650 research outputs found
The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations
Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.48C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model's depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value
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Detailed Visual Cortical Responses Generated by Retinal Sheet Transplants in Rats with Severe Retinal Degeneration.
To combat retinal degeneration, healthy fetal retinal sheets have been successfully transplanted into both rodent models and humans, with synaptic connectivity between transplant and degenerated host retina having been confirmed. In rodent studies, transplants have been shown to restore responses to flashes of light in a region of the superior colliculus corresponding to the location of the transplant in the host retina. To determine the quality and detail of visual information provided by the transplant, visual responsivity was studied here at the level of visual cortex where higher visual perception is processed. For our model, we used the transgenic Rho-S334ter line-3 rat (both sexes), which loses photoreceptors at an early age and is effectively blind at postnatal day 30. These rats received fetal retinal sheet transplants in one eye between 24 and 40 d of age. Three to 10 months following surgery, visually responsive neurons were found in regions of primary visual cortex matching the transplanted region of the retina that were as highly selective as normal rat to stimulus orientation, size, contrast, and spatial and temporal frequencies. Conversely, we found that selective response properties were largely absent in nontransplanted line-3 rats. Our data show that fetal retinal sheet transplants can result in remarkably normal visual function in visual cortex of rats with a degenerated host retina and represents a critical step toward developing an effective remedy for the visually impaired human population.SIGNIFICANCE STATEMENT Age-related macular degeneration and retinitis pigmentosa lead to profound vision loss in millions of people worldwide. Many patients lose both retinal pigment epithelium and photoreceptors. Hence, there is a great demand for the development of efficient techniques that allow for long-term vision restoration. In this study, we transplanted dissected fetal retinal sheets, which can differentiate into photoreceptors and integrate with the host retina of rats with severe retinal degeneration. Remarkably, we show that transplants generated visual responses in cortex similar in quality to normal rats. Furthermore, transplants preserved connectivity within visual cortex and the retinal relay from the lateral geniculate nucleus to visual cortex, supporting their potential application in curing vision loss associated with retinal degeneration
MR diffusion changes in the perimeter of the lateral ventricles demonstrate periventricular injury in post-hemorrhagic hydrocephalus of prematurity
OBJECTIVES: Injury to the preterm lateral ventricular perimeter (LVP), which contains the neural stem cells responsible for brain development, may contribute to the neurological sequelae of intraventricular hemorrhage (IVH) and post-hemorrhagic hydrocephalus of prematurity (PHH). This study utilizes diffusion MRI (dMRI) to characterize the microstructural effects of IVH/PHH on the LVP and segmented frontal-occipital horn perimeters (FOHP).
STUDY DESIGN: Prospective study of 56 full-term infants, 72 very preterm infants without brain injury (VPT), 17 VPT infants with high-grade IVH without hydrocephalus (HG-IVH), and 13 VPT infants with PHH who underwent dMRI at term equivalent. LVP and FOHP dMRI measures and ventricular size-dMRI correlations were assessed.
RESULTS: In the LVP, PHH had consistently lower FA and higher MD and RD than FT and VPT (p\u3c.050). However, while PHH FA was lower, and PHH RD was higher than their respective HG-IVH measures (p\u3c.050), the MD and AD values did not differ. In the FOHP, PHH infants had lower FA and higher RD than FT and VPT (p\u3c.010), and a lower FA than the HG-IVH group (p\u3c.001). While the magnitude of AD in both the LVP and FOHP were consistently less in the PHH group on pairwise comparisons to the other groups, the differences were not significant (p\u3e.050). Ventricular size correlated negatively with FA, and positively with MD and RD (p\u3c.001) in both the LVP and FOHP. In the PHH group, FA was lower in the FOHP than in the LVP, which was contrary to the observed findings in the healthy infants (p\u3c.001). Nevertheless, there were no regional differences in AD, MD, and RD in the PHH group.
