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Dedicated to Professor Vladimir Ya. Gutlyanskii on the occasion of his 70th birthday. We provide various characterizations of quasiisometric homeomorphisms in [R.sup.n] raised by the geometric, metric, analytic, and modular approaches. Keywords. Quasiisometry, quasiconformality, bi-Lipschitz mappings, p-module of k-dimensional surface families, module of ring domains., 1. Introduction Quasiisometric (or bi-Lipschitz) homeomorphisms form a very important subclass of quasiconformal mappings and have deep applications in mathematics and mechanics. The main characterization of quasiisometry relies on a [...]

Oriented assemblies of small crystals forming larger structures are common in nature and crucial for forthcoming technologies as they circumvent the difficulties of structural manipulation at microscopic scale. We have discovered two distinctive concentric assemblies of zinc oxide rods, wherein each rod has an intrinsically positive and a negative polar end induced by the noncentrosymmetric arrangement of Zn and O atoms. All the rods in a single assembly emanate out of a central core maintaining a single polar direction. Due to growth along the two polar surfaces with different atomic arrangements, these assemblies are distinct in their intrinsic properties and exhibit strong UV luminescence in the exterior of Zn-polar assemblies, unlike the O-polar assemblies. Although novel applications can be envisioned, these observations suggest that hierarchical organization with respect to internal asymmetry might be widespread in natural crystal assemblies. cathodoluminescence | crystal assembly doi/ 10.1073/pnas.1008240107

We report the controlled formation and characterization of heterojunctions between carbon nanotubes and different metal nanocrystals (Fe, Co, Ni, and FeCo). The heterojunctions are formed from metal-filled multiwall carbon nanotubes (MWNTs) via intense electron beam irradiation at temperatures in the range of 450-700[degrees]C and observed in situ in a transmission electron microscope. Under irradiation, the segregation of metal and carbon atoms occurs, leading to the formation of heterojunctions between metal and graphite. Metallic conductivity of the metal-nanotube junctions was found by using in situ transport measurements in an electron microscope. Density functional calculations show that these structures are mechanically strong, the bonding at the interface is covalent, and the electronic states at and around the Fermi level are delocalized across the entire system. These properties are essential for the application of such heterojunctions as contacts in electronic devices and vital for the fabrication of robust nanotube-metal composite materials. nanoelectronics | interfacial interactions | conductivity | electron microscopy | composites

Commercial graphite powders are used as the carbon sources to synthesize a variety of tubular carbon nanotubes, aligned carbon microtubes with hexagonal cross-sections, aligned tapered carbon tubes and carbon microhorns by a simple in situ template process. The carbon nano-/microstructures have unique properties and applications in integrated circuits, large-diameter particle encapsulation, nano-/microfluidics, drug delivery and nanoelectronics.

An effective method to remove obstinate boron nitride phase impurities in boron nitride nanotubes (BNNTs) was proposed. The results revealed that the impurities were effectively removed and the resultant BNNTs possessed perfect crystallization.

The GaN nanowires, having average diameters of ~100 nanometer and lengths up to tens of micrometers and with P-doping were synthesized through a simple thermal evaporation process. The scanning electron microscope and high-resolution field-emission transmission electron microscope analyses revealed that P doping results in a rough surface morphology of GaN nonowires.

Epitaxial semiconducting heterostructures (side-to-side Si-ZnS, Si-ZnSe biaxial nanowires, and sandwichlike ZnS-Si-ZnS triaxial nanowires) are grown via a simple two-stage thermal evaporation of mixed SiO d or SiO and ZnSe powders under a precise temperature control. The results suggest that the simple method may be useful for the synthesis of many other heterostructures containing Si and II-VI or III-V semiconducting composite nanowires to meet the growing demands of nanoscale science and technology.

A synthetic method to fill boron nitride (BN) nanotubes with metals or metal alloys was proposed using a vapor-liquid-solid catalytic growth mechanism. The BN nanotube fillings clearly exhibit nanometallurgical behavior, the absorbed liquid metals crystallize in BN nanotubes grow parallel to the innermost tube shell.

The synthesis and structural characterization of a novel graphitic tubular form of graphitic boron nitride (BN) displaying hollow conical-helix geometry is reported. A sole dynamic element, enthalpy or postheating temperature is found to determine the disclination configuration of helical-conical nanotubes (HCNTs).

A study was conducted to determine the effectiveness of the method of Picard iteration by Dawson. Results showed that the Picard iterative method can easily and accurately integrate quasilinear second-order matrix differential equations of structural dynamics. Moreover, the Picard iteration agrees well with the linear modal velocity method developed by Henkel and Mar when used in special cases involving general structural damping with forcing functions that rely only on time and with no aerodynamic forces.

