Sensitivity relative, determination

Use individual data points for each experimental concentration (presented as the arithmetic mean standard error of the mean) to construct concentration-response toxicity curves. Such curves are used to calculate midpoint toxicities or NR50 values, as determined by linear regression analysis. Use this value for comparison and ranking against other chemicals, or for relative sensitivity determination of different cell types. 

The product of isotopic abundance and relative sensitivity determines the overall sensitivity to detection of the isotope relative to hydrogen with its 99.985% natural abundance and unit relative sensitivity. Low y nuclei may be quite difficult to detect as sensitivity is proportional to y (e.g., Fe which is 3 x 10 times less sensitive than protons for equal numbers of nuclei). Sensitivity may be enhanced by repetitive spectral accumulation as the signal-to-noise (S/N) ratio is proportional to the square root of the number of accumulations. It requires 10 accumulations to give a Fe signal 1/50 the S/N of protons - a daunting task. 

Pragmatically, the relative concentrations of elements are determined from the measured ion beam ratios by the application of relative sensitivity factors, which are determined experimentally from standard samples ... 

The ratio Db/Da is a so-called relative sensitivity factor D. This ratio is mostly determined by one element, e. g. the element for insulating samples, silicon, which is one of the main components of glasses. By use of the equation that the sum of the concentrations of all elements is equal to unity, the bulk concentrations can be determined directly from the measured intensities and the known D-factors, if all components of the sample are known. The linearity of the detected intensity and the flux of the sputtered neutrals in IBSCA and SNMS has been demonstrated for silicate glasses [4.253]. For SNMS the lower matrix dependence has been shown for a variety of samples [4.263]. Comparison of normalized SNMS and IBSCA signals for Na and Pb as prominent components of optical glasses shows that a fairly good linear dependence exists (Fig. 4.49). 

This chapter will review some recently completed studies on the long-term effects of MDMA in nonhuman primates. The goals of these studies were to (1) determine if the neurotoxic effects of MDMA, which have been well documented in the rodent (see below), generalize to the primate (2) compare the relative sensitivity of primates and rodents to the neurotoxic effects of MDMA (3) ascertain if the toxic effects of MDMA in the monkey are restricted to nerve fibers (as they are in the rat), or if they involve cell bodies as well (4) evaluate how closely toxic doses of MDMA in the monkey approximate those used by humans and (5) examine whether 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF) can be used to detect MDMA-induced serotonergic damage in the CNS of primates. Before presenting the results of these studies, previous results in the... 

The amount of a certain element which can be detected by XPS depends mainly on the specific scattering cross section. These cross sections are tabulated [15, 22] relative to either C or Na and vary between 0.5 for B and 22.9 for Cs with C as unity. An easy method for sensitivity determinations of the overall system are adsorption measurements. The amount of the adsorbate can be adjusted either electrochemically (UPD of... 

Determined for an equal number of nuclei at a constant field. bProduct of the relative sensitivity and natural abundance. ... 

For vapour detection there are three aspects that are modelled sensitivity, response time, and regeneration. The sensitivity determines at which concentration level the detector will respond. The theoretical detector output (alarm or no alarm) is calculated by comparing the input data (concentration, relative humidity) with empirical detector display outputs, obtained during controlled exposure laboratory experiments. The response time determines how long it takes before the detector actually shows the response and it depends on the concentration level. The regeneration time determines how long it takes, after a positive detection, before the detector can do a new measurement. 

Cheung, C., Hotchkiss, S.A., and Pease, C.K., Cinnamic compound metabolism in human skin and the role metabolism may play in determining relative sensitization potency, J. Dermatol. Sci., 31, 9, 2003. 

Secondary ion mass spectrometry (SIMS) was used to characterise the coatings for their Ti, Ru and O stoichiometry on the surface and as a function of depth into the coating. A PHI 6650 Quadrupole mass spectrometer, with Cs+ as the ion source was used in these studies. The conversion of the measured secondary ion counts to concentration was performed using relative sensitivity factors, which were first determined with a standard sample containing known amounts of RuC>2 and TiC>2. All of the SIMS profiles were repeated several times, to determine the measurement precision, which was typically +10%. 

In one study, however, atmospheric pressure chemical ionisation (APCI)-MS was applied for the simultaneous determination of LAS and octylphenol ethoxylates (OPEO) in surface waters after preconcentration by solid-phase extraction (SPE) on Cis cartridges [1]. In the chromatogram from a Ci-reversed phase (RP) column, peaks arising from both the anionic LAS and the non-ionic OPEO were detected after positive ionisation, while in negative ionisation mode, OPEO were discriminated and only the anionic surfactant was observed. Surprisingly, the relative sensitivity for detection of LAS was approximately five times higher in positive ion mode, which led the authors to the conclusion that this ionisation mode was desirable for quantitative work. 

