Aerospace lubrication technology transfer to industrial applications

Difficulties encountered in entering industrial markets with an aerospace lubrication and coating technology are discussed along with the technical, financial, and managerial solutions that evolved

Pupil remapping for high contrast astronomy: results from an optical testbed

The direct imaging and characterization of Earth-like planets is among the most sought-after prizes in contemporary astrophysics, however current optical instrumentation delivers insufficient dynamic range to overcome the vast contrast differential between the planet and its host star. New opportunities are offered by coherent single mode fibers, whose technological development has been motivated by the needs of the telecom industry in the near infrared. This paper presents a new vision for an instrument using coherent waveguides to remap the pupil geometry of the telescope. It would (i) inject the full pupil of the telescope into an array of single mode fibers, (ii) rearrange the pupil so fringes can be accurately measured, and (iii) permit image reconstruction so that atmospheric blurring can be totally removed. Here we present a laboratory experiment whose goal was to validate the theoretical concepts underpinning our proposed method. We successfully confirmed that we can retrieve the image of a simulated astrophysical object (in this case a binary star) though a pupil remapping instrument using single mode fibers.Comment: Accepted in Optics Expres

The molecular and dusty composition of Betelgeuse's inner circumstellar environment

The study of the atmosphere of red supergiant stars in general and of Betelgeuse (alpha Orionis) in particular is of prime importance to understand dust formation and how mass is lost to the interstellar medium in evolved massive stars. A molecular shell, the MOLsphere (Tsuji, 2000a), in the atmosphere of Betelgeuse has been proposed to account for the near- and mid-infrared spectroscopic observations of Betelgeuse. The goal is to further test this hypothesis and to identify some of the molecules in this MOLsphere. We report on measurements taken with the mid-infrared two-telescope beam combiner of the VLTI, MIDI, operated between 7.5 and 13.5 $\mu$m. The data are compared to a simple geometric model of a photosphere surrounded by a warm absorbing and emitting shell. Physical characteristics of the shell are derived: size, temperature and optical depth. The chemical constituents are determined with an analysis consistent with available infrared spectra and interferometric data. We are able to account for the measured optical depth of the shell in the N band, the ISO-SWS spectrum and K and L band interferometric data with a shell whose inner and outer radii are given by the above range and with the following species: H2O, SiO and Al2O3. These results confirm the MOLsphere model. We bring evidence for more constituents and for the presence of species participating in the formation of dust grains in the atmosphere of the star, i.e. well below the distance at which the dust shell is detected. We believe these results bring key elements to the understanding of mass loss in Betelgeuse and red supergiants in general and bring support to the dust-driven scenario.Comment: 11 pages, 10 figures, accepted for publication in A&

A Slow-Release Nitrogen Fertilizer: Ammonium-Loaded Clinoptilolite

Crops grown in sandy soils require frequent irrigation. As a result, nitrogen (N) fertilizers. such as ammonium sulfate((NH4)2SO4), are leached from the rooting zone of crops. This loss of N increases N fertilizer use and the potential for nitrate (NO3-) contamination of water. Ammonium-loaded clinoptilolite (NH4+-Cp) may reduce this N leaching, increase N fertilizer use-efficiency, and prevent NO3- contamination of water while sustaining normal crop growth. The potential of NH4+-Cp as a N fertilizer was assessed in three leaching experiments without plants and two leaching experiments with plants. Pots containing rounded quartz sand were amended with (NH4)2SO4 and one of three NH4+-Cp size fractions: small ( Finally, in two leaching studies, pots containing the sandy soil were planted with sweet corn and grown for 35 d and 42 d, respectively. No differences were found among N sources in corn relative growth rates, leaf area ratios, and net assimilation rates, even though the corn plants that were fertilized with NH4+-Cp assimilated significantly more N than the (NH4)2SO4-fertilized plants. The pots fertilized with NH5+-Cp leached In the greenhouse, NH4+-Cp is a slow-release fertilizer that will reduce N leaching while maintaining normal plant growth. However, field studies are needed to confirm the suitability of NH4+-Cp as a slow-release fertilizer under field conditions

