Tune-out measurement in lukewarm lithium with phase-patterned atom interferometry

Atom interferometry deploys atoms as sensors, delivering precision measurements that span the gamut of physics. Laser-cooled samples simplify uniform detection strategies and allow meticulous control over degrees of freedom and systematic effects. Advanced cooling and interferometry techniques do apply readily to a few atomic species, but they leave behind a large class of species otherwise suited for precision sensing. This thesis describes atom interferometry with a sample of lukewarm $^7$Li, near the Doppler temperature. High thermal speeds demand rapid atom optics and complicate detection. We nevertheless develop interferometer techniques that considerably relax cooling requirements, including a recoil-sensitive scheme capable of measuring the fine-structure constant that takes advantage of $^7$Li's low mass. We also establish a phase-patterning protocol to inscribe and sense spatially-varying phases with matter-wave interferometers whose sample sizes exceed the arm separation. Phase patterning forms the basis of the first precision measurement of $^7$Li's red tune-out wavelength, the wavelength where AC Stark shifts from the $D$-line transitions cancel and the polarizability vanishes. Our measurement registers a 3-$\sigma$ tension with \emph{ab initio} atomic theory regarding the tensor-shifted tune-out wavelength and a 2-$\sigma$ tension regarding the size of the tensor shift, but agrees with theory regarding the scalar tune-out wavelength. These results motivate further work on lithium's polarizability, enable direct measurements of hyperpolarizability, and empower an assortment of future applications of phase patterning in matter-wave interferometry

Exploring differences between the health and wellness of state police officers and community corrections professionals.

This dissertation is a comparison study of health and wellness outcomes for a sample of law enforcement officers and a sample of community corrections professionals within the same state. As such, it is the first attempt to determine and compare the independent variables which are significant predictors of law enforcement officer and community corrections professionals’ health and wellness for criminal justice employees working in the same context. Data used in the research was gathered from nearly identical health and wellness surveys distributed to the sample of law enforcement officers and the sample of community corrections professionals. Logistic, negative binomial, and Poisson regression analyses were performed to determine which independent variables are significant predictors of officer and professionals’ health and wellness outcomes. Results show several factors are significant predictors of both officer and professionals’ health and wellness, with law enforcement organizational factors being the most frequent predictors of law enforcement health and wellness. Demographic variables are the most frequent significant predictors of professionals’ health and wellness. It is concluded that variables predictive of officer and professionals’ health and wellness differ, necessitating different policy approaches designed to address issues associated with officer and professionals’ health and wellness

SINE RNA Induces Severe Developmental Defects in Arabidopsis thaliana and Interacts with HYL1 (DRB1), a Key Member of the DCL1 Complex

The proper temporal and spatial expression of genes during plant development is governed, in part, by the regulatory activities of various types of small RNAs produced by the different RNAi pathways. Here we report that transgenic Arabidopsis plants constitutively expressing the rapeseed SB1 SINE retroposon exhibit developmental defects resembling those observed in some RNAi mutants. We show that SB1 RNA interacts with HYL1 (DRB1), a double-stranded RNA-binding protein (dsRBP) that associates with the Dicer homologue DCL1 to produce microRNAs. RNase V1 protection assays mapped the binding site of HYL1 to a SB1 region that mimics the hairpin structure of microRNA precursors. We also show that HYL1, upon binding to RNA substrates, induces conformational changes that force single-stranded RNA regions to adopt a structured helix-like conformation. Xenopus laevis ADAR1, but not Arabidopsis DRB4, binds SB1 RNA in the same region as HYL1, suggesting that SINE RNAs bind only a subset of dsRBPs. Consistently, DCL4-DRB4-dependent miRNA accumulation was unchanged in SB1 transgenic Arabidopsis, whereas DCL1-HYL1-dependent miRNA and DCL1-HYL1-DCL4-DRB4-dependent tasiRNA accumulation was decreased. We propose that SINE RNA can modulate the activity of the RNAi pathways in plants and possibly in other eukaryotes

A Collection of Target Mimics for Comprehensive Analysis of MicroRNA Function in Arabidopsis thaliana

Many targets of plant microRNAs (miRNAs) are thought to play important roles in plant physiology and development. However, because plant miRNAs are typically encoded by medium-size gene families, it has often been difficult to assess their precise function. We report the generation of a large-scale collection of knockdowns for Arabidopsis thaliana miRNA families; this has been achieved using artificial miRNA target mimics, a recently developed technique fashioned on an endogenous mechanism of miRNA regulation. Morphological defects in the aerial part were observed for ∼20% of analyzed families, all of which are deeply conserved in land plants. In addition, we find that non-cleavable mimic sites can confer translational regulation in cis. Phenotypes of plants expressing target mimics directed against miRNAs involved in development were in several cases consistent with previous reports on plants expressing miRNA–resistant forms of individual target genes, indicating that a limited number of targets mediates most effects of these miRNAs. That less conserved miRNAs rarely had obvious effects on plant morphology suggests that most of them do not affect fundamental aspects of development. In addition to insight into modes of miRNA action, this study provides an important resource for the study of miRNA function in plants

