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1.
Ann Neurol ; 2024 Jun 27.
Artículo en Inglés | MEDLINE | ID: mdl-38934512

RESUMEN

OBJECTIVE: Although metabolic abnormalities are implicated in the etiology of neurodegenerative diseases, their role in the development of amyotrophic lateral sclerosis (ALS) remains a subject of controversy. We aimed to identify the association between metabolic syndrome (MetS) and the risk of ALS. METHODS: This study included 395,987 participants from the UK Biobank to investigate the relationship between MetS and ALS. Cox regression model was used to estimate hazard ratios (HR). Stratified analyses were performed based on gender, body mass index (BMI), smoking status, and education level. Mediation analysis was conducted to explore potential mechanisms. RESULTS: In this study, a total of 539 cases of ALS were recorded after a median follow-up of 13.7 years. Patients with MetS (defined harmonized) had a higher risk of developing ALS after adjusting for confounding factors (HR: 1.50, 95% CI: 1.19-1.89). Specifically, hypertension and high triglycerides were linked to a higher risk of ALS (HR: 1.53, 95% CI: 1.19-1.95; HR: 1.31, 95% CI: 1.06-1.61, respectively). Moreover, the quantity of metabolic abnormalities showed significant results. Stratified analysis revealed that these associations are particularly significant in individuals with a BMI <25. These findings remained stable after sensitivity analysis. Notably, mediation analysis identified potential metabolites and metabolomic mediators, including alkaline phosphatase, cystatin C, γ-glutamyl transferase, saturated fatty acids to total fatty acids percentage, and omega-6 fatty acids to omega-3 fatty acids ratio. INTERPRETATION: MetS exhibits a robust association with an increased susceptibility to ALS, particularly in individuals with a lower BMI. Furthermore, metabolites and metabolomics, as potential mediators, provide invaluable insights into the intricate biological mechanisms. ANN NEUROL 2024.

2.
Chemistry ; 29(33): e202300552, 2023 Jun 13.
Artículo en Inglés | MEDLINE | ID: mdl-36995358

RESUMEN

Inspired by alkene addition to the Ru and Re tris(thiolate) complexes via carbon-sulfur bond formation/cleavage reactions along with a periodic extension catalysis notion, a comparative study of the electronic structures, mechanisms, and reactivities for ethylene addition to the Os and Tc tris(thiolate) complexes was performed by DFT and high-level ab initio quantum calculations. The oxidized Os and Tc complexes were revealed to exhibit sufficient radical characters on the ligands to support their reaction with ethylene, whereas neutral Tc tris(thiolate) complex featuring little thiyl radical character renders no reactivity toward ethylene. Differential reactivities of these tris(thiolate) complexes was deemed to derive from the synergy of the thiyl radical character, the electronegativity, the row, and the charge. Extending from Ru and Re tris(thiolate) complexes to their Os and Tc counterparts can help us to get insightful rationales that would promote further research on alkene addition to metal-stabilized thiyl radicals.


Asunto(s)
Alquenos , Metales , Ligandos , Etilenos
3.
J Food Sci Technol ; 58(4): 1549-1561, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-33746282

RESUMEN

Tea is one of the most popular beverage with distinct flavor consumed worldwide. It is of significance to establish evaluation method for tea quality controlling. In this work, electronic nose (E-nose) was applied to assess tea quality grades by detecting the volatile components of tea leaves and tea infusion samples. The "35th s value", "70th s value" and "average differential value" were extracted as features from E-nose responding signals. Three data reduction methods including principle component analysis (PCA), multi-dimensional scaling (MDS) and linear discriminant analysis (LDA) were introduced to improve the efficiency of E-nose analysis. Logistic regression (LR) and support vector machine (SVM) were applied to set up qualitative classification models. The results indicated that LDA outperformed original data, PCA and MDS in both LR and SVM models. SVM had an advantage over LR in developing classification models. The classification accuracy of SVM based on the data processed by LDA for tea infusion samples was 100%. Quantitative analysis was conducted to predict the contents of volatile compounds in tea samples based on E-nose signals. The prediction results of SVM based on the data processed by LDA for linalool (training set: R2 = 0.9523; testing set: R2 = 0.9343), nonanal (training set: R2 = 0.9617; testing set: R2 = 0.8980) and geraniol (training set: R2 = 0.9576; testing set: R2 = 0.9315) were satisfactory. The research manifested the feasibility of E-nose for qualitatively and quantitatively analyzing tea quality grades.

