1,720,977 research outputs found
Bacteria and organic matter dynamics during a bioremediation treatment of organic-rich harbour sediments
No full textWe studied the dynamics of bacteria and organic matter in the Ancient Port of Genoa (Italy) during a bioremediation treatment
of sediment (during summer–autumn 1998) in an area characterised by continuous sewage discharge. A strong increase in total
benthic bacterial density (TBN) was recorded at the end of the study, from 14108 to 58–172108 cell g1 in different parts of the
treated area. The TBN increase was linked to organic matter depletion, from more than 40 to less than 20 mg g1. In order to
highlight the main ecological mechanisms involved in bioremediation, a laboratory experiment based on both water and sediment
from the basin studied was carried out. We observed an increase in TBN during the first 20 days and a decrease in sediment organic
matter (up to about 20%). Increases of organic matter (about 2-fold) and TBN (from 21 to 33109 cell l1) occurred in the
overlying water, suggesting a strong association between the sediments and water column processes. Hydrolytic activities, which
double in the sediment and increase up to a 300-fold in the water, are consistent with the decrease in sediment organic matter and
with the water fraction dynamics
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Bacterial response to seasonal changes in labile organic matter composition on the continental shelf and bathyal sediments of the Cretan Sea
No full textDispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Small-scale distribution of bacteria, enzymatic activities and organic matter in coastal sediments
No full textThe small-scale distribution of several structural (bacterial abundance, phytopigment, total and soluble protein, and carbohydrate content) and functional ecological variables (enzymatic activities, frequency of dividing cells) was investigated in coastal sediments during a spring bloom. For bacterial abundance, enzymatic activity, and organic matter determinations, samples were collected at 5-m depth from a sediment surface delimited by a 42 × 42-cm frame, divided into 49 squares. In order to test the influence of the bottom microtopography on the investigated variables, the size of this frame was defined to cover the distance between two subsequent ripples. As indicated by Fisher's index, benthic bacteria, enzymatic activities, proteins, carbohydrates, and their soluble fractions exhibited an aggregate distribution. Sampling size (i.e., sample unit of 36 cm2) was appropriate for all variables, except for chlorophyll a and frequency of dividing cells that displayed a contagious distribution. To estimate the reliability of the current sampling strategy, we compared the mean values from three randomly selected sample units with the average value of the entire sediment surface (i.e., 49 samples). For all variables reported in this study, the use of three replicates was representative of the mean values of the sampled area with a confidence limit within ±20%. Bacterial population sizes did not correlate with their potential food sources (e.g., phytopigments, proteins, and carbohydrates), or with enzymatic activities, suggesting the presence of possible time lags between organic inputs and microbial response. Chlorophyll a during the spring bloom displayed much higher concentrations than phaeopigments and correlated with carbohydrates. Chlorophyll a distribution was autocorrelated and displayed a large patch size (1,134 cm2). Phaeopigments and proteins accumulated in the central depression of the ripple-mark structure, apparently depending upon a passive accumulation due to the reduced current action. In contrast, microphy- tobenthic biomass and bacterial numbers were highest in the two opposite ripples, suggesting that different driving forces operate selectively on the living components
Particulate nucleic acid dynamics in a highly oligotrophic system: the Cretan Sea (Eastern Mediterranean)
No full textSpatial and temporal variations of nucleic acid (DNA and RNA) concentrations and bacterioplankton density were investigated in a highly oligotrophic region of the Eastern Mediterranean in order to evaluate the relative contribution of the pico-, nano- and microparticulate fractions and to estimate bacterioplankton contribution to the nucleic acid pools. The oligotrophic conditions of the Cretan Sea were reflected by the extremely low particulate nucleic acid content. In particular, RNA concentrations (range: 0.1 to 3.8 μg 1-1) were the lowest reported so far in the marine environment. Particulate DNA concentrations (range: 0.8 to 5.9 μg 1-1) also displayed a reduced temporal variability. Picoparticulate RNA and bacterial secondary production displayed similar spatial patterns, suggesting that RNA concentrations increased as a result of enhanced metabolic activity. High DNA concentrations were generally associated with the high salinity (>38.95) Transition Mediterranean Waters (TMW) in summer (August 1994 and September 1995), whereas a sharp decrease in DNA concentrations was observed in non-stratified conditions (e.g. February 1995). Most of the DNA concentration was associated with picoparticles (more than 60 % of total DNA pool), with a ratio of 1:3:6 for micro-, nano- and picoparticulate fractions, respectively. By contrast, particulate proteins and RNA displayed an average annual ratio of about 1:1:2 for micro-, nano-, and picoparticulate fractions, respectively. Bacterial densities in the Cretan Sea ranged from 1.1 to 8.8 x 108 cells 1-1. The bacterial DNA contribution to the total DNA pool in the Cretan Sea was on average 40%, but in February 1995 the living DNA fraction accounted for 85% of the total DNA pool. As phytoplankton DNA annually accounted on average for only 17% of the total DNA, we conclude that bacteria play a role of primary importance as a living DNA component in the Cretan Sea
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