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1.
Zhongguo Dang Dai Er Ke Za Zhi ; 23(8): 814-820, 2021 Aug 15.
Artigo em Inglês, Chinês | MEDLINE | ID: mdl-34511171

RESUMO

OBJECTIVES: To study the survival rate and the incidence of complications of very preterm infants and the factors influencing the survival rate and the incidence of complications. METHODS: The medical data of the very preterm infants with a gestational age of <32 weeks and who were admitted to the Department of Neonatology in 11 hospitals of Jiangsu Province in China from January 2018 to December 2019 were retrospectively reviewed. Their survival rate and the incidence of serious complications were analyzed. A multivariate logistic regression analysis was used to evaluate the risk factors for death and serious complications in very preterm infants. RESULTS: A total of 2 339 very preterm infants were enrolled, among whom 2 010 (85.93%) survived and 1 507 (64.43%) survived without serious complications. The groups with a gestational age of 22-25+6 weeks, 26-26+6 weeks, 27-27+6 weeks, 28-28+6 weeks, 29-29+6 weeks, 30-30+6 weeks, and 31-31+6 weeks had a survival rate of 32.5%, 60.6%, 68.0%, 82.9%, 90.1%, 92.3%, and 94.8% respectively. The survival rate tended to increase with the gestational age (P<0.05) and the survival rate without serious complications in each gestational age group was 7.5%, 18.1%, 34.5%, 52.2%, 66.7%, 75.7%, and 81.8% respectively, suggesting that the survival rate without serious complications increased with the gestational age (P<0.05). The multivariate logistic regression analysis showed that high gestational age, high birth weight, and prenatal use of glucocorticoids were protective factors against death in very preterm infants (P<0.05), and 1-minute Apgar score ≤3 was a risk factor for death in very preterm infants (P<0.05); high gestational age and high birth weight were protective factors against serious complications in very preterm infants who survived (P<0.05), while 5-minute Apgar score ≤3 and maternal chorioamnionitis were risk factors for serious complications in very preterm infants who survived (P<0.05). CONCLUSIONS: The survival rate is closely associated with gestational age in very preterm infants. A low 1-minute Apgar score (≤3) may increase the risk of death in very preterm infants, while high gestational age, high birth weight, and prenatal use of glucocorticoids are associated with the reduced risk of death. A low 5-minute Apgar score (≤3) and maternal chorioamnionitis may increase the risk of serious complications in these infants, while high gestational age and high birth weight may reduce the risk of serious complications.


Assuntos
Doenças do Prematuro , Recém-Nascido Prematuro , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Recém-Nascido de muito Baixo Peso , Gravidez , Estudos Retrospectivos , Taxa de Sobrevida
2.
Zhongguo Dang Dai Er Ke Za Zhi ; 23(6): 588-592, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34130780

RESUMO

OBJECTIVE: To investigate the factors contributing to the withdrawal from treatment in neonates with respiratory failure. METHODS: The medical data of 2 525 neonates with respiratory failure were retrospectively studied, who were reported in 30 hospitals of Jiangsu Province from January to December, 2019. According to whether a complete treatment was given, they were divided into a complete treatment group with 2 162 neonates and a withdrawal group with 363 neonates. A multivariate logistic regression analysis was used to investigate the factors contributing to the withdrawal from treatment in neonates with respiratory failure. RESULTS: The multivariate logistic regression analysis showed that small-for-gestational-age birth, congenital abnormality, gestational age < 28 weeks, living in the rural area or county-level city, and maternal age < 25 years were risk factors for the withdrawal from treatment in neonates with respiratory failure (P < 0.05), while a higher 5-minute Apgar score and cesarean section were protective factors (P < 0.05). Furthermore, 176 answers were obtained from 160 parents of the neonates who were willing to tell the reason for the withdrawal from treatment, among which severe sequelae (44.9%, 79/176) had the highest frequency, followed by uncontrollable disease condition (24.4%, 43/176), family financial difficulties (18.2%, 32/176), and dependence on mechanical ventilation (12.5%, 22/176). CONCLUSIONS: Small-for-gestational-age birth, congenital abnormality, gestational age, living area, maternal age, Apgar score at birth, and method of birth are contributing factors for the withdrawal from treatment in neonates with respiratory failure. A poor prognosis and a low quality of life in future might be major immediate causes of withdrawal from treatment in neonates with respiratory failure, which needs to be confirmed by further studies.


