Density functional theory for dense nematics with steric interactions

The celebrated work of Onsager on hard particle systems, based on the truncated second order virial expansion, is valid at relatively low volume fractions for large aspect ratio particles. While it predicts the isotropic-nematic phase transition, it fails to provide a realistic equation of state in that the pressure remains finite for arbitrarily high densities. In this work, we derive a mean field density functional form of the Helmholtz free energy for nematics with hard core repulsion. In addition to predicting the isotropic-nematic transition, the model provides a more realistic equation of state. The energy landscape is much richer, and the orientational probability distribution function in the nematic phase possesses a unique feature: it vanishes on a nonzero measure set in orientational space

Constant-angle surfaces in liquid crystals

We discuss some properties of surfaces in R3 whose unit normal has constant angle with an assigned direction field. The constant angle condition can be rewritten as an Hamilton-Jacobi equation correlating the surface and the direction field. We focus on examples motivated by the physics of interfaces in liquid crystals and of layered fluids, and discuss the properties of the constant-angle surfaces when the direction field is singular along a line (disclination) or at a point (hedgehog defect

Long-Term Stability of TiS2–Alkylamine Hybrid Materials

Layered TiS2 intercalated with linear alkylamines has recently attracted significant interest as a model compound for flexible n-type thermoelectric applications, showing remarkably high power factors at room temperature. The thermal and, particularly, environmental stability of such materials is, however, a still an open challenge. In this paper, we show that amine-intercalated TiS2 prepared by a simple mechanochemical process is prone to chemical decomposition through sulfur exsolution, and that the presence of molecular oxygen is likely to mediate the decomposition reaction. Through computational analysis of the possible reaction pathways, we propose that Ti-N adducts are formed as a consequence of amine groups substituting for S vacancies on the internal surfaces of the S-Ti-S layers. These findings provide insights for possible future applications of similar hybrid compounds as devices operating in ambient conditions, and suggest isolating them from atmospheric oxygen

random sequence for optimal low power laser generated ultrasound

Low-power laser generated ultrasounds are lately gaining importance in the research world, thanks to the possibility of investigating a mechanical component structural integrity through a non-contact and Non-Destructive Testing (NDT) procedure. The ultrasounds are, however, very low in amplitude, making it necessary to use pre-processing and post-processing operations on the signals to detect them. The cross-correlation technique is used in this work, meaning that a random signal must be used as laser input. For this purpose, a highly random and simple-to-create code called T sequence, capable of enhancing the ultrasound detectability, is introduced (not previously available at the state of the art). Several important parameters which characterize the T sequence can influence the process: the number of pulses Npulses , the pulse duration δ and the distance between pulses dpulses . A Finite Element FE model of a 3 mm steel disk has been initially developed to analytically study the longitudinal ultrasound generation mechanism and the obtainable outputs. Later, experimental tests have shown that the T sequence is highly flexible for ultrasound detection purposes, making it optimal to use high Npulses and δ but low dpulses . In the end, apart from describing all phenomena that arise in the low-power laser generation process, the results of this study are also important for setting up an effective NDT procedure using this technology

Efecto del quitosan de alto peso molecular y del alginato de sodio sobre la proteinasa ácida secretoria de Candida albicans.

Se evaluó el efecto del quitosan de alto peso molecular (QAPM) y del alginato de sodio (NaAL) sobre la producción de proteinasa ácida por una cepa de colección y cinco aislamientos de Candida albicans. Se indujo la secreción de proteinasa ácida con y sin agregado de polímeros a distintas concentraciones y se determinó la actividad enzimática. QAPM y NaAL disminuyeron significativamente la actividad enzimática (>76% cepa de colección y >89% aislamientos, p < 0,05). QAPM no modificó la concentración de proteínas y NaAL produjo una disminución. Se concluye que ambos polímeros son efectivos en inhibir la actividad de proteinasa ácida de Candida albicans.publishedVersio

Estudio preliminar de la combinación de vitaminas y bisfosfonatos en hueso maxilar de ratas

