Multidisciplinary Digital Publishing Institute (Switzerland)
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Syntheses of Marine Natural Products via Matteson Homologations and Related Processes
Matteson homologation, a successive extension of chiral boronic esters, is perfectly suited for the synthesis of complex molecular structures containing several stereogenic centers. The “classical version” allows the introduction of various functional groups in a 1,2-anti-configuration. The absolute configuration is determined by the choice of the chiral auxiliary, which can be used to introduce several stereogenic centers. In contrast, in Aggarwal’s lithiation-borylation strategy, new chiral auxiliary reagents must be used in each reaction step, which on the other hand allows the individual insertion of the desired stereogenic centers. Both methods have their individual advantages and disadvantages and are well suited for the synthesis of marine natural products
Spatially Correlated Network Structure and Influencing Factors of Carbon Emission Efficiency in the Power Industry: Evidence from China
As the largest carbon-emitting industry in China, the power industry has huge potential for carbon emission reductions. It is vital to study the spatial correlation of carbon emission efficiency in the power industry (CEEP) from a system perspective to understand the interaction mechanisms of CEEP in different provinces. This study applies the SBM-undesirable model to measure the CEEP in China, and a modified Gravity model and social network analysis (SNA) method are applied to analyze the interaction mechanism of the CEEP from a system perspective. Finally, the influencing factors of the CEEP’s spatial correlation are investigated using the quadratic allocation procedure (QAP) method. The results show that (1) the national CEEP is gradually increasing, while the CEEP gap between provinces is widening; (2) the overall network size shows an increasing trend, but the hierarchical structure is somewhat fixed; (3) the central province of a network has a high degree of consistency with the geographically central province, but the spatial spillover effect of the central node provinces on the peripheral provinces is not sufficient; and (4) differences in geographic proximity, energy intensity, and technical level of power generation significantly affect the formation of spatially correlated networks in the CEEP
Optimising β-Ti21S Alloy Lattice Structures for Enhanced Femoral Implants: A Study on Mechanical and Biological Performance
The metastable β-Ti21S alloy exhibits a lower elastic modulus than Ti-6Al-4V ELI while maintaining high mechanical strength and ductility. To address stress shielding, this study explores the integration of lattice structures within prosthetics, which is made possible through additive manufacturing. Continuous adhesion between the implant and bone is essential; therefore, auxetic bow-tie structures with a negative Poisson’s ratio are proposed for regions under tensile stress, while Triply Periodic Minimal Surface (TPMS) structures with a positive Poisson’s ratio are recommended for areas under compressive stress. This research examines the manufacturability and quasi-static mechanical behaviour of two auxetic bow-tie (AUX 2.5 and AUX 3.5) and two TPMS structures (TPMS 2.5 and TPMS 1.5) in β-Ti21S alloy produced via laser powder bed fusion. Micro-CT reveals printability issues in TPMS 1.5, affecting pore size and reducing fatigue resistance compared to TPMS 2.5. AUX 3.5’s low stiffness matches cancellous bone but shows insufficient yield strength and fatigue resistance for femoral implants. Biological tests confirm non-toxicity and enhanced cell activity in β-Ti21S structures. The study concludes that the β-Ti21S alloy, especially with TPMS 2.5 structures, demonstrates promising mechanical and biological properties for femoral implants. However, challenges like poor printability in TPMS 1.5 are acknowledged and should be addressed in future research
Dam-Break Hazard Assessment with CFD Computational Fluid Dynamics Modeling: The Tiangchi Dam Case Study
In this research, a numerical model for simulating dam break floods was developed utilizing ArcGIS 10.8, 3ds Max 2021, and Flow-3D v11.2 software, with the aim of accurately representing the dam break disaster at Tianchi Lake in Changbai Mountain. The study involved the construction of a Triangulated Irregular Network (TIN) terrain surface and the application of 3ds Max 2021 to enhance the precision of the three-dimensional terrain data, thereby optimizing the depiction of the region’s topography. The finite volume method, along with multi-block grid technology, was employed to model the dam break scenario at Tianchi Lake. To evaluate the severity of the dam break disaster, the research integrated land use classifications within the study area with the simulated flood depths resulting from the dam break, applying the natural breaks method for hazard level classification. The findings indicated that the computational fluid dynamics (CFD) numerical model developed in this study significantly enhanced both the efficiency and accuracy of the simulations. Furthermore, the disaster assessment methodology that incorporated land use types facilitated the generation of inundation maps and disaster zoning maps across two scenarios, thereby effectively assessing the impacts of the disaster under varying conditions
