On pulsar radio emission

This work intends to contribute to the understanding of the radio emission of pulsars. Pulsars are neutron stars with a radius of about 10^6 cm and a mass of about one to three solar masses, that rotate with a period between seconds and milliseconds. They exhibit tremendous magnetic fields of 10^8 to 10^13 Gauss. These fields facilitate the conversion of rotational energy to mainly dipole radiation, x-ray emission and the pulsar wind. Less than a thousandth of the total energy loss is being emitted as radio emission. This contribution however is generated by a collective plasma radiation process that acts coherently on a time scale of nanoseconds and below. Since the topic has been an active field of research for nearly half a century, we introduce the resulting theoretical concepts and ideas for an emission process and the appearance of the so called “magnetosphere”, the plasma filled volume around a pulsar, in Chapter 1. We show that many basic questions have been answered satisfactorily. Questions concerning the emission process, however, suffer some uncertainty. Especially the exact energy source of the radio emission remains unclear. The early works of Goldreich and Julian [1969] and Ruderman and Sutherland [1975] predict high electric fields to arise that are capable of driving a strong electric current. To supplement the energy to power the radio emission, rather mildly relativistic particle energies and a moderate current are favourable. How the system converts current into flow is unclear. In fact, the earlier theories are opposed by recent simulations that also do not predict a relativistic flow near the pulsar. We examine the observed radiation and its form, especially in light of the illustrated models in Chapter 2. We notice that the radio emission is generated in extremely short time scales, that are comparable to the inverse of the Plasma frequency. We elaborate why this places high demands on the theoretical models leaving in fact only one viable candidate process. We conclude that profound questions of energy flow and energy source remain unanswered by current theory. Furthermore, the compression of available energy in space and time to a few centimetres and nanoseconds remains unclear, especially when facing the fact that only a small fraction of the theoretically available energy is being converted. Since the fluctuations relevant for the compression of the energy take place on an intermediate scale of nanoseconds to micro- and milliseconds, it should be possible to detect these observationally. To facilitate this, we decide to analyse the statistics of the Receiver equation of radio radiation in Chapter 3, also since this is relevant to other topics of Pulsar research. The results presented in Chapter 4 show that the developed Bayesian method excels conventional methods to extract parameters from observation data in both precision and accuracy. The method for example weights rotation phase measurements differently than conventional techniques and assigns a more accurate error estimation to single measurements. This is of great relevance to gravitational wave search with so called “pulsar timing array”, as the validity of the total measurement is substantially dependent on the understanding of the accuracy assigned to the single observations. However, the work on single observation data with Bayesian techniques also exemplifies the numerical limits of this method. It is desirable to enable algorithms to include single observation data in the analysis. Therefore we developed a runtime library that writes out currently unneeded data to hard disk, being capable to manage huge data sets (substantial fractions of the hard disk space, not the main memory) in Chapter 5. This library has been written in a generic form so that it can be also used in other data-intensive areas of research. While we thereby lay the foundations to evaluate fluctuation models by observational data, we approach the problem from theoretical grounds in Chapter 6. We propose that the energetic coupling of radio emission could be of magnetic origin, as this is also a relevant mechanism in solar flare physics. We argue in a general way that the rotation of the pulsar pumps energy into the magnetic field, due to topological reasons. This energy can be released again by current decay. We show that already the annihilation of electrons and positrons may suffice to generate radio emission on non-negligible energy scales. This mechanism is not dependent on relativistic flow and thus does not suffer from the problem of requiring high kinetic particle energies. We conclude that the existing gaps in the theory of the radio emission process could possibly be closed in the future, if we analyse observational data statistically more accurate and especially if we put more effort into understanding the problem of energy transport. This thesis serves as an example that scientific investigation of a very theoretical question such as the origin of radio emission can lead to results that may be used directly in other Areas of research

