Domains pinning

Friedel (2) interpreted the transversal striations on oily streaks as small adjacent confocal domains that have a tendency to gather in lines. We already noted that such a situation exists in DADB (12) (but the lines are attached to the surface), and that c domains pin up on l lines moreover, oily streaks in cholesterics have clear confocal domains. However, the transversal striations on l or L lines are not compatible with c domains since we do not see there the typical Maltese cross on the contrary, the hyperbolic directions would be at a small angle to the sample plane if they exist. We do not reject FriedeFs explanation, but we must make it compatible with observations, particularly with the longitudinal striations. 

Domain pinning behavior of ferroelectric Pb(i 55)Sr IiOj ceramics. 

Nemanich, R.J., and Kingon, A.I. (2002) Nanoscale observation of photoinduced domain pinning and investigation of imprint behavior in ferroelectric thin films. /. Appl Phys., 92 (5), 2734-2739. 

The mechanism for coercivity in the Cr—Co—Fe alloys appears to be pinning of domain walls. The magnetic domains extend through particles of both phases. The evidence from transmission electron microscopy studies and measurement of JT, and anisotropy vs T is that the walls are trapped locally by fluctuations in saturation magnetization. 

We have previously shown that a 209 amino acid region (aa288-497, asymmetric localization domain) of Insc is necessary and sufficient for apical cortical localization and for mitotic spindle orientation along the apical-basal axis (Tio et al 1999). In a yeast two-hybrid screen we identified Partner of Inscuteable (Pins), a novel 658aa protein with multiple repeats of the Tetratricopeptide (TPR) motif. Affinity purification experiments using embryonic extracts demonstrate that Pins complexes with Insc in vivo. In vitro protein interaction assays demonstrates that Pins interacts with the Insc asymmetric localization domain (see Yu et al 2000). 

In Pins - embryos the initiation steps of apical complex formation occur normally. However, this complex cannot be maintained in mitotic neuroblasts. Hence, the importance of the maintenance of this complex for asymmetric cell division can be ascertained by assessing how Pins- neural progenitors divide. Pins- embryos exhibit all of the defects seen in insc mutants. Mitotic spindle orientation is defective. In the cells of mitotic domain 9 the 90° reorientation, which normally occurs in wild-type resulting in the orientation of the spindle along the apical—basal axis (Fig. 3A), fails to occur in the mutant (Fig. 3B). Mitotic spindle orientation of neuroblasts in the segmented CNS, deduced from DNA staining, also often fails to... 

Chia We have looked at the potential phosphorylation sites of Insc, and this is the only apical complex component for which the functional domain has been defined. All the putative Cdc2 phosphorylation sites lie outside the region required for function (at least using an over-expression paradigm). For the other two known components, Baz and Pins, we don t know which the functional parts of the molecule are. It seems more appealing to think in terms of effects on the cytoskeleton, and in particular actin. 

Chia I can t think of a good way of mislocalizing Pins. With Inscuteable, early on in embryogenesis it is expressed in a single domain and nowhere else. The cells give rise to some of the cells that become the larval brain. The spindle in this region forms parallel to the surface and reorients at 90°, perpendicular to the surface of the embryo. These cells which don t express Insc set up their spindle parallel and divide parallel to the surface. If you force Insc expression in these cells they will reorient. 

Pin, J.-P., Joly, C., Heinemann, S. F., and Bockaert, J. (1994) Domains involved in the specificity of G protein activation in phospholipase C-coupled metabotropic glutamate receptors. EMBO J. 13, 342-348. 

A third yeast prion, PIN, is similar in some respects, but its non-prion domain—in this case, the N-terminal part of the molecule—has no established cellular function. The protein Rnqlp is a gain-of-function prion whose activity is expressed via its ability to induce [PS/]. [PIN] forms much more readily than the other two prions, and [PIN] cells induce [PSI] under... 

Note 3 Morphology coarsening can be substantially stopped by, for example, vitrification, crosslinking, and pinning, the slowing down of molecular diffusion across domain interfaces. 

The actual limit of the summation is the extent of the weighting filter. Zero padding is used to ensure that the discretized matrices have sizes which are a power of two so that the computation can be done in the frequency domain using fast fourier transform (FFT) techniques. The effective discretized density, pin, Wj), is then given by... 

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