Epipelic diatoms in the estuaries of South Africa

Epipelic diatom flora was sampled around the South African coast between the Olifants Estuary, on the cool Atlantic Ocean northwest coast, and the St. Lucia Estuary, on the Indian Ocean northeast coast. Altogether, 333 taxa were identified with 14 being ubiquitous, as they were found in the cool temperate, warm temperate, and subtropical areas, as well as in St. Lucia Estuary situated close to Moçambique. There was little difference between the epipelic diatom species present in intertidal and subtidal areas and, because many of the species have a high tolerance to salinity, with some being found in conditions ranging from freshwater to a salinity of more than 150 psu, it was concluded that many of the species sampled do not appear to be reliable indicators for assessing salinity in South African estuaries. Although there was a wide spread of diatoms across all of the estuaries around the coast, the greatest species similarity occurred between the Olifants, Great Berg and Breede estuaries, suggesting that the Breede Estuary, normally considered to fall within the warm temperate region, may be more similar to the cool temperate type estuaries. Data also showed that there was very little similarity between the diatom flora in the rivers flowing into estuaries and the diatom flora in the estuaries.Keywords:diatoms, distribution, estuary, epipelon, salinity, temperature, tida

Transporte do amônio em colunas com agregados de um Latossolo vermelho distrófico.

Para descrever o transporte do íon amônio em diferentes classes de agregados de um Latossolo Vermelho distrófico realizou-se um experimento de laboratório cujos tratamentos corresponderam a um fatorial 3 x 5, sendo: três fontes de NH4 + [(NH4)2SO4, NH4Cl e NH4NO3] e cinco classes de agregados (2,0-1,0; 1,0-0,5; 0,5-0,25; 0,25-0,105; e <0,105 mm). A unidade experimental foi constituída de uma coluna de vidro saturada, sob vácuo, com uma solução de CaCl2 0,005 mol L-1. Aplicou-se, a seguir, a solução saturante até percolação constante, seguida de um pulso de sete volumes de poros da respectiva fonte a 0,01 mol L-1 de NH4 + (Co) para cada classe de agregados. Foram coletadas frações correspondentes a 0,3 volume de poros do efluente (p) determinando-se as concentrações de NH4 + (C). Calculou-se a relação C/Co para cada fração p, traçando-se curvas experimentais de eluição. Os maiores valores dos fatores de retardamento ocorreram nos agregados de menor tamanho, indicando maior retenção do amônio; na maioria dos tratamentos ocorreu superposição das curvas obtidas por meio dos modelos teóricos, o que indicou que o transporte do amônio no solo se deu, predominantemente, por dispersão. Os ânions acompanhantes apresentaram efeitos semelhantes sobre a lixiviação do NH4 +, nas diferentes classes de agregados

Neutron Ionization of Helium near the Neutron-Alpha Particle Collision Resonance

Neutron-impact single and double ionization cross sections of the He atom are calculated near the neutron-alpha particle collision resonance. Calculations using the time-dependent close-coupling method for total and differential cross sections are made at 8 incident neutron energies ranging from 250 to 2000 keV. At the resonance energy peak the double ionization cross sections unexpectedly become larger than the single ionization cross sections. This finding appears to be related to the high velocity of the recoiling alpha particle, which makes it unlikely that the atomic electrons can recombine with the alpha particle nucleus, enhancing the double ionization cross section.Peer ReviewedPostprint (author's final draft

AR-Brillen und Exoskelette in der Baubranche: einfache Entlastungsversprechen gegenüber komplexen Mensch-Maschine-Konfigurationen