Directive Language Input to Children Born Preterm and Full Term

The mothers of children born preterm face many challenges in the formation of high-quality dyadic interactions with their children. Because children born preterm are at risk for many neurodevelopmental delays, it is important to study the language input directed to these children and its contribution to their language development. One type of language input commonly used by mothers of young children is directive language input. The purpose of this study was to examine different types of directives, supportive and intrusive, in the language input of mothers of preterm children compared to mothers of full term children. The relationship between the maternal use of intrusive and supportive directives and language outcomes in their children also was examined. Ten mother-child dyads (five preterm and five full term) participated in this study. The children ranged in age between 9-15 months. Mothers of full term children were matched to the preterm sample controlling for child's gender, child's age, and maternal education. Each mother and child dyad participated in a play session using a standard set of toys. The play session was audio- and videotaped. The difference between production of intrusive and supportive directives by mothers of preterm children and mothers of full term children was not statistically significant. However, practical significance, as determined by moderate effect sizes, were evident, with mothers of children born preterm using more intrusive directives than mothers of children born full term. Additionally, it was found that the maternal use of intrusive directives had a strong negative relationship with child language outcomes for the children in the preterm group. The maternal use of intrusive directives may be detrimental to the language acquisition process because they require the child to devote cognitive resources away from the task of language learning and result in less engagement of the child. The clinical implications of the findings are discussed

A Bayesian method for pulsar template generation

Extracting Times of Arrival from pulsar radio signals depends on the knowledge of the pulsars pulse profile and how this template is generated. We examine pulsar template generation with Bayesian methods. We will contrast the classical generation mechanism of averaging intensity profiles with a new approach based on Bayesian inference. We introduce the Bayesian measurement model imposed and derive the algorithm to reconstruct a "statistical template" out of noisy data. The properties of these "statistical templates" are analysed with simulated and real measurement data from PSR B1133+16. We explain how to put this new form of template to use in analysing secondary parameters of interest and give various examples: We implement a nonlinear filter for determining ToAs of pulsars. Applying this method to data from PSR J1713+0747 we derive ToAs self consistently, meaning all epochs were timed and we used the same epochs for template generation. While the average template contains fluctuations and noise as unavoidable artifacts, we find that the "statistical template" derived by Bayesian inference quantifies fluctuations and remaining uncertainty. This is why the algorithm suggested turns out to reconstruct templates of statistical significance from ten to fifty single pulses. A moving data window of fifty pulses, taking out one single pulse at the beginning and adding one at the end of the window unravels the characteristics of the methods to be compared. It shows that the change induced in the classical reconstruction is dominated by random fluctuations for the average template, while statistically significant changes drive the dynamics of the proposed method's reconstruction. The analysis of phase shifts with simulated data reveals that the proposed nonlinear algorithm is able to reconstruct correct phase information along with an acceptable estimation of the remaining uncertainty.Comment: 21 pages, 16 figures, submitted to MNRA

International experience of gas emission and gas outburst prevention in underground coal mines

With increasing depth of cover, control of gas emissions and prevention of gas outbursts has become a more and more important issue in mine design and mine operation. Long term experience in these fields exists, especially in Australia, Germany, China, Kazakhstan and Ukraine. Based on local conditions including geology, market conditions and mining regulations, different approaches have been developed in these countries. Changes in these parameters have however exposed the limitations of traditional solutions. While the Australian approach is based on the premise that gas content will be reduced below specific threshold values ahead of mining, opportunities of pre-drainage are limited in low permeability coal such as that encountered e.g. in Germany and China. In the case of multi seam mining, a highly effective increase in permeability can however be achieved through pressure relief by unconventional mining sequences. Although practiced at several mines in Europe and Asia, realising this in open market conditions requires a high quality of planning in regard to mine layout, mine development and gas drainage as well as the appropriate geotechnical assessments. A key factor is access and extraction of the first seam at or near to virgin gas contents. Mining at high gas contents by applying local exploration and pressure relief drilling has been practiced in a successful and safe way in several European mines. This has to be connected with a proper management system and safety system, allowing efficient reactions to identified hazards. Apart from international experience and development, the paper will also discuss current and future approaches of technology transfer. Merging the future development in gas drainage with unconventional approaches is therefore an opportunity for accessing deep and difficult deposits

Language-aware foreign language teaching requires competent teachers with great professional knowledge and skills. Practical relevance of pedagogical training in foreign language teacher education put to the test

