161 research outputs found
Streptomycetes: a new model to study cell death
Colonies of streptomycetes are now viewed as multicellular entities containing morphologically and biochemically differentiated cell types which have specific functions and precise spatial relationships to one another. Like multicellular organisms, colony development in streptomycetes is also maintained by a tight balance between cell proliferation and cell death processes. This review describes the current state of knowledge concerning cell death in streptomycetes
Wobbling kinks and shape mode interactions in a coupled two-component theory
The dynamics of a wobbling kink in a two-component coupled scalar
field theory (with an excited orthogonal shape mode) is addressed. For this
purpose, the vibration spectrum of the second order small kink fluctuation is
studied in order to find the corresponding vibration modes associated to the
first (longitudinal) and second (orthogonal) field components. By means of this
analysis, it was found that the number of possible shape modes depends on the
value of the coupling constant. It is notable that when one of the orthogonal
field shape modes is initially triggered, the unique shape mode of the
longitudinal field is also activated. This coupling causes the kink to emit
radiation with twice the frequency of excited mode in the first field
component. Meanwhile, in the orthogonal channel we find radiation with two
different frequencies: one is three times the frequency of the orthogonal
wobbling mode and another is the sum of the frequencies of the longitudinal
shape mode and the triggered mode. All the analytical results obtained in this
study have been successfully contrasted with those obtained through numerical
simulations.Comment: 20 pages, 12 figure
Wobbling kinks in a two-component scalar field theory: Interaction between shape modes
In this paper the interaction between the shape modes of the wobbling kinks
arising in the family of two-component MSTB scalar field theory models is
studied. The spectrum of the second order small kink fluctuation in this model
has two localized vibrational modes associated to longitudinal and orthogonal
fluctuations with respect to the kink orbit. It has been found that the
excitation of the orthogonal shape mode immediately triggers the longitudinal
one. In the first component channel the kink emits radiation with twice the
orthogonal wobbling frequency (not the longitudinal one as happens in the
-model). The radiation emitted in the second component has two dominant
frequencies: one is three times the frequency of the orthogonal wobbling mode
and the other is the sum of the frequencies of the longitudinal and orthogonal
vibration modes. This feature is explained analytically using perturbation
expansion theories.Comment: 28 pages, 11 figure
Orientation of propagating crack paths emanating from fretting-fatigue contact problems
[EN] In this work, the orientation and propagation of cracks in fretting fatigue problems is analyzed numerically using the finite element method (FEM) and the extended finite element method (X- FEM). The analysis is performed by means of a 2D model of a complete-contact fretting problem, consisting of two square indenters pressed onto a specimen subjected to cyclic fatigue. For the simulation, we allow for crack face contact in the implementation during the corresponding parts of the fatigue cycle. The problem is highly nonlinear and non-proportional and we make use of the so-called minimum shear stress range orientation criterion, min(Delta tau), proposed by the authors in previous works. This criterion is introduced to predict the crack path in each step of the crack growth simulation. The objective of the work is to detect which is the relevant parameter affecting the crack path orientation. A parametric study of some a priori relevant magnitudes is carried out, such as normal load on the indenters, bulk load on the specimen, stress ratio and relative stiffness of the indenter and specimen materials. Contrary to previous expectations, it is shown that the relative magnitude of the applied loads has no significant effect. However, it is found that the stiffness of the indenter material with respect to the specimen material has the greatest effect. A simple explanation of this behavior is also provided.The authors gratefully acknowledge the financial support given by the SGPI of the Spanish Ministry of Economy and Competitiveness (Project DPI2013-46641-R).Giner Maravilla, E.; Diaz-Alvarez, J.; Marco Esteban, M.; Miguélez, MH. (2016). Orientation of propagating crack paths emanating from fretting-fatigue contact problems. Frattura e Integrità Strutturale. Fracture and Structural Integrity. (35):417-426. https://doi.org/10.3221/IGF-ESIS.35.33S4174263
