated anaphylaxis. By using skin tests and our ELISA system we were able to confirm Type I allergy in 51 of 53 (96%) patients in this study.

Origin of the conformation dependence of protein charge-state distributions in electrospray ionization mass spectrometry

Abstract: The influence of tertiary structure on the electrospray ionization mass spectra of proteins is a well known and broadly exploited phenomenon. However, the underlying mechanism is not well understood. This paper discusses the bases and the implications of the two current hypotheses (solvent accessibility and Coulombic repulsions), pointing out the remaining open questions. Evidence reported here supports a third hypothesis, i.e. that intramolecular interactions in folded proteins play a key role in determining the observed charge-state distributions. It is proposed that native protein structures stabilize to a large extent pre-existing charges of the opposite polarity to the net charge of the ion, preventing their neutralization during the electrospray process. Thus, the higher charge states of unfolded conformations, relative to the folded structure, would not derive from a more extensive ionization of the former, but rather from a higher content of neutralizing charges in the latter. This interpretation allows several other problematic observations to be explained, including the different shapes of the spectra of folded and unfolded proteins, the discrepancies between observed and predicted gas-phase reactivity of protein ions and the apparent inconsistency of positive- and negative-ion mode results.

Residue Analysis of the Pharmaceutical Diclofenac in Different Water Types Using ELISA and GC−MS

Abstract: A highly sensitive and specific indirect competitive enzyme-linked immunosorbent assay (ELISA) for the determination of diclofenac in water samples was developed. With pure water, the limit of detection (LOD, S/N = 3) and IC50 were found to be 6 ng/L and 60 ng/L, respectively. The analytical working range was about 20−400 ng/L. Highest cross-reactivity (CR) of 26 tested pharmaceuticals, metabolites, and pesticides was found for 5-hydroxydiclofenac (100%). Other estimated values were well below 4% and, therefore, are negligible. The assay was applied for the determination of diclofenac in tap and surface water samples as well as wastewater collected at 20 sewage treatment plants (STPs) in Austria and Germany. Humic substances were identified as main interference in surface water. Wastewater samples which were only submitted to filtration and dilution yielded about 25% higher diclofenac concentrations using the ELISA compared to GC−MS. However, the ELISA turned out to be a simple, inexpensive, and accurate ...

Boundary Element Tearing and Interconnecting Methods

Abstract: In this paper we introduce the Boundary Element Tearing and Interconnecting (BETI) methods as boundary element counterparts of the well-established Finite Element Tearing and Interconnecting (FETI) methods. In some practical important applications such as far field computations, handling of singularities and moving parts etc., BETI methods have certainly some advantages over their finite element counterparts. This claim is especially true for the sparse versions of the BETI preconditioners resp. methods. Moreover, there is an unified framework for coupling, handling, and analyzing both methods. In particular, the FETI methods can benefit from preconditioning components constructed by boundary element techniques. The first numerical results confirm the efficiency and the robustness predicted by our analysis.

Direct determination of strain and composition profiles in SiGe islands by anomalous x-Ray diffraction at high momentum transfer.

Abstract: Anomalous x-ray scattering is employed for quantitative measurements of the Ge composition profile in islands on Si(001). The anomalous effect in SiGe is enhanced exploiting the dependence of the complex atomic form factors on the momentum transfer. Comparing the intensity ratios for x-ray energies below and close to the K edge of Ge at various Bragg reflections in the grazing incidence diffraction setup, the sensitivity for the Ge profile is considerably enhanced. The method is demonstrated for SiGe dome-shaped islands grown on Si(001). It is found that the composition inside the island changes rather abruptly, whereas the lattice parameter relaxes continuously.

Investigating the defect detection effectiveness and cost benefit of nominal inspection teams

Abstract: Inspection is an effective but also expensive quality assurance activity to find defects early during software development. The defect detection process, team size, and staff hours invested can have a considerable impact on the defect detection effectiveness and cost-benefit of an inspection. In this paper, we use empirical data and a probabilistic model to estimate this impact for nominal (noncommunicating) inspection teams in an experiment context. Further, the analysis investigates how cutting off the inspection after a certain time frame would influence inspection performance. Main findings of the investigation are: 1) Using combinations of different reading techniques in a team is considerably more effective than using the best single technique only (regardless of the observed level of effort). 2) For optimizing the inspection performance, determining the optimal process mix in a team is more important than adding an inspector (above a certain team size) in our model. 3) A high level of defect detection effectiveness is much more costly to achieve than a moderate level since the average cost for the defects found by the inspector last added to a team increases more than linearly with growing effort investment. The work provides an initial baseline of inspection performance with regard to process diversity and effort in inspection teams. We encourage further studies on the topic of time usage with defect detection techniques and its effect on inspection effectiveness in a variety of inspection contexts to support inspection planning with limited resources.

