Application of high-resolution techniques in the assessment of the mobility of Cr, Mo, and W at the sediment-water interface of Nansi Lake, China.

There are few studies on the simultaneous behavior of chromium (Cr), molybdenum (Mo), and tungsten (W) belonging to group VIB of the periodic table. Herein, based on high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) technology, the vertical distribution characteristics of DGT-labile and soluble Cr, Mo, and W in two lakes of Nansi Lake (Weishan Lake and Dushan Lake) were analyzed. In addition, the net diffusion fluxes and R-value (CDGT/Csol) were used to evaluate the mobility and release risk of metals at the sediment-water interface. The results showed that the DGT-labile concentrations of the three metal elements (Cr, Mo, and W) in Weishan Lake were higher than those in Dushan Lake, both in overlying water and sediment. This is mainly due to the dredging of the Dushan Lake area, which can permanently remove the polluted sediment in the lake. Meanwhile, the exogenous input is relatively high near the tourist area of Weishan Island. The net diffusion fluxes indicate that the W has a potential release risk of diffusion to the overlying water in Dushan Lake. The release of Cr, Mo, and W is thought to be related to the reductive dissolution of Fe/Mn (hydr)oxides based on Pearson correlation coefficients. The R-values of Cr and W indicate that Cr and W belong to the partial continuity case. The R-value of Mo was lower than the minimum value, meaning that Mo belongs to the single diffusion type and it is difficult for Mo sediments to supply pore water.

Correlations between leaf economics, mechanical resistance and drought tolerance across 41 cycad species.

BACKGROUND AND AIMS: We conducted a comprehensive analysis of the functional traits of leaves (leaflets) of cycads. The aim of this study was to clarify the functional divergence between the earlier origin Cycadaceae and the later differentiated Zamiaceae, and the differences in trait associations between cycads and angiosperms. METHODS: We selected 20 Cycadaceae species and 21 Zamiaceae species from the same cycad garden in South China, and measured their leaf structure, economic traits, mechanical resistance (Fp) and leaf water potential at the turgor loss point (πtlp). In addition, we compiled a dataset of geographical distribution along with climatic variables for these cycad species, and some leaf traits of tropical-sub-tropical angiosperm woody species from the literature for comparison. KEY RESULTS: The results showed significantly contrasting leaf trait syndromes between the two families, with Zamiaceae species exhibiting thicker leaves, higher carbon investments and greater Fp than Cycadaceae species. Leaf thickness (LT) and πtlp were correlated with mean climatic variables in their native distribution ranges, indicating their evolutionary adaptation to environmental conditions. Compared with the leaves of angiosperms, the cycad leaves were thicker and tougher, and more tolerant to desiccation. Greater Fp was associated with a higher structural investment in both angiosperms and cycads; however, cycads showed lower Fp at a given leaf mass per area or LT than angiosperms. Enhancement of Fp led to more negative πtlp in angiosperms, but the opposite trend was observed in cycads. CONCLUSIONS: Our results reveal that variations in leaf traits of cycads are mainly influenced by taxonomy and the environment of their native range. We also demonstrate similar leaf functional associations in terms of economics, but different relationships with regard to mechanics and drought tolerance between cycads and angiosperms. This study expands our understanding of the ecological strategies and likely responses of cycads to future climate change.

Leaf turgor loss point is correlated with drought tolerance and leaf carbon economics traits.

Leaf turgor loss point (πtlp) indicates the capacity of a plant to maintain cell turgor pressure during dehydration, which has been proven to be strongly predictive of the plant response to drought. In this study, we compiled a data set of πtlp for 1752 woody plant individuals belonging to 389 species from nine major woody biomes in China, along with reduced sample size of hydraulic and leaf carbon economics data. We aimed to investigate the variation of πtlp across biomes varying in water availability. We also tested two hypotheses: (i) πtlp predicts leaf hydraulic safety margins and (ii) it is correlated with leaf carbon economics traits. Our results showed that there was a positive relationship between πtlp and aridity index: biomes from humid regions had less negative values than those from arid regions. This supports the idea that πtlp may reflect drought tolerance at the scale of woody biomes. As expected, πtlp was significantly positively correlated with leaf hydraulic safety margins that varied significantly across biomes, indicating that this trait may be useful in modelling changes of forest components in response to increasing drought. Moreover, πtlp was correlated with a suite of coordinated hydraulic and economics traits; therefore, it can be used to predict the position of a given species along the 'fast-slow' whole-plant economics spectrum. This study expands our understanding of the biological significance of πtlp not only in drought tolerance, but also in the plant economics spectrum.

Diagnostic test accuracy of the Montreal Cognitive Assessment in the detection of post-stroke cognitive impairment under different stages and cutoffs: a systematic review and meta-analysis.

The purposes of this review were to give the optimal cutoffs of the Montreal Cognitive Assessment (MoCA) by comparing sensitivity and specificity under different cutoffs and compare the MoCA with other screening tools in post-stroke cognitive impairment (PSCI) determined by a neuropsychological evaluation. Articles were derived from a systematic search in PubMed, Web of science, Embase, and CINAHL and were assessed for internal validity by the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2). The figure of risk of bias was made by Review Manager 5.3, and data of selected studies were synthesized by MetaDisc 1.4. Twelve diagnostic studies, involving 2130 patients, were included. The area under the curve (AUC) under cutoffs of 20v19, 21v20, and 26v25 are 0.90, 0.90, and 0.95, showing high predictive validity for PSCI screening within 1 month. When the sensitivity and specificity are equal important, the optimal cutoff is 20v19 (Youden Index = 0.58). Compared to the Mini-Mental State Examination (MMSE), the MoCA has higher sensitivity but lower specificity. The optimal cutoff differs in different stages of stroke. Both the MMSE and MoCA are appropriate screening tools for PSCI, and the use of these two tools should be in accordance with the aim of screening. The Addenbrooke's Cognitive Examination-Revised (ACE-R) can act as a supplement for the MoCA.

