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1.
Angew Chem Int Ed Engl ; : e202413190, 2024 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-39132953

RESUMEN

Herein, we disclose a simple copper-catalyzed method for enantioselective allylic C(sp3)-H oxidation of unsymmetrical acyclic alkenes, specifically 1-aryl-2-alkyl alkenes. The C-H substrates are used in limiting amounts, and the products are obtained with high enantioselectivity, E/Z-selectivity, and regioselectivity. The method exhibits broad functional group tolerance, and E/Z-alkene mixtures are suitable C-H substrates. The transformation is enabled by light irradiation, which sustains the enantioselective copper catalysis by photoinduced oxidant homolysis.

2.
Transl Psychiatry ; 14(1): 321, 2024 Aug 06.
Artículo en Inglés | MEDLINE | ID: mdl-39107266

RESUMEN

Obsessive-compulsive disorder (OCD) is a clinically challenging and refractory psychiatric disorder characterized by pathologically hyperactivated brain activity. Continuous theta burst stimulation (cTBS) is considered a potentially non-invasive treatment for inducing inhibitory effects on the underlying cortex. Numerous studies showed an unsatisfactory efficacy of cTBS for OCD. Accordingly, it seems that cTBS is ineffective for OCD. However, the neglect of varying OCD severities, modest sample size, absence of a multicenter design incorporating inpatients and outpatients, and lack of personalized imaging-guided targeting may constrain the conclusive findings of cTBS efficacy for OCD. In the preliminary experiment, 50 inpatients with OCD were enrolled to receive cTBS (10 sessions/day for five continuous days) or sham over the personalized right pre-supplementary motor area determined by the highest functional connectivity with the subthalamic nucleus according to our prior study. In the extension experiment, 32 outpatients with OCD received cTBS to generalize the treatment effects. The Yale-Brown Obsessive-Compulsive Scale (YBOCS) was assessed before and after treatment. In the preliminary experiment, the response rates in the cTBS group were 56.52%, respectively, significantly higher than those in the sham group. Further analysis revealed significant YBOCS improvement in patients with moderate OCD symptoms than those with severe OCD symptoms. In the extension experiment, the response rates were 50.00%. Additionally, a significant decrease in YBOCS scores was only found in patients with moderate OCD symptoms. This is the first study with an external validation design across two centers to identify OCD symptoms as playing an important role in cTBS treatment effects, especially in patients with moderate OCD symptoms.


Asunto(s)
Trastorno Obsesivo Compulsivo , Estimulación Magnética Transcraneal , Humanos , Trastorno Obsesivo Compulsivo/terapia , Trastorno Obsesivo Compulsivo/fisiopatología , Masculino , Femenino , Adulto , Estimulación Magnética Transcraneal/métodos , Persona de Mediana Edad , Resultado del Tratamiento , Adulto Joven , Corteza Motora/fisiopatología , Ritmo Teta
3.
Neurochem Res ; 2024 Jul 13.
Artículo en Inglés | MEDLINE | ID: mdl-39002091

RESUMEN

Alzheimer's disease (AD) represents the most widespread neurodegenerative disorder, distinguished by a gradual onset and slow progression, presenting a substantial challenge to global public health. The mitochondrial-associated membrane (MAMs) functions as a crucial center for signal transduction and material transport between mitochondria and the endoplasmic reticulum, playing a pivotal role in various pathological mechanisms of AD. The dysregulation of mitochondrial quality control systems is considered a fundamental factor in the development of AD, leading to mitochondrial dysfunction and subsequent neurodegenerative events. Recent studies have emphasized the role of MAMs in regulating mitochondrial quality control. This review will delve into the molecular mechanisms underlying the imbalance in mitochondrial quality control in AD and provide a comprehensive overview of the role of MAMs in regulating mitochondrial quality control.

