2,614 research outputs found
Alternative methods for the reduction of evaporation: practical exercises for the science classroom
Across the world, freshwater is valued as the most critically important natural resource, as it is required to sustain the cycle of life. Evaporation is one of the primary environmental processes that can reduce the amount of quality water available for use in industrial, agricultural and household applications. The effect of evaporation becomes intensified especially during conditions of drought, particularly in traditionally arid and semi-arid regions, such as those seen in a number of countries over the past 10 years. In order to safeguard against the influence of droughts and to save water from being lost to the evaporative process, numerous water saving mechanisms have been developed and tested over the past century. Two of the most successful and widely used mechanisms have included floating hard covers and chemical film monolayers. This paper describes a laboratory based project developed for senior high school and first year university classes, which has been designed to introduce students to the concepts of evaporation, evaporation modelling and water loss mitigation. Specifically, these ideas are delivered by simulating the large-scale deployment of both monolayers and floating hard covers on a small water tank under numerous user defined atmospheric and hydrodynamic conditions, including varying surface wind speeds and underwater bubble plumes set to changing flow rates
QND measurement of a superconducting qubit in the weakly projective regime
Quantum state detectors based on switching of hysteretic Josephson junctions
biased close to their critical current are simple to use but have strong
back-action. We show that the back-action of a DC-switching detector can be
considerably reduced by limiting the switching voltage and using a fast
cryogenic amplifier, such that a single readout can be completed within 25 ns
at a repetition rate of 1 MHz without loss of contrast. Based on a sequence of
two successive readouts we show that the measurement has a clear quantum
non-demolition character, with a QND fidelity of 75 %.Comment: submitted to PR
Dualities between Poisson brackets and antibrackets
Recently it has been shown that antibrackets may be expressed in terms of
Poisson brackets and vice versa for commuting functions in the original
bracket. Here we also introduce generalized brackets involving higher
antibrackets or higher Poisson brackets where the latter are of a new type. We
give generating functions for these brackets for functions in arbitrary
involutions in the original bracket. We also give master equations for
generalized Maurer-Cartan equations. The presentation is completely symmetric
with respect to Poisson brackets and antibrackets.Comment: 24 pages,Latexfile,corrected (2.7-8) and removed text between (2.9)
and (2.10
Experience with a Pre-Series Superfluid Helium Test Bench for LHC Magnets
The Large Hadron Collider (LHC) under construction at CERN is based on the use of high-field superconducting magnets operating in superfluid helium. For the validation of the machine dipoles and quadrupoles, a magnet test plant is under construction requiring 12 so-called Cryogenic Feeder Units (CFU). Based on experience done at CERN, two pre-series CFUs were designed and built by industry and are currently in use prior to final series delivery. This presentation describes the features of a CFU, its typical characteristics and the experience acquired with the first units
ON NON-RIEMANNIAN PARALLEL TRANSPORT IN REGGE CALCULUS
We discuss the possibility of incorporating non-Riemannian parallel transport
into Regge calculus. It is shown that every Regge lattice is locally equivalent
to a space of constant curvature. Therefore well known-concepts of differential
geometry imply the definition of an arbitrary linear affine connection on a
Regge lattice.Comment: 12 pages, Plain-TEX, two figures (available from the author
Novel Topological Invariant in the U(1) Gauge Field Theory
Based on the decomposition of U(1) gauge potential theory and the
-mapping topological current theory, the three-dimensional knot invariant
and a four-dimensional new topological invariant are discussed in the U(1)
gauge field.Comment: 10 pages, 0 figures accepted by MPL
The effect of temperature and salinity on the stable hydrogen isotopic composition of long chain alkenones produced by <i>Emiliania huxleyi</i> and <i>Gephyrocapsa oceanica</i>
International audienceTwo haptophyte algae, Emiliania huxleyi and Gephyrocapsa oceanica, were cultured at different temperatures and salinities to investigate the impact of these factors on the hydrogen isotopic composition of long chain alkenones synthesized by these algae. Results showed that alkenones synthesized by G. oceanica were on average depleted in D by 30 per mil compared to those of E. huxleyi when grown under similar conditions. The fractionation factor, ?alkenones-H2O, ranged from 0.760 to 0.815 for E. huxleyi and from 0.741 to 0.788 for G. oceanica. There was no significant correlation of ?alkenones-H2O with temperature but a positive linear correlation was observed between ?alkenones-H2O and salinity with ~3 per mil change in fractionation per salinity unit. This suggests that salinity can have a substantial impact on the stable hydrogen isotopic composition of long chain alkenones in natural environments and, vice versa, that ?D can possibly be used as a proxy to estimate paleosalinity
Brownian motion of Massive Particle in a Space with Curvature and Torsion and Crystals with Defects
We develop a theory of Brownian motion of a massive particle, including the
effects of inertia (Kramers' problem), in spaces with curvature and torsion.
This is done by invoking the recently discovered generalized equivalence
principle, according to which the equations of motion of a point particle in
such spaces can be obtained from the Newton equation in euclidean space by
means of a nonholonomic mapping. By this principle, the known Langevin equation
in euclidean space goes over into the correct Langevin equation in the Cartan
space. This, in turn, serves to derive the Kubo and Fokker-Planck equations
satisfied by the particle distribution as a function of time in such a space.
The theory can be applied to classical diffusion processes in crystals with
defects.Comment: LaTeX, http://www.physik.fu-berlin.de/kleinert.htm
Open-closed homotopy algebra in mathematical physics
In this paper we discuss various aspects of open-closed homotopy algebras
(OCHAs) presented in our previous paper, inspired by Zwiebach's open-closed
string field theory, but that first paper concentrated on the mathematical
aspects. Here we show how an OCHA is obtained by extracting the tree part of
Zwiebach's quantum open-closed string field theory. We clarify the explicit
relation of an OCHA with Kontsevich's deformation quantization and with the
B-models of homological mirror symmetry. An explicit form of the minimal model
for an OCHA is given as well as its relation to the perturbative expansion of
open-closed string field theory. We show that our open-closed homotopy algebra
gives us a general scheme for deformation of open string structures
(-algebras) by closed strings (-algebras).Comment: 38 pages, 4 figures; v2: published versio
- …