Energy Efficient and Reliable Wireless Sensor Networks - An Extension to IEEE 802.15.4e

Collecting sensor data in industrial environments from up to some tenth of battery powered sensor nodes with sampling rates up to 100Hz requires energy aware protocols, which avoid collisions and long listening phases. The IEEE 802.15.4 standard focuses on energy aware wireless sensor networks (WSNs) and the Task Group 4e has published an amendment to fulfill up to 100 sensor value transmissions per second per sensor node (Low Latency Deterministic Network (LLDN) mode) to satisfy demands of factory automation. To improve the reliability of the data collection in the star topology of the LLDN mode, we propose a relay strategy, which can be performed within the LLDN schedule. Furthermore we propose an extension of the star topology to collect data from two-hop sensor nodes. The proposed Retransmission Mode enables power savings in the sensor node of more than 33%, while reducing the packet loss by up to 50%. To reach this performance, an optimum spatial distribution is necessary, which is discussed in detail

Renaturierung kleiner Lössbäche – ein Beitrag der Ökologischen Landwirtschaft zum Naturschutz

As a part of the interdisciplinary research project ”Integration of nature protection goals with organic farming: an the example from the Hessian ”state domain” [Staatsdomäne] area Frankenhausen”, different restoration measures have been carried out within this site, 15 km north of Kassel. Since 1998, intensive conventional agricultural practices have been substituted with organic farming here. One intention of the agricultural restructuring was to realise nature protection goals in cooperation with sustainable organic agricultural production. The hydrologic portion of the project addresses both the implementation of restoration measures in rivers and streams and their scientific monitoring. Starting in July 2007, several restoration measures were carried out in the hydrologic systems of the Jungfernbach and Esse streams within the Frankenhausen site. Both systems are formed by typical loess streams (catchment size about 9 km2) which had been heavily degraded for several hundred years by intensive agriculture. The most important restoration measures were removal of a piped section of a tributary of the Jungfernbach at Totenhof, restoration of biological passability by removal of weirs and substitution of narrow pipes under farm paths, relocation of a section of the Jungfernbach from the edge of the floodplain to its original location in the centre, widening of narrow sections and partial raising of the deepened stream bed by means of rough ramps (stone bars) and racks made of oak wood or iron. These physical restoration measures were accompanied by a scientific monitoring programme comprising morphological, hydrochemical and biological (aquatic macrophytes, aquatic macroinvertebrates, fish and amphibians) aspects. The aim of this study was to document the original ecological conditions, the restoration measures and the early ecological effects on the stream sections for the first six months following restoration as a basis for further ecological monitoring. The restoration measures effected clear morphological changes in cross-section and passability. The chemical condition of the streams showed slight changes in some aspects following the restoration, e. g. a reduction of phosphorus, magnesium and potassium concentration. Other than macrophytic algae in the newly shaped sections, aquatic macrophytes did not develop over the winter season before the end of the monitoring phase in April 2008. Within the newly shaped stream sections of a small tributary and of the Jungfernbach, up to 14 aquatic macroinvertebrate taxa started to colonise the new habitats 6 months after restoration. Fish fauna were very poorly represented in the streams and included only a few specimens of brown trout (Salmo trutta). This did not change markedly after restoration, possibly due to the isolation of the population caused by impassable weirs downstream of the investigation area.In einem interdisziplinären „Entwicklungs- und Erprobungs-Vorhaben“ der Universität Kassel „Die Integration von Naturschutzzielen in den Ökologischen Landbau am Beispiel der Hessischen Staatsdomäne Frankenhausen“ wurden unterschiedliche Naturschutz-Maßnahmen auf dem Domänengelände durchgeführt. Seit 1998 wird die Staatsdomäne Frankenhausen, die ca. 15 km nördlich von Kassel liegt, ökologisch bewirtschaftet. Ein Aspekt bei der Umstellung auf ökologische Landwirtschaft war die Umsetzung von naturschutz-orientierten Maßnahmen, die in Kooperation mit dem landwirtschaftlichen Betrieb umgesetzt wurden. Ein gewässerökologisches Teilprojekt umfasste unterschiedliche Entwicklungsmaßnahmen an und in Bächen des Jungfernbach- und Esse-Systems auf dem Gelände der Staatsdomäne ab Juli 2007. Beide Bachsysteme (Einzugsgebietsgröße jeweils ca. 9 km2) werden von typischen lössgeprägten Bördenbächen gebildet. Löss-Gebiete zählen zu den durch intensive Landwirtschaft am tiefgreifendsten veränderten Gebieten Deutschlands. Folgende wesentliche Renaturierungsmaßnahmen wurden auf dem Domänengelände umgesetzt: Entfernung der Verrohrung, Offenlegung und Neugestaltung eines Nebenbaches des Jungfernbaches am Totenhof, Rückverlegung eines Jungfernbach-Abschnitts vom Rand der Aue in seine ursprüngliche Lage im Zentrum der Aue nach historischen Angaben, Wiederherstellung der biologischen Durchgängigkeit durch die Entfernung von Wehren und den Ersatz von unpassierbaren Wege-Durchlässen durch voluminösere Durchlässe mit durchgängiger Sohle, partielle Aufweitung enger Querprofile und Anhebung der Gewässersohle durch Stein-Riegel und Sohlrechen aus Stahl oder Eichenholz. Die Maßnahmen wurden von einem wissenschaftlichen Monitoringvorhaben begleitet. Hauptaspekte der wissenschaftlichen Begleitung waren morphologische, hydrochemische und biologische Untersuchungen aquatischer Makrophyten, des Makrozoobenthos, der Fischfauna und der Amphibien. Sie dienten der Erfassung des ökologischen Status quo der Gewässer vor Durchführung der Maßnahmen und der Dokumentation der ökologischen Situation der Gewässer im Anschluss an die Maßnahmen als Basis für die Beobachtung der künftigen Gewässerentwicklung. Die Renaturierungsmaßnahmen induzierten markante Veränderungen der morphologischen Situation der ehemals zu engen und tiefen Querprofile und verbesserten die biologische Durchgängigkeit auf dem Domänengelände. An den Sohlrechen fand während der Folgemonate nach der Renaturierung wegen zu geringer Wasserführung nur ein geringer Totholztransport und damit noch keine erkennbare Sohlanhebung statt. Die chemischen Qualitätsparameter zeigten bei einigen Wasserinhaltsstoffen (z. B. bei Phosphor, Magnesium und Kalium) einen Rückgang der Konzentrationen, der seine Ursachen im Verzicht auf mineralische Düngung mit diesen Stoffen in der ökologischen Landwirtschaft haben könnte. Bei den Wasserpflanzen traten in den neu gestalteten Gewässerabschnitten unmittelbar nach den Renaturierungsmaßnahmen Pionierbestände makrophytischer Algen wie Spirogyra, Cladophora und Vaucheria auf. Über die Herbst- und Wintermonate nach Abschluss der Maßnahmen im Oktober 2009 bis zum Ende der Monitoring-Phase im April 2008 konnten sich noch keine Makrophytenbestände in den neu gestalteten Gewässerabschnitten entwickeln. Im Gegensatz hierzu fand in diesem Zeitraum eine rasche Ansiedlung von 14 Wirbellosen-Taxa im Jungfernbach und 13 Taxa im kleinen, offengelegten und neu gestalteten Bach am Totenhof statt. In diesem Nebengewässer siedelten sich zahlreiche für Lössbache charakteristische Makroinvertebraten bachaufwärts aus dem Jungfernbach heraus an. Die sehr spärliche Fischpopulation, die aus wenigen Bachforellen in einem einzigen Gewässerabschnitt bestand, veränderte sich infolge ihrer räumlichen Isolation durch unterhalb des Untersuchungsraums gelegene Wehre nicht nennenswert

