Showing papers by "University of Twente published in 2003"
TL;DR: In this paper, the development of ISFETs in an historical setting, but not limited to that, is described, based on the development regarding the theory, the technology, the instrumentation and the experience with many specific applications, also future projects are defined, such as concerning cell acidification, this paperET biasing and a complete new range of FET sensors based on local pressure induction by (bio)chemical interaction with immobilised charged molecules (hydrogels).
Abstract: This paper describes the development of ISFETs in an historical setting, but is not limited to that. Based on the development regarding the theory, the technology, the instrumentation and the experience with many specific applications, also future projects are defined, such as concerning cell acidification, REFET biasing and a complete new range of FET sensors based on local pressure induction by (bio)chemical interaction with immobilised charged molecules (hydrogels). Also the present patent and market position is discussed. It is concluded that in the past 30 years the ISFET research and development made continuous progress on a regular base, but the practical applications stayed behind, especially concerning the dynamic use of ISFETs in combination with an integrated pH actuator. The newly proposed research projects may be good for an other 30 years.
1,472 citations
TL;DR: A fruitful analytical framework for data supposedly related to the concept of the so-called "digital divide" is proposed and it is shown that differential access of skills and usage is likely to increase.
Abstract: The purpose of this article is to propose a fruitful analytical framework for data supposedly related to the concept of the socalled “digital divide.” The extent and the nature of this divide depend on the kind of access defined. Considering the possession of hardware, growing divides among different categories of income, employment, education, age, and ethnicity can be proved to have existed in the 1980s and 1990s according to official American and Dutch statistics. If only by effects of saturation, these gaps will more or less close. However, it is shown that differential access of skills and usage is likely to increase. The growth of a usage gap is projected. Multivariate analyses of Dutch official statistics reveal the striking effect of age and gender as compared to education. The usage gap is related to the evolution of the information and network society. Finally, policy perspectives are discussed.
1,237 citations
TL;DR: The authors revisited the existing scholarly debate on the possible impact of the principal's leadership on student achievement and conducted a quantitative meta-analysis to examine to what extent principals directly affect student outcomes, finding that small positive effects confirmed earlier research findings on the limitations of the direct effects approach to linking leadership with student achievement.
Abstract: This study revisits the existing scholarly debate on the possible impact of the principal's leadership on student achievement. Both `direct effect' and `indirect effect' models are discussed. A quantitative meta-analysis examines to what extent principals directly affect student outcomes. The small positive effects found in this meta-analysis confirm earlier research findings on the limitations of the direct effects approach to linking leadership with student achievement. Finally, lines of future research inquiry are discussed.
838 citations
TL;DR: An experiment in which gentle (linear) bubble oscillations are sufficient to achieve rupture of lipid membranes and the bubble dynamics and the ensuing sonoporation can be accurately controlled.
Abstract: The ability of collapsing (cavitating) bubbles to focus and concentrate energy, forces and stresses is at the root of phenomena such as cavitation damage, sonochemistry or sonoluminescence1, 2. In a biomedical context, ultrasound-driven microbubbles have been used to enhance contrast in ultrasonic images3. The observation of bubble-enhanced sonoporation4, 5, 6?acoustically induced rupture of membranes?has also opened up intriguing possibilities for the therapeutic application of sonoporation as an alternative to cell-wall permeation techniques such as electroporation7 and particle guns8. However, these pioneering experiments have not been able to pinpoint the mechanism by which the violently collapsing bubble opens pores or larger holes in membranes. Here we present an experiment in which gentle (linear) bubble oscillations are sufficient to achieve rupture of lipid membranes. In this regime, the bubble dynamics and the ensuing sonoporation can be accurately controlled. The use of microbubbles as focusing agents makes acoustics on the micrometre scale (microacoustics) a viable tool, with possible applications in cell manipulation and cell-wall permeation as well as in microfluidic devices.
744 citations
TL;DR: In this paper, the authors describe two studies into teacher workplace learning, one aimed at developing a definition of teacher learning at the workplace and the other aimed at exploring factors that may affect teacher learning in the workplace.
732 citations
TL;DR: The large amount of very recent publications treated in this review indicates the rapidly growing interest in this exciting application area of Lab-on-Chip LOC.
