Experimental Results of a Differential Angle-of-Arrival Based 2D Localization Method Using Signals of Opportunity

This paper presents a study of differential AoA (Angle-of-Arrival) based 2D localization method utilizing FM radio signals (88 MHz–108 MHz) as Signals of Opportunity (SOP). Given prior knowledge of the transmitters’ position and signal characteristics, the proposed technique utilizes triangulation to localize receiver’s 2D position. Dual antenna interferometry provides the received signals’ AoA required for triangulation. Reliance on precise knowledge of antenna system’s orientation is removed by utilizing diferential Angle of Arrivals (dAoAs). Te 2D localization accuracy is improved by utilizing colocated transmitters, a concept proposed in this paper as supertowers. Analysis, simulation, and ground-based experiments have been presented; results showed that when the SNR (Signal-to-Noise Ratio) is higher than 45 dB, the proposed method localizes the receiver’s 2D position with an error of less than 15 m

Infrared Optical Properties of Ferropericlase (Mg1-xFexO): Experiment and Theory

The temperature dependence of the reflectance spectra of magnesium oxide (MgO) and ferropericlase (Mg1-xFexO, for x=0.06 and x=0.27) have been measured over a wide frequency range (~50 to 32000 cm-1) at 295 and 6 K. The complex dielectric function has been determined from a Kramers-Kronig analysis of the reflectance. The spectra of the doped materials resembles pure MgO in the infrared region, but with much broader resonances. We use a shell model to calculate the dielectric function of ferropericlase, including both anharmonic phonon-phonon interactions and disorder scattering. These data are relevant to understanding the heat conductivity of ferropericlase in the earth's lower mantle.Comment: 17 pages, 6 figure

C3 Photosynthesis in the Gametophyte of the Epiphytic CAM Fern Pyrrosia Longifolia (Polypodiaceae)

This is the publisher's official version, also available at: http://www.jstor.org/stable/2445689Sporophytes of some epiphytic species in the fern genus Pyrrosia exhibit Crassulacean acid metabolism (CAM), generally considered to be a derived physiological response to xeric habitats. Because these species alternate between independent sporophytic and gametophytic generations yet only the sporophyte has been characterized physiologically, experiments were conducted to determine the photosynthetic pathways present in mature sporophytes, immature sporophytes, and gametophytes of Pyrrosia longifolia. Diurnal C 0 2 exchange and malic acid fluctuations demonstrated that although the mature sporophytes exhibited CAM, only C3 photosynthesis occurred in the gametophytes and young sporophytes. Consideration of the above results and those from previous studies, as well as the life cycle of ferns, indicates that the induction of CAM probably occurs at a certain developmental stage of the sporophyte and/or following exposure to stress. Elucidation of the precise mechanisms underlying this C^-CAM transition awaits further research

Assessing a Hydrodynamic Description for Instabilities in Highly Dissipative, Freely Cooling Granular Gases

An intriguing phenomenon displayed by granular flows and predicted by kinetic-theory-based models is the instability known as particle "clustering," which refers to the tendency of dissipative grains to form transient, loose regions of relatively high concentration. In this work, we assess a modified-Sonine approximation recently proposed [Garz\'o et al., Physica A 376, 94 (2007)] for a granular gas via an examination of system stability. In particular, we determine the critical length scale associated with the onset of two types of instabilities -vortices and clusters- via stability analyses of the Navier-Stokes-order hydrodynamic equations by using the expressions of the transport coefficients obtained from both the standard and the modified-Sonine approximations. We examine the impact of both Sonine approximations over a range of solids fraction \phi <0.2 for small restitution coefficients e=0.25--0.4, where the standard and modified theories exhibit discrepancies. The theoretical predictions for the critical length scales are compared to molecular dynamics (MD) simulations, of which a small percentage were not considered due to inelastic collapse. Results show excellent quantitative agreement between MD and the modified-Sonine theory, while the standard theory loses accuracy for this highly dissipative parameter space. The modified theory also remedies a (highdissipation) qualitative mismatch between the standard theory and MD for the instability that forms more readily. Furthermore, the evolution of cluster size is briefly examined via MD, indicating that domain-size clusters may remain stable or halve in size, depending on system parameters.Comment: 4 figures; to be published in Phys. Rev.

