Bar-graphs

A typical plot of x vs./(x) is considered to have one coordinate dimension, the X, and one data dimension,/(x). These data sets are plotted as line graphs, bar graphs, and so forth. These types of plots are readily made with most spreadsheet programs as well as dedicated graphing programs. Figure 13.1 shows two graphs that are considered to have a one-dimensional data space. 

Modern mass spectrometers are interfaced with computerized data handling sys terns capable of displaying the mass spectrum according to a number of different for mats Bar graphs on which relative intensity is plotted versus m z are the most common Figure 13 40 shows the mass spectrum of benzene m bar graph form... 

Data reduction. The process of transforming the initial digital or analog representation of output from a spectrometer into a form that is amenable to interpretation, e.g., a bar graph, a table of masses versus intensities. 

If further resolution is necessary one-third octave filters can be used but the number of required measurements is most unwieldy. It may be necessary to record the noise onto tape loops for the repeated re-analysis that is necessary. One-third octave filters are commonly used for building acoustics, and narrow-band real-time analysis can be employed. This is the fastest of the methods and is the most suitable for transient noises. Narrow-band analysis uses a VDU to show the graphical results of the fast Fourier transform and can also display octave or one-third octave bar graphs. 

The mass spectrum of a compound is typically presented as a bar graph with masses (m/z values) on the x axis and intensity, or relative abundance of ions of a given m/z striking the detector, on the y axis. The tallest peak, assigned an intensity of 100%, is called the base peak, and the peak that corresponds to the unfragmented cation radical is called the parent peak or the molecular ion (M+). Figure 12.2 shows the mass spectrum of propane. 

The bar graphs show the relative numbers of moles and species before (left) and after (right) acid dissociation occurs. 

Mass spectrum of neon (a) actual appearance, (b) bar graph representation. 

A sample of lead atoms is analyzed by mass spectrometry. The bar graph in the margin shows the results. Use information from the graph to write the elemental symbol that represents each Pb isotope and estimate the natural abundance of each. List the number of protons and neutrons for each isotope. 

C02-0012. Figure 2-17 gives the isotopic composition of naturaiiy occurring chromium (Cr). Draw a bar graph that shows the mass spectrum of Cr. 

The majority of crystallites observed were 3 or 4 nm In size. In Figure 3, a bar graph Illustrates the size range distribution and a comparison of mass variation for the 3 and 4 nm crystallite sizes. Although only thirty analyses were oiade, overall visual analysis confirmed the presence of hundreds of 3 to 4 nm platinum crystals with negligible numbers less or greater than these dimensions. It appears that slight variations In crystallite diameter and thickness have resulted In a fairly uniform number of platinum atoms per crystallite for the majority of the crystallites analyzed. In order to normalize count rates, the decrease In the field emission Intensity was taken Into account. 

FIG. 76. Frequency response characteristics of a conventional, graphite-coaled diaphragm (bar graph) and an o-Si H-coated diaphragm (line graph). 

Fig. 5.14 Experimental (a, black curve), fitted (a, red) and simulated (b) NIS spectrum of the Fe (Ill)-azide complex obtained at the BP86ATZVP level (J = 20 K). Bar graphs represent the corresponding intensities of the individual vibrational transitions. The blue curve represents the fitted spectrum with a background line removed (taken from [63])...

Fig. 7. Total kinetic energy release derived from velocity map images of 0(3P2) and D(2S) fragment atoms following photodissociation of OD at 226 and 243 nm, respectively. The initial vibrational state of OD is determined from energy balance with TKER = hv + E(vib)oD — Do(OD). The bar graphs show the calculated photodissociation yields for OD X2Il(v) at a vibrational temperature of 1700 K. (From Radenovic et al.97)...

Figure 9. Bar graphs giving contact angle information for a series of probe liquids on PTFE, dolomite, marble, and glass.

FIGURE 6.16 Bar graph of (3-carotene and lycopene skin levels measured with selective RRS for seven subjects. White bars represent (3-carotene levels, black bars the lycopene levels. Note strong intersubject variability of (3-carotene to lycopene concentration ratios, indicated above the bar graphs. 

Classifying varying measured values by their magnitude does not, as a rule, result in a uniform distribution over the whole variation range, but gives rise to a frequency distribution around the mean value, as shown, e.g., by the bar graph in Fig. 4.3a. 

Figure 3. A bar graph can be constructed from a table in a single step. (Reproduced with permission from University of South Carolina Press Columbia, S.C., 1986 Channing Russell In Research Data Management in the Ecological Sciences Michener, William, Ed. pp 373-381.)...

The data collection task also displays a simple bar graph of the data as it is being collected so that the user can judge whether the data collection process is proceeding as planned. 

Figure 5. A bar graph of metal cluster reactivities with CO on a linear scale. Cluster size increases going into the page and metal types across. Once beyond a few atoms in size most all clusters react at rates within an order of magnitude of each other.

As already stated, the mass spectrum is a two-dimensional graph that reports the m/z ratio of ions (abscissa) and their relative intensity (ordinate). The most abundant ions are assigned as 100%. A mass spectrum can be displayed as peak profiles or as bar graphs corresponding to the peak centroids, i.e. the weighted centre of mass of the peak, or as a table (Figure 2.16). The most abundant ions in a mass spectrum constitute the base peak whose intensity is assumed equal to 100%. 

Figure 2.16 Different ways to represent a mass spectrum peak profile (a), bar graph (b) and table (c)...

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