2,092 research outputs found
A note on edge oriented reinforced random walks and RWRE
This work introduces the notion of edge oriented reinforced random walk which
proposes in a general framework an alternative understanding of the annealed
law of random walks in random environment.Comment: 5 page
The Arcsine law as the limit of the internal DLA cluster generated by Sinai's walk
We identify the limit of the internal DLA cluster generated by Sinai's walk
as the law of a functional of a Brownian motion which turns out to be a new
interpretation of the Arcsine law.Comment: 10 pages, 1 figur
Fast ignition driven by quasi-monoenergetic ions: Optimal ion type and reduction of ignition energies with an ion beam array
Fast ignition of inertial fusion targets driven by quasi-monoenergetic ion
beams is investigated by means of numerical simulations. Light and intermediate
ions such as lithium, carbon, aluminium and vanadium have been considered.
Simulations show that the minimum ignition energies of an ideal configuration
of compressed Deuterium-Tritium are almost independent on the ion atomic
number. However, they are obtained for increasing ion energies, which scale,
approximately, as Z^2, where Z is the ion atomic number. Assuming that the ion
beam can be focused into 10 {\mu}m spots, a new irradiation scheme is proposed
to reduce the ignition energies. The combination of intermediate Z ions, such
as 5.5 GeV vanadium, and the new irradiation scheme allows a reduction of the
number of ions required for ignition by, roughly, three orders of magnitude
when compared with the standard proton fast ignition scheme
Extended Hamiltonian systems in multisymplectic field theories
We consider Hamiltonian systems in first-order multisymplectic field
theories. We review the properties of Hamiltonian systems in the so-called
restricted multimomentum bundle, including the variational principle which
leads to the Hamiltonian field equations. In an analogous way to how these
systems are defined in the so-called extended (symplectic) formulation of
non-autonomous mechanics, we introduce Hamiltonian systems in the extended
multimomentum bundle. The geometric properties of these systems are studied,
the Hamiltonian equations are analyzed using integrable multivector fields, the
corresponding variational principle is also stated, and the relation between
the extended and the restricted Hamiltonian systems is established. All these
properties are also adapted to certain kinds of submanifolds of the
multimomentum bundles in order to cover the case of almost-regular field
theories.Comment: 36 pp. The introduction and the abstract have been rewritten. New
references are added and some little mistakes are corrected. The title has
been slightly modifie
Random walks in random Dirichlet environment are transient in dimension
We consider random walks in random Dirichlet environment (RWDE) which is a
special type of random walks in random environment where the exit probabilities
at each site are i.i.d. Dirichlet random variables. On , RWDE are
parameterized by a -uplet of positive reals. We prove that for all values
of the parameters, RWDE are transient in dimension . We also prove that
the Green function has some finite moments and we characterize the finite
moments. Our result is more general and applies for example to finitely
generated symmetric transient Cayley graphs. In terms of reinforced random
walks it implies that directed edge reinforced random walks are transient for
.Comment: New version published at PTRF with an analytic proof of lemma
Trematode Centrocestus formosanus Infection and Distribution in Ornamental Fishes in Mexico
Análisis de la distribución del Trematodo Centrocestus formosanus en peces de ornatoThe aim of this study was to determine the ornamental fish species affected by the metacercariae of the digenean trematode Centrocestus formosanus and its distribution in 48 fish farms in Morelos, central Mexico. The parasite was found to form various numbers of branchial cysts in 11 of the 25 species analyzed. Goldfish Carassius auratus was the most commonly affected species; 20 of 30 farms were positive for this parasite, the fish showing severe clinical signs and having a high mortality rate. For the first time in the region, koi (a variant of common carp Cyprinus carpio), zebrafish Danio rerio, suckermouth catfish Hypostomus plecostomus and blue gourami Trichogaster trichopterus (also known as the threespot gourami) were positive; meanwhile, Mexican tetra Astyanax mexicanus, which had previously been reported positive in other studies in this region, was found to be negative. The parasite was observed in fish from 27 of the 48 farms studied. Ten of 15 municipalities had farms that were positive for the parasite. These results suggest that the distribution of C. formosanus is closely related to the use of water that had been contaminated with the parasite and to the presence of a snail, the red-rimmed melania Melanoides tuberculata.Asociación de Productores de Peces de Ornato of Morelos State
Monitoring of patogen parasites in waste waters of agricultural industries
Las aguas residuales son potenciales
portadoras de enteroparásitos patógenos
para el hombre cuya dosis infectiva puede
ser mÃnima y prolongado el tiempo de
sobrevivencia de huevos y quistes en el
ambiente. La reglamentación limita la presencia
de huevos de helmintos y, hasta el
año 2000, no proponÃa una técnica para su
detección. Este trabajo se realizó para caracterizar
parasitológicamente los efluentes
procedentes de agroindustrias.
