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

Evaluation of early stage human bone marrow stromal proliferation, cell migration and osteogenic differentiation on μ-MIM structured stainless steel surfaces

It is well established that surface topography greatly affect cell—surface interactions. In a recent study we showed that microstructured stainless steel surfaces characterized by the presence of defined hexagonally arranged hemisphere-like structures significantly affected cell architecture (shape and focal adhesion size) of primary human bone mesenchymal stromal cells. This study aimed at further investigating the influence these microstructures (microcline protruding hemispheres) on critical aspects of cell behaviour namely; proliferation, migration and osteogenic differentiation. As with previously reported data, we used primary human bone mesenchymal stromal cells to investigate such effects at an early stage in vitro. Cells of different patients were utilised for cell migration studies. Our data showed that an increase in cell proliferation was exhibited as a function of surface topography (hemispheres). Cell migration velocity also varied as a function of surface topography on patient specific basis and seems to relate to the differentiated state of the seeded cell population (as demonstrated by bALP positivity). Osteogenic differentiation, however, did not exhibit significant variations (both up and down-regulation) as a function of both surface topography and time in cultur

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

An improved SPH scheme for cosmological simulations

We present an implementation of smoothed particle hydrodynamics (SPH) with improved accuracy for simulations of galaxies and the large-scale structure. In particular, we combine, implement, modify and test a vast majority of SPH improvement techniques in the latest instalment of the GADGET code. We use the Wendland kernel functions, a particle wake-up time-step limiting mechanism and a time-dependent scheme for artificial viscosity, which includes a high-order gradient computation and shear flow limiter. Additionally, we include a novel prescription for time-dependent artificial conduction, which corrects for gravitationally induced pressure gradients and largely improves the SPH performance in capturing the development of gas-dynamical instabilities. We extensively test our new implementation in a wide range of hydrodynamical standard tests including weak and strong shocks as well as shear flows, turbulent spectra, gas mixing, hydrostatic equilibria and self-gravitating gas clouds. We jointly employ all modifications; however, when necessary we study the performance of individual code modules. We approximate hydrodynamical states more accurately and with significantly less noise than standard SPH. Furthermore, the new implementation promotes the mixing of entropy between different fluid phases, also within cosmological simulations. Finally, we study the performance of the hydrodynamical solver in the context of radiative galaxy formation and non-radiative galaxy cluster formation. We find galactic disks to be colder, thinner and more extended and our results on galaxy clusters show entropy cores instead of steadily declining entropy profiles. In summary, we demonstrate that our improved SPH implementation overcomes most of the undesirable limitations of standard SPH, thus becoming the core of an efficient code for large cosmological simulations.Comment: 21 figures, 2 tables, accepted to MNRA

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

Loss of ceramide synthase 3 causes lethal skin barrier disruption

The stratum corneum as the outermost epidermal layer protects against exsiccation and infection. Both the underlying cornified envelope (CE) and the intercellular lipid matrix contribute essentially to these two main protective barriers. Epidermis-unique ceramides with ultra-long-chain acyl moities (ULC-Cers) are key components of extracellular lipid lamellae (ELL) and are bound to CE proteins, thereby contributing to the cornified lipid envelope (CLE). Here, we identified human and mouse ceramide synthase 3 (CerS3), among CerS1-6, to be exclusively required for the ULC-Cer synthesis in vitro and of mouse CerS3 in vivo. Deficiency of CerS3 in mice results in complete loss of ULC-Cers (≥C26), lack of continuous ELL and a non-functional CLE. Consequently, newborn mutant mice die shortly after birth from transepidermal water loss. Mutant skin is prone to Candida albicans infection highlighting ULC-Cers to be pivotal for both barrier functions. Persistent periderm, hyperkeratosis and deficient cornification are hallmarks of mutant skin demonstrating loss of Cers to trigger a keratinocyte maturation arrest at an embryonic pre-barrier stag

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.

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