Bead, Hoop, and Spring as a Classical Spontaneous Symmetry Breaking Problem

We describe a simple mechanical system that involves Spontaneous Symmetry Breaking. The system consists of two beads constrained to slide along a hoop and attached each other through a spring. When the hoop rotates about a fixed axis, the spring-beads system will change its equilibrium position as a function of the angular velocity. The system shows two different regions of symmetry separated by a critical point analogous to a second order transition. The competitive balance between the rotational diynamics and the interaction of the spring causes an Spontaneous Symmetry Breaking just as the balance between temperature and the spin interaction causes a transition in a ferromagnetic system. In addition, the gravitational potential act as an external force that causes explicit symmetry breaking and a feature of first-order transition. Near the transition point, the system exhibits a universal critical behavior where the changes of the parameter of order is described by the critical exponent beta =1/2 and the susceptibility by gamma =1. We also found a chaotic behavior near the critical point. Through a demostrative device we perform some qualitative observations that describe important features of the system.Comment: 7 pages, 2 tables, 30 figures, LaTeX2

DRYMONIA SQUAMOSA (GESNERIACEAE), A NEW SPECIES FROM LAS ORQUÍDEAS NATIONAL NATURAL PARK (ANTIOQUIA, COLOMBIA)

A new species of Drymonia (Gesneriaceae) from the Cordillera Occidental of the Colombian Andes in the department of Antioquia is described and illustrated. The new species, Drymonia squamosa, is distinguished by dense clusters of scales on the petioles, glabrate leaf blades with minute punctations on the lower surface, calyx appearing swollen at base with lanceolate lobes, corolla villous to lanate, and style with glandular trichomes. Additionally, D. squamosa is categorized as vulnerable (VU) based on the IUCN criteria

The q\textit{q}-metric naked singularity: A viable explanation for the nature of the central object in the Milky Way

In this work, we investigate whether the compact object at the center of the Milky Way is a naked singularity described by the $\textit{q}$-metric spacetime. Our fitting of the astrometric and spectroscopic data for the S2 star implies that similarly to the Schwarzschild black hole, the $\textit{q}$-metric naked singularity offers a satisfactory fit to the observed measurements. Additionally, it is shown that the shadow produced by the naked singularity is consistent with the shadow observed by the Event Horizon Telescope collaboration for Sgr-A*. It is worth mentioning that the spatial distribution of the S-stars favors the notion that the compact object at the center of our Galaxy can be described by an almost static spacetime. Based on these findings, the $\textit{q}$-metric naked singularity turns up as a compelling candidate for further investigation.Comment: Accepted for publication in Classical and Quantum Gravit

Biological reactor retrofitting using CFD-ASM modelling

In recent years, the interest in modelling activated sludge (AS) systems by means of Computational Fluid Dynamics (CFD) techniques has significantly increased. This work shows a successful case study combining CFD hydrodynamics and biokinetic modelling. The hydrodynamics is analysed by using the Reynolds-averaged Navier-Stokes equation for incompressible non-Newtonian fluids and SST turbulence model. Biokinetics has been included in the CFD as transport equations with source and sink terms defined by the Activated Sludge Model n degrees 1 (ASM1). Furthermore, a strategy for reducing the computational cost while maintaining accuracy of the results of these calculations has been proposed. This strategy is based on a two-step solver configuration and the definition of a variable timestep scheme. The resulting CFD-ASM approach permits a proper evaluation of denitrification in the anoxic tanks as well as the reproduction of nitrate and readily biodegradable substrate distributions. To demonstrate the strength of the proposed CFD-ASM, it has been used to evaluate the operation of a full-scale AS system and optimize its performance through changes in the biological reactor anoxic zone. The original configuration has been retrofitted and modified after detecting intrinsic defects in the fluid behaviour within the tank. This study has been assessed by analysing hydrodynamics in detail and validating the simulation results with tracer tests and flow velocity measurements. Substantial variations on the Residence Time Distribution have been confirmed when modifying the internal elements of the tank configuration: the wall-bushing and the stirrer positioning. As a result of this work, an influential short circuiting was corrected improving hydrodynamics and increasing mean residence time, all favouring denitrification efficiency. Outcomes of this study show the benefit of CFD when applied to AS tanks