Abstract: A review of microfluidic devices for cellomics is presented. After a brief description of the historical background of Lab-on-Chip (LOC) devices, different areas are reviewed. Devices for cell sampling are presented, followed by cell trapping and cell sorting devices based upon mechanical and electrical principles. Subsequently, a popular type of cell sorters, flow cytometers, is considered, followed by a chapter describing devices for cell treatment: cell lysis, poration/gene transfection and cell fusion devices. Finally a number of microfluidic devices for cellular studies are reviewed. The large amount of very recent publications treated in this review indicates the rapidly growing interest in this exciting application area of LOC.
721 citations
TL;DR: In this paper, a twin screw extruder with a particle content of 0.07-1.9 µm and surface treatment of the particles (with and without stearic acid) on the toughening properties were studied.
638 citations
TL;DR: In this article, the authors adopt a multi-theoretic approach to investigate the differential impact of foreign institutional and foreign corporate shareholders on the performance of emerging market firms and find that the previously documented positive effect of foreign ownership on firm performance is substantially attributable to foreign corporations that have, on average, larger shareholding, higher commitment and longer-term involvement.
Abstract: We adopt a multi-theoretic approach to investigate a previously unexplored phenomenon in extant literature, namely the differential impact of foreign institutional and foreign corporate shareholders on the performance of emerging market firms. We show that the previously documented positive effect of foreign ownership on firm performance is substantially attributable to foreign corporations that have, on average, larger shareholding, higher commitment and longer-term involvement. We document the positive influence of corporations vis a vis financial institutions with respect to domestic shareholdings as well. We also find an interesting dichotomy in the impact of these shareholders depending on the business group affiliation of firms.
613 citations
01 Jan 2003
TL;DR: The list of discussed NP-complete problems includes the traveling salesman problem, scheduling under precedence constraints, satisfiability, knapsack, graph coloring, independent sets in graphs, bandwidth of a graph, and many more as discussed by the authors.
Abstract: We discuss fast exponential time solutions for NP-complete problems. We survey known results and approaches, we provide pointers to the literature, and we discuss several open problems in this area. The list of discussed NP-complete problems includes the travelling salesman problem, scheduling under precedence constraints, satisfiability, knapsack, graph coloring, independent sets in graphs, bandwidth of a graph, and many more.
532 citations
TL;DR: Chiral aluminum isopropoxides based on enantiopure or racemic cyclohexylsalen ligand (Jacobsen ligand) have been prepared and employed for stereoelective/stereoselective ring-opening polymerization of lactide in toluene at 70 degrees C.
Abstract: Chiral aluminum isopropoxides based on enantiopure or racemic cyclohexylsalen ligand (Jacobsen ligand) have been prepared and employed for stereoelective/stereoselective ring-opening polymerization of lactide in toluene at 70 °C. The kinetics, selectivity of the catalysts, and microstructure of the obtained polylactides, using different combinations of lactide enantiomers and catalysts, were determined. In all cases, polylactides of controlled molecular weight, low polydispersity, and defined end groups were obtained. The polymerizations are first-order in both monomer(s) and catalyst. (R,R)-CyclohexylsalenAlOiPr [(R,R)-1] polymerizes l-lactide significantly faster than d-lactide with a rate constant ratio kl/kd of ∼14. The polymerization of rac-lactide using (R,R)-1 yields crystalline polymers, for which a selectivity factor of ∼5.5 could be calculated up to 50% conversion based on the optical purity of the isolated polymers. The polymerization of a l-lactide/d-lactide (molar ratio: 80/20) mixture by (R...
460 citations
TL;DR: In this paper, a survey of the material properties that govern the performance of mixed-conducting membranes in real operating conditions and highlights significant developments in the field is presented, where the authors mainly focus on material properties.
Journal Article•
University of Minnesota1, Lund University2, Mayo Clinic3, International Osteoporosis Foundation4, Princess Margaret Cancer Centre5, Royal Brisbane and Women's Hospital6, University of Washington7, Boston Children's Hospital8, University of Queensland9, University of Connecticut10, University of Iowa11, University of North Carolina at Chapel Hill12, Southampton General Hospital13, Université catholique de Louvain14, University of Bristol15, University of Paris16, University of Ulm17, University of Pennsylvania18, University of California, San Francisco19, Erasmus University Rotterdam20, University of Maryland, Baltimore21, The Chinese University of Hong Kong22, National Institutes of Health23, Johns Hopkins University24, Apollo Hospitals25, Indian Institute of Technology Delhi26, Russian Academy27, New York University28, Royal Cornwall Hospital29, University of British Columbia30, University of Twente31, University of Lübeck32, University of Liège33, University of Geneva34, University of London35, Ludwig Maximilian University of Munich36, University of Manchester37, Maastricht University38, University of Texas Health Science Center at San Antonio39, Niigata University40, University of California41
TL;DR: It is clear from data collated that the impact from musculoskeletal conditions and trauma varies among different parts of the world and is influenced by social structure, expectation and economics, and that it is most difficult to measure impact in less developed nations, where the predicted increase is greatest.
