Finding Key Factors for Efficient Water and Methanol Activation at Metals, Oxides, MXenes, and Metal/Oxide Interfaces.

Activating water and methanol is crucial in numerous catalytic, electrocatalytic, and photocatalytic reactions. Despite extensive research, the optimal active sites for water/methanol activation are yet to be unequivocally elucidated. Here, we combine transition-state searches and electronic charge analyses on various structurally different materials to identify two features of favorable O-H bond cleavage in H2O, CH3OH, and hydroxyl: (1) low barriers appear when the charge of H moieties remains approximately constant during the dissociation process, as observed on metal oxides, MXenes, and metal/oxide interfaces. Such favorable kinetics is closely related to adsorbate/substrate hydrogen bonding and is enhanced by nearly linear O-H-O angles and short O-H distances. (2) Fast dissociation is observed when the rotation of O-H bonds is facile, which is favored by weak adsorbate binding and effective orbital overlap. Interestingly, we find that the two features are energetically proportional. Finally, we find conspicuous differences between H2O/CH3OH and OH activation, which hints toward the use of carefully engineered interfaces.

Copper-catalyzed chemoselective C-H functionalization of quinoxalin-2(1H)-ones with hexafluoroisopropanol.

An unexpected three-component reaction of quinoxalin-2(1H)-ones, tert-butyl peroxybenzoate (TBPB), and hexafluoroisopropanol (HFIP) is described. Under CuBr-catalyzed and TBPB-oxidized conditions, a variety of hydroxyhexafluoroisobutylated quinoxalin-2(1H)-ones were formed. Furthermore, the first hexafluoroisopropoxylation of the quinoxalin-2(1H)-ones with HFIP is also demonstrated with Cu2O as the catalyst and PhI(OAc)2 as the oxidant. These new transformations of HFIP furnish previously unknown and potentially useful fluorinated quinoxalin-2(1H)-one derivatives.

Trends in C-O and N-O bond scission on rutile oxides described using oxygen vacancy formation energies.

Reactivity trends on transition metals can generally be understood through the d-band model, but no analogous theory exists for transition metal oxides. This limits the generality of analyses in oxide-based catalysis and surface chemistry and has motivated the appearance of numerous descriptors. Here we show that oxygen vacancy formation energy (ΔE Vac) is an inexpensive yet accurate and general descriptor for trends in transition-state energies, which are usually difficult to assess. For rutile-type oxides (MO2 with M = 3d metals from Ti to Ni), we show that ΔE Vac captures the trends in C-O and N-O bond scission of CO2, CH3OH, N2O, and NH2OH at oxygen vacancies. The proportionality between ΔE Vac and transition-state energies is rationalized by analyzing the oxygen-metal bonds, which change from ionic to covalent from TiO2 to NiO2. ΔE Vac may be used to design oxide catalysts, in particular those where lattice oxygen and/or oxygen vacancies participate in the catalytic cycles.

Highly Selective Production of Ethylene by the Electroreduction of Carbon Monoxide.

Conversion of carbon monoxide to high value-added ethylene with high selectivity by traditional syngas conversion process is challenging because of the limitation of Anderson-Schulz-Flory distribution. Herein we report a direct electrocatalytic process for highly selective ethylene production from CO reduction with water over Cu catalysts at room temperature and ambient pressure. An unprecedented 52.7 % Faradaic efficiency of ethylene formation is achieved through optimization of cathode structure to facilitate CO diffusion at the surface of the electrode and Cu catalysts to enhance the C-C bond coupling. The highly selective ethylene production is almost without other carbon-based byproducts (e.g. C1 -C4 hydrocarbons and CO2 ) and avoids the drawbacks of the traditional Fischer-Tropsch process that always delivers undesired products. This study provides a new and promising strategy for highly selective production of ethylene from the abundant industrial CO.

[Expression of MiR101 and EZH2 in Patients with Mantle Cell Lymphoma and Its Clinical Significance].

