The Origin of the Universe as Revealed Through the Polarization of the Cosmic Microwave Background

Modern cosmology has sharpened questions posed for millennia about the origin of our cosmic habitat. The age-old questions have been transformed into two pressing issues primed for attack in the coming decade: How did the Universe begin? and What physical laws govern the Universe at the highest energies? The clearest window onto these questions is the pattern of polarization in the Cosmic Microwave Background (CMB), which is uniquely sensitive to primordial gravity waves. A detection of the special pattern produced by gravity waves would be not only an unprecedented discovery, but also a direct probe of physics at the earliest observable instants of our Universe. Experiments which map CMB polarization over the coming decade will lead us on our first steps towards answering these age-old questions.Comment: Science White Paper submitted to the US Astro2010 Decadal Survey. Full list of 212 author available at http://cmbpol.uchicago.ed

Competitive Benchmarking: An IS Research Approach to Address Wicked Problems with Big Data and Analytics

Wicked problems like sustainable energy and financial market stability are societal challenges that arise from complex socio-technical systems in which numerous social, economic, political, and technical factors interact. Understanding and mitigating them requires research methods that scale beyond the traditional areas of inquiry of Information Systems (IS) “individuals, organizations, and markets” and that deliver solutions in addition to insights. We describe an approach to address these challenges through Competitive Benchmarking (CB), a novel research method that helps interdisciplinary research communities to tackle complex challenges of societal scale by using different types of data from a variety of sources such as usage data from customers, production patterns from producers, public policy and regulatory constraints, etc. for a given instantiation. Further, the CB platform generates data that can be used to improve operational strategies and judge the effectiveness of regulatory regimes and policies. We describe our experience applying CB to the sustainable energy challenge in the Power Trading Agent Competition (Power TAC) in which more than a dozen research groups from around the world jointly devise, benchmark, and improve IS-based solutions

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

More than smell - COVID-19 is associated with severe impairment of smell, taste, and chemesthesis

Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments, such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, and generally lacked quantitative measurements. Here, we report the development, implementation, and initial results of a multilingual, international questionnaire to assess self-reported quantity and quality of perception in 3 distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, and 8 others, aged 19-79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste, and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change ±100) revealed a mean reduction of smell (-79.7 ± 28.7, mean ± standard deviation), taste (-69.0 ± 32.6), and chemesthetic (-37.3 ± 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell but also affects taste and chemesthesis. The multimodal impact of COVID-19 and the lack of perceived nasal obstruction suggest that severe acute respiratory syndrome coronavirus strain 2 (SARS-CoV-2) infection may disrupt sensory-neural mechanisms. © 2020 The Author(s) 2020. Published by Oxford University Press. All rights reserved

Electrostatic uniformity and two-dimensional quantum dot arrays in silicon and germanium

