Termination of the Phase of Quintessence by Gravitational Back-Reaction

We study the effects of gravitational back-reaction in models of Quintessence. The effective energy-momentum tensor with which cosmological fluctuations back-react on the background metric will in some cases lead to a termination of the phase of acceleration. The fluctuations we make use of are the perturbations in our present Universe. Their amplitude is normalized by recent measurements of anisotropies in the cosmic microwave background, their slope is taken to be either scale-invariant, or characterized by a slightly blue tilt. In the latter case, we find that the back-reaction effect of fluctuations whose present wavelength is smaller than the Hubble radius but which are stretched beyond the Hubble radius by the accelerated expansion during the era of Quintessence domination can become large. Since the back-reaction effects of these modes oppose the acceleration, back-reaction will lead to a truncation of the period of Quintessence domination. This result impacts on the recent discussions of the potential incompatibility between string theory and Quintessence.Comment: 7 pages a few clarifying comments adde

Partially premixed flame reactive flow characterization in a bluff body burner

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The present work aims the characterization of a natural gas/air partially premixed flame (PPF) reactive flow in a bluff body burner under laminar conditions in equivalence ratio of 2.1, 1.7 and 1.2. The laboratorial bluff body burner is composed of a central outflow for the premixed reactants and an annular air flow. The latter allows for the stabilization of the flame meanwhile it prevents external aerodynamic influence on the behavior of the flame. For the velocity field measurements, a 2-D Particle Image Velocimetry, PIV, optical diagnostic system is employed. The PIV system comprises of two Nd:YAG lasers with an output wavelength of 532 nm. Titanium dioxide particles, TiO2, are used as seeding particles in the premixed flow. The displacement of the seeding particles between two laser pulses with a known short time difference allows a planar velocity field determination. The stored images are processed using a software integrated with the system in order to obtain the medium velocity field. The software uses statistic data to obtain the correlation between two images acquired in an interval of time of an overlapped interrogation window. The major objective of this study is to examine the flame velocity field of laminar partially premixed natural gas and air flames in rich conditions. Three premixed flames under rich conditions have been studied in the present work with equivalence ratios of 2.1, 1.7 and 1.2 respectively. The study focused on: (1) analyze the instantaneous velocity flow field of the three partially premixed flames, (2) analyze the mean velocity flow field formed from the instantaneous flow fields and (3) analyze the velocity behavior along the center line of the flame.cf201

Isolation and characterization of new genetic types of Toxoplasma gondii and prevalence of Trichinella murrelli from black bear (Ursus americanus)

Black bears (Ursus americanus) are hosts for two important zoonotic parasites, Toxoplasma gondii and Trichinella spp. and bears are hunted for human consumption in the USA. Little is known of the genetic diversity of T. gondii circulating in wildlife. In the present study, antibodies to T. gondii were found in juice from tongues of 17 (25.7%) of 66 wild black bear from Maryland during the hunting season of 2010 and 2011. Antibodies to T. gondii were assessed by the modified agglutination test. Tongues of 17 seropositive bears were bioassayed in mice and viable T. gondii was isolated from three samples. These three T. gondii isolates (TgBbMd1-3) were further propagated in cell culture and DNA isolated from culture-derived tachyzoites was characterized using 11 PCR-RFLP markers (SAG1, 5′ - and 3′ -SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico). Results revealed three genotypes. TgBbMd1 is a Type 12 strain (ToxoDB PCR-RFLP genotype #4) and TgBbMd2 is ToxoDB PCR- RFLP genotype #216, and TgBbMd3 is a Type II clonal strain (ToxoDB PCR-RFLP genotype #1). The isolate TgBbMd2 was highly virulent for outbred Swiss Webster mice; all infected mice died of acute toxoplasmosis. Results indicate that mouse virulent strains of T. gondii are circulating in wildlife in the USA. These 66 tongues in addition to tongues collected during hunts in previous years were further investigated for the presence of muscle larvae of Trichinella spp. Tongues from 40 bears in 2005, 41 in 2006, 51 in 2007, 56 in 2008, 68 in 2009, 67 in 2010, and 66 in 2011 were subjected to digestion with pepsin/HCl and microscopic examination. Two bears were infected with Trichinella spp.; one in 2008 and one in 2009. Genotyping of collected muscle larvae revealed that the infecting species in both cases was Trichinella murrelli

Comparação Da Qualidade Nutricional Das Refeições Antes E Depois Do Plano Nacional De Assistência Estudantil No Rj, Brasil

