2,807 research outputs found
Microbial colonization and competition on the marine alga ulva australis
No full textPseudalteromonas tunicata and Roseobacter gallaeciensis are biofilm-forming marine bacteria that are often found in association with the surface of the green alga Ulva australis. They are thought to benefit the plant host by producing inhibitory compounds that are active against common fouling organisms. We investigated factors that influence the ability of P. tunicata and R. gallaeciensis to attach to and colonize the plant surface and also the competitive interactions that occur between these organisms and other isolates from U. australis during biofilm formation on the plant surface. A surprisingly high number of P. tunicata cells, at least 108 cells ml–1, were required for colonization and establishment of a population of cells that persists on axenic surfaces of U. australis. Factors that enhanced colonization of P. tunicata included inoculation in the dark and pregrowth of inocula in medium containing cellobiose as the sole carbon source (cellulose is a major surface polymer of U. australis). It was also found that P. tunicata requires the presence of a mixed microbial community to colonize effectively. In contrast, R. gallaeciensis effectively colonized the plant surface under all conditions tested. Studies of competitive interactions on the plant surface revealed that P. tunicata was numerically dominant compared with all other bacterial isolates tested (except R. gallaeciensis), and this dominance was linked to production of the antibacterial protein AlpP. Generally, P. tunicata was able to coexist with competing strains, and each strain existed as microcolonies in spatially segregated regions of the plant. R. gallaeciensis was numerically dominant compared with all strains tested and was able to invade and disperse preestablished biofilms. This study highlighted the fact that microbial colonization of U. australis surfaces is a dynamic process and demonstrated the differences in colonization strategies exhibited by the epiphytic bacteria P. tunicata and R. gallaeciensi
Competitive interactions in mixed-species biofilms containing the marine bacterium pseudoalteromonas tunicata
No full textNarayanella, a new name for Narayana Subba Rao (hymenoptera : mymaridae)
No full textThe name Narayana was applied (Subba Rao, 1976) to a genus erected for the new species N. pilipes reared from the gaUs of Lagerstoemia flos reginae. Unfortunately the author overlooked the vulid and prior use of Narayana by Distant (1908). Narayana Distant was erected with rusticitatus as type-species (Issidae: Homoptera). Hence Narayana Subba Rao is a junior homonym which has to be replaced according to the rules of the International Zoological Nomenclature
Low densities of epiphytic bacteria from the marine alga ulva australis inhibit settlement of fouling organisms
No full textBacteria that produce inhibitory compounds on the surface of marine algae are thought to contribute to the defense of the host plant against colonization of fouling organisms. However, the number of bacterial cells necessary to defend against fouling on the plant surface is not known. Pseudoalteromonas tunicata and Phaeobacter sp. strain 2.10 (formerly Roseobacter gallaeciensis) are marine bacteria often found in association with the alga Ulva australis and produce a range of extracellular inhibitory compounds against common fouling organisms. P. tunicata and Phaeobacter sp. strain 2.10 biofilms with cell densities ranging from 102 to 108 cells cm–2 were established on polystyrene petri dishes. Attachment and settlement assays were performed with marine fungi (uncharacterized isolates from U. australis), marine bacteria (Pseudoalteromonas gracilis, Alteromonas sp., and Cellulophaga fucicola), invertebrate larvae (Bugula neritina), and algal spores (Polysiphonia sp.) and gametes (U. australis). Remarkably low cell densities (102 to 103 cells cm–2) of P. tunicata were effective in preventing settlement of algal spores and marine fungi in petri dishes. P. tunicata also prevented settlement of invertebrate larvae at densities of 104 to 105 cells cm–2. Similarly, low cell densities (103 to 104cells cm–2) of Phaeobacter sp. strain 2.10 had antilarval and antibacterial activity. Previously, it has been shown that abundance of P. tunicata on marine eukaryotic hosts is low (<1 x 103 cells cm–2) (T. L. Skovhus et al., Appl. Environ. Microbiol. 70:2373-2382, 2004). Despite such low numbers of P. tunicata on U. australis in situ, our data suggest that P. tunicata and Phaeobacter sp. strain 2.10 are present in sufficient quantities on the plant to inhibit fouling organisms. This strongly supports the hypothesis that P. tunicata and Phaeobacter sp. strain 2.10 can play a role in defense against fouling on U. australis at cell densities that commonly occur in sit
Ability of Pseudoalteromonas tunicata to colonize natural biofilms and its effect on microbial community structure
