Climate warming could free cold-adapted trees from C-conservative allocation strategy of storage over growth.

Carbon allocation has been fundamental for long-lived trees to survive cold stress at their upper elevation range limit. Although carbon allocation between non-structural carbohydrate (NSC) storage and structural growth is well-documented, it still remains unclear how ongoing climate warming influences these processes, particularly whether these two processes will shift in parallel or respond divergently to warming. Using a combination of an in situ downward-transplant warming experiment and an ex situ chamber warming treatment, we investigated how subalpine fir trees at their upper elevation limit coordinated carbon allocation priority among different sinks (e.g., NSC storage and structural growth) at whole-tree level in response to elevated temperature. We found that transplanted individuals from the upper elevation limit to lower elevations generally induced an increase in specific leaf area, but there was no detected evidence of warming effect on leaf-level saturated photosynthetic rates. Additionally, our results challenged the expectation that climate warming will accelerate structural carbon accumulation while maintaining NSC constant. Instead, individuals favored allocating available carbon to NSC storage over structural growth after 1 year of warming, despite the amplification in total biomass encouraged by both in situ and ex situ experimental warming. Unexpectedly, continued warming drove a regime shift in carbon allocation priority, which was manifested in the increase of NSC storage in synchrony to structural growth enhancement. These findings imply that climate warming would release trees at their cold edge from C-conservative allocation strategy of storage over structural growth. Thus, understanding the strategical regulation of the carbon allocation priority and the distinctive function of carbon sink components is of great implication for predicting tree fate in the future climate warming.

The physiological activities of fucoidan and its application in animal breeding.

Fucoidan, a water-soluble heteropolysaccharide predominantly found in brown algae, comprises active components such as fucose and sulfate groups. This polysaccharide exhibits a range of physiological activities, including antioxidant, antiviral, anticancer, and immunomodulatory activities. In light of the global prohibition of antibiotics in animal feed, there is increasing interest in identifying safe, natural antibiotic alternatives that lack toxic side effects. This study focuses on analysing the impact of fucoidan in animal husbandry and provides a comprehensive review of the methods for preparing fucoidan, along with its physical and chemical characteristics. Its applications in the breeding of aquatic species, livestock, and poultry have also been summarized. The aim of this study was to establish a theoretical framework for the use of fucoidan in animal husbandry and to contribute to the theoretical underpinnings of the animal breeding and feed industries.

Zonation of bulk and rhizosphere soil bacterial communities and their covariation patterns along the elevation gradient in riparian zones of three Gorges reservoir, China.

Zonation is a typical pattern of soil distribution and species assembly across riparian habitats. Microorganisms are essential members of riparian ecosystems and whether soil microbial communities demonstrate similar zonation patterns and how bulk and rhizosphere soil microorganisms interact along the elevation (submergence stress) gradient remain largely unknown. In this study, bulk and rhizosphere (dominant plant) soil samples were collected and investigated across riparian zones where the submergence stress intensity increased as the elevation decreased. Results showed that the richness of bacterial communities in bulk and rhizosphere soil samples was significantly different and presented a zonation pattern along with the submergence stress gradient. Bulk soil at medium elevation that underwent moderate submergence stress had the most abundant bacterial communities, while the species richness of rhizobacteria at low elevation that experienced serious submergence stress was the highest. Additionally, principal coordinate analysis (PCoA) and significance tests showed that bulk and rhizosphere soil samples were distinguished according to the structure of bacterial communities, and so were bulk or rhizosphere soil samples from different elevations. Redundancy analysis (RDA) and Mantel test suggested that bacterial communities of bulk soil mainly relied on the contents of soil organic matter, total carbon (TC), total nitrogen (TN), sodium (Na), calcium (Ca) and magnesium (Mg). Contrastingly, the contents of Na and Mg were the main factors explaining the variation in rhizobacterial community composition. Correlation and microbial source tracking analyses showed thatthe relationship of bulk and rhizosphere soil bacteria became much stronger, and the rhizosphere soil may get more bacterial communities from bulk soil with the increase in submergence severity. Our results suggest that the abiotic and biotic components of the riparian ecosystem are closely covariant along the submergence stress gradient and imply that the bacterial community may be a key node linking soil physiochemical properties and vegetation communities.

Temporal network of experience sampling methodology identifies sleep disturbance as a central symptom in generalized anxiety disorder.

