A Determination of the Fine Structure Constant using Precision Measurements of Helium Fine Structure

Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electro-optic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new determination of the fine structure constant {\alpha}. An apparatus was designed and built to overcome limitations encountered in a previous experiment. Not only did this allow an improved level of precision but also enabled new consistency checks, including an extremely useful measurement in 3He. I discuss the details of the experimental setup along with the major changes and improvements. A new value for the J = 0 to 2 fine structure interval in the 23P state of 4He is measured to be 31 908 131.25(30) kHz. The 300 Hz precision of this result represents an improvement over previous results by more than a factor of three. Combined with the latest theoretical calculations, this yields a new determination of {\alpha} with better than 5 ppb uncertainty, {\alpha}-1 = 137.035 999 55(64).Comment: Ph.D. thesis, University of North Texas, August 2010 (results from this thesis are published in Physical Review - M. Smiciklas and D. Shiner, Phys. Rev. Lett. 105, 123001 (2010).

New limits on Anomalous Spin-Spin Interactions

We report the results of a new search for long range spin-dependent interactions using a Rb -$^{21}$Ne atomic comagnetometer and a rotatable electron spin source based on a SmCo$_{5}$ magnet with an iron flux return. By looking for signal correlations with the orientation of the spin source we set new constrains on the product of the pseudoscalar electron and neutron couplings $g^e_p g^n_p/\hbar c<1.7\times10^{-14}$ and on the product of their axial couplings $g^e_A g^n_A/\hbar c<5\times10^{-42}$ to a new particle with a mass of less than about $1~\mu$eV. Our measurements improve by about 2 orders of magnitude previous constraints on such spin-dependent interactions.Comment: 4 pages, 4 figure

A Determination of the Fine Structure Constant Using Precision Measurements of Helium Fine Structure

Spectroscopic measurements of the helium atom are performed to high precision using an atomic beam apparatus and electro-optic laser techniques. These measurements, in addition to serving as a test of helium theory, also provide a new determination of the fine structure constant &#945;. An apparatus was designed and built to overcome limitations encountered in a previous experiment. Not only did this allow an improved level of precision but also enabled new consistency checks, including an extremely useful measurement in 3He. I discuss the details of the experimental setup along with the major changes and improvements. A new value for the J = 0 to 2 fine structure interval in the 23P state of 4He is measured to be 31 908 131.25(30) kHz. The 300 Hz precision of this result represents an improvement over previous results by more than a factor of three. Combined with the latest theoretical calculations, this yields a new determination of &#945; with better than 5 ppb uncertainty, &#945;-1 = 137.035 999 55(64)

Precision measurements of the hyperfine structure in the 23P state of 3He.

The unusually large hyperfine structure splittings in the 23P state of the 3He isotope is measured using electro-optic techniques with high precision laser spectroscopy. Originally designed to probe the fine structure of the 4He atom, this experimental setup along with special modifications I implemented to resolve certain 3He related issues has made possible new high precision hyperfine structure measurements. Discussed are the details of the experimental setup and the modifications, including in depth information necessary to consider while performing these measurements. The results of these hyperfine structure measurements give an order of magnitude improvement in precision over the best previously reported values

The quality of girls' diets declines and tracks across middle childhood

BACKGROUND: Food group intakes by US children are below recommendations and micronutrient inadequacies have been reported. There are few longitudinal data that focus on developmental changes in food and nutrient intake from early to middle childhood. We examined changes in nutrient and food group intakes over time and the tracking of intakes across middle childhood in a longitudinal sample of girls. METHODS: Three multiple-pass 24-hour diet recalls were conducted in a sample of 181 non-Hispanic White girls at ages 5, 7, and 9 years. Food and nutrient data were averaged across 3 days. Analyses of time effects were conducted using repeated measures analysis of variance and tracking of intakes was assessed via rank analysis. RESULTS: We found significant decreases in nutrient densities (intakes per 1000 kcal) of vitamins C and D, calcium, phosphorus, magnesium and zinc at age 9. Girls maintained their relative quartile positions for these micronutrients from ages 5–9. Analysis of food group data showed similar trends. At age 9, significantly fewer girls were meeting the recommendations for dairy, fruit and vegetable servings than at age 5 and girls also tended to remain in their respective quartiles over time, especially for fruit and dairy intakes. CONCLUSIONS: These results highlight the importance of developing healthy eating practices during early childhood when caretakers have considerable control over children's food intake

