High Dissociation Research Articles

Scission of C–O and C–C linkages in lignin over RuRe alloy catalyst

The performance of lignin depolymerization is basically determined by the interunit C–O and C–C bonds. Numerous C–O bond cleavage strategies have been developed, while the cleavage of C–C bond between the primary aromatic units remains a challenging task due to the high dissociation energy of C–C bond. Herein, a multifunctional RuRe alloy catalyst was designed, which exhibited exceptional catalytic activity for the cleavage of both C–O and C–C linkages in a broad range of lignin model compounds (β-1, α-5, 5–5, β-O-4, 4-O-5) and two stubborn lignins (kraft lignin and alkaline lignin), affording 97.5% overall yield of monocyclic compounds from model compounds and up to 129% of the maximum theoretical yield of monocyclic products based on C–O bonds cleavage from realistic lignin. Scanning transmission electron microscopy (STEM) characterization showed that RuRe (1:1) alloy particles with hexagonal close-packed structure were homogeneously dispersed on the support. Quasi-in situ X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) indicate that Ru species were predominantly metallic state, whereas Re species were partially oxidized; meanwhile, there was a strong interaction between Ru and Re, where the electron transfer from Re to Ru was occurred, resulting in great improvement on the capability of C–O and C–C bonds cleavage in lignin conversion.

The Influence of Magnetic Field on Newly Designed Oxyhydrogen and Hydrogen Production by Water Electrolysis

Herein, new prototypes of a dry cell and an H2 generator are designed to produce hydrogen and HHO (oxyhydrogen) gas, and the effect of a magnetic field on both systems is examined. Experiments are conducted in both systems; a 3.5% potassium hydroxide electrolyte is chosen because it is an alkaline type of solution with a high dissociation rate. NdFeB magnets with magnetic fluxes of 1.2 and 1.6 T are added to both systems to reveal the effect of the Lorentz force on gas production. The flow rates of HHO gas in the productions under 1.2 and 1.6 T in the HHO system are 680 and 730 ml min−1, respectively. These values show that the flow velocities were 15.4% (1.2 T) and 23% (1.6 T) greater, respectively than the values recorded without a magnetic field (MF). Additionally, the percentage of hydrogen production increased by 4% for 1.2 T and 11% for 1.6 T compared to the measured value without the MF. In addition, production costs are calculated for both systems in the study: the energy required to obtain the same flow rate as the comparison examples in the literature was lower.

Deposition of Al2O3 coatings in Ar-O2 low-pressure discharge plasma under a high dissociation degree of O2

The deposition of Al2O3 coating with a corundum structure was done by anodic evaporation in a low-pressure arc with a self-heated hollow cathode. The conditions were created for increasing the energy of plasma electrons and a corresponding increase in the frequency of O2 dissociation by contraction of the discharge in the anode region. The discharge was maintained in a combined mode with a constant current (70 – 100 A), on which current pulses (100 μs, 1 kHz) with adjustable amplitude (up to 220 A) were superimposed. This mode ensured a change in the degree of O2 dissociation in the range of 0.3 – 0.5 at constant average discharge current and Al evaporation rate. It is shown that an increase in the degree of O2 dissociation leads to an increase in the rate of coating deposition by a factor of 1.3 and promotion of the preferred (300) orientation of crystallites. The effect is due to the features of the adsorption of molecular and atomic oxygen on the Al2O3.

