3,444 research outputs found
The Emperor\u27s New Clothes: A Survey of Significant Court Decisions Interpreting Pennsylvania\u27s Sovereign Immunity Act and Its Waivers
This article surveys and analyzes the history of sovereign immunity in the Commonwealth of Pennsylvania. The article traces the adoption of sovereign immunity, its abrogation by the Pennsylvania Supreme Court, and the General Assembly\u27s reaffirmation of the doctrine in the Sovereign Immunity Act. The article provides a review of the important sections of the Sovereign Immunity Act and examines many of the appellate decisions which have addressed the Act and the waivers of immunity contained therein
Dynamic Pattern Formation in Electron-Beam-Induced Etching
© 2015 American Physical Society. We report highly ordered topographic patterns that form on the surface of diamond, span multiple length scales, and have a symmetry controlled by the precursor gas species used in electron-beam-induced etching (EBIE). The pattern formation dynamics reveals an etch rate anisotropy and an electron energy transfer pathway that is overlooked by existing EBIE models. We, therefore, modify established theory such that it explains our results and remains universally applicable to EBIE. The patterns can be exploited in controlled wetting, optical structuring, and other emerging applications that require nano- and microscale surface texturing of a wide band-gap material
Maskless milling of diamond by a focused oxygen ion beam
Recent advances in focused ion beam technology have enabled high-resolution, maskless nanofabrication using light ions. Studies with light ions to date have, however, focused on milling of materials where sub-surface ion beam damage does not inhibit device performance. Here we report on maskless milling of single crystal diamond using a focused beam of oxygen ions. Material quality is assessed by Raman and luminescence analysis, and reveals that the damage layer generated by oxygen ions can be removed by non-intrusive post-processing methods such as localised electron beam induced chemical etching
Direct-write milling of diamond by a focused oxygen ion beam
Recent advances in focused ion beam technology have enabled high-resolution, direct-write nanofabrication using light ions. Studies with light ions to date have, however, focused on milling of materials where sub-surface ion beam damage does not inhibit device performance. Here we report on direct-write milling of single crystal diamond using a focused beam of oxygen ions. Material quality is assessed by Raman and luminescence analysis, and reveals that the damage layer generated by oxygen ions can be removed by nonintrusive post-processing methods such as localised electron beam induced chemical etching
Single shot phase contrast imaging using laser-produced Betatron x-ray beams
Development of x-ray phase contrast imaging applications with a laboratory
scale source have been limited by the long exposure time needed to obtain one
image. We demonstrate, using the Betatron x-ray radiation produced when
electrons are accelerated and wiggled in the laser-wakefield cavity, that a
high quality phase contrast image of a complex object (here, a bee), located in
air, can be obtained with a single laser shot. The Betatron x-ray source used
in this proof of principle experiment has a source diameter of 1.7 microns and
produces a synchrotron spectrum with critical energy E_c=12.3 +- 2.5 keV and
10^9 photons per shot in the whole spectrum.Comment: 3 pages, 3 figure
ISO observations of far-infrared rotational emission lines of water vapor toward the supergiant star VY Canis Majoris
We report the detection of numerous far-infrared emission lines of water
vapor toward the supergiant star VY Canis Majoris. A 29.5 - 45 micron grating
scan of VY CMa, obtained using the Short Wavelength Spectrometer (SWS) of the
Infrared Space Observatory (ISO) at a spectral resolving power of approximately
2000, reveals at least 41 spectral features due to water vapor that together
radiate a total luminosity ~ 25 solar luminosities. In addition to pure
rotational transitions within the ground vibrational state, these features
include rotational transitions within the (010) excited vibrational state. The
spectrum also shows the doublet Pi 1/2 (J=5/2) <-- doublet Pi 3/2 (J=3/2) OH
feature near 34.6 micron in absorption. Additional SWS observations of VY CMa