Numerical analysis for design of bioinspired ceramic modular armors for ballistic protections
[EN] The exigent requirements for personal protections in terms of energy absorption and ergonomics have
led to increasing interest in bioinspired protections. This work focuses on the numerical analysis of
ballistic behavior of different bioinspired geometries under impact loadings. Ceramic armors based on
ganoid fish scales (the type exhibited by gars, bichirs and reedfishes), placoid fish scales (characterizing
sharks and rays) and armadillo natural protection have been considered. Different impact conditions are
studied, including perpendicular and oblique impacts to surface protection, different yaw angle, and multiple
impacts. Main conclusion is related to the improved efficiency of modular armors against multiple
shots exhibiting more localized damage and crack arrest properties. Moreover, its potential ergonomic is a
promising characteristic justifying a deeper study.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work has been carried out within the framework of the research program Juan de la Cierva Incorporacion 2015, and research projects DPI2017-88166-R, and RTC-2015-3887-8 of FEDER program financed by the Ministerio de Economia, Industria y Competitividad of Spain. The support of the Generalitat Valenciana, Programme PROMETEO 2016/007 is also acknowledged.González Albuixech, VF.; Rodríguez-Millán, M.; Ito, T.; Loya, JA.; Miguélez, MH. (2019). Numerical analysis for design of bioinspired ceramic modular armors for ballistic protections. International Journal of Damage Mechanics. 28(6):815-837. https://doi.org/10.1177/1056789518795203S815837286Chen, I. H., Kiang, J. H., Correa, V., Lopez, M. I., Chen, P.-Y., McKittrick, J., & Meyers, M. A. (2011). Armadillo armor: Mechanical testing and micro-structural evaluation. Journal of the Mechanical Behavior of Biomedical Materials, 4(5), 713-722. doi:10.1016/j.jmbbm.2010.12.013Chintapalli, R. K., Mirkhalaf, M., Dastjerdi, A. K., & Barthelat, F. (2014). Fabrication, testing and modeling of a new flexible armor inspired from natural fish scales and osteoderms. Bioinspiration & Biomimetics, 9(3), 036005. doi:10.1088/1748-3182/9/3/036005Deka, L. J., Bartus, S. D., & Vaidya, U. K. (2009). Multi-site impact response of S2-glass/epoxy composite laminates. Composites Science and Technology, 69(6), 725-735. doi:10.1016/j.compscitech.2008.03.002Duro-Royo, J., Zolotovsky, K., Mogas-Soldevila, L., Varshney, S., Oxman, N., Boyce, M. C., & Ortiz, C. (2015). MetaMesh: A hierarchical computational model for design and fabrication of biomimetic armored surfaces. Computer-Aided Design, 60, 14-27. doi:10.1016/j.cad.2014.05.005Flores-Johnson, E. A., Shen, L., Guiamatsia, I., & Nguyen, G. D. (2014). Numerical investigation of the impact behaviour of bioinspired nacre-like aluminium composite plates. Composites Science and Technology, 96, 13-22. doi:10.1016/j.compscitech.2014.03.001Grujicic, M., Pandurangan, B., & Coutris, N. (2011). A Computational Investigation of the Multi-Hit Ballistic-Protection Performance of Laminated Transparent-armor Systems. Journal of Materials Engineering and Performance, 21(6), 837-848. doi:10.1007/s11665-011-0004-3Grunenfelder, L. K., Suksangpanya, N., Salinas, C., Milliron, G., Yaraghi, N., Herrera, S., … Kisailus, D. (2014). Bio-inspired impact-resistant composites. Acta Biomaterialia, 10(9), 3997-4008. doi:10.1016/j.actbio.2014.03.022Klasztorny, M., & Świerczewski, M. (2015). NUMERICAL MODELLING AND VALIDATION OF 12.7 MM FSP IMPACT INTO ALFC SHIELD – ARMOX 500T STEEL PLATE SYSTEM. Journal of KONES. Powertrain and Transport, 19(4), 291-299. doi:10.5604/12314005.1138463Liu, P., Zhu, D., Yao, Y., Wang, J., & Bui, T. Q. (2016). Numerical simulation of ballistic impact behavior of bio-inspired scale-like protection system. Materials & Design, 99, 201-210. doi:10.1016/j.matdes.2016.03.040Morka, A., & Nowak, J. (2015). NUMERICAL ANALYSES OF CERAMIC/METAL BALLISTIC PANELS SUBJECTED TO PROJECTILE IMPACT. Journal of KONES. Powertrain and Transport, 19(4), 465-472. doi:10.5604/12314005.1138618Pandya, K., Kumar, C. V. S., Nair, N., Patil, P., & Naik, N. (2014). Analytical and experimental studies on ballistic impact behavior of 2D woven fabric composites. International Journal of Damage Mechanics, 24(4), 471-511. doi:10.1177/1056789514531440Poniżnik, Z., Nowak, Z., & Basista, M. (2015). Numerical modeling of deformation and fracture of reinforcing fibers in ceramic–metal composites. International Journal of Damage Mechanics, 26(5), 711-734. doi:10.1177/1056789515611945Porter, M. M., Ravikumar, N., Barthelat, F., & Martini, R. (2017). 