Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 342
Filtrar
Más filtros

País/Región como asunto
Intervalo de año de publicación
1.
Proc Natl Acad Sci U S A ; 121(4): e2318408121, 2024 Jan 23.
Artículo en Inglés | MEDLINE | ID: mdl-38232282

RESUMEN

We synthesized ammonia (NH3) by bubbling nitrogen (N2) gas into bulk liquid water (200 mL) containing 50 mg polytetrafluoroethylene (PTFE) particles (~5 µm in diameter) suspended with the help of a surfactant (Tween 20, ~0.05 vol.%) at room temperature (25 °C). Electron spin resonance spectroscopy and density functional theory calculations reveal that water acts as the proton donor for the reduction of N2. Moreover, isotopic labeling of the N2 gas shows that it is the source of nitrogen in the ammonia. We propose a mechanism for ammonia generation based on the activation of N2 caused by electron transfer and reduction processes driven by contact electrification. We optimized the pH of the PTFE suspension at 6.5 to 7.0 and employed ultrasonic mixing. We found an ammonia production rate of ~420 µmol L-1 h-1 per gram of PTFE particles for the conditions described above. This rate did not change more than 10% over an 8-h period of sustained reaction.

2.
Proc Natl Acad Sci U S A ; 120(16): e2301206120, 2023 Apr 18.
Artículo en Inglés | MEDLINE | ID: mdl-37036968

RESUMEN

Water (H2O) microdroplets are sprayed onto a magnetic iron oxide (Fe3O4) and Nafion-coated graphite mesh using compressed N2 or air as the nebulizing gas. The resulting splash of microdroplets enters a mass spectrometer and is found to contain ammonia (NH3). This gas-liquid-solid heterogeneous catalytic system synthesizes ammonia in 0.2 ms. The conversion rate reaches 32.9 ± 1.38 nmol s-1 cm-2 at room temperature without application of an external electric potential and without irradiation. Water microdroplets are the hydrogen source for N2 in contact with Fe3O4. Hydrazine (H2NNH2) is also observed as a by-product and is suspected to be an intermediate in the formation of ammonia. This one-step nitrogen-fixation strategy to produce ammonia is eco-friendly and low cost, which converts widely available starting materials into a value-added product.

3.
Proc Natl Acad Sci U S A ; 119(12): e2200991119, 2022 03 22.
Artículo en Inglés | MEDLINE | ID: mdl-35286201

RESUMEN

The anion of pyridine, C5H5N−, has been thought to be short lived in the gas phase and was only previously observed indirectly. In the condensed phase, C5H5N− is known to be stabilized by solvation with other molecules. We provide in this study striking results for the formation of isolated C5H5N− from microdroplets of water containing dissolved pyridine observed in the negative ion mass spectrum. The gas-phase lifetime of C5H5N− is estimated to be at least 50 ms, which is much longer than previously thought. The generated C5H5N− captured CO2 molecules to form a stable (Py-CO2)− complex, further confirming the existence of C5H5N−. We propose that the high electric field at the air­water interface of a microdroplet helps OH− to transfer an electron to pyridine to form C5H5N− and the hydroxyl radical •OH. Oxidation products of the Py reacting with •OH are also observed in the mass spectrum recorded in positive mode, which further supports this mechanism. The present study pushes the limits of the reducing and oxidizing power of water microdroplets to a new level, emphasizing how different the behavior of microdroplets can be from bulk water. We also note that the easy formation of C5H5N− in water microdroplets presents a green chemistry way to synthesize value-added chemicals.

4.
Anal Chem ; 96(1): 28-32, 2024 01 09.
Artículo en Inglés | MEDLINE | ID: mdl-38155587

RESUMEN

We report a technique for the noninvasive detection of skin cancer by imprint desorption electrospray ionization mass spectrometry imaging (DESI-MSI) using a transfer agent that is pressed against the tissue of interest. By noninvasively pressing a tape strip against human skin, metabolites, fatty acids, and lipids on the skin surface are transferred to the tape with little spatial distortion. Running DESI-MSI on the tape strip provides chemical images of the molecules on the skin surface, which are valuable for distinguishing cancer from healthy skin. Chemical components of the tissue imprint on the tape strip and the original basal cell carcinoma (BCC) section from the mass spectra show high consistency. By comparing MS images (about 150-µm resolution) of same molecules from the tape strip and from the BCC section, we confirm that chemical patterns are successfully transferred to the tape stripe. We also used the technique to distinguish cherry angiomas from normal human skin by comparing the molecular patterns from a tape strip. These results demonstrate the potential of the imprint DESI-MSI technique for the noninvasive detection of skin cancers as well as other skin diseases before and during clinical surgery.


