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Your search keyword '"Capel, P. J. A."' showing total 14 results
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14 results on '"Capel, P. J. A."'

1. Ultrafast all-optical gated amplifier based on ZnO nanowire lasing

Author

Versteegh, Marijn A. M., van Capel, Peter J. S., and Dijkhuis, Jaap I.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

We present an ultrafast all-optical gated amplifier, or transistor, consisting of a forest of ZnO nanowire lasers. A gate light pulse creates a dense electron-hole plasma and excites laser action inside the nanowires. Source light traversing the nanolaser forest is amplified, partly as it is guided through the nanowires, and partly as it propagates diffusively through the forest. We have measured transmission increases at the drain up to a factor 34 for 385-nm light. Time-resolved amplification measurements show that the lasing is rapidly self-quenching, yielding pulse responses as short as 1.2 ps., Comment: 3 pages, 3 figures

Published
2016
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3. Invariant Classification and Limits of Maximally Superintegrable Systems in 3D

Author

Capel, Joshua J., Kress, Jonathan M., and Post, Sarah

Subjects
Mathematical Physics
Abstract

The invariant classification of superintegrable systems is reviewed and utilized to construct singular limits between the systems. It is shown, by construction, that all superintegrable systems on conformally flat, 3D complex Riemannian manifolds can be obtained from singular limits of a generic system on the sphere. By using the invariant classification, the limits are geometrically motivated in terms of transformations of roots of the classifying polynomials.

Published
2015
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8. Over de refractiewet van Snellius, circa 600 jaar voor Snellius: Ibn Sahl en de refractiewet

Author

Yandouzi, Y. El, Capel, P. J. S. van (Thesis Advisor), Mosk, A., Holzinger, R., Yandouzi, Y. El, Capel, P. J. S. van (Thesis Advisor), Mosk, A., and Holzinger, R.

Abstract

Tegenwoordig wordt de wet van Snellius aan de Nederlander Willebrord Snellius (1580-1626) toegeschreven, omdat hij volgens Christiaan Huygens (1629-1695) de eerste geweest zou zijn die deze wet heeft bewezen. Aan de nog steeds lopende discussie over de vraag ‘wie heeft deze wet ontdekt?’ voeg ik nog een partij toe, namelijk de Arabischtalige wetenschap. De Frans-Egyptische historicus Roshdi Rashed (1936) beschrijft een wetenschapper uit de tiende eeuw, Abu Saad Al-Ala Ibn Sahl (c. 940-1000), degene die deze wet lang voor Snellius heeft ontdekt. Mijn onderzoeksvraag was dan ook: “komt de wet van Snellius voor in het werk van Ibn Sahl en zo ja, herkent Ibn Sahl die ook als zodanig?”. Om tot een antwoord op deze tweeledige onderzoeksvraag te komen ben ik in eerste instantie uitgegaan van het werk The Treatise on Burning Instruments van Ibn Sahl. Verder heb ik ook werken van Ptolemaeus, Dr. Rashed en Snellius bekeken dan wel bestudeerd. Door stukken uit het werk van Ibn Sahl zelf te vertalen en te vergelijken met de eerder genoemde werken ben ik uiteindelijk tot de conclusie gekomen dat de wet van Snellius voorkomt in het werk van Ibn Sahl; het is echter niet uit zijn werk af te leiden dat hij de wet als zodanig herkende. Daarnaast toetst hij zijn resultaten niet aan de werkelijkheid. Derhalve heb ik geconcludeerd dat Ibn Sahl deze wet niet heeft ontdekt. Kanttekeningen bij mijn conclusie bespreek ik in de discussie. Daar zal ik onder andere het fenomeen ‘ontdekken’ bespreken: wanneer is een natuurkundige wet ontdekt? Afhankelijk van de visie op het gebied van dit fenomeen kan men de wet namelijk wel of niet toeschrijven aan Ibn Sahl.

