Segregation of In to dislocations in InGaN.

Dislocations are one-dimensional topological defects that occur frequently in functional thin film materials and that are known to degrade the performance of InxGa1-xN-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure are expected to occur in and around dislocation cores in InxGa(1-x)N alloy thin films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films.This work was funded in part by the Cambridge Commonwealth trust, St. John’s College and the EPSRC. SKR is funded through the Cambridge-India Partnership Fund and Indian Institute of Technology Bombay via a scholarship. MAM acknowledges support from the Royal Society through a University Research Fellowship. Additional support was provided by the EPSRC through the UK National Facility for Aberration-Corrected STEM (SuperSTEM). The Titan 80- 200kV ChemiSTEMTM was funded through HM Government (UK) and is associated with the capabilities of the University of Manchester Nuclear Manufacturing (NUMAN) capabilities. SJH acknowledges funding from the Defence Treat Reduction Agency (DTRA) USA (grant number HDTRA1-12-1-0013).This is the accepted manuscript. The final version is available at http://pubs.acs.org/doi/abs/10.1021/nl5036513

Lagomorpha as a model morphological system

Due to their global distribution, invasive history, and unique characteristics, European rabbits are recognizable almost anywhere on our planet. Although they are members of a much larger group of living and extinct mammals [Mammalia, Lagomorpha (rabbits, hares, and pikas)], the group is often characterized by several well-known genera (e.g., Oryctolagus, Sylvilagus, Lepus, and Ochotona). This representation does not capture the extraordinary diversity of behavior and form found throughout the order. Model organisms are commonly used as exemplars for biological research, but there are a limited number of model clades or lineages that have been used to study evolutionary morphology in a more explicitly comparative way. We present this review paper to show that lagomorphs are a strong system in which to study macro- and micro-scale patterns of morphological change within a clade that offers underappreciated levels of diversity. To this end, we offer a summary of the status of relevant aspects of lagomorph biology.Brian Kraatz, Rafik Belabbas, Łucja Fostowicz-Frelik, De-Yan Ge, Alexander N. Kuznetsov, Madlen M. Lang ... et al

UERE Analysis for Static Single Frequency Positioning Using Data of IGS Stations

This work analyses the measurements of major errors (ephemeris error, satellite clock error, ionosphere error, troposphere error, multipath and receiver noise error), their correlation laws and their amplitude function depending on time and elevation angle for a static single frequency positioning receiver. The objective is double, first to give a better comprehension of the law of behaviour of error sources in a Global Navigation Satellite System (GNSS) and second to provide a measurement method of the User Equivalent Range Error (UERE)

Adaptive Antenna Against Multipath?

Improvements achieved in GNSS space and control segments as well as in receiver signal processing technologies leave multipath nowadays as the main challenge to the navigation society especially in the case of differential navigation. The use of an adaptive antenna in the navigation receiver can be evidently a prospective solution to the problem of multipath. It allows to discriminate incoming signals in spatial domain and to suppress multipath signals efficiently even when common temporal and frequency domain techniques fail. The adaptive antenna is also able to produce a large gain to the line-of-sight satellite signals and therefore to improve receiver performance in unfavourable signal conditions. This paper presents investigation results for the performance of a basic navigation receiver combined with the adaptive antenna, a 5-by-5 uniform rectangular antenna array. The performance is characterised in terms of the pseudorange error. Three multipath scenarios, namely severe multipath conditions, final approach and urban car, were used with signals of GPS and signals likely to be used in coming Galileo. The signals were tracked with the commonly used non-coherent DLL and Costas PLL. The results indicate that both the multipath induced bias and the standard deviation of the pseudorange error can be reduced up to one order of magnitude. While suppressing multipath echoes, the antenna provides more than 10 dB additional gain to the line-of-sight signal when compared to the standard antenna with a hemispherical diagram. In conclusion, the user equivalent range error (UERE) budget is compared for different types of GNSS receivers (single frequency, dual frequency and differential mode) taking into account the results for multipath error with the standard and adaptive antennas. It is shown that the use of adaptive antennas is the most advantageous for dual frequency receivers and receivers with differential mode

Improvement of UERE receiver performance due to multipath suppression with an adaptive antenna

In this paper we present results of modelling the User Equivalent Range Error (UERE) for a navigation receiver equipped with an adaptive 5×5 square antenna array. The antenna array was used as a spatial filter for short delayed multipath echoes in an urban environment. We simulated the receiver multipath pseudorange error with different navigation signals under signal conditions resulted from the use of the adaptive antenna. In order to assess the UERE for various types of navigation receivers, the obtained multipath error has been combined with standard values of other pseudorange error contributions