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Cnoidal wave In fluid dynamics, a cnoidal wave is a nonlinear and exact periodic wave solution of the Korteweg–de Vries equation. These solutions are in terms of the Jacobi elliptic function "cn", which is why they are coined "cn"oidal waves. They are used to describe surface gravity waves of fairly long wavelength, as compared to the water depth. The cnoidal wave solutions were derived by Korteweg and de Vries, in their 1895 paper in which they also propose their dispersive long-wave equation, now known as the Korteweg–de Vries equation. In the limit of infinite wavelength, the cnoidal wave becomes a solitary wave. The Benjamin–Bona–Mahony equation has improved short-wavelength behaviour, as compared to the Korteweg–de Vries equation, and is another uni-directional wave equation with cnoidal wave solutions. Further, since the Korteweg–de Vries equation is an approximation to the Boussinesq equations for the case of one-way wave propagation, cnoidal waves are approximate solutions to the Boussinesq equations. solutions can appear in other applications than surface gravity waves as well, for instance to describe ion acoustic waves in plasma physics. The Korteweg–de Vries equation (KdV equation) can be used to describe the uni-directional propagation of weakly nonlinear and long waves—where long wave means: having long wavelengths as compared with the mean water depth—of surface gravity waves on a fluid layer. The KdV equation is a dispersive wave equation, including both frequency dispersion and amplitude dispersion effects | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave In its classical use, the KdV equation is applicable for wavelengths "λ" in excess of about five times the average water depth "h", so for "λ" > 5 "h"; and for the period "τ" greater than formula_1 with "g" the strength of the gravitational acceleration. To envisage the position of the KdV equation within the scope of classical wave approximations, it distinguishes itself in the following ways: The KdV equation can be derived from the Boussinesq equations, but additional assumptions are needed to be able to split off the forward wave propagation. For practical applications, the Benjamin–Bona–Mahony equation (BBM equation) is preferable over the KdV equation, a forward-propagating model similar to KdV but with much better frequency-dispersion behaviour at shorter wavelengths. Further improvements in short-wave performance can be obtained by starting to derive a one-way wave equation from a modern improved Boussinesq model, valid for even shorter wavelengths. The cnoidal wave solutions of the KdV equation were presented by Korteweg and de Vries in their 1895 paper, which article is based on the PhD thesis by de Vries in 1894. Solitary wave solutions for nonlinear and dispersive long waves had been found earlier by Boussinesq in 1872, and Rayleigh in 1876. The search for these solutions was triggered by the observations of this solitary wave (or "wave of translation") by Russell, both in nature and in laboratory experiments. solutions of the KdV equation are stable with respect to small perturbations | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave The surface elevation "η"("x","t"), as a function of horizontal position "x" and time "t", for a cnoidal wave is given by: where "H" is the wave height, "λ" is the wavelength, "c" is the phase speed and "η" is the trough elevation. Further cn is one of the Jacobi elliptic functions and "K"("m") is the complete elliptic integral of the first kind; both are dependent on the elliptic parameter "m". The latter, "m", determines the shape of the cnoidal wave. For "m" equal to zero the cnoidal wave becomes a cosine function, while for values close to one the cnoidal wave gets peaked crests and (very) flat troughs. For values of "m" less than 0.95, the cnoidal function can be approximated with trigonometric functions. An important dimensionless parameter for nonlinear long waves ("λ" ≫ "h") is the Ursell parameter: For small values of "U", say "U" < 5, a linear theory can be used, and at higher values nonlinear theories have to be used, like cnoidal wave theory. The demarcation zone between—third or fifth order—Stokes' and cnoidal wave theories is in the range 10–25 of the Ursell parameter. As can be seen from the formula for the Ursell parameter, for a given relative wave height "H"/"h" the Ursell parameter—and thus also the nonlinearity—grows quickly with increasing relative wavelength "λ"/"h". Based on the analysis of the full nonlinear problem of surface gravity waves within potential flow theory, the above cnoidal waves can be considered the lowest-order term in a perturbation series | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave Higher-order cnoidal wave theories remain valid for shorter and more nonlinear waves. A fifth-order cnoidal wave theory was developed by Fenton in 1979. A detailed description and comparison of fifth-order Stokes' and fifth-order cnoidal wave theories is given in the review article by Fenton. descriptions, through a renormalisation, are also well suited to waves on deep water, even infinite water depth; as found by Clamond. A description of the interactions of cnoidal waves in shallow water, as found in real seas, has been provided by Osborne in 1994. The Korteweg–de Vries equation (KdV equation), as used for water waves and in dimensional form, is: where All quantities can be made dimensionless using the gravitational acceleration "g" and water depth "h": The resulting non-dimensional form of the KdV equation is In the remainder, the tildes will be dropped for ease of notation. The form is obtained through the transformation but this form will not be used any further in this derivation. Periodic wave solutions, travelling with phase speed "c", are sought. These permanent waves have to be of the following: Consequently, the partial derivatives with respect to space and time become: where "η’" denotes the ordinary derivative of "η"("ξ") with respect to the argument "ξ". Using these in the KdV equation, the following third-order ordinary differential equation is obtained: This can be integrated once, to obtain: with "r" an integration constant | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave After multiplying with 4 "η’", and integrating once more with "s" another integration constant. This is written in the form The cubic polynomial "f"("η") becomes negative for large positive values of "η", and positive for large negative values of "η". Since the surface elevation "η" is real valued, also the integration constants "r" and "s" are real. The polynomial "f" can be expressed in terms of its roots "η", "η" and "η": Because "f"("η") is real valued, the three roots "η", "η" and "η" are either all three real, or otherwise one is real and the remaining two are a pair of complex conjugates. In the latter case, with only one real-valued root, there is only one elevation "η" at which "f"("η") is zero. And consequently also only one elevation at which the surface slope "η’" is zero. However, we are looking for wave like solutions, with two elevations—the wave crest and trough (physics)—where the surface slope is zero. The conclusion is that all three roots of "f"("η") have to be real valued. Without loss of generality, it is assumed that the three real roots are ordered as: Now, from equation () it can be seen that only real values for the slope exist if "f"("η") is positive. This corresponds with "η" ≤ "η"≤ "η", which therefore is the range between which the surface elevation oscillates, see also the graph of "f("η") | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave This condition is satisfied with the following representation of the elevation "η"("ξ"): in agreement with the periodic character of the sought wave solutions and with "ψ"("ξ") the phase of the trigonometric functions sin and cos. From this form, the following descriptions of various terms in equations () and () can be obtained: Using these in equations () and (), the following ordinary differential equation relating "ψ" and "ξ" is obtained, after some manipulations: with the right hand side still positive, since "η" − "η" ≥ "η" − "η". Without loss of generality, we can assume that "ψ"("ξ") is a monotone function, since "f"("η") has no zeros in the interval "η" < "η" < "η". So the above ordinary differential equation can also be solved in terms of "ξ"("ψ") being a function of "ψ": with: where "m" is the so-called elliptic parameter, satisfying "0" ≤ "m" ≤ 1 (because "η" ≤ "η" ≤ "η"). If "ξ" = 0 is chosen at the wave crest "η"(0) = "η" integration gives with "F"("ψ"|"m") the incomplete elliptic integral of the first kind. The Jacobi elliptic functions cn and sn are inverses of "F"("ψ"|"m") given by With the use of equation (), the resulting cnoidal-wave solution of the KdV equation is found What remains, is to determine the parameters: "η", "η", "Δ" and "m". First, since "η" is the crest elevation and "η" is the trough elevation, it is convenient to introduce the wave height, defined as "H" = "η" − "η" | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave Consequently, we find for "m" and for "Δ": The cnoidal wave solution can be written as: Second, the trough is located at "ψ" = ½ "π", so the distance between "ξ" = 0 and "ξ" = ½ "λ" is, with "λ" the wavelength, from equation (): where "K"("m") is the complete elliptic integral of the first kind. Third, since the wave oscillates around the mean water depth, the average value of "η"("ξ") has to be zero. So where "E"("m") is the complete elliptic integral of the second kind. The following expressions for "η", "η" and "η" as a function of the elliptic parameter "m" and wave height "H" result: Fourth, from equations () and () a relationship can be established between the phase speed "c" and the roots "η", "η" and "η": The relative phase-speed changes are depicted in the figure below. As can be seen, for "m" > 0.96 (so for 1 − "m" < 0.04) the phase speed increases with increasing wave height "H". This corresponds with the longer and more nonlinear waves. The nonlinear change in the phase speed, for fixed "m", is proportional to the wave height "H". Note that the phase speed "c" is related to the wavelength "λ" and period "τ" as: All quantities here will be given in their dimensional forms, as valid for surface gravity waves before non-dimensionalisation. The cnoidal-wave solution of the KdV equation is: with "H" the wave height—the difference between crest and trough elevation, "η" the trough elevation, "m" the elliptic parameter, "c" the phase speed and cn one of the Jacobi elliptic functions | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave The trough level "η" and width parameter "Δ" can be expressed in terms of "H", "h" and "m": with "K"("m") the complete elliptic integral of the first kind and "E"("m") the complete elliptic integral of the second kind. Note that "K"("m") and "E"("m") are denoted here as a function of the elliptic parameter "m" and not as a function of the elliptic modulus "k", with "m" = "k". The wavelength "λ", phase speed "c" and wave period "τ" are related to "H", "h" and "m" by: with "g" the Earth's gravity. Most often, the known wave parameters are the wave height "H", mean water depth "h", gravitational acceleration "g", and either the wavelength "λ" or else the period "τ". Then the above relations for "λ", "c" and "τ" are used to find the elliptic parameter "m". This requires numerical solution by some iterative method. The Benjamin–Bona–Mahony equation (BBM equation), or regularised long wave (RLW) equation, is in dimensional form given by: All quantities have the same meaning as for the KdV equation. The BBM equation is often preferred over the KdV equation because it has a better short-wave behaviour. The derivation is analogous to the one for the KdV equation. The dimensionless BBM equation is, non-dimensionalised using mean water depth "h" and gravitational acceleration "g": This can be brought into the standard form through the transformation: but this standard form will not be used here | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave Analogue to the drivation of the cnoidal wave solution for the KdV equation, periodic wave solutions "η"("ξ"), with "ξ" = "x"−"ct" are considered Then the BBM equation becomes a third-order ordinary differential equation, which can be integrated twice, to obtain: Which only differs from the equation for the KdV equation through the factor "c" in front of ("η′") in the left hand side. Through a coordinate transformation "β" = "ξ" / formula_56 the factor "c" may be removed, resulting in the same first-order ordinary differential equation for both the KdV and BBM equation. However, here the form given in the preceding equation is used. This results in a different formulation for "Δ" as found for the KdV equation: The relation of the wavelength "λ", as a function of "H" and "m", is affected by this change in formula_58 For the rest, the derivation is analogous to the one for the KdV equation, and will not be repeated here. The results are presented in dimensional form, for water waves on a fluid layer of depth "h". The cnoidal wave solution of the BBM equation, together with the associated relationships for the parameters is: The only difference with the cnoidal wave solution of the KdV equation is in the equation for the wavelength "λ". For practical applications, usually the water depth "h", wave height "H", gravitational acceleration "g", and either the wavelength "λ", or—most often—the period (physics) "τ" are provided | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave Then the elliptic parameter "m" has to be determined from the above relations for "λ", "c" and "τ" through some iterative method. In this example, a cnoidal wave according to the Korteweg–de Vries (KdV) equation is considered. The following parameters of the wave are given: Instead of the period "τ", in other cases the wavelength "λ" may occur as a quantity known beforehand. First, the dimensionless period is computed: which is larger than seven, so long enough for cnoidal theory to be valid. The main unknown is the elliptic parameter "m". This has to be determined in such a way that the wave period "τ", as computed from cnoidal wave theory for the KdV equation: is consistent with the given value of "τ"; here "λ" is the wavelength and "c" is the phase speed of the wave. Further, "K"("m") and "E"("m") are complete elliptic integrals of the first and second kind, respectively. Searching for the elliptic parameter "m" can be done by trial and error, or by use of a numerical root-finding algorithm. In this case, starting from an initial guess "m" = 0.99, by trial and error the answer is found. Within the process, the wavelength "λ" and phase speed "c" have been computed: The phase speed "c" can be compared with its value formula_66 according to the shallow water equations: showing a 3.8% increase due to the effect of nonlinear amplitude dispersion, which wins in this case from the reduction of phase speed by frequency dispersion | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave Now the wavelength is known, the Ursell number can be computed as well: which is not small, so linear wave theory is not applicable, but cnoidal wave theory is. Finally, the ratio of wavelength to depth is "λ" / "h" = 10.2 > 7, again indicating this wave is long enough to be considered as a cnoidal wave. For very long nonlinear waves, with the parameter "m" close to one, "m" → 1, the Jacobi elliptic function cn can be approximated by Here sinh, cosh, tanh and sech are hyperbolic functions. In the limit "m" = 1: with sech("z") = 1 / cosh("z"). Further, for the same limit of "m" → 1, the complete elliptic integral of the first kind "K"("m") goes to infinity, while the complete elliptic integral of the second kind "E"("m") goes to one. This implies that the limiting values of the phase speed "c" and minimum elevelation "η" become: Consequently, in terms of the width parameter "Δ", the solitary wave solution to both the KdV and BBM equation is: The width parameter, as found for the cnoidal waves and now in the limit "m" → 1, is different for the KdV and the BBM equation: But the phase speed of the solitary wave in both equations is the same, for a certain combination of height "H" and depth "h". For infinitesimal wave height the results of cnoidal wave theory are expected to converge towards those of Airy wave theory for the limit of long waves "λ" ≫ "h". First the surface elevation, and thereafter the phase speed, of the cnoidal waves for infinitesimal wave height will be examined | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave The Jacobi elliptic function cn can be expanded into a Fourier series "K’"("m") is known as the imaginary quarter period, while "K"("m") is