70 research outputs found

    Measuring the photo-ionization rate, neutral fraction and mean free path of HI ionizing photons at 4.9z6.04.9 \leq z \leq 6.0 from a large sample of XShooter and ESI spectra

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    We measure the mean free path (λmfp,HI\lambda_{\rm mfp,HI}), photo-ionization rate (ΓHI\langle \Gamma_{\rm HI} \rangle) and neutral fraction (fHI\langle f_{\rm HI} \rangle) of hydrogen in 12 redshift bins at 4.85<z<6.054.85<z<6.05 from a large sample of moderate resolution XShooter and ESI QSO absorption spectra. The fluctuations in ionizing radiation field are modeled by post-processing simulations from the Sherwood suite using our new code ''EXtended reionization based on the Code for Ionization and Temperature Evolution'' (EX-CITE). EX-CITE uses efficient Octree summation for computing intergalactic medium attenuation and can generate large number of high resolution ΓHI\Gamma_{\rm HI} fluctuation models. Our simulation with EX-CITE shows remarkable agreement with simulations performed with the radiative transfer code Aton and can recover the simulated parameters within 1σ1\sigma uncertainty. We measure the three parameters by forward-modeling the Lyα\alpha forest and comparing the effective optical depth (τeff,HI\tau_{\rm eff, HI}) distribution in simulations and observations. The final uncertainties in our measured parameters account for the uncertainties due to thermal parameters, modeling parameters, observational systematics and cosmic variance. Our best fit parameters show significant evolution with redshift such that λmfp,HI\lambda_{\rm mfp,HI} and fHI\langle f_{\rm HI} \rangle decreases and increases by a factor 6\sim 6 and 104\sim 10^{4}, respectively from z5z \sim 5 to z6z \sim 6. By comparing our λmfp,HI\lambda_{\rm mfp,HI}, ΓHI\langle \Gamma_{\rm HI} \rangle and fHI\langle f_{\rm HI} \rangle evolution with that in state-of-the-art Aton radiative transfer simulations and the Thesan and CoDa-III simulations, we find that our best fit parameter evolution is consistent with a model in which reionization completes by z5.2z \sim 5.2.Comment: 30 pages (+14 pages appendices), 14 figures (+18 figures appendices); submitted to MNRAS; Main results are summarized in Fig. 10, Fig. 11 and Table

    Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018

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    Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations

    Measuring the photo-ionization rate, neutral fraction and mean free path of HI ionizing photons at 4.9≤z≤6.0 from a large sample of XShooter and ESI spectra

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    We measure the mean free path (⁠λmfp,HI⁠), photo-ionization rate (⁠⟨ΓHI⟩⁠) and neutral fraction (⁠⟨fHI⟩⁠) of hydrogen in 12 redshift bins at 4.85 < z < 6.05 from a large sample of moderate resolution XShooter and ESI QSO absorption spectra. The fluctuations in ionizing radiation field are modeled by post-processing simulations from the Sherwood suite using our new code ‘EXtended reionization based on the Code for Ionization and Temperature Evolution’ (EX-CITE). EX-CITE uses efficient Octree summation for computing intergalactic medium attenuation and can generate large number of high resolution ΓHI fluctuation models. Our simulation with EX-CITE shows remarkable agreement with simulations performed with the radiative transfer code Aton and can recover the simulated parameters within 1σ uncertainty. We measure the three parameters by forward-modeling the Lyα forest and comparing the effective optical depth (⁠τeff,HI⁠) distribution in simulations and observations. The final uncertainties in our measured parameters account for the uncertainties due to thermal parameters, modeling parameters, observational systematics and cosmic variance. Our best fit parameters show significant evolution with redshift such that λmfp,HI and ⟨fHI⟩ decreases and increases by a factor ∼6 and ∼104, respectively from z ∼ 5 to z ∼ 6. By comparing our λmfp,HI⁠, ⟨ΓHI⟩ and ⟨fHI⟩ evolution with that in state-of-the-art Aton radiative transfer simulations and the Thesan and CoDa-III simulations, we find that our best fit parameter evolution is consistent with a model in which reionization completes by z ∼ 5.2. Our best fit model that matches the τeff,HI distribution also reproduces the dark gap length distribution and transmission spike height distribution suggesting robustness and accuracy of our measured parameters

    Damping Wing-Like Features in the Stacked Ly Forest: Potential Neutral Hydrogen Islands at < 6

