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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Extensive spatial analysis of the light environment in a subtropical shallow lake, Laguna Ibera', Argentina
No full textVariations in the attenuation of photosynthetically available radiation were analysed using extensive spatial
sampling in two seasons in a subtropical wetland lake. Simultaneously with the attenuation measurements,
the principal absorption and scattering components of the water column were also measured. The elevated
spatial resolution used in the study allowed the determination of spatially distinct optical water classes
within the lake. Changes in dissolved organic matter, phytoplankton and tripton concentrations led to a
wide variation in the vertical attenuation coefficients. These changes depended on local characteristics of
the ecosystem and time of year. The spatial distribution of the attenuation coefficients was examined in
relation to the hydrological and geomorphological characteristics of the littoral area of the lake. The
impacts of two small rivers on the light environment and attenuation components are shown. Finally, the
resulting model was used to examine the possible impacts of changes in light availability at the lake bottom
in relation to recent changes in lake water level
Penetration of solar radiation into waters of Messina Strait (Italy)
No full textThe optical properties of the waters of five different stations, three located in the Messina Strait and two near the Strait (open sea), were analysed. Direct spectral measurements of the downward solar irradiance (290 - 800 nm) at different depths (0.5 m, 7 m, 10 m, 13 m, 20 m) were made using a cosine sensor connected to a spectroradiometer. Water samples were collected in the surface layer and their absorption spectra were analysed. The natural fluorescence profiles, along the water column, were determined using a fluorometer (SBE 911 plus - Sea Teach). The spectral attenuation coefficient (K-lambda), the variation of K-lambda in different wavelength ranges (Delta K-Delta lambda), the wavelength corresponding to minimum value of K-lambda, the spectral depths of penetration of both 1% and 10% of the sub-surface irradiance values (P-lambda), the depths of 1% of penetration of UVB, UVA and PAR, the depth ranges of the maxim concentration of Chl a and superficial CDOM were measured at each station. The maximum solar UVB penetration was about 65% of the photic zone and the maximum UVA penetration was nearly 100% (data of the Ionic sea station). Thus, a large part of the photic zone was exposed to UV radiation sufficient to cause a possible reduction in the photosynthetic activity of phytoplankton. The spectral penetration of solar radiation, especially UVB radiation, was significantly different in the three stations of the Strait with respect to the two stations studied in the open sea. This shows that variations in the spectral attenuation along the water column can be used as an indicator of properties of the water body
The spatial distribution of the optical properties in the UV and Visible in an aquatic ecosystem.
No full textIn aquatic ecosystems, the UV and visible radiation environment
is strongly influenced by variation in the chemical and
physical parameters of the ecosystems. In shallow lakes, highly
heterogeneous water characteristics produce a wide variety of
optical environments. Such ecosystems require analysis approaches
that consider a potential variability. In this study, 77
stations were used to characterize the optical properties of a
shallow lake (open water surface 54 km2). The vertical
attenuation of solar radiation at 305,313,320 and 340 nm and
at photosynthetically active radiation was measured during the
seasonal cycle. Dissolved organic matter (DOM), turbidity,
fluorescence, pH, temperature, conductance and dissolved oxygen
were simultaneously measured. The spatial variation of the
extinction spectra of the dissolved fraction at each sampling
station was also measured and analyzed between 270 and
400 nm. The spatial heterogeneity of the lake was examined by
determining the distributions of the attenuation coeff~cientsa nd
biooptical parameters at high spatial resolution and describing
the distributions in a series of maps. The methodology permitted
a quantitative description of the interaction between solar radiation
and aquatic ecosystems as well as a spatial classification of
the dominating processes within the lake. This included the
determination of the role played by DOM loading and changing
chemical properties within the lake optical environment
The role of wetlands in the chromophoric dissolved organic matter release and its relation to aquatic ecosystems optical properties. A case of study: Katonga and Bunjako Bays (Victoria Lake; Uganda)
No full textChromophoric Dissolved Organic Matter (CDOM) is an important component in freshwater and marine ecosystems
