Tracking bifurcating solutions of a model biological pattern generator

We study heterogeneous steady-state solutions of a cell-chemotaxis model for generating biological spatial patterns in two-dimensional domains with zero flux boundary conditions. We use the finite-element package ENTWIFE to investigate bifurcation from the uniform solution as the chemotactic parameter varies and as the domain scale and geometry change. We show that this simple cell-chemotaxis model can produce a remarkably wide and surprising range of complex spatial patterns

The Quantum Group Structure of 2D Gravity and Minimal Models II: The Genus-Zero Chiral Bootstrap

The F and B matrices associated with Virasoro null vectors are derived in closed form by making use of the operator-approach suggested by the Liouville theory, where the quantum-group symmetry is explicit. It is found that the entries of the fusing and braiding matrices are not simply equal to quantum-group symbols, but involve additional coupling constants whose derivation is one aim of the present work. Our explicit formulae are new, to our knowledge, in spite of the numerous studies of this problem. The relationship between the quantum-group-invariant (of IRF type) and quantum-group-covariant (of vertex type) chiral operator-algebras is fully clarified, and connected with the transition to the shadow world for quantum-group symbols. The corresponding 3-j-symbol dressing is shown to reduce to the simpler transformation of Babelon and one of the author (J.-L. G.) in a suitable infinite limit defined by analytic continuation. The above two types of operators are found to coincide when applied to states with Liouville momenta going to $\infty$ in a suitable way. The introduction of quantum-group-covariant operators in the three dimensional picture gives a generalisation of the quantum-group version of discrete three-dimensional gravity that includes tetrahedra associated with 3-j symbols and universal R-matrix elements. Altogether the present work gives the concrete realization of Moore and Seiberg's scheme that describes the chiral operator-algebra of two-dimensional gravity and minimal models.Comment: 56 pages, 22 figures. Technical problem only, due to the use of an old version of uuencode that produces blank characters some times suppressed by the mailer. Same content

Strong lens search in the ESO public Survey KiDS

We have started a systematic search of strong lens candidates in the ESO public survey KiDS based on the visual inspection of massive galaxies in the redshift range $0.1<z<0.5$. As a pilot program we have inspected 100 sq. deg., which overlap with SDSS and where there are known lenses to use as a control sample. Taking advantage of the superb image quality of VST/OmegaCAM, the colour information and accurate model subtracted images, we have found 18 new lens candidates, for which spectroscopic confirmation will be needed to confirm their lensing nature and study the mass profile of the lensing galaxies.Comment: 4 pages, 1 figure, to appear on the refereed Proceeding of the "The Universe of Digital Sky Surveys" conference held at the INAF--OAC, Naples, on 25th-28th november 2014, to be published on Astrophysics and Space Science Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic

Saturn's icy satellites and rings investigated by Cassini - VIMS. III. Radial compositional variability

In the last few years Cassini-VIMS, the Visible and Infared Mapping Spectrometer, returned to us a comprehensive view of the Saturn's icy satellites and rings. After having analyzed the satellites' spectral properties (Filacchione et al. (2007a)) and their distribution across the satellites' hemispheres (Filacchione et al. (2010)), we proceed in this paper to investigate the radial variability of icy satellites (principal and minor) and main rings average spectral properties. This analysis is done by using 2,264 disk-integrated observations of the satellites and a 12x700 pixels-wide rings radial mosaic acquired with a spatial resolution of about 125 km/pixel. The comparative analysis of these data allows us to retrieve the amount of both water ice and red contaminant materials distributed across Saturn's system and the typical surface regolith grain sizes. These measurements highlight very striking differences in the population here analyzed, which vary from the almost uncontaminated and water ice-rich surfaces of Enceladus and Calypso to the metal/organic-rich and red surfaces of Iapetus' leading hemisphere and Phoebe. Rings spectra appear more red than the icy satellites in the visible range but show more intense 1.5-2.0 micron band depths. The correlations among spectral slopes, band depths, visual albedo and phase permit us to cluster the saturnian population in different spectral classes which are detected not only among the principal satellites and rings but among co-orbital minor moons as well. Finally, we have applied Hapke's theory to retrieve the best spectral fits to Saturn's inner regular satellites using the same methodology applied previously for Rhea data discussed in Ciarniello et al. (2011).Comment: 44 pages, 27 figures, 7 tables. Submitted to Icaru

Is It Rational to Assume that Infants Imitate Rationally? A Theoretical Analysis and Critique

It has been suggested that preverbal infants evaluate the efficiency of others' actions (by applying a principle of rational action) and that they imitate others' actions rationally. The present contribution presents a conceptual analysis of the claim that preverbal infants imitate rationally. It shows that this ability rests on at least three assumptions: that infants are able to perceive others' action capabilities, that infants reason about and conceptually represent their own bodies, and that infants are able to think counterfactually. It is argued that none of these three abilities is in place during infancy. Furthermore, it is shown that the idea of a principle of rational action suffers from two fallacies. As a consequence, is it suggested that it is not rational to assume that infants imitate rationally. Copyright (C) 2012 S. Karger AG, Base

Anal cancer incidence in men with HIV who have sex with men: are black men at higher risk?

