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A ferroelectric liquid crystal with an end-substituted (-)-isopinocampheol (IPC) group has been studied in isolation and in mixtures with the antiferroelectric compound EHPOCBC. The samples were studied with respect to electroclinic coefficients, tilt angles, X-ray layer spacing, dielectric permittivity, spontaneous polarisation and relative birefringence under an applied field. In the pure isopinocampheol substituted compound, the SmA-SmC phase transition appears strongly first order and is associated with a significant increase in effective birefringence. The smectic layer spacing decreases below the transition approximately with the optical tilt. On increased EHPOCBC concentration the change in birefringence across the transition diminishes, until the point at which the mixture adopts an anticlinic SmC(A) phase, and the expected decrease in birefringence is observed. There is very little change in birefringence with field for the IPC compound, whilst EHPOCBC shows a marked increase with increasing field, for a few degrees above the phase transition. The results are analyzed with respect to two models. In one it is proposed that the bulky IPC group disorders the SmA phase by introducing undulations in the smectic layer. These undulations may disappear in the SmC phase due to an antiparallel arrangement of neighbouring molecules. In the other model the bent shape of the mesogen as a whole plays a crucial role in changing the optical properties at the SmA-SmC transition, due to the biased rotation around the molecular axis of inertia.

This article arrived too late to be included in the appropriate section of the ILCC Proceedings, which is Structural Characterization. Several banana-shaped liquid crystalline molecules have been studied as active media for second harmonic generation (SHG) in their different thermotropic phases [1]. Besides the B2- and B7-phases, which exhibit SHG under external applied electric fields, the so-called “blue” B4-phase exhibits spontaneous SHG without application of any external field [2,3]. Both phases form a complex poly-domain structure which lead us to develop a SHG-Scanning microscope to perform a more detailed study of this complex systems. First experimental 2D-SHG-Scans in this molecules show the possibility to discriminate domains of different polar and NLO-properties, allowing a better understanding and analyses of this structures. A well defined polar structuring by external fields and analyses thereof is a prerequisite for the development of non-linear-optical (NLO)-applications of banana-shaped ...

By use of time-resolved polarized Fourier-transform infrared (FTIR-) spectroscopy the molecular structure and mobility of B2 phase LC banana-shape molecules is investigated. Two samples are investigated: an achiral banana-shaped (B14) system and a mixture of achiral (B14) and chiral (B7*) banana-shaped molecules. The molecules are oriented by shearing the substance between ITO-coated CaF 2 windows. The measurements give detailed information about a) the average orientation, b) the orientational order, c) the reorientation time, d) the reorientation angle and e) the phase relation between the different segments for the different molecular moieties. The experiments are performed in dependence on frequency and strength of the external electric field. The corresponding molecular response of the different moieties is recorded by means of step-scan FTIR spectroscopy with a time resolution of 5 microseconds.

Tilted smectic phases of achiral banana-shaped molecules are polar and may form a number of different states (chiral or racemic, antiferroelectric or ferroelectric), which can be interchanged by external fields. In thin films they may assume various layer structures (vertical, tilted or horizontally modulated), which can be set by external effects. In this paper we describe electric field and mechanical shear induced structural transitions in smectic phases of bent-core molecules. We discuss the field-induced distortion of the antiferroelectric state and the changeover of the chirality.

Time-resolved polarized Fourier transform infrared spectroscopy (FTIR) is employed to analyse the segmental orientation and mobility of achiral bent core molecules in response to an external electric field. By shearing the substance between ITO coated CaF2 windows two types of domain, racemic and homochiral, are formed in the high temperature B2 phase. Each of these domains is characterized by two spontaneous symmetry-breaking instabilities which yield a symmetric and an antisymmetric electro-optical response, respectively. Taking advantage of the specificity of IR spectroscopy, this switching behaviour is analysed on a molecular level for the moieties of the bent core liquid crystal materials. In this way, the electrically induced reorientation of the different segments on a cone and the suppression of the antiferroelectric structure at higher frequencies can be followed in detail. Furthermore the biased rotation of the two carbonyl groups around the molecular long axis is determined. It is shown that al...

Achiral bent-shaped molecules may form chiral and polar smectic phases, due to a spontaneous tilt of the planes of the molecules. The lowest energy-state is racemic, and in the textures of the ground state usually fine fringes appear parallel to the smectic layers. Recently it was found that the formation of the fringes could be suppressed resulting in a uniform texture in the ground state. In this paper we show evidences for field induced tilted and horizontally zigzagging layer structures. We discuss properties of various layer structures and compare them to our experimental observations. Finally we give a qualitative explanation for the observed field-induced-uniform-racemic ground state.

Dielectric and electro-optical properties of the various antiferroelectric and ferrielectric smectic phases of two compounds of the homologous series MHPnCBC (n = 8,9) have been investigated. MHP9C...

The orthoconic antiferroelectric Sm C* A phase is of high potential for electro-optic applications. Therefore, mixtures of calamitic molecules possessing the Sm C* phase with high tilt angle (Θ ≈ 45°) and bent core compounds have been prepared. The induction of an antiferroelectric phase has been found even at low concentrations of the banana shaped dopants (5–10 mol%), what has been shown by optic, electro-optic and dielectric investigations. In systems where the host materials possessed the cholesteric and ferroelectric phases, the iso-N*-Sm C*-Sm C* A -crystal phase sequence has been observed. New materials with perfluorinated end chains exhibiting the Sm A-Sm C* phase transition have shown antiferroelectric phases enveloping the Sm C* phase when doped with biphenyl based bent molecules. The tilt angle of the host material remained almost unchanged, i.e. in the case where the host compound possessed a tilt of 45° doping with bent core molecules led to the formation of the orthoconic antiferroe...

The characteristic function method is employed to study the output spectral density and signal-to-noise ratio of a full-wave error function limiter. The input signal and noise are considered to be sample functions from independent Gaussian random processes. The results are obtained as a function of the input signal-to-noise ratio, degree of limiting and bias, Limiter and signal parameters are expressed in terms of known functions which may be easily programmed to yield numerical results. †Communicated by the Authors.

Unsere Untersuchungen ergaben eine uberrascbend hohe Kanamycin-konzentration in der Peri- und vor allem audi in der Hndolymphe. Sie enthielten z. B. 12 Stunden post injectionem lOmal mehr Kanamycin als das Bint und 20mal mehr als Herz und Leber. Die Tatsachc, das der Kanamycingehalt des Innenolires uber 100inal so hoch ist wie ini Gehirn, weist darauf hin, das wahrscheinlich ini Innenohr und nicht im ZNS der Schadigungsort zu suchen ist.

There are many practical systems in existence that, provide continuous estimation of radar signal parameters. A large number of these belong to a class which performs this function by measuring variations in the energy of the demodulated received signal. A general noise fluctuation analysis of this class of signal parameter estimators is presented. The general results are applied to three systems that estimate the propagation delay of a radar signal. Specifically, the three systems represent existing radar altimeter concepts. Comparative noise fluctuation results are plotted for the three systems as a function of aircraft ground speed, altitude and other relevant system parameters.

Sowohl anatomisch und biochemisch wie funktionell findet man von Windung zu Windung deutliche quantitative Unterschiede. So fallen die DC-Potentiale der Reissnerschen Membran und der O2-Verbrauch der Stria vascularis von basal nach apical ab, ebenso die Groβe und der Eiweiβumsatz der spiralen Ganglienzellen. Die Durchlassigkeit der Reiss-nerschen-Membran hingegen nimmt von basal nach apical zu. Eine Synopsis der verschiedenen Befunde wird versucht.