Transport and degradation of phytoplankton in permeable sediment

In flume and field experiments we demonstrate that interfacial water flows, generated when bottom currents interact with sea bed topography, provide a fast and efficient pathway for the transport of suspended phytoplankton into subsurface layers of permeable sandy sediments. The advective transport, associated with small mounds and ripples as commonly found on shelf sediments, increased penetration depth of unicellular algae (Dunaliella spec.) into sandy sediment (permeability k = 4 × 10−11 m2) up to a factor of 7 and flux up to a factor of 9 relative to a smooth control sediment. The pore water flow field produced a distinct distribution pattern of particulate organic matter in the sediment with subsurface concentration maxima and zones depleted of algae. Flux chamber simulations of advective transport of algae into sands of different grain sizes revealed increasing fluxes, algal penetration depths, and degradation rates with increasing permeability of the sediment. Two experiments conducted in intertidal sand flats confirmed the importance of the advective interfacial transport of phytoplankton for natural settings, showing permeability‐dependent penetration of planktonic algae into embedded sand cores of different grain sizes. The significance of our results is discussed with respect to particulate organic matter flux and mineralization in shelf sands, and we suggest the concept of a decomposition layer

Phase error and associated cross-polarization effects in cassegrainian-fed microwave antennas

Phase error and cross-polarization effects in Cassegrainian and microwave antenna

Digital computer analysis and design of a subreflector of complex shape

Digital computer technique for computing scattered pattern of complex hyperboloid subreflector in Cassegrain antenna feed system

An investigation of the solar cycle response of odd-nitrogen in the thermosphere

This annual report covers the first year of funding for the study of the solar cycle variations of odd-nitrogen (N((sup 2)D), N((sup 4)S), NO) in the Earth's thermosphere. The study uses the extensive data base generated by the Atmosphere Explorer (AE) satellites, and the Solar Mesosphere Explorer Satellite. The AE data are being used, for the first time, to define the solar variability effect on the odd-nitrogen species through analysis of the emissions at 520 nano-m from N((sup 2)D) and the emission from O(+)((sup 2)P). Additional AE neutral and ion density data are used to help define and quantify the physical processes controlling the variations. The results from the airglow study will be used in the next two years of this study to explain the solar cycle changes in NO measured by the Solar Mesosphere Explorer

Book Review: The Power to Spring Up: Postsecondary Education Opportunities for Students with Significant Disabilities

Author: Diana M. Katovitch Reviewer: Frank R. Rusch Publication Data: ­­­­­­­Bethesda, MD: Woodbine House 2009 Softcover: ISBN: 978-1-890627-95-9 Cost: $24.95, 265 page

Investigation of charge carriers in nanocrystal-based aerogels and the influence of micro- and nanostructuring

