Polyvinylidene fluoride - Hydroxyapatite 0-3 biocomposite filaments processed by twin-screw extrusion.

Polyvinylidene fluoride - hydroxyapatite composite filaments were processed by twin-screw extrusion at different processing angular velocities and characterized by scanning electron and atomic force microscopies, differential scanning calorimetry and tensile tests. Polymer-ceramic composites with a 0-3 connectivity were successfully obtained. Regardless of the used processing parameters, all composite filaments present very similar melting (∼152°C) and solidification (∼139°C) points and elastic moduli (∼1.0 GPa) for hydroxyapatite as dispersed phase in the composite with concentrations up to 25 wt%, indicating that they are adequate for twin-screw extrusion and 3D printing. However, the yield strength (∼29 MPa), ultimate tensile strength (∼36 MPa) and tensile point (∼29 MPa) parameters are similar only for hydroxyapatite concentrations up to 15 wt%, once higher concentrations of hydroxyapatite as dispersed phase result in fragile samples (∼50% lower for each studied property).

A nationwide survey of attitudes towards psychiatry among final-year medical students in Sri Lanka.

Stigma towards psychiatry, a debilitating phenomenon worldwide, is likely to have engendered the longstanding lack of recruitment into psychiatry in Sri Lanka (SL). However, as recent expansion of the undergraduate training in psychiatry in SL may have instigated favorable changes in students' attitudes, we assessed the attitudes of students regarding psychiatry by administering Attitude towards psychiatry-30 (ATP-30) scale to final-year medical students in nine medical schools in SL. This 30-item questionnaire covers eight domains of psychiatry and is rated on a Likert scale, producing a total score out of 150. A multiple linear regression was performed to investigate associated factors. A total of 743 fin. l-year students participated. Of them, 54 % were male. The mean attitude score was 107.7 (SD = 12.3) and 92.2 % showed an overall "positive" attitude. 22.2 % of students considered psychiatry as a potential future career. Students with more than one month of clinical exposure to psychiatry showed a better attitude compared to those with shorter exposure. Female gender and the presence of a close person with mental illness were also associated with better attitudes and career interest. The generally positive attitude towards psychiatry among medical students may be explained, at least partly, by recent advances in undergraduate psychiatry education in SL. Longer clinical exposure to psychiatry being associated with better attitudes indicates the need to ensure adequate duration of clinical training in psychiatry in the undergraduate curriculum.

Charge carriers and small-polaron migration as the origin of intrinsic dielectric anomalies in multiferroic TbMnO3 polycrystals.

Temperature-dependent and frequency-dependent dielectric investigations have been performed in TbMnO3 polycrystals sintered in either oxidative or reductive atmospheres. The results revealed the occurrence of two dielectric anomalies above 100 K, which are caused by the thermal activation of charge carriers and their motion in grain cores and grain boundaries. The temperature dependence of the bulk dc conductivity was also analysed and indicates that charge carriers move between inequivalent sites according to a variable-range-hopping mechanism. Also, a strong correlation between dielectric properties and crystalline structure was observed. Furthermore, a low-temperature dielectric relaxation, commonly reported in rare-earth manganite crystals, was observed in both samples. This relaxation follows the empirical Cole-Cole model and was attributed to small-polaron tunnelling. Polaron motion was observed to be affected by the magnetic transitions, structural properties and intrinsic anisotropies in TbMnO3. It is also worth mentioning that the dielectric anomaly due to motion of charge carriers in grain boundaries is the only one of extrinsic origin, while the anomalies related to carrier motion in grain cores and small-polaron tunnelling are intrinsic to TbMnO3.

Defect-antidefect correlations in a lyotropic liquid crystal from a cosmological point of view.

In this work, we analyze the defect and antidefect distribution in the nematic calamitic phase of a lyotropic liquid crystal [the ternary mixture formed by potassium laurate (KL), decanol (DeOH), and water]. We obtain defects with wedge disclinations of strength +/-1/2, and the scaling exponent determined by the defect-antidefect correlation was 0.29+/-0.07. This value is in good agreement with the theoretical value of 14 obtained by the Kibble mechanism. The constant of the scaling relation of the defect and antidefect distribution is also discussed. We compare our results with the values obtained by Digal [Phys. Rev. Lett. 83, 5030 (1999)] who used a thermotropic liquid crystal.