also called the real quarter period of the Jacobi elliptic function. They are related through: "K’"("m") = "K"(1−"m") Since the interest here is in small wave height, corresponding with small parameter "m" ≪ 1, it is convenient to consider the Maclaurin series for the relevant parameters, to start with the complete elliptic integrals "K" and "E": Then the hyperbolic-cosine terms, appearing in the Fourier series, can be expanded for small "m" ≪ 1 as follows: The nome "q" has the following behaviour for small "m": Consequently, the amplitudes of the first terms in the Fourier series are: So, for "m" ≪ 1 the Jacobi elliptic function has the first Fourier series terms: And its square is The free surface "η"("x","t") of the cnoidal wave will be expressed in its Fourier series, for small values of the elliptic parameter "m". First, note that the argument of the cn function is "ξ"/"Δ", and that the wavelength "λ" = 2 "Δ" "K"("m"), so: Further, the mean free-surface elevation is zero. Therefore, the surface elevation of small amplitude waves is Also the wavelength "λ" can be expanded into a Maclaurin series of the elliptic parameter "m", differently for the KdV and the BBM equation, but this is not necessary for the present purpose. For infinitesimal wave height, in the limit "m" → 0, the free-surface elevation becomes: So the wave amplitude is ½"H", half the wave height | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave This is of the same form as studied in Airy wave theory, but note that cnoidal wave theory is only valid for long waves with their wavelength much longer than the average water depth. The phase speed of a cnoidal wave, both for the KdV and BBM equation, is given by: In this formulation the phase speed is a function of wave height "H" and parameter "m". However, for the determination of wave propagation for waves of infinitesimal height, it is necessary to determine the behaviour of the phase speed at constant wavelength "λ" in the limit that the parameter "m" approaches zero. This can be done by using the equation for the wavelength, which is different for the KdV and BBM equation: Introducing the relative wavenumber "κh": and using the above equations for the phase speed and wavelength, the factor "H" / "m" in the phase speed can be replaced by "κh" and "m". The resulting phase speeds are: The limiting behaviour for small "m" can be analysed through the use of the Maclaurin series for "K"("m") and "E"("m"), resulting in the following expression for the common factor in both formulas for "c": so in the limit "m" → 0, the factor "γ" → −. The limiting value of the phase speed for "m" ≪ 1 directly results. The phase speeds for infinitesimal wave height, according to the cnoidal wave theories for the KdV equation and BBM equation, are with "κ" = 2"π" / "λ" the wavenumber and "κh" the relative wavenumber | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave These phase speeds are in full agreement with the result obtained by directly searching for sine-wave solutions of the linearised KdV and BBM equations. As is evident from these equations, the linearised BBM equation has a positive phase speed for all "κh". On the other hand, the phase speed of the linearised KdV equation changes sign for short waves with "κh" > formula_90. This is in conflict with the derivation of the KdV equation as a one-way wave equation. Cnoidal waves can be derived directly from the inviscid, irrotational and incompressible flow equations, and expressed in terms of three invariants of the flow, as shown by in their research on undular bores. In a frame of reference moving with the phase speed, in which reference frame the flow becomes a steady flow, the cnoidal wave solutions can directly be related to the mass flux, momentum flux and energy head of the flow. Following —using a stream function description of this incompressible flow—the horizontal and vertical components of the flow velocity are the spatial derivatives of the stream function "Ψ"("ξ","z"): +"∂Ψ" and −"∂Ψ", in the "ξ" and "z" direction respectively ("ξ" = "x"−"ct"). The vertical coordinate "z" is positive in the upward direction, opposite to the direction of the gravitational acceleration, and the zero level of "z" is at the impermeable lower boundary of the fluid domain | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave While the free surface is at "z" = "ζ"("ξ"); note that "ζ" is the local water depth, related to the surface elevation "η"("ξ") as "ζ" = "h" + "η" with "h" the mean water depth. In this steady flow, the discharge "Q" through each vertical cross section is a constant independent of "ξ", and because of the horizontal bed also the horizontal momentum flux "S", divided by the density "ρ", through each vertical cross section is conserved. Further, for this inviscid and irrotational flow, Bernoulli's principle can be applied and has the same Bernoulli constant "R" everywhere in the flow domain. They are defined as: For fairly long waves, assuming the water depth "ζ" is small compared to the wavelength "λ", the following relation is obtained between the water depth "ζ"("ξ") and the three invariants "Q", "R" and "S": This nonlinear and first-order ordinary differential equation has cnoidal wave solutions. For very long waves of infinitesimal amplitude on a fluid of depth "h" and with a uniform flow velocity "v", the flow constants are according to the shallow water equations: Equation () can be brought into non-dimensional form by use of the discharge "Q" and gravitational acceleration "g", and defining the critical depth "h": related to the critical flow demarcation between subcritical flow and supercritical flow (see also Froude number) | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave Consequently, the non-dimensional form of the equation is with First eliminate the pressure "p" from the momentum flux "S" by use of the Bernoulli equation: The streamfunction "Ψ" is expanded as a Maclaurin series around the bed at "z" = 0, and using that the impermeable bed is a streamline and the irrotationality of the flow: "Ψ" = 0 and ∂"Ψ" = 0 at "z" = 0: with "u" the horizontal velocity at the bed "z" = 0. Because the waves are long, "h" ≫ "λ", only terms up to "z" and "ζ" are retained in the approximations to "Q" and "S". The momentum flux "S" then becomes: The discharge "Q" becomes, since it is the value of the streamfunction "Ψ" at the free surface "z" = "ζ": As can be seen, the discharge "Q" is an O("ζ") quantity. From this, the bed velocity is seen to be Note that "Q" / "ζ" is an order one quantity. This relation will be used to replace the bed velocity "u" by "Q" and "ζ" in the momentum flux "S". The following terms can be derived from it: Consequently, the momentum flux "S" becomes, again retaining only terms up to proportional to "ζ": Which can directly be recast in the form of equation (). The potential energy density with "ρ" the fluid density, is one of the infinite number of invariants of the KdV equation. This can be seen by multiplying the KdV equation with the surface elevation "η"("x","t"); after repeated use of the chain rule the result is: which is in conservation form, and is an invariant after integration over the interval of periodicity—the wavelength for a cnoidal wave | https://en.wikipedia.org/wiki?curid=22463969 |
Cnoidal wave The potential energy is not an invariant of the BBM equation, but ½"ρg" ["η" + "h" ("∂" "η")] is. First the variance of the surface elevation in a cnoidal wave is computed. Note that "η" = −(1/"λ") ∫ "H" cn("ξ"/"Δ"|m) d"x", cn("ξ"/"Δ"|m) = cos "ψ"("ξ") and "λ" = 2 "Δ" "K"("m"), so The potential energy, both for the KdV and the BBM equation, is subsequently found to be The infinitesimal wave-height limit ("m" → 0) of the potential energy is "E" = "ρ" "g" "H", which is in agreement with Airy wave theory. The wave height is twice the amplitude, "H" = 2"a", in the infinitesimal wave limit. | https://en.wikipedia.org/wiki?curid=22463969 |
Porous glass is glass that includes pores, usually in the nanometre- or micrometre-range, commonly prepared by one of the following processes: through metastable phase separation in borosilicate glasses (such as in their system SiO-BO-NaO), followed by liquid extraction of one of the formed phases; through the sol-gel process; or simply by sintering glass powder. The specific properties and commercial availability of porous glass make it one of the most extensively researched and characterized amorphous solids. Due to the possibility of modeling the microstructure, porous glasses have a high potential as a model system. They show a high chemical, thermal and mechanical resistance, which results from a rigid and incompressible silica network. They can be produced in high quality and with pore sizes ranging from 1 nm up to any desired value. An easy functionalization of the inner surface opens a wide field of applications for porous glasses. A further special advantage of porous glasses compared to other porous materials, is that they can be made not only as powder or granulate, but also as larger pieces in almost any user defined shape and texture. In the first half of the 20th century, Turner and Winks discovered that borosilicate glasses can be leached by acids. Their investigations showed that not only the chemical stability can be influenced by thermal treatment but also density, refractive index, thermal expansion and viscosity | https://en.wikipedia.org/wiki?curid=22464823 |
Porous glass In 1934, Nordberg and Hood discovered that alkali borosilicate glasses separate in soluble (sodium borate rich) and insoluble (silica rich) phases if the glass is thermally treated. By extraction using mineral acids the soluble phase can be removed and a porous silica network remains. During a sintering process after extraction, a silica glass is generated, which has properties approaching those of quartz glass. The manufacturing of such high-silica glasses has been published as the VYCOR-process. In scientific literature, porous glass is a porous material containing approximately 96% silica, which is produced by an acidic extraction or a combined acidic and alkaline extraction respectively, of phase separated alkali borosilicate glasses, and features a three-dimensional interconnected porous microstructure. For commercially available porous glasses, the terms porous VYCOR-Glass (PVG) and Controlled Pore Glass (CPG) are used. The pore structure is formed by a syndetic channel system and has a specific surface from 10 to 300 m²/g. Porous glasses can be generated by an acidic extraction of phase separated alkaliborosilica glasses, or by a sol-gel-process. By regulating the manufacturing parameters, it is possible to produce a porous glass with a pore size of between 0.4 and 1000 nm in a very narrow pore size distribution. You can generate various moulds, for example, irregular particles (powder, granulate), spheres, plates, sticks, fibers, ultra thin membranes, tubes and rings | https://en.wikipedia.org/wiki?curid=22464823 |
Porous glass Precondition for repetitious manufacturing of porous glass is the knowledge about structure determining and structure controlling parameters. The composition of the initial glass is a structure controlling parameter. The manufacturing of the initial glass, mainly the cooling process, the temperature and time of thermal treatment, and the after treatment are structure determining parameters. The phase diagram for sodiumborosilica glass shows a miscibility gap for certain glass compositions. The upper critical temperature lies at about 760 °C and the lower one at about 500 °C. O.S. Moltschanova was the first person who exactly described the definition of the exsolution. For a phase separation the initial glass composition must lie in the miscibility gap of the ternary -- glass system. By a thermal treatment, an interpenetration structure is generated, which results from a spinodal decomposition of the sodium-rich borate phase and the silica phase. This procedure is called primary decomposition. Using an initial glass composition, which lies on the line of anomaly, it is possible to attain a maximum decomposition, which is almost strainless. As both phases have a different resistances to water, mineral acids, and inorganic salt solutions, the sodium-rich borate phase in these mediums can be removed by extraction. Optimal extraction is possible only if the initial glass composition and thermal treatment are chosen such that combine structures form, and not droplet structures | https://en.wikipedia.org/wiki?curid=22464823 |
Porous glass The texture is influenced by the composition of the initial glass, which directs size and type of decomposition areas. In the context of porous glasses, "texture" implies properties like specific pore volume, specific surface, pore size, and porosity. The emerging areas of decomposition depend on time and temperature of the thermal treatment. Furthermore, the texture of porous glasses is influenced by the concentration of the extraction medium and the ratio of fluid to solid. Also, colloidal silica is solving in the sodium-rich borate phase, when time and temperature of thermal treatment are increased. This process is called secondary decomposition. The colloidal silica deposit in the macro pores during extraction and obscure the real pore structure. The solubility of colloidal silica in alkaline solutions is higher than network silica, and thus can be removed by an alkaline after-treatment. Because of their high mechanical, thermal and chemical stability, variable manufacturing of pore sizes with a small pore size distribution and variety of surface modifications, a wide array of applications are possible. The fact that porous glasses can be produced in many different shapes is another advantage for application in industry, medicine, pharmacy research, biotechnology and sensor technology. Porous glasses are ideal for material separation, because of the small pore size distribution. This is why they are used in gas chromatography, thin layer chromatography and affinity chromatography | https://en.wikipedia.org/wiki?curid=22464823 |
Porous glass An adaptation of stationary phase for a separation problem is possible by a specific modification of the surface of the porous glass. In biotechnology, porous glasses have benefits for the cleaning of DNA and the immobilization of enzymes or microorganisms. Controlled pore glass (CPG) with pore sizes between 50 and 300 nm is also excellently suited for the synthesis of oligonucleotides. In this application, a linker, a nucleoside or a non-nucleosidic compound, is first attached to the surface of CPG. The chain length of produced oligonucleotides is dependent on the pore size of CPG. In addition, porous glasses are used for manufacturing implants, especially dental implants, for which porous glass powder is processed with plastics to form a composite. The particle size and the pore size influence the elasticity of the composite so as to fit the optical and mechanical properties to surrounding tissue, for example, the appearance and hardness of dental enamel. With the ability to form porous glasses as platelets, membrane technology is another important area of application. Hyper filtration of sea – and brackish water and ultra filtration in "downstream process" are but two. Additionally, they are often appropriate as a carrier for catalysts. For example, the olefin – metathesis was realized on the system metal – metal oxide/porous glass. Porous glasses can be used as membrane reactors as well, again because of their high mechanical, thermal and chemical stability | https://en.wikipedia.org/wiki?curid=22464823 |
Porous glass Membrane reactors can improve conversion of limited balance reactions, while one reaction product is removed by a selective membrane. For example, in the decomposition of hydrogen sulfide on a catalyst in a glass capillary, the conversion by reaction was higher with glass capillary than without. | https://en.wikipedia.org/wiki?curid=22464823 |
Volume (thermodynamics) In thermodynamics, the volume of a system is an important extensive parameter for describing its thermodynamic state. The specific volume, an intensive property, is the system's volume per unit of mass. Volume is a function of state and is interdependent with other thermodynamic properties such as pressure and temperature. For example, volume is related to the pressure and temperature of an ideal gas by the ideal gas law. The physical volume of a system may or may not coincide with a control volume used to analyze the system. The volume of a thermodynamic system typically refers to the volume of the working fluid, such as, for example, the fluid within a piston. Changes to this volume may be made through an application of work, or may be used to produce work. An isochoric process however operates at a constant-volume, thus no work can be produced. Many other thermodynamic processes will result in a change in volume. A polytropic process, in particular, causes changes to the system so that the quantity formula_1 is constant (where formula_2 is pressure, formula_3 is volume, and formula_4 is the polytropic index, a constant). Note that for specific polytropic indexes a polytropic process will be equivalent to a constant-property process. For instance, for very large values of formula_4 approaching infinity, the process becomes constant-volume. Gases are compressible, thus their volumes (and specific volumes) may be subject to change during thermodynamic processes | https://en.wikipedia.org/wiki?curid=22468364 |
