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Crystallization
CRYSTALLIZATION is the (natural or artificial) process by which a solid forms, where the atoms or molecules are highly organized into a structure known as a crystal . Some of the ways by which crystals form are through precipitating from a solution , melting , or more rarely deposition directly from a gas . Attributes of the resulting crystal depend largely on factors such as temperature, air pressure, and in the case of liquid crystals, time of fluid evaporation. Crystallization
Crystallization
occurs in two major steps. The first is nucleation , the appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The second step is known as crystal growth , which is the increase in the size of particles and leads to a crystal state. An important feature of this step is that loose particles form layers at the crystal's surface lodge themselves into open inconsistencies such as pores, cracks, etc
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Solution
In chemistry , a SOLUTION is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent . The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation . The solution assumes the phase of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. The concentration of a solute in a solution is the mass of that solute expressed as a percentage of the mass of the whole solution
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Mineral
A MINERAL is a naturally occurring chemical compound , usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition , whereas a rock can be an aggregate of different minerals or mineraloids . The study of minerals is called mineralogy . There are over 5,300 known mineral species; as of March 2017 , over 5,230 of these have been approved by the International Mineralogical Association (IMA). The silicate minerals compose over 90% of the Earth\'s crust . The diversity and abundance of mineral species is controlled by the Earth's chemistry. Silicon
Silicon
and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals. Minerals are distinguished by various chemical and physical properties . Differences in chemical composition and crystal structure distinguish the various species, which were determined by the mineral's geological environment when formed
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Frequency
FREQUENCY is the number of occurrences of a repeating event per unit of time . It is also referred to as TEMPORAL FREQUENCY, which emphasizes the contrast to spatial frequency and angular frequency . The PERIOD is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second (that is, 60 seconds divided by 120 beats ). Frequency
Frequency
is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio (sound ) signals, radio waves , and light
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Snowflake
A SNOWFLAKE is a single ice crystal that has achieved a sufficient size, and may have amalgamated with others, then falls through the Earth\'s atmosphere as snow . Each flake nucleates around a dust particle in supersaturated air masses by attracting supercooled cloud water droplets, which freeze and accrete in crystal form. Complex shapes emerge as the flake moves through differing temperature and humidity zones in the atmosphere, such that individual snowflakes differ in detail from one another, but may be categorized in eight broad classifications and at least 80 individual variants. The main constituent shapes for ice crystals, from which combinations may occur, are needle, column, plate and rime. Snowflakes appear white in color despite being made of clear ice
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Nucleation
NUCLEATION is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization . Nucleation
Nucleation
is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. Nucleation
Nucleation
is often found to be very sensitive to impurities in the system. Because of this, it is often important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at nucleation sites on surfaces in the system. Homogeneous nucleation occurs away from a surface
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Organic Compound
An ORGANIC COMPOUND is virtually any chemical compound that contains carbon , although a consensus definition remains elusive and likely arbitrary. Organic compounds are rare terrestrially, but of central importance because all known life is based on organic compounds. The most basic petrochemicals are considered the building blocks of organic chemistry
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Biochemical
BIOCHEMISTRY, sometimes called BIOLOGICAL CHEMISTRY, is the study of chemical processes within and relating to living organisms . By controlling information flow through biochemical signaling and the flow of chemical energy through metabolism , biochemical processes give rise to the complexity of life . Over the last decades of the 20th century, biochemistry has become so successful at explaining living processes that now almost all areas of the life sciences from botany to medicine to genetics are engaged in biochemical research. Today, the main focus of pure biochemistry is on understanding how biological molecules give rise to the processes that occur within living cells , which in turn relates greatly to the study and understanding of tissues , organs , and whole organisms —that is, all of biology
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Solvent
A SOLVENT (from the Latin solvō, "loosen, untie, solve") is a substance that dissolves a solute (a chemically distinct liquid, solid or gas), resulting in a solution . A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid . The quantity of solute that can dissolve in a specific volume of solvent varies with temperature . Common uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene ), as paint thinners (e.g. toluene , turpentine ), as nail polish removers and glue solvents (acetone , methyl acetate , ethyl acetate ), in spot removers (e.g. hexane , petrol ether), in detergents (citrus terpenes ) and in perfumes (ethanol ). Water is a solvent for polar molecules and the most common solvent used by living things; all the ions and proteins in a cell are dissolved in water within a cell. Solvents find various applications in chemical, pharmaceutical , oil, and gas industries, including in chemical syntheses and purification processes
