A Russian Dolls ordering of the Hadamard basis for compressive single-pixel imaging

Single-pixel imaging is an alternate imaging technique particularly well-suited to imaging modalities such as hyper-spectral imaging, depth mapping, 3D profiling. However, the single-pixel technique requires sequential measurements resulting in a trade-off between spatial resolution and acquisition time, limiting real-time video applications to relatively low resolutions. Compressed sensing techniques can be used to improve this trade-off. However, in this low resolution regime, conventional compressed sensing techniques have limited impact due to lack of sparsity in the datasets. Here we present an alternative compressed sensing method in which we optimize the measurement order of the Hadamard basis, such that at discretized increments we obtain complete sampling for different spatial resolutions. In addition, this method uses deterministic acquisition, rather than the randomized sampling used in conventional compressed sensing. This so-called ‘Russian Dolls’ ordering also benefits from minimal computational overhead for image reconstruction. We find that this compressive approach performs as well as other compressive sensing techniques with greatly simplified post processing, resulting in significantly faster image reconstruction. Therefore, the proposed method may be useful for single-pixel imaging in the low resolution, high-frame rate regime, or video-rate acquisition

Loss of soil carbon and nitrogen indicates climate change-induced alterations in a temperate forest ecosystem

Climate warming is expected to influence terrestrial biogeochemical cycles by modifying the quality and quantity of plant litter input to soils. Although a growing number of studies recognize the importance of plant litter input in influencing the loss of soil organic matter (SOM) through a phenomenon called the priming effect (PE), the exact mechanisms behind PE are not well known. Importantly, most PE research is based on short term pot experiments in which fresh organic matter (FOM) input is represented by a single addition of compounds of unnaturally simple chemical composition. Furthermore, only a few studies exist in which the PE was explored in terms of organic C (SOC) and total N content in the soil. Here, we report results of a 3-year long litter manip-ulation study conducted under natural conditions in a broadleaved Korean pine forest in N-E China. We show that the extra supply (twice the normal input) of aboveground tree litter composing of conifer needles, leaves and small twigs was associated not only with slightly decreased SOC (by 5%) but especially that of soil total N (STN) (by 15%) content in the top soil (0-5 cm depth). In contrast, removal of litter resulted in an increased (ca. 15%) amount of both SOC and STN during the study when compared to control soils receiving natural litter input. Despite the enhanced leaf litter decomposition rate in the treatment receiving extra litter, the changes in SOC and STN were related neither to soil microbial biomass nor to community composition. The amount of N lost (40.0 g m- 2) in the soil due to litter addition was ca. three times the amount of N added (12.3 g m- 2) via the litter, while the amount of C lost (238 g m- 2) was about one third of that added (940 g m- 2), suggesting that soil N in our research site is more prone to the PE than soil C. As we did not manipulate belowground FOM input, our results suggest that input of aboveground litter rather than that by roots explained the PE in our study. Results of our long-term study conducted under natural conditions in undisturbed forest soils highlight the large potential of recalcitrant, aboveground litter to affect the PE, which should not go unnoticed when predicting the role of forest soils under conditions (such as climate warming) when these soils act as C sinks.Peer reviewe

Gap junction inhibition by heptanol increases ventricular arrhythmogenicity by reducing conduction velocity without affecting repolarization properties or myocardial refractoriness in Langendorff-perfused mouse hearts.

This is the final version of the article. It first appeared from Spandidos via https://doi.org/ 10.3892/mmr.2016.5738In the current study, arrhythmogenic effects of the gap junction inhibitor heptanol (0.05 mM) were examined in Langendorff-perfused mouse hearts. Monophasic action potential recordings were obtained from the left ventricular epicardium during right ventricular pacing. Regular activity was observed both prior and subsequent to application of heptanol in all of the 12 hearts studied during 8 Hz pacing. By contrast, induced ventricular tachycardia (VT) was observed after heptanol treatment in 6/12 hearts using a S1S2 protocol (Fisher's exact test; P0.05). Consequently, excitation wavelengths (λ; CV x ERP) were reduced from 9.1±0.6 to 6.5±0.6 mm (P0.05). Together, these observations demonstrate for the first time, to the best of our knowledge, that inhibition of gap junctions alone using a low heptanol concentration (0.05 mM) was able to reduce CV, which alone was sufficient to permit the induction of VT using premature stimulation by reducing λ, which therefore appears central in the determination of arrhythmic tendency.GT was awarded a BBSRC Doctoral Training Award at the University of Cambridge

Adaptive foveated single-pixel imaging with dynamic super-sampling

As an alternative to conventional multi-pixel cameras, single-pixel cameras enable images to be recorded using a single detector that measures the correlations between the scene and a set of patterns. However, to fully sample a scene in this way requires at least the same number of correlation measurements as there are pixels in the reconstructed image. Therefore single-pixel imaging systems typically exhibit low frame-rates. To mitigate this, a range of compressive sensing techniques have been developed which rely on a priori knowledge of the scene to reconstruct images from an under-sampled set of measurements. In this work we take a different approach and adopt a strategy inspired by the foveated vision systems found in the animal kingdom - a framework that exploits the spatio-temporal redundancy present in many dynamic scenes. In our single-pixel imaging system a high-resolution foveal region follows motion within the scene, but unlike a simple zoom, every frame delivers new spatial information from across the entire field-of-view. Using this approach we demonstrate a four-fold reduction in the time taken to record the detail of rapidly evolving features, whilst simultaneously accumulating detail of more slowly evolving regions over several consecutive frames. This tiered super-sampling technique enables the reconstruction of video streams in which both the resolution and the effective exposure-time spatially vary and adapt dynamically in response to the evolution of the scene. The methods described here can complement existing compressive sensing approaches and may be applied to enhance a variety of computational imagers that rely on sequential correlation measurements.Comment: 13 pages, 5 figure

1000 fps computational ghost imaging using LED-based structured illumination

: Single-pixel imaging uses a single-pixel detector, rather than a focal plane detector array, to image a scene. It provides advantages for applications such as multi-wavelength, three-dimensional imaging. However, low frame rates have been a major obstacle inhibiting the use of computational ghost imaging technique in wider applications since its invention one decade ago. To address this problem, a computational ghost imaging scheme, which utilizes an LED-based, high-speed illumination module is presented in this work. At 32 × 32 pixel resolution, the proof-of-principle system achieved continuous imaging with 1000 fps frame rate, approximately two orders larger than those of other existing ghost imaging systems. The proposed scheme provides a cost-effective and high-speed imaging technique for dynamic imaging application