Narrow-linewidth and low RIN Tm/Ho co-doped fiber laser based on self-injection locking.

A narrow-linewidth and low relative intensity noise (RIN) Tm/Ho co-doped fiber laser based on a saturable absorber and self-injection locking was demonstrated for the first time. Utilizing self-injection locking technology, the frequency noise power spectral density is remarkably reduced by more than 17.1 dB from 1.21 × 106 Hz2/Hz to 7.30 × 103 Hz2/Hz when the frequency is approximately 1 kHz. Furthermore, a laser with a linewidth compressed to a quarter of the original linewidth from 44.386 kHz to 2.850 kHz, a RIN of less than -127.74 dB/Hz, and an optical signal-to-noise ratio of more than 71.6 dB can be obtained. Using a delay fiber, the relaxation oscillation peak frequencies move to lower frequencies, from 27.9 kHz to 15.8 kHz. The proposed laser is highly competitive in advanced coherent light detection fields, including coherent Doppler wind lidar, high-speed coherent optical communication, and precise absolute distance coherent measurement.

Guiding the Formation of Metal-Organic Structures of 1,4-Diaminoanthraquinone through Surface-Based Cu Atoms.

The gradual guidance of the formation of metal-organic structures through surface-based Cu atoms for 1,4-diaminoanthraquinones (DAQs) has been studied by scanning tunneling microscopy (STM) at room temperature. On the Ag(110) surface, the transition from a hydrogen-bond network structure to metal-organic coordination structures of DAQs can be induced by introducing foreign copper atoms. Due to the weak interaction between DAQs and Ag(110), thermal treatment easily leads to the desorption of DAQs from the surface. To address this challenge, Cu(111) is selected as the substrate. Under thermal driving and in the presence of copper adatoms, the hydrogen-bond network structure of DAQs on the surface gradually undergoes a transition into a metal-coordinated structure, eventually leading to the formation of metal-organic complexes through amino dehydrogenation. It is demonstrated that the construction of a metal-organic coordination structure on metal surfaces is a result of the competition among factors such as metal atoms, functional groups of molecules, surface chemical activity, and temperature.

Quantifying shrub-shrub competition in drylands using aerial imagery and a novel landscape competition index.

The Jornada Basin Long-Term Ecological Research Site (JRN-LTER, or JRN) is a semiarid grassland-shrubland in southern New Mexico, USA. The role of intraspecific competition in constraining shrub growth and establishment at the JRN and in arid systems, in general, is an important question in dryland studies. Using information on shrub distributions and growth habits at the JRN, we present a novel landscape-scale (c. 1 ha) metric (the 'competition index', CI), which quantifies the potential intensity of competitive interactions. We map and compare the intensity of honey mesquite (Prosopis glandulosa, Torr.) competition spatially and temporally across the JRN-LTER, investigating associations of CI with shrub distribution, density, and soil types. The CI metric shows strong correlation with values of percent cover. Mapping CI across the Jornada Basin shows that high-intensity intraspecific competition is not prevalent, with few locations where intense competition is likely to be limiting further honey mesquite expansion. Comparison of CI among physiographic provinces shows differences in average CI values associated with geomorphology, topography, and soil type, suggesting that edaphic conditions may impose important constraints on honey mesquite and growth. However, declining and negative growth rates with increasing CI suggest that intraspecific competition constrains growth rates when CI increases above c. 0.5.

The Clinical Relevance of Autonomic Dysfunction, Cerebral Hemodynamics, and Sleep Interactions in Individuals Living With SCI.

A myriad of physiological impairments is seen in individuals after a spinal cord injury (SCI). These include altered autonomic function, cerebral hemodynamics, and sleep. These physiological systems are interconnected and likely insidiously interact leading to secondary complications. These impairments negatively influence quality of life. A comprehensive review of these systems, and their interplay, may improve clinical treatment and the rehabilitation plan of individuals living with SCI. Thus, these physiological measures should receive more clinical consideration. This special communication introduces the under investigated autonomic dysfunction, cerebral hemodynamics, and sleep disorders in people with SCI to stakeholders involved in SCI rehabilitation. We also discuss the linkage between autonomic dysfunction, cerebral hemodynamics, and sleep disorders and some secondary outcomes are discussed. Recent evidence is synthesized to make clinical recommendations on the assessment and potential management of important autonomic, cerebral hemodynamics, and sleep-related dysfunction in people with SCI. Finally, a few recommendations for clinicians and researchers are provided.

