SEM characterization of mm-long nanowires

The fabrication of optical fibre nanowires has recently attracted much attention [1-5]. Nanowires longer than 110mm [2] and with diameters smaller than 20 nm [5] have now been fabricated using a top-down approach. Because of the extraordinarily large ratio between length and diameter (>100000), the characterization of optical fibre nanowires requires instrumentation capable of measuring lengths over a range spanning more than five orders of magnitude. In our experiments dimensional characterization along the nanowire has been performed using an SEM and calibrated references. The samples are first attached to conductive carbon pads to avoid electrostatic build-up. Charging makes accurate metrology difficult because the electron beam can be deflected by the induced electric field on the sample. Fig. 1 illustrates a nanowire with a radius r=30nm wrapped around a microfibre with r=2µm. Variations in radius of another nanowire along its length are shown in fig. 2

Idler-resonant femtosecond optical parametric oscillator with high mid-infra-red beam quality

We report an idler-resonant femtosecond optical parametric oscillator (OPO) with average output power of 520 mW, repetition-rate of 80 MHz, pulse duration of 90 fs and nearly diffraction-limited beam quality at ~2.4 µm

Subsurface microstructural changes in a cast heat resisting alloy caused by high temperature corrosion

A cast HP ModNb alloy (Fe–25Cr–35Ni–1Nb, wt.%) was oxidised and carburised in CO–CO2 corresponding to aC = 0.1 and pO2 = 3 1016 atm at 1080 C. Formation of an external, chromium-rich oxide scale led to depletion of this metal in a deep alloy subsurface zone. Within that zone, secondary chromium-rich carbides dissolved, primary carbides oxidised, solute silicon and aluminium internally oxidised, and extensive porosity developed. Pore volumes correspond to the difference between metal loss by scaling and metal displacement by internal oxidation, assuming the scale–metal interface to be fixed. The pores are concluded to be Kirkendall void

16-µJ pulse energy, picosecond, narrow-linewidth master oscillator power amplifier using direct amplification

We present a gain-switched-diode-seeded 1034.5nm master oscillator power amplifier, employing direct amplification through standard commercial Yb3+-doped fibres to generate 15.6µJ-pulse-energy, 126kW-peak-power, picosecond pulses with 3dB spectral bandwidth of 0.87nm

Ferromagnetic/III-V semiconductor heterostructures and magneto-electronic devices

The interface magnetic and electronic properties of two Fe/III-V semiconductor systems, namely Fe/GaAs and Fe/InAs, grown at room temperature have been studied. A "magnetic interface", which is essential for the fabrication of magneto-electronic (ME) devices, was realized in both Fe/GaAs and Fe/InAs systems with suitable substrate processing and growth conditions. Furthermore, Fe/InAs was shown to have favorable interface electronic properties as Fe forms a low resistance ohmic contact on InAs. Two prototypes of ME device based on Fe/InAs are also discussed

The osteology of Shaochilong maortuensis, a carcharodontosaurid (dinosauria:theropoda) from the Late Cretaceous of Asia

Large-bodied theropod dinosaurs from the Early-mid Cretaceous of the northern continents (Laurasia) are poorly known. One of the most complete and intriguing theropods from this interval is Shaochilong maortuensis Hu, 1964 from the Turonian (< 92 Ma) Ulansuhai Formation of Inner Mongolia, China. The phylogenetic placement of Shaochilong has long been a subject of debate, as it has been referred to several disparate theropod groups (e.g., Megalosauridae, Allosauridae, Tyrannosauroidea, Maniraptora). In a recent taxonomic reassessment, Shaochilong was identified as the first Asian member of Carcharodontosauridae, a clade of allosauroid theropods that was once thought to be restricted to Gondwana and includes some of the largest terrestrial predators to ever live. However, the characters supporting such a placement were only briefly discussed, and a full anatomical description of Shaochilong has yet to be presented. We provide a detailed osteological description of the lectotype and paralectotype series, show that Shaochilong is a small-bodied and short-snouted carcharodontosaurid, and highlight numerous cranial features shared with other carcharodontosaurids. We argue that the vicariant hypothesis of allosauroid biogeography, in which lineages split in concert with the fragmentation of Pangaea, is poorly supported. Finally, large-scale patterns of theropod evolution and faunal replacement are discussed, and it is argued that allosauroids persisted as large-bodied predators later in the Cretaceous than previously thought. Copyright © 2010 Magnolia Press

Formation of the seed black holes: a role of quark nuggets?

Strange quark nuggets (SQNs) could be the relics of the cosmological QCD phase transition, and they could very likely be the candidate of cold quark matter if survived the cooling of the later Universe, although the formation and evolution of these SQNs depend on the physical state of the hot QGP (quark-gluon plasma) phase and the state of cold quark matter. We reconsider the possibility of SQNs as cold dark matter, and find that the formation of black holes in primordial halos could be significantly different from the standard scenario. In a primordial halo, the collision between gas and SQNs could be frequent enough, and thus the viscosity acting on each SQN would decrease its angular momentum and make it to sink into the center of the halo, as well as heat the gas. The SQNs with baryon numbers less than $10^{35}$ could assemble in the center of the halo before the formation of primordial stars. A black hole could form by merger of these SQNs, and then its mass could quickly become about $10^3\ M_\odot$ or higher, by accreting the surrounding SQNs or gas. The black holes formed in this way could be the seeds for the supermassive black holes at redshift as high as $z\sim 6$.Comment: 15 page

Revisiting Cardassian Model and Cosmic Constraint

In this paper, we revisit the Cardassian model in which the radiation energy component is included. It is important for early epoch when the radiation cannot be neglected because the equation of state (EoS) of the effective dark energy becomes time variable. Therefore, it is not equivalent to the quintessence model with a constant EoS anymore. This situation was almost overlooked in the literature. By using the recent released Union2 557 of type Ia supernovae (SN Ia), the baryon acoustic oscillation (BAO) from Sloan Digital Sky Survey and the WiggleZ data points, the full information of cosmic microwave background (CMB) measurement given by the seven-year Wilkinson Microwave Anisotropy Probe observation, we constrain the Cardassian model via the Markov Chain Monte Carlo (MCMC) method. A tight constraint is obtained: $n= -0.0479_{- 0.0732- 0.148}^{+ 0.0730+ 0.142}$ in $1,2\sigma$ regions. The deviation of Cardassian model from quintessence model is shown in CMB anisotropic power spectra at high l's parts due to the evolution of EoS. But it is about the order of 0.1% which cannot be discriminated by current data sets. The Cardassian model is consistent with current cosmic observational data sets.Comment: 6 pages, 5 figures, match the published versio

Magnetic-interference patterns in Josephson junctions with d+is symmetry

The magnetic interference pattern and the spontaneous flux in unconventional Josephson junctions of superconductors with d+is symmetry are calculated for different reduced junction lengths and the relative factor of the d and s wave components. This is a time reversal broken symmetry state. We study the stability of the fractional vortex and antivortex which are spontaneously formed and examine their evolution as we change the length and the relative factor of d and s wave components. The asymmetry in the field modulated diffraction pattern exists for lengths as long as L=10\lambda_J.Comment: 8 pages, 6 eps files, submitted to PR