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Urban-regional economies are developing in highly variegated, uneven ways globally. In economic geography, studies of urban-regional development emphasize the prospects for innovative, globally-competitive industrial sectors to emerge and enhance a city-region’s exchange value in global markets. This focus reflects a productivist bias that may fail to address issues related to the use-value of, or living conditions associated with urban transitions. Such concerns are particularly significant in the Global South where urbanization has often not led to socioeconomic transformations that benefit the majority of urban residents. To examine the relationships between a city’s exchange and use value, this paper argues for a sociotechnical systems approach that conceptualizes cities as constituted by interdependent or coupled regimes related to production, consumption, and infrastructure that stabilize urban-regional economies and determine development pathways. The framework is deployed empirically to examine the case of Nairobi, Kenya – a rapidly growing urban-regional economy characterized by high rates of inward foreign direct investment, principally in speculative real estate ventures in the consumption regime. Domestic manufacturing industries (the production regime) are stagnating, struggling to compete against imports, and failing to generate widespread formal employment and raise tax revenues for the infrastructure regime. The net result is a city characterized by fragmented or splintered regimes that create highly uneven, exclusionary development outcomes. These dynamics and findings are analyzed in relation to a similar study of Dar es Salaam, Tanzania in order to demonstrate the comparative potential of this conceptual approach. The paper concludes with a call for economic geographers to better account for the use-value of urban-regional economies such that development concerns beyond production become more central to our analyses.

This article advances a framework for the study of community economies as assemblages constituted and shaped by three primary dynamics: relations, resources and constraints, and processes of stabilization and destabilization. Drawing on diverse and community economies scholarship, assemblage theory and actor-network theory, we develop a framework that will contribute significantly to understandings of the emergence of community economies and the strategies that make them more resilient and sustainable. The conceptual framework is illustrated through a case study from Turkey’s Kurdish region – a women’s cooperative that remained resilient in the face of armed conflict and political violence.

Recent assessments of economic geographers’ work on global production stress the need for improved understandings of the immanent, structural and contingent drivers of disarticulations—uneven and exclusionary development outcomes that often occur when places become connected to global production networks (GPN). Some argue that a productive approach is to view the places or regions linked to GPN as ‘conjunctures’ of context-specific and multi-scalar processes, social formations, power relations, histories and structures that shape the quality of GPN couplings and help to produce disarticulations. This article argues that an epistemological focus on the practices of firms connected to GPN can yield insights into industry-specific processes (e.g. value creation, upgrading) and region- or place-specific conjunctural factors that produce disarticulations. The approach is elaborated on and applied illustratively to the case of Zanzibar’s (Tanzania) tourism industry, a sector that has grown rapidly but in a manner that has excluded many of the archipelago’s residents from the benefits of increasing integration into GPN. The practices of Zanzibari enterprises and foreign-owned resorts show how local enterprises are increasingly marginal in tourism GPN, while large-scale resorts and non-local firms capture and subsequently offshore much of the value generated by the industry. A qualitative analysis of these practices highlights how they are shaped in part by the conjuncture of several structural factors and processes—political, economic, racial and technological—that help to produce disarticulations in Zanzibar.

Background: HIV-1 set point viral load (SPVL) is a highly variable trait that influences disease progression and transmission risk. Men who are exclusively insertive (EI) during anal intercourse require more sexual contacts to become infected than exclusively receptive (ER) men. Thus, we hypothesize that EIs are more likely to acquire their viruses from highly infectious partners (i.e., with high SPVLs) and to have higher SPVLs than infected ERs. Methods: We used a one-generation Bernoulli model, a dynamic network model, and data from the Multicenter AIDS Cohort Study (MACS) to examine whether and under what circumstances MSM differ in SPVL by sexual role. Results: Both models predicted higher SPVLs in EIs than role versatile (RV) or ER men, but only in scenarios where longer-term relationships predominated. ER and RV men displayed similar SPVLs. EI men remained far less likely than ER men to become infected, however. When the MACS data were limited by some estimates of lower sex partner counts (a proxy for longer relationships), EI men had higher SPVLs; these differences were clinically relevant (>0.3 log10 copies/mL) and statistically significant (p