4.
Neuropsychiatr Dis Treat ; 20: 1107-1115, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38774255

RESUMEN

Objective: Major depressive disorder (MDD) is a common mood disorder. Electroconvulsive therapy (ECT) has a significant effect on treatment-resistant MDD. Esketamine may have potential advantages in improving the efficacy of ECT, and the strong affinity of this compound for NMDAR renders it a viable therapeutic option for the management of depression. This study aims to compare the effects of different doses of esketamine combined with propofol anesthesia versus propofol anesthesia alone in ECT, aiming to provide further insights for optimizing ECT and enhancing comprehensive treatment outcomes for depression. Study Design and Methods: This study was a prospective, randomized, controlled, double-blind trial involving subjects and evaluators. One hundred eleven patients scheduled for ECT were randomly assigned to three groups. In Group P, propofol at 1mg/kg was administered intravenously. In Group P+E, propofol at a dosage of 0.5mg/kg and esketamine at a dosage of 0.5mg/kg was administered intravenously. Patients in Group P+SE received propofol at a dosage of 0.75mg/kg and esketamine at a dosage of 0.25mg/kg. The same anesthesia protocol was used for the same patient until the end of the last treatment. The primary outcome measures were the Hamilton depression scale (HAMD) and the Patient Health Questionnaire-9 (PHQ-9), the Columbia-Suicide Severity Rating Scale (C-SSRS), and the Digit symbol substitution test (DSST). Secondary outcomes included length of hospital stay, readmission rate, hemodynamic status, recovery, and adverse events. Discussion: This study aimed to compare the effects of propofol combined with different doses of esketamine for ECT. The results may provide a better choice for ECT anesthesia.

7.
Natl Sci Rev ; 11(1): nwad138, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38116089

RESUMEN

New particle formation (NPF) in the tropical free troposphere (FT) is a globally important source of cloud condensation nuclei, affecting cloud properties and climate. Oxidized organic molecules (OOMs) produced from biogenic volatile organic compounds are believed to contribute to aerosol formation in the tropical FT, but without direct chemical observations. We performed in situ molecular-level OOMs measurements at the Bolivian station Chacaltaya at 5240 m above sea level, on the western edge of Amazonia. For the first time, we demonstrate the presence of OOMs, mainly with 4-5 carbon atoms, in both gas-phase and particle-phase (in terms of mass contribution) measurements in tropical FT air from Amazonia. These observations, combined with air mass history analyses, indicate that the observed OOMs are linked to isoprene emitted from the rainforests hundreds of kilometers away. Based on particle-phase measurements, we find that these compounds can contribute to NPF, at least the growth of newly formed nanoparticles, in the tropical FT on a continental scale. Thus, our study is a fundamental and significant step in understanding the aerosol formation process in the tropical FT.

8.
Chem Sci ; 14(46): 13278-13289, 2023 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-38033905

RESUMEN

Enantioenriched chiral amines are of exceptional importance in the pharmaceutical industry. Recently, several new methods for the installation of these functional groups directly from non-acidic C(sp3)-H bonds by catalytic intermolecular enantioselective amination have been reported. These methods represent significant advances of the field and most of them display high levels of enantioselectivity, utilize the C(sp3)-H substrate as the limiting reagent, feature good functional group tolerance, and show compatibility with late-stage C(sp3)-H amination of advanced substrates. This perspective provides an overview of the recent developments in this rapidly advancing field and outlines possibilities and limitations, which will help identify unsolved challenges and guide future research efforts.

9.
J Pain Res ; 16: 3289-3296, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37790192

RESUMEN

Purpose: Parturients suffer severe pain during the stages of labor, especially the first and second. Epidural anesthesia is an effective method to alleviate labor pain. L2-3, L3-4 and L4-5 spaces have been reported to be the recommendable puncture points owing to the adequate analgesia effect and high safety. However, the speed of pain alleviation via the three points has hardly been determined, which is of great importance to parturients. Thus, the aim of this study is to compare the onset time of parturients' painless uterine contraction after epidural labor analgesia through different puncture points. Study Design and Methods: It is a prospective, randomized, controlled, and subject- and assessor-blinded study. Totally, 150 subjects scheduled for vaginal delivery are going to be randomly assigned into the L2-3 and L3-4 group. Puncture point in L2-3 group is lumbar 2-3 space, while in L3-4 group it is lumbar 3-4 space. Analgesia initiation and maintenance are the same between the two groups. Primary outcome will be percentage of painless uterine contraction 15 min after epidural labor analgesia initiation. Secondary outcomes will be the sensory blocking level, motor blocking score, adverse effects of parturients, drug liquid consumption in unit interval, apgar score and degree of satisfaction of the parturients. Discussion: This study estimates the onset time of parturients' painless uterine contraction after epidural labor analgesia through L2-3 or L3-4 space. The results may provide a better choice to relieve labor pain as soon as possible.

