First Observation Of Coherent Elastic Neutrino-Nucleus Scattering

Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) has the largest predicted cross-section of all low-energy neutrino couplings. However, as a neutral-current interaction, the only experimental signature of CE$\nu$NS is a low-energy nuclear recoil, which made its detection challenging. CE$\nu$NS remained unobserved for over four decades. This thesis describes the experiment that resulted in a CE$\nu$NS observation at a 6.7-sigma confidence level. A low-background, 14.6-kg CsI[Na] scintillator was exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic CE$\nu$NS signatures in energy and time, compatible with predictions from the Standard Model, were observed in high signal-to-background conditions. CE$\nu$NS provides new opportunities to study neutrino properties, and enables the miniaturization of detectors.Comment: This dissertation was submitted to the faculty of the Division of Physical Sciences at the University of Chicago in candidacy for the degree of Doctor of Philosophy. It was successfully defended on October 16, 201

A cycling state that can lead to glassy dynamics in intracellular transport

Power-law dwell times have been observed for molecular motors in living cells, but the origins of these trapped states are not known. We introduce a minimal model of motors moving on a two-dimensional network of filaments, and simulations of its dynamics exhibit statistics comparable to those observed experimentally. Analysis of the model trajectories, as well as experimental particle tracking data, reveals a state in which motors cycle unproductively at junctions of three or more filaments. We formulate a master equation for these junction dynamics and show that the time required to escape from this vortex-like state can account for the power-law dwell times. We identify trends in the dynamics with the motor valency for further experimental validation. We demonstrate that these trends exist in individual trajectories of myosin II on an actin network. We discuss how cells could regulate intracellular transport and, in turn, biological function, by controlling their cytoskeletal network structures locally

Differentiation in Saccharomyces cerevisiae colonies

Yeast colonies are, alongside to bacterial biofilms, multicellular communities formed by unicellular microorganisms. These specific communities differ in many ways from populations cultivated in planktonic cultivations. Gradients of nutrients, metabolic by- products and other factors are formed and preserved within these structures, which provides a basis for cellular differentiation. Current literature concerning these issues with emphasis on yeast colonies and biofilms is summarised in the Introduction of this work. Section Results then describes my contribution to the knowledge on the differentiation of the colonies of Saccharomyces cerevisiae as a model system for studying microbial multicellular structures. Previously described horizontal differentiation, i.e. differentiation between colony centre and margin, is further characterised with respect to ammonia signalling and stress resistance. The importance of genes conferring the cell`s oxidative stress resistance in colony differentiation was studied and it was concluded that not stress resistance but rather metabolic and other changes promoted by ammonia signal are important for colony differentiation and survival. A new type of colony differentiation - the horizontal, i.e. differentiation between upper and lower part of the colony, is..

The power of genetic diversity in genome-wide association studies of lipids

Abstract Increased blood lipid levels are heritable risk factors of cardiovascular disease with varied prevalence worldwide owing to different dietary patterns and medication use1. Despite advances in prevention and treatment, in particular through reducing low-density lipoprotein cholesterol levels2, heart disease remains the leading cause of death worldwide3. Genome-wideassociation studies (GWAS) of blood lipid levels have led to important biological and clinical insights, as well as new drug targets, for cardiovascular disease. However, most previous GWAS4‐23 have been conducted in European ancestry populations and may have missed genetic variants that contribute to lipid-level variation in other ancestry groups. These include differences in allele frequencies, effect sizes and linkage-disequilibrium patterns24. Here we conduct a multi-ancestry, genome-wide genetic discovery meta-analysis of lipid levels in approximately 1.65 million individuals, including 350,000 of non-European ancestries. We quantify the gain in studying non-European ancestries and provide evidence to support the expansion of recruitment of additional ancestries, even with relatively small sample sizes. We find that increasing diversity rather than studying additional individuals of European ancestry results in substantial improvements in fine-mapping functional variants and portability of polygenic prediction (evaluated in approximately 295,000 individuals from 7 ancestry groupings). Modest gains in the number of discovered loci and ancestry-specific variants were also achieved. As GWAS expand emphasis beyond the identification of genes and fundamental biology towards the use of genetic variants for preventive and precision medicine25, we anticipate that increased diversity of participants will lead to more accurate and equitable26 application of polygenic scores in clinical practice