Asunto(s)
Carcinoma Basocelular , Neoplasias Cutáneas , Humanos , Espectrometría de Masa por Ionización de Electrospray/métodos , Neoplasias Cutáneas/diagnóstico por imagen , Carcinoma Basocelular/diagnóstico , Ácidos Grasos
5.
J Am Chem Soc ; 145(50): 27198-27204, 2023 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-38054976

RESUMEN

The special redox reactivity of water microdroplets causes "mild ignition" of methane gas to form methane oxygenates. The C(sp3)-H bond of methane can be activated by the hydroxyl radical (OH·) or the hydrogen radical (H·) across the air-water interface (AWI) of microdroplets to generate the methyl radical (CH3·). Once CH3· is formed, it undergoes free-radical reactions with O2 in the air, excessive OH· and H· across the AWI, and H2O2 present at the AWI and generated CH3· itself to produce methanol and other species. Production of the methanol and other oxygenates was confirmed by gas chromatography, mass spectrometry, and 1H- and 13C-nuclear magnetic resonance. Formic acid, acetic acid, ethanol, carbon dioxide, and methyl peroxide were also detected as methane oxidation byproducts. This water microdroplet-initiated oxidation process can be further enhanced under ultrasonication to yield 2.66 ± 0.77 mM methanol conversion from the methane gas in a single spray run for 30 min, with a selectivity of 19.2% compared with all other oxygenated species.

6.
J Am Chem Soc ; 145(9): 5342-5352, 2023 Mar 08.
Artículo en Inglés | MEDLINE | ID: mdl-36812430

RESUMEN

Zeolites are widely used as catalysts and adsorbents in the chemical industry, but their potential for electronic devices has been stunted to date, as they are commonly recognized as electronic insulators. Here, we have for the first time demonstrated that Na-type ZSM-5 zeolites are ultrawide-direct-band-gap semiconductors based on optical spectroscopy, variable-temperature current-voltage characteristics, and photoelectric effect as well as electronic structure theoretical calculations and further unraveled the band-like charge transport mechanism in electrically conductive zeolites. The increase in charge-compensating Na+ cations in Na-ZSM-5 decreases the band gap and affects its density of states, shifting the Fermi level close to the conduction band. Remarkably, the semiconducting Na-ZSM-5 zeolites have been first applied for constructing electrically transduced sensors that can sense trace-level (77 ppb) ammonia with unprecedentedly high sensitivity, negligible cross-sensitivity, and high stability under moisture ambient conditions compared with conventional semiconducting materials and conductive metal-organic frameworks (MOFs). The charge density difference shows that the massive electron transfer between NH3 molecules and Na+ cations ascribed to Lewis acid sites enables electrically transduced chemical sensing. This work opens a new era of zeolites in applications of sensing, optics, and electronics.

7.
J Am Chem Soc ; 145(47): 25910-25916, 2023 Nov 29.
Artículo en Inglés | MEDLINE | ID: mdl-37966066

RESUMEN

Water (H2O) microdroplets are sprayed onto a graphite mesh covered with a CuBi2O4 coating using a 1:1 mixture of N2 and CO2 as the nebulizing gas. The resulting microdroplets contain urea [CO(NH2)2] as detected by both mass spectrometry and 13C nuclear magnetic resonance. This gas-liquid-solid heterogeneous catalytic system synthesizes urea in one step on the 0.1 ms time scale. The conversion rate reaches 2.7 mmol g-1 h-1 at 25 °C and 12.3 mmol g-1 h-1 at 65 °C, with no external voltage applied. Water microdroplets serve as the hydrogen source and the electron transfer medium for N2 and CO2 in contact with CuBi2O4. Water-gas and water-solid contact electrification are speculated to drive the reaction process. This strategy couples N2 fixation and CO2 utilization in an ecofriendly process to produce urea, converting a greenhouse gas into a value-added product.