10.
Arthritis Res Ther ; 25(1): 206, 2023 10 19.
Artículo en Inglés | MEDLINE | ID: mdl-37858140

RESUMEN

BACKGROUND: Circular RNAs are involved in autoimmune disease pathogenesis. Our previous study indicated that circPTPN22 is involved in autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis, but the underlying mechanisms remain unclear. METHODS: First, the expression of circPTPN22 was detected by real-time PCR and western blotting. After overexpression or knockdown of circPTPN22, the proliferation of Jurkat cells was detected by the CCK-8 assay, and the apoptosis of Jurkat cells was detected by flow cytometry. In addition, the relationship between circPTPN22-miR-4689-S1PR1 was confirmed by bioinformatic analyses, fluorescence in situ hybridization assays, RNA-binding protein immunoprecipitation, and dual luciferase reporter assays. RESULTS: We found that circPTPN22 expression was downregulated in the PBMCs of SLE patients compared to those of healthy controls. Overexpression of circPTPN22 increased proliferation and inhibited apoptosis of Jurkat T cells, whereas knockdown of circPTPN22 exerted the opposite effects. CircPTPN22 acts as a miR-4689 sponge, and S1PR1 is a direct target of miR-4689. Importantly, the circPTPN22/miR-4689/S1PR1 axis inhibited the secretion of TNF-α and IL-6 in Jurkat T cells. CONCLUSIONS: CircPTPN22 acts as a miR-4689 sponge to regulate T-cell activation by targeting S1PR1, providing a novel mechanism for the pathogenesis of SLE.


Asunto(s)
Lupus Eritematoso Sistémico , MicroARNs , Proteína Tirosina Fosfatasa no Receptora Tipo 22 , ARN Circular , Receptores de Esfingosina-1-Fosfato , Linfocitos T , Humanos , Hibridación Fluorescente in Situ , Células Jurkat , Lupus Eritematoso Sistémico/genética , Lupus Eritematoso Sistémico/inmunología , Activación de Linfocitos/genética , Activación de Linfocitos/inmunología , MicroARNs/genética , MicroARNs/inmunología , Proteína Tirosina Fosfatasa no Receptora Tipo 22/genética , Proteína Tirosina Fosfatasa no Receptora Tipo 22/inmunología , ARN Circular/genética , ARN Circular/inmunología , Receptores de Esfingosina-1-Fosfato/genética , Receptores de Esfingosina-1-Fosfato/inmunología , Linfocitos T/inmunología
11.
Medicine (Baltimore) ; 102(42): e35717, 2023 Oct 20.
Artículo en Inglés | MEDLINE | ID: mdl-37861495

RESUMEN

BACKGROUND: To systematically evaluate the effects of vitamin D supplementation in patients with nonalcoholic fatty liver disease (NAFLD). METHODS: National Library of Medicine, Cochrane Library, Elsevier, China National Knowledge Infrastructure, Web of Science, WANFANG databases, and Google Scholar were retrieved to collect relevant randomized controlled trials, which are published from the earliest records the time the database was created to April 2023. Meta-analysis was conducted by using Review Manager 5.4 software after evaluating in terms of inclusion and exclusion criteria. The outcome indicators include 25-hydroxyvitamin D [25(OH)D] levels, insulin resistance index (homeostasis model assessment of insulin resistance), fasting blood glucose, and fasting insulin levels (FINS). RESULTS: Eight randomized controlled trials with a total of 657 patients are included. Vitamin D supplementation increased 25(OH)D levels significantly (mean difference [MD] = 2.01, 95% confidence intervals [CI]: 0.94 to 3.08, P < .05) and vitamin D supplementation had a significant effect on insulin resistance index (MD = -0.54, 95% CI: -1.28 to 0.20, P = .16), fasting glucose (MD = -0.59, 95% CI: -1.50 to 0.32, P = .20), and FINS levels (MD = -0.30, 95% CI: -0.77 to 0.17, P = .21) had no significant effect. CONCLUSION: Vitamin D supplementation improves 25(OH)D levels in patients with nonalcoholic fatty liver disease, but there is no effect on homeostasis model assessment of insulin resistance, fasting blood glucose, or FINS.