and plays direct and indirect role in biogeochemical cycles. CDOM originates from the degradation process of organic
materials, usually macrophytes and planktons. The present work examines the importance of wetland derived CDOM
on the optical and bio-optical properties of two bays of Lake Victoria (Uganda, Africa). This was achieved by determining
the attenuation and extinction coefficients of filtered and unfiltered water samples from two equatorial bays on the Ugandan
coastline of Lake Victoria. Katonga Bay is a wetland lined bay that receives water from the Katonga river, while Bunjako
Bay is an outer bay between Katonga Bay and Lake Victoria. The results showed that attenuation was highest in
Katonga Bay and the role ofCDOMis most dominant near the river inlet. The quantity and quality ofCDOMis extremely
different in the two bays: in Katonga Bay it is possible to hypothesize a terrestrial origin of CDOM (transported by the
wetland river). On the contrary, in Bunjako Bay, spectral measurements of absorption indicate a modified CDOM and/
or alternative CDOMsource. The terrestrial CDOMin Katonga Bay is more capable of absorbing harmful UV radiation
than theCDOMpresent in the Bunjako Bay. The resulting optical environment in the former bay presented a water column
with a very limited penetration of harmful UV radiation, while a higher penetration was observed in the Bunjako Bay
Relationships between wetland ecotones and inshore water quality in the Ugandan coast of Lake Victoria
No full textMuch of the lake shore in Lake Victoria is covered by extensive wetlands, often dominated by dense papyrus stands that extend out over the lake waters. These wetlands, their extension and management play a role in the physical, chemical and biological conditions of the inshore waters. Continuous transects along 180 km of shoreline together with spatial grids of sampling sites in eight bays were performed in the Ugandan inshore waters in order to analyze the relationships between the wetland characteristics and water quality. Measurements of extension of the wetland ecotones, water temperature (T), pH, Secchi disk depth (SD), dissolved oxygen (DO), total nitrogen (TN), total phosphorous (TP), dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and chlorophyll-a (CHL) were made in each sampling area. Data of T, pH and DO collected during the transects showed that the water characteristics of the bays differ from the open shoreline. Moreover, the magnitude of these physical–chemical differences is strongly conditioned by the dimension of the bordering wetlands. Bays with extensive wetlands ecotones were characterized by cooler, more acidic and poorly oxygenated waters. TN : TP ratios and especially DIN : SRP ratios decreased with the wetland presence along the coastline, showing a higher probability of N limitation in the inshore waters where large wetlands are present. Results point to denitrification processes in the wetland ecotones as the cause of this trend. The distribution of CHL was found to be highest in the presence of two significant point loading sources: a river (in Katonga Bay) and a major population centre (Kampala, in Murchison Bay). The reduction of external P loading is shown as an important step in the management of the eutrophication process of Lake Victoria inshore waters
The estimate of the effects of UV radiation on mortality of Artemia Franciscana in naupliar and adult stages
No full textThe impact of different doses of artificial ultraviolet (UV) radiation on the growth stages of a marine zooplankton was investigated using laboratory microcosms. Mortality percentages of naupliar and adult samples of Artemia franciscana were recorded in relation to different UV doses (single exposure: 75, 150, 300, 600, 1,200, 2,400, 3,900, 7,800 J m-2) at specific observation times after exposure (24, 48, 72, 96 and 120 h). The relationship between mortality percentage and UV dose showed significant differences in relation to the zooplankton growth stage. The elevated susceptibility of the naupliar samples to UV radiation is described through a mortality model based on a logistic equation. The data analysis shows that the slope of mortality versus dose remains the same for the two growth stages while the lethal dose in the naupliar stage was 3.3 smaller than that determined for the adult stage. The slope of the UV mortality rate versus post-incubation time was found to be significantly different (P<0.05) at low UV doses for the two life stages examined, i.e. naupliar and adult. The lower value of LD50 in naupliar stages compared to that for adults confirms that in the early growth stage this marine zooplankton is more susceptible to UV radiation. © ISB 2005
Variations on the Author
Full text link“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
Full text linkWe 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
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