Younan Xia

Bio: Younan Xia is an academic researcher from The Wallace H. Coulter Department of Biomedical Engineering. The author has contributed to research in topics: Nanocages & Nanowire. The author has an hindex of 216, co-authored 943 publications receiving 175757 citations. Previous affiliations of Younan Xia include Washington University in St. Louis & University of Texas at Dallas.

Metallodielectric Photonic Crystals Assembled from Monodisperse Spherical Colloids of Bismuth and Lead

Abstract: Based on the Noether's theorem, we develop systematically and rigorously the spin-dependent formulation of the conservation laws. The effect of the electronic polarization due to the spin-orbit coupling is included in the Maxwell equations. The polarization is related to the antisymmetric components of spin current, and it provides a possibility to measure the spin current directly. The variances of spin and orbit angular momentum currents imply a torque on the "electric dipole" associated with the moving electron. The dependencies of the torque on the polarization and the force on the motions of spin-polarized electrons in a two-dimensional electron gas with the Rashba spin-orbit coupling are discussed.

Rational design and synthesis of noble-metal nanoframes for catalytic and photonic applications

Abstract: Nanoframes are unique for their 3D, highly open architecture. When made of noble metals, they are attractive for use as heterogeneous catalysts because of their large specific surface areas, high densities of catalytically active sites and low vulnerability toward sintering. They promise to enhance the catalytic activity and durability while reducing the material loading and cost. For nanoframes composed of Au and/or Ag, they also exhibit highly tunable plasmonic properties similar to those of nanorods. This article presents a brief account of recent progress in the design, synthesis and utilization of noble-metal nanoframes. We start with a discussion of the synthetic strategies, including those involving site-selected deposition and etching, as well as dealloying of both hollow and solid nanocrystals. We then highlight some of the applications enabled by noble-metal nanoframes. Finally, we discuss the challenges and trends with regard to future development.

Single crystalline nanowires of lead: Large-scale synthesis, mechanistic studies, and transport measurements

Abstract: A solution-phase, precursor method has been demonstrated for the large-scale synthesis of single crystalline nanowires of lead with uniform diameters in the range 50−90 nm and lengths up to several...

Inverse opal scaffolds for applications in regenerative medicine

Abstract: Three-dimensional porous scaffolds are indispensable for regenerative medicine owing to their roles in providing physical supports and adjustable microenvironments for cells to attach, stretch, migrate, proliferate, and differentiate. In order to fulfill these roles, an ideal scaffold must possess certain properties such as appropriate pore size, porosity, and interconnectivity, among others. To this end, porous scaffolds with an inverse opal structure emerged. Unlike other scaffolds that are fabricated by stochastic porogen methods with random structures, an inverse opal scaffold is characterized by uniform and finely tunable pores and interconnecting windows, in addition to their highly reproducible structure among different batches of production. In this opinion article, we start with an analysis of the motivation for using the inverse opal scaffolds and an introduction to the fabrication method. We then highlight the advantages of such porous scaffolds over their counterparts with non-uniform structures through side-by-side comparisons. Finally, we offer some perspectives on the future directions, after discussions of two examples on the unique applications of the inverse opal scaffolds in regenerative medicine.

A Simple Spectroscopic Method for Differentiating Cellular Uptakes of Gold Nanospheres and Nanorods from Their Mixtures

Abstract: This paper presents a simple spectroscopic method for differentiating cellular uptakes of two different types of Au nanostructures (i.e., nanospheres and nanorods) when they are supplied as a mixture. Because Au nanospheres and nanorods have distinctive surface plasmon resonance peaks, we can simultaneously measure their concentrations in a culture mediumbyUV-Vis spectroscopy. For the uptake of Au nanostructures by SK-BR-3 breast cancer cells, we found that the surface functional group had a stronger influence than the shape. We also found that the cellular uptake of one type of Au nanostructure could be affected bythe presence of another type of nanostructure in the medium. This study not only suggests a simple way to compare the cellular uptakes of more than one type of Au nanostructures without incubating them separately but also allows one to investigate the influence of one type of Au nanostructures on the uptake of another type.

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。

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346