CONCLUSION: HG-IVH and PHH results in aberrant LVP/FOHP microstructure, with prominent abnormalities among the PHH group, most notably in the FOHP. Larger ventricular size was associated with greater magnitude of abnormality. LVP/FOHP dMRI measures may provide valuable biomarkers for future studies directed at improving the management and neurological outcomes of IVH/PHH
The Algebra of Patterns
Pattern matching is a popular feature in functional, imperative and object-oriented programming languages. Language designers should therefore invest effort in a good design for pattern matching. Most languages choose a first-match semantics for pattern matching; that is, clauses are tried in the order in which they appear in the program until the first one matches. As a consequence, the order in which the clauses appear cannot be arbitrarily changed, which results in a less declarative programming model. The declarative alternative to this is an order-independent semantics for pattern matching, which is not implemented in most programming languages since it requires more verbose patterns. The reason for this verbosity is that the syntax of patterns is usually not expressive enough to express the complement of a pattern. In this paper, we show a principled way to make order-independent pattern matching practical. Our solution consists of two parts: First, we introduce a boolean algebra of patterns which can express the complement of a pattern. Second, we introduce default clauses to pattern matches. These default clauses capture the essential idea of a fallthrough case without sacrificing the property of order-independence
The Algebra of Patterns - Rocq Proofs (Artifact)
This artifact provides Rocq proofs for all the theorems of section 3 of the paper The Algebra of Patterns. Concretely, these are theorems 3, 4, 7, 8, 9, 10, 11, 12, 13 and 15
Active vitamin D (1,25-dihydroxyvitamin D) and bone health in middle-aged and elderly men: the European male aging study (EMAS)
<p>Context: There is little information on the potential impact of serum 1,25-dihydroxyvitamin D [1,25(OH)2D] on bone health including turnover.</p>
<p>Objective: The objective of the study was to determine the influence of 1,25(OH)2D and 25-hydroxyvitamin D [25(OH)D] on bone health in middle-aged and older European men.</p>
<p>Design, Setting, and Participants: Men aged 40–79 years were recruited from population registers in 8 European centers. Subjects completed questionnaires that included questions concerning lifestyle and were invited to attend for quantitative ultrasound (QUS) of the heel, assessment of height and weight, and a fasting blood sample from which 1,25(OH)2D, 25(OH)D, and PTH were measured. 1,25(OH)2D was measured using liquid chromatography tandem mass spectrometry. Bone markers serum N-terminal propeptide of type 1 procollagen (P1NP) and crosslinks (β-cTX) were also measured. Dual-energy x-ray absorptiometry (DXA) of the hip and lumbar spine was performed in 2 centers.</p>
<p>Main Outcome Measure(s): QUS of the heel, bone markers P1NP and β-cTX, and DXA of the hip and lumbar spine were measured.</p>
<p>Results: A total of 2783 men, mean age 60.0 years (SD 11.0) were included in the analysis. After adjustment for age and center, 1,25(OH)2D was positively associated with 25(OH)D but not with PTH. 25(OH)D was negatively associated with PTH. After adjustment for age, center, height, weight, lifestyle factors, and season, 1,25(OH)2D was associated negatively with QUS and DXA parameters and associated positively with β-cTX. 1,25(OH)2D was not correlated with P1NP. 25(OH)D was positively associated with the QUS and DXA parameters but not related to either bone turnover marker. Subjects with both high 1,25(OH)2D (upper tertile) and low 25(OH)D (lower tertile) had the lowest QUS and DXA parameters and the highest β-cTX levels.</p>
<p>Conclusions: Serum 1,25(OH)2D is associated with higher bone turnover and poorer bone health despite being positively related to 25(OH)D. A combination of high 1,25(OH)2D and low 25(OH)D is associated with the poorest bone health.</p>
A translational framework for public health research
<p><b>Background</b></p>
<p>The paradigm of translational medicine that underpins frameworks such as the Cooksey report on the funding of health research does not adequately reflect the complex reality of the public health environment. We therefore outline a translational framework for public health research.</p>
<p><b>Discussion</b></p>
<p>Our framework redefines the objective of translation from that of institutionalising effective interventions to that of improving population health by influencing both individual and collective determinants of health. It incorporates epidemiological perspectives with those of the social sciences, recognising that many types of research may contribute to the shaping of policy, practice and future research. It also identifies a pivotal role for evidence synthesis and the importance of non-linear and intersectoral interfaces with the public realm.</p>
<p><b>Summary</b></p>
<p>We propose a research agenda to advance the field and argue that resources for 'applied' or 'translational' public health research should be deployed across the framework, not reserved for 'dissemination' or 'implementation'.</p>
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Convective-scale perturbation growth across the spectrum of convective regimes