Assuntos
Cesárea , Insuficiência Respiratória , Índice de Apgar , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Gravidez , Qualidade de Vida , Insuficiência Respiratória/terapia , Estudos Retrospectivos , Fatores de Risco
3.
Zhongguo Dang Dai Er Ke Za Zhi ; 23(6): 593-598, 2021 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-34130781

RESUMO

OBJECTIVE: To evaluate the clinical features of preterm infants with a birth weight less than 1 500 g undergoing different intensities of resuscitation. METHODS: A retrospective analysis was performed for the preterm infants with a birth weight less than 1 500 g and a gestational age less than 32 weeks who were treated in the neonatal intensive care unit of 20 hospitals in Jiangsu, China from January 2018 to December 2019. According to the intensity of resuscitation in the delivery room, the infants were divided into three groups:non-tracheal intubation (n=1 184), tracheal intubation (n=166), and extensive cardiopulmonary resuscitation (ECPR; n=116). The three groups were compared in terms of general information and clinical outcomes. RESULTS: Compared with the non-tracheal intubation group, the tracheal intubation and ECPR groups had significantly lower rates of cesarean section and use of antenatal corticosteroid (P < 0.05). As the intensity of resuscitation increased, the Apgar scores at 1 minute and 5 minutes gradually decreased (P < 0.05), and the proportion of infants with Apgar scores of 0 to 3 at 1 minute and 5 minutes gradually increased (P < 0.05). Compared with the non-tracheal intubation group, the tracheal intubation and ECPR groups had significantly higher mortality rate and incidence rates of moderate-severe bronchopulmonary dysplasia and serious complications (P < 0.05). The incidence rates of grade Ⅲ-Ⅳ intracranial hemorrhage and retinopathy of prematurity (stage Ⅲ or above) in the tracheal intubation group were significantly higher than those in the non-tracheal intubation group (P < 0.05). CONCLUSIONS: For preterm infants with a birth weight less than 1 500 g, the higher intensity of resuscitation in the delivery room is related to lower rate of antenatal corticosteroid therapy, lower gestational age, and lower birth weight. The infants undergoing tracheal intubation or ECRP in the delivery room have an increased incidence rate of adverse clinical outcomes. This suggests that it is important to improve the quality of perinatal management and delivery room resuscitation to improve the prognosis of the infants.


Assuntos
Cesárea , Recém-Nascido Prematuro , Peso ao Nascer , China , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Gravidez , Estudos Retrospectivos
4.
J Phys Chem B ; 125(22): 5786-5793, 2021 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-34037399

RESUMO

Metal-organic frameworks (MOFs) are crystalline materials with novel physical and chemical properties. Computational simulations have become powerful complements to experiment for understanding catalysis in MOFs and developing new MOFs and their applications. However, due to their relatively large and complex structures, MOFs can be burdensome for fully quantum mechanical calculations. A combined quantum mechanical and molecular mechanical (QM/MM) method that combines the accuracy of fully quantum mechanical methods and the efficiency of MM methods is therefore attractive. In this study, we employ a QM/MM method for the study of two classes of chemical process in a MOF: the conversion of reaction intermediates in an Ir-containing borylation catalyst supported on MOF UiO-67 and the diffusion of a diborylated methane molecule in the pristine UiO-67 framework. We compare the QM/MM results with full-quantum mechanical results on large systems to validate the accuracy of the applied QM/MM method. In the first case, we consider a model of the entire system by partitioning it into subsystems that interact covalently, and in the second case the subsystem interaction is mainly steric. We observe that the QM/MM results agree with the full-quantum mechanical results within an average of 4 kcal/mol in the first case with strong electronic interactions and within an average of 3 kcal/mol in the case with only noncovalent interactions. An important lesson learned from the present study is that the quantitative results are very sensitive to the lattice constants predicted by the MM method used in the QM/MM calculations.


