Simulating the Large-Scale Structure of HI Intensity Maps

Intensity mapping of neutral hydrogen (HI) is a promising observational probe of cosmology and large-scale structure. We present wide field simulations of HI intensity maps based on N-body simulations of a $2.6\, {\rm Gpc / h}$ box with $2048^3$ particles (particle mass $1.6 \times 10^{11}\, {\rm M_\odot / h}$). Using a conditional mass function to populate the simulated dark matter density field with halos below the mass resolution of the simulation ($10^{8}\, {\rm M_\odot / h} < M_{\rm halo} < 10^{13}\, {\rm M_\odot / h}$), we assign HI to those halos according to a phenomenological halo to HI mass relation. The simulations span a redshift range of 0.35 < z < 0.9 in redshift bins of width $\Delta z \approx 0.05$ and cover a quarter of the sky at an angular resolution of about 7'. We use the simulated intensity maps to study the impact of non-linear effects and redshift space distortions on the angular clustering of HI. Focusing on the autocorrelations of the maps, we apply and compare several estimators for the angular power spectrum and its covariance. We verify that these estimators agree with analytic predictions on large scales and study the validity of approximations based on Gaussian random fields, particularly in the context of the covariance. We discuss how our results and the simulated maps can be useful for planning and interpreting future HI intensity mapping surveys.Comment: 35 pages, 19 Figures. Accepted for publication in JCA

Accumulation of muscle ankyrin repeat protein transcript reveals local activation of primary myotube endcompartments during muscle morphogenesis

The characteristic shapes and positions of each individual body muscle are established during the process of muscle morphogenesis in response to patterning information from the surrounding mesenchyme. Throughout muscle morphogenesis, primary myotubes are arranged in small parallel bundles, each myotube spanning the forming muscles from end to end. This unique arrangement potentially assigns a crucial role to primary myotube end regions for muscle morphogenesis. We have cloned muscle ankyrin repeat protein (MARP) as a gene induced in adult rat skeletal muscle by denervation. MARP is the rodent homologue of human C-193 (Chu, W., D.K. Burns, R.A. Swerick, and D.H. Presky. 1995. J. Biol. Chem. 270:10236-10245) and is identical to rat cardiac ankyrin repeat protein. (Zou, Y., S. Evans, J. Chen, H.-C. Kuo, R.P. Harvey, and K.R. Chien. 1997. Development. 124:793-804). In denervated muscle fibers, MARP transcript accumulated in a unique perisynaptic pattern. MARP was also expressed in large blood vessels and in cardiac muscle, where it was further induced by cardiac hypertrophy. During embryonic development, MARP was expressed in forming skeletal muscle. In situ hybridization analysis in mouse embryos revealed that MARP transcript exclusively accumulates at the end regions of primary myotubes during muscle morphogenesis. This closely coincided with the expression of thrombospondin-4 in adjacent prospective tendon mesenchyme, suggesting that these two compartments may constitute a functional unit involved in muscle morphogenesis. Transfection experiments established that MARP protein accumulates in the nucleus and that the levels of both MARP mRNA and protein are controlled by rapid degradation mechanisms characteristic of regulatory early response genes. The results establish the existence of novel regulatory muscle fiber subcompartments associated with muscle morphogenesis and denervation and suggest that MARP may be a crucial nuclear cofactor in local signaling pathways from prospective tendon mesenchyme to forming muscle and from activated muscle interstitial cells to denervated muscle fibers

Cosmology with next generation radio telescopes

Philosophiae Doctor - PhDThe next generation of radio telescopes will revolutionize cosmology by providing large three-dimensional surveys of the universe. This work presents forecasts using the technique 21cm intensity mapping (IM) combined with results from the cosmic microwave background, or mock data of galaxy surveys. First, we discuss prospects of constraining curvature independently of the dark energy (DE) model, finding that the radio instrument HIRAX will reach percent-level accuracy even when an arbitrary DE equation of state is assumed. This is followed by a study of the potential of the multi-tracer technique to surpass the cosmic variance limit, a crucial method to probe primordial non-Gaussianity and large scale general relativistic e↵ects. Using full sky simulations for the Square Kilometre Array phase 1 (SKA 1 MID) and the Large Synoptic Survey Telescope (LSST), including foregrounds, we demonstrate that the cosmic variance contaminated scenario can be beaten even in the noise free case. Finally, we derive the signal to noise ratio for the cosmic magnification signal from foreground HI intensity maps combined with background galaxy count maps. Instruments like SKA1 MID and HIRAX are highly complementary and well suited for this measurement. Thanks to the powerful design of the planned radio instruments, all results confirm their potential and promise an exciting future for cosmology