Asunto(s)
Resistencia a la Insulina , Enfermedad del Hígado Graso no Alcohólico , Humanos , Enfermedad del Hígado Graso no Alcohólico/tratamiento farmacológico , Glucemia/análisis , Suplementos Dietéticos , Vitamina D/uso terapéutico , Insulina , Ensayos Clínicos Controlados Aleatorios como Asunto
12.
Iran J Basic Med Sci ; 26(8): 927-933, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37427319

RESUMEN

Objectives: Increased oxidative stress and inflammatory response are risk factors for kidney and cardiovascular diseases in patients with hyperuricemia. Uric acid (UA) has been reported to cause inflammation and oxidative damage in cells by inhibiting the nuclear factor E2-related factor 2 (Nrf2) pathway. Notably, Simvastatin (SIM) can regulate the Nrf2 pathway, but whether SIM can regulate inflammatory response and oxidative stress in vascular endothelial cells induced by high UA via this pathway has not been clarified. Materials and Methods: To demonstrate this speculation, cell activity, as well as apoptosis, was estimated employing CCK-8 and TUNEL, respectively. Indicators of oxidative stress and inflammation were assessed by related kits and western blotting. Subsequently, the effects of SIM on signaling pathways were examined using western blotting. Results: The result showed that after UA exposure, oxidative stress was activated and inflammation was increased, and SIM could reverse this trend. Meanwhile, SIM could inhibit high UA-induced apoptosis. In addition, western blotting results showed that SIM reversed the down-regulation of the expression of Nrf2 pathway-related proteins caused by high UA. Conclusion: SIM alleviated the inflammatory response as well as inhibiting oxidative stress through the Nrf2 pathway, thereby attenuating high UA-induced vascular endothelial cell injury.

13.
Angew Chem Int Ed Engl ; 62(13): e202217638, 2023 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-36721305

RESUMEN

A method for direct access to enantioenriched benzylic amides and carbamate-protected primary benzylamines by C-H functionalization is reported. The C-H substrate is used as limiting reagent with only a small excess of the unactivated amide or carbamate nucleophile. The enantioselective intermolecular dehydrogenative C-N bond formation is enabled by a combination of a chiral copper catalyst, a photocatalyst, and an oxidant, and it takes place under mild conditions, which allow for a broad substrate scope. The method is compatible with late-stage C-H functionalization, and it provides easy access to 15 N-labeled amides and amines starting from cheap 15 NH4 Cl.

14.
Biomarkers ; 28(1): 130-138, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-36420648

RESUMEN

Rheumatoid arthritis (RA) is a type of systemic immune disease characterized by chronic inflammatory disease of the joints. However, the aetiology and underlying molecular events of RA are unclear. Here, we applied bioinformatics analysis to identify potential immune effector molecules involved in RA. The three microarray datasets were downloaded from the Gene Expression Omnibus (GEO) database. We used the R software screen 115 overlapping differentially expressed genes (DEGs). Subsequently, we constructed a protein-protein interaction (PPI) network encoded by these DEGs and identified 10 genes closely associated with RA - LCK, GZMA, GZMB, CD2, LAG3, IL-15, TNFRSF4, CD247, CCR5 and CCR7. Furthermore, in the miRNA-hub gene networks, we screened out hsa-miR-146a-5p, which is the miRNA controlling the largest number of hub genes. Finally, we found some transcription factors that closely interact with hub genes, such as FOXC1, GATA2, YY1, RUNX2, SREBF1, CEBPB and NFIC. This study successfully predicted that LCK, FOXC1 and hsa-miR-146a-5p can be used as potential immune effector molecules of RA. Our study may have potential implications for future prediction of disease progression in patients with symptomatic RA, and has important significance for the pathogenesis and targeted therapy of RA.


Asunto(s)
Artritis Reumatoide , MicroARNs , Humanos , Biología Computacional , Factores de Transcripción Forkhead/genética , Factores de Transcripción Forkhead/metabolismo , Perfilación de la Expresión Génica , Redes Reguladoras de Genes , Análisis por Micromatrices , MicroARNs/genética , Mapas de Interacción de Proteínas
15.
Rev Cardiovasc Med ; 24(11): 325, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-39076451

RESUMEN

Background: Systematic evaluation of the effects of vitamin D supplementation in heart failure (HF) patients. Methods: Searches were conducted on National Library of Medicine, Web of Science, Cochrane Library, Google Scholar, China National Knowledge Infrastructure, and WANFANG databases. We analyzed data by using Review Manager 5.4 software. All are from the earliest records to March 2023. Outcome indicators analyzed the left ventricular ejection fraction (LVEF), the left ventricular end-diastolic internal diameter (LVEDD), the B-type brain natriuretic peptide (BNP) level and the 25-hydroxy vitamin D (25(OH)D) level. Results: Ten studies with 1099 patients were included. LVEF (mean difference (MD) = 0.74, 95% CI: -0.29 to 1.76, p = 0.41), LVEDD (MD = -0.59, 95% CI: -1.83 to 0.66, p = 0.25), BNP (MD = -0.08, 95% CI: -0.24 to 0.08, p = 0.34), 25(OH)D (MD = 0.41, 95% CI: -0.28 to 1.11, p = 0.25) are not statistically significant. And there is no heterogeneity in the results of LVEF, LVEDD and BNP indicators. Conclusions: Vitamin D supplementation may not be helpful in the clinical management of patients with HF.