TiCl4precursor affecting the performance of HTM-free carbon-based perovskite solar cell.

The presence of TiO2used as an efficient electron transport layer is crucial to achieving high-performance solar cells, especially for a hole transport material (HTM)-free carbon-based perovskite solar cell (PSC). The hydrolysis of TiCl4is one of the most widely used routes for forming TiO2layer in solar cells, which includes the stock solution preparation from TiCl4initial precursor and the thermal hydrolysis of the stock solution. The second thermal hydrolysis step has been extensively studied, while the initial hydrolysis reaction in the first step is not receiving sufficient attention, especially for its influence on the photovoltaic performance of HTM-free carbon-based devices. In this study, the role of TiCl4stock solution in the growth process of TiO2layer is examined. Based on the analysis of the Ti(IV) intermediate states for different TiCl4concentrations from Raman spectra, 2 M TiCl4precursor exhibits moderate nucleation and growth kinetics without generating too many intermediates which occurs in 3 M TiCl4precursor, yielding ∼300 nm size spherical TiO2agglomerates with a rutile phase. In the aspect of devices, the HTM-free carbon-based PSCs fabricated using 2 M TiCl4precursor deliver a conversion efficiency beyond 17%, which may be attributed to the reduced defect in compact TiO2layer.

Synergistic role of circulating CD14++CD16+ monocytes and fibrinogen in predicting the cardiovascular events after myocardial infarction.

BACKGROUND: Monocytes and fibrinogen (FIB) play important roles in driving acute and reparative inflammatory pathways after myocardial infarction (MI). In humans, there are three subsets of monocytes, namely, CD14++CD16- (Mon1), CD14++CD16+ (Mon2), and CD14+CD16++ (Mon3). During the inflammatory response, monocyte subsets express high levels of integrin αM ß2 and protease-activated receptors 1 and 3 to interact with FIB. HYPOTHESIS: However, whether there is a synergistic role of FIB combined with Mon2 counts in prioritizing patients at high risk of future major adverse cardiovascular events (MACEs) after MI remains unknown. METHODS: The MI patients who treated with primary percutaneous coronary intervention were enrolled. MI patients were categorized into four groups, that is, low FIB/low Mon2, low FIB/high Mon2, high FIB/low Mon2, and high FIB/high Mon2, according to cutoff values of 3.28 g/L for FIB and 32.20 cells/µL for Mon2. Kaplan-Meier survival analysis and Cox proportional hazards models were used to estimate the risk of MACEs of MI patients during a median follow-up of 2.7 years. Mediating effects of high FIB levels and MACEs associated with high monocyte subsets were calculated by mediation analysis. RESULTS: High FIB/high Mon2 group had the highest risk of MACEs during a median follow-up of 2.7 years. Moreover, mediation analysis showed that a high FIB level could explain 24.9% (p < .05) of the increased risk of MACEs associated with Mon2. CONCLUSION: This work provides evidence indicating the translational potential of a synergistic role of FIB combined with Mon2 in prioritizing patients at high risk of future MACEs after MI.

Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non-forest ecosystems.

Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low-stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R 2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave-one-out cross-validation of 3.9%. Biomass per-unit-of-height was similar within but different among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1-10 ha-1. Photogrammetric approaches could provide much-needed information required to calibrate and validate the vegetation models and satellite-derived biomass products that are essential to understand vulnerable and understudied non-forested ecosystems around the globe.

Syntheses, structures, and magnetic properties of the lanthanide complexes of imidazole-substituted nitronyl nitroxide biradicals.