Influence of Richness and Seeding Density on Invasion Resistance in Experimental Tallgrass Prairie Restorations

In recent years, agricultural producers and non-governmental organizations and agencies have restored thousands of hectares of cropland to grassland in the Great Plains of the United States. However, little is known about the relationships between richness and seeding density in these restorations and resistance to invasive plant species. We assessed the effects of richness and seeding density on resistance to invasive and other unseeded plant species in experimental tallgrass prairie plots in central Nebraska. In 2006, twenty-four 55 m × 55 m plots were planted with six replicates in each of four treatments: high richness (97 species typically planted by The Nature Conservancy), at low and high seeding densities, and low richness (15 species representing a typical Conservation Reserve Program mix, CP25), at low and high seeding densities. There was a significant negative relationship between richness and basal cover of unseeded perennial forbs/legumes and unseeded perennial/annual grasses, abundance of bull thistle (Cirsium vulgare), and the number of inflorescences removed from smooth brome (Bromus inermis) transplants. Invasion resistance may have been higher in the high richness treatments because of the characteristics of the dominant species in these plots or because of greater interspecific competition for limiting resources among forbs/legumes with neighboring plants belonging to the same functional group. Seeding density was not important in affecting invasion resistance, except in the cover of unseeded grasses. Increasing seed mix richness may be more effective than increasing the seeding density for decreasing invasion by unseeded perennial species, bull thistle, and smooth brome

Responses of predatory invertebrates to seeding density and plantspecies richness in experimental tallgrass prairie restorations

In recent decades, agricultural producers and non-governmental organizations have restored thousandsof hectares of former cropland in the central United States with native grasses and forbs. However,the ability of these grassland restorations to attract predatory invertebrates has not been well docu-mented, even though predators provide an important ecosystem service to agricultural producers bynaturally regulating herbivores. This study assessed the effects of plant richness and seeding density onthe richness and abundance of surface-dwelling (ants, ground beetles, and spiders) and aboveground(ladybird beetles) predatory invertebrates. In the spring of 2006, twenty-four 55 m × 55 m-plots wereplanted to six replicates in each of four treatments: high richness (97 species typically planted by TheNature Conservancy), at low and high seeding densities, and low richness (15 species representing a typ-ical Natural Resources Conservation Service Conservation Reserve Program mix, CP25), at low and highseeding densities. Ants, ground beetles, and spiders were sampled using pitfall traps and ladybird beetleswere sampled using sweep netting in 2007–2009. The abundance of ants, ground beetles, and spidersshowed no response to seed mix richness or seeding density but there was a significant positive effect ofrichness on ladybird beetle abundance. Seeding density had a significant positive effect on ground beetleand spider species richness and Shannon–Weaver diversity. These results may be related to differencesin the plant species composition and relative amount of grass basal cover among the treatments ratherthan richness

A flavour of omics approaches for the detection of food fraud

Food fraud has been identified as an increasing problem on a global scale with wide-ranging economic, social, health and environmental impacts. Omics and their related techniques, approaches, and bioanalytical platforms incorporate a significant number of scientific areas which have the potential to be applied to and significantly reduce food fraud and its negative impacts. In this overview we consider a selected number of very recent studies where omics techniques were applied to detect food authenticity and could be implemented to ensure food integrity. We postulate that significant reductions in food fraud, with the assistance of omics technologies and other approaches, will result in less food waste, decreases in energy use as well as greenhouse gas emissions, and as a direct consequence of this, increases in quality, productivity, yields, and the ability of food systems to be more resilient and able to withstand future food shocks

An improved coherent radar depth sounder

This is the published version. Copyright International Glaciological SocietyThe University of Kansas developed a coherent radar depth sounder during the 1980s. This system was originally developed for glacial ice-thickness measurements in the Antarctic. During the field tests in the Antarctic and Greenland, we found the system performance to be less than optimum. The field tests in Greenland were performed in 1993, as a part of the NASA Program for Arctic Climate Assessment ( PARCA ). We redesigned and rebuilt this system to improve the performance. The radar uses pulse compression and coherent signal processing to obtain high sensitivity and fine along-track resolution. It operates at a center frequency of 150 MHz with a radio frequency bandwidth of about 17 MHz, which gives a range resolution of about 5 m in ice. We have been operating it from a NASA P-3 aircraft for collecting ice-thickness data in conjunction with laser surface-elevation measurements over the Greenland ice sheet during the last 4 years. We have demonstrated that this radar can measure the thickness of more than 3 km of cold ice and can obtain ice-thickness information over outlet glaciers and ice margins. In this paper we provide a brief survey of radar sounding of glacial ice, followed by a description of the system and subsystem design and performance. We also show sample results from the field experiments over the Greenland ice sheet and its outlet glaciers