Open path

One can trace the continuous evolution of 0 (or of 0/2) as <() describes the circle q = constant. This will yield the topological phase (as well as intermediate, open-path phase during the circling). We illustrate this in the next two figures for the case q > 1 (encircling the ci s). 

The open-path phase [11,14] associated with a component amplitude can be obtained as the imaginary part of an integral... 

Experimental observation of topological phases is difficult, for one reason (among others) that the dynamic-phase part (which we have subtracted off in our formalism, but is present in any real situation) in general oscillates much faster than the topological phase and tends to dominate the amplitude behavior [306-312]. Several researches have addressed this difficulty, in particular, by neutron-interferornehic methods, which also can yield the open-path phase [123], though only under restricted conditions [313]. 

G. Russwurm and J. W. Childers, FTIR Open Path Monitoring, Guidance Document, EPA Contract 68-D5-0049, ManTech Environmental Technology Inc., Research Park, N.C., 1996. 

The environmental appHcations of infrared spectrometry are many and varied. Many appHcations at industrial sites are analogous to those for on-line process analysis waste streams and recycling processes can be monitored in the same way. Commercial infrared stack-gas monitors are based on either an extractive probe attached to a long-path gas ceU or an open-path (across stack) configuration (69). Stack plume and flare monitoring can be done externally... 

Applications The differential optical absorption spectrometer has been used to monitor concentrations of gases or intermediate compounds such as SO, NO, O5, HCHO, HNO, CS, NO, and OH in the atmosphere.In atmospheric measurements with open paths of 100 to 1000 m, a detection limit of about 1 ppb can be achieved. In the emission measurements, the path length across the duct or the plume can range in meters. 

Carter RE Jr., Thomas MJ, Marotz GA, et al. 1992. Compound detection and concentration estimation by open-path Fourier transform infrared spectrometry and canisters under controlled field conditions. Environ Sci Technol 26(11 ) 2175-2181. 

Bromination of bicyclopropenyl system 369 at ambient temperature in absolute CHCI3 leads either to diene 372 (15%) and trienes 374-376 (15%, 35% and 10%, respectively) when R = H, or to the stable cyclopropenium salt 371 (95%) when R = Ph (equation 134)188. The electrophilic attack of bromine on compounds 369 creates the cationoid intermediates 370 which undergo either fragmentation to salt 371 (path a) or an electrocyclic ring opening (path b). When diene 372 is heated at about 150 °C in the solid state it rearranges to 1,2,3,5-tetraphenylbenzene 373 with concomitant loss of bromine. 

Open Path Gas Detectors (OPGDs) (Figure 7-23) produce an IR beam that is directed across the area to be monitored. The received light is analyzed at two or more frequencies, some of which is absorbed by the target gas or gases the reference frequency is not. Given the initial and final intensities, the average concentration of gas in the path is calculated and transmitted. Some instruments operate with separate trans-... 

Point Combustible Gas Detectors (IR) are used to indicate the presence of gas at a particular location (e.g., in a congested area of the planter in small ducts.) IR technology has proven to be more reliable than catalytic bead detectors. The point detector functions in the same manner as the open path detector, by comparing absorbed and reference frequencies of IR light. The main difference between these and open path type is that the path length of the point type is short (3 inches) and is kept within the confines of the instrument. 

Three-dimensional detector coverage, as shown in Figure 8-5, can be obtained by a triangular grid (isometric) pattern of point or open path detectors, with a maximum separation less than the gas cloud diameter that can... 

Yokelson, R. J., D. W. T. Griffith, and D. E. Ward, Open-Path Fourier Transform Infrared Studies of Large-Scale Laboratory Biomass Fires, . /. Geophys. Res., 101, 21067-21080 (1996). 

The variability of hazardous air pollutants (HAPs) is an important factor in determining hnman exposure to such chemicals, and in designing HAP measurement programs. The factors that contribute to HAP variability in an urban area also affect their global impact. Temporal variation was the major contributor to HAP variability for 19 of the 39 frequently detected compounds (Spicer et al., 1996). In the future, more precise measurement tools will be available to determine HAPs. Open-path monitoring of the atmosphere using Fourier transform infrared spectrometry has recently become... 

This is a major route of decomposition of ethyl 2-furyldiazoacetate (%) (R = H, = C02Et) when heated in dichloromethane or methanol (74JOC2939). The same type of decomposition has been observed with other 2-furylcarbenes which were generated by decomposition of the sodium salts of tosylhydrazones at 3(X)°C (78JA7927). Thermolysis of the diazo compound 96 (R = R = H) in cyclooctane or styrene gave, besides the open-chain acetylene 97, products of intermolecular carbene insertion. This led the authors to favor the carbene mechanism of ring-opening (path A in Scheme 7). 

For all these systems the spontaneous ring-opening path was, however, non-existent. Such a path may be of minor importance (3,90-92). 

A second avenue is to intensively reinvestigate and develop Kron s [43] discovery of the open path for EM networks as a dual of the conventional closed path. 

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