8.
Anal Chem ; 95(17): 6775-6784, 2023 05 02.
Artículo en Inglés | MEDLINE | ID: mdl-37021399

RESUMEN

Metabolic perturbation score-based mass spectrometry imaging (MPS-MSI) is proposed to reveal the spatially resolved functional metabolic response associated with disease progression or drug action including metabolism pathways, species, biofunction, or biotransformation. The MPS-MSI enables the exploration of therapeutic or adverse effects, regional heterogeneous responses to drug treatment, possible molecular mechanisms, and even drug potential targets. MPS-MSI was demonstrated to be a promising molecular imaging tool not only for efficacy and safety evaluation but also for molecular mechanism investigation at the early stage of drug research and development.


Asunto(s)
Imagen Molecular , Espectrometría de Masas/métodos , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción
9.
Small ; 19(45): e2302613, 2023 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-37415556

RESUMEN

Glioblastoma is one of the most aggressive central nervous system malignancies with high morbidity and mortality. Current clinical approaches, including surgical resection, radiotherapy, and chemotherapy, are limited by the difficulty of targeting brain lesions accurately, leading to disease recurrence and fatal outcomes. The lack of effective treatments has prompted researchers to continuously explore novel therapeutic strategies. In recent years, nanomedicine has made remarkable progress and expanded its application in brain drug delivery, providing a new treatment for brain tumors. Against this background, this article reviews the application and progress of nanomedicine delivery systems in brain tumors. In this paper, the mechanism of nanomaterials crossing the blood-brain barrier is summarized. Furthermore, the specific application of nanotechnology in glioblastoma is discussed in depth.


Asunto(s)
Neoplasias Encefálicas , Glioblastoma , Nanopartículas , Humanos , Barrera Hematoencefálica , Glioblastoma/terapia , Glioblastoma/tratamiento farmacológico , Encéfalo , Sistemas de Liberación de Medicamentos , Nanopartículas/uso terapéutico , Neoplasias Encefálicas/terapia , Neoplasias Encefálicas/tratamiento farmacológico
10.
J Magn Reson Imaging ; 57(5): 1376-1389, 2023 05.
Artículo en Inglés | MEDLINE | ID: mdl-36173363

RESUMEN

BACKGROUND: T1 , T2 , and T2 * mappings are seldom performed in a single examination, and their values in evaluating symptomatic atherosclerosis are lacking. PURPOSE: To perform three-dimensional (3D) quantitative T1 , T2 , and T2 * mappings (SQUMA) multi-parametric imaging for carotid vessel wall and evaluate its reliability and value in assessing carotid atherosclerosis. STUDY TYPE: Prospective. SUBJECTS: Eight healthy subjects and 20 patients with symptomatic carotid atherosclerosis. FIELD STRENGTH/SEQUENCE: 3 T, SQUMA imaging T1 -, T2 -, and T2 *-mapping, multi-contrast vessel wall imaging including T1 - and T2 -weighted, time-of-flight, and SNAP sequences. ASSESSMENT: SQUMA was acquired in all subjects and multi-contrast images were acquired in healthy subjects. T1 , T2 , and T2 * values and lumen area (LA), wall area (WA), mean wall thickness (MeanWT), and normalized wall index (NWI) of carotid arteries were measured. SQUMA and multi-contrast measurements were compared in healthy subjects and differences in SQUMA measurements between healthy subjects and patients were assessed. The discriminative value of SQUMA measurements for symptomatic vessel was determined. STATISTICAL TESTS: Paired t or Wilcoxon signed-rank test, independent t or Mann-Whitney U test, area under the receiver operating characteristic curve (AUC), intraclass correlation coefficients, and Bland-Altman plots. Statistically significant level, P < 0.05. RESULTS: There were no significant differences in LA (P = 0.340), WA (P = 0.317), MeanWT (P = 0.088), and NWI (P = 0.091) of carotid arteries between SQUMA and multi-contrast vessel wall images. The values of T2 (50.9 ± 2.9 msec vs. 44.5 ± 4.2 msec), T2 * (28.2 ± 4.3 msec vs. 24.7 ± 2.6 msec), WA (23.7 ± 4.6 mm2 vs. 36.2 ± 7.7 mm2 ), MeanWT (0.99 ± 0.05 mm vs. 1.50 ± 0.28 mm), and NWI (40.7 ± 3.0% vs. 53.8 ± 5.4%) of carotid arteries in healthy subjects were significantly different from those in atherosclerotic patients. The combination of quantitative T1 , T2 , and T2 * values and MeanWT showed greatest AUC (0.81; 95% CI: 0.65-0.92) in discriminating symptomatic vessels. DATA CONCLUSION: Carotid MR 3D quantitative multi-parametric imaging of SQUMA enables acquisition of T1 , T2 , and T2 * maps, reliably measuring carotid morphology and discriminating carotid symptomatic atherosclerosis. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.


