University of Twente Publications
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University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.
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Mostrando recursos 1 - 20 de 6.381
1.
Integrated label-free silicon nanowire sensor arrays for (bio)chemical analysis - De, Arpita; Nieuwkasteele van, Jan; Carlen, Edwin T.; Berg van den, Albert
We present a label-free (bio)chemical analysis platform that uses all-electrical silicon nanowire sensor arrays integrated with a small volume microfluidic flow-cell for real-time (bio)chemical analysis and detection. The
integrated sensing platform contains an automated multi-sample injection system that eliminates erroneous sensor responses from sample switching due to flow rate fluctuations and provides precise sample volumes down to 10 nl. Biochemical sensing is demonstrated with real-time 15-mer DNA–PNA (peptide nucleic acid) duplex hybridization measurements from different sample concentrations in a low ionic strength, and the equilibrium dissociation constant KD z 140 nM has been extracted from the experimental data using the first...
2.
A Design Method For Modular Energy-Aware Software - Brinke te, Steven; Malakuti, Somayeh; Bockisch, Christoph; Bergmans, Lodewijk; Aksit, Mehmet
Nowadays reducing the overall energy consumption of software is important. A well-known solution is extending the functionality of software with energy optimizers, which monitor the energy consumption of software and adapt it accordingly. To make such extensions manageable and to cope with the complexity of the software, modular design of energy-aware software is necessary. Therefore, this paper proposes a dedicated design method for energy-aware software.
3.
A Pointcut Language for Setting Advanced Breakpoints - Yin, Haihan; Bockisch, Christoph; Aksit, Mehmet
In interactive debugging, it is an essential task to set breakpoints specifying where a program should be suspended at runtime to allow interaction. A debugging session may use multiple logically related breakpoints so that the sequence of their (de)activations leads to the expected suspension with the least irrelevant suspensions. A (de)activation is sometimes decided by some runtime context values related to that breakpoint. However, existing breakpoints, which are mainly based on line locations, are not expressive enough to describe the logic and the collaboration. Programmers have to manually perform some repeated tasks, thus debugging efficiency is decreased. In this paper,...
4.
Control of slippage with tunable bubble mattresses - Karatay, E.; Haase, A.S.; Visser, C.W.; Sun, C.; Lohse, D.; Tsai, P.A.; Lammertink, R.G.H.
Tailoring the hydrodynamic boundary condition is essential for both applied and fundamental aspects of drag reduction. Hydrodynamic friction on superhydrophobic substrates providing gas–liquid interfaces can potentially be optimized by controlling the interface geometry. Therefore, establishing stable and optimal interfaces is crucial but rather challenging. Here we present unique
superhydrophobic microfluidic devices that allow the presence of stable and controllable microbubbles at the boundary of microchannels. We experimentally and numerically examine the effect of microbubble geometry on the slippage at high resolution. The effective slip length is obtained for a wide range of protrusion angles, θ, of the microbubbles into the flow,...
5.
Economic and societal dimensions of nanotechnology-enabled drug delivery - Kulve te, H.; Rip, A.
Introduction: There is an increasing interest in nanotechnology-enabled drug delivery systems which are expected to have significant impacts for health care. The economic and societal aspects are uncertain, even ambiguous, at this stage of development, and often not addressed, or only as part of the promises about present options.
Areas covered: In our review we will report on assessments of actors regarding economic and societal aspects and, occasionally, of expected impacts. Topics discussed include: present and future markets of nano-enabled drug delivery, industry dynamics, regulation, cost-effectiveness, and broader ethical issues. We also include a brief discussion of anticipatory activities of...
6.
Modeling tidal sand wave formation in a numerical shallow water model: the role of turbulence formulation, doi: 10.1016/j.csr.2013.04.023 - Borsje, B.W.; Roos, P.C.; Kranenburg, W.M.; Hulscher, S.J.M.H.
Tidal sand waves are prominent dynamic bottom features in shallow sandy seas. Up to now, the processes controlling the formation of these bedforms have only been studied in stability sand wave models, in which geometry, boundary conditions and turbulence models are schematized. In this paper we present simulations of sand wave formation and migration with a numerical shallow water model (Delft3D), in which we restrict us to bedload transport and analyse the initial formation stage only. First, it is shown that the reproduction of the basic sand wave formation mechanisms in a numerical shallow water model requires careful treatment of...
7.
Hydrogen Generation from Photocatalytic Silver|Zinc Oxide Nanowires: Towards Multifunctional Multisegmented Nanowire Devices - Maijenburg, A. Wouter; Rodijk, Eddy J.B.; Maas, Michiel G.; Enculescu, Monica; Blank, Dave H.A.; Elshof ten, Johan E.