Assuntos
Estruturas Metalorgânicas , Teoria Quântica , Catálise
5.
J Am Chem Soc ; 2021 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-33596070

RESUMO

Understanding structural responses of metal-organic frameworks (MOFs) to external stimuli such as the inclusion of guest molecules and temperature/pressure has gained increasing attention in many applications, for example, manipulation and manifesto smart materials for gas storage, energy storage, controlled drug delivery, tunable mechanical properties, and molecular sensing, to name but a few. Herein, neutron and synchrotron diffractions along with Rietveld refinement and density functional theory calculations have been used to elucidate the responsive adsorption behaviors of defect-rich Zr-based MOFs upon the progressive incorporation of ammonia (NH3) and variable temperature. UiO-67 and UiO-bpydc containing biphenyl dicarboxylate and bipyridine dicarboxylate linkers, respectively, were selected, and the results establish the paramount influence of the functional linkers on their NH3 affinity, which leads to stimulus-tailoring properties such as gate-controlled porosity by dynamic linker flipping, disorder, and structural rigidity. Despite their structural similarities, we show for the first time the dramatic alteration of NH3 adsorption profiles when the phenyl groups are replaced by the bipyridine in the organic linker. These molecular controls stem from controlling the degree of H-bonding networks/distortions between the bipyridine scaffold and the adsorbed NH3 without significant change in pore volume and unit cell parameters. Temperature-dependent neutron diffraction also reveals the NH3-induced rotational motions of the organic linkers. We also demonstrate that the degree of structural flexibility of the functional linkers can critically be affected by the type and quantity of the small guest molecules. This strikes a delicate control in material properties at the molecular level.

6.
Chemistry ; 27(16): 5268-5276, 2021 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-33355967

RESUMO

The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO2 ) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO2 (111) thin films and CeO2 powders, and theoretical calculations of CeO2 (111) surfaces with oxygen vacancies (Ov ) at the surface and in the bulk. We show that, on a stoichiometric CeO2 (111) surface, H2 dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO2-x samples, both films and powders, hydroxyls and hydrides (Ce-H) are formed on the surface as well as in the bulk, accompanied by the Ce3+ ↔ Ce4+ redox reaction. As the Ov concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H2 /CeO2 interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere.

7.
J Am Chem Soc ; 142(28): 12515-12523, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32564596

RESUMO

The recombination of electron-hole pairs severely detracts from the efficiency of photocatalysts. This issue could be addressed in metal-organic frameworks (MOFs) through optimization of the charge-transfer kinetics via rational design of structures at atomic level. Herein, a pyrazolyl porphyrinic Ni-MOF (PCN-601), integrating light harvesters, active catalytic sites, and high surface areas, has been demonstrated as a superior and durable photocatalyst for visible-light-driven overall CO2 reduction with H2O vapor at room temperature. Kinetic studies reveal that the robust coordination spheres of pyrazolyl groups and Ni-oxo clusters endow PCN-601 with proper energy band alignment and ultrafast ligand-to-node electron transfer. Consequently, the CO2-to-CH4 production rate of PCN-601 far exceeds those of the analogous MOFs based on carboxylate porphyrin and the classic Pt/CdS photocatalyst by more than 3- and 20-fold, respectively. The reaction avoids the use of hole scavengers and proceeds in a gaseous phase which can take full advantage of the high gas uptake of MOFs. This work demonstrates that the rational design of coordination spheres in MOF structures not only reconciles the contradiction between reactivity and stability but also greatly promotes the interfacial charge transfer to achieve optimized kinetics, providing guidance for the design of highly efficient MOF photocatalysts.

8.
Angew Chem Int Ed Engl ; 59(37): 16039-16046, 2020 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-32458500

RESUMO

There is increasing interest in capturing H2 generated from renewables with CO2 to produce methanol. However, renewable hydrogen production is expensive and in limited quantity compared to CO2 . Excess CO2 and limited H2 in the feedstock gas is not favorable for CO2 hydrogenation to methanol, causing low activity and poor methanol selectivity. Now, a class of Rh-In catalysts with optimal adsorption properties to the intermediates of methanol production is presented. The Rh-In catalyst can effectively catalyze methanol synthesis but inhibit the reverse water-gas shift reaction under H2 -deficient gas flow and shows the best competitive methanol productivity under industrially applicable conditions in comparison with reported values. This work demonstrates a strong potential of Rh-In bimetallic composition, from which a convenient methanol synthesis based on flexible feedstock compositions (such as H2 /CO2 from biomass derivatives) with lower energy cost can be established.