El balance óseo está mediado por una regulación inmunoendócrina, siendo éste un complejo proceso. Entre las acciones llevadas a cabo para mantener la densidad y estructura del esqueleto son variadas las farmacoterapias utilizadas. Diversos estudios han demostrado que tanto Alendronato, Vitamina D3 y Vitamina E contribuyen a la inhibición de la reabsorción ósea. Objetivo: Estudiar el efecto de la administración combinada de alendronato y vitamina D por vía subcutánea y de vitamina E por vía oral sobre la regeneración ósea. Materiales y métodos: La dosificación fue 0,5 mg/kg de peso corporal de AL, 50 mg/kg de vitamina D y 20 mg/kg de vitamina E. El efecto se evaluó en ratas machos Wistar (n=108), de 90 ± 20 g, divididas en 6 grupos. Se realizó la exodoncia de los primeros molares inferiores. La droga se inyectó en forma subcutánea en tiempos 0, 7, 15 y 30 días post cirugía. Se tomaron radiografías de las mandíbulas, en cada tiempo experimental y se analizaron con el Software Image ProPlus versión 4,1 de Media Cibernetics. Los estudios estadísticos se realizaron a través del análisis de la variancia. Resultados: Los estudios radiográficos demostraron un incremento en la densidad mineral ósea promedio (DMO) conforme avanza el tiempo en los grupos problemas analizados con respecto al control, siendo más evidentes los tratamientos con vitamina D a los 30 días. Conclusiones: Los datos evaluados sirven para mostrar una tendencia, pero son insuficientes como para detectar diferencias significativas al contrastar las drogas, si se observan cambios significativos entre etapas, como era previsible. Se continuará con la investigación para poder obtener resultados que permitan emitir conclusiones que avalen nuestra hipótesis de trabajo.Fil: Moro, Cecilia. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra Farmacología y Terapéutica A; Argentina.Fil: Aguzzi, Alejandra. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra Farmacología y Terapéutica A; Argentina.Fil: Virga, María Carolina. Universidad Nacional de Córdoba. Facultad de Odontología. Cátedra Farmacología y Terapéutica B; Argentina.Fil: Romero, S. Universidad Nacional de Tucumán. Facultad de Odontología; Argentina.Fil: Basualdo, MM. Universidad Nacional de Tucumán; Argentina.Otras Ciencias Médica

Parity Breaking in Nematic Tactoids

We theoretically investigate under what conditions the director field in a spindle-shaped nematic droplet or tactoid obtains a twisted, parity-broken structure. By minimizing the sum of the bulk elastic and surface energies, we show that a twisted director field is stable if the twist and bend elastic constants are small enough compared to the splay elastic constant, but only if the droplet volume is larger than some minimum value. We furthermore show that the transition from an untwisted to a twisted director-field structure is a sharp function of the various control parameters. We predict that suspensions of rigid, rod-like particles cannot support droplets with a parity broken structure, whereas they could possibly occur in those of semi-flexible, worm-like particles.Comment: 20 pages, 9 figures, submitted to Journal of Physics: Condensed Matte

Landau-De Gennes theory of nematic liquid\ud crystals: the Oseen-Frank limit and beyond

We study global minimizers of a continuum Landau-De Gennes energy functional for nematic liquid crystals, in three-dimensional domains, subject to uniaxial boundary conditions. We analyze the physically relevant limit of small elastic constant and show that global minimizers converge strongly, in W 1,2 , to a global minimizer predicted by the Oseen-Frank theory for uniaxial nematic liquid crystals with constant order parameter. Moreover, the convergence is uniform in the interior of the domain, away from the singularities of the limiting Oseen-Frank global minimizer. We obtain results on the rate of convergence of the eigenvalues and the regularity of the eigenvectors of the Landau-De Gennes global minimizer.\ud \ud \ud We also study the interplay between biaxiality and uniaxiality in Landau-De Gennes global energy minimizers and obtain estimates for various related quantities such as the biaxiality parameter and the size of admissible strongly biaxial regions

Celery (Apium graveolens L.) Performances as Subjected to Different Sources of Protein Hydrolysates

The vegetable production sector is currently fronting several issues mainly connected to the increasing demand of high quality food produced in accordance with sustainable horticultural technologies. The application of biostimulants, particularly protein hydrolysates (PHs), might be favorable to optimize water and mineral uptake and plant utilization and to increase both production performance and quality feature of vegetable crops. The present study was carried out on celery plants grown in a tunnel to appraise the influence of two PHs, a plant-derived PH (P-PH), obtained from soy extract and an animal PH (A-PH), derived from hydrolyzed animal epithelium (waste from bovine tanneries) on yield, yield components (head height, root collar diameter, and number of stalks), mineral composition, nutritional and functional features, as well as the economic profitability of PHs applications. Fresh weight in A-PH and P-PH treated plants was 8.3% and 38.2% higher, respectively than in untreated control plants. However, no significant difference was found between A-PH treated plants and control plants in terms of fresh weight. Head height significantly increased by 5.5% and 16.3% in A-PH and P-PH treated plants, respectively compared with untreated control (p ≤ 0.05). N content was inferior in PHs treated plants than in untreated control. Conversely, K and Mg content was higher in A-PH and P-PH treated plants as compared to the untreated ones. Furthermore, A-PH and P-PH improved ascorbic acid content by 8.2% and 8.7%, respectively compared with the non-treated control (p ≤ 0.001). Our results confirmed, also, that PHs application is an eco-friendly technique to improve total phenolic content in celery plants. In support of this, our findings revealed that animal or plants PH applications increased total phenolics by 36.9% and 20.8%, respectively compared with untreated plants (p ≤ 0.001)