Three-dimensional simulations of turbulent convective mixing in ONe and CO classical nova explosions

Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in binary systems. The material piles up under degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures about 100 - 400 MK. During these events, about 10-3 - 10-7 Msun, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al) are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, the large concentrations of metals spectroscopically inferred in the ejecta), models require mixing between the (solar-like) material transferred from the secondary and the outermost layers (CO- or ONe-rich) of the underlying white dwarf. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, the feasibility of this mechanism has been explored in the framework of CO white dwarfs, while mixing with different substrates still needs to be properly addressed. Three-dimensional simulations of mixing at the core-envelope interface during nova outbursts have been performed with the multidimensional code FLASH, for two types of substrates: CO- and ONe-rich. We show that the presence of an ONe-rich substrate, as in "neon novae", yields larger metallicity enhancements in the ejecta, compared to CO,rich substrates (i.e., non-neon novae). A number of requirements and constraints for such 3-D simulations (e.g., minimum resolution, size of the computational domain) are also outlined.Comment: Accepted for publication in Astronomy & Astrophysic

Unitary expansion of the time evolution operator

We propose an expansion of the unitary evolution operator, associated to a given Schr\"odinger equation, in terms of a finite product of explicit unitary operators. In this manner, this unitary expansion can be truncated at the desired level of approximation, as shown in the given examples.Comment: 6 pages, 7 figures. Updated version, minor final change

Botulinum toxin: A potential alternative to current treatment of neurogenic and idiopathic urinary incontinence due to detrusor overactivity

Objective: To analyze and report the current data on the treatment of both neurogenic and idiopathic detrusor overactivity with Botulinum toxin.Methods: Literature review using Pub‐Med and Medline from 1990 until June 30, 2006.Results: Case series of patients with neurogenic detrusor dysfunction (NDD) and idiopathic detrusor overactivity (IDO) range from 15 to 200 patients with follow up from 12 to 36 weeks post‐treatment. Significant improvements in cystometric bladder capacity, reflex volume at first urge to void, and bladder compliance are seen in nearly all patients. Approximately 50% of NDD patients achieved urinary continence and almost all had improvement in bladder control up to 36 weeks following treatment. Patients with IDO with urgency alone or with incontinence also had urodynamic as well as symptom improvement. Approximately 75% of patients with IDO and incontinence are dry at 12 weeks post‐treatment. Urgency disappears on average in two thirds of patients. Quality of life scores also shows significant improvement for all groups.Conclusion: Botulinum toxin‐A has emerged as a promising option for the treatment of neurogenic and refractory idiopathic detrusor overactivity. Studies to date have shown that not only is this treatment effective at decreasing urinary symptoms and incontinence, as well as improving potentially dangerous urodynamic measures, but it is also minimally invasive, reversible and safe. Questions over proper dosing and dilution, number of injection sites, and re‐injection rates remain to be answered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135676/1/ijgo305.pd

Two-dimensional simulations of mixing in classical novae: the effect of the white dwarf composition and mass

Context. Classical novae are explosive phenomena that take place in stellar binary systems. They are powered by mass transfer from a low-mass main sequence star onto a white dwarf (either CO or ONe). The material accumulates for 10+4 - 10+5 yr until ignition under degenerate conditions, resulting in a thermonuclear runaway. The nuclear energy released produces peak temperatures of about 0.1 - 0.4 GK. During these events, 10-7 - 10-3 Msun enriched in intermediate-mass elements (with respect to solar abundances) are ejected into the interstellar medium. However, the origin of the large metallicity enhancements and the inhomogeneous distribution of chemical species observed in high-resolution spectra of ejected nova shells is not fully understood. Aims. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities that operate at the core-envelope interface can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, such multidimensional simulations have been performed for a small number of cases, and much of the parameter space remains unexplored. Methods. Here we investigate the dredge-up, driven by Kelvin-Helmholtz instabilities, for white dwarf masses in the range 0.8-1.25 Msun and different core compositions (CO-rich and ONe-rich substrates). We present a set of five numerical simulations performed in two dimensions aimed at analyzing the possible impact of the white dwarf mass (and composition) on the metallicity enhancement and on the explosion characteristics. Results. We observe greater mixing (about 30 per cent higher when measured in the same conditions), at the time we stop the simulations, and more energetic outbursts for ONe-rich substrates than for CO-rich substrates and for more massive white dwarfs.Comment: Accepted for Publication in Astronomy and Astrophysic

Biological activity of glucosinolate derived compounds isolated from seed meal of Brassica crops and evaluated as plant and food protection agents

Glucosinolates are amino acid derived allelochemicals characteristic of plants of the order Capparales. These compounds are present in seeds of agriculturally common Brassica crops in varying quantities depending on the species (ref). The use of the remaining seed cake after oil extraction has traditionally been limited by the concentration of these compounds. However, the extraction of glucosinolates from seed meal is nowadays possible and it further contributes to an increased quality of the seed meal for feed (Sørensen et al., this conference). Glucosinolates are hydrolysed by endogenous enzymes (myrosinases; EC 3.2.1.147) and a number of compounds are produced depending on the parent glucosinolate and the environmental conditions.1 Among these compounds, oxazolidine-2-thiones are known for their antinutritional effects on monogastric animals, whereas isothiocyanates are fungicidal, nematocidal and herbicidal.2,3 The possibility for using glucosinolates as precursors for environmental friendly biocides therefore exists, which could contribute to increase the value of the Brassica seed meal

PRODUCCIÓN DE LO URBANO Y PRODUCCIÓN DE LA CIUDAD.

La Teoría del Habitar debe explicarnos cómo es que los transeúntes producen la ciudad paso a paso, cómo los habitantes de los enclaves tejen sus estrategias de acción, cómo aquellos que atraviesan, día a día, los umbrales que proliferan en la vida urbana, se las arreglan para conferir sentido y oportunidad a la arquitectura urbana. Para lograrlo, debemos reparar en los modos en los que las huellas de los caminantes escriben su historia sobre el palimpsesto urbano. La producción de lo urbano no lo es todo en la construcción de la ciudad, es cierto, pero es preciso reconocer que, sin la primera de las operaciones, la segunda, la producción hegemónica, perdería gran parte de su sentido y su rumbo particular. Para ello, es preciso realizar una semblanza de lo urbano, concebido como la pasión cotidiana por habitar, construir y transformar la ciudad, experimentada por los urbanitas de a pie, los protagonistas frecuentemente ignorados —o, lo que es peor, reducidos a su papel de meros usuarios— por la hegemonía política y profesional que opera planeando desde lo alto sobre la ciudad. Solo cuando reparamos, en efecto, en el papel que desempeñan los habitantes de una ciudad en su efectiva constitución de arquitecturas y urbanizaciones vivas, podemos vislumbrar que los urbanitas tienen un papel productivo que ha permanecido aún en las sombras, no explorado por la Teoría Urbana. Así, también podemos comprobar que, mientras empresarios, arquitectos, urbanistas y administradores locales se dedican a producir transformaciones materiales y formales en el espacio, los urbanitas son los verdaderos artífices de los lugares urbanos, ya que les confieren vida palpitante y sentido habitable. Llegados a este punto, podremos comprender que las ciudades que habitamos resultan de la convergencia contradictoria entre, por una parte, la producción social de lo urbano y la producción formal y material de la ciudad