Hypervelocity Impact Experiments on Epoxy/Ultra-high Molecular Weight Polyethylene Fiber Composites Reinforced with Single-walled Carbon Nanotubes

AbstractNanocomposites of ultra-high molecular weight polyethylene (UHMWPE) fabrics with single-walled carbon nanotubes (SWCNT) in epoxy matrix were prepared in order to study their hypervelocity impact (HVI) characteristics. These nanocomposites were assessed for their use as bumper shields and as rear walls in Whipple shield configurations at impact velocities in the 6.5-7km/s range. The HVI performances of the nanocomposites were compared against that of the epoxy/UHMWPE composites without nanotubes (or simply, neat composites) and aluminum (Al) sheets having areal density similar to both the composites. The results show that the nanocomposites and the neat composites perform better as rear walls than the Al sheets, but are lesser effective bumper shields. Comparatively, the two composites perform similarly to one another as rear walls and as bumper shields. For these epoxy/UHMWPE composite samples, the reinforcement with 0.5 wt% of SWCNT has no noticeable effect on their HVI response

Quark production and thermalization of the quark-gluon plasma

We first assemble a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermalization/hydrodynamization as well as the production of massless quarks and antiquarks in out of equilibrium systems. In the BEDA, the time evolution of a generic system is characterized by the following space-time dependent quantities: the jet quenching parameter, the effective temperature, and two more for each quark flavor that describe the conversion between gluons and quarks/antiquarks via the $2\leftrightarrow2$ processes. Out of the latter two quantities, an effective net quark chemical potential is defined, which equals the net quark chemical potential after thermal equilibration. We then study thermalization and the production of three flavors of massless quarks and antiquarks in spatially homogeneous systems initially filled only with gluons. A parametric understanding of thermalization and quark production is obtained for either initially very dense or dilute systems, which are complemented by detailed numerical simulations for intermediate values of initial gluon occupancy $f_0$. For a wide range of $f_0$, the final equilibration time is determined to be about one order of magnitude longer than that in the corresponding pure gluon systems. Moreover, during the final stage of the thermalization process for $f_0\geq 10^{-4}$, gluons are found to thermalize earlier than quarks and antiquarks, undergoing the top-down thermalization.Comment: 47 pages, 17 figure

Requerimientos, manejo de agua y fertilización nitrogenada en la variedad de arroz Oryzica-3.

En el Centro de Investigación Palmira (Valle) se realizó un experimento para conocer, en Oryzica-3, los mejores niveles de fertilización nitrogenada, el mejor manejo del agua y los requerimientos hídricos, más los coeficientes K (relación entre evapotranspiración real, ETr y evaporación, Ev, en un tanque clase A). Se probaron 3 niveles de N: 80, 120 y 160 kgN/ha, usando úrea como fuente. Se tuvo una lámina de agua L1, de 5.0 cm y otra de saturación (Lo igual 0.0 cm), combinadas en 3 fases del cultivo: vegetativa, reproductiva y maduración. Se empleó un diseño de bloques completos al azar con arreglo en parcelas divididas y 3 repeticiones, donde la parcela principal eran los niveles de N. Para los requerimientos de agua se emplearon lisímetros (canecas de 20 L), donde se midió Ev, transpiración (T) y percolación (Pp), además se tomaron datos de lluvia en un pluviómetro estandarizado, y de Ev en un tanque clase A. La ETr fue de 609.5 mm en 106 dias, el promedio del factor K fue de 1.27, la T representó el 22 por ciento de la ETr. El mayor rendimiento de arroz-cáscara venteado correspondió al tratamiento N3W2 (160 kgN/ha y L1L1L0) con 7.535.44 kg/ha. El mayor volumen de agua aplicada fue de 21.689.40 metros cúbicos/ha para N3W1 (160 kgN/ha y L1L1L1), el menor, 14.818.50 metros cúbicos en N1W6 (80 kgN/ha y L0L1L0). La mayor eficiencia de uso de agua estuvo en los tratamientos de 160kgN/ha, destacándose N3W6 con 4.05 kg arroz/mm de agua aplicada/ha. Según análisis económico, los mejores tratamientos fueron: N3W6 con TRM=291.12 por ciento para agricultores con capital suficiente y N1W6 con TRM igual 272.46 por ciento, el cual por tener menores costos, se recomienda para agricultores con restricciones aconómicas. Como alternativas se recomiendan: N2W4 (120 kgN/ha y saturación constante L0L0L0) y N1W4 (80 kgN/ha y L0L0L0).;La función producción (Y) - agua (W) - fertilización nitrogenada (N) encontrada fue: Y = -75.36N mas 0.3838N2 mas 0.897W - 0.00002178W2 con R2 igual 0.997, para los rangos utilizados en la investigaciónArroz-Oryza sativ

Reaction of Tepary Beans to Eight Virulent Races of the Rust Pathogen that Overcomes All Known Common Bean Rust Resistance Genes

Bean rust, caused by Uromyces appendiculatus, is a major disease of common and snap bean (Phaseolus vulgaris) worldwide (Stavely, 1984). Although host resistance is an important component of rust management (Mmbaga et al., 1996), populations of the rust pathogen comprise an extensive and shifting virulence diversity that could render susceptible all known rust resistance genes in common bean. Conversely, it has been suggested that certain tepary bean (Phaseolus acutifolius) accessions are broadly resistant to bean rust (Miklas & Stavely, 1998). The objectives of this study were to verify if tepary beans are resistant to eight races of the bean rust pathogen, which overcome all known rust resistance genes in common bean. Then, to select the resistant genotypes to cross with common beans without embryo rescue

