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Fig. 3 Example of a false-color array scan image. The image is a composite of the image scanned for cy3 and the image scanned for cy5, resulting from the cohybridization of two target samples to one array. The original scan images are 16-bit grayscale; that is, signal intensities can range from 0 to 65536, and software converts this to color levels for display purposes. Each separate smaller grid within the entirety of the array consists of probes deposited by one of many robotic print tips. The ''gap'' in the middle of the array indicates that all probes have been printed onto the array twice. (View this art in color at www.dekker.com.)

Fig. 3 Example of a false-color array scan image. The image is a composite of the image scanned for cy3 and the image scanned for cy5, resulting from the cohybridization of two target samples to one array. The original scan images are 16-bit grayscale; that is, signal intensities can range from 0 to 65536, and software converts this to color levels for display purposes. Each separate smaller grid within the entirety of the array consists of probes deposited by one of many robotic print tips. The ''gap'' in the middle of the array indicates that all probes have been printed onto the array twice. (View this art in color at www.dekker.com.)

use arrays containing 10,000-30,000 genes, and the use of multiple experimental conditions and replicate samples can easily produce millions of data points for an experiment. Analysis of the data is further complicated by the dimensionality of the data; that is, compared to ''normal'' data with many observations (e.g., patients) and few variables (e.g., weight and blood pressure) there are few biological samples and a large number of response variables—the probes. This poses statistical problems with analysis approaches.

Inference statistics such as t tests or Mann-Whitney U tests on a gene-by-gene basis effectively means hundreds or thousands of tests performed in parallel, which introduces a multiple-testing problem.[8] A proportion of all tests performed is liable to contain false positive results. This can be counteracted by adjustments to the computed p values; common approaches include, but are not limited to, Bonferroni and false discovery rate method.[8]

Following basic inference approaches to discover significant differentially expressed genes, the most common second form of analysis is exploratory, and a large part of this consists of a variety of clustering and classification algorithms.1-9-1 These methods are statistically less rigorous, but often very relevant to the biologist. Interpretation of such results must be made with care, and subsequent result validation is required for hypothetical models of genetic regulation to stand.

The great potential of microarray technology is matched by potentially complicated experimental designs. This applies to statistical experiment design as well as experiment logistics. Experiment design[10-12] for micro-array studies tends to be based on the principle of cohybridizing an experimental sample with a common reference sample (Reference Design). As opposed to a ''loop design'' where experimental samples are cohybrid-ized in pairs, this provides less statistical power for the analysis, but better flexibility and extensibility of the study design. Studies designed around single-target platforms trade in reduced problems with differential label properties against error caused by different hybridization qualities and spot morphologies across arrays. Experiment design can also be driven by interest in either hypothesis-or data-driven approaches to analysis. The former requires high levels of biological replication to provide reliable results; the latter requires new mathematical approaches and potentially the integration of other sources of data.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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