References electronic sources

It is easiest to discuss the electron optics of a TEM instrument by addressing the instrument from top to bottom. Refer again to the schematic in F ure la. At the top of the TEM column is an electron source or gun. An electrostatic lens is used to accelerate electrons emitted by the filament to a h potential (typically 100-1,000 kV) and to focus the electrons to a cross-over just above the anode (the diameter of the cross-over image can be from 0.5 to 30 Mm, depending on the type of gun ). The electrons at the cross-over image of the filament are delivered to the specimen by the next set of lenses on the column, the condensers. 

With ever-increasing frequency, authors also need to know how to format references to electronic sources (e.g., general Web sites, online periodicals, and online books). When this textbook was printed, such references were relatively uncommon. However, we briefly address references to general Web sites in exercise 17.13. For examples of other types of electronic sources and formatting expectations, consult a recent issue of your targeted journal or the most recent edition of The ACS Style Guide. 

Cross-References to Other INDs. At times, IND submissions are supported by a cross-reference to another IND [21 CFR 312.23(b)]. The utility of the electronic IND submission will be further increased if all reference materials are supplied with the IND submission. You should handle these files in the same manner as other electronic files submitted to the IND. For example, you should generate the files from electronic source files rather than from scanned paper documents if at all possible. If the electronic source file is not available, we will accept a scanned copy. You should describe the file format and organization of these files as described in this guidance. 

Chapter 14, References , presents the editorial style for electronic sources listed in reference lists and bibliographies. 

Data sourcing consists of dehning, in existing systems or documentation, the master reference (prime source) for the data entities required to support the new system. In some instances data may need to be created because they do not already exist electronically. 

In addition to N assimilation, nitrogen compounds in nature can also be used as electron sources or sinks, especially by prokaryotes (but not exclusively, see Zvyagil skaya et al., 1996). The enzymes that mediate these dissimilatory reactions have been studied extensively in the context of inputs and losses of fixed N in the marine N budget. Many of these measurements have been based on enzyme activities (e.g., dissimilatory nitrate reductase). Since dissimilatory reactions have been reviewed elsewhere in this volume (Chapter 5 by Ward and Chapter 6 by Devol, this volume), these wiU not be discussed further and we refer the reader to these chapters. 

The encyclopedia is meant to give relatively succinct overviews of sometimes very complex subjects. Formal references and footnotes were dispensed with because these seemed less relevant to the encyclopedia s goals than a simple list of recommended readings designed to lead the reader to more detailed information on a particular subject entry. The entry on Information Resources leads readers to print and electronic sources of information in toxicology. 

If the material you are citing comes from an electronic source that has no page numbers, use the author s last name in the text, if possible. If the author s name is unavailable, use a short reference to the work s title. 

Note Some instructors may ask you to include the paragraph number, the screen number, or the page number of the reference within the electronic source s total number of pages, especially if the document is lengthy. The example that follows shows how a reader could quickly find the information in the sixth paragraph instead of searching through the entire document. 

APA reference entries for electronic sources as shown on the APA Web site do not end with a period. 

For the latest information on APA reference entries for electronic sources, consult the Web site listed above. 

The final class of photosynthetic bacteria, the green sulfur bacteria, are named because of differences in the chemical structure of their bacte-riochlorophyll and carotenoids, giving rise to a different set of absorption bands in whole cells from their purple counterparts. This has little to do with their actual color but refers to the direction of shift of absorption wavelengths in the infrared. As photoautotrophic, strict anaerobes using sulfide or thiosulfate as an electron source, they resemble the purple sulfur bacteria and have similar electron transport chains. The sulfur that is formed as an intermediate between sulfide and sulfate is deposited out-... 

Electron sources used in EBL exposure tools are similar to those used in conventional electron microscopes. They can be divided into two main groups— thermionic or field emission—depending on the way in which they emit electrons. The sources that rely on the emission of electrons from a material that is heated to a temperature at which electrons are emitted from the surface are referred to as thermionic sources. These sources are fabricated from materials such as tungsten, thoriated tungsten, or lanthanum hexaboride (LaBe). ... 

Testing theories of charge transfer at interfaces between biological materials and solutions involves an experimental difficulty the connecting of an electron source (wire) to the membrane. To avoid this, one may employ low area (0.01 cm ) membranes (BLM) within small holes made in thin Teflon sheets with a potential difference applied across the membrane by means of two platinum electrodes (Figure 2). Reference electrodes on either side of the membrane register the total potential difference across it. 

The most cited reference electrode is the platinum-hydrogen electrode, and electrode DC potentials are often given relative to such an electrode. It is an important electrode for absolute calibration, even if it is impractical in many applications. The platinum electrode metal is submerged in a protonic electrolyte solution, and the surface is saturated with continuously supplied hydrogen gas. The reaction at the platinum surface is a hydrogen redox reaction H2 2H (aq) + 2e, of course with no direct chemical participation of the noble metal. Remember that the standard electrode potential is under the condition pH = 0 and hydrogen ion activity 1 mol/L at the reference electrode. Thus the values found in tables must be recalculated for other concentrations. Because of the reaction it is a hydrogen electrode, but it is also a platinum electrode because platinum is the electron source or sink, and perhaps a catalyst for the reaction. 

Microwave radiometer consists of an electronic switch, circulator, isolator, low-noise amplifier, filter, amplitude detector and miniature reference noise source with the temperature sensor. All foregoing components parts must be designed in miniature sizes using MMIC and plastic materials. 

Nucleophilic substitution refers to any reaction in which an electron-rich nucleophile (meaning nucleus loving) (Nu ) replaces a leaving group (Lv). Viewed in the context of the mechanism elements first described in the Mechanism Primer prior to Chapter 6, nucleophilic substitution is a combination of making a new bond between a nucleophile and an electrophile and breaking a bond so that relatively stable molecules or ions are created. All nucleophiles are electron sources and can be considered Lewis bases (Section 4.7). With the exception of radical reactions (Chapter 8), essentially every reaction you will study involves a reaction of a Lewis acid (that can also be considered a good electron sink) with a Lewis base. In these reactions, the Lewis base, which is electron-rich, reacts with the Lewis acid. 

A schematic diagram for a simple pH meter is shown in Figure 5.13. It is nothing more than a conventional potentiometer circuit. The precision slide wire (PSW) is calibrated in units of pH rather than in volts or ohms. A stable power supply is used, which may be a battery or a regulated electronic supply. The reference voltage source may be an unsaturated standard cell or a zener diode electronic reference. 

An electrochemical cell is a device that consists of two electronic conductors (usually a metal) called electrodes each dipping into separate ionic solutions. They are inserted within an electrical circuit (see Chap. 2 and Figs. 2.1 and 2.2). Hence, a cell consists of two compartments, each of which consists of an electrode and a solution into which it dips. Both electrodes seldom dip into the same electrolytic solution. In the literature, the word electrode may refer to the whole compartment where it stands. In brief, an electrochemical cell is a system in which one of the electronic conductors acts as an electron source for particules in an ionic conductor (the solution) and the other as an electron sink that receives electrons from the ionic conductor. 

Cop dng is permitted, with reference to source, but material in this publication may not be used in any documentation or electronic media which is offered for sale, without the prior permission of the copyright owner. 

Unfocused high energy e-beam heating can be accomplished with an electron source by applying a voltage between the electron emitter and the source material or source container, which is usually at ground potential. Such a somce is referred to as a work-accelerated gun. 

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