9.
J Am Chem Soc ; 142(25): 11173-11182, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32459963

RESUMO

Hydrous materials are ubiquitous in the natural environment and efforts have previously been made to investigate the structures and dynamics of hydrated surfaces for their key roles in various chemical and physical applications, with the help of theoretical modeling and microscopy techniques. However, an overall atomic-scale understanding of the water-solid interface, including the effect of water on surface ions, is still lacking. Herein, we employ ceria nanorods with different amounts of water as an example and demonstrate a new approach to explore the water-surface interactions by using solid-state NMR in combination with density functional theory. NMR shifts and relaxation time analysis provide detailed information on the local structure of oxygen ions and the nature of water motion on the surface: the amount of molecularly adsorbed water decreases rapidly with increasing temperature (from room temperature to 150 °C), whereas hydroxyl groups are stable up to 150 °C, and dynamic water molecules are found to instantaneously coordinate to the surface oxygen ions. The applicability of dynamic nuclear polarization for selective detection of surface oxygen species is also compared to conventional NMR with surface selective isotopic-labeling: the optimal method depends on the feasibility of enrichment and the concentration of protons in the sample. These results provide new insight into the interfacial structure of hydrated oxide nanostructures, which is important to improve performance for various applications.

10.
Nat Commun ; 10(1): 5420, 2019 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-31780658

RESUMO

Compared to nanomaterials exposing nonpolar facets, polar-faceted nanocrystals often exhibit unexpected and interesting properties. The electrostatic instability arising from the intrinsic dipole moments of polar facets, however, leads to different surface configurations in many cases, making it challenging to extract detailed structural information and develop structure-property relations. The widely used electron microscopy techniques are limited because the volumes sampled may not be representative, and they provide little chemical bonding information with low contrast of light elements. With ceria nanocubes exposing (100) facets as an example, here we show that the polar surface structure of oxide nanocrystals can be investigated by applying 17O and 1H solid-state NMR spectroscopy and dynamic nuclear polarization, combined with DFT calculations. Both CeO4-termination reconstructions and hydroxyls are present for surface polarity compensation and their concentrations can be quantified. These results open up new possibilities for investigating the structure and properties of oxide nanostructures with polar facets.

11.
J Chem Theory Comput ; 15(7): 4208-4217, 2019 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-31145606

RESUMO

Combined quantum mechanical and molecular mechanical (QM/MM) studies on catalysis in metal-organic frameworks (MOFs) are relatively undeveloped in contrast to the wide use of QM/MM for enzyme catalysis. One reason is that the currently available methods for treating QM-MM boundaries are not fully compatible with the combination of features in MOFs, namely, their high connectivity, their polar bonds (e.g., metal-oxygen bonds), and their potential boundary atoms with high partial atomic charges. The treatment of polar bonds can be improved by using tuned link atoms, but both the widely used H link atom method and the F* link atom method provide limited options in placing the QM-MM boundary in MOFs and other covalently bonded solids, which seriously reduces the efficiency of QM/MM calculations. Here, we propose a generalized version of the F* link atom method with greater flexibility for the placement of the QM-MM boundary in MOFs and with a practical scheme for tuning. The new method, called the multilink F* method, allows a large part of an inorganic node of a MOF to be partitioned into the MM subsystem to increase the efficiency. Our validation calculations on dimerization of ethylene to 1-butene by a nickel catalyst supported on a MOF show that the overall performance of QM/MM calculations with the multilink F* method is excellent for energies, geometries, and partial atomic charges.

12.
J Chem Phys ; 150(4): 041701, 2019 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-30709313

RESUMO

Cerium metal-organic frameworks (Ce-MOFs) show great promise for photocatalytic water splitting as they have low-lying unoccupied 4f orbitals with energies lower than the unoccupied linker orbitals to drive the ligand-to-metal charge transfer (LMCT) of the photo-generated electron at the linker to separate the photo-excited charges. Nevertheless, the large and negative LMCT energies of Ce-MOFs are often accompanied by high photon-absorption energies, which then limit the application of Ce-MOFs as visible-light-driven water splitting photocatalysts. In this work, we propose that metal (Zr or Ti) doping can raise the very negative LMCT energies of Ce-MOFs, consequently leading to the decrease of the absorption energy and promoting the response of Ce-MOFs to visible light. By functionalizing the linker of the mixed-metal MOFs, we found two possible visible-response photocatalysts for water splitting using a single photocatalyst.

