Modulation of absorption

Powell, D.W., Barrier function of epithelia. Am. J. Physiol., 241 G275-G288 (1981). Nellans, H.N., Paracellular intestinal transport modulation of absorption, Adv. Drug Del. Rev., 7 339-364 (1991). 

Troutman MD, Thakker DR. Novel experimental parameters to quantify the modulation of absorptive and secretory transport of compounds by P-glycoprotein in cell culture models of intestinal epithelium. Pharm Res 2003 20(8) 1210-1224. 

Nellans, H.N. Paracellular intestinal transport modulation of absorption. Adv. Drug Delivery Rev. 1991, 7, 339-364. 

A variety of other small molecules and proteins have also been incorporated with liposomes. In all cases, modulation of absorption or the response has been distinguished due to the presence of the phospholipids. A brief discussion on selected molecules now follows. 

However, for the same data collection time, interferometry is more sensitive to multiplicative noise (i.e., noise proportional to the signal) than continuous-scan interferometry [591]. To eliminate the multiplicative and 1// noise, phase modulation (at 400 Hz) of IR radiation in conjunction with LIA demodulation is used [591]. Since the LIA and some IR detectors need the IR signal to be modulated at a single carrier frequency, a mechanical chopper, phase modulation (when at each position the fixed mirror is dithered at a fixed frequency), or modulation of absorption of the sample is used to produce a carrier frequency. In this case, the TR measurement is referred to as a synchronous multiple-modulation experiment. Multiple modulation is unnecessary if the so-called dc coupled detector which does not require a varying signal is used. 

The complete set of the three normal vibrations (0-0 stretch), vg (bend), and vg (0-F stretch), has only been observed by IR absorption of the radical isolated in various matrices. In the gas phase, the band center (at 1489 cm" ) was found with a Fourier transform IR spectrometer [2]. Only a small section of the band around 1480 cm" was observed by tuning the Zeeman splittings of vibration-rotation transitions to selected lines of a CO laser (laser magnetic resonance, LMR) [1]. Vg = 579.31839 0.00035 cm (band origin) was measured with a tunable IR diode laser and using Zeeman modulation of absorption lines [3]. 

The pyrolysis of CR NH (<1 mbar) was perfomied at 1.3 atm in Ar, spectroscopically monitoring the concentration of NH2 radicals behind the reflected shock wave as a fiinction of time. The interesting aspect of this experiment was the combination of a shock-tube experiment with the particularly sensitive detection of the NH2 radicals by frequency-modulated, laser-absorption spectroscopy [ ]. Compared with conventional narrow-bandwidth laser-absorption detection the signal-to-noise ratio could be increased by a factor of 20, with correspondingly more accurate values for the rate constant k T). 

RAIRS is a non-destructive infrared technique with special versatility - it does not require the vacuum conditions essential for electron spectroscopic methods and is, therefore, in principle, applicable to the study of growth processes [4.270]. By use of a polarization modulation technique surfaces in a gas phase can be investigated. Higher surface sensitivity is achieved by modulation of the polarization between s and p. This method can also be used to discriminate between anisotropic near-sur-face absorption and isotropic absorption in the gas phase [4.271]. 

The requirement I > 2 can be understood from the symmetry considerations. The case of no restoring force, 1=1, corresponds to a domain translation. Within our picture, this mode corresponds to the tunneling transition itself. The translation of the defects center of mass violates momentum conservation and thus must be accompanied by absorbing a phonon. Such resonant processes couple linearly to the lattice strain and contribute the most to the phonon absorption at the low temperatures, dominated by one-phonon processes. On the other hand, I = 0 corresponds to a uniform dilation of the shell. This mode is formally related to the domain growth at T>Tg and is described by the theory in Xia and Wolynes [ 1 ]. It is thus possible, in principle, to interpret our formalism as a multipole expansion of the interaction of the domain with the rest of the sample. Harmonics with I > 2 correspond to pure shape modulations of the membrane. 

VAUGELADE P, HOEBLER C, BERNARD F, GUILLON F, LAHAYE M, DUEE P H, DARCY-VRILLON B (2000) Non-Starch polysaccharides extracted from seaweed can modulate intestinal absorption of glucose and insulin response in the pig. Reprod Nutr Dev. 40 33-47. 

The pigment identification is performed by the recognition of its characteristic absorption spectra. The pigment quantification is revealed by the extent of absorption (optical density). Each of these properties may be modulated by the direct environment into which the pigment molecule is incorporated. We look at this in some detail. 

Local surface structure and coordination numbers of neighbouring atoms can be extracted from the analysis of extended X-ray absorption fine structures (EXAFS). The essential feature of the method22 is the excitation of a core-hole by monoenergetic photons modulation of the absorption cross-section with energy above the excitation threshold provides information on the distances between neighbouring atoms. A more surface-sensitive version (SEXAFS) monitors the photoemitted or Auger electrons, where the electron escape depth is small ( 1 nm) and discriminates in favour of surface atoms over those within the bulk solid. Model compounds, where bond distances and atomic environments are known, are required as standards. 

When the absorption is detected via small amplitude field modulation, the signal is proportional to the first derivative of absorption ... 

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