OBJECTIVE: To investigate the expression of miR-101 and EZH2 in patients with mantle cell lymphoma(MCL) and to analyze its correlation with clinical prognosis of MCL patients. METHODS: RQ-PCR and S-P immunohistochemistry were used to detect the expressions of miR-101 and EZH2 in tissue of MCL patients. CCK-8 was used to assay the effect of miR-100 minics on the proliferation of Jeko-1 and Mino cells; the flow cytometry with Annexin V/PI double staining was used to assay the apoptosis; Western blot was used to assay the effect of miR-101 minics on the expression of EZH2 protein in Jeko-1 and Mino cells. RESULTS: Compared with control group, miR-101 lowly expressed, and EZH2 protein highly expressed in MCL group, with very statistically significant difference(P<0.01).There was negative correlation between miR-101 and EZH2 expression(r=-0.638，P<0.05). The expression of miR-101 and EZH2 significantly correlated with B symptoms, International Prognostic Index(IPI) and Ann Arbor stage, respectively. Survival analysis showed that the overall survival(OS) rate of patients with low expression of miR-101 were significantly lower than that of patients with high miR-101 expression (P=0.0014), the OS rate of patients with EZH2 high expression were significantly lower than that of patients with EZH2 low expression (P=0.0093). The miR-100 minics could inhibit the proliferation of Jeko-1 and Mino cells, and increase the apoptotic rate. The expression of EZH2 protein was markedly suppressed by the miR-100 minics. CONCLUSION: The expression of miR-101 and EZH2 is different in MCL patients with different clinical stage and prognosis. The miR-101 can inhibit the cell proliferation and induce cell apoptosis of mantle cell lymphoma by targeting EZH2.

Room-temperature electrochemical water-gas shift reaction for high purity hydrogen production.

Traditional water-gas shift reaction provides one primary route for industrial production of clean-energy hydrogen. However, this process operates at high temperatures and pressures, and requires additional separation of H2 from products containing CO2, CH4 and residual CO. Herein, we report a room-temperature electrochemical water-gas shift process for direct production of high purity hydrogen (over 99.99%) with a faradaic efficiency of approximately 100%. Through rational design of anode structure to facilitate CO diffusion and PtCu catalyst to optimize CO adsorption, the anodic onset potential is lowered to almost 0 volts versus the reversible hydrogen electrode at room temperature and atmospheric pressure. The optimized PtCu catalyst achieves a current density of 70.0 mA cm-2 at 0.6 volts which is over 12 times that of commercial Pt/C (40 wt.%) catalyst, and remains stable for even more than 475 h. This study opens a new and promising route of producing high purity hydrogen.

Carbon induced selective regulation of cobalt-based Fischer-Tropsch catalysts by ethylene treatment.

Various carbonaceous species were controllably deposited on Co/Al2O3 catalysts using ethylene as carbon source during the activation process for Fischer-Tropsch synthesis (FTS). Atomic, polymeric and graphitic carbon were distinguished by Raman spectroscopy, thermoanalysis and temperature programmed hydrogenation. Significant changes occurred in both the catalytic activity and selectivity toward hydrocarbon products after ethylene treatment. The activity decreased along with an increase in CH4 selectivity, at the expense of a remarkable decrease of heavy hydrocarbon production, resulting in enhanced selectivity for the gasoline fraction. In situ XPS experiments show the possible electron transfer from cobalt to carbon and the blockage of metallic cobalt sites, which is responsible for the deactivation of the catalyst. DFT calculations reveal that the activation barrier (Ea) of methane formation decreases by 0.61 eV on the carbon-absorbed Co(111) surface, whereas the Ea of the CH + CH coupling reaction changes unnoticeably. Hydrogenation of CHx to methane becomes the preferable route among the elementary reactions on the Co(111) surface, leading to dramatic changes in the product distribution. Detailed coke-induced deactivation mechanisms of Co-based catalysts during FTS are discussed.

Chemical Insights into the Design and Development of Face-Centered Cubic Ruthenium Catalysts for Fischer-Tropsch Synthesis.

