Filtering effect

McMorrow D and Lotshaw W T 1990 The frequency response of condensed-phase media to femtosecond optical pulses spectral-filter effects Cham. Phys. Lett. 174 85-94... 

The model consists of a two dimensional harmonic oscillator with mass 1 and force constants of 1 and 25. In Fig. 1 we show trajectories of the two oscillators computed with two time steps. When the time step is sufficiently small compared to the period of the fast oscillator an essentially exact result is obtained. If the time step is large then only the slow vibration persists, and is quite accurate. The filtering effect is consistent (of course) with our analytical analysis. Similar effects were demonstrated for more complex systems [7]. 

Despite their theoreticaUy poor washing performance, due to uneven wash distribution and excessive mn-off because the filter surface is not horizontal, many multicompartment dmm filters continue to be used as cake washing filters. Effective washing of the filter cloth can be done only with the belt discharge type, where the cloth leaves the dmm for a brief period and can thus be washed on both sides. 

The lifetime of a filter is dependent on the concentration of dust, type of dust, airflow, and, of course, the selected final pressure loss. Filter material and filter construction are often a compromise or combination of filter effects and installation space. Low speed or large filter surface promotes efficiency, low pressure loss, but above all a longer lifetime. 

The situation may be complicated further by the presence of absorption edges and by the filtering of a polychromatic beam if such is used for excitation. The filtering effect can be approximately treated by choosing a suitable effective wavelength for the polychromatic beam. Sherman10 has given the most complete theoretical treatment of the... 

In addition, Montenegro et al., (2007) determined that the photosensitized RF-mediated degradation of vitamins A, D3, and RF itself in skimmed milk was strongly reduced by the addition of small amounts of lycopene-gum arabic-sucrose microcapsules, prepared by spray-drying. Under these conditions, the bulk properties of the skimmed milk were unmodified. The main photoprotection mechanism of the milk vitamins was the efficient quenching of the 3Rf by the protein moiety of GA. Small contributions (<5%) to the total photoprotection percentage was due to both inner filter effect and 1O2 quenching by the microencapsulated lycopene. 

Here use is made of the approximation ecdl0 a / for OD < 0.05. Low concentrations of both compounds must be used to avoid absorption of the emitted light by an inner filter effect. 

The products of the photodecomposition of the ferrioxalate absorb only weakly at wavelengths absorbed by ferrioxalate and therefore provide no problem with regard to a product filter effect. This can be seen from Table 2.7. 

Energy transfer by the trivial mechanism is characterized by (a) change in the donor emission spectrum (inner filter effect), (b) invariance of the donor emission lifetime, and (c) lack of dependence upon viscosity of the medium. 

Use of an algorithm to eliminate the inner-filter effect in a bioreactor 194... 

Figure 2 Comparison of NO + 03 and NO + O chemiluminescence spectra with blue and red optical filter transmissions and the response of a blue-sensitive photomultiplier tube. Note the blue shift of the NO reaction with O compared to that with 03 and that the addition of a blue filter effectively removes emission from NO + 03, while the red filter effectively removes emission from NO + O.

Detection Inlet heat exchangers Flow cell volume and geometry MS ion sources Sprayers (e.g., in evaporative light scattering detectors) Data filtering effects in high speed applications... 

Barrier filters include a range of porous materials that allow gases to penetrate but prevent the passage of particulates. These filters effectively remove small-diameter particulates in the range of 0.5 to 100 pm in diameter from gas streams. Barrier filters can be designed to remove almost any size of particulate, including those in the sub-micron range, but the pressure differential across the filter will increase as the pore size decreases. 

Some of these problems can be overcome with a different calorimetric design (see later discussion). Other problems, which are more dependent on the chemistry and physics of the process under study than on the instrumentation, require careful attention. Unnoticed side reactions or secondary photolysis are examples, but one of the most serious error sources in photocalorimetry is caused by the quantum yield values, particularly, as explained, when they are small. Unfortunately, many literature quantum yields are unreliable, and it is a good practice to determine n for each photocalorimetric run. Errors in

inner filter effects, that is, photon absorption by reaction products. 

Moreover, when the concentration of fluorescent compound is high, inner filter effects reduce the fluorescence intensity depending on the observation conditions (see Chapter 6). In particular, the photons emitted at wavelengths corresponding to the overlap between the absorption and emission spectra can be reabsorbed (radiative transfer). Consequently, when fluorometry is used for a quantitative evaluation of the concentration of a species, it should be kept in mind that the fluorescence intensity is proportional to the concentration only for diluted solutions. 

Radiative transfer results in a decrease of the donor fluorescence intensity in the region of spectral overlap. Such a distortion of the fluorescence spectrum is called the inner filter effect (see Chapter 6). 

Attention should be paid to possible problems in the measurement of fluorescence quantum yields (some of which are discussed Section 6.1.5) inner filter effects, possible wavelength effects on Op, refractive index corrections, polarization effects, temperature effects, impurity effects, photochemical instability and Raman scattering. 

Pitfalls in steady-state fluorescence measurements inner filter effects and polarization effects... 

Emission inner filter effect (self-absorption) The fluorescence photons emitted in the region overlapping the absorption spectrum can be absorbed (radiative energy trans-... 

Inner filter effects due to the presence of other substances When the solution contains other chromophores that absorb light in the same wavelength range as the fluorescent compound under study, the chromophores act as filters at the excitation wavelength and the fluorescence intensity must be multiplied by a correction factor. If the chromophores do not interact with the fluorescent compound, the correction factor is simply the fraction of light absorbed by the compound at the chosen excitation wavelength, so that the corrected fluorescent intensity is given by ... 

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