Chinese Academy of Sciences

About: Chinese Academy of Sciences is a government organization based out in Beijing, Beijing, China. It is known for research contribution in the topics: Catalysis & Population. The organization has 421602 authors who have published 634849 publications receiving 14894293 citations. The organization is also known as: CAS.

PEGylated WS2 Nanosheets as a Multifunctional Theranostic Agent for in vivo Dual-Modal CT/Photoacoustic Imaging Guided Photothermal Therapy

Abstract: A new generation of photothermal theranostic agents is developed based on PEGylated WS2 nanosheets. Bimodal in vivo CT/photoacoustic imaging reveals strong tumor contrast after either intratumoral or intravenous injection of WS2 -PEG. In vivo photothermal treatment is then conducted in a mouse tumor model, achieving excellent therapeutic efficacy with complete ablation of tumors. This work promises further exploration of transition-metal dichalcogenides for biomedical applications, such as cancer imaging and therapy.

Quantum discord for two-qubit systems

Abstract: Quantum discord, as introduced by Olliver and Zurek [Phys. Rev. Lett. 88, 017901 (2001)], is a measure of the discrepancy between two natural yet different quantum analogs of the classical mutual information. This notion characterizes and quantifies quantumness of correlations in bipartite states from a measurement perspective, and is fundamentally different from the various entanglement measures in the entanglement vs separability paradigm. The phenomenon of nonzero quantum discord is a manifestation of quantum correlations due to noncommutativity rather than due to entanglement, and has interesting and significant applications in revealing the advantage of certain quantum tasks. We will evaluate analytically the quantum discord for a large family of two-qubit states, and make a comparative study of the relationships between classical and quantum correlations in terms of the quantum discord. We furthermore compare the quantum discord with the entanglement of formation, and illustrate that the latter may be larger than the former, although for separable states, the entanglement of formation always vanishes and thus is less than the quantum discord.

The CAS-PEAL Large-Scale Chinese Face Database and Baseline Evaluations

Abstract: In this paper, we describe the acquisition and contents of a large-scale Chinese face database: the CAS-PEAL face database. The goals of creating the CAS-PEAL face database include the following: 1) providing the worldwide researchers of face recognition with different sources of variations, particularly pose, expression, accessories, and lighting (PEAL), and exhaustive ground-truth information in one uniform database; 2) advancing the state-of-the-art face recognition technologies aiming at practical applications by using off-the-shelf imaging equipment and by designing normal face variations in the database; and 3) providing a large-scale face database of Mongolian. Currently, the CAS-PEAL face database contains 99 594 images of 1040 individuals (595 males and 445 females). A total of nine cameras are mounted horizontally on an arc arm to simultaneously capture images across different poses. Each subject is asked to look straight ahead, up, and down to obtain 27 images in three shots. Five facial expressions, six accessories, and 15 lighting changes are also included in the database. A selected subset of the database (CAS-PEAL-R1, containing 30 863 images of the 1040 subjects) is available to other researchers now. We discuss the evaluation protocol based on the CAS-PEAL-R1 database and present the performance of four algorithms as a baseline to do the following: 1) elementarily assess the difficulty of the database for face recognition algorithms; 2) preference evaluation results for researchers using the database; and 3) identify the strengths and weaknesses of the commonly used algorithms.

Replacing Alkoxy Groups with Alkylthienyl Groups: A Feasible Approach To Improve the Properties of Photovoltaic Polymers†