Ruthenium is a promising low-temperature catalyst for Fischer-Tropsch synthesis (FTS). However, its scarcity and modest specific activity limit its widespread industrialization. We demonstrate here a strategy for tuning the crystal phase of catalysts to expose denser and active sites for a higher mass-specific activity. Density functional theory calculations show that upon CO dissociation there are a number of open facets with modest barrier available on the face-centered cubic (fcc) Ru but only a few step edges with a lower barrier on conventional hexagonal-closest packed (hcp) Ru. Guided by theoretical calculations, water-dispersible fcc Ru catalysts containing abundant open facets were synthesized and showed an unprecedented mass-specific activity in the aqueous-phase FTS, 37.8 molCO·molRu-1·h-1 at 433 K. The mass-specific activity of the fcc Ru catalysts with an average size of 6.8 nm is about three times larger than the previous best hcp catalyst with a smaller size of 1.9 nm and a higher specific surface area. The origin of the higher mass-specific activity of the fcc Ru catalysts is identified experimentally from the 2 orders of magnitude higher density of the active sites, despite its slightly higher apparent barrier. Experimental results are in excellent agreement with prediction of theory. The great influence of the crystal phases on site distribution and their intrinsic activities revealed here provides a rationale design of catalysts for higher mass-specific activity without decrease of the particle size.

Establishing and Understanding Adsorption-Energy Scaling Relations with Negative Slopes.

Adsorption-energy scaling relations are widely used for the design of catalytic materials. To date, only linear scaling relations are known in which the slopes are positive. Considering the adsorption energies of F, O, N, C, and B on transition metals, we show here that scaling relations with negative slopes also exist between certain adsorbates. The origin of such unconventional scaling relations is analyzed in terms of common descriptors such as d-band center, work function, number of outer electrons, electronic charge on the adsorbates, integrated crystal orbital overlap populations, and crystal orbital Hamilton populations. Conventional scaling relations are formed between adsorbates such as F, O, N, and C, which create ionic-like bonds with surfaces. Conversely, anomalous scaling relations are established between those and covalently bound adsorbates such as B. This widens the theory of adsorption-energy scaling relations and opens new avenues in physical chemistry and catalysis, for instance, in direct borohydride fuel cells.

Crystallographic dependence of CO activation on cobalt catalysts: HCP versus FCC.

Identifying the structure sensitivity of catalysts in reactions, such as Fischer-Tropsch synthesis from CO and H2 over cobalt catalysts, is an important yet challenging issue in heterogeneous catalysis. Based on a first-principles kinetic study, we find for the first time that CO activation on hexagonal close-packed (HCP) Co not only has much higher intrinsic activity than that of face centered-cubic (FCC) Co but also prefers a different reaction route, i.e., direct dissociation with HCP Co but H-assisted dissociation on the FCC Co. The origin is identified from the formation of various denser yet favorable active sites on HCP Co not available for FCC Co, due to their distinct crystallographic structure and morphology. The great dependence of the activity on the crystallographic structure and morphology of the catalysts revealed here may open a new avenue for better, stable catalysts with maximum mass-specific reactivity.

Platinum-modulated cobalt nanocatalysts for low-temperature aqueous-phase Fischer-Tropsch synthesis.

Fischer-Tropsch synthesis (FTS) is an important catalytic process for liquid fuel generation, which converts coal/shale gas/biomass-derived syngas (a mixture of CO and H2) to oil. While FTS is thermodynamically favored at low temperature, it is desirable to develop a new catalytic system that could allow working at a relatively low reaction temperature. In this article, we present a one-step hydrogenation-reduction route for the synthesis of Pt-Co nanoparticles (NPs) which were found to be excellent catalysts for aqueous-phase FTS at 433 K. Coupling with atomic-resolution scanning transmission electron microscopy (STEM) and theoretical calculations, the outstanding activity is rationalized by the formation of Co overlayer structures on Pt NPs or Pt-Co alloy NPs. The improved energetics and kinetics from the change of the transition states imposed by the lattice mismatch between the two metals are concluded to be the key factors responsible for the dramatically improved FTS performance.

Identifying active surface phases for metal oxide electrocatalysts: a study of manganese oxide bi-functional catalysts for oxygen reduction and water oxidation catalysis.