4.
Sensors (Basel) ; 19(2)2019 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-30669613

RESUMEN

Postharvest kiwifruit continues to ripen for a period until it reaches the optimal "eating ripe" stage. Without damaging the fruit, it is very difficult to identify the ripeness of postharvest kiwifruit by conventional means. In this study, an electronic nose (E-nose) with 10 metal oxide semiconductor (MOS) gas sensors was used to predict the ripeness of postharvest kiwifruit. Three different feature extraction methods (the max/min values, the difference values and the 70th s values) were employed to discriminate kiwifruit at different ripening times by linear discriminant analysis (LDA), and results showed that the 70th s values method had the best performance in discriminating kiwifruit at different ripening stages, obtaining a 100% original accuracy rate and a 99.4% cross-validation accuracy rate. Partial least squares regression (PLSR), support vector machine (SVM) and random forest (RF) were employed to build prediction models for overall ripeness, soluble solids content (SSC) and firmness. The regression results showed that the RF algorithm had the best performance in predicting the ripeness indexes of postharvest kiwifruit compared with PLSR and SVM, which illustrated that the E-nose data had high correlations with overall ripeness (training: R² = 0.9928; testing: R² = 0.9928), SSC (training: R² = 0.9749; testing: R² = 0.9143) and firmness (training: R² = 0.9814; testing: R² = 0.9290). This study demonstrated that E-nose could be a comprehensive approach to predict the ripeness of postharvest kiwifruit through aroma volatiles.

5.
Adv Sci (Weinh) ; : e2406828, 2024 Jul 10.
Artículo en Inglés | MEDLINE | ID: mdl-38984724

RESUMEN

Photothermal CO2 methanation reaction represents a promising strategy for addressing CO2-related environmental issues. The presence of efficient tandem catalytic sites with a localized high-temperature is an effective pathway to enhance the performance of CO2 methanation. Here the bimetallic RuCo nanoparticles anchored on ZrO2 fiber cotton (RuCo/ZrO2) as a photothermal catalyst for CO2 methanation are prepared. A significant photothermal CO2 methanation performance with optimal CH4 selectivity (99%) and rate (169.93 mmol gcat -1 h-1) is achieved. The photothermal energy of the RuCo bimetallic nanoparticles, confined by the infrared insulation and low thermal conductivity of the ZrO2 fiber cotton (ZrO2 FC), provides a localized high-temperature. In situ spectroscopic experiments on RuCo/ZrO2, Ru/ZrO2, and Co/ZrO2 indicate that the construction of tandem catalytic sites, where the Co site favors CO2 conversion to CO while incorporating Ru enhances CO* adsorption for subsequent hydrogenation, results in a higher selectivity toward CH4. This work opens a new insight into designing tandem catalysts with a photothermal confinement effect in CO2 methanation reaction.

6.
Chemosphere ; 359: 142258, 2024 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-38719119

RESUMEN

Iron-containing MOFs have attracted extensive interest as promising Fenton-like catalysts. In this work, magnetic Fe3O4 nanofiber (FNS)/MOFs composites with stable structure, included FNS/MIL-88B, FNS/MIL-88A and FNS/MIL-100, were prepared via the in-situ solvothermal method. The surface of the obtained fibers was covered by a dense and continuous MOFs layer, which could effectively solve the agglomeration problem of MOFs powder and improved the catalytic performance. The adsorption and catalytic properties of FNS/MOFs composites were evaluated by removal of norfloxacin. FNS/MIL-88B showed the best performance with a maximum adsorption capacity up to 214.09 mg/g, and could degrade 99% of NRF in 60 min. Meanwhile, FNS/MIL-88B had a saturation magnetization of 20 emu/g, and could be rapidly separated by an applied magnetic field. The self-supported nanofibers allowed the adequate contact between MOFs and pollutants, and promoted the catalytic activity and high stability. We believe that this work provided a new idea for the design and preparation of Fenton-like catalysts especially MOFs composites.


