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The complex dielectric constant has been measured in a room-temperature ferroelectric liquidcrystal mixture. We have resolved the experimental data into the Goldstone mode and the soft mode and for each mode determined the dielectric strength and the corresponding relaxation frequency. The results are compared with the dielectric strength calculated using the extended Landau type of free-energy density proposed by Zeks [Mol. Cryst. Liq. Cryst. 114, 259 (1984)], and it is shown that this calculation is able to describe the experimental data well~We have shown that by reasonable assumptions we can derive a simple relation between the Goldstone-mode contribution to the dielectric susceptibility +2} and the polarization (Po), tilt (0O), and pitch (p) of the system: g2 --(Pop/00) /8%3~, where K3 is a bend nematic curvature elastic constant. We also predict, on theoretical grounds, a small peak of the dielectric strength to exist at T,.

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The purpose of this study was to investigate pacing-profile differences during the 90 km Vasaloppet ski race related to the categories of sex, age, and race experience. Skiing times from eight sections (S1 to S8) were analyzed. For each of the three categories, 400 pairs of skiers were matched to have a finish time within 60 seconds, the same start group, and an assignment to the same group for the other two categories. Paired-samples Student’s t-tests were used to investigate sectional pacing-profile differences between the subgroups. Results showed that males skied faster in S2 (P=0.0042), S3 (P=0.0049), S4 (P=0.010), and S1–S4 (P<0.001), whereas females skied faster in S6 (P<0.001), S7 (P<0.001), S8 (P=0.0088), and S5–S8 (P<0.001). For the age category, old subjects (40 to 59 years) skied faster than young subjects (19 to 39 years) in S3 (P=0.0029), and for the other sections, there were no differences. Experienced subjects (≥4 Vasaloppet ski race completions) skied faster in S1 (P<0.001) and S1–S4 (P=0.0054); inexperienced skiers (<4 Vasaloppet ski race completions) had a shorter mean skiing time in S5–S8 (P=0.0063). In conclusion, females had a more even pacing profile than that of males with the same finish time, start group, age, and race experience. No clear age-related pacing-profile difference was identified for the matched subgroups. Moreover, experienced skiers skied faster in the first half whereas inexperienced skiers had higher skiing speeds during the second half of the race.

A Raman multispectral imaging technique is presented, which can be used for stand-off detection of single explosives particles. A frequency-doubled Nd:YAG laser operating at 10 Hz illuminates the surface under investigation. The backscattered Raman signal is collected by a receiver subsystem consisting of a 150 mm Schmidt-Cassegrain telescope, a laser line edge filter, a liquid-crystal tunable filter, and a gated intensified charge-coupled device (ICCD) detector. A sequence of images is recorded by the ICCD, where, for each recording, a different wavelength is selected by the tunable filter. By this, a Raman spectrum is recorded for each pixel, which makes it possible to detect even single particles when compared to known spectra for possible explosives. The comparison is made using correlation and least-square fitting. The system is relatively insensitive to environment and light variations. Multispectral Raman images of sulfur, ammonium nitrate, 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene were acquired at a stand-off distance of 10 m. Detection of sulfur particles was done at a distance of 10 m.

The frequency and temperature dependence of the complex dielectric constant was measured near the smectic-C -smectic-A liquid-crystal phase (Sm-C*-Sm-Aj transition for two ferroelectric liquid crystals with a very large spontaneous polarization. The dielectric strengths as well as the corresponding relaxation frequencies of the dielectric modes were determined. Due to the large polarization we were able to resolve the contributions from the soft mode and the Goldstone mode in a comparatively large temperature interval in the Sm-C phase close to the transition to the Sm-A phase. In the Sm-A phase, the relaxation frequency and the inverse dielectric strength of the soft mode decrease linearly when approaching T, . Comparing the experimental data with a recent theoretical calculation of the complex dielectric constant, we conclude that we have a fairly good understanding of the behavior of the complex dielectric constant in the whole Sm-C -Sm-A transition range.