Semantic anomaly detection using self-supervised post-extraction scrambling

This thesis investigates visual anomaly detection with a focus on semantic anomaly detection using transformer-based architectures. While structural anomaly detection has seen extensive research, semantic anomaly detection remains largely underexplored due to its greater complexity and lack of datasets. To address this, the thesis develops an anomaly detection model capable of distinguishing between nominal and semantically anomalous data using a student-teacher transformer model architecture. The approach leverages convolutional feature extraction via a WideResNet50 backbone, followed by transformer encoders that predict the original sequence of feature patches. The model is trained through Post-Extraction Scrambling of patches and evaluated on a custom dataset and the CAD-SD dataset, where the latter includes comparisons to other state-of-the-art models. Final evaluations demonstrate competitive performance in detecting semantic anomalies, though limitations persist in identifying structural defects. This research contributes a transformer-based self-supervised feature extraction method under constrained anomaly detection settings.In dieser Arbeit wird die Erkennung visueller Anomalien untersucht, wobei der Schwerpunkt auf der Erkennung semantischer Anomalien mittels Transformer-basierter Architekturen liegt. Während die Erkennung struktureller Anomalien bereits ausgiebig erforscht wurde, ist die Erkennung semantischer Anomalien aufgrund ihrer höheren Komplexität und des Mangels an Datensätzen noch weitgehend unerforscht. Um dieses Problem zu beheben, wird in dieser Arbeit ein Modell zur Erkennung von Anomalien entwickelt, das in der Lage ist, zwischen normalen und semantisch anomalen Daten zu unterscheiden, wobei eine Student-Teacher-Transformer-Modellarchitektur verwendet wird. Der Ansatz nutzt die Feature-Extraktion über ein WideResNet50-Netzwerk, gefolgt von Transformer-Encodern, die die ursprüngliche Sequenz von Featurepatches vorhersagen. Das Modell wird durch Post-Extraction Scrambling von Patches trainiert und auf einem selbst erstellten Datensatz und dem CAD-SD-Datensatz evaluiert, wobei letzterer Vergleiche mit anderen State-of-the-Art-Modellen enthält. Die abschließenden Auswertungen zeigen eine konkurrenzfähige Leistung bei der Erkennung semantischer Anomalien, während bei der Erkennung struktureller Defekte weiterhin Einschränkungen bestehen. Diese Forschungsarbeit stellt eine Transformer-basierte Methode zur Feature-Extraktion unter eingeschränkten Bedingungen für die Erkennung von Anomalien vor

MeerKLASS: MeerKAT Large Area Synoptic Survey

We discuss the ground-breaking science that will be possible with a wide area survey, using the MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The current specifications of MeerKAT make it a great fit for science applications that require large survey speeds but not necessarily high angular resolutions. In particular, for cosmology, a large survey over $\sim 4,000 \, {\rm deg}^2$ for $\sim 4,000$ hours will potentially provide the first ever measurements of the baryon acoustic oscillations using the 21cm intensity mapping technique, with enough accuracy to impose constraints on the nature of dark energy. The combination with multi-wavelength data will give unique additional information, such as exquisite constraints on primordial non-Gaussianity using the multi-tracer technique, as well as a better handle on foregrounds and systematics. Such a wide survey with MeerKAT is also a great match for HI galaxy studies, providing unrivalled statistics in the pre-SKA era for galaxies resolved in the HI emission line beyond local structures at z > 0.01. It will also produce a large continuum galaxy sample down to a depth of about 5\,$\mu$Jy in L-band, which is quite unique over such large areas and will allow studies of the large-scale structure of the Universe out to high redshifts, complementing the galaxy HI survey to form a transformational multi-wavelength approach to study galaxy dynamics and evolution. Finally, the same survey will supply unique information for a range of other science applications, including a large statistical investigation of galaxy clusters as well as produce a rotation measure map across a huge swathe of the sky. The MeerKLASS survey will be a crucial step on the road to using SKA1-MID for cosmological applications and other commensal surveys, as described in the top priority SKA key science projects (abridged).Comment: Larger version of the paper submitted to the Proceedings of Science, "MeerKAT Science: On the Pathway to the SKA", Stellenbosch, 25-27 May 201

