Thermodynamics of the classical spin-ice model with nearest neighbour interactions using the Wang-Landau algorithm

In this article we study the classical nearest-neighbour spin-ice model (nnSI) by means of Monte Carlo simulations, using the Wang-Landau algorithm. The nnSI describes several of the salient features of the spin-ice materials. Despite its simplicity it exhibits a remarkably rich behaviour. The model has been studied using a variety of techniques, thus it serves as an ideal benchmark to test the capabilities of the Wang Landau algorithm in magnetically frustrated systems. We study in detail the residual entropy of the nnSI and, by introducing an applied magnetic field in two different crystallographic directions ([111] and [100],) we explore the physics of the kagome-ice phase, the transition to full polarisation, and the three dimensional Kasteleyn transition. In the latter case, we discuss how additional constraints can be added to the Hamiltonian, by taking into account a selective choice of states in the partition function and, then, show how this choice leads to the realization of the ideal Kasteleyn transition in the system.Comment: 9 pages, 9 figure

Estabilidade de agregados em solos sódicos e salino-sódicos.

bitstream/item/36226/1/Estabilidade-de-Agregados.pd

Effects of bubbling operations on a thermally stratified reservoir: Implications for water quality amelioration

Artificial thermal mixing of the water column is a common method of addressing water quality problems with the most popular method of destratification being the bubble curtain. The air or oxygen distribution along submerged multiport diffusers is based on similar basic principles as those of outfall disposal systems. Moreover, the disposal of sequestered greenhouse gases into the ocean, as recently proposed by several researchers to mitigate the global warming problem, requires analogous design criteria. In this paper, the influence of a bubble-plume is evaluated using full-scale temperature and water quality data collected in San Roque Reservoir, Argentina. A composite system consisting of seven separated diffusers connected to four 500 kPa compressors was installed at this reservoir by the end of 2008. The original purpose of this air bubble system was to reduce the stratification, so that the water body may completely mix under natural phenomena and remain well oxygenated throughout the year. By using a combination of the field measurements and modelling, this work demonstrates that thermal mixing by means of compressed air may improve water quality; however, if improperly sized or operated, such mixing can also cause deterioration. Any disruption in aeration during the destratification process, for example, may result in a reduction of oxygen levels due to the higher hypolimnetic temperatures. Further, the use of artificial destratification appears to have insignificant influence on reducing evaporation rates in relatively shallow impoundments such as San Roque reservoir. © IWA Publishing 2012.Fil: Fernandez, Rocio Luz. Universidade Federal do Paraná; Brasil. Universidad Blas Pascal. Centro de Investigacion Aplicada y Desarrollo En Ciencias del Ambiente.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Hidráulica; ArgentinaFil: Bonansea, Matias. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; ArgentinaFil: Cosavella, A.. Water Resources Secretary Of Córdoba Province; ArgentinaFil: Monarde, F.. Gobierno de la Provincia de Córdoba. Subsecretaría de Recursos Hídricos; ArgentinaFil: Ferreyra, M.. Gobierno de la Provincia de Córdoba. Subsecretaría de Recursos Hídricos; ArgentinaFil: Bresciano, J.. Gobierno de la Provincia de Córdoba. Subsecretaría de Recursos Hídricos; Argentin

Influence of CaCl2.2H2O Content on the Productive Process of Composites from Cotton Gin Waste

AbstractPrevious studies have shown the feasibility of production of masonry blocks and panels from agglomeration of cotton gin waste and calcium binders. Cotton gin waste is a serious problem for ginning plants, because in Argentina approximately 300,000 t of lignocellulosic wastes are produced annually without any final disposal destination. The accumulation of these residues is associated with pests and fire hazards. Since these composites are produced with simple equipment and a minimum energy requirement, their cost depends mainly on the binder (Portland cement) used and the process efficiency, since with a high productivity model, labor and equipment depreciation costs are significantly reduced. This paper analyzes the influence of CaCl2.2H2O (added as an accelerator for cement paste strength) on the minimum molding time required for composites manufacturing. A central composite experimental design was developed in order to study the interrelated variables. The influence of CaCl2.2H2O content on physical-mechanical cement paste properties and their relationship with composites stability are also evaluated. The results of this work show that CaCl2.2H2O content has significant influence on the efficiency of composites manufacturing as it reduces the molding time required

