Elimination Mechanism Research Articles

Mechanism and Origins of Enantioselectivity in the Nickel-catalyzed Asymmetric Synthesis of Silicon-Stereogenic Benzosiloles.

As important π-skeletons, benzosiloles often possess unique electronic and optical properties and have been widely used in semiconductor materials. Therefore, great attention has been drawn to the area of developing novel synthetic methods for various benzosiloles. However, the synthesis of enantioenriched silicon-stereogenic benzosiloles is still at an early stage and remains to be explored. Herein, we performed systematic density functional theory studies on the recently reported nickel-catalyzed asymmetric synthesis of silicon-stereogenic benosiloles, which was enabled by an enantioselective desymmetrization of (2-alkenyl)aryl-substituted silacyclobutanes. Our computational study shows that the reaction mechanism involves ligand exchange, oxidative addition, alkene insertion, and hydrogen-transfer coupled reductive-demetalation steps. The proposed transmetalation and β-hydride elimination mechanism was not found, which might be due to the unfavorable ring strain of the multicyclic intermediates. The novel hydrogen-transfer coupled reductive-demetalation mechanism was shown to be reasonable for the generation of the silicon-stereogenic benzosilole. Noncovalent interactions (including C-H···π and hydrogen bonding) in the rate-determining alkene insertion transition state account for the origins of the enantioselectivity. Our computational study sheds light on the detailed reaction mechanism and also provides insights for the development of novel approaches for synthesis of high-value silicon-stereogenic compounds.

Lactic acid bacteria reduce the toxicity of tetrodotoxin through peptidoglycan mediated binding

Tetrodotoxin (TTX) is a potent neurotoxin found in nature, the possible presence of TTX in pufferfish ovaries, liver, and other processing waste poses a serious environmental and safety hazard. Lactic acid bacteria (LAB) was found to be able to remove a variety of harmful substances, however, its elimination action and mechanism on TTX is not clear. In this study, the removal effects of different states (activated, inactivated, and fragmented LABs) of three LAB strains on TTX amount and toxicity were tested and compared. It was found that thermal inactivated LABs had the best effect, which could reduce the TTX amount by 49.0%–60.33% and decrease the toxicity of TTX by 57.0%–83.67%. In addition, peptidoglycan (PG) of three strains of LABs was found to be a key component in the removal of TTX, which could decrease the toxicity of TTX by more than 87.0 %. By analyzing the changes of functional groups of PGs, zeta-potential and binding effect between PG and TTX before and after the masking of carboxyl or amino groups of PGs, it was found that the removal effect of PG to TTX was significantly decreased (>55.0%) when the carboxyl or amino groups of PGs were masked. At the same time, the zeta-potential of PG combined with TTX was also decreased. These results suggested that the amino and carboxyl groups of PGs were important action sites for the binding interaction between LAB and TTX, and electrostatic interaction might be one of the ways of binding between PG and TTX. Our study could provide a scientific supporting on the removal action mechanism research of PG to TTX.

Co-Al layered double oxide activated carbon composite for eliminating lead ions from water

In the current study, preparation of cobalt-aluminum layered double oxide doped activated carbon (Co-Al LDO/AC) was achieved by the co-precipitation technique and utilized for the remediation of lead (Pb2+) from water. Various methods were employed to examine the properties of the composite material, including BET, XRD, FTIR, SEM, and EDS analysis. The material characterization outcomes indicated that the LDO structure was successfully incorporated into the AC matrices with a surface area of 189.4 m2/g. The influence of adsorption parameters including Co-Al LDO/AC dosage, period of contact, initial Pb2+ loading, and initial solution pH were investigated. Moreover, the isotherm and kinetic models were investigated to provide a deeper understanding of the elimination mechanism of Pb2+ ions. The adsorption results illustrated that pH has a substantial influence on Pb2+ removal with a highest removal effectiveness at pH = 6 and a fast adsorption rate within 7 h. The kinetic data were well aligned with the pseudo-second-order model while the isotherm data obeyed the Sips model (R2>0.966). The highest adsorption uptake, estimated by the Sips model was 25.09 mg/g. Considering the modeling and characterization of the spent Co-Al LDO/AC, a chemical interaction process was involved in the elimination process and mainly controlled by ion exchange, electrostatic interactions, and surface complexation mechanisms. Accordingly, the Co-Al LDO/AC could have great potential as a promising hybrid for the purification of toxic Pb2+ ions from contaminated water streams.

