1,045 research outputs found
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Signal Characteristics of Civil GPS Jammers
This paper surveys the signal properties of 18 commercially
available GPS jammers based on experimental
data. The paper is divided into two distinct tests.
The first characterizes the jamming signals, and the
second test determines the effective range of 4 of the
jammers. The first test uses power spectra from discrete
Fourier transforms (DFTs) of the time series data
to show that all the jammers employ approximately the same jamming method, i.e. linear frequency modulation
of a single tone. The spectra also show that
there are significant jammer-to-jammer variations, including
between jammers of the same model, and that
a given jammer’s signal may vary over time. The first
test also includes measurements of signal power within
frequency bands centered at the L1 and L2 frequencies,
along with the sweep periods and the sweep range at
both frequencies. The second test presents measurements
of the attenuation of the jamming signal necessary
to allow a commercially available GPS receiver to
acquire and track signals from a GPS simulator. From
the attenuation levels and some assumptions about the
antennas used, upper limits on the effective jamming
ranges are calculated for 4 of the jammers, with a resulting
maximum range of 6–9 km.Aerospace Engineering and Engineering Mechanic
In Vitro Expression of Full-Length and Truncated Bovine Respiratory Syncytial Virus G Proteins and Their Antibody Responses in BALB/c Mice
Bovine respiratory syncytial virus (BRSV) is a primary cause of lower respiratory tract disease in calves. Protection is incomplete following vaccination or natural infection, as re-infections are common. The objectives of this study were to create plasmid DNA constructs encoding the full-length, secreted, or conserved region of the BRSV G glycoprotein, and to compare and evaluate their expression in cell culture and potential to induce antibody responses in BALB/c mice. Transfection of COS-7 cells with plasmid DNA resulted in expression of the BRSV G region from each of the plasmid DNA constructs. Following inoculation of BALB/c mice with plasmid DNA, a significant and equivalent anti-BRSV G IgG response was elicited to the full-length and truncated BRSV G proteins. These constructs may be used to study host pathological and immunological responses
ExoMol line lists -- LIII: Empirical Rovibronic spectra of Yttrium Oxide (YO)
Empirical line lists for the open shell molecule YO (yttrium
oxide) and its isotopologues are presented. The line lists cover the 6 lowest
electronic states: , , , , and up to 60000 cm
( m) for rotational excitation up to . An \textit{ab
initio} spectroscopic model consisting of potential energy curves (PECs),
spin-orbit and electronic angular momentum couplings is refined by fitting to
experimentally determined energies of YO, derived from published YO
experimental transition frequency data. The model is complemented by empirical
spin-rotation and -doubling curves and \textit{ab initio} dipole
moment and transition dipole moment curves computed using MRCI. The \textit{ab
initio} PECs computed using the complete basis set limit extrapolation and the
CCSD(T) method with its higher quality provide an excellent initial
approximation for the refinement. Non-adiabatic coupling curves for two pairs
of states of the same symmetry / and / are computed using a
state-averaged CASSCF and used to built diabatic representations for the , , and
curves. Calculated lifetimes of YO are tuned to agree well with the experiment,
where available. The BRYTS YO line lists for are included into the ExoMol data
base (www.exomol.com)
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Nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface
This article discusses nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface
Numerical Approaches to Spacetime Singularities
This Living Review updates a previous version which its itself an update of a
review article. Numerical exploration of the properties of singularities could,
in principle, yield detailed understanding of their nature in physically
realistic cases. Examples of numerical investigations into the formation of
naked singularities, critical behavior in collapse, passage through the Cauchy
horizon, chaos of the Mixmaster singularity, and singularities in spatially
inhomogeneous cosmologies are discussed.Comment: 51 pages, 6 figures may be found in online version: Living Rev.
Relativity 2002-1 at www.livingreviews.or
The Australian Early Years Learning Framework: learning what?
Early childhood education and care have assumed importance in many government policy agendas. This attention is often accompanied by calls for greater accountability regarding the anticipated learning outcomes for young children. In Australia, the expected learning outcomes for children aged birth to five years are outlined in the recently published Early Years Learning Framework (EYLF). In this article, the author examines the relationship between the EYLF’s outcomes and subject area or content knowledge. The article draws from post-structural and social constructionist understandings of knowledge as unfinished, contestable and contextual. The author concludes that it is not content knowledge itself that is problematic, but it is the way the child and teacher are often positioned in relation to that knowledge that constrains the potential for effective teaching and learning in the early years. The author suggests that revisiting traditional assumptions about content knowledge extends and develops many of the ideas about teaching and learning that are identified in the EYLF, and opens up new identity positions for both children and early childhood educators
Rhizotoxicity of aluminate and polycationic aluminium at high pH
Although monomeric Al species are often toxic in acidic soils, the effects of the aluminate ion (Al(OH)4-) on roots grown in alkaline media are still unclear. Dilute, alkaline (pH 9.5) nutrient solutions were used to investigate the effects of Al(OH)4- on root growth of mungbean (Vigna radiata L.). Root growth was reduced by 13 % after 3 d growth in solutions with an Al(OH)4- activity of 16 μM and no detectable polycationic Al (Al13). This decrease in root growth was associated with the formation of lesions on the root tips (due to the rupturing of the epidermal and outer cortical cells) and a slight limitation to root hair growth (particularly on the lateral roots). When roots displaying these symptoms were transferred to fresh Al(OH)4- solutions for a further 12 h, no root tip lesions were observed and root hair growth on the lateral roots improved. The symptoms were similar to those induced by Al13 at concentrations as low as 0.50 μM Al which are below the detection limit of the ferron method. Thus, Al(OH)4- is considered to be non-toxic, with the observed reduction in root growth in solutions containing Al(OH)4- due to the gradual formation of toxic Al13 in the bulk nutrient solution resulting from the acidification of the alkaline nutrient solution by the plant roots
Setting upper limits on the strength of periodic gravitational waves from PSR J1939+2134 using the first science data from the GEO 600 and LIGO detectors
Data collected by the GEO 600 and LIGO interferometric gravitational wave detectors during their first observational science run were searched for continuous gravitational waves from the pulsar J1939+2134 at twice its rotation frequency. Two independent analysis methods were used and are demonstrated in this paper: a frequency domain method and a time domain method. Both achieve consistent null results, placing new upper limits on the strength of the pulsar's gravitational wave emission. A model emission mechanism is used to interpret the limits as a constraint on the pulsar's equatorial ellipticity
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