3D-printing and mechanics of bio-inspired articulated and multi-material structures. Journal of the Mechanical Behavior of Biomedical Materials, 73, 114-126. doi:10.1016/j.jmbbm.2016.12.016Reaugh, J. E., Holt, A. C., Welkins, M. L., Cunningham, B. J., Hord, B. L., & Kusubov, A. S. (1999). Impact studies of five ceramic materials and pyrex. International Journal of Impact Engineering, 23(1), 771-782. doi:10.1016/s0734-743x(99)00121-9Rostamiyan, Y., & Ferasat, A. (2016). High-speed impact and mechanical strength of ZrO2/polycarbonate nanocomposite. International Journal of Damage Mechanics, 26(7), 989-1002. doi:10.1177/1056789516644312Russell, B. P. (2014). Multi-hit ballistic damage characterisation of 304 stainless steel plates with finite elements. Materials & Design, 58, 252-264. doi:10.1016/j.matdes.2014.01.074Serjouei, A., Chi, R., Sridhar, I., & Tan, G. E. B. (2015). Empirical Ballistic Limit Velocity Model for Bi-Layer Ceramic–Metal Armor. International Journal of Protective Structures, 6(3), 509-527. doi:10.1260/2041-4196.6.3.509Shaktivesh, Nair, N., & Naik, N. (2014). Ballistic impact behavior of 2D plain weave fabric targets with multiple layers: Analytical formulation. International Journal of Damage Mechanics, 24(1), 116-150. doi:10.1177/1056789514524074Yang, W., Chen, I. H., Gludovatz, B., Zimmermann, E. A., Ritchie, R. O., & Meyers, M. A. (2012). Natural Flexible Dermal Armor. Advanced Materials, 25(1), 31-48. doi:10.1002/adma.20120271
Situación actual y evolución del esquema de selección del merino autóctono
Desde la década de los 80, la Asociación Nacional de Criadores de ganado Merino comienza la recogida de información productiva (crecimiento, morfología y reproducción) hacia la nueva orientación cárnica de la raza. En la década de los 90 se organiza un Núcleo de Control Cárnico de la raza Merina, comenzándose a realizar una selección masal para a partir del año 96, con la aprobación del Esquema de Selección por parte del MAPA, realizarse una valoración genética interrebaño con conexión entre rebaños y parideras apoyada en centro de testaje. Desde ese momento hasta la actualidad se han realizado diferentes valoraciones genéticas, la última de ellas utilizando los controles de crecimiento de un total de 24.557 corderos (pertenecientes a las 34 ganaderías adscritas al Esquema de Selección hasta la actualidad). En este trabajo estudiamos la situación actual de las principales variables controladas en este Núcleo de Control Cárnico de la raza Merina, analizando la evolución fenotípica y genética de los principales objetivos de selección del programa de mejora genética de esta raza. Según nuestros resultados, en los 10 últimos alias se ha producido un incremento de 1,20 kg para el peso a los 30 días de los corderos, de 2,51 kg para el peso a los 60 días y de 3,1O kg para el peso a los 75 días. Para las ganancias medias diarias los incrementos han sido de 0,03 kg hasta los 30 días, de 0,04 kg hasta los 60 días, de 0,04 kg hasta los 75 días, de 0,04 kg entre los 30-60 dias, de 0,04 entre los 30-75 dias y de 0,04 kg entre los 60-75 días. En cuanto a otras variables de tipo reproductivo analizadas, el progreso también ha sido evidente, pasando de una fertilidad de 75,64% y una prolificidad de 113,42% de las primeras valoraciones a una fertilidad de 83,64% y una prolificidad de 117,01% de la última valoración
Improving customer engagement through the determinants of employee engagement
In the field of marketing, an engagement orientation urges companies to co-create a broader range of activities with their customers and requires all employees to commit to the company and understand the value of customers engagement (Harmeling et al., 2017). Several previous studies have focused on how companies can develop customer engagement through marketing and employee engagement (Venkatesan, 2017). However, little research has examined the factors that determine the level of employee engagement in this relationship with the customers.