Published
2018

9. Nonlinear ultrafast acoustics at the nano scale

Author

Van Capel, P. J S, Péronne, E., Dijkhuis, J. I., Debye Institute, Sub Practicum, Dep Natuurkunde, Sub Physics of Condensed Matters begr, and Atom optics and ultrafast dynamics

Subjects
Acoustic shock waves, Nonlinear acoustics, Acoustic solitons, Picosecond ultrasonics
Abstract

Pulsed femtosecond lasers can generate acoustic pulses propagating in solids while displaying either diffraction, attenuation, nonlinearity and/or dispersion. When acoustic attenuation and diffraction are negligible, shock waves or solitons can form during propagation. Both wave types are phonon wavepackets with characteristic length scales as short as a few nanometer. Hence, they are well suited for acoustic characterization and manipulation of materials on both ultrafast and ultrashort scales. This work presents an overview of nonlinear ultrasonics since its first experimental demonstration at the beginning of this century to the more recent developments. We start by reviewing the main properties of nonlinear ultrafast acoustic propagation based on the underlying equations. Then we show various results obtained by different groups around the world with an emphasis on recent work. Current issues and directions of future research are discussed.

Published
2015

11. Polydimethylsiloxane and poly(ether) ether ketone functionally graded composites for biomedical applications.

Author

Smith, James A., Mele, Elisa, Rimington, Rowan P., Capel, Andrew J., Lewis, Mark P., Silberschmidt, Vadim V., and Li, Simin

Subjects
FUNCTIONALLY gradient materials, POLYETHERS, BLOOD substitutes, KETONES, POLYDIMETHYLSILOXANE, BULK solids
Abstract

Abstract Functionally graded materials (FGMs), with varying spatial, chemical and mechanical gradients (continuous or stepwise), have the potential to mimic heterogenous properties found across biological tissues. They can prevent stress concentrations and retain healthy cellular functions. Here, we show for the first time the fabrication of polydimethylsiloxane and poly(ether) ether ketone (PDMS-PEEK) composites. These were successfully manufactured as a bulk material and functionally graded (stepwise) without the use of hazardous solvents or the need of additives. Chemical, irreversible adhesion between layers (for the FGMs) was achieved without the formation of hard, boundary interfaces. The mechanical properties of PDMS-PEEK FGMs are proven to be further tailorable across the entirety of the build volume, mimicking the transition from soft to harder tissues. The introduction of 20 wt% PEEK particles into the PDMS matrix resulted in significant rises in the elastic modulus under tensile and compressive loading. Biological and thermal screenings suggested that these composites cause no adverse effects to human fibroblast cell lines and can retain physical state and mass at body temperature, which could make the composites suitable for a range of biomedical applications such as maxillofacial prosthetics, artificial blood vessels and articular cartilage replacement. Graphical abstract fx1 Highlights • PDMS-PEEK successfully functionally graded without formation of boundary interfaces. • Solvent-free fabrication up to 20 wt% weight fraction of PEEK. • Mechanical performance is fine-tunable by PEEK fraction adjustment. • PDMS-PEEK composites thermally stable up to approx. 300 °C. • Cytotoxicity screening of composites does not hinder fibroblast proliferation or morphology. [ABSTRACT FROM AUTHOR]

Published
2019
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13. Neural and Aneural Regions Generated by the Use of Chemical Surface Coatings

Author

Pardo-Figuerez, Maria, Martin, Neil R. W., Player, Darren J., Capel, Andrew J., Christie, Steve D. R., and Lewis, Mark P.

Abstract

The disordered environment found in conventional neural cultures impedes various applications where cell directionality is a key process for functionality. Neurons are highly specialized cells known to be greatly dependent on interactions with their surroundings. Therefore, when chemical cues are incorporated on the surface material, a precise control over neuronal behavior can be achieved. Here, the behavior of SH-SY5Y neurons on a variety of self-assembled monolayers (SAMs) and polymer brushes both in isolation and combination to promote cellular spatial control was determined. APTES and BIBB coatings promoted the highest cell viability, proliferation, metabolic activity, and neuronal maturation, while low cell survival was seen on PKSPMA and PMETAC surfaces. These cell-attractive and repulsive surfaces were combined to generate a binary BIBB-PKSPMA coating, whereby cellular growth was restricted to an exclusive neural region. The utility of these coatings when precisely combined could act as a bioactive/bioinert surface resulting in a biomimetic environment where control over neuronal growth and directionality can be achieved.

Published
2024
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14. Nonlinear ultrafast acoustics at the nano scale

Author

Debye Institute, Sub Practicum, Dep Natuurkunde, Sub Physics of Condensed Matters begr, Atom optics and ultrafast dynamics, Van Capel, P. J S, Péronne, E., Dijkhuis, J. I., Debye Institute, Sub Practicum, Dep Natuurkunde, Sub Physics of Condensed Matters begr, Atom optics and ultrafast dynamics, Van Capel, P. J S, Péronne, E., and Dijkhuis, J. I.

Published
2015

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