The isotope N, with a natural abundance of 99.9%, has nuclear spin 7 = 1 and gives broad signals which are of little use for structural determinations. The N nucleus, with I = 1/2, is therefore preferred. However, the low natural abundance of about 0.4% and the extremely low relative sensitivity (Table 1) make measurements so difficult that N NMR spectroscopy was slow to become an accepted analytical tool. A further peculiarity is the negative magnetogyric ratio since, in proton decoupled spectra, the nuclear Overhauser effect can strongly reduce the signal intensity. DEPT and INEPT pulse techniques are therefore particularly important for N NMR spectroscopy. 

This classification of anticancer drugs has inherent limitations. For instance, it may be difficult to generalize about the phase specificity of a particular drug, since this may vary among cell types. Several techniques are available to synchronize cell populations in such a way that most cells will be in the same phase of the cell cycle. After synchronization, one can treat cells in each phase and determine their relative sensitivity to drugs throughout the cell cycle. 

Larger Scale Testing. The standard card gap test (2) is test No. 1 of a series of larger scale tests designed to determine the sensitivity of liquid propellants to hydrodynamic shock. In this test, relative sensitivities of various propellants are determined in terms of the number of 0.01-inch thick cellulose acetate cards required to attenuate a standard shock sufficiently just to prevent initiation in the test sample. When performed according to the exacting conditions of apparatus and procedure, the results are very reproducible from one laboratory to another. However, small variations in the apparatus or procedure can cause major variations in the resulting data, and therefore the test can be considered only relative. A major drawback of the standard test is that it cannot accommodate materials that are volatile under the test condition. At TCC-RMD some special equipment has been developed that allows tests to be made on confined samples at elevated temperature and pressure. 

There is some reason to expect that conversion of the anhydride to a half-ester might reduce the sensitivity of the copolymers. Hiraoka (10) determined the relative sensitivities of PMMA, PMA (polymethacrylic acid) and PMA AN (polymethacrylic anhydride) by measuring the gaseous products (CO, C02, and H2) given off when these polymers were exposed to electron beam radiation of 2.5 keV at 297 °K. He found that the G values (number of chemical events produced per 100 eV of absorbed radiation) for the removal of side groups are 2.0, 7.4 and 16 for PMMA, PMA and PMA AN, respectively. Anderson (11) found a similar relative order of sensitivity. For copolymers of methylmethacryate with 25% dimethylitaconate, 25% monomethyl itaconate or 25% itaconic acid (or anhydride) the G(s) values were 1, 2, 3, respectively. For the copolymer of alpha-methylstyrene and monomethyl maleate, on the other hand, we find an increase in sensitivity by a factor of 2.5 over the corresponding anhydride as described below. 

Certified reference materials (CRMs) are mainly applied to validate the analytical procedure developed for routine analysis in order to determine the accuracy of analytical data, the recovery for selected elements, the uncertainty of trace element determination and the detection limits. Otherwise, in solid-state mass spectrometric techniques, such as SSMS, LA-ICP-MS, GDMS, SNMS or SIMS, one point calibration using CRMs has been established as an important calibration strategy to obtain reliable analytical data. The one point calibration is performed using the experimentally determined relative sensitivity coefficients (RSCs) on a suitable CRM with a similar trace/matrix composition. An RSC of a chemical element is defined as the ratio of the measured element concentration (experimentally determined) divided by the certified element concentration (accepted or recommended value of element concentration) in a given matrix. 

Quantitative trace element analysis of diamond by LA-ICP-MS using different synthetic multielement carbon based standards (e.g., cellulose pellets) is discussed by Rege et al 2, whereby 13C was used for internal standardization. Concentrations of 41 elements were determined in two fibrous diamonds from Jwaneng Botswana (JWA 110 and 115) by relative sensitivity coefficients measured using the synthetic cellulose standard. The analytical data were verified by means of instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE).72... 

The application of SIMS, SNMS, SSMS and GDMS in quantitative trace analysis for conducting bulk material is restricted to matrices where standard reference materials (SRMs) are available. For quantification purposes, the well characterized multi-element SRMs (e.g., from NIST) are useful. In Table 9.5 the results of the analysis by SNMS and the RSCs (relative sensitivity coefficients) for different elements in a low alloy steel standard (NBS 467) are compared with those of SSMS. Both solid-state mass spectrometric techniques with high vacuum ion sources allow the determination of light non-metals such as C, N, and P in steel, and the RSCs for the elements measured vary from 0.5 to 3 (except C). RSCs are applied as a correction factor in the analytical method used to obtain... 

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