Atomizer filament

Flenderson E, Flaydon P G and Sakaguchi D S 1992 Actin filament dynamics in living glial cells imaged by atomic force microscopy Science 257 1944... 

Schematic diagram showing the development of a dipolar field and ionization on the surface of a metal filament, (a) As a neutral atom or molecule approaches the surface of the metal, the negative electrons and positive nuclei of the neutral and metal attract each other, causing dipoles to be set up in each, (b) When the neutral particle reaches the surface, it is attracted there by the dipolar field with an energy Q,. (c) If the values of 1 and <() are opposite, an electron can leave the neutral completely and produce an ion on the surface, and the heat of adsorption becomes Q,. Similarly, an ion alighting on the surface can produce a neutral, depending on the values of I and <(), On a hot filament the relative numbers of ions and neutrals that desorb are given by Equation 7.1,which includes the difference, I - <(), and the temperature, T,...

Similarly, the rate of evaporation of neutral species from a filament surface is given by Equation 7.4, in which Cq is the surface density of atoms on the surface (a complete monolayer of atoms would have a surface density of about 10 atoms/cm ). 

The F-actin helix has 13 molecules of G-actin in six turns of the helix, repeating every 360 A. Oriented gels of actin fibers yield x-ray fiber diffraction patterns to about 6 A resolution. Knowing the atomic structure of G-actin it was possible for the group of Ken Holmes to determine its orientation in the F-actin fiber, and thus arrive at an atomic model of the actin filament that best accounted for the fiber diffraction pattern. 

Electrothermal vaporization can be used for 5-100 )iL sample solution volumes or for small amounts of some solids. A graphite furnace similar to those used for graphite-furnace atomic absorption spectrometry can be used to vaporize the sample. Other devices including boats, ribbons, rods, and filaments, also can be used. The chosen device is heated in a series of steps to temperatures as high as 3000 K to produce a dry vapor and an aerosol, which are transported into the center of the plasma. A transient signal is produced due to matrix and element-dependent volatilization, so the detection system must be capable of time resolution better than 0.25 s. Concentration detection limits are typically 1-2 orders of magnitude better than those obtained via nebulization. Mass detection limits are typically in the range of tens of pg to ng, with a precision of 10% to 15%. 

Electron impact (El) ion sources are the simplest type. O2, Ar, or another (most often noble) gas flows through an ionization region similar to that depicted in Eig. 3.30. Electrons from an incandescent filament are accelerated to several tens of eV by means of a grid anode. A 20-100 eV electron impact on a gas atom or molecule typically effects its ionization. An extraction cathode accelerates the ions towards electrostatic focusing lenses and scanning electrodes. 

Holmes, K.C., Popp, D., Gebhard, W., Kabsch, W. (1990). Atomic model oftheactin filament. Nature 347, 37- 3. 

FIGURE 12.3 Atomic force microscopy (AFM) phase images of A, unaged and B, aged melamine fiber filaments at a scan area of 5 X 5 p,m. Arrows indicate direction of major fiber axis. (From Rajeev, R.S., Bhowmick, A.K., De, S.K., Gong, B., and Bandyopadhyay, S., J. Adh. Set Technol., 16, 1957, 2002. With permission.)... 

It is now believed that the most critical component in the gas phase mixture is atomic hydrogen, and indeed, this reactive atom drives the whole chemical system. Two hydrogen atoms are made when a hydrogen molecule (H ) splits apart. In a hot filament system, the thermal energy... 

N1 and Zn from a graphite rod were significantly lower than from a tantalum filament, suggesting that these free metal atoms can be liberated by chemical reduction of their respective oxides, rather than by direct thermal dissociation. Findlay et al (19) emphasized the hazards of preatomlzatlon losses of trace met s In electrothermal atomic absorption spectrometry, when the ashing temperature Is permitted to exceed the minimum temperature for vaporization of the analyte. 

Fluorescence Spectroscopy with a Carbon Filament Atom Reservoir". Anal. Chlm. Acta (1969), 27-41. 

Williams, M. and Plepmeler, . H. "Commercial Tungsten Filament Atomizer for Analytical Atomic Spectrometry". 

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