Sample biased

It is important to remember at this point that the metallicities for the two samples of stars plotted in Fig. 1 were derived using exactly the same techniques, and are thus both in the same scale (see [19]). Also, in the CORALIE planet search sample we have never used the stellar [Fe/H] as a criterion to chose a star. The comparison shown in Fig. 1 is thus not sample-biased. Finally, and as shown in [21], the precision in the derived radial-velocities is not a strong function of the stellar metallicity. The observed increasing frequency of planets with increasing [Fe/H] is thus also not due to any bias in the planet searches. 

Thus, for R - 1 pm and D - 10 cm sec, a 1 nA limiting current is obtained for concentrations of electroactive species, CQX re(j — 1.6 /jM. These calculations suggest that in the presence of a reversible redox couple at micro-molar concentrations, even STM tip-sample biases of AEt < 10 mV will drive a faradaic current that is comparable to that of the tip-sample tunneling current. STM imaging under such circumstances is likely to be experimentally demanding using conventional feedback methodology. 

One important area of technology development is the world-to-chip interface. The requirements for an effective interface are ease of fabrication, low dead volume, ease of automation, no sample biasing from the reagent source, and compatibility with existing sample storage formats. One such interface for high... 

Fig. 16.9. STM topograph of a partially oxidized silicon surface. With the sample biased at +2 V relative to the tip, the unoccupied states of a Si(lll)-7 X7 surface exposed to 0,2 L of O2 at 300 K is obtained. (Reproduced from Avouris, Lyo, and Bozso, 1991, with permission.)...

We present the theoretical overview first for the case of voltage bias [1]. In a junction with a low transparency barrier (which corresponds to our samples) biased by a dc voltage V, the current noise spectral density (related to the... 

Fig. 3. A series of STM images (40 nmx 40 nm) incompletely reacted H/Si(lll) surfaces upon irradiation (447nm) in a solution of 1-decene for 3 (top left), 15 (top right), 30 (bottom left) and 120 (bottom right) minutes. Images were acquired in constant current mode at 20pA and sample biases of-2.7 to -3.8 V. Reprinted from [21].

Fig. 16. Electrochemical impedance and fluorescence data for DNA modified Si(lll) upon hybridization and de-hybridization. The real (a) and imaginary (b) parts of the impedance (sample biased into depletion) are shown as a function of frequency. The various curves show the response of the initial surface modified with single stranded DNA (16-mer), after exposure to the complementary sequence S2 and de-hybridization. Exposure to a non-complementary sequence S3, did not significantly change the impedance. A plot of the real versus imaginary parts of the admittance is shown in (c), more clearly showing the hybridization induced changes. The fluorescence image shown in (d) confirms hybridization and de-hybridization, the central bright region corresponds to the area of the sample exposed to the DNA solution in the electrochemical cell. Reprinted from [93].

Sampling biases can occur from differences in particle size distribution, particle density, particle shape, and particle electrostatic charge. Minimizing these particle property differences will increase the likelihood that the blend content uniformity is a true representation of the batch.13,14 It also aids in the reduction of sampling bias which will improve the experimental blend content uniformity. 

The lower size cut must be sharp and in the range of 1-10 urn, and no sampling biases must be introduced for the droplets up to at least 50 ym. 

Systematic sampling involves taking the position of the first sample at random and then taking further samples at fixed distances/directions from this. For example, samples may be taken at intervals of 5 m. This type of sampling has the potential to provide more accurate results than simple random sampling. However, if the soil contains a periodic (systematic) variation which coincides with this type of sampling, biased samples can result. An initial pilot study of the site can help prevent this. 

Figure 1.36. Allcrnalive disconncctivity graphs for TIP4P (H2O)20. (a) Results for a sample biased toward low-energy structures, and (b) a low-energy search seeded from Figure 1.35. The energy scale is in units of kJ mol. ...

Figure 10. (a) Low-magnilication HRTEM micrt ph of cross-section of a sample biased for 1 h and fuither grown for 5 h showing several diamond nucleation sites and an intoifacial layer of a-SiC between Si and diamond. Twin lamellae, prominent defects in CVD diamond, can be observed where the nuclei begin to coalesce, as indicated by the arrows. 

Catalysts were prepared by impregnating the noble metal chloride onto either an alumina washcoat or a proprietary washcoat containing alumina, ceria and other base metals. The catalyst was supported on a monolithic cordierite substrate with 64 square cells/cm. Cylindrical cores used for laboratory evaluations were 2.5 cm in diameter and, unless otherwise noted, 5 cm in length. The length of each core was composed of smaller segments taken from various locations down the monolith bed in order to minimize sampling biases. 

Plate 57 Three STM images of a N13 cluster adsorbed on a M0S2 basal plane at 4 K. All three images show a 60A area and are plotted as three-dimensional representations with the same aspect ratio and with the same angle of view. The images were acquired with sample biases of + 2 V (upper), + 1.4 V (middle), and —2 V (lower). Reproduced with the permission of the American Chemical Society from Kushmerick JG and Weiss PS (1998) Journal of Physical Chemistry B102 10094-10097. See Scanning Probe Microscopes. 

Figure 13.8 STM images of GaAs(llO) acquired at sample biases of +1.9V (a) and — 1.9V (b). (Adopted from Ref [21].) For a positive bias, the surface Ga atoms are visible as a bright protrusion in the STM image, and for a negative bias, the As atoms are...

One of the potential sources of errors is attributed to statistical bias that primarily results from the following three biased effects biased sample, biased estimator, and biased measurement instrument. In a statistical analysis, when most samples are chosen from one specific section of the population, the sample population will have the potential to be biased. For instance, if all the 2024 aluminum alloy samples were provided by one vendor in a hardness analysis, the sample would be biased. Furthermore, the source of samples requires carefully scrutiny to avoid hidden biased effects. For instance, the 2024 aluminum alloy samples might be provided by three different suppliers however, all three suppliers might obtain their materials from the same foundry. 

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