950 research outputs found
A Portable MEMS Gravimeter for the Detection of the Earth Tides
Gravimeters are used for measuring the local gravitational acceleration. The use of current commercially available gravimeters, however, has been limited by their high cost and large size. In this study, a microelectromechanical system (MEMS) based relative gravimeter with an acceleration sensitivity of 8 ÎŒGall / â (Hz) is demonstrated. The MEMS gravimeter, along with the custom interface electronics, is embedded on a battery powered portable platform. The portable platform enables continuous recording of the sensor response, while simultaneously measuring critical temperature and tilt parameters. To demonstrate the long-term stability of the system, the reported MEMS gravimeter platform was used to detect the Earth tides. In this paper, the first results from these measurements have been discussed
Numeric taxonomy approaches for lytic evaluation of Salmonella specific bacteriophages
This study explored the lytic ability of bacteriophages as a future tool for reducing the Salmonella spp. loads in food animals. It investigated (a) the concept of a phage cocktail resulting from an exploratory analysis of the 13 phages which were examined, and (b) the possibility of using them in phage typing techniques for a broad range of serotypes. By using the conventional plaque assay method and cluster analysis, it was possible to select the 2/2, N5, 2a, 135KP and 120 phages, as potential elements of a cocktail as a means of efficiently eliminating the greatest number of several types of Salmonella. The 2/2 and N5 phages were also the most efficacious infective elements against the Typhimurium and Enteritidis serovars, respectively.info:eu-repo/semantics/publishedVersio
Hadamard states from null infinity
Free field theories on a four dimensional, globally hyperbolic spacetime,
whose dynamics is ruled by a Green hyperbolic partial differential operator,
can be quantized following the algebraic approach. It consists of a two-step
procedure: In the first part one identifies the observables of the underlying
physical system collecting them in a *-algebra which encodes their relational
and structural properties. In the second step one must identify a quantum
state, that is a positive, normalized linear functional on the *-algebra out of
which one recovers the interpretation proper of quantum mechanical theories via
the so-called Gelfand-Naimark-Segal theorem. In between the plethora of
possible states, only few of them are considered physically acceptable and they
are all characterized by the so-called Hadamard condition, a constraint on the
singular structure of the associated two-point function. Goal of this paper is
to outline a construction scheme for these states which can be applied whenever
the underlying background possesses a null (conformal) boundary. We discuss in
particular the examples of a real, massless conformally coupled scalar field
and of linearized gravity on a globally hyperbolic and asymptotically flat
spacetime.Comment: 23 pages, submitted to the Proceedings of the conference "Quantum
Mathematical Physics", held in Regensburg from the 29th of September to the
02nd of October 201
Two Mathematically Equivalent Versions of Maxwell's Equations
This paper is a review of the canonical proper-time approach to relativistic
mechanics and classical electrodynamics. The purpose is to provide a physically
complete classical background for a new approach to relativistic quantum
theory. Here, we first show that there are two versions of Maxwell's equations.
The new version fixes the clock of the field source for all inertial observers.
However now, the (natural definition of the effective) speed of light is no
longer an invariant for all observers, but depends on the motion of the source.
This approach allows us to account for radiation reaction without the
Lorentz-Dirac equation, self-energy (divergence), advanced potentials or any
assumptions about the structure of the source. The theory provides a new
invariance group which, in general, is a nonlinear and nonlocal representation
of the Lorentz group. This approach also provides a natural (and unique)
definition of simultaneity for all observers. The corresponding particle theory
is independent of particle number, noninvariant under time reversal (arrow of
time), compatible with quantum mechanics and has a corresponding positive
definite canonical Hamiltonian associated with the clock of the source.
We also provide a brief review of our work on the foundational aspects of the
corresponding relativistic quantum theory. Here, we show that the standard
square-root and the Dirac equations are actually two distinct
spin- particle equations.Comment: Appeared: Foundations of Physic
Mersenne Primes, Polygonal Anomalies and String Theory Classification
It is pointed out that the Mersenne primes and associated
perfect numbers play a significant role in string
theory; this observation may suggest a classification of consistent string
theories.Comment: 10 pages LaTe
Structural characterisation of MBE grown zinc-blende Ga1-xMnxN/GaAs(001) as a function of Ga flux
Ga1-xMnxN films grown on semi-insulating GaAs(001) substrates at 680°C with fixed Mn flux and varied Ga flux demonstrated a transition from zinc-blende/wurtzite mixed phase growth for low Ga flux (N-rich conditions) to zinc-blende single phase growth with surface Ga droplets for high Ga flux (Ga-rich conditions). N-rich conditions were found favourable for Mn incorporation in GaN lattice. α-MnAs inclusions were identified extending into the GaAs buffer layer
The Breakdown of Topology at Small Scales
We discuss how a topology (the Zariski topology) on a space can appear to
break down at small distances due to D-brane decay. The mechanism proposed
coincides perfectly with the phase picture of Calabi-Yau moduli spaces. The
topology breaks down as one approaches non-geometric phases. This picture is
not without its limitations, which are also discussed.Comment: 12 pages, 2 figure
A Point's Point of View of Stringy Geometry
The notion of a "point" is essential to describe the topology of spacetime.
Despite this, a point probably does not play a particularly distinguished role
in any intrinsic formulation of string theory. We discuss one way to try to
determine the notion of a point from a worldsheet point of view. The derived
category description of D-branes is the key tool. The case of a flop is
analyzed and Pi-stability in this context is tied in to some ideas of
Bridgeland. Monodromy associated to the flop is also computed via Pi-stability
and shown to be consistent with previous conjectures.Comment: 15 pages, 3 figures, ref adde
Deformations of calibrated D-branes in flux generalized complex manifolds
We study massless deformations of generalized calibrated cycles, which
describe, in the language of generalized complex geometry, supersymmetric
D-branes in N=1 supersymmetric compactifications with fluxes. We find that the
deformations are classified by the first cohomology group of a Lie algebroid
canonically associated to the generalized calibrated cycle, seen as a
generalized complex submanifold with respect to the integrable generalized
complex structure of the bulk. We provide examples in the SU(3) structure case
and in a `genuine' generalized complex structure case. We discuss cases of
lifting of massless modes due to world-volume fluxes, background fluxes and a
generalized complex structure that changes type.Comment: 52 pages, added references, added comment on ellipticity in appendix
B, made minor changes according to instructions referee JHE
- âŠ