BACKGROUND: A temporal network of generalized anxiety disorder (GAD) symptoms could provide valuable understanding of the occurrence and maintenance of GAD. We aim to obtain an exploratory conceptualization of temporal GAD network and identify the central symptom. METHODS: A sample of participants (n = 115) with elevated GAD-7 scores (Generalized Anxiety Disorder 7-Item Questionnaire [GAD-7] ≥ 10) participated in an online daily diary study in which they reported their GAD symptoms based on DSM-5 diagnostic criteria (eight symptoms in total) for 50 consecutive days. We used a multilevel VAR model to obtain the temporal network. RESULTS: In temporal network, a lot of lagged relationships exist among GAD symptoms and these lagged relationships are all positive. All symptoms have autocorrelations and there are also some interesting feedback loops in temporal network. Sleep disturbance has the highest Out-strength centrality. CONCLUSIONS: This study indicates how GAD symptoms interact with each other and strengthen themselves over time, and particularly highlights the relationships between sleep disturbance and other GAD symptoms. Sleep disturbance may play an important role in the dynamic development and maintenance process of GAD. The present study may develop the knowledge of the theoretical model, diagnosis, prevention and intervention of GAD from a temporal symptoms network perspective.

Analysis of factors influencing medical students' learning engagement and its implications for teaching work-- a network analysis perspective.

PURPOSE: Higher medical education has always been a major project in the fields of education and health, and therefore, the quality of education has received much attention. Learning engagement has emerged as a significant indicator of teaching quality, attracting considerable research attention. This study aims to explore the relationship between medical students' learning engagement and their sense of school belonging, professional identity, and academic self-efficacy. METHODS: We conducted an online survey using convenience sampling method with 311 medical students. We employed Revised version of the Utrech Work Engagement Scale-Student (UWES-S), Chinese version of the Psychological Sense of School Membership (PSSM) scale, Academic Self-Efficacy Scale, and the questionnaire of college students' speciality identity for evaluation. Network analysis was used to analyze the relationships among these factors. RESULTS: Medical students' overall performance in school showed a positive trend. However, there is still room for improvement. In the network structure of learning engagement and its influencing factors, the "emotional" aspect of professional identity (EI = 1.11) was considered to be an important node with strong centrality. And "academic competence self-efficacy" aspect of academic self-efficacy (BEI = 0.72) was considered an important node with strong transitivity. CONCLUSION: Deepening medical students' emotional identification with their profession and enhancing their confidence in their academic abilities may improve their learning engagement and educational quality.

Dietary fulvic acid supplementation improves the growth performance and immune response of sea cucumber (Apostichopus japonicas).

The present study aims to explore the effects of dietary fulvic acid (FA) supplementation on the growth performance, digestive enzyme activity and immune response of sea cucumber (Apostichopus japonicas). FA was used to replace 0 (control), 0.1, 0.5 and 1 g cellulose in the basic diet of sea cucumber to formulate four experimental feeds with equivalent nitrogen and energy denoted as F0, F0.1, F0.3 and F1, respectively. No significant differences were observed in the survival rate among all groups (P > 0.05). Results show that the body weight gain rate, specific growth rate, intestinal trypsin, amylase and lipase activities, serum superoxide dismutase, catalase, lysozyme, alkaline and acid phosphatase activities and disease resistance ability against the pathogen, Vibrio splendidus of the sea cucumbers fed with FA-containing diets were significantly higher than those of the control group (P < 0.05). The optimum dose of dietary FA supplementation required for the maximum growth of sea cucumber was 0.54 g/kg. Therefore, dietary FA supplementation to the feed of sea cucumber can significantly improve its growth performance immune response.

Vertical variation in prokaryotic community composition and co-occurrence patterns in sediments of the Three Gorges Reservoir, China.

