Supersonic through-flow fan assessment

A study was conducted to assess the performance potential of a supersonic through-flow fan engine for supersonic cruise aircraft. It included a mean-line analysis of fans designed to operate with in-flow velocities ranging from subsonic to high supersonic speeds. The fan performance generated was used to estimate the performance of supersonic fan engines designed for four applications: a Mach 2.3 supersonic transport, a Mach 2.5 fighter, a Mach 3.5 cruise missile, and a Mach 5.0 cruise vehicle. For each application an engine was conceptualized, fan performance and engine performance calculated, weight estimates made, engine installed in a hypothetical vehicle, and mission analysis was conducted

Chasing a ghost : Addressing the opalescence/aggregation relationship of an IgG 1 antibody

This study was conducted to address the aggregation/opalescence relationship of an IgG 1 therapeutic antibody under a variety of conditions. The opalescence characteristics of three antibodies, Mab 1, 2 and 3, were examined as a function of salt dependence, protein concentration and temperature, using a variety of biophysical techniques. The high molecular weight species were initially identified using batch static and dynamic light scattering and separated by asymmetric flow field flow fractionation. When the salt dependence was examined, any structural changes were characterized using differential scanning calorimetry, circular dichroism and fluorescence, while the association state and temperature dependence was measured by viscometry. The resulting non-ideality was determined using multi-angle light scattering over a range of NaCl and protein concentration, and then used to assess the nature of the noncovalent association. In addition, the valence of the antibody therapeutics was directly measured using capillary electrophoresis and assessed as a predictive tool of non-ideal behavior. The antibody that exhibited the highest degree of opalescence, and therefore was the main focus of the study, was Mab 1, with Mab 3 exhibiting a lower degree of opalescence and Mab 2 acting as a control. The results suggest that the opalescence phenomenon of Mab 1 was due to a salt induced non-mass-action driven self-association which is mainly entropic in origin and is driven predominantly by NaCl. The intermolecular interactions appear to be facilitated by enhanced flexibility of Fc region and the independent Fab folding domain on Mab 1. The opalescence phenomenon also appears to be a relatively small fraction of discrete HMW material which is freely reversible and results in a liquid-liquid or liquid-solid phase transition which is either clear or cloudy depending on A2. Finally, it was determined that there is a discrepancy between the measured and calculated valence of the IgG1 antibodies in the study and this may be used as a predictive tool of non-ideal behavior. Together, this information was used to propose a model of the opalescence phenomenon of Mab 1 based on an electrostatic interaction involving mainly the CDR region on the Fab

Giant Electron-hole Charging Energy Asymmetry in Ultra-short Carbon Nanotubes

Making full usage of bipolar transport in single-wall carbon nanotube (SWCNT) transistors could permit the development of two-in-one quantum devices with ultra-short channels. We report on clean $\sim$10 to 100 nm long suspended SWCNT transistors which display a large electron-hole transport asymmetry. The devices consist of naked SWCNT channels contacted with sections of SWCNT-under-annealed-gold. The annealed gold acts as an n-doping top gate which creates nm-sharp barriers at the junctions between the contacts and naked channel. These tunnel barriers define a single quantum dot (QD) whose charging energies to add an electron or a hole are vastly different ($e-h$ charging energy asymmetry). We parameterize the $e-h$ transport asymmetry by the ratio of the hole and electron charging energies $\eta_{e-h}$. We show that this asymmetry is maximized for short channels and small band gap SWCNTs. In a small band gap SWCNT device, we demonstrate the fabrication of a two-in-one quantum device acting as a QD for holes, and a much longer quantum bus for electrons. In a 14 nm long channel, $\eta_{e-h}$ reaches up to 2.6 for a device with a band gap of 270 meV. This strong $e-h$ transport asymmetry survives even at room temperature

Direct measurement of the 14N(p,g)15O S-factor

We have measured the 14N(p,g)15O excitation function for energies in the range E_p = 155--524 keV. Fits of these data using R-matrix theory yield a value for the S-factor at zero energy of 1.64(17) keV b, which is significantly smaller than the result of a previous direct measurement. The corresponding reduction in the stellar reaction rate for 14N(p,g)15O has a number of interesting consequences, including an impact on estimates for the age of the Galaxy derived from globular clusters.Comment: 5 pages, 3 figures, submitted to Phys. Rev. Let

STARLIB: A Next-Generation Reaction-Rate Library for Nuclear Astrophysics

STARLIB is a next-generation, all-purpose nuclear reaction-rate library. For the first time, this library provides the rate probability density at all temperature grid points for convenient implementation in models of stellar phenomena. The recommended rate and its associated uncertainties are also included. Currently, uncertainties are absent from all other rate libraries, and, although estimates have been attempted in previous evaluations and compilations, these are generally not based on rigorous statistical definitions. A common standard for deriving uncertainties is clearly warranted. STARLIB represents a first step in addressing this deficiency by providing a tabular, up-to-date database that supplies not only the rate and its uncertainty but also its distribution. Because a majority of rates are lognormally distributed, this allows the construction of rate probability densities from the columns of STARLIB. This structure is based on a recently suggested Monte Carlo method to calculate reaction rates, where uncertainties are rigorously defined. In STARLIB, experimental rates are supplemented with: (i) theoretical TALYS rates for reactions for which no experimental input is available, and (ii) laboratory and theoretical weak rates. STARLIB includes all types of reactions of astrophysical interest to Z = 83, such as (p,g), (p,a), (a,n), and corresponding reverse rates. Strong rates account for thermal target excitations. Here, we summarize our Monte Carlo formalism, introduce the library, compare methods of correcting rates for stellar environments, and discuss how to implement our library in Monte Carlo nucleosynthesis studies. We also present a method for accessing STARLIB on the Internet and outline updated Monte Carlo-based rates.Comment: Accepted for publication in the Astrophysical Journal Supplement Series; 96 pages, 22 figure

Structural and electrical characterization of hybrid metal-polypyrrole nanowires

We present here the synthesis and structural characterization of hybrid Au-polypyrrole-Au and Pt- polypyrrole-Au nanowires together with a study of their electrical properties from room-temperature down to very low temperature. A careful characterization of the metal-polymer interfaces by trans- mission electron microscopy revealed that the structure and mechanical strength of bottom and upper interfaces are very different. Variable temperature electrical transport measurements were performed on both multiple nanowires - contained within the polycarbonate template - and single nanowires. Our data show that the three-dimensional Mott variable-range-hopping model provides a complete framework for the understanding of transport in PPy nanowires, including non-linear current-voltage characteristics and magnetotransport at low temperatures.Comment: Phys. Rev. B Vol. 76 Issue 11 (2007