Accurate laboratory ultraviolet wavelengths for quasar absorption-line constraints on varying fundamental constants

The most precise method of investigating possible space-time variations of the fine-structure constant, using high-redshift quasar absorption lines, is the many-multiplet (MM) method. For reliable results this method requires very accurate relative laboratory wavelengths for a number of UV resonance transitions from several different ionic species. For this purpose laboratory wavelengths and wavenumbers of 23 UV lines from MgI, MgII, TiII, CrII, MnII, FeII and ZnII have been measured using high-resolution Fourier Transform (FT) spectrometry. The spectra of the different ions (except for one FeII line, one MgI line and the TiII lines) are all measured simultaneously in the same FT spectrometry recording by using a composite hollow cathode as a light source. This decreases the relative uncertainties of all the wavelengths. In addition to any measurement uncertainty, the wavelength uncertainty is determined by that of the ArII calibration lines, by possible pressure shifts and by illumination effects. The absolute wavenumbers have uncertainties of typically 0.001 to 0.002 cm^(-1) (0.06 to 0.1 mAA at 2500 AA), while the relative wavenumbers for strong, symmetric lines in the same spectral recording have uncertainties of 0.0005 cm^(-1) (0.03 mAA at 2500 AA) or better, depending mostly on uncertainties in the line fitting procedure. This high relative precision greatly reduces the potential for systematic effects in the MM method, while the new TiII measurements now allow these transitions to be used in MM analyses.Comment: Accepted for publication in MNRAS, 10 pages, 9 figure

Head impact exposure in junior and adult Australian football players

Tis study measured and compared the frequency, magnitude, and distribution of head impacts sustained by junior and adult Australian football players, respectively, and between player positions over a season of games. Twelve junior and twelve adult players were tracked using a skin-mounted impact sensor. Head impact exposure, including frequency, magnitude, and location of impacts, was quantifed using previously established methods. Over the collection period, there were no signifcant diferences in the impact frequency between junior and adult players. However, there was a signifcant increase in the frequency of head impacts for midfelders in both grades once we accounted for player position. A comparable amount of head impacts in both junior and adult players has implications for Australian football regarding player safety and medical coverage as younger players sustained similar impact levels as adult players. Te other implication of a higher impact profle within midfelders is that, by targeting education and prevention strategies, a decrease in the incidence of sports-related concussion may result

Strong Limit on a Variable Proton-to-Electron Mass Ratio from Molecules in the Distant Universe

The Standard Model of particle physics assumes that the so-called fundamental constants are universal and unchanging. Absorption lines arising in molecular clouds along quasar sightlines offer a precise test for variations in the proton-to-electron mass ratio, mu, over cosmological time and distance scales. The inversion transitions of ammonia are particularly sensitive to mu compared to molecular rotational transitions. Comparing the available ammonia spectra observed towards the quasar B0218+357 with new, high-quality rotational spectra, we present the first detailed measurement of mu with this technique, limiting relative deviations from the laboratory value to |dmu/mu| < 1.8x10^{-6} (95% confidence level) at approximately half the Universe's current age - the strongest astrophysical constraint to date. Higher-quality ammonia observations will reduce both the statistical and systematic uncertainties in these measurements.Comment: Science, 20th June 2008. 22 pages, 5 figures (12 EPS files), 2 tables, including Supporting Online Material; v2: Corrected reference for laboratory mu-variation bound

Murphy et al. Reply to the Comment by Kopeikin on "Gravitomagnetic Influence on Gyroscopes and on the Lunar Orbit"

Lunar laser ranging analysis, as regularly performed in the solar system barycentric frame, requires the presence of the gravitomagnetic term in the equation of motion at the strength predicted by general relativity. The same term is responsible for the Lense Thirring effect. Any attempt to modify the strength of the gravitomagnetic interaction would have to do so in a way that does not destroy the fit to lunar ranging data and other observations.Comment: 1 page; accepted for publication in Physcal Review Letters; refers to gr-qc/070202

Population structures in the SARA and SARB reference collections of Salmonella enterica according to MLST, MLEE and microarray hybridization

In the 1980's and 1990's, population genetic analyses based on Multilocus Enzyme Electrophoresis (MLEE) provided an initial overview of the genetic diversity of multiple bacterial species, including Salmonella enterica. The genetic diversity within S. enterica subspecies enterica according to MLEE is represented by the SARA and SARB reference collections, each consisting of 72 isolates, which have been extensively used for comparative analyses. MLEE has subsequently been replaced by Multilocus Sequence Typing (MLST). Our initial MLST results indicated that some strains within the SARB collection differed from their published descriptions. We therefore performed MLST on four versions of the SARB collection from different sources and one collection of SARA, and found that multiple isolates in SARB and SARA differ in serovar from their original description, and other SARB isolates differed between different sources. Comparisons with a global MLST database allowed a plausible reconstruction of the serovars of the original collection. MLEE, MLST and microarrays were largely concordant at recognizing closely related strains. MLST was particularly effective at recognizing discrete population genetic groupings while the two other methods provided hints of higher order relationships. However, quantitative pair-wise phylogenetic distances differed considerably between all three methods. Our results provide a translation dictionary from MLEE to MLST for the extant SARA and SARB collections which can facilitate genomic comparisons based on archival insights from MLEE

An Empirical Analysis of Cigarette Addiction

We use a framework suggested by a model of rational addiction to analyze empirically the demand for cigarettes. The data consist of per capita cigarettes sales (in packs) annually by state for the period 1955 through 1985. The empirical results provide support for the implications of a rational addiction model that cross price effects are negative (consumption in different periods are complements), that long-run price responses exceed short-run responses, and that permanent price effects exceed temporary price effects. A 10 percent permanent increase in the price of cigarettes reduces current consumption by 4 percent in the short run and by 7.5 percent in the long run. In contrast, a 10 percent increase in the price for only one period decreases consumption by only 3 percent. In addition, a one period price increase of 10 percent reduces consumption in the previous period by approximately .7 percent and consumption in the subsequent period by 1.5 percent. These estimates illustrate the importance of the intertemporal linkages in cigarette demand implied by rational addictive behavior.