Asunto(s)
Hierro , Nanofibras , Norfloxacino , Contaminantes Químicos del Agua , Nanofibras/química , Norfloxacino/química , Adsorción , Hierro/química , Contaminantes Químicos del Agua/química , Catálisis , Estructuras Metalorgánicas/química , Peróxido de Hidrógeno/química
7.
Artículo en Inglés | MEDLINE | ID: mdl-36892263

RESUMEN

The inherent brittleness and hydrophilicity of ceramics pose a great challenge to designing a reliable structure that can resist mechanical loads and moisture in extreme conditions with high temperature and high humidity. Here, we report a two-phase hydrophobic silica-zirconia composite ceramic nanofiber membrane (H-ZSNFM) with exceptional mechanical robustness and high-temperature hydrophobic resistance. For the dual-phasic nanofibers, the amorphous silica blocked the connection of zirconia nanocrystals, and the lattice distortion was observed due to Si in the ZrO2 lattice. H-ZSNFM has strong strength (5-8.4 MPa), high hydrophobic temperature resistance (450 °C), high porosity (89%), low density (40 mg/cm3), low thermal conductivity (30 mW/m·K), and excellent thermal radiation reflectivity (90%). By simulating the actual high-temperature and high-humidity environment, 10-mm-thick H-ZSNFMs can reduce the heat source from 1365 to 380 °C and maintain complete hydrophobicity even in a water vapor environment of 350 °C. This means that it has superior insulation and waterproof performance even in a high-temperature water environment. For firefighting clothing, H-ZSNFM displayed waterproof and insulation layers, which have excellent thermal protection performance and achieve incompatibility between water and fire, providing valuable time for fire rescue and a safety line of defense for emergency personnel. This design strategy with mechanical robust and hydrophobic temperature resistance applies to the development of many other types of high-performance thermal insulation materials and presents a competitive material system for thermal protection in extreme conditions.

8.
ACS Appl Mater Interfaces ; 15(35): 41880-41891, 2023 Sep 06.
Artículo en Inglés | MEDLINE | ID: mdl-37625156

RESUMEN

Recent advancements have introduced anisotropic structures, particularly 2D nanosheets, into aerogels, resulting in unique morphologies and exceptional properties that differ from those assembled by isotropic nanoparticles. However, exploration of the distinct porous networks and the resulting properties is limited. We focus on rare earth yttria (Y2O3) aerogels as a case in point and demonstrate the synthesis of aerogels with nanosheet and nanoparticle assemblies using elaborative sol-gel chemistry. With the aid of X-ray computed tomography, three-dimensional visualizations of the aerogels provide relative compressive views of the porous network, revealing that the Y2O3 aerogel assembled by nanosheets possesses a hierarchical pore structure characterized by uneven pore distribution, particularly the presence of macropores throughout; in contrast, these consist of nanoparticles exhibiting a relative uniform pore distribution. High-temperature examinations indicate that the nanosheet aerogels are much more stable with a specific surface area of 64 m2·g-1 after being exposed at 1300 °C; meanwhile, the aerogels present durable and efficient thermal insulation performances. The exceptional thermal properties are attributed to the synergistic effects of the nanosheets' crystalline nature and the hierarchical porous network. The nanosheet Y2O3 aerogel also exhibited superior luminescent emission characteristics, further enhancing its potential for various applications. Our findings provide further insights into optimization of the microstructures in nanoporous aerogels, particularly through the utilization of anisotropic nanosheets.

9.
Life (Basel) ; 12(8)2022 Aug 12.
Artículo en Inglés | MEDLINE | ID: mdl-36013403

RESUMEN

Glioblastoma (GBM) is one of the leading lethal tumors, featuring aggressive malignancy and poor outcome to current standard temozolomide (TMZ) or radio-based therapy. Developing immunotherapies, especially immune checkpoint inhibitors, have improved patient outcomes in other solid tumors but remain fatigued in GBM patients. Emerging evidence has shown that GBM-associated macrophages (GAMs), comprising brain-resident microglia and bone marrow-derived macrophages, act critically in boosting tumor progression, altering drug resistance, and establishing an immunosuppressive environment. Based on its crucial role, evaluations of the safety and efficacy of GAM-targeted therapy are ongoing, with promising (pre)clinical evidence updated. In this review, we summarized updated literature related to GAM nature, the interplay between GAMs and GBM cells, and GAM-targeted therapeutic strategies.

