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David Weitz
David A. Weitz (born October 3, 1951) is a Canadian/American physicist and Mallinckrodt Professor of Physics & Applied Physics at Harvard University. He is the former co-director of the BASF Advanced Research Initiative at Harvard, former co-director of the Harvard Kavli Institute for Bionano Science & Technology (2007-2010), and former director of the Harvard Materials Research Science & Engineering Center (2001-2020). He is known for his work in the areas of diffusing-wave spectroscopy, microrheology, microfluidics, rheology, fluid mechanics, interface and colloid science, colloid chemistry, biophysics, complex fluids, soft condensed matter physics, phase transitions, the study of glass and amorphous solids, liquid crystals, self-assembly, surface-enhanced light scattering, and diffusion-limited aggregation. His laboratory also developed Force spectrum microscopy, which is capable of measuring random intracellular forces. As of June 2023, he has a Hirsch index of 202. W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peter Lu
Peter James Lu, PhD (陸述義) is a post-doctoral research fellow in the Department of Physics and the School of Engineering and Applied Sciences at Harvard University in Cambridge, Massachusetts. He has been recognized for his discoveries of quasicrystal patterns (girih tiles) in medieval Islamic architecture, early precision compound machines in ancient China, and man's first use of diamond in neolithic China. Early life and education Lu was born in Cleveland, Ohio and grew up in the Philadelphia suburb of West Chester, Pennsylvania. His early childhood interest in rockhounding led to his winning national gold medals in the "Rocks, Minerals, and Fossils" event at four National Science Olympiad tournaments. Lu graduated from B. Reed Henderson high school in West Chester in 1996. Lu matriculated at Princeton University in September, 1996, and was advised in his first year by geology professor Kenneth S. Deffeyes. He studied organic chemistry with Maitland Jones, Jr., with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ottawa
Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the core of the Ottawa–Gatineau census metropolitan area (CMA) and the National Capital Region (NCR). Ottawa had a city population of 1,017,449 and a metropolitan population of 1,488,307, making it the fourth-largest city and fourth-largest metropolitan area in Canada. Ottawa is the political centre of Canada and headquarters to the federal government. The city houses numerous foreign embassies, key buildings, organizations, and institutions of Canada's government, including the Parliament of Canada, the Supreme Court, the residence of Canada's viceroy, and Office of the Prime Minister. Founded in 1826 as Bytown, and incorporated as Ottawa in 1855, its original boundaries were expanded through numerous annexations and were ultimately ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colloid Chemistry
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others extend the definition to include substances like aerosols and gels. The term colloidal suspension refers unambiguously to the overall mixture (although a narrower sense of the word ''suspension'' is distinguished from colloids by larger particle size). A colloid has a dispersed phase (the suspended particles) and a continuous phase (the medium of suspension). The dispersed phase particles have a diameter of approximately 1 nanometre to 1 micrometre. Some colloids are translucent because of the Tyndall effect, which is the scattering of light by particles in the colloid. Other colloids may be opaque or have a slight color. Colloidal suspensions are the subject of interface and colloid science. This field of study was introduced in 1845 by Ital ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Force Spectrum Microscopy
Force Spectrum Microscopy (FSM) is an application of active microrheology developed to measure aggregate random forces in the cytoplasm. Large, inert flow tracers are injected into live cells and become lodged inside the cytoskeletal mesh, wherein it is oscillated by repercussions from active motor proteins. The magnitude of these random forces can be inferred from the frequency of oscillation of tracer particles. Tracking the fluctuations of tracer particles using optical microscopy can isolate the contribution of active random forces to intracellular molecular transport from that of Brownian motion. Basic principles FSM was developed by Ming Guo and David A. Weitz to probe stochastic intracellular forces generated by motor proteins. Far from a liquid void, the cytoplasm contains a complex meshwork of actin and myosin conferring structural support to the cell, as well as harbouring vesicles and mitochondria among other organelles. Recent research on the macromolecular crowding ins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffusing-wave Spectroscopy
Diffusing-wave spectroscopy (DWS) is an optical technique derived from dynamic light scattering (DLS) that studies the dynamics of scattered light in the limit of strong multiple scattering. It has been widely used in the past to study colloidal suspensions, emulsions, foams, gels, biological media and other forms of soft matter. If carefully calibrated, DWS allows the quantitative measurement of microscopic motion in a soft material, from which the rheological properties of the complex medium can be extracted via the microrheology approach. One-speckle diffusing-wave spectroscopy Laser light is sent to the sample and the outcoming transmitted or backscattered light is detected by an optoelectric sensor. The light intensity detected is the result of the interference of all the optical waves coming from the different light paths. Image:figureDWS.png, Typical setup of diffusing-wave spectroscopy The signal is analysed by calculating the intensity autocorrelation function called g2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physicist
