Dynamic Light Scattering Signal Research Articles

Research on ultrafine particle size measurement using small amounts of data

The paper puts forward a new method of ultrafine particle size measurement using small amounts of data of a dynamic light-scattering signal, and establishes an arithmetic model of the measurement by wavelet package transform. First, through the wavelet package transform, the ultrafine particle dynamic light-scattering signals were decomposed into multifrequency bands. Then, the noise of signals of different frequency bands were removed and the power spectrum of the wavelet packet coefficients of each frequency band was calculated. Finally, the ultrafine particle size distribution information could be deduced from inversing the power spectrum. The standard polystyrene particles of 100, 300, and 400 nm were measured using this method, and the inversion results indicated that this method can effectively remove noise and improve the accuracy of particle size measurement using small amounts of data.

Simulation of dynamic light scattering signal for ultrafine particles based on the exponential model

According to the autocorrelation function (ACF) of dynamic light scattering (DLS) signals, the exponential model used for scattering signal simulation can be established. Based on this model, nine kinds of DLS signals for unimodal, bimodal and trimodal distribution particles are simulated respectively. The ACF of the simulated signal agrees with its theoretical value very well. Inverted size errors of simulative signals for unimodal distribution particles by Cumulants method and those for bimodal and trimodal distribution particles by nonnegative constraint least squares (NNLS) are less than 0.13%, 2.11% and 3.01%, respectively. Comparing the exponential model with autoregressive (AR) model, the calculation time of the former is less than one tenth of the latter. Hence, the exponential model is more effective in the simulation of DLS signals.

Optimized inversion procedure for retrieval of particle size distributions from dynamic light-scattering signals in current detection mode

Dynamic light-scattering signals in the current detection mode are normally analyzed in the frequency domain. We propose an optimized inversion procedure for retrieval of the size distributions of the measured particles from such signals, including proper signal preprocessing and application of a Chahine-like relaxation technique, to solve a matrix equation. As for the results of the numerical experiments, the median value of the index of the discrepancy between the output distribution and the true one was mostly under 25% with 2% rms noise on the power spectral density of raw signals.

Postoperative follow up by dynamic light scattering: Detection of inflammatory molecular changes in the cornea, the vitreous and the lens

To detect post-op molecular changes and inflammatory processes by dynamic light scattering (DLS) in eye segments. To develop DLS parameters which are appropriate for the control of post-op course after ophthalmologic surgery. METHODS, DESIGN: Three new DLS devices were tested in different post-op clinical settings such as pseudoexfoliation syndrome (PEX), cataract surgery and retinal surgery. In a second step DLS was used to detect molecular changes in the cornea of 6 patients after photo refractive keratectomy (PRK) and 16 patients after photo astigmatic refractive keratectomy (PARK). In PEX-patients cataract surgery changed the DLS signals of the anterior chamber and the lens in a specific way compared to the pre-op situation. Cataract patients without PEX had more scattering particles post-op and retinal surgery modified the DLS signal of the vitreous. Furthermore it was shown that the length of the corneal scattering vector l correlated with the process of the corneal wound healing after PARK. One and three months after surgery the lengths of the scattering vectors had increased significantly but returned to pre-op values twelve months post-op. The post-op transparency of eye segments such as the cornea, the vitreous and the anterior chamber depends primarily on the wound healing mechanisms. DLS seems to be a suitable method to control the corneal recovery after refractive surgery. The length of the scattering vector l correlates well with the wound healing after refractive surgery. However DLS-signals seem to contain information about the molecular composition of tissue too. Therefore further research is needed to refine the interpretation of the DLS signals.

Supramolecular Fluorophores for Biological Studies: Phenylene Vinylene-Amino Acid Amphiphiles

We report here on a family of self-assembling fluorescent organic amphiphiles with a biomolecular L-lysine hydrophile and a photonically active phenylene vinylene hydrophobe. Unlike conventional amphiphiles, these segmented dendrimers feature a rigid, branched hydrophobe, and have packing characteristics controlled by the ratio of cross-sectional areas of the hydrophobe and hydrophile. In dilute solution, the amphiphiles form supramolecular aggregates, which are easily taken in by cells through an endocytic pathway, and have no discernible effect on cell proliferation or morphology. An analogous pyrene-based amphiphile was cytotoxic, suggesting that cell survival may be linked either to the self-assembling nature of the amphiphiles, or to the specific properties of the phenylene vinylene segment. The combination of photonic and biological components in these amphiphiles provides great potential for applications in sensing or delivery of molecules to intracellular targets.