Study of the light-induced metal-insulator transition in SrTiO3 by photoresistance spectroscopy

Photoresistivity and its spectral response has been systematically studied in oxygen deficient SrTiO3 single crystals for a wide range of resistivities, ρ, and carrier densities, n. At roomtemperature we have found a persistent photoresistance that gradually decreases as ρ is diminished or n is increased in addition to relaxation times of seconds to a few minutes suggesting that trapping of carriers is playing a major role. An analysis of the photoresistance excitation spectra shows two distinctive features that are related to the indirect gap of SrTiO3 at (3.25 ± 0.04) eV and to a direct transition at (3.40 ± 0.03) eV. The photoresistive crystals present a temperature dependent resisitivity under illumination that experiences a metal-insulator transition below T ∼ 85 K. Lowtemperature photoresistance spectrum reveals as a suitable technique to understand the origin of this transition, pointing to an enhanced efficiency of the ∼ 3.25 eV gap to promote electrons to the bottom of the conduction band.Fil: Bridoux, German. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Villafuerte, Manuel Jose. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferreyra, J. M.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; ArgentinaFil: Bachi, N.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; ArgentinaFil: Figueroa, C. A.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; ArgentinaFil: Heluani, S. P.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Física del Solido; Argentin

Nidificación y pernocte social del Carpinterito Cuello Canela (Picumnus temminckii) y Carpinterito Común (Picumnus cirratus), e implicaciones para la evolución de la biología reproductiva de los pájaros carpinteros (Picidae)

To understand the evolution of reproductive strategies and social behavior in woodpeckers(Picidae), it is useful to compare breeding biology between the two largest subfamilies: Picinae (truewoodpeckers) and Picumninae (piculets). The piculets include four species in the Old World (Sasia, Verreauxia,and Picumnus spp.) and a recent radiation of 25 Picumnus spp. in the Neotropics; however,information about their breeding biology is limited. We studied four nests and one roost of the Ochre-collaredPiculet (Picumnus temminckii) in the Atlantic Forest of Misiones and eight nests of the White-barredPiculet (Picumnus cirratus) in the Chaco region, of Argentina, and reviewed the published literature onother species of Picumnus. Cavities were excavated in dead branches and tree trunks. Entrance diameterswere 2.2 ± 0.2 cm (mean ± SE) for the Ochre-collared Piculet and 2.5 ± 0.1 cm for the White-barredPiculet. In both species, both parents excavated cavities, incubated eggs, fed nestlings, and maintainedthe cavity clean of feces. In the Ochre-collared Piculet, incubation lasted 13 days, on-bouts were 42 ± 4(± SE) min for females and 48 ± 7 min for males, and nest attentiveness was nearly 100% during incubationand the first 10 days after hatching. Nestling Ochre-collared Piculets hatched without feathers, theireyes and pin feathers opened on day 13, and they fledged on days 26 and 27. Nestlings of both specieswere fed ant larvae and other small prey. In Ochre-collared Piculets, the rate of food delivery (especiallyby the female) increased with nestling age. Females removed 71% and males 29% of fecal sacs. FledglingPicumnus have dark crowns and look like adult females, which is different from Sasia, Verreauxia,and most Picinae. Unlike Picinae, Picumnus parents roost together in their nest cavity before laying,throughout nesting, and (accompanied by their offspring) after fledging. They also roost in pairs or groupswhen not breeding. If Old World piculets also roost socially, this trait may reflect an ancestral condition ofthe woodpeckers.Para entender la evolución de las estrategias reproductivas y del comportamiento social en los pájaros carpinteros (Picidae), es útil comparar la biología reproductiva entre las dos mayores subfamilias: Picinae (verdaderos pájaros carpinteros) y Picumninae (carpinteritos). Picumninae incluye cuatro especies del viejo mundo (Sasia, Verreauxia, y Picumnus spp.) y una radiación reciente de 25 especies de Picumnus en el Neotrópico; sin embargo, es limitada la información sobre su biología reproductiva. Estudiamos cuatro nidos y un pernocte de Carpinterito Cuello Canela (Picumnus temminckii) en la Selva Atlántica y ocho nidos de Carpinterito Común (Picumnus cirratus) en la región Chaqueña, de Argentina, y revisamos la literatura publicada sobre otras especies de Picumnus. Las cavidades fueron excavadas en ramas y troncos secos de árboles. El diámetro de su entrada era 2,2 ± 0,2 cm (media ± EE) para el Carpinterito Cuello Canela y 2,5 ± 0,1 cm para el Carpinterito Común. En ambas especies, macho y hembra excavaron las cavidades, incubaron los huevos, alimentaron los pichones y mantuvieron la cavidad limpia de heces. En el Carpinterito Cuello Canela, el período de incubación duró 13 días, los turnos de incubación duraron 42 ± 4 min (± EE) para hembras y 48 ± 7 min para machos, y la atención en el nido fue casi 100% durante la incubación y los primeros 10 días después del nacimiento de los pichones. Los pichones de Carpinterito Cuello Canela nacieron sin plumas; sus ojos y los canutos en las alas abrieron el día 13, y volaron los días 26 y 27. Los pichones de ambas especies fueron alimentados con larvas de hormigas y otras presas pequeñas. En el Carpinterito Cuello Canela, la tasa de entrega de alimentos (especialmente por la hembra) aumentó con la edad de los pichones. Las hembras extrajeron el 71% de los sacos fecales y los machos 29%. Los volantones de Picumnus tienen corona oscura y se parecen a las hembras adultas, lo que los diferencia de Sasia, Verreauxia, y la mayoría de los Picinae. A diferencia de los Picinae, los padres de Picumnus duermen juntos en su cavidad nido antes de la puesta, a lo largo de la anidación, y (acompañados de sus crías) después de que vuelan los pichones. También pernoctan en parejas o grupos cuando no están criando. Si los carpinteritos del viejo mundo también pernoctan en grupos, el rasgo puede reflejar una condición ancestral de los pájaros carpinteros.Fil: Bodrati, Alejandro. Proyecto Selva de Pino Paraná; ArgentinaFil: Cockle, Kristina Louise. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina. Proyecto Selva de Pino Paraná; Argentina. LSU AgCenter; Estados Unidos. University of British Columbia; CanadáFil: Di Sallo, Facundo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentina. Proyecto Selva de Pino Paraná; ArgentinaFil: Ferreyra, Carlos. Proyecto Selva de Pino Paraná; ArgentinaFil: Salvador, Sergio A.. No especifíca;Fil: Lammertink, J. Martjan. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina. Proyecto Selva de Pino Paraná; Argentina. Cornell University; Estados Unido

