Stability of Magneto-optical Traps with Large Field Gradients: Limits on the Tight Confinement of Single Atoms

We report measurements of the stability of magneto-optical traps (MOTs) for neutral atoms in the limit of tight confinement of a single atom. For quadrupole magnetic field gradients at the trap center greater than ∼1 kG/cm, we find that stochastic diffusion of atoms out of the trapping volume becomes the dominant particle loss mechanism, ultimately limiting the MOT size to greater than ∼5 μm. We measured and modeled the diffusive loss rate as a function of laser power, detuning, and field gradient for trapped cesium atoms. In addition, for as few as two atoms, the collisional loss rates become very high for tightly confined traps, allowing the direct observation of isolated two-body atomic collisions in a MOT

30 Vragen en antwoorden over fosfaat in relatie tot landbouw en milieu

Deze uitgave geeft een antwoord op veel gestelde vragen over fosfaat. Het betreft zowel algemene als landbouwkundige en milieukundige vragen. Deze publicatie is opgesteld voor beleidsmedewerkers van de rijksoverheid en regionale overheden (provincies, waterschappen), maatschappelijke organisaties en voor landbouwers en hun organisaties. In feite voor allen die met fosfaatbeleid te maken hebben. Van nature zit er weinig fosfor in de bodem, zo’n 0,01 tot 0,1%. Fosfor wordt aangevoerd via veevoer en kunstmest. In Nederland wordt meer fosfaat aangevoerd dan afgevoerd. Er is dan ook sprake van een overschot aan fosfaat. Het overgrote deel van het overschot komt op landbouwgronden terecht. De fosfaatophoping in de bodem varieerde in de afgelopen decennia tussen de 80 en 40 miljoen kilo per jaar. Door uit- en afspoeling van fosfaten uit de bodem ontstaan negatieve effecten voor waterecosystemen, zoals een sterke groei van fytoplankton ("algenbloei”). Als gevolg hiervan verdwijnen waterplanten door lichtgebrek en sterven vissen door zuurstofgebrek. Blauwalgen halen zelfs regelmatig de media vanwege de giftige stoffen die zij afscheiden. Het terugdringen van het fosfaatoverschot is dan ook een van de hoofddoelen van het Nederlandse mestbeleid

Equipotential Surfaces and Lagrangian points in Non-synchronous, Eccentric Binary and Planetary Systems

We investigate the existence and properties of equipotential surfaces and Lagrangian points in non-synchronous, eccentric binary star and planetary systems under the assumption of quasi-static equilibrium. We adopt a binary potential that accounts for non-synchronous rotation and eccentric orbits, and calculate the positions of the Lagrangian points as functions of the mass ratio, the degree of asynchronism, the orbital eccentricity, and the position of the stars or planets in their relative orbit. We find that the geometry of the equipotential surfaces may facilitate non-conservative mass transfer in non-synchronous, eccentric binary star and planetary systems, especially if the component stars or planets are rotating super-synchronously at the periastron of their relative orbit. We also calculate the volume-equivalent radius of the Roche lobe as a function of the four parameters mentioned above. Contrary to common practice, we find that replacing the radius of a circular orbit in the fitting formula of Eggleton (1983) with the instantaneous distance between the components of eccentric binary or planetary systems does not always lead to a good approximation to the volume-equivalent radius of the Roche-lobe. We therefore provide generalized analytic fitting formulae for the volume-equivalent Roche lobe radius appropriate for non-synchronous, eccentric binary star and planetary systems. These formulae are accurate to better than 1% throughout the relevant 2-dimensional parameter space that covers a dynamic range of 16 and 6 orders of magnitude in the two dimensions.Comment: 12 pages, 10 figures, 2 Tables, Accepted by the Astrophysical Journa

Interacting Binaries with Eccentric Orbits. Secular Orbital Evolution Due To Conservative Mass Transfer

We investigate the secular evolution of the orbital semi-major axis and eccentricity due to mass transfer in eccentric binaries, assuming conservation of total system mass and orbital angular momentum. Assuming a delta function mass transfer rate centered at periastron, we find rates of secular change of the orbital semi-major axis and eccentricity which are linearly proportional to the magnitude of the mass transfer rate at periastron. The rates can be positive as well as negative, so that the semi-major axis and eccentricity can increase as well as decrease in time. Adopting a delta-function mass-transfer rate of 10^{-9} M_\sun {\rm yr}^{-1} at periastron yields orbital evolution timescales ranging from a few Myr to a Hubble time or more, depending on the binary mass ratio and orbital eccentricity. Comparison with orbital evolution timescales due to dissipative tides furthermore shows that tides cannot, in all cases, circularize the orbit rapidly enough to justify the often adopted assumption of instantaneous circularization at the onset of mass transfer. The formalism presented can be incorporated in binary evolution and population synthesis codes to create a self-consistent treatment of mass transfer in eccentric binaries.Comment: 16 pages, 8 figures, Accepted by The Astrophysical Journa

