Basic Science

Simulation of A Recoiling Supermassive Black Hole Completed

Recently, Dr. Li Shuo, a team member of the Silk Road Project in National Astronomical Observatories (NAOC), together with his collaborators finished a large scale computer simulation of a recoiling supermassive black hole (SMBH) in a galactic center. They investigated the dynamical co-evolution between a recoiling SMBH and its host galaxy with tidal disruption process included, and confirmed the existence of the hypercompact stellar system (HCSS) bound to the recoiling SMBH. The numerical model required very powerful computers; it was made possible with the advanced GPU accelerated technology and the high performance of Laohu HPC (High Performance Computing) cluster in NAOC. The particle number for the simulation achieved one million, which is the largest simulation scale for such kind of issue so far. The paper has been published on the SCI journal ApJ, 748, 65L, 2012. Their results indicate that the recoiling SMBH can result in a HCSS, and also an unbound stellar system in a larger area. Those impacted unbound stars form an axisymmetric cloud like distribution around the recoiling SMBH. This phenomenon reveals that the recoiling SMBH will not only be impacted by dynamical friction effects from surrounding stars, but also conversely change the distribution of the latter. The simulation results show that this kind of axisymmetric cloud have similar mass and scale compared to ultra-compact dwarf galaxies, but with higher stellar velocity dispersion. This work is only one of several parts in Silk Road Project ( http://silkroad.bao.ac.cn/web/ ). The Silk Road Project is devoted to promoting the applications of HPC in astronomy and astrophysics. The Laohu HPC cluster that has been built by the project team, is one of the most powerful supercomputers that has been used by the project PI Prof. Rainer Spurzem with his team members for the galaxy dynamical evolution simulations with the highest particle resolution.

Progress Obtained on Research of Hydroxyl Radical and Chemiluminescence

Recently, a research group headed by Prof. Zhu Benzhan from the State Key Lab of Environmental Chemistry and Ecotoxicology of the Research Center for Eco-Environmental Sciences, CAS reported a significant research progress on hydroxyl radical and chemiluminescence. The paper entitled “Unprecedented hydroxyl radical-dependent two-step chemiluminescence production by polyhalogenated quinoid carcinogens and H2O2 has been published on Proc. Natl. Acad. Sci. USA (PNAS 109: 16046-16051; 2012). They reported that an unprecedented two-step chemiluminescence could be produced by the carcinogenic tetrachloro-1,4-benzoquinone and H2O2, which was found to be well-correlated to and directly dependent on the two-step metal-independent intrinsic production of hydroxyl radicals. They further found that this novel hydroxyl radical-dependent chemiluminescence production is a general phenomenon for all polyhalogenated quinoid carcinogens, which can be applied to detect and quantitatively determine these ubiquitous carcinogenic quinoid compounds. Chemiluminescence could also be produced from hydroxyl radical-dependent advanced oxidation of polyhalogenated aromatics, which were employed to develop a sensitive chemiluminescence method to detect and quantify trace amounts of polyhalogenated persistent organic pollutants and pharmaceuticals such as pentachlorophenol, trichlorophenol, 3,3′,5,5′-tetrabromobisphenol A, Orange Agent, pentachlorobenzene and thyroxine. For pentachlorophenol, the detection limit by this method was as low as 2.6 ppb. This unique chemiluminescence method could be also used to monitor the real time degradation kinetics of polyhalogenated aromatics during the advanced oxidation processes (AOPs). The above findings together with their previous related research have resulted in five continuous publications (Track-II paper) in the prestigious PNAS by Prof. Zhu as first and corresponding author.

Theoretical Breakthrough on Anticancer Nanomedicine

In a research, Profs. Zhao Yuliang and Chen Chunying from the Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, CAS, which is a joint Lab established by CAS Institute of High Energy Physics and National Center for Nanoscience and Technology of China, and Dr. Zhou Ruhong from IBM Watson Research Center have now found a novel molecular mechanism for gadolinium metallofullerenol nanoparticles as anticancer therapeutics (PNAS, 109, 15431, 2012). This article has been highlighted by PNAS (15073-15528) and by EMSL, etc. Based on the newly discovered strategy, Gd@C82(OH)22 nanoparticles not only suppress the tumor growth but also inhibit tumor metastasis. In vivo and in vitro assays revealed that the nanoparticles potently suppressed angiogenesis and inhibited the growth of human pancreatic tumor xenografts in nude mice, and in particular, reduced the expression and activity of matrix metalloproteinases (MMP-2 and MMP-9), two MMPs known to be essential for angiogenesis and tumor development. Computational simulations indicated that the nanoparticles’ action on MMP-9 is indirect such that they bound to the protein far from its active site. This is in distinct contrast to traditional molecular medicines that typically target the MMP active metal-binding site, directly blocking it or damaging the protein’s structure. The authors discovered that the f-NPs form clusters in solution that selectively interact with ligand binding regions near the ligand-specificity loop S1 by nonspecific electrostatic, hydrophobic, and specific hydrogen-bonding interactions, suggesting that the gadolinium metallofullerenol nanoparticles inhibit MMP-9 activity by interfering with binding to incoming substrates. After nine years systemic and thorough research, the authors have finished testing the efficacy of suppressing the tumor growth in vivo through eight tumor models of animal experiments. In addition to mining novel mechanism of antitumor activity by Gd@C82(OH)22 nanoparticles, the preclinical studies are now smoothly moving forward. Moreover, a pilot production line has been built in the Institute of High Energy Physics to produce the f-NPs for the clinical trail.

Theary of Solution for Airy Light Beam

It is well known that light travels in straight line in homogeneous media. But for a special class of beams called accelerating beams, the main maximum of intensity can form a curved trajectory during propagation. In addition to free acceleration, accelerating beams have also nondiffracting property. A typical example of accelerating beams is Airy beam. The acceleration and non-diffraction properties of Airy beam have potential applications in optical trapping and manipulation as well as novel optical imaging. Much work has been done on Airy beam in the paraxial condition at present, while the thoery for describing non-parxaxial Airy beam is absent. By solving the wave equation, the researchers (Yan Shaohui, Yao Baoli et al.) at the Xi'an Institute of Optics and Precision Mechanics, CAS, found that a virtual source placed in the complex space could generate non-paraxial Airy packet. With some approximations, this Airy packet can produce the common paraxial Airy beam as well as a non-parxaxial Airy beam with seond-order correction. This work provides a theory for accurate describing the Airy beam and anylysis of its propagation characteristics. The related results were published in the issue on Nov. 15, 2012 of Optics Letters, a journal of the Optical Society of America, titled "Virtual source for an Airy beam".