Fresh and residual phosphorus uptake by ryegrass from soils with different fertilization histories

Organic farming largely depends on animal manure as a source of phosphorus (P) and the recycling of animal manure globally is becoming increasingly important. In a pot experiment, using radioactive P labeling techniques, we studied ryegrass uptake of P applied with animal manure and water soluble mineral fertilizer to soils that had been cropped for 22years according to organic or conventional farming practices. The soils differed in P status and microbial activity. Labeling soil-available P also allowed assessing the uptake from residual P that remained in the soils because of their different fertilization histories. On each soil, recovery of fresh manure P in four harvests of ryegrass shoots was lower than recovery of mineral P. It ranged from 24% to 35% for manure P and from 37% to 43% for mineral P. Recovery of fresh manure P was affected by soil-available P contents. It was lower at a higher available P in a conventional soil. Different levels in microbial activity among soils were of lesser importance for the recovery of fresh manure P in plants. The recovery of residual P ranged from 9% to 15%. Residual P contained in organic cropped soils contributed less to P nutrition of ryegrass than the residual P contained in conventional cropped soils, probably due to their lower residual P contents being composed of stable P forms. The indirect isotope dilution technique is useful in assessing manure P uptake by plants, but attention must be given to added P interactions, i.e., the potential impact of organic amendments on P uptake from non-labeled soil and residual

Parallels between the U.S. and Russia: The Trump Administration

Russia has come up repeatedly in discussions of Donald Trump and the current U.S. administration. In time for the 100th anniversary of the 1917 Russian revolution, this paper aims to describe the importance and interconnectedness of image, information, hegemony, and power by exploring connections between the U.S. and Russia. An interdisciplinary approach drawing from fields such as cultural studies, linguistics, and anthropology will be applied to selected events and actions of the Trump administration. This study provides a method of framing US political events against Russian history and contemporary reality

Neutral absorber dips in the periodic burster LMXB XB 1323-619 from Suzaku

We present results of an observation with Suzaku of the dipping, periodic bursting low mass X-ray binary XB 1323-619. Using the energy band 0.8 - 70 keV, we show that the source spectrum is well-described as the emission of an extended accretion disk corona, plus a small contribution of blackbody emission from the neutron star. The dip spectrum is well-fitted by the progressive covering model in which the extended ADC is progressively overlapped by the absorbing bulge of low ionization state in the outer accretion disk and that dipping is basically due to photoelectric absorption in the bulge. An energy-independent decrease of flux at high energies (20 - 70 keV) is shown to be consistent with the level of Thomson scattering expected in the bulge. An absorption feature at 6.67 keV (Fe XXV) is detected in the non-dip spectrum and other possible weak features. In dipping, absorption lines of medium and highly ionized states are seen suggestive of absorption in the ADC but there is no evidence that the lines are stronger than in non-dip. We show that the luminosity of the source has changed substantially since the Exosat observation of 1985, increasing in luminosity between 1985 and 2003, then in 2003 - 2007 falling to the initial low value. X-ray bursting has again become periodic, which it ceased to do in its highest luminosity state, and we find that the X-ray bursts exhibit both the fast decay and later slow decay characteristic of the rp burning process. We present arguments against the recent proposal that the decrease of continuum flux in the dipping LMXB in general can be explained as absorption in an ionized absorber rather than in the bulge in the outer disk generally accepted to be the site of absorption.Comment: 12 pages, 6 figures, Astronomy and Astrophysics in pres

Boundary layer emission and Z-track in the color-color diagram of luminous LMXBs

We demonstrate that Fourier-frequency resolved spectra of atoll and Z- sources are identical, despite significant difference in their average spectra and luminosity (by a factor of ~10-20). This result fits in the picture we suggested earlier, namely that the f> 1 Hz variability in luminous LMXBs is primarily due to variations of the boundary layer luminosity. In this picture the frequency resolved spectrum equals the boundary layer spectrum, which therefore can be straightforwardly determnined from the data. The obtained so boundary layer spectrum is well approximated by the saturated Comptonization model, its high energy cut-off follows kT~2.4 keV black body. Its independence on the global mass accretion rate lends support to the theoretical suggestion by Inogamov &Sunyaev (1999) that the boundary layer is radiation pressure supported. With this assumption we constrain the gravity on the neutron star surface and its mass and radius. Equipped with the knowledge of the boundary layer spectrum we attempt to relate the motion along the Z-track to changes of physically meaningful parameters. Our results suggest that the contribution of the boundary layer to the observed emission decreases along the Z-track from conventional ~50% on the horizontal branch to a rather small number on the normal branch. This decrease can be caused, for example, by obscuration of the boundary layer by the geometrically thick accretion disk at Mdot ~ Mdot_Edd. Alternatively, this can indicate significant change of the structure of the accretion flow at Mdot ~ Mdot_ Edd and disappearance of the boundary layer as a distinct region of the significant energy release associated with the neutron star surface.Comment: 9 pages, 7 figures, Accepted in A&

Is there a compact companion orbiting the late O-type binary star HD 164816?

