Density‐dependent recruitment is fundamental to understanding species diversity and community dynamics in plants. Although there is compelling evidence that seeds and seedlings die from conspecific ...negative density dependence (CNDD) as predicted by the Janzen–Connell hypothesis, characterising adult recruitment remains a challenge for long‐living trees. Previous studies have used the decrease in fine‐scale spatial genetic structure (FSGS) across life stages to indicate CNDD; however, this has not been tested rigorously.
We addressed these challenges by integrating dispersal kernels and FSGS. To establish links between density dependence and FSGS, we simulated seedlings based on the estimated dispersal kernels from parentage analyses, and further simulated adults under various seedling‐to‐adult recruitment scenarios, using an individual‐based spatially explicit model. We tested this method in an isolated Cyclobalanopsis glauca population on China's Dajinshan Island.
We detected significant FSGS in the seedlings and weaker, though also significant, FSGS in the adults. As expected, the observed FSGS of seedlings was well predicted by the simulated seedlings, with observations falling inside the 95% confidence envelopes over all distance classes. However, the simulations showed that CNDD enhanced the FSGS while positive density dependence dampened it during the seedling‐to‐adult transition. The adult FSGS of our population was therefore explained by positive rather than negative density‐dependent adult recruitment.
Synthesis. Our study demonstrates that the change of FSGS in conjunction with dispersal‐based model tests can offer a valuable insight into density‐dependent adult recruitment. The results indicate that the transitions from seedlings to adults in C. glauca are dominantly regulated not by Janzen–Connell effects, but by processes of positive density dependence. More broadly, the findings may provide a caution against extrapolations of widespread Janzen–Connell effects in seeds and seedlings to adult recruits, underscoring a critical gap between mechanisms at early stages and long‐term population and community dynamics.
摘要
阐明密度制约更新效应是理解植物群落物种多样性和群落动态的基础。如Janzen–Connell假说所预测，广泛证据表明种子和幼苗的更新易受同种负密度制约作用，但成体更新是否存在密度制约仍难知晓。前期研究以小尺度空间遗传结构随植物发育的衰减表征同种负密度制约效应，但这一关联尚未得到验证。
为建立密度制约与空间遗传结构的直接联系，我们提出：采用基于个体的空间明晰模型，以亲本分析估计的扩散核函数为基础模拟幼苗遗传结构，进而模拟不同更新模式塑造的成体空间遗传结构。我们运用该方法研究中国大金山岛青冈种群成体更新的密度制约效应。
幼苗存在显著的空间遗传结构，其观测值在所有距离等级均处于模型预测的95%置信区间内。与幼苗相比，成体表现出显著但较弱的空间遗传结构。模拟结果显示，在幼苗成长至成体过程中，同种负密度制约将增强空间遗传结构，正密度制约则减弱遗传结构。该种群成体遗传结构与成体更新正密度制约效应模型的预测结果相吻合。
本研究提出并验证了基于扩散对小尺度空间遗传结构的变化进行模型检验可揭示成体更新的密度制约效应。结果表明，青冈种群幼苗发育至成体主要受正密度制约过程调节，而非Janzen–Connell效应。将种子和幼苗中广泛存在的Janzen–Connell效应简单外推至成体更新可能会高估这一机制对植物群落物种多样性维持的贡献。成体更新应是完成从发育早期阶段的生态机制到长期的种群和群落动态不可或缺的一环。
Density‐dependent adult recruitment is necessary for the Janzen−Connell mechanism to regulate plant population and community dynamics, but has rarely been examined. We present an integrative method by combining dispersal kernels and fine‐scale spatial genetic structure to test density dependence in adult recruitment. The results reject the dominant role of Janzen−Connell effects in a Cyclobalanopsis glauca population.
