1,720,965 research outputs found
Determination of Plant Hormone Indole-3-Acetic Acid in Aqueous Solution
No full textAn electroanalytical method was developed for the determination of the phytohormone indole-3-acetic acid in
water using a glassy-carbon electrode. The differential pulse voltammetry was combined with a purification step
which involved the extraction of plant tissue and the separation of plant pigments by passing through column Oasis
MCX. Indole-3-acetic acid can be determined under optimum conditions with a limit of quantification (LOQ) 2.7
106 mol L1. The linearity range was from 1.8106 to 6.6104 mol L1. The electroanalytical determination of
indole-3-acetic acid is selective, fast and economic. The presence of other phytohormones as abscisic acid and cytokinins
as isopentenyladenine, isopentenyladenosine, trans-zeatin, zeatin riboside does not interfere the determination
of indole-3-acetic acid in plant sample
Comparative determination of some phytohormones in wild-type and genetically modified plants by gas chromatography–mass spectrometry and high-performance liquid chromatography–tandem mass spectrometry
No full textThe analytical performances of two optimized analytical methodologies used for the determination of
auxins, cytokinins, and abscisic acid in plant samples were critically compared. Phytohormones were
extracted from Nicotiana glauca samples using a modified Bieleski solvent and determined both by gas
chromatography–mass spectrometry (GC–MS), after derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide
(BSTFA), and by high-performance liquid chromatography–tandem mass spectrometry (HPLC–
MS/MS) on the Bieleski extract without any further treatment. HPLC–MS/MS gave better results in terms
of higher coefficients of determination of the calibration curves, higher and more reproducible recoveries,
lower limits of detection, faster sample preparation, and higher sample throughput. Thus, two sets of N.
glauca and N. langsdorffii samples, both wild-type and genetically modified by inserting the glucocorticoid
receptor (GR) gene encoding for the rat glucocorticoid receptor, were first characterized by reverse transcriptase-
polymerase chain reaction (RT-PCR) analysis and then analyzed by HPLC–MS/MS. Significant differences
in the phytohormone content between the two sample sets were found and are very important
in terms of understanding the mechanisms and effects on growth processes and the development of
transgenic plants
Comparative evaluation of the metabolic profile in genetically modified (GMPs) and non-genetically modified plants (non GMPs).
No full textOccurence of legacy and emerging persistent organic pollutants at the Ross Sea and circumpolar deep water convergence (Antarctica)
Full text linkPersistent organic pollutants (POPs) have attracted the attention of scientists and policy makers in recent decades due to their extreme persistence, semi-volatility, capacity to bio-accumulate in the food chain, and toxic
properties. Despite its geographical isolation, extreme meteorological conditions and an almost total absence of local point sources, the Antarctic continent is vulnerable to contamination by POPs, due to the ability of these
chemicals to undergo long range atmospheric transport (LRAT) and deposition in the open sea. In a few cases and for limited areas, POPs may be also introduced into the Antarctic ecosystem by human activities (scientific
stations, fishing, tourism, accidental oil pills, waste incineration and sewage).
Even if various studiesi.e.1,2,3,4,5 have revealed the presence of POPs in air, seawater, sediments and biota in Antarctica, more investigations are needed to implement the number of observations, integrate the data series
and meet the indications of the Stockholm Convention and the UNECE protocol in terms of improving knowledge of the temporal and spatial trends of POPs in biotic and abiotic environmental compartments.
In this study we present POP concentrations in water samples collected along vertical water columns from seven oceanographic stations located in the Ross Sea and close to the Circumpolar Convergence (see Figure 1).
Moreover, the occurrence of emerging and legacy POPs, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated naphthalenes (PCNs), organochlorine pesticides (OCPs) and
polybrominated diphenylethers (PBDEs) were investigated in order to evaluate their possible sources and relationship with physical and biological processes taking place in the water column.
The Ross sea is the formation site of two shelf waters which constitute an important part of the Antarctic Bottom Water (AABWs): the High Salinity Shelf Water (HSSW), which is relatively cold and generated inside the Ross
Sea basin and the Ice Shelf Water (ISW). The Ross sea is influenced by only one water mass of external origin,
the Circumpolar Deep Water (CDW), which is the largest circulation feature of the Southern Ocean, manly responsible for possible exchange processes between the Antarctic seas and the outer oceans, and thus a possible
source of persistent organic pollutants (POPs)2
.
The CDW is a relatively warm, salty and nutrient rich water mass carried around Antarctica by the Antarctic Circumpolar Current (ACC)6. Associated with the ACC is the Antarctic Convergence where the cold Antarctic
waters meet the warmer waters of the subantarctic creating a zone of upwelling nutrients. Moreover, the Drygalski Glacie Tongue plays an important role in the Polynya development in the Terra Nova Bay, in the Ross
sea. An important environmental concern is the accelerated glacier and snow melting that represent a massive release of both naturally occurring chemical substances and organic/inorganic pollutants of anthropogenic origin, which are stored in the deeper layers of the ice and may be delivered to surrounding ecosystems
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
Metronomic vinorelbine is directly active on Non Small Cell Lung Cancer cells and sensitizes the EGFRL858R/T790M cells to reversible EGFR tyrosine kinase inhibitors
Full text linkMetronomic vinorelbine (mVNR) has been described primarily as an antiangiogenic therapy, and no direct effects of mVNR on Non Small Cell Lung Cancer (NSCLC) cells has yet been demonstrated. The aims of this study were i) to establish the direct activity of mVNR on NSCLC cells either EGFR wt or EGFRL858R/T790M, and ii) to quantify the synergism of the combination with reversible EGFR tyrosine kinase inhibitors (TKIs), investigating the underlying mechanism of action. Proliferation assays were performed on A-549 (wt EGFRhigh), H-292 (EGFR-wt), H-358 (EGFR-wt), H-1975 (EGFRL858R/T790M) NSCLC cell lines exposed to mVNR, its active metabolite deacetyl-VNR (D-VNR), gefitinib and erlotinib for 144 h treatments. The synergism between mVNR and EGFR TKIs was determined by the combination index (CI) in EGFR-wt and H-1975 NSCLC cells. Cyclin-D1 and ABCG2 genes expression and protein levels were measured by RT-PCR and ELISA assays, as well as the phosphorylation of ERK1/2 and Akt. Intracellular concentrations of EGFR TKIs and VNR were investigated with a mass spectrometry system. mVNR, and its active metabolite D-VNR, were extremely active on NSCLC cells, in particular on H-1975 (IC50 = 13.56 ± 2.77 pM), resistant to TKIs. mVNR inhibited the phosphorylation of ERK1/2 and Akt and significantly decreased the expression of both cyclin-D1 and ABCG2 m-RNA and protein. The simultaneous combination of VNR and reversible EGFR TKIs showed a strong synergism on EGFR-wt NSCLC cells and on H-1975 cells (e.g. CI = 0.501 for 50% of affected cells), increasing the intracellular concentrations of EGFR TKIs (e.g. +50.5% vs. gefitinib alone). In conclusions, mVNR has direct effects on NSCLC cells and sensitizes resistant cells to EGFR TKIs, increasing their intracellular concentrations
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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