Male skip-molting, defined for this study as when adolescent male snow or Tanner crab (Chionoecetes opilio and C. bairdi) do not molt during the winter/spring molting season, reduces the abundances of large mature males by requiring skip-molters survive at least one additional year of natural mortality before molting resumes and by increasing terminal molting at smaller sizes. These dynamics have obvious consequences for fisheries that only target and retain large mature males. Though considered common in Atlantic Canada (AC) snow crab and recently documented in Sea of Japan snow crab, skip-molting remains unexamined for Eastern Bering Sea snow and Tanner crab populations. Using chela height and shell condition data collected from 1989 to 2017, size-specific proportions of skip-molting were estimated for each species. Estimated size-specific proportions for snow crab resemble those reported for AC snow crab populations; estimated Tanner crab proportions are about twice that for snow crab when accounting for size differences between the species. Population simulations indicate skip-molting can reduce the biomass of large mature males by 12–47% relative to a population with no skip-molting, depending on species and assumptions of skip-molter survival. Regression models developed to identify important covariates of skip-molting explained only modest variation in the data (i.e., low deviance explained). Additional histological and physiological data are needed to validate classification of skip-molters from field measurements. Skip-molting proportions may have been underestimated due to shell condition misclassification of skip-molters. The stock assessments for EBS snow and Tanner crab do not consider skip-molting and assume all adolescent males molt annually. The effects of misspecified growth dynamics on assessment estimates warrant further research.

Set-point viral load (SPVL) correlates with the age at which people acquire HIV. Although immunosenescence may seem like a parsimonious explanation for this, it does not easily explain the observation that the relationship between age and SPVL attenuates when accounting for source partner SPVL. Here we propose an alternative explanation that encompasses this latter finding: that decreasing risk of acquisition with older age generates a selection bottleneck that selects for more virulent strains with age.We adapted a previously published model of HIV transmission and evolution (EvoNetHIV), parameterized here for men who have sex with men (MSM). We conducted a series of simulation experiments that vary seven behavioral or clinical parameters that affect exposure risk as people age. We conducted regressions to determine the mean increase in SPVL per 10-year increase in seroconversion age, with and without source SPVL in the model.All runs generated significant relationships between seroconversion age and SPVL when not including source SPVL. All saw attenuated relationships, most to near 0, with source SPVL included. Four of our behavioral measures (relational duration, age-related homophily, coital frequency, and mean age at relationship formation) had clear effects on this relationship, all in the hypothesized direction. Combining multiple forms of behavioral heterogeneity yielded an increase of 0.056 log10 copies/mL SPVL per 10-year increase in seroconversion age, nearly as large as that seen in two empirical studies of age-SPVL correlations in MSM.The higher virulence of HIV among those infected later in life may be partly explained by a combination of selective bottlenecks and behavioral heterogeneity by age. Variation in the strength of this effect across populations may be in part due to different behavioral, epidemiological and clinical conditions, and not require assumptions about differences in patterns of immunosenescence among populations.

HIV set point viral load (SPVL), the viral load established shortly after initial infection, is a proxy for HIV virulence: higher SPVLs lead to higher risk of transmission and faster disease progression. Three models of test-and-treat scenarios, mainly in heterosexual populations, found that increasing treatment coverage selected for more virulent viruses. We modeled virulence evolution in a population of men who have sex with men (MSM) with increasing test-and-treat coverage. We extended a stochastic, dynamic network model (EvoNetHIV). We varied relationship patterns (MSM vs. heterosexual), HIV transmission models (increasing vs. plateauing probability of transmission at very high viral loads), and treatment roll-out (with explicit testing or fixed intervals between infection and treatment). In scenarios most similar to previous models (longer relational durations and the plateauing transmission function), we replicated trends previously found: increasing treatment coverage led to increased virulence (0.12 log10 increase in mean population SPVL between 20% and 100% treatment coverage). In scenarios reflecting MSM behavioral data using the increasing transmission function, increasing treatment coverage selected for viruses with lower virulence (0.16 log10 decrease in mean population SPVL between 20% and 100% treatment coverage). These findings emphasize the impact of sexual network conditions and transmission function details on predicted epidemiological and evolutionary outcomes. Varying these features creates very different evolutionary environments, which in turn lead to opposite effects in mean population SPVL evolution. Our results suggest that, under some realistic conditions, effective test-and-treat strategies may not face the previously reported tradeoff in which increasing coverage leads to evolution of greater virulence. This suggests instead that a virtuous cycle of increasing treatment coverage and diminishing virulence is possible.