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    Recent quasar absorption line observations suggest that reionization may end as late as z5.3z \approx 5.3. As a means to search for large neutral hydrogen islands at z<6z<6, we revisit long dark gaps in the Lyβ\beta forest in VLT/X-Shooter and Keck/ESI quasar spectra. We stack the Lyα\alpha forest corresponding to both edges of these Lyβ\beta dark gaps and identify a damping wing-like extended absorption profile. The average redshift of the stacked forest is z=5.8z=5.8. By comparing these observations with reionization simulations, we infer that such a damping wing-like feature can be naturally explained if these gaps are at least partially created by neutral islands. Conversely, simulated dark gaps lacking neutral hydrogen struggle to replicate the observed damping wing features. Furthermore, this damping wing-like profile implies that the volume-averaged neutral hydrogen fraction must be xHI6.1±3.9%\langle x_{\rm HI} \rangle \geq 6.1 \pm 3.9\% at z=5.8z = 5.8. Our results offer robust evidence that reionization extends below z=6z=6.Comment: 8 pages, 5 figures, 1 table; accepted for publication in MNRAS Letter

    Cost-effectiveness of HPV vaccination in 195 countries: A meta-regression analysis

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    Cost-effectiveness analysis (CEA) is a well-known, but resource intensive, method for comparing the costs and health outcomes of health interventions. To build on available evidence, researchers are developing methods to transfer CEA across settings; previous methods do not use all available results nor quantify differences across settings. We conducted a meta-regression analysis of published CEAs of human papillomavirus (HPV) vaccination to quantify the effects of factors at the country, intervention, and method-level, and predict incremental cost-effectiveness ratios (ICERs) for HPV vaccination in 195 countries. We used 613 ICERs reported in 75 studies from the Tufts University’s Cost-Effectiveness Analysis (CEA) Registry and the Global Health CEA Registry, and extracted an additional 1,215 one-way sensitivity analyses. A five-stage, mixed-effects meta-regression framework was used to predict country-specific ICERs. The probability that HPV vaccination is cost-saving in each country was predicted using a logistic regression model. Covariates for both models included methods and intervention characteristics, and each country’s cervical cancer burden and gross domestic product per capita. ICERs are positively related to vaccine cost, and negatively related to cervical cancer burden. The mean predicted ICER for HPV vaccination is 2017 US4,217perDALYaverted(954,217 per DALY averted (95% uncertainty interval (UI): US773–13,448) globally, and below US800perDALYavertedin64countries.PredictedICERsarelowestinSubSaharanAfricaandSouthAsia,withapopulationweightedmeanICERacross46countriesofUS800 per DALY averted in 64 countries. Predicted ICERs are lowest in Sub-Saharan Africa and South Asia, with a population-weighted mean ICER across 46 countries of US706 per DALY averted (95% UI: 1302,245),andacrossfivecountriesofUS130–2,245), and across five countries of US489 per DALY averted (95% UI: $90–1,557), respectively. Meta-regression analyses can be conducted on CEA, where one-way sensitivity analyses are used to quantify the effects of factors at the intervention and method-level. Building on all published results, our predictions support introducing and expanding HPV vaccination, especially in countries that are eligible for subsidized vaccines from GAVI, the Vaccine Alliance, and Pan American Health Organization.</jats:p

    Anemia prevalence in women of reproductive age in low- and middle-income countries between 2000 and 2018

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    Abstract Anemia is a globally widespread condition in women and is associated with reduced economic productivity and increased mortality worldwide. Here we map annual 2000–2018 geospatial estimates of anemia prevalence in women of reproductive age (15–49 years) across 82 low- and middle-income countries (LMICs), stratify anemia by severity and aggregate results to policy-relevant administrative and national levels. Additionally, we provide subnational disparity analyses to provide a comprehensive overview of anemia prevalence inequalities within these countries and predict progress toward the World Health Organization’s Global Nutrition Target (WHO GNT) to reduce anemia by half by 2030. Our results demonstrate widespread moderate improvements in overall anemia prevalence but identify only three LMICs with a high probability of achieving the WHO GNT by 2030 at a national scale, and no LMIC is expected to achieve the target in all their subnational administrative units. Our maps show where large within-country disparities occur, as well as areas likely to fall short of the WHO GNT, offering precision public health tools so that adequate resource allocation and subsequent interventions can be targeted to the most vulnerable populations
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