Sensing of Replication Stress and Mec1 Activation Act through Two Independent Pathways Involving the 9-1-1 Complex and DNA Polymerase ε

Following DNA damage or replication stress, budding yeast cells activate the Rad53 checkpoint kinase, promoting genome stability in these challenging conditions. The DNA damage and replication checkpoint pathways are partially overlapping, sharing several factors, but are also differentiated at various levels. The upstream kinase Mec1 is required to activate both signaling cascades together with the 9-1-1 PCNA-like complex and the Dpb11 (hTopBP1) protein. After DNA damage, Dpb11 is also needed to recruit the adaptor protein Rad9 (h53BP1). Here we analyzed the mechanisms leading to Mec1 activation in vivo after DNA damage and replication stress. We found that a ddc1Δdpb11-1 double mutant strain displays a synthetic defect in Rad53 and H2A phosphorylation and is extremely sensitive to hydroxyurea (HU), indicating that Dpb11 and the 9-1-1 complex independently promote Mec1 activation. A similar phenotype is observed when both the 9-1-1 complex and the Dpb4 non-essential subunit of DNA polymerase ε (Polε) are contemporarily absent, indicating that checkpoint activation in response to replication stress is achieved through two independent pathways, requiring the 9-1-1 complex and Polε

From Craft to Nature: The Emergence of Natural Teleology

A teleological explanation is an explanation in terms of an end or a purpose. So saying that ‘X came about for the sake of Y’ is a teleological account of X. It is a striking feature of ancient Greek philosophy that many thinkers accepted that the world should be explained in this way. However, before Aristotle, teleological explanations of the cosmos were generally based on the idea that it had been created by a divine intelligence. If an intelligent power made the world, then it makes sense that it did so with a purpose in mind, so grasping this purpose will help us understand the world. This is the pattern of teleological explanation that we find in the Presocratics and in Plato. However, with Aristotle teleology underwent a change: instead of thinking that the ends were explanatory because a mind had sought to bring them about, Aristotle took the ends to operate in natural beings independently of the efforts of any creative intelligence. Indeed, he thought that his predecessors had failed to understand what was distinctive of nature, namely, that its ends work from the inside of natural beings themselves

Aristotle on the Matter for Birth, Life, and the Elements

This essay considers three case studies of Aristotle’s use of matter, drawn from three different scientific contexts: menstrual fluid as the matter of animal generation in the Generation of Animals, the living body as matter of an organism in Aristotle’s On the Soul (De Anima), and the matter of elemental transformation in Generation and Corruption. I argue that Aristotle conceives of matter differently in these treatises (1) because of the different sorts of changes under consideration, and (2) because sometimes he is considering the matter for one specific change, and sometimes the matter for all of a thing’s natural changes. My account allows me to explain some of the strange features that Aristotle ascribes to the matter for elemental transformation in Generation and Corruption II. These features were interpreted by later commentators as general features of all matter. I argue that they are a result of the specific way that Aristotle thinks about the transmutation of the elements

Tune-out measurement in lukewarm lithium with phase-patterned atom interferometry

Atom interferometry deploys atoms as sensors, delivering precision measurements that span the gamut of physics. Laser-cooled samples simplify uniform detection strategies and allow meticulous control over degrees of freedom and systematic effects. Advanced cooling and interferometry techniques do apply readily to a few atomic species, but they leave behind a large class of species otherwise suited for precision sensing. This thesis describes atom interferometry with a sample of lukewarm $^7$Li, near the Doppler temperature. High thermal speeds demand rapid atom optics and complicate detection. We nevertheless develop interferometer techniques that considerably relax cooling requirements, including a recoil-sensitive scheme capable of measuring the fine-structure constant that takes advantage of $^7$Li's low mass. We also establish a phase-patterning protocol to inscribe and sense spatially-varying phases with matter-wave interferometers whose sample sizes exceed the arm separation. Phase patterning forms the basis of the first precision measurement of $^7$Li's red tune-out wavelength, the wavelength where AC Stark shifts from the $D$-line transitions cancel and the polarizability vanishes. Our measurement registers a 3-$\sigma$ tension with \emph{ab initio} atomic theory regarding the tensor-shifted tune-out wavelength and a 2-$\sigma$ tension regarding the size of the tensor shift, but agrees with theory regarding the scalar tune-out wavelength. These results motivate further work on lithium's polarizability, enable direct measurements of hyperpolarizability, and empower an assortment of future applications of phase patterning in matter-wave interferometry

Pick Your Poison: Examining Adolescent Substance Use through Opportunity Theory

The present study examines substance use behaviors of middle and high school students, focusing on how varying influences of opportunity measures impact use of specific types of substances. The data used in the present study come from almost 4,000 students within 89 school contexts from students attending public school in a Southern state. Hierarchical logistic modeling is used to explore the influence of various opportunities at both the student and school levels on the use of different types of substances. Results indicate measures of opportunity at both the student and school levels were significant; however, measures at the individual level were consistently more influential