Detection Times

One early program carried out at AUied-Signal, Inc. proposed the use of conductive polymers in remotely readable indicators (210). Conductivity changes induced in the conductive polymer could be read externally and the history of the sample known. Systems designed to detect time—temperature, temperature limit, radiation dosage, mechanical abuse, and chemical exposure were developed. 

Figure 3.3 The mechanics of obtaining a two-dimensional NMR spectrum. As the l value is varied, the magnetization vectors are caught during detection at their various positions on the x /-plane. The value of the detection time l-i is kept constant. The first set of Fourier transformations across is followed by transposition of the data, which aligns the peaks behind one another, and a second set of Fourier transformations across t then affords the 2D plot.

In three-dimensional experiments, two different 2D experiments are combined, so three frequency coordinates are involved. In general, the 3D experiment may be made up of the preparation, evolution (mixing periods of the first 2D experiment, combined with the evolution t ), mixing, and detection ( ) periods of the second 2D experiment. The 3D signals are therefore recorded as a function of two variable evolution times, t and <2, and the detection time %. This is illustrated in Fig. 6.1. 

The most difficult materials to study by NMR microscopy are those with short T2 or T2 relaxation times and/or with low concentrations of the nudear spins, which normally result in poor NMR signal intensities. One possibility for improving the image quality is to adapt the shape and size of the rf coils to the size of the objects in order to achieve the best possible filling factor and therefore the best sensitivity [1]. In addition, methods with short echo or detection times have been developed, such... 

Typical detection times for chemical and biological agents, 18... 

It is likely that with continued investment in research and development, it will be possible in the future to reduce the detection time for biological agent attacks below 1 hour, while maintaining or increasing the POD.10 A faster response time with high POD would increase the benefits of detection systems and the effectiveness of detection-based strategies. 

The leak detection sensitivity refers to the minimum top liner leak rate that can theoretically be detected, collected, and removed by the LDS. The leak detection time is the minimum time needed for liquids passing through the top liner to be detected, collected, and removed in the nearest down-gradient collection pipe. In the case of a composite top liner, the leak detection time refers to the period starting at the point when liquids have passed through the compacted soil component and ending at the point when they are collected in the collection pipe. 

Compliance with U.S. EPA s design performance standards can be demonstrated through one-dimensional, steady-state flow calculations, instead of field tests. For detection sensitivity, the calculation of flow rates should assume uniform top liner leakage. For detection time, factors such as drain spacing, drainage media, bottom slope, and top and bottom liners should all be considered, and the worst-case leakage scenario calculated. 

U.S. EPA specifies that the minimum detection time for the leachate entering the LDS of an LDCR system is <24 h. Response time calculations are based on velocity in the geonet and/or granular soil drainage layer. Darcy s law is used to calculate flow velocity in the geonet, and a true velocity must be used for granular soil. 

A major limitation of CW double resonance methods is the sensitivity of the intensities of the transitions to the relative rates of spin relaxation processes. For that reason the peak intensities often convey little quantitative information about the numbers of spins involved and, in extreme cases, may be undetectable. This limitation can be especially severe for liquid samples where several relaxation pathways may have about the same rates. The situation is somewhat better in solids, especially at low temperatures, where some pathways are effectively frozen out. Fortunately, fewer limitations occur when pulsed radio and microwave fields are employed. In that case one can better adapt the excitation and detection timing to the rates of relaxation that are intrinsic to the sample.50 There are now several versions of pulsed ENDOR and other double resonance methods. Some of these methods also make it possible to separate in the time domain overlapping transitions that have different relaxation behavior, thereby improving the resolution of the spectrum. 

Many advantages arise from a heterogeneous array including the miniaturization of the array, the high density of different sensor types, the presence of many replicates of each sensor type, shorter detection times due to the small sensor sizes, low materials cost, and the ease of preparation. 

In recent years, rapid advancements in photonic technologies have significantly enhanced the photonic bio/chemical sensor performance, especially in the areas of (1) interaction between the light and analyte, (2) device miniaturization and multiplexing, and (3) fluidic design and integration. This has led to drastic improvements in sensor sensitivity, enhanced detection limit, advanced fluidic handling capability, lower sample consumption, faster detection time, and lower overall detection cost per measurement. 

Spot coverage detectors are normally mounted as close as possible to the point of potential ignition. Examples are the extruder/cutter in a high explosives machining operation or the compression point in a shell loading machine. Spot detectors assure the fastest possible detection time by physically being mounted the closest to the point of ignition. 

When properly applied, ultraviolet detectors can serve as excellent fire detectors in munitions manufacturing. Detection times as fast as 10 milliseconds can be achieved while effectively resisting false alarms. 

The infrared (IR) detector is an extremely fast device that is capable of detection times as short as five milliseconds. In the past, infrared detectors have been unsuitable for general applications because of the large number of false alarm sources found in the work place. However, when properly applied in controlled surroundings, they can provide reliable and effective protection. 

System response time can be divided into two phases. The first is the detection time, that is the time from the actual detection of the fire to the time that the signal is amplified and fires the primer in the water control valve or opens the solenoid valve. The second phase is the time required from primer firing or valve opening to the time water exits from the fire protection nozzles. The detection time is the fastest phase and under ideal conditions can be accomplished in as little as 10 milliseconds. The second phase, water delivery time, is the source of most of the time consumption. 

Fig. 8. Laser-induced fluorescence detected times-of-flight for NO desorbed from Pt(foil) using 532 nm laser heating. The three traces were obtained while probing (top) NO (F, J—19.5 ,m° 662cm- ), (middle) NO (F J=12.5 , = 281cm- ) and (bottom) NO (F, J = 3.5, i , = 25cm" ). (Adapted from Rrf. 46.)...

Fuerstenau, S.D. Benner, W.H. Molecular Weight Detenniuation of Megadalton DNA Electrospray Ions Using Charge Detection Time-of-Fhght Mass Spectrometry. Rapid Commun. Mass Spectrom. 1995,9,1528-1538. 

Electrospray Ionization Mass Spectrometry - Fundamentals, Instrumentation and Applications 1st ed. Dole, R.B., editor John Wiley Sons Chichester, 1997. Fenn, J.B. Electrospray Wings for Molecular Elephants (Nobel Lecture). Angew. Chem., Int. Ed. 2003, 42, 3871-3894. Fuerstenau, S.D. Benner, W.H. Molecular Weight Determination of Megadalton DNA Electrospray Ions Using Charge Detection Time-of-Flight-MS. Rapid Commun. Mass Spectrom. 1995, 9, 1528-1538. 

A coelectrophoresed reference for converting detection times into mobilities must not be influenced by the presence of the binding partners. 

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