Volume (thermodynamics) Liquids, however, are nearly incompressible, thus their volumes can be often taken as constant. In general, compressibility is defined as the relative volume change of a fluid or solid as a response to a pressure, and may be determined for substances in any phase. Similarly, thermal expansion is the tendency of matter to change in volume in response to a change in temperature. Many thermodynamic cycles are made up of varying processes, some which maintain a constant volume and some which do not. A vapor-compression refrigeration cycle, for example, follows a sequence where the refrigerant fluid transitions between the liquid and vapor states of matter. Typical units for volume are formula_6 (cubic meters), formula_7 (liters), and formula_8 (cubic feet). Mechanical work performed on a working fluid causes a change in the mechanical constraints of the system; in other words, for work to occur, the volume must be altered. Hence volume is an important parameter in characterizing many thermodynamic processes where an exchange of energy in the form of work is involved. Volume is one of a pair of conjugate variables, the other being pressure. As with all conjugate pairs, the product is a form of energy. The product formula_9 is the energy lost to a system due to mechanical work. This product is one term which makes up enthalpy formula_10: where formula_12 is the internal energy of the system | https://en.wikipedia.org/wiki?curid=22468364 |
Volume (thermodynamics) The second law of thermodynamics describes constraints on the amount of useful work which can be extracted from a thermodynamic system. In thermodynamic systems where the temperature and volume are held constant, the measure of "useful" work attainable is the Helmholtz free energy; and in systems where the volume is not held constant, the measure of useful work attainable is the Gibbs free energy. Similarly, the appropriate value of heat capacity to use in a given process depends on whether the process produces a change in volume. The heat capacity is a function of the amount of heat added to a system. In the case of a constant-volume process, all the heat affects the internal energy of the system (i.e., there is no pV-work, and all the heat affects the temperature). However, in a process without a constant volume, the heat addition affects both the internal energy and the work (i.e., the enthalpy); thus the temperature changes by a different amount than in the constant-volume case and a different heat capacity value is required. Specific volume (formula_13) is the volume occupied by a unit of mass of a material. In many cases the specific volume is a useful quantity to determine because, as an intensive property, it can be used to determine the complete state of a system in conjunction with another independent intensive variable. The specific volume also allows systems to be studied without reference to an exact operating volume, which may not be known (nor significant) at some stages of analysis | https://en.wikipedia.org/wiki?curid=22468364 |
Volume (thermodynamics) The specific volume of a substance is equal to the reciprocal of its mass density. Specific volume may be expressed in formula_14, formula_15, formula_16, or formula_17 . where, formula_3 is the volume, formula_20 is the mass and formula_21 is the density of the material. For an ideal gas, where, formula_23 is the specific gas constant, formula_24 is the temperature and formula_25 is the pressure of the gas. Specific volume may also refer to molar volume. The volume of gas increases proportionally to absolute temperature and decreases inversely proportionally to pressure, approximately according to the ideal gas law: formula_26 where: To simplify, a volume of gas may be expressed as the volume it would have in standard conditions for temperature and pressure, which are 0 °C and 100 kPa. In contrast to other gas components, water content in air, or humidity, to a higher degree depends on vaporization and condensation from or into water, which, in turn, mainly depends on temperature. Therefore, when applying more pressure to a gas saturated with water, all components will initially decrease in volume approximately according to the ideal gas law. However, some of the water will condense until returning to almost the same humidity as before, giving the resulting total volume deviating from what the ideal gas law predicted. Conversely, decreasing temperature would also make some water condense, again making the final volume deviating from predicted by the ideal gas law | https://en.wikipedia.org/wiki?curid=22468364 |
Volume (thermodynamics) Therefore, gas volume may alternatively be expressed excluding the humidity content: "V" (volume dry). This fraction more accurately follows the ideal gas law. On the contrary "V" (volume saturated) is the volume a gas mixture would have if humidity was added to it until saturation (or 100% relative humidity). To compare gas volume between two conditions of different temperature or pressure (1 and 2), assuming nR are the same, the following equation uses humidity exclusion in addition to the ideal gas law: formula_27 Where, in addition to terms used in the ideal gas law: For example, calculating how much 1 liter of air (a) at 0 °C, 100 kPa, "p" = 0 kPa (known as STPD, see below) would fill when breathed into the lungs where it is mixed with water vapor (l), where it quickly becomes 37 °C, 100 kPa, "p" = 6.2 kPa (BTPS): formula_28 Some common expressions of gas volume with defined or variable temperature, pressure and humidity inclusion are: The following conversion factors can be used to convert between expressions for volume of a gas: The partial volume of a particular gas is the volume which the gas would have if it alone occupied the volume, with unchanged pressure and temperature, and is useful in gas mixtures, e.g. air, to focus on one particular gas component, e.g. oxygen. It can be approximated both from partial pressure and molar fraction: | https://en.wikipedia.org/wiki?curid=22468364 |
Davies equation The is an empirical extension of Debye–Hückel theory which can be used to calculate activity coefficients of electrolyte solutions at relatively high concentrations at 25 °C. The equation, originally published in 1938, was refined by fitting to experimental data. The final form of the equation gives the mean molal activity coefficient formula_1 of an electrolyte that dissociates into ions having charges "z" and "z" as a function of ionic strength "I": The second term, 0.30 "I", goes to zero as the ionic strength goes to zero, so the equation reduces to the Debye–Hückel equation at low concentration. However, as concentration increases, the second term becomes increasingly important, so the can be used for solutions too concentrated to allow the use of the Debye–Hückel equation. For 1:1 electrolytes the difference between measured values and those calculated with this equation is about 2% of the value for 0.1 M solutions. The calculations become less precise for electrolytes that dissociate into ions with higher charges. Further discrepancies will arise if there is association between the ions, with the formation of ion pairs, such as MgSO. | https://en.wikipedia.org/wiki?curid=22476314 |
Tipson–Cohen reaction The is a name reaction first discovered by Stuart Tipson and Alex Cohen at the National Bureau of Standards in Washington D.C. The occurs when two neighboring secondary sulfonyloxy groups in a sugar molecule are treated with zinc dust (Zn) and sodium iodide (NaI) in a refluxing solvent such as "N","N"-dimethylformamide (DMF) to give an unsaturated carbohydrate. Unsaturated carbohydrates are desired as they are versatile building blocks that can be used in a variety of reactions. For example, they can be used as intermediates in the synthesis of natural products, or as dienophiles in the Diels-Alder reaction, or as precursors in the synthesis of oligosaccharides. The goes through a "syn" or "anti" elimination mechanism to produce an alkene in high to moderate yields. The reaction depends on the neighboring substituents. A mechanism for glucopyranosides and mannooyranosides is shown below. Scheme 1: "Syn" elimination occurs with the glucopyranosides. Galactopyranosides follows a similar syn mechanism. Whereas, "anti" elimination occurs with mannopyranosides. Note that R could be a methanesulfonyl CHOS (Ms), or a toluenesulfonyl CHCHOS (Ts). Scheme 3: The scheme illustrates the first displacement, the rate determining step and slowest step, where the starting material is converted to the iodo-intermediate. The intermediate is not detectable as it is rapidly converted to the unsaturated sugar. Experiments with azide instead of the iodide confirmed attack occurs at the C-3 as nitrogen-intermediates were isolated | https://en.wikipedia.org/wiki?curid=22480924 |
Tipson–Cohen reaction The order of reactivity from most reactive to least reactive is: β-glucopyranosides > β-mannopyranosides > α-glucopyranosides> α-mannopyranosides. The reaction of β–mannopyranosides gives low yields and required longer reaction times than with β-glucopyranosides due to the presence of a neighboring axial substituent (sulfonyloxy) relative to C-3 sulfonyloxy group in the starting material. The axial substituent increases the steric interactions in the transition state, causing unfavorable eclipsing of the two sulfonyloxy groups. α-Glucopyranosides possess a β-"trans"-axial substituent relative to C-3 sulfonyloxy (anomeric OCH group) in the starting material. The β-"trans"-axial substituent influences the transition state by also causing an unfavorable steric interaction between the two groups. In the case of α-mannopyranosides, both a neighboring axial substituent (2-sulfonyloxy group) and a β-"trans"-axial substituent (anomeric OCH group) are present, therefore significantly increasing the reaction time and decreasing the yield. Table 1: Reaction times and yield vary on the substrate. The β-glucopyranoside was found to be the best substrate for the as the reaction time and yield were much superior that any other substrate proposed in the study. Substrates possess benzylidene protecting groups at C-4 and C-6, OMe groups at anomeric position and OTs groups at C-2 and C-3. Reaction temperature 95–100 ˚C | https://en.wikipedia.org/wiki?curid=22480924 |
Crich beta-mannosylation The Crich β-mannosylation is a synthetic strategy which is used in carbohydrate synthesis to generate a 1,2-cis-glycosidic bond. This type of linkate is generally very difficult to make, and specific methods like the Crich β-mannosylation are used to overcome these issues. The development of facile chemical glycosylation protocols is essential to synthesizing complex oligosaccharides. Among many diverse type of glycosidic linkages, the 1,2-"cis"-β-glycoside, which exists in many biologically relevant glycoconjugates and oligosaccharides, is arguably one of the most difficult to synthesize. The challenges in constructing β-mannose linkage have been well documented in several reviews. To date, a few laboratories have devised efficient methodologies to overcome these synthetic hurdles, and achieved varying degrees of success. Of those elegant approaches, a highly stereoselective β-mannosylation protocol developed by Crich and co-workers was realized as a breakthrough in β-mannoside synthesis. This strategy is based on the initial activation of α-mannosyl sulfoxides 1 with triflic anhydride (TfO) using DTBMP (2,6-di-"tert"-butyl-4-methylpyridine) as a base, followed by nucleophilic substitution of glycosyl acceptors (HOR) to provide the 1,2-"cis"-β-glycoside 2 in good yield and selectivity (Scheme 1). The mechanistic details of this reaction have been extensively explored by Crich’s laboratories | https://en.wikipedia.org/wiki?curid=22483052 |
Crich beta-mannosylation Low-temperature H, C, and F NMR spectroscopic investigations revealed that anomeric triflate 3 derived from 1 is the intermediate glycosyl donor. Moreover, the mechanism of glycosidic bond forming reaction (3→2) was examined thoroughly by the determination of kinetic isotopic effects (KIEs) and NMR spectroscopy. Consequently, the magnitude of KIEs indicated that the displacement of the triflate from 3 proceeded with the development of significant oxacarbenium ion character at the anomeric position. This might be rationalized either by (1) a dissociative mechanism involving the intermediacy of either a transient contact ion pair (CIP) 4 or a solvent-separated ion pair (SSIP) 5, or (2) a mechanistically variant transition state 7 (Scheme 2). For the intermediate CIP 4, the triflate anion is closely associated with face where it just departed thus shields that side against nucleophilic attack. For the alternative intermediate SSIP 5 which is in equilibrium with an initial CIP, the anomeric center could presumably be attacked by incoming alcohol from either face, giving β-mannoside 2 along with the undesired α-anomer 6. Along these lines, the presence of the 4,6-"O"-benzylidene protecting group, which serves to rigidify the pyranoside against rehybridization at the anomeric carbon, is essential in shifting the equilibrium toward the covalent triflate, thus reducing α-glycoside formation | https://en.wikipedia.org/wiki?curid=22483052 |
Crich beta-mannosylation Additionally, the only intermediate observed by NMR spectroscopy is the covalent triflate 3, indicating that the complete set of equilibria between 3, the CIP 4, and SSIP 5 set is very heavily biased towards 3. Some representative examples of Crich’s β-mannosylation are shown in Scheme 3. It is noteworthy that, with this method in hand, primary, secondary, and tertiary alcohols (9, 12, and 13) all serve as glycosyl acceptors effectively in terms of yields and selectivity. In a recent version, the β-mannosylation of thioglycoside 14 and its analogues were examined to prepare sterically hindered glycosides, in which PhSOTf (or other newly developed sulfur-type oxidants) served as a convenient reagent for the "in situ" generation of the glycosyl triflate from 14, thus facilitating the reaction. The polymer-supported synthesis of β-mannosides based on the Crich’s protocol has also been studied in the same laboratories. As shown in Scheme 4, diol 17 was first reacted with polystyrylboronic acid (18) to offer the bound donor 19, in which 4,6-"O"-phenylboronates served as the torsionally disarming protecting group. With that, activation of the thioglycoside 19 was readily achieved, and the coupling reaction with the acceptor alcohol underwent smoothly to provide the bound β-mannoside 20. After removal of the excess reagents and byproducts from the resin, 20 was then treated with aqueous acetone to release 4,6-diol 21 | https://en.wikipedia.org/wiki?curid=22483052 |
Crich beta-mannosylation Overall, this is a powerful method for solid-phase synthesis of β-mannosides, which has great potential to be further extended, was established. | https://en.wikipedia.org/wiki?curid=22483052 |
Gas Safe Register is the official gas registration body for the United Kingdom, Isle of Man and Guernsey, appointed by the relevant Health and Safety Authority for each area. By law all gas engineers must be on the Gas Safe Register. replaced CORGI as the gas registration body in Great Britain and Isle of Man on 1 April 2009 and Northern Ireland and Guernsey on 1 April 2010. The purpose of the is to protect the public from unsafe gas work. It does this in two main ways, operation of the Register itself e.g. ensuring that the list of competent and qualified engineers is accurate and up-to-date, inspecting the work of Gas Safe registered engineers and investigating reports of illegal gas work. The second area is to conduct public awareness campaigns to raise awareness of gas safety issues. A 2006 review by the Health and Safety Executive identified ‘a case for change’ to the CORGI scheme that had been registering gas installers since 1991. In competitive tender, Capita was appointed to overhaul the scheme and operate it for 10 years from April 2009. Before applying to register engineers will need relevant qualifications and evidence of competence. Once an engineer has gained the relevant qualifications and the required evidence, this information will be passed to Gas Safe Register. At present, only accepts the ACS, NVQ or SVQ qualifications. Every Gas Safe registered business renews their registration on an annual basis, and updates their qualifications every 5 years | https://en.wikipedia.org/wiki?curid=22483611 |
