7,523 research outputs found
Experimental phase functions of mm-sized cosmic dust grains
We present experimental phase functions of three types of millimeter-sized
dust grains consisting of enstatite, quartz and volcanic material from Mount
Etna, respectively. The three grains present similar sizes but different
absorbing properties. The measurements are performed at 527 nm covering the
scattering angle range from 3 to 170 degrees. The measured phase functions show
two well defined regions i) soft forward peaks and ii) a continuous increase
with the scattering angle at side- and back-scattering regions. This behavior
at side- and back-scattering regions are in agreement with the observed phase
functions for the Fomalhaut and HR 4796A dust rings. Further computations and
measurements (including polarization) for millimeter sized-grains are needed to
draw some conclusions about the fluffy or compact structure of the dust grains
Twisting solar coronal jet launched at the boundary of an active region
A broad jet was observed in a weak magnetic field area at the edge of active
region NOAA 11106. The peculiar shape and magnetic environment of the broad jet
raised the question of whether it was created by the same physical processes of
previously studied jets with reconnection occurring high in the corona. We
carried out a multi-wavelength analysis using the EUV images from the
Atmospheric Imaging Assembly (AIA) and magnetic fields from the Helioseismic
and Magnetic Imager (HMI) both on-board the SDO satellite. The jet consisted of
many different threads that expanded in around 10 minutes to about 100 Mm in
length, with the bright features in later threads moving faster than in the
early ones, reaching a maximum speed of about 200 km s^{-1}. Time-slice
analysis revealed a striped pattern of dark and bright strands propagating
along the jet, along with apparent damped oscillations across the jet. This is
suggestive of a (un)twisting motion in the jet, possibly an Alfven wave. A
topological analysis of an extrapolated field was performed. Bald patches in
field lines, low-altitude flux ropes, diverging flow patterns, and a null point
were identified at the basis of the jet. Unlike classical lambda or
Eiffel-tower shaped jets that appear to be caused by reconnection in current
sheets containing null points, reconnection in regions containing bald patches
seems to be crucial in triggering the present jet. There is no observational
evidence that the flux ropes detected in the topological analysis were actually
being ejected themselves, as occurs in the violent phase of blowout jets;
instead, the jet itself may have gained the twist of the flux rope(s) through
reconnection. This event may represent a class of jets different from the
classical quiescent or blowout jets, but to reach that conclusion, more
observational and theoretical work is necessary.Comment: 12 pages, 9 figures, accepted for publication in A&
Magnetic upconverting fluorescent NaGdF4:Ln3+ and iron-oxide@NaGdF4:Ln3+ nanoparticles
CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPEMA - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MARANHÃOFAPEAL - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE ALAGOASMicrowave assisted solvothermal method has been employed to synthesize multifunctional upconverting beta-NaGdF4:Ln(3+) and magnetic-upconverting Fe3O4/gamma-Fe2O3@ NaGdF4:Ln3+ ( Ln = Yb and Er) nanoparticles. The powder x-ray diffraction data confirms the hexagonal structure of NaGdF4:Ln(3+) and high resolution transmission electron microscopy shows the formation of rod shaped NaGdF4:Ln(3+) (similar to 20 nm) and ovoid shaped Fe3O4/gamma-Fe2O3@NaGdF4:Ln(3+) (similar to 15 nm) nanoparticles. The magnetic hysteresis at 300 K for beta-NaGdF4:Ln(3+) demonstrates paramagnetic features, whereas iron-oxide@beta-NaGdF4:Ln(3+) exhibits superparamagnetic behavior along with a linear component at large applied field due to paramagnetic NaGdF4 matrix. Both nanoparticle samples provide an excellent green emitting [(H-2(11/ 2), S-4(3/2))-> I-4(15/2) (similar to 540 nm)] upconversion luminescence emission under excitation at 980 nm. The energy migration between Yb and Er in NaGdF4 matrix has been explored from 300-800 nm. Intensity variation of blue, green and red lines and the observed luminescence quenching due to the presence of Fe3O4/gamma-Fe2O3 in the composite has been proposed. These kinds of materials contain magnetic and luminescence characteristics into single nanoparticle open new possibility for bioimaging applications.8516CAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPEMA - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MARANHÃOFAPEAL - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE ALAGOASCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPEMA - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MARANHÃOFAPEAL - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE ALAGOAS62. Annual Conference on Magnetism and Magnetic Materials2017Pittsburgh, PAIEEE Magnetics SocietyAIP PublishingAgências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig
Energy loss of protons and deuterons at low energies in Pd polycrystalline thin films