Objective:To assess differences in anal cancer incidence between racial/ethnic groups among a clinical cohort of men with HIV who have sex with men.Design:Clinical cohort studyMethods:We studied men who have sex with men (MSM) in the Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) who initiated antiretroviral therapy (ART) under HIV care in CNICS. We compared anal cancer incidence between Black and non-Black men and calculated hazard ratios controlling for demographic characteristics (age, CNICS site, year of ART initiation), HIV disease indicators (nadir CD4+, peak HIV RNA), and co-infection/behavioral factors including hepatitis B virus (HBV), hepatitis C virus (HCV), tobacco smoking and alcohol abuse.Results:We studied 7473 MSM with HIV who contributed 41 810 person-years of follow-up after initiating ART between 1996 and 2014 in CNICS. Forty-one individuals had an incident diagnosis of anal cancer under observation. Crude rates of anal cancer were 204 versus 61 per 100 000 person-years among Black versus non-Black MSM. The weighted hazard ratio for anal cancer in Black MSM (adjusting for demographics, HIV disease factors, and co-infection/behavioral factors) was 2.37 (95% confidence interval: 1.17, 4.82) compared to non-Black MSM.Conclusions:In this large multicenter cohort, Black MSM were at significantly increased risk for anal cancer compared to non-Black MSM. Further detailed studies evaluating factors impacting anal cancer incidence and outcomes in Black men with HIV are necessary. Inclusion of more diverse study cohorts may elucidate modifiable factors associated with increased anal cancer risk experienced by Black MSM

Prevalence and Predictors of Substance Use Disorders Among HIV Care Enrollees in the United States

Prior efforts to estimate U.S. prevalence of substance use disorders (SUDs) in HIV care have been undermined by caveats common to single-site trials. The current work reports on a cohort of 10,652 HIV-positive adults linked to care at seven sites, with available patient data including geography, demography, and risk factor indices, and with substance-specific SUDs identified via self-report instruments with validated diagnostic thresholds. Generalized estimating equations also tested patient indices as SUD predictors. Findings were: (1) a 48 % SUD prevalence rate (between-site range of 21–71 %), with 20 % of the sample evidencing polysubstance use disorder; (2) substance-specific SUD rates of 31 % for marijuana, 19 % alcohol, 13 % methamphetamine, 11 % cocaine, and 4 % opiate; and (3) emergence of younger age and male gender as robust SUD predictors. Findings suggest high rates at which SUDs occur among patients at these urban HIV care sites, detail substance-specific SUD rates, and identify at-risk patient subgroups

Internalized HIV stigma predicts subsequent viremia in US HIV patients through depressive symptoms and antiretroviral therapy adherence

Objective:We sought to examine the prospective association between internalized HIV stigma and unsuppressed viral load and to investigate whether this relationship was sequentially mediated by depressive symptoms and antiretroviral therapy (ART) adherence.Design:Longitudinal study in a multisite observational clinical cohort.Methods:The Center for AIDS Research Network of Integrated Clinical Systems patient-reported outcomes survey measures internalized HIV stigma yearly using a four-item assessment (response scale 1 = strongly disagree to 5 = strongly agree). We obtained patient-reported outcome, lab, and appointment data from six center for AIDS research network of integrated clinical systems sites. We used multivariable logistic regression to examine the association between mean stigma and subsequent viremia. We then used Bayesian sequential mediation to fit a longitudinal sequential path model spanning four time points to test if depressive symptoms at T1and ART adherence at T2mediated the effect of stigma at T0on viral load at T3, adjusting for baseline covariates.Results:Between February 2016 and November 2018, 6859 patients underwent stigma assessment and were 81% cis-men, 38% Black, 16% Latinx, 32% heterosexual-identified, and 49% at least 50 years of age. Mean stigma level was 2.00 (SD 1.08). Stigma was significantly associated with subsequent viremia (adjusted odds ratio = 1.16, 95% confidence interval: 1.05-1.28, P = 0.004), as were younger age and Black race. The chained indirect effect from stigma to unsuppressed viral load through depressive symptoms and then adherence was significant (standardized β = 0.002; SD = 0.001).Conclusion:Internalized HIV stigma positively predicts subsequent viremia through depressive symptoms and ART adherence. Addressing the link between stigma and depressive symptoms could help improve viral suppression

Multicenter Development and Validation of a Model for Predicting Retention in Care Among People with HIV

Predictive analytics can be used to identify people with HIV currently retained in care who are at risk for future disengagement from care, allowing for prioritization of retention interventions. We utilized machine learning methods to develop predictive models of retention in care, defined as no more than a 12 month gap between HIV care appointments in the Center for AIDS Research Network of Integrated Clinical Systems (CNICS) cohort. Data were split longitudinally into derivation and validation cohorts. We created logistic regression (LR), random forest (RF), and gradient boosted machine (XGB) models within a discrete-time survival analysis framework and compared their performance to a baseline model that included only demographics, viral suppression, and retention history. 21,267 Patients with 507,687 visits from 2007 to 2018 were included. The LR model outperformed the baseline model (AUC 0.68 [0.67–0.70] vs. 0.60 [0.59–0.62], P < 0.001). RF and XGB models had similar performance to the LR model. Top features in the LR model included retention history, age, and viral suppression