Gas Safe Register The scheme is administered by Capita Group on behalf of the Health and Safety Executive. in the United Kingdom Mainland and for the Health and Safety Executive Northern Ireland. The contract differs in Northern Ireland in relation to the main contract for mainland of the United Kingdom. deals with all aspects of the downstream gas industry covered by the following regulations: The regulations cover both piped natural gas and liquefied petroleum gas (LPG). In 2011 launched a consumer awareness initiative called Gas Safety Week, with the aim of focusing the public's attention on gas safety issues and helping raise awareness of the dangers of carbon monoxide (CO) poisoning. Since 2011, the campaign has grown significantly and has become an industry-wide initiative supported by the large energy providers, retailers, charities and Gas Safe registered engineers. | https://en.wikipedia.org/wiki?curid=22483611 |
Timeline of chemical warfare Chemical warfare is "the use of toxic chemicals in battle." The precise date of the first instances of chemical warfare is unknown, but scholars speculate that smoke have been used as an irritant in both battles and for hunting in prehistoric times. The first records of chemical warfare come from accounts of India in the fourth century BC, when Indian archers dipped their arrows in snake venom. In the same period, the use of smoke against enemies digging tunnels was first recorded in Greece and China. The next several centuries witnessed more and more sophisticated applications of toxic smoke and poisons in warfare. In the Middle Ages and the early modern period, chemical warfare advanced along with the development of chemistry. In 1456, during the Siege of Belgrade, an alchemist created poison clouds by burning rags that may have contained chlorine gas. In the fifteenth century, Leonardo da Vinci designed explosive shells filled with arsenic and sulfur for use against ships, and in the nineteenth century, Thomas Cochrane advocated the use of burning sulfur as a naval weapon. Later in the nineteenth century, the Union Army in the American Civil War devised plans to attack Confederate trenches with hydrochloric acid and sulfur acid, but failed to carry out its intentions. In the late nineteenth century, advances in organic chemistry led to the development of advanced new chemical weapons, such as mustard gas | https://en.wikipedia.org/wiki?curid=22483910 |
Timeline of chemical warfare These weapons were first used during World War I in which the belligerents used more than 125,000 tons of chemical munitions. Despite great public opposition to chemical warfare after World War I, its development and practice continued. In the 1930s, Italy used chemical weapons during the Second Italo-Abyssinian War. At the same time, German chemists discovered a new class of chemical weapons, far more deadly than early agents, nerve agents. During World War Two, Japan used chemical weapons during the Second Sino-Japanese War, but chemical weapons were not used on a large scale in the European theater or in conflict between the United States and Japan. After the war, though, chemical weapons were used in several conflicts, most notably in the Yemeni Civil War and Iran–Iraq War. During this period, the United States and the Soviet Union also continued to refine their chemical arsenals, developing new agents such as VX and binary chemical weapons. In 1993, the Chemical Weapons Convention was signed, outlawing all uses of chemical weapons in war. Since the signing of the convention, there have been numerous incidents of chemical weapons use, including by states parties to the convention. With the advent of industrialised warfare in World War One the use of gas saw its first widespread use. | https://en.wikipedia.org/wiki?curid=22483910 |
Glycosyl donor A glycosyl donor is a carbohydrate mono- or oligosaccharide that will react with a suitable glycosyl acceptor to form a new glycosidic bond. By convention, the donor is the member of this pair that contains the resulting anomeric carbon of the new glycosidic bond. The resulting reaction is referred to as a glycosylation or chemical glycosylation. In a glycosyl donor, a leaving group is required at the anomeric position. The simplest leaving group is the OH group that is naturally present in monosaccharides, but it requires activation by acid catalysis in order to function as leaving group (in the Fischer glycosylation). More effective leaving groups are in general used in the glycosyl donors employed in chemical synthesis of glycosides. Typical leaving groups are halides, thioalkyl groups, or imidates, but acetate, phosphate, and O-pentenyl groups are also employed. Natural glycosyl donors contain phosphates as leaving groups. The so-called “armed-disarmed” principle The concept of armed and disarmed glycosyl donors refers to the increased reactivity of benzylated over benzoylated glycosyl donors, a phenomenon observed very early, and which originates from the greater electron-withdrawing capability of ester blocking groups over ether blocking groups. However, it was Bertram Fraser-Reid who realised that benzylated glycosyl donors can be activated when benzoylated donors are not, and invented the terms armed glycosyl donor for the former, and disarmed glycosyl donor for the latter | https://en.wikipedia.org/wiki?curid=22484288 |
Glycosyl donor He and his group showed that armed glycosyl donors could be coupled to a glycosyl acceptor, that was at the same time a disarmed glycosyl donor, without self-coupling of the disarmed donor/acceptor. This approach allowed him to carry out a one-pot synthesis of a trisaccharide by the n-pentenyl glycoside method. The concept has been extended to superarmed glycosyl donor by Mikael Bols and his collaborators. He realised that the hydroxy groups of carbohydrates are less electron-withdrawing towards the anomeric center when they are axial than when they are equatorial, which means that glycosyl donor conformers with more axial oxy functions are more reactive. Protection of a glycosyl donor with bulky silyl groups (tert-butyldimethylsilyl or triisopropyl) cause it to change conformation to a more axial-rich conformation that, as a consequence, is more reactive, which Bols and his group called superarmed. They showed that a superarmed donor can be coupled to an armed glycosyl donor/acceptor. | https://en.wikipedia.org/wiki?curid=22484288 |
Glycosyl acceptor A glycosyl acceptor is any suitable nucleophile-containing molecule that will react with a glycosyl donor to form a new glycosidic bond. By convention, the acceptor is the member of this pair which did not contain the resulting anomeric carbon of the new glycosidic bond. Since the nucleophilic atom of the acceptor is typically an oxygen atom, this can be remembered using the mnemonic of "the acceptor is the alcohol." A glycosyl acceptor can be a mono- or oligosaccharide that contains an available nucleophile, such as an unprotected hydroxyl. | https://en.wikipedia.org/wiki?curid=22484332 |
Oxocarbenium An oxocarbenium ion (or oxacarbenium ion) is a chemical species characterized by a central sp-hybridized carbon, an oxygen substituent, and an overall positive charge that is delocalized between the central carbon and oxygen atoms. A oxocarbenium ion is represented by two limiting resonance structures, one in the form of a carbenium ion with the positive charge on carbon and the other in the form of an oxonium species with the formal charge on oxygen. As a resonance hybrid, the true structure somewhere between the two. Compared to neutral carbonyl compounds like ketones or esters, the carbenium ion form is a larger contributor to the structure. They are common reactive intermediates in the hydrolysis of glycosidic bonds, and are a commonly used strategy for chemical glycosylation. These ions have since been proposed as reactive intermediates in a wide range of chemical transformations, and have been utilized in the total synthesis of several natural products. In addition, they commonly appear in mechanisms of enzyme-catalyzed biosynthesis and hydrolysis of carbohydrates in nature. Anthocyanins are natural flavylium dyes, which are stabilized oxocarbenium compounds. Anthocyanins are responsible for the colors of a wide variety of common flowers such as pansies and edible plants such as eggplant and blueberry. The best Lewis structure for an oxocarbenium ion contains an oxygen–carbon double bond, with the oxygen atom attached to an additional group and consequently taking on a formal positive charge | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium In the language of canonical structures (or "resonance"), the polarization of the π bond is described by a secondary carbocationic resonance form, with a formal positive charge on carbon (see above). In terms of frontier molecular orbital theory, the Lowest Unoccupied Molecular Orbital (LUMO) of the oxocarbenium ion is a π* orbital that has the large lobe on the carbon atom; the more electronegative oxygen contributes less to the LUMO. Consequently, in an event of a nucleophilic attack, the carbon is the electrophilic site. Compared to a ketone, the polarization of an oxocarbenium ion is accentuated: they more strongly resemble a "true" carbocation, and they are more reactive toward nucleophiles. In organic reactions, ketones are commonly activated by the coordination of a Lewis acid or Brønsted acid to the oxygen to generate an oxocarbenium ion as an intermediate. Numerically, a typical partial charge (derived from Hartree-Fock computations) for the carbonyl carbon of a ketone RC=O (like acetone) is "δ+" = 0.51. With the addition of an acidic hydrogen to the oxygen atom to produce [RC=OH], the partial charge increases to "δ+" = 0.61. In comparison, the nitrogen analogues of ketones and oxocarbenium ions, imines (RC=NR) and iminium ions ([RC=NRH]), respectively, have partial charges of "δ+" = 0.33 and "δ+" = 0.54, respectively. The order of partial positive charge on the carbonyl carbon is therefore imine < ketone < iminium < oxocarbenium | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium This is also the order of electrophilicity for species containing C=X (X = O, NR) bonds. This order is synthetically significant and explains, for example, why reductive aminations are often best carried out at pH = 5 to 6 using sodium cyanoborohydride (Na[HB(CN)]) or sodium triacetoxyborohydride (Na[HB(OAc)]) as a reagent. Bearing an electron-withdrawing group, sodium cyanoborohydride and sodium triacetoxyborohydride are poorer reducing agents than sodium borohydride, and their direct reaction with ketones is generally a slow and inefficient process. However, the iminium ion (but not the imine itself) formed "in situ" during a reductive amination reaction is a stronger electrophile than the ketone starting material and will react with the hydride source at a synthetically useful rate. Importantly, the reaction is conducted under mildly acidic conditions that protonate the imine intermediate to a significant extent, forming the iminium ion, while not being strongly acidic enough to protonate the ketone, which would form the even more electrophilic oxocarbenium ion. Thus, the reaction conditions and reagent ensure that amine is formed selectively from iminium reduction, instead of direct reduction of the carbonyl group (or its protonated form) to form an alcohol. Formation of oxocarbenium ions can proceed through several different pathways. Most commonly, the oxygen of a ketone will bind to a Lewis Acid, which activates the ketone, making it a more effective electrophile | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium The Lewis acid can be a wide range of molecules, from a simple hydrogen atom to metal complexes. The remainder of this article will focus on alkyl oxocarbenium ions, however, where the atom added to the oxygen is a carbon. One way that this sort of ion will form is the elimination of a leaving group. In carbohydrate chemistry, this leaving group is often an ether or ester. An alternative to elimination is direct deprotonation of the molecule to form the ion, however, this can be difficult and require strong bases to achieve. The stereochemistry involved in the reactions of five-membered rings can be predicted by an envelope transition state model. Nucleophiles favor addition from the "inside" of the envelope, or from the top of the figure on the right. The "inside" addition produces a results in a staggered conformation, rather than the eclipsed conformation that results from the "outside" addition. The transition state model for a six-membered oxocarbenium ring was proposed earlier in 1992 by Woods et al. The general strategy for determining the stereochemistry of a nucleophilic addition to a six-membered ring follows a similar procedure to the case of the five-membered ring. The assumption that one makes for this analysis is that the ring is in the same conformation as cyclohexene, with three carbons and the oxygen in a plane with the two other carbon atome puckered out of the plane, with one above and one below (see the figure to the right) | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium Based on the substituients present on the ring, the lowest energy conformation is determined, keeping in mind steric and steroelectronic effects (see the section below for a discussion of stereoelectronic effects in oxocarbenium rings). Once this conformation is established, one can consider the nucleophilic addition. The addition will proceed through the low energy chair transition state, rather than the relatively high energy twist-boat. An example of this type of reaction can be seen below. The example also highlights how the stereoelectronic effect exerted by an electronegative substituent flips the lowest energy conformation and leads to opposite selectivity. In an alkene ring that does not contain an oxygen atom, any large substituent prefers to be in an equatorial position, in order to minimize steric effects. It has been observed in rings containing oxocarbenium ions that electronegative substituents prefer the axial or pseudo-axial positions. When the electronegative atom is in the axial position, its electron density can be donated through space to the positively charged oxygen atom in the ring. This electronic interaction stabilizes the axial conformation. Hydroxyl groups, ethers and halogens are examples of substituents that exhibit this phenomenon. Stereoelectronic effects must be taken into consideration when determining the lowest energy conformation in the analysis for nucleophilic addition to an oxocarbenium ion | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium In organic synthesis, vinyl oxocarbenium ions (structure on right) can be utilized in a wide range of cycloaddition reactions. They are commonly employed as dienophiles in the Diels–Alder reaction. An electron withdrawing ketone is often added to the dienophile to increase the rate of the reaction, and these ketones are often converted to vinyl oxocarbenium ions during the reaction It is not clear that an oxocarbenium ion necessarily will form, but Roush and co-workers demonstrated the oxocarbenium intermediate in the cyclization shown below. Two products were observed in this reaction, which could only form if the oxocarbenium ring is present as an intermediate. [4+3], [2+2], [3+2] and [5+2] cycloadditions with oxocarbenium intermediates have also been reported. Chiral oxocarbenium ions have been exploited to carry out highly diastereoselective and enantioselective acetate aldol addition reactions. The oxocarbenium ion is used as an electrophile in the reaction. When the methyl group increases in size, the diastereoselevtivity increases. ions have been utilized in total synthesis on several occasions. A major subunit of (+)-clavosolide was synthesized with a reduction of a six-membered oxocarbenium ring. All the large substituents were found in an equatorial position, and the transformation went through the chair transition state, as predicted | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium A second example is seen in the key step of the synthesis of (−)-neopeltolide, which uses another six-membered oxocarbenium ring reduction for a diastereoselective hydride addition. In biological systems, oxocarbenium ions are mostly seen during reactions of carbohydrates. Since sugars are present in the structure of nucleic acids, with a ribose sugar present in RNA and a deoxyribose present in the structure of DNA, their chemistry plays an important role in wide range of cellular functions of nucleic acids. In addition to their functions in nucleotides, sugars are also used for structural components of organisms, as energy storage molecules, cell signaling molecules, protein modification and play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development. The abundance of sugar chemistry in biological processes leads many reaction mechanisms to proceed through oxocarbenium ions. Several important biological reactions that utilize oxocarbenium ions are outlined in this section. Nucleotides can undergo enzyme-catalyzed intramolecular cyclization in order to produce several important biological molecules. These cyclizations typically proceed through an oxocarbenium intermediate. An example of this reaction can be seen in the cyclization cyclic ADP ribose, which is an important molecule for intracellular calcium signaling. A glycosidase is an enzyme that catalyzes the breakdown of a glycosidic linkage to produce two smaller sugars | https://en.wikipedia.org/wiki?curid=22484557 |