Quantitative determination of targeted and untargeted pesticide residues in coconut milk by liquid chromatography – Atmospheric pressure chemical ionization – high energy collisional dissociation tandem high-resolution mass spectrometry

Quantitative determination of targeted and untargeted pesticide residues from food products is very important for the assessment of safety of the food products. In the present work, a simple, selective and sensitive method based on liquid chromatography atmospheric pressure chemical ionization high energy collisional dissociation high-resolution tandem mass spectrometry (LC-APCI-HCD-HRMS/MS) for quantification of 19 priority organophosphorus and carbamate pesticides and 10 untargeted pesticides from coconut milk samples was developed and validated. The pesticide residues were extracted by solvent partition followed by dispersive solid-phase extraction clean-up and quantified by LC-APCI-HRMS/MS technique. The method showed the linearity for targeted pesticides in the range of 0.5–1000 ng/g with a limit of detection of ranging 0.5–5 ng/g and limit of quantification of ranging 1–10 ng/g measured at 3:1 and 10:1 signal to noise ratios, respectively. The untargeted pesticide residues were quantified by the response factor method. The method was validated for intraday and interday precision, which was less than 15%. The recovery of the analytes varied between 82 and 117%, and the developed method was applied for the analysis of the coconut milk samples. The analyzed samples showed the presence of quinalphos, malathion, and methiocarb at concentrations of 4.55, 5.54, and 206.99 ng/g.

Quantitative characterization of tetraspanin 8 homointeractions in the plasma membrane.

The spatial distribution of proteins in cell membranes is crucial for signal transduction, cell communication and membrane trafficking. Members of the Tetraspanin family organize functional protein clusters within the plasma membrane into so-called Tetraspanin-enriched microdomains (TEMs). Direct interactions between Tetraspanins are believed to be important for this organization. However, studies thus far have utilized mainly co-immunoprecipitation methods that cannot distinguish between direct and indirect, through common partners, interactions. Here we study Tetraspanin 8 homointeractions in living cells via quantitative fluorescence microscopy. We demonstrate that Tetraspanin 8 exists in a monomer-dimer equilibrium in the plasma membrane. Tetraspanin 8 dimerization is described by a high dissociation constant (Kd = 14 700 ± 1100 Tspan8/µm2), one of the highest dissociation constants measured for membrane proteins in live cells. We propose that this high dissociation constant, and thus the short lifetime of the Tetraspanin 8 dimer, is critical for Tetraspanin 8 functioning as a master regulator of cell signaling.

Enhanced Electrochemical Performance and Durability of the BaCo0.4Fe0.4Zr0.1Y0.1O3−δ Composite Cathode of Protonic Ceramic Fuel Cells via Forming Nickel Oxide Nanoparticles

In protonic ceramic fuel cells (PCFCs), oxygen reduction reaction activity is governed by the oxygen adsorption/dissociation, proton conduction, and electron transfer kinetics. Although various strategies have been explored to enhance the proton and electron conductivity via tuning the oxygen vacancy concentration in the electrode materials and introducing electronic conducting agents, there are few studies on improving oxygen adsorption/dissociation (surface-exchange reaction) kinetics in PCFCs. In this study, we report uniformly distributed thermodynamically stable nickel oxide (NiO) nanoparticles as a catalyst to enhance the electrochemical performance of the BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) cathode, which is a promising cathode material because of its triple (oxygen ion, proton, and electron) conductivity in PCFCs, by improving surface-exchange reaction kinetics. The 0D NiO nanoparticles with high adsorption and fast dissociation ability of oxygen could enlarge the active sites for surface-exchange reactions without fading the BCFZY surface and triple-phase boundaries where the H2O formation reaction occurs. The cathode employing NiO nanoparticles exhibits largely reduced polarization resistance and a superior power density of 780 mW/cm2 at 600 °C. This improvement is attributed to the enhanced surface-exchange reaction kinetics.

Activated N-methyl-D-aspartate receptor ion channels detected in focal epilepsy with [18 F]GE-179 positron emission tomography.

