Migratory navigation in birds: new opportunities in an era of fast-developing tracking technology

Birds have remained the dominant model for studying the mechanisms of animal navigation for decades, with much of what has been discovered coming from laboratory studies or model systems. The miniaturisation of tracking technology in recent years now promises opportunities for studying navigation during migration itself (migratory navigation) on an unprecedented scale. Even if migration tracking studies are principally being designed for other purposes, we argue that attention to salient environmental variables during the design or analysis of a study may enable a host of navigational questions to be addressed, greatly enriching the field. We explore candidate variables in the form of a series of contrasts (e. g. land vs ocean or night vs day migration), which may vary naturally between migratory species, populations or even within the life span of a migrating individual. We discuss how these contrasts might help address questions of sensory mechanisms, spatiotemporal representational strategies and adaptive variation in navigational ability. We suggest that this comparative approach may help enrich our knowledge about the natural history of migratory navigation in birds.

Resistance or Resilience? Tracking the Pathway of Recent Arrivals to a ‘New’ Rural Destination

Recent patterns of migration indicate that international migrants are not confined to urban gateways. Instead many migrants have settled in new destination areas located in rural and small town areas. While this might appear to be a positive phenomenon for rural areas struggling with decline and stagnation, the reality is that many of these areas are ill-equipped to manage the rate and pace of change that has been witnessed in recent years. Migration to established, typically urban areas has been the subject of extensive research. However, little is known about the way in which migrants navigate their way through social structures as they settle into destinations with little experience of immigration. Using empirical research, this article considers the way in which migrants navigate their way through social structures to establish life in a so-called ‘new’ migration destination. It analyses the way in which government and civil society respond to their needs of recent arrivals, showing how both NGO’s and the statutory sector play an important role in this process. It considers the ramifications for these different sectors and the implications for so-called ‘new’ destinations as they become more established or ‘mature’ areas of immigration.

Robust visual tracking based on online learning sparse representation

Handling appearance variations is a very challenging problem for visual tracking. Existing methods usually solve this problem by relying on an effective appearance model with two features: (1) being capable of discriminating the tracked target from its background, (2) being robust to the target's appearance variations during tracking. Instead of integrating the two requirements into the appearance model, in this paper, we propose a tracking method that deals with these problems separately based on sparse representation in a particle filter framework. Each target candidate defined by a particle is linearly represented by the target and background templates with an additive representation error. Discriminating the target from its background is achieved by activating the target templates or the background templates in the linear system in a competitive manner. The target's appearance variations are directly modeled as the representation error. An online algorithm is used to learn the basis functions that sparsely span the representation error. The linear system is solved via ℓ1 minimization. The candidate with the smallest reconstruction error using the target templates is selected as the tracking result. We test the proposed approach using four sequences with heavy occlusions, large pose variations, drastic illumination changes and low foreground-background contrast. The proposed approach shows excellent performance in comparison with two latest state-of-the-art trackers.

Enhanced efficiency of envelope-tracking based broadband inverse class-E power amplifier

In this paper, the envelope-tracking technique is exploited to boost average efficiency of the newly introduced broadband Inverse Class-E power amplifier. A 2.26 GHz - 20.5 dBm - 3 V power amplifier was designed, constructed, and measured. For a multi-carrier input signal with 10 dB peak-to-average ratio, the average PAE was increased from 5.7% to 54.5%. © 2008 IEEE.

Human pose tracking in low dimensional space enhanced by limb correction

This paper proposes a two-level 3D human pose tracking method for a specific action captured by several cameras. The generation of pose estimates relies on fitting a 3D articulated model on a Visual Hull generated from the input images. First, an initial pose estimate is constrained by a low dimensional manifold learnt by Temporal Laplacian Eigenmaps. Then, an improved global pose is calculated by refining individual limb poses. The validation of our method uses a public standard dataset and demonstrates its accurate and computational efficiency. © 2011 IEEE.

