|
Differential Dynamic Microscopy
Differential dynamic microscopy (DDM) is an optical technique that allows performing light scattering experiments by means of a simple optical microscope. DDM is suitable for typical Soft matter, soft materials such as for instance liquids or gels made of colloids, polymers and liquid crystals but also for biological materials like bacteria and Cell (biology), cells. Basic idea The typical DDM data is a time sequence of microscope images (movie) acquired at some height within the sample (typically at its mid-plane). If the image intensity is locally proportional to the concentration of particles or molecules to be studied (possibly convoluted with the microscope Point spread function, point spread function (PSF)), each movie can be analyzed in the Fourier space to obtain information about the dynamics of concentration Fourier modes, ''independent on the fact that the particles/molecules can be individually optically resolved or not''. After suitable calibration also information abou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Scattering
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiation) in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections of radiation that undergo scattering are often called ''diffuse reflections'' and unscattered reflections are called '' specular'' (mirror-like) reflections. Originally, the term was confined to light scattering (going back at least as far as Isaac Newton in the 17th century). As more "ray"-like phenomena were discovered, the idea of scattering was extended to them, so that William Herschel could refer to the scattering of "heat rays" (not then recognized as electromagnetic in nature) in 1800. John Tyndall, a pioneer in light scattering resea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single Particle Tracking
Single-particle tracking (SPT) is the observation of the motion of individual particles within a medium. The coordinates time series, which can be either in two dimensions (''x'', ''y'') or in three dimensions (''x'', ''y'', ''z''), is referred to as a ''trajectory''. The trajectory is typically analyzed using statistical methods to extract information about the underlying dynamics of the particle. These dynamics can reveal information about the type of transport being observed (e.g., thermal or active), the medium where the particle is moving, and interactions with other particles. In the case of random motion, trajectory analysis can be used to measure the diffusion coefficient. Applications In life sciences, single-particle tracking is broadly used to quantify the dynamics of molecules/proteins in live cells (of bacteria, yeast, mammalian cells and live ''Drosophila'' embryos). It has been extensively used to study the transcription factor dynamics in live cells. This method h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microscopy
Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of microscopy: optical, electron, and scanning probe microscopy, along with the emerging field of X-ray microscopy. Optical microscopy and electron microscopy involve the diffraction, reflection, or refraction of electromagnetic radiation/electron beams interacting with the specimen, and the collection of the scattered radiation or another signal in order to create an image. This process may be carried out by wide-field irradiation of the sample (for example standard light microscopy and transmission electron microscopy) or by scanning a fine beam over the sample (for example confocal laser scanning microscopy and scanning electron microscopy). Scanning probe microscopy involves the interaction of a scanning probe with the surface of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scientific Techniques
A scientific technique is any systematic way of obtaining information about a scientific nature or to obtain a desired material or product. Scientific techniques can be divided in many different groups, e.g.: # Preparative techniques ## Synthesis techniques, e.g. the use of Grignard reagents in organic chemistry ## Growth techniques, e.g. crystal growth or cell cultures in biology ## Purification techniques e.g. those in chemistry # Measurement techniques ## Analysis techniques, e.g. ones that reveal atomic or molecular composition. ## Characterization techniques, e.g. ones that measure a certain property of a material. ## Imaging techniques, e.g. microscopy In some cases these methods have evolved into instrumental techniques that require expensive equipment. This is particularly true in sciences like physics, chemistry, and astronomy. It is customary to abbreviate the names of techniques into acronyms, although this does not hold for all of them. Particularly the advent of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colloidal Particle
Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles (''bubbles''). The notion of particle size applies to particles in colloids, in ecology, in granular material (whether airborne or not), and to particles that form a granular material (see also grain size). Measurement There are several methods for measuring particle size and particle size distribution. Some of them are based on light, other on ultrasound,Dukhin, A. S. and Goetz, P. J. ''Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound'', Elsevier, 2017 or electric field, or gravity, or centrifugation. The use of sieves is a common measurement technique, however this process can be more susceptible to human error and is time consuming. Technology such as dynamic image analysis (DIA) can make particle size distribution analyses much easier. This approach can be seen in instruments ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schlieren
Schlieren ( ; , ) are optical inhomogeneities in transparent media that are not necessarily visible to the human eye. Schlieren physics developed out of the need to produce high-quality lenses devoid of such inhomogeneities. These inhomogeneities are localized differences in optical path length that cause deviations of light rays, especially by refraction. This light deviation can produce localized brightening, darkening, or even color changes in an image, depending on the directions the rays deviate. History Schlieren were first observed by Robert HookeHooke, R. (1665), "Of a New Property in the Air," ''Micrographia'', Observation LVIII, pp. 217–219, London. in 1665 using a large concave lens and two candles. One candle served as a light source. The warm air rising from the second candle provided the schliere. The conventional schlieren system is credited mostly to German physicist August Toepler, though Jean Bernard Léon Foucault invented the method in 1859 that To ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shadowgraph
