State preparation and dynamics of ultracold atoms in higher lattice orbitals

We report on the realization of a multi-orbital system with ultracold atoms in the excited bands of a 3D optical lattice by selectively controlling the band population along a given lattice direction. The lifetime of the atoms in the excited band is found to be considerably longer (10-100 times) than the characteristic time scale for inter-site tunneling, thus opening the path for orbital selective many-body physics with ultracold atoms. Upon exciting the atoms from an initial lowest band Mott insulating state to higher lying bands, we observe the dynamical emergence of coherence in 1D (and 2D), compatible with Bose-Einstein condensation to a non-zero momentum state.Comment: 4 pages, 4 figure

Innovation Performance of Family and Founder Firms: Empirical Evidence from German Listed Companies

Based on the agency perspective and the resource-based view of the firm, this study explores the impact of lone founder and family influence on innovation in-put and innovation output. By separating the lone founder and family effect into ownership, management, and governance influence dimensions, we analyze a pan-el data set of 165 German listed companies from 2013 through 2017. We first in-vestigate R&D intensity in lone founder and family firms versus other firms by using investments in research and development as a measure for innovation input. Secondly, we apply a negative binomial regression model to analyze R&D produc-tivity within the three types of firms by proxying innovation output with the filed number of granted patents within a certain year. According to the results, we mainly find that founder firms superiorly invest in innovation and strengthen their competitive position in the market through their entrepreneurial orientation. Family firms, on the other hand, might weaken future growth potential as they invest less in R&D and are not able to convert this lower input in superior innovation output. Keywords: Lone founder firms; Family firms; Innovation performance; R&D intensity; R&D productivity.Based on the agency perspective and the resource-based view of the firm, this study explores the impact of lone founder and family influence on innovation in-put and innovation output. By separating the lone founder and family effect into ownership, management, and governance influence dimensions, we analyze a pan-el data set of 165 German listed companies from 2013 through 2017. We first in-vestigate R&D intensity in lone founder and family firms versus other firms by using investments in research and development as a measure for innovation input. Secondly, we apply a negative binomial regression model to analyze R&D produc-tivity within the three types of firms by proxying innovation output with the filed number of granted patents within a certain year. According to the results, we mainly find that founder firms superiorly invest in innovation and strengthen their competitive position in the market through their entrepreneurial orientation. Family firms, on the other hand, might weaken future growth potential as they invest less in R&D and are not able to convert this lower input in superior innovation output. Keywords: Lone founder firms; Family firms; Innovation performance; R&D intensity; R&D productivity

The core helium flash revisited III. From Pop I to Pop III stars

Degenerate ignition of helium in low-mass stars at the end of the red giant branch phase leads to dynamic convection in their helium cores. One-dimensional (1D) stellar modeling of this intrinsically multi-dimensional dynamic event is likely to be inadequate. Previous hydrodynamic simulations imply that the single convection zone in the helium core of metal-rich Pop I stars grows during the flash on a dynamic timescale. This may lead to hydrogen injection into the core, and a double convection zone structure as known from one-dimensional core helium flash simulations of low-mass Pop III stars. We perform hydrodynamic simulations of the core helium flash in two and three dimensions to better constrain the nature of these events. To this end we study the hydrodynamics of convection within the helium cores of a 1.25 \Msun metal-rich Pop I star (Z=0.02), and a 0.85 \Msun metal-free Pop III star (Z=0) near the peak of the flash. These models possess single and double convection zones, respectively. We use 1D stellar models of the core helium flash computed with state-of-the-art stellar evolution codes as initial models for our multidimensional hydrodynamic study, and simulate the evolution of these models with the Riemann solver based hydrodynamics code Herakles which integrates the Euler equations coupled with source terms corresponding to gravity and nuclear burning. The hydrodynamic simulation of the Pop I model involving a single convection zone covers 27 hours of stellar evolution, while the first hydrodynamic simulations of a double convection zone, in the Pop III model, span 1.8 hours of stellar life. We find differences between the predictions of mixing length theory and our hydrodynamic simulations. The simulation of the single convection zone in the Pop I model shows a strong growth of the size of the convection zone due to turbulent entrainment. Hence we predict that for the Pop I model a hydrogen injection phase (i.e. hydrogen injection into the helium core) will commence after about 23 days, which should eventually lead to a double convection zone structure known from 1D stellar modeling of low-mass Pop III stars. Our two and three-dimensional hydrodynamic simulations of the double (Pop III) convection zone model show that the velocity field in the convection zones is different from that predicted by stellar evolutionary calculations. The simulations suggest that the double convection zone decays quickly, the flow eventually being dominated by internal gravity waves.Comment: 16 pages, 18 figures, submitted to Aa

Fast, accurate, and transferable many-body interatomic potentials by symbolic regression

The length and time scales of atomistic simulations are limited by the computational cost of the methods used to predict material properties. In recent years there has been great progress in the use of machine learning algorithms to develop fast and accurate interatomic potential models, but it remains a challenge to develop models that generalize well and are fast enough to be used at extreme time and length scales. To address this challenge, we have developed a machine learning algorithm based on symbolic regression in the form of genetic programming that is capable of discovering accurate, computationally efficient manybody potential models. The key to our approach is to explore a hypothesis space of models based on fundamental physical principles and select models within this hypothesis space based on their accuracy, speed, and simplicity. The focus on simplicity reduces the risk of overfitting the training data and increases the chances of discovering a model that generalizes well. Our algorithm was validated by rediscovering an exact Lennard-Jones potential and a Sutton Chen embedded atom method potential from training data generated using these models. By using training data generated from density functional theory calculations, we found potential models for elemental copper that are simple, as fast as embedded atom models, and capable of accurately predicting properties outside of their training set. Our approach requires relatively small sets of training data, making it possible to generate training data using highly accurate methods at a reasonable computational cost. We present our approach, the forms of the discovered models, and assessments of their transferability, accuracy and speed