Carbon Monoxide Blocks Lipopolysaccharide-Induced Gene Expression by Interfering with Proximal TLR4 to NF-κB Signal Transduction in Human Monocytes

Carbon monoxide (CO) is an endogenous messenger that suppresses inflammation, modulates apoptosis and promotes vascular remodeling. Here, microarrays were employed to globally characterize the CO (250 ppm) suppression of early (1 h) LPS-induced inflammation in human monocytic THP-1 cells. CO suppressed 79 of 101 immediate-early genes induced by LPS; 19% (15/79) were transcription factors and most others were cytokines, chemokines and immune response genes. The prototypic effects of CO on transcription and protein production occurred early but decreased rapidly. CO activated p38 MAPK, ERK1/2 and Akt and caused an early and transitory delay in LPS-induced JNK activation. However, selective inhibitors of these kinases failed to block CO suppression of LPS-induced IL-1β, an inflammation marker. Of CO-suppressed genes, 81% (64/79) were found to have promoters with putative NF-κB binding sites. CO was subsequently shown to block LPS-induced phosphorylation and degradation of IκBα in human monocytes, thereby inhibiting NF-κB signal transduction. CO broadly suppresses the initial inflammatory response of human monocytes to LPS by reshaping proximal events in TLR4 signal transduction such as stress kinase responses and early NF-κB activation. These rapid, but transient effects of CO may have therapeutic applications in acute pulmonary and vascular injury

Spectral properties of a short-range impurity in a quantum dot

The spectral properties of the quantum mechanical system consisting of a quantum dot with a short-range attractive impurity inside the dot are investigated in the zero-range limit. The Green function of the system is obtained in an explicit form. In the case of a spherically symmetric quantum dot, the dependence of the spectrum on the impurity position and the strength of the impurity potential is analyzed in detail. It is proven that the confinement potential of the dot can be recovered from the spectroscopy data. The consequences of the hidden symmetry breaking by the impurity are considered. The effect of the positional disorder is studied.Comment: 30 pages, 6 figures, Late