Abstract: Polymer solar cells (PSCs) have attracted much attention because of their potential application in flexible, light-weight, and low-cost large-area devices through roll-to-roll printing. The bulk heterojunction PSCs showed advanced features in realizing high efficiencies and solution-processible devices. The active layer in this kind of device consists of an interpenetrating network formed by an electron-donor material blended with an electron-acceptor material. 3] Typically, conjugated polymers are used as electron donors and fullerene derivatives are used as the electron acceptors in the PSCs. Recently, power conversion efficiencies (PCEs) of 6–7% have been realized by using new conjugated polymer donors or new fullerene-derived acceptors. Short circuit current density (Jsc), open circuit voltage (Voc), and fill factors (FF) are key parameters for a PSC device, because the PCE of the device is proportional to the values of the three parameters. To broaden the response wavelength range of a PSC device by using conjugated side chains or narrowband-gap conjugated polymers is an effective way to realize high Jsc values. Conjugated polymers with lower HOMO levels are helpful in realizing high Voc and PCE values, as the Voc value of PSCs is directly proportional to the offset between the HOMO level of electron donor and the LUMO level of electron acceptor. PSiFDTBT, PFDTBT, and PCDTBT are three excellent examples for this concept. Consequently, by using conjugated polymers with lower HOMO levels and also narrow band gaps, high PCEs were realized in different families of conjugated polymers. Conjugated polymers based on benzo[1,2-b :4,5-b’]dithiophene (BDT) units have attracted interest as electron donors in the PSC field in recent years, since the report of Hou and Yang et al. on the synthesis and photovoltaic properties of a series of copolymers based on BDT. Many copolymers of BDT with different conjugated units, such as thieno[3,4b]thiophene (TT), 4,7-dithiophene-2-yl-2,1,3-benzothiadiazole (DTBT), N-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD), and bithiazole, etc. were synthesized, and the copolymers showed promising photovoltaic properties. In these BDT-based polymers, the alternative copolymers of BDT and TT, namely PBDTTTs, are an important family of photovoltaic materials. For additional improvements in the photovoltaic performance of the PBDTTTs, structural modifications brought about by using different substituents on BDT, or the copolymerized moieties is of great importance. For example, Liang et al. introduced a fluorine atom into the TT unit of the PBDTTTs, and the HOMO level of the resulting polymer was successfully lowered by approximately 0.12 eV, and thus a higher Voc value was achieved, resulting in a great improvement of PCE. Hou et al. optimized PBDTTTs further by replacing the alkoxycarbonyl group on the TT unit with the alkylcarbonyl groups. The structural modification can also be carried out on the BDT units. In this work, we designed an 5-alkylthiophene-2-yl-substituted BDT monomer and synthesized two new PBDTTT-based polymers having either the thienylsubstituted BDT with alkoxycarbonyl-substituted thieno[3,4b]thiophene (TT-E) or the alkylcarbonyl-substituted thieno[3,4-b]thiophene (TT-C); that is PBDTTT-E-Tand PBDTTTC-T, respectively (Scheme 1). To fully investigate the effect of the thienyl-substituted BDTon the photovoltaic properties of the polymers, two corresponding PBDTTT polymers based on the alkoxy-substituted BDT (BDT-O), PBDTTT-E and PBDTTT-C (Scheme 1), were also prepared. The synthetic route of the thienyl-substituted BDT monomer (BDT-T) is shown in Scheme 1. The branched alkyl group 2-ethylhexyl was employed as the side chain on the thiophene to guarantee high solubility of the target polymers. The TT-E and TT-C monomers are commercially available. The polymers were prepared through a Stille coupling reaction between the bis(trimethyltin) BDT monomers (BDT-T and BDT-O) and the bromides (TT-E and TTC) as shown in Scheme 1. All the polymers are soluble in chloroform (CHCl3), chlorobenzene, and dichlorobenzene. Thermogravimetric analysis (TGA) measurements were employed to evaluate the thermal stability of the polymers. We found that the two-dimentional (2D) conjugated polymers based on alkylthienyl-substituted BDTs are much more stable than their analogues, the alkoxy-substituted BDTs. The TGA plots of these four polymers are shown in Figure 1. It can be seen that the decomposition temperatures [*] Dr. L. Huo, S. Zhang, F. Xu, Prof. J. Hou State Key Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular Sciences Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 (China) E-mail: hjhzlz@iccas.ac.cn

Sperm tsRNAs contribute to intergenerational inheritance of an acquired metabolic disorder

Abstract: Increasing evidence indicates that metabolic disorders in offspring can result from the father's diet, but the mechanism remains unclear. In a paternal mouse model given a high-fat diet (HFD), we showed that a subset of sperm transfer RNA-derived small RNAs (tsRNAs), mainly from 5' transfer RNA halves and ranging in size from 30 to 34 nucleotides, exhibited changes in expression profiles and RNA modifications. Injection of sperm tsRNA fractions from HFD males into normal zygotes generated metabolic disorders in the F1 offspring and altered gene expression of metabolic pathways in early embryos and islets of F1 offspring, which was unrelated to DNA methylation at CpG-enriched regions. Hence, sperm tsRNAs represent a paternal epigenetic factor that may mediate intergenerational inheritance of diet-induced metabolic disorders.