How galactic environment regulates star formation

In a new simple model I reconcile two contradictory views on the factors that determine the rate at which molecular clouds form stars-internal structure versus external, environmental influences-providing a unified picture for the regulation of star formation in galaxies. In the presence of external pressure, the pressure gradient set up within a self-gravitating turbulent (isothermal) cloud leads to a non-uniform density distribution. Thus the local environment of a cloud influences its internal structure. In the simple equilibrium model, the fraction of gas at high density in the cloud interior is determined simply by the cloud surface density, which is itself inherited from the pressure in the immediate surroundings. This idea is tested using measurements of the properties of local clouds, which are found to show remarkable agreement with the simple equilibrium model. The model also naturally predicts the star formation relation observed on cloud scales and at the same time provides a mapping between this relation and the closer-to-linear molecular star formation relation measured on larger scales in galaxies. The key is that pressure regulates not only the molecular content of the ISM but also the cloud surface density. I provide a straightforward prescription for the pressure regulation of star formation that can be directly implemented in numerical models. Predictions for the dense gas fraction and star formation efficiency measured on large-scales within galaxies are also presented, establishing the basis for a new picture of star formation regulated by galactic environment

Optical Music Recognition with Convolutional Sequence-to-Sequence Models

Optical Music Recognition (OMR) is an important technology within Music Information Retrieval. Deep learning models show promising results on OMR tasks, but symbol-level annotated data sets of sufficient size to train such models are not available and difficult to develop. We present a deep learning architecture called a Convolutional Sequence-to-Sequence model to both move towards an end-to-end trainable OMR pipeline, and apply a learning process that trains on full sentences of sheet music instead of individually labeled symbols. The model is trained and evaluated on a human generated data set, with various image augmentations based on real-world scenarios. This data set is the first publicly available set in OMR research with sufficient size to train and evaluate deep learning models. With the introduced augmentations a pitch recognition accuracy of 81% and a duration accuracy of 94% is achieved, resulting in a note level accuracy of 80%. Finally, the model is compared to commercially available methods, showing a large improvements over these applications.Comment: ISMIR 201

Riskfree Rate Dynamics: Information, Trading and State Space Modeling

Lucas, A. [Promotor]Koopman, S.J. [Promotor]Menkveld, A.J. [Copromotor

Strategies of Climate Change Denial: The case of Thierry Baudet

This paper discusses different strategies of climate change denial and focusses on the specific case of Dutch politician Thierry Baudet. Much of the literature concerning climate change denial focusses on Anglo-American cases, therefore more research non-English speaking countries is necessary. The theoretical framework describes the state of the art concerning climate change denialism and its links to occurring phenomena in Western societies and politics such as post-truth and populism. Afterwards, by conducting a deductive analysis of  Thierry Baudet’s climate denialism in the Netherlands, a more thorough understanding of the different strategies proposed by Stefan Rahmstorf  and Engels et al. is reached. Although all four categories are detected in Baudet’s denialism, consensus denial seems to be the most prevalent. The analysis of his usage of the notion of a climate apocalypse, combined with the analysis of his specific focus on consensus denial, broadens the understanding of how climate change denial can relate to populism.&nbsp

Dihedral Angle Measurements for Structure Determination by Biomolecular Solid-State NMR Spectroscopy

In structural studies of immobilized, aggregated and self-assembled biomolecules, solid-state NMR (ssNMR) spectroscopy can provide valuable high-resolution structural information. Among the structural restraints provided by magic angle spinning (MAS) ssNMR the canonical focus is on inter-atomic distance measurements. In the current review, we examine the utility of ssNMR measurements of angular constraints, as a complement to distance-based structure determination. The focus is on direct measurements of angular restraints via the judicious recoupling of multiple anisotropic ssNMR parameters, such as dipolar couplings and chemical shift anisotropies. Recent applications are highlighted, with a focus on studies of nanocrystalline polypeptides, aggregated peptides and proteins, receptor-substrate interactions, and small molecule interactions with amyloid protein fibrils. The review also examines considerations of when and where ssNMR torsion angle experiments are (most) effective, and discusses challenges and opportunities for future applications

A mass-dependent slope of the galaxy size-mass relation out to z~3: further evidence for a direct relation between median galaxy size and median halo mass