Multisite dependency of an E3 ligase controls monoubiquitylation-dependent cell fate decisions.

Metazoan development depends on tightly regulated gene expression programs that instruct progenitor cells to adopt specialized fates. Recent work found that posttranslational modifications, such as monoubiquitylation, can determine cell fate also independently of effects on transcription, yet how monoubiquitylation is implemented during development is poorly understood. Here, we have identified a regulatory circuit that controls monoubiquitylation-dependent neural crest specification by the E3 ligase CUL3 and its substrate adaptor KBTBD8. We found that CUL3KBTBD8 monoubiquitylates its essential targets only after these have been phosphorylated in multiple motifs by CK2, a kinase whose levels gradually increase during embryogenesis. Its dependency on multisite phosphorylation allows CUL3KBTBD8 to convert the slow rise in embryonic CK2 into decisive recognition of ubiquitylation substrates, which in turn is essential for neural crest specification. We conclude that multisite dependency of an E3 ligase provides a powerful mechanism for switch-like cell fate transitions controlled by monoubiquitylation

Inhomogeneous Temperature Distribution Affecting the Cyclic Aging of Li-Ion Cells. Part II: Analysis and Correlation

Temperature has a significant influence on the behavior of batteries and their lifetime. There are several studies in literature that investigate the aging behavior under electrical load, but are limited to homogeneous, constant temperatures. This article presents an approach to quantifying cyclic aging of lithium-ion cells that takes into account complex thermal boundary conditions. It not only considers different temperature levels but also spatial and transient temperature gradients that can occur despite-or even due to-the use of thermal management systems. Capacity fade and impedance rise are used as measured quantities for degradation and correlated with the temperature boundary conditions during the aging process. The concept and definition of an equivalent aging temperature (EAT) is introduced to relate the degradation caused by spatial and temporal temperature inhomogeneities to similar degradation caused by a homogeneous steady temperature during electrical cycling. The results show an increased degradation at both lower and higher temperatures, which can be very well described by two superimposed exponential functions. These correlations also apply to cells that are cycled under the influence of spatial temperature gradients, both steady and transient. Only cells that are exposed to transient, but spatially homogeneous temperature conditions show a significantly different aging behavior. The concluding result is a correlation between temperature and aging rate, which is expressed as degradation per equivalent full cycle (EFC). This enables both temperature-dependent modeling of the aging behavior and its prediction

