50 research outputs found
Critical Review of Historic Literature Concerning Traditional Lime and Earth-Lime Mortars
A review of historic knowledge and understanding concerning the manipulation of lime and earth-lime mortars; the uses to which they were put, as set out in historic texts from the UK, Ireland, North America, France and Spain, as well as from Ancient Rome. Time-span: 160 BC to 1962. These tell a consistent story very different to that told during the Lime Revival in the UK after 1975. The ubiquitous mortars of construction were earth-lime and hot mixed air lime, with and without pozzolans. Natural Hydraulic Limes have minimal historic precedence for the uses to which they have been put over the last 20 years or so. Lime putty had minimal historic precedence as a binder before the 20thC. This dissertation sets out historic knowledge and understanding of traditional mortars and provides a platform for the essential re-booting of the lime revival and speaks to a paradigm shift in understanding and practice over recent years, a shift inspired primarily by the practical experience of stonemasons and conservators who have been working with traditional, like-for-like and compatible materials over a number of years
Light Trap Manipulation and Its Potential Use in Quantum Computing
During winter quarter 2007, the light polarization dependence of light traps used in quantum computing was researched. Throughout the quarter, a Mathematica program that simulates the trapping potential of light traps was modified; it now takes into account the polarization of light used, as well as the internal state of atoms used in the light traps. The goal for the next quarter, spring 2007, was to use the program that was generated to simulate the trapping potentials of varying parameters. This research was conducted to deduce whether there is any possible way to implement the light polarization dependence of light traps in quantum computing. More specifically, the intent was to investigate potential ways to create a two-qubit gate using the light polarization dependence of the light traps
Evolution of flower color pattern through selection on regulatory small RNAs
Small RNAs (sRNAs) regulate genes in plants and animals. Here, we show that population-wide differences in color patterns in snapdragon flowers are caused by an inverted duplication that generates sRNAs. The complexity and size of the transcripts indicate that the duplication represents an intermediate on the pathway to microRNA evolution. The sRNAs repress a pigment biosynthesis gene, creating a yellow highlight at the site of pollinator entry. The inverted duplication exhibits steep clines in allele frequency in a natural hybrid zone, showing that the allele is under selection. Thus, regulatory interactions of evolutionarily recent sRNAs can be acted upon by selection and contribute to the evolution of phenotypic diversity
Selection and gene flow shape genomic islands that control floral guides
Genomes of closely-related species or populations often display localized regions of enhanced relative sequence divergence, termed genomic islands. It has been proposed that these islands arise through selective sweeps and/or barriers to gene flow. Here, we genetically dissect a genomic island that controls flower color pattern differences between two subspecies of Antirrhinum majus, A.m.striatum and A.m.pseudomajus, and relate it to clinal variation across a natural hybrid zone. We show that selective sweeps likely raised relative divergence at two tightly-linked MYB-like transcription factors, leading to distinct flower patterns in the two subspecies. The two patterns provide alternate floral guides and create a strong barrier to gene flow where populations come into contact. This barrier affects the selected flower color genes and tightlylinked loci, but does not extend outside of this domain, allowing gene flow to lower relative divergence for the rest of the chromosome. Thus, both selective sweeps and barriers to gene flow play a role in shaping genomic islands: sweeps cause elevation in relative divergence, while heterogeneous gene flow flattens the surrounding "sea," making the island of divergence stand out. By showing how selective sweeps establish alternative adaptive phenotypes that lead to barriers to gene flow, our study sheds light on possible mechanisms leading to reproductive isolation and speciation
Quarkonium dissociation by anisotropy
We compute the screening length for quarkonium mesons moving through an
anisotropic, strongly coupled N=4 super Yang-Mills plasma by means of its
gravity dual. We present the results for arbitrary velocities and orientations
of the mesons, as well as for arbitrary values of the anisotropy. The
anisotropic screening length can be larger or smaller than the isotropic one,
and this depends on whether the comparison is made at equal temperatures or at
equal entropy densities. For generic motion we find that: (i) mesons dissociate
above a certain critical value of the anisotropy, even at zero temperature;
(ii) there is a limiting velocity for mesons in the plasma, even at zero
temperature; (iii) in the ultra-relativistic limit the screening length scales
as with \epsilon =1/2, in contrast with the isotropic result
\epsilon =1/4.Comment: 39 pages, 26 figures; v2: minor changes, added reference
Holographic Renormalization for z=2 Lifshitz Space-Times from AdS
Lifshitz space-times with critical exponent z=2 can be obtained by
dimensional reduction of Schroedinger space-times with critical exponent z=0.
