Tailoring chitosan/collagen scaffolds for tissue engineering: Effect of composition and different crosslinking agents on scaffold properties.

Chitosan/collagen (Chit/Col) blends have demonstrated great potential for use in tissue engineering (TE) applications. However, there exists a lack of detailed study on the influence of important design parameters (i.e, component ratio or crosslinking methods) on the essential properties of the scaffolds (morphology, mechanical stiffness, swelling, degradation and cytotoxicity). This work entailed a systematic study of these essential properties of three Chit/Col compositions, covering a wide range of component ratios and using different crosslinking methods. Our results showed the possibility of tailoring these properties by changing component ratios, since different interactions occurred between Chit/Col: samples with Chit-enriched compositions showed a hydrogen-bonding type complex (HC), whereas a self-crosslinking phenomenon was induced in Col-enriched scaffolds. Additionally, material and biological properties of the resultant matrices were further adjusted and tuned by changing crosslinking conditions. In such way, we obtained a wide range of scaffolds whose properties were tailored to meet specific needs of TE applications.The authors are grateful to Dr. von Kobbe (Chimera Pharma of Bionostra Group) for the gift of MCF7 cells. The financial support of the Ministerio de Ciencia e Innovación of Spain (FIS PS09/01513), and the FPI grant from UCM to A. Martínez are gratefully acknowledged.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.carbpol.2015.06.08

Head prediction of centrifugal pump impeller using boundary-element method

У роботі виконано прогнозування напірної характеристики робочого колеса відцентрового насоса. Результати чисельного експерименту на основі методу граничних елементів порівнюються з раніше отриманими результатами розрахунків в Ansys CFX і результатами фізичних експериментів, проведених на стендах ПАТ «ВНДІАЕН». Для розрахунку течії в проточній частині використовується модель ідеальної нестисливої рідини. Потік вважається безвідривним, потенційним, тривимірним, стаціонарним. На основі розв'язання прямої 3D задачі методом граничних елементів був обчислений усереднений по колу і висоті момент абсолютної швидкості на виході з робочого колеса. Величина прогнозованого напору визначалася за формулою Ейлера. Розрахунковий напір робочого колеса якісно узгоджується з результатами фізичного експерименту і чисельним розрахунком в Ansys CFX. Характер прогнозованої напірної характеристики краще відповідає результатам в області робочого інтервалу і праворуч від нього.Purpose. To predict the head-capacity curve of a centrifugal pump impeller. Design/methodology/approach. This article compares the results obtained from a numerical experiment using the boundary-element method with previously reported results obtained from the calculation using Ansys CFX and with the results of physical experiments performed on the test-rig of JSC «VNIIAEN». To calculate the flow in the hydraulic passage we consider the model of nonviscous fluid. The flow is considered to be unseparated, vortex free, three-dimensional, steady. Based on the solution of the direct 3D problem by the boundary-element method we calculated the periphery-averaged and height-averaged moment of the absolute velocity at impeller inlet and outlet. We used the Euler formula to calculate the value of the predicted head. Findings. The rated head of the impeller calculated by using the boundary-element method agrees well with the results of physic experiment and with the results obtained from the calculation using Ansys CFX. The behavior of the predicted head-capacity curve corresponds better to the results in the operating range and in the right side of it. Originality/value. The results are the basis for result-oriented modifications and further improvements of the hydrodynamic characteristics of hydraulic machines.В работе выполнено прогнозирование напорной характеристики рабочего колеса центробежного насоса. Результаты численного эксперимента на основе метода граничных элементов сравниваются с ранее полученными результатами расчетов в Ansys CFX и результатами физических экспериментов, проведенных на стендах ПАО «ВНИИАЭН». Для расчета потока в проточной части принимается модель идеальной несжимаемой жидкости. Течение считается безотрывным, потенциальным, трехмерным, стационарным. На основе решения прямой 3D задачи методом граничных элементов был вычислен осредненный по окружности и высоте момент абсолютной скорости на выходе из рабочего колеса. Величина прогнозируемого напора определялась по формуле Эйлера. Расчетный напор рабочего колеса качественно согласуется с результатами физического эксперимента и численным расчетом в Ansys CFX. Характер прогнозируемой напорной характеристики лучше соответствует результатам в области рабочего интервала и правее его

Principles and Criteria of Phytocenotic Diversity Conservation (Through the Example of European Countries and Russia)

