With its unique combination of excellent timing properties and good energy resolution, LaBr3:Ce detectors have proven to be effective tool in gamma spectroscopy and in particular fast-timing studies. ...Eight 2” x 2” LaBr3:Ce detectors used in conjunction with the 16 channel all-digital waveform 500 MHz acquisition module, PIXIE-16 were commissioned at iThemba Laboratory for Accelerator Based Sciences, South Africa. The results presented here give insight of the performance of the 2” x 2” LaBr3 detectors when used in conjunction with a digital pulse processing (DPP) module and electronic read-out module. Initial commissioning experiments were done using radioactive sources, including 60Co, 152Eu and 67Ga. The detectors were then exposed to an in-beam environment using the AFRODITE array with targets 45Sc and 64Ni, with a proton beam energy of 27 MeV.
Aim
We evaluated the performance of the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI) and Cockcroft–Gault (CG) equations against creatinine ...clearance (CrCl) to estimate glomerular filtration rate (GFR) in 51 patients with Type 2 diabetes.
Methods
The CrCl value was obtained from the average of two consecutive 24‐h urine samples. Results were adjusted for body surface area using the Dubois formula. Serum creatinine was measured using the kinetic Jaffe method and was calibrated to standardized levels. Bland–Altman analysis and kappa statistic were used to examine agreement between measured and estimated GFR.
Results
Estimates of GFR from the CrCl, MDRD, CKD‐EPI and CG equations were similar (overall P = 0.298), and MDRD (r = 0.58; 95% CI: 0.36–0.74), CKD‐EPI (r = 0.55; 95% CI: 0.33–0.72) and CG (r = 0.61; 95% CI: 0.39–0.75) showed modest correlation with CrCl (all P < 0.001). Bias was −0.3 for MDRD, 1.7 for CKD‐EPI and −5.4 for CG. All three equations showed fair‐to‐moderate agreement with CrCl (kappa: 0.38–0.51). The c‐statistic for all three equations ranged between 0.75 and 0.77 with no significant difference (P = 0.639 for c‐statistic comparison).
Conclusions
The MDRD equation seems to have a modest advantage over CKD‐EPI and CG in estimating GFR and detecting impaired renal function in sub‐Saharan African patients with Type 2 diabetes. The overall relatively modest correlation with CrCl, however, suggests the need for context‐specific estimators of GFR or context adaptation of existing estimators.
What's new?
Glomerular filtration rate (GFR) equations for estimating kidney function are routinely used in sub‐Saharan Africa. There is, however, a paucity of data on the performance of these equations in patients with diabetes mellitus who are, for the most part, undiagnosed and unaware of their condition.
We investigated the performance of the Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI) and Cockcroft–Gault (CG) equations in patients with Type 2 diabetes.
Our results suggest that the lowest bias is observed with the MDRD formula compared with the CKD‐EPI and CG equations. However, all three equations performed similarly in predicting altered kidney function based on low GFR.
Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest ...carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.
Current quantification methods of
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I-FP-CIT SPECT rely on anatomical parcellation of the striatum. We propose here to implement a new method based on MRI segmentation and functional atlas of the ...basal ganglia (MR-ATLAS) that could provide a reliable quantification within the sensorimotor, associative, and limbic territories of the striatum. Patients with Parkinson’s disease (PD), idiopathic rapid eye movement sleep behavioral disorder (iRBD), and healthy controls underwent
123
I-FP-CIT SPECT, MRI, motor, and cognitive assessments. SPECT data were corrected for partial volume effects and registered to a functional atlas of the striatum to allow quantification in every functional region of the striatum (nucleus accumbens, limbic, associative, and sensorimotor parts of the striatum). The MR-ATLAS quantification method is proved to be reliable in every territory of the striatum. In addition, good correlations were found between cognitive dysexecutive tests and the binding within the functional (limbic) territories of the striatum using the MR-ATLAS method, slightly better than correlations found using the anatomical quantification method. This new MR-ATLAS method provides a robust and useful tool for studying the dopaminergic system in PD, particularly with respect to cognitive functions. It may also be relevant to further unravel the relationship between dopaminergic denervation and cognitive or behavioral symptoms.
Adenoviruses (AdVs) have a significant impact in both medical and environmental contexts. The objective of this study was to investigate the prevalence of AdV in different water types, such as ...untreated and treated wastewater, surface water, groundwater, drinking water, and other water matrices. A total of 239 articles were included in this meta-analysis. Adenoviruses were detected in various waters worldwide. The overall prevalence in water was found to be 59.2%, with the highest prevalence in untreated wastewater (83.1%) and treated wastewater (75.3%), followed by "other water matrices" (53.4%), surface water (49.5%) drinking water (22.7%), and groundwater (18.5%). Most of the studies did not assess the viability of the viruses, leading to weak links between water contamination and risk. Both human and animal AdV were found in water environments. The findings suggest that water, including drinking water, could be a significant route of AdV transmission in both developed and developing economies.
Tropical tree communities are shaped by local-scale habitat heterogeneity in the form of topographic and edaphic variation, but the life-history stage at which habitat associations develop remains ...poorly understood. This is due, in part, to the fact that previous studies have not accounted for the widely disparate sample sizes (number of stems) that result when trees are divided into size classes. We demonstrate that the observed habitat structuring of a community is directly related to the number of individuals in the community. We then compare the relative importance of habitat heterogeneity to tree community structure for saplings, juveniles and adult trees within seven large (24–50 ha) tropical forest dynamics plots while controlling for sample size. Changes in habitat structuring through tree life stages were small and inconsistent among life stages and study sites. Where found, these differences were an order of magnitude smaller than the findings of previous studies that did not control for sample size. Moreover, community structure and composition were very similar among tree sub-communities of different life stages. We conclude that the structure of these tropical tree communities is established by the time trees are large enough to be included in the census (1 cm diameter at breast height), which indicates that habitat filtering occurs during earlier life stages.