The latter space-times are asymptotically AdS solutions of AdS gravity coupled
to an axion-dilaton system and can be uplifted to solutions of type IIB
supergravity. This basic observation is used to perform holographic
renormalization for 4-dimensional asymptotically z=2 locally Lifshitz
space-times by Scherk-Schwarz dimensional reduction of the corresponding
problem of holographic renormalization for 5-dimensional asymptotically locally
AdS space-times coupled to an axion-dilaton system. We can thus define and
characterize a 4-dimensional asymptotically locally z=2 Lifshitz space-time in
terms of 5-dimensional AdS boundary data. In this setup the 4-dimensional
structure of the Fefferman-Graham expansion and the structure of the
counterterm action, including the scale anomaly, will be discussed. We find
that for asymptotically locally z=2 Lifshitz space-times obtained in this way
there are two anomalies each with their own associated nonzero central charge.
Both anomalies follow from the Scherk--Schwarz dimensional reduction of the
5-dimensional conformal anomaly of AdS gravity coupled to an axion-dilaton
system. Together they make up an action that is of the Horava-Lifshitz type
with nonzero potential term for z=2 conformal gravity.Comment: 32 pages, v2: modified discussion of the central charge
A General Black String and its Microscopics
Using G2(2) dualities we construct the most general black string solution of
minimal five-dimensional ungauged supergravity. The black string has five
independent parameters, namely, the magnetic one-brane charge, smeared electric
zero-brane charge, boost along the string direction, energy above the BPS
bound, and rotation in the transverse space. In one extremal limit it reduces
to the three parameter supersymmetric string of five-dimensional minimal
supergravity; in another extremal limit it reduces to the three parameter
non-supersymmetric extremal string of five-dimensional minimal supergravity. It
also admits an extremal limit when it has maximal rotation in the
four-dimensional transverse space. The decoupling limit of our general black
string is a BTZ black hole times a two sphere. The macroscopic entropy of the
string is reproduced by the Maldacena-Strominger-Witten CFT in appropriate
ranges of the parameters. When the pressureless condition is imposed, our
string describes the infinite radius limit of the most general class of black
rings of minimal supergravity. We discuss implications our solution has for
extremal and non-extremal black rings of minimal supergravity.Comment: 35 pages; 3 figures; v2 section 4.1.1 rewritten + minor changes + ref
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Field theories with anisotropic scaling in 2D, solitons and the microscopic entropy of asymptotically Lifshitz black holes
Field theories with anisotropic scaling in 1+1 dimensions are considered. It
is shown that the isomorphism between Lifshitz algebras with dynamical
exponents z and 1/z naturally leads to a duality between low and high
temperature regimes. Assuming the existence of gap in the spectrum, this
duality allows to obtain a precise formula for the asymptotic growth of the
number of states with a fixed energy which depends on z and the energy of the
ground state, and reduces to the Cardy formula for z=1. The holographic
realization of the duality can be naturally inferred from the fact that
Euclidean Lifshitz spaces in three dimensions with dynamical exponents and
characteristic lengths given by z, l, and 1/z, l/z, respectively, are
diffeomorphic. The semiclassical entropy of black holes with Lifshitz
asymptotics can then be recovered from the generalization of Cardy formula,
where the ground state corresponds to a soliton. An explicit example is
provided by the existence of a purely gravitational soliton solution for BHT
massive gravity, which precisely has the required energy that reproduces the
entropy of the analytic asymptotically Lifshitz black hole with z=3.
Remarkably, neither the asymptotic symmetries nor central charges were
explicitly used in order to obtain these results.Comment: 17 pages, no figures, references corrected and update
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The Met Office Unified Model Global Atmosphere 6.0/6.1 and JULES Global Land 6.0/6.1 configurations
We describe Global Atmosphere 6.0 and Global Land 6.0: the latest science configurations of the Met Office Unified Model and JULES land surface model developed for use across all timescales. Global Atmosphere 6.0 includes the ENDGame dynamical core, which significantly increases mid-latitude variability improving a known model bias. Alongside developments of the model’s physical parametrisations, ENDGame also increases variability in the tropics, which leads to an improved representation of tropical cyclones and other tropical phenomena. Further developments of the atmospheric and land surface parametrisations improve other aspects of model performance, including the forecasting of surface weather phenomena. We also describe Global Atmosphere 6.1 and Global Land 6.1, which include a small number of long-standing differences from our main trunk configurations that we continue to require for operational global weather prediction. Since July 2014, GA6.1/GL6.1 has been used by the Met Office for operational global NWP, whilst GA6.0/GL6.0 was implemented in its remaining global prediction systems over the following year