Pathogen populations can evolve in response to selective pressure from vaccine-induced immune responses. For HIV, models predict that viral adaptation, either via strain replacement or selection on de novo mutation, may rapidly reduce the effectiveness of an HIV vaccine. We hypothesized that behavioral risk compensation after vaccination may accelerate the transmission of vaccine resistant strains, increasing the rate of viral adaptation and leading to a more rapid decline in vaccine effectiveness. To test our hypothesis, we modeled: a) the impact of risk compensation on rates of HIV adaptation via strain replacement in response to a partially effective vaccine; and b) the combined impact of risk compensation and viral adaptation on vaccine-mediated epidemic control. We used an agent-based epidemic model that was calibrated to HIV-1 trends in South Africa, and includes demographics, sexual network structure and behavior, and within-host disease dynamics. Our model predicts that risk compensation can increase the rate of HIV viral adaptation in response to a vaccine. In combination, risk compensation and viral adaptation can, under certain scenarios, reverse initial declines in prevalence due to vaccination, and result in HIV prevalence at 15 years equal to or greater than prevalence without a vaccine.

Sex-specific, state-space population models with size and stage structure and fit to survey and fishery data were developed for the eastern Bering Sea (EBS) snow crab for the years 1982–2017. Motivation for model development was to estimate population dynamics by shell condition for female crabs; estimate sex-specific annual, time-varying natural morality rates; and explore in general the feasibility of state space modeling for EBS snow crab. Model fits were very good and mean natural mortality estimates agreed with previous studies but several quite high and/or quite low annual natural mortality values were estimated for both sexes. Estimated mean female natural mortality was 0.49 yr−1 (s.d. = 0.01) with annual values from 0.04 yr−1 to 3.34 yr−1. Estimated mean male natural mortality was 0.36 yr−1 (s.d. = 0.07) with annual values from 0.03 yr−1 to 0.91 yr−1. Episodic high and low annual natural mortality estimates indicate potential model overfitting which an autoregressive or random walk estimation framework for natural mortality may address. We consider the models as proof-of-concept estimation frameworks and their results preliminary. After further refinement and testing, they could be a complementary approach to ongoing stock assessment modeling or prototypes for state-space assessment models. Additional process variability, such as for growth and maturation, can be incorporated in future work. Abundance estimates by mature female shell condition makes feasible estimation of annual and biennial spawner abundances, necessary for accurate egg production estimation. State-space population dynamics models of other Chionoecetes populations with both size and stage-based data (e.g., maturity status or shell condition) can be developed utilizing this study’s modeling framework.

Africa’s recent growth successes are raising hopes that its cities can generate the positive externalities needed to sustain long-term development. This paper examines the prospects for suc...

The complex life-history of the snow crab suggests that estimates of mature female biomass may not correlate proportionally with actual egg production. We calculate an egg production index (EPI) for the Eastern Bering Sea (EBS) snow crab using a simulation model that follows mature females from the molt-to-maturity through various reproductive stages (primiparous and multiparous) and reproductive cycles (annual and biennial). The model is parameterized with an estimate of annual instantaneous natural mortality, M , from a separate statistical model. The egg production model runs from 1980 to 2014, but the EPI is calculated only for 1985–2014 to be able to unambiguously assign mature females to the various component reproductive categories. Estimated M was 0.68yr −1 for 1980–2014. Linear regression of EPI lagged one year with stock assessment estimates of mature female biomass had an R 2 of 0.78, but with a mean absolute percent error of 82% between observed and model predictions; mature female biomass is thus a variable and uneven predictor of egg production. On average, primiparous females contributed 46% to total annual egg production and multiparous females the remaining 54%. Multiparous females in an annual cycle made the largest contribution to the EPI, responsible for 50% of annual egg production. Sensitivity analysis showed that egg production increased by a factor of 1.75 on average when only annual spawning was assumed. Multiparous females were found to co-occur almost exclusively with larger older males, such as those targeted by the fishery; due to the large proportion of egg production from multiparous females, this co-occurrence pattern has potential fishery management implications. The EPI will allow for future recruitment and population dynamics studies to use a more accurate measure of EBS snow crab reproductive potential, especially when considering the effects of climate change and environmental variability. Further demographic research will help refine EPI estimates.

