Sample history

Results from measurements of time-dependent effects depend on the sample history and experimental conditions and should be considered approximate. For example, the state of an unsheared or undisturbed sample is a function of its previous shear history and the length of time since it underwent shear. The area of a thixotropic loop depends on the shear range covered, the rate of shear acceleration, and the length of time at the highest shear rate. However, measurements of time-dependent behavior can be usehil in evaluating and comparing a number of industrial products and in solving flow problems. 

If sulfonylurea herbicides can reasonably be expected to be present in an analytical sample (based on prior knowledge), one parent-to-daughter ion transition is usually considered sufficient to confirm its presence. In other cases where little is known about the sample history, two parent-to-daughter ion transitions are generally considered to be necessary for a definitive confirmation. Suggested ion transitions for most of the registered sulfonylurea herbicides are listed in Table 2. Furthermore, the ratio of the signals for the two transitions obtained for the sample should match that of an authentic standard within 30%, at most. ... 

SFE-GC is an attractive approach to coupling the extraction, concentration and chromatographic steps for the analysis of samples containing analytes that can be analysed using capillary GC. Often it is difficult to identify all the components which are extracted from samples by FID alone. This is a particular problem when the sample history and/or the identity of the compounds of interest are not known. When SFE-GC is combined to powerful spectroscopic detectors, unique data can be obtained, allowing their use as routine tools in the analytical laboratory. For positive identification of components of interest, multihyphenated techniques such as SFE-GC-AED, SFE-GC-MS, SFE-GC-FUR-MS are employed [46]. 

The major causes of spectral variation were (1) instrumental drift, as Goodacre and Kell realized, but also (2) sample history, as discussed above. In particular, variations in the supplier or even the batch of tryptic soy agar (TSA) used for cell culturing led to spectral variations that differed in degree among disparate species. This phenomenon was attributed to the differential metabolic capabilities of the species with respect to the changed nutrients. 

The analysis of chemicals by reference to a set of library mass spectra was facilitated by the establishment almost 40 years ago of databases such as the NIST/EPA/NIH reference library of electron impact mass spectra (http //www.nist.gov/srd/nistla.htm). Experimentally derived mass spectra are compared to spectra in the library, and the matches are graded by various algorithms. This comparison is valid because electron impact ionization requires that the sample be vaporized and thus isolated from its sampling history. 

Experience shows that the density of Ob-vacs can be varied by changing the anneal temperature or the anneal time [66], Wendt et al. [18] assessed this systematically by demonstrating a linear dependence of the Ob-vac density (measured by STM) on the sample history, the latter being defined as the anneal temperature x anneal time. 

Fig. 4. Sample history of a collisional multizone multi-phase model with stripping at...

Real-Time FTIR. For our IR studies, we utilized a stoichiometrically equivalent amount of a trifunctional thiol, trimethylolpropane tris(2-mercaptoacetate), with a difunctional allyl, trimethylolpropane diallyl ether. The thiols were protected from oxidative polymerization by the addition of hydroquinone. The monomers and hydroquinone were purchased from Aldrich Chemicals and were used as received. This formulation was mixed for five minutes and then a commercial photoinitiator, Esacure TZT (Sartomer Inc.), which contained a blend of methyl benzophenones, was added at a level of 1.0% by weight of monomers to the formulation. Stirring was maintained for a further five minutes following the addition of the photoinitiator. The final formulation contained 2.0% by weight of hydroquinone. The samples were prepared prior to each experiment in order to ensure reproducibility of sample history. 

Shows effects of atmosphere, sample history, purity, etc. Measures sample temperature directly. 

Sampling records for any procedure must be complete and should include, but is not restricted to, items relating to the origin of the sample, methods of storage, analytical tests performed, the test methods used, and the analyst(s) who performed the test methods (Table 6.1). In summary, there must be a means to identify the sample history as carefully as possible so that each sample is tracked and defined in terms of source and activity. Thus, the accuracy of the data from any subsequent procedures and tests for which the sample is used will be placed beyond a reasonable doubt. 

It is noteworthy that prior to the advent of scanning probe microscopy electrochemically driven reconstruction phenomena had been identified and studied using traditional macroscopic electrochemical measurements [210,211], However, STM studies have provided insight as to the various atomistic processes involved in the phase transition between the reconstructed and unreconstructed state and promise to provide an understanding of the macroscopically observed kinetics. An excellent example is provided by the structural evolution of the Au(lOO) surface as a function of potential and sample history [210,211,216-223], Flame annealing of a freshly elec-tropolished surface results in the thermally induced formation of a dense hexagonal close-packed reconstructed phase referred to as Au(100)-(hex). For carefully annealed crystals a single domain of the reconstructed phase... 

SAMPLE AMT SAMPLE FORM SAMPLING PROCESS SAMPLE HISTORY INSTR. AVAIL Then ... 

DSC indicates a gradual increase in Tg with increasing PHBA/diol ratios except for the 60/40 ratio. Otherwise DSC scans of these polyols are complex and are strongly affected by the thermal history of the materials. The 40/60 and 50/50 PHBA/diol ratio materials often have two endothermic peaks, one near 10 and the other near 70°. The relative size of these peaks vary depending on sample history. Small peaks at about 100 are also sometimes observed. 

Because solubility and viscosity are non-equilibrium properties, the measured values are dependent upon measurement conditions, sample preparation, and past sample history. Because of this, it is difficult or sometimes even impossible to compare data, to generalize the data and make predictions, and to interpret the data in terms of the basic molecular forces. 

Polyacrylonitrile has been the subject of investigations by Russian workers, particularly those aspects relating to its thermal degradation. Polyacrylonitrile itself is a semiconductor with an activation energy of 0.32 to 0.84 e. v. (69) or 1.5 to 4.6 e. v. (70) depending upon the method of polymerization, ambient atmosphere and sample history. 

Coprecipitates. Silica-alumina coprecipitates are immensely complicated. As a result of structural disorder and substitution of Al(III) for Si (IV) on tetrahedral sites, they exhibit cation exchange behavior (34). The fraction of total Al which occurs on tetrahedral sites and the CEC vary widely in response to the conditions of precipitation and subsequent sample history, especially thermal history. In general, the fraction... 

Sample History. A malt sample which had been treated with gibberellic acid at a 1-p.p.m. level was submitted to Hiram Walker Sons, Inc., for use in a pilot scale (0.16 bushel) bourbon fermentation. After fermentation, the beer was dealcoholized with steam and the grain residue was concentrated and dried in a tray dryer at 160° to 170° F. 

Sample History. All-malt microbrews containing 100 grams of malt which had been treated with 88 fxg. of labeled gibberellic acid were brewed according to the technique reported by Kneen (3). Fermentation was carried out for 7 days at 12° C. and after fermentation, the beer was transferred to storage flasks, chill-proofed, and stored in the cold for 3 weeks. After storage, the beer was filtered, carbonated, and bottled. 

Sample history Sampling date, sample type, sample origin (mine, location)... 

The major exception to these narrow limits is the oxygen content of bitumen, which can vary from as little as 0.2% to as high as 4.5%. This is not surprising, since when oxygen is estimated by difference the analysis is subject to the accumulation of all of the errors in the other elemental data. Also, bitumen is susceptible to aerial oxygen and the oxygen content is very dependent upon the sample history. In addition, the ultimate composition of the Alberta bitumen does not appear to be influenced by the proportion of bitumen in the oil sand or by the particle size of the oil sand minerals. 

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