Two new bis-bidentate imidazole-substituted nitronyl nitroxide biradicals, BNITIm-C2 (BNITIm-C2 = 1,1'-(1,2-ethanediyl)bis(1H-imidazole-2-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-oxide)) and BNITIm-C4 (BNITIm-C4 = 1,1'-(1,4-butanediyl)bis(1H-imidazole-2-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxy-3-oxide)), and two series of lanthanide complexes, namely [(BNITIm-C2)Ln(NO3)3](MeOH) (Ln = Gd (1Gd) and Tb (2Tb)), (BNITIm-C2)Dy(NO3)3 (3Dy) and (BNITIm-C4)[Ln(hfac)3]2(C7H8)2 (Ln = Gd (4Gd), Tb (5Tb) and Dy (6Dy), hfac = hexafluoroacetylacetonate), have been prepared and characterized structurally and magnetically. Single crystal X-ray crystallographic analyses revealed that complexes 1Gd-3Dy exhibit 1D chain structures where the Ln(NO3)3 units are bridged by the BNITIm-C2 bis-bidentate biradical, while complexes 4Gd-6Dy exhibit binuclear structures with two Ln(hfac)3 units bridged by the BNITIm-C4 biradical. The bulky hfac anions prohibit the further coordination of LnIII to another NIT ligand and the formation of a similar 1D chain structure. Due to the very long intra- and intermolecular distances of the spin centers, complexes 1Gd-3Dy can be magnetically regarded as an isolated 2p-4f-2p tri-spin system while complex 4Gd-6Dy can be regarded as an isolated 2p-4f bi-spin system. Magnetic analyses on the two GdIII compounds revealed the ferromagnetic GdIII-NIT interactions and antiferromagnetic NIT-NIT interactions through the GdIII ion in 1Gd. Alternating-current (ac) magnetic susceptibility investigations revealed that complex 5Tb exhibits the typical SMM behavior under a zero dc field while complex 6Dy was proved to be a field-induced SMM. Ab initio calculations were performed on complexes 2Tb and 5Tb to understand their magnetic anisotropy together with their different magnetic dynamics.

Anion Modified Spin Crossover in [Fe(qsal-4-F)]+ Complexes with a 4-Position Substituted Qsal Ligand.

Four iron(III) complexes, [Fe(qsal-4-F)2]Y·sol (Hqsal-4-F = 4-fluoro-N-(8-quinolyl)salicylaldimine; Y = NO3-, sol = 0.91MeOH·0.57H2O (1NO3); Y = PF6- (2PF6); Y = BF4- (3BF4); Y = OTf-, sol =1.5MeOH (4OTf)), with a new 4-position substituted qsal type ligand Hqsal-4-F have been synthesized and structurally and magnetically characterized. Complexes 1NO3-3BF4 consist of 1D chains formed by the [Fe(qsal-4-F)2]+ cations connected by π-π and C-H···O interactions, which are further linked by more weak interactions to form 2D layers and 3D networks. On the other hand, complex 4OTf has a structure of nearly isolated 1D column where the [Fe(qsal-4-F)2]+ cations are connected by π-π, C-H···π, and C-F···π interactions. Magnetic studies revealed the occurrence of two-step symmetry-breaking SCO in 1NO3 and two-step gradual SCO in 2PF6. Complex 3BF4 undergoes a gradual SCO, whereas 4OTf remains almost high-spin. The smaller anions tend to stabilize the low-spin state, while larger anions tend to stabilize the high-spin state. In addition, the intermediate spin state of 1NO3 could be thermally trapped by quenching from the high temperature, thereby kinetically suppressing the spin transition to the full low-spin state. This work represents a good example that the position of the substituent and the anions plays critical roles in the preparation of SCO materials with tunable properties.

Imbibition-induced ultrafast assembly and printing of colloidal photonic crystals.

HYPOTHESIS: Self-assembly of colloidal particles enables the versatile fabrication of highly ordered structures and materials for optical, sensing, and other applications. Nevertheless, many traditional assembly processes are inefficient, because there exists an inevitable contradiction between time efficiency and crystalline quality. In this work, we introduce an ultrafast, robust, and scalable approach of imbibition-induced assembly. We assume that the instantaneous solvent imbibition induced by the nanoporous media could direct ultrafast self-assembly of colloidal particles into ordered structures. EXPERIMENTS: Self-assembly of colloidal particles from a droplet on a nanoporous substrate was firstly observed and investigated. A phase diagram of the thickness of the colloidal crystal as a function of the printing speed and the particle volume fraction was presented through systematic experiments. FINDINGS: The nanoporous substrate can induce strong capillary flow that will directthe rapid self-assemblyof particles intocolloidalcrystals. The imbibition-induced assembly was spatially and temporally combined with the meniscus-guided printing approach, and the printing speed can be improved by two orders of magnitude than the traditional evaporative assembly methods. We finally demonstrate an effective and ultrafast approach for assembling colloidal particles into photonic crystals with controllable sizes and shapes on the macroscale.

Wall-Confined Spreading Dynamics on the Surface of Surfactant Solution.