La capacitación en la identificación microscópica
demandó la confección de fichas
que describen las caracterÃsticas de huevos
de helmintos. Se efectuaron ensayos con
muestras de bodegas y aceiteras en los puntos
detectados de contaminación. Los métodos
fueron adaptados a las particularidades
de los efluentes.
Los resultados no señalaron presencia
de helmintos; no obstante, se hallaron
Cyclospora e Isospora, protozoarios que, por
su alto poder infectivo, también constituyen
un riesgo para el hombre. Sin embargo, no
están contemplados por la legislación. Respecto
a helmintos, es necesario un estudio
comparativo de las técnicas de detección
para efluentes agroindustriales, con el fin de
establecer las que optimicen su recuperación.
En cuanto a otras especies es preciso
continuar investigando su presencia para
evaluar la conveniencia de incorporarlas a
la reglamentación.Wastewaters are potential human's
pathogenic parasite carriers which could be
infective in small quantities. Besides, the
eggs and cysts survival time could be
prolonged. Regulation, restricts helminths
eggs presence and, until 2000, did not
propose a detection technique. This research
aims to the parasitological characterization
of waste water from agrarian industries.
Training about microscopical identification
led us to write a helminths eggs
characteristics description. Since the
detection of pollution points, essays were
made with samples from wine vault and olive
oil factories. Techniques were adapted,
according to wastewater peculiarities.
The results did not show helminths
presence, but we found Cyclospora and
Isospora. They are protozoa whose high
infective power makes them a human health
risk. However, they are not included in
current legislation. With respect to helminths,
we concluded that it is important to make a
detection techniques comparative study for
wastewater in order to establish which one
is the best for helminths recovery.
Since other species identification, it is
necessary to investigate their presence in
order to evaluate the convenience of
incorporating them to water regulation.Fil: Enriquez, Verónica L..
Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Biomatemática y FisicoquÃmicaFil: Soria, Adriana E..
Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Biomatemática y FisicoquÃmicaFil: Salomón, MarÃa C..
Universidad Nacional de Cuyo. Facultad de Ciencias Médicas. Departamento de PatologÃ
Surface Grafting of Poly(L-glutamates). 2. Helix Orientation
In this paper the average helix orientation of surface-grafted poly(γ-benzyl L-glutamate) (PBLG), poly(γ-methyl L-glutamate) (PMLG), and poly(γ-methyl L-glutamate)-co-(γ-n-stearyl L-glutamate) (PMLGSLG 70/30) was investigated by means of FT-IR transmission spectroscopy. The theoretical relation between the average tilt angle (θ) and the absorption peak areas of three different backbone amide bands could be calculated because their transition dipole moment directions with respect to the helix axis were known. From the normalized absorptions, the average tilt angles of grafted helices of PBLG, PMLG, and PMLGSLG 70/30 were determined. The somewhat larger average angle of PMLG helices of 35 ± 5° with respect to the substrate compared to the value of 32 ± 5° of PBLG was due to the higher grafting density of PMLG. Because of the smaller helix diameter as a result of the smaller size of the methyl side group, more PMLG helices grew on the same surface area. Sterical hindrance and unfavorable polar interactions between unidirectional aligned helices forced the PMLG helices in a more upright arrangement. The even more perpendicular orientation of PMLGSLG 70/30 (48 ± 6°) could be the result of incorporation of mainly γ-methyl L-glutamate N-carboxyanhydride (MLG-NCA) monomers during the initiation step. Incorporation of the much larger γ-n-stearyl L-glutamate N-carboxyanhydride (SLG-NCA) monomers afterward lead to enlarged angles with respect to the substrate. Due to swelling, a pronounced change in helix orientation of grafted PMLGSLG 70/30 in n-hexadecane was observed, resulting in an almost perpendicular helix orientation.
Differences in coastal and oceanic SST trends north of Yucatan Peninsula
The coastal area north of Yucatan has experienced a cooling SST trend from 1982 to 2015 during the upwelling season (May–September) that contrasts with the warming observed at the adjacent ocean area. Different drivers were analyzed to identify the possible causes of that unusual coastal cooling. Changes in coastal upwelling and in sea-atmosphere heat fluxes are not consistent with the observed coastal cooling. The eastward shift of the Yucatan Current observed over the last decades is hypothesized as the most probable cause of coastal cooling. This shift enhances the vertical transport of cold deeper water to the continental shelf from where it is pumped to the surface by upwelling favorable westerly winds.publishe
- …