Girls’ Dairy Intake, Energy Intake, and Weight Status

We explored the relationships among girls’ weight status, dairy servings, and total energy intake. The hypothesis that consuming dairy could reduce risk for overweight was evaluated by comparing energy intake and weight status of girls who met or consumed less than the recommended three servings of dairy per day. Participants included 172 11-year-old non-Hispanic white girls, assessed cross-sectionally. Intakes of dairy, calcium, and energy were measured using three 24-hour recalls. Body mass index and body fat measures from dual-energy x-ray absorptiometry were obtained. Because preliminary analyses suggested systematic underreporting of energy intake, the relationships among dairy servings and measures of weight status were examined for the total sample and for subsamples of under-, plausible, and overreporters. Data for the total sample provided support for the hypothesized relationship among weight status, dairy servings, and energy intake. Thirty-nine percent of girls reported consuming the recommended ≥3 servings of dairy per day; these girls also reported higher energy intake but had lower body mass index z scores and body fat than the girls who consumed fewer than three dairy servings each day. Among plausible reporters, no relationship between dairy intake and weight status was noted. This discrepancy may be attributable to a high percentage (45%) of overweight underreporters in the total sample. Our findings reveal that reporting bias, resulting from the presence of a substantial proportion of underreporters of higher weight status, can contribute to obtaining spurious associations between dairy intake and weight status. These findings underscore the need for randomly controlled trials to assess the role of dairy in weight management. The prevalence of pediatric obesity has been rising for more than 20 years (1). There is evidence that increased intake of dairy foods and calcium may play a significant role in maintaining a healthful weight and moderating body fat (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15). However, results across studies have been inconsistent (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 and 28), and this may be attributable to major challenges in using self-reported dietary intake data. Self-reported intakes tend to be subject to underreporting bias and the underreporting of energy intake tends to be positively related to weight status. Underreporters also tend to weigh more (29 and 30). Doubly labeled water techniques assessing energy expenditure suggest underreporting results in a 10% to 50% underestimation of actual energy intake and is a significant problem in older children (31). Doubly labeled water techniques are expensive and not feasible for large samples; thus, several methods have been developed that use estimated energy requirements to assess reporting bias (29 and 32). Therefore, in this study the method suggested by Huang and colleagues (29) was used to classify children as under-, plausible, or overreporters. The objective of this study was to assess the relationship among girls’ weight status, dairy servings, and total energy intake. The hypothesis that consuming dairy could reduce risk for overweight was evaluated by comparing energy intake and weight status of girls who met or consumed less than the recommended three servings of dairy per day. To explore the effect of reporting bias on this relationship, the hypothesis was evaluated using the total sample, and subgroups of girls identified as plausible, under-, or overreporters

Frequency metrology in quantum degenerate helium: Direct measurement of the 2 3S1 - 2 1S0 transition

Precision spectroscopy of simple atomic systems has refined our understanding of the fundamental laws of quantum physics. In particular, helium spectroscopy has played a crucial role in describing two-electron interactions, determining the fine-structure constant and extracting the size of the helium nucleus. Here we present a measurement of the doubly-forbidden 1557-nanometer transition connecting the two metastable states of helium (the lowest energy triplet state 2 3S1 and first excited singlet state 2 1S0), for which quantum electrodynamic and nuclear size effects are very strong. This transition is fourteen orders of magnitude weaker than the most predominantly measured transition in helium. Ultracold, sub-microkelvin, fermionic 3He and bosonic 4He atoms are used to obtain a precision of 8.10^{-12}, providing a stringent test of two-electron quantum electrodynamic theory and of nuclear few-body theory.Comment: 14 pages, 6 figure

Hypothalamic melanin concentrating hormone neurons communicate the nutrient value of sugar

Sugars that contain glucose, such as sucrose, are generally preferred to artificial sweeteners owing to their post-ingestive rewarding effect, which elevates striatal dopamine (DA) release. While the post-ingestive rewarding effect, which artificial sweeteners do not have, signals the nutrient value of sugar and influences food preference, the neural circuitry that mediates the rewarding effect of glucose is unknown. In this study, we show that optogenetic activation of melanin-concentrating hormone (MCH) neurons during intake of the artificial sweetener sucralose increases striatal dopamine levels and inverts the normal preference for sucrose vs sucralose. Conversely, animals with ablation of MCH neurons no longer prefer sucrose to sucralose and show reduced striatal DA release upon sucrose ingestion. We further show that MCH neurons project to reward areas and are required for the post-ingestive rewarding effect of sucrose in sweet-blind Trpm5(-/-) mice. These studies identify an essential component of the neural pathways linking nutrient sensing and food reward. DOI: http://dx.doi.org/10.7554/eLife.01462.001.JPB Foundation; The Klarman Family Foundation for Eating Disorders; The Rockefeller Foundation; CNPq (Brazil); FCT; National Institutes of Health grants: (DC009997, DK085579, DP1 DK006850)

Lorentz violation, Gravity, Dissipation and Holography

We reconsider Lorentz Violation (LV) at the fundamental level. We show that Lorentz Violation is intimately connected with gravity and that LV couplings in QFT must always be fields in a gravitational sector. Diffeomorphism invariance must be intact and the LV couplings transform as tensors under coordinate/frame changes. Therefore searching for LV is one of the most sensitive ways of looking for new physics, either new interactions or modifications of known ones. Energy dissipation/Cerenkov radiation is shown to be a generic feature of LV in QFT. A general computation is done in strongly coupled theories with gravity duals. It is shown that in scale invariant regimes, the energy dissipation rate depends non-triviallly on two characteristic exponents, the Lifshitz exponent and the hyperscaling violation exponent.Comment: LateX, 51 pages, 9 figures. (v2) References and comments added. Misprints correcte