Lunar tidal acceleration obtained from satellite-derived ocean tide parameters

One hundred sets of mean elements of GEOS-3 computed at 2-day intervals yielded observation equations for the M sub 2 ocean tide from the long periodic variations of the inclination and node of the orbit. The 2nd degree Love number was given the value k sub 2 = 0.30 and the solid tide phase angle was taken to be zero. Combining obtained equations with results for the satellite 1967-92A gives the M sub 2 ocean tide parameter values. Under the same assumption of zero solid tide phase lag, the lunar tidal acceleration was found mostly due to the C sub 22 term in the expansion of the M sub 2 tide with additional small contributions from the 0 sub 1 and N sub 2 tides. Using Lambeck's (1975) estimates for the latter, the obtained acceleration in lunar longitudal in excellent agreement with the most recent determinations from ancient and modern astronomical data

How many metals does it take to fix N2? A mechanistic overview of biological nitrogen fixation

During the process of biological nitrogen fixation, the enzyme nitrogenase catalyzes the ATP-dependent reduction of dinitrogen to ammonia. Nitrogenase consists of two component metalloproteins, the iron (Fe) protein and the molybdenum-iron (MoFe) protein; the Fe protein mediates the coupling of ATP hydrolysis to interprotein electron transfer, whereas the active site of the MoFe protein contains the polynuclear FeMo cofactor, a species composed of seven iron atoms, one molybdenum atom, nine sulfur atoms, an interstitial light atom, and one homocitrate molecule. This Perspective provides an overview of biological nitrogen fixation and introduces three contributions to this special feature that address central aspects of the mechanism and assembly of nitrogenase

Nitrogenase: A nucleotide-dependent molecular switch

In the simplest terms, the biological nitrogen cycle is the reduction of atmospheric dinitrogen (N2) to ammonia with the subsequent reoxidation ammonia to dinitrogen (1). At the reduction level of ammonia, nitrogen incorporated into precursors for biological macromolecules such as proteins and nucleic acids. Reoxidation of ammonia to dinitrogen ("denitrification") by a variety of microbes (by way of nitrite and other oxidation levels of nitrogen) leads to the depletion of the "fixed," biologically usable, nitrogen pool. Besides the relatively small contribution from commercial ammonical fertilizer production, replenishing of the nitrogen pool falls mainly to a limited number of physiologically diverse microbes (e.g. eubacteria and archaebacteria; free-living and symbiotic; aerobic and anaerobic) that contain the nitrogenase enzyme system

A perturbation analysis of existing resonant satellites

Perturbation analysis of existing resonant satellite

Comparable Worth in a General Equilibrium Model of the U.S. Economy

This paper presents a computable general equilibrium model that simulates the effects on employment, output, wages, and economic efficiency of introducing comparable worth into the U.S. economy. The model calculates economy-wide aggregate impacts and disaggregated results for individuals grouped by sex, marital status, and education. The effects depend on the hiring rules that would accompany comparable worth, the source of existing male-female wage differentials, the extent of coverage of comparable worth, the intra-household behavior of married couples, and demand and supply elasticities. If, after comparable worth is introduced, employers are constrained to employ men and women in historical proportions, the adverse effects on aggregate employment, output, and efficiency would be much larger than if the employment constraint is based on applicant proportions. If existing wage gaps are the result of sex differences in productivity, the adverse of facts of comparable worth are relatively large; but if they are the result of discrimination, the efficiency losses are much smaller. If only part of the economy is subject to comparable worth, the efficiency loss is reduced under the productivity gap assumption, but increased if the wage gap is the result of discrimination. The redistributive effects of comparable worth on married men and women are sensitive to assumptions about intra-household behavior and the size of the gains from marriage. By contrast, unmarried women appear to benefit from comparable worth under most sets of assumptions while unmarried men lose.

