Phototrophic microalgal cultivation in cold and light-limited environments

Doctoral thesis (PhD) - Nord University, 2019publishedVersio

How deep is deep enough? -- Quantifying class separability in the hidden layers of deep neural networks

Deep neural networks typically outperform more traditional machine learning models in their ability to classify complex data, and yet is not clear how the individual hidden layers of a deep network contribute to the overall classification performance. We thus introduce a Generalized Discrimination Value (GDV) that measures, in a non-invasive manner, how well different data classes separate in each given network layer. The GDV can be used for the automatic tuning of hyper-parameters, such as the width profile and the total depth of a network. Moreover, the layer-dependent GDV(L) provides new insights into the data transformations that self-organize during training: In the case of multi-layer perceptrons trained with error backpropagation, we find that classification of highly complex data sets requires a temporal {\em reduction} of class separability, marked by a characteristic 'energy barrier' in the initial part of the GDV(L) curve. Even more surprisingly, for a given data set, the GDV(L) is running through a fixed 'master curve', independently from the total number of network layers. Furthermore, applying the GDV to Deep Belief Networks reveals that also unsupervised training with the Contrastive Divergence method can systematically increase class separability over tens of layers, even though the system does not 'know' the desired class labels. These results indicate that the GDV may become a useful tool to open the black box of deep learning

Cooperative information augmentation in a geosensor network

This paper presents a concept for the collaborative distributed acquisition and refinement of geo-related information. The underlying idea is to start with a massive amount of moving sensors which can observe and measure a spatial phenomenon with an unknown, possibly low accuracy. Linking these measurements with a limited number of measuring units with higher order accuracy leads to an information and quality augmentation in the mass sensor data. This is achieved by distributed information integration and processing in a local communication range. The approach will be demonstrated with the example where cars measure rainfall indirectly by the wiper frequencies. The a priori unknown relationship between wiper frequency and rainfall is incrementally determined and refined in the sensor network. For this, neighboring information of both stationary rain gauges of higher accuracy and neighboring cars with their associated measurement accuracy are integrated. In this way, the quality of the measurement units can be enhanced. In the paper the concept for the approach is presented, together with first experiments in a simulation environment. Each sensor is described as an individual agent with certain processing and communication possibilities. The movement of cars is based on given traffic models. Experiments with respect to the dependency of car density, station density and achievable accuracies are presented. Finally, extensions of this approach to other applications are outlined

Quality assessment of landmark based positioning using stereo cameras

Driving autonomously requires highly accurate positioning. Therefore, alternative positioning systems to GPS are required especially to increase the accuracy, and to have a complementary data source in areas where GPS is not available. As more and more on-board sensors are used for safety reasons, information gathered about their environment can be used for positioning based on relative measurements to landmarks along the road. This paper investigates the accuracy potential of positioning using a stereo camera system and landmark maps. Therefore, we simulated several stereo camera systems with variable opening angle and base length to compute the positioning accuracy in a test area. In the first step, localization was calculated based on single positions, in the second step we used a Kalman filter additionally. While positioning in the first case was not successful along the entire trajectory, the Kalman filter led to far better results

Late manifestation of bilateral laryngeal nerve palsy after thyroidectomy

Respiratory distress is a feared complication after thyroid surgery. Differential diagnosis includes bilateral recurrent laryngeal nerve palsy (BRLNP), local hematoma, vocal cord edema and laryngeal trauma. BRLNP results from intraoperative irritation without physical injury (neurapraxia), or intraoperative partial or complete transsection (axonotmesis and neurotmesis, respectively) of the recurrent laryngeal nerve (RLN). RLN palsy typically manifests immediately in the postoperative course. However, in rare cases there is a delayed, progressive development of BRLNP, potentially leading to respiratory failure in emergency setting weeks after initial surgery. Herein we report on a patient developing massive respiratory distress secondary to BRLNP 5 weeks after thyroidectomy for massive goiter. With the current tendency to decrease the length of hospital stay after thyroid surgery, late onset palsy of the RLN should be included into the differential diagnosis for acute respiratory distress in patients with recent history of thyroid surgery

Effects of light quality supplied by light emitting diodes (LEDs) on microalgal production

