Analysis of symmetries in models of multi-strain infections

In mathematical studies of the dynamics of multi-strain diseases caused by antigenically diverse pathogens, there is a substantial interest in analytical insights. Using the example of a generic model of multi-strain diseases with cross-immunity between strains, we show that a significant understanding of the stability of steady states and possible dynamical behaviours can be achieved when the symmetry of interactions between strains is taken into account. Techniques of equivariant bifurcation theory allow one to identify the type of possible symmetry-breaking Hopf bifurcation, as well as to classify different periodic solutions in terms of their spatial and temporal symmetries. The approach is also illustrated on other models of multi-strain diseases, where the same methodology provides a systematic understanding of bifurcation scenarios and periodic behaviours. The results of the analysis are quite generic, and have wider implications for understanding the dynamics of a large class of models of multi-strain diseases

Canalization of the evolutionary trajectory of the human influenza virus

Since its emergence in 1968, influenza A (H3N2) has evolved extensively in genotype and antigenic phenotype. Antigenic evolution occurs in the context of a two-dimensional 'antigenic map', while genetic evolution shows a characteristic ladder-like genealogical tree. Here, we use a large-scale individual-based model to show that evolution in a Euclidean antigenic space provides a remarkable correspondence between model behavior and the epidemiological, antigenic, genealogical and geographic patterns observed in influenza virus. We find that evolution away from existing human immunity results in rapid population turnover in the influenza virus and that this population turnover occurs primarily along a single antigenic axis. Thus, selective dynamics induce a canalized evolutionary trajectory, in which the evolutionary fate of the influenza population is surprisingly repeatable and hence, in theory, predictable.Comment: 29 pages, 5 figures, 10 supporting figure

Clinical Features, Treatment, and Outcome in 102 Adult and Pediatric Patients with Localized High-Grade Synovial Sarcoma

Background. There remains controversy on the routine use of chemotherapy in localized SS. Methods. The records of 87 adult (AP) and 15 pediatric (PP) patients with localized SS diagnosed between 1986 and 2007 at 2 centres in Toronto were reviewed. Results. Median age for AP and PP was 37.6 (range 15–76) and 14 (range 0.4–18) years, respectively. 65 (64%) patients had large tumours (>5 cm). All patients underwent en bloc surgical resection resulting in 94 (92.2%) negative and 8 (7.8%) microscopically positive surgical margins. 72 (82.8%) AP and 8 (53%) PP received radiotherapy. Chemotherapy was administered to 12 (13.8%) AP and 13 (87%) PP. 10 AP and 5 PP were evaluable for response to neoadjuvant chemotherapy, with response rate of 10% and 40%, respectively. 5-year EFS and OS was 69.3 ± 4.8% and 80.3 ± 4.3%, respectively, and was similar for AP and PP, In patients with tumors >5 cm, in whom chemotherapy might be considered most appropriate, relapse occurred in 9/19 (47%) with chemotherapy, compared to 17/46 (37%) In those without. Conclusions. Patients with localized SS have a good chance of cure with surgery and RT. Evidence for a well-defined role of chemotherapy to improve survival In localized SS remains elusive

The unintended consequences of sex education: an ethnography of a development intervention in Latin America

This paper is an ethnography of a four-year, multi-disciplinary adolescent sexual and reproductive health intervention in Bolivia, Nicaragua and Ecuador. An important goal of the intervention – and of the larger global field of adolescent sexual and reproductive health – is to create more open parent-to-teen communication. This paper analyzes the project's efforts to foster such communication and how social actors variously interpreted, responded to, and repurposed the intervention's language and practices. While the intervention emphasized the goal of ‘open communication,’ its participants more often used the term ‘confianza’ (trust). This norm was defined in ways that might – or might not – include revealing information about sexual activity. Questioning public health assumptions about parent–teen communication on sex, in and of itself, is key to healthy sexual behavior, the paper explores a pragmatics of communication on sex that includes silence, implied expectations, gendered conflicts, and temporally delayed knowledge.Cuencavolumen 21, número

The compound Poisson limit ruling periodic extreme behaviour of non-uniformly hyperbolic dynamics

We prove that the distributional limit of the normalised number of returns to small neighbourhoods of periodic points of non-uniformly hyperbolic dynamical systems is compound Poisson. The returns to small balls around a fixed point in the phase space correspond to the occurrence of rare events, or exceedances of high thresholds, so that there is a connection between the laws of Return Times Statistics and Extreme Value Laws. The fact that the fixed point in the phase space is a repelling periodic point implies that there is a tendency for the exceedances to appear in clusters whose average sizes is given by the Extremal Index, which depends on the expansion of the system at the periodic point. We recall that for generic points, the exceedances, in the limit, are singular and occur at Poisson times. However, around periodic points, the picture is different: the respective point processes of exceedances converge to a compound Poisson process, so instead of single exceedances, we have entire clusters of exceedances occurring at Poisson times with a geometric distribution ruling its multiplicity. The systems to which our results apply include: general piecewise expanding maps of the interval (Rychlik maps), maps with indifferent fixed points (Manneville-Pomeau maps) and Benedicks-Carleson quadratic maps.Comment: To appear in Communications in Mathematical Physic

Measurements of the Mass, total Width and Two-Photon Partila Width of the ηc\eta_{c} Meson

Using 13.4 $fb^{-1}$ of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudo-scalar charmonium in the decay $\eta_c$ -> $K_S K^{\mp} \pi^{\pm}$. We have measured the $\eta_c$ mass to be (2980.4 +- 2.3 (stat) +- 0.6 (sys)) MeV and its full width as (27.0 +- 5.8 (stat) +- 1.4 (sys)) MeV. We have determined the two-photon partial width of the $\eta_c$ meson to be (7.6 +- 0.8 (stat) +- 0.4 (sys) +- 2.3 (br)) keV, with the last uncertainty associated with the decay branching fraction.Comment: 9 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

Access and allocation in earth system governance: Water and climate change compared

A significant percentage of the global population does not yet have access to safe drinking water, sufficient food or energy to live in dignity. There is a continuous struggle to allocate the earth's resources among users and uses. This article argues that distributional problems have two faces: access to basic resources or ecospace; and, the allocation of environmental resources, risks, burdens, and responsibilities for causing problems. Furthermore, addressing problems of access and allocation often requires access to social processes (science, movements and law). Analysts, however, have tended to take a narrow, disciplinary approach although an integrated conceptual approach may yield better answers. This article proposes a multi-disciplinary perspective to the problem of access and allocation and illustrates its application to water management and climate change. © The Author(s) 2010

Search for Branons at LEP

We search, in the context of extra-dimension scenarios, for the possible existence of brane fluctuations, called branons. Events with a single photon or a single Z-boson and missing energy and momentum collected with the L3 detector in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are analysed. No excess over the Standard Model expectations is found and a lower limit at 95% confidence level of 103 GeV is derived for the mass of branons, for a scenario with small brane tensions. Alternatively, under the assumption of a light branon, brane tensions below 180 GeV are excluded

Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP

Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events. Decay-plane correlations, consistent with zero and with the Standard Model predictions, are measured