Shadowgraph is an optical method that reveals non-uniformities in transparent media like air, water, or glass. It is related to, but simpler than, the schlieren and schlieren photography methods that perform a similar function. Shadowgraph is a type of flow visualisation. In principle, a difference in temperature, a different gas, or a shock wave in the transparent air cannot be seen by the human eye or cameras. However, all these disturbances refract light rays, so they can cast shadows. The plume of hot air rising from a fire, for example, can be seen by way of its shadow cast upon a nearby surface by the uniform sunlight. Sunlight shadowgraph Some aquatic predators detect their transparent prey by way of their shadows cast upon the ocean floor. It was Robert Hooke who first scientifically demonstrated the sunlight shadowgraph and Jean-Paul Marat who first used it to study fire. A modern account of shadowgraphy is given by Gary S. Settles. Applications Applicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speckle Pattern
Speckle, speckle pattern, or speckle noise is a granular noise texture degrading the quality as a consequence of interference among wavefronts in coherent imaging systems, such as radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography. Speckle is not external noise; rather, it is an inherent fluctuation in diffuse reflections, because the scatterers are not identical for each cell, and the coherent illumination wave is highly sensitive to small variations in phase changes. Although scientists have investigated this phenomenon since the time of Newton, speckles have come into prominence since the invention of the laser. Such reflections may occur on materials such as paper, white paint, rough surfaces, or in media with a large number of scattering particles in space, such as airborne dust or in cloudy liquids. They have been used in a variety of applications in microscopy, imaging, and optical manipulation. The vast majority of surfaces, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Diffusivity
Diffusivity, mass diffusivity or diffusion coefficient is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species (or the driving force for diffusion). Diffusivity is encountered in Fick's law and numerous other equations of physical chemistry. The diffusivity is generally prescribed for a given pair of species and pairwise for a multi-species system. The higher the diffusivity (of one substance with respect to another), the faster they diffuse into each other. Typically, a compound's diffusion coefficient is ~10,000× as great in air as in water. Carbon dioxide in air has a diffusion coefficient of 16 mm2/s, and in water its diffusion coefficient is 0.0016 mm2/s. Diffusivity has dimensions of length2 / time, or m2/s in SI units and cm2/s in CGS units. Temperature dependence of the diffusion coefficient Solids The diffusion coefficient in solids at different temperatures is generally found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brownian Motion
Brownian motion, or pedesis (from grc, πήδησις "leaping"), is the random motion of particles suspended in a medium (a liquid or a gas). This pattern of motion typically consists of random fluctuations in a particle's position inside a fluid sub-domain, followed by a relocation to another sub-domain. Each relocation is followed by more fluctuations within the new closed volume. This pattern describes a fluid at thermal equilibrium, defined by a given temperature. Within such a fluid, there exists no preferential direction of flow (as in transport phenomena). More specifically, the fluid's overall linear and angular momenta remain null over time. The kinetic energies of the molecular Brownian motions, together with those of molecular rotations and vibrations, sum up to the caloric component of a fluid's internal energy (the equipartition theorem). This motion is named after the botanist Robert Brown, who first described the phenomenon in 1827, while looking th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Light Scattering
Static light scattering is a technique in physical chemistry that measures the intensity of the scattered light to obtain the average molecular weight ''Mw'' of a macromolecule like a polymer or a protein in solution. Measurement of the scattering intensity at many angles allows calculation of the root mean square radius, also called the radius of gyration ''Rg''. By measuring the scattering intensity for many samples of various concentrations, the second virial coefficient, ''A2'', can be calculated. Static light scattering is also commonly utilized to determine the size of particle suspensions in the sub-μm and supra-μm ranges, via the Lorenz-Mie (see Mie scattering) and Fraunhofer diffraction formalisms, respectively. For static light scattering experiments, a high-intensity monochromatic light, usually a laser, is launched into a solution containing the macromolecules. One or many detectors are used to measure the scattering intensity at one or many angles. The angular de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Light Scattering
Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In the scope of DLS, temporal fluctuations are usually analyzed using the intensity or photon auto-correlation function (also known as photon correlation spectroscopy or quasi-elastic light scattering). In the time domain analysis, the autocorrelation function (ACF) usually decays starting from zero delay time, and faster dynamics due to smaller particles lead to faster decorrelation of scattered intensity trace. It has been shown that the intensity ACF is the Fourier transform of the power spectrum, and therefore the DLS measurements can be equally well performed in the spectral domain. DLS can also be used to probe the behavior of complex fluids such as concentrated polymer solutions. Setup A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
