Added mass technique

Procedures for the reliable calibration of normal forces (i.e., /iN) are well established. Several methods can be used, such as the thermal fluctuation method [11-13], the reference lever [14], or the added mass technique [15]. We will mention in the following the thermal noise and the reference lever methods in some detail. 

We used a set of silicon and silicon nitride V-shaped cantilevers with nominal spring constants, kn, from 0.06 to 47 N/m, stiffer cantilevers were applied to harder materials. Actual values of spring constants were determined the fundamental resonant frequency calibration proposed earlier and cross-checked by both cantilever-against-cantilever technique and added mass technique (see review of different approaches in Ref. 6). Tip radii were measured using mixed gold nanoparticles. Measured radii were in the range of 20 - 60 nm. Shape of the tip ends at a nanometer scale was virtually symmetrical and for most tips, spherical approximation could be used. 

Introduction The term azeotropic distillation has been apphed to a broad class of fractional distillation-based separation techniques in that specific azeotropic behavior is exploited to effect a separation. The agent that causes the specific azeotropic behavior, often called the entrainer, may already be present in the feed mixture (a self-entraining mixture) or may be an added mass-separation agent. Azeotropic distillation techniques are used throughout the petro-... 

An additional dimension of information can be added to techniques if a second stage of mass analysis is used, an ion is mass-selected with a quadrupole or magnetic allowed to pass into a collision cell. A target... 

Carrier addition is widely used, not only for yield determination, but because the added mass avoids problems of radiocolloidal behavior. Other advantages of added carrier are the ability to use precipitation for radionuclide separation and purification, and avoidance of unintended coprecipitation during scavenging. When carrier is not added because no stable isotope is available or the counting source must be very thin, radionuclide deposition on container walls or on suspended solids must be avoided by applying the techniques discussed in Section 4.4, notably use of nonisotopic carrier or low pH. 

For quantitative measurements of both the interaction forces and the surface topography, the tip shape and the spring constant need to be calibrated. Various approaches to characterize the tip shape are described elsewhere. Concurrently, a series of methodologies induding the added mass methods, unloaded resonant, and reference spring techniques, as well as thermal noise analysis were developed to quantify the spring constant. More recently, new methods have been proposed for calibration of both torsional and normal spring constants with an uncertainty below 10%. " Furthermore, the torsional response of an externally driven cantilever in a viscous medium was analyzed. ... 

Other alloying ingredients in lead, eg, arsenic (0.5—0.7%) and silver [7440-22-4] (0.1—0.15%), inhibit grid growth on overcharge and reduce positive grid corrosion. Tin added to a lead alloy produces well-defined castings that are readily adapted to mass production techniques (84). 

In the carbon-14 expts, HMX/RDX product was isolated qualitatively, separated Into its components, and each component assayed for carbon-14 beta radioactivity using a liquid scintillation counting technique (Ref 11). DPT-l4C was isolated as an intermediate product from the reaction mixt and similarly radioassayed. For the nitrogen-15 tagged AN expts, HMX and RDX were assayed mass spectrometrically for i5N/i4N ratios from which atom %1SN contents were calcd. In die course of these expts, each tagged species was added initially and also at subsequent stages of the reaction process. The important observations and results are summarized as ... 

ESI-MS has emerged as a powerful technique for the characterization of biomolecules, and is the most versatile ionization technique in existence today. This highly sensitive and soft ionization technique allows mass spectrometric analysis of thermolabile, non-volatile, and polar compounds and produces intact ions from large and complex species in solution. In addition, it has the ability to introduce liquid samples to a mass detector with minimum manipulation. Volatile acids (such as formic acid and acetic acid) are often added to the mobile phase as well to protonate anthocyanins. A chromatogram with only the base peak for every mass spectrum provides more readily interpretable data because of fewer interference peaks. Cleaner mass spectra are achieved if anthocyanins are isolated from other phenolics by the use of C18 solid phase purification. - ... 

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