Empirical performance of RSSI-based Monte Carlo localisation for active RFID patient tracking systems

The range of potential applications for indoor and campus based personnel localisation has led researchers to create a wide spectrum of different algorithmic approaches and systems. However, the majority of the proposed systems overlook the unique radio environment presented by the human body leading to systematic errors and inaccuracies when deployed in this context. In this paper RSSI-based Monte Carlo Localisation was implemented using commercial 868 MHz off the shelf hardware and empirical data was gathered across a relatively large number of scenarios within a single indoor office environment. This data showed that the body shadowing effect caused by the human body introduced path skew into location estimates. It was also shown that, by using two body-worn nodes in concert, the effect of body shadowing can be mitigated by averaging the estimated position of the two nodes worn on either side of the body. © Springer Science+Business Media, LLC 2012.

Online Multiperson Tracking With Occlusion Reasoning and Unsupervised Track Motion Model

We address the problem of multi-target tracking in realistic crowded conditions by introducing a novel dual-stage online tracking algorithm. The problem of data-association between tracks and detections, based on appearance, is often complicated by partial occlusion. In the first stage, we address the issue of occlusion with a novel method of robust data-association, that can be used to compute the appearance similarity between tracks and detections without the need for explicit knowledge of the occluded regions. In the second stage, broken tracks are linked based on motion and appearance, using an online-learned linking model. The online-learned motion-model for track linking uses the confident tracks from the first stage tracker as training examples. The new approach has been tested on the town centre dataset and has performance comparable with the present state-of-the-art

Xenopus cytoplasmic linker-associated protein 1 (XCLASP1) promotes axon elongation and advance of pioneer microtubules

Dynamic microtubules (MTs) are required for neuronal guidance, in which axons extend directionally toward their target tissues. We found that depletion of the MT-binding protein Xenopus cytoplasmic linker-associated protein 1 (XCLASP1) or treatment with the MT drug Taxol reduced axon outgrowth in spinal cord neurons. To quantify the dynamic distribution of MTs in axons, we developed an automated algorithm to detect and track MT plus ends that have been fluorescently labeled by end-binding protein 3 (EB3). XCLASP1 depletion reduced MT advance rates in neuronal growth cones, very much like treatment with Taxol, demonstrating a potential link between MT dynamics in the growth cone and axon extension. Automatic tracking of EB3 comets in different compartments revealed that MTs increasingly slowed as they passed from the axon shaft into the growth cone and filopodia. We used speckle microscopy to demonstrate that MTs experience retrograde flow at the leading edge. Microtubule advance in growth cone and filopodia was strongly reduced in XCLASP1-depleted axons as compared with control axons, but actin retrograde flow remained unchanged. Instead, we found that XCLASP1-depleted growth cones lacked lamellipodial actin organization characteristic of protrusion. Lamellipodial architecture depended on XCLASP1 and its capacity to associate with MTs, highlighting the importance of XCLASP1 in actin-microtubule interactions.

PLL with secondary loop control for self tracking antennas

This paper shows a simple, yet highly effective, tracking phase locked loop circuit which has applications for self steered antenna arrays. The tracking PLL has been demonstrated to accurately phase track signal levels as low as -120 dBm, making it suitable for applications such as SATCOM ground terminals. The implementation is simple requiring a low Q voltage controlled oscillator, a downconverting mixer and a PLL circuit.

Tracking the Fate of Microbially Sequestered Carbon Dioxide in Soil Organic Matter

The microbial contribution to soil organic matter (SOM) has recently been shown to be much larger than previously thought and thus its role in carbon sequestration may also be underestimated. In this study we employ C-13 ((CO2)-C-13) to assess the potential CO2 sequestration capacity of soil chemoautotrophic bacteria and combine nuclear magnetic resonance (NMR) with stable isotope probing (SIP), techniques that independently make use of the isotopic enrichment of soil microbial biomass. In this way molecular information generated from NMR is linked with identification of microbes responsible for carbon capture. A mathematical model is developed to determine real-time CO2 flux so that net sequestration can be calculated. Twenty-eight groups of bacteria showing close homologies with existing species were identified. Surprisingly, Ralstonia eutropha was the dominant group. Through NMR we observed the formation of lipids, carbohydrates, and proteins produced directly from CO2 utilized by microbial biomass. The component of SOM directly associated with CO2 capture was calculated at 2.86 mg C (89.21 mg kg(-1)) after 48 h. This approach can,differentiate between SOM derived through microbial uptake of CO2 and other SOM constituents and represents a first step in tracking the fate and dynamics of microbial biomass in soil.