Immature persimmon residue as a novel biosorbent for efficient removal of Pb(II) and Cr(VI) from wastewater: Performance and mechanisms

Owing to the powerful affinity of tannin toward heavy metal ions, it is frequently immobilized on adsorbents to enhance their adsorption properties. However, natural adsorbents containing tannin have been overlooked owing to its water solubility. Herein, a novel natural adsorbent based on the immature persimmon residue (IPR) with soluble tannin removed was fabricated to eliminate Pb(II) and Cr(VI) in aquatic environments. The insoluble tannin in IPR endowed it with prosperous properties for eliminating Pb(II) and Cr(VI), and the IPR achieved maximum Pb(II) and Cr(VI) adsorption quantities of 68.79 mg/g and 139.40 mg/g, respectively. Kinetics and isothermal adsorption analysis demonstrated that the removal behavior was controlled by monolayer chemical adsorption. Moreover, the IPR exhibited satisfactory Pb(II) and Cr(VI) removal efficiencies even in the presence of multiple coexisting ions and showed promising regeneration potential after undergoing five consecutive cycles. Additionally, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analysis unveiled that the elimination mechanisms were primarily electrostatic attraction, chelation and reduction. Overall, the IPR, as a tannin-containing biosorbent, was verified to possess substantial potential for heavy metal removal, which can provide new insights into the development of novel natural adsorbents from the perspective of waste resource utilization.

Evolution of alternative reproductive systems in Bacillus stick insects.

Reproduction is a key feature of all organisms, yet the way in which it is achieved varies greatly across the tree of life. One striking example of this variation is the stick insect genus Bacillus, in which five different reproductive modes have been described: sex, facultative and obligate parthenogenesis, and two highly unusual reproductive modes: hybridogenesis and androgenesis. Under hybridogenesis, the entire genome from the paternal species is eliminated and replaced each generation by mating with the corresponding species. Under androgenesis, an egg is fertilized, but the developing diploid offspring bear two paternal genomes and no maternal genome, as a consequence of unknown mechanisms. Here, we reevaluate the previous descriptions of Bacillus lineages and the proposed F1 hybrid ancestries of the hybridogenetic and obligately parthenogenetic lineages (based on allozymes and karyotypes) from Sicily, where all these reproductive modes are found. We generate a chromosome-level genome assembly for a facultative parthenogenetic species (B. rossius) and combine extensive field sampling with RADseq and mtDNA data. We identify and genetically corroborate all previously described species and confirm the ancestry of hybrid lineages. All hybrid lineages have fully retained their F1 hybrid constitution throughout the genome, indicating that the elimination of the paternal genome in hybridogens is always complete and that obligate parthenogenesis in Bacillus hybrid species is not associated with an erosion of heterozygosity as known in other hybrid asexuals. Our results provide a stepping stone toward understanding the transitions between reproductive modes and the proximate mechanisms of genome elimination.

The synergy of elimination and zero-determinant strategy on dynamic games

Groups often fall into the trap of mutual betrayal because of the free-riding behavior of individuals. To promote cooperation level of the group, a dynamic game mechanism with elimination is proposed in this paper. Then, we study the individual and synergistic effects of the elimination mechanism and zero-determinant strategy on the game evolution. To reduce the number of eliminated players, we analyze the main influencing factors of node's survival rate. It is found that the dynamic game mechanism can change the dilemma of mutual betrayal, however many players will be eliminated. The synergy of zero-determinant strategy and elimination can not only keep a high cooperation level, but also enable more individuals to survive in the games. Moreover, the survival rate of a node is directly related to its degree and its initial strategy. And the results are robust to game model and rule of elimination. This provides a feasible game mechanism for improving the cooperation level of the group and provides the optimal strategy implementation scheme for the individuals to realize the maximization of benefits.

Smart Nanocarriers for the Treatment of Retinal Diseases.