We know less about the structures and processes associated with South–South production networks than about those with a South–North orientation. Using an inductive approach, in this article we explore these differences by analysing the everyday practices that Indian pharmaceutical firms employ to meet production and quality standards, access markets and innovate. We use extensive primary interview evidence to demonstrate that Indian pharmaceutical firms employ different business practices towards Northern and Southern end markets. Our findings reveal the presence of significant discontinuities within the Indian pharmaceutical industry. They also demonstrate how a practice-oriented approach to the study of GPNs can help to identify some of the micro social processes through which governance is achieved and transformed over time, and divergences in value creation, enhancement and capture trajectories between Southern and Northern end markets.

The commentaries and reviews in the section that follow take up the recently popularized notion of 'African futures' in order to explore the geographies, modes, potentialities, politics, and practices of epistemic, socio-economic, political and socio-ecological transformations that may be complementary or antagonistic to the global capitalist project.

This paper is centered on the random graph generated by a Doeblin-type coupling of discrete time processes on a countable state space whereby when two paths meet, they merge. This random graph is studied through a novel subgraph, called a bridge graph, generated by paths started in a fixed state at any time. The bridge graph is made into a unimodular network by marking it and selecting a root in a specified fashion. The unimodularity of this network is leveraged to discern global properties of the larger Doeblin graph. Bi-recurrence, i.e., recurrence both forwards and backwards in time, is introduced and shown to be a key property in uniquely distinguishing paths in the Doeblin graph, and also a decisive property for Markov chains indexed by $\mathbb{Z}$. Properties related to simulating the bridge graph are also studied., 44 pages, 4 figures

Growth in size stops at the terminal molt (molt-to-maturity) for the eastern Bering Sea snow and Tanner crab (Chionoecetes opilio and C. bairdi) and understanding size-at-maturity (SAM) dynamics is critical to manage their fisheries, which target and retain large mature males. Bottom trawl survey data from 1982 to 2017 were analyzed with correlations and spatial regressions to identify temporal and spatial patterns of SAM and size-specific proportions mature (PM) for newshell (recently molted) crab of each sex of each species. While substantial annual variability in SAM was estimated, no long-term directional trends were estimated for either species. Recruitment variability was likely the major driver of temporal trends in SAM for both species, rather than variable ocean temperatures or other possible factors. Recruitment abundances and SAM were negatively correlated for female snow crab but positively correlated for male snow crab and both sexes of Tanner crab. Male and female snow crab SAM had similar periodicities as snow crab recruitment. SAM spatial patterns were relatively stable at decadal time-scales for both species. Annual temporal variability in PM was moderate to negligible for both species and decadal-sale variability was modest, indicating temporally stable size-specific maturation probabilities. Comparison of SAM and PM regression results show strong effects of ontogenetic movement on spatial patterns of SAM for male snow crab. Intra- and inter-species comparisons allowed for broader understanding of SAM dynamics. Strong periodicity of male snow crab SAM may have utility for fisheries management. Elucidating the mechanisms responsible for periodic recruitment for these species will help provide a more complete understanding of both SAM dynamics and general population dynamics. With increasing ocean temperatures in the EBS, the mean size of mature crab for these species may increase but would certainly be accompanied by a decrease in snow crab abundance, the more stenothermic of the two species.

International audience; A key factor to determine the expansion dynamics and future distribution of non-native species is their physiological response to abiotic factors and their changes over time. For this study we developed a spatially explicit, agent-based model of population growth to represent the complex population dynamics of invasive marine macroalgae with heteromorphic biphasic life cycles. The model framework represents this complex life cycle by treating the individual developmental stages (gametophytes/sporophytes) as autonomous agents with unique behaviour/growth parameters. It was parameterised to represent a well-documented invasive algal species, the Asian kelp Undaria pinnatifida, and validated against field results from an in situ population in Brittany, France, showing good quantitative agreement in terms of seasonal changes in abundance/recruitment and growth dynamics. It was then used to explore how local environmental parameters (light availability, temperature and day length) affect the population dynamics of the individual developmental stages and the overall population growth. This type of modelling approach represents a promising tool for understanding the population dynamics of macroalgae from the bottom-up in terms of the individual interactions between the independent life history stages (both microscopic and macroscopic). It can be used to trace back the behaviour of the population as a whole to the underlying physiological and environmental processes impacting each developmental stage and give insights into the roles these play in invasion success.

