Confocal parameter

Figure 4b depicts for the case bAk -0.3 (b is the confocal parameter of the gaussian and Ak is the linear plane-wave, wave-vector mismatch, Ak=3 (n -no )/c). One can see that bAk>0 results in... 

The natural way to increase the efficiency of such a frequency conversion process is to use a focused fundamental beam (or, alternatively, a waveguide structure). An established theory of SHG using focused cw beams " predicts, for negligible birefringence waUc-off, an optimal focusing condition which is expressed by the ratio L/b 2.83, where b is the confocal parameter (b = k wQ, where Wqi and ky are the focal spot radius and the wave vector of the fundamental wave respectively). However, this theory applies only to the long-pulse or cw case, where GVM is negligible... 

The beam size expands due to diffraction as the light propagates away from the waist. The characteristic distance over which the beam radius remains smaller than Vl COo is called the confocal parameter, b, given by... 

A fiuther useful quantity, related to focused laser beams, is the confocal parameter defined as the distance between the two locations at each side of the focus at which the intensity has fallen to 50% of the maximum value ... 

Historically, this has been the most constrained parameter, particularly for confocal laser scanning microscopes that require spatially coherent sources and so have been typically limited to a few discrete excitation wavelengths, traditionally obtained from gas lasers. Convenient tunable continuous wave (c.w.) excitation for wide-held microscopy was widely available from filtered lamp sources but, for time domain FLIM, the only ultrafast light sources covering the visible spectrum were c.w. mode-locked dye lasers before the advent of ultrafast Ti Sapphire lasers. 

Note that parameters ft and 5 depend on signal amplifications in the utilized detectors and on the elements in the optical path (optical filter, spectral detection bands) only, while a and y are additionally influenced by relative excitation intensity. This is usually a fixed constant in wide-field microscopy but in confocal imaging laser line intensities are adjusted independently. Furthermore, note that the a factor equals 5 multiplied by y (see Appendix for further detail). 

In fluorescence correlation spectroscopy (FCS), the temporal fluctuations of the fluorescence intensity are recorded and analyzed in order to determine physical or chemical parameters such as translational diffusion coefficients, flow rates, chemical kinetic rate constants, rotational diffusion coefficients, molecular weights and aggregation. The principles of FCS for the determination of translational and rotational diffusion and chemical reactions were first described in the early 1970s. But it is only in the early 1990s that progress in instrumentation (confocal excitation, photon detection and correlation) generated renewed interest in FCS. 

Imaging is performed using a sensitive, high-resolution confocal system like the Opera instrument (Perkin Elmer). Table 1 summarizes the relevant imaging parameters used (see Note 5). 

Owing to the simphcity and versatility of surface-initiated ATRP, the above-mentioned AuNP work may be extended to other particles for their two- or three-dimensionally ordered assemblies with a wide controllabiUty of lattice parameters. In fact, a dispersion of monodisperse SiPs coated with high-density PMMA brushes showed an iridescent color, in organic solvents (e.g., toluene), suggesting the formation of a colloidal crystal [108]. To clarify this phenomenon, the direct observation of the concentrated dispersion of a rhodamine-labeled SiP coated with a high-density polymer brush was carried out by confocal laser scanning microscopy. As shown in Fig. 23, the experiment revealed that the hybrid particles formed a wide range of three-dimensional array with a periodic structure. This will open up a new route to the fabrication of colloidal crystals. 

The internal structure of the complexes can directly determine the mechanism of transfection [4, 23, 25]. We have found that for Lac CL-DNA complexes, the membrane charge density (aM) is a predictive parameter for transfection efficiency [21] (see Sect. 2), i.e., the data for monovalent and multivalent cationic lipids are described by a simple bell-curve. In contrast, for inverted hexagonal HnC CL-DNA complexes, TE is independent of aM, suggesting a distinctly different mechanism of transfection. Consistent with the TE data, confocal microscopy revealed distinctly different CL-DNA complex pathways and interactions with cells, which depended on both the structure (HnC vs Lac) and, for Lr/ complexes, on aM [25]. Thus, the mechanism of transfection by CL-DNA complexes is dependent both on their structure and, for a given structure, on chemical and physical parameters of the complexes. 

Fig. 21 Steady state incoherent intermediate scattering functions d> (r) as functions of accumulated strain yt for various shear rates y the data were obtained in a col loidal hard sphere dispersion at packing fraction

Mitochondrial parameters Flow cytometry and confocal microscopy Fast large cell numbers Early stages of apoptosis Multiparameter option Indirect early stage changes may not be definitive proof... 

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