Retinal diseases, such as age-related macular degeneration, diabetic retinopathy, and retinoblastoma, stand as the leading causes of irreversible vision impairment and blindness worldwide. Effectively administering drugs for retinal diseases poses a formidable challenge due to the presence of complex ocular barriers and elimination mechanisms. Over time, various approaches have been developed to fabricate drug delivery systems for improving retinal therapy including virus vectors, lipid nanoparticles, and polymers. However, conventional nanocarriers encounter issues related to the controllability, efficiency, and safety in the retina. Therefore, the development of smart nanocarriers for effective or more invasive long-term treatment remains a desirable goal. Recently, approaches have surfaced for the intelligent design of nanocarriers, leveraging specific responses to external or internal triggers and enabling multiple functions for retinal therapy such as topical administration, prolonged drug release, and site-specific drug delivery. This Review provides an overview of prevalent retinal pathologies and related pharmacotherapies to enhance the understanding of retinal diseases. It also surveys recent developments and strategies employed in the intelligent design of nanocarriers for retinal disease. Finally, the challenges of smart nanocarriers in potential clinical retinal therapeutic applications are discussed to inspire the next generation of smart nanocarriers.

MOF-Based Membranes for Remediated Application of Water Pollution.

Membrane separation plays a crucial role in the current increasingly complex energy environment. Membranes prepared by metal-organic framework (MOF) materials usually possess unique advantages in common, such as uniform pore size, ultra-high porosity, enhanced selectivity and throughput, and excellent adsorption property, which have been contributed to the separation fields. In this comprehensive review, we summarize various designs and synthesized strategies of free-standing MOF and composite MOF-based membranes for water treatment. Special emphases are given not only on the effects of MOF on membrane performance, removal efficiencies, and elimination mechanisms, but also on the importance of MOF-based membranes for the applications of oily and micro-pollutant removal, adsorption, separation, and catalysis. The challenges and opportunities in the future for the industrial implementation of MOF-based membranes are also discussed.

Analysis and Comparison of Even-Order Back EMF Harmonics of Fractional-Slot Concentrated-Winding Consequent Pole Permanent Magnet Vernier Machines

Fractional-slot concentrated-winding (FSCW) consequent pole (CP) permanent magnet vernier (PMV) machines have received increasing attention due to their less magnet consumption but larger torque capability. However, the PM magnetomotive force (MMF) distribution is asymmetric in the CP structure. Thus, even-order air-gap flux density and back-electromotive force (back-EMF) harmonics are generated, which increases torque ripples. In this paper, to eliminate the even-order back-EMF harmonics and the resulting torque ripples, a comprehensive investigation on even-order flux density and back-EMF harmonics of five-phase FSCW CP PMV machines was presented, and then the general design rules without even-order back-EMF harmonics were summarized. Firstly, considering single- and double-layer windings, the effects of slot/pole number combination and flux modulator distribution on even-order flux density and back-EMF harmonics were analyzed. Secondly, the optimal slot/pole number combinations were selected, and then the rules for eliminating even-order back-EMF harmonics of CP PMV machines were summarized. As an extension, it was revealed that the harmonic elimination mechanism of CP PMV machines is applicable to CP-Halbach PMV machines. According to the summarized general design rules, the five-phase CP and CP-Halbach PMV machines with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> =20/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P_r</i> =21/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z_f</i> =10 were proposed. Their detailed performance has been comparatively analyzed and then the optimal one was selected for prototyping. Both finite element analysis (FEA) and experiments were carried out to validate theoretical analyses.

Bioaccumulation and Depuration Dynamics of Nickel Chloride in Nile Tilapia (Oreochromis niloticus) Exposed to Sub-lethal Concentrations