The data presented in this article are related to the research article entitled “A modelling approach to explore the critical environmental parameters influencing the growth and establishment of the invasive seaweed Undaria pinnatifida in Europe” [1]. This article describes raw simulation data output from a novel individual-based model of the invasive kelp species Undaria pinnatifida. It also includes field data of monthly abundance and recruitment values for a population of invasive U. pinnatifida (in Brest harbour, France) that were used to validate the model. The raw model output and field data are made publicly available in order to enable critical analysis of the model predictions and to inform future modelling efforts of the study species. Keywords: Macroalgae, Individual-based model, Invasive species, Seaweed, Kelp, Undaria pinnatifida, Recruitment, Abundance

Transition research has recently been criticized to lack of geographically sensitive concepts to address sustainability transitions and environmental innovation processes. This has generated a number of suggestions how space, place and scale can be better incorporated into transitions studies. Moreover, it has led to a quickly growing number of empirical studies that explicitly deal with geographical aspects of transition processes. This special issue takes stock of these recent developments by assembling a set of eight exemplary papers that illustrate the added value of an explicitly geographical perspective on sustainability transitions. The contributions include a conceptual paper, a literature review and six empirical papers that offer representative examples of recent work. Taken together, these contributions testify to the vitality of the emerging research on the geography of sustainability transitions. This introduction to the special issue provides an overview of the special issue and offers suggestions for future research.

Transition researchers recognize increasingly the need to better address the role that spatial and geographical factors play in guiding the evolution of socio-technical and technological innovation systems. At the same time, some geographers are being drawn to transition studies as they strive to better understand the development trajectories of cities, industries, production networks, and economies. Building off these convergences, this paper proposes two interventions through which geographical ideas might further contribute to transitions research. The first focuses on conceptualizations of the socio-spatial dynamics through which TIS or niche contexts are coupled or aligned effectively with socio-technical regimes such that regime shifts become possible. The second brings the concept of place-making to bear on transition studies in order to analyze the political processes that shape the evolution of socio-technical systems. The paper closes with general arguments about ways to expand and diversify the geography-of-sustainability-transitions epistemic community.

Snow crab (Chionoecetes opilio), an arctic species, and Tanner crab (C. bairdi), a subarctic species, support large-scale industrial fisheries in the eastern Bering Sea and are spatially overlapping congeneric species at the opposite boundaries of their distributional ranges in the eastern North Pacific. Using summer bottom trawl survey data from 1982 to 2017, spatial analyses and geostatistical regressions were conducted for each species for three population categories (immature females, oldshell mature females, and oldshell large males) to explore intra and interspecies differences in habitat and spatial distributions as well as interspecific spatial co-occurrence patterns. Variability in depth distributions rather than poleward distributional shifts may be a Tanner crab response to ocean warming, the apparent converse of snow crab. Both temperature and depth have strong effects on the Tanner crab distributions and 2 °C is an approximate minimum temperature threshold for Tanner crab habitat. 2 °C is an important maximum temperature threshold for immature female snow crab but temperature effects are weaker for adult snow crab. Snow crab ontogenetic movement results in loose coupling between settlement and adult habitat and in significant spatial overlap between older snow crab and Tanner crab. The similarity in spatial distributions and habitat of older snow crab with juvenile Tanner crab habitat and the predatory nature of snow suggest a possible regulatory role of snow crab on the northern extent of spatial distributions of Tanner crab, along with other possible factors such as groundfish predation. Snow crab distributions will most probably continue to shift northwards with warming ocean temperatures but a poleward shift for Tanner crab appears more uncertain. The utilities of comparing spatial and non-spatial models and accounting for spatial confounding in spatial regression modeling are also addressed.