The transformation of intricate nanocrystals (NCs) available through colloidal chemical synthesis into branched network structures (referred to as gels) presents a promising pathway to macroscopic solids exhibiting properties of their NC building blocks. In this work, the possibilities to influence these properties at various stages during the gel synthesis sequence will be explored and expanded on. Additionally, the nanoscopic (opto-)electronic properties of networks build up from semiconducting, photoluminescent (PL) NCs will be investigated to gather insights into the electronic structure of such networks and the dynamics of excited charge carriers therein. In chapter 5 the investigation of gel networks based on CdSe/CdS dot/rod NC building blocks is shown. The PL properties of such structures are analysed in regards to their temperature and time dependent emission (down to 4K). It is shown that at cryogenic temperature the emission splits into two discernible processes correlating to dark and bright exciton states. While this observation is comparable to the results obtained for individual NCs, at all temperatures gel networks exhibit a longer PL decay most likely caused by increased electron delocalization. The investigation also includes a look at differently sized CdSe cores used for synthesis of the CdSe/CdS dot/rod building blocks. It is found that the combination of different core sizes and therefore different emission color building blocks allows for straight-forward color tuning of the final networks. The modification of NC-based gels with thin metal oxide shells is shown in chapter 6. Importantly, NC-based aerogels can be influenced not only at the point of NC building block synthesis but also after the gel formation (post-gelation). In this work, the application of wet-chemical methods based on colloidal seeded-growth processes to a NC-based gel network substrate is presented. This results in uniform, thin shells over the whole of the gel network. The approach can be shown to work on different gel substrates (semiconducting and noble metal) and different shell materials (silica and titania) with only minor modifications. The mechanical stability which is one of the common problems in the applicability of NC-based gels is considerably improved by this shell reinforcement. Building on these developed processes the optical properties of modified CdSe/CdS dot/rod gels are investigated in chapter 7. The silica modification of either the individual NC building blocks before gel assembly or the continuous gel after assembly yield two comparable systems only differing in one crucial point. In gels based on silica modified building blocks, these NC building blocks are isolated and thereby decoupled in the final gel network. For a modification after the gel assembly the building blocks are connected first and therefore coupled in the final gel. The crucial influence on charge carrier dynamics in such networks is shown by time-resolved PL spectroscopy and supported by theoretical calculations. Driving this process further, by incorporation of ZnS at the tip of the CdSe/CdS dot/rod building blocks using a cation exchange procedure a large bandgap material of variable length is introduced to the connecting point of the building blocks. Through the length of the ZnS segment separating theCdSe/CdS building blocks the interaction between these building blocks can not simply be coupled and decoupled but even influenced in its strength as also shown by optical spectroscopy.Die Transformation von komplexen Nanokristallen (NC), hergestellt durch kolloid-chemische Synthese, in verzweigte Netzwerkstrukturen (Gele genannt) repräsentiert einen vielversprechenden Weg zu makroskopischen Feststoffen, die die Eigenschaften ihrer NC Baueinheiten zeigen. In dieser Arbeit werden Möglichkeiten untersucht und erweitert, die Eigenschaften dieser Netzwerke an verschiedenen Punkten ihrer Herstellung zu beeinflussen. Zudem werden die (opto-)elektronischen Eigenschaften von Netzwerken basierend auf halbleitenden, lumineszenten NC untersucht, um ein tieferes Verständnis der elektronischen Struktur dieser Netzwerke und der Vorgänge der angeregten Ladungsträger zu generieren. Die Untersuchung von Gelnetzwerken aus stäbchenförmigen CdSe/CdS NC-baueinheiten ist in Kapitel 5 beschrieben. Die Photolumineszenz-(PL-)Eigenschaften dieser Strukturen werden temperaturabhängig (bis zu 4K) in Hinblick auf ihre zeitaufgelöste Emission untersucht. Dabei wird gezeigt, dass im kryogenen Bereich zwei Prozesse zur Emission beitragen, die sich hellen und dunklen Excitonen zuordnen lassen, ein von einzelnen NC bekanntes Verhalten. Die PL-lebenszeit ist allerdings bei allen Temperaturen in Netzwerkstrukturen länger, vermutlich aufgrund einer stärkeren Delokalisierung der angeregten Elektronen. Zusätzlich ist die Untersuchung von Netzwerken, bei denen die Bausteine auf unterschiedlichen Größen an CdSe Quantenpunkten in den CdSe/CdS Stäbchen basieren, gezeigt. Aus unterschiedlichen Größen resultieren unterschiedliche PL-Farben und ein unkomplizierter Weg zur Farbeinstellung in diesen Netzwerkstrukturen wird aufgezeigt. Die Modifikation von Nanokristallgelen mit dünnen Metalloxidschalen wird in Kapitel 6 gezeigt. NC-basierte Aerogele können nicht nur über die gezielte Synthese der Baueinheiten beeinflusst werden, sondern auch nach der Netzwerkbildung (post-Gelierung). In diesem Abschnitt wird die Adaption bekannter nasschemischer Prozesse zur Anwendung an Nanokristallgelen als Substrat beschrieben. Dabei werden Gelnetzwerke vollständig mit einer einheitlichen, dünnen Schale ummantelt. Dieser Prozess kann auf verschiedene Substrate (Gele aus Halbleiter oder Edelmetall NC) und für verschiedenen Schalenmaterialien (Siliziumdioxid und Titandioxid) mit minimalen Änderungen angepasst werden. Die mechanische Stabilität, eine bedeutende Hürde in der Anwendbarkeit von Nanokristallgelen, wird durch die Verstärkung mit einer solchen Schale deutlich erhöht. Darauf aufbauend werden die PL Eigenschaften modifizierter Netzwerke aus CdSe/CdS Stäbchen in Kapitel 7 untersucht. Die Modifikation mit einer Silikatschale wird entweder an einzelnen kolloiden Nanokristallbaueinheiten vor der Netzwerkbildung oder an dem bereits verbundenen Netzwerk durchgeführt. Werden zuerst die Baueinheiten mit einer Silikatschale umschlossen, so sind diese im finalen Netzwerk isoliert bzw. entkoppelt voneinander, während Baueinheiten, die zuerst in ein Netzwerk überführt werden, auch nach dem Wachstum der Silikatschale miteinander kontaktiert bzw. gekoppelt sind. Der entscheidende Einfluss dieser Verbindung auf die Ladungsträgervorgänge wird durch zeitaufgelöste PL-spektroskopie gezeigt und von theoretischen Berechnungen unterstützt. Dieser Ansatz wird durch den gezielten Einbau von ZnS an die Spitzen der CdSe/CdS Stäbchen weiter verfolgt. Durch einen Kationenaustauschprozess ist es möglich, verschiedene Mengen ZnS (ein Material mit großer Bandlücke) so in die Baueinheiten einzubringen, dass es sich im Netzwerk an den Kontaktpunkten befindet. Über die Länge dieser ZnS Abschnitte zwischen den CdSe/CdS Einheiten, können die Einheiten nicht nur gekoppelt und entkoppelt werden, sondern die Stärke der Wechselwirkung zwischen den Baueinheiten, welche sich in den optischen Eigenschaften widerspiegelt, gesteuert werden.ERC/Horizon 2020/714429/E

