Spacing effects on seedlings of northern red oak and yellow-poplar

Seedlings of northern red oak (Quercus rubra L.) and yellow-poplar (Liriodendron tulipifera L.) were grown at spacings of 10.8/m2 (1 per square foot), 26.9/ m2 (2.5 per square foot), and 53.8/m2 (5 per square foot) for 2 years. Spacing had no significant effect on first-year growth of either species, but increasing density significantly reduced second-year growth. Compared to the 53.8/m2 spacing, 2-year-old seedlings of northern red oak were 3 times larger at 10.8/m 2, and 2-year-old seedlings of yellow-poplar were 4.8 times larger at 10.8/m2

The Closest Look at 1H0707-495: X-ray Reverberation Lags with 1.3 Ms of Data

Reverberation lags in AGN were first discovered in the NLS1 galaxy, 1H0707-495. We present a follow-up analysis using 1.3 Ms of data, which allows for the closest ever look at the reverberation signature of this remarkable source. We confirm previous findings of a hard lag of ~100 seconds at frequencies v ~ [0.5 - 4] e-4 Hz, and a soft lag of ~30 seconds at higher frequencies, v ~ [0.6 - 3] e-3 Hz. These two frequency domains clearly show different energy dependences in their lag spectra. We also find evidence for a signature from the broad Fe K line in the high frequency lag spectrum. We use Monte Carlo simulations to show how the lag and coherence measurements respond to the addition of Poisson noise and to dilution by other components. With our better understanding of these effects on the lag, we show that the lag-energy spectra can be modelled with a scenario in which low frequency hard lags are produced by a compact corona responding to accretion rate fluctuations propagating through an optically thick accretion disc, and the high frequency soft lags are produced by short light-travel delay associated with reflection of coronal power-law photons off the disc.Comment: 11 pages, 10 figures. Accepted for publication in MNRA

Transient jets in V617 Sagittarii

Some of the luminous Compact Binary Supersoft X-Ray sources (CBSS) have shown indications of jets, also called satellites due to their appearance in the spectra. In V Sagittae (V Sge) stars, the galactic counterparts of the CBSS, such features have been reported only for WX Cen. If V Sge stars are indeed the analogs of CBSS, one may expect transient jet emission in other objects of this class. Spectroscopic observations of the V Sge star V617 Sgr have been made, both at high photometric state and at decline. We show that V617 Sgr presents Halpha satellites at high photometric state with velocities of +/-780 km/s. This feature confirms, once more, the CBSS nature of the V Sge stars, however the details of the spectral characteristics also suggest that the two groups of stars display some intrinsic spectroscopic differences, which are likely to be due to a selection effect related to chemical abundance.Comment: Four pages, accepted to be published as a Letter in A&

Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra

Observations of thermonuclear X-ray bursts from accreting neutron stars (NSs) in low-mass X-ray binary systems can be used to constrain NS masses and radii. Most previous work of this type has set these constraints using Planck function fits as a proxy: both the models and the data are fit with diluted blackbody functions to yield normalizations and temperatures which are then compared against each other. Here, for the first time, we fit atmosphere models of X-ray bursting NSs directly to the observed spectra. We present a hierarchical Bayesian fitting framework that uses state-of-the-art X-ray bursting NS atmosphere models with realistic opacities and relativistic exact Compton scattering kernels as a model for the surface emission. We test our approach against synthetic data, and find that for data that are well-described by our model we can obtain robust radius, mass, distance, and composition measurements. We then apply our technique to Rossi X-ray Timing Explorer observations of five hard-state X-ray bursts from 4U 1702-429. Our joint fit to all five bursts shows that the theoretical atmosphere models describe the data well but there are still some unmodeled features in the spectrum corresponding to a relative error of 1-5% of the energy flux. After marginalizing over this intrinsic scatter, we find that at 68% credibility the circumferential radius of the NS in 4U 1702-429 is R = 12.4+-0.4 km, the gravitational mass is M=1.9+-0.3 Msun, the distance is 5.1 < D/kpc < 6.2, and the hydrogen mass fraction is X < 0.09.Comment: 15 pages, 11 figures, submitted to A&

A hybrid threat model for smart systems

Cyber-physical systems and their smart components have a pervasive presence in all our daily activities. Unfortunately, identifying the potential threats and issues in these systems and selecting enough protection is challenging given that such environments combine human, physical and cyber aspects to the system design and implementation. Current threat models and analysis do not take into consideration all three aspects of the analyzed system, how they can introduce new vulnerabilities or protection measures to each other. In this work, we introduce a novel threat model for cyber-physical systems that combines the cyber, physical, and human aspects. Our model represents the system’s components relations and security properties by taking into consideration these three aspects. Together with the threat model we also propose a threat analysis method that allows understanding the security state of the system’s components. The threat model and the threat analysis have been implemented into an automatic tool, called TAMELESS, that automatically analyzes threats to the system, verifies its security properties, and generates a graphical representation, useful for security architects to identify the proper prevention/mitigation solutions. We show and prove the use of our threat model and analysis with three cases studies from different sector

A negative mass theorem for surfaces of positive genus

We define the "sum of squares of the wavelengths" of a Riemannian surface (M,g) to be the regularized trace of the inverse of the Laplacian. We normalize by scaling and adding a constant, to obtain a "mass", which is scale invariant and vanishes at the round sphere. This is an anlaog for closed surfaces of the ADM mass from general relativity. We show that if M has positive genus then on each conformal class, the mass attains a negative minimum. For the minimizing metric, there is a sharp logarithmic Hardy-Littlewood-Sobolev inequality and a Moser-Trudinger-Onofri type inequality.Comment: 8 page

Effect of environmental conditions on plant growth regulator activity of fungicidal seed treatments of barley

The triazole fungicide triadimenol is known to have plant growth regulator (PGR) activity in cereals when applied as a seed dressing. The effect of environmental conditions on PGR activity of triadimenol, other triazoles (flutriafol, prothioconazole, tebuconazole), the benzimidazole fuberidazole, imidazoles (imazalil, prochloraz), and the strobilurin fluoxastrobin on barley (Hordeum vulgare) was investigated using commercial seed dressings also including pyrimethanil (anilinopyrimidine) and triazoxide (benzotriazine), under controlled conditions. Irrespective of temperature or soil water content (SWC) triazole-containing seed treatments had a significant effect on the time and rate of plant emergence. Both triadimenolcontaining products significantly reduced the length of subcrown internodes and resulted in reduced shoot length three weeks after sowing. Growth suppression was stronger under optimal environmental conditions (17 to 19°C, 60 % SWC). Under suboptimal conditions – 9 to 10°C and 40 % SWC, respectively – no differences in shoot length were detected five weeks after sowing, whereas under optimal conditions plant growth retardation was still significant. The flutriafol-containing product partly inhibited shoot elongation, but never affected dry mass accumulation and root growth. The strobilurin-containing seed dressing had no marked plant growth activities on seedling emergence, shoot length and subcrown internode, but slightly stimulated root growth under all environmental conditions. The results indicate varying PGR activities of triazole seed dressings in response to mixing partner and growth conditions and suggest an increased stress tolerance of seedlings treated with triadimenol, enabling barley to better cope with suboptimal environmental conditions