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Seashell Surface
In mathematics, a seashell surface is a surface made by a circle which spirals up the ''z''-axis while decreasing its own radius and distance from the ''z''-axis. Not all seashell surfaces describe actual seashells found in nature. Parametrization The following is a parameterization of one seashell surface: :\begin x & = \frac\left(1-\frac\right)\cos(2v)(1+\cos u)+\cos 2v \\ \\ y & = \frac\left(1-\frac\right)\sin(2v)(1+\cos u)+\sin 2v \\ \\ z & = \frac+\frac\left(1-\frac\right)\sin(u)+15 \end where 0\le u<2\pi and \\ Various authors have suggested different models for the shape of shell. David M. Raup proposed a model where there is one magnification for the x-y plane, and another for the x-z plane. Chris IllertDr Chris Illert was awarded his Ph.D. on 26 September 2013 at the University of Western Sydney http://www.uws.edu.au/__data/assets/im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seashell Surface
In mathematics, a seashell surface is a surface made by a circle which spirals up the ''z''-axis while decreasing its own radius and distance from the ''z''-axis. Not all seashell surfaces describe actual seashells found in nature. Parametrization The following is a parameterization of one seashell surface: :\begin x & = \frac\left(1-\frac\right)\cos(2v)(1+\cos u)+\cos 2v \\ \\ y & = \frac\left(1-\frac\right)\sin(2v)(1+\cos u)+\sin 2v \\ \\ z & = \frac+\frac\left(1-\frac\right)\sin(u)+15 \end where 0\le u<2\pi and \\ Various authors have suggested different models for the shape of shell. David M. Raup proposed a model where there is one magnification for the x-y plane, and another for the x-z plane. Chris IllertDr Chris Illert was awarded his Ph.D. on 26 September 2013 at the University of Western Sydney http://www.uws.edu.au/__data/assets/im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astralium Calcar 01
''Astralium'', common name star snails, is a genus of sea snails, marine gastropod mollusks in the family Turbinidae, the turban snails and star snails.Bouchet, P. (2012). ''Astralium'' Link, 1807. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=204985 on 2012-09-09 Description In ''Astralium'' a very rapidly enlarging whorl starts from the multispiral nucleus, forming far the greater portion of the operculum, and usually leaving a pit at the starting point. Distribution This marine genus has a wide distribution ranging from the Eastern Indian Ocean to China and Japan, the Philippines, Indonesia, East India, the Maldives and Australia (New South Wales, Northern Territory, Queensland, South Australia, Tasmania, Victoria, Western Australia). Species According to the World Register of Marine Species (WoRMS), the following species are included within the genus ''Astralium'' : * '' Astralium asteriscum'' (Reeve, 184 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seashell
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another animal. A seashell is usually the exoskeleton of an invertebrate (an animal without a backbone), and is typically composed of calcium carbonate or chitin. Most shells that are found on beaches are the shells of marine mollusks, partly because these shells are usually made of calcium carbonate, and endure better than shells made of chitin. Apart from mollusk shells, other shells that can be found on beaches are those of barnacles, horseshoe crabs and brachiopods. Marine annelid worms in the family Serpulidae create shells which are tubes made of calcium carbonate cemented onto other surfaces. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David M
David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". was, according to the Hebrew Bible, the third king of the United Kingdom of Israel. In the Books of Samuel, he is described as a young shepherd and harpist who gains fame by slaying Goliath, a champion of the Philistines, in southern Canaan. David becomes a favourite of Saul, the first king of Israel; he also forges a notably close friendship with Jonathan, a son of Saul. However, under the paranoia that David is seeking to usurp the throne, Saul attempts to kill David, forcing the latter to go into hiding and effectively operate as a fugitive for several years. After Saul and Jonathan are both killed in battle against the Philistines, a 30-year-old David is anointed king over all of Israel and Judah. Following his rise to power, David ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helix
A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word ''helix'' comes from the Greek word ''ἕλιξ'', "twisted, curved". A "filled-in" helix – for example, a "spiral" (helical) ramp – is a surface called ''helicoid''. Properties and types The ''pitch'' of a helix is the height of one complete helix turn, measured parallel to the axis of the helix. A double helix consists of two (typically congruent) helices with the same axis, differing by a translation along the axis. A circular helix (i.e. one with constant radius) has constant band curvature and constant torsion. A ''conic helix'', also known as a ''conic spiral'', may be defined as a spiral on a conic surface, with the distance to the apex an expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seashell
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washed up on beaches by beachcombers. The shells are empty because the animal has died and the soft parts have decomposed or been eaten by another animal. A seashell is usually the exoskeleton of an invertebrate (an animal without a backbone), and is typically composed of calcium carbonate or chitin. Most shells that are found on beaches are the shells of marine mollusks, partly because these shells are usually made of calcium carbonate, and endure better than shells made of chitin. Apart from mollusk shells, other shells that can be found on beaches are those of barnacles, horseshoe crabs and brachiopods. Marine annelid worms in the family Serpulidae create shells which are tubes made of calcium carbonate cemented onto other surfaces. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiral
In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:Spiral ''American Heritage Dictionary of the English Language'', Houghton Mifflin Company, Fourth Edition, 2009. # a curve on a plane that winds around a fixed center point at a continuously increasing or decreasing distance from the point. # a three-dimensional curve that turns around an axis at a constant or continuously varying distance while moving parallel to the axis; a . The first definition describes a |
Murex Cabritii
''Murex'' is a genus of medium to large sized predatory tropical sea snails. These are carnivorous marine gastropod molluscs in the family Muricidae, commonly called "murexes" or "rock snails".Houart, R.; Gofas, S. (2010). Murex Linnaeus, 1758. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=138196 on 2011-04-09 The common name murex is still used for many species in the family Muricidae which were originally given the Latin generic name ''Murex'' in the past, but have more recently been regrouped into different newer genera. The word ''murex'' was used by Aristotle in reference to these kinds of snails, thus making it one of the oldest classical seashell names still in use by the scientific community. Fossil records This genus is known in the fossil records from the Cretaceous to the Quaternary (age range: from 125.45 to 0.0 milli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