Asunto(s)
Aterosclerosis , Enfermedades de las Arterias Carótidas , Humanos , Reproducibilidad de los Resultados , Estudios Prospectivos , Imagen por Resonancia Magnética/métodos , Imagenología Tridimensional/métodos , Arterias Carótidas
11.
BMC Neurol ; 23(1): 155, 2023 Apr 20.
Artículo en Inglés | MEDLINE | ID: mdl-37081429

RESUMEN

BACKGROUND: Pituitary dysfunction (PD) is a common complication after aneurysmal subarachnoid hemorrhage (aSAH). The prevalence of PD varies widely at a global level and no recent meta-analysis is available. Therefore, the aim of our systematic review and meta-analysis was to summarize the updated estimates of worldwide prevalence of PD after aSAH. METHODS: Scopus, Embase, Web of Science, and PubMed databases were used to comprehensively search the appropriate literature and a random-effects meta-analysis on the results of the available studies was performed. The heterogeneity in the prevalence estimates was evaluated by subgroup analysis in terms of types of PD, and acute and chronic phases of aSAH. The onset of PD within 6 months after aSAH was considered as acute, while that after 6 months was considered as chronic. RESULTS: Twenty-seven studies with 1848 patients were included in this analysis. The pooled prevalence of PD in the acute phase was 49.6% (95% CI, 32.4-66.8%), and 30.4% (95% CI, 21.4-39.4%) in the chronic phase. Among the hormonal deficiencies, growth hormone dysfunction was the most prevalent in the acute phase, being 36.0% (95% CI, 21.0-51.0%), while hypoadrenalism was the most prevalent in the chronic phase, being 21.0% (95% CI, 12.0-29.0%). Among the six World Health Organization regions, the South-East Asia Region has the highest prevalence of PD in the acute phase (81.0%, 95%CI, 77.0-86.0%, P < 0.001), while the European Region had the highest prevalence of PD in the chronic phase (33.0%, 95%CI, 24.0-43.0%, P < 0.001). Moreover, single pituitary hormonal dysfunction occurred more frequently than the multiple one, regardless of acute or chronic phase. CONCLUSIONS: Almost half (49.6%) of the included patients with aSAH developed PD complication in the acute phase, while 30.4% of the patients developed them in the chronic phase. Although prevalence varies globally, the high healthcare burden, morbidity and mortality require greater awareness among clinicians.


Asunto(s)
Hemorragia Subaracnoidea , Humanos , Hemorragia Subaracnoidea/complicaciones , Hemorragia Subaracnoidea/epidemiología , Prevalencia
12.
Inorg Chem ; 62(47): 19288-19297, 2023 Nov 27.
Artículo en Inglés | MEDLINE | ID: mdl-37956183

RESUMEN

Metal-organic frameworks (MOFs) with permanent porosity and multifunctional catalytic sites constructed by two or more organic ligands are regarded as effective heterogeneous catalysts to improve certain organic catalytic reactions. In this work, a pillared-layer Zn-MOF (MOF-LS10) was constructed by 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine (H4TCPP) and 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (DPTZTZ). After activation, MOF-LS10 has a permanent porosity and moderate CO2 adsorption capacity. The introduction of thiazolo[5,4-d]thiazole (TZTZ), a photoactive unit, into the framework endows MOF-LS10 with excellent photocatalytic performance. MOF-LS10 can not only efficiently catalyze the formation of cyclic carbonates from CO2 and epoxide substrates under mild conditions but also can photocatalyze benzylamine coupling at room temperature. In addition, we used another two ligands 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (H4BTEB) and 1,4-di(pyridin-4-yl)benzene (DPB) to synthesize MOF-LS11 (constructed by BTEB4- and DPTZTZ) and MOF-LS12 (constructed by TCPP4- and DPB) in order to explore whether the pyrazine structural unit and the TZTZ structural unit synergistically catalyze the reaction. The electron paramagnetic resonance spectrum demonstrates that the superoxide radical (·O2-), generated by electron transfer from the MOF excited by light to the oxidant, is the main active substance of oxidation. The design and synthesis of MOF-LS10 provide an effective synthetic strategy for the development of versatile heterogeneous catalysts for various organic reactions and a wide range of substrates.

