Validation of a dermatoscopy-based algorithm for the diagnosis of acral melanoma.

INTRODUCTION: Diagnosis of acral melanocytic lesions can be challenging. The BRAAFF checklist was introduced as a tool to help differentiate between acral nevi and melanoma but has not been validated. METHODS: We asked raters with varying expertise in dermatoscopy to diagnose dermatoscopic images of 533 acral nevi and 144 melanomas via an online platform with and without use of the BRAAFF checklist. From the ratings we calculated sensitivity, specificity, and interrater agreement. Additionally, a new simplified version of the checklist was also tested. RESULTS: We collected 6880 ratings from 175 readers. The BRAAFF checklist achieved a sensitivity of 92.5% and a specificity of 65.0%, which was similar to diagnosis from pattern recognition (sensitivity 90.0%, specificity: 72.1%). Interrater agreement for the BRAAFF criteria ranged from fair to moderate, with lowest agreement for parallel ridge and fibrillar pattern (alpha=0.31) and highest for asymmetry of colors and structures (alpha=0.46). Agreement and diagnostic accuracy were higher for more experienced readers. A simplified version with only two criteria achieved similar sensitivity (95.0%) and lower specificity (60.0%) as the original BRAAFF checklist. Conclusion: The BRAAFF checklist is a useful tool for the diagnosis of melanocytic acral lesions with acceptable sensitivity and reasonable specificity but is not superior to pattern recognition. A simplified version of the checklist could be easier to use with equal sensitivity while exhibiting a modest reduction in specificity.

Conventional one-handed compared to two-handed endoscopic ear surgery using an endoscope holder: a single center study.

INTRODUCTION: One-handedness is a challenge in conventional endoscopic ear surgery (EES). We present results on the first-ever application of the passive endoscope holder 'Endofix exo' (Co. AKTORmed GmbH, Neutraubling, Germany) in EES, which enables two-handed surgery. METHODS: This two-sided study compares cut-suture time, operating time, postoperative complications, graft take rates, hearing results and quality of life in patients who underwent first stage tympanoplasty due to tympanic membrane perforation with intact ossicular chain conditions. 25 patients received classic EES (EES-, mean age: 28 ± 21 years) and 15 received EES with the passive holder (EES+, mean age: 48 ± 21 years). RESULTS: Mean operating times (EES-: 96 ± 38 (SD) min; EES+: 107 ± 33 min), cut-suture times (EES-: 68 ± 30 min; EES+: 73 ± 31 min), complications, graft take rates and hearing results (preoperative air bone gap (ABG) (PTA4): 15 dB ± SD 8 dB (EES-); 16 dB ± SD 8 dB (EES+); postoperative ABG (PTA4): 11.25dB ± SD 11.3dB (EES-); 14 dB ± SD 10 dB (EES+)) did not differ significantly (p > 0.05) between the two groups. Postoperative hearing results and quality of life tended to improve in both groups (p > 0.05). DISCUSSION: The passive endoscope holder has been successfully applied during the course of the study. However, modifications of the endoscope holder and further studies are recommended focusing on positioning of grafts and prostheses to obtain conclusive results regarding the superiority of two-handed EES over one-handed conventional EES.

Microbial Inoculants Drive Changes in Soil and Plant Microbiomes and Improve Plant Functions in Abandoned Mine Restoration.

The application of microbial inoculants holds promise for the sustainable restoration of abandoned mine sites by affecting soil nutrients and microbial communities. However, the responses of plant microbial communities to microbial inoculants in mine restoration remain largely unknown. To bridge this knowledge gap, we conducted a 4-year field experiment at an abandoned carbonate mine site to assess the impacts of microbial inoculants on the soil-plant microbiome. Our findings revealed that microbial inoculants significantly changed roots, fine root bacterial and fungal communities. Further, no significant correlations were observed between the soil-plant nutrient content (Z-score) and microbial alpha diversity. However, a significantly positive correlation was found between the relative abundance of the keystone ecological cluster (Module #1) and soil-plant nutrient content. The application of microbial inoculants also increased complexity, albeit decreased stability of plant microbiome networks, alongside a reduction in stochastic assembly. Conversely, they decreased the complexity but increased the stability of soil microbiome networks, accompanied by an increase in stochastic assembly. Notably, the number of specifically enriched microbiome functional traits of roots and root nodules under the microbial inoculant treatments surpassed that of the control. In summary, our findings underscored the potential of microbial inoculants to enhance soil-plant functionality at abandoned mine restoration sites.

