Intrinsic variables

Knowledge of intrinsic co-variables. Concentrations of mercury in fish are typically correlated with age or body size. An understanding of, and ability to account for, the effects of such intrinsic variables is essential for evaluating contaminant trends. 

As concluded by Menzinger et CE will only fully augment chromatographic techniques in the routine determination of pesticide residues when software becomes capable of compensating for the intrinsic variability in analyte migration times. This... 

Chapters 3 6 deal with direct mass spectrometric analysis highlighting the suitability of the various techniques in identifying organic materials using only a few micrograms of samples. Due to the intrinsic variability of artefacts produced in different places with more or less specific raw materials and technologies, complex spectra are acquired. Examples of chemometric methods such as principal components analysis (PCA) are thus discussed to extract spectral information for identifying materials. 

Figure 3.1 Bond and intrinsic variables for triatomic molecules (a) and the Euler angles characterizing the orientation in space of the molecule (b).

From this expression one has to remove the center-of-mass motion. The corresponding Hamiltonian can then be rewritten in terms of the intrinsic variables and the Euler angles. The general form of the Hamiltonian operator is, in the Eckart frame,1... 

The intrinsic variable expressed usually as international units (U) of enzyme activity per milligram protein... 

The intrinsic variable expressed as units of radioactivity (in becquerels or, more traditionally, curies) per mole of a substance. One Bq corresponds to 1 disintegration per second (dps) and one Ci to 3.70 x 10 ° Bq. This parameter is especially useful in quantifying the amount of substance in biological samples. For example, if SAs is the standard specific radioactivity (say, x dps/y mol) of a standard, and if SAg is the experimental specific activity (say, x dps/(y + z) mol), then the content z in a sample can be determined from the expression (SAs/ SAe) = (y + z)/y or z = y ([SAj/SAg] - 1). This intrinsic variable can also be expressed as the gram-atom excess of a stable isotope per mole of a substance. The numerator is typically determined using a ratio mass spectrometer, and the denominator can be estimated by chemical and/or spectroscopic techniques. 

The hypothesis to be tested requires an appropriate test statistic. Since acute toxins are being considered here, it is essential to choose a statistical measure that is likely to identify lognormal distributions that potentially produce large values, even if these values are improbable. A sensitive statistic tic must combine both the overall level (mean) and the intrinsic variability (variance). A test statistic with this property is the estimated 95th percentile defined as... 

Another factor that requires to be taken into account is the intrinsic variability of organisms within what is in effect a mixed culture. There are different species of organism present and even the same species will have cells at different stages of cellular division. Some cells in a mixed system will be very susceptible to the applied stress and others will be more resistant. Obviously it is the resistant cells that will require sufficient stress to kill them, no matter how that term is applied. Filtration to remove as many microorganisms as possible before any sterilizing stress is applied is clearly a sound practice. 

The process of selecting n objects for a lot of size N is called sampling. The n objects are the sample and the total lot size N is the population from which the sample is taken. This lot may be in one mass or distributed among M separate containers. Randomness is critical to sampling because a random sample has minimum errors ideally all the error should be due to the intrinsic variability of the material and the variability due to sampling should be minimized. An attribute is the property of interest that is going to be measured, be it particle size, composition, etc. 

A steam turbine is a machine with an ancient genealogy. It is a direct descendant of the overshot water wheel, used to kick off the industrial revolution in England, and the windmill still used in Portugal. Turbines are widely used in process plants to drive everything from 2-hp pumps to 20,000-hp centrifugal compressors. They are versatile machines, in that they are intrinsically variable-speed devices. Electric motors are intrinsically fixed-speed machines. It is true that there are a variety of ways to convert AC (alternating-current) motors to variable speed, but they are all expensive and complex. 

The peak potential varies linearly with In cswv (Eq- (7.53)), where (SWv includes the influence of the intrinsic variables of the system (Eq. (7.51)). However, it is difficult to find a general expression for the exact value of the peak potential given that this also depends on the step potential and the pulse amplitude ... 

Due to the intrinsic variability of biological matrices, guidelines require to prove that in several independent sources of the same matrix FDA requires a minimum of six, EC requires a minimum of 20 representative blank samples. 

The words in Column 4 of Table 7 mean incompatible that the model does not at all allow for the variation expressed in the series mentioned compatible that the model foresees such a variation but cannot give any useful indication of the actual extent of the variation and rationalizing that the model contains intrinsic variables expressing this variation as a necessity. Of course this is not exactly "explaining in the classical sense of the word. 

It does therefore follow that it is very important to reduce the SD as much as possible. Theophylline clearances are intrinsically variable and there is nothing we can do about that. However, random measurement errors maybe inflating the SD and we should certainly be attempting to eradicate all unnecessary sources of variability. 

Because the activity meter evaluates spontaneous behavior, the behavioral baseline is intrinsically variable and subject to many kinds of influence, including lighting, apparatus cleanliness, ambient temperature, noise level, and even time of day. As a consequence, particular care has to be taken to ensure constant experimental conditions to obtain reproducible results. Furthermore, when comparing different drug treatments, it is important to take advantage of the fact that several animals can be evaluated simultaneously, by distributing the different treatments in a balanced fashion over the test period, and even in the positions within the experimental apparatus or of the observation chambers in the experimental room. 

Special problems can arise from the use of RPs, due to the extreme anisotropy of some of them, the fact that the strength of certain constituent fibers is intrinsically variable, and because the test methods for measuring RPs performance need special consideration if they are to provide meaningful values. 

The equipartition theorem, which describes the correlation structure of the variables of a Hamiltonian system in the NVT ensemble, is a central component of the held of statistical mechanics. Although the intent of this chapter is to introduce aspects of statistical thermodynamics essential for the remainder of this book -and not to be a complete text on statistical mechanics - the equipartition theorem provides an interpretation of the intrinsic variable T that is useful in guiding our intuition about temperature in chemical reaction systems. 

From Eqn. (5) we see that the important intrinsic variables controlling creep are the boundary thickness, w, the grain size, d, and the viscosity of the boundary fluid, tj. If these parameters change in the course of the deformation process, a corresponding change in the creep rate will occur, leading to transient creep behavior. 

In most experimental studies, there are two sources of variation or error. The first arises from the intrinsic variability in individual measurements or observations that are all obtained in the same way. The second arises from errors in the apparatus or procedures which affect all of the measurements in a similar way. This type of variation, which leads to a consistent deviation from the correct or true measurement is termed systematic error. It is important that these two sources of error are clearly distinguished. The first (intrinsic variability) can be analysed statistically, and replicated measurements will give an estimate of the precision of the measurement or procedure. These errors are termed statistical errors. This does not mean, however, that the result obtained is necessarily an accurate or true one. Pipettes may have become uncalibrated, or solutions have deteriorated there are many ways in which systematic errors can lead to false values, and attention to calibration and independent verification of apparatus or procedures is essential to minimise the risk of this happening. Systematic errors are potentially much more problematic in biochemical work, since these can easily occur without the experimenter being aware of them. 

Thummelef al. (21) avoided the intrinsic variability of enzyme acctivity in the human population by predicting in vivo clearances from in vitro kinetic data in liver transplant patients. They were interested in using midazolam (MDZ) as a probe of CYP3A isoforms in the liver. Because biopsies were performed for the medical management of the transplant... 

Intrinsic variability of the endpoints within the experimental population... 

In summary, as with all surrogate assays, care must be exercised by taking into account the sensitivity of different assays, their intrinsic variability, and the possibly cardinal issue of metabolism. 

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