The Influence of an Alternating Current Field on Pack Boriding for Medium Carbon Steel at Moderate Temperature
The influence of alternating current (AC) field on the pack boriding process for medium carbon steel was investigated through characterization of microstructure, phase composition, microhardness, and corrosion resistance of the boride layer and its mechanism was revealed. Results showed that the boride layer obtained by AC field boriding was composed of the outer FeB and the inner Fe2B phase, which was similar to that of conventional boriding. Meanwhile, the effective thickness of the boride layer and proportion of Fe2B increased gradually with increasing current during AC field boriding. The introduction of an AC field during the boriding process served dual purposes. First, it facilitated the decomposition of the boriding medium, leading to an elevation in the concentration of active boron atoms. Second, it reduced the activation energy required for atomic diffusion, thereby accelerating the diffusion of both boron and iron atoms. These combined effects significantly enhanced the hardness distribution and corrosion resistance of the steel. Further insights into the process were gained by fitting the parabolic kinetics curves, which confirmed that the boriding process in an AC field was exclusively controlled by diffusion. This study also clarified the growth mechanism of the boride layer within an AC field
One-Step Ball Milling Synthesis of Zr-Based Mixed Oxides for the Catalytic Study of Methyl Levulinate Conversion into γ-Valerolactone Under Microwave Irradiation
Several mixed oxides composed of Fe3O4, ZrO2, and Al2O3 with different molar ratios were synthesized through a direct and simple mechanochemical approach. Subsequently, their physicochemical properties were investigated using a wide range of techniques, including TEM (transmission electron microscopy), XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction), and N2 adsorption/desorption, among others. These materials showed high surface areas and increased acidity compared to their respective counterparts. The catalytic activity of the synthesized materials was evaluated in the conversion of methyl levulinate (MEL) to γ-valerolactone (GVL) under microwave irradiation conditions, employing different alcohols as H-donor solvents (ethanol, 2-propanol, and 2-butanol). Due to their improved physicochemical properties originating from the ball-milling method, the as-synthesized materials (ZrFeOx 1:1, AlZrFeOx (5), and AlZrFeOx (10)) exhibited conversion rates of up to 99%, with complete selectivity for GVL after a relatively short reaction time of 30 min
The Interspecific Abundance–Occupancy Relationship in Invertebrate Metacommunities Associated with Intertidal Mussel Patches
To explain the distribution and abundance of species, ecology searches for general models. A pattern often encountered in nature is the interspecific abundance–occupancy relationship (AOR), which describes how the mean local abundance of species relates to the proportion of local sites that each species occupies. Both are central variables in ecology and are often positively correlated, although exceptions have been found. As most AOR research has been conducted with terrestrial systems, recent studies are testing for its occurrence in marine systems. This contribution tests the AOR for invertebrate metacommunities associated with intertidal mussel patches. Using data from six coastal locations in Nova Scotia (Canada), this study shows that the negative binomial model properly describes the relationship between abundance and occupancy for these systems. The degree of wave exposure (wave-sheltered versus wave-exposed habitats) had some influence on the shape of the AOR. Overall, these findings extend the applicability of the AOR to intertidal invertebrate metacommunities. The raw data are included as part of this article to help future syntheses on the AOR, which will need data for a variety of terrestrial and aquatic environments
Sustainable Valorization of Rice Straw into Biochar and Carbon Dots Using a Novel One-Pot Approach for Dual Applications in Detection and Removal of Lead Ions