10.
ACS Appl Mater Interfaces ; 13(34): 41339-41350, 2021 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-34423629

RESUMEN

We have developed a tungsten disulfide (WS2)/multiwall carbon nanotubes (MWCNTs) nanocomposite based QCM gas sensor for (trimethylamine) TMA gas sensing of low concentrations. WS2/MWCNTs nanocomposite was synthesized via the hydrothermal method and was characterized for surface morphology, nanostructure, thermal stability, and elementary composition. The TMA-sensing properties of WS2/MWCNTs nanocomposite based QCM sensor were investigated. The composite based QCM sensor showed faster response time, strong response amplitude, good gas capacity, and good selectivity and stability compared with as prepared WS2 and MWCNTs-1 based QCM sensor. The response time of WS2/MWCNTs based QCM sensor was 294.1 and 142.9 s shorter than WS2 and MWCNTs-1 for 500 ppb TMA gas. And the response of the WS2/MWCNTs based QCM sensor was almost stable over 40 days, and the limit of detection (LOD) was 76 ppb calculated by the ICH method. This was ascribed to the fact that MWCNTs provided a skeleton for the growth of WS2 nanosheets and avoided agglomeration. The special structure could not only improve the structure ability but also expose more active adsorption sites. In order to further investigate the adsorption mechanism of the TMA molecule on (pure/functionalized) WS2 materials, density functional theory (DFT) calculations based on first-principle were conducted in the Vienna Ab-initio Simulation Package under ideal conditions.

11.
Nanomaterials (Basel) ; 12(1)2021 Dec 30.
Artículo en Inglés | MEDLINE | ID: mdl-35010058

RESUMEN

Bi1-xSmxFe0.98Mn0.02O3 (x = 0, 0.02, 0.04, 0.06; named BSFMx) (BSFM) films were prepared by the sol-gel method on indium tin oxide (ITO)/glass substrate. The effects of different Sm content on the crystal structure, phase composition, oxygen vacancy content, ferroelectric property, dielectric property, leakage property, leakage mechanism, and aging property of the BSFM films were systematically analyzed. X-ray diffraction (XRD) and Raman spectral analyses revealed that the sample had both R3c and Pnma phases. Through additional XRD fitting of the films, the content of the two phases of the sample was analyzed in detail, and it was found that the Pnma phase in the BSFMx = 0 film had the lowest abundance. X-ray photoelectron spectroscopy (XPS) analysis showed that the BSFMx = 0.04 film had the lowest oxygen vacancy content, which was conducive to a decrease in leakage current density and an improvement in dielectric properties. The diffraction peak of (110) exhibited the maximum intensity when the doping amount was 4 mol%, and the minimum leakage current density and a large remanent polarization intensity were also observed at room temperature (2Pr = 91.859 µC/cm2). By doping Sm at an appropriate amount, the leakage property of the BSFM films was reduced, the dielectric property was improved, and the aging process was delayed. The performance changes in the BSFM films were further explained from different perspectives, such as phase composition and oxygen vacancy content.

12.
Sci Rep ; 10(1): 13904, 2020 Aug 17.
Artículo en Inglés | MEDLINE | ID: mdl-32807806

RESUMEN

ZrO2 nanocrystals with spheres and elongated platelets were systemically prepared through a simple hydrothermal method by the use of ZrOCl2·8H2O and CH3COOK as raw materials. The anisotropic morphology and formation mechanism of the monoclinic and/or tetragonal ZrO2 were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, and high-resolution transmission electron microscope techniques. The uniform elongated platelets and star-like structures were composed of short nanorods with a diameter of approximately 5 nm and a length of approximately 10 nm. The different morphologies were formed due to the different contents of CH3COO- and Cl- and their synergy. The fluorescence band position and the band shape remained about the same for excitation wavelengths below 290 nm and the different morphologies of the nanocrystals.

13.
J Hazard Mater ; 381: 120974, 2020 01 05.
Artículo en Inglés | MEDLINE | ID: mdl-31421554

RESUMEN

SiO2-MgO hybrid fibers (SMHFs) were fabricated by one-step electrospinning process, characterized, and evaluated in heavy metal adsorption, for the first time. High-pressure steam (HPS) pretreated SMHFs showed high specific surface area (SBET) and large number of surface basic sites accompanied by the crystallization of MgO. The SMHFs showed high affinities for Pb(II) and Cu(II) with the distribution coefficients Kd>100 L·g-1 (when pH > 4). Langmuir model and pseudo-second-order kinetic model described the experimental data well, and the maximum adsorption capacities of 787.9 and 493.0 mg·g-1 for Pb(II) and Cu(II) at 298 K were the highest among those of reported SiO2-MgO adsorbents. Thermodynamics indicated SMHFs had the spontaneous and physicochemical adsorption nature. SMHFs kept good capacities in the presence of interfering substances and retained their reusability. The SMHFs with the superiority of high efficiency, low cost, easy preparation and environmentally benign, have promising applications in wastewater treatment and relative fields.

