2,331 research outputs found
Alumina fiber strength improvement
The effective fiber strength of alumina fibers in an aluminum composite was increased to 173,000 psi. A high temperature heat treatment, combined with a glassy carbon surface coating, was used to prevent degradation and improve fiber tensile strength. Attempts to achieve chemical strengthening of the alumina fiber by chromium oxide and boron oxide coatings proved unsuccessful. A major problem encountered on the program was the low and inconsistent strength of the Dupont Fiber FP used for the investigation
Activation mechanisms in sodium-doped Silicon MOSFETs
We have studied the temperature dependence of the conductivity of a silicon
MOSFET containing sodium ions in the oxide above 20 K. We find the impurity
band resulting from the presence of charges at the silicon-oxide interface is
split into a lower and an upper band. We have observed activation of electrons
from the upper band to the conduction band edge as well as from the lower to
the upper band. A possible explanation implying the presence of Hubbard bands
is given.Comment: published in J. Phys. : Condens. Matte
Disorder and electron interaction control in low-doped silicon metal-oxide-semiconductor field effect transistors
We fabricated silicon metal-oxide-semiconductor field effect transistors
where an additional sodium-doped layer was incorporated into the oxide to
create potential fluctuations at the Si-SiO2 interface. The amplitude of these
fluctuations is controlled by both the density of ions in the oxide and their
position relative to the Si-SiO2 interface. Owing to the high mobility of the
ions at room temperature, it is possible to move them with the application of a
suitable electric field. We show that, in this configuration, such a device can
be used to control both the disorder and the electron-electron interaction
strength at the Si-SiO2 interface.Comment: 3 pages, 2 figure
Aortic Leaflet Stress in Surgery for Genetically Determined Root Aneurysms: Biomechanical Insights
Variation of the hopping exponent in disordered silicon MOSFETs
We observe a complex change in the hopping exponent value from 1/2 to 1/3 as
a function of disorder strength and electron density in a sodium-doped silicon
MOSFET. The disorder was varied by applying a gate voltage and thermally
drifting the ions to different positions in the oxide. The same gate was then
used at low temperature to modify the carrier concentration.
Magnetoconductivity measurements are compatible with a change in transport
mechanisms when either the disorder or the electron density is modified
suggesting a possible transition from a Mott insulator to an Anderson insulator
in these systems.Comment: 6 pages, 5 figure
Survey for Transiting Extrasolar Planets in Stellar Systems IV: Variables in the Field of NGC 1245
The Survey for Transiting Extrasolar Planets in Stellar Systems (STEPSS)
project is a search for planetary transits in open clusters. In this paper, we
analyze the STEPSS observations of the open cluster NGC 1245 to determine the
variable star content of the cluster. Out of 6787 stars observed with V < 22,
of which ~870 are cluster members, we find 14 stars with clear intrinsic
variability that are potential cluster members, and 29 clear variables that are
not cluster members. None of these variables have been previously identified.
We present light curves, finding charts, and stellar/photometric data on these
variable objects. Several of the interacting binaries have estimated distances
consistent with the cluster distance determined from isochrone fits to the
color magnitude diagram. Four stars at the main sequence turnoff of the cluster
have light curves consistent with gamma Doradus variability. If these gamma
Doradus candidates are confirmed, they represent the oldest and coolest members
of this class of variable discovered to date.Comment: 20 pages, 15 figures. Submitted to AJ. PDF version with
full-resolution figures at http://www.astronomy.ohio-state.edu/~pepper/ms.pd
Magnetoconductivity of Hubbard bands induced in Silicon MOSFETs
Sodium impurities are diffused electrically to the oxide-semiconductor
interface of a silicon MOSFET to create an impurity band. At low temperature
and at low electron density, the band is split into an upper and a lower
sections under the influence of Coulomb interactions. We used
magnetoconductivity measurements to provide evidence for the existence of
Hubbard bands and determine the nature of the states in each band.Comment: In press in Physica
Evolution of the bilayer nu = 1 quantum Hall state under charge imbalance
We use high-mobility bilayer hole systems with negligible tunneling to
examine how the bilayer nu = 1 quantum Hall state evolves as charge is
transferred from one layer to the other at constant total density. We map
bilayer nu = 1 state stability versus imbalance for five total densities
spanning the range from strongly interlayer coherent to incoherent. We observe
competition between single-layer correlations and interlayer coherence. Most
significantly, we find that bilayer systems that are incoherent at balance can
develop spontaneous interlayer coherence with imbalance, in agreement with
recent theoretical predictions.Comment: 4 pages, 4 figure
Evidence for multiple impurity bands in sodium-doped silicon MOSFETs
We report measurements of the temperature-dependent conductivity in a silicon
metal-oxide-semiconductor field-effect transistor that contains sodium
impurities in the oxide layer. We explain the variation of conductivity in
terms of Coulomb interactions that are partially screened by the proximity of
the metal gate. The study of the conductivity exponential prefactor and the
localization length as a function of gate voltage have allowed us to determine
the electronic density of states and has provided arguments for the presence of
two distinct bands and a soft gap at low temperature.Comment: 4 pages; 5 figures; Published in PRB Rapid-Communication
'Mine's a Pint of Bitter': Performativity, gender, class and representations of authenticity in real-ale tourism
Leisure choices are expressive of individual agency around the maintenance of taste, boundaries, identity and community. This research paper is part of a wider project designed to assess the social and cultural value of real ale to tourism in the north of England. This paper explores the performativity of real-ale tourism and debates about belonging in northern English real-ale communities. The research combines an ethnographic case study of a real-ale festival with semi-structured interviews with organisers and volunteers, northern English real-ale brewers and real-ale tourists visiting the festival. It is argued that real-ale tourism, despite its origins in the logic of capitalism, becomes a space where people can perform Habermasian, communicative leisure, and despite the contradictions of preferring some capitalist industries over others on the basis of their perceived smaller size and older age, real-ale fans demonstrate agency in their performativity
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