Approximate supernova remnant dynamics with cosmic ray production

Supernova explosions are the most violent and energetic events in the galaxy and have long been considered probably sources of Cosmic Rays. Recent shock acceleration models treating the Cosmic Rays (CR's) as test particles nb a prescribed Supernova Remnant (SNR) evolution, indeed indicate an approximate power law momentum distribution f sub source (p) approximation p(-a) for the particles ultimately injected into the Interstellar Medium (ISM). This spectrum extends almost to the momentum p = 1 million GeV/c, where the break in the observed spectrum occurs. The calculated power law index approximately less than 4.2 agrees with that inferred for the galactic CR sources. The absolute CR intensity can however not be well determined in such a test particle approximation

Making sense of deep mathematical learning: A review of some literature

This piece of work was commissioned by Mathematics Mastery – a UKbased non-profit organisation using and advocating a pedagogical approach that seeks to enable all pupils to experience deep mathematical learning. This literature review contributes to the knowledge about deep mathematical learning. The review explores three mathematics education papers that contain ‘deep’ in their titles to consider the authors’ uses of ‘deep’ in the context of mathematical learning and any analytical or theoretical frameworks upon which they drew. We reveal that ‘deep’ was not always clearly defined in the research. Rather, the authors’ interpretations were left implicit in the terminology they used. A word frequency analysis revealed common words used across the articles. These data were used to offer a ‘lexicon for deep mathematical learning’ to assist teachers to describe the quality of pupils’ mathematical understanding

Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium

Probing Nearby CR Accelerators and ISM Turbulence with Milagro Hot Spots

Both the acceleration of cosmic rays (CR) in supernova remnant shocks and their subsequent propagation through the random magnetic field of the Galaxy deem to result in an almost isotropic CR spectrum. Yet the MILAGRO TeV observatory discovered a sharp ($\sim10^{\circ})$ arrival anisotropy of CR nuclei. We suggest a mechanism for producing a weak and narrow CR beam which operates en route to the observer. The key assumption is that CRs are scattered by a strongly anisotropic Alfven wave spectrum formed by the turbulent cascade across the local field direction. The strongest pitch-angle scattering occurs for particles moving almost precisely along the field line. Partly because this direction is also the direction of minimum of the large scale CR angular distribution, the enhanced scattering results in a weak but narrow particle excess. The width, the fractional excess and the maximum momentum of the beam are calculated from a systematic transport theory depending on a single scale $l$ which can be associated with the longest Alfven wave, efficiently scattering the beam. The best match to all the three characteristics of the beam is achieved at $l\sim1$pc. The distance to a possible source of the beam is estimated to be within a few 100pc. Possible approaches to determination of the scale $l$ from the characteristics of the source are discussed. Alternative scenarios of drawing the beam from the galactic CR background are considered. The beam related large scale anisotropic CR component is found to be energy independent which is also consistent with the observations.Comment: 2 figures, ApJ accepted version2 minor changes and correction

Diversity and Scientific Progress in the Information Systems Discipline

The Information Systems (IS) discipline is over a third of a century old. It is a multidisciplinary field of study that covers areas related to the management, deployment, and use of information technology. In response to this extended reach and the growing needs and requirements of its stakeholders, the IS community successfully solidified its foundations through institutionalization and professionalization. However, in light of a complex patronage structure, undisciplined diversity, and unbounded eclecticism in scholarly activities, the progress of IS as a scientific discipline has been attenuated. Drawing lessons from the field of psychology, this paper calls for solidifying the disciplinary matrix of IS. It argues that scientific progress of IS can be advanced further through the development of cumulative and exemplary theories aimed at significant problems. Such a cumulative approach to research tradition and knowledge unification would help demarcate the boundaries of the IS domain not in terms of its subject matters, but by the theories it develops to solve the problems within its domain

A Historiographical Examination of Information Systems

As the Information Systems (IS) field enters its fourth decade of evolution, the time is right to provide a historiographical examination of this discipline. Methodological and thematic trends are gauged through a quarterly analysis of 2098 IS articles published in eight leading journals and the ICIS Proceedings in the 12-year period between 1985-1996. The results of this study show that significant changes occurred in research strategies and themes employed by IS researchers. Even though a large proportion of IS studies are still non-empirical, we see significant upward trend in the proportion of empirical studies. The reliance on reference disciplines increased significantly over the years. Similarly, we see significantly increasing trends in organizational, environmental and educational themes. In contrast, technical issues show decreasing trends. The paper calls for collective efforts to unify knowledge necessary for progress of IS as a scientific field of inquiry