Quality factor/ratio

In QSAR equations, n is the number of data points, r is the correlation coefficient between observed values of the dependent and the values predicted from the equation, is the square of the correlation coefficient and represents the goodness of fit, is the cross-validated (a measure of the quality of the QSAR model), and s is the standard deviation. The cross-validated (q ) is obtained by using leave-one-out (LOO) procedure [33]. Q is the quality factor (quality ratio), where Q = r/s. Chance correlation, due to the excessive number of parameters (which increases the r and s values also), can. 

Quality factor or quality ratio (Q) The high values of Q (2.259-14.646) for these QSAR models suggest that the high predictive power for these models as well as no over-fitting. 

Relative Biological Effectiveness (RBE)—The RBE is a factor used to compare the biological effectiveness of absorbed radiation doses (i.e., rad) due to different types of ionizing radiation. More specifically, it is the experimentally determined ratio of an absorbed dose of a radiation in question to the absorbed dose of a reference radiation (typically 60Co gamma rays or 200 keV x rays) required to produce an identical biological effect in a particular experimental organism or tissue (see Quality Factor). 

RBE is used to denote the experimentally determined ratio of the absorbed dose from one radiation type to the absorbed dose of a reference radiation required to produce an identical biologic effect under the same conditions. Gamma rays from cobalt-60 and 200-250 keV x-rays have been used as reference standards. The term RBE has been widely used in experimental radiobiology, and the term quality factor used in calculations of dose equivalents for radiation safety purposes (ICRP 1977 NCRP 1971 UNSCEAR 1982). RBE applies only to a specific biological end point, in a specific exposure, under specific conditions to a specific species. There are no generally accepted values of RBE. 

Good X-band resonators mounted into a spectrometer and with a sample inside have approximate quality factors of 103 or more, which means that they afford an EPR signal-to-noise ratio that is over circa three orders of magnitude better than that of a measurement on the same sample without a resonator, in free space. This is, of course, a tremendous improvement in sensitivity, and it allows us to do EPR on biomolecules in the sub-pM to mM range, but the flip side of the coin is that we are stuck with the specific resonance frequency of the resonator, and so we cannot vary the microwave frequency, and therefore we have to vary the external magnetic field strength. 

Consider a cantilever with natural frequency coo and quality factor Q driven by an external excitation with frequency o). The ratio of the amplitude of the lever A relative to the maximum amplitude Aa is... 

The one exception in which phase contrast is not due to the dissipation arises when the tip jumps between attraction phases (>90°) and repulsion phases (<90°). Since sine is a symmetric function about 90°, the phase changes symmetric even if there are no losses in the tip-sample interaction. The relative contribution of the repulsive and attractive forces can be estimated experimentally from the frequency-sweep curves in Fig. lib by measuring the effective quality factor as Qe=co0/Ao)1/2, where Ago1/2 is the half-width of the amplitude curve. The relative contribution of the attractive forces was shown to increase with increasing the set-point ratio rsp=As/Af. Eventually, this may lead to the inversion of the phase contrast when the overall force becomes attractive [110,112]. The effect of the attractive forces becomes especially prominent for dull tips due to the larger contact area [147]. 

The figures and the theory developed in this work assume the spectra are based on Fermi-Dirac statistics and are related incrementally based on spectral wavelength. In addition, an analysis has been performed to determine if the individual chromophoric spectra show a variation in the ratio of peak wavelength to I/2 amplitude wavelength difference. A similar ratio, based on frequency at the lower frequencies used in the radio spectrum, is considered a quality factor and is designated by Q. The best available estimates of the Q of the visual chromophores of the human eye appear in Table 5.5.10-1 and in the appendix describing the Standard Eye. 

The expression for the resonator Q in the presence of a sample may be found by defining the sample quality factor as the ratio of energy stored in the cavity to energy dissipated in the sample due to EPR absorption, which may be related to the filling factor 17 and the rf susceptibility x", namely,... 

Note. A quality factor (Q) was also proposed [Pogliani, 1994a] for measuring the quality of the regression models and defined as the ratio between the multiple correlation coefficient R and the standard deviation s. However, s being dependent on the measurement unit used for the response, it should be not used to measure the quality of the regression models. 

Fig. 1.11 Qualitative plots of solutions (normalized damping amplitude and phase shift) for a damped, driven oscillator as a function of the relative frequency ratio. In-phase vibrations correspond to a phase shift of zero, while out-of-phase means a phase shift of 180° (reradian). With increasing quality factor (decreasing damping) the resonance becomes sharper...

Performance and Diode Parameters. For finding the optimum absorber composition, organic solar cells of the type A with various [CuPc] [C60] ratios were prepared at a non-optimised substrate temperature. The Eff behaviour with the absorber composition (Fig. la) is dominated by the behaviour of the Jso and FF [4], In the compositional range investigated, 0.2 < [CuPc]/([CuPc] + [C60]) < 0.8, the devices V00 is almost constant taking values of about 400 mV (not shown). An efficiency of 1.6% is achieved in Fig. la at a [CuPc] [C60] composition of about 1 1 (by weight) [4], The diode quality factor, n. of the devices decreases from 2.6-2.7 at the either minimum of CuPc or C6o content to 1.8 at 1 1 absorber composition. At the same time, the OSCs series resistance decreases almost symmetrically from 0.34-0.38 Q x cm2 at a content of 17% of either CuPc or C to -0.2 Q x cm2 at an identical content of CuPc and C6o-... 

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