Reduction of Cardiac Allograft Vasculopathy by PCI: Quantification and Correlation With Outcome After Heart Transplantation.

BACKGROUND: Percutaneous coronary intervention (PCI) might improve outcome at severe stages of cardiac allograft vasculopathy (CAV) among patients after heart transplantation (HTx). Yet, risk stratification of HTx patients after PCI remains challenging. AIMS: To assess whether the International Society for Heart and Lung Transplantation (ISHLT) CAV classification remains prognostic after PCI and whether risk-stratification models of non-transplanted patients extend to HTx patients with CAV. METHODS: At 2 European academic centers, 203 patients were stratified in cohort 1 (ISHLT CAV1, without PCI, n = 126) or cohort 2 (ISHLT CAV2 and 3, with PCI). At first diagnosis of CAV or first PCI, respectively, ISHLT CAV grades, SYNTAX scores I and II (SXS-I, SXS-II) were used to quantify baseline and residual CAV (rISHLT, rSXS-I, rSXS-II). RSXS-I > 0 defined incomplete revascularization (IR). RESULTS: SXS-II predicted mortality in cohort 1 (P = 0.004), whereas SXS-I (P = 0.009) and SXS-II (P = 0.002) predicted mortality in cohort 2. Post-PCI, IR (P = 0.004), high rISHLT (P = 0.02) and highest tertile of rSXS-II (P = 0.006) were associated with higher 5-year mortality. In bivariable Cox analysis, baseline SXS-II, IR and rSXS-II remained predictors of 5-year mortality post-PCI. There was a strong inverse relationship between baseline and rSXS-I (r = -0.55; P < 0.001 and r = -0.50; P = 0.003, respectively) regarding the interval to first reintervention. CONCLUSION: People with ISHLT CAV classification could apply for risk stratification after PCI. SYNTAX scores could be complemental for risk stratification and individualization of invasive follow-up of HTx patients with CAV.

Global Ecosystem Nitrogen Cycling Reciprocates Between Land-Use Conversion and Its Reversal.

Anthropogenic land-use practices influence ecosystem functions and the environment. Yet, the effect of global land-use change on ecosystem nitrogen (N) cycling remains unquantified despite that ecosystem N cycling plays a critical role in maintaining food security. Here, we analysed 2430 paired observations globally to show that converting natural to managed ecosystems increases ratios of autotrophic nitrification to ammonium immobilisation and nitrate to ammonium, but decreases soil immobilisation of mineral N, causing increased N losses via leaching and gaseous N emissions, such as nitrous oxide (e.g., via denitrification), resulting in a leaky N cycle. Changing land use from intensively managed to one that resembles natural ecosystems reversed N losses by 108% on average, resulting in a more conservative N cycle. Structural equation modelling revealed that changes in soil organic carbon, pH and carbon to N ratio were more important than changes in soil moisture content and temperature in predicting ecosystem N retention capacities following land-use conversion and its reversion. The hotspots of leaky N cycles were mostly in equatorial and tropical regions, as well as in Western Europe, the United States and China. Our results suggest that whether an ecosystem exhibits a conservative N cycle after land-use reversion depends on management practices.

Systematic Comparison of Extract Clean-Up with Currently Used Sorbents for Dispersive Solid-Phase Extraction.

Dispersive solid-phase extraction (dSPE) is a crucial step for multiresidue analysis used to remove matrix components from extracts. This purification prevents contamination of instrumental equipment and improves method selectivity, sensitivity, and reproducibility. Therefore, a clean-up step is recommended, but an over-purified extract can lead to analyte loss due to adsorption to the sorbent. This study provides a systematic comparison of the advantages and disadvantages of the well-established dSPE sorbents PSA, GCB, and C18 and the novel dSPE sorbents chitin, chitosan, multi-walled carbon nanotube (MWCNT), and Z-Sep® (zirconium-based sorbent). They were tested regarding their clean-up capacity by visual inspection, UV, and GC-MS measurements. The recovery rates of 98 analytes, including pesticides, active pharmaceutical ingredients, and emerging environmental pollutants with a broad range of physicochemical properties, were determined by GC-MS/MS. Experiments were performed with five different matrices, commonly used in food analysis (spinach, orange, avocado, salmon, and bovine liver). Overall, Z-Sep® was the best sorbent regarding clean-up capacity, reducing matrix components to the greatest extent with a median of 50% in UV and GC-MS measurements, while MWCNTs had the largest impact on analyte recovery, with 14 analytes showing recoveries below 70%. PSA showed the best performance overall.