Convection-permitting ensembles have led to improved forecasts of many atmospheric phenomena. However, to fully utilize these forecasts the dependence of predictability on synoptic conditions needs to be understood. In this study, convective regimes are diagnosed based on a convective timescale which identifies the degree to which convection is in equilibrium with the large-scale forcing. Six convective cases are examined in a convection-permitting ensemble constructed using the Met Office Unified Model. The
ensemble members were generated using small-amplitude buoyancy perturbations added into the boundary layer, which can be considered to represent turbulent fluctuations close to the gridscale. Perturbation growth is shown to occur on different scales with an order of magnitude difference between the regimes (O(1 km) for cases closer to non-equilibrium convection and O(10 km) for cases closer to equilibrium convection). This difference reflects the fact that cell locations are essentially random in the equilibrium events after the first 12 h of the forecast, indicating a more rapid upscale perturbation growth compared to the non-equilibrium events. Furthermore, large temporal
variability is exhibited in all perturbation growth diagnostics for the nonequilibrium regime. Two boundary condition driven cases are also considered and show similar characteristics to the non-equilibrium cases, implying that caution is needed to interpret the timescale when initiation is not within the domain. Further understanding of perturbation growth within the different regimes could lead to a better understanding of where ensemble design improvements can be made beyond increasing the model resolution and could improve interpretation of forecasts
Active vitamin D (1,25-dihydroxyvitamin D) and bone health in middle-aged and elderly men: the European male aging study (EMAS)
<p>Context: There is little information on the potential impact of serum 1,25-dihydroxyvitamin D [1,25(OH)2D] on bone health including turnover.</p>
<p>Objective: The objective of the study was to determine the influence of 1,25(OH)2D and 25-hydroxyvitamin D [25(OH)D] on bone health in middle-aged and older European men.</p>
<p>Design, Setting, and Participants: Men aged 40–79 years were recruited from population registers in 8 European centers. Subjects completed questionnaires that included questions concerning lifestyle and were invited to attend for quantitative ultrasound (QUS) of the heel, assessment of height and weight, and a fasting blood sample from which 1,25(OH)2D, 25(OH)D, and PTH were measured. 1,25(OH)2D was measured using liquid chromatography tandem mass spectrometry. Bone markers serum N-terminal propeptide of type 1 procollagen (P1NP) and crosslinks (β-cTX) were also measured. Dual-energy x-ray absorptiometry (DXA) of the hip and lumbar spine was performed in 2 centers.</p>
<p>Main Outcome Measure(s): QUS of the heel, bone markers P1NP and β-cTX, and DXA of the hip and lumbar spine were measured.</p>
<p>Results: A total of 2783 men, mean age 60.0 years (SD 11.0) were included in the analysis. After adjustment for age and center, 1,25(OH)2D was positively associated with 25(OH)D but not with PTH. 25(OH)D was negatively associated with PTH. After adjustment for age, center, height, weight, lifestyle factors, and season, 1,25(OH)2D was associated negatively with QUS and DXA parameters and associated positively with β-cTX. 1,25(OH)2D was not correlated with P1NP. 25(OH)D was positively associated with the QUS and DXA parameters but not related to either bone turnover marker. Subjects with both high 1,25(OH)2D (upper tertile) and low 25(OH)D (lower tertile) had the lowest QUS and DXA parameters and the highest β-cTX levels.</p>
<p>Conclusions: Serum 1,25(OH)2D is associated with higher bone turnover and poorer bone health despite being positively related to 25(OH)D. A combination of high 1,25(OH)2D and low 25(OH)D is associated with the poorest bone health.</p>
Improvements in forecasting intense rainfall: results from the FRANC (forecasting rainfall exploiting new data assimilation techniques and novel observations of convection) project
The FRANC project (Forecasting Rainfall exploiting new data Assimilation techniques and Novel observations of Convection) has researched improvements in numerical weather prediction of convective rainfall via the reduction of initial condition uncertainty. This article provides an overview of the project’s achievements. We highlight new radar techniques: correcting for attenuation of the radar return; correction for beams that are over 90% blocked by trees or towers close to the radar; and direct assimilation of radar reflectivity and refractivity. We discuss the treatment of uncertainty in data assimilation: new methods for estimation of observation uncertainties with novel applications to Doppler radar winds, Atmospheric Motion Vectors, and satellite radiances; a new algorithm for implementation of spatially-correlated observation error statistics in operational data assimilation; and innovative treatment of moist processes in the background error covariance model. We present results indicating a link between the spatial predictability of convection and convective regimes, with potential to allow improved forecast interpretation. The research was carried out as a partnership between University researchers and the Met Office (UK). We discuss the benefits of this approach and the impact of our research, which has helped to improve operational forecasts for convective rainfall event
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