160,861 research outputs found
Light-scattering polarization measurements as a new parameter in flow cytometry
Polarization measurement of orthogonal light scattering is introduced as a new optical parameter in flow cytometry. \ud
In the experimental setup, the electrical field of the incident laser beam is polarized in the direction of the sample flow. The intensity of the orthogonal light scattering polarized along the direction of the incoming laser beam is called depolarized orthogonal light scattering. Theoretical analysis shows that for small values of the detection aperture, the measured depolarization is caused by anisotropic cell structures and multiple scattering processes inside the cell. \ud
Measurements of the orthogonal depolarized light scattering in combination with the normal orthogonal light scattering of human leucocytes revealed two populations of granulocytes. By means of cell sorting it was shown that the granulocytes with a relatively high depolarization are eosinophilic granulocytes. Similar experiments with human lymphocytes revealed a minor subpopulation of yet-unidentified lymphocytes with a relative large orthogonal light-scattering depolarization. The results were obtained with an argonion laser tuned at different wavelengths as well as with a 630-nm helium neon laser. These results show that measurement of depolarized orthogonal light scattering is a useful new parameter for flow-cytometric cell differentiation
Laser light scattering applications in biotechnology
Recent advancement of laser light scattering applications in biotechnology are reviewed with emphasis on their use in the biopharmaceutical industry. Light scattering methods have been used to date to characterize biomolecules in solution. They can provide information about the size and conformation of proteins and their aggregation state as well as their ability to crystallise. In addition, modern light scattering instrumentation is becoming method of choice for studying macromolecular interactions. Interactions between macromolecules such as proteins and nucleic acids mediate fundamental processes and their modulation has led to new strategies for developing therapeutics. Light scattering approaches offer significant advantage to other approaches for studying molecular interactions. Compared with other techniques, light scattering is very quick, uses minimal sample quantities, allows recovery of the sample and does nor require derivatisation
Elastic Light Scattering by Semiconductor Quantum Dots
Elastic light scattering by low-dimensional semiconductor objects is
investigated theoretically. The differential cross section of resonant light
scattering on excitons in quantum dots is calculated. The polarization and
angular distribution of scattered light do not depend on the quantum-dot form,
sizes and potential configuration if light wave lengths exceed considerably the
quantum-dot size. In this case the magnitude of the total light scattering
cross section does not depend on quantum-dot sizes. The resonant total light
scattering cross section is about a square of light wave length if the exciton
radiative broadening exceeds the nonradiative broadening. Radiative broadenings
are calculated
Phase sensitive Brillouin scattering measurements with a novel magneto-optic modulator
A recently reported phase sensitive Brillouin light scattering technique is
improved by use of a magnetic modulator. This modulator is based on Brillouin
light scattering in a thin ferrite film. Using this magnetic modulator in time-
and space Brillouin light scattering measurements we have increased phase
contrast and excluded influence of optical inhomogeneities in the sample. We
also demonstrate that the quality of the resulting interference patterns can be
improved by data postprocessing using the simultaneously recorded information
about the reference light
Four-Parameter white blood cell differential counting based on light scattering measurements
Measurement of the depolarized orthogonal light scattering in flow cytometry enables one to discriminate human eosinephilic granulocytes from neutrophilic granulocytes. We use this method to perform a four-parameter differential white blood cell analysis. \ud
A simple flow cytometer was built equipped with a 5-mW helium neon laser that measures simultaneously four light scattering parameters. Lymphocytes, monocytes, and granulocytes were identified by simultaneously measuring the light scattering intensity at angles between 1.0° and 2.6° and angles between 3.0° and 11.0°. Eosinophilic granulocytes were distinguished from neutrophilic granulocytes by simultaneous measurement of the orthogonal and depolarized orthogonal light scattering. \ud
Comparison of a white blood cell differentiation of 45 donors obtained by the Technicon H-6000 and our instrument revealed good correlations. The correlation coefficients (r2) found were: 0.99 for lymphocytes, 0.76 for monocytes, 0.99 for neutrophilic granulocytes, and 0.98 for eosinophilic granulocytes. The results demonstrate that reliable white blood cell differentiation of the four most clinically relevant leukocytes can be obtained by measurement of light scattering properties of unstained leukocytes
Light Scattering by Cholesteric Skyrmions
We study the light scattering by localized quasi planar excitations of a
Cholesteric Liquid Crystal known as spherulites. Due to the anisotropic optical
properties of the medium and the peculiar shape of the excitations, we
quantitatively evaluate the cross section of the axis-rotation of polarized
light. Because of the complexity of the system under consideration, first we
give a simplified, but analytical, description of the spherulite and we compare
the Born approximation results in this setting with those obtained by resorting
to a numerical exact solution. The effects of changing values of the driving
external static electric (or magnetic) field is considered. Possible
applications of the phenomenon are envisaged.Comment: 18 pages, 14 figure
Critical light scattering in liquids
We compare theoretical results for the characteristic frequency of the
Rayleigh peak calculated in one-loop order within the field theoretical method
of the renormalization group theory with experiments and other theoretical
results. Our expressions describe the non-asymptotic crossover in temperature,
density and wave vector. In addition we discuss the frequency dependent shear
viscosity evaluated within the same model and compare our theoretical results
with recent experiments in microgravity.Comment: 17 pages, 12 figure
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