Abstract: Musculoskeletal conditions are extremely common and include more than 150 different diseases and syndromes, which are usually associated with pain and loss of function. In the developed world, where these conditions are already the most frequent cause of physical disability, ageing of the most populous demographic groups will further increase the burden these conditions impose. In the developing world, successful care of childhood and communicable diseases and an increase in road traffic accidents is shifting the burden to musculoskeletal and other noncommunicable conditions. To help better prepare nations for the increase in disability brought about by musculoskeletal conditions, a Scientific Group meeting was held to map out the burden of the most prominent musculoskeletal conditions at the start of the Bone and Joint Decade. In particular, the Group gathered data on the incidence and prevalence of rheumatoid arthritis, osteoarthritis, osteoporosis, major limb trauma and spinal disorders. Data were collected and organized by world region, gender and age groups to assist with the ongoing WHO Global Burden of Disease 2000 study. The Group also considered what is known about the severity and course of these conditions, along with their economic impact. The most relevant domains to assess and monitor the consequences of these conditions were identified and used to describe health states for the different stages of the conditions. Instruments that measure these most important domains for the different conditions were recommended. It is clear from data collated that the impact from musculoskeletal conditions and trauma varies among different parts of the world and is influenced by social structure, expectation and economics, and that it is most difficult to measure impact in less developed nations, where the predicted increase is greatest.
TL;DR: Compared with commonly used porosifying methods such as sintering, compression moulding combined with salt leaching, and freeze-drying, this process allows excellent control over pore size and porosity and yields scaffolds with a much more homogeneous pore morphology.
TL;DR: Results show that concurrent and retrospective think-aloud protocols reveal comparable sets of usability problems, but that these problems come to light in different ways and raises questions about the reactivity of concurrent think- aloud protocols, especially in the case of high task complexity.
Abstract: Think-aloud protocols are a dominant method in usability testing. There is, however, only little empirical evidence on the actual validity of the method. This paper describes an experiment that compares concurrent and retrospective think-aloud protocols for a usability test of an online library catalogue. There were three points of comparison: usability problems detected, overall task performance, and participant experiences. Results show that concurrent and retrospective think-aloud protocols reveal comparable sets of usability problems, but that these problems come to light in different ways. In retrospective think-aloud protocols, more problems were detected by means of verbalisation, while in concurrent think-aloud protocols, more problems were detected by means of observation. Moreover, in the concurrent think-aloud protocols, the requirement to think aloud while working had a negative effect on the task performance. This raises questions about the reactivity of concurrent think-aloud protocols, especially in the case of high task complexity.
TL;DR: In the control (nonapoptotic) HeLa cells, it is shown, for the first time by Raman microspectroscopy, the presence of the RNA in a cell nucleus.
TL;DR: In this article, the authors argue that there is a key role for the government to co-design framework conditions and facilitate interaction in a more demand-driven and liberalised higher education sector.
Abstract: While government intervention in the higher education market may be justified, it may come at the cost of lower consumer sovereignty and restricted producer autonomy. Through marketisation policy, students and higher education providers have more room to make their own trade-offs and interact more closely on the basis of reliable information. This article discusses eight conditions for a market and the extent to which these are met in Dutch higher education. It is argued that there is still a key role for the government to co-design framework conditions and facilitate interaction in a more demand-driven and liberalised higher education sector.
TL;DR: In this paper, surface-coated nanoparticles of LaF3 and LaPO4 doped with the luminescent trivalent lanthanide ions Eu3+, Nd3+, Er3+, Pr3+, Ho3+, and Yb3+ have been prepared.