Imaging activated glutamate N-methyl-D-aspartate receptor ion channels (NMDAR-ICs) using positron emission tomography (PET) has proved challenging due to low brain uptake, poor affinity and selectivity, and high metabolism and dissociation rates of candidate radioligands. The radioligand [18 F]GE-179 is a known use-dependent marker of NMDAR-ICs. We studied whether interictal [18 F]GE-179 PET would detect foci of abnormal NMDAR-IC activation in patients with refractory focal epilepsy. Ten patients with refractory focal epilepsy and 18 healthy controls had structural magnetic resonance imaging (MRI) followed by a 90-min dynamic [18 F]GE-179 PET scan with simultaneous electroencephalography (EEG). PET and EEG findings were compared with MRI and previous EEGs. Standard uptake value (SUV) images of [18 F]GE-179 were generated and global gray matter uptake was measured for each individual. To localize focal increases in uptake of [18 F]GE-179, the individual SUV images were interrogated with statistical parametric mapping in comparison to a normal database. Additionally, individual healthy control SUV images were compared with the rest of the control database to determine their prevalence of increased focal [18 F]GE-179 uptake. Interictal [18 F]GE-179 PET detected clusters of significantly increased binding in eight of 10 patients with focal epilepsy but none of the controls. The number of clusters of raised [18 F]GE-179 uptake in the patients with epilepsy exceeded the focal abnormalities revealed by the simultaneously recorded EEG. Patients with extensive clusters of raised [18 F]GE-179 uptake showed the most abnormal EEGs. Detection of multiple foci of abnormal NMDAR-IC activation in 80% of our patients with refractory focal epilepsy using interictal [18 F]GE-179 PET could reflect enhanced neuronal excitability due to chronic seizure activity. This indicates that chronic epileptic activity is associated with abnormal NMDAR ion channel activation beyond the initial irritative zones. [18 F]GE-179 PET could be a candidate marker for identifying pathological brain areas in patients with treatment-resistant focal epilepsy.

Oligosaccharide mapping analysis by HILIC-ESI-HCD-MS/MS for structural elucidation of fucoidan from sea cucumber Holothuria floridana

The elucidation of precise structure of fucoidan is essential for understanding their structure-function relationship and promoting the development of marine drugs. In this work, we firstly reported the oligosaccharide mapping of fucoidan from Holothuria floridana using a combination of hydrothermal depolymerization, hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray mass spectrometry (ESI-FTMS) and high energy collision-induced dissociation (HCD-MS/MS) and 2D NMR analysis. With careful selection of fully deprotonated molecular ions of fucoidan oligosaccharides and their NaBD4 reduced alditols, HILIC-ESI-HCD-MS/MS provided structurally relevant glycosidic product ions with no sulfate loss for definitive assignment of sequence and sulfation pattern of all the oligosaccharides and their isomers from dp2 to dp7 from hydrothermal depolymerization. The oligosaccharide mapping clarified the structure of fucoidan with various oligosaccharide domains with 2,4-di-O-sulfated and 2-O sulfated fucose residues.

305 RISK OF GENERALIZATON IN PATIENTS WITH HIGH-RISK EARLY ESOPHAGEAL CANCER: RETROSPECTIVE ANALYSIS OF PROSPECTIVELY COLLECTED DATA INCLUDING LYMPH-NODE MICROMETASTASES ASSESSMENT

Abstract Esophagectomy is a standard of care for patients with "high-risk" early esophageal cancer (HRC) despite a growing evidence that endoscopic treatment may be a safe alternative. Our aims were 1. to prospectively evaluate the long-term results of endoscopic and surgical treatments in consecutive patients with HRC and 2. to determine the risk of lymph node (LN) metastases and micrometastases in patients with HRC. Methods HRC was defined as any cancer with submucosal (sm) invasion or mucosal cancer with at least one of the following: poor differentiation, invasion to blood or lymphatic vessels and high tumor cell dissociation (TCD3). All patients (n = 69) underwent endoscopic resection (ER or ESD) and after the histopathological diagnosis of HRC, patients without contraindications were referred to surgery (n = 30). The remaining patients (n = 39) continued in endoscopic treatment, if necessary. All resected LNs were stained for hematoxylin–eosin to evaluate metastases and immunohistochemistry was used for the detection of micrometastases or isolated tumor cells. Results Eighteen patients (26%) had T1a and 51 (74%) had T1b cancer; 51 had adenocarcinoma (AC) and 18 had squamous cell carcinoma (SCC). The median follow-up was 32 months (3–120). No patient with mucosal invasion (15 AC, 3 SCC) experienced LN involvement. Among 17 patients with sm1 invasion, only 2 (12%, both AC)experienced generalization or LN involvement. The further rates of LN involvement were 0% (0/5) in sm2 AC, 50% (3/6) in sm2 SCC, 25% (4/16) in sm3 AC and 29% (2/7) in sm3 SCC. 60% (18/30) of surgically treated patients would have been completely cured by endoscopy (Table 1). Conclusion The risk of LN metastases/micrometastases was lower than expected. No patients with high-risk mucosal cancer or low-risk sm1 cancer experienced lymph node involvement. Endoscopic treatment provided long-term remission (or cure) in considerable number of patients and it may represent a valid alternative to surgery in patients with high-risk early esophageal cancer.