Material Engineering Solutions toward Selective Redox Catalysts for Chemical-Looping-Based Olefin Production Schemes: A Review.

Chemical looping (CL) has emerged as a promising approach in the oxidative dehydrogenation (ODH) of light alkanes, offering an opportunity for significant reductions in emissions and energy consumption in the ethylene and propylene production industry. While high olefin yields are achievable via CL, the material requirements (e.g., electronic and geometric structures) that prevent the total conversion of alkanes to CO x are not clearly understood. This review aims to give a concise understanding of the nucleophilic oxygen species involved in the selective reaction pathways for olefin production as well as of the electrophilic oxygen species that promote an overoxidation to CO x products. It further introduces advanced characterization techniques such as X-ray photoelectron spectroscopy, Raman spectroscopy, electron paramagnetic resonance spectroscopy, and resonant inelastic X-ray scattering, which have been employed successfully in identifying such reactive oxygen species. To mitigate CO x formation and enhance olefin selectivity, material engineering solutions are discussed. Common techniques include doping of the bulk or surface and the deposition of functional coatings. In the context of energy consumption and CO2 intensity, techno-economic assessments of CL-ODH systems have predicted energy savings of up to 80% compared to established olefin production processes such as steam cracking or dehydrogenation. Finally, although their practical application has been limited to date, the potential advantages of the use of fluidized bed reactors in CL-ODH are presented.

Imaging the pancreas with photon-counting CT - A review of normal pancreatic anatomy.

PURPOSE: Compared to conventional energy integrating detector CT, Photon-Counting CT (PCCT) has the advantage of increased spatial resolution. The pancreas is a highly complex organ anatomically. The increased spatial resolution of PCCT challenges radiologists' knowledge of pancreatic anatomy. The purpose of this review was to review detailed macroscopic and microscopic anatomy of the pancreas in the context of current and future PCCT. METHOD: This review is based on a literature review of all parts of pancreatic anatomy and a retrospective imaging review of PCCT scans from 20 consecutively included patients without pancreatic pathology (mean age 61.8 years, 11 female), scanned in the workup of pancreatic cancer with a contrast enhanced multiphase protocol. Two radiologists assessed the visibility of the main and accessory pancreatic ducts, side ducts, ampulla, major papilla, minor papilla, pancreatic arteries and veins, regional lymph nodes, coeliac ganglia, and coeliac plexus. RESULTS: The macroscopic anatomy of the pancreas was consistently visualized with PCCT. Visualization of detailed anatomy of the ductal system (including side ducts), papillae, arteries, vein, lymph nodes, and innervation was possible in 90% or more of patients with moderate to good interreader agreement. CONCLUSION: PCCT scans of the pancreas visualizes previously unseen or inconsistently seen small anatomical structures consistently. Increased knowledge of pancreatic anatomy could have importance in imaging of pancreatic cancer and other pancreatic diseases.

A global dataset of gross nitrogen transformation rates across terrestrial ecosystems.

Rates of nitrogen transformations support quantitative descriptions and predictive understanding of the complex nitrogen cycle, but measuring these rates is expensive and not readily available to researchers. Here, we compiled a dataset of gross nitrogen transformation rates (GNTR) of mineralization, nitrification, ammonium immobilization, nitrate immobilization, and dissimilatory nitrate reduction to ammonium in terrestrial ecosystems. Data were extracted from 331 studies published from 1984-2022, covering 581 sites. Globally, 1552 observations were appended with standardized soil, vegetation, and climate data (49 variables in total) potentially contributing to the observed variations of GNTR. We used machine learning-based data imputation to fill in partially missing GNTR, which improved statistical relationships between theoretically correlated processes. The dataset is currently the most comprehensive overview of terrestrial ecosystem GNTR and serves as a global synthesis of the extent and variability of GNTR across a wide range of environmental conditions. Future research can utilize the dataset to identify measurement gaps with respect to climate, soil, and ecosystem types, delineate GNTR for certain ecoregions, and help validate process-based models.

Structural insight into the DNMT1 reaction cycle by cryo-electron microscopy.

