Background: The application of bioceramic hydroxyapatite (HA) derived from materials high in calcium to tissue engineering has been of concern, namely scaffold. Scaffold pores allow for cell mobility metabolic processes, and delivery of oxygen and nutrients by blood vessel. Thus, pore architecture affects cell seeding efficiency, cell viability, migration, morphology, cell proliferation, cell differentiation, angiogenesis, mechanical strength of scaffolds, and, eventually, bone formation. Therefore, to improve the efficacy of bone regeneration, several important parameters of the pore architecture of scaffolds must be carefully controlled, including pore size, geometry, orientation, uniformity, interconnectivity, and porosity, which are interrelated and whose coordination affects the effectiveness of bone tissue engineering. The honeycomb (HCB) as natural polymeric porogen is used to pore forming agent of scaffolds. It is unique for fully interconnected and oriented pores of uniform size and high mechanical strength in the direction of the pores. The aim of this study was therefore to evaluate the effect of HCB concentration on macropore structure of the scaffolds. Methods: Bioceramic hydroxyapatite (HA) was synthesized from abalone mussel shells ( Halioitis asinina ) using a precipitation method, and HA-based scaffolds were fabricated with honeycomb (HCB) as the porogen agent. Pore structure engineering was successfully carried out using HCB at concentrations of 10, 20, and 30 wt%. Results: The Energy Dispersive X-Ray Spectroscopy (EDS) analysis revealed that the Ca/P molar ratio of HA was 1.67 (the stoichiometric ratio of HA). The Fourier Transform Infrared Spectroscopy (FTIR) spectra results for porous HA-based scaffolds and synthesized HA showed that no chemical decomposition occurred in the HA-based scaffold fabrication process. The porosity of the scaffold tended to increase when higher concentrations of HCB were added. XRD data show that the HCB was completely degraded from the scaffold material. The cell metabolic activity and morphology of the HA + HCB 30 wt% scaffold enable it to facilitate the attachment of MC3T3E1 cells on its surface. Conclusion: HCB 30 wt% is the best concentration to fabricate the scaffold corresponding to the criteria for pores structure, crystallographic properties, chemical decomposition process and cell viability for bone tissue engineering.

We experimentally investigate, in detail, electromechanical effects in liquid-crystal elastomers (LCEs) previously swollen with low-molecular-weight liquid crystals (LMWLCs). Both polydomain (POLY) and monodomain (MONO) LCEs were studied. We used a well known LMWLC, 4-$n$-pentyl-4-cyanobiphenyl (5CB) as a solvent. After swelling POLY and MONO LCEs (LSCE) with 5CB, shape changes were measured by recording the displacement of the edge of the swollen LCE at different voltages, V, and temperature. With $100\mu \mathrm{m}$ distance between electrodes, measurable shape changes $(\sim 1–20\mu \mathrm{m})$ are observed with small voltages $(V\sim 0.5–10\mathrm{V})$. In particular, we note that, compared to unswollen L(S)CEs, a dramatic $\sim 200$ times decrease of the threshold field was found for electromechanical effects in swollen L(S)CEs. While swollen MONO LCEs showed electromechanical effects in the planar geometry, homeotropic MONO swollen with homeotropically oriented 5CB did not. This is easy to understand because, in the homeotropic case, the liquid-crystal preferred axis is already aligned with the field so the field has no reorienting effect. The inverse of the response time when the field was switched on in both POLY and MONO was proportional to $E^2$, which is the same field dependence as the response time of LMWLCs. When the field was switched off, the relaxation time showed a field dependence different from that of LMWLCs that we attribute to relaxation of the LCE network.

We experimentally investigated the swelling behavior of thin films $\left(\sim 150\mu \mathrm{m}\right)$ of liquid crystalline elastomers (LCEs) by low molecular weight liquid crystals (LMWLCs). The two LMWLCs used are the well-known nematic liquid crystals, 4-$n$-pentyl-4-cyanobiphenyl, and 4-methoxy-benzilidene-4-butyl-aniline. Both polydomain (POLY) and monodomain (MONO) LCE swelling are studied. In MONO LCEs (LSCEs), the director $\mathbf{n}^$ is uniformly oriented throughout the film. POLY films are made of many domains with different orientations. Its swelling behavior was similar to isotropic gels. In contrast, LSCEs revealed interesting results not anticipated by any theory. First, the LMWLC enters the LSCE by front propagation about three-times faster $\Vert \mathbf{n}^$ than $\perp \mathbf{n}^.$ Second, only the LSCE dimensions $\perp \mathbf{n}^$ expanded, while that $\Vert \mathbf{n}^$ did not change at all. Third, when the LMWLC director and the LSCE director are aligned (MONO2 samples), swelling takes place about twice as fast as when they are not aligned. Volume change dynamics of swollen L(S)CEs investigated as a function of temperature revealed several phase transitions by optical and calorimetry techniques.

An electronic nose (E-nose), comprising eight metal oxide semiconductor (MOS) gas sensors, was used in situ for real-time classification of black tea according to its quality level. Principal component analysis (PCA) coupled with signal preprocessing techniques (i.e., time set value preprocessing, F1; area under curve preprocessing, F2; and maximum value preprocessing, F3), allowed grouping the samples from seven brands according to the quality level. The E-nose performance was further checked using multivariate supervised statistical methods, namely, the linear and quadratic discriminant analysis, support vector machine together with linear or radial kernels (SVM-linear and SVM-radial, respectively). For this purpose, the experimental dataset was split into two subsets, one used for model training and internal validation using a repeated K-fold cross-validation procedure (containing the samples collected during the first three days of tea production); and the other, for external validation purpose (i.e., test dataset, containing the samples collected during the 4th and 5th production days). The results pointed out that the E-nose-SVM-linear model together with the F3 signal preprocessing method was the most accurate, allowing 100% of correct predictive classifications (external-validation data subset) of the samples according to their quality levels. So, the E-nose-chemometric approach could be foreseen has a practical and feasible classification tool for assessing the black tea quality level, even when applied in-situ, at the harsh industrial environment, requiring a minimum and simple sample preparation. The proposed approach is a cost-effective and fast, green procedure that could be implemented in the near future by the tea industry.

A kind of electrohydrodynamic instability, the prewavy instability, in nematic liquid crystals is reported. The characteristic of the instability was optically investigated and discussed in comparison with some similar instabilities. Obviously the instability partially shows an isotropic feature around the nematic-isotropic transition temperature. Owing to the characteristic properties of the flow and the spatial periodicity, it should be distinguished from a previously proposed isotropic instability.