Dynamical Mass Ejection from Binary Neutron Star Mergers

We present fully general-relativistic simulations of binary neutron star mergers with a temperature and composition dependent nuclear equation of state. We study the dynamical mass ejection from both quasi-circular and dynamical-capture eccentric mergers. We systematically vary the level of our treatment of the microphysics to isolate the effects of neutrino cooling and heating and we compute the nucleosynthetic yields of the ejecta. We find that eccentric binaries can eject significantly more material than quasi-circular binaries and generate bright infrared and radio emission. In all our simulations the outflow is composed of a combination of tidally- and shock-driven ejecta, mostly distributed over a broad $\sim 60^\circ$ angle from the orbital plane, and, to a lesser extent, by thermally driven winds at high latitudes. Ejecta from eccentric mergers are typically more neutron rich than those of quasi-circular mergers. We find neutrino cooling and heating to affect, quantitatively and qualitatively, composition, morphology, and total mass of the outflows. This is also reflected in the infrared and radio signatures of the binary. The final nucleosynthetic yields of the ejecta are robust and insensitive to input physics or merger type in the regions of the second and third r-process peaks. The yields for elements on the first peak vary between our simulations, but none of our models is able to explain the Solar abundances of first-peak elements without invoking additional first-peak contributions from either neutrino and viscously-driven winds operating on longer timescales after the mergers, or from core-collapse supernovae.Comment: 19 pages, 10 figures. We corrected a problem in the formulation of the neutrino heating scheme and re-ran all of the affected models. The main conclusions are unchanged. This version also contains one more figure and a number of improvements on the tex

Druckloses Sintern von Cu für Hochleistungsanwendungen

Die vorliegende Arbeit befasst sich mit den Grundlagen zum drucklosen Sintern von Kupferpulver. Dazu wurden Grünkörper mit unterschiedlicher Packungsdichte über ein Suspensionsgießverfahren hergestellt und drucklos gesintert. Die Gründichte wurde über die Suspensionseigenschaften variiert und die Einflüsse der Prozessparameter Temperatur und Haltezeit auf die mikrostrukturelle Entwicklung untersucht. Die neu eingeführte Korngrenzen-Hit-Rate ermöglicht die quantitative und qualitative Bewertung gesinterter Mikrostrukturen. Daraus können die Gründe für eine begrenzte Verdichtung mittels der metallographischen Gefügeanalyse herausgearbeitet werden. Aus diesen Ergebnissen lassen sich die Grenzen der konventionellen Sinterung ableiten. Aus den Erkenntnissen durch die Gefügeanalyse konventionell gesinterter Cu-Proben werden neuartige mehrstufige Sinterprofile abgeleitet, die die Entwicklung der Mikrostruktur gezielt kontrollieren und dadurch höhere Sinterdichten in kürzeren Prozesszeiten ermöglichen. Des Weiteren wird die Wärmeleitfähigkeit von gesintertem Cu in Abhängigkeit der Porosität und der Verunreinigungen des Ausgangsmaterials analytisch, numerisch und experimentell untersucht. Aus den Ergebnissen dieser Untersuchungen wird ein Modell zur Vorhersage der Leitfähigkeit von gesintertem Cu in Abhängigkeit der Porosität und des Verunreinigungsgrads hergeleitet. Die systematische Sinteroptimierung sowie die Erkenntnisse zu den Zusammenhängen zwischen Mikrostruktur und Leitfähigkeit können auf sinterbasierte Fertigungsverfahren wie z.B. Binder Jetting, Fused Filament Fabrication und Metallpulverspritzgießen übertragen werden. Dadurch wird die pulverbasierte Fertigung von komplexen und hochleitfähigen Kupfer-Bauteilen für Hochleistungsanwendungen im Bereich der Elektronik ermöglicht.This dissertation deals with the fundamentals of pressureless sintering of copper powder. For this purpose, green bodies with different packing densities were produced by a suspension based process route and pressure-less sintered afterwards. In addition to the variation of the green density via the suspension properties, the influences of the process parameters temperature and holding time on the microstructural development are investigated. The newly introduced parameter Grain Boundary Hit Rate allows the quantitative and qualitative evaluation of sintered microstructures. According to this microstructural analysis the reasons for limited densification can be determined and the general limits of conventional sintering are derived from these results. Based on the findings from the microstructural analysis of conventionally sintered Cu samples, novel types of multistep sintering profiles are derived to control the microstructural evolution to enable higher sintering densities in shorter process times. In addition, the thermal conductivity of sintered Cu is investigated analytically, numerically and experimentally as a function of the porosity and impurities of the starting material. From the results of these investigations, a model for predicting the conductivity of sintered Cu is derived. The systematic sintering optimization can be transferred to sintering-based manufacturing processes such as Binder Jetting, Fused Filament Fabrication, and Metal Injection Molding to facilitate the fabrication of complex and highly conductive Cu parts for high-performance applications in the field of electronics