The current objective of this research is to examine the bioaccumulation and subsequent depuration levels of nickel chloride within vital organs such as the gills, liver, and kidney of Oreochromis niloticus under controlled laboratory conditions. The fish were subjected to exposure under two sub-lethal concentrations, i.e., 1/5th (9.39 ppm) and 1/10th (4.69 ppm), for 28 days of absorption and subsequently transferred to uncontaminated, good aerated water for 28days of elimination (depuration). Following 28 days of exposure to lower sub-lethal and higher sub-lethal nickel chloride concentrations, the sequence of bioaccumulation of nickel chloride in organs was observed as kidney &gt; liver &gt; gills. The depuration trend for higher and lower concentrations was gills&gt; liver &gt; kidney. The kidney exhibited the highest accumulation of Ni. Meanwhile, the Ni depuration in the gills was significantly (p&lt;0.05) more when compared to other routes following exposure to both concentrations. This research assessed nickel chloride's bioaccumulation and depuration dynamics in Oreochromis niloticus, providing insights into its physiological responses to metal exposure. The study concludes that nickel accumulates predominantly in the kidney, with gills exhibiting the highest depuration rates, highlighting the importance of understanding metal uptake and elimination mechanisms in aquatic organisms for effective pollution management.

A cytoprotective role for optineurin during mycobacterial infection of macrophages

Autophagy has emerged as a critical innate immune mechanism for host elimination of intracellular pathogens, however, the role of the autophagy receptor Optineurin during mycobacterial infection is not fully understood. To address this lacuna, we infected bone marrow-derived macrophages (BMDMs) derived from Optn+/+ and Optn−/− mice with Mycobacterium smegmatis, and observed the infection outcome at sequential time points. While low multiplicity of infection (MOI) did not show any significant difference between BMDMs from the two groups, at high MOI Optn−/− mice-derived BMDMs showed significantly lower colony forming unit counts, as well as lower cell counts at 12 h and 24 h post-infection. Quantification of cell numbers and nuclear morphologies at various time points post-infection indicated a markedly higher cell death in the Optineurin-deficient macrophages. Optineurin-deficient BMDMs showed significantly lower levels of the autophagosomal protein LC3-II upon infection, indicating a potential role for Optineurin in regulating autophagy during mycobacterial infection. Moreover, when stimulated by bacterial LPS, Optineurin deficient macrophages, showed altered levels of the inflammatory cytokine pro-IL-1β. These observations taken together suggest a novel regulatory role for Optineurin during mycobacterial infection. Its deficiency leads to an impairment in macrophage responses, directly impacting the pathophysiology of infection.

Catalytic elimination of NOx and CH3SH over synergistic reaction induced active sites

The synergistic elimination of hazardous NOx and CH3SH is of significance in various industrial production processes. However, the synergistic elimination mechanism is ambiguous and the efficient synergistic catalysts have never been reported. Herein, the synergistic reaction is originally demonstrated over CuOx modified CeO2/TiO2 catalysts via coupling with selective catalytic reduction of NOx by NH3 and catalytic oxidation of CH3SH. CuOx modification notably improves the acidity and redox ability, and promotes the absorption and oxidation of CH3SH, thus generating more CO2 rather than toxic CO and HCN by-products. Moreover, the CH3SH oxidation reaction induces the formation of SO42- on CeOx sites that contribute to NOx reduction reaction via improving the reactivity of adsorbed NH4+ species with nitrogen oxide species. This work provides insights into the synergistic catalytic elimination of NOx and CH3SH, and guides the development of environmental catalysis techniques for eliminating multiple pollutants in actual complex operating conditions.

Sustainable remediation of Cr(VI)-contaminated soil by soil washing and subsequent recovery of washing agents using biochar supported nanoscale zero-valent iron

Soil contamination by Cr(VI) has attracted widespread attention globally in recent years, but it remains a significant challenge in developing an environmentally friendly and eco-sustainable technique for the disposal of Cr(VI)-contaminated soil. Herein, a sustainable cyclic soil washing system for Cr(VI)-polluted soil remediation and the recovery of washing agents using biochar supported nanoscale zero-valent iron (nZVI-BC) was established. Citric acid (CA) was initially screened to desorb Cr(VI) from contaminated soil, mobilizing Cr from the highly bioaccessible fractions. The nZVI-BC exhibited superior properties for Cr(VI) and Cr(total) removal from spent effluent, allowing effective recovery of the washing agents. The elimination mechanism of Cr(total) by nZVI-BC involved the coordinated actions of electrostatic adsorption, reduction, and co-precipitation. The contributions to Cr(VI) reduction by Fe0, surface-bound Fe(II), and soluble Fe(II) were 0.6 %, 39.8 %, and 59.6 %, respectively. Meanwhile, CA favored the activity of surface-bound Fe(II) and Fe0 in nZVI-BC, enhancing the production of soluble Fe(II) to strengthen Cr(VI) removal. Finally, the recovered washing agent was proven to be reused three times. This study showcases that the combined soil washing using biodegradable chelant CA and effluent treatment by nZVI-BC could be a sustainable and promising strategy for Cr(VI)-contaminated soil remediation.

