1,720,984 research outputs found
Ion scanning or ion trapping: Why not both?
Full text linkThe present contribution describes analogies and differences between the quadrupolar ion trap (QIT) and the quadrupole mass analyzers, shows the potentialities of their combination in a single instrument and presents a review of applications of such a technology in different fields. The first section describes the quadrupole mass filter (QMF), outlining its principles of operation and the ion sorting procedure according to the use of oscillating electric fields inducing stable trajectories to the ions allowing them to reach the detector. Multiple quadrupole systems (normally triple quadrupoles) are then explained, showing their use in tandem mass spectrometry in space experiments (MS/MS-in-space). QIT principles of operation are then examined, pointing out that in this case the use of the same combination of oscillating electric fields takes advantage of unstable ion trajectories for their sorting. Substantially, analogies and differences between QMF and QIT come out, which consist in the fact that QMF is a scanning mass analyzer, whereas QIT is a sequential mass analyzer. In addition, the section underlines that QIT is capable to perform tandem mass spectrometry in time experiments (MS/MS-in-time). Later, the possibility to use a quadrupole as a trapping system with a prevailing dimension (linear ion trap [LIT]) is taken into consideration, and the possibility to combine both QMF and LIT in a single instrument, a QTrap mass spectrometer, is illustrated. In this frame, a lot more experiment types are possible with respect to both standalone triple quadrupoles and LIT, and they are described as well. Several combinations of these QTrap features can be used in information dependent acquisition (IDA) mode, allowing the high versatility of this instrumental configuration. The second section deals with a review of applications in different fields. These are organized by kind of QTrap and IDA features and cover different topics in biological, medical, agrochemical, nutritional and environmental fields
Degradation of exogenous caffeine by Populus alba and its effects on endogenous caffeine metabolism
No full textThis is the first study reporting the presence of endogenous caffeine, theobromine, and theophylline in all organs of poplar plants. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was used in order to evaluate the uptake, translocation, and metabolism of caffeine-(trimethyl-(13)C) in Populus alba L. Villafranca clone grown in hydroponic conditions. We investigated the remediation of caffeine since it is one of the most widely consumed drugs and it is frequently detected in wastewater treatment plant effluents, surface water, and groundwater worldwide. Our results demonstrated that poplar can absorb and degrade exogenous caffeine without negative effects on plant health. Data showed that concentrations of all endogenous compounds varied depending on caffeine-(trimethyl-(13)C) treatments. In particular, in control conditions, endogenous caffeine, theobromine, and theophylline were mainly distributed in roots. On the other hand, once caffeine-(trimethyl-(13)C) was provided, this compound and its dimethy-(13)C metabolites are mainly localized at leaf level. In conclusion, our results support the possible use of Villafranca clone in association with other water treatment systems in order to complete the process of caffeine remediation
Growth and Accumulation of Caffeic Acid Derivatives in Echinacea angustifolia DC. var. angustifolia grown in Hydroponic Culture
No full textIn separate experiments conducted in 2007 and 2008, growth and accumulation of selected caffeic acid
derivatives (CADs; i.e., caftaric acid, chlorogenic acid, echinacoside, caffeic acid, cynarin, p-coumaric acid,
ferulic acid and cichoric acid) were determined in Echinacea angustifolia DC. var. angustifolia seedlings
grown in hydroponic culture (floating raft system) at a density of 122 plant m−2 (at planting). Plants
were harvested 11 (2007) or 16 (2008) weeks after transplanting (i.e., 15 or 20 weeks after sowing). In
both years, plants grew vigorously and at harvest approximately half of the plants under observation had
developed one to three inflorescences. In 2008, the root yield (2940 kg ha−1) harvested in nearly eight
months from two consecutive hydroponic cultures was within the yield reported in the literature for
field cultivations lasting two to four years. None of the selected CADs was found in the leaves, while
the inflorescences (stem and capitulum) contained only caftaric acid and echinacoside at concentrations
higher than the detection limits (0.05 mg g−1 dry weight). Echinacoside, cynarin and chlorogenic acid were
found in root tissues at concentrations ranging from 0.36 to 5.25 mg g−1 dry weight. In all plant samples,
echinacoside, which is the marker compound for E. angustifolia material, did not reach the minimum
quality standard (10 mg g−1 dry weight) for the production of standardized extract. We concluded that
