Improved Maximum Entropy Analysis with an Extended Search Space

The standard implementation of the Maximum Entropy Method (MEM) follows Bryan and deploys a Singular Value Decomposition (SVD) to limit the dimensionality of the underlying solution space apriori. Here we present arguments based on the shape of the SVD basis functions and numerical evidence from a mock data analysis, which show that the correct Bayesian solution is not in general recovered with this approach. As a remedy we propose to extend the search basis systematically, which will eventually recover the full solution space and the correct solution. In order to adequately approach problems where an exponentially damped kernel is used, we provide an open-source implementation, using the C/C++ language that utilizes high precision arithmetic adjustable at run-time. The LBFGS algorithm is included in the code in order to attack problems without the need to resort to a particular search space restriction.Comment: 18 pages, 6 figures, v3 includes several changes in text and figures, t.b.p. in Journal of Computational Physics, source code at http://www.scicode.org/ExtME

Hunting for neutral, long-lived exotica at the LHC using a missing transverse energy signature

Searches at the Large Hadron Collider (LHC) for neutral, long-lived particles have historically relied on the detection of displaced particles produced by their decay $\textit{within}$ the detector volume. In this paper we study the potential of the complementary signature comprising of the missing transverse energy ($E_T^{miss}$) signal, traditionally used to look for dark matter, e.g., the lightest supersymmetric particle (LSP), to extend the LHC coverage to models with long-lived (LL) particles when they decay $\textit{outside}$ the detector. Using CMS and ATLAS analyses at the 8 TeV LHC, we set an upper limit at the 95% confidence level (CL) on the production cross sections for two specific scenarios: (i) a model with a heavy non-standard model Higgs boson decaying to a LL scalar and (ii) an R-parity violating RPV SUSY model with a LL neutralino. We show that this method can significantly extend the LHC sensitivity to neutral, LL particles with arbitrary large lifetimes and that the limits obtained from a $E_T^{miss}$ signal are comparable to those from displaced particle searches for decay distances above a few meters. Results obtained in this study do not not depend on the specific decay channel of the LL particle and therefore are model-independent in this sense. We provide limits for the whole two-dimensional plane in terms of the mass of the LL particle and the mass of the mediator up to masses of 2 TeV including particular benchmarks studied in the original experimental papers. We have made these limits available in the form of a grid which can be used for the interpretation of various other new physics models.Comment: 28 page

A BIOMECHANICAL ANALYSIS OF THE ESKIMO ROLL IN KAYAKING

The purpose of the present study was to develop a mechanical model of the Eskimo roll in kayaking, in order to eventually develop an Eskimo roll simulator. The Eskimo roll is a very difficult skill to master, as the starting position is a stable position upside down in the water. A land-based simulator would assist the teaching and learning of this skill in a safe environment, but accurate simulation of the skill is difficult. Several trials of the Eskimo roll were filmed while being performed in an indoor pool; using four different camera views. Two cameras were Gen-locked together to film the sagittal and frontal views of the skill from the pool deck. One underwater camera filmed the skill from underneath the kayak, and one overhead camera filmed the skill from the top of the three-meter diving board. This film data was used to input actual values into an equation developed to determine the torques required to right the kayak. A computer program was written to produce the torques from the equation, with estimates for each of the terms. The Eskimo roll was modelled as an irregular cylinder, rotating around the longitudinal axis of the system consisting of the kayak plus kayaker. The kayaker used the paddle to apply torques to the water, to overcome his inertia and move the kayak to the upright position. The inertia of the kayak was due to the mass of the kayak, the mass of the kayaker, the drag force of the water against the system, and the torque due to gravity which had to be overcome during the righting movements. The righting torques were due to the lift forces and drag forces applied by the kayaker, as well as the buoyant force of the water as rotation began. These torques had to be estimated from film data, and from tabled values of moment of inertia, drag, and lift. The peak torques due to lift were estimated to be 150 N.m, while the peak torques due to drag forces were found to be 300 N.m. These estimates will be used to assist in the development of an on-land simulator which can be rolled only by application of torques of this approximate magnitude and direction

