Orientational order parameters of a de Vries-type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction.

The orientational order parameters (P{2}) and (P{4}) of the ferroelectric, de Vries-type liquid crystal 9HL have been determined in the SmA and SmC phases by means of polarized Raman spectroscopy, and in the SmA phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a "sugar loaf" orientational distribution in the SmA phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries-type behavior is considered.

Polarization splay as the origin of modulation in the B1 and B7 smectic phases of bent-core molecules.

We report a generalized scenario for the formation of modulated smectic phases of bent-core molecules based on locally ferroelectric layering and spontaneous splay of the polarization. Twelve phases are proposed, distinguished by neighboring splay stripes with either syn- or antiorder of the polarization and undulation slope, in addition to layer continuity versus layer discontinuity at the intervening defects. We outline the experimental techniques necessary to differentiate among the phases and interpret previous results in the present context, using high resolution x-ray scattering diffraction and block and undulation models of the layer organization to distinguish among the three 2D lattice types which emerge.

Orientational order of a liquid crystal with three chiral centers by a combined 13C NMR and DFT approach.

In this work, the liquid crystal (S)-2-methylbutyl-[4'-(4' '-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/*) was investigated by means of 13C NMR spectroscopy. This compound has a very peculiar mesomorphic behavior, showing the following phases: paraelectric SmA, ferroelectric SmC*, antiferroelectric SmC*A, re-entrant ferroelectric SmC*re, and ferroelectric hexatic Sm*HEX. The structural and orientational ordering properties of ZLL 7/* have been determined by exploiting the nuclear chemical shielding properties of 13C. To this aim, solid-state NMR techniques such as CP, SPINAL-64, and SUPER have been used in combination with DFT calculations. The agreement between experimental and in vacuo DFT shielding parameters appears to be satisfactory. The orientational order parameters obtained from the 13C shielding analysis have been discussed, taking into account different data analysis approaches and comparing them to those previously obtained from an independent 2H NMR study.

Temperature difference between bulk and surface transition in freely suspended smectic films.

We report an ellipsometric study of freely suspended films of a chiral liquid-crystal compound possessing the phase sequence smectic-C-smectic-A-isotropic with a very broad (67 K) smectic-A phase range. We observe a smectic-C-smectic-A surface transition which is situated more than 60 K above the bulk smectic-C-smectic-A transition temperature. Possible reasons for this unusually large temperature shift are discussed.

Smectic-A*-smectic-C* transition in a ferroelectric liquid crystal without smectic layer shrinkage.

The smectic layer spacing of a nonfluorinated ferroelectric liquid crystal (FLC) compound with almost no shrinkage and only minor tendency to form zigzag defects was characterized by small angle x-ray diffraction. The material lacks a nematic phase. The smectic-A*-smectic-C* phase transition was studied by measuring the thermal and electric field response of the optical tilt and the electric polarization. These properties are described very well by a Landau expansion even without introduction of a higher-order Theta(6) term. This result suggests a pure second-order phase transition far from tricriticality and differs considerably from the typical behavior of the A*-C* transition in most FLC materials.

[Late pseudocysts of the spleen and their surgical treatment]. / Pozdní nepravé cysty sleziny a jejich chirurgická lécba.

The authors present their experience with the treatment of late posttraumatic pseudocysts of the spleen. They recommend surgical revision of confirmed pseudocysts of the spleen and, depending on the peroperative finding, selection of optimal surgery. They do not recommend percutaneous punctures of late postoperative pseudocysts of the spleen.

[Metoprolol and metipranolol in the treatment of hypertension-- comparison of the effects of a single dose and administration for 1 month]. / Metoprolol a metipranolol v lécbe hypertenze--srovnání úcinku jednorázové dávky a jednomesícního podávání.

In six subjects the hypotensive action of metoprolol (Betaloc, Egis) after a dose of 166.7 +/- 47.1 mg and metipranolol (Trimepranol, Spofa) 21.7 +/- 3.7 mg was investigated. Betaloc influences after one month's administration the systolic blood pressure more effectively in a recumbent position and upright position and the diastolic pressure in a sitting position and after walking. The authors investigated also indicators of the circulation, blood sugar values, values of immunoreactive insulin, aldosterone and plasma renin activity after a single dose of 10 mg Trimepranol or 100 mg Betaloc. Betaloc caused a significant drop of the systolic blood pressure already after 15 minutes, Trimepranol after 30 minutes, in both instances the maximum effect was recorded after 45 minutes and persisted throughout the six-hour investigation. The diastolic blood pressure and heart rate were influenced only little. The blood sugar levels after Betaloc rose significantly during the first hour, after both drugs during the third hour. No correlation was found between changes of the blood sugar level and immunoreactive insulin levels. No differences were revealed as regards the effect on plasma renin activity and aldosterone levels.