short-cycle, high-density greenhouse hydroponic culture stimulates plant growth and root production
in E. angustifolia, but it does not ensure sufficient CADs accumulation in dried roots
Morpho-physiological response of Populus alba to erythromycin: A timeline of the health status of the plant
No full textPopulus alba Villafranca clone was chosen for a proof of concept study to determine the potential uptake and accumulation of antibiotics by trees. Plants were grown hydroponically and irrigated with a recirculating Hoagland's nutrient solution (control) and Hoagland's nutrient solution fortified with erythromycin at 0.01, 0.1 and 1 mg L− 1. After 3 and 28 days of treatment, poplar plants were separated into roots, stem, and leaves. Plants showed good health all over the period of treatment, and no differences in poplar growth for all the concentrations of erythromycin tested were observed. Quantification of erythromycin was performed using liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS) in positive ion mode using multiple reaction ion monitoring. Erythromycin was detected in all organs analyzed. Roots showed an erythromycin concentration tenfold higher than leaves. The photochemical efficiency of photosystem II did not show a dose-dependant trend. From the quenching analysis of chlorophyll fluorescence, low nonphotochemical quenching (NPQ) and high photochemical quenching (qP) for the first week of erythromycin exposure was observed, depending on leaves position along the stem. Results suggest a short term adaptation of the photosynthetic apparatus of Populus alba in response to environmental realistic erythromycin concentrations
ESI and APCI LC-MS/MS in Model Investigations on the Absorption and Transformation of Organic Xenobiotics by Poplar Plants (Populus alba L.)
No full textPopulus alba Villafranca clone was chosen for a proof of concept study to determine the potential uptake and accumulation of xenobiotics by trees. Caffeine, erythromycin, and sodium dodecyl sulphate (SDS) were studied as representative elements of, respectively, widely present organic pollutants, antibiotics, and surfactants. Plants were grown hydroponically and irrigated with a recirculating Hoagland's nutrient solution (control) and Hoagland's nutrient solution fortified with the desired pollutant. Different plantsâ tolerance was observed in relation to xenobiotics applied. Under caffeine and erythromycin treatments, plants showed good health all over the period of experiments, and no differences in poplar growth were observed. On the contrary diffused necrosis at leavesâ level was observed when SDS was applied to nutrient solution. Xenobiotics uptake was investigated in roots, stem, and leaves, and quantification was performed using liquid chromatography, coupled with tandem mass spectrometry using selected reaction ion monitoring on a triple quadrupole mass spectrometer, with electrospray or atmospheric pressure chemical ionization, depending on the analyte. All the pollutants were detected in all organs analyzed. Poplar plants also showed an active role in the elimination of the pollutants as some of them were metabolized by the tree
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
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
Effects of Caffeine, Zinc, and Their Combined Treatments on the Growth, Yield, Mineral Elements, and Polyphenols of Solanum lycopersicum L.
Full text link(1) Background: The effects of Zn and caffeine as promoters of fruit quality in the Solanum lycopersicum L. cultivar ‘Panarea’ were tested. (2) Methods: During the 56 days of the experiment, plants were treated weekly with 100 mL of 1 mM Zn (Zn), 1 mg L−1 caffeine trimethyl-13C (caffeine), and 1 mM Zn + 1 mg L−1 caffeine trimethyl-13C (Zn + caffeine) and compared to plants that were given tap water (control). (3) Results: Caffeine was taken up by the roots and translocated to the leaves, which positively influenced the number of fruits per plant. After 56 days of treatment, Zn induced a positive increase in tomato dry weight, reducing shoot length (−16.7%) compared to the other treatments. Zn + caffeine had a positive effect on the phenylpropanoid pathway of fruits, and 4-coumaric acid, caffeic acid, and t-ferulic acid were significantly increased, as well as the total antioxidant capacity of the tomatoes. In the flavonoid pathway, only apigenin and luteolin contents were reduced by treatments. The tomatoes showed similar concentrations of the mineral elements Cu, Mn, Fe, Na, Ca, Mg, and K. The Zn and caffeine target hazard quotients were <1, indicating that health risks via the consumption of these tomatoes did not occur. (4) Conclusions: Tomato plants could be irrigated with water containing lower values of Zn, caffeine, and a combination of the two. The treated fruits are rich in antioxidant compounds, such as coumaric acid, caffeic acid, and t-ferulic acid, which are beneficial for human health. No considerable health risks associated with human consumption have been detected
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