Sodium hydroxide-enhanced acetaminophen elimination in heat/peroxymonosulfate system: Production of singlet oxygen and hydroxyl radical

Owing to the high peroxide bond dissociation energy (377 kJ mol−1), peroxymonosulfate (PMS) is rather difficult to be activated by heat for degrading organic pollutants. This work is the first to add sodium hydroxide (NaOH) to enhance the elimination of acetaminophen in heat/PMS system. Heat/PMS system even possessed a better Performance than heat/peroxydisulfate (PDS) system with the addition of NaOH. Quenching experiments and electron paramagnetic resonance tests demonstrated that singlet oxygen and hydroxyl radical were the primary reactive oxygen species responsible for acetaminophen elimination in NaOH-enhanced heat/PMS system. Singlet oxygen mainly came from the alkaline activation of PMS, while hydroxyl radical was generated from the thermolysis of peroxide bond. Increasing PMS concentration and reaction temperature favored the production of reactive oxygen species and the elimination of acetaminophen. Nine degradation intermediates of acetaminophen were identified by LC/TOF/MS and the corresponding degradation pathways were proposed. Chloride ion significantly accelerated the elimination of acetaminophen, while humic acid and carbonate ion slightly retarded acetaminophen removal. NaOH-enhanced heat/PMS system was highly efficient in eliminating many organic pollutants and more prone to degrading electron-rich organics. This study developed a simple and efficient approach to strengthening the oxidation capacity of heat-activated PMS and highlighted the superiority of PMS to PDS in thermolysis under alkaline conditions.

Turn-on, photostable, nontoxic and specific, iron(II) sensor

The pressing need to develop a specific analytical sensor that can identify and quantify Fe(II) without a cytotoxic response was the major motivation drive in this work. The turn-on fluorescent sensor here described can successfully detect Fe(II) and discriminate this ion from other analytes that commonly act as interferents in biological media. Moreover, this reduced fluoresceinamine-based sensor has a high photostability and high dissociation constant, which is an indication that the complex obtained between reduced fluoresceinamine (RFL) and Fe(II) is highly stable. This fluorescence-based sensor has a binding mechanism of 1:1 and a positive cooperativity was found between analyte and sensor. The detection, quantification and sensitivity parameters of the sensor were determined: 21.6 ± 0.1 μM; 65.6 ± 0.1 μM and 48 ± 3 (×107) μM, respectively. To evaluate a possible cytotoxicity effect an erythrocyte assay was performed and the obtained data were evaluated considering CdTe Quantum Dots (QDs) passivated with mercaptoacetic acid has experimental control. According to the resulting data RFL is not cytotoxic even when used in high concentrations, 660 mM. On the other hand QDs are quite different. Indeed it was proven that these heavy metal-based nanoparticles are responsible for 40% erytrocytes hemolysis in concentrations of 600 mM.