Archaea and bacteria are distributed throughout the sediment; however, our understanding of their biodiversity patterns, community composition, and interactions is primarily limited to the surface horizons (0-20 cm). In this research, sediment samples were collected from three vertical sediment profiles (depths of 0-295 cm) in the Three Gorges Reservoir (TGR), one of the largest reservoirs in the world. Through 16S rRNA sequencing, it was shown that sediment microbial diversity did not significantly vary across the sediment. Nevertheless, a decline in the similarity of archaeal and bacterial communities over distance along sediment vertical profiles was noted. Nonmetric multidimensional scaling (NMDS) analysis revealed that archaeal and bacterial communities could be clearly separated into two groups, located in the upper sediments (0-135 cm) and deep sediments (155-295 cm). Meanwhile, at the fine-scale of the vertical section, noteworthy variations were observed in the relative abundance of prominent archaea (e.g., Euryarchaeota) and bacteria (e.g., Proteobacteria). The linear discriminant analysis effect size (LEfSe) demonstrated that twenty-four bacterial and twenty-six archaeal biomarker microbes exist in the upper and deep sediment layers. Each layer exhibited distinctive microbial divisions, suggesting that microbes with diverse biological functions are capable of thriving and propagating along the sediment profile. Co-occurrence network analysis further indicated that the microbial network in the upper sediments was more complex than that in the deep sediments. Additionally, the newly discovered anaerobic methanotrophic archaeon Candidatus Methanoperedens was identified as the most abundant keystone archaeal taxon in both sediment layers, highlighting the significance of methane oxidation in material cycling within the TGR ecosystem. In summary, our study examined the biodiversity and coexistence patterns of benthic microbial communities throughout the vertical sediment profile, providing detailed insights into the vertical geography of archaeal and bacterial communities in typical deep-water reservoir ecosystems.

Relationship of sleep-quality and social-anxiety in patients with breast cancer: a network analysis.

BACKGROUND: There is a complex relationship between social anxiety and sleep quality. However, network analysis studies of associations between social anxiety and sleep quality are lacking, particularly among patients with breast cancer. The current study aimed to extend this research to a sample of patients with breast cancer and to examine symptom-level associations between social anxiety and sleep quality using network analysis. METHODS: Network analysis was conducted to explore their associations and identify bridge items of social anxiety and sleep quality. RESULTS: The network structure revealed 9 important edges between social anxiety and sleep quality. "Subjective sleep quality" had the highest EI value in the network. "Working difficulty under watching" and "Sleep disorders" had the highest BEI values in their own communities. CONCLUSION: There are complex pathological correlation pathways between social anxiety and sleep quality in breast cancer patients. "Subjective sleep quality", "Working difficulty under watching" and "Sleep disorders" have the potential to be intervention targets for sleep disorder-social anxiety comorbidity. Medical staff can take corresponding interventions according to the the centrality indices and bridge centrality indicators identified in this study, which is likely to effectively reduce the comorbidity of sleep disorders and social anxiety.

An investigation of the relationships between suicidal ideation, psychache, and meaning in life using network analysis.

BACKGROUND: Previous studies have investigated the relationships between psychache or meaning in life and suicidal ideation based on sum score of corresponding scale. However, this practice has hampered the fine-grained understanding of their relationships. This network analysis study aimed to conduct a dimension-level analysis of these constructs and the relationships among them in a joint framework, and identify potential intervention targets to address suicidal ideation. METHODS: Suicidal ideation, psychache, and meaning in life were measured using self-rating scales among 738 adults. A network of suicidal ideation, psychache, and meaning in life was constructed to investigate the connections between dimensions and calculate the expected influence and bridge expected influence of each node. RESULTS: "Psychache" was positively linked to "sleep" and "despair", while "presence of meaning in life" had negative associations with "psychache", "despair", and "pessimism". The most important central nodes were "sleep" and "despair", and the critical bridge nodes were "presence of meaning in life" and "psychache". CONCLUSION: These preliminary findings uncover the pathological pathways underlying the relationships between psychache, meaning in life, and suicidal ideation. The central nodes and bridge nodes identified may be potential targets for effectively preventing and intervening against the development and maintenance of suicidal ideation.

How loneliness linked to anxiety and depression: a network analysis based on Chinese university students.

BACKGROUND: There is conclusive evidence of a multifaceted and bidirectional relationship between loneliness and depression and anxiety. Nonetheless, more extensive research is needed to examine their relationships at a more granular level. This study employed a network analysis approach to identify the pathological mechanisms underpinning those relationships and to identify important bridge nodes as potential targets for intervention. METHODS: 941 University students were included in this study. The ULS-6 (the short-form UCLA Loneliness Scale) was used to assess loneliness, the PHQ-9 (Patient Health questionnaire-9) and GAD-7 (Generalized anxiety disorder 7-item) scales were used to assess the symptoms of depression and anxiety. We constructed two network structures of loneliness-anxiety and loneliness-depression and computed bridge expected influence for each symptom. In addition, we showed a flow network of "Suicide" containing symptoms of depression and loneliness. RESULTS: All edges were positive in both networks constructed and the strongest edges were present within disorder communities. The overall connection between loneliness and depression was stronger compared to anxiety. The results demonstrated that the loneliness item "People are around me but not with me" was identified as bridge symptom in both networks. Furthermore, "Suicide" was directly connected to five symptoms of depression and four items of loneliness, with the strongest connections being between it and "Feeling of worthlessness" and "Psychomotor agitation/retardation". CONCLUSIONS: Our findings provide a more nuanced explanation of the link between loneliness and depression and anxiety. The results identified the bridge symptom "People are around me but not with me", which had the strongest effect on enhancing symptoms of depression and anxiety. Clinical improvements based on the findings of this study and the impact of the intervention are discussed.