We reassess the galaxy size-mass relation out to z~3 using a new definition of size and a sample of >29,000 galaxies from the 3D-HST, CANDELS, and COSMOS-DASH surveys. Instead of the half-light radius r_50 we use r_80, the radius containing 80% of the stellar light. We find that the r_80 -- M_star relation has the form of a broken power law, with a clear change of slope at a pivot mass M_p. Below the pivot mass the relation is shallow (r_80 \propto M_star^0.15) and above it it is steep (r_80\propto M_star^0.6). The pivot mass increases with redshift, from log(M_p/M_sun)~ 10.2 at z=0.4 to log(M_p/M_sun)~ 10.9 at z=1.7-3. We compare these r_80-M_star relations to the M_halo-M_star relations derived from galaxy-galaxy lensing, clustering analyses, and abundance matching techniques. Remarkably, the pivot stellar masses of both relations are consistent with each other at all redshifts, and the slopes are very similar both above and below the pivot when assuming M_halo \propto r_80^3. The implied scaling factor to relate galaxy size to halo size is r_80 / R_vir = 0.047, independent of stellar mass and redshift.From redshift 0 to 1.5, the pivot mass also coincides with the mass where the fraction of star-forming galaxies is 50%, suggesting that the pivot mass reflects a transition from dissipational to dissipationless galaxy growth. Finally, our results imply that the scatter in the stellar-to-halo mass ratio is relatively small for massive halos (~0.2 dex for M_halo>10^12.5 M_sun).Comment: Accepted in ApJL. Please also see complementary paper Miller et al. 201

Confirmation of the compactness of a z=1.91 quiescent galaxy with Hubble Space Telescope's Wide Field Camera 3

We present very deep Wide Field Camera 3 (WFC3) photometry of a massive, compact galaxy located in the Hubble Ultra Deep Field. This quiescent galaxy has a spectroscopic redshift z=1.91 and has been identified as an extremely compact galaxy by Daddi et al. 2005. We use new H-F160W imaging data obtained with Hubble Space Telescope/WFC3 to measure the deconvolved surface brightness profile to H = 28 mag arcsec**-2. We find that the surface brightness profile is well approximated by an n=3.7 Sersic profile. Our deconvolved profile is constructed by a new technique which corrects the best-fit Sersic profile with the residual of the fit to the observed image. This allows for galaxy profiles which deviate from a Sersic profile. We determine the effective radius of this galaxy: r_e=0.42 +- 0.14 kpc in the observed H-F160W-band. We show that this result is robust to deviations from the Sersic model used in the fit. We test the sensitivity of our analysis to faint "wings" in the profile using simulated galaxy images consisting of a bright compact component and a faint extended component. We find that due to the combination of the WFC3 imaging depth and our method's sensitivity to extended faint emission we can accurately trace the intrinsic surface brightness profile, and that we can therefore confidently rule out the existence of a faint extended envelope around the observed galaxy down to our surface brightness limit. These results confirm that the galaxy lies a factor of 10 off from the local mass-size relation.Comment: 6 pages, 4 figures. Accepted for publication in ApJ Letters

Customer flow, intermediaries, and the discovery of the equilibrium riskfree rate

Macro announcements change the equilibrium riskfree rate. We find that treasury prices reflect part of the impact instantaneously, but intermediaries rely on their customer order flow in the 15 minutes after the announcement to discover the full impact. We show that this customer flow informativeness is strongest at times when analyst forecasts of macro variables are highly dispersed. We study 30 year treasury futures to identify the customer flow. We further show that intermediaries appear to benefit from privately recognizing informed customer flow, as, in the cross-section, their own-account trade profitability correlates with access to customer orders, controlling for volatility, competition, and the announcement surprise. These results suggest that intermediaries learn about equilibrium riskfree rates through customer orders

Microparticle assembly pathways on lipid membranes

Understanding interactions between microparticles and lipid membranes is of increasing importance, especially for unraveling the influence of microplastics on our health and environment. Here, we study how a short-ranged adhesive force between microparticles and model lipid membranes causes membrane-mediated particle assembly. Using confocal microscopy, we observe the initial particle attachment to the membrane, then particle wrapping, and in rare cases spontaneous membrane tubulation. In the attached state, we measure that the particle mobility decreases by 26%. If multiple particles adhere to the same vesicle, their initial single-particle state determines their interactions and subsequent assembly pathways: 1) attached particles only aggregate when small adhesive vesicles are present in solution, 2) wrapped particles reversibly attract one another by membrane deformation, and 3) a combination of wrapped and attached particles form membrane-mediated dimers, which further assemble into a variety of complex structures. The experimental observation of distinct assembly pathways induced only by a short ranged membrane-particle adhesion, shows that a cellular cytoskeleton or other active components are not required for microparticle aggregation. We suggest that this membrane-mediated microparticle aggregation is a reason behind reported long retention times of polymer microparticles in organisms.Comment: 20 pages, 11 figures (including supporting material

The development of the Ghana sugar industry1960-70: An exercise in ex-post evaluation

The present report contains very little in the way of factual information about the two projects; neither does it attempt to present a detailed analysis of the many different factors which caused the projects to deviate from the original project plans. It tries to explain what we had in mind when undertaking this study and how our originat ideas had to be adjusted after confrontation with the actual project histories (Sections 1 and 2). How far all this is relevant, either to project analysis in developing countries, in general, or to future project work in Ghana, will be discussed in the final part of this report (Section 3)