Progress in the field of electrocatalysis is often hampered by the difficulty in identifying the active site on an electrode surface. Herein we combine theoretical analysis and electrochemical methods to identify the active surfaces in a manganese oxide bi-functional catalyst for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). First, we electrochemically characterize the nanostructured α-Mn(2)O(3) and find that it undergoes oxidation in two potential regions: initially, between 0.5 V and 0.8 V, a potential region relevant to the ORR and, subsequently, between 0.8 V and 1.0 V, a potential region between the ORR and the OER relevant conditions. Next, we perform density function theory (DFT) calculations to understand the changes in the MnO(x) surface as a function of potential and to elucidate reaction mechanisms that lead to high activities observed in the experiments. Using DFT, we construct surface Pourbaix and free energy diagrams of three different MnO(x) surfaces and identify 1/2 ML HO* covered Mn(2)O(3) and O* covered MnO(2), as the active surfaces for the ORR and the OER, respectively. Additionally, we find that the ORR occurs through an associative mechanism and that its overpotential is highly dependent on the stabilization of intermediates through hydrogen bonds with water molecules. We also determine that OER occurs through direct recombination mechanism and that its major source of overpotential is the scaling relationship between HOO* and HO* surface intermediates. Using a previously developed Sabatier model we show that the theoretical predictions of catalytic activities match the experimentally determined onset potentials for the ORR and the OER, both qualitatively and quantitatively. Consequently, the combination of first-principles theoretical analysis and experimental methods offers an understanding of manganese oxide oxygen electrocatalysis at the atomic level, achieving fundamental insight that can potentially be used to design and develop improved electrocatalysts for the ORR and the OER and other important reactions of technological interest.

[Clinical analysis of pulmonary embolism in a child with Mycoplasma pneumoniae pneumonia].

OBJECTIVE: To explore the essential points for diagnosis of pulmonary embolism in children with mycoplasma pneumonia. METHOD: Retrospective analysis of the clinical and laboratory data of a pediatric case who developed pulmonary embolism after mycoplasma pneumonia was performed for the key points for diagnosis. RESULT: A-six-year old boy was admitted with chief complaint of fever and cough for half a month, combined with chest pain and mild labored breath. Vital signs were stable. Breathing movement of the left side weakened and there was left lower lobe percussion dullness. Breath sound was found weakened in the left lung, and a few fine crackles were audible. The results of laboratory tests were as follows: mycoplasma antibody (IgM) 1:128, cold agglutinin test 1:1024, blood D dimer 14.81 mg/L; anticardiolipin antibody was positive; plasma protein C activity was 60% (normal range 70% - 130%). Pulmonary artery computed tomographic angiography revealed a mass opaque shadow in left lower lobe, the branch of left lower bronchial artery was partially obstructed. Echocardiography showed tricuspid valve mild regurgitation, estimated pulmonary pressure was 5.1 kPa. Single-photon emission computed tomography indicated that radioactivity distribution was apparently sparse in the dorsal segment, anterior basal segment, outer basal segment and inferior lingular segment of the left lung. The preliminary diagnosis on admission was mycoplasma pneumonia with pleural effusion, pulmonary embolism. Intravenous erythromycin combined with meropenem were administered. Anticoagulation therapy was initiated with low molecular weight heparin and then oral warfarin tablets. Pleural effusion disappeared soon, D dimer descended to 0.38 mg/L, and pulmonary artery pressure declined. After 3-month follow-up, anti-cardiolipin antibody was negative, plasma protein C activity recovered, and lung lesions were absorbed. CONCLUSION: When mycoplasma pneumonia is accompanied by chest pain or dyspnea and there are bloody pleural effusion, pulmonary hypertension, positive antiphospholipid antibody and elevated D dimer, pulmonary embolism should be considered. Diagnosis could be clarified by the result of pulmonary artery computed tomographic angiography.

CO oxidation at the perimeters of an FeO/Pt(111) interface and how water promotes the activity: a first-principles study.

The catalytic role of the Pt--Fe cation ensemble presented at the perimeters of the FeO film supported on Pt(111) for low-temperature CO oxidation and the promotion of water on activity were studied by using DFT calculations. We found that the perimeter sites along the edge of the FeO islands on Pt provided a favorable ensemble that consisted of coordinatively unsaturated ferrous species and nearby Pt atoms for O(2) and H(2) O activation free from CO poison. A dissociative oxygen atom at the Pt--Fe cation ensemble reacts easily with CO adsorbed on nearby Pt. The OH group from water dissociation not only facilitates activation of the oxygen molecule, more importantly it opens a facile reaction channel for CO oxidation through the formation of the carboxyl intermediate. The presence of the OH group on the FeO film strengthens interfacial interactions between FeO and Pt(111), which would make the FeO film more resistant to further oxidation. The importance of the Pt--Fe cation ensemble and the role of water as a cocatalyst for low-temperature CO oxidation is highlighted.