Different leaf cost-benefit strategies of ferns distributed in contrasting light habitats of sub-tropical forests.

BACKGROUND AND AIMS: Ferns are abundant in sub-tropical forests in southern China, with some species being restricted to shaded understorey of natural forests, while others are widespread in disturbed, open habitats. To explain this distribution pattern, we hypothesize that ferns that occur in disturbed forests (FDF) have a different leaf cost-benefit strategy compared with ferns that occur in natural forests (FNF), with a quicker return on carbon investment in disturbed habitats compared with old-growth forests. METHODS: We chose 16 fern species from contrasting light habitats (eight FDF and eight FNF) and studied leaf functional traits, including leaf life span (LLS), specific leaf area (SLA), leaf nitrogen and phosphorus concentrations (N and P), maximum net photosynthetic rates (A), leaf construction cost (CC) and payback time (PBT), to conduct a leaf cost-benefit analysis for the two fern groups. KEY RESULTS: The two groups, FDF and FNF, did not differ significantly in SLA, leaf N and P, and CC, but FDF had significantly higher A, greater photosynthetic nitrogen- and phosphorus-use efficiencies (PNUE and PPUE), and shorter PBT and LLS compared with FNF. Further, across the 16 fern species, LLS was significantly correlated with A, PNUE, PPUE and PBT, but not with SLA and CC. CONCLUSIONS: Our results demonstrate that leaf cost-benefit analysis contributes to understanding the distribution pattern of ferns in contrasting light habitats of sub-tropical forests: FDF employing a quick-return strategy can pre-empt resources and rapidly grow in the high-resource environment of open habitats; while a slow-return strategy in FNF allows their persistence in the shaded understorey of old-growth forests.

Methods of assessment of tophus and bone erosions in gout using dual-energy CT: reproducibility analysis.

This study aims to evaluate the intraobserver and interobserver reproducibility of the tophus urate volume, erosion volume, and the erosion score measurements in patients with gout by using dual-energy CT (DECT) scans comparing their bone erosion volumes against bone erosion scores and also to determine a valid measure of joint destruction in chronic gout. Sixty-six subjects underwent DECT scans of the hands or feet. Two independent observers measured the tophus urate volumes and bone erosion volumes using automated volume assessment software and the erosion scores based on the rheumatoid arthritis magnetic resonance imaging score (RAMRIS). The intraobserver and interobserver reproducibility were analyzed by intraclass correlation coefficient (ICC) and limits of agreements analysis. The relationship between erosion volumes and erosion scores was analyzed. The intraobserver and interobserver ICC for tophus urate volume measurements (n = 636) were 1.000 (95 % confidence interval (95 % CI) 1.000 to 1.000) and 1.000 (95 % CI 1.000 to 1.000), 0.999 (0.999, 0.999) and 0.999 (0.999, 0.999) for bone erosion volumes (n = 350), 0.937 (0.928, 0.946) and 0.899 (0.883, 0.912) for erosion scores (n = 350). Strong positive correlations were demonstrated between individual erosion volumes and scores (r s = 0.914, p < 0.001) as well as total erosion volume and score per patient (r = 0.838-0.867, p < 0.001). This study demonstrated a high reproducibility of tophus urate volumes, erosion volumes, and erosion score measurements using DECT. Erosion volumes show to be a more direct and accurate method to evaluate bone erosion compared with erosion score, strongly supporting it as a superior and standard measure of structural joint damage in gout.

Contrasting cost-benefit strategy between lianas and trees in a tropical seasonal rain forest in southwestern China.

Lianas are an important component of tropical forests and often abundant in open habitats, such as tree-fall gaps, forest edges, and disturbed forests. The abundance of lianas in tropical forests has been increasing as a result of global environmental change and increasing forest fragmentation. In order to understand this phenomenon in terms of leaf functional traits and to evaluate their competitive potential, we conducted a cost-benefit analysis of leaves from 18 liana species and 19 tree species in a tropical seasonal rain forest. The results revealed that lianas were scattered in a group distinct from trees along the first axis of a principal component analysis using 15 leaf ecophysiological traits, being located at the quick-return end of the leaf economics spectrum, with higher specific leaf area and photosynthetic rates (A), higher photosynthetic nitrogen (N) and phosphorus (P) use efficiencies, a lower leaf construction cost per unit leaf area (CC) and cost-benefit ratio (CC/A), and a shorter leaf life span (LLS). Trees showed the opposite trends. The results indicate that lianas can grow faster and capture resources more efficiently than trees in disturbed, open habitats. The positive relationship between LLS and CC/A revealed a trade-off between leaf construction cost and benefit over time. The 37 species analyzed had a mean foliar N/P ratio of 20, indicating that the forest was characterized by a P deficit. With an increasing atmospheric CO(2) concentration, the higher nutrient use efficiency could benefit lianas more than trees in terms of productivity, possibly also contributing to the increasing abundance of lianas in nutrient-limited tropical forests.