The Size and Development of the Shadow Economies in the Asia-Pacific

Abstract: * Professor Dr. Friedrich Schneider, Department of Economics, Johannes Kepler University of Linz, Altenbergerstrasse 69, A-4040 Linz-Auhof, Austria. Phone: 0043-70-2468-8210, Fax: 0043-70-2468-8209. Email: friedrich.schneider@jku.at, http://www.economics.uni-linz.ac.at/Members/Schneider/default.htm . Dr. Christopher Bajada, School of Finance and Economics, University of Technology, Sydney, P.O Box 123 Broadway, Syndey NSW Australia 2007. Phone: +61-2-9514-7786, Fax: +61-2-9514-7711. E-mail: chris.bajada@uts.edu.au

On Schwarz-type Smoothers for Saddle Point Problems

Abstract: In this paper we consider additive Schwarz-type iteration methods for saddle point problems as smoothers in a multigrid method. Each iteration step of the additive Schwarz method requires the solutions of several small local saddle point problems. This method can be viewed as an additive version of a (multiplicative) Vanka-type iteration, well-known as a smoother for multigrid methods in computational fluid dynamics. It is shown that, under suitable conditions, the iteration can be interpreted as a symmetric inexact Uzawa method. In the case of symmetric saddle point problems the smoothing property, an important part in a multigrid convergence proof, is analyzed for symmetric inexact Uzawa methods including the special case of the additive Schwarz-type iterations. As an example the theory is applied to the Crouzeix-Raviart mixed finite element for the Stokes equations and some numerical experiments are presented.

Asymptotic behavior of polynomials orthonormal on a homogeneous set

Abstract: LetE be a homogeneous compact set, for instance a Cantor set of positive length. Further, let σ be a positive measure with supp(σ)=E. Under the condition that the absolutely continuous part of σ satisfies a Szego-type condition, we give an asymptotic representation, on and off the support, for the polynomials orthonomal with respect to σ. For the special case thatE consists of a finite number of intervals and that σ has no singular component, this is a well-known result of Widom. IfE=[a,b], it becomes a classical result due to Szego; and in case that there appears in addition a singular component, it is due to Kolmogorov-krein. In fact, the results are presented for the more general case that the orthogonality measure may have a denumerable set of mass-points outside ofE which are supposed to accumulate only onE and to satisfy (together with the zeros of the associated Stieltjes function) the free-interpolation Carleson-type condition. Up to the case of a finite number of mass points, this is even new for the single interval case. Furthermore, as a byproduct of our representations, we obtain that the recurrence coefficients of the orthonormal polynomials behave asymptotically almost periodic. In other words, the Jacobi matrices associated with the above discussed orthonomal polynomials are compact perturbations of a onesided restriction of almost periodic Jacobi matrices with homogeneous spectrum. Our main tool is a theory of Hardy spaces of character-automorphic functions and forms on Riemann surfaces of Widom type; we use also some ideas of scattering theory for one-dimensional Schrodinger equations.

How to understand nucleation in crystallizing polymer melts under real processing conditions

Abstract: As has been shown experimentally in our laboratory, the number of athermal nuclei, as found in unnucleated quiescent melts, increases tremendously with decreasing temperatures of crystallization, down to severe degrees of undercooling. One cannot assume that the presence of heterogeneous nuclei can explain this horrible temperature dependence. Moreover, one can conclude that the number fraction of macromolecules participating in these athermal nuclei is extremely low. Macroscopically, these nuclei seem to form a number of spots in a sea of homogeneous undercooled liquid.In the present paper the proposal is made that this number can be estimated from the probability of the occurrence of local molecular arrangements of varying quality, which preexist by accidence in a so-called living equilibrium in the stable melt, i.e. above the equilibrium melting point. During a rapid quench, realistic for processing conditions, these local arrangements are successively stabilized and serve as precursors for the start of crystallization. Dependent on their quality, this stabilization occurs over a broad range of crystallization temperatures. A selection rule for their effectiveness is derived from thermodynamics. In addition, reasons are discussed for the observed strong influence of flow on the formation of nuclei. From the "short-term" creep experiments, which are successful even at low degrees of undercooling, the impression has been obtained that during flow an unimaginable long-distance mechanical interaction becomes effective between the nuclei of crystallization. However, a more convincing explanation has been found recently: it is described at the end of this paper.