There are global increases in the use of HIV antiretroviral therapy (ART), guided by clinical benefits of early ART initiation, and the efficacy of treatment as prevention of transmission. UNAIDS has set forth an ambitious 90-90-90 strategy for 2020. Separately, it has been shown theoretically and empirically that HIV virulence can evolve over time. Observed virulence levels may reflect an adaptive balance between infected lifespan and per-contact transmission rate. Critically, the potential effects of widespread ART usage on HIV virulence are unknown. To predict these effects, we used an agent-based stochastic model to simulate changes in HIV virulence, using set point viral load as a virulence proxy. We calibrated our epidemic model to the prevalence and incidence trends of South Africa. We also repeated our analysis using a separate model calibration, as a sensitivity analysis, and found that predicted impact of ART on virulence was relatively insensitive to calibration. We explored two distinct ART scenarios, at increasing coverage levels: ART initiation based on patients reaching a CD4+ T cell count threshold, or based on time elapsed since infection (a scenario that mimics the "universal testing and treatment" aspirations in the 90-90-90 UNAIDS targets). We found that HIV virulence is generally unchanged in scenarios of CD4-based initiation. However, with ART initiation based on time since infection (universal test and treat), virulence can increase moderately within several years of ART rollout, under high coverage levels and early treatment initiation albeit within the context of epidemics that are rapidly decreasing in size. We also show that, compared to non-evolutionary HIV epidemic models, allowing for evolving virulence predicts greater declines in HIV incidence after ART rollout. Our modeling study suggests that increasing virulence driven by universal test and treat is likely not a major public health concern, but could be monitored in sentinel surveillance, in a manner similar to transmitted drug resistance.

HIV viral load (VL) predicts both transmission potential and rate of disease progression. For reasons that are still not fully understood, the set point viral load (SPVL) established after acute infection varies across individuals and populations. Previous studies have suggested that population mean SPVL (MSPVL) has evolved near an optimum that reflects a trade-off between transmissibility and host survival. Sexual network structures affect rates of potential exposure during different within-host phases of infection marked by different transmission probabilities, and thus affect the number and timing of transmission events. These structures include relational concurrency, which has been argued to explain key differences in HIV burden across populations. We hypothesize that concurrency will alter the fitness landscape for SPVL in ways that differ from other network features whose impacts accrue at other times during infection. To quantitatively test this hypothesis, we developed a dynamic, stochastic, data-driven network model of HIV transmission, and evolution to assess the impact of key sexual network phenomena on MSPVL evolution. Experiments were repeated in sensitivity runs that made different assumptions about transmissibility during acute infection, SPVL heritability, and the functional form of the relationship between VL and transmissibility. For our main transmission model, scenarios yielded MSPVLs ranging from 4.4 to 4.75 log10 copies/ml, covering much of the observed empirical range. MSPVL evolved to be higher in populations with high concurrency and shorter relational durations, with values varying over a clinically significant range. In linear regression analyses on these and other predictors, main effects were significant (P < 0.05), as were interaction terms, indicating that effects are interdependent. We also noted a strong correlation between two key emergent properties measured at the end of the simulations—MSPVL and HIV prevalence—most clearly for phenomena that affect transmission networks early in infection. Controlling for prevalence, high concurrency yielded higher MSPVL than other network phenomena. Interestingly, we observed lower prevalence in runs in which SPVL heritability was zero, indicating the potential for viral evolution to exacerbate disease burden over time. Future efforts to understand empirical variation in MSPVL should consider local HIV burden and basic sexual behavioral and network structure.

Land-use-change drivers related to institutional dynamics, including historical path dependencies and political dynamics associated with urban land transformation, are difficult to relate to specific spatial locations and thus are not easily included in spatial models of urban land-use change. In this paper we describe a land-use model with variables representing such institutional dynamics in the Greater Boston region, a metropolitan area characterized by periurban sprawl, for the period 1985–99. An aggregate land-use model is developed at the municipal level, based on a narrative analysis drawn from in-depth interviews with town planners, state officials, and land developers, to explain land-development patterns documented over that study period using aerial photography. Explanatory variables, including town financial variables, school quality measures, and spatial variables associated with access and location, are linked to land-change outcomes through the selection environment framework, a framework borrowed from economic geography to describe how regional growth patterns are shaped by locally specific institutional, market, and spatial contexts that constrain individual land-use decision makers. Results of the analysis suggest that institutional dynamics associated with housing values and associated tax revenues, educational expenditures, and exclusive zoning practices significantly explain municipal land-use change in the suburban or periurban context. Keywords: land use, metropolitan areas, model calibration, policy support