Tragbare digitale Technologien wie Exoskelette oder AR-Brillen versprechen in der Baubranche als zukünftige "Verschmelzung" von Mensch, Maschine und Software, schwere körperliche Arbeit und kognitiv komplexe Tätigkeiten zu erleichtern. Um Risiken und neue Formen der Belastung zu minimieren, kommt es allerdings auf eine kluge Integration von menschlicher und künstlicher Handlungsfähigkeit an. Gegenwärtig befinden sich Exoskelette und AR-Softwarelösungen für die Bauwirtschaft noch in der Entwicklung. Die versprochenen Entlastungseffekte stützen sich auf ingenieur- und informationswissenschaftliche Annahmen, Erfahrungswerte aus anderen Anwendungskontexten (Automobilindustrie) sowie auf technikeuphorische Darstellungen (Werbung). Der Beitrag stellt auf der Basis von Dokumentenanalysen und Leitfadeninterviews verschiedene Annahmen über Entlastungseffekte durch digitale Unterstützungstechnologien vor und diskutiert ihre Realisierungschancen anhand von typisierten Mensch-Maschine-Konfigurationen im Bausektor.Wearable digital technologies such as exoskeletons or augmented reality (AR) glasses promise to facilitate heavy physical work and cognitively complex activities in the construction industry as a future "fusion" of humans, machines and software. However, to minimize possible risks and new forms of stress, it is important to integrate human and artificial capabilities in a clever way. At present, exoskeletons and AR software solutions for the construction indus-try are still in development. The promised assistance and relief effects are based on assumptions from engineering and information science, experiences from other application contexts (automotive industry) as well as on technology euphoria in advertisement. Based on document analyses and guideline interviews, this article introduces visions of relief effects through digital assistive technologies and discusses their chances of realisation on the basis of typified human-machine configurations in the construction sector

Fracture Mechanics for Composites: State of the Art and Challenges

Interlaminar fracture mechanics has proven useful for characterizing the onset of delaminations in composites and has been used with limited success primarily to investigate onset in fracture toughness specimens and laboratory size coupon type specimens. Future acceptance of the methodology by industry and certification authorities however, requires the successful demonstration of the methodology on the structural level. In this paper, the state-of-the-art in fracture toughness characterization, and interlaminar fracture mechanics analysis tools are described. To demonstrate the application on the structural level, a panel was selected which is reinforced with stringers. Full implementation of interlaminar fracture mechanics in design however remains a challenge and requires a continuing development effort of codes to calculate energy release rates and advancements in delamination onset and growth criteria under mixed mode conditions

Submillimeter wave detection with superconducting tunnel diodes

Superconductor-Insulator-Superconductor (SIS) diodes are the detector elements in the most sensitive heterodyne receivers available from 100 to 500 GHz. SIS mixers are the front end of radio astronomical systems around the world. SIS mixer technology is being extended to 1 THz and higher frequencies for eventual use on spaceborne astronomical experiments. Here is a short review of submillimeter SIS mixers. The role of impedance matching in the proper design of an SIS mixer is described. A variety of methods for achieving good impedance match at submillimeter frequencies are presented. The experimental state of the submillimeter SIS mixer art is described and summarized

Documenting museum records of west African Coccinellidae (Coleoptera) in Benin and Senegal

Open Access JournalThis work provides a preliminary inventory of West African Coccinellidae. This was based on the West African Coccinellidae (WAC) specimens in the holdings of insect collections at the Laboratoire de Zoologie des Invertébrés Terrestres at the Institut Fondamental d’Afrique Noire Cheikh Anta Diop (IFAN), Senegal and the Biodiversity Center at the International Institute of Tropical Agriculture (IITAB), Benin

A catalogue of twentieth-century cello ensemble music

This document contains over 700 entries of cello ensemble music written in the twentieth and the beginning of the twenty-first centuries by 530 composers from around the world. Pieces presented in this catalogue are largely original works. A few exceptions have been allowed mostly when the composer arranged his/her own piece. For each entry, as much of the available information as possible is provided in the following general order: composer name, composer dates, title of the piece, approximate duration, and availability. Under a section named remarks, additional information is provided such as number and titles of the movements, first performance, sound recordings, record locator numbers, dedications, and other notes by the composer. The document also contains the following appendices: list of the publishers and music centers holding said entries, and an alphabetical list of the composers