The spin of a single electron or hole provides an attractive candidate for implementing a quantum bit when confined in a semiconductor quantum dot. Such a spin qubit is characterized by long coherence and short gate times. High-fidelity single and two-qubit operations have been demonstrated as well. Additionally, semiconductor quantum dots have a small footprint (~ 100 nm x 100 nm) and their fabrication employs techniques similar to processes commonly used in modern semiconductor technology foundries. This promises the realization of dense qubit arrays, leverage through industrial fabrication, and direct co-integration with classical control circuits.Thus far, one-dimensional quantum dot arrays have been studied extensively. Yet, only by realizing two-dimensional quantum dot arrays the small footprint of quantum dots is fully exploited. Also, due to their small size quantum dots are extremely sensitive to their local environment and fabrication imperfections. In current devices, an individually tailored set of gate electrode voltages is required for each quantum dot to confine a single charge. The limited space available for routing these voltages on the device, coupled with the associated overhead in required voltage sources, presents a challenge in scaling quantum dot arrays, especially two-dimensional arrays.This thesis focuses on two-dimensional quantum dot arrays and gate voltage uniformity. The first part (chapter 3 and 4) reports the realization of two-dimensional quantum dot arrays in a silicon/silicon-germanium (Si/SiGe) and a germanium/silicon-germanium (Ge/SiGe) heterostructure. Afterward (chapter 5 and 6), a novel all-electric method is presented to achieve increased homogeneity of the required gate voltages.In chapter 3 a 2 x 2 quantum dot array in a Si/SiGe heterostructure is presented. It is tuned to be occupied by a single electron per quantum dot reaching the (1,1,1,1) charge state. Dedicated barrier gate electrodes on the device allow for controlling the interdot tunnel couplings between neighbouring quantum dots from about 30 ueV up to approximately 400 ueV as characterized through polarization line measurements.In chapter 4 the focus is shifted towards a more scalable gate architecture for two-dimensional quantum dot arrays. It is inspired by random access architectures that are found in classical electronics. Specifically, a 4 x 4 quantum dot array in a Ge/SiGe heterostructure with shared gate electrode voltages is introduced. In this device, an odd charge occupancy is reached with either one or three holes in all 16 quantum dots simultaneously. Also, two shared barrier gate electrodes are placed between adjacent quantum dots. These enable selective control of the interdot tunnel coupling from less than 3 GHz to more than 10 GHz.Spatial fluctuations in the electric background potential still limit the scalability of such a shared control array. Therefore, chapter 5 introduces a new method to increase the electrical uniformity in quantum dot devices. The presented method is based on applying stress voltages to the device gate electrodes. It enables the tuning of pinch-off voltages in quantum dot devices over hundreds of millivolts. Afterward, the new pinch-off voltages remain stable for hours at least. The method is used to homogenize the pinch-off voltages of the plunger gates in a linear array designed for four quantum dots. It reduces their spread by one order of magnitude from 153 mV to 20 mV.Motivated by this demonstration, in the experiment presented in chapter 6 the stress voltage tuning method is applied to control the plunger gate voltages required to reach single electron occupation in a quantum dot array. In a double quantum dot, a stable (1,1) charge state is reached at identical and predetermined plunger gate voltage and for various interdot couplings. Finally, by applying stress voltages a 2 x 2 quantum dot array is tuned such that the (1,1,1,1) charge state is reached when all plunger gates are set to 1 V.QCD/Veldhorst La

Strong effects of weak ac driving in short superconducting junctions

We study a short multichannel superconducting junction subject to dc and ac phase biases. The ac modulation changes the occupation of the Andreev bound states formed at the constriction by transitions between bound states and the continuum. In a short junction, the nonequilibrium Andreev bound-state population may relax through processes that conserve parity of the occupation number on the same bound state and processes that do not conserve it. We argue that the parity-conserving processes occur on a much faster time scale. In this case, even a weak driving may lead to a large nonequilibrium quasiparticle population scaling with the number of channels and results in a large deviation of the supercurrent from its equilibrium value. We show that this effect is accompanied by a quasiparticle current which may lead to a measurable charge imbalance in the vicinity of the junction. Furthermore, we study the time evolution of the supercurrent after switching off the ac drive. On a time scale where parity relaxation is negligible, the supercurrent relaxes to a stationary nonequilibrium state. Finally, we briefly outline the regime of ultraweak driving where the ac-induced processes occur on a time scale comparable to that of parity relaxation.QN/Quantum NanoscienceApplied Science

The carbon starvation response of Aspergillus niger during submerged cultivation: Insights from the transcriptome and secretome