14.
Food Chem ; 289: 482-489, 2019 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-30955639

RESUMEN

Electronic nose (E-nose), electronic tongue (E-tongue) and electronic eye (E-eye) combined with chemometrics methods were applied for qualitative identification and quantitative prediction of tea quality. Main chemical components, such as amino acids, catechins, polyphenols and caffeine were measured by traditional methods. Feature-level fusion strategy for the integration of the signals was introduced to integrate the E-nose, E-tongue and E-eye signals, aiming at improving the performances of identification and prediction models. Perfect results with an accuracy of 100% were obtained for qualitative identification of tea quality grades, based on fusion signals by support vector machine and random forest. Quantitative models were established for predicting the contents of the chemical components based on independent electronic signals and fusion signals by partial least squares regression, support vector machine and random forest. Random forest based on the fusion signals achieved the best performance in predicting the concentration of those chemical components.


Asunto(s)
Análisis de los Alimentos/instrumentación , Calidad de los Alimentos , Té/química , Aminoácidos/análisis , Cafeína/análisis , Catequina/análisis , Nariz Electrónica , Ojo , Análisis de los Alimentos/métodos , Análisis de los Mínimos Cuadrados , Polifenoles/análisis , Control de Calidad , Gusto , Lengua
15.
Anal Chim Acta ; 1050: 60-70, 2019 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-30661592

RESUMEN

In the study, the voltammetric electronic tongue based on three nanocomposites modified electrodes was applied for the identification of rice wines of different geographical origins. The nanocomposites were prepared by gold and copper nanoparticles in the presence of conducting polymers (polymer sulfanilic acid, polymer glutamic acid) and carboxylic multi - walled carbon nanotubes. The modified electrodes showed high sensitivity to guanosine - 5' - monophosphate disodium salt, tyrosine and gallic acid which have good correlation with the geographical origins of rice wines. Scanning electron microscopy was performed to display the surface morphologies of the nanocomposites, and cyclic voltammetry was applied to study the electrochemical behaviors of the taste substances on the electrode surfaces. Four types of electrochemical parameters (pH, scan rates, accumulation potentials and time) were optimized for getting a low limit of the detection of each taste substance. The geographical information of rice wines was obtained by the modified electrodes based on two types of multi - frequency large amplitude pulse voltammetry, and "area method" was applied for extracting the feature data from the original information obtained. Based on the area feature data, principal component analysis, locality preserving projection (LPP), and linear discriminant analysis were applied for the classification of the rice wines of different geographical origins, and LPP presented the best results; extreme learning machine (ELM) and alibrary for support vector machines were applied for predicting the geographical origins of rice wines, and ELM performed better.


Asunto(s)
Técnicas Electroquímicas , Nariz Electrónica , Geografía , Nanocompuestos/química , Oryza/química , Vino/análisis , Electrodos
16.
RSC Adv ; 9(37): 21164-21174, 2019 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-35521344

RESUMEN

'Hongyang' kiwifruit is a new breed of red-fleshed cultivar that has become broadly popular with consumers in recent years. In this study, the internal quality and aroma of this kiwifruit during ripening were investigated by means of gas chromatography-mass spectrometry (GC-MS) and electronic nose (E-nose). Results showed that the green note aldehydes declined, the main fruity esters increased, and the terpenes had no obvious changes during ripening. Correlations between quality indices, volatile compounds, and E-nose data were analyzed by ANOVA partial least squares regression (APLSR), and the results showed that firmness and titratable acidity (TA) had highly positive correlations with (E)-2-hexenal and hexanal, while soluble solids content (SSC) and SSC/TA ratio had positive correlations with ester compounds. The E-nose sensors of S7, S10, S8, S6, S9, and S2 were positively correlated with ester compounds, S1, S3, and S5 were mainly correlated with hexanal, and S4 was correlated with terpene compounds. Partial least squares regression (PLSR) and support vector machine (SVM) were employed to predict the quality indices by E-nose data, and SVM presented a better performance in predicting firmness, SSC, TA, and SSC/TA ratio (R 2 > 0.98 in the training set and R 2 > 0.94 in the testing set). This study demonstrated that the E-nose technique could be used as an alternative to trace the flavor quality of kiwifruit during ripening.