13.
Acta Pharmacol Sin ; 44(5): 969-983, 2023 May.
Artículo en Inglés | MEDLINE | ID: mdl-36807413

RESUMEN

Nuclear pore complex in the nuclear envelope plays an important role in controlling the transportation of RNAs, proteins and other macromolecules between the nucleus and cytoplasm. The relationship between abnormal expression of nucleoporins and cardiovascular diseases is unclear. In this study we investigated how myocardial infarction affected the expression and function of nucleoporins in cardiomyocytes. We separately knocked down 27 nucleoporins in rat primary myocardial cells. Among 27 nucleoporins, knockdown of Nup93, Nup210 and Nup214 markedly increased the expression of ANP and BNP, two molecular markers of cardiomyocyte function. We showed that Nup93 was significantly downregulated in hypoxic cardiomyocytes. Knockdown of Nup93 aggravated hypoxia-induced injury and cell death of cardiomyocytes, whereas overexpression of Nup93 led to the opposite effects. RNA-seq and bioinformatics analysis revealed that knockdown of Nup93 did not affect the overall transportation of mRNAs from the nucleus to the cytoplasm, but regulated the transcription of a large number of mRNAs in cardiomyocytes, which are mainly involved in oxidative phosphorylation and ribosome subunits. Most of the down-regulated genes by Nup93 knockdown overlapped with the genes whose promoters could be directly bound by Nup93. Among these genes, we demonstrated that Nup93 knockdown significantly down-regulated the expression of YAP1. Overexpression of YAP1 partially rescued the function of Nup93 knockdown and attenuated the effects of hypoxia on cell injury and cardiomyocyte death. We conclude that down-regulation of Nup93, at least partially, contributes to hypoxia-induced injury and cardiomyocyte death through abnormal interaction with the genome to dynamically regulate the transcription of YAP1 and other genes. These results reveal a new mechanism of Nup93 and might provide new therapeutic targets for the treatment of ischemia-induced heart failure.


Asunto(s)
Miocitos Cardíacos , Proteínas de Complejo Poro Nuclear , Animales , Ratas , Apoptosis , Regulación hacia Abajo , Hipoxia/metabolismo , Hipoxia/patología , Miocitos Cardíacos/metabolismo , Proteínas de Complejo Poro Nuclear/genética , Proteínas de Complejo Poro Nuclear/metabolismo , Transcripción Genética
14.
J Chem Phys ; 158(10): 104701, 2023 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-36922139

RESUMEN

Revealing the coaction effect of radiative and non-radiative damping on the lifetime of the localized surface plasmon resonance (LSPR) mode is a prerequisite for the applications of LSPR. Here, we systematically investigated the coaction effect of radiative and non-radiative damping on the lifetime of the super-radiant and sub-radiant LSPR modes of gold nanorods using time-resolved photoemission electron microscopy (TR-PEEM). The results show that the lifetime of the LSPR mode depends on the length of the gold nanorod, and the different variation behavior of an LSPR mode lifetime exists between the super-radiative mode and the sub-radiative one with the increase of nanorod length (volume). Surprisingly, it is found that the lifetime of the super-radiant LSPR mode can be comparable to or even longer than that of the sub-radiant LSPR mode, instead of the usual claim that a sub-radiant LSPR mode has a longer life than the super-radiant mode. Those TR-PEEM experimental results are supported by finite-difference time-domain simulations and are well explained by the coaction effect with the calculation of the radiative and non-radiative damping rate with the increase of the nanorod volume. We believe that this study is beneficial to build a low-threshold nano-laser and ultrasensitive molecular spectroscopy system.

