Aligned Samples

Samples for infra-red absorption measurement were introduced between two rubbed nylon coated calcium fluoride substrates spaced 10 pm apart. To insure proper parallel alignment, samples were cooled at 0.02° C/minute from the isotropic to the Smectic C phase. The alignment was then checked using polarizing microscopy. Polarized IR spectra (32 scans per spectrum) were obtained using an FTIR spectrometer (IFS-66 Bruker, Pillerica, MA) equipped with a wire grid polarizer at a resolution of 2 cm"1. 

All automated algorithms require extensive tests and traps to detect unusual and fault conditions, such as failure of the X-ray source, grossly misaligned samples, and even perfectly aligned samples ... 

Angular distribution measurements of the SHG were carried out on BADP/PAA composites, in a manner similar to that described for mNA/PMMA. Analogous behaviour was observed, and Figure 3 illustrates the distribution obtained from a well-aligned sample. In this case, the angular distribution of the SH is very narrow, and most of the SH flux is confined to a narrow cone in the forward direction. 

Fig. 21 Small-angle X-ray diffraction pattern of an aligned sample of 134b at 110 °C. Reproduced by permission of The Royal Society of Chemistry from [127]...

Figure 10 Examples of the analysis of long-range cross peaks in (A) isotropic and (B) aligned sample of Me-/ -D-xylopyranoside. Short-dashed and solids lines show anti-phase (AP) and in-phase (IP) multiplets. Long-dashed singlets were obtained by the addition and subtraction of the IP and AP multiplets using appropriate scaling factors. (C) Overlay of two one-bond cross peaks from isotropic (solid line) and aligned (dashed line) samples. The multiplets were shifted to overlay on one line of the doublet in order to accentuate the difference between J and D.

Two approaches are commonly used for NMR investigations of biological membranes and membrane-bound peptides first, the measurement of static spectra of uniformly aligned samples second measurement of the sample spun under MAS. The former method requires precise preparation and well-oriented samples in order to provide the high-resolution data. In the latter approach, individual species of PLs are randomly oriented in the rotor. The MAS technique is used for averaging the spin interactions (see Section 2.1). A method that combines both the above approaches (MAOSS) will be discussed in Section 3.1.3.2. 

The Optical-Induced Freedericksz Transition of Nematic Liquid Crystal (5CB) doped with l%(w/w) of 5, 10, 15, 20-tetraphenylporphyrinatozinc( II) (ZnTPP) were studied. Excited by Ti Sappire laser with the 82MHz repetition rate and lOOfs pulse duration, the optical Freedericksz threshold of a 23.6pm-thickness planar alignment sample occurred at an intensity level of0.35mW/mm in contrast to the normally observed 83mW/mm value for pure 5CB. The coordination-bonding interaction between 5CB and ZnTPP were discussed by UV-vis and fluorescence spectra. We attribute the reduction of the optical Freedericksz threshold to the coordination-bonding interaction. 

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