Gemäss Lehrplan sind im Fremdsprachenunterricht Sprachkompetenzen und Kompetenzen im Bereich «Sprache und Kultur» zu erwerben. Wie diese Ziele erreicht werden und wie diese Bereiche zusammenspielen, ist allerdings noch unklar. Dass professionelle Kompetenzen von Lehrpersonen das Erreichen von Bildungszielen beeinflussen, davon kann aber sicher ausgegangen werden. Im Zentrum des Beitrags steht deshalb die Frage, wie Studierende der Pädagogischen Hochschule Thurgau ihre professionellen Kompetenzen und ihren Kompetenzaufbau in der Französischdidaktik wahrnehmen. Eine Schlussbemerkung zur Optimierung der Ausbildungsdidaktik mit Blick auf berufspraktische Fragen rundet den Beitrag ab. (DIPF/Orig.)According to the curriculum, language skills and skills in the area of language and culture are to be acquired in foreign language education. How these goals are achieved and how these areas interact, however, is still not clear. Nevertheless, it can be safely assumed that teachers’ professional skills influence the achievement of educational goals. The article therefore focuses on the question of how students of the University of Teacher Education Thurgau perceive their professional skills and their competence development in subject-specific pedagogy of French teaching. A concluding remark on the optimization of higher-education pedagogy in teacher education with respect to questions of professional practice rounds off the article. (DIPF/Orig.

Sprachbewusster Fremdsprachenunterricht braucht kompetente Lehrpersonen mit grossem fachlichem Wissen und Können. Praxisbezug der fremdsprachendidaktischen Ausbildung auf dem Prüfstand

Gemäss Lehrplan sind im Fremdsprachenunterricht Sprachkompetenzen und Kompetenzen im Bereich «Sprache und Kultur» zu erwerben. Wie diese Ziele erreicht werden und wie diese Bereiche zusammenspielen, ist allerdings noch unklar. Dass professionelle Kompetenzen von Lehrpersonen das Erreichen von Bildungszielen beeinflussen, davon kann aber sicher ausgegangen werden. Im Zentrum des Beitrags steht deshalb die Frage, wie Studierende der Pädagogischen Hochschule Thurgau ihre professionellen Kompetenzen und ihren Kompetenzaufbau in der Französischdidaktik wahrnehmen. Eine Schlussbemerkung zur Optimierung der Ausbildungsdidaktik mit Blick auf berufspraktische Fragen rundet den Beitrag ab

Corpus Statistics for Measuring Business Process Similarity

In a rapidly changing environment, organizations must adapt their business processes continuously. While numerous methods enable enterprises to conceptualize and analyze their organizational structure, the task of business process modeling remains complex and time-consuming. However, by reusing and adapting existing process models, enterprises can reduce the task’s complexity while improving the quality of results. To facilitate the identification of adaptable processes, several techniques of business process similarity (BPS) have been proposed in recent years. Although most approaches produce sound results in controlled evaluations, this paper argues that their applicability is limited when analyzing real-world processes, which do not fully comply with notational labeling specifications. Consequently, we aim to enhance existing BPS techniques by using corpus statistics to account for the explanatory power of words within labels of process models. Results from our evaluation suggest that corpus statistics can improve BPS computations and can positively influence the quality of practical implications

