NEP

Bock et al [4] have an electrical NEP (noise-equivalent power) of 4 x 10 W Hz when cooled to 300 mK. For those who desire less exotic cryogenic options, conmiercially available Si-composite bolometers offer an... 

In practice, the NEP of a room-temperature THz spectrometer is usually limited by fluctuations (shot-noise) in the ambient blackbody radiation. Usmg an optical bandwidth Av = 3 THz (limited by, for example, a polyethylene/diamond dust window), a field of view (at nomial incidence) 0 = 9 and a detecting diameter (using a so-called Winston cone, which condenses the incident radiation onto the detecting element) laboratory applications, the background-limited NEP of a bolometer is given by... 

THz. Therefore, for laboratory absorption experiments, a typical FIR detector provides an estimated detection limit (NEP/source power) of 10 with a source output of 20 nW. In general, high-sensitivity bolometers... 

The NEP may be written in terms of the detector element active area, the number of detector pixels elements cormected for additive output the electronic noise bandwidth B and the detector element detectivity, D. Typically = 1, but may be increased for improved sensitivity with an attendant loss in resolution. 

Thermographic Sensitivity. The noise equivalent temperature difference (sensitivity to scene temperature variations ia degrees C) maybe expressed ia terms of the NEP ... 

The sensitivity equation can be developed by differentiating equation 4 with respect to J. Since the signal is proportional to J and detection is defined as to when the measured signal to noise ratio equals 3, the gas detection sensitivity (ppm) in terms of the NEP for gas detection becomes ... 

This expression includes the use of detector arrays of detectors with additive signals and sample addition of samples to improve sensitivity. Typical sensor parameters are = 1 mW/cm, NEP = 30 pW, = 1.5E — 5 cm, = 60, = 1 for imaging and ca 600 for nonimaging gas detection. 

Fig. 4. Sensitivity for the detection of CO using spectral thermography as a function of absorbing path length. Detector NEP = 30 pW, J = 1.0 mW/cm, A = 1.5E — 5 cm, samples = 60, number of detectors = 600, G = 6.6E5 ppm-cm center wavelength = 4.65 /im spectral bandwidth = 0.2 fim.

Because NEP is roughly proportional to D is more useful for comparing detectors of differing sizes. D depends on the wavelength distribution striking the detector (if it is quantum) and the frequency at which the radiation is modulated, so these measurement parameters need to be included for a D value to have meaning. Often detectivity is written as where Tis the temperature of the blackbody source of radiation or the wavelength of the... 

Litde is known about metaboHc inactivation of ( -endorphin and the dynorphins. NEP, and to a lesser extent APN, are only weaMy active against P-endorphin (183). Enzymes are known which degrade P-endorphin in vitro under nonphysiological conditions (202) or which inactivate P-endorphin by N-acetjlation (203). Alack of specific degradative enzymes for these peptides may account for their relatively long half-life in vivo though this has not been definitively estabUshed. 

Detectivity. Detector sensitivity (1,2) is expressed in terms of the minimum detectable signal power or noise equivalent power (NEP) given in units of watts or W. The reciprocal function when normalized for detector area, M, and noise bandwidth, is defined as detectivity, D, in units of /W. Thus,... 

EP. The noise components may be combined with the responsivity to give the noise equivalent power (NEP) equation ... 

Pavlinec and Lazar [39] reported that organic hydroperoxide and piperidine(PD) could be used as an initiator for MMA polymerization. In our laboratory, we also found that TBH-NMMP, TBH-NEMP [20], TBH-PD(piperidine) [31], TBH-NEP(N-ethylpiperdine) [31], TBH-TMDAPM (N,N -tertramethyl-diamin-odiphenyl-methane), and TBH-TMEDA(MN.NW -tera-methylethylenediamine) [15] systems could initiate MMA to polymerize. The kinetic equation of MMA polymerization initiated with CHP-DMT system has been investigated in our laboratory and the rate equation of polymerization is shown as follows ... 

Area of Segment nep- Area of Circle — Area of Segment nop... 

FIGURE 9.20 Design of multiple ligancl activity, (a) Dual histamine HI receptor and leukotriene receptor antagonist incorporating known antihistaminic properties of cyproheptadine and LTD4. (b) Joint ACE/NEP inhibitor formed from incorporating similarities in substrate structures for both enzymes. From [57],... 

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