EXPERIMENTAL MODAL ANALYSIS OF A PALM TREE LOG UNDER RADIAL VIBRATIONAL EXCITATION

   Trees may be subject to rot-inducing agents that degrade the strength of the material making their trunk, and decrease the quality of their crop. Several techniques, both non-destructive and destructive, are available for assessing the extent of damage caused by rot in a tree trunk. The present work presents the results of a preliminary study conducted on a palm tree trunk for isolating a specific mode from its response to a vibrational excitation, namely the so-called “ovalling” mode. This latter is cross-sectional and in a circular cylinder manifests itself relatively locally, i.e. has little dependence on the lateral extension of the cylinder. An experimental modal analysis is made on a piece of a date palm tree trunk when set into vibration through a radial mechanical excitation, and the response is collected at points along a circumference on the trunk. The value of the resonance frequency of the ovalling mode was found to be somehow variable, probably resulting from some coupling phenomena between various modes of vibration due to the inhomogeneity, anisotropy and fibre-like structure of the trunk wood. As rot usually affects markedly the strength of the trunk wood, the frequency of the ovalling mode, which depends on the strength of the material, can be used for estimating the severity of rot attack in the trunk. A numerical simulation is also made to a cylinder as a simplified representation of a tree trunk

Chemical Analysis, Antioxidant and Antibacterial Activities of Aniseeds Essential Oil

This study was conducted to evaluate the chemical composition, antioxidant and antibacterial activities of the essential oil of Pimpinella anisum L. seeds. The main constituents of the essential oil obtained by hydrodistillation using a Clevenger-type apparatus were identified by GC, GC/MS-EI, GC/MS-CI, and NMR spectroscopy. The antioxidant potential was assessed by using the DPPH method and the ferric reducing power. The antibacterial activity was determined by using the disk diffusion and the micro dilution methods against some Gram-positive and negative pathogenic bacteria. Results showed that aniseeds essential oil was characterized by a higher yield 2.6 ± 0.02% and good physic-chemical characteristics. Chemical analysis showed that the major components of the essential oil identified were anethole and estragole with percentages of 94.82 and 1.69%. Aniseeds essential oil showed a higher percentage of inhibition of DPPH 88.3 ± 0.5% and a lower value of IC50 118 ± 1.5 µg mL-1 determined at concentration of 1000 µg mL-1. This oil displayed a good ability to reduce Fe+3 to Fe+2 and provided an optical density of 1.78 ± 0.3 and IC50 of 60 ± 0.2 µg mL-1. Tested oil showed bactericidal activity against Pseudomonas aeruginosa and Escherichia coli with report MBC/MIC of 2 and antibacterial effect against Staphylococcus aureus with MBC/MIC of 32. It can be concluded that aniseeds essential oil contains substances with significant biological potential such as anethole and estragole that can be exploited in different pharmaceutical and therapeutic fields

Antioxidant Properties of the Aerial Part of Celery and Flaxseeds

The aim of the present study was to evaluate the antioxidant activity of essential oil and extracts obtained from the aerial parts of celery (Apium graveolens L.) and from flaxseeds (Linum usitatissimum (Linn.)). In vitro antioxidant activity was determined by 2,2-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing power assay. Results showed that the essential oil of celery and methanol extracts of celery and flaxseeds exhibited a good scavenging activity of DPPH radical respectively 84 ± 0.4%, 79 ± 0.5%, and 78 ± 0.3% at concentration of 1000 µg mL-1 comapred to the queous extracts. These results were lower than those found with ascorbic acid 96.23 ± 1.2% and catechin 94.50 ± 1.4% at the same concentration. IC50 is defined as concentration of substrate that inhibits 50% of the DPPH radicals present in the reaction medium. The positive control catechin and ascorbic acid displayed lower values of IC50 (7.81 ± 0.1, 31.5 ± 0.3 µg mL-1), followed by methanol extract of celery and flaxseeds (130 ± 0.2, 150 ± 0.4 µg mL-1), essential oil of celery (180 ± 0.2 µg mL-1), then aqueous extracts of flaxseeds and celery (950 ± 0.5, 980 ± 0.4 µg mL-1). For aerial part of celery, significant activities for reducing iron were obtained, values observed by optical density (OD) of 1.8 ± 0.2 for essential oil and 1.7 ± 0.1 for methanol extract, while ascorbic acid and catechin provided an OD of 2.069 ± 0.03 and 2.66 ± 0.016 in the same concentration 1000 µg mL-1. The results of the current study showed that flaxseeds and celery exhibited a higher antioxidant activities that could be exploited in food and pharmaceutical industries.&nbs

¿Qué significa ser profesor/a en una situación de guerra (Siria)? Historias de vida

