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Biomedical subjects

Jesper Glückstad

Publications and source records attributed to Jesper Glückstad.

8 recordsLinked to original sources
PubMed2005

Interactive optical trapping shows that confinement is a determinant of growth in a mixed yeast culture.

Applying a newly developed user-interactive optical trapping system, we controllably surrounded individual cells of one yeast species, Hanseniaspora uvarum, with viable cells of another yeast species, Saccharomyces cerevisiae, thus creating a confinement of the former. Growth of surrounded and non-surrounded H. uvarum cells was followed under a microscope by determining their generation time. The average generation time of surrounded H. uvarum cells was 15% higher than that of non-surrounded cells, thereby showing that the confinement imposed by viable S. cerevisiae cells on H. uvarum inhibits growth of the latter. This study is the first to demonstrate that confinement is a determinant of growth in a microbial ecosystem.

Culture Media↗
PubMed2004

Real-time three-dimensional optical micromanipulation of multiple particles and living cells.

Counterpropagating light fields provide a stationary optical potential well for a Brownian particle. Introducing variability in the relative strengths of the counterpropagating beams allows us to create a more general configuration-the optical elevator. An optical elevator dynamically controls the axial location of the potential minimum where the particle finds a stable equilibrium position. We describe the implementation of multiple real-time reconfigurable optical elevators with the generalized phase contrast method for dynamic manipulation of polystyrene spheres and yeast cells S. cerevisiae in three dimensions.

Cell Movement↗
PubMed2004

Dynamic formation of optically trapped microstructure arrays for biosensor applications.

We explore the dynamic properties of multiple-beam optical traps to manipulate arrays of microstructures for biosensor applications. Multiple optical traps are generated by a virtually loss-less transformation of input phase patterns into high-intensity trapping-beams. A direct image projection of the phase patterns enables an adjustable number of optical traps in addition to instantaneous control of the position, size, shape and intensity of each trapping-beam. We present experimental results showing various colloidal formations through dynamic optical manipulation of polystyrene microspheres and yeast cells in aqueous media. The experimental configurations are geared towards the use of multiple-beam optical traps for biosensor applications.

Biosensing Techniques↗
PubMed2003

Spatial light modulator-controlled alignment and spinning of birefringent particles optically trapped in an array.

We demonstrate the use of a phase-only liquid-crystal spatial light modulator (SLM) for polarization-controlled rotation and alignment of an array of optically trapped birefringent particles. A collimated beam incident upon a two-dimensional lenslet array yields multiple foci, scaled to produce optical gradient traps with efficient three-dimensional trapping potentials. The state of polarization of each trapping beam is encoded by the SLM, which acts as a matrix of wave plates with computer-controlled phase retardations. Control of the rotation frequency and alignment direction of the particles is achieved by the transfer of tunable photon spin angular momentum.

Birefringence↗
PubMed2003

Comment: Influence of illuminating beyond the object support on Zernike-type phase contrast filtering.

In this comment, we clarify some serious misinterpretations that can arise from an uncritical use of the results presented in [Appl. Opt. 41, 2607, (2002)]. In particular, we point out that their suggestion of using "illumination beyond the object support" for measuring phase disturbances can result in distorted or strongly inaccurate interference patterns. We also point out that Llave and Castillo have misinterpreted our previous work describing the effect of phase object fill factor on the output interference patterns, which is in fact one of the key factors considered in the generalized phase contrast (GPC) method. Unlike the Zernike method, the GPC method results in an optimized visualization of the phase disturbance by the achievement of a matching condition between the applied filter and the spatial average of a given phase disturbance, thereby implying the optimal use of fill factor information.

Comment↗
PubMed2002

Reverse phase contrast: an experimental demonstration.

We present experimental results showing that the reverse phase contrast (RPC) technique is a viable method for the generation of a binary phase distribution from a spatially varying amplitude pattern using Fourier plane filtering techniques. Experimental results are shown for the generation of a binary 0-pi phase only distribution using either an amplitude mask or a spatial light modulator to provide the input and the results are shown to be in agreement with theoretical predictions for the RPC technique.

Journal Article↗