Self-Organized Criticality in Developing Neuronal Networks

Recently evidence has accumulated that many neural networks exhibit self-organized criticality. In this state, activity is similar across temporal scales and this is beneficial with respect to information flow. If subcritical, activity can die out, if supercritical epileptiform patterns may occur. Little is known about how developing networks will reach and stabilize criticality. Here we monitor the development between 13 and 95 days in vitro (DIV) of cortical cell cultures (n = 20) and find four different phases, related to their morphological maturation: An initial low-activity state (≈19 DIV) is followed by a supercritical (≈20 DIV) and then a subcritical one (≈36 DIV) until the network finally reaches stable criticality (≈58 DIV). Using network modeling and mathematical analysis we describe the dynamics of the emergent connectivity in such developing systems. Based on physiological observations, the synaptic development in the model is determined by the drive of the neurons to adjust their connectivity for reaching on average firing rate homeostasis. We predict a specific time course for the maturation of inhibition, with strong onset and delayed pruning, and that total synaptic connectivity should be strongly linked to the relative levels of excitation and inhibition. These results demonstrate that the interplay between activity and connectivity guides developing networks into criticality suggesting that this may be a generic and stable state of many networks in vivo and in vitro

CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence

A Petri-Net Based Model for PBS System on Linus Enterprise Server

: A typical batch queuing system can schedule jobs for execution by using of a set of queue controls; these queuing controls decide the queue from which jobs will be selected. Typically Jobs are selected within each queue in a first –in –first –out order which limits the set of scheduling policies. The use of the Portable Batch System (PBS) is a suitable solution to this limitation. We present a robust and intelligent Portable Batch System (PBS) implemented with petri-net segmentation and firing squad model with the integration of an external scheduling module that employs the Maui Scheduler which has full knowledge of the available queued jobs, running jobs and usable system resource

Analysis of along track profiles of chlorophyll fluorescence derived from hyperspectral imaging data

Remote sensing of sun-induced chlorophyll fluorescence is a promising approach to track photosynthetic activity at various scales. So far, knowledge on the spatial patterns of the signal is very limited. In this study, we investigate the possibility to derive sun-induced chlorophyll fluorescence over an intensive agricultural area by means of airborne hyperspectral data. Main focus of the analysis is to interpret the spatial variability of the estimated fluorescence signal on the basis of its interdependency with different proxies for green vegetation. Results indicate that the fluorescence signal has potential to explain intra-field variations concerning vegetation state and cover

Mechanical weed control

Side effects of herbicides and increasing prevalence of organic farming nduce the need of further developments in mechanical weed control. Mechanical weed control is mainly associated with cultivating tillage (e.g. tertiary tillage), but also primary and secondary tillage influence weeds. Cultivating tillage is performed in growing crops with harrows, hoes, brushes and a number of special tools for intra-row weed control. Inter-row cultivations have been used in many decades in row crops and perform in general well. To increase their capacity and accuracy, guidance systems are important to steer the hoes along the rows. The success of inter- and intra-row cultivation is highly influenced by selectivity factors. The control mechanisms of all cultivating tillage methods are burring in soil, uprooting,and tearing plants into pieces. Especially for whole crop and intra-row cultivators, successful weed control is highly influenced by appropriate adjustment of the intensity (aggressiveness) of cultivation according to the variations of soil resistance, crop and weed resistance to cultivation and the competitive interactions between crop and weeds. Site-specific weed management aims to identify the spatial and temporal variability of weeds and manage them correspondingly. New technologies for sensing crops and weeds in real-time and robotics allow a precise operation of mechanical tools, to improve efficacy of control and reduce operation costs. Hence in this chapter, implements for mechanical weeding are described together with their options for site-specific weed control strategies. Harrows and rotary hoes are used for whole crop treatment, but it is essential to find the right timing and intensity to obtain the best selectivity and yield response. Different implements attached to the same vehicle are combined together attempting more selective weed control,like the in-row cultivator, the rotary harrow, and the precision hoe. Lately, there are prototypes intending automatic adjustment of the aggressiveness for the springtine harrow and autonomous guidance for hoes, thus getting closer to a real-time site-specific weed management approach

Imaging Spectroscopy of Urban Environments

© 2018 Springer Nature B.V. Future spaceborne imaging spectroscopy data will offer new possibilities for mapping ecosystems globally, including urban environments. The high spectral information content of such data is expected to improve accuracies and thematic detail of maps on urban composition and urban environmental condition. This way, urgently needed information for environmental models will be provided, for example, for microclimate or hydrological models. The diverse vertical structures, highly frequent spatial change and a great variety of materials cause challenges for urban environmental mapping with Earth observation data, especially at the 30 m spatial resolution of data from future spaceborne imaging spectrometers. This paper gives an overview of the state-of-the-art in urban imaging spectroscopy considering decreasing spatial resolution, the related user requirements and existing knowledge gaps, as well as expected future directions for the work with new data sets.status: Published onlin

Thermal evaluation of the Local Climate Zone scheme in Belgium

Global warming and the increasing world population will only put more pressure on the living conditions in urban environments. From a thermal comfort point of view, it is clear that there is a need for sustainable urban planning in which the thermal behavior of new developments can be accounted for. Mapping the city into local climate zones (LCZs), with unique air temperature regimes, could be a useful tool supporting urban planners in their decision making. The LCZ scheme is currently being used to globally map LCZs as a part of the World Urban Database and Access Portal Tools (WUDAPT) initiative. In this paper we evaluate the thermal behavior of LCZs for three Belgian cities, Brussels, Antwerp and Ghent, based on modelled air temperature. Preliminary results show similarities for the thermal behavior of the built zones which can point at the generic applicability of the LCZ scheme, even in old European cities characterized by heterogeneous urban morphologies at small horizontal scales