Application of static signal-to-noise theory to the detection and integration of dynamic signals

Static, time-independent noise terms are combined to estimate the noise and signal-to-noise ratio (S/N) of dynamic, time-dependent methods. Simplified S/N equations for shot-noise-limited and flicker-noise-limited analyte signals with and without background signal noises are given. The intuitive aspects of peak integration are justified by these equations. For an ideal Gaussian peak, the equations are used to derive the chromatographic limit of detection (LOD). A comparison of the chromatographic detection limit with the detection limit for a static system using the same amount of sample predicts poorer chromatographic detection limits because of peak broadening. A possible determinate error in area measurement is shown to result when integration limits are chosen on the basis of the static detection limit.     

ICP-AES法测定色漆可溶性金属含量

用ICP-AES法测定了色漆中的“可溶性”金属铬、镉、铅元素，考察了不同酸度对分析结果的影响，优化了测试条件。进行了回收率和精密度试验。并用原子吸收光谱国标方法进行对照，结果一致。     

Backscattering techniques for the measurement of stable isotope abundances and tracers

Prompt ion beam analysis methods can be used to measure the isotopic composition of materials. When applied using microbeams of charged particles they have the potential to measure the spatial distribution of isotopes. The value of Rutherford backscattering for isotope measurement is examined both from the point of view of the measurement of stable isotope abundances and the spatial distribution of stable isotope tracers. Parametes which affect the mass resolution and sensitivity are examined including incident particle energy and mass, scattering angle, energy spread of the incident beam, detector resolution and solid angle effects. Experimental measurement of the isotopic abundances of several elements are presented including magnesium, nickel and silver. A variety of incident ions and energies and different detection systems are used. The limitations of the method are discussed and its extension to nuclear microprobe application, with its spatial tracer determination capabilities, is appraised.     

NEAR ULTRAVIOLET AND POSTIRRADIATION DNA DEGRADATION: EFFECTS ON THE INDUCIBLE INHIBITOR OF IONIZING RADIATION-INDUCED DNA DEGRADATION

Abstract— Possible effects of near ultraviolet radiation (near UV) on DNA degradation were examined. Postirradiation DNA degradation induced by ionizing radiation in strain B_s-l ( uur-, lex- ) is shown to be inhibited by carbon monoxide (CO) and potassium cyanide (KCN) if the cells are grown on glycerol. Presumably the blockage of respiration by these agents lowers the amount of ATP in the cell. 50 kJ/m² near UV did not simulate the action of CO and KCN, indicating that at this Ruence the supply of ATP remains adequate for postirradiation DNA degradation. Near UV did not, itself, produce DNA degradation. In a strain (B/r) in which an inhibitor of postirradiation DNA degradation can be induced by both UV and ionizing radiation, near UV affects the inhibitor formation, whether administered before or after induction.     

Modelling the time dependent flow over riblets in the viscous wall region

The flow over riblets is examined computationally using a time dependent model of the viscous wall region. This 2 1/2 D model, developed by Hatziavramidis and Hanratty (1979) and modified by Nikolaides (1984) and Chapman and Kuhn (1981, 1986) assumes homogeneity in the streamwise direction so that the flow is solved only in the cross-sectional plane. The flow at the upper boundary of the computational domain (y ⁺ 40) is described using a streamwise eddy model consisting of two scales, one of the streak spacing (⁺ 100), which dominates vertical momentum transport, and a larger scale that accounts for the influence of large outer flow eddies.The protrusion height concept (Bechert and Bartenwerfer, 1989) is used to define ay ⁺=0 location for surfaces with riblets. A control volume finite element method utilizing triangular meshes is used to exactly fit the riblet cross-sectional geometry. Results obtained using fairly large riblets compare well with the limited experimental evidence available. Observations of the transient flow suggest that the riblets interact with the near-wall streamwise vortices, weakening them by the generation of intermittent secondary vortices within the riblet valleys. The riblets also appear to limit the lateral spread of inrushes towards the wall and retain low momentum fluid in the riblet valleys effectively isolating much of the wall from such inrushes.