DNMT1 is an essential DNA methyltransferase that catalyzes the transfer of methyl groups to CpG islands in DNA and generates a prominent epigenetic mark. The catalytic activity of DNMT1 relies on its conformational plasticity and ability to change conformation from an auto-inhibited to an activated state. Here, we present four cryo-EM reconstructions of apo DNMT1 and DNTM1: non-productive DNA, DNTM1: H3Ub2-peptide, DNTM1: productive DNA complexes. Our structures demonstrate the flexibility of DNMT1's N-terminal regulatory domains during the transition from an apo 'auto-inhibited' to a DNA-bound 'non-productive' and finally a DNA-bound 'productive' state of DNMT1. Furthermore, we address the regulation of DNMT1's methyltransferase activity by a DNMT1-selective small-molecule inhibitor and ubiquitinated histone H3. We observe that DNMT1 binds DNA in a 'non-productive' state despite the presence of the inhibitor and present the cryo-EM reconstruction of full-length DNMT1 in complex with a di-ubiquitinated H3 peptide analogue. Taken together, our results provide structural insights into the reaction cycle of DNMT1.

Antibiotic-loaded nanoparticles for the treatment of intracellular methicillin-resistant Staphylococcus Aureus infections: In vitro and in vivo efficacy of a novel antibiotic.

Antimicrobial resistance is considered one of the biggest threats to public health worldwide. Methicillin-resistant S. aureus is the causative agent of a number of infections and lung colonization in people suffering from cystic fibrosis. Moreover, a growing body of evidence links the microbiome to the development of cancer, as well as to the success of the treatment. In this view, the development of novel antibiotics is of critical importance, and SV7, a novel antibiotic active against MRSA at low concentrations, represents a promising candidate. However, the low aqueous solubility of SV7 hampers its therapeutic translation. In this study, SV7 was encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) to improve the solubility profile, to ensure sustained release and eventually support deposition in the airways. Furthermore, PLGA NPs were formulated as dry powder to extend their shelf-life and were shown to efficiently target intracellular infections. After identifying a formulation with suitable physico-chemical characteristics, SV7-loaded NPs were investigated in vitro in terms of inhibitory activity against MRSA, and their safety profile in lung epithelial cells. Subsequently, the activity against MRSA intracellular infections was investigated in a co-culture model of MRSA and macrophages. To test the translatability of our findings, SV7-loaded NPs were tested in vivo in a Galleria mellonella infection model. In conclusion, SV7-loaded NPs showed a safe profile and efficient inhibitory activity against MRSA at low concentrations. Furthermore, their activity against intracellular infections was confirmed, and was retained in vivo, rendering them a promising candidate for treatment of MRSA lung infections.

Plant-based and planetary-health diets, environmental burden, and risk of mortality: a prospective cohort study of middle-aged and older adults in China.

BACKGROUND: Plant-based diets (PBDs) and planetary-health diets (PHDs) are recommended for their potential health and environmental benefits, but population-based evidence in diverse cultures is scarce. METHODS: We included 9364 adults aged 45 years and older (52·3% female, 47·7% male) from the open cohort of the China Health and Nutrition Survey. Dietary intake was assessed using 3-day 24 h dietary recalls combined with weighing methods from 1997 to 2011, and mortality was documented from 1997 to 2015. We calculated the overall PBD index (PDI), healthful PBD index (hPDI), and unhealthful PBD index (uPDI; ranges 18-90), and the PHD score (range 0-140). We also estimated the related greenhouse gas emissions, land appropriation, and total water footprint and examined their associations with mortality. FINDINGS: PBD indices were inversely related to greenhouse gas emissions, land appropriation, and total water footprint, whereas higher PHD score was related to higher environmental burdens (p<0·0001). During follow-up (mean 9·2 years), 792 (8·5%) death cases were documented. PDI (HR 1·08 [95% CI 0·88-1·32]) and hPDI (0·98 [0·80-1·21]) were not significantly associated with mortality, whereas higher uPDI was related to a higher mortality risk (1·55 [1·26-1·91]). In contrast, higher PHD score was associated with lower mortality risk (0·79 [0·63-0·99]). INTERPRETATION: The PBDs showed environmental benefits, but are not necessarily associated with lower mortality risk. The PHD, developed mainly in western populations, was related to lower mortality risk but higher environmental burdens in the Chinese population. FUNDING: Fundamental Research Funds for the Central Universities, Zhejiang University Global Partnership Fund, and National Natural Science Foundation of China.

Enhancing soil gross nitrogen transformation through regulation of microbial nitrogen-cycling genes by biodegradable microplastics.

