Metal sensing

The Series 1151 differential pressure transmitter manufactured by Rosemount (MinneapoHs, Minnesota) uses a capacitance sensor in which capacitor plates are located on both sides of a stretched metal-sensing diaphragm. This diaphragm is displaced by an amount proportional to the differential process pressure, and the differential capacitance between the sensing diaphragm and the capacitor plates is converted electronically to a 4—20 m A d-c output. 

To explain the properties of more concentrated solutions it was suggested that solvated electrons were released to form electrons essentially free in the metallic sense. 

Non-aqueous synthetic methods have recently been used to assemble mesoporous transition metal oxides and sulfides. This approach may afford greater control over the condensation-polymerization chemistry of precursor species and lead to enhanced surface area materials and well ordered structures [38, 39], For the first time, a rational synthesis of mesostructured metal germanium sulfides from the co-assembly of adamantanoid [Ge4S ()]4 cluster precursors was reported [38], Formamide was used as a solvent to co-assemble surfactant and adamantanoid clusters, while M2+/1+ transition metal ions were used to link the clusters (see Fig. 2.2). This produced exceptionally well-ordered mesostructured metal germanium sulfide materials, which could find application in detoxification of heavy metals, sensing of sulfurous vapors and the formation of semiconductor quantum anti-dot devices. 

Several pathways exist in which the metal sensing and the transcriptional regulatory functions are handled by two separate proteins (6, 15). A sensor protein spans the cytoplasmic membrane, senses the amount of metals in the periplasm, and communicates this information to the regulatory protein that is inside of the cell. When the concentration of the appropriate metal reaches critical levels, the internal kinase domain of the sensor protein phosphorylates the cytosolic regulatory protein, which activates it to control transcription. These two-component systems are thought to help protect the periplasm from damage. 

Harvie DR, Andreini C, Connolly BA, Yoshida K, Fujita Y, Harwood CR, Radford DS, Tottey S, Cavet JS, Robinson NJ. lYedict-ing metals sensed by ArsR-SmtB repressors Allosteric interference by a non-effector metal. Mol. Microbiol. 2006 59 1341-1356. 

FIGURE 5.17 Fluorescent dendrimers for metal sensing by (a) quenching or (b) enhancement of the emission. 

FIGURE 5.18 G2 dendrimer capped with 1,8-naphthalimide chromophores encompassing allyamine or diamine pincers for metal sensing. 

Many natural waters possess the property of partially masking the presence of metal ions by rendering them unavailable for measurement by conventional chemical and biological metal-sensing techniques. Although it is as yet not possible to distinguish which of the many possible mechanisms (e.g. precipitation, colloidal adsorption, complexation, etc.) gives rise to this... 

A resistance temperature detector (RTD) is a device to measure temperature by relating it to changes in the electrical resistance of a metallic sensing element. The resistance of a typical RTD increases by about 0.3-0.4 % of its room-temperature value for every degree Kelvin of temperature increase. With care, RTDs can achieve accuracies of better than 0.1 K at temperatures ranging from about 14 K to over 900 °C. 

Wanekaya, A.K. (2011) Applications of nanoscale carbon-based materials in heavy metal sensing and detection. Analyst, 136, 4383. 

Waldron K, Rutherford JC, Ford D, Robinson NJ (2009) Metalloproteins and metal sensing. Nature 460 823-830... 

Another mechanism used to manipulate fluorescence characteristics of a fluorophore is called internal charge transfer (ICT). Principles of ICT were first applied in an effort to rationalize increased acidity of phenol." However, until Valeur s reports, generalization of these ideas and systematic exploitation in metal sensing were not realized. 

Sensors for measurements of oxygen in molten steel are the most important application in liquid metal sensing. As an electrolyte MgO partially stabilized, zirconia is used because of its high thermal shock resistance due to phase transformations. 

The nuclei in metals sense the spin polarization of conduction electrons through the hyperfine interaction. Thus the observed nuclear resonance frequency (Wobs is shifted with respect to Eq. (3.7) by an amount that depends on the paramagnetic spin susceptibility of the electrons. This is the Knight shift K given by... 

It should be noted that the preceding representations are merely mathematical models enabling the analyses to extend beyond the earlier elastic solutions. The actual adhesive bonds do not yield in the classical ductile metal sense. What actually happens is that the adhesive fails under the tensile component of the applied combination of shear and peel stresses, as explained by Gosse [8]. The failure mode for the peel-dominated case is a simple single fracture surface parallel to the adherends which, once started, will not arrest. Under dominant in-plane shear loads, however, the failure mode is a series of hackles inclined at... 

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