On pulsar radio emission

This work intends to contribute to the understanding of the radio emission of pulsars. Pulsars are neutron stars with a radius of about 10^6 cm and a mass of about one to three solar masses, that rotate with a period between seconds and milliseconds. They exhibit tremendous magnetic fields of 10^8 to 10^13 Gauss. These fields facilitate the conversion of rotational energy to mainly dipole radiation, x-ray emission and the pulsar wind. Less than a thousandth of the total energy loss is being emitted as radio emission. This contribution however is generated by a collective plasma radiation process that acts coherently on a time scale of nanoseconds and below. Since the topic has been an active field of research for nearly half a century, we introduce the resulting theoretical concepts and ideas for an emission process and the appearance of the so called “magnetosphere”, the plasma filled volume around a pulsar, in Chapter 1. We show that many basic questions have been answered satisfactorily. Questions concerning the emission process, however, suffer some uncertainty. Especially the exact energy source of the radio emission remains unclear. The early works of Goldreich and Julian [1969] and Ruderman and Sutherland [1975] predict high electric fields to arise that are capable of driving a strong electric current. To supplement the energy to power the radio emission, rather mildly relativistic particle energies and a moderate current are favourable. How the system converts current into flow is unclear. In fact, the earlier theories are opposed by recent simulations that also do not predict a relativistic flow near the pulsar. We examine the observed radiation and its form, especially in light of the illustrated models in Chapter 2. We notice that the radio emission is generated in extremely short time scales, that are comparable to the inverse of the Plasma frequency. We elaborate why this places high demands on the theoretical models leaving in fact only one viable candidate process. We conclude that profound questions of energy flow and energy source remain unanswered by current theory. Furthermore, the compression of available energy in space and time to a few centimetres and nanoseconds remains unclear, especially when facing the fact that only a small fraction of the theoretically available energy is being converted. Since the fluctuations relevant for the compression of the energy take place on an intermediate scale of nanoseconds to micro- and milliseconds, it should be possible to detect these observationally. To facilitate this, we decide to analyse the statistics of the Receiver equation of radio radiation in Chapter 3, also since this is relevant to other topics of Pulsar research. The results presented in Chapter 4 show that the developed Bayesian method excels conventional methods to extract parameters from observation data in both precision and accuracy. The method for example weights rotation phase measurements differently than conventional techniques and assigns a more accurate error estimation to single measurements. This is of great relevance to gravitational wave search with so called “pulsar timing array”, as the validity of the total measurement is substantially dependent on the understanding of the accuracy assigned to the single observations. However, the work on single observation data with Bayesian techniques also exemplifies the numerical limits of this method. It is desirable to enable algorithms to include single observation data in the analysis. Therefore we developed a runtime library that writes out currently unneeded data to hard disk, being capable to manage huge data sets (substantial fractions of the hard disk space, not the main memory) in Chapter 5. This library has been written in a generic form so that it can be also used in other data-intensive areas of research. While we thereby lay the foundations to evaluate fluctuation models by observational data, we approach the problem from theoretical grounds in Chapter 6. We propose that the energetic coupling of radio emission could be of magnetic origin, as this is also a relevant mechanism in solar flare physics. We argue in a general way that the rotation of the pulsar pumps energy into the magnetic field, due to topological reasons. This energy can be released again by current decay. We show that already the annihilation of electrons and positrons may suffice to generate radio emission on non-negligible energy scales. This mechanism is not dependent on relativistic flow and thus does not suffer from the problem of requiring high kinetic particle energies. We conclude that the existing gaps in the theory of the radio emission process could possibly be closed in the future, if we analyse observational data statistically more accurate and especially if we put more effort into understanding the problem of energy transport. This thesis serves as an example that scientific investigation of a very theoretical question such as the origin of radio emission can lead to results that may be used directly in other Areas of research

Language, Motor, and Cognitive Outcomes of Toddlers Who Were Born Preterm

Purpose: The purpose of this study was to examine the language, motor, and cognitive abilities of children born preterm in four categories: (a) healthy preterm infants, (b) infants of diabetic mothers, (c) infants with respiratory distress syndrome, and (d) infants with chronic lung disease when the children were 30 months, uncorrected age. Comorbidity of language, motor, and cognitive skills was examined, along with predictor variables. Method: A total of 148 children who were born preterm participated and were assessed using bivariate tests and logistic regression on standardized assessment scores. Results: Controlling for the children’s gestational age (GA), overall language ability was significantly lower in the infants of diabetic mothers group compared to the healthy preterm infant group, and expressive language skills were significantly lower for the chronic lung disease group than the respiratory distress syndrome group. The children with language delays on at least one measure were significantly more likely to have cognitive, motor, or both delays. Lower maternal education was a significant predictor for language and cognitive delays, and younger GA was a significant predictor for language, motor, and cognitive delays. Conclusion: Assessment of the preterm infant from a biosystems approach allows the speech-language pathologist to take into consideration maternal education, diagnosis at preterm birth, and GA, which were found to impact the language, motor, and cognitive outcomes of children born preterm. Our findings further reinforce the concept of the whole child in that children born preterm who display language delays should be screened for co-occurring motor and/or cognitive delays

Expressive Language in Preschoolers Born Preterm: Results of Language Sample Analysis and Standardized Assessment

Children born preterm constitute one of the largest populations of children at risk for the development of language impairments. A little over one in ten pregnancies result in a preterm birth and approximately 25% of these children go on to experience subsequent difficulties with language (CDC, 2015; Foster-Cohen, Friesen, Champion, & Woodward, 2010). Despite the high risk for language deficits in this population, few studies have investigated the conversational language skills of these children. In particular, the objective of this study was to investigate the grammatical and semantic skills of children born preterm via language sample analysis. A second aim of the study was to determine the relationship between conversational language skills and the results of standardized assessment of language in this population and investigate the role that non-linguistic factors such as attention and non-verbal intelligence play in standardized assessment results. Twenty-nine preschoolers born preterm and a comparison group of 29 full term peers participated in this study. The children in the preterm group performed more poorly than the full term group on measures of conversational semantic and grammatical skills obtained from language sample analysis. In contrast, the two groups performed similarly on all but one of the measures obtained from standardized assessments. The clinical implications of these findings are discussed