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.

Elastomeric light valves

Abstract: Electromagnetic radiation valves are provided. In one system, a transparent, elastomeric article is provided having a contoured surface including protrusions and intervening indentations. The contoured surface is placed adjacent a transparent plate and a void pattern defined by indentations of the contoured surface is filled with an opaque fluid. The protrusions decrease in cross-sectional area in the direction in which they extend away from the bulk of the elastomeric article, thus compression of the elastomeric protrusions against the transparent plate results in an increase in surface area in elastomeric protrusions against the transparent plate due to deformation of the protrusions, and the opaque fluid is displaced from the voids. Increased transmission of the electromagnetic radiation results. In another system, a similar elastomeric article includes an array of corner cubes that are totally internally reflective of the electromagnetic radiation. Increased deformation of the protrusions of the transparent plate results in decreased total internal reflection of light, due to the progressive destruction of the corner-cube geometry, and the passage of light is increased with compression.

Preparation of uniform microspheres using a simple fluidic device and their crystallization into close-packed lattices.

Abstract: A versatile technique for producing monodisperse microspheres from both hydrophobic and hydrophilic polymers using a simple fluidic device fabricated with a poly(vinyl chloride) (PVC) tube, a syringe needle, and a glass capillary tube is described. The technique is successfully applied to a variety of different materials, including poly(e-caprolactone) (PCL) as an example of a hydrophobic polymer, ethyl-2cyanoacrylate (ECA) as an example of organic monomer, and gelatin as an example of a hydrophilic, natural polymer. From the calculated capillary number (Ca) andWeber number (We), the system is confirmed to work in the dripping regime. Precise control over particle size can be achieved by varying the polymer concentration and/or the flow rate for the continuous phase. An increase in flow rate for the continuous phase or a decrease in polymer concentration results in the reduction of particle size. The production of raspberry-like microspheres with a mixture of PCL and ECA is also demonstrated. In addition, we have developed a tapping method based on solvent evaporation on a concave glass for crystallizing these microspheres into close-packed lattices. Microspheres with uniform diameters are of great importance in many applications, including, among others, cosmetics, printing, coating, drug delivery, tissue engineering, and photonics. The best established method for producing such spheres relies on the formation of stable oil-in-water (O/ W) or water-in-oil (W/O) emulsions. Two approaches are commonly employed to make these emulsions: emulsification under amechanical or shear force and emulsification involving uniform breakup of a stream of the discontinuous phase as

Tailoring the Optical and Catalytic Properties of Gold-Silver Nanoboxes and Nanocages by Introducing Palladium.

Abstract: Noble metal nanostructures are of great interest because of their potential applications including biomedical imaging,[1,2] surface-enhanced Raman scattering (SERS),[3] and catalysis.[4–6] Gold and silver nanostructures, in particular, have been most extensively studied because their localized surface plasmon resonance (LSPR) peaks are positioned in the visible and near-infrared regions, an attribute that allows for easy probing. Recent studies indicate that Pd-based nanostructures are also promising for photonic applications. For example, we have demonstrated that Pd-Ag alloy nanoboxes can have their LSPR peaks tuned across the visible spectrum and thus be employed as active substrates for SERS.[7] Palladium-based nanostructures are also attractive for a number of catalytic applications and have been demonstrated in a variety of reactions that include Heck coupling,[8] Suzuki coupling,[9] and hydrogenation.[10]

Growth of Large Crystals of Monodispersed Spherical Colloids in Fluidic Cells Fabricated Using Non-photolithographic Methods

Abstract: This paper describes a convenient approach to the fabrication of fluidic cells to be used for crystallizing spherical colloids into three-dimensionally periodic lattices over large areas. The major component of the fluidic cell was a rectangular gasket sandwiched between two glass substrates. Here we demonstrate that these gaskets could be simply cut out of commercial Mylar films. Three non-photolithographic methods were also demonstrated to create shadow channels between the Mylar film and two glass substrates: (i) by wiping (along one single direction) both sides of the Mylar film with a piece of soft paper (Kimwipes EX-L); (ii) by coating both surfaces of the Mylar film with polymer beads whose size was smaller than those to be packed in the cell; and (iii) by patterning the surface of the bottom glass substrate with an array of gold channels using a combination of microcontact printing and selective etching. When an aqueous dispersion of monodispersed spherical colloids was injected into this packing...

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