13.
Molecules ; 23(6)2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29848948

RESUMO

Combined quantum mechanical and molecular mechanical (QM/MM) methods are the most powerful available methods for high-level treatments of subsystems of very large systems. The treatment of the QM-MM boundary strongly affects the accuracy of QM/MM calculations. For QM/MM calculations having covalent bonds cut by the QM-MM boundary, it has been proposed previously to use a scheme with system-specific tuned fluorine link atoms. Here, we propose a broadly parametrized scheme where the parameters of the tuned F link atoms depend only on the type of bond being cut. In the proposed new scheme, the F link atom is tuned for systems with a certain type of cut bond at the QM-MM boundary instead of for a specific target system, and the resulting link atoms are call bond-tuned link atoms. In principle, the bond-tuned link atoms can be as convenient as the popular H link atoms, and they are especially well adapted for high-throughput and accurate QM/MM calculations. Here, we present the parameters for several kinds of cut bonds along with a set of validation calculations that confirm that the proposed bond-tuned link-atom scheme can be as accurate as the system-specific tuned F link-atom scheme.


Assuntos
Modelos Químicos , Modelos Moleculares , Teoria Quântica , Algoritmos
14.
J Am Chem Soc ; 140(25): 7904-7912, 2018 06 27.
Artigo em Inglês | MEDLINE | ID: mdl-29807431

RESUMO

Ligand-to-metal charge transfer (LMCT) can bring about the separation of photogenerated charges. Here we calculate the electronic structures of metal-organic frameworks (MOFs) having the UiO-66 architecture and M6O4(OH)4 inorganometallic nodes with M = Zr, Hf, Th, Ti, U, or Ce. We find that LMCT is favorable only in the Ce case, where it is promoted by the low-lying empty 4f orbitals of Ce4+. We therefore propose that incorporating Ce4+ into the node is an effective way to facilitate LMCT in a MOF. In addition, we show that by functionalizing the linker, it should be possible to engineer the electronic structure of the Ce-MOF for a desired reaction (e.g., water splitting) while preserving favorable LMCT. We also find that linker functionalization with electron donating or withdrawing groups allows tuning of the LMCT energy, and increasing the number of functional groups on each linker enhances the tuning; these findings are encouraging for applying Ce-MOFs for visible-response photocatalytic water splitting.

15.
Phys Chem Chem Phys ; 20(3): 1778-1786, 2018 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-29271426

RESUMO

Metal-organic frameworks (MOFs) are materials with applications in catalysis, gas separations, and storage. Quantum mechanical (QM) calculations can provide valuable guidance to understand and predict their properties. In order to make the calculations faster, rather than modeling these materials as periodic (infinite) systems, it is useful to construct finite models (called cluster models) and use subsystem methods such as fragment methods or combined quantum mechanical and molecular mechanical (QM/MM) methods. Here we employ a QM/MM methodology to study one particular MOF that has been of widespread interest because of its wide pores and good solvent and thermal stability, namely NU-1000, which contains hexanuclear zirconium nodes and 1,3,6,8-tetrakis(p-benzoic acid)pyrene (TBAPy4-) linkers. A modified version of the Bristow-Tiana-Walsh transferable force field has been developed to allow QM/MM calculations on NU-1000; we call the new parametrization the NU1T force field. We consider isomeric structures corresponding to various proton topologies of the [Zr6(µ3-O)8O8H16]8+ node of NU-1000, and we compute their relative energies using a QM/MM scheme designed for the present kind of problem. We compared the results to full quantum mechanical (QM) energy calculations and found that the QM/MM models can reproduce the full QM relative energetics (which span a range of 334 kJ mol-1) with a mean unsigned deviation (MUD) of only 2 kJ mol-1. Furthermore, we found that the structures optimized by QM/MM are nearly identical to their full QM optimized counterparts.