Oxocarbenium This process has important implications in the utilization of stored energy, like glycogen in animals, as well as in the breakdown of cellulose by organisms that feed on plants. In general, aspartic or glutamic acid residues in the active site of the enzyme catalyze the hydrolysis of the glycosidic bond. The mechanism of these enzymes involves an oxocarbenium ion intermediate, a general example of which is shown below. | https://en.wikipedia.org/wiki?curid=22484557 |
Gold number Gold Number is the number of milligrams of a protective colloid which prevents the coagulation of 10 ml of a standard hydro gold sol,on coagulation changes from red to blue, which is prevented by a protective colloid. of 1ml 10% NaCl solution.<ref> Physical Pharmacy, page Coagulation of gold sol is indicated by colour change from red to blue/purple when particle size just increases. More is the gold number, less is the protective power of the lyophilic colloid since it means that the amount required is more. It was first used by Richard Adolf Zsigmondy. The amount is taken in terms of weight in milligrams. The gold number of some colloids are given below. gold number of total | https://en.wikipedia.org/wiki?curid=22489171 |
Coupled-wave method In physics, the coupled-wave method (CWM) is a method for analysing the interaction between two electromagnetic waves in a crystal or a grating. | https://en.wikipedia.org/wiki?curid=22491755 |
Alessandro Vaciago (September 11, 1931 – November 17, 1993) was a Professor of Chemical Structure, University of Rome from 1971 to 1993. He also served as a Cultural Counselor for the Italian Embassy. The Accademia dei Lincei awards yearly the Vaciago Prize to distinguished researchers in different fields of science. | https://en.wikipedia.org/wiki?curid=22494743 |
Double bond rule The double bond rule states that chemical elements with a principal quantum number greater than 2 for their valence electrons (period 3 elements and lower) should not form multiple bonds (e.g. double bonds and triple bonds) with themselves or with other elements. The double bonds, when they exist, are often weak due to poor orbital overlap. Although such compounds are not intrinsically unstable, they instead tend to polymerize. An example is the rapid polymerization that occurs upon condensation of disulfur, the heavy analogue of O. This rule was challenged and ultimately disproven starting from 1981 with the isolation of crystalline samples of compounds with silicon=silicon and phosphorus=phosphorus double bonds. Double bonds that would ordinarily not form can often be stabilized with proper functional groups either electronically or sterically. Another unrelated double bond rule exists that relates to the enhanced reactivity of sigma bonds once removed from a double bond. In bromoalkenes the C–Br bond is very stable but in an allyl bromide this bond is very reactive. Likewise bromobenzenes are generally inert whereas benzylic bromides are reactive. The first to observe the phenomenon was Conrad Laar in 1885. The name for the rule was coined by Otto Schmidt (1874–1943) in 1932 | https://en.wikipedia.org/wiki?curid=22497638 |
Abalone (molecular mechanics) Abalone is a general purpose molecular dynamics and molecular graphics program for simulations of bio-molecules in a periodic boundary conditions in explicit (flexible SPC water model) or in implicit water models. Mainly designed to simulate the protein folding and DNA-ligand complexes in AMBER force field. | https://en.wikipedia.org/wiki?curid=22497840 |
Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. This can include the synthesis of monosaccharide residues or structures containing more than one monosaccharide, known as oligosaccharides. Generally speaking, carbohydrates can be classified into two groups, simple sugars and complex carbohydrates. Simple sugars, also called monosaccharides, are carbohydrates which can not be converted into smaller sugars by hydrolysis. When two or more monosaccharide units are connected to one another via a glycoside linkage, complex carbohydrates are formed. Complex carbohydrates, according to the different number of monosaccharide units, can be classed into three groups, disaccharides, oligosaccharides, and polysaccharides. A disaccharide is formed from two monosaccharides. Oligosaccharides can be formed by a small number of monosaccharides linked together. Higher oligosaccharides are called polysaccharides. It is now well known that glycoconjugates play an indispensable role in many biological processes. These biological processes in which carbohydrates are involved are typically associated not to monosaccharides, but to oligosaccharides structures of glycoconjugates. Therefore, the oligosaccharide synthesis becomes more and more important in studying the biological activities. Oligosaccharides have diverse structures | https://en.wikipedia.org/wiki?curid=22497985 |
Carbohydrate synthesis The number of monosaccharides, ring size, the different anomeric stereochemistry, and the existence of the branched-chain sugars all contribute to the amazing complexity of the oligosaccharide structures. The essence of the reducing oligosaccharide synthesis is connecting the anomeric hydroxyl of the glycosyl donors to the alcoholic hydroxyl groups of the glycosyl acceptors. Protection of the hydroxyl groups of the acceptor with the target alcoholic hydroxyl group unprotected can assure the regiochemical control. Additionally, factors such as the different protecting groups, the solvent, and the glycosylation methods can influence the anomeric configurations. This concept is illustrated by an oligosaccharide synthesis in Scheme 1. Oligosaccharide synthesis normally consists of four parts: preparation of the glycosyl donors, preparation of the glycosyl acceptors with a single unprotected hydroxyl group, the coupling of them, and the deprotection process. Common donors in oligosaccharide synthesis are glycosyl halides, glycosyl acetates, thioglycosides, trichloroacetimidates, pentenyl glycosides, and glycals. Of all these donors, glycosyl halides are classic donors, which played a historical role in the development of glycosylation reactions. Thioglycoside and trichloroacetimidate donors are used more than others in contemporary glycosylation methods. When it comes to the trichloroacetimidate method, one of the advantages is that there is no need to introduce heavy metal reagents in the activation process | https://en.wikipedia.org/wiki?curid=22497985 |
Carbohydrate synthesis Moreover, using different bases can selectively lead to different anomeric configurations. (Scheme 2) As to the thioglycosides, the greatest strength is that they can offer a temporary protection to the anomeric centre because they can survive after most of the activation processes. Additionally, a variety of activation methods can be employed, such as NIS/ AgOTf, NIS/ TfOH, IDCP (Iodine dicollidine perchlorate), iodine, and PhSO/ TfO. Furthermore, in the preparation of 1, 2-trans glycosidic linkage, using thioglycosides and imidates can promote the rearrangement of the orthoester byproducts, since the reaction mixtures are acidic enough. The structures of acceptors play a critical role in the rate and stereoselectivity of glycosylations. Generally, the unprotected hydroxyl groups are less reactive when they are between bulky protecting groups. That is the reason why the hydroxyl group at OH-4 in pyranosides is unreactive. Hyperconjugation is involved when OH-4 is anti-periplanar to the ring oxygen, which can also reduce its reactivity. (Scheme 3) Furthermore, acyl protecting groups can reduce the reactivity of the acceptors compared with alkyl protecting groups because of their electron-withdrawing ability. Hydroxyl group at OH-4 of N-acetylglucosamine derivatives is particularly unreactive. The glycosidic bond is formed from a glycosyl donor and a glycosyl acceptor. There are four types of glycosidic linkages: 1, 2-trans-α, 1, 2-trans-beta, 1, 2-cis-α, and 1, 2-cis-beta linkages | https://en.wikipedia.org/wiki?curid=22497985 |
Carbohydrate synthesis 1, 2-trans glycosidic linkages can be easily achieved by using 2-O-acylated glycosyl donors (neighboring group participation). To prevent the accumulation of the orthoester intermediates, the glycosylation condition should be slightly acidic. It is somewhat more difficult to prepare 1, 2-cis-β-glycosidic linkages stereoselectively. Typically, when non-participating groups on O-2 position, 1, 2-cis-β-linkage can be achieved either by using the historically important halide ion methods, or by using 2-O-alkylated glycosyl donors, commonly thioglycosides or trichloroacetimidates, in nonpolar solvents. In the early 1990s, it was still the case that the beta mannoside linkage was too challenging to be attempted by amateurs. However, the method introduced by Crich (Scheme 4), with 4,6-benzylidene protection a prerequisite and anomeric alpha triflate a key intermediate leaves this problem essentially solved. The concurrently developed but rather more protracted intramolecular aglycon delivery (IAD) approach is a little used but nevertheless stereospecific alternative. | https://en.wikipedia.org/wiki?curid=22497985 |
Inherent chirality In chemistry, inherent chirality is a property of asymmetry in molecules arising, not from a stereogenic or chiral center, but from a twisting of the molecule in 3-D space. The term was first coined by Volker Boehmer in a 1994 review, to describe the chirality of calixarenes arising from their non-planar structure in 3-D space. This phenomenon was described as resulting from "the absence of a place of symmetry or an inversion center in the molecule as a whole". Boehmer further explains this phenomenon by suggesting that if an inherently chiral calixarene macrocycle were opened up it would produce an "achiral linear molecule". There are two commonly used notations to describe a molecules inherent chirality: cR/cS (arising from the notation used for classically chiral compounds, with "c" denoting curvature) and P/M. Inherently chiral molecules, like their classically chiral counterparts, can be used in chiral host–guest chemistry, enantioselective synthesis, and other applications. There are naturally occurring inherently chiral molecules as well. Retinal, a chromophore in rhodopsin. exists in solution as a racemic pair of enantiomers due to the curvature of an achiral polyene chain. After creating a series of traditionally chiral calixarenes (through the addition of a chiral substituent group on the top or bottom rim of the macrocycle,) the first inherently chiral calixarenes were synthesized in 1982, though the molecules were not yet described as such | https://en.wikipedia.org/wiki?curid=22506127 |
Inherent chirality The inherently chiral calixarenes featured an XXYZ or WXYZ substitution pattern, such that the planar representation of the molecule does not show any chirality, and if the macrocycle were to be broken open, this would produce an achiral linear molecule. The chirality in these calixarenes is instead derived from the curvature of the molecule in space. Due to the initial lack of a formal definition after the initial conception, the term inherent chirality was utilized to describe a variety of chiral molecules that don't fall into other defined chirality types. The first fully formulated definition of inherent chirality was published in 2004 by Mandolini and Schiaffino, (and later modified by Szumna): inherent chirality arises from the introduction of a curvature in an ideal planar structure that is devoid of perpendicular symmetry planes in its bidimensional representation. has been known by a variety of names in the literature including bowl chirality (in fullerene fragments), intrinsic chirality, helicity (see section 3a) residual enantiomers (as applied to sterically hindered molecular propellers,) and cyclochirality (though this is often considered to be a more specific example and cannot be applied to all inherently chiral molecules). A simple example of inherent chirality is that of corannulene commonly referred to as "bowl chirality" in the literature | https://en.wikipedia.org/wiki?curid=22506127 |
Inherent chirality The chirality of an unsubstituted corranulene (containing no classic stereogenic centers) cannot be seen in a 2D representation, but becomes clear when a 3D representation is evoked, as the C symmetry of corranulenes provides the molecules with a source of chirality (figure 2.) Racemization of these molecules is possible through an inversion of curvature, though some inherently chiral molecules have inversion barriers comparable to a classic chiral center. Some inherently chiral molecules contain chirality planes, or planes within a given molecules across which the molecule is dissymmetric. Paracyclophanes often contain chiral planes if the bridge across the phenylene unit is short enough, or if the phenylene contains another substituent, not in the bridge, that hinders rotation of the phenylene unit. Similar to chirality planes, chirality axes arise from an axis about which the spatial arrangement of substituents creates chirality. This can be seen in helical molecules (see section 3a) as well as some alkenes. Helical molecules are considered to have inherent chirality, but this is sometimes referred to as helical chirality or "helicity". The IUPAC definition of helicity is: "chirality of a helical, propeller or screw-shaped molecular entity." Helicenes (figure 4) are chiral polycyclic aromatic compounds that lack conventional chiral centers, but are chiral due to the helical shape of the 3D molecules | https://en.wikipedia.org/wiki?curid=22506127 |
Inherent chirality Spiro compounds (compounds with a twisted structure of two or more rings) can have inherent chirality at the spiroatom, due to the twisting of the achiral ring system. Inherently chiral alkenes have been synthesized through the use of a "buckle" where in an achiral, linear alkene is forced into a chiral conformation. Alkenes have no classical chirality, so generally, an external stereogenic center must be introduced. However, by locking the alkene into a conformation through the use of an achiral buckle allows for the creation of an inherently chiral alkene. Inherently chiral alkenes have been synthesized through the use of dialkoxysilanes, with a large enough racemization barrier that enantiomers have been isolated. | https://en.wikipedia.org/wiki?curid=22506127 |
Photothermal optical microscopy / "photothermal single particle microscopy" is a technique that is based on detection of non-fluorescent labels. It relies on absorption properties of labels (gold nanoparticles, semiconductor nanocrystals, etc.), and can be realized on a conventional microscope using a resonant modulated heating beam, non-resonant probe beam and lock-in detection of photothermal signals from a single nanoparticle. It is the extension of the macroscopic photothermal spectroscopy to the nanoscopic domain. The high sensitivity and selectivity of photothermal microscopy allows even the detection of single molecules by their absorption. Similar to Fluorescence Correlation Spectroscopy (FCS), the photothermal signal may be recorded with respect to time to study the diffusion and advection characteristics of absorbing nanoparticles in a solution. This technique is called photothermal correlation spectroscopy (PhoCS). In this detection scheme a conventional scanning sample or laser-scanning transmission microscope is employed. Both, the heating and the probing laser beam are coaxially aligned and superimposed using a dichroic mirror. Both beams are focused onto a sample, typically via a high-NA illumination microscope objective, and recollected using a detection microscope objective. The thereby collimated transmitted beam is then imaged onto a photodiode after filtering out the heating beam. The photothermal signal is then the change formula_1 in the transmitted probe beam power formula_2 due to the heating laser | https://en.wikipedia.org/wiki?curid=22507026 |
