X-ray emission from pre-main sequence stars with multipolar magnetic fields

The large-scale magnetic fields of several pre-main sequence (PMS) stars have been observed to be simple and axisymmetric, dominated by tilted dipole and octupole components. The magnetic fields of other PMS stars are highly multipolar and dominantly non-axisymmetric. Observations suggest that the magnetic field complexity increases as PMS stars evolve from Hayashi to Henyey tracks in the Hertzsprung–Russell diagram. Independent observations have revealed that X-ray luminosity decreases with age during PMS evolution, with Henyey track PMS stars having lower fractional X-ray luminosities (𝐿X/𝐿∗) compared to Hayashi track stars. We investigate how changes in the large-scale magnetic field topology of PMS stars influences coronal X-ray emission. We construct coronal models assuming pure axisymmetric multipole magnetic fields, and magnetic fields consisting of a dipole plus an octupole component only. We determine the closed coronal emitting volume, over which X-ray emitting plasma is confined, using a pressure balance argument. From the coronal volumes we determine X-ray luminosities. We find that 𝐿X decreases as the degree ℓ of the multipole field increases. For dipole plus octupole magnetic fields we find that 𝐿X tends to decrease as the octupole component becomes more dominant. By fixing the stellar parameters at values appropriate for a solar mass PMS star, varying the magnetic field topology results in two orders of magnitude variation in 𝐿X. Our results support the idea that the decrease in 𝐿X as PMS stars age can be driven by an increase in the complexity of the large-scale magnetic field

X-ray Emission Models for Multipolar fields of Pre-Main Sequence Stars

The large-scale magnetic fields of several pre-main sequence (PMS) stars have been observed to be simple and axisymmetric, dominated by tilted dipole and octupole components. The magnetic fields of other PMS stars are highly multipolar and dominantly non-axisymmetric. Observations suggest that the magnetic field complexity increases as PMS stars evolve from Hayashi to Henyey tracks in the Hertzsprung--Russell diagram. Independent observations have revealed that X-ray luminosity decreases with age during PMS evolution, with Henyey track PMS stars having lower fractional X-ray luminosities ($L_\textrm{X}/L_*$) compared to Hayashi track stars. We investigate how changes in the large-scale magnetic field topology of PMS stars influences coronal X-ray emission. We construct coronal models assuming pure axisymmetric multipole magnetic fields, and magnetic fields consisting of a dipole plus an octupole component only. We determine the closed coronal emitting volume, over which X-ray emitting plasma is confined, using a pressure balance argument. From the coronal volumes we determine X-ray luminosities. We find that $L_\textrm{X}$ decreases as the degree $\ell$ of the multipole field increases. For dipole plus octupole magnetic fields we find that $L_\textrm{X}$ tends to decrease as the octupole component becomes more dominant. By fixing the stellar parameters at values appropriate for a solar mass PMS star, varying the magnetic field topology results in two orders of magnitude variation in $L_\textrm{X}$. Our results support the idea that the decrease in $L_\textrm{X}$ as PMS stars age can be driven by an increase in the complexity of the large-scale magnetic field.Comment: 13 pages with 13 figures, plus 1 page with 1 figure in the appendix, accepted for publication in MNRAS 2023 August 0

A Delphi study on collaborative learning in distance education

Collaborative Learning (CL) is increasingly being used in Distance Education (DE), as it has been identified as an effective solution to known weaknesses such as high average rates of dropout and low quality of learning attainment. Information Technology is a core component of this type of learning as it not only provides the means to collaborate over distance but also has the potential to enable higher learning outcomes. There are a rapidly growing number of technologies in use today and the importance of these to collaborative learning initiatives, and the role they play, is an area of active research in the Information Systems (IS) community. IS educators and practitioners face an increasing challenge therefore to successfully implement CL in DE, precipitated not only from technical advances but also from wider social and organisational concerns. Using a Delphi study, this research is the first to investigate the factors that influence collaborative learning in distance education by surveying the opinions of an expert panel in this area. The aim was to produce an integrated list of the most important implementation factors and to investigate the role technology is perceived to contribute. The findings identified seventeen of the most important factors. These factors cover a range of themes including course rationale and design, instructor characteristics, training, group dynamics, the development of a learning community and technology. The potential of technology however does not seem to be fully realised and newer technologies such as multi-user environments would seem to be of limited use in practice, according to the expert panel

Corporate social responsibility reporting of international oil companies in Nigeria:an historical materialism analysis