Translating ribosome affinity purification identifies markers of atherosclerosis-associated smooth muscle cells

Background and Aims: Vascular smooth muscle cells (SMCs) and SMC-derived cells are a major source of plaque cells and extracellular matrix at all stages of atherosclerosis. Recent single cell sequencing studies have identified new subsets of SMCs and demonstrated disease-associated changes in gene expression. Still, single cell studies are limited by the high cost and tissue dissociation artefacts. To address these limitations, we developed a mouse model that allows cost-effective analysis of SMC-specific translatome from any tissue using Translating Ribosome Affinity Purification (TRAP-Seq).

Atomistic observations on the structure evolution of glass-ceramics induced by the cascade collisions

Quantifying the response heterogeneity induced by the structural heterogeneity of Glass-Ceramics (GCs) during the collision procedures remains challenging. In this study, the Molecular dynamics (MD) method with continuous controlled melting, quenching, electron stopping effect, and the collisions is developed. The details of structure evolution of both crystalline phase (CP) and glass phase (GP) in GCs induced by the cascade collisions, as well as thermal peak effect are simulated. The results show that the period of the cascade collisions in GP is more extended than that in CP. During the cascade collisions, both kinetic and potential energy change sharply induced by the high dissociation threshold in CP. On the contrary, the conversion between kinetic and potential energy is relatively smooth in GP. Also, unlike in CP, the high-energy state atoms in GP are easier to leave after absorbing energy, leading to more irreversible structural changes. In addition, the atoms in CP are easier to propagate energy over a long distance, however, the atoms in GP are more likely to accumulate energy in a small range. These understandings as the theoretical basis are crucial for controlling the nanostructure of heterogeneous materials like GCs to meet specific property requirements.

Mechanochemistry of Cationic Cobaltocenium Mechanophore.

Recent research on the mechanochemistry of metallocene mechanophores has shed light on the force-responsiveness of these thermally and chemically stable organometallic compounds. In this work, we report a combination of experimental and computational studies on the mechanochemistry of main-chain cobaltocenium-containing polymers. Ester derivatives of the cationic cobaltocenium, though isoelectronic to neutral ferrocene, are unstable in the nonmechanical control experimental conditions that were accommodated by their ferrocene analogs. Replacing the electron withdrawing C-ester linkages with electron-donating C-alkyls conferred the necessary stability and enabled the mechanochemistry of the cobaltocenium to be assessed. Despite their high bond dissociation energy, cobaltocenium mechanophores are found to be selective sites of main chain scission under sonomechanical activation. Computational CoGEF calculations suggest that the presence of a counterion to cobaltocenium plays a vital role by promoting a peeling mechanism of dissociation in conjunction with the initial slipping.

Photoinduced transition-metal and external photosensitizer free phosphonation of unactivated C(sp2)–F bond via SET process under mild conditions

Transition-metal catalyzed cross-couplings of aryl halides (ArI, ArBr and ArCl) with a broad range of nucleophiles have been developed as powerful methods for carbon–carbon and carbon–heteroatom bonds formation. However, due to the high bond dissociation energy of unactivated C(sp2)–F, cross-couplings of mono-fluoroarenes are the most challenging, especially without using transition-metal catalysts. Herein, a photo-induced transition-metal and external photosensitizer free defluorophosphonation of monofluoroarenes via unactivated C(sp2)–F bond cleavage is reported. Different mono-fluoroarenes have been successfully cross-coupled with dialkyl phosphites in moderate to excellent yields under mild conditions. Mechanistic studies have revealed the possible involvement of a photo-induced SET process and aryl free radical intermediates.

High Yields of Aromatic Monomers from Acidolytic Oxidation of Kraft Lignin in a Biphasic System