Los tornillos como método suplementario de fijación de las cúpulas acetabulares: Utilidad de la digitalización de imágenes

La fijación suplementaria con tornillos de los componentes acetabulares hemisféricos no cementados es utilizada para proporcionar estabilidad primaria al implante. No obstante su empleo se asocia a un mayor riesgo de lesiones neurovasculares, complicaciones propias de los tornillos e incremento de osteolisis. Se han estudiado retrospectivamente las radiografías de 30 cúpulas cotiloideas no cementadas modelo Bihapro, suplementadas con tornillos, con un seguimiento mínimo de 5 años. Se utilizó, además, un programa de análisis y procesamiento de imágenes por ordenador. No se produjeron lesiones neurovasculares o viscerales, no se apreció ninguna movilización de la cúpula y sólo se observó un caso e osteolisis alrededor de un tornillo en un paciente sometido a cirugía de revisión. La digitalización de imágenes es una técnica que permite entre otras ventajas graduar densidades óseas periprotésicas facilitando un diagnóstico precoz de zonas líticas y microdeslizamientos protésicos, eliminando la subjetividad del observador.The supplementary fixation with screws non-cemented acetabular hemispheric components is used to provide primary stability to the implants. However, their use has been associated to a bigger risk of neurological and vascular damage, characteristic complications of the screws and osteolysis. The X-rays of 30 non-cemented acetabular cups model Bihapro supplemented with screws have been studied retrospectively with a 5 year-old minimum follow-up. It was also used an analysis program and computer store of images. No neurological or vascular damage took place. Any mobilization of the cup was not appreciated and only in one case of an osteolytic area was observed around a screw in a patient who unfderwent revision surgery. The digitalization of images is a technique that allows among other advantages to graduate periprosthetic bone densities facilitating an early diagnose of lytic areas and prosthetic micromovements eliminating the observer's subjectivity

Metabolitos aislados de raputia heptaphylla y esenbeckia alata (rutaceae) y síntesis de precursores de análogos de alcaloides quinolínicos

Abstract. Previous studies on the Esenbeckia alata and Raputia heptaphylla,both species belonging to the Rutaceae family, have shownimportant results with respect to their chemistry. These species havesecondary metabolites (coumarins and alkaloids mainly), which act aschemotaxonomic markers. This paper presents, for the first time, the phytochemicalwork and isolated metabolites in these species: four coumarins:bergapten, xanthyletin, xanthotoxin, 3-isoprenyl-4-methoxy-coumarin;four alkaloids: skinmianine, kokusaginine, dictamnine, and 1-methyl-2-methoxy-4-quinolone; two lignans: sesamin and mesodihydroguaiareticacid; two sterols: -sitosterol, stigmasterol; and a pentacyclic triterpene:lupeol that have been isolated from leaves of E. alata. Five alkaloids7-methoxy-2,2-dimethyl-2,6-dihidro-piran[3,2,c] quinolin-5-one, flindersiamine,skinmianine, kokusaginine and dictamnine that have been isolatedfrom leaves of R. heptaphylla. Moreover, it presents a new method byobtaining quinolone alkaloid analogue precursors trough the condensationsof Mannich adduct vinylogous and aldehydes followed by radicalcyclization to obtain products with high regio- and stereoselectivity.

Efecto de diferentes poblaciones y niveles de nitrógeno y fósforo sobre el cultivo asociado de papa y fríjol en el Oriente de Cundinamarca.

Fríjol-Phaseolus vulgarisPapa-Solanum tuberosu

Affordable laparoscopic simulator to acquire basic skills in undergraduate surgery students

Background: The simulation emerges as an option that allows students to practice in a safe environment, all this in a scenario that resembles the real situation.Methods: We developed a prototype of a low-cost simulator that mimics the dimensions of the abdominal cavity and allows the undergraduate students to acquire the basic skills in minimally invasive surgery.Results: In the 10 competencies evaluated, statistically significant improvement was found in both groups being higher in the students who were trained by our simulator of laparoscopic surgery compared with students who attended surgeries and participated as seconds assistants, taking as reference a value of p ≤0.05.Conclusions: The simulation as new teaching strategy generates a real environment and scenarios that can be recreated in multiple occasions, being able to change depending on the objectives for the acquisition of skills. This simulator gives the user skills for more types of simulation as it progresses in its surgical training

Identification of the dynamics of biofouled underwater gliders

Marine growth has been observed to cause a drop in the horizontal and vertical velocities of underwater gliders, thus making them unresponsive and needing immediate recovery. Currently, no strategies exist to correctly identify the onset of marine growth for gliders and only limited datasets of biofouled hulls exist. Here, a field test has been run to investigate the impact of marine growth on the dynamics of underwater gliders. A Slocum glider was deployed first for eight days with drag stimulators to simulate severe biofouling; then the vehicle was redeployed with no additions to the hull for a further 20 days. The biofouling caused a speed reduction due to a significant increase in drag. Additionally, the lower speed causes the steadystate flight stage to last longer and thus a shortening of mission duration. As actual biofouling due to p. pollicipes happened during the deployment, it was possible to develop and test a system that successfully detects and identifies high levels of marine growth on the glider using steady-state flight data. The system will greatly help pilots re-plan missions to safely recover the vehicle if significant biofouling is detected