Automated data pre-processing via meta-learning

The final publication is available at link.springer.comA data mining algorithm may perform differently on datasets with different characteristics, e.g., it might perform better on a dataset with continuous attributes rather than with categorical attributes, or the other way around. As a matter of fact, a dataset usually needs to be pre-processed. Taking into account all the possible pre-processing operators, there exists a staggeringly large number of alternatives and nonexperienced users become overwhelmed. We show that this problem can be addressed by an automated approach, leveraging ideas from metalearning. Specifically, we consider a wide range of data pre-processing techniques and a set of data mining algorithms. For each data mining algorithm and selected dataset, we are able to predict the transformations that improve the result of the algorithm on the respective dataset. Our approach will help non-expert users to more effectively identify the transformations appropriate to their applications, and hence to achieve improved results.Peer ReviewedPostprint (published version

Baade's red sheet resolved into stars with HST in the Blue Compact Dwarf Galaxy VII Zw 403

HST WFPC2 observations of the nearby Blue Compact Dwarf Galaxy VII~Zw~403 (= UGC 6456) resolve single stars down to M$_I$$\approx$-2.5, deep enough to identify red giants. This population has a more uniform spatial distribution than the young main-sequence stars and supergiants, forming the structure known as "Baade's red sheet". We conclude that VII~Zw~403 is not a primeval galaxy.Comment: submitted to: ApJ Letter

Simulation studies of improved sounding systems

Two instrument designs for indirect satellite sounding of the atmosphere in the infrared are represented by the High Resolution Infra-Red Sounder, Model 2 (HIRS-2) and by the Advanced Meteorological Temperature Sounder (AMTS). The relative capabilities of the two instruments were tested by simulating satellite measurements from a group of temperature soundings, allowing the two participants to retrieve the temperature profiles from the simulated data, and comparing the results with the original temperature profiles. Four data sets were produced from radiosondes data extrapolated to a suitable altitude, representing continents and oceans, between 30S and 30N. From the information available, temperature profiles were retrieved by two different methods, statistical regression and inversion of the radiative transfer equation. Results show the consequence of greater spectral purity, concomitant increase in the number of spectral intervals, and the better spatial resolution in partly clouded areas. At the same time, the limitation of the HIRS-2 without its companion instrument leads to some results which should be ignored in comparing the two instruments. A clear superiority of AMTS results is shown

Morphology Effectively Controls Singlet-Triplet Exciton Relaxation and Charge Transport in Organic Semiconductors

We present a comparative study of ultrafast photo-conversion dynamics in tetracene (Tc) and pentacene (Pc) single crystals and Pc films using optical pump-probe spectroscopy. Photo-induced absorption in Tc and Pc crystals is activated and temperature-independent respectively, demonstrating dominant singlet-triplet exciton fission. In Pc films (as well as C$_{60}$-doped films) this decay channel is suppressed by electron trapping. These results demonstrate the central role of crystallinity and purity in photogeneration processes and will constrain the design of future photovoltaic devices.Comment:

Persistence and Quiescence of Seismicity on Fault Systems

We study the statistics of simulated earthquakes in a quasistatic model of two parallel heterogeneous faults within a slowly driven elastic tectonic plate. The probability that one fault remains dormant while the other is active for a time Dt following the previous activity shift is proportional to the inverse of Dt to the power 1+x, a result that is robust in the presence of annealed noise and strength weakening. A mean field theory accounts for the observed dependence of the persistence exponent x as a function of heterogeneity and distance between faults. These results continue to hold if the number of competing faults is increased. This is related to the persistence phenomenon discovered in a large variety of systems, which specifies how long a relaxing dynamical system remains in a neighborhood of its initial configuration. Our persistence exponent is found to vary as a function of heterogeneity and distance between faults, thus defining a novel universality class.Comment: 4 pages, 3 figures, Revte

Mental health first aid for the UK Armed Forces

Education programmes in mental health literacy can address stigma and misunderstanding of mental health. This study investigated self-rated differences in knowledge, attitudes and confidence around mental health issues following participation in a bespoke Mental Health First Aid (MHFA) training course for the Armed Forces. The mixed methods approach comprised quantitative surveys and qualitative interviews. A survey, administered immediately post training (n=602) and again at 10- months post attendance (n=120), asked participants to rate their knowledge, attitudes and confidence around mental health issues pre and post training. Quantitative findings revealed a significant increase in knowledge, positive attitudes and confidence from the post training survey which was sustained at 10-months follow-up. Semi-structured telephone interviews (n=13) were conducted at follow-up, 6- months post attendance. Qualitative findings revealed that participation facilitated an ‘ambassador’ type role for participants. This study is the first to have investigated the effect of Mental Health First Aid (MHFA) in an Armed Forces community. Findings show participants perceived the training to increase knowledge regarding mental health and to enhance confidence and aptitude for identifying and supporting people with mental health problems. Results suggest that such an intervention can provide support for personnel, veterans and their families, regarding mental health in Armed Forces communities

Institutional influences on SME exporters under divergent transition paths: comparative insights from Tajikistan and Kyrgyzstan

This paper compares the influence of national institutional environments on the internationalisation of SME exporters from two countries, Tajikistan and Kyrgyzstan, which followed divergent paths in the transition process. It contributes in several ways, notably by extending scholarly debate on divergent paths of transition to the IB literature, and enriching the institution-based view of IB with perspectives from the new institutional economics and comparative institutionalism and offering fresh evidence of how formal and informal institutions and the enforcement mechanism interact to create specific incentives and barriers for internationalising SMEs. The study, one of the first to examine SME exporters from the former Soviet Republics of Central Asia, cautions against the tendency to attribute countries in the transitional periphery with homogenous institutional environments. Analysis of case study evidence suggests appreciable differences in the institutional environments facing SME exporters in the comparator countries. More specifically, SME exporters in Tajikistan seem to experience tougher institutional constraints relative to their Kyrgyzstan counterparts, and this divergence in institutional environments appears to affect the internationalisation prospects and competitiveness of Tajikistan and Kyrgyzstan SME exporters adversely and favourably respectively. The above findings are richly illustrated in the paper, which also discusses implications for theory, managerial and policy decision making and future research

Differential electrophysiological response during rest, self-referential, and non-self-referential tasks in human posteromedial cortex

The electrophysiological basis for higher brain activity during rest and internally directed cognition within the human default mode network (DMN) remains largely unknown. Here we use intracranial recordings in the human posteromedial cortex (PMC), a core node within the DMN, during conditions of cued rest, autobiographical judgments, and arithmetic processing. We found a heterogeneous profile of PMC responses in functional, spatial, and temporal domains. Although the majority of PMC sites showed increased broad gamma band activity (30-180 Hz) during rest, some PMC sites, proximal to the retrosplenial cortex, responded selectively to autobiographical stimuli. However, no site responded to both conditions, even though they were located within the boundaries of the DMN identified with resting-state functional imaging and similarly deactivated during arithmetic processing. These findings, which provide electrophysiological evidence for heterogeneity within the core of the DMN, will have important implications for neuroimaging studies of the DMN

Social support for and through exercise and sport in a sample of men with serious mental illness.

Social support is important for people experiencing serious mental illness and is also important during the initiation and maintenance of exercise. In this article we draw on interpretive research into the experiences of 11 men with serious mental illness to explore four dimensions of social support both for and through exercise. Our findings suggest that informational, tangible, esteem, and emotional support were both provided for and given by participants through exercise. We conclude that experiences of both receiving and giving diverse forms of support in this way are significant for some people living with and recovering from serious mental illness