Yang Zhao

Bio: Yang Zhao is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Ansatz & Phonon. The author has an hindex of 46, co-authored 357 publications receiving 7795 citations. Previous affiliations of Yang Zhao include University of Science and Technology of China & Dalian Institute of Chemical Physics.

Flexible layer-structured Bi2Te3 thermoelectric on a carbon nanotube scaffold

Abstract: Inorganic chalcogenides are traditional high-performance thermoelectric materials. However, they suffer from intrinsic brittleness and it is very difficult to obtain materials with both high thermoelectric ability and good flexibility. Here, we report a flexible thermoelectric material comprising highly ordered Bi2Te3 nanocrystals anchored on a single-walled carbon nanotube (SWCNT) network, where a crystallographic relationship exists between the Bi2Te3 < $$\bar{1}2\bar{1}0$$ > orientation and SWCNT bundle axis. This material has a power factor of ~1,600 μW m−1 K−2 at room temperature, decreasing to 1,100 μW m−1 K−2 at 473 K. With a low in-plane lattice thermal conductivity of 0.26 ± 0.03 W m−1 K−1, a maximum thermoelectric figure of merit (ZT) of 0.89 at room temperature is achieved, originating from a strong phonon scattering effect. The origin of the excellent flexibility and thermoelectric performance of the Bi2Te3–SWCNT material is attributed, by experimental and computational evidence, to its crystal orientation, interface and nanopore structure. Our results provide insight into the design and fabrication of high-performance flexible thermoelectric materials. Bi2Te3 materials suffer from brittleness, limiting their application for thermoelectric harvesting. By depositing ordered nanocrystals onto single-wall carbon nanotubes, a flexible material is formed that achieves ZT of 0.89 at room temperature.

Symmetry breaking of graphene monolayers by molecular decoration.

Abstract: Aromatic molecules can effectively exfoliate graphite into graphene monolayers, and the resulting graphene monolayers sandwiched by the aromatic molecules exhibit a pronounced Raman G-band splitting, similar to that observed in single-walled carbon nanotubes. Raman measurements and calculations based on the force-constant model demonstrate that the absorbed aromatic molecules are responsible for the G-band splitting by removing the energy degeneracy of in-plane longitudinal and transverse optical phonons at the Gamma point.

A Preloaded Amorphous Calcium Carbonate/Doxorubicin@Silica Nanoreactor for pH-Responsive Delivery of an Anticancer Drug

Abstract: Biomedical applications of nontoxic amorphous calcium carbonate (ACC) nanoparticles have mainly been restricted because of their aqueous instability. To improve their stability in physiological environments while retaining their pH-responsiveness, a novel nanoreactor of ACC–doxorubicin (DOX)@silica was developed for drug delivery for use in cancer therapy. As a result of its rationally engineered structure, this nanoreactor maintains a low drug leakage in physiological and lysosomal/endosomal environments, and responds specifically to pH 6.5 to release the drug. This unique ACC–DOX@silica nanoreactor releases DOX precisely in the weakly acidic microenvironment of cancer cells and results in efficient cell death, thus showing its great potential as a desirable chemotherapeutic nanosystem for cancer therapy.

Energy dissipation mechanisms in carbon nanotube oscillators.

Abstract: Multiwalled carbon nanotubes (MWNTs) have been proposed as candidates for nanoscale molecular bearings, springs, and oscillators [1‐3]. Zheng and Jiang have estimated that these nano-oscillators can have frequencies far beyond 1 GHz, pointing to a path for creating nanomachines operating in the gigahertz range [3], which has been viewed as one of the milestones on the road map of molecular manufacturing [4,5]. Despite unlimited prospects of applications for low-friction nanobearings, nanosprings, and nano-oscillators, performance, wear and load-bearing properties of fundamental components of nanomachines are largely not understood. We investigate in this Letter possible scenarios for realizing nearly frictionless and superefficient nano-oscillators. Our aim is to provide an understanding of nanoscale motioninduced heating mechanisms and to propose means for reducing frictional effects that hinder oscillator performance and efficiency. The friction phenomenon, or the energy dissipation between two contacting parties which slide with respect to each other, is in general taken to denote the conversion of orderly translational energies into disorderly vibrational energies. In this Letter, using molecular dynamics (MD), double-walled carbon nanotube (DWNT) oscillators of various lengths and constructions are compared for their oscillation resilience under motion-induced selfheating. We show that friction in these oscillators is primarily associated with an off-axial rocking motion of the inner nanotube and a wavy deformation of the outer nanotube, which may or may not occur, depending upon both configurations of individual oscillators and initial system energies, and that oscillation is nearly frictionless in the absence of the rocking motion and the wavy deformation. Our model DWNT has an inner tube and an outer tube of chiralities (5; 0) and (8; 8), respectively, and an intertube spacing � 3:4 � A, which is also the spacing between adjacent sheets in graphite. Both ends of the outer wall are open and those of the inner wall are closed. Structure optimization and simulation of the two-tube oscillators are carried out using the CHARMM force field [6]. A time step of 1 fs is used for all simulations. A precise description of interactions between graphene sheets may include interlayer electronic delocalization [7], although the van der Waals forces are dominant for our purpose here. To check the accuracy of the force field, the radial breathing mode frequency of an (8; 8) carbon nanotube is calculated to be 232 cm � 1 in good agreement with that from observed Raman lines, 211 cm � 1 [8]. We define the relative kinetic energy of two tubes

Enhanced thermopower of graphene films with oxygen plasma treatment.

Abstract: Inthiswork,weshowthatthemaximumthermopoweroffewlayersgraphene(FLG) films could be greatly enhanced up to ∼700 μV/K after oxygen plasma treatment. The electrical conductivities of these plasma treated FLG films remain high, for example, ∼10 4 S/m, which results in power factors as high as ∼4.5 � 10 � 3 WK � 2 m � 1 . In comparison, the pristine FLG films show a maximum thermopower of ∼80 μV/K with an electrical conductivity of ∼5 � 10 4 S/m. The proposed mechanism is due to generation of local disordered carbon that opens the band gap. Measured thermopowers of single-layer graphene (SLG) films and reduced graphene oxide (rGO) films were in the range of � 40 to 50 and � 10 to 20 μV/K, respectively. However, such oxygen plasma treatment is not suitable for SLG and rGO films. The SLG films were easily destroyed during the treatment while the electrical conductivity of rGO films is too low.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。