A liquid spreading over another is a universal physical process in the nature, which was investigated by the scaling law to reveal the underlying mechanical mechanism over the decades. However, scaling laws are restricted to piecewise physical stages, respectively. It is a challenge to present a full physical picture for a dynamic spreading process covering a wide-spectrum speed. We propose a general wall-confined spreading dynamics (WCSD) model originating from molecular kinetic theory (MKT). It creatively illustrates the order and domination between driving energy and energy dissipation (or transfer) using a phase diagram according to theory and experiments. This work reveals the deep mechanical mechanism of WCSD which provides an indirect guidance on the solution processing methods of two-dimensional molecular crystals (2DMCs) growth.

Pascal's Triangle Fractal Symmetries.

We introduce a model of interacting bosons exhibiting an infinite collection of fractal symmetries-termed "Pascal's triangle symmetries"-which provides a natural U(1) generalization of a spin-(1/2) system with Sierpinski triangle fractal symmetries introduced in Newman et al., [Phys. Rev. E 60, 5068 (1999).PLEEE81063-651X10.1103/PhysRevE.60.5068]. The Pascal's triangle symmetry gives rise to exact degeneracies, as well as a manifold of low-energy states which are absent in the Sierpinski triangle model. Breaking the U(1) symmetry of this model to Z_{p}, with prime integer p, yields a lattice model with a unique fractal symmetry which is generated by an operator supported on a fractal subsystem with Hausdorff dimension d_{H}=ln(p(p+1)/2)/lnp. The Hausdorff dimension of the fractal can be probed through correlation functions at finite temperature. The phase diagram of these models at zero temperature in the presence of quantum fluctuations, as well as the potential physical construction of the U(1) model, is discussed.

Temporal and Spatial Characterization of Mononuclear Phagocytes in Circulating, Pulmonary Alveolar, and Interstitial Compartments in LPS-Induced Acute Lung Injury.

Peripheral circulating monocytes and resident macrophages are heterogeneous effector cells that play a critical role in the maintenance and restoration of pulmonary integrity. However, their detailed dynamic changes in lipopolysaccharide (LPS)-induced acute lung injury (ALI) remain unclear. Here, we investigated the impact of mononuclear phagocyte cells in the development of LPS-induced ALI/Acute respiratory distress syndrome (ARDS) and described the relations between the dynamic phenotypic changes and pulmonary pathological evolution. In this study, mice were divided into two groups and intraperitoneally injected with normal saline (NS) or LPS, respectively. A series of flow cytometry assay was performed for the quantification of peripheral circulating monocyte subpopulations, detection of the polarization state of bronchoalveolar lavage fluid (BALF)-isolated alveolar macrophages (AMϕ) and pulmonary interstitial macrophages (IMϕ) separated from lung tissues. Circulating Ly6Clo monocytes expanded rapidly after the LPS challenge on day 1 and then decreased to day 7, while Ly6Chi monocytes gradually increased and returned to normal level on the 7th day. Furthermore, the expansion of M2-like AMϕ (CD64+CD206+) was peaked on day 1 and remained high on the third day, while the polarization state of IMϕ (CD64+ CD11b+) was not influenced by the LPS challenge at all the time points. Taken together, our findings show that Ly6Clo monocytes and M2-like AMϕ form the major peripheral circulation and pulmonary immune cell populations, respectively. The dynamic changes of mononuclear phagocyte in three compartments after the LPS challenge may provide novel protective strategies for mononuclear phagocytes.

High-resolution bin-based linkage mapping uncovers the genetic architecture and heterosis-related loci of plant height in indica-japonica derived populations.

Plant height (PH) is an important trait affecting the plant architecture, seed yield, and harvest index. However, the molecular mechanisms underlying PH heterosis remain unclear. In addition, useful PH-related genes must be urgently identified to facilitate ideal plant architecture breeding in rice (Oryza sativa L.). In the present study, to explore rice quantitative trait loci (QTLs) and heterosis-related loci of PH in rice, we developed a high-generation (>F15 ) population of 272 recombinant inbred lines (RIL) from a cross of two elite varieties, Luohui 9 (indica/xian) × RPY geng (japonica/geng), and two testcross hybrid populations derived from the crosses of RILs and two cytoplasmic male sterile lines (YTA [indica] and Z7A [japonica]). Using deep resequencing data, a high-density genetic map containing 4758 bin markers was constructed, with a total map distance of 2356.41 cM. Finally, 31 PH-related QTLs for different PH component lengths or tiller numbers across five seasons were identified. Two major environment-specific PH QTLs were stably detected in Hainan (qPH-3.1) or Hubei (qPH-5.1), which have undergone significant functional alterations in rice with changes in geographical environment. Based on comparative genomics, gene function annotation, homolog identification, and existing literature (pioneering studies), candidate genes for multiple QTLs were fine-mapped, and the candidate genes qPH-3.1 and qPH-5.1 for PH were further validated using CRISPR-Cas9 gene editing. Specifically, qPH-3.1 was characterized as a pleiotropic gene, and the qPH-3.1 knockout line showed reduced PH, delayed heading, a decreased seed setting rate, and increased tiller numbers. Importantly, 10 PH heterosis-related QTLs were identified in the testcross populations, and a better-parent heterosis locus (qBPH-5.2) completely covered qPH-5.1. Furthermore, the cross results of fixed-genotype RILs verified the dominant effects of qPH-3.1 and qPH-5.1. Together, these findings further our understanding of the genetic mechanisms of PH and offer multiple highly reliable gene targets for breeding rice varieties with ideal architecture and high yield potential in the immediate future.