Dissertação de mestrado, Aquacultura, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2014Light-emitting diodes (LEDs) will become one of the world´s most important light sources and their integration in microalgal production systems (photobioreactors) needs to be considered. Microalgae need a balanced mix of wavelengths for normal growth, responding to light differently according to the pigments acquired or lost during their evolutionary history. In the present study, Nannochloropsis oculata and Tetraselmis chuii were exposed to different light qualities, and their effects on growth, biochemical components (carbohydrate, protein, total lipid and fatty acids) and morphologic traits (cell shape, size, growth phase, absorption spectrum, N-P-C elemental composition in biomass) were investigated. An additional experiment employed different LEDs in order to obtain di- and multichromatic tailored light to increase biomass production. Both N. oculata and T. chuii showed a higher maximal volumetric ash free dry weight content in the culture when exposed to blue (465 nm) and red (660 nm) light, respectively. However, balanced light quality, provided via fluorescent light (FL) and dichromatic blue and red light treatment, was found to be beneficial for biomass growth rates of both algae. Significant changes in the biochemical composition were observed among treatments. Furthermore, algae treated with monochromatic blue light (λe = 405 and 465 nm) often displayed higher nutrient uptake and different morphological traits as compared to algae exposed to red light (λe = 630 and 660 nm). It is suggested that differential response to light quality is partially influenced by observed changes in nutrient consumption and biomass productivity. In terms of biomass per input energy, the most efficient light sources were those with photon output peaks at 660 nm (e.g. LED 660 and FL for plant growth). Research and the application of LED technology to microalgal production is often hindered by inadequate light quantity measurements as well as by inadequate LED manufacture and engineering, leading to the use of inefficient LED modules, which, in turn, may affect microalgal growth and biochemistry

"Was gestatten deutsche Verlage ihren Autoren?" - Der deutschsprachige Zugang zu den Open-Access-Informationen der SHERPA/RoMEO-Datenbank

Das Thema "Open Access" ist nicht erst seit dem sogenannten "Heidelberger Appell" aus dem Frühjahr 2009 in aller Munde. Vielmehr befasst sich auch die Bibliothekswelt spätestens seit Beginn der 2000er Jahre mit dieser Thematik und ist inzwischen eine treibende Kraft in der internationalen "Open-Access-Bewegung". Dies spiegelt(e) sich auch wider in einer Vielzahl von (bibliothekarischen) Projekten, die sich mit Open Access umfassend und in vielfältiger Form befass(t)en. Eines der ersten Projekte aus einer Reihe von Vorhaben, die von der Deutschen Initiative für Netzwerkinformation (DINI) e.V. angeregt und unter Begleitung der DINI-AG Elektronisches Publizieren durchgeführt wurden, war das Projekt "Open Access Policies – Was gestatten deutsche Verlage ihren Autoren?". Im Rahmen des von der Deutschen Forschungsgemeinschaft (DFG) in mehreren Phasen geförderten Vorhabens wurden die an zahlreichen deutschen Hochschulen und wissenschaftlichen Einrichtungen vorhandenen Informationen zusammengestellt: Die Möglichkeiten der zusätzlichen Bereitstellung von bereits in einem Verlag veröffentlichten oder noch zu veröffentlichenden wissenschaftlichen Arbeiten (self-archiving von Preprints bzw. Postprints) wurden erfasst, strukturiert, aufbereitet und mit Hilfe des internationalen Informationssystems der SHERPA/RoMEO-Liste zugänglich gemacht. Hierzu wurde der Bekanntheitsgrad der SHERPA/RoMEO-Liste in Deutschland gesteigert, Handreichungen für die Kommunikation mit Verlagen übersetzt und Hilfestellung bei der lokalen Erfassung von Open-Access-Informationen gegeben. In diesem Beitrag werden die internationalen und nationalen Initiativen und Projekte kurz vorgestellt, die verschiedenen Entwicklungsschritte dokumentiert und die Zielrichtung des Vorhabens sowie die Anwendungsszenarien präsentiert. Zudem werden der aktuelle Stand des Vorhabens nach Abschluss der Projektphasen sowie die weiteren Pläne und potenziellen zukünftigen Entwicklungen skizziert