Purpose: This study aims to identify factors influencing corporate social responsibility reporting (CSRR) practices of international oil companies (IOCs) in Nigeria. It aims at distinguishing CSRR levels by examining both the quantity and quality of reporting. Design/methodology/approach: The paper analyses annual reports through content analysis. CSRR extent and type are measured by the number of sentences. CSRR are further classified into three subcategories according to whether they are negative, neutral or positive reports and then their proportions compared through descriptive analysis. Findings: For the extent and quality of CSRR, community was the most reported category. The majority of the total CSRR in the IOCs is positive with little evidence of negative news. None of the IOCs in the sample reported on the environment in their annual reports. Research limitations/implications: The measurement of CSRR focuses only on annual reports, without consideration of other reporting media such as standalone reports and corporate websites. CSRR are assumed to be voluntary for the companies and they may choose not to report any information in annual reports, as there are no regulations or reporting guidelines in Nigeria to be followed. Practical implications: The results reveal the absence of environmental reporting in the CSRR of IOCs in Nigeria suggests that they are less concerned with meeting local demands for accountability. The study recommends the need for regulatory intervention on the part of the Nigerian Government. Social implications: The findings of study indicate that predominant existence of positive CSRR news among all the IOCs suggests there’s an attempt to encourage stakeholders and the public to believe that they are conscious of society and the environment. Originality/value: The main contribution of this study lies in identifying the factors that have led to diversity and uniqueness in CSRR in IOCs. As such, this study seeks to contribute to the development of understanding multiple factors that could give rise to changing patterns of CSRR

Influencing students' construction of personalised concept maps through the use of query expansion (QE) searching of the World Wide Web

Despite the on-going development of search engines, users of the World Wide Web, including school and undergraduate students, still find searching for appropriate information problematic. Keener students may seek relevant information to help them to construct a better understanding of the various concepts within a taught subject. Unfortunately there is no guarantee that the information contained in the located documents is of sufficient educational quality; measured for example in terms of the information's usefulness, accuracy, relevancy, trustworthiness, level of language, completeness and status. In this research it is argued that a domain expert (perhaps in the form of a "web literate" subject tutor) has several major advantages over a school or undergraduate student when it comes to searching for relevant subject-related informatio

Restructuring the Michigan Child Care Fund: Reducing Costs and Improving Outcomes

Michigan’s policy to distribute the Child Care Fund (CCF) to counties at a flat rate of 50% as stated in the Michigan Comprehensive Laws 400.117a provides no structured incentive to the counties to use evidence based practices that are cost-effective for locally based delinquent youth intervention programs. This policy analysis answers the following questions: (1) would retaining delinquent youth in the community produce a cost benefit and/or better outcomes than confinement and (2) is public safety at risk if delinquent youth are retained in the community? Utilizing a policy analysis framework our evidence found that community based services provide better outcomes than confinement for delinquent youth and that retaining delinquent youth in the community does not represent an increased risk to public safety. Policy change is recommended to incentivize the use of best practices which may produce significant economic and social benefits to the state and delinquent youth who should receive the best possible care. This can be accomplished through a shift in state reimbursement rates from the current 50% rate to an increased rate for evidence based strategies

Towards a Toolset for Intranet Evaluation

Usability is an important component of information systems acceptance. Independent consultants in the assessment of organisational intranets often perform heuristic appraisal, a common method of usability evaluation. However, there are alternative usability models that offer valuable analysis in the evaluation process. Using a government organisation’s intranet as a case study, this paper assesses the value of an independent heuristic-based intranet audit by providing a comparable approach to assessment realisable internally in the organisation using questionnaires. Using a single case study, we empirically apply the Technology Acceptance Model (TAM), together with some heuristic aspects, to provide an alternative tool for intranet usability and acceptance. We provide insight into the usability impact of intranet design changes, and compare the findings of an external usability audit with the approach outlined. An overall toolset for intranet evaluation is proposed as an initial step for further exploration and potential use

Influencing students' construction of personalised concept maps through the use of query expansion (QE) searching of the World Wide Web

Despite the on-going development of search engines, users of the World Wide Web, including school and undergraduate students, still find searching for appropriate information problematic. Keener students may seek relevant information to help them to construct a better understanding of the various concepts within a taught subject. Unfortunately there is no guarantee that the information contained in the located documents is of sufficient educational quality; measured for example in terms of the information's usefulness, accuracy, relevancy, trustworthiness, level of language, completeness and status. In this research it is argued that a domain expert (perhaps in the form of a "web literate" subject tutor) has several major advantages over a school or undergraduate student when it comes to searching for relevant subject-related informatio

Dietary Manipulation for Therapeutic Effect in Prostate Cancer

Given that there is a wealth of literature on the potential effect of a wide variety of phytochemicals on the growth of prostate cancer cells, we have limited our discussion to arguably four of the most important: isoflavones, lycopene, resveratrol, and curcumin. The focus of this review is on the clinical pharmacology of these compounds, as there are already an extensive number of reviews in the literature on all of these compounds for various cancers, including our previous review of isoflavones in prostate cancer (de Souza et al., 2009). Here, we use the loose term “phytochemicals” to describe this group of plant–based compounds with biological activity in vitro, for simplicity. Like other phytochemicals, isoflavones, lycopene, resveratrol and curcumin have a wide variety of potential mechanisms of action in many different cancer cell lines. Many of these biological effects involve key components of signal transduction pathways within cancer cells, but in this review, we will be focusing on studies specifically in prostate cancer