No full textWe investigated the effectiveness of surface colonization by the epiphytic marine bacterium Pseudoalteromonas tunicata firstly on a complex biofilm community on glass slides, and secondly, on the epiphytic community of Ulva australis. The effectiveness of P. tunicata was compared with the performance of Phaeobacter sp. 2.10, also a marine epiphytic isolate in the U. australis colonization experiments. Pseudoalteromonas tunicata cells were able to colonize the glass slide community at densities found naturally in the water column (9.7 x 10(4) cells mL(-1)). However, P. tunicata was a poor invader of the epiphytic community on U. australis at densities of 10(6) cells mL(-1). At densities of 10(8) cells mL(-1), P. tunicata again exerted little impact on the epiphytic community. Phaeobacter sp. 2.10 was also a poor invader at lower densities, but was able to invade and become dominant at densities of 10(8) cells mL(-1). Differences in the ability of P. tunicata and Phaeobacter sp. 2.10 to invade natural communities may be due to differences in the antibacterial compounds produced by the two species. These experiments suggest that epiphytic communities may have protective effects compared with inanimate surfaces
Sensor Selection for Angle of Arrival Estimation Based on the Two-Target Cramér-Rao Bound
No full textSensor selection is a useful method to help reduce data throughput, as well as computational, power, and hardware requirements, while still maintaining acceptable performance. Although minimizing the Cramér-Rao bound has been adopted previously for sparse sensing, it did not consider multiple targets and unknown source models. In this work, we propose to tackle the sensor selection problem for angle of arrival estimation using the worst-case Cramér-Rao bound of two uncorrelated sources. To do so, we cast the problem as a convex semi-definite program and retrieve the binary selection by randomized rounding. Through numerical examples related to a linear array, we illustrate the proposed method and show that it leads to the natural selection of elements at the edges plus the center of the linear array. This contrasts with the typical solutions obtained from minimizing the single-target Cramér-Rao bound.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System
Sketch Studies and Lu Yen’s Harmony
No full textThis paper introduces the various types of music manuscripts and current issues in music sketch studies. It argues that the study of musical manuscripts is not simply the direct conversion of composition processes into music analysis. Nor is it limited to the function of providing a basis for choosing performance editions. Rather, it allows the researchers to weigh and ponder on many entangled issues, such as the composer's intentions, musical influences and music trends, composition habits, manuscripts chronology order, revisions to the draft, and traces of pre-composition plans. In addition, manuscripts could be situated in the network of various cultural or historical moments, and of a variety of musical styles and trends. It can be linked to a large web of associations contributing in different ways to the production of the manuscripts. Manuscripts are deeply rooted in historical processes and are essentially open text. The diversity of the twentieth century music manuscript, both in terms of musical language and medium, also raise new issues for sketch studies. Borrowing from Philip Gossett, this paper examines three areas of manuscript studies—confirmatory, suggestive, and conceptual—to ponder on the analysis of 20th century music. From this angle, the paper analyzes the manuscripts of Taiwanese composer Lu Yan. It focuses on several diagrams of integers in the composer’s sketches. In particular the paper examines how these diagrams reflect abstract conceptualization of pitch structure and harmony language, and how they are connected to his composition, “Woodwind Quintet.” These sketches of “pitch material” illustrate the profound thinking encompassing his harmony, melody and tone row and balanced relationship of sound world.Peer reviewedPrimarily in Chinese; abstract, annotations, notes, and some references in English
A Comparison of Trichordal Relations in Milton Babbitt's String Quartet No. 2 and Elliott Carter's A Symphony for Three Orchestras
No full textPeer reviewe
The Color of Music Heritage: Chinese America in American Ultra-Modern Music
No full textThis essay considers American ultra-modern music from the vantage point of Chinese America. It argues that the interiority of this racial terrain was molded by the negotiation, mimicry, and transformation necessarily attended musical activities across racial boundaries. Cowell‘s ultra-modern composition bears witness to Asian confluence in the American musical landscape at the beginning of the century, and raises the question of musical heritage. Rejecting the typical orientalist analysis and its self-other framework, this essay explores the significance of Chinatown music, and how a sonic idea that was engendered from it found expression in the dialogical space of American ultra-modern music.Peer reviewe
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