were carried out in the instrument's Fabry-Perot mode for three water
transitions: the 7(25)-6(16) line at 29.8367 micron, the 4(41)-3(12) line
31.7721 micron, and the 4(32)-3(03) line at 40.6909 micron. The higher spectral
resolving power of approximately 30,000 thereby obtained permits the line
profiles to be resolved spectrally for the first time and reveals the "P Cygni"
profiles that are characteristic of emission from an outflowing envelope.Comment: 11 pages (inc. 2 figures), LaTeX, uses aaspp4.sty, accepted for
publication in ApJ Letter
MSK1 regulates transcriptional induction of Arc/Arg3.1 in response to neurotrophins
The immediate early gene activity-regulated cytoskeletal protein (Arc)/Arg3.1 and the neurotrophin brain-derived neurotrophic factor (BDNF) play important roles in synaptic plasticity and learning and memory in the mammalian brain. However, the mechanisms by which BDNF regulates the expression of Arc/Arg3.1 are unclear. In this study, we show that BDNF acts via the ERK1/2 pathway to activate the nuclear kinase mitogen- and stress-activated protein kinase 1 (MSK1). MSK1 then induces Arc/Arg3.1 expression via the phosphorylation of histone H3 at the Arc/Arg3.1 promoter. MSK1 can also phosphorylate the transcription factor cyclic-AMP response element-binding protein (CREB) on Ser133. However, this is not required for BDNF-induced Arc.Arg3.1 transcription as a Ser133Ala knockin mutation had no effect on Arc/Arg3.1 induction. In parallel, ERK1/2 directly activates Arc/Arg3.1 mRNA transcription via at least one serum response element on the promoter, which bind a complex of the Serum Response Factor (SRF) and a Ternary Complex Factor (TCF)
Transient evolution of C-type shocks in dusty regions of varying density
Outflows of young stars drive shocks into dusty, molecular regions. Most
models of such shocks assume that they are steady and propagating perpendicular
to the magnetic field. Real shocks often violate both of these assumptions and
the media through which they propagate are inhomogeneous. We use the code
employed previously to produce the first time-dependent simulations of
fast-mode, oblique C-type shocks interacting with density perturbations. We
include a self-consistent calculation of the thermal and ionisation balances
and a fluid treatment of grains. We identify features that develop when a
multifluid shock encounters a density inhomogeneity to investigate whether any
part of the precursor region ever behaves in a quasi-steady fashion. If it does
the shock may be modelled approximately without solving the time-dependent
hydromagnetic equations. Simulations were made for initially steady oblique
C-type shocks encountering density inhomogeneities. For a semi-finite
inhomogeneity with a density larger than the surrounding medium, a transmitted
shock evolves from being J-type to a steady C-type shock on a timescale
comparable to the ion-flow time through it. A sufficiently upstream part of the
precursor of an evolving J-type shock is quasi-steady. The ion-flow timescale
is also relevant for the evolution of a shock moving into a region of
decreasing density. The models for shocks propagating into regions in which the
density increases and then decreases to its initial value cannot be entirely
described in terms of the results obtained for monotonically increasing and
decreasing densities. For the latter model, the long-term evolution to a C-type
shock cannot be approximated by quasi-steady models.Comment: 11 pages, 9 figure
Influence of severe plastic deformation on the precipitation hardening of a FeSiTi steel
The combined strengthening effects of grain refinement and high precipitated
volume fraction (~6at.%) on the mechanical properties of FeSiTi alloy subjected
to SPD processing prior to aging treatment were investigated by atom probe
tomography and scanning transmission electron microscopy. It was shown that the
refinement of the microstructure affects the precipitation kinetics and the
spatial distribution of the secondary hardening intermetallic phase, which was
observed to nucleate heterogeneously on dislocations and sub-grain boundaries.
It was revealed that alloys successively subjected to these two strengthening
mechanisms exhibit a lower increase in mechanical strength than a simple
estimation based on the summation of the two individual strengthening
mechanisms
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