Biomedical subjects

M G Somekh

Publications and source records attributed to M G Somekh.

5 recordsLinked to original sources

PubMed2005

Two-photon fluorescence surface wave microscopy.

This paper demonstrates the principle of two-photon surface wave microscopy with a view to applications on biological samples. We describe a modified scanning optical microscope, which uses specially prepared coverslips. These coverslips are designed to support the propagation of surface waves capable of large field enhancements. We also discuss the beam conditioning necessary to ensure efficient use of the available illumination. Two-photon surface wave fluorescent excitation is demonstrated on fluorescent nanospheres, demonstrating a point spread function width of approximately 220 nm at an illumination wavelength of 925 nm. The potential of non-linear surface wave excitation for both fluorescence and harmonic imaging microscopy is discussed.

Membrane Microdomains↗

PubMed2004

High-resolution wide-field surface plasmon microscopy.

This paper describes the application of a Köhler illuminated high-resolution wide-field microscope using surface plasmons to provide the image contrast. The response of the microscope to a grating structure in both the Fourier and the image planes is presented to demonstrate image formation by surface waves. The effect of spatial filtering in the back focal (Fourier) plane to enhance image contrast is described. We also discuss how the surface wave contrast mechanism affects the imaging performance of the microscope and discuss factors that can be expected to lead to even greater improvements in lateral resolution and sensitivity.

Journal Article↗

PubMed2004

Quantitative optical microscope with enhanced resolution using a pixelated liquid crystal spatial light modulator.

This paper presents a brief account of a novel optical microscope, which combines the advantages of two well-known techniques, namely phase contrast and phase stepping, to provide high contrast imaging and precision measurements. The inclusion of a programmable liquid crystal spatial light modulator provides for the phase stepping required, while also allowing flexibility for future improvements. The results shown reveal an important aspect of the system to facilitate quantitative sample measurements, with an enhancement of optical resolution compared with conventional optical imaging systems.

Journal Article↗

PubMed2002

Surface plasmon fluorescence microscopy: an analysis.

This paper examines the imaging performance of surface plasmon microscopes operating in the far field. Until recently the accepted view has been that the achievable lateral resolution with a surface plasmon imaging system is limited by propagation decay length of the surface plasmons rather than by diffraction. We show by simulation that the lateral resolution of a surface plasmon imaging system can be comparable to that of the best optical microscopes. We also show that new imaging modes such as two-photon and also second harmonic surface plasmon microscopy are extremely promising imaging modes that may be expected to be powerful techniques for the analysis of surface structures.

Journal Article↗

PubMed1992

Wavelet transform as a potential tool for ECG analysis and compression.

The recently introduced wavelet transform is a member of the class of time-frequency representations which include the Gabor short-time Fourier transform and Wigner-Ville distribution. Such techniques are of significance because of their ability to display the spectral content of a signal as time elapses. The value of the wavelet transform as a signal analysis tool has been demonstrated by its successful application to the study of turbulence and processing of speech and music. Since, in common with these subjects, both the time and frequency content of physiological signals are often of interest (the ECG being an obvious example), the wavelet transform represents a particularly relevant means of analysis. Following a brief introduction to the wavelet transform and its implementation, this paper describes a preliminary investigation into its application to the study of both ECG and heart rate variability data. In addition, the wavelet transform can be used to perform multiresolution signal decomposition. Since this process can be considered as a sub-band coding technique, it offers the opportunity for data compression, which can be implemented using efficient pyramidal algorithms. Results of the compression and reconstruction of ECG data are given which suggest that the wavelet transform is well suited to this task.

Electrocardiography↗