Ultrafast Laser Manufacture of Stable, Efficient Ultrafine Noble Metal Catalysts Mediated with MOF Derived High Density Defective Metal Oxides.

Supported metal nanoparticles (MNPs) undergo severe aggregation, especially when the interaction between MNPs and their supports are limited and weak where their performance deteriorates dramatically. This becomes more severe when catalysts are operated under high temperature. Here, it is reported that MNPs including Pt, Au, Rh, and Ru, with sub-2 nm size can be stabilized on densely packed defective CeO2 nanoparticles with sub-5 nm size via strong coupling by direct laser conversion of corresponding metal ions encapsulated cerous metal-organic frameworks (Ce-MOFs). Ce-MOF serves as an ideal dispersion precursor to uniformly encapsulate noble metal ions in their orderly arranged pores. Ultrafast laser vaporization and cooling forms uniform, ultrasmall, well-mixed, and exceptionally dense nanoparticles of metal and metal oxide concurrently. The laser-induced ultrafast reaction (within tens of nanoseconds) facilitates the precipitation of CeO2 nanoparticles with abundant surficial defects. Due to the well-mixed ultrasmall Pt and CeO2 components with strong coupling, this catalyst exhibits exceptionally high stability and activity both at low and high temperatures (170-1100 °C) for CO oxidation in long-term operation, significantly exceeding catalysts prepared by traditional methods. The scalable feature of laser and huge MOF family make it a versatile method for the production of MNP-based nanocomposites in wide applications.

Ammonia Formation over Pd/Rh Three-Way Catalysts during Lean-to-Rich Fluctuations: The Effect of the Catalyst Aging, Exhaust Temperature, Lambda, and Duration in Rich Conditions.

The formation of ammonia (NH3) as a byproduct during the operation of a three-way catalyst (TWC) in a simulated exhaust stream was investigated using a commercially available Pd/Rh TWC under steady-state and lean/rich cycling conditions. Ion molecular reaction-mass spectrometry was applied to determine NO, NO2, and NH3 concentrations at a time resolution of 0.6 s. Catalyst aging was shown to result in a significant increase in the amount of NH3 formed, which has received limited attention in the literature to date. The selectivity toward NH3 formation has been shown to increase with the decrease in the oxygen storage capacity (OSC) of a TWC induced by thermal aging. NH3 has been shown to mainly form within the exhaust temperature range of 250-550 °C. Typical lambda and rich operational condition duration periods found in vehicle test procedures were also employed to investigate their effects on NH3 formation. The results suggest that a decrease in the lambda and/or an increase in the duration of rich operating conditions will lead to an increase in the selectivity toward NH3 formation. Improving the OSC of TWCs and effectively controlling the lambda near to 1.0 with limited duration in rich operating conditions are therefore significant factors in the reduction of NH3 emissions.

Clinical outcomes after medial temporal lobe epilepsy surgery: Anterior temporal lobectomy versus selective amygdalohippocampectomy.

OBJECTIVE: To compare the anterior temporal lobectomy (ATL) with transsylvian selective amygdalohippocampectomy (SeAH) in 72 patients with medial temporal lobe epilepsy (MTLE) regarding the seizure control and neuropsychological outcomes.
 Methods: Clinical data and follow-up data were collected and retrospectively analyzed. SeAH and ATL were used in 39 and 33 patients, respectively. All eligible patients were followed up at least one year. Wechsler Adult Intelligence Scale-Revised and the Wechsler Memory Scale-Revised were used to test the patients' neuropsychology before and after the surgery for one year.
 Results: Fifty-nine patients (81.9%) achieved satisfactory seizure control (62.5% Engel Class I and 19.4% Class II). ATL obtained 84.8% satisfactory seizure control (28 patients), and the success rate was 79.5% (31 patients) for SeAH. There was no significant difference in seizure control between SeAH and ATL (P=0.760). The postoperative verbal IQ of SeAH group increased significantly in both side surgery (P<0.05), while the increase was not significant in the group of ATL of both side surgery (P>0.05). Regarding left-side surgery, postoperative verbal memory and total memory were increased significantly in the group of SeAH (P<0.05), while the increases were not significant in the group of ATL (P>0.05). In the right-side surgery, postoperative verbal memory and total memory were increased significantly in the two surgery strategy groups (P<0.05), while no significant increases were seen in non-verbal memory of the two surgery strategy groups (P>0.05).
 Conclusion: Microsurgery for the treatment of refractory MTLE is successful and safe, and should be encouraged. The seizure outcome is not different between ATL and SeAH, while regarding as verbal IQ and verbal memory outcomes, SeAH may be superior to ATL in dominant hemisphere surgery.

The Effect P Additive on the CeZrAl Support Properties and the Activity of the Pd Catalysts in Propane Oxidation.