Calculation of lepton magnetic moments in quantum electrodynamics: A justification of the flexible divergence elimination method

The flexible method of reduction to finite integrals, briefly described in earlier publications of the author, is described in detail. The method is suitable for the calculation of all quantum electrodynamical contributions to the magnetic moments of leptons. It includes mass-dependent contributions. The method removes all divergences (UV, IR, and mixed) point-by-point in Feynman parametric space without any usage of limitlike regularizations. It yields a finite integral for each individual Feynman graph. The subtraction procedure is based on the use of linear operators applied to the Feynman amplitudes of UV-divergent subgraphs; a placement of all terms in the same Feynman parametric space is implied. The final result is simply the sum of the individual graph contributions; no residual renormalization is required. The method also allows us to split the total contribution into the contributions of small gauge-invariant classes. The procedure offers a great freedom in the choice of the linear operators. This freedom can be used for improving the computation speed and for a reliability check. The mechanism of divergence elimination is explained, as well as the equivalence of the method and the on shell renormalization. For illustrative purposes, all 4-loop contributions to the anomalous magnetic moments of the electron and muon are given for each small gauge-invariant class, as well as their comparison with previously known results. This also includes the contributions that depend on the ratios of the tau-lepton mass to the electron and muon mass. Published by the American Physical Society 2024

Autophagy Genes and Otitis Media Outcomes.

Otitis media (OM) is a common cause of hearing loss in children that requires corrective surgery. Various studies have investigated the pathomechanisms and treatment of OM. Autophagy, an essential cellular recycling and elimination mechanism implicated in various diseases, is known to play an important role in the pathogenesis of OM. Here, we conducted a literature review on autophagy in OM, highlighting the relationship between expression patterns of autophagy-related factors and pathophysiological and clinical aspects of OM. We summarized the existing research results on the expression of autophagy-related factors in acute OM (AOM), OM with effusion (OME), chronic OM (COM) with cholesteatoma, and COM without cholesteatoma (CholeOM) in animals and humans. Autophagy-related factors are expressed in the middle ear mucosa or fluid of AOM, effusion of OME, granulation tissue of COM, and cholesteatoma of CholeOM. Among ATGs and other autophagy-related factors, the most extensively studied in relation to the pathogenesis of OM are mTOR, LC3II/I, PI3K, Beclin-1, FLIP, Akt, and Rubicon. Expression of autophagy-related factors is associated with AOM, OME, COM, and CholeOM. Inadequate expression of these factors or a decrease/increase in autophagy responses can result in OM, underscoring the critical role of ATGs and related factors in the pathogenesis of OM.

Insights into embryonic chromosomal instability: mechanisms of DNA elimination during mammalian preimplantation development.

Mammalian preimplantation embryos often contend with aneuploidy that arose either by the inheritance of meiotic errors from the gametes, or from mitotic mis-segregation events that occurred following fertilization. Regardless of the origin, mis-segregated chromosomes become encapsulated in micronuclei (MN) that are spatially isolated from the main nucleus. Much of our knowledge of MN formation comes from dividing somatic cells during tumorigenesis, but the error-prone cleavage-stage of early embryogenesis is fundamentally different. One unique aspect is that cellular fragmentation (CF), whereby small subcellular bodies pinch off embryonic blastomeres, is frequently observed. CF has been detected in both in vitro and in vivo-derived embryos and likely represents a response to chromosome mis-segregation since it only appears after MN formation. There are multiple fates for MN, including sequestration into CFs, but the molecular mechanism(s) by which this occurs remains unclear. Due to nuclear envelope rupture, the chromosomal material contained within MN and CFs becomes susceptible to double stranded-DNA breaks. Despite this damage, embryos may still progress to the blastocyst stage and exclude chromosome-containing CFs, as well as non-dividing aneuploid blastomeres, from participating in further development. Whether these are attempts to rectify MN formation or eliminate embryos with poor implantation potential is unknown and this review will discuss the potential implications of DNA removal by CF/blastomere exclusion. We will also extrapolate what is known about the intracellular pathways mediating MN formation and rupture in somatic cells to preimplantation embryogenesis and how nuclear budding and DNA release into the cytoplasm may impact overall development.