Two-body anticorrelation in a harmonically trapped ideal Bose gas

We predict the existence of a dip below unity in the second-order coherence function of a partially condensed ideal Bose gas in harmonic confinement, signaling the anticorrelation of density fluctuations in the sample. The dip in the second-order coherence function is revealed in a canonical-ensemble calculation, corresponding to a system with fixed total number of particles. In a grand-canonical ensemble description, this dip is obscured by the occupation-number fluctuation catastrophe of the ideal Bose gas. The anticorrelation is most pronounced in highly anisotropic trap geometries containing small particle numbers. We explain the fundamental physical mechanism which underlies this phenomenon, and its relevance to experiments on interacting Bose gases.Comment: 10 pages, 5 figures. v2: Minor changes and corrections to figures and text. To appear in PR

Critical Rotation of an Annular Superfluid Bose Gas

We analyze the excitation spectrum of a superfluid Bose-Einstein condensate rotating in a ring trap. We identify two important branches of the spectrum related to outer and inner edge surface modes that lead to the instability of the superfluid. Depending on the initial circulation of the annular condensate, either the outer or the inner modes become first unstable. This instability is crucially related to the superfluid nature of the rotating gas. In particular we point out the existence of a maximal circulation above which the superflow decays spontaneously, which cannot be explained by invoking the average speed of sound.Comment: 5 pages, 5 figures, PRA Rapid Com

Performance of astrometric detection of a hotspot orbiting on the innermost stable circular orbit of the galactic centre black hole

The galactic central black hole Sgr A* exhibits outbursts of radiation in the near infrared (so-called IR flares). One model of these events consists in a hotspot orbiting on the innermost stable circular orbit (ISCO) of the hole. These outbursts can be used as a probe of the central gravitational potential. One main scientific goal of the second generation VLTI instrument GRAVITY is to observe these flares astrometrically. Here, the astrometric precision of GRAVITY is investigated in imaging mode, which consists in analysing the image computed from the interferometric data. The capability of the instrument to put in light the motion of a hotspot orbiting on the ISCO of our central black hole is then discussed. We find that GRAVITY's astrometric precision for a single star in imaging mode is smaller than the Schwarzschild radius of Sgr A*. The instrument can also demonstrate that a body orbiting on the last stable orbit of the black hole is indeed moving. It yields a typical size of the orbit, if the source is as bright as m_K=14. These results show that GRAVITY allows one to study the close environment of Sgr A*. Having access to the ISCO of the central massive black hole probably allows constraining general relativity in its strong regime. Moreover, if the hotspot model is appropriate, the black hole spin can be constrained.Comment: 13 pages, 11 figures ; accepted by MNRA

The K giant star Arcturus: the hybrid nature of its infrared spectrum

We study infrared spectrum of Arcturus to clarify the nature of the cool component of its atmosphere, referred to as the CO-mosphere, with the use of the IR spectral atlas by Hinkle et al.(1995). The nature of CO lines shows an abrupt change at logW/nu = -4.75, and the lines stronger than this limit can no longer be analyzed by the classical line-formation theory. A more simple manifestation of this fact is that the curves-of-growth (CG) of CO lines show an unpredictable upturn at logW/nu = -4.75. Similar unusual behaviors of empirical CG are confirmed in other red (super)giant stars, and it looks as if the CG is a hybrid of at least two components of different origins. Although strong lines of the CO fundamentals observed in Arcturus show strengthening compared with the predicted photospheric spectrum, the weaker lines show slight weakening, and we interpret these results as due to absorption/emission by the molecular clouds formed in the extended atmosphere. Now do clouds exist in stellar atmospheres? It is by no means easy to answer this question by spectroscopic observations alone, but we find several arguments in favor of such a possibility in Arcturus by analyzing the CO lines. In cooler (super)giant stars in which CO lines show similar unusual behaviors as in Arcturus, the presence of molecular clouds in the outer atmospheres was demonstrated by direct observations with spatial interferometry. We suggest that the formation of molecular clouds is a general feature in cool luminous stars from early K to late M (super)giant stars.Comment: 18 pages, 15 Postscript figures, 1 Table in electronic form, Accepted for publication in Astronomy and Astrophysic