14,485 research outputs found
Direct observation of a highly spin-polarized organic spinterface at room temperature
The design of large-scale electronic circuits that are entirely
spintronics-driven requires a current source that is highly spin-polarised at
and beyond room temperature, cheap to build, efficient at the nanoscale and
straightforward to integrate with semiconductors. Yet despite research within
several subfields spanning nearly two decades, this key building block is still
lacking. We experimentally and theoretically show how the interface between Co
and phthalocyanine molecules constitutes a promising candidate. Spin-polarised
direct and inverse photoemission experiments reveal a high degree of spin
polarisation at room temperature at this interface. We measured a magnetic
moment on the molecules's nitrogen pi orbitals, which substantiates an
ab-initio theoretical description of highly spin-polarised charge conduction
across the interface due to differing spinterface formation mechanims in each
spin channel. We propose, through this example, a recipe to engineer simple
organic-inorganic interfaces with remarkable spintronic properties that can
endure well above room temperature
Ion yields and erosion rates for Si1âxGex(0x1) ultralow energy O2+ secondary ion mass spectrometry in the energy range of 0.25â1 keV
We report the SIMS parameters required for the quantitative analysis of Si1âxGex across the range of 0 †x †1 when using low energy O2+ primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio Rx of erosion rates, Si1âxGex/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. Rx shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1âx) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of ±0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x
The materials processing research base of the Materials Processing Center
The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis
Apparent movement phenomena on CRT displays - Threshold determinations of apparent movements of pulsed light sources
Apparent movement phenomena on cathode ray tube displays - threshold determinations of apparent movements of pulsed light source
Collisions of boosted black holes: perturbation theory prediction of gravitational radiation
We consider general relativistic Cauchy data representing two nonspinning,
equal-mass black holes boosted toward each other. When the black holes are
close enough to each other and their momentum is sufficiently high, an
encompassing apparent horizon is present so the system can be viewed as a
single, perturbed black hole. We employ gauge-invariant perturbation theory,
and integrate the Zerilli equation to analyze these time-asymmetric data sets
and compute gravitational wave forms and emitted energies. When coupled with a
simple Newtonian analysis of the infall trajectory, we find striking agreement
between the perturbation calculation of emitted energies and the results of
fully general relativistic numerical simulations of time-symmetric initial
data.Comment: 5 pages (RevTex 3.0 with 3 uuencoded figures), CRSR-107
Anisotropic dehydration of hydrogel surfaces
Efforts to develop tissue-engineered skin for regenerative medicine have explored natural, synthetic, and hybrid hydrogels. The creation of a bilayer material, with the stratification exhibited by native skin is a complex problem. The mechanically robust, waterproof epidermis presents the stratum corneum at the tissue/air interface, which confers many of these protective properties. In this work we explore the effect of high temperatures on alginate hydrogels, which are widely employed for tissue engineering due to their excellent mechanical properties and cellular compatibility. In particular, we investigate the rapid dehydration of the hydrogel surface which occurs following local exposure to heated surfaces with temperatures in the range 100-200 oC. We report the creation of a mechanically strengthened hydrogel surface, with improved puncture resistance and increased coefficient of friction, compared to the unheated surface. The use of a mechanical restraint during heating promoted differences in the rate of mass loss; the rate of temperature increase within the hydrogel, in the presence and absence of restraint, is simulated and discussed. It is hoped that the results will be of use in the development of processes suitable for preparing skin-like analogues; application areas could include wound healing and skin restoration
Teleportation as a Depolarizing Quantum Channel, Relative Entropy and Classical Capacity
We show that standard teleportation with an arbitrary mixed state resource is
equivalent to a generalized depolarizing channel with probabilities given by
the maximally entangled components of the resource. This enables the usage of
any quantum channel as a generalized depolarizing channel without additional
twirling operations. It also provides a nontrivial upper bound on the
entanglement of a class of mixed states. Our result allows a consistent and
statistically motivated quantification of teleportation success in terms of the
relative entropy and this quantification can be related to a classical
capacity.Comment: Version published in Phys. Rev. Let
Dephasing representation of quantum fidelity for general pure and mixed states
General semiclassical expression for quantum fidelity (Loschmidt echo) of
arbitrary pure and mixed states is derived. It expresses fidelity as an
interference sum of dephasing trajectories weighed by the Wigner function of
the initial state, and does not require that the initial state be localized in
position or momentum. This general dephasing representation is special in that,
counterintuitively, all of fidelity decay is due to dephasing and none due to
the decay of classical overlaps. Surprising accuracy of the approximation is
justified by invoking the shadowing theorem: twice--both for physical
perturbations and for numerical errors. It is shown how the general expression
reduces to the special forms for position and momentum states and for wave
packets localized in position or momentum. The superiority of the general over
the specialized forms is explained and supported by numerical tests for wave
packets, non-local pure states, and for simple and random mixed states. The
tests are done in non-universal regimes in mixed phase space where detailed
features of fidelity are important. Although semiclassically motivated, present
approach is valid for abstract systems with a finite Hilbert basis provided
that the discrete Wigner transform is used. This makes the method applicable,
via a phase space approach, e. g., to problems of quantum computation.Comment: 11 pages, 4 figure
Oncolog, Volume 36, Issue 02, April-June 1991
Redefining the risks of chemotherapy during pregnancy Renewing the assault on pancreatic cancer Significance of cancer volume in radiotherapyhttps://openworks.mdanderson.org/oncolog/1034/thumbnail.jp
Sagnac Interferometer Enhanced Particle Tracking in Optical Tweezers
A setup is proposed to enhance tracking of very small particles, by using
optical tweezers embedded within a Sagnac interferometer. The achievable
signal-to-noise ratio is shown to be enhanced over that for a standard optical
tweezers setup. The enhancement factor increases asymptotically as the
interferometer visibility approaches 100%, but is capped at a maximum given by
the ratio of the trapping field intensity to the detector saturation threshold.
For an achievable visibility of 99%, the signal-to-noise ratio is enhanced by a
factor of 200, and the minimum trackable particle size is 2.4 times smaller
than without the interferometer
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