Forced vibration analysis of rotating cyclic structures in NASTRAN

A new capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axis of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical, user's, programmer's and demonstration manuals for this new capability are presented

Spectral estimates of solar radiation intercepted by corn canopies

Reflectance factor data were acquired with a Landsat band radiometer throughout two growing seasons for corn (Zea mays L.) canopies differing in planting dates, populations, and soil types. Agronomic data collected included leaf area index (LAI), biomass, development stage, and final grain yields. The spectral variable, greenness, was associated with 78 percent of the variation in LAI over all treatments. Single observations of LAI or greenness have limited value in predicting corn yields. The proportions of solar radiation intercepted (SRI) by these canopies were estimated using either measured LAI or greenness. Both SRI estimates, when accumulated over the growing season, accounted for approximately 65 percent of the variation in yields. Models which simulated the daily effects of weather and intercepted solar radiation on growth had the highest correlations to grain yields. This concept of estimating intercepted solar radiation using spectral data represents a viable approach for merging spectral and meteorological data for crop yield models

Effect of hydrophobic solutes on the liquid-liquid critical point

Jagla ramp particles, interacting through a ramp potential with two characteristic length scales, are known to show in their bulk phase thermodynamic and dynamic anomalies, similar to what is found in water. Jagla particles also exhibit a line of phase transitions separating a low density liquid phase and a high density liquid phase, terminating in a liquid-liquid critical point in a region of the phase diagram that can be studied by simulations. Employing molecular dynamics computer simulations, we study the thermodynamics and the dynamics of solutions of hard spheres (HS) in a solvent formed by Jagla ramp particles. We consider the cases of HS mole fraction x = 0.10, 0.15 and 0.20, and also the case x = 0.50 (a 1:1 mixture of HS and Jagla particles). We find a liquid-liquid critical point, up to the highest HS mole fraction; its position shifts to higher pressures and lower temperatures upon increasing x. We also find that the diffusion coefficient anomalies appear to be preserved for all the mole fractions studied.Comment: 8 pages, 7 figures, 1 table. In press (Phys. Rev. E

An X-ray view of Mrk 705: A borderline narrow-line Seyfert 1 galaxy

Mrk 705 exhibits optical properties of both narrow- and broad-line Seyfert 1 galaxies. We examine the X-ray properties of this borderline object utilising proprietary and public data from Chandra, ASCA, ROSAT and RXTE, spanning more than twelve years. Though long-term flux variability from the pointed observations appears rather modest (about 3 times), we do find examples of rare large amplitude outbursts in the RXTE monitoring data. There is very little evidence of long-term spectral variability as the low- and high-energy spectra appear constant with time. A 6.4 keV emission line is detected in the ASCA spectra of Mrk 705, but not during the later, higher flux state Chandra observation. However, the upper limit on the equivalent width of a line in the Chandra spectrum is consistent with a constant-flux emission line and a brighter continuum, suggesting that the line is emitted from distant material such as the putative torus. Overall, the X-ray properties of Mrk 705 appear typical of BLS1 activity.Comment: 7 pages, 7 figures. Accepted for publication in A&A (Research Note

Multi-epoch X-ray observations of the Seyfert 1.2 galaxy Mrk 79: bulk motion of the illuminating X-ray source

Multi-epoch X-ray spectroscopy (0.3-25 keV) of the Seyfert 1.2 galaxy Mrk 79 (UGC 3973) spanning nearly eight years and a factor of three in broadband flux are analysed. The data are obtained at seven epochs with either XMM-Newton or Suzaku. Comparison with contemporaneous RXTE monitoring indicate that all flux states of Mrk 79 are represented by the data. The spectra are fitted in a self-consistent manner adopting a power law and ionised reflection to describe the broadband continuum. Modification of the spectra by a distant photoionised medium, seen predominantly in emission, are also included. Under the assumption that the inner disk is at the innermost stable circular orbit, our blurred reflection models give a spin of a = 0.7+/-0.1. The reflection component in each spectrum is weaker than predicted by simple reflection models. If the illuminating X-ray emission is produced by flares above the disk that move at mildly relativistic velocities, however, diminished reflection is expected. Light bending due to strong gravity near black holes can influence how the illuminating and reflected flux are observed; variations in Mrk 79 do not suggest that light bending is important in this source.Comment: 13 pages. Accepted for publication in MNRA

Effects of Atrial Fibrillation on the Coronary Flow at Different Heart Rates: A Computational Approach

Atrial fibrillation (AF) has several effects on the cardiovascular system responses. This study focuses on the consequences of AF on the coronary blood flow, by exploiting a computational approach. 2000 heartbeat periods (RR) were simulated for 5 different mean heart rates (HR), ranging from 50 to 130 bpm. The resulting flow rate signals at the coronary level were analysed through a specific set of hemodynamic parameters. Three main results emerge during AF: (i) maximal coronary flow rates modify with HR, (ii) the coronary perfusion begins to be impaired when exceeding 90-110 bpm, and (iii) the coronary perfusion pressure is not a good estimate of the coronary blood flow at HRs higher than 90-110 bpm

The hard X-ray perspective on the soft X-ray excess

The X-ray spectra of many active galactic nuclei (AGN) exhibit a `soft excess' below 1keV, whose physical origin remains unclear. Diverse models have been suggested to account for it, including ionised reflection of X-rays from the inner part of the accretion disc, ionised winds/absorbers, and Comptonisation. The ionised reflection model suggests a natural link between the prominence of the soft excess and the Compton reflection hump strength above 10keV, but it has not been clear what hard X-ray signatures, if any, are expected from the other soft X-ray candidate models. Additionally, it has not been possible up until recently to obtain high-quality simultaneous measurements of both soft and hard X-ray emission necessary to distinguish these models, but upcoming joint XMM-NuSTAR programmes provide precisely this opportunity. In this paper, we present an extensive analysis of simulations of XMM+NuSTAR observations, using two candidate soft excess models as inputs, to determine whether such campaigns can disambiguate between them by using hard and soft X-ray observations in tandem. The simulated spectra are fit with the simplest "observer's model" of a black body and neutral reflection to characterise the strength of the soft and hard excesses. A plot of the strength of the hard excess against the soft excess strength provides a diagnostic plot which allows the soft excess production mechanism to be determined in individual sources and samples using current state-of-the-art and next generation hard X-ray enabled observatories. This approach can be straightforwardly extended to other candidate models for the soft excess.Comment: 12 pages, 11 figures, accepted for publication in ApJ. Added reference

Research Notes : Screening for cyst nematode resistance in soybean breeding

As the soybean cyst nematode (SCN), Heterodera glycines Ichinohe, has become a serious pest of soybeans in the USA, development of resistant culti-vars has received greater attention. This necessitates screening of large numbers of plant progenies to locate SCN-resistant isolates in segregating generations. Ross and Brim (1957) used a double-row method to detect SCN-resistant strains of soybeans