The Brazilian National Plan for Student Assistance (NPSA) aims at improving overall academic performance of undergraduate student. It is important to identify whether the investment in food assistance had a positive impact on the nutritional quality of meals. Aims: To compare the nutritional quality of meals in a university restaurant (UR) before and after the restructure by NPSA. Methods: The portioning of meals at lunch as served to students was registered in 2011 (Phase I) and 2013 (Phase II) for determination of percent carbohydrates, proteins and lipids, as well as the total energy value (TEV), cholesterol, sodium, and fruits and vegetables (FV). The meal quality index (MQI) was estimated from those observations at both phases. Portioning of meals and MQI were compared between phases, and according to current recommendations. Results: Significant lower values of TEV, lipid, cholesterol and sodium were observed at Phase II (p<0.001 all comparisons). Conversely, significant higher values of proteins and FV were observed at Phase II (p<0.001 both comparisons). The number of meals within the recommended MQI was significantly higher (p<0.001) at Phase II (73.1%) than Phase I (47.7%), whereas the proportion of meals with proteins, FV, cholesterol and sodium was significantly higher (p<0.001). Conclusions: Nutritional quality of meals at an UR improved after the implementation of the NPSA. Nonetheless, serving standard meals is strongly recommended, mainly regarding salt intake. Finally, these data highlight the need for educational actions with undergraduate students aiming to reduce salt intake and proper portioning of the meal. © Copyright 2012. Fundación Alimentación Saludable.362748

Perturbation evolution with a non-minimally coupled scalar field

We recently proposed a simple dilaton-derived quintessence model in which the scalar field was non-minimally coupled to cold dark matter, but not to `visible' matter. Such couplings can be attributed to the dilaton in the low energy limit of string theory, beyond tree level. In this paper we discuss the implications of such a model on structure formation, looking at its impact on matter perturbations and CMB anisotropies. We find that the model only deviates from $\Lambda$CDM and minimally coupled theories at late times, and is well fitted to current observational data. The signature left by the coupling, when it breaks degeneracy at late times, presents a valuable opportunity to constrain non-minimal couplings given the wealth of new observational data promised in the near future.Comment: Version appearing in Physical Review D. 10 pages, 9 figs. Comparison with SN1a and projected MAP results, and appendix adde

Evidence for geometry-dependent universal fluctuations of the Kardar-Parisi-Zhang interfaces in liquid-crystal turbulence

We provide a comprehensive report on scale-invariant fluctuations of growing interfaces in liquid-crystal turbulence, for which we recently found evidence that they belong to the Kardar-Parisi-Zhang (KPZ) universality class for 1+1 dimensions [Phys. Rev. Lett. 104, 230601 (2010); Sci. Rep. 1, 34 (2011)]. Here we investigate both circular and flat interfaces and report their statistics in detail. First we demonstrate that their fluctuations show not only the KPZ scaling exponents but beyond: they asymptotically share even the precise forms of the distribution function and the spatial correlation function in common with solvable models of the KPZ class, demonstrating also an intimate relation to random matrix theory. We then determine other statistical properties for which no exact theoretical predictions were made, in particular the temporal correlation function and the persistence probabilities. Experimental results on finite-time effects and extreme-value statistics are also presented. Throughout the paper, emphasis is put on how the universal statistical properties depend on the global geometry of the interfaces, i.e., whether the interfaces are circular or flat. We thereby corroborate the powerful yet geometry-dependent universality of the KPZ class, which governs growing interfaces driven out of equilibrium.Comment: 31 pages, 21 figures, 1 table; references updated (v2,v3); Fig.19 updated & minor changes in text (v3); final version (v4); J. Stat. Phys. Online First (2012

Distribution of black flies (Diptera: Simuliidae) in the State of Espírito Santo, Brazil

Entre os anos de 2004 e 2008 foram realizadas coletas de Simuliidae em várias localidades no Estado do Espírito Santo, Brasil. No total, 66 córregos e rios das doze principais bacias hidrográficas do estado foram amostrados. Dezessete espécies foram coletadas, sendo que nove delas representam ocorrências novas para o estado (Simulium pertinax, S. jujuyense, S. rubrithorax, S. subnigrum, S. travassosi, S. spinibranchium, S. hirtipupa, S. lutzianum e S. anamariae), duplicando o número de espécies conhecidas no estado.We conducted a freshwater survey from 2004 to 2008 in several localities of Espírito Santo, Brazil. In total, 66 streams and rivers were sampled in the 12 hydrographic basins of the state. We collected and identified 17 species of which nine represent new records (Simulium pertinax, S. jujuyense, S. rubrithorax, S. subnigrum, S. travassosi, S. spinibranchium, S. hirtipupa, S. lutzianum e S. anamariae). These findings doubled the number of records of black fly species to the State of Espírito Santo, Brazil