Effect of erythropoietin levels on mortality in old age: the Leiden 85-plus Study

BACKGROUND: The production of erythropoietin is triggered by impaired oxygen delivery to the kidney, either because of anemia or hypoxemia. High erythropoietin levels have been shown to predict the risk of death among patients with chronic heart failure. We investigated the prognostic value of elevated erythropoietin levels on mortality among very elderly people in the general population. METHODS: The Leiden 85-plus Study is a population-based prospective follow-up study involving 599 people aged 85 years in Leiden, the Netherlands, enrolled between September 1997 and September 1999. Erythropoietin levels were determined at age 86. For this analysis, we included 428 participants with a creatinine clearance of at least 30 mL/min. Mortality data, recorded until Feb. 1, 2008, were obtained from the municipal registry. RESULTS: During follow-up, 324 (75.7%) participants died. Compared with participants whose erythropoietin levels were in the lowest tertile (reference group), those whose levels were in the middle tertile had a 25% increased risk of death (hazard ratio [HR] 1.25, 95% confidence interval [CI] 0.95–1.64), and those whose levels were in the highest tertile had a 73% increased risk (HR 1.73, 95% CI 1.32–2.26) (p value for trend < 0.01). The association between erythropoietin levels and mortality remained largely unchanged after we adjusted for sex, creatinine clearance, hemoglobin level, comorbidity, smoking status and C-reactive protein level, and was similar for deaths from cardiovascular and noncardiovascular causes. INTERPRETATION: Among people aged 85 years and older, elevated erythropoietin levels were associated with an increased risk of death, independent of hemoglobin levels

Generation of a flat-top laser beam for gravitational wave detectors by means of a nonspherical Fabry-Perot resonator

We have tested a new kind of Fabry-Perot long-baseline optical resonator proposed to reduce the thermal noise sensitivity of gravitational wave interferometric detectors--the "mesa beam" cavity--whose flat top beam shape is achieved by means of an aspherical end mirror. We present the fundamental mode intensity pattern for this cavity and its distortion due to surface imperfections and tilt misalignments, and contrast the higher order mode patterns to the Gauss-Laguerre modes of a spherical mirror cavity. We discuss the effects of mirror tilts on cavity alignment and locking and present measurements of the mesa beam tilt sensitivity

Tank test of vessel entry and exit for third set of Panama locks

The Panama Canal Authority (ACP) plans to extend the capacity of and allow larger ships to the Canal by building a so-called third lane, consisting of a new set of locks parallel to the existing ones. The design ship is a so-called Post-Panamax 12000 TEU container carrier. In order to optimise the approach to and the manoeuvres within the locks, in 2007-2008 experimental research has been conducted at Flanders Hydraulics Research, Antwerp, Belgium on a 1/80 scale model of the approach lane, the lock and the design vessel. With the ship model moving along a guiding rail, lateral forces acting on the ship and movements of the vessel can be recorded during a selection of entrance and exit manoeuvres. During a number of tests, the effect of density exchange current was examined. The present article offers an overview of the test-setup with a discussion of a few interesting results of the test runs

Influence of ionic and non-ionic radiographic contrast media on leukocyte adhesion molecules.

BACKGROUND: Many papers have focused on the importance of granulocytes in the process of reperfusion and ischemia. Most of the clinical studies measured several parameters of this process during and after coronary angiography, without taking into account the effect of the radiographic contrast media (RCM) used during this procedure. MATERIALS AND METHODS: We performed a randomized patient study (n = 37) to evaluate the effect of ionic and non-ionic RCM on granulocyte adhesion during coronary angiography. We also evaluated the influence of the ionicity and osmolarity of the different substances on granulocyte adhesion molecules in in vitro experiments. RESULTS: The osmolarity of patient serum samples increased from 302 +/- 1 to 309 +/- 1 mOsm/kg (p < 0.05) after infusion of RCM. The CD11b expression in the samples of the non-ionic RCM treated group increased from 221 +/- 21 MFI to 377 +/- 30 MFI (p < 0.05) measured as the absolute mean fluorescence intensity (MFI), yet did not alter significantly in the ionic RCM group. In contrast, the in vitro experiments showed a reduction of the CD11b expression from 360 +/- 70 MFI to 149 +/- 30 MFI (p < 0.05) in the ionic RCM group. CONCLUSIONS: The upregulation of adhesion molecules was significantly reduced in vivo with ionic RCM, while ionic substances caused opposite effects in vitro. This effect should be taken into account when performing leukocyte functional analysis of samples taken during angiography