Inhomogeneous Temperature Distribution Affecting the Cyclic Aging of Li-Ion Cells. Part I: Experimental Investigation

Alongside electrical loads, it is known that temperature has a strong influence on battery behavior and lifetime. Investigations have mainly been performed at homogeneous temperatures and non-homogeneous conditions in single cells have at best been simulated. This publication presents the development of a methodology and experimental setup to investigate the influence of thermal boundary conditions during the operation of lithium-ion cells. In particular, spatially inhomogeneous and transient thermal boundary conditions and periodical electrical cycles were superimposed in different combinations. This required a thorough design of the thermal boundary conditions applied to the cells. Unlike in other contributions that rely on placing cells in a climatic chamber to control ambient air temperature, here the cell surfaces and tabs were directly connected to individual cooling and heating plates. This improves the control of the cells’ internal temperature, even with high currents accompanied by strong internal heat dissipation. The aging process over a large number of electrical cycles is presented by means of discharge capacity and impedance spectra determined in repeated intermediate characterizations. The influence of spatial temperature gradients and temporal temperature changes on the cyclic degradation is revealed. It appears that the overall temperature level is indeed a decisive parameter for capacity fade during cyclic aging, while the intensity of a temperature gradient is not as essential. Furthermore, temperature changes can have a substantial impact and potentially lead to stronger degradation than spatial inhomogeneities

Three-body resonances in pionless effective field theory

We investigate the appearance of resonances in three-body systems using pionless effective field theory at leading order. The Faddeev equation is analytically continued to the unphysical sheet adjacent to the positive real energy axis using a contour rotation. We consider both, the three-boson system and the three-neutron system. For the former, we calculate the trajectory of Borromean three-body Efimov states turning into resonances as they cross the three-body threshold. For the latter, we find no sign of three-body resonances or virtual states at leading order. This result is validated by exploring the level structure of three-body states in a finite volume approach.Comment: 18 pages, 10 figures, version published in Phys. Rev.

Cell-fate determination by ubiquitin-dependent regulation of translation.

Metazoan development depends on the accurate execution of differentiation programs that allow pluripotent stem cells to adopt specific fates. Differentiation requires changes to chromatin architecture and transcriptional networks, yet whether other regulatory events support cell-fate determination is less well understood. Here we identify the ubiquitin ligase CUL3 in complex with its vertebrate-specific substrate adaptor KBTBD8 (CUL3(KBTBD8)) as an essential regulator of human and Xenopus tropicalis neural crest specification. CUL3(KBTBD8) monoubiquitylates NOLC1 and its paralogue TCOF1, the mutation of which underlies the neurocristopathy Treacher Collins syndrome. Ubiquitylation drives formation of a TCOF1-NOLC1 platform that connects RNA polymerase I with ribosome modification enzymes and remodels the translational program of differentiating cells in favour of neural crest specification. We conclude that ubiquitin-dependent regulation of translation is an important feature of cell-fate determination

Shock Waves in Nanomechanical Resonators

The dream of every surfer is an extremely steep wave propagating at the highest speed possible. The best waves for this would be shock waves, but are very hard to surf. In the nanoscopic world the same is true: the surfers in this case are electrons riding through nanomechanical devices on acoustic waves [1]. Naturally, this has a broad range of applications in sensor technology and for communication electronics for which the combination of an electronic and a mechanical degree of freedom is essential. But this is also of interest for fundamental aspects of nano-electromechanical systems (NEMS), when it comes to quantum limited displacement detection [2] and the control of phonon number states [3]. Here, we study the formation of shock waves in a NEMS resonator with an embedded two-dimensional electron gas using surface acoustic waves. The mechanical displacement of the nano-resonator is read out via the induced acoustoelectric current. Applying acoustical standing waves we are able to determine the anomalous acoustocurrent. This current is only found in the regime of shock wave formation. We ontain very good agreement with model calculations.Comment: 14 Pages including 4 figure

Characterization of the stability radius via bifurcation techniques

Robustness of stability of linear time-invariant systems using the relationship between the structured compex stability radius and a prametrized algebraic Riccato equation is analysed. Our approach is based on the observation that the algebraic Riccati equation can bie viewed as a bifurcation problem. It ist proves that the stability radius ist, under certain assumptions, associated with a turning point of the bifurcation problem given by the parametrized algebraic Riccati equation. As a byproduct, the stability radius can be computed via path following. Some numerical examples are presented