15.
Proc Natl Acad Sci U S A ; 117(28): 16167-16173, 2020 07 14.
Artículo en Inglés | MEDLINE | ID: mdl-32601197

RESUMEN

Saliva is a noninvasive biofluid that can contain metabolite signatures of oral squamous cell carcinoma (OSCC). Conductive polymer spray ionization mass spectrometry (CPSI-MS) is employed to record a wide range of metabolite species within a few seconds, making this technique appealing as a point-of-care method for the early detection of OSCC. Saliva samples from 373 volunteers, 124 who are healthy, 124 who have premalignant lesions, and 125 who are OSCC patients, were collected for discovering and validating dysregulated metabolites and determining altered metabolic pathways. Metabolite markers were reconfirmed at the primary tissue level by desorption electrospray ionization MS imaging (DESI-MSI), demonstrating the reliability of diagnoses based on saliva metabolomics. With the aid of machine learning (ML), OSCC and premalignant lesions can be distinguished from the normal physical condition in real time with an accuracy of 86.7%, on a person by person basis. These results suggest that the combination of CPSI-MS and ML is a feasible tool for accurate, automated diagnosis of OSCC in clinical practice.


Asunto(s)
Carcinoma de Células Escamosas/diagnóstico , Metabolómica , Neoplasias de la Boca/diagnóstico , Saliva/metabolismo , Adulto , Anciano , Biomarcadores de Tumor/metabolismo , Carcinoma de Células Escamosas/metabolismo , Carcinoma de Células Escamosas/patología , Femenino , Humanos , Aprendizaje Automático , Masculino , Persona de Mediana Edad , Neoplasias de la Boca/metabolismo , Neoplasias de la Boca/patología , Estadificación de Neoplasias , Pruebas en el Punto de Atención , Reproducibilidad de los Resultados , Espectrometría de Masa por Ionización de Electrospray
16.
Angew Chem Int Ed Engl ; 62(9): e202216969, 2023 02 20.
Artículo en Inglés | MEDLINE | ID: mdl-36622964

RESUMEN

We present immunoassay-based desorption electrospray ionization mass spectrometry imaging (immuno-DESI-MSI) to visualize functional macromolecules such as drug targets and cascade signaling factors. A set of boronic acid mass tags (BMTs) were synthesized to label antibodies as MSI probes. The boronic ester bond is employed to cross-link the BMT with the galactosamine-modified antibody. The BMT can be released from its tethered antibody by ultrafast cleavage of the boronic ester bond caused by the acidic condition of sprayed DESI microdroplets containing water. The fluorescent moiety enables the BMT to work in both optical and MS imaging modes. The positively charged quaternary ammonium group enhances the ionization efficiency. The introduction of the boron element also makes mass tags readily identified because of its unique isotope pattern. Immuno-DESI-MSI provides an appealing strategy to spatially map macromolecules beyond what can be observed by conventional DESI-MSI, provided antibodies are available to the targeted molecules of interest.


Asunto(s)
Diagnóstico por Imagen , Espectrometría de Masa por Ionización de Electrospray , Espectrometría de Masa por Ionización de Electrospray/métodos
17.
Angew Chem Int Ed Engl ; 62(29): e202306261, 2023 Jul 17.
Artículo en Inglés | MEDLINE | ID: mdl-37222120

RESUMEN

The development of efficient catalyst for selective oxidation of hydrocarbon to functional compounds remains a challenge. Herein, mesoporous Co3 O4 (mCo3 O4 -350) showed excellent catalytic activity for selective oxidation of aromatic-alkanes, especially for oxidation of ethylbenzene with a conversion of 42 % and selectivity of 90 % for acetophenone at 120 °C. Notably, mCo3 O4 presented a unique catalytic path of direct oxidation of aromatic-alkanes to aromatic ketones rather than the conventional stepwise oxidation to alcohols and then to ketones. Density functional theory calculations revealed that oxygen vacancies in mCo3 O4 activate around Co atoms, causing electronic state change from Co3+ (Oh) →Co2+ (Oh) . Co2+ (Oh) has great attraction to ethylbenzene, and weak interaction with O2 , which provide insufficient O2 for gradual oxidation of phenylethanol to acetophenone. Combined with high energy barrier for forming phenylethanol, the direct oxidation path from ethylbenzene to acetophenone is kinetically favorable on mCo3 O4 , sharply contrasted to non-selective oxidation of ethylbenzene on commercial Co3 O4 .