16.
J Clin Pharm Ther ; 47(12): 2320-2324, 2022 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-36511097

RESUMEN

WHAT IS KNOWN AND OBJECTIVE: Immune disorder is a key trigger of recurrent spontaneous abortion (RSA); meanwhile, tumour necrosis factor inhibitor (TNFi) is a fundamental therapeutic for multiple immune and inflammatory diseases. Hence, this real-world study aimed to explore the efficacy and safety of TNFi combined with intravenous immunoglobin (IVIG) and heparin therapy in RSA patients. METHODS: A total of 105 RSA patients who received TNFi+IVIG+Heparin (enoxaparin) (n = 48) or IVIG+Heparin (enoxaparin) (n = 57) were retrospectively included in this two-centre cohort study. RESULTS AND DISCUSSION: The live birth rate of RSA patients in the TNFi+IVIG+heparin group was 72.9% (95% confidence interval [CI]: 69.6%-85.9%). Besides, the live birth rate in the IVIG+heparin group was 52.6% (95% CI: 42.8%-62.4%). By comparison, the live birth rate was higher in the TNFi+IVIG+heparin group compared to the IVIG+heparin group (p = 0.033). After adjustment by the multivariate logistic regression model using the enter method, TNFi+IVIG+Heparin was also superior to IVIG+Heparin regarding increased live birth rate (odds ratio [OR] = 2.941, p = 0.015). Moreover, TNFi+IVIG+Heparin (vs. IVIG+Heparin) also served as an independent factor for increased live birth rate (OR = 2.423, p = 0.035) by the forward stepwise method in the multivariate analysis. Gestational weeks at delivery (38.3 ± 1.3 vs. 37.7 ± 2.0 weeks, p = 0.155), newborn weight (3123.9 ± 332.1 vs. 3056.6 ± 287.4 g, p = 0.390), Apgar score of newborns (9.8 ± 0.5 vs. 9.7 ± 0.7, p = 0.271) were of no difference between TNFi+IVIG+Heparin and IVIG+Heparin groups. In terms of safety profile, the adverse events were of no difference between the TNFi+IVIG+Heparin and the IVIG+Heparin groups (all p > 0.05), either. WHAT IS NEW AND CONCLUSION: TNFi combined with IVIG and heparin therapy improves the live birth rate but does not elevate the adverse events compared to IVIG and heparin therapy in RSA patients.


Asunto(s)
Aborto Habitual , Heparina , Embarazo , Femenino , Recién Nacido , Humanos , Heparina/efectos adversos , Inmunoglobulinas Intravenosas/efectos adversos , Estudios Retrospectivos , Inhibidores del Factor de Necrosis Tumoral/uso terapéutico , Estudios de Cohortes , Enoxaparina/uso terapéutico , Anticoagulantes/efectos adversos , Aborto Habitual/tratamiento farmacológico
17.
J Nutr Educ Behav ; 54(6): 510-520, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-35618404

RESUMEN

OBJECTIVE: To examine food access, dietary intake, and perceptions about diet and associations with health among adults on probation. DESIGN: Using a mixed-methods approach, interviews were used to understand food access, dietary intake, and diet and associations with health. A survey measured self-assessed diet quality and diet and associations with health. SETTING: One probation office in Rhode Island. PARTICIPANTS: English-speaking adults on probation in 2016 (n = 22 interviews, n = 304 surveys). MAIN OUTCOME MEASURE(S): Food access, dietary intake, knowledge about diet and health, and perceptions about healthy food. ANALYSIS: We used a thematic analytic approach to analyze the interviews. Descriptive statistics were performed for the survey. RESULTS: Many interviewees had inadequate food access, although most participated in the Supplemental Nutrition Assistance Program, and some received food from food banks. Interviewees primarily shopped at grocery stores and prepared food at home, and dietary intakes did not meet the 2020-2025 Dietary Guidelines for Americans. Almost two-thirds (64.2%) of survey participants reported good or fair diet quality. Based on the survey results, the majority of participants strongly agreed and agreed with the statements, "The types of foods I eat affect my health" and "The types of food I eat affect my weight." CONCLUSIONS AND IMPLICATIONS: This study identified low-quality dietary intake and food acquisition strategies, such as shopping sales, buying bulk, and going to multiple stores, by US adults on probation to access food with limited resources. Participants reported interest in eating healthier foods and knew there was a connection between dietary intake and health. These data support addressing ways to improve food access and dietary quality, focusing on future programs and policies for this population.