Heart failure (HF) is a common clinical syndrome associated with substantial morbidity, a heavy economic burden, and high risk of readmission. eHealth self-management interventions may be an ...effective way to improve HF clinical outcomes. The aim of this study was to systematically review the evidence for the effectiveness of eHealth self-management in patients with HF. This study included only randomized controlled trials (RCTs) that compared the effects of eHealth interventions with usual care in adult patients with HF using searches of the EMBASE, PubMed, CENTRAL (Cochrane Central Register of Controlled Trials), and CINAHL databases from January 1, 2011, to July 12, 2022. The Cochrane Risk of Bias tool (RoB 2) was used to assess the risk of bias for each study. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) criteria were used to rate the certainty of the evidence for each outcome of interest. Meta-analyses were performed using Review Manager (RevMan v.5.4) and R (v.4.1.0 x64) software. In total, 24 RCTs with 9634 participants met the inclusion criteria. Compared with the usual-care group, eHealth self-management interventions could significantly reduce all-cause mortality (odds ratio OR 0.83, 95% CI 0.71-0.98, P=.03; GRADE: low quality) and cardiovascular mortality (OR 0.74, 95% CI 0.59-0.92, P=.008; GRADE: moderate quality), as well as all-cause readmissions (OR 0.82, 95% CI 0.73-0.93, P=.002; GRADE: low quality) and HF-related readmissions (OR 0.77, 95% CI 0.66-0.90, P<.001; GRADE: moderate quality). The meta-analyses also showed that eHealth interventions could increase patients’ knowledge of HF and improve their quality of life, but there were no statistically significant effects. However, eHealth interventions could significantly increase medication adherence (OR 1.82, 95% CI 1.42-2.34, P<.001; GRADE: low quality) and improve self-care behaviors (standardized mean difference –1.34, 95% CI –2.46 to –0.22, P=.02; GRADE: very low quality). A subgroup analysis of primary outcomes regarding the enrolled population setting found that eHealth interventions were more effective in patients with HF after discharge compared with those in the ambulatory clinic setting. eHealth self-management interventions could benefit the health of patients with HF in various ways. However, the clinical effects of eHealth interventions in patients with HF are affected by multiple aspects, and more high-quality studies are needed to demonstrate effectiveness.
In order to formalize and extend on previous ad-hoc analysis and synthesis methods a theoretical treatment using vector representations of directional modulation (DM) systems is introduced and used ...to achieve DM transmitter characteristics. An orthogonal vector approach is proposed which allows the artificial orthogonal noise concept derived from information theory to be brought to bear on DM analysis and synthesis. The orthogonal vector method is validated and discussed via bit error rate (BER) simulations.
We report the hydroxide (OH
) and oxide (O
) experimental electroadsorption free energies, their dependences on pH, and their correlations to the oxygen evolution reaction (OER) electrocatalysis on ...RuO
(110) surface. The Sabatier principle predicts that catalyst is most active when the intermediate stabilization is moderate, not too strong such that the bound intermediate disrupts the subsequent catalytic cycle, nor too weak such that the surface is ineffective. For decades, researchers have used this concept to rationalize the activity trend of many OER electrocatalysts including RuO
, which is among the state-of-the-art OER catalysts. In this article, we report an experimental assessment of the Sabatier principle by comparing the oxygen electroadsorption energy to the OER electrocatalysis for the first time on RuO
. We find that the OH
and O
electroadsorption energies on RuO
(110) depend on pH and obey the scaling relation. However, we did not observe a direct correlation between the OH
and O
electroadsorption energies and the OER activity in the comparative analysis that includes both RuO
(110) and IrO
(110). Our result raises a question of whether the Sabatier principle can describe highly active electrocatalysts, where the kinetic aspects may influence the electrocatalysis more strongly than the electroadsorption energy, which captures only the thermodynamics of the intermediates and not yet kinetics.
Featuring the simultaneous generation of a library of compounds from a certain intermediate, divergent synthesis has found increasing applications in the construction of natural products and ...potential medicines. Inspired by this approach, presented herein is a general strategy to introduce functionality, in a divergent manner, into covalent organic frameworks (COFs). This modular protocol includes two stages of covalent assembly, through which functional COFs can be constructed by a three‐step transformation of a key platform molecule, such as 4,7‐dibromo‐2‐chloro‐1H‐benzodimidazole (DBCBI). Constructed herein are four types of chiral COFs (CCOFs) from DBCBI by nucleophilic substitution, Suzuki coupling, and imine formation. The unique array of eight isoframework CCOFs allowed investigation of their catalytic performance and structure–activity relationship in an asymmetric amination reaction.
COF it up: A divergent strategy has been used to construct a combinatorial library of functional covalent organic frameworks (COFs) from a platform molecule. An array of eight isoframework chiral COFs allowed investigation of their catalytic performance and structure–activity relationship in an asymmetric amination reaction.