Limited utility of qPCR-based detection of tumor-specific circulating mRNAs in whole blood from clear cell renal cell carcinoma patients

BACKGROUND: RNA sequencing data is providing abundant information about the levels of dysregulation of genes in various tumors. These data, as well as data based on older microarray technologies have enabled the identification of many genes which are upregulated in clear cell renal cell carcinoma (ccRCC) compared to matched normal tissue. Here we use RNA sequencing data in order to construct a panel of highly overexpressed genes in ccRCC so as to evaluate their RNA levels in whole blood and determine any diagnostic potential of these levels for renal cell carcinoma patients. METHODS: A bioinformatics analysis with Python was performed using TCGA, GEO and other databases to identify genes which are upregulated in ccRCC while being absent in the blood of healthy individuals. Quantitative Real Time PCR (RT-qPCR) was subsequently used to measure the levels of candidate genes in whole blood (PAX gene) of 16 ccRCC patients versus 11 healthy individuals. PCR results were processed in qBase and GraphPadPrism and statistics was done with Mann-Whitney U test. RESULTS: While most analyzed genes were either undetectable or did not show any dysregulated expression, two genes, CDK18 and CCND1, were paradoxically downregulated in the blood of ccRCC patients compared to healthy controls. Furthermore, LOX showed a tendency towards upregulation in metastatic ccRCC samples compared to non-metastatic. CONCLUSIONS: This analysis illustrates the difficulty of detecting tumor regulated genes in blood and the possible influence of interference from expression in blood cells even for genes conditionally absent in normal blood. Testing in plasma samples indicated that tumor specific mRNAs were not detectable. While CDK18, CCND1 and LOX mRNAs might carry biomarker potential, this would require validation in an independent, larger patient cohort

R-process Nucleosynthesis from Three-Dimensional Magnetorotational Core-Collapse Supernovae

We investigate r-process nucleosynthesis in three-dimensional (3D) general-relativistic magnetohydrodynamic simulations of rapidly rotating strongly magnetized core collapse. The simulations include a microphysical finite-temperature equation of state and a leakage scheme that captures the overall energetics and lepton number exchange due to postbounce neutrino emission and absorption. We track the composition of the ejected material using the nuclear reaction network SkyNet. Our results show that the 3D dynamics of magnetorotational core-collapse supernovae (CCSN) are important for their nucleosynthetic signature. We find that production of r-process material beyond the second peak is reduced by a factor of 100 when the magnetorotational jets produced by the rapidly rotating core undergo a kink instability. Our results indicate that 3D magnetorotationally powered CCSNe are a robust r-process source only if they are obtained by the collapse of cores with unrealistically large precollapse magnetic fields of order $10^{13}$G. Additionally, a comparison simulation that we restrict to axisymmetry, results in overly optimistic r-process production for lower magnetic field strengths.Comment: 10 pages, 9 figures, 2 tables. submitted to Ap

Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disk ejecta from neutron star mergers

We investigate the nucleosynthesis of heavy elements in the winds ejected by accretion disks formed in neutron star mergers. We compute the element formation in disk outflows from hypermassive neutron star (HMNS) remnants of variable lifetime, including the effect of angular momentum transport in the disk evolution. We employ long-term axisymmetric hydrodynamic disk simulations to model the ejecta, and compute r-process nucleosynthesis with tracer particles using a nuclear reaction network containing $\sim 8000$ species. We find that the previously known strong correlation between HMNS lifetime, ejected mass, and average electron fraction in the outflow is directly related to the amount of neutrino irradiation on the disk, which dominates mass ejection at early times in the form of a neutrino-driven wind. Production of lanthanides and actinides saturates at short HMNS lifetimes ($\lesssim 10$ ms), with additional ejecta contributing to a blue optical kilonova component for longer-lived HMNSs. We find good agreement between the abundances from the disk outflow alone and the solar r-process distribution only for short HMNS lifetimes ($\lesssim 10$ ms). For longer lifetimes, the rare-earth and third r-process peaks are significantly under-produced compared to the solar pattern, requiring additional contributions from the dynamical ejecta. The nucleosynthesis signature from a spinning black hole (BH) can only overlap with that from a HMNS of moderate lifetime ($\lesssim 60$ ms). Finally, we show that angular momentum transport not only contributes with a late-time outflow component, but that it also enhances the neutrino-driven component by moving material to shallower regions of the gravitational potential, in addition to providing additional heating.Comment: 18 pages, 11 figures, published version with small change

