Conspicuous plumage patches have evolved in birds as conspecific signals for mate attraction and assessment, intersexual competition or to signal alarm. Signals may alternatively be directed at potential predators to discourage pursuit. Rails (Family Rallidae) are ground-dwelling birds, many of which inhabit wetlands, while others occur in forests and grasslands. They are renown for their secretive nature and the tendency to flick their tails when observed. This behavior is more conspicuous in species with white undertail coverts that contrast sharply with darker body plumage. Using species comparisons and controlling for phylogeny, we investigated four hypotheses for the evolution of white undertail coverts in rails. We found little support for the hypothesis that white tails are sexually selected: white tails were not more common in species with polygamous as opposed to monogamous mating systems, species with sexual dimorphism, nor species that display their tails in courtship. Nor did our results support the hypothesis that white tail plumage evolved for intersexual competition during territorial interactions. Instead, we found that species that flock for at least part of the year and species found in open as opposed to concealing habitats were significantly more likely to have white undertail coverts. Rail species inhabiting concealing habitats are less commonly gregarious and more likely selected for crypsis. Using phylogenetically-controlled statistical inference we found that adaptation to open wetland habitats significantly precedes the evolution of white undertails, whereas gregariousness likely evolved later in some lineages. The inferred order of trait evolution suggests that this plumage characteristic could have been selected primarily for enhancement of an anti-predator signal rather than a social signal for conspecifics.

Multiple solutions arise when fitting complicated multi-step kinetic models to spectroscopic data. For consecutive reactions of the type A ! B ! C this well-known ambiguity is due to the presence of multiple equivalent global minima in the response surfaces associated with the non-linear least squares fitting of rate constants to spectroscopic data. Several methods have been described to overcome the ambiguity when fitting consecutive reactions with univariate data but few attempts to solve the problem have been described for multivariate data. Additionally, for complicated multistep reaction schemes there may be several local minima that make selection of the initial parameter guesses difficult. This paper reports a general approach to overcome these types of ambiguities in multivariate kinetic fitting methods using non-negativity constraints for the determination of the pure component spectra estimated during the model-fitting process. Under many conditions these constraints reduce or eliminate entirely the incorrect local minima. The effectiveness and reliability of the new constraints were tested with several simulated and real data sets.

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BackgroundHepatitis C virus (HCV) is an important cause of chronic hepatitis resulting in end stage liver disease and hepatocellular carcinoma. Direct acting antivirals (DAAs) interfere with the HCV lifecycle and result in high rates of sustained virologic response (SVR). We hypothesized that treatment with DAAs in a real world setting is as successful in HCV/HIV coinfected patients as it is in HCV monoinfected patients, and that some degree of fibrosis regression can be observed after completion of therapy in both groups.MethodsWe retrospectively reviewed data from patients who received treatment for HCV from 2014 to 2016 at the Infectious Diseases clinic and collected demographic characteristics, HCV genotype and viral load, DAA regimen, SVR rates, and whether or not fibrosis improved at 12 or 24 weeks after treatment completion defined as one METAVIR stage improvement in FibroSURE™ score to estimate fibrosis. In those with HIV, HIV viral load, CD4 count and HIV antiretroviral regimen were examined.ResultsOut of 41 patients in each group, 24 had completed therapy in the monoinfected group and 26 in the coinfected group. In the monoinfected group, 22 (92%) achieved SVR. In the coinfected group, 26 (100%) achieved SVR. The SVR rates of the monoinfected group and coinfected group did not differ significantly (P = .956). In the monoinfected group, 10/17 (59%) had an improvement in FibroSURE™ score, and 7/17 (41%) had no change. In the coinfected group, 2/9 (22.2%) patients demonstrated an improvement in FibroSURE™ score, 4/9 (44.4%) had no change, and 3/9 (33%) had an increase in FibroSURE™ score. There was no significant difference in the change in FibroSURE™ score before and after SVR between the two groups (P = .100).ConclusionIn this small study, although not statistically significant, coinfected patients treated with DAAs had higher SVR rates than monoinfected patients. Treatment failure in the monoinfected group was linked to nonadherence, whereas, success of the coinfected patients was likely related to engagement in routine HIV care. Although not statistically significant, there were more patients in the monoinfected group that had an improvement in FibroSURE™ score, however the small sample size precludes any definitive conclusions.Disclosures P. P. Cook, Merck: Speaker’s Bureau, Grant recipient; Pfizer: Shareholder, Grant recipient; Gilead: Clinical Trials, Grant recipient; D. Siraj, Gilead: Speaker’s Bureau, Grant recipient