Lead (Pb) is a highly toxic heavy metal that causes significant health hazards and environmental damage. Thus, the detection and removal of Pb2+ ions in freshwater sources are imperative for safeguarding public health and the environment. Moreover, the transformation of single resources into multiple high-value products is vital for achieving sustainable development goals (SDGs). In this regard, the present work focused on the preparation of two efficient materials, i.e., biochar (R-BC) and carbon dots (R-CDs) from a single resource (rice straw), via a novel approach by using extraction and hydrothermal process. The various microscopic and spectroscopy techniques confirmed the formation of porous structure and spherical morphology of R-BC and R-CDs, respectively. FTIR analysis confirmed the presence of hydroxyl (–OH), carboxyl (–COO) and amine (N–H) groups on the R-CDs’ surface. The obtained blue luminescent R-CDs were employed as chemosensors for the detection of Pb2+ ions. The sensor exhibited a strong linear correlation over a concentration range of 1 µM to 100 µM, with a limit of detection (LOD) of 0.11 µM. Furthermore, the BET analysis of R-BC indicated a surface area of 1.71 m2/g and a monolayer volume of 0.0081 cm3/g, supporting its adsorption potential for Pb2+. The R-BC showed excellent removal efficiency of 77.61%. The adsorption process followed the Langmuir isotherm model and second-order kinetics. Therefore, the dual use of rice straw-derived provides a cost-effective, environmentally friendly solution for Pb2+ detection and remediation to accomplish the SDGs
Electrochemical Detection of Dopamine with Graphene Oxide Carbon Dots Modified Electrodes
In this work, the influence of surface functionalization due to synthesis conditions of graphene oxide quantum dots GOQDs was evaluated for dopamine (DA) detection. GOQDs were synthesized using HNO3 (6 M or 8 M) through a liquid-phase oxidation method. The characterization (HRTEM, FTIR, Raman, and XRD) and evaluation by amperometry (AMP) and differential pulse voltammetry (DPV) showed that GOQDs-8 synthesized with higher oxygen content were more sensitive and selective in DA detection than GOQDs-6. The synergistic effects of electrostatic attraction from glassy carbon electrode negatively charged surface, functionalization for inner-sphere mechanism, and edge effect from lower particle size resulted in amplified electrochemical signal achieving detection at nanomolar level using AMP and DPV. When evaluated using AMP, GCE/GOQDs-8 showed a sensitivity of 0.0422 μA μM–1, a limit of detection (LOD) of 17.6 nM, a linear range from 0.1 to 100 μM, and minimal interference for uric acid, levodopa, and acetaminophen. In contrast, using DPV, the GCE/GOQDs-8 exhibited a sensitivity of 0.0616 μA μM–1, a LOD of 506 nM, and a linear range from 0.1–30 μM with remarkable selectivity from all interferent species. The assay of GOQDs-8/GCE sensor in normal human serum proved to be feasible for the practical determination of DA. The recovery obtained was in the range of 94.1 to 112.8% with a relative standard deviation (RSD), n = 3 of less than 3.62%. The oxygen-rich material showed a promising performance that can be further improved with additional nanocarbon or conducting polymers supports
Comparison of a Scheimpflug Camera and Optical Coherence Tomography in Evaluating Keratoconic Eyes Post Keratoplasty
Background/Objective: The aim of this retrospective study was to compare corneal parameters and compliance using a Pentacam HR–Scheimpflug (Pentacam HR) and a swept-source OCT Casia (Casia) in keratoconus (KC) patients post penetrating keratoplasty (PKP) and KC patients without PKP, as well as a control group. Pachymetry measurements were also analyzed using a spectral domain OCT Solix (OCT Solix), Pentacam HR, and Casia. Methods: The study included 71 patients (136 keratoconic eyes; group A), 86 eyes with KC post-PKP (group B), 50 eyes with KC without PKP (group C), and 52 control participants (104 eyes). All participants were adults, Polish Caucasian, and met specific inclusion criteria. Patients with ophthalmological or systemic diseases, cognitive impairment, or pregnancy were excluded. Corneal parameters were measured using two devices (Casia and Pentacam HR), while pachymetry was assessed with three devices (Casia, Pentacam HR, and OCT Solix), with the inter-device agreement and group differences analyzed. Results: Significant differences (p < 0.05) were found across all groups. The post-PKP KC eyes showed significant differences in all front parameters and K2 and Astig. back, while the non-PKP KC eyes showed differences in the K1 back (p = 0.025). The controls displayed differences in all parameters except front astigmatism (p = 0.61). The Pentacam HR overestimated the thinnest corneal thickness (TCT) compared to the OCT Casia across groups. The inter-device agreement was excellent for the anterior parameters (ICC > 0.9) but good for the posterior parameters and TCT. Conclusions: This study highlights significant variability in corneal and pachymetry measurements across devices, with OCT Casia providing more consistent and clinically reliable results than Pentacam HR. Clinicians should exercise caution when using these devices interchangeably, particularly for posterior parameters and TCT