We present a multi-wavelength (X-ray, $\gamma$-ray, optical and radio) study of HD 194816, a late O-type X-ray detected spectroscopic binary. X-ray spectra are analyzed and the X-ray photon arrival times are checked for pulsation. In addition, newly obtained optical spectroscopic monitoring data on HD 164816 are presented. They are complemented by available radio data from several large scale surveys as well as the \emph{FERMI} $\gamma$-ray data from its \emph{Large Area Telescope}. We report the detection of a low energy excess in the X-ray spectrum that can be described by a simple absorbed blackbody model with a temperature of $\sim$ 50 eV as well as a 9.78 s pulsation of the X-ray source. The soft X-ray excess, the X-ray pulsation, and the kinematical age would all be consistent with a compact object like a neutron star as companion to HD 164816. The size of the soft X-ray excess emitting area is consistent with a circular region with a radius of about 7 km, typical for neutron stars, while the emission measure of the remaining harder emission is typical for late O-type single or binary stars. If HD 164816 includes a neutron star born in a supernova, this supernova should have been very recent and should have given the system a kick, which is consistent with the observation that the star HD 164816 has a significantly different radial velocity than the cluster mean. In addition we confirm the binarity of HD 164816 itself by obtaining an orbital period of 3.82 d, projected masses $m_1 {\rm sin}^{3} i$ = 2.355(69) M$_\odot$, $m_2 {\rm sin}^{3} i$ = 2.103(62) M$_\odot$ apparently seen at low inclination angle, determined from high-resolution optical spectra.Comment: Accepted for publication by MNRAS, 11 pages, 6 figures, 4 table

BeppoSAX observation of 4U\u20091705-44: detection of hard X-ray emission in the soft state

Context. 4U 1705-44 is one of the best-studied type I X-ray burster and atoll sources. Aims. Since it covers a wide range in luminosity (from a few to 50 x 10(36) erg s(-1)) and shows clear spectral state transitions, it represents a good laboratory for testing the accretion models proposed for atoll sources. Methods. We analyzed the energy spectrum accumulated with BeppoSAX observations (43.5 ks) in August 2000 when the source was in a soft spectral state. Results. The continuum of the wide-band energy spectrum is well-described by the sum of a blackbody (kT(bb) similar to 0.56 keV) and a Comptonized component (seed-photon temperature kT(W) similar to 1 keV, electron temperature kT(e) similar to 2.7 keV, and optical depth tau similar to 11). A hard tail was detected at energies above similar to 25 keV. The latter can be modeled by a power law having a photon index similar to 2.9, which contributes similar to 11% of the total flux in the range 0.1-200 keV. A broad emission line, possibly from a relativistic accretion disk, models the feature in the Fe K line region of the spectrum. Conclusions. This is the first time that a high-energy tail has been observed during a soft state of the source

Toward volume manufacturing of high-performance soft x-ray critical-angle transmission gratings

High-resolution ($R = \lambda /\Delta \lambda > 2000$) x-ray absorption and emission line spectroscopy in the soft x-ray band is a crucial diagnostic for the exploration of the properties of ubiquitous warm and hot plasmas and their dynamics in the cosmic web, galaxy clusters, galaxy halos, intragalactic space, and star atmospheres. Soft x-ray grating spectroscopy with $R > 10{,}000$ has been demonstrated with critical-angle transmission (CAT) gratings. CAT gratings combine the relaxed alignment and temperature tolerances and low mass of transmission gratings with high diffraction efficiency blazed in high orders. They are an enabling technology for the proposed Arcus grating explorer and were selected for the Lynx design reference mission grating spectrometer instrument. Both Arcus and Lynx require the manufacture of hundreds to perhaps $\approx 2000$ large-area CAT gratings. We are developing new patterning and fabrication process sequences that are conducive to large-format volume processing on state-of-the-art 200 mm wafer tools. Recent x-ray tests on 200 nm-period gratings patterned using e-beam-written masks and 4x projection lithography in conjunction with silicon pore focusing optics demonstrated $R \approx 10^4$ at 1.49 keV. Extending the grating depth from 4 $\mu$m to 6 $\mu$m is predicted to lead to significant improvements in diffraction efficiency and is part of our current efforts using a combination of deep reactive-ion etching and wet etching in KOH solution. We describe our recent progress in grating fabrication and report our latest diffraction efficiency and modeling results.Comment: 11 pages, 8 figures, submitted to Proc. SPIE 1144

Discovery and identification of infrared counterpart candidates of four Galactic centre low mass X-ray binaries

The near infrared (nIR)/optical counterparts of low mass X-ray binaries (LMXBs) are often observationally dim and reside in high source density fields which make their identification problematic; however, without such a counterpart identification we are unable to investigate many of the properties of LMXB systems. Here, in the context of a larger identification campaign, we examine the fields of four LMXB systems near the Galactic centre, in a bid to identify nIR/optical counterparts to the previously detected X-ray point sources. We obtain nIR/optical images of the fields with the ESO - New Technology Telescope and apply standard photometric and astrometric calibrations; these data are supplemented by Spitzer-GLIMPSE catalog data. On the basis of positional coincidence with the arcsecond accurate X-ray positions, we identify unambiguous counterpart candidates for XTE J1637-498, IGR J17379-3747, IGR J17585-3057 and GX 9+1. We propose tentative nIR counterparts of four LMXBs which require further investigation to confirm their associations to the X-ray sources.Comment: Accepted to A&A (5 pages, 4 figures