16.
Nat Commun ; 8(1): 581, 2017 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-28924155

RESUMO

Facet engineering of oxide nanocrystals represents a powerful method for generating diverse properties for practical and innovative applications. Therefore, it is crucial to determine the nature of the exposed facets of oxides in order to develop the facet/morphology-property relationships and rationally design nanostructures with desired properties. Despite the extensive applications of electron microscopy for visualizing the facet structure of nanocrystals, the volumes sampled by such techniques are very small and may not be representative of the whole sample. Here, we develop a convenient 17O nuclear magnetic resonance (NMR) strategy to distinguish oxide nanocrystals exposing different facets. In combination with density functional theory calculations, we show that the oxygen ions on the exposed (001) and (101) facets of anatase titania nanocrystals have distinct 17O NMR shifts, which are sensitive to surface reconstruction and the nature of the steps on the surface. The results presented here open up methods for characterizing faceted nanocrystalline oxides and related materials.The exposed facets of oxide nanocrystals are key to their properties. Here, the authors use 17O solid-state NMR spectroscopy to discriminate between oxygen species on different facets of anatase titania nanocrystals, providing compelling evidence for the value of NMR spectroscopy in characterizing faceted oxides.

17.
J Ultrasound Med ; 36(1): 37-47, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27943376

RESUMO

OBJECTIVE: To determine the diagnostic efficiency of oral contrast-enhanced gastric ultrasonography in the evaluation of gastric lesions, based on large-scale multicenter study. METHODS: The study enrolled 383,945 patients with suspect gastric lesions who underwent complete oral contrast-enhanced gastric ultrasonography and endoscopic evaluation. Two operators, unaware of the results of other diagnostic procedures, performed each examination independently. The accuracies of conventional ultrasonography, oral contrast-enhanced gastric ultrasonography, and upper gastrointestinal endoscopy were determined. RESULTS: After oral contrast, the anatomy of the stomach and morphologic features of gastric lesions were clearly visualized. The sensitivities, specificities, positive predictive values, negative predictive values and accuracies of oral contrast-enhanced ultrasonography in detecting the sites, sizes, numbers, and the extent of gastric lesions,were similar to those of upper gastrointestinal endoscopy (P > .05) and far greater than those of conventional ultrasonography (P < .01). Moreover, oral contrast-enhanced ultrasonography was far better than upper gastrointestinal endoscopy (P < .01) and was better than conventional ultrasonography (P < .05) in detecting the submucosal abnormalities (<5mm) and the adjacent structures abnormalities identified in surgical pathology. However, oral contrast-enhanced ultrasonography was a bit poorer than upper gastrointestinal endoscopy (P < .05) and far better than conventional ultrasonography (P < .01) in detecting the minor mucosal abnormalities (<5mm). CONCLUSION: Oral contrast-enhanced gastric ultrasonography is superior to conventional gastric ultrasonography in defining the anatomic location and extension of gastric lesions. Its diagnostic performance is not worse than upper gastrointestinal endoscopy and it can be used as a useful supplement to upper gastrointestinal endoscopy.

18.
Phys Rev Lett ; 116(8): 086102, 2016 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-26967428

RESUMO

By performing density functional theory calculations corrected by an on site Coulomb interaction, we find that the defects at the CeO_{2}(111) surface observed by the scanning tunneling microscopy (STM) measurements of Esch et al. [Science 309, 752 (2005)] are not mere oxygen vacancies or fluorine impurities as suggested by Kullgren et al. [Phys. Rev. Lett. 112, 156102 (2014)], but actually the hydroxyl-vacancy combined species. Specifically, we show that hydroxyls play a critical role in the formation and propagation of oxygen vacancy clusters (VCs). In the presence of neighboring hydroxyls, the thermodynamically unstable VCs can be significantly stabilized, and the behaviors of oxygen vacancies become largely consistent with the STM observations. In addition to the clarification of the long term controversy on the surface defect structures of CeO_{2}(111), the "hydroxyl-vacancy model" proposed in this work emphasizes the coexistence of hydroxyls and oxygen vacancies, especially VCs, which is important for understanding the catalytic and other physicochemical properties of reducible metal oxides.

19.
Chem Commun (Camb) ; 52(13): 2827-30, 2016 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-26779575

RESUMO

The irreversible formation of carbonate deposits on CeO2 leads to complete switching of catalytic selectivity resulting in the formation of benzene in gas-phase oxidation of benzyl alcohol. By integrating experimental spectra and theoretical calculations, we expect that such a shift is derived from further decarbonylation of benzaldehyde via easy trapping of CO fragments by surface carbonate species.

20.
Phys Rev Lett ; 117(27): 279602, 2016 12 30.
Artigo em Inglês | MEDLINE | ID: mdl-28084755
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