Laser Doppler, speckle and related techniques for blood perfusion mapping and imaging

Briers, J. D.

doi:10.1088/0967-3334/22/4/201

Cited by 626 publications

(500 citation statements)

References 129 publications

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“…The scattering centers are moving in a complex manner, as a result of sedimentation and stochastic Brownian motion [13]. As it has been shown in [9], the scattering centers velocity associated with the sedimentation is few orders of magnitude smaller than the velocity associated with Brownian motion for the size ranges corresponding to nanoparticles.…”

Section: Introductionmentioning

confidence: 94%

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Using Dynamic Light Scattering Experimental Setup and Neural Networks For Particle Sizing

Rei

Chicea

2017

ACTA Universitatis Cibiniensis

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Using a Lorentzian function fit as reference, a basic experiment was designed for processing IntroductionThe study of nanoparticles is a topic of major interest in the last decades due to the wide array of applications, especially in the area of biology and medicine. As a consequence of their small size, one order of magnitude smaller than the living cells, they can be used to deliver various substances to living cells, producing, in general, only minor perturbations. The applications of these nanomaterials were presented in several papers, such as [1]. During development of these applications, there were concerns about the toxicity of these methods. As a result, techniques for monitoring the nanoparticles concentration were also developed [2].The properties of the systems of nanoparticles are in direct relation to the size distribution of the particles in the fluid. For this reason, the size characterization of these systems is one relevant aspect for further development of the nanotechnology applications. There are various techniques used for this. One modern technique is the Transmission Electron Microscopy (TEM) which evaluates particles in the range from nanometers to micrometers. This method has a good resolution but is in general expensive, time consuming and does not work in-situ. Another method is the X-Ray powder diffraction which can offer the size distribution of the particles [3]. For metal oxides, for which the assumption used is that the crystallite size is the same as the particle size, the Scherrer equation [4] can offer the mean particle size. For colloidal particles, the Guinier formula [5] can be used in a similar way. However, also these two methods are slow and do not work in-situ. The particle size for nano-systems can also be assessed by the method called "Atomic Force Microscopy" (AFM) [6], [7]. Paper [7] shows a comparison of AFM with TEM. Results show that AFM sizing requires very thin samples over several layers. The samples are scanned line by line and this takes a lot of time. Comparisons and reviews of other techniques used for nanoparticle size characterization are presented in many papers, such as [8]. As in [9], the properties of the nanofluid change very fast during nanoparticle aggregation, and as a consequence, a fast procedure for monitoring the size is needed. A valid option for this are the optical procedures, which use coherent light scattering.The optical methods make use of an incident coherent beam of light which illuminates an active sample volume containing the nanoparticles. Each particle represents a scattering center and becomes a secondary light source. The intensity of the scattered light is anisotropic and depends on the size and shape of the scattering centers. This is described by the phase function, for which there are several models used to represent it [10], [11], [12].If the incident beam is coherent, so are the secondary waves emitted by each scattering center. If a screen or a detector is present, all the wavelets emitted by all the scattering...

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Section: Introductionmentioning

confidence: 94%

“…The theoretical foundation for this method is explained in many papers, such as [13], [16], and [17]. This paper presents an innovative alternative approach for extracting the size information from the time series recorded in a Dynamic Light Scattering experiment, using a specialized Neural Network.…”

Section: Introductionmentioning

confidence: 99%

Using Dynamic Light Scattering Experimental Setup and Neural Networks For Particle Sizing

Rei

Chicea

2017

ACTA Universitatis Cibiniensis

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“…The theoretical foundation of this method is described in various papers, [2], [3], [4] being some of them. This method is an optical procedure which uses coherent light to monitor in a fast manner the particles found in a suspension.…”

Section: Introductionmentioning

confidence: 99%

“…The motion of the particles is complex, being consisted mainly on sedimentation and Brownian motion [2]. It has been shown [8] that the sedimentation velocity is few orders of magnitude smaller than the velocity of the Brownian motion, when the particles size is in the nanometer scale.…”

Section: Introductionmentioning

confidence: 99%

“…The intensity of the light scattered by each center is anisotropic and depends mainly on the size and on the shape of the respective center. This information can be found in the phase function, which can be represented by various computational models [5], [6], [7].The motion of the particles is complex, being consisted mainly on sedimentation and Brownian motion [2]. It has been shown [8] that the sedimentation velocity is few orders of magnitude smaller than the velocity of the Brownian motion, when the particles size is in the nanometer scale.…”

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confidence: 99%

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Dynamic Light Scattering Signal Conditioning for Data Processing

Rei

Chicea

Ilie

et al. 2017

ACTA Universitatis Cibiniensis

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When performing data acquisition for a Dynamic Light Scattering experiment, one of the most important aspect is the filtering and conditioning of the electrical signal. The signal is amplified first and then fed as input for the analog digital convertor. As a result a digital time series is obtained. The frequency spectrum is computed by the logical unit offering the basis for further Dynamic Light Scattering analysis methods. This paper presents a simple setup that can accomplish the signal conditioning and conversion to a digital time series.Key words: Dynamic Light Scattering, Signal Conditioning, Time Series. IntroductionNanostructured materials have several applications in biology and medicine [1], mainly for investigating and delivering useful substances to the living cells. The physical properties of the relevant nanofluids and nanoparticles are in close connection to the particle size and size distribution. Therefore, the techniques used for estimating these physical properties are of major importance.One method for determining the average particle size for nanoparticles found in a suspension is the Dynamic Light Scattering or Photon Correlation Spectroscopy. The theoretical foundation of this method is described in various papers, [2], [3], [4] being some of them. This method is an optical procedure which uses coherent light to monitor in a fast manner the particles found in a suspension. The particles act as scattering centers and become secondary light sources when the incident coherent light interacts with them. This is a process of elastic scattering. As the incident light is coherent, the secondary waves emitted by the scattering centers are also coherent and due to interference they produce a scattering field. When placing a screen or a detector at a certain angle and distance from the sample, the interference field will have minima and maxima, randomly distributed, with the visual appearance of "boiling speckles". The intensity of light in each point of this field carries information on the phase of all the scattering centers from the active volume of the sample. The intensity of the light scattered by each center is anisotropic and depends mainly on the size and on the shape of the respective center. This information can be found in the phase function, which can be represented by various computational models [5], [6], [7].The motion of the particles is complex, being consisted mainly on sedimentation and Brownian motion [2]. It has been shown [8] that the sedimentation velocity is few orders of magnitude smaller than the velocity of the Brownian motion, when the particles size is in the nanometer scale. As a consequence, the phase function is affected mainly be Brownian motion, and since this motion is in relation to the size of the particles via the Einstein -Stokes relation, information about the size of the particles can be extracted by studying this phase. For this, the method is recording a time series using a light detector. The light detector generates an electrical signal, conv...

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