Surgical Treatment & Long-term Follow Up of Giant Spherical Coronary Artery Aneurysm with Fistula to Left Ventricle: A Case Report.

Congenital fistula between the first diagonal branch of the coronary artery and left ventricle with a giant coronary artery aneurysm is extremely rare. We present the case of a 50-year-old asymptomatic male patient with such a condition that was diagnosed by transthoracic echocardiography, coronary computed tomography angiography, and coronary angiography. The patient was treated by surgical fistula closure under cardiopulmonary bypass. The postoperative coronary computed tomography angiography showed the patient got a complete cure, and the patient remains asymptomatic after 5-year follow up.

Right Coronary-Left Ventricular Fistula and Its Course: A Case Report.

BACKGROUND: Coronary fistula is a relatively rare cardiac disease. The incidence of coronary fistula flowing into the right heart structure is much higher than in inflow into the left heart structures. Opportunities for surgical intervention and treatment strategies for these patients still need to build more consensus.  Case presentation: Here, we report a case of right coronary artery-left ventricular fistula combined with a giant coronary artery aneurysm during the treatment course. CONCLUSION: Because of its rarity as well as its specificity of coronary artery fistula, each case requires an individualized evaluation. More consideration also can be given to the choice of surgical approach.

Reservoir NO3- pollution and chemical weathering: by dual isotopes of δ15N-NO3-, δ18O-NO3- and geochemical constraints.

Reservoir dams alter the nutrient composition and biogeochemical cycle. Thus, dual isotopes of δ18O-NO3- and δ15N-NO-3 and geochemical signatures were employed to study the NO3- pollution and chemical weathering in the Three Gorges Reservoir (TGR), China. This study found that the TGR dam alters the δ15N-NO3- composition and is enriched in the recharge period. Values of δ15N-NO3- varied from 4.5 to 12.9‰ with an average of 9.8‰ in the recharge period, while discharge period δ15N-NO3- ranged from 3.2 to 12.5‰, with an average of 9.3‰. δ18O-NO3- varies (1.2-11.3‰) with an average of 6.5‰ and (2.4-12.4‰) with an average of 7.5‰, in the recharge and discharge periods, respectively. Stable isotopic values sharply decreased from upstream to downstream, indicating the damming effects. δ18O-NO3- and δ15N NO3- confirm that sewage effluents, nitrification of soil organic material, and NH4+ fertilizers were the primary sources of NO3- in the reservoir. Carbonate weathering mainly provides ions to the reservoir. HCO3- + SO42- and Ca2+ + Mg2+ represent 90% of major ions in the TGR. Downstream sampling sites showed low solute concentration during the recharge period, indicating the dam effect on solute concentration. Ca-Mg-Cl-, Ca-HCO3- and Ca-Cl- were the main water types in the TGR. The average percentage of solutes contribution revealed the carbonate weathering, evaporites dissolution, silicate weathering, and atmospheric input were 51.9%, 41%, 7.8%, and 1.7% for the recharge period. In contrast, the discharge period contributed 66.4%, 29.2%, 10%, and 4.3%, respectively. TGR water is moderately suitable for irrigation, and hardness is high in drinking water. This study provides new insight into the dual isotopic approach and geochemical signatures to interpret the NO3- cycle and chemical weathering process under dam effects in the TGR. However, this isotopic application has some limitations in source identification, isotope fractionation, and transformation mechanisms of nitrate. Thus, further studies need to be done on these topics for a better undestanding.

Mercury contamination in the riparian ecosystem during the reservoir discharging regulated by a mega dam.