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Temperature
TEMPERATURE is a physical quantity expressing hot and cold . Temperature
Temperature
is measured with a thermometer , historically calibrated in various temperature scales and units of measurement . The most commonly used scales are the Celsius scale , denoted in °C (informally, degrees centigrade), the Fahrenheit scale (°F), and the Kelvin scale . The kelvin (K) is the unit of temperature in the International System of Units
International System of Units
(SI), in which temperature is one of the seven fundamental base quantities . The coldest theoretical temperature is absolute zero , at which the thermal motion of all fundamental particles in matter reaches a minimum. Although classically described as motionless, particles still possess a finite zero-point energy in the quantum mechanical description
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Citric Acid
CITRIC ACID is a weak organic tricarboxylic acid having the chemical formula C6H8O7. It occurs naturally in citrus fruits . In biochemistry , it is an intermediate in the citric acid cycle , which occurs in the metabolism of all aerobic organisms . More than a million tons of citric acid are manufactured every year. It is used widely as an acidifier , as a flavoring and chelating agent . A CITRATE is a derivative of citric acid; that is, the salts , esters , and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate ; an ester is triethyl citrate . When part of a salt, the formula of the citrate ion is written as C6H5O73− or C3H5O(COO)33−
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Time-lapse
TIME-LAPSE PHOTOGRAPHY is a technique whereby the frequency at which film frames are captured (the frame rate ) is much lower than that used to view the sequence. When played at normal speed, time appears to be moving faster and thus lapsing. For example, an image of a scene may be captured once every second, then played back at 30 frames per second; the result is an apparent 30 times speed increase. In a similar manner, film can also be played at a much lower rate than it was captured at, slowing down fast action, as slow motion or high-speed photography . Processes that would normally appear subtle to the human eye, e.g. the motion of the sun and stars in the sky or plant growth, become very pronounced. Time-lapse is the extreme version of the cinematography technique of undercranking
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Protein
PROTEINS (/ˈproʊˌtiːnz/ or /ˈproʊti.ᵻnz/ ) are large biomolecules , or macromolecules , consisting of one or more long chains of amino acid residues . Proteins perform a vast array of functions within organisms , including catalysing metabolic reactions , DNA replication
DNA replication
, responding to stimuli , and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes , and which usually results in protein folding into a specific three-dimensional structure that determines its activity. A linear chain of amino acid residues is called a polypeptide . A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides , or sometimes oligopeptides
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Crystal Bar Process
The CRYSTAL BAR PROCESS (also known as IODIDE PROCESS or the VAN ARKEL–DE BOER PROCESS) was developed by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925. This process was the first industrial process for the commercial production of pure ductile metallic zirconium . It is used in the production of small quantities of ultra-pure titanium and zirconium. It primarily involves the formation of the metal iodides and their subsequent decomposition to yield pure metal. This process was superseded commercially by the Kroll process . PROCESSAs seen in the diagram below, impure titanium , zirconium , hafnium , vanadium , thorium or protactinium is heated in an evacuated vessel with a halogen at 50–250 °C. The patent specifically involved the intermediacy of TiI4 and ZrI4 , which were volatilized (leaving impurities as solid)
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Crystal Structure
In crystallography , CRYSTAL STRUCTURE is a description of the ordered arrangement of atoms , ions or molecules in a crystalline material . Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes the repeating pattern is the UNIT CELL of the structure. The unit cell completely defines the symmetry and structure of the entire crystal lattice, which is built up by repetitive translation of the unit cell along its principal axes. The repeating patterns are said to be located at the points of the Bravais lattice . The lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants , also called lattice parameters. The symmetry properties of the crystal are described by the concept of space groups
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Scanning Electron Microscope
A SCANNING ELECTRON MICROSCOPE (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons . The electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface topography and composition. The electron beam is scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Specimens can be observed in high vacuum in conventional SEM, or in low vacuum or wet conditions in variable pressure or environmental SEM, and at a wide range of cryogenic or elevated temperatures with specialized instruments. The most common SEM mode is detection of secondary electrons emitted by atoms excited by the electron beam. The number of secondary electrons that can be detected depends, among other things, on specimen topography
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