Microwave scattering parameters of ferro-nano-carbon–composites for tracking range countermeasures

Ditching radar seekers at a microwave tracking range is of utmost tactical importance which could be realized by developing insight into designing an effective electromagnetic interference (EMI) shield. We report...

Assessing Seaglider® Model-based Position Accuracy on an Acoustic Tracking Range

Seagliders® are buoyancy-driven autonomous underwater vehicles whose sub-surface position estimates are typically derived from velocities inferred using a flight model. We present a method for computing velocities and positions during the different phases typically encountered during a dive-climb profile based on a buoyancy-driven flight model. We compare these predictions to observations gathered from a Seaglider deployment on the acoustic tracking range in Dabob Bay (200 m depth, mean vehicle speeds ~30 cm s-1), permitting us to bound the position accuracy estimates and understand sources of various errors. We improve position accuracy estimates during long vehicle accelerations by numerically integrating the flight-model's fundamental momentum-balance equations. Overall, based on an automated estimation of flight-model parameters, we confirm previous work that predicted vehicle velocities in the dominant dive and climb phases are accurate to < 1 cm s-1, which bounds the accumulated position error in time. However, in this energetic tidal basin, position error also accumulates due to unresolved depth-dependent flow superimposed upon an inferred depth-averaged current.

Structured Back Focal Plane Interferometry (SBFPI)

Back focal plane interferometry (BFPI) is one of the most straightforward and powerful methods for achieving sub-nanometer particle tracking precision at high speed (MHz). BFPI faces technical challenges that prohibit tunable expansion of linear detection range with minimal loss to sensitivity, while maintaining robustness against optical aberrations. In this paper, we devise a tunable BFPI combining a structured beam (conical wavefront) and structured detection (annular quadrant photodiode). This technique, which we termed Structured Back Focal Plane Interferometry (SBFPI), possesses three key novelties namely: extended tracking range, low loss in sensitivity, and resilience to spatial aberrations. Most importantly, the conical wavefront beam preserves the axial Gouy phase shift and lateral beam waist that can then be harnessed in a conventional BFPI system. Through a series of experimental results, we were able to tune detection sensitivity and detection range over the SBFPI parameter space. We also identified a figure of merit based on the experimental optimum that allows us to identify optimal SBPFI configurations that balance both range and sensitivity. In addition, we also studied the resilience of SBFPI against asymmetric spatial aberrations (astigmatism of up to 0.8 λ) along the lateral directions. The simplicity and elegance of SBFPI will accelerate its dissemination to many associated fields in optical detection, interferometry and force spectroscopy.

Rapid range shifts in African Anopheles mosquitoes over the last century

Anopheles mosquitoes are the vector of malaria and several neglected tropical diseases, such as lymphatic filariasis and O’nyong’nyong fever. Like many species, mosquitoes are expected to track warming temperatures in a changing climate, possibly introducing disease into previously protected higher-latitude and higher-elevation communities. Tracking range shifts is fundamental for forecasting disease risk, but has proven challenging to do in real-time. Here, we use historical data to trace those shifts in Anopheles for the first time. We test for range shifts using a new comprehensive dataset of Anopheles occurrences in sub-Saharan Africa, with over 500,000 species-locality pair records spanning 1898 to 2016. We propose a simple regression-based method of measuring range shifts in larger datasets, which identifies a more coherent signal in anopheline range shifts than the Mann-Whitney method popular in ecology. We estimate range-shifting species gained 1.56 meters of elevation annually, and moved southward 6.28 km per year in their outer range limits, a full order of magnitude faster than some “rapid” shifts observed in the literature. We expect these results to have major implications for malaria control work in sub-Saharan Africa, and for our broader picture of vector responses to climate change.