Interface-confined ferrous centers for catalytic oxidation.

Coordinatively unsaturated ferrous (CUF) sites confined in nanosized matrices are active centers in a wide range of enzyme and homogeneous catalytic reactions. Preparation of the analogous active sites at supported catalysts is of great importance in heterogeneous catalysis but remains a challenge. On the basis of surface science measurements and density functional calculations, we show that the interface confinement effect can be used to stabilize the CUF sites by taking advantage of strong adhesion between ferrous oxides and metal substrates. The interface-confined CUF sites together with the metal supports are active for dioxygen activation, producing reactive dissociated oxygen atoms. We show that the structural ensemble was highly efficient for carbon monoxide oxidation at low temperature under typical operating conditions of a proton-exchange membrane fuel cell.

Reversible structural modulation of Fe-Pt bimetallic surfaces and its effect on reactivity.

Tunable surface: The surface structure of the Fe-Pt bimetallic catalyst can be reversibly modulated between the iron-oxide-rich Pt surface and the Pt-skin structure with subsurface Fe via alternating reduction and oxidation treatments (see figure). The regenerated active Pt-skin structure is active in reactions involving CO and/or O.

[Association between metabolic syndrome and the 10 years mortality of cerebro-cardiovascular diseases in the senile population].

OBJECTIVE: To assess the prevalence of metabolic syndrome (MS) and its association with mortality of cerebro-cardiovascular diseases in senile population. METHODS: Data were collected from 1926 people aged 60 and over, who took part in routine health examination in our hospital from 1996 to 1997. All subjects were followed up for 10 years. MS was diagnosed by using the definition recommended by Chinese Diabetic Society in 2004. Cox-proportional hazards models were used in survival analyses and to calculate the relative risk (RR) of cerebro-cardiovascular diseases mortality. RESULTS: The prevalence of MS was 25.03% (n = 482, Group 2) in this population. The 10 year mortality of cerebro-cardiovascular diseases was significantly higher (6.82/1000-person year vs. 2.55/1000-person year, P < 0.05) and the cumulative survival rate was significantly lower (92.46%vs. 97.14%, P < 0.05) in group 2 compared that in group 1 (non-MS, n = 1444). Compared with group 1, RR of cerebro-cardiovascular diseases mortality was 2.52 (95% CI 1.367 - 4.661, P < 0.05) in group 2. CONCLUSION: There was a high prevalence of MS in the senile population and MS was associated with higher 10 years mortality of cerebro-cardiovascular diseases.

[Association between fasting plasma glucose and the 5 years outcome post PCI in aged patients with coronary artery disease].

OBJECTIVE: To observe the association between fasting plasma glucose (FPG) and 5 years outcome post PCI in aged patients with coronary artery disease (CAD). METHODS: A total of 269 patients (mean age 63.8 +/- 9.4 years, 236 males) with CAD underwent PCI between January 2000 and December 2001 were followed up and data on angiographic restenosis, the major adverse cardiac events, the cumulative survival rates and the correlated risk factors were collected and analyzed. Patients were divided into 4 groups according to the levels of their FPG at baseline (group 1: FPG < 5.6 mmol/L; group 2: 5.6 mmol/L < or = FPG < 6.1 mmol/L; group 3: 6.1 mmol/L < or = FPG < 7.0 mmol/L; group 4: FPG > or = 7.0 mmol/L). RESULTS: At the end of the 5 years follow-up, the incidences of major adverse cardiac events, target lesion revascularization, recurring angina pectoris and angiographic restenosis of group 2 were significantly higher than those of group 1 (P < 0.05) and similar as those in group 3 (P > 0.05). The cumulative survival rates of cardiovascular events of group 2, group 3 and group 4 were all significantly decreased compared with group 1 (P < 0.05). The logistic regression model analysis showed that FPG was an independent risk factor for angiographic restenosis, incidence of major adverse cardiac events, all-cause mortality and recurring angina pectoris (P < 0.05). CONCLUSION: FPG > or = 5.6 mmol/L and over is associated with increased incidences of major adverse cardiac events in aged patients with CAD who underwent PCI.