Asunto(s)
Asistencia Alimentaria , Alimentos , Adulto , Dieta , Ingestión de Alimentos , Abastecimiento de Alimentos , Humanos , Estados Unidos
18.
Int J Nanomedicine ; 17: 1483-1494, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35378882

RESUMEN

Ventilator-associated pneumonia (VAP) is a common and serious nosocomial infection in mechanically ventilated patients, increasing mortality, prolonging the patient length of stay, and increasing costs. In recent years, extensive studies on ventilator-associated pneumonia have shown that tracheal intubation plays an essential role in the pathogenesis of VAP, with the primary mechanism being the rapid colonization of the tracheal intubation surface by microbiota. Antibiotics do not combat microbial airway colonization, and antimicrobial coating materials offer new ideas to solve this problem. This paper reviews the current research progress on the role of endotracheal tube (ET) biofilms in the pathogenesis of VAP and antimicrobial coating materials.


Asunto(s)
Microbiota , Neumonía Asociada al Ventilador , Antibacterianos/farmacología , Humanos , Intubación Intratraqueal/efectos adversos , Neumonía Asociada al Ventilador/etiología , Neumonía Asociada al Ventilador/prevención & control , Respiración Artificial/efectos adversos
19.
Anal Chem ; 94(14): 5690-5698, 2022 Apr 12.
Artículo en Inglés | MEDLINE | ID: mdl-35357157

RESUMEN

A linearly decreasing electric field has been previously proven to be effective for diffusional correction of ions in a varying field drift tube (VFDT) system, leading to higher resolving powers compared to a conventional drift tube due to its capacity to narrow distributions midflight. However, the theoretical predictions in resolving power of the VFDT were much higher than what was observed experimentally. The reason behind this discrepancy has been identified as the difference between the theoretically calculated resolving power (spatial) and the experimental one (time). To match the high spatial resolving power experimentally, a secondary high voltage pulse (HVP) at a properly adjusted time is used to provide the ions with enough momentum to increase their drift velocity and hence their time-resolving power. A series of systematic numerical simulations and experimental tests have been designed to corroborate our theoretical findings. The HVP-VFDT atmospheric pressure portable system improves the resolving power from the maximum expected of 60-80 for a regular drift tube to 250 in just 21 cm in length and 7kV, an unprecedent accomplishment.

20.
Dalton Trans ; 50(21): 7356-7363, 2021 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-33960360

RESUMEN

Treatment of bis(arylimino)acenaphthene (ArBIAN) with Ni(COD)2 in toluene afforded dmpBIANNi(COD) (2a, dmp = 2,6-Me2C6H3) and dippBIANNi(COD) (2b, dipp = 2,6-iPrC6H3), respectively, in moderate yields. Complexes 2a and 2b can be oxidized by a small amount of oxygen at low temperature leading to oxygen-bridged dinuclear Ni(ii) complexes (dmpBIANNi)2(µ-O)2 (4a) and (dippBIANNi)2(µ-O)2 (4b), respectively, as a purple powder. The reaction of ArBIAN with 0.5 equiv of Ni(COD)2 or Ni(Ph3P)4 gave bisligated complexes (dmpBIAN)2Ni (3a) and (dippBIAN)2Ni (3b), which can be considered as Ni(0) complexes supported by two neutral BIAN ligands. Oxidation of the bisligated nickel complexes 3a and 3b with [Cp2Fe][B(C6F5)4] afforded cationic Ni(i) complexes [(dmpBIAN)2Ni][B(C6F5)4] (5a) and [(dippBIAN)2Ni][B(C6F5)4] (5b), respectively, in which the Ni(i) centre is chelated by two neutral Ar-BIAN ligands. These complexes were characterized by NMR and IR spectroscopy and DFT calculation, and the molecular structures of 3b, 4b, and 5b were well established by X-ray diffraction analysis. These complexes were evaluated as catalysts for ethylene polymerization in which 2b showed high activity in the presence of AlMe3. 13C NMR analysis of polymers showed that the 2b/AlMe3 catalytic system gave less-branched polymers when compared to that obtained with dippBIANNiBr2 under the same conditions.

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