22,283 research outputs found
From chips to dust: the MEMS shatter secure chip
pre-printThis paper presents the implementation of a transience mechanism for silicon microchips via low-temperature post-processing steps that transform almost any electronic, optical or MEMS substrate chips into transient ones. Transience is achieved without any hazardous or explosive materials. Triggered chip transience is achieved by the incorporation of a distributed, thermally-activated expanding material on the chip backside. When heated at 160oC the expanding material produces massive chip cleavage mechanically shattering the chip into a heap of silicon dust
Noncommuting Electric Fields and Algebraic Consistency in Noncommutative Gauge theories
We show that noncommuting electric fields occur naturally in
-expanded noncommutative gauge theories. Using this noncommutativity,
which is field dependent, and a hamiltonian generalisation of the
Seiberg-Witten Map, the algebraic consistency in the lagrangian and hamiltonian
formulations of these theories, is established. A comparison of results in
different descriptions shows that this generalised map acts as canonical
transformation in the physical subspace only. Finally, we apply the hamiltonian
formulation to derive the gauge symmetries of the action.Comment: 16 pages, LaTex, considerably expanded version with a new section on
`Gauge symmetries'; To appear in Phys. Rev.
NaAlSi: a self-doped semimetallic superconductor with free electrons and covalent holes
The layered ternary sp conductor NaAlSi, possessing the iron-pnictide "111"
crystal structure, superconducts at 7 K. Using density functional methods, we
show that this compound is an intrinsic (self-doped) low-carrier-density
semimetal with a number of unusual features. Covalent Al-Si valence bands
provide the holes, and free-electron-like Al 3s bands, which propagate in the
channel between the neighboring Si layers, dip just below the Fermi level to
create the electron carriers. The Fermi level (and therefore the
superconducting carriers) lies in a narrow and sharp peak within a pseudogap in
the density of states. The small peak arises from valence bands which are
nearly of pure Si, quasi-two-dimensional, flat, and coupled to Al conduction
bands. Isostructural NaAlGe, which is not superconducting above 1.6 K, has
almost exactly the same band structure except for one missing piece of small
Fermi surface. Certain deformation potentials induced by Si and Na
displacements along the c-axis are calculated and discussed. It seems likely
that the mechanism of pairing is related to that of several other lightly doped
two-dimensional nonmagnetic semiconductors (TiNCl, ZrNCl, HfNCl), which is not
well understood but apparently not of phonon origin.Comment: 9 pages, 7 figures, 1 tabl
Production of Manganese and Manganese Dioxide - Pilot Plant Investigations
Investigations on production of electrolytic manganese
and electrolytic manganese dioxide were initiated in this laboratory in 1950 for the utilisation of low-grade manganese ores. Basic data for the two processes were collected by 1953 and the processes developed were covered by patents. Before the processes could be handed over
for commercial exploitation, it was thought necessary that the processes should be tried on a comparatively larger scale of a pilot plant to find the soundness of the processes, to visualise the relative sizes of various equipment, materials of construction, relative effects of
different stages of the processes, working conditions, quality of products and a preliminary idea about cost, i.e., in short to find how far the conditions and data found in laboratory scale experiments were applicable on a large scale. A beginning in the establishment of a pilot plant was made in 1954
Anomalies in noncommutative gauge theories, Seiberg-Witten transformation and Ramond-Ramond couplings
We propose an exact expression for the unintegrated form of the star gauge
invariant axial anomaly in an arbitrary even dimensional gauge theory. The
proposal is based on the inverse Seiberg-Witten map and identities related to
it, obtained earlier by comparing Ramond-Ramond couplings in different
decsriptions. The integrated anomalies are expressed in terms of a simplified
version of the Elliott formula involving the noncommutative Chern character.
These anomalies, under the Seiberg-Witten transformation, reduce to the
ordinary axial anomalies. Compatibility with existing results of anomalies in
noncommutative theories is established.Comment: 16 pages. LaTe
Higher Derivative Corrections to Locally Black Brane Metrics
In this paper we generalize the construction of locally boosted black brane
space time to higher derivative gravities. We consider the Gauss-Bonnet term
(with coefficient ) as a toy example. We find the solution to the
corrected Einstein equations to first order in the boundary
derivative expansion. This allows us to find the corrections to the
boundary stress tensor in the presence of the Gauss-Bonnet term in the bulk
action. We therefore obtain the ratio of shear viscosity to entropy which
agrees with other methods of computation in the literature.Comment: 0+17 page
Unraveling the Infrared Transient VVV-WIT-06: The Case for the Origin as a Classical Nova
Indexación: Scopus.E.Y.H. acknowledges the support provided by the National Science Foundation under Grant No. AST-1613472 and by the Florida Space Grant Consortium. L.G. acknowledges support from the FINCA visitor programme. The research work at the Physical Research Laboratory is funded by the Department of Space, Government of India. Facility: Magellan: Baade(FIRE).The enigmatic near-infrared transient VVV-WIT-06 underwent a large-amplitude eruption of unclear origin in 2013 July. Based on its light curve properties and late-time post-outburst spectra, various possibilities have been proposed in the literature for the origin of the object, namely a Type I supernova, a classical nova (CN), or a violent stellar merger event. We show that, of these possibilities, an origin in a CN outburst convincingly explains the observed properties of VVV-WIT-06. We estimate that the absolute K-band magnitude of the nova at maximum was M k = -8.2 ±0.5, its distance d = 13.35 ±2.18 kpc, and the extinction A v = 15.0 ±0.55 mag. © 2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-4357/aae5d
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