Balance Bot - ein unkonventioneller Segway

Im Zuge der Globalisierung ist es immer wichtiger geworden Güter, die um die Welt geschickt werden sollen, in Lagerhallen aufzubewahren. Hierbei ergibt sich jedoch das Problem, dass mehr Platz für die ganzen Waren benötigt wird.Häufig werden zum Einlagern der Waren große Gabelstapler benötigt, welche jedoch viel Platz in Anspruch nehmen und somit weniger Stellfläche für Lagerregale vorhanden ist. Eine Lösung dieses Problems ist ein auf nur zwei Rädern aufrecht fahrender Roboter, welcher nur mit einem Lichtsensor auskommt. Im Folgenden wird dessen Entwicklung und Funktionsweise genauer erläutert, unter der Zielstellung, Lagerungsabläufe mittels des Balance Bots zu optimieren

Lead-free, luminescent perovskite nanocrystals obtained through ambient condition synthesis

Heterovalent substitution of toxic lead is an increasingly popular design strategy to obtain environmentally sustainable variants of the exciting material class of halide perovskites. Perovskite nanocrystals (NCs) obtained through solution-based methods exhibit exceedingly high optical quality. Unfortunately, most of these synthesis routes still require reaction under inert gas and at very high temperatures. Herein we present a novel synthesis routine for lead-free double perovskite NCs. We combine hot injection and ligand-assisted reprecipitation (LARP) methods to achieve a low-temperature and ambient atmosphere-based synthesis for manganese-doped Cs_{2}NaBiCl_{6} NCs. Mn incorporation is critical for the otherwise non-emissive material, with a 9:1 Bi:Mn precursor ratio maximizing the bright orange photoluminescence (PL) and quantum yield (QY). Higher temperatures slightly increased the material's performance, yet NCs synthesized at room temperature were still emissive, highlighting the versatility of the synthetic approach. Furthermore, the NCs show excellent long-term stability in ambient conditions, facilitating additional investigations and energy-related applications

Precision tools and models to narrow in on the 750 GeV diphoton resonance

The hints for a new resonance at 750 GeV from ATLAS and CMS have triggered a significant amount of attention. Since the simplest extensions of the standard model cannot accommodate the observation, many alternatives have been considered to explain the excess. Here we focus on several proposed renormalisable weakly-coupled models and revisit results given in the literature. We point out that physically important subtleties are often missed or neglected. To facilitate the study of the excess we have created a collection of 40 model files, selected from recent literature, for the Mathematica package SARAH. With SARAH one can generate files to perform numerical studies using the tailor-made spectrum generators FlexibleSUSY and SPheno. These have been extended to automatically include crucial higher order corrections to the diphoton and digluon decay rates for both CP-even and CP-odd scalars. Additionally, we have extended the UFO and CalcHep interfaces of SARAH, to pass the precise information about the effective vertices from the spectrum generator to a Monte-Carlo tool. Finally, as an example to demonstrate the power of the entire setup, we present a new supersymmetric model that accommodates the diphoton excess, explicitly demonstrating how a large width can be obtained. We explicitly show several steps in detail to elucidate the use of these public tools in the precision study of this model.Comment: 184 pages, 24 figures; model files available at http://sarah.hepforge.org/Diphoton_Models.tar.gz; v2: added a few clarifications and reference

Bridging separate communities : the aspirations and experiences of minority ethnic RE teachers in England

This article takes as its starting point concerns about community separation that arose in 2001, following outbreaks of violence in English urban centres, and again in 2014, following the so-called ‘Trojan Horse’ case. Despite a series of reports which have highlighted the need to address ‘separation’, promote ‘meaningful contact’ between those who differ in terms of ethnicity and worldview and identify teachers of religious education (RE) as key players, researchers have paid no attention to teachers of RE from minority ethnic and religious backgrounds. The article draws on a qualitative study of teachers from Hindu, Muslim and Sikh backgrounds to explore their concerns about pupils’ perceptions of separation and the ways in which they attempted to address these in white majority and Muslim majority schools. Communication research and studies based on social capital theory are used to suggest that the teachers used ‘bonding’ and ‘bridging’ strategies as means of encouraging pupils to explore their perceptions of separation, engage in a mediated form of meaningful contact with ‘the Other’ and expand their thinking. The conclusion calls for further research in to the strategies reported and for policy makers to support the recruitment, training and career development of minority ethnic teachers of RE

Biological activity of a genetically modified BMP-2 variant with inhibitory activity