We have investigated experimentally and by computer simulations the energy loss distributions of low energy (E <10 keV) protons and deuterons transmitted through polycrystalline palladium thin flms. In contrast with previous experiments on various transition metals we find that the stopping power of Pd is proportional to the ion velocity. Data of protons and deuterons are coincident within the experimental uncertainties, showing the absence of an isotopic effect on the stopping power of Pd in this energy range. The experimental results were analyzed and compared with Monte Carlo computer simulations and previous theoretical models. The dference in the velocity dependence of the energy loss of hydrogen ions in Pd with respect to other transition metals (Cu, Ag and Au) is explained by a theoretical analysis based on the properties of the d-electron bands of those elements.Fil: Celedón, C.. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Sanchez, Esteban Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Moreno, Mario Sergio Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Arista, Nestor Ricardo. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; ArgentinaFil: Uribe, J. D.. Universidad Técnica Federico Santa María. Departamento de Física. Laboratorio de Colisiones Atómicas; ChileFil: Mery, M.. Universidad Técnica Federico Santa María. Departamento de Física. Laboratorio de Colisiones Atómicas; ChileFil: Valdés, J. E.. Universidad Técnica Federico Santa María. Departamento de Física. Laboratorio de Colisiones Atómicas; ChileFil: Vargas, P.. Universidad Técnica Federico Santa María. Departamento de Física. Laboratorio de Colisiones Atómicas; Chil
Improving construction processes of concrete building structures using load limiters on shores
This paper analyses the redistribution of maximum loads using a system of load limiters on shores in which the limiters yield at a given load and thus reduce the maximum load absorbed by the shores. For this analysis a finite element modelling (FEM) of an experimental building was developed in which load limiters had been fitted to the shores to restrict their maximum load to a given value. This was designed to: (a) optimise slab construction costs by using shores of lower load-bearing capacities, (b) improve safety during the construction of consecutive concrete slab floors by reducing maximum loads and redistributing loads amongst the shores; and (c) increase structural efficiency by more efficient use of the materials employed due to load redistribution. It has been estimated that using load limiters in this way can reduce total shoring costs in a building project by between 30% and 40%.The authors would like to express their gratitude to the Universitat Politecnica de Valencia for funding this research project (PAID-06-11) and also to the Encofrados J. Alsina Company for their invaluable cooperation.Buitrago Moreno, M.; Alvarado Vargas, YA.; Adam Martínez, JM.; Calderón García, PA.; Gasch, I.; Moragues, JJ. (2015). Improving construction processes of concrete building structures using load limiters on shores. Engineering Structures. 100:104-115. doi:10.1016/j.engstruct.2015.06.007S10411510
An integrated biochemical system for nitrate assimilation and nitric oxide detoxification in Bradyrhizobium japonicum
Rhizobia are recognized to establish N(2)-fixing symbiotic interactions with legume plants. Bradyrhizobium japonicum, the symbiont of soybeans, can denitrify and grow under free-living conditions with nitrate (NO(3)(−)) or nitrite (NO(2)(−)) as sole nitrogen source. Unlike related bacteria that assimilate NO(3)(−), genes encoding the assimilatory NO(3)(−) reductase (nasC) and NO(2)(−) reductase (nirA) in B. japonicum are located at distinct chromosomal loci. The nasC gene is located with genes encoding an ABC-type NO(3)(−) transporter, a major facilitator family NO(3)(−)/NO(2)(−) transporter (NarK), flavoprotein (Flp) and single-domain haemoglobin (termed Bjgb). However, nirA clusters with genes for a NO(3)(−)/NO(2)(−)-responsive regulator (NasS-NasT). In the present study, we demonstrate NasC and NirA are both key for NO(3)(−) assimilation and that growth with NO(3)(−), but not NO(2)(−) requires flp, implying Flp may function as electron donor to NasC. In addition, bjgb and flp encode a nitric oxide (NO) detoxification system that functions to mitigate cytotoxic NO formed as a by-product of NO(3)(−) assimilation. Additional experiments reveal NasT is required for NO(3)(−)-responsive expression of the narK-bjgb-flp-nasC transcriptional unit and the nirA gene and that NasS is also involved in the regulatory control of this novel bipartite assimilatory NO(3)(−)/NO(2)(−) reductase pathway
Manejo de la plaga de la procesionaria del pino Thaumetopoea pityocampa (Den. & Schiff.) en Zaragoza, ciudad.
La procesionaria del pino (Thaumetopoea pityocampa Den. & Schiff.) es uno de los principales insectos defoliadores de la región mediterránea. Su abundancia en la ciudad, junto con el riesgo para la salud de personas y animales domésticos en zonas recreativas o con alta afluencia, han motivado la realización de este trabajo. Con él se pretendía estudiar el comportamiento de la plaga en la ciudad, con el fin de poder definir una estrategia de control para reducir sus niveles.Para conocer el estado actual de la procesionaria se aplicaron distintas estrategias basadas en el manejo de la plaga. En primer lugar se colocaron trampas de feromona para la captura de mariposas macho, lo que nos permitió conocer el vuelo de la procesionaria en nuestra ciudad. Posteriormente se aplicaron tratamientos de endoterapia y Bacillus thuringiensis para provocar la muerte de las larvas en sus primeros estadios, antes de que la aparición de los pelos urticantes. Al inicio de la aparición de los nidos, se aplicaron métodos físicos para su eliminación. Y finalmente se colocaron trampas barreras en los troncos para tratar de capturar a los individuos que hubiesen sobrevivido a los tratamientos anteriores durante la fase de descenso del árbol para enterrarse en el suelo.Se realizó un análisis estadístico del número de bolsones eliminados en el año anterior al estudio y durante nuestro año de estudio, tras la aplicación de los tratamientos.Una vez analizados estadísticamente los datos proporcionados, se comprobó que la plaga presenta un comportamiento errático para las variables consideradas en este estudio por lo que sería recomendable continuar estudiándola. Asimismo se aconseja repetir los tratamientos aplicados durante este trabajo durante al menos dos años para lograr controlar la plaga.<br /
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