Covalent organic frameworks (COFs) are crystalline porous solids with well-defined two- or three-dimensional molecular structures. Although the structural regularity provides this new type of porous ...material with high potentials in catalysis, no example has been presented so far. Herein, we report the first application of a new COF material, COF-LZU1, for highly efficient catalysis. The easily prepared imine-linked COF-LZU1 possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. Via a simple post-treatment, a Pd(II)-containing COF, Pd/COF-LZU1, was accordingly synthesized, which showed excellent catalytic activity in catalyzing the Suzuki–Miyaura coupling reaction. The superior utility of Pd/COF-LZU1 in catalysis was elucidated by the broad scope of the reactants and the excellent yields (96–98%) of the reaction products, together with the high stability and easy recyclability of the catalyst. We expect that our approach will further boost research on designing and employing functional COF materials for catalysis.
Single‐crystalline nanotubes of spinel LiMn2O4 with a diameter of about 600 nm, a wall thickness of about 200 nm and a length of 1–4 μm have been synthesized via a template‐engaged reaction using ...β‐MnO2 nanotubes as a self‐sacrifice template. In this fabrication, a minimal structural reorganization can be responsible for the chemical transformation from 001‐oriented β‐MnO2 template to 110‐oriented LiMn2O4. Galvanostatic charge/discharge measurements indicate that the nanotubes exhibit superior high‐rate capabilities and good cycling stability. About 70% of its initial capacity can be retained after 1500 cycles at 5 C rate. Importantly, the tubular nanostructures and the single‐crystalline nature of the most LiMn2O4 nanotubes are also well preserved after prolonged charge/discharge cycling at a relatively high current density, indicating good structural stability of the single‐crystalline nanotubes during lithium intercalation/deintercalation process. As is confirmed from Raman spectra analyses, no evident microstructural changes occur upon long‐term cycling. These results reveal that single‐crystalline nanotubes of LiMn2O4 will be one of the most promising cathode materials for high‐power lithium ion batteries.
1D single‐crystalline nanotubes of spinel LiMn2O4 targeted for high‐power lithium ion batteries are fabricated based on a template‐engaged reaction. This product delivers superior high‐rate capabilities and good cycling stability. Even after prolonged cycling at high‐current densities, the tubular morphology and high‐crystallinity characteristics of LiMn2O4 can be retained, indicating their potential application in high‐power lithium ion batteries, especially for electric vehicles.
Not only high efficiency but also high selectivity of the electrocatalysts is crucial for high‐performance, low‐cost, and sustainable energy storage applications. Herein, we systematically ...investigate the edge effect of carbon‐supported single‐atom catalysts (SACs) on oxygen reduction reaction (ORR) pathways (two‐electron (2 e−) or four‐electron (4 e−)) and conclude that the 2 e−‐ORR proceeding over the edge‐hosted atomic Co−N4 sites is more favorable than the basal‐plane‐hosted ones. As such, we have successfully synthesized and tuned Co‐SACs with different edge‐to‐bulk ratios. The as‐prepared edge‐rich Co−N/HPC catalyst exhibits excellent 2 e−‐ORR performance with a remarkable selectivity of ≈95 % in a wide potential range. Furthermore, we also find that oxygen functional groups could saturate the graphitic carbon edges under the ORR operation and further promote electrocatalytic performance. These findings on the structure–property relationship in SACs offer a promising direction for large‐scale and low‐cost electrochemical H2O2 production via the 2 e−‐ORR.
The edge‐hosted Co−N4 sites in the carbon matrix are more efficient and selective than basal plane‐hosted ones in catalyzing 2 e−‐ORR, achieving a remarkable selectivity of ≈95 % in the electrochemical production of H2O2.
Diplomatic and corporate networks Li, Jing; Meyer, Klaus E; Zhang, Hua ...
Journal of international business studies,
08/2018, Letnik:
49, Številka:
6
Journal Article
Recenzirano
Firms and governments operate in broad networks in which the home government and its diplomatic service are a critical node–or a “referral point” – between firms and potential partners in foreign ...locations. Thus diplomatic relations between countries matter for the choice of foreign investment location. Using a network perspective, we argue that the extent to which good diplomatic relations induce firms to invest in friendly host countries depends on their political connections to home governments. Those with stronger ties to home governments can better access and leverage intergovernmental diplomatic connections, thus benefiting potentially from enhanced access to information, reduced political risks, and increased legitimacy. Such ability of politically connected firms is more useful where weak institutional impartiality in the host country inhibits neutral treatment of foreign investors. Empirically, using overseas investment location decisions by Chinese firms, we find that the types of home government ties (i.e., whether they are organizational or personal and whether those relationships are with central or local goverments) and the impartiality of host institutions are both important contingencies affecting firms’ utilization of diplomatic relations. We discuss the implications of our study to research on network theory, political ties, and internationalization of emerging market firms.
PDF
