An experimental comparison of a genetic algorithm and a hill-climber for term selection

Purpose – The term selection problem for selecting query terms in information filtering and routing has been investigated using hill-climbers of various kinds, largely through the Okapi experiments in the TREC series of conferences. Although these are simple deterministic approaches which examine the effect of changing the weight of one term at a time, they have been shown to improve the retrieval effectiveness of filtering queries in these TREC experiments. Hill-climbers are, however, likely to get trapped in local optima, and the use of more sophisticated local search techniques for this problem that attempt to break out of these optima are worth investigating. To this end, we apply a genetic algorithm (GA) to the same problem. Design/Methodology/Approach – We use a standard TREC test collection from the TREC-8 filtering track, recording mean average precision and recall measures to allow comparison between the hillclimber and GA algorithms. We also vary elements of the GA, such as probability of a word being included, probability of mutation and population size in order to measure the effect of these variables. Different strategies such as Elitist and Non-Elitist methods are used, as well as Roulette Wheel and Rank selection GA algorithms. Findings – The results of tests suggest that both techniques are, on average, better than the baseline, but the implemented GA does not match the overall performance of a hill-climber. The Rank selection algorithm does better on average than the Roulette Wheel algorithm. There is no evidence in this study that varying word inclusion probability, mutation probability or Elitist method make much difference to the overall results. Small population sizes do not appear to be as effective as larger population sizes. Research limitations/implications – The evidence provided here would suggest that being stuck in a local optima for the term selection optimization problem does not appear to be detrimental to the overall success of the hill-climber. The evidence from term rank order would appear to provide extra useful evidence which hill-climbers can use efficiently and effectively to narrow the search space. Originality/Value – The paper represents the first attempt to compare hill-climbers with GAs on a problem of this type

Scattering hypervolume for ultracold bosons from weak to strong interactions

The elastic scattering properties of three bosons at low energy enter the many-body description of ultracold Bose gases via the three-body scattering hypervolume $D$. We study this quantity for identical bosons that interact via a pairwise finite-range potential. Our calculations cover the regime from strongly repulsive potentials towards attractive potentials supporting multiple two-body bound states and are consistent with the few existing predictions for $D$. We present the first numerical confirmation of the universal predictions for $D$ in the strongly interacting regime, where Efimov physics dominates, for a local nonzero-range potential. Our findings highlight how $D$ is influenced by three-body quasibound states with strong $d$-wave or $g$-wave characteristics in the weakly interacting regime.Comment: 13 pages, 8 figure

The multichannel nature of three-body recombination for ultracold 39^{39}K

We develop a full multichannel spin model in momentum space to investigate three-body recombination of identical alkali-metal atoms colliding in a magnetic field. The model combines the exact three-atom spin structure and realistic pairwise atom-atom interactions. By neglecting the interaction between two particles when the spectating particle is not in its initial spin state we arrive at an approximate model. With this approximate model we achieve excellent agreement with the recent precise measurement of the ground Efimov resonance position in potassium-39 close to 33.58 G [Chapurin $et$ $al$., Phys. Rev. Lett. 123, 233402 (2019)]. We analyze the limitations of our approximation by comparing to the numerical results for the full system and find that it breaks down for Feshbach resonances at larger magnetic fields in the same spin channel. There the relevant three-body closed channel thresholds are much closer to the open channel threshold, which enhances the corresponding multichannel couplings. Therefore the neglected components of the interaction should be included for those Feshbach resonances

DULIP: A dual luminescence-based co-immunoprecipitation assay for interactome mapping in mammalian cells

Mapping of protein-protein interactions (PPIs) is critical for understanding protein function and complex biological processes. Here, we present DULIP, a dual luminescence-based co-immunoprecipitation assay, for systematic PPI mapping in mammalian cells. DULIP is a second-generation luminescence-based PPI screening method for the systematic and quantitative analysis of co-immunoprecipitations using two different luciferase tags. Benchmarking studies with positive and negative PPI reference sets revealed that DULIP allows the detection of interactions with high sensitivity and specificity. Furthermore, the analysis of a PPI reference set with known binding affinities demonstrated that both low- and high-affinity interactions can be detected with DULIP assays. Finally, using the well-characterized interaction between Syntaxin-1 and Munc18, we found that DULIP is capable of detecting the effects of point mutations on interaction strength. Taken together, our studies demonstrate that DULIP is a sensitive and reliable method of great utility for systematic interactome research. It can be applied for interaction screening as well as for the validation of PPIs in mammalian cells. Moreover, DULIP permits the specific analysis of mutation-dependent binding patterns