Abstract: Surface-coated nanoparticles of LaF3 and LaPO4 doped with the luminescent trivalent lanthanide ions Eu3+, Nd3+, Er3+, Pr3+, Ho3+, and Yb3+ have been prepared. These ions emit in the visible and in the near-infrared part of the electromagnetic spectrum. The ions Nd3+, Er3+, Pr3+, and Ho3+ are the main focus in this research because they show emissions in telecommunication windows. The Yb3+ ion is of interest because it can be used as a sensitizer for Er3+. The Eu3+ ion has been used as a probe for the structural environment of the luminescent ion. It is shown that these lanthanide ions are incorporated in the inorganic host of the particles and that the particles are dispersable in organic solvents. The luminescent lifetimes of the ions are increased by orders of magnitude compared to organic complexes, with values ranging from several microseconds for Pr3+ and Ho3+, up to about 200 μs for Nd3+, and 1 ms for Er3+. This increase in the luminescence lifetime is indicative of an effective shielding of the lan...
TL;DR: The results suggest that the CCM is a promising candidate matrix for implantable bioartificial livers and has excellent blood and cell compatibility.
TL;DR: Topographical confinement is used to template the formation of nanoscale domains in a self-assembled block copolymer film as mentioned in this paper, which can deliberately introduce defects in the arrays and pins the lateral position of the polymer array.
Abstract: Topographical confinement is used to template the formation of nanoscale domains in a self-assembled block copolymer film. The topographical template controls the row spacings and feature dimensions of the copolymer and can deliberately introduce defects in the arrays (see Figure). For example, a sharp edge feature leads to a missing domain and pins the lateral position of the polymer array. (See also inside cover.)
TL;DR: The propagation of light in nonperiodic quasicrystals is studied by ultrashort pulse interferometry and a theoretical description based on transfer matrix theory allows to interpret the results in terms of Fibonacci band-edge resonances.
Abstract: The propagation of light in nonperiodic quasicrystals is studied by ultrashort pulse interferometry. Samples consist of multilayer dielectric structures of the Fibonacci type and are realized from porous silicon. We observe mode beating and strong pulse stretching in the light transport through these systems, and a strongly suppressed group velocity for frequencies close to a Fibonacci band gap. A theoretical description based on transfer matrix theory allows us to interpret the results in terms of Fibonacci band-edge resonances.
TL;DR: This article found that those with high levels of political knowledge rely more heavily on evaluations of EU institutions when assessing democracy in the EU and also found evidence that evaluations of democratic performance are motivated by the economic benefits and costs associated with membership.
Abstract: Recent reforms have been designed to enhance the power of the European Parliament to counter criticisms of a "democratic deficit" in the European Union (EU). We examine how citizens now view these institutions and whether such evaluations influence their satisfaction with the way democracy works in the EU. Previous research has maintained that evaluations of the quality of democracy are difficult to assess because opinions about the EU largely reflect opinions about national institutions. Our results indicate that this is not necessarily the case, particularly among those who are politically aware. Those with high levels of political knowledge rely more heavily on evaluations of EU institutions when assessing democracy in the EU. We also find evidence that evaluations of democratic performance in the EU are motivated by the economic benefits and costs associated with membership. The implications for the democratic deficit and the satisfaction with democracy measure are discussed.
TL;DR: In this paper, the surface species formed during adsorption of NOx on a commercial NSR catalyst (containing barium oxide, Pt, and alumina as the main components) were investigated by in situ IR spectroscopy.
TL;DR: The results presented in this study demonstrate that poly(TMC) and both TMC copolymers are biodegradable and biocompatible materials, making these polymers attractive for the preparation of short- and long-term degradable devices for soft tissue engineering.
Abstract: The degradation and the tissue response evoked by poly(1,3-trimethylene carbonate) [poly(TMC)] and copolymers of TMC with either 52 mol % D,L-lactide (DLLA) or 89 mol % -caprolactone (CL) were evaluated in vivo by subcutaneous implantation of polymer films in rats for periods up to one year. Poly(TMC) specimens were extensively degraded after 3 weeks and, as confirmed by histology, totally resorbed in less than a year. A fast linear decrease in thickness and mass without a change in molecular weight was observed. Initially an acute sterile inflammatory tissue reaction, caused by the implantation procedure, was observed, followed by a mild macrophage-mediated foreign body reaction that lasted during the resorption period of the polymer. It is concluded that in vivo, poly(TMC) is degraded via surface erosion involving cellular-mediated processes. The degradation of the copolymers was slower than that of poly(TMC), taking place via autocatalyzed bulk hydrolysis, preferentially of ester bonds. The TMC-DLLA copolymer degraded 20 times faster than the TMC-CL one. In both cases, the tissue reaction upon implantation resembled a sterile inflammatory reaction followed by a foreign body reaction that led to the polymer encapsulation. Significant mass loss was only observed for the TMC-DLLA copolymer, which underwent 96% mass loss in 1 year. When extensive mass loss started, a mild-to-moderate secondary foreign body reaction, related to clearance of the polymer fragments, was triggered. The results presented in this study demonstrate that poly(TMC) and both TMC copolymers are biodegradable and biocompatible materials, making these polymers attractive for the preparation of short- and long-term degradable devices for soft tissue engineering.