Surface-mediated periodate activation by nano zero-valent iron for the enhanced abatement of organic contaminants.

Periodate (PI)-based advanced oxidation processes have recently received increasing attentions. Herein, PI was readily activated by nano zero-valent iron (nZVI) and subsequently led to the enhanced oxidation of organic contaminants, with the removal performance of sulfadiazine (SDZ) in the nZVI/PI process even higher than that in the nZVI/peroxydisulfate process under identical conditions. Kinetic experiments indicated that the decay of SDZ was susceptible to the dosage of nZVI and PI, but was barely affected by pH values (4.0-7.0) under buffered conditions, suggesting the promising performance of the nZVI/PI process in a relatively wide pH range. Selective degradation of contaminants and 18O-isotope labeling assays collectively demonstrated that iodate radical (•IO3), high-valent iron-oxo species (Fe(IV)) and hydroxyl radical (•OH) were responsible for the abatement of organic contaminants. More importantly, due to the relatively weak steric hindrance effect of PI, PI easily adsorbed on the surface of nZVI and no iron leaching was detected throughout the reaction, implying that PI activation induced by nZVI was a surface-mediated process. Besides, PI was not transformed into harmful reactive iodine species. This study proposed an environmental-friendly approach for PI activation and shed new lights on the PI-based processes.

Highly selective oxidation of organic contaminants in the RuIII-activated peroxymonosulfate process: The dominance of RuVO species.

Ruthenium (RuIII)-activated peroxymonosulfate (the RuIII/PMS process) is one of the most efficient PMS-based advanced oxidation processes for the abatement of organic contaminants. Here we interestingly found that phenyl methyl sulfoxide (PMSO) was significantly oxidized to phenyl methyl sulfone (PMSO2) in the RuIII/PMS process at the pH range of 3.0-6.0, with the conversion ratio of ΔPMSO to ΔPMSO2 was close to 100%, which favored the dominance of high-valent ruthenium-oxo species (RuVO) instead of the widely-recognized radicals (i.e, hydroxyl radical and sulfate radical). Scavenging experiments further indicated that RuVO was unreactive to tert-butyl alcohol, but could be scavenged by methanol and dimethyl sulfoxide. Besides, sulfamethoxazole, acetaminophen, carbamazepine, diclofenac, 2,4,6-trichlorophenol were readily degraded in the RuIII/PMS process, but atrazine, ibuprofen, benzoic acid and 4-nitrobenzoic acid were barely removed, suggesting the high selectivity of RuVO species. This study enriched the understandings on the mechanism of RuIII-mediated PMS activation and the nature of RuVO species.

LncRNA HCP5 in hBMSC-derived exosomes alleviates myocardial ischemia reperfusion injury by sponging miR-497 to activate IGF1/PI3K/AKT pathway.