Photothermal optical microscopy To increase the signal-to-noise ratio a lock-in technique may be used. To this end, the heating laser beam is modulated at a high frequency of the order of MHz and the detected probe beam power is then demodulated on the same frequency. For quantitative measurements, the photothermal signal may be normalized to the background detected power formula_3 (which is typically much larger than the change formula_4), thereby defining the relative photothermal signal formula_5 formula_6 The physical basis for the photothermal signal in the transmission detection scheme is the lensing action of the refractive index profile that is created upon the absorption of the heating laser power by the nanoparticle. The signal is homodyne in the sense that a steady state difference signal accounts for the mechanism and the forward scattered field's self-interference with the transmitted beam corresponds to an energy redistribution as expected for a simple lens. The lens is a Gadient Refractive INdex (GRIN) particle determined by the 1/r refractive index profile established due to the point-source temperature profile around the nanoparticle | https://en.wikipedia.org/wiki?curid=22507026 |
Photothermal optical microscopy For a nanoparticle of radius formula_7 embedded in a homogeneous medium of refractive index formula_8 with a thermorefractive coefficient formula_9 the refractive index profile reads: formula_10 in which the contrast of the thermal lens is determined by the nanoparticle absorption cross-section formula_11 at the heating beam wavelength, the heating beam intensity formula_12 at the point of the particle and the embedding medium's thermal conductivity formula_13 via formula_14. Although the signal can be well-explained in a scattering framework, the most intuitive description can be found by an intuitive analogy to the Coulomb scattering of wave packets in particle physics. In this detection scheme a conventional scanning sample or laser-scanning transmission microscope is employed. Both, the heating and the probing laser beam are coaxially aligned and superimposed using a dichroic mirror. Both beams are focused onto a sample, typically via a high-NA illumination microscope objective. Alternatively, the probe-beam may be laterally displaced with respect to the heating beam. The retroreflected probe-beam power is then imaged onto a photodiode and the change as induced by the heating beam provides the photothermal signal The detection is heterodyne in the sense that the scattered field of the probe beam by the thermal lens interferes in the backwards direction with a well-defined retroreflected part of the incidence probing beam. | https://en.wikipedia.org/wiki?curid=22507026 |
Iron phosphide is a chemical compound of iron and phosphorus, with a formula of FeP. Its physical appearance is grey, hexagonal needles. Manufacturing of iron phosphide takes place at elevated temperatures, where the elements combine directly. reacts with moisture and acids producing phosphine (PH), a toxic and pyrophoric gas. can be used as a semiconductor. It has use in high power, high frequency applications, such as laser diodes. is a hazardous substance. Proper eye protection such as goggles should always be used when handling iron phosphide. It can be very harmful to the eyes, especially for individuals wearing contact lenses. Contact lenses have been known to react poorly with iron phosphide due to its corrosive properties, but the scientific world does not all agree on the use of contact lenses in association with iron phosphide. In case of inhalation, the person should be moved to fresh air or given artificial respiration if not breathing. In case of ingestion, the person's mouth should be rinsed with water unless unconscious. In case of eye contact, immediate eye flushing is necessary. | https://en.wikipedia.org/wiki?curid=22509369 |
Snf3 is a protein which regulates glucose uptake in yeast. It senses glucose in the environment with high affinity. Glucose sensing and signaling in budding yeast is similar to the mammalian system in many ways. However, there are also significant differences. Mammalian cells regulate their glucose uptake via hormones (i.e. insulin and glucagon) or intermediary metabolites. In contrast, yeast as a unicellular organism does not depend on hormones but on nutrients in the medium. The presence of glucose induces a conformational change in the membrane proteins Snf3/Rgt2 or Gpr1, and regulates expression of genes involved in glucose metabolism. is homologous to multiple sugar transporters, it shares high similarity to the glucose transporters of rat brain cells and human HepG2 hepatoma cells, as well as to the arabinose and xylose transporters (AraE and XylE) of "Escherichia coli". Based on this homology and on genetic studies, was initially thought to be a high affinity glucose transporter. Later, it was found that is not a glucose transporter, but rather a high affinity glucose sensor. It senses glucose at low concentrations and regulates transcription of the HXT genes, which encode for glucose transporters. If glucose is absent is quiescent and transcription of the HXT genes is inhibited by a repressing complex. The complex consisting of several subunits such as Rgt1, Mth1/Std1, Cyc8 and Tup1 binds to the promoters of the HXT genes, thereby blocking their transcription | https://en.wikipedia.org/wiki?curid=22513078 |
Snf3 is able to bind even low amounts of glucose due to its high affinity. The induction of by glucose leads to the activation of YckI, a yeast casein kinase. This is followed by the recruitment of Mth1 and Std1 to the C-terminus of which facilitates the phosphorylation of the two proteins by YckI. Phosphorylated Mth1 and Std1 are subsequently tagged for proteasome dependent degradation by SCF, an E3 ubiquitin ligase. Therefore, the inhibitory complex misses two of its key components and cannot be assembled. Thus, repression of the HXT genes is abolished, leading to the expression of the glucose transporters and subsequently glucose import. is a plasma membrane protein in yeasts that consists of 12 (2x6) transmembrane domains, like the homologous glucose transporters. Its structure is distinct from the homologous transporters in particular by a long C-terminal tail which is predicted to reside in the cytoplasm. The long C-terminal tail plays an important role in glucose signaling and is probably the signaling domain itself. A soluble version of the C-terminal tail alone is sufficient to induce glucose transport. All glucose transporters including contain an arginine residue situated in a cytoplasmic loop preceding the fifth transmembrane domain. If this position is mutated, adopts a state of constant glucose induction irrespective of whether there are nutrients present or not; this suggests an involvement in the glucose sensing process. The regulation of in "S | https://en.wikipedia.org/wiki?curid=22513078 |
Snf3 cerevisiae" and its downstream events are still poorly understood, but it seems clear that a second glucose sensor Rgt2 influences and vice versa. Furthermore, it is unclear whether these two proteins sense the glucose concentration on the outside or inside the cell. and Rgt2 influence directly or indirectly several Hxt-transporters which are responsible for the glucose uptake. Low extracellular glucose concentrations are sensed by the protein which probably leads to the expression of Hxt2-Genes for high affinity glucose transporters, while Rgt2 senses high glucose concentrations and leads to the expression of low affinity glucose transporters, like Hxt1 Although the downstream pathway is poorly understood it seems that and Rgt2 transmit a signal directly or indirectly to Grr1, the DNA binding protein Rgt1, and the two cofactors Ssn6 and Tup1. Also needed for the transcription are the two nuclear proteins Mth1 and Std1. | https://en.wikipedia.org/wiki?curid=22513078 |
Gold party A gold party is similar to a Tupperware party in that a small group gathers at a host's home to sell their gold jewelry to a gold buyer. They were popular as people looked for ways to raise money during the Obama Recession. The buyer, generally, weighs and tests jewelry and other items for party guests. The testing includes a variety of means, including acid tests, magnet tests, arocking, and other methods to determine gold content. If a guest decides to sell the items, the buyer pays her at the party, and the item is sent to a refinery to be melted down. The host receives a commission for each sale, usually around 10%, but sometimes up to 87% Consumer advocates advise attendees to value their gold before attending a party, as valuations given at gold parties are not always the best possible price, and can be affected by the profit margins required by the two middlemen (the host and the buyer) between the seller and the refinery. | https://en.wikipedia.org/wiki?curid=22514360 |
1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC, EDAC or EDCI) is a water-soluble carbodiimide usually handled as the hydrochloride. It is typically employed in the 4.0-6.0 pH range. It is generally used as a carboxyl activating agent for the coupling of primary amines to yield amide bonds. Additionally, EDC can also be used to activate phosphate groups in order to form phosphomono-esters and phosphodiesters. Common uses for this carbodiimide include peptide synthesis, protein crosslinking to nucleic acids, but also in the preparation of immunoconjugates. EDC is often used in combination with "N"-hydroxysuccinimide (NHS) for the immobilisation of large biomolecules. Recent work has also used EDC to assess the structure state of uracil nucleobases in RNA. EDC is commercially available. It may be prepared by coupling ethyl isocyanate to "N","N"-dimethylpropane-1,3-diamine to give a urea, followed by dehydration: EDC couples primary amines to carboxylic acids by creating an activated ester leaving group. First, the carbonyl of the acid attacks the carbodiimide of EDC, and there is a subsequent proton transfer. The primary amine then attacks the carbonyl carbon of the acid which forms a tetrahedral intermediate before collapsing and discharging the urea byproduct. The desired amide is obtained. | https://en.wikipedia.org/wiki?curid=22516223 |
Biodyl is a trademark of Merial for a dietary supplement used in animals. It is manufactured in two formulations: a powder for use in an individual animal's drinking water, and an injectable solution. The injectable solution is available by veterinary prescription in some countries and over the counter in others. is formulated as a powder to be given in water, and as an injectable solution. The injectable solution is given under the skin, in the muscle, or in a vein, depending on the species of animal. Its intended uses include reducing physiological stress such as due to being transported, and preventing azoturia in performance animals. The manufacturer's own product information describes as an "injection solution containing metabolic constituents (adenosine triphosphoric acid or ATP, magnesium and potassium aspartate, sodium selenite and vitamin B 12) for debility, convalescence and myopathies." Composition: In the United States, is not FDA approved, "in that there is not in effect an approval of an application filed with respect to its intended use or uses". The manufacturer however, states that "is safe when used as directed. It has been around from the 1950s and adverse reactions have been exceedingly rare over many years of tracking. Less than one animal in over 2 million doses." In April 2009, the sudden deaths of 21 polo ponies at Palm Beach International Polo Club in Florida were attributed by a polo team captain to error or tampering in the team's supply of Biodyl | https://en.wikipedia.org/wiki?curid=22523721 |
Biodyl A newspaper in Argentina reported 3 similar deaths of horses at an international competition in Uruguay. In the United States, concerns about a possible manufacturing error or tampering were lost amid a media outcry about the "illegal" use of "illegal" drugs not approved by the FDA, even "banned" by the FDA. In the US, is neither an illegal drug nor a banned drug, but it is an unapproved drug. Although is a dietary supplement, a type of product that normally is not subject to FDA approval, FDA approval is required to market injectable solutions (except animal vaccines, which are subject to USDA approval). An Associated Press story misreported an October 2008 FDA refusal to permit commercial importation of the solution as a refusal to approve the solution. In fact, is not FDA-approved because the manufacturer has never submitted an application for FDA approval. Also, the FDA may permit the importation of unapproved drugs for personal use for pets. However, on April 23 a new concern emerged when a reputable pharmacy in Ocala, Florida disclosed that in compounding a preparation for the polo ponies which may have been intended to substitute for Biodyl, the pharmacy accidentally used an incorrect quantity of one of the ingredients. Compounding of drugs for use in animals is a subject of concern for the FDA. | https://en.wikipedia.org/wiki?curid=22523721 |
Benzopyrene A benzopyrene is an organic compound with the formula CH. Structurally speaking, the colorless isomers of benzopyrene are pentacyclic hydrocarbons and are fusion products of pyrene and a phenylene group. Two isomeric species of benzopyrene are benzo["a"]pyrene and the less common benzo["e"]pyrene. They belong to the chemical class of polycyclic aromatic hydrocarbons. Related compounds include cyclopentapyrenes, dibenzopyrenes, indenopyrenes and naphthopyrenes. is a component of pitch and occurs together with other related pentacyclic aromatic species such as picene, benzofluoranthenes, and perylene. It is naturally emitted by forest fires and volcanic eruptions and can also be found in coal tar, cigarette smoke, wood smoke, and burnt foods such as coffee. Fumes that develop from fat dripping on blistering charcoal are rich in benzopyrene, which can condense on grilled goods. Benzopyrenes are harmful because they form carcinogenic and mutagenic metabolites (such as (+)-benzo["a"]pyrene-7,8-dihydrodiol-9,10-epoxide from benzo["a"]pyrene) which intercalate into DNA, interfering with transcription. They are considered pollutants and carcinogens. The mechanism of action of benzo[a]pyrene-related DNA modification has been investigated extensively and relates to the activity of cytochrome P450 subclass 1A1 (CYP1A1). Seemingly, the high activity of CYP1A1 in the intestinal mucosa prevents major amounts of ingested benzo[a]pyrene from entering portal blood and systemic circulation | https://en.wikipedia.org/wiki?curid=22523849 |
Benzopyrene The intestinal (but not hepatic) detoxification mechanism seems to depend on receptors that recognize bacterial surface components (TLR2). Evidence exists to link benzo["a"]pyrene to the formation of lung cancer. In February 2014, NASA announced a greatly upgraded database for tracking polycyclic aromatic hydrocarbons (PAHs), including benzopyrene, in the universe. According to scientists, more than 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life. PAHs seem to have been formed shortly after the Big Bang, are widespread throughout the universe, and are associated with new stars and exoplanets. | https://en.wikipedia.org/wiki?curid=22523849 |
Thallium iodide can refer to: | https://en.wikipedia.org/wiki?curid=22527943 |