A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of phenomena, and usually frame their understanding in mathematical terms. Physicists work across a wide range of research fields, spanning all length scales: from sub-atomic and particle physics, through biological physics, to cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: experimental physicists who specialize in the observation of natural phenomena and the development and analysis of experiments, and theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their knowledge towards solving practical problems or to developing new technologies (also known as applie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffusion-limited Aggregation
Diffusion-limited aggregation (DLA) is the process whereby particles undergoing a random walk due to Brownian motion cluster together to form aggregates of such particles. This theory, proposed by T.A. Witten Jr. and L.M. Sander in 1981, is applicable to aggregation in any system where diffusion is the primary means of transport in the system. DLA can be observed in many systems such as electrodeposition, Hele-Shaw flow, mineral deposits, and dielectric breakdown. The clusters formed in DLA processes are referred to as Brownian trees. These clusters are an example of a fractal. In 2D these fractals exhibit a dimension of approximately 1.71 for free particles that are unrestricted by a lattice, however computer simulation of DLA on a lattice will change the fractal dimension slightly for a DLA in the same embedding dimension. Some variations are also observed depending on the geometry of the growth, whether it be from a single point radially outward or from a plane o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluid Mechanics
Fluid mechanics is the branch of physics concerned with the mechanics of fluids ( liquids, gases, and plasmas) and the forces on them. It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and biomedical engineering, geophysics, oceanography, meteorology, astrophysics, and biology. It can be divided into fluid statics, the study of fluids at rest; and fluid dynamics, the study of the effect of forces on fluid motion. It is a branch of continuum mechanics, a subject which models matter without using the information that it is made out of atoms; that is, it models matter from a ''macroscopic'' viewpoint rather than from ''microscopic''. Fluid mechanics, especially fluid dynamics, is an active field of research, typically mathematically complex. Many problems are partly or wholly unsolved and are best addressed by numerical methods, typically using computers. A modern discipline, called computational fluid dynamics (CFD), is dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-assembly
Self-assembly is a process in which a disordered system of pre-existing components forms an organized structure or pattern as a consequence of specific, local interactions among the components themselves, without external direction. When the constitutive components are molecules, the process is termed molecular self-assembly. Self-assembly can be classified as either static or dynamic. In ''static'' self-assembly, the ordered state forms as a system approaches equilibrium, reducing its free energy. However, in ''dynamic'' self-assembly, patterns of pre-existing components organized by specific local interactions are not commonly described as "self-assembled" by scientists in the associated disciplines. These structures are better described as "self-organized", although these terms are often used interchangeably. Self-assembly in chemistry and materials science Self-assembly in the classic sense can be defined as ''the spontaneous and reversible organization of molec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid Crystals
Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many types of LC phases, which can be distinguished by their optical properties (such as textures). The contrasting textures arise due to molecules within one area of material ("domain") being oriented in the same direction but different areas having different orientations. LC materials may not always be in a LC state of matter (just as water may be ice or water vapor). Liquid crystals can be divided into 3 main types: * thermotropic, *lyotropic, and * metallotropic. Thermotropic and lyotropic liquid crystals consist mostly of organic molecules, although a few minerals are also known. Thermotropic LCs exhibit a phase transition into the LC phase as temperature changes. Lyotropic LCs exhibit phase transitions as a function of bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amorphous Solids
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek ''a'' ("without"), and ''morphé'' ("shape, form"). In some older articles and books, the term was used synonymously with glass. Today, "glassy solid" or "amorphous solid" is considered the overarching concept. Polymers are often amorphous. Structure Amorphous materials have an internal structure comprising interconnected structural blocks that can be similar to the basic structural units found in the corresponding crystalline phase of the same compound. Unlike crystalline materials, however, no long-range order exists. Localized order in amorphous materials can be categorized as short or medium range order. By convention, short range order extends only to the nearest neighbor shell, typically only 1-2 atomic spacings. Medium range order is then def ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda–lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term ''glass'', in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material. Despite bei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