Microplastics (MPs) in agricultural plastic film mulching system changes microbial functions and nutrient dynamics in soils. However, how biodegradable MPs impact the soil gross nitrogen (N) transformations and crop N uptake remain significantly unknown. In this study, we conducted a paired labeling 15N tracer experiment and microbial N-cycling gene analysis to investigate the dynamics and mechanisms of soil gross N transformation processes in soils amended with conventional (polyethylene, PE) and biodegradable (polybutylene adipate co-terephthalate, PBAT) MPs at concentrations of 0 %, 0.5 %, and 2 % (w/w). The biodegradable MPs-amended soils showed higher gross N mineralization rates (0.5-16 times) and plant N uptake rates (16-32 %) than soils without MPs (CK) and with conventional MPs. The MPs (both PE and PBAT) with high concentration (2 %) increased gross N mineralization rates compared to low concentration (0.5 %). Compare to CK, MPs decreased the soil gross nitrification rates, except for PBAT with 2 % concentration; while PE with 0.5 % concentration and PBAT with 2 % concentration increased but PBAT with 0.5 % concentration decreased the gross N immobilization rates significantly. The results indicated that there were both a concentration effect and a material effect of MPs on soil gross N transformations. Biodegradable MPs increased N-cycling gene abundance by 60-103 %; while there was no difference in the abundance of total N-cycling genes between soils without MPs and with conventional MPs. In summary, biodegradable MPs increased N cycling gene abundance by providing enriched nutrient substrates and enhancing microbial biomass, thereby promoting gross N transformation processes and maize N uptake in short-term. These findings provide insights into the potential consequences associated with the exposure of biodegradable MPs, particularly their impact on soil N cycling processes.

Reinforcement learning-based anatomical maps for pancreas subregion and duct segmentation.

BACKGROUND: The pancreas is a complex abdominal organ with many anatomical variations, and therefore automated pancreas segmentation from medical images is a challenging application. PURPOSE: In this paper, we present a framework for segmenting individual pancreatic subregions and the pancreatic duct from three-dimensional (3D) computed tomography (CT) images. METHODS: A multiagent reinforcement learning (RL) network was used to detect landmarks of the head, neck, body, and tail of the pancreas, and landmarks along the pancreatic duct in a selected target CT image. Using the landmark detection results, an atlas of pancreases was nonrigidly registered to the target image, resulting in anatomical probability maps for the pancreatic subregions and duct. The probability maps were augmented with multilabel 3D U-Net architectures to obtain the final segmentation results. RESULTS: To evaluate the performance of our proposed framework, we computed the Dice similarity coefficient (DSC) between the predicted and ground truth manual segmentations on a database of 82 CT images with manually segmented pancreatic subregions and 37 CT images with manually segmented pancreatic ducts. For the four pancreatic subregions, the mean DSC improved from 0.38, 0.44, and 0.39 with standard 3D U-Net, Attention U-Net, and shifted windowing (Swin) U-Net architectures, to 0.51, 0.47, and 0.49, respectively, when utilizing the proposed RL-based framework. For the pancreatic duct, the RL-based framework achieved a mean DSC of 0.70, significantly outperforming the standard approaches and existing methods on different datasets. CONCLUSIONS: The resulting accuracy of the proposed RL-based segmentation framework demonstrates an improvement against segmentation with standard U-Net architectures.

An investigation of the structural and electronic origins of enhanced chemical looping air separation performance of B-site substituted SrFe1-xCoxO3-δ perovskites.

Chemical looping air separation (CLAS) is a promising process intensification technology for extracting oxygen from air for oxygen enrichment in process streams. Co-doped strontium ferrites (SrFe1-xCoxO3-δ) have been found to have outstanding activities for CLAS processes. In this study, we explore the underlying factors driving the enhancement in oxygen uptake and release performance of perovskite structured SrFe1-xCoxO3-δ oxygen carriers for CLAS. Phase-pure perovskites, with B site substituted by up to 75 mol% Co, were prepared by a sol-gel method and systematically investigated through a wide range of well controlled experimental and computational approaches. While all SrFe1-xCoxO3-δ oxygen carriers showed excellent cyclic stability and structural reversibility over CLAS cycles, increased B site occupancy by Co resulted in monotonic decrease in onset temperature for oxygen release and increase in oxygen carrying capacity. These experimental trends can be fundamentally explained by an increase in the structural tolerance factor, an elevation in transition metal d-band, as well as an increased degree of hybridization between the metal d-band and the O p band. Therefore, these ab initio structural and electronic descriptors are useful design rationales for the hypothesis-driven synthesis of high-performing oxygen carriers for CLAS.

Toxic eburicol accumulation drives the antifungal activity of azoles against Aspergillus fumigatus.