Resonant satellite geodesy study Final report

Resonant satellite orbits for determining geopotential constant

Microwave ISM Emission Observed by WMAP

We investigate the nature of the diffuse Galactic emission in the Wilkinson Microwave Anisotropy Probe (WMAP) temperature anisotropy data. Substantial dust-correlated emission is observed at all WMAP frequencies, far exceeding the expected thermal dust emission in the lowest frequency channels (23, 33, 41 GHz). The WMAP team (Bennett et al.) interpret this emission as dust-correlated synchrotron radiation, attributing the correlation to the natural association of relativistic electrons produced by SNae with massive star formation in dusty clouds, and deriving an upper limit of 5% on the contribution of Draine & Lazarian spinning dust at K-band (23 GHz). We pursue an alternative interpretation that much, perhaps most, of the dust-correlated emission at these frequencies is indeed spinning dust, and explore the spectral dependence on environment by considering a few specific objects as well as the full sky average. Models similar to Draine & Lazarian spinning dust provide a good fit to the full-sky data. The full-sky fit also requires a significant component with free-free spectrum uncorrelated with \Halpha, possibly hot (~million K) gas within 30 degrees of the Galactic center.Comment: ApJ in press (accepted 5 Dec 2003), version 2: corrected typos and added references. 23 pages, 5 figures, 2 tables. Free-free haze map is available at http://skymaps.inf

Average motion of emerging solar active region polarities I: Two phases of emergence

Our goal is to constrain models of active region formation by tracking the average motion of active region polarity pairs as they emerge onto the surface. We measured the motion of the two main opposite polarities in 153 emerging active regions (EARs) using line-of-sight magnetic field observations from the Solar Dynamics Observatory Helioseismic Emerging Active Region (SDO/HEAR) survey (Schunker et al. 2016). We first measured the position of each of the polarities eight hours after emergence and tracked their location forwards and backwards in time. We find that, on average, the polarities emerge with an east-west orientation and the separation speed between the polarities increases. At about 0.1 days after emergence, the average separation speed reaches a peak value of 229 +/- 11 m/s, and then starts to decrease, and about 2.5 days after emergence the polarities stop separating. We also find that the separation and the separation speed in the east-west direction are systematically larger for active regions with higher flux. Our results reveal two phases of the emergence process defined by the rate of change of the separation speed as the polarities move apart. Phase 1 begins when the opposite polarity pairs first appear at the surface, with an east-west alignment and an increasing separation speed. We define Phase 2 to begin when the separation speed starts to decrease, and ends when the polarities have stopped separating. This is consistent with the picture of Chen, Rempel, & Fan (2017): the peak of a flux tube breaks through the surface during Phase 1. During Phase 2 the magnetic field lines are straightened by magnetic tension, so that the polarities continue to move apart, until they eventually lie directly above their anchored subsurface footpoints.Comment: accepted A&

Clearing residual planetesimals by sweeping secular resonances in transitional disks: a lone-planet scenario for the wide gaps in debris disks around Vega and Fomalhaut

Extended gaps in the debris disks of both Vega and Fomalhaut have been observed. These structures have been attributed to tidal perturbations by multiple super-Jupiter gas giant planets. Within the current observational limits, however, no such massive planets have been detected. Here we propose a less stringent `lone-planet' scenario to account for the observed structure with a single eccentric gas giant and suggest that clearing of these wide gaps is induced by its sweeping secular resonance. During the depletion of the disk gas, the planet's secular resonance propagates inward and clears a wide gap over an extended region of the disk. Although some residual intermediate-size planetesimals may remain in the gap, their surface density is too low to either produce super-Earths or lead to sufficiently frequent disruptive collisions to generate any observable dusty signatures. The main advantage of this lone-planet sweeping-secular-resonance model over the previous multiple gas giant tidal truncation scenario is the relaxed requirement on the number of gas giants. The observationally inferred upper mass limit can also be satisfied provided the hypothetical planet has a significant eccentricity. A significant fraction of solar or more massive stars bear gas giant planets with significant eccentricities. If these planets acquired their present-day kinematic properties prior to the depletion of their natal disks, their sweeping secular resonance would effectively impede the retention of neighboring planets and planetesimals over a wide range of orbital semi-major axes.Comment: 20 pages, 12 figures. Accepted for publication in Ap

Exploring taboo issues in professional sport through a fictional approach

While the need to consider life course issues in elite sport research and practice is increasingly recognised, some experiences still seem to be considered too dangerous to explore. Consequently, stories of these experiences are silenced and the ethical and moral questions they pose fail to be acknowledged, understood or debated. This paper presents an ethnographic fiction through which we explore a sensitive set of experiences that were uncovered during our research with professional sportspeople. Through a multi‐layered reconstruction, the story reveals the complex, but significant, relationships that exist between identity, cultural narratives and embodied experiences. After the telling we consider how the story has stimulated reflective practice among students, researchers and practitioners. While there are risks involved in writing and sharing taboo stories, the feedback we have received suggests that storytelling can be an effective pedagogical tool in education and professional development