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Natural polymers as alternative consolidants for the preservation of waterlogged archaeological wood
In recent years there has been increased interest in examining alternative polymers for the conservation of archaeological artefacts, particularly waterlogged timbers, providing better, renewable, greener alternatives to poly(ethylene glycol) (PEG). The degradation of PEG consolidants in the timbers of the 16th century warship Mary Rose has been examined and the rheological and thermal properties of PEG has been compared to its monomethyl and dimethyl ethers and several polysaccharide consolidants (chitosan, guar and 2-hydroxyethyl cellulose) in order to evaluate their potential as alternative consolidants for the conservation of waterlogged wooden artefacts. Additionally, the effect of the polymers on the archaeological wood was characterised by thermogravimetric analysis and solid state NMR. The results suggest that the future of conservation technologies lies with polysaccharide consolidant materials, which show enhanced compatibility with wooden artefacts with no detectable side-effects while also being cheap, with extremely low toxicity, renewable and sustainably resourced.ZW and OAS acknowledge financial support from European Research Council Starting Investigators Grant (No. 240629, ASPiRe), the EPSRC and the Mary Rose Trust. ERJ thanks Dr. D. Reid for useful discussions on ssNMR techniques and the EPSRC for a doctoral training grant.This is the final version of the article. It first appeared from Maney via https://doi.org10.1179/2047058414Y.000000014
A System for Aligning Geographical Entities from Large Heterogeneous Sources
Aligning points of interest (POIs) from heterogeneous geographical data sources is an important task that helps extend map data with information from different datasets. This task poses several challenges, including differences in type hierarchies, labels (different formats, languages, and levels of detail), and deviations in the coordinates. Scalability is another major issue, as global-scale datasets may have tens or hundreds of millions of entities. In this paper, we propose the GeographicaL Entities AligNment (GLEAN) system for efficiently matching large geographical datasets based on spatial partitioning with an adaptable margin. In particular, we introduce a text similarity measure based on the local-context relevance of tokens used in combination with sentence embeddings. We then come up with a scalable type embedding model. Finally, we demonstrate that our proposed system can efficiently handle the alignment of large datasets while improving the quality of alignments using the proposed entity similarity measure
On algebraic structures of numerical integration on vector spaces and manifolds
Numerical analysis of time-integration algorithms has been applying advanced
algebraic techniques for more than fourty years. An explicit description of the
group of characters in the Butcher-Connes-Kreimer Hopf algebra first appeared
in Butcher's work on composition of integration methods in 1972. In more recent
years, the analysis of structure preserving algorithms, geometric integration
techniques and integration algorithms on manifolds have motivated the
incorporation of other algebraic structures in numerical analysis. In this
paper we will survey structures that have found applications within these
areas. This includes pre-Lie structures for the geometry of flat and torsion
free connections appearing in the analysis of numerical flows on vector spaces.
The much more recent post-Lie and D-algebras appear in the analysis of flows on
manifolds with flat connections with constant torsion. Dynkin and Eulerian
idempotents appear in the analysis of non-autonomous flows and in backward
error analysis. Non-commutative Bell polynomials and a non-commutative Fa\`a di
Bruno Hopf algebra are other examples of structures appearing naturally in the
numerical analysis of integration on manifolds.Comment: 42 pages, final versio
The response of a neutral atom to a strong laser field probed by transient absorption near the ionisation threshold
We present transient absorption spectra of an extreme ultraviolet attosecond pulse train in helium dressed by an 800 nm laser field with intensity ranging from W/cm to W/cm. The energy range probed spans 16-42 eV, straddling the first ionisation energy of helium (24.59 eV). By changing the relative polarisation of the dressing field with respect to the attosecond pulse train polarisation we observe a large change in the modulation of the absorption reflecting the vectorial response to the dressing field. With parallel polarized dressing and probing fields, we observe significant modulations with periods of one half and one quarter of the dressing field period. With perpendicularly polarized dressing and probing fields, the modulations of the harmonics above the ionisation threshold are significantly suppressed. A full-dimensionality solution of the single-atom time-dependent Schr odinger equation obtained using the recently developed ab-initio time-dependent B-spline ADC method reproduce some of our observations
Comparing Climate Change and Species Invasions as Drivers of Coldwater Fish Population Extirpations
Species are influenced by multiple environmental stressors acting simultaneously. Our objective was to compare the expected effects of climate change and invasion of non-indigenous rainbow smelt (Osmerus mordax) on cisco (Coregonus artedii) population extirpations at a regional level. We assembled a database of over 13,000 lakes in Wisconsin, USA, summarising fish occurrence, lake morphology, water chemistry, and climate. We used A1, A2, and B1 scenarios from the Intergovernmental Panel on Climate Change (IPCC) of future temperature conditions for 15 general circulation models in 2046–2065 and 2081–2100 totalling 78 projections. Logistic regression indicated that cisco tended to occur in cooler, larger, and deeper lakes. Depending upon the amount of warming, 25–70% of cisco populations are predicted to be extirpated by 2100. In addition, cisco are influenced by the invasion of rainbow smelt, which prey on young cisco. Projecting current estimates of rainbow smelt spread and impact into the future will result in the extirpation of about 1% of cisco populations by 2100 in Wisconsin. Overall, the effect of climate change is expected to overshadow that of species invasion as a driver of coldwater fish population extirpations. Our results highlight the potentially dominant role of climate change as a driver of biotic change
The chromatic Point Spread Function of weak lensing measurement in Chinese Space Station survey Telescope
The weak gravitational lensing is a powerful tool in modern cosmology. To
accurately measure the weak lensing signal, one has to control the systematic
bias to a small level. One of the most difficult problems is how to correct the
smearing effect of the Point Spread Function (PSF) on the shape of the
galaxies. The chromaticity of PSF for a broad-band observation can lead to new
subtle effects. Since the PSF is wavelength dependent and the spectrum energy
distributions between stars and galaxies are different, the effective PSF
measured from the star images will be different from that smears the galaxies.
Such a bias is called colour bias. We estimate it in the optical bands of the
Chinese Space Station Survey Telescope from simulated PSFs, and show the
dependence on the colour and redshift of the galaxies. Moreover, due to the
spatial variation of spectra over the galaxy image, there exists another
higher-order bias, colour gradient bias. Our results show that both colour bias
and colour gradient bias are generally below percent in CSST. Only for
small-size galaxies, one needs to be careful about the colour gradient bias in
the weak lensing analysis using CSST data
Informing the Design of Collaborative Activities in MOOCs using Actionable Predictions
With the aim of supporting instructional designers in setting up collaborative learning activities in MOOCs, this paper derives prediction models for student participation in group discussions. The salient feature of these models is that they are built using only data prior to the learning activity, and can thus provide actionable predictions, as opposed to post-hoc approaches common in the MOOC literature. Some learning design scenarios that make use of this actionable information are illustrated
Do mutual funds have consistency in their performance?
Using a comprehensive data set of 714 Chinese mutual funds from 2004 to 2015, the study investigates these funds’ performance persistence by using the Capital Asset Pricing model, the Fama-French three-factor model and the Carhart Four-factor model. For persistence analysis, we categorize mutual funds into eight octiles based on their one year lagged performance and then observe their performance for the subsequent
12 months. We also apply Cross-Product Ratio technique to assess the performance
persistence in these Chinese funds. The study finds no significant evidence of persis- tence in the performance of the mutual funds. Winner (loser) funds do not continue to be winner (loser) funds in the subsequent time period. These findings suggest that future performance of funds cannot be predicted based on their past performance.info:eu-repo/semantics/publishedVersio
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