Azole antifungals inhibit the sterol C14-demethylase (CYP51/Erg11) of the ergosterol biosynthesis pathway. Here we show that the azole-induced synthesis of fungicidal cell wall carbohydrate patches in the pathogenic mold Aspergillus fumigatus strictly correlates with the accumulation of the CYP51 substrate eburicol. A lack of other essential ergosterol biosynthesis enzymes, such as sterol C24-methyltransferase (Erg6A), squalene synthase (Erg9) or squalene epoxidase (Erg1) does not trigger comparable cell wall alterations. Partial repression of Erg6A, which converts lanosterol into eburicol, increases azole resistance. The sterol C5-desaturase (ERG3)-dependent conversion of eburicol into 14-methylergosta-8,24(28)-dien-3ß,6α-diol, the "toxic diol" responsible for the fungistatic activity against yeasts, is not required for the fungicidal effects in A. fumigatus. While ERG3-lacking yeasts are azole resistant, ERG3-lacking A. fumigatus becomes more susceptible. Mutants lacking mitochondrial complex III functionality, which are much less effectively killed, but strongly inhibited in growth by azoles, convert eburicol more efficiently into the supposedly "toxic diol". We propose that the mode of action of azoles against A. fumigatus relies on accumulation of eburicol which exerts fungicidal effects by triggering cell wall carbohydrate patch formation.

Uncovering Atomic-scale Dynamics in Solid Catalysts via X-ray-based Methods.

Deciphering the structural intricacies of catalysts is essential to advance their atomic-scale engineering. Solid catalysts are complex, with structural features spanning multiple length scales and involving dynamics, which possess challenges in understanding structure-performance relationships. However, advanced operando X-ray characterization techniques, including X-ray absorption spectroscopy (XAS), diffraction (XRD), and pair distribution function analysis (PDF) allow elucidation of structural features under working conditions, discovering transitions from supported nanocrystals to dispersed sites, from solid solutions to supported nanoparticles, or structural changes at the local level. In this mini-review, we discuss case studies exploring the structure of catalysts over different lengths and time scales under different applications, such as CO2 hydrogenation to methanol or the dry reforming of methane, using a combination of operando XAS, XRD and PDF.

Meta-analysis reveals the effects of microbial inoculants on the biomass and diversity of soil microbial communities.

Microbial inoculation involves transplanting microorganisms from their natural habitat to new plants or soils to improve plant performance, and it is being increasingly used in agriculture and ecological restoration. However, microbial inoculants can invade and alter the composition of native microbial communities; thus, a comprehensive analysis is urgently needed to understand the overall impact of microbial inoculants on the biomass, diversity, structure and network complexity of native communities. Here we provide a meta-analysis of 335 studies revealing a positive effect of microbial inoculants on soil microbial biomass. This positive effect was weakened by environmental stress and enhanced by the use of fertilizers and native inoculants. Although microbial inoculants did not alter microbial diversity, they induced major changes in the structure and bacterial composition of soil microbial communities, reducing the complexity of bacterial networks and increasing network stability. Finally, higher initial levels of soil nutrients amplified the positive impact of microbial inoculants on fungal biomass, actinobacterial biomass, microbial biomass carbon and microbial biomass nitrogen. Together, our results highlight the positive effects of microbial inoculants on soil microbial biomass, emphasizing the benefits of native inoculants and the important regulatory roles of soil nutrient levels and environmental stress.

Implications for the Hydrogenation of Propyne and Propene with Parahydrogen due to the in†situ Transformation of Rh2C to Rh0/C.

NMR spectroscopy studies using parahydrogen-induced polarization have previously established the existence of the pairwise hydrogen addition route in the hydrogenation of unsaturated hydrocarbons over heterogeneous catalysts, including those based on rhodium (Rh0). This pathway requires the incorporation of both hydrogen atoms from one hydrogen molecule to the same product molecule. However, the underlying mechanism for such pairwise hydrogen addition must be better understood. The involvement of carbon, either in the form of carbonaceous deposits on the surface of a catalyst or as a metal carbide phase, is known to modify catalytic properties significantly and thus could also affect the pairwise hydrogen addition route. Here, we explored carbon's role by studying the hydrogenation of propene and propyne with parahydrogen on a Rh2C catalyst and comparing the results with those for a Rh0/C catalyst obtained from Rh2C via H2 pretreatment. While the catalysts Rh2C and Rh0/C differ notably in the rate of conversion of parahydrogen to normal hydrogen as well as in terms of hydrogenation activity, our findings suggest that the carbide phase does not play a significant role in the pairwise H2 addition route on rhodium catalysts.