Hepatitis E virus (HEV) is responsible for acute hepatitis in humans, through foodborne, zoonotic, and waterborne transmission routes. This study aimed to assess the prevalence of HEV in water ...matrices. Six categories were defined: untreated and treated wastewater, surface water (river, lake, and seawater), drinking water, groundwater, and other water environments (irrigation water, grey water, reservoir water, flood water, and effluent of pig slaughterhouse). We searched PubMed, Web of Science, Global Index Medicus, and Excerpta Medica Database. Study selection and data extraction were performed by at least two independent investigators. Heterogeneity (
I
2
) was assessed using the
χ
2
test on the Cochran
Q
statistic and
H
parameter. Sources of heterogeneity were explored by subgroup analysis. This study is registered with PROSPERO, number CRD42021289116. We included 87 prevalence studies from 58 papers, 66.4% of which performed in Europe. The overall prevalence of HEV in water was 9.8% (95% CI 6.4–13.7). The prevalence was higher in untreated wastewater (15.1%) and lower in treated wastewater (3.8%) and in drinking water (4.7%). In surface water, prevalence was 7.4%, and in groundwater, the percentage of positive samples, from only one study available, was 8.3%. Overall, only 36.8% of the studies reported the genotype of HEV, with genotype 3 (HEV-3) prevalent (168 samples), followed by HEV-1 (148 sample), and HEV-4 (2 samples). High-income countries were the most represented with 59/87 studies (67.8%), while only 3/87 (3.5%) of the studies were performed in low-income countries. The overall prevalence obtained of this study was generally higher in industrialized countries. Risk of bias was low in 14.9% of the studies and moderate in 85.1%. The results of this review showed the occurrence of HEV in different waters environments also in industrialized countries with sanitation and safe water supplies. While HEV transmission to humans through water has been widely demonstrated in developing countries, it is an issue still pending in industrialized countries. Better knowledge on the source of pollution, occurrence, survival in water, and removal by water treatment is needed to unravel this transmission path.
Graphical Abstract
1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true ...for forests, which represent a majority of global biomass, productivity and biodiversity. 2. Here, we conduct an analysis of relationships between tree species richness, biomass and productivity in 25 forest plots of area 8-50 ha from across the world. The data were collected using standardized protocols, obviating the need to correct for methodological differences that plague many studies on this topic. 3. We found that at very small spatial grains (0.04 ha) species richness was generally positively related to productivity and biomass within plots, with a doubling of species richness corresponding to an average 48% increase in productivity and 53% increase in biomass. At larger spatial grains (0.25 ha, 1 ha), results were mixed, with negative relationships becoming more common. The results were qualitatively similar but much weaker when we controlled for stem density: at the 0.04 ha spatial grain, a doubling of species richness corresponded to a 5% increase in productivity and 7% increase in biomass. Productivity and biomass were themselves almost always positively related at all spatial grains. 4. Synthesis. This is the first cross-site study of the effect of tree species richness on forest biomass and productivity that systematically varies spatial grain within a controlled methodology. The scale-dependent results are consistent with theoretical models in which sampling effects and niche complementarity dominate at small scales, while environmental gradients drive patterns at large scales. Our study shows that the relationship of tree species richness with biomass and productivity changes qualitatively when moving from scales typical of forest surveys (0.04 ha) to slightly larger scales (0.25 and 1 ha). This needs to be recognized in forest conservation policy and management.
Large tropical trees and a few dominant species were recently identified as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches ...which are essential to understand, predict and monitor forest functions and composition over large, often poorly accessible territories. Here we show that the above-ground biomass (AGB) of the whole forest can be predicted from a few large trees and that the relationship is proved strikingly stable in 175 1-ha plots investigated across 8 sites spanning Central Africa. We designed a generic model predicting AGB with an error of 14% when based on only 5% of the stems, which points to universality in forest structural properties. For the first time in Africa, we identified some dominant species that disproportionally contribute to forest AGB with 1.5% of recorded species accounting for over 50% of the stock of AGB. Consequently, focusing on large trees and dominant species provides precise information on the whole forest stand. This offers new perspectives for understanding the functioning of tropical forests and opens new doors for the development of innovative monitoring strategies.
Summary
Tree size shapes forest carbon dynamics and determines how trees interact with their environment, including a changing climate. Here, we conduct the first global analysis of among‐site ...differences in how aboveground biomass stocks and fluxes are distributed with tree size.
We analyzed repeat tree censuses from 25 large‐scale (4–52 ha) forest plots spanning a broad climatic range over five continents to characterize how aboveground biomass, woody productivity, and woody mortality vary with tree diameter. We examined how the median, dispersion, and skewness of these size‐related distributions vary with mean annual temperature and precipitation.
In warmer forests, aboveground biomass, woody productivity, and woody mortality were more broadly distributed with respect to tree size. In warmer and wetter forests, aboveground biomass and woody productivity were more right skewed, with a long tail towards large trees. Small trees (1–10 cm diameter) contributed more to productivity and mortality than to biomass, highlighting the importance of including these trees in analyses of forest dynamics.
Our findings provide an improved characterization of climate‐driven forest differences in the size structure of aboveground biomass and dynamics of that biomass, as well as refined benchmarks for capturing climate influences in vegetation demographic models.
See also the Commentary on this article by Zuidema & van der Sleen, 234: 1544–1546.
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