New methods for preparation of tailor-made fluorine-containing compounds are in extremely high demand in nearly every sector of chemical industry. The asymmetric construction of quaternary C−F stereogenic centers is the most synthetically challenging and, consequently, the least developed area of research. As a reflection of this apparent methodological deficit, pharmaceutical drugs featuring C−F stereogenic centers constitute less than 1% of all fluorine-containing medicines currently on the market or in clinical development. Here we provide a comprehensive review of current research activity in this area, including such general directions as asymmetric electrophilic fluorination via organocatalytic and transition-metal catalyzed reactions, asymmetric elaboration of fluorine-containing substrates via alkylations, Mannich, Michael, and aldol additions, cross-coupling reactions, and biocatalytic approaches. CONTENTS

China is one of the regions with highest PM concentration in the world. In this study, we review the spatio-temporal distribution of PM mass concentration and components in China and the effect of control measures on PM concentrations. Annual averaged PM concentrations in Central-Eastern China reached over 100μgm, in some regions even over 150μgm. In 2013, only 4.1% of the cities attained the annual average standard of 35μgm. Aitken mode particles tend to dominate the total particle number concentration. Depending on the location and time of the year, new particle formation (NPF) has been observed to take place between about 10 and 60% of the days. In most locations, NPF was less frequent at high PM mass loadings. The secondary inorganic particles (i.e., sulfate, nitrate and ammonium) ranked the highest fraction among the PM species, followed by organic matters (OM), crustal species and element carbon (EC), which accounted for 6-50%, 15-51%, 5-41% and 2-12% of PM, respectively. In response to serious particulate matter pollution, China has taken aggressive steps to improve air quality in the last decade. As a result, the national emissions of primary PM, sulfur dioxide (SO), and nitrogen oxides (NO) have been decreasing since 2005, 2006, and 2011, respectively. The emission control policies implemented in the last decade could result in noticeable reduction in PM concentrations, contributing to the decreasing PM trends observed in Beijing, Shanghai, and Guangzhou. However, the control policies issued before 2010 are insufficient to improve PM air quality notably in future. An optimal mix of energy-saving and end-of-pipe control measures should be implemented, more ambitious control policies for NMVOC and NH should be enforced, and special control measures in winter should be applied. 40-70% emissions should be cut off to attain PM standard.

We demonstrate a self-transformation approach for the synthesis of ordered mesoporous silica hollow spheres with radially oriented mesochannels. The method is simple and facile, in which mesostructured silica spheres synthesized in a Stober solution can spontaneously transform to hollow structure when they are incubated with water. The formation of the hollow structure does not require any sacrificial templates, emulsion droplets, or surface protective agents. The obtained mesoporous silica hollow spheres possess controllable diameter, tunable shell thickness, high specific surface area, and uniform mesopore. Transmission electron microscopy (TEM) observations show that the formation of the hollow spheres undergoes a selective etching process in the inner section. 29 Si NMR spectra and detailed reactions demonstrate that the solid-to-hollow transformation of the Stober silica spheres in water is attributed to the difference in the degree of condensation of silica between their outer layer and inner section. Cytotoxicity and histological assays confirm that the obtained mesoporous silica hollow spheres possess good biocompatibility. Besides, the capability of the hollow spheres as contrast agents for untrasound imaging is conducted in vitro. Moreover, yolk−shell microspheres with a Fe 3 O 4 @ nSiO 2 core and a mesoporous silica shell are successfully prepared based on the facile self-transformation strategy, which provides a general method to create various yolk−shell structured multifunctional composites for different applications.

In January 2013, a severe regional haze occurred over the North China Plain. An online-coupled meteorology-chemistry model was employed to simulate the impacts of aerosol-meteorology interactions on fine particles (PM 2.5 ) pollution during this haze episode. The response of PM 2.5 to meteorology change constituted a feedback loop whereby planetary boundary layer (PBL) dynamics amplified the initial perturbation of PM 2.5 . High PM 2.5 concentrations caused a decrease of surface solar radiation. The maximal decrease in daily average solar radiation reached 53% in Beijing, thereby leading to a more stable PBL. The peak PBL height in Beijing decreased from 690 m to 590 m when the aerosol extinction was considered. Enhanced PBL stability suppressed the dispersion of air pollutants, and resulted in higher PM 2.5 concentrations. The maximal increase of PM 2.5 concentrations reached 140 μg m −3 in Beijing. During most PM 2.5 episodes, primary and secondary particles increased simultaneously. These results imply that the aerosol-radiation interactions played an important role in the haze episode in January 2013.