106 research outputs found
Self healing slip pulses along a gel/glass interface
We present an experimental evidence of self-healing shear cracks at a
gel/glass interface. This system exhibits two dynamical regimes depending on
the driving velocity : steady sliding at high velocity (> Vc = 100-125 \mu
m/s), caracterized by a shear-thinning rheology, and periodic stick-slip
dynamics at low velocity. In this last regime, slip occurs by propagation of
pulses that restick via a ``healing instability'' occuring when the local
sliding velocity reaches the macroscopic transition velocity Vc. At driving
velocities close below Vc, the system exhibits complex spatio-temporal
behavior.Comment: 4 pages, 6 figure
Does the continuum theory of dynamic fracture work?
We investigate the validity of the Linear Elastic Fracture Mechanics approach
to dynamic fracture. We first test the predictions in a lattice simulation,
using a formula of Eshelby for the time-dependent Stress Intensity Factor.
Excellent agreement with the theory is found. We then use the same method to
analyze the experiment of Sharon and Fineberg. The data here is not consistent
with the theoretical expectation.Comment: 4 page
Nonlinear stability of oscillatory wave fronts in chains of coupled oscillators
We present a stability theory for kink propagation in chains of coupled
oscillators and a new algorithm for the numerical study of kink dynamics. The
numerical solutions are computed using an equivalent integral equation instead
of a system of differential equations. This avoids uncertainty about the impact
of artificial boundary conditions and discretization in time. Stability results
also follow from the integral version. Stable kinks have a monotone leading
edge and move with a velocity larger than a critical value which depends on the
damping strength.Comment: 11 figure
Toxicity of lunar dust
The formation, composition and physical properties of lunar dust are
incompletely characterised with regard to human health. While the physical and
chemical determinants of dust toxicity for materials such as asbestos, quartz,
volcanic ashes and urban particulate matter have been the focus of substantial
research efforts, lunar dust properties, and therefore lunar dust toxicity may
differ substantially. In this contribution, past and ongoing work on dust
toxicity is reviewed, and major knowledge gaps that prevent an accurate
assessment of lunar dust toxicity are identified. Finally, a range of studies
using ground-based, low-gravity, and in situ measurements is recommended to
address the identified knowledge gaps. Because none of the curated lunar
samples exist in a pristine state that preserves the surface reactive chemical
aspects thought to be present on the lunar surface, studies using this material
carry with them considerable uncertainty in terms of fidelity. As a
consequence, in situ data on lunar dust properties will be required to provide
ground truth for ground-based studies quantifying the toxicity of dust exposure
and the associated health risks during future manned lunar missions.Comment: 62 pages, 9 figures, 2 tables, accepted for publication in Planetary
and Space Scienc
Diferencias en rendimiento y calidad fĂsica de grano de especialidades de maĂz
En las dos fechas de siembra utilizadas se observaron diferencias significativas en rendimiento y calidad entre los genotipos flint del mercado. Ya que no todos los atributos de calidad especĂficos se compor taron de la misma manera, es importante evaluar y jerarquizar estos parámetros paracada genotipo particular.Los resultados de este ensayo muestran que la brecha en rendimiento entre todos los flint evaluados y los genotipos semi dentados se ubicĂł alrededor del 17% para la zona templada, pero la magnitud de esta brecha dependiĂł de la calidad del ambien te evaluado (fecha de siembra temprana o tardĂa). Este resultado podrĂa explicarse a partir de la tendencia observada en trabajosprevios del grupo donde los flint mostraron una mayor diferencia en rendimiento conlos semidentados cuando el ambiente fue de peor calidad (Tamagno et al,, 2016). Sin embargo, si calculamos la brecha de ren dimiento entre los hĂbridos semidentados y los genotipos flint comerciales con mayor rendimiento, esa brecha se reduce a un 10%, considerando el promedio de los dos ambientes.Fil: SeguĂ Rosales, Micaela. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; ArgentinaFil: MercĂ©, Mariano. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Maggio, S.. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Barnada, F. J.. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Saenz, Ezequiel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; ArgentinaFil: Gerde, Jose Arnaldo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentin
Diferencias en rendimiento y calidad fĂsica de grano de especialidades de maĂz
En las dos fechas de siembra utilizadas se observaron diferencias significativas en rendimiento y calidad entre los genotipos flint del mercado. Ya que no todos los atributos de calidad especĂficos se compor taron de la misma manera, es importante evaluar y jerarquizar estos parámetros paracada genotipo particular.Los resultados de este ensayo muestran que la brecha en rendimiento entre todos los flint evaluados y los genotipos semi dentados se ubicĂł alrededor del 17% para la zona templada, pero la magnitud de esta brecha dependiĂł de la calidad del ambien te evaluado (fecha de siembra temprana o tardĂa). Este resultado podrĂa explicarse a partir de la tendencia observada en trabajosprevios del grupo donde los flint mostraron una mayor diferencia en rendimiento conlos semidentados cuando el ambiente fue de peor calidad (Tamagno et al,, 2016). Sin embargo, si calculamos la brecha de ren dimiento entre los hĂbridos semidentados y los genotipos flint comerciales con mayor rendimiento, esa brecha se reduce a un 10%, considerando el promedio de los dos ambientes.Fil: SeguĂ Rosales, Micaela. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; ArgentinaFil: MercĂ©, Mariano. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Maggio, S.. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Barnada, F. J.. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; ArgentinaFil: Saenz, Ezequiel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; ArgentinaFil: Gerde, Jose Arnaldo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Rosario. Instituto de Investigaciones en Ciencias Agrarias de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias. Instituto de Investigaciones en Ciencias Agrarias de Rosario; Argentin
Microalgae Lipid Characterization
To meet the growing interest of utilizing microalgae biomass in the production of biofuels and nutraceutical and pharmaceutical lipids, we need suitable analytical methods and a comprehensive database for their lipid components. The objective of the present work was to demonstrate methodology and provide data on fatty acid composition, lipid class content and composition, characteristics of the unsaponifiables, and type of chlorophylls of five microalgae. Microalgae lipids were fractionated into TAG, FFA, and polar lipids using TLC, and the composition of fatty acids in total lipids and in each lipid class, hydrocarbons, and sterols were determined by GC-MS. Glyco- and phospholipids were profiled by LC/ESI-MS. Chlorophylls and their related metabolites were qualified by LC/APCI-MS. The melting and crystallization profiles of microalgae total lipids and their esters were analyzed by DSC to evaluate their potential biofuel applications. Significant differences and complexities of lipid composition among the algae tested were observed. The compositional information is valuable for strain selection, downstream biomass fractionation, and utilization
Collective effects at frictional interfaces
We discuss the role of the long-range elastic interaction between the
contacts inside an inhomogeneous frictional interface. The interaction produces
a characteristic elastic correlation length (where
is the distance between the contacts, is the elastic constant of a
contact, and is the Young modulus of the sliding body), below which the
slider may be considered as a rigid body. The strong inter-contact interaction
leads to a narrowing of the effective threshold distribution for contact
breaking and enhances the chances for an elastic instability to appear. Above
the correlation length, , the interaction leads to screening of
local perturbations in the interface, or to appearance of collective modes ---
frictional cracks propagating as solitary waves
- …