Economic burden of air pollution in Colombia

To estimate indirect costs related to the loss of productivity due to premature mortality associated with air quality risk factors in Colombia, 2016. We estimated potential productivity years of life lost (PPYLL) related to indoor (biomass fuels) and outdoor pollution (PM2.5 and ozone). We analyzed deaths records of the Departamento Administrativo Nacional de Estadística, 2016, with the following basic causes of death related to air quality risk factors: isquemic hearth disease (IHD), cardiovascular disease (CD), lower respiratory tract infections (LRTI), lung cancer (LC) and chronic obstructive pulmonary disease(COPD), according to ICD-10. PPYLL were valued considering the productive age in Colombia, which ranges from 18-57 years for women and up to 62 for men. Three scenarios were built: lower loss (minimum legal wage), average loss [one per capita gross domestic product (GDPpc)] and higher loss (three GDPpc). PPYLL for the mentioned causes were multiplied by the fraction attributable to each air risk factor. The latest were estimated from IDEAM (outdoor) and the survey of Quality of Life 2016 and systematic reviews (indoor pollution). Costs were reported in American dollars, using the December 31 (2016) exchange rate: 1USD=3,000.7 Colombian Pesos. The economic burden due to premature deaths caused by the analyzed diseases was US$845,967,999 ($444,320,058-$2,537,903,997). From this burden, 17.8$150,585,143 ($79,090,461-451,755,428). Regarding to the studied diseases, IHD deaths caused by air quality risk factors accounted US$83.007.582. The second with the highest economic burden attributable to air quality risk factors was CD (US$32,750,315), followed by LRTI (US$22,077,091), LC (US$6,909,659) and COPD (US$5,840,495). The exposure to PM2.5 particulate matter represented the largest share of the economic burden attributable to air quality risk factors. Our estimations suggest that premature deaths caused by exposure to air qualityrisk factors represented 0.052% of GDP for 2016

Reliable resolution of ambiguous hepatitis C virus genotype 1 results with the Abbott HCV Genotype Plus RUO assay

Hepatitis C; Genotype; Abbott HCVHepatitis C; Genotip; Abbott HCVHepatitis C; Genotipo; Abbott HCVAccurate subtyping of hepatitis C virus genotype 1 (HCV-1) remains clinically and epidemiologically relevant. The Abbott HCV Genotype Plus RUO (GT Plus) assay, targeting the core region, was evaluated as a reflex test to resolve ambiguous HCV-1 results in a challenging sample collection. 198 HCV-1 specimens were analysed with GT Plus (38 specimens with and 160 without subtype assigned by the Abbott RealTime Genotype II (GT II) assay targeting the 5'NC and NS5B regions). Sanger sequencing of the core and/or NS5B regions were performed in 127 specimens without subtype assignment by GT II, with "not detected" results by GT Plus, or with mixed genotypes/subtypes. The remaining GT Plus results were compared to LiPA 2.0 (n = 45) or just to GT II results if concordant (n = 26). GT Plus successfully assigned the subtype in 142/160 (88.8%) samples. "Not detected" results indicated other HCV-1 subtypes/genotypes or mismatches in the core region in subtype 1b. The subtyping concordance between GT Plus and either sequencing or LiPA was 98.6% (140/142). Therefore, combined use of GT II and GT Plus assays represents a reliable and simple approach which considerably reduced the number of ambiguous HCV-1 results and enabled a successful subtyping of 98.9% of all HCV-1 samples

Rapid within- and transgenerational changes in thermal tolerance and fitness in variable thermal landscapes

Phenotypic plasticity may increase the performance and fitness and allow organisms to cope with variable environmental conditions. We studied within-generation plasticity and transgenerational effects of thermal conditions on temperature tolerance and demographic parameters in Drosophila melanogaster. We employed a fully factorial design, in which both parental (P) and offspring generations (F1) were reared in a constant or a variable thermal environment. Thermal variability during ontogeny increased heat tolerance in P, but with demographic cost as this treatment resulted in substantially lower survival, fecundity, and net reproductive rate. The adverse effects of thermal variability (V) on demographic parameters were less drastic in flies from the F1, which exhibited higher net reproductive rates than their parents. These compensatory responses could not totally overcome the challenges of the thermally variable regime, contrasting with the offspring of flies raised in a constant temperature (C) that showed no reduction in fitness with thermal variation. Thus, the parental thermal environment had effects on thermal tolerance and demographic parameters in fruit fly. These results demonstrate how transgenerational effects of environmental conditions on heat tolerance, as well as their potential costs on other fitness components, can have a major impact on populations’ resilience to warming temperatures and more frequent thermal extremes