Mercury (Hg) is extremely poisonous and can be absorbed through touch, inhalation, or consumption. In the living environment, Hg in contaminated sediment can be transferred into grass by the direct absorption through the roots or shoots. The intake of Hg due to Hg emissions may pose a threat to living bodies especially to human beings. The present study aims to provide a novel insight about total mercury (THg) and methyl mercury (MeHg) in a riparian grass (Cynodon dactylon (L).Pers) and sediments during the discharging phase (summertime at 145 m water level) in Three Gorges Reservoir (TGR-China); where C. dactylon is a dominant perennial herb in the riparian zone. Yet, the potential risk of Hg contamination in the riparian ecosystem is not thoroughly assessed in the dam regulated reservoir. This study was conducted in the riparian zones of the reservoir formed by a mega dam (Three Gorge Dam) which regulates the water levels during the summer and winter period in the TGR. Our results showed that riparian sediments were acting as a sink for THg and MeHg. Insignificant correlation of THg and MeHg was found between the amphiphyte C. dactylon and its surrounding sediments in the TGR. Bioconcentration factors values for MeHg were found higher than 1 in all study locations in the riparian zones in TGR, which could be due to action of certain bacteria/purely chemical-based methylation on inorganic form of Hg. Additionally, translocation factor indices also highlighted that the amphiphyte C. dactylon was MeHg accumulator in riparian zones. These results suggested that since riparian sediment was found acting as the sink for THg and MeHg during discharging phase, MeHg contamination in the amphiphyte C. dactylon in riparian zones was not caused by the riparian sediments but by other factors, for instance, the anthropogenic activities in the TGR. Finally, this study leads to conclude that amphiphyte C. dactylon can be used as biomonitoring agent for Hg pollution in the TGR.

Four novel suture-sealing techniques to repair varying size paravalvular leaks.

BACKGROUND: Paravalvular leak (PVL) is a well-known complication of aortic valve replacement. Currently, there is no consensus on optimal intraoperative management of patients with mild-to-moderate or moderate PVL. TECHNIQUE: In this paper we present four novel surgical techniques, each combining suturing with sealing technique, to repair aortic PVLs, nullifying the need to replace the prosthesis. CONCLUSION: These techniques will offer cardiac surgeons new alternatives to the repair techniques currently used.

Plant Morphological, Physiological and Anatomical Adaption to Flooding Stress and the Underlying Molecular Mechanisms.

Globally, flooding is a major threat causing substantial yield decline of cereal crops, and is expected to be even more serious in many parts of the world due to climatic anomaly in the future. Understanding the mechanisms of plants coping with unanticipated flooding will be crucial for developing new flooding-tolerance crop varieties. Here we describe survival strategies of plants adaptation to flooding stress at the morphological, physiological and anatomical scale systemically, such as the formation of adventitious roots (ARs), aerenchyma and radial O2 loss (ROL) barriers. Then molecular mechanisms underlying the adaptive strategies are summarized, and more than thirty identified functional genes or proteins associated with flooding-tolerance are searched out and expounded. Moreover, we elaborated the regulatory roles of phytohormones in plant against flooding stress, especially ethylene and its relevant transcription factors from the group VII Ethylene Response Factor (ERF-VII) family. ERF-VIIs of main crops and several reported ERF-VIIs involving plant tolerance to flooding stress were collected and analyzed according to sequence similarity, which can provide references for screening flooding-tolerant genes more precisely. Finally, the potential research directions in the future were summarized and discussed. Through this review, we aim to provide references for the studies of plant acclimation to flooding stress and breeding new flooding-resistant crops in the future.

The item network and domain network of burnout in Chinese nurses.

BACKGROUND: As a common social phenomenon, nurses' occupational burnout has a high incidence rate, which seriously affects their mental health and nursing level. The current assessment mostly uses the total score model and explores the influence of external factors on burnout, while the correlation between burnout items or dimensions is less explored. Ignoring the correlation between the items or dimensions may result in a limited understanding of nurse occupational burnout. This paper explores the item and dimension network structure of the Maslach Burnout Inventory-General Survey (MBI-GS) in Chinese nurses, so as to gain a deeper understanding of this psychological construct and identify potential targets for clinical intervention. METHODS: A total of 493 Chinese nurses were recruited by cluster sampling. All participants were invited to complete the survey on symptoms of burnout. Network analysis was used to investigate the item network of MBI-GS. In addition, community detection was used to explore the communities of MBI-GS, and then network analysis was used to investigate the dimension network of MBI-GS based on the results of community detection. Regularized partial correlation and non-regularized partial correlation were used to describe the association between different nodes of the item network and dimension network, respectively. Expected influence and predictability were used to describe the relative importance and the controllability of nodes in both the item and dimension networks. RESULTS: In the item network, most of the strongly correlated edges were in the same dimension of emotional exhaustion (E), cynicism (C) and reduced professional efficacy (R), respectively. E5 (Item 5 of emotional exhaustion, the same below) "I feel burned out from my work", C1 "I have become more callous toward work since I took this job", and R3 "In my opinion, I am good at my job" had the highest expected influence (z-scores = 0.99, 0.81 and 0.94, respectively), indicating theirs highest importance in the network. E1 "I feel emotionally drained from my work" and E5 had the highest predictability (E1 = 0.74, E5 = 0.74). It shows that these two nodes can be interpreted by their internal neighbors to the greatest extent and have the highest controllability in the network. The spinglass algorithm and walktrap algorithm obtained exactly the same three communities, which are consistent with the original dimensions of MBI-GS. In the dimension network, the emotional exhaustion dimension was closely related to the cynicism dimension (weight = 0.65). CONCLUSIONS: The network model is a useful tool to study burnout in Chinese nurses. This study explores the item and domain network structure of nurse burnout from the network perspective. By calculating the relevant indicators, we found that E5, C1, and R3 were the most central nodes in the item network and cynicism was the central node in the domain network, suggesting that interventions aimed at E5, C1, R3 and cynicism might decrease the overall burnout level of Chinese nurses to the greatest extent. This study provides potential targets and a new way of thinking for the intervention of nurse burnout, which can be explored and verified in clinical practice.

Wnt/ß-catenin signaling regulates brain-derived neurotrophic factor release from spinal microglia to mediate HIV1 gp120-induced neuropathic pain.

HIV-associated neuropathic pain (HNP) is a common complication for AIDS patients. The pathological mechanism governing HNP has not been elucidated, and HNP has no effective analgesic treatment. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophic factor family related to the plasticity of the central nervous system. BDNF dysregulation is involved in many neurological diseases, including neuropathic pain. However, to the best of our knowledge, the role and mechanism of BDNF in HNP have not been elucidated. In this study, we explored this condition in an HNP mouse model induced by intrathecal injection of gp120. We found that Wnt3a and ß-catenin expression levels increased in the spinal cord of HNP mice, consequently regulating the expression of BDNF and affecting hypersensitivity. In addition, the blockade of Wing-Int/ß-catenin signaling, BDNF/TrkB or the BDNF/p75NTR pathway alleviated mechanical allodynia. BDNF immunoreactivity was colocalized with spinal microglial cells, which were activated in HNP mice. Inhibition of spinal microglial cell activation by minocycline relieved mechanical allodynia in HNP mice. This study helped to elucidate the role of the Wing-Int/ß-catenin/BDNF signaling axis in HNP and may establish a foundation for further research investigating the Wing-Int/ß-catenin/BDNF signaling axis as a target for HNP treatment.

The Role of the Spinal Wnt Signaling Pathway in HIV-Related Neuropathic Pain.

Human immunodeficiency virus (HIV)-related neuropathic pain includes HIV-induced neuropathic pain (HNP) and antiretroviral therapy-induced neuropathic pain (ART-NP). A significant amount of evidence from the past few years has shown that the development of HIV-related neuropathic pain is closely related to the activation of the Wnt signaling pathway in the spinal cord. This review summarizes the function of the spinal Wnt signaling pathway in HIV-induced neuropathic pain, focusing on the role of the spinal Wnt signaling pathway in HNP, and provides a theoretical basis for further studies and the exploration of new target drugs.

Catalytic Dehydrogenation of Ammonia Borane Mediated by a Pt(0)/Borane Frustrated Lewis Pair: Theoretical Design.

A new efficient metal-based frustrated Lewis pair constructed by (Pt Bu3 )2 Pt and B(C6 F5 )3 was designed through density functional theory calculations for the catalytic dehydrogenation of ammonia borane (AB). The reaction was composed by the successive dehydrogenation of AB and H2 liberation, which occurs through the cooperative functions of the Pt(0) center and the B(C6 F5 )3 moiety. Two equivalents of H2 were predicted to be liberated from each AB molecule. The generation of the second H2 is the rate-determining step, with a Gibbs energy barrier and reaction energy of 27.4 and 12.8 kcal/mol, respectively.