TL;DR: In this article, the authors argue that limited network horizons are both inevitable and useful, and they introduce and discuss three mediating functions of counterparts: a joining, a relating, and an insulating function.
TL;DR: In this article, the authors measured the reaction between CO2 and aqueous potassium salts of taurine and glycine at 295 K in a stirred-cell reactor with a flat gas-liquid interface.
Abstract: The kinetics of the reaction between CO2 and aqueous potassium salts of taurine and glycine was measured at 295 K in a stirred-cell reactor with a flat gas-liquid interface. For aqueous potassium taurate solutions, the temperature effect on the reaction kinetics was measured at 285 and 305 K. Unlike aqueous primary alkanolamines, the partial reaction order in amino acid salt changes from one at low salt concentration to approximately 1.5 at salt concentrations as high as 3,000 mol·m-3. At low salt concentrations, the measured apparent rate constant (kapp) for potassium glycinate is comparable to the values in literature. In the absence of reliable information in the literature on the kinetics and mechanism of the reaction, the applicability of the zwitterion and termolecular mechanism (proposed originally for alkanolamines) was explored. For the zwitterion mechanism, the forward second-order reaction rate constant (k2) of the CO2 reaction with amino acid salt seems to be much higher than for alkanolamines of similar basicity, indicating that the Bronsted plot for amino acid salts might differ from that of alkanolamines. The contribution of water to the deprotonation of zwitterion seems to be more significant than reported values for aqueous secondary alkanolamines.
Posted Content•
TL;DR: This paper studied the relationship between some characteristics of the corporate board and the firm's capital structure in Chinese listed firms and found that managers tend to pursue lower financial leverage when they face stronger corporate governance from the board.
Abstract: This paper studies the relationship between some characteristics of the corporate board and the firm's capital structure in Chinese listed firms. The findings provide some preliminary empirical evidence and seem to suggest that managers tend to pursue lower financial leverage when they face stronger corporate governance from the board. However, the empirical results of the relationships are statistically significant only in the case of the board composition and the CEO tenure. The results are statistically insignificant in the case of the board size and fixed CEO compensation. This may in general suggest that, up to the time period of our investigation, the corporate board structures and processes in Chinese listed firms might not as yet be fully working in the manner, or as well, as might have been so far assumed on the basis of Western theoretical finance literature.
TL;DR: A novel minutiae matching method that describes elastic distortions in fingerprints by means of a thin-plate spline model that gives considerably higher matching scores compared to rigid matching algorithms, while only taking 100 ms on a 1 GHz P-III machine.
TL;DR: In this paper, the average energy requirement of households in 11 EU member states was evaluated by investigating both the direct (electricity, natural gas, gasoline, etc.) and indirect energy requirement, i.e. the energy embodied in consumer goods and services.
TL;DR: In this article, the preparation of polyethersulfone (PES) hollow fiber membranes has been studied using N-methylpyrrolidone (NMP) as solvent, polyethylene glycol 400 (PEG 400) as weak nonsolvent and water as strong nonsoline.
TL;DR: This paper found that watching television news on the public service channels has positive effects on cognition, efficacy, and turnout, whereas regularly opting for commercial television news has negative effects, revealing what might be described as a "virtuous circle" for some and a "spiral of cynicism" for others.
Abstract: Research examining media effects on political attitudes has put forth broadly conflicting explanations: media use diminishes knowledge and involvement and contributes to political cynicism and declining turnout; media use contributes to learning, political involvement, trust, efficacy, and mobilization. We address these explanations with detailed measures for the Netherlands in 1998. A dual effects hypothesis is supported: regularly watching television news on the public service channels has positive effects on cognition, efficacy, and turnout, whereas regularly opting for commercial television news has negative effects. Viewing behavior thus separates the more knowledgeable, the efficacious, and the politically involved from those who are not, revealing what might be described as a "virtuous circle" for some and a "spiral of cynicism" for others.