802 research outputs found
Organic light-emitting diodes based on a cohost electron transporting composite
The efficiency of green organic electroluminescent devices have been improved by cohosting the electron dominant complex, 4,7-diphenyl-1,10- phenanthroline into the traditional electron transporting layer of tris (8-hydroxyquinoline) aluminum. In this cohost strategy, we demonstrate that the luminous efficiency is enhanced by >20% while the driving voltage can be reduced by ∼30% in a uniformly mixed composition as compared to the traditional device configuration. The corresponding device lifetime under atmospheric condition is extended by a factor of ∼1.8, attributed to the reduction of the accumulated positive charges near the electron-hole recombination regime. Results indicate that the knowledge of bulk conductivity engineering of organic n-type transporters is essential in enhancing organic light-emitting devices. © 2006 American Institute of Physics.published_or_final_versio
Properties of Si-SiO2 interface traps due to low-energy Ar+ backsurface bombardment in n-channel nitrided MOSFETs
Flicker noise in backsurface gettered, nitrided n-channel MOSFETs is characterized over a wide range of temperatures and biases. The gettering time ranged from 10 to 40 minutes. The noise power spectra for devices with different gettering times are compared to the ungettered devices which serve as the control. It is found that flicker noise is reduced by backsurface gettering for short gettering times. A rebound in the noise magnitude is observed for long gettering times. Investigations of the temperature dependencies of the noise power spectra indicates that the low-frequency noise arises from thermal activation of carriers to traps at the Si-SiO2 interface. Backsurface gettering results in the modification of the energy distribution of the interface traps, probably due to stress relaxation at the Si-SiO2 interface.published_or_final_versio
The electronic specific heat in the pairing pseudogap regime
When pairing correlations in a quasi two dimensional electron system induce a
pseudogap in the single particle density of states, the specific heat must also
contain a sizeable pair contribution. The theoretically calculated specific
heat for such a system is compared to the experimental results of Loram and his
collaborators for underdoped YBa_2Cu_3O_{6+x} and La_{2-x}Sr_{x}CuO_4 samples.
The size and doping dependence of the extracted pseudogap energy scale for both
materials is comparable to the values obtained from a variety of other
experiments.Comment: 4 pages, 5 eps figure
Sirtuin 1 facilitates generation of induced pluripotent stem cells from mouse embryonic fibroblasts through the miR-34a and p53 pathways
published_or_final_versio
Aerial virtual reality 360 research-creation
This paper presents a development of an aerial virtual reality 360 video capture approach. A drone was converted and retrofitted with a 360 spherical panorama camera for acquiring source aerial visual content. In this case study, an experiment of a 360-fly-by video was reproduced for the intended use of an event launching where user perception was being observed in terms of practicality and suitability. Utilizing a consumer 360 camera the Samsung Gear 360 and the DJI Inspire 1, it allowed the researcher to capture aerial 360-degree video. The paper documented the process of retrofitting the 360-camera onto the drone. Research findings on why certain drones are suitable for the 360-degree camera will be presented. A user study was conducted to gauge the usability for comparing aerial VR360 being experienced on hand-held multimedia tablets and head-mount-devices (HMD). In this paper we describe the proposed configuration and workflow of aerial 360-video and identifying its potential capabilities and limitation, a user evaluation study and directions for future work
Incommensurate Charge and Spin Fluctuations in d-wave Superconductors
We show analytic results for the irreducible charge and spin
susceptibilities, , where is the momentum
transfer between the nodes in d-wave superconductors. Using the BCS theory and
a circular Fermi surface, we find that the singular behavior of the irreducible
charge susceptibility leads to the dynamic incommensurate charge collective
modes. The peaks in the charge structure factor occur at a set of wave vectors
which form an ellipse around and in
momentum space with momentum dependent spectral weight. It is also found that,
due to the non-singular irreducible spin susceptibility, an extremely strong
interaction via random phase approximation is required to support the magnetic
peaks near . Under certain conditions, the peaks in the magnetic
structure factor occur near and .Comment: 5 pages, 3 figure
Tomb of a sultan: a VR digital heritage approach
This project presents the development of a room-scale Virtual Reality (VR) cultural heritage experience, a transmedia storytelling approach for showing museology VR content in a public setting. "Tomb of a Sultan: A VR Digital Heritage Approach" features the 19 th century tomb of Sultan Hussein Shah as a three dimensional model reproduced using photogrammetry from the actual heritage site in Malacca. Room-scale VR experience has been made possible with the introduction of sensor-based head mount displays (HMD). However, the user experience and criteria for hyper-realistic VR in the cultural heritage context requires further study in terms of method and apparatus. In this paper we describe a prototype system, a user evaluation study and directions for future work
The connection between superconducting phase correlations and spin excitations in YBaCuO: A magnetic field study
One of the most striking universal properties of the
high-transition-temperature (high-) superconductors is that they are all
derived from the hole-doping of their insulating antiferromagnetic (AF) parent
compounds. From the outset, the intimate relationship between magnetism and
superconductivity in these copper-oxides has intrigued researchers. Evidence
for this link comes from neutron scattering experiments that show the
unambiguous presence of short-range AF correlations (excitations) in cuprate
superconductors. Even so, the role of such excitations in the pairing mechanism
and superconductivity is still a subject of controversy. For
YBaCuO, where controls the hole-doping level, the most
prominent feature in the magnetic excitations spectra is the ``resonance''.
Here we show that for underdoped YBaCuO, where and
are below the optimal values, modest magnetic fields suppress the resonance
significantly, much more so for fields approximately perpendicular rather than
parallel to the CuO planes. Our results indicate that the resonance
measures pairing and phase coherence, suggesting that magnetism plays an
important role in the superconductivity of cuprates. The persistence of a field
effect above favors mechanisms with preformed pairs in the normal state
of underdoped cuprates.Comment: 12 pages, 4 figures, Nature (in press
Why Some Interfaces Cannot be Sharp
A central goal of modern materials physics and nanoscience is control of
materials and their interfaces to atomic dimensions. For interfaces between
polar and non-polar layers, this goal is thwarted by a polar catastrophe that
forces an interfacial reconstruction. In traditional semiconductors this
reconstruction is achieved by an atomic disordering and stoichiometry change at
the interface, but in multivalent oxides a new option is available: if the
electrons can move, the atoms don`t have to. Using atomic-scale electron energy
loss spectroscopy we find that there is a fundamental asymmetry between
ionically and electronically compensated interfaces, both in interfacial
sharpness and carrier density. This suggests a general strategy to design sharp
interfaces, remove interfacial screening charges, control the band offset, and
hence dramatically improving the performance of oxide devices.Comment: 12 pages of text, 6 figure
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