17.
RSC Adv ; 8(24): 13333-13343, 2018 Apr 09.
Artículo en Inglés | MEDLINE | ID: mdl-35542510

RESUMEN

In this paper, poly(acid chrome blue K) (PACBK)/AuNP/glassy carbon electrode (GCE), polysulfanilic acid (PABSA)/AuNP/GCE and polyglutamic acid (PGA)/CuNP/GCE were self-fabricated for the identification of rice wines of different brands. The physical and chemical characterization of the modified electrodes were obtained using scanning electron microscopy and cyclic voltammetry, respectively. The rice wine samples were detected by the modified electrodes based on multi-frequency large amplitude pulse voltammetry. Chronoamperometry was applied to record the response values, and the feature data correlating with wine brands were extracted from the original responses using the 'area method'. Principal component analysis, locality preserving projections and linear discriminant analysis were applied for the classification of different wines, and all three methods presented similarly good results. Extreme learning machine (ELM), the library for support vector machines (LIB-SVM) and the backpropagation neural network (BPNN) were applied for predicting wine brands, and BPNN worked best for prediction based on the testing dataset (R 2 = 0.9737 and MSE = 0.2673). The fabricated modified electrodes can therefore be applied to identify rice wines of different brands with pattern recognition methods, and the application also showed potential for the detection aspects of food quality analysis.

18.
J Hazard Mater ; 346: 82-92, 2018 03 15.
Artículo en Inglés | MEDLINE | ID: mdl-29247957

RESUMEN

One-dimension ZrO2 mesoporous fibers were successfully synthesized by utilizing the electrospinning device combining with the soft-template method. The morphology and composite of the fibers were characterized by XRD, SEM, TEM, FT-IR, TGA/DSC and XPS, and the pore structure and surface area were calculated according the BET measured results. The fluoride adsorption performance of the fibers was investigated and the adsorption capacity was upto 297.70 mg g-1. Moreover, the equilibrium concentration could be reached to 1.41 mg L-1 with the initial of 30 mg L-1, and the removal rate could be reached to 95.3%. The adsorption data were well fitted with the Freundlich isotherm model and pseudo-second-order kinetic model. The fibers had a good reusability and long-term utilization for fluoride adsorption. All the results suggested that the as-prepared ZrO2 mesoporous fibers with high surface area could be an excellent adsorbent for the wastewater defluoridation treatment.

19.
RSC Adv ; 8(72): 41603-41611, 2018 Dec 07.
Artículo en Inglés | MEDLINE | ID: mdl-35559281

RESUMEN

Zirconia (ZrO2) aerogels are potential candidates for use at temperatures higher than those attainable with silica aerogels. However, fabricating a robust ZrO2 aerogel with a high thermal stability is still a challenge. The extreme electronegativity of Zr makes the hydrolysis and polycondensation of zirconium precursors difficult to control, leading to poor structural integrity and unsatisfactory physical properties. In the present research, we prepared a ZrO2 aerogel by using a synthetic zirconium precursor, namely polyacetylacetonatozirconium (PAZ), and ammonia hydroxide as the gel initiator. The ammonia hydroxide catalyzes the cross-linking of PAZ via promotion of the dehydration between hydroxyls in PAZ and the acetylacetonate group in PAZ binds the zirconium ion firmly upon the addition of ammonia hydroxide to avoid a gel precipitate. A monolithic ZrO2 aerogel with a large diameter size of 4.4 cm and high optical transmittance was achieved after drying. The surface area and pore volume of the as-dried ZrO2 aerogel were as high as 630.72 m2 g-1 and 5.12 cm3 g-1, respectively. They decreased to 188.62 m2 g-1 and 0.93 cm3 g-1 after being heat-treated at 1000 °C for 2 h. The best mechanical performances of the ZrO2 aerogels showed a compressive strength of 0.21 ± 0.05 MPa and a modulus of 1.9 ± 0.3 MPa with a density of 0.161 ± 0.008 g cm-3. Both pore structures and mechanical performances varied according to the ammonia hydroxide gel initiator used. The thermal insulating properties of the ZrO2 aerogel performed better than a silica aerogel blanket with a thermal conductivity of 0.020 W (m-1 K-1).

20.
Org Lett ; 18(10): 2387-90, 2016 05 20.
Artículo en Inglés | MEDLINE | ID: mdl-27145022

RESUMEN

An efficient organocatalytic Michael/aldol/hemiacetalization cascade reaction for construction of enantioenriched spirocyclic oxindoles fused with tetrahydropyrane has been developed. The desired highly functionalized 5',6'-dihydro-2'H,4'H-spiro[indoline-3,3'-pyran]-2-one derivatives containing multiple stereogenic centers were obtained in moderate to high chemical yields and with high stereoselectivities.

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