Polaron Coherence as Origin of the Pseudogap Phase in High Temperature Superconducting Cuprates

Within a two component approach to high Tc copper oxides including polaronic couplings, we identify the pseudogap phase as the onset of polaron ordering. This ordering persists in the superconducting phase. A huge isotope effect on the pseudogap onset temperature is predicted and in agreement with experimental data. The anomalous temperature dependence of the mean square copper oxygen ion displacement observed above, at and below Tc stems from an s-wave superconducting component of the order parameter, whereas a pure d-wave order parameter alone can be excluded.Comment: 7 pages, 2 figure

Spatio-temporal modelling of malaria incidence for evaluation of public health policy interventions in Ghana, West Africa

Malaria is a major challenge to both the public health and the socio-economic development of Ghana. Major factors which account for this situation include poor environmental conditions and the lack of prevention services. In spite of the numerous intervention measures, the disease continues to be the most prevalent health problem in the country. The risk assessment reports for Ghana were based on household surveys which provide inadequate data for accurate analysis of incidence cases. This poses a serious threat to planning and management for the health care delivery system in Ghana. Malaria transmission varies with geographical location and time (or season). Spatio-temporal modelling coupled with adequate data has shown to better define the public burden of the disease, providing risk maps to describe the incidence variation in space and time and also identifying high risk areas for health policy implementation. Geostatistics contributes immensely to the prediction of the random processes distributed in space or time in epidemiological studies. In this study, we conduct spatial statistical analysis of malaria incidence to produce evidence-based monthly maps of Ghana illustrating the patterns of malaria risk over space and time. This is achieved using monthly morbidity cases reported on the disease from public health facilities at district level and population data over the period 1998-2010 to compute the malaria incidence rates, being the number of reported cases per unit resident population of 10,000. Lognormal ordinary kriging is used to model the spatial and temporal correlations, and then back-transformed to estimate the monthly malaria risk at local level. The space-time experimental variogram describing the correlations structure is modelled with nested spherical and exponential-cosine functions coupled with nugget effect. The modelled variogram indicate both short and long spatial and temporal dependence of the malaria incidence rates at local level with the temporal component exhibiting an increasing seasonal pattern of period of 12 months. The results also indicate varied spatial distribution of malaria incidence across the country, the highest risk being observed in the northern most and several locations in central and western parts of the country, and lowest in some areas in the north and south along the coast. This statistical-based model approach of malaria epidemiology will be useful for short-term prediction and also provide a basis for resource allocation for the disease’s control in the country

Melting Down Protein Stability: PAPS Synthase 2 in Patients and in a Cellular Environment

Within the crowded and complex environment of the cell, a protein experiences stabilizing excluded-volume effects and destabilizing quinary interactions with other proteins. Which of these prevail, needs to be determined on a case-by-case basis. PAPS synthases are dimeric and bifunctional enzymes, providing activated sulfate in the form of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) for sulfation reactions. The human PAPS synthases PAPSS1 and PAPSS2 differ significantly in their protein stability as PAPSS2 is a naturally fragile protein. PAPS synthases bind a series of nucleotide ligands and some of them markedly stabilize these proteins. PAPS synthases are of biomedical relevance as destabilizing point mutations give rise to several pathologies. Genetic defects in PAPSS2 have been linked to bone and cartilage malformations as well as a steroid sulfation defect. All this makes PAPS synthases ideal to study protein unfolding, ligand binding, and the stabilizing and destabilizing factors in their cellular environment. This review provides an overview on current concepts of protein folding and stability and links this with our current understanding of the different disease mechanisms of PAPSS2-related pathologies with perspectives for future research and application

Clinical epidemiology, diagnosis and treatment of visceral leishmaniasis in the Pokot endemic area of Uganda and Kenya.

Between 2000 and 2010, Médecins Sans Frontières diagnosed and treated 4,831 patients with visceral leishmaniasis (VL) in the Pokot region straddling the border between Uganda and Kenya. A retrospective analysis of routinely collected clinical data showed no marked seasonal or annual fluctuations. Males between 5 and 14 years of age were the most affected group. Marked splenomegaly and anemia were striking features. An rK39 antigen-based rapid diagnostic test was evaluated and found sufficiently accurate to replace the direct agglutination test and spleen aspiration as the first-line diagnostic procedure. The case-fatality rate with sodium stibogluconate as first-line treatment was low. The VL relapses were rare and often diagnosed more than 6 months post-treatment. Post-kala-azar dermal leishmaniasis was rare but likely to be underdiagnosed. The epidemiological and clinical features of VL in the Pokot area differed markedly from VL in Sudan, the main endemic focus in Africa

Analysis and interpretation of high energy cosmic rays measured on Spacelab-2

Under the contract with NASA's Marshall Space Flight Center (NAS8-32828) the University of Chicago designed, built and delivered the CRN instrument for flight in the Spacelab-2 configuration. The instrument was flown from July 29 to August 5, 1985 on the Space Shuttle Challenger. The performance of our experiment was entirely successful and we reached our scientific goals. The contract included funds for the first year of data analysis. Further data analysis was carried out under the grant NAGW-1311 which ran from January 1, 1988 through December 31, 1990, and on which we report. The final products of this grant are the published scientific papers with the results from the experiment. We attach copies of the papers that have been published to date, and which we consider the most important part of this report. However, in order to put them into context we give a brief account of the project as a whole for which the grant covered the final phase