Types of Experiments

Several types of experiments have been carried out to investigate the stress state in the head of the bolt created by the body forces. The results of the finite element model experiment can be seen in Fig. 2, and those of the optical plane model experiment are presented in Fig. 3. 

Although all real surfaces have steps, they are not usually labelled as vicinal unless they are purposely misoriented in order to create a regular array of steps. Vicinal surfaces have unique properties, which make them useful for many types of experiments. For example, steps are often more chemically reactive than terraces, so that vicinal surfaces provide a means for investigating reactions at step edges. Also, it is possible to grow nanowires by deposition of a metal onto a surface of another metal in such a way that the deposited metal diflfiises to and attaches at the step edges [3]. 

The design of a pulsed EPR spectrometer depends heavily on tlie required pulse lengdi and pulse power which in turn are mainly dictated by the relaxation times of tlie paramagnetic species to be studied, but also by the type of experiment perfomied. When pulses of the order of a few nanoseconds are required (either to compete... 

A number of different types of experiment can be designed, in which disc and ring can either be swept to investigate the potential region at which the electron transfer reactions occur, or held at constant potential (under mass-transport control), depending on the infomiation sought. 

Pump-probe absorption experiments on the femtosecond time scale generally fall into two effective types, depending on the duration and spectral width of the pump pulse. If tlie pump spectrum is significantly narrower in width than the electronic absorption line shape, transient hole-burning spectroscopy [101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112 and 113] can be perfomied. The second type of experiment, dynamic absorption spectroscopy [57, 114. 115. 116. 117. 118. 119. 120. 121 and 122], can be perfomied if the pump and probe pulses are short compared to tlie period of the vibrational modes that are coupled to the electronic transition. 

The bimodal pore distribution model used by Gibilaro et aL may also be used to analyze the results of this type of experiment. If it is assumed that all extraneous effects due to mixing in the interstices between the pellets have been eliminated by means of a control experiment, the results corresponding to equations (10.39) and (10.40) are now... 

If the applied force varies sinusoidally with time, the period of the oscillation defines the time scale. Quite different mechanical responses are expected at different frequencies. This type of experiment will be described in Secs. 3.10 and 3.11. 

Now suppose we consider another extreme of the same type of experiment. This time we alternate extremely short light and dark periods of equal duration. If we again start with [M-] =0 when the light goes on, we expect the type of behavior shown in Fig. 6.5d, where the radical buildup is interrupted by the extinction of the light before it reaches [M-] We could use Eq. (6.43) to evaluate the maximum radical concentration achieved, if that were the... 

We take the position that [77] is known from experiment and assume that M is also known from some other type of experiment, say, o smostic pressure. Assuming that these data are available enables us to evaluate V2, and we consider next what this quantity tells us about the state of solvation of the polymer. 

Figure 9.50(a) illustrates the ionization process in a UPS experiment. In this type of experiment the incident radiation always has much more energy than is necessary to ionize the molecule M into either the zero-point level or a vibrationally excited level of M. The excess energy is then removed as kinetic energy of the photoelectron. 

Another type of experiment to measure separately from other factors consists of saturating packings made from porous materials using a volatile... 

Another type of experiment involves a fluid filament being drawn upward against gravity from a reservoir of the fluid (101,213,214), a phenomenon often called the tubeless siphon. The maximum height of the siphon is a measure of the spinnabiUty and extensional viscosity of the fluid. Mote quantitative measures of stress, strain, and strain rate can be determined from the pressure difference and filament diameter. A more recent filament stretching device ia which the specimen is held between two disks that move apart allows measurements ia low viscosity Hquids (215). AH of these methods are limited to spinnable fluids under small total strains and strain rates. High strain rates tend to break the column or filament. 

Carbon Dioxide Transport. Measuring the permeation of carbon dioxide occurs far less often than measuring the permeation of oxygen or water. A variety of methods ate used however, the simplest method uses the Permatran-C instmment (Modem Controls, Inc.). In this method, air is circulated past a test film in a loop that includes an infrared detector. Carbon dioxide is appHed to the other side of the film. AH the carbon dioxide that permeates through the film is captured in the loop. As the experiment progresses, the carbon dioxide concentration increases. First, there is a transient period before the steady-state rate is achieved. The steady-state rate is achieved when the concentration of carbon dioxide increases at a constant rate. This rate is used to calculate the permeabiUty. Figure 18 shows how the diffusion coefficient can be deterrnined in this type of experiment. The time lag is substituted into equation 21. The solubiUty coefficient can be calculated with equation 2. 

For the following calculations it is assumed that experiments are conducted in a good recycle reactor that is close to truly gradientless. Conceptually the same type of experiment could be conducted in a differential reactor but measurement errors make this practically impossible (see later discussion.) The close to gradientless conditions is a reasonable assumption in a good recycle reactor, yet it would be helpful to know just how close the conditions come to the ideal. 