18.
Neuroimage ; 263: 119644, 2022 11.
Artículo en Inglés | MEDLINE | ID: mdl-36170952

RESUMEN

White matter (WM) neuroplasticity in the human brain has been tracked non-invasively using advanced magnetic resonance imaging techniques, with increasing evidence for improved axonal transmission efficiency as a central mechanism. The current study is the culmination of a series of studies, which characterized the structure-function relationship of WM transmission efficiency in the cortico-spinal tract (CST) during motor learning. Here, we test the hypothesis that increased transmission efficiency is linked directly to increased myelination using myelin water imaging (MWI). MWI was used to evaluate neuroplasticity-related improvements in the CST. The MWI findings were then compared to diffusion tensor imaging (DTI) results, with the secondary hypothesis that radial diffusivity (RD) would have a stronger relationship than axial diffusivity (AD) if the changes were due to increased myelination. Both MWI and RD data showed the predicted pattern of significant results, strongly supporting that increased myelination plays a central role in WM neuroplasticity.


Asunto(s)
Sustancia Blanca , Humanos , Sustancia Blanca/diagnóstico por imagen , Sustancia Blanca/patología , Imagen de Difusión Tensora/métodos , Encéfalo/diagnóstico por imagen , Imagen de Difusión por Resonancia Magnética , Imagen por Resonancia Magnética , Agua
19.
J Am Chem Soc ; 144(37): 16744-16748, 2022 09 21.
Artículo en Inglés | MEDLINE | ID: mdl-36075012

RESUMEN

We report the use of 1,2,3-triazole (Tz)-containing water microdroplets for gas-phase carbon dioxide (CO2) reduction at room temperature. Using a coaxial sonic spraying setup, the CO2 can be efficiently captured by Tz and converted to formic acid (HCOOH; FA) at the gas-liquid interface (GLI). A mass spectrometer operated in negative ion mode monitors the capture of CO2 to form the bicarbonate anion (HCO3-) and conversion to form the formate anion (HCOO-). Varied FA species were successfully identified by MS/MS experiments including the formate monomer ([FA - H]-, m/z 45), the dimer ([2FA - H]-, m/z 91; [2FA + Na - 2H]-, m/z 113), the trimer ([3FA - H]-, m/z 137), and some other adducts (such as [FA - H + H2CO3]-, m/z 107; [2FA + Na - 2H + Tz]-, m/z 182). The reaction conditions were systematically optimized to make the maximum conversion yield reach over 80% with an FA concentration of approximately 71 ± 3.1 µM. The mechanism for the reaction is speculated to be that Tz donates the proton and the hydroxide (OH-) at the GLI, resulting in a stepwise yield of electrons to reduce gas-phase CO2 to FA.


Asunto(s)
Dióxido de Carbono , Agua , Bicarbonatos , Formiatos , Hidróxidos , Protones , Espectrometría de Masas en Tándem , Triazoles
20.
J Am Chem Soc ; 144(51): 23534-23542, 2022 Dec 28.
Artículo en Inglés | MEDLINE | ID: mdl-36512747

RESUMEN

Polyimide covalent organic framework (PI-COF) materials that can realize intrinsic redox reactions by changing the charge state of their electroactive sites are considered as emerging electrode materials for rechargeable devices. However, the highly crystalline PI-COFs with hierarchical porosity are less reported due to the rapid reaction between monomers and the poor reversibility of the polyimidization reaction. Here, we developed a water-assistant synthetic strategy to adjust the reaction rate of polyimidization, and PI-COF (COFTPDA-PMDA) with kgm topology consisting of dual active centers of N,N,N',N'-tetrakis(4-aminophenyl)-1,4-benzenediamine (TPDA) and pyromellitic dianhydride (PMDA) ligands was successfully synthesized with high crystallinity and porosity. The COFTPDA-PMDA possesses hierarchical micro-/mesoporous channels with the largest surface area (2669 m2/g) in PI-COFs, which can promote the Li+ ions and bulky bis(trifluoromethanesulfonyl)imide (TFSI-) ions in organic electrolyte to sufficiently interact with the dual active sites on COF skeleton to increase the specific capacity of cathode materials. As a cathode material for lithium-ion batteries, COFTPDA-PMDA@50%CNT which integrated high surface area and dual active center of COFTPDA-PMDA with carbon nanotubes via π-π interactions gave a high initial charge capacity of 233 mAh/g (0.5 A/g) and maintains at 80 mAh/g even at a high current density of 5.0 A/g after 1800 cycles.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA