Carboxy to methyl reduction is an important transformation in organic synthesis, yet existing methodologies often require multi‐step procedures or use hazardous metal hydrides. Herein, a metal‐free ...catalytic system is reported for the one‐step reduction of esters, carboxylic acids, and carbamates to a methyl group, in the presence of catalytic amounts of boronic acids. By using ammonia borane as a hydrogen donor, a wide range of products bearing different functional groups can be obtained in high yields under relatively mild conditions. Mechanistic studies and control experiments elucidate the complexity of the mechanism and provide an explanation for the observed selectivity.
The multi‐step reduction of carboxy groups to methyl groups commonly used in organic synthesis is simplified by a new metal‐free catalyst system. It uses boronic acids to catalyze the single‐step reduction of esters, carboxylic acids and carbamates to methyl groups. High‐yield, multifunctional product formation is achieved under mild conditions using ammonia borane as the hydrogen donor.
The young‐of‐the‐year (YOY) Argentina hake Merluccius hubbsi remained at particular distances off the seabed at pelagic habitat, in a nursery area located in the San Jorge Gulf off south‐western ...Atlantic. Older specimens were daylight distributed near the bottom in the demersal habitat. In this paper the authors show that the pelagic habitat is favourable for YOY hake compared to the surrounding demersal habitat by decreasing the probability of encounter with larger hake protecting the YOY against conspecific predation, and providing a better food supply. From 303 stomachs of pelagic YOY Argentine hake analysed (60–250 mm), 274 (90.43%) contained prey. Pelagic Argentine YOY hake fed almost exclusively on zooplanktonic crustaceans (Euphausia spp. and Themisto gaudichaudii). From 980 demersal specimens (14–82 cm), 572 (58.36%) contained prey, mainly the lobster krill Munida gregaria, followed by other hakes by cannibalism. The intensity of feeding was higher on pelagic layers. The allometric weight–length relationship revealed that the YOY Argentine hake find sufficient food in the pelagic habitat to live and develop, by increasing their relative body thickness. The cannibalism increases from close to zero when the YOY hake are c. 20 m off the seabed, to between 15% (cold season) and 20% (warm season) when they are 10 m off the seabed. These results suggest that the pelagic habitat is a feeding ground for YOY hake, and it is a favourable one compared to the surrounding demersal habitat by protecting the YOY from cannibalism. Pelagic YOY hakes were less abundant and more distant from the bottom during the cold season (14.3 m) than during warm one (11.4 m), probably because of natural mortality and progressive recruitment to demersal habits.
High-temperature polymers are attractive for applications in extreme temperatures, where they maintain their mechanical flexibility and electrical insulating properties. However, their heat ...dissipation capability is limited due to their intrinsically low thermal conductivities. Hexagonal boron nitride (hBN) is a chemically inert, thermally stable, and electrically insulative compound with a high thermal conductivity, making it an ideal candidate as a filler within a high-temperature polymer matrix to increase the thermal conductivity. This study evaluates the effect of filler size and dispersion on thermal conductivity by producing homogeneous composite samples using a combination of solvent mixing and resonant acoustic mixing (RAM). We carefully characterized our samples, including the spread of the size distribution, and observed that the smaller sized hBN centered around 5 μm was able to integrate more seamlessly into the polytetrafluoroethylene (PTFE) matrix with particle size in the 15 μm range and hence outperformed 30 μm, in contrast to the conventional wisdom, which asserts that larger fillers universally perform better than smaller ones. Our thermal conductivity of hBN/PTFE composites at 30 wt % is 2× higher than the literature values. Notably, we reached the record-high value of 3.5 W/m K at 40 wt % with an onset of percolation at 20 wt %, attributed to optimized hBN dispersion that facilitates the formation of thermal percolation. Our findings provide general guidelines to enhance the thermal conductivity of polymer composites for thermal management, ranging from power transmission to microelectronics cooling.
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•Complementary sampling methods detected species not attracted to dung-baited pitfalls.•Additional species increased the functional volume of the dung beetle assemblage.•Functional ...traits of additional species were rarer than expected by chance.•FITs and visual transects had the highest values of taxonomic and functional turnover.•Visual transects detect functionally rare trophic specialists.
The functional space of an ecological community is not evenly filled by its species. Instead, it is usually divided into areas of high species density, where species with common combinations of functional traits are grouped into species rich clusters, while lower density areas are filled with species poor clusters or isolated species with uncommon or unique combinations of traits. Species whose functional traits differ from those of the rest of the community are expected to play distinct ecological roles and over-contribute to ecosystem functionality. Sampling methods used to characterize arthropod assemblages usually target subsets of the community and filter species based on their functional traits, reducing the probability of detecting species with uncommon combinations of functional traits. Consideration of these species is particularly important for characterizing the functional structure and resilience of ecological communities inhabiting threatened ecosystems such as lowland Amazonian rainforests, in which dung beetles play multiple ecological roles and are commonly used as ecological indicators. In this study, we characterize the functional structure of a diverse Amazonian dung beetle assemblage using five different sampling methods (dung- and carrion-baited pitfalls, dung-baited aerial traps, flight interception traps, and visual transects) and 18 different functional traits. Our main objective is to assess the suitability of these methods for the detection of the functional volume of the assemblage and of species with uncommon or unique combinations of functional traits that are expected to support vulnerable ecosystem functions. We found that, although dung-baited pitfalls (DPF) detected the highest species richness and proportion of the functional volume, they did not detect 30 species out of 103 and over 20% of the functional volume of the assemblage. The additional sampling methods captured more species with uncommon combinations of functional traits than expected by chance, some of which were trophic specialists not attracted to DPFs. The use of complementary sampling methods resulted in a better characterization of the functional structure of dung beetle communities inhabiting both terra firme and floodplain Amazonian rainforests and revealed functional resilience and rare species playing ecological roles overlooked by DPFs. The consideration of these species is of great importance given the threats that tropical rainforests face worldwide.
Medical and health system advances have brought cure to more than 80% of children with cancer in high-income countries (HICs),1 but such advances have eluded children in most LMICs, where inequities ...can yield cure percentages anywhere from 5% to 60%.2 Multiple factors contribute to the inadequate care of childhood cancers in LMICs, including resource scarcity, health system fragility, limited provider awareness, and absence of political attention.3 These conditions are abetted by a lack of sustained political attention to childhood cancer at the international level. Core functions of the Working Group include: (1) health system evidence development; (2) knowledge exchange and capacity building among country-level stakeholders; (3) knowledge translation for policy development on issues with regional scope; and (4) regional interface with national governments. Because of its collaboration between national Ministries of Health throughout the region, PAHO, the UICC, and North and South American academic partners, we believe that the Working Group is uniquely positioned to identify and promote effective strategies for policy reform and health system strengthening for children with cancer. Challenges Lessons Governance Insufficient governance capacity: absence of national childhood cancer plans, accreditation processes and treatment protocolsCompeting agendas in context of multiple needs divert attention from childhood cancer International collaboration as facilitator of knowledge translation for context-sensitive programmes and standardsBroad stakeholder engagement is key to increase political visibility of childhood cancer agenda Access to medicines Erratic supply of EML medicines for children with cancer: decentralised purchasing, weak procurement and supply management processes, and poor pharmacovigilance Role of PAHO Strategic...
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•New hybrid waterborne polyurethane dispersions were synthesized by using Bis-GMA.•Bis-GMA was first time reported as both chain extender and grafting agent.•Colloidal stable ...dispersions were obtain by using the self-emulsifying method.•The mean particles size is reduced when Bis-GMA is used instead of HEMA.•The Bis-GMA improve the thermal and adhesive properties of the dispersions.
New hybrid waterborne polyurethane/acrylate (WPUA) dispersions were synthesized by grafting with bisphenol-A-glycidyl dimethacrylate (Bis-GMA) in order to create chemical bonds between polyurethane and polyacrylate chains. WPUAs were prepared by using prepolymer self-emulsifying method with isophorone diisocianate, poly(tetramethylene ether) glycol, dimethylolpropionic acid, and ethylenediamine in the polyurethanic part, and styrene and n-butyl acrylate in the polyacrylate portion. A redox pair system consisting of ascorbic acid and hydrogen peroxide were used as polymerization initiator. The particle size of the WPUA dispersions increased by increasing the Bis-GMA/1,4 butanediol ratio, stable dispersions of negatively charged particles were obtained, and they had low viscosity (around 1.3 mPa.s) in spite of the relatively high solids content (27 wt%). Higher thermal stability was obtained when 50 mol% of chain extension was carried out with Bis-GMA. Using Bis-GMA/BD, instead of HEMA, as grafting agent, allowed obtaining hybrid polyurethane dispersions with the lowest mean particle size and better colloidal stability. Finally, the addition of 35 wt% Bis-GMA increased noticeably the cross-cut adhesion of polyurethane/acrylate coatings to stainless steel.
Boron nitride (BN) is an exceptional material, and among its polymorphs, two-dimensional (2D) hexagonal and three-dimensional (3D) cubic BN (h-BN and c-BN) phases are most common. The phase stability ...regimes of these BN phases are still under debate, and phase transformations of h-BN/c-BN remain a topic of interest. Here, we investigate the phase stability of 2D/3D h-BN/c-BN nanocomposites and show that the coexistence of two phases can lead to strong nonlinear optical properties and low thermal conductivity at room temperature. Furthermore, spark-plasma sintering of the nanocomposite shows complete phase transformation to 2D h-BN with improved crystalline quality, where 3D c-BN possibly governs the nucleation and growth kinetics. Our demonstration might be insightful in phase engineering of BN polymorph-based nanocomposites with desirable properties for optoelectronics and thermal energy management applications.
Understanding the emergent electronic structure in twisted atomically thin layers has led to the exciting field of twistronics. However, practical applications of such systems are challenging since ...the specific angular correlations between the layers must be precisely controlled and the layers have to be single crystalline with uniform atomic ordering. Here, an alternative, simple, and scalable approach is suggested, where nanocrystallinetwo‐dimensional (2D) film on 3D substrates yields twisted‐interface‐dependent properties. Ultrawide‐bandgap hexagonal boron nitride (h‐BN) thin films are directly grown on high in‐plane lattice mismatched wide‐bandgap silicon carbide (4H‐SiC) substrates to explore the twist‐dependent structure‐property correlations. Concurrently, nanocrystalline h‐BN thin film shows strong non‐linear second‐harmonic generation and ultra‐low cross‐plane thermal conductivity at room temperature, which are attributed to the twisted domain edges between van der Waals stacked nanocrystals with random in‐plane orientations. First‐principles calculations based on time‐dependent density functional theory manifest strong even‐order optical nonlinearity in twisted h‐BN layers. This work unveils that directly deposited 2D nanocrystalline thin film on 3D substrates could provide easily accessible twist‐interfaces, therefore enabling a simple and scalable approach to utilize the 2D‐twistronics integrated in 3D material devices for next‐generation nanotechnology.
Hexagonal boron nitride (h‐BN) thin films have been grown on silicon carbide substrates exhibiting strong non‐linear second‐harmonic generation and ultra‐low cross‐plane thermal conductivity, attributed to the inherent formation of twisted nano‐domain edges between the stacked h‐BN nanocrystals with random in‐plane orientations, as revealed by the first‐principles time‐dependent density functional theory.
The analysis of Corporate Social Responsibility (CSR) practices in Ecuadorian companies is a relevant topic due to the indeterminacies existing in their implementation. The general objective of this ...analysis is to evaluate CSR practices in companies, considering aspects such as environmental sustainability, responsibility to employees, business ethics, and financial performance. To achieve this, the criteria and comprehensive solutions were evaluated through the modeling of the neutrosophic ELECTRE method. The results of the analysis indicate that the implementation of CSR practices can have multiple benefits, and comprehensive solutions with higher scores were identified, such as the implementation of ethics and transparency policies and the implementation of training and professional development programs. To enhance these comprehensive solutions, it is significant to establish clear and transparent policies, train the personnel, and communicate effectively with the community, and other relevant stakeholders. This ensures that CSR practices in Ecuadorian companies have a positive impact on the community. Keywords: Environmental sustainability, business ethics, corporate social responsibility.
The purpose of this study was to implement the neutrosophic logic in order to identify the most favorable corporate social responsibility strategies to be applied in the short and medium term in a ...small and medium-sized food company located in the city of Santo Domingo. To achieve this objective, the COPRAS method approach was expanded by incorporating single-valued neutrosophic sets as an essential part of the decision-making process related to the aforementioned area of study. The adoption of the neutrosophic COPRAS method provided an effective framework for evaluating and prioritizing the various facets of corporate social responsibility, empowering the organization to make more informed and ethical decisions. As a result, it was confirmed that the application of neutrosophic logic proved to be a valuable tool for addressing the inherent uncertainty present in decision-making focused on corporate social responsibility. Keywords: corporate social responsibility, neutrosophic logic, decision-making, COPRAS, SVNN.
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