The objective of this research is to identify which variables of the organization, associated with employee engagement, show a relationship or incidence in the customer engagement. To achieve this goal present study uses Radial Basis Function Neural Networks in order to model the behavior of the employee engagement of the selected sample.
The results obtained provide significant information on how relationships with stakeholders, and especially customer engagement, can be improved.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Identifying explanatory factors of bitcoin price with artificial neural networks
This study aims to develop a new model that allows determining with high precision the factors that explain the price of bitcoin. To do this, an extensive database of variables related to bitcoin and artificial neural network techniques has been used. The results obtained have made it possible to identify that aspects related to the number of forum posts, the volume of transactions on the blockchain, and the hash rate provide an excellent strategy for predicting the price of bitcoi
Programa de Conservación del Merino Negro: Caracterización de la aptitud productiva y valoración genética para caracteres de crecimiento
A pesar de que el merino negro como miembro del
tronco merino nativo español, ha sufrido la mayoría de
los vaivenes del merino blanco, no ha existido paralelismo
en la evolución de los censos de ambas poblaciones
a lo largo de la historia, principalmente debido al color de
su fibra.
En la actualidad está considerada una raza en peligro
de extinción. Dentro de las actuaciones llevadas a cabo
por la Asociación Nacional de Criadores para su conservación
in situ, y en el ámbito del proyecto de investigación
lNIA (RZ- 2004-00024), se ha realizado el control
productivo de 170 corderos hijos de 5 moruecos pertenecientes
al Censyra de Extremadura (Badajoz) que fueron
sometidos a prueba de descendencia. Se realizaron 4
pesadas por cordero desde el nacimiento hasta el sacrificio (edad media 75 días). La ganancia media diaria osciló
en el caso de los machos entre los 0,223 Kg. (ganancia
en el primer mes de vida) hasta los 0,265 Kg. (en la última
fase del cebo) y los 0,195 Kg. a 0,221 Kg. en los mismos
periodos para las hembras. Esto determinó que los
pesos medios obtenidos fueron en todos los casos estadísticamente
menores a los del merino blanco que se controla dentro del Esquema de Selección de la raza (alrededor
de 1 Kg. de media a los 30 días de edad, y 2 kgs. al
final del cebo). Esto justifica en parte la situación en la
que se encuentra actualmente esta raza. No obstante consideramos
que las diferencias detectadas son más bien un
reflejo de la diferente historia selectiva de ambas razas en
la última década. Finalmente se ha realizado la primera valoración genética de esta raza empleando la metodología
BLUP modelo animal para caracteres de crecimiento
utilizando para ello los mismos parámetros y modelo que
el merino blanco, contando en la actualidad con el valor
genético de 898 animales para 4 caracteres de crecimiento
(gmd hasta los 30 días y de 30 a los 75 dias, peso
a los 3O y 75 días), y la calificación morfológica
- …