Search results | TU Delft Repositories

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Strain-dependent damping in nanomechanical resonators from thin MoS2 crystals

Kramer, E. (author), Van Dorp, J. (author), Van Leeuwen, R. (author), Venstra, W.J. (author)

We investigate the effect of mechanical strain on the dynamics of thin MoS2 nanodrum resonators. Using a piezoelectric crystal, compressive and tensile biaxial strain is induced in initially flat and buckled devices. In the flat device, we observe a remarkable strain-dependence of the resonance line width, while the change in the resonance...

journal article 2015

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Nanoscale mechanical resonators and oscillators

Van Leeuwen, R. (author)

In this thesis the physics of nanoscale mechanical resonators and oscillators is studied. We discuss two types of resonators. First, a top-down fabricated doubly clamped beam resonator with an integrated piezoelectric actuator is introduced. The second type of resonators are based on layered two-dimensional materials, such as graphene and...

doctoral thesis 2015

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uPAR-targeted multimodal tracer for pre- and intraoperative imaging in cancer surgery

Boonstra, M.C. (author), Van Driel, P.B.A.A. (author), Van Willigen, D.M. (author), Stammes, M.A. (author), Prevoo, H.A.J.M. (author), Tummers, Q.R.J.G. (author), Mazar, A.P. (author), Beekman, F.J. (author), Kuppen, P.J.K. (author), Van de Velde, C.J.H. (author), Löwik, C.W.G.M. (author), Frangioni, J.V. (author), Van Leeuwen, F.W.B. (author), Sier, C.F.M. (author), Vahrmeijer, A.L. (author)

Pre- and intraoperative diagnostic techniques facilitating tumor staging are of paramount importance in colorectal cancer surgery. The urokinase receptor (uPAR) plays an important role in the development of cancer, tumor invasion, angiogenesis, and metastasis and over-expression is found in the majority of carcinomas. This study aims to develop...

journal article 2015

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U-SPECT-BioFluo: An integrated radionuclide, bioluminescence, and fluorescence imaging platform

Van Oosterom, M.N. (author), Kreuger, R. (author), Buckle, T. (author), Mahn, W.A. (author), Bunschoten, A. (author), Josephson, L. (author), Van Leeuwen, F.W.B. (author), Beekman, F.J. (author)

Background: In vivo bioluminescence, fluorescence, and single-photon emission computed tomography (SPECT) imaging provide complementary information about biological processes. However, to date these signatures are evaluated separately on individual preclinical systems. In this paper, we introduce a fully integrated bioluminescence-fluorescence...

journal article 2014

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Ultra-compact silicon photonic integrated interferometer for swept-source optical coherence tomography

Yurtsever, G. (author), Weiss, N. (author), Kalkman, J. (author), Van Leeuwen, T.G. (author), Baets, R. (author)

We demonstrate an ultra-compact silicon integrated photonic interferometer for swept-source optical coherence tomography (SS-OCT). The footprint of the integrated interferometer is only 0.75×5??mm2. The design consists of three 2×2 splitters, a 13 cm physical length (50.4 cm optical length) reference arm, and grating couplers. The photonic...

journal article 2014

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Nonlinear dynamics of a microelectromechanical oscillator with delayed feedback

Van Leeuwen, R. (author), Karabacak, D.M. (author), Van der Zant, H.S.J. (author), Venstra, W.J. (author)

We study the dynamics of a nonlinear electromechanical oscillator with delayed feedback. Compared to their linear counterparts, we find that the dynamics is dramatically different. The well-known Barkhausen stability criterion ceases to exist, and two modes of operation emerge: one characterized by hysteresis in combination with a bistable...

journal article 2013

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Localized measurement of longitudinal and transverse flow velocities in colloidal suspensions using optical coherence tomography

Weiss, N. (author), Van Leeuwen, T.G. (author), Kalkman, J. (author)

We report on localized measurement of the longitudinal and transverse flow velocities in a colloidal suspension using optical coherence tomography. We present a model for the path-length resolved autocorrelation function including diffusion and flow, which we experimentally verify. For flow that is not perpendicular to the incident beam, the...

journal article 2013

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Strongly coupled modes in a weakly driven micromechanical resonator

Venstra, W.J. (author), Van Leeuwen, R. (author), Van der Zant, H.S.J. (author)

We demonstrate a strong coupling between the flexural vibration modes of a clamped-clamped micromechanical resonator vibrating at low amplitudes. This coupling enables the direct measurement of the frequency response via amplitude- and phase modulation schemes using the fundamental mode as a mechanical detector. In the linear regime, a frequency...

journal article 2012

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Fermentative production of isobutene

Van Leeuwen, B.N.M. (author), Van der Wulp, A.M. (author), Duijnstee, I. (author), Van Maris, A.J.A. (author), Straathof, A.J.J. (author)

Isobutene (2-methylpropene) is one of those chemicals for which bio-based production might replace the petrochemical production in the future. Currently, more than 10 million metric tons of isobutene are produced on a yearly basis. Even though bio-based production might also be achieved through chemocatalytic or thermochemical methods, this...

journal article 2012

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Development of a bioreactor with integrated on-line sensing for batch and fed-batch cultivation on a 100 ?L-scale

Van Leeuwen, M. (author)

doctoral thesis 2008

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Production of 200,000 tons/a Vinyl Chloride Monomer via direct chlorination and oxychlorination

Koren, A.E. (author), Van Leeuwen, J.C.M. (author), Spruijt, R.A. (author), Weststrate, J. (author)

report 1998

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Precipitation and mixing

Van Leeuwen, M.L.J. (author)