Throwing the dice for the diagnosis of vaginal complaints?

BACKROUND: Vaginitis is among the most common conditions women are seeking medical care for. Although these infections can easily be treated, the relapse rate is high. This may be due to inadequate use of the diagnostic potential. METHODS: We evaluated the misjudgement rate of the aetiology of vaginal complaints. A total of 220 vaginal samples from women with a vaginal complaint were obtained and analysed for numbers of total lactobacilli, H(2)O(2)-producing lactobacilli, total aerobic cell counts and total anaerobic cell counts including bifidobacteria, Bacteroides spp., Prevotella spp. Additionally, the presence of Atopobium vaginae, Gardnerella vaginalis, Candida spp. and Trichomonas vaginalis was evaluated by DNA-hybridisation using the PCR and Affirm VPIII Microbial Identification Test, respectively. RESULTS: The participating physicians diagnosed Bacterial vaginosis (BV) as origin of discomfort in 80 cases, candidiasis in 109 cases and mixed infections in 8 cases. However, a present BV, defined as lack of H(2)O(2)-lactobacilli, presence of marker organisms, such as G. vaginalis, Bacteroides spp. or Atopobium vaginae, and an elevated pH were identified in only 45 cases of the women examined. Candida spp. were detected in 46 cases. Interestingly, an elevated pH corresponded solely to the presence of Atopobium vaginae, which was detected in 11 cases. CONCLUSION: Errors in the diagnosis of BV and candida vulvovaginitis (CV) were high. Interestingly, the cases of misjudgement of CV (77%) were more numerous than that of BV (61%). The use of Amsel criteria or microscopy did not reduce the number of misinterpretations. The study reveals that the misdiagnosis of vaginal complaints is rather high