2,392 research outputs found

    The Contribution of the Smectic-Nematic Interface to the Surface Energy

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    The contribution of the smectic-nematic interface to the surface energy of a nematic liquid crystal sample is analyzed. By means of a simple model it is shown that the surface energy depends on the thickness of the region over which the transition smectic-nematic takes place. For perfectly flat substrates this thickness is of the order of the correlation length entering in the transition. An estimate of this contribution shows that it is greater than the one arising from the nematic-substrate interaction. Moreover, it is also shown that the surface energy determined in this way presents a non-monotonic behavior with the temperature.Comment: 10 pages, revte

    IN-SHOE PRESSURE DISTRIBUTION DURING FENCING LUNGE

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    Fencing is a sport involving sharp backward and forward movements interspersed with several slower gliding steps in which lower limb agility is crucial to good movements and correct body positioning. Thus, while the upper extremity uses the weapon, the legs and feet work to get the fencer in position to it. From a biomechanical point of view, particularly stressed are the feet. Incidence of foot injury in fencing is high, and there have been many cases reported of metatarsal stress fractures, capsulitis, plantar fasciitis, and interdigital neuromas. Although it would be useful to accurately evaluate the high pressure points so that overall lower limb salvage may be improved, to our knowledge, no information about the force and pressure distribution beneath the foot of fencers performing technical actions is available. The purpose of this study was, therefore, to evaluate dynamic in-shoe plantar pressure during fencing lunge. Six right-handed foilists of national level (age: 24k5.5) were the subjects of this study. Each athlete was asked to perform the following technical actions: simple lunge; step forward-lunge; step backward-lunge; jump forward-lunge. Data for at least six trials per condition was collected. The Fscan in-shoe pressure measurement system was used to measure plantar pressure during all trials. The system uses an ultra-thin flexible and trimmable sensor with 960sensing locations distributed evenly across the entire plantar surface. These footsensors can be customized to the individual needs and sizing of each subject. The parameters examined included the centre of pressure path, time-pressure relationships, and the force and pressure in three regions of the foot (rear, mid, and forepart).Despite the apparent intersubject similarities in performing the actions, clear differences were observed in most of the examined parameters. In contrast to the above finding, the variability within-subject was low indicating a high consistency in movement execution, As expected, in all the technical actions, an asymmetrical load was placed on the lower extremities, with the right foot of the athletes particularly subjected to stress in the forward actions. The results showed that the majority of the right foot pressure was localized in the forefoot and especially over the head of the first and second metatarsal and hallux. High pressure levels, as those found here, applied too often and over a long periods of time can cause structural damage to the foot. Shoe and plantar orthosis designers should attempt to reduce such risks designing sager footwear and proper shoe inserts

    director profile of a nematic between two concentric cylinders with inhomogeneous boundary conditions

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    The tilt angle profile in a nematic cell limited by two concentric cylindrical surfaces with inhomogeneous distribution of easy axes is investigated in the one-constant approximation. The results are presented in terms of the Green function approach by considering the strong anchoring case and the presence of an external electric field for small distortions

    Effect of ricinoleic acid in acute and subchronic experimental models of inflammation.

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    Observational studies indicate that topical application of ricinoleic acid (RA), the main component of castor oil, exerts remarkable analgesic and anti-inflammatory effects. Pharmacological characterization has shown similarities between the effects of RA and those of capsaicin, suggesting a potential interaction of this drug on sensory neuropeptide-mediated neurogenic inflammation. The aim of this study was to assess RA anti-inflammatory activities in comparison with capsaicin in several models of acute and subchronic inflammation. The acute inflammation was induced by intradermal injection of carrageenan in the mouse or by histamine in the guinea-pig eyelid. In either experiment, the extent of the oedema thickness was measured. Subchronic oedema was induced by complete Freund's adjuvant injection in the ventral right paw of mice. Tissue substance P (SP) was measured in the carrageenan experiments by radioimmunoassay (RIA). It was found that the acute topical application of RA (0.9 mg/mouse) or capsaicin (0.09 mg/mouse) significantly increased the mouse paw oedema induced by carrageenan, while an 8-day repeated topical treatment with the same doses of both compounds resulted in a marked inhibition of carrageenan-induced paw oedema matched by a reduction in SP tissue levels. Similar effects were found against histamine-induced eyelid oedema in guinea-pigs after acute or repeated application of RA or capsaicin. RA and capsaicin given for 1-3 weeks reduced the established oedema induced by Freund's adjuvant, a subchronic model of inflammation, particularly if given by the intradermal route. Either in mouse paw or in guinea-pig eyelid, capsaicin but not RA by itself produced a slight hyperemia and activation of a behavioural response (e.g. scratching of the eyelids). On the basis of the present results, RA may be seen as a new capsaicin-like, non-pungent anti-inflammatory agent suitable for peripheral application
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