The properties of a catalyst support are closely related to the catalyst activity, yet the focus is often placed on the active species, with little attention given to the support properties. In this work, we specifically investigated the changes in support properties after the addition of P, as well as their impact on catalyst activity when used for catalyst preparation. We prepared the CeO2-ZrO2-P2O5-Al2O3 (CeZrPAl) composite oxides using the sol-gel, impregnation, and mechanical mixing methods, and characterized the support properties using techniques such as XRD, XPS, SEM-EDS, N2 adsorption-desorption, and Raman spectra. The results showed that the support prepared using the sol-gel method can exhibit a more stable phase structure, larger surface area, higher adsorption capacity for oxygen species, and greater oxygen storage capacity. The addition of an appropriate amount of P is necessary. On the one hand, the crystallization and growth of CePO4 can lead to a decrease in the Ce content in the cubic phase ceria-zirconia solid solution, resulting in a phase separation of the ceria-zirconia solid solution. On the other hand, CePO4 can lock some of the Ce3+/Ce4+ redox pairs, leading to a reduction in the adsorption of oxygen species and a decrease in the oxygen storage capacity of the CeZrPAl composite oxides. The research results indicated that the optimal P addition is 6 wt.% in the support. Therefore, we prepared a Pd/CeZrPAl catalyst using CeZrAl with 6 wt.% P2O5 as the support and conducted the catalytic oxidation of C3H8. Compared with the support without P added, the catalyst activity of the support loaded with P was significantly improved. The fresh and aged (1000 °C/5 h) catalysts decreased by 20 °C and 5 °C in T50 (C3H8 conversion temperature of 50%), and by 81 °C and 15 °C in T90 (C3H8 conversion temperature of 90%), respectively.

Understanding ammonia and nitrous oxide formation in typical three-way catalysis during the catalyst warm-up period.

Ammonia (NH3) and nitrous oxide (N2O) have been regarded as the typical secondary pollutants emitted from vehicles equipped with a three-way catalyst (TWC). MultiGas FT-IR Analyzer was applied to determine the outlet gas concentrations in the light-off experiments, in order to understand how different reaction conditions and catalyst aging affect the production of these two pollutants. It was found that N2O formation is favored by the existence of excess oxygen during NO reduction, whereas NH3 is readily formed within the lack of reactive oxygen species. Interestingly, the reduction of NO by H2 in presence of excess oxygen can also lead to NH3 formation when the active metal particles are large enough, which provides the rational explanation why the increased NH3 was emitted from older gasoline vehicles. The loss of the catalytically active sites and reducibility caused by thermal aging requires longer time to warm-up thereby favors the N2O and NH3 formation, which is the major reason for the higher CO, NOx, HC, N2O and NH3 emissions from the old gasoline vehicles than that of low-mileage gasoline vehicles.

Ammonia removal in selective catalytic oxidation: Influence of catalyst structure on the nitrogen selectivity.

Selective catalytic oxidation is regarded as an effective and favored method for the removal of hazardous ammonia. A number of M-Pt/USY (M=Mn, Fe, Ce and Pr) catalysts were prepared and the resulting materials were characterized using N2 adsorption/desorption, XRD, TEM, NH3-TPD, XPS and H2-TPR. It was found that the addition of non-stoichiometric metal oxides to Pt/USY leads to the generation of additional acid sites for ammonia chemisorption and that N2 selectivity improved with increased strong acidity of the bi-functional catalysts. The oxidation state of active Pt could be adjusted by the introduction of non-stoichiometric metal oxides with increased concentrations of oxidized Ptδ+ species observed in the order of FeOx >CeO2-x >MnO2-x >Pr6O11. High valence platinum surrounded by atomic oxygen that can act as a proton scavenger to drive ammonia activation, inhibiting O2 dissociation and therefore improve N2 selectivity. Fe-containing USY zeolite is demonstrated to be a preferred catalyst for the removal of ammonia, due to its high N2 selectivity and good hydrothermal stability.

A Single-Atomic Noble Metal Enclosed Defective MOF via Cryogenic UV Photoreduction for CO Oxidation with Ultrahigh Efficiency and Stability.

Noble metal single-atom catalysts (SACs) can provide maximized interaction with the reactants and tunable electronic structure dictated by the coordinated support, thus enabling unprecedented high activity at a reduced noble metal cost. However, the practical utilization of SACs that enabled heterogeneous catalysis has the bottlenecks in high manufacturing cost, low catalytic efficiency, and low atomic utilization of metals due to poor porosity of supporting structures, low affinity between SACs and supports, and high-temperature synthesis involved. A scalable and low-energy consumption synthesis of SACs strongly coordinated with an atomically designed 3D nanostructure is needed to realize higher catalytic efficiency and atomic utilization efficiency. Here, a facile synthesis strategy is developed by applying low-cost cerous MOF (Ce-MOF) with tailored defects across the porous and crystalline structure. SACs (Pt) synthesized by cryogenic photoreduction can be enclosed at the defects in Ce-MOF. Due to the uniform dispersion and the unique electronic hybridization with Ce-MOF, the conjugated catalyst with a low weight content of 0.12 wt % exhibited 100% conversion of CO at a low temperature of 150 °C, consuming only 10% of Pt required by state-of-the-art catalysts operating under the same conditions, standing as the most effective catalyst reported to date.

[Principal component analysis for exploring gene expression patterns].

When projecting microarray data of yeast time series into principal component space based on time-points (arrays), we can not only ascribe biologically meaningful explanations to the first few principal components, but also discover sensible gene expression patterns and the according genes with periodic fluctuation this helps the subsequent research of gene periodic expression and gene regulatory network.