Walter White (Breaking Bad) Walter Hartwell White Sr., also known by his clandestine alias Heisenberg, is a fictional character and the main protagonist of the American neo-Western crime drama television series "Breaking Bad". He is portrayed by Bryan Cranston. A graduate of the California Institute of Technology (Caltech), Walter co-founded the company Gray Matter Technologies with his close friend Elliott Schwartz and his then-girlfriend Gretchen. He left Gray Matter abruptly, selling his shares for $5,000. Soon afterward, the company made a fortune, much of it from his research. Walt subsequently moved to Albuquerque, New Mexico, where he became a high school chemistry teacher. "Breaking Bad" begins on Walt's 50th birthday, when he is diagnosed with Stage IIIA lung cancer. After this discovery, he resorts to manufacturing methamphetamine and drug dealing with his former student Jesse Pinkman (Aaron Paul) to ensure his family's financial security after his death. He is pulled deeper into the illicit drug trade, becoming more and more ruthless as the series progresses, and later adopts the alias "Heisenberg", which becomes recognizable as the kingpin figure in the local drug trade. Series creator Vince Gilligan has described his goal with Walter White as "turning Mr. Chips into Scarface" and deliberately made the character less sympathetic over the course of the series. Walt's evolution from mild-mannered school teacher and family man to a ruthless criminal mastermind and murderer is the show's central focus | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Although AMC officials initially hesitated to cast Cranston due to his previous comedic role on "Malcolm in the Middle", Gilligan cast him based on the actor's past performance in the "X-Files" episode "Drive", which Gilligan wrote. Cranston contributed greatly to the creation of his character, including Walt's backstory, physical appearance, and personality traits. Both the character and Cranston's performance have received critical acclaim, with White frequently being mentioned as one of the greatest and most iconic television characters of all time. Cranston won four Primetime Emmy Awards for Outstanding Lead Actor in a Drama Series, three of them being consecutive, becoming the second actor to do so, after Bill Cosby for "I Spy" in the 1960s. Following his fourth win, Cranston tied Dennis Franz for the most wins in the category's history. He is the first man to win a Critics' Choice, Golden Globe, Primetime Emmy, and Screen Actors Guild Award for his performance. In the Spanish-language remake "Metástasis", his character is renamed Walter Blanco ("blanco" being the Spanish translation of "white") and is portrayed by Diego Trujillo. "Breaking Bad" creator Vince Gilligan had wanted his lead character to be a protagonist that turned into an antagonist over the course of the show, or as Gilligan had described in other ways, turning Mr. Chips into Scarface | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Gilligan needed to have this character come into a midlife crisis that would put him into seeking risky options that would turn him into more criminal activities. As the premise of "Breaking Bad" was based on a humorous idea that he and his fellow writer from "The X-Files", Thomas Schnauz had come with of driving around in an RV making methamphetamine, Gilligan made Walter a chemistry teacher and who, until the start of the show, would have never violated the law. Gilligan cast Bryan Cranston for the role of Walter White based on having worked with him in a sixth season episode of the science fiction television series "The X-Files", where Gilligan worked as a writer. Cranston played an anti-Semite with a terminal illness who took Fox Mulder (David Duchovny) hostage. Gilligan said the character had to be simultaneously loathsome and sympathetic, and that "Bryan alone was the only actor who could do that, who could pull off that trick. And it is a trick. I have no idea how he does it." AMC officials were initially reluctant with the casting choice, having known Cranston only as the over-the-top character Hal on the comedy series "Malcolm in the Middle" and approached actors John Cusack and Matthew Broderick about the role. When both actors declined, the executives were persuaded to cast Cranston after seeing the "X-Files" episode. Cranston contributed a great deal to the character's persona | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) When Gilligan left much of Walter's past unexplained during the development of the series, the actor wrote his own backstory for the character. At the start of the show, Cranston gained 10 pounds to reflect the character's personal decline. He had the natural red highlights of his hair dyed a regular brown. He collaborated with costume designer Kathleen Detoro on a wardrobe of mostly neutral green and brown colors to make the character bland and unremarkable, and worked with makeup artist Frieda Valenzuela to create a mustache he described as "impotent" and like a "dead caterpillar". Cranston also repeatedly identified elements in scripts where he disagreed with how the character was handled, and would go so far as to call Gilligan directly when he could not work out disagreements with the episode's screenwriter(s). Cranston has said he was inspired partially by his father for how Walt carries himself physically, which he described as "a little hunched over, never erect, [as if] the weight of the world is on this man's shoulders". In contrast to his character, Cranston has been described as extremely playful on set, with Aaron Paul describing him as "a kid trapped in a man's body". Gilligan has said it has been difficult to write for Walter White because the character is so dark and morally questionable: "I'm going to miss the show when it's over, but on some level, it'll be a relief to not have Walt in my head anymore | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) " As the series progressed, Gilligan and the writing staff of "Breaking Bad" made Walt more and more unsympathetic. Gilligan said: "He's going from being a protagonist to an antagonist. We want to make people question who they're pulling for, and why." Cranston said by the fourth season: "I think Walt's figured out it's better to be a pursuer than the pursued. He's well on his way to badass." Regarding White's fate in the series ending, Cranston foresaw it as "ugly [with no] redemption", although earlier, Gilligan divulged his plans to "end on a high note, in a way that will satisfy everyone". Walter White was an only child. Walt's father died of Huntington's disease when he was six years old. He studied chemistry at the California Institute of Technology, where he conducted research on proton radiography that helped a team win a Nobel Prize in Chemistry in 1985. After graduate school, Walt founded the firm Gray Matter Technologies with Elliott Schwartz (Adam Godley), his former classmate and close friend. Around this time, Walt dated his lab assistant, Gretchen (Jessica Hecht). He left both Gretchen and Gray Matter Technologies, selling his financial interest in the company for $5,000. Gretchen and Elliott later married and made a fortune, much of it from Walt's research. Though they remain friendly, Walt secretly resents both Gretchen and Elliott for profiting from his work | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) At the age of 50, Walt works as a high school chemistry teacher in Albuquerque, New Mexico, providing instruction to uninterested and disrespectful students. Walt also has another job at a local car wash to supplement his income, which proves to be particularly humiliating when he has to clean the cars of his own students. Walt and his wife Skyler (Anna Gunn) have a teenage son named Walter Jr. (RJ Mitte), who has cerebral palsy. Skyler is also pregnant with their second child, Holly, who is born at the end of season two. Walt's other family includes Skyler's sister, Marie Schrader (Betsy Brandt); her husband, Hank (Dean Norris), who is a DEA agent; and his mother, who is never seen. On Walt's 50th birthday, during his surprise party, he watches a news report about Hank arresting methamphetamine dealers. Walt is impressed by the monetary returns from the meth operation, and Hank offers to take him as a ride-along to a DEA bust. The next day, Walt faints at the car wash and is taken to a hospital; there, he is told he has inoperable lung cancer and will likely die in two years. During the ride-along, Hank busts a crystal meth lab, taking cook Emilio Koyama (John Koyama) into custody. Walt sees Emilio's partner fleeing the scene; it is one of his former students, Jesse Pinkman (Aaron Paul). Looking to secure his family's well-being by producing and selling meth, Walt tracks Jesse down and blackmails him into selling the meth that Walt will cook | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt gives Jesse his life savings to buy an RV that they can use as a rolling meth lab. After their first cook in the RV, Jesse brings a sample of the extremely pure meth to distributor Domingo "Krazy-8" Molina (Max Arciniega), and then brings Krazy-8 and the now-released Emilio to see the cook site. Emilio recognizes Walt as accompanying the DEA during the bust, and believes he is an informant. Krazy-8 forces Walt to show them how he cooked such pure meth or be killed. Walt pretends to start a cook but instead produces toxic phosphine gas which kills Emilio and incapacitates Krazy-8. Walt and Jesse secure Krazy-8 to a structural post in Jesse's basement with a U-lock around his neck, and Walt struggles with the decision on whether to kill him. After Krazy-8 promises not to retaliate, Walt starts to unlock the lock to let Krazy-8 go, but sees him reach for a broken piece of plate to stab Walt with as soon as he was freed. Walt panics and garrotes him to death with the lock. The experience shakes Walt, and he tells Jesse he will not cook meth anymore. Walt eventually tells his family about his cancer diagnosis, and they urge him to undergo expensive chemotherapy. He initially does not want to go through the treatment, fearing that his family will remember him as a burden and a helpless invalid, much as he remembers his own father. Later he relents and agrees to undergo treatment, but refuses Gretchen and Elliot's offer to pay for it, choosing to re-enter the drug trade with Jesse | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) He shaves his head to hide his chemotherapy-induced hair loss. Dissatisfied with Jesse's slow pace of selling the meth, Walt pushes him to sell it in bulk to local drug lord Tuco Salamanca (Raymond Cruz), who has taken over Krazy-8's former territory. Discovering that Tuco stole the meth and savagely beat Jesse, Walt visits Tuco's lair with another bag of crystals, claiming to be "Heisenberg" (a reference to the theoretical physicist Werner Karl Heisenberg). After Tuco mocks Jesse, refuses to pay for the bag, and implies that Walt will suffer the same fate as Jesse, Walt blows up part of the lair; the bag contained fulminated mercury, not meth. Impressed by the boldness of "Heisenberg", Tuco reluctantly agrees to pay for his meth upon delivery in the future. Walt revels in his success and adopts the Heisenberg alias in his business dealings going forward. In order to make larger batches of meth to take advantage of their new arrangement with Tuco, Walt and Jesse switch from using pseudoephedrine to methylamine as a precursor. This tints their meth blue, which becomes a signature of Walt's product. The pair begin to fear for their lives when, after testing the purity of the meth they delivered by snorting some of it, Tuco senselessly beats to death one of his own men, No-Doze (Cesar Garcia). Walt's "blue meth" becomes incredibly popular, to the point that Hank takes notice and raids Tuco's operation. A paranoid Tuco evades the bust, carjacks Jesse, and kidnaps Walt | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) He brings them to an isolated house in the desert, planning to take them deep into Mexico where they would be forced to cook their blue meth for the cartel. After a failed attempt to poison Tuco, they manage to escape on foot. Hank, who had been searching for Jesse, spots his car at the house and kills Tuco in a gunfight. Walt is arrested when he takes off all his clothes in a grocery store. He explains his disappearance by claiming that he had gone into a fugue state as a result of his cancer medication and simply wandered off. Walt finds out that his cancer is in remission, and plans to leave the meth business again after selling the final 38 lb (17 kg) of meth. He hires unscrupulous criminal attorney Saul Goodman (Bob Odenkirk) to cover his involvement in the drug trade and launder his drug money. Seeing they need a new distributor to sell the large quantity of product they have remaining, Saul arranges a meeting at a local restaurant with a mysterious meth kingpin. Jesse shows up for the meeting high on heroin, and leaves when the kingpin does not show. Walt realizes that the restaurant owner, Gus Fring (Giancarlo Esposito) was the man they were supposed to meet. Under questioning by Walt, Gus explains that he was observing the pair, and refuses to work with them because Jesse is a drug addict. However, a few days later he gives Walt a chance to prove himself by delivering all the meth to a truck stop within an hour | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt breaks into Jesse's apartment where the meth is stored, and finds him passed out with his girlfriend Jane Margolis (Krysten Ritter). Walt finds the meth and makes the delivery on time, but misses the birth of his daughter. Jane blackmails Walt into giving Jesse his share of their drug money, after Walt initially refused due to Jesse's drug use. After talking to a stranger at a bar about family – not knowing that the man is Jane's father Donald (John de Lancie) – Walt again breaks into Jesse's apartment to find the lovers passed out in a heroin stupor. Jane rolls onto her back, vomits, and begins to choke. Walt does nothing to help her, and watches her die. Walt has Saul's cleaner, Mike Ehrmantraut (Jonathan Banks), clear any connection Jesse has to Jane's death, and convinces Jesse to enter rehab. Walt undergoes an operation to remove the remaining cancerous growth. Walt's anesthesia-induced references to a "second cell phone" – the one he uses to deal drugs – makes Skyler suspicious, leading her to uncover many of his lies and leave with their children. Just after her departure, two passenger planes collide directly above Walt's house; the accident was caused by Donald, who works as an air traffic controller and was so overcome with grief that he was not paying attention to his work. Walt watches the accident in horror, unaware that he is indirectly responsible for it | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt decides to get out of the meth business, refusing Gus' offer to produce meth in a state-of-the-art laboratory hidden under an industrial laundry for a million dollars a month. Now separated from Skyler and living in an apartment, Walt admits to her that he has been financing his treatment by cooking meth. Horrified, Skyler asks for a divorce in return for her silence, and demands that Walt have nothing to do with their children. After he discovers Jesse is cooking and selling his own version of the blue meth, Walt agrees to cook his meth for Gus. He is assisted by accomplished chemist Gale Boetticher (David Costabile) and the business seems to be running smoothly. Jesse continues to cook his own version of the blue meth, with Skinny Pete and Badger as his distributors, but this leads to Hank nearly catching Jesse and Walt while he was following a lead on an RV he believed was being used to cook blue meth. To avoid being discovered hiding in the RV, Walt and Jesse, aided by Saul, place a phone call to distract Hank, making him believe his wife Marie has suffered a car accident. Hank decides to leave the pursuit of the RV only to find out that Marie is fine, allowing Walt and Jesse to dispose of the RV. This enrages Hank enough to badly beat up Jesse at his house and send him to the hospital. Jesse threatens Walt by telling him he’ll press charges on Hank; he also tells Walt that if he’s caught, he would make a deal to give up Heisenberg | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Fearing that any of this will derail Hank’s career in law enforcement, Walt is forced to convince Gus to hire Jesse to replace Gale as his assistant. He also agrees to share 50% of his earnings with Jesse. Gambling that Skyler will not turn him in to the police due to the harm it would cause to their son, Walt returns to his house. After a few attempts at bluffing him, Skyler comes to uneasily accept the situation and helps Walt launder his drug money, but refuses to have anything to do with him outside of business. The rift in their marriage worsens when Skyler sleeps with her boss, Ted Beneke (Christopher Cousins). Walt tries to get back at her by making a pass at the principal at his school, who puts him on indefinite suspension. Tuco's cousins Marco and Leonel Salamanca (Luis and Daniel Moncada) seek revenge against those responsible for his death, and find out Walt's identity from their uncle Hector Salamanca (Mark Margolis). Believing that Walt betrayed Tuco, they go to his house and prepare to kill him with a silver axe. Gus discovers this, and to protect his investment in Walt, he convinces them to instead target Hank, who actually killed Tuco. The cousins die in the attempt on Hank's life, while Hank survives, but is temporarily paralyzed from the waist down. Skyler strong-arms Walt into paying for Hank's care, and creates a cover story about Walt counting cards at casinos to explain how