"The dearest of our possessions": applying Floridi's information privacy concept in models of information behavior and information literacy

This conceptual paper argues for the value of an approach to privacy in the digital information environment informed by Luciano Floridi's philosophy of information and information ethics. This approach involves achieving informational privacy, through the features of anonymity and obscurity, through an optimal balance of ontological frictions. This approach may be used to modify models for information behavior and for information literacy, giving them a fuller and more effective coverage of privacy issues in the infosphere. For information behavior, the Information Seeking and Communication Model, and the Information Grounds conception, are most appropriate for this purpose. For information literacy, the metaliteracy model, using a modification a privacy literacy framework, is most suitable

Dwarf galaxies in Hickson Compact Groups

We observed 5 Hickson Compact Groups with the ESO/MPI 2.2m telescope and WFI to investigate the dwarf galaxy content and distribution in these galaxy groups. Our deep imaging and careful selection of the candidate galaxies revealed a rich population of mainly passively evolving dwarf galaxies, which is spatially much more extended than the originally defined Hickson Compact groups. The composite luminosity function of the 5 groups shows a bimodal structure with a very steep rise in the low luminosity regime. The faint end slope is close to the predictions of CDM theory for the slope of the Dark Matter halo mass function.Comment: 5 pages, 4 figures, to appear in the proceedings of the ESO Astrophysics Symposium: "Groups of Galaxies in the Nearby Universe", eds. I. Saviane, V. Ivanov, J. Borissova, Springer-Verla

Research in and application of modern automatic control theory to nuclear rocket dynamics and control, volume I Semiannual status report

Linear optimal feedback control theory for nuclear rocket dynamics and control problem

Still dreaming: service users' employment, education & training goals

Background: Enabling service users to find and keep real jobs is a significant strand of UK mental health policy. An evidence-based approach to employment support is well documented, but is not widely implemented in the UK. Aim: To inform the development of vocational services in South Essex by ascertaining service users' employment, education and training goals. Method: Face-to-face interviews with a randomly selected sample of service users on enhanced CPA carried out by a team of service user researchers using an adapted version of a questionnaire developed for a previous similar survey. A postal survey of a further randomly selected sample of service users on enhanced CPA using a brief version of the questionnaire was also carried out. Results: Interviews were carried out with 82 service users. A further 159 returned a postal questionnaire. 42.7% had no regular day time activity. Only 15% were in paid work. 60.6% were definitely interested in finding work. Seventy-seven percent of respondents to the interviews who were interested in work were not currently receiving support to achieve this. The main help wanted was support in work, help with mental health problems and benefits advice. The main barriers identified were employers' attitudes and threat to benefits. Service user researchers reported benefits from undertaking the work. Conclusions: High numbers of mental health service users are interested in pursuing employment, education or training goals but currently lack the support they need to do so. Implementation of an evidence-based approach to employment support has the potential to enable service users to achieve their goals. Service users are well able to undertake research with considerable benefits for themselves and other stakeholders

Photometric redshifts as a tool to study the Coma cluster galaxy populations

We investigate the Coma cluster galaxy luminosity function (GLF) at faint magnitudes, in particular in the u* band by applying photometric redshift techniques applied to deep u*, B, V, R, I images covering a region of ~1deg2 (R 24). Global and local GLFs in the B, V, R and I bands obtained with photometric redshift selection are consistent with our previous results based on a statistical background subtraction. In the area covered only by the u* image, the GLF was also derived after applying a statistical background subtraction. The GLF in the u* band shows an increase of the faint end slope towards the outer regions of the cluster (from alpha~1 in the cluster center to alpha~2 in the cluster periphery). This could be explained assuming a short burst of star formation in these galaxies when entering the cluster. The analysis of the multicolor type spatial distribution reveals that late type galaxies are distributed in clumps in the cluster outskirts, where X-ray substructures are also detected and where the GLF in the u* band is steeper.Comment: 14 pages, 2 figures in jpeg format, accepted in A&