<i>t</i>‑BuOK-Catalyzed Regio- and Stereoselective Intramolecular Hydroamination Reaction Leading to Phthalazinoquinazolinone Derivatives

We report herein an efficient and practical strategy for the preparation of 5H-phthalazino[1,2-b]quinazolin-8(6H)-one derivatives through a t-BuOK-catalyzed intramolecular hydroamination reaction of functionalized quinazolinones under extremely mild reaction conditions. A variety of quinazolinone substrates are well tolerated to furnish the corresponding products in good to high yields via an exclusive 6-exo-dig cyclization process. The present protocol has the advantages of readily obtainable starting materials, broad substrate scope, and high regio- and stereoselectivity

Intrinsic Role of Excess Electrons in Surface Reactions on Rutile TiO₂ (110): Using Water and Oxygen as Probes

Reactions on catalytically active surfaces often involve complex mechanisms with multiple interactions between adsorbates and various subsequently formed intermediates, and a variable number of excess electrons further complicates the involved mechanisms. Experimental techniques face challenges in precisely tuning or determining the number of excess electrons and in elucidating these complex reactions. In this work, the thermodynamic details and reaction pathways of interactions between the most prevalent and important molecular species, H₂O and O₂, on a prototypical rutile TiO₂ (110) surface are investigated using density functional theory calculations on 10 elementary reaction steps with the intention of gaining further insight into surface catalysis. The results suggest that the final product is independent of the reaction pathway when the number of excess electrons is sufficient. The intrinsic role of excess electrons at the reaction level is thus proposed to extend the understanding of the origin, distribution, and transfer of excess electrons. Such an understanding is beneficial to develop high-performance catalysts

A Time-Critical Adaptive Approach for Visualizing Natural Scenes on Different Devices

<div><p>To automatically adapt to various hardware and software environments on different devices, this paper presents a time-critical adaptive approach for visualizing natural scenes. In this method, a simplified expression of a tree model is used for different devices. The best rendering scheme is intelligently selected to generate a particular scene by estimating the rendering time of trees based on their visual importance. Therefore, this approach can ensure the reality of natural scenes while maintaining a constant frame rate for their interactive display. To verify its effectiveness and flexibility, this method is applied in different devices, such as a desktop computer, laptop, iPad and smart phone. Applications show that the method proposed in this paper can not only adapt to devices with different computing abilities and system resources very well but can also achieve rather good visual realism and a constant frame rate for natural scenes.</p></div

The Enhancement of Surface Reactivity on CeO₂ (111) Mediated by Subsurface Oxygen Vacancies

Surface reactivity on metal oxide surfaces and its enhancement play important roles in heterogeneous catalytic reactions. In this work, the interactions of O₂ and H₂O with reduced CeO₂ (111) surface are studied by density-functional theory calculations. The corresponding adsorption geometries, adsorption energies, and reaction barriers are reported. It is found that the diffusion of subsurface oxygen vacancies toward surface can be promoted by the adsorption of O₂ on the CeO₂ (111) surface. Then those oxygen vacancies diffused onto surface sites will be healed by the adsorbed O₂, leaving behind an O adatom on the surface. Interestingly, at moderate temperatures, the surface O adatom will swap positions with surface lattice O dynamically. The adsorption of H₂O may also induce the diffusion of oxygen vacancies from subsurface to surface, leading to the formation of two hydroxyls on the CeO₂ (111) surface. In addition, the interaction between the paired hydroxyl groups and O₂ will result in the formation of water and oxygen adatom on the surface. Our results have revealed important roles played by the subsurface oxygen vacancies in the enhancement of surface reactivity, especially when involving the adsorption of water and oxygen

Natural scene of traditional LOD.

<p>a. Scene at viewpoint p1 with traditional LOD. With traditional LOD method, at viewpoint p1, the LOD level of Tree 1 and Tree2 is LOD2. b. Scene at viewpoint p2 with traditional LOD. At viewpoint p2, the LOD level of Tree 1 and Tree 2 is LOD1.</p

Configuration of computer 2.

<p>Configuration of computer 2.</p

Comparison of rendering time on computer 1.

<p>The blue line represents the rendering time before using time-critical technology on computer 1, while the red line represents the rendering time after using time-critical technology. The red line is much smoother, and it takes less time to render natural scenes than the blue line, indicating that time-critical technology is effective and reasonable.</p

Rendering framework of natural scene.

<p>The framework includes three layers: interactive layer, core layer and data layer. In the interactive layer, users set initial data based on their requirements and roam virtual scenes. In the core layer, the system adjusts the rendering strategy according to the data set in the interactive layer and then renders natural scenes. The tree models, textures and other data used in the core layer are all stored in the data layer.</p

Evaluation of tree importance.

<p>a. Our method to evaluate tree importance. The level of detail for a tree is related to viewpoint, tree position, visual angle and tree size. P4 has a higher level of LOD than P3 because P3 has a longer distance to viewpoint. P1 has the same distance to viewpoint as P2, but P1 has a higher level of LOD because it has a smaller visual angle. Although P4 and P5 have the same distance to viewpoint and the same visual angle, P4 has a higher level of LOD than P5 because P4 has a larger crown. b. Comparison with traditional LOD. Using traditional LOD method, P1 and P3 between range R1 and R2 have lower LOD level than P5, which is different from the result of our method.</p

Configuration of iPad4.

<p>Configuration of iPad4.</p