Directional sense

There are many types of sen.sors used to feed-back the process operating conditions to the switching logistics of an inverter unit. They can be in terms of temperature, pressure, volume, flow, time or any activity on which depends the accuracy and quality of the process. Direct sensing devices used commonly for the control of a drive and used frequently in the following text are speed. sensors, as noted below. 

Figure 12.25 Power and control scheme for a current-operated single-phasing preventor (direct sensing up to =- 30 A)...

Some wave phenomena, familiar to many people from the human senses, include the easy undulation of water waves from a dropped stone or the sharp shock of the sonic boom from high-speed aircraft. The great power and energy of shock events is apparent to the human observer as he stands on the rim of the Meteor Crater of Arizona. Human senses provide little insight into the transition from these directly sensed phenomena to the high-pressure, shock-compression effects in solids. This transition must come from development of the science of shock compression, based on the usual methods of scientific experimentation, theoretical modeling, and numerical simulation. 

Nucleic acids are linear polymers of nucleotides linked 3 to 5 by phosphodi-ester bridges (Figure 11.17). They are formed as 5 -nucleoside monophosphates are successively added to the 3 -OH group of the preceding nucleotide, a process that gives the polymer a directional sense. Polymers of ribonucleotides are named ribonucleic acid, or RNA. Deoxyribonucleotide polymers are called deoxyribonucleic acid, or DNA. Because C-1 and C-4 in deoxyribonucleotides are involved in furanose ring formation and because there is no 2 -OH, only... 

The foregoing examples do not represent useful chiral formyl anion equivalents in a direct sense since the stereoselectivity of the initial addition to aldehydes is poor, although as has been explained, the situation is salvaged by oxidation and re-reduction. On the other hand, by lithiation at the 2 position of the achiral oxazo-lidine 53 in the presence of (-)-sparteine followed by addition of benzaldehyde, useful levels of d.e. and e.e. are achieved directly (98TA3125). For example, by adding MgBr2 before the benzaldehyde, the major product obtained is 54 in 80% d.e. and 86% e.e. 

The effect, which arises in cases where the interfacial tension is strongly dependent on the concentration of diffusing solute, will generally be dependent on the direction (sense) in which mass transfer is taking place. 

Since spillover phenomena have been most directly sensed through the use of IR in OH-OD exchange [10] (in addition, in the case of reactions of solids, to phase modification), we used this technique to correlate with the catalytic results. One of the expected results of the action of Hjp is the enhancement of the number of Bronsted sites. FTIR analysis of adsorbed pyridine was then used to determine the relative amounts of the various kinds of acidic sites present. Isotopic exchange (OH-OD) experiments, followed by FTIR measurements, were used to obtain direct evidence of the spillover phenomena. This technique has already been successfully used for this purpose in other systems like Pt mixed or supported on silica, alumina or zeolites [10]. Conner et al. [11] and Roland et al. [12], employed FTIR to follow the deuterium spillover in systems where the source and the acceptor of Hjp were physically distinct phases, separated by a distance of several millimeters. In both cases, a gradient of deuterium concentration as a function of the distance to the source was observed and the zone where deuterium was detected extended with time. If spillover phenomena had not been involved, a gradientless exchange should have been observed. 

Merlot S, Firtel RA. Leading the way directional sensing through phosphatidylino-sitol 3-kinase and other signaling pathways. J Cell Sci 2003 116(Pt 17) 3471-3478. 

The above system of directly sensing a process stream without more is often not sufficiently accurate for process control so, robot titration is preferred in that case by means of for instance the microcomputerized (64K) Titro-Analyzer ADI 2015 (see Fig. 5.28) or its more flexible type ADI 2020 (handling even four sample streams) recently developed by Applikon Dependable Instruments20. These analyzers take a sample directly from process line(s), size it, run the complete analysis and transmit the calculated result(s) to process operation (or control) they allow for a wide range of analyses (potentiometric, amperometric and colorimetric) by means of titrations to a fixed end-point or to a full curve with either single or multiple equivalent points direct measurements with or without (standard) addition of auxiliary reagents can be presented in any units (pH, mV, temperature, etc.) required. 

