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The controllable preparation of ligand-protected clusters is still an unresolved problem, which may be due to that their formation mechanism is unclear. We propose that the ligand is the key to solve the above problems. Here, by using p-, m-, and o-methylbenzenethiol ligand protected gold clusters as examples, we try to explore the effect of ligand structures on ligand-protected gold clusters. The geometrical structures, relative stabilities and surface properties of small-sized ligand-protected gold clusters [Au–SR]1–8(SR = p-/m-/o-MBT) have been systematically studied based on the density functional theory. The results show that the ground state structures of [Au–SR]1–8clusters tend to form closed rings except for [Au–SR]1,2. The different structures of ligand have significant effect on the structures and stabilities of ligand-protected clusters. By analyzing their surface properties and possible growth patterns, it is found that [Au–SR]1,2clusters serve as the basic building blocks, and the larger clusters can be regarded as the combinations of them. This study provides some insights into the effect of ligands on ligand-protected clusters, which is useful for understanding the formation mechanism of ligand-protected clusters.

Horisfieldones A (1) and B (2), two dimeric diarylpropanes featuring an unprecedentedly aromatic ring-contracted framework, were isolated from Horsfieldia kingii. Their structures and absolute configurations were determined by the inspection of extensive spectroscopic data and electronic circular dichroism calculations. Molecular modeling analysis, in vitro enzyme-based bioassays, and structure–activity relationship analysis of these isolates revealed that (+)-1(IC50= 35.1 ± 3.9 μM, SI > 11.4) could present a new class of human DOPA decarboxylase inhibitor.

Using the first-principles plan-wave pseudo-potential method, a systematic investigation on structural property, magnetism, and pressure-induced phase transitions of cobalt is carried out. Cobalt with our hcp (α), fcc (β), bcc (γ), and epsilon (ε) phases both in ferromagnetic (FM) and nonmagnetic (NM) states is considered. Issues of fitting equation of states in the energy volume data points containing magnetism are discussed. Our results reveal two stable phase transition points, namely, from FM β-phase to FM a-phase at -28:2 GPa and from FM a-phase to NM β-phase at 123:7 GPa, which are consistent with previous experimental predictions. The meta-stable magnetic transformation points from FM to NM state for a, b, and e structures are 135:7 GPa, 84:0 GPa, and 168:7 GPa, respectively. Furthermore, both FM γ-phase and FM ε-phase undergo a meta-stable transformation to NM b-phase at 25:0 GPa and 42:3 GPa, respectively.

An efficient watershed algorithm is proposed in order to solve the problem that touching rice is difficult to process during consequent image segmentation. First, the binary image is ultra-eroded by using a different structuring element to form different distance image. Second, watershed image is obtained by using the watershed algorithm. Finally, the real watershed can be extracted. Compared with other watershed algorithms, the experiment results demonstrated that this method segmented out rice successfully in the touching rice image and improved the measurement accuracy, and also overcome over-segmentation effectively.