Boron nitride nanotubes were synthesized by a carbon-free chemical vapor deposition method using boron and metal oxide as reactants with SnO2 particles functionalized on them through a simple wet chemistry method. The detailed transmission electron microscopy observations reveal that SnO2 nanoparticles may cover the tube surface or be encapsulated in tube channels.

Research was conducted to examine the precise structure of multiwalled boron nitride (BN) nanotubes using electron energy loss spectroscopy and high-resolution transmission electron microscopy. The nanotubes were generated from carbon nanotubes via the novel substitution chemical reaction. Results demonstrate that in contrast to the starting carbon nanotubes, which displayed a large number of shells, wide distribution of helicities and poor degree of graphitization, the resultant BN exhibited perfectly straight shapes, remarkable ordering of the graphene-like sheets and limited number of shells.

Post-synthesis carbon doping of individual boron nitride nanotubes (BNNTs) is achieved via in situ electron-beam irradiation inside an energy-filtering 300 eV high-resolution transmission electron microscope. The substitution of C for B and N atoms in the honeycomb lattice is shown through electron energy loss spectroscopy and substitutional C doping has transformed BNNTs from electrical insulators to conductors.

The isolation of individual boron nitride nanotubes (BNNTs) in aqueous phases is achieved from raw materials based on the combination of peptide wrapping with a sonication procedure. The modulation of the BNNT band gap with peptide wrapping has potential applications of the peptide/BNNT complexes to various nanotechnologies.

A study on Salmonella-plant interactions leading to plant colonization were conducted to gain better insight into outbreaks of salmonellosis related to consumption of fresh produce. The findings for Salmonella internalization of leaves might provide a partial explanation for the failure of sanitizers to efficiently eradicate food-borne pathogens in leafy greens.

The article studies electron transport variations in individual ZnS nanowires through a chemical vapor deposition process by in situ in transmission electron microscope under convergent electron-beam irradiation (EBI). Results suggested that the generation of midbands within a ZnS band gap might contribute to the improved conductivity.

The mechanisms involved in the aqueous noncovalent functionalization and controlled near-surface carbon doping of multiwalled boron nitride nanotubes (BNNTs) are studied. The doping of these BNNTs with carbon is shown to highly affect the electronic and mechanical properties of the system.

Byline: Guozhen Shen, Yoshio Bando, Dmitri Golberg Since Sumio Iijima identified the hollow Carbon Nanotubes (CNTs) in the early 1990s, there have been significant research efforts to synthesise inorganic nanotubes of various solids. Generally, the formation of tubular nanostructures requires layered, anisotropic, or pseudo-layered crystal structures. Inorganic nanotubes, which typically do not possess such structures, are usually synthesised using template-based methods. However, these nanotubes are either amorphous, polycrystalline or exist only in ultrahigh vacuum. Recently, an 'epitaxial casting' method using removable ZnO nanowires as templates has been developed to synthesise single-crystal GaN nanotubes. This opens up an exciting field of research on the synthesis of single-crystal nanotubes with non-layered or non-anisotropic structures. In this paper, we review recent research activities on single-crystal inorganic nanotubes synthesised using removable templates via vapour phase methods based on similar 'epitaxial casting' concepts. The applications and nanodevices that have been built using these novel inorganic nanotubes are also presented.

A new technique to synthesize SiO2 nanotubes with tunable diameters and lengths via a simple in situ template like process by thermal evaporation of SiO, ZnS, and GaN in a vertical induction furnace is presented. It was found that the diameters and lengths of the SiO2 nanotubes can be tuned efficiently only by changing the evaporation temperature and the method can also be used to protect ZnS nanowires from oxidation using SiO2 surface coatings and/or make complex SiO2-based structures on a large scale.

Synthesis of single-crystalline ZnS nanowires coated with graphitic carbon shells is presented by thermal evaporation of a mixture of ZnS and SnS powders in a graphite crucible. Photoluminescence spectrum shows that the carbon-coated ZnS nanowires have a strong emission band centered at 586 nm and a shoulder band ad 645 nm.

Unconventional zigzag indium phosphide (InP) single-crystalline and twinned nanowires are produced through thermal evaporation of indium phosphide in the presence of zinc selenide. Studies found that two type of nanowires exist in the products, namely, the periodic-rhombus-decorated single-crystalline InP nanowires and jagged twinned InP nanowires.

The large-scale synthesis of ZnO nanoplatelets, as thin as 10 nm is reported. The nanoplatelets show higher efficiency in photodegrading organic dyes than ZnO nanorodes do and the photocatalytic decomposition of organic dyes (eosin B) by ZnO nanoplatelets compares favorably to the performance of ZnS porous nanoparticles and commercial Degussa P25 titania particles.

Zinc sulfide (ZnS) sheathed zinc (Zn)-cadmium (Cd) nanowire heterojunctions are prepared by thermal evaporating of ZnS and CdS powders in a vertical induction furnace at 1200 degree Celsius. The Zn/Cd interface structure in the ZnS sheathed Zn-Cd nanowire heterojunctions is experimentally studied by highly-resolution transmission electron microscopy and theoretically studied by using a near-coincidence site lattice (NCSL) concept.