In order to characterize the surface regions of a sample that has been modified in some way, as is usually the case in adhesion-related investigations, some sort of a reflection experiment is required. Two types of experiments, attenuated total reflection (ATR) and reflection-absorption infrared spectroscopy (RAIR),... 

The observation of molecular size or polydispersity and the subsequent determination of relative molecular mass, (MJ or molecular mass (weight) distribution (MWD), is the most common analytical application of SEC. The goal of these types of experiments is to either observe the solvated size of one or more molecular species or to observe the distribution of sizes present in a mixture... 

These combined HDF and GPC separations require the use of detectors such as static light scattering or viscometers to help sort out the convoluted elution profiles seen in those type of experiments. It should also be remembered in these situations that the typical refractive index or ultraviolet detector responses may not be representative of the actual mass fraction of insolubles eluting from the column because of the significant light scattering that can occur with those large particles in the detector cell. 

The kinetics of alkaline hydrolysis of an ester can be followed by the pH-stat method, in which the pH is held constant by adding a solution of strong alkali to the reacting ester solution. The volume of alkali added in order to keep the pH constant is recorded as a function-time. Find the volume function needed to determine the rate constant that is, given the volume-time data for this type of experiment, what plot or calculation will yield the rate constant ... 

Ag, convention for the equilibrium dissociation constant of an antagonist-receptor complex usually determined in a functional assay denoting antagonism of a physiological response, although it can be associated with an antagonist when it is used in other types of experiment. It has units of M and is the concentration that occupies half the receptor population at equilibrium. It also can be thought of as the reciprocal of affinity. 

This generalization is of great value. It is based upon exactly the type of experiment you have performed. We have confidence in the rule because this type of experiment has been conducted successfully on hundreds of thousands of substances. The melting behavior is one of the most commonly used methods of characterizing a substance. It leads us to wonder if every solid can be converted to a liquid if the temperature is raised sufficiently. Further, it leads us to wonder... 

This proposal is called the atomic theory. As with any theory, its value depends upon its ability to aid us in explaining facts of nature. There is no more valuable theory in science than the atomic theory. We shall use it throughout this course. Later, in Chapter 14, we shall review many of the types of experiments which cause chemists to regard the atomic theory as the cornerstone of their science. 

Yet we must agree, there are advantages to the direct vision type of experiment. Often more detailed information can be obtained this way. Is the garbage collector tall Does he have a mustache Could the garbage collector be a woman This type of information is less easily obtained from other methods of observation. It is worthwhile setting the alarm clock, even after we have become convinced there is a garbage collector. 

The shape of the ethylene molecule has been learned by a variety of types of experiments. Ethylene is a planar molecule—the four hydrogen and the two carbon atoms all lie in one plane. The implication of this experimental fact is that there is a rigidity of the double bond which prevents a twisting movement of one of the CHj groups relative to the other. Rotation of one CHt group relative to the other—with the C—C bond as an axis—must be energetically restricted or the molecule would not retain this flat form. 

It has been noted that results of steady radiolysis experiments provide adequate data for separations related problems. The difficulty is that in the absence of kinetic data for the primary process it becomes necessary to repeat this type of experiment for each particular set of concentrations and times. 

In the dual-electrode techniques, the potential of each electrode is controlled with a bipotentiostat so that a small constant potential difference is maintained across the polymer film as its potential is slowly scanned, relative to a reference electrode. Figure 10 shows the results of this type of experiment for poly(3-methylthiophene) in SO20).37... 

Most information concerning ion-molecule reactions in flames has been obtained from mass spectrometric measurements, but some inferences have been drawn from results of other types of experiments... 

The results of this type of experiment show that CH2 itself is usually formed as a singlet species, that can decay to the triplet state, which consequently has a lower energy (MO calculations and experimental determinations show that the difference in energy between singlet and triplet CH2 is 8-10kcal mol or 33-42 kJ moP ). However, it is possible to prepare triplet CH2 directly by a photosensitized decomposition of diazomethane.Methylene (CH2) is so reactive " that it generally reacts as the singlet before it has a chance to decay to the triplet state. 

In investigating the mechanism of addition to a double bond, perhaps the most useful type of information is the stereochemistry of the reaction. The two carbons of the double bond and the four atoms immediately attached to them are all in a plane (p. 8) there are thus three possibilities. Both Y and W may enter from the same side of the plane, in which case the addition is stereospecific and syn they may enter from opposite sides for stereospecific anti addition or the reaction may be nonstereospecific. In order to determine which of these possibilities is occurring in a given reaction, the following type of experiment is often done YW is added to the cis and trans isomers of an alkene of the form ABC=CBA. We may use the cis alkene as an example. If the addition is syn, the product will be the erythro dl pair, because each carbon has a 50% chance of being attacked by Y ... 

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