Separable time-causal and time-recursive spatio-temporal receptive fields

We present an improved model and theory for time-causal and time-recursive spatio-temporal receptive fields, obtained by a combination of Gaussian receptive fields over the spatial domain and first-order integrators or equivalently truncated exponential filters coupled in cascade over the temporal domain. Compared to previous spatio-temporal scale-space formulations in terms of non-enhancement of local extrema or scale invariance, these receptive fields are based on different scale-space axiomatics over time by ensuring non-creation of new local extrema or zero-crossings with increasing temporal scale. Specifically, extensions are presented about parameterizing the intermediate temporal scale levels, analysing the resulting temporal dynamics and transferring the theory to a discrete implementation in terms of recursive filters over time.Comment: 12 pages, 2 figures, 2 tables. arXiv admin note: substantial text overlap with arXiv:1404.203

Glucocorticoid receptor mRNA levels are selectively decreased in neutrophils of children with sepsis

Objective: Corticosteroids are used in sepsis treatment to benefit outcome. However, discussion remains on which patients will benefit from treatment. Inter-individual variations in cortisol sensitivity, mediated through the glucocorticoid receptor, might play a role in the observed differences. Our aim was to study changes in mRNA levels of three glucocorticoid receptor splice variants in neutrophils of children with sepsis. Patients and design: Twenty-three children admitted to the pediatric intensive care unit with sepsis or septic shock were included. Neutrophils were isolated at days 0, 3 and 7, and after recovery (>3 months). mRNA levels of the glucocorticoid receptor splice variants GR-α (determining most of the cortisol effect), GR-P (increasing GR-α effect) and GR-β (inhibitor of GR-α) were measured quantitatively. Main results: Neutrophils from sepsis patients showed decreased levels of glucocorticoid receptor mRNA of the GR-α and GR-P splice variants on day 0 compared to after recovery. GR-α and GR-P mRNA levels showed a gradual recovery on days 3 and 7 and normalized after recovery. GR-β mRNA levels did not change significantly during sepsis. GR expression was negatively correlated to interleukin-6 (a measure of disease severity, r = -0.60, P = 0.009). Conclusions: Children with sepsis or septic shock showed a transient depression of glucocorticoid receptor mRNA in their neutrophils. This feature may represent a tissue-specific adaptation during sepsis leading to increased cortisol resistance of neutrophils. Our study adds to understanding the mechanism of cortisol sensitivity in immune cells. Future treatment strategies, aiming at timing and tissue specific regulation of glucocorticoids, might benefit patients with sepsis or septic shock

Laguerre-domain adaptive filters

Using a tapped-delay-line as an adaptive fitter, the complexity of the filter increases with increasing correlation length of input and reference signal. The author seeks simple adaptive filter structures such that for a long correlation length only a minor complexity of the filter is needed. He considers adaptive mechanisms governed by an exponentially weighted squared-error criterion. Laguerre-domain adaptive filters are introduced, which lead to a tapped IIR-filter line. These filters contain a discount factor as a free variable, which makes it possible to set the memory and the number of adaptive coefficients independently. Convergence properties of the proposed adaptive filters are discusse

Linear and quadrature models for data from treshold measurements of the transient visual system

III this paper two models are considered for the transient visual system at threshold. One is a linear model and the other a model contain ing a quadrature element. Both models are commonly used on evidence from different experimental sources. It is shown that both models act in a similar fashion for the experiments using a perturbation technique as is the case at IPO. It is however possible to distinguish between these models in an experiment with a. perturbation technique using a statistical test. This test is discussed and pe.rformed and it is shown that it supports the linear and rejects the quadrature modeJ

Modified RGB Cameras for Infrared Remote-PPG

Multi-wavelength cameras play an essential role in remote photoplethysmography (PPG). Whereas these are readily available for visible light, this is not the case for near infrared (NIR). We propose to modify existing RGB cameras to make them suited for NIR-PPG. In particular, we exploit the spectral leakage of the RGB channels in infrared in combination with a narrow dual-band filter. Such camera modification is simple, cost-effective, easy to implement, and it is shown to attain a pulse rate extraction performance comparable to that of multiple narrow-band NIR cameras

Full video pulse extraction

\u3cp\u3eThis paper introduces a new method to automate heart-rate detection using remote photoplethysmography (rPPG). The method replaces the commonly used region of interest (RoI) detection and tracking, and does not require initialization. Instead, it combines a number of candidate pulse-signals computed in the parallel, each biased towards differently colored objects in the scene. The method is based on the observation that the temporally averaged colors of video objects (skin and background) are usually quite stable over time in typical application-driven scenarios, such as the monitoring of a subject sleeping in bed, or an infant in an incubator. The resulting system, called full video pulse extraction (FVP), allows the direct use of raw video streams for pulse extraction. Our benchmark set of diverse videos shows that FVP enables long-term sleep monitoring in visible light and in infrared, and works for adults and neonates. Although we only demonstrate the concept for heart-rate monitoring, we foresee the adaptation to a range of vital signs, thus benefiting the larger video health monitoring field.\u3c/p\u3

Construction of local bases

A local signal analysis represents the properties of a signal on selected bounded domains. In the one-dimensional case, the local signal analysis can be based on orthogonal projections which are related to the subdivision into intervals. The multidimensional situation is more difficult to analyze. Some ideas of how to transfer the one-dimensional case to the multidimensional one are considered, replacing intervals by polytopes. As an example, the hexagonal subdivision of the two-dimensional space is treated

Single element remote-PPG

\u3cp\u3eCamera-based remote photoplethysmography (remote-PPG) technology has shown great potential for contactless pulse-rate monitoring. However, remote-PPG systems typically analyze face images, which may restrict applications in view of privacy-preserving regulations such as the recently announced General Data Protection Regulation in the European Union. In this paper, we investigate the case of using single-element sensing as an input for remote-PPG extraction, which prohibits facial analysis and thus evades privacy issues. It also improves the efficiency of data storage and transmission. In contrast to known remote-PPG solutions using skin-selection techniques, the input signals in a single-element setup will contain a non-negligible degree of signal components associated with non-skin areas. Current remote-PPG extraction methods based on physiological and optical properties of skin reflections are therefore no longer valid. A new remote-PPG method, named Soft Signature based extraction (SoftSig), is proposed to deal with this situation by softening the dependence of pulse extraction on prior knowledge. A large-scale experiment validates the concept of single-element remote-PPG monitoring and shows the improvement of SoftSig over general purpose solutions.\u3c/p\u3