Ischemia/reperfusion (I/R) injury is an inevitable process during heart transplant and suppressing I/R injury could greatly improve the survival rate of recipients. Mesenchymal stem cells (MSCs) have positive effects on I/R. We aimed to investigate the mechanisms underlying the protective roles of MSCs in I/R. Both cell model and rat model of myocardial I/R were used. MTT assay and flow cytometry were used to measure cell viability and apoptosis, respectively. QRT-PCR and western blotting were employed to measure levels of lncRNA HCP5 (HLA complex P5), miR-497, apoptosis-related proteins, and insulin-like growth factor (IGF1)/PI3K/AKT pathway. Dual luciferase assay was used to validate interactions of HCP5 and miR-497, miR-497 and IGF1. Echocardiography was performed to evaluate cardiac function of rats. Serum levels of CK-MB and LDH were measured. H&E and Masson staining were used to examine morphology of myocardial tissues. hBMSC-derived exosomes (hBMSC-Exos) increased the viability of cardiomyocytes following hypoxia/reperfusion (H/R) and decreased apoptosis. H/R diminished HCP5 expression in cardiomyocytes while hBMSC-Exos recovered the level. Overexpression of HCP5 in hBMSC-Exos further enhanced the protective effects in H/R while HCP5 knockdown suppressed. HCP5 directly bound miR-497 and miR-497 targeted IGF1. miR-497 mimics or si-IGF1 blocked the effects of HCP5 overexpression. Further, hBMSC-Exos alleviated I/R injury in vivo and knockdown of HCP5 in hBMSC-Exos decreased the beneficial effects. AntagomiR-497 blocked the effects of HCP5 knockdown. HCP5 from hBMSC-Exos protects cardiomyocytes against I/R injury via sponging miR-497 to disinhibit IGF1/PI3K/AKT pathway. These results shed light on mechanisms underlying the protective role of hBMSC-Exos in I/R.

Study becomes insight: Ecological learning from machine learning.

The ecological and environmental science communities have embraced machine learning (ML) for empirical modelling and prediction. However, going beyond prediction to draw insights into underlying functional relationships between response variables and environmental 'drivers' is less straightforward. Deriving ecological insights from fitted ML models requires techniques to extract the 'learning' hidden in the ML models.We revisit the theoretical background and effectiveness of four approaches for deriving insights from ML: ranking independent variable importance (Gini importance, GI; permutation importance, PI; split importance, SI; and conditional permutation importance, CPI), and two approaches for inference of bivariate functional relationships (partial dependence plots, PDP; and accumulated local effect plots, ALE). We also explore the use of a surrogate model for visualization and interpretation of complex multi-variate relationships between response variables and environmental drivers. We examine the challenges and opportunities for extracting ecological insights with these interpretation approaches. Specifically, we aim to improve interpretation of ML models by investigating how effectiveness relates to (a) interpretation algorithm, (b) sample size and (c) the presence of spurious explanatory variables.We base the analysis on simulations with known underlying functional relationships between response and predictor variables, with added white noise and the presence of correlated but non-influential variables. The results indicate that deriving ecological insight is strongly affected by interpretation algorithm and spurious variables, and moderately impacted by sample size. Removing spurious variables improves interpretation of ML models. Meanwhile, increasing sample size has limited value in the presence of spurious variables, but increasing sample size does improves performance once spurious variables are omitted. Among the four ranking methods, SI is slightly more effective than the other methods in the presence of spurious variables, while GI and SI yield higher accuracy when spurious variables are removed. PDP is more effective in retrieving underlying functional relationships than ALE, but its reliability declines sharply in the presence of spurious variables. Visualization and interpretation of the interactive effects of predictors and the response variable can be enhanced using surrogate models, including three-dimensional visualizations and use of loess planes to represent independent variable effects and interactions.Machine learning analysts should be aware that including correlated independent variables in ML models with no clear causal relationship to response variables can interfere with ecological inference. When ecological inference is important, ML models should be constructed with independent variables that have clear causal effects on response variables. While interpreting ML models for ecological inference remains challenging, we show that careful choice of interpretation methods, exclusion of spurious variables and adequate sample size can provide more and better opportunities to 'learn from machine learning'.

Woody-biomass projections and drivers of change in sub-Saharan Africa.

Africa's ecosystems have an important role in global carbon dynamics, yet consensus is lacking regarding the amount of carbon stored in woody vegetation and the potential impacts to carbon storage in response to changes in climate, land use, and other Anthropocene risks. Here, we explore the socio-environmental conditions that shaped the contemporary distribution of woody vegetation across sub-Saharan Africa and evaluate ecosystem response to multiple scenarios of climate change, anthropogenic pressures, and fire disturbance. Our projections suggest climate change will have a small but negative effect on above ground woody biomass at the continental scale, and the compounding effects of population growth, increasing human pressures, and socio-climatic driven changes in fire behavior further exacerbate climate-driven trends. Relatively modest continental-scale trends obscure much larger regional perturbations, with climatic and anthropogenic factors leading to increased carbon storage potential in East Africa, offset by large deficits in West, Central, and Southern Africa.