Differences in Relevant Physicochemical Properties Correlate with Synergistic Activity of Antimicrobial Peptides.

With the urgent need for new medical approaches due to increased bacterial resistance to antibiotics, antimicrobial peptides (AMPs) have been considered as potential treatments for infections. Experiments indicate that combinations of several types of AMPs might be even more effective at inhibiting bacterial growth with reduced toxicity and a lower likelihood of inducing bacterial resistance. The molecular mechanisms of AMP-AMP synergistic antimicrobial activity, however, remain not well understood. Here, we present a theoretical approach that allows us to relate the physicochemical properties of AMPs and their antimicrobial cooperativity. It utilizes correlation and bioinformatics analysis. A concept of physicochemical similarity is introduced, and it is found that less similar AMPs with respect to certain physicochemical properties lead to greater synergy because of their complementary antibacterial actions. The analysis of correlations between the similarity and the antimicrobial properties allows us to effectively separate synergistic from nonsynergistic AMP pairs. Our theoretical approach can be used for the rational design of more effective AMP combinations for specific bacterial targets, for clarifying the mechanisms of bacterial elimination, and for a better understanding of cooperativity phenomena in biological systems.

The Characteristics and Reflections of Engineering Doctorate Training System in China

The doctoral education in engineering has emerged to cultivate adept leaders in applied engineering technology, contributing to the establishment of an innovative nation. The engineering doctoral education in China has evolved over a decade. This study analyzes doctoral degrees in engineering at four Chinese universities, examining the current state of engineering doctoral education across various dimensions, including training objectives, admission criteria, curriculum design, pedagogical approaches, and graduation requirements. Overall, China's engineering doctoral training system exhibits a gradual improvement, concomitant with a progressive expansion in scale. Looking forward, it is imperative to broaden the spectrum of enrollment, enhance the theoretical foundation of engineering doctoral students, fortify quality control measures, and implement an elimination mechanism. This research contributes to a nuanced understanding of the developmental trajectory of engineering doctoral education in China.

Photocatalytic TiO2-Based Nanostructures as a Promising Material for Diverse Environmental Applications: A Review

Contemporary technological and industrial advancements have led to increased reliance on chemicals for product innovation, leading to heightened contamination of water sources by traditional pollutants (organic dyes, heavy metals) and disease-causing microorganisms. Wastewater treatment processes now reveal “emerging pollutants”, including pharmaceuticals, endocrine disruptors, and agricultural chemicals. While some are benign, certain emerging pollutants can harm diverse organisms. Researchers seek cost-effective water purification methods that completely degrade pollutants without generating harmful by-products. Semiconductor-based photocatalytic degradation, particularly using titanium dioxide (TiO2), is popular for addressing water pollution. This study focuses on recent applications of TiO2 nanostructures in photocatalysis for eliminating various water pollutants. Structural modifications, like doping and nanocomposite formation, enhance photocatalyst performance. The study emphasizes photocatalytic elimination mechanisms and comprehensively discusses factors impacting both the mechanism and performance of nano-TiO2-based photocatalysts. Characteristics of TiO2, such as crystal structure and energy band-gap, along with its photocatalytic activity mechanism, are presented. The review covers the advantages and limitations of different TiO2 nanostructure production approaches and addresses potential toxicity to human health and the environment. In summary, this review provides a holistic perspective on applying nano-TiO2 materials to mitigate water pollution.

Disturbance Propagation Model of Pedestrian Fall Behavior in a Pedestrian Crowd and Elimination Mechanism Analysis

Disturbance Propagation Model of Pedestrian Fall Behavior in a Pedestrian Crowd and Elimination Mechanism Analysis