1,094 research outputs found
An Editor for Helping Novices to Learn Standard ML
This paper describes a novel editor intended as an aid in the learning of the functional programming language Standard ML. A common technique used by novices is programming by analogy whereby students refer to similar programs that they have written before or have seen in the course literature and use these programs as a basis to write a new program. We present a novel editor for ML which supports programming by analogy by providing a collection of editing commands that transform old programs into new ones. Each command makes changes to an isolated part of the program. These changes are propagated to the rest of the program using analogical techniques. We observed a group of novice ML students to determine the most common programming errors in learning ML and restrict our editor such that it is impossible to commit these errors. In this way, students encounter fewer bugs and so their rate of learning increases. Our editor, C Y NTHIA, has been implemented and is due to be tested on st..
A Proof Strategy Language and Proof Script Generation for Isabelle/HOL
We introduce a language, PSL, designed to capture high level proof strategies
in Isabelle/HOL. Given a strategy and a proof obligation, PSL's runtime system
generates and combines various tactics to explore a large search space with low
memory usage. Upon success, PSL generates an efficient proof script, which
bypasses a large part of the proof search. We also present PSL's monadic
interpreter to show that the underlying idea of PSL is transferable to other
ITPs.Comment: This paper has been submitted to CADE2
Bioinformatics tools in predictive ecology: Applications to fisheries
This article is made available throught the Brunel Open Access Publishing Fund - Copygith @ 2012 Tucker et al.There has been a huge effort in the advancement of analytical techniques for molecular biological data over the past decade. This has led to many novel algorithms that are specialized to deal with data associated with biological phenomena, such as gene expression and protein interactions. In contrast, ecological data analysis has remained focused to some degree on off-the-shelf statistical techniques though this is starting to change with the adoption of state-of-the-art methods, where few assumptions can be made about the data and a more explorative approach is required, for example, through the use of Bayesian networks. In this paper, some novel bioinformatics tools for microarray data are discussed along with their ‘crossover potential’ with an application to fisheries data. In particular, a focus is made on the development of models that identify functionally equivalent species in different fish communities with the aim of predicting functional collapse
Some Empirical Criteria for Attributing Creativity to a Computer Program
Peer reviewedPostprin
The development of an age structured model for schistosomiasis transmission dynamics and control and its validation for Schistosoma mansoni
Mathematical models are potentially useful tools to aid in the design of control programmes for parasitic diseases. In this paper, a fully age structured epidemiological model of human schistosomiasis is developed and parameterized, and used to predict trends in infection prevalence, intensity and prevalence of heavy infections over age and time during several rounds of mass and age targeted treatment. The model is validated against data from a Schistosoma mansoni control programme in Keny
The Bimodal Galaxy Stellar Mass Function in the COSMOS Survey to z~1: A Steep Faint End and a New Galaxy Dichotomy
We present a new analysis of stellar mass functions (MF) in the COSMOS field
to fainter limits than has been previously probed to z~1. Neither the total nor
the passive or star-forming MF can be well fit with a single Schechter function
once one probes below 3e9 Msun. We observe a dip or plateau at masses ~1e10
Msun, and an upturn towards a steep faint-end slope of -1.7 at lower mass at
any z<1. This bimodal nature of the MF is not solely a result of the blue/red
dichotomy. The blue MF is by itself bimodal at z~1. This suggests a new
dichotomy in galaxy formation that predates the appearance of the red sequence.
We propose two interpretations for this bimodality. If the gas fraction
increases towards lower mass, galaxies with M_baryon~1e10 Msun would shift to
lower stellar masses, creating the observed dip. This would indicate a change
in star formation efficiency, perhaps linked to supernovae feedback becoming
much more efficient. Therefore, we investigate whether the dip is present in
the baryonic (stars+gas) MF. Alternatively, the dip could be created by an
enhancement of the galaxy assembly rate at ~1e11 Msun, a phenomenon that
naturally arises if the baryon fraction peaks at M_halo ~1e12 Msun. In this
scenario, galaxies occupying the bump around M* would be identified with
central galaxies and the second fainter component having a steep faint-end
slope with satellites. While the dip is apparent in the total MF at any z, it
appears to shift from the blue to red population, likely as a result of
transforming high-mass blue galaxies into red ones. At the same time, we detect
a drastic upturn in the number of low-mass red galaxies. Their increase with
time reflects a decrease in the number of blue systems and so we tentatively
associate them with satellite dwarf galaxies that have undergone quenching.Comment: 16 pages, 10 figures, accepted for publication in Ap
Luminous Satellites of Early-Type Galaxies I: Spatial Distribution
We study the spatial distribution of faint satellites of intermediate
redshift (0.1<z<0.8), early-type galaxies, selected from the GOODS fields. We
combine high resolution HST images and state-of-the-art host subtraction
techniques to detect satellites of unprecedented faintness and proximity to
intermediate redshift host galaxies (up to 5.5 magnitudes fainter and as close
as 0."5/2.5 kpc to the host centers). We model the spatial distribution of
objects near the hosts as a combination of an isotropic, homogenous
background/foreground population and a satellite population with a power law
radial profile and an elliptical angular distribution. We detect a significant
population of satellites, Ns =1.7 (+0.9,-0.8) that is comparable to the number
of Milky Way satellites with similar host-satellite contrast.The average
projected radial profile of the satellite distribution is isothermal, gamma_p=
-1.0(+0.3,-0.4), which is consistent with the observed central mass density
profile of massive early-type galaxies. Furthermore, the satellite distribution
is highly anisotropic (isotropy is ruled out at a >99.99% confidence level).
Defining phi to be the offset between the major axis of the satellite spatial
distribution and the major axis of the host light profile, we find a maximum
posterior probability of phi = 0 and |phi| less than 42 degrees at the 68%
confidence level. The alignment of the satellite distribution with the light of
the host is consistent with simulations, assuming that light traces mass for
the host galaxy as observed for lens galaxies. The anisotropy of the satellite
population enhances its ability to produce the flux ratio anomalies observed in
gravitationally lensed quasars.Comment: 21 pages, 16 figures, Accepted for publication in Ap
The Build-Up of the Hubble Sequence in the COSMOS Field
We use ~8,600 >5e10 Msol COSMOS galaxies to study how the morphological mix
of massive ellipticals, bulge-dominated disks, intermediate-bulge disks,
bulge-less disks and irregular galaxies evolves from z=0.2 to z=1. The
morphological evolution depends strongly on mass. At M>3e11 Msol, no evolution
is detected in the morphological mix: ellipticals dominate since z=1, and the
Hubble sequence has quantitatively settled down by this epoch. At the 1e11 Msol
mass scale, little evolution is detected, which can be entirely explained with
major mergers. Most of the morphological evolution from z=1 to z=0.2 takes
place at masses 5e10 - 1e11 Msol, where: (i) The fraction of spirals
substantially drops and the contribution of early-types increases. This
increase is mostly produced by the growth of bulge-dominated disks, which vary
their contribution from ~10% at z=1 to >30% at z=0.2 (cf. the elliptical
fraction grows from ~15% to ~20%). Thus, at these masses, transformations from
late- to early-types result in disk-less elliptical morphologies with a
statistical frequency of only 30% - 40%. Otherwise, the processes which are
responsible for the transformations either retain or produce a non-negligible
disk component. (ii) The bulge-less disk galaxies, which contribute ~15% to the
intermediate-mass galaxy population at z=1, virtually disappear by z=0.2. The
merger rate since z=1 is too low to account for the disappearance of these
massive bulge-less disks, which most likely grow a bulge via secular evolution.Comment: 5 pages, 3 figures, submitted to ApJ
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