Jun Lu

Bio: Jun Lu is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Medicine & Materials science. The author has an hindex of 135, co-authored 1526 publications receiving 99767 citations. Previous affiliations of Jun Lu include Drexel University & Argonne National Laboratory.

Third-harmonic Mie scattering from semiconductor nanohelices

Abstract: Chiroptical spectroscopies provide structural analyses of molecules and nanoparticles but they require sample volumes that are incompatible with generating large chemical libraries. New optical tools are needed to characterize chirality for the ultrasmall (<1 µl) volumes required in the high-throughput synthetic and analytical stations for chiral compounds. Here we show experimentally a novel photonic effect that enables such capabilities—third-harmonic Mie scattering optical activity—observed from suspensions of CdTe nanostructured helices in volumes <<1 µl. Third-harmonic Mie scattering was recorded on illuminating CdTe helices with 1,065, 1,095 and 1,125 nm laser beams and the intensity was around ten-times higher in the forward direction than sideways. The third-harmonic ellipticity was as high as 3° and we attribute this effect to the interference of chiral and achiral effective nonlinear susceptibility tensor components. Third-harmonic Mie scattering on semiconductor helices opens a path for rapid high-throughput chiroptical characterization of sample volumes as small as 10−5 µl. Third-harmonic Mie scattering optical activity from suspensions of semiconductor (CdTe) nanostructured helices is observed, opening ways for chiroptical characterization of semiconductor and other chiral non-metallic particles in volumes potentially of the order of 10–17 m3.

Phase-stabilization and substrate effects on nucleation and growth of (Ti,V)(n+1)GeC(n) thin films

Abstract: Phase-pure epitaxial thin films of (Ti,V)(2)GeC have been grown onto Al(2)O(3)(0001) substrates via magnetron sputtering. The c lattice parameter is determined to be 12.59 A, corresponding to a 50/50 Ti/V solid solution according to Vegards law, and the overall (Ti,V): Ge: C composition is 2:1:1 as determined by elastic recoil detection analysis. The minimum temperature for the growth of (Ti,V)(2)GeC is 700 degrees C, which is the same as for Ti(2)GeC but higher than that required for V(2)GeC (450 degrees C). Reduced Ge content yields films containing (Ti,V)(3)GeC(2) and (Ti,V)(4)GeC(3). These results show that the previously unknown phases V(3)GeC(2) and V(4)GeC(3) can be stabilized through alloying with Ti. For films grown on 4H-SiC(0001), (Ti,V)(3)GeC(2) was observed as the dominant phase, showing that the nucleation and growth of (Ti,V)(n+1)GeC(n) is affected by the choice of substrate; the proposed underlying physical mechanism is that differences in the local substrate temperature enhance surface diffusion and facilitate the growth of the higher-order phase (Ti,V)(3)GeC(2) compared to (Ti,V)(2)GeC.

The reagent-free, microwave-assisted purification of carbon nanotubes

Abstract: We have developed a microwave-assisted, reagent-free method for the efficient primary purification of MW and SW carbon nanotubes that is extremely fast compared to previously reported processes. The treatment dissociates and disperses non-nanotube carbon in an organic solvent to yield very pure carbon nanotubes within a few minutes of heating and a simple filtration, without the involvement of acidic/oxidative reagents. According to thermogravimetric analysis, Raman and IR spectroscopy, as well as scanning and transmission electron microscopy, the process yields pure nanotubes with a low degree of defects.

Molecular-beam-epitaxy growth of ferromagnetic Ni2MnGe on GaAs(001)

Abstract: Single-crystal Heusler alloy Ni2MnGe thin films have been grown on GaAs(001) by molecular-beam epitaxy. X-ray diffraction and transmission electron microscopy were used for postgrowth structural characterization. The Ni2MnGe grew in a tetragonally distorted L21-like structure (a=5.65 A, c=5.96 A) with the c axis perpendicular to the film surface. An in-plane ordering with 2× periodicity and an out-of-plane ordering with 3× periodicity was observed for the as-grown films. Magnetometry measurements performed at 50 K indicate that the films are ferromagnetic and have a weak in-plane anisotropy with a coercivity ∼5.5 Oe and saturation magnetization of ∼450 emu/cm3. The Curie temperature was measured to be ∼320 K.

Gene set enrichment analysis: A knowledge-based approach for interpreting genome-wide expression profiles

Abstract: Although genomewide RNA expression analysis has become a routine tool in biomedical research, extracting biological insight from such information remains a major challenge. Here, we describe a powerful analytical method called Gene Set Enrichment Analysis (GSEA) for interpreting gene expression data. The method derives its power by focusing on gene sets, that is, groups of genes that share common biological function, chromosomal location, or regulation. We demonstrate how GSEA yields insights into several cancer-related data sets, including leukemia and lung cancer. Notably, where single-gene analysis finds little similarity between two independent studies of patient survival in lung cancer, GSEA reveals many biological pathways in common. The GSEA method is embodied in a freely available software package, together with an initial database of 1,325 biologically defined gene sets.

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.