The thermal conductivity of bulky pellets made of various boron nitride based nanomaterials including spherical nanoparticles, perfectly structured, bamboo-like nanotubes and collapsed nanotubes is measured. The thermal conductivity strongly depends on the morphology of the boron nitride nanomaterials, especially on the surface structure.

A study related with the direct, large-scale synthesis of ternary (carbon nanotubes-carbon single-walled nanotubes (BCN-SWNTs) through a bias-assisted hot filament (chemical vapor desposition) CVD (HF-CVD) process is presented. EELS and XPS characterization results confirmed that the B and N atoms are incorporated into the SWNTs' lattice by substitutional doping and the element EELS mapping further indicated that all constituting B, C, and N elements are homogeneously distributed within SWNT tube shells.

Novel hierarchical heterostructures formed by wrapping ZnS nanowires with highly dense Si[O.sub.2] nanowires were synthesized by vapor-liquid-solid process. The study indicated that a typical hierarchical ZnS/Si[O.sub.2] heterostructure consists of a single-crystalline ZnS nanowire (core) with diameter gradually decreasing from several hundred nanometers to 20 nm and adjacent amorphous Si[O.sub.2] nanowires (branches) with diameter of about 20 nm.

The optical features and band gap energy of specific BCN tubular fibers are evaluated through spatially determined cathodoluminescence (CL). Finally, the CL spectra distinctly shows powerful ultraviolet emission centered at 319 nm, which indicates the features of a semiconductor with a band gap of 3.89 eV.

Thermal evaporation process was used to synthesize needlelike GaN bicrystalline nanowires with uniform morphology, size, on an Au-coated Si substrate. The excellent field-emission property of GaN bicrystalline nanowires is attributed to structure defects and sharp tips.

The bulk synthesis of uniform liquid Gallium (Ga) columns, which are encapsulated into carbon nanotubes through high-temperature chemical reaction between Ga and CH(sub 4), are reported. The results reveal that the condensation of a Ga vapor and carbon clusters generates Ga-filled carbon nanotubes.

A study is conducted, in which fluorine-functionalized BN nanotubes are selected in order to pursue applications in nanoelectronics. The fluorination of BN nanotubes results in highly curled tubular BN sheets and makes insulating BN nanotubes semiconducting.

Boron nitride whiskers with a special structure are synthesized by a thermal reaction process. The result indicates that the ultraviolet-vis absorption spectrum displays the energy band gap of the boron nitride whiskers and multiple fine absorption peaks of the phonon electron coupling.

The electron field emission, with high current density equivalent 0.9 A/cm2 at a low electric field of 8.6 V/mu(m), from self-organized electron emitters with high beta, cone-shape structures and micrometer dimensions made of sp(super 3)-bonded 5H boron nitride is reported. The robustness of sp(super 3)-bonded BN with its excellent electron emission characteristics and the self-organization of emitter shaped structures provide new applications for electron emitting devices.

Crystalline tubular magnesium oxide nanostructures were obtained through carbon-thermal evaporation of a MgO powder. All the analyses indicate that the prepared tubular MgO nanostructures are single crystals.

The wide range of prospective technological applications in electronics, optics, biomedicine, mechanics, and integrated nanostructures are of great interest. The two fundamental steps in nanotechnological processes include, control of nanocrystal structures, and arrangement of nanostructures within the building blocks of special nanodevices.

Award-winning author Stephen Jay Gould shares some of his personal history as well as his views on education and contemporary American culture. Strictly speaking, Stephen Jay Gould is not an [...]

The effect of immobilization of proteins on boron nitride nanotubes (BNNTs) is studied and the immobilization is thought to be due to carboxylation of BNNT-bound amino groups or prominent tube/protein electrostatic interactions. Noncovalently functionalized BNNTs are used for the most effective immobilization.

Highly pure boron nitride nanotubes (BNNTs) are synthesized at high yield by a carbon-free chemical vapor deposition method and are functionalized by wrapping them with a conjugated polymer, poly[m-phenylenevinylene-co-(2,5-dioctoxy-p-phenylenevinylene)] (PmPV). These polymer-wrapped soluble BNNTs have numerous applications in composites and optical devices due to good dispersion and unique luminescence properties.

An effective method is developed for the generation of insulating tubular BN-sheathed nanostructures. ZnS nanowires and multilayered Si-SiO2 nanowires are successfully sheathed with insulating tubular BN shells.

The BN nanotubes were synthesized in a high yield via the CVD method using a novel precurser mixture of B2O2 and Mg vapors. The morphology of the collapsed BN nanotubes causes the enlargement of a specific surface area which remarkably enhances their hydrogen storage capacity.