In this work, acidic oxidation in a biphasic water/octanol system was applied to mitigate condensation and increase the yields of high-value aromatic monomers from Kraft lignin, a waste product, and an industrially relevant feedstock. Biphasic depolymerization (BPD) is a one-pot multistep technique in which target molecules are protected from degradation in the reactive aqueous milieu (necessary for the cleavage of β-O-4 bonds as well as the recalcitrant high dissociation energy carbon–carbon moieties) by an in situ transfer of the products into the protective octanol phase. The results have shown overall monomeric yields up to 13 wt % and yields of vanillin up to 7 wt % (FeCl3 as a catalyst and O2 as an oxidant), significantly outperforming the previously reported monophasic and biphasic outcomes for Kraft lignin. In addition to increased yields, BPD also resulted in an expansion of the product pool from few molecules typically reported in the literature to 64 aromatic monomers detected at various concentration levels in the current work. The identified aromatic alcohols, carbonyl compounds, and carboxylic acids incorporating varying side chain lengths show potential as green and sustainable replacements to BTX (benzene, toluene, and xylene) petrochemicals. BPD as a process coupled mild conversion conditions, cheap oxidants, and common homogeneous catalysts with an in situ separation of the products from the reaction mixture to yield excellent results in converting industrial waste and recalcitrant feedstocks into value.

Neutral all metal aromatic half-sandwich complexes between alkaline earth and transition metals: an ab initio exploration

Sandwich complexes find their interests among the chemists after the breakthrough discovery of ferrocene. Since then, a number of sandwich and half-sandwich complexes were predicted and synthesized. Herein, we have theoretically proposed a series of half-sandwich complexes involving a neutral Be3 ring and transition metal. Quantum chemical calculations have shown that the proposed complexes are quite stable involving high bond dissociation energies. The thermodynamics of their formation is also favorable. The Be3 ring in all cases possesses dual aromaticity which has been ascertained based on magnetic as well as topological feature of electron density.

Beyond internalizing and externalizing symptoms: The association between body disconnection and the symptoms of Internet gaming disorder

As the vast majority of online videogames imply the immersion into an alternative reality where a virtual body is also involved, the current cross-sectional study aims to investigate the contribution of low body awareness (i.e. low attention to sensory cues indicating bodily state) and body dissociation (i.e. low emotional connection with one’s own body) in predicting Internet gaming disorder (IGD) symptoms, after controlling for internalizing (i.e., depression, anxiety, and stress) and externalizing symptoms (i.e., aggression). A total of 370 online-game players (73% men; mean age 29.63 ± 7.64 years) recruited in online player communities took part in the study and were given a survey that included gaming characteristics, the Depression, Anxiety and Stress Scale −21, the Aggression Questionnaire, the Body Disconnection Scale, and the Internet Gaming Disorder Scale- Short Form. A hierarchical regression analysis showed that low body awareness and high body dissociation predicted IGD scores after controlling for all the other factors. Moreover, we found an interaction effect between physical aggression and body dissociation in predicting IGD scores. On the one hand, these results provide support to previous studies that stressed the potential association between dissociative detachment (in terms of bodily disconnections) and problematic videogaming; on the other hand, the current study provides first evidence of the opportunity to focus on the integration of bodily experiences in clinical practice with people suffering from problematic gaming, as this factor might be incisively related to their aggressive and internalizing symptoms.

A study of relative dissociation energy through electro-optics effect as a potential tool for evaluation of cooking oil quality

The electro-optics effect is a potential tool to observe and evaluate different oil quality. In this research, we study relative dissociation energy through the electro-optics effect to evaluate vegetable oil quality. Some vegetable cooking oil samples with different quality were placed in an external potential difference between parallel plates to obtain the electro-optical characteristics by measuring the polarization change using red pointer laser (650 nm). The empirical values of dissociation energy was obtained by fitting experimental data of the average polarization changes per unit potential difference with Lenard-Jones potential formula under the assumption that the interaction between molecules is a Vander Waals interaction. The results show that the average change in polarization is proportional to Lenard-Jones potential energy. An important result showed that a good oil quality is indicated by relatively high dissociation energy. Reducing the oil quality leads to increasing relative dissociation energy. This provides electro-optics as a very potential method in differentiating various cooking oil qualities and new perspective of interacting linear polarized light with oil molecules.

Electrophotocatalytic Si–H Activation Governed by Polarity-Matching Effects

Electrophotocatalytic Si–H Activation Governed by Polarity-Matching Effects