he made his money | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt angers Gus by killing two of Gus' dealers in an attempt to protect Jesse, who had been planning to kill them himself for their murder of a child gang member. Gus responds by putting a hit on Jesse and re-hiring Gale as Walt's assistant, with the intention of replacing Walt as soon as possible. Walt plots to kill Gale to avoid becoming disposable, but Gus' henchman Victor lures Walt to the laundry facility, where Mike is waiting to kill him. Walt frantically calls Jesse and tells him that he is about to be killed and Jesse will have to take out Gale himself. Victor rushes to Gale's house but finds him shot dead. In the aftermath of Gale's murder, Mike holds Walt at the lab to await Gus' arrival. Victor arrives with Jesse, and proceeds to start the cook process himself to show Gus that Walt and Jesse are not indispensable. Gus, however, kills Victor in front of Mike, Walt, and Jesse, in a gruesome show of force. The tension of working under tighter security creates a rift between Walt and Jesse, and Gus uses the opportunity to bring Jesse to his side by having Mike train him. Walt deduces that Gus plans to eventually kill him and replace him with Jesse. He gives Jesse homemade ricin with which to poison Gus, but Jesse never goes through with it. Walt shows up at Jesse's house and tries to convince him to betray Gus, but Jesse refuses and tells Walt they are finished. Meanwhile, Skyler buys the car wash where Walt used to work and uses it to launder his drug money | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Hank suspects that Gus is involved in the blue meth business. With the DEA skeptical and unable to drive due to his condition, he enlists Walt's help in the investigation as a driver and tracker. Walt manages to sabotage the investigation, but Gus blames him nonetheless. Gus rids himself of the Mexican cartel's influence in the area with the help of Mike and Jesse. He then fires Walt and threatens to kill Walt's entire family if he causes any more trouble. Walt tries to use one of Saul's connections to get him and his family relocated, but finds that Skyler has used most of his drug money to pay off Ted Beneke's IRS fines to avoid having their own lives investigated. After arranging for Saul to report that Hank was being targeted for assassination again, so that his family would be protected by the DEA, Walt resolves to kill Gus. When Brock, the son of Jesse's new girlfriend Andrea, falls desperately ill with ricin-like symptoms, Jesse attacks Walt, believing that he poisoned him. Walt manages to convince Jesse that Gus is the one responsible. After an attempt to kill Gus with a car bomb fails, Walt discovers from Saul that Gus has been visiting Tuco's uncle Hector in his nursing home, to taunt him about the cartel's defeat and the end of the Salamanca family. Walt makes a deal with Hector to draw Gus in by setting up a meeting with the DEA. When Gus comes to the nursing home to kill Hector for turning informant, Hector detonates a pipe bomb Walt made, killing both himself and Gus | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt rescues Jesse, who had been kept as a prisoner in the lab, and together they destroy all the evidence and torch the lab. After Brock recovers, Jesse learns that the boy had likely been poisoned by accidentally eating Lily of the Valley berries, not ricin. Walt responds that killing Gus was still the right thing to do. Walt calls Skyler to tell her they are safe and that he has "won", as the camera pans to a potted Lily of the Valley plant next to Walt's pool, indicating that Walt had in fact poisoned Brock to goad Jesse into action. Mike attempts to kill Walt in retaliation for Gus' death, but Jesse intervenes and convinces the two men to work together to eliminate their connection to the destroyed lab. The three eventually start a new meth production system with the help of a corrupt pest control company, using residents' homes to cook meth while they are fumigated, using methylamine provided by Lydia Rodarte-Quayle (Laura Fraser), a representative for the conglomerate that owned Gus's franchise. When her supply is discovered to be tracked by the police, she leaks them information on a train carrying the chemical so they can plan a robbery. The robbery is successful, but Todd Alquist (Jesse Plemons), one of the pest control workers, kills a young boy who had seen them. Horrified, Jesse and Mike resolve to leave the business. A Phoenix drug lord named Declan offers to buy out the operation for $15 million in order to remove his competition | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt convinces him to pay off Jesse and Mike and begin distributing Walt's meth instead. Hank connects Mike to the blue meth, and begins pressing several of his associates, who are now in prison, to give information on the blue meth operation. When Walt delivers Mike's share of Declan's payment, Mike refuses to reveal these prisoners' identities and insults Walt, blaming him for all the problems they've encountered; Walt shoots him dead in a fit of rage. Obtaining a list of the prisoners from Lydia, he enlists Todd's uncle Jack (Michael Bowen), a criminal with ties to the Aryan Brotherhood prison gang, to kill the nine men simultaneously at multiple prisons to prevent the DEA from realizing that they were being targeted until it was too late. After a few months, Walt has earned more than $80 million from meth, and Skyler convinces him to stop. Walter leaves the meth business, and the kids return home. During a family barbecue, Hank finds a copy of Walt Whitman's "Leaves of Grass" in the bathroom, the same copy given to Walt by Gale; upon reading Gale's handwritten inscription referring to Walt as "the other W.W." Hank realizes that Walt is the drug lord he has been pursuing. Hank accuses Walt of being Heisenberg, which a stunned Walt neither confirms nor denies. Walt says that his cancer is back and he will likely be dead in six months, making an arrest pointless. Hank says they can talk if Walt gives up his children, but Walt refuses and tells Hank to "tread lightly" | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt eventually forces Hank to remain silent by crafting a fake confessional videotape in which he states that Hank is Heisenberg. Walt buries his money in seven barrels on the Tohajiilee Indian Reservation, and convinces Jesse to go into a relocation program. While waiting to be picked up, Jesse figures out that Walt poisoned Brock. Hank approaches Jesse and offers to help bring down Walt. With Hank's help, Jesse lures Walt into a trap by claiming to have found his money. Walt makes arrangements with Jack and his men to kill Jesse, in exchange for promising to help teach Todd how to cook meth. When Walt realizes Jesse is with Hank, he tries to call off the deal to protect Hank, but is subdued by Hank and his DEA partner Steven Gomez (Steven Michael Quezada). Just then, Jack and his men arrive and fire on the group, killing Gomez and wounding Hank; Jack then executes Hank, despite Walt pleading for his brother-in-law's life. Jack's men take all but one barrel of Walt's money and abduct Jesse; as Jesse is taken away, Walt spitefully tells him that he watched Jane die. Walt tries to persuade Skyler and Walter Jr. to go on the run with him, but they refuse. He kidnaps Holly, but has a moment of conscience and leaves her to be found and returned. He calls Skyler, knowing that the police are listening in, and berates her for failing to follow his orders, as a way of clearing her of involvement in his crimes. Walt then goes into hiding and is sent to live in isolation in New Hampshire | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) After several months alone, Walt goes to a local bar, where he calls Walter Jr. and tries to give him money. Walter Jr. angrily rejects the gesture, however, and hangs up. Feeling hopeless, Walt calls the DEA and gives himself up. As he waits for them, however, he sees Gretchen and Elliott on "Charlie Rose" downplaying his contributions to Gray Matter and resolves to return to Albuquerque to put things right. When Walter arrives in Albuquerque – on his 52nd birthday – he confronts Gretchen and Elliott at their home and intimidates them into putting his remaining money into a trust fund for Walter Jr. He then visits Skyler and provides her the location of Hank and Steve's unmarked grave which he suggests she use to barter for a deal with the prosecutor, and finally admits to her that he entered the meth business for himself, not his family. As a token of appreciation, Skyler lets him see his daughter, Holly, one last time. He then arranges to see Lydia, surreptitiously poisoning her drink with ricin after learning where Jack has taken Jesse. Walt drives to Jack's compound and demands to see Jesse. When they bring Jesse, who has been chained up in a lab and forced to cook meth since his abduction, Walt dives atop him while simultaneously activating a remote machine gun mounted in his car that injures Jack and kills all of his men except for Todd. Jesse proceeds to strangle Todd to death, while Walt finishes off Jack by shooting him in the head. Walt asks Jesse to kill him, but Jesse tells him to do it himself | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) Walt then finds that he has been wounded by a ricocheted bullet. He answers a call from Lydia on Todd's phone and coldly informs her that she is going to die as a result of the poisoned drink she consumed. He exchanges a knowing nod with Jesse, who escapes the compound. Walt takes a moment to admire the lab equipment Jesse had been using, then collapses dead on the floor just as the police arrive. Cranston reprises his role in the movie " " in a flashback scene, taking place during the events of "4 Days Out" from the show's second season. Walt and Jesse are sitting down at a buffet breakfast talking about how they are going to move a batch of recently cooked meth. Walt asks Jesse what he would like to study if he went to college and encourages Jesse to find a life outside of cooking meth in the future. He suggests that Jesse should study business and marketing, remarking that Jesse is a natural at it and that he "could practically teach the class" himself using his vast knowledge. Afterwards, Walt tells Jesse: "You're really lucky, you know that? You didn't have to wait your whole life to do something special." In the present, Jesse, Skinny Pete and Badger see various news reports on the aftermath of Walt's massacre. In a news report Jesse listens to, Walt is confirmed to be dead with the same report mentioning an investigation of a Houston woman poisoned by Walt – implied to be Lydia – who is in critical condition and not expected to survive | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) The character development of Walter White, as well as Bryan Cranston's performance, has received near-universal acclaim, from both critics and audiences. Walter White is considered to be one of the greatest and most iconic characters in television history. The web magazine "Grantland" quotes Andy Greenwald as analyzing Walter White differently from some others, including Vince Gilligan. Greenwald states: Since watching [the fifth season episode, "Confessions"], I've been thinking a lot about Walter White, the 'shadow' on his recent CAT scan, and the black cloud that has long since overtaken his heart. The closer we get to the end, the more Walt scrabbles around and lashes out like a rat when it's surrounded, the less I'm buying Vince Gilligan's whole 'Mr. Chips to Scarface' quote as an analogy for Walt's transformation. That's the route the character has taken these five seasons, sure, in terms of his changing context. But I think the most horrifying part of "Breaking Bad" may be that Walt, at his core, didn't really transform at all. It wasn't greed or generosity or cancer or fear that fueled this reign of death and destruction. It was resentment. Seething, burning resentment, the kind that forms not due to poor treatment but due to an innate knowledge that you, the aggrieved, are better than said treatment, better than everyone who has somehow gotten the better of you over the years. ... Every moment Walt spent in front of a classroom he was thinking about how beneath him it all was | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) He was a genius; he was meant to be a millionaire, not this castrated cross between stepping stone and doormat. When you got down to it, Walt desperately wanted to teach every one ... a lesson, and I don't mean in the style of Mr. Chips. Similarly, Scott Meslow wrote in "The Atlantic" that Walt's capacity for villainy was present well before the series even began, and that cancer was only the catalyst: "all the elements that have since turned him into a monster were already in place." "New York" magazine writer Emma Rosenblum said Bryan Cranston "pulls off the unassuming White with flawless subtlety: a waxy pallor, a slump of the shoulders, and a sense of doom that is palpable". "The Hollywood Reporter" writer Tim Goodman praised as courageous Vince Gilligan's decision to transform Walter White into an unsympathetic character: "You don't take your main character and make him unlikable. You just don't. Nobody does that. Nobody has ever really done that to this extent." Robert Bianco of "USA Today" called Walt "one of the greatest dramatic creations ever to grace our TV screens". In 2011, the "New York Times" named Cranston as one of the "eight actors who turn television into art". Following the show's conclusion, actor Anthony Hopkins wrote a fan letter to Cranston, wherein he praised the show and called Cranston's performance as Walter White the best acting he had ever seen. Cranston has received various awards and nominations for his performance as Walter White | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) For the first three seasons, he won the Primetime Emmy Award for Outstanding Lead Actor in a Drama Series thrice consecutively, becoming the first actor to accomplish this feat since Bill Cosby for "I Spy". Cranston was also nominated in 2012 and 2013 for season four and the first half of season five, but lost out to Damian Lewis for "Homeland" and Jeff Daniels for "The Newsroom", respectively. He also won his fourth Primetime Emmy Award for Outstanding Lead Actor in a Drama Series, at the 66th Primetime Emmy Awards At the annual Golden Globe Awards, Cranston has been nominated for the Best Actor – Television Series Drama accolade on four occasions for his role in "Breaking Bad", in 2011, 2012, 2013 and 2014, winning in 2014 for the second half of season five. At the Screen Actors Guild Awards, Cranston has been nominated for Male Actor in a Drama Series five times, in 2010, 2011, 2012, 2013 and 2014, winning in 2013 and 2014, for both parts of season five. Also, Cranston has been nominated with the rest of the cast for Performance by an Ensemble in a Drama Series, in 2012, 2013 and 2014, winning in 2014. In addition, Cranston has won the Satellite Award for Best Actor: Drama Series three times consecutively, in 2008, 2009 and 2010, for seasons one, two and three, and has been nominated in 2011, 2012 and 2014 for seasons four and five | https://en.wikipedia.org/wiki?curid=22530352 |
Walter White (Breaking Bad) He won the TCA Award for Individual Achievement in Drama in 2009, and was nominated in 2010, 2012 and 2013; was nominated twice for the Prism Award for Best Performance in a Drama Series Multi-Episode Storyline; won two Saturn Awards for Best Actor on Television in 2012 and 2013 (tying with Kevin Bacon for "The Following" on the latter occasion), and was nominated in 2009, 2010 and 2011; and won the Golden Nymph Award for Outstanding Actor in a Drama Series in 2013. Over time Walter White had developed a cult following, spawning fan websites like "Heisenberg Labs", "Walt's Wardrobe", and "Save Walter White", which is an exact replica of the website Walter White's son creates in the series to raise money to pay for his father's cancer treatments. A platform-style "Breaking Bad" video game has been created as a tribute to Walter White. In 2015, series creator Vince Gilligan publicly requested fans of the series to stop reenacting a scene in which Walt angrily throws a pizza on his roof after Skyler refuses to let him inside; this came after complaints from the home's real-life owner. Cranston reprised his role of the character in a commercial for Esurance which aired during Super Bowl XLIX, one week before the premiere of "Breaking Bad" spin-off "Better Call Saul". A "Breaking Bad" fan group placed a paid obituary for Walter White in the "Albuquerque Journal" on October 4, 2013 | https://en.wikipedia.org/wiki?curid=22530352 |
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