The relationship between biodiversity and ecosystem functions (BEFs) has attracted great interest. Studies on BEF have so far focused on the average trend of ecosystem function as species diversity increases. A tantalizing but rarely addressed question is why large variations in ecosystem functions are often observed across systems with similar species diversity, likely obscuring observed BEFs. Here we use a multi‐trophic food web model in combination with empirical data to examine the relationships between species richness and the variation in ecosystem functions (VEFs) including biomass, metabolism, decomposition, and primary and secondary production. We then probe the mechanisms underlying these relationships, focusing on the role of trophic interactions. While our results reinforce the previously documented positive BEF relationships, we found that ecosystem functions exhibit significant variation within each level of species richness and the magnitude of this variation displays a hump‐shaped relationship with species richness. Our analyses demonstrate that VEFs is reduced when consumer diversity increases through elevated nonlinearity in trophic interactions, and/or when the diversity of basal species such as producers and decomposers decreases. This explanation is supported by a 34‐year empirical food web time series from the Gulf of Riga ecosystem. Our work suggests that biodiversity loss may not only result in ecosystem function decline, but also reduce the predictability of functions by generating greater function variability among ecosystems. It thus helps to reconcile the debate on the generality of positive BEF relationships and to disentangle the drivers of ecosystem stability. The role of trophic interactions and the variation in their strengths mediated by functional responses in shaping ecosystem function variation warrants further investigations and better incorporation into biodiversity—ecosystem functioning research.

Objective: To investigate the value of the noninvasive pressure-strain loop (PSL) technique for assessing left ventricular myocardial work done in patients with essential hypertension. Methods: Prospectively, 60 patients with hypertension visiting the hospital from August 2020 to July 2021 were collected and divided into the mild hypertension group (SBP 140-159 mmHg, 35 cases) and the moderate-to-severe hypertension group (SBP ≥160 mmHg, 25 cases). Another 40 cases of healthy adults were collected as the control group. The differences in the global long-axis strain (GLS) and peak strain dispersion (PSD) of the left ventricle, global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE) were compared among the three groups. The receiver operating characteristic curve was used to evaluate the PSD, GWI, GCW, and GWW. The myocardial work index (MWI) and MWI percentages in the apical, middle, and basal segments of the heart were also compared among the groups.Results: (1) The PSD, GWI, GCW, and GWW were significantly different among the groups (Χ 2 = 57. 605, 79.203, 76.973, and 17.429, respectively, p < .05), while the GLS and GWE were not (Χ 2 = 1.559 and 5.849, respectively, p > .05). (2) The GWI had the highest specificity (97.5%) and the GCW the highest sensitivity (95%) in predicting hypertension. The percentage of apical MWI gradually increased (F = 11.230, p < .05) and the percentage of basal MWI gradually decreased (F = 10.665, p < .05) from the control group to the mild hypertension group to the moderate-to-severe hypertension group; there was no significant difference in the percentage of mid-MWI (F = 0.593, p > .05).

Background The level of lipoprotein-associated phospholipase A2 (LP-PLA2) in serum is independently correlated to coronary artery diseases (CAD). The aim of the study was to determine whether LP-PLA2 activity is positively associated with the seriousness of CAD. Methods Amount to 1056 patients suspected of having CAD underwent coronary angiography (CAG) to determine the seriousness of CAD. According to the amount of diseased coronary branches, the 1056 patients were split into three groups: single-vessel stenosis group, multiple-vessels stenosis group (> or = 2 diseased coronary branches),and control group (no diseased coronary branches). According to CAG results, electrocardiography, cardiac biomarker, and clinical presentation, all patients were split into four groups: acute myocardial infarction (AMI), unstable angina (UA), stable angina (SA), and control groups (excluding CAD). The activity of LP-PLA2 was compared statistically among the subgroups. Receiver operating characteristic analysis was applied to investigate the role of LP-PLA2 in evaluating the presence and seriousness of CAD. Results The level of LP-PLA2 increased in line with the number of diseased coronary branches. The levels of LP-PLA2 in the AMI and UA groups were observably higher when compared with the control and SA groups. LP-PLA2 had 75.6% sensitivity and 67.3% specificity for recognizing CAD, and 53.0% sensitivity and 80.3% specificity for recognizing severe coronary artery lesions. Conclusion The activity of LP-PLA2 is positively correlated to the seriousness of CAD.