Photoactive nanowires: A novel photo-electrochemical nanowire diode that catalyzes the conversion of methanol and water to hydrogen under UV light is demonstrated. The wire consists of a metal and a metal oxide segment that are connected via a Schottky barrier. Other functions, such as remote- controlled autonomous movement, can be easily added to these wires in a modular fashion
9.
Electrodeposition in Capillaries: Bottom-up Micro- and Nanopatterning of Functional Materials on Conductive Substrates - George, Antony; Maijenburg, A. Wouter; Maas, Michiel G.; Blank, Dave H.A.; Elshof ten, Johan E.
A cost-effective and versatile methodology for bottom-up patterned growth of inorganic and metallic materials on the micro- and nanoscale is presented. Pulsed electrodeposition was employed to deposit arbitrary patterns of Ni, ZnO, and FeO(OH) of high quality, with lateral feature sizes down to 200–290 nm. The pattern was defined by an oxygen plasma-treated patterned PDMS mold in conformal contact with a conducting substrate and immersed in an electrolyte solution, so that the solid phases were deposited from the solution in the channels of the patterned mold. It is important that the distance between the entrance of the channels, and the...
10.
Photocatalytic segmented nanowires and single-step iron oxide nanotube synthesis: templated electrodeposition as all-round tool - Maas, Michiel G.; Rodijk, Eddy J.B.; Maijenburg, Wouter; Elshof ten, Johan E.; Blank, Dave H.A.
Templated electrodeposition was used to synthesize silver-zinc oxide nanowires and iron oxide (Fe2O3) nanotubes in polycarbonate track etched (PCTE) membranes. Metal/oxide segmented nanowires were made to produce hydrogen gas from a water/methanol mixture under ultraviolet irradiation. It was observed that gas production increased during irradiation. Iron oxide nanotubes were synthesized via a gel synthesis route, avoiding clogging of the membrane pores during growth. The nanotubes formed without thermal after-treatment. Transmission electron microscopy (TEM) analysis and selected area electron diffraction (SAED) revealed a completely amorphous iron oxide structure. By demonstrating the synthesis of photocatalytically active segmented nanowire and nanotubes without post-treatment...
11.
Exploring the transferability of large supramolecular assemblies to the vacuum-solid interface - Xu, Wei; Dong, Mingdong; Gersen, Henkjan; Vázquez-Córdova, Socorro; Bouju, Xavier; Laegsgaard, Erik; Stensgaard, Ivan; Crego-Calama, Mercedes; Reinhoudt, David N.; Linderoth, Trolle R.; Besenbacher, Flemming
We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111) surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces. The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111) surface under ultra-high vacuum conditions; the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly, suggesting that the assembly itself can be transferred...
12.
Combinatorial libraries of fluorescent monolayers on glass - Basabe-Desmonts, Lourdes; Reinhoudt, David N.; Crego-Calama, Mercedes
Fluorescent self-assembled monolayers (SAMs) on glass surfaces are discussed as new sensing materials for metal ions and inorganic anions. The sensing SAMs are created by sequential deposition of two building blocks, a fluorophore and a ligand molecule onto an amino terminated SAM on glass slides. A large number of different systems can be fabricated by combinatorial techniques and parallel synthesis. A collection of sensing SAMs constitute a cross-reactive sensor array, with which analytes can be identified by differential sensing using the collective response of the SAMs array, instead of the individual response of a single SAM. Arrays of fluorescent SAMs...
14.
Combinatorial method for surface-confined sensor design and fabrication - Basabe-Desmonts, Lourdes; Zimmerman, Rebecca S.; Reinhoudt, David N.; Crego-Calama, Mercedes
The procedure for the combinatorial fabrication of new sensing materials for cations and anions based on self-assembled monolayers (SAM) is discussed. A library of different sensitive substrates is generated by sequential deposition of fluorophores and small ligand molecules onto an amino-terminated SAM coated glass. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on individually deposited small molecules. Additionally the sensing system has been miniaturized to the microscale using microcontact printing and integrating the sensory SAMs on the walls of microchannels.
15.
Nanostructured hydrogen-bonded rosette assemblies - Crego-Calama, Mercedes; Reinhoudt, David N.; Garcia-Lopez, Juán J.; Kerckhoffs, Jessica M.C.A.