We used an agent-based network model to examine the effect of targeting different risk groups with unsuppressed HIV viral load for linkage or re-linkage to HIV-related treatment services in a heterosexual population with annual testing. Our model identifies prevention strategies that can reduce incidence to negligible levels (i.e., less than 0.1 infections per 100 person-years) 20 years after a targeted Treatment-as-Prevention (TasP) campaign. The model assumes that most (default 95%) of the population is reachable (i.e., could, in principle, be linked to effective care) and a modest (default 5% per year) probability of a treated person dropping out of care. Under random allocation or CD4-based targeting, the default version of our model predicts that the TasP campaign would need to suppress viral replication in ~80% of infected people to halt the epidemic. Under age-based strategies, by contrast, this percentage drops to 50% to 60% (for strategies targeting those

Exact coupling of random walks is studied. Conditions for admitting a successful exact coupling are given that are necessary and in the Abelian case also sufficient. In the Abelian case, it is shown that a random walk $S$ with step-length distribution $\mu$ started at $0$ admits a successful exact coupling with a version $S^x$ started at $x$ if and only if there is $n\geq 1$ with $\mu^{n} \wedge \mu^{n}(x+\cdot) \neq 0$. Moreover, when a successful exact coupling exists, the total variation distance between $S_n$ and $S^x_n$ is determined to be $O(n^{-1/2})$ if $x$ has infinite order, or $O(\rho^n)$ for some $\rho \in (0,1)$ if $x$ has finite order. In particular, this paper solves a problem posed by H. Thorisson on successful exact coupling of random walks on $\mathbb{R}$. It is also noted that the set of such $x$ for which a successful exact coupling can be constructed is a Borel measurable group. Lastly, the weaker notion of possible exact coupling and its relationship to successful exact coupling are studied., Comment: This is a post-peer-review, pre-copyedit version of an article to appear in Journal of Theoretical Probability. 16 pages

Background Development of an HIV vaccine might be essential to ending the HIV/AIDS pandemic. However, vaccines can result in the emergence and spread of vaccine-resistant strains. Indeed, analyses of breakthrough infections in the HIV phase 3 vaccine trial RV144 identified HIV genotypes with differential rates of transmission in vaccine and placebo recipients. We hypothesized that, for HIV vaccination programs based on partially effective vaccines similar to RV144, HIV adaptation will rapidly diminish the expected vaccine impact. Methods and findings Using two HIV epidemic models, we simulated large-scale vaccination programs and, critically, included HIV strain diversity with respect to the vaccine response. We show here that rapid population-level viral adaptation can lead to decreased overall vaccine efficacy and substantially fewer infections averted by vaccination, when comparing scenarios with and without viral evolution (with outcomes depending on vaccination coverage, vaccine efficacy against the sensitive allele, and the initial resistant allele frequency). Translating this to the epidemic in South Africa, a scenario with 70% vaccination coverage may result in 250,000 infections (non-averted by vaccination) within 10 years of vaccine rollout that are due solely to HIV adaptation, all else being equal. Conclusions These findings suggest that approaches to HIV vaccine development, program implementation, and epidemic modeling may require attention to viral adaptation in response to vaccination.

International audience; Invasive macroalgae form a substantial component of marine invaders at a global level. However, it is poorly understood how the complex interactions between local environmental conditions and life cycle dynamics contribute to invasion success from a mechanistic viewpoint. The aim of this study was to use a model (UndariaGEN) that incorporates a detailed representation of the individual heteromorphic life history stages (sporophytes and gametophytes) of the species in order to explore how interactions between these components contribute to the overall population dynamics. The latest version of the model was validated against field data from a real-life population in Brittany, France. This was followed by an assessment of the role of temperature limitations in determining its potential global range and then a more detailed examination of how environmental factors affect the life cycle dynamics of U. pinnatifida across a range of conditions characteristic of European populations. In terms of both relative abundance and recruitment, the model matches closely the patterns observed from field studies in Brittany, France (R2 = 0.98 respectively). Furthermore, the model predicted theoretical temperature limits for growth (9.1–22.5 °C) match closely the actual current global range limits for the species (9.5–22.4 °C) reported in the literature. In addition, the size of the species’ ecological niche is shown to be directly related to the amplitude in seasonal variation of temperature. This demonstrates that U. pinnatifida has a wider ecological niche in conditions of high seasonality; this finding is consistent with theories that propose the heteromorphic life cycle may have evolved as an optimal growth strategy for highly seasonal environments.