Soft trade-offs and the stochastic emergence of diversification in E. coli evolution experiments

Laboratory experiments of bacterial colonies (e.g., \emph{Escherichia coli}) under well-controlled conditions often lead to evolutionary diversification in which (at least) two ecotypes, each one specialized in the consumption of a different set of metabolic resources, branch out from an initially monomorphic population. Empirical evidence suggests that, even under fixed and stable conditions, such an ``evolutionary branching'' occurs in a stochastic way, meaning that: (i) it is observed in a significant fraction, but not all, of the experimental repetitions, (ii) it may emerge at broadly diverse times, and (iii) the relative abundances of the resulting subpopulations are variable across experiments. Theoretical approaches shedding light on the possible emergence of evolutionary branching in this type of conditions have been previously developed within the theory of ``adaptive dynamics''. Such approaches are typically deterministic -- or incorporate at most demographic or finite-size fluctuations which become negligible for the extremely large populations of these experiments -- and, thus, do not permit to reproduce the empirically observed large degree of variability. Here, we make further progress and shed new light on the stochastic nature of evolutionary outcomes by introducing the idea of ``soft'' trade-offs (as opposed to ``hard'' ones). This introduces a natural new source of stochasticity which allows one to account for the empirically observed variability as well as to make predictions for the likelihood of evolutionary branching to be observed, thus helping to bridge the gap between theory and experiments

Tratamiento del Síndrome del Túnel Carpiano con la Técnica del Retinaculotomo de PAINE

Los autores han realizado un estudio con 36 casos intervenidos quirúrgicamente en el Servicio de Neurocirugía del Hospital General de Especialidades "Virgen de las Nieves" de Granada, tanto a corto como a largo plazo, empleando la técnica quirúrgica de PAINE, basada en el instrumento por él diseñado, el retinaculotomo. Realizan un estudio de los resultados obtenidos, siendo totalmente satisfactorios en el 74% de los casos. Finalmente exponen las ventajas de esta técnica quirúrgica, así como, la práctica ausencia de complicaciones.36 Patients with Carpal Tunnel Syndrome are colected. All of them -were operated on by PAINE's Technique and Procedur e (Retinaculotome). The authors made a study of the results obtained, 74% of good results. Finally, they explain the advantage s of this surgical procedure, as well as, absence of complications

On First-Passage Times and Sojourn Times in Finite QBD Processes and Their Applications in Epidemics

In this paper, we revisit level-dependent quasi-birth-death processes with finitely many possible values of the level and phase variables by complementing the work of Gaver, Jacobs, and Latouche (Adv. Appl. Probab. 1984), where the emphasis is upon obtaining numerical methods for evaluating stationary probabilities and moments of first-passage times to higher and lower levels. We provide a matrix-analytic scheme for numerically computing hitting probabilities, the number of upcrossings, sojourn time analysis, and the random area under the level trajectory. Our algorithmic solution is inspired from Gaussian elimination, which is applicable in all our descriptors since the underlying rate matrices have a block-structured form. Using the results obtained, numerical examples are given in the context of varicella-zoster virus infections

Perturbation analysis in finite LD‐QBD processes and applications to epidemic models

In this paper, our interest is in the perturbation analysis of level‐dependent quasi‐birth‐and‐death (LD‐QBD) processes, which constitute a wide class of structured Markov chains. An LD‐QBD process has the special feature that its space of states can be structured by levels (groups of states), so that a tridiagonal‐by‐blocks structure is obtained for its infinitesimal generator. For these processes, a number of algorithmic procedures exist in the literature in order to compute several performance measures while exploiting the underlying matrix structure; among others, these measures are related to first‐passage times to a certain level L(0) and hitting probabilities at this level, the maximum level visited by the process before reaching states of level L(0), and the stationary distribution. For the case of a finite number of states, our aim here is to develop analogous algorithms to the ones analyzing these measures, for their perturbation analysis. This approach uses matrix calculus and exploits the specific structure of the infinitesimal generator, which allows us to obtain additional information during the perturbation analysis of the LD‐QBD process by dealing with specific matrices carrying probabilistic insights of the dynamics of the process. We illustrate the approach by means of applying multitype versions of the susceptible‐infective (SI) and susceptible‐infective‐susceptible (SIS) epidemic models to the spread of antibiotic‐sensitive and antibiotic‐resistant bacterial strains in a hospital ward

A Markov chain model to investigate the spread of antibiotic-resistant bacteria in hospitals

Ordinary differential equation (ODE) models used in mathematical epidemiology assume explicitly or implicitly large populations. For the study of infections in a hospital this is an extremely restrictive assumption as typically a hospital ward has a few dozen, or even fewer, patients. This work reframes a well-known model used in the study of the spread of antibiotic-resistant bacteria in hospitals, to consider the pathogen transmission dynamics in small populations. In this vein, this paper proposes a Markov chain model to describe the spread of a single bacterial species in a hospital ward where patients may be free of bacteria or may carry bacterial strains that are either sensitive or resistant to antimicrobial agents. We determine the probability law of the \emph{exact} reproduction number ${\cal R}_{exact,0}$, which is here defined as the random number of secondary infections generated by those patients who are accommodated in a predetermined bed before a patient who is free of bacteria is accommodated in this bed for the first time. Specifically, we decompose the exact reproduction number ${\cal R}_{exact,0}$ into two contributions allowing us to distinguish between infections due to the sensitive and the resistant bacterial strains. Our methodology is mainly based on structured Markov chains and the use of related matrix-analytic methods. This guarantees the compatibility of the new, finite-population model, with large population models present in the literature and takes full advantage, in its mathematical analysis, of the intrinsic stochasticity.Comment: 30 pages, 9 figure