Satisfaction Not Guaranteed - Institutions and Satisfaction with Democracy in Western Europe

Abstract: What determines citizens' satisfaction with the "constitution in operation"? We make two contributions towards an answer to this important policy question. First, we place stronger emphasis than existing studies on quantitative interpretations of the importance of different factors. We use scenario analysis to show that a consensual system generally promotes satisfaction, but affects different types of citizens differently. Second, we focus on informal institutions and rules of the game in European societies. Corporatism and group membership as a measure of social capital are good for satisfaction, and people who live in countries with a high degree of income inequality tend to be less satisfied. The findings for trust and for the rule of law are ambiguous.

Customisation for ubiquitous web applications: a comparison of approaches

Abstract: Ubiquitous web applications adhering to the anytime/anywhere/anymedia paradigm are required to be customisable meaning the adaptation of their services towards a certain context. Several approaches for customising ubiquitous Web applications have been already proposed, each of them having different origins and pursuing different goals for dealing with the unique characteristics of ubiquity. This paper compares some of these proposals, trying to identify their strengths and shortcomings. As a prerequisite, an evaluation framework is suggested which categorises the major characteristics of customisation into different dimensions. On the basis of this framework, customisation approaches are surveyed and compared to each other, pointing the way to next-generation customisation approaches.

Current practice in space charge and polarization profile measurements using thermal techniques

Abstract: Thermal techniques for probing space charge and electric field distributions in dielectric materials became available approximately 30 years ago. The techniques have reached maturity and they have been employed not only for the primary purpose of electric field or polarization profiling, but also in a wide range of problems posed by materials research. The present survey provides an overview of the historical development, the experimental implementation of the different techniques, the theoretical foundation, methods for the data analysis and a comparison of thermal and acoustic techniques. The thermal wave technique LIMM is used as an example among the thermal techniques, for a discussion of data analysis techniques and for the spatial resolution that can be achieved with thermal wave techniques. A tour d'horizon is provided through recent applications of thermal techniques, in order to demonstrate their capabilities for dielectric material characterisation.

Recognizing and Predicting Context by Learning from User Behavior 1

Abstract: Summary Current mobile devices like mobile phones or personal digital assistants have become more and more powerful; they already offer features that only few users are able to exploit to their whole extent. With a number of upcoming mobile multimedia applications, ease of use becomes one of the most important aspects. One way to improve usability is to make devices aware of the user’s context, allowing them to adapt to the user instead of forcing the user to adapt to the device. Our work is taking this approach one step further by not only reacting to the current context, but also predicting future context, hence making the devices proactive. Mobile devices are generally suited well for this task because they are typically close to the user even when not actively in use. This allows such devices to monitor the user context and act accordingly, like automatically muting ring or signal tones when the user is in a meeting or selecting audio, video or text communication depending on the user’s current occupation. This article presents an architecture that allows mobile devices to continuously recognize current and anticipate future user context. The major challenges are that context recognition and prediction should be embedded in mobile devices with limited resources, that learning and adaptation should happen on-line without explicit training phases and that user intervention should be kept to a minimum with non-obtrusive user interaction. To accomplish this, the presented architecture consists of four major parts: feature extraction, classification, labeling and prediction. The available sensors provide a multi -dimensional, highly heterogeneous input vector as input to the classification step, realized by data clustering. Labeling associates recognized context classes with meaningful names specified by the user, and prediction allows

Laser-induced nano-patterning by means of interference subpatterns generated by microspheres

Abstract: Interference patterns generated by a regular lattice of SiO2 microspheres on a transparent support are used for the surface patterning of polyimide (PI) foils. Using 248 nm excimer-laser radiation, thousands to millions of holes with a full width at half maximum (FWHM) of 160±40 nm can be generated with a single laser pulse.