[ES]¿Qué pasa cuando un día, de repente, tú vida cambia? Esto es lo que ha pasado en Siria, que desde el año 2011 está en situación de crisis de guerra. En este escenario, donde antes estaban los hogares, escuelas, centros de trabajo, lugares de ocio, espacios de descanso, escenarios para compartir, etc., ahora está vacío. De repente y sin previo aviso, empieza una guerra que sacude toda la vida de los civiles en Siria. Situación que influye gravemente sobre los niños y niñas, que dejan de poder ir con normalidad a la escuela. Una escuela que antes de la Guerra era moderna y estaba ubicada en edificios físicos con cuatro paredes, allí se realizaban actividades colaborativas, se trabajaba con tecnología haciendo cosas sencillas en primaria y secundaria. Con opciones tecnológicas para personas discapacitadas, la posibilidad de navegar en internet, etc. Con la situación de guerra las escuelas son utilizadas como refugios para la gente que escapa de zonas conflictivas, por lo que aquellas que se usan para desarrollar la labor educativa están masificadas e incrementaron mucho su ratio, y esto sólo cuando los niños y niñas pueden salir y asistir a la escuela. En este contexto qué hace un profesor, sin libros, sin alumnos, sin electricidad, en una guerra. Como objetivo de la investigadora quiere conocer el riesgo que tiene vivir una situación de guerra en los alumnos sirios. a pregunta de investigación es ¿qué significa ser profesor en una situación en guerra? Para recoger la información sobre el estado del sistema educativo y la condición de las escuelas, alumnos, el proceso didáctico y los profesores en Siria, se plantea una investigación a través de historias de vida. Se seleccionan tres profesores/profesoras de primaria de tres escuelas ubicadas en tres ciudades diferentes de Siria (Tartous, Der alzoor y Damasco). Durante el curso escolar 2013-2014 los docentes recogen en un diario el resumen de la jornada educativa centrado en una serie de dimensiones, los días que hay escuela, y la envían por WhatsApp o correo electrónico, la única manera de comunicarse con los profesores, a la investigadora. Todos estos registros se archivan y clasifican para proceder a su análisis. Consideraciones Finales La relevancia de la investigación en curso se centra en poner de manifiesto la necesidad de que se mantenga el proceso educativo para todos los niños y niñas en edad escolar, ya que son alumnos que todavía no tienen la formación básica que les permita continuar en su vida. Esta investigación innovadora manifiesta una gran preocupación porque la guerra provoque una generación perdida, de personas analfabetas; y las consecuencias que esto puede tener en el país.[EN]What if one day, all of a sudden, your life changes? This is what has happened to people in Syria, which has been in a civil war since 2011. A place where there were homes, schools, workplaces, holiday resorts, spaces of rest, etc. is empty now. Suddenly and without a warning, a war shook people’s life. This situation has a serious impact on children, who are unable to function normally at school. A school that was modern before the war and located in physical buildings with four walls, carried out collaborative activities, worked with technology to do different kinds of tasks in primary and secondary, school with technological options for people with disabilities, access to the Internet, etc. With the war, schools have become shelters for people who escape from conflict zones, so that educational centers are overcrowded and used much more frequently, but only if children can go out and attend school. What does a teacher do without books, without students, without electricity, in a war? As the purpose of this paper is to present the risk Syrian students experience when living in a situation of war, the research question is: What does it mean to be a teacher in a situation of war? In order to collect information on the situation of the educational system and the condition of the schools, the students, the didactic process and the teachers in Syria, the research includes real life stories / testimonies by three primary teachers from schools located in three different cities in Syria (Tartous, Der alzoor and Damascus). During the academic year 2013-2014, these teachers recorded their working days in a diary focusing on different aspects and sent their notes via WhatsApp or email to the author, the only way to get in touch with each other. All these records are archived and classified to be analyzed afterwards. Final considerations The relevance of the research focuses on highlighting the need to maintain the educational process for all school-age children as they have not achieved a basic education yet, which is essential for them to make progress in their lives. This innovative research expresses a great concern that the war may cause a lost generation, of illiterate people; and the consequences this may have for the country

Corrosion mechanism and bioactivity of borate glasses analogue to Hench’s bioglass

Bioactive borate glasses (from the system Na2O-CaO-B2O3-P2O5) and corresponding glass-ceramics as a new class of scaffold material were prepared by full replacement of SiO2 with B2O3 in Hench patented bioactive glass. The prepared samples were investigated by differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The DTA data were used to find out the proper heat treatment temperatures for preparation of the appropriate glass-ceramics with high crystallinity. The prepared crystalline glass-ceramics derivatives were examined by XRD to identify the crystalline phases that were precipitated during controlled thermal treatment. The FTIR spectroscopy was used to justify the formation of hydroxyapatite as an indication of the bioactivity potential or activity of the studied ternary borate glasses or corresponding glass-ceramics after immersion in aqueous phosphate solution. The corrosion results are interpreted on the basis of suggested recent views on the corrosion mechanism of such modified borate glasses in relation to their composition and constitution

Modeling rot in wood by replacement of wood with sand : an experimental study

Rot is known to affect the strength properties of wood. At the same time, the damping properties of the attacked material have also been shown to change. This article presents the results of an experimental study in which rot in wood was modeled by the replacement of wood with sand. The procedure entailed the drilling of holes in the body of a wooden beam, filling the holes with sand, and monitoring the changes induced by the sand-filled holes on the values of the modulus of elasticity (MOE) and of the loss factor. The MOE was calculated from the resonance frequency of the first longitudinal mode of vibration, and the loss factor was obtained indirectly from the impulse response by means of a room acoustical technique. The results show that the MOE value, and hence the strength characteristic of the wood specimen, decreases at the same time as the loss factor increase