The article presents the review of currently existing views on the problem of phytocoenotic diversity protection in European countries and Russia. The principles and criteria for the identification of rare plant communities in need of protection, used by scientists from different countries are described. The authors had defined already published works of a monographic nature and projects, containing the information on the phytocenotic diversity of Europe in need of protection, and Green Books, published in the Russian Federation. Special attention is paid to the determination process of plant communities. It is noted that nowadays there is no single concept for the creation of Green Books. The phytocenosis protection inventories created in European countries that have a legislative basis, the Russian Green Books include vegetation monitoring data and have no legal basis

Development of an integral criterion for evaluating the degree of aging of transformer oils

The technical condition of the transformer oil affects the condition of the solid insulation, and therefore the residual life of electrical equipment, so it is important to study the aging mechanisms of the oil. The mechanism of transformer oil aging is studied using factor analysis of oil quality indicators, such as moisture content, acid number and dissipation factor tangent. Factors that have the greatest influence on the rate of oil aging have been found. In accordance with the found influence factors the permissible values of oil quality parameters of 110 kV power transformers with division by equipment tightness, oil brands and operating time have been determined. Oil aging models, taking into account the mutual influence of oil quality parameters, have been developed for transformers with different oil brands, type of oil protection and service life. An integral index, characterizing different aging processes of the oil, has been proposed. The criterion for evaluating the integral index of oil aging rates is calculated. © Published under licence by IOP Publishing Ltd

Estudio in vitro de la actividad citotóxica de resinas dentales tipo BIS-GMA

Las resinas composites se emplean desde hace varias décadas en distintas aplicaciones estomatológicas, volviéndose indispensables para lograr una alta calidad en los servicios modernos. Uno de los monómeros acrílicos más utilizados en estos materiales poliméricos de recubrimiento es el 2-bis-[p-(2-hidroxi-3-metacriloxipropoxi) fenil] propano, conocido comúnmente como Bis- GMA. El conocimiento de las interacciones de estos materiales con el sistema biológico es de vital importancia debido al uso tan difundido de los mismos en la práctica clínica. El comportamiento de una célula viva en contacto con un material extraño es un problema esencial en las aplicaciones biomédicas de polímeros sintéticos. Los ensayos in vitro son sistemas muy útiles para la evaluación de los efectos biológicos de los biomateriales. En el laboratorio de Inmunofarmacología del INOR se llevó a cabo la evaluación de la toxicidad de dos resinas dentales tipo Bis-GMA producidas por el Centro de Biomateriales de la Universidad de La Habana: el Obtudent Fotocurado (FC), resina fotopolimerizable para restauraciones dentales y el Cubridem Autocurado (AC), sellante dental para fosas y fisuras. Este estudio forma parte de las evaluaciones preclínicas biológicas de biomateriales y equipos médicos implantables que se lleva a cabo en Cuba a través de la Red Funcional de Implantología del Ministerio de Salud Pública. Se aplicó el método de citotoxicidad in vitro descrito por Stanley para la evaluación toxicológica de materiales dentales. Ambos composites resultaron citotóxicos para la línea de fibroblastos L929, lo que se corresponde con lo descrito en la literatura para este tipo de material. Su citotoxicidad se encontró en el rango de la de los análogos comerciales evaluados.Peer Reviewe

Space-borne Observations of Atmospheric Pre-Earthquake Signals in Seismically Active Areas: Case Study for Greece 2008-2009

We are conducting theoretical studies and practical validation of atm osphere/ionosphere phenomena preceding major earthquakes. Our approach is based on monitoring of two physical parameters from space: outgoi ng long-wavelength radiation (OLR) on the top of the atmosphere and e lectron and electron density variations in the ionosphere via GPS Tot al Electron Content (GPS/TEC). We retrospectively analyzed the temporal and spatial variations of OLR an GPS/TEC parameters characterizing the state of the atmosphere and ionosphere several days before four m ajor earthquakes (M>6) in Greece for 2008-2009: M6.9 of 02.12.08, M6. 2 02.20.08; M6.4 of 06.08.08 and M6.4 of 07.01.09.We found anomalous behavior before all of these events (over land and sea) over regions o f maximum stress. We expect that our analysis reveal the underlying p hysics of pre-earthquake signals associated with some of the largest earthquakes in Greece

Investigation of mutual influence of transformer oil parameters

Представлены результаты корреляционного анализа показателей качества трансформаторного масла. Показана актуальность анализа по диагностированию силовых трансформаторов в снижении вероятности и риска отказа.This article presents the results of correlation analysis of transformer oil quality indicators. The urgency of the analysis for the diagnosis of power transformers to reduce the probability and risk of failure