Influence of drought on foliar water uptake capacity of temperate tree species

Foliar water uptake (FWU) has been investigated in an increasing number of species from a variety of areas but has remained largely understudied in deciduous, temperate tree species from non- foggy regions. As leaf wetting events frequently occur in temperate regions, FWU might be more important than previously thought and should be investigated. As climate change progresses, the number of drought events is expected to increase, basically resulting in a decreasing number of leaf wetting events, which might make FWU a seemingly less important mechanism. However, the impact of drought on FWU might not be that unidirectional because drought will also cause a more negative tree water potential, which is expected to result in more FWU. It yet remains unclear whether drought results in a general increase or decrease in the amount of water absorbed by leaves. The main objectives of this study are, therefore: (i) to assess FWU- capacity in nine widely distributed key tree species from temperate regions, and (ii) to investigate the e ff ect of drought on FWU in these species. Based on measurements of leaf and soil water potential and FWU- capacity, the e ff ect of drought on FWU in temperate tree species was assessed. Eight out of nine temperate tree species were able to absorb water via their leaves. The amount of water absorbed by leaves and the response of this plant trait to drought were species- dependent, with a general increase in the amount of water absorbed as leaf water potential decreased. This relationship was less pronounced when using soil water potential as an independent variable. We were able to classify species according to their response in FWU to drought at the leaf level, but this classification changed when using drought at the soil level, and was driven by iso- and anisohydric behavior. FWU hence occurred in several key tree species from temperate regions, be it with some variability, which potentially allows these species to partly reduce the e ff ects of drought stress. We recommend including this mechanism in future research regarding plant- water relations and to investigate the impact of di ff erent pathways used for FWU

Renewables grabbing : Land and resource appropriations in the global energy transition

The global land rush intersects with the global energy transition and the emergence of new renewable energy frontiers demanding vast amounts of land and other resources. This chapter provides an overview of the processes of land and resource grabbing associated with renewable energies and discusses the environmental injustices emerging in the global energy transition. After a brief examination of the multiple drivers of the global energy transition and their specific implications for resource and land grabbing, a sectoral perspective on the four major renewable energy sources describes the emergence of new energy-land frontiers: biofuels, hydropower dams, mega solar power, and wind parks. For each frontier, the chapter points to key resources required and appropriated and discusses the related environmental conflicts and justice concerns that are arising. Close examination of these conflicts provides important lessons for moving toward a socially just energy transition

Low mass binary neutron star mergers : gravitational waves and neutrino emission

Neutron star mergers are among the most promising sources of gravitational waves for advanced ground-based detectors. These mergers are also expected to power bright electromagnetic signals, in the form of short gamma-ray bursts, infrared/optical transients, and radio emission. Simulations of these mergers with fully general relativistic codes are critical to understand the merger and post-merger gravitational wave signals and their neutrinos and electromagnetic counterparts. In this paper, we employ the SpEC code to simulate the merger of low-mass neutron star binaries (two $1.2M_\odot$ neutron stars) for a set of three nuclear-theory based, finite temperature equations of state. We show that the frequency peaks of the post-merger gravitational wave signal are in good agreement with predictions obtained from simulations using a simpler treatment of gravity. We find, however, that only the fundamental mode of the remnant is excited for long periods of time: emission at the secondary peaks is damped on a millisecond timescale in the simulated binaries. For such low-mass systems, the remnant is a massive neutron star which, depending on the equation of state, is either permanently stable or long-lived. We observe strong excitations of l=2, m=2 modes, both in the massive neutron star and in the form of hot, shocked tidal arms in the surrounding accretion torus. We estimate the neutrino emission of the remnant using a neutrino leakage scheme and, in one case, compare these results with a gray two-moment neutrino transport scheme. We confirm the complex geometry of the neutrino emission, also observed in previous simulations with neutrino leakage, and show explicitly the presence of important differences in the neutrino luminosity, disk composition, and outflow properties between the neutrino leakage and transport schemes.Comment: Accepted by PRD; 23 pages; 24 figures; 4 table

SpECTRE: A Task-based Discontinuous Galerkin Code for Relativistic Astrophysics

We introduce a new relativistic astrophysics code, SpECTRE, that combines a discontinuous Galerkin method with a task-based parallelism model. SpECTRE's goal is to achieve more accurate solutions for challenging relativistic astrophysics problems such as core-collapse supernovae and binary neutron star mergers. The robustness of the discontinuous Galerkin method allows for the use of high-resolution shock capturing methods in regions where (relativistic) shocks are found, while exploiting high-order accuracy in smooth regions. A task-based parallelism model allows efficient use of the largest supercomputers for problems with a heterogeneous workload over disparate spatial and temporal scales. We argue that the locality and algorithmic structure of discontinuous Galerkin methods will exhibit good scalability within a task-based parallelism framework. We demonstrate the code on a wide variety of challenging benchmark problems in (non)-relativistic (magneto)-hydrodynamics. We demonstrate the code's scalability including its strong scaling on the NCSA Blue Waters supercomputer up to the machine's full capacity of 22,380 nodes using 671,400 threads.Comment: 41 pages, 13 figures, and 7 tables. Ancillary data contains simulation input file