Self-assembly1 has become a promising option for the construction of molecular nanoscale devices.2,3 Well-defined nanostructures, also termed “supramolecular aggregates”, are formed by self-assembly of a limited number of well-defined building blocks with strong affinity for each other. They are formed via reversible noncovalent interactions such as hydrophobic and electrostatic effect, π—π stacking, hydrogen bonds and/or metal coordination.4 These noncovalent systems, generally highly dynamic on the human time scale, are distinctly different from the non-reversible covalent molecules, and they offer some advantages. The advantage of noncovalent synthesis is that noncovalent bonds are formed spontaneously and reversibly under conditions of thermodynamic equilibrium,...
16.
Preparation and X-ray structures of complexes of 18-membered crown ethers with polyfunctional guests: Urea and (O-alkyliso)uronium salts - Uiterwijk, Jos W.H.M.; Hummel van, Gerrit J.; Harkema, Sybolt; Aarts, Veronika M.L.J.; Daasvatn, Kari; Geevers, Jan; Hertog Jr. den, Herman J.; Reinhoudt, David N.
The preparation and X-ray structure determinations of six complexes of urea and (O-n-butyliso)uronium salts with crown ethers are presented. Urea forms isostructural 5:1 adducts with 18-crown-6 (1) and aza-18-crown-6 (2), in which two urea molecules are each hydrogen bonded to two neighbouring hetero atoms of the macroring. The remaining urea molecules form two-dimensional layers alternating with crown ether layers. In both complexes the macroring has theg+g+a ag−a ag−a g−g−a ag+a ag+a conformation withCi symmetry. In the solid 1:1 complex of O-n-butylisouronium picrate with 18-crown-6 (3) two types of conformations of the macroring were observed: theg+g+a ag−a ag+a ag−g−ag−a ag+a conformation...
17.
Energy propagation in linear hyperbolic systems - Mainardi, F.; Groesen van, E.
The concept of energy velocity for linear dispersive waves is usually given for a normal mode solution of the system as the ratio between the mean energy flux and the mean energy density. In the absence of dissipation this velocity is known to coincide with the corresponding group velocity. When dispersion is accompanied by dissipation, this interpretation is not correct since the group velocity loses its original meaning and can assume nonphysical values. In this note the relation between energy velocity and group velocity is derived for dissipative, uniaxial waves, governed by a linear hyperbolic system. An example is provided...
18.
Porous membrane structures as stationary phase for capillary electrochromatography - Kopec, K.K.; Wessling, M.; Stamatialis, D.
This work presents the application of membrane technology for the fabrication of stationary phase for CEC columns using the technique based on phase inversion of polymer solution. A blend of polyimide P84 and sulphonated poly(ether ether ketone was processed via immersion precipitation dry-wet spinning into small-bore porous fiber. The morphology, zeta potential, and performance of the porous structure in the CEC separation were investigated. Noncharged molecules (as markers of the electroosmotic flow) and small organic compounds were injected into the column, driven under the application of voltage, and detected on the electropherogram. The proof of concept of applying porous membrane...
19.
Electron-induced dynamics of heptathioeter ß-cyclodextrin molecules - Kumar, A.; Heimbuch, R.U.; Wimbush, K.S.; Atesci, H.; Acun, A.; Reinhoudt, D.N.; Velders, A.H.; Zandvliet, H.J.W.
Variable-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) measurements are performed on heptathioether β-cyclodextrin (β-CD) self-assembled monolayers (SAMs) on Au. The β-CD molecules exhibit very rich dynamical behavior, which is not apparent in ensemble-averaged studies. The dynamics are reflected in the tunneling current–time traces, which are recorded with the STM feedback loop disabled. The dynamics are temperature independent, but increase with increasing tunneling current and sample bias, thus indicating that the conformational changes of the β-CD molecules are induced by electrons that tunnel inelastically. Even for sample biases as low as 10 mV, well-defined levels are observed in the tunneling...
20.
In-depth compositional analysis of ceramic $(Bi_2O_3)_{0.75}(Er_2O_3)_{0.25}$ by AES and XPS - Hanekamp, Lambertus J.; Berg van den, Albert H.J.; Bouwmeester, Henny J.M.; Sasse, Antonius G.B.M.; Kruidhof, Henk
The chemical composition of dense ceramics of erbia-stabilized δ-Bi2O3 was analyzed by Auger electron spectroscopy (AES) depth profiling using Ar+ ion sputtering. The relative sensitivity factors (rsf) and sputter rates of bismuth and erbium in this material have been determined by electron probe microanalysis (EPMA) and chemical analysis. These results, supplemented by data from angle resolved X-ray photoelectron spectroscopy (ARXPS), shows a bismuth enrichment at the surface. Evidence has been found for reduction of the bismuth-oxide at the outermost part of the surface layer.
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