<p>Abstract</p> <p>Background</p> <p>Alterations of the binding epitopes of bone morphogenetic protein-2 (BMP-2) lead to a modified interaction with the ectodomains of BMP receptors. In the present study the biological effect of a BMP-2 double mutant with antagonistic activity was evaluated in vivo.</p> <p>Methods</p> <p>Equine-derived collagenous carriers were loaded with recombinant human BMP-2 (rhBMP-2) in a well-known dose to provide an osteoinductive stimulus. The study was performed in a split animal design: carriers only coupled with rhBMP-2 (control) were implanted into prepared cavities of lower limb muscle of rats, specimens coupled with rhBMP-2 as well as BMP-2 double mutant were placed into the opposite limb in the same way. After 28 days the carriers were explanted, measured radiographically and characterized histologically.</p> <p>Results</p> <p>As expected, the BMP-2 loaded implants showed a typical heterotopic bone formation. The specimens coupled with both proteins showed a significant decreased bone formation in a dose dependent manner.</p> <p>Conclusion</p> <p>The antagonistic effect of a specific BMP-2 double mutant could be demonstrated in vivo. The dose dependent influence on heterotopic bone formation by preventing rhBMP-2 induced osteoinduction suggests a competitive receptor antagonism.</p

Invertible residual networks in the context of regularization theory for linear inverse problems

Learned inverse problem solvers exhibit remarkable performance in applications like image reconstruction tasks. These data-driven reconstruction methods often follow a two-step scheme. First, one trains the often neural network-based reconstruction scheme via a dataset. Second, one applies the scheme to new measurements to obtain reconstructions. We follow these steps but parameterize the reconstruction scheme with invertible residual networks (iResNets). We demonstrate that the invertibility enables investigating the influence of the training and architecture choices on the resulting reconstruction scheme. For example, assuming local approximation properties of the network, we show that these schemes become convergent regularizations. In addition, the investigations reveal a formal link to the linear regularization theory of linear inverse problems and provide a nonlinear spectral regularization for particular architecture classes. On the numerical side, we investigate the local approximation property of selected trained architectures and present a series of experiments on the MNIST dataset that underpin and extend our theoretical findings

A silent H-bond can be mutationally activated for high-affinity interaction of BMP-2 and activin type IIB receptor

BACKGROUND: Bone morphogenetic proteins (BMPs) are key regulators in the embryonic development and postnatal tissue homeostasis in all animals. Loss of function or dysregulation of BMPs results in severe diseases or even lethality. Like transforming growth factors β (TGF-βs), activins, growth and differentiation factors (GDFs) and other members of the TGF-β superfamily, BMPs signal by assembling two types of serine/threonine-kinase receptor chains to form a hetero-oligomeric ligand-receptor complex. BMP ligand receptor interaction is highly promiscuous, i.e. BMPs bind more than one receptor of each subtype, and a receptor bind various ligands. The activin type II receptors are of particular interest, since they bind a large number of diverse ligands. In addition they act as high-affinity receptors for activins but are also low-affinity receptors for BMPs. ActR-II and ActR-IIB therefore represent an interesting example how affinity and specificity might be generated in a promiscuous background. RESULTS: Here we present the high-resolution structures of the ternary complexes of wildtype and a variant BMP-2 bound to its high-affinity type I receptor BMPR-IA and its low-affinity type II receptor ActR-IIB and compare them with the known structures of binary and ternary ligand-receptor complexes of BMP-2. In contrast to activin or TGF-β3 no changes in the dimer architecture of the BMP-2 ligand occur upon complex formation. Functional analysis of the ActR-IIB binding epitope shows that hydrophobic interactions dominate in low-affinity binding of BMPs; polar interactions contribute only little to binding affinity. However, a conserved H-bond in the center of the type II ligand-receptor interface, which does not contribute to binding in the BMP-2 – ActR-IIB interaction can be mutationally activated resulting in a BMP-2 variant with high-affinity for ActR-IIB. Further mutagenesis studies were performed to elucidate the binding mechanism allowing us to construct BMP-2 variants with defined type II receptor binding properties. CONCLUSION: Binding specificity of BMP-2 for its three type II receptors BMPR-II, Act-RII and ActR-IIB is encoded on single amino acid level. Exchange of only one or two residues results in BMP-2 variants with a dramatically altered type II receptor specificity profile, possibly allowing construction of BMP-2 variants that address a single type II receptor. The structure-/function studies presented here revealed a new mechanism, in which the energy contribution of a conserved H-bond is modulated by surrounding intramolecular interactions to achieve a switch between low- and high-affinity binding