Female brain size affects the assessment of male attractiveness during mate choice

Mate choice decisions are central in sexual selection theory aimed to understand how sexual traits evolve and their role in evolutionary diversification. We test the hypothesis that brain size and cognitive ability are important for accurate assessment of partner quality and that variation in brain size and cognitive ability underlies variation in mate choice. We compared sexual preference in guppy female lines selected for divergence in relative brain size, which we have previously shown to have substantial differences in cognitive ability. In a dichotomous choice test, large-brained and wild-type females showed strong preference for males with color traits that predict attractiveness in this species. In contrast, small-brained females showed no preference for males with these traits. In-depth analysis of optomotor response to color cues and gene expression of key opsins in the eye revealed that the observed differences were not due to differences in visual perception of color, indicating that differences in the ability to process indicators of attractiveness are responsible. We thus provide the first experimental support that individual variation in brain size affects mate choice decisions and conclude that differences in cognitive ability may be an important underlying mechanism behind variation in female mate choice

Preparation of Palladium-Supported Periodic Mesoporous Organosilicas and their Use as Catalysts in the Suzuki Cross-Coupling Reaction

Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt%) were prepared by the incipient wetness method and subsequently reduced in an H2 stream at 200 °C. Both hydrogen chemisorption and temperature programmed reduction experiments revealed significant differences depending on the support. Pd2+ species were more reducible on the mesoporous organosilicas than on their silica counterpart. Also, remarkable differences on the particle morphology were observed by transmission electron microscopy. All Pd-supported samples were active in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic aci

Lifetime and reproduction of a marked individual in a two-species competition process

The interest is in a stochastic model for the competition of two species, which was first introduced by Reuter [18] and Iglehart [11], and then analyzed by Ridler-Rowe [19]. The model is related to the two-species autonomous competitive model (Zeeman [24]), where individuals compete either directly or indirectly for a limited food supply and, consequently, birth and death rates depend on the population size of one or both of the species. The aim is to complement the treatment of the model we started in [8,9] by focusing here on probabilistic descriptors that are inherently linked to an individual: its residual lifetime and the number of direct descendants. We present an approximating model based on the maximum size distribution, and we discuss on various models defined in terms of the underlying killing and reproductive strategies. Numerical examples are presented to show the effects of the killing and reproductive strategies on the behavior of an individual, and how the impact of these strategies on the descriptors vanishes in highly competitive ecosystems

Comparison of an exercise program with and without manual therapy for patients with chronic neck pain and upper cervical rotation restriction. Randomized controlled trial

Background: Cervical exercise has been shown to be an effective treatment for neck pain, but there is still a need for more clinical trials evaluating the effectiveness of adding manual therapy to the exercise approach. There is a lack of evidence on the effect of these techniques in patients with neck pain and upper cervical rotation restriction. Purpose: To compare the effectiveness of adding manual therapy to a cervical exercise protocol for the treatment of patients with chronic neck pain and upper cervical rotation restriction. Methods: Single-blind randomized clinical trial. Fifty-eight subjects: 29 for the Manual Therapy+Exercise (MT+Exercise) Group and 29 for the Exercise group. Neck disability index, pain intensity (0-10), pressure pain threshold (kPa), flexion-rotation test (°), and cervical range of motion (°) were measured at the beginning and at the end of the intervention, and at 3-and 6-month follow-ups. The MT+Exercise Group received one 20-min session of manual therapy and exercise once a week for 4 weeks and home exercise. The Exercise Group received one 20-min session of exercise once a week for 4 weeks and home exercise. Results: The MT+Exercise Group showed significant better values post-intervention in all variables: neck disability index: 0% patient with moderate, severe, or complete disability compared to 31% in the Exercise Group (p = 0.000) at 6-months; flexion-rotation test (p = 0.000) and pain intensity (p = 0.000) from the first follow-up to the end of the study; cervical flexion (p = 0.002), extension (p = 0.002), right lateral-flexion (p = 0.000), left lateral-flexion (p = 0.001), right rotation (p = 0.000) and left rotation (p = 0.005) at 6-months of the study, except for flexion, with significative changes from 3-months of follow up; pressure pain threshold from the first follow-up to the end of the study (p values range: 0.003-0.000). Conclusion: Four 20-min sessions of manual therapy and exercise, along with a home-exercise program, was found to be more effective than an exercise protocol and a home-exercise program in improving the neck disability index, flexion-rotation test, pain intensity, and pressure pain threshold, in the short, medium, and medium-long term in patients with chronic neck pain and upper rotation restriction. Cervical range of motion improved with the addition of manual therapy in the medium and medium-long term. The high dropout rate may have compromised the external validity of the study. Copyright © 2021 Rodríguez-Sanz et al

Preparation of palladium-supported periodic mesoporous organosilicas and their use as catalysts in the Suzuki cross-coupling reaction

Three periodic mesoporous materials, i.e., two organosilicas with either ethylene or phenylene bridges and one silica, have been used as supports for Pd nanoparticles. All Pd-supported samples (1.0 wt%) were prepared by the incipient wetness method and subsequently reduced in an H2 stream at 200 °C. Both hydrogen chemisorption and temperature programmed reduction experiments revealed significant differences depending on the support. Pd2+ species were more reducible on the mesoporous organosilicas than on their silica counterpart. Also, remarkable differences on the particle morphology were observed by transmission electron microscopy. All Pd-supported samples were active in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic acid