1,721,006 research outputs found
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
Detoxification of tuna from mercury through L-cysteine: a speciation-based study.
Full text linkMercury (Hg) contamination in tuna, especially as methylmercury (MeHg), remains a persistent food safety concern. This study assessed the effectiveness of l-cysteine in reducing total Hg (tHg) and MeHg in canned tuna and fresh fillets. Samples were treated with a 1.2% (w/w) cysteine solution and analysed by ICP-MS for tHg and frontal chromatography ICP-MS for MeHg. Untreated canned tuna contained 0.066-0.225 mg kg-1 tHg, whereas fresh fillets reached 1.036 mg kg-1. Cysteine treatment significantly reduced Hg levels, with mean removal of 48% in canned tuna and 64% in fillets. MeHg decreased proportionally with tHg, indicating cysteine binds both Hg and MeHg without species selectivity. Removal was more consistent in fillets than canned tuna, likely due to processing effects on protein binding. Overall, cysteine treatment represents a simple, low-cost, food-safe intervention that lowers Hg exposure and reduces concentrations below regulatory limits, providing additional protection for vulnerable consumers (pregnant women and infants)
Accumulation of Selected Trace Elements in Shads from Three Lakes: First Insights from Italian Pre-Alpine Area
No full textThe investigation of trace element pollution is important for the environmental assessment and management of lacustrine ecosystems, especially when these represent critical freshwater resources in densely populated areas. In this context, this study determined the levels of 15 trace elements in muscles of shad, Alosa agone (Scopoli 1786), a commercialized zooplanktivourous fish, from three primary, but currently still poorly studied, Italian lakes, namely, Lake Como, Iseo, and Garda. Research findings show that shads present similar trace element accumulation patterns among lakes, except for arsenic, which occurs at lower levels in Lake Como. Results provide evidence also for mercury biomagnification in fish, whereas all the other selected trace elements undergo bio-dilution through the same trophic chain. Maximum allowable limits for foodstuff were exceeded for chromium and selenium in shads, whereas mercury levels exceeded the European Environmental Quality Standard biota. These results highlight the need for regular monitoring activities of trace elements in the biota of these lakes
Metal Ion Isotope Ratio Using ESI-Orbitrap HRMS: Proof of Concept and Initial Performance Evaluation for Lead Isotopic Ratios
No full textThis study introduces a novel approach using an electrospray source coupled to an Orbitrap MS instrument to determine metal isotope ratios. The procedure involves forming a complex between the ion of interest and an appropriate ligand, generating gas-phase ions via electrospray ionization, selecting the complex mass by quadrupole filtering, and performing collisional fragmentation to yield free metal ions. The isotopic pattern of the free ion is then analyzed by high-resolution MS. The approach ensures high selectivity and interference-free spectra. A proof-of-concept study was conducted to determine Pb isotope ratios, focusing on identifying the factors that influence the accuracy and precision of the procedure. At this early stage, optimal accuracy was achieved even in the presence of matrix components by applying mass bias correction methods originally developed for other isotope ratio techniques; precision is comparable to that achieved by single-collector ICP-MS instrumentation. This approach may complement conventional methods that suffer from limited mass resolution and usually require extensive sample preparation
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
Tellurium Speciation via Frontal Chromatography ICP-MS: An Innovative and Effective Approach for the Ultratrace Detection in Environmental Matrices
Full text linkThe increasing use of tellurium (Te) in electronics and renewable energy technologies has elevated its environmental concentration, posing ecological and health risks. This study addresses the critical need for effective methods to speciate Te by focusing on its two primary redox states—tellurite (Te(IV)) and tellurate (Te(VI))—which differ in reactivity, mobility, and toxicity. Existing analytical methods for Te speciation are often limited in sensitivity and can’t simultaneously determine both species. In response, we present a novel, rapid, practical, and highly sensitive approach for determining Te(IV) and Te(VI) using frontal chromatography coupled with inductively coupled plasma mass spectrometry (FC-ICP-MS). Multivariate optimization of chromatographic conditions, along with the exploitation of the “carbon effect” and careful isotope selection, yield detection limits of 1.0 ng/L for Te(IV) and 1.3 ng/L for Te(VI) with a total analysis time of five minutes. Acidification with nitric acid is the only sample pretreatment required. Applied to natural waters, sediments, and soils, the method demonstrates high accuracy, superior sensitivity, greenness, and practicality, compared to state-of-the-art methodologies, offering an alternative and advantageous solution for routine Te speciation analysis across various environmental compartments
A high-throughput, straightforward procedure for biomonitoring organomercury species in human hair
Full text linkMercury is a pervasive and concerning pollutant due to its toxicity, mobility, and tendency to biomagnify in aquatic and terrestrial ecosystems. Speciation analysis is crucial to assess exposure and risks associated with mercury, as different mercury species exhibit varying properties and toxicities. This study aimed at developing a selective detection method for organic mercury species in a non-invasive biomonitoring matrix like human hair. The method is based on frontal chromatography (FC) in combination with inductively coupled plasma mass spectrometry (ICP-MS), using a low pressure, homemade, anion exchange column inserted in a standard ICP-MS introduction system, without requiring high-performance liquid chromatography (HPLC) hyphenation. In addition to the extreme simplification and cost reduction of the chromatographic equipment, the proposed protocol involves a fast, streamlined and fully integrated sample preparation process (in contrast to existing methods): the optimized procedure features a 15-min ultrasonic assisted extraction procedure and 5 min analysis time. Consequently, up to 100 samples could be analyzed daily, making the method highly productive and suitable for large-scale screening programs in public and environmental health. Moreover, the optimized procedure enables a limit of detection (LOD) of 5.5 μg/kg for a 10 mg hair microsample. All these features undeniably demonstrate a significant advancement in routine biomonitoring practices. To provide additional evidence, the method was applied to forty-nine human hair samples from individuals with varying dietary habits successfully finding a clear correlation between methylmercury levels (ranging from 0.02 to 3.2 mg/kg) in hair and fish consumption, in line with previous literature data
Introducing Frontal Chromatography-Inductively Coupled Plasma-Mass Spectrometry as a Fast Method for Speciation Analysis: The Case of Inorganic Arsenic
No full textA frontal chromatography-ICP-MS method (FC-ICP-MS) is proposed as an innovative approach for fast elemental speciation analysis: inorganic arsenic speciation was selected as the first case study to prove the feasibility of the technique and to explore its potentialities and limits. The principal benefits of the FC-ICP-MS approach are the short analysis time and the very simple instrumental setup. As(III) and As(V) front separation is performed over a strong anion exchanger at pH 7.5. After the optimization of the instrumental setup and the frontal chromatographic parameters, As(III) and As(V) concentrations up to 240 μg/kg can be determined within 120-140 s using different univariate and multivariate calibration approaches. Best results in terms of accuracy in prediction were obtained using the partial least squares (PLS) calibration achieving limits of detection of 0.18 and 0.21 μg/kg for As(III) and As(V), respectively. This approach was also used to establish the figures of merit of the method. The proved feasibility and good performances (in terms of analysis time and accuracy) of this technique lay the groundwork for future applications of FC-ICP-MS for the speciation of other elements
High-throughput, multi-batch system for the efficient microwave digestion of biological samples
Full text linkIn this paper, we proposed a high-throughput microwave digestion system based on multi-batch reactors (three quartz test tubes inside commercial PTFE vessels). This original configuration was validated by ICP-MS analysis of several elements in biological certified reference materials (fish tissues and plankton). The proposed system was proved to be free from contamination showing very low LODs. The improved hardware configuration is therefore highly beneficial for the detection of trace elements in microsamples from the marine food web
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