Background: Filamentous fungi are confronted with changes and limitations of their carbon source during growth in their natural habitats and during industrial applications. To survive life-threatening starvation conditions, carbon from endogenous resources becomes mobilized to fuel maintenance and self-propagation. Key to understand the underlying cellular processes is the system-wide analysis of fungal starvation responses in a temporal and spatial resolution. The knowledge deduced is important for the development of optimized industrial production processes. Results: This study describes the physiological, morphological and genome-wide transcriptional changes caused by prolonged carbon starvation during submerged batch cultivation of the filamentous fungus Aspergillus niger. Bioreactor cultivation supported highly reproducible growth conditions and monitoring of physiological parameters. Changes in hyphal growth and morphology were analyzed at distinct cultivation phases using automated image analysis. The Affymetrix GeneChip platformwas used to establish genome-wide transcriptional profiles for three selected time points during prolonged carbon starvation. Compared to the exponential growth transcriptome, about 50% (7,292) of all genes displayed differential gene expression during at least one of the starvation time points. Enrichment analysis of Gene Ontology, Pfam domain and KEGG pathway annotations uncovered autophagy and asexual reproduction as major global transcriptional trends. Induced transcription of genes encoding hydrolytic enzymes was accompanied by increased secretion of hydrolases including chitinases, glucanases, proteases and phospholipases as identified by mass spectrometry. Conclusions: This study is the first system-wide analysis of the carbon starvation response in a filamentous fungus. Morphological, transcriptomic and secretomic analyses identified key events important for fungal survival and their chronology. The dataset obtained forms a comprehensive framework for further elucidation of the interrelation and interplay of the individual cellular events involved.Applied Science

High-frequency multibeam echosounder classification for rapid environmental assessment

Remote SensingAerospace Engineerin

Tunneling spectroscopy of few-monolayer NbSe2 in high magnetic fields: Triplet superconductivity and Ising protection

In conventional Bardeen-Cooper-Schrieffer superconductors, Cooper pairs of electrons of opposite spin (i.e., singlet structure) form the ground state. Equal-spin triplet pairs (ESTPs), as in superfluid He3, are of great interest for superconducting spintronics and topological superconductivity, yet remain elusive. Recently, odd-parity ESTPs were predicted to arise in (few-)monolayer superconducting NbSe2, from the noncollinearity between the out-of-plane Ising spin-orbit field (due to the lack of inversion symmetry in monolayer NbSe2) and an applied in-plane magnetic field. These ESTPs couple to the singlet order parameter at finite field. Using van der Waals tunnel junctions, we perform spectroscopy of superconducting NbSe2 flakes, of 2-25 monolayer thickness, measuring the quasiparticle density of states (DOS) as a function of applied in-plane magnetic field up to 33 T. In flakes ≲15 monolayers thick the DOS has a single superconducting gap. In these thin samples, the magnetic field acts primarily on the spin (vs orbital) degree of freedom of the electrons, and superconductivity is further protected by the Ising field. The superconducting energy gap, extracted from our tunneling spectra, decreases as a function of the applied magnetic field. However, in bilayer NbSe2, close to the critical field (up to 30 T, much larger than the Pauli limit), superconductivity appears to be more robust than expected from Ising protection alone. Our data can be explained by the above-mentioned ESTPs. QRD/Kouwenhoven La

Single-cell analysis of the Dps response to oxidative stress

Microorganisms have developed an elaborate spectrum of mechanisms to respond and adapt to environmental stress conditions. Among these is the expression of dps, coding for the DNA-binding protein from starved cells. Dps becomes the dominant nucleoid- organizing protein in stationary-phase Escherichia coli cells and is required for robust survival under stress conditions, including carbon or nitrogen starvation, oxidative stress, metal exposure, and irradiation. To study the complex regulation of Dps in E. coli, we utilized time-lapse fluorescence microscopy imaging to examine the kinetics, input encoding, and variability of the Dps response in single cells. In the presence of an oxidative stressor, we observed a single pulse of activation of Dps production. Increased concentrations of H2O2 led to increased intensity and duration of the pulse. While lower concentrations of H2O2 robustly activated the Dps response with little effect on the growth rate, higher concentrations of H2O2 resulted in dramatically lower and highly varied growth rates. A comparison of cells exposed to the same concentration of H2O2 revealed that increased levels of Dps expression did not confer a growth advantage, indicating that recovery from stress may rely primarily upon variation in the amount of damage caused to individual cells.Accepted Author ManuscriptBN/Anne Meyer LabApplied Science