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In chemical engineering, a Stefan tube is a device that was devised by Josef Stefan in 1874. [1] It is often used for measuring diffusion coefficients . [ 1 ] [ 2 ] It comprises a vertical tube, over the top of which a gas flows and at the bottom of which is a pool of volatile liquid that is maintained in a constant-temperature bath.
By 1963, a new structural system of framed tubes had appeared in skyscraper design and construction. Fazlur Rahman Khan, a structural engineer from Bangladesh (then called East Pakistan) who worked at Skidmore, Owings & Merrill, defined the framed tube structure as "a three dimensional space structure composed of three, four, or possibly more frames, braced frames, or shear walls, joined at or ...
From these conclusions about plants and animals, two of the three tenets of cell theory were postulated. 1. All living organisms are composed of one or more cells 2. The cell is the most basic unit of life. Schleiden's theory of free cell formation through crystallization was refuted in the 1850s by Robert Remak, Rudolf Virchow, and Albert ...
Tubulin and microtubule-mediated processes, like cell locomotion, were seen by early microscopists, like Leeuwenhoek (1677). However, the fibrous nature of flagella and other structures were discovered two centuries later, with improved light microscopes, and confirmed in the 20th century with the electron microscope and biochemical studies.
A phototube or photoelectric cell is a type of gas-filled or vacuum tube that is sensitive to light. Such a tube is more correctly called a 'photoemissive cell' to distinguish it from photovoltaic or photoconductive cells. Phototubes were previously more widely used but are now replaced in many applications by solid state photodetectors.
This theory is also known as a theory of cellularization. It is a theory to explain the origin of the Metazoa. The idea was proposed by Hadži (1953) [4] and Hanson (1977). [13] This cellularization (syncytial) theory states that metazoans evolved from a unicellular ciliate with multiple nuclei that went through cellularization. Firstly, the ...
Construction of a Wigner–Seitz primitive cell. The general mathematical concept embodied in a Wigner–Seitz cell is more commonly called a Voronoi cell, and the partition of the plane into these cells for a given set of point sites is known as a Voronoi diagram. The construction process for the Wigner–Seitz cell of a hexagonal lattice.
Structure of a plant cell. Plant cells are the cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae.Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids with the capability to perform photosynthesis and store starch, a large vacuole that regulates turgor pressure, the absence of flagella or ...