A Large Sky Survey with MeerKAT

We discuss the ground-breaking science that will be possible with a wide area survey, using the MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The current specifications of MeerKAT make it a great fit for cosmological applications, which require large volumes. In particular, a large survey over ~4,000 deg^2 for ~4,000 hours will potentially provide the first ever measurements of the baryon acoustic oscillations using the 21cm intensity mapping technique, with enough accuracy to impose constraints on the nature of dark energy. The combination with multi-wavelength data will give unique additional information, such as the first constraints on primordial non-Gaussianity using the multi-tracer technique, as well as a better handle on foregrounds and systematics. The survey will also produce a large continuum galaxy sample down to a depth of 5 µJy in L-band, unmatched by any other concurrent telescope, which will allow to study the large-scale structure of the Universe out to high redshifts. Finally, the same survey will supply unique information for a range of other science applications, including a large statistical investigation of galaxy clusters, and the discovery of rare high-redshift AGN that can be used to probe the epoch of reionization as well as produce a rotation measure map across a huge swathe of the sky. The MeerKLASS survey will be a crucial step on the road to using SKA1-MID for cosmological applications, as described in the top priority SKA key science projects

Prospects for cosmic magnification measurements using HI intensity mapping

We investigate the prospects of measuring the cosmic magnification effect by cross-correlating neutral hydrogen intensity mapping (H I IM) maps with background optical galaxies. We forecast the signal-to-noise ratio for H i IM data from SKA1-MID and HIRAX, combined with LSST photometric galaxy samples. We find that, thanks to their different resolutions, SKA1-MID and HIRAX are highly complementary in such an analysis. We predict that SKA1-MID can achieve a detection with a signal-to-noise ratio of ∼15 on a multipole range of ℓ ≲ 200, while HIRAX can reach a signal-to-noise ratio of ∼50 on 200 < ℓ < 2000. We conclude that measurements of the cosmic magnification signal will be possible on a wide redshift range with foreground H I intensity maps up to z ≲ 2, while optimal results are obtained when 0.6 ≲ z ≲ 1.3

MuSK induces in vivo acetylcholine receptor clusters in a ligand-independent manner

Muscle-specific receptor tyrosine kinase (MuSK) is required for the formation of the neuromuscular junction. Using direct gene transfer into single fibers, MuSK was expressed extrasynaptically in innervated rat muscle in vivo to identify its contribution to synapse formation. Spontaneous MuSK kinase activity leads, in the absence of its putative ligand neural agrin, to the appearance of ε-subunit–specific transcripts, the formation of acetylcholine receptor clusters, and acetylcholinesterase aggregates. Expression of kinase-inactive MuSK did not result in the formation of acetylcholine receptor (AChR) clusters, whereas a mutant MuSK lacking the ectodomain did induce AChR clusters. The contribution of endogenous MuSK was excluded by using genetically altered mice, where the kinase domain of the MuSK gene was flanked by loxP sequences and could be deleted upon expression of Cre recombinase. This allowed the conditional inactivation of endogenous MuSK in single muscle fibers and prevented the induction of ectopic AChR clusters. Thus, the kinase activity of MuSK initiates signals that are sufficient to induce the formation of AChR clusters. This process does not require additional determinants located in the ectodomain

HR outsourcing:The impact on HR's strategic role and remaining in-house HR function

Past research on HR outsourcing (HRO) has offered conflicting views about its impact on HR's strategic position. This study highlights the processes by which decisions to outsource HR are made, followed by the processes implemented post such decisions and their effect on the HR function. Using a case study approach and semi-structured interviews (N = 35) within a German subsidiary of a US MNC, we provide a framework of HR processes seeking to achieve standardization in terms of harmonization of HR activities across the subsidiary. The findings reveal that the effects of outsourcing on in-house HR showed a decrease in flexibility of the HR function, a slowdown in processing time of transactional HR as well as a decrease in satisfaction and work intensification for HR managers. Further, it remains questionable as to whether the function of HR was able to enhance its strategic position through outsourcing