Cush R., Cronin J.M., Stewart W.J., Maule C.H., Molloy J., Goddard N. J., The resonant mirror a novel optical biosensor for direct sensing of biomolecular interactions, Part I Principle of operation and associated instrumentation, Biosensors and Bioelectronics 1993 8 347-353. 

Buckle, P. E. Davies, R. J. Kinning, T. Yeung, D. Edwards, P. R. Pollard Knight, D. Lowe, C. R., The resonant mirror A novel optical biosensor for direct sensing of biomelcular interactions. Part II Applications, Biosens. Bioelectron. 1993, 8, 355 363... 

Many compounds exhibit near-IR and mid-IR absorption. By using IR transparent optical fibers, detection of an absorption band in the IR region is possible for optical sensing. Both direct sensing using the absorption property of the analyte or indicator sensing are widely exploited. Most mid-IR sensing schemes are based on the principles of internal reflection spectroscopy, or the attenuated total reflection (ATR) [3,14-21],... 

R. Cush, J. M. Cronin, W. J. Stewart, C. H. Maule, J. Molloy, and N. J. Goddard, "The Resonant Mirror A Novel Optical Biosensor for Direct Sensing of Biomolecular Interactions Part I Principle of Operation and Associated Instrumentation," Biosensors Bioelectronics 8, 347-354 (1993). 

Macromolecule, the structure of which essentially comprises the repetition of a single constitutional unit with all units connected identically with respect to directional sense. 

Type of crystal resulting from parallel packing of stems, irrespective of the stems directional sense. 

An irregular polymer is a substance composed of irregular macromolecules, the structure of which essentially comprises the repetition of more than one type of constitutional unit, or of macromolecules, the structure of which comprises constitutional units not all connected identically with respect to directional sense. 

Any number of amino acids can be joined by successive peptide linkages, forming a polypeptide chain. The polypeptide chain, like the dipeptide, has a directional sense. One end, called the N-terminal, or amino-terminal, end, has a free a-amino group, whereas the other end, the C-terminal, or carboxyl-terminal, end, has a free a-carboxyl group. The sequence of main-chain atoms from the N-terminal end to the C-terminal end is N—Ca—C—N and so on, and in the opposite direction it is C—Ca—N—C and so on. Short polypeptide chains, up to a length of about 20 amino acids, are called peptides or oligopeptides if they are fragments of whole polypeptide chains. A small protein mole-... 

The polynucleotide chain has a directional sense with 5 and 3 ends. Either of these ends may contain a free hydroxyl group or a phosphorylated hydroxyl group. The structure shown in figure 25.3 contains a phosphate group on the 5 end but none on the 3 end. By convention, one writes a nucleic acid sequence from the 5 to the 3 end so that a comparable structure is written pTpApCpG. With no... 

While searching for the meaning of these equalities, James Watson noted that hydrogen-bonded base pairs with the same overall dimensions could be formed between A and T and between G and C (fig. 25.4). The A-T base-paired structure has two hydrogen bonds, whereas the G-C base pair has three. The hydrogen-bonded pairs are formed between bases of opposing strands and can only arise if the directional senses of the two interacting chains are opposite or antiparallel (fig. 25.5). With this notion in mind Francis Crick took a closer look at the x-ray diffraction pattern produced by DNA and was able to interpret the diffraction pattern in terms of a helix (see Methods of Biochemical... 

Polynucleotide. A chain structure containing nucleotides linked together by phosphodiester (5 -3 ) bonds. The polynucleotide chain has a directional sense, with a 5 and a 3 end. 

Polypeptide. A linear polymer of amino acids held together by peptide linkages. The polypeptide has a directional sense, with an amino- and a carboxyl-terminal end. 

The anows can be written in either directional sense since these reactions are concerted rearrangements with all bond making-bond breaking taking place at die same time. This example emphasizes the fact that curved-arrow notation is merely an electron bookkeeping method. 

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